JP2006184476A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus capable of preventing the appearance of an image quality difference due to a difference in surface smoothness in transfer paper P different in kinds from each other and the appearance of an image quality difference between the front and back surfaces due to a difference in the surface smoothness between the front and back surfaces of the transfer paper P. <P>SOLUTION: A toner image forming means is constituted so as to input information on the surface smoothness of the objective surface for transfer of the toner image in the transfer paper P to an operation display unit 90 so that the number of the output lines per unit length in a halftone part of the toner image or the degree of dot concentration is changed according to the input information. The toner image forming means comprises four first process units 80Y, M, C, K, four second process units 82 Y, M, C, K, a first transfer unit 20, a second transfer unit 30, a controller 95, etc. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an image forming apparatus such as a copying machine, a facsimile, or a printer that transfers a toner image formed on the surface of a toner image carrier onto a recording material such as transfer paper.

  Conventionally, as an image forming apparatus that forms an image on both sides of a recording medium, an apparatus using a switchback system described in Patent Document 1 and an apparatus using a one-pass system described in Patent Document 2 or Patent Document 3 are known. ing. In the switchback method, the recording medium is passed through a transfer unit and a fixing unit, an image is recorded on one surface of the recording unit, and then the recording unit is reversed by a reverse conveyance path. Then, the image is recorded on the other side by switching back to the transfer unit and the fixing unit. On the other hand, the one-pass method uses a transfer device that can transfer a toner image continuously on both sides of a recording medium. Then, by passing the recording medium after passing through the transfer device through the fixing means, it is possible to record images on both sides without switching back the recording medium.

JP-A-5-8948 JP 2000-352889 A JP 2002-202638 A

  In any of the methods, there is a problem that a difference in image quality between the front and back of the recording medium becomes conspicuous. Specifically, the roughness of the image may differ between the front and back of the recording medium. In particular, in the halftone part (intermediate image density part) and the highlight part (low image density part) in a solid image such as a photographic image or a picture image, a difference in roughness between the front and back surfaces is noticeable.

  Therefore, the present inventor conducted extensive research on the cause of this problem and found the following. That is, when the same image is formed on a plurality of recording bodies under the same imaging conditions, an image formed on a recording body having poor surface smoothness is compared with an image formed on a recording body having excellent surface smoothness. , It was found that the feeling of roughness was increased. That is, the roughness of the image increases as the surface smoothness of the recording medium deteriorates. Among various types of recording materials, there are those in which the surface smoothness is greatly different between the front and back surfaces by providing a coating layer only on one side. For example, in the field of bookbinding printing, which is mainly used for light printing, as the cover of a booklet or paper on which an illustration with a photographic image or the like is performed, paper having surface smoothness greatly different between front and back is often used. When such paper is used, the roughness of the image formed on the surface of the recording medium that is inferior to the surface smoothness is greater than the roughness of the image formed on the other surface, The image quality difference between the front and back is conspicuous. In the case of a booklet, such a difference in image quality is a serious problem because it lowers the product value.

  The reason why the surface smoothness affects the image quality is as follows. In other words, the dots made of toner constituting the image adhere to the recording medium following the fine irregularities on the surface. For this reason, the larger the irregularities on the surface of the recording body, that is, the worse the surface smoothness, the more the dot shape is disturbed and the image quality is lowered. In addition, when transferring an image from a transfer source such as a photoconductor to a recording body, as the surface smoothness of the recording body deteriorates, the adhesion between the transfer source and the recording body deteriorates, and the toner is placed around the dots. It becomes easy to scatter. This also causes the smoothness of the surface to be disturbed by the surface smoothness. Since each dot is formed without a gap in a high image density portion in a solid image such as a photographic image, it is difficult to visually recognize dot shape disturbance. For this reason, even if the shape of each dot is disturbed, it hardly affects the image quality. However, since dots are formed at a certain interval in the halftone part and the highlight part, it is easy to visually recognize the irregular shape of the dots. Since the size of the dots is as small as several tens of μm, the disturbance of the individual dots is not visible to the eye, but the halftone part and the highlight part are visually recognized as having a rough feeling as a whole.

  Note that the image forming apparatus not only having a mechanism for forming an image on both sides of the recording medium, but also an image forming apparatus not having such a mechanism, has an image quality on both sides of the recording medium due to the difference in surface smoothness. The problem that a difference appears can occur. The user may perform an operation in which an operator forms an image on one side by turning the front and back of the recording medium and setting it on a paper feed tray or the like, and forming an image on the other side. It is.

  In addition, the problem that the graininess changes depending on the type of the recording body according to the surface smoothness is not a problem that the image quality difference occurs between the front and back of the recording body, even when an image is formed on only one side of the recording body. obtain.

  The present invention has been made in view of the above background, and an object thereof is to provide the following image forming apparatus. That is, there are situations in which image quality differences appear due to differences in surface smoothness between different types of recording media, and image quality differences appear on both sides due to differences in surface smoothness between the recording media. This is an image forming apparatus that can be suppressed.

In order to achieve the above object, a first aspect of the present invention is a toner image forming unit that forms a toner image on the surface of a toner image carrier, and a transfer unit that transfers toner on the toner image carrier to a recording member. In the image forming apparatus using the toner image forming unit that expresses the gradation by the density of the toner-attached pixels to which the toner is attached among the pixels in the entire area of the image, the toner in the recording body Smoothness information input means for inputting information on the surface smoothness of the transfer target surface of the image is provided, and the output per unit length in the halftone portion of the toner image according to the input information to the smoothness information input means The toner image forming means is configured to change the number of lines.
According to a second aspect of the present invention, there is provided a toner image forming unit for forming a toner image on the surface of the toner image carrier, and a transfer unit for transferring the toner on the toner image carrier to a recording member. In the image forming apparatus using as the forming unit, one that expresses the gradation by the density of the toner-attached pixels to which the toner is attached among the pixels in the entire region of the image, the surface of the transfer target surface of the toner image on the recording body Smoothness information input means for inputting information relating to surface smoothness is provided, and the concentration degree of the toner adhering pixels in the halftone portion of the toner image is changed according to the input information to the smoothness information input means. The toner image forming means is configured.
According to a third aspect of the present invention, there is provided a toner image forming means for forming a toner image on the surface of the toner image carrier, and a transfer means for transferring the toner on the toner image carrier to a recording material. In the image forming apparatus using as the forming unit, one that expresses the gradation by the density of the toner-attached pixels to which the toner is attached among the pixels in the entire region of the image, the surface of the transfer target surface of the toner image on the recording body The toner image forming unit includes a smoothness detecting unit that detects surface smoothness, and changes the number of output lines per unit length in a halftone portion of the toner image according to a detection result of the smoothness detecting unit. It is characterized by comprising means.
According to a fourth aspect of the present invention, there is provided a toner image forming means for forming a toner image on the surface of the toner image carrier, and a transfer means for transferring the toner on the toner image carrier to a recording material. In the image forming apparatus using as the forming unit, one that expresses the gradation by the density of the toner-attached pixels to which the toner is attached among the pixels in the entire region of the image, the surface of the transfer target surface of the toner image on the recording body Smoothness detecting means for detecting surface smoothness is provided, and the toner image forming means is arranged to change the concentration degree of the toner adhering pixels in the halftone portion of the toner image according to the detection result by the smoothness detecting means. It is characterized by comprising.
According to a fifth aspect of the present invention, in the image forming apparatus of the first or second aspect, at least a first toner image carrier and a second toner image carrier are provided as the toner image carrier, and the toner image forming means is provided. A first toner image forming portion for forming a first toner image transferred to the first surface of the recording medium on the first toner image carrier, and a second toner image transferred to the second surface of the recording medium. And a second toner image forming unit for forming the second toner image on the second toner image carrier, and the output corresponding to the first surface according to input information to the smoothness information input means. A device that changes the number of lines or the degree of concentration and the number of output lines or the degree of concentration corresponding to the second surface is used as the transfer unit, and the first toner image is transferred from above the first toner image carrier. The second toner image is transferred to the first surface and the second toner image is transferred to the second toner image. Using the one that is transferred from the image carrier to the second surface, and the smoothness information input means that can individually input surface smoothness information on the first surface and the second surface. It is characterized by the fact that
According to a sixth aspect of the present invention, in the image forming apparatus of the first or second aspect, at least a first toner image carrier and a second toner image carrier are provided as the toner image carrier, and the toner image forming means is provided. The first toner image transferred to the first surface of the recording member and the second toner image transferred to the second surface of the recording member are formed on the first toner image carrier and have the smoothness. According to the input information to the information input means, the one that changes the number of output lines or the degree of concentration corresponding to the first surface and the number of output lines or the degree of concentration corresponding to the second surface, respectively, As a transfer means, the first toner image on the first toner image carrier is directly transferred to the first surface, and the second toner image on the first toner image carrier is passed through the second toner image carrier. Using the material transferred to the second surface, As, it is characterized in that using respectively the first and the second surfaces capable inputs individually surface smoothness information.
According to a seventh aspect of the present invention, in the image forming apparatus of the third or fourth aspect, at least a first toner image carrier and a second toner image carrier are provided as the toner image carrier, and the toner image forming means is provided. A first toner image forming portion for forming a first toner image transferred to the first surface of the recording medium on the first toner image carrier, and a second toner image transferred to the second surface of the recording medium. And a second toner image forming unit for forming the second toner image on the second toner image carrier, and the output line corresponding to the first surface according to a detection result by the smoothness detecting means. The first toner image is transferred from the first toner image carrier onto the first toner image carrier as the transfer means using one that changes the number or the degree of concentration and the number of output lines or the degree of concentration corresponding to the second surface. The second toner image is transferred to the first surface and the second toner image is transferred. What is transferred from the body to the second surface, and the smoothness detecting means is a device capable of individually detecting surface smoothness on the first surface and the second surface. To do.
According to an eighth aspect of the present invention, in the image forming apparatus according to the third or fourth aspect, at least a first toner image carrier and a second toner image carrier are provided as the toner image carrier, and the toner image forming means is provided. The first toner image transferred to the first surface of the recording member and the second toner image transferred to the second surface of the recording member are formed on the first toner image carrier and have the smoothness. Using the one that changes the number of output lines or the degree of concentration corresponding to the first surface and the number of output lines or the degree of concentration corresponding to the second surface in accordance with the detection result by the detection means, As a means, the first toner image on the first toner image carrier is directly transferred to the first surface, and the second toner image on the first toner image carrier is passed through the second toner image carrier. Using what is transferred to the second surface, as the smoothness detection means, It is characterized in that used as capable of detecting the surface smoothness individually between the first and the second surfaces.
According to a ninth aspect of the present invention, in the image forming apparatus according to any of the fifth to eighth aspects, the output line corresponding to a surface having a lower surface smoothness among the first surface and the second surface. Reduce the number of the output lines corresponding to the other surface, or make the concentration corresponding to the surface with lower surface smoothness higher than the concentration corresponding to the other surface. Thus, the toner image forming means is configured.
According to a tenth aspect of the present invention, in the image forming apparatus according to the seventh or eighth aspect, as the smoothness detecting means, surface smoothness on at least one of the first surface and the second surface of the recording body is provided. What detects based on the light reflectivity in the surface is used.
According to an eleventh aspect of the present invention, in the image forming apparatus according to the tenth aspect, as the smoothness detecting means, regular reflection light on the surface of the light emitted from the light emitting means is received by the light receiving means, and the light reflectance is obtained. It is characterized by using what is detected.
According to a twelfth aspect of the present invention, in the image forming apparatus according to the eleventh aspect, as the smoothness detecting means, diffuse reflected light on the surface of the light emitted from the light emitting means is different from the light receiving means. It is characterized by using a device that receives light by the light receiving means.
According to a thirteenth aspect of the present invention, in the image forming apparatus according to the seventh, eighth, tenth, eleventh or twelfth aspect, as the smoothness detecting means, at least one of the first surface and the second surface of the recording body. One of them is that which detects the surface smoothness based on the surface electrical resistance of the recording material.
According to a fourteenth aspect of the invention, in the image forming apparatus according to the seventh, eighth, tenth, eleventh, or thirteenth aspect, the first surface detection that detects the surface smoothness of the first surface as the smoothness detecting means. And a second surface detecting means for detecting the surface smoothness of the second surface.
According to a fifteenth aspect of the present invention, in the image forming apparatus of the fourteenth aspect, the first surface detection unit and the second surface detection unit interfere with each other across a recording medium conveyance path through which the recording medium is conveyed. Is arranged so as to be shifted from a position where the maximum is.
According to a sixteenth aspect of the present invention, in the image forming apparatus according to any one of the first to fifteenth aspects, as the toner image forming means, the toner image is 600 [dpi] or more in both the main scanning direction and the sub scanning direction. It is characterized by using a material formed with a resolution of.
According to a seventeenth aspect of the present invention, in the image forming apparatus according to any one of the first to sixteenth aspects, the toner image is formed by attaching toner to the latent image formed on the surface of the latent image carrier as the toner image forming means. And the one that forms the latent image in which the diameter of each pixel is 60 [μm] or less is used.
According to an eighteenth aspect of the present invention, in the image forming apparatus of the fifth or seventh aspect, as the first toner image forming portion, a plurality of single-color first toner images having different colors are superimposed on the first toner image carrier. The second toner image forming unit is configured to superimpose a plurality of single-color second toner images having different colors on the second toner image carrier as the second toner image forming unit. It is characterized in that what is formed to obtain a multicolor second toner image is used.
According to a nineteenth aspect of the present invention, in the image forming apparatus of the sixth or eighth aspect, as the toner image forming means, a plurality of single-color first toner images having different colors are superimposed on the first toner image carrier. Forming a multi-color first toner image, or forming a multi-color second toner image by superimposing a plurality of single-color second toner images of different colors on the first toner image carrier. It is characterized by using.
According to a twentieth aspect of the present invention, in the image forming apparatus according to any one of the first to nineteenth aspects, a toner storage unit that stores toner used in the toner image forming unit is provided, and the weight average particle diameter is 3 to 7 [ μm] and a toner having a weight average particle diameter divided by a number average particle diameter of 1.00 to 1.30 is stored in the toner storage means.
The invention according to claim 21 is the image forming apparatus according to any one of claims 1 to 19, wherein the toner used in the toner image forming means has a weight average particle diameter of 3 to 7 [μm] and a weight average. A value obtained by dividing the particle diameter by the number average particle diameter is 1.00 to 1.30.

In these image forming apparatuses having the configurations of claims 1 and 3, the number of output lines per unit length in the halftone portion of the toner image is changed according to the surface smoothness of the recording medium. The inventor has found that the roughness of the toner image can be changed by changing the number of output lines by an experiment described later. Therefore, in the image forming apparatus having the configuration of claim 1 or claim 3, the number of output lines is changed in accordance with the surface smoothness of a plurality of different types of recording bodies, and the toner image feels rough. By performing the adjustment, it is possible to suppress a situation in which a difference in image quality occurs between different types of recording media. In addition, by changing the number of output lines according to the surface smoothness on the front and back sides of the recording medium and adjusting the roughness of the toner image on each side, it is possible to suppress the occurrence of a difference in image quality between the front and back sides. You can also.
Further, in the image forming apparatus having the configuration of claim 2 or 4, the concentration degree of the toner adhering pixels in the halftone portion of the toner image is changed according to the surface smoothness of the recording medium. The inventor of the present invention has found through experiments to be described later that the roughness of the toner image can be changed by changing the degree of concentration. Therefore, in the image forming apparatus having the configuration according to claim 2 or 4, the concentration degree of the toner image is changed by changing the concentration degree according to the surface smoothness of a plurality of different types of recording media. By performing the adjustment, it is possible to suppress a situation in which a difference in image quality occurs between different types of recording media. In addition, by adjusting the degree of concentration of the toner image on each surface by changing the concentration degree according to the surface smoothness on the front and back of the recording medium, it is possible to suppress a situation in which a difference in image quality occurs between the front and back. it can.

A first embodiment in which the present invention is applied to an electrophotographic color copying machine (hereinafter simply referred to as a copying machine) as an image forming apparatus will be described below.
FIG. 1 is a schematic configuration diagram showing a copying machine according to the first embodiment. In this figure, the copier has a printer unit 100, an operation / display unit 90, a paper feeding device 40, an automatic image reading device 200, a paper supply device 300, and the like.

  The printer unit 100 includes a first image forming unit disposed above and a second image forming unit disposed below the paper conveyance path 43A. The first image forming unit includes a first transfer unit 20 having a first intermediate transfer belt 21 that moves endlessly in the direction of the arrow in the drawing. Further, the second image forming unit includes a second transfer unit 30 having a second intermediate transfer belt 31 that moves endlessly in the direction of the arrow in the drawing. Four first process units 80Y, 80M, 80C, and 80K are arranged above the upper stretched surface of the first intermediate transfer belt 21. On the other hand, four second process units 81Y, 81M, 81C, and 81K are arranged on the side of the side tension surface of the second intermediate transfer belt 31. The subscripts Y, M, C, and K attached to the numbers of the first and second process units indicate the colors of toner to be handled. The same subscript is attached to each device in the process unit.

  Each process unit (80Y, M, C, K, 81Y, M, C, K) has a photoreceptor (1Y, M, C, K) as a latent image carrier. The photoreceptors 1Y, 1M, 1C, and 1K of the first process units 80Y, 80M, 80M, 80K, 80K, 80K, 80K, and 80K are arranged at regular intervals, and at least at the time of image formation, contact the upper stretched surface of the first intermediate transfer belt 21, respectively. Hereinafter, the belt surface that contacts in this way is referred to as a first image receiving surface.

  On the other hand, the photoreceptors 1Y, 1M, 1C, and 1K of the second process units 81Y, 81M, 81C, and 81K are also arranged at equal intervals, and at least at the time of image formation, contact the upper stretched surface of the second intermediate transfer belt 21, respectively. . Hereinafter, the belt surface that contacts in this way is referred to as a second image receiving surface.

  The first intermediate transfer belt 21 is stretched by a plurality of rollers in a horizontally long posture with a space in the horizontal direction rather than in the vertical direction, and in a posture in which the first image receiving surface extends substantially horizontally. The first process units 80Y, 80M, 80C, and 80K are arranged in parallel so as to be in contact with the substantially horizontal first image receiving surface.

  On the other hand, the second intermediate transfer belt 31 is in a vertically long posture with a plurality of rollers to take a space in the vertical direction rather than in the horizontal direction, and the second image receiving surface is inclined in a posture to be inclined from the upper left to the lower right in the drawing. It is built. The second process units 81Y, 81M, 81C, 81K are in contact with the second image receiving surface inclined in this way, on the left side of the second intermediate transfer belt 31 in the drawing, from the upper left to the lower right in the drawing. It is arrange | positioned so that it may become a diagonal arrangement | sequence.

  FIG. 2 is an enlarged configuration diagram showing one of the four first process units 80Y, 80M, 80C, 80K. The four first process units 80Y, 80M, 80C, 80K, 80K, 80K, 80K, 80K, 80K, 80K, Y80, Y80, 80K, 80K, Y80, Y80, 80K, 80K, Y80, Y80, 80K The subscript K is omitted. In the figure, the photosensitive member 1 is driven to rotate counterclockwise in the drawing by a driving means (not shown) during operation of the printer unit (100). Around the photosensitive member 1, there are image forming members such as a scorotron charger 3, an exposure device 4, a developing device 5, a cleaning device 2 and a photostatic device Q which are charging means, a potential sensor S1, an image sensor S2, and the like. It is arranged.

  The drum-shaped photoreceptor 1 is formed by coating an organic photosensitive layer (OPC), which is a photoconductive substance, on an aluminum cylinder surface having a diameter of about 30 to 120 [mm], for example. An amorphous silicon (a-Si) layer may be coated. Further, it may be a belt shape instead of a drum shape.

  The cleaning device 2 includes a cleaning brush 2a, a cleaning blade 2b, a recovery member 2c, and the like, and removes and recovers transfer residual toner remaining on the surface of the photoreceptor after passing through a primary transfer nip described later.

  The scorotron charger 3 is for uniformly charging the surface of the photoconductor 1 that is rotationally driven to, for example, a negative polarity. As a charging means for performing such uniform charging, a corotron charger may be used instead of the scorotron charger. Alternatively, a charging bias member to which a charging bias is applied may be in contact with the surface of the photoreceptor 1.

  The exposure device 4 optically scans the surface of the uniformly charged photoreceptor 1 with light generated based on image data corresponding to one of the colors, and an electrostatic latent image is formed on the surface of the photoreceptor 1. Form. In the example shown in the figure, the exposure device 4 is composed of an LED (light emitting diode) array and an imaging element. A laser scanning method using a light beam modulated according to image data to be formed using a laser light source, a polygon mirror, or the like may be used.

  The developing device 5 is of a two-component developing system that develops an electrostatic latent image on the photoreceptor 1 using a two-component developer containing toner and a magnetic carrier. The two-component developer is conveyed in the depth direction in the figure while being agitated by two conveying screws 5c. The developer conveying directions of these two conveying screws 5c are opposite to each other. For example, if the developer conveying direction of the left conveying screw 5c in the figure is the front side from the back side in the figure, the developer conveying direction of the right conveying screw 5c in the figure is the front side to the back side in the figure. The two-component developer transported to the end in the depth direction of the developing device 5 by the former transport screw 5c is transferred to the latter transport screw 5c. Then, in the process of being stirred and conveyed from the end portion toward the opposite end portion, a part is carried on the developing roll 5b described later. Further, the two-component developer that is not carried or returned from the developing roll 5b to the right conveying screw 5c is delivered to the left conveying screw 5c at the opposite end. In this way, the two-component developer is circulated and conveyed in the developing device 5. As the developing device 5, a one-component developing system using a one-component developer containing toner as a main component without including a magnetic carrier may be used.

  The developing roll 5a is a non-magnetic cylinder made of stainless steel, aluminum, or the like, and has a sleeve that is driven to rotate clockwise in the drawing by a driving means (not shown), and a magnet roller that is internally fixed so as not to rotate. is doing. The magnet roller has a plurality of magnetic poles divided in the circumferential direction inside the sleeve. The two-component developer conveyed by the conveyance screw 5c on the right side in the drawing is attracted by the magnetic force generated by the magnet roller, and is pumped up on the surface of the sleeve that is rotationally driven. Then, prior to being transported to the developing area facing the photoreceptor 1 along with the sleeve surface, it passes through a regulation position that is a position facing the blade 5b.

  The blade 5b is disposed so that its tip is close to the sleeve surface through a predetermined gap. Then, when the two-component developer on the sleeve surface passes through the regulation position immediately below, the thickness of the two-component developer is regulated to a predetermined size.

  The two-component developer whose layer thickness is regulated in this way is conveyed to a developing region that is a position facing the photoreceptor 1 as the sleeve rotates. The electrostatic latent image formed by attenuating the charge by optical scanning on the surface of the photoreceptor 1 uniformly charged to the negative polarity is rubbed against the two-component developer on the sleeve surface in the development region. . Then, it is developed into one of Y, M, C, and K colors by the adhesion of negatively chargeable toner having the same polarity as the latent image. In the first process unit 80, so-called reversal development is performed. As a result, a toner image of any one of Y, M, C, and K is formed on the photoreceptor 1.

  The two-component developer that has consumed toner in the developing region returns to the developing device 5 as the sleeve rotates. Then, under the influence of the repulsive magnetic field formed by the magnetic poles of the same polarity and adjacent to each other of the magnet roller, the magnet roller is separated from the sleeve surface and returned to the right conveying screw 5c in the drawing, and then the left side in the drawing. It is delivered to the conveying screw 5c.

  A toner concentration sensor 5e is disposed below the left conveying screw 5c in the drawing, and detects the magnetic permeability of the two-component developer conveyed by the left conveying screw 5c. Since the magnetic permeability of the two-component developer has a correlation with the toner density, the toner density sensor 5e detects the toner density.

  When the control unit (not shown) determines that the toner density of the two-component developer is less than a predetermined target density value based on the output signal from the toner density sensor 5e, of the two toner supply units (not shown), The one corresponding to the component developer is driven for a predetermined time. These eight toner supply units are respectively provided for four developing devices of the first process unit (80Y, M, C, K) or four developing devices of the second process unit (81Y, M, C, K). It corresponds to any one. It is connected to one of the four Y, M, C, and K toner bottles (86Y, M, C, and K in FIG. 1) that are detachably set in the bottle storage unit 85 at the top of the printer unit (100). . Then, the toner of a predetermined color is supplied from the connected toner bottle onto the conveying screw 5c on the left side in the drawing in the corresponding developing device. As a result, the toner concentration of the two-component developer that has consumed the toner by the development is recovered. As the toner supply means having such a configuration, a method of sucking the toner in the toner bottle and transporting it to the inside of the developing device with a suction force by a conventionally known Mono pump is preferable. According to this method, there are few restrictions on the installation location of the toner bottle, which is advantageous for space allocation inside the printer unit (100). Further, since the toner can be replenished in a timely manner, it is not necessary to provide a large toner storage space in the developing device 5, and the developing device 5 can be downsized.

  FIG. 3 is an enlarged configuration diagram showing one of the four second process units (81Y, M, C, K). Since the four second process units (81Y, M, C, K) have almost the same configuration except that the colors of the toners to be handled are different, the second process unit 81 includes the first process unit (81Y, M, C, K). 80) and the constituent members are the same, but the rotation direction of the photoreceptor 1 is different. However, they are mutually shaped with respect to the y-axis passing through the rotation axis 1a of the photoreceptor 1. Although this shape is related to the arrangement of members provided around the photoreceptor 1, it is an important matter. Specifically, consideration is given to a method of connecting a connecting portion with the main body of the printer unit 100, for example, a connecting portion with a driving means, an electrical connecting portion, a toner supplying portion, and a toner discharging portion. Thereby, the first process unit (80Y, M, C, K) and the second process unit (81Y, M, C, K) can be made compatible. Accordingly, it is not necessary to separately manufacture the developing device, the cleaning device, and the parts for the first process unit and the second process unit, so that the efficiency in manufacturing parts and managing parts is high, and the overall cost can be reduced. it can.

  In FIG. 1 described above, the first image forming unit includes a plurality of first process units (80Y, M, C, K) and a first transfer unit 20. Further, the second image forming unit includes a plurality of second process units (81Y, M, C, K) and a second transfer unit 30. In the printer unit 100, the first transfer unit 20 and the second transfer unit 30 constitute a double-side transfer device.

  In the first transfer unit 20, the first intermediate transfer belt 21 is stretched by a plurality of rollers 22 (four), 23, 24, 25, 26 (two), 27, 28, 29, and the first process unit. 80 Y, M, C, and K photoconductors 1 Y, M, C, and K are brought into contact with each other. By this contact, the first transfer unit 20 causes the Y, M, C, and K toner images (hereinafter also referred to as single-color first toner images) on the photoreceptors 1Y, 1M, 1C, and 1K to be transferred to the first intermediate transfer belt 21. A primary transfer nip for Y, M, C, and K to be superimposed and transferred is formed. The first intermediate transfer belt 21 is endlessly moved clockwise in the figure while forming these four primary transfer nips. In each primary transfer nip, any one of the four primary transfer rollers 22 to which a primary transfer bias is applied by a power source (not shown) is placed between the photoreceptors 1Y, M, C, and K and the first intermediate transfer belt 21. Is sandwiched. Due to the influence of the primary transfer bias and the nip pressure, a single monochrome first toner image is primarily transferred onto the first intermediate transfer belt 21 at each primary transfer nip. By this superposition, a first toner image of another color is formed on the first intermediate transfer belt 21 that is an image carrier.

  A cleaning device 20 </ b> A is provided on the outer periphery of the first intermediate transfer belt 21 at a position facing the roller 23. The cleaning device 20 </ b> A wipes off the transfer residual toner remaining on the surface of the first intermediate transfer belt 21 after passing through each primary transfer nip and foreign matters such as paper dust. Members related to the first intermediate transfer belt 21 are integrally formed as the first transfer unit 20 and can be attached to and detached from the printer unit 100.

  On the other hand, in the second transfer unit 30, the second intermediate transfer belt 31 is stretched by a plurality of rollers 32 (four), 33, 34, 35, and 36 (two), and the photoreceptors 1Y, 1M, 1C, and 1K. Is in contact with By this contact, the second transfer unit 30 transfers the Y, M, C, and K second toner images (hereinafter also referred to as single-color second toner images) on the photoreceptors 1Y, 1M, 1C, and 1K to the second intermediate transfer. A primary transfer nip for Y, M, C, and K to be superimposed and transferred on the belt 31 is formed. The second intermediate transfer belt 31 moves endlessly counterclockwise in the figure while forming these four primary transfer nips. In each primary transfer nip, any one of the four primary transfer rollers 32 to which a primary transfer bias is applied by a power source (not shown) is placed between the photoreceptors 1Y, M, C, and K and the second intermediate transfer belt 31. Is sandwiched. Due to the influence of the primary transfer bias and the nip pressure, the Y, M, C, and K second toner images are primarily transferred onto the second intermediate transfer belt 31 at each primary transfer nip. By this superposition, a second toner image of another color is formed on the second intermediate transfer belt 31 that is an image carrier.

  A cleaning device 30 </ b> A is provided on the outer periphery of the second intermediate transfer belt 31 at a position facing the roller 33. The cleaning device 30A wipes off unnecessary toner remaining on the surface of the intermediate transfer belt 31 after passing through each primary transfer nip and foreign matters such as paper dust. Members related to the second intermediate transfer belt 31 are also integrally formed as the second transfer unit 30 and can be attached to and detached from the printer unit 100.

Each of the two intermediate transfer belts (21, 31) is a belt having a base made of a resin film or rubber having a base thickness of 50 to 600 [μm], for example. The toner image, which is a visible image carried on the photosensitive member 1, has an electric resistance value that enables electrostatic transfer to the belt surface by the primary transfer bias applied to the primary transfer rollers (22, 32). Demonstrate. As an example of such an intermediate transfer belt, a material in which carbon is dispersed in polyamide and the volume resistance value is adjusted to about 10 ⁶ to 10 ¹² [Ωcm] can be exemplified. Belt detent ribs for stabilizing the running of the belt are provided on one side or both ends of the belt. The circumference of the belt is about 1500 [mm].

As the four primary transfer rollers 22 as the primary transfer means of the first transfer unit 20 and the four primary transfer rollers 32 as the primary transfer means of the second transfer unit 30, for example, those having the following configurations are used. Can be used. That is, the surface of a metal roller as a core metal is coated with a conductive rubber material, and a bias is applied to the core metal part from a power source (not shown). In the first embodiment, a conductive rubber material obtained by dispersing carbon in urethane rubber is used, and the volume resistance is adjusted to about 10 ⁵ Ωcm.

  The printer unit 100 can also output a monochrome image using only K toner. When outputting a monochrome image, the Y, M, C process units 80Y, 80M, 80C in the first transfer unit 20 are not used. In addition to not operating the process units 80Y, 80M, and 80C, a mechanism is provided for keeping them in contact with the first intermediate transfer belt 21. An internal frame (not shown) that supports the roller 26 and the primary transfer roller 22 is provided, and is supported so as to be rotatable about a certain point. Then, by rotating in a direction away from the photosensitive member, only the photosensitive member 1K is brought into contact with the first intermediate transfer belt 21, and an image forming process is executed to create a monochrome image using black toner. Such a configuration is advantageous in terms of improving the life of the photoreceptor. Similarly, the second transfer unit 30 is configured to retract the process units 81Y, 81M, and 81C from the second intermediate transfer belt 31 when outputting a monochrome image.

  A secondary transfer roller 46 sandwiches the first intermediate transfer belt 21 between the outer periphery of the first intermediate transfer belt 21 and a support roller 28 that supports the first intermediate transfer belt 21 with its back surface supported. It is arranged. Thereby, in the first transfer unit 20, a secondary transfer nip in which the first intermediate transfer belt 21 and the secondary transfer roller 46 come into contact with each other is formed. A region from the support roller 28 through the secondary transfer nip to the secondary transfer roller 46 is a first transfer portion in the double-side transfer device.

The secondary transfer roller 46 is a metal roller that is a core metal, and the surface of the metal roller is coated with a conductive rubber. A secondary transfer bias is applied to the core metal part from a secondary transfer bias power source (not shown). The conductive rubber has a volume resistance adjusted to about 10 ⁷ Ωcm by carbon dispersion.

  A registration roller pair 45 is disposed on the right side of the secondary transfer nip in the drawing. The registration roller pair 45 temporarily suspends the rotation of both rollers after the transfer paper P sent from the paper feeding device 40 disposed on the right side of the printer unit 100 in the drawing is sandwiched between the rollers. Then, the transfer paper P is sent out toward the secondary transfer nip at a timing that can be synchronized with the four-color toner image that is the superimposed toner image on the first intermediate transfer belt 21. The transferred transfer paper P has a four-color toner image brought into close contact with a first surface (a surface facing the upper side in the drawing) which is one surface of the transfer paper P at the secondary transfer nip. The four-color toner images on the first intermediate transfer belt 21 are secondarily transferred collectively onto the first surface under the influence of the secondary transfer bias and the nip pressure. The transfer paper P that has passed through the secondary transfer nip is separated from the first intermediate transfer belt 21 and the secondary transfer roller 46 and transferred to the second intermediate transfer belt 31.

  In the second transfer unit 30, a belt-wrapped portion by the upper stretching roller 34 that stretches the second intermediate transfer belt 31 is an upper stretched surface of the second intermediate transfer belt 31. Above this upper stretch surface, a transfer charger 47, which is a charge applying means, is disposed so as to face the upper stretch surface with a predetermined gap. A region from the transfer charger 47 through the predetermined gap to the upper stretching roller 34 is the second transfer unit of the second transfer unit 30.

  The transfer charger 47 is a known type, and a thin wire of tungsten or gold is used as a discharge electrode, held by a casing, and a transfer current is applied to the discharge electrode from a power source (not shown). While passing the transfer paper P between the second intermediate transfer belt 31 and the transfer charger 47, the four-color toner on the second intermediate transfer belt 31 is applied to the first surface with an electric charge generated from the transfer charger 47. The image is secondarily transferred collectively onto the second surface of the transfer paper P. Both the secondary transfer bias and the charge applied by the transfer charger 47 have a positive polarity opposite to the polarity of the toner.

  On the right side of the printer unit 100 in the drawing, a paper feeding device 40 that accommodates transfer paper P is provided. The paper feeding device includes a plurality of paper storage means. Specifically, the uppermost sheet feed tray 40a, the first sheet feed cassette 40b disposed below the sheet feed tray 40a, the second sheet feed cassette 40c disposed below the first sheet feed cassette 40b, and the lower section thereof Is provided with a third paper feed cassette 40d. Each of these paper storage means is disposed so as to be able to be drawn out to the near right side (operation surface side) with respect to the paper surface. In addition, transfer sheets P of different sizes are accommodated. In each paper storage means, the uppermost transfer paper P is selectively fed and separated by the corresponding paper feeding / separating means 41A to 41D, and only one sheet is reliably fed by the plurality of conveying roller pairs 42B to the paper conveying path 43B. And sent to 43A.

  The paper transport path 43A is provided with a pair of registration rollers 45 for taking a feeding timing for feeding the transfer paper P to the first transfer unit and the second transfer unit of the double-side transfer device. Further, a lateral registration correction mechanism 44 for setting a position perpendicular to the conveyance direction of the transfer paper P to a normal position is provided in the paper conveyance path 43A. Examples of the lateral registration correcting mechanism 44 include the following. That is, the transfer paper P is slid and conveyed so as to be composed of a horizontal reference guide (not shown) and a pair of skew rollers, so that the horizontal end of the transfer paper is pressed against the reference guide. Then, the transfer paper is aligned with a predetermined position. The reference guide is moved and arranged at a predetermined position according to the size of the transfer paper P. The lateral registration correction mechanism 44 regulates the transfer paper P to be aligned at a predetermined position by pressing both sides of the transfer paper P for a short time and a plurality of times from both lateral directions of the transfer paper P with respect to the transfer direction of the transfer paper P. A jogger system composed of members may be used.

  The transfer paper P is conveyed from the registration roller pair 45 toward the first transfer portion where the secondary transfer nip is formed by the contact between the first intermediate transfer belt 21 and the secondary transfer roller 46. Thereafter, the second intermediate transfer belt 31 and the transfer charger 47 are sent toward the second transfer portion facing each other.

  In the paper feeding device 40, the transfer paper P discharged from the uppermost paper feeding tray 40 a among the plurality of paper feeding trays is bent with respect to the paper conveyance path 43 </ b> A of the printer unit 100. It is transported almost horizontally and straight. Therefore, even thick transfer paper P or highly rigid paperboard can be reliably fed into the paper transport furnace 43A of the printer unit 100 if it is accommodated in the paper feed tray 40a. In addition, it is convenient to adopt an air sheet feeding composed of a vacuum mechanism so that the sheet feeding tray 40a can reliably feed a transfer sheet having various characteristics. Although not shown, a sensor for detecting the transfer paper P is provided at a key point of the paper transport path 43A, and serves as a trigger for various signals based on the presence of the transfer paper P.

  A second paper feed path 43C is provided above the uppermost paper feed tray 40a. The transfer paper P can be supplied to the second paper feed path 43C from the second paper feed device 300 installed on the right side of the paper feed device 40 in the drawing.

  On the left side of the second transfer unit 30 in the figure, a paper transport unit 50 that moves the paper transport belt 51 endlessly counterclockwise while stretching the paper transport belt 51 by a plurality of stretching rollers 52, 53, 54, 55, 56. Is arranged. The paper transport belt 51 is a paper transport belt 51 where the transfer paper P discharged from the second transfer unit of the second transfer unit 30 is wound around a belt by a receiving roller 52 which is one of a plurality of stretching rollers. Receive on. Charge is applied to the front surface of the paper transport belt 51 by the electrostatic adsorption charger 57 at a timing earlier than the reception. By applying this charge, the paper transport unit 50 can electrostatically attract the transfer paper P discharged from the second transfer unit to the front surface of the paper transport belt 51.

  The paper conveyance belt 51 having the transfer paper P electrostatically adsorbed on the front surface conveys the transfer paper P from the right side to the left side in the drawing along with the endless movement thereof. Then, the transfer paper P is delivered to the fixing device 60 as fixing means disposed on the left side of the paper transport unit 50 in the drawing. Charge is applied by the separation charger 58 to the transfer paper P that is electrostatically attracted to the front surface of the paper transport belt 51 at a timing earlier than this delivery. By applying this electric charge, the transfer paper P that has been electrostatically attracted to the front surface of the paper transport belt 51 until then is easily separated from the belt. Of the plurality of stretching rollers, a belt that suddenly changes the moving direction in accordance with the curvature of the separation roller 54 at a belt winding position by the separation roller 54 disposed closest to the fixing device 60. The transfer paper P is separated from the paper and transferred to the fixing device 60.

  As the fixing device 60, a system having a heater inside the fixing roller, a system in which a belt to be heated is run, a system using induction heating, or the like can be used. In the figure, a fixing nip formed by abutting two fixing rollers is used to fix the first toner image of the other color and the second toner image of the other color by heating the transfer paper P from both sides. Adopted. In order to make the color tone and glossiness of the images on both sides of the transfer paper P the same, the belt material, hardness, surface property, etc. of the two fixing rollers are the same up and down. Further, various parameters of the fixing device 60 are controlled so as to create an optimal fixing condition for each surface depending on whether it is a full-color image and a monochrome image, or one surface or both surfaces.

  The transfer paper P that has been subjected to the fixing process by the fixing device 60 is sent out toward the discharge path. In this discharge path, a cooling roller pair 70 having a cooling function is disposed for the purpose of cooling the transfer paper P after the fixing process and stabilizing the unstable toner state at an early stage. As the cooling roller pair 70, a heat pipe structure roller having a heat radiating portion can be adopted. The transfer paper P cooled by the cooling roller pair 70 is discharged and stacked by a discharge roller pair 71 on a discharge stack unit 75 provided on the left side of the printer unit 100. This discharge stacking unit employs a mechanism in which a receiving member moves up and down according to a stack level by an elevator mechanism (not shown) so that a large amount of transfer paper can be stacked. Note that the transfer paper can also be transported to another post-processing apparatus through the paper discharge stack section 75. As another post-processing apparatus, an apparatus for bookbinding such as punching, cutting, folding, and binding can be provided.

  On the upper surface of the printer unit 100, toner bottles 86Y, 86M, 86C, and 86K of each color in which unused toner is stored are detachably stored in the bottle storage unit 85. The bottle housing portion 85 is on the back side when viewed from the operation direction on the upper surface of the printer unit 100, and a flat surface portion is secured on the front side of the upper surface of the printer unit 100, so that it can be used as a work table. The toner supply means described above supplies toner to each developing device as necessary. In the first embodiment, the first image forming unit and the second image forming unit disposed above and below supply toner from a common toner bottle to a developing device that handles toner of the same color. It can be separated. The toner bottle 86K for black toner that is highly consumed can have a particularly large capacity.

  The operation / display unit 90 provided on the upper surface of the printer unit 100 is provided with an input operation unit (not shown) including a keyboard and the like, thereby inputting conditions for image formation. In addition, various types of information can be displayed on a display unit (not shown) such as a display, so that information exchange between the operator and the printer unit 100 is facilitated.

  A waste toner storage unit 87 provided in the printer unit 100 is connected to the cleaning device 2, the intermediate transfer belt cleaning devices 20A and 30A, and the like. Then, foreign substances such as waste toner and paper dust sent from these are collected and stored in a lump. Since these cleaning devices (2, 20A, 30A, and 50A) do not include a large-capacity waste toner storage unit, the cleaning device can be reduced in size, and the waste toner disposal operability is good. A full sensor (not shown) is used to issue a warning such as toner disposal in the waste toner storage unit 87 or container replacement.

  Various power supplies, control boards, and the like are protected and housed in a sheet metal frame in a control unit 95 provided in the printer unit 100. The inside of the image forming apparatus becomes hot due to heat from the fixing device 60 or heat generated from the electrical device. However, as a countermeasure against this, a fan F is provided to prevent deterioration of the function due to heat of the internal members. The fan F is coupled to the heat radiating portion of the cooling roller pair 70 to ensure the cooling effect of the cooling roller pair 70.

  An automatic image reading device (ADF) 200 that reads an image of a document while automatically conveying the document by a well-known technique is provided on the upper portion of the paper feeding device 40, and reading information obtained by this is sent to the control unit 95. . Based on the sent read information, the printer unit 100 is driven and controlled, and the same image as the original is output. Further, image information from a personal computer (not shown) or the like can be sent to the printer unit 100 and an image corresponding to the image information can be output. Furthermore, it is also possible to send image information sent from a telephone line (not shown) and output an image corresponding to the image information. As described above, the second paper supply device 300 that supplies the transfer paper P to the paper supply device 40 is disposed on the right side of the paper supply device 40 in the drawing.

Next, an operation at the time of single-sided recording in which the printer unit 100 forms a full-color image on one side of the transfer paper will be described.
There are basically two types of single-sided recording methods that can be selected. One of the two types is a method in which the four-color toner images transferred to the first intermediate transfer belt 21 are collectively transferred onto the first surface of the transfer paper P. Another method is a method in which the four-color toner image transferred to the second intermediate transfer belt 31 is secondarily transferred onto the second surface of the transfer paper P at once. Hereinafter, the former method will be described as an example.

  When the printer unit 100 is operated, the first intermediate transfer belt 21 and the photoreceptors 1Y, 1M, 1C, and 1K in the first process units 80Y, 80M, 80C, 80K rotate. At the same time, the second intermediate transfer belt 31 moves endlessly, but the photosensitive members 1Y, M, C, and K in the second process units 81Y, 81M, 81C, and 81K are separated from the second intermediate transfer belt 31 and are not rotated. Is done. Then, image formation by the first process unit 80Y is started. By the operation of the exposure device 4 composed of an LED (light emitting diode) array and an imaging element, light corresponding to image data for yellow emitted from the LED is irradiated onto the surface of the photoreceptor 1Y uniformly charged by the charging device 3. Thus, an electrostatic latent image is formed.

  The electrostatic latent image is developed into a Y toner image by the developing device of the first process unit 81Y for Y, and is electrostatically primary-transferred onto the first intermediate transfer belt 21 at the primary transfer nip for Y. The Such latent image formation, development, and primary transfer operations are sequentially performed in the same manner on the photoconductors 1M, 1C, 1K, and K side. Then, the M, C, and K toner images are sequentially superimposed on the Y toner image on the first intermediate transfer belt 21 at the primary transfer nip for M, C, and K, and are primarily transferred. A four-color toner image is formed on the first intermediate transfer belt 21 by this superimposing primary transfer.

  On the other hand, the paper feeding device 40 sends out transfer paper corresponding to the image data from the internal paper feeding tray 40a or the paper feeding cassettes 40bc, 40bc, d by any one of the paper feeding / separating means 41A, B, C, D. . And it conveys toward the paper conveyance path 43C of the printer part 100 by conveyance roller pair 42B, 42C. Then, it is sent to the lateral registration correction mechanism 44.

  The lateral registration correction mechanism 44 adjusts the inclination of the posture of the transfer sheet P in the middle of being conveyed from the paper feeding device 40 serving as the recording medium supply unit toward the double-sided transfer device (first and second transfer units) from the conveyance direction. It is an inclination correction means for correcting. A pair of guide plates arranged in the paper surface direction orthogonal to the transport direction on the upstream side of the registration roller pair 45 is abutted against both ends orthogonal to the transport direction of the transfer paper P, so that the posture of the transfer paper P is adjusted. Correct the tilt. The two guide plates of the pair of guide plates are movable in the direction of the paper surface orthogonal to the transport direction. By moving according to the width of the fed transfer paper P, the distance between the plates can be reduced. Can be adjusted to the width.

  The transfer paper P whose posture inclination is corrected by the lateral registration correction mechanism 44 reaches between the rollers of the registration roller pair 45, and is timed and sent to the first transfer portion. Then, the four-color toner images on the first intermediate transfer belt 21 are secondarily transferred onto the first surface at the secondary transfer nip of the first transfer portion. The transfer residual toner is cleaned on the front surface of the first intermediate transfer belt 21 that has passed through the secondary transfer nip by the belt cleaning device 20A.

  In each of the first process units 80Y, 80M, 80C, 80K, the transfer residual toner remaining on the photoreceptors 1Y, 1M, 1C, 1K after passing through the primary transfer nip is cleaned by the cleaning device (2). Is done. As shown in FIG. 2, the cleaning device (2) removes transfer residual toner from the first intermediate transfer belt 21 by the cleaning brush 2a and the cleaning blade 2b. The removed foreign matter such as toner is sent to the collecting unit 87 by the collecting unit 2c. Sensors S1 and S2 detect whether the surface potential after exposure on the surface of the photoconductor and the concentration of toner attached to the surface of the photoconductor after the development process are appropriate, and appropriately set image forming conditions. Information is sent to a control means (not shown) for control. Further, the surface of the photoreceptor 1 after cleaning is initialized by removing the residual charges by the static eliminating device Q.

  The transfer paper on which the four-color toner image is secondarily transferred on the first surface at the secondary transfer nip of the first transfer unit is transferred to the second intermediate transfer belt 31 of the second transfer unit 30, and then the paper transport unit. 50. Then, the paper is transferred from the paper transport unit 50 to the fixing device 60. Prior to this transfer, the transfer paper P is charged by the separation charger 58. With this application, the transfer paper that has been electrostatically attracted to the second intermediate transfer belt 31 can be easily separated from the belt.

  In the fixing device 60, each color toner in the full-color image carried on the first surface of the transfer paper P is melted and mixed by heating. Since the transfer paper P has toner only on its first side, less heat energy is required for fixing compared to double-sided recording with toner on both sides. The control unit 95 optimally controls the power used by the fixing device 60 according to the image. Even after the fixing process is performed, until the toner image is completely fixed on the transfer paper P, the toner image is rubbed against a guide member or the like in the conveyance path, and the image is lost or distorted. In order to prevent this problem, the transfer paper that has passed through the fixing device 60 is provided with a pair of cooling rollers 70 as cooling means.

  In the present copying machine, since the image forming order is programmed so that the transfer sheets of the young pages are sequentially stacked on the discharge stack unit 75, the page order is aligned in the stack unit 75. Since the discharge stacking unit 75 is lowered as the number of transfer sheets P to be discharged increases, the transfer sheets can be stacked in an orderly and reliable manner, and the page order is not disturbed. Instead of directly stacking the recorded transfer paper on the paper discharge stack section 75, a punching process can be performed, or the transfer paper can be conveyed to a post-processing device such as a sorter, a collator, a binding device, or a folding device.

  In another method for forming an image on one side of the transfer paper P, image data of a young page is not used for page alignment because the image is not formed in the first process units 80Y, 80M, 80C, 80K. The difference is that images are formed sequentially. However, the description is omitted because it is basically the same as the one-side recording process described above.

Next, the operation during double-sided recording in which images are formed on both sides of the transfer paper will be described.
When an image signal is input to the printer unit 100, Y, M, C, K toners are applied to the photoreceptors 1Y, M, C, K of the first process units 80Y, 80M, 80C, 80K described in the single-side recording operation. An image is formed. These are primary-transferred by being sequentially superimposed on the first intermediate transfer belt 21 at the primary transfer nips for Y, M, C, and K. Almost in parallel with this step, Y, M, C, and K toner images are formed on the photoreceptors 1Y, M, C, and K of the second process units 81Y, 81M, 81C, and 81K. These are primarily transferred onto the second intermediate transfer belt 31 in sequence by primary transfer nips for Y, M, C, and K. In this way, four-color toner images are formed on the first intermediate transfer belt 21 and the second intermediate transfer belt 31, respectively.

  The unit intervals of the second process units 81Y, 81M, 81C, 81K are smaller than the unit intervals of the first process units 80Y, 80M, 80C, 80K. As a result, the second transfer unit 30 completes the primary transfer with superimposition faster than the first transfer unit 20.

  The four-color toner image on the first intermediate transfer belt 21 is secondarily transferred onto the first surface of the transfer paper P that is timed and sent from the registration roller pair 45 to the secondary transfer nip of the first transfer unit. And then transferred to the second transfer unit. Then, at the second transfer portion where the second intermediate transfer belt 31 and the transfer charger 47 are opposed to each other with a predetermined gap, the four-color toner image on the second intermediate transfer belt 31 is secondary on the second surface. Transcribed.

  The transfer paper P having the full-color image formed on both sides in this way is delivered to the fixing device 60 via the paper transport unit 50. Then, a fixing process by heating or pressurization is performed in the fixing device 60, and the toner images on both sides are respectively melted and mixed. Further, after passing through the cooling roller pair 70 and the paper discharge roller 71, the paper is discharged onto the paper discharge stack 75.

  When double-sided recording is performed on a plurality of pages of transfer paper, the image forming order is controlled so that the image of the young page becomes the bottom surface and is stacked on the paper discharge stack unit 75. As a result, when the paper is taken out from the paper discharge stack 75 and the top and bottom surfaces are reversed, the recorded matter is one page in order from the top, the second page on the back, the third page on the second sheet, and the fourth page on the back. Such control of image forming sequence and control such as increasing the power input to the fixing device compared to the one-side recording are executed by the control unit 95.

  Although an example in which full-color recording is performed regarding the single-sided recording operation and the double-sided recording operation has been described, monochrome recording using only black toner is also possible. When the need for maintenance or replacement of parts arises, maintenance is performed by opening an unillustrated exterior cover or the like.

  In the copying machine configured as described above, the combination of the first image forming unit and the control unit 95 described above allows the multicolor first toner image as the first toner image on the surface of the first intermediate transfer belt 21 as the first toner image carrier. A first toner image forming unit for forming one toner image is configured. A second toner image that forms a multi-color second toner image as a second toner image on the surface of the second intermediate transfer belt 31 as a second toner image carrier by a combination of the second image forming unit and the control unit 95. A forming part is configured. In addition, a toner image forming unit is configured by a combination of the first image forming unit, the second image forming unit, and the control unit 95. The first toner image is a first toner image of another color obtained by superimposing a plurality of single-color first toner images, and a toner image composed of only a single-color first toner image of Y, M, C, or K. It is a generic name. The second toner image is a second toner image of another color obtained by superimposing a plurality of single-color second toner images, and a toner image including only a single-color second toner image of any one of Y, M, C, and K. It is a generic name.

  The first image forming unit and the second image forming unit express gradations according to the density of dots that are toner-attached pixels that are pixels to which toner is attached among the pixels constituting the toner image. Therefore, in the halftone portion or highlight portion of the toner image, a certain amount of space is provided between each dot or between dot units formed by a set of a predetermined number of dots.

Next, a characteristic configuration of the copying machine according to the first embodiment will be described.
The toner image formed on the transfer paper P becomes more rough as the surface smoothness of the transfer paper P becomes worse. For example, FIG. 4 is a graph showing the relationship between Beck smoothness and granularity obtained by the experiment of the present inventors. The Beck smoothness (JIS P8119) indicates that the higher the value is, the better the surface smoothness is. Further, there is a high correlation between the graininess and granularity of an image, and the graininess becomes less noticeable as the granularity is improved. As shown in the figure, it can be seen that the roughness of the image becomes more conspicuous as the Beck smoothness of the transfer paper P becomes lower (as the surface smoothness becomes worse). The granularity measurement method shown in FIG. 23 (1997), “Noise Evaluation Method for Halftone Color Images”, is described in detail in this specification.

  The inventor has intensively studied the cause of the surface smoothness of the transfer paper P having a great influence on the roughness of the toner image as shown in the figure. Then, it has been found that the shape of the dots constituting the toner image is more disturbed as the surface smoothness becomes worse. Even if the dot shape is disturbed, there is no significant effect in the high density area where the dots are lined up without gaps. I will continue. And the more rough the dot shape, the more noticeable the feeling of roughness.

  In the case of expressing density (brightness) gradation by dot density as in this copying machine, a pixel group matrix called a dither matrix is generally used in the control for controlling the dot density. This dither matrix is a matrix obtained by dividing the entire image formation target area on a photoconductor or the like as an image formation target for each pixel group composed of a predetermined number of pixels. For example, the entire image formation target area is divided into vertical n × horizontal n pixel groups. Then, the dot density is adjusted so that the number of dots (toner-attached pixels) is the same between the pixel groups.

  Further, in the case where the density gradation is expressed by the dot density as in this copying machine, as the number of output lines per unit length in the halftone portion (hereinafter simply referred to as output line number L) increases, Generally, the resolution becomes high. The number of output lines L can be obtained by the relational expression “L = r / n [lpi]” (where r is the resolution, and n is the number of pixels on one side in each pixel group of the dither matrix. Show). For example, when an image having a resolution r of 600 [dpi] is formed using a dither matrix partitioned by a pixel group of n × n = 4 pixels × 4 pixels, the number of lines is “L = 600/4 = 150 [ lpi] ”.

  The inventor conducted an experiment to form toner images with two different numbers of lines on a plurality of types of transfer papers P having different Beck smoothness and to examine the granularity thereof. The relationship between the granularity and the Beck smoothness in this experiment is shown in FIG. In the figure, curves connected by “▲” -shaped plot points show the same relationship when imaged with a larger number of output lines L than curves connected by “◯” -shaped plot points. . As shown in the figure, it was found that the smaller the output line number L, the better the granularity. From this result, it was found that the granularity of the image can be adjusted by changing the number L of output lines.

  FIG. 6 is a block diagram showing a part of an electric circuit in the copying machine. In the figure, the control unit 95 is connected to the first process units (80Y, M, C, K) and the first transfer unit 20. As described above, each of the first process units and the first transfer unit 20 constitutes a first image forming unit. The control unit 95 is connected to each second process unit (81Y, M, C, K) and the second transfer unit 30. As described above, each of the second process units and the second transfer unit 30 constitutes a second image forming unit.

  An operation display unit 90 shown in FIG. 1 is also connected to the control unit 95 constituting a part of the toner image forming unit. The operation display unit 90 includes an input operation unit 91 including a keyboard and a display unit 92 including a display. On the other hand, the ROM 95c of the control unit 95 stores a program for displaying on the display unit 92 a display for allowing the operator to input data of smoothness F, which is information relating to surface smoothness, using the input operation unit 91. Has been. Based on the display on the display unit 92 by the program, the operator can smooth the transfer paper P accommodated in the paper feed tray 40a, the paper feed cassettes 40b, c, d, and the paper supply device 300 shown in FIG. F data can be individually input.

  FIG. 7 is a flowchart showing an outline of the control flow of the smoothness input control performed by the control unit (95). In the figure, when smoothness information is input to the input operation unit 91 (Y in step 1; hereinafter, step is denoted as S), the control unit transfers the smoothness information in the paper feed tray 40a. It is determined whether the smoothness information of the paper P is present (S2). If this is the case (Y in S2), the input smoothness information is stored in the RAM (95b) as the smoothness Fa (S3), and then the series of control flows is terminated. On the other hand, if not (N in S2), it is next determined whether or not the inputted smoothness information is the smoothness information of the transfer paper P in the first paper feed cassette 40b (S4). .

  In the step of S4, when the control unit determines that this is the case (Y in S4), the input smoothness information is stored in the RAM as the smoothness Fb (S5), and then the series of control flows is terminated. . On the other hand, if not (N in S4), it is next determined whether or not the input smoothness information is the smoothness information of the transfer paper P in the second paper feed cassette 40c (S6). .

  In the step of S6, if the control unit determines that this is the case (Y in S6), the input smoothness information is stored in the RAM as the smoothness Fc (S7), and then the series of control flows is terminated. . On the other hand, if not (N in S6), it is next determined whether or not the input smoothness information is the smoothness information of the transfer paper P in the third paper feed cassette 40d (S8). .

  In the step S8, if the control unit determines that this is the case (Y in S8), the input smoothness information is stored in the RAM as the smoothness Fd (S9), and then the series of control flows is terminated. . On the other hand, if not (N in S8), the inputted smoothness information is stored in the RAM as the smoothness Fe corresponding to the transfer paper P accommodated in the paper supply device (300). (S10).

  With such smoothness input control, the paper feed tray 40a, the first paper feed cassette 40b, the second paper feed cassette 40c, the third paper feed cassette 40d, and the paper supply device 300 are accommodated in the RAM of the control unit. The smoothness of the transferred transfer paper P is individually stored. In this configuration, smoothness information input means for inputting information relating to the surface smoothness of the transfer target surface of the toner image on the transfer paper P, which is a recording medium, is configured by the operation display unit 90, the control unit 95, and the like. .

  In FIG. 6 described above, the control unit 95 changes the number L of output lines at the time of the print job in accordance with the smoothness information input to the input operation unit 91 and the paper storage means used at the time of the print job. It is comprised so that line number change control may be implemented. FIG. 8 is a flowchart showing an outline of a control flow of such line number change control. In the figure, when the control unit starts a print job (Y in S1), the control unit specifies a cassette (paper storage unit) to be used in the print job (S2). Then, after specifying the smoothness (any of Fa, Fb, Fc, Fd, Fe) of the transfer paper P corresponding to the specified cassette (S3), the number L of output lines is determined based on the smoothness. Next, in the print job, optical writing is performed with the determined number of output lines L to form a toner image, and then the print job is terminated (Y in S5). The output line number L is determined based on a data table or algorithm stored in the RAM. Further, this data table or algorithm shows such a relationship that the output line number L having a smaller value is determined as the Beck smoothness becomes lower.

  In this copying machine that performs such line number change control, the sheet feeding tray 40a, the first sheet feeding cassette 40b, the second sheet feeding cassette 40c, the third sheet feeding cassette 40d, and the sheet supply device 300 are accommodated. For a plurality of transfer papers P of different types, the output line number L is changed according to the respective surface smoothness. By adjusting the roughness of the toner image due to this change, it is possible to suppress a situation in which a difference in image quality occurs between different types of transfer paper P.

  Although an example in which the operator inputs smoothness F (Beck smoothness) as smoothness information has been described, paper type information such as “coated paper”, “plain paper”, “rough paper”, and the like is input. You may do it.

  Further, the relational expression “L = r / n” has been exemplified as an expression for obtaining the number L of output lines. This is based on the fact that the x-axis and y-axis of the dither matrix are the main scanning direction and the sub-scanning direction, respectively. Is the expression of the case. As shown in FIG. 9, the number of output lines L ′ when the x-axis and y-axis of the dither matrix are inclined by an angle θ from the main scanning direction and the sub-scanning direction, respectively, is “L ′ = resolution r / (sub-pixel group). The number of pixels in the scanning direction n ′ × sin θ) ”is obtained. In this case, for example, when the angle θ = 63.4 ° and n ′ = 5 pixels, the number of output lines L ′ is 133 [lpi].

  Also, the numerical values entered in each pixel of the dither matrix shown in FIG. 9 represent the dot formation selection order in each pixel group section. Specifically, FIG. 10 is a schematic diagram showing one of the pixel group sections arranged in the dither matrix of FIG. 9, but in the case of forming a halftone portion having the lowest image density, FIG. Only one dot is formed for a pixel group section composed of pixels. At this time, dots are formed only in one pixel region indicated as “1” in FIG. When four dots are formed in each pixel group section, dots are respectively formed in the four pixel areas to which the numerical values “1 to 4” in FIG.

  FIG. 11 is a graph showing the relationship between the granularity of the toner image confirmed by the experiment of the present inventor and the diameter of the light beam when the photosensitive member is exposed. The diameter of the light beam is the same as the diameter of each pixel of the latent image formed on the photoconductor. As shown in the figure, the granularity improves as the diameter of the light beam becomes smaller. However, when the diameter of the light beam becomes 60 [μm] or less, it can be seen that the slope of the curve showing the relationship starts to decrease rapidly. That is, when the diameter of the light beam exceeds 60 [μm], the granularity greatly depends on the diameter of the light beam, but when the diameter is 60 [μm] or less, the granularity is not so large as the diameter. It will not be influenced. In the case of such characteristics, the deterioration of granularity due to the relatively large diameter can be satisfactorily suppressed by setting the diameter of the light beam to 60 [μm] or less. Therefore, in this copying machine, optical writing is performed with a light beam having a diameter of 60 [μm] or less.

  FIG. 12 is a graph showing the relationship between the granularity of the toner image confirmed by the experiment of the present inventors and the resolution. As shown in the figure, the higher the toner image resolution, the better the granularity. However, when the resolution is 600 [dpi] or higher, it can be seen that the slope of the curve indicating the relationship starts to decrease rapidly. That is, when the resolution is lower than 600 [pi], the granularity greatly depends on the resolution, but when the resolution is 600 [dpi] or higher, the granularity does not greatly depend on the resolution. In the case of such characteristics, by setting the resolution to 600 [dpi] or higher, it is possible to satisfactorily suppress deterioration in granularity due to the relatively low resolution. Therefore, in this copying machine, a toner image is formed with a resolution of 600 [dpi] or more.

This copier specifies to the user that Y, M, C, and K toners used to form a toner image should satisfy the following conditions (a) to (d). ing.
(A) The weight average particle diameter D4 is 3 to 7 [μm].
(B) A value (D4 / D1) obtained by dividing the weight average particle diameter D4 by the number average particle diameter D1 is 1.00 to 1.30.
(C) The shape factor SF-1 is 100 to 160.
(D) The shape factor SF-2 is 100 to 160.

  As a method for instructing the user to use such toner, for example, a toner having all the above conditions (a) to (d) can be packaged and shipped together with a copying machine. Further, for example, the product number or the product name of the toner may be specified on the copying machine main body or the instruction manual. Further, for example, it may be performed by notifying the user of the product number, product name, etc. in writing or electronic data. Further, for example, it can be performed by shipping a toner bottle which is a toner containing means for containing such toner in a state where it is set in the copying machine main body. This copying machine employs all these methods, but it is sufficient to employ at least one method.

  The reason why the toner satisfying the conditions (a) to (b) is specified is as follows. That is, when the weight average particle diameter D4 is less than 3 [μm], the transfer rate starts to rapidly decrease and the toner cleaning property starts to rapidly decrease. On the other hand, when the weight average particle diameter D4 exceeds 7 [μm], the toner tends to scatter rapidly around characters and lines during transfer, and the granularity starts to deteriorate rapidly. On the other hand, when D4 / D1 exceeds 1.30, scumming starts to occur rapidly due to the spread of the charge amount distribution of the toner. By satisfying the above conditions (a) to (b), it becomes possible to form dots having a stable shape by following the unevenness of the paper surface even on the transfer paper P having a relatively low smoothness. The shape of the small dot, which is the basic iodine of the dither, can be stabilized. It is also possible to achieve higher image quality by improving dot reproducibility associated with smaller toner particle diameters, stabilizing the charge amount by sharpening the particle size distribution, and improving transfer rate by lowering the pile height. It becomes possible. If the conditions (a) to (b) are not satisfied, the density of the halftone portion due to the dither matrix having a large number of output lines L is particularly unstable.

  In the case of reproducing minute dots having a resolution of 600 dpi or more, the characteristic of a weight average particle diameter of 3 to 7 μm is particularly effective. In this range, since the toner particles have a sufficiently small particle size with respect to the minute latent image dots, the dot reproducibility is excellent.

  When D4 / D1 is in the range of 1.00 to 1.30, various merits occur. For example, a phenomenon in which toner particles having a particle size suitable for an electrostatic latent image pattern contributes to development preferentially over other toners, so that various patterns of images can be stably formed. There is a merit that it becomes possible to do. In addition, when the apparatus adopts a configuration in which toner remaining on an image carrier such as a photoreceptor is collected and recycled, a large amount of small-size toner particles that are difficult to be transferred are recycled. In such recycling, when the above-mentioned one having a relatively large value is used, the development performance is adversely affected due to a large change in the toner particle size from the new toner supply to the next toner supply.

  The weight average particle diameter D4 and the number average particle diameter D1 of the toner can be measured by a measuring device using a Coulter counter method, for example, Coulter Counter TA-II or Coulter Multisizer II (both manufactured by Coulter). . Specifically, first, 0.1 to 5 ml of a surfactant (preferably alkylbenzene sulfonate) is added as a dispersant to 100 to 150 ml of the electrolytic aqueous solution. As the electrolytic aqueous solution, approximately 1% NaCl aqueous solution is prepared using primary sodium chloride, and for example, ISOTON-II (manufactured by Coulter) can be used. Further, 2 to 20 mg of a measurement sample is added to the obtained solution. Then, the solution is dispersed for about 1 to 3 minutes with an ultrasonic disperser, and the weight and number of toners are measured by the above-described measuring apparatus using a 100 μm aperture as an aperture to calculate the weight distribution and the number distribution. To do. From the obtained distribution, the weight average particle diameter D4 and the number average particle diameter D1 of the toner can be obtained. In addition, as a channel, it is less than 2.00-2.52 micrometer; 2.52-3.17 micrometer; 3.17-4.00 micrometer; 4.00-5.04 micrometer; 5.04-6.35 micrometer 6.35 to less than 8.00 μm; 8.00 to less than 10.08 μm; 10.08 to less than 12.70 μm; 12.70 to less than 16.00 μm; 16.00 to less than 20.20 μm; Intended for toner particles having a particle size of 2.00 μm to less than 40.30 μm using 13 channels of less than 25.40 μm; 25.40 to less than 32.00 μm; 32.00 to less than 40.30 μm.

The reason why the toner having the above conditions (c) to (d) is specified is as follows. That is, the shape factor SF-1 and the shape factor SF-2 are parameters representing the shape of the toner, and are familiar parameters in the field of powder engineering. The shape factor SF-1 referred to here is a value indicating the degree of roundness in a spherical substance such as toner particles. This is a value obtained by dividing the square of the length MXLNG of the maximum diameter portion in an elliptical figure obtained by projecting a spherical substance on a two-dimensional plane by the area AREA and further multiplying by 100π / 4. That is, it can be expressed by an equation “shape factor SF-1 = {(MXLNG) ² / AREA} × (100π / 4)”. A spherical substance having a shape factor SF-1 of 100 is a true sphere, and the larger the value of SF-1, the more irregular the shape of the spherical substance.

The shape factor SF-2 is a numerical value indicating the degree of unevenness on the surface of the spherical substance. This is a value obtained by dividing the square of the perimeter PERI of the figure obtained by projecting the spherical substance on the two-dimensional plane by the area AREA and further multiplying by 100 / 4π. In other words, the shape factor SF-2 can be expressed by a mathematical expression of “shape factor SF-2 = {(PERI) ² / AREA} × (100 / 4π)”. Note that the spherical material having a shape factor SF-2 of 100 has no irregularities on the surface. As the value of the shape factor SF-2 increases, the irregularities on the surface of the spherical substance become more prominent.

  It has been clarified by the present inventors that the transfer efficiency increases as the toner shape approaches a true sphere (both SF-1 and SF-2 approach 100). This is because the closer to the true sphere, the smaller the contact area between the toner particles and the thing (toner particles, image carrier, etc.) in contact with the toner particles, and the toner fluidity is increased. This is considered to be because the (mirror power) is weakened and is easily affected by the transfer electric field. According to the inventor's research, it has been clarified that when the shape factor SF-1 exceeds 160 or the shape factor SF-2 exceeds 160, the transfer efficiency starts to deteriorate rapidly. By setting each to 160 or less, it is possible to maintain a good transfer rate and stably form dots even on irregularities on the paper surface with relatively low smoothness. A small dot can be formed in a stable shape.

  The shape factor SF-1 and the shape factor SF-2 can be obtained as follows. That is, using a FE-SEM (S-800) manufactured by Hitachi, 100 images of toner particles are selected at random, and the images are sequentially taken, and the image information is introduced into an image analyzer (LUSEX 3) manufactured by Nireco. Obtain MXLING, AREA, and PERI. And it calculates as an average value per 100 shape factors obtained by the above-mentioned formula.

Next, a copying machine according to a second embodiment to which the present invention is applied will be described.
Note that the configuration of the copier according to the second embodiment is the same as that of the copier according to the first embodiment unless otherwise specified.

  FIG. 13 is a schematic diagram showing an example of a dither matrix in the present copying machine. As shown in the figure, this copying machine uses a dither matrix in which a plurality of pixel groups of 4 pixels × 4 pixels are arranged vertically and horizontally. As described above, in each pixel group section of the halftone portion, the toner adhesion pixels are selected in order from the pixel having the smallest numerical value shown in FIG. This figure shows a state in which when one dot is formed in each pixel group section, a pixel having a numerical value “1” is selected as a toner adhesion pixel in each pixel group section. Yes. In the halftone unit, a plurality of dither matrices having different numerical values in each pixel group section are prepared, and the dither matrix to be used is appropriately switched at the time of a print job. , That is, the dot concentration can be changed. For example, it is assumed that three types of dither matrices are prepared which are composed of only one of the three types of pixel group sections shown in FIGS. Then, it is assumed that eight dots are formed in each pixel group section using the dither matrix composed of the pixel group sections shown in FIG. 14A. In this case, in each pixel group section, the eight dots are not adjacent to each other, and a gap of one pixel or more is provided between the dots (between the main and sub directions). When the number of dots was increased from 8 to 9, finally, the three dots formed in the three pixels with the numbers “1”, “9”, and “3” in the figure were connected to each other. To match. As described above, when the dither matrix including the pixel group sections shown in FIG. 14A is used, the dots are formed in a relatively dispersed state in each pixel group section. That is, such a dither matrix is a matrix that makes the dot concentration degree relatively low.

  On the other hand, using a dither matrix composed of pixel group sections shown in FIG. 14B, it can be seen that only two dots are formed in each pixel group section and they are connected to each other. It can also be seen that the third and fourth dots are connected to the first and second dots, respectively. Such a dither matrix is a matrix in which the degree of dot concentration is higher than that shown in FIG.

  On the other hand, even if the dither matrix composed of the pixel group sections shown in FIG. 14C is used, only two dots are formed in each pixel group section, and they are connected to each other. Here, a comparison between the case where four dots are formed in the pixel group section shown in FIG. 14B and the case where four dots are formed in the pixel group section shown in FIG. The following can be understood. That is, in the former case, the dots are connected to each other in an arrangement of vertical × horizontal = 4 × 1 and the circumference of these dot groups is 4n × 2 + 1n × 2 = 10n. On the other hand, in the latter case, the dots are connected to each other in an arrangement of vertical × horizontal = 2 × 2 and the circumference of these dot groups is 2n × 4 = 8n. As a matter of course, a dot group composed of a plurality of dots connected to each other has a higher dot concentration degree as the circumference thereof becomes shorter. Therefore, the dither matrix composed of the set of pixel group sections shown in FIG. 14C is a matrix that makes the dot concentration higher than that shown in FIG.

  The present inventor conducted an experiment to form toners with different dot concentration degrees on a plurality of transfer sheets P having the same Beck smoothness and to examine the respective granularities. FIG. 15 shows the relationship between the granularity and the dot concentration in this experiment. As shown in the figure, it was found that when the toner image is formed on the transfer paper P having the same Beck smoothness, the higher the dot concentration, the better the granularity. Therefore, the granularity of the toner image can be adjusted by changing the dot concentration degree.

  Also in the copying machine according to the second embodiment, the control unit (95) is configured to perform the smoothness input control previously shown in FIG. Further, in the copier according to the second embodiment, the control unit is configured to perform the dot concentration degree change control shown in FIG. 16 instead of the line number change control shown in FIG. . As a premise for performing this dot concentration degree change control, the control unit stores a plurality of types of dither matrices having different dot concentration degrees in the ROM.

  In FIG. 16, when the control unit starts a print job (Y in S1), the control unit specifies a cassette (paper storage unit) to be used in the print job (S2). Then, after specifying the smoothness (any of Fa, Fb, Fc, Fd, Fe) of the transfer paper P corresponding to the specified cassette (S3), the dot concentration is determined based on the smoothness. Next, in the print job, a toner image is formed using a dither matrix capable of realizing the determined dot concentration degree, and then the print job is ended (Y in S5). Note that the dot concentration degree is determined based on a data table or algorithm stored in the RAM. Further, this data table or algorithm shows such a relationship that the higher the value of dot concentration, the lower the Beck smoothness.

  In the present copying machine that performs such dot concentration level change control, it is housed in the paper feed tray 40a, the first paper feed cassette 40b, the second paper feed cassette 40c, the third paper feed cassette 40d, and the paper supply device 300, respectively. The dot concentration degree is changed in accordance with the surface smoothness of a plurality of transfer papers P of different types. By adjusting the roughness of the toner image due to this change, it is possible to suppress a situation in which a difference in image quality occurs between different types of transfer paper P.

Next, a copying machine according to a third embodiment to which the present invention is applied will be described.
The configuration of the copier according to the third embodiment is the same as that of the copier according to the first embodiment unless otherwise specified.

  The copier according to the third embodiment includes smoothness detecting means 500 on the upstream side in the transport direction of the lateral registration correction mechanism 44 in the paper transport path 43A of the printer unit 100 shown in FIG. As shown in FIG. 17, the smoothness detecting means 500 has a surface smoothness of a first surface (a surface facing upward in the drawing) and a second surface (a surface facing downward in the drawing) of the transfer paper P as a recording medium. The first surface detection unit 510 and the second surface detection unit 520 for individually detecting the surface smoothness of the first surface detection unit. The first surface detection unit 510 serving as the first surface detection unit and the second surface detection unit 520 serving as the second surface detection unit are disposed at positions that are not opposed to each other with the paper conveyance path 43A serving as the recording medium conveyance path interposed therebetween. ing.

  The transfer paper P that is sandwiched between the rollers of the pair of transport rollers 42A and transported in the paper transport path 43A sequentially passes directly above the second surface detector 520 and directly below the first surface detector of the smoothness detector 500. Pass through. Then, when passing over the second surface detection unit 520, the surface smoothness of the second surface is detected. Further, the surface smoothness of the first surface is detected when passing just below the first surface detection unit 510.

  FIG. 18 is a block diagram showing a part of an electric circuit in the copying machine. 6 is substantially the same as the electric circuit previously shown in FIG. The detection result by the first surface detection unit 510 of the surface smoothness detection unit 500 and the detection result by the second surface detection unit 520 are each sent as an electrical signal to the control unit 95 of the toner image forming unit.

  The control unit 95 sets the number of output lines L corresponding to the first surface of the transfer paper P according to the detection result by the first surface detection unit 510, that is, according to the surface smoothness of the first surface of the transfer paper P. It is supposed to change. Further, the number of output lines L corresponding to the second surface of the transfer paper P is changed according to the detection result by the second surface detection unit 520, that is, according to the surface smoothness of the first surface of the transfer paper P. It has become.

  In the conventional image forming apparatus, the first toner image is formed to have a rough feeling corresponding to the surface smoothness of the first surface of the transfer paper P, while the second toner image is smoothed to the surface of the second surface. It was formed to have a rough feeling according to the sex. Then, if the surface smoothness is different between the first surface and the second surface, the first toner image and the second toner image have different roughness feelings. This caused a difference in image quality between the front and back of the transfer paper P. On the other hand, in this copying machine, the number of output lines L is changed according to the surface smoothness on the first and second surfaces of the transfer paper P to adjust the roughness of the toner image on each surface. By doing so, it is possible to suppress a situation in which a difference in image quality occurs between the first surface and the second surface.

FIG. 19 is a flowchart showing an outline of a control flow of the line number change control performed by the control unit of the copying machine. In this line number change control, the control unit performs the following control. That is, first, after the second surface smoothness _{F 2} was detected by the second face detection unit (520) (S1), detecting a first surface smoothness _{F 1} by the first surface detection unit (510) (S2) . Next, it is determined whether or not it is a double-sided printing mode (S3). If it is not the double-sided print mode (N in S3), the control flow is terminated because there is no difference in image quality between the two sides. On the other hand, the (Y in S3) if a double-sided printer mode, determines whether the first surface smoothness F ₁ and the second surface smoothness F ₂ are the same (S4). If they are the same (Y in S4), the control flow is terminated because there is no difference in image quality due to the difference in surface smoothness.

If the first surface smoothness F ₁ and the second surface smoothness F ₂ are not the same, whether or not the first surface smoothness F ₁ is a numerical value lower than the second surface smoothness F ₂ (first It is determined whether or not the surface is rougher than the second surface (S5). If so (Y in S5), the number of output lines L by the first image forming unit is made smaller than the number of output lines L by the second image forming unit (S6). With respect to the output line number L by the second image forming unit, the control flow is terminated while keeping the standard value. In contrast, the (N in S5) first surface smoothness F ₁ and the second surface smoothness is lower than F _2, the output line an output line number L by the second image forming unit by the first image forming unit The number is made smaller than the number L (S7). With respect to the number L of output lines by the first image forming unit, the control flow is terminated while keeping the standard value.

Note that when the smoothness detecting means that detects the surface smoothness based on the light reflectance on the paper surface is used, the value of the detection result by the detecting means decreases as the smoothness of the paper surface deteriorates. Therefore, in this case, the step shown in S5 is a determination step of “F ₁ <F ₂ ”. On the other hand, when the value of the detection result by the detection means becomes larger as the smoothness of the paper surface becomes worse, the step shown in S5 becomes the determination step “F ₁ > F ₂ ”.

  In the copying machine having the above configuration, the output line number L corresponding to the lower smoothness is determined based on the difference between the first surface smoothness F1 and the second surface smoothness F2. In this way, unlike the modified apparatus described later, it is not necessary to store the line number parameter table having a comparatively large storage capacity in the RAM of the control unit, and both toner images can be stored only by storing a simple correction formula. Image quality difference can be suppressed.

Next, a modification apparatus of the copying machine according to the third embodiment will be described.
In this modified apparatus, the RAM 95b serving as the storage means of the control unit 95 stores a line number parameter table. This line number parameter table is a data table for associating the surface smoothness data of the transfer paper P with the output line number L. It is constructed based on the result of an experiment for investigating the value of the number of output lines L that can effectively suppress dot disturbance using various transfer papers P having different surface smoothness. Therefore, if the value of the output line number L corresponding to the measurement result of the surface smoothness of the transfer paper P is specified from the line number parameter table and the output line number L at the time of printing is set to that value, the dot shape Can be effectively suppressed.

FIG. 20 is a flowchart illustrating an outline of a control flow of the line number change control performed by the control unit of the present modification device. In this line number change control, the control unit performs the following control. That is, first, after detecting the second surface smoothness F ₂ a second surface detecting portion is the surface smoothness of the second surface of the transfer paper P (520) (S1), the surface smoothness of the first surface of the transfer paper first surface smoothness of the _{F 1} first surface detection unit is a sex sensed by (510) (S2). Next, it is determined whether or not it is a double-sided printing mode (S3). Then, when a duplex printing mode is set to a value corresponding (Y in S3), the output line number L by the second image forming unit on the second surface smoothness F ₂ (S4). Further, the number L of output lines by the first image forming unit is set to a value corresponding to the first surface smoothness F1 (S5). On the other hand, if it is determined in step S3 that the mode is not the double-sided printing mode (N in S3), the control flow is looped to S5. As a result, the series of controls is terminated without setting the number of output lines L by the second image forming unit to the standard value. This is because in the single-sided print mode, only the first toner image is formed by the first image forming unit.

  In the modified apparatus having the above-described configuration, the toner image forming unit is configured as follows. That is, the number of output lines corresponding to the first surface is changed according to the detection result by the first surface detection unit (510), while the second surface is supported according to the detection result by the second surface detection unit (520). The number of output lines to be changed is changed. In such a configuration, the first toner image and the second toner image are formed with the number of output lines L suitable for the surface smoothness of the first surface and the second surface, respectively. It is possible to suppress deterioration in image quality due to poorness of the image. In addition, it is possible to effectively suppress a difference in image quality caused by a large difference in surface smoothness between the first surface and the second surface.

Next, a copier according to a fourth embodiment to which the present invention is applied will be described.
Unless otherwise specified, the configuration of the copying machine according to the fourth embodiment is the same as that of the copying machine according to the third embodiment.

In this copying machine, instead of the output line number L, the dot concentration is changed. FIG. 21 is a flowchart showing an outline of a control flow of the dot concentration degree change control performed by the control unit of the copying machine. In this dot concentration degree change control, the control unit performs the following control. That is, first, after the second surface smoothness _{F 2} was detected by the second face detection unit (520) (S1), detecting a first surface smoothness _{F 1} by the first surface detection unit (510) (S2) . Next, it is determined whether or not it is a double-sided printing mode (S3). If it is not the double-sided print mode (N in S3), the control flow is terminated because there is no difference in image quality between the two sides. On the other hand, the (Y in S3) if a double-sided printer mode, determines whether the first surface smoothness F ₁ and the second surface smoothness F ₂ are the same (S4). If they are the same (Y in S4), the control flow is terminated because there is no difference in image quality due to the difference in surface smoothness.

If the first surface smoothness F ₁ and the second surface smoothness F ₂ are not the same, whether or not the first surface smoothness F ₁ is a numerical value lower than the second surface smoothness F ₂ (first It is determined whether or not the surface is rougher than the second surface (S5). If this is the case (Y in S5), the dot concentration degree of the halftone portion formed by the first image forming portion is made higher than that by the second image forming portion (S6). With respect to the dot concentration degree of the halftone portion formed by the second image forming portion, the control flow is terminated while keeping the standard value. On the other hand, when the first surface smoothness F ₁ is lower than the second surface smoothness F ₂ (N in S5), the dot concentration of the halftone portion formed by the second image forming portion is set to the first image. The height is higher than that of the formation portion (S7). With respect to the dot concentration degree of the halftone portion formed by the first image forming portion, the control flow is terminated while keeping the standard value.

  In the copying machine configured as described above, the dot concentration corresponding to the lower smoothness is determined based on the difference between the first surface smoothness F1 and the second surface smoothness F2. In this way, unlike the modified apparatus described later, it is not necessary to store a parameter table having a relatively large storage capacity in the RAM of the control unit, and it is only necessary to store a simple correction formula to store both toner images. The difference in image quality can be suppressed.

Next, a description will be given of a first modified example of the copying machine according to the fourth embodiment.
In the first modified apparatus, the RAM 95b serving as the storage means of the control unit 95 stores a dot concentration degree parameter table. The dot concentration parameter table is a data table that associates the surface smoothness data of the transfer paper P with the dot concentration. It is constructed based on the results of an experiment that uses various transfer papers P having different surface smoothness to investigate the value of dot concentration that can effectively suppress dot disturbance. For this reason, the dot concentration degree dither matrix corresponding to the measurement result of the surface smoothness of the transfer paper P is specified from the dot concentration degree parameter table, and the use of the dither matrix at the time of printing effectively corrects the dot shape. Can be suppressed.

FIG. 22 is a flowchart showing an outline of a control flow of dot concentration degree change control performed by the control unit of the first modification device. In this dot concentration degree change control, the control unit performs the following control. That is, first, after detecting the second surface smoothness F ₂ a second surface detecting portion is the surface smoothness of the second surface of the transfer paper P (520) (S1), the surface smoothness of the first surface of the transfer paper first surface smoothness of the _{F 1} first surface detection unit is a sex sensed by (510) (S2). Next, it is determined whether or not it is a double-sided printing mode (S3). Then, when a duplex printing mode is set to be capable of the dot concentration degree corresponding (Y in S3), the dither matrix to be used when printing the second image forming unit on the second surface smoothness F ₂ (S4 ). Further, the dither matrix used at the time of printing by the first image forming unit is set so as to have a dot concentration degree corresponding to the first surface smoothness F1 (S5). On the other hand, if it is determined in step S3 that the mode is not the double-sided printing mode (N in S3), the control flow is looped to S5. As a result, the series of controls is terminated without setting the dot concentration in the second image forming unit to the standard value. This is because in the single-sided print mode, only the first toner image is formed by the first image forming unit.

  In the first modified apparatus having the above-described configuration, the toner image forming means is configured as follows. That is, while the dot concentration corresponding to the first surface is changed according to the detection result by the first surface detection unit (510), the second surface is supported according to the detection result by the second surface detection unit (520). The dot concentration to be changed is changed. In such a configuration, the first toner image and the second toner image are formed with the dot concentration suitable for the surface smoothness of the first surface and the second surface, respectively. Deterioration of image quality due to badness can be suppressed. In addition, it is possible to effectively suppress a difference in image quality caused by a large difference in surface smoothness between the first surface and the second surface.

Next, a description will be given of a copying machine of each example in which a more characteristic configuration is added to the copying machine according to the fourth embodiment.
[First embodiment]
FIG. 23 is an enlarged configuration diagram showing an optical sensor unit 500A as smoothness detecting means used in the copying machine according to the first embodiment. In this optical sensor unit 500A, the first surface detection unit 510A and the second surface detection unit 520A are each composed of a reflective photosensor. Since the configurations of both detection units are the same, only the first surface detection unit 510A will be described here. The first surface detection unit 510A includes a light emitting element 511A and a light receiving element 512A, and irradiates the first surface of the transfer paper P with light emitted from the light emitting element 511A. Then, the reflected light regularly reflected on the first surface is detected by the light receiving element 512A, and a signal corresponding to the light reflectance (the amount of received light / the amount of emitted light) on the first surface is sent from the light receiving element 512A to the control unit. Light reflectance of the first surface is correlated with the first surface smoothness F _1. Therefore, the first surface detection unit 510A can detect the surface smoothness of the first surface by detecting the light reflectance on the first surface. Similarly, the second surface detection unit 520A detects the surface smoothness of the second surface of the transfer paper P.

  Note that, as shown in FIG. 24, regular reflection is a reflection in which a light incident angle θ1 and a reflection angle θ2 are the same among a plurality of reflected light reflected at various angles on the surface irradiated with light. Light. Further, the incident angle θ1 is an angle formed by the optical axis of the light generated from the light emitting element 511A and a line orthogonal to the light irradiation surface of the light irradiation target (transfer paper P in this example). The reflection angle θ2 is an angle formed by the optical axis of the reflected light and a line perpendicular to the light irradiation surface of the light irradiation object. As schematically shown by a dotted line in FIG. 24, the amount of specularly reflected light is the largest among various reflected lights on a surface having a certain degree of smoothness. And the light quantity of regular reflection light shows the best correlation with surface smoothness. Therefore, by detecting the specularly reflected light, the surface smoothness can be detected with higher accuracy than when only diffusely reflected light (diffuse reflected light) that is reflected at an angle different from the specularly reflected light is detected.

[Second Embodiment]
Also in the copying machine according to the second embodiment, as in the first embodiment, the optical sensor unit 500A that detects the surface smoothness based on the light reflectance is used as the smoothness detecting means. However, the configurations of the first surface detection unit 510A and the second surface detection unit 520A are slightly different from those of the first embodiment.

  FIG. 25 is an enlarged configuration diagram showing the first surface detection unit 510A of the optical sensor unit 500A used in the copying machine. The first surface detector 510A receives the diffusely reflected light diffusely reflected on the first surface in addition to the light receiving element 512A that receives the regularly reflected light regularly reflected on the first surface of the transfer paper P. An element 513A is included. If the detection level of the specular reflection light component is Ra and the detection level of the diffuse reflection component is Rb, the ratio Ra / Rb is used so that the surface smoothness is more improved than when only the specular reflection light is received. It can be detected with high accuracy. In addition, the thing of the same structure is used also for 520 A of 2nd surface detection parts.

[Third embodiment]
FIG. 26 is an enlarged configuration diagram showing a surface electrical resistance detection unit 500B as smoothness detection means used in the copying machine according to the third embodiment. The first surface detection unit 510B and the second surface detection unit 520B of the surface electrical resistance detection unit 500B have the same configuration except that the detection target surfaces are different. Therefore, only the first surface detection unit 510B will be described here.

  The first surface detection unit 510B includes a current detection unit 513B, an output roller 511B and an input roller 512B that are supported by the current detection unit 513B in a freely rotatable manner, and a calculation unit (not shown). These rollers (511B, 512B) are each made of a conductive metal material and function as electrodes. Then, they are arranged at a predetermined distance from each other in the paper conveyance direction, and rotate while being in contact with the first surface of the transfer paper P. A predetermined voltage V (for example, 1.0 V) is applied between the output roller 511B and the input roller 512B. Then, an electric current is generated between both rollers via the first surface of the transfer paper P. The current detection unit 513B detects a current value I generated between both rollers by a known technique. This current value I has a correlation with the surface electrical resistance R of the first surface of the transfer paper P (R = V / I). A calculation unit (not shown) calculates the surface electrical resistance R of the first surface based on the current value I detected by the current detection unit 513B. The surface electrical resistance R of the first surface has a correlation with the surface smoothness of the first surface. Therefore, the first surface detection unit 510B can detect the surface smoothness of the first surface. Similarly, the second surface detector 520B can detect the surface smoothness of the second surface. The voltage V is preferably set in the range of 0.5 to 2.5 [kV].

  The control unit (95) described above is configured to determine the dot concentration degree corresponding to the first surface and the dot concentration degree corresponding to the second surface based on the detection result by the surface electrical resistance detection unit 500B. Yes. This determination is made by the dot concentration degree change control described above.

[Fourth embodiment]
In the copying machine according to the fourth embodiment, the first surface detection unit 510 and the second surface detection unit 520 are positioned at a position where the mutual interference is maximized across the paper conveyance path (43A) through which the transfer paper is conveyed. It is arranged away from. The position where the interference is maximum is a position as described below.

  When the optical sensor unit 500A shown in FIG. 23 is used as the smoothness detecting means 500, the position is as follows. That is, the light receiving element 512A of the first surface detection unit 510A is fixed on an extension line of the light emitting element 521A of the second surface detection unit 520A, and the light reception element 521A of the second surface detection unit 520A is the first surface detection unit. The position is fixed on the extension line 510A in the light emitting direction. When the light from the light emitting element of one detection part passes through the transfer paper P, the amount of transmitted light is the largest on the extended line in the light emission direction, and the light receiving element of the other detection part detects it. Because.

  Moreover, when using the surface electrical resistance detection unit 500B shown in FIG. 26 as the smoothness detection means 500, it is the following positions. That is, one of these rollers and one of the two rollers (521B, 522B) in the second surface detection unit 520B, rather than the distance L1 between the output roller 511B of the first surface detection unit 510B and the input roller 512B. This is the position that will reduce the distance. In addition, the distance L2 between the output roller 521B and the input roller 522B of the second surface detection unit 520B, and either one of these rollers or one of the two rollers (511B, 512B) in the first surface detection unit 510B. The same is true for the position where the distance to is reduced. In these positional relationships, depending on the electric resistance in the thickness direction of the transfer paper, current is more likely to be generated between the rollers of different detection units than between the output roller and the input roller of the same detection unit. This will cause the detector to interfere strongly.

  Further, as the smoothness detecting means, the surface smoothness of the first surface is detected based on the vibration amount of the first contact member brought into contact with the first surface, while the second contact member brought into contact with the second surface. When using what detects the surface smoothness of the second surface based on the vibration amount, the position is as follows. That is, the projected image in the transfer sheet thickness direction of the contact area between the first contact member and the first surface overlaps the contact area between the second contact member and the second surface. This is because the transfer paper is sandwiched between the contact members at such a position, and the amount of vibration conduction from one contact member to the other contact member is maximized.

Next, a second variation apparatus of the copying machine according to the fourth embodiment will be described.
FIG. 27 is a schematic configuration diagram showing the main configuration of the second modified apparatus. The second modified apparatus is different from the copying machine according to the fourth embodiment in the following points. That is, in the copying machine according to the fourth embodiment, the first process units 80Y, 80M, 80C, 80K, and 80K for exclusively forming the first toner image out of the first toner image and the second toner image; The second process units 81Y, 81M, 81C, and 81K for exclusively forming the second toner image are included. On the other hand, the second modification apparatus has only the first process units 80Y, 80M, 80C, 80K. These first process units 80Y, 80M, 80C, 80K, and 80K form a first toner image and a second toner image on the first intermediate transfer belt 21 as a first toner image carrier.

  In the second modified apparatus, a second single-color toner image to be transferred onto the second surface of the transfer paper P is transferred onto the first surface of the transfer paper P by each of the first process units 80Y, 80M, 80C, 80K. The toner image is formed before the first single color toner image to be transferred, and is transferred onto the first intermediate transfer belt 21 in a superimposed manner. Thus, a second multicolor toner image is first formed on the first intermediate transfer belt 21. The second multicolor toner image is secondarily transferred onto the second intermediate transfer belt 31 at a secondary transfer nip where the first intermediate transfer belt 21 and the second intermediate transfer belt 31 are in contact with each other.

  Each of the first process units 80Y, 80M, 80C, 80K forms a first single color toner image for a while, and then forms a second single color toner image and superimposes it on the first intermediate transfer belt 21. Transcript. Thereafter, the transfer paper P is fed into the secondary transfer nip. Then, at the secondary transfer nip, the first multicolor toner image on the first intermediate transfer belt 21 is in close contact with the first surface of the transfer paper P and is collectively secondary transferred. Next, when the transfer paper P passes through the secondary transfer nip and is conveyed to a position facing the transfer charger 47, the second multicolor toner image on the second intermediate transfer belt 31 is formed on the second surface of the transfer paper P. Batch transfer is performed.

  In the second modified apparatus having such a configuration, the first image forming unit including the first process unit dedicated for forming the first toner image and the second dedicated for forming the second toner image. A toner image can be formed on each side of the transfer paper by the one-pass method without providing both of the second image forming unit composed of a process unit or the like. However, since it is necessary to form the first toner image and the second toner image at different times, compared with the copying machine according to the fourth embodiment that can form both the toner images in parallel. The image forming speed is reduced. On the other hand, in the copying machine according to the fourth embodiment, by providing both the first image forming unit and the second image forming unit, it is possible to increase the image forming speed instead of increasing the cost.

  Heretofore, an example using a drum-shaped photoconductor as a latent image carrier has been described, but other types such as a belt-type photoconductor may be used. Further, although an example of forming a full-color image has been described, an image forming apparatus that forms a single-color image using one photoconductor (image carrier) may be used. Further, the copying machine for transferring the toner image from the intermediate transfer belt as the toner image carrier onto the transfer paper P has been described. However, the toner image is transferred onto the transfer paper P from a latent image carrier such as a photoreceptor as the toner image carrier. The present invention can also be applied to the image forming apparatus. Further, although a copying machine that forms an image by an electrophotographic method has been described, the present invention can also be applied to an image forming apparatus that forms a toner image by other methods such as a direct recording method. This direct recording method is not related to a latent image carrier, but forms a dot image by directly adhering a toner group that has been ejected in a dot shape from a toner flying device to a recording medium or an intermediate recording medium. In this method, a toner image is directly formed on an intermediate recording medium. In the configuration in which the toner image is transferred from the intermediate recording medium to a recording medium such as transfer paper after the toner is ejected from the toner flying device toward the intermediate recording medium, the recording medium is similar to the electrophotographic system. The roughness of the image differs depending on the surface smoothness.

  As described above, in the copying machine according to the third embodiment or the fourth embodiment, the first intermediate transfer belt 21 as the first toner image carrier and the second intermediate transfer as the second toner image carrier as the toner image carrier. A belt 31 is provided. In addition, as a toner image forming unit, a first image forming unit as a first toner image forming unit for forming a first toner image to be transferred onto the first surface of the transfer paper P on the first intermediate transfer belt 21; And a second image forming unit as a second toner image forming unit for forming a second toner image to be transferred onto the two surfaces on the second intermediate transfer belt 31, and the first transfer unit 20 As a transfer means including the second transfer unit 30 and the like, the first toner image is transferred from the first intermediate transfer belt 21 to the first surface of the transfer paper P, and the second toner image is transferred from the second intermediate transfer belt 31. A material that is transferred to the second surface of the paper P is used. In such a configuration, as the toner image forming unit, the number of output lines L corresponding to the first surface or the dot concentration degree, and the first degree according to the smoothness information input result to the smoothness information input unit including the operation display unit 90 and the like. Surface smoothness information can be input separately for the first and second surfaces as the smoothness information input means using the one that changes the number of output lines L or dot concentration corresponding to the two surfaces. In the same manner as in the modified example device that changes the number L of output lines and the dot concentration degree according to the detection result by the smoothness detecting means, the first toner image and the second toner image are respectively transferred to the first surface. By forming with the number of output lines L or dot concentration suitable for the surface smoothness of the second surface, it is possible to suppress image quality deterioration due to poor surface smoothness for both toner images. In addition, it is possible to effectively suppress a difference in image quality caused by a large difference in surface smoothness between the first surface and the second surface. Further, the first toner image and the second toner image are formed by dedicated process units, respectively, so that the first toner image and the second toner image are formed in parallel to increase the image forming speed. Can do.

  In the second modification of the copying machine according to the fourth embodiment, the first intermediate transfer belt 21 as the first toner image carrier and the second intermediate as the second toner image carrier as the toner image carrier. A transfer belt 31 is provided. Further, as the toner image forming means, one that forms on the first intermediate transfer belt 21 a first toner image transferred onto the first surface of the transfer paper P and a second toner image transferred onto the second surface is used. . Further, as a transfer unit, the first toner image of the first intermediate transfer belt 21 is directly transferred onto the first surface of the transfer paper P, and the second toner image on the first intermediate transfer belt 21 is transferred to the second intermediate transfer belt 31. A material that is transferred to the second surface is used. In such a configuration, as the toner image forming unit, the number of output lines L corresponding to the first surface or the dot concentration degree, and the first degree according to the smoothness information input result to the smoothness information input unit including the operation display unit 90 and the like. Surface smoothness information can be input separately for the first and second surfaces as the smoothness information input means using the one that changes the number of output lines L or dot concentration corresponding to the two surfaces. In the same manner as in the modified example device that changes the number L of output lines and the dot concentration degree according to the detection result by the smoothness detecting means, the first toner image and the second toner image are respectively transferred to the first surface. By forming with the number of output lines L or dot concentration suitable for the surface smoothness of the second surface, it is possible to suppress image quality deterioration due to poor surface smoothness for both toner images. In addition, it is possible to effectively suppress a difference in image quality caused by a large difference in surface smoothness between the first surface and the second surface. Further, by forming the first toner image and the second toner image by a common process unit, the configuration can be simplified and the cost can be reduced as compared with the case of forming by a separate process unit.

  In the modification device of the copying machine according to the third embodiment and the first modification device of the copying machine according to the fourth embodiment, the first intermediate transfer belt 21 and the second intermediate transfer are used as toner image carriers. A belt 31 is provided. In addition, as a toner image forming unit, a first image forming unit for forming on the first intermediate transfer belt 21 a first toner image transferred onto the first surface of the transfer paper P, and a first image transferred onto the second surface. A second image forming unit for forming two toner images on the second intermediate transfer belt 31, and corresponds to the first surface of the transfer paper P according to the detection result by the smoothness detecting means 500. The output line number L or the dot concentration degree to be changed and the output line number L or the dot concentration degree corresponding to the second surface are respectively changed. Further, as the transfer means, one that transfers the first toner image from the first intermediate transfer belt 21 to the first surface and transfers the second toner image from the second intermediate transfer belt 31 to the second surface is used. Furthermore, as the smoothness detecting means 500, a device capable of individually detecting surface smoothness on the first surface and the second surface is used. In this configuration, for the reasons described above, the first toner image and the second toner image are formed with the number of output lines L or the dot concentration suitable for the surface smoothness of the first surface and the second surface, respectively. For both toner images, it is possible to suppress deterioration in image quality due to poor surface smoothness. In addition, it is possible to effectively suppress a difference in image quality caused by a large difference in surface smoothness between the first surface and the second surface. Further, the first toner image and the second toner image are formed by dedicated process units, respectively, so that the first toner image and the second toner image are formed in parallel to increase the image forming speed. Can do. Further, unlike the copying machines according to the first and second embodiments, the smoothness detecting unit 500 can detect the first and second surfaces without causing the user to input smoothness information. By detecting the surface smoothness, a toner image can be formed with the number of output lines L and the dot concentration degree corresponding to each surface smoothness.

  In the second modification of the copying machine according to the fourth embodiment, a first intermediate transfer belt 21 and a second intermediate transfer belt 31 are provided as toner image carriers. Further, as the toner image forming means, the first toner image transferred to the first surface and the second toner image transferred to the second surface are formed on the first intermediate transfer belt 21, and smoothness detection is performed. In accordance with the detection result by the means 500, a dot concentration degree corresponding to the first surface and a dot concentration degree corresponding to the second surface are respectively changed. Further, as a transfer unit, the first toner image on the first intermediate transfer belt 21 is directly transferred onto the first surface, and the second toner image on the first intermediate transfer belt 21 is transferred via the second intermediate transfer belt 31 to the first surface. What is transferred to two sides is used. Furthermore, as the smoothness detecting means 500, a device capable of individually detecting surface smoothness on the first surface and the second surface is used. In such a configuration, for the reasons described above, the first toner image and the second toner image are formed with the dot concentration suitable for the surface smoothness of the first surface and the second surface, respectively. It is possible to suppress deterioration in image quality due to poor smoothness. In addition, it is possible to effectively suppress a difference in image quality caused by a large difference in surface smoothness between the first surface and the second surface. Further, by forming the first toner image and the second toner image by a common process unit, the configuration can be simplified and the cost can be reduced as compared with the case where they are formed by separate process units. Further, unlike the copying machines according to the first and second embodiments, the smoothness detecting unit 500 can detect the first and second surfaces without causing the user to input smoothness information. By detecting the surface smoothness, a toner image can be formed with a dot concentration degree corresponding to each surface smoothness.

  In the copying machine according to the third embodiment or the fourth embodiment, the number of output lines L corresponding to the surface having the lower surface smoothness among the first surface and the second surface of the transfer paper P is already set. The number of output lines corresponding to one surface should be less than L, or the dot concentration corresponding to the surface with lower surface smoothness should be made higher than the dot concentration corresponding to the other surface. In addition, a toner image forming unit is configured. In such a configuration, the number of output lines L corresponding to the surface with lower surface smoothness is made larger than the number of output lines L corresponding to the other surface, or the surface with lower surface smoothness is used. It is possible to avoid a situation in which the corresponding dot concentration degree is made lower than the dot concentration degree corresponding to the other surface and the image quality difference between the first surface and the second surface is deteriorated.

  In the copying machine according to the first embodiment, as the smoothness detecting means 500, the surface smoothness on at least one of the first surface and the second surface of the transfer paper P is set to the light reflectance on the surface. Based on what is detected. In such a configuration, in this configuration, the surface smoothness can be detected without contact with the paper surface.

  In the copying machine according to the first embodiment, the optical sensor unit 500A serving as the smoothness detecting means receives the regular reflected light on the paper surface of the light emitted from the light emitting element serving as the light emitting means by the light receiving element serving as the light receiving means. What detects the reflectance is used. In such a configuration, as described above, the surface smoothness can be detected with higher accuracy than in the case of detecting only the diffuse reflected light reflected at an angle different from the regular reflected light.

  In the copying machine according to the second embodiment, as the optical sensor unit 500A, the diffused light reflected on the paper surface of the light emitted from the light emitting element is converted into a second light receiving element (not the light receiving element that receives the regular reflected light). 513A) is used. In this configuration, as described above, the surface smoothness can be detected with higher accuracy than in the case of using a device that receives only regular reflection light.

  In the copying machine according to the third embodiment, as the smoothness detecting means, the surface smoothness of at least one of the first surface and the second surface of the transfer paper P is changed to the surface electrical resistance of the transfer paper P. A surface electrical resistance detection unit 500B that detects the base is used. In such a configuration, unlike the case of using the one that detects surface smoothness based on the light reflectance, the surface smoothness is detected without causing deterioration in detection accuracy due to light leaking from the outside of the printer unit housing. be able to.

  In the copiers according to the first, second, and third embodiments, the smoothness detecting means 500 is a first surface detecting means that detects the surface smoothness of the first surface of the transfer paper. A single surface detection unit 510 and a second surface detection unit 520 that is a second surface detection unit that detects surface smoothness of the second surface are used. In such a configuration, even when the one-pass method in which the transfer paper cannot be passed twice at the detection position by the smoothness detecting means 500 as in the switchback method, the surface smoothness of the first surface and the second surface of the transfer paper is adopted. Can be detected respectively.

  In the copying machine according to the fourth embodiment, the first surface detection unit 510 and the second surface detection unit 520 interfere with each other across the paper conveyance path 43A that is a recording medium conveyance path through which transfer paper is conveyed. Since the position is shifted from the maximum position, it is possible to suppress deterioration in detection accuracy due to interference between the two detection units.

  In the copying machine according to each embodiment, the toner image forming unit that forms a toner image with a resolution of 600 [dpi] or more in both the main scanning direction and the sub-scanning direction is used. It is possible to satisfactorily suppress the deterioration of granularity due to the fact that is relatively small.

  Further, in the copying machine according to each embodiment, as a toner image forming unit, a toner image is formed by attaching toner to a latent image formed on the surface of a photosensitive member as a latent image carrier, and the diameter of each pixel is set. A device that forms a latent image of 60 [μm] or less is used. With such a configuration, it is possible to satisfactorily suppress deterioration in granularity due to a relatively large diameter.

  In the copying machine according to each embodiment, a plurality of single-color first toner images having different colors are superimposed on the first intermediate transfer belt 21 as the first image forming unit serving as the first toner image forming unit. In order to obtain a multi-color first toner image, a plurality of single-color second toner images having different colors are superposed on the second intermediate transfer belt 31 as a second image forming unit as a second toner image forming unit. A multi-color second toner image is obtained by forming. With this configuration, it is possible to form toner images of other colors on both the first surface and the second surface.

  In the copying machine according to each embodiment, the toner used for the toner image forming unit has a weight average particle diameter of 3 to 7 [μm] and a value obtained by dividing the weight average particle diameter by the number average particle diameter. A value between 1.00 and 1.30 is specified. In such a configuration, it is possible to form dots having a stable shape by following the unevenness of the paper surface even on the transfer paper P having a relatively low smoothness, and the shape of the small dots, which are the basic iodine of the dither, can be formed. Can be stabilized. It is also possible to achieve higher image quality by improving dot reproducibility associated with smaller toner particle diameters, stabilizing the charge amount by sharpening the particle size distribution, and improving transfer rate by lowering the pile height. It becomes possible.

1 is a schematic configuration diagram showing a copier according to a first embodiment. FIG. 2 is an enlarged configuration diagram showing a first process unit of the copier. FIG. 3 is an enlarged configuration diagram showing a second process unit of the copier. The graph which shows the relationship between Beck smoothness and granularity. The graph which shows the relationship between granularity and Beck smoothness. FIG. 2 is a block diagram showing a part of an electric circuit in the copier. 6 is a flowchart showing an outline of a control flow of smoothness input control performed by the control unit of the copier. The flowchart which shows the outline | summary of the control flow of the line number change control implemented by the control part. FIG. 4 is a schematic diagram illustrating an example of a dither matrix tilted with respect to both main and sub scanning directions. The schematic diagram which expands and shows one of the pixel group divisions in the dither matrix. 6 is a graph showing the relationship between the granularity of a toner image and the diameter of a light beam when the photosensitive member is exposed. 6 is a graph showing the relationship between the granularity of a toner image and the resolution. FIG. 9 is a schematic diagram illustrating an example of a dither matrix in a copying machine according to a second embodiment. (A) is a schematic diagram which shows an example of the pixel group division which makes dot concentration degree comparatively low, (b) is a schematic diagram which shows an example of the pixel group division which makes dot concentration degree higher than this pixel group division. FIG. 8C is a schematic diagram illustrating an example of a pixel group section that further increases the dot concentration degree. The graph which shows the relationship between a granularity and a dot concentration degree. 6 is a flowchart showing an example of a control flow of dot concentration degree deformation control performed by the control unit of the copier. FIG. 9 is an enlarged configuration diagram showing smoothness detection means of a copying machine according to a third embodiment. FIG. 2 is a block diagram showing a part of an electric circuit in the copier. 3 is a flowchart showing an outline of a control flow of line number change control performed by the control unit of the copier. 6 is a flowchart showing an outline of line number change control performed by a control unit of a modification apparatus of the copier. 10 is a flowchart showing an outline of a control flow of dot concentration degree change control performed by a control unit of a copier according to a fourth embodiment. 9 is a flowchart showing an outline of a control flow of dot concentration degree change control performed by a control unit of the first modification apparatus of the copier. FIG. 3 is an enlarged configuration diagram illustrating an example of an optical sensor unit of the copying machine according to the first embodiment. The schematic diagram for demonstrating the regular reflection of light. The expanded block diagram which shows 510 A of 1st surface detection parts of the optical sensor unit used for the copying machine which concerns on 2nd Example. The expansion block diagram which shows the surface electrical resistance detection unit used for the copying machine which concerns on 3rd Example. FIG. 9 is a schematic configuration diagram showing a main configuration of a second modification apparatus of a copying machine according to a fourth embodiment.

Explanation of symbols

P Transfer paper (recording medium)
1Y, M, C, K photoconductor (latent image carrier)
5 Development device (developing means)
20 First transfer unit (part of transfer means)
21 First intermediate transfer belt (first toner image carrier)
30 Second transfer unit (part of transfer means)
80Y, M, C, K First process unit (part of toner image forming means and first toner image forming unit)
81Y, M, C, K Second process unit (part of toner image forming means and second toner image forming unit)
90 Operation display unit (part of smoothness information input means)
95 Control unit (part of toner image forming means and smoothness information input means)
500 Smoothness detection means 510 First surface detection unit 520 Second surface detection unit

Claims (21)

A toner image forming unit that forms a toner image on the surface of the toner image carrier; and a transfer unit that transfers the toner on the toner image carrier to a recording member. In an image forming apparatus using a pixel that expresses a gradation according to a density of a toner-attached pixel to which toner is attached,
Smoothness information input means for inputting information on the surface smoothness of the transfer target surface of the toner image on the recording medium is provided, and in the halftone portion of the toner image according to input information to the smoothness information input means An image forming apparatus, wherein the toner image forming means is configured to change the number of output lines per unit length. A toner image forming unit that forms a toner image on the surface of the toner image carrier; and a transfer unit that transfers the toner on the toner image carrier to a recording member. In an image forming apparatus using a pixel that expresses a gradation according to a density of a toner-attached pixel to which toner is attached,
Smoothness information input means for inputting information on the surface smoothness of the transfer target surface of the toner image on the recording medium is provided, and in the halftone portion of the toner image according to input information to the smoothness information input means An image forming apparatus, wherein the toner image forming unit is configured to change a concentration degree of toner adhering pixels. A toner image forming unit that forms a toner image on the surface of the toner image carrier; and a transfer unit that transfers the toner on the toner image carrier to a recording member. In an image forming apparatus using a pixel that expresses a gradation according to a density of a toner-attached pixel to which toner is attached,
Smoothness detecting means for detecting the surface smoothness of the transfer target surface of the toner image on the recording medium is provided, and the output per unit length in the halftone portion of the toner image according to the detection result by the smoothness detecting means An image forming apparatus comprising the toner image forming unit configured to change the number of lines. A toner image forming unit that forms a toner image on the surface of the toner image carrier; and a transfer unit that transfers the toner on the toner image carrier to a recording member. In an image forming apparatus using a pixel that expresses a gradation according to a density of a toner-attached pixel to which toner is attached,
A smoothness detecting means for detecting the surface smoothness of the transfer target surface of the toner image on the recording medium is provided, and the concentration degree of the toner adhering pixels in the halftone portion of the toner image according to the detection result by the smoothness detecting means. An image forming apparatus characterized in that the toner image forming means is configured to change the temperature. The image forming apparatus according to claim 1 or 2,
As the toner image carrier, at least a first toner image carrier and a second toner image carrier are provided,
As the toner image forming means, a first toner image forming portion for forming a first toner image to be transferred onto the first surface of the recording medium on the first toner image carrier, and a transfer onto the second surface of the recording medium. A second toner image forming unit for forming the second toner image to be formed on the second toner image carrier, and according to the input information to the smoothness information input means, Using the one that changes the number of output lines or concentration corresponding to the surface and the number of output lines or concentration corresponding to the second surface, respectively,
As the transfer means, the first toner image is transferred from the first toner image carrier to the first surface, and the second toner image is transferred from the second toner image carrier to the second surface. Use things
An image forming apparatus using the smoothness information input means capable of individually inputting surface smoothness information on the first surface and the second surface, respectively. The image forming apparatus according to claim 1 or 2,
As the toner image carrier, at least a first toner image carrier and a second toner image carrier are provided,
As the toner image forming means, a first toner image transferred to the first surface of the recording medium and a second toner image transferred to the second surface of the recording medium are formed on the first toner image carrier. And the number of output lines or the degree of concentration corresponding to the first surface and the number of output lines or the degree of concentration corresponding to the second surface are changed in accordance with input information to the smoothness information input unit. Use what
As the transfer means, the first toner image on the first toner image carrier is directly transferred to the first surface, and the second toner image on the first toner image carrier is transferred to the second toner image carrier. Using what is transferred to the second surface via
An image forming apparatus using the smoothness information input means capable of individually inputting surface smoothness information on the first surface and the second surface, respectively. The image forming apparatus according to claim 3 or 4,
As the toner image carrier, at least a first toner image carrier and a second toner image carrier are provided,
As the toner image forming means, a first toner image forming portion for forming a first toner image to be transferred onto the first surface of the recording medium on the first toner image carrier, and a transfer onto the second surface of the recording medium. A second toner image forming unit for forming a second toner image to be formed on the second toner image carrier, and the first surface according to a detection result by the smoothness detecting means. Using the one that changes the number of output lines or the degree of concentration corresponding to and the number of output lines or the degree of concentration corresponding to the second surface,
As the transfer means, the first toner image is transferred from the first toner image carrier to the first surface, and the second toner image is transferred from the second toner image carrier to the second surface. Use things
An image forming apparatus characterized in that as the smoothness detecting means, a device capable of individually detecting surface smoothness on the first surface and the second surface is used. The image forming apparatus according to claim 3 or 4,
As the toner image carrier, at least a first toner image carrier and a second toner image carrier are provided,
As the toner image forming means, a first toner image transferred to the first surface of the recording medium and a second toner image transferred to the second surface of the recording medium are formed on the first toner image carrier. And the number of output lines or the degree of concentration corresponding to the first surface and the number of output lines or the degree of concentration corresponding to the second surface are changed according to the detection result by the smoothness detecting means. Use things
As the transfer means, the first toner image on the first toner image carrier is directly transferred to the first surface, and the second toner image on the first toner image carrier is transferred to the second toner image carrier. Using what is transferred to the second surface via
An image forming apparatus characterized in that as the smoothness detecting means, a device capable of individually detecting surface smoothness on the first surface and the second surface is used. The image forming apparatus according to any one of claims 5 to 8,
Of the first surface and the second surface, the number of output lines corresponding to the surface with the lower surface smoothness is made smaller than the number of output lines corresponding to the other surface, or the surface smoothness An image forming apparatus, wherein the toner image forming means is configured to make the concentration corresponding to the surface having the lower property higher than the concentration corresponding to the other surface. The image forming apparatus according to claim 7 or 8,
As the smoothness detecting means, one that detects surface smoothness on at least one of the first surface and the second surface of the recording body based on the light reflectance on the surface is used. Image forming apparatus. The image forming apparatus according to claim 10.
An image forming apparatus characterized in that the smoothness detecting means uses a light receiving means that receives regular reflection light on the surface of light emitted from a light emitting means and detects the light reflectance. The image forming apparatus according to claim 11.
An image forming apparatus, wherein the smoothness detecting means receives diffusely reflected light on the surface of the light emitted from the light emitting means by a second light receiving means different from the light receiving means. The image forming apparatus according to claim 7, 8, 10, 11, or 12.
As the smoothness detecting means, a device that detects the surface smoothness of at least one of the first surface and the second surface of the recording body based on the surface electrical resistance of the recording body is used. Image forming apparatus. The image forming apparatus according to claim 7, 8, 10, 11, 12, or 13.
As the smoothness detecting means, one having a first surface detecting means for detecting the surface smoothness of the first surface and a second surface detecting means for detecting the surface smoothness of the second surface is used. An image forming apparatus. The image forming apparatus according to claim 14.
The first surface detecting means and the second surface detecting means are arranged so as to be shifted from a position where the mutual interference is maximized across a recording material conveyance path through which the recording material is conveyed. apparatus. The image forming apparatus according to any one of claims 1 to 15,
An image forming apparatus using the toner image forming unit that forms the toner image with a resolution of 600 [dpi] or more in both the main scanning direction and the sub-scanning direction. The image forming apparatus according to claim 1,
As the toner image forming means, toner is attached to the latent image formed on the surface of the latent image carrier to form the toner image, and the latent image is formed with each pixel having a diameter of 60 [μm] or less. An image forming apparatus using the apparatus. The image forming apparatus according to claim 5 or 7,
As the first toner image forming unit, a plurality of single-color first toner images having different colors are superimposed on the first toner image carrier to obtain a multicolor first toner image, and
The second toner image forming unit is a unit that obtains a multicolor second toner image by forming a plurality of single-color second toner images of different colors on the second toner image carrier. An image forming apparatus. The image forming apparatus according to claim 6 or 8,
As the toner image forming means, a plurality of single color first toner images of different colors are formed on the first toner image carrier to obtain a multicolor first toner image, or a plurality of single colors of different colors are used. An image forming apparatus using an apparatus that obtains a multicolor second toner image by superimposing a second toner image on the first toner image carrier. The image forming apparatus according to claim 1,
A toner containing means for containing toner used in the toner image forming means;
A toner having a weight average particle diameter of 3 to 7 [μm] and a value obtained by dividing the weight average particle diameter by the number average particle diameter of 1.00 to 1.30 is stored in the toner storage unit. An image forming apparatus. The image forming apparatus according to claim 1,
As the toner used in the toner image forming unit, a toner having a weight average particle diameter of 3 to 7 [μm] and a value obtained by dividing the weight average particle diameter by the number average particle diameter is 1.00 to 1.30. An image forming apparatus characterized by being specified.

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