JP5429477B2 - Image forming apparatus - Google Patents

Description

The present invention relates to an image forming apparatus .

  Conventionally, in a tandem type color printer as a kind of image forming apparatus, there are four image units for forming yellow (Y), magenta (M), cyan (C), and black (K) single color toner images. Is provided.

  Each image unit is provided with members such as a charging device, a developing device, and a latent image holding member (photosensitive drum).

  By the way, the charging device and the developing device for each color are connected to individually provided power sources, but there is a problem that the cost of the power source device becomes high.

  In view of this, an image forming apparatus has been developed that reduces the cost of the power supply device by sharing the power supply of the charging device and the developing device provided for each color.

  On the other hand, the image quality of a toner image on a recording medium such as printing paper is affected by the surface potential of the photosensitive drum and the developing conditions of the developing device.

  For this reason, conventionally, various techniques for controlling the surface potential of the photosensitive member and the developing conditions of the developing device during the operation of forming the toner image on the recording medium have been proposed.

  For example, Japanese Patent Application Laid-Open No. 2002-162801 has a plurality of electrostatic latent image holders and developing means, and has means for detecting a parameter caused by image density and means for controlling it, A technique is disclosed in which at least a part of a circuit for supplying a voltage to a charging unit or a developing unit is shared.

  Japanese Patent Application Laid-Open No. 2003-131448 gradually adjusts the state of the image forming apparatus in the direction in which an image having a desired density is formed over the image formation on a plurality of recording media according to the state detection result. Techniques to do this are disclosed.

  Japanese Patent Application Laid-Open No. 2004-163502 discloses a tandem type color printer that includes a first high-voltage power supply commonly connected to each color developing device and a second high-voltage power source commonly connected to each color charging device. A technique is disclosed in which the solid density is controlled using the development bias of each color as a voltage in a region where development efficiency of all colors is saturated and overlapped.

JP 2002-162801 A JP 2003-131448 A Japanese Patent Laid-Open No. 2004-163502

An object of the present invention is to provide an image forming apparatus capable of reducing density fluctuations in an image forming area.

In order to solve the above problem, an image forming apparatus according to the invention of claim 1 is provided corresponding to a plurality of colors, and holds a plurality of electrostatic latent images that hold an electrostatic latent image formed based on image information. Means corresponding to the plurality of electrostatic latent image holding means, exposure means for exposing each of the electrostatic latent image holding means, and provided corresponding to the plurality of electrostatic latent image holding means. A plurality of charging means for charging each of the electrostatic latent image holding means and an electrostatic latent image formed on the surface of each of the electrostatic latent image holding means. A plurality of developing means for developing an image as an image using a developer; a plurality of transferring means for transferring the image; and a power source for supplying a voltage to the charging means or the plurality of developing means or the plurality of transferring means Power supply means for sharing at least part of the circuit, and each of the electrostatic latent images The distance between the lifting means, the relationship between the distance between the developed image by the developing unit, the than the distance between the image distance between has been developed by the developing means of each electrostatic latent image holding means If it is smaller, switching is performed to switch at least one image forming condition of the electrostatic latent image holding unit, the exposure unit, the charging unit, the developing unit, and the transfer unit from the first image forming condition to the second image forming condition. And when the plurality of common colors are three colors, the switching means uses the developing means for a color intermediate between the three colors in the arrangement order of the electrostatic latent image holding means. The image forming conditions are switched between developed images .
In order to solve the above problem, an image forming apparatus according to the invention of claim 2 is provided corresponding to a plurality of colors, and includes a plurality of electrostatic latent images that hold an electrostatic latent image formed based on image information. An image holding means, an exposure means provided corresponding to the plurality of electrostatic latent image holding means, and exposing to each of the electrostatic latent image holding means, and corresponding to the plurality of electrostatic latent image holding means. A plurality of charging means for charging each electrostatic latent image holding means, and a plurality of charging means provided corresponding to the plurality of electrostatic latent image holding means and formed on the surface of each electrostatic latent image holding means. Voltage is supplied to a plurality of developing means for developing the electrostatic latent image as an image using a developer, a plurality of transferring means for transferring the image, and the charging means, the plurality of developing means, or the plurality of transferring means. Power supply means for sharing at least a part of the power supply circuit, and each of the static circuits The relationship between the distance between the latent image holding means and the distance between the images developed by the developing means is such that the distance between the electrostatic latent image holding means is the distance between the images developed by the developing means. The image forming condition of the electrostatic latent image holding unit, the exposure unit, the charging unit, the developing unit, and the transfer unit is changed from the first image forming condition to the second image forming condition. Switching means for switching, and the switching means switches the image forming conditions at the leading edge of the image developed by the developing means.

According to a third aspect of the present invention, in the image forming apparatus according to the first or second aspect of the present invention, the image forming conditions include the electrostatic latent image holding unit, the exposure unit, and the The charging unit, the developing unit, and the transfer unit have image forming conditions common to all or a part of the plurality of colors.

According to a fourth aspect of the present invention, the image forming apparatus according to any one of the first to third aspects further comprises a detecting means for detecting a density detection pattern formed on the transfer means, and the switching means. Is characterized in that the image forming conditions are switched based on the detection result of the detecting means.

  According to the present invention, the following effects can be obtained.

That is, according to the first aspect of the present invention, it is possible to provide an image forming apparatus capable of reducing density fluctuations in the image forming area.
According to the first aspect of the present invention, the image forming condition for the color intermediate between the three colors in the arrangement order of the electrostatic latent image holding means is within the image (interimage) developed by the developing means. Can be switched to reduce the density fluctuation in the image forming region.
According to the second aspect of the present invention, it is possible to provide an image forming apparatus capable of reducing density fluctuations in the image forming region.
According to a second aspect of the present invention, there is provided an image forming apparatus capable of reducing density fluctuations in an image forming area by switching image forming conditions at the leading edge of the image developed by the developing means. Can do.

According to the third aspect of the present invention, it is possible to provide an image forming apparatus capable of reducing density fluctuations in an image forming area under image forming conditions common to all or part of a plurality of colors. it can.

According to the fourth aspect of the present invention, it is possible to provide an image forming apparatus capable of switching the image forming conditions based on the detection result of the detecting means and reducing the density fluctuation in the image forming area.

1 is a configuration diagram illustrating a configuration of an image forming apparatus PR1 according to an embodiment. 2 is a functional block diagram illustrating a configuration of an image forming apparatus PR1 according to an embodiment. FIG. It is a flowchart which shows the process sequence of an image formation process. It is a flowchart which shows the process sequence of an image formation condition control process. It is explanatory drawing which shows the example in the case of switching image formation conditions within an inter image. 10 is a timing chart when switching image forming conditions in an inter image when YMC color development biases are common. It is explanatory drawing which shows the example in the case of switching image formation conditions within an inter image. It is explanatory drawing which shows the example in the case of switching image formation conditions within an inter image. It is explanatory drawing which shows the example in the case of switching image formation conditions outside an inter image. 10 is a timing chart in the case of switching image forming conditions outside the inter image when the YMC color development bias is common. It is explanatory drawing which shows the example in the case of switching image formation conditions outside an inter image.

  Hereinafter, an exemplary embodiment of the present invention will be described in detail with reference to the drawings. Here, in the accompanying drawings, the same reference numerals are given to the same members, and duplicate descriptions are omitted. In addition, since description here is the best form by which this invention is implemented, this invention is not limited to the said form.

  An image forming apparatus PR1 according to an embodiment of the present invention will be described with reference to FIGS.

  FIG. 1 shows a main body of a tandem type digital color copying machine as an image forming apparatus PR1 according to the present embodiment.

  A platen cover 3 that presses the document 2 against the platen glass 5 and an image reading device 4 that reads an image of the document 2 placed on the platen glass 5 are disposed at the upper end of the digital color copying machine main body 1. Is provided.

  The image reading device 4 illuminates a document 2 placed on a platen glass 5 with a light source 6, and reflects a reflected light image from the document 2 from a full-rate mirror 7, half-rate mirrors 8 and 9, and an imaging lens 10. The image reading element 11 composed of a CCD or the like is scanned and exposed through a reduction optical system, and the color reading light image of the original 2 is read at a predetermined dot density by the image reading element 11.

  The color material reflected light image of the document 2 read by the image reading device 4 is sent to the image forming device 12 as document reflectance data of three colors, for example, red (R), green (G), and blue (B). In the image forming apparatus 12, the reflectance data of the document 2 is subjected to predetermined image processing such as shading correction, position shift correction, brightness / color space conversion, gamma correction, frame deletion, color / moving editing, and the like. Is done.

  The image data that has been subjected to predetermined image processing by the image forming apparatus 12 is the original color material gradation data (raster of four colors) of yellow (Y), magenta (M), cyan (C), and black (K). Data), and as described below, the image forming units 13Y, 13M, 13C, and 13K for the yellow (Y), magenta (M), cyan (C), and black (K) image forming units 14Y and 14M , 14C, 14K (an example of exposure means; hereinafter collectively referred to simply as “exposure device 14”), these exposure devices 14 emit laser light in accordance with original color material gradation data of a predetermined color. Image exposure is performed.

  As described above, the tandem type digital color copying machine main body 1 includes four image forming units 13Y, 13M, 13C of yellow (Y), magenta (M), cyan (C), and black (K). 13K (hereinafter collectively referred to simply as “image forming unit 13”) are arranged in parallel across a certain distance D1 (more precisely, a distance between photosensitive drums 15 to be described later) D1 in the horizontal direction. ing.

  In the present embodiment, the distance between the centers of the adjacent photosensitive drums 15 is defined as D1, but the adjacent image forming units 13 are assumed when an intermediate transfer member or the like is arranged on a curve. It may be defined as the distance of the transfer image carrier between the transfer positions.

  In addition, an electric circuit 201 including an image processing circuit that performs image processing on an image signal, a high-voltage power supply circuit (common power supply apparatus 200; an example of power supply means), and the like are provided.

  The four image forming units 13Y, 13M, 13C, and 13K are all configured in the same manner and rotate at a predetermined rotational speed along the direction of arrow A (an example of an electrostatic latent image holding unit). A charger 16 for primary charging (an example of a charging unit) that uniformly charges the surface of the photosensitive drum 15 and an image corresponding to each color on the surface of the photosensitive drum 15 to expose the electrostatic latent image. An exposure device 14 that forms an image and developing devices 17Y, 17M, 17C, and 17K that develop an electrostatic latent image formed on the photosensitive drum 15 (an example of a developing unit. And a cleaning device 18.

  The exposure device 14 modulates the semiconductor laser 19 according to the original color material gradation data, and emits a laser beam LB from the semiconductor laser 19 according to the gradation data. The laser beam LB emitted from the semiconductor laser 19 is deflected and scanned by the rotary polygon mirror 22 through the reflection mirrors 20 and 21, and electrostatically passes through the reflection mirrors 20 and 21 and the plurality of reflection mirrors 23 and 24 again. Scanning exposure is performed on a photosensitive drum 15 as a latent image holding unit.

  The image forming apparatus 12 sequentially outputs image data (raster data) of each color to the exposure device 14 of the image forming unit 13 for each color of yellow (Y), magenta (M), cyan (C), and black (K). The laser beams LB emitted according to the image data from these exposure devices 14 are scanned and exposed on the surfaces of the respective photosensitive drums 15 to form electrostatic latent images.

  The electrostatic latent image formed on each photosensitive drum 15 is developed as a toner image of each color of yellow (Y), magenta (M), cyan (C), and black (K) by the developing device 17.

  The yellow (Y), magenta (M), cyan (C), and black (K) toner images sequentially formed on the photoconductive drums 15 of the image forming units 13 are image forming units 13Y and 13M. , 13C, and 13K, a plurality of images are transferred onto the intermediate transfer belt 25 as an intermediate transfer member by the primary transfer rolls 26Y, 26M, 26C, and 26K.

  The intermediate transfer belt 25 is wound around the belt driving roll 27, the stripping roll 28, the steering roll 29, the idle roll 30, the backup roll 31, and the idle roll 32 with a constant tension. The belt is driven to circulate at a predetermined speed in the direction of arrow A by a belt driving roll 27 driven and rotated by a driving force transmission roll driven to rotate by a driving motor (not shown).

  As the intermediate transfer belt 25, for example, a synthetic resin film such as polyamideimide having flexibility is formed in a band shape, and both ends of the synthetic resin film formed in a band shape are connected by means such as welding, thereby being endless. A belt-shaped one is used.

  The yellow (Y), magenta (M), cyan (C), and black (K) toner images transferred onto the intermediate transfer belt 25 are transferred by the secondary transfer roll 33 in pressure contact with the backup roll 31. The recording paper 34 secondarily transferred onto the recording paper 34 as a recording medium by the pressure contact force and the electrostatic force, and the toner image of each color transferred thereto is conveyed to the fixing device 37 by the two conveying belts 35 and 36. The

The recording paper 34 onto which the toner images of the respective colors have been transferred undergoes a fixing process with heat and pressure by a fixing device 37 and is discharged onto a discharge tray 38 provided outside the copying machine main body 1.
As shown in FIG. 1, the recording paper 34 has a predetermined size from any of a plurality of paper feed trays 39, 40, 41, and a pair of paper feed rollers 42 and a pair of paper transport rollers 43, 44. , 45 is temporarily transported to the registration roll 47 via a paper transport path 46.

  The recording paper 34 supplied from any of the paper feed trays 39, 40, 41 is sent onto the intermediate transfer belt 25 by a registration roll 47 that is rotationally driven at a predetermined timing.

  In the four image forming units 13Y, 13M, 13C, and 13K of black, yellow, magenta, and cyan, black, yellow, magenta, and cyan toner images are sequentially formed at predetermined timings as described above. It has become so.

  After the toner image transfer process is completed, the photosensitive drum 15 is prepared for the next image forming process by removing residual toner, paper dust, and the like by the cleaning device 18.

  Further, residual toner is removed from the intermediate transfer belt 25 by a belt cleaner 48.

  The image forming apparatus PR1 has a configuration as shown in FIG. 2 in addition to the above configuration.

  That is, as shown in FIG. 2, a distance D1 between primary transfer devices 50Y, 50, M, 50C, and 50K (an example of a transfer unit) that are provided for each color and can be shared, and the photosensitive drum 15, and development The distance comparison unit 300 (an example of comparison means) that compares the distance (inter-image length) D2 between the images developed between the devices 17 (image-formable regions) and the comparison result of the distance comparison unit 300 are sensitive. At least one image forming condition of charging voltage of the body drum 15, light quantity of the exposure device 14, voltage of the charger 16, AC voltage waveform of the developing device 17, AC voltage frequency, voltage, current, transfer voltage of the transfer device 25, and current An image forming condition switching unit 400 (an example of a switching unit).

  Note that the image forming conditions may include a change in the distance between images (inter-image length) D2.

  Further, a toner density sensor SE (an example of a detection unit) that detects a density detection pattern formed on the intermediate transfer belt 25 is provided. Accordingly, the image forming condition switching unit 400 may switch the image forming conditions based on the detection result of the toner density sensor SE.

  Further, the image forming conditions are the image forming conditions common to all or part of the plurality of colors for the photosensitive drum 15, the exposure device 14, the charger 16, and the developing device 17 for each color. It may be a premise.

  Further, in the image forming condition switching unit 400, the distance comparison unit 300 determines that the distance D1 between the photosensitive drums 15 is smaller than the distance (inter-image length) D2 between images developed by the developing device 17. In this case, the image forming conditions may be switched between images developed by the developing device 17 (interimage) for at least one of the plurality of colors.

  Further, the image forming condition switching unit 400, when there are a plurality of colors, is an inter-image (interimage) developed by the developing device 17 for a color that is intermediate between the three colors in the arrangement order of the photosensitive drums 15. The image forming conditions may be switched within (long).

  In the image forming condition switching unit 400, the distance between the photosensitive drums 15 in the distance comparison unit 300 is set to be smaller than the distance (interimage length) D2 between images developed by the developing device 17. In this case, the image forming conditions may be switched at a position where the photoconductor drum 15 of any two of the plurality of colors sandwiches an image (interimage) developed by the developing device 17.

  Further, at least one of the plurality of colors or any two of the plurality of colors may include either magenta or cyan.

  Thereby, the density fluctuation | variation by image correction is suppressed.

  Next, an example of the processing procedure of the image forming process executed by the image processing apparatus PR1 having the above configuration will be described with reference to the flowchart of FIG.

  When this processing is started, first, normal image formation is performed in step S10, and it is determined in step S11 whether or not setup (initialization) execution timing is reached.

  If the determination result is “No”, the process proceeds to step S15. If the determination result is “Yes”, the process proceeds to step S12.

  In step S12, an image density pattern is created, and the process proceeds to step S13.

  In step S13, the image density pattern is detected by the toner density sensor SE, and the process proceeds to step S14.

  In step S14, the image forming conditions are calculated, and the process proceeds to step S15.

  In step S15, it is determined whether or not the job is finished. If “No”, the process returns to step S10, and if “Yes”, the process is finished.

  Next, a processing procedure of a subroutine of the image forming condition control process executed by the image processing apparatus PR1 having the above configuration will be described with reference to the flowchart of FIG.

  In step S20, it is determined whether or not the image forming conditions are switched between the inter-images (between the images developed by the developing device 17). If “No”, the process is terminated as it is, and if “Yes”, the processing is terminated. The process proceeds to step S21.

  In step S21, it is determined whether the image forming apparatus PR1 is in a high image quality mode. If “No”, the process proceeds to step S22, and the inter image length is set to normal, and the process proceeds to step S23.

  On the other hand, if “Yes” is determined in step S21, the process proceeds to step S24, the inter-image length is increased, and the process proceeds to step S23.

  In step S23, the image forming conditions are switched and the process is terminated.

  Here, an example of switching image forming conditions will be described with reference to FIG. 5 to FIG. 11, but prior to that, the problems of the prior art as a comparison target will be briefly described.

  For example, in a conventional image forming apparatus, when performing density correction after the initialization process, if the correction is performed once, the density fluctuation of the output image before and after correction becomes conspicuous, so the density gradually increases over a plurality of pages. It was necessary to make corrections.

  Here, it is desirable to switch the image forming conditions of all colors with the inter image length. However, in order to reduce the cost, in the image forming apparatus using the common image forming conditions, the inter image length is the maximum of the engine using the common power source. Unless the distance between the upstream and the most downstream engines is greater than that, the image forming conditions must be switched in the middle of the image forming area.

  Therefore, in the image forming apparatus PR1 according to the present invention, when the common image forming conditions are used, when switching the image forming conditions, the switching timing is set so that the change in density of the switching is less noticeable. did.

  First, with reference to FIG. 5, an example in which the image forming conditions are switched within the inter image length will be described.

  Note that the example of FIG. 5 is a case where common image forming conditions are used for YMCK.

  For yellow (Y), the density variation is relatively inconspicuous even if the image forming conditions are switched in the image areas G1 and G2.

  For magenta (M) or cyan (C), the density fluctuation is easily noticeable when the image forming conditions in the image regions G1 and G2 are switched. Therefore, the image is in the inter-image IM or the image has a low probability. The image forming conditions are switched at the leading edge and trailing edge of.

  In the example shown in FIG. 5A, the magenta (M) image forming conditions are switched at the leading edge of the image G2.

  In the example shown in FIG. 5B, the cyan (C) image forming conditions are switched at the rear end of the image area G1.

  On the other hand, black (K) is often used in a single color, and density fluctuations are relatively inconspicuous even when the image forming conditions are switched in the image areas G1 and G2.

  When the common image forming conditions are used for YMC, the rest is the same except that black (K) is not taken into consideration for the above-described contents.

  FIG. 6 shows an example of a timing chart when the image forming conditions are switched in the inter image when the YMC color development bias is common.

  In the example shown in FIG. 6, for magenta (M), the image forming conditions are switched in the inter image, and for cyan (C), the image forming conditions are switched at the rear end of the image.

  The example shown in FIG. 7A is a case where a common image forming condition is used for MYC, and the position of yellow (Y) is intermediate between cyan (C) and magenta (M). The yellow (Y) image forming conditions are switched near the center of the areas G1 and G2.

  The example shown in (b) of FIG. 7 is a case where a common image forming condition is used for MYC, and the position of yellow (Y) is intermediate between cyan (C) and magenta (M). The switching position from the front end of G1 is made shorter than the switching position from the rear end of the image G1. This is because there is less probability that the user's image is at the rear end of the image.

  The example shown in FIG. 8 is a case where YM uses common image forming conditions and CK uses common image forming conditions.

  In this case, for yellow (Y), even if the image forming condition is switched within the image region, the density variation is relatively inconspicuous, and the image forming condition is switched at the leading edge of the image G2 with a low probability of having an image.

  Further, for magenta (M) and cyan (C), since the density fluctuation is relatively conspicuous when the image forming conditions in the image area are switched, the image forming conditions are switched in the inter image IM.

  On the other hand, black (K) is often used in a single color, and even if the image forming conditions are switched within the image area, density fluctuation is relatively inconspicuous, and image formation is performed at the rear end of the image G1 with a low probability of having an image. The condition is switched.

  Next, an example in which the image forming conditions are switched outside the inter image will be described with reference to FIG.

  Note that the example of FIG. 9 is a case where common image forming conditions are used for YMCK.

  For yellow (Y), the density variation is relatively inconspicuous even if the image forming conditions are switched within the image area.

  Further, for magenta (M) and cyan (C), density change is conspicuous when the image forming conditions are switched in the image area. Therefore, magenta (M) and cyan (M) The cyan (C) image forming conditions are switched.

  In the example shown in FIG. 9, the inter image IM is sandwiched between cyan (C) and magenta (M), the image forming condition of cyan (C) is switched at the rear end of the image G1, and magenta (M) is changed at the front end of the image G2. The image forming conditions are switched.

  On the other hand, black (K) is often used in a single color, and density fluctuations are relatively inconspicuous even when the image forming conditions are switched within the image area.

  When the common image forming conditions are used for YMC, the rest is the same except that black (K) is not taken into consideration for the above-described contents.

  FIG. 10 shows an example of a timing chart when the image forming conditions are switched outside the inter image when the YMC color development bias is common.

  In the example shown in FIG. 10, for magenta (M), the image forming conditions are switched at the leading edge of the image, and for cyan (C), the image forming conditions are switched at the trailing edge of the image.

  The example shown in FIG. 11 is a case where YM uses common image forming conditions and CK uses common image forming conditions.

  For yellow (Y), even if the image forming conditions are switched within the image region, the density variation is relatively inconspicuous, and the image forming conditions are switched at the rear end of the image G1 with a low probability of having an image.

  Further, for magenta (M) and cyan (C), density change is conspicuous when the image forming conditions are switched in the image region, so the image forming conditions are switched in the vicinity of the inter image IM.

  Note that black (K) is often used in a single color, and even if the image forming condition is switched within the image area, the density variation is relatively inconspicuous, and the image forming condition is low at the leading edge of the image G2 with a low probability of having an image. Is switched.

  It should be noted that the image forming conditions may be corrected by prediction based on photoreceptor deterioration, temperature / humidity change, developer deterioration, remaining toner amount, image density, and the like.

  Further, the image forming conditions may be corrected based on the detection result of the potential sensor or the image density sensor.

  As described above, according to the image forming apparatus PR1 according to the present embodiment, even when the inter-image length is shorter than the inter-engine distance, continuous output is performed so that density fluctuations in the image forming area are not noticeable. The image forming conditions are changed.

  Although the invention made by the present inventor has been specifically described based on the embodiments, the embodiments disclosed herein are illustrative in all respects and are not limited to the disclosed technology. Should not be considered. That is, the technical scope of the present invention should not be construed restrictively based on the description in the above embodiment, but should be construed according to the description of the scope of claims. All modifications that fall within the scope of the claims and the equivalent technology are included.

  When using a program, it can be provided via a network or stored in a recording medium such as a CD-ROM.

  That is, the predetermined program including the image processing program is not limited to being recorded in a storage device such as a hard disk as a recording medium, and the predetermined program can be provided as follows.

  For example, a predetermined program may be stored in the ROM, and the CPU may load the predetermined program from the ROM to the main storage device and execute it.

  The predetermined program may be stored in a computer-readable recording medium such as a DVD-ROM, a CD-ROM, an MO (magneto-optical disk), a flexible disk, and distributed.

  Further, the image forming apparatus or the like is connected to a server apparatus or a host computer via a communication line (for example, the Internet), and after the predetermined program is downloaded from the server apparatus or the host computer, the predetermined program is executed. You may do it. In this case, examples of the download destination of the predetermined program include a memory such as a RAM and a storage device (recording medium) such as a hard disk.

  The image forming apparatus and the processing program according to the present invention can be applied to a color printer, a multifunction machine, and the like.

PR1 Image forming apparatus 3 Platen cover 4 Image reading apparatus 5 Platen glass 6 Light source 7 Full rate mirror 8 Half rate mirror 10 Imaging lens 11 Image reading element 12 Image forming apparatus 13 Image forming unit 14 Exposure apparatus 15 Photosensitive drum 16 Charger 17 Developing device 18 Cleaning device 19 Semiconductor laser 20 Reflecting mirror 22 Rotating polygon mirror 23 Reflecting mirror 25 Intermediate transfer belt 26 Primary transfer roll 27 Belt drive roll 28 Stripping roll 29 Steering roll 30 Idle roll 31 Backup roll 32 Idle roll 33 Next transfer roll 34 recording paper 35 transport belt 37 fixing device 38 discharge tray 39 paper feed tray 42 paper feed roller 43 roller pair 46 paper transport path 47 registration roll 48 belt cleaner 200 common power source Device 201 Electric circuit 300 Distance comparison unit 400 Image formation condition switching unit SE Toner density sensor G1, G2 Image IM Inter image

Claims (4)

A plurality of electrostatic latent image holding means provided corresponding to a plurality of colors and holding an electrostatic latent image formed based on image information;
An exposure unit that is provided corresponding to the plurality of electrostatic latent image holding units, and that exposes each electrostatic latent image holding unit;
A plurality of charging means provided corresponding to the plurality of electrostatic latent image holding means and charging each electrostatic latent image holding means;
A plurality of developing means provided corresponding to the plurality of electrostatic latent image holding means, and developing the electrostatic latent image formed on the surface of each electrostatic latent image holding means as an image using a developer;
A plurality of transfer means for transferring the image;
A power supply unit that shares at least a part of a power supply circuit that supplies a voltage to the charging unit or the plurality of developing units or the plurality of transfer units;
The relationship between the distance between the electrostatic latent image holding means and the distance between the images developed by the developing means is the distance between the electrostatic latent image holding means developed by the developing means. When the distance is smaller than the distance between images , at least one image forming condition of the electrostatic latent image holding unit, the exposing unit, the charging unit, the developing unit, and the transferring unit is changed from the first image forming condition to the second image forming condition. Switching means for switching to image forming conditions ,
The switching means is
In the case where the plurality of common colors are three colors, the image in the middle of the three colors in the arrangement order of the electrostatic latent image holding means is between the images developed by the developing means. Switching the forming conditions,
An image forming apparatus. A plurality of electrostatic latent image holding means provided corresponding to a plurality of colors and holding an electrostatic latent image formed based on image information;
An exposure unit that is provided corresponding to the plurality of electrostatic latent image holding units, and that exposes each electrostatic latent image holding unit;
A plurality of charging means provided corresponding to the plurality of electrostatic latent image holding means and charging each electrostatic latent image holding means;
A plurality of developing means provided corresponding to the plurality of electrostatic latent image holding means, and developing the electrostatic latent image formed on the surface of each electrostatic latent image holding means as an image using a developer;
A plurality of transfer means for transferring the image;
A power supply unit that shares at least a part of a power supply circuit that supplies a voltage to the charging unit or the plurality of developing units or the plurality of transfer units;
The relationship between the distance between the electrostatic latent image holding means and the distance between the images developed by the developing means is the distance between the electrostatic latent image holding means developed by the developing means. When the distance is smaller than the distance between images, at least one image forming condition of the electrostatic latent image holding unit, the exposing unit, the charging unit, the developing unit, and the transferring unit is changed from the first image forming condition to the second image forming condition. Switching means for switching to image forming conditions,
The switching means is
Switching the image forming conditions at the leading edge of the image developed by the developing means;
An image forming apparatus. The image forming conditions are such that the electrostatic latent image holding unit, the exposure unit, the charging unit, the developing unit, and the transfer unit relating to each color are shared by all or part of the plurality of colors. the image forming apparatus according to claim 1 or claim 2 characterized in that it is a condition. It further comprises detection means for detecting a density detection pattern formed on the transfer means,
The switching means is
4. The image forming apparatus according to claim 1, wherein the image forming condition is switched based on a detection result of the detecting unit.

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