JP2005208090A - Image forming apparatus, toner counter, and toner consumption quantity calculation method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a technology capable of precisely obtaining the quantity of toner consumed in an image forming apparatus. <P>SOLUTION: Based upon video signals transmitted to an image forming means, dots to be formed are classified into five stages (<1U, <1.5U, <1.75U, <4.5U, and >4.5U; wherein 1U is the length of unit dot) according to the sizes of the dots. Dot length are integrated for each stage. Next, they are multiplied by correction coefficients k1 to k5 set according to the corresponding stages, and then they are added. Subsequently, thus obtained result is multiplied by a standard rate KO at which toner is attached. Thereby, a quantity of toner consumed for the formation of the dots is calculated. An offset value Coff, corresponding to a quantity of toner consumed for actions other than the formation of the dots, is added to the quantity calculated above. Thus, the total quantity TC of toner consumed in the apparatus is obtained. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a technique for calculating toner consumption in an image forming apparatus.

  In an electrophotographic image forming apparatus that uses toner to form an image, such as a printer, a copying machine, or a facsimile machine, it is necessary to grasp the amount of toner consumed or the remaining amount for the convenience of maintenance such as toner replenishment. Therefore, a technique for accurately obtaining the toner consumption amount (hereinafter referred to as “toner counting technique”) has been proposed. For example, in the toner consumption detection method described in Japanese Patent Application Laid-Open No. H10-228707, a print dot row is set as an isolated dot, two continuous dots, and an intermediate dot in consideration of a non-linear relationship between dot continuity and toner consumption. It classifies into three patterns of value dots, counts the number of each occurrence, and calculates the toner consumption based on the counted value.

JP 2002-174929 A (FIG. 3)

  In recent years, it is desired to use the toner filled in the apparatus as effectively as possible without wasting it, to accurately grasp when the toner is exhausted, and to prevent image quality deterioration due to insufficient toner remaining. The demand is getting stronger. Therefore, in this type of image forming apparatus, further improvement in the accuracy of the toner counting technique is required.

  However, in the above-described prior art, the unit of counting is “number of printing dots”, and the toner adhesion amount for each print dot is detailed, such as calculating the toner adhesion amount uniformly for intermediate value dots. There was no consideration. As a result, there has been a case where it is not possible to sufficiently meet such a demand for higher accuracy.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide a technique capable of accurately obtaining a toner consumption amount in an image forming apparatus.

  It has been conventionally known that the relationship between the continuity of the dots constituting the toner image and the toner consumption is nonlinear, but quantitative analysis and establishment of a high-accuracy toner counting technique based on the quantitative analysis have been made so far. It was not reached. Accordingly, the inventor of the present application, in an image forming apparatus that visualizes an electrostatic latent image with toner, determines the size of a dot portion (region to which toner should be attached) on the electrostatic latent image and the toner attached to the dot portion. Quantitative relationship between the amount of and was investigated.

  As a result, the correlation between the value obtained by dividing the total amount of toner adhering to one dot part by the area of the dot part (hereinafter referred to as “toner adhesion rate”) and the size of the dot part was clarified. That is, the toner adhesion rate becomes the largest when the dot portion has a specific size. The toner adhesion rate becomes lower at smaller dot portions, while the toner adhesion rate approaches a substantially constant value at larger dot portions. Thus, the phenomenon that the toner adhesion rate varies depending on the size of the dot portion is considered to be mainly caused by the edge effect caused by the potential distribution in the electrostatic latent image. That is, there is a tendency that more toner adheres to the peripheral portion of the dot portion than the central portion due to the edge effect. Then, in the dot portion of a specific size, the edge effect in each peripheral portion acts synergistically, and in particular, the toner adhesion amount increases. Further, it has been clarified that the relationship between the size of the dot portion and the amount of toner attached to the dot portion is determined by the configuration and operating conditions of the apparatus and has high reproducibility.

  Therefore, a relationship between the size of the dot portion to be visualized and the amount of toner adhering to the dot portion of that size (hereinafter referred to as “toner adhesion property”) is obtained in advance, and the thus obtained toner adhesion property is taken into consideration. Thus, by obtaining the toner consumption amount, it is possible to accurately count the toner.

  In view of the above knowledge, in order to achieve the above object, an image forming apparatus according to the present invention visualizes an electrostatic latent image with toner to form a toner image, and toner consumption by the image forming means A toner consumption amount calculating means for calculating the toner consumption amount calculating means, wherein the toner consumption amount calculating means determines the amount of toner consumed to visualize the dot portion to which the toner is to be adhered in the electrostatic latent image. It is characterized in that it is obtained on the basis of the size of the part and the toner adhesion characteristic obtained in advance for each size of the dot part as the characteristic indicating the toner adhesion amount corresponding to the size of the dot part.

  A toner counter according to the present invention is a toner counter used in an image forming apparatus for forming a toner image by developing an electrostatic latent image with toner. The amount of toner consumed to visualize the dot portion to which the toner is to be attached is obtained in advance for each dot portion size as a characteristic representing the size of the dot portion and the toner attachment amount corresponding to the dot portion size. It is characterized in that it is determined based on the toner adhesion characteristics.

  Further, the toner consumption calculation method according to the present invention is a toner consumption calculation method in an image forming apparatus for forming a toner image by developing an electrostatic latent image with toner. In the latent image, the amount of toner consumed to visualize the dot portion to which the toner is to be attached is expressed as the size of the dot portion and the dot portion size as a characteristic indicating the amount of toner adhesion corresponding to the size of the dot portion. It is characterized in that it is obtained on the basis of the toner adhesion characteristics obtained in advance.

  In these inventions, the toner adhesion characteristics for each size of the dot portion are obtained in advance. Therefore, if the size of the dot portion to be visualized is known, the toner adhesion amount to the dot portion can be determined from the toner adhesion characteristics. As described above, in these inventions, since the toner consumption amount is obtained in consideration of the toner adhesion characteristic obtained in advance according to the size of the dot portion, it is possible to obtain the toner consumption amount with high accuracy.

  In the prior art described in Patent Document 1 described above, the relationship between the continuity between adjacent dots and the toner adhesion amount is considered, but the size of each dot is not fully considered. . Therefore, there remains room for improvement in terms of calculation accuracy.

  As a specific method for obtaining the toner consumption amount, for example, the amount of toner consumed for visualizing the dot portion, the dot information value regarding the size of the dot portion, the dot information value, and the toner It can be calculated by multiplying by a coefficient set based on the adhesion characteristics. That is, even if the size of the dot portion is not directly determined, the size of the dot portion to be formed is indirectly determined from the value of the dot information. Therefore, the product of the value and the proportional coefficient set based on the toner adhesion characteristics. Thus, it is possible to accurately represent the toner consumption amount for the dot portion.

  According to another aspect of the image forming apparatus of the present invention, in order to achieve the above object, an image forming unit that visualizes an electrostatic latent image with toner to form a toner image, and the electrostatic latent image A toner consumption amount calculating means for calculating a toner consumption amount by the image forming means based on dot information relating to the size of the dot portion to which the toner is to be attached, wherein the toner consumption amount calculating means visualizes each dot portion. The amount of toner consumed for conversion is calculated by multiplying the value of dot information corresponding to the dot portion by a predetermined coefficient, and the coefficient is calculated based on the size of the dot portion determined in advance and the dot portion. Based on the relationship with the toner adhesion amount, it is set according to the dot information.

  According to another aspect of the present invention, there is provided a toner consumption calculation method for achieving the above object in a toner consumption calculation method in an image forming apparatus that visualizes an electrostatic latent image with toner to form a toner image. The coefficient based on the relationship between the size of the dot portion obtained in advance and the amount of toner attached to the dot portion according to the value of the dot information related to the size of the dot portion to which the toner is to be attached in the electrostatic latent image. The amount of toner consumed to set and visualize each dot portion is calculated by multiplying the value of dot information corresponding to the dot portion by the coefficient corresponding to the dot portion. .

  In these inventions as well, by calculating the product of the value of dot information that indirectly indicates the size of the dot portion to be visualized and the coefficient set based on the toner adhesion characteristic obtained in advance, The toner consumption amount for the dot portion can be obtained with high accuracy.

  Further, each of the image forming apparatuses described above may be configured as follows. For example, the image forming means includes: a latent image carrier whose surface is formed by a photosensitive member and capable of carrying the electrostatic latent image; and an exposure unit that irradiates a light beam toward the surface of the latent image carrier. And the electrostatic latent image may be formed on the surface of the latent image carrier by scanning and exposing a region corresponding to the dot portion of the surface of the latent image carrier with a light beam. In the apparatus configured as described above, the size of the dot portion formed during the time of scanning the surface of the latent image carrier while continuously irradiating the light beam, more specifically, the length in the scanning direction is determined. Therefore, the toner consumption amount corresponding to the size of the dot portion can be obtained by setting the irradiation time of the light beam applied to the latent image carrier from the exposure means to visualize the dot portion as the dot information. Can be sought.

  Further, for example, a signal processing unit that performs signal processing on the image signal to generate a multi-value signal related to a dot portion to be formed and output the signal to the image forming unit may be further provided. In the apparatus configured as described above, the size of the dot portion to be formed is determined according to the value of the multilevel signal given to the image forming means. Therefore, by using the multilevel signal corresponding to the dot portion as the dot information, it is possible to obtain the toner consumption amount corresponding to the size of the dot portion.

  Further, in this type of image forming apparatus, the image forming unit is disposed so as to face a latent image carrier capable of carrying an electrostatic latent image with a predetermined gap from the latent image carrier, and a toner is formed on the surface. And a toner carrier that carries the toner image, and the toner image is formed by moving the toner from the toner carrier to the latent image carrier. In the apparatus having such a configuration, the toner carrier and the latent image carrier are separated from each other, and as a result, a local difference in toner adhesion due to the edge effect is likely to occur. Therefore, in such an apparatus, the nonlinearity between the size of the dot portion and the toner adhesion amount is large. Therefore, by obtaining the toner consumption amount in consideration of the toner adhesion characteristics as described above, it is possible to obtain the toner consumption amount with high accuracy even in such an apparatus.

  Further, for each of the plurality of dot portions, the toner consumption amount for each of the plurality of dot portions can be obtained by calculating the toner consumption amount for each dot portion as described above. That is, it is possible to calculate the toner consumption amount during the period by integrating the toner consumption amount for each dot portion visualized within the predetermined period. Further, by adding an offset value according to the usage status of the apparatus, for example, a value considering the amount of toner consumed in addition to the visualization of the dot portion, to the integrated value, the toner within the period in the apparatus The consumption can be calculated more accurately.

  By the way, although the size of the dot portion can take various values depending on the toner image to be formed, if the toner adhesion amount corresponding to the size is stored and used for the toner consumption calculation for all sizes, the information to be stored The amount is enormous and the processing is complicated. However, according to experiments by the inventors of the present application, the size of the dot portion is divided into several stages according to the size, and sufficient accuracy can be obtained even if the coefficient corresponding to the toner adhesion property is the same value in each division. It was confirmed that

  That is, as a specific and simple calculation method of the toner consumption amount calculation method, for example, the value of dot information is divided into a plurality of stages according to the size in advance, and the coefficient is set for each division. The dot information is divided on the basis of the division, and the value of the dot information divided into the same division is integrated for each division, and for each division, the integrated value for the division and the corresponding division By calculating a product with the set coefficient and summing the products, the total amount of toner consumed for visualization of the plurality of dot portions corresponding to the plurality of dot information can be calculated.

  According to this calculation method, it is possible to obtain the toner consumption amount with a relatively simple process and with high accuracy. However, in providing each section, a relatively fine section is provided in a region where the change in the toner adhesion amount with respect to the size of the dot portion is large, while a relatively coarse section is provided in a region where the change in the toner attachment amount with respect to the size of the dot portion is small. Thus, it is necessary to appropriately carry out in consideration of actual toner adhesion characteristics.

  Also in this calculation method, the toner consumption of the entire apparatus including the amount of toner consumed in addition to the visualization of the dot portion is obtained by adding the offset value according to the usage status of the apparatus to the above total value. It is possible to determine the quantity.

  FIG. 1 is a diagram showing the configuration of an embodiment of an image forming apparatus according to the present invention. FIG. 2 is a block diagram showing an electrical configuration of the image forming apparatus of FIG. This apparatus 1 forms a full color image by superposing four color toners (developers) of yellow (Y), cyan (C), magenta (M), and black (K), or black (K) toner. This is an image forming apparatus that forms a monochrome image using only the image forming apparatus. In the image forming apparatus 1, when an image signal is given to the main controller 11 from an external device such as a host computer, the engine controller 10 controls each part of the engine unit EG in accordance with a command from the main controller 11 to obtain a predetermined image. The forming operation is executed, and an image corresponding to the image signal is formed on the sheet S.

  In the engine unit EG, the photosensitive member 22 is provided to be rotatable in the arrow direction D1 in FIG. A charging unit 23, a rotary developing unit 4 and a cleaning unit 25 are arranged around the photosensitive member 22 along the rotation direction D1. The charging unit 23 is applied with a predetermined charging bias, and uniformly charges the outer peripheral surface of the photoconductor 22 to a predetermined surface potential. The cleaning unit 25 removes the toner remaining on the surface of the photosensitive member 22 after the primary transfer, and collects it in a waste toner tank provided inside. The photosensitive member 22, the charging unit 23, and the cleaning unit 25 integrally constitute the photosensitive member cartridge 2, and this photosensitive member cartridge 2 is detachably attached to the main body of the apparatus 1 as a whole.

  Then, the light beam L is irradiated from the exposure unit 6 toward the outer peripheral surface of the photosensitive member 22 charged by the charging unit 23. The exposure unit 6 exposes the light beam L onto the photosensitive member 22 in accordance with an image signal given from an external device, and forms an electrostatic latent image corresponding to the image signal.

  The electrostatic latent image thus formed is developed with toner by the developing unit 4. That is, in this embodiment, the developing unit 4 is configured as a support frame 40 that is rotatably provided about a rotation axis center orthogonal to the paper surface of FIG. A yellow developing device 4Y, a cyan developing device 4C, a magenta developing device 4M, and a black developing device 4K are provided. The developing unit 4 is controlled by the engine controller 10. Based on the control command from the engine controller 10, the developing unit 4 is driven to rotate, and the developing units 4Y, 4C, 4M, and 4K selectively face the photoconductor 22 with a predetermined gap therebetween. When positioned at a predetermined development position, the toner is applied to the surface of the photosensitive member 22 from a metal developing roller 44 that is provided in the developing unit and carries a charged toner of a selected color and is applied with a predetermined development bias. Is granted. As a result, the electrostatic latent image on the photosensitive member 22 is visualized with the selected toner color. In this embodiment, it is assumed that the toner is negatively charged.

  Each of the developing devices 4Y, 4C, 4M, and 4K is provided with non-volatile memories 91 to 94 for storing information related to the developing devices. One of the connectors 49Y, 49C, 49M, and 49K provided in each developing device is selected as necessary, and the connector 109 provided on the main body side is connected to each other, and the CPU 101 of the engine controller 10 and the memory Communication is performed with 91-94. In this way, information about each developing device is transmitted to the CPU 101, and information in each of the memories 91 to 94 is updated and stored.

  The toner image developed by the developing unit 4 as described above is primarily transferred onto the intermediate transfer belt 71 of the transfer unit 7 in the primary transfer region TR1. The transfer unit 7 includes an intermediate transfer belt 71 stretched between a plurality of rollers 72 to 75, and a drive unit (not shown) that rotates the intermediate transfer belt 71 in a predetermined rotation direction D2 by rotationally driving the roller 73. It has. When a color image is transferred to the sheet S, each color toner image formed on the photosensitive member 22 is superimposed on the intermediate transfer belt 71 to form a color image and taken out from the cassette 8 one by one. The color image is secondarily transferred onto the sheet S conveyed to the secondary transfer region TR2 along the conveyance path F.

  At this time, in order to correctly transfer the image on the intermediate transfer belt 71 to a predetermined position on the sheet S, the timing of feeding the sheet S to the secondary transfer region TR2 is managed. Specifically, a gate roller 81 is provided on the transport path F on the front side of the secondary transfer region TR2, and the gate roller 81 rotates in accordance with the timing of the circumferential movement of the intermediate transfer belt 71. S is sent to the secondary transfer region TR2 at a predetermined timing.

  Further, the sheet S on which the color image is thus formed is conveyed to the discharge tray portion 89 provided on the upper surface portion of the apparatus main body via the fixing unit 9, the pre-discharge roller 82 and the discharge roller 83. Further, when images are formed on both sides of the sheet S, when the rear end portion of the sheet S on which the image is formed on one side as described above is conveyed to the reversal position PR behind the pre-discharge roller 82. The rotation direction of the discharge roller 83 is reversed, whereby the sheet S is conveyed in the direction of the arrow D3 along the reverse conveyance path FR. Then, the sheet is again placed on the transport path F before the gate roller 81. At this time, the surface of the sheet S to which the image is transferred by contacting the intermediate transfer belt 71 in the secondary transfer region TR2 is first transferred. It is the opposite surface. In this way, images can be formed on both sides of the sheet S.

  Further, a density sensor 60 and a cleaner 76 are provided in the vicinity of the roller 75. The density sensor 60 optically detects the amount of toner constituting the toner image formed on the intermediate transfer belt 71 as necessary. That is, the density sensor 60 irradiates light toward the toner image, receives reflected light from the toner image, and outputs a signal corresponding to the reflected light amount. The cleaner 76 is configured to be able to come into contact with and separate from the intermediate transfer belt 71, and scrapes the residual toner on the belt 71 by contacting the intermediate transfer belt 71 as necessary.

  In addition, the apparatus 1 includes a display unit 12 controlled by the CPU 111 of the main controller 11 as shown in FIG. The display unit 12 is constituted by, for example, a liquid crystal display, and in accordance with a control command from the CPU 111, the operation guidance to the user, the progress of the image forming operation, the occurrence of an abnormality in the apparatus, the replacement timing of any unit, etc. A predetermined message for notification is displayed.

  In FIG. 2, reference numeral 113 denotes an image memory provided in the main controller 11 for storing an image given from an external device such as a host computer via the interface 112. Reference numeral 106 is a ROM for storing a calculation program executed by the CPU 101, control data for controlling the engine unit EG, and the like. Reference numeral 107 is a RAM for temporarily storing calculation results in the CPU 101 and other data. is there.

  FIG. 3 is a diagram showing signal processing blocks in this apparatus. In this image forming apparatus, when an image signal is input from an external device such as the host computer 100, the main controller 11 performs predetermined signal processing on the image signal. The main controller 11 includes functional blocks such as a color conversion unit 114, a gradation correction unit 115, a halftoning unit 116, a pulse modulation unit 117, a gradation correction table 118, and a correction table calculation unit 119.

  In addition to the CPU 101, ROM 106, and RAM 107 shown in FIG. 2, the engine controller 10 includes a laser driver 121 for driving a laser light source provided in the exposure unit 6 and a detection result of the engine unit EG based on the detection result of the density sensor 60. A gradation characteristic detecting unit 123 that detects a gradation characteristic indicating a gamma characteristic is provided.

  In the main controller 11 and the engine controller 10, these functional blocks may be configured by hardware, or may be realized by software executed by the CPUs 111 and 101.

  In the main controller 11 to which the image signal is given from the host computer 100, the color conversion unit 114 converts the RGB gradation data indicating the gradation level of the RGB component of each pixel in the image corresponding to the image signal into the corresponding CMYK. Conversion into CMYK gradation data indicating the gradation level of the component. In this color conversion unit 114, the input RGB gradation data is, for example, 8 bits per pixel per color component (that is, representing 256 gradations), and the output CMYK gradation data is similarly 8 bits per pixel per color component ( That is, it represents 256 gradations). The CMYK gradation data output from the color conversion unit 114 is input to the gradation correction unit 115.

  The gradation correction unit 115 performs gradation correction on the CMYK gradation data of each pixel input from the color conversion unit 114. That is, the gradation correction unit 115 refers to the gradation correction table 118 registered in advance in the nonvolatile memory, and in accordance with the gradation correction table 118, the input CMYK gradation data of each pixel from the color conversion unit 114. Is converted into corrected CMYK gradation data indicating the corrected gradation level. The purpose of the gradation correction is to compensate for the change in the gamma characteristic of the engine unit EG configured as described above, and to keep the overall gamma characteristic of the image forming apparatus always ideal.

  The corrected CMYK gradation data corrected in this way is input to the halftoning unit 116. The halftoning unit 116 performs halftoning processing such as an error diffusion method, a dither method, and a screen method, and inputs halftone CMYK gradation data of 8 bits per pixel to the pulse modulation unit 117. The content of the halftoning process varies depending on the type of image to be formed. That is, based on a determination criterion such as whether the image is a monochrome image, a color image, a line drawing, or a graphic image, the optimum processing content for the image is selected and executed.

  The CMYK gradation data after halftoning input to the pulse modulation unit 117 is a multilevel signal indicating the size and arrangement of toner dots of CMYK colors to be attached to each pixel. The unit 117 uses the halftone CMYK gradation data to create a video signal for pulse width modulating the exposure laser pulses of the CMYK color images of the engine unit EG, and the engine controller via a video interface (not shown) 10 is output. Upon receiving this video signal, the laser driver 121 controls ON / OFF of the semiconductor laser of the exposure unit 6 to form an electrostatic latent image of each color component on the photosensitive member 22. In this way, image formation corresponding to the image signal is performed.

  Further, in this type of image forming apparatus, the gamma characteristic of the apparatus changes for each apparatus and also in the same apparatus depending on the use situation. Therefore, in order to eliminate the influence of the variation in gamma characteristics on the image quality, a gradation control process is executed to update the contents of the gradation correction table 118 based on the actual measurement result of the image density at a predetermined timing. To do.

  In this gradation control process, for each toner color, a gradation patch gradation image prepared in advance for measuring the gamma characteristic is formed on the intermediate transfer belt 71 by the engine unit EG, and each gradation patch is obtained. The density sensor 60 reads the image density of the image, and the gradation characteristic detecting unit 123 based on the signal from the density sensor 60 determines the gradation characteristic (corresponding to the gradation level of each gradation patch image and the detected image density). The gamma characteristics of the engine unit EG are created and output to the correction table calculation unit 119 of the main controller 11. Then, the correction table calculation unit 119 compensates the actually measured gradation characteristic of the engine unit EG based on the gradation characteristic given from the gradation characteristic detection unit 123 to obtain an ideal gradation characteristic. The tone correction table data is calculated, and the content of the tone correction table 118 is updated to the calculation result. Thus, the gradation correction table 118 is changed and set. By doing so, this image forming apparatus can form an image with stable quality regardless of variations in gamma characteristics of the apparatus and changes over time.

  Next, a method for calculating the amount of toner stored in each developing device 4Y and the like consumed by image formation in this image forming apparatus will be described. The toner image is composed of a large number of toner dots, and the total amount of toner consumed is obtained by obtaining the total amount of toner consumed for forming each toner dot. In this image forming apparatus, in order to obtain the toner consumption amount, a toner counter 220 for calculating the toner consumption amount based on a video signal given from the main controller 11 to the engine controller 10 is provided in the engine controller 10 as shown in FIG. Is provided.

  As described in detail below, in this type of image forming apparatus, there is a non-linear relationship between the dot size and the toner adhesion amount, and the toner consumption amount can be accurately obtained simply by integrating the dot size or the number of dots. I can't. The inventor of the present application pays attention to the phenomenon (edge effect) in which high-density toner adheres locally at the edge of the toner dot, and introduces a toner consumption calculation method that considers the effect, thereby reducing the toner consumption amount. It was found that it can be obtained with high accuracy.

  FIG. 4 is a diagram for explaining a change in toner density due to the edge effect. As shown in FIG. 4A, the photoconductor 22 includes a cylindrical base 22a and a surface layer 22b made of a photosensitive material formed on the surface thereof. On the surface of the photosensitive member 22 carrying the electrostatic latent image, the surface potential is different between the image part IM to which the toner is to be attached and the non-image part NI to which the toner is not attached. That is, the surface of the photoreceptor 22 is charged to a substantially uniform surface potential by the charging unit 3 (FIG. 1), and the light beam L from the exposure unit 6 (FIG. 1) is scanned and exposed only to the image portion IM. As a result, an electrostatic latent image is formed. As a result, the surface potential of the non-image portion NI is maintained at a non-image portion potential Vni that is substantially close to the original surface potential, while the surface potential of the image portion IM is an image portion potential Vim that is closer to zero. . For this reason, a locally strong electric field Ee is generated in the vicinity of the boundary between the image part IM and the non-image part NI as shown in FIG.

  As shown in FIG. 4C, a developing roller 44 carrying a negatively charged toner and applied with a developing bias voltage having an average value Vdc is disposed opposite to the photosensitive member 22 with a gap G therebetween. Think. Due to the surface potential of the photosensitive member 22 and the developing bias applied to the developing roller 44, an electric field Eg indicated by a dotted arrow in FIG. Due to the action of the electric field Eg, among the toner T carried on the surface of the developing roller 44, the toner carried in the region facing the image portion IM of the photosensitive member 22 moves to the photosensitive member 22 (solid line arrow), while the photosensitive member 22 The toner in the region facing the non-image part NI of the body 22 remains on the developing roller 44. However, the toner in the region facing the vicinity of the boundary between the image portion IM and the non-image portion NI is attracted to the local electric field Ee and adheres to the end portion of the image portion IM. Therefore, the toner adheres at a higher density at the end of the image part IM than at other parts of the image part IM. As described above, an “edge effect” in which the toner adheres at a higher density than other portions appears at the end of the image portion IM.

  FIG. 5 is a diagram showing the relationship between dot size and toner density. By intermittently scanning and exposing the surface of the photoconductor 22 with the light beam L, latent image dots corresponding to an image portion to which toner is to be adhered are formed on the photoconductor 22. The length of the latent image dot in the scanning direction (main scanning direction) of the light beam L becomes longer as the continuous irradiation time of the light beam L is longer. For example, as shown in FIG. 5, when exposure is performed four times with different continuous irradiation times, latent image dots 501 to 504 having a length corresponding to the irradiation time are formed accordingly. In the relatively short latent image dot 501, the potential valley appearing on the surface of the photoconductor 22 is shallow and its width is small, but as the latent image dot becomes longer, the potential valley becomes wider. However, the depth is generally constant.

  When a developing bias voltage having an average value Vdc is applied to the developing roller 44 disposed opposite to the photoreceptor 22 on which the latent image dots are formed in this manner, the potential of each latent image dot depends on the depth and length of the potential. A large amount of toner adheres. In the small latent image dot 501, the potential valley is shallow and the width is small, so that the amount of toner adhering is small. As the latent image dot increases, the toner amount increases. Further, in the long latent image dot 504, the toner density is substantially constant inside, but at the end portion, the toner adheres at a higher density than the central portion due to the edge effect. In the latent image dot 503 having a specific length, the increase in the toner amount due to the edge effect at both ends of the dot acts synergistically, and the toner adheres to the entire dot at a particularly high density.

  As described above, the latent image dots having different sizes not only have different areas, but also the density of toner adhering to the size varies depending on the size. If the toner density is constant, the toner adhesion amount of the entire dot can be obtained by multiplying the dot area by a proportional coefficient corresponding to the toner density. However, since the toner density is actually not constant as described above. In such a method, the toner consumption cannot be obtained accurately. Therefore, it is desirable to obtain and quantify in advance a toner adhesion characteristic indicating the relationship between the dot size and the toner adhesion amount, and obtain the toner consumption amount at the dot in light of the characteristics of the dot size to be formed.

  FIG. 6 is a graph showing an example of toner adhesion characteristics. In FIG. 6, the dot size (here, the length of the latent image dot in the main scanning direction) is taken on the horizontal axis, and the toner adhesion rate for each dot size (the value obtained by dividing the toner adhesion amount of the entire dot by the area of the dot). Is plotted on the vertical axis. As described above, in a region where the dot size is small, a small amount of toner adheres and the toner adhesion rate is low. As the dot size increases, the toner adhesion rate also increases, but becomes maximum at a certain size, and as the dot size becomes larger than that, the toner adhesion rate gradually decreases and gradually approaches a certain value K0. The reason why the toner adhesion rate decreases on the larger dot size side is that the ratio of the dot end portion where the toner density increases due to the edge effect occupies the area of the entire dot decreases.

  In the image forming apparatus of this embodiment, an isolated dot having a gradation level of 100% is defined as a unit dot (corresponding to a unit pixel when halftone reproduction is not performed), and its length is defined as 1U. As shown in FIG. 8, the toner adhesion rate has the maximum dot size of 2U corresponding to about two unit dots.

  Based on the relationship between the dot size thus obtained and the toner adhesion rate (corresponding to the “toner adhesion property”), the toner consumption when each dot is visualized is represented by the dot size and the toner adhesion. It can be obtained as a product of rate. The size of the dots to be formed can be known from the video signal sent from the main controller 11 to the engine controller 10 and determining the continuous irradiation time of the exposure beam L for exposing the photosensitive member 22, so that the toner adhesion rate for each size is preliminarily used as information. If it is stored in the memory, the toner consumption amount for the dot can be obtained.

  However, the dot size can take various values depending on the type of image to be formed and the content of signal processing in the main controller 11. Therefore, if all the toner adhesion rates corresponding to an arbitrary dot size are stored in a table, the amount of information to be stored becomes enormous. Further, in order to obtain the toner consumption amount by referring to the table for each dot, complicated and high-speed processing is required. Therefore, it is practical to reduce the amount of information and simplify the processing by approximating the toner adhesion characteristics to a polygonal line or some function curve or simplifying the table.

  In the toner counter 220 of this embodiment, the size of dots is divided into several sections, and the table is simplified by regarding the toner adhesion rate as constant in each section. Specifically, based on the video signal output from the main controller 11, the dots to be formed are divided into five stages according to their lengths, and the deviation from the standard toner adhesion rate K0 is determined for each division. “Correction coefficient” corresponding to is set. A more specific calculation method using this will be described with reference to FIGS.

  FIG. 7 is a diagram showing correction coefficients for each dot size. As shown in FIG. 7A, the dot size (converted to the unit dot size) is divided into five stages, and correction coefficients k1 to k5 are assigned to the respective sections, whereby the staircase shape shown in FIG. 7B is obtained. A polygonal line is obtained. This polygonal line corresponds to the toner adhesion characteristic curve of FIG. 6 which is normalized by the toner adhesion rate K0 and quantized. Thus, by approximating the toner adhesion characteristics, the amount of information to be tabulated can be greatly reduced. In addition, since the same correction coefficient is applied to all the dots classified into the same category, the lengths of the dots classified into the same category can be simply integrated as will be described later. It will also be easy.

  FIG. 8 is a signal flow showing the configuration of the toner counter. The first to fourth filters 231 to 234 are filters for discriminating each dot indicated by the input video signal according to its length. For example, if the video signal is a PWM signal, the pulse width represents the dot length. Further, the first to fifth counters 241 to 245 are counters that accumulate the dot lengths indicated by the input signals. The video signal input to the toner counter 220 is input to the first filter 231. The first filter 231 outputs the input video signal having a dot length less than 1U to the right first counter 241. If the video signal indicates a dot having a length of 1 U or more, it is output to the second filter 232 below.

  Similarly, the second filter 232, the third filter 233, and the fourth filter 234 output signals having dot lengths of less than 1.5U, 1.75U, and 4.5U, respectively, on the right side of the figure. Further, signals having dot lengths of 1.5 U, 1.75 U, and 4.5 U or more are output in the lower part of the figure. Thereby, each dot represented by the input video signal is classified into one of five stages according to the dot size.

  The first counter 241 that has received the signal from the first filter 231 integrates the dot length indicated by the signal. Therefore, the first counter 241 sequentially accumulates the lengths of the dots that are less than 1 U among the dots to be formed. Similarly, the second to fourth counters 242 to 244 that have received signals from the second to fourth filters 232 to 234 accumulate the dot lengths indicated by the signals, respectively. That is, the second counter 242 has a length of 1 U or more and less than 1.5 U, the third counter 243 has a length of 1.5 U or more and less than 1.75 U, and the fourth counter 244 has a length of 1.75 U or more 4 Integrate each length of dots less than 5U. Further, the fifth counter 245 accumulates the lengths of the dots having a length of 4.5 U or more based on the signal output downward from the fourth filter 234. In this way, each toner dot constituting the toner image is classified into one of the categories according to its length, and its length is integrated.

  When the engine controller 10 issues a command to the toner counter 220 regularly at a predetermined timing, such as every predetermined time or when the number of images formed reaches a predetermined number, the count values d1 to d5 during that period are the counters 241. ˜245 to the computing unit 221. For example, the count value d1 output from the first counter 241 is a value obtained by adding all the lengths of toner dots formed within the period with a length less than 1U.

The arithmetic unit 221 multiplies these count values d1 to d5 by the correction coefficients k1 to k5, respectively. By doing so, the deviation of the toner adhesion rate due to the dot size is compensated. Then, the respective multiplication results are summed together, and the sum is multiplied by the toner adhesion rate K0 and the offset value Coff is added to obtain the final toner consumption amount TC in the period. That is, the toner consumption amount TC is expressed by the following formula:
TC = K0 (k1 · d1 + k2 · d2 + k3 · d3 + k4 · d4 + k5 · d5) + Coff
Is required.

  The offset value Coff is a value corresponding to the amount of toner consumed without contributing to image formation corresponding to a given image signal. Such toner is separated from the developing roller 44 and adheres to the photosensitive member 22 to cause fogging or scatter inside the apparatus, or is consumed inside the apparatus in the control operation for maintaining the performance of the apparatus. Toner etc. Since the amount of toner consumed in this manner is correlated with the operation time of the apparatus, the number of images formed, the operation conditions of the apparatus, and the like, the toner in the period is based on these pieces of information managed by the engine controller 10. The consumption amount is estimated and set as an offset value Coff.

FIG. 9 is a graph showing a calculation result of toner consumption in this embodiment. When various types of different image formation such as a character image and a graphic image are performed, the toner consumption calculation method of this embodiment applies a toner adhesion rate according to the size of each toner dot to be formed. Since the consumption amount is calculated, as shown in FIG. 9A, the calculation result by the toner counter 220 and the measured toner consumption amount are in good agreement (correlation coefficient R ² = 0.9924). ). On the other hand, when the calculation is performed with the toner adhesion rate being constant (corresponding to the case where all of the correction coefficients k1 to k5 are set to 1), as shown in FIG. It could not be said that the values agreed with high accuracy (correlation coefficient R ² = 0.8421). From this result, it was confirmed that the toner consumption amount can be accurately obtained by the toner consumption amount calculation method of the present invention.

  The toner consumption thus obtained is stored in the RAM 107 of the engine controller 10 for each toner color and, if necessary, in the memory 91 such as each developing device 4Y. It can be used for managing the remaining amount of toner of each developing device. When the remaining amount of toner in any of the developing devices becomes low, a message prompting replacement of the developing device is displayed on the display unit 12. In this case, since the toner consumption is accurately obtained, the remaining amount of toner in each developing device can be accurately grasped. As a result, the inconvenience for the user that the developing device cannot be used before the toner is used up or the toner is used up without preparing a new developing device for replacement is solved.

  As described above, in this embodiment, in view of the knowledge that the toner adhesion rate varies depending on the size of toner dots to be formed, the size of each dot to be formed and the toner adhesion characteristics for each dot size quantitatively obtained in advance. Based on the above, toner consumption is calculated. More specifically, the dot size is classified into five levels, and the correction coefficient k1 to k5 different from the standard toner adhesion rate K0 is set for each division, thereby defining the toner adhesion rate for each dot size. To do. Then, the lengths of the dots classified into the respective categories are integrated for each category, the sum is multiplied by the correction coefficient corresponding to the category, and the result is multiplied by the toner adhesion rate K0. The amount of toner consumed to form all dots is obtained.

  By obtaining the toner consumption amount in this way, the toner attachment characteristic having a different toner attachment rate for each dot size is reflected in the calculation, so that the toner consumption amount can be obtained with high accuracy. Further, by adding the toner amount consumed in addition to visualizing the dot portion as an offset value, it is possible to obtain the toner consumption amount of the entire apparatus.

  As described above, in this embodiment, the engine unit EG functions as the “image forming unit” of the present invention. Further, the exposure unit 6, the photosensitive member 22, and the developing roller 44 provided in the engine unit EG function as “exposure unit”, “latent image carrier”, and “toner carrier” of the present invention, respectively. Further, the toner counter 220 is the “toner counter” of the present invention, and also functions as “toner consumption calculation means”. Further, the main controller 11 functions as the “signal processing means” of the present invention.

  In this embodiment, the latent image dots 501 to 504 formed on the photosensitive member 22 correspond to the “dot portion” of the present invention. Further, the video signal output from the main controller 11 corresponds to “dot information” of the present invention, and in the video signal subjected to pulse width modulation, the pulse width indicates the size of each dot.

  The present invention is not limited to the above-described embodiment, and various modifications other than those described above can be made without departing from the spirit of the present invention. For example, in the toner counter 220 of the above embodiment, the toner consumption amount is calculated using the video signal output from the pulse modulation unit 117 of the main controller 11. Any signal including information indicating the size can be used. For example, the continuous consumption time of the exposure beam L may be directly measured, or the toner consumption amount may be obtained using a multi-value signal such as gradation data that is expressed by a numerical value and input to the pulse modulation unit 117. It is possible.

  The image forming apparatus according to the above-described embodiment is a so-called “non-contact developing type” image forming apparatus in which the photosensitive member 22 and the developing roller 44 are disposed to face each other with a gap therebetween. In the non-contact development type apparatus, the toner density non-uniformity is likely to occur due to the edge effect, and in the conventional toner consumption calculation method that does not consider this, an error between the actual toner consumption tends to be large. . Accordingly, the toner consumption calculation method of the present invention has a particularly remarkable effect in such an apparatus. However, in the “contact development system” apparatus in which the photosensitive member 22 and the developing roller 44 are arranged to contact each other. In addition, it is possible to improve the accuracy of toner consumption calculation by applying the present invention.

  Further, the above-described dot size classification is an example, and the present invention is not limited to this. Regardless of which division is set, the dot size is finely divided in an area where the change in the toner adhesion rate with respect to the dot size is relatively large as in this embodiment, while the division is coarsened in an area where the change is small. Thus, it is possible to reduce the amount of information to be stored while maintaining sufficient accuracy.

  In this embodiment, since the dot size is quantified based on the unit dot size, the toner adhesion rate is maximized in the vicinity of the dot length 2U corresponding to two unit dots. Each category of dot size is set. However, the number of dot sizes with the maximum toner adhesion rate converted to unit dots varies depending on the configuration and specifications of the apparatus, and it is needless to say that this classification needs to be appropriately changed according to the specifications of the apparatus. Yes.

  In the above-described embodiment, the dot length is integrated for each section, and the integrated value is multiplied by the correction coefficient. However, the order of calculation is changed, and the length of each dot is multiplied by the correction coefficient. Even if they are integrated, the result is naturally the same.

  In the above embodiment, the toner adhesion rate for each category is expressed by the standard toner adhesion rate K0 and the correction coefficient k1 for each category, and the toner consumption is obtained by multiplying the count value of each counter. However, instead of doing this, a coefficient that directly represents the toner adhesion rate in each section may be determined and multiplied by the count value.

  Further, when further high accuracy is required, as described above, the number of the above-mentioned sections should be increased, or the toner adhesion characteristics should be approximated by a polygonal line or a function curve, and the toner adhesion characteristics expressed in this way should be formed. The toner consumption may be obtained based on the dot size. However, in the case where the toner adhesion characteristics are expressed by a polygonal line or a curve, it is not possible to use a calculation method in which the dot sizes are first integrated and the toner adhesion rate is collectively multiplied as in this embodiment. For each dot, it is necessary to calculate the toner consumption by multiplying the dot size and the toner adhesion rate, and then add the values.

  In addition, although the toner adhesion characteristics vary depending on the configuration of the apparatus, the same characteristics are generally exhibited if the configurations are the same. Therefore, it is not always necessary to obtain the toner adhesion characteristics for each apparatus in the same configuration apparatus, and the toner adhesion characteristics typically obtained for one or a plurality of apparatuses are applied to other apparatuses to reduce the toner consumption amount. You may make it ask.

  The toner counter 220 described above is realized by, for example, a hardware configuration using a gate array or a discrete element, a software configuration executed by the CPU 101 or a dedicated processor, or a configuration in which these are mixed. May be.

  Further, the present invention is not limited to the configuration of the above-described embodiment. For example, an apparatus that includes only a developing device corresponding to black toner and forms a monochrome image, and an apparatus that includes a transfer medium (transfer drum, transfer sheet, etc.) other than the intermediate transfer belt. In addition, the present invention can be applied to other image forming apparatuses such as copying machines and facsimile machines.

1 is a diagram illustrating an embodiment of an image forming apparatus according to the present invention. FIG. 2 is a block diagram illustrating an electrical configuration of the image forming apparatus in FIG. 1. It is a figure which shows the signal processing block in this apparatus. It is a figure for demonstrating the fluctuation | variation of the toner density by an edge effect. It is a figure which shows the relationship between dot size and a toner density. 6 is a graph illustrating an example of a toner adhesion rate. It is a figure which shows the correction coefficient for every dot size. 3 is a signal flow showing a configuration of a toner counter. It is a figure which shows the calculation result of toner consumption.

Explanation of symbols

DESCRIPTION OF SYMBOLS 22 ... Photosensitive body (latent image carrier) 44 ... Developing roller (toner carrier), 10 ... Engine controller, 11 ... Main controller (signal processing means), 220 ... Toner counter (toner consumption calculation means), 234... Filter, 241-245. k5: Correction coefficient, TC: Toner consumption

Claims (14)

Image forming means for visualizing the electrostatic latent image with toner to form a toner image;
Toner consumption calculating means for calculating toner consumption by the image forming means,
The toner consumption calculating means includes:
Of the electrostatic latent image, the amount of toner consumed to visualize the dot portion to which the toner is to be adhered,
An image forming apparatus characterized in that it is obtained based on a size of the dot part and a toner adhesion characteristic obtained in advance for each size of the dot part as a characteristic representing a toner adhesion amount corresponding to the size of the dot part. The toner consumption calculating means includes:
The amount of toner consumed to visualize the dot portion is calculated by multiplying the dot information value related to the size of the dot portion by a coefficient set based on the dot information value and the toner adhesion characteristics. Item 2. The image forming apparatus according to Item 1. Image forming means for visualizing the electrostatic latent image with toner to form a toner image;
Toner consumption calculation means for calculating toner consumption by the image forming means based on dot information relating to the size of the dot portion to which toner is to be attached in the electrostatic latent image,
The toner consumption calculating means includes:
The amount of toner consumed to visualize each dot portion is calculated by multiplying the value of dot information corresponding to the dot portion by a predetermined coefficient,
The image forming apparatus according to claim 1, wherein the coefficient is set according to the dot information based on a relationship between a size of the dot portion obtained in advance and a toner adhesion amount to the dot portion. The image forming means comprises a latent image carrier capable of carrying the electrostatic latent image whose surface is formed by a photoconductor, and an exposure means for irradiating a light beam toward the surface of the latent image carrier, The electrostatic latent image is formed on the surface of the latent image carrier by scanning and exposing a region corresponding to the dot portion of the surface of the latent image carrier with a light beam,
The image forming apparatus according to claim 2, wherein the dot information is an irradiation time of the light beam applied to the latent image carrier from the exposure unit in order to visualize the dot portion. Signal processing means for performing signal processing on the image signal, generating a multi-value signal related to the dot portion to be formed, and outputting the multi-value signal to the image forming means;
The image forming apparatus according to claim 2, wherein the dot information is the multilevel signal corresponding to the dot portion.   The image forming means includes a latent image carrier capable of carrying an electrostatic latent image, and a toner carrier which is disposed to face the latent image carrier with a predetermined gap and bears toner on the surface, 6. The image forming apparatus according to claim 1, wherein the toner image is formed by moving toner from the toner carrier to the latent image carrier.   7. The image formation according to claim 1, wherein the toner consumption amount for each dot portion visualized by the image forming unit within a predetermined period is integrated to calculate the toner consumption amount within the period. apparatus.   The image forming apparatus according to claim 7, wherein an offset value corresponding to a use state of the apparatus is added to the integrated value to calculate a toner consumption amount in the period in the apparatus. In a toner counter used in an image forming apparatus that visualizes an electrostatic latent image with toner and forms a toner image,
Of the electrostatic latent image, the amount of toner consumed to visualize the dot portion to which the toner is to be adhered,
A toner counter that is obtained based on a size of the dot part and a toner adhesion characteristic that is obtained in advance for each size of the dot part as a characteristic that represents a toner adhesion amount corresponding to the size of the dot part. In a toner consumption calculation method in an image forming apparatus that visualizes an electrostatic latent image with toner and forms a toner image,
In the electrostatic latent image, the amount of toner consumed to visualize the dot portion to which the toner is to be attached is expressed as a characteristic representing the size of the dot portion and the toner adhesion amount corresponding to the size of the dot portion. A method for calculating a toner consumption amount, wherein the toner consumption amount is calculated based on a toner adhesion characteristic obtained in advance for each size of a part.   The amount of toner consumed to visualize the dot portion is calculated by multiplying the dot information value related to the size of the dot portion by the coefficient set based on the dot information value and the toner adhesion characteristics. The toner consumption calculation method according to claim 10. In a toner consumption calculation method in an image forming apparatus that visualizes an electrostatic latent image with toner and forms a toner image,
A coefficient based on the relationship between the dot size determined in advance and the toner adhesion amount to the dot portion is set according to the value of dot information relating to the size of the dot portion to which the toner is to be adhered in the electrostatic latent image. And
The amount of toner consumed to visualize each dot portion is calculated by multiplying the value of dot information corresponding to the dot portion by the coefficient corresponding to the dot portion. Calculation method. For the value of dot information, preliminarily classify into multiple stages according to its size and set the coefficient for each class,
Dividing a plurality of the dot information based on the division, and integrating the value of the dot information divided into the same division for each division,
For each of the segments, a product of an integrated value for the segment and the coefficient set corresponding to the segment is obtained, and by summing the products, the plurality of dots corresponding to the plurality of dot information The toner consumption calculation method according to claim 11 or 12, wherein a total amount of toner consumed for visualization of a part is calculated.   The toner consumption calculation method according to claim 13, wherein an offset value corresponding to a usage state of the image forming apparatus is added to the total value.

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