JP2006178036A - Image forming apparatus, toner counter and method for calculating toner consumption - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To accurately obtain toner consumption in an image forming apparatus. <P>SOLUTION: A calculation error in the toner consumption arises because the set values (E1 and E2) of exposure power E for obtaining target density Dlow are different from calculative optimum values (Eopt1 and Eopt2). In order to restrain such an error, a coefficient substituted in the calculation expression of the toner consumption is changed according to the largeness of deviation (ΔE1 and ΔE2) between the set values and the optimum values. <P>COPYRIGHT: (C)2006,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 Patent Document 1, a print dot row is classified into a plurality of patterns according to the continuous state of the dots, and the number of occurrences thereof is counted individually. Then, the total toner consumption is calculated by multiplying the count values by a predetermined coefficient, respectively, and adding them. By doing so, the toner consumption amount is obtained with high accuracy irrespective of the non-linearity between the number of dots and the toner adhesion amount due to the difference in the continuous state of the dots.

JP 2002-174929 A (FIG. 2)

  The prior art is based on the premise that the relationship between the number of dots and the toner adhesion amount is always constant. However, in an actual device, the above relationship may vary depending on various factors such as the usage status of the device and the surrounding environment, and is not necessarily constant. As a result, the toner consumption may vary even if the images to be formed are the same. The above-described conventional technology has a problem that it cannot cope with such variations, and there is still room for improvement in terms of calculation accuracy of toner consumption.

  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.

  In order to achieve the above object, an image forming apparatus according to the present invention includes an image forming unit that forms a toner image according to image data, and a toner consumption amount calculating unit that calculates a toner consumption amount by the image forming unit. The toner consumption amount calculating means includes divergence information indicating the degree of divergence between the actual density of the toner image formed by the image forming means and a target density that is an image density that the toner image should originally have; and The toner consumption is calculated based on the image data.

A toner counter and a toner consumption calculation method according to the present invention are used in an image forming apparatus that forms a toner image according to image data, and a toner counter that calculates a toner consumption when forming the toner image. In the toner consumption calculation method, based on the deviation information indicating the degree of deviation between the actual density of the toner image to be formed and the target density, which is the image density that the toner image should originally have, and the image data The toner consumption is calculated.

  As described above, even if the images to be formed are the same, the amount of toner consumed for the formation may vary. Further, for example, there may be a case where image formation is intentionally performed under conditions deviating from the target density with emphasis on saving toner rather than image quality. If a uniform calculation method is applied without considering such variations and density differences, a calculation error increases.

  Therefore, in the present invention, deviation information is introduced when calculating the toner consumption based on the image data, and the degree of deviation between the actual density of the toner image and the target density is taken into account. By doing so, the toner consumption amount can be calculated in a manner closer to the actual toner consumption state. Therefore, according to the present invention, the toner consumption amount in the image forming apparatus can be accurately obtained. For example, when the deviation information indicates that the actual density of the formed toner image is higher than the target density, the toner consumption may be calculated to be larger than the reverse case. Whether the actual image density is shifted to the high density side or the low density side compared to the target density or the extent of the shift is estimated from various information as illustrated below. It is possible.

  The deviation information does not necessarily directly represent the difference between the actual density and the target density. For example, the actual operation condition of the apparatus and the ideal operation that is the operation condition for obtaining the target density Information representing a difference from the condition may be used. This is because the degree of deviation of the actual density from the target density can be estimated from such information. Since such information is information that can be acquired without actually measuring the density of the toner image, it can be suitably used as deviation information of the present invention.

  Some image forming apparatuses of this type are configured to adjust operation conditions by appropriately changing and setting density control factors that affect image density. In this type of apparatus, the concentration control factor may not be able to be set to an optimal value in the calculation due to restrictions on the apparatus configuration. For example, this corresponds to the case where the calculated optimum value is out of the variable range of the concentration control factor, or the case where the concentration control factor can take only discrete values. In such a case, it is realistic to set the concentration control factor so as to be closest to the optimum value within the settable range. In this case, the toner consumption amount shifts due to the difference between the set value of the density control factor and the optimum value. However, since the difference is known, the toner consumption amount shift can also be estimated.

  Further, in this type of apparatus, it is known that the image density fluctuates due to changes in the ambient environment such as temperature and humidity, and the toner consumption also fluctuates accordingly. Therefore, changes in the surrounding environment may be used as deviation information. In particular, in the case of an apparatus that performs density control at a predetermined timing, the tendency of fluctuations in toner consumption can be estimated based on the difference between the environment in which the density control is executed and the current environment.

  Of course, the density of the actually formed toner image may be detected, and the detection result may be compared with the ideal density value of the toner image.

  A specific method for calculating the toner consumption based on the deviation information and the image data will be exemplified below. For example, the toner consumption can be obtained by multiplying the number of toner dots to be formed obtained based on the image data by a coefficient set based on the deviation information. Further, the integrated value of the gradation values of the toner dots to be formed obtained based on the image data may be multiplied by a coefficient set based on the deviation information. The “toner dot” herein refers to a dot to which toner should be attached in a toner image grasped as an aggregate of many dots.

  Further, for example, an approximate value of toner consumption may be obtained based on the image data, and the approximate value may be corrected based on the deviation information. In this case, in order to obtain an approximate value of toner consumption, for example, a known calculation method such as a method of multiplying the integrated value of the number of toner dots and the gradation value obtained from the image data by a certain coefficient is applied. Can do. Then, by correcting the approximate value obtained in this way based on the deviation information, it is possible to obtain the toner consumption more accurately than the known toner counting technique.

  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 (color printing mode) by superposing four color toners (developers) of yellow (Y), cyan (C), magenta (M), and black (K), or black This is an image forming apparatus that forms a monochrome image (monochrome print mode) using only the toner of (K). 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 photoconductor 22 in accordance with an image signal given from an external device to form 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.

  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. Then, the color image is secondarily transferred onto the sheet S conveyed along the conveyance path F to the secondary transfer region TR2.

  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 time 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, the ROM 106, and the RAM 107 shown in FIG. 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 each color of CMYK 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.

  Further, in this image forming apparatus, in order to obtain the toner consumption amount, the toner consumption amount is calculated based on the pulse signal (video signal) output from the pulse modulation unit 117 of the main controller 11 as shown in FIG. A toner counter 200 or 300 (described later) is provided in the engine controller 10. 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. The inventor of the present application has developed a toner counter, which will be described in detail later, based on the results of various experiments.

  In this image forming apparatus 1, a patch image is formed and its density is detected at a predetermined timing such as when the total number of image forming sheets reaches a predetermined number immediately after power-on or after returning from sleep, and the density detection result The CPU 101 executes a density control process for adjusting the operating conditions of the apparatus based on the built-in program. As a result, the density of the formed image is kept constant. More specifically, as will be described below, among the operating parameters of each part of the apparatus, the developing bias (hereinafter referred to as symbol Vb) applied to the developing roller 44 and the light beam L applied to the photosensitive member 22 from the exposure unit 6 are described. The intensity (hereinafter referred to as “exposure power E”) is adjusted for each toner color. Since there are many known techniques for this type of density control processing, the processing flow will be briefly described here.

  FIG. 4 is a flowchart showing the density control process in this embodiment. In this density control process, the development bias Vb is first adjusted. That is, first, a predetermined patch image is formed on the surface of the intermediate transfer belt 71 with each bias value while changing and setting the developing bias in multiple stages (here, 5 stages) (step S101). The patch image in this case is a solid image. Then, the density of each formed patch image is detected using the density sensor 60 (step S102), and the optimum value of the developing bias is calculated based on the detection result (step S103).

  FIG. 5 is a diagram showing the relationship between the developing bias and the image density. As the magnitude of the developing bias | Vb | increases, the image density also increases. From the density detection result of the patch image with respect to each value V1 to V5 of the developing bias, the relationship between the developing bias and the image density is obtained as shown by the solid curve in FIG. From this relationship, the value Vopt of the developing bias is obtained so that the image density becomes the target value Dhigh.

  Returning to FIG. 4, the description of the density control process will be continued. Subsequently, the exposure power is adjusted. First, in a state where the developing bias is set to the optimum value Vopt described above, a predetermined patch image is formed with each exposure power while changing and setting the exposure power in multiple stages (here, 5 stages) (step S104). The patch image in this case is a thin line image. The magnitude of the exposure power is related to the depth of the latent image on the photoreceptor 22. Therefore, the influence on the density of the fine line image is larger than that of the solid image. Therefore, it is preferable to use a patch image having an image pattern composed of fine lines for adjusting the exposure power. Further, it is preferable that the lines are spaced apart from each other so that a 1 on 10 off image is used as a patch image.

  The density of the thin line patch image at each exposure power thus formed is detected by the density sensor 60 (step S105), and the optimum value of the exposure power is calculated based on the density detection result (step S106). In the configuration of the apparatus 1, the value of the exposure power can be set to any one of the five levels E1 to E5 and cannot be set to any other value.

  FIG. 6 is a diagram showing the relationship between exposure power and image density. As in the case of adjusting the developing bias Vb, the relationship between the exposure power and the image density is obtained from the density detection result of the patch image for each of the exposure power values E1 to E5. Then, the optimum value of the exposure power E is obtained from this relationship. From this relationship, the exposure power value at which the image density is closest to the target density Dlow and equal to or higher than the target density Dlow is set as the optimum value. When the density control process is executed in this way, it is possible to stably obtain a desired image density by setting the developing bias and the exposure power to the optimum values in the subsequent image forming operations.

  Here, the variable range of the exposure power is determined in advance, and the possible values are discrete. For this reason, the actual exposure power setting value does not necessarily match the calculated optimum value. For example, when the density detection result at each exposure power is a white circle shown in FIG. 6, it is estimated that the relationship between the exposure power and the image density is like a curve 6a. At this time, the optimum value of the calculated exposure power is the value Eopt1 shown in the figure, but this value is outside the variable range of the exposure power, and the actual set value is E1 closest to this calculated value. Further, for example, when the density detection result at each exposure power is the hatched circle shown in FIG. 6, the relationship between the exposure power and the image density is represented by a curve 6b. For the optimum value Eopt2, the actual set value is equal to or greater than the optimum value Eopt2 among the settable values.

  Such a difference between the calculated optimum value and the actual set value is not a problem from the viewpoint of image density unless it is a level that can be clearly discerned visually. However, this difference becomes a problem in calculating the toner consumption. This is because if the toner consumption amount is cumulatively added as the number of images to be formed increases, the calculation error also increases. Conventional toner counters are generally configured so that the calculated toner consumption is greater than the actual consumption in order to prevent image quality degradation due to toner out at unexpected timing. It was the target. However, in this case, it is determined that the toner has run out in spite of the fact that usable toner still remains in the developing device. This causes a problem that the filled toner cannot be used up to the end. There was a thing.

  Therefore, in this embodiment, the calculation formula for the toner consumption is changed in accordance with the amount of deviation from the optimum value for the calculation of the setting value of the exposure power E. That is, in the apparatus in which the relationship between the exposure power and the image density is represented by the curve 6a shown in FIG. 6, the setting value E1 of the exposure power is a value higher than the optimum value Eopt1 by ΔE1, The toner consumption amount in the apparatus is slightly larger than the toner consumption amount originally assumed. It is clear that the deviation amount of the actual toner consumption with respect to the assumed value increases as the difference between the set value of the exposure power E and the calculated optimum value increases. Therefore, the toner consumption amount can be obtained more accurately by changing the calculation formula of the toner consumption amount according to the difference between the setting value of the exposure power E and the optimum value (hereinafter referred to as ΔE). .

  FIG. 7 is a diagram showing the configuration of the toner counter in this embodiment. The toner counter 200 counts the number of toner dots to be formed based on a video signal supplied from the pulse modulation unit 117 of the main controller 10 to the laser driver 121 of the engine controller 11, and calculates the toner consumption from the count value. calculate. At this time, instead of simply counting the number of toner dots, each toner dot is classified according to the interval between adjacent toner dots and counted individually. This is based on the knowledge of the inventor of the present application that the amount of toner adhering to each toner dot varies depending on the distance from other adjacent toner dots. The specific configuration will be described below.

  The toner counter 200 is provided with a pattern determination circuit 201 that determines the arrangement state of the toner dots based on the video signal. The pattern determination circuit 201 classifies each toner dot according to an interval between the toner dot and the toner dot that appears immediately before (hereinafter referred to as “off interval”). Specifically, when the OFF interval is zero, that is, when the toner dot appears following the previous toner dot, the pattern determination circuit 201 outputs a value 1 to the continuous dot counter 210.

  When the toner dot appears with an interval of one dot with respect to the immediately preceding toner dot, the off interval is 1, and in this case, the value 1 is output to the first counter 211. The Similarly, the value 1 is output to the second counter 212 when the off interval is 2, the third counter 213 when the off interval is 3, and the fourth counter 214 when the off interval is 4, respectively. Further, the value 1 is output to the fifth counter 215 when the off interval is 5 to 8, and the sixth counter 216 is output when the off interval is 9 or more.

  The continuous dot counter 210 and the first to sixth counters 211 to 216 respectively accumulate values output from the pattern determination circuit 201 to the counter. Therefore, in these counters, the number of toner dots to be formed is classified for each OFF interval and counted individually. The count values C0 to C6 thus accumulated are output from each counter for each predetermined calculation unit such as one page or one job unit. Then, the count values C0 to C6 are multiplied by coefficients K0 to K6 for applying a weight corresponding to the magnitude of the toner adhesion amount that varies depending on the off interval. In this embodiment, by changing the values of the coefficients K0 to K6 according to the amount of deviation ΔE between the set value of the exposure power and the optimum value, the occurrence of toner consumption calculation errors is suppressed. .

  FIG. 8 is a diagram illustrating the relationship between the off interval and the toner adhesion amount. FIG. 9 is a diagram showing an example of setting the weighting coefficient. According to the experiment by the inventor of the present application, as shown in FIG. 8, the toner adhesion amount per one toner dot varies greatly depending on the size of the off-interval. It also varies depending on the amount of deviation ΔE in exposure power. The weighting coefficients K0 to K6 are determined as shown in FIG. 9 so as to correspond to such a tendency. In FIG. 9, the amount of deviation of the exposure power is expressed in arbitrary units, and the numerical values of 0 to 3 are not particularly meaningful.

Returning to FIG. 7, the description of the toner counter 200 will be continued. When the output values C0 to C6 of the counters are multiplied by weighting coefficients K0 to K6 and added to each other, the substantial number of toner dots weighted corresponding to the difference in the toner adhesion amount is obtained. By multiplying this value by a coefficient Kx corresponding to the toner adhesion amount per dot in the solid image, the amount of toner consumed for forming each toner dot can be obtained. A value TC obtained by adding the offset value Coff to the value is set as a toner consumption amount in the present embodiment. That is, in this embodiment, the toner consumption TC is expressed by the following formula:
TC = Kx (K0 · C0 + K1 · C1 + ... + K5 · C5 + K6 · C6) + Coff
It is represented by

  Here, 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. This includes toner consumed for forming various patch images in this embodiment. 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.

  The toner consumption thus obtained is managed by the CPU 101 provided in the engine controller 10 and stored in the RAM 107 or the memory 91 such as each developing device 4Y as necessary. Further, it is possible to estimate the toner remaining amount of each developing device from the obtained toner consumption value, and when it is determined that the toner remaining amount in the developing device has decreased to a predetermined value or less, the display unit 12 For example, a message prompting the developer to be replaced can be displayed, which can be useful for managing consumables of the apparatus.

  As described above, in this embodiment, considering that the density of the image formed under the current operating conditions of the apparatus may be different from the target density that the image should originally have, The calculation formula for the toner consumption is changed based on information indicating the degree of density deviation. More specifically, the number of toner dots depends on the amount of deviation ΔE in exposure power in order to cope with fluctuations in toner consumption that occur when the set value of exposure power E is different from the calculated optimum value. The weighting coefficient to be multiplied is changed. By doing this, it is possible to suppress the calculation error caused by the difference between the set value of the exposure power and the optimum value, and to obtain the toner consumption with high accuracy.

  Further, since the exposure power deviation amount ΔE can be calculated by calculation based on the result of the density control processing, a special configuration for improving calculation accuracy is not required, and the apparatus cost can be kept low. it can.

  As described above, in this embodiment, the engine unit EG that forms an image based on the video signal functions as the “image forming unit” of the present invention, and the video signal corresponds to “image data” of the present invention. To do. The toner counter 200 corresponds to “toner consumption calculation means” of the present invention. In this embodiment, the developing bias Vb and the exposure power E correspond to the “density control factor” of the present invention, and the CPU 101 that controls them functions as the “control unit” of the present invention. Further, the target density Dlow at the time of adjusting the exposure power corresponds to the “target density” of the present invention, and the deviation amount ΔE between the set value of the exposure power E and the optimum value corresponds to the “deviation information” of the present invention. Yes.

  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 above-described embodiment, the toner consumption amount is calculated based on the principle that the deviation amount ΔE of the exposure power is set as “deviation information” and a calculation formula is determined according to the value. In addition to this, for example, an approximate value of toner consumption may be obtained by a conventional toner counting technique (not considering deviation information), and the calculation accuracy may be improved by correcting the estimated value using deviation information. Good.

  FIG. 10 is a diagram showing another configuration of the toner counter. In the toner counter 300, the counter 301 counts the number of toner dots formed based on the video signal. By multiplying this by a coefficient Kx corresponding to the toner adhesion amount per dot, an approximate value of toner consumption can be obtained. At this stage, the degree of deviation between the actual image density and the target density is not taken into account, and there is a possibility that a large calculation error is included. Therefore, the calculation accuracy can be further improved by multiplying the correction coefficient K set by the CPU 101 based on the deviation information in order to correct the approximate value in accordance with the degree of deviation. Further, as in the above embodiment, the offset value Coff may be further added.

  Further, in the above embodiment, the difference between the actual density and the target density of the image to be formed is not actually measured, but the set value of the exposure power E that affects the image density and the calculated optimum value. The shift amount ΔE between them is used as a parameter that indirectly represents the shift amount of the image density, that is, the deviation information of the present invention. On the other hand, the density of the actually formed image may be detected, and the deviation information may be derived from the detection result. For example, when a known image pattern is included in the image to be formed, the image density of the region is detected by the density sensor 60, and the detection result is compared with the ideal image density assumed from the image pattern. Thus, the deviation information may be obtained. In such a case, the density sensor 60 functions as the “detecting means” of the present invention.

  Further, for example, in the above-described embodiment, the calculation formula of the toner consumption amount is changed according to the value of the deviation amount ΔE of the exposure power that is the deviation information, but other than this, for example, the setting value of the development bias Vb When the deviation between the value and the optimum value occurs, the deviation amount can be used as “deviation information”, and the same can be considered when other parameters are used as the concentration control factor.

  In the above embodiment, the set value of the exposure energy E is “a value that is equal to or greater than the optimum value and is closest to the optimum value among settable values”, but it may be simply set to a value that is closest to the optimum value. In this case, since the exposure power deviation amount ΔE may be negative, it is necessary to prepare a coefficient corresponding thereto. Also, the amount of deviation is not limited to the difference between the set value and the optimum value, and may be represented by the ratio between the two.

  In the above embodiment, the toner consumption amount is obtained by counting the number of toner dots to be formed and multiplying the count value by a coefficient. However, when each toner dot is expressed in multiple gradations, Instead of counting the number, the gradation value of each toner dot may be integrated.

  In this type of image forming apparatus, characteristics of the engine unit EG and toner may change due to environmental changes such as the internal temperature and humidity of the apparatus, and as a result, toner consumption may fluctuate. For example, in the experiment of the present inventor, it has been observed that the toner consumption increases under a high temperature and high humidity environment even under the same operating conditions. The degree of such variation can be estimated from the degree of change in the environment of the apparatus. Therefore, the amount of change in temperature and humidity inside the device (or surroundings) is used as deviation information, and the toner consumption calculation method is changed accordingly, so that the toner consumption can be accurately measured regardless of these environmental changes. It can be obtained stably. For example, when the internal temperature of the apparatus when the density control process is executed is stored, and the toner consumption amount is subsequently obtained, the internal temperature of the apparatus at that time and the stored density control process at the time of execution are stored. By using the difference from the internal temperature as the deviation information, the calculation formula can be changed according to the value.

  In addition, the toner consumption may vary due to changes in the characteristics of the apparatus over time. Therefore, the operation amount of the apparatus (for example, the number of image formations and the operation time) may be measured, and the measurement result may be used as the deviation information of the present invention.

  In the above embodiment, the number of dots is accumulated based on the video signal supplied from the pulse modulation unit 117 of the main controller 11 to the laser driver 121 of the engine controller 10, but the present invention is not limited to this. Other data can be used as long as it represents the number of dots to be printed and their shading (gradation level).

  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 showing a 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 in FIG. 1. The figure which shows the signal processing block in this apparatus. The flowchart which shows a density control process. The figure which shows the relationship between a developing bias and image density. The figure which shows the relationship between exposure power and image density. FIG. 3 is a diagram showing a configuration of a toner counter in this embodiment. The figure which shows the relationship between an OFF space | interval and toner adhesion amount. The figure which shows the example of a setting of a weighting coefficient. FIG. 6 is a diagram illustrating another configuration of a toner counter.

Explanation of symbols

  60 ... density sensor (detection means) 101 ... CPU (control means) 200, 300 ... toner counter (toner consumption calculation means), Dlow ... target density, EG ... engine (image forming means)

Claims (13)

Image forming means for forming a toner image according to image data;
Toner consumption calculating means for calculating toner consumption by the image forming means,
The toner consumption amount calculating means includes divergence information indicating the degree of divergence between the actual density of the toner image formed by the image forming means and the target density that is the image density that the toner image should originally have, and An image forming apparatus, wherein the toner consumption is calculated based on the image data.   The image forming apparatus according to claim 1, wherein the deviation information is information representing a difference between an actual operating condition of the image forming unit and an ideal operating condition that is an operating condition for obtaining the target density.   The toner consumption amount calculating unit calculates the toner consumption amount by multiplying the number of toner dots to be formed by the image forming unit obtained based on the image data by a coefficient set based on the deviation information. The image forming apparatus according to claim 1.   The toner consumption amount calculating unit multiplies the integrated value of the gradation values of the toner dots to be formed by the image forming unit obtained based on the image data by a coefficient set based on the deviation information. The image forming apparatus according to claim 1, wherein the toner consumption is calculated.   3. The toner consumption calculating means calculates an approximate value of toner consumption based on the image data and calculates the toner consumption by correcting the approximate value based on the deviation information. The image forming apparatus described in 1.   The toner consumption amount calculating means is set based on the deviation information to an approximate value obtained by multiplying a predetermined proportionality coefficient by the number of toner dots to be formed by the image forming means or the number of toner dots to be formed based on the image data. The image forming apparatus according to claim 5, wherein the toner consumption is calculated by multiplying the corrected correction coefficient.   The toner consumption amount calculating means calculates an integrated value of gradation values of toner dots to be formed by the image forming means obtained based on the image data, or an approximate value obtained by multiplying the integrated value by a predetermined proportional coefficient. The image forming apparatus according to claim 5, wherein the toner consumption is calculated by multiplying a correction coefficient set based on the deviation information. Control means for controlling the image density to the target density by determining a set value of a density control factor that affects the image density within a predetermined variable range, and an optimum value of the density control factor corresponding to the target density Is outside the variable range,
The control means sets the value closer to the optimum value among the upper limit value or the lower limit value of the variable range as a set value of the concentration control factor,
The image forming apparatus according to claim 1, wherein the toner consumption amount calculation unit uses a difference between the set value and the optimum value as the deviation information. Control means for controlling the image density to the target density by selecting a set value of a density control factor that affects the image density from a plurality of preset candidate values, and the density control corresponding to the target density When the optimal value of the factor is not among the candidate values,
The control means sets a value closest to the optimum value among the candidate values as a set value of the concentration control factor,
The image forming apparatus according to claim 1, wherein the toner consumption amount calculation unit uses a difference between the set value and the optimum value as the deviation information. A control means for executing a control process for controlling the image density to the target density by adjusting a density control factor that affects the image density;
The image according to any one of claims 1 to 7, wherein the toner consumption amount calculation means uses the difference between the ambient environment of the apparatus when the control process is executed and the ambient environment of the current apparatus as the deviation information. Forming equipment. A detector for detecting an image density of the toner image formed by the image forming unit;
8. The toner consumption amount calculation unit uses the difference between the image density of the toner image detected by the detection unit and an ideal value of the image density that the toner image should originally have as the deviation information. An image forming apparatus according to claim 1. In a toner counter that is used in an image forming apparatus that forms a toner image according to image data and calculates a toner consumption amount when the toner image is formed,
The toner consumption amount is calculated based on the deviation information indicating the degree of deviation between the actual density of the toner image to be formed and the target density, which is the image density that the toner image should originally have, and the image data. A toner counter. In a toner consumption amount calculating method for calculating a toner consumption amount when forming a toner image in an image forming apparatus that forms a toner image according to image data,
Obtaining divergence information indicating the degree of divergence between the actual density of the toner image to be formed and the target density, which is the image density that the toner image should originally have,
A toner consumption amount calculating method, wherein the toner consumption amount is calculated based on the deviation information and the image data.

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