Image forming apparatus

Abstract

To improve the accuracy of calculating the toner consumption.SOLUTION: An image forming apparatus comprises: a photoconductor drum 5; an exposure unit 10 that exposes a surface of the photoconductor drum 5 according to on / off of an image signal based on image data to form an electrostatic latent image; and a developing roller 8R configured to supply toner to the electrostatic latent image on the photoconductor drum 5 to form a toner image on the photoconductor drum 5, and the image forming apparatus transfers the toner image to a recording material. The image forming apparatus comprises an engine control unit 203 that acquires an on-ratio including a value larger than 0% and smaller than 100% of the image signal in each of image pixels of the image data, and a toner consumption ratio corresponding to the on-ratio, and calculates the total toner consumption of all the image pixels of the image data based on the on-ratio and the toner consumption ratio acquired for each of the image pixels (S501, S504-S506).SELECTED DRAWING: Figure 8

Description

Technical Field

[0001] The present invention relates to an image forming apparatus such as a copying machine or a printer.

Background Art

[0002] Conventionally, image forming apparatuses using an electrophotographic method such as copying machines and laser printers have been known. In an electrophotographic color image forming apparatus, a photosensitive member charged to a uniform potential is irradiated with laser light from an exposure means to form an electrostatic latent image on the photosensitive member, and toner is attached to the electrostatic latent image by a developing device, thereby forming a toner image on the photosensitive member. The irradiation of the laser light is executed by performing on (lighting) and off (extinguishing) control of a laser element included in the exposure means based on a control signal input to a laser driver. And the prediction of toner consumption is performed based on the measurement result of pixel count control that measures the number of control signals for turning on the laser signal input to the laser driver. For example, in Patent Document 1, the prediction accuracy of toner consumption is improved by the following method. That is, in order to improve the prediction accuracy of toner consumption, a pattern image for pixel count correction is formed, the density of the formed pattern image is detected, and the detected density result is fed back to the toner consumption prediction. Thereby, the prediction accuracy of toner consumption by pixel count control is improved.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, conventional technology corrects the pixel count based on the density measurement result from a single measurement point, rather than the density measurement results from multiple measurement points. Therefore, for example, in light halftone images that are far from the measurement point, or in dark images such as text, the pixel count correction may not be accurate. As a result, there was a problem in that the accuracy of the calculated toner consumption was not sufficient.

[0005] This invention was made under these circumstances and aims to improve the accuracy of toner consumption calculation. [Means for solving the problem]

[0006] To solve the above-mentioned problems, the present invention has the following configuration. (1) An image forming apparatus for transferring a toner image to a recording material, comprising: a photosensitive drum; exposure means for exposing the surface of the photosensitive drum to form an electrostatic latent image in accordance with the on / off status of an image signal based on image data; and a developing roller configured to supply toner to the electrostatic latent image on the photosensitive drum to form a toner image on the photosensitive drum, wherein the apparatus includes an acquisition unit for acquiring an on-ratio for each image pixel of the image data that includes a value greater than 0% and less than 100% of the image signal, and a toner consumption rate corresponding to the on-ratio; and a calculation unit for calculating the total toner consumption of all image pixels of the image data based on the on-ratio and toner consumption rate acquired by the acquisition unit for each image pixel. The acquisition unit samples the image signal multiple times during the period in which one image pixel is formed, and acquires the ON ratio based on the number of times the image signal is detected to be ON during the multiple samplings. An image forming apparatus characterized by the following features. [Effects of the Invention]

[0007] According to the present invention, the accuracy of calculating toner consumption can be improved. [Brief explanation of the drawing]

[0008] [Figure 1] Cross-sectional view showing the configuration of the image forming apparatus in Examples 1-3 [Figure 2]Hardware configuration diagrams of the image forming apparatus in Examples 1-3 [Figure 3] Functional block diagrams of the engine control unit of the image forming apparatus in Examples 1-3 [Figure 4] Examples of patch images from Examples 1-3, and a diagram illustrating the relationship between reference concentration, measured concentration, and LUT. [Figure 5] Diagram illustrating the toner consumption rate of the halftone areas in Examples 1-3. [Figure 6] Diagram illustrating the pixel count in Example 1 [Figure 7] Diagram illustrating the method for calculating toner consumption in Example 1. [Figure 8] Flowchart showing the toner consumption calculation process in Example 1 [Figure 9] This figure illustrates the detection density and pixel count detection density of the patch image in Example 2. [Figure 10] Diagram illustrating the method for calculating toner consumption in Example 2 [Figure 11] Flowchart showing the toner consumption calculation process in Example 2 [Figure 12] Diagram illustrating the pixel count in Example 3 [Figure 13] Flowchart showing the toner consumption calculation process in Example 3 [Modes for carrying out the invention]

[0009] Embodiments of the present invention will be described in detail below with reference to the drawings. [Examples]

[0010] [Configuration of the image forming apparatus] Figure 1 is a cross-sectional view showing the overall configuration of an image forming apparatus 100 of Embodiment 1 to which the present invention is applied. In Figure 1, in the image forming apparatus 100, an electrostatic latent image is formed on the photoreceptor by exposure light generated based on an image signal transmitted from a video controller (not shown), and a toner image is formed by developing the formed electrostatic latent image into a visible image. The toner image on the photoreceptor is superimposed and transferred onto a transfer medium to form a color image, the formed color image is transferred to a recording medium sheet, and the transferred color image is fixed to the sheet, completing the image formation process.

[0011] In the image forming apparatus 100, the image forming unit (image forming means) is equipped with a photosensitive drum 5 (5Y, 5M, 5C, 5K), a charging unit 7 (7Y, 7M, 7C, 7K), and a developing unit 8 (8Y, 8M, 8C, 8K) for each station arranged side-by-side, corresponding to the number of toner colors. Furthermore, the image forming unit is equipped with a primary transfer roller 4 (4Y, 4M, 4C, 4K) and an intermediate transfer belt 12. As shown in Figure 1, the image forming apparatus 100 is equipped with stations for forming images with toner colors of yellow (Y), magenta (M), cyan (C), and black (K). Note that the configuration and operation of each station shown in Figure 1 are substantially the same. In addition, the Y, M, C, and K appended to the end of the symbols of the components constituting each station indicate that they are components of the station with toner colors of yellow (Y), magenta (M), cyan (C), and black (K), respectively. In the following, the letters Y, M, C, and K attached to the end of component codes will be omitted unless they refer to components of a specific station.

[0012] The photosensitive drum 5 serving as a support, the charging unit 7 serving as a charging means, and the developing unit 8 serving as a developing means are mounted on a process cartridge 22 that is detachable from the image forming apparatus 100. The photosensitive drum 5 is formed by applying an organic photoconductive layer to the outer periphery of an aluminum cylinder and rotates in the direction of the arrow in the figure (clockwise direction) by a drive motor (not shown). The photosensitive drum 5 is exposed on its surface according to the on / off of an image signal based on image data from an exposure unit 10 serving as an exposure means, and an electrostatic latent image is formed on the surface of the photosensitive drum 5. The charging unit 7 has a charging roller 7R for charging the photosensitive drum 5, and charges the photosensitive drum 5 to a uniform potential before the photosensitive drum 5 is exposed by the exposure unit 10. The developing unit 8 has a developing roller 8R, and a toner image is formed on the photosensitive drum 5 by attaching toner to the electrostatic latent image formed on the photosensitive drum 5 (on the photosensitive drum) using the developing roller 8R. The developing roller 8R is configured to supply toner to the electrostatic latent image on the photosensitive drum 5 to form a toner image on the photosensitive drum 5.

[0013] The intermediate transfer belt 12 serving as an intermediate transfer member is an endless belt that rotates and moves in the direction of the arrow in the figure (counterclockwise direction). The intermediate transfer belt 12 contacts the photosensitive drum 5 of each station during image formation, and when a primary transfer voltage is applied to the primary transfer roller 4, the toner images formed on the photosensitive drum 5 are sequentially and superimposedly transferred, and the transferred toner images move to the secondary transfer roller 9.

[0014] The image forming apparatus 100 includes a cassette paper feed tray 101 for accommodating a sheet 2 serving as a recording material at the lower part of the apparatus. During image formation, in synchronization with the image forming operations at the above-described respective stations, the sheet 2 accommodated in the cassette paper feed tray 101 is fed to a conveyance path 25 by a paper feed roller 102 and a paper feed conveyance roller 40 driven by a paper feed motor (not shown). Then, the sheet 2 fed to the conveyance path 25 is conveyed to the secondary transfer roller 9 by a registration roller 3. The image forming apparatus 100 detects the leading end and the trailing end in the conveyance direction of the sheet 2 being conveyed by a registration sensor 4, controls the conveyance of the sheet 2, and determines whether the sheet 2 is being normally conveyed from the cassette paper feed tray 101.

[0015] The secondary transfer roller 9 contacts the intermediate transfer belt 12 to form a secondary transfer nip portion. The sheet 2 fed from the cassette paper feed tray 101 is pinched and conveyed to the secondary transfer nip portion, and a secondary transfer voltage is applied to the secondary transfer roller 9, so that the toner image (color image) formed on the intermediate transfer belt 12 (on the intermediate transfer member) is transferred to the sheet 2. The sheet 2 onto which the toner image has been transferred is conveyed to the fixing device 13.

[0016] The fixing device 13 includes a fixing roller 14 that heats the conveyed sheet 2 and a pressure roller 15 for pressing the sheet 2 against the fixing roller 14. The fixing roller 14 and the pressure roller 15 are formed in a hollow shape, and a heater is built into the fixing roller 14. The sheet 2 onto which the color image has been transferred is pinched and conveyed by the fixing roller 14 and the pressure roller 15, and the color image (toner image) is fixed to the sheet 2 by heating and pressurization.

[0017] Also, the image forming apparatus 100 is provided with a configuration for reversely conveying the sheet 2 in order to perform image formation (double-sided printing) on the second side of the sheet 2 after the image formation on the first side is completed. Therefore, the image forming apparatus 100 has a reversing roller 62 that rotates forward and backward under the driving force of a reversing motor (not shown). The reversing roller 62 can reverse and convey the sheet 2 conveyed from the double-sided conveyance path 60 by the reverse rotation of the reversing motor to the double-sided conveyance path 56. Further, the double-sided conveyance path 56 is provided with a double-sided conveyance roller 55 and a double-sided re-feed roller 57 that are rotated by a double-sided conveyance motor (not shown). The double-sided conveyance roller 55 and the double-sided re-feed roller 57 can convey the sheet 2 reversely conveyed from the reversing roller 62 along the double-sided conveyance path 56 and merge it into the middle of the conveyance path 25.

[0018] Furthermore, the image forming apparatus 100 has a double-sided flapper 51 that guides the sheet 2, which has been guided along the transport path 25 and passed through the fuser 13, to either the discharge roller 52 or the reversing roller 62. The double-sided flapper 51 guides the sheet 2 to either the discharge roller 52 (indicated by a solid line) or the reversing roller 62 (indicated by a dashed line) by switching its position. The sheet 2 guided to the discharge roller 52 is discharged onto the discharge tray 27 and loaded.

[0019] Furthermore, the image forming apparatus 100 is equipped with a density sensor 70, which is a measuring means for measuring the density of the patch image 71 (toner patch image) formed on the intermediate transfer belt 12. The density of the patch image detected by the density sensor 70 is used for image density control by the video controller 202 (described later) and for notifying toner consumption.

[0020] [Hardware configuration of image forming apparatus] Next, the hardware configuration of the image forming apparatus 100 in this embodiment will be described. Figure 2 is a diagram showing the hardware configuration of the image forming apparatus 100 shown in Figure 1, mainly related to control in this embodiment.

[0021] In Figure 2, the video controller 202 receives print jobs, including print commands and image information, from the host computer 201, an external computer, via the communication line 504. Upon receiving the print job, the video controller 202 transmits commands, including images and instructions from the host computer 201, to the engine control unit 203 via the signal line 505 during the image formation operation. The video controller 202 also controls the image data for image formation by receiving status data regarding the image formation operation from the engine control unit 203.

[0022] The engine control unit 203 is a control IC that controls the image forming apparatus 100. The engine control unit 203 has a CPU 508 that controls various operations of the image forming apparatus 100, a RAM 509 that temporarily stores control data necessary for image forming operations, and a ROM 510 that stores programs and control tables necessary for image forming operations. Furthermore, the engine control unit 203 has a communication circuit 511 that performs communication processing with the video controller 202, a system timer 512 that generates timings necessary for various controls, and an I / O port 513 that inputs and outputs control signals to various devices within the image forming apparatus 100. The CPU 508, RAM 509, ROM 510, communication circuit 511, system timer 512, and I / O port 513 are connected to the engine control unit 203 via a bus 514.

[0023] The video controller 202 processes image information transmitted from the host computer 201 and sends a video signal 506 to the engine control unit 203. The details of image processing by the video controller 202 will be described later. The video signal 506 transmitted to the engine control unit 203 is input to the laser drive circuit 515 of the exposure unit 10 via the image pixel count detection circuit 518, which is a measurement means. The image pixel count detection circuit 518 counts the ON signals that cause the laser light to be emitted from the laser element 75, which is the light source, in the video signal 506 transmitted for each toner color, and outputs the count result to the CPU 508 via the bus 514.

[0024] The exposure unit 10 includes a laser drive circuit 515, a laser element 75, a scanner motor drive circuit 516, and a scanner 76. The laser drive circuit 515 drives the laser element 75 in response to control instructions from the engine control unit 203 and a video signal 506 transmitted from the video controller 202. The scanner motor drive circuit 516 drives a scanner (rotating polyhedron mirror) that deflects the laser light emitted from the laser element 75 and irradiates it onto the photosensitive drum 5 in response to control instructions from the engine control unit 203.

[0025] The intermediate transfer belt / drum motor drive circuit 519 receives a control signal from the engine control unit 203 and drives the motors 223 that drive the intermediate transfer belt 12 and the photosensitive drums 5 of each station. The paper feed motor drive circuit 520 receives a control signal from the engine control unit 203 and drives the paper feed motor 210. The fuser motor drive circuit 521 receives a control signal from the engine control unit 203 and drives the fuser motor 211.

[0026] The high-voltage drive circuit 522 receives a control signal from the engine control unit 203 and controls the output of the high voltage from the high-voltage device 224. The high voltage output from the high-voltage device 224 is supplied to the charging roller 7R, developing roller 8R, primary transfer roller 4, and secondary transfer roller 9 as charging voltage, developing voltage, primary transfer voltage, and secondary transfer voltage, respectively. The CPU 508 of the engine control unit 203 acquires the image density of the patch image formed on the intermediate transfer belt 12, detected by the density sensor 70, via the density sensor input circuit 517 and I / O port 513. The engine control unit 203 functions as an acquisition unit that acquires the on-percentage, which includes a value greater than 0% and less than 100% of the image signal at each image pixel of the image data (described later), and the toner consumption rate corresponding to the on-percentage. The CPU 508 also transmits the acquired density data as the measured density to the video controller 202 via the communication circuit 511.

[0027] [System configuration of an image forming apparatus] Next, the system configuration of the engine control unit 203 of the image forming apparatus 100 will be described. Figure 3 is a functional block diagram showing the functions performed by the engine control unit 203 by controlling various devices. As shown in Figure 3, the engine control unit 203 includes a control unit 204, an image forming control unit 205, a multiple halftone density detection unit 206, a pixel count unit 207, an intermediate transfer belt / photosensitive drum drive unit 208, a sheet transport unit 209, and a communication circuit 511. The control unit 204 controls the image forming control unit 205, the intermediate transfer belt / photosensitive drum drive unit 208, and the sheet transport unit 209 to control image forming operations, etc. Furthermore, the control unit 204 acquires density data and image pixel count information from the multiple halftone density detection unit 206 and the pixel count unit 207, and transmits them to the video controller 202 via the communication circuit 511.

[0028] The sheet transport unit 209, based on control instructions from the control unit 204, drives the register roller 3 and the fixing roller 14 via the fixing motor drive circuit 521 during image formation to transport the sheet 2. The control unit 204 also controls the intermediate transfer belt / photosensitive drum drive unit 208 during image formation to drive the motor 223 via the intermediate transfer belt / drum motor drive circuit 519, thereby rotating the intermediate transfer belt 12 and the photosensitive drum 5. Furthermore, during image formation, the control unit 204 controls the image formation control unit 205 to drive the scanner 76 in the exposure unit 10, causing the laser element 75 to emit laser light. In addition, during image formation, the control unit 204 controls the image formation control unit 205 to drive the high-voltage drive circuit 522 to output a charging voltage, a developing voltage, and a primary transfer voltage from the high-voltage device 224, which are then applied to the charging roller 7, the developing roller 8, and the primary transfer roller 4. As a result, the toner images formed on the photosensitive drums 5 at each station are sequentially superimposed and transferred onto the intermediate transfer belt 12. Then, during image formation, the control unit 204 controls the image formation control unit 205 to drive the high-voltage drive circuit 522 to output a secondary transfer voltage from the high-voltage device 224, which is applied to the secondary transfer roller 9, thereby transferring the toner image on the intermediate transfer belt 12 to the sheet 2. In this way, the control unit 204 performs image formation with the image formation control unit 205, the sheet transport unit 209, and the intermediate transfer belt / photosensitive drum drive unit 208.

[0029] The multiple halftone density detection unit 206 detects the density of multiple patch images 71 formed on the intermediate transfer belt 12 using a density sensor 70 and outputs the detection result to the control unit 204. The pixel count unit 207 uses an image pixel count detection circuit 518 to count the number of image pixels in the image data (pixel data) from the video controller 202 and outputs it to the control unit 204. The control unit 204 calculates the toner consumption based on the density detection result from the multiple halftone density detection unit 206 and the image pixel count result from the pixel count unit 207. The engine control unit 203 functions as a calculation unit that calculates the total toner consumption of all image pixels in the image data based on the on-ratio and toner consumption rate acquired by the acquisition unit for each image pixel, as described later.

[0030] [Patch density detection using a video controller] The video controller 202 forms a patch image on the intermediate transfer belt 12 for which the image density to be measured. The engine control unit 203 obtains the density of the patch image formed on the intermediate transfer belt 12, measured by the multiple halftone density detection unit 206 (density sensor 70), from the multiple halftone density detection unit 206. The engine control unit 203 then transmits the measured density of the patch image to the video controller 202. Based on the measured density of the patch image received from the engine control unit 203, the video controller 202 creates a lookup table (hereinafter referred to as LUT) that performs tone level-density conversion. When performing density detection of a patch image, the engine control unit 203 does not need to perform image formation that involves transporting the sheet 2. When creating a LUT using a patch image, the engine control unit 203 only measures the density of the patch image using the multiple halftone density detection unit 206 and does not perform any calculations related to the LUT.

[0031] Next, we will explain the image density processing performed by patch image formation using the multiple halftone density detection unit 206 and the video controller 202. Figure 4(a) is a schematic diagram of the patch image formed on the intermediate transfer belt 12 when the video controller 202 performs patch image density processing, as viewed from the vertically downward direction of the image forming apparatus 100 shown in Figure 1. The arrows indicate the direction of movement of the intermediate transfer belt 12. Figure 4(b) shows the relationship between the density (reference density) of the patch image formed based on the video signal 506 output from the video controller 202 and the measured density of the patch image detected by the density sensor 70.

[0032] In this embodiment, the video controller 202 transmits video signals 506 corresponding to multiple reference density patch images to the engine control unit 203 in order to form patch images (toner patch images) on the intermediate transfer belt 12 for which image density is to be measured. The engine control unit 203, with the help of the image formation control unit 205 and the intermediate transfer belt / photosensitive drum drive unit 208, forms multiple patch images on the intermediate transfer belt 12 according to the video signals 506. In this embodiment, as shown in Figure 4(a), four patch images are formed: patch image 1 (20%), patch image 2 (40%), patch image 3 (60%), and patch image 4 (80%). The numbers in parentheses indicate the halftone density as the reference density for each patch image. Thus, the multiple reference densities are halftone densities. Density sensors 70 are positioned in the direction in which patch images 1 to 4 move, and the density sensors 70 detect the density of patch images 1 to 4. In the engine control unit 203, the multiple halftone density detection unit 206 acquires the densities of patch images 1 to 4 detected by the density sensor 70 as measured densities 1 to 4, and transmits the acquired measured densities 1 to 4 to the video controller 202.

[0033] The video controller 202 creates a LUT 700 (image tone level-density conversion table) based on the measured densities 1-4 of patch images 1-4 received from the engine control unit 203. In Figure 4(b), patch images 1-4 shown on the horizontal axis represent the density (reference density) of the patch image indicated by the video signal 506 output from the video controller 202. The measured densities 1-4 shown on the vertical axis represent the densities of patch images 1-4 detected by the density sensor 70. In the figure, the dashed curve 700 is the LUT that performs image tone level-density conversion. The video controller 202 creates the LUT based on the measured densities of patch images 1-4 detected by the density sensor 70, and performs image formation based on the LUT when executing a print job.

[0034] [Calculation of toner consumption using an image pixel count detection circuit] Next, the method for calculating toner consumption using the image pixel count detection circuit 518, which is a measurement means shown in Figure 2, will be explained. The image pixel count detection circuit 518 samples the video signal 506 (Figure 2), which is a laser drive signal output from the video controller 202. When the video signal 506 is at a high level (hereinafter referred to as "H"), which instructs the laser element 75 of the exposure unit 10 to emit laser light, the image pixel count detection circuit 518 updates the count value of its internal H level measuring counter. On the other hand, when the video signal 506 is at a low level (hereinafter referred to as "L"), which instructs the laser element 75 of the exposure unit 10 to turn off, the image pixel count detection circuit 518 does not update the counter.

[0035] The CPU 508 of the engine control unit 203 obtains the number of times the video signal 506 has become "H" from the image pixel count detection circuit 518, i.e., the counter count value, each time the video controller 202 finishes outputting a video signal corresponding to each color of toner. The CPU 508 has a toner consumption calculation unit 507 (Figure 2), which is a calculation means for calculating toner consumption. The toner consumption calculation unit 507 calculates the toner consumption of each color based on the count value received from the image pixel count detection circuit 518 and the measured image density. The CPU 508 then transmits the calculation results of the toner consumption of each color, calculated by the toner consumption calculation unit 507, to the video controller 202 via the communication circuit 511.

[0036] [Relationship between image density and toner consumption] Figure 5(a) shows the relationship between solid density (100% image density), halftone density (image density greater than 0% and less than 100%), and toner consumption per unit dot. The horizontal axis represents halftone density, and the vertical axis represents toner consumption per unit dot area (hereinafter also referred to as image pixel). In Figure 5(a), when the toner consumption per unit area at a toner density of 100% is set to 1.0, the toner consumption per unit area at halftone densities of 20%, 40%, 60%, and 80% is 0.35, 0.6, 0.8, and 0.92, respectively. Generally, the lower the halftone density, the less toner adheres to the photosensitive drum. Therefore, it is known that the toner consumption per unit area decreases, resulting in the curve shown in Figure 5(a).

[0037] Figure 5(b) is a schematic diagram showing the result when 2 out of 10 image pixels arranged in the main scanning direction (from left to right in the figure) are printed at 100% density. In Figure 5(b), image pixels 600 to 609 represent image pixels printed at a resolution of 600 dpi (size of 0.042 mm per dot) in the main scanning direction and the sub-scanning direction (a direction perpendicular to the main scanning direction, referring to the vertical direction in the figure), respectively. Of image pixels 600 to 609, image pixels 600 and 601 are printed at 100% density, while the other image pixels 602 to 609 are printed at 0% density, resulting in a total laser emission amount of 200% (= 100% × 2 image pixels).

[0038] On the other hand, Figure 5(c) is a schematic diagram of 10 image pixels (pixels) arranged in the main scanning direction (from left to right in the figure) printed with a halftone density of 20%. Image pixels 610 to 619 represent image pixels when printed with a resolution of 600 dpi in the main scanning direction and the sub-scanning direction (a direction perpendicular to the main scanning direction, referring to the up and down direction in the figure), and all have a print density of 20% halftone density. Generally, when forming a halftone image, one image pixel (pixel) is divided using PWM (pulse width modulation) relative to the main scanning direction, with a constant length in the sub-scanning direction, and the laser element 75 is made to emit light according to the halftone density to form a halftone image. The total amount of laser light emitted at this time is 20% × 10 image pixels = 200%, which is the same as the amount of laser light emitted in Figure 5(b). However, in terms of toner consumption, in the case of Figure 5(b), it is 100% (toner density) × 1.0 (toner consumption rate) × 2 (image pixels) = 200%. On the other hand, in the case of Figure 5(c), it is 20% (toner density) × 0.35 (toner consumption rate) × 10 (image pixels) = 70%. Although the total laser emission amount is the same 200% in Figure 5(c) as in Figure 5(b), the toner consumption is 200% in Figure 5(b) compared to 70% in Figure 5(c), indicating that toner consumption is decreasing.

[0039] [Detection of image pixel count] Figure 6 illustrates the detection and counting method for the number of image pixels in this embodiment. Figure 6(a) is a schematic diagram showing the printing of a total of 10 image pixels with halftone densities of 20% to 80% and 100% density in the main scanning direction (from left to right in the figure). Image pixels 620 to 629 represent image pixels when printed with a resolution of 600 dpi in the main scanning direction and sub-scanning direction (a direction perpendicular to the main scanning direction, referring to the up and down direction in the figure), respectively. Figure 6(b) shows the signal waveform of the video signal 506 output from the video controller 202 and input to the laser drive circuit 515 via the image pixel count detection circuit 518 in order to print the image pixels in Figure 6(a). In Figure 6(b), the video signal 506 is ON only during the period when the laser light is irradiated in Figure 6(a).

[0040] Figure 6(c) shows the sampling timing of the image pixel count detection circuit 518 (black circles in the figure), the sampling result shown as 0 or 1, and the sampling result for each image pixel. In this embodiment, as shown in Figure 6(c), the image pixel count detection circuit 518 performs 5 samples on the input video signal 506 during the time it takes for one image pixel to be formed in the video signal 506. The number of times the video signal 506 is ON out of the 5 samples is defined as the ON ratio. For image pixel 620, the ON state of the video signal 506 is detected once out of the 5 samples, resulting in a count of 1 (ON ratio of 20%). For image pixel 621, the ON state of the video signal 506 is not detected out of the 5 samples, resulting in a count of 0 (ON ratio of 0%). For image pixels 622 and 623, the ON state of the video signal 506 is detected twice out of the 5 samples, resulting in a count of 2 (ON ratio of 40%). In image pixels 624 and 625, the ON state of video signal 506 was detected 3 times out of 5 samples, resulting in a count of 3 (60% ON rate). In image pixel 626, the ON state of video signal 506 was not detected out of 5 samples, resulting in a count of 0. In image pixel 627, the ON state of video signal 506 was detected 4 times out of 5 samples, resulting in a count of 4 (80% ON rate). In image pixels 628 and 629, the ON state of video signal 506 was detected 5 times (full count) out of 5 samples, resulting in a count of 5 (100% ON rate).

[0041] Figure 6(d) is a table summarizing the sampling results of the image pixel count detection circuit 518 shown in Figure 6(c). In the table in Figure 6(d), the left column shows the count of the image pixel count detection circuit 518. Since one image pixel is sampled 5 times, there are 6 possible counts from 0 to 5. In other words, there are 6 possible ON percentages: 0%, 20%, 40%, 60%, 80%, and 100% (6 patterns). In the table in Figure 6(d), the center column shows the density of the image pixels corresponding to the count of the image pixel count detection circuit 518. Counts of 0, 1, 2, 3, 4, and 5 (ON percentages of 0%, 20%, 40%, 60%, 80%, and 100%) correspond to halftone densities of 0%, 20%, 40%, 60%, 80%, and 100%, respectively. In the table in Figure 6(d), the right-hand column shows the number of detected image pixels corresponding to the count of the image pixel count detection circuit 518. In the case of the video signal 506 shown in Figure 6(b), as shown in Figure 6(d), 5 counts (100% no halftone) correspond to 2 image pixels, and 4 counts (80% halftone density) correspond to 1 image pixel. Also, in the case of the video signal 506 shown in Figure 6(b), 3 counts (60% halftone density) correspond to 2 image pixels, 2 counts (40% halftone density) correspond to 2 image pixels, and 1 count (20% halftone density) corresponds to 1 image pixel. Furthermore, in the case of the video signal 506 shown in Figure 6(b), 0 counts (0% halftone density) correspond to 2 image pixels.

[0042] [How to calculate toner consumption] Next, the method for calculating toner consumption in this embodiment will be explained. Toner consumption is calculated by calculating the toner consumption for printing at the density of each halftone area and the toner consumption for printing at 100% density outside the halftone area, and then adding them together.

[0043] Figure 7(a) shows the relationship between the reference density and the measured density for each halftone density, and the toner consumption weighting coefficient (ratio). Reference densities 1 to 4 represent the density of the patch image formed by the video signal transmitted from the video controller 202. Measured densities 1 to 4 represent the density detected by the density sensor 70 in the patch images 1 to 4 formed on the intermediate transfer belt 12 by the video signal transmitted from the video controller 202. The toner consumption weighting coefficients 1 to 4 (weighting coefficients in the figure) represent the toner consumption per unit image pixel when printing at each reference density 1 to 4, and are the values ​​of the toner consumption rate per unit dot shown on the vertical axis of the graph in Figure 5(a) above. Figure 7(b) shows the number of image pixels for each halftone density shown in the table in Figure 6(d) above. Figure 7(b) shows that the number of image pixels with halftone densities of 20%, 40%, 60%, and 80% are 1, 2, 2, and 1, respectively, while the number of image pixels with 100% density (not halftone) is 2.

[0044] First, the concentration correction coefficient for each halftone concentration is determined using the measured concentration and the reference concentration for each halftone concentration. The concentration correction coefficient is the ratio of the measured concentration to the reference concentration and is expressed by the following (Equation 1). The concentration correction coefficient, which is the correction value, is calculated by the control unit 204, which is the correction value calculation means. Concentration correction factor = Measured concentration / Reference concentration ... (Equation 1)

[0045] Furthermore, the toner consumption correction coefficient per image pixel for each density in the halftone area can be determined for each density by multiplying the density correction coefficient obtained by (Equation 1) by the toner consumption weighting coefficient for the corresponding density. Toner consumption correction coefficient per image pixel for each density in the halftone area = Toner consumption weighting coefficient × Density correction coefficient ... (Equation 2) This is the result.

[0046] The toner consumption for the halftone area can be determined by the following formula (Equation 3). Specifically, the toner consumption for the halftone area is calculated by multiplying the toner consumption correction coefficient per image pixel for each density of the halftone area by the print density of each density and the number of image pixels for each density to obtain the toner consumption for each density, and then summing up the toner consumption for each density. Toner consumption for halftone areas = Toner consumption correction factor per image pixel: 1 × 0.2 × number of image pixels 1 +1 Toner consumption correction factor per image pixel: 2 × 0.4 × Number of image pixels: 2 +1 Toner consumption correction factor per image pixel: 3 × 0.6 × Number of image pixels: 3 +1 Toner consumption correction factor per image pixel: 4 × 0.8 × Number of image pixels: 4 ...(Formula 3)

[0047] In (Equation 3), the toner consumption correction coefficients 1, 2, 3, and 4 per image pixel represent the toner consumption correction coefficients per image pixel for halftone areas with densities of 20%, 40%, 60%, and 80%, respectively. Furthermore, the number of image pixels 1, 2, 3, and 4 represent the number of image pixels for halftone areas with densities of 20%, 40%, 60%, and 80%, respectively.

[0048] Furthermore, the toner consumption rate for an image pixel with a density of 100% is 1.0, as shown in Figure 5(a). Therefore, the toner consumption for areas other than the halftone areas, i.e., the toner consumption for image pixels with a density of 100%, can be expressed as the number of image pixels with a count of 5 in the image pixel count detection circuit 518 in Figure 6(d), as shown in (Equation 4) below. Toner consumption excluding halftone areas = number of image pixels = 5... (Equation 4)

[0049] The toner consumption for each color can then be calculated by adding the toner consumption for the halftone area, calculated using (Equation 3), to the toner consumption for areas other than the halftone area, calculated using (Equation 4), and using the following (Equation 5). Toner consumption = Toner consumption for areas other than the halftone area + Toner consumption for the halftone area... (Equation 5) In this explanation, we described the processing of 10 image pixels in Figure 6 as an example of a printed image, but this method can also be applied to the entire printed image on one page of a sheet.

[0050] [Process flowchart for calculating toner consumption] Figure 8 is a flowchart showing the process of calculating the toner consumption of each color in this embodiment and notifying the user. The process shown in Figure 8 is started when the power of the image forming apparatus 100 is turned on and is executed by the engine control unit 203. In the following, the process will be explained using the functional blocks of the engine control unit 203 described in Figure 3.

[0051] In step 501 (hereinafter referred to as S), density detection is performed using patch images in order to create a LUT (Lookup Table). The video controller 202 performs image formation based on the LUT when executing a print job. The control unit 204 calculates a toner consumption correction coefficient for each halftone density using (Equation 1) and (Equation 2) based on the density of the patch images acquired from the multiple halftone density detection unit 206 and the density of the patch images transmitted from the video controller 202.

[0052] In S502, the engine control unit 203 determines whether or not it has received a print job (print instruction) from the video controller 202. If the engine control unit 203 determines that it has received a print job from the video controller 202, it proceeds to S503; if it determines that it has not received a print job, it returns to S502.

[0053] In S503, the engine control unit 203 controls the image forming control unit 205 to start printing one sheet 2 and determine whether printing for each toner color has been completed. If the engine control unit 203 finds that printing has been completed for any of the multiple toner colors based on the video signal 506 from the video controller 202, it proceeds to S504 to calculate the consumption of the toner that has been printed. On the other hand, if the engine control unit 203 determines that there is no toner of any color that has been printed, it returns to S503.

[0054] In S504, the control unit 204 obtains the number of image pixels (image pixel count) from the pixel count unit 207 where the count of one image pixel is 5 (image pixels with 100% density other than halftone). In S505, the control unit 204 obtains the number of image pixels (image pixel count) from the pixel count unit 207 for each halftone density of 20%, 40%, 60%, and 80% where the count of one image pixel is less than 5. In S506, the control unit 204 calculates the toner consumption of one color using the toner consumption calculation unit 507 of the CPU 508. The toner consumption calculation unit 507 calculates the toner consumption using the above-mentioned (Equations 3) to (Equations 5). In S507, the control unit 204 transmits the toner consumption corresponding to the toner color to the video controller 202 via the communication circuit 511. The video controller 202 displays the received toner consumption on the display unit (not shown) of the image forming apparatus 100 and notifies the user.

[0055] In S508, the control unit 204 determines whether printing of all sheets 2 has finished and whether the print job has ended. If the control unit 204 determines that the print job has ended, it returns to S502. If it determines that the print job has not ended, it returns to S503 to print the next sheet 2.

[0056] In this embodiment, when the image forming apparatus 100 is powered on, a patch image is formed and density detection is performed, and a LUT is created according to the detected density. For example, as a control of the engine control unit 203, there is a configuration in which a density value is predicted at a predetermined frequency and the density value is determined without forming a patch image when the power is turned on. By using such a configuration, the frequency of density detection by the video controller 202 can be reduced, the amount of toner consumed due to patch image formation can be reduced, and the downtime due to printing interruption for patch image formation can be reduced. In addition, in such a configuration that predicts the density of a patch image, the density prediction is performed using parameters such as the environment of the image forming apparatus (temperature, humidity), the output value of the high-voltage device 224, and the amount of consumables used, and the predicted density value can be used as the measured density to calculate the amount of toner consumed. Furthermore, in this embodiment, the amount of toner consumed was calculated using the density measurement results of four types of halftone densities (20%, 40%, 60%, 80%), but the types of densities are not limited to four types. In order to improve the accuracy of the toner consumption calculation, the amount of toner consumed may be calculated using density measurement results using even more types of densities. Furthermore, although this embodiment shows a configuration for measuring patch images on the intermediate transfer belt 12, a configuration for measuring patch images on the photosensitive drum 5 may also be used.

[0057] As described above, the engine control unit 203 obtains the ratio of multiple measured densities, each measured by the density sensor 70 for the toner densities of multiple toner patch images formed on the intermediate transfer belt 12 at multiple reference densities, and the reference densities corresponding to the multiple measured densities. The engine control unit 203 calculates the total toner consumption using a corrected toner consumption rate obtained by correcting the toner consumption rate corresponding to the on-percentage by the ratio. Here, the number of on-percentage patterns that can take place in the range greater than 0% and less than 100% (4 patterns) matches the number of toner patch images formed on the intermediate transfer belt 12 (4). Also, the multiple reference densities are toner densities that correspond to on-percentages that can take place in the range greater than 0% and less than 100%. As explained above, this embodiment makes it possible to improve the accuracy of calculating toner consumption. [Examples]

[0058] Example 1 describes an example in which the density of the patch used by the video controller to create the LUT and the density of the halftone area determined by the pixel count detected by the engine control unit are the same. Example 2 describes an example in which the density of the patch used by the video controller to create the LUT and the density of the halftone area determined by the image pixel count detected by the engine control unit are different. In Example 2, the engine control unit 203 calculates the toner density corresponding to the on-ratio by interpolating using multiple reference densities and multiple measured densities.

[0059] [Patch density detection using a video controller] The video controller 202 forms multiple patch images of specific densities on the intermediate transfer belt 12 and creates a LUT (lookup table) based on the measured density of the patch images detected by the density sensor 70 notified by the engine control unit 203. When the video controller 202 wants to stabilize the density overall, it sets a wide range for the density of the patch images to be created, and when it wants to stabilize the density of the halftone mid-section, it narrows the range for the density of the patch images to be created by concentrating it in the halftone mid-section region. In this way, the range of multiple reference densities is narrower than the range of toner densities that can be taken in the range greater than 0% and less than 100%.

[0060] Figure 9(a) is a graph showing the relationship between the patch image formed based on the video signal 506 output from the video controller 202 and the measured density of the patch image detected by the density sensor 70. The patch image in Figure 9(a) shows the image when the density adjustment range is narrowed by concentrating it in the halftone mid-region. Specifically, the video controller 202 forms patch images 1', 2', 3', and 4' corresponding to halftone densities of 35%, 45%, 55%, and 65% on the intermediate transfer belt 12. The density sensor 70 detects the patch images 1' to 4' on the intermediate transfer belt 12, and the engine control unit 203 transmits the measured densities 1' to 4', which were detected with a focus on the halftone mid-region, to the video controller 202. The video controller 202 creates the LUT 701 based on the measured density of the patch image received from the engine control unit 203.

[0061] Figure 9(b) shows the number of image pixels for each count detected by the pixel count unit 207 based on the output of the image pixel count detection circuit 518, and shows the same results as the counts shown in Figure 6(d) above. The detection accuracy of the pixel count for each density in the halftone area depends on the processing speed of the engine control unit 203 and is often lower than the resolution of the density specified range of the video controller 202. Therefore, as shown in Figures 9(a) and 9(b), it may not match the density range of the patch image used by the video controller 202.

[0062] [How to calculate toner consumption] Figure 10 illustrates how toner consumption is calculated when the density of the patch image used by the video controller 202 to create the LUT differs from the density of the halftone area determined by the image pixel count detected by the engine control unit 203. In Figure 10, the reference densities 1', 2', 3', and 4' represent the densities of the patch image created by the video controller 202 (35%, 45%, 55%, and 65%), respectively. Figure 10 also shows that the density sensor 70 detects patch images 1' to 4', and the measured densities are the measured densities 1', 2', 3', and 4'.

[0063] Furthermore, the halftone densities of 20%, 40%, 60%, and 80% represent the halftone densities determined from the pixel count detected by the engine control unit 203. The weighting coefficients 1 to 4 represent the toner consumption per unit image pixel when printing at standard densities of 20%, 40%, 60%, and 80%, respectively, and are the same values ​​as the weighting coefficients in Figure 7(a) of Example 1.

[0064] The following describes a method for calculating density correction coefficients for halftone areas with densities of 20%, 40%, 60%, and 80% by interpolating them based on the reference density and measured density of patch images with halftone areas with densities of 35%, 45%, 55%, and 65%.

[0065] The density correction coefficient 1' for a halftone area with a density of 20% is calculated by interpolating between the measured density 1' of the patch image with a halftone area density of 35%, the reference density 1', and the density at 0%. The density correction coefficient at 0% is set to 1. Concentration correction factor 1' = 1 +{(Measurement concentration 1' / Reference concentration 1')-1} ×{(20%-0%) / (35%-0%)} (Formula 6)

[0066] The density correction coefficient 2' for a halftone density of 40% is calculated by interpolation using the measured density 1' and reference density 1' of the patch image when the halftone density is 35%, and the measured density 2' and reference density 2' of the patch image when the halftone density is 45%. Concentration correction coefficient 2' = (Measurement concentration 1' / Reference concentration 1') +{(Measurement concentration 2' / Reference concentration 2')-(Measurement concentration 1' / Reference concentration 1')} ×{(40%-35%) / (45%-35%)} (Equation 7)

[0067] The density correction coefficient 3' for a halftone area with a density of 60% is calculated by interpolation using the measured density 3' and reference density 3' of the patch image when the halftone area density is 55%, and the measured density 4' and reference density 4' of the patch image when the halftone area density is 65%. Concentration correction coefficient 3' = (Measurement concentration 3' / Reference concentration 3') +{(Measurement concentration 4' / Reference concentration 4')-(Measurement concentration 3' / Reference concentration 3')} ×{(60%-55%) / (65%-55%)} (Equation 8)

[0068] The density correction coefficient 4' for a halftone area with a density of 80% is calculated by interpolating between the measured density 4' of the patch image with a halftone area density of 65%, the reference density 4', and the density of 100%. The density correction coefficient for a density of 100% is set to 1. Concentration correction coefficient 4' = (Measurement concentration 4' / Reference concentration 4') +{1-(measured concentration 4' / reference concentration 4')}×{(80%-65%) / (100%-65%)} (Equation 9)

[0069] Using the density correction coefficients 1' to 4' calculated using (Equations 6) to (9), the toner consumption of the halftone area is determined by the following (Equation 10) in the same manner as in Example 1. Toner consumption for halftone areas = Density correction coefficient 1' × Toner consumption per image pixel Correction coefficient 1 × 0.2 × Number of image pixels 1 + Density correction factor 2' × Toner consumption correction factor per image pixel 2 × 0.4 × Number of image pixels 2 + Density correction factor 3' × Toner consumption per image pixel × 0.6 × Number of image pixels 3 + Density correction coefficient 4' × Toner consumption correction coefficient per image pixel 4 × 0.8 × Number of image pixels 4 ... (Equation 10)

[0070] The toner consumption correction coefficients 1, 2, 3, and 4 per image pixel represent the toner consumption correction coefficients per image pixel for halftone areas with densities of 20%, 40%, 60%, and 80%, respectively, as described in Example 1. The number of image pixels 1, 2, 3, and 4 represent the number of image pixels for halftone areas with densities of 20%, 40%, 60%, and 80%, respectively.

[0071] Furthermore, the toner consumption for areas other than the halftone areas, i.e., the toner consumption for areas with a density of 100%, can be expressed as the number of image pixels with a count of 5, as shown in (Equation 4) of Example 1 above. The toner consumption for each color can then be determined by adding the toner consumption for the halftone areas and the toner consumption for areas other than the halftone areas, using (Equation 5) of Example 1 above.

[0072] [Process flowchart for calculating toner consumption] Figure 11 is a flowchart showing the process for calculating toner consumption in this embodiment and notifying the user. The process shown in Figure 11 is started when the power of the image forming apparatus 100 is turned on and is executed by the engine control unit 203. In the following, the process will be described using the functional blocks of the engine control unit 203 described in Figure 3 of Embodiment 1.

[0073] In S511, density detection is performed using patch images to create a LUT. The video controller 202 performs image formation based on the LUT when executing a print job. The control unit 204 calculates density correction coefficients 1' to 4' from equations (6) to (9) based on the density of the patch images acquired from the multiple halftone density detection unit 206 and the density of the patch images transmitted from the video controller 202. The toner consumption correction coefficients 1, 2, 3, and 4, which are toner consumption correction coefficients per image pixel for halftone densities of 20%, 40%, 60%, and 80%, are stored in advance in the ROM 510 of the engine control unit 203 and acquired by the control unit 204.

[0074] The processing in S512 to S515 is the same as the processing in S502 to S505 in Figure 8 of Example 1, and therefore will not be explained here. In S516, the control unit 204 calculates the density correction coefficients 1' to 4'. In S517, the control unit 204 calculates the halftone pixel count using the density correction coefficients 1' to 4' calculated in S516. That is, the control unit 204 corrects the number of pixel counts for halftone areas with densities of 20%, 40%, 60%, and 80% using the density correction coefficients 1' to 4'. Specifically, the halftone pixel count for a halftone area with a density of 20% can be calculated by multiplying the density correction coefficient 1' by the number of pixels in the halftone area with a density of 20%, which is 1. Similarly, the halftone pixel counts for halftone areas with densities of 40%, 60%, and 80% can be calculated by multiplying the density correction coefficients 2', 3', and 4', respectively, by the number of image pixels with halftone densities of 40%, 60%, and 80%.

[0075] In S518, the control unit 204 calculates the toner consumption for areas other than the halftone area using the above-mentioned (Equation 4), calculates the toner consumption for the halftone area using the above-mentioned (Equation 10), and calculates the toner consumption for one color by adding the two toner consumption amounts together. The processing in S519 and S520 is the same as the processing in S507 and S508, and is therefore omitted from this explanation.

[0076] In this embodiment, the video controller 202 had a reference density for each patch density it formed and performed calculations accordingly. However, it is also possible to have a reference density value for each pixel count detection density, interpolate the measured density to obtain a density correction coefficient, and then perform toner consumption calculations.

[0077] As explained above, this embodiment makes it possible to improve the accuracy of calculating toner consumption. [Examples]

[0078] In Examples 1 and 2, the video signal drives a laser element to form a halftone image in the center of one image pixel, and toner consumption is calculated based on the count of the pixel count unit that detects the ON state of the video signal driving the laser element. In the image processing of the video controller, the ON state corresponding to the halftone portion in the video signal may be distributed to the front and rear edges of one image pixel, rather than to the center. In such cases, even if one image pixel contains a halftone image, if the adjacent image pixels are not halftone images with a density of 100%, the toner consumption may be the same as that for 100% print density of one image pixel. Therefore, Example 3 describes an example in which, instead of detecting the number of ON signals that drive the laser element of the video signal for each image pixel, the number of consecutive ON signals that drive the laser element is detected, and toner consumption is calculated based on the number of detected ON signals.

[0079] [Detection of image pixel count] Figure 12 illustrates the detection and counting method for the number of image pixels in this embodiment. Figure 12(a) is a schematic diagram showing the printing of a total of 10 image pixels in the main scanning direction (from left to right in the figure), with halftone densities of 20% to 80% and 100% density. Image pixels 630 to 639 represent image pixels printed with a resolution of 600 dpi in the main scanning direction and sub-scanning direction (a direction perpendicular to the main scanning direction, referring to the up and down direction in the figure), respectively. Figure 12(b) shows the signal waveform of the video signal 506 output from the video controller 202 and input to the laser drive circuit 515 via the image pixel count detection circuit 518 in order to print the image pixels in Figure 12(a). In Figure 12(b), the video signal 506 is ON only during the period when the laser light is irradiated in Figure 12(a). Here, in image pixels 631 and 638, the ON signal that drives the laser element during halftone is set to the edge side of the image pixel, rather than the center.

[0080] Figure 12(c) shows the sampling timing of the image pixel count detection circuit 518 (black circles in the figure), the sampling result shown as 0 or 1, and the sampling result for each image pixel. In this embodiment, as shown in Figure 12(c), five samples are taken from the video signal 506 during the time it takes to form one image pixel. In this embodiment, the engine control unit 203 detects the number of consecutive ON signals in the video signal 506 that drives the laser element, rather than on a per-image-pixel basis, and the number of image pixels corresponding to the number of detected ON signals. For example, in image pixels 630 and 631, there are six consecutive ON signals, which is more than the size of one image pixel (five ON signals), and the sampling result is 6 counts, with a density of 100%. Similarly, image pixels 638 and 639 have densities of 80% and 100%, respectively, but because there are nine consecutive ON signals, the density is detected as 100% after 9 counts.

[0081] Figure 12(d) is a table summarizing the sampling results of the image pixel count detection circuit 518 shown in Figure 12(c). As shown in Figure 12(d), out of 10 image pixels, there is one with a count of 9 (100% density, not halftone), one with a count of 6 (100% density, not halftone), and zero with a count of 4 (80% halftone density). Furthermore, there are two with a count of 3 (60% halftone density), three with a count of 2 (40% halftone density), zero with a count of 1 (20% halftone density), and one with a count of 0 (0% density).

[0082] [How to calculate toner consumption] The toner consumption for the halftone area is calculated using equations (1) to (3), similar to the first example described above. On the other hand, the toner consumption for areas other than the halftone area is the sum of the counts of 5 or more recorded by the image pixel detection circuit 518 in Figure 12(d). For example, if an image pixel has a count of 5 in the image pixel detection circuit 518 in Figure 12(d), the density is 100%, and the toner consumption is expressed as 1. Also, if the image pixels in the image pixel detection circuit 518 shown in Figure 12(d) have counts of 6 and 9, the toner consumption is expressed as 1.2 (=6 / 5) and 1.8 (=9 / 5), respectively. The engine control unit 203 calculates the toner consumption of the 100% image pixel and its adjacent image pixels based on the toner consumption rate corresponding to the 100% on ratio, when an image pixel adjacent to an image pixel with an on ratio of 100% is continuously on with the 100% image pixel. As a result, the toner consumption for areas other than the halftone area shown in Figure 12(d) is 3.0 (=1.2 + 1.8). The toner consumption for each toner color in this embodiment is given by the following (Equation 11), similar to the above-described Example 1. Toner consumption = Toner consumption for areas other than the halftone area + Toner consumption for the halftone area... (Equation 11)

[0083] [Process flowchart for calculating toner consumption] Figure 13 is a flowchart showing the process of calculating the toner consumption of each color in this embodiment and notifying the user. The process shown in Figure 13 is started when the power of the image forming apparatus 100 is turned on, and is executed by the engine control unit 203, similar to Figure 8 in Embodiment 1. In the following, the process will be explained using the functional blocks of the engine control unit 203 described in Figure 3 of Embodiment 1.

[0084] The processing in S531 to S533 is the same as the processing in S501 to S503 in Figure 8 of Example 1, and therefore the explanation is omitted here. In S534, the control unit 204 obtains the number of image pixels for each consecutive count for image pixels where the consecutive count of the image pixel count detection circuit 518 is 5 or more, from the pixel count unit 207. In S535, the control unit 204 obtains the number of image pixels for each consecutive count (which is also the density of the halftone part) for image pixels where the consecutive count of the image pixel count detection circuit 518 is 4 or less (less than 5), from the pixel count unit 207. In S536, the control unit 204 calculates the toner consumption of one color using the toner consumption calculation unit 507 of the CPU 508. The toner consumption calculation unit 507 calculates the toner consumption using the above-mentioned (Equation 11). The processing in S537 and S538 is the same as the processing in S507 and S508 in Figure 8 of Example 1, and therefore the explanation is omitted here.

[0085] As explained above, this embodiment makes it possible to improve the accuracy of calculating toner consumption.

[0086] The present invention comprises the following configuration. [Configuration 1] Photosensitive drum and An exposure means that exposes the surface of the photosensitive drum to form an electrostatic latent image in response to the on / off state of an image signal based on image data, A developing roller configured to supply toner to the electrostatic latent image on the photosensitive drum to form a toner image on the photosensitive drum, An image forming apparatus having a toner image transferred to a recording material, An acquisition unit that acquires an ON ratio for each image pixel of the image data, which includes a value greater than 0% and less than 100% of the image signal, and a toner consumption rate corresponding to the ON ratio. A calculation unit that calculates the total toner consumption of all image pixels in the image data based on the ON ratio and toner consumption rate acquired by the acquisition unit for each of the aforementioned image pixels, An image forming apparatus characterized by comprising: [Configuration 2] An intermediate transfer body onto which the toner image is transferred from the photosensitive drum, A measuring means for measuring the toner density of the toner patch image transferred to the intermediate transfer medium, It has, The acquisition unit acquires the ratio of a plurality of measured concentrations, each measured by the measuring means, of the toner densities of a plurality of toner patch images formed on the intermediate transfer body at a plurality of reference concentrations, and the reference concentration corresponding to the plurality of measured concentrations. The image forming apparatus according to configuration 1, characterized in that the calculation unit calculates the total toner consumption using a corrected toner consumption rate obtained by correcting the toner consumption rate corresponding to the ON ratio by the ratio. [Configuration 3] The image forming apparatus according to configuration 1 or configuration 2, characterized in that the number of on-ratio patterns that the acquisition unit can take within a range greater than 0% and less than 100% matches the number of toner patch images formed on the intermediate transfer body. [Structure 4] The image forming apparatus according to any one of configurations 1 to 3, characterized in that the plurality of reference concentrations are toner concentrations corresponding to the on-percentage, which can be taken in a range greater than 0% and less than 100%. [Composition 5] The image forming apparatus according to any one of configurations 1 to 4, characterized in that the plurality of reference densities are halftone densities. [Composition 6] The image forming apparatus according to any one of configurations 1 to 5, characterized in that the range of the multiple reference densities is narrower than the range of toner densities corresponding to the on-percentage, which can be taken in a range greater than 0% and less than 100%. [Composition 7] The image forming apparatus according to configuration 6, characterized in that the calculation unit calculates the toner concentration corresponding to the ON ratio by interpolating using the plurality of reference concentrations and the plurality of measurement concentrations. [Structure 8] The image forming apparatus according to any one of configurations 1 to 7, characterized in that the calculation unit calculates the toner consumption of the 100% image pixel and the adjacent image pixel based on the toner consumption rate corresponding to the 100% on ratio when an image pixel adjacent to the 100% on ratio is continuously on with the 100% image pixel. [Explanation of symbols]

[0087] 5 Photosensitive drum 8R developing roller 10 Exposure area 70 Concentration Sensor 203 Engine Control Unit

Claims

1. Photosensitive drum and An exposure means that exposes the surface of the photosensitive drum to form an electrostatic latent image in response to the on / off state of an image signal based on image data, A developing roller configured to supply toner to the electrostatic latent image on the photosensitive drum to form a toner image on the photosensitive drum, An image forming apparatus having a toner image transferred to a recording material, An acquisition unit that acquires an ON ratio for each image pixel of the image data, which includes a value greater than 0% and less than 100% of the image signal, and a toner consumption rate corresponding to the ON ratio. The system includes a calculation unit that calculates the total toner consumption of all image pixels in the image data based on the ON ratio and toner consumption rate acquired by the acquisition unit for each of the aforementioned image pixels, The image forming apparatus is characterized in that the acquisition unit samples the image signal multiple times during the period for forming one image pixel, and acquires the ON ratio based on the number of times the image signal is detected to be ON among the multiple samples.

2. An intermediate transfer body onto which the toner image is transferred from the photosensitive drum, A measuring means for measuring the toner density of the toner patch image transferred to the intermediate transfer medium, It has, The acquisition unit acquires the ratio of a plurality of measured concentrations, each measured by the measuring means, of the toner densities of a plurality of toner patch images formed on the intermediate transfer body at a plurality of reference concentrations, and the reference concentration corresponding to the plurality of measured concentrations. The image forming apparatus according to claim 1, characterized in that the calculation unit calculates the total toner consumption using a corrected toner consumption rate obtained by correcting the toner consumption rate corresponding to the ON ratio by the ratio.

3. The image forming apparatus according to claim 2, characterized in that the number of on-ratio patterns that the acquisition unit can take within a range greater than 0% and less than 100% is equal to the number of toner patch images formed on the intermediate transfer body.

4. The image forming apparatus according to claim 2, characterized in that the plurality of reference densities are toner densities corresponding to the on-percentage, which can be taken in a range greater than 0% and less than 100%.

5. The image forming apparatus according to claim 2, characterized in that the plurality of reference densities are halftone densities.

6. The image forming apparatus according to claim 2, characterized in that the range of the multiple reference densities is narrower than the range of toner densities corresponding to the on-percentage, which can be taken in a range greater than 0% and less than 100%.

7. The image forming apparatus according to claim 6, characterized in that the calculation unit calculates the toner concentration corresponding to the ON ratio by interpolating using the plurality of reference concentrations and the plurality of measurement concentrations.

8. The image forming apparatus according to claim 1, characterized in that the calculation unit calculates the toner consumption of the 100% image pixel and the adjacent image pixel based on the toner consumption rate corresponding to the 100% on ratio when an image pixel adjacent to the 100% on ratio is continuously on with the 100% image pixel.

Images