JP5588955B2 - Image forming apparatus - Google Patents

Description

  The present invention relates to a technique for preventing deterioration of a photosensitive drum provided in an image forming apparatus.

  In an electrophotographic image forming apparatus, a photosensitive drum is irradiated with a light beam generated by modulating image data to form an electrostatic latent image on the photosensitive drum, and toner is supplied to the electrostatic latent image. A toner image is formed, and the toner image is formed on a sheet and output. In such an image forming apparatus, a technique has been proposed in which toner is used as an abrasive and the peripheral surface of the photosensitive drum is refreshed by polishing the peripheral surface of the photosensitive drum with toner (see, for example, Patent Document 1). ).

JP 2008-203620 A

  In supplying toner to the electrostatic latent image formed on the photosensitive drum, an area where toner is frequently supplied to the photosensitive drum (for example, an area corresponding to the center of the paper) and an area where the toner is not (for example, paper) Area corresponding to the left and right edges of the image). When the state where the toner is not supplied or the state where the supply amount is small continues, the portion of the region of the photosensitive drum deteriorates.

  Generally, when a photosensitive drum is charged to form an electrostatic latent image on the photosensitive drum, discharge products adhere to the photosensitive drum due to discharge due to charging, and an oxide film is formed. The The titanium oxide fine powder containing the discharge product and the oxide film in the toner is adhered to a cleaning blade or the like and scraped off by the cleaning blade. However, if the supplied toner is small, it cannot be scraped off sufficiently. Therefore, on the photosensitive drum, the area where the supplied toner is small is in a state where the surface of the photosensitive body is not properly charged.

  Therefore, the photosensitive drum is virtually divided into a plurality of areas along the main scanning direction, and if a predetermined condition is satisfied (for example, every predetermined number of prints), an operation of forming an image on a sheet is executed. If the toner is forcibly supplied to an area where the toner supply amount is small when the toner is not supplied, the above-described deterioration can be suppressed.

  The area where the toner supply amount is small can be determined by the following method, for example. Using the density value included in the pixel data of each pixel constituting one main scanning line, the density value is calculated for each of the plurality of regions for each main scanning line. Then, a process for adding density values for each of the plurality of areas is executed by the counter circuit unit, and after a predetermined number of prints, an area in which the value counted by the counter circuit unit is smaller than the threshold value Use a small area.

  However, in this method, the density value is added for each of the plurality of regions. For this reason, for example, when an area for forcibly supplying toner is determined every time 1000 sheets are printed, the value counted by the counter circuit unit becomes large, so the scale of the counter circuit unit becomes large.

  According to the present invention, when the photosensitive drum is virtually divided into a plurality of areas along the main scanning direction, and the toner is forcibly supplied to an area where the toner supply amount is small, the scale of the counter circuit unit is increased. An object of the present invention is to provide an image forming apparatus capable of determining a region where toner is forcibly supplied.

  An image forming apparatus according to the present invention that achieves the above object is an image forming apparatus that forms an image on a sheet, and is rotated by a photosensitive drum and a light beam generated based on image data representing the image. The image forming apparatus repeats drawing one main scanning line on the photosensitive drum, and supplies toner to the photosensitive drum on which the electrostatic latent image is formed and an exposure unit that forms the electrostatic latent image of the image. The developing unit for forming a toner image and the photosensitive drum are virtually divided into a plurality of regions in the main scanning direction, and density values included in pixel data of each pixel constituting one main scanning line are used. Determining the region having the lowest toner density among the plurality of regions for each main scanning line drawn on the photosensitive drum and the region determining unit to determine the smallest region To be an area A counter circuit unit that counts a predetermined number of times for each of the plurality of regions, and when a predetermined condition is satisfied, a numerical value counted by the counter circuit unit is referred to, A region where toner is forcibly supplied is determined, and the developing unit is controlled to supply toner to the determined region when the image forming apparatus is not performing an operation of forming the image on a sheet. A toner forced supply unit.

  In the present invention, when supplying toner to the electrostatic latent image formed on the photosensitive drum, the toner density is the highest among a plurality of regions virtually provided on the photosensitive drum along the main scanning direction. The determination of the low region is executed for each main scanning line drawn on the photosensitive drum. Then, the number of times determined to be the lowest toner density area is counted for each of the plurality of areas. An area where toner is forcibly supplied is determined using the determined number of times. Therefore, according to the present invention, it is possible to determine a region where toner is forcibly supplied without increasing the scale of the counter circuit unit.

  The predetermined condition is every time a predetermined number of sheets are printed (for example, every 1000 sheets) or every time a predetermined period elapses.

  In the above configuration, the toner forced supply unit compares the number of determinations of each of the plurality of regions counted by the counter circuit unit with a predetermined threshold value, and the determination number of times is the threshold value. An area exceeding the threshold is determined as an area where toner is forcibly supplied.

  In this configuration, processing for forcibly supplying toner is performed in an area where the number of determinations exceeds a threshold value, that is, in an area where toner is not supplied or a supply amount is low. On the other hand, the process of forcibly supplying the toner is not performed in an area where the number of determinations does not exceed the threshold value, that is, an area where the toner is not supplied or the supply amount is not low. Accordingly, it is possible to supply the toner to all the areas where it is necessary to forcibly supply the toner and not to supply the toner to all the areas where it is not necessary to forcibly supply the toner.

  In the above-described configuration, the toner forced supply unit compares the determined times of the plurality of regions counted by the counter circuit unit, and determines a predetermined upper nth (n: the plurality of regions). An area up to an integer smaller than the number is determined as an area where toner is forcibly supplied.

  According to this configuration, the predetermined upper n-th areas are determined as areas for forcibly supplying toner. Therefore, in the process of forcibly supplying toner, the number of toner supply areas can be made the same in each process (in other words, the amount of toner used can be made the same in each process). .

  In the above configuration, the number of the plurality of regions is selected in advance from a predetermined number of ranges in the region determination unit, and one counter is provided for each of the plurality of regions in the counter circuit unit. And the number of counters is the same as the maximum value of the predetermined number range.

  According to this configuration, the counter circuit unit is shared when the number of areas is changed depending on the model of the image forming apparatus (for example, a model that can print A3 paper and a model that cannot print A3 paper). can do.

  According to the present invention, when the photosensitive drum is virtually divided into a plurality of areas along the main scanning direction, and the toner is forcibly supplied to an area where the toner supply amount is small, the size of the counter circuit unit is increased. A region where toner is forcibly supplied can be determined without increasing the size.

1 is a diagram illustrating an outline of an internal structure of an image forming apparatus according to an embodiment of the present invention. FIG. 2 is a block diagram illustrating a configuration of the image forming apparatus illustrated in FIG. 1. It is a figure which shows 16 area | regions virtually provided in the photoconductor drum. It is a figure which shows an example of the data structure of 1 line of main scanning. It is the 1st explanatory view explaining the field where the density value is the smallest in each main scanning 1 line. It is the 2nd explanatory view. It is the 3rd explanatory view. 5 is a flowchart (part 1) illustrating an operation of determining an area for forcibly supplying toner in the image forming apparatus according to the present embodiment. 6 is a flowchart (part 2) illustrating an operation of determining an area for forcibly supplying toner in the image forming apparatus according to the present embodiment.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a diagram showing an outline of the internal structure of an image forming apparatus 1 according to an embodiment of the present invention. The image forming apparatus 1 can be applied to, for example, a digital multi-function peripheral having a copy, printer, scanner, and facsimile function. The image forming apparatus 1 includes an apparatus body 100, a document reading unit 200, and a document feeding unit 300.

  A document reading unit 200 is disposed on the apparatus main body 100, and a document feeding unit 300 is disposed on the document reading unit 200.

  The document feeder 300 functions as an automatic document feeder, and can continuously send a plurality of documents placed on the document placement unit 301 to the document reading unit 200.

  The document reading unit 200 includes a carriage on which an exposure lamp or the like is mounted, a document table made of a transparent member such as glass, a CCD (Charge Coupled Device) sensor, and a document reading slit (all not shown). The CCD sensor outputs the read original as image data.

  The apparatus main body 100 includes a sheet storage unit 101, an image forming unit 103, and a fixing unit 105. The sheet storage unit 101 is disposed at the lowermost part of the apparatus main body 100 and includes two sheet cassettes 101a and 101b that can store a bundle of sheets.

  Among the paper cassettes 101a and 101b, in the bundle of paper stored in the selected cassette, the uppermost paper is sent out toward the paper conveyance path 107 of the apparatus main body 100 by driving a pickup roller (not shown). . The sheet is conveyed to the image forming unit 103 through the sheet conveyance path 107.

  The sheet conveyance path 107 extends in a substantially vertical direction from the lower side to the upper side along one side surface (right side surface in FIG. 1) of the apparatus main body 100, and the other side surface (left side surface in FIG. 1) above. And extends substantially horizontally along the lower side of the document reading unit 200. A discharge tray 131 is provided at the end.

  The image forming unit 103 forms a toner image on the conveyed paper. The image forming unit 103 includes a yellow image forming unit 111Y, a magenta image forming unit 111M, a cyan image forming unit 111C, and a black image forming unit 111BK, which are arranged according to the order in which the toner images are transferred to the transfer belt 113. These units have the same configuration and will be described by taking the yellow image forming unit 111Y as an example.

  The yellow image forming unit 111Y includes a photosensitive drum 115 and an exposure unit 117. Around the photosensitive drum 115, a charging unit 119, a developing unit 121, and a cleaning unit 123 are arranged. The charging unit 119 uniformly charges the peripheral surface of the photosensitive drum 115. The exposure unit 117 generates a modulated light beam corresponding to the image data (image data output from the document reading unit 200, image data transmitted from a personal computer, image data received by facsimile, etc.), and is uniformly charged. Irradiate the peripheral surface of the photoconductor drum 115. As a result, an electrostatic latent image corresponding to yellow image data is formed on the peripheral surface of the photosensitive drum 115. In this state, by supplying yellow toner from the developing unit 121 to the peripheral surface of the photosensitive drum 115, a toner image corresponding to yellow image data is formed on the peripheral surface.

  The transfer belt 113 can move counterclockwise while being sandwiched between the photosensitive drum 115 and the primary transfer roller 125. The yellow toner image is transferred from the photosensitive drum 115 to the transfer belt 113. The yellow toner remaining on the peripheral surface of the photosensitive drum 115 is removed by the cleaning unit 123. The above is the description of the yellow image forming unit 111Y.

  Above the yellow image forming unit 111Y, the magenta image forming unit 111M, the cyan image forming unit 111C, and the black image forming unit 111BK, containers containing corresponding color toners, that is, a yellow toner container 127Y, a magenta toner container 127M, A cyan toner container 127C and a black toner container 127BK are arranged. Toner for each color is supplied with toner from the corresponding container.

  As described above, the yellow toner image is transferred to the transfer belt 113, and the magenta toner image is transferred onto the toner image. Similarly, the cyan toner image and the black toner image are transferred onto the transfer belt 113. As a result, a color toner image is formed on the transfer belt 113. In this way, a toner image of each color pattern is superimposed and transferred onto the transfer belt 113, whereby a color toner image is formed on the transfer belt 113. The color toner image is transferred by the secondary transfer roller 129 onto the sheet conveyed from the sheet storage unit 101 described above.

  The sheet on which the color toner image is transferred is sent to the fixing unit 105. The fixing unit 105 includes a heating roller and a fixing roller. The paper on which the color toner image is transferred is sandwiched between these rollers. As a result, heat and pressure are applied to the color toner image and the paper, and the color toner image is fixed to the paper. The sheet is discharged to a discharge tray 131.

  FIG. 2 is a block diagram showing a configuration of the image forming apparatus 1 shown in FIG. The image forming apparatus 1 has a configuration in which an apparatus main body 100, a document reading unit 200, a document feeding unit 300, an operation unit 400, a control unit 500, and a communication unit 600 are connected to each other by a bus. Since the apparatus main body 100, the document reading unit 200, and the document feeding unit 300 have already been described, description thereof will be omitted.

  The operation unit 400 includes an operation key unit 401 and a display unit 403. The display unit 403 has a touch panel function, and displays a screen including soft keys. The user operates the soft keys while viewing the screen to make settings necessary for executing functions such as copying.

  The operation key unit 401 is provided with operation keys including hard keys. Specifically, a function switch key for switching between a start key, a numeric keypad, a stop key, a reset key, a copy, a printer, a scanner, and a facsimile is provided.

  The start key is a key for starting operations such as copying and facsimile transmission. The numeric keypad is a key for inputting numbers such as the number of copies and a facsimile number. The stop key is a key for stopping the copy operation or the like halfway. The reset key is a key for returning the set contents to the initial setting state.

  The function switching key includes a copy key, a transmission key, and the like, and is a key for switching between a copy function, a transmission function, and the like. When the copy key is operated, an initial copy screen is displayed on the display unit 403. When the transmission key is operated, an initial screen for facsimile transmission and mail transmission is displayed on the display unit 403.

  The control unit 500 includes a CPU (Central Processing Unit), a ROM (Read Only Memory), a RAM (Random Access Memory), an image memory, and the like. The CPU executes control necessary for operating the image forming apparatus 1 on the above-described components of the image forming apparatus 1 such as the apparatus main body 100. The ROM stores software necessary for controlling the operation of the image forming apparatus 1. The RAM is used for temporary storage of data generated during execution of software, storage of application software, and the like. The image memory temporarily stores image data (image data output from the document reading unit 200, image data transmitted from a personal computer, image data received by facsimile, etc.).

  The control unit 500 includes an area determination unit 501, a counter circuit unit 503, and a toner forced supply unit 505 as functional blocks. Details of these blocks will be described later.

  The communication unit 600 includes a facsimile communication unit 601 and a network I / F unit 603. The facsimile communication unit 601 includes an NCU (Network Control Unit) for controlling connection of a telephone line with a destination facsimile and a modulation / demodulation circuit for modulating / demodulating a signal for facsimile communication. The facsimile communication unit 601 is connected to the telephone line 605.

  A network I / F unit 603 is connected to a LAN (Local Area Network) 607. A network I / F unit 603 is a communication interface circuit for executing communication with a terminal device such as a personal computer connected to the LAN 607.

  FIG. 3 is a diagram showing 16 regions (an example of a plurality of regions) virtually provided on the photosensitive drum 115. The rotation direction D of the photosensitive drum 115 is the sub-scanning direction. The exposure unit (FIG. 2) repeats drawing one main scanning line on the photosensitive drum 115 rotating in the rotation direction D by the light beam generated based on the image data. As a result, an electrostatic latent image of the image indicated by the image data is formed on the photosensitive drum 115. The developing unit 121 (FIG. 2) supplies toner to the electrostatic latent image, thereby forming a toner image.

  The area determining unit 501 (FIG. 2) virtually divides the peripheral surface of the photosensitive drum 115 into 16 areas R1 to R16 in the main scanning direction. If it is not necessary to distinguish these regions, they are referred to as region R. The area determination unit 501 uses the density value included in the pixel data of each pixel constituting one main scanning line to determine the area R having the lowest toner density among the 16 areas R1 to R16. This is executed for each main scanning line drawn on the body drum 115. This will be described in detail.

  As shown in FIG. 2, the region determination unit 501 includes a density value calculation unit 51 and a density value storage unit 53. These functions will be described. FIG. 4 is a diagram showing an example of the data structure of one main scanning line. Since one main scanning line is composed of a plurality of pixels, the data of one main scanning line is composed of pixel data of a plurality of pixels. The pixel data includes pixel density value data.

  The density value calculation unit 51 equally divides the data of one main scanning line into 16 divided data that is the number of regions R, and adds density values included in pixel data constituting the divided data in each divided data. This is stored in the density value storage unit 53 as the density value (toner density) of each region R. For example, a value obtained by adding the density values included in the pixel data constituting the divided data corresponding to the area R1 is the density value (toner density) of the area R1.

  The area determination unit 501 determines the area R having the smallest density value (toner density) among the areas R1 to R16 for each main scanning line. For example, as shown in FIG. 5, in the first page image, the density value of the region R1 is the smallest in the first main scanning line. As shown in FIG. 6, in the second main scanning line 1, the density value of the region R16 is the smallest. In each main scanning line, a flag F is attached to the region R having the smallest density value among the regions R1 to R16.

  The counter circuit unit 503 counts the number of times that the region determination unit 501 determines that the region R has the smallest density value for each of the regions R1 to R16. The counter circuit unit 503 is realized by an ASIC (Application Specific Integrated Circuit) including 16 counters 3. The number of times that the density value is determined to be the smallest in each region R is counted by the counter 3 assigned to each region R. For example, the number of times that the density value is determined to be the smallest in the region R1 is counted by the counter 3-1. In the present embodiment, the case where the number of regions R is 16 is described. For example, when the number of regions R is 14, the counter 3-15 assigned to the region R15 and the counter 3 assigned to the region R16. -16 is not used.

  FIG. 7 is a diagram showing a region R having the smallest density value in each main scanning line in the image of the first page to the image of the 1000th page. Each counter 3 counts the number of flags F for each region R. That is, each counter 3 counts the number of times each region R is determined as the region R having the smallest density value. For example, the counter 3-1 counts the number of times that the density value of the area R1 is determined to be the smallest area R. In FIG. 7, the number of determinations for the region R1 is N1, the number of determinations for the region R2 is N2, the number of determinations for the region R3 is N3, the number of determinations for the region R15 is N15, and the number of determinations for the region R16 is N16. Has been.

  The toner forced supply unit 505 refers to the numerical values (N1 to N16) counted by the counter circuit unit 503 every time 1000 sheets are printed by the image forming apparatus 1 (when a predetermined condition is satisfied). Then, the region R forcibly supplying the toner among the regions R1 to R16 is determined.

  The case where a predetermined condition is satisfied is a case where the peripheral surface of the photosensitive drum 115 is refreshed. For example, the refresh is executed every time a predetermined number of sheets are printed or every elapse of a predetermined period.

  One of the criteria for determining the region R for forcibly supplying the toner is a threshold value. That is, the toner forced supply unit 505 compares the number of determinations (N1 to N16) of each of the regions R1 to R16 counted by the counter circuit unit 503 with a predetermined threshold value. The region R exceeding the threshold R is determined as the region R for forcibly supplying the toner. According to this aspect, the process for forcibly supplying the toner is performed in the region R in which the number of determinations exceeds the threshold value, that is, the region R in which the toner is not supplied or the supply amount is low. . On the other hand, the process for forcibly supplying the toner is not performed in the region R where the number of determinations does not exceed the threshold value, that is, in the region R where the toner is not supplied or the state where the supply amount is small is not continued. Accordingly, it is possible to supply the toner to all the regions R where it is necessary to forcibly supply the toner and not to supply the toner to all the regions R where it is not necessary to forcibly supply the toner.

  As another criterion for determining the region R for forcibly supplying the toner, there is the n-th region R that is the highest in the number of determinations. That is, the toner forcible supply unit 505 compares the respective determination times (N1 to N16) of the regions R1 to R16 counted by the counter circuit unit 503, and is smaller than a predetermined upper nth (n: 16). A region R up to an integer) is determined as a region R for forcibly supplying toner. If n is 1, the region R having the largest number of determinations, in other words, the region R having the smallest density value and the region R having the largest number of determinations is the region R for forcibly supplying the toner. It is determined. If n is 3, the region R with the largest number of determinations, the region R with the next largest number, and the region R with the next largest number are determined as regions R for forcibly supplying toner. n can be set by operating the operation unit 400 within a range of 16, which is the number of the regions R1 to R16.

  According to this aspect, the upper nth predetermined region R is determined as the region R for forcibly supplying the toner. Accordingly, in the process of forcibly supplying toner, the number of regions R to which toner is supplied can be made the same in each process (in other words, the amount of toner used can be made the same in each process). ).

  The toner forced supply unit 505 controls the developing unit 121 to determine when the image forming apparatus 1 is not performing an operation of forming an image on a sheet after determining the region R forcibly supplying the toner. Toner is supplied to the region R. Thereby, it is possible to prevent the photosensitive drum 115 from deteriorating in the region R where the toner is not supplied or in the region R where the toner supply amount is small.

  Next, an operation for determining the region R forcibly supplying the toner in the image forming apparatus 1 according to the present embodiment will be described. 8 and 9 are flowcharts for explaining this. This operation is executed by each of the yellow image forming unit 111Y, the magenta image forming unit 111M, the cyan image forming unit 111C, and the black image forming unit 111BK.

  The control unit 500 determines whether a print command has been issued by the image forming apparatus 1 (step S1). The print command is a command for forming an image on a sheet, and specifically, a command for executing a printer function, a copy function, or the like of the image forming apparatus 1. If the controller 500 does not determine that a print command has been issued (No in step S1), the process in step S1 is repeated.

  When the control unit 500 determines that a print command has been issued (Yes in step S1), in step S2 to step S9 described below, the region R having the smallest density value is determined for the first main scanning line. To do.

  The density value calculation unit 51 calculates the density values of the regions R1 to R16 using the data of the first main scanning line, and stores the calculated density values in the density value storage unit 53 (step S2). . The area determination unit 501 sets n = 1 among the numbers n = 1 to 16 that specify the areas R1 to R16 (step S3).

  The area determination unit 501 reads the density value V (R1) of the area R1 that is the first area R from the density value storage unit 53 (step S4). The area determination unit 501 compares the density value of the area R having the smallest density value so far with the density value V (R1) of the area R1 to determine which area R has the smaller density value (step S5). . The region determination unit 501 determines the region R having the smallest density value determined in step S5 as the region R having the smallest density value so far (step S6). Since the region R does not exist before the region R1, the region R1 is determined as the region R having the smallest density value so far.

  The region determination unit 501 determines whether n = 16 (step S7). That is, it is determined whether the comparison of density values for the region R16, which is the 16th region R, is completed. Since n = 1, the region determination unit 501 sets n = 2 (step S8) and returns to step S4.

  The region determination unit 501 reads the density value V (R2) of the region R2 that is the second region R from the density value storage unit 53 (step S4). The area determination unit 501 compares the density value of the area R having the smallest density value so far with the density value V (R2) of the second area R2, and determines which area R has the smaller density value ( Step S5).

  Here, the density value V (R1) of the region R1 and the density value V (R2) of the region R2 are compared to determine which region R has the smaller density value. The region determining unit 501 determines the region R having the smallest density value determined in step S5 as the region R having the smallest density value so far (step S6). When the density value V (R1) is smaller than the density value V (R2), the area R1 is determined as the area R having the smallest density value so far. On the other hand, when the density value V (R2) is smaller than the density value V (R1), the area R2 is determined as the area R having the smallest density value so far.

  The area determination unit 501 repeats the processes in steps S4 to S8 until n = 16 is reached. If the region determination unit 501 determines that n = 16 has been reached (Yes in step S7), the region R having the smallest density value among the regions R1 to R16 is determined in the first main scanning line 1 (step S7). S9). In the case shown in FIG. 5, the density value of the region R1 is the smallest in the first main scanning line. The counter 3-1 assigned to the region R1 counts 1 and the remaining counter 3 remains 0.

  The region determination unit 501 determines whether printing of one page image has been completed (step S10). If the area determination unit 501 does not determine that printing of one page image has been completed (No in step S10), the process of steps S2 to S9 is executed for the second main scanning line (step S11).

  When the area determination unit 501 determines that printing of one page of image has been completed (Yes in step S10), it determines whether this page is the 1000th page (an example of a predetermined number of sheets) (step S12). If the area determination unit 501 does not determine the 1000th page (No in step S12), the process returns to step S1.

  When the area determination unit 501 determines that it is the 1000th page (Yes in step S12), the toner forced supply unit 505 refers to the values indicated by the 16 counters 3 and forcibly supplies the toner among the areas R1 to R16. The region R to be supplied to is determined (step S13).

  The main effects of this embodiment will be described. In the present embodiment, when toner is supplied to the electrostatic latent image formed on the photoconductive drum 115, the density of the regions R1 to R16 virtually provided on the photoconductive drum 115 along the main scanning direction. The determination of the region R having the lowest value (toner density) is executed for each main scanning line drawn on the photosensitive drum 115. Then, the number of times that the density value (toner density) is determined to be the lowest region R is counted for each of the regions R1 to R16. The region R forcibly supplying the toner is determined using the determined number of times. Therefore, according to the present embodiment, the region R forcibly supplying the toner can be determined without increasing the size of the counter circuit unit 503.

  Further, as shown in FIG. 7, in the present embodiment, the case where the number of regions R is 16 is described. For example, when the number of regions R is 14, the counter 3-15 assigned to the region R15. And the counter 3-16 assigned to the region R16 is not used. That is, in the region determination unit 501, the number of the plurality of regions R is selected in advance from a predetermined number of ranges (for example, when the number of regions R is 16 or 14). In the counter circuit unit 503, one counter 3 is assigned to each of the plurality of regions R, and the number of the counters 3 is the same as the maximum value (16) in a predetermined number range. Thus, the counter circuit unit 503 is shared when the number of the plurality of regions R is changed according to the model of the image forming apparatus 1 (for example, a model that can print A3 paper and a model that cannot print A3 paper). can do.

DESCRIPTION OF SYMBOLS 1 Image forming apparatus 115 Photosensitive drum 117 Exposure part 121 Developing part R Area

Claims (4)

An image forming apparatus for forming an image on paper,
A photosensitive drum;
An exposure unit for forming an electrostatic latent image of the image by repeatedly drawing one main scanning line on the rotating photosensitive drum with a light beam generated based on image data indicating the image;
A developing unit for supplying toner to the photosensitive drum on which the electrostatic latent image is formed to form a toner image;
The photosensitive drum is virtually divided into a plurality of areas in the main scanning direction, and the toner density of the plurality of areas is determined by using density values included in pixel data of each pixel constituting one main scanning line. An area determining unit that determines the smallest area for each main scanning line drawn on the photosensitive drum;
A counter circuit unit that counts the number of times the region determination unit determines the smallest region for each of the plurality of regions;
When a predetermined condition is satisfied, a numerical value counted by the counter circuit unit is referred to determine an area for forcibly supplying toner among the plurality of areas, and the image forming apparatus reads the image. An image forming apparatus comprising: a toner forcible supply unit that controls the developing unit to supply toner to the determined area when an operation for forming on a sheet is not performed.   The toner forced supply unit compares the number of determinations of each of the plurality of areas counted by the counter circuit unit with a predetermined threshold value, and determines an area where the number of determinations exceeds the threshold value. The image forming apparatus according to claim 1, wherein the image forming apparatus determines that the toner is forcibly supplied.   The toner compulsory supply unit compares the determination times of each of the plurality of regions counted by the counter circuit unit, and determines a predetermined upper n-th (n: an integer smaller than the number of the plurality of regions). The image forming apparatus according to claim 1, wherein the area up to) is determined as an area for forcibly supplying toner. In the region determination unit, the number of the plurality of regions is selected in advance from a predetermined number of ranges,
4. The counter circuit unit according to claim 1, wherein one counter is assigned to each of the plurality of areas, and the number of the counters is the same as the maximum value in the predetermined number range. The image forming apparatus according to claim 1.

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