Image forming apparatus

Abstract

In an image forming apparatus in which a replenishment opening is provided in a portion of the longitudinal region of the developing container (developing roller housing), the occurrence of white areas in the image is reduced. [Solution] The developing roller housing has an opening shorter in length than the length of the developing roller in the direction of the developing roller's rotation axis, and houses toner supplied from the developer housing through this opening. The pixel integration unit determines the number of pixels in both the first and second regions, which are part of the image forming area of ​​the recording material and are divided in the direction of the developing roller's rotation axis, based on the information contained in the print job. The CPU controls the toner supply operation from the developer housing to the developing roller housing when predetermined conditions are met. The predetermined conditions are that at least one of the following is met: the number of first pixels in the first region exceeds a first threshold, or the number of second pixels in the second region exceeds a second threshold that is different from the first threshold.

Description

Technical Field

[0001] The present invention relates to an image forming apparatus.

Background Art

[0002] In an electrophotographic image forming apparatus, in order to prevent density unevenness from occurring in a toner image formed by developing an electrostatic latent image with toner, it is required that the toner be uniformly supplied to the entire developing member (developing roller). Patent Document 1 describes a configuration in which the rotational speed of a toner conveying member is controlled based on the detection result of the toner density in order to uniformly supply the toner to the developing member.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, in the above-described conventional technology, when a supply opening is provided in a partial region in the longitudinal direction of the developing container, a white-out image may occur due to insufficient supply of toner to the developing member.

[0005] Therefore, an object of the present invention is to reduce the occurrence of white-out images in an image forming apparatus in which a supply opening is provided in a partial region in the longitudinal direction of a developing container (developing roller housing portion).

Means for Solving the Problems

[0006] An image forming apparatus according to one aspect of the present invention includes a developer container for containing a developer, a developing roller container for developing an electrostatic latent image formed on a photoreceptor, the developing roller container having an opening in the direction of the rotation axis of the developing roller that is shorter than the length of the developing roller, and the developing roller container for containing the developer supplied from the developer container through the opening, an image forming control unit that receives a print job including information on the number of pixels of an image formed on a recording material and executes an image forming operation based on the print job, and an operation to supply a developer from the developer container to the developing roller container when predetermined conditions are met. The invention comprises a supply operation determination unit that determines to perform a supply operation, and a pixel count determination unit that determines the number of pixels in both a first region and a second region, which are part of the image forming region of the recording material and divided in the direction of the rotation axis, based on the information, wherein when the number of pixels in the first region determined by the pixel count determination unit is set as the first pixel count and the number of pixels in the second region determined by the pixel count determination unit is set as the second pixel count, the predetermined condition is that at least one of the following is satisfied: the number of pixels in the first region exceeds a first threshold, or the number of pixels in the second region exceeds a second threshold that is different from the first threshold. [Effects of the Invention]

[0007] According to the present invention, in an image forming apparatus in which a replenishment opening is provided in a part of the longitudinal region of the developing container (developing roller housing), it becomes possible to reduce the occurrence of whiteout images. [Brief explanation of the drawing]

[0008] [Figure 1] A cross-sectional view showing an example of the hardware configuration of an image forming apparatus. [Figure 2] A diagram showing examples of the rotary tiller's standby and refueling positions. [Figure 3] A diagram showing an example of the motor configuration of an image forming apparatus. [Figure 4] A cross-sectional view showing an example configuration of a toner cartridge and a developing unit, and a diagram showing an example arrangement of the replenishment opening. [Figure 5]A diagram showing an example of the toner state inside the developing unit. [Figure 6] A block diagram showing an example of the control configuration of an image forming apparatus. [Figure 7] A diagram showing an example of an image region division method. [Figure 8] A diagram showing an example of the arrangement of supply openings (second embodiment). [Figure 9] A diagram showing an example of an image region division method (second embodiment). [Figure 10] A cross-sectional view showing an example of the hardware configuration of an image forming apparatus (third embodiment). [Figure 11] A cross-sectional view showing an example configuration of a developing apparatus (third embodiment). [Figure 12] A diagram showing the toner state inside the developing unit (third embodiment). [Figure 13] A diagram showing an example of an image region division method (third embodiment). [Figure 14] A flowchart illustrating an example of a processing procedure for toner replenishment control. [Modes for carrying out the invention]

[0009] The embodiments will be described in detail below with reference to the attached drawings. Note that the following embodiments do not limit the invention as defined in the claims. While the embodiments describe multiple features, not all of these features are essential to the invention, and the features may be combined in any way. Furthermore, in the attached drawings, identical or similar configurations are given the same reference numerals, and redundant descriptions are omitted.

[0010] [First Embodiment] <1. Image forming apparatus> Figure 1 is a cross-sectional view showing a schematic hardware configuration example of the image forming apparatus 1 in the first embodiment. In the following description and in each drawing, the vertical direction when the image forming apparatus 1 is installed on a horizontal plane is referred to as the Z direction. The direction intersecting the Z direction, which is the direction of the rotation axis 90C of the rotary body 90 (the rotation axis direction of the rotary), is referred to as the Y direction. The direction intersecting both the Z direction and the Y direction is referred to as the X direction. The X direction and the Y direction are preferably horizontal. Furthermore, the X direction, Y direction and Z direction are preferably orthogonal to each other. Also, as necessary, the directions of the arrows X, Y, and Z shown in each drawing are referred to as the +X side, +Y side, and +Z side, respectively, and the opposite sides are referred to as the -X side, -Y side, and -Z side, respectively. In this embodiment, the Y side is the longitudinal direction.

[0011] Image forming apparatus 1 is a color laser beam printer equipped with four developing units 50y, 50m, 50c, and 50k (developing containers or developing roller housings). As the recording material (recording medium) sheet S, various types of paper such as plain paper and cardboard, as well as sheet materials of different sizes and materials, can be used. In the following description, the subscripts y, m, c, and k appended to the end of each reference numeral indicate that the corresponding component is for yellow, magenta, cyan, and black developer (toner), respectively. The basic configuration and function of the developing units 50y, 50m, 50c, and 50k are common. The basic configuration and function of the toner cartridges 70y, 70m, 70c, and 70k are common. The basic configuration and function of the trays 80y, 80m, 80c, and 80k are common. Therefore, when there is no need to distinguish between them, the subscripts y, m, c, and k are omitted, and any one of the four units, cartridges, or trays is described as such.

[0012] As shown in FIG. 1, the image forming apparatus 1 includes a device main body 1A and toner cartridges 70y, 70m, 70c, and 70k that are detachable from the device main body 1A. The device main body 1A of the present embodiment is the part of the image forming apparatus 1 excluding the toner cartridges 70y, 70m, 70c, and 70k. The toner cartridges 70y, 70m, 70c, and 70k are an example of a developer storage unit (toner container) that stores a developer (toner).

[0013] The device main body 1A has an electrophotographic photoreceptor (hereinafter, photosensitive drum) 2 having a drum shape (cylindrical shape) as an image carrier that holds an electrostatic latent image. Around the photosensitive drum 2, a charging roller 3, a scanner 4 as an exposure device, and a cleaning unit 6 are arranged. The charging roller 3 uniformly charges the photosensitive drum 2. The scanner 4 irradiates the photosensitive drum 2 with laser light according to image information (input image data) to perform exposure. By irradiating the charged photosensitive drum 2 with laser light by the scanner 4, an electrostatic latent image is formed on the photosensitive drum 2 (on the photoreceptor). The cleaning unit 6 removes toner remaining on the surface of the photosensitive drum 2.

[0014] The device main body 1A further includes a sheet storage unit 300, a pickup roller 310, a feed roller 311, a separation roller 312, a pair of conveyance rollers 320, a secondary transfer roller 12, a fixing device 40, and an intermediate transfer unit 10. The pickup roller 310 feeds the sheet S to the conveyance path. The feed roller 311 and the separation roller 312 constitute a sheet separation unit that separates and conveys the sheets S one by one by frictional force. The secondary transfer roller 12 transfers an image (toner image) from the intermediate transfer belt 10a to the sheet S.

[0015] The intermediate transfer unit 10 (intermediate transfer member) includes an intermediate transfer belt 10a, a belt driving roller 10b, a tension roller 10c, a cleaning device 13, and a primary transfer roller 11. The intermediate transfer belt 10a carries the image transferred (primary transfer) from the photosensitive drum 2 and conveys it for transfer (secondary transfer) to the sheet S. The intermediate transfer belt 10a is stretched over the belt driving roller 10b and the tension roller 10c. The belt driving roller 10b is a driving member that conveys the intermediate transfer belt 10a by being rotationally driven by a driving source.

[0016] The apparatus main body 1A has a rotary main body (rotary body, rotating body) 90 having developing units 50y, 50m, 50c, 50k (developing roller accommodating portions). As will be described later, in this embodiment, trays 80y, 80m, 80c, 80k are attached to the rotary main body 90. Toner cartridges 70y, 70m, 70c, 70k are detachably mounted on the trays 80y, 80m, 80c, 80k, respectively.

[0017] The developing units 50y, 50m, 50c, 50k develop (visualize) the electrostatic latent image formed on the photosensitive drum 2 into a toner image using toner (developer) of the corresponding color. Specifically, the developing units 50y, 50m, 50c, 50k develop the electrostatic latent image formed on the photosensitive drum 2 using yellow toner, magenta toner, cyan toner, and black toner, respectively.

[0018] The developing unit 50y includes a developing roller 51y, a supply roller 52y, and a developing blade. The developing roller 51y is a developer carrier that carries toner as a developer and rotates to supply it to the photosensitive drum 2. The supply roller 52y is disposed in contact with the developing roller 51y and is a supply member that supplies toner to the developing roller 51. The developing blade is a regulating member that regulates the thickness of the toner layer carried on the developing roller 51y. The other developing units 50m, 50c, 50k also include developing rollers 51m, 51c, 51k, supply rollers 52m, 52c, 52k, and developing blades similar to those of the developing unit 50y, respectively.

[0019] The rotary unit 90 is equipped with toner cartridges 70y, 70m, 70c, and 70k, which correspond to the developing units 50y, 50m, 50c, and 50k, respectively. The toner cartridges 70y, 70m, 70c, and 70k contain yellow toner, magenta toner, cyan toner, and black toner, respectively, to supply toner to the developing units 50y, 50m, 50c, and 50k.

[0020] The rotary body 90 has a rotary frame 90f that supports the developing units 50y, 50m, 50c, and 50k. The rotary frame 90f is a rotatable rotating support. In this specification, the rotary body 90 and the trays 80y, 80m, 80c, and 80k attached to the rotary body 90 are referred to as the rotary unit 90U. That is, the rotary unit 90U comprises the rotary body 90 and the trays 80y, 80m, 80c, and 80k.

[0021] As described above, the toner cartridges 70y, 70m, 70c, and 70k are detachably held by trays 80y, 80m, 80c, and 80k, respectively. The trays 80y, 80m, 80c, and 80k are supported so as to be slidable to the outside of the rotary body 90. In this specification, the portion comprising the rotary unit 90U and the toner cartridges 70y, 70m, 70c, and 70k is referred to as the rotary assembly 90A. That is, the rotary assembly 90A comprises the rotary unit 90U and the toner cartridges 70y, 70m, 70c, and 70k.

[0022] The rotary body 90 is configured to rotate around a rotation axis (center of rotation) 90C. The rotation axis 90C coincides with the rotation axes of the rotary frame 90f, the rotary unit 90U, and the rotary assembly 90A. The rotation axis 90C is also substantially parallel to the rotation axis (center of rotation) of the photosensitive drum 2.

[0023] The rotary body 90 rotates around the rotation axis 90C, allowing it to assume a developing position in which any of the developing rollers 51y, 51m, 51c, or 51k faces the photosensitive drum 2. The position in which the developing roller 51y faces the photosensitive drum 2 is called the yellow developing position. The position in which the developing roller 51m faces the photosensitive drum 2 is called the magenta developing position. The position in which the developing roller 51c faces the photosensitive drum 2 is called the cyan developing position. The position in which the developing roller 51k faces the photosensitive drum 2 is called the black developing position. Thus, the rotary body 90 is configured to rotate around the rotation axis 90C so that the positions of the developing rollers 51y, 51m, 51c, and 51k relative to the photosensitive drum 2 change.

[0024] The image forming apparatus 1 of this embodiment has two operating modes for image formation: a color mode for forming a color image (multicolor image) on a sheet S, and a monochrome mode for forming a monochrome image (monochromatic image) on a sheet S.

[0025] In the image forming apparatus 1, the color mode image forming process is performed as follows: When a yellow toner image is developed (formed) on the photosensitive drum 2, the toner image on the photosensitive drum 2 is first transferred to the intermediate transfer belt 10a by the primary transfer roller 11 located inside the intermediate transfer belt 10a. Then, by rotating the rotary body 90 and sequentially moving the developing rollers 51m, 51c, and 51k to the developing position, toner images of each color are sequentially formed on the photosensitive drum 2. As described above, after the yellow toner image is formed on the intermediate transfer belt 10a, the rotary body 90 takes the magenta developing position and a magenta toner image is formed on the intermediate transfer belt 10a. After the magenta toner image is formed on the intermediate transfer belt 10a, the rotary body 90 takes the cyan developing position and a cyan toner image is formed on the intermediate transfer belt 10a. After the cyan toner image is formed on the intermediate transfer belt 10a, the rotary body 90 takes the black developing position and a black toner image is formed on the intermediate transfer belt 10a.

[0026] In this way, the four toner images are sequentially transferred from the photosensitive drum 2 to the intermediate transfer belt 10a. During this process, the primary transfer is repeated so that the four toner images are superimposed on the intermediate transfer belt 10a, thereby forming a color image on the intermediate transfer belt 10a. Note that the secondary transfer roller 12 and the cleaning device 13 are not in contact with the intermediate transfer belt 10a until the color image is formed on the intermediate transfer belt 10a.

[0027] Meanwhile, the sheets S are fed into the transport path from a sheet storage section 300 located at the bottom of the main body 1A of the device by a pickup roller 310. The sheets S are separated one by one by a feed roller 311 and a separation roller 312, and then transported along the transport path to a transport roller pair 320. The transport roller pair 320 sends the sheets S that have been transported from the sheet storage section 300 through the transport path to the transfer section (secondary transfer section), which is the nip of the intermediate transfer belt 10a and the secondary transfer roller 12. The color image on the intermediate transfer belt 10a is transferred (secondary transfer) to the surface of the transported sheets S in the secondary transfer section.

[0028] The sheet S onto which the color image has been transferred is transported to the fixing device 40. In the fixing device 40, the sheet S is heated and pressurized, and the image is fixed to the sheet S. After passing through the fixing device 40, the sheet S is discharged outside the image forming apparatus 1 as a finished product.

[0029] Furthermore, in the image forming apparatus 1, the monochrome image forming process is performed as follows. First, the rotary body 90 assumes the black developing position, thereby positioning the developing roller 51k at the developing position. In this state, an electrostatic latent image is formed on the surface of the photosensitive drum 2 by charging and exposure of the photosensitive drum 2, and then the electrostatic latent image is developed with black toner at the developing position by the developing roller 51k. The black toner image formed on the photosensitive drum 2 is first transferred to the intermediate transfer belt 10a, and then secondarily transferred to the sheet S. The subsequent steps are the same as when forming a color image.

[0030] In monochrome mode, of the developing units 50y, 50m, 50c, and 50k, only the developing unit 50k, which corresponds to black toner, is used for image formation. Therefore, when forming images on multiple sheets in monochrome mode, it is possible to continuously form images on multiple sheets without rotating the rotary body 90 after image formation on one sheet is completed, while maintaining the rotary body 90 in the black developing position.

[0031] The rotary body 90 rotates around the rotation axis 90C, allowing it to assume a position where the developing rollers 51y, 51m, 51c, and 51k are not facing the photosensitive drum 2. In this embodiment, as shown in Figure 2(A), the standby position is set to a state where the photosensitive drum 2 is positioned between the developing rollers 51c and 51k, and the developing rollers 51 and the photosensitive drum 2 are separated. When the image forming apparatus 1 is in a standby state without performing image forming, it stops the rotary body 90 so that it assumes this standby position.

[0032] Figure 3 shows an example of the motor configuration in the image forming apparatus 1 of this embodiment. As shown in the figure, the apparatus body 1A has motors M1, M2, and M3 as drive sources for driving each component within the image forming apparatus 1. Motor M1 supplies driving force to rotate the rotary body 90 around the rotation axis 90C. As a result, the rotary assembly 90A and the rotary unit 90U rotate around the rotation axis 90C.

[0033] Furthermore, the main body 1A of the device has a drive unit 98 including a motor M2 and a transmission unit. The transmission unit includes drive racks 15L and 15R as drive gears and a transmission unit 15t. The driving force of the motor M2 is transmitted to the drive racks 15L and 15R by the transmission unit 15t. As a result, the trays 80y, 80m, 80c, and 80k move relative to the rotary body 90 via the drive racks 15L and 15R.

[0034] Motor M3 drives components other than those driven by motors M1 and M2. For example, motor M3 drives the photosensitive drum 2, developing units 50y, 50m, 50c, 50k, pickup roller 310, feed roller 311, transport roller pair 320, secondary transfer roller 12, belt-driven roller 10b, and fixing device 40. Note that the components driven by motors M1, M2, and M3 may be changed from the above example. Also, the roles of any two or all three of motors M1, M2, and M3 may be combined into a single motor. Alternatively, additional drive sources other than motors M1, M2, and M3 may be added.

[0035] <2. Toner cartridge and developer unit> Figure 4(A) is a cross-sectional view showing an example configuration of a toner cartridge 70 and a developing unit 50. As shown in the figure, the toner cartridge 70 has a toner frame 71. The toner frame 71 includes a toner storage section 71a for storing toner and an discharge opening 71b communicating with the toner storage section 71a.

[0036] The developing unit 50 has a developing frame (storage frame) 53. The developing frame 53 includes a developing-side storage section 53a and a receiving opening 53b which constitutes a supply opening communicating with the developing-side storage section (toner supply chamber) 53a. The developing unit 50 has a developing roller 51 and a supply roller 52, etc., inside.

[0037] The toner cartridge 70 is movable between an installed position and a retracted position relative to the developing frame 53. When the toner cartridge 70 is in the installed position relative to the developing frame 53, the discharge opening 71b faces the receiving opening 53b. In other words, the toner storage section 71a of the toner cartridge 70 and the developing-side storage section 53a of the developing unit 50 are in communication via the discharge opening 71b and the receiving opening 53b. When toner is supplied from the toner cartridge 70 to the developing unit 50, at least a portion of the receiving opening 53b is positioned below at least a portion of the discharge opening 71b.

[0038] Figure 4(B) shows an example of the arrangement of the replenishment opening, which is the communication point between the discharge opening 71b of the toner cartridge 70 and the receiving opening 53b of the developing unit 50, and shows an example of its arrangement relative to the developing frame 53 (developing unit 50) when viewed from above. As shown in the figure, the width of the replenishment opening (replenishment opening width) is shorter than the length of the developing frame 53 in the direction along the rotation axis of the developing roller 51 (developing frame width). This is to prevent toner clogging in the developing unit 50 and toner leakage at the replenishment opening (communication point) caused by a large amount of toner being supplied from the toner cartridge 70 to the developing unit 50 at once. Therefore, it is desirable to set the width of the replenishment opening (to a small width) so that toner is supplied from the toner cartridge 70 to the developing unit 50 in small amounts. In this embodiment, as an example, the width of the replenishment opening in the short direction is set to 1 / 3 or less of the width of the developing unit 50 in the short direction.

[0039] Thus, the developing unit 50 (developing roller housing) has a receiving opening 53b formed therein, which is shorter than the length of the developing roller 51 in the direction of the rotation axis of the developing roller 51. The developing unit 50 (developing roller housing) is configured to house the toner (developer) supplied from the toner cartridge 70 (developer housing) through the receiving opening 53b for development by the developing roller 51.

[0040] Furthermore, although not shown in the figures, it is desirable that the toner cartridge 70 has a sealing member (first sealing member) that covers the discharge opening 71b to prevent toner from flowing out of the developer side storage section 53a into the toner storage section 71a. In addition, it is desirable that the developer unit 50 has a sealing member (second sealing member) that covers the receiving opening 53b. Moreover, when the toner cartridge 70 is not installed in the developer unit 50, it is desirable that the discharge opening 71b and the receiving opening 53b are covered with sealing members to prevent toner from flowing out of the discharge opening 71b and the receiving opening 53b, respectively.

[0041] <3. Toner replenishment procedure> In this embodiment, among the positions of the rotary body 90 that rotate as described above, the position in which toner is supplied from the toner cartridge 70 to the developing unit 50 is referred to as the supply position. The supply position is the position of the rotary body 90 when the toner cartridge 70 and the developing unit 50 are located in such a position that the toner in the toner cartridge 70 falls downward due to gravity, and the toner moves from the discharge opening 71b through the supply opening into the developing unit 50.

[0042] Figure 2(B) shows an example of the black toner supply position for supplying black toner from the toner cartridge 70k in this embodiment. In this figure, it can be seen that the black toner discharge opening 71b is located below the toner cartridge 70k. In this case, black toner is supplied from the toner cartridge 70k to the developing unit 50k by gravity. Similarly for the other colors, when the rotary body 90 rotates and takes the toner supply position for each color (when the toner cartridges 70 of each color move to the position of the toner cartridge 70k shown in Figure 2(B)), toner is supplied from the toner cartridges 70 to the developing unit 50. The toner supplied from the toner cartridge 70k to the developing unit 50k is supplied to the developing roller 51k by the supply roller 52k. Note that the developing unit 50k may be configured without the supply roller 52k if it can supply sufficient toner to the developing roller 51k.

[0043] The control that rotates the rotary body 90 to assume the replenishment position for the target color and replenishes the toner of the target color from the toner cartridge 70 to the developing unit 50 is called toner replenishment control. Note that the replenishment position of the rotary body 90 is not limited to the position shown in Figure 2(B). The replenishment position is one in which the discharge opening 71b is located below the toner cartridge 70, and the toner cartridge 70 is in a position where the toner can move from the discharge opening 71b through the replenishment opening into the developing unit 50 by gravity.

[0044] Figure 5(A) shows an example of the state of toner on the developing roller 51 immediately after toner is supplied to the developing unit 50 through the receiving opening 53b. As shown in the figure, immediately after toner replenishment, most of the toner supplied to the developing unit 50 is located in the region centered on the position directly below the receiving opening 53b on the developing roller 51.

[0045] Figure 5(B) shows an example of the state after rotating the rotary body 90 once from the state shown in Figure 5(A). As shown in the figure, by rotating the rotary body 90 once, the toner supplied to the developing unit 50 spreads throughout the entire longitudinal area of ​​the developing roller 51. This is because the toner in the developing unit 50 is leveled in the height direction by the change in gravity accompanying the rotation of the rotary body 90. The more rotations the rotary body 90 makes, the more the toner in the developing unit 50 is leveled by the change in gravity, and the faster the rotation speed of the rotary body 90, the more it is leveled by centrifugal force.

[0046] <4. Control Unit> Figure 6 is a block diagram showing an example of the control configuration in the image forming apparatus 1 of this embodiment. The image forming apparatus 1 includes a printer control device 504. The printer control device 504 communicates with the host computer 500 by connecting to it using a controller interface 505.

[0047] The printer control device 504 includes a controller unit 501 and an engine control unit 502. The controller unit 501 includes an image processing unit 503. The controller unit 501 (controller I / F 505) receives information from the host computer 500 regarding instructions given by the user operating the host computer 500. User instructions may include instructions to execute or cancel a printing process (image formation), or instructions to stop a printing process that is currently in progress.

[0048] The controller unit 501 performs image processing, such as bitmap conversion of character codes and halftoning of grayscale images, based on image information contained in the print job received from the host computer 500, via the image processing unit 503. The print job includes information on the number of pixels in the image formed on the recording material. The controller unit 501 transmits the processed image information to the video I / F 510 of the engine control unit 502. The image information transmitted to the engine control unit 502 includes pixel information indicating the pixels contained in the input image to be printed. The image information further includes control information for controlling image formation conditions (process conditions) such as transfer bias and fixing temperature, and size information indicating the size of the input image.

[0049] The engine control unit 502 includes a video interface 510, a CPU 511, a ROM 512, a RAM 513, an application-specific integrated circuit (ASIC), and a pixel integration unit 540. Pixel information contained in the image information received from the controller unit 501 via the video interface 510 is sent to the ASIC 514. Based on the input pixel information, the ASIC 514 counts the pixels to be printed (in each region) in the input image and outputs the obtained pixel count value to the pixel integration unit 540.

[0050] The pixel integration unit 540 acquires an integrated value (pixel count integrated value) S by accumulating the pixel count values ​​for each predetermined area in a print job based on the pixel count value input from the ASIC 514. The predetermined area corresponds to an area obtained by dividing the image forming area (the area with the maximum image width in which an image can be formed) in the width direction perpendicular to the sheet transport direction into a plurality of areas, as will be described later. The plurality of areas include a first area and a second area, which are part of the image forming area of ​​the recording material and are divided in the direction of the rotation axis of the developing roller 51. In this embodiment, the ASIC 514 and the pixel integration unit 540 function as an example of a pixel count determination unit that determines the number of pixels in both the first area and the second area, which are part of the image forming area of ​​the recording material and are divided in the direction of the rotation axis, based on information on the number of pixels in the image formed on the recording material.

[0051] Furthermore, control information and image size information included in the image information received from the controller unit 501 via the video I / F 510 are sent to the CPU 511. The CPU 511 controls the image formation operation by reading and executing a program stored in the ROM 512 or RAM 513. The CPU 511 uses the RAM 513 as a work area as needed. The CPU 511 performs, for example, setting the image formation area, controlling the process speed, development control, charging control, and transfer control. In this embodiment, the CPU 511 functions as an example of an image formation control unit that receives a print job including information on the number of pixels in an image formed on a recording material and executes an image formation operation based on the print job.

[0052] As described above, in this embodiment, when the image forming apparatus 1 receives a print job from the host computer 500 instructing it to form images on multiple sheets in color mode, it rotates the rotary body 90 for each sheet to be formed. On the other hand, when it receives a print job instructing it to form images on multiple sheets in monochrome mode, it forms images on multiple sheets while keeping the rotary body 90 in the black development position without rotating it.

[0053] <5. Calculation of the integrated pixel count value> Next, the process of obtaining (calculating) the pixel count integrated value (hereinafter referred to as the integrated value) S by the pixel integration unit 540 will be described. In the image forming apparatus 1 of this embodiment, when the execution of a print job is started, the ASIC 514 performs the process of counting the pixels contained in one page of the input image based on the input pixel information and obtaining the pixel count value. Specifically, the ASIC 514 counts the pixels to be printed based on the image information (image data) input from the host computer 500. The pixels to be printed correspond to the pixels that are developed using toner (pixels included in the area where toner adheres in the electrostatic latent image formed on the photosensitive drum 2).

[0054] Figure 7(A) shows an example of a method for dividing the image area (image forming area) in this embodiment. In the image forming apparatus 1 of this embodiment, the maximum sheet width for sheets that can be used for image forming is, for example, 215.9 mm for LTR paper, and in this case, the maximum width of the image forming area (maximum image width) is 206 mm. Figure 7(A) shows an example of dividing the image area when printing an LTR size image (215.9 mm × 279 mm) as an example.

[0055] In the example shown in Figure 7(A), the image area with the maximum image width is divided into three equal regions (divided regions) called Zones 1 to 3 in the width direction perpendicular to the sheet transport direction. Of these three regions, Zone 2 includes the position of the replenishment opening, which is the communication point between the discharge opening 71b of the toner cartridge 70 and the receiving opening 53b of the developing unit 50. Based on the image information (image data) corresponding to the input image of one page, the ASIC 514 counts the pixels to be printed in each divided region (Zone) and outputs a pixel count value indicating the number of pixels to be printed.

[0056] The pixel integration unit 540 performs the process of accumulating the pixel count value of each page for each divided region (Zone) when image formation is performed continuously on multiple sheets in a single print job, thereby obtaining an accumulated value S. When the execution of the print job is completed, the pixel integration unit 540 resets the accumulated value S to 0 and performs the process of accumulating the newly input pixel count value from the ASIC 514 when the next print job is executed.

[0057] In this embodiment, the integrated value S can be stored in the pixel integration unit 540 as a value obtained by multiplying the pixel count value output from the ASIC 514 by a predetermined coefficient (e.g., 1 / 100000) and integrating the resulting values. By multiplying the pixel count value by a predetermined coefficient in this way, it is possible to reduce the unit of the integrated value stored in the pixel integration unit 540, reduce the memory area used for storing the integrated value, and shorten the processing time.

[0058] In this embodiment, the image forming apparatus 1 is assumed to have a resolution of 600 dpi. In this case, for example, when printing a high-print-rate image in which toner is applied to the entire image forming area on an LTR-sized sheet, the maximum pixel count value per page in each divided area (Zone) is approximately 104. Therefore, for example, when printing a solid black image continuously on multiple sheets, a pixel count value of 104 dots is accumulated in the cumulative value S for each page.

[0059] In this way, the pixel integration unit 540, in a single print job that forms an image on a recording material based on image information, integrates the number of pixels that are developed with toner from among the pixels included in the input image corresponding to the image information, for each different region in the width direction of the sheet. The pixel integration unit 540 then obtains an integrated value S and stores the integrated value S. The integrated value S is used by the CPU 511 for toner replenishment control.

[0060] <6. Toner supply control> This section describes toner supply control in the image forming apparatus 1 of this embodiment. In the image forming apparatus 1, for example, when printing (forming) images on multiple sheets in succession in monochrome mode, there is a possibility that white areas may occur in the printed images. Figure 7(B) shows an example of a white area that occurs when printing high-print-rate black images (solid black images in this example) in succession in monochrome mode. In this example, when solid black images are formed consecutively across Zones 1 to 3, white areas occur in Zones 1 and 3 before Zone 2. This is because Zone 2 is an area where toner is supplied through the receiving opening 53b, whereas Zones 1 and 3 are far from the receiving opening 53b, and therefore the toner supplied through the receiving opening 53b is less readily available to Zones 1 and 3 than to Zone 2. Such white areas occur, for example, when the cumulative value S in Zones 1 and 3 exceeds a predetermined value, resulting in insufficient toner supply to the developing roller 51 and the supply roller 52.

[0061] Therefore, the image forming apparatus 1 (CPU 511) of this embodiment controls the toner supply operation from the toner cartridge 70 to the developing unit 50 based on the integrated value S obtained by the pixel integration unit 540. Specifically, the image forming apparatus 1 sets a threshold value (integration threshold) for the integrated value S for each different region (Zone) obtained by dividing the image area in the width direction of the sheet, and executes the toner supply operation when the integrated value S exceeds the threshold value in a single print job. In this embodiment, the toner supply operation includes, for example, the operation of rotating the rotary body 90 once. As described above, toner is supplied from the toner cartridge 70 to the developing unit 50 through the receiving opening 53b by the rotation of the rotary body 90.

[0062] Thus, in this embodiment, the CPU 511 functions as an example of a replenishment operation determination unit that determines to perform a replenishment operation, which is the operation of supplying developer (toner) from the developer storage unit (toner cartridge 70) to the developer roller storage unit (development unit 50), when predetermined conditions are met. When the number of pixels in the first region determined by the pixel count determination unit (ASIC 514 and pixel integration unit 540) is called the first pixel count, and the number of pixels in the second region determined by the same pixel count determination unit is called the second pixel count, the predetermined conditions are that at least one of the following is met: the first pixel count exceeds a first threshold, or the second pixel count exceeds a second threshold that is different from the first threshold. In this embodiment, the first pixel count and the second pixel count are, respectively, the integrated value S of the number of pixels for a plurality of recording materials on which an image is formed based on a print job.

[0063] The toner replenishment operation may also include rotating the rotary body 90 so that it assumes a position (replenishment position) that allows toner that has fallen by gravity from inside the toner cartridge 70 (inside the developer housing) to move through the replenishment opening into the developing unit 50 (inside the developing roller housing). For example, the toner replenishment operation may also involve rotating the rotary body 90 once after it has assumed the replenishment position.

[0064] In the image forming apparatus 1 of this embodiment, the CPU 511 executes a toner replenishment operation when the accumulated value S for any of the divided regions exceeds the accumulation threshold. Table 1 below shows the accumulation threshold set for each divided region (Zone). TIFF2026082048000002.tif52136

[0065] In the example in Table 1, the multiple divided regions include a first region (Zone 1 and 3) and a second region (Zone 2) that is closer to the replenishment opening than the first region in the longitudinal direction of the developing unit 50. The accumulation threshold for the first region (Zone 1 and 3) is set to a smaller value than the accumulation threshold for the second region (Zone 2). In this way, as shown in Figure 7(B), by setting a smaller accumulation threshold for the first region (Zone 1 and 3), which is a divided region where whiteout images are more likely to occur, it becomes possible to perform toner replenishment at the appropriate timing (before whiteout images occur).

[0066] When using the cumulative threshold shown in Table 1, for example, if a solid black image is printed continuously across multiple sheets, the cumulative value S corresponding to Zones 1 and 3 will reach the cumulative threshold when printing on the 6th sheet. As a result, the CPU 511 performs a toner replenishment operation (rotating the rotary body 90 once) to prevent the occurrence of white areas. Specifically, the CPU 511 performs rotational control to rotate the rotary body 90 once after image formation on the 6th sheet is complete and before image formation on the 7th sheet begins. After that, it continues the execution of the print job by starting image formation on the 7th sheet.

[0067] When printing a solid black image, pixels are formed (printed) at a uniform printing rate in each divided region (Zone 1 to 3). In this case, as in the example above, for Zones 1 and 3 (where the same accumulation threshold is set as shown in Table 1), the accumulated value S will reach the accumulation threshold when the same number of sheets are formed. On the other hand, when forming images with different printing rates for each divided region, the CPU 511 performs a toner replenishment operation when the accumulated value S for any of the divided regions reaches the accumulation threshold. For example, as shown in Figure 7(C), when printing a solid black image (an image with 100% printing rate) in Zone 2 only on multiple sheets consecutively, the CPU 511 performs a toner replenishment operation when the accumulated value S corresponding to Zone 2 reaches the accumulation threshold when the image is formed on the 10th sheet. The CPU 511 resets the accumulated value S held by the pixel accumulation unit 540 to 0 each time it performs a toner replenishment operation (an operation that rotates the rotary body 90 once).

[0068] <7. Processing Procedure> Figure 14 is a flowchart showing an example of a processing procedure for toner replenishment control performed in the image forming apparatus 1 of this embodiment. The processing according to the procedure in Figure 14 is performed by the CPU 511 (engine control unit 502) in the image forming apparatus 1. When the CPU 511 starts executing a print job (a single print job that forms an image on a recording material based on image information) received from an external device such as a host computer 500, it starts processing according to the procedure in Figure 14.

[0069] In S101, the CPU 511 starts printing the input image for one page based on the image information of the page to be printed. Once the CPU 511 starts printing the input image for one page, it proceeds to S102. In S102, the CPU 511 uses the pixel integration unit 540 to integrate the number of pixels in the input image corresponding to the image information of the page to be printed that will be developed with toner, for each different region (divided region) in the width direction of the sheet (longitudinal direction of the development unit 50). This obtains an integrated value S for each divided region.

[0070] When the accumulated value S is obtained, in S103 the CPU 511 determines whether the accumulated value S for any of the divided regions has exceeded the accumulation threshold. If the CPU 511 determines that the accumulated value S for any of the divided regions has not exceeded the accumulation threshold, it proceeds to S106. On the other hand, if in S103 the CPU 511 determines that the accumulated value S for any of the divided regions has exceeded the accumulation threshold, it proceeds to S104. For example, if the CPU 511 finds that the accumulated value S for the first region (Zone 1) has exceeded the corresponding accumulation threshold (first threshold), or that the accumulated value S for the second region (Zone 2) has exceeded the corresponding accumulation threshold (second threshold), it proceeds to S104.

[0071] In S104, the CPU 511 decides to perform the toner replenishment operation described above. Specifically, the CPU 511 performs the toner replenishment operation after the printing of the input image for one page, which was started in S101, is completed. Then, in S105, the CPU 511 resets the accumulated value S corresponding to each divided region, which is held in the pixel integrating unit 540, to 0, and proceeds to S106.

[0072] In S106, if there are pages remaining to be printed in the print job, the CPU 511 returns to S101 and starts printing the input image for the next page. On the other hand, if there are no pages remaining to be printed in the print job, the CPU 511 terminates the execution of the print job and ends the process according to the procedure in Figure 14. Upon completion of the print job, the CPU 511 resets the cumulative value S corresponding to each divided area to 0.

[0073] <8. Summary> As described above, the image forming apparatus 1 of this embodiment includes a developer storage unit (toner cartridge 70) for storing developer, and a developer roller storage unit (developing unit 50) for developing an electrostatic latent image formed on a photoreceptor (photosensitive drum 2), with an opening formed therein in the direction of the rotation axis of the developer roller that is shorter than the length of the developer roller. The developer roller storage unit stores the developer supplied from the developer storage unit (toner cartridge 70) through the opening. The image forming control unit (CPU 511) receives a print job including information on the number of pixels in the image formed on the recording material and executes an image forming operation based on the print job. The replenishment operation determination unit (CPU 511) decides to perform a replenishment operation, which is the operation of supplying developer from the developer storage unit (toner cartridge 70) to the developer roller storage unit (developing unit 50), when predetermined conditions are met. The pixel count determination unit (ASIC 514 and pixel integration unit 540) determines the number of pixels in both the first region and the second region, which are parts of the image forming area of ​​the recording material divided in the direction of the rotation axis of the developing roller, based on the information information contained in the print job. When the number of pixels in the first region determined by the pixel count determination unit is taken as the first pixel count, and the number of pixels in the second region determined by the same pixel count determination unit is taken as the second pixel count, the predetermined conditions are that at least one of the following is satisfied: the number of pixels in the first region exceeds the first threshold, or the number of pixels in the second region exceeds a second threshold that is different from the first threshold.

[0074] According to this embodiment, when a replenishment opening is provided in a portion of the longitudinal region of the developing container (developing roller housing), it becomes possible to reduce the occurrence of white areas. In particular, it becomes possible to reduce the occurrence of white areas when printing high print-rate images continuously on multiple sheets (recording materials). Furthermore, by setting an integration threshold for the integrated value S for each different region in the longitudinal region of the developing container, it is possible to change the execution timing of the toner replenishment operation according to the input image to be formed. This makes it possible to delay the toner replenishment operation timing when, for example, a high print-rate image is formed only in the region close to the replenishment opening, thereby reducing unnecessary downtime.

[0075] In this embodiment, an example has been described in which the image area in the longitudinal direction (width direction) is divided into multiple areas of equal size, but the method of dividing the image area is not limited to this. For example, the size of each divided area (Zone) may be determined according to the size of the replenishment opening (receiving opening 53b) of the developing unit 50, and an accumulation threshold may be set accordingly. Also, the replenishment opening (receiving opening 53b) of the developing unit 50 is not limited to the center position in the longitudinal direction as in the example above, but may be located at other positions, and an accumulation threshold may be set accordingly. For example, the accumulation threshold is set to a smaller value the further a corresponding divided area is from the replenishment opening (receiving opening 53b) in the width direction (first direction) of the sheet. Furthermore, the toner replenishment operation is not limited to the operation of rotating the rotary body 90 once, but may be realized by, for example, increasing the number of rotations of the rotary body 90 or changing the rotation speed.

[0076] [Second Embodiment] In the second embodiment, an example is described in which the developing unit 50 has multiple openings (receiving openings) for supplying toner from the toner cartridge 70 (developer storage section). The following describes the differences from the first embodiment.

[0077] <1. Image forming apparatus> The configuration and operation of the image forming apparatus 1 in this embodiment are the same as those of the image forming apparatus 1 in the first embodiment. However, the replenishment openings, which are the communication points between the discharge opening 71b of the toner cartridge 70 and the receiving opening 53b of the developing unit 50, are provided at two locations in the longitudinal direction of the developing unit 50 (the width direction perpendicular to the sheet transport direction).

[0078] <2. Toner cartridge and developer unit> Figure 8(A) shows an example of the arrangement of the replenishment openings, which are the communication points between the discharge opening 71b of the toner cartridge 70 and the receiving opening 53b of the developing unit 50. This is an example of the arrangement relative to the developing frame 53 (developing unit 50) when viewed from above. As shown in the figure, in this embodiment, two replenishment openings are provided at two positions that are substantially symmetrical with respect to the center in the longitudinal direction of the developing unit 50. Furthermore, the width of each replenishment opening in the longitudinal direction (width direction) is smaller than that of the replenishment openings provided in the image forming apparatus 1 of the first embodiment. This is to reduce the amount of toner supplied from the toner cartridge 70 to the developing unit 50 in a single toner replenishment operation through the replenishment openings. This suppresses toner clogging or leakage, while shortening the time it takes for the toner to spread uniformly throughout the entire longitudinal region within the developing unit 50 after toner replenishment.

[0079] <3. Toner replenishment procedure> In the image forming apparatus 1 of this embodiment, the replenishment position of the rotary body 90 is the same as in the first embodiment. For example, when the replenishment position shown in Figure 2(B) is taken, black toner is replenished from the toner cartridge 70k to the developing unit 50k.

[0080] Figure 8(B) shows an example of the state of toner on the developing roller 51 immediately after toner is supplied to the developing unit 50 through the receiving opening 53b. As shown in the figure, immediately after toner replenishment, most of the toner supplied to the developing unit 50 is located in a region centered on the position directly below the two receiving openings 53b on the developing roller 51.

[0081] Figure 8(C) shows an example of the state after rotating the rotary body 90 once from the state shown in Figure 8(B). As shown in the figure, by rotating the rotary body 90 once, the toner supplied to the developing unit 50 spreads throughout the entire longitudinal area of ​​the developing roller 51. In this embodiment, by providing two supply openings, more toner is uniformly distributed throughout the entire longitudinal area of ​​the developing roller 51 when the rotary body 90 is rotated once.

[0082] <4. Control Unit> The control configuration of the image forming apparatus 1 in this embodiment is the same as the control configuration of the image forming apparatus 1 in the first embodiment (Figure 6).

[0083] <5. Calculation of the integrated pixel count value> The process for obtaining (calculating) the integrated value S by the pixel integration unit 540 in this embodiment will be described. When the execution of a print job is started, the ASIC 514, similar to the first embodiment, counts the pixels contained in one page of the input image based on the input pixel information and performs the process of obtaining a pixel count value.

[0084] Figure 9(A) shows an example of the method for dividing the image area (image forming area) in this embodiment. In the example in Figure 9(A), the image area with the maximum image width is divided into five equal areas (divided areas) called Zone 1 to Zone 5 in the width direction perpendicular to the sheet transport direction. Of these five areas, Zones 2 and 4 include the position of the replenishment opening, which is the communication position between the discharge opening 71b of the toner cartridge 70 and the receiving opening 53b of the developing unit 50. Similar to the first embodiment, the ASIC 514 counts the pixels to be printed in each divided area (Zone) based on the image information (image data) corresponding to the input image of one page, and outputs a pixel count value indicating the number of pixels to be printed.

[0085] Similar to the first embodiment, the pixel integration unit 540 performs the process of acquiring an integrated value S by accumulating the pixel count value of each page for each divided region (Zone) when image formation is performed continuously on multiple sheets in a single print job. Also, similar to the first embodiment, the integrated value S can be stored in the pixel integration unit 540 as a value obtained by multiplying the pixel count value output from the ASIC 514 by a predetermined coefficient (e.g., 1 / 100000) and accumulating the resulting values.

[0086] In this embodiment, the image forming apparatus 1 is assumed to have a resolution of 600 dpi. In this case, for example, when printing a high-print-rate image in which toner is applied to the entire image forming area on an LTR-sized sheet, the maximum pixel count value per page in each divided area (Zone) is approximately 62. Therefore, for example, when printing a solid black image continuously on multiple sheets, a pixel count value of 62 dots is accumulated in the cumulative value S for each page.

[0087] <6. Toner supply control> The toner supply control in the image forming apparatus 1 of this embodiment is the same as in the first embodiment. Figure 9(B) shows an example of a white-out image that occurs when a high-print-rate black image (a solid black image in this example) is printed continuously in monochrome mode. In this example, when solid black images are continuously formed across Zones 1 to 5, white-out images are more likely to occur in Zones 1, 3, and 5 than in Zones 2 and 4. This is because Zones 2 and 4 are areas where toner is supplied through the receiving opening 53b, whereas Zones 1, 3, and 5 are far from the receiving opening 53b, and therefore the toner supplied through the receiving opening 53b is less likely to reach them than in Zones 2 and 4. Such white-out images occur, for example, when the cumulative value S in Zones 1, 3, and 5 exceeds a predetermined value, resulting in insufficient toner supply to the developing roller 51 and the supply roller 52.

[0088] Similar to the first embodiment, the CPU 511 executes a toner replenishment operation when the accumulated value S for any of the divided regions exceeds the accumulation threshold. Table 2 below shows the accumulation threshold set for each divided region (Zone). TIFF2026082048000003.tif67136

[0089] When using the cumulative threshold shown in Table 2, for example, when printing a solid black image across multiple sheets consecutively, the cumulative value S corresponding to Zones 1 and 5 reaches the cumulative threshold when printing on the 7th sheet. As a result, the CPU 511 performs a toner replenishment operation (rotating the rotary body 90 once) to reduce the occurrence of white areas. Specifically, the CPU 511 performs rotational control to rotate the rotary body 90 once after image formation on the 7th sheet is complete and before image formation on the 8th sheet begins. After that, it continues the execution of the print job by starting image formation on the 8th sheet.

[0090] In the above example, the number of continuous printable solid black images is increased compared to the example described using Table 1 in the first embodiment because the increase in supply openings makes it easier for the toner supplied to the developing unit 50 to spread throughout the entire longitudinal area of ​​the developing roller 51. Furthermore, for Zone 3, the number of continuous printable solid black images is increased compared to Zones 1 and 5. This is because Zone 3 is the region between Zones 2 and 4, which correspond to the two supply openings, and the toner supplied to Zone 3 through the two supply openings results in a larger toner supply amount than in Zones 1 and 5.

[0091] In this embodiment, as described above, the width of the replenishment opening is smaller than in the first embodiment. As a result, although the number of continuous printable solid black images for Zones 2 and 4 corresponding to the two replenishment openings is reduced compared to the first embodiment, the increase in the number of divisions of the image area enables more precise toner replenishment control according to the pattern of the input image.

[0092] <7. Processing Procedure> An example of the processing procedure for toner replenishment control performed in the image forming apparatus 1 of this embodiment is the same as in the first embodiment. When the CPU 511 starts executing a print job received from an external device such as a host computer 500, it performs the processing according to the procedure in Figure 14, as in the first embodiment.

[0093] <8. Summary> As described above, in this embodiment, the developing unit 50 is provided with multiple openings (receiving openings) for supplying toner from the toner cartridge 70 (toner container). This makes it possible to reduce the occurrence of blank images, as in the first embodiment, and to increase the number of high-print-rate images that can be printed continuously.

[0094] In this embodiment, an example of dividing the image area in the longitudinal direction (width direction) into multiple equal areas has been described, but the method of dividing the image area is not limited to this. For example, the size of each divided area (Zone) may be determined according to the size of the replenishment opening (receiving opening 53b) of the developing unit 50, and an accumulation threshold may be set accordingly. Also, the two replenishment openings (receiving openings 53b) of the developing unit 50 may be placed at positions other than those corresponding to the center position in the longitudinal direction, as in the example above, and an accumulation threshold may be set accordingly. Furthermore, in this embodiment, two replenishment openings (receiving openings) are provided, but three or more replenishment openings may be provided.

[0095] [Third Embodiment] In the third embodiment, as a modification of the first and second embodiments, an example of applying the above-described toner supply control to an image forming apparatus having a different configuration from the first and second embodiments will be described. The differences from the first embodiment will be described below.

[0096] <1. Image forming apparatus> Figure 10 is a cross-sectional view showing a schematic hardware configuration example of the image forming apparatus 200 in this embodiment. The image forming apparatus 200 is an in-line image forming apparatus equipped with four image forming units, each performing image formation using four different toners (yellow, magenta, cyan, and black). The basic configuration and function of each image forming unit are common. Therefore, when it is not necessary to distinguish between them, the subscripts y, m, c, and k are omitted, and the members that constitute any one of the four image forming units are described accordingly.

[0097] Each image forming unit has an electrophotographic photoreceptor (hereinafter referred to as a photosensitive drum) 201 (201y, 201m, 201c, 201k) having a drum shape (cylindrical shape) as an image carrier for holding an electrostatic latent image. Around the photosensitive drum 201 are a charger 202 (202y, 202m, 202c, 202k), a scanner 203 (203y, 203m, 203c, 203k), a developing device 204 (204y, 204m, 204c, 204k), a transfer roller 206 (206y, 206m, 206c, 206k), and a cleaning unit 207 (207y, 207m, 207c, 207k). The scanner 203 is positioned above the photosensitive drum 201. Each image forming unit has a similar configuration and will be collectively referred to as image forming unit P below.

[0098] The image formation sequence (image formation process) in the image forming apparatus 200 will now be described. First, the charger 202 uniformly charges the photosensitive drum 201. The scanner 203 exposes the photosensitive drum 201 by irradiating it with laser light corresponding to the image information (input image data). When the laser light is irradiated onto the charged photosensitive drum 201 by the scanner 203, an electrostatic latent image is formed on the surface of the photosensitive drum 201. After the electrostatic latent image is formed, the developing apparatus 204 develops the electrostatic latent image at the development position with toner of the corresponding color. By performing this process in each image forming unit, yellow, magenta, cyan, and black toner images are formed on the photosensitive drums 201y, 201m, 201c, and 201k, respectively.

[0099] The image forming apparatus 200 further includes an intermediate transfer belt (intermediate transfer body) 205 positioned below each image forming section. The intermediate transfer belt 205 is stretched over rollers 51, 52, and 53 and transported in the direction of arrow T. The toner images on each photosensitive drum 201 are sequentially superimposed and transferred (primary transfer) onto the intermediate transfer belt 205 by the corresponding transfer roller 206. As a result, a color image (multicolor image) is formed on the intermediate transfer belt 205 by superimposing the toner images of four colors: yellow, magenta, cyan, and black. The cleaning unit 207 removes (recovers) the toner remaining on the surface of the photosensitive drum 201 after the primary transfer to the intermediate transfer belt 205.

[0100] The color image on the intermediate transfer belt 205 is transferred (secondary transfer) to the surface of the sheet S that has been transported from the sheet storage unit 240 through the transport path in the secondary transfer unit. Toner remaining on the intermediate transfer belt 205 after secondary transfer to the sheet S is removed (recovered) by the cleaning unit 250. The sheet S on which the color image has been transferred is transported to the fixing unit 208. In the fixing unit 208, the sheet S is heated and pressurized, and the image is fixed to the sheet S. The sheet S that has passed through the fixing unit 208 is discharged outside the image forming apparatus 200 as a finished product.

[0101] <2. Toner cartridge and developer unit> Figure 11 is a cross-sectional view showing an example of the configuration of the developing apparatus 204 in the image forming apparatus 200 of this embodiment. The developing apparatus 204 comprises a toner container 220 and a developing container 210. The toner container 220 (developer storage section) is detachable from the image forming apparatus 200 and contains toner (developer) for supplying toner to the developing container 210. The toner container 220 is equipped with a rotatable transport screw 221 (screw member) that transports toner to supply toner to the developing container 210.

[0102] The transport screw 221 rotates to transport toner within the toner container 220 toward the replenishment opening 222 in the direction of arrow C. The toner transported by the transport screw 221 within the toner container 220 is replenished (supplied) to the developer container 210 through the replenishment opening 222, which is located in a portion of the longitudinal direction (width direction perpendicular to the sheet transport direction) of the toner container 220. Thus, the transport screw 221 is an example of a rotatable screw member that transports toner within the toner container 220 in order to replenish the toner to the developer container 210 through the replenishment opening 222.

[0103] The developing container 210 (developing roller housing) houses a developing roller 215 and a regulating blade 216. The developing roller 215 is a developer carrier (developing member) that carries toner as a developer, rotates, and supplies it to the corresponding photosensitive drum 201. The interior of the developing container 210 is divided into two developing chambers vertically by a partition wall 217 located approximately in the center and extending vertically over the surface of the sheet S being transported. Transport screws 211 and 212 are located in the upper and lower developing chambers, respectively. The transport screws 211 and 212 are arranged parallel to the rotation axis of the developing roller 215.

[0104] Toner supplied from the toner container 220 through the supply opening 222 falls by gravity within the developing container 210 and is transported in the direction of arrow A in the lower developing chamber as the transport screw 211 rotates. The transported toner is pumped up to the upper developing chamber by the pumping section 213 and transported in the direction of arrow B in the upper developing chamber as the transport screw 212 rotates. In this way, the toner circulates between the upper and lower developing chambers through openings provided at both ends of the longitudinal direction of the partition wall 217 by the transport accompanying the rotation of the transport screws 211 and 212. Within the developing container 210, toner is supplied to the developing roller 215 by the transport screw 212 of the upper developing chamber. The developing roller 215 carries toner whose layer thickness is regulated by the regulating blade 216.

[0105] In this embodiment, the image forming apparatus 200 has a configuration in which the transport screw 221 inside the toner container 220 is driven by a different drive motor (drive source) than the drive motor (drive source) that drives the developing roller 215. This configuration allows the rotational speed of the developing roller 215 and the rotational speed of the transport screw 221 to be controlled independently. For example, the ratio of the rotational speed of the transport screw 221 to the rotational speed of the developing roller 215 can be controlled (changed).

[0106] The developing container 210 has an opening located at a position corresponding to the developing area facing the photosensitive drum 201. The developing roller 215 is positioned such that a portion of the developing roller 215 is exposed toward the photosensitive drum 201 through the opening in the developing container 210, allowing it to rotate. The developing roller 215 rotates in the direction of arrow C in Figure 11 (counterclockwise), supplying the toner it carries to the electrostatic latent image formed on the photosensitive drum 201, thereby developing the electrostatic latent image. This forms a toner image on the photosensitive drum 201.

[0107] <3. Toner replenishment procedure> Figure 12(A) is a cross-sectional view showing an example of the state of the toner container 220 and the developing container 210 when printing a high-print-rate black image (solid black image in this example) continuously on multiple sheets in monochrome mode. In the upper developing chamber of the developing container 210, there is more toner on the side of the upper part 213 in the longitudinal direction of the developing container 210 than on the opposite side (the supply opening side). This indicates that the toner supply to the developing roller 215 is insufficient because the toner consumption is high in order to develop the high-print-rate image. In the upper developing chamber of the developing container 210, the toner is transported in the direction of arrow B. Therefore, when printing high-print-rate images continuously, there is insufficient toner supply on the downstream side (the supply opening side) in the toner transport direction.

[0108] Figure 12(B) shows an example of a white-out image that occurs when solid black images are printed consecutively. As described above, in this example, there is insufficient toner supply to the developing roller 215 on the supply opening side of the developing container 210. As a result, a white-out image occurs in the region near the developing opening in the longitudinal direction (sheet width direction) of the developing container 210 due to insufficient toner supply.

[0109] In this embodiment, when printing high-print-rate images continuously on multiple sheets, the rotation speed (number of rotations) of the transport screw 221 of the toner container 220 is changed to promote the transport of toner to the replenishment opening within the toner container 220. This adjusts the amount of toner supplied from the toner container 220 to the developing container 210 through the replenishment opening, thereby reducing the occurrence of white areas in the image.

[0110] <4. Control Unit> The control configuration of the image forming apparatus 200 in this embodiment is the same as the control configuration of the image forming apparatus 1 in the first embodiment (Figure 6).

[0111] <5. Calculation of the integrated pixel count value> Figure 13 shows an example, similar to the second embodiment (Figure 9), in which the image area with the maximum image width is divided into five equal areas (divided areas) Zone 1 to Zone 5 in the width direction perpendicular to the sheet transport direction. Similar to the first embodiment, the ASIC 514 counts the pixels to be printed in each divided area (Zone) based on the image information (image data) corresponding to the input image of one page, and outputs a pixel count value indicating the number of pixels to be printed. Similar to the first embodiment, the pixel integration unit 540 performs a process to obtain an integrated value S by accumulating the pixel count value of each page for each divided area (Zone) when image formation is performed continuously on multiple sheets in one print job.

[0112] <6. Toner supply control> In the image forming apparatus 200 of this embodiment, for example, when printing (forming) images on multiple sheets in monochrome mode in succession, there is a possibility that white areas may occur in the printed image (downstream in the direction of toner transport by the transport screw 212, as shown in Figure 13). In the image forming apparatus 200 of this embodiment, in a single print job, the amount of toner supplied from the toner container 220 is adjusted for each divided region (Zone) obtained by dividing the image area in the width direction of the sheet, based on the cumulative threshold value for the cumulative value S and the cumulative value S. The adjustment of the toner supply amount is performed by changing the rotation speed (rotational speed) of the transport screw 221. Table 3 below shows the cumulative threshold values ​​set for each divided region (Zone). TIFF2026082048000004.tif75136

[0113] In the example in Table 3, three accumulation thresholds are defined for each divided region (Zone), and the rotation speed of the transport screw 221 is defined for each accumulation threshold. For example, the CPU 511 controls the rotation speed of the transport screw 221 to the rotation speed (1.3 times or 1.5 times) determined in accordance with the accumulation threshold each time the corresponding accumulation value S reaches the accumulation threshold for each divided region. This increases the amount of toner supplied from the toner container 220 to the developing container 210, thereby reducing the occurrence of the aforementioned white-out images. Note that the adjustment of the toner supply amount may be performed by changing the rotation speed (rotation speed) of the transport screw 212 instead of changing the rotation speed (rotation speed) of the transport screw 221.

[0114] <7. Processing Procedure> An example of the processing procedure for toner replenishment control performed in the image forming apparatus 1 of this embodiment is the same as in the first embodiment. When the CPU 511 starts executing a print job received from an external device such as a host computer 500, it performs the processing according to the procedure in Figure 14, as in the first embodiment. However, as the toner replenishment operation in S104, the CPU 511 replenishes toner by rotating the transport screw 221 (screw member) or increases the amount of toner replenished by increasing the rotational speed of the transport screw 221. Also, the CPU 511 does not perform the processing in S105 (i.e., does not reset the cumulative value S after the completion of the toner replenishment operation). As a result, the CPU 511 increases the amount of toner replenished in stages by performing the processing in S104 to increase the rotational speed of the transport screw 221 each time it reaches one of the three cumulative thresholds exemplified in Table 3 for each divided region.

[0115] <8. Summary> As described above, according to this embodiment, by controlling the rotation speed of the transport screw 221, the toner supply operation can be controlled, thereby reducing the occurrence of blank images when printing high-print-rate images continuously.

[0116] In this embodiment, an example of dividing the image area in the longitudinal direction (width direction) into multiple areas of equal size has been described, but the method of dividing the image area is not limited to this. For example, the size of each divided area (Zone) may be changed according to the size of the replenishment opening of the developing container 210 (developing unit), and the accumulation threshold may be changed (set) accordingly.

[0117] The disclosures herein include the following image forming apparatus. (Item 1) A developer container for storing the developer, A developing roller housing comprises a developing roller for developing an electrostatic latent image formed on a photoreceptor, and has an opening formed in the direction of the rotation axis of the developing roller that is shorter than the length of the developing roller, and the developing roller housing housing contains the developing agent supplied from the developing agent housing through the opening, An image forming control unit receives a print job containing information on the number of pixels in an image formed on a recording material and performs an image forming operation based on the print job, A replenishment operation determination unit determines whether to perform a replenishment operation, which is the operation of supplying developer from the developer storage unit to the developer roller storage unit, when predetermined conditions are met. Based on the above information, a pixel count determination unit determines the number of pixels in both a first region and a second region, which are part of the image forming region of the recording material and divided in the direction of the rotation axis. Equipped with, When the number of pixels in the first region determined by the pixel count determination unit is defined as the first pixel count, and the number of pixels in the second region determined by the pixel count determination unit is defined as the second pixel count, The predetermined conditions are that at least one of the following is satisfied: the number of first pixels exceeds a first threshold, or the number of second pixels exceeds a second threshold that is different from the first threshold. An image forming apparatus characterized by the following features. (Item 2) The first pixel count and the second pixel count are, respectively, the integrated values ​​of the pixel counts of multiple recording materials on which an image is formed based on the print job. The image forming apparatus according to item 1, characterized in that it is a picture forming apparatus. (Item 3) The second region is a region that is closer to the opening than the first region in the direction of the rotation axis, The first threshold is set to a value smaller than the second threshold. An image forming apparatus according to item 1 or 2, characterized by the features described above. (Item 4) The image forming region is divided into a plurality of regions in the direction of the rotation axis, and a threshold is set for each of the plurality of regions, including the first region and the second region. The replenishment operation determination unit determines to perform the replenishment operation when the number of pixels corresponding to at least one of the plurality of regions exceeds the threshold set for that region. An image forming apparatus according to any one of items 1 to 3, characterized in that it is an image forming apparatus. (Item 5) The threshold is set to a smaller value the further a corresponding region among the plurality of regions is from the opening in the direction of the rotation axis. The image forming apparatus according to item 4, characterized in that it is a picture forming apparatus. (Item 6) The size of each of the aforementioned multiple regions is determined according to the size of the opening. The image forming apparatus according to item 4 or 5, characterized in that it is a picture forming apparatus. (Item 7) Depending on the size of each of the multiple regions, the corresponding threshold is set. The image forming apparatus according to item 6, characterized in that it is a picture forming apparatus. (Item 8) The pixel count determination unit determines, based on the information, the number of pixels to be developed with the developer in each of the first and second regions. An image forming apparatus according to any one of items 1 to 7, characterized in that it is an image forming apparatus. (Item 9) The developing roller housing section has a plurality of openings for supplying developer from the developer housing section. The developing roller housing is configured such that the length of each opening in the direction of the rotation axis decreases as the number of openings provided in the developing roller housing increases. An image forming apparatus according to any one of items 1 to 8, characterized by the above. (Item 10) The rotary further includes the developing roller housing and the developer housing, and the developer housing can be attached to and detached. The replenishment operation includes the operation of rotating the rotary once. An image forming apparatus according to any one of items 1 to 9, characterized in that it is an image forming apparatus. (Item 11) The replenishment operation includes rotating the rotary so that the developer that has fallen into the developer storage section by gravity can move into the developer roller storage section through the opening. The image forming apparatus according to item 10, characterized in that it is a picture forming apparatus. (Item 12) The aforementioned replenishment operation is the operation of rotating the rotary once after the rotary has assumed the aforementioned position. The image forming apparatus according to item 11, characterized in that it is a picture forming apparatus. (Item 13) The developer storage section has a rotatable screw member that transports the developer within the developer storage section in order to supply the developer to the developer roller storage section through the opening, The replenishment operation is an operation that rotates the screw member or increases the rotational speed of the screw member. An image forming apparatus according to any one of items 1 to 9, characterized in that it is an image forming apparatus. (Item 14) The developing roller housing section has a rotatable screw member that transports the developer supplied from the developer housing section through the opening to the developing roller housing section for supply, The replenishment operation is an operation that rotates the screw member or increases the rotational speed of the screw member. An image forming apparatus according to any one of items 1 to 9, characterized in that it is an image forming apparatus. (Item 15) The first pixel count and the second pixel count are, respectively, the integrated values ​​of the pixel counts of multiple recording materials on which an image is formed based on the print job. The supply operation determination unit decides to increase the rotational speed of the screw member when the accumulated value corresponding to the first region reaches the first threshold, and then decides to further increase the rotational speed of the screw member when the accumulated value reaches a third threshold greater than the first threshold. The supply operation determination unit decides to increase the rotational speed of the screw member when the accumulated value corresponding to the second region reaches the second threshold, and then decides to further increase the rotational speed of the screw member when the accumulated value reaches a fourth threshold greater than the second threshold. The image forming apparatus according to item 14, characterized in that it is a picture forming apparatus. (Item 16) The pixel count determination unit resets the accumulated value to 0 when the replenishment operation is performed. An image forming apparatus according to item 2 or 15, characterized in that it is an image forming apparatus. (Item 17) The pixel count determination unit resets the accumulated value to 0 when the execution of the print job is completed. An image forming apparatus according to any one of items 2, 15, and 16, characterized by the features described above.

[0118] The invention is not limited to the embodiments described above, and various modifications and variations are possible without departing from the spirit and scope of the invention. Accordingly, claims are attached to disclose the scope of the invention. [Explanation of Symbols]

[0119] 1: Image forming apparatus, 2: Photosensitive drum, 50: Developing unit, 70: Toner cartridge, 2: Photosensitive drum, 90: Rotary body, 211, 212, 221: Conveyor screw, 502: Engine control unit, 511: CPU

Claims

1. A developer container for storing the developer, A developing roller housing comprises a developing roller for developing an electrostatic latent image formed on a photoreceptor, and has an opening formed in the direction of the rotation axis of the developing roller that is shorter than the length of the developing roller, and the developing roller housing housing contains the developing agent supplied from the developing agent housing through the opening, An image forming control unit receives a print job containing information on the number of pixels in an image formed on a recording material and performs an image forming operation based on the print job, A replenishment operation determination unit determines whether to perform a replenishment operation, which is the operation of supplying developer from the developer storage unit to the developer roller storage unit, when predetermined conditions are met. Based on the above information, a pixel count determination unit determines the number of pixels in both a first region and a second region, which are part of the image forming region of the recording material and divided in the direction of the rotation axis. Equipped with, When the number of pixels in the first region determined by the pixel count determination unit is defined as the first pixel count, and the number of pixels in the second region determined by the pixel count determination unit is defined as the second pixel count, The predetermined conditions are that at least one of the following is satisfied: the number of first pixels exceeds a first threshold, or the number of second pixels exceeds a second threshold that is different from the first threshold. An image forming apparatus characterized by the following:

2. The first pixel count and the second pixel count are, respectively, the integrated values ​​of the pixel counts of multiple recording materials on which an image is formed based on the print job. The image forming apparatus according to feature 1.

3. The second region is a region that is closer to the opening than the first region in the direction of the rotation axis, The first threshold is set to a value smaller than the second threshold. The image forming apparatus according to feature 1.

4. The image forming region is divided into a plurality of regions in the direction of the rotation axis, and a threshold is set for each of the plurality of regions, including the first region and the second region. The replenishment operation determination unit determines to perform the replenishment operation when the number of pixels corresponding to at least one of the plurality of regions exceeds the threshold set for that region. The image forming apparatus according to feature 1.

5. The threshold is set to a smaller value the further a corresponding region among the plurality of regions is from the opening in the direction of the rotation axis. The image forming apparatus according to feature 4.

6. The size of each of the aforementioned multiple regions is determined according to the size of the opening. The image forming apparatus according to feature 4.

7. Depending on the size of each of the multiple regions, the corresponding threshold is set. The image forming apparatus according to feature 6.

8. The pixel count determination unit determines, based on the information, the number of pixels to be developed with the developer in each of the first and second regions. The image forming apparatus according to any one of claims 1 to 7.

9. The developing roller housing section has a plurality of openings for supplying developer from the developer housing section. The developing roller housing is configured such that the length of each opening in the direction of the rotation axis decreases as the number of openings provided in the developing roller housing increases. The image forming apparatus according to any one of claims 1 to 7.

10. The rotary further includes the developing roller housing and the developer housing, and the developer housing can be attached to and detached. The replenishment operation includes the operation of rotating the rotary once. The image forming apparatus according to any one of claims 1 to 7.

11. The replenishment operation includes rotating the rotary so that the developer that has fallen into the developer storage section by gravity can move into the developer roller storage section through the opening. The image forming apparatus according to feature 10.

12. The aforementioned replenishment operation is the operation of rotating the rotary once after the rotary has assumed the aforementioned position. The image forming apparatus according to feature 11.

13. The developer storage section has a rotatable screw member that transports the developer within the developer storage section in order to supply the developer to the developer roller storage section through the opening, The replenishment operation is an operation that rotates the screw member or increases the rotational speed of the screw member. The image forming apparatus according to any one of claims 1 to 7.

14. The developing roller housing section has a rotatable screw member that transports the developer supplied from the developer housing section through the opening to the developing roller housing section for supply, The replenishment operation is an operation that rotates the screw member or increases the rotational speed of the screw member. The image forming apparatus according to any one of claims 1 to 7.

15. The first pixel count and the second pixel count are, respectively, the integrated values ​​of the pixel counts of multiple recording materials on which an image is formed based on the print job. The supply operation determination unit decides to increase the rotational speed of the screw member when the accumulated value corresponding to the first region reaches the first threshold, and then decides to further increase the rotational speed of the screw member when the accumulated value reaches a third threshold greater than the first threshold. The supply operation determination unit decides to increase the rotational speed of the screw member when the accumulated value corresponding to the second region reaches the second threshold, and then decides to further increase the rotational speed of the screw member when the accumulated value reaches a fourth threshold greater than the second threshold. The image forming apparatus according to feature 14.

16. The pixel count determination unit resets the accumulated value to 0 when the replenishment operation is performed. The image forming apparatus according to feature 2.

17. The pixel count determination unit resets the accumulated value to 0 when the execution of the print job is completed. The image forming apparatus according to feature 2.

Images