JP4998245B2 - Image forming apparatus - Google Patents

Description

  The present invention relates to an image forming apparatus, and more particularly to an image forming apparatus that forms a toner image by electrophotography.

  In an image forming apparatus such as a copying machine or a printer, an operation called forced toner consumption is periodically performed to prevent accumulation of deteriorated toner (hereinafter referred to as deteriorated toner) in a developing device. . Hereinafter, taking a non-magnetic / non-contact / one-component color image forming apparatus as an example, the principle of generation of deteriorated toner and forced toner consumption will be described with reference to the drawings. FIG. 14 is a cross-sectional structure diagram of the developing device 7 of the non-magnetic / non-contact / one-component color image forming apparatus. FIGS. 15 and 16 are diagrams illustrating toner images transferred to the transfer belt of the image forming apparatus during forced toner consumption. Here, non-magnetic means that the developer does not contain a magnetic substance. Further, non-contact means that the developing roller and the photosensitive drum are in a non-contact state. One component means that the developer is made of toner and does not contain a carrier.

  As shown in FIG. 14, the developing device 7 includes a developer tank 72, a feed blade 74, a supply roller 76, a developing roller 78, and a regulating blade 80. The photosensitive drum 4 is provided at a position away from the developing roller 78 by a predetermined distance.

  The developer tank 72 stores toner and holds a feed blade 74, a supply roller 76, a development roller 78, and a regulation blade 80. The feed blade 74 serves to feed the toner in the developer tank 72 to the supply roller 76 by rotating clockwise in FIG. The supply roller 76 rotates counterclockwise in FIG. 14 and supplies toner to the developing roller 78. More specifically, toner adheres to the periphery of the supply roller 76 as shown in FIG. Since the supply roller 76 and the developing roller 78 are in contact with each other, friction between the toners occurs at the contact point between the supply roller 76 and the developing roller 78, and the toner is negatively charged by this friction. Since a voltage higher than that of the supply roller 76 is applied to the developing roller 78, the negatively charged toner moves from the supply roller 76 to the developing roller 78 at the contact point.

  The tip of the regulation blade 80 is pressed against the developing roller 78. As a result, a toner layer having a predetermined thickness is formed on the peripheral surface of the developing roller 78. As shown in FIG. 14, the developing roller 78 rotates clockwise and conveys toner to the photosensitive drum 4. An electrostatic latent image having a voltage higher than that of the developing roller 78 is formed on the peripheral surface of the photosensitive drum 4. Therefore, the negatively charged toner moves from the developing roller 78 to the photosensitive drum 4 at a position where the developing roller 78 and the photosensitive drum 4 face each other. As a result, a toner image is formed on the peripheral surface of the photosensitive drum 4. The toner that has passed through the position where the developing roller 78 and the photosensitive drum 4 face each other is collected in the developer tank 72 by the supply roller 76.

  By the way, in the developing device 7, the regulating blade 80 is pressed against the developing roller 78 to generate friction between the toners to charge the toner. In the toner, an additive for promoting charging is mixed. For this reason, when a frictional force is generated between the toners, the additive may be peeled off from the toner or may be embedded in the toner. As a result, deteriorated toner having a reduced charging ability is generated. If such deteriorated toner accumulates in the developing device 7, the print quality is lowered.

  Therefore, the image forming apparatus forcibly discharges the deteriorated toner to the outside of the developing device 7 by the forced toner consumption. Specifically, when the control unit (not shown) of the image forming apparatus determines that a predetermined amount or more of the deteriorated toner has accumulated, yellow (hereinafter, Y) as shown in FIG. ), Magenta (hereinafter referred to as M), cyan (hereinafter referred to as C), and black (hereinafter referred to as K) solid images are formed side by side in the transfer belt conveyance direction. As a result, the deteriorated toner accumulated in the developing device 7 is forcibly discharged. Here, the solid image refers to a state in which a toner image is formed in a predetermined area of the transfer belt without a gap.

  However, the forced toner consumption has a problem that normal toner that has not deteriorated is consumed together with deteriorated toner. Therefore, in the image forming apparatus described in Patent Document 1, as shown in FIG. 16, a square area to which toner is applied (hereinafter referred to as a toner application portion) and an area to which toner is not applied (hereinafter referred to as a blank area). Toner images arranged in a checkered pattern are arranged side by side in the transfer belt conveyance direction for each of Y, M, C, and K colors. Thereby, the deteriorated toner can be efficiently discharged out of the developing device 7 by utilizing the edge effect. Hereinafter, the edge effect will be described in detail with reference to the drawings. FIG. 17 is an enlarged view of the toner applying portion 100 formed on the photosensitive drum 4. FIG. 18A is a cross-sectional structure diagram of the toner applying portion 100 formed on the photosensitive drum 4. FIG. 18B is a diagram showing the voltage of the photosensitive drum 4 in the vicinity of the toner applying portion 100.

  At the time of forced toner consumption, as shown in FIG. 17, a region to which toner is applied, called an edge portion 102, is formed around the toner application portion 100. The edge portion 102 is formed with deteriorated toner instead of normal toner. The reason is as follows.

  As shown in FIG. 18B, the peripheral surface of the photosensitive drum 4 is charged so that the voltage of the toner applying portion 100 is higher than the voltage of the blank portion 102. Therefore, an electric field is generated upward in the toner application portion 100. As a result, the negatively charged toner receives a force from the developing roller 78 side to the photosensitive drum 4 side due to an electric field and adheres to the toner application portion 100.

  However, at the edge of the toner application portion 100, the electric field is generated so as to wrap around the peripheral surface of the photosensitive drum 4 without going upward (hereinafter, this electric field is referred to as a wraparound electric field). Such a sneak electric field prevents negatively charged toner from adhering to the toner application portion 100. In particular, since the deteriorated toner has a smaller charge amount than normal toner, once it is taken into the wraparound electric field, it cannot return to the toner application portion 100 again. As a result, the deteriorated toner is preferentially attached to the edge portion 102 under the influence of the wraparound electric field.

  Due to the phenomenon (edge effect) as described above, the edge portion 102 consumes more deteriorated toner than normal toner. That is, when the forced toner consumption is performed using a pattern having a wide edge area like the toner application portion 100, the ratio of the deteriorated toner in the toner discharged from the developing device 7 can be increased. .

However, in the image forming apparatus described in Patent Document 1, since the toner application portion 100 is arranged in a checkered pattern, when the same amount of toner is consumed, the toner is forcibly consumed using a solid toner image. Compared with the case where it carries out, the travel distance of a transfer belt will become long. When the travel distance of the transfer belt becomes long, the developing unit 7 operates even during the travel of the transfer belt, and new deteriorated toner is generated. That is, the discharge efficiency of deteriorated toner is reduced.
JP 2000-206770 A

  Accordingly, an object of the present invention is to provide an image forming apparatus that can efficiently discharge deteriorated toner.

  According to the present invention, in the image forming apparatus, a plurality of photoconductors, an electrostatic latent image forming unit that forms an electrostatic latent image on a peripheral surface of the plurality of photoconductors, and toner are applied to the plurality of photoconductors. Developing means for forming toner images on the peripheral surfaces of the plurality of photoconductors, a transfer body to which toner images formed on the plurality of photoconductors are transferred, and deteriorated toner present in the plurality of developing means. When discharging, a toner image in which a blank portion to which no toner is applied is present on a part of the solid image is formed on the peripheral surface of the plurality of photosensitive members, and the plurality of toner images are superimposed on the transfer member. And a control unit that controls the photosensitive member, the electrostatic latent image forming unit, and the developing unit so as to be transferred.

  According to the present invention, a toner image is formed on the peripheral surface of each photoconductor, where a blank portion to which no toner is applied is present on a part of the solid image. Therefore, an edge effect occurs in the blank portion. As a result, an edge portion is formed by the deteriorated toner in the blank portion, and the deteriorated toner is forcibly discharged.

  Further, according to the present invention, since the toner images of the respective colors are transferred in a superimposed manner, the travel distance of the transfer body can be reduced as compared with the case where the toner images are transferred side by side in the transport direction of the transfer body as shown in FIG. Can be shortened. As a result, the generation of new deteriorated toner while the transfer body is running is suppressed, and the deteriorated toner is efficiently discharged.

  In the present invention, the toner image formed on the photoconductor when the deteriorated toner is discharged has a pattern in which island-like toner application portions and blank portions are alternately arranged in the main scanning direction and the sub-scanning direction. You may have.

  In the present invention, when the plurality of toner images are superimposed on the transfer body, toner applying portions of different colors may be adjacent to each other in the main scanning direction and the transport direction of the transfer body.

  In the present invention, the toner applying portions for the respective colors may not overlap on the transfer body.

  In the present invention, the developer comprising the toner may be a one-component / non-magnetic developer.

(Configuration of image forming apparatus)
Hereinafter, a configuration of an image forming apparatus according to an embodiment of the present invention will be described with reference to the drawings. The image forming apparatus is a non-magnetic, non-contact, one-component color image forming apparatus. FIG. 1 is a diagram showing an overall configuration of the image forming apparatus 1.

  An image forming apparatus 1 shown in FIG. 1 is an electrophotographic color printer, and synthesizes images of four colors (Y: yellow, M: magenta, C: cyan, K: black) in a so-called tandem system. It is composed. The image forming apparatus 1 has a function of receiving a print job and forming an image on a printing medium such as paper, and includes a printing unit 2, a paper feeding unit 14, a control unit 18, a fixing device 19, and a paper discharge tray 20. .

  The control unit 18 is constituted by, for example, a CPU, and serves as a control unit that controls operations of the printing unit 2, the paper feeding unit 14, and the fixing device 19. The paper supply unit 14 serves to supply paper one by one, and includes a paper tray 15 and a paper supply roller 16. On the paper tray 15, a plurality of sheets in a state before printing are stacked and placed. The paper feed roller 16 takes out the paper placed on the paper tray 15 one by one.

  The printing unit 2 forms a toner image on the paper supplied from the paper supply unit 14, and forms image forming stations 21Y, 21M, 21C, and 21K, primary transfer rollers 8Y, 8M, 8C, and 8K, a transfer belt 10, and a drive. A roller 11, a driven roller 12, a transfer roller 13 and a cleaning blade 17 are included. The image forming stations 21Y, 21M, 21C, and 21K include photosensitive drums 4Y, 4M, 4C, and 4K, chargers 5Y, 5M, 5C, and 5K, exposure devices 6Y, 6M, 6C, and 6K, and developing units 7Y and 7M. , 7C, 7K and cleaners 9Y, 9M, 9C, 9K. Hereinafter, when the photosensitive drum, the charger, the exposure device, the developing device, the primary transfer roller, the cleaner, and the image forming station are collectively referred to, the photosensitive drum 4, the charger 5, The exposure device 6, the developing device 7, the primary transfer roller 8, the cleaner 9, and the image forming station 21 are described as individual photosensitive drums, chargers, exposure devices, developing devices, primary transfer rollers, cleaners, and When referring to the image forming station, the photosensitive drums 4Y, 4M, 4C, and 4K, the chargers 5Y, 5M, 5C, and 5K, the exposure devices 6Y, 6M, 6C, and 6K, and the developing devices 7Y, 7M, 7C, and 7K The primary transfer rollers 8Y, 8M, 8C, and 8K, cleaners 9Y, 9M, 9C, and 9K, and image forming stations 21Y, 21M, 21C, and 21K are described.

  The charger 5 charges the peripheral surface of the photosensitive drum 4. The exposure apparatus 6 irradiates a laser under the control of the control unit 18. As a result, an electrostatic latent image is formed on the peripheral surface of the photosensitive drum 4. That is, the charger 5 and the exposure device 6 serve as an electrostatic latent image forming unit that forms an electrostatic latent image on the peripheral surface of the photosensitive drum 4.

  As shown in FIG. 14, the developing device 7 includes a developer tank 72, a feed blade 74, a supply roller 76, a developing roller 78, and a regulating blade 80. Further, the photosensitive drum 4 is provided in a non-contact state with the developing roller 78 at a position separated from the developing roller 78 by a predetermined distance. The developing device 7 serves as a developing unit that applies toner to the photosensitive drum 4 and forms toner images on the peripheral surfaces of the plurality of photosensitive drums 4. This will be described in detail below.

  The developer tank 72 stores a one-component / nonmagnetic developer made of toner, and holds a feed blade 74, a supply roller 76, a development roller 78, and a regulating blade 80. The feed blade 74 serves to feed the toner in the developer tank 72 to the supply roller 76 by rotating clockwise in FIG. The supply roller 76 rotates counterclockwise in FIG. 14 and supplies toner to the developing roller 78. More specifically, toner adheres to the periphery of the supply roller 76 as shown in FIG. Since the supply roller 76 and the developing roller 78 are in contact with each other, friction between the toners occurs at the contact point between the supply roller 76 and the developing roller 78, and the toner is negatively charged by this friction. Since a voltage higher than that of the supply roller 76 is applied to the developing roller 78, the negatively charged toner moves from the supply roller 76 to the developing roller 78 at the contact point.

  The tip of the regulation blade 80 is pressed against the developing roller 78. As a result, a toner layer having a predetermined thickness is formed on the peripheral surface of the developing roller 78. As shown in FIG. 14, the developing roller 78 rotates clockwise and conveys toner to the photosensitive drum 4. An electrostatic latent image having a voltage higher than that of the developing roller 78 is formed on the peripheral surface of the photosensitive drum 4. Therefore, the negatively charged toner moves from the developing roller 78 to the photosensitive drum 4 at a position where the developing roller 78 and the photosensitive drum 4 face each other. As a result, a toner image is formed on the peripheral surface of the photosensitive drum 4. The toner that has passed through the position where the developing roller 78 and the photosensitive drum 4 face each other is collected in the developer tank 72 by the supply roller 76.

  The transfer belt 10 is stretched between the driving roller 11 and the driven roller 12 and functions as a transfer body on which the toner image formed on the photosensitive drum 4 is primarily transferred. The primary transfer roller 8 is disposed so as to be in contact with the inner peripheral surface of the transfer belt 10 and plays a role of primary transfer of the toner image formed on the photosensitive drum 4 to the transfer belt 10. The cleaner 9 serves to collect the toner remaining on the peripheral surface of the photosensitive drum 4 after the primary transfer. The drive roller 11 is driven by a power source such as a motor (not shown) to drive the transfer belt 10. The toner image is conveyed to the transfer roller 13 when the transfer belt 10 is driven. The transfer roller 13 secondarily transfers the toner image onto the paper conveyed from the paper supply unit 14. The cleaning blade 17 removes the toner remaining on the transfer belt 10 after the secondary transfer of the toner image onto the paper.

  The sheet on which the toner image is secondarily transferred is conveyed to the fixing device 19. The fixing device 19 serves as a fixing unit that fixes the toner image on the paper by performing heat treatment and pressure treatment on the paper. Printed paper is placed on the paper discharge tray 20.

(Operation of image forming apparatus)
The operation of the image forming apparatus 1 configured as described above will be described below with reference to the drawings. Of the operations performed by the image forming apparatus 1, the printing operation is the same as a general printing operation performed by the image forming apparatus, and therefore only the forced toner consumption operation will be described below. The printing operation refers to an operation for printing an image on a recording medium such as paper, and the toner forced consumption operation refers to an operation for forcibly discharging the deteriorated toner out of the developing device 7.

  Here, FIG. 2 is a diagram showing a toner image transferred to the transfer belt 10 when the image forming apparatus 1 performs the forced toner consumption operation. FIG. 3 is a flowchart showing an operation performed by the control unit 18 during the forced toner consumption operation. FIG. 4A is a diagram illustrating a toner image formed on the photosensitive drum 4Y during the forced toner consumption operation. FIG. 4B is a diagram illustrating a toner image formed on the photosensitive drum 4M during the toner forced consumption operation. FIG. 5A is a diagram illustrating a toner image formed on the photosensitive drum 4C during the toner forced consumption operation. FIG. 5B is a diagram illustrating a toner image formed on the photosensitive drum 4K during the toner forced consumption operation.

  In the following, the direction in which the central axis of the photosensitive drum 4 extends is defined as the main scanning direction, and the rotation direction of the photosensitive drum 4 is defined as the sub-scanning direction. Further, on the surface of the transfer belt 10, a direction perpendicular to the transfer direction of the transfer belt 10 is defined as a main scanning direction.

  The image forming apparatus 1 generally performs the following operation during the forced toner consumption operation. First, a toner image in which a blank portion to which toner is not applied is present in a part of the solid image is formed on the peripheral surface of each photosensitive drum 4. At this time, the deteriorated toner is consumed in the blank portion due to the edge effect. Next, the toner images of the respective colors are transferred on the same area of the transfer belt 10. As described above, in the image forming apparatus 1, the toner images of the respective colors are transferred to be overlapped on the same area, and therefore, as shown in FIG. The traveling distance of 10 can be shortened.

  As an example of the toner image, for example, as shown in FIG. 2, when each toner image is superimposed on the transfer belt 10, toner application portions having different colors in the main scanning direction and the conveyance direction of the transfer belt 10. For example, toner images adjacent to each other can be cited. The toner application portion refers to an area where toner is applied. On the other hand, a region to which no toner is applied is hereinafter referred to as a blank portion. In the toner image shown in FIG. 2, a square (in FIG. 2, square) Y toner application portion is arranged at the upper left, a square M toner application portion is arranged at the upper right, and a square K toner application portion at the lower left. And a pattern in which a square C toner application portion is formed in the lower right is arranged in a matrix. However, the positional relationship between the toner application portions of each color is not limited to this. The toner consumption operation for forming the toner image shown in FIG. 2 will be described in detail below with reference to FIG.

  The control unit 18 determines whether or not to perform the forced toner consumption operation (step S1). In this process, the control unit 18 counts the number of dots based on image data that has been printed in the past, and determines whether or not the number of dots has reached a predetermined number. This is because there is a predetermined relationship between the number of dots of image data and the amount of deteriorated toner generated in the printing operation. When the number of dots reaches the predetermined number, the control unit 18 determines that the toner forced consumption operation is performed, and the process proceeds to step S2. If the number of dots has not reached the predetermined number, the control unit 18 determines that the toner forced consumption operation is not performed, and the process ends.

  When the forced toner consumption operation is performed, the control unit 18 causes the image forming station 21Y to start forming the Y toner image shown in FIG. 4A on the peripheral surface of the photosensitive drum 4Y (step S2). The toner image shown in FIG. 4A has a pattern in which square island-shaped toner application portions and square blank portions are alternately arranged in the main scanning direction and the sub-scanning direction. More specifically, a blank portion having the same shape as the toner applying portion is arranged so as to surround the toner applying portion.

  Next, the control unit 18 causes the printing unit 2 to start transferring the Y toner image formed on the photosensitive drum 4Y to the transfer belt 10 (step S3). Thereafter, the process proceeds to step S4. Since the transfer process here is the same as a general transfer process, detailed description thereof is omitted.

  Next, the control unit 18 causes the image forming station 21M to start forming the M toner image shown in FIG. 4B on the peripheral surface of the photosensitive drum 4M (step S4). The toner image shown in FIG. 4B has the same pattern as the toner image shown in FIG. However, in the toner image shown in FIG. 4B, the pattern is shifted to the downstream side in the sub-scanning direction by one toner application portion as compared with the toner image shown in FIG.

  Next, the control unit 18 causes the printing unit 2 to start transferring the M toner image formed on the photosensitive drum 4M to the transfer belt 10 (step S5). In steps S4 and S5, an M toner image is formed and transferred so that the M toner application portion is adjacent to the Y toner application portion downstream in the sub-scanning direction without overlapping. Thereafter, the process proceeds to step S6.

  Next, the control unit 18 causes the image forming station 21C to start forming the C toner image shown in FIG. 5A on the peripheral surface of the photosensitive drum 4C (step S6). The toner image shown in FIG. 5A has the same pattern as the toner image shown in FIG. However, in the toner image shown in FIG. 5A, compared to the toner image shown in FIG. 4A, the pattern is shifted to the downstream side in the scanning direction and the downstream side in the sub-scanning direction by one toner application portion. Yes.

  Next, the control unit 18 causes the printing unit 2 to start transferring the C toner image formed on the photosensitive drum 4C to the transfer belt 10 (step S7). In step S6 and step S7, a C toner image is formed such that the C toner application portion is positioned on the downstream side in the sub-scanning direction of the Y toner application portion and on the downstream side in the main scanning direction without overlapping. And transferred. Thereafter, the process proceeds to step S8.

  Next, the control unit 18 causes the image forming station 21K to start forming the K toner image shown in FIG. 5B on the peripheral surface of the photosensitive drum 4K (step S8). The toner image shown in FIG. 5B has the same pattern as the toner image shown in FIG. However, in the toner image shown in FIG. 5B, the pattern is shifted downstream in the main scanning direction by one toner application portion as compared with the toner image shown in FIG.

  Next, the control unit 18 causes the printing unit 2 to start transferring the K toner image formed on the photosensitive drum 4K to the transfer belt 10 (step S9). In steps S8 and S9, a K toner image is formed and transferred so that the K toner application portion is adjacent to the Y toner application portion downstream in the main scanning direction without overlapping. As a result, as shown in FIG. 2, a toner image in which the toner applying portions of the respective colors are not overlapped is formed on the transfer belt 10. Thereafter, the toner image shown in FIG. 2 is removed by the cleaning blade 17.

(effect)
As described above, according to the image forming apparatus 1, a large number of island-like toner application portions that are not connected to any toner application portion are formed on the peripheral surface of each photosensitive drum 4. Edge effects occur at the edges of As a result, an edge portion is formed by the deteriorated toner around the toner application portion, and the deteriorated toner is forcibly discharged from the developing device 7. As a result, when printing is performed on the paper, fogging due to the deteriorated toner adhering to the white portion of the paper is prevented. This will be described below with reference to FIG. FIG. 6 shows the amount of toner discharged during forced toner consumption (hereinafter referred to as “discharge amount”) and the amount of deteriorated toner (hereinafter referred to as “fogging”) that adheres to the paper when the paper is passed without forming a toner image. It is the graph which showed the relationship with quantity). The vertical axis represents the discharge amount, and the horizontal axis represents the fogging amount.

  From the graph shown in FIG. 6, it can be understood that the toner image shown in FIG. 2 can reduce the fog amount more than the toner image shown in FIG. Therefore, for example, when the discharge amount is constant, the toner image shown in FIG. 2 requires less fog than the toner image shown in FIG. Similarly, when the fogging amount is constant, the toner image shown in FIG. 2 requires less discharge than the toner image shown in FIG.

  Furthermore, according to the image forming apparatus 1, since the toner images of the respective colors are transferred in a superimposed manner, the toner image of the transfer belt 10 is compared with the case where the toner images are transferred side by side in the transfer belt conveying direction as shown in FIG. The mileage can be shortened. As a result, in the image forming apparatus 1, the generation of new deteriorated toner while the transfer belt 10 is running is suppressed, and the deteriorated toner is efficiently discharged. In particular, in the toner image shown in FIG. 2, since the toner application portion is arranged without a gap after the transfer, the travel distance of the transfer belt 10 can be shortened more effectively.

  Further, according to the image forming apparatus 1, the toner application portion is transferred so as not to overlap on the transfer belt 10. Therefore, in the image forming apparatus 1, the cleaning blade 17 can easily remove the toner image from the transfer belt 10 as compared with the case where the toner application portion is transferred in an overlapping manner.

(First modification)
Hereinafter, a first modification of the image forming apparatus 1 will be described with reference to FIG. FIG. 7 is a diagram illustrating a toner image transferred to the transfer belt 10 by the image forming apparatus 1 according to the first modification during the forced toner consumption operation.

  In the toner image shown in FIG. 2, the size of the toner application portion of each color is the same. On the other hand, in the toner image shown in FIG. 7, the K toner application portion is relatively large, and the other color toner application portions are relatively small. When the generation of the specific color deteriorated toner is large, it is possible to discharge only the specific color deteriorated toner by forming a toner image as shown in FIG. The size of the toner-applied portion is determined based on, for example, the control unit 18 counting the number of dots based on image data that has been printed in the past, and the number of dots. In this case, the image forming apparatus 1 forms a relatively large toner application portion for a color with a small number of dots, and forms a relatively small toner application portion for a color with a large number of dots.

(Second modification)
Hereinafter, a second modification of the image forming apparatus 1 will be described with reference to FIGS. FIG. 8 is a diagram illustrating a toner image transferred to the transfer belt 10 by the image forming apparatus 1 according to the second modification example during the forced toner consumption operation. FIG. 9A is a diagram illustrating a toner image formed on the photosensitive drum 4Y during the forced toner consumption operation of the image forming apparatus 1 according to the second modification. FIG. 9B is a diagram illustrating a toner image formed on the photosensitive drum 4M during the forced toner consumption operation of the image forming apparatus 1 according to the second modification. FIG. 10A is a diagram illustrating a toner image formed on the photosensitive drum 4C during the forced toner consumption operation of the image forming apparatus 1 according to the second modification. FIG. 10B is a diagram illustrating a toner image formed on the photosensitive drum 4K during the forced toner consumption operation of the image forming apparatus 1 according to the second modification.

  In the toner image shown in FIG. 2, each toner application portion was transferred to the transfer belt 10 so as not to overlap. In contrast, in the toner image shown in FIG. 8, the Y toner application portion and the M toner application portion overlap, and the K toner application portion and the C toner application portion overlap. Such a toner image is formed by the following procedure.

  In step S2 of FIG. 3, a toner image in which Y toner application portions and blank portions as shown in FIG. 9A are arranged in a checkered pattern is formed on the peripheral surface of the photosensitive drum 4Y. Further, in step S4 of FIG. 3, a toner image in which M toner application portions and blank portions as shown in FIG. 9B are arranged in a checkered pattern is formed on the peripheral surface of the photosensitive drum 4M. The position where the M toner application portion is formed and the position where the Y toner application portion is formed are the same.

  Further, in step S6 of FIG. 3, a toner image in which a C toner application portion and a blank portion as shown in FIG. 10A are arranged in a checkered pattern is formed on the peripheral surface of the photosensitive drum 4C. Further, in step S8 of FIG. 3, a toner image in which a K toner application portion and a blank portion as shown in FIG. 10B are arranged in a checkered pattern is formed on the peripheral surface of the photosensitive drum 4K. The position where the K toner application portion is formed is the same as the position where the C toner application portion is formed. However, the positions where the C and K toner application portions are formed are the positions where the blank portions of the Y and M toner images are formed.

  The toner images shown in FIGS. 9 and 10 are transferred onto the transfer belt 10 in an overlapping manner in steps S3, S5, S7, and S9 in FIG. As a result, the toner image shown in FIG. 8 is transferred to the transfer belt 10.

  According to the image forming apparatus 1 according to the second modified example, as shown in FIG. 8, the two color toner application portions are formed so as to overlap each other, so that compared with the case where the toner image shown in FIG. 2 is formed. The travel distance of the transfer belt 10 can be shortened. However, in the toner image shown in FIG. 8, since the toner application portion is transferred in an overlapping manner, the cleaning blade 17 needs to remove the toner application portion for two layers.

(Third Modification)
Hereinafter, a third modification of the image forming apparatus 1 will be described with reference to FIGS. FIG. 11 is a diagram illustrating a toner image transferred to the transfer belt 10 by the image forming apparatus 1 according to the third modified example during the forced toner consumption operation. FIG. 12A is a diagram illustrating a toner image formed on the photosensitive drum 4Y during the forced toner consumption operation of the image forming apparatus 1 according to the third modification. FIG. 12B is a diagram showing a toner image formed on the photosensitive drum 4M during the forced toner consumption operation of the image forming apparatus 1 according to the third modification. FIG. 13A is a diagram showing a toner image formed on the photosensitive drum 4C during the forced toner consumption operation of the image forming apparatus 1 according to the third modification. FIG. 13B is a diagram illustrating a toner image formed on the photosensitive drum 4K during the forced toner consumption operation of the image forming apparatus 1 according to the third modification.

  In the toner image shown in FIG. 2, a large number of island-like toner application portions are transferred to the transfer belt 10 in each toner application portion. On the other hand, in the toner image shown in FIG. 11, a plurality of rectangular toner application portions extending in the main scanning direction are arranged so as to be arranged at predetermined intervals along the conveyance direction of the transfer belt 10. Yes. The Y toner application portion and the C toner application portion overlap, and the M toner application portion and the K toner application portion overlap. Such a toner image is formed by the following procedure.

  In step S2 of FIG. 3, a toner image in which a plurality of Y toner application portions are arranged in the upstream region in the sub-scanning direction as shown in FIG. 12A is formed on the peripheral surface of the photosensitive drum 4Y. The Further, in step S4 of FIG. 3, a toner image in which a plurality of M toner application portions as shown in FIG. 12B are arranged in the downstream region in the sub-scanning direction is formed on the peripheral surface of the photosensitive drum 4M. It is formed.

  Further, in step S6 of FIG. 3, a toner image in which a plurality of C toner application portions are arranged in the upstream region in the sub-scanning direction as shown in FIG. 13A is formed on the peripheral surface of the photosensitive drum 4C. It is formed. Further, in step S8 in FIG. 3, a toner image in which a plurality of K toner application portions are arranged in the downstream region in the sub-scanning direction as shown in FIG. 13B is formed on the peripheral surface of the photosensitive drum 4K. It is formed. The position where the Y toner application portion is formed is the same as the position where the C toner application portion is formed. The position where the M toner application portion is formed and the position where the K toner application portion is formed are the same.

  The toner images shown in FIGS. 12 and 13 are transferred onto the transfer belt 10 in an overlapping manner in Step S3, Step S5, Step S7 and Step S9 in FIG. As a result, the toner image shown in FIG. 11 is transferred to the transfer belt 10.

  According to the image forming apparatus 1 according to the third modified example, as shown in FIG. 11, since the two color toner application portions are formed in an overlapping manner, compared to the case where the toner image shown in FIG. 2 is formed. The travel distance of the transfer belt 10 can be shortened. However, in the toner image shown in FIG. 11, since the toner application portion is transferred in an overlapping manner, the cleaning blade 17 needs to remove the toner application portion for two layers.

(Other variations)
In the image forming apparatus 1, the photosensitive drum 4 and the developing roller 78 are not in contact with each other, but they may be in contact with each other. Further, the developer is a one-component developer composed only of toner, but may be a two-component developer composed of toner and carrier. The developer is a non-magnetic developer, but may be a magnetic developer.

1 is a diagram illustrating an overall configuration of an image forming apparatus according to an embodiment of the present invention. 6 is a diagram illustrating a toner image transferred to a transfer belt by the image forming apparatus during a forced toner consumption operation. FIG. 6 is a flowchart illustrating an operation performed by a control unit during a toner forced consumption operation. FIG. 4A is a diagram illustrating a toner image formed on the photosensitive drum during the forced toner consumption operation. FIG. 4B is a diagram illustrating a toner image formed on the photosensitive drum during the forced toner consumption operation. FIG. 5A is a diagram illustrating a toner image formed on the photosensitive drum during the toner forced consumption operation. FIG. 5B is a diagram illustrating a toner image formed on the photosensitive drum during the forced toner consumption operation. 6 is a graph showing the relationship between the amount of toner discharged during forced toner consumption and the amount of deteriorated toner adhering to a sheet when the sheet is passed without forming a toner image. FIG. 10 is a diagram illustrating a toner image that is transferred to a transfer belt by the image forming apparatus according to the first modified example during a forced toner consumption operation. FIG. 10 is a diagram illustrating a toner image that is transferred to a transfer belt by an image forming apparatus according to a second modification during a forced toner consumption operation. FIG. 10 is a diagram illustrating a toner image formed on a photosensitive drum during a forced toner consumption operation of an image forming apparatus according to a second modification. FIG. 10 is a diagram illustrating a toner image formed on a photosensitive drum during a forced toner consumption operation of an image forming apparatus according to a second modification. FIG. 10 is a diagram illustrating a toner image transferred to a transfer belt by an image forming apparatus according to a third modification during a forced toner consumption operation. FIG. 10 is a diagram illustrating a toner image formed on a photosensitive drum during a forced toner consumption operation of an image forming apparatus according to a third modification. FIG. 10 is a diagram illustrating a toner image formed on a photosensitive drum during a forced toner consumption operation of an image forming apparatus according to a third modification. FIG. 2 is a cross-sectional structure diagram of a developing device of a nonmagnetic / noncontact / one-component color image forming apparatus. FIG. 4 is a diagram illustrating a toner image transferred to a transfer belt of the image forming apparatus when toner is forcibly consumed. FIG. 4 is a diagram illustrating a toner image transferred to a transfer belt of the image forming apparatus when toner is forcibly consumed. FIG. 4 is an enlarged view of a toner application portion formed on a photoreceptor. FIG. 18A is a cross-sectional structure diagram of a toner application portion formed on the photosensitive drum. FIG. 18B is a diagram showing the voltage of the photosensitive drum in the vicinity of the toner application portion.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Image forming apparatus 2 Printing part 4,4Y, 4M, 4C, 4K Photosensitive drum 5,5Y, 5M, 5C, 5K Charger 6,6Y, 6M, 6C, 6K Exposure apparatus 7,7Y, 7M, 7C, 7K Developing unit 8, 8Y, 8M, 8C, 8K Primary transfer roller 9, 9Y, 9M, 9C, 9K Cleaner 10 Transfer belt 11 Drive roller 12 Drive roller 13 Transfer roller 14 Paper feed unit 15 Paper tray 16 Paper feed roller 17 Cooling Blade 18 Control unit 19 Fixing device 20 Paper discharge tray 21, 21, Y, 21M, 21C, 21K Image forming station 72 Developer tank 74 Feed blade 76 Supply roller 78 Development roller 80 Regulator blade

Claims (5)

A plurality of photoreceptors;
Electrostatic latent image forming means for forming an electrostatic latent image on the peripheral surfaces of the plurality of photoconductors;
Developing means for applying toner to the plurality of photoconductors to form toner images on the peripheral surfaces of the plurality of photoconductors;
A transfer body onto which toner images formed on the plurality of photoconductors are transferred;
When discharging the deteriorated toner present in the plurality of developing units, a toner image in which a blank portion to which no toner is applied is present on a part of the solid image is formed on the peripheral surface of the plurality of photoconductors, Control means for controlling the photoconductor, the electrostatic latent image forming means, and the developing means so that the plurality of toner images are transferred to the transfer body in an overlapping manner;
Providing
An image forming apparatus. The toner image formed on the photoconductor when the deteriorated toner is discharged has a pattern in which island-like toner application portions and blank portions are alternately arranged in the main scanning direction and the sub-scanning direction. thing,
The image forming apparatus according to claim 1. When the plurality of toner images are superimposed on the transfer body, toner application portions of different colors are adjacent to each other in the main scanning direction and the transport direction of the transfer body,
The image forming apparatus according to claim 2. The toner-applying portion of each color does not overlap on the transfer body;
The image forming apparatus according to claim 1, wherein the image forming apparatus is an image forming apparatus. The developer composed of the toner is a one-component non-magnetic developer;
The image forming apparatus according to claim 1, wherein the image forming apparatus is an image forming apparatus.

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