JP2019174542A - Image formation apparatus - Google Patents

Abstract

To suppress mixture of developers in different colors on a development roller in forcible discharge processing.SOLUTION: An image formation apparatus (color printer 1) includes: a first photoreceptor (first photoreceptor drum 51K); a first development roller 53K which supplies the developer to the first photoreceptor; second photoreceptors (second photoreceptor drums 51Y, 51M, 51C); second development rollers 53Y, 53M, 53C which can contact/separate with respect to the second photoreceptors, and supply the developer to the second photoreceptors; a belt 73 which contacts each photoreceptor; a cleaning device 10 which recovers the developer on the belt 73; and a control unit 100. The control unit 100 can execute the forcible discharge processing for moving the developer on the first development roller 53K to the cleaning device 10 through the first photoreceptor and belt 73 at the non-image formation. The forcible discharge processing is executed when the second development rollers 53Y,... separate from the second photoreceptors.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an image forming apparatus including a plurality of developing rollers and a photosensitive drum.

  2. Description of the Related Art Conventionally, an image forming apparatus that includes a plurality of photosensitive drums, a plurality of developing rollers that supply developer to the photosensitive drum, and a belt that contacts the plurality of photosensitive drums is known (Patent Document). 1). In this technique, a forced discharge process is performed in which the developer on the developing roller is forcibly moved to the belt via the photosensitive drum and the developer on the belt is cleaned.

Patent 4261824

  However, in the prior art, the developer of a predetermined color discharged from one developing roller to the belt via the photosensitive drum is reversely transferred from the belt to the other photosensitive drum, and the other color on the other developing roller is transferred. There was a problem of being mixed with the developer.

  Therefore, an object of the present invention is to suppress the mixing of different color developers on the developing roller in the forced discharge process.

In order to solve the above problems, an image forming apparatus according to the present invention includes a first photosensitive member, a first developing roller that supplies a developer to the first photosensitive member, a second photosensitive member, and the second photosensitive member. A second developing roller for supplying developer to the second photosensitive member, a belt contacting the first photosensitive member and the second photosensitive member, and collecting the developer on the belt. A cleaning device; and a control unit.
The controller discharges the developer on the first developing roller onto the first photosensitive member during non-image formation, and causes the developer discharged from the first developing roller to pass through the first photosensitive member and the belt. Through the cleaning device, the forced discharge processing can be executed when the second developing roller is separated from the second photosensitive member.

  According to this configuration, when the second developing roller is separated from the second photosensitive member, the forced discharge process for collecting the developer on the first developing roller by the cleaning device is executed. The developer that has moved onto the belt via the first photoconductor can be prevented from moving to the second developing roller via the second photoconductor of another color. Therefore, it is possible to suppress the mixing of different color developers on the second developing roller in the forced discharge process.

  Further, the image forming apparatus includes a first charger that charges the first photoconductor and a second charger that charges the second photoconductor, and the control unit is configured to perform the forced discharge process. The voltage applied to the second charger may be smaller than the voltage applied to the first charger.

  According to this, for example, compared with a method of applying the same voltage to each charger in the forced discharge process, the power consumption can be reduced.

  The image forming apparatus includes a first recovery member that recovers the developer on the first photoconductor, and a second recovery member that recovers the developer on the second photoconductor, and the control unit In the forced ejection process, the same voltage as that during printing may be applied to the first recovery member and the second recovery member.

  According to this, the developer on the photoconductor can be recovered by the recovery member in the same manner as during printing.

  In addition, the control unit has a developer consumption amount from when the first developing roller is in a new state or a developer consumption amount after the previous execution of the forced ejection process is equal to or greater than a predetermined threshold value. In this case, the forced ejection process may be executed.

  Further, the control unit may execute the forced ejection process after receiving a print job and before executing printing.

  The controller may form a developer image having a density of 100% on the first photosensitive member in the forced ejection process.

  In the forced discharge process, the control unit may rotate the belt until the developer moved from the first photosensitive member onto the belt passes through the cleaning device twice.

  According to this, in the forced discharge process, the developer on the belt can be satisfactorily removed by the cleaning device.

  In addition, the cleaning device includes a backup roller disposed inside the belt, and a cleaning roller that sandwiches the belt between the backup roller, and the control unit includes the backup roller in the forced discharge process. And the current flowing between the cleaning rollers may be larger than that during printing.

  According to this, since the current flowing between the backup roller and the cleaning roller in the forced discharge process is made larger than that during printing, the developer recovery capability in the cleaning device can be made higher than that during printing. In the discharging process, the developer on the belt can be removed satisfactorily.

  The control unit can execute a density correction process for correcting the density of a developer image formed on the first photoconductor or the second photoconductor, and execute the density correction process and the forced ejection process. When the timings to be overlapped, the forced ejection process may be executed prior to the density correction process.

  According to this, when the timings for executing the density correction process and the forced discharge process overlap, the forced discharge process is executed before the density correction process, so that the deteriorated developer is not used in the density correction process. The density correction can be performed satisfactorily.

  The image forming apparatus includes a first recovery member that recovers the developer on the first photoconductor, and a second recovery member that recovers the developer on the second photoconductor, and the control unit In the forced discharge process, the developer is recovered by the first recovery member and the second recovery member, and the developer recovered by the first recovery member and the second recovery member is transferred to the first photoreceptor, The recovery process of moving the cleaning device to the cleaning device via the second photosensitive member and the belt may be executed after the printing is completed.

  According to this, since the collection process is executed after the printing is completed, the developer remaining on the belt by the execution of the forced discharge process and the printing can be collected by the cleaning device in one collection process. Therefore, for example, compared with the case where the collection process is executed even after the forced ejection process, the number of collection processes can be reduced and the time until the start of printing can be shortened.

  In the forced ejection process, the control unit is configured to interval a plurality of developer images having a width ranging from one end to the other end of the image forming range on the first photoconductor in the rotation direction of the first photoconductor. It may be formed with a gap.

  According to this, in the forced discharge process, a plurality of developer images having a width from one end to the other end of the image forming range are formed on the first photoconductor at intervals in the rotation direction of the first photoconductor. Therefore, for example, the length of one developer image can be shortened as compared with a configuration in which one developer image long in the rotation direction of the first photoconductor is collected by the cleaning device. For this reason, the developer image having a short length can be reliably collected one by one by the cleaning device, so that it is possible to suppress the developer leakage from the cleaning device.

  In addition, the total length of the plurality of developer images in the rotation direction may be a natural number times the circumferential length of the first developing roller.

  According to this, the deteriorated developer on the first developing roller can be sufficiently discharged. Specifically, for example, when the total length in the rotation direction of a plurality of developer images is a natural number multiple of the length different from the circumferential length of the first developing roller, the surface of the developer on the first developing roller is There is a possibility that a step is generated and the deteriorated developer remains, but by setting the length as described above, it is possible to suppress the deterioration of the deteriorated developer.

  The control unit may increase the frequency of the forced ejection process as the average consumption, which is the consumption of developer per print job, is smaller.

  When the average consumption is small, the developer on the first developing roller is likely to deteriorate. In this case, the deteriorated developer can be quickly recovered by increasing the frequency of the forced discharge process. .

  In addition, the image forming apparatus includes a sensor that detects whether the type of the cartridge that stores the developer to be supplied to the first developing roller is a large-capacity type, and the control unit has a large-capacity cartridge type. When it is determined that the cartridge type is the type, the forced ejection process may be performed more frequently than when the cartridge type is determined not to be a large capacity type.

  According to this, the forced ejection process can be appropriately performed according to the capacity of the cartridge.

  Further, the control unit may estimate the consumption amount of the developer based on the number of printed sheets specified in the print job.

  According to the present invention, it is possible to suppress the mixing of different color developers on the developing roller in the forced discharge process.

1 is a cross-sectional view illustrating a color printer according to an embodiment of the present invention. FIG. 5 is a diagram illustrating a contact / separation state between a photosensitive drum and a developing roller. It is a flowchart which shows operation | movement of a control part. It is a flowchart which shows a forced discharge process. It is a flowchart which shows a collection process. It is a flowchart which shows a reset process. It is a flowchart which shows operation | movement of the control part which concerns on a 1st modification. It is the flowchart (a) which shows operation | movement of the control part which concerns on a 2nd modification, and the figure (b) which shows the map referred by step S82. It is a flowchart which shows operation | movement of the control part which concerns on a 3rd modification.

  Next, embodiments of the present invention will be described in detail with reference to the drawings as appropriate. In the following description, directions will be described in the directions shown in FIG. That is, in FIG. 1, the left toward the paper surface is “front”, the right toward the paper surface is “rear”, the back toward the paper surface is “left”, and the front toward the paper surface is “right”. In addition, the top and bottom are “up and down” toward the page.

  As shown in FIG. 1, a color printer 1 as an example of an image forming apparatus includes a paper supply unit 20 that supplies paper P and an image formation that forms an image on the supplied paper P in a main body housing 2. The unit 30, a paper discharge unit 90 that discharges the paper P on which an image is formed, and a control unit 100 are provided.

  An opening 2A is formed in the upper part of the main body housing 2, and the opening 2A is opened and closed by an upper cover 3 that is rotatably supported by the main body housing 2. The upper surface of the upper cover 3 is a paper discharge tray 4 that accumulates the paper P discharged from the main body housing 2, and a plurality of LED attachment members 5 that hold the LED units 40 are provided on the lower surface.

  The paper feed unit 20 is provided in the lower part of the main body housing 2, and can be attached to and detached from the main body housing 2, and a paper supply mechanism 22 that transports the paper P from the paper feed tray 21 to the image forming unit 30. And. The paper supply mechanism 22 is provided on the front side of the paper feed tray 21 and includes a paper feed roller 23, a separation roller 24, a separation pad 25, a paper dust removing roller 26, a pinch roller 27, and a registration roller 29. ing.

  In the paper feeding unit 20, the paper P sent out from the paper feeding tray 21 by the paper feeding roller 23 is separated one by one by the separation roller 24 and the separation pad 25 and sent upward, and the paper dust removing roller 26 and the pinch roller In the process of passing between 27, paper dust is removed. Thereafter, the sheet P is turned backward through the conveyance path 28, corrected for skew by the registration rollers 29, and then supplied to the image forming unit 30.

  The image forming unit 30 includes four LED units 40, four process cartridges 50, a transfer unit 70, a cleaning device 10, and a fixing device 80.

  The LED unit 40 is swingably connected to the LED mounting member 5, and is appropriately positioned and supported by a positioning member provided in the main body housing 2.

  The process cartridge 50 is arranged side by side in the front-rear direction between the upper cover 3 and the paper feeding unit 20, and includes a drum cartridge 510 and a developing cartridge 530. The drum cartridge 510 includes a photosensitive drum 51 as an example of a photosensitive member, a charger 52, and a recovery roller 55 as an example of a recovery member. The developing cartridge 530 is attachable to and detachable from the drum cartridge 510, and includes a developing roller 53, a supply roller 56, a layer thickness regulating blade 57, and a toner storage chamber 54 that stores toner as an example of a developer. Configured.

  The process cartridge 50 is indicated by reference numerals 50K, 50Y, 50M, and 50C containing toners for black, yellow, magenta, and cyan from upstream in the transport direction of the paper P (the moving direction of the belt surface). They are arranged in this order. In the present specification and drawings, when specifying the photosensitive drum 51, the developing roller 53, the collecting roller 55, and the like corresponding to the toner color, K, corresponding to each of black, yellow, magenta, and cyan, , Y, M, and C are attached.

  The photosensitive drums 51 are provided in each of the plurality of drum cartridges 510, and are arranged in a line along the front-rear direction.

  The developing roller 53 is in contact with the photosensitive drum 51 and supplies toner to the electrostatic latent image on the photosensitive drum 51. The supply roller 56 supplies toner to the developing roller 53. The layer thickness regulating blade 57 regulates the toner layer thickness on the developing roller 53 to a predetermined thickness. In this embodiment, when the toner is supplied from the developing roller 53 to the photosensitive drum 51, the toner is charged by, for example, sliding the toner between the developing roller 53 and the supply roller 56. It is like that.

  As shown in FIG. 2, the developing roller 53 can be brought into contact with and separated from the photosensitive drum 51 by controlling a known contact / separation mechanism 110 by the control unit 100, and specifically, can be brought into contact / separated. Specifically, in the color mode, all of the developing rollers 53K, 53Y, 53M, and 53C come into contact with the corresponding photosensitive drums 51K, 51Y, 51M, and 51C, and the photosensitive drums 51K, 51Y, 51M, and 51C are in contact with each other. Toner is supplied to the printer. In the monochrome mode or forced discharge processing described later, only the black (monochrome) developing roller 53K comes into contact with the photosensitive drum 51K, and the other three colors of developing rollers 53Y, 53M, and 53C correspond to the corresponding photosensitive drums. The body drums 51Y, 51M and 51C are separated from each other. Further, in the collection process described later, all the developing rollers 53K, 53Y, 53M, and 53C are separated from the corresponding photosensitive drums 51K, 51Y, 51M, and 51C, respectively.

  As shown in FIG. 1, a plurality of recovery rollers 55 are provided adjacent to each photosensitive drum 51 so as to correspond to each photosensitive drum 51. A collecting voltage having a polarity opposite to that of the toner is applied to the collecting roller 55, whereby the toner attached on the photosensitive drum 51 can be collected by the collecting roller 55. . Further, a discharge voltage having the same polarity as that of the toner is applied to the collection roller 55, so that the toner held by the collection roller 55 can be discharged (moved) to the photosensitive drum 51. It has become.

  The transfer unit 70 is provided between the paper feeding unit 20 and each process cartridge 50, and includes a driving roller 71, a driven roller 72, a belt 73, and a transfer roller 74.

  The driving roller 71 and the driven roller 72 are spaced apart and arranged in parallel in the front-rear direction, and a belt 73 made of an endless belt is stretched therebetween. The belt 73 has, as an outer surface thereof, a belt surface 73A that comes into contact with each photoconductive drum 51, and is driven by a driving roller 71 so that the belt surface 73A moves along the arrangement direction of the photoconductive drums 51. It is designed to rotate. In addition, four transfer rollers 74 that sandwich the belt 73 between the photosensitive drums 51 are arranged inside the belt 73 so as to face the photosensitive drums 51. A transfer voltage is applied to the transfer roller 74 by constant current control during transfer.

  The cleaning device 10 is a device that slidably contacts the belt 73 and collects toner or the like adhering to the belt 73, and is disposed facing the lower side of the belt 73. The cleaning device 10 includes a cleaning roller 11, a sliding contact roller 12, a blade 13, a waste toner container 14, and a backup roller 15.

  The backup roller 15 is disposed inside the belt 73. The cleaning roller 11 is disposed outside the belt 73 and sandwiches the belt 73 with the backup roller 15. The moving direction of the portion of the cleaning roller 11 that contacts the belt 73 is opposite to the moving direction of the portion of the belt 73 that contacts the cleaning roller 11. The cleaning roller 11 can collect the toner on the belt 73 by applying a cleaning voltage to the backup roller 15.

  The sliding roller 12 is a roller that is in sliding contact with the cleaning roller 11 and collects toner adhering to the cleaning roller 11. The toner on the slidable contact roller 12 is scraped off by a blade 13 disposed so as to be in slidable contact with the slidable contact roller 12 and enters the waste toner container 14.

  The fixing device 80 is disposed on the rear side of each process cartridge 50 and the transfer unit 70, and includes a heating roller 81 and a pressure roller 82 that presses the heating roller 81.

  In the image forming unit 30 configured as described above, in the color mode, first, the surface of each photosensitive drum 51 is charged by the charger 52 and then exposed by each LED unit 40. As a result, the potential of the exposed portion is lowered, and an electrostatic latent image based on the image data is formed on each photosensitive drum 51. Thereafter, toner is supplied to the electrostatic latent image from the developing roller 53, so that the toner image is carried on the photosensitive drum 51.

  The sheet P supplied on the belt 73 passes between each photosensitive drum 51 and each transfer roller 74 disposed inside the belt 73, so that a toner image formed on each photosensitive drum 51 is formed. Transferred onto the paper P. Then, as the paper P passes between the heating roller 81 and the pressure roller 82, the toner image transferred onto the paper P is thermally fixed.

  The paper discharge unit 90 includes a paper discharge-side conveyance path 91 that extends upward from the exit of the fixing device 80 and is reversed forward, and a plurality of pairs of conveyance rollers 92 that convey the paper P. Yes. The paper P on which the toner image has been transferred and heat-fixed is transported through a paper discharge-side transport path 91 by a transport roller 92, discharged outside the main body housing 2, and accumulated in the paper discharge tray 4.

Hereinafter, the control unit 100 will be described in detail.
The control unit 100 includes a CPU, a ROM, a RAM, and the like, and receives a print job and controls the paper feeding unit 20, the image forming unit 30, the paper discharge unit 90, and the contact / separation mechanism 110 according to a program prepared in advance. It is configured as follows.

  In the present embodiment, the name of each member corresponding to black is referred to as “first member” by adding “first”, and the name of each member of other colors is assigned as “second” to the second member. It shall be called. For example, the photosensitive drum 51K corresponding to black is referred to as a first photosensitive drum 51K, and the photosensitive drums 51Y, 51M, and 51C of other colors are also referred to as second photosensitive drums 51Y, 51M, and 51C, respectively.

  The control unit 100 discharges the toner on the first developing roller 53K onto the first photosensitive drum 51K and forms the toner discharged from the first developing roller 53K on the first photosensitive drum 51K and the belt 73 during non-image formation. The forced discharge process of moving to the cleaning device 10 can be executed. The control unit 100 is configured to execute the forced discharge process when the second developing rollers 53Y, 53M, and 53C are separated from the second photosensitive drums 51Y, 51M, and 51C.

  In addition, the control unit 100 is configured to execute the forced ejection process when the toner consumption amount from when the first developing roller 53K is in a new state becomes equal to or greater than a predetermined threshold value. In the present embodiment, the control unit 100 uses the number of prints designated in the print job as the amount of toner consumption, and the number of prints from when the first developing roller 53K is in a new state (hereinafter referred to as “cumulative”). When the “number of printed sheets” is equal to or greater than a predetermined threshold value, the forced ejection process is executed. That is, the control unit 100 estimates the toner consumption based on the number of printed sheets specified in the print job.

  The control unit 100 can execute a new article detection process for determining whether or not the process cartridge 50 attached to the main body housing 2 is a new article. Specifically, the main body housing 2 includes a sensor SE that detects whether or not the process cartridge 50 is new and whether or not the type of the process cartridge 50 is a large capacity type.

  When the control unit 100 determines that the process cartridge 50 corresponding to the predetermined color is new based on the information from the sensor SE, the control unit 100 resets the accumulated number of printed sheets corresponding to the predetermined color to zero. It is configured. In the new article detection process, for example, a protrusion that moves irreversibly is provided on the process cartridge 50, and it is detected by the sensor SE that is an optical sensor whether or not the protrusion is pushing the detection lever in the main body housing 2. Or by detecting information in the IC chip provided in the process cartridge 50 by the sensor SE. Similarly, the determination as to whether the process cartridge 50 is of a large capacity type is made by setting the time for pressing the detection lever with a protrusion that moves irreversibly according to the type of the process cartridge 50, and selecting the type based on this time. The determination may be made, or information in the IC chip may be detected by the sensor SE.

  Further, the control unit 100 is configured to execute a forced ejection process after receiving a print job and before executing printing.

  Further, the control unit 100 collects toner by the first collection roller 55K and the second collection rollers 55Y, 55M, and 55C in the forced discharge process, and also at the time of printing, the first collection roller 55K and the second collection rollers 55Y, 55M, and so on. The toner is collected at 55C. Then, the control unit 100 removes the toner collected by the first collection roller 55K and the second collection rollers 55Y, 55M, and 55C on the first photosensitive drum 51K, the second photosensitive drums 51Y, 51M, and 51C and the belt 73. The collection process of moving to the cleaning device 10 is executed after printing is completed.

Next, the operation of the control unit 100 will be described in detail.
When the control unit 100 receives a print job, the control unit 100 executes the processing shown in FIG. Here, in a standby state before receiving a print job, all the developing rollers 53 are separated from the corresponding photosensitive drums 51.

  In the process shown in FIG. 3, the control unit 100 first determines whether or not the purge flag Fp for executing the forced ejection process is 1 (S1). When it is determined in step S1 that Fp = 1 (Yes), the control unit 100 executes a forced ejection process (S2). The forced ejection process will be described later in detail.

  After step S2, the control unit 100 resets the purge flag Fp to 0 (S3). After step S3 or when it is determined No in step S1, the control unit 100 acquires the cumulative number of printed sheets stored in the main body memory such as a RAM (S4).

  After step S4, the control unit 100 determines whether or not the cumulative number of printed sheets is the first predetermined number (S5). If it is determined in step S5 that the cumulative number of printed sheets is not the first predetermined number (No), the control unit 100 determines whether or not the cumulative number of printed sheets is a second predetermined number that is smaller than the first predetermined number. (S6).

  If it is determined in step S6 that the cumulative number of printed sheets is not the second predetermined number (No), the control unit 100 determines whether the cumulative number of printed sheets is a third predetermined number that is smaller than the second predetermined number. (S7). Here, the first predetermined number of sheets, the second predetermined number of sheets, and the third predetermined number of sheets are threshold values for executing the forced ejection process, respectively, and the difference between the first predetermined number of sheets and the second predetermined number of sheets and the second predetermined number of sheets The difference between the number of sheets and the third predetermined number is the same. For example, the first predetermined number, the second predetermined number, and the third predetermined number can be set to 1350, 900, and 450.

  When it is determined Yes in any of steps S5 to S7, that is, when it is determined that the cumulative number of printed sheets has reached the threshold value, the control unit 100 sets the purge flag Fp for executing the forced discharge process to 1. After (S8), printing for one page is executed (S9). If it is determined No in step S7, that is, if it is determined that the cumulative number of printed sheets does not match the threshold value, the control unit 100 skips step S8 and proceeds to step S9.

  When the monochrome mode is designated in the print job in step S9, the control unit 100 presses only the black first developing roller 53K against the first photosensitive drum 51K and the other second developing roller 53Y. , 53M, 53C are kept away from the second photosensitive drums 51Y, 51M, 51C. If the color mode is designated in the print job in step S9, all the developing rollers 53 are brought into pressure contact with the corresponding photosensitive drums 51.

  In step S9, the control unit 100 applies a voltage suitable for printing to the developing roller 53, the charger 52, the transfer roller 74, and the like corresponding to the color used for printing, and also applies a collection voltage to each collection roller 55. In addition, a cleaning voltage is applied so that a predetermined first current flows between the backup roller 15 and the cleaning roller 11. As a result, during printing, the toner on each photoconductor drum 51 is collected by each collection roller 55, and the toner that accidentally adheres to the belt 73 is collected by the cleaning device 10.

  After executing printing for one sheet in step S9, the control unit 100 counts up the cumulative number of printed sheets (S10). After step S10, the control unit 100 determines whether printing for the number of prints specified in the print job has been completed (S11).

  If it is determined in step S11 that printing has not ended (No), the control unit 100 returns to the process of step S4. If it is determined in step S11 that printing has ended (Yes), the control unit 100 ends the control after executing the collection process (S12). The recovery process will be described later in detail.

  In the forced discharge process shown in FIG. 4, the control unit 100 first presses only the black first developing roller 53K against the first photosensitive drum 51K (S21), and the other second developing rollers 53Y, 53M, and 53C The second photosensitive drums 51Y, 51M, and 51C are kept apart. After step S21, the control unit 100 charges the black first photosensitive drum 51K to the same first surface potential as that during printing, and sets the other second photosensitive drums 51Y, 51M, and 51C to be higher than the first surface potential. Charge to a small second surface potential (S22). Specifically, in step S22, the control unit 100 applies the same first charging voltage to the black first charger 52K as that during printing, and applies the other second chargers 52Y, 52M, and 52C to the first charging voltage. A small second charging voltage is applied.

  The first charging voltage can be set to a voltage such that the current flowing through the first charger 52K becomes 230 μA, for example, and the second charging voltage is set such that the current flowing through the second chargers 52Y, 52M, and 52C, for example. The voltage can be 55 μA.

  After step S22, the control unit 100 applies the same recovery voltage to each recovery roller 55 as during printing (S23). Here, the recovery voltage can be a voltage at which a current of 300 μA flows in the recovery roller 55 in the same direction as during printing.

  After step S23, the control unit 100 applies a cleaning voltage so that a second current larger than the first current during printing flows between the backup roller 15 and the cleaning roller 11 (S24). Here, the first current can be set to 20 μA, for example, and the second current can be set to 30 μA, for example.

  Note that when the current between the backup roller 15 and the cleaning roller 11 is the second current, the rotational speeds of the backup roller 15 and the cleaning roller 11 are preferably made larger than those during printing. For example, the rotation speed may be double that during printing. As described above, since the current between the backup roller 15 and the cleaning roller 11 is set as the second current, and the rotational speed of the backup roller 15 and the cleaning roller 11 is made larger than that during printing, the toner collecting ability can be increased. It is possible to shorten the waiting time until the printing process starts.

  After step S24, the control unit 100 starts driving the photosensitive drums 51 and the belts 73 (S25). After step S25, the same developing voltage as that during printing is applied to the black first developing roller 53K, and the black first photosensitive drum 51K is exposed (S26). The development voltage can be set to 250 to 500V, for example.

  In the exposure process in step S26, the control unit 100 exposes the entire width of the printable area in the main scanning direction. That is, the control unit 100 forms an electrostatic latent image having a width extending from one end to the other end of the printable region (image forming range) on the first photosensitive drum 51K. In the exposure process, the control unit 100 forms one electrostatic latent image having a predetermined length in the rotation direction (sub-scanning direction) of the first photosensitive drum 51K in the entire printable area.

  Then, by supplying toner from the first developing roller 53K to such a plurality of electrostatic latent images, one toner having a width extending from one end to the other end of the printable area on the first photosensitive drum 51K. An image is formed with a predetermined length in the rotation direction of the first photosensitive drum 51K. Further, the control unit 100 performs the exposure process so that the length of the plurality of toner images formed on the first photosensitive drum 51K in the rotation direction is a natural number multiple of the circumferential length of the first developing roller 53K. Execute. Specifically, for example, when the circumferential length of the first developing roller 53K is 30 mm, the length of the toner image in the rotation direction is, for example, 120 mm (4 rounds), 150 mm (5 rounds),. -It can be set to 240 mm (8 laps).

  In the exposure process, the controller 100 continuously emits light from the first LED unit 40K from one end to the other end of the printable area. Thus, in the forced ejection process, a toner image having a density of 100% is formed on the first photosensitive drum 51K.

  After step S26, the control unit 100 applies the same first transfer voltage as that during printing to the black first transfer roller 74K (S27). As a result, the plurality of toner images formed on the first photosensitive drum 51K are transferred onto the belt 73.

  After step S27, the control unit 100 determines whether or not a predetermined time has elapsed from the start of driving of the belt 73 (S28). Here, the predetermined time is set such that each of the plurality of toner images transferred onto the belt 73 can pass through the cleaning roller 11 twice. As a result, in the forced ejection process, the control unit 100 rotates the belt 73 until the toner image moved from the first photosensitive drum 51K onto the belt 73 passes through the cleaning device 10 twice.

  If it is determined in step S28 that the predetermined time has not elapsed since the start of driving of the belt 73 (No), the control unit 100 repeats the process of step S28. If it is determined in step S28 that a predetermined time has elapsed since the start of driving of the belt 73 (Yes), the control unit 100 stops driving the photosensitive drums 51 and the belt 73 (S29). After step S29, the control unit 100 turns off each applied voltage applied to each member (S30). After step S30, the control unit 100 separates the black first developing roller 53K from the first photosensitive drum 51K (S31), and ends this control.

  In the collection process shown in FIG. 5, the control unit 100 first stops driving the photosensitive drums 51, the belts 73 and the like that were driven at the time of printing (S41). After step S41, the control unit 100 separates each developing roller 53 from each photosensitive drum 51 (S42).

  After step S42, the control unit 100 starts driving the photosensitive drums 51 and the belts 73 (S43). After step S43, the control unit 100 applies a discharge voltage to each collection roller 55 (S44). As a result, the toner held by each collecting roller 55 is discharged onto each photosensitive drum 51. Here, the discharge voltage can be a voltage at which a current of 300 μA flows through the collection roller 55 in the direction opposite to that during printing.

  After step S44, the control unit 100 applies a second transfer voltage smaller than the first transfer voltage during printing to each transfer roller 74 (S45). Here, the first transfer voltage can be, for example, a voltage that allows a current of 15 μA to flow through the transfer roller, and the second transfer voltage can be, for example, a voltage that allows a current of 8 μA to flow through the transfer roller. .

  After step S45, the control unit 100 determines whether or not a predetermined time has elapsed from the start of driving of the belt 73 (S46). Here, the predetermined time is set such that each of the plurality of toner images transferred onto the belt 73 can pass through the cleaning roller 11 twice.

  If it is determined in step S46 that the predetermined time has not elapsed since the start of driving of the belt 73 (No), the control unit 100 repeats the process of step S46. If it is determined in step S46 that a predetermined time has elapsed since the start of driving of the belt 73 (Yes), the control unit 100 stops driving the photosensitive drums 51 and the belt 73 (S47). After step S47, the control unit 100 turns off each applied voltage applied to each member (S48), and ends this control.

Further, the control unit 100 can execute a reset process for resetting the cumulative number of printed sheets as shown in FIG. Based on information from an opening / closing sensor (not shown) that detects that the upper cover 3 is closed, the control unit 100 starts a reset process when the upper cover 3 is not closed. In other words, the control unit 100 starts the reset process when the upper cover 3 is opened.
In the reset process shown in FIG. 6, the control unit 100 first determines whether or not the upper cover 3 is closed (S61). Specifically, the control unit 100 executes the process of step S61 based on information from an opening / closing sensor (not shown) that detects that the upper cover 3 is closed.

  If it is determined in step S61 that the upper cover 3 is not closed (No), the control unit 100 repeats the process of step S61. If it is determined in step S61 that the upper cover 3 is closed (Yes), the control unit 100 executes a new article detection process for each process cartridge 50 (S62). After step S62, the control unit 100 determines whether or not at least one of the plurality of process cartridges 50 is new (S63).

  If it is determined in step S63 that the process cartridge 50 of the predetermined color is new (Yes), the control unit 100 resets the cumulative number of printed sheets in the main body memory corresponding to the predetermined color (S64). After step S64 or when it is determined in step S63 that all the process cartridges 50 are not new (No), the control unit 100 ends this control.

According to the above, the following effects can be obtained in the present embodiment.
When the second developing rollers 53Y, 53M, and 53C are separated from the second photosensitive drums 51Y, 51M, and 51C, a forced discharge process for collecting the toner on the first developing roller 53K by the cleaning device 10 is executed. The toner moved from the first developing roller 53K to the belt 73 via the first photosensitive drum 51K is transferred to the second developing rollers 53Y, 53M, and 51C via the second photosensitive drums 51Y, 51M, and 51C of other colors. It can suppress moving to 53C. Therefore, it is possible to suppress mixing of different color toners on the second developing rollers 53Y, 53M, and 53C in the forced discharge process.

  In the forced discharge process, the second charging voltage applied to the second chargers 52Y, 52M, and 52C is made smaller than the first voltage applied to the first charger 52K. Compared with a method of applying a charging voltage, power consumption can be reduced.

  In the forced ejection process, the same recovery voltage as that during printing is applied to each recovery roller 55, so that the toner on each photosensitive drum 51 can be recovered by each recovery roller 55 with the same recovery capability as during printing.

  The belt 73 is rotated until the toner image moved from the first photosensitive drum 51K onto the belt 73 in the forced discharge process passes through the cleaning device 10 twice. Therefore, the toner image on the belt 73 is cleaned in the forced discharge process. 10 can be removed satisfactorily.

  In the forced ejection process, the current flowing between the backup roller 15 and the cleaning roller 11 is made larger than that during printing, so that the toner recovery capability in the cleaning device 10 can be made higher than that during printing. The toner on the belt 73 can be removed well.

  Since the collection process is executed after the printing is completed, the toner remaining on the belt 73 by the execution of the forced ejection process and the printing can be collected by the cleaning device 10 in one collection process. Therefore, for example, compared with the case where the collection process is executed even after the forced ejection process, the number of collection processes can be reduced and the time until the start of printing can be shortened.

  In the forced ejection process, a plurality of toner images having a width from one end to the other end of the printable area are formed on the first photosensitive drum 51K at intervals in the rotation direction of the first photosensitive drum 51K. For example, the length of one toner image can be shortened as compared with a configuration in which one toner image that is long in the rotation direction of the first photosensitive drum is collected by the cleaning device 10. Therefore, since the toner image having a short length can be reliably collected one by one by the cleaning device 10, it is possible to suppress the toner collection leakage in the cleaning device 10.

  Since the total length in the rotation direction of the plurality of toner images formed on the first photosensitive drum 51K in the forced discharge process is set to a natural number multiple of the circumferential length of the first developing roller 53K, the first developing roller 53K It is possible to sufficiently discharge the deteriorated toner. Specifically, for example, when the total length of the plurality of toner images in the rotation direction is a natural number multiple of the length different from the circumferential length of the first developing roller, there is a step on the surface of the toner on the first developing roller. This may occur and deteriorated toner may remain. However, by setting the length as described above, it is possible to suppress the deterioration of remaining toner.

  In addition, this invention is not limited to the said embodiment, It can utilize with various forms so that it may illustrate below. In the following description, the same reference numerals are given to substantially the same structures and processes as in the above embodiment, and the description thereof is omitted.

  The control unit 100 may have a function of executing density correction processing for correcting the density of toner formed on the paper P. Here, in the density correction process, a test toner image is formed on the belt 73, the density of the test toner image is detected by an optical sensor, and the development voltage, the charging voltage, and the like are determined based on the detection result. This is a correction process. In this density correction processing, an electrostatic latent image corresponding to the test toner image is formed on the photosensitive drum 51, and toner on the developing roller 53 is supplied to the electrostatic latent image, whereby the photosensitive drum 51 is supplied. A test toner image is formed thereon. Then, the test toner image on the photosensitive drum 51 is transferred onto the belt 73 by the transfer roller 74.

  As shown in FIG. 7, the control unit 100 capable of executing such density correction processing executes the forced ejection processing before the density correction processing when the timings for executing the density correction processing and the forced ejection processing overlap. It is desirable to be configured to do so. Hereinafter, the process of FIG. 7 will be described in detail. 7 is obtained by adding new processes (S71 to S75) to the processes (S1 to S12) of FIG. 3 described above. The description of steps S1 to S12 described above will be omitted as appropriate. Also, illustration of steps S5 to S10 is omitted.

  As illustrated in FIG. 7, when the control unit 100 determines that the purge flag Fp is 1 in Step S <b> 1 (Yes), it is determined whether or not the concentration correction flag Fc for executing the concentration correction process is 1 or not. Is determined (S71). Here, the density correction flag Fc is set to 1 when, for example, the cumulative number of printed sheets is equal to or greater than the density correction threshold.

  If it is determined in step S71 that Fc = 1 is not satisfied (No), the control unit 100 executes the processes of steps S2 and S3 described above, and proceeds to the process of step S4 described above. When it is determined in step S71 that Fc = 1 (Yes), the control unit 100 executes the forced ejection process similar to step S2 (S72).

  After step S72, the control unit 100 executes density correction processing (S73). After step S73, the control unit 100 resets the flags Fp and Fc to 0 (S74), and proceeds to the process of step S4 described above.

  If it is determined in step S1 that Fp = 1 is not satisfied (No), the control unit 100 determines whether or not the density correction flag Fc is 1 (S75). If it is determined in step S75 that Fc = 1 (Yes), the control unit 100 executes density correction processing (S73). If it is determined in step S75 that Fc = 1 is not satisfied (No), the control unit 100 proceeds to the process of step S4 described above.

  As described above, according to the form of FIG. 7, when the timings for executing the density correction process and the forced ejection process overlap (S1: Yes, S71: Yes), the forced ejection process is executed before the density correction process. (S72, S73) Since the deteriorated toner is not used in the density correction process, the density correction can be performed satisfactorily.

  The control unit 100 may be configured to increase the frequency of forced ejection processing as the average number of printed sheets, which is the number of printed sheets per print job, is smaller. Specifically, the control unit 100 increases the frequency of forced ejection processing when the average number of printed sheets, which is the number of printed sheets per print job, is equal to or less than a specified value, compared to when the average number of printed sheets is greater than the specified value. It may be configured to. Further, the control unit 100 increases the frequency of forced ejection processing when the average number of printed sheets per print job is less than a specified value, compared to when the average number of printed sheets is equal to or greater than the specified value. It may be configured as follows. Here, the average number of printed sheets can be calculated by dividing the accumulated number of printed sheets by the number of accumulated print jobs.

  Specifically, the control unit 100 is configured to execute a process as shown in FIG. In addition, the process of FIG. 8A adds a new process (S81, S82) to each process (S1-S12) of FIG. 3 mentioned above. The description of steps S1 to S12 described above will be omitted as appropriate. Also, illustration of steps S5 to S10 is omitted.

  As shown in FIG. 8A, the control unit 100 calculates and obtains the average number of printed sheets, which is the number of printed sheets per print job, after determining No in step S1 or after step S3. (S81). After step S81, the control unit 100 sets threshold values (first predetermined number of sheets, second predetermined number of sheets, and third predetermined number of sheets) for executing the forced ejection process based on the average number of printed sheets (S82). . After step S82, the control unit 100 proceeds to the process of step S4 described above.

  Specifically, in step S82, the control unit 100 sets a threshold with reference to the map shown in FIG. The map is a map showing the relationship between each threshold and the average number of printed sheets Ap. In this map, when the average number of printed sheets Ap is less than 2, the predetermined number of sheets is set every 400 sheets. Specifically, when the average number of printed sheets Ap is less than 2, the first predetermined number is set to 1200, the second predetermined number is set to 800, and the third predetermined number is set to 400.

  Further, when the average number of printed sheets Ap is 2 or more and less than 5, the predetermined number is set every 450 sheets. Specifically, when 2 ≦ Ap <5, the first predetermined number is set to 1,350 sheets, which is larger than that when Ap <2, and the second predetermined number is set to 900 sheets, which is larger than the case where Ap <2. (3) The predetermined number of sheets is set to 450, which is larger than when Ap <2.

  When the average number of printed sheets Ap is 5 or more, each predetermined number is set every 500 sheets. Specifically, in the case of 5 ≦ Ap, the first predetermined number is set to 1500, which is larger than in the case of 2 ≦ Ap <5, and the second predetermined number is set to 1000, which is larger than in the case of 2 ≦ Ap <5. The third predetermined number is set to 500, which is larger than the case of 2 ≦ Ap <5.

As described above, according to the embodiment of FIG. 8, the following effects can be obtained.
When the average number of printed sheets is as small as a specified value or less, the toner on the first developing roller 53K is likely to deteriorate. Therefore, when the average number of printed sheets is equal to or less than a specified value (for example, Ap <2), the forced ejection process is executed as compared with the case where the average number of printed sheets is larger than the specified value (for example, 2 ≦ Ap <5). By reducing the threshold value (for example, the third predetermined number of sheets) and increasing the frequency of forced ejection processing, it is possible to quickly collect deteriorated toner.

Hereinafter, the reason why the toner on the first developing roller 53K tends to deteriorate when the average number of printed sheets is as small as a predetermined value or less will be described.
In the process shown in FIG. 3, the control unit 100 first executes a print preparation operation before step S1. In the printing preparation operation, the control unit 100 performs rotation start of the motor, preheating of the heater of the fixing device 80, data processing of image data, and the like. When the control unit 100 starts the rotation of the motor, the photosensitive drum 51, the developing roller 53, the supply roller 56, and the like are rotated. At this time, the toner stored in the toner storage chamber 54 is carried on the surface of the supply roller 56. Then, the toner is moved from the supply roller 56 to the developing roller 53.
During the printing preparation operation or printing, the toner on the developing roller 53 is worn and deteriorated by being physically acted on by the layer thickness regulating blade 57 and the supply roller 56 or the photosensitive drum 51.

  Here, the case where the average number of printed sheets is as small as a predetermined value or less means that the total number of rotations of the developing roller 53 (the number of rotations from when the print job is received until printing is completed and the collection process is completed) is printed. This is a case where the ratio of the number of rotations of the developing roller 53 in the preparatory operation becomes a predetermined ratio or more, and the toner remains on the developing roller 53 without being used for printing, and the layer thickness regulating blade 57 and the supply roller 56 or the photoconductor. By being physically acted on by the drum 51, it is worn and deteriorated.

The case where the average number of printed sheets is larger than the specified value is a case where the ratio of the number of rotations of the developing roller 53 in the print preparation operation is less than a predetermined ratio out of the total number of rotations of the developing roller 53. It remains on the developing roller 53 without being used, and is physically worn by the layer thickness regulating blade 57 and the supply roller 56 or the photosensitive drum 51 to be worn and deteriorated. However, when the average number of printed sheets is larger than the specified value, it is more likely that the toner is used for printing before being worn and deteriorated than when the average number of printed sheets is less than the specified value.
Therefore, it is considered that the toner on the first developing roller 53K is likely to deteriorate when the average number of printed sheets is as small as a predetermined value or less.

  In the form of FIG. 8, as a method for increasing the frequency of forced ejection processing, a method for reducing the threshold value for executing forced ejection processing is exemplified, but the present invention is not limited to this. As a method for increasing the frequency of forced ejection processing, for example, when the average number of printed sheets is equal to or less than a specified value, the number of times of forced ejection processing may be increased as compared with the case where the average number of printed sheets is larger than the specified value. . Specifically, for example, in the map shown in FIG. 8B, when Ap <2, a fourth predetermined number (for example, 600) is added as a new threshold value, and four or more threshold values are set. It is only necessary to set three threshold values when 2 ≦ Ap <5.

  Based on the information from the sensor SE, the control unit 100 determines that the type of the black process cartridge 50K is a large-capacity type, as compared with the case where it is determined that the type of the process cartridge 50K is not a large-capacity type. Alternatively, the number of executions of the forced ejection process may be increased.

  Here, the determination as to whether the type is a large capacity type may be made by comparing the process cartridge 50K to be determined with another process cartridge 50K. For example, as a plurality of types of process cartridges 50K used in the color printer 1, there are an A type that contains 50 g of toner, a B type that contains 100 g of toner, and a C type that contains 150 g of toner. In the case, it can be determined as follows.

  When the control unit 100 determines that the type of the process cartridge 50K is the B type, the control unit 100 determines that the type of the process cartridge 50K is a larger capacity type than the A type, and performs the forced ejection process more than when it determines that the type is the A type. Increase the number of executions. In addition, when the control unit 100 determines that the type of the process cartridge 50K is the C type, the control unit 100 determines that the type of the process cartridge 50K is a larger capacity type than the B type. Increase the number of executions of the discharge process.

  The process cartridge 50K may be similarly processed when there are four or more types. Hereinafter, control according to the type of the process cartridge 50K will be described with reference to FIG. In FIG. 9, for the sake of convenience, control according to two types of process cartridges 50K, that is, a large capacity type and a non-large capacity type will be described.

  The process of FIG. 9 is obtained by adding new processes (S91 to S94) to the processes (S1 to S12) of FIG. 3 described above. The description of steps S1 to S12 described above will be omitted as appropriate. Also, illustration of steps S9 to S10 is omitted.

  As shown in FIG. 9, when receiving a print job (START), the control unit 100 first determines whether or not the black process cartridge 50K is a large capacity type (S91). If it is determined in step S91 that it is a large capacity type (Yes), the control unit 100 sets a large capacity flag Fb indicating that it is a large capacity type to 1 (S92).

  If it is determined in step S91 that it is not a large capacity type (No), the control unit 100 sets the large capacity flag Fb to 0 (S93). After step S92 or step S93, the control unit 100 proceeds to the process of step S1 described above. Then, the control part 100 performs the process of step S1-S4 similarly to the said embodiment.

  After step S4, the control unit 100 determines whether or not the large capacity flag Fb is 1 (S94). If it is determined in step S94 that Fb = 1 (Yes), the control unit 100 proceeds to step S5 and determines whether or not the cumulative number of printed sheets has reached the first predetermined number. If it is determined in step S94 that Fb = 1 is not satisfied (No), the control unit 100 skips step S5, proceeds to step S6, and determines whether or not the cumulative number of printed sheets has reached the second predetermined number. Judging. That is, the control unit 100 uses three threshold values as threshold values for executing the forced ejection process when the process cartridge 50K is a large capacity type, but when the process cartridge 50K is not a large capacity type, Only two threshold values (second and third predetermined number) are used. Thereby, when the type of the process cartridge 50K is a large capacity type, the number of executions of the forced ejection process is larger than when the type of the process cartridge 50K is not a large capacity type.

  As described above, according to the embodiment shown in FIG. 9, the forced ejection process can be appropriately performed according to the capacity of the process cartridge 50.

  In the embodiment, the number of printed sheets is exemplified as the developer consumption. However, the present invention is not limited to this, and for example, the number of dots of an image may be used as the developer consumption. Further, the consumption amount of the developer is the consumption amount (cumulative number of printed sheets) from when the first developing roller is in a new state. However, the present invention is not limited to this. For example, the forced discharge process is executed last time. It may be a consumption amount of the developer after long. In this case, the threshold for executing the forced ejection process may be set to one threshold without being changed. Specifically, the amount of consumption from when the first developing roller is in a new state is accumulated and compared with a threshold. When the amount of consumption reaches the threshold and the forced ejection process is executed, the amount of consumption is reset to 0, Just accumulate again.

  In the above embodiment, the forced ejection process is performed after receiving a print job and before executing printing. However, the present invention is not limited to this, for example, after executing printing and before collecting processing. Alternatively, the forced ejection process may be executed.

  In the above embodiment, in the forced discharge process, the rotation of the belt is stopped when the developer moved from the first photosensitive member onto the belt passes through the cleaning device twice. However, the present invention is limited to this. is not. For example, the number of times the developer passes through the cleaning device for determining the belt stop timing may be one time, or may be three times or more. However, it is desirable that the number of passes is at least twice.

  In the above embodiment, the photosensitive drum 51 is exemplified as the photosensitive member, but the present invention is not limited to this, and the photosensitive member may be, for example, a belt-shaped photosensitive member.

  In the above-described embodiment, the photoconductor and the developing roller corresponding to the color of black are the first photoconductor and the first developing roller. However, the present invention is not limited to this, and the photoconductor corresponding to a color other than black. The developing roller may be the first photosensitive member and the first developing roller, and the photosensitive member and developing roller corresponding to other colors may be the second photosensitive member and the second developing roller. Further, the number of photoconductors is not limited to four and may be any number.

  The exposure member that exposes the photosensitive member is not limited to the LED unit 40, and may be, for example, a scanner that emits laser light.

  In the above embodiment, the present invention is applied to the color printer 1 including the LED unit 40, but the present invention is not limited to this, and other image forming apparatuses, for example, a color printer having a configuration different from the above embodiment, The present invention may be applied to a copying machine, a multifunction machine, and the like.

  In the embodiment, in the exposure process, only one electrostatic latent image covering the entire width of the printable area is formed, but the present invention is not limited to this. For example, the controller 100 may form a plurality of electrostatic latent images over the entire width of the printable area at intervals in the rotation direction (sub-scanning direction) of the first photosensitive drum 51K in the exposure process.

  Then, by supplying toner from the first developing roller 53K to such a plurality of electrostatic latent images, a plurality of toners having a width extending from one end to the other end of the printable area on the first photosensitive drum 51K. Images may be formed at intervals in the rotation direction of the first photosensitive drum 51K. In this case, the control unit 100 causes the total length in the rotation direction of the plurality of toner images formed on the first photosensitive drum 51K to be a natural number multiple of the circumferential length of the first developing roller 53K. An exposure process may be executed. Specifically, for example, when the circumferential length of the first developing roller 53K is 30 mm, the total length in the rotation direction of the plurality of toner images is, for example, 120 mm (for 4 rounds), 150 mm (for 5 rounds). ),..., 240 mm (eight laps).

  You may implement combining each element demonstrated by embodiment mentioned above and the modification arbitrarily.

DESCRIPTION OF SYMBOLS 1 Color printer 10 Cleaning apparatus 51K 1st photoreceptor drum 51Y 2nd photoreceptor drum 53K 1st developing roller 53Y 2nd developing roller 73 Belt 100 Control part

Claims (15)

A first photoreceptor;
A first developing roller for supplying a developer to the first photoreceptor;
A second photoreceptor,
A second developing roller capable of contacting and separating from the second photoconductor, and supplying a developer to the second photoconductor;
A belt in contact with the first photosensitive member and the second photosensitive member;
A cleaning device for collecting the developer on the belt;
A control unit,
The controller is
During non-image formation, the developer on the first developing roller is discharged onto the first photosensitive member, and the developer discharged from the first developing roller is discharged to the cleaning device via the first photosensitive member and the belt. The forced discharge process to move to
The image forming apparatus, wherein the forced ejection process is executed when the second developing roller is separated from the second photosensitive member. A first charger for charging the first photoreceptor;
A second charger for charging the second photoconductor,
The image forming apparatus according to claim 1, wherein the control unit makes a voltage applied to the second charger smaller than a voltage applied to the first charger in the forced discharge process. A first recovery member for recovering the developer on the first photoreceptor;
A second recovery member for recovering the developer on the second photoconductor,
3. The image forming apparatus according to claim 1, wherein the control unit applies the same voltage to the first recovery member and the second recovery member during printing in the forced discharge process. 4. .   In the control unit, the consumption amount of the developer since the first developing roller is in a new state or the consumption amount of the developer after the previous execution of the forced discharge processing has become a predetermined threshold value or more. 4. The image forming apparatus according to claim 1, wherein the forced ejection process is executed in a case. 5.   5. The image forming apparatus according to claim 1, wherein the control unit executes the forced ejection process after receiving a print job and before executing printing. 6.   6. The image formation according to claim 1, wherein the control unit forms a developer image having a density of 100% on the first photosensitive member in the forced discharge process. 7. apparatus.   The control unit rotates the belt until the developer moved from the first photosensitive member onto the belt passes through the cleaning device twice in the forced discharge process. The image forming apparatus according to claim 1. The cleaning device includes a backup roller disposed inside the belt, and a cleaning roller that sandwiches the belt between the backup roller,
The said control part makes the electric current which flows between the said backup roller and the said cleaning roller in the said forced discharge process larger than the time of printing, The Claim 1 characterized by the above-mentioned. Image forming apparatus. The controller is
A density correction process for correcting a density of a developer image formed on the first photosensitive member or the second photosensitive member;
9. The forced discharge process is executed prior to the density correction process when the density correction process and the forced discharge process are performed at the same timing. The image forming apparatus described in 1. A first recovery member for recovering the developer on the first photoreceptor;
A second recovery member for recovering the developer on the second photoconductor,
The controller is
In the forced discharge process, the developer is recovered by the first recovery member and the second recovery member,
A collection process for moving the developer collected by the first collection member and the second collection member to the cleaning device via the first photoconductor, the second photoconductor, and the belt is executed after printing is completed. The image forming apparatus according to claim 5, wherein: The controller is
In the forced ejection process, a plurality of developer images having a width from one end to the other end of the image forming range are formed on the first photoconductor at intervals in the rotation direction of the first photoconductor. The image forming apparatus according to claim 1, wherein the image forming apparatus is an image forming apparatus.   12. The image forming apparatus according to claim 11, wherein a total length of the plurality of developer images in the rotation direction is a natural number multiple of a circumferential length of the first developing roller.   13. The control unit according to claim 1, wherein the control unit increases the frequency of the forced ejection processing as the average consumption amount, which is a consumption amount of a developer per print job, is smaller. The image forming apparatus described. A sensor for detecting whether the type of the cartridge containing the developer supplied to the first developing roller is a large-capacity type;
When the controller determines that the cartridge type is a large-capacity type, the number of executions of the forced ejection process is greater than when the cartridge type is not determined to be a large-capacity type. The image forming apparatus according to claim 1, wherein the image forming apparatus is configured as follows.   The image forming apparatus according to claim 4, wherein the control unit estimates a consumption amount of the developer based on a number of printed sheets designated in a print job.

Images