Image forming apparatus control method and image forming apparatus

Abstract

A processor (81) acquires an output image density that is the detected density of a first toner image detected by a density detecting unit (5). The processor (81) causes a cleaning unit (45) to execute a toner recovery process when a second toner image passes through a recovery member (451). The processor (81) causes the cleaning unit (45) to execute a toner discharge process. The processor (81) acquires a discharge toner density that is the detected density of the discharge toner detected by the density detecting unit (5). The processor (81) derives an index value of a toner discharge performance of the recovery member (451) by comparing the output image density and the discharge toner density.

Description

[Technical Field]

[0001] The present invention relates to an image forming apparatus and a control method thereof that are capable of evaluating the performance of a cleaning unit that collects residual toner from the surface of a photosensitive member. [Background technology]

[0002] An electrophotographic image forming apparatus forms a toner image on the surface of a photoreceptor, transfers the toner image from the photoreceptor to a sheet, and includes a cleaning unit that collects residual toner from the surface of the photoreceptor.

[0003] The cleaning unit may include a collection member and a collection voltage output unit (see, for example, Patent Document 1). The collection member is disposed in contact with the surface of the photosensitive member and is capable of holding toner. For example, the collection member is a porous member such as a sponge.

[0004] The collection voltage output unit is capable of applying a collection bias voltage or a release bias voltage to the collection member. The collection bias voltage is a bias voltage having a polarity different from the charge polarity of the toner. The release bias voltage is a bias voltage having the same polarity as the charge polarity of the toner.

[0005] When the collection bias voltage is applied to the collection member, the toner remaining on the surface of the photosensitive member is electrically attracted to the collection member, and the attracted toner is held by the collection member.

[0006] When toner accumulates on the collection member, the toner collection performance of the collection member decreases.

[0007] On the other hand, when the release bias voltage is applied to the collection member, the toner held by the collection member is released onto the photosensitive member, thereby improving the toner collection performance of the collection member.

[0008] The toner released from the recovery member is carried on the photosensitive member and recovered by the developing device. [Prior art documents] [Patent documents]

[0009] [Patent Document 1] Japanese Patent Application Laid-Open No. 2015-87416 Summary of the Invention [Problem to be solved by the invention]

[0010] However, as the toner collection and toner release by the collection member are repeated, the toner release performance of the collection member gradually deteriorates. When the toner release performance of the collection member deteriorates, the toner collection performance of the collection member also deteriorates. When the performance of the collection member deteriorates, there is a risk that unnecessary toner will remain on the surface of the photosensitive member.

[0011] Residual toner on the surface of the photoreceptor can cause poor print quality. On the other hand, if the performance of the recovery member is correctly evaluated, the deteriorated performance of the recovery member can be compensated for by correcting the control parameters.

[0012] For example, the recovery bias voltage is corrected to be larger, thereby compensating for the deteriorated performance of the recovery member.

[0013] An object of the present invention is to provide an image forming apparatus and a control method for the image forming apparatus that can correctly evaluate the performance of a recovery member that recovers toner from the surface of a photosensitive member. [Means for solving the problem]

[0014] A method according to one aspect of the present invention is a control method for an image forming apparatus. The image forming apparatus includes an image forming unit, a transfer unit, a cleaning unit, and a density detection unit. The image forming unit includes a rotating photoconductor and is capable of forming a toner image on the surface of the photoconductor. The transfer unit includes a rotating intermediate transfer member and is capable of performing a primary transfer process at a primary transfer position to transfer the toner image on the surface of the photoconductor to the surface of the intermediate transfer member, and a secondary transfer process at a secondary transfer position to transfer the toner image on the surface of the intermediate transfer member to a sheet. The cleaning unit is capable of performing a toner recovery process to recover toner present on a portion of the surface of the photoconductor that has passed the primary transfer position, and a toner release process to release the recovered toner onto the surface of the photoconductor. The density detection unit detects the density of the toner image on the intermediate transfer member. The cleaning unit includes a recovery member and a recovery voltage output unit. The recovery member rotates while contacting the surface of the photoconductor and is capable of retaining the toner. The collection voltage output unit applies a collection bias voltage of a polarity different from the charge polarity of the toner to the collection member in the toner collection process, and applies a release bias voltage of a polarity equal to the charge polarity of the toner to the collection member in the toner release process. The control method includes a processor causing the image forming unit to execute a first image output process to form a first toner image on the surface of the photoconductor. The control method further includes the processor causing the transfer unit to execute the primary transfer process for the first toner image. The control method further includes the processor acquiring an output image density for the first toner image, the output image density being the detected density of the density detection unit. The control method further includes the processor causing the image forming unit to execute a second image output process to form a second toner image identical to the first toner image on the surface of the photoconductor. The control method further includes the processor causing the transfer unit to execute a non-transfer process in which the second toner image is not transferred to the intermediate transfer body. The control method further includes the processor causing the cleaning unit to execute the toner collection process when the second toner image passes the collection member.The control method further includes the processor causing the cleaning unit to perform the toner release process after the toner recovery process corresponding to the second toner image has been performed.The control method further includes the processor causing the transfer unit to perform the primary transfer process on the released toner released onto the surface of the photosensitive member by the release process.The control method further includes the processor acquiring the released toner concentration, which is the detected concentration by the concentration detection unit, of the released toner transferred to the surface of the intermediate transfer member.The control method further includes the processor deriving an index value for the toner release performance of the recovery member by comparing the output image density with the released toner concentration.

[0015] An image forming apparatus according to another aspect of the present invention includes the image forming unit, the transfer unit, the cleaning unit, the density detection unit, and the processor that realizes the control method. [Effects of the Invention]

[0016] According to the present invention, it is possible to provide an image forming apparatus and a control method for the image forming apparatus that can correctly evaluate the performance of a recovery member that recovers toner from the surface of a photosensitive member. [Brief explanation of the drawings]

[0017] [Figure 1] FIG. 1 is a diagram illustrating the configuration of an image forming apparatus according to an embodiment. [Figure 2] FIG. 2 is a block diagram showing the configuration of a control device in the image forming apparatus according to the embodiment. [Figure 3] FIG. 3 is a flowchart showing an example of a procedure for the toner collection adjustment process in the image forming apparatus according to the embodiment. [Figure 4] FIG. 4 is a flowchart showing an example of a procedure for parameter adjustment processing in the image forming apparatus according to the embodiment. [Figure 5]FIG. 5 is a graph showing the relationship between test image density and emitted toner concentration under three measurement conditions related to the number of prints and control parameters in the image forming apparatus. DETAILED DESCRIPTION OF THE INVENTION

[0018] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. Note that the following embodiment is an example of the present invention, and does not limit the technical scope of the present invention.

[0019] The image forming apparatus 10 according to the embodiment is an apparatus that performs a printing process using an electrophotographic method. The printing process is a process of forming an image on a sheet 9. The sheet 9 is an image forming medium such as paper or a sheet-like resin member.

[0020] [Configuration of image forming apparatus 10] 1, the image forming apparatus 10 includes a sheet storage unit 2, a sheet transport path 30, a sheet transport device 3, and a printing device 4. The image forming apparatus 10 further includes an operation device 801, a display device 802, and a control device 8.

[0021] The sheet transport path 30, the sheet transport device 3, the printing device 4, and the control device 8 are housed in a housing 1.

[0022] The sheet storage unit 2 stores sheets 9. The sheet transport device 3 sends out the sheets 9 from the sheet storage unit 2 to a sheet transport path 30, and further transports the sheets 9 along the sheet transport path 30.

[0023] The sheet conveying device 3 includes a sheet feeding mechanism 31 and a plurality of pairs of conveying rollers 32 .

[0024] The sheet feeding mechanism 31 sends out the sheet 9 in the sheet storage unit 2 to the sheet conveying path 30. Multiple pairs of conveying rollers 32 convey the sheet 9 along the sheet conveying path 30. Furthermore, one of the multiple pairs of conveying rollers 32 discharges the sheet 9 from the sheet conveying path 30 onto the discharge tray 101.

[0025] The printing device 4 performs the printing process on the sheet 9 conveyed along the sheet conveying path 30. In this embodiment, the printing device 4 is a tandem color printing device.

[0026] The printing device 4 forms a toner image on the sheet 9 conveyed along the sheet conveying path 30. The toner image is an image made of toner as a developer. The toner is an example of the granular developer.

[0027] The printing device 4 includes a plurality of monochrome image forming units 4x, an optical scanning device 40, a transfer device 44, and a fixing device 46. In this embodiment, the printing device 4 includes four monochrome image forming units 4x corresponding to four colors: yellow, cyan, magenta, and black.

[0028] Each of the monochrome image forming units 4x includes a drum-shaped photosensitive member 41, a charging device 42, a developing device 43, a drum cleaning device 45, and the like.

[0029] In each of the monochrome image forming units 4x, the photoconductor 41 rotates, and the charging device 42 performs a charging process. The charging process is a process of charging the surface of the photoconductor 41. Furthermore, the optical scanning device 40 forms an electrostatic latent image on the charged surface of the photoconductor 41 by scanning with a laser beam.

[0030] The optical scanning device 40 is an example of a latent image forming unit that forms the electrostatic latent image on the surface of the charged photosensitive member 41 .

[0031] Furthermore, the developing device 43 develops the electrostatic latent image into the toner image by supplying the toner to the surface of the photoconductor 41. The developing device 43 supplies the toner to the photoconductor 41 at a development position on the outer periphery of the photoconductor 41. The developing device 43 is an example of a developing unit.

[0032] The charging device 42 includes a charging member 421 and a charging voltage output device 422. The charging member 421 is disposed opposite the photosensitive member 41 at a charging position on the outer periphery of the photosensitive member 41. The charging voltage output device 422 applies a charging bias voltage to the charging member 421. The charging bias voltage is a bias voltage applied in the charging process.

[0033] The charging bias voltage is applied to the photoconductor 41 from the charging voltage output device 422 through the charging member 421. This charges the surface of the photoconductor 41. The charging device 42 is an example of a charging section.

[0034] The developing device 43 includes a developing roller 431 and a developing voltage output device 432. The developing roller 431 is disposed at the developing position so as to face the photoconductor 41. The developing roller 431 rotates while carrying toner.

[0035] The developing voltage output device 432 applies a developing bias voltage to the developing roller 431. In this embodiment, the developing bias voltage is a voltage in which an AC voltage is superimposed on a DC voltage.

[0036] The developing roller 431 rotates while carrying toner, and supplies the toner to the surface of the photoconductor 41 at the developing position. The developing roller 431 is an example of a developing body. The developing voltage output device 432 is an example of a developing voltage output unit.

[0037] The toner carried by the developing roller 431 is transferred to the electrostatic latent image on the surface of the photoreceptor 41 by an electric field generated between the developing roller 431 and the photoreceptor 41 .

[0038] At the developing position, the toner is transferred from the developing roller 431 to the portion of the electrostatic latent image on the surface of the photoreceptor 41. This develops the electrostatic latent image into the toner image. Each of the four photoreceptors 41 is an example of an image carrier that carries the toner image.

[0039] As described above, the optical scanning device 40 and each of the four monochrome image forming units 4x are capable of forming the toner image on the surface of the photoreceptor 41. The optical scanning device 40 and each of the four monochrome image forming units 4x are examples of image forming units.

[0040] In this embodiment, the developing device 43 performs development using a two-component development method. That is, the developing device 43 charges the toner by stirring a two-component developer containing the toner and a magnetic carrier. Furthermore, the developing device 43 supplies the charged toner to the photoconductor 41.

[0041] The magnetic carrier is a granular material having magnetic properties. For example, the magnetic carrier is a granular magnetic material having a surface coating. The coating is made of a synthetic resin such as an epoxy resin.

[0042] The transfer device 44 includes an intermediate transfer belt 441, four primary transfer devices 442 corresponding to the four monochrome image forming units 4x, a secondary transfer device 443, and a belt cleaning device 444.

[0043] The intermediate transfer belt 441 is supported by a plurality of support rollers 440. One of the plurality of support rollers 440 is rotated by power received from a motor (not shown), thereby causing the intermediate transfer belt 441 to rotate.

[0044] Each photoconductor 41 is in contact with an intermediate transfer belt 441 at a primary transfer position on the outer periphery of each photoconductor 41 .

[0045] Each primary transfer device 442 is capable of performing a primary transfer process. The primary transfer process is a process of transferring the toner image on the surface of the photosensitive member 41 onto the surface of the intermediate transfer belt 441 at the primary transfer position.

[0046] The plurality of primary transfer devices 442 perform the primary transfer process, so that the toner images of a plurality of colors are formed on the surface of the intermediate transfer belt 441 .

[0047] Each of the primary transfer devices 442 includes a primary transfer member 4421 and a primary voltage output device 4422. The primary transfer member 4421 is disposed opposite the photosensitive member 41 with the intermediate transfer belt 441 interposed therebetween.

[0048] A primary voltage output device 4422 applies a primary transfer bias voltage to the primary transfer member 4421. The toner image formed on the surface of the photosensitive member 41 is transferred to the surface of the intermediate transfer belt 441 by an electric field generated between the photosensitive member 41 and the primary transfer member 4421. The polarity of the primary transfer bias voltage is opposite to the charge polarity of the toner.

[0049] The secondary transfer device 443 is capable of performing a secondary transfer process. The secondary transfer process is a process of transferring the toner image formed on the intermediate transfer belt 441 onto the sheet 9 at a secondary transfer position on the sheet transport path 30.

[0050] The secondary transfer device 443 includes a secondary transfer member 4431 and a secondary voltage output device 4432. The secondary transfer member 4431 is in contact with the intermediate transfer belt 441 at the secondary transfer position. The sheet 9 passes between the intermediate transfer belt 441 and the secondary transfer member 4431.

[0051] A secondary voltage output device 4432 applies a secondary transfer bias voltage to the secondary transfer member 4431. The toner image formed on the surface of the intermediate transfer belt 441 is transferred to the sheet 9 by an electric field generated between the intermediate transfer belt 441 and the secondary transfer member 4431. The polarity of the secondary transfer bias voltage is opposite to the charge polarity of the toner.

[0052] The intermediate transfer belt 441 is an example of an intermediate transfer body. The transfer device 44 is an example of a transfer unit that can perform the primary transfer process and the secondary transfer process.

[0053] The drum cleaning device 45 performs a toner recovery process, which is a process for recovering toner that exists on the surface of the photoreceptor 41 in a portion that has passed the primary transfer position.

[0054] Furthermore, the drum cleaning device 45 can also perform a toner releasing process. The toner releasing process is a process of releasing the toner collected from the surface of the photoreceptor 41 back onto the surface of the photoreceptor 41. The drum cleaning device 45 is an example of a cleaning unit.

[0055] The drum cleaning device 45 includes a collection member 451 and a collection voltage output device 452. The collection member 451 is a member capable of holding the toner. For example, the collection member 451 is a porous member such as a sponge.

[0056] The recovery member 451 rotates while contacting the surface of the photoreceptor 41. The recovery member 451 contacts the surface of the photoreceptor 41 at a recovery position on the outer periphery of the photoreceptor 41. The recovery position is a position on the outer periphery of the photoreceptor 41 between the primary transfer position and the charging position.

[0057] The recovery voltage output device 452 is capable of applying a recovery bias voltage or a release bias voltage to the recovery member 451. The recovery voltage output device 452 is an example of a recovery voltage output unit.

[0058] The collection bias voltage is a voltage having a polarity different from the charge polarity of the toner, and the release bias voltage is a voltage having a polarity the same as the charge polarity of the toner.

[0059] The collection voltage output device 452 applies the collection bias voltage to the collection member 451 during the toner collection process. As a result, the toner on the surface of the photoconductor 41 is electrically attracted to the collection member 451 and held by the collection member 451. The toner collected by the collection member 451 is accumulated in a plurality of holes formed on the surface of the collection member 451.

[0060] On the other hand, in the toner releasing process, the recovery voltage output device 452 applies the release bias voltage to the recovery member 451. As a result, the toner held by the recovery member 451 is electrically attracted to the surface of the photoreceptor 41 and released from the recovery member 451 onto the surface of the photoreceptor 41.

[0061] The recovery process is performed when the print process is performed. By performing the recovery process, the toner that has not been transferred to the intermediate transfer belt 441 at the primary transfer position is recovered by a recovery member 451.

[0062] However, as the toner accumulates on the collection member 451, the toner collection performance of the collection member 451 decreases.

[0063] On the other hand, when a predetermined release condition is met while the printing process is not being performed, the release process is performed. By performing the release process, the toner collection performance of the collection member 451 is improved.

[0064] In this embodiment, the developing voltage output device 432 can also output an attraction bias voltage to the developing roller 431. The attraction bias voltage is a voltage of a polarity different from the charge polarity of the toner.

[0065] When the release process is performed, the developing voltage output device 432 applies the attraction bias voltage to the developing roller 431. As a result, the toner released from the recovery member 451 is recovered into the developing device 43 by the developing roller 431.

[0066] The belt cleaning device 444 removes toner remaining on the portion of the intermediate transfer belt 441 that has passed the secondary transfer position.

[0067] The fixing device 46 applies heat and pressure to the toner image on the sheet 9. In this way, the fixing device 46 fixes the toner image to the sheet 9.

[0068] The operation device 801 is a device that accepts operations by a person, and includes, for example, operation buttons and a touch panel.

[0069] The display device 802 is a device that displays information, and includes, for example, a panel display device such as a liquid crystal display unit.

[0070] The image forming apparatus 10 further includes a density sensor 5 (see FIG. 1). The density sensor 5 detects the density of the toner image on the surface of the intermediate transfer belt 441 at a portion that has passed the secondary transfer position.

[0071] The density sensor 5 detects the density of the toner image at a position between the secondary transfer position and the position of the belt cleaning device 444 on the outer periphery of the intermediate transfer belt 441 .

[0072] For example, the density sensor 5 is a CIS (Contact Image Sensor). The density sensor 5 is an example of a density detection unit that detects the density of the toner image on the intermediate transfer body.

[0073] [Configuration of control device 8] As shown in FIG. 2, the control device 8 includes a central processing unit (CPU) 81, a random access memory (RAM) 82, a secondary storage device 83, a signal interface 84, a communication device 85, and the like.

[0074] The secondary storage device 83 is a computer-readable non-volatile storage device. The secondary storage device 83 can store and update computer programs and various data. For example, a flash memory or a hard disk drive, or both, may be used as the secondary storage device 83.

[0075] The signal interface 84 converts signals output by various sensors into digital data and transmits the converted digital data to the CPU 81. Furthermore, the signal interface 84 converts control commands output by the CPU 81 into control signals and transmits the control signals to the devices to be controlled.

[0076] The communication device 85 executes communication with other devices such as a host device (not shown). The CPU 81 communicates with the other devices through the communication device 85.

[0077] The CPU 81 is a processor that executes the computer program to perform various data processing and control operations. The control device 8 including the CPU 81 controls the sheet transport device 3, the printing device 4, the display device 802, the communication device 85, etc.

[0078] The RAM 82 is a computer-readable volatile storage device that temporarily stores the computer programs executed by the CPU 81 and data that is output and referenced by the CPU 81 during the execution of various processes.

[0079] The CPU 81 includes a plurality of processing modules that are realized by executing the computer programs, including a main processing unit 8a, a job control unit 8b, and an adjustment control unit 8c.

[0080] The main processing unit 8a executes processes to start various processes in response to operations on the operation device 801, controls the display device 802, and the like.

[0081] The job control unit 8b controls the sheet conveying device 3. As a result, the job control unit 8b controls the feeding of the sheet 9 from the sheet storage unit 2 and the conveyance of the sheet 9 in the sheet conveying path 30.

[0082] Furthermore, the job control unit 8b controls the printing device 4. In synchronization with the conveyance of the sheet 9 by the sheet conveying device 3, the job control unit 8b causes the printing device 4 to execute the printing process.

[0083] The adjustment control unit 8c determines whether the discharge condition is met when the print process is not being performed. For example, the discharge condition is met every time the number of page prints reaches a predetermined number. The page print is the print process for one page of the sheet 9.

[0084] Furthermore, when it is determined that the release condition is met, the adjustment control section 8c executes regeneration control.

[0085] In the regeneration control, the adjustment control section 8c causes the drum cleaning device 45 to perform the toner releasing process.

[0086] Furthermore, the adjustment control section 8c causes the developing voltage output device 432 to output the attraction bias voltage during the regeneration control.

[0087] On the other hand, in the reproduction control, the adjustment control section 8c does not cause the charging voltage output device 422 to output a voltage, and does not cause the optical scanning device 40 to form the electrostatic latent image.

[0088] However, repeated toner collection and toner release by collection member 451 gradually reduces the toner release performance of collection member 451. When the toner release performance of collection member 451 decreases, the toner collection performance of collection member 451 also decreases. When the performance of collection member 451 decreases, there is a risk that unnecessary toner will remain on the surface of photoconductor 41.

[0089] 5 is a graph showing the relationship between test image density and emitted toner concentration under three measurement conditions in the image forming apparatus 10. The horizontal axis of the graph represents test image density, and the vertical axis of the graph represents emitted toner concentration.

[0090] The test image density is the density of a test image formed on the surface of the photoreceptor 41. The test image density is the density in image data representing the test image.

[0091] The discharged toner density is the density of the toner discharged onto the surface of the photoreceptor 41 when the discharge process is performed on the test image.

[0092] Specifically, the recovery process is performed without the primary transfer process when the test image is formed on the surface of the photosensitive member 41. When the release process is performed in this manner, the primary transfer device 442 performs the primary transfer process on the released toner on the surface of the photosensitive member 41.

[0093] Furthermore, the density sensor 5 detects the density of the released toner on the surface of the intermediate transfer belt 441. The density detected by the density sensor 5 at this time is the released toner density.

[0094] When the density sensor 5 detects the density after the discharge process, the secondary voltage output device 4432 does not output the secondary transfer bias voltage.

[0095] The first measurement condition among the three measurement conditions is a condition in which the reference discharge voltage is applied to the recovery member 451 as the discharge bias voltage in the initial state of the image forming apparatus 10.

[0096] The second measurement condition among the three measurement conditions is a condition in which the reference release voltage is applied as the release bias voltage to the collection member 451 in a load test state of the image forming apparatus 10. The load test state is a state after the page printing accompanied by the toner collection process and the toner release process have each been performed a predetermined number of times from the initial state.

[0097] The third measurement condition among the three measurement conditions is a condition in which a correction discharge voltage is applied as the discharge bias voltage to the recovery member 451 in the load test state of the image forming apparatus 10. The correction discharge voltage is a bias voltage greater than the reference discharge voltage.

[0098] In FIG. 5, first measurement data D11, second measurement data D12, and third measurement data D13 are data on a plurality of emitted toner densities corresponding to a plurality of test image densities, respectively.

[0099] The first measurement data D11 is data under the first measurement conditions, the second measurement data D12 is data under the second measurement conditions, and the third measurement data D13 is data under the third measurement conditions.

[0100] The difference between the first measurement data D11 and the second measurement data D12 indicates that the toner releasing performance of the collection member 451 is reduced as the toner collection process and the toner releasing process are repeated.

[0101] The difference between the second measurement data D12 and the third measurement data D13 indicates that the performance of the recovery member 451 that has deteriorated can be compensated for by correcting the release bias voltage.

[0102] Residual toner on the surface of the photoreceptor 41 causes poor print quality. On the other hand, if the performance of the collection member 451 is correctly evaluated, the performance of the deteriorated collection member 451 can be compensated for by correcting the control parameters such as the collection bias voltage or the release bias voltage.

[0103] In the image forming apparatus 10, the adjustment control unit 8c can execute a toner collection adjustment process (see FIG. 3). This allows the performance of the collection member 451 that collects toner on the surface of the photosensitive member 41 to be correctly evaluated. Furthermore, the control parameters are corrected according to the evaluation results of the performance of the collection member 451.

[0104] [Toner collection adjustment process] The adjustment control unit 8c executes the toner collection adjustment process when a predetermined adjustment condition is met while the print process is not being performed. The adjustment control unit 8c executes the toner collection adjustment process for each of the monochrome image forming units 4x.

[0105] The adjustment control unit 8c determines whether the adjustment conditions are met when the print process is not being executed. For example, the adjustment conditions include one or both of a print count condition and a remaining toner condition.

[0106] The print count condition is a condition that the number of page prints has reached a predetermined number based on the time when the image forming apparatus 10 was first used or the time when the toner collection adjustment process was last executed.

[0107] The remaining toner condition is a condition in which the density detected by the density sensor 5 when the print process is executed exceeds an allowable density.

[0108] An example of the procedure for the toner collection adjustment process will be described below with reference to the flowchart shown in FIG.

[0109] The toner collection adjustment process is an example of a process that realizes a control method for the image forming apparatus 10. The CPU 81 is an example of a processor that realizes a control method for the image forming apparatus 10.

[0110] In the following description, S101, S102, ... represent identification symbols of a plurality of steps in the toner collection adjustment process. In the toner collection adjustment process, step S101 is first executed.

[0111] <Process S101> In step S101, the adjustment control unit 8c causes the monochrome image forming unit 4x and the optical scanning device 40 to execute the first image output process.

[0112] The first image output process is a process of forming a first toner image on the surface of the photoconductor 41. For example, the first toner image is a patch image of a predetermined density.

[0113] After executing the process of step S101, the adjustment control unit 8c shifts the process to step S102.

[0114] <Process S102> In step S102, the adjustment control unit 8c causes the primary transfer device 442 to perform the primary transfer process on the first toner image.

[0115] Specifically, the adjustment control unit 8c causes the primary voltage output device 4422 to output the primary transfer bias voltage when the first toner image passes through the primary transfer position.

[0116] After executing the process of step S102, the adjustment control unit 8c shifts the process to step S103.

[0117] <Process S103> In step S103, the adjustment control unit 8c acquires the output image density from the density sensor 5. The output image density is the density detected by the density sensor 5 for the first toner image.

[0118] Specifically, the adjustment control unit 8c acquires the density detected by the density sensor 5 when the first toner image passes the position of the density sensor 5 as the output image density.

[0119] It should be noted that, when the toner collection adjustment process is being performed, the adjustment control unit 8c does not cause the secondary voltage output device 4432 to output the secondary transfer bias voltage. For example, the adjustment control unit 8c causes the secondary voltage output device 4432 to output a bias voltage having a polarity opposite to that of the secondary transfer bias voltage. As a result, the toner transferred to the intermediate transfer belt 441 passes through the secondary transfer position and the position of the density sensor 5, and is then removed by the belt cleaning device 444.

[0120] Furthermore, when the toner collection adjustment process is being performed, the adjustment control section 8c may cause the secondary voltage output device 4432 to output a bias voltage of the same polarity as the charge polarity of the toner.

[0121] After executing the process of step S103, the adjustment control unit 8c shifts the process to step S104.

[0122] <Process S104> In step S104, the adjustment control unit 8c causes the monochrome image forming unit 4x and the optical scanning device 40 to execute the second image output process.

[0123] The second image output process is a process of forming a second toner image on the surface of the photoconductor 41. The second toner image is the same toner image as the first toner image.

[0124] After executing the process of step S104, the adjustment control unit 8c shifts the process to step S105.

[0125] <Process S105> In step S105, the adjustment control unit 8c causes the primary transfer device 442 to perform a non-transfer process in which the second toner image is not transferred onto the intermediate transfer belt 441.

[0126] Specifically, in step S105, the adjustment control unit 8c causes the primary voltage output device 4422 to output a bias voltage having the same polarity as the charging polarity of the toner.

[0127] After executing the process of step S105, the adjustment control unit 8c shifts the process to step S106.

[0128] <Process S106> In step S106, the adjustment control section 8c causes the drum cleaning device 45 to perform the toner collection process when the second toner image passes through the collection member 451.

[0129] By performing the process of step S106, the toner constituting the second toner image is collected by the collection member 451.

[0130] After executing the process of step S106, the adjustment control unit 8c shifts the process to step S107.

[0131] <Process S107> In step S107, the adjustment control unit 8c causes the drum cleaning device 45 to perform the release process.

[0132] By performing the process of step S107 after the process of step S06, the toner constituting the second toner image is released from the recovery member 451 onto the surface of the photosensitive member 41. In the following description, the toner released onto the surface of the photosensitive member 41 by the process of step S107 is referred to as released toner.

[0133] After executing the process of step S107, the adjustment control unit 8c shifts the process to step S108.

[0134] <Process S108> In step S108, the adjustment control section 8c executes roller retraction control when the released toner passes the developing position.

[0135] In this embodiment, the developing device 43 includes a roller moving mechanism 433 that moves the developing roller 431 from the operating position to the retracted position (see FIG. 1).

[0136] The operating position is a position where toner can be supplied from the developing roller 431 to the photosensitive member 41. The retracted position is a position farther from the photosensitive member 41 than the operating position. When the developing roller 431 is in the retracted position, no toner transfer occurs between the photosensitive member 41 and the developing roller 431.

[0137] For example, the roller moving mechanism 433 includes a motor and a cam mechanism driven by the motor. The cam mechanism is a mechanism that moves the developing roller 431 between the operating position and the retracted position.

[0138] For example, the cam mechanism includes a spacer rotatably supported on the rotation shaft of the developing roller 431, and a drive mechanism that rotates the spacer. The spacer is formed in an elliptical plate shape. The spacer maintains the gap between the photosensitive member 41 and the developing roller 431 by contacting the surface of the photosensitive member 41.

[0139] The roller retraction control is a control for causing the roller moving mechanism 433 to execute an operation of moving the developing roller 431 from the operating position to the retracted position.

[0140] After executing the process of step S108, the adjustment control unit 8c shifts the process to step S109.

[0141] The developing device 43 may include a carrier holding mechanism instead of the roller moving mechanism 433. The carrier holding mechanism includes a cylindrical body, a magnet contained in the cylindrical body, and a magnet moving mechanism.

[0142] The cylindrical body is disposed opposite to the developing roller 431 in the developing device 43. The magnet moving mechanism moves the magnet between a close position and a separate position.

[0143] In step S108, the adjustment control unit 8c controls the magnet moving mechanism to hold the magnet at the close position.

[0144] At the close position, the magnet attracts the magnetic carrier carried by the developing roller 431 together with the toner. As a result, the magnetic carrier and the toner carried by the developing roller 431 are not transported to the developing position, but are held between the developing roller 431 and the cylindrical body. As a result, the released toner passes through the developing position without coming into contact with the magnetic carrier.

[0145] On the other hand, when development is performed by the developing device 43, the adjustment control unit 8c controls the magnet moving mechanism to hold the magnet at the separated position. The separated position is a position farther away from the developing roller 431 than the close position. When the magnet is in the separated position, the magnetic carrier and the toner carried by the developing roller 431 are transported to the developing position.

[0146] <Process S109> In step S109, the adjustment control unit 8c causes the primary transfer device 442 to perform the primary transfer process on the released toner.

[0147] Specifically, the adjustment control unit 8c causes the primary voltage output device 4422 to output the primary transfer bias voltage when the released toner on the surface of the photosensitive member 41 passes through the primary transfer position.

[0148] After executing the process of step S109, the adjustment control unit 8c shifts the process to step S110.

[0149] <Process S110> In step S110, the adjustment control unit 8c acquires the released toner density from the density sensor 5. The released toner density is the density detected by the density sensor 5 for the released toner transferred onto the surface of the intermediate transfer belt 441.

[0150] Specifically, the adjustment control unit 8c acquires the detected density of the density sensor 5 when the released toner on the intermediate transfer belt 441 passes the position of the density sensor 5 as the released toner density.

[0151] After executing the process of step S110, the adjustment control unit 8c shifts the process to step S111.

[0152] <Process S111> In step S111, the adjustment control unit 8c executes a release performance evaluation process, which is a process for deriving an index value of the toner release performance of the collection member 451 by comparing the output image density with the released toner concentration.

[0153] For example, the index value is the difference between the output image density and the emitted toner density, or the ratio of the emitted toner density to the output image density.

[0154] After executing the process of step S111, the adjustment control unit 8c shifts the process to step S112.

[0155] <Process S112> In step S112, the adjustment control unit 8c executes a parameter adjustment process based on the index value of the toner release performance, which will be described later.

[0156] After executing the process of step S112, the adjustment control unit 8c ends the toner collection adjustment process.

[0157] [Parameter adjustment processing] Next, an example of the procedure for the parameter adjustment process will be described with reference to the flowchart shown in FIG.

[0158] In the following description, S201, S202, ... represent identification symbols of a plurality of steps in the parameter adjustment process. In the parameter adjustment process, step S201 is executed first.

[0159] <Process S201> In step S201, the adjustment control unit 8c determines whether the index value of the toner release performance is within a predetermined reference range or outside the reference range.

[0160] If the adjustment control unit 8c determines that the index value is within the reference range, it ends the parameter adjustment process.

[0161] On the other hand, when the adjustment control unit 8c determines that the index value is outside the reference range, it shifts the processing to step S202.

[0162] <Process S202> In step S202, the adjustment control unit 8c determines whether the index value of the toner release performance is within a predetermined allowable range or outside the allowable range, which is a range wider than the reference range.

[0163] If the adjustment control unit 8c determines that the index value is within the allowable range, it shifts the processing to step S203.

[0164] On the other hand, if the adjustment control unit 8c determines that the index value is outside the allowable range, it shifts the processing to step S206.

[0165] <Process S203> In step S203, the adjustment control unit 8c derives correction values ​​for one or more of the control parameters according to the index value of the toner release performance.

[0166] The control parameters include one or more of the discharge bias voltage, the collection bias voltage, the rotation speed of the collection member 451, the primary transfer bias voltage, and the charging bias voltage.

[0167] 5, the discharging bias voltage is corrected to a larger bias voltage, thereby compensating for the toner discharging performance of the collection member 451. Note that the discharging bias voltage is a bias voltage applied in the discharging process.

[0168] Furthermore, if the toner release performance of the collection member 451 is degraded, the toner collection performance of the collection member 451 is also degraded. The collection bias voltage is corrected to a larger bias voltage, thereby compensating for the toner collection performance of the collection member 451.

[0169] At the portion where recovery member 451 contacts photoconductor 41, the surface of recovery member 451 moves in the same direction as the moving direction of the surface of photoconductor 41. By correcting the circumferential speed of recovery member 451 to be slower than the circumferential speed of photoconductor 41, the efficiency of toner recovery by recovery member 451 is improved. In other words, the toner recovery performance of recovery member 451 is compensated for.

[0170] Furthermore, by correcting the primary transfer bias voltage to a larger bias voltage, the amount of toner remaining on the surface of the photosensitive member 41 is reduced, thereby compensating for the toner recovery performance of the recovery member 451. The primary transfer bias voltage is a bias voltage applied in the primary transfer process.

[0171] Furthermore, by correcting the charging bias voltage to a larger bias voltage, the amount of toner remaining on the surface of the photosensitive member 41 is reduced, thereby improving the toner recovery performance of the recovery member 451.

[0172] After executing the process of step S203, the adjustment control unit 8c shifts the process to step S204.

[0173] <Process S204> In step S204, the adjustment control unit 8c determines whether the correction value derived in step S204 is within a predetermined allowable correction range or is outside the allowable correction range.

[0174] If the adjustment control unit 8c determines that the correction value is within the correction tolerance range, the adjustment control unit 8c shifts the process to step S205. On the other hand, if the adjustment control unit 8c determines that the correction value is outside the correction tolerance range, the adjustment control unit 8c shifts the process to step S206.

[0175] <Process S205> In step S205, the adjustment control unit 8c corrects the control parameters in accordance with the correction values ​​derived in step S203.

[0176] After executing the process of step S205, the adjustment control unit 8c ends the parameter adjustment process.

[0177] <Process S206> In step S206, the adjustment control unit 8c executes a warning process to prompt replacement of the collection member 451. For example, the warning process is a process of causing the display device 802 to display a predetermined message.

[0178] The process of step S206 is executed when the correction value of the control parameter or the index value falls outside the allowable range. After executing the process of step S206, the adjustment control unit 8c ends the parameter adjustment process.

[0179] By executing the toner collection adjustment process, the performance of the collection member 451 is correctly evaluated. As a result, by executing the parameter adjustment process, the performance of the collection member 451 that has deteriorated is compensated for.

[0180] Furthermore, the adjustment control unit 8c may execute the processes of steps S101 to S110 multiple times under multiple output density conditions under which the densities of the first toner image and the second toner image are different from each other. For example, the output density condition may be the number of pixels drawn in each of the first toner image and the second toner image. Furthermore, the output density condition may be the light intensity of the beam of light from the optical scanning device 40.

[0181] The processing of steps S101 to S110 a plurality of times includes causing the monochrome image forming unit 4x and the optical scanning device 40 to execute the first image output process and the second image output process a plurality of times (see steps S102 and S104).

[0182] In addition, the processing of steps S101 to S110 multiple times includes causing the transfer device 44 to perform the primary transfer process for the first toner image multiple times, the non-transfer process for the second toner image multiple times, and the primary transfer process for the released toner multiple times (see steps S102, S105, S109).

[0183] Furthermore, the processing of steps S101 to S110 a plurality of times includes causing the drum cleaning device 45 to perform the toner recovery process and the toner release process on the second toner image a plurality of times (see steps S106 and S107).

[0184] When the processes of steps S101 to S110 are performed under the plurality of output density conditions, a plurality of pairs of the output image density and the discharged toner density are obtained corresponding to the plurality of output density conditions.

[0185] In the above case, the adjustment control unit 8c may derive the index value of the release performance based on a plurality of pairs of the output image density and the released toner density in step S111.

[0186] For example, the adjustment control unit 8c derives a plurality of index value candidates corresponding to a plurality of pairs of the output image density and the emitted toner density. In this case, the adjustment control unit 8c derives a representative value of the plurality of index value candidates as the index value. The representative value may be, for example, an average value, a weighted average value, a maximum value, or a minimum value.

[0187] Furthermore, the adjustment control unit 8c may execute the processes of steps S101 to S111 in the initial state of the image forming apparatus 10. In this case, the adjustment control unit 8c records the initial index value obtained in step S111 in the secondary storage device 83 as a reference value.

[0188] Then, the adjustment control section 8c may derive a comparison value by comparing the output image density with the released toner density in step S111 of the toner collection adjustment process.

[0189] Furthermore, the adjustment control unit 8c may derive the difference or ratio between the comparison value and the reference value as the index value. The comparison value is the difference or ratio between the output image density and the emitted toner density.

[0190] Alternatively, the adjustment control unit 8c may set the reference range of the index value based on the reference value (see step S201 in FIG. 4).

[0191] Furthermore, the developing device 43 may be an interactive touch-down developing device or a jumping developing device. In this case, the developing device 43 does not include the roller moving mechanism 433. The adjustment control unit 8c does not cause the developing voltage output device 432 to output a voltage in step S108 of the toner collection adjustment process.

Claims

1. A control method for an image forming apparatus, comprising: the image forming apparatus, an image forming unit including a rotating photoreceptor and capable of forming a toner image on the surface of the photoreceptor; a transfer unit including a rotating intermediate transfer body, capable of performing a primary transfer process of transferring the toner image on the surface of the photosensitive body to the surface of the intermediate transfer body at a primary transfer position, and a secondary transfer process of transferring the toner image on the surface of the intermediate transfer body to a sheet at a secondary transfer position; a cleaning unit capable of performing a toner recovery process for recovering toner present on a portion of the surface of the photosensitive member that has passed through the primary transfer position and a toner release process for releasing recovered toner onto the surface of the photosensitive member; a density detection unit that detects the density of the toner image on the intermediate transfer body, The cleaning unit includes: a collection member that rotates while contacting the surface of the photosensitive member and is capable of holding the toner; a collection voltage output unit that applies a collection bias voltage having a polarity different from the charge polarity of the toner to the collection member in the toner collection process, and applies a release bias voltage having a polarity the same as the charge polarity of the toner to the collection member in the toner release process, The control method includes: a processor causing the image forming unit to execute a first image output process for forming a first toner image on the surface of the photosensitive member; the processor causes the transfer unit to perform the primary transfer process on the first toner image; the processor acquires an output image density of the first toner image, the output image density being the density detected by the density detection unit; the processor causes the image forming unit to execute a second image output process for forming a second toner image identical to the first toner image on the surface of the photosensitive member; the processor causes the transfer unit to perform a non-transfer process in which the second toner image is not transferred to the intermediate transfer body; the processor causes the cleaning unit to perform the toner recovery process when the second toner image passes the recovery member; the processor causes the cleaning unit to perform the toner release process after the toner recovery process corresponding to the second toner image has been performed; the processor causes the transfer unit to perform the primary transfer process on the released toner released onto the surface of the photoreceptor by the toner releasing process; The processor acquires a released toner density, which is a detected density of the released toner transferred to the surface of the intermediate transfer body by the density detection unit; the processor deriving an index value of the toner releasing performance of the recovery member by comparing the output image density with the released toner concentration.

2. The method of controlling an image forming apparatus according to claim 1 , further comprising the processor correcting one or more control parameters in response to the index value.

3. 3. The control method for an image forming apparatus according to claim 2, wherein the control parameters include one or more of the discharge bias voltage, the recovery bias voltage, the rotational speed of the recovery member, a primary transfer bias voltage applied in the primary transfer process by the transfer unit, and a charging bias voltage applied in the charging process of the surface of the photosensitive member by the image forming unit.

4. The method for controlling an image forming apparatus according to claim 2 , further comprising the processor executing a warning process when the correction amount of the control parameter or the index value falls outside an allowable range.

5. the processor causes the image forming unit to execute the first image output process and the second image output process a plurality of times under a plurality of output density conditions in which the densities of the first toner image and the second toner image are different from each other; Further, the processor causes the transfer unit to perform the primary transfer process for the first toner image a plurality of times, the non-transfer process for the second toner image a plurality of times, and the primary transfer process for the released toner a plurality of times under the plurality of output density conditions; Further, the processor causes the cleaning unit to perform the toner recovery process and the toner release process on the second toner image a plurality of times under the plurality of output density conditions, 2. The method for controlling an image forming apparatus according to claim 1, wherein the processor further derives the index value based on a plurality of pairs of the output image density and the emitted toner density obtained corresponding to the plurality of output density conditions.

6. an image forming unit including a rotating photoreceptor and capable of forming a toner image on the surface of the photoreceptor; a transfer unit including a rotating intermediate transfer body, capable of performing a primary transfer process of transferring the toner image on the surface of the photosensitive body to the surface of the intermediate transfer body at a primary transfer position, and a secondary transfer process of transferring the toner image on the surface of the intermediate transfer body to a sheet at a secondary transfer position; a cleaning unit capable of performing a toner recovery process to recover toner present on a portion of the surface of the photosensitive member that has passed through the primary transfer position; a density detection unit that detects the density of the toner image on the intermediate transfer body; a processor that implements the control method for an image forming apparatus according to claim 1; The cleaning unit includes: a collection member that rotates while contacting the surface of the photosensitive member and is capable of holding the toner; the image forming apparatus further comprising: a collection voltage output unit that applies a collection bias voltage having a polarity different from the charge polarity of the toner to the collection member in the toner collection process.

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