JP6558197B2 - Image forming apparatus and control program for image forming apparatus - Google Patents

Description

  The present invention relates to an image forming apparatus and a control program for the image forming apparatus. More specifically, the present invention relates to an image forming apparatus including an image carrier that is rotationally driven, and a control program for the image forming apparatus.

  The electrophotographic image forming apparatus includes a scanner function, a facsimile function, a copying function, a function as a printer, a data communication function, and a server function, an MFP (Multi Function Peripheral), a facsimile apparatus, a copying machine, a printer, and the like. is there.

  In general, an image forming apparatus develops an electrostatic latent image formed on an image carrier to form a toner image, transfers the toner image to a sheet, and then fixes the toner image on the sheet by a fixing device. An image is formed on a sheet. In addition, in the image forming apparatus, the electrostatic latent image formed on the photosensitive member is developed using a developing device to form a toner image, and the toner image is formed on an intermediate transfer belt using a primary transfer roller. Some transfer and secondary transfer the toner image on the intermediate transfer belt onto a sheet using a secondary transfer roller. In this case, the photosensitive member and the intermediate transfer belt serve as an image carrier.

  Technologies relating to the photoreceptor of the image forming apparatus are disclosed in, for example, the following Patent Documents 1 and 2. Japanese Patent Application Laid-Open No. 2004-228561 discloses a technique for suppressing the deterioration of characteristics of a photoconductor by setting a peripheral speed difference between the photoconductor and a charging roller to 1.1 or more. Patent Document 2 below discloses a technique for removing discharge products from a photoconductor by polishing the photoconductor by a circumferential difference between the photoconductor and a charging roller.

JP 2002-132013 A JP 2011-237689

  While the surface of the photoconductor is required to be hard to be scraped off, discharge products adhere to the surface of the photoconductor as the number of printed sheets increases. In order to remove the discharge products, the surface of the photoreceptor needs to be scraped by a required amount as the number of printed sheets increases.

  FIG. 11 is a graph showing the amount of abrasion on the surface of the photosensitive member as the number of printed sheets increases.

  Referring to FIG. 11, line L101 indicates the change in the amount of photoconductor abrasion when the printing of an image having a coverage of 10% is repeated. A line L102 indicates the transition of the lower limit value of the amount of abrasion on the surface of the photosensitive member necessary for suppressing the image flow. Coverage refers to when developing an electrostatic latent image of an image based on the amount of toner used when developing an electrostatic latent image (solid image) that forms a toner image in the entire image forming area. This is a percentage of the toner amount to be used.

  The surface of the photoconductor is scraped with an increase in the number of printed sheets by a cleaning blade or the like that contacts the photoconductor. When the amount of abrasion on the surface of the photoconductor reaches the upper limit, the photoconductor has a lifetime. In recent years, in order to extend the life of the photoconductor, the surface of the photoconductor is made hard to be scraped by increasing the hardness of the photoconductor and optimizing the contact condition of the cleaning blade. However, when the amount of abrasion on the surface of the photoconductor is insufficient, the discharge product adhering to the surface of the photoconductor is not sufficiently removed, and image flow occurs. The image flow is a phenomenon in which the electrostatic latent image charge on the surface of the photoconductor flows in the rotation direction of the photoconductor and the formed image is blurred.

  FIG. 12 is a graph showing the relationship between coverage and the amount of photoconductor abrasion.

  Referring to FIG. 12, the toner and the abrasive contained in the toner have an effect of promoting the abrasion of the photosensitive member by a cleaning blade or the like. For this reason, when the coverage is lowered, the amount of toner supplied to the surface of the photoreceptor is reduced, and the amount of abrasion of the photoreceptor is reduced.

  FIG. 13 is a graph showing changes in the amount of photoconductor abrasion when the image forming apparatus continuously executes low coverage image print jobs.

  Referring to FIG. 13, a line L103 indicates a change in the amount of photoconductor scraping when a low coverage image print job of 2% is repeated. When the image forming apparatus continuously executes a low coverage print job, as shown by a line L103, the amount of abrasion of the photoconductor falls below the line L102 before the photoconductor reaches its original life. That is, when the image forming apparatus continuously executes a low-coverage print job, the discharge product attached to the photoconductor cannot be sufficiently removed before the photoconductor reaches its original life. An image defect (image flow) occurs.

  As described above, when a photoconductor whose surface is hard to be scraped is used, the number of printed sheets and the frequency of occurrence of image flow are worse than before. Therefore, it is necessary for the image forming apparatus to actively scrape the photoconductor when continuously printing low coverage images.

  As a method of increasing the abrasion amount of the photosensitive member, a method of hitting a patch (supplying a predetermined amount of toner from the developing device to the photosensitive member) can be considered. However, this method has a problem in that the toner consumption increases and the life of the toner bottle is reduced.

  SUMMARY An advantage of some aspects of the invention is that it provides an image forming apparatus and an image forming apparatus control program capable of preventing the occurrence of an image flow.

An image forming apparatus according to an aspect of the present invention includes an image carrier that is rotationally driven, a generation unit that generates an image pattern to form an image, and a surface of the image carrier that is irradiated with a light beam. An irradiating means for forming an electrostatic latent image on the surface of the image carrier; and a developing means for forming a toner image on the surface of the image carrier by developing the electrostatic latent image formed by the irradiating means with toner; When the amount of toner used when developing the electrostatic latent image formed by the irradiation unit is smaller than the required value, the process condition is changed from the process condition for forming the image of the image pattern. And a transfer belt to which a toner image formed on the surface of the image carrier is transferred, and the shaving means changes the process conditions of the transfer belt. , Sharpening means Contains transcriptional current increasing means for increasing the transfer current flowing between the transfer belt and the image carrier.

  Preferably, the image forming apparatus further includes a charging unit that contacts the image carrier and is applied with an AC voltage to charge the surface of the image carrier, and the shaving unit changes a process condition of the charging unit.

  Preferably, in the image forming apparatus, the shaving unit includes an amplitude increasing unit that increases the amplitude of the AC voltage applied to the charging unit.

  Preferably, in the image forming apparatus, the shaving unit includes a frequency increasing unit that increases the frequency of the AC voltage applied to the charging unit.

  Preferably, in the above image forming apparatus, the charging unit is driven to rotate independently of the rotation of the image carrier, and the shaving unit increases the charging speed that increases the ratio of the rotation speed of the charging unit to the rotation speed of the image carrier. Including means.

  Preferably, in the image forming apparatus, the shaving unit includes a pressure increasing unit that increases a force with which the transfer belt contacts the image carrier.

  Preferably, in the image forming apparatus, the shaving unit includes a belt speed increasing unit that increases a ratio of a rotation speed of the transfer belt to a rotation speed of the image carrier.

  Preferably, in the image forming apparatus, the generation unit generates an image pattern of each of a plurality of pages related to one job, and the scraping unit forms a toner image of one page of the plurality of pages by the developing unit. After that, before the toner image of the next page of one page is formed by the developing means, the amount of scraping the surface of the image carrier is increased.

  Preferably, in the image forming apparatus, the scraping unit increases the amount of scraping the surface of the image carrier after all the toner images related to one job are formed by the developing unit.

  Preferably, in the image forming apparatus, the shaving unit has a process condition for forming an image of an image pattern as the amount of toner used when the electrostatic latent image formed by the irradiation unit is developed by the developing unit is smaller. Increase the amount of change in process conditions from

  Preferably, in the image forming apparatus, a receiving unit that receives image data to be printed, and a toner amount that is used when the electrostatic latent image formed by the irradiation unit is developed by the developing unit is calculated based on the image data. And a calculating means.

  Preferably, in the image forming apparatus, a setting receiving unit that receives a setting of a type of image data to be printed, and an electrostatic latent image formed by the irradiation unit based on the setting received by the setting receiving unit is developed by the developing unit. And a calculation means for calculating the amount of toner used for development.

According to another aspect of the present invention, there is provided a control program for an image forming apparatus including: an image carrier that is rotationally driven; and a transfer belt onto which a toner image formed on the surface of the image carrier is transferred. A generation step for generating an image pattern for image formation; and an irradiation step for forming an electrostatic latent image of the image pattern on the surface of the image carrier by irradiating the surface of the image carrier with a light beam. The electrostatic latent image formed in the irradiation step is developed with toner to form a toner image on the surface of the image carrier, and the electrostatic latent image formed in the irradiation step is developed in the development step. When the amount of toner to be used is smaller than the required value, the amount of scraping the surface of the image carrier by changing the process conditions from the process conditions for forming the image of the image pattern To execute the cutting steps is increased to a computer, in cutting step, by changing the process conditions of the transfer belt, scraping step comprises transferring current increase step of increasing the transfer current flowing between the transfer belt and the image carrier .

  According to the present invention, it is possible to provide an image forming apparatus and an image forming apparatus control program capable of preventing the occurrence of image flow.

1 is a cross-sectional view illustrating a configuration of an image forming apparatus 100 according to a first embodiment of the present invention. FIG. 2 is a block diagram illustrating a control configuration of the image forming apparatus 100 according to the first embodiment of the present invention. FIG. 3 is a side view showing a configuration (configuration of a drum unit) of the photoconductor 104 and the charging roller 105 in the first embodiment of the present invention. It is a graph which shows the relationship between the charging amplitude Vpp and the amount of abrasion of a photoreceptor. 7 is a table showing a relationship among coverage, a reduction amount of a scraping amount, and a charging amplitude Vpp when scraping the surface of the photosensitive member 104 in the first embodiment of the present invention. 4 is a flowchart illustrating an operation in which the image forming apparatus 100 actively scrapes the surface of the photoconductor 104 in the first embodiment of the present invention. FIG. 6 is a cross-sectional view illustrating a configuration in the vicinity of a photoconductor 104 and an intermediate transfer belt 109 in a second embodiment of the present invention. 6 is a graph showing the relationship between the contact force of the intermediate transfer belt 109 and the amount of abrasion of the photoreceptor. 10 is a table showing a relationship among coverage, a reduction amount of a scraping amount, and a contact force of the intermediate transfer belt 109 when scraping the surface of the photosensitive member 104 in the second embodiment of the present invention. 6 is a flowchart illustrating an operation in which the image forming apparatus 100 actively scrapes the surface of the photoreceptor 104 in the second embodiment of the present invention. 6 is a graph showing the amount of abrasion on the surface of the photoreceptor due to an increase in the number of printed sheets. It is a graph which shows the relationship between a coverage and the amount of abrasion of a photoreceptor. 6 is a graph showing a change in the amount of photoconductor abrasion when the image forming apparatus continuously executes low coverage image print jobs.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  In the following embodiment, a case where the image forming apparatus is an MFP will be described. In addition to the MFP, the image forming apparatus may be a facsimile machine, a copier, a printer, or the like.

  [First Embodiment]

  First, the configuration of the image forming apparatus in the present embodiment will be described.

  FIG. 1 is a cross-sectional view showing a configuration of an image forming apparatus 100 according to the first embodiment of the present invention.

  Referring to FIG. 1, image forming apparatus 100 in the present embodiment is an MFP, and mainly includes a paper transport unit 10, a toner image forming unit 20, and a fixing device 30.

  The paper transport unit 10 includes a paper feed tray 102, a paper feed roller 103a, transport rollers 103b, 103c, 103e, 103f, and 103g, a paper discharge roller 103d, and a paper discharge tray 115. The paper feed tray 102 accommodates paper for forming an image. There may be a plurality of paper feed trays 102. The paper feed roller 103a is provided between the paper feed tray 102 and the transport path TR1. Each of the transport rollers 103b and 103c is provided along the transport path TR1. Each of the transport rollers 103e, 103f, and 103g is provided along the transport path TR2. The paper discharge roller 103d is provided in the most downstream portion of the transport path TR1. The paper discharge tray 115 is provided at the top of the image forming apparatus main body 101.

  The toner image forming unit 20 synthesizes four color images of Y (yellow), M (magenta), C (cyan), and K (black) by a so-called tandem method, and transfers the toner image onto a sheet. The toner image forming unit 20 includes four sets of image forming units 21Y, 21M, 21C, and 21K, an exposure device (laser unit) 106 (an example of an irradiation unit), an intermediate transfer belt 109, and primary transfer rollers 108a and 108b. , 108c and 108d, a secondary transfer roller 111, a cleaning device 112, a density detection sensor 118, and the like. The intermediate transfer belt 109, the primary transfer rollers 108a, 108b, 108c, and 108d, and the secondary transfer roller 111 constitute a transfer device.

  Each of the image forming units 21Y, 21M, 21C, and 21K is juxtaposed directly below the intermediate transfer belt 109. The image forming unit 21Y includes a photoreceptor 104a, a charging roller 105a, a developing device 107a, a cleaning device 110a, and the like. The photoconductor 104a is rotationally driven in a direction indicated by an arrow AR1 in FIG. Around the photoconductor 104a, a charging roller 105a, a developing device 107a, and a cleaning device 110a are arranged.

  The image forming unit 21M includes a photoreceptor 104b, a charging roller 105b, a developing device 107b, a cleaning device 110b, and the like. The image forming unit 21C includes a photoreceptor 104c, a charging roller 105c, a developing device 107c, a cleaning device 110c, and the like. The image forming unit 21K includes a photoreceptor 104d, a charging roller 105d, a developing device 107d, a cleaning device 110d, and the like. Each of the image forming units 21M, 21C, and 21K has the same configuration as the image forming unit 21Y.

  The exposure device 106 is provided below the image forming units 21Y, 21M, 21C, and 21K. The intermediate transfer belt 109 is provided below the image forming units 21Y, 21M, 21C, and 21K. The intermediate transfer belt 109 has an annular shape and rotates in the direction indicated by the arrow AR2 in FIG. Each of the primary transfer rollers 108a, 108b, 108c, and 108d is opposed to each of the photoreceptors 104a, 104b, 104c, and 104d with the intermediate transfer belt 109 interposed therebetween. The secondary transfer roller 111 is in contact with the intermediate transfer belt 109 in the transport path TR1. The distance between the secondary transfer roller 111 and the intermediate transfer belt 109 can be adjusted by a pressure contact / separation mechanism (not shown). The cleaning device 112 is provided in the vicinity of the intermediate transfer belt 109.

  The fixing device 30 includes a heating roller 116 and a pressure roller 117. The fixing device 30 fixes the toner image on the sheet by conveying the sheet carrying the toner image along the conveying path TR1 while holding the sheet carrying the toner image by the nip portion between the heating roller 116 and the pressure roller 117.

  When the image forming apparatus 100 receives a print job execution instruction, a recording medium such as a sheet stored in the sheet feed tray 102 is taken out one by one by the sheet feed roller 103a and is conveyed by each of the conveyance rollers 103b and 103c. It is conveyed along TR1. In parallel with the sheet feeding, the surfaces of the YMCK-colored photoreceptors 104a, 104b, 104c, and 104d are charged by the YMCK-colored charging rollers 105a, 105b, 105c, and 105d, and then the exposure device 106. The exposure based on the image data is performed by the light beam emitted from. As a result, an electrostatic latent image of an image pattern for image formation is formed on the surface of each of the photoreceptors 104a, 104b, 104c, and 104d. These electrostatic latent images are developed with toner by the developing devices 107a, 107b, 107c, and 107d for each color of YMCK. Thereby, a toner image is formed on the surface of each of the photoreceptors 104a, 104b, 104c, and 104d. These toner images are transferred onto the intermediate transfer belt 109 by a transfer bias applied to each of the primary transfer rollers 108a, 108b, 108c, and 108d of each color of YMCK. As a result, toner images of each color of YMCL are formed on the intermediate transfer belt 109 in an overlapping manner. Image forming parameters such as development bias are adjusted according to the detection result of the density detection sensor 118. Thereby, the toner density is stabilized. Residual toner on the surface of each of the photoreceptors 104a, 104b, 104c, and 104d is removed by each of the YMCK cleaning devices 110a, 110b, 110c, and 110d.

  The toner image on the intermediate transfer belt 109 is transferred onto a recording medium conveyed between the intermediate transfer belt 109 and the secondary transfer roller 111 by a secondary transfer bias applied to the secondary transfer roller 111. Thereafter, residual toner on the intermediate transfer belt 109 is removed by the cleaning device 112.

  The toner image formed on the recording medium is fixed to the recording medium by applying heat and pressure when the recording medium passes through the fixing device 30. The recording medium on which the toner image is fixed is discharged to the discharge tray 115 by the discharge roller 103d.

  When the toner in each of the developing devices 107a, 107b, 107c, and 107d decreases due to image formation, the toner stored in each of the YMCK color toner bottles 114a, 114b, 114c, and 114d is transferred to the developing device 107a. , 107b, 107c, and 107d. Each of the toner bottles 114a, 114b, 114c, and 114d is removable, and when the toner in any one of the toner bottles 114a, 114b, 114c, and 114d runs out, the user replaces the toner bottle. To do. As a result, the toner is continuously supplied to the image forming apparatus 100.

  When forming images on both sides of the recording medium, the recording medium is introduced into the transport path TR2 by rotating the paper discharge roller 103d in reverse after the recording medium passes through the fixing device 30. The recording medium is transported by each of the transport rollers 103e, 103f, and 103g, and is again introduced into the transport path TR1. Then, a toner image is formed on the back surface of the recording medium, and the recording medium is discharged to the discharge tray 115 by the discharge roller 103d.

  Thereafter, the photosensitive member, the charging roller, and the developing device in any image forming unit among the image forming units 21Y, 21M, 21C, and 21K are replaced with the photosensitive member 104 (an example of an image carrier) and the charging roller 105 ( An example of a charging unit) and a developing device 107 (an example of a developing unit) may be described. Of the primary transfer rollers 108a, 108b, 108c, and 108d, any primary transfer roller may be referred to as a primary transfer roller 108.

  FIG. 2 is a block diagram showing a control configuration of the image forming apparatus 100 according to the first embodiment of the present invention.

  Referring to FIG. 2, the image forming apparatus 100 includes a control unit 200, a charge control unit 211, an exposure control unit 212, a development control unit 213, a transfer control unit 214, a fixing control unit 215, and image processing. 216 and a print job receiving unit 217.

  The control unit 200 includes a CPU (Central Processing Unit) 201, a ROM (Read Only Memory) 202, and a RAM (Random Access Memory) 203. Each of the CPU 201, ROM 202, RAM 203, charging control unit 211, exposure control unit 212, development control unit 213, transfer control unit 214, fixing control unit 215, image processing unit 216, print job reception unit 217, and density detection sensor 118 Are connected to each other.

  The CPU 201 controls the operation of the entire image forming apparatus 100. The CPU 201 performs processing based on the control program.

  The ROM 202 stores a control program executed by the CPU 201 and the like.

  A RAM 203 is a working memory for the CPU 201 and temporarily stores data regarding various jobs.

  The charging controller 211 controls the operation of the charging roller 105 such as the voltage applied to the charging roller 105 and the rotation speed of the charging roller 105.

  The exposure control unit 212 controls the operation of the exposure apparatus 106 such as the intensity of exposure light and the timing of irradiating each of the photoconductors 104 with exposure light.

  The development control unit 213 controls operations of the development device 107 such as a development bias of the development device 107, toner replenishment to the development device 107, and a rotation speed of the development roller 131 (FIG. 1) in the development device 107. The developing roller 131 may not be driven to rotate by the development control unit 213 but may rotate following the rotation of the photosensitive member 104.

  The transfer control unit 214 includes a primary transfer roller 108, an intermediate transfer, such as a primary transfer bias, a primary transfer current, a pressure contact force of the primary transfer roller 108 to the intermediate transfer belt 109, a rotation speed of the intermediate transfer belt 109, and a secondary transfer bias. Each operation of the belt 109 and the secondary transfer roller 111 is controlled.

  The fixing control unit 215 controls the operation of the fixing device 30 such as the temperature of the heating roller 116 and the rotation speed of the pressure roller 117.

  The image processing unit 216 generates an image pattern for image formation by performing RIP (Raster Image Processor) processing on the image data of the print job.

  The print job accepting unit 217 accepts settings relating to a print job, image data, or the type of image data (photos, characters, etc.).

  FIG. 3 is a side view showing the configuration of the photoconductor 104 and the charging roller 105 (configuration of the drum unit) in the first embodiment of the present invention.

  Referring to FIG. 3, the charging roller 105 includes a core bar 141a and an elastic body layer 141b. The cored bar 141a is made of, for example, stainless steel. The cored bar 141a has a cylindrical shape and a diameter of 6 mm. The elastic body layer 141b is formed on the outer periphery of the cored bar 141a. The elastic body layer 141b is made of, for example, a conductive resin. The elastic body layer 141b has a hollow cylindrical shape and has a thickness of 3 mm.

  Both ends of the cored bar 141a are held by a bearing 142 in a rotatable state. One end of the bearing 142 is urged by a spring 143 fixed to the image forming apparatus main body 101. As a result, the charging roller 105 is in contact with the photosensitive member 104 with a predetermined pressing force. A charging bias is applied to the core bar 141a from the power source S1. The charging bias is obtained by superimposing a DC voltage of −600 V on an AC voltage having a frequency of 2 kHz and an amplitude of 1200 V, for example.

  FIG. 4 is a graph showing the relationship between the charging amplitude Vpp and the amount of abrasion of the photoreceptor.

  Referring to FIG. 4, the charging amplitude Vpp corresponds to the amplitude of the AC voltage of the charging bias. From this table, it can be seen that, by increasing the charging amplitude Vpp, the amount of discharge to the photoconductor 104 increases and the amount of abrasion on the surface of the photoconductor 104 increases.

  In view of this, the image forming apparatus 100 according to the present embodiment sets the charging amplitude Vpp to a normal value at a required timing when a predetermined number of images are printed with a coverage smaller than the standard coverage (low coverage image). By increasing from (process conditions for forming an image of an image pattern), the surface of the photoconductor 104 is actively shaved, and the amount of shaving the surface of the photoconductor 104 is increased.

  The image forming apparatus 100 may calculate the coverage based on the image data received by the print job receiving unit 217. The image forming apparatus 100 may calculate the coverage based on the setting of the type of image data received by the print job receiving unit 217. For example, when the type of image data of a print job is set to characters, the image forming apparatus 100 may determine that all images of the print job are low coverage.

  FIG. 5 is a table showing the relationship among the coverage, the decrease in the amount of shaving, and the charging amplitude Vpp when shaving the surface of the photoconductor 104 in the first embodiment of the present invention.

  Referring to FIG. 5, here, the standard coverage is assumed to be 10%, and the photoreceptor 104 after printing 100 images with the coverages of 0%, 2%, 4%, 6%, and 8%, respectively. This shows the decrease in the amount of shaving. The reduction amount of the scraping amount is a reduction amount of the scraping amount based on the scraping amount of the photoconductor 104 after printing 100 images with the standard coverage. From this table, it can be seen that the amount of shaving of the photoconductor 104 decreases as the coverage decreases, and the image flow tends to occur.

  As shown in the table of FIG. 5, the image forming apparatus 100 preferably sets the charging amplitude Vpp when the surface of the photoconductor 104 is scraped to a larger value as the coverage becomes smaller than the standard coverage. As a result, it is possible to appropriately compensate for the decrease in the amount of photoconductor shaving due to continued low coverage printing.

  The timing for actively scraping the surface of the photoconductor 104 is preferably the timing between papers or after all the toner images related to the print job are formed (that is, after the end of the print job). The inter-paper timing is a timing after forming a toner image of one page of a plurality of pages related to one job and before forming a toner image of the next page.

  When the surface of the photosensitive member 104 is actively scraped at the timing between sheets, the time for actively scraping the photosensitive member 104 is not limited to the time required for execution of the print job (for example, after completion of the print job or image formation). Since it is not necessary to secure the device immediately after the apparatus is turned on, the time until the start of the print job can be shortened. When the surface of the photoconductor 104 is actively scraped at the timing after the end of the print job, there is a difference between the process conditions for actively scraping the photoconductor and the process conditions for executing a normal print job. Even when large, the process conditions can be easily changed.

  FIG. 6 is a flowchart showing an operation in which the image forming apparatus 100 actively scrapes the surface of the photoconductor 104 in the first exemplary embodiment of the present invention.

  Referring to FIG. 6, upon receiving a print job execution instruction, CPU 201 of image forming apparatus 100 calculates a print image coverage in the received print job, and determines whether the print image coverage is equal to or less than a predetermined value. Is discriminated (S1).

  If it is determined in step S1 that the coverage of the print image is equal to or less than the predetermined value (YES in S1), the CPU 201 increments the count of the low coverage print pages by 1, and the count of the low coverage print pages is predetermined. It is determined whether or not the value has reached or exceeded (S3).

  When it is determined in step S1 that the coverage in the received print job is greater than the predetermined value (No in S1), or in step S3, it is determined that the count number of the low coverage print pages is less than the predetermined value (S3). No), the CPU 201 proceeds to the process of step S13.

  If it is determined in step S3 that the count number of low-coverage printed pages is equal to or greater than a predetermined value (YES in S3), the CPU 201 performs a process of actively scraping the surface of the photoconductor 104 (S9). Specifically, the CPU 201 increases the charging amplitude Vpp of the charging roller 105 from the normal value according to the coverage of the received print job (S5). Next, the CPU 201 rotates the photosensitive member 104 in a state where the charging amplitude Vpp of the charging roller 105 is increased from a normal value, thereby rotating the charging roller 105 following the photosensitive member 104 (S7).

  Following the process of step S9, the CPU 201 returns the charging amplitude Vpp to a normal value (S11), restarts the print job (S13), and ends the process.

  According to the present embodiment, when the surface of the photoconductor 104 is not sufficiently scraped due to continuous printing of images with low coverage, the surface of the photoconductor 104 is increased by increasing the charging amplitude Vpp of the charging roller. Is actively scraped. As a result, the discharge products adhering to the surface of the photoconductor 104 can be sufficiently removed without increasing the toner consumption, and the occurrence of image defects can be suppressed.

  Note that the image forming apparatus 100 may increase the amount of the surface of the photosensitive member 104 by changing the process conditions of the charging roller 105 other than the charging amplitude Vpp. For example, the image forming apparatus 100 may increase the frequency of the AC voltage applied to the charging roller 105 or may increase the ratio of the rotation speed of the charging roller 105 to the rotation speed of the photoconductor 104 (in this case). The charging roller 105 is driven to rotate independently of the rotation of the photoconductor 104). In these cases as well, the amount of discharge to the photoconductor 104 per unit time increases, so that the photoconductor scraping amount can be increased in the same manner as when the charging amplitude Vpp is increased.

  [Second Embodiment]

  FIG. 7 is a cross-sectional view showing a configuration in the vicinity of the photoreceptor 104 and the intermediate transfer belt 109 in the second embodiment of the present invention.

  Referring to FIG. 7, the primary transfer roller 108, the intermediate transfer belt 109, and the secondary transfer roller 111 (FIG. 1) constitute a transfer device. The transfer device is driven to rotate at the same time as the photosensitive member 104 starts to rotate. When the transfer device starts to rotate, the intermediate transfer belt 109 is separated from the photosensitive member 104. After the rotational driving of the transfer device is started, after the photosensitive member 104 and the intermediate transfer belt 109 reach a predetermined speed, the intermediate transfer belt 109 is brought into contact with the photosensitive member 104 by the primary transfer roller 108. When the series of operations relating to the print job is completed and the image formation for copying or printing is completed, the intermediate transfer belt 109 is separated from the photoreceptor 104.

  Here, when the primary transfer roller 108 is urged toward the intermediate transfer belt 109 by the spring 143, the free length of the spring 143 is changed to contact and separate the photosensitive member 104 and the intermediate transfer belt 109. May be switched. The contact and separation between the photosensitive member 104 and the intermediate transfer belt 109 may be switched by an eccentric cam, an actuator, or a gear drive.

  FIG. 8 is a graph showing the relationship between the contact force of the intermediate transfer belt 109 and the amount of abrasion of the photosensitive member.

  Referring to FIG. 8, the contact force of intermediate transfer belt 109 corresponds to the force with which intermediate transfer belt 109 contacts photoconductor 104. From this table, it can be seen that increasing the contact force of the intermediate transfer belt 109 increases the force applied to the photoconductor 104 and increases the amount of abrasion on the surface of the photoconductor 104.

  Therefore, the image forming apparatus 100 according to the present embodiment actively scrapes the surface of the photoreceptor 104 by increasing the contact force of the intermediate transfer belt 109 at a required timing when the coverage is smaller than the standard coverage. Then, the amount by which the surface of the photoconductor 104 is scraped is increased from a normal value (process conditions for forming an image of an image pattern).

  FIG. 9 is a table showing the relationship among the coverage, the decrease in the amount of scraping, and the contact force of the intermediate transfer belt 109 when scraping the surface of the photosensitive member 104 in the second embodiment of the present invention.

  Referring to FIG. 9, the relationship between the coverage and the reduction amount of the shaving amount is the same as in the case of FIG. 5. As shown in the table of FIG. 8, the image forming apparatus 100 preferably sets the contact force of the intermediate transfer belt 109 when scraping the surface of the photoreceptor 104 to a larger value as the coverage becomes smaller than the standard coverage. As a result, it is possible to appropriately compensate for the decrease in the amount of photoconductor shaving due to continued low coverage printing.

  The timing for actively scraping the surface of the photoconductor 104 is preferably the timing between papers or after all the toner images related to the print job are formed (that is, after the end of the print job).

  FIG. 10 is a flowchart showing an operation in which the image forming apparatus 100 actively scrapes the surface of the photosensitive member 104 in the second embodiment of the present invention.

  Referring to FIG. 10, upon receiving a print job execution instruction, CPU 201 of image forming apparatus 100 calculates a print image coverage in the received print job, and determines whether the print image coverage is equal to or less than a predetermined value. Is discriminated (S101).

  If it is determined in step S101 that the coverage of the print image is equal to or smaller than the predetermined value (YES in S101), the CPU 201 increments the count of the low coverage print pages by 1, and the count of the low coverage print pages is predetermined. It is determined whether or not the value has reached or exceeded (S103).

  When it is determined in step S101 that the coverage in the accepted print job is larger than the predetermined value (No in S101), or in step S103, it is determined that the count number of the low coverage print pages is less than the predetermined value (S103). No), the CPU 201 proceeds to the process of step S113.

  If it is determined in step S103 that the count number of low-coverage print pages has reached or exceeded a predetermined value (YES in S103), the CPU 201 performs a process of actively scraping the surface of the photoconductor 104 (S109). Specifically, the CPU 201 increases the contact force of the intermediate transfer belt 109 from the normal value according to the coverage of the received print job (S105). Next, the CPU 201 rotates the photosensitive member 104 and the intermediate transfer belt 109 with the contact force of the intermediate transfer belt 109 increased from the normal value (S107).

  Subsequent to step S109, the CPU 201 returns the contact force of the intermediate transfer belt 109 to a normal value (S111), restarts the print job (S113), and ends the process.

  Since the configuration and operation of image forming apparatus 100 other than those described above are the same as those in the first embodiment, description thereof will not be repeated.

  According to the present embodiment, when the surface of the photoconductor 104 is not sufficiently scraped due to continuous print jobs with low coverage, the surface of the photoconductor 104 is increased by increasing the contact force of the intermediate transfer belt 109. Is actively scraped. As a result, the discharge products adhering to the surface of the photoconductor 104 can be sufficiently removed without increasing the toner consumption, and the occurrence of image defects can be suppressed.

  Note that the image forming apparatus 100 may increase the amount of the surface of the photosensitive member 104 by changing the transfer belt process conditions other than the contact force of the intermediate transfer belt 109. For example, the image forming apparatus 100 may increase the primary transfer current flowing between the intermediate transfer belt 109 and the photoconductor 104, or increase the ratio of the rotation speed of the intermediate transfer belt 109 to the rotation speed of the photoconductor 104. You may let them.

  When the primary transfer current is increased, the amount of abrasion of the photosensitive member 104 increases. When the primary transfer current is increased, the attractive force between the intermediate transfer belt 109 and the photosensitive member 104 increases due to electrostatic adsorption. This is because the force that the intermediate transfer belt 109 applies to the photosensitive member 104 increases. When the rotational speed of the intermediate transfer belt 109 is increased with respect to the rotational speed of the photoconductor 104, the amount of abrasion of the photoconductor 104 increases because the contact area of the intermediate transfer belt 109 to the photoconductor 104 per unit time increases. It is to do. Therefore, also in these cases, the amount of abrasion of the photosensitive member can be increased in the same manner as when the contact force of the intermediate transfer belt 109 is increased.

  [Others]

  The present invention only needs to increase the amount of scraping of the surface of the image carrier by changing the process conditions from the process conditions for forming the image of the image pattern, except for the charging roller 105 and the intermediate transfer belt 109. The process condition of the member may be changed. In this case, the smaller the coverage, the larger the change amount of the process condition from the process condition when forming the image of the image pattern.

  The image forming apparatus has a configuration in which the toner image formed on the surface of the photoconductor is directly transferred to the recording medium instead of the configuration in which the toner image formed on the surface of the photoconductor is transferred to the recording medium via the intermediate transfer belt. There may be.

  The above-described embodiments can be combined as appropriate. For example, the method of changing the process condition of the charging roller 105 of the first embodiment and the method of changing the process condition of the intermediate transfer belt 109 of the second embodiment may be combined.

  The processing in the above-described embodiment may be performed by software or by using a hardware circuit. It is also possible to provide a program for executing the processing in the above-described embodiment, and record the program on a recording medium such as a CD-ROM, a flexible disk, a hard disk, a ROM, a RAM, or a memory card and provide it to the user. You may decide to do it. The program is executed by a computer such as a CPU. The program may be downloaded to the apparatus via a communication line such as the Internet.

  The above-described embodiments and examples are to be considered in all respects as illustrative and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

DESCRIPTION OF SYMBOLS 10 Paper conveyance part 20 Toner image formation part 21C, 21K, 21M, 21Y Image formation unit 30 Fixing apparatus 100 Image formation apparatus 101 Image formation apparatus main body 102 Paper feed tray 103a Paper feed roller 103b, 103e Conveyance roller 103d Paper discharge roller 104, 104a, 104b, 104c, 104d Photosensitive member (an example of an image carrier)
105, 105a, 105b, 105c, 105d Charging roller (an example of charging means)
106 Exposure apparatus (an example of irradiation means)
107, 107a, 107b, 107c, 107d Developing device (an example of developing means)
108, 108a, 108b, 108c, 108d Primary transfer roller 109 Intermediate transfer belt (an example of a transfer belt)
110a, 110b, 110c, 110d Cleaning device 111 Secondary transfer roller 112 Cleaning device 114a, 114b, 114c, 114c Toner bottle 115 Discharge tray 116 Heating roller 117 Pressure roller 118 Concentration detection sensor 131 Developing roller 141a Core metal 141b Elastic body Layer 142 Bearing 143 Spring 200 Controller 201 CPU (Central Processing Unit)
202 ROM (Read Only Memory)
203 RAM (Random Access Memory)
211 Charging Control Unit 212 Exposure Control Unit 213 Development Control Unit 214 Transfer Control Unit 215 Fixing Control Unit 216 Image Processing Unit 217 Print Job Accepting Unit TR1, TR2 Transport Path

Claims (13)

A rotationally driven image carrier;
Generating means for generating an image pattern for image formation;
Irradiation means for forming an electrostatic latent image of the image pattern on the surface of the image carrier by irradiating the surface of the image carrier with a light beam;
Developing means for forming a toner image on the surface of the image carrier by developing the electrostatic latent image formed by the irradiation means with toner;
When the amount of toner used when developing the electrostatic latent image formed by the irradiation unit is smaller than a required value, the process condition is changed from the process condition when forming the image of the image pattern. By changing, a shaving means that increases the amount of shaving the surface of the image carrier ,
A transfer belt to which a toner image formed on the surface of the image carrier is transferred,
The shaving means changes a process condition of the transfer belt,
The image forming apparatus , wherein the shaving unit includes a transfer current increasing unit that increases a transfer current flowing between the transfer belt and the image carrier . A charging means for contacting the image carrier, to which an AC voltage is applied, and charging the surface of the image carrier;
The image forming apparatus according to claim 1, wherein the shaving unit changes a process condition of the charging unit.   The image forming apparatus according to claim 2, wherein the shaving unit includes an amplitude increasing unit that increases an amplitude of an AC voltage applied to the charging unit.   The image forming apparatus according to claim 2, wherein the shaving unit includes a frequency increasing unit that increases a frequency of an AC voltage applied to the charging unit. The charging means is rotationally driven independently of the rotation of the image carrier,
The image forming apparatus according to claim 2, wherein the shaving unit includes a charging speed increasing unit that increases a ratio of a rotational speed of the charging unit to a rotational speed of the image carrier. Said scraping means includes a pressure increasing means for increasing the force which the transfer belt is in contact with said image bearing member, an image forming apparatus according to claim 1. It said scraping means includes a belt speed increasing means for increasing the ratio of the rotational speed of the transfer belt with respect to the rotational speed of the image bearing member, an image forming apparatus according to claim 1. The generation unit generates an image pattern of each of a plurality of pages related to one job,
The shaving means is after forming the toner image of one page of the plurality of pages by the developing means and before forming the toner image of the next page of the one page by the developing means. to increase the amount of scraping the surface of the image bearing member, an image forming apparatus according to any one of claims 1-7. It said scraping means, after forming all the toner image for one job in the developing unit, increases the amount of scraping the surface of the image bearing member, an image forming apparatus according to any one of claims 1-8 . The shaving means has a process condition from a process condition for forming an image of the image pattern as the amount of toner used when developing the electrostatic latent image formed by the irradiating means is reduced by the developing means. of the increased amount of change, the image forming apparatus according to any one of claims 1-9. Receiving means for receiving image data to be printed;
Based on the image data, an electrostatic latent image formed by the irradiation unit further comprising a calculation means for calculating an amount of toner used for development by said developing means, any claim 1-10 An image forming apparatus according to claim 1. Setting accepting means for accepting the setting of the type of image data to be printed;
And a calculating unit that calculates a toner amount used when the electrostatic latent image formed by the irradiation unit is developed by the developing unit based on the setting received by the setting receiving unit. Item 11. The image forming apparatus according to any one of Items 1 to 10 . A control program for an image forming apparatus comprising: an image carrier that is rotationally driven; and a transfer belt to which a toner image formed on the surface of the image carrier is transferred .
A generation step for generating an image pattern for image formation;
Irradiating the surface of the image carrier with a light beam to form an electrostatic latent image of the image pattern on the surface of the image carrier; and
A developing step of forming a toner image on the surface of the image carrier by developing the electrostatic latent image formed in the irradiation step with toner;
When the amount of toner used when developing the electrostatic latent image formed in the irradiation step is smaller than a required value, the process condition is changed from the process condition when forming the image of the image pattern. By changing, causing the computer to execute a shaving step that increases the amount of shaving the surface of the image carrier ,
In the shaving step, the process condition of the transfer belt is changed,
The control program for an image forming apparatus, wherein the shaving step includes a transfer current increasing step for increasing a transfer current flowing between the transfer belt and the image carrier .

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