JP2012123352A - Image forming apparatus and method for driving image carrier - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming apparatus in which a reverse rotation operation of an image carrier with a printing operation temporarily interrupted is conducted merely if necessary, in performing printing continuously on a large number of paper sheets.SOLUTION: An image forming apparatus comprises: an image carrier carrying an image corresponding to an original image, formed with a developing material, and rotatively driven; a transferring member for transferring onto a transfer medium the image which is formed with the developing material on the image carrier; and a cleaning part for removing the developing material remaining on the image carrier after transfer by the transferring member. When a number of sheets to be continuously printed in one printing job exceeds a first number of sheets, a printing rate of an original image of the printing job is calculated, so as to determine, on the basis of the calculated printing rate, whether or not the image carrier is to be rotated reversely to its rotation for the transfer, and the image carrier is driven to rotate reversely with the currently executed printing job temporarily interrupted in accordance with a determination result.

Description

  Embodiments described herein relate generally to an image forming apparatus and an image carrier driving method of the image forming apparatus.

  In an electrophotographic image forming apparatus, a toner image is formed on the surface of an image carrier and transferred to a transfer medium such as paper. Then, the toner remaining on the surface of the image carrier without being transferred and other adhering substances are removed by a cleaning blade or the like.

  In such an image forming apparatus, when printing is repeated, toner or the like adheres to the vicinity of the edge of the blade, resulting in problems such as poor cleaning and degradation of image quality. For this reason, the image carrier is rotated backwards every time the job is completed or at a timing according to the number of printed sheets, the amount of print information, etc. And the deterioration of image quality.

  However, when a large amount of printing is continuously performed with one print job, there is a possibility that problems such as defective cleaning may occur during printing only by performing the reverse rotation operation of the image carrier after the end of the print job. For this reason, it is desirable to temporarily interrupt printing during printing and to perform a reverse rotation operation of the image carrier.

  JP 2007-199169 A

  On the other hand, even if the number of printed sheets is the same, the manner in which deposits are generated near the blade differs depending on the printing rate. That is, even when printing a large number of sheets continuously, depending on the printing rate, there is a case where it is not necessary to sandwich the reverse rotation operation of the image carrier during the job.

  Therefore, the problem to be solved by the present invention is that the reverse rotation of the image carrier is performed based on the relationship between the continuous print number and the print rate when the number of continuous prints in one print job is equal to or greater than a predetermined number. It is an object of the present invention to provide an image forming apparatus capable of determining whether or not to temporarily stop printing during execution of a print job and performing a reverse rotation operation of the image carrier according to the determination result.

  An image forming apparatus according to an embodiment of the present invention includes an input unit that inputs printing conditions including the number of prints, an image carrier that carries an image of a developer corresponding to an input document image, and is driven to rotate. A transfer member for transferring an image formed by a developer on the image carrier to be rotated to a transfer medium; a cleaning unit for removing the developer attached to the image carrier after the transfer by the transfer member; and the input When the number of continuous prints in one print job input from the printing unit is equal to or greater than the first number, the print rate of the original image of the print job is calculated, and the image carrier is attached to the image carrier based on the calculated print rate. A control unit that determines whether or not to rotate in a direction opposite to the rotation at the time of transfer, and temporarily interrupts printing that is being executed according to the determination result to drive the image carrier to rotate in reverse. And

1 is a schematic diagram of an image forming apparatus to which an embodiment of the present invention is applied. 1 is a schematic diagram of an image forming unit to which an embodiment of the present invention is applied. 1 is a block diagram illustrating a processing unit of an image forming apparatus to which an embodiment of the present invention is applied. 6 is a flowchart of the reverse rotation operation of the image carrier in the first embodiment. 6 is a flowchart of the reverse rotation operation of the image carrier in the first embodiment. 6 is a flowchart of the reverse rotation operation of the image carrier in the first embodiment. 10 is a flowchart of a reverse rotation operation of the image carrier in the second embodiment. 10 is a flowchart of a reverse rotation operation of the image carrier in the second embodiment. 10 is a flowchart of a reverse rotation operation of the image carrier in the second embodiment.

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

(First embodiment)
A first embodiment will be described with reference to FIGS. FIG. 1 is a cross-sectional view schematically showing an image forming apparatus to which an embodiment of the present invention is applied.

  The image forming apparatus 1 includes an image reading unit 4 that captures a document as image data, and an image forming unit 2 that outputs the image data as a visible image. The image forming unit 2 includes an image forming unit, a fixing device, and the like described later including an image carrier such as a drum-shaped photoconductor. The image forming apparatus 1 further includes a paper supply unit 3 that can supply an arbitrary size paper P used as an image recording medium to the image forming unit 2.

  The image reading unit 4 includes a light-transmitting document placing table 8, a carriage 9, an exposure lamp 10, a reflecting mirror 11, an imaging lens 12 that converges reflected light, and a CCD (Charge) that converts image information from the reflected light into an analog signal. (Coupled Device) 13 is provided.

  The image forming units 15Y, 15M, 15C, and 15K that contain yellow (Y), magenta (M), cyan (C), and black (K) color materials constituting the image forming unit 2 have the same configuration. In order to perform the same operation, the black (K) image forming unit 15K will be described as an example.

  The image forming unit 15K includes a laser unit 17K that forms an electrostatic latent image on a drum-shaped photoconductor 16K as an image carrier, a charging device 18K, a developing device 19K, and a cleaner 22K that are sequentially arranged around the photoconductor 16K. And a static elimination lamp 23K. The configuration of the image forming unit will be described later.

  The document to be copied is placed on the document table 8 or set on a known automatic document feeder 30 arranged on the table 8. When a copy button (not shown) is pressed, the carriage 9 and the exposure lamp 10 provided on the carriage 9 are provided on the document on the table 8 or the document sent to the exposure device on the table 8 by the document feeder 30. Light is applied from below the document table 8 by the exposure means. Reflected light from the document is guided by the reflecting mirror 11, converged by the imaging lens 12, and the reflected light image is projected onto the CCD 13. The light from the exposure lamp 10 scans the document surface in synchronization with the movement of the carriage 9 (from left to right in FIG. 1). This scanning light is taken into the CCD 13 as image information, outputted as an analog signal, and then converted into a digital signal. Thereafter, the digitized image information is subjected to image processing as necessary, and then transmitted as image data to the laser unit 17K. The image information converted into the digital signal may be temporarily stored in a recording device such as an HDD (Hard Disk Drive).

  When image formation is started in the image forming unit 2, the charging device 18K supplies electric charges to the outer peripheral surface of the rotating photoconductor 16K, and charges the outer surface of the photoconductor 16K to a uniform potential. Next, the laser unit 17K irradiates a laser beam modulated by the image data transmitted from the CCD 13 toward the outer surface of the photosensitive member 16K. This laser beam is scanned along the rotation axis of the drum-shaped photoconductor, and an electrostatic latent image corresponding to image data is formed and held on the outer peripheral surface of the rotating photoconductor 16K. Further, a color material (developer) such as toner is supplied to the outer peripheral surface of the photoreceptor 16K by the developing device 19K, and the electrostatic latent image is converted into a toner image, that is, a developed image.

  The developing device 19K includes a developing roller 24K that is rotatably provided. When the developing roller 24K is disposed so as to face the photoconductor 16K and rotates, toner is supplied to the photoconductor 16K. When a toner image is formed on the outer peripheral surface of the photoreceptor 16K, the toner image is electrostatically transferred to the intermediate transfer belt 14 by the primary transfer roller 20K, which is a transfer member that contacts the photoreceptor 16K via the intermediate transfer belt 14. Transferred to (transfer medium).

  Further, the toner on the photoconductor 16K that has not been transferred is removed by the cleaner 22K located downstream of the primary transfer roller 20K in the rotation direction of the photoconductor 16K, and further, the residual toner on the outer peripheral surface of the photoconductor 16K. The electric charge is removed by the static elimination lamp 23K. In the case of forming a color image, the above operation is similarly performed in the image forming units 15Y, 15M, and 15C. Accordingly, a color image in which the color materials are superimposed and transferred is formed on the intermediate transfer belt 14 described above.

  The toner image transferred to the intermediate transfer belt 14 is electrostatically transferred onto the paper transported from the paper supply unit 3 through the transport path by the secondary transfer roller 25. Thereafter, the paper P on which the toner image is transferred is conveyed to the fixing device 26, and the toner image transferred onto the paper is fixed on the paper by the fixing device 26. The paper on which the toner image has been fixed and the image formation has been completed is discharged onto a paper tray 28 serving as a discharge unit by a transport roller 27.

  In the above description, since the color image printing is described as an object, the transfer medium for the toner image on the photosensitive member is the transfer belt. However, in the case of monochrome printing, the sheet is the transfer medium. Therefore, in this case, the secondary transfer roller is a transfer member.

  The above is the outline of the operation for forming an image on a sheet as a recording medium.

  Next, details of the image forming units 15Y, 15M, 15C, and 15K will be described with reference to FIG. As described above, the Y, M, C, and K image forming units 15Y, 15M, 15C, and 15K have the same configuration.

  FIG. 2 is a cross-sectional view showing the structure of the image forming unit. Since the configurations of the Y, M, C, and K image forming units are the same as described above, the K image forming unit 15K will be described as an example. The cleaner 22K has a cleaning blade 25K. The cleaner 22K removes residual toner on the surface of the photoconductor 16K with a cleaning blade 25K in contact with the surface of the photoconductor 16K.

  Next, a control system of the image forming apparatus 1 according to the present embodiment will be described. FIG. 3 is a block diagram of a control system of the image forming apparatus 1 in the present embodiment.

  The image forming apparatus 1 according to the present exemplary embodiment includes an operation panel 101, the above-described image reading unit 4, the image forming unit 2, the control unit 104, a communication unit 105 that communicates with an external device 115, and the number of print jobs of a plurality of print jobs. A cumulative count unit 106 (first count unit) that counts the totals, an execution number count unit 107 (second count unit) that counts the number of print executions that have been printed during printing, and the like are included. Examples of the external device 115 include a PC (Personal Computer) having a printer driver of the image forming apparatus 1. It is possible to send a print instruction or print conditions such as the number of prints to the image forming apparatus 1 via the printer driver of the external device 115. Accordingly, the external device 115 functions as an input unit of the image forming apparatus 1.

  The operation panel 101 functions as an input unit and is a user interface through which an operation instruction from a user is input. The operation panel 101 includes a hard key such as a numeric keypad, and a display device with a built-in touch panel, for example, a touch key of a display unit such as an LCD (Liquid Crystal Display). The user inputs an operation instruction or printing conditions such as the number of prints via the operation panel 101.

  As described above, the image forming unit 2 includes the Y, M, C, and K image forming units 15Y, 15M, 15C, and 15K. Further, the image forming unit 15Y, 15M, 15C, and 15K includes a drive motor 102 that functions as a drive unit that drives the image carriers.

  The control unit 104 includes a CPU (Central Processing Unit) 110, a RAM (Random Access Memory) 111, and a ROM (Read Only Memory) 112. The CPU 110 is a processor that controls the entire control unit 104. The RAM 111 is a memory that temporarily stores work data and stores reference data. The ROM 112 is a nonvolatile memory, and stores a control program and control data for controlling the image forming apparatus 1. The CPU 110 implements various processes and various functions by operating based on a control program stored in the ROM 112. The control unit 104 also selects a paper cassette for feeding paper to the image forming unit 2. In addition, although CPU110 was used as a processor, the kind of processor is not restricted to this.

  The control unit 104 calculates the document printing rate from the document image data read by the image reading unit 4 or the document image data sent from the external device 115 via the communication unit 105.

  Next, a flow relating to the reverse rotation operation of the image carrier when performing mass printing will be described with reference to the flowchart of FIG. In the present embodiment, the reverse rotation operation of the image carrier is performed when the condition specified when a large amount of printing is performed in one print job and when the total number of print jobs of a plurality of print jobs by the total count unit 106 is calculated. It is performed when the predetermined number is exceeded. The condition specified when performing a large amount of printing is the condition of the printing rate.

  When the printing rate of the original image is high, the amount of toner adhering to the image carrier increases, and the amount of toner that is not transferred to the recording medium and remains on the image carrier increases. The toner tends to accumulate on the surface. If the low printing rate of the original image is low, the amount of toner adhering to the edge surface of the cleaning blade is small, but if printing is performed continuously, the toner deposited on the edge surface of the cleaning blade is not exchanged. For this reason, the state where the toner or the external additive peeled off from the toner surface continues to be stuck in the same portion of the edge surface of the cleaning blade, and the image carrier is damaged by the external additive. Therefore, when a large amount of printing is performed, the condition that the document image has a low printing rate and a high printing rate is defined as a condition for performing the reverse rotation operation of the image carrier.

  Hereinafter, the reverse rotation operation of the image carrier will be described using specific numerical values. In the present embodiment, for example, printing of 500 sheets or more is regarded as a large number of printings. That is, the first number is set to 500. For example, the low printing rate is 3% or less, and the high printing rate is 30% or more. That is, the first value of the printing rate is 3%, and the second value is 30%. Furthermore, the number of prints is larger than 500 sheets, and regardless of the print rate, the printing is interrupted during the printing and the image carrier is reversely rotated when, for example, 1000 sheets or more are printed. That is, the second number is 1000. In addition, the cumulative specified number (third number) of the number of prints of a plurality of print jobs counted by the cumulative count unit 106 is, for example, 1000. Regardless of the above, the first, second and third numbers are arbitrarily selected according to the physical properties of the toner used and the performance of the image carrier and the cleaning blade of the cleaning unit.

  In FIG. 4, when a print job including a print condition such as the number of prints is received via the operation panel 101 of the image forming apparatus 1 or an input unit such as the external device 115 (S101), the control unit 104 displays the received job. It is determined whether the number of printed sheets (that is, the number of continuous printed sheets) is 1000 or more, which is the second number (S102). When the number of continuous prints is less than 1000 (NO in S102), the control unit 104 determines that a plurality of jobs are being printed based on the received print job print count and the cumulative print count counted by the cumulative count unit 106. It is determined whether or not the cumulative number of printed sheets exceeds 1000, which is a predetermined number (S103).

  If it is determined in S103 that the cumulative number of printed sheets exceeds 1000 during printing (YES in S103), the control unit 104 calculates the number of printed sheets in the received print job and the total number of printed sheets reaches 1000. (S111).

Thereafter, printing is executed (S112). After execution of printing, when the execution number of prints counted by the execution number counting unit 107 reaches the number calculated in S111 (S113), the control unit 104 temporarily stops printing, and the drive motor 102 causes the image carrier to be printed. The reverse rotation operation is executed (S114 in FIG. 5).

  In S114, when printing is temporarily interrupted and the image carrier is reversely rotated, the cumulative number of prints counted by the cumulative count unit 106 is reset (S115). When the reverse rotation operation of the image carrier is completed, the control unit 104 resumes printing (S116). Thereafter, the cumulative number counting unit 106 counts the number of printed sheets after the resumption of printing (S117), and the print job ends. In this case, as a matter of course, the execution sheet counter 107 further counts, and when the count value reaches the accepted print execution number, the print job ends.

  If it is determined in S103 of FIG. 4 that the cumulative number of printed sheets does not exceed 1000 during printing (YES in S103), the control unit 104 determines that the continuous print number of the received print job is 500 or more, which is the first number. It is determined whether or not there is (S104). When the control unit 104 determines in S104 that the number of printed sheets is 500 or more (YES in S104), the control unit 104 reads the image data of the document read by the image reading unit 4 or the document sent from the external device 115. The printing rate of the document image is calculated from the image data (S105). Note that the printing rate is the blank area with no printing in the printing area, the printing ratio is 0%, the state that is completely filled with printing is 100%, the printing area in the printing area and non-printing Defined as a percentage of area.

  The control unit 104 determines whether the print rate of the acquired document image is equal to or less than 3%, which is the first value, or equal to or greater than 30%, which is the second value (S106 in FIG. 5). If it is determined in S106 that the document image printing rate is 3% or less, or 30% or more (YES in S106), after executing printing in S107, the control unit 104 continues until the predetermined number of sheets is reached. Print. In the present embodiment, for example, the predetermined number is set to 500. After execution of printing, when the number of prints counted by the execution number counting unit 107 reaches 500 (S108), the process proceeds to S114, printing is temporarily interrupted, and the image carrier is reversely rotated. Thereafter, the operations of S115 to S117 described above are performed, and the print job ends.

  When it is determined in S103 of FIG. 4 that the number of print jobs is less than 500 (NO in S103), or when it is determined in S106 that the printing rate is greater than 3% or less than 30%. The control unit 104 causes the image forming unit 2 to perform printing (S120 in FIG. 5), and after printing, adds the number of prints of the current print job to the total number of printed sheets of the total counting unit 106 (S121). Thereafter, the print job ends.

  If it is determined in S102 in FIG. 4 that the number of continuous prints is 1000 or more (YES in S102), the control unit 104 causes the image forming unit 2 to perform printing (S130 in FIG. 6). After the execution of printing, when the number of print executions counted by the execution number counting unit 107 reaches 500 (S131), the control unit 104 temporarily suspends printing and executes the reverse rotation operation of the image carrier (S132).

  When the reverse rotation operation of the image carrier is executed (S132), the cumulative number of prints counted by the cumulative count unit 106 is reset to an initial value, for example, 0 (S133). Thereafter, the control unit 104 determines whether or not the remaining continuous printing number is 500 or more (S134). If it is determined that the remaining continuous printing number is 500 or more (YES in S134), after resuming printing (S135), the process returns to S131, and the above-described steps are repeated.

If it is determined in S134 that the remaining number of continuous prints is less than 500 (S
134, NO), the process proceeds to the above-described S116 (FIG. 5), the same operation is performed thereafter, and the print job is ended.

  As described above, the reverse rotation operation of the image carrier is controlled based on the number of prints and the print rate of the received print job. Further, the reverse rotation operation is also performed based on the total number of printed sheets of a plurality of jobs. This is because the reverse rotation operation is periodically performed even when a print job that is determined not to need to be reversely rotated in the reverse rotation control of the image carrier that is performed for each print job is performed. This is to prevent poor body cleaning.

  By taking the above-described embodiment, it is possible to prevent image defects due to deposits in the vicinity of the cleaning blade from occurring during printing when printing in large quantities continuously in one print job, and Even when printing a large amount continuously, if it is determined that the reverse rotation operation of the image carrier is not necessary during the printing according to the printing rate, the printing operation is interrupted and the reverse rotation operation of the image carrier is performed. Therefore, it is possible to prevent the image carrier from deteriorating due to unnecessary reverse rotation of the image carrier, and to extend the life of the image carrier. Further, it is possible to prevent an increase in time required for printing due to an unnecessary reverse rotation operation of the image carrier.

  In addition, by taking into account the total number of prints of a plurality of print jobs, it is possible to determine the timing of the reverse rotation operation of the image carrier required not only when the number of continuous prints is large but also by the accumulation of a plurality of print jobs.

  In the above-described embodiment, when the cumulative number of printed sheets reaches a predetermined number, the printing is temporarily interrupted during printing and the image carrier is reversely rotated. The reverse rotation of the image carrier may be performed after completion. For example, when the number of printed sheets is small, even if the cumulative number of printed sheets reaches a predetermined number during printing, it is not necessary to temporarily stop printing and perform the reverse rotation operation of the image carrier. In such a case, it is preferable to perform reverse rotation of the image carrier after completion of the print job, since an increase in time required for printing can be prevented. Therefore, a threshold is set for the number of print jobs, and if the number of prints is equal to or less than the threshold, the image carrier is not rotated in the middle of printing, and the image carrier is rotated after the print job is completed. Is also effective.

(Second Embodiment)
A second embodiment will be described with reference to FIGS. Hereinafter, the same reference numerals are used for the same parts as those of the first embodiment, and only the characteristic parts of the present embodiment will be described.

  In the first embodiment, it is assumed that a document of one page is printed. In the present embodiment, a process for printing a document of a plurality of pages will be described.

  FIG. 5 shows a flowchart when a print request for a document of a plurality of pages in the present embodiment is received. In addition, in operation | movement common with the operation | movement in the flowchart of FIG. 4 of 1st Embodiment, a common code | symbol is attached | subjected and description is omitted.

  If it is determined in S104 in FIG. 7 that the number of printed sheets is 500 or more (YES in S104), the control unit 104 acquires the print ratios of all pages of the multi-page document (S204 in FIG. 9). . Thereafter, the control unit 104 calculates the average of the printing rates of the plurality of pages of the document acquired in S204 (S205). Next, the control unit 104 determines whether the average printing rate calculated in S205 is 3% or less or 30% or more (S206).

  If it is determined in S206 that the average printing rate calculated in S205 is 3% or less or 30% or more (YES in S206), the operations after S107 in the flowchart of the first embodiment are performed as shown in FIG. Do.

  If it is determined in S206 that the printing rate is greater than 3% and less than 30% (NO in S206), similarly, the operations after S120 in the flowchart of the first embodiment are performed.

  According to this embodiment, when printing a large number of documents continuously over a plurality of pages, the reverse rotation operation of the image carrier is controlled based on the number of prints and the printing rate, and the reverse rotation operation of the image carrier is performed. It can be done only when necessary.

Although several embodiments of the present invention have been described, these embodiments are presented by way of example and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the spirit of the invention. These embodiments and modifications thereof are included in the scope and gist of the invention, and are included in the invention described in the claims and the equivalents thereof.

DESCRIPTION OF SYMBOLS 1 Image forming apparatus 2 Image forming part 3 Paper supply part 4 Image reading part 15Y, 15M, 15C, 15K Image forming unit 20K Primary transfer roller 25K Cleaning blade 101 Operation panel 104 Control part 105 Communication part 106 Accumulation count part 107 Execution number count Unit 110 CPU
111 RAM
112 ROM
115 External equipment

Claims (12)

An input section for inputting printing conditions including the number of copies;
An image carrier that carries an image of a developer corresponding to an input document image and is driven to rotate;
A transfer member for transferring an image of the developer on the image carrier to be rotated and driven to a transfer medium;
A cleaning section that removes the developer adhering to the image carrier after the transfer by the transfer member;
When the number of continuous prints in one print job input from the input unit is equal to or more than the first number, the print rate of the original image of the print job is calculated, and the image carrier is based on the calculated print rate A controller that determines whether or not to rotate the rotation opposite to the rotation at the time of the transfer, and temporarily suspends the printing that is being executed according to the determination result to drive the image carrier in a reverse rotation;
An image forming apparatus comprising:   The control unit determines whether the print rate is smaller than the first value or the print rate is less than the first value when the input continuous print number is greater than or equal to the first number and less than the second number. 2. The image forming apparatus according to claim 1, wherein when the second value is larger than the second value, the printing in progress is temporarily interrupted and the image carrier is driven to rotate backward.   The control unit, when the number of continuous prints is equal to or greater than the second number, temporarily suspends printing being performed and drives the image carrier to rotate in reverse regardless of the print rate. Item 3. The image forming apparatus according to Item 2.   A second count unit configured to count the number of printed sheets to be executed in the one print job, and the control unit determines whether the count value of the second count unit is the first number or the first number during printing. 4. The image forming apparatus according to claim 1, wherein the image carrier is reversely rotated when the number of sheets reaches two.   The control unit further includes a first counting unit that counts the total number of printed sheets of the plurality of print jobs, and the control unit is a third unit in which the total number of printed sheets counted by the first counting unit is larger than the first number. 3. The image forming apparatus according to claim 1, wherein the image carrier is driven to rotate in a reverse direction when the number of images reaches a predetermined number.   The control unit further includes a second count unit that counts the number of prints of the print job that is being executed, and the control unit determines that the cumulative number of printed sheets by the first count unit is a third value during the execution of the print job. When the cumulative number of printed sheets by the first counting unit exceeds the third number during execution of the print job, it is determined until the cumulative number of printed sheets reaches the third number. When the count value of the second count unit reaches the required number, the job is temporarily interrupted during execution, or the image carrier is driven to rotate backward after the job being executed is completed. The image forming apparatus according to claim 5.   The image forming apparatus according to claim 5, wherein the cumulative number of printed sheets of the first count unit is reset to an initial value when reverse rotation driving of the image carrier is executed.   When printing a plurality of pages of a document in one print job, the control unit calculates a printing rate of an image of each page of the document, averages the calculated printing rates of each page, and averages the printing rate 3. The image forming apparatus according to claim 1, wherein whether or not the image carrier is driven to rotate backward is determined based on the image quality. Accept print conditions including the print conditions including the number of prints and the document image to be printed,
Based on the print job, the image carrier is rotationally driven to form an image corresponding to the original image with a developer,
Determining whether the number of continuous prints of the received print job is a predetermined number or more;
When the number of printed sheets is equal to or greater than a predetermined number, the printing rate of the original image of the print job is calculated, and the image carrier is rotated during the image formation during printing based on the calculated printing rate. Determining whether or not to reversely rotate, and temporarily interrupting printing in the middle of printing according to the determination result to drive the image carrier to rotate reversely.   When the continuous print number of the print job is equal to or greater than the first number equal to or greater than the predetermined number and less than the second number, the print rate is less than a first value or the print rate is equal to the print rate. Printing is temporarily interrupted when the second value is larger than the first value and the image carrier is rotated in the reverse direction. When the number is equal to or larger than the second number, printing is performed regardless of the printing rate value. 10. The image carrier driving method according to claim 9, wherein the image carrier is reversely rotated to temporarily rotate the image carrier. Count the total number of prints of multiple print jobs,
11. The image carrier driving method according to claim 9, wherein the image carrier is reversely rotated when the counted total number of printed sheets reaches a predetermined number. When printing a plurality of pages of a document in one print job, the printing rate of the image of each page of the document is calculated,
Average the calculated print ratio of each page,
11. The image carrier driving method according to claim 9, wherein it is determined whether to temporarily stop printing and reversely rotate the image carrier based on the average printing rate.

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