JP2009075456A - Image forming device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming device capable of cleaning a transfer roller while suppressing deterioration of the transfer roller. <P>SOLUTION: In the image forming device in which an intermediate transfer belt and a secondary transfer roller are disposed facing each other in a state that they are in contact with each other, and which secondarily transfers a toner image formed on the intermediate transfer belt to a sheet when the sheet passes through the contact part, an amount of adhesion of the residual toner on the secondary transfer roller is detected (S13), and if the amount is larger than a stipulated value (YES in S14), the intermediate transfer belt and the secondary transfer roller are driven rotatably in such a manner that a difference is generated between the velocity of the intermediate transfer belt and that of the secondary transfer roller so that the secondary transfer roller is cleaned (S15). If the amount of adhesion is smaller than the stipulated value (NO in S14), the cleaning is not performed. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a toner image formed on an image carrier when the conveyed sheet passes through a contact portion between an image carrier such as a photosensitive drum or an intermediate transfer belt and a transfer rotary member such as a transfer roller. The present invention relates to an image forming apparatus for transferring a sheet to a sheet.

In such an image forming apparatus, it is desired that all of the toner image formed on the image carrier is transferred to the sheet surface, but the toner (residual toner) remaining on the image carrier without being actually transferred. Exists. Most of the residual toner on the image carrier is cleaned by a cleaner, but part of the toner adheres to the transfer roller.
If the amount of adhesion to the transfer roller is small, even if the residual toner adhering to the transfer roller adheres to the back of the sheet when the sheet passes through the contact portion between the image carrier and the transfer rotator during transfer, It is not reflected until it is dirty. However, if the amount of residual toner attached to the transfer roller increases, the amount of residual toner attached to the back surface of the sheet also increases, and the stain becomes conspicuous, resulting in the back of the sheet being contaminated with toner.

As a method for preventing the back of the sheet from being stained, for example, the image carrier and the transfer roller during the period when the transfer to the sheet is not executed (during non-transfer), and the surface of the image carrier and the transfer roller with a difference in both peripheral speeds. There is a method of cleaning by rotating the surface so as to shift and rubbing the residual toner adhering to the transfer roller. Many transfer rollers use rubber or foamed sponge.
JP-A-8-272233

  However, although the residual toner adhering to the transfer roller can be removed by the above-described cleaning method, since it is always performed during non-transfer, the image carrier and the transfer roller are worn due to friction between the image carrier surface and the transfer roller surface. There is a problem that deterioration tends to proceed, such as scraping. If powdery debris generated by shaving the transfer roller adheres to the image carrier, the image quality may be deteriorated if it cannot be completely cleaned on the image carrier.

  SUMMARY An advantage of some aspects of the invention is that it provides an image forming apparatus capable of cleaning a transfer roller while suppressing deterioration of a transfer rotating body such as a transfer roller. .

  In order to achieve the above object, an image forming apparatus according to the present invention includes a rotating image carrier and a transfer rotator in contact with the surface of the image carrier, and the conveyed sheet is an image carrier and a transfer rotator. An image forming apparatus for transferring a toner image formed on an image bearing member onto the sheet when passing through the contact portion of the image bearing member, and detecting a value indicating the amount of toner adhering to the transfer rotating member When it is determined from the detection means and the detection result by the detection means that the amount of toner adhering to the transfer rotator is equal to or greater than a specified value, the relative speed to the peripheral speed of the image carrier and the transfer rotator is determined during non-transfer. And a control means for controlling the rotation of at least one of the image carrier and the transfer rotator so as to create a speed difference.

As described above, the rotation control is performed so that a relative speed difference is made between the peripheral speeds of the image carrier and the transfer rotator according to the amount of toner adhering to the transfer rotator. Regardless of the configuration in which the rotation is controlled so that a speed difference is always obtained regardless of the above, it is possible to suppress the deterioration of the transfer rotator while cleaning the transfer rotator.
Further, the control means controls the rotation so that the transfer rotator has a lower peripheral speed than the image carrier.

In this way, it is possible to control only the rotation of the transfer rotator without changing the rotation speed of the image carrier, and the control can be simplified.
Further, the control means changes the speed difference in accordance with the amount of toner adhering to the transfer rotator.
In this way, the transfer rotator can be cleaned more effectively.

Here, the control means increases the speed difference as the amount of the adhered toner increases.
In this way, even when a large amount of toner adheres to the transfer rotator, cleaning can be performed more reliably.
The detecting means is a sensor that optically detects the amount of toner adhering to the transfer rotator as a value indicating the amount of toner.

In this way, for example, a known optical sensor can be used, which is advantageous in terms of cost.
In addition, the image forming apparatus includes a cleaning unit that electrostatically cleans the transfer roller surface by applying a transfer voltage to the transfer roller, and the control unit sets the end of cleaning by the cleaning unit as a condition for starting the control. It is characterized by.

  In this way, it becomes possible to perform cleaning by the control means after first performing electrostatic cleaning. For example, if toner can be removed by electrostatic cleaning, cleaning by the control means may not be performed, It becomes possible to further suppress the deterioration of the transfer rotator.

Hereinafter, an embodiment of an image forming apparatus according to the present invention will be described using a tandem color digital printer (hereinafter simply referred to as “printer”) as an example.
<First Embodiment>
(1) Overall Configuration of Printer FIG. 1 is a diagram illustrating the overall configuration of the printer 10.

  As shown in the figure, the printer 10 forms an image by a well-known electrophotographic system, and includes an image processing unit 11, a feeding unit 12, a fixing unit 13, and a control unit 14, and includes a network ( For example, when a print job execution instruction is received from an external terminal device (not shown) connected to a LAN, color image formation of yellow, magenta, cyan, and black is executed based on the instruction. Hereinafter, the reproduction colors of yellow, magenta, cyan, and black are represented as Y, M, C, and K, and Y, M, C, and K are added as subscripts to the numbers of the components related to the reproduction colors.

The image processing unit 11 includes image forming units 20Y, 20M, 20C, and 20K, an intermediate transfer belt 21, and the like corresponding to each of Y to K colors.
The image forming units 20Y to 20K include photosensitive drums 1Y to 1K, chargers 2Y to 2K disposed around the photosensitive drums 1Y to 1K, exposure units 3Y to 3K, developing units 4Y to 4K, primary transfer rollers 5Y to 5K, and photosensitive drums. Cleaners 6Y to 6K for cleaning the toner, and Y to K color toner images are formed on the photosensitive drums 1Y to 1K. The exposure unit 3Y includes a laser diode, a polygon mirror, a scanning lens, and the like for deflecting a laser beam emitted from the laser diode and exposing and scanning the surface of the photosensitive drum 1Y in the main scanning direction. This configuration is the same for the other exposure units 3M to 3K.

The intermediate transfer belt 21 is an endless belt, is stretched around the driving roller 22 and the driven roller 23, and is rotationally driven in the direction of the arrow in FIG.
The feeding unit 12 includes a paper feed cassette 31 that stores paper S as a recording sheet, a feed roller 32 that feeds the paper S in the paper feed cassette 31 one by one onto the transport path 37, and the fed paper. A pair of conveying rollers 33 for conveying S, a pair of timing rollers 34 for taking the timing of sending to the secondary transfer position 351, and a secondary pressed against the drive roller 22 across the intermediate transfer belt 21 at the secondary transfer position 351. A transfer roller 35 and the like are provided.

  The secondary transfer roller 35 as a transfer rotator is, for example, a conductive elastic roller in which an ion conductive material is added to NBR rubber and foamed. The secondary transfer roller 35 receives the driving force of the secondary transfer roller driving motor 52 and receives the driving force from the secondary transfer roller driving motor 52. It is driven to rotate in the direction of the arrow. A secondary transfer voltage output from the secondary transfer voltage output unit 40 is applied to the secondary transfer roller 35. As a result, an electrostatic force for secondary transfer acts between the secondary transfer roller 35 and the drive roller 22.

The fixing unit 13 includes a fixing roller and a pressure roller, and heats and presses the sheet S at a predetermined fixing temperature to fix the toner image.
The control unit 14 converts an image signal from an external terminal device into a digital signal for Y to K colors, and generates a drive signal for driving the laser diodes of the exposure units 3Y to 3K. The laser diodes of the exposure units 3Y to 3K are driven by the generated drive signal, the laser beam L is emitted, and the photosensitive drums 1Y to 1K are exposed and scanned.

Before the exposure scanning, the photosensitive drums 1Y to 1K are uniformly charged by the chargers 2Y to 2K, and electrostatic latent images are formed on the photosensitive drums 1Y to 1K by the exposure of the laser beam L. Is done.
Each electrostatic latent image is developed with toner by the developing devices 4Y to 4K. The toner images of the respective colors are primarily transferred onto the intermediate transfer belt 21 by electrostatic force acting between the primary transfer rollers 5Y to 5K and the photosensitive drums 1Y to 1K. At this time, the image forming operations for the respective colors are executed at different timings so that the toner images are superimposed and transferred at the same position on the intermediate transfer belt 21. The color toner images superimposed on the intermediate transfer belt 21 are moved to the secondary transfer position 351 by the rotation of the intermediate transfer belt 21.

In accordance with the timing of the image forming operation, the sheet S is fed from the feeding unit 12 via the timing roller pair 34, and the sheet S includes the intermediate transfer belt 21 and the secondary transfer roller 35. The toner images on the intermediate transfer belt 21 are secondarily transferred onto the sheet S all at once by electrostatic force acting between the secondary transfer roller 35 and the drive roller 22.
The sheet S that has passed through the secondary transfer position 351 is conveyed to the fixing unit 13 where the toner image is heated and pressed to be fixed on the sheet S, and then discharged through the discharge roller 36 to be stored in the storage tray 38. Is housed.

  The toner that is not secondarily transferred to the sheet S and remains on the intermediate transfer belt 21 is basically cleaned by the cleaner 24, but a part of the toner may remain on the intermediate transfer belt 21. . When the toner adheres to the secondary transfer roller 35 that is in contact with the intermediate transfer belt 21, the toner on the secondary transfer roller 35 becomes dirty. This toner contamination is detected by the contamination detection sensor 39.

  The dirt detection sensor 39 is a known optical sensor disposed near the secondary transfer roller 35, and optically detects the amount of residual toner adhering to the secondary transfer roller 35 and controls the detection signal. Send to part 14. Note that it is only necessary to be able to detect the degree of contamination of the secondary transfer roller 35 with toner (a value indicating the amount of toner). For example, a CCD sensor can be used. Further, since the frictional force between the secondary transfer roller 35 and the intermediate transfer belt 21 decreases as the toner adhesion amount increases, the frictional force may be detected by an acceleration sensor, and the adhesion amount may be indexed from the detection result.

(2) Configuration of Control Unit 14 FIG. 2 is a block diagram showing the configuration of the control unit 14.
As shown in the figure, the control unit 14 includes a communication interface (I / F) unit 101, an image processing unit 102, an image memory 103, a laser diode driving unit 104, a CPU 105, a ROM 106, a RAM 107, a motor driving unit 108, and the like. These can communicate with each other via a bus 109.

  The communication I / F unit 101 is an interface for connecting to a LAN such as a LAN card or a LAN board, receives print job data from the outside, and sends the received data to the image processing unit 102. The image processing unit 102 converts the print job data from the communication I / F unit 101 into image data of reproduction colors Y to K, and outputs the converted image data to the image memory 103 for storage. The laser diode driving unit 104 reads out image data from the image memory 103 when a job is executed, and drives the laser diodes of the exposure units 3Y to 3K.

In response to an instruction from the CPU 105, the motor driving unit 108 drives the belt driving motor 51 and the secondary transfer roller driving motor 52.
The ROM 106 stores a control program related to image formation, a control program related to a roller cleaning operation for cleaning the secondary transfer roller 35, and the like. The RAM 107 is used as a work area for the CPU 105.

  The CPU 105 reads a necessary program from the ROM 106 and controls the operations of the image processing unit 11 and the feeding unit 12 in a unified manner with timing to execute a smooth printing operation. Further, during image formation, the motor drive unit 108 is instructed to rotate the intermediate transfer belt 21 and the secondary transfer roller 35 so that the peripheral speeds of both become a specified speed (speed corresponding to the system speed of the apparatus). Let Further, the secondary transfer voltage output unit 40 is instructed to apply a voltage having a polarity opposite to the polarity of the toner to the secondary transfer roller 35 as a secondary transfer voltage. Also, a roller cleaning operation is executed.

  FIG. 3 is a flowchart showing the control contents of the roller cleaning operation. The roller cleaning operation is performed during a period when the secondary transfer operation is not performed (during non-transfer), for example, after the rear end of the nth sheet S passes the secondary transfer position 351, the (n + 1) th sheet S. It may be executed until the leading edge of the ink reaches the secondary transfer position 351 (paper interval), immediately before the start of job execution, immediately after the job ends, after a predetermined number of times of printing, or the like. Here, it is assumed that the job is executed immediately before the start of job execution.

As shown in the figure, the intermediate transfer belt 21 and the secondary transfer roller 35 are rotated at a prescribed speed (same speed) (step S11). Then, a voltage (cleaning voltage) having the same polarity as that of the toner is applied to the secondary transfer roller 35 for a predetermined time (step S12).
Since the cleaning voltage has the same polarity as the toner, an electrostatic force in a direction away from the secondary transfer roller 35 acts on the residual toner adhering to the secondary transfer roller 35. Of the residual toner, the toner separated from the secondary transfer roller 35 moves to the intermediate transfer belt 21 and is collected (cleaned) on the intermediate transfer belt 21 by the cleaner 24.

  The cleaning voltage is not limited to the same polarity as that of the toner. It is only necessary that the residual toner can be separated from the secondary transfer roller 35 by using an electrostatic force. For example, an alternating voltage can be used. The predetermined time is, for example, a time required for the secondary transfer roller 35 to rotate at least once, preferably 3 to 5 times. Hereinafter, cleaning by electrostatic force is referred to as electrical cleaning.

  Residual toner adhering to the secondary transfer roller 35 includes those that can be removed by electrostatic force of electrical cleaning and those that cannot be removed. If the residual toner that cannot be removed by such electrical cleaning is accumulated on the secondary transfer roller 35, the toner on the paper S will eventually become dirty. Therefore, in the present embodiment, after the electrical cleaning, when the predetermined condition is satisfied, the secondary transfer roller 35 and the intermediate transfer belt 21 are rotated so that the peripheral speeds of the two are different from each other, Physical cleaning for cleaning the secondary transfer roller 35 is executed.

Specifically, after the electrical cleaning is completed, a detection signal from the dirt detection sensor 39 is received, and the amount of residual toner (the amount of residual toner attached) adhering to the secondary transfer roller 35 is detected ( Step S13) As a predetermined condition, it is determined whether the amount of residual toner is equal to or greater than a specified value (Step S14).
Here, the specified value means that if a larger amount of residual toner adheres, the residual toner adheres to the back surface of the paper S during transfer, and the paper S is discharged through the fixing unit 13. The amount of toner is such that it is assumed that the back surface of the paper S is felt as a back stain due to toner when the back surface of the paper S is viewed with human eyes, and remains on the secondary transfer roller 35 without being cleaned by electrical cleaning. The toner (for example, a toner charged to a polarity opposite to the normal polarity of the toner) plays a role of a certain amount of lubricant between the intermediate transfer belt 21 and the secondary transfer roller 35, thereby performing physical cleaning. Even if it is used, it corresponds to an amount that the surface of the secondary transfer roller 35 is assumed not to be worn (the frictional force to the extent that the secondary transfer roller 35 is worn does not occur). Data indicating the amount of residual toner is obtained in advance through experiments or the like, and the data is stored in the ROM 106 or the like.

If it is determined that the residual toner adhesion amount is greater than or equal to the specified value (“YES” in step S14), the peripheral speed of the secondary transfer roller 35 is made slower than that of the intermediate transfer belt 21 assuming that the predetermined condition is satisfied. A physical cleaning is performed for rotational control (step S15).
Due to the speed difference, the intermediate transfer belt 21 and the secondary transfer roller 35 rotate while being displaced, and the frictional force generated between them rotates into the residual toner adhering to the surface of the secondary transfer roller 35 and the foaming of the secondary transfer roller 35. However, the residual toner is peeled off, moves away from the secondary transfer roller 35, moves to the intermediate transfer belt 21, and can be collected by the cleaner 24. A suitable value of the speed difference can be obtained from, for example, FIG.

  FIG. 4 (a) shows how much toner back contamination has occurred on the sheet S that has actually been passed through in an endurance experiment in which residual toner that cannot be removed by electrical cleaning is cleaned by changing the peripheral speed difference in physical cleaning. As a result of measuring with a measuring device such as a known reflection densitometer, three examples are △ (stained but not visible to the human eye), ○ (nearly dirty), ◎ (stainless) It is the figure shown in the step.

  The numerical values in the figure are represented by [(V1−V2) / V1] × 100 [%] where the peripheral speed V1 of the intermediate transfer belt 21 and the peripheral speed V2 of the secondary transfer roller 35 (<V1). It is. When the numerical value is increased, the peripheral speed of the secondary transfer roller 35 is decreased, which means that it takes time (a decrease in productivity) to rotate the secondary transfer roller 35 a predetermined number of times. If it exceeds 15 [%], the peripheral speed of the secondary transfer roller 35 becomes too slow and the productivity is lowered. If 0 to 3 [%], the result is Δ, so 3 to 15 [%] ], More preferably within the range of 5 to 10%.

Returning to FIG. 3, it is determined whether or not a predetermined time has elapsed from the start of physical cleaning (step S16). The predetermined time can be, for example, a time required for the secondary transfer roller 35 to rotate 3 to 5 times. The time is not limited to this, and may be a time required for at least the secondary transfer roller 35 to make one rotation.
If it is determined that the predetermined time has elapsed ("YES" in step S16), the rotation of the intermediate transfer belt 21 and the secondary transfer roller 35 is returned to the specified speed (same speed) (step S17), and the process ends. Thereafter, image formation based on the job is started.

  If it is determined in step S14 that the residual toner adhesion amount is smaller than the specified value (“NO” in step S14), it is determined that the predetermined condition is not satisfied, and the process proceeds to step S17 as it is (without performing physical cleaning). Move. The physical cleaning is performed under such conditions as shown in FIG. 4B. As shown in the result of the endurance experiment in the case where the physical cleaning is always performed, the secondary transfer roller 35 has a speed difference of 3%. This is because deterioration such as wear begins to occur (result: Δ), and when it exceeds 5%, it appears remarkably (result: x).

When the residual toner adhesion amount is less than the specified value, the back side of the paper S due to the toner does not occur. Since physical cleaning is not performed, the time required for cleaning and the power required for driving the intermediate transfer belt 21 can be omitted.
As described above, in the present embodiment, the secondary transfer roller 35 is first cleaned by electrical cleaning, and the residual toner that could not be removed accumulates in the secondary transfer roller 35. Since physical cleaning is executed when the value exceeds the specified value, it is possible to suppress roller deterioration as well as toner backside contamination of the paper S.

<Second Embodiment>
In the above embodiment, an example in which the speed difference between the intermediate transfer belt 21 and the secondary transfer roller 35 is constant in the physical cleaning has been described. However, in this embodiment, the speed difference is variable. The point is different from the first embodiment. Hereinafter, in order to avoid duplication of description, the description of the same contents as those of the first embodiment will be omitted, and the same components will be denoted by the same reference numerals.

FIG. 5 is a diagram showing the control contents of the roller cleaning operation according to the present embodiment, with only the portions different from the roller cleaning operation according to the first embodiment extracted.
That is, if it is determined that the amount of residual toner attached to the secondary transfer roller 35 is equal to or greater than a specified value (“YES” in step S14), the speed difference is determined according to the amount of attachment (step S21). This determination is performed by referring to a table 210 illustrating the correspondence between the residual toner adhesion amount and the speed difference shown in FIG. The value m shown in the table 210 has a magnitude relationship of a prescribed value <m1 <m2 <m3. For example, when the adhesion amount of the residual toner is in a range of m1 or less from a specified value, the speed difference is determined to be 5%, and when it is more than m1 and less than m2, the speed difference is 7%. decide.

When the speed difference is larger, the shift between the intermediate transfer belt 21 and the secondary transfer roller 35 becomes larger, so that the residual toner is easily removed, but on the other hand, it is easily worn. Each value of the table 210 is obtained in advance from an experiment or the like and stored in the ROM 106 or the like in an optimum range in which the residual toner can be efficiently removed and the deterioration of the secondary transfer roller 35 can be prevented.
When the speed difference is determined, the process proceeds to step S15, and the intermediate transfer belt 21 and the secondary transfer roller 35 are controlled to rotate at the determined speed difference.

As described above, the speed difference is determined according to the degree of residual toner adhesion (roller dirt). For example, the speed difference is reduced when the dirt is small, and the speed difference is increased when the dirt is severe. Roller cleaning and roller deterioration can be efficiently suppressed.
In FIG. 6, the speed difference is switched so as to increase stepwise. However, it is sufficient if the cleaning can be performed satisfactorily. For example, the speed difference may be gradually increased. The speed difference may be fixed.

  The present invention is not limited to the image forming apparatus, and may be a method for cleaning the secondary transfer roller. Furthermore, the method may be a program executed by a computer. The program according to the present invention includes, for example, a magnetic disk such as a magnetic tape and a flexible disk, an optical recording medium such as a DVD-ROM, DVD-RAM, CD-ROM, CD-R, MO, and PD, and a flash memory recording medium. It can be recorded on various computer-readable recording media, and may be produced, transferred, etc. in the form of the recording medium, wired and wireless various networks including the Internet in the form of programs, In some cases, the data is transmitted and supplied via broadcasting, telecommunication lines, satellite communications, or the like.

[Modification]
As described above, the present invention has been described based on the embodiment. However, the present invention is not limited to the above-described embodiment, and the following modifications may be considered.
(1) In the above embodiment, as a configuration example in the case where a relative speed difference is provided between the intermediate transfer belt 21 and the secondary transfer roller 35, the peripheral speed of the secondary transfer roller 35 is made slower than that of the intermediate transfer belt 21. However, it is not limited to this. For example, the peripheral speed of the secondary transfer roller 35 may be increased. Further, although the peripheral speed of the intermediate transfer belt 21 is constant at a specified speed (system speed), the present invention is not limited to this. For example, the speed of the intermediate transfer belt 21 may be varied by setting the secondary transfer roller 35 to a constant speed. In view of the relative speed difference, the secondary transfer roller 35 may be rotated with the intermediate transfer belt 21 stopped as a physical cleaning. In this case, the residual toner removed from the secondary transfer roller 35 can be collected by the cleaner 24 by starting rotation when the stop time of the intermediate transfer belt 21 elapses for a predetermined time.

  (2) In the above embodiment, the physical cleaning is performed following the end of the electrical cleaning, with the end of the electrical cleaning being a condition for starting the physical cleaning. However, the present invention is not limited to this. For example, only physical cleaning can be performed without performing electrical cleaning. In this configuration, if the amount of residual toner on the secondary transfer roller 35 is equal to or greater than a specified value, physical cleaning may be performed (steps S13 to S16). As a result, the secondary transfer roller 35 can be prevented from being deteriorated as compared with the configuration in which the toner S on the sheet S can be prevented from being stained and the physical cleaning is performed unconditionally. If the amount of residual toner is less than the specified value, electrical cleaning may be performed.

  (3) In the above embodiment, the amount of residual toner adhering to the secondary transfer roller 35 is optically detected by the sensor, but the detection method is not limited to this. It is sufficient if a value indicating the amount of residual toner can be detected. For example, values such as the image formation time, the number of image formations, and the number of prints that are expected to be the amount of residual toner (roller contamination) exceeding a specified value are obtained in advance from empirical rules and experiments, and each time the job is executed The formation time, the number of image formations, and the number of prints are accumulated as index values for the residual toner amount. A method of detecting an index value of the current residual toner amount by reading the accumulated value, and determining that the residual toner adhesion amount is equal to or greater than a predetermined value when the detected value reaches the predetermined value. It is also possible to take In this method, the accumulated value is reset to zero when cleaning is performed.

  (4) In the above embodiment, an example in which the image forming apparatus of the present invention is applied to a tandem color digital printer has been described. However, the present invention is not limited to this. Regardless of color or monochrome image formation, primary transfer or secondary transfer, the image carrier such as a photosensitive drum or an intermediate transfer belt, and a transfer roller held in contact with the surface of the image carrier Image formation comprising a transfer rotator and transferring a toner image formed on the surface of the image carrier onto the sheet when the conveyed sheet passes through the contact portion between the image carrier and the transfer rotator. The apparatus can be applied to, for example, a copying machine, a FAX, and an MFP (Multiple Function Peripheral).

  Therefore, for example, the present invention can be applied to a configuration in which one transfer roller is opposed to one photoconductor drum (image carrier) and the sheet passes through the contact portion. Moreover, although the example which used the roller-shaped transfer roller was demonstrated as a transfer rotary body, what is necessary is just a rotary body, and a material and a shape are not restricted to said thing. For example, a material such as a resin may be used instead of rubber, or a brush-like material may be used. An appropriate speed difference value is determined according to the material of the transfer rotator used.

  The contents of the above embodiment and the above modification may be combined.

  INDUSTRIAL APPLICABILITY The present invention is useful as a technique for cleaning a transfer rotator that is in contact with an image carrier and suppressing deterioration of the transfer rotator.

1 is a diagram illustrating an overall configuration of a printer according to a first embodiment. FIG. 2 is a block diagram illustrating a configuration of a control unit of the printer. FIG. It is a flowchart which shows the control content of the roller cleaning operation | movement which a control part performs. (A) is a figure which shows the result of the endurance experiment which cleans residual toner by changing the peripheral speed difference in physical cleaning, (b) is a figure which shows the endurance experiment result in the case of always performing physical cleaning. is there. It is the figure which extracted and showed only the part different from the roller cleaning operation | movement which concerns on 1st Embodiment about the control content of the roller cleaning operation | movement which concerns on 2nd Embodiment. FIG. 6 is a diagram illustrating a configuration example of a table showing a correspondence relationship between a residual toner adhesion amount and a speed difference.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Printer 14 Control part 21 Intermediate transfer belt 35 Secondary transfer roller 39 Dirt detection sensor 51 Belt drive motor 52 Secondary transfer roller drive motor 108 Motor drive part

Claims (6)

A rotating image carrier and a transfer rotator that contacts the surface of the image carrier, and are formed on the image carrier when the conveyed sheet passes through the contact portion between the image carrier and the transfer rotator. An image forming apparatus for transferring the toner image to the sheet,
Detecting means for detecting a value indicating the amount of toner adhering to the transfer rotator;
When it is determined from the detection result by the detection means that the amount of toner adhering to the transfer rotator is greater than or equal to a specified value, there is a relative speed difference between the peripheral speed of the image carrier and the transfer rotator during non-transfer. Control means for controlling the rotation of at least one of the image carrier and the transfer rotator so as to be attached;
An image forming apparatus comprising: The control means includes
2. The image forming apparatus according to claim 1, wherein the rotation of the transfer rotator is controlled so that the peripheral speed is slower than that of the image carrier. The control means includes
The image forming apparatus according to claim 1, wherein the magnitude of the speed difference is changed according to the amount of toner adhering to the transfer rotator. The control means includes
The image forming apparatus according to claim 3, wherein the speed difference is increased as the amount of adhered toner increases. The detection means includes
The image forming apparatus according to claim 1, wherein the image forming apparatus is a sensor that optically detects the amount of toner adhering to the transfer rotator as a value indicating the amount of toner. A cleaning means for electrostatically cleaning the transfer roller surface by applying a transfer voltage to the transfer roller;
The control means includes
6. The image forming apparatus according to claim 1, wherein the end of cleaning by the cleaning unit is a condition for starting the control.

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