JP2010243829A - Image forming apparatus and cleaning capability recovery process control method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus, recovering cleaning capability of a cleaner blade in a suitable timing so that a black spot and filming generated on an image carrier, which will cause deterioration of image quality, are cleaned away properly without lowering productivity more than needed. <P>SOLUTION: When an integrated value of integrating values obtained by multiplying the number (n) of prints of a print job by a coefficient determined according to the system speed of image formation in the print job is A, and if the A exceeds a predetermined threshold value (e.g. 1000), the cleaning capability recovery process for rotating a photoreceptor drum and an intermediate transfer belt in the direction opposite to the direction during the image formation for a predetermined amount (e.g. about 1 mm in the direction of circumferential surface on the peripheral surface) is performed. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an image forming apparatus having a cleaning member that contacts and cleans the surface of an image carrier, and a method for controlling the execution timing of a cleaning ability recovery process of a cleaner blade that cleans the image carrier.

In an electrophotographic image forming apparatus, a photosensitive drum is charged to a uniform potential by a charger, and this is exposed and scanned to form an electrostatic latent image. The electrostatic latent image is supplied with toner from the developing device to become a toner image, and an image is formed by transferring the toner image onto a recording sheet.
In such an image forming apparatus, if the toner is not completely transferred onto the recording sheet and remains on the photosensitive drum, the subsequent image is deteriorated. Therefore, in order to remove the residual toner, a cleaning made of elastic rubber or the like is used. The blade is brought into contact with the peripheral surface of the photosensitive drum to scrape off residual toner.

  However, since the cleaner blade is always in contact with the image carrier, dust such as residual toner, silica, and paper dust scraped from the surface of the image carrier by the cleaner blade accumulates. When sandwiched between the blade and the image carrier (FIG. 12 (a)), a minute gap is formed between the cleaner blade and the image carrier, and the residual toner particles different from the sandwiched dust are formed in the gap. And dust such as silica may slip through and cause poor cleaning.

On the other hand, recently, there has been a tendency for toner particles to be reduced in size due to demands for higher image quality and higher resolution. However, in order to prevent deterioration in toner fluidity and transportability due to the reduction in diameter of the toner particles, silica ( Silicon dioxide) particles are added.
In addition, the use of a corona discharge type transfer device or charging device oxidizes the components in the air to produce minute discharge products.

The silica particles and the discharge products are pressed and fixed at the nip of the transfer portion or buried in the surface of the photosensitive drum, and become a nucleus. Eventually, image quality will be degraded.
When the cleaning ability of the cleaner blade is reduced as described above, not only is the deposit difficult to be removed from the surface of the image carrier, but also the amount of dust adhering to the image carrier surface without being removed is increased. The growth of the deposit will be further promoted.

Large deposits such as silica particles and discharge products generated on the surface of the photosensitive drum are called black spots. Conventional measures have been taken to prevent the occurrence of black spots. Has been.
Therefore, in Patent Document 1, the past number of printed sheets, the continuous printing time, or the count value of the number of rotations of the photosensitive drum is accumulated and stored, and when the value exceeds a predetermined threshold, the photosensitive drum is only stored by a predetermined amount. A process for recovering the cleaning ability of the cleaner blade by reverse rotation (hereinafter referred to as “cleaning ability recovery process”) is executed.

  Here, a mechanism for recovering the cleaning ability of the cleaner blade by reverse rotation will be described below. As shown in FIG. 12A, when dust such as paper dust is sandwiched between the cleaner blade and the image carrier, the cleaning ability may be deteriorated as described above to cause cleaning failure. Therefore, when the rotation direction of the photosensitive drum and the intermediate transfer belt at the time of image formation is the forward direction, if the photosensitive drum is rotated in the reverse direction (reverse rotation), it is sandwiched between the cleaner blade and the photosensitive member surface. As shown in FIG. 12 (b), the dust is released and freed. When the dust is separated from the cleaner blade by being scattered around and rotated in the forward direction as shown in FIG. The state of contact with the body returns to a normal state from which dust has been removed, and the cleaning ability of the cleaner blade is restored.

JP 2005-31431 A

  However, the deposition amount of silica and discharge products on the peripheral surface of the photosensitive drum, in particular, the deposition amount of silica is estimated by simply accumulating the number of printed sheets, the continuous printing time, and the number of rotations of the photosensitive drum as in Patent Document 1. If the timing of the cleaning performance recovery process is determined based on these, the cleaning performance recovery process may be executed frequently even if not necessary, and productivity may be reduced. However, there is a possibility that the cleaning ability recovery process is not executed even though the image is deteriorated due to the occurrence of the above.

  Such black spots are generated not only on the photosensitive drum, but also on the intermediate transfer belt in an image forming apparatus configured to transfer the toner image to the intermediate transfer belt and then transfer the toner image to a recording sheet. This may also occur on the surface (in this case, referred to as “filming”). In addition, this is a problem that may occur in a member (image carrier) that carries a toner image in an image forming process.

  The present invention has been made in view of the above circumstances, and estimates the amount of deposition of silica or the like on the image carrier more accurately than before, and executes the cleaning ability recovery process at an appropriate timing. Accordingly, it is an object of the present invention to provide an image forming apparatus capable of maintaining a good image quality while suppressing unnecessary reduction in productivity, and a cleaning ability recovery processing control method executed in the image forming apparatus.

The inventors' research has revealed that the occurrence of black spots and filming is greatly affected by predetermined conditions during image formation.
Therefore, an image forming apparatus according to the present invention is an image forming apparatus that transfers a toner image formed on an image carrying rotator to a recording sheet, and is in contact with the surface of the image carrying rotator to A cleaning member that cleans the surface with rotation, and a rotation direction during image formation of the image carrier is a forward direction, and the image carrier rotator is reversely rotated when the image carrier is not in an image forming operation. Control means for controlling the execution of reverse rotation processing for recovering the cleaning ability of the cleaning member, and the control means determines in advance the number of images to be formed under a predetermined image forming condition with respect to the image forming condition. When the accumulated number exceeds a predetermined threshold value, the reverse rotation process is executed.

  With the above configuration, for a plurality of factors that affect the occurrence of black spots and filming, a predetermined coefficient corresponding to the degree of influence of the corresponding factor is applied to the number of image formations that are executed under the circumstances where each factor exists. By using the cumulative number of images that have been multiplied by the number of image formations, it is possible to estimate the deposition of silica or the like on the image carrier more accurately than in the past, and perform the reverse rotation process at a precise timing to clean the cleaning member. By recovering the capability so that the cleaning is appropriately performed, it is possible to maintain a good image quality without reducing productivity more than necessary.

Here, a plurality of image forming modes for forming images at different system speeds may be provided, the image forming condition may be the system speed, and the predetermined coefficient may be larger as the system speed is slower.
As a result, the slower the system speed, the larger the accumulated number and the faster the predetermined threshold is exceeded, and the reverse rotation process can be executed earlier by that amount. Therefore, the cleaning performance of the cleaning member can be recovered earlier as the system speed is slower, and the cleaning capability of the cleaning member can be maintained higher, and the deposits on the surface of the image carrier can be more effectively removed, resulting in better image quality. Can be maintained.

The image forming condition may be the thickness of the recording sheet, and the predetermined coefficient may be larger as the recording sheet is thicker.
As a result, the greater the thickness of the recording sheet, the larger the accumulated number of sheets, and the predetermined threshold value is quickly exceeded, so that the reverse rotation process can be executed earlier. Therefore, the thicker the recording sheet, the sooner the cleaning ability of the cleaning member can be recovered and the cleaning ability of the cleaning member can be maintained high, and the deposits on the surface of the image carrier can be more effectively removed. Image quality can be maintained.

  The present invention can also be a control method for controlling an image forming apparatus so as to have the above-described features. Even in this case, the same effect as described above can be obtained.

1 is a schematic diagram illustrating an overall configuration of an image forming apparatus according to an embodiment of the present invention. 3 is a block diagram illustrating a schematic configuration of a control unit of the image forming apparatus according to the embodiment of the present invention. FIG. 1 is a cross-sectional view illustrating a schematic configuration of an image forming unit of an image forming apparatus according to an embodiment of the present invention. 6 is a table showing the peripheral speed of the photosensitive drum and the developing roller and the peripheral speed difference according to the system speed in the first and third embodiments of the present invention. It is a flowchart which shows the content of the cleaning capability recovery | restoration timing control in Embodiment 1 of this invention. It is a flowchart which shows the content of the cleaning capability recovery process in Embodiment 1, 2, and 3 of this invention. It is a table showing the correspondence of the sheet | seat kind and basic weight in Embodiment 2 of this invention. It is a flowchart which shows the content of the cleaning capability recovery | restoration timing control in Embodiment 2 of this invention. It is a table which shows the correspondence with the system speed in Embodiment 3 of this invention, a sheet | seat kind, and a weighting coefficient. It is a flowchart which shows the content of the cleaning capability recovery | restoration timing control in Embodiment 3 of this invention. It is a figure for demonstrating the fall and recovery of the cleaning capability of a cleaner blade.

Hereinafter, an embodiment of an image reading apparatus according to the present invention will be described by taking as an example a case where it is applied to a digital color printer (hereinafter simply referred to as “printer”).
<Embodiment 1>
(1-1. Overall Configuration of Printer)
FIG. 1 is a schematic cross-sectional view showing the overall configuration of a printer 100 according to an embodiment of the present invention. The printer 100 includes an image forming unit 10, a paper feeding unit 20, a transfer unit 30, a fixing device 40, a control unit 50, and the like.

When this printer 100 is connected to a network (for example, LAN: Local Area Network) and receives an instruction to execute a print job from an external terminal device (not shown), cyan, magenta, yellow, and black are received based on the instruction. The toner images of the respective colors are formed, and these are multiplex-transferred to form a full-color image.
Hereinafter, the reproduction colors of cyan, magenta, yellow, and black are represented as C, M, Y, and K, and the C, M, Y, and K are added as subscripts to the numbers of the components related to the reproduction colors.

The image forming unit 10 includes image forming units 1C, 1M, 1Y, and 1K, an optical unit 15, an intermediate transfer belt 31, cleaner blades 14 and 37, and the like.
The intermediate transfer belt 31 is an endless belt, is stretched around a driving roller 32 and a driven roller 33 and is driven to rotate in the direction of arrow A.
The cleaner blades 14 and 37 are disposed in contact with the photosensitive drum 11 and the intermediate transfer belt 31 in the counter direction, respectively, and residual toner, paper dust, and the like on the surfaces of the photosensitive drum 11 and the intermediate transfer belt 31 are arranged. Clean up trash.

  The optical unit 15 includes a light emitting element such as a laser diode. The optical unit 15 emits laser light L1 (see FIG. 3) for image formation of C to K colors in response to a drive signal from the control unit 50, and outputs photosensitive drums 11C to 11K. Scan exposure. By this exposure scanning, electrostatic latent images are formed on the photosensitive drums 11C to 11K charged by the chargers 12C to 12K. Each electrostatic latent image is formed by the developing devices 13C to 13K, and the C to K color toner images are superimposed on the same positions on the intermediate transfer belt 31 on the photosensitive drums 11C to 11K. This is executed at different timings. Then, the electrostatic images applied by the primary transfer rollers 34 </ b> C to 34 </ b> K sequentially transfer the toner images of the respective colors onto the intermediate transfer belt 31 to form a full-color toner image, and further move toward the secondary transfer position 36.

  On the other hand, the paper feeding unit 20 includes a paper feeding cassette 21 that accommodates the sheets S, a feeding roller 22 that feeds the sheets S in the paper feeding cassette 21 one by one onto the conveying path 23, and a second feeding of the fed sheets S. A timing roller pair 24 and the like for taking the timing to send to the transfer position 36 are provided, and the sheet S is fed from the paper supply unit 20 to the secondary transfer position 36 in accordance with the movement timing of the toner image on the intermediate transfer belt 31. Then, the toner image on the intermediate transfer belt 31 is collectively transferred onto the sheet S by the action of electrostatic force by the secondary transfer roller 35.

The sheet S that has passed through the secondary transfer position 36 is further conveyed to the fixing device 40, and after the toner image (unfixed image) on the sheet S is fixed to the sheet S by heating and pressing in the fixing device 40, The paper is discharged onto the discharge tray 62 via the discharge roller pair 61.
In addition, the control unit 50 executes communication with an external terminal, image processing, drive control of the above-described units, and the like.

  An operation panel 2 (see FIG. 2) is provided at an easy-to-operate position on the upper front surface of the printer 100. In addition to a numeric keypad for inputting the number of copies, a copy start key for instructing the start of copying, and a key for selecting an image forming mode, the operation panel 2 displays the status of the printer 100, for example, a job execution instruction. It has a touch panel type liquid crystal display that displays a message screen indicating that it is in a waiting state (standby). The touch panel function of the liquid crystal display allows the selection of the paper feed tray and the copy density. Accept adjustments.

  FIG. 2 is a block diagram showing a configuration of the control unit 50. As shown in the drawing, the control unit 50 includes, as main components, a CPU (Central Processing Unit) 51, a communication interface (I / F) unit 52, a ROM (Read Only Memory) 53, a RAM (Random Access Memory) 54, And a cumulative weighted print number storage unit 55 and the like.

The communication I / F unit 52 is an interface for connecting to a LAN, such as a LAN card or a LAN board, and receives print job data from the outside.
The CPU 51 reads a necessary program from the ROM 53, controls the operations of the image forming unit 10, the paper feeding unit 20, the transfer unit 30, and the fixing device 40 in a unified manner with timing, and the communication I / F unit 52 The printing operation based on the received print job data is smoothly executed.

The cumulative weighted print number storage unit 55 is a storage unit composed of a non-volatile memory such as an EEPROM (Electrically Erasable and Programmable Read Only Memory), and stores a cumulative weighted print number obtained by adding up the weighted print number described later.
(1-2. Overall configuration of image forming unit)
FIG. 3 is an enlarged sectional view showing a schematic configuration of the image forming unit 1C. The image forming unit 1C includes a photosensitive drum 11C, a charging charger 12C disposed around the photosensitive drum 11C, a developing device 13C, a primary transfer roller 34C, a cleaner blade 14C for cleaning the photosensitive drum 11C, and a photosensitive member after transfer. A neutralizing light irradiation unit 16C for irradiating the neutralizing light L2 for removing charges remaining on the surface of the photosensitive drum 11C is provided, and a C-color toner image is formed on the photosensitive drum 11C. After the toner image formed on the photoconductive drum 11C by the above-described method is transferred onto the intermediate transfer belt 31, the photoconductive drum 11C is provided with a cleaner blade 14C disposed in the counter direction with respect to the photoconductive drum 11C. Thus, cleaning is performed to remove toner remaining on the surface, adhered foreign matter, and the like. The surface of the photosensitive drum 11C that has been cleaned is uniformly exposed by the charge removal light L2 emitted from the charge removal light irradiation section 16C, and the charge removal is performed. This series of steps is repeated to form an image. The other image forming units 1M to 1K also have the configuration of charging chargers 12M to 12K and the like, similar to the image forming unit 1C, except that the toner color is different. In the figure, a thick line arrow without a symbol indicates a direction in which the photosensitive drum 11C, the intermediate transfer belt 31, and the primary transfer roller 34C are rotationally driven.
(1-3. Control of cleaning performance recovery timing by system speed)
According to the study by the present inventors, it has been found that the occurrence of black spots and filming is greatly influenced by the thickness of the recording sheet.

  In other words, in a test in which the photosensitive drum was reversely rotated by the cumulative number of prints, the cumulative printing time, and the cumulative rotational speed of the photosensitive drum to recover the cleaning ability of the cleaner blade, black paper was used when plain paper was used. While spot and filming problems did not occur during the test period, they could occur when using cardboard.

  The system speed in image formation is different between the case of using plain paper and the case of using thick paper. With thick paper, the system speed is slower than with plain paper. This is because cardboard has a larger heat capacity than plain paper and takes more heat from the heating roller in the fixing device, so the conveyance speed of the cardboard is reduced and the amount of heat taken by the cardboard per unit time is reduced by the heating roller. This is because the heating roller temperature does not exceed the fixing temperature so as not to exceed the heating capacity of the heating roller.

As a factor in which black spots and filming are likely to occur when the system speed is slow, a relative peripheral speed difference between the photosensitive drum 11 and the developing roller 131 (hereinafter simply referred to as “peripheral speed difference”) is considered. It is done.
That is, the photosensitive drum 11 and the developing roller 131 are installed with a very small predetermined gap between them, but the toner is smoothly transferred from the developing roller 131 to the photosensitive drum 11. Thus, these peripheral speeds are usually configured to rotate with a constant peripheral speed ratio. In this way, when two rotating bodies arranged via a very small gap rotate at different peripheral speeds, the toner particles with respect to the rotating body surface due to the peripheral speed difference at the closest part of both rotating bodies. Further, mechanical polishing force is generated through the external additive. Due to this polishing force, dust such as silica adhering to the surface of the photosensitive drum 11 and discharge products due to corona discharge during charging is removed from the surface of the photosensitive drum 11, thereby suppressing the occurrence of black spots to some extent. It is thought that there is.

Further, the polishing force is larger as the peripheral speed difference between the rotating bodies is larger, and is larger when the rotating direction of the two rotating bodies is the reverse direction than when the rotating direction is the forward direction.
For the reasons described above, the lower the system speed, the smaller the peripheral speed difference of the rotating body and the smaller the polishing force, and the more dust that has adhered to the surface of the photosensitive drum 11 without being removed. As a result, black spots are likely to occur. Further, the black spot formed on the surface of the photosensitive drum 11 may move on the intermediate transfer belt 31 to cause filming.

Therefore, it can be said that the degree of black spot generation is greatly influenced by the system speed when image formation is executed.
FIG. 4 shows the peripheral speeds of the photosensitive drum 11 and the developing roller 131 at different system speeds, and the peripheral speed difference between them. In the present embodiment, there are three system speeds, a full speed mode, a half speed mode, and a 1/3 speed mode, and the peripheral speed ratio between the photosensitive drum 11 and the developing roller 131 (the developing roller 131 peripheral speed / The peripheral speed of the photosensitive drum 11) is 2.

Since the developing roller 131 and the photosensitive drum 11 are rotationally driven by the same motor, the peripheral speed ratio is kept constant, and the peripheral speed difference between the developing roller 131 and the photosensitive drum 11 is also proportional to the change in system speed. Change.
These system speeds can be selected and designated by the user depending on the glossiness of the print image, whether or not an OHP sheet is used, the resolution of the print image, the thickness of the paper used for printing, and the like. For example, “full speed mode” is set for plain paper, and “1/3 speed mode” is set for OHP sheets and high resolution printing.

  FIG. 5 is a flowchart showing the contents of execution timing control (hereinafter referred to as “cleaning capability recovery timing control”) of the cleaning capability recovery processing executed by the control unit 50 in the present embodiment. In the cleaning capability recovery timing control, the execution timing of the cleaning capability recovery processing is determined, and the cleaning capability recovery processing is executed accordingly. Note that there is a separate main routine (not shown) for controlling the entire printer 100, and this routine is executed each time a subroutine for the cleaning ability recovery timing control is called in the main routine.

  When a print job is received, the number of prints n of the received print job is acquired, and the cumulative weighted print number A stored in the cumulative weighted print number storage unit 55 is acquired (step S1: YES, step S2, step S3). . The cumulative weighted print number A mentioned here is a value obtained by accumulating a weighted print number obtained by multiplying the print number by a predetermined coefficient determined according to the system speed in consideration of the degree of influence on the occurrence of black spots and filming. The degree of occurrence of the estimated black spot and filming is indicated by the number of printed sheets.

  Next, the system speed (print speed) of the accepted print job is determined (step S4). The determination of the system speed is described in a header portion of a print job execution instruction issued by a user on a terminal such as a PC or the operation panel 2 (see FIG. 2) connected to the printer 100 via a network such as a LAN. This is performed by acquiring information (for example, glossiness selected by the user, resolution of the print image, etc.) and referring to a table that stores the print conditions and the system speed in association with each other. When the system speed is the full speed mode, n is added to A as it is (step S4: full speed, step S5). When the system speed is the half speed mode, black spots and filming are more likely to occur than in the full speed mode, and 2n obtained by multiplying the number of prints n by the weighting factor 2 is added to A (step S4: Half speed, step S6). When the system speed is the 1/3 speed mode, black spots and filming are likely to occur three times as much as in the full speed mode, and 3n obtained by multiplying the number of prints n by the weighting factor 3 is added to A (step) S4: 1/3 speed, step S7).

  Subsequently, it is determined whether or not A exceeds 1000. When A exceeds 1000, after performing the cleaning ability recovery process shown in the flowchart of FIG. 6 to be described later, A is reset to 0, and the reset A is stored in the cumulative weighted print number storage unit 55 (step S8: YES, step S9, step S10, step S11), return to the main routine. If A does not exceed 1000, the value of A is stored in the cumulative weighted print number storage unit 55 (step S8: NO, step S11), and the process returns to the main routine.

FIG. 6 is a flowchart showing the contents of a subroutine of the cleaning ability recovery process in step S9 in the cleaning ability recovery timing control flow shown in FIG. When the subroutine for the cleaning ability recovery process is called, the photosensitive drum 11 and the intermediate transfer belt 31 are rotated in reverse by a predetermined amount, for example, about 1 mm in the circumferential direction on the circumferential surfaces of the photosensitive drum 11 and the intermediate transfer belt 31. Thus, the cleaning ability of the cleaner blade is recovered (step S21), and the process returns to the cleaning ability recovery timing control.
(1-4. Summary of Embodiment 1)
As described above, in this embodiment, the weighted coefficient determined according to the system speed is multiplied by the number of prints, and the value obtained by multiplication is added to calculate the cumulative weighted print number A. When the cumulative weighted print number A exceeds a predetermined threshold value (for example, 1000 in this embodiment), the photosensitive drum 11 and the intermediate transfer belt 31 are rotated in reverse to execute the cleaning ability recovery process. As described above, black spots and filming are more likely to occur as the system speed is slower. Therefore, the weighting factor is increased accordingly and weighting is performed accordingly. The cleaning ability of the cleaner blades 14 and 37 is recovered at an appropriate timing by more accurately estimating the degree of occurrence, and good image quality can be maintained without reducing productivity more than necessary.
<Embodiment 2>
(2-1. Control of cleaning ability recovery timing based on recording sheet thickness)
The inventors of the present application have increased the pressure that the intermediate transfer belt 31 receives from the secondary transfer roller 35, in addition to the system speed described in the first embodiment, for the reason that black spots are likely to occur when using cardboard. Also focused on.

  Usually, the secondary transfer roller 35 presses the recording paper passing through the secondary transfer position 36 against the intermediate transfer belt 31 so that the toner image on the intermediate transfer belt 31 is properly transferred onto the recording sheet. That is, the intermediate transfer belt 31 is urged by an elastic body such as a spring in a direction in which the intermediate transfer belt 31 is pressed against the driving roller 32. Since the driving roller 32 rotates at the fixed position, the elastic body that urges the secondary transfer roller 35 contracts as the thickness of the recording sheet passing through the secondary transfer position 36 increases (the urging direction). The elastic body urges the secondary transfer roller 35 with a larger force as a result. As a result, dust such as silica, paper dust, and discharge products is pressed against the intermediate transfer belt 31 with a stronger force, and is firmly fixed on the surface of the intermediate transfer belt 31 and causes filming. Further, the filming formed on the intermediate transfer belt 31 may move to the surface of the photosensitive drum 11 and become a black spot.

  Therefore, in the present embodiment, the sheet thickness is classified into four sheet types of thin paper, plain paper, thick paper (1), and thick paper (2) according to the basis weight, and the weighting coefficient corresponding to each is used. A configuration for performing cleaning execution control will be described. In addition, in order to avoid duplication of description, the description is abbreviate | omitted about the same content as Embodiment 1, and shall attach | subject the same code | symbol about the same component.

FIG. 7 is a table showing the relationship between the sheet type and the basis weight B (g / m ² ). When the basis weight B of the recording sheet is 50 or more and less than 56, the paper is thin, when B is 56 or more and less than 91, plain paper, when B is 91 or more and less than 164, thick paper (1), and B is 164 or more and less than 209 Is classified as cardboard (2).
FIG. 8 is a flowchart showing the contents of the cleaning ability recovery timing control in the present embodiment. Note that there is a separate main routine (not shown) for controlling the entire printer 100, and this routine is executed each time a subroutine for the cleaning ability recovery timing control is called in the main routine.

When a print job is received, the number n of prints of the received print job is acquired, and the cumulative weighted print number A stored in the cumulative weighted print number storage unit 55 is acquired (step S31: YES, step S32, step S33). .
Next, the sheet type is determined (step S34). The determination of the sheet type is performed by identifying the paper feed tray selected by the user in the print job issued by the user. When the sheet type is thin paper, the force with which dust is pressed against the intermediate transfer belt is half that of plain paper, and 0.5n obtained by multiplying the number of prints n by a weighting factor of 0.5 is added to A (step S34: Thin paper, step S35). When the sheet type is plain paper, n is added to A as it is (step S34: plain paper, step S36). If the sheet type is neither thin paper nor plain paper, the sheet type is thick paper, so it is next determined whether the thick paper type is thick paper (1) or thick paper (2) (step S34: ≠ thin paper, Plain paper, step S37).

  In the present embodiment, when the cardboard type is cardboard (1), the force with which dust is pressed against the intermediate transfer belt is double that of plain paper, and 2n obtained by multiplying the number of printed sheets n by a weighting factor 2 is A. (Step S37: cardboard (1), step S38). If the cardboard type is cardboard (2), the force with which dust is pressed against the intermediate transfer belt is three times that of plain paper, and 3n obtained by multiplying the number of prints n by the weighting factor 3 is added to A (step) S37: Cardboard (2), Step S39).

Subsequently, it is determined whether or not A exceeds 1000. When A exceeds 1000, after the cleaning ability recovery process shown in the flowchart of FIG. 6 is executed, A is reset to 0, and the reset A is stored in the cumulative weighted print number storage unit 55 (step S40). : YES, step S41, step S42, step S43), the process returns to the main routine. If A does not exceed 1000, the value of A is stored in the cumulative weighted print number storage unit 55 (step S40: NO, step S43), and the process returns to the main routine.
(2-2. Summary of Embodiment 2)
As described above, in the present embodiment, the number of prints is obtained by multiplying the number of prints by the weighting factor determined according to the thickness of the recording sheet classified as the sheet type based on the basis weight B. The cumulative weighted print number A is calculated by integrating the values. When the cumulative weighted print number A exceeds a predetermined threshold value (for example, 1000 in the present embodiment), the photosensitive drum 11 and the intermediate transfer belt 31 are used. Is reversely rotated to execute the cleaning ability recovery process. As a result, the cleaning ability of the cleaner blades 14 and 37 is recovered at a more appropriate timing, and black spots and filming, which are easily generated depending on the thickness of the recording sheet, are properly cleaned before the growth proceeds. Image quality can be maintained.
<Embodiment 3>
(3-1. Control of timing to recover cleaning ability by system speed and recording sheet thickness)
In the first and second embodiments, the configuration in which the cleaning execution control is performed according to the system speed and the recording sheet thickness (sheet type) has been described. In the present embodiment, a configuration in which a weighting coefficient is determined according to both the system speed and the sheet type and cleaning execution control is performed will be described. In addition, in order to avoid duplication of description, the description is abbreviate | omitted about the thing with the same content as Embodiment 1, and shall attach | subject the same code | symbol about the same component.

  FIG. 9 is a table for determining the weighting coefficient C according to the system speed and the sheet type. It is classified into 12 categories according to the system speed and sheet type, and a weighting coefficient C of 0.5 to 9 is assigned to each category. Assuming that black spots and filming are most unlikely to occur in the thin paper in the full speed mode, the weighting coefficient C = 0.5 is set in this category, and the black spot and filming is in the case of the thick paper (2) in the 1/3 speed mode. Is most likely to occur, a weighting coefficient C = 9 is assigned to the category.

FIG. 10 is a flowchart showing the contents of the cleaning ability recovery timing control in the present embodiment. Note that there is a separate main routine (not shown) for controlling the entire printer 100, and this routine is executed each time a subroutine for the cleaning ability recovery timing control is called in the main routine.
When a print job is received, the number of prints n of the received print job is acquired, and the cumulative weighted print number A stored in the cumulative weighted print number storage unit 55 is acquired (step S51: YES, step S52, step S53). .

  Next, system speed and sheet type information is acquired, and a corresponding weighting coefficient C is acquired with reference to the table shown in FIG. 9 based on the acquired information (steps S54 and S55). The system speed and sheet type information acquisition is performed in the same manner as in the first and second embodiments. Then, Cn obtained by multiplying the number n of prints by the obtained weighting coefficient C is added to A (step S56).

Subsequently, it is determined whether or not A exceeds 1000. If A exceeds 1000, the cleaning ability recovery process shown in the flowchart of FIG. 6 is executed, then A is reset to 0, and the reset A is stored in the cumulative weighted print number storage unit 55 (step S57). : YES, step S58, step S59, step S60), the process returns to the main routine. If A does not exceed 1000, the value of A is stored in the cumulative weighted print number storage unit 55 (step S57: NO, step S60), and the process returns to the main routine. Thereafter, a print job is executed in the main routine.
(3-2. Summary of Embodiment 3)
As described above, in the present embodiment, the number of prints is multiplied by the weighting coefficient C determined according to both the thickness of the recording sheet classified as the sheet type based on the basis weight B and the system speed, A cumulative weighted printed sheet number A is calculated by adding up the values obtained by multiplication, and the photosensitive drum when the cumulative weighted printed sheet number A exceeds a predetermined threshold (for example, 1000 in the present embodiment). 11 and the intermediate transfer belt 31 are rotated in the reverse direction, and the cleaning ability recovery processing of the cleaner blades 14 and 37 is executed. As a result, it is possible to perform more appropriate cleaning in consideration of both the system speed and the thickness of the recording sheet, which are considered to be related to the likelihood of black spots and filming, and maintain good image quality. .
<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 can be implemented.
(1) In each of the above embodiments, the cleaning performance recovery timing control is executed when the printer 100 accepts a print job, and the cumulative weighted print number A at the end of the print job based on the number of print jobs received and the system speed. If A exceeds 1000, the cleaner blade cleaning ability recovery processing is executed before the execution of the print job. However, the present invention is not limited to this. The cleaning capability recovery process may be executed when it is not executed.

Accordingly, A is updated every time one print job is executed, and if A exceeds 1000 during the execution of the print job, the print job may be temporarily interrupted to execute the cleaning ability recovery process. Is possible. When A is updated every time a print job is executed, the remaining number of prints is acquired, and if the remaining number of prints is greater than a predetermined number (for example, 10), the print job is temporarily suspended. However, if the number of sheets is equal to or less than a predetermined number, the execution of the job may be prioritized and the cleaning ability recovery process may be executed after the print job ends.
(2) In each of the above embodiments, the reverse rotation execution amount is 1 mm, and the threshold A of the cumulative weighted print number for executing the cleaning ability recovery process is 1000. However, the present invention is not limited to this. The execution amount of the reverse rotation may be an arbitrary value of several mm to several cm, as long as the cleaning ability of the cleaner blade is restored and an unnecessarily long time is not required. As the value of A, a value capable of suppressing the occurrence of black spots and filming is obtained by experiments or the like.
(3) In the above embodiments, the system speed classification is not limited to three, and may be two or four or more. Furthermore, the classification of the sheet type is not limited to four, and the threshold value of the basis weight B serving as a classification reference may be a value different from that shown in FIG. Moreover, the specific value of each weighting coefficient is not limited to the above.
(4) Programs that can cause a computer to execute the operations described in the above embodiments and modifications are, for example, magnetic disks such as magnetic tapes and flexible disks, CD-ROMs, DVD-ROMs, MOs, and PDs. It is possible to record on various computer-readable recording media such as optical recording media such as Smart Media (registered trademark), COMPACTFLASH (registered trademark), etc. There are cases where production, transfer, and the like are made, and there are cases where the program is transmitted and supplied via various wired and wireless networks including the Internet, broadcasting, telecommunication lines, satellite communications, etc. in the form of programs.
(5) In each of the above-described embodiments, the case where the present invention is applied to a digital color printer including an intermediate transfer belt has been described as an example. However, the present invention is not limited to this, and a direct transfer type printer may be used. In addition to the printer function, a multifunction machine having a FAX function or a copy function may be used.

  Further, the contents of the above embodiments and the above modifications may be combined.

  The present invention can be widely applied to an image forming apparatus that cleans an image carrier with a cleaning member.

DESCRIPTION OF SYMBOLS 1 Image forming part 10 Image forming part 100 Printer 11 Photosensitive drum 12 Charging charger 13 Developing device 131 Developing roller 14, 37 Cleaner blade 15 Optical part 16 Static elimination light irradiation part 20 Paper feeding part 30 Transfer part 31 Intermediate transfer belt 32 Drive roller 33 Follower Roller 34 Primary Transfer Roller 35 Secondary Transfer Roller 36 Secondary Transfer Position 40 Fixing Device 50 Control Unit

Claims (6)

An image forming apparatus for transferring a toner image formed on an image bearing rotating body to a recording sheet,
A cleaning member that contacts the surface of the image bearing rotator and cleans the surface as the image bearing rotator rotates;
When the rotation direction during image formation of the image carrier is a positive direction, reverse rotation processing is performed to restore the cleaning ability of the cleaning member by reversely rotating the image carrier rotator at times other than during the image forming operation. And a control means for controlling
The control means includes
When the number of images to be formed under a predetermined image forming condition is multiplied by a predetermined coefficient determined in advance for the image forming condition and accumulated, and the accumulated number exceeds a predetermined threshold, An image forming apparatus that executes a rotation process. Equipped with multiple image forming modes to form images at different system speeds,
The image forming apparatus according to claim 1, wherein the image forming condition is the system speed, and the predetermined coefficient increases as the system speed decreases.   The image forming apparatus according to claim 1, wherein the image forming condition is a thickness of the recording sheet, and the predetermined coefficient increases as the thickness of the recording sheet increases. A cleaning ability recovery processing control method executed in an image forming apparatus for transferring a toner image formed on an image bearing rotating body to a recording sheet,
A weighted accumulation step of multiplying the number of images to be formed under a predetermined image forming condition by a predetermined coefficient determined in advance for the image forming condition and accumulating;
When the number of image formations weighted and accumulated in the weighted accumulation step exceeds a predetermined threshold value, the cleaning capability of the cleaning member is increased by rotating the image carrier rotator in reverse when the image forming operation is not performed. A cleaning ability recovery process control method comprising: a cleaning ability recovery step for executing a reverse rotation process for recovery. The predetermined image forming condition is a system speed at the time of image formation,
5. The cleaning ability recovery processing control method according to claim 4, wherein the predetermined coefficient in the weighted accumulation step is set to be larger as the system speed is slower. The predetermined image forming condition is a thickness of the recording sheet,
6. The cleaning capability recovery process control method according to claim 4, wherein the predetermined coefficient in the weighted accumulation step is set to be larger as the recording sheet is thicker.

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