CN112051717A - Image forming apparatus and computer-readable storage medium storing program - Google Patents

Abstract

The invention provides an image forming apparatus and a computer-readable storage medium storing a program, which can remove aggregates from a cleaning member more reliably. The image forming apparatus includes an image carrier (e.g., a transfer belt (21)) and a cleaning member (e.g., a cleaning blade (2)) that scrapes off residual toner on the transfer belt as the image carrier moves relative to the transfer belt. The image forming apparatus performs a maintenance operation of removing aggregates generated between the transfer belt and the cleaning blade. The maintenance operation includes a patch forming operation for forming a toner image (patch image (P50)) for removing the aggregates on the transfer belt and a moving operation for moving the transfer belt toward the cleaning blade to cause the patch image (P50) on the transfer belt to collide with the cleaning blade. An edge (E1) on the downstream side in the traveling direction (D1) of the patch image (P50) extends in a direction (C1) that is not perpendicular to the traveling direction (D1).

Description

Image forming apparatus and computer-readable storage medium storing program

Technical Field

The present invention relates to an image forming apparatus and a technique related thereto.

Background

In an image forming apparatus (specifically, an electrophotographic image forming apparatus), a toner image formed on an image carrier (for example, a transfer belt) is transferred onto a sheet (transfer material), thereby forming an image on the sheet.

After such an image forming operation (transfer operation of the toner image to the paper), a part of the toner remains on the image bearing member. Since the toner remaining on the image bearing member (also referred to as residual toner) interferes with the formation of a new image, the toner is scraped off by a cleaning member (cleaning blade or the like) disposed in contact with the surface of the image bearing member and collected in a toner collecting portion or the like.

Further, not only residual toner but also various foreign substances are present on the image carrier after the image forming operation is performed on the sheet. As the various foreign substances, there are paper powder containing a filler or the like added to paper, an external additive externally added to a toner, and/or a lubricant (lubricant) applied to a photoreceptor or the like.

In the case where such foreign matter exists on the image carrier, when the foreign matter passes through a contact portion between the image carrier and the cleaning member (a linear contact portion where the image carrier and the cleaning member contact each other), there occurs a problem that the surface of the image carrier is damaged or the like. If the surface of the image bearing member is damaged, the rubber layer under the coating layer covering the surface of the image bearing member is exposed, and the friction coefficient with the cleaning member becomes large, which may cause deformation of the cleaning member. As a result, the service life of the cleaning member may be shortened.

There is a technique for preventing such a problem from occurring.

For example, patent document 1 discloses a technique of forming a rectangular patch image (toner patch image) on an image carrier and causing the patch image to collide with a cleaning member in a state where the patch image is mixed with paper dust (foreign matter) to remove the paper dust on the image carrier.

Documents of the prior art

Patent document

Patent document 1: japanese laid-open patent publication No. 11-258919

Patent document 2: japanese patent laid-open publication No. 2017-21138

However, even when the technique described in patent document 1 is used, if the image forming operation is repeated on the sheet, various foreign substances are gradually accumulated (accumulated) in the gap between the cleaning member (for example, the cleaning blade 2) and the image carrier (for example, the intermediate transfer belt 21) to generate (generate) an aggregate M10 (see fig. 20).

In this case, if the patch image in the technique described in patent document 1 is formed on the image carrier (intermediate transfer belt 21), as described below, the aggregate M10 may not be removed, and a cleaning failure (stripe-like image noise or the like) may occur.

Specifically, in the technique described in patent document 1, the edge on the downstream side in the traveling direction of the rectangular patch image extends in the direction perpendicular to the traveling direction. Therefore, as shown in fig. 21, in the case where the aggregate M10 is present in the gap between the cleaning blade 2 and the intermediate transfer belt 21, if the edge (edge extending in the perpendicular direction with respect to the traveling direction D1) E90 collides with the aggregate M10, the aggregate M10 is pushed to the downstream side in the traveling direction D1 by the powder pressure of the toner traveling to the downstream side in the traveling direction D1.

As a result, the aggregate M10 bites into the space between the cleaning blade 2 and the intermediate transfer belt 21 (see fig. 22), and a gap may be generated between the cleaning blade 2 and the intermediate transfer belt 21. Specifically, a gap may be generated in both side portions of the aggregate M10 (both side portions in the direction D2 perpendicular to the moving direction D1 of the intermediate transfer belt 21) in the contact portion of the cleaning blade 2 with the intermediate transfer belt 21 (refer to fig. 23). Fig. 23 is a view of a state in which the aggregate M10 bites into between the cleaning blade 2 and the intermediate transfer belt 21 as viewed from the downstream side in the moving direction D1 of the intermediate transfer belt 21.

When a gap is generated between the cleaning blade 2 and the intermediate transfer belt 21, for example, as shown in fig. 24, when the residual toner N10 reaches the position where the aggregate M10 is generated in the cleaning blade 2, a part of the residual toner N10 (toner N5) slides through the gap at the portion on both sides of the aggregate M10. As a result, the squeezed toner N5 may be transferred to an image in the next image forming operation, and stripe-like image noise (cleaning failure) may occur.

Disclosure of Invention

Accordingly, an object of the present invention is to provide an image forming apparatus capable of more reliably removing aggregates from a cleaning member, and a technique related thereto.

In order to solve the above-described problem, the invention according to claim 1 is an image forming apparatus including: an image carrier that temporarily carries a toner image and transfers the toner image to a sheet; a cleaning member that scrapes off residual toner remaining on the image carrier after transfer to the sheet of paper, in association with relative movement with the image carrier; a control mechanism that performs a maintenance operation of removing aggregates generated between the image carrier and the cleaning member; the maintenance operation includes a patch forming operation of forming a patch image on the image bearing member, the patch image being a toner image for removing the agglutinated matter, and a moving operation of causing the image bearing member to travel toward the cleaning member to cause the patch image on the image bearing member to collide with the cleaning member, an edge of the patch image on a downstream side of a travel direction of the patch image extending in a direction not perpendicular to the travel direction.

The invention of the technical scheme 2 is as follows: the image forming apparatus according to claim 1 is characterized in that the control means includes determination means for determining whether or not to execute the patch forming operation based on paper type information of a plurality of output sheets printed and output.

The invention of the technical scheme 3 is as follows: in the image forming apparatus according to the invention of claim 2, the paper type information includes information indicating whether each of the plurality of output sheets is a coated paper or a non-coated paper, and the determination means determines that the patch forming operation is to be executed on the condition that a ratio of the non-coated paper to all of the plurality of output sheets is larger than a reference value.

The invention of technical scheme 4 is: the image forming apparatus according to claim 3 is characterized in that the image forming apparatus further includes a photoreceptor configured to transfer a toner image to the image carrier, and the reference value is changed according to a supply amount of the lubricant supplied to a surface of at least one of the image carrier and the photoreceptor.

The invention of the technical scheme 5 is as follows: the image forming apparatus according to any one of claims 2 to 4, wherein the determination means determines an estimated presence range in which the aggregate is estimated to be present in a linear contact portion where the image carrier and the cleaning member contact each other, and determines that the patch image is to be formed in an area on the image carrier corresponding to the estimated presence range.

The invention of technical scheme 6 is: the image forming apparatus according to claim 5 is characterized in that the assumed passage positions are assumed passage positions on the image bearing member at both ends of a non-coated sheet included in the plurality of output sheets in a direction perpendicular to the traveling direction, and the specifying means specifies, as the estimated existence range, a range having a predetermined width in the direction perpendicular to the traveling direction around each of the assumed passage positions.

The invention of technical scheme 7 is: the image forming apparatus according to claim 5 is characterized in that the specifying means specifies, as the estimated existence range, a range in which an image forming rate in an image forming operation performed before the maintenance operation is less than a predetermined degree among the plurality of ranges, while the specifying means divides the image carrier into the plurality of divided ranges in a direction perpendicular to the traveling direction.

The invention of technical scheme 8 is: the image forming apparatus according to the invention of any one of claim 1 to claim 7, wherein the patch image is formed of a solid image of toner.

The invention of technical scheme 9 is: the image forming apparatus according to the invention of claim 8 is characterized in that the patch image is formed by superimposing solid images of two or more color toners.

The invention of the technical scheme 10 is as follows: the image forming apparatus according to the invention of any one of claims 1 to 9 is characterized in that, in the patch forming operation, a first patch image and a second patch image are arranged in the traveling direction, an edge on a downstream side in the traveling direction of the first patch image is inclined in a direction in which one end portion of one side and the other side in a direction perpendicular to the traveling direction collides with the cleaning member before the other end portion collides with the cleaning member, and an edge on a downstream side in the traveling direction of the second patch image is inclined in a direction in which the other end portion of the one side and the other side collides with the cleaning member before the one end portion collides with the cleaning member.

The invention according to claim 11 is a program for causing a computer incorporated in an image forming apparatus including an image carrier that temporarily carries a toner image and transfers the toner image to a sheet, and a cleaning member that scrapes off residual toner remaining on the image carrier after transfer to the sheet as the cleaning member moves relative to the image carrier, to execute a series of steps including: a) a step of executing a patch forming operation of forming a patch image on the image carrier, the patch image being a toner image for removing aggregates generated between the image carrier and the cleaning member; b) a step of executing a moving action of causing the image carrier to travel toward the cleaning member to cause the patch image on the image carrier to collide with the cleaning member; wherein an edge of the patch image on a downstream side in a traveling direction of the patch image extends in a direction not perpendicular to the traveling direction.

The invention of technical scheme 12 is: in the program according to claim 11 of the present invention, the step a) includes: a-1) determining whether to execute the patch forming operation based on the sheet type information of a plurality of output sheets printed and output.

The invention of technical scheme 13 is: the program according to claim 12 of the present invention is characterized in that the paper type information includes information indicating whether each of the plurality of output papers is a coated paper or a non-coated paper, and in the step a-1), the patch forming operation is determined to be executed on the condition that a ratio of the non-coated paper to all of the plurality of output papers is larger than a reference value.

The invention of technical scheme 14 is: the program according to claim 13 is characterized in that the image forming apparatus further includes a photoreceptor configured to transfer a toner image to the image carrier, and the reference value is changed according to a supply amount of the lubricant supplied to a surface of at least one of the image carrier and the photoreceptor.

The invention of technical scheme 15 is: the program according to any one of claims 12 to 14 is characterized in that the program further causes the computer to execute: c) a step of determining an estimated presence range in which the aggregate is estimated to be present, of linear contact portions where the image carrier and the cleaning member contact each other; d) a step of determining that the patch image should be formed in an area on the image carrier corresponding to the presumed existence range.

The invention of technical scheme 16 is: in the program according to claim 15 of the present invention, the assumed passage position is an assumed passage position on the image carrier at both ends of the non-coated paper included in the plurality of output sheets in the direction perpendicular to the traveling direction, and in the step c), a range having a predetermined width in the direction perpendicular to the traveling direction with each of the assumed passage positions as a center is determined as the estimated existence range.

The invention of technical scheme 17 is: in the program according to claim 15 of the present invention, the step c) includes: c-1) a step of dividing the image carrier into a plurality of divided ranges in a direction perpendicular to the traveling direction; c-2) determining, as the estimated existence range, a divided range in which an image forming rate in the image forming operation performed before the step a) is less than a predetermined degree among the plurality of divided ranges.

The invention of technical scheme 18 is: the program according to any one of claims 11 to 17, wherein the patch image is formed of a solid image of toner.

The invention of technical scheme 19 is: the program according to claim 18 of the present invention is characterized in that the patch image is formed by superimposing solid images of two or more colors of toner.

The invention according to claim 20 is the program according to any one of claims 11 to 19, wherein, in the patch forming operation, a first patch image and a second patch image are arranged in the traveling direction, an edge on a downstream side in the traveling direction of the first patch image is inclined in a direction in which one end portion of one side and the other side in a direction perpendicular to the traveling direction collides with the cleaning member before the other end portion collides with the cleaning member, and an edge on a downstream side in the traveling direction of the second patch image is inclined in a direction in which the other end portion of the one side and the other side collides with the cleaning member before the one end portion collides with the cleaning member.

According to the inventions described in claims 11 to 20, since the edge on the downstream side in the traveling direction of the patch image extends in the direction not perpendicular to the traveling direction, the toner in the portion of the edge that reaches the cleaning member first and is scraped off by the cleaning member is pushed in the direction perpendicular to the traveling direction by the powder pressure of the toner that newly reaches the cleaning member, and flows toward the aggregate in the direction perpendicular to the traveling direction. Then, if the toner flowing toward the aggregate in the direction perpendicular to the traveling direction collides with the aggregate, the aggregate is peeled off from the image carrier and the cleaning member, and flows in the direction perpendicular to the traveling direction together with the toner and is removed. Therefore, the collected matter can be prevented from biting into between the image carrier and the cleaning member, and the collected matter can be more reliably removed from the cleaning member.

In particular, according to the inventions described in claim 2 and claim 12, since whether or not the patch forming operation is to be executed can be determined based on the paper type information of the plurality of output sheets that have been printed and output, whether or not the patch forming operation is to be executed can be determined more appropriately.

In particular, according to the inventions described in claim 3 and claim 13, since the execution of the patch forming operation can be determined on the condition that the ratio of the non-coated paper to the entire plurality of output sheets of the printout is larger than the reference value, whether or not the patch forming operation is to be executed can be determined more appropriately.

In particular, according to the inventions described in claim 4 and claim 14, since the reference value regarding whether or not the patch forming operation is to be executed is changed in accordance with the supply amount of the lubricant supplied to the surface of at least one of the image carrier and the photoreceptor, the patch forming operation can be executed more reliably than in the case where whether or not the patch forming operation is to be executed is determined using the reference value that is always the same.

In particular, according to the inventions described in claim 5 and claim 15, the estimated existing range, which is a range in which the presence of the aggregate is estimated, is determined in the linear contact portion where the image bearing member and the cleaning member contact each other, and the patch image is determined to be formed in the region corresponding to the estimated existing range on the image bearing member, so that the toner consumption can be suppressed as compared with a case where the patch image is formed in the region corresponding to the entire range of the contact portion on the image bearing member at all times.

In particular, according to the inventions described in claim 9 and claim 19, since the patch image is formed by superimposing solid images of two or more colors of toners, the amount of toner forming the patch image is larger than in the case of forming the patch image by using a solid image of a single color of toner, and the toner collides with the aggregates adhering to the cleaning member with a larger powder pressure. Therefore, the aggregates adhering to the cleaning member can be more reliably peeled off from the cleaning member.

In particular, according to the inventions described in claim 10 and claim 20, the toner flow at the edge of the first patch image and the toner flow at the edge of the second patch image are directed in opposite directions to each other. Therefore, the toner collides with the aggregate adhering to the cleaning member from both sides of the one side and the other side in the direction perpendicular to the traveling direction of the patch image. As a result, even when the aggregates are not peeled off from the cleaning member by the toner of the first patch image, the aggregates can be peeled off from the cleaning member by the toner of the second patch image. Therefore, the aggregates adhering to the cleaning member can be more reliably peeled off from the cleaning member.

Drawings

Fig. 1 is a diagram showing a schematic configuration of an image forming apparatus.

Fig. 2 is a sectional view of the cleaning device as viewed from the + X side.

Fig. 3 is a diagram showing a patch image.

Fig. 4 is a flowchart relating to the patch forming action.

Fig. 5 is a diagram showing a subroutine process related to a process of specifying a candidate arrangement region of a patch image.

Fig. 6 is a diagram showing print history information.

Fig. 7 is a diagram showing a range in the vicinity of the end of the sheet.

Fig. 8 is a diagram showing a plurality of division ranges.

Fig. 9 is a conceptual diagram showing a case where a patch image is scraped off by a cleaning blade.

Fig. 10 is a conceptual diagram showing a case where a patch image is scraped off by a cleaning blade.

Fig. 11 is a conceptual diagram showing a case where a patch image is scraped off by a cleaning blade.

Fig. 12 is a diagram (graph) showing transition of occurrence of a cleaning failure in a case where the patch forming operation is executed and transition of occurrence of a cleaning failure in a case where the patch forming operation is not executed.

Fig. 13 is a view showing a portion where the sheet is in direct contact with the intermediate transfer belt.

Fig. 14 is a flowchart relating to the patch forming operation according to the second embodiment.

Fig. 15 is a cross-sectional view of the photoreceptor cleaning device as viewed from the + X side.

Fig. 16 is a graph (graph) showing the life ratio of the lubricant cake.

Fig. 17 is a diagram showing a patch image according to a modification.

Fig. 18 is a diagram showing a patch image according to a modification.

Fig. 19 is a conceptual diagram illustrating a modified example in which a patch image is scraped off by a cleaning blade.

Fig. 20 is a view showing aggregates generated between the cleaning blade and the intermediate transfer belt.

Fig. 21 is a view showing a state in which the aggregate is pressed toward the downstream side in the traveling direction.

Fig. 22 is a view showing a state in which the aggregates bite between the cleaning blade and the intermediate transfer belt.

Fig. 23 is a view showing a state in which the aggregates bite between the cleaning blade and the intermediate transfer belt, as viewed from the downstream side in the moving direction of the cleaning member.

Fig. 24 is a diagram showing a state where toner slides from both sides of the aggregate.

Description of the reference numerals

1 image forming apparatus

2 cleaning blade

8-belt cleaning device

11 photosensitive body

17 photoreceptor cleaning device

21 intermediate transfer belt

70 lubricant coating mechanism

71 lubricant applying brush

72 lubricant block

73 elastic member

M10 agglutinate

P50 patch image

Detailed Description

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

< 1. first embodiment >

< 1-1. apparatus outline >

The image forming apparatus 1 is an apparatus that develops an electrostatic latent image on an image carrier to form an image. Here, as the image forming apparatus, an electrophotographic type print output apparatus, more specifically, a tandem type full-color print output apparatus is exemplified. In fig. 1 and the like, directions and the like are shown using an XYZ rectangular coordinate system.

As shown in fig. 1, the image forming apparatus 1 includes a plurality of (specifically, four) image forming units 10 (specifically, 10Y, 10M, 10C, 10K). Specifically, the image forming apparatus 1 includes an image forming unit 10Y of yellow, an image forming unit 10M of magenta, an image forming unit 10C of cyan, and an image forming unit 10K of black. Each image forming unit 10 forms an image of each color component (specifically, each component of Y (yellow), M (magenta), C (cyan), and K (black)) in a final output image by an electrophotographic method, and transfers the image to an intermediate transfer belt (also referred to as an intermediate transfer body) 21. Then, in the second transfer device (transfer roller (secondary transfer roller)) 22, the images (toner images) of the respective color components superimposed on the intermediate transfer belt 21 are further transferred onto a sheet (transfer material), and a full-color image is formed on the sheet. The intermediate transfer belt 21 also serves as an image carrier that temporarily carries the toner images (toner images) transferred from the photosensitive members 11.

The four image forming units 10(10Y, 10M, 10C, 10K) are arranged in series along a right side straight portion of the intermediate transfer belt 21.

Each image forming unit 10 has a photoreceptor 11, a charger 12, an exposer (optical writing device) 13, a developer 14, a first transferor (first transferor) 15, and a cleaner (photoreceptor cleaning device) 17, respectively. Specifically, in each image forming unit 10, the developer 14, the exposer 13, the charger 12, the cleaner 17, and the first transferer 15 are arranged clockwise in this order around the outer circumference of the substantially cylindrical photosensitive body 11. The first transfer device 15 (more specifically, a transfer roller) is disposed at a position facing the photoreceptor 11 with the intermediate transfer belt 21 interposed therebetween.

The intermediate transfer belt 21 is wound around a plurality of rollers including a driving roller, and is moved (rotated) in the direction of an arrow D1 (fig. 1) according to the rotational driving of the driving roller.

Further, a belt cleaning device 8 is provided downstream of the position of the transfer roller 22 in the moving direction (rotating direction) D1 of the intermediate transfer belt 21. The detailed structure of the belt cleaning device 8 will be described later.

A paper feed portion 30, a paper feed tray 31, and the like are provided below the image forming unit 10K (upstream in the conveyance path of each image forming unit 10).

Further, a fixer 26 is provided on the downstream side in the conveying direction of the sheet of paper passing through the position of the transfer roller 22, and a paper discharge portion 27 is provided on the downstream side in the conveying direction thereof.

The image forming apparatus 1 functions as a color printer by printing and outputting an image based on image data transmitted from another information processing apparatus (such as a personal computer) connected via a network or the like using the printing mechanism as described above.

The image forming apparatus 1 includes a controller (control unit) 9 (see fig. 1).

The controller 9 is a control device incorporated in the image forming apparatus 1 and integrally controls the image forming apparatus 1. The controller 9 is configured as a computer system including a CPU and various semiconductor memories (RAM, ROM, and the like). The controller 9 implements various processing units by executing a predetermined software program (hereinafter, simply referred to as a program) stored in a ROM (e.g., EEPROM) in the CPU. The program (more specifically, the program module group) may be installed in the image forming apparatus 1 via a portable storage medium such as a USB memory or a network.

The controller 9 realizes various processing units including the determination section 91 by executing the program.

The determination unit 91 is a control unit that executes a maintenance operation (controls execution of the maintenance operation) for removing the aggregates M10 generated (generated) between the intermediate transfer belt 21 and the cleaning blade 2.

The maintenance operation (maintenance processing) includes a patch forming operation (described below) and a moving operation (described below).

The patch forming operation (patch forming process) is an operation of forming a toner image (patch image P50 (fig. 3 and 7)) for removing the aggregate M10 on the intermediate transfer belt 21. The moving operation (moving process) is an operation of causing the intermediate transfer belt 21 to travel (move) toward the cleaning blade 2 and causing the patch image P50 on the intermediate transfer belt 21 to collide with the cleaning blade 2.

The determination unit 91 executes a determination process of determining whether or not to execute a maintenance operation (a patch forming operation, a moving operation, and the like) when the maintenance operation is executed. Specifically, the determination unit 91 determines whether or not to execute the patch forming operation based on the sheet type information of a plurality of output sheets (output sheets) printed and output in accordance with the print job.

< 1-2. detailed structure with cleaning device

Fig. 2 is a sectional view of the belt cleaning device 8 (fig. 1) viewed from the + X side.

The belt cleaning device 8 includes a cleaning blade 2, a toner recovery roller 3, and a housing 4.

The cleaning blade 2 is a member (cleaning member) capable of scraping off toner (also referred to as residual toner, waste toner, or the like) remaining on the intermediate transfer belt 21 after transfer to paper (after an image forming operation) with relative movement with respect to the intermediate transfer belt 21 (rotation of the intermediate transfer belt 21).

The cleaning blade 2 is a thin plate-like member having an elongated rectangular shape.

The cleaning blade 2 is formed of an elastic member (e.g., a rubber member such as Nitrile Butadiene Rubber (NBR)).

The cleaning blade 2 is mounted to the housing 4, and as shown in fig. 2, a leading end portion (blade edge) 2A of the cleaning blade 2 is disposed in contact with the surface of the intermediate transfer belt 21. Specifically, the front end of the cleaning blade 2 is disposed in contact with the surface of the intermediate transfer belt 21 in a posture facing the upstream side of the moving direction D1 of the intermediate transfer belt 21 (in other words, a direction perpendicular to the axial direction of the driving roller of the intermediate transfer belt 21). Also, the cleaning blade 2 is in contact with the intermediate transfer belt 21, and the intermediate transfer belt 21 moves (travels) toward the cleaning blade 2.

The residual toner on the intermediate transfer belt 21 also moves toward the cleaning blade 2 along with the movement of the intermediate transfer belt 21, and if the residual toner collides with the cleaning blade 2, the residual toner is scraped off from the intermediate transfer belt 21. The toner (residual toner) scraped off by the cleaning blade 2 is accumulated in a lower portion of the housing 4, and is transported to a waste toner collecting container (not shown) by the toner collecting roller 3 and collected.

< 1-3 > action on Patch formation

Next, a patch forming operation will be described.

As described above, the patch forming operation is an operation of forming the patch image P50 on the intermediate transfer belt 21. This patch forming operation is performed to remove an aggregate M10 (described below) generated between the cleaning blade 2 and the intermediate transfer belt 21 (see fig. 20). Fig. 20 is a diagram showing an aggregate M10 generated between the cleaning blade 2 and the intermediate transfer belt 21.

Various foreign substances are present on the intermediate transfer belt 21 after the image forming operation is performed on the sheet, and an aggregate M10 is generated (generated) by accumulation (accumulation) of the various foreign substances in a gap between the cleaning blade 2 and the intermediate transfer belt 21 (see fig. 20). As the various foreign substances, there are paper powder containing a filler or the like added to paper, an external additive externally added to a toner, and/or a lubricant (also referred to as a lubricant) applied to the photoreceptor 11 or the like.

Here, since the coated paper (coated paper or the like) has a coating layer on its surface, the coated paper is less likely to generate paper dust than non-coated paper (plain paper, recycled paper or the like). On the other hand, uncoated paper, which has no coating layer on its surface, is more likely to generate paper dust than coated paper. Therefore, in the case of conveying the uncoated paper, more paper dust is transferred to the intermediate transfer belt 21 than in the case of conveying the coated paper, and the aggregate M10 is easily generated (easily generated) in the gap between the cleaning blade 2 and the intermediate transfer belt 21 (see fig. 20).

In consideration of this, whether to execute the patch forming operation is determined based on the sheet type information of a plurality of output sheets (output sheets) that are printed and output. Specifically, whether the patch forming action is performed is determined according to whether the ratio of the non-coated paper to the entire plurality of output sheets (also referred to as a non-coated paper ratio) is greater than a reference value V10 (here, V11 (e.g., 60%)).

Fig. 4 is a flowchart relating to the patch forming action. The operation of fig. 4 is executed at a predetermined timing (for example, at a timing when the number of printed output sheets reaches a predetermined number (for example, 1 ten thousand sheets)).

Note that, before the operation of fig. 4, every time a print job is executed, the paper type information is stored as a print history (print history information) (see fig. 6).

The sheet type information is information indicating whether each of a plurality of output sheets is a coated sheet or a non-coated sheet. The paper type information is stored as a print history based on the setting content of the print job to which the execution instruction was given before step S11.

Here, in the image forming apparatus 1, the type of paper (paper type) to be placed in each paper feed tray of the image forming apparatus 1 is set in advance. For example, the arrangement of plain paper in the paper feed tray T1 (not shown) and the arrangement of coated paper in the paper feed tray T2 (not shown) are set in advance.

The user designates the paper feed tray when instructing execution of a print job. In response to a user's operation to specify a paper feed tray, the image forming apparatus 1 stores, as a print history, paper type information (paper type setting information) of paper (output paper) printed and output in a print job based on the paper feed tray specified by the user. For example, when the paper feed tray T1 is designated by the user, the paper type information indicating that the output paper (here, plain paper) placed in the paper feed tray T1 is non-coated paper is stored as the print history. When the paper feed tray T2 is designated by the user, paper type information indicating that the output paper (here, coated paper) placed in the paper feed tray T2 is coated paper is stored as a print history.

In this way, the operation of fig. 4 is started after the paper type information on the plurality of output sheets is stored in advance as the print history (fig. 6).

First, in step S11, the determination section 91 acquires the paper type information (paper type information of already output paper) stored as the print history, and determines whether or not the non-coated paper ratio is larger than the reference value V11 based on the paper type information. Here, it is determined whether the uncoated paper ratio is larger than the reference value V11 based on the paper type information of the output paper of the latest predetermined number of sheets (for example, 1 ten thousand sheets). For example, based on the paper type information (paper type setting information) in the latest predetermined number of jobs (for example, the latest 10 jobs), it may be determined whether or not the non-coated paper ratio is larger than the reference value V11.

Fig. 6 is a diagram showing a print history (print history information). Here, it is assumed that 10 print jobs are executed until the latest predetermined number of sheets (1 ten thousand) are output.

As shown in fig. 6, the total number of uncoated sheets in the 1 ten thousand output sheets of the print output was 6400, and the uncoated sheet ratio (the ratio of uncoated sheets to the total of the most recent 1 ten thousand output sheets) was 64%. In this case, the determination section 91 determines in step S11 that the uncoated paper ratio (64%) is greater than the reference value V11 (here, 60%).

Next, the process proceeds from step S11 to step S12, and the determination unit 91 determines that the patch forming operation is to be executed. If the uncoated paper ratio is smaller than the reference value V11, the process proceeds from step S11 to step S15, and it is determined that the patch forming operation is not to be performed.

In this way, the determination unit 91 determines that the patch forming operation is to be executed on the condition that the non-coated paper ratio is greater than the reference value V10 (here, V11). Then, the process advances from step S12 to step S13.

In step S13, the determination unit 91 determines the candidate arrangement region of the patch image P50 in the patch forming operation (the candidate region in which the patch image P50 should be arranged (formed) in the entire surface region of the intermediate transfer belt 21).

Fig. 5 is a diagram showing a subroutine process related to the candidate area specifying process (step S13) of specifying the candidate arrangement area (arrangement target area) of the patch image P50.

In step S13, a range in which the presence of aggregate M10 is estimated (estimated presence range B1) is determined at a linear contact portion (contact portion extending in a direction D2 perpendicular to the traveling direction D1) R10 (see fig. 7 and 8) at which the intermediate transfer belt 21 and the cleaning blade 2 contact each other (steps S21 to S25). Next, a corresponding area F1 (described later) on the intermediate transfer belt 21 corresponding to the estimated existence range B1 is determined as a candidate arrangement area of the patch image P50 (step S26).

Here, the estimated existence range B1 is determined using two references, respectively (steps S21 to S25). Specifically, the estimated existence range B1 is determined using the first references relating to both ends of the uncoated paper (steps S21, S22), and thereafter, the estimated existence range B1 is further determined using the second references relating to the image forming rate (steps S23 to S25).

First, the operation (steps S21 and S22) of determining the estimated existence range B1 using the first criterion will be described.

Here, as shown in fig. 13, in the intermediate transfer belt 21, a portion where the toner image N1 is formed during an image forming operation on the sheet (specifically, non-coated sheet) 100 is not in direct contact with the sheet 100, and a portion where the toner image N1 is not formed is in direct contact with the sheet 100. Therefore, in the intermediate transfer belt 21, the paper dust is more easily transferred from the paper sheet (uncoated paper) 100 to a portion in direct contact with the paper sheet 100 (not via the toner image N1) (the amount of paper dust transferred from the paper sheet 100 is large) than to a portion not in direct contact with the paper sheet 100.

For example, printing margins are often provided at both end portions in the direction D2 of the sheet (the width direction of the sheet), and a toner image (print) is formed less frequently than at the center portion of the sheet. Therefore, there are many opportunities for the paper to come into direct contact (without passing through the toner image) with the intermediate transfer belt 21 at both end portions of the paper. That is, in the intermediate transfer belt 21, more paper dust is transferred from the paper (uncoated paper) to the portions in contact with both end portions of the paper (uncoated paper) than the portions in contact with the central portion of the paper. Therefore, it is estimated that the possibility of forming the aggregate M10 is high in a portion corresponding to the passing position Q10 of both ends of the non-coated paper on the intermediate transfer belt 21 in the contact portion R10 (fig. 7) between the intermediate transfer belt 21 and the cleaning blade 2.

Further, although the passing position (passing position in the direction D2 perpendicular to the traveling direction D1) Q10 (fig. 7) of both ends of the sheet on the intermediate transfer belt 21 is predetermined for each sheet size, there is a case where the sheet is conveyed slightly deviated in the direction D2 from the predetermined passing position (assumed passing position) Q10 in actual sheet conveyance.

In view of these points, in steps S21, S22, a range (also referred to as a paper end vicinity range (or paper end prescribed range) a10) (see fig. 7) having a prescribed width (for example, a width of 10 mm) in the direction D2 centered around the assumed passing position Q10 on the intermediate transfer belt 21 at both ends (both ends in the direction D2) of the non-coated paper included in the plurality of output sheets of paper is determined as an estimated existing range B1.

In more detail, the sheet end vicinity range a10 regarding the sheet size of the non-coated sheet included in the plurality of output sheets is determined as the estimated presence range B1, taking into account that the passing position Q10 is assumed to differ for each sheet size. In other words, the paper end vicinity range a10 regarding all the non-coated paper sizes (non-coated paper sizes) included in the print history (fig. 6) may be determined as the estimated presence range B1.

First, in step S21, the determination unit 91 acquires the sheet size of the uncoated paper included in the plurality of (here, 1 ten thousand) output sheets based on the setting information (print history) in the print job. Here, three paper sizes (A3 size, a4 size, and postcard size) are obtained (see fig. 6).

Next, in step S22, the determination section 91 determines the paper end vicinity range a10 (fig. 7) of the uncoated paper for each paper size as the estimated existing range B1 based on the paper size of the uncoated paper. Here, the paper end portion vicinity range a10 concerning the a4 size, the A3 size, and the postcard size, respectively, is determined as the estimated presence range B1.

Thus, the estimated existing range B1 is determined using the first reference with respect to both ends of the uncoated paper (steps S21, S22). Next, the process advances from step S22 to steps S23 to S25.

Next, an operation (steps S23 to S25) of determining the estimated existence range B1 using the second criterion regarding the image forming rate will be described.

In steps S23 to S25, a low formation rate range (described below) is determined as the estimated presence range B1.

The low formation rate range is a divided range in which the image formation rate (printing rate) in the image forming operation performed before the maintenance operation is less than a predetermined level among a plurality of (eight in this case) divided ranges a50 (see fig. 8) obtained by dividing the intermediate transfer belt 21 in a direction D2 perpendicular to the traveling direction D1. More specifically, the low formation rate range is a divided range in which the image formation rate in a corresponding region (a predetermined length region (described later)) is less than a predetermined level among the plurality of divided ranges a 50. This low formation rate range is also referred to as a low print rate range or the like.

First, in step S23, the determination section 91 divides the intermediate transfer belt 21 (contact portion R10) into a plurality of (here, eight) divided ranges a50 (refer to fig. 8) in the direction D2, and determines whether each of the divided ranges a50(a51 to a58) is a low formation rate range.

Specifically, for each of the plurality of divisional ranges a51 through a58, the ratio (image forming ratio) of the area of adhesion of toner (toner for transfer to paper) to the area of the corresponding region of predetermined length is calculated. The predetermined length region is a region extending in the traveling direction D1 by a predetermined section K1 (described below) with the division range a50 as the short side direction. The predetermined section K1 is a section (section of 500 m) between a position back-traced by a predetermined distance (for example, 500 m) from the end position of the closest image forming operation and the end position. That is, the area of the predetermined-length region is calculated by multiplying the width of the division range a50 by the predetermined distance (the width of the division range a50 × the predetermined distance). Next, it is determined whether or not the image formation rate in the corresponding predetermined length region is smaller than a predetermined value W1 (e.g., 3%) for each of the plurality of division ranges a51 to a 58. For example, when the image formation rate with respect to the division range a58 is smaller than the predetermined value W1, it is determined in step S23 that the division range a58 is a low formation rate range.

Next, in step S24, the determination unit 91 determines whether or not a low formation rate range exists.

For example, when it is determined in step S23 that any one of the plurality of division ranges a51 to a58 (for example, division range a58) is a low formation rate range, it is determined in step S24 that a low formation rate range exists, and the process proceeds from step S24 to step S25. If it is determined in step S23 that none of the plurality of division ranges a51 to a58 is the low formation rate range, it is determined in step S24 that no low formation rate range is present, and the process proceeds from step S24 to step S26 without going through step S25.

In step S25, the determination unit 91 determines, as the estimated existence range B1, the division range a50 (e.g., a58) determined to be the low formation rate range among the plurality of division ranges a51 to a 58.

In this manner, the estimated existence range B1 is determined using the first references relating to both ends of the uncoated paper (steps S21, S22), and the estimated existence range B1 is further determined using the second references relating to the image forming rate (steps S23 to S25).

Next, the process advances from step S25 to step S26.

In step S26, the determination unit 91 determines that the patch image P50 should be formed in the corresponding region (two-dimensional region) F1 (see fig. 7 and 8) on the intermediate transfer belt 21 corresponding to the estimated existence range B1 (the paper end vicinity range a10 and the low formation rate range (the division range determined as the low formation rate range) a 50). Specifically, the determination unit 91 determines the corresponding region F1 as a candidate arrangement region of the patch image P50. Specifically, in the entire surface area of the intermediate transfer belt 21, an elongated rectangular area F1 extending in the traveling direction D1 and having the estimated existing range B1 as the entire width (the length in the short side direction is the width of the estimated existing range B1) is determined as a candidate arrangement area of the patch image P50.

If the candidate arrangement region of the patch image P50 is thus determined (step S13), the process proceeds from step S13 (fig. 4) to step S14, and maintenance actions (patch forming action and moving action) are performed.

Specifically, on the intermediate transfer belt 21, the patch image P50 is formed in an area determined as a candidate arrangement area (a corresponding area F1 (refer to fig. 7 and 8) corresponding to the estimated existing range B1).

Fig. 7 shows a patch image P50 formed in a corresponding region F1 corresponding to the paper end vicinity range a10 (estimated existing range B1). Further, in fig. 8, a patch image P50 formed in a corresponding region F1 corresponding to the dividing range a50 (estimated existing range B1) determined to be the low formation rate range is shown. In the case where both the sheet end vicinity range a10 and the low formation rate range a50 are determined as the estimated presence range B1, the patch image P50 is formed in both the corresponding region F1 of fig. 7 and the corresponding region F1 of fig. 8. In this case, when at least a part of the sheet end vicinity range a10 overlaps at least a part of the low formation rate range a50, the patch image P50 is formed in the corresponding region (placement candidate region) corresponding to the range of the union of the sheet end vicinity range a10 and the low formation rate range a 50.

Next, the intermediate transfer belt 21 travels toward the cleaning blade 2 so that the patch image P50 on the intermediate transfer belt 21 collides with the cleaning blade 2.

Fig. 3 is a diagram showing a patch image P50.

The patch image P50 is a toner image for removing the aggregate M10 generated between the intermediate transfer belt 21 and the cleaning blade 2. Here, the patch image P50 is formed of a solid image of a single color (any one of YMCK colors) of toner (toner layer). The patch image P50 is not limited to a solid image, and may be a halftone image of a predetermined level (e.g., 90%) or more, for example.

An edge E1 (boundary portion) of the patch image P50 on the downstream side of the traveling direction D1 of the patch image P50 (moving direction of the intermediate transfer belt 21) extends in a direction C1 that is not perpendicular (and not parallel) to the traveling direction D1. In other words, the angle θ (fig. 3) formed by the extending direction C1 of the edge E1 (edge inclined with respect to the traveling direction D1) on the downstream side in the traveling direction D1 of the patch image P50 and the traveling direction D1 is not a right angle. The angle θ is preferably 30 to 60 degrees (more preferably 45 degrees). Further, the edge E1 preferably extends linearly.

As shown in fig. 3, the patch image P50(P51A) is formed in a triangular shape. Note that, for example, as shown in fig. 17, the patch image P50(P52) may be formed in a rectangular shape (rectangular shape or the like). In this case, each side of the rectangular patch image P52 is inclined with respect to the traveling direction D1.

Here, the length (width) of one patch image P50 (specifically, the edge E1 of the patch image P50) in the direction D2 is the same as the length (width) of the estimated existence range B1 (fig. 3) (the length (width) of the candidate arrangement region in the direction D2). Note that, without being limited to this, the width of the patch image P50 (edge E1) in the direction D2 may be larger than the length of the estimated presence range B1, or may be smaller than the length of the estimated presence range B1.

Here, a plurality of (specifically, three) patch images P50 are arranged in a row in the traveling direction D1. Specifically, as shown in fig. 3, the edge E1 on the downstream side in the traveling direction D1 of each of the plurality of patch images P50(P51A) arranged in the traveling direction D1 is inclined in a direction in which the left end (left end) of one side (left side) and the other side (right side) in the direction D2 collides with the cleaning blade 2 before the right end (right end). More specifically, the widths (lengths in the direction D2) of the plurality of patch images P51A are the same length as each other. These patch images P51A are aligned in a row in the traveling direction D1 (in a direction parallel to the traveling direction D1) in the candidate arrangement region.

In the patch forming operation, the patch image P50 is transferred from the photosensitive member 11 to the intermediate transfer belt 21 and formed on the intermediate transfer belt 21.

When the maintenance operation (moving operation) is performed, a separating operation is performed to separate the secondary transfer roller 22 (fig. 1) from the intermediate transfer belt 21. Thereby, all of the patch images P50 formed on the intermediate transfer belt 21 reach (collide with) the cleaning blade 2. However, without being limited to this, for example, a secondary transfer bias (secondary transfer voltage) having the same polarity as that of the toner image (patch image P50) may be applied to the secondary transfer roller 22 so that the toner image is not electrostatically transferred to the secondary transfer roller 22 and the entire patch image P50 on the intermediate transfer belt 21 may reach the cleaning blade 2.

When the patch image P50 formed on the intermediate transfer belt 21 reaches the cleaning blade 2, the patch image P50 is scraped off by the cleaning blade 2. At this time, as described below, in the edge E1 of the patch image P50, the toner of the patch image P50 scraped off by the cleaning blade 2 flows to one side (right side here) in the direction D2 (left-right direction in fig. 9 to 11 and the like) perpendicular to the traveling direction D1 of the patch image P50 at the portion reaching the cleaning blade 2.

Fig. 9 to 11 are views (plan views) showing a state where the patch image P50 of the intermediate transfer belt 21 is scraped off by the cleaning blade 2.

First, when the left end of the edge E1 of the patch image P50 reaches the cleaning blade 2 (see fig. 9), the toner at the left end of the edge E1 (toner on the intermediate transfer belt 21) is scraped off from the intermediate transfer belt 21 by the cleaning blade 2. The toner (powder) peeled off from the intermediate transfer belt 21 slightly moves (overflows) to the right side of fig. 9 (the direction in which the toner can move) from the position where it reaches the cleaning blade 2.

In this state, when new toner (subsequent toner) reaches the cleaning blade 2, the toner that has first reached the cleaning blade 2 and has been peeled off from the intermediate transfer belt 21 is pressed to the right side in fig. 9 by the powder pressure of the subsequent toner (pressure received from the surface on the right side of the portion of the edge E1 that has newly reached the intermediate transfer belt 21). The toner pushed to the right falls down and is collected in the lower portion of the housing 4 (fig. 2).

Then, similarly, when the patch image P50 further advances from the state of fig. 9 to the downstream side in the advancing direction D1 (see fig. 10), the toner in the portion of the edge E1 of the patch image P50 that has reached the cleaning blade 2 is scraped off by the cleaning blade 2 and slightly moved to the right side, and is pressed to the right side by the subsequent powder pressure of the toner.

In this manner, the toner (powder) of the portion of the edge E1 extending in a direction not perpendicular to the traveling direction D1 that reaches the cleaning blade 2 first and is scraped off by the cleaning blade 2 is pushed to the right side by the powder pressure of the subsequent toner. More specifically, this phenomenon occurs continuously with the movement (travel) of the intermediate transfer belt 21.

When the edge E1 collides with the aggregate M10, the toner in the portion of the edge E1 scraped off by the cleaning blade 2 immediately before reaching the aggregate M10 is pushed toward the aggregate M10 (from the left side of the aggregate M10). When the toner flowing to the right collides with the aggregate M10 (specifically, the left surface of the aggregate M10), the aggregate M10 is peeled off from the cleaning blade 2 by the force (powder pressure) of the toner from the left side. Then, the aggregate M10 flows to the right side (see fig. 11) together with the toner, and is collected (removed) in the lower portion of the housing 4 (fig. 2).

As described above, the aggregate M10 was removed. Therefore, the agglutinated matter M10 is prevented from biting into between the intermediate transfer belt 21 and the cleaning blade 2, and therefore the agglutinated matter M10 can be more reliably removed from the cleaning blade 2, as compared with the technique described in patent document 1 (the technique of causing the edge E90 (fig. 21) extending in the direction D2 perpendicular to the traveling direction D1 to collide with the agglutinated matter M10). Further, the occurrence of cleaning failure can be suppressed.

Fig. 12 is a diagram (graph) showing transition of occurrence of a cleaning failure (here, striped image noise) in the case where the above-described patch forming operation is performed and transition of occurrence of a cleaning failure in the case where the patch forming operation is not performed.

Here, when the external additive of the toner and the lubricant on the photoreceptor 11 are transferred to the intermediate transfer belt 21 in a state where a large amount of paper powder is present on the intermediate transfer belt 21, the aggregate M10 is easily generated particularly between the cleaning blade 2 and the intermediate transfer belt 21. In order to compare the transition of the occurrence of the cleaning failure according to the execution or non-execution of the patch forming operation in a situation where the aggregate M10 is easily generated, an experiment is performed in which the following operations are repeated: 4000 sheets of uncoated paper (recycled paper or the like) with a low coverage (e.g., 0%) and 1000 sheets of uncoated paper with a high coverage (e.g., 30%) are conveyed. More specifically, 4000 sheets of uncoated paper with a low coverage rate are conveyed so that a large amount of paper dust is present on the intermediate transfer belt 21, and 1000 sheets of uncoated paper with a high coverage rate are conveyed so that the external additive and the lubricant are transferred to the intermediate transfer belt 21. In this way, in a situation where the aggregate M10 is easily generated, the transition of the occurrence of the cleaning failure regarding whether the patch forming operation is performed or not is compared. When the occurrence of a cleaning failure is confirmed when the patch forming operation is executed, the patch forming operation is executed at the timing when a predetermined number of sheets (for example, 1 ten thousand sheets) of paper are conveyed. That is, the patch forming operation is executed every predetermined number of sheets.

The results of such experiments are: when the patch forming operation is not performed, when the number of printed output sheets reaches 8 ten thousand, a cleaning failure (striped image noise) starts to occur. On the other hand, when the patch forming operation for forming the patch image P50 (fig. 3) is performed every predetermined number of sheets (here, 1 ten thousand sheets), it is confirmed that the cleaning failure does not occur even if the number of printed output sheets exceeds 20 ten thousand sheets (see fig. 12). As can be seen from the experimental results, the occurrence of cleaning failure can be suppressed by executing the patch forming operation.

In the first embodiment, whether or not to execute the patch forming operation is determined based on the sheet type information of the plurality of output sheets that have been printed and output (step S11). More specifically, the execution of the patch forming operation is determined on the condition that the ratio of the non-coated paper to the entire plurality of output sheets (non-coated paper ratio) is greater than the reference value V10. Therefore, whether to perform the patch forming action can be determined more appropriately.

Specifically, in the first embodiment, in response to the arrival of a predetermined time (for example, a time at which the number of printed output sheets reaches a predetermined number of sheets (for example, 1 ten thousand sheets)), the size relationship between the uncoated paper ratio and the reference value V10 is compared, and whether or not the patch forming operation is to be executed is determined (step S11). More specifically, even when the predetermined time has come, when the non-coated paper ratio is smaller than the reference value V10, it is determined that the patch forming operation is not performed (step S15) and the patch image P50 formed of toner is not formed on the intermediate transfer belt 21. Therefore, compared to the case where the patch forming operation is always executed in response to the arrival of the predetermined time, the frequency of execution of the patch forming operation is reduced, and therefore, the consumption of toner can be suppressed.

In the first embodiment, the range in which the aggregate M10 is estimated to be present (estimated presence range B1) is identified in the contact portion R10 between the intermediate transfer belt 21 and the cleaning blade 2, and the patch image P50 is determined to be formed in the region F1 (see fig. 7 and 8) corresponding to the estimated presence range B1 on the intermediate transfer belt 21 (step S13). Therefore, compared to the case where the patch image P50 is formed all the time in the area corresponding to the entire range of the contact portion R10, the consumption of toner can be further suppressed.

In the image forming apparatus, image stabilization processing (image stabilization operation) may be performed to correct the formation position of the toner image of each color YMCK and the density of the reproduced image. In this image stabilization processing, registration correction processing and the like are performed.

For example, patent document 2 discloses a technique for performing such an image stabilization operation (alignment correction processing or the like).

In the registration correction process of patent document 2, registration patterns formed of toner are formed on the intermediate transfer belt in a linear shape and at an angle of, for example, 45 degrees with respect to the traveling direction of the intermediate transfer belt for each color of YMCK, and the registration patterns of each color are aligned in the traveling direction of the intermediate transfer belt in a predetermined region on the intermediate transfer belt. The formation position of the alignment pattern of each color YMCK is detected by an optical sensor, and the amount of positional deviation of each color is determined based on the detection result. The image forming positions of the respective colors are corrected based on the thus obtained positional shift amounts.

When the amount of change (amount of change) in the temperature and humidity in the image forming apparatus exceeds a predetermined value, such an image stabilizing operation (an operation of forming a toner image for correcting the toner forming position of each color YMCK on the intermediate transfer belt) is performed.

On the other hand, the patch forming operation in the present application is performed for a purpose different from the image stabilizing operation, and is performed based on a condition different from the image stabilizing operation.

Specifically, in the image stabilizing operation in the technique described in patent document 2, a pattern image for correcting the image forming position of each color YMCK is formed on the intermediate transfer belt, and in the patch forming operation of the present application, as described above, a patch image P50 for removing the aggregate M10 generated between the intermediate transfer belt 21 and the cleaning blade 2 is formed on the intermediate transfer belt 21. The image forming operation in the technique described in patent document 2 is performed when the amount of change in the temperature and humidity in the image processing apparatus exceeds a predetermined value, and the patch forming operation in the present application is performed based on the paper type information of a plurality of output paper sheets that have been printed and output (whether each of the plurality of output paper sheets is coated paper or uncoated paper), as described above.

As described above, the patch forming operation in the present application is greatly different from the technique described in patent document 2.

< 2. second embodiment >

The second embodiment is a modification of the first embodiment. Hereinafter, differences from the first embodiment will be mainly described.

In the first embodiment, the reference value V10(V11) regarding whether or not the patch forming operation is executed is fixed.

In contrast, in the second embodiment, the reference value V10 is changed according to the supply amount of the lubricant supplied to the surface of the photosensitive body 11.

Here, a lubricant (lubricant) that reduces the friction coefficient of the photoreceptor 11 is applied (supplied) to the surface of the photoreceptor 11 (fig. 1). The lubricant applied to the surface of the photoreceptor 11 is transferred from the photoreceptor 11 to the intermediate transfer belt 21 during an image forming operation. When the lubricant transferred from the photoreceptor 11 to the intermediate transfer belt 21 and the paper powder transferred from the paper (uncoated paper) to the intermediate transfer belt 21 are mixed together, the paper powder is easily solidified. Therefore, when the supply amount of the lubricant supplied (applied) to the photoreceptor 11 is larger than a certain level, the growth rate of the aggregate M10 on the cleaning blade 2 (the rate at which the aggregate M10 becomes larger) is higher than when the supply amount of the lubricant is smaller than a certain level. In contrast, in the case where the supply amount of the lubricant is less than a certain degree, the growth rate of the agglomerate M10 is slower than in the case where the supply amount of the lubricant is greater than a certain degree.

In view of this, in the second embodiment, the reference value V10 is changed according to the supply amount of the lubricant supplied to the surface of the photosensitive body 11.

The lubricant is applied (supplied) to the surface of the photoreceptor 11 by a lubricant application mechanism 70 (described below) provided in the photoreceptor cleaning device 17 (fig. 1).

Fig. 15 is a cross-sectional view of the photoreceptor cleaning device 17 viewed from the + X side.

The lubricant applying mechanism 70 has a brush (lubricant applying brush) 71, a lubricant block (solid lubricant) 72, and an elastic member 73.

The brush 71 scrapes off the lubricant from the lubricant block 72 and applies (supplies) the scraped lubricant to the photoreceptor 11. The brush 71 is provided in contact with the surface of the photoreceptor 11 and is configured to be rotatable.

The elastic member 73 presses the lubricant block 72 toward the brush 71. As the elastic member 73, a compression coil spring (a compression coil spring in a state compressed from a natural length) is exemplified.

In the lubricant applying mechanism 70, the brush 71 scrapes the lubricant from the lubricant block 72 in accordance with the rotation of the brush 71, and the scraped lubricant is applied (supplied) to the photoreceptor 11.

As described below, the supply amount of the lubricant from the lubricant block 72 to the photoreceptor 11 decreases with time.

Fig. 16 is a diagram showing changes in the amount of lubricant supplied. The vertical axis in fig. 16 indicates the supply amount of the lubricant supplied to the photoreceptor 11, and the horizontal axis in fig. 16 indicates the lifetime ratio. The lifetime ratio is a ratio of the current supply amount of the lubricant to the supply amount of the lubricant supplied from the lubricant cake 72 in the lifetime reached state (the state in which the lubricant cake 72 should be replaced with the lubricant cake 72 in the new state (lifetime reached state)) to the photoreceptor 11. The smaller the life ratio, the closer the lubricant cake 72 is to the new state, and the larger the life ratio, the closer the lubricant cake 72 is to the end-of-life state.

When the lubricant cake 72 is in a new state (when the life ratio of the lubricant cake 72 is 0%), the amount of lubricant applied (supplied amount) to the photoreceptor 11 is the largest. Thereafter, each time the brush 71 scrapes the lubricant of the lubricant block 72, the lubricant block 72 gradually decreases (the life ratio of the lubricant block 72 increases), and the supply amount of the lubricant to the photoreceptor 11 decreases with time. For example, when the life ratio of the lubricant cake 72 reaches 50%, the supply amount of the lubricant supplied from the lubricant cake 72 to the photosensitive body 11 is reduced to an amount of about 2/3(≈ 0.42/0.65) with respect to the supply amount (initial supply amount) of the lubricant supplied from the lubricant cake 72 in a new state.

In the second embodiment, the reference value V10 regarding whether or not the patch forming operation is to be executed is changed in accordance with the supply amount (the supply amount of the lubricant from the lubricant block 72 to the photosensitive body 11) that decreases with the passage of time in this manner. Specifically, the reference value V10 is switched according to whether or not the life ratio of the lubricant cake 72 is smaller than a predetermined value G (e.g., 50%).

Fig. 14 is a flowchart relating to the patch forming action of the second embodiment. As shown in fig. 14, in the second embodiment, the processing of steps S31, S32 is performed in addition to steps S11 to S15.

In step S31, the determination unit 91 determines whether or not the life ratio is smaller than a predetermined value G (e.g., 50%). In other words, it is determined whether the supply amount of the lubricant supplied from the lubricant block 72 to the photosensitive body 11 is reduced to the amount of 2/3 of the initial supply amount (the supply amount of the lubricant supplied from the lubricant block 72 in a new state).

In the case where the life ratio of the lubricant block 72 is less than the prescribed value G (50%) (in other words, in the case where the supply amount of the lubricant is more than the amount 2/3 of the initial supply amount), the process proceeds from step S31 to step S11, and the determination section 91 determines whether or not the patch forming operation is to be performed using the reference value V11(V10) (e.g., 60%).

On the other hand, when the life ratio of the lubricant block 72 is equal to or greater than the predetermined value G (50%) (in other words, when the supply amount of the lubricant is smaller than the amount 2/3 of the initial supply amount), the process proceeds from step S31 to step S32, and the determination unit 91 determines whether or not the patch forming operation is to be performed using the reference value V12 (V10). The reference value V12 (e.g., 80%) is a value greater than the reference value V11 (60%) (V12> V11). Specifically, whether to perform the patch forming action is determined according to whether the non-coated paper rate is greater than a reference value V12 (80%).

The processing contents of steps S12 to S15 are the same as those of the first embodiment.

In this manner, in the second embodiment, the reference value V10 regarding whether or not to perform the patch forming operation is changed according to the supply amount of the lubricant supplied to the photosensitive body 11, and therefore, the patch forming operation can be performed more appropriately than in the case where whether or not to perform the patch forming operation is determined always at the same reference value V10 (e.g., V11).

Specifically, in the case where the supply amount of the lubricant is less than a certain degree (here, the amount of 2/3 of the initial supply amount), the reference value V12 (80%) that is greater than the reference value V11 (60%) is used to determine whether to perform the patch forming action (step S32). In other words, when the growth rate of the aggregate M10 is slow (compared to the case where the supply amount of the lubricant is more than a certain amount) due to the supply amount of the lubricant being less than a certain amount, the frequency of execution of the patch forming operation is reduced. Therefore, consumption of the toner can be suppressed.

Here, when the lubricant is supplied to the photosensitive member 11, the reference value V10 is changed according to the amount of the lubricant supplied, but the present invention is not limited to this. For example, when lubricant is supplied to the intermediate transfer belt 21 without supplying lubricant to the photosensitive member 11, the reference value V10 may be changed according to the supply amount of lubricant supplied to the intermediate transfer belt 21. In the case where the lubricant is supplied to both the photosensitive member 11 and the intermediate transfer belt 21, the reference value V10 may be changed according to the supply amount of the lubricant supplied to both the photosensitive member 11 and the intermediate transfer belt 21.

< 3. variants, etc. >

The embodiments of the present invention have been described above, but the present invention is not limited to the above description.

For example, in the above embodiments and the like, the patch image P50 is formed by a solid image of a single color toner (toner layer), but the present invention is not limited to this, and the patch image P50 may be formed by overlapping (using toner layers of two colors) solid images of two colors of toners (toner of about 2 times the single color toner layer). Alternatively, patch image P50 may be formed by superimposing solid images of three or more colors of toner.

Accordingly, the amount of toner forming the patch image P50 is larger than that in the case where the patch image P50 is formed by a solid image of monochromatic toner, and the toner collides with the aggregate M10 attached to the cleaning blade 2 with a larger powder pressure. Therefore, the aggregate M10 adhering to the cleaning blade 2 can be more reliably peeled off from the cleaning blade 2.

The belt cleaning device 8 has a limit (cleaning limit) of the amount of toner that can be cleaned by the cleaning blade 2. When the toner amount (amount of adhesion) of the toner reaching the cleaning blade 2 is larger than the cleaning limit, some toner may pass between the cleaning blade 2 and the intermediate transfer belt 21, resulting in occurrence of cleaning failure such as streak image noise.

In order to prevent such a problem, when the patch image P50 is formed by superimposing solid images of two or more colors of toner, the intermediate transfer belt 21 may be rotated by 2 or more revolutions, for example, during the patch forming operation. In detail, even when some of the toners in the patch image P50 formed of two or more colors of toners temporarily pass through between the cleaning blade 2 and the intermediate transfer belt 21 during the 1 st rotation of the intermediate transfer belt 21, these toners can be scraped off by the cleaning blade 2 during the 2 nd rotation.

In the above-described embodiments and the like, the edge E1 on the downstream side of the traveling direction D1 of each of the plurality of patch images P51A (see fig. 3) arranged in the traveling direction D1 is inclined (is "right shoulder descent edge") in a direction in which the left end (left end) of the both sides in the direction D2 collides with the cleaning blade 2 before the right end (right end) (in short, the direction in which the right shoulder descends). In other words, in each of the above embodiments and the like, the toner of each of the plurality of patch images P50 is caused to collide with the aggregate M10 adhering to the cleaning blade 2 from one side (left side) of both sides in the direction D2 perpendicular to the traveling direction D1 (see also fig. 11).

Here, the shape of the agglomerate M10 is amorphous. Therefore, depending on the shape of the aggregate M10, if only the toner (the toner of the patch image P50) is caused to collide with the aggregate M10 attached to the cleaning blade 2 from one side (for example, the left side) in the direction D2 perpendicular to the traveling direction D1, the aggregate M10 may not be peeled off from the cleaning blade 2.

In view of this, as described below, it may be: the toner collides with the aggregate M10 attached to the cleaning blade 2 not only from one side (left side) of both sides of the direction D2 perpendicular to the traveling direction D1 but also with the aggregate M10 attached to the cleaning blade 2 from the other side (right side) of both sides of the direction D2 perpendicular to the traveling direction D1. This enables the aggregate M10 adhering to the cleaning blade 2 to be more reliably separated from the cleaning blade 2.

Fig. 18 is a diagram showing a patch image P50 according to this modification.

Here, the three patch images P50 are arranged in a row in the traveling direction D1. In detail, in the candidate arrangement region, the patch images P51A, P51B, and P51A are sequentially arranged in a row along the traveling direction D1 (in a direction parallel to the traveling direction D1). In other words, the patch images P51A, P51B are alternately arranged in a column along the traveling direction D1.

As shown in fig. 18, the edge E1 on the downstream side in the traveling direction D1 of the patch image P51A is inclined (is "right shoulder lowering edge") in a direction in which the left end of both sides in the direction D2 collides with the cleaning blade 2 before the right end (in short, the direction in which the right shoulder is lowered). On the other hand, the edge E1 on the downstream side in the traveling direction D1 of the patch image P51B is inclined (is "left shoulder descending edge") in a direction in which the right end of both sides in the direction D2 collides with the cleaning blade 2 earlier than the left end (in short, in a direction in which the left shoulder descends). In detail, the width (length in the direction D2) of the edge E1 (right shoulder descent edge) of the patch image P51A is the same length as the width of the edge E1 (left shoulder descent edge) of the patch image P51B. More specifically, the patch image P51A and the patch image P51B are formed so as to be line-symmetric with respect to the center line (center line parallel to the traveling direction D1) U1 of the patch image P51A (patch image P51B).

Such patch images P51A, P51B may be arranged in the traveling direction D1.

Accordingly, when each of the patch images P51A, P51B is scraped off by the cleaning blade 2, the toner flow at the edge E1 of the patch image P51A and the toner flow at the edge E1 of the patch image P51B are opposite to each other. Specifically, as shown by the right arrow in fig. 9 to 11, when the cleaning blade 2 scrapes off the edge E1 of the patch image P51A, the toner of the portion scraped off by the cleaning blade 2 in the edge E1 of the patch image P51A is pushed to the right in the direction D2 perpendicular to the traveling direction D1. On the other hand, as shown by the leftward arrow in fig. 19, when the cleaning blade 2 scrapes the edge E1 of the patch image P51B, the toner of the portion scraped by the cleaning blade 2 in the edge E1 of the patch image P51B is pushed to the left in the direction D2 perpendicular to the traveling direction D1.

Therefore, by using both the patch images P51A, P51B, the toner collides with the aggregate M10 adhering to the cleaning blade 2 from both sides of one side (right side) and the other side (left side) in the direction D2 perpendicular to the traveling direction D1. In other words, the direction of the toner colliding with the aggregate M10 adhering to the cleaning blade 2 (the direction of the force acting on the aggregate M10) is switched between the patch image P51A and the patch image P51B. As a result, even when the aggregate M10 cannot be peeled off from the cleaning blade 2 by the toner of the patch image P51A, the aggregate M10 can be peeled off from the cleaning blade 2 by the toner of the patch image P51B. Therefore, the aggregate M10 adhering to the cleaning blade 2 can be more reliably peeled off from the cleaning blade 2.

In the above embodiments and the like, the paper end vicinity range a10 (fig. 7) regarding the paper size (for example, A3 size, a4 size, and postcard size) of all the uncoated papers included in the plurality of output papers that have been printed and output is determined as the estimated existence range B1, but the present invention is not limited thereto.

Here, as described above, when a sheet (specifically, a non-coated sheet) is subjected to an image forming operation, the more chance the sheet is in direct contact with the intermediate transfer belt 21 (without a toner image), the more chance the paper powder is transferred from the sheet (the non-coated sheet) to the intermediate transfer belt 21, and the more easily the aggregate M10 is generated.

In view of this, the sheet end vicinity range a10 relating to the sheet size of non-coated sheets that are conveyed (output) in an integrated manner by more than a certain number (for example, 100 sheets) of sheets out of all the sheet sizes of non-coated sheets included in a plurality of output sheets may be determined as the estimated existence range B1. In other words, the paper end vicinity range a10 related to the non-coated paper size (i.e., the non-coated paper size in which the cumulative number of passes (cumulative number of outputs) of the non-coated paper having the same size is larger than the predetermined number of passes) among all the non-coated paper sizes (i.e., the size of the non-coated paper) included in the print history (fig. 6) may be determined as the estimated presence range B1.

In the example of fig. 6, the cumulative number of non-coated sheets (350 sheets) of a4 size and the cumulative number of non-coated sheets (6000 sheets) of a postcard size in all the sheet sizes (here, A3 size, a4 size, and postcard size) of the non-coated sheets included in the plurality of output sheets are larger than the fixed number of sheets (100 sheets), respectively. Further, the cumulative number of non-coated sheets of a3 size (50 sheets) out of all the sheet sizes of the non-coated sheets included in the plurality of output sheets is smaller than the certain number (100 sheets). In this case, the paper end vicinity range a10 relating to the A3 size may not be determined as the estimated presence range B1, and the paper end vicinity ranges a10 relating to the a4 size and the postcard size may be respectively determined as the estimated presence ranges B1.

In this way, the paper end vicinity range a10 relating to the paper size of the uncoated paper having the cumulative number of passes greater than the predetermined number of passes among all the paper sizes of the uncoated paper included in the plurality of output sheets can be determined as the estimated presence range B1.

Accordingly, from the sheet end vicinity range a10 regarding the sheet size of all the non-coated sheets included in the plurality of output sheets, a range in which the possibility of the presence of the aggregate M10 is higher than a certain degree is determined. In other words, the estimated existence range B1 is narrowed from the sheet end vicinity range a10 regarding all sheet sizes (here, the A3 size, the a4 size, and the postcard size) of the uncoated sheets included in the plurality of output sheets to the sheet end vicinity range a10 regarding the sheet size (here, the a4 size and the postcard size) of the uncoated sheets that are conveyed (output) cumulatively more than a certain number of sheets. Therefore, compared to the case where the sheet end vicinity range a10 regarding the sheet size of all the non-coated sheets included in the plurality of output sheets is determined as the estimated presence range B1, it is possible to suppress toner consumption while appropriately removing the aggregate M10.

Further, the paper end vicinity range a10 relating to the paper size of non-coated paper sheets that are continuously conveyed (output) more than a certain number of sheets of non-coated paper, out of all the paper sizes of non-coated paper sheets included in a plurality of output paper sheets, may be determined as the estimated existing range B1. In other words, the paper end vicinity range a10 related to the non-coated paper size in which the number of continuous passes (number of continuous output sheets) of the non-coated paper having the same size is larger than the predetermined number of sheets (in short, the non-coated paper size in which the number of continuous passes is larger than the predetermined number of sheets) among all the non-coated paper sizes included in the print history (fig. 6) may be determined as the estimated existence range B1.

Here, when the non-coated paper of "the same size" is conveyed "continuously" by a predetermined number of sheets or more, the aggregate M10 is easily generated in the range corresponding to the vicinity of both ends of the non-coated paper in the contact portion R10 between the cleaning blade 2 and the intermediate transfer belt 21. Conversely, even when the cumulative number of non-coated sheets of "the same size" is equal to or greater than the predetermined number, when the "number of continuous passes" of the non-coated sheets is not equal to or greater than the predetermined number, it is difficult to generate the aggregates M10 in the range corresponding to the vicinity of both ends of the non-coated sheets in the contact portion R10.

In view of this, the paper end vicinity range a10 relating to the paper size of uncoated paper having a continuous number of sheets passing through more than a certain number of sheets, out of all the paper sizes of uncoated paper included in a plurality of output sheets, may be determined as the estimated existing range B1.

In the example of fig. 6, the number of continuous sheets of uncoated paper having a postcard size (here, the A3 size, the a4 size, and the postcard size) in all the sheet sizes of the uncoated paper included in the plurality of output sheets is greater than a predetermined number (for example, 100 sheets). In addition, the number of continuous passes of a non-coated paper having a size of A3 and the number of continuous passes of a non-coated paper having a size of a4, out of all the sheet sizes of non-coated paper included in the plurality of output sheets, are less than a certain number (100 sheets), respectively. In this case, the paper end vicinity range a10 relating to the A3 size and the paper end vicinity range a10 relating to the a4 size may not be determined as the estimated presence range B1, respectively, while the paper end vicinity range a10 relating to the postcard size may be determined as the estimated presence range B1.

Accordingly, from the sheet end vicinity range a10 regarding the sheet size of all the non-coated sheets included in the plurality of output sheets, a range in which the possibility of the presence of the aggregate M10 is higher than a certain degree is determined. In other words, the estimated existence range B1 is further narrowed from the sheet end vicinity range a10 relating to the sheet size (here, the a4 size and the postcard size) of "cumulatively" conveying (outputting) the uncoated sheets more than the certain number to the sheet end vicinity range a10 relating to the sheet size (here, the postcard size) of "continuously" conveying (outputting) the uncoated sheets more than the certain number. Therefore, compared to the case where the paper end vicinity range a10 regarding the paper size of the non-coated paper having the cumulative number of passes greater than the predetermined number of passes among all the paper sizes of the non-coated paper included in the plurality of output sheets is determined as the estimated existence range B1, the toner consumption can be further suppressed while the aggregate M10 is more appropriately removed.

In the above-described embodiments and the like, both the first specification operation (steps S21 and S22 (fig. 5)) for specifying the estimated presence range B1 using the first criteria relating to both ends of the uncoated paper and the second specification operation (steps S23 to S25) for specifying the estimated presence range B1 using the second criteria relating to the image formation rate are performed, but the present invention is not limited to this. For example, the first determination operation may be performed without performing the second determination operation, and conversely, the second determination operation may be performed without performing the first determination operation.

Claims (20)

1. An image forming apparatus is characterized by comprising:

an image carrier that temporarily carries a toner image and transfers the toner image to a sheet;

a cleaning member that scrapes off residual toner remaining on the image carrier after transfer to the sheet of paper, in association with relative movement with the image carrier;

a control mechanism that performs a maintenance operation of removing aggregates generated between the image carrier and the cleaning member;

the maintenance operation includes a patch forming operation of forming a patch image on the image bearing member, the patch image being a toner image for removing the aggregates, and a moving operation of moving the image bearing member toward the cleaning member to cause the patch image on the image bearing member to collide with the cleaning member,

an edge of the patch image on a downstream side of a traveling direction of the patch image extends in a direction not perpendicular to the traveling direction.

2. The image forming apparatus as claimed in claim 1,

the control means includes determination means for determining whether or not to execute the patch forming operation based on paper type information of a plurality of output sheets printed and output.

3. The image forming apparatus as claimed in claim 2,

the sheet type information contains information indicating whether the plurality of output sheets are coated sheets or non-coated sheets, respectively,

the determination means determines to execute the patch forming operation on the condition that a ratio of non-coated paper to all of the plurality of output sheets is larger than a reference value.

4. The image forming apparatus as claimed in claim 3,

the image forming apparatus further includes a photoreceptor for transferring a toner image to the image carrier,

the reference value is changed according to a supply amount of the lubricant supplied to a surface of at least one of the image carrier and the photoreceptor.

5. The image forming apparatus according to any one of claims 2 to 4,

the determination mechanism determines an estimated presence range that is a range in which the agglutinate is estimated to be present in a linear contact portion where the image carrier and the cleaning member contact each other,

the determination means determines that the patch image should be formed in an area on the image carrier corresponding to the estimated existence range.

6. The image forming apparatus as claimed in claim 5,

the determination means determines, as the estimated presence range, a range having a predetermined width in a direction perpendicular to the traveling direction with each of the assumed passage positions as a center.

7. The image forming apparatus as claimed in claim 5,

the determination mechanism divides the image carrier into a plurality of division ranges in a direction perpendicular to the traveling direction, and,

the determination means determines, as the estimated existence range, a range in which an image formation rate in an image forming operation performed before the maintenance operation is less than a predetermined degree, among the plurality of ranges.

8. The image forming apparatus according to any one of claims 1 to 7,

the patch image is formed of a solid image of toner.

9. The image forming apparatus as claimed in claim 8,

the patch image is formed by overlapping solid images of two or more colors of toner.

10. The image forming apparatus according to any one of claims 1 to 9,

in the patch forming operation, the first patch image and the second patch image are arranged along the traveling direction,

an edge on a downstream side in the traveling direction of the first patch image is inclined in a direction in which an end portion on one side of the traveling direction and an end portion on the other side of the traveling direction collide with the cleaning member before the end portion on the other side,

an edge on a downstream side in the traveling direction of the second patch image is inclined in a direction in which an end portion on the other side of the one side and the other side collides with the cleaning member before the end portion on the one side collides with the cleaning member.

11. A computer-readable storage medium storing a program for causing a computer incorporated in an image forming apparatus including an image carrier that temporarily carries a toner image and transfers the toner image to a sheet, and a cleaning member that scrapes off residual toner remaining on the image carrier after transfer to the sheet in association with relative movement with respect to the image carrier, to execute a series of steps of:

a) a step of executing a patch forming operation of forming a patch image on the image carrier, the patch image being a toner image for removing aggregates generated between the image carrier and the cleaning member;

b) a step of executing a moving action of causing the image carrier to travel toward the cleaning member to cause the patch image on the image carrier to collide with the cleaning member;

the computer-readable storage medium is characterized in that,

an edge of the patch image on a downstream side of a traveling direction of the patch image extends in a direction not perpendicular to the traveling direction.

12. The computer-readable storage medium storing a program according to claim 11,

the step a) comprises the following steps: a-1) determining whether to execute the patch forming operation based on the sheet type information of a plurality of output sheets printed and output.

13. The computer-readable storage medium storing a program according to claim 12,

the sheet type information contains information indicating whether the plurality of output sheets are coated sheets or non-coated sheets, respectively,

in the step a-1), the patch forming operation is determined to be performed on the condition that a ratio of the non-coated paper to the entire plurality of output sheets is larger than a reference value.

14. The computer-readable storage medium storing a program according to claim 13,

the image forming apparatus further includes a photoreceptor for transferring a toner image to the image carrier,

the reference value is changed according to a supply amount of the lubricant supplied to a surface of at least one of the image carrier and the photoreceptor.

15. The computer-readable storage medium storing a program according to any one of claims 12 to 14, wherein the program further causes the computer to execute the steps of:

c) a step of determining an estimated presence range in which the aggregate is estimated to be present, of linear contact portions where the image carrier and the cleaning member contact each other;

d) a step of determining that the patch image should be formed in an area on the image carrier corresponding to the presumed existence range.

16. The computer-readable storage medium storing a program according to claim 15,

assuming that the passing position is an assumed passing position on the image bearing member at both ends of the non-coated paper included in the plurality of output sheets in the direction perpendicular to the traveling direction, in the step c), a range having a predetermined width in the direction perpendicular to the traveling direction with each of the assumed passing positions as a center is determined as the estimated existence range.

17. The computer-readable storage medium storing a program according to claim 15,

the step c) comprises:

c-1) a step of dividing the image carrier into a plurality of divided ranges in a direction perpendicular to the traveling direction;

c-2) determining, as the estimated existence range, a divided range in which an image forming rate in the image forming operation performed before the step a) is less than a predetermined degree among the plurality of divided ranges.

18. The computer-readable storage medium storing a program according to any one of claims 11 to 17,

the patch image is formed of a solid image of toner.

19. The computer-readable storage medium storing a program according to claim 18,

the patch image is formed by overlapping solid images of two or more colors of toner.

20. The computer-readable storage medium storing a program according to any one of claims 11 to 19,

in the patch forming operation, the first patch image and the second patch image are arranged along the traveling direction,

an edge on a downstream side in the traveling direction of the first patch image is inclined in a direction in which an end portion on one side of the traveling direction and an end portion on the other side of the traveling direction collide with the cleaning member before the end portion on the other side,

an edge on a downstream side in the traveling direction of the second patch image is inclined in a direction in which an end portion on the other side of the one side and the other side collides with the cleaning member before the end portion on the one side collides with the cleaning member.

Images