阅读说明：本技术 图像形成装置以及记录介质 (Image forming apparatus and recording medium ) 是由 速水俊树 前山健志 北田朋 川中子隆 村上大辅 于 2020-02-06 设计创作，主要内容包括：本发明涉及图像形成装置以及记录介质。在中间转印方式的图像形成装置(1)中,中间转印带(421)具备基材层(421a)以及配置在基材层(421a)上的涂层(421b),图像形成装置(1)具备：一次转印辊(422),隔着中间转印带(421)与感光鼓(413)对置地配置,并与感光鼓(413)形成辊隙部；压力可变机构(422a),使一次转印辊(422)对感光鼓(413)的按压力改变；以及控制部,基于图像形成对象的纸张S的表面形状信息通过压力可变机构(422a)来控制一次转印辊(422)对感光鼓(413)的按压力。(The invention relates to an image forming apparatus and a recording medium. In an image forming apparatus (1) of an intermediate transfer system, an intermediate transfer belt (421) includes a base material layer (421a) and a coating layer (421b) disposed on the base material layer (421a), and the image forming apparatus (1) includes: a primary transfer roller (422) which is disposed opposite to the photosensitive drum (413) with an intermediate transfer belt (421) therebetween and forms a nip portion with the photosensitive drum (413); a pressure variable mechanism (422a) for changing the pressing force of the primary transfer roller (422) to the photosensitive drum (413); and a control unit that controls the pressing force of the primary transfer roller (422) against the photosensitive drum (413) by means of a pressure variable mechanism (422a) on the basis of the surface shape information of the sheet S to be subjected to image formation.)

1. An image forming apparatus of an intermediate transfer type for forming an image by transferring a toner image formed on an image carrier to a sheet through an intermediate transfer member,

the intermediate transfer body comprises a base material layer and a coating layer disposed on the base material layer,

the image forming apparatus includes:

a transfer member disposed opposite to the image carrier with the intermediate transfer member interposed therebetween, and forming a nip portion with the image carrier;

a pressure variable mechanism that changes a pressing force of the transfer member against the image carrier; and

and a control unit configured to control a pressing force of the transfer member against the image carrier by the pressure variable mechanism based on information on a surface shape of a sheet to be image-formed.

2. The image forming apparatus according to claim 1,

in the case where the sheet to be image-formed is a concave-convex sheet, the control section reduces the pressing force of the transfer member against the image carrier based on the information, as compared with the case where the sheet to be image-formed is a plain sheet.

3. The image forming apparatus according to claim 1 or 2,

when the sheet to be subjected to image formation is a concave-convex sheet, the control unit decreases the pressing force of the transfer member against the image carrier as the depth of the concave-convex as the information increases.

4. The image forming apparatus according to claim 2 or 3,

the control unit decreases the tension of the intermediate transfer member as the pressing force of the transfer member against the image carrier decreases.

5. The image forming apparatus according to claim 2 or 3,

the image forming apparatus includes a moving mechanism that moves the transfer member in a direction along a traveling direction of the intermediate transfer body,

the control unit decreases the pressing force of the transfer member against the image carrier, and moves the pressing position of the transfer member against the image carrier upstream in the traveling direction.

6. The image forming apparatus according to any one of claims 1 to 5,

the control section increases a transfer current in association with a decrease in pressing force of the transfer member against the image carrier.

7. The image forming apparatus according to any one of claims 1 to 6,

a plurality of the image carriers are provided on the outer peripheral side of the intermediate transfer body along the direction of travel of the intermediate transfer body,

the image forming apparatus includes a metallic blade that is in sliding contact with a surface of the intermediate transfer body, upstream of the image carrier that is most upstream in the traveling direction.

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

the image forming apparatus includes a lubricant applying mechanism that applies a lubricant to an outer surface of the intermediate transfer body or a member that is in contact with the outer surface of the intermediate transfer body.

9. The image forming apparatus according to claim 8,

the control unit controls the amount of lubricant applied by the lubricant applying unit based on the information.

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

the control section executes a removal process of removing the adhering matter on the intermediate transfer body before starting image formation on the uneven paper.

11. The image forming apparatus according to claim 10,

the control unit performs an idling operation of the intermediate transfer body as the removal processing.

12. The image forming apparatus according to claim 10,

the image forming apparatus includes a cleaning unit disposed downstream of a transfer position to a sheet and upstream of a toner image forming position by the image carrier in a traveling direction of the intermediate transfer member,

the control unit performs an operation of feeding the toner belt to the cleaning unit of the intermediate transfer body as the removal process.

13. The image forming apparatus according to any one of claims 1 to 12,

the coating is a coating comprising an inorganic oxide containing an organic component.

14. A non-transitory computer-readable recording medium storing a program, wherein the program is recorded in a computer-readable recording medium,

the computer of the image forming apparatus is caused to function as a control section,

the image forming apparatus is an intermediate transfer type image forming apparatus which performs image formation by transferring a toner image formed on an image carrier to a sheet through an intermediate transfer member,

the intermediate transfer body comprises a base material layer and a coating layer disposed on the base material layer,

the image forming apparatus includes:

a transfer member disposed opposite to the image carrier with the intermediate transfer member interposed therebetween, and forming a nip portion with the image carrier; and

a pressure variable mechanism for changing a pressing force of the transfer member to the image carrier,

the control section controls a pressing force of the transfer member against the image carrier by the pressure variable mechanism based on information on a surface shape of a sheet of an image forming object.

15. The recording medium of claim 14,

in the case where the sheet to be image-formed is a concave-convex sheet, the control section reduces the pressing force of the transfer member against the image carrier based on the information, as compared with the case where the sheet to be image-formed is a plain sheet.

16. The recording medium according to claim 14 or 15,

when the sheet to be subjected to image formation is a concave-convex sheet, the control unit decreases the pressing force of the transfer member against the image carrier as the depth of the concave-convex as the information increases.

17. The recording medium according to claim 15 or 16,

the control unit decreases the tension of the intermediate transfer member as the pressing force of the transfer member against the image carrier decreases.

18. The recording medium according to claim 15 or 16,

the image forming apparatus includes a moving mechanism that moves the transfer member in a direction along a traveling direction of the intermediate transfer body,

the control unit decreases the pressing force of the transfer member against the image carrier, and moves the pressing position of the transfer member against the image carrier upstream in the traveling direction.

19. The recording medium according to any one of claims 14 to 18,

the control section increases a transfer current in association with a decrease in pressing force of the transfer member against the image carrier.

20. The recording medium according to any one of claims 14 to 19,

a plurality of the image carriers are provided on the outer peripheral side of the intermediate transfer body along the direction of travel of the intermediate transfer body,

the image forming apparatus includes a metallic blade that is in sliding contact with a surface of the intermediate transfer body, upstream of the image carrier that is most upstream in the traveling direction.

21. The recording medium according to any one of claims 14 to 20,

the image forming apparatus includes a lubricant applying mechanism that applies a lubricant to an outer surface of the intermediate transfer body or a member that is in contact with the outer surface of the intermediate transfer body.

22. The recording medium according to claim 21,

the control unit controls the amount of lubricant applied by the lubricant applying unit based on the information.

23. The recording medium according to any one of claims 14 to 22,

the control section executes a removal process of removing the adhering matter on the intermediate transfer body before starting image formation on the uneven paper.

24. The recording medium of claim 23,

the control unit performs an idling operation of the intermediate transfer body as the removal processing.

25. The recording medium of claim 23,

the image forming apparatus includes a cleaning unit disposed downstream of a transfer position to a sheet and upstream of a toner image forming position by the image carrier in a traveling direction of the intermediate transfer member,

the control unit performs an operation of feeding the toner belt to the cleaning unit of the intermediate transfer body as the removal process.

26. The recording medium according to any one of claims 14 to 25,

the coating is a coating comprising an inorganic oxide containing an organic component.

Technical Field

The invention relates to an image forming apparatus and a recording medium.

Background

Conventionally, an intermediate transfer type image forming apparatus has been widely used which primarily transfers a toner image formed on a photoreceptor (image bearing member) to an intermediate transfer belt (intermediate transfer member) and secondarily transfers the toner image on the intermediate transfer belt to a sheet of paper.

In such an image forming apparatus, it is desired to form an image on a sheet having an uneven surface (uneven sheet) such as an embossed paper or a rough paper.

It is known that uneven paper is difficult for toner to reach the recessed portions during secondary transfer, and secondary transfer performance is deteriorated as compared with ordinary paper. This tendency becomes more remarkable if the toner has a large adhesion force to the intermediate transfer belt.

In order to reduce the adhesion of the toner, it has been proposed to coat a substrate layer containing Polyimide (PI) with Silica (SiO)₂) And a coating layer (also referred to as a surface layer) containing an inorganic oxide as a main component (see, for example, japanese patent application laid-open No. 2014-109586). In this intermediate transfer belt, the thicker the coating layer, the larger the distance between the toner and the opposite charge, and the smaller the adhesion force, so the secondary transferability becomes good.

However, the studies of the present inventors have revealed that when such an intermediate transfer belt is continuously used, the transferability to the uneven paper is deteriorated with the use as shown in fig. 14.

This is because the discharge product is more likely to adhere to the surface of the intermediate transfer belt coated with the coating layer than to the intermediate transfer belt not coated with the coating layer. It is considered that the contact angle of pure water is lowered as shown in fig. 15 due to the adhesion of discharge products, and the toner is hard to separate.

Further, it is considered that discharge products are likely to be depositedThe coating surface is formed by the silicon dioxide (SiO) of the coating₂) Is a structure having OH-groups bonded as terminal groups, and is a discharge product (NO)_x) Is a property of being easily attached to OH-groups.

Disclosure of Invention

The purpose of the present invention is to provide an image forming apparatus and a recording medium that can maintain good transferability to uneven paper.

In order to achieve at least one of the above objects, according to one aspect of the present invention, there is provided an image forming apparatus of an intermediate transfer system for forming an image by transferring a toner image formed on an image bearing member to a sheet of paper via an intermediate transfer member,

the intermediate transfer member includes a base material layer and a coating layer disposed on the base material layer,

the image forming apparatus includes:

a transfer member disposed opposite to the image carrier with the intermediate transfer member interposed therebetween, and forming a nip portion with the image carrier;

a pressure variable mechanism for changing a pressing force of the transfer member to the image carrier; and

and a control unit configured to control a pressing force of the transfer member against the image carrier by the pressure varying mechanism based on information on a surface shape of a sheet to be subjected to image formation.

In order to achieve at least one of the above objects, according to another aspect of the present invention, a recording medium on which an aspect of the present invention is reflected is a non-transitory computer-readable recording medium storing a program,

the computer of the image forming apparatus is caused to function as a control section,

the image forming apparatus is an intermediate transfer type image forming apparatus that forms an image by transferring a toner image formed on an image carrier to a sheet through an intermediate transfer member,

the intermediate transfer member includes a base material layer and a coating layer disposed on the base material layer,

the image forming apparatus includes:

a transfer member disposed opposite to the image carrier with the intermediate transfer member interposed therebetween, and forming a nip portion with the image carrier; and

a pressure variable mechanism for changing a pressing force of the transfer member to the image carrier,

the control unit controls the pressing force of the transfer member against the image carrier by the pressure varying mechanism based on information on a surface shape of a sheet to be subjected to image formation.

Drawings

The advantages and features provided by one or more embodiments of the present invention will become apparent from the following detailed description and drawings, which are given by way of illustration only and are not intended to limit the scope of the invention. In the drawings:

fig. 1 is a diagram schematically showing the overall configuration of an image forming apparatus according to a first embodiment.

Fig. 2 is a block diagram showing a main functional configuration of the image forming apparatus of fig. 1.

Fig. 3 is a schematic cross-sectional view of the intermediate transfer belt.

Fig. 4 is a diagram showing an example of the setting table.

Fig. 5 is a flowchart showing a flow of operations related to image formation by the image forming apparatus.

Fig. 6 is a graph showing transition of the transferability level when the pressing force adjustment process is executed and the image forming process is continuously performed on the uneven paper.

Fig. 7 is a graph showing changes in the contact angle of pure water when the pressing force adjustment process is performed and the image forming process is continuously performed on the uneven paper.

Fig. 8 is a diagram illustrating a second cleaning portion of the image forming apparatus according to the second embodiment.

Fig. 9 is a diagram showing an example of the setting table.

Fig. 10 is a schematic view showing a secondary transfer unit of an image forming apparatus according to a third embodiment.

Fig. 11 is a diagram showing an example of the setting table.

Fig. 12 is a graph showing transition of the transferability level when the pressing force adjustment process is performed and the image forming process is continuously performed on the uneven paper.

Fig. 13A is a diagram for explaining another manner of tension change.

Fig. 13B is a diagram for explaining another manner of tension change.

Fig. 14 is a diagram for explaining a conventional problem.

Fig. 15 is a diagram for explaining a conventional problem.

Detailed Description

Hereinafter, embodiments of the present invention will be described with reference to the drawings. However, the scope of the invention is not limited to the disclosed embodiments.

< first embodiment >

A first embodiment of the present invention will be explained.

[ Structure of image Forming apparatus ]

Fig. 1 is a diagram schematically showing the overall configuration of an image forming apparatus 1 according to the present embodiment. Fig. 2 is a block diagram showing a main functional configuration of the image forming apparatus 1.

The image forming apparatus 1 shown in fig. 1 and 2 is an intermediate transfer type color image forming apparatus using an electrophotographic process technique.

The image forming apparatus 1 adopts a tandem system in which photosensitive drums 413 corresponding to four colors of Y (yellow), M (magenta), C (cyan), and K (black) are arranged in series in a traveling direction of an intermediate transfer belt (intermediate transfer body) 421, and toner images of the respective colors are sequentially transferred to the intermediate transfer belt 421.

As shown in fig. 1 and 2, the image forming apparatus 1 includes, for example, an image reading unit 10, an operation display unit 20, an image processing unit 30, an image forming unit 40, a paper conveying unit 50, a fixing unit 60, a storage unit 70, a communication unit 80, and a control unit 100.

The control Unit 100 includes a CPU (Central Processing Unit) 101, a ROM (Read only Memory) 102, a RAM (Random Access Memory) 103, and the like. The CPU101 reads out a program corresponding to the processing contents from the ROM102, develops the program into the RAM103, and collectively controls operations of the respective blocks of the image forming apparatus 1 shown in fig. 2 in accordance with the developed program.

The image reading unit 10 includes an automatic Document Feeder 11 called an ADF (Auto Document Feeder), a Document image scanning device 12 (scanner), and the like.

The automatic document feeder 11 feeds the document D placed on the document tray to the document image scanner 12 by the feeding mechanism. The automatic document feeder 11 can continuously read images (including both sides) of a plurality of documents D placed on the document tray at once.

The original image scanning device 12 optically scans an original transported from the automatic original feeder 11 to the contact glass or an original placed on the contact glass, forms an image of reflected light from the original on a light receiving surface of a CCD (Charge coupled device) sensor 12a, and reads an original image.

The image reading unit 10 generates input image data based on the reading result of the document image scanning device 12. The image processing unit 30 performs predetermined image processing on the input image data.

The operation Display unit 20 is formed of, for example, a Liquid Crystal Display (LCD) with a touch panel, and functions as a Display unit 21 and an operation unit 22. The display unit 21 displays various operation screens, image status displays, operation statuses of the functions, and the like, in accordance with a display control signal input from the control unit 100. The operation unit 22 includes various operation keys such as a numeric keypad and a start key, receives various input operations by the user, and outputs an operation signal to the control unit 100.

The image processing unit 30 includes a circuit and the like for performing digital image processing corresponding to initial setting or user setting on image data (input image data) of an input job. For example, the image processing unit 30 performs gradation correction based on gradation correction data (gradation correction table) under the control of the control unit 100. In addition to the gradation correction, the image processing unit 30 performs various correction processes such as color correction and shading correction, compression processing, and the like on the input image data. The image forming unit 40 is controlled based on the image data subjected to these processes.

The image forming unit 40 includes image forming units 41Y, 41M, 41C, and 41K for forming images of respective color toners of Y component, M component, C component, and K component based on input image data having been subjected to image processing, an intermediate transfer unit 42, and the like.

The image forming units 41Y, 41M, 41C, and 41K for the Y component, the M component, the C component, and the K component have the same configuration. For convenience of illustration and description, common constituent elements are denoted by the same reference numerals, and when the respective configurations are distinguished, Y, M, C or K is added to the reference numerals. In fig. 1, only the constituent elements of the image forming unit 41Y for the Y component are denoted by reference numerals, and the reference numerals are omitted for the constituent elements of the other image forming units 41M, 41C, and 41K.

The image forming unit 41 includes an exposure device 411, a developing device 412, a photosensitive drum 413 (image carrier), a charging device 414, a drum cleaning device 415, and the like.

The exposure device 411 is composed of a laser light source, a polygon mirror, a lens, and the like, and forms an electrostatic latent image by scanning and exposing the surface of the photosensitive drum 413 with a laser beam based on image data of each color.

The developing device 412 includes a developing sleeve disposed to face the photosensitive drum 413 through a developing region. By applying a developing bias obtained by superimposing an ac voltage on a dc voltage having the same polarity as the charging polarity of the charging device 414, i.e., a negative polarity, to the developing sleeve, for example, a developer is supplied to the electrostatic latent image formed on the photosensitive drum 413, and a toner image of each color is formed on the photosensitive drum 413. The developer includes a toner and a carrier for charging the toner. The toner is not particularly limited, and a generally used known toner can be used.

The photosensitive drum 413 is formed of an organic photoreceptor in which a photosensitive layer made of a resin containing an organic photoconductor is formed on the outer peripheral surface of a drum-shaped metal base.

The charging device 414 charges the photosensitive drum 413 with a negative polarity to a constant potential using a charger.

The drum cleaning device 415 has a drum cleaning blade or the like which is in sliding contact with the surface of the photosensitive drum 413, and removes transfer residual toner remaining on the surface of the photosensitive drum 413 after primary transfer.

The intermediate transfer unit 42 includes an intermediate transfer belt 421, a primary transfer roller (transfer member) 422, a plurality of support rollers 423, a secondary transfer roller 424, a cleaning unit 426, and the like.

Fig. 3 is a schematic cross-sectional view of the intermediate transfer belt 421.

As shown in fig. 3, the intermediate transfer belt 421 in the present embodiment has at least two layers, i.e., a base material layer 421a and a coating layer 421b disposed on the base material layer 421 a.

As the base layer 421a, for example, a synthetic resin in which a conductive material such as a Polyimide (PI) resin, a polyamideimide resin, a polyphenylene sulfide resin, or a polyamide resin is dispersed is used. The base material layer 421a may have a single-layer structure or a multilayer structure.

The coating 421b is a layer containing an inorganic oxide containing an organic component, and is formed of, for example, silicon dioxide (SiO)₂) A material as a main component. Specifically, as the silicon oxide containing an alkyl group in the coating layer 421b, a siloxane compound such as methyltrimethoxysilane, dimethyldimethoxysilane, phenyltrimethoxysilane, or methyltriethoxysilane can be used.

The material used for the base layer 421a and the coating layer 421b is not limited to these.

Returning to fig. 1 and 2, the intermediate transfer belt 421 is an endless belt, and is looped by a plurality of support rollers 423.

At least one of the plurality of support rollers 423 is formed of a drive roller, and the other rollers are formed of driven rollers. For example, the roller 423A disposed on the downstream side in the belt traveling direction from the primary transfer roller 422 for K component is preferably a drive roller. This makes it easy to keep the belt running speed of the primary transfer unit constant. By the rotation of the driving roller 423A, the intermediate transfer belt 421 travels at a constant speed in the arrow a direction.

The roller 423B disposed on the upstream side in the belt traveling direction of the primary transfer roller 422 for the Y component includes a tension adjustment mechanism, not shown, for adjusting the tension of the intermediate transfer belt 421. The tension adjusting machine is configured to include, for example, a cam that moves a holder provided on a rotating shaft of the primary transfer roller 422 in the vertical direction and a driving unit that drives the cam, and by driving the cam by a predetermined amount by the driving unit, the rotating shaft and thus the primary transfer roller 422 can be moved by a predetermined distance. This enables adjustment of the tension of the intermediate transfer belt 421.

The primary transfer roller 422 is disposed on the inner peripheral surface side of the intermediate transfer belt 421 so as to face the photosensitive drums 413 of the respective color components. The primary transfer roller 422 is pressed against the photosensitive drum 413 with a predetermined pressing force via the intermediate transfer belt 421, thereby forming a primary transfer nip for transferring the toner image from the photosensitive drum 413 to the intermediate transfer belt 421.

The primary transfer roller 422 of the present embodiment includes a pressure variable mechanism 422a that changes the pressing force of the primary transfer roller 422 against the photosensitive drum 413 (hereinafter, simply referred to as "pressing force of the primary transfer roller 422").

The pressure variable mechanism 422a is configured to include, for example, a biasing member such as a spring that biases the primary transfer roller 422 and a driving unit that changes the biasing force of the biasing member, and can change the pressing force of the primary transfer roller 422 by changing the biasing force of the biasing member by the driving unit.

Specifically, the pressing force of the primary transfer roller 422 is controlled by the control unit 100 based on the information (surface shape information) on the surface shape of the sheet S to be subjected to image formation, and when the sheet S is plain paper, the pressing force of the primary transfer roller 422 is set to a predetermined pressing force (F1). When the sheet S is a corrugated sheet, the pressing force of the primary transfer roller 422 is set to a pressing force smaller than a predetermined pressing force (F2).

The secondary transfer roller 424 is disposed on the outer peripheral surface side of the intermediate transfer belt 421 so as to face a facing roller 423C disposed on the belt traveling direction downstream side of the driving roller 423A. The secondary transfer roller 424 is pressed against the counter roller 423C via the intermediate transfer belt 421, thereby forming a secondary transfer nip for transferring the toner image from the intermediate transfer belt 421 to the sheet S.

A transfer current corresponding to the applied voltage flows in the primary transfer roller 422. Thereby, when the intermediate transfer belt 421 passes through the primary transfer nip, the toner images developed on the surface of the photosensitive drum 413 are sequentially transferred to the intermediate transfer belt 421 in an overlapping manner (primary transfer). Specifically, a primary transfer bias is applied to the primary transfer roller 422, whereby an electric charge having a polarity opposite to that of the toner is applied to the back surface side of the intermediate transfer belt 421 (the side in contact with the primary transfer roller 422), and the toner image is electrostatically transferred to the intermediate transfer belt 421.

After that, the toner image on the intermediate transfer belt 421 is transferred to the sheet S while the sheet S passes through the secondary transfer nip (secondary transfer). Specifically, by applying a secondary transfer bias to the secondary transfer roller 424, an electric charge having a polarity opposite to that of the toner is applied to the back surface side of the sheet S (the side in contact with the secondary transfer roller 424), and the toner image is electrostatically transferred to the sheet S. The sheet S on which the toner image is transferred is conveyed toward the fixing section 60.

The cleaning section 426 includes a cleaning blade 426a and the like which are in sliding contact with the surface of the intermediate transfer belt 421.

The cleaning blade 426a is a plate body made of, for example, urethane rubber, and the like, and the tip thereof is in sliding contact with the traveling intermediate transfer belt 421, and can remove transfer residual toner, discharge products, and the like remaining on the surface of the intermediate transfer belt 421 after the secondary transfer.

The fixing unit 60 heats and pressurizes the sheet S, to which the toner image is secondarily transferred and which is conveyed, at the fixing nip, thereby fixing the toner image to the sheet S.

The paper conveying unit 50 includes a paper feeding unit 51, a paper discharging unit 52, a conveying path unit 53, and the like. The three paper feed tray units 51a to 51c constituting the paper feed unit 51 store sheets S identified by basis weight, size, and the like according to a predetermined type. The conveying path portion 53 includes a plurality of conveying roller pairs such as a registration roller pair 53 a.

The sheets S stored in the sheet feed tray units 51a to 51c are fed out one by one from the uppermost portion, and are conveyed to the image forming unit 40 through the conveying path unit 53. At this time, the skew of the supplied sheet S is corrected and the conveyance timing is adjusted by the registration roller section in which the registration roller pair 53a is disposed. Then, in the image forming section 40, the toner images of the intermediate transfer belt 421 are collectively secondarily transferred to one surface of the sheet S, and a fixing process is performed in the fixing section 60. The sheet S on which the image is formed is discharged to the outside of the apparatus by a sheet discharge unit 52 having sheet discharge rollers 52 a.

In the present embodiment, as the sheet S, a sheet having an uneven surface (uneven paper) such as embossed paper or coarse paper is used in addition to plain paper having a flat surface. When image formation is performed on the uneven paper as the paper S, the paper S may be stored in a paper feeding device (not shown) connected to the image forming apparatus 1, and the paper feeding device may store the paper S and feed the paper S from the paper feeding device to the image forming apparatus 1 through a paper feeding port 54 and to the conveying path section 53.

The storage unit 70 is configured by, for example, a nonvolatile semiconductor memory (so-called flash memory), a hard disk drive, or the like. The storage unit 70 stores various data including various setting information related to the image forming apparatus 1.

For example, the storage unit 70 stores a setting table T1 used when forming an image on the sheet S.

Fig. 4 is a diagram showing an example of the setting table T1.

As shown in fig. 4, the setting table T1 stores setting information on each section (primary transfer section, intermediate transfer belt, secondary transfer section, cleaning section) of the image forming apparatus 1.

The primary transfer section is a generic term for a portion related to primary transfer, and specifically includes a primary transfer roller 422, a pressure variable mechanism 422a, and the like. The secondary transfer section is a general term for the secondary transfer section, and specifically includes a secondary transfer roller 424, an opposing roller 423C, and the like.

The communication unit 80 is configured by a communication control card such as a LAN (Local Area Network) card, for example, and transmits and receives various data to and from an external device (for example, a personal computer) connected to a communication Network such as a LAN or a WAN (Wide Area Network).

[ operation of image Forming apparatus ]

In the image forming apparatus 1 of the present embodiment, when an image is formed on a sheet S, the pressing force of the primary transfer roller 422 is controlled based on the surface shape information of the sheet S to be subjected to the image formation. Specifically, when the sheet S to be subjected to image formation is the uneven paper, the pressing force of the primary transfer roller 422 is reduced as compared with the case where the sheet S to be subjected to image formation is the plain paper. This makes it possible to maintain good transferability of the toner to the uneven paper.

Fig. 5 is a flowchart showing a flow of operations related to image formation in the image forming apparatus 1.

Here, since the frequency of executing image forming processing on plain paper is generally higher than the frequency of executing image forming processing on uneven paper, each unit of the image forming apparatus 1 is set to perform image forming on plain paper during standby in which a job is waiting.

First, when the user selects the paper type of the sheet S to be subjected to image formation via the operation display unit 20, the control unit 100 acquires the groove depth (surface shape information) of the predetermined unevenness from the paper type of the sheet S (step S1).

Next, the control section 100 determines whether or not the pressing force of the primary transfer roller 422 needs to be switched based on the acquired surface shape information (step S2).

Specifically, when the groove depth of the surface irregularities is equal to or greater than a predetermined value, the control unit 100 determines that the pressing force of the primary transfer roller 422 needs to be switched.

Therefore, when the user selects the embossed paper such as embossed paper or rough paper, the control unit 100 determines that the pressing force of the primary transfer roller 422 needs to be switched, and when the user selects plain paper, the control unit 100 determines that the pressing force of the primary transfer roller 422 does not need to be switched.

The determination may be performed by inputting the groove depth of the sheet S to be subjected to image formation by user setting.

When it is determined that the pressing force of the primary transfer roller 422 does not need to be switched (no in step S2), the control unit 100 proceeds to step S5, which will be described later.

On the other hand, when determining that the pressing force of the primary transfer roller 422 needs to be switched (step S2: YES), the control unit 100 executes a removal process for removing the transfer residual toner, the discharge products, and the like adhering to the intermediate transfer belt 421 (step S3).

Here, the control unit 100 idles the intermediate transfer belt 421 for a predetermined time (here, 2 minutes) as set in the setting table T1, and performs the removal processing.

Further, the time of idling can be set and changed as appropriate. In addition, the rotation speed of the intermediate transfer belt 421 may be set instead of the idling time. Further, since the cleaning blade 426a of the cleaning section 426 may be wound up due to the execution of the removal process, a toner band of a degree to prevent this can be formed.

The removal process is performed before the image forming process on the uneven paper is started, but it is particularly preferable to perform the removal process when the sheet S to be subjected to image formation is switched from plain paper to uneven paper. This is to prevent the discharge product adhering to the intermediate transfer belt 421 from affecting the transferability to the uneven paper.

Next, the control section 100 switches the pressing force of the primary transfer roller 422 (step S4).

Specifically, the controller 100 drives the pressure variable mechanism 422a to switch the pressing force of the primary transfer roller 422 to the set value set in the setting table T1. That is, the pressing force of the primary transfer roller 422 is switched from a predetermined pressing force (F1) set at the time of image formation on plain paper to a pressing force (F2) smaller than the predetermined pressing force.

Further, the control unit 100 refers to the map T1, and adjusts the tension and transfer current of the intermediate transfer belt 421 as the pressing force of the primary transfer roller 422 is reduced.

Specifically, the control section 100 decreases the tension of the intermediate transfer belt 421 and increases the transfer current as the pressing force of the primary transfer roller 422 decreases.

Next, the control section 100 performs an image forming process of forming an image on the sheet S by the image forming section 40 (step S5), and ends the process.

Fig. 6 is a graph (solid line) showing transition of the transferability level when the image forming process is continuously performed on the uneven paper (LEAHAC 66 white 203gsm paper) after the pressing force is switched as described above.

Fig. 6 also shows an example (broken line) in which image forming processing is performed on the same uneven paper sheet without switching the pressing force (in other words, while maintaining the setting for plain paper) for comparison.

In fig. 6, the horizontal axis represents the number of formed images [ kp ], and the vertical axis represents the transferability level [ - ].

The transferability level was visually determined by the user based on the following criteria.

5: has no problem

4: the halftone part has blank space

3: two solid layers with blank

2: a half-tone part, a two-layer/single-layer solid part and a blank

1: the whole surface has a large margin

As is clear from fig. 6, the improvement in the level of transferability is seen when the pressing force is reduced to form an image on the uneven paper.

Fig. 7a is a graph (solid line) showing the transition of the pure water contact angle when the image forming process is continuously performed on the uneven paper (the LEATHAC 66 white 203gsm paper) after the pressing force is switched as described above.

Fig. 7a also shows an example (broken line) in which image forming processing is performed on the same uneven paper sheet without switching the pressing force (in other words, while maintaining the setting for plain paper) for comparison.

In fig. 7a, the horizontal axis represents the number of formed images [ kp ], and the vertical axis represents the contact angle of pure water [ ° ].

Fig. 7B and C are graphs showing the amounts of discharge products (NOx) detected in the respective image forming processes at the initial stage and after 30 kp.

As is clear from fig. 7a to C, when the pressing force of the primary transfer roller 422 is reduced, the amount of discharge product deposited after the image forming process is continuously performed is reduced as compared with the case where the pressing force is not reduced.

Here, generally, the pressing force of the primary transfer roller is increased in order to prevent the generation of the discharge product. That is, the primary transfer voltage is reduced to prevent the generation of discharge products, and the primary transfer nip needs to be secured as wide as possible to reduce the primary transfer voltage, so that the pressing force of the primary transfer roller is increased.

However, in the present invention, the pressing force of the primary transfer roller 422 is reduced.

Therefore, it is considered that the amount of discharge products generated increases because the primary transfer nip is narrowed and the transfer voltage increases, but it is considered that the adhesion force of the discharge products is reduced by reducing the pressing force as shown in fig. 7a to C.

The discharge product having the weakened adhesion can be removed by the cleaning portion 426 of the intermediate transfer belt 421 or by friction with the sheet S or the transfer member at the time of secondary transfer.

Therefore, when an image is formed on the uneven paper, the pressing force of the primary transfer roller 422 is reduced as compared with the normal state, thereby maintaining transferability.

From the above, it is clear that: in comparison with the reduction of the amount of discharge product generated by increasing the pressing force of the primary transfer roller, the reduction of the adhesion force of the discharge product to the belt by decreasing the pressing force of the primary transfer roller becomes dominant, and the latter is more effective for the maintenance of transferability.

In addition, it is desirable that the pressing force is set to a normal setting stronger than that of the uneven paper. The weaker setting is preferable as far as possible under normal settings because the transfer voltage increases, which may shorten the life of each member or cause white voids when foreign matter is caught. In this regard, since the surface of the uneven paper has unevenness, it is difficult to discriminate the occurrence of white voids as compared with plain paper, and there is no problem.

Further, although the generation and adhesion amount of the discharge product are increased under normal pressure, transfer to a sheet other than the uneven paper is not problematic because the secondary transfer portion has high adhesion, and therefore, the secondary transfer portion is hardly affected by the discharge product and the transfer property can be maintained.

[ Effect of the present embodiment ]

As described above, according to the present embodiment, in the image forming apparatus 1 of the intermediate transfer system, the intermediate transfer belt 421 includes the base material layer 421a and the coating layer 421b which is disposed on the base material layer 421a and includes the inorganic oxide containing the organic component, and the image forming apparatus 1 includes: a primary transfer roller 422 disposed opposite to the photosensitive drum 413 with the intermediate transfer belt 421 interposed therebetween and forming a nip portion with the photosensitive drum 413; a pressure variable mechanism 422a for changing the pressing force of the primary transfer roller 422 to the photosensitive drum 413; and a control unit 100 for controlling the pressing force of the primary transfer roller 422 on the photosensitive drum 413 by the pressure variable mechanism 422a based on the surface shape information of the sheet S to be subjected to image formation.

Specifically, in the case where the sheet S to be image-formed is a concave-convex sheet, the control portion 100 reduces the pressing force of the primary transfer roller 422 against the photosensitive drum 413 based on the surface shape information, as compared with the case where the sheet S to be image-formed is plain paper.

Therefore, in the apparatus for forming an image on a sheet having unevenness by using the intermediate transfer belt 421 having the coating layer 421b, the pressing force of the primary transfer roller 422 is made smaller than usual, so that even if the discharge product adheres to the intermediate transfer belt 421, the discharge product can be easily removed, and as a result, the transferability to the sheet having unevenness can be maintained well.

In addition, since the discharge products are easily removed even if they adhere to the intermediate transfer belt 421, it is not necessary to frequently perform the removal process, and it is possible to maintain good transferability without lowering productivity.

Further, according to the present embodiment, the control section 100 decreases the tension of the intermediate transfer belt 421 as the pressing force of the primary transfer roller 422 against the photosensitive drum 413 decreases.

Therefore, the influence of the push-back by reducing the pressing force of the primary transfer roller 422 can be reduced, and appropriate image forming conditions can be set.

Further, according to the present embodiment, the control section 100 increases the transfer current as the pressing force of the primary transfer roller 422 against the photosensitive drum 413 is reduced.

Therefore, appropriate image forming conditions can be set.

In the above embodiment, the control unit 100 acquires the sheet surface information in accordance with the setting operation by the user, but the paper feed unit 51 or the transport path unit 53 may be provided with a sheet detection unit that detects the groove depth of the surface irregularities of the sheet S (sheet surface information), and the switching of the pressing force may be determined based on the detection result of the sheet detection unit.

In the above embodiment, as set in the setting table T1, the control of switching the pressing force in two stages of "plain paper" and "uneven paper" is exemplified, but the pressing force may be switched in a plurality of stages depending on the groove depth of the unevenness.

That is, when the sheet to be subjected to image formation is a concave-convex sheet, the pressing force of the primary transfer roller 422 against the photosensitive drum 413 may be reduced as the depth of the concave-convex as the sheet surface information is increased.

In this way, since the pressing force of the primary transfer roller 422 is adjusted for each kind of the uneven paper, the transferability to each kind of the uneven paper can be maintained more favorably.

< second embodiment >

The second embodiment of the present invention will be described mainly focusing on differences from the first embodiment.

Note that the same components as those of the first embodiment are denoted by the same reference numerals, and description thereof is omitted.

Fig. 8 is a diagram showing a configuration of a main part of the image forming apparatus according to the present embodiment.

As shown in fig. 8, the image forming apparatus according to the present embodiment is configured such that a second cleaning unit 427 is provided in the image forming apparatus 1 according to the first embodiment.

That is, the intermediate transfer unit 42 of the image forming apparatus of the present embodiment includes an intermediate transfer belt 421, a primary transfer roller 422, a plurality of support rollers 423, a secondary transfer roller 424, a cleaning portion 426, a second cleaning portion 427, and the like.

The second cleaning portion 427 is used to remove the discharge product attached to the intermediate transfer belt 421 and to trap the transfer residual toner that has not been removed (missed) by the cleaning portion 426.

The second cleaning portion 427 is disposed downstream of the cleaning portion 426 and upstream of the primary transfer roller 422Y as viewed in the traveling direction of the intermediate transfer belt 421.

The second cleaning portion 427 includes a cleaning blade 427a supported by a support portion, not shown.

The cleaning blade 427a is a plate body made of metal such as SUS (stainless steel), for example, and its tip is in sliding contact with the intermediate transfer belt 421 which is looped. Thus, the cleaning blade 427a can remove the discharge product and the transfer residual toner on the intermediate transfer belt 421.

Fig. 9 is a diagram showing an example of a setting table T2 stored in the storage unit 70 of the image forming apparatus according to the present embodiment. As shown in fig. 9, the setting table T2 stores setting information about each section (primary transfer section, intermediate transfer belt, secondary transfer section, cleaning section, second cleaning section) of the image forming apparatus.

Thus, not only the rubber blade but also the metal blade having high hardness is used, and the discharge product can be effectively removed.

Further, although the cleaning blade 427a of SUS304 is illustrated here, if a blade coated with DLC (Diamond-Like-Carbon) is used, the discharge product can be removed more effectively.

< third embodiment >

The third embodiment of the present invention will be mainly described with respect to the differences from the second embodiment.

Note that the same components as those of the second embodiment are denoted by the same reference numerals, and description thereof is omitted.

Fig. 10 is a diagram showing a configuration of a main part of the image forming apparatus according to the present embodiment.

As shown in fig. 10, the image forming apparatus according to the present embodiment includes a secondary transfer unit 425 formed by unitizing a plurality of members including the secondary transfer roller 424, instead of the secondary transfer roller 424 of the image forming apparatus according to the second embodiment.

The secondary transfer unit 425 includes a secondary transfer roller 424, an endless secondary transfer belt 424a looped by the secondary transfer roller 424 and a plurality of support rollers, a cleaner portion 424b that abuts against the secondary transfer belt 424a and scrapes off a residue on the secondary transfer belt 424a, and a lubricant applying mechanism 424c that applies a lubricant to the secondary transfer belt 424 a.

The lubricant applying mechanism 424c is provided downstream of the cleaner unit 424b in the rotation direction of the secondary transfer belt 424a, and applies lubricant to the surface of the secondary transfer belt 424 a.

The lubricant applying mechanism 424c includes an applying brush 424c1, a solid lubricant 424c2, and a pressing member 424c 3.

The application brush 424c1 is provided in contact with both the solid lubricant 424c2 and the secondary transfer belt 424 a. The application brush 424C1, by rotating in the direction indicated by the arrow C in fig. 10 in this state, supplies the lubricant scraped off from the solid lubricant 424C2 to the secondary transfer belt 424 a. The coating brush 424c1 is rotationally driven by a driving unit not shown. Further, the rotation direction of the coating brush 424c1 may be rotated in the direction opposite to the direction indicated by the arrow B in fig. 10 depending on the system.

Examples of the material of the solid lubricant 424c2 include (higher) fatty acid metal salt particles such as zinc, aluminum, copper, magnesium, and calcium salts of stearic acid, zinc, manganese, iron, copper, and magnesium salts of oleic acid, zinc, copper, magnesium, and calcium salts of palmitic acid, zinc, calcium salts of linoleic acid, and zinc, calcium salts of ricinoleic acid.

The pressing member 424c3 is formed of a spring or the like, and presses the solid lubricant 424c2 against the application brush 424c 1.

Fig. 11 is a diagram showing an example of a setting table T3 stored in the storage unit 70 of the image forming apparatus according to the present embodiment. As shown in fig. 11, the setting table T3 stores setting information about each unit (primary transfer unit, intermediate transfer belt, secondary transfer unit, cleaning unit, and second cleaning unit) of the image forming apparatus.

In the setting table T3, the setting for forming the toner band is performed as the removal processing. This removal process is an operation of feeding the toner belt to the cleaning section 426 of the intermediate transfer belt 421. In this removal process, the toner sent to the cleaning section 426 by the toner belt enters a gap between the cleaning blade 426a and the intermediate transfer belt 421, and the discharge product on the intermediate transfer belt 421 is scraped off by the abrasive to more rapidly remove the discharge product.

Needless to say, the setting of the setting table T3 is not limited to the size of the toner band, the number of times of feeding, and the like.

Fig. 12 is a graph (solid line) showing transition of transfer level when the image forming apparatus of the present embodiment is used to continuously perform the image forming process on the uneven paper (LEATHAC 66 white 203gsm paper) by switching the pressing force.

Fig. 12 also shows a graph (broken line) showing transition of the transferability level when the pressing force is switched and the image forming process is performed on the same sheet of paper using the image forming apparatus according to the first embodiment. Fig. 12 also shows an example (two-dot chain line) in which the image forming process is performed on the same uneven paper sheet using the image forming apparatus according to the first embodiment without switching the pressing force (in other words, while maintaining the setting for plain paper).

In fig. 12, the horizontal axis represents the number of formed images [ kp ], and the vertical axis represents the transferability level [ - ].

As shown in fig. 12, it can be seen that the transferability level is further improved by using the image forming apparatus of the present embodiment.

This is considered to be because, by applying a lubricant (zinc stearate or the like) by the secondary transfer unit 425, the discharge product NOx (negative ions) reacts with zinc Zn (positive ions) contained in the lubricant before adhering to the surface of the intermediate transfer belt 421, forming a salt. According to this configuration, the discharge product can be more effectively and easily removed.

Further, for the application of the lubricant, it is advantageous from the viewpoint of durability (consumption of the lubricant) if the rotation speed is changed in accordance with the groove depth of the unevenness of the sheet S or the like. The pressing force to the coating brush 424c1 may also be changed instead of the rotational speed. The pressing force may be changed in a plurality of stages, and the groove depth of the unevenness of the sheet S may be considered, and the sheet detection unit may be used in addition to the operation of the screen by the user.

Although the present embodiment shows an example in which the lubricant is applied to the secondary transfer belt 424a, the lubricant may be applied to other members (for example, photosensitive drums) that contact the intermediate transfer belt 421, or may be directly applied to the intermediate transfer belt 421.

< Others >

The embodiment to which the present invention can be applied is not limited to the above-described embodiment, and can be appropriately changed within a range not departing from the gist of the present invention.

Although embodiments of the present invention have been described and illustrated in detail, the disclosed embodiments are presented for purposes of illustration and example only, and not limitation. The scope of the invention should be construed by the appended claims.

For example, in the first to third embodiments, the control is performed to reduce the tension of the intermediate transfer belt 421 when the pressing force of the primary transfer roller 422 is reduced, but instead of reducing the tension of the intermediate transfer belt 421, the control may be performed to set the contact position of the primary transfer roller 422 with respect to the intermediate transfer belt 421 (hereinafter, simply referred to as "the contact position of the primary transfer roller 422").

In this case, as shown in fig. 13, the primary transfer roller 422 includes a moving mechanism 422b, and the moving mechanism 422b moves the primary transfer roller 422 in a direction along the moving direction of the intermediate transfer belt 421.

The moving mechanism 422b is configured to include, for example, a cam for moving a holder provided on the rotating shaft of the primary transfer roller 422 and a driving unit for driving the cam, and the rotating shaft and thus the primary transfer roller 422 can be moved by a predetermined distance by driving the cam by a predetermined amount by the driving unit.

Further, in the case where the pressing force F1 is set as the pressing force of the primary transfer roller 422 (in the case of plain paper), the primary transfer roller 422 is set at the position P1 as shown in fig. 13B. In addition, when the pressing force F2 is set as the pressing force of the primary transfer roller 422 (in the case of the uneven paper), the primary transfer roller 422 is set at a position P2 on the upstream side in the traveling direction of the intermediate transfer belt 421 from the position P1 as shown in fig. 13A.

In the first to third embodiments, the coating 421b containing an inorganic oxide containing an organic component is exemplified as the coating, but in addition to this, a coating of an organic compound such as urethane, acrylic, PFA (perfluoroalkoxyalkane), PTFE (polytetrafluoroethylene), or the like may be used as the coating.