JP2011158615A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To correct deviations in the degree of unit magnification in the sub-scanning direction, when performing image formation on recording paper without deteriorating productivity, in an image forming apparatus that conducts image formation on a recording paper by a secondary transfer method which uses an intermediate transfer belt. <P>SOLUTION: The image forming apparatus 1 includes a development unit 120; the intermediate transfer belt 125; a secondary transfer roller 210; a driving roller 125a for the intermediate transfer belt 125; a backup roller 125d, that corrects the approach angle of the intermediate transfer belt 125 to a nip part N between the secondary transfer roller 210 and the driving roller 125a, by pressing the intermediate transfer belt 125 in an outward direction from an inner circumferential surface side, at an upstream side from the nip part N, in the traveling direction of the intermediate transfer belt 125; a correction roller movement mechanism 200 that moves an arrangement position of the backup roller 125d; and a movement mechanism control part 312, that controls the moving operation of the backup roller 125d by the correction roller movement mechanism 200. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a technique for correcting an equal magnification deviation in the sub-scanning direction in image formation in an image forming apparatus that forms an image on a recording sheet by a secondary transfer method using an intermediate transfer belt.

  In an image forming apparatus that forms an image on a recording paper by a secondary transfer method using an intermediate transfer belt, an image having a size different from the planned size is caused by expansion / contraction of the intermediate transfer belt accompanying a temperature change or the like. In other words, a so-called equal magnification shift may occur. For example, when the temperature of the intermediate transfer belt rises, the intermediate transfer belt expands and the toner image transferred on the surface of the intermediate transfer belt expands, and an image having a size larger than the original size is recorded in the recording medium. Formed on paper.

  Conventionally, in order to correct the equal magnification deviation, for example, an image forming apparatus disclosed in Patent Document 1 detects a sub-scanning magnification error of a transfer conveyance device based on speed information of the transfer conveyance device, and detects the error. The correction amount of the sub-scanning magnification error is calculated, and control is performed to vary the drive speed of the transfer conveyance device so as to reduce the sub-scanning magnification error based on the calculated correction amount.

JP 2006-259173 A

  However, if the equality deviation is corrected by changing the driving speed of the transfer conveying apparatus, that is, the recording paper conveying speed, the printing speed may decrease and the productivity may decrease. When correcting the same magnification deviation, the same magnification deviation in the main scanning direction in image formation can be easily corrected only by electrical correction, but the same magnification in the sub scanning direction in image formation. The degree deviation has been a problem because it is difficult to correct because mechanical correction is required.

  The present invention has been made to solve such a conventional problem, and reduces productivity in an image forming apparatus that forms an image on a recording sheet by a secondary transfer method using an intermediate transfer belt. Rather, the object is to correct the same magnification deviation in the sub-scanning direction during image formation on the recording paper.

The invention according to claim 1 of the present application includes a developing unit that forms a toner image according to image data;
An intermediate transfer belt that is stretched between a plurality of rollers so as to be able to run endlessly in the sub-scanning direction in image formation, and on which the toner image is transferred to an outer peripheral surface by the developing unit;
A secondary transfer counter roller that is one of the plurality of rollers and on which the intermediate transfer belt is stretched;
The toner image on the intermediate transfer belt is in contact with the outer peripheral surface of the intermediate transfer belt at a portion where the intermediate transfer belt is stretched around the secondary transfer counter roller, and at a nip portion with the secondary transfer counter roller. A secondary transfer roller for transferring the toner onto the recording paper,
One of the plurality of rollers, the endless rotation being possible upstream of the nip portion formed by pressing the secondary transfer counter roller by the secondary transfer roller in the intermediate transfer belt traveling direction. A correction roller that presses the stretched intermediate transfer belt from the inner peripheral surface thereof toward the outer side to correct the approach angle of the intermediate transfer belt into the nip portion;
A correction roller moving mechanism for moving the position of the correction roller;
The image forming apparatus includes a moving mechanism control unit that controls the roller moving operation by the correction roller moving mechanism.

  According to this invention, the correction roller moving mechanism changes the pressing state of the correction roller from the inner peripheral surface side toward the outer side by moving the position where the correction roller is disposed. . As a result, the angle of entry of the intermediate transfer belt into the nip changes, so the pressing state of the intermediate transfer belt by the secondary transfer roller that presses the outer peripheral surface of the intermediate transfer belt toward the secondary transfer counter roller is changed. Can be made.

  That is, when the intermediate transfer belt bends to the outer peripheral side at the nip portion, the outer peripheral surface of the intermediate transfer belt on which the toner image is formed is extended, and the toner image is also extended. On the other hand, when the intermediate transfer belt is bent toward the inner peripheral side at the nip portion, the outer peripheral surface of the intermediate transfer belt on which the toner image is formed contracts and the toner image also contracts. In the present invention, by the movement amount control of the position where the correction roller is arranged by the correction roller moving mechanism, the approach angle of the intermediate transfer belt to the nip portion is changed, so that the secondary transfer counter roller and the secondary transfer roller Since it is possible to change the pressing state to the intermediate transfer belt, the moving mechanism control unit causes the intermediate transfer belt to move in the endless running direction (sub-scanning direction in image formation) of the intermediate transfer belt caused by changes in the surrounding environment. By controlling the amount of movement of the correction roller by the correction roller moving mechanism according to the expansion and contraction, the amount of deflection of the intermediate transfer belt can be made to correspond to the amount of expansion and contraction, and the image on the recording paper It is possible to correct the same magnification deviation in the sub-scanning direction that occurs during formation.

  Therefore, according to each of the above inventions, in an image forming apparatus that forms an image on a recording paper by a secondary transfer method using an intermediate transfer belt, the sub-recording at the time of image formation on the recording paper is performed without reducing productivity. It is possible to correct a unity degree deviation in the scanning direction.

The invention according to claim 2 is the image forming apparatus according to claim 1, further comprising a temperature detection unit that detects a belt temperature of the intermediate transfer belt,
The moving mechanism control unit controls the roller moving operation by the correction roller moving mechanism according to the belt temperature detected by the temperature detecting unit.

  According to this invention, the moving mechanism control unit changes the arrangement position of the correction roller according to the belt temperature detected by the temperature detection unit. The intermediate transfer belt by the secondary transfer counter roller and the secondary transfer roller is changed in accordance with the amount of expansion and contraction of the intermediate transfer belt that expands and contracts at a thermal expansion rate by changing the angle of entry of the intermediate transfer belt into the nip portion by the correction roller. The belt pressing state can be changed. Accordingly, it is possible to correct the same magnification deviation in the sub-scanning direction that occurs when an image is formed on the recording paper in an appropriate manner corresponding to the expansion / contraction amount of the intermediate transfer belt.

The invention according to claim 3 is the image forming apparatus according to claim 1, further comprising a paper thickness setting unit for setting a paper thickness of the recording paper,
The moving mechanism control unit controls the roller moving operation by the correction roller moving mechanism according to the paper thickness set by the paper thickness setting unit.

  According to the present invention, the moving mechanism control unit accurately adjusts the expansion / contraction amount of the intermediate transfer belt, which changes based on the change in the thickness of the recording paper used for image formation, to the recording nip portion by the correction roller. By changing the approach angle of the intermediate transfer belt, the pressing state of the intermediate transfer belt by the secondary transfer counter roller and the secondary transfer roller can be changed. Accordingly, it is possible to correct the same magnification deviation in the sub-scanning direction that occurs when an image is formed on the recording paper in an appropriate manner corresponding to the expansion / contraction amount of the intermediate transfer belt.

An invention according to claim 4 is the image forming apparatus according to any one of claims 1 to 3, wherein the correction roller moving mechanism includes:
An urging mechanism attached to a rotation shaft of the correction roller and urging the correction roller toward an outer side of the circulation line of the intermediate transfer belt that is stretched around the rollers and circulates in an endless manner; ,
And a positioning mechanism that positions the correction roller urged toward the outer side by the urging mechanism in the outer direction against the urging by the urging mechanism.

  According to this aspect of the invention, the correction roller is urged by the urging mechanism toward the outer side of the intermediate transfer belt that is stretched around the roller so as to be able to run endlessly. Thus, it is possible to accurately position at a desired position. As a result, the correction roller can change the angle of entry of the intermediate transfer belt into the nip portion in response to a change in the amount of expansion / contraction of the intermediate transfer belt. The degree deviation can be corrected with high accuracy.

The invention according to claim 5 is the image forming apparatus according to claim 4, wherein the urging mechanism of the correction roller moving mechanism includes:
A tension spring connecting the rotation shaft of the correction roller and the inner wall of the apparatus main body located outside the intermediate transfer belt stretched so as to be able to travel endlessly;
The positioning mechanism is
A circular guide member that is concentric with the rotation axis of the correction roller and rotates around the rotation axis;
A cam member that is rotatable in direct or indirect contact with the guide member;
A cam drive mechanism for rotating the cam member around a rotation axis of the cam;
The moving mechanism control unit controls an amount by which the cam driving mechanism rotates the cam member.

  According to the present invention, the outer side of the intermediate transfer belt is biased by the pulling spring that connects the rotation shaft of the correction roller and the inner wall of the apparatus main body positioned outside the intermediate transfer belt stretched endlessly. The tension is applied stably to the intermediate transfer belt to adjust the approach angle, the cam member is rotated by the cam drive mechanism, and the guide member on the tension roller side that contacts the cam member is pressed to pull the intermediate transfer belt. The position of the correction roller biased in the outward direction by the spring can be reliably positioned at a desired position. Further, if the amount of expansion / contraction of the intermediate transfer belt is converted into the amount of rotation of the cam member of the cam drive mechanism used for control by the moving mechanism control unit, the moving mechanism control unit can accurately cope with the expansion / contraction of the intermediate transfer belt. Because the correction roller can change the angle of entry of the intermediate transfer belt into the nip portion, it is possible to accurately correct the equal magnification deviation in the sub-scanning direction.

  According to the present invention, when an image is formed on a recording sheet by a secondary transfer method using an intermediate transfer belt, the sub-scanning direction or the like at the time of image formation on the recording sheet is reduced without reducing productivity. The double shift can be corrected.

1 is a front sectional view showing a structure of an image forming apparatus 1 according to an embodiment of the present invention. FIG. 3 is a diagram illustrating a cross-sectional structure of an intermediate transfer belt. FIG. 2 is a functional block diagram illustrating an electrical configuration of the image forming apparatus. (A), (B), and (C) are side views showing an example of a correction roller moving mechanism, (A) shows a state in which the arrangement position of the backup roller is moved upward, and (B) shows the backup roller. (C) shows a state where the arrangement position of the backup roller is moved to the lowest position. (A), (B), and (C) are diagrams schematically showing a state in which the intermediate transfer belt expands and contracts at the nip portion. The moving mechanism control unit determines the number of drive pulses of the cam driving mechanism according to the internal temperature of the image forming apparatus detected by the temperature sensor and the type of recording paper set in the input operation unit, and backs up to the correction roller moving mechanism. It is a flowchart which shows the control which moves a roller.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. The present invention can be applied to an image forming apparatus that employs an electrophotographic system and includes an intermediate transfer belt, such as a copier, a printer, a facsimile machine, and a multifunction machine having these functions.

  FIG. 1 is a front sectional view showing the structure of an image forming apparatus 1 according to an embodiment of the present invention. The image forming apparatus 1 includes an apparatus main body 11 including an image forming unit 12, a fixing device 13, a paper feeding unit 14, a paper discharging unit 15, a document reading unit 16, and the like.

  The apparatus main body 11 includes a lower main body 111, an upper main body 112 disposed opposite to the lower main body 111, and a connecting portion 113 interposed between the upper main body 112 and the lower main body 111. . The connecting portion 113 is a structure for connecting the sheet discharge portion 15 between the lower main body 111 and the upper main body 112 and is erected from the left and rear portions of the lower main body 111. It has an L shape in plan view. The upper body 112 is supported on the upper end portion of the connecting portion 113.

  The lower main body 111 includes an image forming unit 12, a fixing device 13, and a paper feeding unit 14, and the upper main body 112 is equipped with a document reading unit 16. The paper feed unit 14 has a paper feed cassette 142 that can be inserted into and removed from the apparatus main body 11. In this paper feed cassette 142, a paper bundle P1 formed by stacking recording papers P is accommodated. In this embodiment, the paper feed cassette 142 is provided in one stage, but it may be provided in two or more stages.

  The image forming unit 12 performs an image forming operation for forming a toner image on the recording paper P fed from the paper feeding unit 14. The image forming unit 12 uses a magenta developing unit 12M that uses magenta toner, a cyan developing unit 12C that uses cyan toner, and a yellow toner that are sequentially arranged from the upstream side to the downstream side. The yellow developing unit 12Y and the black developing unit 12K using black toner (hereinafter, each developing unit will be referred to as “developing unit 120”) and a driving roller 125a (two Intermediate transfer belt 125 stretched between a plurality of rollers (second transfer counter roller) and the like so as to be able to run endlessly in the sub-scanning direction in image formation, and intermediate transfer at a portion where intermediate transfer belt 125 is stretched by drive roller 125a A secondary transfer roller 210 in contact with the outer peripheral surface of the belt 125, a belt cleaning device 128, It is equipped with a.

  Each developing unit 120 includes a photosensitive drum 121 (photosensitive member), a developing device 122 that supplies toner to the photosensitive drum 121, a toner cartridge (not shown) that contains toner, a charging device 123, and an exposure device 124. And an intermediate transfer belt 125 and a drum cleaning device 127, respectively.

  The photosensitive drum 121 forms an electrostatic latent image and a toner image along the electrostatic latent image on the peripheral surface thereof. The developing device 122 supplies toner to the photosensitive drum 121. Each developing device 122 is appropriately supplied with toner from the toner cartridge.

  The charging device 123 is provided at a position directly below each photosensitive drum 121. The exposure device 124 is provided at a position below each charging device 123. The charging device 123 uniformly charges the peripheral surface of each photosensitive drum 121. The exposure device 124 irradiates the peripheral surface of the charged photosensitive drum 121 with laser light corresponding to each color based on image data input from a computer or the like or image data acquired by the document reading unit 16, and each photosensitive member. An electrostatic latent image is formed on the peripheral surface of the drum 121. The developing device 122 supplies toner to the electrostatic latent image on the peripheral surface of the photoconductive drum 121 rotating in the direction of the arrow and stacks the toner, and the toner corresponding to the image data is formed on the peripheral surface of the photoconductive drum 121. Form an image.

  The intermediate transfer belt 125 is disposed above the photosensitive drums 121. The intermediate transfer belt 125 is provided with the left driving roller 125a in FIG. 1 and a driven roller 125b that is provided on the right side of the intermediate transfer belt 125 so as to face the driving roller 125a and that rotates following the endless running of the intermediate transfer belt 125. And an intermediate transfer belt 125 provided corresponding to each photoconductive drum 121 so as to be able to run endlessly, and a lower outer peripheral surface is in contact with a peripheral surface of each photoconductive drum 121. The intermediate transfer belt 125 is driven by a driving roller 125a in a state where an image carrying surface onto which the toner image is transferred is set on the outer peripheral surface and pressed against the peripheral surface of the photosensitive drum 121 by the intermediate transfer belt 125. It runs endlessly between the driving roller 125a and the driven roller 125b while synchronizing with each photosensitive drum 121.

  FIG. 2 is a diagram illustrating a cross-sectional structure of the intermediate transfer belt 125. In FIG. 2, a portion where the intermediate transfer belt 125 is stretched around the driving roller 125a is shown in an enlarged manner. In this embodiment, the intermediate transfer belt 125 includes a base layer 1251 formed on the inner peripheral side by a resin material such as polyvinylidene fluoride (PVDF), and an elastic layer formed on the outer peripheral side by, for example, chloroplane rubber or urethane rubber. 1252 is laminated. By providing the elastic layer 1252 on the intermediate transfer belt 125, the followability of the intermediate transfer belt 125 to the recording paper P is improved, so that the transferability of the color image onto the recording paper P is increased, and the secondary transfer onto the recording paper P is achieved. The image quality of the transferred color image can be improved.

  Referring to FIG. 1 again, in this embodiment, a tension applying roller 125c is provided at a position between the driving roller 125a and the driven roller 125b and closer to the driven roller 125b. The tension applying roller 125c is a roller that applies tension to the intermediate transfer belt 125, and is biased upward by a biasing force of a biasing member (not shown). Accordingly, the intermediate transfer belt 125 is pushed upward by the tension applying roller 125c, whereby the intermediate transfer belt 125 has a mountain shape in which the portion of the tension applying roller 125c is a peak.

  A control unit 31 to be described later causes the intermediate transfer belt 125 to run endlessly, transfer the magenta toner image to the surface of the intermediate transfer belt 125 by the magenta developing unit 12M, and then to cyan at the same position on the intermediate transfer belt 125. Transfer of the cyan toner image by the developing unit 12C, transfer of the yellow toner image by the yellow developing unit 12Y to the same position of the intermediate transfer belt 125, and transfer of the black toner image by the final black developing unit 12K Is performed on the surface of the intermediate transfer belt 125 to form a color toner image in which each color toner is superimposed (intermediate transfer (primary transfer)).

  The secondary transfer roller 210 is applied with a transfer bias by a transfer bias application mechanism (not shown), and the color toner image formed on the surface of the intermediate transfer belt 125 is conveyed from the paper feeding unit 14 to the recording paper P. Secondary transfer. The secondary transfer roller 210 is provided in contact with the outer peripheral surface of the intermediate transfer belt 125 in a sheet conveyance path 190 where the intermediate transfer belt 125 is stretched around the driving roller 125a. That is, the drive roller 125a functions as a secondary transfer counter roller. The secondary transfer roller 210 forms a nip portion N where the toner image is secondarily transferred to the recording paper P with the driving roller 125a. The recording paper P being conveyed along the paper conveyance path 190 is pressed and nipped by the intermediate transfer belt 125 and the secondary transfer roller 210 at the nip portion N, whereby the toner image on the intermediate transfer belt 125 is transferred to the recording paper P. Next transferred.

  In addition, the intermediate transfer belt 125 is disposed on the upstream side in the traveling direction of the intermediate transfer belt 125 with respect to the nip portion N between the driving roller 125a and the secondary transfer roller 210 (in the downward direction in FIG. 1). A backup roller (an example of a correction roller in the claims) 125d that presses toward is provided. The backup roller 125d corrects the approach angle of the intermediate transfer belt 125 to the nip portion N by pressing the intermediate transfer belt 125 in the outward direction of the circulation line. The backup roller 125 d brings the intermediate transfer belt 125 close to the secondary transfer roller 210 side at the nip portion N by the pressing against the intermediate transfer belt 125, and the outer periphery of the secondary transfer roller 210 and the intermediate transfer belt 125 at the nip portion N. By increasing the contact area with the surface (the surface on which the toner image is formed by the developing unit 120), the reliability of secondary transfer of the toner image onto the recording paper P conveyed to the nip portion N is improved. Is for.

  The backup roller 125d is directed toward the inside and outside of the circumference line of the intermediate transfer belt 125, which is stretched around the drive roller 125a and the driven roller 125b by the correction roller moving mechanism 200, which will be described later, and circulates in an endless manner. It is urged to move. Intermediate transfer entering the nip portion N of the drive roller 125a and the secondary transfer roller 210 by moving the position of the backup roller 125d in the direction toward the inside and outside of the intermediate transfer belt 125 by the correction roller moving mechanism 200. The angle of the belt 125 changes, and the tension state of the intermediate transfer belt 125 with respect to the driving roller 125a changes due to the change in the belt angle. Due to the change in the tension state of the intermediate transfer belt 125, the entrance angle of the intermediate transfer belt 125 entering the nip portion N of the drive roller 125a and the secondary transfer roller 210 is varied, and the outer peripheral surface of the intermediate transfer belt 125 is changed to the drive roller. The pressing state of the intermediate transfer belt 125 by the secondary transfer roller 210 pressing toward 125a is changed.

  Details of the movement of the backup roller 125d by the correction roller moving mechanism 200 and the change in the pressing state of the intermediate transfer belt 125 by the driving roller 125a and the secondary transfer roller 210 accompanying the movement will be described later.

  The drum cleaning device 127 is provided at the left position of each photoconductive drum 121 and removes residual toner on the peripheral surface of the photoconductive drum 121 for cleaning. The peripheral surface of the photosensitive drum 121 cleaned by the drum cleaning device 127 is directed to the charging device 123 for a new charging process.

  The belt cleaning device 128 is provided at a position facing the driven roller 125b with the intermediate transfer belt 125 interposed therebetween. The belt cleaning device 128 removes residual toner remaining on the intermediate transfer belt 125 after the toner image formed on the intermediate transfer belt 125 is transferred to the recording paper P, and cleans it.

  A paper conveyance path 190 extending in the vertical direction is formed at the left position of the image forming unit 12. A conveyance roller pair 192 is provided at an appropriate position in the sheet conveyance path 190, and the conveyance roller pair 192 conveys the recording sheet P fed from the sheet feeding unit 14 toward the nip N.

  The fixing device 13 includes a heating roller 132 provided with an energization heating element as a heating source therein, and a pressure roller 134 disposed to face the heating roller 132. The fixing device 13 uses the heating roller 132 while the recording paper P passes through the fixing nip portion between the heating roller 132 and the pressure roller 134 with respect to the toner image on the recording paper P transferred by the image forming unit 12. Then, heat is applied to perform fixing processing. The color-printed recording paper P for which the fixing process has been completed is discharged toward a paper discharge tray 151 provided on the top of the apparatus main body 11 through a paper discharge conveyance path 194 extending from the upper part of the fixing device 13. The

  The sheet feeding unit 14 is provided with a manual feed tray 141 that can be freely opened and closed on the right side wall in FIG. 1 of the apparatus main body 11, and a sheet feeding cassette 142 that is detachably mounted at a position below the exposure apparatus 124 in the apparatus main body 11. And.

  The manual feed tray 141 is a tray provided at a position below the right surface of the lower main body 111 for feeding the recording paper P one by one toward the image forming unit 12 by manual feed operation. The paper feed cassette 142 accommodates a paper bundle P1 formed by stacking a plurality of recording papers P. A pickup roller 143 is provided above the sheet feeding cassette 142, and the pickup roller 143 feeds the uppermost recording sheet P of the sheet bundle P 1 stored in the sheet feeding cassette 142 toward the sheet conveyance path 190.

  The paper discharge unit 15 is formed between the lower main body 111 and the upper main body 112. The paper discharge unit 15 includes a paper discharge tray 151 formed on the upper surface of the lower main body 111. The paper discharge tray 151 is a tray from which the recording paper P on which the toner image is formed by the image forming unit 12 is discharged after the fixing process is performed by the fixing device 13.

  The document reading unit 16 includes a contact glass 161 mounted on the upper surface opening of the upper main body 112 for placing a document, an openable / closable document pressing cover 162 for pressing the document placed on the contact glass 161, And a scanning mechanism 163 that scans and reads an image of the document placed on the contact glass 161. The scanning mechanism 163 optically reads an image of an original using an image sensor such as a charge coupled device (CCD) or a complementary metal oxide semiconductor (CMOS), and generates image data.

  FIG. 3 is a functional block diagram showing an electrical configuration of the image forming apparatus 1. The image forming apparatus 1 includes a control unit 31, an image forming unit 12, a fixing device 13, a document reading unit 16, an image memory 33, an image processing unit 34, an input operation unit 35, a network I / F unit 36, a temperature sensor 40, and The correction roller moving mechanism 200 is provided. Since description has been made based on FIG. 1, descriptions of the image forming unit 12, the fixing device 13, and the document reading unit 16 are omitted below.

  The image memory 33 temporarily stores image data output from the document reading unit 16 and image data transmitted from an external device via the network I / F unit 36. The image processing unit 34 performs image processing such as image correction and enlargement / reduction on the image data stored in the image memory 33.

  The input operation unit 35 receives various operation commands such as a display panel on which the user can visually recognize an operation screen and various messages, a power key, a numeric keypad for inputting the number of copies, a start button for instructing reading start of a document, and the like. An operation button for inputting is provided. The input operation unit 35 receives the input of the operation command by the user, and sets the type of the recording paper P such as plain paper or thick paper and the number of copies to be printed. The input operation unit 35 functions as a paper thickness setting unit that sets the paper thickness corresponding to the recording paper P by setting the type of the recording paper P. When the image forming apparatus 1 performs the printer function, when the user selects the type of recording paper P or the number of copies on the computer connected via the network I / F unit 36, the computer Functions as the paper thickness setting section.

  The network I / F unit 36 includes a communication module such as a LAN (Local Area Network) board, and transmits / receives various data to / from an external device. The temperature sensor 40 is a contact-type or non-contact-type temperature sensor provided in the vicinity of the nip portion N in the image forming apparatus 1, for example, and detects the temperature of the intermediate transfer belt 125.

  The correction roller moving mechanism 200 is a mechanism for moving the position of the backup roller 125d in the direction toward the inner side and the outer side of the intermediate transfer belt 125. The correction roller moving mechanism 200 includes a tension spring 201a and a positioning mechanism 202, as will be described later. The operation of the positioning mechanism 202 is controlled by the movement mechanism control unit 312.

  The control unit 31 includes a storage unit 313 having a RAM (Random Access Memory) and a ROM (Read Only Memory), a CPU (Central Processing Unit), and the like. Further, the control unit 31 includes an overall control unit 311 and a moving mechanism control unit 312.

  The overall control unit 311 reads and processes a program stored in the storage unit 313 according to an instruction signal or the like input from an input operation unit 35 or a computer (not shown) connected via the network I / F unit 36. Is executed, and the image forming apparatus 1 is comprehensively controlled by outputting instruction signals to each functional unit, transferring data, and the like.

  The movement mechanism control unit 312 responds to a temperature change amount calculated based on the temperature of the intermediate transfer belt 125 detected by the temperature sensor 40 with respect to a cam drive mechanism (stepping motor) 2023 provided in the correction roller movement mechanism 200 described later. The change amount of the paper thickness corresponding to the drive pulse of the cam drive mechanism (stepping motor) 2023 or the type of the recording paper P set by the input operation unit 35 (for example, when the paper thickness of plain paper is used as a reference) A drive pulse of the cam drive mechanism (stepping motor) 2023 corresponding to the recording paper type change amount) or a drive pulse obtained by adding these drive pulses is output to control the movement amount of the backup roller 125d.

  4A, 4B, and 4C are side views illustrating an example of the correction roller moving mechanism 200. FIG.

  The correction roller moving mechanism 200 includes an urging mechanism 201 and a positioning mechanism 202. The urging mechanism 201 includes an inner wall 111a of the apparatus main body that is positioned outside the rotation line of the intermediate transfer belt 125 that is stretched around the rotation shaft of the backup roller 125d, the drive roller 125a, the driven roller 125b, and the like. A pulling spring 201a is provided. By this pulling spring 201a, the backup roller 125d is urged toward the outer side of the circumference line of the intermediate transfer belt 125 (the arrow direction in FIGS. 4A, 4B, and 4C).

  The positioning mechanism 202 includes a guide member 2021, a cam member 2022, and a cam drive mechanism 2023. The guide member 2021 is concentric with the rotation shaft of the backup roller 125d and is configured to rotate around the rotation shaft, and has a circular shape as shown in FIGS. 4 (A), (B), and (C). . The cam member 2022 is configured to be rotatable while being in contact with the guide member 2021. The cam drive mechanism 2023 includes a stepping motor or the like, and rotates the cam member 2022 around the rotation axis of the cam member 2022.

  The cam member 2022 includes a rotation shaft 2022a that is rotatably fixed to the casing of the lower main body 111. The cam member 2022 is driven to rotate by a rotation driving force from the cam drive mechanism 2023, and the cam drive mechanism (stepping) is centered on the rotation shaft 2022a. Motor) rotates at a rotation angle corresponding to the number of drive pulses of 2023.

  The roller 240 is configured to be slidably contacted with the outer peripheral surface 2021a of the guide member 2021 of the backup roller 125d and move along the inter-axis direction between the rotation shaft of the backup roller 125d and the rotation shaft of the cam member 2022.

  The backup roller 125d is urged toward the outside of the intermediate transfer belt 125 by the pulling spring 201a (downward in the present embodiment shown in FIG. 1), but the roller 240 abuts against the peripheral surface 2022b of the cam member 2022. At the point of contact, the movement of the backup roller 125d is stopped against the urging force of the pulling spring 201a. Therefore, when the cam member 2022 is rotated by the rotational driving force from the cam drive mechanism 2023, the position of the backup roller 125d toward the outer side of the intermediate transfer belt 125 is the rotation of the rotation shaft 2022a of the cam member 2022 and the backup roller 125d. In the direction between the shafts, it moves in a direction (FIGS. 4 (A), (B), (C), and a vertical direction in FIG. 1) that is close to and away from the shaft center of the backup roller 125d.

  4 (B) shows a state where the arrangement position of the backup roller 125d is at the reference position, and FIG. 4 (A) shows a state where the arrangement position of the backup roller 125d is moved to the uppermost position. Indicates a state in which the arrangement position of the backup roller 125d is moved to the lowest position. As a result, the cam member 2022 is moved from the reference position shown in FIG. 4B (the position where the cam member 2022 moves the least amount of the backup roller 125d) to the cam member 2022 from the cam drive mechanism. (Stepping motor) By selectively rotating in the direction of the arrow shown in FIG. 4B at a rotation angle corresponding to the number of drive pulses of 2023, the position of the backup roller 125d can be controlled.

  That is, the cam member 2022 has a backup roller 125d biased toward the outer side of the intermediate transfer belt 125 by the pulling spring 201a against the biasing force of the pulling spring 201a. Position the position.

  When the amount of movement of the backup roller 125d toward the outer side of the intermediate transfer belt 125 increases, the drive roller 125a and the secondary transfer roller 210 located downstream of the backup roller 125d in the traveling direction of the intermediate transfer belt 125. In the nip portion N, the intermediate transfer belt 125 stretched around the driving roller 125a is separated from the driving roller 125a at the entry point to the nip portion N, and is disposed below the driving roller 125a in this embodiment. It approaches the secondary transfer roller 210. That is, the angle of entry of the intermediate transfer belt 125 into the nip portion N with respect to the tangent to the peripheral surface of the drive roller 125a is increased. Conversely, when the amount of movement of the backup roller 125d toward the outer side of the intermediate transfer belt 125 decreases, the intermediate transfer belt 125 stretched around the drive roller 125a is moved to the drive roller 125a at the entry point to the nip portion N. Approaches and moves away from the secondary transfer roller 210. That is, the entry angle of the intermediate transfer belt 125 to the nip portion N with respect to the tangent to the peripheral surface of the drive roller 125a is reduced.

  Accordingly, by controlling the positioning mechanism 202, the entry angle of the intermediate transfer belt 125 entering the nip N between the drive roller 125a and the secondary transfer roller 210 can be adjusted. For example, the part used for the control on the peripheral surface of the cam member 2022 has a cam profile in which the cam diagram is a straight line, and the number of drive pulses of the cam drive mechanism 2023 is proportional to the amount of movement of the backup roller 125d. It is preferable from the viewpoint of positioning control of the backup roller 125d according to the expansion and contraction of the intermediate transfer belt 125 and control of the approach angle to the nip portion N of the intermediate transfer belt 125. The cam member 2022 may be formed of an eccentric cam as long as the same action as the cam member 2022 can be obtained. Alternatively, the roller 240 may be omitted and the circumferential surface of the cam member 2022 and the guide member 2021 may be in direct sliding contact.

  The bearing 500 of the rotating shaft of the backup roller 125d is formed in the housing of the lower main body 111, and the shape of the bearing 500 is formed in accordance with the amount of movement of the backup roller 125d that moves by the rotation of the cam member 2022.

  Note that the configuration of the correction roller moving mechanism 200 and the configuration using the cam member 2022 as described above are merely examples, and the correction roller moving mechanism 200 moves the arrangement position of the backup roller 125d to the inside of the intermediate transfer belt 125 and the intermediate transfer belt 125. Other configurations may be employed as long as the configuration moves in the outward direction.

  5A to 5C are diagrams schematically illustrating a state in which the intermediate transfer belt 125 expands and contracts in the nip portion N. FIG. 5A to 5C show a state in which the angle of entry of the intermediate transfer belt 125 into the nip portion N between the drive roller 125a and the secondary transfer roller 210 is increased.

In FIG. 5 (A) ~ (C) to _{M v1} / or indicated by _{M v2} nip N (area where the toner image is _{transferred),} the toner image is a portion that is convex to the outer peripheral direction indicated by the _{M v1} The toner image contracts at a portion that is extended and convex in the inner circumferential direction indicated by _Mv2 . The correction roller moving mechanism 200 moves the arrangement position of the backup roller 125d toward the outside of the circulation line of the intermediate transfer belt 125 so that the entry angle of the intermediate transfer belt 125 into the nip portion N is changed to the driving roller 125a. When the angle of entry of the intermediate transfer belt 125 into the nip portion N with respect to the tangent to the peripheral surface of the intermediate transfer belt is changed from a small state to a large state, the intermediate transfer belt 125 stretched around the drive roller 125 a Then, on the upstream side in the running direction of the intermediate transfer belt 125, the state shown in FIG. 5 (A) is lowered as shown in FIG. 5 (B). At this time, the intermediate transfer belt 125 is pressed by the secondary transfer roller 210, and since the outer peripheral surface of the intermediate transfer belt 125 is recessed inwardly in the nip portion N (M _v2 ), this M _v2 Accordingly, the toner image formed on the outer peripheral surface of the intermediate transfer belt 125 is shrunk to a small extent.

When the correction roller moving mechanism 200 moves the arrangement position of the backup roller 125 d toward the outside of the circulation line of the intermediate transfer belt 125, the intermediate transfer belt 125 travels with respect to the nip portion N. On the upstream side in the direction, the state shown in FIG. 5 (B) is further lowered downward as shown in FIG. 5 (C). At this time, the intermediate transfer belt 125, at the nip N, because the contract is recessed on the outer peripheral surface thereof an inner larger (M _v2), minute the M _v2, the formed on the outer circumferential surface of the intermediate transfer belt 125 The toner image is further reduced.

  On the other hand, when the correction roller moving mechanism 200 moves the arrangement position of the backup roller 125d toward the inside of the circumferential line of the intermediate transfer belt 125, FIGS. 5 (C) to 5 (B), FIG. The state of the intermediate transfer belt 125 changes to the state of A).

Here, when the boundary between the base layer 1251 and the elastic layer 1252 of the intermediate transfer belt 125 is a speed determining surface,
D ₁ : Roller outer diameter (mm) of the drive roller 125a
D ₂ : outer diameter of the secondary transfer roller 210 (mm)
L _B1 : thickness of base layer 1251 (mm)
L _B2 : thickness of elastic layer 1252 (mm)
θ ₁ : Angle (radian) formed by both ends of M _v1 and the center of the driving roller 125a
θ ₂ : An angle (radian) formed by both ends of M _v2 and the center of the secondary transfer roller 210
, The lengths of M _v1 and M _v2 with respect to the rotation direction of the intermediate transfer belt can be expressed by the following equations, respectively.
M _v1 = π × (D ₁ +2 (L _B1 + L _B2 )) × θ ₁ (mm) (1)
M _v2 = π × D ₂ × θ ₂ (mm) (2)

Here, when the length of the speed determination surface corresponding to M _v1 is A ₁ and the length of the speed reference surface corresponding to M _v2 is A ₂ ,
A ₁ = π × (D ₁ + 2L _B1 ) × θ ₁ (mm) (3)
A ₂ = π × (D ₂ + 2L _B2 ) × θ ₂ (mm) (4)
_Therefore , M _v1 and M _v2 are
M _v1 = A ₁ + 2π × L _B2 × θ ₁ (mm) (5)
M _v2 = π × (D ₂ +2 (L _B2 −L _B2 )) × θ ₂
= A ₂ −2π × L _{B 2} × θ ₂ (mm) (6)
It can be expressed as.

Here, when the secondary transfer magnification M _2,
Since M ₂ = (M _v1 + M _v2 ) / (A ₁ + A ₂ ),
M ₂ = (A ₁ + A ₂ + 2π × L _B2 × (θ ₁ −θ ₂ )) / (A ₁ + A ₂ ) (7)
It becomes. That is, if θ ₁ is made larger than θ ₂ , the toner image on the intermediate transfer belt 125 is enlarged and secondarily transferred to the recording paper P, and if θ ₁ is made smaller than θ ₂ , the toner on the intermediate transfer belt 125 is made. The image is reduced and secondarily transferred onto the recording paper P.

Therefore, the correction roller moving mechanism 200 changes the amount of movement of the backup roller 125d from the arrangement reference position in accordance with the increase or decrease of the contraction of the intermediate transfer belt 125, and the intermediate transfer belt 125 enters the nip portion N. By changing the angle, the angle of the intermediate transfer belt 125 entering the nip portion N between the drive roller 125a and the secondary transfer roller 210 is changed as shown in FIGS. By varying ₁ and θ ₂ to vary the secondary transfer magnification M ₂ , it is possible to correct the same-size deviation in the sub-scanning direction (traveling direction of the intermediate transfer belt 125) caused by the expansion and contraction of the intermediate transfer belt 125. It becomes possible.

Incidentally, when the temperature of the intermediate transfer belt 125 rises, the intermediate transfer belt 125 expands, so that the toner image formed on the outer peripheral surface of the intermediate transfer belt 125 expands. That is, the secondary transfer magnification M ₂ is increased. Conversely, when the temperature of the intermediate transfer belt 125 decreases, the intermediate transfer belt 125 contracts, so that the toner image contracts. That reduces the secondary transfer magnification M _2.

  For example, rubber such as chloroprene rubber and urethane rubber has a larger thermal expansion coefficient than a resin material such as PVDF. Therefore, when the elastic layer 1252 is formed on the outer peripheral side of the intermediate transfer belt 125 by using, for example, chloroprene rubber or urethane rubber as in the present embodiment, the intermediate transfer belt 125 is formed by using only a resin material such as PVDF, for example. However, it is easy to cause a 1 × magnification shift.

  Therefore, in this embodiment, the moving mechanism control unit 312 reads the temperature of the intermediate transfer belt 125 detected by the temperature sensor 40 at a predetermined sampling interval, and the change amount ΔT of the temperature T of the intermediate transfer belt 125 detected by the temperature sensor 40. The drive pulse DP1 corresponding to the output pulse number DP1 is output, the arrangement position of the backup roller 125d is moved by a movement amount proportional to the number of drive pulses DP1, and the same magnification in the sub-scanning direction as the temperature T of the intermediate transfer belt 125 increases or decreases. Correct the degree deviation.

For example, the moving mechanism control section 312, in order to reduce the secondary transfer magnification M ₂ in accordance with the increase of the temperature T of the intermediate transfer belt 125 by the temperature sensor 40 detects, circulating line of the intermediate transfer belt 125 to the backup roller 125d The intermediate transfer belt 125 is increased in angle with respect to the tangent line of the driving roller 125a at the nip portion N. The movement mechanism control unit 312 outputs the drive pulse number DP1 corresponding to the change amount ΔT at this time to the cam drive mechanism (stepping motor) 2023, and moves the backup roller 125d in the outward direction.

  In this embodiment, a table in which the number of drive pulses DP1 of the cam drive mechanism (stepping motor) 2023 that determines the position of the secondary transfer roller 210 and the amount of change ΔT are associated with each other is stored in the storage unit 313 in advance. The moving mechanism control unit 312 reads the number of drive pulses DP1 corresponding to the change amount ΔT from the table. Further, the drive pulse number DP1 takes both positive and negative values, and the cam drive mechanism (stepping motor) 2023 can output drive force in both the clockwise and counterclockwise directions. Therefore, in FIGS. 4A to 4C, the cam member 2022 rotates in both the clockwise and counterclockwise directions.

When the paper thickness increases according to the type of the recording paper P conveyed to the nip portion N, the intermediate transfer belt 125 is pressed by the recording paper P in the nip portion N in the inner peripheral direction. That is, θ ₂ increases and the secondary transfer magnification M ₂ decreases.

Therefore, in the present embodiment, the moving mechanism control unit 312 uses the plain paper thickness as the reference paper thickness th, and the reference paper thickness th and the respective paper thicknesses th1, th2,... Of other types of recording paper. Thickness difference d1, d2... The drive pulse DP2 corresponding to the paper thickness difference d1, d2... Is determined and output, and the backup roller 125d is moved from the previous position by the movement amount corresponding to the drive pulse value DP2. Then, the same-size deviation in the sub-scanning direction that occurs with the increase / decrease of the recording paper thickness is corrected. In other words, the moving mechanism control unit 312 increases or decreases the value of θ ₂ with respect to the reference paper thickness th of plain paper according to the amount of change in the paper thickness of the recording paper used for image formation, and performs secondary transfer. adjusting the magnification _{M 2.} In the present embodiment, a table in which the paper thickness difference d1, d2,... And the drive pulse DP2 corresponding to the paper thickness difference d1, d2. The moving mechanism control unit 312 reads out the driving pulse value DP2 corresponding to the paper thickness difference d1, d2,... From the table. In the case the paper thickness difference with respect to the reference paper thickness th d1, d2 ... is less than or equal to zero, the driving pulse value DP2 reduce secondary transfer magnification M ₂ increases the value of theta ₂ is stored in the table .

That is, in this embodiment, the movement mechanism control unit 312 outputs the drive pulse number DP2 corresponding to the amount of change of θ ₂ that changes according to the type of the recording paper P set in the input operation unit, and the drive pulse number The position of the backup roller 125d is moved by a movement amount proportional to the correction amount, and the same magnification deviation in the sub-scanning direction caused by the difference in the type of the recording paper P is corrected. That is, the moving mechanism control unit 312, if the paper thickness, such as cardboard large paper in the input operation unit 35 is set as the recording paper increases the secondary transfer magnification M ₂ decreases the value of theta ₂ for outputs a drive pulse number DP2 corresponding to the recording paper and the amount of change caused theta ₂ by the difference in sheet thickness of plain paper to the cam drive mechanism (stepping motor) 2023, an intermediate transfer belt backup roller 125d It is moved toward the inner side of the 125 circulation lines.

A table in which the drive pulse number DP2 is associated with the change amount of θ ₂ is stored in the storage unit 313 in advance, and the moving mechanism control unit 312 reads the drive pulse number DP2 corresponding to the change amount ΔT from the table. Further, the fact that the drive pulse number DP2 takes both positive and negative values is output by the moving mechanism control unit 312 when correcting the same magnification deviation in the sub-scanning direction that occurs as the temperature T of the intermediate transfer belt 125 increases or decreases. This is the same as in the case of the drive pulse number DP1.

  In the present embodiment, the moving mechanism control unit 312 outputs a driving pulse number (DP1 + DP2) obtained by adding the driving pulse number DP2 to the driving pulse number DP1 to the cam driving mechanism (stepping motor) 2023 to move the backup roller 125d. Let

  In FIG. 6, the moving mechanism control unit drives the cam driving mechanism (stepping motor) 2023 according to the internal temperature of the image forming apparatus detected by the temperature sensor 40 and the type of the recording paper P set in the input operation unit 35. 10 is a flowchart showing control for determining the number of pulses and causing the correction roller moving mechanism 200 to move the backup roller 125d.

  When the image forming operation by the image forming unit 12 is started, the moving mechanism control unit 312 reads the temperature T of the intermediate transfer belt 125 detected by the temperature sensor 40 at a predetermined sampling interval (step S1), and at the sampling interval. A change amount ΔT of the temperature T of the intermediate transfer belt 125 is calculated (step S2). Subsequently, the movement mechanism control unit 312 reads out the number of drive pulses DP1 corresponding to the change amount ΔT from the table stored in the storage unit 313 (step S3).

  If the recording paper P set in the input operation unit 35 is plain paper (YES in step S4), the moving mechanism control unit 312 reads out because there is no change in paper thickness with respect to the reference paper thickness th of plain paper. The drive pulse number DP1 is output to the cam drive mechanism (stepping motor) 2023 (step S5). On the other hand, when the recording paper P set in the input operation unit 35 is not plain paper (NO in step S4), the moving mechanism control unit 312 stores the drive pulse number DP2 corresponding to the type of the recording paper P in the storage unit 313. (Step S6), the number of drive pulses obtained by adding DP2 to DP1 (DP1 + DP2) is output to the cam drive mechanism (stepping motor) 2023 (step S7). As a result, the backup roller 125d moves by an amount proportional to the number of drive pulses (DP1 + DP2), and the same magnification in the sub-scanning direction that occurs due to the increase / decrease in the temperature T of the intermediate transfer belt 125 and the difference in the type of the recording paper P. The deviation is corrected.

  Note that the number of drive pulses output by the movement mechanism control unit 312 for only one of the change amount ΔT of the temperature T of the intermediate transfer belt 125 detected by the temperature sensor 40 or the type of the recording paper P set in the input operation unit. It is also possible to adopt a mode for determining.

  According to the image forming apparatus 1 according to the embodiment described above, the backup roller 125d moves from the original position by the amount of movement proportional to the drive pulse value (DP1 + DP2), and the entry angle with respect to the nip N changes. Then, the same-size deviation in the sub-scanning direction that occurs with the increase / decrease in the belt temperature T and the difference in the type of the recording paper P is corrected. Therefore, in the image forming apparatus that forms an image on the recording paper by the secondary transfer method using the intermediate transfer belt 125, it is possible to correct the same magnification deviation in the sub-scanning direction without reducing the productivity. Therefore, it is possible to correct the same-magnification deviation in the sub-scanning direction when forming an image on the recording paper P without reducing productivity due to a decrease in printing speed.

  The image forming apparatus 1 according to the embodiment of the present invention has been described above. However, the embodiment is merely an example, and the present invention is not limited to the embodiment, and various modifications can be made without departing from the spirit thereof. Changes, improvements, etc. are possible.

  For example, in the above embodiment, the backup roller 125d functions as a correction roller in the scope of claims, and the position where the backup roller 125d is disposed is controlled by the correction roller moving mechanism 200. A roller which is arranged upstream of the intermediate transfer belt 125 in the running direction with respect to N and biases the intermediate transfer belt 125 toward the outer side of the circuit line (downward in FIG. 1) as shown in FIG. A configuration may be employed in which the roller is moved by the moving mechanism control unit 312 and the correction roller moving mechanism 200 in the same manner as the movement control of the position of the backup roller 125d described above.

  In addition, a rubber such as chloroprene rubber or urethane rubber used for the elastic layer 1252 expands due to moisture absorption although it has less influence than expansion and contraction due to temperature change. Therefore, a humidity sensor is provided inside the image forming apparatus 1, and the humidity sensor The moving mechanism control unit 312 may perform control to change the arrangement position of the backup roller 125d in accordance with the amount of change in humidity detected by.

DESCRIPTION OF SYMBOLS 1 Image forming apparatus 35 Input operation part 40 Temperature sensor 120 Developing unit 125 Intermediate transfer belt 1251 Base layer 1252 Elastic layer 125a Drive roller 125d Backup roller 200 Correction roller moving mechanism 201a Pulling spring 201 Energizing mechanism 202 Positioning mechanism 2021 Guide member 2022 Cam member 2022a Rotating shaft 2022b Peripheral surface 2023 Cam drive mechanism 240 Roller 210 Secondary transfer roller 31 Control unit 311 Overall control unit 312 Moving mechanism control unit 313 Storage unit

Claims (5)

A developing unit for forming a toner image according to image data;
An intermediate transfer belt that is stretched between a plurality of rollers so as to be able to run endlessly in the sub-scanning direction in image formation, and on which the toner image is transferred to an outer peripheral surface by the developing unit;
A secondary transfer counter roller that is one of the plurality of rollers and on which the intermediate transfer belt is stretched;
The toner image on the intermediate transfer belt is in contact with the outer peripheral surface of the intermediate transfer belt at a portion where the intermediate transfer belt is stretched around the secondary transfer counter roller, and at a nip portion with the secondary transfer counter roller. A secondary transfer roller for transferring the toner onto the recording paper,
One of the plurality of rollers, the endless rotation being possible upstream of the nip portion formed by pressing the secondary transfer counter roller by the secondary transfer roller in the intermediate transfer belt traveling direction. A correction roller that presses the stretched intermediate transfer belt from the inner peripheral surface thereof toward the outer side to correct the approach angle of the intermediate transfer belt into the nip portion;
A correction roller moving mechanism for moving the position of the correction roller;
An image forming apparatus including a moving mechanism control unit that controls the roller moving operation by the correction roller moving mechanism. A temperature detection unit for detecting a belt temperature of the intermediate transfer belt;
The image forming apparatus according to claim 1, wherein the moving mechanism control unit controls the roller moving operation by the correction roller moving mechanism according to the belt temperature detected by the temperature detecting unit. A paper thickness setting unit for setting the paper thickness of the recording paper;
The image forming apparatus according to claim 1, wherein the moving mechanism control unit controls the roller moving operation by the correction roller moving mechanism according to the paper thickness set by the paper thickness setting unit. The correction roller moving mechanism is
An urging mechanism attached to a rotation shaft of the correction roller and urging the correction roller toward an outer side of the circulation line of the intermediate transfer belt that is stretched around the rollers and circulates in an endless manner; ,
4. A positioning mechanism for positioning the correction roller urged toward the outer side by the urging mechanism in the outer direction against the urging by the urging mechanism. The image forming apparatus according to any one of the above. The biasing mechanism of the correction roller moving mechanism is
A tension spring connecting the rotation shaft of the correction roller and the inner wall of the apparatus main body located outside the intermediate transfer belt stretched so as to be able to travel endlessly;
The positioning mechanism is
A circular guide member that is concentric with the rotation axis of the correction roller and rotates around the rotation axis;
A cam member that is rotatable in direct or indirect contact with the guide member;
A cam drive mechanism for rotating the cam member around a rotation axis of the cam;
The image forming apparatus according to claim 4, wherein the moving mechanism control unit controls an amount by which the cam driving mechanism rotates the cam member.

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