JP2006273470A - Curl correcting device and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a curl correcting device and the like enabling miniaturization of the device and correction of both of down curling and upper curling caused in recording materials such as paper sheets. <P>SOLUTION: In the case of down-curled sheets, a gate 77 is set in a position indicated by a continuous line in the figure, and a conveyor belt 80 is rotated in the direction of an arrow indicated by the continuous line in the figure so that a first penetration shaft 83 abuts on the conveyor belt 80 with prescribed pressure. Thus, the sheets are conveyed along a conveyor path R3a for correcting the down curling, and the down curling is corrected by the first penetration shaft 83. In the case of upper-curled sheets, the gate 77 is set in a position indicated by a broken line in the figure, and the conveyor belt 80 is rotated in the direction of an arrow indicated by the broken line in the figure so that a second penetration shaft 84 abuts on the conveyor belt 80 with prescribed pressure. The sheets are conveyed along the conveyor path R3a for correcting the down curling, and the upper curling is corrected. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a curl correction apparatus that is used in an image forming apparatus such as an electrophotographic copying machine and corrects curling of a recording material.

  In image forming apparatuses such as copying machines, printers, and facsimiles, a toner image formed on a photosensitive drum or the like is directly or indirectly transferred onto a sheet, and the toner transferred on the sheet is melted by heating and pressurizing. And then fixed, and then discharged to a discharge tray. In this type of image forming apparatus, the fixed sheet discharged in this way may bend and deform so as to warp on the front side or the back side. Therefore, the curl correction to correct the curl generated on the paper for the purpose of avoiding problems such as paper jam caused by the curl generated on the paper, bulkiness on the discharge tray, and deterioration of image quality during double-sided image formation. A device is provided.

  Conventionally, as this type of curl correction device, an endless belt stretched between two rolls provided along a paper conveyance path and a pressing roll pressed against the endless belt with a predetermined pressure are provided. Are known (see Patent Documents 1 and 2). In this technique, the curled paper is sandwiched between an endless belt and a pressing roll, and the curled paper is bent so as to bend to the opposite side of the curling to correct the curl.

JP-A-4-338060 (5th page, FIG. 9, FIG. 10) JP-A-6-156852 (page 6, FIG. 4, FIG. 5)

By the way, the curl generated in the paper includes a curl in which the end of the paper faces downward, and a curl in which the end of the paper faces upward. The curl generated on the paper varies depending on the type of paper, the environment, the density of the image formed on the paper, and the like.
Therefore, in Patent Documents 1 and 2, it is described that two of the above-described curl correction devices are arranged in series or in parallel with the sheet conveyance path and are used as a down curl correction unit and an upper curl correction unit, respectively.

  However, when such a configuration is employed, it is difficult to reduce the size of the apparatus because the down curl correction unit and the upper curl correction unit must be provided separately. Further, there is a problem that the cost increases because the down curl correction unit and the upper curl correction unit must be provided separately.

The present invention has been made to solve such a technical problem, and an object of the present invention is to correct both down curl and upper curl generated in a recording material such as paper while reducing the size of the apparatus. It is an object of the present invention to provide a curl correction device and the like that can perform the above.
Another object of the present invention is to provide a curl correction device or the like that can correct curl according to the direction and degree of curl generated in a recording material.

  For this purpose, a curl correction device to which the present invention is applied is stretched on a stretching member, is disposed so as to be rotatable in forward and reverse directions, and has a first side surface for conveying a sheet and An endless belt having a second side surface formed by a tension member; a first pressing member that presses a sheet conveyed along the first side surface by contacting the first side surface of the endless belt; A second pressing member that presses the sheet conveyed along the second side surface in a direction opposite to the first pressing member by contacting the second side surface of the endless belt is included.

  Here, the pressing force of the first pressing member and / or the second pressing member with respect to the endless belt by adjusting the position of the supporting member that supports the first pressing member and the second pressing member and the supporting member. And a pressing force variable member that varies the pressure. Further, the image forming apparatus may further include a gate member that is provided upstream of the endless belt in the sheet conveyance direction and that switches the sheet conveyance direction to the first side surface side or the second side surface side. In this case, the rotation direction of the endless belt can be switched in conjunction with the switching operation of the gate member, and the first end relative to the endless belt can be linked to the switching operation of the gate member. The pressing force of the pressing member or the second pressing member can be changed.

  From another viewpoint, an image forming apparatus to which the present invention is applied includes an image forming unit that forms a toner image on a recording material, a fixing unit that fixes a toner image formed on the recording material, and a fixing unit. A curl correction unit that corrects the curl generated in the recording material that has passed through, and the curl correction unit is stretched around the stretching member and is disposed so as to be rotatable in the forward and reverse directions and conveys the recording material. An endless belt having a first side surface and a second side surface formed by a stretching member, and a recording material conveyed along the first side surface by contacting the first side surface of the endless belt. A first pressing member that presses and a second side that presses the recording material conveyed along the second side in a direction opposite to the first pressing member by contacting the second side of the endless belt. A pressing member.

  Here, in the case of further including a control unit that controls the curl correction unit, the control unit rotates the endless belt based on information on the recording material and / or information on a toner image formed in the image forming unit. Can be characterized. Further, the control unit determines the pressing force of the first pressing member or the second pressing member against the endless belt based on the information on the recording material and / or the information on the toner image formed in the image forming unit. Can be characterized. When the control unit further controls the curl correction unit, the control unit performs control so that the next recording material enters the endless belt after the recording material passes through the endless belt. Can do.

  According to the present invention, since the down curl and the upper curl are corrected on both side surfaces of one endless belt, both the down curl and the upper curl generated in the recording material such as paper are reduced while downsizing the apparatus. It can be corrected.

The best mode for carrying out the present invention (hereinafter referred to as an embodiment) will be described below in detail with reference to the accompanying drawings.
FIG. 1 is a schematic diagram showing an overall configuration of a full-color image forming apparatus 1 according to an embodiment, and FIG. 2 is an enlarged view of a main part thereof. The full-color image forming apparatus 1 is a so-called tandem type, so-called intermediate transfer type image forming apparatus, an image reading unit 2 that reads an image of a document, an image forming unit 3 that forms an image on paper, and an image forming unit 3 The paper supply unit 4 supplies paper as a recording material, and the paper discharge unit 5 discharges paper after image formation.

  In the present embodiment, the image reading unit 2 reads an image of a document set on a transparent document table. For example, an optical scanning system including a lamp, a mirror, a carriage, and the like, and scanning with this optical scanning system. A lens system that forms an optical image formed thereon, and an image reading sensor such as a CCD that receives the optical image formed by the lens system and converts it into an electrical signal.

  The image forming unit 3 includes a plurality of image forming units 10 (10Y, 10M, 10C, and 10K) that form toner images of respective color components by electrophotography. The image forming unit 3 sequentially transfers (primary transfer) each color component toner image formed by each image forming unit 10 and holds the toner image transferred onto the intermediate transfer belt 15. A secondary transfer unit 20 that performs batch transfer (secondary transfer) onto a sheet P that is a recording material (sheet) is provided. Further, the image forming unit 3 includes a fixing unit 46 that fixes the secondary transferred image on the paper P. Further, the image forming unit 3 receives image forming data based on image data output from the control unit 40 that controls the operation of each device (each unit), the image reading unit 2 or a PC (Personal Computer) (not shown). An IPS (Image Processing System) 44 to be created is included. In this embodiment, the image forming units are configured by the image forming units 10Y, 10M, 10C, and 10K, the intermediate transfer belt 15, the secondary transfer unit 20, and the like.

  Each image forming unit 10 (10Y, 10M, 10C, 10K) is provided around the photosensitive drum 11 and the photosensitive drum 11 that rotate in the direction of the arrow α, and a charger that charges the photosensitive drum 11 to a predetermined potential. 12, a laser exposure device 13 (an exposure beam is indicated by a symbol Bm in the drawing) in which an electrostatic latent image is written on the photosensitive drum 11; each color component toner is accommodated and an electrostatic latent image on the photosensitive drum 11 is A developing device 14 that visualizes the toner image is provided. Further, around the photosensitive drum 11, a primary transfer roll 16 that transfers each color component toner image formed on the photosensitive drum 11 to the intermediate transfer belt 15 and a drum from which residual toner on the photosensitive drum 11 is removed. An electrophotographic device such as a cleaner 17 is also provided.

  The intermediate transfer belt 15 is circulated and driven (rotated) at a predetermined speed in the β direction shown in the figure by various rolls. As these various rolls, a drive roll 31 that is driven by a constant speed drive motor (not shown) to circulate and drive the intermediate transfer belt 15, and an intermediate transfer that extends substantially linearly along the arrangement direction of the photosensitive drums 11. A support roll 32 that supports the belt 15, a tension roll 33 that functions as a correction roll that applies a constant tension to the intermediate transfer belt 15 and prevents meandering of the intermediate transfer belt 15, and a backup roll provided in the secondary transfer unit 20. 22 and an idle roll 34 provided downstream of the secondary transfer portion 20 in the transport direction of the intermediate transfer belt 15.

Each primary transfer roll 16 provided on the inner side of the intermediate transfer belt 15 facing the respective photosensitive drums 11 and extending substantially linearly has a voltage having a polarity opposite to that of the toner (positive polarity in the present embodiment). It is to be applied. As a result, the toner images on the respective photosensitive drums 11 are sequentially electrostatically attracted to the intermediate transfer belt 15 to form toner images superimposed on the intermediate transfer belt 15.
The secondary transfer unit 20 includes a secondary transfer roll 21 disposed on the toner image carrying surface side of the intermediate transfer belt 15, a backup roll 22, and the like. The backup roll 22 is disposed on the back side of the intermediate transfer belt 15 to constitute a counter electrode of the secondary transfer roll 21, and a metal power supply roll 23 to which a secondary transfer bias is stably applied is disposed in contact with the backup roll 22. ing.

  Further, on the downstream side of the secondary transfer portion 20 of the intermediate transfer belt 15, the intermediate transfer belt 15 is disposed so as to face the drive roll 31, and residual toner on the intermediate transfer belt 15 after the secondary transfer or A belt cleaner 35 that removes paper dust and cleans the surface of the intermediate transfer belt 15 is provided so as to be able to contact with and separate from the intermediate transfer belt 15. On the other hand, on the upstream side of the yellow image forming unit 10Y, a reference sensor (home position sensor) 41 that generates a reference signal serving as a reference for matching the image forming timing in each image forming unit 10 is disposed. . Further, an image density sensor 42 for adjusting the image quality of each color is disposed on the downstream side of the black image forming unit 10K. The reference sensor 41 recognizes a predetermined mark provided on the back side of the intermediate transfer belt 15 and generates a reference signal. Each image forming unit is instructed by an instruction from the control unit 40 based on the recognition of the reference signal. 10 (10Y, 10M, 10C, 10K) is configured to start image formation. A temperature sensor 47 and a humidity sensor 48 are disposed inside the intermediate transfer belt 15.

  Further, on the downstream side of the secondary transfer unit 20, a vacuum transport unit 45 that transports the paper P after the secondary transfer while sucking is provided. The vacuum transport unit 45 transports the paper P on which the toner image is transferred by the secondary transfer roll 21 to the fixing unit 46 while sucking the paper P. The fixing unit 46 applies the toner to the paper P by heating and pressurizing. It fixes the image. In the present embodiment, the fixing unit 46 includes a heating roll 46a that is disposed to face the image forming surface of the paper P, a pressure belt 46b that is disposed in pressure contact with the heating roll 46a to form a fixing nip, and a heating roll 46a. And a halogen lamp 46c serving as a heating source.

  On the other hand, the paper supply unit 4 conveys each paper P stored in the first tray 50, the second tray 51, and the third tray 52 through a predetermined path. In the vicinity of each of the trays 50 to 52, corresponding delivery rolls 53, 54, and 55 are disposed. Each of the feed rollers 53 to 55 nips the paper P separated and taken out one by one from the corresponding trays 50 to 52 and temporarily stops the paper P on the paper transport path, and at the timing based on a predetermined start signal, the paper transport direction The sheet P is sent out to the downstream side. Further, an operation panel 56 operated by the user and an input keyboard 56a are disposed adjacent to the operation panel 56 in the vicinity of the image reading unit 2 above the paper supply unit 4. A power source 43 of the full-color image forming apparatus 1 is disposed below the tray 52. In the present embodiment, each tray number (the numbers assigned to the first tray 50, the second tray 51, and the third tray 52) is assigned to the tray using the operation panel 56, the keyboard 56a, and the like. Input of the type (for example, basis weight, presence / absence of coat layer, type of coat layer, etc.) of the sheet P to be accommodated is accepted. This content is stored in a memory (not shown), and when a predetermined tray number is input on the operation panel 56 and the keyboard 56a, information about the attributes of the paper P stored in the corresponding tray is displayed. It has become.

  Here, a series of paper conveyance paths R1 to R5 from the delivery position of the paper P by the delivery rolls 53 to 55 to the discharge tray 57 via the image formation processing position of the image forming unit 3 are respectively used for paper conveyance. The conveyance roll for this is arrange | positioned suitably. The paper P accommodated in the first tray 50 is sent out by the feed roll 53 and then sent to the merging and transporting unit 58 via the first paper transport path R1. Further, the paper P stored in the second tray 51 is sent out by the feed roll 54 and then sent to the merging and transporting portion 58 via the first paper transport path R1. On the other hand, the paper P stored in the third tray 52 is sent directly to the merging and conveying unit 58 by the delivery roll 55.

  Further, the sheet P sent to the merging / conveying section 58 is sent to the secondary transfer section 20 of the image forming section 3 via the second sheet conveying path R2. Further, the sheet P that has passed through the secondary transfer unit 20 is sent to the fixing unit 46 by the vacuum conveyance unit 45 and then discharged to the discharge tray 57 via the third sheet conveyance path R3. On the other hand, after the paper P on which images are formed on both sides passes through the fixing unit 46, it is sent to the double-sided reversing unit 59 via the fourth paper transport path R4, where it is turned upside down. Then, it is sent again to the merging / conveying section 58 via the fifth sheet conveying path R5.

  In such paper transport paths R1 to R5, an attitude correction unit 60 and a registration roll 61 are disposed in the second paper transport path R2. The attitude correction unit 60 corrects the attitude of the paper P conveyed on the second paper conveyance path R2, and the registration roll 61 is composed of a pair of rolls held in pressure contact with each other. The sheet P is fed into the secondary transfer unit 20 by rotating the roll pair at a timing based on a predetermined start signal while the sheet P is nipped between the rolls.

  In addition, a first curl correction unit (curl correction unit) 62 that corrects curling of the paper P generated when fixing is performed in the fixing unit 46 is provided in the third paper transport path R3 provided in the paper discharge unit 5. Is provided. On the other hand, a fifth paper conveyance path R5 provided in the image forming unit 3 is a second curl correction unit 63 that corrects curling of the paper P that is reversely conveyed so as to pass through the fixing unit 46 and perform double-sided image formation. Is provided. Details of the first curl correction unit 62 will be described later.

  Subsequently, a basic image forming operation of the tandem type full color image forming apparatus 1 according to the present embodiment will be described. First, when an image of a document is read by the image reading unit 2, a toner image is formed by the image forming unit 3 based on an image signal obtained thereby. In the image forming unit 3, while rotating the four photosensitive drums 11, yellow, magenta, cyan, black on the surface of each photosensitive drum 11 by the corresponding charger 12, laser exposure device 13, and developing device 14. The toner image is formed. The toner images of the respective colors formed in this manner are sequentially transferred onto the intermediate transfer belt 15 by the primary transfer roll 16. As a result, a multicolor (full color) toner image is formed on the intermediate transfer belt 15 by superimposing four color toner images. The toner image formed on the intermediate transfer belt 15 is sent to the secondary transfer unit 20 while being carried on the intermediate transfer belt 15.

  On the other hand, when the paper P in the tray selected by the user using the operation panel 56 or the paper P in the tray selected by the automatic selection function, the toner image on the intermediate transfer belt 15 reaches the secondary transfer unit 20. For example, when the selected tray is the first tray 50, the paper P sent out by the sending roll 53 joins via the first paper transport path R1. After being sent to the transport unit 58 and further corrected by the posture correction unit 60 via the second paper transport path R2, it is sent to the secondary transfer unit 20 by the registration roll 61.

  In the secondary transfer unit 20 of the image forming unit 3, the toner image (full color image) carried on the intermediate transfer belt 15 is collectively transferred (secondary transfer) onto the paper P by the secondary transfer roll 21. Thereafter, the sheet P on which the toner image has been transferred is sent to the fixing unit 46 by the vacuum conveying unit 45, and after the heat and pressure fixing, the first curl correcting unit 62 passes through the third sheet conveying path R3. After the curl correction is performed, the sheet is discharged to the discharge tray 57.

  When image formation is performed on both sides of the sheet P, the sheet P on which image formation has been performed on one side is sent to the both-side reversing unit 59 via the fourth sheet conveyance path R4, where the front and back are reversed and the fifth To the paper transport path R5. Thereafter, the paper P on which the image is formed on one side is subjected to curl correction by passing through the second curl correction unit 63, and further conveyed along the fifth paper conveyance path R5, and then the fifth paper. The sheet is abutted against a delivery roll 64 provided near the end of the sheet transport path R5 and temporarily stops. Then, the sheet P on which the image is formed on one side is adjusted in timing by the rotation of the feeding roll 64 based on a predetermined restart signal, and is sent again to the merging and conveying unit 58. Thereafter, similarly, after the toner image is transferred and fixed on the paper P, the curl is corrected by the first curl correction unit 62 via the third paper transport path R3, and then discharged to the discharge tray 57. The

  Next, details of the first curl correction unit 62 described above will be described with reference to FIG. The first curl correction unit 62 includes a first upstream guide 71 and a second upstream guide 72 that guide the paper P conveyed from the image forming unit 3 (see FIG. 1). The first upstream guide 71 and the second upstream guide 72 are formed so that the distance between them increases toward the downstream side in the paper transport direction.

  In the first curl correction unit 62, a first middle guide 73 and a second middle guide 74 are provided on the downstream side of the first upstream guide 71 and the second upstream guide 72 in the sheet conveyance direction. Yes. The first intermediate flow guide 73 is attached to the first upstream guide 71 side, and the second intermediate flow guide 74 is attached to the second upstream guide 72 side. The first middle-stream guide 73 and the second middle-stream guide 74 are formed so that the distance therebetween decreases toward the downstream side in the sheet conveyance direction. Here, the upstream end portion of the first middle flow guide 73 is outside the downstream end portion of the first upstream guide 71, and the upstream end portion of the second middle flow guide 74 is second It is outside the downstream end of the upstream guide 72.

  Further, in the first curl correction unit 62, a first downstream guide 75 and a second downstream guide 76 are provided on the downstream side of the first middle flow guide 73 and the second middle flow guide 74 in the sheet conveyance direction. Yes. Here, the first downstream guide 75 is on the first middle flow guide 73 (first upstream guide 71) side, and the second downstream guide 76 is on the second middle flow guide 74 (second upstream guide 72) side. , Each is attached. In addition, the first downstream guide 75 and the second downstream guide 76 are formed so that the distance between them decreases toward the downstream side in the paper transport direction. The upstream end of the first downstream guide 75 is outside the downstream end of the first middle guide 73, and the upstream end of the second downstream guide 76 is It is outside the downstream end of the middle flow guide 74.

  Further, in the first curl correction unit 62, the transport direction of the transported paper P is set to the first center of the spread portion formed by the first upstream guide 71 and the second upstream guide 72. A gate 77 as a gate member for regulating the upstream guide 71 side or the second upstream guide 72 side is disposed so as to be swingable. The first upstream guide 71 and the second upstream guide 72 are provided with a slit (not shown) so that the free end side of the gate 77 can pass through the slit when swinging. Has been.

Furthermore, the first curl correction unit 62 includes a drive roll 78 that is rotatably disposed at a substantially center of an expansion portion formed by the first downstream guide 75 and the second downstream guide 76, A driven roll 79 is provided between the middle flow guide 73 and the second middle flow guide 74 so as to be rotatable. A transport belt 80 as an endless belt is stretched around the drive roll 78 and the driven roll 79 that function as a stretch member. The driving roll 78 and the driven roll 79 are made of, for example, metal, and the conveyor belt 80 is made of, for example, a stretchable material such as a rubber material. The driving roll 78, the driven roll 79, and the conveyor belt 80 constitute a belt unit 81. Further, in the conveyance belt 80 stretched by the driving roll 78 and the driven roll 79, the first side face 80a is provided on the first middle flow guide 73 side, and the second side face 80b is provided on the second middle flow guide 74 side. , Each formed.
Furthermore, the first downstream guide 75 and the second downstream guide 76 are formed in parallel with the first downstream guide 75 and the second downstream guide 76 on the downstream side in the sheet conveyance direction of the drive roll 78 and inside the first downstream guide 75 and the second downstream guide 76, respectively. As a result, a V-shaped guide 82 having a substantially V-shaped shape whose distance is reduced toward the downstream side is attached.

A first penetration shaft 83 as a first pressing member is rotatably disposed between the first middle guide 73 and the first downstream guide 75 as viewed from the sheet conveying direction. On the other hand, a second penetration shaft 84 as a second pressing member is rotatably disposed between the second middle guide 74 and the second downstream guide 76 as viewed from the sheet conveying direction. That is, the first penetration shaft 83 and the second penetration shaft 84 are arranged outside the conveyance belt 80 with the conveyance belt 80 interposed therebetween. The first penetration shaft 83 and the second penetration shaft 84 are made of, for example, a stainless steel round bar having a diameter of 8 mm. The first penetration shaft 83 and the second penetration shaft 84 can be moved in a direction substantially perpendicular to the paper conveyance direction by a moving mechanism described later, and are in contact with and separated from the conveyance belt 80. It is also possible to change the contact state at the time of contact. 3 illustrates a state in which the first penetration shaft 83 and the second penetration shaft 84 are in contact with the conveyance belt 80.
The second upstream guide 72 is attached with a paper detection sensor 85 for detecting the arrival or passage of the paper P between the first upstream guide 71 and the second upstream guide 72. The paper detection sensor 85 is not necessarily provided in the first curl correction unit 62, and can be attached further upstream in the paper conveyance direction.

FIG. 4 is a view for explaining the driving mechanism of the belt unit 81 and the moving mechanism of the first penetration shaft 83 and the second penetration shaft 84 described above.
First, a transport belt drive motor 91 is attached to the drive roll 78 of the belt unit 81 via a gear or the like. As the conveyor belt drive motor 91, a stepping motor capable of rotating in the forward and reverse directions is employed. As a result, the conveyor belt 80 can be rotated in the first direction (the direction indicated by the solid line arrow in FIG. 3) and the second direction (the direction indicated by the broken line arrow in FIG. 3).

  Further, both ends of the first penetration shaft 83 and the second penetration shaft 84 are rotatably supported by brackets 86 as support members. A spring 87 is attached to one end side (upper side) of the bracket 86, and the other end side of the spring 87 is attached to the frame of the paper discharge unit 5 (see FIG. 1). On the other hand, the other end side (lower side) of the bracket 86 has a polygonal shape (a pentagonal shape in the present embodiment), and comes into contact with a cam 88 as a pressing force variable member that is rotatably disposed. ing. A cam drive motor 92 is attached to the cam 88 via a gear or the like. Then, by rotating the cam 88 by the cam drive motor 92, the position (height) of the bracket 86 is changed, and as a result, the first penetration shaft 83 and the second penetration shaft 84 attached to the bracket 86 are transported. The contact state with the belt 80 changes.

Here, FIGS. 5A to 5E show the contact of the first and second penetration shafts 83 and 84 with the conveyor belt 80 when the cam 88 shown in FIG. It is a figure which shows the change of a state.
For example, in the state shown in FIG. 5A, the bracket 86 (see FIG. 4) is placed at the highest position as the cam 88 rotates, and as a result, the first penetration shaft 83 is separated from the conveyor belt 80, The second penetration shaft 84 comes into contact with the conveying belt 80 in a state where it is strongly bitten. Further, for example, in the state shown in FIG. 5B, the position of the bracket 86 is slightly lowered, and as a result, the first penetration shaft 83 makes a slight contact with the conveyance belt 80 and the second penetration shaft 84 contacts the conveyance belt 80. It touches in a state where it bites in to some extent. Further, for example, in the state shown in FIG. 5C, the position of the bracket 86 is further lowered, and as a result, the first penetration shaft 83 and the second penetration shaft 84 are both weakly biting into the conveyor belt 80. Contact. Furthermore, in the state shown in FIG. 5 (d), the position of the bracket 86 is further lowered, and as a result, the first penetration shaft 83 is in contact with the conveyor belt 80 in a state of being bitten to some extent, and the second penetration shaft 84 is Lightly contacts the conveyor belt 80. For example, in the state shown in FIG. 5 (e), the position of the bracket 86 is further lowered, and as a result, the first penetration shaft 83 comes into contact with the conveyance belt 80 in a state of being strongly bitten, and the second penetration shaft 84 is brought into contact. Is separated from the conveyor belt 80.
As described above, in the present embodiment, the position of the bracket 86 is changed in five stages by devising the shape of the cam 88, the distance between the first penetration shaft 83 and the second penetration shaft 84, and the like. Only the contact state between the first penetration shaft 83 and the conveyor belt 80 and the contact state between the second penetration shaft 84 and the conveyor belt 80 can be changed in four stages.

Next, a curl correction operation in the first curl correction unit 62, which is a characteristic point of the image forming apparatus according to the present embodiment, will be described with reference to FIG.
The sheet P on which the image has been fixed by passing through the fixing unit 46 is curved so that the image forming surface is on the outside or the image forming surface is on the inside due to heat received by the fixing unit 46. Sometimes. In the case of the image forming apparatus according to the present embodiment, the former is a down curl in which both ends in the transport direction of the paper P are lowered, and the latter is an upper curl in which both ends in the transport direction of the paper P are raised. Hereinafter, the curl correction operation for the down-curled paper P and the curl correction operation for the upper-curled paper P will be described.

(1) Curling Correction Operation for Down-curled Paper P When the down-curled paper P is conveyed, the gate 77 is set at a position indicated by a solid line in FIG. Further, the drive roll 78 is rotationally driven in the direction indicated by the solid line in FIG. 3, and the conveyance belt 80 starts to rotate accordingly. Then, the first penetration shaft 83 is arranged so as to abut on the conveying belt 80 with a predetermined pressure, that is, in the state shown in FIG.
Next, when the down-curled sheet P is conveyed between the first upstream guide 71 and the second upstream guide 72, the conveyance direction of the sheet P is regulated by the gate 77, and the first upstream guide 71. It is conveyed along. Then, the paper P reaches a region sandwiched between the first middle-stream guide 73 and the conveyance belt 80. At this time, the first middle-stream guide 73 side of the transport belt 80 rotates in the same direction as the movement direction of the paper P, and the paper P is further transported by the transport force of the transport belt 80 this time. The contact portion with the penetration shaft 83 is reached. Then, the paper P is urged to the opposite side of the down curl by the first penetration shaft 83 that urges the conveyance belt 80, and as a result, the down curl is corrected. Then, the paper P subjected to the curl correction is further transported by the transport belt 80, and is discharged toward the discharge tray 57 (see FIG. 1) via the first downstream guide 75 and the V-shaped guide 82.

(2) Curling Correction Operation for Upper Curled Paper P When the upper curled paper P is conveyed, the gate 77 is set at a position indicated by a broken line in FIG. Further, the drive roll 78 is rotationally driven in the direction indicated by the broken line in FIG. 3, and the conveyance belt 80 starts to rotate accordingly. In this case, the second penetration shaft 84 is disposed so as to abut on the conveyor belt 80 with a predetermined pressure.
Next, when the upper curled paper P is conveyed between the first upstream guide 71 and the second upstream guide 72, the conveyance direction of the paper P is regulated by the gate 77, and the second upstream guide 72. It is conveyed along. Then, the paper P reaches a region sandwiched between the second middle-stream guide 74 and the conveyance belt 80. At this time, the second middle-stream guide 74 side of the transport belt 80 is rotated in the same direction as the movement direction of the paper P, and the paper P is further transported by the transport force of the transport belt 80 this time. The contact portion with the penetration shaft 84 is reached. Then, the paper P is urged to the opposite side of the upper curl by the second penetration shaft 84 that urges the conveying belt 80, and as a result, the upper curl is corrected. The curled paper P is further transported by the transport belt 80 and discharged toward the discharge tray 57 (see FIG. 1) via the second downstream guide 76 and the V-shaped guide 82. In the third sheet conveyance path R3, the sheet conveyance path passing through the first penetration shaft 83 side is the down curl correction conveyance path R3a, and the sheet conveyance path passing through the second penetration shaft 84 side is the upper curl correction conveyance. This is called road R3b.

  Incidentally, in the image forming apparatus according to the present embodiment, the curl correction can be manually set as described above, the environment such as temperature and humidity, the type of the paper P (information on the recording material), and the image information ( Toner image information) or the like is used to predict whether the curl generated on the paper P that has passed through the fixing unit 46 is down curl or upper curl, and the curl correction is automatically performed based on the prediction result. You can also. Next, this control will be described.

FIG. 6 is a block diagram for explaining the function of the control unit 40. Although the control unit 40 controls the entire image forming apparatus, FIG. 6 shows only functional blocks related to the curl correction control in the first curl correction unit 62.
The CPU 101 of the control unit 40 executes processing while appropriately exchanging data with the RAM 103 in accordance with a program stored in the ROM 102. The control unit 40 is provided with a timer 104. The control unit 40 also receives job start instruction information, paper type information (first tray 50, second tray 51, and the like received by the operation panel 56 and the keyboard 56a via the input / output interface 105. Information on which of the third trays 52 the paper P stored in is used) is input. Further, the density information (image density information) of the image formed on the paper P from the IPS 44 is input to the control unit 40 for each paper P via the input / output interface 105. Further, temperature information from the temperature sensor 47, humidity information from the humidity sensor 48, and paper detection information from the paper detection sensor 85 are input to the control unit 40 via the input / output interface 105. On the other hand, the control unit 40 outputs drive signals to the conveyor belt drive motor 91, the cam drive motor 92, and the gate drive motor 93 that drives the gate 77 via the input / output interface 105, and controls the drive of each motor. ing.

  Next, processing related to the curl correction operation in the first curl correction unit 62 will be described with reference to the flowchart shown in FIG. Before this process is started, designation of the number of the tray that stores the paper P used in this job is accepted via the operation panel 56 or the keyboard 56a. Then, the control unit 40 reads out the type (for example, basis weight, presence / absence of coat layer, type of coat layer, etc.) of the paper P stored in the received tray from the memory.

  The control unit 40 first determines whether or not the sheet that has passed through the fixing unit 46 has been detected by the sheet detection sensor 85 (step 101). If the paper P is not detected, the process returns to step 101 and waits for the paper P to be conveyed. On the other hand, if the paper P is detected, the timer 104 starts measuring time (step 102), and then from the type of the paper P based on the tray information input via the operation panel 56 or the keyboard 56a, from the temperature sensor 47. Based on the temperature information, the humidity information from the humidity sensor 48, and the image density information from the IPS 44, an appropriate curl correction condition is acquired by referring to the table (step 103). Here, the curl correction conditions include the direction of the gate 77, the direction of rotation of the conveyor belt 80, and the position of the cam 88 (the pressing state against the conveyor belt 80 by the first penetration shaft 83 or the second penetration shaft 84). included. In the above table, these various conditions (the type of paper P, temperature, humidity, and image density) correspond to the set values of each member (the direction of the gate 77, the rotation direction of the transport belt 80, the position of the cam 88). In the attached state, for example, it is stored in the ROM 102.

  Next, the control unit 40 sets the conveyor belt 80, the first penetration shaft 83, the second penetration shaft 84, and the gate 77 to a predetermined state based on the curl correction condition acquired in Step 103 (Step S40). 104). More specifically, the conveyance belt drive motor 91 is controlled to rotate the conveyance belt 80 in a predetermined direction (forward direction or reverse direction), and the cam drive motor 92 is controlled to control the first penetration shaft 83. Alternatively, the second penetration shaft 84 is brought into contact with the conveyor belt 80 with a predetermined pressing force, and the gate drive motor 93 is controlled to move the gate 77 to a predetermined position (on the first upstream guide 71 side or the second side). Set on the upstream guide 72 side. Note that the setting operation of each member in step 104 is completed until the leading edge of the paper P detected by the paper detection sensor 85 reaches the gate 77. At this time, the sheet P is discharged after the curl (down curl or upper curl) is corrected by the first curl correction unit 62 set according to the curl state.

  Then, the control unit 40 determines whether or not the time measured by the timer 104 has passed a predetermined time from the paper detection (step 105). The predetermined time is set based on the time from when the leading edge of the paper P is detected by the paper detection sensor 85 to when the trailing edge of the paper P passes the transport belt 80. That is, when the predetermined time has elapsed, the sheet P is not conveyed by the conveyance belt 80. If the predetermined time has not elapsed, the process returns to step 105 to wait for the predetermined time to elapse. On the other hand, if the predetermined time has elapsed, the conveyance belt drive motor 91 is controlled to stop the rotation of the conveyance belt 80 (step 106). Then, it is determined whether or not the next sheet P is present (step 107). If the next sheet P is present, the process returns to step 101 to continue the processing. On the other hand, if the next paper P does not exist in step 107, the series of processing is terminated.

  In the image forming apparatus according to the present embodiment, for example, depending on the type of the paper P, a down curl may easily occur or an upper curl may easily occur. Even if exactly the same type of paper P is used, depending on the environmental conditions such as temperature and humidity and the density of the image to be formed, down curling is likely to occur or upper curling is likely to occur. As a specific example, for example, the higher the image density formed on the paper P, the greater the shrinkage of the toner image that accompanies fixing, so that the curl that curves with the image bearing surface side inward (in this embodiment, the upper curl) ) Is likely to occur.

  Therefore, in this embodiment, for each sheet, based on these various conditions, it is determined whether the condition is likely to cause down curl or upper curl, and the degree of curl that can occur in that case is also determined. The curl correction conditions in the first curl correction unit 62 are set. Accordingly, the first curl correction unit 62 of the image forming apparatus may carry the paper P that has been curled up next to the paper P that has been curled down. For this reason, in the present embodiment, control is performed so that the next sheet P does not enter the first curl correction unit 62 until the time measured by the timer 104 has passed the predetermined time in step 105. This is because, in the first curl correction unit 62, the rotation direction of the conveyance belt 80 differs depending on whether a down curl or an upper curl occurs in the paper P.

  Thus, in this embodiment, the conveyance belt 80 of the belt unit 81 can be rotated in the forward and reverse directions, and the first penetration shaft is provided on both sides of the conveyance belt 80, that is, on the first side surface 80a side. 83, the second penetration shaft 84 is provided on the second side face 80b side. Further, the guide direction of the paper P is switched to the down curl correction conveyance path R3a or the upper curl correction conveyance path R3b by the gate 77. As a result, it is possible to correct both the down curl and the upper curl generated on the paper P by the single conveyance belt 80. Further, as described with reference to FIGS. 4 and 5, the amount of biting (pressing force) of the first penetration shaft 83 and the second penetration shaft 84 with respect to the conveyance belt 80 can be adjusted. The force applied to the paper P can be adjusted according to the degree of generated down curl or upper curl, and curl correction can be performed in a wide range.

  Further, in the present embodiment, it is determined whether the curl generated on the paper P is a down curl or an upper curl based on the type of the paper P, the image density of the image formed on the paper P, and the like. . In addition, the degree of curl generated at that time was also judged. Based on these determination results, the position of the gate 77, the rotation direction of the conveyor belt 80, and the pressing force of the first penetration shaft 83 or the second penetration shaft 84 against the conveyor belt 80 can be automatically set. I did it. Thereby, curl correction according to the direction of curl (down curl, upper curl) generated on the paper P that has passed through the fixing unit 46 and the degree of curl can be performed.

  In the present embodiment, the first curl correction unit 62 has been described as an example, but the second curl correction unit 63 can use the same mechanism. Further, in the present embodiment, the conveyance belt 80 is stretched by two rolls (the drive roll 78 and the driven roll 79), but the first side face 80a and the second side face 80b are formed. If there is, the conveyor belt 80 may be stretched by three or more rolls. Further, in the present embodiment, the first penetration shaft 83 and the second penetration shaft 84 are supported by the bracket 86, but may be supported separately.

1 is a schematic diagram illustrating an overall configuration of a full-color image forming apparatus according to an embodiment. 1 is a diagram illustrating a main part of a full-color image forming apparatus according to an embodiment. It is a figure which shows a 1st curl correction part. It is a figure for demonstrating the drive mechanism of a belt unit, and the moving mechanism of a 1st penetration shaft and a 2nd penetration shaft. (a)-(e) is a figure which shows the change of the contact state with a 1st penetration shaft and a 2nd penetration shaft, and a conveyance belt. It is a block diagram for demonstrating the function of a control part. It is a flowchart which shows the process regarding the curl correction operation | movement in a 1st curl correction part.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Full color image forming apparatus, 2 ... Image reading part, 3 ... Image forming part, 4 ... Paper supply part, 5 ... Paper discharge part, 10 (10Y, 10M, 10C, 10K) ... Image forming unit, 20 ... Secondary Transfer unit 40... Control unit 44. IPS 46. Fixing unit 47. Temperature sensor 48. Humidity sensor 56 Operation panel 56 a Keyboard 57 Discharge tray 62 First curl correction unit 63: second curl correction unit, 77: gate, 78 ... drive roll, 79 ... driven roll, 80 ... conveyor belt, 81 ... belt unit, 83 ... first penetration shaft, 84 ... second penetration shaft, 85 ... paper detection sensor, 86 ... bracket, 87 ... spring, 88 ... cam, 91 ... conveyance belt drive motor, 92 ... cam drive motor, R1 ... first paper conveyance path, R2 ... second The paper transport path, R3 ... the third paper conveying path, R3a ... down curl correction for the transport path, R3b ... upper curl correction for the transport path, R4 ... the fourth sheet conveying path of, R5 ... fifth paper transport path of the

Claims (9)

An endless belt that is stretched by a tension member and is disposed so as to be rotatable in forward and reverse directions, and a first side surface and a second side surface for conveying a sheet are formed by the tension member;
A first pressing member that presses the sheet conveyed along the first side surface by contacting the first side surface of the endless belt;
A curl including a second pressing member that abuts against the second side surface of the endless belt and presses the sheet conveyed along the second side surface in a direction opposite to the first pressing member. Correction device. A support member for supporting the first pressing member and the second pressing member;
It further includes a pressing force variable member that varies the pressing force of the first pressing member and / or the second pressing member against the endless belt by adjusting the position of the support member. Item 4. The curl correction apparatus according to Item 1.   2. The apparatus according to claim 1, further comprising a gate member that is provided upstream of the endless belt in the sheet conveying direction and switches the sheet conveying direction to the first side surface or the second side surface. The curl correction apparatus as described.   4. The curl correction apparatus according to claim 3, wherein the rotation direction of the endless belt is switched in conjunction with the switching operation of the gate member.   4. The curl correction apparatus according to claim 3, wherein the pressing force of the first pressing member or the second pressing member against the endless belt is changed in conjunction with the switching operation of the gate member. An image forming unit for forming a toner image on a recording material;
A fixing unit for fixing the toner image formed on the recording material;
A curl correction unit that corrects curl generated in the recording material that has passed through the fixing unit,
The curl correction unit
An endless belt that is stretched by a tension member and is disposed so as to be rotatable in forward and reverse directions, and has a first side surface and a second side surface for conveying a recording material formed by the tension member; ,
A first pressing member that presses the recording material conveyed along the first side surface by contacting the first side surface of the endless belt;
A second pressing member that presses the recording material conveyed along the second side surface in a direction opposite to the first pressing member by contacting the second side surface of the endless belt; An image forming apparatus. A control unit for controlling the curl correction unit;
The image according to claim 6, wherein the control unit determines a rotation direction of the endless belt based on information on a recording material and / or information on a toner image formed in the image forming unit. Forming equipment.   The controller controls the pressing force of the first pressing member or the second pressing member on the endless belt based on information on the recording material and / or information on a toner image formed in the image forming unit. The image forming apparatus according to claim 7, wherein: A control unit for controlling the curl correction unit;
The image forming apparatus according to claim 6, wherein the control unit performs control so that a next recording material enters the endless belt after the recording material passes through the endless belt.

Images