JP2018155941A - Curl correction device, fixation device and image formation apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the damage on a toner image at the curl correction and prevent the sheet jam occurrence.SOLUTION: A curl correction device 200 includes: a first rotor pair (drive roller 204, driven roller 203) which is arranged on the downstream side of a fixation nip N1; a guide member 205; a sheet discharge direction change mechanism 300 of the first rotor pair; a second rotor pair (sheet discharge roller pair 13); a detection mechanism 400 which detects whether or not the tip of a sheet-like body reaches the second rotor pair; and a control mechanism 500 which controls the sheet discharge direction change mechanism 300 on the basis of the detection result. The control mechanism 500 controls the sheet discharge direction change mechanism so as to maintain a butting angle at a prescribed angle θ1 larger than the right angle until the detection mechanism 400 detects the tip of the sheet-like body P, and controls the sheet discharge direction change mechanism so as to change θ1 to a prescribed angle θ2(θ1>θ2) closer to the right angle when the detection mechanism 400 detects the tip of the sheet-like body P.SELECTED DRAWING: Figure 3B

Description

The present invention relates to a curl correction device, a fixing device, and an image forming apparatus, and more particularly to a curl correction device that corrects a sheet-like body curled by heat of the fixing device, and a fixing device and an image forming apparatus including the curl correction device.

In general, a fixing device includes a heating member and a pressure member, and a toner image formed as a developer image is passed through a fixing nip where both members are pressed against each other. Heat-fixed. In recent fixing devices, the heat capacity of the heating member has been reduced in order to save energy and shorten the first print time. For this reason, the temperature difference between the heating member and the pressure member during the first print tends to increase, and the sheet-like body may curl greatly toward the pressure member immediately after passing through the fixing nip.

In order to solve the problem, for example, a curl correction device described in Patent Document 1 (Japanese Patent Laid-Open No. 2006-118688) is known. In this apparatus, a roller pair disposed on the downstream side of the fixing device is disposed so as to be displaceable between a first position (DP1) that does not correct paper curl and a second position (DP2) that corrects paper curl. For example, when the paper is passed without being heated and fixed, the roller pair is moved to the first position (DP1), and when the paper is heated and fixed and is passed, the roller is moved to the second position (DP2). .

However, in the curl correcting apparatus of Patent Document 1, the toner image side of the paper is bent deeply into a concave shape when correcting the paper. For this reason, the toner image may be rubbed with the roller and partially damaged. Further, since the paper is bent deeply into a concave shape, paper jam may occur.

Accordingly, an object of the present invention is to prevent damage to a toner image during curl correction and to suppress the occurrence of paper jam.

In order to solve the above problems, the curl correction device of the present invention is disposed on the downstream side in the paper discharge direction of a fixing device having a fixing member and a pressure member, and is formed between the fixing member and the pressure member. A curl straightening device for correcting curling of a sheet-like body discharged from a fixing nip, the curl straightening device being disposed downstream of the fixing nip in a paper discharge direction, wherein the sheet-like body is placed at an auxiliary nip. A first rotating body pair that is nipped and conveyed, and is disposed on the downstream side in the paper discharge direction of the first rotating body pair, and the sheet-like body is brought into contact with the fixing member side by abutting the leading end of the sheet-like body A guide member that can be bent straightly, a paper discharge direction changing mechanism that can change a paper discharge direction of the auxiliary nip to change the abutment angle of the sheet-like body with respect to the guide member, and a paper discharge direction of the guide member The sheet is arranged on the downstream side And a detection mechanism for detecting whether or not the leading end of the sheet-like body has reached the conveyance nip of the second rotation body pair. And a control mechanism that controls the discharge direction changing mechanism based on the detection result of the detection mechanism, and the control mechanism is configured to push the protrusion until the detection mechanism detects the leading end of the sheet-like body. When the sheet discharge direction changing mechanism is controlled to maintain a contact angle at a predetermined angle θ1 larger than a right angle, and the detection mechanism detects the leading end of the sheet-like body, the predetermined angle θ1 approaches a right angle. The discharge direction changing mechanism is controlled to change to θ2 (θ1> θ2).

According to the present invention, the abutting angle with respect to the guide member is changed from θ1 to θ2 in a state where the leading end portion of the sheet-like body reaches the conveyance nip. A stronger curl correction effect can be obtained, and a decrease in paper transportability due to a change in the abutting angle can be suppressed to prevent the occurrence of paper jam.

1 is a schematic view of an image forming apparatus according to an embodiment of the present invention. It is sectional drawing of the fixing device and curl correction apparatus which concern on embodiment of this invention (at the time of thin paper single-sided printing in weak curl correction). FIG. 2 is a cross-sectional view of the fixing device and the curl correction device according to the embodiment of the present invention (when printing on one side of thin paper with strong curl correction). 1 is a cross-sectional view of a fixing device and a curl correction device according to an embodiment of the present invention (at the time of cardboard single-side printing without curl correction). The positional relationship between the auxiliary nip and the guide surface of the curl correction apparatus is shown, wherein (a) is a diagram during weak curl correction and (b) is a diagram during strong curl correction. 2A and 2B show a sheet-like body conveyance path by an auxiliary nip and a guide surface of the curl correction apparatus, where FIG. 3A shows a conveyance path during weak curl correction, and FIG. 2B shows a conveyance path during strong curl correction. It is a figure which shows the relationship between the temperature of the heating side and pressurization side in a fixing nip, and the contact angle of the sheet-like object with respect to a guide member. It is a figure which shows the paper passing pattern (I)-(III) of a curl correction apparatus. It is the figure seen from the arrow VI direction of FIG. 2C. FIG. 7 is a perspective view of a part of the fixing device when viewed from the conveyance path side when the guide member is in the “first position”. FIG. 6 is an enlarged perspective view of a part of the fixing device when viewed from the conveyance path side when the guide member is at the “second position”. FIG. 6 is a view of a part of the fixing device when the guide member moving mechanism is operated and the guide member is in the “second position” as viewed from the conveyance path side. It is a side view of a curl correction apparatus when a guide member exists in a "1st position." It is a side view of a curl correction apparatus when a guide member exists in a "2nd position." It is a figure which shows the abutting angle of the discharge direction of the correction | amendment nip with respect to the guide surface of a guide member.

Hereinafter, a fixing device and an image forming apparatus according to an embodiment of the present invention will be described with reference to the drawings.

(Image forming device)
First, the overall configuration of an image forming apparatus according to an embodiment of the present invention will be described. An image forming apparatus 100 shown in FIG. 1 is a color laser printer, and includes an image forming unit A, a paper feeding unit B, a fixing device 20, a pair of paper discharge rollers 13 as a second rotating body pair, and a discharge unit. It has a paper tray 14 and the like.

The image forming unit A includes four image forming units 4Y, 4M, 4C, and 4K, an exposure device 9, a transfer device 3, and the like, which will be described later. The image forming apparatus 100 includes a curl correction device 200 in the fixing device 20 as a characteristic configuration. This will be described in detail below.

In the center of the image forming apparatus main body of the image forming apparatus 100, four image forming units 4Y, 4M, 4C, and 4K are provided. Each of the image forming units 4Y, 4M, 4C, and 4K contains developers of different colors of yellow (Y), magenta (M), cyan (C), and black (K) corresponding to the color separation components of the color image. The configuration is the same except that.

Specifically, each of the image forming units 4Y, 4M, 4C, and 4K has a drum-shaped photoconductor 5 as a latent image carrier, a charging device 6 that charges the surface of the photoconductor 5, and a surface of the photoconductor 5. A developing device 7 that supplies toner and a cleaning device 8 that cleans the surface of the photoreceptor 5 are included.

In FIG. 1, only the photoconductor 5, the charging device 6, the developing device 7, and the cleaning device 8 included in the black image forming unit 4 </ b> K are denoted by reference numerals, and the other image forming units 4 </ b> Y, 4 </ b> M, and 4 </ b> C are illustrated. Since the configuration is the same as that of the black image forming unit 4K, the reference numerals thereof are omitted.

Under the image forming units 4Y, 4M, 4C, and 4K, an exposure device 9 that exposes the surface of the photoreceptor 5 is disposed. The exposure device 9 includes a laser light source, a polygon mirror 51a, an f-θ lens 51b, a plurality of reflection mirrors 51c, and the like, and irradiates the surface of each photoconductor 5 with laser light based on image data. An electrostatic latent image is formed on the surface.

A transfer device 3 is disposed above the image forming units 4Y, 4M, 4C, and 4K. The transfer device 3 includes an intermediate transfer belt 30 as an intermediate transfer member, four primary transfer rollers 31 as primary transfer means, a secondary transfer roller 36 as secondary transfer means, a secondary transfer backup roller 32, A cleaning backup roller 33, a tension roller 34, and a belt cleaning device 35 are provided.

The intermediate transfer belt 30 is an endless belt and is stretched by a secondary transfer backup roller 32, a cleaning backup roller 33, and a tension roller 34. Here, by rotating the secondary transfer backup roller 32, the intermediate transfer belt 30 runs (rotates) in the direction indicated by the arrow in the figure.

Each of the four primary transfer rollers 31 sandwiches the intermediate transfer belt 30 with each photoconductor 5 to form a primary transfer nip. Further, a power source is connected to each primary transfer roller 31 so that a predetermined DC voltage (DC) or a predetermined AC voltage (AC) is applied to each primary transfer roller 31.

The secondary transfer roller 36 sandwiches the intermediate transfer belt 30 with the secondary transfer backup roller 32 to form a secondary transfer nip. Similarly to the primary transfer roller 31, a power source is also connected to the secondary transfer roller 36 so that a predetermined DC voltage (DC) or AC voltage (AC) is applied to the secondary transfer roller 36. It has become.

The belt cleaning device 35 includes a cleaning brush and a cleaning blade disposed so as to contact the intermediate transfer belt 30. The waste toner collected by the belt cleaning device 35 is accommodated in a waste toner container via a waste toner transfer hose.

A bottle container 2 is provided at the upper part of the main body of the image forming apparatus, and four toner bottles 2Y, 2M, 2C, and 2K that store replenishing toner are detachably attached to the bottle container 2. ing. Toner is supplied from each toner bottle 2Y, 2M, 2C, 2K to each developing device 7 via a supply path provided between each toner bottle 2Y, 2M, 2C, 2K and each developing device 7.

On the other hand, a sheet feeding unit B is provided at the lower part of the image forming apparatus main body. The paper feed unit B includes a paper feed tray 10 that stores recording paper P as a sheet-like body (recording medium), a paper feed roller 11 that carries the recording paper P out of the paper feed tray 10, and the like.

In addition to plain paper, the recording paper P includes thick paper, postcards, envelopes, thin paper, coated paper (coated paper, art paper, etc.), tracing paper, OHP sheet, and the like. Further, a manual paper feed mechanism may be provided. In this embodiment, “thick paper” refers to paper having a basis weight of 160 g / m 2 or more.

In the image forming apparatus main body, a conveyance path R is provided for discharging the recording paper P from the paper feed tray 10 through the secondary transfer nip to the outside of the apparatus. In the transport path R, a pair of registration rollers 12 serving as timing rollers for transporting the recording paper P to the secondary transfer nip at the transport timing is arranged upstream of the position of the secondary transfer roller 36 in the recording paper transport direction. It is installed.

Further, on the downstream side in the recording paper conveyance direction from the position of the secondary transfer roller 36, the fixing device 20 that pressurizes and heats the recording paper P carrying an unfixed toner image and fixes the toner image on the recording paper P. Is arranged. Further, a pair of paper discharge rollers 13 for discharging the recording paper P to the outside of the apparatus is provided on the downstream side in the recording paper conveyance direction of the conveyance path R from the fixing device 20. Further, a paper discharge tray 14 for stocking the recording paper P discharged outside the apparatus is provided on the upper surface of the image forming apparatus main body.

Further, a curl correction device 200 described later is provided between the paper discharge roller pair 13 and the fixing device 20 at a position close to the fixing device 20.

(Basic operation of image forming apparatus)
Next, a basic operation of the image forming apparatus 100 according to the embodiment of the present invention will be described. First, when an image forming operation is started, each photoconductor 5 in each of the image forming units 4Y, 4M, 4C, and 4K is rotationally driven clockwise in the drawing, and the surface of each photoconductor 5 is predetermined by the charging device 6. Uniformly charged to polarity. The surface of each charged photoconductor 5 is irradiated with laser light from the exposure device 9 to form an electrostatic latent image on the surface of each photoconductor 5.

At this time, the image information to be exposed on each photoconductor 5 is monochromatic image information obtained by separating a desired full-color image into color information of yellow, magenta, cyan, and black. The toner is supplied to the electrostatic latent images formed on the respective photoreceptors 5 by the developing devices 7 in this way, whereby the electrostatic latent images are visualized (visualized) as images.

When the image forming operation is started, the secondary transfer backup roller 32 is driven to rotate counterclockwise in the figure, and the intermediate transfer belt 30 is caused to run in the direction indicated by the arrow in the figure. Further, by applying a constant voltage having a polarity opposite to the toner charging polarity or a voltage controlled by a constant current to each primary transfer roller 31, the primary transfer nip between each primary transfer roller 31 and each photoreceptor 5 is applied. A transfer electric field is formed.

Thereafter, when each color image on the photoconductor 5 reaches the primary transfer nip as each photoconductor 5 rotates, the image on each photoconductor 5 is intermediated by the transfer electric field formed in the primary transfer nip. The images are sequentially superimposed and transferred onto the transfer belt 30.

In this way, a full color image is carried on the surface of the intermediate transfer belt 30. Further, the toner on each photoconductor 5 that could not be transferred to the intermediate transfer belt 30 is removed by the cleaning device 8. Then, the surface of each photoconductor 5 is neutralized by the neutralization device, and the surface potential is initialized.

In the lower part of the printer, the paper feed roller 11 starts to rotate, and the recording paper P is sent out from the paper feed tray 10 to the transport path R. The recording paper P delivered to the transport path R is temporarily stopped by the registration rollers 12.

Thereafter, rotation of the registration roller 12 is started at a predetermined timing, and the recording paper P is conveyed to the secondary transfer nip in accordance with the timing when the image on the intermediate transfer belt 30 reaches the secondary transfer nip. At this time, a transfer voltage having a polarity opposite to the toner charging polarity of the image on the intermediate transfer belt 30 is applied to the secondary transfer roller 36, thereby forming a transfer electric field in the secondary transfer nip.

Then, the image on the intermediate transfer belt 30 is collectively transferred onto the recording paper P by this transfer electric field. At this time, the residual toner on the intermediate transfer belt 30 that could not be transferred onto the recording paper P is removed by the belt cleaning device 35 and conveyed to a waste toner container.

Thereafter, the recording paper P is conveyed to the fixing device 20, and the image on the recording paper P is fixed to the recording paper P by the fixing device 20. The recording paper P conveyed from the fixing device 20 passes through a curl correction device 200 described later and is discharged onto a discharge tray 14 outside the apparatus.

The above description is an image forming operation when a full-color image is formed on the recording paper P. A single-color image is formed using any one of the four image forming units 4Y, 4M, 4C, and 4K. It is also possible to form a two-color or three-color image using two or three image forming units.

(Fixing device)
Next, the curl correction device 200 used in the image forming apparatus 100 according to the embodiment of the present invention and the fixing device 20 having the curl correction device will be described in detail. 2A to 2C are cross-sectional views of the fixing device having the curl correcting device 200 according to the present embodiment.

As shown in FIGS. 2A to 2C, the fixing device 20 is used to fix the toner image T after being transferred, which is carried on the recording paper P, by melting and infiltrating it with heat and pressure. A flexible fixing belt 21 capable of endless running is provided.

As shown in FIGS. 2A to 2C, the fixing device 20 passes the recording paper P on which the toner image is transferred in the image forming unit A through the fixing nip N1, and applies heat and pressure to the toner image by the fixing nip N1. Is fixed on the recording paper P.

In addition to the endless fixing belt (fixing member) 21, the fixing device 20 is opposed to form a fixing nip N <b> 1 by applying pressure to the fixing belt 21 in contact with the fixing belt 21. A pressure roller (pressure member) 22 that is a rotating body is provided. Inside the fixing belt 21, a heater (heat source) 23 including a plurality of halogen lamps 23a and 23b for heating the inner surface side of the fixing belt 21 at a place other than the fixing nip N1 is provided.

Inside the fixing belt 21, a nip forming member 24 that is a base member for forming a nip disposed inside the fixing belt 21, a stay 25 that supports the nip forming member 24, and light emitted from the heater 23. Is provided on the fixing belt 21.

The nip forming member 24, which is a base member for forming the nip, has a plane perpendicular to a line connecting the rotation center of the pressure roller 22 and the central portion in the conveyance direction of the fixing nip N1. The nip forming member 24 is in direct contact with the fixing belt 21 or in contact with a sliding member (low friction sheet) wound around the base pad.

The temperature of the fixing belt 21 is detected by a temperature sensor 27 provided on the side where the recording paper P enters the fixing nip N1 and is used for feedback processing of the heater 23. 2A to 2C, the arrow A1 indicates the conveyance direction of the recording paper P.

The fixing belt 21 is an endless belt formed in a thin and flexible sleeve shape, and is composed of a base material and a release layer located on the surface thereof. For the substrate, a metal material such as nickel or A-SUS or a resin material such as polyimide is used. For the release layer, tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA), polytetrafluoroethylene (PTFE), or the like having releasability with respect to the toner is used.

The pressure roller 22 opposes the nip forming member 24 on the opposite side with respect to the fixing belt 21 and presses the fixing belt 21 to form the fixing nip N1 in cooperation with the nip forming member 24.

The pressure roller 22 includes a cored bar 22a, an elastic layer 22b made of foamable silicone rubber, silicone rubber, or fluororubber provided on the peripheral surface of the cored bar 22a, and a PFA provided on the surface of the elastic layer 22b. Or it is comprised by the mold release layer which consists of PTFE etc. The pressure roller 22 is pressed toward the fixing belt 21 by the pressing unit and is in contact with the nip forming member 24 as a base member in contact with the fixing belt 21.

At the place where the pressure roller 22 and the fixing belt 21 contact each other, the elastic layer 22b of the pressure roller 22 is crushed so that pressure is applied to the fixing belt 21 and the nip forming member 24 has a predetermined width. The fixing nip N1 is secured.

The pressure roller 22 is configured to be rotationally driven by a drive source such as a motor provided in the printer main body. When the pressure roller 22 is rotationally driven, the driving force is transmitted to the fixing belt 21 through the fixing nip N1, and the fixing belt 21 is driven to rotate.

In the fixing device 20 according to the present embodiment, the pressure roller 22 is a solid roller, but may be a hollow roller. In that case, a heating source such as a halogen heater using radiant heat may be disposed inside the pressure roller 22. In addition, when the elastic layer 22b is not provided, the heat capacity is reduced and the fixability is improved. However, when the unfixed toner is crushed and fixed, minute irregularities on the belt surface are transferred to the image and the solid portion of the image is glossy. Unevenness may occur. In order to prevent this, it is desirable to provide an elastic layer having a thickness of 100 μm or more.

Aluminum, iron, stainless steel, or the like can be selected as the pipe-shaped metal used for the hollow roller. When providing a heat source in the pressure roller 22, in order to prevent the support from being heated by radiant heat from the heat source, a heat insulating layer is provided on the support surface or a heat ray reflecting surface is provided by mirror treatment. Is desirable. The heat source in this case is not limited to the halogen heater described above, and an IH heater, a resistance heating element, or a carbon heater can also be used.

In the case of the fixing device 20 described above, since the heating member having a low heat capacity is directly heated, the fixing device 20 has a very fast temperature rise, and thus has an advantage that the first print can be accelerated. However, from the viewpoint of curling of the recording paper P, the fixing device 20 performs fixing before the pressure roller is sufficiently warmed, so that the curling due to the temperature difference between the front and back as described above becomes very large.

On the recording paper exit side of the fixing device 20, a separation transport mechanism is provided that separates the recording paper P that has passed through the fixing nip N1 in the vicinity of the fixing nip N1 and guides the recording paper P toward the paper discharge portion in the discharge direction. The separation / conveying mechanism includes a belt-side separation / conveying member 201 having a leading end 201a close to the fixing belt 21 on the downstream side in the moving direction of the recording paper P moving from the fixing nip N1, and a swing close to the pressure roller 22 side. And a pressure-side separating and conveying member 202 having an end 202a.

The belt-side separating / conveying member 201 is provided to peel off the recording paper P that sticks and sticks to the fixing belt 21 from the fixing belt 21. For this reason, a metal sheet is used so as to obtain an accuracy capable of positioning the attached recording sheet P at a close position where the recording sheet P can be lifted from the surface of the fixing belt 21.

The pressure-side separating / conveying member 202 is formed of a resin molded product, and a support rod 202A is disposed at the lower end thereof as shown in FIGS. 2A to 2C. The support rod 202A is provided in parallel with the axial direction of the fixing device 20, and both ends thereof are rotatably supported on the housing side. Therefore, the pressure-side separating / conveying member 202 can swing in the left-right direction in FIGS. 2A to 2C around the support rod 202A. The swinging end 202 a provided at the lower end portion of the pressure-side separating / conveying member 202 is configured to come into contact with and separate from the outer peripheral surface of the pressure roller 22 by the swinging in the left-right direction.

For example, when the jammed recording paper P is removed from the fixing nip N1, the pressure-side separation / conveyance member 202 swings in a direction far away from the pressure roller 22, for example. Is done. Thereby, a space for inserting a hand into the fixing nip N1 can be created, and the recording paper P can be pulled out.

(Curl correction device)
The curl correction device 200 disposed on the downstream side in the transport direction of the fixing device 20 includes a driving roller 204 and a driven roller 203, a guide member 205, a guide member moving mechanism D, and a second rotating body pair. It has a pair of conveying rollers (a pair of paper discharge rollers 13) as a pair of rotating bodies. A detection mechanism 400 using an optical sensor for detecting whether or not the leading end of the recording paper P has reached the conveyance nip of the paper discharge roller pair 13 is disposed immediately downstream of the paper discharge roller pair 13. Yes.

The driving roller 204 and the driven roller 203 are disposed on the downstream side of the separation conveying members 201 and 202. The driving roller 204 and the driven roller 203 are in contact with each other at a predetermined pressure, and an auxiliary nip N2 is formed at the contact portion.

The auxiliary nip N2 has an effect of regulating the conveyance path of the recording paper P immediately before the upstream side of the guide member 205 in the conveyance direction. That is, it is possible to prevent the recording paper P from being bent between the fixing nip N1 and the curl correction position by the guide member 205, and to assist the conveyance of the recording paper after the fixing nip. Therefore, the distance between the auxiliary nip N2 and the upstream end of the guide member 205 is preferably as short as possible.

The driving roller 204 is provided on the recording paper P passing through the fixing device 20 on the side where the curling of the recording paper P occurs in the fixing nip N1 (the pressure roller 22 side). Since the pressure roller 22 side of the recording paper P is extended in the transport direction by the driving roller 204, the effect of curling suppression and curling correction force increase can be obtained.

The driven roller 203 is provided on the side for heating the recording paper P (the fixing belt 21 side) in the fixing nip N1 with respect to the recording paper conveyance path passing through the fixing device 20. The driving roller 204 and the driven roller 203 rotate and rotate by forming an auxiliary nip N2, and assist the conveyance of the recording paper P. The distance between the fixing nip N1 and the auxiliary nip N2 is set to be shorter than the length of the recording paper P.

In order to prevent a jam from occurring between the fixing nip N1 and the auxiliary nip N2, the following 1) to 3) are configured. 1) The diameter of the driving roller 204 is set to be larger than the diameter of the driven roller 203. 2) The recording paper conveyance speed at the auxiliary nip N2 is set slightly higher (faster) than the recording paper conveyance speed at the fixing nip N1. 3) The nip pressure of the auxiliary nip N2 is set to be smaller than the nip pressure of the fixing nip N1. With the configurations 1) to 3), a light tension acts on the recording paper P between the fixing nip N1 and the auxiliary nip N2, thereby suppressing the occurrence of a jam between the fixing nip N1 and the auxiliary nip N2. The

The drive roller 204 only needs to have at least a roller peripheral surface formed of rubber. The driven roller 203 only needs to be formed so that at least the roller peripheral surface portion is harder than the roller peripheral surface portion of the driving roller 204 and has releasability.

In the embodiment of the present invention, the driving roller 204 is composed of a core metal 204a (hereinafter referred to as a roller shaft 204a) and a high friction material made of silicon, EPDM, urethane, fluororubber or the like provided on the surface of the core metal 204a. It is composed of a short cylindrical member 204c made of a solid rubber material having a coefficient so that a recording paper conveying force can be obtained. The driven roller 203 has a structure in which a hollow pipe-shaped metal surface is covered with a low μ tube (thickness 30 to 300 μm) such as PFA, ETFA, FEP or the like.

The reason for using a hollow pipe-shaped metal is to prevent condensation caused by the evaporation of water from the paper during fixing and adhere to the driven roller, and to reduce the heat capacity so that the heat from the fixing immediately warms up. Because.

The reason why the low μ tube is arranged on the surface is that a minute amount of toner that has not melted after fixing is difficult to adhere and does not accumulate even if it adheres. That is, the driven roller 203 side is conveyed while always in contact with the image surface side, and thus has the above-described configuration.

The driven roller 203 is held on the image forming apparatus main body via a holder 230 biased by a spring 231. The holder 230 is biased and pressed toward the drive roller 204 by a spring 231. Therefore, the driven roller 203 receives the urging force of the spring 231, contacts the driving roller 204, and forms an auxiliary nip N 2 with the driving roller 204. The recording paper P is sandwiched between the auxiliary nips N2 so that the recording paper P is conveyed in the direction of arrow A3 in FIG. 2A, that is, in the tangential direction of the auxiliary nip N2.

(Guide member)
The guide member 205 is disposed on the pressure-side separation / conveyance member 202 so that the center of rotation of the guide member 205 is coaxial with the roller shaft 204 a of the drive roller 204. The guide member 205 is moved to a “first position” (advance position in contact with the recording paper P) shown in FIGS. 2A and 2B and a “second position” shown in FIG. It is moved to any one of (a retreat position where it does not contact the recording paper P).

Since the guide member 205 needs to guide the recording paper P in a predetermined direction, the angle cannot be freely changed. In the embodiment of the present invention, the drive roller 204 is moved in the direction of arrow F as shown in FIG. 2B in order to increase the curl correction force without changing the direction of the guide member 205 in such a restriction. I did it. The movement in the direction of the arrow F is performed by a paper discharge direction changing mechanism 300 described later.

The difference between FIG. 2A and FIG. 2B is the difference in the tangential direction of the auxiliary nip N2. This is because the weak curl correction is performed in FIG. 2A and the strong curl correction is performed in FIG. 2B as described later. That is, the tangential direction of the auxiliary nip N2 in FIG. 2B is inclined more to the right than the tangential direction of the auxiliary nip N2 in FIG. 2A. This makes strong curl correction possible.

The guide member 205 is provided on the same side as the pressure roller 22 with respect to the conveyance path of the recording paper P on the downstream side in the conveyance direction of the fixing nip N1. In the “first position” shown in FIGS. 2A and 2B, the leading end of the recording paper P can be abutted against the linear guide surface 205c. In the embodiment of the present invention, the guide surface 205c is illustrated as a straight line, but the guide surface 205c is not necessarily limited to a straight line, and is effective for curling suppression corresponding to the type of recording paper P and the like. It may be a curved line.

2A and 2B, the guide surface 205c is disposed so as to be inclined with respect to the tangential direction of the auxiliary nip N2 so as to form predetermined abutting angles θ1 and θ2. Here, θ1 and θ2 are inferior angles formed by the tangential direction of the auxiliary nip N2 and the guide surface 205c. θ1 is a predetermined angle larger than a right angle, for example, θ1 = 125 to 175 °. Θ2 is a predetermined angle that is closer to the right angle than θ1, for example, θ2 = 95 to 125 ° (θ1> θ2).

Accordingly, the recording paper P discharged from the auxiliary nip N2 is bent toward the driven roller 203 while being guided to be conveyed downstream along the guide surface 205c. In other words, the recording paper P is conveyed and guided along the guide surface 205c so as to bend in the direction opposite to the direction of curl generated in the fixing nip N1.

2A and 2B, the timing for changing the contact angle θ1 → θ2 is when the leading edge of the recording paper P reaches the conveyance nip of the paper discharge roller pair 13 in the embodiment of the present invention. Here, “when it arrives” does not necessarily need to be the moment it arrives. If the conveyance force of the paper discharge roller pair 13 acts on the recording paper P, the abutting angle θ1 → θ2 can be changed.

When the leading end of the recording paper P reaches the conveyance nip of the paper discharge roller pair 13, the rear end side of the recording paper P is still nipped by the auxiliary nip. Therefore, by changing the abutting angle from θ1 to θ2, the recording paper P is bent more toward the fixing belt 21 on the rear end side. That is, the rear end side of the recording paper P is bent in a direction opposite to the curling direction. In this way, the recording paper P is corrected with a weak curl correction force on the front end side and corrected with a strong curl correction force on the rear end side.

(Change of butt angle)
When the recording paper P is brought into contact with the guide member 205, the discharge direction of the auxiliary nip N2 is set so that the abutting angle θ2 is set from the beginning. As soon as the front end hits the guide member 205, it greatly snakes and jamming is likely to occur. Therefore, in the embodiment of the present invention, as described above, the discharge direction of the auxiliary nip N2 is initially set so that the gentle abutting angle θ1 is formed. The abutting angle is changed from θ1 to θ2 when the latter half of the conveyance direction of the recording paper P starts to hit the guide member 205.

This is consistent with the phenomenon that the degree of curling of the recording paper P is small on the leading end side of the recording paper P, but rather increases toward the trailing end side of the recording paper P. That is, for example, when the paper is A3 (conveyance length 420 mm) and the pressure roller diameter is φ30 (conveyance distance 94.2 mm), the temperature of the fixing belt 21 having the heating source hardly changes when the recording paper passes.

On the other hand, when the recording paper P passes through the pressure roller 22 that does not have a heating source, the temperature decreases for each rotation of the roller. At the rear end of the A3 paper where the pressure roller makes about 4.5 turns, the temperature drops significantly with respect to the front end of the paper.

FIG. 4 is a diagram illustrating the relationship between the temperature on the heating side and the pressure side in the fixing nip N1 and the abutting angle of the recording paper P with respect to the guide member 205. The recording paper leading edge enters the fixing nip N1 at t1 on the time axis, the recording paper leading edge enters the conveyance nip of the discharge roller pair 13 at t2, and the recording paper trailing edge passes through the fixing nip N1 at t3. .

As can be seen from FIG. 4, the temperature difference between the fixing sleeve 21 and the pressure roller 22 in the fixing nip N1 is small on the leading end side of the recording paper P, but gradually increases on the trailing end side. Since the curl of the recording paper P is generated due to the paper moisture amount being biased due to the temperature difference between the front and back surfaces, the curling gradually becomes stronger toward the rear end side of the recording paper.

Therefore, on the front side of the recording paper where there is little need for curl correction, a gentle abutting angle θ1 is used with more emphasis on transportability. However, after the leading edge of the recording paper enters the conveying roller 13, even the thin paper having low rigidity is not easily jammed, and the abutting angle θ2 is used so as to positively increase the curl correction force.

By the control of changing the abutting angle, a stronger curl correction effect can be obtained on the trailing edge side of the recording paper where the curl becomes large without causing a problem such as a jam, that is, without adversely affecting the paper transportability. Therefore, the control method is a very rational and effective curl correction method.

In FIG. 2B, the pressure-side separating / conveying member 202, and hence the drive roller 204, can swing in the left-right direction along an arc locus of radius L in the same figure with the support rod 202A as the center. The drive roller 204 is configured to be movable in the arrow F direction by a paper discharge direction changing mechanism 300 described below.

The change mechanism 300 can be configured by, for example, a pusher 310 that acts in the direction of arrow F with respect to the pressure-side separation / conveyance member 202. The direction of the arrow F acts at right angles to the radius L centered on the support rod 202A.

In the paper discharge direction changing mechanism 300, the signal from the detection mechanism 400 disposed immediately downstream of the paper discharge roller pair 13, that is, the leading end of the recording paper P reaches the conveyance nip of the paper discharge roller pair 13. It can act upon receiving a signal indicating that Specifically, for example, the control mechanism 500 can receive a signal from the detection mechanism 400, and the control mechanism 500 can control the operation of the pusher 310 of the paper discharge direction changing mechanism 300.

On the other hand, the driven roller 203 is urged substantially horizontally toward the drive roller 204 by a holder 230 urged by a spring 231. Therefore, the tangential direction of the auxiliary nip, that is, the paper discharge direction is determined by the rotation angle of the support rod 202A and the position of the driven roller 203.

Usually, as shown in FIG. 2A, the curl is gently corrected by the guide surface 205c of the guide member 205 while maintaining a predetermined abutting angle θ1. When it is necessary to strongly correct the curl, the drive roller 204 is pushed toward the driven roller 203 against the spring 231 as shown in FIG. 2B. As a result, the tangential direction of the auxiliary nip N2 can be changed as shown in FIGS. 3A and 3B.

By doing so, the abutting angle θ1 → θ2 can be changed without changing the inclination angle of the guide surface 205c of the guide member 205. A stronger curl correction force can be obtained by changing the abutment angle θ1 → θ2. The curl correction can also cause a jam due to the nature of the recording paper P, but the leading end of the recording paper P has already reached the paper discharge roller pair 13 in the states (b) of FIGS. 3A and 3B. Therefore, paper jam can be prevented even when the curl correction power is strong.

(Operation of guide member)
In the state of “first position” shown in FIGS. 2A and 2B, the guide member 205 is guided from the same side as the driving roller 204 with respect to the front side portion in the transport direction of the recording paper P passing through the auxiliary nip N2. The surface 205c is slidably contacted so as to press, and functions to bend the recording paper P in a concave shape on the side opposite to the curled side after fixing.

That is, the guide member 205 guides the direction of the recording paper P passing through the auxiliary nip N2 (the tangential direction of the auxiliary nip N2) from the same side as the drive roller 204 while being held at the “first position”. It arrange | positions in the position which block | closes with the surface 205c.

Therefore, the leading edge of the recording paper P comes into contact with the guide member 205 at the contact angles θ1 and θ2 shown in FIGS. 2A and 2B, and then the recording paper P is pressed by the guide member 205 while driving roller 204 and driven roller 203. The auxiliary nip N2 is used for auxiliary conveyance.

That is, since the guide member 205 transports the recording paper P with the contact angles θ1 and θ2 finally starting from the auxiliary nip N2 with respect to the recording paper P, the recording paper P is opposite to the curl. It is curved to form a concave curved surface, which makes curl correction. By using such a conveyance path, the recording paper P passing through the guide member 205 can improve curl generated in the fixing nip N1, and can be discharged to the paper discharge tray.

However, since the “first position” of the guide member 205 is a position where the guide member 205 is actively brought into contact with the back surface of the recording paper P, the conveyance resistance between the back surface of the recording paper P and the guide member 205 is large. The paper itself will be stressed. In particular, when the second side of the recording paper P that is not thick paper is passed in the double-sided mode, the surface on which the image exists (the first side) comes into contact with the guide member 205, so that there is no image blur or gloss streak. Likely to happen.

Further, when the second surface is passed, during the fixing of the second image surface in the fixing unit, the first surface image as the back surface is also reheated through the fixing nip N1. For this reason, when the warmed first surface image is rubbed strongly by the guide surface 205c of the guide member 205, the toner of the first surface image is liable to be peeled off or the gloss is easily changed.

Therefore, in such a case, the guide member 205 is positioned at the “second position” shown in FIG. 2C. This “second position” is an open position where the recording paper P is not bent, and the guide member 205 functions so as not to be in contact with the recording paper P passing through the auxiliary nip N2 and to bend the recording paper P. To do.

In the “second position” in FIG. 2C, the guide member 205 is largely retracted in the conveyance direction (tangential direction of the auxiliary nip) of the recording paper P discharged from the auxiliary nip N2, and does not actively contact the paper. Become position. In this case, the curl at the time of paper conveyance cannot be corrected, but since no stress is applied to the paper, the above-described problems such as back surface scratches, abrasion, image blurring, and gloss streaks do not occur.

When the second surface of the recording paper P that is not a thick paper is passed in the double-sided paper passing mode, curling does not occur unlike the fixing of the first surface image, so the guide member 205 is in the “second position” where the curl is not corrected. Retreating is rather convenient.

Note that when the recording paper P that is not a thick paper is passed through the second side in the double-sided paper passing mode, the guide member 205 may be stopped near the “second position” without being retracted to the “second position”. . The guide member 205 may be configured to be in the “first position” at least during single-sided printing or single-sided printing.

On the other hand, when the recording paper P is a strong thick paper or the like, if the guide member 205 is positioned at the “first position”, the guide paper 205 is less than the recording paper P that is a thin paper with a weak stiffness. High contact resistance. For this reason, in the “first position”, the stress applied to the paper itself is further increased, a trace of contact is likely to occur on the back side of the paper, and problems such as wear of the guide member 205 itself are likely to occur.

Further, when the recording paper P is a strong thick paper or the like, curling hardly occurs. Therefore, in this case, the guide member 205 is positioned at the “second position” in FIG. 2C both when the first side of the single-sided paper passing mode is passed and when the second side of the double-sided paper passing mode is passed. Is done.

As described above, according to the curl correction device 200 according to the embodiment of the present invention, the guide member 205 is switched between the “first position” and the “second position”, so that the curl correction and the image collocation are performed. It is possible to achieve both avoidance and the like.

5 (I) to (III) are diagrams for explaining the arrangement pattern of the guide member 205 and the branching member 215. FIG. The branch member 215 is for switching the first surface to the second surface in the duplex mode.

In the double-side mode, the guide member 205 is arranged at the open position on both the first and second surfaces (III). A branching member 215 for switching between a path for discharging the recording paper P to the outside of the apparatus and a double-sided reversing path is moved and arranged, so that after the first surface fixing, the reverse refeeding conveyance path is reached, and after the second surface fixing, the discharging path. The recording paper P is guided to the front.

By providing a heater in the driving roller 204, the curl correction effect at the time of discharging the main body at the time of one-sided paper passing is enhanced, and at the time of discharging the tray on the single side where the curl correction effect cannot be obtained by the guide member 205 alone (III ), The curl reduction effect can be obtained even when both sides of the first side are passed (III).

Table 1 below summarizes which of the arrangement patterns (I) to (III) is used depending on the paper type, the paper passing mode, and the paper discharge destination of the recording paper P to be passed. The heater ON / OFF at the right end indicates ON / OFF of the heater when the heater is provided in the drive roller 204. In the case of single-side / upper tray discharge and double-sided first-side / double-side reversal paths, the guide member 205 is opened and the recording paper P is not corrected, so the heater is always turned on.

(Guide member and its moving means)
Next, the structure of the guide member 205 and the guide member moving mechanism D will be described with reference to FIGS. As shown in FIG. 6, the driving roller 204 is fitted and fixed to the pressure-side separating and conveying member 202 with a roller shaft 204 a that is rotatably supported at both ends via a sliding bearing 208, and the roller shaft 204 a with a predetermined interval. And a plurality of short cylindrical members 204c made of rubber.

The driving roller 204 is rotatable by transmitting the rotational driving force from the guide member moving mechanism D shown in FIGS. 7B and 7C to the driving gear 210 fixed to the end of the roller shaft 204a via the idler gear 211. is there.

As shown in FIGS. 6 to 7C, the guide member 205 is fixed to a support shaft 205a that is rotatably supported at both ends by upper ends of a pair of bracket arms 206.

The pair of bracket arms 206 are fitted on the outer diameter portion of the sliding bearing 208 and are rotatable. A plurality of guide members 205 are respectively provided on a plurality of bosses 205b fitted and fixed to the support shaft 205a.

The guide member 205 has a base end fixed to the boss 205 b and extends so that a protruding end covers the drive roller 204. As shown in FIG. 8A, the stopper portion 206 b of the bracket arm 206 is configured to stop at a position where it comes into contact with a part of the pressure-side separation / conveyance member 202. The guide surface 205c of the guide member 205 corresponding to this stop position becomes the “first position” for changing the angle of the recording sheet discharged from the auxiliary nip N2.

As shown in FIGS. 7A to 7C, the guide member moving mechanism D includes a solenoid 220 as a drive source, a link mechanism 207 that swings when the solenoid 220 is actuated, and a tension spring 209. The casing of the solenoid 220 is fixed to the main body of the image forming apparatus. The guide member moving mechanism D is driven based on a control signal from the main body control unit.

One end of the tension spring 209 is locked to the side surface portion of the pressure-side separation / conveyance member 202, and the other end is locked to the middle of the arm portion 206a of the bracket arm 206. The guide member 205 is shown in FIG. A tension force of the spring is applied so that the bracket arm 206 is rotated in the direction of “position”.

As shown in FIG. 7C, in the link mechanism 207, one end 207a in the horizontal direction is supported by the fixed pin shaft 207A. The operating end 207b, which is the other end of the link mechanism 207, abuts so as to surround the tip end portion of the arm portion 206a of the bracket arm 206 from below. A long hole 207d provided at the upper end of the upward extension 207c extending upward from the middle part in the horizontal direction is connected to the rod 220a of the solenoid 220 by a pin.

When the rod 220a of the solenoid 220 is extended as shown by a dotted line in FIG. 7C, the operating end 207b of the link mechanism 207 is lowered with respect to the distal end portion of the arm portion 206a of the bracket arm 206 as shown in FIG. 7B. Away.

When a current flows through the internal coil of the solenoid 220 based on the control signal of the control device from the state shown in FIG. 7B, the rod 220a of the solenoid 220 is shortened. As a result, the link mechanism 207 is rotated against the tensile force of the tension spring 209, and the operating end 207b lifts the tip of the arm portion 206a of the bracket arm 206 (state shown in FIG. 7C). As a result, the guide member 205 moves backward from the “first position” shown in FIGS. 2A and 8A to the “second position” shown in FIGS. 2C and 8B.

On the other hand, when the current to the internal coil of the solenoid 220 is cut off from the state shown in FIG. 7C based on the control signal of the control device, the bracket arm 206 is rotated by the tensile force of the tension spring 209, and the guide member 205 is moved to FIG. Return to the “first position” shown in FIG. At the same time, the rod 220a of the solenoid 220 is extended by the tensile force of the tension spring 209 and becomes in the state shown in FIGS. 7B and 7C (broken line).

By configuring as described above, the gap between the driving roller 204 and the guide member 205 is configured so that the dimensional tolerances of the parts are least accumulated (only the radial distance tolerance from the axis center of each part). Can do. The guide member 205 can move in a state where the gap between the driving roller 204 and the guide member 205 is kept constant with high accuracy.

As shown in FIG. 6, the guide member 205 has a plurality of rib shapes in the longitudinal direction, and a rib-shaped discharge path forming member 215 is interposed between the rib shapes as shown in FIGS. 6 and 7B. Has entered.

9 shows a case where the rotation center of the guide member 205 is provided so as to match the rotation center of the drive roller 204 (position indicated by a solid line in the drawing), and the rotation center of the guide member 205 is from the rotation center of the drive roller 204. The comparison figure at the time of arrange | positioning apart with a certain gap (position of the dotted line shown by code | symbol 205c 'in a figure) is shown.

As can be seen from FIG. 9, the curl correction effect when the guide member 205 is at the solid line position is the same as the curl correction effect when the guide member 205 is at the dotted line position.

The recording paper passing through the auxiliary nip N2 is discharged in the direction perpendicular to the line connecting the centers of the driving roller 204 and the driven roller 203, that is, in the tangential direction of the auxiliary nip N2. Therefore, the contact angle θ ′ between the front end of the paper near the auxiliary nip N2 and the guide member 205 when the guide member 205 is at the dotted line position is the paper near the auxiliary nip N2 when the guide member 205 is at the solid line position. It becomes smaller than the contact angle θ between the tip and the guide member 205.

As the contact angle decreases, the leading edge of the sheet buckles and bends and is conveyed. In the worst case, the risk of jamming the sheet increases. On the other hand, when the guide member 205 is arranged such that the extension line of the guide surface 205c is shifted from the rotation center of the driving roller 204 and the contact angle is larger than the contact angle θ, the curling for bending the sheet by the guide member 205 is performed. This leads to a decrease in the correction effect.

Therefore, in the embodiment of the present invention, the rotation center of the guide member 205 is aligned with the rotation center of the drive roller 204 so that the contact angle is large, and the extension line of the guide surface 205c of the guide member 205 is It passes through the center of rotation.

In order to obtain an appropriate curl correction effect, it is necessary to tilt the guide member 205 so that the guide surface 205c of the guide member 205 covers the tangential direction of the auxiliary nip N2. Therefore, a plurality of rubber portions of the driving roller 204 are provided so as to leave a predetermined space interval, and the guide member 205 is configured to enter the space interval between the rubber portion and the rubber portion.

In the image forming apparatus according to the embodiment of the present invention, the driving roller 204 and the driven roller 203 are provided immediately after the downstream side of the fixing device 20, and the “first position” is set by the guide member moving mechanism D immediately after the downstream side of the auxiliary nip N 2. ”And“ second position ”, a guide member 205 that can be switched is provided. As a result, the curl generated on the recording paper P by the fixing device 20 can be corrected by the conveyance path bent by the guide member 205 in the direction opposite to the curl direction.

By the guide member 205, it is possible to switch between the “first position” without correction or weak correction and the “second position” with strong correction. Further, since the guide member 205 can be switched between the “first position” and the “second position”, the correction can be performed only under a condition where the curl correction is necessary.

For example, in the case of passing a thick paper, the curling of the recording paper P does not occur in the fixing device 20. Therefore, when the guide member 205 is always in the “first position”, the guide member 205 causes a face curl in the reverse direction. End up. Further, since the cardboard has a strong contact force with the guide member 205, the guide member 205 causes damage (scratches) on the back surface of the cardboard and wear of the guide member 205.

Further, since the cardboard has high sheet rigidity, there is a risk that the cardboard tip bends as soon as the cardboard tip coming out of the auxiliary nip N2 contacts the guide member 205. Therefore, in the case of transporting thick paper, it is not necessary to set the guide member 205 to the “first position”.

According to the fixing device or the curl correcting device 200 of the embodiment of the present invention, from the above viewpoint, the driving unit that switches the position of the guide member 205 is provided, and the position of the guide member 205 can be switched depending on conditions. As a result, it is possible to achieve both reduction of curling occurring during fixing, stabilization of conveyance, and reduction of damage to the recording paper P.

According to the fixing device of the embodiment of the present invention, the auxiliary nip N2 is formed with the driving roller 204 disposed on the back side of the image and the driven roller 203 disposed on the front side of the image immediately before the guide member 205. ing. The presence of the correction nip N2N2 can prevent the folding between the fixing nip N1 and the curl correction position of the guide member 205, and can assist the conveyance of the recording paper after the fixing nip.

Further, the correction nip N2 is located at a position upstream from the curl correction position by the guide member 205, and the recording paper P is highly restrained. For this reason, the recording paper P is effectively bent (forced) by the guide member 205, so that curling after fixing can be effectively reduced.

As described above, according to the embodiment of the present invention, the toner image is prevented from being damaged at the time of curl correction, the occurrence of paper jam is suppressed by maintaining good transportability, and the curl becomes strong. By increasing the curl correction effect on the side, curling can be reduced after fixing. The curl correction apparatus of the present invention can be applied to all fixing apparatuses and image forming apparatuses using electrophotographic methods such as copying machines, facsimile machines, and printers.

The detection mechanism 400 uses an optical sensor to detect that the leading end of the recording paper P has reached the conveyance nip of the paper discharge roller pair 13, but the same detection can be performed by means other than the optical sensor. For example, by using a timer instead of the optical sensor, it is possible to accurately predict and detect the timing at which the leading edge of the recording paper P reaches the conveyance nip of the paper discharge roller pair 13. The timer setting can be appropriately set based on input information from the operation panel of the image forming apparatus 100, a signal for detecting that the recording paper P has entered the fixing nip N1, and the like.

The discharge direction changing mechanism 300 is configured to press the pressure-side separation / conveyance member 202 in the direction of arrow F. The pressure-side separation / conveyance member 202 is fixedly arranged, while the driven roller 203 is shown in FIGS. 3A and 3B. It may be configured to be movable so as to ride on the driving roller 204 as shown in each (b). In this case, for example, the holder 230 of the driven roller 203 is configured to be pressed rightward in FIGS. 3A and 3B by a pusher or the like.

In the embodiment, the abutting angle is changed from θ1 to θ2 after the leading end of the recording paper P reaches the conveyance nip of the paper discharge roller pair 13, but the abutting angle is once changed from θ1 to θ2. Instead of changing to θ1, it may be changed from θ1 to θ2 continuously or in a plurality of stages. At this time, it may be changed continuously or in multiple steps from θ1 to θ2 in accordance with the progress of the temperature drop of the pressure roller 22 shown in FIG.

2Y, 2M, 2C, 2K: Toner bottle 3: Transfer device 4Y, 4M, 4C, 4K: Image forming unit 5: Photoconductor 6: Charging device 7: Developing device 8: Cleaning device 9: Exposure device 10: Paper feed tray 11: paper feed roller 12: registration roller 13: paper discharge roller pair 14: paper discharge tray 15: branching member 20: fixing device 21: fixing belt 22: pressure roller 22a: metal core 22b: elastic layer 23: heater 24: Nip forming member 25: Stay 26: Reflecting member 27: Temperature sensor 30: Intermediate transfer belt 31: Primary transfer roller 32: Secondary transfer backup roller 33: Cleaning backup roller 34: Tension roller 35: Belt cleaning device 36: Secondary transfer Roller 51a: Polygon mirror 51b: Lens 51c: Reflection mirror 100: Image forming apparatus 00: Curl correction device 201, 202: Separating and conveying member 202A: Support rod 202a: Swing end 203: Driven roller 204: Drive roller 204a: Pipe-shaped metal 204b: Heat source 204c: Short cylindrical member 205: Guide member 205a: Support Shaft 205b: Boss 205c: Guide surface 206: Bracket arm 206a: Arm portion 206b: Stopper portion 207: Link mechanism 207A: Fixed pin shaft 207a: One end 207b: Working end 207c: Upper extension portion 207d: Long hole 208: Sliding bearing 209: tension spring 210: drive gear 211: idler gear 215: discharge path forming member 220: solenoid 220a: rod 230: holder 231: spring 300: discharge direction changing mechanism 310: pusher 400: detection mechanism 500: control mechanism D: guide Member moving mechanism

Japanese Patent Laid-Open No. 2006-118688 Japanese Patent Laying-Open No. 2006-177099

Claims (8)

Arranged downstream of the fixing device having the fixing member and the pressure member in the paper discharge direction, the curling of the sheet-like body discharged from the fixing nip formed between the fixing member and the pressure member is corrected. A curl correction device, the curl correction device,
A first rotating body pair disposed downstream of the fixing nip in the paper discharge direction and sandwiching and transporting the sheet-like body with an auxiliary nip;
A guide member that is disposed on the downstream side in the paper discharge direction of the first pair of rotating bodies and capable of correcting the bending of the sheet-like member toward the fixing member by abutting the leading end of the sheet-like member;
A paper discharge direction changing mechanism capable of changing a paper discharge direction of the auxiliary nip to change a contact angle of the sheet-like body with respect to the guide member;
A second rotating body pair disposed downstream of the guide member in the paper discharge direction and sandwiching the sheet-like body in a transport nip and transporting it in the paper discharge direction;
A detection mechanism for detecting whether or not the leading end of the sheet-like body has reached the conveyance nip of the second rotating body pair;
A control mechanism for controlling the discharge direction changing mechanism based on the detection result of the detection mechanism,
Until the detection mechanism detects the leading end of the sheet-like body, the discharge direction changing mechanism is controlled to maintain the abutting angle at a predetermined angle θ1 larger than a right angle, and the detection mechanism A curl correction apparatus that controls the paper discharge direction changing mechanism so as to change the predetermined angle θ1 to a predetermined angle θ2 (θ1> θ2) that approaches a right angle when a leading end of the shape is detected.   The curl correction apparatus according to claim 1, wherein the control mechanism changes the abutting angle from an angle θ1 to an angle θ2 continuously or stepwise.   The guide member is rotatably arranged, and when the sheet-like body having a larger basis weight is conveyed, the guide member is turned to an open position where the sheet-like body is not corrected for bending. The curl correction apparatus according to claim 1 or 2.   2. The first rotating body pair includes a driving roller and a driven roller, the driving roller is disposed on the pressure member side, and the driven roller is disposed on the heating member side. 4. The curl correcting device according to any one of items 1 to 3.   The curl correction apparatus according to claim 4, wherein a heater is built in the drive roller.   The curl correction apparatus according to claim 1, wherein a conveyance speed of the auxiliary nip is larger than a conveyance speed of the fixing nip.   A fixing device comprising the curl correcting device according to claim 1. An image forming apparatus comprising the fixing device according to claim 7.