JP2003206063A - Curl removing device for sheet and image formation device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a curl removing device provided with a structure capable of simultaneously cooling a sheet and correcting the curl without increasing the size or the cost of the device. <P>SOLUTION: This curl removing device for a sheet is provided with: a carrying roller 18C disposed in a carrying passage for a sheet; and a plurality of backup rollers 18A and 18B disposed side by side in the circumferential direction of the carrying roller and capable of gearing with each other while coming into press contact with the carrying roller 18C. The device can carry the sheet in a form following the circumferential surface of the carrying roller 18C. The backup rollers 18A and 18B are so disposed that their disposing interval along the circumferential direction of the carrying roller 18C can be changed, and the device is characterized in that the disposing interval can be set according to the amount of emergence of the curl of the sheet. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sheet curl removing apparatus and an image forming apparatus, and more particularly to a structure for correcting a curl occurring in a sheet.

[0002]

2. Description of the Related Art In an image forming apparatus such as a copying machine, a printer or a facsimile machine, an electrostatic latent image formed on a latent image carrier is processed by a visible image in a developing process and then the visible image is recorded. A visible image that is electrostatically transferred onto a sheet such as recording paper, which is one of the media, is heat-fixed to obtain a copy or a recorded product.

In one of the structures used for fixing, a heating roller and a pressure roller which are opposed to each other with a sheet conveying path sandwiched therebetween are arranged, and heat is applied to the toner image in the process of sandwiching and conveying the sheet by these both rollers. There is a configuration using a heat roller fixing method in which pressure is applied to fix. The heat roller fixing method is
It has been widely used in recent years due to its advantages such as high thermal efficiency and high speed, high heat transfer efficiency and stable fixing efficiency, and simple structure because it can be used as a sheet conveying medium. ing.

The sheet after fixing is discharged to a discharge tray or the like by a discharge roller arranged in the vicinity of the heating roller and the pressure roller, or re-sheeted toward the registration roller without going to the discharge tray. A case may be selected in which an image is formed again on the back side of the image surface when the image is fed, inverted in the re-feeding process, and passed through the fixing device, and then discharged to the paper discharge tray.

A sheet passing through the fixing device is caused by a stress limit generated when it expands due to the supply of heat received when passing through a plurality of rollers provided in the fixing device or contracts due to evaporation of moisture due to heat. Then, a deformation called curl may occur. If the paper is ejected with curl still occurring, the tip will hang downward when it is ejected to the paper ejection tray, causing the tip to hit the placement surface of the paper ejection tray and prevent progress. May cause jams.

The curl tends to be proportional to the amount of toner carried on the sheet. For example, the amount of toner carried on the sheet increases during monochrome image formation and full color image formation. If so, the expansion / contraction phenomenon described above becomes more remarkable when a full-color image is formed.

In general, the above-described curling of the sheet may occur from the beginning due to the method of manufacturing the sheet, but internal distortion occurs due to the alteration of the sheet that occurs at the time of fixing. It can be said that the size of the curl that appears on each sheet varies from sheet to sheet.

If the sheet remains curled, the position between the two becomes inaccurate due to the curl when trying to align the toner image and the transfer position of the sheet. There is a problem that a member is disposed on the conveyance path to cause a jam, and further, the edge alignment (stacking property) between discharged sheets is impaired.

Conventionally, as a constitution of a conveying roller which is a sheet conveying member, two pressure rollers are provided in abutting contact with each other along the circumferential direction of one through roller, and the pressure roller is provided on its rotation axis. A configuration has been proposed in which a plurality of sheets are arranged at predetermined intervals along the axial direction, and a curl is removed by imposing a sheet fed between these rollers in conformity with the peripheral surface shape of the through roller. (For example, JP-A-11-1
89363).

On the other hand, the temperature of the sheet that has passed through the fixing device rises due to the heating process, and there is a tendency that the temperature of the member constituting the conveying path or the member arranged around the fixing device rises. For this reason, some of the constituent members may be deformed or destroyed due to temperature rise, or the toner carried on the surface due to contact between the sheets may be generated during the post-processing step of the sheet, for example, the sheet edge alignment processing. In some cases, the toner may be remelted and peeled off, or the toner having a reduced viscosity may be attached to the transport member to contaminate it. Further, when the ambient temperature rises due to the temperature of the sheet that has passed through the fixing device, the internal temperature of a device arranged near the fixing device, such as a cleaning device or a developing device, may also rise. In addition, there is a possibility that the toner collected by the cleaning device may be remelted or the toner contained in the developing device may be deteriorated.

Further, there is a case where the curl formation is promoted due to the form of the conveying path between the sheet and the curl straightening device due to the heat accumulated when the sheet is heated in the fixing device. For example, when the conveyance path from the fixing device to the curl straightening device is formed by a sharp curved path, the iron effect due to heat storage of the sheet, that is, wrinkles are extended when heated by the iron and pressed. Similarly, if the sheet is apt to have a shape depending on the form of the conveying path, curling according to the form of the conveying path is likely to occur. In particular, such a transport path configuration is used for the purpose of preventing an increase in size of the structure when preventing an increase in the size of the structure in a configuration for forming a color image that requires a large number of development processing units unlike a monochrome image. It is often used to bend a sheet to reduce the space in the horizontal direction or the vertical direction, or may be used when the sheet is inverted to form an image on both sides of the sheet.

In order to eliminate such a harmful effect due to the temperature rise, a structure has been proposed in which a sheet is conveyed by a conveying belt, a part of which contacts a heat pipe, in a sheet conveying path (for example, Japanese Patent Laid-Open No. 11- No. 119489).

[0013]

However, in the configuration disclosed in the above publication, the curl correction of the sheet and the cooling of the sheet are performed by separate configurations, and when the configurations having the respective functions are provided. There is a possibility that the configuration may become large and the cost may increase.

The object of the present invention is to solve the problems in the above-described conventional sheet conveying apparatus, particularly, the problem related to the curl correction of the sheet, and to simultaneously cool the sheet and correct the curl without increasing the size of the apparatus and increasing the cost. An object of the present invention is to provide a sheet decurling device and an image forming apparatus having a configuration capable of performing the above.

[0015]

The invention according to claim 1 is
A plurality of conveying rollers arranged in a sheet conveying path, and a plurality of backup rollers arranged side by side along the circumferential direction of the conveying rollers and capable of interlocking with each other while being in pressure contact with the conveying rollers are provided. In a sheet curl removing device capable of nipping and transporting the sheet in a contoured shape, the backup roller is provided so as to be able to change the arrangement interval along the circumferential direction of the conveyance roller, and the arrangement interval is the curl of the sheet. It is characterized in that it is provided so that it can be set according to the amount of generation.

According to a second aspect of the present invention, in addition to the first aspect of the invention, the backup roller is subdivided in the axial direction so that the arrangement phase in the axial direction alternates between the rollers. It is characterized in that it is composed of a plurality of rollers and that the operation timing of each backup roller can be changed.

The invention according to claim 3 is the invention according to claim 1 or 2.
In addition to the invention described above, the conveying roller is used as a cooling member for the sheet, and the frictional force between the conveying roller and the sheet is set to be smaller than the frictional force between the backup roller and the sheet. It is characterized by

According to a fourth aspect of the present invention, in addition to the invention according to one of the first to third aspects, the peripheral speeds of the conveying roller and the backup roller can be relatively changed. It is characterized by being.

According to a fifth aspect of the present invention, the sheet curl removing device according to any one of the first to fourth aspects is used in an image forming apparatus, and the conveying roller can cool the sheet. It is characterized by that. According to a sixth aspect of the invention, a fixing device for discharging a sheet on which a toner image is fixed by heat and pressure by using a heating member and a pressing member which are arranged to face each other in a conveying path of the sheet carrying the toner image. And an inversion device that inverts and conveys the sheet discharged from the fixing device, in the sheet conveyance path from the fixing device to the inversion device, forced cooling is possible. A conveyance roller that has a configuration and that constitutes a cooling member that can be conveyed while cooling the sheet,
A plurality of backup rollers which are juxtaposed along the circumferential direction of the transport roller and which can sandwich and transport the sheet in a state of following the shape of the circumferential surface of the transport roller, wherein the transport roller and the backup roller are the fixing device. It is characterized in that an arrangement relationship is set so that the sheet discharged from the sheet can be bent in the direction opposite to the curl generation direction of the sheet and moved toward the reversing device.

[0020]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the embodiments shown in the drawings. FIG. 1 shows an image forming apparatus using a sheet decurling device according to an example for explaining an embodiment of the present invention. The image forming apparatus shown in the figure forms an electrostatic latent image on a photosensitive member, which is a latent image carrier, based on monochrome image information obtained by exposing and scanning a document, and then the electrostatic latent image is visualized. Although the present invention is a copier that performs image processing, the present invention is not limited to a copier, but a printer that is an output device from a host computer or a facsimile that can form an electrostatic latent image according to image information transmitted by optical writing processing. In addition to including an apparatus, an intermediate transfer body and an image on which an image of each color is superposed and transferred by primary transfer of an image for each of a plurality of visible image processing units and a color for which the visible image is processed It also includes a multicolor image forming apparatus capable of forming a full-color image by using a configuration including a secondary transfer device capable of collectively transferring sheets to a sheet, a configuration in which images of different colors are superposed and transferred onto a sheet in the process of being conveyed, and the like. .

The copying machine shown in FIG. 1 includes a sheet feeding device 3 including four sheet feeding trays 10 capable of accommodating sheets such as transfer sheets and respective sheet feeding rollers 11, and the sheet feeding device 3. The image forming apparatus 1 is arranged on the upper side, and the automatic document feeding and exposing apparatus 4 is arranged on the upper side and takes in image information from a document.

In the image forming apparatus 1, the transfer means 14 is arranged so as to be in contact with the photosensitive drum 13, and the sheet conveying direction relative to the photosensitive drum 13 (in the figure,
A registration roller 12 for adjusting the transfer timing of the sheet is provided on the upstream side (in the direction indicated by the arrow), and a fixing unit 15 for heating and fixing the transferred sheet is provided on the downstream side in the sheet conveying direction. Fixing means 1 in this embodiment
5 is a heat roller fixing method in which a heating roller located on the toner image bearing surface side of the sheet and a pressure roller capable of being conveyed while pressing the sheet against the heating roller are used.

On the extension of the conveying path of the sheet discharged from the fixing means 15, rotatable discharging rollers 32A and 32B are in contact with the sheet reversing section 5 with the sheet conveying path interposed therebetween.
A sheet discharge port 37 is provided in which a sheet discharge device 32 including (see FIG. 2) is arranged.

The structure of the paper output reversing section 5 is shown in FIG. In FIG. 2, the discharge reversing unit 5 is a backup roller 18A that constitutes a decurl mechanism 18 for removing the curl of the sheet, which will be described in detail later on the upstream side along the discharge direction of the sheet P from the fixing unit 15. The sheet that has passed through the decurling mechanism 18 and the sheet discharge port 37 or the guide plates 35, 44,
The swingable reversal switching claws 16 that can switch the transport direction toward any of the reversal paths provided with 45 are arranged.

The reversing path is a path selected when an image is formed on both sides of the sheet or when the sheet is discharged in a reversing state, and the sheet to be reversed is introduced into the conveying path constituted by the guide plates 44 and 45 once. After the switchback processing is performed in a reversing unit (indicated by reference numeral 2 in FIG. 1) described later, the re-feeding state and the feeding-out position 37 are selected. There is. For this reason, the inner sheet discharge roller 17 capable of conveying the sheet in a predetermined direction is provided in the conveyance path constituted by the guide plates 44, 45 and the conveyance path constituted by the guide plates 35, 44 on the side where the sheet is introduced. The outer paper discharge roller 30 and the interlocking roller 31 that can be brought into contact with and interlock with these rollers are arranged at predetermined positions.

In the reversing path shown in FIG. 2, the reversing roller 21 and the branching claw 22 which rotate in the direction indicated by the symbol D and switch back the sheet introduced into the conveying path constituted by the guide plates 44 and 45. Further, the double-sided branch claw 2 in which a path for re-feeding the sheet subjected to the switchback process and a reverse discharge path 28 for transporting the sheet toward the discharge port 37 can be set.
7 are provided respectively.

The reversing unit 2 has the structure shown in FIG. In FIG. 3, the reversing unit 2 is provided so that the branching claw 22 overlaps the reversing roller 21 that is always rotating in the direction of the arrow D, which is the sheet conveying direction. The reversing roller 21, as shown in FIG.
On the other hand, a plurality of roller portions 21B are provided at substantially equal intervals, while in the branch claw 22, a plurality of claw portions 22A are provided at a shaft portion 22C at substantially equal intervals. The claw portion 22A of the branch claw 22 is
As shown in FIG. 3, the reversing roller 21 is pivotally supported by the shaft portion 22C on the side of the main body of the apparatus so as to be swingable while being inserted toward the shaft portion 21A. The action member 22E is fixed to a predetermined position of the shaft portion 22C of the branch claw 22, and the other end of the spring 23, one end of which is fixed to the apparatus main body side, is attached to the tip end of the action member 22E. 22A is biased toward the shaft portion 21A of the reversing roller 21.

A switchback driven roller 24 rotatable in the direction of arrow E is behind the reversing roller 21 in the sheet conveying direction (direction shown by arrow A in FIG. 3) obtained by the rotation direction of the reversing roller 21. A switchback roller 25 that constantly rotates in the direction of arrow B is provided, and a double-sided roller 26 and a lower guide plate 43 that form a part of a conveyance path during double-sided printing are provided in front of the reversing roller 21 in the sheet conveyance direction. And are provided. The double-sided roller 26 is provided with a double-sided branch claw 27 in the vicinity of the double-sided roller 26, and depending on the switching position thereof, the reverse discharge path 28 or the double-sided paper re-feed path 2
9 is formed.

The decurling mechanism 18 arranged at the position where the sheet discharged from the fixing means 15 reaches is shown in FIGS. 2 and 5 to 7. Note that FIG. 5 is a plan view showing the decurling mechanism 18 from the transport roller 18C side. In FIG. 2, the decurling mechanism 18 is a backup roller 18 that faces the sheet conveyance path and is opposed to the backup roller 18.
The backup rollers 18A and 18B are arranged side by side along the circumferential direction of the carrying roller 18C and are in contact with the circumferential surface of the carrying roller 18C so as to face each other.

In FIG. 2, the backup roller 18A,
18B has a backing function of bringing the sheet into contact with the conveying roller 18C, and as shown in FIG. 5, the axial direction parallel to the sheet width direction, which is the direction perpendicular to the sheet conveying direction, is set. A plurality of support shafts 18F and a plurality of support shafts 18F fixed to or integrally formed with the support shafts 18F, the support shafts 18F having a plurality of support shafts 18F, and the support shafts 18F each having an arrangement phase shifted relative to each other along the axial direction of the support shafts 18F. And the roller portion 18G. Each roller 18G is a roller portion 1 on the side of the opposing support shaft 18F.
The relative position with 8G is shifted, and one support shaft 18F
The roller portion 18G located on the other support shaft 18F side is inserted between the positions where the roller portions 18G are arranged in the state where the peripheral surface is close to the support shaft 18F side.

The plurality of rollers 18G except the shafts 18F of the backup rollers 18A, 18B are made of a material having a relatively low thermal conductivity (rubber such as EP rubber, urethane, silicon rubber, or polyacetal, polyethylene terephthalate, polycarbonate). The resin is used to prevent abnormal temperatures on the surfaces of the backup rollers 18A and 18B.

In FIG. 5, the backup roller 18
A and 18B rotate via a timing belt (not shown) hung on pulleys 40A and 41A attached to the support shaft 18F in drive units 40 and 41 provided at one axial end of the support shaft 18F. It is driven and the timing belt is wound around a driving source (not shown).

In FIG. 6, the carrying roller 18C is a member used as a cooling member in the decurling mechanism 18, and is a heat pipe 18D whose base is a metal pipe whose surface can directly contact the toner image carried on the sheet.
Is used. The heat pipe 18D has a structure in which a heat medium is enclosed, and has a structure in which the heat medium vapor generated in the high temperature portion moves to the low temperature portion at a high speed and is instantaneously condensed to transfer heat. An iron pipe plated with nickel is used as the metal pipe for the heat pipe 18D, and pure water having a volume ratio of about 20% is used as the heat medium.

At one end of the conveying roller 18C in the axial direction, in this embodiment, as shown in FIGS. 5 and 7, at the end located outside the sheet passage range, there are radiating fins 101 made of a plurality of good heat conductors. As shown in FIG. 7, the radiation fin 101 is housed in a radiation chamber 102 attached to the inner wall of the image forming apparatus that supports the decurling mechanism 18.

In the heat dissipation chamber 102, the cooling fan 1
03 is provided, and the radiation fin 101 is forcibly cooled. In this embodiment, the cooling fan 103
Air flow rate in the conveyor roller 18C using a heat pipe
It is set according to the surface temperature of. Therefore, as shown in FIG. 7, the cooling fan 103 is connected to the output side of the control unit 104 to which the temperature sensor 105 for detecting the surface temperature of the carrying roller 18C is connected to the input side, and the control unit 104. The rotation is controlled by the output signal from the. The cooling fan 103 employs a control mode in which the cooling fan 103 starts rotating when the surface temperature of the transport roller 18C reaches or exceeds a predetermined temperature.

On the other hand, the decurling mechanism 18 is provided with a structure for taking out the jammed sheet and eliminating the jam. That is, in this configuration, the upper guide member 19 which can be swung about the spindle indicated by reference numeral 19A in FIG. 2 is used, and the conveying roller 18C is supported on the swing end side of the upper guide member 19. As shown in FIG. 6, the conveying roller 18C provided on the upper guide member 19 has a rotating shaft 18E inserted through the bearing member 38, and the bearing member 38 floats with respect to the upper guide member 19 by a spring 39. Supported by the state. With this configuration, the bearing member 38 improves the contact state between the backup rollers 18A and 18B and the conveying roller 18C to form the nip portions 20A and 20B at the positions where the rollers are in contact with each other, and further, the decurling mechanism. Bending rigidity that changes depending on the thickness of the sheet passing through the sheet 18, so-called waist strength, allows the sheet to move up and down, causing an inadvertent increase in pressing force from the conveying roller 18C side to the sheet in the process of moving. I try not to.

The backup rollers 18A and 18B mounted on the decurling mechanism 18 can be arranged at different intervals in the circumferential direction of the conveying roller 18C. Figure 6
(B) shows one of the configurations for changing the arrangement interval, and in the figure, the backup rollers 18A, 1
8B is provided on the swing end side of support arms 180 and 181 which are swingable with the base end side being supported by the rotary shaft 18E of the transport roller 18C. Support arms 180, 1 in this case
The base end of 81 is inserted and supported so as to be swingable with respect to the rotary shaft 18E.

The support arms 180 and 181 are given a habit of approaching each other by an elastic body 182 such as a coil spring whose ends are hooked at positions facing each other on the way from the base end to the swing end. The limit position is defined by abutting against the locking member 183. The approach limit position is a position where the arrangement interval between the backup rollers 18A and 18B is the smallest when the backup rollers 18A and 18B are closest to each other. Actuators of solenoids 184 and 185 are respectively hooked on the opposite sides of the support arms 180 and 181 from the latching position of the elastic body 182, and the operation of the solenoid 184 causes the support arms 80 and 181 to swing in the direction away from each other. You can do it.

FIG. 8 is a view showing a state in which the arrangement intervals of the backup rollers 18A and 18B are changed according to the swing amount of the support arms 180 and 181, and FIG. 8A shows the backup rollers 18A and 18B. Shows the closest state, and FIG. 8B shows the state in which the arrangement interval is increased from the initial state.

Such a change in the arrangement interval is executed by controlling the excitation of the solenoids 184 and 185, as shown in FIG.
In the case shown in FIG. 8B, the slack of the seat can be set larger than in the case shown in FIG. The slack can change the curvature of the sheet as compared with the case of moving in the circumferential direction of the transport roller 18C.
In the case of (A), the curvature of the sheet is small, and
In the case of (B), the curvature of the sheet becomes large. As a result, as compared with the case where the conveyance roller 18C moves along the circumferential direction corresponding to the direction opposite to the curl occurrence direction, the curvature is increased and the curl correction action is increased. In FIG. 8, reference numeral 18H indicates a guide plate that prevents the sheets from falling off when the arrangement interval becomes large.

The control unit shown in FIG. 9 is used for the configuration for changing the arrangement interval of the backup rollers 18A, 18B. FIG. 9 shows the solenoid 18 shown in FIG.
4 is a block diagram showing the configuration of a control unit that controls the driving of the control units 185 and 185. In FIG. 4, the control unit 186 has an operation panel 187 on the input side and an output side on the output side via an I / O interface (not shown). Solenoid 184, 185
Drive units 184A and 185A are respectively connected.

The operation panel 187 is a switch for inputting the amount of curl generated on the sheet directly by the user, or a sheet is selected when the fixing temperature and the amount of curl are associated with each other by experiments beforehand. A seat selection switch for automatically setting the adjustment amount according to the contents is provided. In the present embodiment, since a member that can control two positions, such as a solenoid, is used, the curl adjustment amount is selected in the normal time and the time when the curl adjustment amount is set to be larger than the curl adjustment amount. It is possible to classify thick paper and thin paper, which have different bending rigidity, which affects the occurrence of curl.

In the control unit 186, the solenoid 184 outputs a signal for setting the arrangement interval between the backup rollers that can obtain the slack amount corresponding to the input curl adjustment amount.
The output is output to the drive units 184A and 185A of the 185. In particular, when the curl adjustment amount is large, the solenoids 184 and 185 are excited to widen the arrangement interval.

The backup rollers 18A, 18B
As a structure for changing the arrangement interval of the above, a combination of a sector gear formed at the base ends of the support arms 180 and 181 and a pulse motor provided with a drive gear meshing with the sector gear may be used instead of the solenoid described above. With this configuration, it is possible to change the arrangement interval according to the meshing position of the gears. According to this structure, unlike the solenoid, the swing amount of the support arms 180 and 181 can be changed in a different manner, that is, the arrangement interval can be changed in a plurality of steps. There can be many types.

Since the present embodiment is configured as described above, the sheet discharged from the fixing device 15 reaches the decurling mechanism 18. In the decurling mechanism 18, the conveying roller 18C located on the side where the sheet can be curved and corrected in the direction opposite to the direction in which the curl is generated on the side in contact with the toner image carried on the sheet is a heat pipe 18D which is a good conductor of heat.
And its surface is directly used for cooling the sea. For this reason, when the sheet reaching the decurling mechanism 18 comes into contact with the transport roller 18C, it is cooled and the rigidity of the sheet is increased, so that the original rigidity is restored.

Although the heat medium is repeatedly vaporized and liquefied on the carrying roller 18C, the heat radiation fin 101 provided on the carrying roller 18C is cooled by the cooling fan 103, so that heat circulation is instantaneously performed. For this reason,
The temperature of the sheet and the toner image that come into contact with the transport roller 18C can start to drop when they come into contact with each other.

The temperature to be lowered is preferably such that the penetration of the softened toner into the sheet is not impaired. In particular, in the case of a multicolor image in which multiple toner layers are formed unlike a monochrome image, the amount of heat required for fixing is larger than that of a monochrome image, so the amount of heat stored in the sheet discharged from the fixing unit 15 is also large. However, it is possible to set the above-mentioned temperature drop by optimizing the heat radiation amount at the transport roller 18C by controlling the air volume of the cooling fan 103. As a result, it is possible to restore the bending rigidity of the sheet, which has been reduced by softening due to heat storage, by a temperature drop, and moreover, it is possible to maintain a temperature that does not hinder the permeation of toner, in other words, the fixing, so It is possible to prevent hot offset which is likely to occur in some cases.

On the other hand, when the arrangement interval between the backup rollers is changed in accordance with the increase in rigidity due to cooling of the curl, the amount of slack generated in the sheet changes, and the curl is corrected by changing the curvature at this slack portion. be able to. That is, when the setting content is input on the operation panel 187 (see FIG. 9) in a state where the curl adjustment amount is increased, the solenoids 184 and 185 are excited and the support arms 180 and 181 swing from the initial state to support. The arms 180 and 181 are separated from each other, and the arrangement interval between the backup rollers 18A and 18B is expanded. As a result, the backup rollers 18A, 1
The curvature of the sheet is changed by the amount of slack generated in the sheet passing between the 8B arrangement positions. When the curvature is increased, the curl becomes stronger in the direction opposite to the curl generation direction than when the curvature is small, and the curl The correction effect is enhanced.

Next, another example according to the embodiments of the invention described in claims 2 and 3 will be described. In another embodiment,
Unlike the case shown in FIG. 8, it is characterized in that the operation timings of the backup rollers are made different to change the amount of slack without changing the arrangement interval of the backup rollers.

In this embodiment, each backup roller 18 has the structure of the drive mechanisms 40 and 41 shown in FIG.
An independent drive source is used for each of A and 18B. In FIG. 5, the drive unit of each backup roller 18A, 18B is provided with a timing belt (not shown) wound around pulleys 40A, 41A provided on a support shaft 18F of the backup rollers 18A, 18B, respectively. Is driven by the drive source.

On the other hand, in the present embodiment, regarding the frictional force between the backup rollers 18A and 18B and the conveying roller 18C, the frictional force between the sheet and the conveying roller 18C is the frictional force between the backup rollers 18A and 18B and the sheet. It is related so that it becomes smaller than. Accordingly, the sheet can be moved by the rotational force from the backup rollers 18A and 18B without being affected by the rotation of the transport roller 18C.

The backup roller 18A, as shown in FIG.
A configuration for drive control of 18B will be described. For the sake of convenience, the drive section for the drive source that drives each timing belt will be replaced with the drive section of the solenoids 184, 185.

In FIG. 9, the control unit 186 conveys the rotation start timing of the backup roller 18B, which is located on the downstream side in the sheet conveying direction, of the backup rollers 18A and 18B according to the curl adjustment amount from the operation panel 187. The amount of slack of the sheet caused between the positions where the rollers are arranged is changed by making the backup rollers 18A different from the backup roller 18A located on the upstream side in the direction. Figure 10
6 is a timing chart showing a case where the rotation start timing of the backup roller 18B is delayed with respect to the backup roller 18A, and the delay time indicated by the symbol T in the figure is set according to the curl adjustment amount.

Since this embodiment has the above-mentioned structure,
The sheet that reaches the decurling mechanism 18 is conveyed by the conveyance roller 18
Backup roller 18A, which has a large frictional force against C,
It is possible to move under the influence of the frictional force from 18B. That is, the peripheral surface of the transport roller 18C can be slid.

When the backup rollers 18A and 18B have different rotation start timings, the sheets are loosened in the state shown in FIG. In FIG. 11, the sheet reaching the nip portion between the backup roller 18A and the conveying roller 18C is nipped and conveyed by the pressure contact between the rollers (the state shown in FIG. 11A), and the leading end of the sheet moves toward the backup roller 18B. To do. At this time, the backup roller 18B has not started to rotate. At this time, the carrying roller 18C is the backup roller 18C.
Although the interlocking relationship with A is not established, it is possible to rotate because the peripheral surface of the backup roller 18A can slide due to the relationship of the frictional force between the two with respect to the sheet. When the leading edge of the sheet reaches the nip portion between the backup roller 18B and the transport roller 18C, the sheet is pushed from the rear. At this time, the transport roller 18C
Since the frictional force against the backup roller 18A is smaller than that against the backup roller 18A, the sheet moves toward the nip portion of the backup roller 18B while sliding on the peripheral surface of the transport roller 18C.
Looseness occurs between 8A and 18B (see FIG. 11 (B)).

Since the backup roller 18B starts to rotate after the lapse of a predetermined delay time T, the sheet is nipped and conveyed by the nip portion between the backup roller 18B and the conveyance roller 18C with the slack that has been generated up to that point. (See FIGS. 11C and 11D).

According to this embodiment, the amount of slack of the sheet can be changed in accordance with the curl adjustment amount by making the sheet slide and changing the operation timing of the backup roller. Can be increased.

Next, another example according to the embodiment of the present invention will be described. Another embodiment is an embodiment relating to the invention described in claim 4, and in this embodiment, the relationship of the frictional force between the conveying roller 18C and the backup roller with respect to the sheet is the same as that shown in FIG. In this case, the peripheral speed of the transport roller 18C and the backup roller can be changed.

FIG. 12 is a block diagram showing the configuration of a control unit (indicated by reference numeral 186 'for convenience) for controlling the drive of the conveying roller 18C and the backup rollers 18A and 18B. In FIG.
18B is rotationally driven via a timing belt driven by the same drive source as in the case shown in FIG.
The transport rollers 18C are backup rollers 18A, 18
It is rotationally driven by a drive source different from B. Control unit 18
6'includes an operation panel 187 on the input side and a drive unit (denoted by 184A 'for convenience) of the drive source for the backup rollers 18A and 18B on the output side and a drive source for the transport roller 18C. Drive (for convenience,
185A ') is connected.

The controller 186 'changes the relative peripheral speed between the backup rollers 18A and 18B and the conveying roller 18C in accordance with the curl adjustment amount input on the operation panel 187. Now, assuming that the peripheral speeds of the backup rollers 18A and 18B are V1 and the peripheral speed of the carrying roller 18C is V2, the relationship of (1) V2> V1 (2) V2 <V1 can be set. There is.

When the relationship (1) is set, the frictional force between the conveying roller 18C and the sheet is smaller than the frictional force between the backup rollers 18A and 18B and the sheet, so that the sheet surface Thus, the peripheral surface of the transport roller 18C can slide. As a result, since the transport roller 18C is a sheet cooling member, there is more opportunity for a new peripheral surface corresponding to the sheet to come into contact with the sheet. As a result, the heat absorption phenomenon from the sheet becomes remarkable, and the temperature drop of the sheet can be promoted to restore the rigidity of the sheet.

When the relationship of (2) is set,
Compared with the relationship of (1), the chance that the new peripheral surface of the transport roller 18C comes into contact with the sheet is reduced, and thus the heat absorption phenomenon from the sheet is suppressed as compared with (1). . In this way, the cooling action of the sheet can be made different.

Since this embodiment has the above-mentioned structure,
The sheet that has reached the decurling mechanism 18 can have a different cooling action depending on the amount of curl that is generated.
In particular, when the curl adjustment amount input on the operation panel is large, the relationship of (1) above is set in order to accelerate the cooling of the sheet and to restore the rigidity of the sheet itself.

When the relationship (1) is set, the transport roller 18C slides on the sheet surface, increasing the chances of bringing a new peripheral surface, in other words, a surface having a lowered temperature into contact with the sheet surface. Therefore, the cooling is promoted and the temperature drop is easily realized. Since the bending rigidity of the sheet can be restored by the temperature drop, it is possible to prevent the curl from being generated due to the shape of the reversing path when being conveyed toward the reversing path after passing through the decurling tortoiseshell 18. .

Incidentally, the temperature drop amount of the sheet obtained by relating the peripheral velocities in this embodiment may be set to an extent not impairing the penetration of the softened toner into the sheet, as in the embodiment shown in FIG. preferable. Further, in addition to setting the peripheral speed relationship between the transport roller 18C and the backup rollers 18A and 18B, the operation timing between the backup rollers 18A and 18B is set to be the same as that of the embodiment described in FIG. The rotation start timing of 18C may be matched with the rotation start timing of the backup roller 18A. FIG. 13 shows the state in this case, in which the backup roller 18A and the conveyance roller 18C are not separated until the leading edge of the sheet reaching the decurling mechanism 18 reaches the nip portion between the backup roller 18A and the conveyance roller 18C. Is stopped (FIG. 13 (A),
(See (B)) When the sheet is loosened between the backup rollers 18A and 18B, the backup roller 18A and the transport roller 18C are rotated as shown in FIG. 13 (C). Even in such a procedure, even when the backup roller 18A and the conveyance roller 18C are stopped due to the relationship of the frictional force between the backup roller 18A and the conveyance roller 18C on the basis of the sheet, the backup roller 18B and the sheet are separated from each other. The sheet can move due to the frictional force between the rollers, and slack can be generated according to the curl adjustment amount by setting the operation timing between the rollers.

According to the present embodiment, particularly when the sheet is conveyed to the reversing path for image formation on both sides of the sheet after fixing, the cooling of the sheet is promoted to curl the reversing path. Occurrence can be suppressed. Moreover, since the carrying roller 18C, which is a cooling member, is arranged on the side that comes into contact with the toner carried on the sheet, the toner carried on the sheet is also cooled and solidified by the cooling promoting action of the carrying roller 18C. Therefore, it is possible to prevent image rubbing and inadvertent transfer of toner which are likely to occur when the toner is softened.

[0067]

According to the first aspect of the present invention, the arrangement interval of the backup rollers along the circumferential direction of the conveying rollers can be changed according to the amount of curl generated on the sheet. It is possible to change the amount of slack in the seat that occurs. As a result, the curl correction degree can be set according to the curl generation amount by setting the curvature according to the amount of slack that occurs between the backup rollers in the direction opposite to the curl generation direction. Curls can be corrected regardless of the amount.

According to the second aspect of the present invention, the backup roller is composed of rollers subdivided in the axial direction, and the arrangement phases of the rollers arranged side by side in the circumferential direction of the conveying roller are set alternately. As a result, the bending rigidity of the sheet that is nipped and conveyed in the axial direction can be increased.
Moreover, since the operation timing of the backup rollers can be changed, the amount of slack of the sheet caused in the moving process can be made to correspond to the amount of curl adjustment, so that the curl of the sheet can be efficiently corrected.

According to the third aspect of the invention, the frictional force between the conveying roller and the sheet is set smaller than the frictional force between the backup roller and the sheet, and the conveying roller is used as the cooling member. When the operation timings of the backup rollers are different from each other, in addition to the rigidity restoration due to the temperature drop of the sheet, the slack of the sheet corresponding to the adjustment amount can be surely caused by the difference in the operation timing. This makes it possible to achieve the configuration for correcting the curl regardless of the curl amount of the sheet with a simple configuration of only the operation timing.

According to the fourth aspect of the present invention, since the peripheral speeds of the conveying roller and the backup roller for the sheet can be changed, the cooling action of the sheet by the conveying roller can be changed. As a result, the tendency of the temperature of the sheet to drop due to the cooling action can be made to correspond to the amount of curl generated in the sheet, and it is possible to reliably prevent curl reoccurrence.

According to the fifth aspect of the invention, it is possible to simultaneously achieve sheet cooling and curl correction without increasing the size of the apparatus and increasing the cost.

According to the sixth aspect of the invention, the sheet can be conveyed in the sheet conveying path from the fixing device to the reversing device while being cooled and the sheet can be conveyed along the peripheral surface of the conveying roller. Since the sheet is equipped with a backup roller that can be nipped and conveyed by following the peripheral surface of the conveyance roller, the bending rigidity of the sheet is restored to the original rigidity of the sheet by cooling the sheet before reversing. It is possible to prevent the occurrence of curl due to the form of the conveyance path. In particular, in the case of a sheet conveyance mode in which the sheet is reversed and moved again toward the feeding section, it is possible to prevent curling due to the tendency of the reversing section. In addition, since the image carried on the sheet is cooled and solidified by cooling the sheet toward the reversing device by the transport roller, it is possible to prevent image defects due to image rubbing and the like.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing an example of an image forming apparatus to which a sheet curl removing apparatus according to an exemplary embodiment of the present invention is applied.

FIG. 2 is a schematic diagram for explaining a configuration of a paper discharge reversing unit provided in the image forming apparatus shown in FIG.

FIG. 3 is a schematic diagram for explaining the configuration of a reversing unit used in the paper ejection reversing unit shown in FIG.

FIG. 4 is a plan view for explaining a configuration of members used in the reversing unit shown in FIG.

FIG. 5 is a plan view for explaining a configuration of a main part of the sheet ejection device according to the example according to the embodiment of the present invention.

6A and 6B are diagrams showing a configuration of a decurling mechanism having the configuration of the main part shown in FIG. 6, in which FIG. 6A is a side view, and FIG. 6B is an arrangement interval of backup rollers for the configuration shown in FIG. It is a schematic diagram which shows a change structure.

7 is a plan view for explaining the configuration of a cooling member used in the decurling mechanism shown in FIG.

FIG. 8 shows a state in which the arrangement interval between the backup rollers in the decurling mechanism shown in FIG. 6 is changed, and (A) shows a state in which the arrangement interval is narrowed.
(B) shows the state where the arrangement interval is expanded.

FIG. 9 is a block diagram for explaining a configuration of a drive control unit targeted for the arrangement interval changing structure shown in FIG. 6B.

FIG. 10 is a timing chart for explaining operation timings of the backup rollers when the configuration shown in FIG. 6A is targeted.

FIG. 11 is a schematic diagram for explaining the loosening occurrence state of the sheet based on the operation timing shown in FIG. 10 based on the operation timing of the backup rollers.

FIG. 12 is a block diagram for explaining a configuration of a drive control unit for changing the peripheral speed of the backup rollers in the configuration shown in FIG. 6 (A).

FIG. 13 is a schematic diagram for explaining a modified example regarding a sheet conveyance mode when the drive control unit illustrated in FIG. 12 is used.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Image forming apparatus 2 Reversing unit 3 Paper feeding apparatus 5 Paper ejection reversing section 15 Fixing means 18 Decal mechanisms 18A, 18B for correcting curl of a sheet Backup roller 18C which is a constituent member of a decal mechanism A cooling member is a constituent member of a decal mechanism Conveyance rollers 180,181 Support arms 184,185 having backup rollers Solenoids 186,186 'for driving support arms Control section P Sheet

Claims (6)

[Claims] 1. A conveyance roller comprising: a conveyance roller disposed in a sheet conveyance path; and a plurality of backup rollers arranged side by side along the circumferential direction of the conveyance roller and rotatable while being in pressure contact with the conveyance roller. In a sheet curl removing device capable of nipping and conveying the sheet in a shape following the peripheral surface of the roller, the backup roller is provided so that the arrangement interval along the circumferential direction of the conveyance roller can be changed, and the arrangement interval is A sheet curl removing device, which is provided so as to be settable in accordance with the amount of curl of the sheet. 2. A conveyance roller provided in a sheet conveyance path, and a plurality of backup rollers arranged in parallel along the circumferential direction of the conveyance roller and rotatable while being in pressure contact with the conveyance roller. In a sheet curl removing device capable of nipping and conveying the sheet in a shape following the peripheral surface of the roller, the backup roller is subdivided in the axial direction and arranged such that the arrangement phase in the axial direction alternates between the rollers. A sheet curl removing device, which is configured by a plurality of rolled rollers and is configured to be able to change the operation timing of each backup roller. 3. The sheet decurling device according to claim 2, wherein the conveying roller is used as a cooling member for the sheet, and a frictional force between the conveying roller and the sheet is generated between the backup roller and the sheet. A decurling device for a sheet, which is set to be smaller than the frictional force between the sheets. 4. A conveyance roller comprising: a conveyance roller arranged in a sheet conveyance path; and a plurality of backup rollers arranged side by side along the circumferential direction of the conveyance roller and rotatable while being in pressure contact with the conveyance roller. In a sheet curl removing device capable of nipping and transporting the sheet in a shape following the peripheral surface of the roller, the transport roller is used as a cooling member for the sheet, and the frictional force between the transport roller and the sheet is It is set to be smaller than the frictional force between the backup roller and the sheet, and the conveyance roller and the backup roller are in a relationship capable of changing the relative peripheral speed. apparatus. 5. An image forming apparatus using the sheet curl removing device according to claim 1, wherein the conveying roller is configured to cool the sheet. 6. A fixing device for discharging a sheet on which a toner image is fixed by heat and pressure by using a heating member and a pressing member which are arranged to face each other in a conveyance path of a sheet carrying a toner image, An image forming apparatus including a reversing device that reverses and conveys the sheet discharged from the fixing device, including a configuration capable of forced cooling in a conveyance path of the sheet from the fixing device to the reversing device. And a conveying roller that constitutes a cooling member that can convey the sheet while cooling the sheet, and a plurality of sheets are juxtaposed along the circumferential direction of the conveying roller to sandwich and convey the sheet in a state of following the shape of the peripheral surface of the conveying roller. And a back-up roller which is capable of feeding the sheet discharged from the fixing device in a direction opposite to the direction of the curl generated on the sheet. By the image forming apparatus characterized by arrangement relationship can be moved toward the reversing device is set.