JP2019015896A - Fixing device - Google Patents

Abstract

To variously change the shape or pressure distribution of a nip surface.SOLUTION: A fixing device comprises a first cam 150 which comes into contact with a second surface 142, the first cam which being configured to rotate to a first rotary position and a second rotary position around a first axial line 150A extending in an axial line direction of a roller (pressure roller 180); and a second cam 160 which comes into contact with the second surface 142, which being arranged at a downstream side in a conveyance direction with respect to the first cam 150, and configured to rotate to a third rotary position and a fourth rotary position around a second axial line 160A extending in the axial line direction. The first cam 150 has a first upstream contact surface 151 and a second upstream contact surface 152, and the second cam 160 has a first downstream contact surface 161 and a second downstream contact surface. The positions of the first cam 150 and the second cam 160 are changed such that the shape or pressure distribution in the coaxial direction and conveyance direction of a nip surface is changed.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a fixing device that thermally fixes a developer image on a recording sheet in an image forming apparatus.

  A fixing device having a configuration in which a pressure pad is provided in an endless belt and an endless belt is sandwiched between the pressure pad and a roller is known (Patent Document 1). The fixing device heat-fixes the developer image on a sheet while conveying a recording sheet on which the developer image is formed between an endless belt and a roller.

  In this fixing device, the nip width, which is the width in the recording sheet conveyance direction, of the nip surface between the endless belt and the roller is changed by moving the pressure pad relative to the roller.

JP, 2015-108721, A

  By the way, depending on the type of recording sheet and the usage environment of the image forming apparatus, the shape of the nip surface and the pressure distribution may be changed according to the situation in order to suppress the wrinkling of the recording sheet or to suppress the paper jam. Is desired.

  However, when the entire pressure pad is simply moved forward and backward as in the prior art, the nip width can be changed over the entire width of the recording sheet. The shape of the surface and the pressure distribution in the nip surface could not be changed freely.

  Accordingly, an object of the present invention is to provide a fixing device capable of variously changing the shape of the nip surface and the pressure distribution.

In order to solve the above-described problem, a fixing device of the present invention includes an endless belt, a first surface that is in contact with an inner peripheral surface of the endless belt, and a second surface that is located on the opposite side of the first surface. A roller that sandwiches an endless belt between the pad and the pressure pad and conveys the recording sheet between the endless belt and a first cam that contacts the second surface, and is in the axial direction of the roller A first cam that rotates around a first axis that extends, a first cam that rotates to a second rotation position different from the first rotation position, and a second cam that contacts the second surface, A second cam which is disposed downstream of the one cam in the transport direction and rotates to a third rotation position and a fourth rotation position different from the third rotation position around a second axis extending in the axial direction. And a cam.
The first cam has a first upstream contact surface that contacts the second surface when in the first rotational position, and a second upstream contact surface that contacts the second surface when in the second rotational position. .
The second cam has a first downstream contact surface that contacts the second surface when in the third rotational position, and a second downstream contact surface that contacts the second surface when in the fourth rotational position. .
The distance from the first axis to the center of the first upstream contact surface in the axial direction is D1uc,
D1ue, the distance from the first axis to the end of the first upstream contact surface in the axial direction,
The distance from the first axis to the center of the second upstream contact surface in the axial direction is D2uc,
The distance from the first axis to the end of the second upstream contact surface in the axial direction is D2ue,
D1dc, the distance from the second axis to the center of the first downstream contact surface in the axial direction
The distance from the second axis to the end of the first downstream contact surface in the axial direction is D1de,
The distance from the second axis to the center of the second downstream contact surface in the axial direction is D2dc,
The distance from the second axis to the end of the second downstream contact surface in the axial direction is D2de,
D2uc-D2ue is different from D1uc-D1ue,
D2dc-D2de is different from D1dc-D1de,
D2dc-D2de is different from D2uc-D2ue.

  According to such a configuration, the first cam is positioned at either the first rotation position or the second rotation position, and the second cam is positioned at either the third rotation position or the fourth rotation position. By doing so, the upstream portion of the pressure pad in the transport direction is pressed by the first upstream contact surface or the second upstream contact surface, and the downstream portion of the transport direction is the first downstream contact surface or the second downstream contact. Pressed by the surface. For this reason, the pressing force at the central portion and the end portion in the axial direction of the upstream portion in the conveyance direction of the pressure pad and the pressing force at the central portion and the end portion in the axial direction of the downstream portion in the conveyance direction are It can change suitably according to the shape of a cam and a 2nd cam. Therefore, according to this fixing device, it is possible to variously change the shape and pressure distribution of the nip surface between the endless belt and the roller.

In order to solve the above-described problems, a fixing device of the present invention includes an endless belt, a first surface that is in contact with the inner peripheral surface of the endless belt, and a second surface that is located on the opposite side of the first surface. A roller that sandwiches an endless belt between the pressure pad and the pressure pad and conveys a recording sheet between the pressureless pad and the endless belt, and a cam that contacts the second surface, and extends in the axial direction of the roller. A first rotation position and a cam that can rotate to a second rotation position different from the first rotation position are provided around the cam axis.
When the cam is in the first rotation position, the first upstream contact surface that contacts the second surface and the first downstream contact that contacts the second surface on the downstream side in the transport direction from the first upstream contact surface. A second upstream contact surface that contacts the second surface when in the second rotational position, and a second downstream contact surface that contacts the second surface downstream of the second upstream contact surface in the transport direction. And have.
And the distance from the cam axis to the center of the first upstream contact surface in the axial direction is D1uc,
D1ue, the distance from the cam axis to the end of the first upstream contact surface in the axial direction,
D2uc is the distance from the cam axis to the center of the second upstream contact surface in the axial direction.
D2ue, the distance from the cam axis to the end of the second upstream contact surface in the axial direction
The distance from the cam axis to the center of the first downstream contact surface in the axial direction is D1dc,
The distance from the cam axis to the end of the first downstream contact surface in the axial direction is D1de,
D2dc, the distance from the cam axis to the center of the second downstream contact surface in the axial direction
The distance from the cam axis to the end of the second downstream contact surface in the axial direction is D2de,
D2uc-D2ue is different from D1uc-D1ue,
D2dc-D2de is different from D1dc-D1de,
D2dc-D2de is different from D2uc-D2ue.

  According to such a configuration, by positioning the cam at either the first rotational position or the second rotational position, the portion of the pressure pad on the upstream side in the transport direction is moved to the first upstream contact surface or the first rotational surface. 2 Pressed by the upstream contact surface, and the portion on the downstream side in the transport direction is pressed by the first downstream contact surface or the second downstream contact surface. For this reason, the pressing force at the central portion and the end portion in the axial direction of the upstream portion in the conveyance direction of the pressure pad and the pressing force at the central portion and the end portion in the axial direction at the downstream portion in the conveyance direction are It can change suitably according to a shape. Therefore, according to this fixing device, it is possible to variously change the shape and pressure distribution of the nip surface between the endless belt and the roller.

In order to solve the above-described problems, a fixing device of the present invention includes an endless belt, a first surface that is in contact with the inner peripheral surface of the endless belt, and a second surface that is located on the opposite side of the first surface. An endless belt is sandwiched between the pressure pad and the pressure pad, a roller that conveys the recording sheet in the conveying direction between the endless belt, and a plurality of rollers that can press the second surface arranged in the axial direction of the roller. An upstream pressing mechanism having an upstream pressing pin, and a plurality of downstream pressing pins arranged on the downstream side in the transport direction with respect to the upstream pressing mechanism and arranged in the axial direction of the roller and capable of pressing the second surface. A downstream pressing mechanism, a plurality of upstream pressing pins and a plurality of downstream pressing pins that are capable of moving forward and backward with respect to the second surface, the plurality of upstream pressing pins and the plurality of downstream pressing pins With the first state The and a control device that moves in a different second state to the first state.
And
A plane that is parallel to a plane passing through both end portions in the transport direction of the first surface and that is opposite to the roller axis with respect to the respective tip portions of the plurality of upstream pressing pins and the plurality of downstream pressing pins is a reference plane. age,
In the first state, the distance from the reference plane to the tip of the upstream pressing pin at the center in the axial direction is D1uc,
In the first state, the distance from the reference plane to the tip of the upstream pressing pin at the end in the axial direction is D1ue,
In the second state, D2uc represents the distance from the reference plane to the tip of the upstream pressing pin at the center in the axial direction.
In the second state, the distance from the reference plane to the tip of the upstream pressing pin at the end in the axial direction is D2ue,
In the first state, the distance from the reference plane to the tip of the downstream pressing pin at the center in the axial direction is D1dc,
In the first state, the distance from the reference plane to the tip of the downstream pressing pin at the end in the axial direction is D1de,
In the second state, the distance from the reference plane to the tip of the downstream pressing pin at the center in the axial direction is D2dc,
In the second state, the distance from the reference plane to the tip of the downstream pressing pin at the end in the axial direction is D2de,
D2uc-D2ue is different from D1uc-D1ue,
D2dc-D2de is different from D1dc-D1de,
D2dc-D2de is different from D2uc-D2ue.

  According to such a configuration, the plurality of upstream pressing pins of the upstream pressing mechanism and the plurality of downstream pressing pins of the downstream pressing mechanism are set to the first state or the second state, so that the pressure pad on the upstream side in the transport direction This part is pressed by the upstream pressing pin and the downstream pressing pin, and the pressure pad is pressed according to the protruding amount of each pressing pin. Therefore, according to this fixing device, it is possible to variously change the shape and pressure distribution of the nip surface between the endless belt and the roller.

  According to the present invention, it is possible to variously change the shape and pressure distribution of the nip surface between the endless belt and the roller.

1 is a cross-sectional view of a laser printer provided with a fixing device according to the present invention. 1 is a cross-sectional view of a fixing device according to a first embodiment. FIG. 3 is a perspective view illustrating a configuration of a fixing device. It is sectional drawing of a cam, and shows the 4A cross section (a), 4B cross section (b), and 4C cross section (c) of FIG. It is sectional drawing of a cam and shows 5A cross section (a), 5B cross section (b), and 5C cross section (c) of FIG. FIG. 4A is a diagram showing the position of each cam when the first cam and the second cam are in the first state, and FIG. 5B is a diagram showing the shape of the nip surface. FIG. 4A is a diagram showing the position of each cam when the first cam and the second cam are in the second state, and FIG. 5B is a diagram showing the shape of the nip surface. FIG. 5A is a diagram showing the position of each cam when the first cam and the second cam are in the third state, and FIG. 5B is a diagram showing the shape of the nip surface. FIG. 6 is a cross-sectional view of a fixing device according to a second embodiment, and is a view where a cam is in a first rotation position. FIG. 6 is a cross-sectional view of a fixing device according to a second embodiment, and is a view where a cam is in a second rotation position. It is sectional drawing of a cam, and shows 10A cross section (a), 10B cross section (b), 10C cross section (c), and 10D cross section (d) of FIG. FIG. 10 is a cross-sectional view of a fixing device according to a third embodiment. It is sectional drawing of the fixing device which concerns on 4th Embodiment. It is the figure (a) which looked at the some upstream press pin in the 1st state from the conveyance direction, and the figure (b) which looked at the some downstream press pin in the 1st state from the conveyance direction. It is the figure (a) which looked at the some upstream press pin in the 2nd state from the conveyance direction, and the figure (b) which looked at the some downstream press pin in the 2nd state from the conveyance direction.

[First Embodiment]
Next, the fixing device according to the first embodiment of the present invention will be described in detail with reference to the drawings as appropriate. In the following description, unless otherwise specified, the vertical direction shown in FIG. 1 is up and down, the right side in FIG. 1 is front, the left side is rear, the front side of the paper is left, and the back side of the paper is right. Indicates.

  As shown in FIG. 1, the laser printer 10 including the fixing device 100 according to the first embodiment includes a paper feeding unit 30 that supplies a sheet P as an example of a recording sheet into a main body housing 20, and an exposure device 40. And a process cartridge 50 for transferring the toner image onto the paper P, and a fixing device 100 for thermally fixing the toner image on the paper P.

  The paper feed unit 30 is provided in the lower part of the main body housing 20, and includes a paper feed tray 31 that accommodates the paper P, a paper pressing plate 32 that lifts the front side of the paper P, a paper feed roller 33, and a paper feed pad 34. And paper dust removing rollers 35 and 36 and a registration roller 37 are mainly provided. The paper P in the paper feed tray 31 is brought close to the paper feed roller 33 by the paper pressing plate 32 and separated one by one by the paper feed roller 33 and the paper feed pad 34, and the paper dust removing rollers 35 and 36 and the registration roller 37. And is conveyed toward the process cartridge 50.

  The exposure apparatus 40 is disposed in the upper part of the main body housing 20 and mainly includes a laser light emitting unit (not shown), a polygon mirror 41 that is rotationally driven, lenses 42 and 43, and reflecting mirrors 44, 45, and 46. Yes. In the exposure apparatus 40, the laser light emitted from the laser light emitting unit is reflected or passed through the polygon mirror 41, the lens 42, the reflecting mirrors 44 and 45, the lens 43, and the reflecting mirror 46 in this order. Scanned at high speed.

  The process cartridge 50 is disposed below the exposure device 40 and is detachable from the main body casing 20 through an opening formed when the front cover 21 provided on the main body casing 20 is opened. The process cartridge 50 includes a drum unit 60 and a developing unit 70.

  The drum unit 60 mainly includes a photosensitive drum 61, a charger 62, and a transfer roller 63. The developing unit 70 is detachable from the drum unit 60, and mainly includes a developing roller 71, a supply roller 72, a layer thickness regulating blade 73, and a toner containing portion 74 that contains toner. Yes.

  In the process cartridge 50, the surface of the photosensitive drum 61 is uniformly charged by the charger 62 and then exposed by high-speed scanning of the laser light from the exposure device 40, thereby electrostatically charging the photosensitive drum 61 on the photosensitive drum 61. A latent image is formed. Further, the toner in the toner container 74 is supplied to the developing roller 71 via the supply roller 72 and enters between the developing roller 71 and the layer thickness regulating blade 73 to form a thin layer of a certain thickness on the developing roller 71. It is carried on.

  The toner carried on the developing roller 71 is supplied from the developing roller 71 to the electrostatic latent image formed on the photosensitive drum 61. As a result, the electrostatic latent image is visualized and a toner image is formed on the photosensitive drum 61. Thereafter, the paper P is conveyed between the photosensitive drum 61 and the transfer roller 63, whereby the toner image on the photosensitive drum 61 is transferred onto the paper P.

  The fixing device 100 is provided behind the process cartridge 50. The toner image transferred onto the paper P passes through the fixing device 100 and is thermally fixed onto the paper P. The paper P on which the toner image is thermally fixed is discharged onto the paper discharge tray 22 by the transport rollers 23 and 24.

  As shown in FIGS. 2 and 3, the fixing device 100 includes an endless belt 110, a halogen lamp 120 as a heater, a reflecting member 130, a pressure pad 140, a first cam 150, and a second cam 160. , A support member 170, motors 81 and 82, a control device 90, and a pressure roller 180 as an example of a roller.

  The endless belt 110 is an endless belt having heat resistance and flexibility, and includes an element tube made of a metal such as stainless steel and a coat layer made of a fluororesin or the like formed on the surface of the element tube. It is mainly configured. Both ends of the endless belt 110 are rotatably supported by side guides (not shown). Inside the endless belt 110, a halogen lamp 120, a reflecting member 130, a pressure pad 140, a first cam 150, and a second cam 160 are arranged.

  The halogen lamp 120 is a heater that heats the endless belt 110. The halogen lamp 120 is disposed at a predetermined interval from the inner peripheral surface 111 of the endless belt 110.

  The reflecting member 130 is a member that reflects the radiant heat from the halogen lamp 120 toward the inner peripheral surface 111 of the endless belt 110, and is disposed at a predetermined interval from the halogen lamp 120. Specifically, the reflecting member 130 is disposed on the lower side of the halogen lamp 120, reflects the radiant heat from the halogen lamp 120 upward, and heats the upper portion of the endless belt 110.

  The pressure pad 140 is a flat plate-like member that is long in the left-right direction. The pressure pad 140 is a member having elasticity such as rubber, foamed rubber, or foamed resin. The pressure pad 140 has a first surface 141 that contacts the inner peripheral surface of the endless belt 110 and a second surface 142 that is located on the opposite side of the first surface 141.

  The pressure roller 180 is configured to rotate around the axis 181A when a driving force is transmitted from a motor (not shown) provided in the main body housing 20, and the endless belt 110 is rotated when driven. The endless belt 110 is driven to rotate by the frictional force. The sheet P on which the toner image is transferred is conveyed between the pressure roller 180 and the heated endless belt 110, whereby the toner image is thermally fixed.

  The pressure roller 180 is a roller that sandwiches the endless belt 110 with the pressure pad 140 and transports the paper P in the transport direction with the endless belt 110. The pressure roller 180 mainly includes a metal shaft 181 and an elastic roller body 182 provided on the outer periphery of the shaft 181.

  The first cam 150 is a cam that has a shaft 159 and rotates around a first axis 150 </ b> A that extends in the axial direction of the pressure roller 180 (hereinafter simply referred to as “axial direction”). As shown in FIG. 2, the first cam 150 has a first upstream contact surface 151, a second upstream contact surface 152, and a third upstream contact surface 153 at different positions around the first axis 150 </ b> A. The first cam 150 is in contact with the second surface 142 of the pressure pad 140, and the first rotation position shown in FIGS. 2 and 6A is different from the first rotation position shown in FIG. It rotates to a rotation position and a fifth rotation position shown in FIG. 8 different from the first rotation position and the second rotation position.

  The second cam 160 is a cam that has a shaft 169 and rotates around a second axis 160 </ b> A extending in the axial direction of the pressure roller 180. As shown in FIG. 2, the second cam 160 has a first downstream contact surface 161, a second downstream contact surface 162, and a third downstream contact surface 163 at different positions around the second axis 160A. The second cam 160 is in contact with the second surface 142 of the pressure pad 140 and is different from the third rotation position shown in FIGS. 2 and 6A and the third rotation position shown in FIG. It rotates to a rotation position and a sixth rotation position shown in FIG. 8 different from the third rotation position and the fourth rotation position.

As shown in FIG. 3, a gear 158 is fixed to the end of the shaft 159. An idle gear 157 is engaged with the gear 158, and the driving force of the motor 81 is input to the idle gear 157 via a gear group (not shown).
A gear 168 is fixed to the shaft 169. An idle gear 167 is engaged with the gear 168, and the driving force of the motor 82 is input to the idle gear 167 via a gear group (not shown).

  The motors 81 and 82 are stepping motors, for example. The motors 81 and 82 are connected to the control device 90, and can be rotated by an arbitrary angle by the control device 90. That is, the first cam 150 and the second cam 160 can be rotated independently.

  The shafts 159, 169, the idle gears 157, 167, and the pressure pad 140 are supported by a support member 170. Although FIG. 3 shows only one end side of the endless belt 110, the shafts 159 and 169 and the pressure pad 140 are supported by a support member 170 (not shown) also on the other end side of the endless belt 110. That is, the relative positions of the pressure pad 140 and the shafts 159 and 169 are fixed by the support member 170.

  The control device 90 includes a CPU, a ROM, a RAM, and the like, and outputs a control signal to each device of the laser printer 10 to control the entire image forming operation. The control device 90 outputs a control signal to the motors 81 and 82 in accordance with the type of paper P included in the print data and an instruction from the operation panel, and rotates the first cam 150 and the second cam 160, Is transitioned to the first state, the second state, or the third state.

  The first state is a state where the first cam 150 is in the first rotation position and the second cam 160 is in the third rotation position, as shown in FIGS. When the first cam 150 is in the first rotation position, the first upstream contact surface 151 contacts the second surface 142 of the pressure pad 140. When the second cam 160 is in the third rotation position, the first downstream contact surface 161 contacts the second surface 142 of the pressure pad 140.

  As shown in FIG. 7, the second state is a state in which the first cam 150 is in the second rotation position and the second cam 160 is in the fourth rotation position. When the first cam 150 is in the second rotation position, the second upstream contact surface 152 contacts the second surface 142 of the pressure pad 140. When the second cam 160 is in the third rotation position, the second downstream contact surface 162 contacts the second surface 142 of the pressure pad 140.

  As shown in FIG. 8, the third state is a state where the first cam 150 is in the fifth rotation position and the second cam 160 is in the sixth rotation position. When the first cam 150 is in the fifth rotation position, the third upstream contact surface 153 contacts the second surface 142 of the pressure pad 140. When the second cam 160 is in the sixth rotation position, the third downstream contact surface 163 contacts the second surface 142 of the pressure pad 140.

As shown to Fig.4 (a), as for the 1st upstream contact surface 151 of the 1st cam 150, the center part in the axial direction protrudes in the radial direction rather than the edge part. That is, the distance D1uc from the first axis 150A to the central portion of the first upstream contact surface 151 in the axial direction is larger than the distance D1ue from the first axis 150A to the end of the first upstream contact surface 151 in the axial direction.
In the present invention, the end in the axial direction on each contact surface means an end in a range in contact with the pressure pad 140.

  As shown in FIG. 4B, the third upstream contact surface 153 of the first cam 150 has a central portion and an end portion in the axial direction at the same position in the radial direction. That is, the distance D3uc from the first axis 150A to the center of the third upstream contact surface 153 in the axial direction is equal to the distance D3ue from the first axis 150A to the end of the third upstream contact surface 153 in the axial direction.

As shown in FIG.4 (c), as for the 2nd upstream contact surface 152 of the 1st cam 150, the center part in the axial direction is dented in the radial direction rather than the edge part. That is, the distance D2uc from the first axis 150A to the center of the second upstream contact surface 152 in the axial direction is smaller than the distance D2ue from the first axis 150A to the end of the second upstream contact surface 152 in the axial direction.
That is, D2uc-D2ue is different from D1uc-D1ue.
Further, D2uc-D2ue <D1uc-D1ue.

As shown to Fig.5 (a), as for the 1st downstream contact surface 161 of the 2nd cam 160, the center part in the axial direction protrudes in the radial direction rather than the edge part. That is, the distance D1dc from the second axis 160A to the center of the first downstream contact surface 161 in the axial direction is larger than the distance D1de from the second axis 160A to the end of the first downstream contact surface 161 in the axial direction. And the protrusion amount with respect to the edge part of the center part in the axial direction of the 1st downstream contact surface 161 is larger than the protrusion amount with respect to the edge part of the center part in the axial direction of the 1st upstream contact surface 151.
That is, D1dc-D1de is different from D1uc-D1ue.
Further, D1dc-D1de> D1uc-D1ue.

  As shown in FIG. 5B, the third downstream contact surface 163 of the second cam 160 has a central portion and an end portion in the axial direction at the same position in the radial direction. That is, the distance D3dc from the second axis 160A to the center of the third downstream contact surface 163 in the axial direction is equal to the distance D3de from the second axis 160A to the end of the third downstream contact surface 163 in the axial direction.

As shown in FIG. 5C, the second downstream contact surface 162 of the second cam 160 has a central portion in the axial direction that is recessed in the radial direction from the end portion. That is, the distance D2dc from the second axis 160A to the center of the second downstream contact surface 162 in the axial direction is smaller than the distance D2de from the second axis 160A to the end of the second downstream contact surface 162 in the axial direction.
That is, D2dc-D2de is different from D1dc-D1de.
Further, D2dc-D2de <D1dc-D1de.
Then, the amount of recess with respect to the end of the central portion in the axial direction of the second downstream contact surface 162 is larger than the amount of recess with respect to the end of the central portion in the axial direction of the second upstream contact surface 152.
That is, D2dc-D2de is different from D2uc-D2ue.
Further, D2dc-D2de <D2uc-D2ue (| D2dc-D2de |> | D2uc-D2ue |).

The operation and effect of the fixing device 100 of the laser printer 10 configured as described above will be described.
The fixing device 100 outputs a control signal to the motors 81 and 82 to rotate the first cam 150 and the second cam 160 in a predetermined direction in accordance with the type of paper P included in the print data and an instruction from the operation panel. Let

For example, when a landscape paper (paper whose fiber direction is orthogonal to the transport direction) is designated, as shown in FIG. 6A, the control device 90 sets the first cam 150 to the first rotation position, 2 Set the cam 160 to the third rotation position to the first state. In the first state, the first cam 150 and the second cam 160 have the first upstream contact surface 151 and the first downstream contact surface 161 in contact with the second surface 142. As for the 1st upstream contact surface 151 and the 1st downstream contact surface 161, the center part of the axial direction has protruded with respect to the edge part. In particular, the protruding amount of the central portion with respect to the end portion of the first downstream contact surface 161 on the downstream side in the transport direction is larger than the protruding amount of the central portion with respect to the end portion of the first upstream contact surface 151.
In this state, as shown in FIG. 6B, the nip surface N has a shape in which the central portion in the axial direction protrudes in the transport direction from the end on the upstream side and the downstream side in the transport direction. At this time, with respect to the width of the nip surface N between the endless belt 110 and the pressure roller 180 in the conveyance direction (hereinafter simply referred to as “nip width”), the width of the central portion in the axial direction is N1c, and the end portion in the axial direction is N1c. When the width is N1e, N1c> N1e is satisfied. Since the nip surface N is protruded from the end on the downstream side in the transport direction, the wrapping around the endless belt 110 is suppressed even when the sheet is a horizontal sheet, and the paper is separated from the endless belt 110. Will be better.

For example, when thin paper is designated, as shown in FIG. 7A, the control device 90 sets the first cam 150 to the second rotation position and sets the second cam 160 to the fourth rotation position. Set to the second state. In the second state, the first cam 150 and the second cam 160 have the second upstream contact surface 152 and the second downstream contact surface 162 in contact with the second surface 142. The second upstream contact surface 152 and the second downstream contact surface 162 both have a central portion in the axial direction that is recessed with respect to the end portion. In particular, the amount of depression at the center with respect to the end of the second downstream contact surface 162 on the downstream side in the conveying direction is larger than the amount of depression at the center with respect to the end of the second upstream contact surface 152 on the upstream side in the conveying direction. Yes.
In this state, as shown in FIG. 7B, the nip surface N has a shape in which the central portion in the axial direction is recessed in the transport direction from the end on the upstream side and the downstream side in the transport direction. The nip width at this time satisfies N2c <N2e, where N2c is the width at the center in the axial direction and N2e is the width at the end in the axial direction. Since the nip surface N is recessed in the central part in the axial direction on the downstream side in the transport direction, the transport speed at the end part in the axial direction is increased, and the thin paper can be transported while being pulled outward in the axial direction. Since it can, it can suppress that a thin paper wrinkles.

  Further, for example, when thick paper is designated, as shown in FIG. 8A, the control device 90 sets the first cam 150 to the fifth rotation position and sets the second cam 160 to the sixth rotation position. Set to the third state. In the third state, the first cam 150 and the second cam 160 have the third upstream contact surface 153 and the third downstream contact surface 163 in contact with the second surface 142. The third upstream contact surface 153 and the third downstream contact surface 163 are both equidistant from the axial lines 150A and 160A of the cams 150 and 160 at the center and the end in the axial direction. Therefore, as shown in FIG. 8B, the nip surface N has a substantially linear shape on the upstream side and the downstream side in the transport direction. By making the nip width of the nip surface N uniform in the axial direction, the thick paper can be transported satisfactorily.

  As described above, according to the fixing device 100 of the present embodiment, the first cam 150 is positioned at any one of the first rotation position, the second rotation position, and the fifth rotation position, and the second cam 160 is moved. By positioning the pressure pad 140 at any one of the third rotation position, the fourth rotation position, and the sixth rotation position, the upstream portion of the pressure pad 140 in the transport direction becomes the first upstream contact surface 151 and the second upstream position. It is pressed by the contact surface 152 or the third upstream contact surface 153, and the portion on the downstream side in the transport direction is pressed by the first downstream contact surface 161, the second downstream contact surface 162, or the third downstream contact surface 163. Therefore, the pressing force at the central portion and the end portion in the axial direction of the portion on the upstream side in the conveyance direction of the pressure pad 140 and the pressing force at the central portion and the end portion in the axial direction at the portion on the downstream side in the conveyance direction are The position can be appropriately changed depending on the positions of the first cam 150 and the second cam 160. Therefore, according to the fixing device 100, the shape and pressure distribution of the nip surface N between the endless belt 110 and the pressure roller 180 can be variously changed.

  Note that the present embodiment can be implemented with appropriate modifications. For example, in order to independently rotate the first cam 150 and the second cam 160, the fixing device 100 includes two motors, one for each cam. 150 and the second cam 160 may be driven. In this case, for example, at least one idle gear that meshes with both the gear 158 and the gear 168 may be provided so that the first cam 150 and the second cam 160 are interlocked.

  Further, the combination of the rotational positions of the first cam 150 and the second cam 160 is not limited to the above. For example, when the first cam 150 is set to the first rotation position, the second cam 160 may be set to the fourth rotation position or the sixth rotation position. Further, when the first cam 150 is set to the third rotation position, the second cam 160 may be set to the second rotation position or the sixth rotation position. Further, when the first cam 150 is set to the fifth rotation position, the second cam 160 may be set to the second rotation position or the fourth rotation position.

That is, in the first embodiment, the configuration is such that D2dc-D2de <D2uc-D2ue, but the configuration may be such that D2dc-D2de> D2uc-D2ue.
In the first embodiment, the configuration is such that D1dc-D1de> D1uc-D1ue, but the configuration may be such that D1dc-D1de <D1uc-D1ue.

[Second Embodiment]
Next, a second embodiment of the present invention will be described. The fixing device 200 according to the second embodiment shown in FIG. 9 differs from the fixing device 100 of the first embodiment in a mechanism for pressing the pressure pad 140. In the second embodiment, only different points from the first embodiment will be described, and the same parts are denoted by the same reference numerals and the description thereof will be omitted.

  The fixing device 200 includes a cam 250 that contacts the second surface 142 as a mechanism for pressing the pressure pad 140. The cam 250 has a first rotation position shown in FIG. 9 and a second rotation position shown in FIG. 10 different from the first rotation position around a cam axis 250A extending in the axial direction of the pressure roller 180. It can be rotated.

  The cam 250 has a first cam surface 210 and a second cam surface 220 arranged around the cam axis 250A, and has a substantially hexagonal column shape. The first cam surface 210 contacts the second surface 142 of the pressure pad 140 when in the first rotation position. The second cam surface 220 contacts the second surface 142 of the pressure pad 140 when in the second rotation position.

  As shown in FIG. 9, the first cam surface 210 includes a first upstream contact surface 211 that contacts an upstream position of the second surface 142 and a downstream side when the cam 250 is in the first rotation position. A first downstream contact surface 212 is in contact with the position. That is, the first upstream contact surface 211 and the first downstream contact surface 212 are located on the first cam surface 210. The first downstream contact surface 212 is in contact with the second surface on the downstream side in the transport direction from the first upstream contact surface 211.

  As shown in FIG. 10, the second cam surface 220 includes a second upstream contact surface 221 that contacts an upstream position of the second surface 142 and a downstream side when the cam 250 is in the second rotation position. It has a second downstream contact surface 222 that contacts the position. That is, the second upstream contact surface 221 and the second downstream contact surface 222 are located on the second cam surface 220. The second downstream contact surface 222 is in contact with the second surface 142 on the downstream side in the transport direction from the second upstream contact surface 221.

As shown in FIG. 11A, the first upstream contact surface 211 has the same shape as the first upstream contact surface 151 of the first embodiment.
As shown in FIG. 11B, the first downstream contact surface 212 has the same shape as the first downstream contact surface 161 of the first embodiment.
As shown in FIG. 11C, the second upstream contact surface 221 has the same shape as the second upstream contact surface 152 of the first embodiment.
As shown in FIG. 11D, the second downstream contact surface 222 has the same shape as the second downstream contact surface 162 of the first embodiment.

For this reason, as in the first embodiment,
The distance from the cam axis 250A to the end of the first upstream contact surface 211 in the axial direction is D1ue,
The distance from the cam axis 250A to the central portion of the first upstream contact surface 211 in the axial direction is D1uc,
The distance from the cam axis 250A to the end of the second upstream contact surface 221 in the axial direction is D2ue,
The distance from the cam axis 250A to the center of the second upstream contact surface 221 in the axial direction is D2uc,
The distance from the cam axis 250A to the end of the first downstream contact surface 212 in the axial direction is D1de,
The distance from the cam axis 250A to the central portion of the first downstream contact surface 212 in the axial direction is D1dc,
The distance from the cam axis 250A to the end of the second downstream contact surface 222 in the axial direction is D2de,
The distance from the cam axis 250A to the center of the second downstream contact surface 222 in the axial direction is D2dc,
D2uc-D2ue is different from D1uc-D1ue,
D2dc-D2de is different from D1dc-D1de,
D2dc-D2de is different from D2uc-D2ue.

Also,
D2uc-D2ue <D1uc-D1ue,
D2dc-D2de <D1dc-D1de,
D2dc-D2de> D2uc-D2ue.

Furthermore, the width in the conveyance direction of the nip surface N between the endless belt 110 and the pressure roller 180 is
When the cam 250 is in the first rotation position, the width of the central portion in the axial direction is N1c, the width of the end portion in the axial direction is N1e,
When the cam 250 is in the second rotation position, the width of the central portion in the axial direction is N2c, and the width of the end portion in the axial direction is N2e.
N1c> N1e
And N2c <N2e
Meet.

  The fixing device 200 according to the second embodiment has only one motor 81 including a stepping motor as a motor for driving the cam 250. The motor 81 is driven by the control device 90 to position the cam 250 at the first drive position and the second drive position.

  According to the fixing device 200 having such a configuration, like the fixing device 100 of the first embodiment, the cam 250 is positioned at the first rotation position or the second rotation position, thereby The upstream portion in the transport direction is pressed by the first upstream contact surface 211 or the second upstream contact surface 221, and the downstream portion in the transport direction is pressed by the first downstream contact surface 212 or the second downstream contact surface 222. . For this reason, the pressing force at the central portion and the end in the axial direction of the upstream portion of the pressure pad 140 in the conveying direction and the pressing force at the central portion and the end in the axial direction of the downstream portion in the conveying direction are The position can be appropriately changed according to the position 250. Therefore, according to the fixing device 200, the shape and pressure distribution of the nip surface N between the endless belt 110 and the pressure roller 180 can be variously changed.

[Third Embodiment]
Next, a third embodiment of the present invention will be described. The fixing device 300 according to the third embodiment shown in FIG. 12 differs from the fixing device 200 of the second embodiment only in the shape of the cam 350, and therefore only the differences from the second embodiment will be described. Similar parts are denoted by the same reference numerals in the drawings, and description thereof is omitted.

The cam 350 has a shaft 360 that extends along the cam axis 250A.
The cam 350 includes a first projecting portion 351, a second projecting portion 352, a third projecting portion 353, and a fourth projecting portion 354 that project from the shaft 360 in a direction perpendicular to the cam axis 250A.

The first protrusion 351 has a first upstream contact surface 211 at the tip.
The second protrusion 352 has a first downstream contact surface 212 at the tip.
The third protrusion 353 has a second upstream contact surface 221 at the tip.
The fourth protrusion 354 has a second downstream contact surface 222 at the tip.

The cam 350 can be rotated to a first rotation position and a second rotation position by the motor 81. At the first rotation position shown in FIG. 12, the first upstream contact surface 211 and the first downstream contact surface 212 are provided. Contacts the second surface 142 of the pressure pad 140.
The second rotation position is a position rotated 180 degrees around the cam axis 250A with respect to the first rotation position (not shown). At the first rotation position, the second rotation contact surface 221 and The second downstream contact surface 222 contacts the second surface 142 of the pressure pad 140.

  Also with the fixing device 300 having such a configuration, the same operational effects as those of the fixing device 200 of the second embodiment can be obtained.

[Fourth Embodiment]
Next, a fourth embodiment of the present invention will be described. The fixing device 400 according to the fourth embodiment shown in FIG. 13 differs from the fixing device 100 according to the first embodiment in a mechanism for pressing the pressure pad 140. In the fourth embodiment, only different points from the first embodiment will be described, and the same parts are denoted by the same reference numerals and description thereof will be omitted.

The fixing device 400 includes a pressing mechanism 420 as a mechanism for pressing the second surface 142, and a control device 490 that controls the pressing mechanism 420.
The pressing mechanism 420 includes a base 430, an upstream pressing mechanism 450 and a downstream pressing mechanism 460 provided on the base 430.

  The upstream pressing mechanism 450 has a plurality of upstream pressing pins 452 arranged in the axial direction of the pressure roller 180 and capable of pressing the second surface 142 of the pressure pad 140 (see FIG. 14A). The upstream pressing pin 452 is supported by the cylinder 451 so as to move forward and backward toward the second surface 142. The upstream pressing pin 452 has a magnet (not shown), and the cylinder 451 has a coil (not shown).

  The downstream pressing mechanism 460 is disposed on the downstream side in the transport direction with respect to the upstream pressing mechanism 450. The downstream pressing mechanism 460 includes a plurality of downstream pressing pins 462 that can press the second surface 142 of the pressure pad 140 arranged in the axial direction of the pressure roller 180 (see FIG. 14B). The downstream pressing pin 462 has a magnet (not shown), and the cylinder 461 has a coil (not shown).

The control device 490 is configured to move the plurality of upstream pressing pins 452 and the plurality of downstream pressing pins 462 forward and backward with respect to the second surface 142 of the pressure pad 140. Specifically, an instruction is output from the control device 490 to a power source (not shown), and current is supplied to the coils of the cylinders 451 and 461 so that the upstream pressing pins 452 and the downstream pressing pins 462 are connected to the current. Advancing toward the second surface 142 with a pressing force according to.
The control device 490 sets the plurality of upstream pressing pins 452 and the plurality of downstream pressing pins 462 in the first state shown in FIG. 14 and the first state according to the type of the paper P included in the print data and the instruction from the operation panel. A transition is made to the second state shown in FIG. 15, which is different from the state.

As shown in FIGS. 14A and 14B, in the first state, the upstream pressing pin 452 and the downstream pressing pin 462 at the center in the axial direction are more than the upstream pressing pin 452 and the downstream pressing pin 462 at the end. It is in a protruding state.
Specifically, first, a plane passing through both end portions 142E and 142E (see FIG. 13) in the transport direction of the first surface 141 of the pressure pad 140 is defined as a plane PL1. A plane that is parallel to the plane PL1 and that is opposite to the axis 181A of the pressure roller 180 with respect to the tip portions of the plurality of upstream pressing pins 452 and the plurality of downstream pressing pins 462 is a reference plane. PL2 is assumed. The reference plane PL2 is not particularly limited as long as the above condition is satisfied. In the present embodiment, for example, the reference plane PL2 is a plane that passes through the positions of the upper ends of the cylinders 451 and 461.
In the first state, the distance from the reference plane PL2 to the tip of the upstream pressing pin 452 at the center in the axial direction is D1uc,
In the first state, the distance from the reference plane PL2 to the tip of the upstream pressing pin 452 at the end in the axial direction is D1ue,
In the first state, the distance from the reference plane PL2 to the tip of the downstream pressing pin 462 at the center in the axial direction is D1dc,
In the first state, the distance from the reference plane PL2 to the tip of the downstream pressing pin 462 at the end in the axial direction is D1de,
D1uc-D1ue> 0
And D1dc-D1de> 0
It is.
Moreover, it is D1dc-D1de> D1uc-D1ue like 1st Embodiment.

As shown in FIGS. 15A and 15B, in the second state, the upstream pressing pin 452 and the downstream pressing pin 462 at the center in the axial direction are more than the upstream pressing pin 452 and the downstream pressing pin 462 at the end. It is in a retreated state.
In the second state, the distance from the reference plane PL2 to the tip of the upstream pressing pin 452 at the center in the axial direction is D2uc,
In the second state, the distance from the reference plane PL2 to the tip of the upstream pressing pin 452 at the end in the axial direction is D2ue,
In the second state, the distance from the reference plane PL2 to the tip of the downstream pressing pin 462 at the center in the axial direction is D2dc,
In the second state, the distance from the reference plane PL2 to the tip of the downstream pressing pin 462 at the end in the axial direction is D2de,
D2uc-D2ue <0
And D2dc−D2de <0
It is.
Similarly to the first embodiment, D2dc-D2de <D2uc-D2ue (| D2dc-D2de |> | D2uc-D2ue |).

That is,
D2uc-D2ue is different from D1uc-D1ue,
D2uc-D2ue <D1uc-D1ue.
Also,
D2dc-D2de is different from D1dc-D1de,
D1dc-D1de> D1uc-D1ue.
Also,
D2dc-D2de is different from D2uc-D2ue,
It is D2dc-D2de <D2uc-D2ue.

  With such a configuration, the control device 490 causes the plurality of upstream pressing pins 452 and the plurality of downstream pressing pins 462 to be in the first state shown in FIG. Then, as in the first embodiment, the nip surface N has a shape as shown in FIG. Further, for example, when thin paper or the like is fed, the control device 490 puts the plurality of upstream pressing pins 452 and the plurality of downstream pressing pins 462 into the second state shown in FIG. Then, as in the first embodiment, the nip surface N has a shape as shown in FIG.

For this reason, in the first state, the center nip width in the axial direction is N1c, the end nip width in the axial direction is N1e,
In the second state, the center nip width in the axial direction is N2c, the end nip width in the axial direction is N2e,
N1c> N1e
And N2c <N2e
Meet.

  Thus, according to the fixing device 400 of the present embodiment, the plurality of upstream pressing pins 452 of the upstream pressing mechanism 450 and the plurality of downstream pressing pins 462 of the downstream pressing mechanism 460 are set to the first state or the second state. As a result, the upstream portion of the pressure pad 140 in the conveying direction is pressed by the upstream pressing pin 452 and the downstream pressing pin 462, and the pressure is applied according to the protruding amount of each upstream pressing pin 452 and each downstream pressing pin 462. The pad 140 is pressed. Therefore, according to the fixing device 400, the shape and pressure distribution of the nip surface N between the endless belt 110 and the pressure roller 180 can be variously changed.

  In this embodiment, the arrangement of the protrusion amounts of the upstream pressing pin 452 and the downstream pressing pin 462 is shown only in the first state in FIG. 14 and the second state in FIG. Can be realized. For example, an arrangement that realizes all the shapes of the first cam 150 and the second cam 160 shown in the first embodiment can be stored in advance in a storage unit included in the control device 490. Further, the arrangement of protrusion amounts may be corrected according to the environment such as temperature and humidity with respect to the arrangement of protrusion amounts stored in advance.

  Although the embodiment of the present invention has been described above, the present invention is not limited to the above-described embodiment, and can be implemented with appropriate modifications.

  For example, in the above-described embodiment, the configuration is such that D2uc-D2ue <D1uc-D1ue, but the configuration may be such that D2uc-D2ue> D1uc-D1ue.

  Moreover, in the said embodiment, although it was comprised so that it might become D2dc-D2de> D1dc-D1de, you may comprise so that it may become D2dc-D2de> D1dc-D1de.

  In the embodiment, the heater is provided in the endless belt, but the heater may not be provided in the endless belt.

  In the above-described embodiment, the paper P such as a horizontal paper, a thick paper, and a thin paper has been exemplified as the recording sheet. There may be.

  In addition, you may implement combining each element demonstrated by the said embodiment and the modification arbitrarily.

DESCRIPTION OF SYMBOLS 10 Laser printer 81 Motor 82 Motor 90 Control apparatus 100 Fixing apparatus 110 Endless belt 111 Inner peripheral surface 140 Pressure pad 141 1st surface 142 2nd surface 150 1st cam 150A 1st axis 151 151 1st upstream contact surface 152 2nd upstream Contact surface 160 Second cam 160A Second axis 161 First downstream contact surface 162 Second downstream contact surface 180 Pressure roller N Nip surface P Paper PL2 Reference plane

Claims (20)

Endless belt,
A pressure pad having a first surface in contact with the inner peripheral surface of the endless belt, and a second surface located on the opposite side of the first surface;
A roller for sandwiching the endless belt between the pressure pad and conveying the recording sheet in the conveying direction with the endless belt;
A first cam in contact with the second surface, wherein the first cam rotates around a first axis extending in an axial direction of the roller to a first rotation position and a second rotation position different from the first rotation position; A first cam that
A second cam that is in contact with the second surface, and is disposed downstream of the first cam in the transport direction and extends around the second axis extending in the axial direction; A second cam that rotates to a fourth rotation position different from the third rotation position;
The first cam is
A first upstream contact surface that contacts the second surface when in the first rotational position;
A second upstream contact surface that contacts the second surface when in the second rotational position;
The second cam is
A first downstream contact surface that contacts the second surface when in the third rotational position;
A second downstream contact surface that contacts the second surface when in the fourth rotational position;
D1uc, the distance from the first axis to the central portion of the first upstream contact surface in the axial direction
A distance from the first axis to the end of the first upstream contact surface in the axial direction is D1ue,
D2uc, the distance from the first axis to the center of the second upstream contact surface in the axial direction
A distance from the first axis to the end of the second upstream contact surface in the axial direction is D2ue,
D1dc, the distance from the second axis to the central portion of the first downstream contact surface in the axial direction
The distance from the second axis to the end of the first downstream contact surface in the axial direction is D1de,
A distance from the second axis to the center of the second downstream contact surface in the axial direction is D2dc,
The distance from the second axis to the end of the second downstream contact surface in the axial direction is D2de,
D2uc-D2ue is different from D1uc-D1ue,
D2dc-D2de is different from D1dc-D1de,
A fixing device, wherein D2dc-D2de is different from D2uc-D2ue.   The fixing device according to claim 1, wherein the first cam and the second cam are independently rotatable.   The fixing device according to claim 1, further comprising at least one motor that rotates the first cam and the second cam. The width of the nip surface between the endless belt and the roller in the transport direction is:
When the first cam is in the first rotation position and the second cam is in the third rotation position, the width of the central portion in the axial direction is N1c, and the width of the end portion in the axial direction is N1e. ,
When the first cam is in the second rotation position and the second cam is in the fourth rotation position, the width of the central portion in the axial direction is N2c, and the width of the end portion in the axial direction is N2e. As,
N1c> N1e
And N2c <N2e
The fixing device according to claim 1, wherein the fixing device satisfies the following conditions. Endless belt,
A pressure pad having a first surface in contact with the inner peripheral surface of the endless belt, and a second surface located on the opposite side of the first surface;
A roller for sandwiching the endless belt between the pressure pad and conveying the recording sheet in the conveying direction with the endless belt;
A cam that contacts the second surface and is rotatable about a cam axis extending in the axial direction of the roller to a first rotation position and a second rotation position different from the first rotation position. And
The cam
A first upstream contact surface that contacts the second surface when in the first rotation position, and a first downstream surface that contacts the second surface downstream of the first upstream contact surface in the transport direction. A contact surface, a second upstream contact surface that contacts the second surface when in the second rotation position, and the second surface on the downstream side in the transport direction from the second upstream contact surface. A second downstream contact surface,
A distance from the cam axis to the center of the first upstream contact surface in the axial direction is D1uc,
A distance from the cam axis to the end of the first upstream contact surface in the axial direction is D1ue,
D2uc, the distance from the cam axis to the center of the second upstream contact surface in the axial direction
A distance from the cam axis to the end of the second upstream contact surface in the axial direction is D2ue,
A distance from the cam axis to the center of the first downstream contact surface in the axial direction is D1dc,
A distance from the cam axis to the end of the first downstream contact surface in the axial direction is D1de,
A distance from the cam axis to the center of the second downstream contact surface in the axial direction is D2dc,
The distance from the cam axis to the end of the second downstream contact surface in the axial direction is D2de,
D2uc-D2ue is different from D1uc-D1ue,
D2dc-D2de is different from D1dc-D1de,
A fixing device, wherein D2dc-D2de is different from D2uc-D2ue. The cam has a first cam surface and a second cam surface disposed around the cam axis;
The first upstream contact surface and the first downstream contact surface are located on the first cam surface,
The fixing device according to claim 5, wherein the second upstream contact surface and the second downstream contact surface are positioned on the second cam surface. The cam
A shaft extending along the cam axis;
A first protrusion protruding from the shaft in a direction perpendicular to the cam axis, and having the first upstream contact surface at a tip;
A second protrusion that protrudes from the shaft in a direction perpendicular to the cam axis, and has the first downstream contact surface at a tip;
A third protrusion that protrudes from the shaft in a direction perpendicular to the cam axis and has the second upstream contact surface at the tip;
The fixing device according to claim 5, further comprising: a fourth protrusion that protrudes from the shaft in a direction orthogonal to the cam axis and has the second downstream contact surface at a tip.   The fixing device according to claim 5, further comprising a motor that rotates the cam. The width of the nip surface between the endless belt and the roller in the transport direction is:
When the cam is in the first rotation position, the width of the central portion in the axial direction is N1c, the width of the end portion in the axial direction is N1e,
When the cam is in the second rotation position, the width of the central portion in the axial direction is N2c, the width of the end portion in the axial direction is N2e,
N1c> N1e
And N2c <N2e
The fixing device according to claim 5, wherein the fixing device satisfies the following condition. Endless belt,
A pressure pad having a first surface in contact with the inner peripheral surface of the endless belt, and a second surface located on the opposite side of the first surface;
A roller for sandwiching the endless belt between the pressure pad and conveying the recording sheet in the conveying direction with the endless belt;
An upstream pressing mechanism having a plurality of upstream pressing pins arranged in the axial direction of the roller and capable of pressing the second surface;
A downstream pressing mechanism having a plurality of downstream pressing pins arranged on the downstream side in the transport direction with respect to the upstream pressing mechanism and arranged in the axial direction of the roller and capable of pressing the second surface;
A control device capable of moving the plurality of upstream pressing pins and the plurality of downstream pressing pins forward and backward relative to the second surface, wherein the plurality of upstream pressing pins and the plurality of downstream pressing pins A control device that moves between a first state and a second state different from the first state,
The first surface is parallel to a plane passing through both end portions in the transport direction, and is opposite to the roller axis with respect to the tip portions of the plurality of upstream pressing pins and the plurality of downstream pressing pins. Is the reference plane,
In the first state, D1uc represents the distance from the reference plane to the tip of the upstream pressing pin at the center in the axial direction,
In the first state, D1ue is the distance from the reference plane to the tip of the upstream pressing pin at the end in the axial direction,
In the second state, the distance from the reference plane to the tip of the upstream pressing pin at the center in the axial direction is D2uc,
In the second state, the distance from the reference plane to the tip of the upstream pressing pin at the end in the axial direction is D2ue,
In the first state, the distance from the reference plane to the tip of the downstream pressing pin at the center in the axial direction is D1dc,
In the first state, the distance from the reference plane to the tip of the downstream pressing pin at the end in the axial direction is D1de,
In the second state, the distance from the reference plane to the tip of the downstream pressing pin at the center in the axial direction is D2dc,
In the second state, the distance from the reference plane to the tip of the downstream pressing pin at the end in the axial direction is D2de,
D2uc-D2ue is different from D1uc-D1ue,
D2dc-D2de is different from D1dc-D1de,
A fixing device, wherein D2dc-D2de is different from D2uc-D2ue. The width of the nip surface between the endless belt and the roller in the transport direction is:
In the first state, the width of the central portion in the axial direction is N1c, the width of the end portion in the axial direction is N1e,
In the second state, the width of the central portion in the axial direction is N2c, the width of the end portion in the axial direction is N2e,
N1c> N1e
And N2c <N2e
The fixing device according to claim 10, wherein:   The fixing device according to any one of claims 1 to 11, wherein D1dc-D1de is different from D1uc-D1ue.   The fixing device according to claim 1, wherein D2uc−D2ue> D1uc−D1ue.   The fixing device according to claim 1, wherein D2uc−D2ue <D1uc−D1ue.   The fixing device according to claim 1, wherein D2dc−D2de> D1dc−D1de.   The fixing device according to claim 1, wherein D2dc−D2de <D1dc−D1de.   The fixing device according to claim 1, wherein D2dc−D2de> D2uc−D2ue.   The fixing device according to claim 1, wherein D2dc−D2de <D2uc−D2ue.   The fixing device according to claim 1, wherein D1dc−D1de> D1uc−D1ue.   The fixing device according to claim 1, wherein D1dc−D1de <D1uc−D1ue.

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