JP2019061160A - Fixation device - Google Patents

Abstract

To reduce pressure pad manufacturing errors and fitting errors and reduce a difference in lateral nip pressure distribution.SOLUTION: A fixation device comprises a first pressure pad 110 for sandwiching an endless belt 83 between a counter member (heating roller 81) and itself and elastically deforming the endless belt 83, and a stay (first stay 120) including a support surface 121A for supporting the first pressure pad 110 from the side opposite the counter member and having higher rigidity than the first pressure pad 110. The support surface 121A is inclined so as to be located increasingly away from the counter member as it gets nearer from the middle toward either lateral end of the endless belt 83 in a nip release state where the endless belt 83 is not sandwiched between the counter member and the first pressure pad 110. The first pressure pad 110 is fixed to the support surface 121A. The thickness of the first pressure pad 110 in a nip release state is constant at least in an area TA where the first pressure pad 110 comes in contact with the inner circumferential surface 83A of the endless belt 83.SELECTED DRAWING: Figure 5

Description

  The present invention relates to a fixing device for fixing a developer on a recording medium.

  Conventionally, as a fixing device, one having a heating roller and a pressure pad sandwiching an endless belt between the heating roller is known (see Patent Document 1). Specifically, in this technology, the pressure pad is made of an elastic material such as rubber, and the thickness of the central portion is larger than the thickness of both ends in the direction in which the heating roller and the pressure pad are opposed. This makes it possible to suppress the pressure drop at the center of the pressure pad, so that it is possible to suppress the nip pressure distribution from being greatly different between the central portion and both ends in the width direction of the endless belt. It has become.

JP, 2009-109932, A

  However, in the case where the shape of the pressure pad made of an elastic body is formed into the complicated shape as described above as in the prior art, the manufacturing error of the pressure pad and the attachment when attaching the pressure pad to other members Since errors and the like tend to be large, it may not be possible to reduce the difference in nip pressure distribution in the width direction.

  Therefore, an object of the present invention is to reduce the difference in the nip pressure distribution in the width direction while reducing the manufacturing error and the mounting error of the pressure pad.

In order to solve the above problems, the fixing device according to the present invention is in contact with a heater, an opposing member heated by the heater, an endless belt, and the inner circumferential surface of the endless belt, and between the opposing member It has a first pressure pad that elastically deforms across the endless belt, and a support surface that supports the first pressure pad from the opposite side to the opposing member, and has higher rigidity than the first pressure pad. And a stay.
The support surface is located at a position farther from the opposing member as it goes from the center to both ends in the width direction of the endless belt in a nip release state in which the endless belt is not sandwiched between the opposing member and the first pressure pad. Tilt to position.
The first pressure pad is fixed to the support surface.
The thickness of the first pressure pad in the nip release state is constant in at least a region where the first pressure pad and the inner circumferential surface of the endless belt are in contact with each other.

  According to this configuration, since the first pressure pad having a constant thickness is fixed to the convex support surface formed in the stay having higher rigidity than the first pressure pad, for example, the thickness of the first pressure pad The difference in the nip pressure distribution in the width direction can be reduced while making the manufacturing error and the mounting error of the first pressure pad smaller, as compared with the case where the nip pressure distribution in the width direction is adjusted by changing.

  According to the present invention, it is possible to reduce the difference in the nip pressure distribution in the width direction while reducing the manufacturing error and the mounting error of the pressure pad.

FIG. 1 is a cross-sectional view of an image forming apparatus provided with a fixing device according to an embodiment of the present invention. FIG. 2 is a cross-sectional view of a fixing device. It is a perspective view which disassembles and shows a 1st pressurizing unit. It is a perspective view which shows the state which assembled the 1st pressurization unit. It is a figure which shows the heating roller and 1st pressurization unit in a nip release state. It is a figure which shows the heating roller and 1st pressurization unit in a nip state. It is a graph which shows nip pressure distribution in the cross direction. They are a perspective view (a) which disassembles and shows a 2nd pressurization unit, and a perspective view (b) showing the state where it was assembled. They are a top view (a) which looked at the 2nd pressurization unit of a nip release state from the top, and a top view (b) which looked at the 2nd pressurization unit of the nip state from the top. Sectional drawing (a) which shows the cross section of the center part of the width direction of each pressurization unit in a nip state, graph (b) which shows the nip pressure distribution in the moving direction of FIG. 10 (a), Each pressurization in a nip state It is sectional drawing (c) which shows the cross section of the edge part of the width direction of a unit, and graph (d) which shows nip pressure distribution in the moving direction of FIG.10 (c). FIG. 7A is a cross-sectional view showing a cross-section of the central portion in the width direction of each pressing unit in the nip release state, and FIG. 7B is a cross-sectional view showing the cross section in the width direction of each pressing unit in the nip release state. .

  Next, an embodiment of the present invention will be described in detail with reference to the drawings as appropriate. In the following description, the direction is “front” on the right side toward the paper surface in FIG. 1 and “rear” on the left side toward the paper surface, “left” on the paper surface, and back toward the paper surface. Let the side be "right". Also, the up and down direction is referred to as “up and down” toward the paper surface.

  As shown in FIG. 1, the laser printer 1 mainly includes a sheet feeding unit 3, an exposure device 4, a process cartridge 5, and a fixing device 8 in a housing 2.

  The sheet feeding unit 3 is mainly provided with a sheet feeding tray 31 provided at a lower portion in the housing 2 and accommodating the sheet S, a sheet pressing plate 32 and a sheet feeding mechanism 33. The sheet S accommodated in the sheet feeding tray 31 is moved upward by the sheet pressing plate 32, and is supplied to the process cartridge 5 by the sheet feeding mechanism 33.

  The exposure device 4 is disposed at the upper portion in the housing 2 and includes a light source device (not shown), a polygon mirror, a lens, a reflecting mirror, etc. In the exposure device 4, the light beam based on the image data emitted from the light source device is scanned at high speed on the surface of the photosensitive drum 61 to expose the surface of the photosensitive drum 61.

  The process cartridge 5 is disposed below the exposure device 4 and is attachable to and detachable from the housing 2 through an opening formed when the front cover 21 provided on the housing 2 is opened. The process cartridge 5 includes a drum unit 6 and a developing unit 7. The drum unit 6 mainly includes a photosensitive drum 61, a charger 62, and a transfer roller 63. Further, the developing unit 7 is attachable to and detachable from the drum unit 6, and mainly includes a developing roller 71, a supply roller 72, a layer thickness regulating blade 73, and an accommodating portion 74 for accommodating toner. .

  In the process cartridge 5, the surface of the photosensitive drum 61 is uniformly charged by the charger 62, and then exposed by the light beam from the exposure device 4. An electrostatic latent image is formed. Further, the toner in the housing portion 74 is supplied to the developing roller 71 through 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 fixed thickness on the developing roller 71. It is carried. 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 sheet S 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 sheet S.

  The fixing device 8 is disposed behind the process cartridge 5. The sheet S on which the toner image is transferred passes through the fixing device 8 and the toner image is fixed. The sheet S on which the toner image is fixed is discharged onto the sheet discharge tray 22 by the conveyance rollers 23 and 24.

  As shown in FIG. 2, the fixing device 8 includes a heating roller 81 as an example of an opposing member, a heater 82, an endless belt 83, a first pressure unit 100, and a second pressure unit 200. ing. In the following description, the width direction of endless belt 83 is simply referred to as “width direction”, and a portion of endless belt 83 sandwiched by heating roller 81 and first pressure unit 100 or second pressure unit 200. The moving direction of is simply referred to as "moving direction", and the direction perpendicular to the moving direction and the width direction is also referred to as "first direction". In the present embodiment, the width direction is along the left-right direction, the movement direction is along the front-rear direction, and the first direction is along the up-down direction.

  The heating roller 81 is a cylindrical member and, as an example, is formed by forming a releasing layer made of a fluorocarbon resin or the like on the outer peripheral surface of a raw pipe made of a metal such as aluminum. The heating roller 81 is rotatably supported by a frame (not shown) of the fixing device 8, and the driving force is inputted from the motor (not shown) provided in the housing 2 of the laser printer 1 in the clockwise direction of FIG. Drive to rotate.

  The heater 82 is a heater that heats the heating roller 81, and is disposed inside the heating roller 81. As the heater 82, for example, a halogen lamp which emits light by energization and heats the heating roller 81 by radiant heat can be used.

  The endless belt 83 is a tubular member and has flexibility. The endless belt 83 is formed, for example, by forming a release layer made of fluorine resin or the like on the outer peripheral surface of a base material made of metal such as stainless steel or resin such as polyimide resin. The endless belt 83 is provided so as to be driven to rotate counterclockwise in FIG. 2 by the rotation of the heating roller 81.

  A lubricant such as grease is disposed on the inner circumferential surface 83A of the endless belt 83. Thus, the slidability between the inner circumferential surface 83A of the endless belt 83 and the pressure units 100 and 200 can be enhanced, so that the endless belt 83 can be rotated satisfactorily.

  Each pressing unit 100 and 200 has a nip state (see FIG. 10) sandwiching the endless belt 83 with the heating roller 81 and a nip release state (see FIG. 11) in which the endless belt 83 is not pinched between the heating roller 81 And is configured to be able to take Specifically, for example, one end and the other end in the width direction of each pressure unit 100, 200 are integrally held by two holding members 300 shown in FIG. Each of the two holding members 300 is biased toward the heating roller 81 by the spring 310 and configured to be pushed away from the heating roller 81 against the biasing force of the spring 310 by a cam (not shown). ing. As a result, it is possible to switch the pressure units 100 and 200 between the nip state and the nip release state. On the contrary, the heating roller 81 is biased toward the pressure units 100 and 200 by a spring to make a nip state, and the heating roller 81 is pressed by the cam against the biasing force of the spring. By pressing in a direction away from the units 100 and 200, a nip release state may be set.

  The first pressure unit 100 includes a first pressure pad 110, a first stay 120 as an example of a stay, an upstream holder 130, and a downstream holder 140. The first pressure pad 110 is in contact with the inner circumferential surface 83 A of the endless belt 83 and sandwiches the endless belt 83 with the heating roller 81.

  The second pressure unit 200 includes a second pressure pad 210, a second stay 220, and a holder 230. The second pressure pad 210 is in contact with the inner circumferential surface 83 A of the endless belt 83 and sandwiches the endless belt 83 with the heating roller 81. The second pressure pad 210 is disposed upstream of the first pressure pad 110 of the first pressure unit 100 in the movement direction.

  As shown in FIG. 3, the first pressure pad 110 of the first pressure unit 100 is a rectangular solid, and is formed in a long shape that is long in the left-right direction. The first pressure pad 110 is elastically deformable by being formed of an elastic material such as rubber.

  The first stay 120 is a frame for supporting the first pressure pad 110. The first stay 120 is made of resin or metal that is more rigid than the first pressure pad 110. The first stay 120 is larger than the first pressure pad 110 in the width direction (see FIG. 4). The first stay 120 includes a base 121 to which the first pressure pad 110 is fixed, an upstream wall 122 extending from the upstream end of the movement direction of the base 121 in a direction away from the first pressure pad 110, and movement of the base 121 And a downstream wall 123 extending in the direction away from the first pressure pad 110 from the downstream end in the direction.

  The upper surface of the base 121 is a support surface 121 A that supports the first pressure pad 110 from the side opposite to the heating roller 81. The base 121 is curved to be convex toward the heating roller 81. Thereby, as shown in FIG. 5, in the nip release state where the support surface 121A does not sandwich the endless belt 83 between the heating roller 81 and the first pressure pad 110, the support surface 121A is from the center in the width direction of the endless belt 83. It inclines so that it may be located in the position far from the heating roller 81 as it goes to the both ends.

  In other words, the support surface 121 </ b> A is a curved surface that is convex toward the heating roller 81. In the present embodiment, in the width direction, the first pressure pad 110 is larger than the endless belt 83, and the support surface 121A is larger than the first pressure pad 110. Then, both ends of the first pressure pad 110 protrude from both ends of the endless belt 83, and both ends of the support surface 121A protrude from both ends of the first pressure pad 110.

  In the present embodiment, the entire support surface 121A is a curved surface, but the present invention is not limited to this. For example, the shape of the support surface 121A may be a curved surface at least in the image forming area GA of the largest sheet that can be fixed by the fixing device 8. For example, the shape of the support surface 121A may be a curved surface only within the width BS of the maximum sheet that can be fixed by the fixing device 8, or the width BL of the release layer 81A formed on the outer peripheral surface of the heating roller 81 It may be a curved surface only. The shape of the support surface 121A may be a curved surface only in the area TA where the first pressure pad 110 and the inner circumferential surface 83A of the endless belt 83 contact.

  The first pressure pad 110 is fixed to the support surface 121A. Specifically, the first pressure pad 110 is adhesively fixed directly to the support surface 121A. As shown in FIGS. 4 and 5, the thickness TH of the first pressure pad 110 in the nip release state, specifically, the thickness TH in the direction in which the first pressure pad 110 and the heating roller 81 face each other is at least the first Within the area TA where the pressure pad 110 and the inner circumferential surface 83A of the endless belt 83 come into contact, it is constant. In other words, in the nip release state, the height from the support surface 121A of the first pressure pad 110 is constant at least in the area TA.

  As shown in FIG. 3, the upstream wall 122 of the first stay 120 is formed with a plurality of holes H3. A plurality of screws SC for fixing the upstream holder 130 to the upstream wall 122 are fastened to the plurality of holes H3.

  In the downstream wall 123 of the first stay 120, a plurality of holes H4 are formed. A plurality of screws SC for fixing the downstream holder 140 to the downstream wall 123 are fastened to the plurality of holes H4.

  The upstream holder 130 is a plate-like member made of resin or metal, and is disposed upstream of the first pressure pad 110 in the movement direction. The upstream holder 130 is formed with a plurality of holes H5 through which the plurality of screws SC can be inserted.

  The downstream holder 140 has substantially the same structure as the upstream holder 130, and more specifically, has a symmetrical structure in the front-rear direction. Specifically, the downstream holder 140 is a plate-like member made of resin or metal, and is disposed downstream of the first pressure pad 110 in the movement direction. The downstream holder 140 is formed with a plurality of holes H6 through which the plurality of screws SC can be inserted.

  As shown in FIGS. 4 and 5, in the state where the upstream holder 130 and the downstream holder 140 are attached to the first stay 120, a part thereof protrudes from the support surface 121A toward the heating roller 81 side. The upstream holder 130 and the downstream holder 140, and more specifically, the portions of the holders 130 and 140 that project from the support surface 121A toward the heating roller 81 are in contact with the first pressure pad 110 in the nip release state.

  The first edge E1, which is the edge on the heating roller 81 side of the upstream holder 130, is inclined along the support surface 121A. Specifically, the first edge E1 is formed in a convex curve along the support surface 121A which is a convex curved surface.

  The second edge E2, which is the edge on the heating roller 81 side of the downstream holder 140, is inclined along the support surface 121A (see also FIG. 3). Specifically, the second edge E2 is formed in a convex curve along the support surface 121A which is a convex curve.

  As shown in FIG. 6, both ends of the first stay 120 are biased toward the heating roller 81 in the nip state of the first pressure unit 100. Therefore, if the support surface 121A is flat, as shown by a broken line in FIG. 7, the distribution of the nip pressure between the heating roller 81 and the first pressure pad 110 is high at both ends, and the central portion Distribution becomes lower. On the other hand, in the present embodiment, since the support surface 121A is a convex curved surface, as shown by a solid line in FIG. 7, the nip pressure at the central portion in the width direction can be increased, and the nip pressure in the width direction It is possible to reduce the difference in distribution.

  As shown in FIGS. 8A and 8B, the second pressure pad 210 of the second pressure unit 200 is a rectangular solid, and is formed in a long shape that is long in the left-right direction. The second pressure pad 210 can be elastically deformed by being formed of an elastic material such as rubber.

  The second stay 220 is a frame for supporting the second pressure pad 210. The second stay 220 is made of resin or metal. The second stay 220 includes a base 221 to which the second pressure pad 210 is fixed, an upstream wall 222 extending away from the second pressure pad 210 from an upstream end in the moving direction of the base 221, and a movement of the base 221 And a downstream wall 223 extending in a direction away from the second pressure pad 210 from the downstream end in the direction. The upstream wall 222 is formed with a plurality of holes H1. A plurality of screws SC for fixing the holder 230 to the upstream wall 222 are fastened to the plurality of holes H1.

  The holder 230 is made of resin or metal. The holder 230 has a base 231 overlapping the second stay 220 in the movement direction, and a wall 232 not overlapping the second stay 220 in the movement direction (see FIG. 2). The base 231 is formed with a plurality of holes H2 through which a plurality of screws SC for fixing the holder 230 to the upstream wall 222 of the second stay 220 can be inserted.

  The wall 232 protrudes toward the heating roller 81 more than the base 221 of the second stay 220 and also protrudes upstream of the base 231 of the holder 230 in the moving direction. The wall 232 is disposed upstream of the second pressure pad 210 in the movement direction. The wall 232 has a height such that the endless belt 83 is not pinched with the heating roller 81 (see FIG. 2). In the present embodiment, the wall 232 is disposed at a position away from the endless belt 83.

  As shown in FIG. 9A, the wall 232 has an opposing surface F1 that faces the second pressure pad 210 in the movement direction. Here, FIG. 9A shows a nip release state in which the endless belt 83 is not pinched between the heating roller 81 and the second pressure pad 210. In this nip release state, among the side surfaces of the second pressure pad 210, the upstream side face F2 opposite to the wall 232, and more specifically, the upstream side face F2 opposite to the wall 232 in the movement direction is a plane orthogonal to the movement direction. There is.

  The opposing surface F1 has a first contact portion F11 located at one end side in the width direction, a second contact portion F12 located at the other end side in the width direction, and a central portion F13 located at the center in the width direction ing. The first contact portion F11 and the second contact portion F12 are flat along the upstream side face F2 of the second pressure pad 210. The first contact portion F11 and the second contact portion F12 are in contact with the upstream side surface F2 of the second pressure pad 210 in the nip release state.

  A portion of the facing surface F1 between the first contact portion F11 and the second contact portion F12 is a continuous curved surface F14 recessed toward the upstream side in the movement direction. Thus, the central portion F13, which is a portion near the center of the facing surface F1, is located upstream of the first contact portion F11 and the second contact portion F12 in the moving direction. The central portion F13 is not in contact with the second pressure pad 210 in the nip release state. In other words, the central portion F13 is separated from the upstream side face F2 of the second pressure pad 210 in the nip release state.

  The wall 232 has a first corner C1 located at the boundary between the first contact area F11 and the curved surface F14, and a second corner C2 located at the boundary between the second contact area F12 and the curved surface F14. . The first corner C1 and the second corner C2 are positioned outside the image forming area GA of the largest sheet that can be fixed by the fixing device 8 in the width direction and inside the width BS of the largest sheet. doing.

Next, the function and effect of the fixing device 8 according to the present embodiment will be described.
When each pressing unit 100, 200 shown in FIG. 2 is changed from the nip release state to the nip state, as shown in FIG. 9 (b), the central portion 213 of the second pressure pad 210 is deformed upstream in the moving direction. Do. In the present embodiment, in the nip state, the central portion 213 of the second pressure pad 210 is separated without contacting the wall 232. On the other hand, the deformation of the end portions 211 and 212 of the second pressure pad 210 to the upstream side in the moving direction is restricted by the first contact portion F11 and the second contact portion F12 of the wall 232.

  As a result, as shown in FIGS. 10A to 10D, the pressure peak P1 of each end portion 211, 212 of the second pressure pad 210 is larger than the pressure peak P2 of the central portion 213 and is upstream. When the leading edge of the sheet S penetrates into the nip portion between the second pressure pad 210 and the heating roller 81, each end of the sheet S is easily restrained, and generation of wrinkles of the sheet S occurs. It can be suppressed.

  In the nip state, the distribution of the nip pressure in the width direction of the first pressure pad 110 is substantially uniform as shown in FIG. Therefore, in the nip portion between the first pressure pad 110 and the heating roller 81, the nip pressure can be applied to the sheet S substantially uniformly, so that the toner image can be heat-fixed to the sheet S favorably.

According to the above, the following effects can be obtained in the present embodiment.
In order to control the deformation of the second pressure pad 210 by the shape of the facing surface F1 of the wall 232, the respective end portions 211 and 212 of the second pressure pad 210 are formed regardless of the manufacturing error of the second pressure pad 210. By setting the position of the pressure peak P1 upstream of the pressure peak P2 of the central portion 213, generation of wrinkles of the sheet S can be suppressed.

  Since the portion between the first contact portion F11 and the second contact portion F12 in the facing surface F1 is a continuous curved surface F14, for example, the nip width is smaller than when the recessed portion of the facing surface has a step shape. And the change in nip pressure can be made continuous, and the generation of wrinkles on the sheet S can be further suppressed.

  A portion of the second pressure pad 210 whose deformation is restricted by the first corner C1 and the second corner C2 may adversely affect the image formed in the image forming area GA. On the other hand, in the present embodiment, since the corner portions C1 and C2 are located outside the image forming area GA, a portion of the second pressure pad 210 whose deformation is restricted by the corner portions C1 and C2 is an image. The pressing on the formation area GA can be suppressed, and the deterioration of the image quality can be suppressed.

  Further, the corner portions C1 and C2 are positioned inward of the maximum sheet width BS, so that the width direction of the maximum sheet in the portion of the second pressure pad 210 whose deformation is restricted by the contact portions F11 and F12. Since the nip pressure can be reliably applied to both ends, the occurrence of wrinkles on the maximum sheet can be favorably suppressed.

  Since the second pressure pad 210 is a rectangular parallelepiped, for example, the manufacturing error of the second pressure pad 210 and the second pressure pad 210 as the second stay 220 as compared with the case where the second pressure pad has a complicated shape. Installation error when attaching to

  Since the first pressure pad 110 having a constant thickness is fixed to the convex support surface 121A formed on the first stay 120 having higher rigidity than the first pressure pad 110, for example, the thickness of the first pressure pad The difference in the nip pressure distribution in the width direction can be reduced while the manufacturing error and the mounting error of the first pressure pad 110 are reduced, as compared with the case where the nip pressure distribution in the width direction is adjusted by changing .

  Since the edges E1 and E2 of the holders 130 and 140 are along the convex support surface 121A, for example, compared to the case where the edges of the holders are linear along the width direction, the first The deformation of the widthwise central portion of the pressure pad 110 can be restricted by the holders 130 and 140, and image quality deterioration due to pressure loss at the central portion can be more reliably suppressed.

  Since the shape of the support surface 121A is a curved surface in the image forming area GA of the largest sheet that can be fixed by the fixing device 8, the image quality is deteriorated compared to, for example, a step shape in the image forming area. It can be suppressed.

  Since the first pressure pad 110 is directly adhered and fixed to the support surface 121A, the convex shape of the support surface 121A can be obtained, for example, as compared with a structure in which another member is interposed between the first pressure pad and the support surface. Since one pressure pad 110 can be made to follow, the difference in the nip pressure distribution in the width direction can be made smaller.

  Since the first pressure pad 110 is a rectangular parallelepiped, the manufacturing error of the first pressure pad 110 and the first pressure pad 110 at the first stay 120 can be compared with, for example, a case where the first pressure pad has a complicated shape. Installation error when attaching to

  The present invention is not limited to the above embodiment, and can be used in various forms as exemplified below.

  In the embodiment, the configuration including the two pressure units 100 and 200 as the fixing device 8 is illustrated, but the present invention is not limited thereto, and the fixing device may include at least the first pressure unit. .

  In the embodiment, the second pressure pad 210 is a rectangular solid, but the present invention is not limited to this, and the second pressure pad may have any shape. For example, the second pressure pad may be shaped as in the prior art. Specifically, the second pressure pad may be formed in such a manner that both ends of the upstream edge thereof are positioned upstream of the central portion of the upstream edge.

  In the embodiment, the central portion 213 of the second pressure pad 210 is configured not to contact the wall 232 in the nip state, but the present invention is not limited to this. For example, the central portion of the second pressure pad, specifically, the central portion of the opposite surface may be in contact with the wall in the nip state.

  Although the halogen lamp is illustrated as the heater 82 in the embodiment, the present invention is not limited to this, and the heater may be, for example, a carbon heater.

  Although the heating roller 81 incorporating a heater is illustrated as the facing member in the embodiment, the present invention is not limited to this, and may be an endless heating belt in which the inner circumferential surface is heated by the heater, for example. . Alternatively, an external heating method may be employed in which the heater is disposed outside the facing member and the outer peripheral surface of the facing member is heated, or an induction heating (IH) method. Also, a heater may be disposed inside the endless belt to indirectly heat the opposing member. In addition, the opposing member and the endless belt may each incorporate a heater.

  In the embodiment, the wall 232 is formed on the holder 230 fixed to the second stay 220, but the present invention is not limited to this. For example, in the case of providing a support member provided with a base for supporting the pressure pad from the lower side, the wall may be formed to project from the base toward the heating roller.

  In the embodiment, although the first contact portion F11 and the second contact portion F12 are flat, the present invention is not limited to this, and the first contact portion and the second contact portion may be, for example, curved surfaces. .

  In the said embodiment, although the part between the 1st contact part F11 and the 2nd contact part F12 was made into the continuous curved surface F14 among the opposing surfaces F1, this invention is not limited to this, It dented to the upstream side Any shape may be used as long as it has a shape. Specifically, the portion between the first contact portion and the second contact portion may be a step-like recess or a V-shaped recess.

  In the embodiment, although the first pressure pad 110 is a rectangular solid, the present invention is not limited to this, and the first pressure pad may have any shape. Specifically, the first pressure pad may be formed in such a manner that both ends of its upstream edge are located upstream of the center of the upstream edge. Also in this case, if the thickness of the first pressure pad is constant, the same effect as that of the present embodiment can be obtained.

  In the embodiment, the shape of the support surface 121A is a curved surface, but the present invention is not limited to this, and the support surface may be, for example, a step-like convex shape or a V-shaped convex shape It may be.

  Although the two holders 130 and 140 sandwiching the first pressure pad 110 in the movement direction are provided in the embodiment, the present invention is not limited to this. For example, a holder may be provided only on one side in the moving direction of the first pressure pad, or without providing the holders on both sides in the moving direction of the first pressure pad. Each side may be exposed.

  In addition, each element described in the above-described embodiment and modification may be implemented in any combination.

Reference Signs List 8 fixing device 81 heating roller 82 heater 83 endless belt 83A inner circumferential surface 110 first pressure pad 120 first stay 121A support surface TA area

Claims (6)

With the heater,
An opposing member heated by the heater;
Endless belt,
A first pressure pad that contacts the inner circumferential surface of the endless belt and elastically deforms with the endless belt interposed between the first pressure pad and the opposing member;
A support surface for supporting the first pressure pad from the side opposite to the opposing member, and a stay having a higher rigidity than the first pressure pad;
The support surface is located at a position farther from the opposing member as it goes from the center to both ends in the width direction of the endless belt in a nip release state in which the endless belt is not sandwiched between the opposing member and the first pressure pad. Inclined to be located in
The first pressure pad is fixed to the support surface,
The fixing device according to claim 1, wherein a thickness of the first pressure pad in the nip release state is constant in a region where at least the first pressure pad and the inner circumferential surface of the endless belt contact each other. An upstream holder disposed upstream of the first pressure pad and moving in contact with the first pressure pad in a moving direction of a portion of the endless belt sandwiched by the opposing member and the first pressure pad; ,
A downstream holder disposed downstream of the first pressure pad in the movement direction and in contact with the first pressure pad;
A first end edge which is an end edge on the facing member side of the upstream holder and a second end edge which is an end edge on the facing member side of the downstream holder are inclined along the support surface. The fixing device according to claim 1.   The fixing device according to claim 1, wherein a shape of the supporting surface is a curved surface at least in an image forming area of the largest sheet which can be fixed by the fixing device.   The fixing device according to any one of claims 1 to 3, wherein the first pressure pad is adhesively fixed directly to the support surface.   The fixing device according to any one of claims 1 to 4, wherein the first pressure pad is a rectangular parallelepiped. The endless belt is disposed upstream of the first pressure pad in the moving direction of the portion sandwiched between the opposing member and the first pressure pad, and the endless belt is interposed between the endless belt and the opposing member. A second pressure pad which is elastically deformed by sandwiching
And a wall disposed upstream of the second pressure pad in the movement direction and not sandwiching the endless belt with the opposing member,
The wall has an opposite surface facing the second pressure pad in the movement direction,
The opposite surface is
A first contact portion positioned on one end side in the width direction and in contact with the second pressure pad;
A second contact portion positioned on the other end side in the width direction and in contact with the second pressure pad;
And a central portion located at the center in the width direction and located upstream of the first contact portion and the second contact portion in the moving direction,
The fixing device according to any one of claims 1 to 5, wherein the central portion is not in contact with the second pressure pad in the nip release state.

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