Fixing device and image forming apparatus

Abstract

The invention provides a fixing device and an image forming apparatus. The fixing device includes a fixing member, a heater, a sliding member, a holding member, and a pressing member, an ointment is applied between the heater and the sliding member, and the sliding member includes: a sliding friction portion extending in a second direction and sliding friction with an inner surface of the fixing member; a first rising portion rising from an upstream end of the sliding friction portion in the second direction toward a side away from the pressing member in the third direction; a second rising portion rising from a downstream end of the sliding friction portion in the second direction toward a side away from the pressing member in the third direction; and a protruding part which is provided on at least one of the first rising part and the second rising part, and which protrudes in a direction intersecting with the extending direction of the rising part when viewed in the first direction.

Description

Technical Field

[0001] The present invention relates to a fixing device for fixing an image on a recording material and an image forming device for forming an image on a recording material. Background Art

[0002] Japanese Patent Application Publication No. 2020-3611 (JP2020-003611A) describes a fixing device including: an endless fixing belt; a pressure roller that clamps a recording material together with the fixing belt; a heater arranged on the inner peripheral side of the fixing belt; and a metal plate (heat diffusion member) arranged between the heater and the fixing belt. Summary of the invention

[0003] The present invention provides a new technology capable of improving the performance of a fixing device and an image forming device.

[0004] According to one embodiment of the present invention, a fixing device includes the following components:

[0005] A fixing member, which is annular and rotatable;

[0006] a heater disposed in the internal space of the fixing member and generating heat by supplying electricity;

[0007] a sliding member disposed between the heater and an inner surface of the fixing member and sliding on the inner surface of the fixing member;

[0008] a holding member that holds the heater and the sliding member; and

[0009] a pressing member, the pressing member being arranged to sandwich the fixing member together with the sliding member, and forming a nip portion between the pressing member and the fixing member,

[0010] The fixing device is configured to heat the image on the recording material by the fixing member while the recording material is held and conveyed by the holding portion.

[0011] Grease is applied between the heater and the sliding member.

[0012] The longitudinal direction of the clamping portion is set as the first direction, the recording material conveying direction at the clamping portion is set as the second direction, and the direction orthogonal to both the first direction and the second direction is set as the third direction. In this case,

[0013] The sliding member comprises: a sliding friction portion extending along the second direction and slidingly rubbing against the inner surface of the fixing member; a first rising portion rising from an upstream end of the sliding friction portion in the second direction toward a side away from the pressing member in the third direction; a second rising portion rising from a downstream end of the sliding friction portion in the second direction toward a side away from the pressing member in the third direction; and a protrusion provided on at least one of the first rising portion and the second rising portion, and protruding in a direction intersecting with an extending direction of the rising portion when viewed in the first direction.

[0014] According to another aspect of the present invention, a fixing device includes the following components:

[0015] A fixing member, which is annular and rotatable;

[0016] a heater disposed in the internal space of the fixing member and generating heat by supplying electricity;

[0017] a sliding member disposed between the heater and an inner surface of the fixing member and sliding on the inner surface of the fixing member;

[0018] a holding member that holds the heater and the sliding member; and

[0019] a pressing member, the pressing member being arranged to sandwich the fixing member together with the sliding member, and forming a nip portion between the pressing member and the fixing member,

[0020] The fixing device is configured to heat the image on the recording material by the fixing member while the recording material is held and conveyed by the holding portion.

[0021] The longitudinal direction of the clamping portion is set as the first direction, the recording material conveying direction at the clamping portion is set as the second direction, and the direction orthogonal to both the first direction and the second direction is set as the third direction. In this case,

[0022] The sliding member has a sliding friction portion that slides against the inner surface of the fixing member.

[0023] The holding member comprises: a first facing portion, the first facing portion facing the inner surface of the fixing member upstream of the sliding friction portion in the second direction; and a second facing portion, the second facing portion facing the inner surface of the fixing member downstream of the sliding friction portion in the second direction,

[0024] In the third direction, the first facing portion and the second facing portion are retracted toward a side farther from the pressing member than the sliding friction portion.

[0025] According to another aspect of the present invention, a fixing device includes the following components:

[0026] A fixing member, which is annular and rotatable;

[0027] a heater disposed in the internal space of the fixing member and generating heat by supplying electricity;

[0028] a sliding member disposed between the heater and an inner surface of the fixing member and sliding on the inner surface of the fixing member;

[0029] a holding member that holds the heater and the sliding member; and

[0030] a pressing member, the pressing member being arranged to sandwich the fixing member together with the sliding member, and forming a nip portion between the pressing member and the fixing member,

[0031] The fixing device is configured to heat the image on the recording material by the fixing member while the recording material is held and conveyed by the holding portion.

[0032] The longitudinal direction of the clamping portion is set as the first direction, the recording material conveying direction at the clamping portion is set as the second direction, and the direction orthogonal to both the first direction and the second direction is set as the third direction. In this case,

[0033] The sliding member comprises: a sliding friction portion extending along the second direction and slidingly rubbing against the inner surface of the fixing member; a first guide portion extending in the second direction toward the upstream side of the sliding friction portion to guide the fixing member; and a second guide portion extending in the second direction toward the downstream side of the sliding friction portion to guide the fixing member.

[0034] The first guide portion and the second guide portion are curved along a rotation trajectory of the fixing member when viewed in the first direction.

[0035] According to another aspect of the present invention, a fixing device includes the following components:

[0036] A fixing member, which is annular and rotatable;

[0037] a heater disposed in the internal space of the fixing member and generating heat by supplying electricity;

[0038] a sliding member disposed between the heater and an inner surface of the fixing member and sliding on the inner surface of the fixing member;

[0039] a holding member that holds the heater and the sliding member; and

[0040] a pressing member, the pressing member being arranged to sandwich the fixing member together with the sliding member, and forming a nip portion between the pressing member and the fixing member,

[0041] The fixing device is configured to heat the image on the recording material by the fixing member while the recording material is held and conveyed by the holding portion.

[0042] The longitudinal direction of the clamping portion is set as the first direction, the recording material conveying direction at the clamping portion is set as the second direction, and the direction orthogonal to both the first direction and the second direction is set as the third direction. In this case,

[0043] The width of the clamping portion in the second direction at both ends of the clamping portion in the first direction is greater than the width of the clamping portion in the second direction at the center of the clamping portion in the first direction.

[0044] A width of the sliding member in the second direction at both ends of the clamping portion is greater than a width of the sliding member in the second direction at a center of the clamping portion.

[0045] According to another aspect of the present invention, a fixing device includes the following components:

[0046] A fixing member, which is annular and rotatable;

[0047] a heater disposed in the internal space of the fixing member and generating heat by supplying electricity;

[0048] a sliding member disposed between the heater and an inner surface of the fixing member and sliding on the inner surface of the fixing member;

[0049] a holding member that holds the heater and the sliding member; and

[0050] a pressing member, the pressing member being arranged to sandwich the fixing member together with the sliding member, and forming a nip portion between the pressing member and the fixing member,

[0051] The fixing device is configured to heat the image on the recording material by the fixing member while the recording material is held and conveyed by the holding portion.

[0052] The longitudinal direction of the clamping portion is defined as a first direction, the recording material conveying direction at the clamping portion is defined as a second direction, and a direction orthogonal to both the first direction and the second direction is defined as a third direction.

[0053] The width of the clamping portion in the second direction at both ends of the clamping portion in the first direction is smaller than the width of the clamping portion in the second direction at the center of the clamping portion in the first direction.

[0054] A width of the sliding member in the second direction at both ends of the clamping portion is smaller than a width of the sliding member in the second direction at a center of the clamping portion.

[0055] According to another aspect of the present invention, a fixing device includes the following components:

[0056] A fixing member, which is annular and rotatable;

[0057] a heater disposed in the internal space of the fixing member and generating heat by supplying electricity;

[0058] a sliding member disposed between the heater and an inner surface of the fixing member and sliding on the inner surface of the fixing member;

[0059] a holding member that holds the heater and the sliding member; and

[0060] a pressing member, the pressing member being arranged to sandwich the fixing member together with the sliding member, and forming a nip portion between the pressing member and the fixing member,

[0061] The fixing device is configured to heat the image on the recording material by the fixing member while the recording material is held and conveyed by the holding portion.

[0062] The longitudinal direction of the clamping portion is defined as a first direction, the recording material conveying direction at the clamping portion is defined as a second direction, and a direction orthogonal to both the first direction and the second direction is defined as a third direction.

[0063] The fixing device further includes a guide member for guiding both end portions of the fixing member in the first direction.

[0064] The end surface of the sliding member on the downstream side in the second direction is curved such that a center portion of the end surface in the first direction protrudes toward the downstream side in the second direction more than both ends of the end surface in the first direction.

[0065] According to another aspect of the present invention, a fixing device includes the following components:

[0066] A fixing member, which is annular and rotatable;

[0067] a heater disposed in the internal space of the fixing member and generating heat by supplying electricity;

[0068] a sliding member disposed between the heater and an inner surface of the fixing member and sliding on the inner surface of the fixing member;

[0069] a holding member that holds the heater and the sliding member; and

[0070] a pressing member, the pressing member being arranged to sandwich the fixing member together with the sliding member, and forming a nip portion between the pressing member and the fixing member,

[0071] The fixing device is configured to heat the image on the recording material by the fixing member while the recording material is held and conveyed by the holding portion.

[0072] The longitudinal direction of the clamping portion is defined as a first direction, the recording material conveying direction at the clamping portion is defined as a second direction, and a direction orthogonal to both the first direction and the second direction is defined as a third direction.

[0073] The end surface of the sliding member on the downstream side in the second direction is curved so that both ends of the end surface in the first direction protrude toward the downstream in the second direction more than the center portion of the end surface in the first direction.

[0074] According to another aspect of the present invention, a fixing device includes the following components:

[0075] A fixing member, which is annular and rotatable;

[0076] a heater disposed in the internal space of the fixing member and generating heat by supplying electricity;

[0077] a sliding member disposed between the heater and an inner surface of the fixing member and sliding on the inner surface of the fixing member;

[0078] a holding member that holds the heater and the sliding member; and

[0079] a pressing member, the pressing member being arranged to sandwich the fixing member together with the sliding member, and forming a nip portion between the pressing member and the fixing member,

[0080] The fixing device is configured to heat the image on the recording material by the fixing member while the recording material is held and conveyed by the holding portion.

[0081] The longitudinal direction of the clamping portion is defined as a first direction, the recording material conveying direction at the clamping portion is defined as a second direction, and a direction orthogonal to both the first direction and the second direction is defined as a third direction.

[0082] The fixing device further includes a heat retaining member, which is arranged between the holding member and the heater in the third direction and is used to retain the heat of the heater.

[0083] The heat retaining member is in contact with the sliding member.

[0084] According to another aspect of the present invention, a fixing device includes the following components:

[0085] A fixing member, which is annular and rotatable;

[0086] a heater disposed in the internal space of the fixing member and generating heat by supplying electricity;

[0087] a sliding member disposed between the heater and an inner surface of the fixing member and sliding on the inner surface of the fixing member;

[0088] a holding member that holds the heater and the sliding member; and

[0089] a pressing member, the pressing member being arranged to sandwich the fixing member together with the sliding member, and forming a nip portion between the pressing member and the fixing member,

[0090] The fixing device is configured to heat the image on the recording material by the fixing member while the recording material is held and conveyed by the holding portion.

[0091] The longitudinal direction of the clamping portion is defined as a first direction, the recording material conveying direction at the clamping portion is defined as a second direction, and a direction orthogonal to both the first direction and the second direction is defined as a third direction.

[0092] The sliding member comprises: a sliding friction portion which slides and rubs against the inner surface of the fixing member; and a heat preservation portion which is arranged between the retaining member and the heater in the third direction and is used to maintain the heat of the heater, and the sliding friction portion is formed integrally with the heat preservation portion.

[0093] According to another aspect of the present invention, a fixing device includes the following components:

[0094] A fixing member, which is annular and rotatable;

[0095] a heater disposed in the internal space of the fixing member and generating heat by supplying electricity;

[0096] a sliding member disposed between the heater and an inner surface of the fixing member and sliding on the inner surface of the fixing member;

[0097] a holding member that holds the heater and the sliding member;

[0098] a pressing member, the pressing member being arranged to sandwich the fixing member together with the sliding member, and forming a nip portion between the pressing member and the fixing member;

[0099] a force applying member, the force applying member being used to apply pressure to the clamping portion; and

[0100] a reinforcing member that reinforces the holding member and receives the force of the biasing member to press the holding member toward the pressing member,

[0101] The fixing device is configured to heat the image on the recording material by the fixing member while the recording material is held and conveyed by the holding portion.

[0102] Grease is applied between the heater and the sliding member.

[0103] The longitudinal direction of the clamping portion is defined as a first direction, the recording material conveying direction at the clamping portion is defined as a second direction, and a direction orthogonal to both the first direction and the second direction is defined as a third direction.

[0104] The sliding member comprises: a sliding friction portion extending along the second direction and slidingly rubbing against the inner surface of the fixing member; a first rising portion rising from an upstream end of the sliding friction portion in the second direction toward a side away from the pressing member in the third direction; and a second rising portion rising from a downstream end of the sliding friction portion in the second direction toward a side away from the pressing member in the third direction.

[0105] The holding member has a first recessed portion for accommodating the first rising portion and a second recessed portion for accommodating the second rising portion.

[0106] The position where the reinforcing member presses the holding member is downstream of the first recess and upstream of the second recess in the second direction.

[0107] Further features of the present invention will become apparent from the following description of exemplary embodiments with reference to the attached drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0108] Figure 1 This is a schematic diagram of the image forming apparatus according to Embodiment 1.

[0109] Figure 2 This is a cross-sectional view of the fixing device according to Embodiment 1.

[0110] Figure 3 It is a side view of the fixing device according to the first embodiment.

[0111] Figure 4 This is a cross-sectional view of the belt heating portion according to Example 1.

[0112] Figure 5 It is a diagram showing the movement of thermally conductive paste in a reference example.

[0113] 6( a ) to 6 ( c ) are diagrams showing the movement of the thermally conductive paste in Example 1. FIG.

[0114] Figure 7 This is a diagram for explaining the width of the protrusion according to Example 1.

[0115] Figure 8 This is a perspective view showing an end portion of the sliding plate according to the first embodiment.

[0116] Fig. 9 This is a schematic diagram of an image forming apparatus according to Embodiment 2.

[0117] Fig.10 This is a cross-sectional view of a belt heating portion according to the second embodiment.

[0118] Fig.11This is a diagram showing the movement of the thermally conductive grease in Example 2.

[0119] Fig.12 This is a diagram showing the movement of the thermally conductive grease in Example 2.

[0120] Fig.13 This is a cross-sectional view of a belt heating portion according to the third embodiment.

[0121] Fig.14 1 is a diagram showing the movement of the thermally conductive grease in Example 3.

[0122] Fig.15 This is a cross-sectional view of a fixing device according to Embodiment 4.

[0123] Fig.16 This is a cross-sectional view of a belt heating portion according to the fourth embodiment.

[0124] Fig.17 It is a cross-sectional view of a fixing device according to a reference example.

[0125] Fig.18 It is a cross-sectional view of a belt heating portion according to a reference example.

[0126] Fig.19 These are cross-sectional views (a, b) of a belt heating portion according to a modification of the fourth embodiment.

[0127] Fig. 20 This is a diagram showing the experimental results related to Example 4.

[0128] Fig.21 This is a cross-sectional view of the belt heating portion involved in Example 5.

[0129] Fig. 22 It is a cross-sectional view of a belt heating portion according to a modification of the fifth embodiment.

[0130] Fig.23 It is a cross-sectional view of a belt heating portion according to a modification of the fifth embodiment.

[0131] Fig.24 This is an explanatory diagram regarding the warping of the rear end of the recording material.

[0132] Fig.25 This is an explanatory diagram regarding the warping of the rear end of the recording material.

[0133] Fig.26 These are explanatory diagrams (a, b) regarding the deflection of the pressure roller, stays, etc.

[0134] Fig. 27 : is a graph which shows the distribution of the clamping pressure and the clamping width in Example 6.

[0135] Fig.28These are explanatory diagrams (a, b) showing the shape of a sliding plate according to the sixth embodiment.

[0136] Fig.29 These are explanatory diagrams (a, b) of the temperature distribution within the clamp in Example 6.

[0137] Fig.30 This is a diagram showing the experimental results related to Example 6.

[0138] Fig.31 Graph showing distribution of the clamping pressure and the clamping width in a modification of Example 6.

[0139] Fig.32 These are explanatory diagrams (a, b) regarding the deflection of the pressure roller, stays, etc.

[0140] Fig.33 It is an explanatory diagram of the shape of the slide plate in a modified example of the sixth embodiment.

[0141] Fig.34 These are explanatory diagrams (a, b) of the deflection of the fixing belt in the reference example.

[0142] Fig.35 These are explanatory diagrams (a, b) of the curvature radius of the fixing belt in a reference example.

[0143] Fig.36 This is an explanatory diagram of the deflection of the fixing belt in Example 7.

[0144] Fig.37 These are explanatory diagrams (a, b) of the curvature radius of the fixing belt in Example 7.

[0145] Fig.38 These are diagrams for explaining the temperature rise in the non-paper-passing portion (a, b).

[0146] Fig.39 This is a cross-sectional view of the belt heating portion involved in Example 8.

[0147] Fig.40 These are diagrams (a, b) showing the configuration of a heater according to Example 8.

[0148] Fig.41 These are explanatory diagrams of a heat-retaining plate in Example 8 (a, b).

[0149] Fig.42 This is a diagram showing the experimental results related to Example 8.

[0150] Fig.43 It is a graph showing the temperature distribution of the fixing device in Reference Example (a) and Example 8 (b).

[0151] Fig.44These are explanatory diagrams (a, b) of a heat retaining plate in a modified example of Example 8.

[0152] Fig.45 This is an explanatory diagram of variant example 1 of embodiment 8.

[0153] Fig.46 These are illustrations (a, b) of Modification 2 of Example 8.

[0154] Fig.47 These are illustrations (a, b) of Modification 3 of Example 8.

[0155] Fig.48 This is an explanatory diagram of Modification 3-2 of Example 8.

[0156] Fig.49 These are explanatory diagrams (a to c) of Modifications 4-1 to 4-3 of Example 8.

[0157] Fig.50 This is a diagram showing experimental results related to a modified example of Example 8.

[0158] Fig.51 This is a cross-sectional view of the fixing device involved in Example 9.

[0159] Fig.52 This is an explanatory diagram of the fixing device involved in Example 9.

[0160] Fig.53 This is a cross-sectional view of the fixing device involved in Example 10.

[0161] Fig.54 It is a top view of a holding member and a stay according to the tenth embodiment.

[0162] Fig.55 This is an explanatory diagram regarding the movement of excess paste in Example 10.

[0163] Fig.56 It is a cross-sectional view of a fixing device in a modified example of Embodiment 10.

[0164] Fig.57 This is an explanatory diagram of the movement of excess paste in a modified example of the tenth embodiment. DETAILED DESCRIPTION

[0165] Hereinafter, embodiments according to the present disclosure will be described with reference to the drawings.

[0166] In the following description, an “image forming apparatus” generally refers to an apparatus having an image forming function (printing function) of forming an image on a recording material S. The “image forming apparatus” may be a single-function printer, a copier, or a multifunction machine having multiple functions.

[0167] 《Example 1》

[0168] use Figure 1 The image forming apparatus 100 according to the first embodiment will be described in detail. The image forming apparatus 100 is a direct transfer electrophotographic color printer having a maximum width of letter size, and a plurality of image forming units PY, PM, PC, and PK are arranged along a conveyor belt (transfer belt 8) that conveys a recording material S. The maximum width refers to the paper width of the recording material S that has the largest length (paper width) in the width direction (main scanning direction during image formation) perpendicular to the recording material conveying direction among the recording materials S on which the image forming apparatus 100 can form an image. In addition, in the image forming apparatus 100, the situation in which the image forming apparatus 100 performs an image forming operation on the recording material S is referred to as "paper passing".

[0169] exist Figure 1 . The coordinate axes of the xyz coordinate system are shown in FIG. 1 . The z axis is a coordinate axis parallel to the height direction of the fixing device 200. The height direction of the fixing device 200 refers to the direction in which the pressure roller 202 and the belt unit 201 of the fixing device 200 are arranged. The +z direction (the direction of the arrow indicating the z axis) is the direction from the pressure roller 202 to the belt unit 201, and the −z direction (the opposite direction of the arrow) is the direction from the belt unit 201 to the pressure roller 202. The y axis is a coordinate axis parallel to the conveying direction of the recording material S in the fixing device 200. The +y direction (the direction of the arrow indicating the y axis) is the direction toward the downstream of the conveying direction of the recording material in the fixing device 200, and the −y direction (the opposite direction of the arrow) is the direction toward the upstream of the conveying direction of the recording material in the fixing device 200. The x axis is a coordinate axis parallel to the length direction of the belt unit 201 in the fixing device 200 (the width direction of the fixing belt 21). In other words, the x axis is a coordinate axis parallel to the support shaft of the pressure roller 202. In addition, the g-axis represents the direction of gravity, and in this embodiment, the direction of gravity is substantially the same as the -z direction. The x-axis, y-axis, and z-axis are preferably orthogonal to each other.

[0170] In the following embodiments, the x-axis direction can be regarded as the length direction (first direction) of the clamping portion N of the fixing device 200 described later. The +y direction can be regarded as the recording material conveying direction (second direction) at the clamping portion N. The z-axis direction can be regarded as the third direction orthogonal to both the first direction and the second direction.

[0171] The image forming apparatus 100 includes a plurality of image forming units PK, PC, PM, PY, a transfer belt 8, and a plurality of transfer rollers 5K, 5C, 5M, 5Y. The plurality of image forming units PK, PC, PM, PY are configured to form images (toner images) by electrophotographic processing using toner as a developer. The transfer belt 8 is a conveying member for conveying a recording material S along the plurality of image forming units PK, PC, PM, PY. The transfer rollers 5K, 5C, 5M, 5Y are arranged on the inner circumference side of the transfer belt 8, and are arranged at positions corresponding to the respective image forming units across the transfer belt 8.

[0172] A feed box 61 storing recording material S is provided at the lower part of the image forming apparatus 100. A conveying path 60 for the recording material S is formed inside the image forming apparatus 100, which passes through the plurality of image forming units PK, PC, PM, PY and the fixing device 200 from the feed box 61 to the discharge tray 70. The image forming apparatus 100 includes a feed roller 62, a conveying roller pair 63, a registration roller pair 64, a conveying roller pair 65, a transfer belt 8, and the plurality of image forming units PK, PC, PM, PY. In addition, the image forming apparatus 100 includes the fixing device 200, a conveying roller pair 66, a discharge roller pair 67, and a discharge tray 70. The above-mentioned components for conveying the recording material S are arranged in the above-mentioned order along the conveying path 60.

[0173] The image forming apparatus 100 receives image information from an external device such as a manuscript reading device connected to the apparatus body of the image forming apparatus 100 or a personal computer connected to the apparatus body in a communicable manner, and forms an image on a recording material S based on the image information. As the recording material S (recording medium), paper such as plain paper and thick paper, surface-treated sheets such as coated paper, sheets of special shapes such as cover or index paper, and various sheets of different materials such as plastic films and cloth can be used. In addition, the recording material S can use sheets of various sizes including A4 size and letter size.

[0174] The conveying process of the recording material S is described. The recording material S loaded in the feeding box 61 is fed to the conveying path 60 one by one by the feeding roller 62 in accordance with the timing of image formation. In addition, the image forming apparatus 100 may also include a feeding unit (manual feeding unit) for feeding the recording material S loaded on the manual tray (not shown) one by one to the conveying path 60. The recording material S fed to the conveying path 60 is conveyed to the registration roller pair 64 by the conveying roller pair 63, and the registration roller pair 64 performs skew correction and timing correction of the recording material S. Thereafter, the recording material S is fed to the transfer belt 8 by the conveying roller pair 65.

[0175] The transfer belt 8 is an endless belt member mounted on a driving roller 9 and a tension roller 10. When the driving roller 9 is driven to rotate by a driving force from a motor (not shown), the transfer belt 8 moves in the traveling direction (rotation direction) indicated by the arrow R2. When the recording material S is conveyed from the conveying roller pair 65 to the transfer belt 8, the recording material S is conveyed downstream in the conveying direction of the recording material in the conveying path 60 as the transfer belt 8 moves, with the recording material S carried on the upper surface of the transfer belt 8. While the recording material S is conveyed by the transfer belt 8, a toner image is formed on the recording material S by each image forming unit PK, PC, PM, PY.

[0176] In this embodiment, four image forming units PK, PC, PM, and PY as a plurality of image forming units are arranged above the transfer belt 8. An exposure device 3 is arranged above the image forming units PK, PC, PM, and PY. The image forming units PK, PC, PM, and PY may be cartridges (process cartridges) that are attachable to and detachable from the main body of the image forming apparatus 100. The image forming units PK, PC, PM, and PY use toners of black, cyan, magenta, and yellow to form toner images of the respective colors on the recording material S. The four image forming units PK, PC, PM, and PY have substantially the same configuration except for the toner colors.

[0177] The image forming unit PK includes a photosensitive drum 1K, a charging device 2K, a developing device 4K, and a drum cleaner 6K. The image forming unit PC includes a photosensitive drum 1C, a charging device 2C, a developing device 4C, and a drum cleaner 6C. The image forming unit PM includes a photosensitive drum 1M, a charging device 2M, a developing device 4M, and a drum cleaner 6M. The image forming unit PY includes a photosensitive drum 1Y, a charging device 2Y, a developing device 4Y, and a drum cleaner 6Y.

[0178] Each photosensitive drum 1K, 1C, 1M, 1Y is a rotating image carrier (electrophotographic photosensitive body). The charging device 2K, 2C, 2M, 2Y uniformly charges the surface of the corresponding photosensitive drum 1K, 1C, 1M, 1Y. The exposure device 3 irradiates light to each photosensitive drum 1K, 1C, 1M, 1Y based on image information to form an electrostatic latent image on each photosensitive drum 1K, 1C, 1M, 1Y. The developing device 4K, 4C, 4M, 4Y develops the electrostatic latent image into a toner image using a toner. The toner image is transferred to the recording material S at four transfer sections formed between the photosensitive drum 1K, 1C, 1M, 1Y and the transfer rollers 5K, 5C, 5M, 5Y. In the transfer section, the toner images on the photosensitive drums 1K, 1C, 1M, 1Y are pressed toward the recording material S by the transfer rollers 5K, 5C, 5M, 5Y, and the toner images are transferred by the bias electric field formed by the transfer rollers 5K, 5C, 5M, 5Y. Foreign matter such as transfer residual toner attached to the surfaces of the photosensitive drums 1K, 1C, 1M, 1Y after passing through the transfer section is removed by the drum cleaners 6K, 6C, 6M, 6Y.

[0179] In the case of an image forming operation (multi-color printing) using multi-color toners, the image forming units PK, PC, PM, and PY are sequentially started. In addition, the timing of creating the toner images of the image forming units PK, PC, PM, and PY (specifically, the timing of starting to write the electrostatic latent image using the exposure device 3) is controlled so that the toner images of each color overlap on the recording material S. While the recording material S is conveyed by the transfer belt 8, the toner images of the multi-colors are transferred so that the toner images of the multi-colors overlap, and a color image is formed on the recording material S. The control unit of the image forming apparatus 100 controls the driving amount and driving timing of each image forming unit PK, PC, PM, and PY and the transfer belt 8 so that the toner images of each color are aligned with each other.

[0180] The fixing device 200 is arranged downstream of the transfer belt 8 in the recording material conveying direction. The fixing device 200 applies heat and pressure to the toner image on the recording material S while conveying the recording material S to which the toner image is transferred in the transfer section, thereby fixing the toner image on the recording material S. The fixing device 200 will be described in detail later.

[0181] The recording material S passing through the fixing device 200 is conveyed by the conveying roller pair 66 and discharged onto the discharge tray 70 by the discharge roller pair 67. In addition, the belt cleaner 11 removes the attached matter on the transfer belt 8 after the recording material S is conveyed to the fixing device 200.

[0182] The image forming apparatus 100 repeatedly performs the above-described image forming operation, thereby being able to continuously form images on a plurality of recording materials S in response to a single image forming instruction.

[0183] [Fixing unit]

[0184] Next, use Figure 2 as well as Figure 3 The fixing device 200 of this embodiment will be described. Figure 2 2 is an enlarged view showing the fixing device 200 in this embodiment. Figure 3 From the transport direction F ( Figure 2 ) is a diagram showing the positional relationship of the elements in the length direction of the fixing device 200. The length direction of the fixing device 200 refers to the direction along the x-axis. Figure 3 In the figure, in order to facilitate understanding of the situation in the belt unit 201, the fixing belt 21 is shown in a see-through state.

[0185] like Figure 2 as well as Figure 3 As shown in the figure, the fixing device 200 comprises: a fixing belt 21 which is rotatable and endless as a fixing member; and a heater 26 (also see Figure 4 ). In addition, the fixing device 200 includes a sliding plate 27 (also see Figure 4 ); and a holding member 23 holding the heater 26 and the slide plate 27. In addition, the fixing device 200 includes a pressure roller 202 as a pressure member which is arranged to sandwich the fixing belt 21 together with the slide plate 27 and forms a nip portion N between the pressure roller 202 and the fixing belt. The fixing device 200 heats the image on the recording material by the fixing belt 21 while sandwiching and conveying the recording material at the nip portion N.

[0186] The structure of the fixing device 200 will be further described below. The fixing device 200 includes a belt unit 201 as a heating device and a pressure roller 202 as a pressure member in contact with the belt unit 201. A nip portion N (fixing nip) is formed between the belt unit 201 and the pressure roller 202. The fixing device 200 performs a fixing process: while the recording material S is clamped by the belt unit 201 and the pressure roller 202 and transported in the transport direction F, the toner image t on the recording material S is heated and pressurized in the nip portion N. The fixing device 200 is detachably mounted on the device body of the image forming device 100. The fixing device 200 may also be formed integrally with the device body.

[0187] The belt unit 201 includes: a rotatable endless fixing belt 21; a stay 22 disposed inside the fixing belt 21; a holding member 23 supported by the stay 22; and a belt heating unit 210 for heating the fixing belt 21. The stay 22, the holding member 23, and the belt heating unit 210 are all disposed in the internal space of the fixing belt 21, and each has a shape extending elongated with the x-axis direction as the length direction.

[0188] The fixing belt 21 is a flexible, endless belt member (endless belt) formed of a material with high thermal conductivity and low heat capacity, such as a resin such as polyimide or a metal such as stainless steel. The fixing belt 21 may be a film member (fixing film) formed into a cylindrical shape using a thin film material. The fixing belt 21 may be appropriately in the form of a base material (base layer) formed of a polyimide resin in an endless shape, an elastic layer formed on the periphery of the base material, and a surface layer (release layer) formed on the periphery of the elastic layer. The fixing belt 21 is rotatably arranged, and belt guides 250 are provided at both ends of the fixing belt 21 in the width direction (x-axis direction) of the fixing belt 21 to guide the rotation of the fixing belt 21 and limit the movement of the fixing belt 21 in the width direction. The belt guide 250 is a flange-shaped member (fixing flange) including: a rotation guide surface that contacts the inner surface (inner circumference) of the fixing belt 21; and an end restriction surface that extends from the rotation guide surface in a direction intersecting the x-axis direction to restrict the end of the fixing belt 21.

[0189] The stay 22 is made of a metal with high rigidity, such as stainless steel or spring steel. The stay 22 of this embodiment is formed into a roughly U-shaped cross section, which further improves the rigidity. The stay 22 holds the holding member 23, and the holding member 23 holds the belt heating unit 210. The two ends of the stay 22 in the x-axis direction are subjected to the force of the pressure spring 251 composed of a coil spring or the like. Due to the force of the pressure spring 251, the holding member 23 and the belt heating unit 210 are held in the z-axis direction toward the side of the pressure roller 202 (-z direction, Figure 3 Thus, the belt heating unit 210 and the pressure roller 202 are pressed while sandwiching the fixing belt 21, and a nip N having a predetermined width in the conveying direction F of the recording material S is formed between the fixing belt 21 and the pressure roller 202.

[0190] The holding member 23 holds a thermistor and a heater, etc., which will be described later, and forms a belt heating portion 210 ( Figure 2 The belt heating unit 210 will be described later.

[0191] The pressure roller 202, for example, has a metal core 202a as a rotation axis and a peripheral portion 202b. The peripheral portion 202b is formed on the periphery of the core 202a. The peripheral portion 202b is the portion that contacts the outer surface (peripheral surface) of the fixing belt 21 at the clamping portion N. The peripheral portion 202b has, for example, an elastic layer of silicone rubber or the like and a surface layer (release layer) formed on the periphery of the elastic layer by fluororesin such as PTFE, PFA, or FEP. The elastic layer can be either a foamed rubber (sponge rubber) obtained by foaming a rubber material or a solid rubber that is not foamed. In addition, the two ends of the core 202a in the direction of the rotation axis (x-axis direction) of the pressure roller 202 are supported by bearing portions 252 ( Figure 3 ) is rotatably supported.

[0192] The pressure roller 202 rotates at a predetermined circumferential speed in the direction of the arrow R3 by inputting a driving force from a driving motor (not shown) to a driving gear 253 provided at the end of a rotating shaft in the x-axis direction. Then, the rotational force of the pressure roller 202 is transmitted to the fixing belt 21 by the friction force generated in the clamping portion N. In this way, the fixing belt 21 rotates following the pressure roller 202. That is, this embodiment is a driving method (so-called pressure roller driving method) in which a driving force is input to the pressure roller 202 so that the fixing belt 21 rotates following the pressure roller 202.

[0193] Next, use Figure 4 The belt heating unit 210 will be described. Figure 4 is an enlarged cross-sectional view showing the belt heating portion 210 in this embodiment, and Figure 2 The dotted part in is equivalent.

[0194] As described above, the belt heating unit 210 is disposed in the internal space of the fixing belt 21. The belt heating unit 210 is in pressure contact with the pressure roller 202 via the fixing belt 21. The belt heating unit 210 heats the fixing belt 21 while sliding and rubbing against the inner surface of the rotating fixing belt 21.

[0195] The belt heating section 210 includes: a thermistor 24 as a temperature detection section; a heat retaining plate 25 as a heat retaining member for retaining heat of the heater 26; the heater 26 as a heating body; and a slide plate 27 as a slide member.

[0196] The thermistor 24 is an example of a temperature detection unit for detecting the temperature of the heater 26 or the belt heating unit 210 for temperature control of the fixing belt 21. The heater 26 is an example of a heating body that generates heat (that is, converts electrical energy into thermal energy) for heating the fixing belt 21 by energizing. The control unit of the image forming apparatus 100 controls the energization / blocking of the heater 26 and the amount of power supplied based on the detection signal of the thermistor 24 so as to maintain the fixing belt 21 at a predetermined target temperature (fixing temperature) suitable for fixing the toner image t.

[0197] The thermistor 24, the heat preservation plate 25, the heater 26, and the slide plate 27 are arranged in sequence in the -z direction. The heat preservation plate 25, the heater 26, and the slide plate 27 are respectively elongated plate-shaped members with the x-axis direction as the length direction, the y-axis direction as the width direction (short side direction), and the z-axis direction as the thickness direction.

[0198] The heat-retaining plate 25, the heater 26, and the sliding plate 27 are held by the holding member 23. A heat-conducting paste G1, which will be described later, is applied between the heat-retaining plate 25 and the heater 26, and between the heater 26 and the sliding plate 27. A sliding paste G2, which will be described later, is applied to the outer surface of the sliding plate 27 (the surface that slides on the inner surface of the fixing belt 21).

[0199] The heat preservation plate 25 has a heat storage performance of temporarily storing the heat generated by the heater 26, and a heat uniformity performance of transferring the heat generated by the heater 26 in the longitudinal direction (x-axis direction) and reducing the temperature unevenness in the longitudinal direction. The heat preservation plate 25 is, for example, a metal plate of an aluminum alloy. The heat preservation plate 25 may be omitted, and the heater 26 may be directly supported by the holding member 23.

[0200] The heater 26 is arranged so that its length direction is roughly parallel to the width direction (x-axis direction) of the fixing belt 21. The heater 26 is a long strip component with a metal material such as stainless steel or aluminum, or a ceramic material such as aluminum oxide or aluminum nitride as a base material and a pattern of a resistive heating element formed on the base material. In the case of a metal material as the base material, an insulating layer is formed on the metal material with an insulating material such as glass. The metal material is formed thin in order to have strength and flexibility, and as a result, the heat capacity of the heater 26 becomes smaller. Therefore, in the heater 26 with a metal material as the base material, there is an advantage of being able to accelerate the temperature rise of the fixing belt 21 when heating starts (high quick start-up). On the other hand, since the ceramic material has insulating properties, the heater with a ceramic material as the base material can directly form a resistive heating element on the base material, which has the advantages of reducing manufacturing time and cost.

[0201] In this embodiment, a heater 26 having the following structure can be appropriately used. First, as a substrate, a stainless steel material (SUS) having high corrosion resistance and high strength among metal materials is used. In addition, a glass thin film layer is formed on the substrate as an insulating layer, and a pattern is formed on the insulating layer, the pattern including a resistive heating element as a heating component, a terminal for receiving power supply from an external circuit, and wiring connecting the terminal and the resistive heating element. Furthermore, in order to protect the pattern, a glass protective layer is formed in a manner covering the pattern.

[0202] The slide plate 27 is arranged in a non-rotating manner relative to the rotating fixing belt 21. The slide plate 27 is a sliding friction member (sliding member) that slides and rubs against the inner surface of the fixing belt 21. The slide plate 27 is a long strip extending in the width direction (x-axis direction). The slide plate 27 has the function of a heat diffusion member that slides and rubs against the inner surface of the fixing belt 21 to diffuse the heat of the heater 26 to the fixing belt 21; and the function of a nip forming member that forms a desired nip portion N by pressing the fixing belt 21 with the pressure roller 202.

[0203] The sliding plate 27 of this embodiment has: a sliding friction portion 271 that slides against the fixing belt 21; and a rising portion 272 that is bent relative to the sliding friction portion 271 in a curved shape (bent shape) so as not to damage the inner surface of the fixing belt 21 due to the cutting edge of the sliding plate end.

[0204] The sliding friction portion 271 includes a heater contact surface 271 a that contacts the heater 26 and a sliding friction surface 271 b that slides against the fixing belt 21 . The heater contact surface 271 a extends along the nip portion N in the direction (y-axis direction) along the recording material conveying direction and receives heat from the heater 26 .

[0205] The rising portion 272 is formed continuously with the upstream end and the downstream end of the sliding friction portion 271 in the recording material conveying direction (+y direction). The rising portion 272 on the upstream side is an example of the first rising portion, and the rising portion 272 on the downstream side is an example of the second rising portion. Each rising portion 272 rises from the upstream end and the downstream end of the sliding friction portion 271 in the z-axis direction toward the side (+z direction) away from the pressure roller 202 so as not to slide and rub on the inner surface of the fixing belt 21. The terminal end of the rising portion 272 is accommodated in the groove portion 231 (escape groove portion, concave portion) formed in the upstream and downstream portions of the retaining member 23 in the recording material conveying direction (+y direction).

[0206] A protrusion 273 is formed on at least one of the upstream and downstream protrusions 272. The protrusion 273 protrudes in a direction intersecting with the extending direction of the protrusion when viewed in the x-axis direction. In the present embodiment, the protrusion 273 is formed on the upstream and downstream protrusions 272, respectively. The protrusion formed on the upstream protrusion 272 is an example of a first protrusion, and the protrusion formed on the downstream protrusion is an example of a second protrusion. The details of the protrusion 273 will be described later.

[0207] In order to efficiently transfer the heat of the heater 26, the material of the sliding plate 27 is preferably a thin plate of metal such as stainless steel, aluminum alloy or iron. In addition, a coating of polyimide, fluororesin or glass may be applied to the sliding friction surface 271b that slides against the fixing belt 21 to improve the sliding property and wear resistance.

[0208] [Problem]

[0209] In order to efficiently transfer the heat of the heater 26 to the sliding plate 27 and the heat preservation plate 25, a thermal conductive paste G1 is sometimes applied to the surface 26a and / or the back surface 26b of the heater 26. The surface 26a of the heater 26 is the surface facing the heater contact surface 271a of the sliding plate 27, and the back surface 26b is the surface facing the heat preservation plate 25.

[0210] When the belt unit 201 and the pressure roller 202 are pressed together, pressure is applied to the belt heating portion 210, and the thermal paste G1 may be squeezed out from between the heater 26 and the sliding plate 27 or between the heater 26 and the heat-retaining plate 25. If the squeezed thermal paste G1 leaks along the surface of the sliding plate 27 toward the sliding friction surface 271b of the sliding plate 27, the thermal paste G1 may impair the sliding properties between the sliding plate 27 and the fixing belt 21, and there is a risk of accelerating the wear of the inner surface of the fixing belt 21.

[0211] Therefore, in this embodiment, a configuration is proposed that can reduce the possibility that the grease applied between the heater and the sliding member adheres to the inner surface of the fixing belt.

[0212] [Details of ointment movement]

[0213] More specifically, in this embodiment, in order to improve the sliding properties of the fixing belt 21 and the sliding plate 27, the sliding grease G2 is applied to the sliding friction surface 271b of the sliding plate 27. If the heat-conducting grease G1 applied to the heater 26 leaks out to the sliding friction surface 271b of the sliding plate 27 as described above, the heat-conducting grease G1 will be mixed into the sliding grease G2, and there is a risk that the wear of the inner surface of the fixing belt 21 will be accelerated. In addition, the following assumes that the heat-conducting grease G1 is mixed into the sliding grease G2, and the structure of this embodiment can be applied even in the case where the sliding friction surface 271b of the sliding plate 27 is not applied with the sliding grease G2. For example, even in the case where the sliding friction surface 271b is made of a self-lubricating material and the sliding grease G2 is not required, the sliding properties on the inner surface of the fixing belt 21 will be reduced due to the leakage of the heat-conducting grease G1 to the sliding friction surface 271b.

[0214] Below, use Figure 5 The movement of the thermally conductive grease G1 will be described in detail. Figure 52 is a diagram showing the movement of the thermally conductive paste G1 in the fixing device 200 using the sliding plate 27 of the reference example. The reference example has a configuration in which the protrusion 273 ( Figure 4 ) Except for this point, the rest of the structure is the same as that of the fixing device 200 of Example 1.

[0215] In addition, Figure 4 , Figure 5 In order to schematically illustrate the movement of the paste, the paste layer is depicted thicker than the actual thickness of the fixing device 200. Therefore, for example, the reduction ratio in the z direction in the figure may be different from that of the actual fixing device 200. The same applies to the following embodiments 2 and 3.

[0216] like Figure 5 As shown in the figure, in the reference example, the sliding plate 27, the heater 26 and the heat preservation plate 25 are also held by the holding member 23. In addition, the sliding plate 27 has a sliding friction portion 271 and a rising portion 272. Here, between the heater 26 and the sliding plate 27 and between the heater 26 and the heat preservation plate 25, in order to reduce temperature unevenness and improve thermal conductivity, a thermal conductive paste G1 is applied.

[0217] In the present embodiment and the reference example, as the thermal conductive paste G1, a paste obtained by mixing metal fillers such as zinc oxide in silicone oil can be used. In the present embodiment and the reference example, as the thermal conductive paste G1, DOWSIL SC102 compound (density 2.5 g / cm 3 ). The application range of the thermal conductive paste G1 relative to the heater 26 is, for example, 10.5 mm in the y-axis direction, which is the same as the width of the heater, and 218 mm in the x-axis direction. Within this application range, 250 mg of the thermal conductive paste G1 is applied between the heater 26 and the sliding plate 27 and between the heater 26 and the heat preservation plate 25.

[0218] On the other hand, in order to improve the sliding property and reduce the wear between the fixing belt 21 and the sliding friction part 271 of the sliding plate 27, it is preferable to apply a sliding paste G2 which is different from the thermal conductive paste G1. As the sliding paste G2, a fluorine paste or silicone oil can be used. In this embodiment and the reference example, MOLYKOTE HP-300 paste (density 2.0 g / cm 3). The application range of the sliding paste G2 relative to the sliding plate 27 is, for example, 10.5 mm in the y-axis direction and 218 mm in the x-axis direction. Within the application range, 500 mg of the sliding paste G2 is applied between the fixing belt 21 and the sliding friction portion 271 of the sliding plate 27. The sliding paste G2 adheres to the inner surface of the fixing belt 21 as the fixing belt 21 rotates, thereby improving the sliding property relative to the sliding friction surface 271b. As a result, the wear of the inner surface of the fixing belt 21 can be suppressed.

[0219] The thermal conductive paste G1 and the sliding paste G2 are both semi-solid or semi-fluid, but have different physical properties. The thermal conductive paste G1 is a first paste containing fillers for improving thermal conductivity, and the sliding paste G2 is a second paste with different ingredients from the first paste for improving sliding properties.

[0220] In order to efficiently transfer heat to the heater contact surface 271a of the sliding plate 27, the width of the heater 26 and the heat-retaining plate 25 disposed inside the sliding plate 27 in the y-axis direction is preferably as large as possible. However, in order to assemble inside the sliding plate 27, the width of the heater 26 and the heat-retaining plate 25 in the y-axis direction is smaller than the distance between the two rising portions 272. Therefore, a gap is formed between the heater 26 and the heat-retaining plate 25 and the rising portion 272 of the sliding plate 27.

[0221] In addition, considering the thermal expansion of the sliding plate 27, it is preferable that the groove 231 of the holding member 23 is larger than the width in the y-axis direction of the distal end of the rising portion 272 of the sliding plate 27. Therefore, a gap is also formed between the groove 231 of the holding member 23 and the rising portion 272 of the sliding plate 27.

[0222] Here, when the pressure roller 202 and the belt unit 201 are pressed to form the nip portion N, the heater 26 and the slide plate 27 and the heater 26 and the heat retaining plate 25 are brought into close contact. At this time, a portion of the thermally conductive paste G1 between the heater 26 and the slide plate 27 or between the heater 26 and the heat retaining plate 25 is squeezed out onto the inner surfaces of the rising portions 272 upstream and downstream of the slide plate 27.

[0223] However, in Figure 5 In the reference example shown, there is a risk that a part of the squeezed-out thermally conductive paste G1 may leak out toward the sliding friction surface 271 b side of the sliding plate 27 as described below.

[0224] First, if Figure 5As shown by arrow A in FIG. 1 , the heat-conducting paste G1 squeezed out from between the heater 26 and the sliding plate 27 or between the heater 26 and the heat-retaining plate 25 rises along the inner wall of the rising portion 272 of the sliding plate 27 due to the interfacial tension (wetting phenomenon) with the rising portion 272 of the sliding plate 27. The rising heat-conducting paste G1 bypasses the end of the rising portion 272 in the groove portion 231 of the retaining member 23 and moves toward the inner surface of the fixing belt 21. As a result, the heat-conducting paste G1 is mixed into the sliding paste G2 and reaches between the fixing belt 21 and the sliding friction surface 271b of the sliding plate 27. If the heat-conducting paste G1 is mixed into the sliding paste G2, the sliding property of the sliding friction surface 271b of the fixing belt 21 and the sliding plate 27 is deteriorated due to the difference in characteristics between the two, such as the influence of the metal filler in the heat-conducting paste G1, and there is a risk of accelerating the wear of the inner surface of the fixing belt 21.

[0225] [Details of the sliding plate]

[0226] In view of the above point, in this embodiment, even if part of the thermal conductive paste G1 applied to the heater 26 is squeezed out onto the inner surface of the rising portion 272, it is difficult to reach the sliding friction surface 271b of the sliding plate 27. Figure 4 , Figure 6 (a) to Figure 6 (c), Figure 7 , Figure 8 FIG. 6( a ) to FIG. 6( c ) are diagrams showing the movement of the thermally conductive grease G1 when the slide plate 27 in this embodiment is used. Figure 7 1 is a diagram showing the relationship among the lengths of the slide plate 27 , the protrusion 273 , the fixing belt 21 , and the pressure roller 202 in the width direction (x-axis direction) in this embodiment. Figure 8 1 is a perspective view showing an end portion of the slide plate 27 in the x-axis direction in the present embodiment.

[0227] like Figure 4 As shown in FIG. 6A and FIG. 6B , the slide plate 27 of the present embodiment has folded shapes as protrusions 273 formed on the rising portions 272 on the upstream and downstream sides in the recording material conveying direction (+y direction). Figure 8 As shown in FIG. 1 , the protrusion 273 is a bent shape formed by bending the tip of the standing portion 272 in the y-axis direction toward the heater 26. That is, the standing portion 272 on the downstream side in the conveying direction forms the protrusion 273 protruding toward the upstream side in the conveying direction. The standing portion 272 on the upstream side in the conveying direction forms the protrusion 273 protruding toward the downstream side in the conveying direction.

[0228] The protrusion 273 functions as a so-called “return shape” for restricting the movement of the thermally conductive paste G1 squeezed out from between the heater 26 and the slide plate 27 or between the heater 26 and the heat retaining plate 25 .

[0229] In order to more reliably restrict the movement of the thermally conductive paste G1, the protrusion 273 preferably protrudes in the recording material conveying direction (y-axis direction) toward the heater 26 disposed between the two upright portions 272. However, the protrusion 273 may protrude in the recording material conveying direction (y-axis direction) toward the side opposite to the heater 26, or may protrude in a direction inclined with respect to the y-axis direction.

[0230] The protrusion 273 is not limited to the bent shape shown in FIG6 (a). The protrusion 273 may also be a curved shape formed by curling the end of the rising portion 272 as shown in FIG6 (b). In addition, the protrusion 273 may also be a folded curved shape formed by folding the end of the rising portion 272 as shown in FIG6 (c).

[0231] By providing the protrusion 273, as shown in FIG. 6 (a) to FIG. 6 (c), the heat conductive paste G1 can be restricted from moving toward the sliding friction surface 271b side of the sliding plate 27. That is, even if a part of the heat conductive paste G1 is squeezed out from between the heater 26 and the sliding plate 27 or between the heater 26 and the heat retaining plate 25 onto the inner surface of the rising portion 272 and rises along the rising portion 272 in the +z direction, it will be pushed back by the protrusion 273 (arrow B). Therefore, it is difficult for the heat conductive paste G1 to bypass the end of the rising portion 272 and reach the sliding friction surface 271b side of the sliding plate 27, thereby reducing the possibility of promoting wear of the inner surface of the fixing belt 21.

[0232] When viewed in a cross section perpendicular to the x-axis direction as shown in FIG6(a), Figure 5 Compared with the reference example, due to the presence of the protrusion 273, the creeping distance measured along the surface of the sliding plate 27 from the heater contact surface 271a of the sliding plate 27 through the inner wall and outer wall of the rising portion 272 to the sliding friction surface 271b becomes longer. Therefore, it is difficult for the thermal conductive paste G1 to reach the sliding friction surface 271b side of the sliding plate 27, and the possibility of promoting the wear of the inner surface of the fixing belt 21 can be reduced.

[0233] Preferably, if Figure 7As shown in FIG. 1 , the width W273 of the protrusion 273 in the x-axis direction is greater than the width (referred to as roller width W202) of the outer peripheral portion 202b of the pressure roller 202 (W273>W202). In other words, it is preferred that the pressure member has an outer peripheral portion that contacts the fixing member at the nip portion, and the length of the protrusion in the first direction is greater than the length of the outer peripheral portion in the first direction.

[0234] Preferably, both ends of the protrusion 273 in the x-axis direction are located outside the both ends of the outer peripheral portion 202b of the pressure roller 202 in the x-axis direction. In this embodiment, the pressure roller 202 and the belt unit 201 are pressed together to form the nip portion N, so the pressure on the inner side of the roller width W202 is higher than that on the outer side of the roller width W202, and the thermal paste G1 is easily squeezed out. Therefore, by providing the protrusion 273 with the above-mentioned width W273, the possibility of the thermal paste G1 reaching the sliding friction surface 271b side of the sliding plate 27 can be further reduced.

[0235] In addition, it is preferable that the width W273 of the protrusion 273 is larger than the width W21 of the fixing belt 21 (W273>W21), and the end of the protrusion 273 is located outside the end of the fixing belt 21 in the x-axis direction. In other words, it is preferable that the length of the protrusion in the first direction is larger than the length of the fixing member in the first direction. Thereby, the possibility that the thermal conductive paste G1 reaches the sliding friction surface 271b side of the sliding plate 27 can be further reduced.

[0236] In addition, if Figure 7 , Figure 8 As shown in FIG. 1 , the width W273 of the protrusion 273 in the x-axis direction may not necessarily be the same as the width W27 of the slide plate 27 in the x-axis direction. Figure 8 As shown in FIG. 2 , the two end surfaces of the slide plate 27 in the x-axis direction do not form a return shape such as the rising portion 272. However, as long as the width W27 of the slide plate 27 is larger than the width W21 of the fixing belt 21, the two end surfaces of the slide plate 27 can be located outside the two end portions of the fixing belt 21 in the x-axis direction. This is because, in this case, the possibility that the thermal conductive paste G1 will go around the two end surfaces of the slide plate 27 and reach the inner surface of the fixing belt 21 is low.

[0237] In addition, even outside the roller width W202 of the pressure roller 202, the heat conductive paste G1 is subjected to pressure due to the rigidity of the heater 26 or the sliding plate 27. Depending on the viscosity of the heat conductive paste G1, the width W273 of the protrusion 273 may be further increased to be further away from the end of the outer peripheral portion 202b of the pressure roller 202. When the end of the protrusion 273 in the x-axis direction is located outside the end of the fixing belt 21, even if the heat conductive paste G1 moves in the x-axis direction along the rising portion 272, it is possible to more reliably prevent the heat conductive paste G1 from reaching the sliding friction surface 271b.

[0238] [Summary of this embodiment]

[0239] As described above, in the present embodiment, the protrusion 273 is formed at the tip of the rising portion 272 formed in the vertical direction (+z direction) in the slide plate 27 so as not to slide and rub against the inner surface of the fixing belt 21. The protrusion 273 can prevent the movement of a part of the thermal conductive paste G1 squeezed out from between the heater 26 and the slide plate 27 or between the heater 26 and the heat-retaining plate 25 due to the pressure contact between the pressure roller 202 and the belt unit 201. That is, even if the squeezed thermal conductive paste G1 rises along the rising portion 272, the protrusion 273 makes it difficult for the thermal conductive paste G1 to reach the contact surface of the slide plate 27 that contacts the fixing belt 21, that is, the sliding friction surface 271b.

[0240] Thus, it is possible to suppress the reduction in sliding performance and the acceleration of wear on the inner surface of the fixing belt 21 caused by the presence of the thermal conductive paste G1 between the sliding friction surface 271b and the inner surface of the fixing belt 21. In particular, in this embodiment, it is possible to suppress the reduction in sliding performance and the acceleration of wear on the inner surface of the fixing belt 21 caused by the mixing of the thermal conductive paste G1 into the sliding paste G2.

[0241] That is, according to this embodiment, the sliding member has a protrusion, which is provided on at least one of the first and second rising portions and projects in a direction intersecting with the extending direction of the rising portion when viewed in the first direction. According to this configuration, the possibility of the grease applied between the heater and the sliding member adhering to the inner surface of the fixing belt can be reduced.

[0242] 《Example 2》

[0243] In this embodiment, an example is described in which the protrusion 273 is provided only on the rising portion 272 on one side of the sliding plate 27. Hereinafter, for the elements marked with the same reference numerals as those in the first embodiment, unless otherwise specified, they have substantially the same structure and function as those described in the first embodiment, and the description will be mainly based on the parts different from the first embodiment.

[0244] [Problem]

[0245] Similar to the first embodiment, in the present embodiment, a configuration is proposed that can reduce the possibility that the grease applied between the heater and the sliding member adheres to the inner surface of the fixing belt.

[0246] [Image forming device]

[0247] Fig. 9 It is a schematic diagram of the image forming apparatus 100 according to the present embodiment. Fig.10 1 is a cross-sectional view showing the belt heating section 210 of the fixing device 200 according to the present embodiment.

[0248] In the first embodiment, an example is described in which the height direction of the fixing device 200, i.e., the -z direction, is substantially the same direction as the gravity direction (+g direction). That is, in the first embodiment, the sliding friction portion 271 of the sliding plate 27 extends in a direction substantially perpendicular to the gravity direction. On the other hand, the orientation or arrangement of the fixing device 200 or the image forming unit PK, etc., may be changed, the conveying path 60 may be changed, and the layout of the image forming device 100 may be changed. Due to the layout change, for example, the installation area of ​​the image forming device 100 may be reduced or the first printing time may be reduced.

[0249] exist Fig. 9 In the image forming apparatus 100 of the present embodiment shown in FIG. 1 , the −z direction, which is the height direction of the fixing device 200, is significantly different from the gravity direction (+g direction). Fig.10 As shown in the figure, in this embodiment, the sliding friction portion 271 of the sliding plate 27 in the fixing device 200 is greatly inclined from the horizontal plane perpendicular to the gravity direction (g direction). That is, the fixing device 200 is arranged to be inclined in such a way that the recording material conveying direction (+y direction) at the clamping portion N of the fixing device 200 intersects with the horizontal direction. The inclination angle of the sliding friction portion 271 relative to the horizontal plane can be, for example, 45 degrees or more. The closer the extension direction (y-axis direction) of the sliding friction portion 271 is to the gravity direction, the easier it is for the thermal paste G1 to leak out from between the heater 26 and the sliding plate 27 or between the heater 26 and the heat preservation plate 25 due to the influence of gravity.

[0250] [Slide panel]

[0251] use Fig.10The slide plate 27 in this embodiment is described. The slide plate 27 includes a sliding friction portion 271 extending in the recording material conveying direction (+y direction), and two rising portions 272a and 272b provided on the upstream and downstream sides of the sliding friction portion 271 in the conveying direction (+y direction). The rising portion 272a on the upstream side is located on the lower side in the gravity direction (+g direction) relative to the sliding friction portion 271, and the rising portion 272b on the downstream side is located on the upper side in the gravity direction (-g direction) relative to the sliding friction portion 271. The rising portions 272a and 272b stand up toward the side (+z direction) away from the pressure roller 202 in the height direction (z-axis direction) of the fixing device 200 where the belt unit 201 and the pressure roller 202 are arranged, so as not to contact the inner surface of the fixing belt 21.

[0252] The protrusion 273 is provided only on the upstream side (downward side in the direction of gravity) of the two protrusions 272a and 272b. The protrusion 273 of this embodiment is, for example, a bent shape formed by bending the end of the protrusion 272a in the y-axis direction toward the side of the sliding friction portion 271, that is, the downstream side (+y direction) in the recording material conveying direction. The protrusion 273 is continuous in the x-axis direction with a predetermined width. The width W273 of the protrusion 273 in the x-axis direction can be the same as that of the first embodiment.

[0253] use Fig.11 as well as Fig.12 The movement of the thermally conductive grease G1 in this embodiment will be described. Fig.11 as well as Fig.12 This is a diagram showing the movement of the thermally conductive grease G1 when the slide plate 27 in this embodiment is used. Fig.11 This is an enlarged view of the vicinity of the rising portion 272a on the lower side in the gravity direction (+g direction). Fig.12 It is an enlarged view of the vicinity of the rising portion 272 b on the upper side in the gravity direction (−g direction).

[0254] Consider the following situation: Fig.11 As shown by arrow C, near the rising portion 272a on the lower side in the gravity direction (+g direction), the thermally conductive paste G1 is squeezed out from between the heater 26 and the slide plate 27 or between the heater 26 and the heat retaining plate 25. A portion of the squeezed thermally conductive paste G1 moves along the inner wall of the rising portion 272a.

[0255] Here, since the protrusion 273 is formed on the rising portion 272a on the lower side in the gravity direction (+g direction), the thermally conductive paste G1 is prevented from moving around the tip of the rising portion 272a, and the thermally conductive paste G1 can be held on the heater contact surface 271a side of the sliding plate 27. That is, the thermally conductive paste G1 is difficult to reach the sliding friction surface 271b of the sliding plate 27 due to the protrusion 273.

[0256] On the other hand, consider the following situation: Fig.12 As shown by the arrow D, the thermal paste G1 is squeezed out from between the heater 26 and the slide plate 27 or between the heater 26 and the heat retaining plate 25 near the rising portion 272b on the upper side in the gravity direction (-g direction). A portion of the squeezed thermal paste G1 moves along the inner wall of the rising portion 272b. Although the protrusion 273 is not formed on the rising portion 272b, since the inner wall of the rising portion 272b faces the lower side in the gravity direction (+g direction), the thermal paste G1 attached to the inner wall of the rising portion 272b is subjected to gravity in the direction of returning to the heater 26. Therefore, even near the rising portion 272b, the thermal paste G1 is retained on the heater contact surface 271a side of the slide plate 27. That is, near the rising portion 272b on the upper side in the gravity direction (-g direction), due to the effect of gravity, it is difficult for the thermal paste G1 to reach the sliding friction surface 271b of the sliding plate 27. Therefore, even without the protrusion 273, it is difficult for the thermal paste G1 to reach the sliding friction surface 271b of the sliding plate 27.

[0257] [Summary of this embodiment]

[0258] As described above, in the sliding plate 27 of the present embodiment, the protrusion 273 is formed on the rising portion 272a located on the lower side (+g direction) in the gravity direction relative to the sliding friction portion 271. Due to the protrusion 273, the thermal conductive paste G1 squeezed out from between the heater 26 and the sliding plate 27 or between the heater 26 and the heat retaining plate 25 is unlikely to bypass the rising portion 272a and reach the sliding friction surface 271b of the sliding plate 27. In addition, in the rising portion 272b located on the upper side (-g direction) in the gravity direction relative to the sliding friction portion 271, the thermal conductive paste G1 is subjected to gravity in the direction of returning to the heater 26 side, so the thermal conductive paste G1 is less likely to bypass the rising portion 272b and reach the sliding friction surface 271b of the sliding plate 27.

[0259] Therefore, according to the configuration of this embodiment, it is also possible to suppress a decrease in the sliding property between the slide plate 27 and the fixing belt 21 and an acceleration of wear of the inner surface of the fixing belt 21 due to the thermally conductive grease G1 .

[0260] That is, according to this embodiment, the sliding member has a protrusion, which is provided on at least one of the first and second rising portions and projects in a direction intersecting with the extending direction of the rising portion when viewed in the first direction. According to this configuration, the possibility of the grease applied between the heater and the sliding member adhering to the inner surface of the fixing belt can be reduced.

[0261] The slide plate 27 of this embodiment has the protrusion 273 only arranged on the rising portion 272a on the lower side in the gravity direction, and does not have the protrusion 273 arranged on the rising portion 272b on the upper side. That is, one of the first rising portion and the second rising portion (rising portion 272a) is located on the lower side relative to the other of the first rising portion and the second rising portion (rising portion 272b) in the gravity direction. The protrusion 273 is provided on the rising portion 272a located on the lower side of the first rising portion and the second rising portion. Therefore, compared with the case where the protrusion 273 is arranged on the rising portions 272a and 272b on both sides, the workability of the slide plate 27 can be improved.

[0262] 《Example 3》

[0263] In this embodiment, an example is described in which the protrusion 273 of the sliding plate 27 is formed by a member different from the sliding friction portion 271 and the rising portion 272. Hereinafter, for the elements marked with the same reference numerals as those in the first embodiment, unless otherwise specified, they have substantially the same structure and function as those described in the first embodiment, and the description will be mainly based on the parts different from the first embodiment.

[0264] [Problem]

[0265] Similar to the first embodiment, in the present embodiment, a configuration is proposed that can reduce the possibility that the grease applied between the heater and the sliding member adheres to the inner surface of the fixing belt.

[0266] [Slide panel]

[0267] use Fig.13 as well as Fig.14 The slide plate 27 in this embodiment will be described. Fig.13 It is an enlarged view of the belt heating portion 210 in this embodiment. Fig.14 This is a diagram showing the movement of the thermally conductive grease G1 when the slide plate 27 in this embodiment is used.

[0268] In this embodiment, Fig.13 As shown in the figure, the slide plate 27 has a sliding friction portion 271 extending in the recording material conveying direction (+y direction) and a rising portion 272 formed continuously with the upstream end and the downstream end of the sliding friction portion 271 in the recording material conveying direction (+y direction). Each rising portion 272 is formed to rise in the vertical direction (+z direction) so as not to slide and rub against the inner surface of the fixing belt 21.

[0269] Additional members as protrusions 273 are respectively arranged on the upstream and downstream sides of the rising portions 272. The protrusions 273 are fixed to the rising portions 272 by mechanical engagement with the rising portions 272 or by bonding or other bonding methods. The protrusions 273 are continuous with a predetermined width in the x-axis direction. The width W273 of the protrusions 273 in the x-axis direction may be the same as that in the first embodiment.

[0270] In the sliding plate 27 of the present embodiment, a protrusion 273 is provided which is a member different from the sliding friction portion 271 and the rising portion 272. Therefore, the protrusion 273 may be formed of a material different from that of the sliding friction portion 271 and the rising portion 272, or the protrusion 273 may be subjected to a separate surface treatment. Thus, the interfacial tension (wettability) between the thermal conductive paste G1 and the protrusion 273 can be reduced, and the thermal conductive paste G1 can be easily separated from the protrusion 273. In the present embodiment, a glass coating is applied to the surface of the protrusion 273.

[0271] [Summary of this embodiment]

[0272] use Fig.14 The movement of the thermal conductive paste G1 in this embodiment is described below. Fig.14 As shown by the arrow E, a part of the thermally conductive paste G1 squeezed out from between the heater 26 and the sliding plate 27 or between the heater 26 and the heat retaining plate 25 rises along the inner wall of the rising portion 272. However, since the protrusion 273 is disposed on the rising portion 272, even if the thermally conductive paste G1 rises along the rising portion 272, the protrusion 273 prevents the thermally conductive paste from moving around the rising portion 272. That is, it is difficult for the thermally conductive paste G1 to reach the sliding friction surface 271b of the sliding plate 27.

[0273] Therefore, also in the configuration of this embodiment, it is possible to suppress a decrease in the sliding property between the slide plate 27 and the fixing belt 21 and an acceleration of the wear of the inner surface of the fixing belt 21 due to the thermally conductive grease G1 .

[0274] That is, according to this embodiment, the sliding member has a protrusion, which is provided on at least one of the first and second rising portions and projects in a direction intersecting with the extending direction of the rising portion when viewed in the first direction. According to this configuration, the possibility of the grease applied between the heater and the sliding member adhering to the inner surface of the fixing belt can be reduced.

[0275] In addition, by setting the protrusion 273 as a component different from the sliding friction portion 271 and the upright portion 272 of the sliding plate 27, the design freedom regarding material selection and surface processing is improved, and the performance of the protrusion 273, the sliding friction portion 271 and the upright portion 272 can be improved.

[0276] For example, by applying a glass coating to the protrusion 273, the thermal conductive paste G1 can be easily removed from the protrusion 273. In this case, even if the thermal conductive paste G1 reaches the protrusion 273, it is easy to return to the heater 26 side and is easy to be held on the heater contact surface 271a side of the slide plate 27. In other words, it is more difficult for the thermal conductive paste G1 to reach the sliding friction surface 271b. On the other hand, the sliding friction portion 271 can be made of a material that has good sliding properties with the fixing belt 21 and good compatibility with the sliding paste G2.

[0277] 《Example 4》

[0278] In this embodiment, the following configuration is described: the end of the holding member 23 facing the inner surface of the fixing belt 21 is retracted toward the side (+z direction) away from the pressure roller 202 in the height direction of the fixing device 200 compared with the sliding friction surface 271b of the sliding plate 27. Hereinafter, the elements marked with the same reference numerals as those in the embodiment 1 have substantially the same configuration and function as those described in the embodiment 1 unless otherwise specified, and the description will be mainly based on the parts different from the embodiment 1.

[0279] In addition, the following will first describe an embodiment without the heat-retaining plate 25 , but the fixing device 200 may include the heat-retaining plate 25 similar to that of the first embodiment as in a modified example described later.

[0280] Fig.15 2 is a cross-sectional view of the fixing device 200 in this embodiment. The fixing device 200 includes: a belt unit 201 as a heating device; and a pressure roller 202 as a pressure member in contact with the belt unit 201 . Fig.16 is an enlarged view of the belt heating unit 210 in this embodiment, and Fig.15 The dotted part in is equivalent.

[0281] The belt heating unit 210 is provided inside the fixing belt 21 as in Examples 1 to 3, and heats the fixing belt 21 while sliding and rubbing against the inner surface of the fixing belt 21, and forms a nip N with the pressure roller 202 via the fixing belt 21. The belt heating unit 210 includes, in order in the −z direction: a thermistor 24 as a temperature detection unit embedded in the holding member 23; a plate-shaped heater 26 as a heating body for heating the fixing belt 21; and a sliding plate 27 for transferring the heat of the heater 26 to the fixing belt 21. The heater 26 and the sliding plate 27 are held by the holding member 23.

[0282] A heat transfer paste G1 is applied between the heater 26 and the slide plate 27 so that the heat generated by the heater 26 can be efficiently transferred to the slide plate 27. On the other hand, a slide paste G2 is applied between the fixing belt 21 and the sliding friction portion 271 of the slide plate 27 in order to improve the sliding property and reduce the wear. The heat transfer paste G1 and the slide paste G2 can use the same configuration as that described in the first embodiment.

[0283] [Problem]

[0284] In order to improve the energy-saving performance of the fixing device 200, it is necessary to transfer the heat of the heater 26 as a heat source to the fixing belt 21 as little as possible (to improve the thermal efficiency). However, when the fixing belt 21 is in contact with the holding member 23, part of the heat transferred from the heater 26 to the fixing belt 21 escapes to the holding member through the contact area between the fixing belt 21 and the holding member 23.

[0285] Therefore, in this embodiment, a configuration that can improve the energy saving performance of the fixing device is proposed.

[0286] [Heat escape in reference example]

[0287] A specific example of the thermal escape path will be described using a reference example. Fig.17 It is a cross-sectional view of a fixing device 200 ′ according to a reference example. Fig.18 is an enlarged view showing a belt heating unit 210 of a fixing device 200' according to a reference example, and Fig.17 The dotted part is equivalent to .

[0288] The holding member 23 of the fixing device 200' has guide surfaces 23A' and 23B' for guiding the fixing belt 21 upstream and downstream of the slide plate 27 in the recording material conveying direction (+y direction). The guide surfaces 23A' and 23B' are curved surfaces having a predetermined curvature when viewed in the x-axis direction in order to guide the fixing belt 21 more smoothly.

[0289] The end points P23A′ and P23B′ of the guide surfaces 23A′ and 23B′ closest to the pressure roller 202 in the z-axis direction (−z direction side) are at the same height as the position of the sliding friction surface 271b of the slide plate 27 in the z-axis direction. Fig.17 When the fixing belt 21 rotates in the direction of arrow R3 and follows the pressure roller 202, the inner surface of the fixing belt 21 sequentially contacts the guide surface 23A′ on the upstream side, the sliding friction surface 271b of the sliding plate 27, and the guide surface 23B′ on the downstream side. The fixing belt 21 is heated by receiving heat from the heater 26 via the sliding plate 27 and the grease layer.

[0290] Here, since the fixing belt 21 is also in contact with the guide surfaces 23A′ and 23B′ of the holding member 23, part of the heat received by the fixing belt 21 escapes to the holding member 23. Therefore, in order to maintain the fixing belt 21 at a temperature suitable for fixing the toner image t, it is necessary to set the heating value of the heater 26 so as to compensate for the heat escaping to the holding member 23. For example, the greater the heating value of the heater 26 relative to a certain detection temperature of the thermistor 24, the greater the heating value of the heater 26 becomes.

[0291] However, the heat escaping to the holding member 23 is energy not used for fixing the toner image t, and setting the heating amount of the heater 26 to compensate for the heat escaping to the holding member 23 is not ideal from the viewpoint of improving energy saving performance.

[0292] [Slide panel]

[0293] In this embodiment, based on the above-mentioned problem, the holding member 23 is configured not to contact the inner surface of the fixing belt 21, or the contact area is smaller than that of the reference example. Fig.15 As shown, the holding member 23 of this embodiment has guide surfaces 23A and 23B for guiding the fixing belt 21 upstream and downstream of the slide plate 27 in the recording material conveying direction (+y direction). The guide surfaces 23A and 23B are curved surfaces having a predetermined curvature when viewed in the x-axis direction in order to guide the fixing belt 21 more smoothly.

[0294] The guide surface 23A is an example of a first facing portion that faces the inner surface of the fixing member upstream of the sliding friction portion in the second direction. The guide surface 23B is an example of a second facing portion that faces the inner surface of the fixing member downstream of the sliding friction portion in the second direction. The first facing portion and the second facing portion do not necessarily need to be curved surfaces, but if they are curved surfaces, the fixing belt 21 can be smoothly guided even if the rotation track of the fixing belt 21 changes.

[0295] The end points P23A and P23B of the guide surfaces 23A and 23B that are closest to the pressure roller 202 in the z-axis direction (the -z direction side) are located on the opposite side (the +z direction side) to the pressure roller 202 than the position of the sliding friction surface 271b of the slide plate 27 in the z-axis direction. That is, in the third direction, the first facing portion and the second facing portion are retreated to the side away from the pressure member compared to the sliding friction portion.

[0296] Therefore, when the pressure roller 202 moves toward Fig.15When the fixing belt 21 is driven to rotate in the direction of arrow R3 and follows the rotation of the pressure roller 202, the inner surface of the fixing belt 21 mainly contacts the sliding friction surface 271b of the sliding plate 27 and is difficult to contact the guide surfaces 23A and 23B of the holding member 23. In other words, the holding member is configured so that when the pressure member is driven to rotate and the fixing member follows the rotation of the pressure member, the fixing member does not contact the first facing portion and the second facing portion. That is, it is difficult for the heat of the fixing belt 21 to escape to the holding member 23 via the guide surfaces 23A and 23B.

[0297] In the present embodiment, the width of the slide plate 27 in the recording material conveying direction (+y direction) is set larger than that in the reference example. This adjusts the rotation trajectory of the fixing belt 21 .

[0298] The width of the slide plate 27 will be further described. The rotation track of the fixing belt 21 is determined by the contact start point and separation point of the member (slide plate 27 and / or holding member 23) that contacts the inner surface of the fixing belt 21. Fig.18 In the reference example, the contact start point is the end point P23A′ of the guide surface 23A′ on the upstream side of the holding member 23 , and the separation point is the end point P23B′ of the guide surface 23B′ on the downstream side of the holding member 23 .

[0299] According to the construction of the reference example, if the guide surfaces 23A' and 23B' are simply moved upward to avoid contact with the fixing belt 21, the contact start point and the separation point are offset. That is, the contact start point becomes the upstream end of the sliding friction surface 271b of the sliding plate 27, and the separation point becomes the downstream end of the sliding friction surface 271b. Therefore, there is a possibility that the rotation track of the fixing belt 21 changes.

[0300] Therefore, in this embodiment, the contact start point and the separation point are maintained by increasing the width of the sliding friction surface 271b of the sliding plate 27 in the recording material conveying direction (y-axis direction) compared with the reference example. The width of the sliding friction surface 271b of the sliding plate 27 can be appropriately adjusted according to the main factors such as the outer diameter of the fixing belt 21 or the pressure at the nip portion N.

[0301] like Fig.15As shown, the fixing belt 21 in the fixing device 200 of this embodiment is basically held only by the sliding plate 27 and the pressure roller 202 to limit the rotation track. The fixing belt 21 relies on its own rigidity to maintain a roughly cylindrical shape in the maximum paper passing area in the length direction (x-axis direction). The fixing belt 21 is basically not in contact with the retaining member 23 or the stay 22. In addition, the so-called paper passing area refers to the area where the recording material S passes in the width direction (x-axis direction) at the clamping portion N that is orthogonal to the recording material conveying direction. In addition, the so-called maximum paper passing area refers to the paper passing area when the recording material S of the maximum size that can form an image by the image forming device 100 passes through.

[0302] In order for the fixing belt 21 to maintain its cylindrical shape by its own rigidity, the thickness of the fixing belt 21 is preferably 40 μm or more, for example.

[0303] use Fig.15 The following will explain the movement of heat related to the fixing belt 21 when the fixing device 200 performs a fixing action (when performing an image forming action). If the image forming action starts, the pressure roller 202 is driven to rotate in the direction of R3 in the figure. The fixing belt 21 follows the pressure roller 202 and rotates in the direction of R4 in the figure due to the friction force received from the pressure roller 202 in the clamping portion N. On the other hand, by energizing the resistive heating element, the heater 26 generates heat, and the heat of the heater 26 is transferred to the fixing belt 21 via the sliding plate 27. During the execution of the fixing action, the fixing belt 21 is maintained at a specified fixing temperature by the heat supplied via the sliding plate 27.

[0304] Here, in this embodiment, the fixing belt 21 is basically in contact with only the slide plate 27 and the pressure roller 202, and the heat escape path of the fixing belt 21 is mainly to the contact portion (nip portion) with the pressure roller 202 and the heat dissipation in the air. That is, since the fixing belt 21 is not in contact with the guide surfaces 23A and 23B of the holding member 23, the heat escape from the fixing belt 21 can be reduced.

[0305] [Summary of this embodiment]

[0306] According to the above configuration, heat from the heater 26 as a heat source can be transferred to the fixing belt 21 as little as possible and used to fix the toner image t on the recording material S. Therefore, it is possible to improve thermal efficiency and energy saving performance.

[0307] In other words, in this embodiment, the first facing portion and the second facing portion are retracted toward the side farther from the pressure member than the sliding friction portion in the third direction. According to this configuration, the energy saving performance of the fixing device can be improved.

[0308] In addition, in this embodiment, the fixing belt 21 is basically clamped only by the slide plate 27 and the pressure roller 202, and is basically maintained in a state of not contacting other members. This state is maintained when the recording material S is clamped by the clamping portion N and when the recording material S is not clamped by the clamping portion N. Therefore, it is possible to achieve further improvement in thermal efficiency and improvement in energy saving performance.

[0309] [Variation example]

[0310] In this embodiment, the heater 26 is arranged between the holding member 23 and the slide plate 27, but it may also be arranged between the holding member 23 and the slide plate 27. Fig.19 As in (a), the heat-retaining plate 25 is arranged between the holding member 23 and the heater 26. In this case, as in the present embodiment, the guide surfaces 23A and 23B of the holding member 23 are arranged to be retracted in the +z direction relative to the sliding friction surface 271b of the sliding plate 27 so as not to contact the inner surface of the fixing belt 21. Thus, the same effect as in the present embodiment can be obtained.

[0311] Alternatively, it can be Fig.19 As in (b), the guide surfaces 23A′ and 23B′ ( Fig.18 By removing the portions corresponding to the guide surfaces 23A′ and 23B′, the heat capacity of the holding member 23 becomes smaller, so that the amount of heat accumulated from the heater 26 to the holding member 23 via, for example, the support surface of the heater 26 in the holding member 23 can be suppressed to a low level.

[0312] Fig.19 The modified example shown in (b) is a configuration in which the holding member 23 has a strength within a range where it does not deform when receiving a pressing force (a pressing force in the g direction in the figure) from the stay 22, and the guide surfaces 23A′ and 23B′ are cut out from the holding member 23. As a result, it is no longer necessary to store heat in the cut out portion, and the fixing belt 21 can be maintained at the fixing temperature with less heat.

[0313] The shape of the holding member 23 is not limited to the shape described in the present embodiment or the modified example, and may be any shape as long as it does not contact the fixing belt 21 as much as possible. The shape of the holding member 23 is more preferably set so that the fixing belt 21 is held only by the sliding plate 27 and the pressure roller 202, and the fixing belt 21 does not contact the holding member 23 and other members.

[0314] [Comparison with reference example]

[0315] exist Fig.17 , Fig.18 The fixing device 200' of the reference example shown in FIG. Fig.19The fixing performance and power consumption are compared between the fixing devices 200 of the configuration shown in (a). The two fixing devices 200 and 200' differ in whether the guide surfaces 23A and 23B (23A' and 23B') of the holding member 23 are retracted in the +z direction compared to the sliding friction surface 271b of the sliding plate 27, and the other configurations are common.

[0316] The comparative experiment confirmed the fixing performance and the accumulated power consumption when the image forming apparatus 100 equipped with the fixing device 200 or the fixing device 200′ was subjected to continuous paper feeding. The experiment was conducted under an environment of 23.0°C. The fixing temperature was set to 180°C and the processing speed was set to 200 mm / s. As the recording material S, a recording material with a unit weight of 120 g / m 2 A4 paper. In the continuous paper feed, a test image (a black monochrome halftone image) is continuously formed on 20 sheets of recording material.

[0317] The evaluation of fixability was performed by calculating the density reduction rate using the following method. The measurement instrument was a MACBETH reflection densitometer RD914. For a halftone image fixed on paper, five lens cleaning papers (Dusper K-3 manufactured by Ozu Industry) were stacked and measured at a load of 0.4 N / cm. 2 The density before and after the next five reciprocating wipes. In this embodiment, the density before wiping D1 is about 0.7 as the halftone density. If the density after wiping is set to D2, the density reduction rate is calculated by (D1-D2) / D1.

[0318] After the paper is continuously passed, the concentration reduction rate is calculated by the above method. If the concentration reduction rate is less than 10%, it is judged as "OK" (good fixability), and if the concentration reduction rate is more than 10%, it is judged as "NG" (bad fixability). In addition, the cumulative power amount is the cumulative value of the power supplied to the heater 26 during the above-mentioned continuous paper passing.

[0319] exist Fig. 20 The results of fixability and cumulative power consumption are shown in FIG. Fig.19In the fixing device 200 of (a), good fixing performance was achieved by setting the fixing temperature to 180°C. In addition, the cumulative power amount was 5.136Wh. On the other hand, in the case of the fixing device 200' of the reference example, when the fixing temperature was set to 180°C, the cumulative power amount was 5.140Wh (100.1% when the present embodiment was set to 100%), which was exactly the same as that of the present embodiment, but poor fixing occurred. In the fixing device 200' of the reference example, when the fixing temperature was set to 182°C, good fixing performance was achieved, but the cumulative power amount became 5.268Wh (102.6% when the present embodiment was set to 100%), which was more than that of the fixing device 200 of the present embodiment.

[0320] Therefore, it was confirmed that by applying the configuration of this embodiment, good fixing performance can be obtained with less power consumption than the reference example, and energy saving performance can be improved.

[0321] 《Example 5》

[0322] This embodiment is a structure that can further achieve improved thermal efficiency and energy-saving performance compared to embodiment 4. In the following, for elements marked with reference numerals common to embodiment 1, unless otherwise specified, they refer to structures and functions that are substantially the same as those described in embodiment 1, and the description will focus on the parts that are different from embodiment 1.

[0323] [Problem]

[0324] In this embodiment, a structure that can improve the energy-saving performance of the fixing device similarly to the fourth embodiment is proposed.

[0325] [Slide panel]

[0326] Fig.21 It is a cross-sectional view of the belt heating section 210 of the fixing device 200 according to the present embodiment, and shows a state in which the fixing belt 21 travels during a fixing operation.

[0327] In the fixing device 200 of the present embodiment, the sliding plate 27 is formed to cover the holding member 23 , so that the fixing belt 21 does not contact the holding member 23 and the contact area between the sliding plate 27 and the fixing belt 21 is increased.

[0328] The slide plate 27 is adjacent to the heater 26 as in the fourth embodiment and is arranged on the pressure roller 202 side of the heater 26. The slide plate 27 includes: a planar sliding friction portion 271 that slides against the inner surface of the fixing belt 21; and a guide portion 274 that extends from the sliding friction portion 271 to the upstream / downstream side in the recording material conveying direction (-y direction, +y direction in the figure). The guide portion 274 includes an extended portion 274a that extends to cover the side surfaces of the holding member 23 in the +y direction and -y direction. The guide portion 274 is formed in a curved surface shape having a center inside the substantially cylindrical shape drawn by the fixing belt 21 so as to follow the rotation track of the fixing belt 21.

[0329] The guide portion 274 on the upstream side is an example of a first guide portion, and the guide portion 274 on the downstream side is an example of a second guide portion. The curvature of the guide portion 274 in this embodiment is set to be larger than the curvature of the fixing belt 21. At the ends of the upstream / downstream sides of the sliding plate 27 in the recording material conveying direction, a bent portion 275 is formed which is bent at a substantially right angle relative to the extended portion 274a of the guide portion 274. The bent portion 275 is hooked on the corner of the retaining member 23. Since the bent portion 275 of the sliding plate 27 is provided at the ends of both the upstream / downstream sides in the recording material conveying direction, the sliding plate 27 is fixed relative to the retaining member 23 and does not fall off.

[0330] When viewed in the +z direction, the entire holding member 23 may be covered by the sliding friction portion 271 and the guide portion 274. This prevents the fixing belt 21 from contacting the holding member 23, thereby preventing heat from escaping through the holding member 23.

[0331] During the fixing operation, the slide plate 27 contacts the heater 26 via the heat-conducting grease G1 and is heated by the heat from the heater 26. Since the slide plate 27 is made of metal as described above, the heat of the sliding friction portion 271 of the slide plate 27 is transferred to the guide portion 274, and the guide portion 274 is heated in the same manner as the sliding friction portion 271. During the fixing operation, the guide portion 274 is maintained at a temperature equal to that of the fixing belt 21.

[0332] [Comparison with Example 4]

[0333] The fixing device 200 in this embodiment has the guide portion 274 as a curved surface that is curved in the same direction along the track of the fixing belt 21 on the slide plate 27 as described above. Fig.21 ), not only the sliding friction portion 271 of the sliding plate 27 but also the guide portion 274 contacts the fixing belt 21. On the other hand, in the belt heating portion 210 ( Fig.16 ), the part in contact with the fixing belt 21 is basically only the sliding friction portion 271 of the sliding plate 27.

[0334] That is, in the fixing device 200 of the present embodiment, the contact area between the slide plate 27 and the fixing belt 21 is expanded compared with that of the embodiment 4. That is, when compared at the same process speed, the slide plate 27 of the present embodiment is in contact with the fixing belt 21 for a longer time than the slide plate 27 of the embodiment 4. Therefore, the slide plate 27 can transfer more heat to the fixing belt 21.

[0335] That is, in the case of this embodiment, the fixing belt 21 can be maintained at a predetermined fixing temperature while the temperature of the sliding plate 27 is lower than that of the embodiment 4. In addition, since the temperature of the sliding plate 27 during the fixing operation is low, even if the control target temperature of the heater 26 is set lower than that of the embodiment 4, good fixing performance can be obtained. Furthermore, when the control target temperature of the heater 26 becomes lower, the heat that escapes from the heater 26 to the air or the holding member 23 also becomes less.

[0336] Therefore, by applying the configuration of this embodiment, good fixing performance can be obtained with less power consumption than that of Embodiment 4, and energy saving performance can be improved.

[0337] [Summary of this embodiment]

[0338] In this embodiment, the guide portions 274 on the upstream and downstream sides of the slide plate 27 are curved to guide the fixing belt 21. In other words, the first guide portion and the second guide portion are curved along the rotation track of the fixing member when viewed in the first direction. According to this configuration, the energy saving performance of the fixing device can be improved.

[0339] In addition, in this embodiment, since the slide plate 27 is extended to the upstream and downstream sides of the heater 26 in the recording material conveying direction (y-axis direction), it is possible to suppress the leakage of the thermal conductive paste G1 to the sliding friction surface 271b of the slide plate 27. Figure 21 to Figure 23 In this way, when viewed in a cross section perpendicular to the x-axis direction, the creeping distance of the path from the heater contact surface 271a of the sliding plate 27 through the inner wall and the outer wall of the guide portion 274 to the sliding friction surface 271b is greater than that of the fourth embodiment ( Fig.18 ) is the distance along the path from the heater contact surface 271a through the inner wall and outer wall of the rising portion 272 to the sliding friction surface 271b. Therefore, the thermal conductive paste G1 is unlikely to reach the sliding friction surface 271b side of the sliding plate 27, which can reduce the possibility of promoting wear on the inner surface of the fixing belt 21.

[0340] [Variation example]

[0341] In this embodiment, the example in which the bent portion 275 is formed at the end of the slide plate 27 and the extended portion 274a of the guide portion 274 is provided so as to cover the entire side surface of the holding member 23 in the recording material conveying direction (y-axis direction) is described. Fig. 22 Thus, the groove 232 is provided on the side of the holding member 23, and the bent portion 275 provided on the slide plate 27 is fitted into the groove 232. The groove 232 may be formed over the entire region of the holding member 23 in the x-axis direction, or may be formed only in a portion of the holding member 23.

[0342] exist Fig. 22 In the modified example, when viewed from the side of the pressure roller 202 in the z-axis direction, the slide plate 27 covers the entire holding member 23. Therefore, the same effect as that of the present embodiment can be obtained. Fig. 22 In the modified example, there is an advantage that the area of ​​the plate material used for the sliding plate 27 is smaller than that of the present embodiment.

[0343] In addition, Fig.23 In the modification shown, the slide plate 27 has a rising portion 272 in addition to the guide portion 274. The guide portion 274 is continuously provided on the upstream side and the downstream side of the recording material conveying direction (y-axis direction) with respect to the sliding friction portion 271 and is curved with a predetermined curvature. In this modification, the rising portion 272 is respectively arranged on the upstream side and the downstream side of the recording material conveying direction (y-axis direction). The rising portion 272 on the upstream side (the first rising portion) is continuously provided on the upstream side of the guide portion 274 on the upstream side, and the rising portion 272 on the downstream side (the second rising portion) is continuously provided on the downstream side of the guide portion 274 on the downstream side. The rising portions 272 are curved relative to the guide portion 274 so as to extend toward the side (+z direction side) away from the pressure roller 202 in the z-axis direction, and are accommodated in the groove portion 231 of the holding member 23. The groove portion 231 on the upstream side is an example of a first recessed portion. The groove portion 231 on the downstream side is an example of a second recessed portion.

[0344] In addition, the holding member 23 has a concave heater housing portion 234 (third concave portion) for housing the heater 26. The upstream guide portion 274 (first guide portion) covers the convex portion between the upstream groove portion 231 (first concave portion) and the heater housing portion 234 (third concave portion) when viewed in the +z direction (third direction). In addition, the downstream guide portion 274 (second guide portion) covers the convex portion between the downstream groove portion 231 (second concave portion) and the heater housing portion 234 (third concave portion) when viewed in the +z direction (third direction).

[0345] exist Fig.23In the modified example of FIG. 2 , the curved guide portion 274 is also provided, so that the contact area between the slide plate 27 and the inner surface of the fixing belt 21 is expanded compared with the fourth embodiment. Therefore, the same effect as that of the present embodiment can be obtained.

[0346] In addition, since the sliding plate 27 can be engaged with the holding member 23 without using the bent portion 275, Fig.21 , Fig. 22 Compared with the method of FIG. 1 , the processing steps of the sliding plate 27 are reduced, and the processing cost can be reduced.

[0347] Example 6

[0348] In this embodiment, a slide plate 27 having a shape in which the width in the recording material conveying direction varies depending on the position in the longitudinal direction is used. Hereinafter, for elements marked with reference numerals common to those in Embodiment 1, unless otherwise specified, they have substantially the same structure and function as those described in Embodiment 1, and the description will be mainly based on the parts different from Embodiment 1.

[0349] [Problem]

[0350] When a recording material having a large width (paper width) in the x-axis direction (hereinafter referred to as large-size paper) is passed through, the fixability may be reduced in the end area of ​​the recording material in the x-axis direction. The reduction in fixability is caused by the following reasons: the heat is diffused by the pressure roller 202 to the non-paper passing portion outside the paper passing area, so that the temperature of the fixing belt 21 and the pressure roller 202 at the end of the paper passing area is reduced (hereinafter referred to as end temperature drop). The so-called non-paper passing portion refers to the area where the recording material does not pass in the length direction (x-axis direction) of the clamping part N.

[0351] Hereinafter, the width of the clamping portion N in the recording material conveying direction (y-axis direction) is referred to as the clamping width. As a countermeasure for the temperature drop at the end, the clamping width at the end of the clamping portion N in the length direction (x-axis direction) is sometimes made larger than the clamping width at the center, thereby achieving uniform fixability in the length direction. On the other hand, when the difference in the clamping width between the end and the center of the clamping portion N is large, image scratches may occur due to the warping of the rear end of the recording material.

[0352] Therefore, in this embodiment, a configuration is proposed that can simultaneously achieve uniformity of fixability and reduction of image defects caused by rear end lift.

[0353] [Slide panel]

[0354] In this embodiment, in order to reduce the reduction in fixability in the end region of the recording material due to the temperature drop at the end, the sliding plate 27 is formed in such a manner that the width of the sliding plate 27 in the recording material conveying direction becomes larger toward both outer sides in the length direction of the nip N. The width of the sliding plate 27 in this embodiment refers to the width of the sliding friction surface 271b that slides against the fixing belt 21.

[0355] The larger the cross-sectional area of ​​the sliding plate 27 perpendicular to the longitudinal direction, the greater the heat conductivity of the sliding plate 27 in the longitudinal direction. Therefore, by increasing the width of the sliding plate 27 in the recording material conveying direction toward the two outer sides in the longitudinal direction, the heat conductivity of the area near the two end portions in the longitudinal direction becomes greater. Since the sliding plate has a function as a heat diffusion member, by increasing the width of the end portions of the sliding plate 27 as in this embodiment, the diffusion of heat from the central portion to the end portions in the paper passing area can be promoted, and the fixability in the end portions of the recording material can be improved.

[0356] Fig.28 (a) is a perspective view (left side) showing a sliding plate 27 of a reference example in which the width Sw of the sliding plate 27 is constant through the center and the ends, and a schematic diagram (right side) showing the positional relationship between the sliding friction surface 271b of the sliding plate 27 of the reference example and the clamping part N. Fig.28 (b) is a perspective view (left) of the sliding plate 27 of this embodiment showing that the width Tw of the end portion is larger than the width Cw of the central portion, and a schematic diagram (right) showing the positional relationship between the sliding friction surface 271b of the sliding plate 27 of this embodiment and the clamping portion N.

[0357] The width (clamping width) of the clamping portion N in the recording material conveying direction (y-axis direction) is common to the reference example and the present embodiment. The clamping width is 8.0 mm in the center of the clamping portion N in the length direction (x-axis direction), and 8.8 mm at both ends of the clamping portion N in the length direction (x-axis direction).

[0358] exist Fig.28 In the reference example shown in (a), the slide plate 27 is a straight shape with a width Sw of 12.0 mm across the entire area in the longitudinal direction. In the central portion of the clamping portion N, the width of the slide plate 27 is 33% larger than the clamping width (8.0 mm) (the upstream and downstream sides in the recording material conveying direction are 2 mm larger). On the other hand, at the end of the clamping portion N, the width of the slide plate 27 is 26% larger than the clamping width (8.8 mm) (the upstream and downstream sides in the recording material conveying direction are 1.6 mm larger).

[0359] exist Fig.28In the present embodiment shown in (b), the sliding plate 27 is a shape in which the width Tw at the end is larger than the width Cw at the center (a necked shape, a narrow shape in the middle). The width Cw of the sliding plate 27 at the center of the clamping portion N is 12.0 mm, and the width Tw of the sliding plate 27 at the end of the clamping portion N is 13.0 mm. In the center of the clamping portion N, the width of the sliding plate 27 is 33% larger than the clamping width (8.0 mm) (and 2 mm larger on the upstream and downstream sides in the recording material conveying direction). On the other hand, at the end of the clamping portion N, the width of the sliding plate 27 is 32% larger than the clamping width (8.8 mm) (and 2.1 mm larger on the upstream and downstream sides in the recording material conveying direction). By setting it in such a shape, the sliding plate 27 toward the outside in the longitudinal direction in the paper passing area can easily diffuse heat, and the reduction in the fixability in the end area of ​​the recording material can be reduced.

[0360] Fig.29 (a) and (b) respectively represent Fig.28 Temperature distribution of the slide plate 27 at the end positions shown in (a) and (b). Fig.29 (a) is a reference example. Fig.29 (b) is the case of this embodiment.

[0361] On the inner side of the nip N in the recording material conveying direction (y-axis direction), the slide plate 27 contacts the pressure roller 202 via the fixing belt 21, so that the heat is absorbed by the pressure roller 202 and the temperature of the slide plate 27 decreases. On the other hand, on the outer side of the nip N in the recording material conveying direction (y-axis direction), the slide plate 27 does not contact the pressure roller 202, so the temperature of the slide plate 27 becomes higher than that of the inner side of the nip N.

[0362] and Fig.29 Compared with the straight sliding plate of the reference example (a), Fig.29 In the sliding plate 27 of this embodiment shown in (b), the width of the sliding plate 27 at the end of the clamping portion N is sufficiently larger than the clamping width, and the area outside the clamping portion N is large. Therefore, the heat from the outside of the clamping portion N in the recording material conveying direction (y-axis direction) is transferred to the inside of the clamping portion N, and the temperature drop of the clamping portion N can be suppressed. More preferably, as in this embodiment, the width (2.1 mm) of the area outside the clamping portion N of the sliding plate 27 at the end of the clamping portion N is greater than the width (2.0 mm) of the area outside the clamping portion N of the sliding plate 27 at the center.

[0363] In addition, the greater the width of the slide plate 27, the higher the heat diffusion effect. However, if it is too large relative to the nip width, the heat dissipation effect (the effect of heat escaping from the slide plate 27 to the air, etc. outside the nip portion N) becomes greater, and there is also a possibility that the fixing performance is reduced. Therefore, the width of the slide plate 27 can be appropriately changed according to the specific structure such as the structure of the elastic layer of the pressure roller 202, the heat conductivity and thickness of the slide plate 27.

[0364] [Temperature drop at the end and material of the pressure roller]

[0365] As one of the factors that easily cause the end temperature drop, the material of the elastic layer of the pressure roller 202 will be described.

[0366] As the elastic layer of the pressure roller 202, sponge rubber (foamed rubber) or solid rubber can be used. However, when solid rubber is used as the elastic layer, the end temperature drop is more likely to occur than when sponge rubber is used as the elastic layer. This is because the thermal conductivity of solid rubber is generally higher than that of sponge rubber. Therefore, if solid rubber is used as the elastic layer of the pressure roller 202, heat is more likely to escape to the non-paper passing portion.

[0367] Sponge rubber can improve thermal insulation and reduce heat capacity, and can improve the start-up performance (quick start-up performance) of the fixing device 200. On the other hand, it may have lower durability than solid rubber. In addition, when recording materials with small paper width (hereinafter referred to as small-size paper) are passed through, the surface temperature of the pressure roller 202 is likely to rise in the non-paper passing portion. If the paper passing interval is increased to prevent the surface temperature of the pressure roller 202 in the non-paper passing portion from exceeding the heat resistance temperature of the pressure roller 202, there is a disadvantage that the productivity of small-size paper is reduced.

[0368] When productivity and durability are required, solid rubber is sometimes used as the elastic layer of the pressure roller 202. Solid rubber has a higher thermal conductivity than sponge rubber, so it is inferior to sponge rubber in terms of startup. On the other hand, it is easy to diffuse heat in the longitudinal direction (x-axis direction), so it can reduce the temperature rise of the non-paper passing part, which is advantageous in terms of productivity of small-sized paper.

[0369] In this embodiment, solid rubber is used as the elastic layer of the pressure roller 202, but the structure of this embodiment can also be applied to the case where sponge rubber is used as the elastic layer.

[0370] [Image scratches caused by rear end warping]

[0371] By setting the nip width at the end portions of the nip portion N in the longitudinal direction (x-axis direction) to be larger than the nip width at the center portion, the temperature drop at the end portions can be reduced, and uniform fixing properties can be achieved.

[0372] The larger the clamping width, the faster the recording material conveying speed of the clamping portion N. This is affected by the following factors: when the pressing force of the clamping portion N is high and the clamping width is large, the recording material and the pressure roller 202 are difficult to slide, and the elastic layer of the pressure roller 202 is deformed and stretched, so the apparent circumference becomes longer. In addition, when the clamping width at the end portion in the length direction (x-axis direction) of the clamping portion N is larger than the clamping width at the center portion, the recording material conveying speed at the end portion is faster than the recording material conveying speed at the center portion. According to this structure, wrinkles of the recording material can be reduced.

[0373] However, when there is a difference in the recording material conveying speed between the center and the end of the clamping portion N, there is a possibility that the rear end of the recording material S will be lifted. Fig.24 as well as Fig.25 Schematic diagram to illustrate.

[0374] When the recording material conveying speed at the end of the clamping portion N is faster than that at the center, the recording material S moves toward Fig.24 The recording material S is pulled in the direction of the arrow T1, and thus, a force is generated such that the rear end portion of the recording material S is lifted in the direction of the arrow T2 as the recording material S passes through the clamping portion N. Fig.25 As shown in the figure, if the rear end of the recording material S is separated from the transfer section, the rear end of the recording material S will be lifted in the direction of arrow T2 (referred to as rear end lift), and may collide with the drum cleaner 6Y or the cover of the fixing device 200. Due to such rear end lift, the unfixed toner image transferred to the recording material S may be disordered, and the image quality may be reduced (hereinafter referred to as image scratch).

[0375] [Clamping width setting]

[0376] In this embodiment, in order to reduce the temperature drop at the end, the pressure at the end of the clamping portion N is set higher than that at the center, and the clamping width at the end is increased.

[0377] exist Fig.26 (a) shows the deflection in the longitudinal direction caused by the pressure of the stay 22 and the pressure roller 202. Fig.26 As shown in (a) of FIG. 2 , both ends of the stay 22 are pressurized by the pressurizing spring 251. The pressurizing force acts on the pressure roller 202 from the belt unit 201 at the clamping portion N. The pressure roller 202 is supported by the bearing portions 252 at both ends to the frame of the fixing device 200. Therefore, the belt unit 201 receives an upward reaction force in the figure from the pressure roller 202. That is, the both ends of the stay 22 in the length direction (x-axis direction) receive a downward force in the figure, and the center portion in the length direction receives an upward force in the figure. In addition, the both ends of the pressure roller 202 in the length direction (x-axis direction) receive an upward force in the figure, and the center portion in the length direction receives a downward force in the figure.

[0378] Therefore, the stay 22 is Fig.26 In (a), the straight shape shown by the solid line 22c is bent as shown by the dotted line 22d. On the other hand, the core metal 202a of the pressure roller 202 is bent as shown by the dotted line 22d. Fig.26 In (a), the straight shape indicated by the solid line 202c is bent as indicated by the dotted line 202d.

[0379] If the stay 22 and the pressure roller 202 are bent, the clamping pressure at the center of the clamping portion N becomes lower, and the clamping width in the recording material conveying direction (y-axis direction) becomes smaller at the center of the clamping portion N. On the other hand, the clamping pressure at the ends of the clamping portion N becomes higher, and the clamping width in the recording material conveying direction (y-axis direction) becomes larger at the ends of the clamping portion N. If the clamping width at the center and ends of the clamping portion N differs greatly, image scratches may occur due to the rear end warping as described above.

[0380] Therefore, in this embodiment, if Fig.26 As shown in (a) of FIG. 1 , the clamping pressure and the clamping width are adjusted by using a holding member 23 having a different thickness T depending on the position in the longitudinal direction of the clamping portion N. Hereinafter, the holding member 23 is set to a shape in which the thickness T varies depending on the position in the longitudinal direction, and this is referred to as the crown correction of the holding member 23. In addition, the difference between the thickness T of the holding member 23 at the center of the clamping portion N in the longitudinal direction and the thickness T of the holding member 23 at the end of the clamping portion N in the longitudinal direction is referred to as the crown correction amount.

[0381] The thickness T of the retaining member 23 is the distance in the z-axis direction between the heater-facing surface of the retaining member 23 that faces the heater 26 (the surface facing the -z direction, or the surface facing the heat retaining plate 25 when a heat retaining plate 25 is provided) and the surface facing the +z direction on the back side of the heater-facing surface.

[0382] If the thickness T of the central portion of the retaining member 23 is thickened by correcting the convexity of the retaining member 23, the reduction in the clamping pressure of the central portion can be suppressed even when the stay 22 is bent, and the clamping width of the central portion becomes larger. However, if the clamping width of the central portion is too large, there is a possibility that the fixability of the end portion will be reduced due to the temperature drop of the end portion. From the viewpoint of uniformity of fixability in the length direction, in the configuration of this embodiment, it is more preferred to set the clamping width of the end portion to be 15% larger than that of the central portion. However, if the clamping width of the end portion is set to be more than 12% larger than that of the central portion, the above-mentioned image scratches caused by the warping of the rear end may sometimes occur.

[0383] Therefore, in this embodiment, the crown correction amount of the holding member 23 is set to 400 μm so that the clamping width at the end portion is approximately 10% larger than that at the center portion.

[0384] In addition, the method of adjusting the clamping pressure and the clamping width is not limited to the crown correction. As a method other than the crown correction of this embodiment, for example, the seat surface of the holding member 23 supporting the heat-retaining plate 25 and the heater 26 may be bent in the +z direction or -z direction in the longitudinal direction. In addition, for example, the outer diameter of the pressure roller 202 may be changed according to the position in the longitudinal direction.

[0385] Fig. 27 The measurement results of the clamping width at each position in the longitudinal direction and the pressure distribution of the clamping portion N in this embodiment are shown. The horizontal axis is the position in the longitudinal direction (x-axis direction) based on one end of the outer peripheral portion 202b of the pressure roller 202 in the longitudinal direction (x-axis direction) of the clamping portion N.

[0386] The method for measuring the nip width is as follows. Prepare a test paper having a width in the longitudinal direction (x-axis direction) greater than the roller width W202 ( Figure 7 ) on a large paper, a black monochrome image (all-black image) is formed over the entire effective image area in the length direction (x-axis direction). The test paper is clamped in the clamping portion N of the fixing device 200 and heated by the heater 26 when the drive of the pressure roller 202 is stopped. The temperature of the heater 26 is controlled to 150°C by the thermistor 24 and heated for 10 seconds. As a result, only the area clamped by the clamping portion N in the all-black image is heated, the gloss increases, and the trace of the clamping portion N is transferred to the all-black image. The clamping width is measured based on the trace of the clamping portion N. The clamping width is measured at intervals of 10 mm in the length direction. In addition, the pressure distribution in the length direction is measured using a surface pressure distribution measurement system (NITTA Corporation I-SCAN, with a length direction resolution of 0.5 mm).

[0387] like Fig. 27 As shown in FIG. 1 , the clamping width increases from the center to the two ends, and is 8.0 mm in the center and 8.8 mm at the two ends. That is, in this embodiment, the clamping width at the ends of the clamping portion N is 10% larger than the clamping width at the center. Thus, the reduction in the fixing performance of the end regions caused by the temperature drop at the end regions can be reduced.

[0388] In this embodiment, the configuration in which the clamping width at both ends of the clamping portion N is larger than that at the center is used in combination with the sliding plate 27 in which the width at both ends is larger than that at the center as described above. This can avoid image scratches due to the rear end warping, and can more effectively suppress the reduction of fixability in the end area due to the temperature drop at the end.

[0389] [Comparative test]

[0390] exist Fig.28The straight sliding plate 27 of the reference example shown in (a) and Fig.28 The test of evaluating the fixing property and the rear end lifting was conducted between the sliding plate 27 of the present embodiment shown in (b). Two fixing devices using the sliding plate 27 of the reference example were prepared. The first one was configured such that the clamping width at the end of the clamping portion N was 15% larger than the clamping width at the center (referred to as Comparative Example 1). The second one was configured such that the clamping width at the end of the clamping portion N was 10% larger than the clamping width at the center (referred to as Comparative Example 2).

[0391] Fixability was confirmed by forming 50 completely black images in succession to confirm whether there was any image defect or peeling. Back end lift was confirmed by confirming whether there was any image scratch caused by back end lift in the continuous paper passing of 50 completely black images. Even if there was any image defect or peeling in 1 out of 50, fixability was rated as "NG". Even if there was any image scratch in 1 out of 50, back end lift was rated as "NG". If there was no image defect in any of the above, it was rated as "OK". The results are shown in Fig.30 .

[0392] In Comparative Example 1, since the clamping width at the end was increased, there was no poor fixation due to the temperature drop at the end, but since the recording material conveying speed at the end was high, the rear end was lifted and the image was scratched. On the other hand, in Comparative Example 2, since the clamping width at the end was not too large, there was no image scratch due to the rear end lifting, but poor fixation due to the temperature drop at the end occurred after the 30th.

[0393] In contrast, in this embodiment, the clamping width of the end portion is not too large, similarly to Comparative Example 2, so that no image scratches due to the rear end warping occur. In addition, in this embodiment, since the width of the end portion of the sliding plate 27 is large, no poor fixing occurs due to the heat diffusion effect of the sliding plate 27.

[0394] [Summary of this embodiment]

[0395] As described above, in this embodiment, when the shape of the clamping portion N is set to a narrow shape in the middle portion in which the clamping width at the ends of the clamping portion N is larger than the clamping width at the center, the sliding plate 27 is also set to a shape in which the width of the sliding plate 27 becomes larger toward the ends in the longitudinal direction. In other words, the width of the clamping portion in the second direction at both ends of the clamping portion in the first direction is larger than the width of the clamping portion in the second direction at the center of the clamping portion in the first direction. In addition, the width of the sliding member in the second direction at both ends of the clamping portion is larger than the width of the sliding member in the second direction at the center of the clamping portion. According to this structure, uniformity of fixability and reduction of image defects caused by rear end warping can be achieved at the same time.

[0396] In addition, in the present embodiment, the upstream edge and the downstream edge of the slide plate 27 in the recording material conveying direction (y-axis direction) are bent in a symmetrical shape, so that the width of the end portion of the slide plate 27 is larger than the width of the central portion. The present invention is not limited to this, and for example, an asymmetrical shape may be adopted in which one of the upstream edge and the downstream edge extends linearly in the longitudinal direction (x-axis direction) of the clamping portion N and only the other of the upstream edge and the downstream edge is bent.

[0397] 《Variation of Example 6》

[0398] In Example 6, a configuration is described in which the clamping width of the end of the clamping portion N is larger than that of the central portion and the width of the end of the sliding plate 27 is larger than that of the central portion. As a modified example, a configuration example is described in which the clamping width of the end of the clamping portion N is smaller than that of the central portion and the width of the end of the sliding plate 27 is smaller than that of the central portion.

[0399] [Problem]

[0400] Sometimes, contrary to Example 6, the clamping width at the end of the clamping portion N in the recording material conveying direction (y-axis direction) is set smaller than the clamping width at the center, thereby reducing the wrinkles of the recording material. However, when the convexity of the holding member holding the heater is corrected to adjust the clamping width, the temperature of the center in the longitudinal direction is lowered due to the contact between the fixing belt and the holding member, and there is a possibility that the fixing performance in the center is reduced.

[0401] Therefore, in this embodiment, a configuration is proposed that can reduce wrinkles of the recording material and suppress a decrease in fixability at the center of the nip portion.

[0402] [Cornerance amount when using sponge rubber]

[0403] As described above, sponge rubber obtained by foaming silicone rubber or the like may be used as the elastic layer of the pressure roller 202. When sponge rubber is used, wrinkles of the recording material may be prevented by making the clamping width at the center larger than that at the ends.

[0404] When the sponge rubber is crushed at the nip portion N, the air therein is discharged and the volume becomes smaller. Therefore, compared with the case where solid rubber is used, the rotation radius of the pressure roller 202 at the nip portion N becomes substantially smaller, and the outer circumference of the pressure roller 202 near the nip portion N becomes shorter. Therefore, the more the elastic layer at the nip portion N is crushed, the slower the recording material conveying speed at the nip portion N. That is, when sponge rubber is used as the elastic layer, there is a relationship that the larger the nip width, the slower the recording material conveying speed, contrary to the case where solid rubber is used.

[0405] Therefore, when sponge rubber is used as the elastic layer of the pressure roller 202, the nip width at the end of the nip portion N in the longitudinal direction is smaller than the nip width at the center. As a result, the recording material conveying speed at the end of the nip portion N is faster than that at the center, and wrinkles of the recording material are less likely to occur.

[0406] As a means for increasing the clamping width of the central portion of the clamping portion N, there is the convexity correction of the holding member 23 as described above. As an example, the following configuration is described: in the fixing device 200 of Embodiment 6, the elastic layer of the pressure roller 202 is formed of sponge rubber, and the convexity correction of the holding member 23 makes the clamping width of the central portion larger than that of the end portions.

[0407] [Clamping width]

[0408] Fig.31 The figure shows the distribution of the clamping width and the pressure (clamping pressure) of the clamping portion N at various positions in the length direction in the configuration example of performing convexity correction of the holding member 23. Here, the convexity correction amount of the holding member 23 is set to 600 μm, and the clamping width of the central portion of the clamping portion N is adjusted to be approximately 10% larger than that of the end portion. The horizontal axis is the position in the length direction (x-axis direction) based on one end of the outer peripheral portion 202b of the pressure roller 202 in the length direction (x-axis direction) of the clamping portion N. Measurement method and use of clamping width and clamping pressure Fig. 27 The method of description is the same.

[0409] like Fig.31 As shown in the figure, by correcting the convexity of the holding member 23, the clamping width increases as it approaches the center from the two ends of the clamping portion N. The clamping width of the center is 8.8 mm, and the clamping width of the two ends is 8.0 mm. That is, by increasing the convexity correction amount of the holding member 23, the clamping pressure of the center can be increased, thereby setting the clamping width of the center to be larger than that of the two ends.

[0410] However, when the crowning correction amount of the holding member 23 is increased, there is a possibility that the center portion of the fixing belt 21 may come into contact with the stay 22 . Fig.32 (a) shows the state where the fixing belt 21, the stay 22, and the pressure roller 202 are bent when the belt unit 201 is pressed against the pressure roller 202. If the thickness T of the central portion of the holding member 23 is increased by the convexity correction, the fixing belt 21 is bent so that the central portion of the fixing belt 21 protrudes toward the pressure roller 202 side (-z direction side) more than the both ends. Due to such bending of the fixing belt 21, there is a possibility that the portion of the fixing belt 21 on the opposite side (+z direction side) of the clamping portion N may contact the stay 22.

[0411] When the fixing belt 21 contacts the stay 22, the heat of the fixing belt 21 is absorbed by the stay 22, and the surface temperature of the fixing belt 21 decreases. As a result, there is a possibility that poor fixing occurs in the contact range between the fixing belt 21 and the stay 22 in the longitudinal direction (x-axis direction). In order to increase the strength, the stay 22 is often made of a metal material. Metal materials have a large heat capacity and a high thermal conductivity, so poor fixing is easily caused.

[0412] In order to suppress poor fixing, Fig.32 As shown in (b) of FIG. 2 , it is considered to provide a contact preventing member 254. The contact preventing member 254 is disposed between the stay 22 and the inner surface of the fixing belt 21 to prevent the inner surface of the fixing belt 21 from contacting the stay 22. In addition, the contact preventing member 254 is formed of a resin material having a lower thermal conductivity than the stay 22 in order to less easily absorb the heat of the fixing belt 21. Examples of the resin material are heat-resistant liquid crystal polymer (LCP) or heat-resistant polycarbonate (PC).

[0413] The contact preventing member 254 can prevent the fixing belt 21 from contacting the stay 22, but the temperature of the center portion of the fixing belt 21 is lower than that of the two end portions to a certain extent due to the contact between the fixing belt 21 and the contact preventing member 254. Therefore, even when the contact preventing member 254 is provided, it is preferable to make it more difficult for poor fixing to occur in the center portion of the nip portion N.

[0414] Therefore, in this variation, if Fig.33 As shown, the sliding plate 27 is formed in a shape in which the width Tw of the end portion is smaller than the width Cw of the central portion (a shape in which the central portion is expanded). For example, the width Cw of the sliding plate 27 at the central portion of the clamping portion N is 13.0 mm, and the width Tw of the sliding plate 27 at the end portion of the clamping portion N is 12.0 mm.

[0415] By adopting such a shape, the heat diffusion effect of the slide plate 27 in the central portion of the nip portion N can be improved, and the reduction in the fixing performance in the central portion can be reduced. That is, according to this modification, the fixing performance can be made uniform.

[0416] [Summary of this modification]

[0417] In this modified example, when the shape of the clamping portion N is set to a middle bulging shape in which the clamping width at the ends of the clamping portion N is smaller than the clamping width at the center, the sliding plate 27 is also set to a shape in which the width of the sliding plate 27 becomes smaller toward the ends in the longitudinal direction. In other words, the width of the clamping portion in the second direction at both ends of the clamping portion in the first direction is smaller than the width of the clamping portion in the second direction at the center of the clamping portion in the first direction. In addition, the width of the sliding member in the second direction at both ends of the clamping portion is smaller than the width of the sliding member in the second direction at the center of the clamping portion. According to this configuration, wrinkles of the recording material can be reduced, and the reduction in fixability at the center of the clamping portion can be suppressed.

[0418] Example 7

[0419] In this embodiment, the slide plate 27 is bent so that the center portion of the slide plate 27 in the longitudinal direction (x-axis direction) of the clamping portion N protrudes toward the downstream side (+y direction) in the recording material conveying direction compared with both end portions. Hereinafter, elements marked with reference numerals common to those in the first embodiment have substantially the same configuration and function as those described in the first embodiment unless otherwise specified, and the description will be mainly based on the parts different from the first embodiment.

[0420] [Problem]

[0421] During the fixing operation, the fixing belt 21 is bent in such a manner that the center portion of the fixing belt 21 in the length direction (x-axis direction) of the nip portion N protrudes toward the downstream side (+y direction) in the recording material conveying direction compared with both ends. Due to such bending, the curvature radius of the fixing belt 21 on the downstream side (+y direction) in the recording material conveying direction relative to the nip portion N becomes larger, and the recording material passing through the nip portion N is difficult to separate from the fixing belt 21, and there is a possibility that the recording material is entangled with the fixing belt 21.

[0422] Therefore, this embodiment proposes a configuration that can reduce the possibility of the recording material being entangled with the fixing belt.

[0423] [Bending of the fixing belt]

[0424] First, a case where the fixing belt 21 is bent during the fixing operation will be described using a specific configuration example. Fig.34(a) and (b) show the Fig.17 A schematic diagram of the fixing device 200 viewed from the belt unit 201 side toward the pressure roller 202 side (-z direction) in the reference example of FIG. Figure 3 (see figure from the direction of arrow P). Fig.34 (a) is a diagram when the pressure roller 202 is stopped. Fig.34 (b) is a diagram showing a state where the pressure roller 202 is driven to rotate.

[0425] In such Fig.34 When the rotation of the pressure roller 202 stops as shown in (a), the fixing belt 21 does not bend. Fig.34 As shown in (b) of FIG. 1 , the pressure roller 202 rotates and the fixing belt 21 rotates following the pressure roller 202 . The fixing belt 21 is bent so that the center portion in the longitudinal direction protrudes toward the downstream side (+y direction) in the recording material conveyance direction compared with both ends.

[0426] The fixing belt 21 is about to move as a whole toward the downstream side (+y direction) in the recording material conveying direction by the rotation drive of the pressure roller 202. However, the end surface of the belt guide 250 on the -y direction side that holds the two ends of the fixing belt 21 is located on the upstream side (-y direction) in the recording material conveying direction compared to the end surface of the holding member 23 on the -y direction side. In this case, the y-axis direction positions of the two ends of the fixing belt 21 are restricted by the end surfaces of the belt guide 250, while the central portion of the fixing belt 21 moves toward the +y direction until it contacts the end surface of the holding member 23. As a result, the fixing belt 21 is bent in such a way that the central portion in the length direction (x-axis direction) protrudes toward the downstream side (+y direction) in the recording material conveying direction compared to the two ends.

[0427] [Recording material winding]

[0428] like Fig.34 As shown in (b) of FIG. 1 , when the sheet of paper is passed through the fixing device 200 in a state where the fixing belt 21 is bent, there is a possibility that the recording material will be entangled with the fixing belt 21 . Fig.35 (a) and (b) are cross-sectional views of the belt heating unit 210 during the paper passing process of large-size paper. Fig.35 (a) shows a cross section at the center of a large-size paper. Fig.35 (b) shows a cross section at the end of a large-size paper.

[0429] like Fig.35As shown in (a), at both ends of the fixing belt 21, the rotation track of the fixing belt 21 is restricted by the belt guide 250 (guide member), and there is less slack on the downstream side (+y direction) of the recording material conveying direction relative to the nip portion N. Therefore, the curvature radius Rt of the fixing belt 21 on the downstream side (+y direction) of the recording material conveying direction relative to the nip portion N is relatively small, and the recording material S is easily separated from the fixing belt 21.

[0430] On the other hand, Fig.35 As shown in (b), in the central part of the fixing belt 21, the rotation track of the fixing belt 21 is loosened toward the downstream side (+y direction) of the recording material conveying direction relative to the clamping part N. Therefore, the curvature radius Rc of the fixing belt 21 at the downstream side (+y direction) of the recording material conveying direction relative to the clamping part N is larger than the curvature radius Rt of the end. As a result, it is difficult for the recording material S to be separated from the fixing belt 21. Therefore, there is a possibility that the recording material S is not separated from the fixing belt 21 and is entangled in the fixing belt 21. Conveying defect.

[0431] The recording material is easily wound around the fixing belt 21, especially in the case of small-sized paper. Fig.35 In the case of large-sized paper (recording material S with a large paper width) shown in (a) and (b), the end of the recording material S is first separated from the fixing belt 21, and it is relatively easy to separate even if the center of the fixing belt 2 is slack. In the case of small-sized paper with a short paper width, the entire small-sized paper contacts the fixing belt 21 near the center of the fixing belt 21 where the curvature radius is large, so it is difficult to separate compared with large-sized paper.

[0432] In addition, the winding of the recording material S to the fixing belt 21 also depends on the density of the image formed on the recording material S. That is, when an image with a large amount of toner (the weight of toner attached per unit area) or an image with a high printing rate (the ratio of the area covered by toner to the unit area) is formed, the adhesion of the recording material S to the fixing belt 21 becomes large, and winding is likely to occur.

[0433] [Shape of the sliding plate]

[0434] In the present embodiment, the shape of the slide plate 27 is set in accordance with the curved shape of the fixing belt 21 so that the radius of curvature also becomes smaller in the central portion of the fixing belt 21 .

[0435] In addition, the slide plate 27 of this embodiment is similar to that of Embodiments 4 and 5, and the fixing belt 21 is basically not in contact with the holding member 23, and is held only by the slide plate 27 and the pressure roller 202. Therefore, the structure described below has the same effect of improving thermal efficiency and energy saving performance as that of Embodiments 4 and 5. However, in this embodiment, the fixing belt 21 may be in contact with the holding member 23 and other members at the upstream side of the nip portion N that is not related to the winding of the recording material around the fixing belt 21.

[0436] Fig.36 A schematic diagram showing a state in which the fixing device 200 of the present embodiment is viewed from the belt unit 201 side toward the pressure roller 202 side (−z direction) ( FIG. Figure 3 As described above, when the pressure roller 202 is driven to rotate (during the fixing operation), the fixing belt 21 is bent so that the center portion of the fixing belt 21 protrudes toward the downstream side (+y direction) in the recording material conveying direction relative to both ends.

[0437] The sliding plate 27 of this embodiment is as follows Fig.36 As shown in FIG. 1 , the end surface 27d on the downstream side in the recording material conveying direction when viewed in the z-axis direction is curved. The end surface 27d on the downstream side is curved in such a manner that the central portion of the end surface 27d in the length direction (x-axis direction) of the clamping portion N protrudes toward the downstream side (+y direction) in the recording material conveying direction more than both ends of the end surface 27d. In addition, when viewed in the z-axis direction, the width of the sliding plate 27 in the recording material conveying direction (y-axis direction) at the central portion of the sliding plate 27 is larger than the width of the sliding plate 27 in the recording material conveying direction (y-axis direction) at the end portions of the sliding plate 27.

[0438] Fig.37 (a) and (b) are cross-sectional views of the belt heating portion 210 during the passage of large-size paper in the fixing device of this embodiment. Fig.37 (a) shows a cross section at the center of a large-size paper. Fig.37 (b) shows a cross section at the end of a large-size paper.

[0439] like Fig.37 As shown in (a) and (b) of FIG. 1 , the position of the end surface 27d on the downstream side of the slide plate 27 at the center of the nip portion N protrudes toward the downstream side (+y direction) in the recording material conveying direction than the position of the end surface 27d at the end position of the large-size paper. According to this shape, even if the center portion of the fixing belt 21 is loosened on the downstream side (+y direction) in the recording material conveying direction due to the deflection of the fixing belt 21, the rotation track of the fixing belt 21 can be restricted by the slide plate 27 on the downstream side relative to the nip portion N.

[0440] And, with Fig.35 Compared with the reference example shown in (b), Fig.37 In the central portion of the fixing belt 21 of this embodiment shown in (b), the curvature radius Rc of the fixing belt 21 on the downstream side (+y direction) in the recording material conveying direction relative to the nip portion N can be reduced. As a result, the possibility of the recording material being wound around the fixing belt 21 can be reduced. In particular, according to this embodiment, even in the case of small-sized paper or in the case of forming an image with a high toner load or printing rate, it is difficult for the recording material to be wound around the fixing belt 21.

[0441] In addition, in the configuration in which the fixing belt 21 does not contact the holding member 23 and the rotation track of the fixing belt 21 is restricted by the sliding plate 27 as in the present embodiment, the curvature of the fixing belt 21 can be controlled by changing the width or shape of the sliding plate 27. The sliding plate 27 is formed by, for example, stamping a metal plate. Therefore, it has advantages of being stronger than a guide made of resin, less warping or bending in the longitudinal direction, and being easy to obtain shape accuracy.

[0442] [Summary of this embodiment]

[0443] As described above, in the present embodiment, in the configuration in which both ends of the fixing belt 21 are guided by the belt guide 250, the end surface 27d of the slide plate 27 is formed to be bent toward the downstream side (+y direction) in the recording material conveying direction. In other words, the end surface of the sliding member on the downstream side in the second direction is bent in such a manner that the center of the end surface in the first direction protrudes toward the downstream in the second direction more than both ends of the end surface in the first direction. According to this configuration, the possibility of the recording material being entangled with respect to the fixing belt 21 can be reduced.

[0444] 《Variation of Example 7》

[0445] In Example 7, the example in which the downstream end surface 27 d of the slide plate 27 is formed so that the center portion in the longitudinal direction (x-axis direction) protrudes more toward the downstream side (+y direction) in the recording material conveying direction than both ends is described, but the present invention is not limited to this.

[0446] [Problem]

[0447] In the case of large-sized paper with a low basis weight (thin paper), separation failure is likely to occur at the corners of the recording material because the rigidity (hardness) of the recording material is low.

[0448] Therefore, in this modification, a configuration is proposed that can improve the separability of the corners of the recording material.

[0449] [Slide panel]

[0450] In this modified example, the end surface 27d on the downstream side of the slide plate 27 is formed so that both ends in the longitudinal direction (x-axis direction) protrude from the central portion toward the downstream side (+y direction) in the recording material conveying direction. According to such a shape, the curvature radius of the fixing belt 21 located on the downstream side (+y direction) in the recording material conveying direction relative to the clamping portion N can be reduced at both ends of the fixing belt 21. As a result, the corners of the recording material are easily separated from the fixing belt 21, and even when a recording material with low rigidity is passed through, the possibility of the recording material being entangled with the fixing belt 21 can be reduced.

[0451] In other words, the end surface of the sliding member on the downstream side in the second direction is curved in such a manner that both ends of the end surface in the first direction protrude toward the downstream in the second direction compared to the center of the end surface in the first direction. According to this configuration, the separability of the corners of the recording material can be improved.

[0452] 《Example 8》

[0453] In this embodiment, in order to suppress the temperature rise of the non-paper-passing portion, the heat-retaining plate is brought into contact with the sliding plate. In the following, for the elements marked with the same reference numerals as those in the first embodiment, unless otherwise specified, they have substantially the same structure and function as those described in the first embodiment, and the description will be mainly based on the parts different from the first embodiment.

[0454] [Problem]

[0455] When a recording material having a paper width smaller than the heating area of ​​the heater is passed through, the temperature of the fixing belt 21 or the pressure roller 202 rises in the area (non-paper passing area) where the recording material does not pass in the length direction (x-axis direction) of the nip N. If the temperature difference between the paper passing area and the non-paper passing area becomes large, the temperature of the fixing belt 21 or the pressure roller 202 in the non-paper passing area will rise excessively (heat rise in the non-paper passing area), and there is a possibility that the heat resistance temperature of the components will be exceeded. In addition, since the heat energy in the non-paper passing area is not used for fixing the image, the thermal efficiency and energy saving performance of the fixing device are not ideal.

[0456] Therefore, in this embodiment, a configuration is proposed that can reduce the temperature difference between the area through which paper passes and the area through which paper does not pass.

[0457] [Non-paper passing area temperature rise]

[0458] The non-paper-passing portion temperature increase will be described using a specific configuration example. Fig.38 (a) shows a general heater 26 used in a fixing device of a belt heating type. Fig.38 (a) is a diagram showing a surface of the heater 26 having the resistance heating element 262. In this embodiment, the resistance heating element 262 is arranged on the surface of the heater 26 facing the slide plate 27 ( Figure 4 on the surface 26a).

[0459] like Fig.38 As shown in (a), the heater 26 has a substrate 261, a resistive heating element 262, a conductor 263, and an electrode portion 264, each formed on the substrate 261. The resistive heating element 262 is arranged in a series circuit from the electrode portion 264 on one side through the conductor 263 to the electrode portion 264 on the other side. By applying a voltage to the electrode portion 264 from an external power supply circuit to energize the series circuit, the resistive heating element 262 generates heat. However, Fig.38 The configuration of the heater 26 shown in (a) is an example, and for example, a plurality of resistance heating elements 262 may be arranged in parallel, or the heater 26 may include a single resistance heating element 262 .

[0460] Here, if Fig.38 As shown in (b) of FIG. 1 , when a recording material having a smaller paper width than the width of the resistance heating element 262 (hereinafter referred to as small-size paper in this embodiment) is passed through, there is a non-paper-passing area (non-paper-passing portion) that is within the heating area of ​​the resistance heating element 262 and outside the paper-passing area. In the non-paper-passing portion, the fixing belt 21 or the pressure roller 202 is supplied with heat from the resistance heating element 262, while, on the other hand, the recording material does not absorb heat in the clamping portion N. Therefore, as shown in FIG. Fig.38 As shown in (b) of FIG. 1 , in the non-paper-passing portion, the temperature of members such as the fixing belt 21 and the pressure roller 202 increases.

[0461] In order to prevent the temperature of the fixing belt 21 or the pressure roller 202 from excessively rising (for example, exceeding the heat resistance temperature of the fixing belt 21) in the non-paper-passing portion, control is sometimes performed to expand the conveying interval (paper spacing) of the recording material for small-sized paper compared to the case of large-sized paper. By expanding the paper spacing, the temperature distribution in the longitudinal direction (x-axis direction) of the nip N is uniform during the period when the recording material does not pass through the nip N, and the disadvantage of the non-paper-passing portion being heated is less likely to occur. However, by expanding the paper spacing, there is a disadvantage that the productivity of small-sized paper is reduced.

[0462] In addition, as another countermeasure method for the temperature rise of the non-paper-passing portion, the following structure is sometimes adopted: a plurality of resistance heating elements 262 with different lengths in the x-axis direction are arranged on the heater 26, and the resistance heating elements 262 are selectively energized according to the paper width of the recording material used. However, the paper width of the recording material selected by the user includes not only fixed sizes such as A4 or B5, but also irregular sizes. Therefore, in the structure in which the plurality of resistance heating elements 262 can be selectively energized, the temperature rise of the non-paper-passing portion sometimes occurs. In addition, there are also disadvantages such as the complication of the control accompanying the selective energization and the increase in the number of components due to the configuration of the plurality of temperature detection elements corresponding to the plurality of resistance heating elements 262.

[0463] As another countermeasure for the temperature rise in the non-paper-passing portion, there is a configuration in which a heat-equalizing member is brought into contact with the heater 26 to promote heat diffusion in the length direction (x-axis direction) of the clamping portion N, thereby making the temperature distribution uniform. As the heat-equalizing member, a metal plate with high thermal conductivity such as an aluminum alloy is used. However, even when a heat-equalizing member is used, in the case of printing a large number of small-sized papers continuously, in order to avoid the disadvantage of the temperature rise in the non-paper-passing portion, the paper spacing is sometimes increased, and a configuration that can suppress the temperature rise in the non-paper-passing portion is sought.

[0464] [Contact between heat-retaining plate and sliding plate]

[0465] In this embodiment, in order to suppress the temperature rise of the non-paper-passing portion, the heat-retaining plate 25 and the slide plate 27 are arranged in a state of contact with each other. Fig.39 It is an enlarged view showing a cross section of the belt heating portion 210 in this embodiment.

[0466] The fixing belt 21 in this embodiment includes a base material (base layer), an elastic layer, and a surface layer. The elastic layer is formed on the periphery of the base material, and the surface layer is formed on the periphery of the elastic layer.

[0467] The substrate is, for example, a member formed into a ring shape by a resin film having polyimide as the main component and fillers added thereto to improve heat conduction. The inner diameter of the substrate is 30 mm and the thickness is 80 μm. In this embodiment, polyimide having high heat resistance and mechanical strength is the main component of the substrate, but it is not limited thereto, and for example, stainless steel, polyetheretherketone materials, etc. may also be included. In addition, the thickness of the substrate is not limited to the value shown in the example.

[0468] The elastic layer is mainly composed of, for example, silicone rubber having heat resistance that can withstand the fixing temperature. The thickness of the elastic layer is 200 μm, which is a rubber hardness that can form the clamping portion N. In this embodiment, silicone rubber is used as the main component from the viewpoint of high heat resistance, but it is not limited to this, and for example, fluororubber or the like may also be included. In addition, the thickness is not limited to the value shown in the example.

[0469] The surface layer is mainly composed of, for example, soluble polytetrafluoroethylene (PFA). The thickness is 20 μm. In this embodiment, PFA is the main component from the viewpoint of high mold release and heat resistance, but it is not limited to this, and the thickness is not limited to the exemplified value.

[0470] The cross-sectional shape of the surface perpendicular to the x-axis direction of the sliding plate 27 of this embodiment is composed of a sliding friction portion 271 and a rising portion 272. The rising portion 272 is continuous with the upstream and downstream sides of the sliding friction portion 271 in the recording material conveying direction (y-axis direction), and is bent toward the +z direction relative to the sliding friction portion 271 extending in the y-axis direction. The ends of the rising portion 272 in the +z direction are accommodated in the grooves 231 formed in the upstream and downstream portions of the holding member 23 in the recording material conveying direction (y-axis direction).

[0471] The length of the sliding plate 27 in the longitudinal direction (x-axis direction) is configured to be longer than the outer peripheral portion 202b of the fixing belt 21 or the pressure roller 202 so that the clamping portion N can be formed with a sufficient length in the longitudinal direction. In addition, the sliding plate 27 is made of an aluminum alloy with a thickness of 0.5 mm as a base material. On the sliding friction surface 271b of the sliding friction portion 271 that slides and rubs against the fixing belt 21, a fluororesin coating is applied to improve sliding properties and wear resistance. In this embodiment, a base material mainly composed of aluminum with high thermal conductivity is used, but the base material of the sliding plate 27 can also contain stainless steel or copper, zinc as a main component, for example. In addition, the thickness of the sliding plate 27 is not limited to the value shown in the example. Furthermore, in this embodiment, a fluororesin coating is applied to the sliding friction surface 271b, but for example, sliding properties and wear resistance can also be imparted by acid-resistant processing of the aluminum of the base material.

[0472] Fig.40 (a) and (b) show the structure of the heater 26 of this embodiment. Fig.40 (a) is a cross-sectional view of the surface of the heater 26 perpendicular to the x-axis direction. The substrate 261 is a stainless steel (SUS) with a thickness of 0.3 mm, and an insulating glass layer 265a is formed on the surface of the substrate 261 that contacts the sliding plate 27. An insulating glass layer 265b is formed on the surface of the substrate 261 that contacts the heat preservation plate 25. The insulating glass layers 265a and 265b are 50 μm thick respectively. A pattern including a resistive heating element 262 as a heating component is formed on the insulating glass layer 265a, and then an insulating glass layer 265c with a thickness of 50 μm is formed in a manner to cover and protect the pattern.

[0473] Fig.40 (b) is a diagram showing the surface of the heater 26 in this embodiment having a resistive heating element. On the substrate 261, two resistive heating elements 262 are arranged with a total length of 220 mm, with a length of 110 mm about the center x0 of the clamping portion N in the x-axis direction. The two resistive heating elements 262 are connected in series via a conductor 263. The total resistance of the series circuit including the two resistive heating elements 262 is 15Ω.

[0474] In this embodiment, stainless steel (SUS) with relatively high thermal conductivity is used as the base material of the heater 26, but it can also be made of ceramics such as aluminum nitride or aluminum oxide with similarly high thermal conductivity. In addition, the protective layer of the pattern can also be a fluororesin coating, etc., and is not limited to the illustrated structure. In addition, in this embodiment, an example is described in which the resistance heating element 262 is not divided in the x-axis direction and two resistance heating elements 262 are connected in series, but it can also be a structure in which the resistance heating element 262 is arranged in multiple areas divided in the x-axis direction.

[0475] use Fig.41 (a) and (b) illustrate the heat retaining plate 25 of this embodiment. Fig.41 (a) is a perspective view of the heat preservation plate 25 in this embodiment. The heat preservation plate 25 is, for example, a sheet metal of aluminum alloy with a thickness of 0.5 mm. The heat preservation plate 25 is 218 mm in length, with a length of 109 mm around the center x0 of the clamping part N in the x-axis direction.

[0476] Fig.41 (b) is a cross-sectional view of the heat retaining plate 25 taken along a plane perpendicular to the x-axis direction. The dotted line shows the heat retaining plate 25 before contacting the heater 26 disposed in the slide plate 27. The solid line shows the heat retaining plate 25 after contacting the heater 26 disposed in the slide plate 27.

[0477] The heat preservation plate 25 has a plane portion 255 and a bent portion 256. The plane portion 255 is formed so as to extend in the y-axis direction and is in contact with the back surface 26b of the heater 26. That is, the plane portion 255 is a surface facing the back surface 26b of the heater 26, and extends in the x-axis direction and the y-axis direction substantially parallel to the back surface 26b of the heater 26. The bent portion 256 is formed continuously with the upstream side and the downstream side of the plane portion 255 in the y-axis direction, and is bent toward the +z direction side in the z-axis direction.

[0478] In the state before the heat-retaining plate 25 is attached to the inner side of the sliding plate 27 (dashed line), the length of the heat-retaining plate 25 in the y-axis direction (the length from the end on the -y-direction side to the end on the +y-direction side) is longer than the length of the sliding friction portion 271 of the sliding plate 27 in the y-axis direction. In addition, in the state before the heat-retaining plate 25 is attached to the inner side of the sliding plate 27 (dashed line), the length of the heat-retaining plate 25 in the y-axis direction is longer than the interval between the two rising portions 272 of the sliding plate 27 in the y-axis direction. The heat-retaining plate 25 is pressed into the inner side of the sliding plate 27 in a state where the bent portion 256 is bent. As a result, the heat-retaining plate 25 can be more reliably brought into contact with the sliding plate 27, and the flat surface portion 255 of the heat-retaining plate 25 can be brought into contact with the heater 26.

[0479] [Comparative test]

[0480] The configuration and use of the embodiment described above Fig.18 The structure of the heat-retaining plate 25 of the reference example shown is used to compare the temperature of the fixing belt 21 . Fig.18 The heat-retaining plate 25 of the reference example shown has no bent portion but only a flat portion, and the length of the flat portion in the y-axis direction is shorter than the length of the sliding friction portion of the sliding plate. Therefore, in the reference example, the heat-retaining plate 25 and the sliding plate 27 do not contact each other.

[0481] (Experiment 1)

[0482] In order to confirm the effect of suppressing the temperature rise of the non-paper-passing area obtained by this embodiment, the minimum heater temperature at which the image forming apparatus 100 using the fixing device 200 equipped with this embodiment can fix the image was confirmed, and the temperature of the fixing belt 21 in the non-paper-passing area and the paper-passing area at this heater temperature was confirmed. The minimum heater temperature is the temperature of the heater 26 indicated by the detection signal of the thermistor 24. The minimum heater temperature is the lowest heater temperature at which a full black image is formed in front of the recording material without causing image loss or peeling. In addition, the common point of this embodiment and the reference example is that when the temperature of the fixing belt 21 in the paper-passing area is 161°C or more, fixability without causing image loss or peeling is obtained. In addition, as for the temperature of the fixing belt 21, the fixing belt 21 when the paper is passed is photographed using the infrared thermal imager CPA-E5A manufactured by CHINO, and the maximum temperature of the non-paper-passing area and the average temperature of the paper-passing area are extracted from the temperature curve data in the longitudinal direction of the fixing belt 21. The processing speed of the image forming apparatus 100 used in the experiment was 200 mm / s, and the interval (paper gap) between the preceding recording material S and the following recording material S was 30 mm. As the recording material, general laser printer paper with a unit weight of 80 g / m 2 The temperature of the fixing belt 21 was measured while 20 sheets of recording material were continuously passed through the fixing belt 21 .

[0483] The results of Experiment 1 are shown in Fig.42 The minimum heater temperature is 201°C in the present embodiment and 205°C in the reference example. The temperature of the non-paper-passing portion of the fixing belt 21 when continuous paper passing is performed at these minimum heater temperatures is 7°C lower in the present embodiment than in the reference example. In addition, the temperature of the paper-passing portion is 161°C in both configurations without any difference. That is, according to the present embodiment, the temperature of the non-paper-passing portion of the fixing belt 21 is lowered compared to the reference example, and the minimum heater temperature that can fix the image can be lowered.

[0484] use Fig.43 (a) and (b) illustrate the mechanism. Fig.43 (a) shows the longitudinal temperature curve of each component of the belt unit 201 in this embodiment. Fig.43 (b) shows a longitudinal temperature profile of each component of the belt unit 201 in the reference example. Fig.43 In both the configurations (a) and (b), the recording material passing through the clamping portion N absorbs heat in the paper passing area, so the temperature of each component becomes lower. However, the farther the component is from the recording material in the z-axis direction, the less likely it is to be affected by the temperature drop caused by the recording material. Therefore, the temperature difference between the paper passing portion and the non-paper passing portion of the heat preservation plate 25 is smaller than the temperature difference between the paper passing portion and the non-paper passing portion of the sliding plate 27. In addition, the temperature of the heat preservation plate 25 in the paper passing area is higher than the temperature of the sliding plate 27 in the paper passing area.

[0485] And, in Fig.43 In the present embodiment shown in (a), Fig.43 Compared with the reference example shown in (b) of FIG. 1 , the temperature difference between the heat-retaining plate 25 and the sliding plate 27 in the paper-passing area is smaller. This is because the heat-retaining plate 25 and the sliding plate 27 are in contact with each other on the upstream and downstream sides in the recording material conveying direction (y-axis direction), so heat moves from the heat-retaining plate 25 with a high temperature to the sliding plate 27 with a low temperature. Due to the heat transfer, the temperature of the sliding plate 27 in the paper-passing area rises, and the temperature of the fixing belt 21 in the paper-passing area also rises. Therefore, if the target temperature of the fixing belt 21 is the same, the present embodiment can maintain the fixing belt 21 at the target temperature when the temperature of the heater 26 is low compared with the reference example. That is, in the present embodiment, since the heat energy from the heater 26 is efficiently transferred to the fixing belt 21 via the sliding plate 27, the energy-saving performance can be improved.

[0486] According to the present embodiment, the difference between the temperature of the sliding plate 27 at the non-paper-passing portion and the temperature of the sliding plate 27 at the paper-passing portion is reduced compared to the reference example. Furthermore, the difference between the temperature of the fixing belt 21 at the non-paper-passing portion and the temperature of the fixing belt 21 at the paper-passing portion is also reduced. Thus, the temperature rise of the non-paper-passing portion of each component of the belt unit 201 can be suppressed. That is, in the present embodiment, in addition to the effect of the heat-retaining plate 25 and the sliding plate 27 each independently diffusing heat in the length direction (x-axis direction) of the clamping portion N, heat also moves at the contact portion between the heat-retaining plate 25 and the sliding plate 27. Thus, in each component of the belt unit 201, the temperature difference between the non-paper-passing portion and the paper-passing portion is mitigated, and the temperature rise of the non-paper-passing portion can be more effectively suppressed.

[0487] In addition, in this embodiment, the following example is exemplified. Fig.41 As shown in the figure, the heat preservation plate 25 is provided with a bent portion 256 on both sides of the flat portion 255, but it is also possible to use a heat preservation plate 25 as shown in the figure. Fig.44As shown in (a) of FIG. 1 , the heat-retaining plate 25 is provided with a bent portion 256 only on one side of the flat portion 255. In this case, the heat-retaining plate 25 is attached to the sliding plate 27 in such a manner that both ends of the heat-retaining plate 25 in the recording material conveying direction (y-axis direction) contact the rising portions 272 of the sliding plate 27, thereby obtaining the same effect as that of the present embodiment.

[0488] In addition, Fig.44 In the case of the modification shown in (a), Fig.44 As shown in (b), the heat retaining plate 25 can be pressed toward the sliding plate 27 while the end surface without the bent portion 256 is brought into contact with the rising portion 272 of the sliding plate 27, while the bent portion 256 is bent. Thus, the heat retaining plate 25 can be brought into contact with the sliding plate 27 more reliably.

[0489] In addition, in the above-mentioned embodiment, the contact portion between the heat preservation plate 25 and the sliding plate 27 is set on both the upstream side and the downstream side in the recording material conveying direction, but it can also be a structure in which the two are in contact only on either the upstream side or the downstream side. In addition, in this embodiment, the length of the heat preservation plate 25 in the longitudinal direction (x-axis direction) is set to 218 mm, but the same effect can be obtained even if it is longer or shorter. However, if the heat preservation plate 25 is longer than the resistance heating element 262 of the heater 26, there is a concern that the fixing is not good due to the temperature drop at the end, and if it is too short, the effect of reducing the temperature rise of the non-paper passing part or improving the energy saving performance will be reduced, so the length should be adjusted appropriately.

[0490] (Variant 1)

[0491] As a modification example 1, the same as in Example 8 ( Fig.41 Compared with (a) and (b), the contact area between the heat preservation plate 25 and the sliding plate 27 can be enlarged. Fig.45 2 shows the cross-sectional shapes of the heat-retaining plate 25 and the sliding plate 27 of this modification. The heat-retaining plate 25 of this modification has: a plane portion 255 in contact with the heater 26; and rising portions 257 provided on both sides of the plane portion 255 and rising by bending. The rising portions 257 are formed continuously with the upstream and downstream sides of the plane portion 255 in the recording material conveying direction (y-axis direction), and extend in a direction (+z direction) substantially perpendicular to the extension direction of the plane portion 255. The rising portions 257 are formed so as to make surface contact with the rising portions 272 of the sliding plate 27 when the heat-retaining plate 25 is mounted on the sliding plate 27. Therefore, compared with the structure of the eighth embodiment in which the end edge of the heat-retaining plate 25 is substantially in line contact with the sliding plate 27, the heat transfer between the heat-retaining plate 25 and the sliding plate 27 can be promoted.

[0492] Thermally conductive paste may be applied to the contact area between the raised portion 257 of the heat retaining plate 25 and the raised portion 272 of the sliding plate 27. For example, the thermally conductive paste may be DOWSIL SC102 compound from Dow Toray Industries, Inc. The thermally conductive paste can further promote heat transfer between the heat retaining plate 25 and the sliding plate 27.

[0493] (Variant 2)

[0494] As a second modification, another configuration that can increase the contact area between the heat retaining plate 25 and the sliding plate 27 will be described. Fig.46 (a) shows the cross-sectional shapes of the heat-retaining plate 25 and the sliding plate 27 of this modification. The heat-retaining plate 25 of this modification is composed only of the flat surface portion 255. The sliding plate 27 of this modification has: a sliding friction portion 271 that slides against the fixing belt 21; and a folded portion 278 that is folded back by bending relative to the sliding friction portion 271. The folded portion 278 is provided continuously with the upstream side and the downstream side of the sliding friction portion 271 in the recording material conveying direction (y-axis direction). The folded portion 278 on the upstream side is folded back approximately 180 degrees from the upstream end of the sliding friction portion 271 and extends toward the downstream side (+y direction) of the recording material conveying direction. The folded portion 278 on the downstream side is folded back approximately 180 degrees from the downstream end of the sliding friction portion 271 and extends toward the upstream side (+y direction) of the recording material conveying direction.

[0495] The heat preservation plate 25 is accommodated in the space formed between the sliding friction portion 271 and the folded portion 278 of the sliding plate 27 in the z-axis direction. Fig.46 As shown in (b), the heat preservation plate 25 and the heater 26 are installed in the space between the sliding friction portion 271 and the folded portion 278 of the sliding plate 27 by sliding in the x-axis direction. The surface of the heat preservation plate 25 on the +z direction side is in surface contact with the folded portion 278 of the sliding plate 27. Therefore, compared with the structure of Example 8 in which the edge of the heat preservation plate 25 is substantially in line contact with the sliding plate 27, the heat transfer between the heat preservation plate 25 and the sliding plate 27 can be promoted.

[0496] Thermally conductive grease may be applied to the contact area between the heat retaining plate 25 and the folded portion 278 of the sliding plate 27. The thermally conductive grease can further promote heat transfer between the heat retaining plate 25 and the sliding plate 27.

[0497] According to this modification, the heat retaining plate 25 and the folded portion 278 of the slide plate 27 are pressed by the pressure for generating the clamping pressure in the clamping portion N. Therefore, there is an advantage that the heat retaining plate 25 and the slide plate 27 can be more reliably brought into a surface contact state.

[0498] (Variant 3)

[0499] As a modification example 3, another configuration that makes it easy to ensure the contact between the heat retaining plate 25 and the slide plate 27 will be described. Fig.47 (a) shows the cross-sectional shapes of the heat preservation plate 25 and the sliding plate 27 of this modification. The heat preservation plate 25 of this modification has: a plane portion 255; and a rising portion 257 provided near the end of either the upstream side or the downstream side of the plane portion 255 in the recording material conveying direction (y-axis direction). The rising portion 257 is bent relative to the plane portion 255 extending in the recording material conveying direction (y-axis direction) and extends in the +z direction. The sliding plate 27 has: a sliding friction portion 271; and rising portions 272 provided on both sides of the sliding friction portion 271 in the recording material conveying direction (y-axis direction).

[0500] like Fig.47 As shown in (b) of FIG. 1 , each of the rising portions 272 is provided with a through hole 279 extending in the longitudinal direction (x-axis direction). By inserting the flat portion 255 of the heat-retaining plate 25 from one side of the recording material conveying direction (y-axis direction) relative to the through hole 279, the sliding plate 27 and the heat-retaining plate 25 can be integrated. For example, after the heater 26 is provided on the sliding friction portion 271 of the sliding plate 27 from the +z direction side, the heat-retaining plate 25 is inserted into the through hole 279 of the sliding plate 27. Thus, the heater 26, the heat-retaining plate 25, and the sliding plate 27 are integrated in a state where the heater 26 is sandwiched between the heat-retaining plate 25 and the sliding plate 27.

[0501] According to this modification, since the heat preservation plate 25 and the sliding plate 27 are engaged (fitted) in the through hole 279, the heat preservation plate 25 and the sliding plate 27 can be more reliably brought into contact with each other, and heat transfer between the heat preservation plate 25 and the sliding plate 27 can be promoted. In addition, this modification has advantages such as high tolerance of component accuracy and relatively simple assembly work compared with Modification 2. Thermal conductive grease can also be applied to the through hole 279. The thermal conductive grease can further promote heat transfer between the heat preservation plate 25 and the sliding plate 27.

[0502] As a further variation (variation 3-2), it is also possible to Fig.48As shown in the figure, through holes 258 extending in the longitudinal direction (x-axis direction) are provided at both ends of the flat surface 255 of the heat-retaining plate 25 in the recording material conveying direction (y-axis direction), and the sliding plate 27 is fitted into the through holes 258. The sliding plate 27 has a sliding friction portion 271; a rising portion 272 provided on the upstream side and the downstream side of the sliding friction portion 271 in the recording material conveying direction (y-axis direction); and a hook portion 276 provided at the end of each rising portion 272. The hook portion 276 is a shape obtained by bending the ends of the rising portions 272 that rise in the +z direction by approximately 90 degrees in the y-axis direction toward the side away from the heater 26. According to this modification, since the heat-retaining plate 25 and the sliding plate 27 are engaged (fitted) in the through holes 258, the heat-retaining plate 25 and the sliding plate 27 can be more reliably contacted, and heat transfer between the heat-retaining plate 25 and the sliding plate 27 can be promoted.

[0503] (Variant 4)

[0504] As a modification example 4, a configuration in which a heat retaining plate (heat retaining portion) and a sliding plate (sliding member) are integrally formed will be described. Fig.49 (a) shows the cross-sectional shape of a sliding heat-retaining plate 27A of one example of Modification 4 (Modification 4-1). The sliding heat-retaining plate 27A has: a sliding friction portion 271 that slides against the fixing belt 21; a rising portion 272 that is continuous with either the upstream side or the downstream side of the sliding friction portion 271 in the recording material conveying direction (y-axis direction); and a heat-retaining portion 277 that is continuous with the other of the upstream side and the downstream side of the sliding friction portion 271. The sliding heat-retaining plate 27A is formed by folding a metal plate as a material back approximately 180 degrees between the sliding friction portion 271 and the heat-retaining portion 277 and bending approximately 90 degrees between the sliding friction portion 271 and the rising portion 272. The heater 26 is accommodated in the space between the sliding friction portion 271 and the heat-retaining portion 277 of the sliding heat-retaining plate 27A.

[0505] Fig.49 (b) shows the cross-sectional shape of the sliding heat-retaining plate 27B of another example (variant 4-2) of variant 4. The sliding heat-retaining plate 27B has: a sliding friction portion 271 that slides and rubs against the fixing belt 21; and a heat-retaining portion 277 that is continuous with the upstream side and the downstream side of the sliding friction portion 271 in the recording material conveying direction (y-axis direction). The sliding heat-retaining plate 27B is formed by folding a metal plate as a material back approximately 180 degrees between the sliding friction portion 271 and the heat-retaining portion 277. The heater 26 is accommodated in the space between the sliding friction portion 271 and the heat-retaining portion 277 of the sliding heat-retaining plate 27B.

[0506] Fig.49(c) shows the cross-sectional shape of the sliding heat-retaining sleeve 28 of another modification (modification 4-3). The sliding heat-retaining sleeve 28 has: a sliding friction portion 281 (sliding friction member) that slides and rubs against the fixing belt 21; and a heat-retaining portion 282 (heat-retaining portion) that sandwiches the heater 26 between the sliding friction portion 281 in the z-axis direction. The sliding heat-retaining sleeve 28 is, for example, a metal member formed into a cylindrical shape by deep drawing. The heater 26 is accommodated in the space between the sliding friction portion 281 and the heat-retaining portion 282 of the sliding heat-retaining sleeve 28.

[0507] In the above Fig.49 In the examples (a) to (c) of FIG. 1 , the sliding friction member (sliding friction portion 271, 281) and the heat retaining member (heat retaining portion 277, 282) are formed as the same member. Therefore, there is no thermal resistance at the contact portion as in the case where the sliding friction member and the heat retaining member are different members. Therefore, heat transfer between the heat retaining plate 25 and the sliding plate 27 can be promoted.

[0508] (Experiment 2)

[0509] In order to confirm the effect of suppressing the temperature rise of the non-paper-passing portion of the above-mentioned Modifications 1 to 4, Fig.18 The temperature of the fixing belt 21 is compared between the reference example and each modified example shown. The lowest heater temperature at which the image forming apparatus 100 equipped with the fixing device 200 of the modified examples 1 to 4 can fix an image is confirmed, and the temperature of the fixing belt 21 in the non-paper passing area and the paper passing area at the heater temperature is confirmed. The details of the experimental method are the same as those of the above-mentioned Experiment 1.

[0510] The results of Experiment 2 are shown in Fig.50 In all of the modified examples 1 to 4, the temperature of the fixing belt 21 in the non-paper-passing area is lower than that in the reference example, so that the minimum heater temperature that can fix the image can be lowered. This is because in all of the modified examples 1 to 4, the temperature of the sliding friction member is increased by heat transfer from the heat retaining member (heat retaining member 277, 282) to the sliding friction member (sliding friction member 271, 281) in the paper-passing area, and the temperature of the fixing belt 21 is increased (reference example). Fig.43 (a)). In addition, not only the sliding friction member (the sliding friction parts 271 and 281) but also the heat retaining member (the heat retaining parts 277 and 282) contribute to the relaxation of the temperature gradient in the longitudinal direction (the x-axis direction).

[0511] Therefore, according to Modifications 1 to 4, even if the temperature of the heater 26 is set lower than that of the reference example, the temperature of the fixing belt 21 in the paper passing area can be maintained at a desired fixing temperature. That is, the thermal efficiency of the fixing device 200 can be improved, and the energy saving performance can be improved. In addition, according to Modifications 1 to 4, the temperature difference between the non-paper passing portion and the paper passing portion is alleviated in each component of the belt unit 201, and the temperature rise of the non-paper passing portion can be suppressed.

[0512] [Summary of this embodiment]

[0513] As described above, in the present embodiment and the modified example, a path is provided to enable heat to move from the heat retaining plate (heat retaining part) to the sliding plate (sliding friction part). This can reduce the temperature difference between the paper passing area and the non-paper passing area, improve thermal efficiency, and suppress the temperature rise of the non-paper passing area.

[0514] In the eighth embodiment and the first to third variations, the heat-retaining plate 25 is in contact with the sliding plate 27. That is, the fixing device further includes a heat-retaining member disposed between the holding member and the heater in the third direction to retain the heat of the heater, and the heat-retaining member is in contact with the sliding member. According to this configuration, the temperature difference between the paper-passing area and the non-paper-passing area can be reduced.

[0515] In the fourth modification, the portion that performs the function of the heat retaining member (heat retaining portion) is formed integrally with the sliding member. That is, the sliding member includes: a sliding friction portion that slides against the inner surface of the fixing member; and a heat retaining portion that is disposed between the holding member and the heater in the third direction and is used to retain the heat of the heater, and the sliding friction portion and the heat retaining portion are formed integrally. According to this configuration, the temperature difference between the paper passing area and the non-paper passing area can be reduced.

[0516] 《Example 9》

[0517] In this embodiment, the shape or positional relationship of the holding member 23 and the stay 22 is different from that of the embodiment 1. Hereinafter, for the elements marked with the same reference numerals as those of the embodiment 1, unless otherwise specified, they have substantially the same structure and function as those described in the embodiment 1, and the description will be mainly based on the parts different from the embodiment 1.

[0518] [Problem]

[0519] The retaining member described in Japanese Patent Publication No. 2020-3611 is provided with grooves (front limiting grooves and rear limiting grooves) for accommodating the two ends of the heat diffusion member (sliding member) formed in the shape of a U, and the stay abuts against the retaining member just above the groove. However, since the pressure from the stay acts on the portion where the wall thickness of the retaining member is thinned due to the groove, there is a possibility of creep deformation of the retaining member. If creep deformation of the retaining member occurs, the clamping pressure at the clamping portion will change or the shape of the clamping portion will change, and there is a possibility of reduced performance of the fixing device.

[0520] Therefore, in this embodiment, a structure capable of reducing the creep deformation of the holding member is proposed.

[0521] [Excess grease and groove of retaining member]

[0522] One side reference Figure 5 While referring to the configuration of the reference example shown, the relationship between the shape of the holding member 23 and the creep deformation will be described in detail.

[0523] In the reference example, in order to promote heat transfer from the heater 26 to the sliding plate 27, the thermally conductive paste G1 is applied between the heater 26 and the sliding plate 27. The amount of the thermally conductive paste G1 applied is set so that it will not be exhausted during the service life of the fixing device 200 even if the variation in the amount of application during manufacturing is taken into account. Therefore, the amount of the thermally conductive paste G1 applied is larger than the minimum amount for filling the gap between the heater 26 and the sliding plate 27, and there is excess paste.

[0524] In order to achieve high thermal conductivity, the thermally conductive paste G1 sometimes contains hard solid particles such as metal oxides, ceramics, or carbon as a thermally conductive filler. If these solid particles adhere to the inner surface of the fixing belt 21, the inner surface of the fixing belt 21 will be abraded more, and there is a possibility of causing disadvantages such as reduced sliding properties.

[0525] Here, by setting the internal space of the groove 231 to be larger than the volume of the rising portion 272 of the sliding plate 27 accommodated in the groove 231, the excess grease can be accommodated in the groove 231. However, in order to ensure that the groove 231 has a sufficient width to accommodate the excess grease, the wall thickness of the holding member 23 must be reduced, and the mechanical strength of the holding member 23 is reduced near the groove 231.

[0526] Figure 4 The embodiment 1 shown in the figure is the same as the reference example in terms of the positional relationship between the groove 231 and the stay 22. Figure 4As shown in the figure, in the first embodiment and the reference example, the stay 22 presses the holding member 23 just above the groove 231. That is, the contact area between the end surface of the stay 22 facing the -z direction and the surface of the holding member 23 pressed by the end surface (the surface facing the +z direction) is in a positional relationship that overlaps at least partially with the groove 231 when viewed in the z-axis direction. In this positional relationship, due to the pressure spring 251 ( Figure 3 ) due to the pressure in the -z direction acting from the stay 22 to the holding member 23, there is a possibility that creep deformation of the holding member 23 may occur near the bottom surface of the groove portion 231 having low mechanical strength.

[0527] That is, if the capacity of the groove 231 for accommodating the excess grease is to be sufficient, creep deformation of the retaining member 23 is likely to occur, and disadvantages of creep deformation (change in shape of the clamping portion N or reduction in clamping pressure) are likely to occur.

[0528] [Positional relationship between stays and grooves]

[0529] Fig.51 It is a cross-sectional view of the fixing device 200 according to the present embodiment. Fig.52 The belt heating unit 210 ( Fig.51 In this embodiment, in view of the above-mentioned problem, the groove portion is configured so as not to be located on the pressure transmission path.

[0530] like Fig.51 , Fig.52 As shown, the belt unit 201 of the fixing device 200 includes a stay 22, a holding member 23, a thermistor 24, a heat-retaining plate 25, a heater 26, and a sliding plate 27. The stay 22 is an example of a reinforcing member for reinforcing the holding member 23. The stay 22 is subjected to a force in the -z direction by the pressure spring 251 as a biasing member, similar to the first embodiment, and presses the holding member 23 in the -z direction. The end surfaces of the stay 22 that press the holding member 23 are set as pressing parts P1 and P2. The pressing part P1 presses the holding member 23 at a position upstream of the center of the heater 26 in the conveying direction F (y-axis direction) of the recording material S. The pressing part P2 presses the holding member 23 at a position downstream of the center of the heater 26 in the conveying direction F (y-axis direction).

[0531] The holding member 23 has two grooves 231 that can accommodate the rising portion 272 of the slide plate 27. Hereinafter, the groove 231 on the upstream side in the recording material conveying direction (y-axis direction) is referred to as "groove 231a", and the groove 231 on the downstream side is referred to as "groove 231b". The groove 231a on the upstream side is an example of a first recessed portion that can accommodate the rising portion 272 (first rising portion) on the upstream side. The groove 231b on the downstream side is an example of a second recessed portion that can accommodate the rising portion 272 (second rising portion) on the downstream side.

[0532] like Fig.52 As shown in the figure, in this embodiment, the pressing parts P1 and P2 of the stay 22 are arranged on the central side of the clamping part N in the recording material conveying direction (y-axis direction) compared with the grooves 231a and 231b of the holding member 23. That is, the pressing part P1 on the upstream side (first pressing part) is located on the downstream side (+y direction) of the recording material conveying direction compared with the groove 231a on the upstream side. In addition, the pressing part P2 on the downstream side (second pressing part) is located on the upstream side (-y direction) of the recording material conveying direction compared with the groove 231b on the downstream side. When viewed in the z-axis direction, the pressing parts P1 and P2 do not overlap with the bottom surfaces of the grooves 231a and 231b.

[0533] According to the above-mentioned structure, the bending stress caused by the pressure from the stay 22 and the reaction force from the pressure roller 202 is unlikely to act on the thin-walled portion St of the holding member 23 formed by the grooves 231a and 231b. That is, the holding member 23 receives the pressure in the -z direction from the pressing portions P1 and P2 of the stay 22. In addition, the holding member 23 receives the reaction force in the +z direction from the pressure roller 202 via the slide plate 27, the heater 26, and the heat-retaining plate 25, mainly in the area between the pressing portions P1 and P2 in the recording material conveying direction (y-axis direction). Due to the pressure and reaction force, a bending stress is generated in the portion between the pressing portions P1 and P2 in the recording material conveying direction (y-axis direction) of the holding member 23, so that the central portion of the holding member 23 protrudes toward the +z direction side. In this embodiment, since the thin portion St is located outside the region between the pressing portions P1 and P2 in the recording material conveyance direction (y-axis direction), it is possible to avoid concentration of bending stress on the thin portion St.

[0534] Therefore, according to the configuration of this embodiment, the possibility of creep deformation of the holding member 23 occurring in the thin-walled portion St can be reduced, and the possibility of adverse effects of creep deformation (shape change of the clamping portion N or reduction in clamping pressure) occurring can be reduced.

[0535] [Summary of this embodiment]

[0536] As described above, the position (P1, P2) where the stay 22 presses the holding member 23 is downstream of the groove 231a on the upstream side of the holding member 23 and upstream of the groove 231b on the downstream side in the y-axis direction. In other words, the position where the reinforcing member presses the holding member is downstream of the first recess and upstream of the second recess in the second direction. According to this configuration, creep deformation of the holding member can be reduced.

[0537] [Variation example]

[0538] In addition, in the present embodiment, the configuration example in which the points of action (pressing portions P1, P2) of the stay 22 pressing the holding member 23 are two locations on the upstream side and the downstream side is described. The points of action of the stay 22 pressing the holding member 23 may be three or more locations. Even in this case, if the most upstream point of action is located downstream of the groove portion 231a on the upstream side and the most downstream point of action is located upstream of the groove portion 231a on the downstream side in the recording material conveying direction (y-axis direction), the same effect as in the present embodiment can be obtained.

[0539] 《Example 10》

[0540] In this embodiment, a configuration example in which the shape of the retaining member 23 is different from that of Embodiments 1 and 9 is described. Hereinafter, for elements marked with reference numerals common to Embodiment 1, unless otherwise specified, they are referred to as having substantially the same configuration and function as those described in Embodiment 1, and the description will be mainly based on the parts that are different from Embodiment 1.

[0541] [Problem]

[0542] In this embodiment, similarly to the ninth embodiment, a structure capable of reducing the creep deformation of the holding member is proposed.

[0543] [Oil-inducing hole]

[0544] Fig.53 2 is a cross-sectional view of the fixing device 200 according to the embodiment 10. In the holding member 23 of the embodiment, a paste guiding hole 481 for guiding excess paste is formed. The paste guiding hole 481 is a through hole extending from the bottom surface of the groove portion 231 in the z-axis direction to the upward surface 233 (the surface facing the +z direction) of the holding member 23 located on the back side of the groove portion 231.

[0545] The fixing device 200 is configured the same as that of Embodiment 9 except for the presence of the paste guide hole 481. That is, in this embodiment, the thin-walled portion St generated by the groove portion 231 is located outside the region between the pressing portions P1 and P2 in the recording material conveying direction (y-axis direction). Therefore, it is possible to avoid the concentration of bending stress on the thin-walled portion St.

[0546] like Fig.54 As shown, the grease guide holes 481 are arranged in a row along the longitudinal direction (x-axis direction) at the bottom of each groove portion 231. However, the arrangement and number of the grease guide holes 481 can be appropriately changed according to the amount and viscosity of the remaining grease.

[0547] like Fig.55 As schematically shown, if the gap between the groove 231 and the rising portion 272 is filled with the thermally conductive paste G1 (residual paste) squeezed out from between the heater 26 and the sliding plate 27 or between the heater 26 and the heat-retaining plate 25, the residual paste is guided toward the paste guide hole 481. The end of the paste guide hole 481 becomes an open space, and the residual paste can be discharged into the space. By providing the paste guide hole 481, the possibility of the residual paste overflowing from the groove 231 and adhering to the inner surface of the fixing belt 21 can be reduced. In addition, although the end of the paste guide hole 481 is an open space, a closed space for storing the residual paste can also be provided at the end of the paste guide hole 481.

[0548] Thus, in this embodiment, the excess paste receiving capacity can be improved by providing the paste guide hole 481 in the groove portion 231 of the holding member 23. This can increase the tolerance of the amount of thermally conductive paste G1 applied during manufacturing, making it easier to assemble the fixing device 200.

[0549] [Summary of this embodiment]

[0550] In this embodiment, the thin-walled portion St formed by the groove portion 231 is located outside the region between the pressing portions P1 and P2 in the recording material conveying direction (y-axis direction). Therefore, the concentration of bending stress in the thin-walled portion St can be avoided, and the possibility of creep deformation of the holding member 23 can be reduced.

[0551] Furthermore, by providing the grease guide hole 481, even if the mechanical strength of the holding member 23 is reduced compared to Example 9, since the thin-walled portion St is located outside the region between the pressing portions P1 and P2, creep deformation of the holding member 23 is less likely to occur. Therefore, the assembly work of the fixing device 200 can be facilitated, and the possibility of creep deformation of the holding member 23 can be reduced.

[0552] (Variation)

[0553] Fig.56 It is a cross-sectional view of a fixing device 200 according to a modification of the tenth embodiment. Fig.57 Yes Fig.56Schematic diagram of an enlarged portion of . In the present variation, a wall portion 524 for preventing leakage of excess paste is provided on the upward surface 233 of the retaining member 23 in which the paste induction hole 481 is provided. The wall portion 524 is respectively arranged on the upstream side and the downstream side in the recording material conveying direction (y-axis direction) relative to the support bar 22. The wall portion 524 on the upstream side protrudes in the +z direction from the upward surface 233 of the retaining member 23 at a position on the upstream side of the paste induction hole 481 on the upstream side in the recording material conveying direction (y-axis direction). The wall portion 524 on the downstream side protrudes in the +z direction from the upward surface 233 of the retaining member 23 at a position on the downstream side of the paste induction hole 481 on the downstream side in the recording material conveying direction (y-axis direction).

[0554] like Fig.57 As schematically shown, the thermally conductive paste G1 (excess paste) overflowing from the paste guide hole 481 of this modification is retained in the space between the wall portion 524 and the stay 322. The excess paste is stably retained in the above space by the surface tension acting between the wall portion 524 and the stay 322. This action can further increase the upper limit of the excess paste that can be retained in the open space at the end of the paste guide hole 481.

[0555] In the tenth embodiment, the paste guiding holes 481 are provided in the grooves 231 on both the upstream side and the downstream side of the nip portion N. However, depending on the form of excess paste generation, the paste guiding holes 481 may be provided only on one of the upstream side and the downstream side. For example, when the excess paste generation direction is determined in advance by the influence of gravity by arranging the fixing device 200 obliquely as described in the second embodiment, the paste guiding holes 481 may be provided only on the side where the excess paste is generated. The same is true for the wall portion 524 shown in the modified example.

[0556] Other Examples

[0557] The configurations of the above-mentioned embodiments and their modifications are not exclusive, and can be implemented in combination as long as the effects are not contradictory. For example, the protrusions described in embodiments 1 to 3 may be provided on the sliding plates of embodiments 4 to 10.

[0558] In the above-mentioned embodiments, an electrophotographic color printer of a direct transfer method having a plurality of image forming units is exemplified as an image forming apparatus, but the image forming apparatus is not limited thereto. The image forming apparatus may also be a monochrome printer having only one image forming unit (processing unit) and forming a monochrome image using one type of toner. In addition, the image forming apparatus may also be provided with an image forming unit of an intermediate transfer method that transfers a toner image formed on an image carrier (photosensitive body) to an intermediate transfer body such as an intermediate transfer belt and transfers the toner image to a recording material from the intermediate transfer body.

[0559] As described above, according to the present disclosure, a new technology capable of improving the performance of a fixing device and an image forming apparatus can be provided.

[0560] Other embodiments

[0561] While the present invention has been described with reference to exemplary embodiments, it is to be understood that the invention is not limited to the disclosed exemplary embodiments.The scope of the following claims is to be accorded the broadest interpretation so as to encompass all such modifications and equivalent structures and functions.

Claims

1. A fixing device, wherein: The fixing device has the following components: A fixing member, which is annular and rotatable; a heater disposed in the internal space of the fixing member and generating heat by supplying electricity; a sliding member disposed between the heater and an inner surface of the fixing member and sliding on the inner surface of the fixing member; a holding member that holds the heater and the sliding member; as well as a pressing member, the pressing member being arranged to sandwich the fixing member together with the sliding member, and forming a nip portion between the pressing member and the fixing member, The fixing device is configured to heat the image on the recording material by the fixing member while the recording material is held and conveyed by the holding portion. Grease is applied between the heater and the sliding member. The longitudinal direction of the clamping portion is set as the first direction, the recording material conveying direction at the clamping portion is set as the second direction, and the direction orthogonal to both the first direction and the second direction is set as the third direction. In this case, The sliding member comprises: a sliding friction portion extending along the second direction and slidingly rubbing against the inner surface of the fixing member; a first rising portion rising from an upstream end of the sliding friction portion in the second direction toward a side away from the pressing member in the third direction; a second rising portion rising from a downstream end of the sliding friction portion in the second direction toward a side away from the pressing member in the third direction; and a protrusion provided on at least one of the first rising portion and the second rising portion, and protruding in a direction intersecting with an extending direction of the rising portion when viewed in the first direction.

2. The fixing device according to claim 1, wherein: The protrusion is a first protrusion provided on the first rising portion. The sliding member further includes a second protrusion provided on the second rising portion and protruding in a direction intersecting with an extending direction of the second rising portion when viewed in the first direction.

3. The fixing device according to claim 1, wherein: One of the first rising portion and the second rising portion is located below the other of the first rising portion and the second rising portion in the direction of gravity, The protrusion is provided on the rising portion located on the lower side between the first rising portion and the second rising portion.

4. The fixing device according to claim 1, wherein: The heater is arranged between the first rising portion and the second rising portion in the second direction. The protrusion protrudes toward the heater in the second direction relative to the one rising portion on which the protrusion is provided.

5. The fixing device according to claim 1, wherein: The sliding friction portion, the first rising portion and the second rising portion are formed by a metal plate. The protrusion is a bent shape obtained by bending a portion of the one metal plate.

6. The fixing device according to claim 1, wherein: The protrusion is a member different from the sliding friction portion, the first rising portion, and the second rising portion.

7. The fixing device according to claim 1, wherein: The pressing member has an outer peripheral portion that contacts the fixing member at the nip portion. A length of the protrusion in the first direction is greater than a length of the outer peripheral portion in the first direction.

8. The fixing device according to claim 7, wherein: A length of the protrusion in the first direction is greater than a length of the fixing member in the first direction.

9. The fixing device according to claim 1, wherein: The fixing device further includes a heat retaining member, which is arranged between the holding member and the heater in the third direction and is used to retain the heat of the heater. The grease is applied between the heater and the heat retaining member.

10. The fixing device according to claim 1, wherein The above-mentioned paste is a first paste containing a filler for improving thermal conductivity. A second paste having a component different from that of the first paste for improving sliding properties is applied between the sliding member and the inner surface of the fixing member.

11. A fixing device, wherein: The fixing device has the following components: A fixing member, which is annular and rotatable; a heater disposed in the internal space of the fixing member and generating heat by supplying electricity; a sliding member disposed between the heater and an inner surface of the fixing member and sliding on the inner surface of the fixing member; a holding member that holds the heater and the sliding member; as well as a pressing member, the pressing member being arranged to sandwich the fixing member together with the sliding member, and forming a nip portion between the pressing member and the fixing member, The fixing device is configured to heat the image on the recording material by the fixing member while the recording material is held and conveyed by the holding portion. The longitudinal direction of the clamping portion is set as the first direction, the recording material conveying direction at the clamping portion is set as the second direction, and the direction orthogonal to both the first direction and the second direction is set as the third direction. In this case, The sliding member has a sliding friction portion that slides against the inner surface of the fixing member. The holding member comprises: a first facing portion, the first facing portion facing the inner surface of the fixing member upstream of the sliding friction portion in the second direction; and a second facing portion, the second facing portion facing the inner surface of the fixing member downstream of the sliding friction portion in the second direction, In the third direction, the first facing portion and the second facing portion are retracted toward a side farther from the pressing member than the sliding friction portion.

12. The fixing device according to claim 11, wherein The first facing portion and the second facing portion have curved surfaces that are curved along a rotation trajectory of the fixing member when viewed in the first direction.

13. The fixing device according to claim 11, wherein: The holding member is configured so that, when the fixing member follows the rotation of the pressing member by the rotational driving of the pressing member, the fixing member does not come into contact with the first facing portion and the second facing portion.

14. A fixing device, wherein: The fixing device has the following components: A fixing member, which is annular and rotatable; a heater disposed in the internal space of the fixing member and generating heat by supplying electricity; a sliding member disposed between the heater and an inner surface of the fixing member and sliding on the inner surface of the fixing member; a holding member that holds the heater and the sliding member; as well as a pressing member, the pressing member being arranged to sandwich the fixing member together with the sliding member, and forming a nip portion between the pressing member and the fixing member, The fixing device is configured to heat the image on the recording material by the fixing member while the recording material is held and conveyed by the holding portion. The longitudinal direction of the clamping portion is set as the first direction, the recording material conveying direction at the clamping portion is set as the second direction, and the direction orthogonal to both the first direction and the second direction is set as the third direction. In this case, The sliding member comprises: a sliding friction portion extending along the second direction and slidingly rubbing against the inner surface of the fixing member; a first guide portion extending in the second direction toward the upstream side of the sliding friction portion to guide the fixing member; and a second guide portion extending in the second direction toward the downstream side of the sliding friction portion to guide the fixing member, The first guide portion and the second guide portion are curved along a rotation trajectory of the fixing member when viewed in the first direction.

15. The fixing device according to claim 14, wherein: When viewed from the pressing member side toward the fixing member side in the third direction, the entire holding member is covered by the sliding friction portion, the first guide portion, and the second guide portion.

16. The fixing device according to claim 14, wherein: The sliding member comprises: a first rising portion rising from an upstream end of the sliding friction portion in the second direction toward a side away from the pressing member in the third direction; and a second rising portion rising from a downstream end of the sliding friction portion in the second direction toward a side away from the pressing member in the third direction. The holding member has a first recess for accommodating the first rising portion, a second recess for accommodating the second rising portion, and a third recess for accommodating the heater. The first guide portion covers the convex portion between the first concave portion and the third concave portion when viewed in the third direction. The second guide portion covers the convex portion between the second concave portion and the third concave portion when viewed in the third direction.

17. A fixing device, wherein: The fixing device has the following components: A fixing member, which is annular and rotatable; a heater disposed in the internal space of the fixing member and generating heat by supplying electricity; a sliding member disposed between the heater and an inner surface of the fixing member and sliding on the inner surface of the fixing member; a holding member that holds the heater and the sliding member; as well as a pressing member, the pressing member being arranged to sandwich the fixing member together with the sliding member, and forming a nip portion between the pressing member and the fixing member, The fixing device is configured to heat the image on the recording material by the fixing member while the recording material is held and conveyed by the holding portion. The longitudinal direction of the clamping portion is set as the first direction, the recording material conveying direction at the clamping portion is set as the second direction, and the direction orthogonal to both the first direction and the second direction is set as the third direction. In this case, The width of the clamping portion in the second direction at both ends of the clamping portion in the first direction is greater than the width of the clamping portion in the second direction at the center of the clamping portion in the first direction. A width of the sliding member in the second direction at both ends of the clamping portion is greater than a width of the sliding member in the second direction at a center of the clamping portion.

18. The fixing device according to claim 17, wherein: The pressurizing member includes a core and an elastic layer formed on the periphery of the core. The elastic layer is formed of solid rubber.

19. A fixing device, wherein: The fixing device has the following components: A fixing member, which is annular and rotatable; a heater disposed in the internal space of the fixing member and generating heat by supplying electricity; a sliding member disposed between the heater and an inner surface of the fixing member and sliding on the inner surface of the fixing member; a holding member that holds the heater and the sliding member; as well as a pressing member, the pressing member being arranged to sandwich the fixing member together with the sliding member, and forming a nip portion between the pressing member and the fixing member, The fixing device is configured to heat the image on the recording material by the fixing member while the recording material is held and conveyed by the holding portion. The longitudinal direction of the clamping portion is defined as a first direction, the recording material conveying direction at the clamping portion is defined as a second direction, and a direction orthogonal to both the first direction and the second direction is defined as a third direction. The width of the clamping portion in the second direction at both ends of the clamping portion in the first direction is smaller than the width of the clamping portion in the second direction at the center of the clamping portion in the first direction. A width of the sliding member in the second direction at both ends of the clamping portion is smaller than a width of the sliding member in the second direction at a center of the clamping portion.

20. The fixing device according to claim 19, wherein The pressurizing member includes a core and an elastic layer formed on the periphery of the core. The elastic layer is formed of foam rubber.

21. A fixing device, wherein: The fixing device has the following components: A fixing member, which is annular and rotatable; a heater disposed in the internal space of the fixing member and generating heat by supplying electricity; a sliding member disposed between the heater and an inner surface of the fixing member and sliding on the inner surface of the fixing member; a holding member that holds the heater and the sliding member; as well as a pressing member, the pressing member being arranged to sandwich the fixing member together with the sliding member, and forming a nip portion between the pressing member and the fixing member, The fixing device is configured to heat the image on the recording material by the fixing member while the recording material is held and conveyed by the holding portion. The longitudinal direction of the clamping portion is defined as a first direction, the recording material conveying direction at the clamping portion is defined as a second direction, and a direction orthogonal to both the first direction and the second direction is defined as a third direction. The fixing device further includes a guide member for guiding both end portions of the fixing member in the first direction. The end surface of the sliding member on the downstream side in the second direction is curved such that a center portion of the end surface in the first direction protrudes toward the downstream side in the second direction more than both ends of the end surface in the first direction.

22. A fixing device, wherein: The fixing device has the following components: A fixing member, which is annular and rotatable; a heater disposed in the internal space of the fixing member and generating heat by supplying electricity; a sliding member disposed between the heater and an inner surface of the fixing member and sliding on the inner surface of the fixing member; a holding member that holds the heater and the sliding member; as well as a pressing member, the pressing member being arranged to sandwich the fixing member together with the sliding member, and forming a nip portion between the pressing member and the fixing member, The fixing device is configured to heat the image on the recording material by the fixing member while the recording material is held and conveyed by the holding portion. The longitudinal direction of the clamping portion is defined as a first direction, the recording material conveying direction at the clamping portion is defined as a second direction, and a direction orthogonal to both the first direction and the second direction is defined as a third direction. The end surface of the sliding member on the downstream side in the second direction is curved so that both ends of the end surface in the first direction protrude toward the downstream in the second direction more than the center portion of the end surface in the first direction.

23. A fixing device, wherein: The fixing device has the following components: A fixing member, which is annular and rotatable; a heater disposed in the internal space of the fixing member and generating heat by supplying electricity; a sliding member disposed between the heater and an inner surface of the fixing member and sliding on the inner surface of the fixing member; a holding member that holds the heater and the sliding member; as well as a pressing member, the pressing member being arranged to sandwich the fixing member together with the sliding member, and forming a nip portion between the pressing member and the fixing member, The fixing device is configured to heat the image on the recording material by the fixing member while the recording material is held and conveyed by the holding portion. The longitudinal direction of the clamping portion is defined as a first direction, the recording material conveying direction at the clamping portion is defined as a second direction, and a direction orthogonal to both the first direction and the second direction is defined as a third direction. The fixing device further includes a heat retaining member, which is arranged between the holding member and the heater in the third direction and is used to retain the heat of the heater. The heat retaining member is in contact with the sliding member.

24. The fixing device according to claim 23, wherein: The heat retaining member is in surface contact with the sliding member.

25. A fixing device, wherein: The fixing device has the following components: A fixing member, which is annular and rotatable; a heater disposed in the internal space of the fixing member and generating heat by supplying electricity; a sliding member disposed between the heater and an inner surface of the fixing member and sliding on the inner surface of the fixing member; a holding member that holds the heater and the sliding member; as well as a pressing member, the pressing member being arranged to sandwich the fixing member together with the sliding member, and forming a nip portion between the pressing member and the fixing member, The fixing device is configured to heat the image on the recording material by the fixing member while the recording material is held and conveyed by the holding portion. The longitudinal direction of the clamping portion is defined as a first direction, the recording material conveying direction at the clamping portion is defined as a second direction, and a direction orthogonal to both the first direction and the second direction is defined as a third direction. The sliding member comprises: a sliding friction portion which slides and rubs against the inner surface of the fixing member; and a heat preservation portion which is arranged between the retaining member and the heater in the third direction and is used to maintain the heat of the heater, and the sliding friction portion is formed integrally with the heat preservation portion.

26. The fixing device according to claim 25, wherein: The sliding friction portion and the heat retaining portion are formed of a metal plate that is bent between the sliding friction portion and the heat retaining portion, or a tubular metal member in which the sliding friction portion and the heat retaining portion are continuous.

27. A fixing device, wherein: The fixing device has the following components: A fixing member, which is annular and rotatable; a heater disposed in the internal space of the fixing member and generating heat by supplying electricity; a sliding member disposed between the heater and an inner surface of the fixing member and sliding on the inner surface of the fixing member; a holding member that holds the heater and the sliding member; a pressing member, the pressing member being arranged to sandwich the fixing member together with the sliding member, and forming a nip portion between the pressing member and the fixing member; A force-applying member, the force-applying member is used to apply pressure to the clamping portion; as well as a reinforcing member that reinforces the holding member and receives the force of the biasing member to press the holding member toward the pressing member, The fixing device is configured to heat the image on the recording material by the fixing member while the recording material is held and conveyed by the holding portion. Grease is applied between the heater and the sliding member. The longitudinal direction of the clamping portion is defined as a first direction, the recording material conveying direction at the clamping portion is defined as a second direction, and a direction orthogonal to both the first direction and the second direction is defined as a third direction. The sliding member comprises: a sliding friction portion extending along the second direction and slidingly rubbing against the inner surface of the fixing member; a first rising portion rising from an upstream end of the sliding friction portion in the second direction toward a side away from the pressing member in the third direction; and a second rising portion rising from a downstream end of the sliding friction portion in the second direction toward a side away from the pressing member in the third direction. The holding member has a first recessed portion for accommodating the first rising portion and a second recessed portion for accommodating the second rising portion. The position where the reinforcing member presses the holding member is downstream of the first recess and upstream of the second recess in the second direction.

28. The fixing device according to claim 27, wherein: The reinforcing member comprises: a first pressing portion that presses the holding member at a position upstream of the center of the heater in the second direction; and a second pressing portion that presses the holding member at a position downstream of the center of the heater in the second direction. The first pressing portion is located downstream of the first recess in the second direction. The second pressing portion is located upstream of the second recessed portion in the second direction.

29. The fixing device according to claim 27, wherein: The holding member is formed with a through hole that penetrates the holding member in the third direction from the bottom surface of the first recess or the second recess to the side opposite to the bottom surface, and can guide the grease.

30. An image forming apparatus, wherein: The image forming device comprises: an image forming unit that forms an image on a recording material using toner; and The fixing device according to any one of claims 1 to 29, which fixes the image on the recording material.

Images