Fixing device and image forming apparatus

Abstract

To provide a new technique that can improve the performance of a fixing device and an image forming apparatus.SOLUTION: A longitudinal direction of a nip part is defined as a first direction, a recording material conveyance direction at the nip part as a second direction, and a direction orthogonal to both the first direction and second direction as a third direction. A slide member has: a rubbing part that is rubbed against an inner face of a fixing member; a first erection part that is erected from an upstream end of the rubbing part in the second direction to a side separating from a pressure member in the third direction; a second erection part that is erected from a downstream end of the rubbing part in the second direction to a side separating from the pressure member in the third direction; and a projection that is provided in at least one of the first erection part and second erection part, and projects in a direction intersecting an extension direction of the erection part when seen in the first direction.SELECTED DRAWING: Figure 4

Description

[Technical field]

[0001] The present invention relates to a fixing device that fixes an image onto a recording material, and an image forming apparatus that forms an image on a recording material. [Background technology]

[0002] Patent document 1 describes a fixing device that includes an endless fixing belt, a pressure roller that clamps the recording material together with the fixing belt, a heater arranged on the inner side of the fixing belt, and a metal plate (thermal diffusion member) arranged between the heater and the fixing belt. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2020-3611 A Summary of the Invention [Problem to be solved by the invention]

[0004] An object of the present invention is to provide a new technique capable of improving the performance of a fixing device and an image forming apparatus. [Means for solving the problem]

[0005] One aspect of the present invention is a fixing device that includes a rotatable endless fixing member, a heater that is disposed in an internal space of the fixing member and generates heat when electricity is applied, a sliding member that is disposed between the heater and an inner surface of the fixing member and slides against the inner surface of the fixing member, a holding member that holds the heater and the sliding member, and a pressure member that is disposed together with the sliding member to sandwich the fixing member and form a nip portion between the fixing member and the pressing member, and heats an image on the recording material with the fixing member while sandwiching and transporting the recording material in the nip portion, wherein grease is applied between the heater and the sliding member, a longitudinal direction of the nip portion is a first direction, and a pressing member that presses the fixing member against the pressing member and the pressing member to press the pressing member against the pressing member, and a pressing member that presses the pressing ..., and a pressing member that presses the pressing member against the pressing member and the pressing member, and a pressing member that presses the pressing member against the pressing member and the pressing member, and a pressing member that presses the pressing member against the pressing member and the pressing member, and a pressing member that presses the pressing member against the pressing member and the pressing member, and a pressing member that presses the pressing member against the pressing member and the pressing member, and a pressing member that presses the pressing member against the pressing member and the pressing member, and a pressing member that presses the pressing member against the The fixing device is characterized in that the feed direction is defined as a second direction, and a direction perpendicular to both the first direction and the second direction is defined as a third direction, and the sliding member has a sliding portion extending along the second direction and rubbing against the inner surface of the fixing member, a first standing portion standing from an upstream end of the sliding portion in the second direction to a side moving away from the pressure member in the third direction, a second standing portion standing from a downstream end of the sliding portion in the second direction to a side moving away from the pressure member in the third direction, and a protrusion portion provided on at least one of the first standing portion and the second standing portion and protruding in a direction intersecting the extension direction of the standing portion when viewed in the first direction.

[0006] One aspect of the present invention is a fixing device that includes a rotatable endless fixing member, a heater that is disposed in an internal space of the fixing member and generates heat when electricity is applied, a sliding member that is disposed between the heater and an inner surface of the fixing member and slides against the inner surface of the fixing member, a holding member that holds the heater and the sliding member, and a pressure member that is disposed together with the sliding member to sandwich the fixing member and form a nip portion between the fixing member and the pressure member, and heats an image on the recording material with the fixing member while sandwiching and transporting the recording material in the nip portion, the longitudinal direction of the nip portion being a first direction, and the nip portion being a second direction. a second direction is a recording material transport direction in a tip portion, and a third direction is a direction perpendicular to both the first direction and the second direction; the sliding member has a rubbing portion that rubs against the inner surface of the fixing member, the holding member has a first opposing portion that faces the inner surface of the fixing member upstream of the rubbing portion in the second direction, and a second opposing portion that faces the inner surface of the fixing member downstream of the rubbing portion in the second direction, and in the third direction, the first opposing portion and the second opposing portion are retracted to a side away from the pressure member compared to the rubbing portion.

[0007] One aspect of the present invention is a fixing device comprising: a rotatable endless fixing member; a heater that is disposed in an internal space of the fixing member and generates heat when electricity is applied; a sliding member that is disposed between the heater and an inner surface of the fixing member and slides against the inner surface of the fixing member; a holding member that holds the heater and the sliding member; and a pressure member that is disposed together with the sliding member to sandwich the fixing member and form a nip portion between the fixing member and the pressure member, and the fixing device heats an image on the recording material by the fixing member while sandwiching and transporting the recording material in the nip portion, the longitudinal direction of the nip portion being a first direction, the recording material transport direction in the nip portion being a second direction, and a fixing device that is perpendicular to both the first direction and the second direction. a direction in which the pressure member is pressed against the pressing member is defined as a third direction, and the sliding member has a sliding portion that extends along the second direction and rubs against the inner surface of the fixing member, a first guide portion that extends upstream of the sliding portion in the second direction and guides the fixing member, and a second guide portion that extends downstream of the sliding portion in the second direction and guides the fixing member, wherein the first guide portion and the second guide portion are curved along a rotational trajectory of the fixing member when viewed in the first direction, and cover at least a portion of the holding member upstream and downstream of the heater in the second direction when viewed from the pressure member side toward the fixing member side in the third direction.

[0008] One aspect of the present invention is a fixing device that includes a rotatable endless fixing member, a heater that is disposed in an internal space of the fixing member and generates heat when electricity is applied, a sliding member that is disposed between the heater and an inner surface of the fixing member and slides against the inner surface of the fixing member, a holding member that holds the heater and the sliding member, and a pressure member that is disposed to sandwich the fixing member together with the sliding member and forms a nip portion between the fixing member and the pressure member, and the fixing device heats an image on the recording material with the fixing member while sandwiching and transporting the recording material in the nip portion, the longitudinal direction of the nip portion being a direction in which the fixing member extends. A fixing device characterized in that a first direction is a recording material transport direction in the nip portion, a second direction is a direction perpendicular to both the first direction and the second direction, and a third direction is a direction in which the recording material is transported, the width of the nip portion in the second direction at both ends of the nip portion in the first direction is wider than the width of the nip portion in the second direction at a center of the nip portion in the first direction, and the width of the sliding member in the second direction at both ends of the nip portion is wider than the width of the sliding member in the second direction at the center of the nip portion.

[0009] One aspect of the present invention is a fixing device that includes a rotatable endless fixing member, a heater that is disposed in an internal space of the fixing member and generates heat when electricity is applied, a sliding member that is disposed between the heater and an inner surface of the fixing member and slides against the inner surface of the fixing member, a holding member that holds the heater and the sliding member, and a pressure member that is disposed to sandwich the fixing member together with the sliding member and forms a nip portion between the fixing member and the pressure member, and the fixing device heats an image on the recording material with the fixing member while sandwiching and transporting the recording material in the nip portion, the longitudinal direction of the nip portion being a direction in which the fixing member extends. A fixing device characterized in that a first direction is a recording material transport direction in the nip portion, a second direction is a direction perpendicular to both the first direction and the second direction, a width of the nip portion in the second direction at both ends of the nip portion in the first direction is narrower than a width of the nip portion in the second direction at a center of the nip portion in the first direction, and a width of the sliding member in the second direction at both ends of the nip portion is narrower than a width of the sliding member in the second direction at the center of the nip portion.

[0010] One aspect of the present invention is a fixing device comprising: a rotatable endless fixing member; a heater that is disposed in an internal space of the fixing member and generates heat when electricity is applied; a sliding member that is disposed between the heater and an inner surface of the fixing member and slides against the inner surface of the fixing member; a holding member that holds the heater and the sliding member; and a pressure member that is disposed to sandwich the fixing member together with the sliding member and forms a nip portion between the fixing member and the pressure member, and the fixing device heats an image on the recording material with the fixing member while sandwiching and transporting the recording material in the nip portion. the longitudinal direction of the nip portion is a first direction, the recording material transport direction in the nip portion is a second direction, and a direction perpendicular to both the first direction and the second direction is a third direction, the fixing device further includes guide members that guide both end portions of the fixing member in the first direction, and a downstream end face of the sliding member in the second direction is curved so that a central portion of the end face in the first direction protrudes downstream in the second direction compared to both end portions of the end face in the first direction.

[0011] One aspect of the present invention is a fixing device comprising: a rotatable, endless fixing member; a heater that is disposed in an internal space of the fixing member and generates heat when electricity is applied; a sliding member that is disposed between the heater and an inner surface of the fixing member and slides against the inner surface of the fixing member; a holding member that holds the heater and the sliding member; and a pressure member that is disposed to sandwich the fixing member together with the sliding member and form a nip portion between the fixing member and the pressing member, the fixing device heating an image on a recording material with the fixing member while sandwiching and transporting the recording material in the nip portion, the fixing device being characterized in that a longitudinal direction of the nip portion is a first direction, a recording material transport direction in the nip portion is a second direction, and a direction perpendicular to both the first direction and the second direction is a third direction, and an end face on a downstream side of the sliding member in the second direction is curved so that both ends of the end face in the first direction protrude downstream in the second direction compared to a central portion of the end face in the first direction.

[0012] One aspect of the present invention is a fixing device comprising: a rotatable, endless fixing member; a heater that is disposed in an internal space of the fixing member and generates heat when electricity is applied; a sliding member that is disposed between the heater and an inner surface of the fixing member and slides against the inner surface of the fixing member; a holding member that holds the heater and the sliding member; and a pressure member that is disposed together with the sliding member to sandwich the fixing member and form a nip portion between the fixing member and the pressing member, the fixing device heating an image on a recording material with the fixing member while sandwiching and transporting the recording material in the nip portion, the longitudinal direction of the nip portion being a first direction, a recording material transport direction in the nip portion being a second direction, and a direction perpendicular to both the first direction and the second direction being a third direction, the fixing device further comprising a heat retention member that is disposed between the holding member and the heater in the third direction and that retains heat from the heater, the heat retention member being in contact with the sliding member.

[0013] One aspect of the present invention is a fixing device comprising: a rotatable, endless fixing member; a heater that is disposed in an internal space of the fixing member and generates heat when electricity is applied; a sliding member that is disposed between the heater and an inner surface of the fixing member and slides against the inner surface of the fixing member; a holding member that holds the heater and the sliding member; and a pressure member that is disposed to sandwich the fixing member together with the sliding member and form a nip portion between the fixing member and the pressing member, the fixing device heating an image on a recording material by the fixing member while sandwiching and transporting the recording material in the nip portion, the longitudinal direction of the nip portion being a first direction, a recording material transport direction in the nip portion being a second direction, and a direction perpendicular to both the first direction and the second direction being a third direction, the sliding member has a sliding portion that rubs against the inner surface of the fixing member, and a heat retention portion that is disposed between the holding member and the heater in the third direction and retains heat of the heater, the sliding portion and the heat retention portion being integrally formed.

[0014] One aspect of the present invention is a fixing device comprising: a rotatable endless fixing member; a heater that is disposed in an internal space of the fixing member and generates heat when electricity is applied; a sliding member that is disposed between the heater and an inner surface of the fixing member and slides against the inner surface of the fixing member; a holding member that holds the heater and the sliding member; a pressure member that is disposed to sandwich the fixing member together with the sliding member and forms a nip portion between the fixing member and the holding member; an urging member for applying pressure to the nip portion; and a reinforcing member that reinforces the holding member and presses the holding member toward the pressure member by receiving an urging force of the urging member. The fixing device heats an image on the recording material by the fixing member while sandwiching and transporting the recording material in the nip portion, and grease is applied between the heater and the sliding member, and the longitudinal direction of the nip portion is oriented in a direction perpendicular to the longitudinal direction of the fixing member. a first direction is a first direction, a recording material transport direction in the nip portion is a second direction, and a direction perpendicular to both the first direction and the second direction is a third direction, the sliding member has a sliding portion extending along the second direction and rubbing against the inner surface of the fixing member, a first upstanding portion standing from an upstream end of the sliding portion in the second direction to a side moving away from the pressure member in the third direction, and a second upstanding portion standing from a downstream end of the sliding portion in the second direction to a side moving away from the pressure member in the third direction, the holding member has a first recess that receives the first upstanding portion and a second recess that receives the second upstanding portion, and the position at which the reinforcing member presses the holding member is downstream of the first recess and upstream of the second recess in the second direction. Effect of the Invention

[0015] According to the present invention, it is possible to provide a new technique capable of improving the performance of a fixing device and an image forming apparatus. [Brief description of the drawings]

[0016] [Figure 1] 1 is a schematic diagram of an image forming apparatus according to a first embodiment. [Diagram 2] FIG. 2 is a cross-sectional view of the fixing device according to the first embodiment. [Diagram 3]FIG. 2 is a side view of the fixing device according to the first embodiment. [Figure 4] FIG. 3 is a cross-sectional view of a belt heating unit according to the first embodiment. [Diagram 5] FIG. 11 is a diagram showing the movement of thermal conductive grease in a reference example. [Figure 6] 4A to 4C are views showing the movement of thermal conductive grease in Example 1. [Figure 7] FIG. 4 is a diagram for explaining the width of a protrusion according to the first embodiment. [Figure 8] FIG. 3 is a perspective view showing an end portion of a sliding plate according to the first embodiment. [Figure 9] FIG. 11 is a schematic diagram of an image forming apparatus according to a second embodiment. [Figure 10] FIG. 11 is a cross-sectional view of a belt heating unit according to a second embodiment. [Figure 11] FIG. 11 is a diagram showing the movement of thermal conductive grease in Example 2. [Figure 12] FIG. 11 is a diagram showing the movement of thermal conductive grease in Example 2. [Figure 13] FIG. 11 is a cross-sectional view of a belt heating unit according to a third embodiment. [Figure 14] FIG. 11 is a diagram showing the movement of thermal conductive grease in Example 3. [Figure 15] FIG. 11 is a cross-sectional view of a fixing device according to a fourth embodiment. [Figure 16] FIG. 11 is a cross-sectional view of a belt heating unit according to a fourth embodiment. [Figure 17] FIG. 4 is a cross-sectional view of a fixing device according to a reference example. [Figure 18] FIG. 4 is a cross-sectional view of a belt heating unit according to a reference example. [Figure 19] 13A and 13B are cross-sectional views of a belt heating portion according to a modified example of the fourth embodiment. [Figure 20] FIG. 13 shows experimental results for Example 4. [Figure 21] FIG. 13 is a cross-sectional view of a belt heating unit according to a fifth embodiment. [Figure 22] FIG. 13 is a cross-sectional view of a belt heating unit according to a modified example of the fifth embodiment. [Diagram 23] FIG. 13 is a cross-sectional view of a belt heating unit according to a modified example of the fifth embodiment. [Figure 24] 11 is an explanatory diagram of the trailing edge of the recording material bouncing. [Diagram 25] 11 is an explanatory diagram of the trailing edge of the recording material bouncing. [Figure 26] 6A and 6B are explanatory diagrams of the deflection of the pressure roller, the stay, etc. [Figure 27] 13 is a graph showing the distribution of nip pressure and nip width in Example 6. [Figure 28] 13A and 13B are explanatory views of a sliding plate shape according to Example 6. [Figure 29] 13A and 13B are explanatory views of the temperature distribution in the nip in Example 6. [Diagram 30] FIG. 13 shows experimental results for Example 6. [Diagram 31] 13 is a graph showing the distribution of nip pressure and nip width in a modified example of Example 6. [Diagram 32] 6A and 6B are explanatory diagrams of the deflection of the pressure roller, the stay, etc. [Diagram 33] FIG. 23 is an explanatory diagram of a sliding plate shape in a modified example of the sixth embodiment. [Diagram 34] 6A and 6B are explanatory diagrams of deflection of a fixing belt in a reference example. [Diagram 35] 6A and 6B are explanatory diagrams of the radius of curvature of a fixing belt in a reference example. [Diagram 36] 13 is an explanatory diagram of the deflection of a fixing belt in the seventh embodiment. FIG. [Figure 37] 13A and 13B are explanatory views of the radius of curvature of a fixing belt in Example 7. [Figure 38] FIG. 6 is an explanatory diagram of a temperature rise in a non-sheet passing portion. [Figure 39] FIG. 13 is a cross-sectional view of a belt heating unit according to an eighth embodiment. [Diagram 40] 13(a,b) shows the configuration of a heater according to Example 8. FIG. [Diagram 41] 13A and 13B are explanatory views of a heat retention plate in Example 8. [Diagram 42] FIG. 13 shows experimental results for Example 8. [Diagram 43] FIG. 13 is a graph showing temperature distributions in the fixing device in the reference example (a) and in the embodiment 8 (b). [Diagram 44] 13A and 13B are explanatory views of a heat retention plate in a modified example of Example 8. [Diagram 45]FIG. 23 is an explanatory diagram of a first modified example of the eighth embodiment. [Figure 46] 13(a,b) is an explanatory diagram of a second modified example of the eighth embodiment. [Figure 47] 13(a,b) is an explanatory diagram of a third modified example of the eighth embodiment. [Figure 48] FIG. 23 is an explanatory diagram of a modified example 3-2 of the eighth embodiment. [Figure 49] 13A to 13C are explanatory diagrams of modified examples 4-1 to 4-3 of the eighth embodiment. [Figure 50] FIG. 23 is a diagram showing an experimental result for a modified example of the eighth embodiment. [Figure 51] FIG. 13 is a cross-sectional view of a fixing device according to a ninth embodiment. [Figure 52] FIG. 13 is an explanatory diagram of a fixing device according to a ninth embodiment. [Figure 53] FIG. 23 is a cross-sectional view of a fixing device according to a tenth embodiment. [Figure 54] FIG. 23 is a top view of a retaining member and a stay according to a tenth embodiment. [Figure 55] FIG. 23 is an explanatory diagram of the movement of excess grease in the tenth embodiment. [Figure 56] FIG. 23 is a cross-sectional view of a fixing device according to a modified example of the tenth embodiment. [Figure 57] FIG. 23 is an explanatory diagram of the movement of excess grease in a modified example of the tenth embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0017] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings.

[0018] In the following description, the term "image forming apparatus" refers to a general apparatus equipped with an image forming function (printing function) for 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.

[0019] Example 1 An overview of an image forming apparatus 100 according to a first embodiment will be described with reference to Fig. 1. The image forming apparatus 100 is a direct transfer type electrophotographic color printer having a maximum width of letter size, in which 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 sheet width of the recording material S that has the largest length (sheet 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. Also, causing the image forming apparatus 100 to perform an image forming operation on the recording material S is referred to as "passing the paper through" the image forming apparatus 100.

[0020] FIG. 1 shows the coordinate axes of the xyz coordinate system. 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 is the direction in which the pressure roller 202 and the belt unit 201 of the fixing device 200 are aligned. 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 direction opposite to 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 recording material conveying direction in the fixing device 200, and the -y direction (the direction opposite to the arrow) is the direction toward the upstream of the recording material conveying direction in the fixing device 200. The x-axis is a coordinate axis parallel to the longitudinal 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. The g-axis indicates the direction of gravity, which is approximately the same as the -z direction in this embodiment. The x-axis, y-axis, and z-axis are preferably perpendicular to each other.

[0021] In each of the following embodiments, the x-axis direction can be considered to be the longitudinal direction (first direction) of a nip portion N of a fixing device 200 described later. The +y direction can be considered to be the recording material conveying direction (second direction) in the nip portion N. The z-axis direction can be considered to be a third direction perpendicular to both the first and second directions.

[0022] The image forming apparatus 100 includes a plurality of image forming units PK, PC, PM, and PY, a transfer belt 8, and a plurality of transfer rollers 5K, 5C, 5M, and 5Y. Each of the plurality of image forming units PK, PC, PM, and PY is configured to form an image (toner image) by an electrophotographic process using toner as a developer. The transfer belt 8 is a conveying member that conveys a recording material S along the plurality of image forming units PK, PC, PM, and PY. The transfer rollers 5K, 5C, 5M, and 5Y are disposed on the inner periphery side of the transfer belt 8, and are disposed at positions corresponding to each image forming unit via the transfer belt 8.

[0023] A feed cassette 61 that stores recording material S is disposed at the bottom of the image forming apparatus 100. Inside the image forming apparatus 100, a conveying path 60 for the recording material S is formed, which passes from the feed cassette 61 through a plurality of image forming sections PK, PC, PM, PY and a fixing device 200 to a discharge tray 70. The image forming apparatus 100 includes a feed roller 62, a pair of conveying rollers 63, a pair of registration rollers 64, a pair of conveying rollers 65, a transfer belt 8, and a plurality of image forming sections PK, PC, PM, PY. The image forming apparatus 100 also includes a fixing device 200, a pair of conveying rollers 66, a pair of discharge rollers 67, and a discharge tray 70. The above-mentioned members involved in the conveying of the recording material S are arranged in the above-mentioned order along the conveying path 60.

[0024] The image forming apparatus 100 receives image information from an external device, such as a document reading device connected to the main body of the image forming apparatus 100 or a personal computer connected to the main body so as to be able to communicate with the main body, and forms an image on a recording material S based on the image information. As the recording material S (recording medium), various sheet materials of different materials can be used, such as paper such as plain paper and thick paper, sheet materials with surface treatments such as coated paper, sheet materials of special shapes such as envelopes and index paper, plastic films, cloth, etc. Furthermore, sheet materials of various sizes, including A4 size and letter size, can be used as the recording material S.

[0025] The conveying process of the recording material S will be described. The recording material S loaded in a feeding cassette 61 is fed to a conveying path 60 one by one by a feeding roller 62 in accordance with the image formation timing. The image forming apparatus 100 may also be provided with a feeding section (manual feeding section) for feeding the recording material S loaded on a manual feed tray (not shown) one by one to the conveying path 60. The recording material S fed to the conveying path 60 is conveyed by a conveying roller pair 63 to a registration roller pair 64, which performs skew correction and timing correction on the recording material S. Thereafter, the recording material S is sent to the transfer belt 8 by a conveying roller pair 65.

[0026] The transfer belt 8 is an endless belt member stretched around a drive roller 9 and a tension roller 10. When the drive roller 9 is driven to rotate by a driving force from a motor (not shown), the transfer belt 8 runs in a running direction (rotation direction) indicated by an arrow R2. When the recording material S is sent from the conveying roller pair 65 to the transfer belt 8, the recording material S is conveyed downstream in the recording material conveying direction in the conveying path 60 as the transfer belt 8 runs, with the recording material S being supported 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 of the image forming units PK, PC, PM, and PY.

[0027] In this embodiment, four image forming units PK, PC, PM, and PY are disposed above a transfer belt 8 as a plurality of image forming units. An exposure device 3 is disposed further 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 detachable from the main body of the image forming apparatus 100. The image forming units PK, PC, PM, and PY use black, cyan, magenta, and yellow toners to form toner images of the respective colors on a recording material S. The four image forming units PK, PC, PM, and PY have substantially the same configuration except for the color of the toner.

[0028] The image forming unit PK has a photosensitive drum 1K, a charging device 2K, a developing device 4K, and a drum cleaner 6K. The image forming unit PC has a photosensitive drum 1C, a charging device 2C, a developing device 4C, and a drum cleaner 6C. The image forming unit PM has a photosensitive drum 1M, a charging device 2M, a developing device 4M, and a drum cleaner 6M. The image forming unit PY has a photosensitive drum 1Y, a charging device 2Y, a developing device 4Y, and a drum cleaner 6Y.

[0029] Each of the photosensitive drums 1K, 1C, 1M, and 1Y is a rotating image carrier (electrophotographic photosensitive member). The charging devices 2K, 2C, 2M, and 2Y uniformly charge the surfaces of the corresponding photosensitive drums 1K, 1C, 1M, and 1Y. The exposure device 3 irradiates light onto each of the photosensitive drums 1K, 1C, 1M, and 1Y based on image information to form an electrostatic latent image on each of the photosensitive drums 1K, 1C, 1M, and 1Y. The developing devices 4K, 4C, 4M, and 4Y develop the electrostatic latent image into a toner image using toner. This toner image is transferred to the recording material S at four transfer sections formed between the photosensitive drums 1K, 1C, 1M, and 1Y and the transfer rollers 5K, 5C, 5M, and 5Y. In the transfer portion, the toner images on the photosensitive drums 1K, 1C, 1M, and 1Y are pressed onto the recording material S by the transfer rollers 5K, 5C, 5M, and 5Y, and the toner images are transferred by the bias electric field formed by the transfer rollers 5K, 5C, 5M, and 5Y. Foreign matter such as residual toner adhering to the surfaces of the photosensitive drums 1K, 1C, 1M, and 1Y after the photosensitive drums have passed through the transfer portion is removed by drum cleaners 6K, 6C, 6M, and 6Y.

[0030] In the case of an image forming operation using toner of multiple colors (multi-color printing), the image forming units PK, PC, PM, and PY are started in this order. Then, the timing of creating the toner images in the image forming units PK, PC, PM, and PY (specifically, the timing of starting writing of the electrostatic latent image by the exposure device 3) is controlled so that the toner images of each color are superimposed on the recording material S. While the recording material S is transported by the transfer belt 8, the toner images are transferred so that the toner images of each color are superimposed on each other, and a color image is formed on the recording material S. The control unit of the image forming apparatus 100 controls the drive amount and drive timing of each image forming unit PK, PC, PM, and PY and the transfer belt 8 so as to align the toner images of each color with each other.

[0031] The fixing device 200 is disposed downstream of the transfer belt 8 in the recording material transport direction. The fixing device 200 applies heat and pressure to the toner image on the recording material S while transporting the recording material S to which the toner image has been transferred in the transfer section, thereby fixing the toner image to the recording material S. The fixing device 200 will be described in detail later.

[0032] The recording material S that has passed through the fixing device 200 is transported via a pair of transport rollers 66 and is discharged onto a discharge tray 70 by a pair of discharge rollers 67. In addition, any deposits adhering to the transfer belt 8 after the recording material S has been transported to the fixing device 200 are removed from the transfer belt 8 by a belt cleaner 11.

[0033] The image forming apparatus 100 repeats the above image forming operation, thereby making it possible to successively form images on a plurality of sheets of recording material S in response to a single image formation instruction.

[0034] [Fixing device] Next, the fixing device 200 of this embodiment will be described with reference to Figures 2 and 3. Figure 2 is an enlarged view of the fixing device 200 of this embodiment. Figure 3 is a view of the fixing device 200 as seen from the upstream side in the transport direction F (Figure 2), and shows the positional relationship of elements in the longitudinal direction of the fixing device 200. The longitudinal direction of the fixing device 200 is the direction along the x-axis. In Figure 3, the fixing belt 21 is shown in a see-through state so that the state inside the belt unit 201 can be easily seen.

[0035] 2 and 3, the fixing device 200 includes a fixing belt 21 as a rotatable endless fixing member, and a heater 26 that is disposed in the internal space of the fixing member and generates heat when energized. The fixing device 200 also includes a sliding plate 27 that is disposed between the heater 26 and the inner surface of the fixing belt 21 and serves as a sliding member that slides against the inner surface of the fixing belt 21, and a holding member 23 that holds the heater 26 and the sliding plate 27. The fixing device 200 also includes a pressure roller 202 that is disposed to sandwich the fixing belt 21 together with the sliding plate 27 and serves as a pressure member that forms a nip portion N between the fixing belt 21 and the pressure roller 202. The fixing device 200 heats an image on the recording material by the fixing belt 21 while conveying the recording material by nipping the recording material at the nip portion N.

[0036] The configuration of the fixing device 200 will be further described below. The fixing device 200 has a belt unit 201 as a heating device, and a pressure roller 202 as a pressure member that contacts 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 in which the toner image t on the recording material S is heated and pressurized at the nip portion N while the recording material S is sandwiched between the belt unit 201 and the pressure roller 202 and conveyed in a conveying direction F. The fixing device 200 is detachably mounted on the main body of the image forming apparatus 100. The fixing device 200 may be formed integrally with the main body of the apparatus.

[0037] The belt unit 201 includes a rotatable endless fixing belt 21, a stay 22 arranged inside the fixing belt 21, a holding member 23 supported by the stay 22, and a belt heating unit 210 that heats the fixing belt 21. The stay 22, the holding member 23, and the belt heating unit 210 are all arranged in the internal space of the fixing belt 21, and each has an elongated shape with the x-axis direction as the longitudinal direction.

[0038] The fixing belt 21 is a flexible endless belt member (endless belt) made of a material with high thermal conductivity and low heat capacity, for example, 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 preferably include a base material (base layer) made of an endless polyimide resin, an elastic layer formed on the outer periphery of the base material, and a surface layer (release layer) formed on the outer periphery of the elastic layer. The fixing belt 21 is provided to be rotatable, 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 regulate 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 peripheral surface) of the fixing belt 21 and an end regulation surface that extends from the rotation guide surface in a direction intersecting the x-axis direction and regulates the end of the fixing belt 21.

[0039] The stay 22 is made of a metal having high rigidity, such as stainless steel or spring steel. The stay 22 in this embodiment is formed with a substantially U-shaped cross section to further increase its rigidity. The stay 22 holds the holding member 23, which holds the belt heating unit 210. Both ends of the stay 22 in the x-axis direction receive a biasing force from a pressure spring 251 formed of a coil spring or the like. The biasing force of the pressure spring 251 biases the holding member 23 and the belt heating unit 210 toward the pressure roller 202 in the z-axis direction (-z direction, the direction of the arrow P in FIG. 3). As a result, the belt heating unit 210 and the pressure roller 202 are pressed across 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.

[0040] The holding member 23 holds a thermistor, a heater, and the like, which will be described later, and forms a belt heating section 210 (a portion indicated by a broken line in FIG. 2) inside the fixing belt 21. The belt heating section 210 will be described later.

[0041] The pressure roller 202 has, for example, a metal core 202a as a rotating shaft, and an outer circumferential portion 202b. The outer circumferential portion 202b is formed on the outer periphery of the core 202a. The outer circumferential portion 202b is a portion that contacts the outer surface (outer circumferential surface) of the fixing belt 21 at the nip portion N. The outer circumferential portion 202b has, for example, an elastic layer such as silicone rubber, and a surface layer (release layer) formed of a fluororesin such as PTFE, PFA, or FEP on the outer periphery of the elastic layer. The elastic layer may be foamed rubber (balloon rubber) obtained by foaming a rubber material, or may be solid rubber that is not foamed. The core 202a is rotatably supported by bearings 252 (FIG. 3) at both ends in the rotation axis direction (x-axis direction) of the pressure roller 202.

[0042] The pressure roller 202 is rotated at a predetermined peripheral speed in the direction of arrow R3 by inputting a driving force from a driving motor (not shown) to a driving gear 253 provided at an end of the rotation shaft in the x-axis direction. Then, the rotation force of the pressure roller 202 is transmitted to the fixing belt 21 by frictional force generated at the nip portion N. In this way, the fixing belt 21 rotates following the pressure roller 202. That is, this embodiment is a drive method (so-called pressure roller drive method) in which a driving force is input to the pressure roller 202 to rotate the fixing belt 21 following the pressure roller 202.

[0043] Next, the belt heating unit 210 will be described with reference to Fig. 4. Fig. 4 is an enlarged cross-sectional view showing the belt heating unit 210 in this embodiment, and corresponds to the portion enclosed by the dashed line in Fig. 2.

[0044] 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 with the fixing belt 21 sandwiched therebetween. The belt heating unit 210 heats the fixing belt 21 while rubbing the inner surface of the fixing belt 21 as it rotates.

[0045] The belt heating unit 210 includes a thermistor 24 as a temperature detector, a heat retention plate 25 as a heat retention member that retains heat from a heater 26, the heater 26 as a heating body, and a sliding plate 27 as a sliding member.

[0046] 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 in order to control the temperature of the fixing belt 21. The heater 26 is an example of a heating element that generates heat for heating the fixing belt 21 when energized (that is, converts electrical energy into thermal energy). Based on a detection signal from the thermistor 24, the control unit of the image forming apparatus 100 controls energization / cutoff of the heater 26 and the amount of power supply so as to maintain the fixing belt 21 at a predetermined target temperature (fixing temperature) suitable for fixing the toner image t.

[0047] The thermistor 24, heat retention plate 25, heater 26, and sliding plate 27 are arranged in this order in the -z direction. The heat retention plate 25, heater 26, and sliding plate 27 are each a long and narrow plate-like member whose longitudinal direction is the x-axis direction, whose width direction (short side direction) is the y-axis direction, and whose thickness direction is the z-axis direction.

[0048] The heat retention plate 25, the heater 26, and the sliding plate 27 are held by a holding member 23. A thermally conductive grease G1, which will be described later, is applied between the heat retention plate 25 and the heater 26, and between the heater 26 and the sliding plate 27. A sliding grease G2, which will be described later, is applied to the outer surface of the sliding plate 27 (the surface that slides against the inner surface of the fixing belt 21).

[0049] The heat retention plate 25 has a heat storage performance of temporarily storing the heat generated by the heater 26, and a heat uniformity performance of transmitting the heat generated by the heater 26 in the longitudinal direction (x-axis direction) and reducing temperature unevenness in the longitudinal direction. The heat retention plate 25 is, for example, a metal plate made of an aluminum alloy. The heat retention plate 25 may be omitted, and the holding member 23 may directly support the heater 26.

[0050] The heater 26 is disposed so that its longitudinal direction is substantially parallel to the width direction (x-axis direction) of the fixing belt 21. The heater 26 is an elongated member having a base material of a metal material such as stainless steel or aluminum, or a ceramic material such as alumina or aluminum nitride, on which a pattern of a resistance heating element is formed. When a metal material is used as the base material, an insulating layer is formed on the metal material with an insulating material such as glass. Metal materials have strength and flexibility, so that they can be formed thin, and as a result, the heat capacity of the heater 26 is small. Therefore, the heater 26 having a base material of a metal material has the advantage that the temperature can be quickly raised when the heating of the fixing belt 21 starts (high quick start performance). On the other hand, since ceramic materials have insulating properties, a heater having a base material of a ceramic material has the advantage that a resistance heating element can be formed directly on the base material, and thus the manufacturing man-hours and costs can be reduced.

[0051] In this embodiment, a heater 26 having the following configuration can be preferably used. First, stainless steel (SUS), which is highly corrosion-resistant and strong among metal materials, is used as the base material. In addition, a thin glass layer is formed as an insulating layer on the base material, and a pattern including a resistance heating element as a heat generating member, a terminal for receiving power supply from an external circuit, and wiring for connecting the terminal and the resistance heating element is formed on the insulating layer. Furthermore, in order to protect the pattern, a glass protective layer is formed so as to cover the pattern.

[0052] The sliding plate 27 is provided so as not to rotate with respect to the rotating fixing belt 21. The sliding plate 27 is a sliding member (sliding member) that rubs against the inner surface of the fixing belt 21. The sliding plate 27 is long and extends in the width direction (x-axis direction). The sliding plate 27 has a function as a heat diffusion member that rubs against the inner surface of the fixing belt 21 and diffuses the heat of the heater 26 to the fixing belt 21, and a function as a nip forming member that forms a desired nip portion N by being pressed against the pressure roller 202 via the fixing belt 21.

[0053] The sliding plate 27 in this embodiment has a sliding portion 271 that rubs against the fixing belt 21, and a standing portion 272 that is bent relative to the sliding portion 271 with a curved shape (curved shape) so that the cut edge at the end of the sliding plate does not damage the inner surface of the fixing belt 21.

[0054] The sliding portion 271 has a heater contact surface 271a that comes into contact with the heater 26, and a sliding surface 271b that slides against the fixing belt 21. The heater contact surface 271a extends in the recording material conveying direction (y-axis direction) along the nip portion N, and receives heat from the heater 26.

[0055] The standing portions 272 are formed continuously with the upstream end and downstream end of the rubbing portion 271 in the recording material transport direction (+y direction). The upstream standing portion 272 is an example of a first standing portion, and the downstream standing portion 272 is an example of a second standing portion. Each standing portion 272 stands from the upstream end and downstream end of the rubbing portion 271 toward the side away from the pressure roller 202 in the z-axis direction (+z direction) so as not to rub against the inner surface of the fixing belt 21. The tip of the standing portion 272 is accommodated in a groove portion 231 (relief groove portion, recessed portion) formed in the upstream portion and downstream portion of the holding member 23 in the recording material transport direction (+y direction).

[0056] A protrusion 273 is formed on at least one of the upstream and downstream standing portions 272. The protrusion 273 protrudes in a direction intersecting the extension direction of the standing portion when viewed in the x-axis direction. In this embodiment, the protrusion 273 is formed on each of the upstream and downstream standing portions 272. The protrusion formed on the upstream standing portion 272 is an example of a first protrusion, and the protrusion formed on the downstream standing portion is an example of a second protrusion. Details of the protrusion 273 will be described later.

[0057] The material of the sliding plate 27 is preferably a thin metal plate such as stainless steel, aluminum alloy, or iron so as to efficiently transmit the heat of the heater 26. In addition, the sliding surface 271b that rubs against the fixing belt 21 may be coated with polyimide, fluororesin, glass, or the like to improve the sliding property and abrasion resistance.

[0058] [Problem] In order to efficiently transfer heat from the heater 26 to the sliding plate 27 and the heat retention plate 25, a thermally conductive grease G1 may be applied to the front surface 26a and / or rear surface 26b of the heater 26. The front surface 26a of the heater 26 is the surface facing the heater contact surface 271a of the sliding plate 27, and the rear surface 26b is the surface facing the heat retention plate 25.

[0059] When the belt unit 201 and the pressure roller 202 are pressed against each other, pressure is applied to the belt heating unit 210, and the thermally conductive grease G1 may be pushed out from between the heater 26 and the sliding plate 27, or between the heater 26 and the heat retention plate 25. If the pushed-out thermally conductive grease G1 leaks out onto the sliding surface 271b of the sliding plate 27 along the surface of the sliding plate 27, the thermally conductive grease G1 may impair the sliding properties between the sliding plate 27 and the fixing belt 21, and may accelerate the wear of the inner surface of the fixing belt 21.

[0060] 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.

[0061] [Grease transfer details] More specifically, in this embodiment, in order to improve the sliding property between the fixing belt 21 and the sliding plate 27, the sliding grease G2 is applied to the sliding surface 271b of the sliding plate 27. If the heat conductive grease G1 applied to the heater 26 leaks onto the sliding surface 271b of the sliding plate 27 as described above, the heat conductive grease G1 may mix with the sliding grease G2, which may promote the scraping of the inner surface of the fixing belt 21. In the following, a case in which the heat conductive grease G1 mixes with the sliding grease G2 is assumed, but the configuration of this embodiment can be applied even if the sliding grease G2 is not applied to the sliding surface 271b of the sliding plate 27. For example, even if the sliding grease G2 is not required, such as when the sliding surface 271b is made of a material having self-lubricating properties, the heat conductive grease G1 may leak onto the sliding surface 271b, thereby reducing the sliding property with the inner surface of the fixing belt 21.

[0062] The movement of the thermally conductive grease G1 will be described in detail below with reference to Fig. 5. Fig. 5 is a diagram showing the movement of the thermally conductive grease G1 in the fixing device 200 using the sliding plate 27 of the reference example. The reference example has the same configuration as the fixing device 200 of the first embodiment, except that the protrusion 273 (Fig. 4) is not provided on the rising portion 272 of the sliding plate 27.

[0063] 4 and 5, in order to explain the movement of the grease in a schematic manner, the grease layer is drawn thicker than the thickness in the actual fixing device 200. Therefore, for example, the scale in the z direction in the drawings may differ from that of the actual fixing device 200. The same may be true in the following Examples 2 and 3.

[0064] 5, in the reference example as well, the sliding plate 27, the heater 26, and the heat retention plate 25 are held by the holding member 23. The sliding plate 27 has a sliding portion 271 and an upright portion 272. Here, thermally conductive grease G1 is applied between the heater 26 and the sliding plate 27, and between the heater 26 and the heat retention plate 25, in order to reduce temperature unevenness and improve thermal conductivity.

[0065] In this embodiment and the reference example, grease made by mixing metal filler such as zinc oxide with silicone oil can be used as the thermal conductive grease G1. In this embodiment and the reference example, DOWSIL SC102 compound (density 2.5 g / cm^3) made by Dow Toray Industries, Inc. is used as the thermal conductive grease G1. The application range of the thermal conductive grease G1 on the heater 26 is, for example, 10.5 mm in the y-axis direction, which is the same as the heater width, and 218 mm in the x-axis direction. Within this application range, 250 mg of the thermal conductive grease G1 is applied between the heater 26 and the sliding plate 27, and between the heater 26 and the heat retention plate 25.

[0066] On the other hand, it is preferable to apply a sliding grease G2, which is different from the thermal conductive grease G1, between the fixing belt 21 and the sliding portion 271 of the sliding plate 27 in order to increase the sliding property and reduce wear. As the sliding grease G2, fluorine-based grease, silicone oil, etc. are used. In this embodiment and the reference example, MOLYKOTE HP-300 grease (density 2.0 g / cm^3) manufactured by DuPont-Toray Specialty Materials Co., Ltd. is used as the sliding grease G2. The application range of the sliding grease G2 on the sliding plate 27 is, for example, 10.5 mm in the y-axis direction and 218 mm in the x-axis direction. Within this application range, 500 mg of the sliding grease G2 is applied between the fixing belt 21 and the sliding portion 271 of the sliding plate 27. The sliding grease G2 adheres to the inner surface of the fixing belt 21 as the fixing belt 21 rotates, and increases the sliding property with the sliding surface 271b. This prevents the inner surface of the fixing belt 21 from being worn down.

[0067] Both the thermal conductive grease G1 and the sliding grease G2 are semi-solid or semi-liquid, but have different physical properties. The thermal conductive grease G1 is a first grease containing a filler for enhancing thermal conductivity, and the sliding grease G2 is a second grease with a different composition from the first grease for enhancing sliding properties.

[0068] The width in the y-axis direction of the heater 26 and heat retention plate 25 arranged inside the sliding plate 27 is preferably as wide as possible so that heat can be efficiently transferred to the heater contact surface 271a of the sliding plate 27. However, in order to incorporate them inside the sliding plate 27, the width in the y-axis direction of the heater 26 and heat retention plate 25 is made smaller than the distance between the two upright portions 272. Therefore, a gap is created between the heater 26 and heat retention plate 25 and the upright portions 272 of the sliding plate 27.

[0069] In addition, taking into account the thermal expansion of the sliding plate 27, it is preferable that the groove portion 231 of the holding member 23 is wider than the width in the y-axis direction of the tip portion of the standing portion 272 of the sliding plate 27. Therefore, a gap is also generated between the groove portion 231 of the holding member 23 and the standing portion 272 of the sliding plate 27.

[0070] Here, when the pressure roller 202 and the belt unit 201 are pressed together to form the nip portion N, the heater 26 and the sliding plate 27, and the heater 26 and the heat retention plate 25 come into close contact with each other. At this time, a part of the thermal conductive grease G1 between the heater 26 and the sliding plate 27, or between the heater 26 and the heat retention plate 25, is pushed out onto the inner surface of the rising portion 272 on the upstream and downstream sides of the sliding plate 27.

[0071] However, in the reference example shown in FIG. 5, there was a risk that a part of the extruded heat conductive grease G1 would leak onto the sliding surface 271b of the sliding plate 27 in the following manner.

[0072] First, as shown by the arrow A in FIG. 5, the thermally conductive grease G1 extruded from between the heater 26 and the sliding plate 27 or between the heater 26 and the heat retention 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 thermally conductive grease G1 moves toward the inner surface of the fixing belt 21 by going around the tip of the rising portion 272 in the groove portion 231 of the holding member 23. As a result, the thermally conductive grease G1 mixes with the sliding grease G2 and reaches the gap between the fixing belt 21 and the sliding surface 271b of the sliding plate 27. When the thermally conductive grease G1 mixes with the sliding grease G2, the sliding property between the fixing belt 21 and the sliding surface 271b of the sliding plate 27 deteriorates due to the difference in characteristics between the two, for example, due to the influence of the metal filler in the thermally conductive grease G1, and the wear of the inner surface of the fixing belt 21 may be accelerated.

[0073] [Details of the sliding plate] In view of the above, this embodiment is configured such that even if a part of the thermally conductive grease G1 applied to the heater 26 is pushed out onto the inner surface of the standing portion 272, it is unlikely to reach the sliding surface 271b of the sliding plate 27. Hereinafter, the detailed shape of the sliding plate 27 in this embodiment will be described with reference to FIG. 4, FIG. 6(a)-(c), FIG. 7, and FIG. 8. FIG. 6(a)-(c) are diagrams showing the movement of the thermally conductive grease G1 when the sliding plate 27 in this embodiment is used. FIG. 7 is a diagram showing the relationship in length in the width direction (x-axis direction) of the sliding plate 27, the protrusions 273, the fixing belt 21, and the pressure roller 202 in this embodiment. FIG. 8 is a perspective view showing the x-axis direction end of the sliding plate 27 in this embodiment.

[0074] As shown in Fig. 4, in the sliding plate 27 of this embodiment, a folded shape is formed as a protrusion 273 on each of the upright portions 272 on the upstream side and the downstream side in the recording material transport direction (+y direction). As shown in Fig. 6(a) and Fig. 8, the protrusion 273 has a folded shape in which the tip of the upright portion 272 is bent so as to be folded back toward the heater 26 in the y-axis direction. That is, the upright portion 272 on the downstream side in the transport direction is formed with the protrusion 273 protruding toward the upstream side in the transport direction. The upright portion 272 on the upstream side in the transport direction is formed with the protrusion 273 protruding toward the downstream side in the transport direction.

[0075] The protrusion 273 functions as a so-called “barb shape” for restricting the movement of the thermal conductive grease G1 extruded from between the heater 26 and the sliding plate 27 or between the heater 26 and the heat retention plate 25.

[0076] In order to more reliably restrict the movement of the thermally conductive grease G1, the protrusion 273 preferably protrudes toward the heater 26 disposed between the two standing portions 272 in the recording material transport direction (y-axis direction). However, the protrusion 273 may protrude toward the opposite side to the heater 26 in the recording material transport direction (y-axis direction), or may protrude in a direction oblique to the y-axis direction.

[0077] The protrusion 273 is not limited to the bent shape shown in Fig. 6(a). The protrusion 273 may have a curved shape in which the tip of the standing portion 272 is curled as shown in Fig. 6(b). The protrusion 273 may also have a hemmed bent shape in which the tip of the standing portion 272 is hemmed as shown in Fig. 6(c).

[0078] 6(a) to 6(c), the protrusion 273 restricts the thermal conductive grease G1 from moving to the sliding surface 271b of the sliding plate 27. That is, even if a part of the thermal conductive grease G1 is pushed out from between the heater 26 and the sliding plate 27 or between the heater 26 and the heat retention plate 25 to the inner surface of the standing portion 272 and rises in the +z direction along the standing portion 272, it is pushed back by the protrusion 273 (arrow B). Therefore, the thermal conductive grease G1 is less likely to go around the tip of the standing portion 272 and less likely to reach the sliding surface 271b of the sliding plate 27, so that the possibility of accelerating the scraping of the inner surface of the fixing belt 21 can be reduced.

[0079] 6(a), when viewed in a cross section perpendicular to the x-axis direction, the presence of the protrusions 273 increases the creepage distance measured along the surface of the sliding plate 27 of the path from the heater contact surface 271a of the sliding plate 27 to the sliding surface 271b via the inner and outer walls of the standing portion 272, compared to the reference example of FIG. 5. This makes it difficult for the thermal conductive grease G1 to reach the sliding surface 271b side of the sliding plate 27, thereby reducing the possibility of accelerating wear of the inner surface of the fixing belt 21.

[0080] 7, it is preferable that the width W273 of the protrusion 273 in the x-axis direction is larger than the width (referred to as roller width W202) of the outer periphery 202b of the pressure roller 202 (W273>W202). In other words, it is preferable that the pressure member has an outer periphery that contacts the fixing member in the nip portion, and the length of the protrusion in the first direction is longer than the length of the outer periphery in the first direction.

[0081] Both ends of the protrusion 273 in the x-axis direction are preferably located outside both ends of the outer periphery 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 against each other to form the nip N, so that the pressure on the thermal conductive grease G1 inside the roller width W202 is higher than that on the outside of the roller width W202, and the thermal conductive grease G1 is likely to be extruded. Therefore, by providing the protrusion 273 with the above-mentioned width W273, the possibility that the thermal conductive grease G1 will reach the sliding surface 271b side of the sliding plate 27 can be further reduced.

[0082] Also, preferably, the width W273 of the protrusion 273 is wider than the width W21 of the fixing belt 21 (W273>W21), and the end of the protrusion 273 is formed to be located outward in the x-axis direction from the end of the fixing belt 21. In other words, it is preferable that the length of the protrusion in the first direction is longer than the length of the fixing member in the first direction. This can further reduce the possibility that the heat conductive grease G1 reaches the sliding surface 271b side of the sliding plate 27.

[0083] 7 and 8, the width W273 of the protrusion 273 in the x-axis direction does not necessarily have to be the same as the width W27 of the sliding plate 27 in the x-axis direction. As shown in FIG. 8, a barb shape like the upright portion 272 is not formed on both end faces of the sliding plate 27 in the x-axis direction. However, it is sufficient that the width W27 of the sliding plate 27 is larger than the width W21 of the fixing belt 21 and both end faces of the sliding plate 27 are located outside the both ends of the fixing belt 21 in the x-axis direction. In this case, the heat conductive grease G1 is unlikely to wrap around both end faces of the sliding plate 27 and reach the inner surface of the fixing belt 21.

[0084] Even if the thermal conductive grease G1 is outside the roller width W202 of the pressure roller 202, the thermal conductive grease G1 may be subjected to pressure due to the rigidity of the heater 26 and the sliding plate 27. Depending on the viscosity of the thermal conductive grease G1, the width W273 of the protrusion 273 may be made wider and moved away from the end of the outer circumferential 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 thermal conductive grease G1 moves in the x-axis direction along the standing portion 272, it is possible to more reliably prevent the thermal conductive grease G1 from reaching the sliding surface 271b.

[0085] [Summary of this Example] As described above, in this embodiment, the protrusion 273 is formed at the tip of the rising portion 272 formed in the vertical direction (+z direction) of the sliding plate 27 so as not to rub against the inner surface of the fixing belt 21. This protrusion 273 inhibits the movement of a part of the thermal conductive grease G1 extruded from between the heater 26 and the sliding plate 27 or between the heater 26 and the heat retention plate 25 due to the pressure contact between the pressure roller 202 and the belt unit 201. In other words, even if the extruded thermal conductive grease G1 rises along the rising portion 272, the protrusion 273 makes it difficult for the thermal conductive grease G1 to reach the sliding surface 271b, which is the contact surface of the sliding plate 27 with the fixing belt 21.

[0086] This makes it possible to suppress a decrease in sliding property and promotion of abrasion of the inner surface of the fixing belt 21 caused by the presence of the heat conductive grease G1 between the sliding surface 271b and the inner surface of the fixing belt 21. In particular, in this embodiment, it is possible to suppress a decrease in sliding property and promotion of abrasion of the inner surface of the fixing belt 21 caused by the heat conductive grease G1 being mixed into the sliding grease G2.

[0087] That is, according to this embodiment, the sliding member has a protrusion provided on at least one of the first and second standing portions and protruding in a direction intersecting the extending direction of the standing portion when viewed in the first direction. This configuration can reduce the possibility that the grease applied between the heater and the sliding member adheres to the inner surface of the fixing belt.

[0088] Example 2 In this embodiment, an example will be described in which the protrusion 273 is provided only on the standing portion 272 on one side of the sliding plate 27. Hereinafter, unless otherwise specified, elements having the same reference symbols as those in the first embodiment will have substantially the same configurations and functions as those described in the first embodiment, and differences from the first embodiment will be mainly described.

[0089] [Problem] As in the first embodiment, this embodiment proposes a configuration 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.

[0090] [Image forming device] Fig. 9 is a schematic diagram of an image forming apparatus 100 according to this embodiment. Fig. 10 is a cross-sectional view showing a belt heating section 210 of a fixing device 200 according to this embodiment.

[0091] In the first embodiment, an example has been described in which the -z direction, which is the height direction of the fixing device 200, is substantially the same as the direction of gravity (+g direction). That is, in the first embodiment, the sliding portion 271 of the sliding plate 27 extends in a direction substantially perpendicular to the direction of gravity. On the other hand, there are cases in which the layout of the image forming apparatus 100 is changed by changing the orientation or arrangement of the fixing device 200, the image forming unit PK, etc., and changing the conveying path 60. By changing the layout, for example, there are cases in which the installation area of ​​the image forming apparatus 100 can be reduced and the first print time can be reduced.

[0092] In the image forming apparatus 100 of this embodiment shown in FIG. 9, the -z direction, which is the height direction of the fixing device 200, is significantly different from the gravity direction (+g direction). Therefore, as shown in FIG. 10, in this embodiment, the sliding portion 271 of the sliding plate 27 in the fixing device 200 is significantly inclined from a horizontal plane perpendicular to the gravity direction (g direction). In other words, the fixing device 200 is disposed at an incline so that the recording material conveying direction (+y direction) in the nip portion N of the fixing device 200 intersects with the horizontal direction. The inclination angle of the sliding portion 271 with respect to the horizontal plane may be, for example, 45 degrees or more. The closer the extension direction (y-axis direction) of the sliding portion 271 is to the gravity direction, the more likely the heat conductive grease G1 leaks out from between the heater 26 and the sliding plate 27 or between the heater 26 and the heat retention plate 25 due to the influence of gravity.

[0093] [Sliding plate] The sliding plate 27 in this embodiment will be described with reference to FIG. 10. The sliding plate 27 has a rubbing portion 271 extending along the recording material conveying direction (+y direction), and two standing portions 272a and 272b provided on the upstream side and downstream side of the rubbing portion 271 in the conveying direction (+y direction). The upstream standing portion 272a is located on the lower side in the gravity direction (+g direction) with respect to the rubbing portion 271, and the downstream standing portion 272b is located on the upper side in the gravity direction (-g direction) with respect to the rubbing portion 271. The standing portions 272a and 272b stand on the side (+z direction) away from the pressure roller 202 in the height direction (z axis direction) of the fixing device 200 in which the belt unit 201 and the pressure roller 202 are arranged so as not to come into contact with the inner surface of the fixing belt 21.

[0094] The protrusion 273 is provided only on the upright portion 272a on the upstream side (lower side in the direction of gravity) of the two upright portions 272a, 272b. The protrusion 273 in this embodiment has a bent shape in which, for example, the tip of the upright portion 272a is bent in the y-axis direction toward the side of the rubbing portion 271, that is, toward the downstream side (+y direction) in the recording material conveying direction. The protrusion 273 is continuous with a predetermined width in the x-axis direction. The width W273 of the protrusion 273 in the x-axis direction can be the same as in the first embodiment.

[0095] The movement of the thermal conductive grease G1 in this embodiment will be described with reference to Fig. 11 and Fig. 12. Fig. 11 and Fig. 12 are diagrams showing the movement of the thermal conductive grease G1 when the sliding plate 27 in this embodiment is used. Fig. 11 is an enlarged view of the vicinity of the standing portion 272a on the lower side in the direction of gravity (+g direction), and Fig. 12 is an enlarged view of the vicinity of the standing portion 272b on the upper side in the direction of gravity (-g direction).

[0096] 11, consider a case where the thermally conductive grease G1 is pushed out from between the heater 26 and the sliding plate 27 or between the heater 26 and the heat retention plate 25 near the standing portion 272a on the lower side in the gravity direction (+g direction). A part of the pushed-out thermally conductive grease G1 moves along the inner wall of the standing portion 272a.

[0097] Here, since the protrusion 273 is formed on the standing portion 272a on the lower side in the gravity direction (+g direction), the thermal conductive grease G1 is prevented from moving around the tip of the standing portion 272a, and the thermal conductive grease G1 is held on the heater contact surface 271a side of the sliding plate 27. In other words, the protrusion 273 makes it difficult for the thermal conductive grease G1 to reach the sliding surface 271b of the sliding plate 27.

[0098] On the other hand, as shown by the arrow D in FIG. 12, a case will be considered in which the thermal conductive grease G1 is pushed out from between the heater 26 and the sliding plate 27 or between the heater 26 and the heat retention plate 25 in the vicinity of the standing portion 272b on the upper side in the direction of gravity (-g direction). A part of the pushed out thermal conductive grease G1 moves along the inner wall of the standing portion 272b. Although the protrusion 273 is not formed on the standing portion 272b, the inner wall of the standing portion 272b faces the lower side in the direction of gravity (+g direction), so that the thermal conductive grease G1 attached to the inner wall of the standing portion 272b is subjected to gravity in a direction returning to the heater 26. As a result, the thermal conductive grease G1 is held on the heater contact surface 271a side of the sliding plate 27 even in the vicinity of the standing portion 272b. In other words, near the upright portion 272b on the upper side in the gravity direction (-g direction), the heat conductive grease G1 is unlikely to reach the sliding surface 271b of the sliding plate 27 due to the effect of gravity, so even if the protrusion 273 is not present, the heat conductive grease G1 is unlikely to reach the sliding surface 271b of the sliding plate 27.

[0099] [Summary of this Example] As described above, in the sliding plate 27 of this embodiment, the protrusion 273 is formed on the rising portion 272a located on the lower side in the gravity direction (+g direction) with respect to the sliding portion 271. This protrusion 273 makes it difficult for the thermal conductive grease G1 pushed out from between the heater 26 and the sliding plate 27 or between the heater 26 and the heat retention plate 25 to reach the sliding surface 271b of the sliding plate 27 by going around the rising portion 272a. In addition, in the rising portion 272b located on the upper side in the gravity direction (-g direction) with respect to the sliding portion 271, the thermal conductive grease G1 is subjected to gravity in a direction returning to the heater 26 side, so that the thermal conductive grease G1 is unlikely to reach the sliding surface 271b of the sliding plate 27 by going around the rising portion 272b.

[0100] Therefore, in the configuration of this embodiment, it is possible to suppress the deterioration of the sliding properties between the sliding plate 27 and the fixing belt 21 caused by the heat conductive grease G1, and the promotion of abrasion of the inner surface of the fixing belt 21.

[0101] That is, according to this embodiment, the sliding member has a protrusion provided on at least one of the first and second standing portions and protruding in a direction intersecting the extending direction of the standing portion when viewed in the first direction. This configuration can reduce the possibility that the grease applied between the heater and the sliding member adheres to the inner surface of the fixing belt.

[0102] In the sliding plate 27 of this embodiment, the protrusion 273 is arranged only on the rising portion 272a on the lower side in the gravity direction, and the protrusion 273 is not arranged on the rising portion 272b on the upper side. In other words, one of the first and second rising portions (the rising portion 272a) is located on the lower side in the gravity direction with respect to the other of the first and second rising portions (the rising portion 272b). The protrusion 273 is provided on the rising portion 272a located on the lower side of the first and second rising portions. Therefore, the workability of the sliding plate 27 can be improved compared to the case where the protrusions 273 are arranged on the rising portions 272a, 272b on both sides.

[0103] Example 3 In this embodiment, an example will be described in which the protrusion 273 of the sliding plate 27 is formed by a separate member from the sliding portion 271 and the standing portion 272. Hereinafter, unless otherwise specified, elements having the same reference symbols as those in the first embodiment will have substantially the same configurations and functions as those described in the first embodiment, and differences from the first embodiment will be mainly described.

[0104] [Problem] As in the first embodiment, this embodiment proposes a configuration 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.

[0105] [Sliding plate] The sliding plate 27 in this embodiment will be described with reference to Fig. 13 and Fig. 14. Fig. 13 is an enlarged view of the belt heating unit 210 in this embodiment. Fig. 14 is a diagram showing the movement of the thermally conductive grease G1 when the sliding plate 27 in this embodiment is used.

[0106] 13, the sliding plate 27 also has a rubbing portion 271 extending in the recording material transport direction (+y direction) and standing portions 272 formed continuously with the upstream end and downstream end of the rubbing portion 271 in the recording material transport direction (+y direction). Each standing portion 272 is formed to stand in the vertical direction (+z direction) so as not to rub against the inner surface of the fixing belt 21.

[0107] An additional member as a protrusion 273 is disposed on each of the upstream and downstream standing portions 272. The protrusion 273 is fixed to the standing portion 272 by mechanically engaging with the standing portion 272 or by joining to the standing portion 272 by a joining method such as adhesive. The protrusion 273 is continuous with a predetermined width in the x-axis direction. The width W273 of the protrusion 273 in the x-axis direction can be the same as in the first embodiment.

[0108] The sliding plate 27 of this embodiment is provided with a protrusion 273 which is a separate member from the sliding portion 271 and the standing portion 272. Therefore, the protrusion 273 can be formed from a material different from that of the sliding portion 271 and the standing portion 272, or the protrusion 273 can be subjected to a separate surface treatment. This reduces the interfacial tension (wettability) between the thermal conductive grease G1 and the protrusion 273, making it easier for the thermal conductive grease G1 to separate from the protrusion 273. In this embodiment, a glass coating is applied to the surface of the protrusion 273.

[0109] [Summary of this Example] The movement of the thermal conductive grease G1 in this embodiment will be described with reference to Fig. 14. As shown by the arrow E in Fig. 14, a part of the thermal conductive grease G1 pushed out from between the heater 26 and the sliding plate 27 or between the heater 26 and the heat retention plate 25 rises along the inner wall of the standing portion 272. However, since the protrusion 273 is arranged on the standing portion 272, even if the thermal conductive grease G1 rises along the standing portion 272, the protrusion 273 prevents the thermal conductive grease G1 from moving around the standing portion 272. In other words, the thermal conductive grease G1 is less likely to reach the sliding surface 271b of the sliding plate 27.

[0110] Therefore, in the configuration of this embodiment, it is possible to suppress the deterioration of the sliding properties between the sliding plate 27 and the fixing belt 21 caused by the heat conductive grease G1, and the promotion of abrasion of the inner surface of the fixing belt 21.

[0111] That is, according to this embodiment, the sliding member has a protrusion provided on at least one of the first and second standing portions and protruding in a direction intersecting the extending direction of the standing portion when viewed in the first direction. This configuration can reduce the possibility that the grease applied between the heater and the sliding member adheres to the inner surface of the fixing belt.

[0112] Furthermore, by making the protrusion portion 273 a separate component from the sliding portion 271 and the standing portion 272 of the sliding plate 27, the design freedom in terms of material selection and surface processing is increased, and the performance of the protrusion portion 273, the sliding portion 271, and the standing portion 272 can be improved.

[0113] For example, the protrusion 273 may be glass-coated to make it easier for the thermally conductive grease G1 to separate from the protrusion 273. In this case, even if the thermally conductive grease G1 reaches the protrusion 273, it is more likely to be returned to the heater 26 side and is more likely to be retained on the heater contact surface 271a side of the sliding plate 27. In other words, it becomes even more difficult for the thermally conductive grease G1 to reach the sliding surface 271b. On the other hand, the sliding portion 271 may be made of a material that has good sliding properties with the fixing belt 21 and good compatibility with the sliding grease G2, for example.

[0114] Example 4 In this embodiment, a configuration will be described in which the end of the holding member 23 facing the inner surface of the fixing belt 21 is retracted to the side (+z direction) away from the pressure roller 202 in the height direction of the fixing device 200 compared to the sliding surface 271b of the sliding plate 27. Hereinafter, elements with common reference symbols to those in the first embodiment have substantially the same configurations and functions as those described in the first embodiment, unless otherwise specified, and differences from the first embodiment will be mainly described.

[0115] Although an embodiment not having the heat retaining plate 25 will be described below first, the fixing device 200 may be provided with the heat retaining plate 25 similar to that of the first embodiment, as in a modified example described later.

[0116] Fig. 15 is a cross-sectional view of the fixing device 200 in this embodiment. The fixing device 200 has a belt unit 201 as a heating device, and a pressure roller 202 as a pressure member that contacts the belt unit 201. Fig. 16 is an enlarged view of the belt heating unit 210 in this embodiment, which corresponds to the dashed line portion in Fig. 15.

[0117] The belt heating unit 210 is provided inside the fixing belt 21 as in the first to third embodiments, heats the inner surface of the fixing belt 21 while rubbing against it, and forms a nip portion N between the pressure roller 202 and the fixing belt 21. The belt heating unit 210 includes, 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 that heats the fixing belt 21, and a sliding plate 27 that transfers heat from the heater 26 to the fixing belt 21. The heater 26 and the sliding plate 27 are held by the holding member 23.

[0118] Between the heater 26 and the sliding plate 27, thermally conductive grease G1 is applied so that heat generated by the heater 26 is efficiently transferred to the sliding plate 27. Meanwhile, between the fixing belt 21 and the sliding portion 271 of the sliding plate 27, sliding grease G2 is applied to improve sliding properties and reduce wear. The thermally conductive grease G1 and the sliding grease G2 may be the same as those described in the first embodiment.

[0119] [Problem] In order to improve the energy saving performance of the fixing device 200, it is necessary to transfer the heat of the heater 26, which is a heat source, to the fixing belt 21 as efficiently as possible (to increase the thermal efficiency). However, when the fixing belt 21 and the holding member 23 are in contact with each other, a part of the heat transferred from the heater 26 to the fixing belt 21 escapes to the holding member 23 through the contact area between the fixing belt 21 and the holding member 23.

[0120] Therefore, in this embodiment, a configuration capable of improving the energy saving performance of the fixing device is proposed.

[0121] [Heat escape in reference example] A specific example of the heat escape path will be described using a reference example. Fig. 17 is a cross-sectional view of a fixing device 200' according to the reference example. Fig. 18 is an enlarged view showing a belt heating section 210 of the fixing device 200' according to the reference example, which corresponds to the dashed line part in Fig. 17.

[0122] 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 sliding plate 27 in the recording material transport 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.

[0123] End points P23A', P23B' of guide surfaces 23A', 23B' closest to pressure roller 202 in the z-axis direction (-z direction side) are at the same height as the position of sliding surface 271b of sliding plate 27 in the z-axis direction. Therefore, when pressure roller 202 is rotationally driven in the direction of arrow R3 in Fig. 17 and fixing belt 21 rotates following pressure roller 202, the inner surface of fixing belt 21 contacts guide surface 23A' on the upstream side, sliding surface 271b of sliding plate 27, and downstream guide surface 23B' in that order. Fixing belt 21 is heated by receiving heat from heater 26 via sliding plate 27 and the grease layer.

[0124] Here, since the fixing belt 21 is also in contact with the guide surfaces 23A' and 23B' of the holding member 23, a part of the heat received by the fixing belt 21 escapes to the holding member 23. For this reason, in order to maintain the fixing belt 21 at a temperature suitable for fixing the toner image t, it is necessary to set the heat generation amount of the heater 26 so as to compensate for the amount of heat escaping to the holding member 23. For example, the greater the heat generation amount of the heater 26 is set for a certain temperature detected by the thermistor 24, the greater the heat generation amount of the heater 26.

[0125] However, the heat dissipated to the holding member 23 is energy that is not used to fix the toner image t, and setting the heat generation amount of the heater 26 to compensate for the amount of heat dissipated to the holding member 23 is not preferable from the viewpoint of improving energy saving performance.

[0126] [Sliding plate] In this embodiment, in consideration of the above-mentioned problems, the holding member 23 is configured so as not to come into contact with the inner surface of the fixing belt 21, or so as to have a smaller contact area than in the reference example. As shown in Fig. 15, the holding member 23 in this embodiment has guide surfaces 23A and 23B for guiding the fixing belt 21 upstream and downstream of the sliding plate 27 in the recording material transport 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.

[0127] The guide surface 23A is an example of a first opposing portion that faces the inner surface of the fixing member upstream of the rubbing portion in the second direction. The guide surface 23B is an example of a second opposing portion that faces the inner surface of the fixing member downstream of the rubbing portion in the second direction. The first opposing portion and the second opposing portion do not necessarily have to be curved surfaces, but if they are curved surfaces, the fixing belt 21 can be smoothly guided even if the rotational trajectory of the fixing belt 21 fluctuates.

[0128] End points P23A, P23B of the guide surfaces 23A, 23B that are closest to the pressure roller 202 in the z-axis direction (-z direction side) are located on the opposite side to the pressure roller 202 (+z direction side) in the z-axis direction from the position of the rubbing surface 271b of the sliding plate 27. That is, in the third direction, the first opposing portion and the second opposing portion are retreated to the side away from the pressure member compared to the rubbing portion.

[0129] 15, when the fixing belt 21 rotates following the pressure roller 202, the inner surface of the fixing belt 21 mainly comes into contact with the sliding surface 271b of the sliding plate 27, and is unlikely to come into contact with the guide surfaces 23A, 23B of the holding member 23. In other words, the holding member is configured so that the fixing member does not come into contact with the first opposing portion and the second opposing portion when the pressure member is rotated to rotate the fixing member following the pressure member. In other words, heat of the fixing belt 21 is unlikely to escape to the holding member 23 via the guide surfaces 23A, 23B.

[0130] In this embodiment, the width of the sliding plate 27 in the recording material transport direction (+y direction) is made larger than that in the reference example, thereby adjusting the rotational trajectory of the fixing belt 21.

[0131] The width of the sliding plate 27 will be further described. The rotational trajectory of the fixing belt 21 is determined by the contact start point and separation point between the inner surface of the fixing belt 21 and the member (sliding plate 27 and / or holding member 23) that comes into contact with the fixing belt 21. In the reference example of FIG. 18, the contact start point is an end point P23A' of the guide surface 23A' on the upstream side of the holding member 23, and the separation point is an end point P23B' of the guide surface 23B' on the downstream side of the holding member 23.

[0132] In the configuration 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 will be shifted. That is, the contact start point is the upstream end of the rubbing surface 271b of the sliding plate 27, and the separation point is the downstream end of the rubbing surface 271b. This may cause the rotational trajectory of the fixing belt 21 to change.

[0133] Therefore, in this embodiment, the contact start point and the separation point are maintained by increasing the width of the sliding surface 271b of the sliding plate 27 in the recording material transport direction (y-axis direction) compared to the reference example. The width of the sliding surface 271b of the sliding plate 27 may be appropriately adjusted depending on factors such as the outer diameter of the fixing belt 21 and the pressure force at the nip portion N.

[0134] 15, 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, and its rotational trajectory is regulated. The fixing belt 21 maintains a substantially cylindrical shape due to its own rigidity within the maximum paper passing area in the longitudinal direction (x-axis direction). The fixing belt 21 basically does not contact the holding member 23 or the stay 22. The paper passing area is an area through which the recording material S passes in the width direction (x-axis direction) perpendicular to the recording material transport direction in the nip portion N. The maximum paper passing area is an area through which the image forming apparatus 100 passes the maximum size recording material S on which an image can be formed.

[0135] In order for the fixing belt 21 to maintain its cylindrical shape due to its own rigidity, the thickness of the fixing belt 21 is preferably, for example, 40 μm or more.

[0136] The transfer of heat in the fixing belt 21 when the fixing device 200 performs a fixing operation (when an image forming operation is being performed) will be described with reference to FIG. 15. When the image forming operation is started, the pressure roller 202 is driven to rotate in the direction R3 in the figure. The fixing belt 21 rotates in the direction R4 in the figure following the pressure roller 202 due to the frictional force it receives from the pressure roller 202 at the nip portion N. Meanwhile, the heater 26 generates heat when electricity is applied to the resistance heating element, and the heat of the heater 26 is transferred to the fixing belt 21 via the sliding plate 27. During the fixing operation, the fixing belt 21 is maintained at a predetermined fixing temperature by the heat supplied via the sliding plate 27.

[0137] In this embodiment, the fixing belt 21 basically comes into contact only with the sliding plate 27 and the pressure roller 202, and the heat of the fixing belt 21 escapes mainly through the contact portion (nip portion) with the pressure roller 202 and into the air. In other words, since the fixing belt 21 does not come into contact with the guide surfaces 23A and 23B of the holding member 23, the escape of heat from the fixing belt 21 can be reduced.

[0138] [Summary of this Example] With the above-described configuration, it is possible to transfer heat from the heater 26, which is a heat source, to the fixing belt 21 as efficiently as possible and use the heat for fixing the toner image t on the recording material S. Therefore, it is possible to improve the thermal efficiency and the energy saving performance.

[0139] In other words, in the present embodiment, the first and second opposing portions are retracted away from the pressure member in the third direction compared to the sliding portion. With this configuration, it is possible to improve the energy saving performance of the fixing device.

[0140] Furthermore, in this embodiment, the fixing belt 21 is basically only sandwiched between the sliding plate 27 and the pressure roller 202, and is basically maintained in a state where it does not come into contact with other members. This state is maintained throughout the time when the recording material S is sandwiched in the nip portion N and the time when the recording material S is not sandwiched in the nip portion N. Therefore, it is possible to further improve the thermal efficiency and the energy saving performance.

[0141] [Variations] In this embodiment, the heater 26 is disposed between the holding member 23 and the sliding plate 27, but the heat retention plate 25 may be disposed between the holding member 23 and the heater 26 as shown in Fig. 19(a). Even in this case, similar to this embodiment, the guide surfaces 23A and 23B of the holding member 23 may be retracted in the +z direction from the sliding surface 271b of the sliding plate 27 so as not to come into contact with the inner surface of the fixing belt 21. This provides the same effect as this embodiment.

[0142] 19(b), a configuration may be adopted in which the portions corresponding to guide surfaces 23A', 23B' (FIG. 18) of holding member 23 in the reference example are deleted. By deleting the portions corresponding to guide surfaces 23A', 23B', the heat capacity of holding member 23 is reduced, so that the amount of heat accumulated in holding member 23 from heater 26 via, for example, the support surface of heater 26 in holding member 23 can be kept low.

[0143] 19(b) is a configuration in which guide surfaces 23A' and 23B' are cut out from holding member 23 while providing holding member 23 with a strength within a range in which deformation does not occur when it receives a pressing force (a pressing force in the g direction in the figure) from stay 22. This eliminates the need for heat that would have accumulated in the cut-out portions, and makes it possible to maintain fixing belt 21 at the fixing temperature with a smaller amount of heat.

[0144] The shape of the holding member 23 is not limited to those described in this embodiment or the modified example, and may be any shape that does not come into contact with the fixing belt 21 as much as possible. It is more preferable that the shape of the holding member 23 is 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 come into contact with the holding member 23 or other members.

[0145] [Comparison with reference example] A comparison was made between fixability and power consumption between a fixing device 200' of a reference example shown in Figures 17 and 18 and a fixing device 200 having a configuration shown in Figure 19(a). The two fixing devices 200, 200' differ in whether or not the guide surfaces 23A, 23B (23A', 23B') of the holding member 23 are retracted in the +z direction from the sliding surface 271b of the sliding plate 27, but have the same other configurations.

[0146] In the comparative experiment, the fixing performance and the cumulative power consumption were confirmed when sheets were continuously passed through the image forming apparatus 100 equipped with the fixing device 200 or the fixing device 200'. The experiment was carried out in an environment of 23.0°C. The fixing temperature was 180°C, and the process speed was 200 mm / s. A4 paper with a basis weight of 120 g / m^2 was used as the recording material S. In the continuous paper passing, a test image (a black monochromatic halftone image) was continuously formed on 20 sheets of the recording material.

[0147] Fixability was evaluated by the density loss rate calculated by the following method. A Macbeth reflection densitometer RD914 was used as the measuring instrument, and the halftone image fixed on the paper was rubbed five times back and forth with a load of 0.4 N / cm^2 on five sheets of lens cleaning paper (Dusper K-3 made by Ozu Sangyo) stacked on top of each other, and the density was measured before and after. In this example, a halftone density D1 before rubbing was approximately 0.7. If the density after rubbing is D2, the density loss rate is calculated by (D1-D2) / D1.

[0148] After the continuous paper feed, the density reduction rate was calculated using the above method, and if the density reduction rate was less than 10%, it was judged as "OK" (good fixing), and if the density reduction rate was 10% or more, it was judged as "NG" (poor fixing). The integrated power consumption is the integrated value of the power supplied to the heater 26 during the continuous paper feed period.

[0149] FIG. 20 shows the results of fixability and integrated power consumption. In the fixing device 200 to which this embodiment (FIG. 19(a)) is applied, good fixability was achieved by setting the fixing temperature to 180° C. The integrated power consumption was 5.136 Wh. 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 integrated power consumption was 5.140 Wh (100.1% assuming this embodiment as 100%), which was equivalent to that of this embodiment, but fixing failure occurred. In the fixing device 200′ of the reference example, when the fixing temperature was set to 182° C., good fixability was obtained, but the integrated power consumption was 5.268 Wh (102.6% assuming this embodiment as 100%), which was higher than that of the fixing device 200 of this embodiment.

[0150] Therefore, it was confirmed that by applying the configuration of this embodiment, good fixing performance can be obtained with less power consumption than in the reference example, and energy saving performance can be improved.

[0151] Example 5 This embodiment has a configuration that can further improve the thermal efficiency and energy saving performance compared to Example 4. Hereinafter, unless otherwise specified, elements with the same reference symbols as those in Example 1 have substantially the same configurations and functions as those described in Example 1, and differences from Example 1 will be mainly described.

[0152] [Problem] In this embodiment, similarly to the fourth embodiment, a configuration capable of improving the energy saving performance of the fixing device is proposed.

[0153] [Sliding plate] FIG. 21 is a cross-sectional view of the belt heating section 210 of the fixing device 200 according to this embodiment, showing a state in which the fixing belt 21 is running during the fixing operation.

[0154] In the fixing device 200 of this embodiment, the sliding plate 27 is shaped to cover the holding member 23, thereby preventing the fixing belt 21 from coming into contact with the holding member 23 and increasing the contact area between the sliding plate 27 and the fixing belt 21.

[0155] The sliding plate 27 is adjacent to the heater 26 and disposed on the pressure roller 202 side of the heater 26, as in the fourth embodiment. The sliding plate 27 has a planar sliding portion 271 that slides against the inner surface of the fixing belt 21, and a guide portion 274 that extends from the sliding portion 271 to the upstream / downstream side in the recording material conveying direction (-y direction and +y direction in the figure). The guide portion 274 includes an extension portion 274a that is extended so as 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 approximately cylindrical shape described by the fixing belt 21 so as to follow the rotational orbit of the fixing belt 21.

[0156] The upstream guide portion 274 is an example of a first guide portion, and the downstream guide portion 274 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 upstream / downstream ends of the sliding plate 27 in the recording material transport direction, a bent portion 275 is formed which is bent at a substantially right angle to the extended portion 274a of the guide portion 274. The bent portion 275 is hooked onto a corner of the holding member 23. Since the bent portion 275 of the sliding plate 27 is provided at both the upstream / downstream ends in the recording material transport direction, the sliding plate 27 is fixed to the holding member 23 and is prevented from falling off.

[0157] When viewed in the +z direction, the entire holding member 23 can be covered by the sliding portion 271 and the guide portion 274. This prevents the fixing belt 21 from coming into contact with the holding member 23, and prevents heat from escaping through the holding member 23.

[0158] During the fixing operation, the sliding plate 27 is in contact with the heater 26 via the thermally conductive grease G1, and is heated by the heat from the heater 26. Since the sliding plate 27 is made of metal as described above, the heat of the sliding portion 271 of the sliding plate 27 is transferred to the guide portion 274, and the temperature of the guide portion 274 rises in the same manner as the sliding portion 271. During the fixing operation, the guide portion 274 is maintained at a temperature equivalent to that of the fixing belt 21.

[0159] [Comparison with Example 4] As described above, the fixing device 200 in this embodiment has the guide portion 274, which is a curved surface bent in the same direction as the track of the fixing belt 21, on the sliding plate 27. Therefore, in the belt heating unit 210 (FIG. 21), not only the rubbing 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 unit 210 (FIG. 16) of the fixing device 200 in Example 4, it is basically only the rubbing portion 271 of the sliding plate 27 that contacts the fixing belt 21.

[0160] That is, in the fixing device 200 of this embodiment, the contact area between the sliding plate 27 and the fixing belt 21 is larger than that of the fourth embodiment. That is, when compared at the same process speed, the sliding plate 27 of this embodiment contacts the fixing belt 21 for a longer time than the sliding plate 27 of the fourth embodiment. Therefore, the sliding plate 27 can transmit more heat to the fixing belt 21.

[0161] That is, in this embodiment, the fixing belt 21 can be maintained at a predetermined fixing temperature with the temperature of the sliding plate 27 lower than in embodiment 4. Also, since the temperature of the sliding plate 27 during the fixing operation is lower, good fixing performance can be obtained even if the control target temperature of the heater 26 is set lower than in embodiment 4. Furthermore, if the control target temperature of the heater 26 is lower, less heat escapes from the heater 26 into the air or the holding member 23.

[0162] Therefore, by applying the configuration of this embodiment, good fixability can be obtained with even less power consumption than in the fourth embodiment, and energy saving performance can be improved.

[0163] [Summary of this Example] In this embodiment, the upstream and downstream guide portions 274 of the sliding 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 path of the fixing member when viewed in the first direction. This configuration can improve the energy saving performance of the fixing device.

[0164] In addition, in this embodiment, since the sliding plate 27 is extended on the upstream side and downstream side of the heater 26 in the recording material conveying direction (y-axis direction), it is possible to suppress the heat conductive grease G1 from leaking to the sliding surface 271b of the sliding plate 27. That is, when viewed in a cross section perpendicular to the x-axis direction as in FIGS. 21 to 23, the creeping distance of the path from the heater contact surface 271a of the sliding plate 27 to the sliding surface 271b via the inner wall and outer wall of the guide portion 274 is longer than the creeping distance of the path from the heater contact surface 271a to the sliding surface 271b via the inner wall and outer wall of the standing portion 272 in the fourth embodiment (FIG. 18). Therefore, it becomes difficult for the heat conductive grease G1 to reach the sliding surface 271b side of the sliding plate 27, and the possibility of promoting scraping of the inner surface of the fixing belt 21 can be reduced.

[0165] [Variations] In this embodiment, an example has been described in which a bent portion 275 is formed at the end of the sliding plate 27, and an 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 transport direction (y-axis direction). Without being limited to this, a groove portion 232 may be provided on the side surface of the holding member 23 as shown in Fig. 22, and the bent portion 275 provided on the sliding plate 27 may be fitted into this groove portion 232. The groove portion 232 may be formed over the entire area of ​​the holding member 23 in the x-axis direction, or may be formed only in a part of the holding member 23.

[0166] 22, when viewed from the pressure roller 202 side in the z-axis direction, the entire holding member 23 is covered with the sliding plate 27. Therefore, the same effect as in this embodiment can be obtained. Also, the modification of FIG. 22 has the advantage that the area of ​​the plate material used for the sliding plate 27 is smaller than that of this embodiment.

[0167] In the modified example shown in FIG. 23, the sliding plate 27 has a standing portion 272 in addition to the guide portion 274. The guide portion 274 is provided continuously on the upstream side and downstream side in the recording material conveying direction (y-axis direction) with respect to the rubbing portion 271, and has a curved shape with a predetermined curvature. In this modified example, the standing portion 272 is provided on the upstream side and downstream side in the recording material conveying direction (y-axis direction). The upstream standing portion 272 (first standing portion) is provided continuously on the upstream side of the upstream guide portion 274, and the downstream standing portion 272 (second standing portion) is provided continuously on the downstream side of the downstream guide portion 274. The standing portions 272 are bent with respect to the guide portion 274 so as to extend toward the side away from the pressure roller 202 in the z-axis direction (the +z direction side), and are accommodated in the groove portion 231 of the holding member 23. The upstream groove portion 231 is an example of a first recess. The downstream groove 231 is an example of a second recess.

[0168] Furthermore, the holding member 23 has a concave heater accommodating portion 234 (third recess) that accommodates the heater 26. The upstream guide portion 274 (first guide portion) covers the convex portion between the upstream groove portion 231 (first recess) and the heater accommodating portion 234 (third recess) when viewed in the +z direction (third direction). Furthermore, the downstream guide portion 274 (second guide portion) covers the convex portion between the downstream groove portion 231 (second recess) and the heater accommodating portion 234 (third recess) when viewed in the +z direction (third direction).

[0169] 23, the curved guide portion 274 is provided, so that the contact area between the sliding plate 27 and the inner surface of the fixing belt 21 is enlarged compared to Example 4. Therefore, the same effect as in this example can be obtained.

[0170] Furthermore, since the sliding plate 27 can be engaged with the holding member 23 without using the bent portion 275, the number of processing steps for the sliding plate 27 is reduced compared to the embodiment shown in FIGS. 21 and 22, which may reduce processing costs.

[0171] Example 6 In this embodiment, a sliding plate 27 is used that has a shape in which the width in the recording material transport direction varies depending on the position in the longitudinal direction. In the following, unless otherwise specified, elements that are given the same reference symbols as in Example 1 have substantially the same configurations and functions as those described in Example 1, and differences from Example 1 will be mainly described.

[0172] [Problem] When a recording material (hereinafter referred to as large size paper) having a relatively wide width (sheet width) in the x-axis direction is passed through, fixability may decrease in the edge region of the recording material in the x-axis direction. This decrease in fixability is caused by a decrease in temperature of the fixing belt 21 and the pressure roller 202 at the edge of the paper-passing area (hereinafter referred to as edge temperature sag) as a result of heat being diffused by the pressure roller 202 to a non-paper-passing area outside the paper-passing area. The non-paper-passing area is an area in the longitudinal direction (x-axis direction) of the nip N where the recording material does not pass.

[0173] The width of the nip portion N in the recording material transport direction (y-axis direction) is hereinafter referred to as the nip width. As a countermeasure against end temperature drop, the nip width at the end of the longitudinal direction of the nip portion N (x-axis direction) may be made wider than the nip width at the center, thereby achieving uniform fixability in the longitudinal direction. On the other hand, if there is a large difference in nip width between the end and center of the nip portion N, image smearing may occur due to the trailing edge of the recording material bouncing.

[0174] Therefore, in this embodiment, a configuration is proposed that can achieve both uniform fixability and reduction in image defects caused by trailing edge splashing.

[0175] [Sliding plate] In this embodiment, in order to reduce the deterioration of fixability in the edge regions of the recording material due to edge temperature sagging, the sliding plate 27 is formed so that the width of the sliding plate 27 in the recording material conveying direction increases toward both outer sides in the longitudinal direction of the nip portion N. The width of the sliding plate 27 in this embodiment refers to the width of the rubbing surface 271b that slides against the fixing belt 21.

[0176] The larger the cross-sectional area perpendicular to the longitudinal direction of the sliding plate 27, the greater the thermal conductivity of the sliding plate 27 in the longitudinal direction. Therefore, by widening the width of the sliding plate 27 in the recording material transport direction toward both outer sides in the longitudinal direction, the thermal conductivity of the area close to both ends in the longitudinal direction increases. Since the sliding plate functions as a heat diffusion member, by widening the width of the ends of the sliding plate 27 as in this embodiment, it is possible to promote the diffusion of heat from the center to the ends in the paper passing area, and improve the fixability in the end areas of the recording material.

[0177] Fig. 28(a) is a perspective view (left side) showing the sliding plate 27 of a reference example in which the width Sw of the sliding plate 27 is constant from the center to the ends, and a schematic diagram (right side) showing the positional relationship between the sliding surface 271b of the sliding plate 27 of the reference example and the nip portion N. Fig. 28(b) is a perspective view (left side) showing the sliding plate 27 of this embodiment in which the width Tw of the ends is wider than the width Cw of the center, and a schematic diagram (right side) showing the positional relationship between the sliding surface 271b of the sliding plate 27 of this embodiment and the nip portion N.

[0178] The width (nip width) of the nip portion N in the recording material transport direction (y-axis direction) is common to the reference example and this embodiment. The nip width at the center of the nip portion N in the longitudinal direction (x-axis direction) is 8.0 mm, and the nip width at both ends of the nip portion N in the longitudinal direction (x-axis direction) is 8.8 mm.

[0179] 28(a), sliding plate 27 has a straight shape with a width Sw of 12.0 mm throughout the entire length. At the center of nip N, the width of sliding plate 27 is 33% wider than the nip width (8.0 mm) (2 mm wider on both the upstream and downstream sides in the recording material transport direction). On the other hand, at the ends of nip N, the width of sliding plate 27 is 26% wider than the nip width (8.8 mm) (1.6 mm wider on both the upstream and downstream sides in the recording material transport direction).

[0180] In this embodiment shown in FIG. 28(b), the sliding plate 27 has a shape (constricted shape, medium-thin shape) in which the width Tw at the end is wider than the width Cw at the center. The width Cw of the sliding plate 27 at the center of the nip N is 12.0 mm, and the width Tw of the sliding plate 27 at the end of the nip N is 13.0 mm. At the center of the nip N, the width of the sliding plate 27 is 33% wider than the nip width (8.0 mm) (2 mm wider on the upstream side and downstream side in the recording material conveying direction). On the other hand, at the end of the nip N, the width of the sliding plate 27 is 32% wider than the nip width (8.8 mm) (2.1 mm wider on the upstream side and downstream side in the recording material conveying direction). By adopting such a shape, the sliding plate 27 can easily diffuse heat toward the outside in the longitudinal direction within the paper passing area, and the deterioration of fixability in the end area of ​​the recording material can be reduced.

[0181] Figures 29(a) and (b) show the temperature distribution of the sliding plate 27 at the end positions shown in Figures 28(a) and (b), respectively. Figure 29(a) shows the case of the reference example, and Figure 29(b) shows the case of this embodiment.

[0182] Inside the nip portion N in the recording material transport direction (y-axis direction), the sliding plate 27 comes into contact with the pressure roller 202 with the fixing belt 21 sandwiched therebetween, so that the temperature of the sliding plate 27 drops as heat is absorbed by the pressure roller 202. On the other hand, outside the nip portion N in the recording material transport direction (y-axis direction), the sliding plate 27 does not come into contact with the pressure roller 202, so that the temperature of the sliding plate 27 becomes higher than that inside the nip portion N.

[0183] In the sliding plate 27 of this embodiment shown in Fig. 29(b), the width of the sliding plate 27 is sufficiently wider than the nip width at the ends of the nip portion N, and the area outside the nip portion N is wider, compared to the straight-shaped sliding plate of the reference example in Fig. 29(a). Therefore, heat from the outside of the nip portion N in the recording material conveying direction (y-axis direction) is transferred to the inside of the nip portion N, and a decrease in temperature of the nip portion N can be suppressed. It is more preferable that the width (2.1 mm) of the area outside the nip portion N of the sliding plate 27 at the ends of the nip portion N is equal to or greater than the width (2.0 mm) of the area outside the nip portion N of the sliding plate 27 at the center, as in this embodiment.

[0184] It should be noted that the wider the width of sliding plate 27, the higher the heat diffusion effect, but if it is made too wide relative to the nip width, the heat dissipation effect (the effect of heat escaping from sliding plate 27 into the air outside nip portion N) becomes greater, and fixability may decrease. Therefore, the width of sliding plate 27 can be appropriately changed depending on the specific configuration such as the configuration of the elastic layer of pressure roller 202 and the thermal conductivity and thickness of sliding plate 27.

[0185] [Edge temperature sagging and pressure roller material] As one of the factors that cause the end temperature sagging to occur easily, the material of the elastic layer of the pressure roller 202 will be described.

[0186] Balloon rubber (foamed rubber) or solid rubber can be used as the elastic layer of the pressure roller 202. Among these, end temperature sagging is more likely to occur when solid rubber is used as the elastic layer than when balloon rubber is used. This is because solid rubber generally has a higher thermal conductivity than balloon rubber, and therefore when solid rubber is used as the elastic layer of the pressure roller 202, heat is more likely to escape to non-paper passing parts.

[0187] Balloon rubber can improve heat insulation and reduce heat capacity, and can improve the start-up performance (quick start performance) of the fixing device 200, but it may have lower durability than solid rubber. Also, when a recording material with a narrow sheet width (hereinafter referred to as small size paper) is 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 widened so that the surface temperature of the pressure roller 202 in the non-paper passing portion does not exceed the heat resistance temperature of the pressure roller 202, there is a disadvantage that the productivity of small size paper decreases.

[0188] When productivity and durability are required, solid rubber may be used as the elastic layer of the pressure roller 202. Solid rubber has a higher thermal conductivity than balloon rubber, so it is inferior to balloon rubber in terms of start-up, but it is advantageous in terms of productivity of small size paper because it can reduce the temperature rise in non-paper passing areas because it is easy to diffuse heat in the longitudinal direction (x-axis direction).

[0189] In this embodiment, solid rubber is used as the elastic layer of the pressure roller 202, but the configuration of this embodiment is also applicable to the case where balloon rubber is used as the elastic layer.

[0190] [Image smearing due to rear edge bouncing] By making the nip width at the ends in the longitudinal direction (x-axis direction) of the nip portion N wider than the nip width at the center, it is possible to reduce temperature drop at the ends and achieve uniform fixability.

[0191] The larger the nip width, the faster the recording material conveying speed in the nip portion N. This is because, as the pressure applied in the nip portion N increases and the nip width increases, the recording material and pressure roller 202 do not easily slip, and the elastic layer of the pressure roller 202 is crushed and stretched, resulting in a longer apparent circumference. Also, when the nip width at the ends is wider than the nip width at the center in the longitudinal direction (x-axis direction) of the nip portion N, the recording material conveying speed at the ends is faster than the recording material conveying speed at the center. This configuration can reduce wrinkles in the recording material.

[0192] However, if there is a difference in recording material conveying speed between the center and ends of the nip portion N, there is a possibility that the trailing edge of the recording material S will bounce. The trailing edge blade will be described with reference to the schematic diagrams of FIGS.

[0193] When the recording material conveying speed is faster at the ends of the nip portion N than at the center, the recording material S is pulled in the direction of arrow T1 in Fig. 24, and as the recording material S passes through the nip portion N, a force is generated that lifts the trailing end portion of the recording material S in the direction of arrow T2. Therefore, as shown in Fig. 25, when the trailing end of the recording material S passes through the transfer portion, the trailing end of the recording material S may bounce up in the direction of arrow T2 (referred to as trailing end bounce) and hit the drum cleaner 6Y or the cover of the fixing device 200. Such trailing end bounce may disturb the unfixed toner image transferred to the recording material S, resulting in a decrease in image quality (hereinafter referred to as image rubbing).

[0194] [Nip width setting] In this embodiment, in order to reduce the temperature drop at the end portions, the pressure applied to the end portions of the nip portion N is made higher than that applied to the center portion, and the nip width at the end portions is made wider.

[0195] FIG. 26(a) shows the bending in the longitudinal direction caused by the pressure of the stay 22 and the pressure roller 202. As shown in FIG. 26(a), the stay 22 is pressurized at both ends by pressure springs 251. This pressure acts on the pressure roller 202 from the belt unit 201 at the nip N. The pressure roller 202 is supported by the frame of the fixing device 200 at bearings 252 at both ends. Therefore, the belt unit 201 receives a reaction force in the upward direction in the figure from the pressure roller 202. In other words, the stay 22 receives a downward force in the figure at both ends in the longitudinal direction (x-axis direction) and receives an upward force in the figure at the center in the longitudinal direction. Moreover, the pressure roller 202 receives an upward force in the figure at both ends in the longitudinal direction (x-axis direction) and receives a downward force in the figure at the center in the longitudinal direction.

[0196] As a result, the stay 22 bends from the straight shape shown by the solid line 22c in Fig. 26(a) to the dotted line 22d, while the core metal 202a of the pressure roller 202 bends from the straight shape shown by the solid line 202c in Fig. 26(a) to the dotted line 202d.

[0197] When the stay 22 and the pressure roller 202 bend, the nip pressure in the center of the nip N decreases, and the nip width in the recording material transport direction (y-axis direction) decreases in the center of the nip N. On the other hand, the nip pressure in the ends of the nip N increases, and the nip width in the recording material transport direction (y-axis direction) increases in the ends of the nip N. If the nip width differs greatly between the center and ends of the nip N, image smearing due to the trailing edge bouncing may occur as described above.

[0198] Therefore, in this embodiment, the nip pressure and nip width are adjusted by using a holding member 23 whose thickness T varies depending on the position in the longitudinal direction of the nip portion N, as shown in Fig. 26(a). Hereinafter, forming the holding member 23 so that the thickness T varies depending on the position in the longitudinal direction is referred to as crown correction of the holding member 23. Also, the difference between the thickness T of the holding member 23 at the center of the nip portion N in the longitudinal direction and the thickness T of the holding member 23 at the end of the nip portion N in the longitudinal direction is referred to as the crown correction amount.

[0199] The thickness T of the holding member 23 is the distance in the z-axis direction between the heater facing surface of the holding member 23 that faces the heater 26 (the surface facing the -z direction; if a heat retention plate 25 is present, the surface facing the heat retention plate 25) and the surface facing the +z direction on the back side of the heater facing surface.

[0200] When the thickness T of the central portion of the holding member 23 is increased by correcting the crown of the holding member 23, the decrease in nip pressure in the central portion is suppressed even when the stay 22 is bent, and the nip width in the central portion is increased. However, if the nip width in the central portion is made too wide, the fixing property at the end portion may decrease due to the temperature drop at the end portion. From the viewpoint of uniform fixing property in the longitudinal direction, it is preferable to make the nip width at the end portion 15% wider than the central portion in the configuration of this embodiment. However, if the nip width at the end portion is made 12% or more wider than the central portion, image rubbing due to the above-mentioned trailing edge bounce may occur.

[0201] Therefore, in this embodiment, the crown correction amount of the holding member 23 is set to 400 μm so that the nip width at the end portion is about 10% wider than that at the center portion.

[0202] The method of adjusting the nip pressure and nip width is not limited to the crown correction. As a method other than the crown correction of this embodiment, for example, the bearing surface of the holding member 23 supporting the heat retention plate 25 and the heater 26 may be bent in the +z direction or the -z direction in the longitudinal direction. Also, for example, the outer diameter of the pressure roller 202 may be changed depending on the position in the longitudinal direction.

[0203] 27 shows the measurement results of the nip width for each position in the longitudinal direction and the pressure distribution in the nip portion N in this embodiment. The horizontal axis represents the position in the longitudinal direction (x-axis direction) of the nip portion N, based on one end of the outer circumferential portion 202b of the pressure roller 202 in the longitudinal direction (x-axis direction).

[0204] The method of measuring the nip width is as follows. A test paper is prepared on which a black monochromatic image (solid black image) is formed over the entire effective image area in the longitudinal direction (x-axis direction) on a sheet of paper that is wider in the longitudinal direction (x-axis direction) than the roller width W202 (FIG. 7) of the pressure roller 202. The test paper is sandwiched in the nip portion N of the fixing device 200, and heated by the heater 26 while the pressure roller 202 is stopped. The temperature of the heater 26 is controlled to 150° C. by the thermistor 24, and the paper is heated for 10 seconds. Then, only the area of ​​the solid black image sandwiched in the nip portion N is heated, the gloss increases, and the mark of the nip portion N is transferred to the solid black image. The nip width was measured based on the mark of the nip portion N. The nip width was measured at 10 mm intervals in the longitudinal direction. The pressure distribution in the longitudinal direction was measured using a surface pressure distribution measurement system (Nitta Corporation I-SCAN, longitudinal resolution 0.5 mm).

[0205] 27, the nip width is wider from the center to both ends, being 8.0 mm in the center and 8.8 mm at both ends. In other words, in this embodiment, the nip width at the ends is 10% wider than the nip width at the center of nip N. This reduces the deterioration of fixability in the end regions due to end temperature sagging.

[0206] In this embodiment, a configuration in which the nip width at both ends is wider than the nip width at the center of the nip portion N is used in combination with the sliding plate 27 whose both ends are wider than the width at the center as described above. This makes it possible to more effectively suppress the deterioration of fixability in the edge regions due to edge temperature sagging while avoiding image smearing due to trailing edge bounce.

[0207] [Comparative test] A test was conducted to evaluate fixability and trailing edge bounce between the straight-shaped sliding plate 27 of the reference example shown in Fig. 28(a) and the sliding plate 27 of this embodiment shown in Fig. 28(b). Two types of fixing devices using the sliding plate 27 of the reference example were prepared. The first one was configured so that the nip width at the end of the nip portion N was 15% wider than the nip width at the center (referred to as Comparative Example 1). The second one was configured so that the nip width at the end of the nip portion N was 10% wider than the nip width at the center (referred to as Comparative Example 2).

[0208] Fixation was checked by printing 50 solid black images in succession and checking for image chipping or peeling. Trailing edge bounce was checked by printing 50 solid black images in succession and checking for image rubbing caused by trailing edge bounce. If even one of the 50 sheets had image chipping or peeling, the fixation was rated "NG," if even one of the 50 sheets had image rubbing, the trailing edge bounce was rated "NG," and if none of the 50 sheets had these image defects, the sheet was rated "OK." The results are shown in Figure 30.

[0209] In Comparative Example 1, since the nip width at the end was wide, there was no fixing failure due to temperature drop at the end, but the recording material conveying speed at the end was high, so the trailing edge bounce occurred and image rubbing occurred. On the other hand, in Comparative Example 2, since the nip width at the end was not so wide, there was no image rubbing due to trailing edge bounce, but after the 30th sheet, there was fixing failure due to temperature drop at the end.

[0210] In contrast, in this embodiment, the nip width at the end is not so wide as in Comparative Example 2, so image smearing due to the trailing edge bounce did not occur. In addition, in this embodiment, the end width of the sliding plate 27 is wide, so the thermal diffusion effect of the sliding plate 27 did not cause fixing failure.

[0211] [Summary of this Example] As described above, in this embodiment, when the shape of the nip portion N is a medium-thin shape in which the nip width at the end is wider than the nip width at the center of the nip portion N, the sliding plate 27 is also shaped so that the width of the sliding plate 27 becomes wider toward the end in the longitudinal direction. In other words, the width of the nip portion in the second direction at both ends of the nip portion in the first direction is wider than the width of the nip portion in the second direction at the center of the nip portion in the first direction. Also, the width of the sliding member in the second direction at both ends of the nip portion is wider than the width of the sliding member in the second direction at the center of the nip portion. This configuration can achieve both uniform fixability and reduction of image defects due to trailing edge bounce.

[0212] In this embodiment, the upstream edge and downstream edge of sliding plate 27 in the recording material transport direction (y-axis direction) are curved symmetrically, so that sliding plate 27 has a shape in which the width of the ends is wider than the width of the center. However, the present invention is not limited to this, and may have an asymmetric shape, for example, in which one of the upstream edge or the downstream edge extends linearly in the longitudinal direction of nip portion N (x-axis direction), and only the other of the upstream edge or the downstream edge is curved.

[0213] Variation of the Sixth Embodiment In the sixth embodiment, a configuration has been described in which the nip width at the ends of the nip portion N is wider than the center, and the width of the ends is wider than the width of the center of the sliding plate 27. As a modified example, a configuration example will be described in which the nip width at the ends of the nip portion N is narrower than the center, and the width of the ends is narrower than the width of the center of the sliding plate 27.

[0214] [Problem] Contrary to Example 6, wrinkles in the recording material may be reduced by making the nip width at the ends of the nip portion N in the recording material transport direction (y-axis direction) narrower than the nip width at the center. However, when crown correction of the holding member that holds the heater is performed to adjust the nip width, the fixing belt comes into contact with the holding member at the center in the longitudinal direction, lowering the temperature, which may result in poor fixability at the center.

[0215] Therefore, in this embodiment, a configuration is proposed that can suppress the deterioration of fixability in the center of the nip portion while reducing wrinkles in the recording material.

[0216] [Crown correction amount when using balloon rubber] As described above, balloon rubber made of foamed silicone rubber or the like may be used as the elastic layer of the pressure roller 202. When using balloon rubber, wrinkles in the recording material may be prevented by making the nip width wider in the center than at the ends.

[0217] When the balloon rubber is crushed in the nip portion N, the air inside is released and the volume becomes smaller. Therefore, compared to when solid rubber is used, the rotation radius of the pressure roller 202 in the nip portion N is substantially smaller, and the outer circumferential length of the pressure roller 202 in the vicinity of the nip portion N is shorter. Therefore, the greater the crushing amount of the elastic layer in the nip portion N, the slower the recording material conveying speed in the nip portion N. In other words, when balloon rubber is used as the elastic layer, as opposed to when solid rubber is used, the wider the nip width, the slower the recording material conveying speed becomes.

[0218] Therefore, when balloon rubber is used as the elastic layer of pressure roller 202, the nip width at the ends in the longitudinal direction is made narrower than the nip width at the center of nip portion N. This makes the recording material conveying speed at the ends faster than the recording material conveying speed at the center of nip portion N, making it less likely for wrinkles to occur in the recording material.

[0219] As described above, the crown correction of the holding member 23 is one means for widening the nip width at the center of the nip portion N. As an example, a configuration will be described in which the elastic layer of the pressure roller 202 in the fixing device 200 of the sixth embodiment is formed of balloon rubber, and the crown correction of the holding member 23 is used to make the nip width at the center wider than the ends.

[0220] [Nip width] 31 shows the distribution of the nip width and the applied force (nip pressure) of the nip portion N at each position in the longitudinal direction in a configuration example in which crown correction of the holding member 23 was performed. Here, the amount of crown correction of the holding member 23 was set to 600 μm, and adjustment was made so that the nip width at the center of the nip portion N was approximately 10% wider than at the ends. The horizontal axis represents the position in the longitudinal direction (x-axis direction) of the nip portion N, based on one end of the outer circumferential portion 202b of the pressure roller 202 in the longitudinal direction (x-axis direction). The method of measuring the nip width and nip pressure is the same as the method described using FIG. 27.

[0221] 31, due to the crown correction of the holding member 23, the nip width becomes wider from both ends to the center of the nip portion N. The nip width at the center was 8.8 mm, and the nip widths at both ends were 8.0 mm. In other words, by increasing the amount of crown correction of the holding member 23, the nip pressure at the center can be increased, and therefore the nip width at the center can be made wider than at both ends.

[0222] However, when the amount of crown correction of the holding member 23 is increased, the center of the fixing belt 21 may come into contact with the stay 22. Fig. 32(a) shows a state in which the fixing belt 21, the stay 22, and the pressure roller 202 are deflected when the belt unit 201 and the pressure roller 202 are in pressure contact with each other. When the thickness T of the center of the holding member 23 is increased by the crown correction, the fixing belt 21 is deflected so that the center of the fixing belt 21 protrudes toward the pressure roller 202 side (-z direction side) compared to both ends. Due to such deflection of the fixing belt 21, a portion of the fixing belt 21 opposite to the nip portion N (+z direction side) may come into contact with the stay 22.

[0223] When the fixing belt 21 comes into contact with the stay 22, heat from the fixing belt 21 is absorbed by the stay 22, causing the surface temperature of the fixing belt 21 to drop. As a result, fixing failure may occur in the contact area between the fixing belt 21 and the stay 22 in the longitudinal direction (x-axis direction). Since high strength is required for the stay 22, it is often made of a metal material. Metal materials have a large heat capacity and high thermal conductivity, which can easily lead to fixing failure.

[0224] In order to prevent poor fixing, it is possible to provide a contact prevention member 254 as shown in Fig. 32(b). The contact prevention member 254 is disposed between the stay 22 and the inner surface of the fixing belt 21, and prevents the inner surface of the fixing belt 21 from contacting the stay 22. The contact prevention member 254 is formed of a resin material with a lower thermal conductivity than the stay 22 so that it is less likely to remove heat from the fixing belt 21. Examples of the resin material include heat-resistant liquid crystal polymer (LCP) and heat-resistant polycarbonate (PC).

[0225] Although the provision of the contact prevention member 254 can prevent the fixing belt 21 from contacting the stay 22, the temperature of the center of the fixing belt 21 becomes somewhat lower than that of both ends due to the contact of the fixing belt 21 with the contact prevention member 254. Therefore, even when the contact prevention member 254 is provided, it is desirable to make it even more difficult for poor fixing to occur in the center of the nip portion N.

[0226] Therefore, in this modification, the sliding plate 27 has a shape in which the width Tw at the end is narrower than the width Cw at the center (a bulging shape) as shown in Fig. 33. For example, the width Cw of the sliding plate 27 at the center of the nip portion N is 13.0 mm, and the width Tw of the sliding plate 27 at the end of the nip portion N is 12.0 mm.

[0227] By adopting such a shape, it is possible to improve the thermal diffusion effect of the sliding plate 27 in the center of the nip portion N, and to reduce the deterioration of the fixability in the center. In other words, according to this modification, it is possible to achieve uniform fixability.

[0228] [Summary of this modified example] In this modification, when the shape of the nip portion N is a bulging shape in which the nip width at the ends is narrower than the nip width at the center of the nip portion N, the sliding plate 27 is also shaped so that the width of the sliding plate 27 narrows toward the ends in the longitudinal direction. In other words, the width of the nip portion in the second direction at both ends of the nip portion in the first direction is narrower than the width of the nip portion in the second direction at the center of the nip portion in the first direction. Also, the width of the sliding member in the second direction at both ends of the nip portion is narrower than the width of the sliding member in the second direction at the center of the nip portion. With this configuration, it is possible to suppress a decrease in fixability at the center of the nip portion while reducing wrinkles in the recording material.

[0229] Example 7 In this embodiment, sliding plate 27 is curved so that the center of sliding plate 27 in the longitudinal direction (x-axis direction) of nip portion N protrudes downstream in the recording material transport direction (+y direction) compared to both ends. Hereinafter, elements with common reference symbols to those in embodiment 1 have substantially the same configurations and functions as those described in embodiment 1, unless otherwise specified, and differences from embodiment 1 will be mainly described.

[0230] [Problem] During the fixing operation, the fixing belt 21 is bent such that the center of the fixing belt 21 in the longitudinal direction (x-axis direction) of the nip N protrudes further downstream in the recording material transport direction (+y direction) than both end portions. Due to this bending, the radius of curvature of the fixing belt 21 becomes larger on the downstream side in the recording material transport direction (+y direction) with respect to the nip N, so that the recording material that has passed through the nip N becomes difficult to separate from the fixing belt 21 and may wind around the fixing belt 21.

[0231] In view of this, this embodiment proposes a configuration capable of reducing the possibility of the recording material being wrapped around the fixing belt.

[0232] [Deflection of fixing belt] First, the bending of the fixing belt 21 during the fixing operation will be described using a specific configuration example. In the reference example of FIG. 17 described above, schematic diagrams of the fixing device 200 as viewed from the belt unit 201 side toward the pressure roller 202 side (-z direction) (as viewed in the direction of the arrow P in FIG. 3) are shown in FIG. 34(a) and (b). FIG. 34(a) is a diagram when the pressure roller 202 is stopped. FIG. 34(b) is a diagram when the pressure roller 202 is being driven to rotate.

[0233] As shown in Fig. 34(a), when the pressure roller 202 is stopped rotating, the fixing belt 21 is not bent. On the other hand, as shown in Fig. 34(b), when the pressure roller 202 rotates and the fixing belt 21 rotates following the pressure roller 202, the fixing belt 21 is bent such that the central part in the longitudinal direction protrudes further downstream in the recording material conveying direction (+y direction) than both end parts.

[0234] By the rotational drive of the pressure roller 202, the fixing belt 21 tends to move downstream (+y direction) in the recording material transport direction as a whole. However, the end face on the -y direction side of the belt guide 250 that holds both ends of the fixing belt 21 is located upstream (-y direction) in the recording material transport direction than the end face on the -y direction side of the holding member 23. In this case, the positions of both ends of the fixing belt 21 in the y axis direction are restricted by the end faces of the belt guide 250, while the center of the fixing belt 21 moves in the +y direction until it contacts the end face of the holding member 23. As a result, the fixing belt 21 is bent so that the center in the longitudinal direction (x axis direction) protrudes downstream (+y direction) in the recording material transport direction compared to both ends.

[0235] [Recording material wrapping] It will be explained that when the fixing belt 21 is bent as shown in Fig. 34(b) and the recording material is passed through the fixing device 200, there is a possibility that the recording material may be wrapped around the fixing belt 21. Figs. 35(a) and (b) are cross-sectional views of the belt heating section 210 while a large-size sheet is passing through. Fig. 35(a) shows the cross section at the center of the large-size sheet, and Fig. 35(b) shows the cross section at the edge of the large-size sheet.

[0236] 35(a), at both ends of the fixing belt 21, the rotational trajectory of the fixing belt 21 is regulated by belt guides 250 (guide members), and there is little slack in the recording material transport direction downstream (+y direction) from the nip N. Therefore, the radius of curvature Rt of the fixing belt 21 on the recording material transport direction downstream (+y direction) from the nip N is relatively small, and the recording material S is easily separated from the fixing belt 21.

[0237] 35(b), in the center of the fixing belt 21, the rotational path of the fixing belt 21 is slackened toward the downstream side (+y direction) in the recording material transport direction from the nip portion N. Therefore, the radius of curvature Rc of the fixing belt 21 on the downstream side (+y direction) in the recording material transport direction from the nip portion N is larger than the radius of curvature Rt of the end portion. As a result, the recording material S is difficult to separate from the fixing belt 21. Therefore, there is a possibility that a transport failure will occur in which the recording material S is not separated from the fixing belt 21 and is wound around the fixing belt 21.

[0238] The wrapping of the recording material around the fixing belt 21 is particularly likely to occur with small-sized paper. In the case of large-sized paper (recording material S with a comparatively large sheet width) shown in Figures 35(a) and (b), the end of the recording material S is separated from the fixing belt 21 first, so that the recording material S is relatively easy to separate even when there is slack in the center of the fixing belt 21. In the case of small-sized paper with a narrow sheet width, the entire small-sized paper comes into contact with the fixing belt 21 near the center where the radius of curvature of the fixing belt 21 is large, so separation is more difficult than with large-sized paper.

[0239] The wrapping of the recording material around the fixing belt 21 also depends on the density of the image formed on the recording material S. That is, when forming an image with a large toner loading (weight of toner adhering per unit area) or an image with a high printing rate (ratio of area covered by toner to unit area), the adhesion of the recording material S to the fixing belt 21 increases, and wrapping is more likely to occur.

[0240] [Shape of sliding plate] In this embodiment, the shape of the sliding plate 27 is set in accordance with the deflection shape of the fixing belt 21 so that the radius of curvature is small even in the central portion of the fixing belt 21 .

[0241] In addition, in the sliding plate 27 of this embodiment, similarly to the fourth and fifth embodiments, the fixing belt 21 does not basically come into contact with the holding member 23, and is held only by the sliding plate 27 and the pressure roller 202. Therefore, the configuration described below has the effect of improving thermal efficiency and energy saving performance, similarly to the fourth and fifth embodiments. However, in this embodiment, on the upstream side of the nip portion N that is not related to the winding of the recording material around the fixing belt 21, the fixing belt 21 may come into contact with the holding member 23 and other members.

[0242] 36 is a schematic diagram (as viewed in the direction of arrow P in FIG. 3) showing the fixing device 200 of this embodiment as viewed from the belt unit 201 side toward the pressure roller 202 side (-z direction). As described above, when the pressure roller 202 is rotationally driven (during fixing operation), the fixing belt 21 is bent so that the center of the fixing belt 21 protrudes further downstream in the recording material conveying direction (+y direction) than both ends.

[0243] The sliding plate 27 of this embodiment has a curved end face 27d on the downstream side in the recording material transport direction when viewed in the z-axis direction as shown in Fig. 36. The downstream end face 27d is curved such that the center of the end face 27d protrudes downstream in the recording material transport direction (+y direction) compared to both ends of the end face 27d in the longitudinal direction (x-axis direction) of the nip portion N. Also, when viewed in the z-axis direction, the width of the sliding plate 27 in the recording material transport direction (y-axis direction) at the center of the sliding plate 27 is wider than the width of the sliding plate 27 in the recording material transport direction (y-axis direction) at the ends of the sliding plate 27.

[0244] 37(a) and (b) are cross-sectional views of the belt heating unit 210 during the passage of large-size paper in the fixing device of this embodiment. Fig. 37(a) shows the cross section at the center of the large-size paper, and Fig. 37(b) shows the cross section at the edge of the large-size paper.

[0245] 37(a) and (b), the position of downstream end face 27d of sliding plate 27 at the center of nip portion N protrudes further downstream in the recording material transport direction (+y direction) than the position of end face 27d at the edge position of large size paper. Due to this shape, even if the central portion of fixing belt 21 slackens downstream in the recording material transport direction (+y direction) due to bending of fixing belt 21, the rotational trajectory of fixing belt 21 can be regulated by sliding plate 27 on the downstream side of nip portion N.

[0246] 35(b), the radius of curvature Rc of the fixing belt 21 on the downstream side (+y direction) in the recording material transport direction with respect to the nip portion N can be made smaller in the central portion of the fixing belt 21 in this embodiment shown in FIG. 37(b). As a result, it is possible to reduce the possibility that the recording material will wrap around the fixing belt 21. In particular, according to this embodiment, even in the case of small-sized paper or when forming an image with a high toner loading amount or print rate, the recording material is less likely to wrap around the fixing belt 21.

[0247] In the configuration in this embodiment in which the fixing belt 21 does not come into contact with the holding member 23 and the rotational trajectory of the fixing belt 21 is regulated by the sliding plate 27, the curvature of the fixing belt 21 can be controlled by changing the width and shape of the sliding plate 27. The sliding plate 27 is formed, for example, by pressing a metal plate. Therefore, it has the advantage that it is stronger than a resin guide, has less warping or bending in the longitudinal direction, and is easier to achieve precision in the shape.

[0248] [Summary of this Example] As described above, in this embodiment, in a configuration in which both ends of the fixing belt 21 are guided by the belt guide 250, the end face 27d of the sliding plate 27 is bent toward the downstream side (+y direction) in the recording material conveying direction. In other words, the downstream end face of the sliding member in the second direction is curved such that the center part of the end face in the first direction protrudes downstream in the second direction compared to both ends of the end face in the first direction. With this configuration, it is possible to reduce the possibility of the recording material being wrapped around the fixing belt 21 during pre-cooling.

[0249] Variation of the Seventh Embodiment In the seventh embodiment, an example was described in which the downstream end face 27d of the sliding plate 27 is formed so that the central portion protrudes downstream in the recording material transport direction (+y direction) compared to both ends in the longitudinal direction (x-axis direction), but this is not limited to this.

[0250] [Problem] In the case of large-size paper with a small basis weight (thin paper), the recording material has low rigidity (weak stiffness), and therefore separation failure is likely to occur at the corners of the recording material.

[0251] Therefore, in this modified example, a configuration is proposed that can improve the separability of the corners of the recording material.

[0252] [Sliding plate] In this modified example, downstream end surface 27d of sliding plate 27 is formed so that both ends protrude downstream in the recording material transport direction (+y direction) compared to the center in the longitudinal direction (x-axis direction). With this shape, the radius of curvature of fixing belt 21 on the downstream side in the recording material transport direction (+y direction) with respect to nip portion N can be made smaller at both ends of fixing belt 21. This makes it easier for corners of the recording material to be separated from fixing belt 21, and reduces the possibility of the recording material wrapping around fixing belt 21 even when a recording material with low rigidity is passed through.

[0253] In other words, the end face on the downstream side of the sliding member in the second direction is curved such that both ends of the end face in the first direction protrude downstream in the second direction compared to the center part of the end face in the first direction. With this configuration, it is possible to improve the separation property of the corners of the recording material.

[0254] Example 8 In this embodiment, the heat retention plate and the sliding plate are brought into contact with each other in order to suppress the temperature rise in the non-sheet passing area. In the following, unless otherwise specified, elements having the same reference symbols as those in the first embodiment have substantially the same configurations and functions as those described in the first embodiment, and the differences from the first embodiment will be mainly described.

[0255] [Problem] When a recording material having a narrow sheet width compared to the heating area of ​​the heater is passed through, the temperatures of the fixing belt 21 and the pressure roller 202 rise in the area (non-paper passing area) where the recording material does not pass in the longitudinal 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 temperatures of the fixing belt 21 and the pressure roller 202 rise excessively in the non-paper passing area (non-paper passing area temperature rise), and may exceed the heat resistance temperature of the members. Also, since thermal energy is not used to fix an image in the non-paper passing area, this is not preferable in terms of thermal efficiency and energy saving performance of the fixing device.

[0256] Therefore, in this embodiment, a configuration capable of reducing the temperature difference between the paper passing area and the non-paper passing area is proposed.

[0257] [Temperature rise in non-paper passing area] The non-paper passing portion temperature rise will be described using a specific configuration example. First, Fig. 38(a) shows a typical heater 26 used in a fixing device of the belt heating type. Fig. 38(a) is a diagram showing a surface of the heater 26 having a resistance heating element 262. In this embodiment, the resistance heating element 262 is disposed on the surface of the heater 26 facing the sliding plate 27 (surface 26a in Fig. 4).

[0258] As shown in Fig. 38(a), the heater 26 has a substrate 261, and a resistive heating element 262, a conductor 263, and an electrode portion 264, each of which is formed on the substrate 261. The resistive heating element 262 is arranged in a series circuit extending from one electrode portion 264 to the other electrode portion 264 via the conductor 263. When a voltage is applied to the electrode portion 264 from an external power supply circuit to pass electricity through the series circuit, the resistive heating element 262 generates heat. However, the configuration of the heater 26 shown in Fig. 38(a) is merely an example, and for example, a plurality of resistive heating elements 262 may be arranged in parallel, or the heater 26 may have only one resistive heating element 262.

[0259] Here, as shown in Fig. 38(b), when a recording material (hereinafter referred to as small size paper in this embodiment) having a sheet width narrower than the width of the resistance heating element 262 is passed through, a non-paper passing area (non-paper passing portion) exists that is within the heat generating area of ​​the resistance heating element 262 and outside the paper passing area. In the non-paper passing portion, the fixing belt 21 and the pressure roller 202 are supplied with heat from the resistance heating element 262, while the heat is not absorbed by the recording material at the nip portion N. Therefore, as shown in Fig. 38(b), the temperatures of the members such as the fixing belt 21 and the pressure roller 202 rise in the non-paper passing portion.

[0260] In order to prevent the temperature of fixing belt 21 or pressure roller 202 from rising excessively (for example exceeding the heat resistance temperature of fixing belt 21) in the non-paper passing areas, control may be performed to widen the recording material conveyance interval (paper gap) for small size paper compared to large size paper. By widening the paper gap, the temperature distribution in the longitudinal direction (x-axis direction) of nip portion N is equalized during the period when no recording material is passing through nip portion N, making it less likely that the adverse effect of temperature rise in non-paper passing areas will occur. However, widening the paper gap has the disadvantage of reducing the productivity of small size paper.

[0261] As another countermeasure against the temperature rise in the non-paper passing area, a configuration may be adopted in which multiple resistance heating elements 262 with different lengths in the x-axis direction are arranged in the heater 26, and electricity is selectively applied to the resistance heating elements 262 depending on the sheet width of the recording material being used. However, the sheet width of the recording material selected by the user includes not only standard sizes such as A4 and B5, but also non-standard sizes. Therefore, even in a configuration in which multiple resistance heating elements 262 can be selectively energized, a temperature rise in the non-paper passing area may occur. In addition, there are disadvantages such as the complexity of control due to selective energization and an increase in the number of parts due to the arrangement of multiple temperature detection elements corresponding to the multiple resistance heating elements 262.

[0262] As yet another method for dealing with the temperature rise in the non-paper passing areas, there is a configuration in which a heat equalizing member is brought into contact with the heater 26 to promote thermal diffusion in the longitudinal direction (x-axis direction) of the nip N and equalize the temperature distribution. As the heat equalizing member, for example, a metal plate with high thermal conductivity such as an aluminum alloy is used. However, even when a heat equalizing member is used, in cases such as when continuously printing a large amount of small size paper, the distance between the papers may need to be increased to avoid the adverse effect of the temperature rise in the non-paper passing areas, and a configuration that can further suppress the temperature rise in the non-paper passing areas is therefore required.

[0263] [Contact between heat retention plate and sliding plate] In this embodiment, in order to suppress the temperature rise in the non-paper passing portion, the heat retention plate 25 and the sliding plate 27 are arranged in contact with each other. Fig. 39 is an enlarged view showing a cross section of the belt heating unit 210 in this embodiment.

[0264] The fixing belt 21 in this embodiment has a base material (base layer), an elastic layer, and a surface layer. The elastic layer is formed on the outer periphery of the base material, and the surface layer is formed on the outer periphery of the elastic layer.

[0265] The substrate is an endless resin film mainly made of polyimide with filler added to enhance thermal conductivity. The substrate has an inner diameter of 30 mm and a thickness of 80 μm. In this embodiment, the substrate is mainly made of polyimide, which has high heat resistance and mechanical strength, but is not limited to this and may contain, for example, stainless steel, polyether ether ketone, etc. The thickness of the substrate is not limited to the value shown in the example.

[0266] The elastic layer is mainly made of silicone rubber having heat resistance that can withstand the fixing temperature. The thickness of the elastic layer is 200 μm, and the rubber hardness is sufficient to form the nip portion N. In this embodiment, the main component is silicone rubber from the viewpoint of high heat resistance, but the main component is not limited to this, and may include, for example, fluororubber. The thickness is not limited to the value shown as an example.

[0267] The surface layer is mainly composed of perfluoroalkoxyalkane (PFA), for example. The thickness is 20 μm. In this embodiment, PFA is used as the main component from the viewpoint of high releasability and heat resistance, but this is not limited to this, and the thickness is not limited to the exemplified value.

[0268] In this embodiment, the cross-sectional shape of the surface perpendicular to the x-axis direction of the sliding plate 27 is composed of a sliding portion 271 and an upright portion 272. The upright portion 272 is continuous with the upstream and downstream sides of the sliding portion 271 in the recording material transport direction (y-axis direction), and is bent in the +z direction with respect to the sliding portion 271 extending in the y-axis direction. The tip of the upright portion 272 in the +z direction is accommodated in a groove portion 231 formed in the upstream and downstream portions of the holding member 23 in the recording material transport direction (y-axis direction).

[0269] The length of the sliding plate 27 in the longitudinal direction (x-axis direction) is longer than the fixing belt 21 and the outer circumferential portion 202b of the pressure roller 202 so that the nip portion N can be formed with a sufficient length in the longitudinal direction. The sliding plate 27 is made of an aluminum alloy having a thickness of 0.5 mm as a base material. The sliding surface 271b of the sliding portion 271 that rubs against the fixing belt 21 is coated with a fluororesin to improve sliding properties and wear resistance. In this embodiment, a base material mainly composed of aluminum having a high thermal conductivity is used, but the base material of the sliding plate 27 may contain, for example, stainless steel, copper, or zinc as a main component. The thickness of the sliding plate 27 is not limited to the value exemplified. In this embodiment, the sliding surface 271b is coated with a fluororesin, but the aluminum base material may be anodized to impart sliding properties and wear resistance.

[0270] The configuration of heater 26 of this embodiment is shown in Figures 40(a) and (b). Figure 40(a) is a cross-sectional view of heater 26 in a plane perpendicular to the x-axis direction. Substrate 261 is stainless steel (SUS) with a thickness of 0.3 mm, and insulating glass layer 265a is formed on the surface of substrate 261 with which sliding plate 27 comes into contact. Insulating glass layer 265b is formed on the surface of substrate 261 with which heat retention plate 25 comes into contact. Insulating glass layers 265a and 265b each have a thickness of 50 µm. A pattern including resistance heating element 262 as a heat generating member is formed on insulating glass layer 265a, and insulating glass layer 265c with a thickness of 50 µm is further formed to cover and protect the pattern.

[0271] Fig. 40(b) is a diagram showing the surface having the resistive heating element of the heater 26 in this embodiment. Two resistive heating elements 262 are arranged on a substrate 261, with a total length of 220 mm, 110 mm on either side of the center x0 of the nip 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 15 Ω.

[0272] In this embodiment, stainless steel (SUS), which has a relatively high thermal conductivity, is used as the base material of the heater 26, but it may be made of ceramics such as aluminum nitride or alumina, which also have high thermal conductivity. The protective layer of the pattern may be a fluororesin coat or the like, and is not limited to the configuration shown in the example. In this embodiment, the resistive heating element 262 is not divided and arranged in the x-axis direction, and two resistive heating elements 262 are connected in series, but the resistive heating element 262 may be arranged in multiple regions divided in the x-axis direction.

[0273] The heat retention plate 25 of this embodiment will be described with reference to Figs. 41(a) and (b). Fig. 41(a) is a perspective view of the heat retention plate 25 of this embodiment. The heat retention plate 25 is, for example, an aluminum alloy sheet metal having a thickness of 0.5 mm. The heat retention plate 25 has a length of 218 mm in total, 109 mm on both sides relative to the center x0 of the nip portion N in the x-axis direction.

[0274] 41(b) is a cross-sectional view of the heat retention plate 25 in a plane perpendicular to the x-axis direction. The dashed line shows the heat retention plate 25 before it is brought into contact with the heater 26 arranged in the sliding plate 27. The solid line shows the heat retention plate 25 after it is brought into contact with the heater 26 arranged in the sliding plate 27.

[0275] The heat retention plate 25 has a flat portion 255 and a bent portion 256. The flat 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. In other words, the flat 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 on the upstream side and downstream side of the flat portion 255 in the y-axis direction, and is bent toward the +z direction in the z-axis direction.

[0276] In a state (dashed line) before the heat retention plate 25 is attached inside the sliding plate 27, the length of the heat retention 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 part 271 of the sliding plate 27 in the y-axis direction. Also, in a state (dashed line) before the heat retention plate 25 is attached inside the sliding plate 27, the length of the heat retention plate 25 in the y-axis direction is longer than the distance in the y-axis direction between the two upright parts 272 of the sliding plate 27. The heat retention plate 25 is pressed into the inside of the sliding plate 27 with the bent part 256 bent. This makes it possible to bring the flat part 255 of the heat retention plate 25 into contact with the heater 26 while bringing the heat retention plate 25 into contact with the sliding plate 27 more reliably.

[0277] [Comparative test] The temperature of the fixing belt 21 was compared between the configuration of this embodiment described above and the configuration using the heat retention plate 25 of the reference example shown in Fig. 18. The heat retention plate 25 of the reference example shown in Fig. 18 is configured only with a flat portion without any bent portions, and the length of the flat portion in the y-axis direction is shorter than the length of the sliding portion of the sliding plate. Therefore, in the reference example, the heat retention plate 25 and the sliding plate 27 are not in contact with each other.

[0278] (Experiment 1) In order to confirm the effect of suppressing the temperature rise in the non-paper passing area by this embodiment, the minimum heater temperature at which an image can be fixed was confirmed using the image forming apparatus 100 equipped with the fixing device 200 of this embodiment, and the temperature of the fixing belt 21 in the non-paper passing area and the paper passing area at that 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 minimum heater temperature at which a solid black image is formed on the front side of the recording material and no chipping or peeling of the image occurs. In addition, in common with this embodiment and the reference example, when the temperature of the fixing belt 21 in the paper passing area is 161° C. or higher, fixability without chipping or peeling of the image was obtained. In addition, the temperature of the fixing belt 21 was measured by photographing the fixing belt 21 during paper passing using a Chino infrared thermography camera CPA-E5A, and the maximum temperature of the non-paper passing area and the average temperature of the paper passing area were extracted from the longitudinal temperature profile data of the fixing belt 21. The process speed of the image forming apparatus 100 used in the experiment was 200 mm / s, and the interval (paper interval) between the preceding recording material S and the next recording material S was 30 mm. As the recording material, general laser printer paper with a basis weight of 80 g / m^2 and B5 size (width 182 mm, length 257 mm) was used. The temperature of the fixing belt 21 was measured while 20 sheets of recording material were continuously passed through.

[0279] The results of Experiment 1 are shown in Fig. 42. The minimum heater temperature was 201°C in this embodiment and 205°C in the reference embodiment. When continuous paper was passed at these minimum heater temperatures, the temperature of the non-paper passing portion of the fixing belt 21 in this embodiment was 7°C lower than in the reference embodiment. Also, the temperature of the paper passing portion was 161°C in both configurations, with no difference. In other words, according to this embodiment, the temperature of the fixing belt 21 in the non-paper passing portion was lower than in the reference embodiment, and it was possible to lower the minimum heater temperature at which an image can be fixed.

[0280] This mechanism will be described with reference to Figs. 43(a) and (b). Fig. 43(a) shows the longitudinal temperature profile of each component of the belt unit 201 in this embodiment, and Fig. 43(b) shows the longitudinal temperature profile of each component of the belt unit 201 in the reference example. In both configurations of Figs. 43(a) and (b), in the paper passing area, heat is taken by the recording material passing through the nip portion N, so the temperature of each component is lower. However, the further away from the recording material in the z-axis direction the member is, the less susceptible to 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 retention plate 25 is smaller than the temperature difference between the paper passing portion and the non-paper passing portion of the sliding plate 27. Also, the temperature of the heat retention plate 25 in the paper passing area is higher than the temperature of the sliding plate 27 in the paper passing area.

[0281] In the present embodiment shown in FIG. 43(a), the temperature difference between the heat retention plate 25 and the sliding plate 27 in the paper passing area is smaller than that in the reference embodiment shown in FIG. 43(b). This is because the heat retention plate 25 and the sliding plate 27 are in contact with each other on the upstream side and downstream side in the recording material conveying direction (y-axis direction), and heat is transferred from the heat retention plate 25, which has a higher temperature, to the sliding plate 27, which has a lower temperature. This transfer of heat increases the temperature of the sliding plate 27 in the paper passing area, and also increases the temperature of the fixing belt 21 in the paper passing area. Therefore, if the target temperature of the fixing belt 21 is the same, this embodiment can maintain the fixing belt 21 at the target temperature in a state where the temperature of the heater 26 is lower than that in the reference embodiment. In other words, in this embodiment, the heat from the heater 26 is efficiently transferred to the fixing belt 21 via the sliding plate 27, and energy saving performance can be improved.

[0282] According to this embodiment, the difference between the temperature of the sliding plate 27 in the non-paper passing portion and the temperature of the sliding plate 27 in the paper passing portion is smaller than that in the reference embodiment. And the difference between the temperature of the fixing belt 21 in the non-paper passing portion and the temperature of the fixing belt 21 in the paper passing portion is also smaller. Therefore, it is possible to suppress the temperature rise of the non-paper passing portion of each component of the belt unit 201. That is, in this embodiment, in addition to the effect that each of the heat retention plate 25 and the sliding plate 27 independently diffuses heat in the longitudinal direction (x-axis direction) of the nip portion N, heat is transferred at the contact portion between the heat retention plate 25 and the sliding plate 27. As a result, the temperature difference between the non-paper passing portion and the paper passing portion is mitigated in each component of the belt unit 201, and the temperature rise of the non-paper passing portion can be suppressed more effectively.

[0283] Incidentally, in this embodiment, as shown in Fig. 41, the heat retention plate 25 having the bent portions 256 on both sides of the flat portion 255 is exemplified, but as shown in Fig. 44(a), a heat retention plate 25 having the bent portion 256 only on one side of the flat portion 255 may be used. Even in this case, by attaching the heat retention plate 25 to the sliding plate 27 so that both ends of the heat retention plate 25 in the recording material transport direction (y-axis direction) come into contact with the upright portions 272 of the sliding plate 27, the same effect as in this embodiment can be obtained.

[0284] In the case of the modification shown in Fig. 44(a), as shown in Fig. 44(b), it is preferable to press the heat retention plate 25 into the sliding plate 27 while bending the bent portion 256 in a state where the end face without the bent portion 256 is abutted against one of the standing portions 272 of the sliding plate 27. This allows the heat retention plate 25 and the sliding plate 27 to contact each other more reliably.

[0285] In the above embodiment, the contact portions of the heat retaining plate 25 and the sliding plate 27 are provided on both the upstream side and the downstream side in the recording material conveying direction, but the contact portions may be configured to contact only on either the upstream side or the downstream side. In the present embodiment, the length of the heat retaining 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 than this. However, if the heat retaining plate 25 is longer than the length of the resistance heating element 262 of the heater 26, there is a concern that poor fixing may occur due to temperature sagging at the end portions, and if it is too short, the effect of reducing the temperature rise in non-paper passing areas and the effect of improving energy saving performance are reduced, so the length should be adjusted appropriately.

[0286] (Variation 1) As Modification 1, a configuration that can increase the contact area between the heat retention plate 25 and the sliding plate 27 compared to Example 8 (FIGS. 41(a) and (b)) will be described. FIG. 45 shows the cross-sectional shapes of the heat retention plate 25 and the sliding plate 27 of this modification. The heat retention plate 25 of this modification has a flat portion 255 that contacts the heater 26, and standing portions 257 that are provided on both sides of the flat portion 255 and are erected by bending. The standing portions 257 are formed continuously on the upstream and downstream sides of the flat portion 255 in the recording material conveying direction (y-axis direction), and extend toward a direction (+z direction) approximately perpendicular to the extension direction of the flat portion 255. The standing portions 257 are formed so as to come into surface contact with the standing portions 272 of the sliding plate 27 when the heat retention plate 25 is attached to the sliding plate 27. Therefore, compared to the configuration of the eighth embodiment in which the edge of the heat retention plate 25 is substantially in line contact with the sliding plate 27, heat transfer between the heat retention plate 25 and the sliding plate 27 can be promoted.

[0287] Thermally conductive grease may be applied to the contact area between the rising portion 257 of the heat retention plate 25 and the rising portion 272 of the sliding plate 27. For example, DOWSIL SC102 compound from Dow Toray Industries, Inc. is used as the thermally conductive grease. The thermal transfer between the heat retention plate 25 and the sliding plate 27 can be further promoted by the thermally conductive grease.

[0288] (Variation 2) As Modification 2, another configuration capable of increasing the contact area between the heat retention plate 25 and the sliding plate 27 will be described. FIG. 46(a) shows the cross-sectional shapes of the heat retention plate 25 and the sliding plate 27 of this modification. The heat retention plate 25 of this modification is composed of only a flat portion 255. The sliding plate 27 of this modification has a rubbing portion 271 that rubs against the fixing belt 21, and a folded portion 278 folded back by bending the rubbing portion 271. The folded portion 278 is provided continuously on the upstream side and downstream side of the rubbing 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 rubbing portion 271 and extends to the downstream side (+y direction) of the recording material conveying direction. The downstream side folded back portion 278 is folded back approximately 180 degrees from the downstream end of the rubbing portion 271 and extends toward the upstream side (+y direction) in the recording material transport direction.

[0289] The heat retention plate 25 is accommodated in a space formed between the sliding portion 271 and the folded portion 278 of the sliding plate 27 in the z-axis direction. For example, as shown in FIG. 46(b), the heat retention plate 25 and the heater 26 are slid in the x-axis direction to be mounted in the space between the sliding portion 271 and the folded portion 278 of the sliding plate 27. The surface of the heat retention plate 25 on the +z direction side is in surface contact with the folded portion 278 of the sliding plate 27. Therefore, compared to the configuration of the eighth embodiment in which the edge of the heat retention plate 25 is in substantial line contact with the sliding plate 27, the heat transfer between the heat retention plate 25 and the sliding plate 27 can be promoted.

[0290] Thermally conductive grease may be applied to the contact area between the heat retention plate 25 and the folded portion 278 of the sliding plate 27. The thermally conductive grease can further promote heat transfer between the heat retention plate 25 and the sliding plate 27.

[0291] According to this modification, the heat retention plate 25 and the folded portion 278 of the sliding plate 27 are pressed against each other by the pressure for generating the nip pressure in the nip portion N. This has the advantage that the heat retention plate 25 and the sliding plate 27 can be more reliably brought into surface contact with each other.

[0292] (Variation 3) As Modification 3, another configuration that can easily ensure contact between the heat retention plate 25 and the sliding plate 27 will be described. FIG. 47(a) shows the cross-sectional shapes of the heat retention plate 25 and the sliding plate 27 of this modification. The heat retention plate 25 of this modification has a flat portion 255 and a standing portion 257 provided near either one of the ends on the upstream side or downstream side in the recording material transport direction (y-axis direction) with respect to the flat portion 255. The standing portion 257 is bent with respect to the flat portion 255 extending in the recording material transport direction (y-axis direction) and extends in the +z direction. The sliding plate 27 has a rubbing portion 271 and standing portions 272 provided on both sides of the rubbing portion 271 in the recording material transport direction (y-axis direction).

[0293] As shown in FIG. 47(b), each of the standing portions 272 is provided with a through hole 279 extending in the longitudinal direction (x-axis direction). The sliding plate 27 and the heat retention plate 25 can be integrated by inserting the flat portion 255 of the heat retention plate 25 into this through hole 279 from one side in the recording material conveying direction (y-axis direction). For example, after the heater 26 is set on the sliding portion 271 of the sliding plate 27 from the +z direction side, the heat retention plate 25 can be inserted into the through hole 279 of the sliding plate 27. As a result, the heater 26, the heat retention plate 25, and the sliding plate 27 are integrated with each other in a state in which the heater 26 is sandwiched between the heat retention plate 25 and the sliding plate 27.

[0294] According to this modification, the heat retention plate 25 and the sliding plate 27 engage (fit) at the through hole 279, so that the heat retention plate 25 and the sliding plate 27 can be brought into contact with each other more reliably, and heat transfer between the heat retention plate 25 and the sliding plate 27 can be promoted. In addition, this modification has the advantage that the tolerance for part precision is higher and the assembly work is relatively simple compared to, for example, modification 2. Thermally conductive grease may be applied to the through hole 279. The thermally conductive grease can further promote heat transfer between the heat retention plate 25 and the sliding plate 27.

[0295] As a further modification (modification 3-2), as shown in Fig. 48, through holes 258 extending in the longitudinal direction (x-axis direction) may be provided at both ends in the recording material transport direction (y-axis direction) of the flat portion 255 of the heat retention plate 25, and the sliding plate 27 may be fitted into the through holes 258. The sliding plate 27 has a rubbing portion 271, standing portions 272 provided on the upstream side and downstream side of the rubbing portion 271 in the recording material transport direction (y-axis direction), and hook portions 276 provided at the respective tips of the standing portions 272. The hook portions 276 are shaped by bending the tips of the standing portions 272 standing in the +z direction by approximately 90 degrees toward the side away from the heater 26 in the y-axis direction. According to this modification, the heat retention plate 25 and the sliding plate 27 engage (fit) at the through hole 258, thereby enabling the heat retention plate 25 and the sliding plate 27 to come into more reliable contact with each other, thereby promoting heat transfer between the heat retention plate 25 and the sliding plate 27.

[0296] (Variation 4) As a fourth modification, a configuration in which a heat retention plate (heat retention portion) is integrally formed with a sliding plate (sliding member) will be described. FIG. 49(a) shows a cross-sectional shape of a sliding / heat retention plate 27A in an example (fourth modification 4-1) of the fourth modification. The sliding / heat retention plate 27A has a sliding portion 271 that slides against the fixing belt 21, a standing portion 272 that continues to either the upstream side or the downstream side of the sliding portion 271 in the recording material conveying direction (y-axis direction), and a heat retention portion 277 that continues to the other of the upstream side or the downstream side of the sliding portion 271. The sliding / heat retention plate 27A is formed by folding back a metal plate, which is a material, by approximately 180 degrees between the sliding portion 271 and the heat retention portion 277, and folding it by approximately 90 degrees between the sliding portion 271 and the standing portion 272. The heater 26 is accommodated in the space between the sliding portion 271 and the heat retention portion 277 of the sliding / heat retention plate 27A.

[0297] 49(b) shows a cross-sectional shape of the sliding / heat retention plate 27B in another example (variation 4-2) of variation 4. The sliding / heat retention plate 27B has a sliding portion 271 that rubs against the fixing belt 21, and heat retention portions 277 that are continuous with the upstream and downstream sides of the sliding portion 271 in the recording material conveying direction (y-axis direction). The sliding / heat retention plate 27B is formed by folding back a metal plate, which is the material, by approximately 180 degrees between the sliding portion 271 and the heat retention portion 277. The heater 26 is accommodated in the space between the sliding portion 271 and the heat retention portion 277 of the sliding / heat retention plate 27B.

[0298] 49(c) shows a cross-sectional shape of the sliding / heat-retaining sleeve 28 in yet another example of the modified example (modified example 4-3). The sliding / heat-retaining sleeve 28 has a sliding portion 281 (rubbing member) that rubs against the fixing belt 21, and a heat retention portion 282 (heat retention portion) that sandwiches the heater 26 between the sliding portion 281 in the z-axis direction. The sliding / heat-retaining sleeve 28 is a metal member formed into a cylindrical shape by, for example, drawing. The heater 26 is accommodated in the space between the sliding portion 281 and the heat retention portion 282 of the sliding / heat-retaining sleeve 28.

[0299] In the above examples of Fig. 49(a) to (c), the rubbing member (rubbing portion 271, 281) and the heat retention member (heat retention portion 277, 282) are formed as the same member. Therefore, there is no thermal resistance at the contact portion when the rubbing member and the heat retention member are separate members. Therefore, it is possible to promote the heat transfer between the heat retention plate 25 and the sliding plate 27.

[0300] (Experiment 2) In order to confirm the effect of suppressing the temperature rise in the non-paper passing area in the above-mentioned modified examples 1 to 4, the temperature of the fixing belt 21 was compared between the reference example shown in Fig. 18 and each modified example. The minimum heater temperature at which an image can be fixed was confirmed using an image forming apparatus 100 equipped with the fixing device 200 of modified examples 1 to 4, and the temperatures of the fixing belt 21 in the non-paper passing area and the paper passing area at that heater temperature were confirmed. The details of the experimental method were the same as those of Experiment 1 described above.

[0301] The results of experiment 2 are shown in Fig. 50. In all of modified examples 1 to 4, the temperature of the fixing belt 21 in the non-paper passing area was lower than in the reference example, and the minimum heater temperature at which an image can be fixed could be lowered. This is because in all of modified examples 1 to 4, the temperature of the rubbing member increases due to heat transfer from the heat retention member (heat retention sections 277, 282) to the rubbing member (rubbing sections 271, 281) in the paper passing area, and the temperature of the fixing belt 21 is raised (see Fig. 43(a)). Also, not only the rubbing member (rubbing sections 271, 281) but also the heat retention member (heat retention sections 277, 282) contribute to mitigating the temperature gradient in the longitudinal direction (x-axis direction).

[0302] Therefore, according to the first to fourth modifications, the temperature of the fixing belt 21 in the paper passing area can be maintained at a desired fixing temperature even if the temperature of the heater 26 is set lower than in the reference example. In other words, it is possible to improve the thermal efficiency of the fixing device 200 and improve the energy saving performance. Furthermore, according to the first to fourth modifications, the temperature difference between the non-paper passing portion and the paper passing portion in each component of the belt unit 201 is mitigated, and the temperature rise in the non-paper passing portion can be suppressed.

[0303] [Summary of this Example] As described above, in this embodiment and the modified example, a path is provided that allows heat to move from the heat retention plate (heat retention section) to the sliding plate (sliding section). This reduces the temperature difference between the paper passing area and the non-paper passing area, improving thermal efficiency and suppressing the temperature rise in the non-paper passing area.

[0304] In the eighth embodiment and the first to third modifications, the heat retention plate 25 and the sliding plate 27 are in contact with each other. That is, the fixing device is further provided with a heat retention member arranged between the holding member and the heater in the third direction for retaining heat from the heater, and the heat retention member and the sliding member are in contact with each other. This configuration can reduce the temperature difference between the paper passing area and the non-paper passing area.

[0305] In the fourth modification, a portion (heat retention portion) that functions as a heat retention member is integrally formed with the sliding member. That is, the sliding member has a rubbing portion that rubs against the inner surface of the fixing member, and a heat retention portion that is disposed between the holding member and the heater in the third direction and retains the heat of the heater, and the rubbing portion and the heat retention portion are integrally formed. This configuration can reduce the temperature difference between the paper passing area and the non-paper passing area.

[0306] Example 9 In this embodiment, a configuration will be described in which the shape or positional relationship between the retaining member 23 and the stay 22 is different from that of embodiment 1. Hereinafter, unless otherwise specified, elements having the same reference symbols as embodiment 1 have substantially the same configurations and functions as those described in embodiment 1, and differences from embodiment 1 will be mainly described.

[0307] [Problem] The holding member described in Patent Document 1 is provided with grooves (front and rear restricting grooves) that accommodate both ends of a U-shaped heat diffusion member (sliding member), and the stays abut against the holding member directly above the grooves. However, creep deformation of the holding member may occur because pressure from the stays acts on the portion of the holding member that has been thinned by the grooves. If creep deformation of the holding member occurs, the nip pressure in the nip area may change, or the shape of the nip area may change, which may degrade the performance of the fixing device.

[0308] Therefore, in this embodiment, a configuration capable of reducing creep deformation of the retaining member is proposed.

[0309] [Excess grease and groove of retaining member] With reference to the configuration of the reference example shown in FIG. 5, the relationship between the shape of the retaining member 23 and creep deformation in a specific configuration will be described.

[0310] In the reference example, in order to promote the transfer of heat from the heater 26 to the sliding plate 27, thermally conductive grease G1 is applied between the heater 26 and the sliding plate 27. The amount of thermally conductive grease G1 applied is set so that it will not run out during the service life of the fixing device 200, even taking into account variations in the amount applied during manufacturing. Therefore, the amount of thermally conductive grease G1 applied is more than the minimum amount required to fill the gap between the heater 26 and the sliding plate 27, and excess grease is present.

[0311] Since the thermal conductive grease G1 is required to have high thermal conductivity, it may contain hard solid particles such as metal oxides, ceramics, carbon, etc. as a thermal conductive filler. If these solid particles adhere to the inner surface of the fixing belt 21, the inner surface of the fixing belt 21 may be worn down, which may cause problems such as a decrease in sliding properties.

[0312] Here, by making the internal space of groove portion 231 larger than the volume of upright portion 272 of sliding plate 27 housed in groove portion 231, it is possible to accommodate excess grease in groove portion 231. However, if an attempt is made to ensure that groove portion 231 is wide enough to accommodate the excess grease, the thickness of holding member 23 will have to be reduced, and the mechanical strength of holding member 23 in the vicinity of groove portion 231 will decrease.

[0313] Example 1 shown in Fig. 4 is the same as the reference example in the positional relationship between the groove 231 and the stay 22. As shown in Fig. 4, in Example 1 and the reference example, the stay 22 presses the holding member 23 directly above the groove 231. That is, the contact area between the end face of the stay 22 facing the -z direction and the face of the holding member 23 (face facing the +z direction) pressed against the end face is in a positional relationship at least partially overlapping with the groove 231 when viewed in the z-axis direction. In this positional relationship, creep deformation of the holding member 23 may occur near the bottom surface of the groove 231, which has low mechanical strength, due to the pressure force in the -z direction acting from the stay 22 to the holding member 23 due to the biasing force of the pressure spring 251 (Fig. 3).

[0314] In other words, if an attempt is made to provide a larger capacity for the groove portion 231 to accommodate excess grease, creep deformation of the retaining member 23 becomes more likely to occur, and the adverse effects of creep deformation (changes in the shape of the nip portion N and a decrease in nip pressure) can become more likely to occur.

[0315] [Positional relationship between stay and groove] Fig. 51 is a cross-sectional view of fixing device 200 according to this embodiment. Fig. 52 is an enlarged view of belt heating section 210 (the portion enclosed by the dashed line in Fig. 51) according to this embodiment. In this embodiment, in consideration of the above-mentioned problems, the grooves are arranged so as not to be positioned on the pressure force transmission path.

[0316] As shown in FIG. 51 and FIG. 52, the belt unit 201 of the fixing device 200 includes a stay 22, a holding member 23, a thermistor 24, a heat retention plate 25, a heater 26, and a sliding plate 27. The stay 22 is an example of a reinforcing member that reinforces the holding member 23. As in the first embodiment, the stay 22 receives a biasing force in the -z direction by a pressure spring 251 as a biasing member, and presses the holding member 23 in the -z direction. The end faces of the stay 22 that press the holding member 23 are defined as pressing parts P1 and P2. The pressing part P1 presses the holding member 23 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 downstream of the center of the heater 26 in the conveying direction F (y-axis direction).

[0317] The holding member 23 has two grooves 231 that receive the upright portion 272 of the sliding plate 27. Hereinafter, the upstream groove 231 in the recording material transport direction (y-axis direction) will be referred to as "groove 231a" and the downstream groove 231 will be referred to as "groove 231b." The upstream groove 231b is an example of a first recess that receives the upstream upright portion 272 (first upright portion). The downstream groove 231b is an example of a second recess that receives the downstream upright portion 272 (second upright portion).

[0318] As shown in Fig. 52, in this embodiment, the pressing portions P1 and P2 of the stay 22 are disposed closer to the center of the nip portion N than the grooves 231a and 231b of the holding member 23 in the recording material transport direction (y-axis direction). In other words, the upstream pressing portion P1 (first pressing portion) is located downstream (+y direction) of the upstream groove 231a in the recording material transport direction. The downstream pressing portion P2 (second pressing portion) is located upstream (-y direction) of the downstream groove 231b in the recording material transport direction. When viewed in the z-axis direction, the pressing portions P1 and P2 do not overlap with the bottom surfaces of the grooves 231a and 231b.

[0319] With the above configuration, the thin-walled portion St of the holding member 23 formed by the grooves 231a and 231b is less likely to be subjected to bending stress caused by the pressure force from the stay 22 and the reaction force from the pressure roller 202. That is, the holding member 23 receives a pressure force in the -z direction from the pressing portions P1 and P2 of the stay 22. Also, the holding member 23 receives a reaction force in the +z direction from the pressure roller 202 via the sliding plate 27, the heater 26, and the heat retention plate 25 mainly in the region between the pressing portions P1 and P2 in the recording material conveying direction (y-axis direction). Due to this pressure force and reaction force, a bending stress is generated in the portion of the holding member 23 between the pressing portions P1 and P2 in the recording material conveying direction (y-axis direction) such that the center of the holding member 23 protrudes toward the +z direction. In this embodiment, the thin-walled portion St is located outside the region between the pressing portions P1 and P2 in the recording material conveying direction (y-axis direction), so that the bending stress can be prevented from concentrating on the thin-walled portion St.

[0320] Therefore, according to the configuration of this embodiment, the possibility of creep deformation of the retaining member 23 occurring in the thin-walled portion St can be reduced, and the possibility of adverse effects of creep deformation (change in shape of the nip portion N and reduction in nip pressure) occurring can be reduced.

[0321] [Summary of this Example] As described above, the positions (P1, P2) at which the stay 22 presses the holding member 23 are downstream of the upstream groove 231a of the holding member 23 in the y-axis direction and upstream of the downstream groove 231b. In other words, the position at which the reinforcing member presses the holding member is downstream of the first recess and upstream of the second recess in the second direction. This configuration can reduce creep deformation of the holding member.

[0322] [Variations] In this embodiment, a configuration example has been described in which the points of action (pressing portions P1, P2) at which the stay 22 presses the holding member 23 are two, one on the upstream side and one on the downstream side. The points of action at which the stay 22 presses the holding member 23 may be three or more. Even in this case, the same effect as in this embodiment can be obtained as long as the most upstream point of action in the recording material transport direction (y-axis direction) is located downstream of the upstream groove portion 231a and the most downstream point of action is located upstream of the downstream groove portion 231a.

[0323] Example 10 In this embodiment, a configuration example will be described in which the shape of the holding member 23 is different from that of embodiments 1 and 9. Hereinafter, unless otherwise specified, elements having the same reference symbols as those in embodiment 1 will have substantially the same configurations and functions as those described in embodiment 1, and differences from embodiment 1 will be mainly described.

[0324] [Problem] In this embodiment, similarly to the ninth embodiment, a configuration capable of reducing creep deformation of a retaining member is proposed.

[0325] [Grease guide hole] 53 is a cross-sectional view of a fixing device 200 according to Example 10. A grease guide hole 481 for guiding excess grease is formed in the holding member 23 of this example. The grease guide hole 481 is a through hole that extends in the z-axis direction from the bottom surface of the groove portion 231 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.

[0326] The fixing device 200 has the same configuration as in the ninth embodiment, except for having the grease guide hole 481. That is, in this embodiment, the thin 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 prevent bending stress from concentrating on the thin portion St.

[0327] 54, the grease guide holes 481 are arranged in a row along the longitudinal direction (x-axis direction) in the bottom of each groove portion 231. However, the arrangement and number of the grease guide holes 481 can be changed as appropriate depending on the amount, viscosity, etc. of the surplus grease.

[0328] As shown in FIG. 55, when the gap between the groove portion 231 and the rising portion 272 is filled with the thermally conductive grease G1 (excess grease) extruded from between the heater 26 and the sliding plate 27 or between the heater 26 and the heat retention plate 25, the excess grease is guided to the grease guide hole 481. The end of the grease guide hole 481 is an open space, and the excess grease can be discharged into this space. By providing the grease guide hole 481, the possibility that the excess grease overflows from the groove portion 231 and adheres to the inner surface of the fixing belt 21 can be reduced. Note that, although the configuration in which the end of the grease guide hole 481 is an open space has been exemplified here, a closed space that receives the excess grease may be provided beyond the grease guide hole 481.

[0329] In this manner, in this embodiment, the capacity to accommodate excess grease can be increased by providing the grease guide hole 481 in the groove portion 231 of the holding member 23. This increases the tolerance for variation in the amount of thermally conductive grease G1 applied during manufacturing, making the assembly work of the fixing device 200 easier.

[0330] [Summary of this Example] In this embodiment, the thin portion St generated by the groove portion 231 is also 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 prevent bending stress from concentrating on the thin portion St, and it is possible to reduce the possibility of creep deformation of the holding member 23.

[0331] Furthermore, even if the mechanical strength of the holding member 23 is reduced compared to that of Example 9 due to the provision of the grease guide hole 481, the holding member 23 is unlikely to undergo creep deformation because the thin-walled portion St is located outside the region between the pressing portions P1 and P2. Therefore, the assembly work of the fixing device 200 can be made easier while reducing the possibility of the holding member 23 undergoing creep deformation.

[0332] (Modification) FIG. 56 is a cross-sectional view of a fixing device 200 according to a modification of the tenth embodiment. FIG. 57 is a schematic diagram enlarging a part of FIG. 56. In this modification, a wall portion 524 for preventing leakage of excess grease is provided on the upward surface 233 of the holding member 23 where the grease guide hole 481 opens. The wall portion 524 is disposed on the upstream side and the downstream side in the recording material conveying direction (y-axis direction) with respect to the stay 22. The upstream wall portion 524 protrudes in the +z direction from the upward surface 233 of the holding member 23 on the upstream side of the upstream grease guide hole 481 in the recording material conveying direction (y-axis direction). The downstream wall portion 524 protrudes in the +z direction from the upward surface 233 of the holding member 23 on the downstream side of the downstream grease guide hole 481 in the recording material conveying direction (y-axis direction).

[0333] 57, the thermally conductive grease G1 (excess grease) overflowing from the grease guide hole 481 of this modified example is held in the space between the wall portion 524 and the stay 322. The excess grease is stably held in the space by the surface tension acting between the wall portion 524 and the stay 322. This action makes it possible to further increase the upper limit amount of excess grease that can be held in the open space beyond the grease guide hole 481.

[0334] In the tenth embodiment, the grease guide hole 481 is provided in the groove portion 231 on both the upstream side and the downstream side of the nip portion N, but depending on the manner in which the excess grease is generated, the grease guide hole 481 may be provided only on either the upstream side or the downstream side. For example, when the direction in which the excess grease is generated due to the influence of gravity is known in advance by arranging the fixing device 200 at an angle as described in the second embodiment, the grease guide hole 481 may be provided only on the side where the excess grease is generated. The same applies to the wall portion 524 shown in the modified example.

[0335] Other Embodiments The configurations of the above-mentioned embodiments and their modified examples are not exclusive, and can be combined as long as there is no contradiction in the operational effects. For example, the protrusions described in the first to third embodiments may be provided on the sliding plates of the fourth to tenth embodiments.

[0336] In the above-described embodiments, a direct transfer type electrophotographic color printer having multiple image forming units has been exemplified as the image forming apparatus, but the image forming apparatus is not limited to this. The image forming apparatus may be a monochrome printer having only one image forming unit (process unit) and forming a monochromatic image using one type of toner. The image forming apparatus may also be equipped with an intermediate transfer type image forming unit that primarily transfers a toner image formed on an image carrier (photosensitive member) to an intermediate transfer body such as an intermediate transfer belt, and secondarily transfers the toner image from the intermediate transfer body to a recording material.

[0337] Summary of the Disclosure The present disclosure includes at least the following configurations or methods.

[0338] (Configuration 1) a rotatable endless fixing member; a heater that is disposed in an internal space of the fixing member and generates heat when energized; a sliding member disposed between the heater and an inner surface of the fixing member and sliding against the inner surface of the fixing member; a holding member for holding the heater and the sliding member; a pressing member disposed to sandwich the fixing member together with the sliding member and forming a nip portion between the pressing member and the fixing member; a fixing device that heats an image on a recording material by the fixing member while nipping and transporting the recording material at the nip portion, Grease is applied between the heater and the sliding member, a longitudinal direction of the nip portion is defined as a first direction, a recording material conveying direction in the nip portion is defined as a second direction, and a direction perpendicular to both the first direction and the second direction is defined as a third direction, the sliding member has a rubbing portion extending along the second direction and rubbing against the inner surface of the fixing member, a first standing portion standing from an upstream end of the rubbing portion in the second direction to a side moving away from the pressure member in the third direction, a second standing portion standing from a downstream end of the rubbing portion in the second direction to a side moving away from the pressure member in the third direction, and a protrusion provided on at least one of the first standing portion and the second standing portion and protruding in a direction intersecting an extension direction of the standing portion when viewed in the first direction. A fixing device comprising:

[0339] (Configuration 2) the protrusion is a first protrusion provided on the first upright portion, The sliding member further has a second protrusion provided on the second upright portion. 2. The fixing device according to claim 1,

[0340] (Configuration 3) one of the first standing portion and the second standing portion is located below the other of the first standing portion and the second standing portion in a gravitational direction, The protrusion is provided on the first standing portion and the second standing portion, the first standing portion and the second standing portion being located on the lower side. 2. The fixing device according to claim 1,

[0341] (Configuration 4) the heater is disposed between the first upright portion and the second upright portion in the second direction, the protrusion protrudes toward the heater in the second direction relative to the one of the upright portions on which the protrusion is provided. 4. The fixing device according to any one of configurations 1 to 3.

[0342] (Configuration 5) The sliding portion, the first upright portion, and the second upright portion are formed of a single metal plate, The protrusion has a bent shape formed by bending a part of the single metal plate. 5. The fixing device according to any one of configurations 1 to 4.

[0343] (Configuration 6) The protrusion portion is a separate member from the sliding portion, the first standing portion, and the second standing portion. 5. The fixing device according to any one of configurations 1 to 4.

[0344] (Configuration 7) the pressure member has an outer circumferential portion that contacts the fixing member at the nip portion, The length of the protrusion in the first direction is longer than the length of the outer circumferential portion in the first direction. 7. The fixing device according to any one of configurations 1 to 6.

[0345] (Configuration 8) a length of the protrusion in the first direction is longer than a length of the fixing member in the first direction; 8. The fixing device according to configuration 7.

[0346] (Configuration 9) a heat retention member disposed between the holding member and the heater in the third direction and configured to retain heat from the heater; The grease is applied between the heater and the heat retaining member. 9. The fixing device according to any one of configurations 1 to 8.

[0347] (Configuration 10) The grease is a first grease containing a filler for enhancing thermal conductivity, A second grease having a different composition from the first grease is applied between the sliding member and the inner surface of the fixing member to enhance slidability. 10. The fixing device according to any one of configurations 1 to 9.

[0348] (Configuration 11) a rotatable endless fixing member; a heater that is disposed in an internal space of the fixing member and generates heat when energized; a sliding member disposed between the heater and an inner surface of the fixing member and sliding against the inner surface of the fixing member; a holding member for holding the heater and the sliding member; a pressing member disposed to sandwich the fixing member together with the sliding member and forming a nip portion between the pressing member and the fixing member; a fixing device that heats an image on a recording material by the fixing member while nipping and transporting the recording material at the nip portion, a longitudinal direction of the nip portion is defined as a first direction, a recording material conveying direction in the nip portion is defined as a second direction, and a direction perpendicular to both the first direction and the second direction is defined as a third direction, the sliding member has a sliding portion that slides against the inner surface of the fixing member, the holding member has a first opposing portion facing the inner surface of the fixing member upstream of the rubbing portion in the second direction, and a second opposing portion facing the inner surface of the fixing member downstream of the rubbing portion in the second direction, In the third direction, the first opposing portion and the second opposing portion are retreated to a side away from the pressure member compared to the sliding portion. A fixing device comprising:

[0349] (Configuration 12) the first opposing portion and the second opposing portion have curved surfaces that are curved along a rotation path of the fixing member when viewed in the first direction; 12. The fixing device according to claim 11,

[0350] (Configuration 13) the holding member is configured so that the fixing member does not come into contact with the first opposing portion and the second opposing portion when the pressure member is rotationally driven to rotate the fixing member following the pressure member. 13. The fixing device according to configuration 11 or 12.

[0351] (Configuration 14) a rotatable endless fixing member; a heater that is disposed in an internal space of the fixing member and generates heat when energized; a sliding member disposed between the heater and an inner surface of the fixing member and sliding against the inner surface of the fixing member; a holding member for holding the heater and the sliding member; a pressing member disposed to sandwich the fixing member together with the sliding member and forming a nip portion between the pressing member and the fixing member; a fixing device that heats an image on a recording material by the fixing member while nipping and transporting the recording material at the nip portion, a longitudinal direction of the nip portion is defined as a first direction, a recording material conveying direction in the nip portion is defined as a second direction, and a direction perpendicular to both the first direction and the second direction is defined as a third direction, the sliding member has a sliding portion that extends along the second direction and slides against the inner surface of the fixing member, a first guide portion that extends upstream of the sliding portion in the second direction and guides the fixing member, and a second guide portion that extends downstream of the sliding portion in the second direction and guides the fixing member, the first guide portion and the second guide portion are curved along a rotation path of the fixing member when viewed in the first direction. A fixing device comprising:

[0352] (Configuration 15) when viewed in the third direction from the pressure member side toward the fixing member side, the holding member is entirely covered by the sliding portion, the first guide portion, and the second guide portion. 15. The fixing device according to configuration 14.

[0353] (Configuration 16) the sliding member has a first upright portion that stands from an upstream end of the rubbing portion in the second direction to a side moving away from the pressure member in the third direction, and a second upright portion that stands from a downstream end of the rubbing portion in the second direction to a side moving away from the pressure member in the third direction, the holding member has a first recess that receives the first standing portion, a second recess that receives the second standing portion, and a third recess that houses the heater, the first guide portion covers a convex portion between the first recess and the third recess when viewed in the third direction, The second guide portion covers a convex portion between the second recess and the third recess when viewed in the third direction. 15. The fixing device according to configuration 14.

[0354] (Configuration 17) a rotatable endless fixing member; a heater that is disposed in an internal space of the fixing member and generates heat when energized; a sliding member disposed between the heater and an inner surface of the fixing member and sliding against the inner surface of the fixing member; a holding member for holding the heater and the sliding member; a pressing member disposed to sandwich the fixing member together with the sliding member and forming a nip portion between the pressing member and the fixing member; a fixing device that heats an image on a recording material by the fixing member while nipping and transporting the recording material at the nip portion, a longitudinal direction of the nip portion is defined as a first direction, a recording material conveying direction in the nip portion is defined as a second direction, and a direction perpendicular to both the first direction and the second direction is defined as a third direction, a width of the nip portion in the second direction at both ends of the nip portion in the first direction is wider than a width of the nip portion in the second direction at a center of the nip portion in the first direction, a width of the sliding member in the second direction at both ends of the nip portion is wider than a width of the sliding member in the second direction at a center of the nip portion; A fixing device comprising:

[0355] (Configuration 18) The pressure member has a core and an elastic layer formed on an outer periphery of the core, The elastic layer is formed of solid rubber. 18. The fixing device according to claim 17,

[0356] (Configuration 19) a rotatable endless fixing member; a heater that is disposed in an internal space of the fixing member and generates heat when energized; a sliding member disposed between the heater and an inner surface of the fixing member and sliding against the inner surface of the fixing member; a holding member for holding the heater and the sliding member; a pressing member disposed to sandwich the fixing member together with the sliding member and forming a nip portion between the pressing member and the fixing member; a fixing device that heats an image on a recording material by the fixing member while nipping and transporting the recording material at the nip portion, a longitudinal direction of the nip portion is defined as a first direction, a recording material conveying direction in the nip portion is defined as a second direction, and a direction perpendicular to both the first direction and the second direction is defined as a third direction, a width of the nip portion in the second direction at both ends of the nip portion in the first direction is narrower than a width of the nip portion in the second direction at a center of the nip portion in the first direction, a width of the sliding member in the second direction at both ends of the nip portion is narrower than a width of the sliding member in the second direction at a center of the nip portion; A fixing device comprising:

[0357] (Configuration 20) The pressure member has a core and an elastic layer formed on an outer periphery of the core, The elastic layer is made of foam rubber. 20. The fixing device according to claim 19,

[0358] (Configuration 21) a rotatable endless fixing member; a heater that is disposed in an internal space of the fixing member and generates heat when energized; a sliding member disposed between the heater and an inner surface of the fixing member and sliding against the inner surface of the fixing member; a holding member for holding the heater and the sliding member; a pressing member disposed to sandwich the fixing member together with the sliding member and forming a nip portion between the pressing member and the fixing member; a fixing device that heats an image on a recording material by the fixing member while nipping and transporting the recording material at the nip portion, a longitudinal direction of the nip portion is defined as a first direction, a recording material conveying direction in the nip portion is defined as a second direction, and a direction perpendicular to both the first direction and the second direction is defined as a third direction, the fixing device further includes guide members that guide both ends of the fixing member in the first direction, a downstream end face of the sliding member in the second direction is curved such that a central portion of the end face in the first direction protrudes downstream in the second direction compared to both end portions of the end face in the first direction; A fixing device comprising:

[0359] (Configuration 22) a rotatable endless fixing member; a heater that is disposed in an internal space of the fixing member and generates heat when energized; a sliding member disposed between the heater and an inner surface of the fixing member and sliding against the inner surface of the fixing member; a holding member for holding the heater and the sliding member; a pressing member disposed to sandwich the fixing member together with the sliding member and forming a nip portion between the pressing member and the fixing member; a fixing device that heats an image on a recording material by the fixing member while nipping and transporting the recording material at the nip portion, a longitudinal direction of the nip portion is defined as a first direction, a recording material conveying direction in the nip portion is defined as a second direction, and a direction perpendicular to both the first direction and the second direction is defined as a third direction, A downstream end face of the sliding member in the second direction is curved such that both ends of the end face in the first direction protrude downstream in the second direction compared to a central portion of the end face in the first direction. A fixing device comprising:

[0360] (Configuration 23) a rotatable endless fixing member; a heater that is disposed in an internal space of the fixing member and generates heat when energized; a sliding member disposed between the heater and an inner surface of the fixing member and sliding against the inner surface of the fixing member; a holding member for holding the heater and the sliding member; a pressing member disposed to sandwich the fixing member together with the sliding member and forming a nip portion between the pressing member and the fixing member; a fixing device that heats an image on a recording material by the fixing member while nipping and transporting the recording material at the nip portion, a longitudinal direction of the nip portion is defined as a first direction, a recording material conveying direction in the nip portion is defined as a second direction, and a direction perpendicular to both the first direction and the second direction is defined as a third direction, the fixing device further includes a heat retention member disposed between the holding member and the heater in the third direction and configured to retain heat from the heater; The heat retaining member and the sliding member are in contact with each other. A fixing device comprising:

[0361] (Configuration 24) The heat retaining member and the sliding member are in surface contact with each other. 24. The fixing device according to configuration 23.

[0362] (Configuration 25) a rotatable endless fixing member; a heater that is disposed in an internal space of the fixing member and generates heat when energized; a sliding member disposed between the heater and an inner surface of the fixing member and sliding against the inner surface of the fixing member; a holding member for holding the heater and the sliding member; a pressing member disposed to sandwich the fixing member together with the sliding member and forming a nip portion between the pressing member and the fixing member; a fixing device that heats an image on a recording material by the fixing member while nipping and transporting the recording material at the nip portion, a longitudinal direction of the nip portion is defined as a first direction, a recording material conveying direction in the nip portion is defined as a second direction, and a direction perpendicular to both the first direction and the second direction is defined as a third direction, the sliding member has a sliding portion that slides against the inner surface of the fixing member, and a heat retention portion that is disposed between the holding member and the heater in the third direction and that retains heat from the heater, and the sliding portion and the heat retention portion are integrally formed. A fixing device comprising:

[0363] (Configuration 26) The sliding portion and the heat retention portion are formed of a metal plate bent between the sliding portion and the heat retention portion, or a cylindrical metal member in which the sliding portion and the heat retention portion are continuous. 26. The fixing device according to configuration 25.

[0364] (Configuration 27) a rotatable endless fixing member; a heater that is disposed in an internal space of the fixing member and generates heat when energized; a sliding member disposed between the heater and an inner surface of the fixing member and sliding against the inner surface of the fixing member; a holding member for holding the heater and the sliding member; a pressing member disposed to sandwich the fixing member together with the sliding member and forming a nip portion between the pressing member and the fixing member; a biasing member for applying pressure to the nip portion; a reinforcing member that reinforces the holding member and presses the holding member toward the pressing member by receiving a biasing force of the biasing member; a fixing device that heats an image on a recording material by the fixing member while nipping and transporting the recording material at the nip portion, Grease is applied between the heater and the sliding member, a longitudinal direction of the nip portion is defined as a first direction, a recording material conveying direction in the nip portion is defined as a second direction, and a direction perpendicular to both the first direction and the second direction is defined as a third direction, the sliding member has a sliding portion that extends along the second direction and slides against the inner surface of the fixing member, a first standing portion that stands from an upstream end of the sliding portion in the second direction toward a side moving away from the pressure member in the third direction, and a second standing portion that stands from a downstream end of the sliding portion in the second direction toward a side moving away from the pressure member in the third direction, The holding member has a first recess that receives the first upright portion and a second recess that receives the second upright portion, a 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; A fixing device comprising:

[0365] (Configuration 28) the reinforcing member has a first pressing portion that presses the holding member upstream of a center of the heater in the second direction, and a second pressing portion that presses the holding member 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 recess in the second direction. 28. The fixing device according to configuration 27.

[0366] (Configuration 29) The holding member has a through hole formed therein that penetrates the holding member from a bottom surface of the first recess or the second recess to an opposite side to the bottom surface in the third direction and that can introduce the grease. 29. The fixing device according to configuration 27 or 28.

[0367] (Configuration 30) an image forming unit that forms an image on a recording material using toner; 30. A fixing device according to any one of configurations 1 to 29, which fixes the image on the recording material; An image forming apparatus comprising: [Explanation of symbols]

[0368] 21... fixing member (fixing belt) / 22... reinforcing member (stay) / 23... holding member / 231... first recess, second recess (groove portion) / 23A, 23B... first opposing portion, second opposing portion (guide portion) / 25... heat retaining member (heat retaining plate) / 26... heater / 27... sliding member (sliding plate) / 271... sliding portion / 272... standing portion / 27d... end surface / 200... fixing device / 202... pressure member (pressure roller) / 250... guide member (belt guide) / 273... protrusion portion / 274... first guide portion, second guide portion (guide portion)

Claims

1. a rotatable endless fixing member; a heater that is disposed in an internal space of the fixing member and generates heat when energized; a sliding member disposed between the heater and an inner surface of the fixing member and sliding against the inner surface of the fixing member; a holding member for holding the heater and the sliding member; a pressing member disposed to sandwich the fixing member together with the sliding member and forming a nip portion between the pressing member and the fixing member; a fixing device that heats an image on a recording material by the fixing member while nipping and transporting the recording material at the nip portion, Grease is applied between the heater and the sliding member, a longitudinal direction of the nip portion is defined as a first direction, a recording material conveying direction in the nip portion is defined as a second direction, and a direction perpendicular to both the first direction and the second direction is defined as a third direction, the sliding member has a rubbing portion extending along the second direction and rubbing against the inner surface of the fixing member, a first standing portion standing from an upstream end of the rubbing portion in the second direction to a side moving away from the pressure member in the third direction, a second standing portion standing from a downstream end of the rubbing portion in the second direction to a side moving away from the pressure member in the third direction, and a protrusion provided on at least one of the first standing portion and the second standing portion, protruding in a direction intersecting an extension direction of the standing portion when viewed in the first direction. A fixing device comprising:

2. The protrusion is a first protrusion provided on the first upright portion, The sliding member further includes a second protrusion provided on the second upright portion.

2. The fixing device according to claim 1,

3. one of the first standing portion and the second standing portion is located below the other of the first standing portion and the second standing portion in a gravitational direction, The protrusion is provided on a rising portion located on a lower side of the first rising portion and the second rising portion.

2. The fixing device according to claim 1,

4. the heater is disposed between the first upright portion and the second upright portion in the second direction, the protrusion protrudes toward the heater in the second direction relative to the one of the upright portions on which the protrusion is provided.

2. The fixing device according to claim 1,

5. The sliding portion, the first upright portion, and the second upright portion are formed of a single metal plate, The protrusion has a bent shape formed by bending a part of the single metal plate.

2. The fixing device according to claim 1,

6. The protrusion portion is a separate member from the sliding portion, the first standing portion, and the second standing portion.

2. The fixing device according to claim 1,

7. the pressure member has an outer circumferential portion that contacts the fixing member at the nip portion, The length of the protrusion in the first direction is longer than the length of the outer circumferential portion in the first direction.

2. The fixing device according to claim 1,

8. a length of the protrusion in the first direction is longer than a length of the fixing member in the first direction; 8. The fixing device according to claim 7,

9. a heat retention member disposed between the holding member and the heater in the third direction to retain heat from the heater; The grease is applied between the heater and the heat retaining member.

2. The fixing device according to claim 1,

10. The grease is a first grease containing a filler for enhancing thermal conductivity, a second grease having a composition different from that of the first grease is applied between the sliding member and the inner surface of the fixing member to enhance slidability; 2. The fixing device according to claim 1,

11. a rotatable endless fixing member; a heater that is disposed in an internal space of the fixing member and generates heat when energized; a sliding member disposed between the heater and an inner surface of the fixing member and sliding against the inner surface of the fixing member; a holding member for holding the heater and the sliding member; a pressing member disposed to sandwich the fixing member together with the sliding member and forming a nip portion between the pressing member and the fixing member; a fixing device that heats an image on a recording material by the fixing member while nipping and transporting the recording material at the nip portion, a longitudinal direction of the nip portion is defined as a first direction, a recording material conveying direction in the nip portion is defined as a second direction, and a direction perpendicular to both the first direction and the second direction is defined as a third direction, the sliding member has a sliding portion that slides against the inner surface of the fixing member, the holding member has a first opposing portion facing the inner surface of the fixing member upstream of the rubbing portion in the second direction, and a second opposing portion facing the inner surface of the fixing member downstream of the rubbing portion in the second direction, In the third direction, the first opposing portion and the second opposing portion are retreated to a side away from the pressure member compared to the sliding portion. A fixing device comprising:

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

13. the holding member is configured so that the fixing member does not come into contact with the first opposing portion and the second opposing portion when the pressure member is rotationally driven to rotate the fixing member following the pressure member. The fixing device according to claim 11 .

14. a rotatable endless fixing member; a heater that is disposed in an internal space of the fixing member and generates heat when energized; a sliding member disposed between the heater and an inner surface of the fixing member and sliding against the inner surface of the fixing member; a holding member for holding the heater and the sliding member; a pressing member disposed to sandwich the fixing member together with the sliding member and forming a nip portion between the pressing member and the fixing member; a fixing device that heats an image on a recording material by the fixing member while nipping and transporting the recording material at the nip portion, a longitudinal direction of the nip portion is defined as a first direction, a recording material conveying direction in the nip portion is defined as a second direction, and a direction perpendicular to both the first direction and the second direction is defined as a third direction, the sliding member has a sliding portion that extends along the second direction and slides against the inner surface of the fixing member, a first guide portion that extends upstream of the sliding portion in the second direction and guides the fixing member, and a second guide portion that extends downstream of the sliding portion in the second direction and guides the fixing member, the first guide portion and the second guide portion are curved along a rotation path of the fixing member when viewed in the first direction. A fixing device comprising:

15. when viewed in the third direction from the pressure member side toward the fixing member side, the holding member is entirely covered by the sliding portion, the first guide portion, and the second guide portion. The fixing device according to claim 14 .

16. the sliding member has a first upright portion that stands from an upstream end of the sliding portion in the second direction to a side moving away from the pressure member in the third direction, and a second upright portion that stands from a downstream end of the sliding portion in the second direction to a side moving away from the pressure member in the third direction, the holding member has a first recess that receives the first rising portion, a second recess that receives the second rising portion, and a third recess that houses the heater, the first guide portion covers a convex portion between the first recess and the third recess when viewed in the third direction, The second guide portion covers a convex portion between the second recess and the third recess when viewed in the third direction. The fixing device according to claim 14 .

17. a rotatable endless fixing member; a heater that is disposed in an internal space of the fixing member and generates heat when energized; a sliding member disposed between the heater and an inner surface of the fixing member and sliding against the inner surface of the fixing member; a holding member for holding the heater and the sliding member; a pressing member disposed to sandwich the fixing member together with the sliding member and forming a nip portion between the pressing member and the fixing member; a fixing device that heats an image on a recording material by the fixing member while nipping and transporting the recording material at the nip portion, a longitudinal direction of the nip portion is defined as a first direction, a recording material conveying direction in the nip portion is defined as a second direction, and a direction perpendicular to both the first direction and the second direction is defined as a third direction, a width of the nip portion in the second direction at both ends of the nip portion in the first direction is wider than a width of the nip portion in the second direction at a center of the nip portion in the first direction, a width of the sliding member in the second direction at both ends of the nip portion is wider than a width of the sliding member in the second direction at a center of the nip portion; A fixing device comprising:

18. The pressure member has a core and an elastic layer formed on an outer periphery of the core, The elastic layer is formed of solid rubber. The fixing device according to claim 17 .

19. a rotatable endless fixing member; a heater that is disposed in an internal space of the fixing member and generates heat when energized; a sliding member disposed between the heater and an inner surface of the fixing member and sliding against the inner surface of the fixing member; a holding member for holding the heater and the sliding member; a pressing member disposed to sandwich the fixing member together with the sliding member and forming a nip portion between the pressing member and the fixing member; a fixing device that heats an image on a recording material by the fixing member while nipping and transporting the recording material at the nip portion, a longitudinal direction of the nip portion is defined as a first direction, a recording material conveying direction in the nip portion is defined as a second direction, and a direction perpendicular to both the first direction and the second direction is defined as a third direction, a width of the nip portion in the second direction at both ends of the nip portion in the first direction is narrower than a width of the nip portion in the second direction at a center of the nip portion in the first direction, a width of the sliding member in the second direction at both ends of the nip portion is narrower than a width of the sliding member in the second direction at a center of the nip portion; A fixing device comprising:

20. The pressure member has a core and an elastic layer formed on an outer periphery of the core, The elastic layer is made of foam rubber. The fixing device according to claim 19 .

21. a rotatable endless fixing member; a heater that is disposed in an internal space of the fixing member and generates heat when energized; a sliding member disposed between the heater and an inner surface of the fixing member and sliding against the inner surface of the fixing member; a holding member for holding the heater and the sliding member; a pressing member disposed to sandwich the fixing member together with the sliding member and forming a nip portion between the pressing member and the fixing member; a fixing device that heats an image on a recording material by the fixing member while nipping and transporting the recording material at the nip portion, a longitudinal direction of the nip portion is defined as a first direction, a recording material conveying direction in the nip portion is defined as a second direction, and a direction perpendicular to both the first direction and the second direction is defined as a third direction, the fixing device further includes guide members that guide both ends of the fixing member in the first direction, a downstream end surface of the sliding member in the second direction is curved such that a central portion of the end surface in the first direction protrudes downstream in the second direction compared to both end portions of the end surface in the first direction; A fixing device comprising:

22. a rotatable endless fixing member; a heater that is disposed in an internal space of the fixing member and generates heat when energized; a sliding member disposed between the heater and an inner surface of the fixing member and sliding against the inner surface of the fixing member; a holding member for holding the heater and the sliding member; a pressing member disposed to sandwich the fixing member together with the sliding member and forming a nip portion between the pressing member and the fixing member; a fixing device that heats an image on a recording material by the fixing member while nipping and transporting the recording material at the nip portion, a longitudinal direction of the nip portion is defined as a first direction, a recording material conveying direction in the nip portion is defined as a second direction, and a direction perpendicular to both the first direction and the second direction is defined as a third direction, a downstream end surface of the sliding member in the second direction is curved such that both ends of the end surface in the first direction protrude downstream in the second direction compared to a central portion of the end surface in the first direction; A fixing device comprising:

23. a rotatable endless fixing member; a heater that is disposed in an internal space of the fixing member and generates heat when energized; a sliding member disposed between the heater and an inner surface of the fixing member and sliding against the inner surface of the fixing member; a holding member for holding the heater and the sliding member; a pressing member disposed to sandwich the fixing member together with the sliding member and forming a nip portion between the pressing member and the fixing member; a fixing device that heats an image on a recording material by the fixing member while nipping and transporting the recording material at the nip portion, a longitudinal direction of the nip portion is defined as a first direction, a recording material conveying direction in the nip portion is defined as a second direction, and a direction perpendicular to both the first direction and the second direction is defined as a third direction, the fixing device further includes a heat retention member disposed between the holding member and the heater in the third direction and configured to retain heat from the heater; The heat retaining member and the sliding member are in contact with each other. A fixing device comprising:

24. The heat retaining member and the sliding member are in surface contact with each other. The fixing device according to claim 23 .

25. a rotatable endless fixing member; a heater that is disposed in an internal space of the fixing member and generates heat when energized; a sliding member disposed between the heater and an inner surface of the fixing member and sliding against the inner surface of the fixing member; a holding member for holding the heater and the sliding member; a pressing member disposed to sandwich the fixing member together with the sliding member and forming a nip portion between the pressing member and the fixing member; a fixing device that heats an image on a recording material by the fixing member while nipping and transporting the recording material at the nip portion, a longitudinal direction of the nip portion is defined as a first direction, a recording material conveying direction in the nip portion is defined as a second direction, and a direction perpendicular to both the first direction and the second direction is defined as a third direction, the sliding member has a sliding portion that slides against the inner surface of the fixing member, and a heat retention portion that is disposed between the holding member and the heater in the third direction and that retains heat from the heater, and the sliding portion and the heat retention portion are integrally formed. A fixing device comprising:

26. The sliding portion and the heat retention portion are formed of a metal plate bent between the sliding portion and the heat retention portion, or a cylindrical metal member in which the sliding portion and the heat retention portion are continuous.

26. The fixing device according to claim 25.

27. a rotatable endless fixing member; a heater that is disposed in an internal space of the fixing member and generates heat when energized; a sliding member disposed between the heater and an inner surface of the fixing member and sliding against the inner surface of the fixing member; a holding member for holding the heater and the sliding member; a pressing member disposed to sandwich the fixing member together with the sliding member and forming a nip portion between the pressing member and the fixing member; a biasing member for applying pressure to the nip portion; a reinforcing member that reinforces the holding member and presses the holding member toward the pressing member by receiving a biasing force of the biasing member; a fixing device that heats an image on a recording material by the fixing member while nipping and transporting the recording material at the nip portion, Grease is applied between the heater and the sliding member, a longitudinal direction of the nip portion is defined as a first direction, a recording material conveying direction in the nip portion is defined as a second direction, and a direction perpendicular to both the first direction and the second direction is defined as a third direction, the sliding member has a rubbing portion that extends along the second direction and rubs against the inner surface of the fixing member, a first standing portion that stands from an upstream end of the rubbing portion in the second direction to a side moving away from the pressure member in the third direction, and a second standing portion that stands from a downstream end of the rubbing portion in the second direction to a side moving away from the pressure member in the third direction, The holding member has a first recess that receives the first upright portion and a second recess that receives the second upright portion, a 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; A fixing device comprising:

28. the reinforcing member has a first pressing portion that presses the holding member upstream of a center of the heater in the second direction, and a second pressing portion that presses the holding member 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 recess in the second direction.

28. The fixing device according to claim 27.

29. The holding member has a through hole formed therein, the through hole passing through the holding member from a bottom surface of the first recess or the second recess to an opposite side to the bottom surface in the third direction, and through which the grease can be introduced.

28. The fixing device according to claim 27.

30. an image forming unit that forms an image on a recording material using toner; The fixing device according to claim 1 , which fixes the image on the recording material; An image forming apparatus comprising:

Images