Fixing device

Abstract

To provide a fixing device capable of suppressing unevenness of an image.SOLUTION: A fixing device includes a tubular body, a heater unit, a frame, a guide member, a first contact portion, and a second contact portion. The heater unit is inside the tubular body and contacts the tubular body. The frame is inside the tubular body and supports the heater unit. The guide member is inside the tubular body and on a side opposite the heater unit across the frame. The guide member has a plurality of contact portions that is arranged in a longitudinal direction along an axial direction of the tubular body and that can contact the tubular body. The first contact portion of the plurality of contact portions is in an end portion in the longitudinal direction. The second contact portion of the plurality of contact portions is in a central portion in the longitudinal direction. The second contact portion has a heat transfer coefficient to the tubular body that is less than a heat transfer coefficient of the first contact portion to the tubular body.SELECTED DRAWING: Figure 7

Description

[Technical Field]

[0001] FIELD An embodiment of the present invention relates to a fixing device. [Background technology]

[0002] Image forming apparatuses that form images on sheets are used. Image forming apparatuses have a fixing device. The fixing device applies heat and pressure to the toner image on the sheet to fix the toner image to the sheet. A fixing device that can suppress unevenness in the image is required. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2019-164181 Summary of the Invention [Problem to be solved by the invention]

[0004] The problem to be solved by the present invention is to provide a fixing device that can suppress unevenness in an image. [Means for solving the problem]

[0005] The fixing device of the embodiment has a cylindrical body, a heater unit, a frame, a guide member, a first contact portion, and a second contact portion. The heater unit is located inside the cylindrical body and contacts the cylindrical body. The frame is located inside the cylindrical body and supports the heater unit via a support member. The guide member is located inside the cylindrical body and on the opposite side of the frame from the heater unit. The guide member has multiple contact portions arranged in a longitudinal direction along the axial direction of the cylindrical body and capable of contacting the cylindrical body. The first contact portion is located at an end of the multiple contact portions in the longitudinal direction. The second contact portion is located at a central portion of the multiple contact portions in the longitudinal direction. The second contact portion has a lower heat transfer rate between the cylindrical body and the second contact portion than between the first contact portion and the cylindrical body. When the direction in which the heater unit and the frame are aligned is defined as a third direction, the thickness of the support member in the third direction at the central portion in the longitudinal direction is greater than the thickness of the support member in the third direction at the end portions in the longitudinal direction. With a nip formed between the heater unit and the cylindrical body and the pressure roller, the frame and the guide member are curved along the surface of the support member on the frame side. [Brief explanation of the drawings]

[0006] [Figure 1] FIG. 1 is a schematic diagram illustrating the configuration of an image processing device. [Figure 2] FIG. [Figure 3] FIG. 5 is a cross-sectional view of the heater unit taken along line III-III in FIG. 4. [Figure 4] FIG. [Figure 5] FIG. 3 is a cross-sectional view of the fixing device taken along line VV in FIG. 2. [Figure 6] FIG. [Figure 7] FIG. 3 is a plan view of a guide member according to the first embodiment. [Figure 8] 8 is a cross-sectional view taken along line VIII-VIII in FIG. 7. [Figure 9] FIG. 10 is a plan view of a guide member according to a second embodiment. [Figure 10] FIG. 10 is a plan view of a guide member according to a third embodiment. [Figure 11] 11 is a cross-sectional view taken along line XI-XI in FIG. DETAILED DESCRIPTION OF THE INVENTION

[0007] Hereinafter, a fixing device according to an embodiment will be described with reference to the drawings. FIG. 1 is a schematic diagram of an image forming apparatus. The image forming apparatus 1 performs a process of forming an image on a sheet S. The sheet S may be paper. The image forming apparatus 1 includes a housing 10, a scanner section 2, an image forming unit 3, a sheet supply section 4, a conveyance section 5, a reversing unit 9, a tray 7, a control panel 8, and a control section 6.

[0008] The housing 10 forms the outer shape of the image forming apparatus 1 . The scanner unit 2 reads image information of the object to be copied as light and darkness, and generates an image signal. The scanner unit 2 outputs the generated image signal to the image forming unit 3. The image forming unit 3 forms a toner image based on an image signal from the scanner unit 2 or an external device. The toner image is an image formed with toner or other materials. The image forming unit 3 transfers the toner image onto the surface of the sheet S. The image forming unit 3 applies heat and pressure to the toner image on the surface of the sheet S to fix the toner image to the sheet S.

[0009] The sheet supply section 4 supplies the sheets S one by one to the conveyance section 5 in synchronization with the timing at which the image forming unit 3 forms a toner image. The sheet supply section 4 includes a sheet storage section 20 and a pickup roller . The sheet storage section 20 stores sheets S of a predetermined size and type. The pickup roller 21 picks up the sheets S one by one from the sheet storage unit 20. The pickup roller 21 supplies the picked-up sheets S to the conveying unit 5.

[0010] The conveying section 5 conveys the sheet S supplied from the sheet supplying section 4 to the image forming unit 3. The conveying section 5 includes a conveying roller 23 and a registration roller 24. The conveying roller 23 conveys the sheet S supplied from the pickup roller 21 to the registration roller 24. The conveying roller 23 abuts the leading edge of the sheet S in the conveying direction against the nip RN of the registration roller 24. The registration rollers 24 bend the sheet S at the nip RN to adjust the position of the leading edge of the sheet S in the conveying direction. The registration rollers 24 convey the sheet S in accordance with the timing at which the image forming unit 3 transfers a toner image onto the sheet S.

[0011] The image forming unit 3 will now be described. The image forming unit 3 includes a plurality of image forming sections F, a laser scanning unit 26, an intermediate transfer belt 27, a transfer section 28, and a fixing device 30. The image forming unit F has a photosensitive drum D. The image forming unit F forms a toner image on the photosensitive drum D in accordance with an image signal. The multiple image forming units FY, FM, FC, and FK form toner images using yellow, magenta, cyan, and black toner, respectively.

[0012] The charger charges the surface of the photosensitive drum D. The developer contains developer containing yellow, magenta, cyan, and black toner. The developer develops the electrostatic latent image on the photosensitive drum D to form a toner image of each color on the photosensitive drum D.

[0013] The laser scanning unit 26 scans the charged photosensitive drum D with laser light L to expose the photosensitive drum D. The laser scanning unit 26 exposes the photosensitive drum D of each color image forming unit FY, FM, FC, FK with separate laser light LY, LM, LC, LK to form an electrostatic latent image on the photosensitive drum D.

[0014] The toner image on the surface of the photosensitive drum D is primarily transferred onto the intermediate transfer belt 27. The transfer unit 28 transfers the toner image that has been primarily transferred onto the intermediate transfer belt 27 onto the surface of the sheet S at the secondary transfer position. The fixing device 30 applies heat and pressure to the toner image transferred onto the sheet S to fix the toner image onto the sheet S.

[0015] The reversing unit 9 reverses the sheet S to form an image on the back side of the sheet S. The reversing unit 9 reverses the sheet S discharged from the fixing device 30 by a switchback. The reversing unit 9 conveys the reversed sheet S toward the registration rollers 24. The tray 7 holds the sheet S on which an image has been formed and discharged. The control panel 8 is a part of an input unit through which an operator inputs information for operating the image forming apparatus 1. The control panel 8 has a touch panel and various hard keys. The control unit 6 controls the operations of the various components of the image forming apparatus 1.

[0016] The fixing device 30 will now be described in detail. 2 is a front cross-sectional view of the fixing device 30. The fixing device 30 includes a pressure roller 31 and a heating roller 34. A nip N is formed between the pressure roller 31 and the heating roller 34.

[0017] In this application, the z direction, x direction, and y direction are defined as follows: The z direction is the thickness direction of the substrate 41, and is the direction in which the heating roller 34 and the pressure roller 31 are aligned. The +z direction is the direction from the heating roller 34 toward the pressure roller 31. The x direction (first direction) is the widthwise direction of the substrate 41, and is the conveyance direction of the sheet S at the nip N. The +x direction is the downstream side of the conveyance direction of the sheet S. The y direction (second direction) is the lengthwise direction of the substrate 41, and is the axial direction of the tubular film 35 of the heating roller 34.

[0018] The pressure roller 31 applies pressure to the toner image on the sheet S that has entered the nip N. The pressure roller 31 has a core metal 32 and an elastic layer 33. The configuration of the pressure roller 31 is not limited to the above, and various configurations are possible.

[0019] The core metal 32 is formed into a cylindrical shape from a metal material such as stainless steel. The elastic layer 33 is formed from an elastic material such as silicone rubber. The elastic layer 33 has a constant thickness on the outer circumferential surface of the core metal 32. A release layer made of a resin material such as PFA (tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer) may be provided on the outer circumferential surface of the elastic layer 33.

[0020] The pressure roller 31 is driven to rotate by a motor. When the pressure roller 31 rotates with the nip N formed, the cylindrical film 35 of the heating roller 34 is rotated accordingly. The pressure roller 31 rotates with the sheet S in the nip N, thereby conveying the sheet S in the conveying direction W.

[0021] The heating roller 34 heats the toner image on the sheet S that has entered the nip N. The heating roller 34 has a cylindrical film (cylindrical body) 35, a heater unit 40, a heat transfer member 48, a support member 50, a frame 36, and temperature-sensing elements 37-39. The configuration of the heating roller 34 is not limited to the above, and various configurations are possible.

[0022] The cylindrical film 35 has a cylindrical shape. The cylindrical film 35 has, in order from the inner periphery, a base layer, an elastic layer, and a release layer. The base layer is made of a resin material such as polyimide (PI) to reduce heat capacity. The elastic layer is made of an elastic material such as silicone rubber. The release layer is made of a material such as PFA resin.

[0023] Heater unit 40 is located inside tubular film 35. The surface of heater unit 40 in the +z direction contacts the inner surface of tubular film 35 via grease. Fig. 3 is a cross-sectional view of the heater unit taken along line III-III in Fig. 4. Fig. 4 is a bottom view (viewed from the +z direction) of the heater unit. Heater unit 40 has a substrate 41, a heating element 45, and wiring 46.

[0024] Substrate 41 is made of a metal material such as stainless steel or a ceramic material such as aluminum nitride. As shown in FIG. 4, substrate 41 is in the form of a long, narrow rectangular plate. The longitudinal direction of substrate 41 is the axial direction of tubular film 35. As shown in FIG. 3, insulating layer 42 made of a glass material or the like is formed on the surface of substrate 41 in the +z direction. Similar to insulating layer 42 formed in the +z direction of substrate 41, an insulating layer may be formed in the -z direction of substrate 41.

[0025] Heating element 45 is made of a silver-palladium alloy or the like. Heating element 45 generates heat when electricity is applied. Heating element 45 and wiring 46 are arranged on the surface of substrate 41 in the +z direction via insulating layer 42. Protective layer 43 is formed of a glass material or the like so as to cover heating element 45 and wiring 46. Similar to protective layer 43 formed in the +z direction of substrate 41, a protective layer may also be formed in the -z direction of substrate 41.

[0026] As shown in FIG. 4, the heating element 45 has a central heating element and a pair of end heating elements. The central heating element is located in the center in the y direction. The pair of end heating elements are located on both ends of the central heating element in the y direction. The central heating element and the pair of end heating elements are controlled to generate heat independently of each other. The pair of end heating elements are controlled to generate heat in the same way.

[0027] 2 is made of a metal material with high thermal conductivity, such as copper. The outer shape of the heat transfer member 48 is the same as that of the substrate 41 of the heater unit 40. The heat transfer member 48 is disposed in the −z direction of the substrate 41 and is in contact with the substrate 41.

[0028] The support member 50 is made of a resin material such as a liquid crystal polymer. The support member 50 covers both sides of the heater unit 40 in the x direction and in the -z direction. The support member 50 supports the heater unit 40 in the -z direction of the heater unit 40 via the heat transfer member 48. The support member 50 supports the inner circumferential surface of the tubular film 35 at both ends of the heater unit 40 in the x direction.

[0029] The support member 50 has a pair of ribs 51, 52, an upstream rib 51 and a downstream rib 52. The upstream rib 51 extends upstream in the rotation direction of the tubular film 35. The downstream rib 52 extends downstream in the rotation direction of the tubular film 35. The pair of ribs 51, 52 can abut against the inner surface of the tubular film 35. The pair of ribs 51, 52 maintain the tubular film 35 in a predetermined shape. The pair of ribs 51, 52 are plate-shaped with the thickness direction in the y direction. Multiple upstream ribs 51 and multiple downstream ribs 52 are aligned in the y direction. The upstream ribs 51 and downstream ribs 52 may be located at different positions in the y direction. This reduces temperature unevenness in the fixing device 30.

[0030] The frame 36 is made of a steel plate material or the like. The frame 36 is located inside the tubular film 35. The cross section of the frame 36 perpendicular to the y direction is U-shaped. The frame 36 is attached to the support member 50 in the -z direction so that the opening of the U is closed by the support member 50. The frame 36 extends in the y direction. Both ends of the frame 36 in the y direction are fixed to the housing 10 of the image forming apparatus 1. The frame 36 supports the heater unit 40 via the support member 50 and the heat transfer member 48.

[0031] The temperature-sensing elements 37-39 are a heater thermometer 37, a thermostat 38, and a film thermometer 39. The heater thermometer 37 and the thermostat 38 are located in the -z direction of the heater unit 40, sandwiching a heat transfer member 48 between them. The heater thermometer 37 measures the temperature of the heater unit 40 via the heat transfer member 48. The thermostat 38 cuts off power to the heating element 45 when the temperature of the heater unit 40 detected via the heat transfer member 48 exceeds a predetermined temperature. The film thermometer 39 comes into contact with the inner surface of the tubular film 35 and measures the temperature of the tubular film 35. The film thermometer 39 measures the temperature of the tubular film 35 at positions in the y direction corresponding to the central heating element and the end heating elements.

[0032] The guide member 60 is formed from a resin material such as a liquid crystal polymer. The guide member 60 is located inside the tubular film 35. The guide member 60 is located on the opposite side of the frame 36 from the heater unit 40. The guide member 60 covers approximately half of the +x-direction surface of the frame 36 in the -z direction and the entire -z-direction surface. The guide member 60 has a base portion 61 and a rib 62. The base portion 61 is located in the +x direction and the −z direction of the frame 36. The base portion 61 is fixed to the frame 36. The base portion 61 is long in the y direction.

[0033] The ribs (contact portions) 62 are capable of coming into contact with the tubular film 35. The ribs 62 protrude radially outward from the base portion 61 of the tubular film 35. The ribs 62 extend in the circumferential direction of the tubular film 35. The ribs 62 come into contact with the tubular film 35, thereby supporting the tubular film 35. The trajectory of the tubular film 35 is ensured even when the tubular film 35 is formed thin using a low-rigidity resin material.

[0034] 6 is a perspective view of the guide member. The rib 62 is plate-shaped with the thickness direction being the y direction. A plurality of ribs 62 are aligned in the y direction. The plurality of ribs 62 may be located at positions in the y direction different from the upstream rib 51 and downstream rib 52 of the support member 50 shown in FIG. 2. This suppresses temperature unevenness in the fixing device 30.

[0035] As shown in FIG. 6, the base portion 61 has a recess 63. The recess 63 is located at the center of the base portion 61 in the y direction and at the end in the +y direction. The recess 63 is located at the end in the +x direction of the base portion 61 and is recessed in the -x direction. FIG. 2 is a cross-sectional view taken along line II-II in FIG. 6. The film thermometer 39 is disposed inside the recess 63. As shown in FIG. 6, the multiple ribs 62 include a pair of recess ribs 64. The pair of recess ribs 64 is located on both sides of the recess 63 in the y direction. The pair of recess ribs 64 contact the tubular film 35, thereby stabilizing the position of the tubular film 35 at the position of the film thermometer 39. This improves the accuracy of temperature measurement by the film thermometer 39.

[0036] 5 is a cross-sectional view of the fixing device taken along line VV in FIG. 2. The pressure roller 31 has an inverted crown shape. The diameter of the pressure roller 31 at the center in the y direction is smaller than the diameters at both ends in the y direction. This prevents wrinkles in the sheet passing through the nip N of the fixing device 30.

[0037] The support member 50 of the heating roller 34 has a crown shape. The thickness of the support member 50 in the z direction at the center in the y direction is greater than the thickness in the z direction at both ends in the y direction. The width in the x direction of the nip N formed between the pressure roller 31 and the heating roller 34 is uniform in the y direction. This makes the fixing performance of the fixing device 30 uniform in the y direction.

[0038] The frame 36 is connected to the support member 50 via a positioning member 55. The positioning member 55 is attached to the center of the frame 36 in the y direction. The locking claws 56 of the support member 50 are inserted into the locking holes of the positioning member 55. The frame 36 curves along the surface of the support member 50 in the -z direction. The frame 36 curves so that the center in the y direction is convex in the -z direction. In contrast, the end of the tubular film 35 in the -z direction is not restrained by other members and is therefore parallel to the y direction.

[0039] The guide member 60 is curved in the same manner as the frame 36. The guide member 60 is curved so that the central portion in the y direction is convex in the -z direction. It is assumed that the shapes of the multiple ribs 62 of the guide member 60 are all the same. In this case, the tip of the second rib 66 in the central portion in the y direction is positioned further in the -z direction than the tip of the first rib 65 at the end portion in the y direction. Second Rib 66 The distance in the z direction between the tip of the nozzle and the cylindrical film 35 is 1st rib 65 The distance between the tip of the rib 62 and the tubular film 35 in the z direction is smaller than the distance between the tip of the rib 62 and the tubular film 35 in the z direction. The second rib 66 is more likely to come into contact with the tubular film 35 than the first rib 65. The contact between the multiple ribs 62 and the tubular film 35 transfers heat from the tubular film 35 to the multiple ribs 62. The temperature of the center of the tubular film 35 in the y direction becomes lower than the temperature of the end portions in the y direction. This causes temperature unevenness in the fixing device 30, resulting in uneven gloss in the image formed on the sheet.

[0040] (First embodiment) 7 is a plan view of the guide member of the first embodiment. The guide member 60 has a plurality of ribs 62, which are first ribs (first contact portions) 65 and second ribs (second contact portions) 66. Three first ribs 65 are arranged at each end in the y direction. Nine second ribs 66 are arranged in the center in the y direction. The numbers of first ribs 65 and second ribs 66 are not limited to these.

[0041] The first rib 65 and the second rib 66 have the same width in the y direction. 8 is a cross-sectional view taken along line VIII-VIII in FIG. 7. The heights of the first rib 65 and the second rib 66 in the radial direction of the tubular film 35 are equal. The length of the second rib 66 in the circumferential direction of the tubular film 35 is shorter than the first rib 65. The length of the ribs 65, 66 in the circumferential direction of the tubular film 35 is the outer periphery of the ribs 65, 66. The length of the second rib 66 is approximately half the length of the first rib 65. The contact area between the second rib 66 and the tubular film 35 is smaller than the contact area between the first rib 65 and the tubular film 35. Ease of heat transfer is a gap between the first rib 65 and the tubular film 35 Ease of heat transfer Smaller than.

[0042] As described above in detail, the fixing device 30 of this embodiment has a tubular film 35, a heater unit 40, a frame 36, a guide member 60, a first rib 65, and a second rib 66. The heater unit 40 is located inside the tubular film 35 and contacts the tubular film 35. The frame 36 is located inside the tubular film 35 and supports the heater unit 40. The guide member 60 is located inside the tubular film 35, on the opposite side of the frame 36 from the heater unit 40. The guide member 60 has multiple ribs 62 that are aligned in the y direction and can contact the tubular film 35. The first rib 65 is located at the end of the multiple ribs 62 in the y direction. The second rib 66 is located in the center of the multiple ribs 62 in the y direction. The second rib 66 is located between the tubular film 35 and the heater unit 40. Ease of heat transferis smaller than the first rib 65.

[0043] As described above, the guide member 60 is curved so that the central portion in the y direction is convex in the -z direction. Ease of heat transfer However, between the first rib 65 and the tubular film 35 Ease of heat transfer Heat transfer from tubular film 35 to ribs 62 is uniform in the y direction. Temperature unevenness in fixing device 30 is suppressed, and image unevenness is also suppressed.

[0044] The contact area between the second rib 66 and the tubular film 35 is smaller than the contact area between the first rib 65 and the tubular film 35 . As a result, the gap between the second rib 66 and the tubular film 35 Ease of heat transfer However, between the first rib 65 and the tubular film 35 Ease of heat transfer It becomes smaller.

[0045] In the guide member 60 of the second embodiment, the length of the second rib 66 in the circumferential direction is shorter than the length of the first rib 65 in the circumferential direction. As a result, the contact area between the second ribs 66 and the tubular film 35 is smaller than the contact area between the first ribs 65 and the tubular film 35.

[0046] (Second embodiment) 9 is a plan view of a guide member of the second embodiment. The guide member 60 of the second embodiment differs from the first embodiment in that the widths in the y direction of the first rib 65 and the second rib 67 are different. Explanation of the second embodiment regarding the similarities with the first embodiment may be omitted.

[0047] The heights of the first rib 65 and the second rib 67 in the radial direction of the tubular film 35 are equal. The lengths of the first rib 65 and the second rib 67 in the circumferential direction of the tubular film 35 are equal. The width of the second rib 67 in the y direction is narrower than that of the first rib 65. The width of the second rib 67 is about half the width of the first rib 65. The contact area between the second rib 67 and the tubular film 35 is smaller than the contact area between the first rib 65 and the tubular film 35. Ease of heat transfer is a gap between the first rib 65 and the tubular film 35 Ease of heat transfer Smaller than.

[0048] As described above, the width of second rib 67 in the y direction is narrower than the width of first rib 65 in the y direction. Heat is transferred uniformly in the y direction from tubular film 35 to multiple ribs 62. Temperature unevenness in fixing device 30 is suppressed, and image unevenness is also suppressed.

[0049] (Third embodiment) 10 is a plan view of a guide member of the third embodiment. Guide member 60 of the third embodiment differs from the first embodiment in that the heights of first ribs 65 and second ribs 68 in the radial direction of tubular film 35 are different. Explanation of the third embodiment regarding the same aspects as the first embodiment may be omitted.

[0050] The first rib 65 and the second rib 68 have the same width in the y direction. 11 is a cross-sectional view taken along line XI-XI in FIG. 10. The lengths of the first rib 65 and the second rib 68 in the circumferential direction of the tubular film 35 are equal. The height of the second rib 68 in the radial direction of the tubular film 35 is lower than the first rib 65. The height of the ribs 65, 68 in the radial direction of the tubular film 35 is the distance from the central axis of the tubular film 35 to the outer periphery of the ribs 65, 68. The heights of the ribs 65, 68 are compared at positions in the same phase in the circumferential direction of the tubular film 35. The contact area between the second rib 68 and the tubular film 35 is smaller than the contact area between the first rib 65 and the tubular film 35. Ease of heat transfer is a gap between the first rib 65 and the tubular film 35 Ease of heat transferSmaller than.

[0051] As described above, the height of the second ribs 68 in the radial direction of the tubular film 35 is lower than the height of the first ribs 65 in the radial direction of the tubular film 35. Heat is transferred uniformly from the tubular film 35 to the multiple ribs 62 in the y direction. This reduces temperature unevenness in the fixing device 30 and reduces image unevenness.

[0052] (Fourth embodiment) The guide member 60 of the fourth embodiment differs from the first embodiment in that the materials of the first rib (first contact portion) 65 and the second rib (second contact portion) 69 are different. Explanation of the fourth embodiment regarding the similarities with the first embodiment may be omitted.

[0053] The first rib 65 and the second rib 69 have the same shape. The contact area between the second rib 69 and the tubular film 35 is the same as the contact area between the first rib 65 and the tubular film 35. The base portion 61 and the first rib 65 of the guide member 60 are integrally formed from a resin material such as a liquid crystal polymer. The second rib 69 is formed separately from the base portion 61. The second rib 69 is formed from a material having a lower thermal conductivity than the first rib 65. For example, the second rib 69 is formed from a resin material such as PFA (tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer). Ease of heat transfer is a gap between the first rib 65 and the tubular film 35 Ease of heat transfer Smaller than.

[0054] For example, an attachment pin is formed on the second rib 69, and an attachment hole is formed in the base portion 61. The attachment pin of the second rib 69 is inserted into the attachment hole of the base portion 61, and the second rib 69 is fixed to the base portion 61. The method of attaching the second rib 69 to the base portion 61 is not limited to this.

[0055] As described above, the thermal conductivity of the material of second rib 69 is lower than the thermal conductivity of the material of first rib 65. Heat is transferred uniformly in the y direction from tubular film 35 to multiple ribs 62. Temperature unevenness in fixing device 30 is suppressed, and image unevenness is also suppressed.

[0056] In the fourth embodiment, the entire second rib 69 is made of a different material than the first rib 65. In contrast, the material of the outer peripheral surface of the second rib 69, which can come into contact with the tubular film 35, may be different from the material of the outer peripheral surface of the first rib 65. For example, the outer peripheral surface of the second rib 69 may be coated with a material with low thermal conductivity, such as PFA resin. In this case, the entire guide member 60, including the second rib 69, is integrally formed from a resin material, such as a liquid crystal polymer.

[0057] The second ribs 66-69 in the first to fourth embodiments are different from the first rib 65. Alternatively, a second rib that combines the differences of the first to fourth embodiments may be adopted.

[0058] The guide member 60 of the embodiment has a plurality of ribs 62 between the tubular film 35. Ease of heat transfer The guide member has two types of ribs, a first rib 65 and a second rib 66-69. Ease of heat transfer The guide member may have three or more types of ribs. Ease of heat transfer The ribs may have a shape that changes gradually in the y direction.

[0059] The guide member 60 of the embodiment has a first rib 65 as the first contact portion and second ribs 66-69 as the second contact portion. In contrast, the guide member may have a first contact surface as the first contact portion and a second contact surface as the second contact portion. For example, the first contact surface and the second contact surface in the y direction may be separated by a groove or the like.

[0060] The image forming apparatus 1 of the embodiment is a type of image processing device, and the fixing device 30 is a type of heating device. In contrast, the image processing device may be an erasing device, and the heating device may be an erasing unit. The erasing device performs a process of erasing (erasing) an image formed on a sheet with erasing toner. The erasing unit heats and erases the erasing toner image formed on the sheet passing through the nip.

[0061] According to at least one embodiment described above, the gap between the tubular film 35 Ease of heat transfer However, between the first rib 65 and the tubular film 35 Ease of heat transfer The smaller second ribs 66-69 are provided, which can suppress unevenness in the image.

[0062] Although several embodiments of the present invention have been described, these embodiments are presented as examples and are not intended to limit the scope of the invention. These embodiments can be implemented in various other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their modifications are included within the scope and spirit of the invention, as well as within the scope of the invention described in the claims and their equivalents. [Explanation of symbols]

[0063] 30...fixing device, 35...cylindrical film (cylindrical body), 36...frame, 40...heater unit, 62...rib (contact portion), 65...first rib (first contact portion), 66-69...second ribs (second contact portions).

Claims

1. A cylindrical body; a heater unit located inside the cylindrical body and in contact with the cylindrical body; a frame located inside the cylindrical body and supporting the heater unit via a support member; a guide member located inside the cylindrical body, on the opposite side of the frame from the heater unit, the guide member having a plurality of contact portions arranged in a longitudinal direction along the axial direction of the cylindrical body and capable of coming into contact with the cylindrical body; a first contact portion at an end in the longitudinal direction of the plurality of contact portions; a second contact portion that is located at a center portion in the longitudinal direction among the plurality of contact portions and has a lower heat transferability between the second contact portion and the cylindrical body than between the first contact portion and the cylindrical body, a thickness of the support member in the third direction at a central portion in the longitudinal direction is greater than a thickness of the support member in the third direction at an end portion in the longitudinal direction, when a direction in which the heater unit and the frame are aligned is defined as a third direction; the frame and the guide member are curved along the surface of the support member on the frame side in a state where a nip is formed between the heater unit and the cylindrical body and the pressure roller; Fixing device.

2. a contact area between the second contact portion and the cylindrical body is smaller than a contact area between the first contact portion and the cylindrical body; The fixing device according to claim 1 .

3. the plurality of contact portions are a plurality of ribs that are aligned in the longitudinal direction, protrude in a radial direction of the cylindrical body, and extend in a circumferential direction of the cylindrical body, the first contact portion is a first rib located at an end of the plurality of ribs in the longitudinal direction, the second contact portion is a second rib located at a center portion in the longitudinal direction among the plurality of ribs, The length of the second rib in the circumferential direction is shorter than the length of the first rib in the circumferential direction. The fixing device according to claim 2 .

4. the plurality of contact portions are a plurality of ribs that are aligned in the longitudinal direction, protrude in a radial direction of the cylindrical body, and extend in a circumferential direction of the cylindrical body, the first contact portion is a first rib located at an end of the plurality of ribs in the longitudinal direction, the second contact portion is a second rib located at a center portion in the longitudinal direction among the plurality of ribs, The width of the second rib in the longitudinal direction is narrower than the width of the first rib in the longitudinal direction. The fixing device according to claim 2 .

5. the plurality of contact portions are a plurality of ribs that are aligned in the longitudinal direction, protrude in a radial direction of the cylindrical body, and extend in a circumferential direction of the cylindrical body, the first contact portion is a first rib located at an end of the plurality of ribs in the longitudinal direction, the second contact portion is a second rib located at a center portion in the longitudinal direction among the plurality of ribs, a height of the second rib in the radial direction is lower than a height of the first rib in the radial direction; The fixing device according to claim 2 .

6. the thermal conductivity of the material of the second contact portion is lower than the thermal conductivity of the material of the first contact portion; The fixing device according to claim 1 .

Images