Fixing device

Abstract

The objective is to provide a fixing device that can suppress image inconsistencies. [Solution] The fixing device of the embodiment comprises 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 is in contact with the cylindrical body. The frame is located inside the cylindrical body and supports the heater unit. The guide member is located inside the cylindrical body and is on the opposite side of the heater unit, with the frame in between. The guide member has a plurality of contact portions arranged in the longitudinal direction along the axial direction of the cylindrical body and capable of contacting the cylindrical body. The first contact portion is located at the end of the plurality of contact portions in the longitudinal direction. The second contact portion is located in the central part of the plurality of contact portions in the longitudinal direction. The heat transfer coefficient between the second contact portion and the cylindrical body is smaller than the heat transfer coefficient between the first contact portion and the cylindrical body.

Description

Technical Field

[0001] Embodiments of the present invention relate to a fixing device.

Background Art

[0002] An image forming apparatus for forming an image on a sheet is used. The image forming apparatus has a fixing device. The fixing device heats and presses the toner image on the sheet to fix the toner image on the sheet. There is a need for a fixing device that can suppress unevenness in the image.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems 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 the image.

Means for Solving the Problems

[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 inside the cylindrical body and contacts the cylindrical body. The frame is inside the cylindrical body and supports the heater unit. The guide member is inside the cylindrical body and is on the opposite side of the heater unit with the frame interposed therebetween. The guide member has a plurality of contact portions that are arranged in the longitudinal direction along the axial direction of the cylindrical body and can contact the cylindrical body. The first contact portion is at an end in the longitudinal direction among the plurality of contact portions. The second contact portion is at the center in the longitudinal direction among the plurality of contact portions. The heat transfer rate between the second contact portion and the cylindrical body is smaller than the heat transfer rate between the first contact portion and the cylindrical body.

Brief Description of the Drawings

[0006] [Figure 1] A schematic diagram of the image processing device. [Figure 2] Front cross-sectional view of the fixing device. [Figure 3] Cross-sectional view of the heater unit along line III-III in Figure 4. [Figure 4] Bottom view of the heater unit. [Figure 5] Figure 2 shows a cross-sectional view of the fixing device in the VV line. [Figure 6] Perspective view of the guide member. [Figure 7] A plan view of the guide member according to the first embodiment. [Figure 8] Cross-sectional view along line VIII-VIII in Figure 7. [Figure 9] A plan view of the guide member of the second embodiment. [Figure 10] A plan view of the guide member according to the third embodiment. [Figure 11] Figure 10 shows a cross-sectional view along the line XI-XI. [Modes for carrying out the invention]

[0007] The fixing device of the embodiment will be described below with reference to the drawings. Figure 1 is a schematic diagram of the image forming apparatus. The image forming apparatus 1 performs the 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 unit 2, an image forming unit 3, a sheet supply unit 4, a transport unit 5, an inversion unit 9, a tray 7, a control panel 8, and a control unit 6.

[0008] The housing 10 forms the outer shape of the image forming apparatus 1. The scanner unit 2 reads the image information of the object to be copied as brightness 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 source. The toner image is an image formed from 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 heats and pressurizes the toner image on the surface of the sheet S to fix the toner image to the sheet S.

[0009] The sheet supply unit 4 supplies sheets S one by one to the transport unit 5 in accordance with the timing at which the image forming unit 3 forms the toner image. The sheet supply unit 4 includes a sheet storage unit 20 and a pickup roller 21. The seat storage section 20 stores seats S of a predetermined size and type. The pickup roller 21 removes the sheets S one by one from the sheet storage section 20. The pickup roller 21 supplies the removed sheets S to the conveying section 5.

[0010] The transport unit 5 transports the sheet S supplied from the sheet supply unit 4 to the image forming unit 3. The transport unit 5 has a transport roller 23 and a registration roller 24. The conveyor roller 23 transports the sheet S supplied from the pickup roller 21 to the register roller 24. The conveyor roller 23 abuts the leading edge of the sheet S in the transport direction against the nip RN of the register roller 24. The registration roller 24 adjusts the position of the leading edge of the sheet S in the transport direction by bending the sheet S at the nip RN. The registration roller 24 transports the sheet S in accordance with the timing at which the image forming unit 3 transfers the toner image to 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 corresponding to an image signal on the photosensitive drum D. The plurality of image forming units FY, FM, FC, FK form toner images using yellow, magenta, cyan, and black toners, respectively.

[0012] The charger charges the surface of the photosensitive drum D. The developing unit accommodates a developer containing yellow, magenta, cyan, and black toners. The developing unit 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 drums D of the image forming units FY, FM, FC, FK of each color with separate laser lights LY, LM, LC, LK to form an electrostatic latent image.

[0014] The toner image on the surface of the photosensitive drum D is primarily transferred to the intermediate transfer belt 27. The transfer unit 28 transfers the toner image primarily transferred onto the intermediate transfer belt 27 onto the surface of the sheet S at the secondary transfer position. The fixing device 30 heats and presses 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 surface of the sheet S. The reversing unit 9 reverses the front and back of the sheet S discharged from the fixing device 30 by a switchback. The reversing unit 9 conveys the reversed sheet S toward the registration roller 24. The tray 7 places the sheet S on which an image is formed and discharged. The control panel 8 is a part of the input unit for the operator to input 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 each part of the image forming apparatus 1.

[0016] The fixing device 30 will be explained in detail. Figure 2 is a front cross-sectional view of the fixing device. 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, x, and y directions 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 short-side direction of the substrate 41 and is the conveying direction of the sheet S at the nip N. The +x direction is the downstream side of the conveying direction of the sheet S. The y direction (second direction) is the longitudinal 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 can be configured in various ways.

[0019] The core metal 32 is formed in 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 certain thickness on the outer surface of the core metal 32. The release layer may be made of a resin material such as PFA (tetrafluoroethylene perfluoroalkyl vinyl ether copolymer) and may be on the outer 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 rotates in response. The pressure roller 31 rotates with the sheet S on 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 includes a tubular film (tubular 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 can be configured in various ways.

[0022] The tubular film 35 is cylindrical. The tubular film 35 has, in order from the inner circumference, 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] The heater unit 40 is located inside the tubular film 35. The surface of the heater unit 40 in the +z direction is in contact with the inner surface of the tubular film 35 via grease. Figure 3 is a cross-sectional view of the heater unit along line III-III in Figure 4. Figure 4 is a bottom view of the heater unit (viewed from the +z direction). The heater unit 40 includes a substrate 41, a heating element 45, and wiring 46.

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

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

[0026] As shown in Figure 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 at both ends of the central heating element in the y-direction. The heating of the central heating element and the pair of end heating elements is controlled independently of each other. The heating of the pair of end heating elements is controlled similarly.

[0027] The heat transfer member 48 shown in Figure 2 is made of a metal material with high thermal conductivity, such as copper. The external shape of the heat transfer member 48 is equivalent to that of the substrate 41 of the heater unit 40. The heat transfer member 48 is positioned in the -z direction of the substrate 41 and is in contact with the substrate 41.

[0028] The support member 50 is formed from 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 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 and 52, consisting of an upstream rib 51 and a downstream rib 52. The upstream rib 51 extends upstream of the tubular film 35 in the direction of rotation. The downstream rib 52 extends downstream of the tubular film 35 in the direction of rotation. The pair of ribs 51 and 52 can contact the inner surface of the tubular film 35. The pair of ribs 51 and 52 hold the tubular film 35 in a predetermined shape. The pair of ribs 51 and 52 are plate-shaped with the y-direction as the thickness direction. Multiple upstream ribs 51 and multiple downstream ribs 52 are arranged in the y-direction. The upstream ribs 51 and downstream ribs 52 may be in different positions in the y-direction. This suppresses temperature unevenness in the fixing device 30.

[0030] The frame 36 is formed from a steel plate 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 mounted on the support member 50 in the -z direction such that the support member 50 closes the U-shaped opening. 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 thermostat 38 are located in the -z direction of the heater unit 40, with the heat transfer member 48 in between. The heater thermometer 37 measures the temperature of the heater unit 40 via the heat transfer member 48. The thermostat 38 cuts off the power supply 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 contacts 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 element.

[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 heater unit 40, across the frame 36. The guide member 60 covers approximately half of the -z direction surface of the frame 36 in the +x direction, and the entire -z direction surface. The guide member 60 has a base portion 61 and ribs 62. The base portion 61 is located in the +x and -z directions of the frame 36. The base portion 61 is fixed to the frame 36. The base portion 61 is elongated in the y direction.

[0033] The rib (contact portion) 62 is capable of contacting the tubular film 35. The rib 62 protrudes radially outward from the base portion 61 of the tubular film 35. The rib 62 extends circumferentially around the tubular film 35. The tubular film 35 is supported by the contact of the rib 62 with the tubular film 35. Even if the tubular film 35 is formed thinly using a low-rigidity resin material, a trajectory for the tubular film 35 is ensured.

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

[0035] As shown in Figure 6, the base portion 61 has a recess 63. The recess 63 is located in 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 of the base portion 61 in the +x direction and is recessed in the -x direction. Figure 2 is a cross-sectional view taken along line II-II in Figure 6. The film thermometer 39 is positioned inside the recess 63. As shown in Figure 6, the multiple ribs 62 include a pair of recess ribs 64. The pair of recess ribs 64 are located on both sides of the recess 63 in the y direction. The contact between the pair of recess ribs 64 and the tubular film 35 stabilizes the orientation 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] Figure 5 is a cross-sectional view of the fixing device along the VV line in Figure 2. The pressure roller 31 has an inverted crown shape. The diameter of the central part of the pressure roller 31 in the y-direction is smaller than the diameters of both ends in the y-direction. This suppresses wrinkles in the sheet as it passes 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 in the z direction at the center of the support member 50 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. As a result, the fixing performance of the fixing device 30 becomes 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 mounted on 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 is curved along the -z-direction surface of the support member 50. The frame 36 is curved such that its center in the y-direction is convex in the -z-direction. In contrast, the -z-direction end of the tubular film 35 is not constrained by other members and is therefore parallel to the y-direction.

[0039] The guide member 60 is curved in the same way as the frame 36. The guide member 60 is curved such that its central part in the y-direction is convex in the -z-direction. Assume that the shape of all of the multiple ribs 62 of the guide member 60 is the same. In this case, the tip of the second rib 66 in the central part in the y-direction is positioned in the -z-direction more than the tip of the first rib 65 in the y-direction. The distance in the z-direction between the tip of the first rib 65 and the tubular film 35 is smaller than the distance in the z-direction between the tip of the second rib 66 and the tubular film 35. The second rib 66 is more likely to contact the tubular film 35 than the first rib 65. Due to the contact between the multiple ribs 62 and the tubular film 35, heat from the tubular film 35 is transferred to the multiple ribs 62. The temperature of the central part of the tubular film 35 in the y-direction becomes lower than the temperature of the ends in the y-direction. Temperature unevenness occurs in the fixing device 30, and gloss unevenness occurs in the image formed on the sheet.

[0040] (First Embodiment) Figure 7 is a plan view of the guide member of the first embodiment. The guide member 60 has a plurality of ribs 62, which include first ribs (first contact portion) 65 and second ribs (second contact portion) 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 number of first ribs 65 and second ribs 66 is not limited to these.

[0041] The widths of the first rib 65 and the second rib 66 in the y-direction are equivalent. Figure 8 is a cross-sectional view along line VIII-VIII in Figure 7. The heights of the first rib 65 and the second rib 66 are equivalent in the radial direction of the tubular film 35. The length of the second rib 66 in the circumferential direction of the tubular film 35 is shorter than that of the first rib 65. The lengths of the ribs 65 and 66 in the circumferential direction of the tubular film 35 refer to the lengths of the outer circumference of the ribs 65 and 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. The heat transfer coefficient between the second rib 66 and the tubular film 35 is smaller than the heat transfer coefficient between the first rib 65 and the tubular film 35.

[0042] As detailed above, the fixing device 30 of the embodiment includes 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 is in contact with 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 and is on the opposite side of the frame 36 from the heater unit 40. The guide member 60 has a plurality of ribs 62 aligned in the y-direction and capable of contacting the tubular film 35. The first rib 65 is located at the y-direction end of the plurality of ribs 62. The second rib 66 is located in the y-direction center of the plurality of ribs 62. The second rib 66 has a lower heat transfer coefficient between itself and the tubular film 35 than the first rib 65.

[0043] As described above, the guide member 60 is curved such that its central portion in the y-direction is convex in the -z-direction. The heat transfer coefficient between the second rib 66 and the tubular film 35 is smaller than the heat transfer coefficient between the first rib 65 and the tubular film 35. Heat transfer from the tubular film 35 to the multiple ribs 62 becomes uniform in the y-direction. Temperature unevenness in the fixing device 30 is suppressed, and image unevenness is 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 heat transfer coefficient between the second rib 66 and the tubular film 35 becomes smaller than the heat transfer coefficient between the first rib 65 and the tubular film 35.

[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 rib 66 and the tubular film 35 becomes smaller than the contact area between the first rib 65 and the tubular film 35.

[0046] (Second embodiment) Figure 9 is a plan view of the guide member of the second embodiment. The guide member 60 of the second embodiment differs from that of the first embodiment in that the widths of the first rib 65 and the second rib 67 in the y-direction are different. Descriptions of the second embodiment that are the same as those of 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 equivalent. The lengths of the first rib 65 and the second rib 67 in the circumferential direction of the tubular film 35 are equivalent. 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 approximately 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. The heat transfer coefficient between the second rib 67 and the tubular film 35 is smaller than the heat transfer coefficient between the first rib 65 and the tubular film 35.

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

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

[0050] The widths of the first rib 65 and the second rib 68 in the y-direction are equivalent. Figure 11 is a cross-sectional view along the line XI-XI in Figure 10. The lengths of the first rib 65 and the second rib 68 are equivalent in the circumferential direction of the tubular film 35. The height of the second rib 68 in the radial direction of the tubular film 35 is lower than that of the first rib 65. The height of the ribs 65 and 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 circumference of the ribs 65 and 68. The heights of the ribs 65 and 68 are compared at positions that are in 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. The heat transfer coefficient between the second rib 68 and the tubular film 35 is smaller than the heat transfer coefficient between the first rib 65 and the tubular film 35.

[0051] As described above, the height of the second rib 68 in the radial direction of the tubular film 35 is lower than the height of the first rib 65 in the radial direction of the tubular film 35. Heat transfer from the tubular film 35 to the multiple ribs 62 becomes uniform in the y direction. Temperature unevenness in the fixing device 30 is suppressed, and image unevenness is suppressed.

[0052] (Fourth embodiment) The guide member 60 of the fourth embodiment differs from that of 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. The description of the fourth embodiment in respect of aspects that are the same as those of the first embodiment may be omitted.

[0053] The shapes of the first rib 65 and the second rib 69 are equivalent. The contact area between the second rib 69 and the tubular film 35 is equivalent to 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 with 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). The heat transfer coefficient between the second rib 69 and the tubular film 35 is smaller than the heat transfer coefficient between the first rib 65 and the tubular film 35.

[0054] For example, a mounting pin is formed on the second rib 69 and a mounting hole is formed on the base portion 61. The mounting pin of the second rib 69 is inserted into the mounting hole of the base portion 61, thereby fixing the second rib 69 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 the second rib 69 is lower than that of the material of the first rib 65. Heat transfer from the tubular film 35 to the multiple ribs 62 becomes uniform in the y-direction. Temperature unevenness in the fixing device 30 is suppressed, and image unevenness is suppressed.

[0056] In the fourth embodiment, the overall material of the second rib 69 is different from that of the first rib 65. Conversely, the material of the outer circumferential surface of the second rib 69 that can contact the tubular film 35 may be different from that of the outer circumferential surface of the first rib 65. For example, the outer circumferential 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 differences between the second ribs 66-69 and the first rib 65 in the first to fourth embodiments are all different. Alternatively, a second rib that combines the differences of the first to fourth embodiments may be adopted.

[0058] In this embodiment, the guide member 60 has a plurality of ribs 62, with two types of first ribs 65 and second ribs 66-69 having different heat transfer coefficients with respect to the tubular film 35. In contrast, the guide member may have three or more types of ribs having different heat transfer coefficients with respect to the tubular film 35. The guide member may also have ribs with a heat transfer coefficient with respect to the tubular film 35 that changes in steps in the y-direction.

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

[0060] In this embodiment, the image forming apparatus 1 is a type of image processing apparatus, and the fixing apparatus 30 is a type of heating apparatus. In contrast, the image processing apparatus may be a decolorizing apparatus, and the heating apparatus may be a decolorizing unit. The decolorizing apparatus performs a process to decolorize (erase) the image formed on the sheet with decolorizing toner. The decolorizing unit heats and decolorizes the decolorizing toner image formed on the sheet as it passes through the nip.

[0061] According to at least one embodiment described above, the second ribs 66-69 have a heat transfer coefficient between them and the tubular film 35 that is smaller than the heat transfer coefficient between the first rib 65 and the tubular film 35. This makes it possible to suppress image unevenness.

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

[0063] 30... Fixing device, 35... Tubular film (tubular body), 36... Frame, 40... Heater unit, 62... Rib (contact part), 65... First rib (first contact part), 66-69... Second rib (second contact part).

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, A guide member located inside the cylindrical body, on the opposite side of the heater unit across the frame, and having a plurality of contact portions arranged in the longitudinal direction along the axial direction of the cylindrical body and capable of contacting the cylindrical body, Among the plurality of contact portions, the first contact portion is located at the end in the longitudinal direction, The plurality of contact portions includes a second contact portion located in the central part in the longitudinal direction, the heat transfer coefficient between the contact portion and the cylindrical body being smaller than the heat transfer coefficient between the first contact portion and the cylindrical body, Fixing device.

2. The contact area between the second contact portion and the cylindrical body is smaller than the 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 arranged in the longitudinal direction, protrude in the radial direction of the cylindrical body, and extend in the circumferential direction of the cylindrical body. The first contact portion is the first rib located at the end of the longitudinal direction among the plurality of ribs, The second contact portion is the second rib located in the central part of 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 arranged in the longitudinal direction, protrude in the radial direction of the cylindrical body, and extend in the circumferential direction of the cylindrical body. The first contact portion is the first rib located at the end of the longitudinal direction among the plurality of ribs, The second contact portion is the second rib located in the central part of 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 arranged in the longitudinal direction, protrude in the radial direction of the cylindrical body, and extend in the circumferential direction of the cylindrical body. The first contact portion is the first rib located at the end of the longitudinal direction among the plurality of ribs, The second contact portion is the second rib located in the central part of the longitudinal direction among the plurality of ribs, The height of the second rib in the radial direction is lower than the height of the first rib in the radial direction. The fixing device according to claim 2.

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

Images