Fixing device

Abstract

To provide a fixing device capable of suppressing the occurrence of unevenness in temperature distribution in a heater unit.SOLUTION: A fixing device includes a cylindrical body, a heater unit, and a heat transfer member. The tubular body has a film shape. The heater unit is disposed inside the cylindrical body. In the heater unit, the axial direction of the cylindrical body is the longitudinal direction. The heater unit has a heating element set including a heating element that generates heat by energization. The heat transfer member has a contact portion and an opposite surface. The contact portion is in contact with the heater unit. The opposite surface faces a side opposite to the contact portion. Both ends of the opposite surface in the longitudinal direction are located outside the contact portion in the longitudinal direction. Both ends of the contact portion in the longitudinal direction are located inside both ends of the heating element set in the longitudinal direction.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 as image processing devices. Image forming apparatuses have a fixing device that heats toner (recording material) to fix the toner on the sheet. The fixing device includes a cylindrical body that rotates in contact with the sheet, and a heater unit that heats the cylindrical body. The heater unit is required to suppress uneven temperature distribution. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 6242471 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 uneven temperature distribution in a heater unit. [Means for solving the problem]

[0005] The fixing device according to the first aspect has a cylindrical body, a heater unit, and a heat transfer member. The cylindrical body is film-shaped. The heater unit is disposed inside the cylindrical body. The heater unit has a longitudinal direction along the axial direction of the cylindrical body. The heater unit has a heat generating element set including a heat generating element that generates heat when energized. The heat transfer member has a contact portion and an opposite surface. The contact portion contacts the heater unit. The opposite surface faces the opposite side from the contact portion. Both longitudinal ends of the opposite surface are located outside the contact portion in the longitudinal direction. Both longitudinal ends of the contact portion are located inside the longitudinal ends of the heat generating element set in the longitudinal direction.

[0006] A fixing device according to a second aspect has a cylindrical body, a heater unit, and a heat transfer member. The cylindrical body is film-shaped. The heater unit is disposed inside the cylindrical body. The heater unit has a longitudinal direction along the axial direction of the cylindrical body. The heater unit has a heat generating element set including a heat generating element that generates heat when energized. The heat transfer member has a heater-facing surface and an opposite surface. The heater-facing surface faces the heater unit. The opposite surface faces the opposite side from the heater-facing surface. The heater-facing surface has a contact portion and an end portion. The contact portion contacts the heater unit. Both longitudinal ends of the contact portion are located longitudinally inside both longitudinal ends of the heat generating element set. The end portions are adjacent to the contact portion on both longitudinal outsides. The contact area per unit length of the end portion with respect to the heater unit in the longitudinal direction is smaller than that of the contact portion.

[0007] A fixing device according to a third aspect may be the fixing device according to the first aspect, wherein an end portion in the longitudinal direction of the heat transfer member is not in contact with the heater unit.

[0008] A fixing device according to a fourth aspect is a fixing device according to any one of the first to third aspects, wherein both longitudinal ends of the heat transfer member may be located longitudinally outward of both ends of the heat generating element set.

[0009] A fixing device according to a fifth aspect is the fixing device according to any one of the first to fourth aspects, wherein the heat transfer member has a higher thermal conductivity than the substrate of the heater unit.

[0010] A fixing device according to a sixth aspect may be the fixing device according to any one of the first to fifth aspects, in which the heat transfer member is a single member extending from the contact portion to the opposite surface.

[0011] A fixing device according to a seventh aspect may be a fixing device according to any one of the first to sixth aspects, wherein the heat transfer member comprises a first plate having a contact portion, and a second plate having an opposite surface, overlapping the first plate, and having both longitudinal ends located longitudinally outward of both longitudinal ends of the first plate.

[0012] The fixing device according to the eighth aspect may be the fixing device according to any one of the first to seventh aspects, further comprising an insulating member arranged longitudinally outward of the contact portion and interposed between the heat transfer member and the heater unit.

[0013] A fixing device according to a ninth aspect may be the fixing device according to the eighth aspect, wherein the heat insulating member has a lower thermal conductivity than the heat transfer member. [Brief explanation of the drawings]

[0014] [Figure 1] FIG. 1 is a schematic configuration diagram of an image processing apparatus according to an embodiment. [Figure 2] FIG. 1 is a diagram illustrating a hardware configuration of an image processing apparatus according to an embodiment. [Figure 3] FIG. 2 is a front cross-sectional view of the fixing device according to the first embodiment. [Figure 4] FIG. 6 is a front cross-sectional view of the heater unit taken along line IV-IV in FIG. 5. [Figure 5] FIG. 2 is a bottom view of the heater unit according to the first embodiment. [Figure 6] FIG. 2 is a plan view of the heater thermometer and thermostat according to the first embodiment. [Figure 7] FIG. 2 is a cross-sectional view of a heater unit and a heat transfer member according to the first embodiment. [Figure 8] FIG. 2 is a perspective view showing a heat transfer member according to the first embodiment. [Figure 9] FIG. 10 is a cross-sectional view of a heater unit, a heat transfer member, and a heat insulating member according to a second embodiment. [Figure 10] FIG. 10 is a perspective view showing a heat transfer member and a heat insulating member according to a second embodiment. [Figure 11]FIG. 10 is a cross-sectional view of a heater unit, a heat transfer member, and a heat insulating member according to a third embodiment. [Figure 12] FIG. 10 is a perspective view showing a heat transfer member according to a fourth embodiment. [Figure 13] FIG. 11 is a bottom view of the heater unit according to the fifth embodiment. [Figure 14] FIG. 13 is a bottom view of the heater unit according to the sixth embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0015] Hereinafter, a fixing device according to an embodiment will be described with reference to the drawings. In the following description, components having the same or similar functions will be denoted by the same reference numerals, and redundant descriptions of those components may be omitted.

[0016] FIG. 1 is a schematic diagram of an image processing apparatus according to an embodiment. The image processing device according to this embodiment is, for example, an image forming device 1 such as a multifunction peripheral (MFP) printer or copier. For example, the image forming device 1 is installed in a workplace. The image forming device 1 performs a process of forming an image on a sheet S. The sheet S may be paper. The image forming device 1 has a housing 10, a scanner section 2, an image forming unit 3, a sheet supply section 4, a conveying section 5, a paper output tray 7, a reversing unit 9, a control panel 8, and a control section 6.

[0017] 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 using a recording agent such as toner based on an image signal received from the scanner unit 2 or an image signal received from an external source. 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. Details of the image forming unit 3 will be described later.

[0018] 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.

[0019] 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 N of the registration roller 24. The registration rollers 24 adjust the position of the leading edge of the sheet S in the conveying direction by bending the sheet S at the nip N. 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.

[0020] The image forming unit 3 will now be described. The image forming unit 3 includes a plurality of image forming sections 25, a laser scanning unit 26, an intermediate transfer belt 27, a transfer section 28, and a fixing device 30. The image forming unit 25 has a photosensitive drum 29. The image forming unit 25 forms a toner image on the photosensitive drum 29 in response to an image signal from the scanner unit 2 or an external device. The multiple image forming units 25 form toner images using yellow, magenta, cyan, and black toner, respectively.

[0021] A charger, a developer, and other components are arranged around the photosensitive drum 29. The charger charges the surface of the photosensitive drum 29. The developer contains developer containing yellow, magenta, cyan, and black toner. The developer develops the electrostatic latent image on the photosensitive drum 29. As a result, a toner image made of toner of each color is formed on the photosensitive drum 29.

[0022] The laser scanning unit 26 scans the charged photosensitive drum 29 with laser light L to expose the photosensitive drum 29. The laser scanning unit 26 exposes the photosensitive drum 29 of the image forming unit 25 for each color with separate laser light LY, LM, LC, and LK. In this way, the laser scanning unit 26 forms an electrostatic latent image on the photosensitive drum 29.

[0023] The toner image on the surface of the photosensitive drum 29 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, thereby fixing the toner image to the sheet S. The fixing device 30 will be described in detail later.

[0024] 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 sheet discharge 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 each unit of the image forming apparatus 1.

[0025] FIG. 2 is a diagram showing the hardware configuration of the image forming apparatus according to the embodiment. 2, the image forming apparatus 1 includes a CPU (Central Processing Unit) 91, a memory 92, an auxiliary storage device 93, and the like, which are connected via a bus, and executes a program. By executing the program, the image forming apparatus 1 functions as a device including a scanner section 2, an image forming unit 3, a sheet supply section 4, a conveyance section 5, a reversing unit 9, a control panel 8, and a communication section 90.

[0026] The CPU 91 functions as the control unit 6 by executing programs stored in the memory 92 and the auxiliary storage device 93. The control unit 6 controls the operation of each functional unit of the image forming apparatus 1. The auxiliary storage device 93 is configured using a storage device such as a magnetic hard disk device, a semiconductor storage device, etc. The auxiliary storage device 93 stores information. The communication unit 90 includes a communication interface for connecting the device to an external device, and communicates with the external device via the communication interface.

[0027] (First embodiment) The basic configuration of the fixing device 30 will be described. FIG. 3 is a front cross-sectional view of the fixing device of the first embodiment. As shown in Fig. 3, the fixing device 30 has a pressure roller 31 and a film unit 35. A fixing nip FN is formed between the pressure roller 31 and the film unit 35. The pressure roller 31 applies pressure to the toner image on the sheet S that has entered the fixing nip FN. The pressure roller 31 rotates to transport the sheet S. The film unit 35 heats the toner image on the sheet S that has entered the fixing nip FN.

[0028] In this application, the z direction, x direction, and y direction are defined as follows: The z direction is the direction in which the pressure roller 31 and the film unit 35 are aligned. The +z direction is the direction from the film unit 35 toward the pressure roller 31. The x direction is the conveyance direction of the sheet S in the fixing nip FN, and the +x direction is the downstream side of the conveyance direction of the sheet S. The y direction is the direction perpendicular to the z direction and the x direction, and is the axial direction of the pressure roller 31.

[0029] The pressure roller 31 includes a core metal 32, an elastic layer 33, and a release layer. The core 32 is formed into a cylindrical shape from a metal material such as stainless steel. Both axial ends of the core 32 are rotatably supported. The core 32 is driven to rotate by a motor. The core 32 abuts against a cam member. As the cam member rotates, the core 32 moves toward and away from the film unit 35.

[0030] The elastic layer 33 is made of an elastic material such as silicone rubber, etc. The elastic layer 33 is formed on the outer circumferential surface of the core metal 32 with a constant thickness. The release layer is formed on the outer peripheral surface of the elastic layer 33 and is made of a resin material such as PFA (tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer). The hardness of the outer peripheral surface of the pressure roller 31 is preferably 40° to 70° when subjected to a load of 9.8 N using an ASKER-C hardness tester. This ensures the area of ​​the fixing nip FN and the durability of the pressure roller 31.

[0031] The pressure roller 31 can move toward and away from the film unit 35 by rotating a cam member. When the pressure roller 31 is brought close to the film unit 35 and pressed by a pressure spring, a fixing nip FN is formed. Meanwhile, if a sheet S jams in the fixing device 30, the sheet S can be removed by moving the pressure roller 31 away from the film unit 35. Furthermore, when the cylindrical body 36 is stopped from rotating, such as during sleep mode, plastic deformation of the cylindrical body 36 is prevented by moving the pressure roller 31 away from the film unit 35.

[0032] The pressure roller 31 is driven to rotate by a motor. When the pressure roller 31 rotates on its axis with the fixing nip FN formed, the cylindrical body 36 of the film unit 35 rotates accordingly. The pressure roller 31 rotates on its axis with the sheet S placed in the fixing nip FN, thereby conveying the sheet S in the conveying direction W.

[0033] The film unit 35 includes a cylindrical body 36 , a heater unit 40 , a heat transfer member 80 , a support member 37 , a stay 38 , a temperature sensing element 60 , and a film thermometer 64 .

[0034] The cylindrical body 36 is a fixing belt. The cylindrical body 36 is a cylindrical film extending along the y direction. The cylindrical body 36 has, in order from the inner periphery, a base layer, an elastic layer, and a release layer. The base layer is formed into a cylindrical shape from a material such as polyimide. The elastic layer is laminated on the outer periphery of the base layer. The elastic layer is formed from an elastic material such as silicone rubber. The release layer is laminated on the outer periphery of the elastic layer. The release layer is formed from a material such as PFA resin.

[0035] The heater unit 40 is located inside the cylindrical body 36. The heater unit 40 is formed in the shape of a rectangular plate with the y direction as the longitudinal direction and the x direction as the transverse direction. In the x and y directions, the direction toward the center of the heater unit 40 is sometimes referred to as the inside, and the direction away from the center of the heater unit 40 is sometimes referred to as the outside. The heater unit 40 has a first surface 41 in the +z direction and a second surface 42 facing the opposite side to the first surface 41. The first surface 41 of the heater unit 40 heats the cylindrical body 36. The first surface 41 contacts the inner surface of the cylindrical body 36 via grease 47.

[0036] Fig. 4 is a front cross-sectional view of the heater unit taken along line IV-IV in Fig. 5. Fig. 5 is a bottom view (viewed from the +z direction) of the heater unit of the first embodiment. As shown in FIGS. 4 and 5, the heater unit 40 includes a substrate 43, a heating element set 45, and a wiring set 55.

[0037] The substrate 43 is made of a metal material such as stainless steel, or a ceramic material such as aluminum nitride. The substrate 43 is a rectangular plate with its longitudinal direction in the y direction and its transverse direction in the x direction. An insulating layer 44 made of a glass material or the like is formed on the surface of the substrate 43 facing in the +z direction. The surface of the substrate 43 facing in the -z direction is the second surface 42 of the heater unit 40. The second surface 42 of the heater unit 40 is formed in a flat shape perpendicular to the z direction.

[0038] As shown in FIG. 5, the heating element set 45 is disposed on the substrate 43. The heating element set 45 has at least one heating element 50. The heating element 50 is formed by disposing a material such as a silver-palladium alloy on the substrate 43 by screen printing. The overall outer shape of the heating element set 45 is formed into a rectangular shape with the y direction as the longitudinal direction and the x direction as the lateral direction. Both ends of the heating element set 45 in the y direction are located inside the y direction of both ends of the y direction of the portion of the pressure roller 31 that contacts the cylindrical body 36. The center of the heating element set 45 in the y direction coincides with the width center of the sheet S passing through the fixing device 30. The center hc of the heating element set 45 in the x direction is located in the -x direction from the center pc of the substrate 43 in the x direction.

[0039] The heating element set 45 has multiple heating elements 50. The multiple heating elements 50 include a first end heating element 51, a central heating element 52, and a second end heating element 53, which are arranged side by side in the y direction. The central heating element 52 is arranged in the center of the heating element set 45 in the y direction. The central heating element 52 may be composed of multiple small heating elements arranged side by side in the y direction. The first end heating element 51 is arranged in the +y direction of the central heating element 52, at the end of the heating element set 45 in the +y direction. The second end heating element 53 is arranged in the -y direction of the central heating element 52, at the end of the heating element set 45 in the -y direction. The length of the central heating element 52 in the y direction is greater than the minimum width of the sheet S that passes through the fixing device 30. The length of the central heating element 52 in the y direction is smaller than the maximum width of the sheet S that passes through the fixing device 30. The length of the heat generating element set 45 in the y direction is greater than the maximum width of the sheet S passing through the fixing device 30. The length of the heat generating element set 45 in the y direction is the distance between the edge of the first end heat generating element 51 in the +y direction and the edge of the second end heat generating element 53 in the -y direction.

[0040] Wiring of the wiring set 55 is connected to each heating element 50. The heating element set 45 generates heat when power is supplied via the wiring set 55. A sheet S having a small width in the y direction passes through the center of the fixing device 30 in the y direction. In this case, the control unit 6 controls only the central heating element 52, which is located on the inside, among the multiple heating elements 50 to generate heat. On the other hand, in the case of a sheet S having a large width in the y direction, the control unit 6 controls all of the heating elements 50 to generate heat.

[0041] 4, a heating element set 45 and a wiring set 55 are formed on the surface of the insulating layer 44 in the +z direction. A protective layer 46 is formed of a glass material or the like so as to cover the heating element set 45 and the wiring set 55. The protective layer 46 forms the first surface 41 of the heater unit 40. When the heater unit 40 generates heat, the viscosity of the grease 47 between the protective layer 46 and the cylindrical body 36 decreases, thereby ensuring the sliding properties between the heater unit 40 and the cylindrical body 36.

[0042] Similar to the insulating layer 44 formed in the +z direction of the substrate 43, the insulating layer 44 may be formed in the −z direction of the substrate 43. Similar to the protective layer 46 formed in the +z direction of the substrate 43, the protective layer 46 may be formed in the −z direction of the substrate 43. This suppresses warping of the substrate 43.

[0043] As shown in Figure 3, a straight line CL is defined that connects the center rc of the pressure roller 31 and the center fc of the film unit 35. The center pc of the substrate 43 in the x direction is located in the +x direction from the line CL. The center hc of the heating element set 45 in the x direction is located on the line CL. The entire heating element set 45 is included within the area of ​​the fixing nip FN and is located at the center of the fixing nip FN. This results in an even heat distribution in the fixing nip FN, and the sheet S passing through the fixing nip FN is evenly heated.

[0044] The heat transfer member 80 overlaps the heater unit 40. The heat transfer member 80 contacts at least a portion of the second surface 42 of the heater unit 40. The heat transfer member 80 evens out the temperature distribution in the heater unit 40. The heat transfer member 80 has a rectangular plate shape that corresponds to the outer shape of the substrate 43 of the heater unit 40.

[0045] The support member 37 is made of a resin material such as a liquid crystal polymer. The support member 37 has a length in the y direction. The support member 37 is arranged so as to cover the heater unit 40 on both sides in the -z direction and the x direction. The support member 37 holds the heater unit 40 via a heat transfer member 80. Both ends of the support member 37 in the x direction are rounded and chamfered. The support member 37 supports the inner circumferential surface of the cylindrical body 36 on both ends of the heater unit 40 in the x direction.

[0046] The support member 37 includes a base 70, an upstream wall 71, and a downstream wall 72. The base 70 supports the heater unit 40 from the second surface 42 side. The upstream wall 71 protrudes from the -x-direction end of the base 70 toward the pressure roller 31. The downstream wall 72 protrudes from the +x-direction end of the base 70 toward the pressure roller 31. The heater unit 40 is disposed between the upstream wall 71 and the downstream wall 72.

[0047] The stay 38 is formed from a steel plate material or the like. The stay 38 has a length in the y direction. The cross section of the stay 38 perpendicular to the y direction is U-shaped. The stay 38 is attached to the support member 37 in the -z direction so that the opening of the U is closed by the base 70 of the support member 37. Both ends of the stay 38 in the y direction are fixed to the housing 10 of the image forming device 1. This allows the film unit 35 to be supported by the image forming device 1. The stay 38 improves the bending rigidity of the film unit 35.

[0048] The temperature sensing element 60 is arranged in the -z direction of the heater unit 40. The temperature sensing element 60 contacts the surface of the heat transfer member 80 in the -z direction. The temperature sensing element 60 is arranged inside a hole that penetrates the base 70 of the support member 37 in the z direction. The wiring of the temperature sensing element 60 is drawn out in the -z direction from the hole in the support member 37. The temperature sensing element 60 is a heater thermometer 61 and a thermostat 62. For example, the heater thermometer 61 is a thermistor.

[0049] 6 is a plan view (viewed from the −z direction) of the heater thermometer and thermostat of the first embodiment. In FIG. 6, the illustration of the support member 37 is omitted. 6, the heater thermometer 61 has a central heater thermometer 611 and an end heater thermometer 612. The thermostat 62 has a central thermostat 621 and an end thermostat 622. The central heater thermometer 611 and the central thermostat 621 are arranged in the -z direction of the central heating element 52. Meanwhile, the end heater thermometer 612 and the end thermostat 622 are arranged in the -z direction of the first end heating element 51 and the second end heating element 53.

[0050] The heater thermometer 61 detects the temperature of the heater unit 40 via the heat transfer member 80 . When the fixing device 30 starts up, the control unit 6 (see FIG. 1) measures the temperature of the heating element set 45 using the heater thermometer 61. If the temperature of the heating element set 45 is lower than a predetermined temperature, the control unit 6 causes the heating element set 45 to generate heat for a short period of time. Thereafter, the control unit 6 starts the rotation of the pressure roller 31. The heat generated by the heating element set 45 reduces the viscosity of the grease 47 applied to the inner circumferential surface of the cylindrical body 36. This ensures the sliding properties between the heater unit 40 and the cylindrical body 36 when the pressure roller 31 starts to rotate.

[0051] The heater thermometer 61 detects the temperature of the heat transfer member 80 . During operation of the fixing device 30, the control unit 6 measures the temperature of the heat transfer member 80 using the heater thermometer 61. Based on the temperature measurement result of the heat transfer member 80, the control unit 6 controls the power supply to the heating element set 45. As a result, the temperature of the heat transfer member 80 in contact with the support member 37 is maintained below the heat resistance temperature of the support member 37.

[0052] When the temperature of the heater unit 40 detected via the heat transfer member 80 exceeds a predetermined temperature, the thermostat 62 cuts off the power supply to the heating element set 45. As a result, excessive heating of the cylindrical body 36 by the heater unit 40 is suppressed.

[0053] 3, the film thermometers 64 are in contact with a portion of the inner circumferential surface of the cylindrical body 36. The film thermometers 64 are arranged at intervals in the y direction. The film thermometers 64 detect the temperatures of different portions of the cylindrical body 36 in the y direction.

[0054] When the fixing device 30 is in operation, the control unit 6 measures the temperature of each part of the cylindrical body 36 in the y direction using the film thermometer 64. The control unit 6 controls the power supply to the heating element set 45 based on the temperature measurement results of each part of the cylindrical body 36 in the y direction.

[0055] The heat transfer member 80 of the first embodiment will be described in detail. Fig. 7 is a view of the yz cross section of the heater unit and the heat transfer member of the first embodiment as viewed from the x direction, and Fig. 8 is a perspective view showing the heat transfer member of the first embodiment.

[0056] As shown in FIGS. 7 and 8 , the heat transfer member 80 has a thin plate shape. The heat transfer member 80 is made of a material with a higher thermal conductivity than the substrate 43 of the heater unit 40. The heat transfer member 80 is made of a metal material with a relatively high thermal conductivity, such as copper or aluminum. The thickness direction of the heat transfer member 80 is along the z direction. The heat transfer member 80 is rectangular with the y direction as its longitudinal direction and the x direction as its transverse direction. The heat transfer member 80 contacts the second surface 42 of the heater unit 40. The heat transfer member 80 overlaps all of the heating elements 50 in a plan view from the z direction. The heat transfer member 80 overlaps the entire heating element set 45 in a plan view. The center of the heat transfer member 80 in the y direction coincides with the center of the heating element set 45 in the y direction. Both ends of the heat transfer member 80 in the y direction are located outside the y direction of both ends of the heating element set 45 in the y direction. The length of the heat transfer member 80 in the y direction is equal to or greater than the maximum width of the sheet S passing through the fixing device 30. Both ends of the heat transfer member 80 in the y direction are located outside the both ends in the y direction of the portion of the pressure roller 31 that contacts the cylindrical body 36.

[0057] The heat transfer member 80 is a single member. The heat transfer member 80 has a heater-facing surface 81 facing the heater unit 40 and an opposite surface 84 facing the opposite side from the heater-facing surface 81. The heat transfer member 80 is configured as a single member from the entire heater-facing surface 81 to the entire opposite surface 84, but may also be configured from a plurality of members that are thermally continuous with each other.

[0058] The center of the heater facing surface 81 in the y direction coincides with the center of the heating element set 45 in the y direction. The heater facing surface 81 includes a contact portion 82 formed in the middle in the y direction and in contact with the second surface 42 of the heater unit 40, and a pair of end portions 83 adjacent to the contact portion 82 on both outer sides in the y direction.

[0059] The contact portion 82 is a flat surface along the x and y directions. The contact portion 82 contacts the heater unit 40 over its entire length in the x and y directions. The contact portion 82 is formed in a rectangular shape in a plan view. The center of the contact portion 82 in the y direction coincides with the center of the heater facing surface 81 in the y direction. Both ends of the contact portion 82 in the y direction are located more inward in the y direction than both ends of the heat generating element set 45 in the y direction. The length of the contact portion 82 in the y direction is equal to or greater than the maximum width of the sheet S passing through the fixing device 30.

[0060] Each end 83 is a flat surface along the x and y directions. Each end 83 is connected to the y-direction edge of the contact portion 82 via a stepped surface facing outward in the y direction. The entirety of each end 83 is out of contact with the second surface 42 of the heater unit 40. The contact area per unit length in the y direction of each end 83 with the heater unit 40 is smaller than the contact area per unit length in the y direction of the contact portion 82 with the heater unit 40. In this embodiment, since the entirety of each end 83 has a gap with the heater unit 40, the contact area per unit length in the y direction of each end 83 with the heater unit 40 is zero.

[0061] The opposite surface 84 is a flat surface extending in the x and y directions. The outer shape of the opposite surface 84 matches the outer shape of the heat transfer member 80 in a plan view. Both ends of the opposite surface 84 in the y direction are located further outward in the y direction than the contact portions 82 of the heater-facing surface 81. The opposite surface 84 faces the base 70 of the support member 37. The opposite surface 84 may be in direct contact with the base 70 of the support member 37, or another member may be interposed between the opposite surface 84 and the base 70 of the support member 37.

[0062] The operation of the fixing device 30 and the image forming apparatus 1 of this embodiment will be described. When the heating element set 45 is made to generate heat in order to heat the cylindrical body 36 of the fixing device 30, a temperature distribution occurs in the heater unit 40. In particular, in the initial stage of heating the heater unit 40, the heater unit 40 reaches a higher temperature than the heat transfer member 80, and heat is easily dissipated from the heater unit 40 to the heat transfer member 80, causing unevenness in the temperature distribution of the heater unit 40.

[0063] In this embodiment, the heater-facing surface 81 of the heat transfer member 80 has a contact portion 82 that contacts the heater unit 40 and end portions 83 that are adjacent to the contact portion 82 on both outer sides in the y direction. Both ends of the contact portion 82 in the y direction are located more inward in the y direction than both ends of the heating element set 45 in the y direction. The contact area of ​​the end portions 83 with the heater unit 40 per unit length in the y direction is smaller than the contact area of ​​the contact portion 82 with the heater unit 40 per unit length in the y direction.

[0064] With this configuration, the contact portion 82 of the heater-facing surface 81 of the heat transfer member 80 is provided so as to avoid positions corresponding to both ends in the y direction of the heat generating element set 45. This makes it possible to prevent heat from transferring to the heat transfer member 80 from the ends in the y direction, from which heat is particularly likely to escape, of the heat generating element set 45. Therefore, it is possible to prevent the portions of the heater unit 40 corresponding to the ends of the heat generating element set 45 from becoming lower in temperature than the portion corresponding to the middle part of the heat generating element set 45.

[0065] Furthermore, because end portion 83 is adjacent to contact portion 82 on heater facing surface 81, opposite surface 84 facing the opposite side from heater facing surface 81 can be enlarged in the y direction compared to a configuration in which the entire length of the heat transfer member in the y direction is the same as the entire length of the contact portion in the y direction. This allows heat that moves from contact portion 82 of heater facing surface 81 to opposite surface 84 within heat transfer member 80 to be diffused in the y direction. This suppresses a temperature rise on opposite surface 84 of heat transfer member 80, thereby suppressing damage caused by a temperature rise on support member 37 that is arranged on the opposite side of heat transfer member 80 from heater unit 40.

[0066] Moreover, the end 83 of the heater facing surface 81 is not in contact with the heater unit 40. With this configuration, compared to a configuration in which the end of the heater facing surface is in contact with the heater unit, it is possible to more effectively suppress the transfer of heat from the end in the y direction of the heat generating element set 45 to the heat transfer member 80 at the initial stage of heating by the heater unit 40.

[0067] Incidentally, when the sheet S passes through the fixing device 30 after the heater unit 40 starts heating, heat is transferred from the heater unit 40 to the sheet S. The transfer of heat from the heater unit 40 to the sheet S can cause a temperature drop in the central portion of the heater unit 40 in the y direction, which corresponds to the range through which the sheet S passes. If the heating element set 45 is turned on to generate heat in order to suppress the temperature drop in the central portion, the end portion of the heating element set 45 in the y direction, which is outside the range through which the sheet S passes, becomes even hotter.

[0068] In this embodiment, the length in the y direction of the contact portion 82 on the heater-facing surface 81 of the heat transfer member 80 is equal to or greater than the maximum width of the sheet S, so heat can be efficiently transferred from the y-direction end of the heat generating element set 45 to the heat transfer member 80 through the y-direction end of the contact portion 82. Therefore, the temperature distribution of the heater unit 40 in the fixing device 30 after the sheet S has passed through can be uniformed.

[0069] Furthermore, in this embodiment, both ends in the y direction of the opposite surface 84 of the heat transfer member 80 are located further outward in the y direction than both ends in the y direction of the contact portion 82, so that the heat at the end of the y direction of the contact portion 82 that has become hot can be diffused outward in the y direction toward the opposite surface 84. Therefore, a local temperature rise on the opposite surface 84 of the heat transfer member 80 can be suppressed, and damage caused by a temperature rise in the support member 37 that is arranged on the opposite side of the heat transfer member 80 from the heater unit 40 can be suppressed.

[0070] Both ends of heat transfer member 80 in the y direction are located further outward in the y direction than both ends of heat generating element set 45. With this configuration, opposite surface 84 is formed longer in the y direction than heat generating element set 45, so that when sheets S successively pass through fixing device 30, it is possible to suppress a temperature rise in portions of heat transfer member 80 that are outside the range through which sheets S pass in the y direction. Therefore, it is possible to suppress damage to support member 37 due to a temperature rise.

[0071] The heat transfer member 80 has a higher thermal conductivity than the substrate 43 of the heater unit 40. With this configuration, the heat transfer member 80 can conduct heat faster than within the substrate 43. Therefore, the temperature distribution of the heater unit 40 can be uniformed efficiently.

[0072] For example, if the heat transfer member is made up of multiple components and a joint between the components is formed between the contact portion of the heater-facing surface and the opposite surface, heat transfer may be hindered at the joint. In this embodiment, the heat transfer member 80 is a single component that extends from the contact portion 82 of the heater-facing surface 81 to the opposite surface 84. With this configuration, heat can be transferred more efficiently from the contact portion 82 of the heater-facing surface 81 to the opposite surface 84 within the heat transfer member 80, compared to when a joint between the components is formed between the contact portion of the heater-facing surface and the opposite surface. Therefore, heat can be efficiently diffused using the entire thickness of the heat transfer member 80.

[0073] (Second embodiment) A film unit 35 of a second embodiment will be described with reference to Figures 9 and 10. The configuration other than that described below is the same as that of the first embodiment. Figure 9 is a view of the yz cross section of the heater unit, heat transfer member, and heat insulating member of the second embodiment, viewed from the x direction. Figure 10 is a perspective view showing the heat transfer member and heat insulating member of the second embodiment.

[0074] The second embodiment differs from the first embodiment in that a heat insulating member 86 is interposed between an end 83 of the heater-facing surface 81 of the heat transfer member 80 and the second surface 42 of the heater unit 40. The heat insulating member 86 is disposed further outward in the y direction than the contact portion 82 of the heater-facing surface 81. The heat insulating member 86 contacts the end 83 of the heater-facing surface 81 and the second surface 42 of the heater unit 40 to prevent them from approaching each other. The heat insulating member 86 is formed of a material having a lower thermal conductivity than the heat transfer member 80. For example, the heat insulating member 86 is formed of resin, felt, or the like. The resin forming the heat insulating member 86 may be the same as the resin forming the support member 37. The shape of the heat insulating member 86 matches the shape of the end 83 of the heater-facing surface 81 in a plan view. However, the shape of the heat insulating member 86 does not have to match the shape of the end 83 of the heater-facing surface 81 in a plan view. For example, the heat insulating member 86 may be smaller than the end 83 of the heater-opposing surface 81 in a plan view.

[0075] This embodiment achieves the same effects as the first embodiment. In addition, in this embodiment, the heat insulating member 86 can prevent the heater unit 40 from being pressed by the pressure roller 31 and bending toward the end 83 of the heater facing surface 81. Therefore, the fixing nip FN can be reliably formed within a desired range in the y direction.

[0076] (Third embodiment) A heat transfer member 180 of the third embodiment will be described with reference to Fig. 11. Configurations other than those described below are the same as those of the first embodiment. Fig. 11 is a view of the yz cross section of the heater unit, heat transfer member, and heat insulating member of the third embodiment as viewed from the x direction.

[0077] In the first embodiment, the heat transfer member 80 is a single member. In contrast, the third embodiment differs from the first embodiment in that the heat transfer member 180 is formed of multiple members. The heat transfer member 180 is formed by overlapping a first plate 187 and a second plate 188. The first plate 187 and the second plate 188 are formed from a metal material with relatively high thermal conductivity, such as copper or aluminum, or a graphite sheet. The thickness direction of each of the first plate 187 and the second plate 188 is aligned with the thickness direction of the heat transfer member 180.

[0078] The first plate 187 is located between the second plate 188 and the heater unit 40. The first plate 187 is formed in a rectangular shape with its longitudinal direction in the y direction. The first plate 187 has a contact portion 82 of the heater facing surface 81. The second plate 188 is overlapped on the first plate 187 from the side opposite the heater unit 40. The second plate 188 is formed in a rectangular shape with its longitudinal direction in the y direction. The second plate 188 has the same width in the x direction as the first plate 187. Both ends of the second plate 188 in the y direction are located further outward in the y direction than both ends of the first plate 187 in the y direction. The outer shape of the second plate 188 matches the outer shape of the heat transfer member 180 in a plan view. The second plate 188 has the entire opposite surface 84 of the heat transfer member 180. The second plate 188 has an end 83 of the heater facing surface 81 further outward in the y direction than the first plate 187. The second plate 188 may be joined to the first plate 187. Grease or the like having excellent thermal conductivity may be placed between the first plate 187 and the second plate 188.

[0079] This embodiment provides the same effects as those of the first embodiment. In addition, in this embodiment, the contact portion 82 and the end portion 83 can be formed on the heater-facing surface 81 by overlapping the first plate 187 and the second plate 188, so that the heat transfer member 180 can be easily formed.

[0080] Furthermore, the heat transfer member 180 of this embodiment may be combined with the heat insulating member 86 of the second embodiment. According to this configuration, the heat insulating member 86 can prevent the end of the heat transfer member 180 in the y direction from bending toward the heater unit 40. Therefore, the heat transfer member 180 can be maintained in a desired shape. This is particularly effective when the first plate 187 and the second plate 188 are formed from flexible graphite sheets.

[0081] (Fourth embodiment) A heat transfer member 280 of the fourth embodiment will be described with reference to Fig. 12. The configuration other than that described below is the same as that of the first embodiment. Fig. 12 is a perspective view showing the heat transfer member of the fourth embodiment.

[0082] In the first embodiment, the entire end 83 of the heater facing surface 81 of the heat transfer member 80 is out of contact with the heater unit 40. In contrast, the fourth embodiment differs from the first embodiment in that the end 283 of the heater facing surface 281 has a recess 289 that prevents the end 283 from contacting the heater unit 40.

[0083] A recess 289 is formed in an end 283 of the heater-facing surface 281 of the heat transfer member 280. The recess 289 may have a bottom surface, or may penetrate the heat transfer member 280 in the z direction. By having the recess 289, the end 283 reduces the contact area with the second surface 42 of the heater unit 40. As a result, the contact area per unit length in the y direction of each end 283 with the heater unit 40 is smaller than the contact area per unit length in the y direction of the contact portion 282 with the heater unit 40.

[0084] This embodiment achieves the same effects as the first embodiment. In addition, in this embodiment, the end 283 of the heater facing surface 281 contacts the heater unit 40, which prevents the heater unit 40 from being pressed by the pressure roller 31 and bending toward the heat transfer member 280. Therefore, the fixing nip FN can be reliably formed within a desired range in the y direction.

[0085] (Fifth embodiment) A heater unit 340 according to the fifth embodiment will be described with reference to Fig. 13. The configuration other than that described below is the same as that of the first embodiment. Fig. 13 is a bottom view of the heater unit according to the fifth embodiment.

[0086] The fifth embodiment differs from the first embodiment in the arrangement of the heat generating elements 350 of the heater unit 340. The heater unit 340 includes a substrate 43, a heat generating element set 345, and a wiring set 355.

[0087] The heat generating element set 345 is disposed on the substrate 43. The overall outer shape of the heat generating element set 345 is formed in a rectangular shape with the y direction as the longitudinal direction and the x direction as the lateral direction. The heating element set 345 has multiple heating elements 350. The multiple heating elements 350 have a pair of a first heating element 351, a second heating element 352, and a third heating element 353. The multiple heating elements 350 are arranged in the x direction in the following order: one first heating element 351, the second heating element 352, the third heating element 353, and the other first heating element 351. The longitudinal direction of each heating element 350 is the y direction. Each heating element 350 has a length corresponding to various sheet widths. The second heating element 352 is shorter in the y direction than the first heating element 351. Both ends of the second heating element 352 in the y direction are located more inward than both ends of the first heating element 351 in the y direction. The third heating element 353 is shorter in the y direction than the second heating element 352. Both ends of the third heating element 353 in the y direction are located more inward than both ends of the second heating element 352 in the y direction. Wiring of a wiring set 355 is connected to each heating element 350. The heating element set 345 generates heat when electricity is applied via the wiring set 355. The control unit 6 causes the corresponding heating element 350 to generate heat in accordance with the width of the sheet S passing through.

[0088] In the fifth embodiment described above, the heat transfer members 80, 180, 280 may be overlapped on the heater unit 340, as in the above embodiments. In this case, by arranging both ends in the y direction of the contact portion 82 of the heater facing surface 81 on the inner side in the y direction of both ends in the y direction of the heat generating element set 345, the same effect as in the above embodiments can be achieved.

[0089] (Sixth embodiment) A heater unit 440 according to the sixth embodiment will be described with reference to Fig. 14. The configuration other than that described below is the same as that of the first embodiment. Fig. 14 is a bottom view of the heater unit according to the sixth embodiment.

[0090] The sixth embodiment differs from the first embodiment in the arrangement of the heat generating elements 450 of the heater unit 440. The heater unit 440 includes a substrate 43, a heat generating element set 445, and a wiring set 455.

[0091] The heat generating element set 445 is disposed on the substrate 43. The overall outer shape of the heat generating element set 445 is formed in a rectangular shape with the y direction as the longitudinal direction and the x direction as the lateral direction. The heating element set 445 has a plurality of heating elements 450. The plurality of heating elements 450 has a pair of first heating elements 451 and second heating elements 452. The plurality of heating elements 450 are arranged in the x direction in the following order: one first heating element 451, the second heating element 452, and the other first heating element 451. The longitudinal direction of each heating element 450 is the y direction. The first heating element 451 becomes thicker from the center toward the ends in the y direction. Both ends of the pair of first heating elements 451 are located at approximately the same position as each other in the y direction. The second heating element 452 becomes thinner from the center toward the ends in the y direction. Both ends of the second heating element 452 are located at approximately the same position as both ends of each first heating element 451 in the y direction.

[0092] Wiring of the wiring set 455 is connected to each heating element 450. The heating element set 445 generates heat when current is applied via the wiring set 455. The control unit 6 controls the corresponding heating element 450 to generate heat according to the width of the sheet S passing through. When only the first heating element 451 is activated, the heat generation amount of the heating element set 445 decreases from the center toward the ends in the y direction. On the other hand, when the pair of first heating element 451 and second heating element 452 are activated simultaneously, the heat generation amount of the heating element set 445 is more averaged over the entire length in the y direction than when only the first heating element 451 is activated. Therefore, when a sheet S with a smaller width passes through, the control unit 6 applies current only to the first heating element 451. When a sheet S with a larger width passes through, the control unit 6 applies current to the first heating element 451 and the second heating element 452.

[0093] In the sixth embodiment described above, the heat transfer members 80, 180, 280 may be overlapped on the heater unit 440, as in the above embodiments. In this case, by arranging both ends in the y direction of the contact portion 82 of the heater facing surface 81 on the inner side in the y direction of both ends in the y direction of the heat generating element set 445, the same effect as in the above embodiments can be achieved.

[0094] In the above embodiment, the first surface 41 of the heater unit 40 is in contact with the inner surface of the cylindrical body 36, but another heat equalizing member may be interposed between the first surface of the heater unit and the inner surface of the cylindrical body.

[0095] According to at least one of the embodiments described above, both longitudinal ends of the contact portion of the heat transfer member are located longitudinally inward of both longitudinal ends of the heating element set, and both longitudinal ends of the opposite surface of the heat transfer member are located longitudinally outward of the contact portion, thereby preventing the portions of the heater unit corresponding to the ends of the heating element set from becoming colder than the portions corresponding to the middle of the heating element set, and suppressing the temperature rise of the opposite surface of the heat transfer member, thereby suppressing damage caused by the temperature rise of the support member arranged on the opposite side of the heat transfer member from the heater unit.

[0096] 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]

[0097] 30... fixing device, 36... cylindrical body, 40, 340, 440... heater unit, 43... substrate, 45, 345, 445... heating element set, 50, 350, 450... heating element, 80, 180, 280... heat transfer member, 81, 281... heater facing surface, 82, 282... contact portion, 83, 283... end portion, 84... opposite surface, 86... heat insulating member, 187... first plate, 188... second plate

Claims

1. A film-like cylindrical body; a heater unit disposed inside the cylindrical body, with the axial direction of the cylindrical body as the longitudinal direction, and including a heating element set including a heating element that generates heat when energized; a heat transfer member having a heater-facing surface facing the heater unit and an opposite surface facing the opposite side to the heater-facing surface; A fixing device comprising: The heater-facing surface is a contact portion that contacts the heater unit and has both ends in the longitudinal direction located inside both ends in the longitudinal direction of the heating element set; end portions adjacent to the contact portion on both outer sides in the longitudinal direction, the end portions having a contact area with the heater unit per unit length in the longitudinal direction smaller than that of the contact portion; and the length of the contact portion in the longitudinal direction is equal to or greater than the maximum width of a sheet passing through the fixing device; Fixing device.

2. Both ends of the heat transfer member in the longitudinal direction are located outside the both ends of the heat generating element set in the longitudinal direction. The fixing device according to claim 1 .

3. the heat transfer member has a higher thermal conductivity than the substrate of the heater unit; The fixing device according to claim 1 .

4. The heat transfer member is a single member extending from the contact portion to the opposite surface. The fixing device according to claim 1 .

5. The heat transfer member is a first plate having the contact portion; a second plate having the opposite surface, overlapping the first plate, and having both ends in the longitudinal direction located outside the both ends in the longitudinal direction of the first plate; Equipped with The fixing device according to claim 1 .

6. a heat insulating member disposed outside the contact portion in the longitudinal direction and interposed between the heat transfer member and the heater unit; The fixing device according to claim 1 .

7. The heat insulating member has a lower thermal conductivity than the heat transfer member. The fixing device according to claim 6 .

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