Fixing device

Abstract

The invention discloses a fixing device. According to one embodiment, a fixing device includes a cylindrical body, a heater, a holder, a sensor, a roller, and a pressing mechanism. The pressing mechanism changes the pressure between the cylindrical body and the roller.

Description

Technical Field

[0001] The present invention relates to a fixing device.

[0002] This application claims priority based on Japanese Patent Application No. 2023-095583 filed in Japan on June 9, 2023, the contents of which are incorporated herein by reference. Background Art

[0003] As an image processing apparatus, an image forming apparatus that forms an image on a sheet is used. The image forming apparatus includes a fixing device that fixes a toner to the sheet. Improved durability of the fixing device is being sought.

[0004] Patent Document 1: Japanese Patent Application Publication No. 2008-304866 Summary of the invention

[0005] Technical problem to be solved by the invention

[0006] An object of the present invention is to provide a fixing device having high durability.

[0007] Technical solutions for solving technical problems

[0008] A fixing device of one type comprises: a cylindrical body; a heater, which is arranged on the inner side of the cylindrical body and has a heating area with the axial direction of the cylindrical body as the long side direction and generates heat by energizing; a retaining frame, which retains the heater; a sensor, which contacts the heater and detects the temperature of the heater; a roller, which contacts the outer peripheral surface of the cylindrical body and forms a clamping portion between the roller and the cylindrical body; and a pressurizing mechanism, which changes the pressure between the cylindrical body and the roller.

[0009] In one embodiment of the fixing device, the pressure-applying mechanism may change the pressure in such a manner as to transfer the state between the cylindrical body and the roller, wherein the state is a first state or a second state. In the first state, the clamping portion is formed by the cylindrical body and the roller, and in the second state, the cylindrical body and the roller are in contact with each other and the force applied to each other by the cylindrical body and the roller is smaller than that in the first state.

[0010] The fixing device according to one aspect may include a moving mechanism that moves the pressing mechanism so that the state in the pressing mechanism shifts to the first state or the second state.

[0011] In one embodiment of the fixing device, the pressure mechanism may support the roller in a manner that allows it to rotate and move in a direction orthogonal to the axial direction, and the moving mechanism may include: a cam follower arranged on the pressure mechanism; a cam having a cam surface abutting against the cam follower and being rotatable, the cam and the cam follower cooperate to move the roller in the orthogonal direction via the pressure mechanism, and the small diameter portion with the smallest outer diameter in the cam surface abuts against the cam follower in the second state; and a driving source that causes the cam to rotate in one direction.

[0012] In one embodiment of the fixing device, the state may be capable of being transferred to a third state in the pressure-applying mechanism. In the third state, the roller is separated from the cylindrical body, and the retaining frame retains the heater so as to form a gap between the heater and the retaining frame within a range overlapping with the heating area in the axial direction.

[0013] In the fixing device according to one aspect, when the state in the pressure applying mechanism shifts to the first state or the second state, displacement of the heater may be restricted by the roller.

[0014] In one aspect of the fixing device, the cylindrical body may include a contact portion that contacts the heater in a state where the cylindrical body is separated from the roller.

[0015] In the fixing device according to one aspect, a gap may be formed between the heater and the cylindrical body in a state in which the cylindrical body is separated from the roller.

[0016] In one aspect of the fixing device, the gap may increase from the contact portion toward the outside in the axial direction.

[0017] In one aspect of the fixing device, the heater may include a heater unit and a heat transfer member, and the heat transfer member may be located between the heater unit and the holder.

[0018] In the fixing device according to one aspect, the heater may be held by the holding frame outside the heat generating region in the axial direction.

[0019] In one aspect of the fixing device, the sensor may be biased toward the heater with respect to the holder, and the heater may be pressed toward the roller by the sensor.

[0020] In the fixing device according to one aspect, the roller may include an elastic layer, and an amount of deformation of the elastic layer in the second state may be smaller than an amount of deformation of the elastic layer in the first state.

[0021] In the fixing device according to one aspect, when the nip portion is not formed in the pressure applying mechanism, the cylindrical body and the roller may be in contact with each other.

[0022] In one aspect of the fixing device, the sensor may include a center sensor and an end sensor, and in the third state, the center sensor may be spaced apart from the heat transfer member, and the end sensor may be in contact with the heat transfer member.

[0023] In one embodiment of the fixing device, the central sensor and the end sensors may be supported by the retaining frame, the central sensor may be arranged to face the central portion of the heater unit, and the end sensors may be arranged between the ends of the heater unit and the central sensor.

[0024] In the fixing device according to one aspect, the heater may be pressed toward the roller by the edge sensor.

[0025] In one embodiment of the fixing device, the heater may include a heater unit and a heat transfer component, the heat transfer component may be located between the heater unit and the retaining frame, the sensor may include a central sensor and an end sensor, and in the second state, the central sensor and the end sensor may be in contact with the heat transfer component.

[0026] In one embodiment of the fixing device, the central sensor and the end sensors may be supported by the retaining frame, the central sensor may be arranged to face the central portion of the heater unit, and the end sensors may be arranged between the ends of the heater unit and the central sensor.

[0027] An image processing device of one type comprises: a cylindrical body; a heater, which is arranged on the inner side of the cylindrical body and has a heating area with the axial direction of the cylindrical body as the long side and generates heat by energizing; a retaining frame, which retains the heater; a sensor, which contacts the heater and detects the temperature of the heater; a roller, which contacts the outer peripheral surface of the cylindrical body and forms a clamping portion between the roller and the cylindrical body; and a pressurizing mechanism, which changes the pressure between the cylindrical body and the roller. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 It is a schematic structural diagram of an image processing device according to an embodiment.

[0029] Figure 2 FIG. 1 is a diagram showing a hardware configuration of an image forming apparatus according to an embodiment.

[0030] Figure 3 It is a front cross-sectional view of the fixing device according to the first embodiment.

[0031] Figure 4 yes Figure 5 A front cross-sectional view of the heater unit taken along line IV-IV is shown.

[0032] Figure 5 It is a bottom view of the heater unit according to the first embodiment.

[0033] Figure 6 It is a top view of the thermometer and thermostat.

[0034] Figure 7 yes Figure 3 A cross-sectional view of the thin film unit along line VII-VII is shown.

[0035] Figure 8 It is a front view of the fixing device.

[0036] Fig. 9 This is a diagram illustrating the operation of the pressurizing mechanism.

[0037] Fig.10 yes Figure 3 A cross-sectional view of the fixing device taken along line VII-VII is shown.

[0038] Fig.11 It is a block diagram showing the functional structure of the control unit.

[0039] Fig.12 It is a bottom view of the heater unit according to the second embodiment.

[0040] Fig.13 It is a bottom view of the heater unit according to the third embodiment.

[0041] Description of Reference Numerals

[0042] 30: fixing device; 31: roller; 36: heater; 37: cylinder; 38: retaining frame; 45, 245, 345: heating area; 61: thermometer (sensor); 70: pressing mechanism; 80: moving mechanism; 81: cam follower; 82: cam; 83: driving source; 84: cam surface; 371: contact portion; 842: small diameter portion; FN: fixing clamping portion (clamping portion). DETAILED DESCRIPTION

[0043] Hereinafter, the fixing device according to the embodiment will be described with reference to the drawings. In the following description, the same reference numerals may be given to components having the same or similar functions, and repeated descriptions of these components may be omitted.

[0044] Figure 1 It is a schematic structural diagram of an image processing device according to an embodiment.

[0045] The image processing apparatus of the present embodiment is, for example, an image forming apparatus 1 such as a multifunction peripheral (MFP) printer or a copier. For example, the image forming apparatus 1 is installed in a workplace. The image forming apparatus 1 performs a process of forming an image on a sheet S. The sheet S may also be paper. The image forming apparatus 1 includes a housing 10, a scanner unit 2, an image forming unit 3, a sheet feeding unit 4, a conveying unit 5, a paper discharge tray 7, a reversing unit 9, a control panel 8, and a control unit 6.

[0046] The housing 10 forms the outer appearance of the image forming apparatus 1 .

[0047] The scanner unit 2 reads image information of the copy object as light brightness and darkness, and generates an image signal. The scanner unit 2 outputs the generated image signal to the image forming unit 3.

[0048] 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 the outside. 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 onto the sheet S. Details of the image forming unit 3 will be described later.

[0049] The sheet supply section 4 supplies sheets S one by one to the conveying section 5 in accordance with the timing of forming a toner image by the image forming unit 3. The sheet supply section 4 includes a sheet storage section 20 and a pickup roller 21.

[0050] The sheet storage section 20 stores sheets S of a predetermined size and type.

[0051] The pickup roller 21 takes out the sheets S one by one from the sheet storage portion 20 . The pickup roller 21 supplies the taken-out sheets S toward the conveying portion 5 .

[0052] The conveying section 5 conveys the sheet S supplied from the sheet supply section 4 to the image forming unit 3. The conveying section 5 includes a conveying roller 23 and a registration roller 24.

[0053] The conveying roller 23 conveys the sheet S supplied from the pickup roller 21 toward the registration roller 24 . The conveying roller 23 causes the leading end of the sheet S in the conveying direction to hit the nip portion N of the registration roller 24 .

[0054] The registration roller 24 adjusts the position of the leading end of the sheet S in the conveying direction by bending the sheet S at the nip portion N. The registration roller 24 conveys the sheet S in accordance with the timing at which the image forming unit 3 transfers the toner image to the sheet S.

[0055] The image forming unit 3 will be described.

[0056] 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 .

[0057] The image forming unit 25 includes a photosensitive drum 29. The image forming unit 25 forms a toner image according to an image signal from the scanner unit 2 or the outside on the photosensitive drum 29. The plurality of image forming units 25 form toner images using yellow, magenta, cyan, and black toners, respectively.

[0058] A charger, a developer, and the like are arranged around the photosensitive drum 29. The charger charges the surface of the photosensitive drum 29. The developer contains developers including yellow, magenta, cyan, and black toners. The developer develops the electrostatic latent image on the photosensitive drum 29. As a result, a toner image of toners of various colors is formed on the photosensitive drum 29.

[0059] 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 has a plurality of light sources corresponding to the laser light LY, LM, LC, and LK, respectively. The laser scanning unit 26 exposes the yellow, magenta, cyan, and black photosensitive drums 29 in the image forming unit 25 with the laser light LY, LM, LC, and LK, respectively. Thus, the laser scanning unit 26 forms an electrostatic latent image on the photosensitive drum 29.

[0060] The toner image on the surface of the photosensitive drum 29 is primarily transferred to the intermediate transfer belt 27 .

[0061] The transfer section 28 transfers the toner image primarily transferred onto the intermediate transfer belt 27 onto the surface of the sheet S at a secondary transfer position.

[0062] The fixing device 30 heats and pressurizes the toner image transferred to the sheet S, thereby fixing the toner image to the sheet S. Details of the fixing device 30 will be described later.

[0063] 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 front and back sides of the sheet S discharged from the fixing device 30 by switching back. The reversing unit 9 conveys the reversed sheet S toward the registration rollers 24 .

[0064] The sheet discharge tray 7 places the sheet S on which an image is formed and discharged.

[0065] 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 includes a touch panel and various hardware keys.

[0066] The control unit 6 controls each unit of the image forming apparatus 1 .

[0067] Figure 2It is a hardware configuration diagram of the image processing device according to the embodiment.

[0068] like Figure 2 As shown, the image forming apparatus 1 includes a CPU (Central Processing Unit) 91, a memory 92, an auxiliary storage device 93, etc. connected via a bus, and executes a program. The image forming apparatus 1 functions as a device including a scanner unit 2, an image forming unit 3, a sheet feeding unit 4, a conveying unit 5, a reversing unit 9, a control panel 8, and a communication unit 90 by executing the program.

[0069] 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 functional configuration of the control unit 6 will be described later.

[0070] 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.

[0071] The communication unit 90 includes a communication interface for connecting the device to an external device. The communication unit 90 communicates with the external device via the communication interface.

[0072] (First Embodiment)

[0073] The fixing device 30 according to the first embodiment will be described.

[0074] Figure 3 It is a front cross-sectional view of the fixing device according to the first embodiment.

[0075] like Figure 3 As shown, the fixing device 30 includes a roller 31, a film unit 35, a pressure mechanism 70, a moving mechanism 80, and a frame 34. A fixing nip FN is formed between the roller 31 and the film unit 35. The roller 31 presses the toner image of the sheet S entering the fixing nip FN. The roller 31 rotates to convey the sheet S. The film unit 35 heats the toner image of the sheet S entering the fixing nip FN. The frame 34 is fixed to the housing 10 of the image forming apparatus 1. The frame 34 supports the roller 31, the film unit 35, and the moving mechanism 80.

[0076] In the present application, the z direction, the x direction, and the y direction are defined as follows. The z direction is the direction in which the roller 31 and the film unit 35 are arranged. The +z direction is the direction from the film unit 35 toward the roller 31. The -z direction is the opposite direction to the +z direction. The x direction is the conveying direction of the sheet S in the fixing nip FN. The +x direction is the direction toward the downstream side of the conveying direction of the sheet S. The -x direction is the opposite direction to the +x direction. The y direction is the direction orthogonal to the z direction and the x direction. The y direction is the axial direction of the roller 31. The direction from one end toward the other end of the roller 31 is the +y direction. The -y direction is the opposite direction to the +y direction.

[0077] The roller 31 can rotate around the roller rotation center rc. The roller 31 has a core rod 32, an elastic layer 33 and a release layer. The roller 31 can also be called a pressure roller.

[0078] The mandrel 32 is formed into a cylindrical shape by a metal material such as stainless steel. Both ends of the mandrel 32 in the axial direction are supported in a rotatable manner. The mandrel 32 is driven to rotate by a motor. The mandrel 32 abuts against the cam member. The cam member rotates to move the mandrel 32 toward and away from the film unit 35.

[0079] The elastic layer 33 is formed of an elastic material such as silicone rubber, etc. The elastic layer 33 is formed on the outer peripheral surface of the core rod 32 with a certain thickness.

[0080] The mold release layer is formed of a resin material such as PFA (tetrafluoroethylene / perfluoroalkyl vinyl ether copolymer) and is formed on the outer peripheral surface of the elastic layer 33 .

[0081] The hardness of the outer peripheral surface of the roller 31 is preferably 40° to 70° using an ASKER-C hardness meter under a load of 9.8 N. This ensures the area of ​​the fixing nip FN and the durability of the roller 31 .

[0082] The roller 31 is driven by a motor to rotate. When the roller 31 rotates with the fixing nip FN formed, the cylindrical body 37 of the film unit 35 rotates. The roller 31 conveys the sheet S in the conveying direction W by rotating with the sheet S arranged in the fixing nip FN.

[0083] The film unit 35 includes a cylindrical body 37 , a heater 36 , a holder 38 , a support column 39 , a temperature sensing element 60 , and a film thermometer 64 .

[0084] The cylindrical body 37 is a fixing belt. The cylindrical body 37 is a cylindrical film extending in the y direction. The cylindrical body 37 has a base layer, an elastic layer 33, and a release layer in the order from the inner peripheral side to the outer peripheral side of the cylindrical body 37. The base layer is formed into a cylindrical shape by a material such as polyimide. The elastic layer 33 is stacked on the outer peripheral surface of the base layer. The elastic layer 33 is formed by an elastic material such as silicone rubber. The release layer is stacked on the outer peripheral surface of the elastic layer 33. The release layer is formed by a material such as PFA resin.

[0085] The heater 36 is located inside the cylindrical body 37. The heater 36 includes a heater unit 40 and a heat transfer member 65. The heater 36 may also be referred to as a heat-generating sliding member.

[0086] The heater unit 40 is formed in a rectangular plate shape. The long side direction in which the long side (first side) of the heater unit 40 extends is the y direction, and the short side direction in which the short side (second side) of the heater unit 40 extends is the x direction. In the x direction and the y direction, the direction close to the center of the heater unit 40 is sometimes referred to as the inside, the inner side, and the inner side direction, and the direction away from the center of the heater unit 40 is sometimes referred to as the outside, the outer side, and the outer side direction. The heater unit 40 has a first surface 41 in the +z direction and a second surface 42 facing the opposite side of the first surface 41. The first surface 41 of the heater unit 40 heats the cylindrical body 37. The first surface 41 contacts the inner surface of the cylindrical body 37 via the grease 47.

[0087] Figure 4 yes Figure 5 A front cross-sectional view of the heater unit taken along line IV-IV is shown. Figure 5 It is a bottom view (viewed from the +z direction) of the heater unit according to the first embodiment.

[0088] like Figure 4 as well as Figure 5 As shown, the heater unit 40 has a substrate 43 , a heat generating area 45 , and a wiring group 55 .

[0089] The substrate 43 is formed of a metal material such as stainless steel, a ceramic material such as aluminum nitride, etc. The substrate 43 is formed in a rectangular plate shape. The long side direction of the long side (first side) of the substrate 43 is the y direction, and the short side direction of the short side (second side) of the substrate 43 is the x direction. On the surface of the substrate 43 facing the +z direction, an insulating layer 44 is formed of a glass material or the like. The surface of the substrate 43 facing 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 plane shape orthogonal to the z direction.

[0090] like Figure 5As shown, the heating area 45 is arranged on the substrate 43. The heating area 45 has at least one heating element 50. The heating element 50 is formed by placing a material such as a silver / palladium alloy on the substrate 43 by screen printing. The heating area 45 is defined by the area between two heating elements 50 located at both ends of the y direction and between two heating elements 50 located at both ends of the x direction among all the heating elements 50. The overall shape of the heating area 45 is a rectangle. The long side direction of the long side (first side) of the heating area 45 is the y direction, and the short side direction of the short side (second side) of the heating area 45 is the x direction. The heating area 45 is arranged at a position closer to the inside than the two ends of the substrate 43 in the y direction, and is arranged at a position closer to the inside than the two ends of the substrate 43 in the x direction.

[0091] The heating area 45 of the present embodiment has a plurality of heating elements 50. The plurality of heating elements 50 include a first end heating element 51, a central heating element 52, and a second end heating element 53 arranged in the y direction. The central heating element 52 is arranged in the central part of the heating area 45 in the y direction. The central heating element 52 can also be composed of a combination of a plurality of small heating elements arranged in the y direction. The first end heating element 51 is located next to the central heating element 52 in the +y direction, and is arranged at the end of the heating area 45 in the +y direction. The second end heating element 53 is located next to the central heating element 52 in the -y direction, and is arranged at the end of the heating area 45 in the -y direction.

[0092] The wiring of the wiring group 55 is connected to each of the plurality of heating elements 50. The heating area 45 is energized via the wiring group 55 to generate heat. The sheet S having a small width in the y direction passes through the center portion in the y direction of the fixing device 30. In this case, the control unit 6 generates heat only by the center heating element 52 located inside the plurality of heating elements 50. On the other hand, in the case of the sheet S having a large width in the y direction, the control unit 6 generates heat by all the heating elements 45.

[0093] like Figure 4 As shown, the heating element 50 and the wiring group 55 are formed on the surface of the insulating layer 44 facing the +z direction. The protective layer 46 is formed of a glass material or the like so as to cover the heating element 50 and the wiring group 55. The protective layer 46 forms the first surface 41 of the heater unit 40. Since the viscosity of the grease 47 between the protective layer 46 and the cylindrical body 37 decreases when the heater unit 40 generates heat, the sliding property between the heater unit 40 and the cylindrical body 37 is ensured.

[0094] 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. Thus, the warping of the substrate 43 is suppressed.

[0095] like Figure 3 As shown, the entire heating region 45 is included in the region of the fixing nip FN and is disposed at the center of the fixing nip FN. Thus, the heat distribution in the fixing nip FN becomes uniform, and the sheet S passing through the fixing nip FN is uniformly heated.

[0096] The heat transfer member 65 is formed of a material having a higher thermal conductivity than the substrate 43. For example, the heat transfer member 65 is formed of a metal material such as copper, aluminum, or a graphite sheet. The heat transfer member 65 overlaps the heater unit 40 in the z direction. The heat transfer member 65 is a rectangular plate corresponding to the outer shape of the substrate 43 of the heater unit 40. The heat transfer member 65 overlaps all the heat generating elements 50 in a plan view from the z direction (see FIG. 1 ). Figure 5 The heat transfer member 65 is in contact with at least a portion of the second surface 42 of the heater unit 40. The heat transfer member 65 makes the temperature distribution of the heater unit 40 uniform.

[0097] The holder 38 is formed of a resin material such as a liquid crystal polymer. The holder 38 has a length in the y direction. The holder 38 is arranged so as to cover the portion of the heater unit 40 in the -z direction and the portions located on both sides in the x direction. The holder 38 holds the heater 36. In a state where the heat transfer member 36 is clamped between the holder 38 and the heater unit 40, the holder 38 only holds the two ends of the substrate 43 of the heater unit 40 in the y direction so that they cannot be separated in the +z direction. Round chamfers are formed at both ends of the holder 38 in the x direction. The holder 38 supports the inner circumferential surface of the cylindrical body 37 at both ends of the heater unit 40 in the x direction.

[0098] The retainer 38 includes a base 381, an upstream side wall 382, ​​and a downstream side wall 383. The base 381 supports the second surface 42 of the heater unit 40 of the heater 36. The retainer 38 sandwiches an insulating sheet between the base 381 and the heat transfer member 65. For example, the insulating sheet is a polyimide sheet. The upstream side wall 382 protrudes from the end of the base 381 in the -x direction toward the roller 31. The downstream side wall 383 protrudes from the end of the base 381 in the +x direction toward the roller 31. The heater 36 is arranged between the upstream side wall 382 and the downstream side wall 383. The ends of the upstream side wall 382 and the downstream side wall 383 in the +z direction extend in the y direction. The ends of the upstream side wall 382 and the downstream side wall 383 in the +z direction are respectively located at approximately the same position as the first surface 41 of the heater unit 40 in the z direction.

[0099] The support 39 is formed of a steel plate material or the like. The support 39 has a length in the y direction. The cross section of the support 39 perpendicular to the y direction is U-shaped. The support 39 is installed in the -z direction of the holder 38 in such a way that the opening of the U is blocked by the base 381 of the holder 38. Both ends of the support 39 in the y direction are fixed to the frame 34. The support 39 increases the bending rigidity of the membrane unit 35.

[0100] The temperature sensing element 60 is arranged at a position in the -z direction of the heater unit 40. The temperature sensing element 60 is arranged in a range overlapping with the heat generation area 45 in the y direction. The temperature sensing element 60 is in contact with the surface of the heat transfer member 65 facing the -z direction via an insulating sheet interposed between the base 381 of the retaining frame 38 and the heat transfer member 65. The temperature sensing element 60 is arranged on the inner side of the hole 384 that penetrates the base 381 of the retaining frame 38 in the z direction. The wiring of the temperature sensing element 60 is led out from the hole 384 of the retaining frame 38 in the -z direction. The temperature sensing element 60 is a thermometer 61 and a thermostat 62. The thermometer 61 is a thermistor. In the following description, the thermometer 61 and the thermostat 62 are sometimes referred to as a plurality of temperature sensing elements 60.

[0101] Figure 6 This is a top view of the thermometer and thermostat (viewed from the -z direction). Figure 6 In the figure, the description of the retainer 38 is omitted.

[0102] like Figure 6 As shown, the thermometer 61 detects the temperature of the heater 36. The thermometer 61 detects the temperature of the heater unit 40 via the heat transfer member 65. The thermometer 61 includes a central thermometer 611 and an end thermometer 612. The thermostat 62 includes a central thermostat 621 and an end thermostat 622. The central thermometer 611 and the central thermostat 621 are arranged at the position of the -z direction of the central heating element 50. On the other hand, the end thermostat 622 and the end thermometer 612 are arranged at the position of the -z direction of the first end heating element 51 and the second end heating element 53.

[0103] The thermometer 61 and the thermostat 62 are arranged in the y direction. Specifically, the end thermometer 612, the central thermometer 611, the central thermostat 621, and the end thermostat 622 are arranged in order in the +y direction. Specifically, the central thermometer 611 and the central thermostat 621 are arranged so as to face the central part of the heater unit 40 in the y direction. The end thermometer 612 is arranged next to the central thermometer 611 in the -y direction. In other words, the end thermometer 612 is arranged between the end of the substrate 43 of the heater unit 40 in the -y direction and the central thermometer 611. The end thermostat 622 is arranged next to the central thermostat 621 in the +y direction. In other words, the end thermostat 622 is arranged between the end of the substrate 43 of the heater unit 40 in the +y direction and the central thermostat 621.

[0104] like Figure 3 As shown, the plurality of temperature sensing elements 60 are urged by the urging member in the +z direction so as to protrude from the hole 384 of the holder 38 toward the heater unit 40. The temperature sensing elements 60 push the heater 36 in the +z direction relative to the holder 38. The temperature sensing elements 60 push the heat transfer member 65 in the +z direction, thereby indirectly pushing the heater unit 40 in the +z direction relative to the holder 38.

[0105] Figure 7 yes Figure 3 A cross-sectional view of the thin film unit along line VII-VII is shown.

[0106] Figure 7 The state in which the roller 31 is separated from the film unit 35 is shown. Figure 7 The state shown is an example of the third state. Figure 7 As shown, the heater 36 is configured to be pushed by the thermometer 61 and the thermostat 62. The heater 36 is configured to be partially separated from the base 381 of the holder 38 by being pushed by the thermometer 61 and the thermostat 62. Both ends of the heater unit 40 in the y direction are held by the holder 38. Therefore, the entire range of the heater 36 overlapping with the heat generation area 45 in the y direction is bent in a manner that a gap can be formed between the heater 36 and the base 381 of the holder 38.

[0107] In particular, since only the two ends in the y direction of the substrate 43 of the heater unit 40 are held so as not to be separated in the +z direction, the heater 36 is bent so as to generate a gap between the two ends in the y direction of the substrate 43. For example, the heater 36 is bent so as to have an arc shape. Therefore, regarding the size of the gap in the z direction, the size of the gap becomes the largest at the center in the y direction, and the size of the gap becomes the smallest at the ends in the y direction. At the ends in the y direction, the size of the gap is, for example, zero.

[0108] The end thermometer 612, the center thermometer 611, the center thermostat 621, and the end thermostat 622 are provided in the film unit 35. When the heater 36 is bent, the end thermometer 612 and the end thermostat 622 are in contact with the heat transfer member 65, and the center thermometer 611 and the center thermostat 621 are separated from the heat transfer member 65. Here, the end thermometer 612 and the end thermostat 622 are examples of end sensors. The center thermometer 611 and the center thermostat 621 are examples of center sensors. The heater 36 is pressed toward the roller 31 side by the end thermometer 612 and the end thermostat 622.

[0109] The cylindrical body 37 has a contact portion 371 that contacts the center portion in the y direction of the heater 36. The cylindrical body 37 is pressed by the center portion in the y direction of the heater 36 to form a gap with the heater unit 40. The gap between the cylindrical body 37 and the heater unit 40 increases from the contact portion 371 toward the outside in the y direction.

[0110] like Figure 6 As shown, when the temperature of the heater unit 40 detected via the heat transfer member 65 exceeds a predetermined temperature, the thermostat 62 cuts off the supply of electricity to the heat generating element 50. As a result, excessive heating of the cylindrical body 37 by the heater unit 40 is suppressed.

[0111] like Figure 3 As shown, the thin film thermometer 64 is in contact with the inner peripheral surface of a part of the cylindrical body 37. The thin film thermometers 64 are arranged at intervals in the y direction. The thin film thermometers 64 detect the temperatures of different parts of the cylindrical body 37 in the y direction.

[0112] Figure 8 It is a front view of the fixing device.

[0113] like Figure 8 As shown, the pressure mechanism 70 presses the roller 31 toward the cylindrical body 37. The pressure mechanism 70 is configured to change the pressure between the roller 31 and the cylindrical body 37. The pressure refers to the pressure applied between the roller 31 and the cylindrical body 37. In other words, the pressure mechanism 70 is configured to control the pressure. For example, the pressure mechanism 70 is configured to apply a first pressure between the roller 31 and the cylindrical body 37, and the pressure mechanism 70 is configured to apply a second pressure between the roller 31 and the cylindrical body 37. Here, the second pressure is smaller than the first pressure. The pressure mechanism 70 is configured to change the state between the roller 31 and the cylindrical body 37 by changing the pressure. Here, the "state between the roller 31 and the cylindrical body 37" means, for example, whether the fixing nip FN is formed, whether the roller 31 and the cylindrical body 37 are in contact, whether the roller 31 is away from the cylindrical body 37, and the change in the magnitude of the force applied between the roller 31 and the cylindrical body 37 when the roller 31 and the cylindrical body 37 are in contact.

[0114] The pressure mechanism 70 is configured to displace the roller 31 relative to the cylindrical body 37 in such a manner that the roller rotation center rc approaches and moves away from the cylindrical body 37 when the roller 31 is in contact with the cylindrical body 37. In the pressure mechanism 70, the above state can be transferred to a first state or a second state. The first state is a state in which a fixing nip FN is formed between the roller 31 and the cylindrical body 37. The second state is a state in which the force applied to the cylindrical body 37 and the roller 31 is smaller than that in the first state. Figure 8 The pressure mechanism 70 is shown in the first state. The fixing nip FN is defined in a state where the fixing device 30 can perform the fixing operation of the toner image on the sheet S. The second state corresponds to the energy saving mode or the sleep mode. For example, the sleep state is a state where the memory 92 is powered but the heater unit 40 is not powered. In the second state, the plastic deformation of the cylindrical body 37 is prevented by the pressure of the relaxation roller 31 against the cylindrical body 37.

[0115] The pressurizing mechanism 70 includes an arm 71, a push rod 72, a pin 73, and an elastic member 74. The structural members of the pressurizing mechanism 70 are respectively provided at both ends of the roller 31 in the y direction. The pressurizing mechanism 70 is plane-symmetrical with the xz plane passing through the center point of the roller 31 in the y direction as a symmetry plane. In the following, the structural members of the pressurizing mechanism 70 in the +y direction of the roller 31 are described.

[0116] The arm 71 has a length in the x direction. The arm 71 may also be formed of a steel plate material or the like. The arm 71 can rotate around the arm rotation center ac. The arm rotation center ac is located near the end of the arm 71 in the -x direction, and the central axis passing through the arm rotation center ac is parallel to the y direction.

[0117] The arm 71 includes an arm main body plate 711 and an arm connecting portion 712 .

[0118] The arm main body plate 711 is parallel to the xz plane. The pair of arm main body plates 711 is spaced apart in the y direction. A semicircular notch for rotatably supporting the roller 31 is provided in the arm main body plate 711 in the -y direction.

[0119] The arm connection part 712 connects the ends of the pair of arm main body plates 711 in the −z direction. The arm connection part 712 is located at both ends of the arm 71 in the x direction.

[0120] The push rod 72 may also be formed of a steel plate material or the like. The push rod 72 can rotate around the arm rotation center ac. The arm rotation center ac is located in the middle of the push rod 72 in the x direction. One side of the push rod 72 has a length in the +x direction from the arm rotation center ac. The other side of the push rod 72 has a length in the -x direction and the -z direction from the arm rotation center ac.

[0121] The push rod 72 includes a push rod body plate 721 and a push rod connecting portion 722 .

[0122] The push rod body plate 721 is parallel to the xz plane. The pair of push rod body plates 721 is spaced apart in the y direction. The pair of push rod body plates 721 is located on the inner side of the pair of arm body plates 711 in the y direction.

[0123] The push rod connection portion 722 connects the ends of the pair of push rod body plates 721 in the +z direction to each other.

[0124] The pin 73 is located at the ends of the arm 71 and the push rod 72 in the +x direction. The pin 73 is along the z direction. The pin 73 has a body 731 and a head 732 .

[0125] The body 731 is in the shape of a round bar. The first end of the body 731 in the -z direction is fixed to the arm connection part 712 by screwing or the like. The body 731 has a length in the +z direction from the arm connection part 712 toward the push rod connection part 722. The body 731 is inserted into the through hole formed in the push rod connection part 722 and has a length in the +z direction up to the push rod connection part 722.

[0126] The head portion 732 is located at the second end portion in the +z direction of the body portion 731. The diameter of the head portion 732 is larger than the diameter of the through hole of the push rod connection portion 722.

[0127] The elastic member 74 is supported by the pin 73. The elastic member 74 is on the same side (+x direction) as the roller rotation center rc relative to the arm rotation center ac. The elastic member 74 is between the arm 71 and the push rod 72. The elastic member 74 is located between the arm connection portion 712 and the push rod connection portion 722 in a compressed state. The elastic member 74 applies force to the arm 71 in the direction in which the roller 31 abuts against the cylindrical body 37. The elastic member 74 is a coil spring. The elastic member 74 is externally inserted into the body portion 731 of the pin 73.

[0128] The moving mechanism 80 moves the pressurizing mechanism 70 so that the above-mentioned state in the pressurizing mechanism 70 is transferred to the first state or the second state. By operating the moving mechanism 80, the pressurizing mechanism 70 can take only one of the first state and the second state. The moving mechanism 80 includes a cam follower 81, a cam 82, and a drive source 83. The cam follower 81 and the cam 82 are respectively arranged at both ends of the roller 31 in the y direction. The cam follower 81 is plane-symmetrical with the xz plane passing through the center point of the roller 31 in the y direction as a symmetry plane. The cam 82 is plane-symmetrical with the xz plane passing through the center point of the roller 31 in the y direction as a symmetry plane. In the following, the cam follower 81 and the cam 82 in the y direction of the roller 31 are described.

[0129] The cam follower 81 is located at the ends of the push rod 72 in the -x direction and the -z direction. The cam follower 81 is cylindrical and is located between the pair of push rod body plates 721. The cam follower 81 is a roller rotatable around a cam follower rotation center fc parallel to the y direction.

[0130] The cam 82 is adjacent to the cam follower 81 and is located in the +x direction of the cam follower 81. The cam 82 can rotate around the cam rotation center cc. The cam surface 84 constituting the profile of the cam 82 can abut against the outer peripheral surface of the cam follower 81. A pair of cams 82 located at both ends of the roller 31 in the y direction are connected by a cam shaft having a length in the y direction. The cam rotation center cc is located on the opposite side of the roller rotation center rc across the arm rotation center ac. The cam 82 receives the output of the drive source 83 and rotates around the cam rotation center cc only in the direction of the arrow C. The rotation angle of the cam 82 is detected by a sensor.

[0131] The cam surface 84 is formed so that the distance from the cam surface 84 to the cam rotation center cc changes according to the rotation angle of the cam 82. Hereinafter, the distance from the cam rotation center cc to the cam surface 84 is referred to as the outer diameter. The cam surface 84 includes a large diameter portion 841 having the largest outer diameter in the cam surface 84 and a small diameter portion 842 having the smallest outer diameter in the cam surface 84. The cam surface 84 extends continuously from the large diameter portion 841 to the small diameter portion 842 in the direction opposite to the rotation direction of the cam 82. The outer diameter of the cam surface 84 gradually decreases from the large diameter portion 841 to the small diameter portion 842 as it moves toward the direction opposite to the rotation direction of the cam 82. The cam surface 84 enables the cam follower 81 to roll continuously over the entire circumference as the cam 82 rotates.

[0132] The driving source 83 drives the cam shaft connecting the pair of cams 82 to rotate via a worm gear or the like. The driving source 83 drives the cam shaft to rotate the pair of cams 82. The driving source 83 rotates the cam 82 in only one direction around the cam rotation center cc. The driving source 83 is controlled by the control unit 6.

[0133] The operation of the pressurizing mechanism 70 will be described.

[0134] When the fixing device 30 performs the fixing operation, the moving mechanism 80 causes the roller 31 to come into contact with the cylindrical body 37. Figure 8 3 shows a first state in which the roller 31 is in contact with the cylindrical body 37. In the first state, the cam 82 is in contact with the large diameter portion 841 of the cam follower 81. In the first state, the fixing nip FN is formed by the cylindrical body 37 and the roller 31. In the first state, the roller 31 is elastically deformed.

[0135] Fig. 9 It is a diagram for explaining the operation of the pressurizing mechanism 70 . Fig. 9The pressing mechanism 70 is shown in the second state. The cam 82 is in contact with the small diameter portion 842 of the cam follower 81 in the second state. In the second state, the cylindrical body 37 and the roller 31 are in contact with each other, and the force applied to the cylindrical body 37 and the roller 31 is smaller than that in the first state. In the second state, the width of the clamping portion formed by the cylindrical body 37 and the roller 31 in the x direction is smaller than the width of the fixing clamping portion FN in the x direction. In the second state, the roller 31 can also be elastically deformed.

[0136] The transition operation of the moving mechanism 80 from the first state to the second state and the transition operation from the second state to the first state will be described.

[0137] exist Figure 8 In the first state shown, the roller 31 is elastically deformed by the reaction force that pushes the cylindrical body 37 between the roller 31 and the heater unit 40. The roller 31 is applied with a force in the +z direction by the restoring force of the elastic deformation. The roller 31 is pressed by the force in the +z direction around the arm rotation center ac in the direction of the arrow A. The arm 71 pressed by the roller 31 presses the push rod 72 in the direction of the arrow A around the arm rotation center ac via the compressed elastic member 74, and presses the cam follower 81 against the cam 82. The push rod 72 presses the roller 31 against the cylindrical body 37 via the elastic member 74 and the arm 71 by the reaction force of the cam follower 81 against the cam 82.

[0138] The cam 82 rotates in the direction of arrow C around the cam rotation center cc from the first state. The cam follower 81 moves relatively from the large diameter portion 841 toward the small diameter portion 842 along the cam surface 84 of the cam 82 while approaching the cam rotation center cc. The push rod 72 is allowed to rotate in the direction of arrow A around the arm rotation center ac. The push rod 72 rotates in the direction of arrow A around the arm rotation center ac by the restoring force of the elastic member 74. While the push rod 72 rotates, the arm 71 rotates in the direction of arrow A around the arm rotation center ac in a manner that matches the restoring force of the elastic member 74 with the restoring force of the roller 31. By the arm 71 rotating in the direction of arrow A around the arm rotation center ac, the roller 31 is displaced in the +z direction, so that the roller rotation center rc is away from the film unit 35.

[0139] Furthermore, when the cam 82 rotates in the direction of arrow C around the cam rotation center cc, the push rod 72 rotates in the direction of arrow A around the arm rotation center ac. The cam follower 81 abuts against the small diameter portion 842 of the cam surface 84 of the cam 82, and the push rod 72 completely rotates in the direction of arrow A around the arm rotation center ac. In the second state, the roller 31 contacts the entire length of the cylindrical body 37 in the y direction. Compared with the first state, the roller 31 reduces the force applied to the cylindrical body 37. In the second state, the roller 31 presses the heater unit 40 and the heat transfer member 65 in the -z direction via the cylindrical body 37, so that no gap is formed between the heat transfer member 65 and the base 381 of the retaining frame 38. In other words, in the second state, the fixing nip FN is not formed in the pressure mechanism 70. In this case, the cylindrical body 37 and the roller 31 are in contact with each other.

[0140] The cam 82 rotates in the direction of arrow C around the cam rotation center cc from the second state. The cam follower 81 moves away from the cam rotation center cc while relatively moving along the cam surface 84 of the cam 82 from the small diameter portion 842 toward the large diameter portion 841. The push rod 72 compresses the elastic member 74 and rotates in the direction of arrow B around the arm rotation center ac. As the push rod 72 rotates, the arm 71 receives the restoring force of the elastic member 74 and rotates in the direction of arrow B around the arm rotation center ac. The arm 71 rotates in the direction of arrow B around the arm rotation center ac, and the roller 31 is pressed against the cylindrical body 37. The roller 31 is pressed against the cylindrical body 37, thereby being displaced in the -z direction, so that the roller rotation center rc approaches the film unit 35.

[0141] Furthermore, when the cam 82 rotates around the cam rotation center cc in the direction of the arrow C, the push rod 72 rotates around the arm rotation center ac in the direction of the arrow B. The cam follower 81 abuts against the large diameter portion 841 of the cam surface 84 of the cam 82, and the push rod 72 is in the first state in which it is completely rotated around the arm rotation center ac in the direction of the arrow B. Based on the above, the moving mechanism 80 causes the pressing mechanism 70 to shift from the first state to the second state, or from the second state to the first state.

[0142] The deformation amount of the elastic layer 33 in the second state is smaller than the deformation amount of the elastic layer 33 in the first state.

[0143] Fig.10 yes Figure 3 A cross-sectional view of the fixing device taken along line VII-VII shows the pressurizing mechanism in the second state.

[0144] like Fig.10As shown, in the second state, the roller 31 presses the heat transfer member 65 against the base 381 via the cylindrical body 37 and the heater unit 40, so that the heat transfer member 65 does not float from the base 381 of the holder 38. In this state, the heat sensitive element 60 is restricted from protruding from the hole 384 of the holder 38 toward the heater unit 40 by the heat transfer member 65. In the first state, the force applied to the cylindrical body 37 and the roller 31 is greater than that in the second state. Therefore, the roller 31 presses the heat transfer member 65 against the base 381 via the cylindrical body 37 and the heater unit 40, so that the heat transfer member 65 does not float from the base 381 of the holder 38. In all states that can be transferred by the operation of the moving mechanism 80, the heat transfer member 65, the heater unit 40 and the temperature sensitive element 60 are pressed against the holder 38 side by the roller 31 and do not move relative to the holder 38.

[0145] and Figure 7 The third state shown is different, in Fig.10 In the second state shown, the center thermometer 611 and the center thermostat 621 are in contact with the heat transfer member 65 , and the end thermometer 612 and the end thermostat 622 are in contact with the heat transfer member 65 .

[0146] The functional structure of the control unit 6 will be described.

[0147] Fig.11 It is a block diagram showing the functional structure of the control unit.

[0148] like Fig.11 As shown, the control unit 6 includes a heating control unit 94, a pressurization control unit 95, a counting unit 96 and a drive control unit 97. More specifically, the control unit 6 includes, for example, a recording medium and a processor. In other words, the heating control unit 94, the pressurization control unit 95, the counting unit 96 and the drive control unit 97 may also include a recording medium and a processor, respectively. On the recording medium, for example, a computer program for controlling the image forming device 1 is stored. The processor is configured to process various information. The various information refers to, for example, information stored in the recording medium, information obtained by executing the computer program, etc. The control unit 6 controls the operation of the image forming device 1 in a comprehensive manner.

[0149] The heating control unit 94 energizes the heater unit 40 in the heating mode, and stops energizing the heater unit 40 in the stop mode. The heating control unit 94 measures the temperature of the heating area 45 by the thermometer 61 when the fixing device 30 is started. When the temperature of the heating area 45 is lower than the predetermined temperature, the heating control unit 94 heats the heating area 45 for a short time before the roller 31 starts rotating. The viscosity of the grease 47 applied to the inner peripheral surface of the cylindrical body 37 is reduced by the heating of the heating area 45. Thus, the sliding property between the heater unit 40 and the cylindrical body 37 is ensured when the roller 31 starts rotating.

[0150] The heating control unit 94 measures the temperature of the heat transfer member 65 by the thermometer 61 when the fixing device 30 is in operation. The heating control unit 94 controls the power supply to the heat generating area 45 based on the temperature measurement result of the heat transfer member 65. Thus, the temperature of the heat transfer member 65 in contact with the holder 38 is maintained lower than the heat resistance temperature of the holder 38.

[0151] The heating control unit 94 measures the temperature of each portion of the cylindrical body 37 in the y direction using the film thermometer 64 when the fixing device 30 is in operation. The heating control unit 94 controls the energization of the heat generating area 45 based on the temperature measurement result of each portion of the cylindrical body 37 in the y direction.

[0152] The pressurization control unit 95 controls the moving mechanism 80. The pressurization control unit 95 controls the driving source 83 of the moving mechanism 80 to transfer the state of the pressurization mechanism 70 to the first state or the second state. The pressurization control unit 95 determines whether the state of the pressurization mechanism 70 is the first state or the second state based on the detection result of the sensor that detects the rotation angle of the cam 82, and stops the driving of the driving source 83 that rotates the cam 82. In the stop mode of the heating control unit 94, when the detected temperature of the thermometer 61 is below the specified value, the pressurization control unit 95 controls the driving source 83 of the moving mechanism 80 to make the pressurization mechanism 70 the second state.

[0153] The counting unit 96 counts at least one of the transition from the first state to the second state and the transition from the second state to the first state.

[0154] When the count of the counting unit 96 is equal to or greater than a predetermined value, the drive control unit 97 restricts the transition to the second state.

[0155] In the present embodiment, the pressure mechanism 70 can be transferred to the following states: a first state in which the fixing nip FN is formed by the cylindrical body 37 and the roller 31; and a second state in which the cylindrical body 37 and the roller 31 are in contact with each other and the force applied to the cylindrical body 37 and the roller 31 is smaller than that in the first state. According to this structure, when the first state or the second state is transferred, the heater 36 held by the retaining frame 38 does not move. Since the heater 36 does not move, the change of the load applied to the thermometer 61 in contact with the heater 36 can be suppressed. Therefore, the deterioration of the internal components of the thermometer 61 can be suppressed, and the durability of the fixing device 30 can be improved. In the case where the thermometer 61 is a thermistor, the above-mentioned effect can be clearly obtained.

[0156] The moving mechanism 80 has a cam 82, and the small diameter portion 842 of the cam surface 84 with the smallest outer diameter abuts against the cam follower 81 in the second state. According to this structure, in the second state, the cam follower 81 is closest to the cam rotation center cc of the cam 82. Therefore, even if the cam 82 rotates only in one direction, when the cam 82 is rotated, the pressurizing mechanism 70 can only take one of the first state and the second state regardless of the rotation angle of the cam 82. Therefore, it is possible to reliably prevent the heater 36 from being displaced when the cam 82 is rotated.

[0157] The state of the pressure mechanism 70 can be transferred to the third state. In the third state, the holder 38 separates the roller 31 from the cylindrical body 37 and holds the heater 36 in a manner that a gap can be formed between the heater 36 and the holder 38. According to this structure, when the roller 31 is separated from the cylindrical body 37, the heater 36 is displaced and a load change occurs in the thermometer 61. Therefore, in the fixing device 30 of this embodiment, since the cylindrical body 37 and the roller 31 are in contact with each other in the second state, the displacement of the heater 36 is restricted, and it is preferable to obtain the above-mentioned effect.

[0158] A heat transfer member 65 is disposed between the base 381 of the holder 38 and the heater unit 40. According to this structure, compared with a structure without a heat transfer member, more parts are deformed or displaced by the change in the pressure applied by the roller 31 to the film unit 35. Therefore, an element causing a load change is added to the thermometer 61, and the deterioration of the internal components of the thermometer 61 may be accelerated. Therefore, the fixing device 30 of this embodiment preferably obtains the above-mentioned effect by limiting the displacement of the heater 36.

[0159] When the state of the pressurizing mechanism 70 is shifted to the first state or the second state, the displacement of the heater 36 is restricted by the roller 31. According to this structure, it is possible to suppress the variation of the load applied to the thermometer 61. Therefore, the above-mentioned effects can be achieved.

[0160] The heater 36 is held by the holder 38 outside the heat generating area 45 in the axial direction. According to this structure, when the roller 31 is separated from the film unit 35, the heater 36 is pressed by the thermometer 61 and may bend, and the load applied to the thermometer 61 varies due to the bending of the heater 36. Therefore, in the fixing device 30 of this embodiment, since the cylindrical body 37 and the roller 31 are also in contact with each other in the second state, the displacement of the heater 36 is restricted, and it is preferable to obtain the above-mentioned effect.

[0161] The heater 36 is pressed toward the roller 31 by the thermometer 61. According to this structure, when the heater 36 is displaced, the load applied to the thermometer 61 pressing the heater 36 varies. Therefore, in the fixing device 30 of this embodiment, since the cylindrical body 37 and the roller 31 are also in contact with each other in the second state, the displacement of the heater 36 is restricted, and thus the above-mentioned effect is preferably obtained.

[0162] The cylindrical body 37 has a contact portion 371 that contacts the heater 36 when the cylindrical body 37 is separated from the roller 31. When the cylindrical body 37 is separated from the roller 31, a gap is formed between the cylindrical body 37 and the heater 36 that expands as it moves from the contact portion 371 toward the outside in the y direction. According to this structure, when the roller 31 is separated from the cylindrical body 37, the cylindrical body 37 is pressed by the heater 36 and displaced in a manner that forms a gap with respect to the heater 36. Therefore, in the fixing device 30 of this embodiment, since the cylindrical body 37 and the roller 31 are also in contact with each other in the second state, the displacement of the heater 36 and the deformation of the cylindrical body 37 are restricted, and thus deterioration due to repeated deformation of the cylindrical body 37 can be suppressed.

[0163] When the temperature detected by the thermometer 61 is below the predetermined value, the pressurizing control unit 95 controls the driving source 83 of the moving mechanism 80 to bring the pressurizing mechanism 70 into the second state. According to this structure, when the temperature detected by the thermometer 61 is higher than the predetermined value and there is a high possibility that the fixing device 30 will be used immediately, the transition to the second state can be suppressed. Therefore, frequent operation of the moving mechanism 80 can be suppressed, and the deterioration of the internal components of the thermometer 61 can be more effectively suppressed.

[0164] The counting unit 96 counts at least one of the transition from the first state to the second state in the pressurizing mechanism 70 and the transition from the second state to the first state in the pressurizing mechanism 70. The drive control unit 97 controls the moving mechanism 80. When the count of the counting unit 96 is greater than a predetermined value, the drive control unit 97 restricts the transition to the second state. According to this structure, the degree of deterioration of the internal components of the thermometer 61 can be suppressed from exceeding a certain standard. Therefore, it is possible to avoid failure of the thermometer 61 due to life.

[0165] The control unit 6 may control each unit of the image forming apparatus 1 to restrict the process of forming an image on the sheet S in the second state. According to this configuration, it is possible to suppress the sheet S from being conveyed to the fixing device 30 in a state where the fixing nip FN is not formed.

[0166] In the first embodiment, the heater 36 has the heat transfer member 65, but the heater may not have the heat transfer member. In this case, the temperature sensing element 60 is provided in contact with the heater unit 40. According to this structure, since the state of the pressurizing mechanism 70 is configured such that no gap is formed between the heater unit 40 and the base 381 of the holder 38 in either the first state or the second state, the above-mentioned effect is achieved.

[0167] (Second Embodiment)

[0168] Reference Fig.12 The heater unit 240 of the second embodiment will be described. The configuration other than that described below is the same as that of the first embodiment. Fig.12 It is a bottom view of the heater unit according to the second embodiment.

[0169] In the second embodiment, the arrangement of the heat generating element 250 of the heater unit 240 is different from that of the first embodiment. The heater unit 240 includes a heat generating region 245 and a wiring group 255 instead of the heat generating region 45 and the wiring group 55 of the first embodiment.

[0170] The heat generating region 245 is disposed on the substrate 43. The entire outer shape of the heat generating region 245 is formed in a rectangular shape with the y direction as the long side direction and the x direction as the short side direction.

[0171] The heating area 245 has a plurality of heating elements 250. The plurality of heating elements 250 have a pair of first heating elements 251, a second heating element 252, and a third heating element 253. The plurality of heating elements 250 are arranged in the order of the first heating element 251, the second heating element 252, the third heating element 253 on one side, and the first heating element 251 on the other side in the x direction. Each heating element 250 has a long side in the y direction. Each heating element 250 has a length corresponding to the width of various sheets. The second heating element 252 is shorter than the first heating element 251 in the y direction. Both ends of the second heating element 252 in the y direction are located at a position closer to the inside than both ends of the first heating element 251 in the y direction. The third heating element 253 is shorter than the second heating element 252 in the y direction. Both ends of the third heating element 253 in the y direction are located at a position closer to the inside than both ends of the second heating element 252 in the y direction. The wiring of the wiring group 255 is connected to each heating element 250. The heat generating area 245 generates heat by being energized via the wiring group 255. The control unit 6 controls the corresponding heat generating element 250 to generate heat in accordance with the width of the sheet S passing through.

[0172] In the second embodiment described below, since the displacement of the heater 36 including the heater unit 240 is also restricted, the same effects as those of the first embodiment are achieved.

[0173] (Third Embodiment)

[0174] Reference Fig.13 A heater unit 340 according to the third embodiment will be described. The configuration other than that described below is the same as that of the first embodiment. Fig.13 It is a bottom view of the heater unit according to the third embodiment.

[0175] In the third embodiment, the arrangement of the heat generating element 350 of the heater unit 340 is different from that of the first embodiment. The heater unit 340 has a heat generating region 345 and a wiring group 355 instead of the heat generating region 45 and the wiring group 55 of the first embodiment.

[0176] The heat generating region 345 is disposed on the substrate 43. The entire outer shape of the heat generating region 345 is formed in a rectangular shape with the y direction as the long side direction and the x direction as the short side direction.

[0177] The heating area 345 has a plurality of heating elements 350. The plurality of heating elements 350 have a pair of first heating elements 351 and a second heating element 352. The plurality of heating elements 350 are arranged in the order of the first heating element 351 on one side, the second heating element 352 on the other side, and the first heating element 351 on the other side in the x direction. Each heating element 350 has the y direction as the long side direction. The first heating element 351 becomes thicker as it goes from the center of the y direction toward the end. In the y direction, the two ends of the pair of first heating elements 351 are at approximately the same position as each other. The second heating element 352 becomes thinner as it goes from the center of the y direction toward the end. In the y direction, the two ends of the second heating element 352 are at approximately the same position as the two ends of each first heating element 351.

[0178] The wiring of the wiring group 355 is connected to each heating element 350. The heating area 345 is energized via the wiring group 355 to generate heat. The control unit 6 makes the corresponding heating element 350 generate heat in accordance with the width of the sheet S passing through. When only the first heating element 351 is heated, the heat generated in the heating area 345 decreases from the center of the y direction toward the end. On the other hand, when a pair of the first heating element 351 and the second heating element 352 are heated at the same time, the heat generated in the heating area 345 is averaged over the entire length in the y direction compared to the case where only the first heating element 351 is heated. Therefore, when a sheet S of a relatively small width passes through, the control unit 6 only energizes the first heating element 351. When a sheet S of a relatively large width passes through, the control unit 6 energizes the first heating element 351 and the second heating element 352.

[0179] In the third embodiment described above, since the displacement of the heater 36 including the heater unit 340 is also restricted, the same effects as those of the first embodiment are achieved.

[0180] In the above embodiment, the pressurizing mechanism 70 presses the roller 31 toward the cylindrical body 37, but the present invention is not limited to this structure. The pressurizing mechanism may be configured to pressurize a film unit having a cylindrical body toward the roller.

[0181] In the above embodiment, the first surface 41 of the heater unit 40 is in contact with the inner surface of the cylindrical body 37, but it is not limited to this structure. The heater may also have a heat-distributing member between the first surface of the heater unit and the inner surface of the cylindrical body. In this case, the heater may not have a heat transfer member between the heater unit and the holder.

[0182] According to at least one embodiment described above, the state of the pressure mechanism can be transferred to a first state or a second state. In the first state, a fixing clamp is formed by the cylindrical body and the roller. In the second state, the cylindrical body and the roller are in contact with each other, and the force applied to the cylindrical body and the roller is smaller than that in the first state. According to this structure, when the state of the pressure mechanism is transferred to the first state or the second state, the heater held on the retaining frame does not move. Since the heater does not move, changes in the load applied to the thermometer can be suppressed. Therefore, it is possible to suppress the deterioration of the internal components of the thermometer and improve the durability of the fixing device.

[0183] Several embodiments of the present invention have been described, but these embodiments are only presented as examples and are not intended to limit the scope of the invention. These embodiments can be implemented in various other ways, and various omissions, substitutions, and changes can be made without departing from the scope of the purpose of the invention. These embodiments and their variations are included in the scope and purpose of the invention, and are also included in the invention described in the claims and their equivalents.

Claims

1. A fixing device, comprising: cylindrical body; A heater is arranged inside the cylindrical body and has a heating area with the axial direction of the cylindrical body as the long side direction and generates heat by energizing; a holding frame for holding the heater; a sensor, in contact with the heater, to detect a temperature of the heater; a roller in contact with the outer peripheral surface of the cylindrical body and forming a nip portion between the roller and the cylindrical body; and The pressurizing mechanism changes the pressure between the cylindrical body and the roller.

2. The fixing device according to claim 1, wherein: The pressurizing mechanism changes the pressure so as to cause a state transition between the cylindrical body and the roller. The state is the first state or the second state, In the first state, the clamping portion is formed by the cylindrical body and the roller. In the second state, the cylindrical body and the roller are in contact with each other, and the force applied to each other by the cylindrical body and the roller is smaller than that in the first state.

3. The fixing device according to claim 2, wherein: The roller has an elastic layer, The deformation amount of the elastic layer in the second state is smaller than the deformation amount of the elastic layer in the first state.

4. The fixing device according to claim 2, wherein: In the pressurizing mechanism, the state can be transferred to a third state, In the third state, the roller is separated from the cylindrical body, and the holder holds the heater so that a gap can be formed between the heater and the holder within a range overlapping with the heat generating region in the axial direction.

5. The fixing device according to claim 2, wherein: The heater includes a heater unit and a heat transfer member, wherein the heat transfer member is located between the heater unit and the holder. The sensor includes a central sensor and an end sensor, In the second state, the center sensor and the end sensors are in contact with the heat transfer member.

6. The fixing device according to claim 5, wherein: The center sensor and the end sensor are supported by the retaining frame, The center sensor is arranged to face the center portion of the heater unit, and the end sensor is arranged between the end portion of the heater unit and the center sensor.

7. The fixing device according to claim 1, wherein: The cylindrical body has a contact portion that contacts the heater in a state of being away from the roller. When the cylindrical body is away from the roller, a gap is formed between the heater and the cylindrical body. The gap increases from the contact portion toward the outer side in the axial direction.

8. The fixing device according to claim 2, wherein: The heater includes a heater unit and a heat transfer member between the heater unit and the holder.

9. The fixing device according to claim 8, wherein: The sensor includes a central sensor and an end sensor, In the pressurizing mechanism, the state can be transferred to a third state, In the third state, the center sensor is spaced apart from the heat transfer member, and the end sensors are in contact with the heat transfer member.

10. The fixing device according to claim 9, wherein: The center sensor and the end sensor are supported by the retaining frame, The center sensor is arranged to face the center portion of the heater unit, and the end sensor is arranged between the end portion of the heater unit and the center sensor.

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