Heating device, fixing device, and image forming apparatus

Abstract

To provide a heating device that can easily assemble a heater, a heater holder, and a stay in a normal assembly state.SOLUTION: A heating device according to the present application invention has: a fixing belt 20; a plate-like heater 22; a heater holder 23; a stay 24; a pair of end holding members 53 that each has a bridging part 53h that opens and is in direct or indirect contact with end sides of the fixing belt 20, heater 22, heater holder 23, and stay 24 to bridge the components, and a stay support part that faces the bridging part 53h and supports the end of the stay, in which the end sides other than a heat generation part of the heater are included inside the openings; and a pressure roller 21. When the height from the stay 24 to a regulation part 23c of the heater holder 23 in a normal assembly state is defined as A, the opening width between a stay support part 53d and the bridging part 53h of the end holding member 53 as B, and the thickness of the heater 22 as C, the relationship of A<B<A+C is satisfied.SELECTED DRAWING: Figure 13

Description

Technical Field

[0001] The present invention relates to a heating device, a fixing device, and an image forming apparatus.

Background Art

[0002] In a fixing device used in an image forming apparatus such as a copying machine or a printer, a generally known one uses an elongated plate-shaped heater that is slidable on the inner surface of a fixing belt as a rotatable cylindrical member. The heater is held by a heater holder, and the heater holder is supported by a stay.

[0003] In a correct assembled state where the assembly of the heater, the heater holder, and the stay is correctly assembled, both ends of the assembly are held by a pair of end holding members. The end holding member has a U-shaped opening for receiving both ends of the assembly. It is also known that both ends of the U-shaped opening are connected by a bridging portion for reinforcement (Patent Document 1: Japanese Patent No. 5924915). Further, the end holding member has a guide groove, and the end holding member is assembled to the side wall frame of the fixing device by engaging the guide groove with an insertion groove formed in a pair of left and right side wall frames that are part of the frame of the fixing device.

[0004] The heater holder has a fitting groove for fitting the heater. There is no problem if the assembly is in the correct assembled state, but the correct assembly of the assembly is not easy.

[0005] That is, since the elongated plate-shaped heater is thin and easily bendable, it is not easy to correctly fit into the fitting groove of the heater holder. Even if the heater is correctly fitted into the fitting groove of the heater holder, when the fixing belt is placed over it, the heater may unexpectedly come out of the fitting groove, and moreover, this fitting defect is often not visually confirmable.

[0006] Thus, it is difficult to surely grasp the normal assembled state of the assembly, and there may be a case where the assembly is assembled to the fixing device with the heater protruding from the fitting groove. If this is done, the pressing force of the pressing roller may concentrate on a part of the heater, causing the heater to crack, or there may be a fixing failure due to poor heat conduction of the heater to the fixing belt during printing, or the heater may crack due to thermal stress.

Summary of the Invention

Problems to be Solved by the Invention

[0007] An object of the present invention is to provide a heating device capable of easily assembling a heater, a heater holder, and a stay in a normal assembled state.

Means for Solving the Problems

[0008] In order to solve the above problems, the invention according to claim 1 includes an endless cylindrical member that is rotatable and has a rotational axis direction, a plate-shaped heater that has a longitudinal direction along the rotational axis direction and slides on the inner surface of the cylindrical member, a heater holder that holds the heater, a stay that supports the back side of the heater holder, a bridging portion that directly or indirectly contacts each end side of the cylindrical member, the heater, the heater holder, and the stay in the rotational axis direction and bridges them so as to open, a stay support portion that faces the bridging portion and supports the end of the stay, a pair of end holding members that include an end side more than the heat generating portion of the heater inside the opening, and a pressing member that is pressed against the heater via the cylindrical member and forms a nip portion with the heater. In a heating device that heats a recording material using the cylindrical member heated by the heater while sandwiching and conveying the recording material at the nip portion, the heater holder has a holding portion where the heater is held and a restricting portion that is located at an end in the longitudinal direction of the holding portion and restricts the longitudinal movement of the heater. When the height from the stay support portion to the restricting portion of the heater holder in the normal assembled state of the heater, the heater holder, and the stay is A, the opening width between the stay support portion and the bridging portion of the end holding member is B, and the thickness of the heater is C, the heating device is characterized in that the relationship of A < B < A + C is satisfied.

Advantages of the Invention

[0009] According to the present invention, the heater, the heater holder, and the stay can be easily assembled in a normal assembled state.

Brief Description of the Drawings

[0010]

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Mode for Carrying Out the Invention

[0011] Embodiments according to the present invention will be described below with reference to the drawings. In each drawing, components such as members and constituent parts having the same function or shape are given the same reference numerals as much as possible, and the description thereof will be omitted after being described once.

[0012] ●Configuration of Image Forming Apparatus FIG. 1 is a schematic configuration diagram of an image forming apparatus according to an embodiment of the present invention. The image forming apparatus 100 shown in FIG. 1 includes four image forming units 1Y, 1M, 1C, and 1Bk that are detachable from the image forming apparatus main body.

[0013] Each of the image forming units 1Y, 1M, 1C, and 1Bk has the same configuration except that it contains different color developers of yellow, magenta, cyan, and black corresponding to the color separation components of a color image. Specifically, each of the image forming units 1Y, 1M, 1C, and 1Bk includes a drum-shaped photoreceptor 2 as an image carrier, a charging device 3 that charges the surface of the photoreceptor 2, a developing device 4 that supplies toner as a developer to the surface of the photoreceptor 2 to form a toner image, and a cleaning device 5 that cleans the surface of the photoreceptor 2.

[0014] The image forming apparatus 100 also includes an exposure device 6 that exposes the surface of each photoreceptor 2 to form an electrostatic latent image, a paper feeding device 7 that supplies a sheet of paper P as a recording medium, a transfer device 8 that transfers the toner image formed on each photoreceptor 2 to the sheet of paper P, a fixing device 9 that fixes the toner image transferred to the sheet of paper P, and a paper discharging device 10 that discharges the sheet of paper P outside the apparatus.

[0015] The transfer device 8 includes an endless intermediate transfer belt 11 as an intermediate transfer member stretched by a plurality of rollers, four primary transfer rollers 12 as primary transfer members that transfer the toner image on each photoreceptor 2 to the intermediate transfer belt 11, and a secondary transfer roller 13 as a secondary transfer member that transfers the toner image transferred onto the intermediate transfer belt 11 to the sheet of paper P. The plurality of primary transfer rollers 12 are each in contact with the photoreceptor 2 via the intermediate transfer belt 11.

[0016] As a result, the intermediate transfer belt 11 and each photoreceptor 2 are in contact with each other, and a primary transfer nip is formed therebetween. On the other hand, the secondary transfer roller 13 is in contact with one of the rollers that stretch the intermediate transfer belt 11 via the intermediate transfer belt 11. As a result, a secondary transfer nip is formed between the secondary transfer roller 13 and the intermediate transfer belt 11.

[0017] Also, a paper conveyance path 14 through which the sheet of paper P sent out from the paper feeding device 7 is conveyed is formed inside the image forming apparatus 100. A pair of timing rollers 15 are provided midway between the paper feeding device 7 and the secondary transfer nip (secondary transfer roller 13) in the paper conveyance path 14.

[0018] ● Printing operation of the image forming apparatus Next, referring to FIG. 1, the printing operation of the image forming apparatus will be described. When an instruction to start the printing operation is given, in each image forming unit 1Y, 1M, 1C, 1Bk, the photosensitive member 2 is rotationally driven clockwise in FIG. 1, and the surface of the photosensitive member 2 is charged to a uniform high potential by the charging device 3. Next, based on the image information of the document read by the document reading device or the print information instructed from the terminal, the exposure device 6 exposes the surface of each photosensitive member 2, so that the potential of the exposed portion decreases and an electrostatic latent image is formed. Then, toner is supplied from the developing device 4 to this electrostatic latent image, and a toner image is formed on each photosensitive member 2.

[0019] When the toner image formed on each photosensitive member 2 reaches the primary transfer nip (the position of the primary transfer roller 12) as the photosensitive member 2 rotates, it is transferred so as to sequentially overlap the intermediate transfer belt 11 that is rotationally driven counterclockwise in FIG. 1. Then, the toner image transferred onto the intermediate transfer belt 11 is conveyed to the secondary transfer nip (the position of the secondary transfer roller 13) as the intermediate transfer belt 11 rotates, and is transferred to the sheet P conveyed to the secondary transfer nip.

[0020] This sheet P is supplied from the paper feeding device 7. The sheet P supplied from the paper feeding device 7 is once stopped by the timing roller 15, and then is conveyed to the secondary transfer nip in accordance with the timing when the toner image on the intermediate transfer belt 11 reaches the secondary transfer nip.

[0021] Thus, a full-color toner image is carried on the sheet P. Also, after the toner image is transferred, the toner remaining on each photosensitive member 2 is removed by each cleaning device 5.

[0022] The sheet P onto which the toner image has been transferred is conveyed to the fixing device 9, and the toner image is fixed to the sheet P by the fixing device 9. Thereafter, the sheet P is discharged outside the apparatus by the paper discharging device 10, and a series of printing operations is completed.

[0023] ● Fixing device according to this embodiment Next, the fixing device in the embodiment according to the present embodiment will be described. Hereinafter, the longitudinal direction of the heater according to the present embodiment is the direction along the surface on which the resistance heating element of the base material is provided, and is denoted as X.

[0024] Also, the longitudinal direction of the heater may also be expressed as a direction parallel to the rotation axis direction of the fixing belt or the like, and the direction in which the resistance heating elements are arranged (arrangement direction). And the short side direction of the heater (sometimes also referred to as the width direction of the heater) is the direction orthogonal to the longitudinal direction, and is denoted as Y. Further, the thickness (height) direction of the heater is the direction orthogonal to the longitudinal direction and the short side direction of the heater, and is denoted as Z.

[0025] As shown in FIG. 2, the fixing device 9 according to the present embodiment includes a fixing belt 20 formed of an endless belt, a pressure roller 21 as a pressure member that contacts the outer peripheral surface of the fixing belt 20 to form a nip portion N, a heater 22 as a heating member that heats the fixing belt 20, a heater holder 23 as a holding member that holds the heater 22, a stay 24 as a support member that supports the heater holder 23, a thermistor 25 as a temperature detection means for detecting the temperature of the fixing belt 20, and the like.

[0026] The fixing belt 20 has, for example, a cylindrical base made of polyimide (PI) with an outer diameter of 25 mm and a thickness of 40 to 120 μm. On the outermost layer of the fixing belt 20, in order to enhance durability and ensure releasability, a release layer with a thickness of 5 to 50 μm made of a fluororesin such as PFA or PTFE is formed.

[0027] An elastic layer made of rubber or the like with a thickness of 50 to 500 μm may be provided between the base and the release layer. Also, the base of the fixing belt 20 is not limited to polyimide, and may be a heat-resistant resin such as PEEK or a metal base such as nickel (Ni) or SUS. The inner peripheral surface of the fixing belt 20 may be coated with polyimide, PTFE, or the like as a sliding layer.

[0028] The pressing roller 21 has, for example, an outer diameter of 25 mm and is composed of a solid iron core 21a, an elastic layer 21b formed on the surface of this core 21a, and a release layer 21c formed outside the elastic layer 21b. The elastic layer 21b is formed of silicone rubber and has a thickness of, for example, 3.5 mm. In order to enhance the releasability of the surface of the elastic layer 21b, it is desirable to form a release layer 21c of a fluororesin layer having a thickness of about 40 μm.

[0029] When the pressing roller 21 is biased toward the fixing belt 20 by a biasing means, the pressing roller 21 is pressed against the heater 22 via the fixing belt 20. Thereby, a nip portion N is formed between the fixing belt 20 and the pressing roller 21. Further, the pressing roller 21 is configured to be rotationally driven by a driving means. When the pressing roller 21 rotates in the direction of the arrow in FIG. 2, the fixing belt 20 is driven to rotate accordingly.

[0030] The heater 22 is a planar heating member provided longitudinally across the width direction of the fixing belt 20 and is composed of a plate-like base material 30, a resistance heating element 31 provided on the base material 30, an insulating layer 32 covering the resistance heating element 31, and the like. Further, the heater 22 is in contact with the inner peripheral surface of the fixing belt 20 on the insulating layer 32 side, and the heat generated from the resistance heating element 31 is transmitted to the fixing belt 20 through the insulating layer 32.

[0031] In the present embodiment, the resistance heating element 31 and the insulating layer 32 are provided on the fixing belt 20 side (nip portion N side) of the base material 30. Conversely, the resistance heating element 31 and the insulating layer 32 may be provided on the heater holder 23 side of the base material 30. In that case, since the heat of the resistance heating element 31 is transmitted to the fixing belt 20 through the base material 30, it is desirable that the base material 30 be made of a material having a high thermal conductivity such as aluminum nitride.

[0032] Also, by forming the base material 30 with a material having good thermal conductivity, even if the resistance heating element 31 is arranged on the side opposite to the fixing belt 20 side of the base material 30, it is possible to sufficiently heat the fixing belt 20. Note that the heater 22 according to the present embodiment has a plurality of forms described below, and these can be applied.

[0033] The heater holder 23 and the stay 24 are arranged on the inner circumferential side of the fixing belt 20. The stay 24 is composed of a metal channel material, and both end portions thereof are supported by both side plates of the fixing device 9. By supporting the heater holder 23 and the heater 22 held thereby by the stay 24, in a state where the pressure roller 21 is pressed against the fixing belt 20, the heater 22 surely receives the pressing force of the pressure roller 21 and stably forms the nip portion N.

[0034] Since the heater holder 23 is likely to become high temperature due to the heat of the heater 22, it is desirable to be formed of a heat-resistant material. For example, when the heater holder 23 is formed of a heat-resistant resin with low thermal conductivity such as LCP, heat transfer from the heater 22 to the heater holder 23 is suppressed and the fixing belt 20 can be efficiently heated.

[0035] Also, in order to reduce the contact area of the heater holder 23 with respect to the heater 22 and reduce the amount of heat transmitted from the heater 22 to the heater holder 23, the heater holder 23 is in contact with the base material 30 of the heater 22 via the protrusion 23a. Further, as in the present embodiment, by bringing the protrusion 23a of the heater holder 23 into contact with a portion other than the back side of the portion where the resistance heating element 31 of the base material 30 is arranged, that is, avoiding a portion where the temperature of the base material 30 is likely to rise, the amount of heat transmitted to the heater holder 23 can be further reduced and the fixing belt 20 can be efficiently heated.

[0036] Also, the heater holder 23 is provided with a guide portion 26 for guiding the fixing belt 20. The guide portions 26 are provided on the upstream side (the lower side of the heater 22 in FIG. 2) and the downstream side (the upper side of the heater 22 in FIG. 2) in the belt rotation direction of the heater 22, respectively.

[0037] Further, as shown in FIG. 3, a plurality of guide portions 26 on the upstream side and the downstream side are arranged at intervals across the longitudinal direction (belt width direction) of the heater 22. Each guide portion 26 is formed in a substantially fan shape and has an arcuate or convex curved surface belt facing surface 260 that extends in the belt circumferential direction so as to face the inner circumferential surface of the fixing belt 20 (see FIG. 2). Further, as shown in FIG. 3, in the present embodiment, except that the width β of the guide portions 26 arranged at both longitudinal ends of the heater 22 is formed larger than that of the other guide portions 26, the width β of each guide portion 26, the length in the belt circumferential direction (circumference) L, and the height E are formed to be the same.

[0038] In the fixing device 9 according to the present embodiment, when the printing operation is started, the pressure roller 21 is rotationally driven, and the fixing belt 20 starts to rotate passively. At this time, the inner circumferential surface of the fixing belt 20 contacts the belt facing surface 260 of the guide portion 26 and is guided, so that the fixing belt 20 rotates stably and smoothly.

[0039] Further, when electric power is supplied to the resistance heating element 31 of the heater 22, the fixing belt 20 is heated. Then, in a state where the temperature of the fixing belt 20 reaches a predetermined target temperature (fixing temperature), as shown in FIG. 2, the sheet P carrying the unfixed toner image is conveyed between the fixing belt 20 and the pressure roller 21 (nip portion N), so that the unfixed toner image is heated and pressurized and fixed to the sheet P.

[0040] ● First form of the heater FIG. 4 is a plan view of the first form of the heater. As shown in FIG. 4, the heater 22 of the first form has a plurality of resistance heating elements 31 arranged at intervals in its longitudinal direction (belt width direction). In other words, a plurality of divided heating portions 35 are configured in the belt width direction by the plurality of resistance heating elements 31.

[0041] Each resistive heating element 31 is electrically connected in parallel via a power supply line 33 to a pair of electrode portions 34 provided at both longitudinal ends of the base material 30. The power supply line 33 is composed of a conductor having a resistance value smaller than that of the resistive heating element 31.

[0042] From the viewpoint of ensuring the insulation between the resistive heating elements 31, the gap between adjacent resistive heating elements 31 is preferably 0.2 mm or more, and more preferably 0.4 mm or more. Further, if the gap between adjacent resistive heating elements 31 is too large, temperature drop is likely to occur in the gap portion, so from the viewpoint of suppressing temperature unevenness in the longitudinal direction, it is preferably 5 mm or less, and more preferably 1 mm or less.

[0043] The resistive heating element 31 is composed of a material having PTC (positive temperature coefficient) characteristics, and has the characteristic that the resistance value increases (the heater output decreases) as the temperature rises.

[0044] Due to this characteristic, for example, when a sheet of paper narrower than the overall width of the heating portion 35 is passed, in the region outside the paper width, the heat of the fixing belt 20 is not taken away by the paper, so the temperature of the resistive heating element 31 corresponding to that portion rises. Since the voltage applied to the resistive heating element 31 is constant, when the temperature of the resistive heating element 31 outside the paper width rises and its resistance value increases, conversely the output (heating amount) relatively decreases, suppressing the rise in the end portion temperature.

[0045] Also, since a plurality of resistive heating elements 31 are electrically connected in parallel, it is possible to suppress the temperature rise in the non-paper-passing portion while maintaining the printing speed. Note that the heating element constituting the heating portion 35 may be other than a resistive heating element having PTC characteristics. Further, the heating elements may be arranged in a plurality of rows in the short hand direction of the heater 22.

[0046] The resistive heating element 31 can be formed, for example, by applying a paste prepared by blending silver palladium (AgPd), glass powder, etc. to the base material 30 by screen printing or the like, and then firing the base material 30. In this embodiment, the resistance value of the resistive heating element 31 is set to 80 Ω at normal temperature.

[0047] As the material of the resistance heating element 31, in addition to silver palladium (AgPd), a resistance material such as silver alloy (AgPt) or ruthenium oxide (RuO2) may be used. As the material of the power supply line 33 and the electrode portion 34, silver (Ag) or silver palladium (AgPd) can be formed by screen printing or the like.

[0048] As the material of the base material 30, ceramics such as alumina and aluminum nitride, which are excellent in heat resistance and insulation, or non-metallic materials such as glass and mica are preferable. In this embodiment, an alumina base material with a short-side width of 8 mm, a long-side width of 270 mm, and a thickness of 1.0 mm is used.

[0049] Alternatively, a structure in which an insulating material is laminated on a conductive material such as metal may be used to form the base material 30. As the metal material, aluminum, stainless steel, etc. are preferable because of their low cost. Further, in order to improve the heat uniformity of the heater 22 and enhance the image quality, the base material 30 may be made of a material with high thermal conductivity such as copper, graphite, or graphene.

[0050] The insulating layer 32 is made of, for example, heat-resistant glass with a thickness of 75 μm. The insulating layer 32 covers the resistance heating element 31 and the power supply line 33, insulates and protects them, and maintains the slidability with the fixing belt 20.

[0051] FIG. 5 is a diagram showing a power supply circuit to the heater of the first embodiment.

[0052] As shown in FIG. 5, in this embodiment, the power supply circuit for supplying power to each resistance heating element 31 is configured by electrically connecting an AC power supply 400 and the electrode portion 34 of the heater 22. Further, a triac 401 for controlling the supplied power amount is provided in the power supply circuit.

[0053] The power supply amount to each resistance heating element 31 is controlled by the control unit 402 via the triac 401 based on the detected temperature of the thermistor 25 as the temperature detection means. The control unit 402 is composed of a microcomputer including a CPU, a ROM, a RAM, an I / O interface, and the like.

[0054] In this embodiment, the thermistors 25 as the temperature detection means are respectively arranged in the central region in the longitudinal direction of the heater 22 within the minimum paper feed width and on one end side in the longitudinal direction of the heater 22. Further, on one end side in the longitudinal direction of the heater 22, a thermostat 27 as the power cut-off means for cutting off the power supply to the resistance heating element 31 when the temperature of the resistance heating element 31 becomes a predetermined temperature or higher is arranged. The thermistors 25 and the thermostat 27 are in contact with the back surface of the base material 30 (the side opposite to the side where the resistance heating element 31 is arranged) to detect the temperature of the resistance heating element 31.

[0055] Subsequently, with reference to the flowchart of FIG. 6, the control operation of the heater according to this embodiment will be described.

[0056] First, when the printing operation is started in the image forming apparatus (S1 in FIG. 6), the control unit 402 starts supplying power from the AC power supply 400 to each resistance heating element 31 of the heater 22 (S2 in FIG. 6). Thereby, each resistance heating element 31 starts generating heat, and the fixing belt 20 is heated.

[0057] At this time, the temperature T4 of the resistance heating element 31 located in the central region of the heater 22 is detected by the thermistor (central thermistor) 25 arranged in the central region in the longitudinal direction of the heater 22 (S3 in FIG. 6). Then, based on the temperature T4 obtained from the central thermistor 25, the control unit 402 controls the power supply amount to each resistance heating element 31 by the triac 401 so that each resistance heating element 31 reaches a predetermined temperature (S4 in FIG. 6).

[0058] Also, the temperature T8 of the resistance heating element 31 is detected by a thermistor (end thermistor) 25 disposed on the longitudinal end side of the heater 22 at the same time (S5 in FIG. 6). Then, it is determined whether the temperature T8 detected by the end thermistor 25 is equal to or higher than a predetermined temperature TN (T8≧TN) (S6 in FIG. 6). If it is lower than the predetermined temperature TN, the power supply to the heater 22 is cut off as an abnormally low temperature occurs (a disconnection occurs) (S7 in FIG. 6), and an error display is shown on the operation panel of the image forming apparatus (S8 in FIG. 6). On the other hand, if the detected temperature T8 is equal to or higher than the predetermined temperature TN, the printing operation is started assuming that there is no abnormally low temperature (S9 in FIG. 6).

[0059] Also, in the unlikely event that the temperature control based on the detection by the central thermistor 25 becomes impossible due to breakage or disconnection of the resistance heating element 31, there is a risk that other resistance heating elements 31 including the resistance heating element 31 at the longitudinal end will become abnormally hot. In that case, when the resistance heating element 31 reaches a predetermined temperature or higher, the thermostat 27 operates to cut off the power supply to the resistance heating element 31, thereby avoiding the resistance heating element 31 from becoming abnormally hot.

[0060] By the way, in a configuration using a thin fixing belt 20 like the fixing device 9 according to the present embodiment, since the heat capacity of the fixing belt 20 is small, the surface temperature of the fixing belt 20 is easily affected by the heat generation amount distribution of the heater 22. Therefore, in a configuration in which the heat generating portion 35 is divided across the belt width direction like the fixing device 9 according to the present embodiment, the temperature of the fixing belt 20 tends to be low at locations corresponding to the divided regions of the heat generating portion 35.

[0061] ●Second form of the heater Subsequently, a second form of the heater will be described with reference to FIG. 7. In the following description, mainly the parts different from the above-described embodiment will be described, and the description of the other parts will be omitted as appropriate since they have basically the same configuration. And the heater of the second form may be referred to as an in-line type for convenience in this specification.

[0062] FIG. 7 is a plan view of the heater of the second form. As shown in FIG. 7, the heater 22 according to the present embodiment has a plate-like base material 55 extending in one direction (the direction of arrow X in FIG. 7). The base material 55 is arranged such that its longitudinal direction X faces the longitudinal direction of the fixing belt 20 or the axial direction of the pressure roller 21. On the surface of the base material 55, two resistance heating elements 56 extend in the longitudinal direction X of the base material 55 and are arranged side by side in the short side direction Y of the base material 55.

[0063] As shown in FIG. 7, on one side in the longitudinal direction X of the base material 55, a pair of electrode portions 58 are provided. Each electrode portion 58 is connected to each resistance heating element 56 via a power supply line 59. Also, the ends of each resistance heating element 56 on the side opposite to the end connected to the electrode portion 58 are connected to each other via another power supply line 59.

[0064] Each resistance heating element 56 and each power supply line 59 are covered by an insulating layer 57 to ensure insulation. On the other hand, each electrode portion 58 is not covered by the insulating layer 57 and is exposed so that a connector as a power supply terminal can be connected.

[0065] The base material 55 is made of a material excellent in heat resistance and insulation, such as ceramic such as alumina or aluminum nitride, glass, mica, or polyimide. Also, the base material 55 may be formed by forming an insulating layer on a metal material (conductive material) such as stainless steel (SUS), iron, or aluminum.

[0066] In particular, when the material of the base material 55 is a high heat conduction material such as aluminum, copper, silver, graphite, or graphene, the heat uniformity of the heater 22 is improved and the image quality can be enhanced. The insulating layer 57 is made of a material excellent in heat resistance and insulation, such as ceramic such as alumina or aluminum nitride, glass, mica, or polyimide.

[0067] The resistance heating element 56 is formed, for example, by screen-printing a paste prepared by blending silver palladium (AgPd) and glass powder or the like on the surface of the base material 55 and then firing the base material 55. Also, as the material of the resistance heating element 56, it is also possible to use a resistance material such as silver alloy (AgPt) or ruthenium oxide (RuO2). Further, the electrode portion 58 and the power supply line 59 are formed by screen-printing silver (Ag) or silver palladium (AgPd) or the like.

[0068] FIG. 8 is a perspective view showing a state in which a connector 40 as a power supply member is connected to the heater 22. As shown in FIG. 8, the connector 40 includes a resin housing 41 formed in a U-shaped cross section, a plurality of contact terminals 42 provided on the housing 41, and a power supply harness 43 connected to each contact terminal 42. Each contact terminal 42 is constituted by an elastically deformable member such as a leaf spring.

[0069] As shown in FIG. 8, the connector 40 is attached so as to sandwich the heater 22 and the heater holder 23 together. Thereby, the heater 22 and the heater holder 23 are held together by the connector 40.

[0070] Also, in this state, the tips (contact portions 42a) of the respective contact terminals 42 of the connector 40 are elastically contacted (pressure-welded) to the corresponding electrode portions 58, whereby each contact terminal 42 and each electrode portion 58 are electrically connected. As a result, power can be supplied from the power supply provided in the image forming apparatus to the heater 22 (each resistance heating element 56) via the connector 40.

[0071] ● Apparatus frame of the fixing device FIG. 9A is a perspective view of a fixing device, and FIG. 9B is an exploded perspective view thereof. As shown in FIGS. 9A and 9B, the device frame 80 of the fixing device 9 includes a first device frame 65 composed of a pair of side wall portions 68 and a front wall portion 67, and a second device frame 66 composed of a rear wall portion 69. The pair of side wall portions 68 are arranged on one end side and the other end side in the width direction of the fixing belt 20 (hereinafter referred to as the "belt width direction"), and both end sides of the pressure roller 21 and the heating device 19 are supported by the both side wall portions 68.

[0072] A plurality of engaging protrusions 68a are provided on each side wall portion 68, and the first device frame 65 and the second device frame 66 are assembled by engaging each engaging protrusion 68a with an engaging hole 69a provided in the rear wall portion 69. Further, each side wall portion 68 is provided with an insertion groove 68b for inserting the rotation shaft of the pressure roller 21 or the like. The insertion groove 68b is open on the rear wall portion 69 side and is a butting portion that is not open on the opposite side.

[0073] A bearing 70 for supporting the rotation shaft of the pressure roller 21 is provided at the end on the butting portion side. The pressure roller 21 is rotatably supported by the both side wall portions 68 by mounting both end portions of its rotation shaft on the bearing 70 respectively.

[0074] Further, a drive transmission gear 71 as a drive transmission member is provided on one end side of the rotation shaft of the pressure roller 21. The drive transmission gear 71 is arranged in a state of being exposed outside the side wall portion 68 with the pressure roller 21 supported by the both side wall portions 68. Thereby, when the fixing device 9 is mounted on the image forming apparatus main body, the drive transmission gear 71 is connected to a gear provided in the image forming apparatus main body, and a drive force from a drive source can be transmitted.

[0075] On one end side in the longitudinal direction of the rear wall portion 69, a hole portion 69b is provided as a positioning portion for positioning the fixing device main body with respect to the image forming apparatus main body. When attaching the fixing device main body to the image forming apparatus main body, a protrusion 101 provided as a positioning portion on the image forming apparatus main body is inserted into the hole portion 69b of the fixing device 9, so that the protrusion 101 and the hole portion 69b are fitted, and the positioning in the longitudinal direction (belt width direction) of the fixing device main body with respect to the image forming apparatus main body is performed.

[0076] A pair of end holding members 53 for supporting the fixing belt 20 and the like are provided at both longitudinal ends of the heating device 19. This end holding member 53 is the device frame of the heating device 19 and is also a part of the device frame 80 of the fixing device 9. The fixing belt 20 is supported by the end holding member 53 in a so-called free belt method in which basically no circumferential tension is applied in the non-rotating state. Further, a guide groove 53a is provided in each end holding member 53, and by entering the guide groove 53a along the edge of the insertion groove 68b of the side wall portion 68, it is assembled to the side wall portion 68.

[0077] Also, a pair of springs 73 as biasing members are provided between each end holding member 53 and the rear wall portion 69. By biasing the end holding member 53 toward the pressure roller 21 by each spring 73, the fixing belt 20 is pressed against the pressure roller 21, and a nip portion N is formed between the fixing belt 20 and the pressure roller 21.

[0078] ● Heating device FIG. 10A is a perspective view of the heating device 19, and FIG. 10B is an exploded perspective view thereof. As shown in FIGS. 10A and 10B, a rectangular recess 23b as a holding portion for holding and accommodating the heater 22 is provided on the surface of the heater holder 23 on the fixing belt 20 side (nip portion N side). The heater 22 is held in a state of being accommodated in the recess 23b and being sandwiched together with the heater holder 23 by the connector 40 in FIG. 8.

[0079] As shown in FIGS. 10A, 10B, and 11A, a pair of end holding members 53 includes a C-shaped belt support portion 53b that is inserted into the inner circumference of the fixing belt 20 to support the fixing belt 20, a flange-shaped belt regulating portion 53c that contacts the end face of the fixing belt 20 to regulate movement (lateral displacement) in the belt width direction, and a stay support portion 53d into which both end portions of a stay 24 that supports a heater holder 23 are inserted. A step portion 24a formed at the end of the stay 24 abuts against the inner end portion of the stay support portion 53d to position the longitudinal direction.

[0080] ● Regarding the problems of the end holding member As a fixing device, for example, a fixing device described in Patent Document 2 (Japanese Patent Application Laid-Open No. 2020-052347) can be cited. In the fixing device of this document, a heating device provided with a pair of frames at both ends in the longitudinal direction (rotation axis direction) of the fixing belt is inserted in the thickness direction of the heater while being fitted to the frames in the short hand direction of the heater.

[0081] This frame is both the device frame of the heating device and a part of the device frame of the fixing device. And the pair of frames has an end holding member that is inserted into the inner circumference of the fixing belt to support the fixing belt.

[0082] The end holding member 53 is provided with a guide groove 53a formed by a guide groove forming portion 53f and a belt regulating portion 53c. The end holding member 53 is assembled to the frame by entering the guide groove 53a along the edge of the insertion groove of the frame.

[0083] FIG. 11B is a diagram for explaining the problems regarding the shape of the end holding member 53. The problems caused by the shape of the end holding member 53 will be described below with reference to this figure.

[0084] The end holding member 53 is often molded from resin and is often configured in a substantially U-shaped (substantially U-shaped) configuration as viewed from the direction of the rotation axis of the fixing belt (see the left figure in Fig. 11B(a)). Therefore, the end holding member 53 may be deformed such that the tip portion (the cut portion of the U-shaped or U-shaped) in its substantially U-shaped (substantially U-shaped) configuration closes due to shrinkage during molding or the pressure received from the pressure roller (see the right figure in Fig. 11B(a)).

[0085] At this time, the fixing device is configured such that the heater is positioned on the heater holder, the heater holder is positioned on the stay that supports it, the stay is positioned on the end holding member 53, and the end holding member 53 is positioned on the frame (see the left figure in Fig. 11B(b)). Here, the heater rotates as the pressure roller rotates, and accordingly, the end holding member 53 comes into contact with the downstream side of the pressure roller of the frame in the rotation direction.

[0086] Therefore, when the end holding member 53 is deformed, the heater is displaced from the predetermined position (see the right figure in Fig. 11B(b)). If the position of the heater is displaced, the heat of the heater is not sufficiently transmitted to the fixing belt, which may cause fixing failure. In addition, if the position of the heater is displaced, the temperature may rise excessively in part, and the heater may be damaged by the thermal stress caused by this excessive temperature rise.

[0087] Here, Fig. 11C shows a diagram for explaining the case where a bridging portion 53h is provided on the end holding member 53. As shown in Fig. 11C, with respect to the above problems, a bridging portion 53h is provided at the tip portion so as to connect the cut of the U-shaped (U-shaped) (see Fig. 11C(a)), and the end holding member 53 is configured in a substantially C-shaped (rectangular ring-shaped) configuration (see Fig. 11C(b)), so that deformation of the end holding member 53 can be prevented.

[0088] FIG. 11D is an end view of the end holding member 53 in FIG. 11C(b) provided with the bridging portion 53h with an assembly of the heater 22, the heater holder 23, and the stay 24 inserted therein. Since the rigidity of the end holding member 53 is increased by the bridging portion 53h and it becomes difficult to deform, displacement of the heater 22 can be prevented and a predetermined contact state or heat transfer state with the fixing belt can be maintained.

[0089] The bridging portion 53h contacts directly or indirectly with each end portion side of the heater holder 23 and the stay 24. The inner side of the opening formed by the bridging portion 53h includes a portion closer to the end than the heat generating portion 35 (see FIG. 4) of the heater 22.

[0090] FIG. 12A is a view showing a fixing device in which the heater 22, the heater holder 23, and the stay 24 are in a properly assembled state. Note that the fixing belt 20 is omitted in FIG. 12A. Here, the "properly assembled state" means that the heater 22, the heater holder 23, and the stay 24 are correctly assembled without displacement from each other. As shown in FIG. 12A(d), a gap is formed between the heater 22 and the bridging portion 53h. In the properly assembled state, since the heater 22 is correctly fitted in the recess 23b of the heater holder 23, the pressing force of the pressure roller 21 can be uniformly applied in the longitudinal direction of the heater 22.

[0091] FIG. 12B is a view showing a fixing device in which the heater 22, the heater holder 23, and the stay 24 are not in a properly assembled state (the fixing belt 20 is omitted). As shown in the figure, since one end portion of the heater 22 floats from the recess 23b of the heater holder 23 and is not in the properly assembled state, bending stress due to the pressing force of the pressure roller 21 acts on one end portion of the heater 22, and the heater 22 may crack.

[0092] ● End holding member used in this embodiment The end holding member used in the fixing device of this embodiment is shown in FIG. 13. In FIG. 13(a), when the height from the stay 24 to the regulating portion 23c of the heater holder 23 in the proper assembled state of the heater 22, the heater holder 23, and the stay 24 is A, the opening width between the stay support portion 53d and the bridging portion 53h of the end holding member 53 is B, and the thickness of the heater 22 is C, the relationship of A < B < A + C is set. By setting the opening width B of the end holding member 53 within such a range (A < B < A + C), the heater 22, the heater holder 23, and the stay 24 can be easily assembled in the proper assembled state.

[0093] That is, when the heater 22 is not in the proper assembled state with respect to the recess 23b of the heater holder 23, that is, when one end of the heater 22 floats as shown in FIG. 13(a) and rides on the regulating portion 23c of the heater holder 23, when the end holding member 53 is moved in the arrow direction and inserted into one longitudinal end of the assembly of the heater 22, the heater holder 23, and the stay 24, as shown in FIG. 13(b), one longitudinal end of the heater 22 that has ridden on the regulating portion 23c of the heater holder 23 abuts (interferes) with the bridging portion 53h and cannot be inserted. Therefore, the operator can surely notice that the heater 22 is not in the proper assembled state, and the heater 22 can be inserted again into the recess 23b of the heater holder 23.

[0094] On the other hand, when the opening width B is larger than A + C (A + C < B), one longitudinal end of the heater 22 easily passes inside the bridging portion 53h in FIG. 13(b). For this reason, it is difficult to notice the misassembly of the heater 22, and there is a risk that the fixing device 9 will be assembled with the heater 22 misassembled.

[0095] ● Influence of the biasing force by the temperature detection member FIG. 14A is a view showing a state in which the back surface of the heater 22 is pushed up by the biasing spring 25a of the thermistor 25 as a temperature detection member. The thermistor 25 is often disposed at a position slightly eccentric from the longitudinal center of the heater 22. When a position slightly eccentric from the longitudinal center of the heater 22 is pressed by the biasing spring 25a of the thermistor 25, one end portion of the heater 22 is likely to float from the recess 23b of the heater holder 23. The same applies when the temperature detection member is a thermostat 27.

[0096] In a state where one end portion of the heater 22 is lifted in this way, when the fixing belt 20 is inserted into the assembly of the heater 22, the heater holder 23, and the stay 24 in the direction of the arrow as shown in FIG. 14B, the heater 22 is dragged by the fixing belt 20 and displaced in the rightward direction, and one end portion of the heater 22 is likely to ride on the regulating portion 23c of the heater holder 23. Therefore, not only is the relationship of A < B < A + C set, but as shown in FIG. 14C, tapered portions 53g1 and 53g2 are formed at the inner end portion of the bridging portion 53h.

[0097] The tapered portions 53g1 and 53g2 are preferably formed to have a length such that one end portion of the heater 22 that has ridden on the regulating portion 23c of the heater holder 23 surely abuts. That is, the tapered portion 53g1 of the end portion holding member 53 on the side where the thermistor 25 as the temperature detection member is eccentrically arranged is preferably formed longer than the tapered portion 53g2 of the end portion holding member 53 on the opposite side.

[0098] The angle of the tapered portion 53g can be formed, for example, at 45°. The angle of the tapered portion 53g can be made larger or smaller than 45°, but preferably it is within the range of 30° to 60°. FIG. 15 is a view for explaining the action of the tapered portion 53g.

[0099] ● Action of the tapered portion With reference to FIG. 15, the operation of the tapered portion 53g formed in the bridging portion 53h of the end holding member 53 will be described. As shown in FIGS. 15(a) to (b), when the end holding member 53 is to be mounted in the direction of the arrow toward the end of the assembly of the heater 22, the heater holder 23, and the stay 24, the tapered portion 53g of the bridging portion 53h of the end holding member 53 abuts against the end of the heater 22 that has climbed onto the restricting portion 23c.

[0100] As a result, a pressing force F in a direction perpendicular to the tapered portion 53g acts on the end of the heater 22. The pressing force F can be divided into a component force Fx in the longitudinal direction of the heater 22 and a component force Fy in a direction perpendicular to the longitudinal direction of the heater 22.

[0101] The heater 22 that has climbed onto the restricting portion 23c is moved leftward by the component force Fx acting on its end. As a result, after the end of the heater 22 reaches the edge of the recess 23b of the heater holder 23 as shown in FIG. 15(c), it is then correctly set (fitted) into the recess 23b of the heater holder 23 by the component force Fy as shown in FIG. 15(d), and the climbing of the heater 22 is corrected. To optimize the magnitudes of the component force Fx and the component force Fy, the angle of the tapered portion 53g is preferably in the range of 30° to 60°.

[0102] ● Insertion of the connector into the heater holder FIG. 16A(a) shows the connector insertion state when the heater 22 is in the normal assembled state with respect to the heater holder 23. In FIG. 16A(a), restricting portions 23d for restricting the movement of the heater 22 in the short-side direction are formed on both sides in the short-side direction of the recess 23b of the heater holder 23.

[0103] Assuming that the height from the restricting portion 23d of the heater holder 23 to the back surface of the heater holder 23 is A, the opening width of the U-shaped cross-section connector 40 is B, and the thickness of the heater is C, the magnitudes of A, B, and C are set such that A < B < A + C.

[0104] In Fig. 16A(a), since the heater 22 is correctly fitted into the recess 23b of the heater holder 23 (in the normal assembled state), the connector 40 can be smoothly inserted from the direction of the arrow (the short side direction of the heater 22). On the other hand, Fig. 16A(b) shows the connector insertion state when the heater 22 is not in the normal assembled state with respect to the heater holder 23. Since the heater 22 is not correctly fitted into the recess 23b of the heater holder 23 (in the non-normal assembled state), a part of the heater 22 (one end in the longitudinal direction) rides on the surface of the heater holder 23.

[0105] Therefore, when trying to insert the connector 40 into the heater holder 23 in the direction of the arrow (the short side direction of the heater 22), the tip 40a of the connector 40 abuts against a part of the heater 22 (one end in the longitudinal direction) that rides on the surface of the heater holder 23. Accordingly, the operator can know that the heater 22 is not in the normal assembled state with respect to the heater holder 23.

[0106] Next, after the operator correctly reinserts the heater 22 into the recess 23b of the heater holder 23, the connector 40 is inserted from the direction of the arrow as shown in Fig. 16A(a). In this way, incorrect assembly of the heater 22 can be prevented.

[0107] When other components are interposed between the heater 22 and the heater holder 23, for example, when a heat sink plate or the like is interposed between the heater 22 and the heater holder 23, if the height from the surface of the heater 22 in the normal assembled state including the heat sink plate to the back surface of the heater holder 23 is set as A.

[0108] In order to facilitate the normal assembly of the heater 22 when the heater 22 is not correctly fitted into the recess 23b of the heater holder 23, a tapered portion 40b can be formed at the tip 40a of the heater holder 23 as shown in Figs. 16A(c) and (d). The length of the tapered portion 40b is formed to be such that the end in the short side direction of the heater 22 that rides on the restricting portion 23d of the heater holder 23 surely abuts.

[0109] The angle of the tapered portion 40b can be formed, for example, at 45°. The angle of the tapered portion 40b can be made larger or smaller than 45°, but preferably it is within the range of 30° to 60°.

[0110] When trying to insert the connector 40 as shown in Fig. 16A(c) with respect to the longitudinal end of the assembly of the heater 22 and the heater holder 23, the tapered portion 40b of the connector 40 abuts against the short-side end of the heater 22 that has ridden up on the restricting portion 23d. As a result, after the short-side end of the heater 22 reaches the edge of the recess 23b of the heater holder 23 in Fig. 16A(c), it is correctly set (fitted) as shown in Fig. 16A(d), and the riding-up of the heater 22 is corrected. The details of the action of the tapered portion 40b are the same as those in Fig. 15, so they are omitted.

[0111] ● Irregular assembly of the heater in the short-side direction Figs. 16B(a) and (b) show a state where the heater 22 is in an irregular assembly state in the short-side direction with respect to the heater holder 23. In the irregular assembly state of Fig. 16B(a), the heater 22 is inclined in the short-side direction and has ridden up on the restricting portion 23d of the heater holder 23.

[0112] In this irregular assembly state, when attaching the end holding member 53 to the longitudinal end of the assembly of the heater 22, the heater holder 23, and the stay 24 as shown in Fig. 16B(b), since the height of A + C exceeds the opening width B of the heater holder 23, the short-side end of the heater 22 abuts against (interferes with) the bridging portion 53h of the heater holder 23 and cannot be inserted. Therefore, the operator can surely notice that the heater 22 is not in the regular assembly state, and the heater 22 can be reinserted into the recess 23b of the heater holder 23 as shown in Fig. 16B(c).

[0113] When the height of A + C slightly exceeds the opening width B, it is also possible to fit the heater 22 into the recess 23b as it is without reinserting the heater 22. For example, by forming a taper on the short-side edge of the recess 23b, the fitting of the heater 22 can be facilitated.

[0114] ● Modification Example of Thermistor Arrangement Regarding the fixing device described above, the arrangement of the thermistors in the array crossing direction can be as follows. For example, as shown in FIG. 17, in the present embodiment, the thermistor 25 is provided on the upstream side in the rotation direction of the fixing belt 20 from the central position NA of the fixing nip N in the array crossing direction, in other words, on the inlet side of the fixing nip N. Since the inlet side of the fixing nip N is a region where heat is particularly easily taken away by the paper P, by the thermistor 25 detecting the temperature of this portion, the fixability of the fixing device 9 can be ensured and the above-mentioned fixing offset can be effectively suppressed.

[0115] ● Modification Example of Fixing Device Further, the present invention is applicable not only to the fixing device described above but also to fixing devices as shown in FIGS. 18 to 20. Hereinafter, the configurations of the respective fixing devices shown in FIGS. 18 to 20 will be briefly described.

[0116] First, in the fixing device 9 shown in FIG. 18, a pressing roller 44 is disposed on the side opposite to the pressure roller 21 side with respect to the fixing belt 20. The pressing roller 44 is an opposing rotating member that rotates facing the fixing belt 20 as a rotating member. The pressing roller 44 and the heater 22 are configured to heat the fixing belt 20 therebetween. On the other hand, on the pressure roller 21 side, a nip forming member 45 is disposed on the inner circumference of the fixing belt 20. The nip forming member 45 is supported by a stay 24. The nip forming member 45 and the pressure roller 21 form a fixing nip N by sandwiching the fixing belt 20.

[0117] Next, in the fixing device 9 shown in FIG. 19, the above-mentioned pressing roller 44 is omitted, and in order to ensure the circumferential contact length between the fixing belt 20 and the heater 22, the heater 22 is formed in an arc shape according to the curvature of the fixing belt 20. Otherwise, the configuration is the same as that of the fixing device 9 shown in FIG. 13.

[0118] Finally, the fixing device 9 shown in FIG. 20 will be described. The fixing device 9 includes a heating assembly 92, a fixing roller 93 as a fixing member, and a pressure assembly 94 as a counter member. The heating assembly 92 includes a heater 22, a heater holder 23, a stay 24, a heating belt 120 as a rotating member, etc. described in the previous embodiment. The fixing roller 93 is a counter-rotating member that rotates facing the heating belt 120 as a rotating member. Further, the fixing roller 93 is composed of a solid iron core 93a, an elastic layer 93b formed on the surface of this core 93a, and a release layer 93c formed outside the elastic layer 93b. Further, a pressure assembly 94 is provided on the side opposite to the heating assembly 92 side with respect to the fixing roller 93. The pressure assembly 94 arranges a nip forming member 95 and a stay 96, and rotatably arranges a pressure belt 97 so as to enclose these nip forming member 95 and stay 96. Then, the sheet P is passed through the fixing nip N2 between the pressure belt 97 and the fixing roller 93 and heated and pressed to fix the image.

[0119] ● Modification example of the image forming apparatus The image forming apparatus according to the present invention is not limited to the color image forming apparatus shown in FIG. 1, and may be a monochrome image forming apparatus, a copying machine, a printer, a facsimile machine, or a multifunction machine thereof.

[0120] For example, as shown in FIG. 21, the image forming apparatus 100 of the present embodiment includes an image forming unit 50 composed of a photosensitive drum or the like, a sheet conveying unit composed of a pair of timing rollers 15 or the like, a paper feeding device 7, a fixing device 9, a paper discharging device 10, and a reading unit 51. The paper feeding device 7 includes a plurality of paper feeding trays, and each paper feeding tray accommodates sheets of different sizes.

[0121] The reading unit 51 reads the image of the document J. The reading unit 51 generates image data from the read image. The paper feeding device 7 accommodates a plurality of sheets P and sends out the sheets P to the conveyance path. The timing roller 15 conveys the sheet P on the conveyance path to the image forming unit 50.

[0122] The image forming means 50 forms a toner image on the paper P. Specifically, the image forming means 50 includes a photosensitive drum, a charging roller, an exposure device, a developing device, a replenishing device, a transfer roller, a cleaning device, and a discharging device. The toner image shows, for example, the image of the document Q. The fixing device 9 heats and presses the toner image to fix the toner image on the paper P. The paper P with the fixed toner image is conveyed to the paper discharging device 10 by a conveying roller or the like. The paper discharging device 10 discharges the paper P to the outside of the image forming apparatus 100.

[0123] ● Further modification example of the fixing device Next, a further modification example of the fixing device of the present embodiment will be described. Regarding the configuration common to the fixing device of the above-described embodiment, the description thereof will be omitted as appropriate.

[0124] As shown in Fig. 22, the fixing device 9 includes a fixing belt 20, a pressure roller 21, a heater 22, a heater holder 23, a stay 24, a thermistor 25, etc.

[0125] A fixing nip N is formed between the fixing belt 20 and the pressure roller 21. The nip width of the fixing nip N is 10 mm, and the linear speed of the fixing device 9 is 240 mm / s.

[0126] The fixing belt 20 includes a polyimide substrate and a release layer, and does not have an elastic layer. The release layer is made of a heat-resistant film material made of, for example, a fluororesin. The outer diameter of the fixing belt 20 is about 24 mm.

[0127] The pressure roller 21 includes a core metal 21a, an elastic layer 21b, and a release layer 21c. The outer diameter of the pressure roller 21 is formed to be 24 to 30 mm, and the thickness of the elastic layer 21b is formed to be 3 to 4 mm.

[0128] The heater 22 includes a base material, a heat insulating layer, a conductor layer including a resistance heating element, etc., and an insulating layer, and the overall thickness is formed to be 1 mm. Further, the width Y of the heater 22 in the short side direction (array intersection direction) is 13 mm.

[0129] FIG. 23 is a plan view of a fixing device equipped with a heater of the fourth form. Note that the heater of the fourth form also has a configuration in which a plurality of resistance heating elements 31 are divided into divided regions in the arrangement direction in the longitudinal direction of the heater, similar to the heater of the first form. As shown in FIG. 23, the conductor layer of the heater 22 includes a plurality of resistance heating elements 31, a power supply line 33, and electrode portions 34A to 34C. Also in this embodiment, as shown in the enlarged view of FIG. 23, a divided region B in which a plurality of resistance heating elements 31 are divided in the arrangement direction is formed (however, in FIG. 23, only the range of the enlarged view shows the divided region B, but actually, divided regions are provided between all the resistance heating elements 31). Three heating portions 35A to 35C are constituted by the resistance heating elements 31. By energizing the electrode portions 34A and 34B, the heating portions 35A and 35C generate heat. By energizing the electrode portions 34A and 34C, the heating portion 35B generates heat. For example, when performing a fixing operation on small-sized paper, the heating portion 35B can be made to generate heat, and when performing a fixing operation on large-sized paper, all the heating portions can be made to generate heat.

[0130] As shown in FIG. 24, the heater holder 23 holds the heater 22 in its recess 23b. The recess 23b is provided on the heater 22 side of the heater holder 23. The recess 23b includes a surface 23b1 substantially parallel to the base material 30 that is recessed toward the stay 24 side from the other surface of the heater 22, a wall portion 23b2 provided inside the heater holder 23 on both sides in the arrangement direction of the heater holder 23 (either one side may be sufficient), and a wall portion 23b3 provided inside the heater holder 23 on both sides in the arrangement intersection direction. The heater holder 23 has a guide portion 26. The heater holder 23 is formed of LCP (liquid crystal polymer).

[0131] As shown in FIG. 25, the connector 70 includes a resin housing (for example, LCP) and a plurality of contact terminals provided inside the housing.

[0132] The connector 70 is attached so as to sandwich the heater 22 and the heater holder 23 together from the front side and the back side. In this state, each contact terminal contacts (pressure contacts) each electrode portion of the heater 22, so that the heat generating portion 35 and the power supply provided in the image forming apparatus are electrically connected via the connector 70. As a result, power can be supplied from the power supply to the heat generating portion 35. Note that at least a part of each electrode portion 34 is not covered with an insulating layer and is in an exposed state in order to ensure connection with the connector 70.

[0133] The end holding members 53 are provided on both sides in the arrangement direction of the fixing belt 20, and hold both ends of the fixing belt 20 from the inside of the belt. The end holding members 53 are fixed to the housing of the fixing device 9. The end holding members 53 are inserted into both ends of the stay 24 (see the arrow direction from the end holding member 53 in FIG. 25).

[0134] The attachment direction of the connector 70 to the heater 22 and the heater holder 23 is the direction intersecting the heater arrangement (see the arrow direction from the connector 70 in FIG. 25). When the connector 70 is attached to the heater holder 23, a convex portion provided on one of the connector 70 and the heater holder 23 may be engaged with a concave portion provided on the other, and the convex portion may be configured to relatively move within the concave portion. Further, the connector 70 is attached to the heater 22 and the heater holder 23 on one side in the arrangement direction, which is the side opposite to the side where the drive motor of the pressure roller 21 is provided.

[0135] As shown in FIG. 26, thermistors 25 are provided on the central side and the end side in the arrangement direction of the fixing belt 20, respectively, facing the inner peripheral surface of the fixing belt 20. The heater 22 is controlled based on the temperatures of the central side and the end side in the arrangement direction of the fixing belt 20 detected by the thermistors 25. Note that one of these thermistors 25 is provided at a position corresponding to the division region between the resistance heating elements of the heater 22, as in the above-described embodiment.

[0136] Thermostats 27 are provided on the inner peripheral surface of the fixing belt 20, respectively on the central side and the end side in the arrangement direction of the fixing belt 20. When the temperature of the fixing belt 20 detected by the thermostat 27 exceeds a predetermined threshold value, the power supply to the heater 22 is stopped.

[0137] End holding members 53 for holding each end of the fixing belt 20 are provided at both ends in the arrangement direction of the fixing belt 20. The end holding members 53 are formed of LCP (liquid crystal polymer).

[0138] As shown in FIG. 27, the end holding member 53 is provided with a slide groove 53a. The slide groove 53a extends in the direction of approach and separation of the fixing belt 20 with respect to the pressure roller 21. An engaging portion of the housing of the fixing device 9 engages with the slide groove 53a. By the relative movement of this engaging portion within the slide groove 53a, the fixing belt 20 can move in the direction of approach and separation with respect to the pressure roller 21.

[0139] ● Example of a fixing device having a high heat conduction member Next, yet another embodiment of the fixing device will be described. Here, for the sake of convenience of explanation, the reference signs are newly assigned as before.

[0140] The fixing device 160 shown in FIG. 28 has a second high heat conduction member 90 between the heater holder 164 and the first high heat conduction member 89. The second high heat conduction member 90 is provided at a position different from that of the first high heat conduction member 89 in the stacking direction (the left - right direction in FIG. 28) of members such as the heater holder 164, the stay 165, and the first high heat conduction member 89. More specifically, the second high heat conduction member 90 is provided so as to overlap the first high heat conduction member 89.

[0141] Also, in this embodiment, a temperature sensor (thermistor) 167 is provided in the same manner as in the above - described embodiment. However, FIG. 28 shows a cross - section in which the temperature sensor 167 is not arranged.

[0142] The second high thermal conductivity member 90 is composed of a member having a higher thermal conductivity than the base material 155, for example, graphene or graphite. In the present embodiment, the second high thermal conductivity member 90 is composed of a graphite sheet having a thickness of 1 mm. Further, the second high thermal conductivity member 90 may be composed of a plate material such as aluminum, copper, or silver.

[0143] As shown in FIG. 29, a plurality of second high thermal conductivity members 90 are arranged in the concave portion 164b of the heater holder 164, and a longitudinal interval is interposed between the second high thermal conductivity members 90. A depression that is one step deeper than other portions is formed in the portion of the heater holder 164 where the second high thermal conductivity member 90 is provided. The second high thermal conductivity member 90 is provided with gaps on both sides in the longitudinal direction between it and the heater holder 164. Thereby, heat transfer from the second high thermal conductivity member 90 to the heater holder 164 is suppressed, and the fixing belt 161 is efficiently heated by the heater 163.

[0144] The heater shown in FIG. 30 takes, as an example, a heater in which a plurality of resistive heating elements are divided in the longitudinal direction of the heater. As shown in FIG. 30, the second high thermal conductivity member 90 (see the hatched portion) is arranged at a position overlapping at least a part of the adjacent resistive heating elements 156 at a position corresponding to the interval B1 in the longitudinal direction (arrow X direction). In particular, in the present embodiment, the second high thermal conductivity member 90 is arranged over the entire interval B1. In FIG. 30 (and FIG. 32), the case where the first high thermal conductivity member 89 is arranged over the entire longitudinal direction of the region where all the resistive heating elements 156 are arranged is shown, but the arrangement range of the first high thermal conductivity member 89 is not limited to this.

[0145] As in this embodiment, in addition to the first high heat conduction member 89, at a position corresponding to the longitudinal interval B and at a position overlapping at least a part of adjacent resistance heating elements 156, the second high heat conduction member 90 is arranged. As a result, the longitudinal heat transfer efficiency in the interval B1 can be further improved, and the temperature unevenness in the longitudinal direction of the heater 163 can be more effectively suppressed. Most preferably, as shown in FIG. 31, the first high heat conduction member 89 and the second high heat conduction member 90 are provided only in the whole area at the position corresponding to the interval B. Thereby, at the position corresponding to the interval B1, the heat transfer efficiency can be particularly improved as compared with other regions. In FIG. 31, for the sake of convenience, the resistance heating element 156, the first high heat conduction member 89, and the second high heat conduction member 90 are shown shifted in the vertical direction of the figure, but they are arranged at substantially the same position in the longitudinal intersection direction (arrow Y direction). However, the present invention is not limited to this, and the first high heat conduction member 89 and the second high heat conduction member 90 may be arranged in a part of the longitudinal intersection direction of the resistance heating element 156, or may be arranged so as to cover the whole of the longitudinal intersection direction.

[0146] ● Graphene sheet Also, both the first high heat conduction member 89 and the second high heat conduction member 90 may be constituted by the graphene sheet. In this case, the first high heat conduction member 89 and the second high heat conduction member 90 having high thermal conductivity in a predetermined direction along the plane of graphene, that is, in the longitudinal direction rather than the thickness direction can be formed. Therefore, the temperature unevenness in the longitudinal direction of the heater 163 and the fixing belt 161 can be effectively suppressed.

[0147] Graphene is a flaky powder. As shown in FIG. 34, graphene is composed of a planar hexagonal lattice structure of carbon atoms. A graphene sheet is a sheet-like graphene, usually a single layer. Further, the graphene sheet may contain impurities in a single layer of carbon, or may have a fullerene structure. The fullerene structure is generally recognized as a compound formed by a polycyclic body in which the same number of carbon atoms are condensed in a cage shape with 5-membered rings and 6-membered rings. For example, C60, C70, and C80 fullerenes or other closed cage structures having 3-coordinate carbon atoms.

[0148] The graphene sheet is an artificial product and can be produced, for example, by chemical vapor deposition (CVD).

[0149] Commercially available products can be used for the graphene sheet. The size, thickness, or the number of layers of the graphite sheet, etc. are measured, for example, by a transmission electron microscope (TEM).

[0150] Furthermore, graphite with multilayered graphene has large thermal conductivity anisotropy. As shown in Fig. 35, graphite has layers in which the condensed six-membered ring planes of carbon atoms spread out in a planar manner, and has a crystal structure in which these layers are stacked multiple times. Between carbon atoms in this crystal structure, adjacent carbon atoms within the layer form a covalent bond, and carbon atoms between layers form a van der Waals bond. And the covalent bond has a greater bonding force compared to the van der Waals bond, and has a large anisotropy between the bond within the layer and the bond between layers. That is, by forming the first high thermal conductivity member 89 or the second high thermal conductivity member 90 with graphite, the heat transfer efficiency in the longitudinal direction in the first high thermal conductivity member 89 or the second high thermal conductivity member 90 becomes larger compared to the thickness direction (that is, the member stacking direction), and the heat transfer to the heater holder 164 can be suppressed. Therefore, the temperature unevenness in the longitudinal direction of the heater 163 can be efficiently suppressed, and the heat flowing out to the heater holder 164 side can be minimized. Also, by forming the first high thermal conductivity member 89 or the second high thermal conductivity member 90 with graphite, the first high thermal conductivity member 89 or the second high thermal conductivity member 90 can be provided with excellent heat resistance that does not oxidize up to about 700 degrees.

[0151] The physical properties and dimensions of the graphite sheet can be appropriately changed according to the functions required for the first high thermal conductivity member 89 or the second high thermal conductivity member 90. For example, high-purity graphite or single-crystal graphite can be used, or the anisotropy of heat conduction can be enhanced by increasing the thickness of the graphite sheet. Also, in order to increase the speed of the fixing device, a graphite sheet with a small thickness can be used to reduce the heat capacity of the fixing device. Further, when the widths of the nip portion N and the heater 163 are large, the longitudinal width of the first high thermal conductivity member 89 or the second high thermal conductivity member 90 may be increased accordingly.

[0152] From the viewpoint of enhancing mechanical strength, the number of layers of the graphite sheet is preferably 11 or more. Also, the graphite sheet may partially include a single-layer portion and a multi-layer portion.

[0153] The second high thermal conductivity member 90 may be provided at a position overlapping at least a part of the adjacent resistance heating elements 156 at a position corresponding to the interval B1 (and further the enlarged divided region C) in the longitudinal direction, and is not limited to the arrangement in FIG. 30. For example, as in the example shown in FIG. 32, the second high thermal conductivity member 90A may be provided so as to protrude to both sides in the longitudinal intersection direction (short side direction, arrow Y direction) more than the base material 155 in the longitudinal intersection direction. Also, the second high thermal conductivity member 90B may be provided in the range where the resistance heating element 156 is provided in the longitudinal intersection direction. Also, the second high thermal conductivity member 90C may be provided in a part of the interval B1.

[0154] Further, in another embodiment shown in FIG. 33, a gap in the thickness direction (the left - right direction in FIG. 33) is provided between the first high - heat - conduction member 89 and the heater holder 164. That is, a relief portion 164c as a heat - insulating layer is provided in a partial region of the recess 164b (see FIG. 29) of the heater holder 164 where the heater 163, the first high - heat - conduction member 89, and the second high - heat - conduction member 90 are arranged. The relief portion 164c is provided in a partial region in the longitudinal direction other than the portion where the second high - heat - conduction member 90 (not shown in FIG. 33) is provided. Also, the relief portion 164c is formed by making the depth of the recess 164b of the heater holder 164 deeper than other portions. Thereby, the contact area between the heater holder 164 and the first high - heat - conduction member 89 can be minimized, so that heat transfer from the first high - heat - conduction member 89 to the heater holder 164 is suppressed, and the fixing belt 161 can be efficiently heated by the heater 163. In the cross - section where the longitudinal second high - heat - conduction member 90 is provided, as in the embodiment shown in FIG. 28, the second high - heat - conduction member 90 abuts on the heater holder 164.

[0155] Also, in the present embodiment, the relief portion 164c is provided over the entire range where the resistance heating element 156 is provided in the longitudinal intersection direction (the up - down direction in FIG. 33). Thereby, heat transfer from the first high - heat - conduction member 89 to the heater holder 164 is effectively suppressed, and the heating efficiency of the fixing belt 161 by the heater 163 is improved. As the heat - insulating layer, in addition to the configuration of providing a space like the relief portion 164c, a configuration of providing a heat - insulating member having a lower thermal conductivity than the heater holder 164 may also be used.

[0156] Also, in the present embodiment, the second high - heat - conduction member 90 is provided as a member different from the first high - heat - conduction member 89, but it is not limited to this. For example, by making the portion corresponding to the interval B1 of the first high - heat - conduction member 89 thicker than other portions, the first high - heat - conduction member 89 may also serve as the second high - heat - conduction member 90.

[0157] As described above, in the present embodiment, there are provided a fixing belt 20 as an endless cylindrical member that is rotatable and has a rotational axis direction, a plurality of heating elements 31, 56, a heater 22 as a heating body that heats the fixing belt 20, and an end holding member 53 that holds an end portion of the fixing belt 20 in the rotational axis direction and the heater 22 and has a bridging portion 53h that bridges to open a portion for holding the heating body. The heater 22 has a protruding portion 22p in which at least one of both end portions in the rotational axis direction protrudes to the side opposite to the side where the heating elements 31, 56 in the rotational axis direction are located with respect to the bridging portion 53h.

[0158] This prevents the identifiable mark from becoming difficult to visually recognize.

[0159] As described above, in the present embodiment, the protruding portion 22p has an identifiable mark 22m for the characteristic value of the heater 22, and the mark 22m protrudes to the side opposite to the bridging portion 53h.

[0160] This can improve the visibility of the mark. Also, the working efficiency during assembly is improved.

[0161] As described above, in the present embodiment, the protruding width of the protruding portion 22p is larger than the width of the heater 22 in the direction orthogonal to the rotational axis direction.

[0162] This makes it possible to suppress the size of the heater in the short side direction.

[0163] As described above, in the present embodiment, the heating device 200 has a connector 40 connected to the electrode portion 58 of the heater 22, and the protruding portion 22p has an end portion protruding on the side opposite to the position of the connector 40.

[0164] This can suppress the size of the heater in the longitudinal direction and suppress a small temperature deviation at both ends in the longitudinal direction of the heater.

[0165] As described above, in the present embodiment, the end holding member 53 is formed of resin.

[0166] This can prevent molding shrinkage, creep deformation, etc.

[0167] As described above, in this embodiment, the pressure roller 21 has a core metal 21a, and the protruding portion 22p protrudes on the side opposite to the core metal 21a, and it is the fixing device 9.

[0168] This can reduce the size of the heater in the short side direction and improve the visibility of the mark.

[0169] As described above, in this embodiment, the thickness of the opposing portion 53t of the bridging portion 53h facing the pressure roller 21 is smaller than the thickness of the portion other than the opposing portion 53t.

[0170] This can avoid interference with the core metal of the pressure roller and realize miniaturization of the device.

[0171] As described above, in this embodiment, the fixing device 9 has a heater holder 23 that holds the heater 22 and a stay 24 that supports the heater holder 23, and the end holding member 53 and the stay 24 are in contact.

[0172] This can prevent deformation due to load.

[0173] As described above, in this embodiment, it has a heating device 200 and a side wall portion 68 that holds the end holding member 53 so as to be relatively movable, and the bridging portion 53h is a fixing device 9 that is positioned so as to overlap the side plate 80 in a direction orthogonal to the rotation axis direction.

[0174] This can suppress deformation due to the fitting portion of the side plate and improve the positional accuracy.

[0175] As described above, in this embodiment, it has a heating device 200 and a side plate 80 that holds the end holding member 53 so as to be relatively movable, and the width of the bridging portion 53h is larger than the thickness of the side plate 80, and it is the fixing device 9. This can suppress deformation of the end holding member 53.

[0176] As described above, the fixing device 9 of this embodiment includes a heating device 200 and a side plate 80 that holds the end holding member 53 so as to be relatively movable, and the thickness of the bridging portion 53h is greater than the thickness of the heater 22. This can suppress deformation of the end holding member 53.

[0177] ● Modifications of the image forming apparatus and its other applications The image forming apparatus according to the present invention is not limited to the color image forming apparatus shown in FIG. 1, and may be a monochrome image forming apparatus, a copying machine, a printer, a facsimile machine, or a combination machine thereof. Regarding other applications, for example, the heating device 19 according to the present invention may be applied as a drying device for an inkjet type image forming apparatus. Further, the fixing device 19 according to the present invention may be applied to a laminating device.

[0178] As described above, the embodiments of the present invention have been described. However, the present invention is not limited to the above-described embodiments, and it goes without saying that various changes can be made without departing from the gist of the present invention. And what has been described above is an example, and the present invention has specific effects for each of the following aspects.

[0179] [First Aspect] The first aspect includes an endless cylindrical member that is rotatable and has a rotational axis direction, a plate-shaped heater that has a longitudinal direction along the rotational axis direction and slides on the inner surface of the cylindrical member, a heater holder that holds the heater, a stay that supports the back side of the heater holder, a bridging portion that directly or indirectly contacts and bridges each end side of the cylindrical member, the heater, the heater holder, and the stay in the rotational axis direction so as to open, a stay support portion that faces the bridging portion and supports the end of the stay, a pair of end holding members that include the end side of the heater inside the opening, and a pressing member that is pressed against the heater via the cylindrical member and forms a nip portion between the heater and the pressing member. In a heating device that heats a recording material using the cylindrical member heated by the heater while sandwiching and conveying the recording material at the nip portion, the heater holder has a holding portion where the heater is held and a restricting portion that is located at the longitudinal end of the holding portion and restricts the longitudinal movement of the heater. When the height from the stay support portion to the restricting portion of the heater holder in the normal assembled state of the heater, the heater holder, and the stay is A, the opening width between the stay support portion and the bridging portion of the end holding member is B, and the thickness of the heater is C, the heating device is characterized in that the relationship A < B < A + C is satisfied. [Second Aspect] The second aspect includes an endless cylindrical member that is rotatable and has a rotation axis direction, a plate-shaped heater that has a longitudinal direction along the rotation axis direction and slides on the inner surface of the cylindrical member, a heater holder that holds the heater, a stay that supports the back side of the heater holder, a bridging portion that directly or indirectly contacts each end side of the cylindrical member, the heater, the heater holder, and the stay in the rotation axis direction and bridges them so as to open, a stay support portion that faces the bridging portion and supports the end of the stay, a pair of end holding members that include an end side more than the heat generating portion of the heater inside the opening, and a pressing member that is pressed against the heater via the cylindrical member and forms a nip portion with the heater. In a heating device that heats a recording material using the cylindrical member heated by the heater while sandwiching and conveying the recording material at the nip portion, the heater holder has a holding portion where the heater is held and a lateral direction restricting portion that is located at an end in the lateral direction of the holding portion and restricts the lateral movement of the heater. When the height from the stay support portion to the lateral direction restricting portion of the heater holder in the normal assembled state of the heater, the heater holder, and the stay is A, the opening width between the stay support portion and the bridging portion of the end holding member is B, and the thickness of the heater is C, the heating device is characterized in that the relationship A < B < A + C is satisfied. [Third Aspect] The third aspect is a heating device having a plate-shaped heater having a longitudinal direction, a heater holder that holds the heater, and a connector having a U-shaped cross-section that is inserted into the heater holder from a lateral direction orthogonal to the longitudinal direction so as to sandwich the heater and the heater holder with respect to an end of the heater holder holding the heater and is connected to the heater to supply power. The heater holder has a holding portion where the heater is held and a restricting portion that is located at an end in the lateral direction orthogonal to the longitudinal direction of the holding portion and restricts the lateral movement of the heater. When the height from the restricting portion to the back surface of the heater holder is A, the opening width of the connector is B, and the thickness of the heater is C, the heating device is characterized in that the relationship A < B < A + C is satisfied. [Fourth Aspect] The fourth aspect is a heating device according to any one of the first to third aspects, characterized by having a biasing member that biases the heater toward the pressing member. [Aspect 5] The fifth aspect is a heating device according to the fourth aspect, characterized in that a temperature detection member for detecting the temperature of the heater is pressed against the back surface of the heater by the biasing member. [Aspect 6] The sixth aspect is a heating device according to the first aspect, characterized in that when the end holding member is attached to the longitudinal end of the assembly of the heater, the heater holder, and the stay, a tapered portion that contacts the end of the heater is formed at the bridging portion of the end holding member when the assembly is not in the normal assembled state. [Aspect 7] The seventh aspect is a heating device according to the second aspect, characterized in that when the heater holder is inserted into the longitudinal end of the assembly of the heater and the heater holder, a tapered portion that contacts the short-side end of the heater is formed at the tip of the heater holder when the assembly is not in the normal assembled state. [Aspect 8] The eighth aspect is a heating device according to the sixth aspect, characterized in that when the temperature detection member is disposed at a position eccentric from the longitudinal center of the heater, the length of the tapered portion of the end holding member attached to the longitudinal end of the assembly on the eccentric side is larger than the length of the tapered portion of the end holding member attached to the longitudinal end on the opposite side of the assembly. [Aspect 9] The ninth aspect is a heating device according to the sixth aspect, characterized in that the angle of the tapered portion is within the range of 30° to 60°. [Aspect 10] The tenth aspect is a heating device according to the seventh aspect, characterized in that the angle of the tapered portion is within the range of 30° to 60°. [Aspect 11] The eleventh aspect is a fixing device characterized by having a heating device according to any one of the first to tenth aspects. [Aspect 12] The twelfth aspect is an image forming apparatus characterized by including the fixing device of the tenth aspect.

Explanation of Signs

[0180] 1Y, 1M, 1C, 1Bk: Image forming unit 2: Photoconductor 3: Charging device 4: Developing device 5: Cleaning device 6: Exposure device 7: Paper feeding device 8: Transfer device 9: Fixing device 10: Paper discharging device 11: Intermediate transfer belt 12: Primary transfer roller 13: Secondary transfer roller 14: Paper conveyance path 15: Timing roller 19: Heating device 20: Fixing belt 21: Pressing roller 21a: Core metal 21b: Elastic layer 21c: Release layer 221: Elastic layer 222: Release layer 22: Heater 22p: Protrusion 22q: Electrode-side protrusion 22m: Mark 23: Heater holder 23a: Protrusion 23b: Recess (holding part) 23b1: Parallel surface 23c, 23d: Regulation part 23b2: Wall part 23b3: Wall part 24: Stay 25: Thermistor (temperature detecting member) 25a: Biasing spring 26: Guide part 27: Thermostat 30, 55: Base material 31, 56: Resistance heating element 34, 34A~34C: Electrode part 35, 35A~35C: Heating part 40, 70: Connector 40a: Tip of connector 40 40b: Taper part 41: Housing 42: Plurality of contact terminals 42a: Contact part 43: Power supply harness 44: Pressing roller 45: Nip forming member 50: Image forming means 51: Reading part 53: End holding member 53a: Slide groove 53b: Belt support part 53c: Belt regulation part 53d: Support recess 53f: Guide groove forming part 53g1: Taper part 53g2: Taper part 53h: Bridging part 53t: Opposing part 57: Insulating layer 58: Electrode part 59: Feeding wire 65: First device frame 66: Second device frame 67: Front wall part 68: Side wall part 68a: Engaging protrusion 68b: Insertion groove 69: Rear wall part 70: Bearing 80: Device frame 89: First high thermal conductivity member 90: Second high thermal conductivity member 92: Heating assembly 93: Fixing roller 93a: Core metal 93b: Elastic layer 93c: Release layer 94: Pressing assembly 95: NiP forming member 96: Stay 97: Pressing belt 100: Image forming apparatus 101: Protrusion 120: Heating belt 155: Base material 156: Resistance heating element 160: Fixing device 161: Fixing belt 163: Heater 164: Heater holder 164b: Recess 164c: Relief part 165: Stay 167: Temperature sensor (thermistor) 200: Heating device 260: Belt opposing surface 400: AC power supply 401: Triac 402: Control part B: Opening width N: NiP part P: Paper

Prior art documents

Patent documents

[0181]

Patent Document 1

Patent Document 2

Claims

1. An endless cylindrical member that is rotatable and has a rotational axis direction, A plate-shaped heater that has a longitudinal direction along the rotational axis direction and slides on the inner surface of the cylindrical member, A heater holder that holds the heater, A stay that supports the back side of the heater holder, A bridging portion that directly or indirectly contacts and bridges each end side of the cylindrical member, the heater, the heater holder, and the stay in the rotational axis direction so as to open, and a stay support portion that supports the end of the stay facing the bridging portion, and a pair of end holding members that include an end side more than the heat generating portion of the heater inside the opening, A pressing member that is pressed against the heater via the cylindrical member and forms a nip portion between the heater and the cylindrical member, In a heating device that heats a recording material using the cylindrical member heated by the heater while sandwiching and conveying the recording material at the nip portion, The heater holder has a holding portion where the heater is held, and a restricting portion that is located at an end in the longitudinal direction of the holding portion and restricts the longitudinal movement of the heater, When the height from the stay support portion to the restricting portion of the heater holder in the normal assembled state of the heater, the heater holder, and the stay is A, the opening width between the stay support portion and the bridging portion of the end holding member is B, and the thickness of the heater is C, the heating device is characterized in that the relationship is A < B < A + C.

2. An endless cylindrical member that is rotatable and has a rotational axis direction, A plate-shaped heater that has a longitudinal direction along the rotational axis direction and slides on the inner surface of the cylindrical member, A heater holder that holds the heater, A stay that supports the back side of the heater holder, A bridging portion that directly or indirectly contacts and bridges each end side of the cylindrical member, the heater, the heater holder, and the stay in the rotational axis direction so as to open, and a stay support portion that supports the end of the stay facing the bridging portion, and a pair of end holding members that include an end side more than the heat generating portion of the heater inside the opening, A pressing member that is pressed against the heater via the cylindrical member and forms a nip portion between the heater and the cylindrical member, In a heating device that heats a recording material using the cylindrical member heated by the heater while sandwiching and conveying the recording material at the nip portion, The heater holder has a holding portion for holding the heater, and a lateral direction restricting portion that is located at an end portion of the holding portion in the lateral direction and restricts movement of the heater in the lateral direction. In a heating device, when the height from the stay support portion to the lateral direction restricting portion of the heater holder in a normal assembled state of the heater, the heater holder, and the stay is A, the opening width between the stay support portion and the bridging portion of the end portion holding member is B, and the thickness of the heater is C, a relationship of A < B < A + C is satisfied.

3. A plate-shaped heater having a longitudinal direction, A heater holder for holding the heater, In a heating device having a U-shaped cross-section connector that is inserted into the heater holder from a lateral direction orthogonal to the longitudinal direction so as to sandwich the heater and the heater holder with respect to an end portion of the heater holder holding the heater, and is connected to the heater to supply power. The heater holder has a holding portion for holding the heater, and a restricting portion that is located at an end portion of the holding portion in a lateral direction orthogonal to the longitudinal direction and restricts movement of the heater in the lateral direction. In a heating device, when the height from the restricting portion to the back surface of the heater holder is A, the opening width of the connector is B, and the thickness of the heater is C, a relationship of A < B < A + C is satisfied.

4. The heating device according to claim 1, further comprising a biasing member that biases the heater toward the pressing member.

5. The heating device according to claim 4, wherein a temperature detecting member that detects the temperature of the heater is pressed against the back surface of the heater by the biasing member.

6. When the end portion holding member is attached to a longitudinal direction end portion of an assembly of the heater, the heater holder, and the stay, when the assembly is not in the normal assembled state, a tapered portion that abuts against an end portion of the heater is formed on the bridging portion of the end portion holding member. The heating device according to claim 1, characterized in that.

7. When the heater holder is inserted into a longitudinal direction end portion of an assembly of the heater and the heater holder, when the assembly is not in the normal assembled state, a tapered portion that abuts against a lateral direction end portion of the heater is formed at a tip portion of the heater holder. The heating device according to claim 3, characterized in that.

8. When the temperature detection member is disposed at a position eccentric from the longitudinal center of the heater, the length of the tapered portion of the end holding member attached to the longitudinal end of the assembly on the eccentric side is greater than the length of the tapered portion of the end holding member attached to the longitudinal end of the assembly on the opposite side of the longitudinal direction of the assembly. The heating device according to claim 6, characterized in that.

9. The heating device according to claim 6, characterized in that the angle of the tapered portion is within a range of 30° to 60°.

10. The heating device according to claim 7, characterized in that the angle of the tapered portion is within a range of 30° to 60°.

11. A fixing device, characterized in that it has the heating device according to any one of claims 1 to 10.

12. An image forming apparatus, characterized in that it has the fixing device according to claim 11.

Images