Heating device, fixing device, drying device, and image forming apparatus

Abstract

To prevent a situation where an identifiable mark is difficult to be visually recognized.SOLUTION: A heating device comprises: an endless cylindrical member that is rotatable and has a rotation axis direction; a heating body that has a plurality of heating elements, and heats the cylindrical member; and end holding members that each hold an end in the rotation axis direction of the cylindrical member and the heating body, and each have a bridging part bridging the leading ends of the end holding member to form an opening in a portion to hold the heating body. The heating body has a projecting part in which at least one end of both ends in the rotation axis direction projects beyond the bridging part to the opposite side of a side where the heating element is located in the rotation axis direction.SELECTED DRAWING: Figure 17

Description

[Technical field]

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

[0002] Generally, in fixing devices in image forming devices such as copiers and printers, a planar heater (heating resistor) is used as a heating means for heating a fixing belt. Also, a configuration is known in which an identification mark is provided on an end of the planar heater in the direction of the rotation axis of the fixing belt. This identification mark is visually recognized by an operator or the like so that the operator can check whether or not the fixing device has a heater with the desired specifications in terms of power supply voltage, etc., when assembling the fixing device.

[0003] For example, Patent Document 1 discloses a configuration including a substrate having at least a surface made of an insulating material, a resistor pattern formed on the substrate surface, a conductor pattern formed on the substrate surface and electrically connected to the resistor pattern, and a power supply electrode electrically connected to the conductor pattern, and a base pattern for printing visible identification information formed on the substrate surface using a material different from that of the substrate surface.

[0004] In addition, belt support members are provided at both ends of the fixing belt in the rotation axis direction to support the belt. For example, Patent Document 2 discloses a heating device that includes an endless belt member supported rotatably and a support member disposed at an end of the belt member in the rotation axis direction to support an end of a stay and a heating member, and heats a recording material passing through a nip portion, the support member having a first support portion that supports the end of the stay and a second support portion that supports the end of the heating member, the first support portion and the second support portion being detachable integrally with the end of the stay and the heating member, and being relatively movable at least in the pressure direction by a pressure applying member.

[0005] The identification information may be hidden and not visible depending on the configuration of the belt support member, so the fixing device needs to be configured to prevent such a problem from occurring. Summary of the Invention [Problem to be solved by the invention]

[0006] An object of the present invention is to prevent a identifiable mark from becoming difficult to see. [Means for solving the problem]

[0007] In order to solve the above-mentioned problems, the invention of claim 1 comprises an endless tubular member that is rotatable and has a rotational axis direction, a heating element having a plurality of heating elements and heating the tubular member, and an end holding member that holds an end of the tubular member in the rotational axis direction and the heating element and has a bridging portion that bridges the portion that holds the heating element so as to open, and the heating element is characterized in that at least one of both ends in the rotational axis direction has a protrusion that protrudes further than the bridging portion on the side opposite to the side on which the heating element is located in the rotational axis direction. Effect of the Invention

[0008] According to the present invention, it is possible to prevent a identifiable mark from becoming difficult to see. [Brief description of the drawings]

[0009] [Figure 1] 1 is a schematic configuration diagram of an image forming apparatus according to an embodiment of the present invention. [Diagram 2] FIG. 2 is a diagram showing a fixing device according to an embodiment of the present invention. [Diagram 3] FIG. 1 is a view showing a first embodiment of a heater according to the present invention. [Figure 4] FIG. 2 is a plan view of the heater according to the first embodiment. [Diagram 5] FIG. 2 is a diagram showing a power supply circuit to a heater according to the first embodiment. [Figure 6]FIG. 4 is a flow chart of a heater control operation according to the first embodiment. [Figure 7] FIG. 4 is a plan view of a heater according to a second embodiment. [Figure 8] FIG. 4 is a perspective view showing a state in which a connector serving as a power supply member is connected to the heater. [Figure 9] FIG. 4 is a plan view of a heater according to a second embodiment. [Figure 10] FIG. 13 is a diagram showing a fixing device equipped with a heater according to a second embodiment. [Figure 11] FIG. 13 is a diagram showing another fixing device equipped with a heater according to the second embodiment. [Figure 12] FIG. 13 is a diagram showing a fixing device equipped with a heater according to a third embodiment. [Figure 13] FIG. [Figure 14] 11A and 11B are diagrams for explaining problems regarding the shape of a flange. [Figure 15] FIG. 13 is a diagram for explaining a case where a bridging portion is provided on a flange. [Figure 16] FIG. 2 is a diagram showing a fixing device equipped with a heater which is a characteristic feature of the present invention. [Figure 17] FIG. 2 is a diagram showing a heater which is a characteristic feature of the present invention. [Figure 18] FIG. 13 is a diagram for explaining the relationship between a heater and temperature distribution in the comparative example. [Figure 19] FIG. 4 is a diagram for explaining the relationship between a heater and temperature distribution according to the present invention. [Figure 20] 5A and 5B are diagrams for explaining the configuration of a heater according to the resistance value of a heating element. [Figure 21] 11A and 11B are diagrams for explaining the configuration of a heater when the area of ​​a heat generating element is changed. [Figure 22] 11A and 11B are diagrams for explaining the configuration of a heater when the area of ​​a heat generating element is changed. [Figure 23] FIG. 4 is a diagram for explaining a bridging portion. [Figure 24] 11 is a side cross-sectional view of the fixing device showing a modified example of the arrangement of the thermistor. [Diagram 25] FIG. 4 is a side cross-sectional view showing a schematic configuration of a fixing device different from the above. [Figure 26] FIG. 4 is a side cross-sectional view showing a schematic configuration of a fixing device different from the above. [Figure 27] FIG. 4 is a side cross-sectional view showing a schematic configuration of a fixing device different from the above. [Figure 28] FIG. 2 is a schematic diagram illustrating a configuration of an image forming apparatus different from that in FIG. [Figure 29] FIG. 4 is a side cross-sectional view showing a schematic configuration of a fixing device different from the above. [Diagram 30] FIG. 13 is a plan view of a heater according to a fourth embodiment. [Diagram 31] FIG. [Diagram 32] FIG. 4 is a perspective view showing a state in which a connector is attached to a heater. [Diagram 33] A diagram showing the arrangement of thermistors and thermostats. [Diagram 34] FIG. [Diagram 35] FIG. 4 is a diagram showing a configuration of a fixing device different from that of the above embodiment. [Diagram 36] FIG. 2 is a perspective view of a heater, a first highly thermally conductive member, a second highly thermally conductive member, and a heater holder. [Figure 37] FIG. 4 is a plan view of the heater showing the arrangement of the first high thermal conductive member and the second high thermal conductive member. [Figure 38] 11 is a plan view of a heater showing another example of the arrangement of the first high thermal conductive member and the second high thermal conductive member. FIG. [Figure 39] FIG. 11 is a plan view of a heater showing still another example of the arrangement of the second high thermal conductive member. [Diagram 40] FIG. 4 is a diagram showing a configuration of a fixing device different from that of the above embodiment. [Diagram 41] A diagram showing the atomic crystal structure of graphene. [Diagram 42] A diagram showing the atomic crystal structure of graphite. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings.

[0011] In addition, in each drawing for explaining the embodiments of the present invention, components such as parts and components having the same function or shape are given the same symbols as far as possible to distinguish them, and once they have been explained, their explanations will be omitted.

[0012] FIG. 1 is a schematic diagram of an image forming apparatus according to an embodiment of the present invention.

[0013] The image forming apparatus 100 shown in Fig. 1 includes four imaging units 1Y, 1M, 1C, and 1Bk that are detachable from the image forming apparatus main body. Each imaging unit 1Y, 1M, 1C, and 1Bk has the same configuration except that it contains a developer of a different color, yellow, magenta, cyan, or black, which corresponds to the color separation components of a color image. Specifically, each imaging unit 1Y, 1M, 1C, and 1Bk includes a drum-shaped photoconductor 2 as an image carrier, a charging device 3 that charges the surface of the photoconductor 2, a developing device 4 that supplies toner as a developer to the surface of the photoconductor 2 to form a toner image, and a cleaning device 5 that cleans the surface of the photoconductor 2.

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

[0015] The transfer device 8 has an endless intermediate transfer belt 11 as an intermediate transfer body stretched by a plurality of rollers, four primary transfer rollers 12 as primary transfer members that transfer the toner image on each photoconductor 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 a sheet of paper P. Each of the primary transfer rollers 12 contacts the photoconductor 2 via the intermediate transfer belt 11. As a result, the intermediate transfer belt 11 and each photoconductor 2 contact each other, and a primary transfer nip is formed between them. Meanwhile, the secondary transfer roller 13 contacts 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.

[0016] Further, a paper transport path 14 along which the paper P sent out from the paper feeder 7 is transported is formed within the image forming apparatus 100. A pair of timing rollers 15 is provided on the paper transport path 14 midway from the paper feeder 7 to the secondary transfer nip (secondary transfer roller 13).

[0017] Next, the printing operation of the image forming apparatus will be described with reference to FIG.

[0018] When an instruction to start a printing operation is given, in each of the imaging units 1Y, 1M, 1C, and 1Bk, the photoconductor 2 is rotated clockwise in FIG. 1, and the surface of the photoconductor 2 is charged to a uniform high potential by the charging device 3. Next, the exposure device 6 exposes the surface of each photoconductor 2 based on the image information of the document read by the document reading device or the print information instructed to be printed from the terminal, thereby lowering the potential of the exposed portion and forming an electrostatic latent image. Then, toner is supplied from the developing device 4 to this electrostatic latent image, and a toner image is formed on each photoconductor 2.

[0019] When the toner images formed on each photoconductor 2 reach the primary transfer nip (the position of the primary transfer roller 12) as each photoconductor 2 rotates, they are transferred to the intermediate transfer belt 11, which rotates counterclockwise in FIG. 1, so as to be sequentially superimposed on each other. Then, the toner images transferred onto the intermediate transfer belt 11 are transported to the secondary transfer nip (the position of the secondary transfer roller 13) as the intermediate transfer belt 11 rotates, and are transferred to the paper P transported at the secondary transfer nip. This paper P is supplied from the paper supply device 7. The paper P supplied from the paper supply device 7 is temporarily stopped by the timing roller 15, and then transported to the secondary transfer nip in accordance with the timing at which the toner image on the intermediate transfer belt 11 reaches the secondary transfer nip. Thus, a full-color toner image is carried on the paper P. After the toner image is transferred, the toner remaining on each photoconductor 2 is removed by each cleaning device 5.

[0020] The paper P onto which the toner image has been transferred is transported to a fixing device 9, which fixes the toner image onto the paper P. Thereafter, the paper P is discharged outside the apparatus by a paper discharge device 10, completing a series of printing operations.

[0021] <About the fixing device according to the present invention> Next, a fixing device according to an embodiment of the present invention will be described. Hereinafter, the longitudinal direction of the heater according to the present invention is the direction along the surface of the base material on which the resistance heating element is provided, and is indicated as X. The longitudinal direction of the heater may also be expressed as the direction parallel to the rotation axis direction of the fixing belt or the like, or the direction in which the resistance heating elements are arranged (arrangement direction). The short-side direction of the heater (sometimes referred to as the width direction of the heater) is the direction perpendicular to the longitudinal direction, and is indicated as Y. Furthermore, the thickness (height) direction of the heater is the direction perpendicular to the longitudinal direction and short-side direction of the heater, and is indicated as Z.

[0022] As shown in FIG. 2, the fixing device 9 according to this embodiment includes a fixing belt 20 consisting of an endless belt, a pressure roller 21 as an opposing 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, and a thermistor 25 as a temperature detection means that detects the temperature of the fixing belt 20.

[0023] The fixing belt 20 has a cylindrical substrate made of polyimide (PI) having an outer diameter of 25 mm and a thickness of 40 to 120 μm. A release layer made of fluororesin such as PFA or PTFE and having a thickness of 5 to 50 μm is formed on the outermost surface of the fixing belt 20 in order to increase durability and ensure releasability. An elastic layer made of rubber or the like having a thickness of 50 to 500 μm may be provided between the substrate and the release layer. The substrate of the fixing belt 20 is not limited to polyimide, and may be a heat-resistant resin such as PEEK or a metal substrate 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.

[0024] The pressure roller 21 has an outer diameter of, for example, 25 mm, and is composed of a solid iron core 21a, an elastic layer 21b formed on the surface of the core 21a, and a release layer 21c formed on the outside of the elastic layer 21b. The elastic layer 21b is made of silicone rubber and has a thickness of, for example, 3.5 mm. In order to improve the release property of the surface of the elastic layer 21b, it is desirable to form the release layer 21c made of a fluororesin layer having a thickness of, for example, about 40 μm.

[0025] The pressure roller 21 is urged toward the fixing belt 20 by the urging means, so that the pressure roller 21 is pressed against the heater 22 via the fixing belt 20. This forms a nip N between the fixing belt 20 and the pressure roller 21. The pressure roller 21 is configured to be rotationally driven by a driving means, and when the pressure roller 21 rotates in the direction of the arrow in FIG. 2, the fixing belt 20 is rotated accordingly.

[0026] 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-shaped 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. The heater 22 is in contact with the inner circumferential surface of the fixing belt 20 on the insulating layer 32 side, and heat generated from the resistance heating element 31 is transferred to the fixing belt 20 via the insulating layer 32. In this 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, but 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 transferred to the fixing belt 20 via the base material 30, it is desirable that the base material 30 be made of a material with high thermal conductivity such as aluminum nitride. Furthermore, by forming the base material 30 from a material with good thermal conductivity, it is possible to sufficiently heat the fixing belt 20 even if the resistance heating element 31 is disposed on the opposite side of the base material 30 from the fixing belt 20 side. The heater 22 according to the present invention has a number of forms, which will be described below, and these forms can be applied.

[0027] The heater holder 23 and the stay 24 are disposed on the inner circumferential side of the fixing belt 20. The stay 24 is made of a metal channel material, and both ends thereof are supported by both side plates of the fixing device 9. Since the heater holder 23 and the heater 22 held thereby are supported by the stay 24, when the pressure roller 21 is pressed against the fixing belt 20, the heater 22 reliably receives the pressing force of the pressure roller 21, and the nip portion N is stably formed.

[0028] The heater holder 23 is desirably made of a heat-resistant material since it is likely to become hot due to the heat of the heater 22. For example, when the heater holder 23 is made of a heat-resistant resin with low thermal conductivity such as LCP, the heat transfer from the heater 22 to the heater holder 23 is suppressed, and the fixing belt 20 can be heated efficiently. In addition, in order to reduce the contact area of ​​the heater holder 23 with the heater 22 and reduce the amount of heat transferred from the heater 22 to the heater holder 23, the heater holder 23 contacts the base material 30 of the heater 22 via the protrusions 23a. Furthermore, as in this embodiment, the protrusions 23a of the heater holder 23 are brought into contact with the base material 30 other than the back side of the portion where the resistance heating element 31 of the base material 30 is arranged, that is, by avoiding the portion of the base material 30 where the temperature is likely to be high, the amount of heat transferred to the heater holder 23 can be further reduced and the fixing belt 20 can be heated efficiently.

[0029] The heater holder 23 is provided with guide portions 26 for guiding the fixing belt 20. The guide portions 26 are provided on the upstream side (below the heater 22 in FIG. 2) and downstream side (upper side of the heater 22 in FIG. 2) of the belt rotation direction of the heater 22. As shown in FIG. 3, the upstream and downstream guide portions 26 are arranged at intervals in the longitudinal direction (belt width direction) of the heater 22. Each guide portion 26 is formed in a substantially fan shape and has a belt facing surface 260 in the shape of an arc or a convex curved surface extending in the belt circumferential direction so as to face the inner circumferential surface of the fixing belt 20 (see FIG. 2). As shown in FIG. 3, in this embodiment, the width β of the guide portions 26 arranged at both ends in the longitudinal direction of the heater 22 is larger than the other guide portions 26, and the width β, the length (circumferential length) L in the belt circumferential direction, and the height E of each guide portion 26 are formed to be the same.

[0030] In the fixing device 9 according to the present embodiment, when a printing operation is started, the pressure roller 21 is rotationally driven and the fixing belt 20 starts to rotate. At this time, the inner circumferential surface of the fixing belt 20 contacts and is guided by the belt facing surface 260 of the guide portion 26, so that the fixing belt 20 rotates stably and smoothly. In addition, the fixing belt 20 is heated by supplying power to the resistance heating element 31 of the heater 22. Then, in a state where the temperature of the fixing belt 20 has reached a predetermined target temperature (fixing temperature), as shown in FIG. 2, the paper P carrying an 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 to be fixed to the paper P.

[0031] [First embodiment of the heater according to the present invention] FIG. 4 is a plan view of a first embodiment of a heater according to the present invention.

[0032] As shown in FIG. 4, the heater 22 of the first embodiment has a plurality of resistance heating elements 31 arranged at intervals in the longitudinal direction (belt width direction). In other words, the plurality of resistance heating elements 31 constitute a heating section 35 divided into a plurality of parts in the belt width direction. Each resistance heating element 31 is electrically connected in parallel to a pair of electrode parts 34 provided at both ends of the substrate 30 in the longitudinal direction via a power supply line 33. The power supply line 33 is made of a conductor having a smaller resistance value than the resistance heating element 31. From the viewpoint of ensuring insulation between the resistance heating elements 31, the gap between the adjacent resistance heating elements 31 is preferably 0.2 mm or more, and more preferably 0.4 mm or more. In addition, if the gap between the adjacent resistance heating elements 31 is too large, a temperature drop is likely to occur in the gap, so from the viewpoint of suppressing temperature unevenness over the longitudinal direction, the gap is preferably 5 mm or less, and more preferably 1 mm or less.

[0033] The resistance heating element 31 is made of a material having a PTC (positive temperature coefficient of resistance) characteristic, and is characterized in that the resistance value increases (heater output decreases) as the temperature increases.

[0034] Due to this feature, for example, when a paper sheet narrower than the overall width of the heat generating section 35 is passed through, the heat of the fixing belt 20 is not taken away by the paper sheet in the area outside the paper width, so the temperature of the resistance heating element 31 corresponding to that part rises. Since the voltage applied to the resistance heating element 31 is constant, when the temperature of the resistance heating element 31 outside the paper width rises and the resistance value rises, the output (heat generation amount) decreases relatively, and the end temperature rise is suppressed. In addition, since multiple resistance heating elements 31 are electrically connected in parallel, it is possible to suppress the temperature rise of the non-paper passing part while maintaining the printing speed. Note that the heating element constituting the heat generating section 35 may be other than the resistance heating element having the PTC characteristic. In addition, the heating elements may be arranged in multiple rows in the short direction of the heater 22.

[0035] The resistance heating element 31 can be formed, for example, by applying a paste made of silver palladium (AgPd) and glass powder to the substrate 30 by screen printing or the like, and then firing the substrate 30. In this embodiment, the resistance value of the resistance heating element 31 is set to 80Ω at room temperature. In addition to the above-mentioned materials, the resistance heating element 31 may be made of resistance materials such as silver alloy (AgPt) and ruthenium oxide (RuO2). The power supply line 33 and the electrode portion 34 can be made of silver (Ag) or silver palladium (AgPd) by screen printing or the like.

[0036] The material of the substrate 30 is preferably a ceramic such as alumina or aluminum nitride, which has excellent heat resistance and insulation, or a non-metallic material such as glass or mica. In this embodiment, an alumina substrate having a short side width of 8 mm, a long side width of 270 mm, and a thickness of 1.0 mm is used. Alternatively, the substrate 30 may be formed by laminating an insulating material onto a conductive material such as a metal. As the metallic material, aluminum or stainless steel is preferable because of its low cost. In addition, in order to improve the thermal uniformity of the heater 22 and enhance the image quality, the substrate 30 may be formed of a material with high thermal conductivity such as copper, graphite, or graphene.

[0037] The insulating layer 32 is made of heat-resistant glass having a thickness of, for example, 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 sliding property with the fixing belt 20.

[0038] FIG. 5 is a diagram showing a power supply circuit to the heater in the first embodiment.

[0039] 5, in this embodiment, a power supply circuit for supplying power to each resistance heating element 31 is configured by electrically connecting an AC power source 400 and the electrode portion 34 of the heater 22. The power supply circuit is also provided with a triac 401 for controlling the amount of power supplied. The amount of power supplied to each resistance heating element 31 is controlled by a control unit 402 via the triac 401 based on the temperature detected by a thermistor 25 serving as a temperature detection means. The control unit 402 is configured by a microcomputer including a CPU, a ROM, a RAM, an I / O interface, etc.

[0040] In this embodiment, thermistors 25 as temperature detection means are disposed in a longitudinal central region of the heater 22 within the minimum paper passing width, and at one longitudinal end of the heater 22. Furthermore, at one longitudinal end of the heater 22, a thermostat 27 is disposed as 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 reaches or exceeds a predetermined temperature. The thermistor 25 and thermostat 27 are in contact with the rear surface of the substrate 30 (the side opposite to the side where the resistance heating element 31 is disposed) to detect the temperature of the resistance heating element 31.

[0041] Next, the heater control operation according to this embodiment will be described with reference to the flowchart of FIG.

[0042] First, when a printing operation is started in the image forming apparatus (S1 in FIG. 6), the control unit 402 starts supplying power from the AC power source 400 to each resistance heating element 31 of the heater 22 (S2 in FIG. 6). As a result, each resistance heating element 31 starts generating heat, and the fixing belt 20 is heated. At this time, the thermistor (central thermistor) 25 disposed in the longitudinal central region of the heater 22 detects the temperature T4 of the resistance heating element 31 located in the central region 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 amount of power supplied to each resistance heating element 31 by the triac 401 so that each resistance heating element 31 becomes a predetermined temperature (S4 in FIG. 6).

[0043] At the same time, the temperature T8 of the resistance heating element 31 is also detected by the thermistor (end thermistor) 25 arranged on the longitudinal end side of the heater 22 (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, an abnormally low temperature has occurred (a disconnection has occurred), and the power supply to the heater 22 is cut off (S7 in FIG. 6), and an error message is displayed 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, it is determined that an abnormally low temperature has not occurred, and the printing operation is started (S9 in FIG. 6).

[0044] In addition, in the unlikely event that the resistance heating element 31 is damaged or disconnected, making it impossible to control the temperature based on the detection of the central thermistor 25, there is a risk that the other resistance heating elements 31, including the resistance heating element 31 at the longitudinal end portions, will reach an abnormally high temperature. 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 preventing the resistance heating element 31 from reaching an abnormally high temperature.

[0045] Incidentally, in a configuration using a thin fixing belt 20 like the fixing device 9 according to the present embodiment, the heat capacity of the fixing belt 20 is small, so the surface temperature of the fixing belt 20 is easily affected by the heat generation distribution of the heater 22. Therefore, in a configuration in which the heat generating section 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 the places corresponding to the divided areas of the heat generating section 35.

[0046] [Second embodiment of the heater according to the present invention] Next, a second embodiment of the heater according to the present invention will be described. In the following description, the differences from the above-mentioned embodiment will be mainly described, and the other parts will be omitted as they are basically the same. For convenience, the heater of the second embodiment will be referred to as a series type in this specification.

[0047] FIG. 7 is a plan view of the heater of the second embodiment.

[0048] 7, the heater 22 according to this embodiment has a plate-shaped substrate 55 extending in one direction (the direction of the arrow X in FIG. 7). The substrate 55 is disposed so 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 substrate 55, two resistance heating elements 56 extend in the longitudinal direction X of the substrate 55 and are disposed side by side in the lateral direction Y of the substrate 55.

[0049] 7, a pair of electrode portions 58 are provided on one side of the base material 55 in the longitudinal direction X. Each electrode portion 58 is connected to each resistance heating element 56 via a power supply line 59. In addition, the ends of each resistance heating element 56 opposite to the ends connected to the electrode portion 58 are connected to each other via another power supply line 59. Each resistance heating element 56 and each power supply line 59 are covered with an insulating layer 57 to ensure insulation. In contrast, each electrode portion 58 is not covered with the insulating layer 57 and is exposed so that a connector serving as a power supply terminal described later can be connected.

[0050] The substrate 55 is made of a material having excellent heat resistance and insulation, such as ceramics such as alumina or aluminum nitride, glass, mica, or polyimide. The substrate 55 may be made of a metal material (conductive material) such as stainless steel (SUS), iron, or aluminum, on which an insulating layer is formed. In particular, when the substrate 55 is made of a highly heat-conductive material such as aluminum, copper, silver, graphite, or graphene, the uniform heat distribution of the heater 22 is improved, and image quality can be improved. The insulating layer 57 is made of a material having excellent heat resistance and insulation, such as ceramics such as alumina or aluminum nitride, glass, mica, or polyimide. The resistance heating element 56 is formed by applying a paste made of a mixture of silver palladium (AgPd) and glass powder to the surface of the substrate 55 by screen printing or the like, and then baking the substrate 55. The resistance heating element 56 may be made of a resistance material such as silver alloy (AgPt) or ruthenium oxide (RuO2). The electrode portion 58 and the power supply line 59 are formed by screen printing silver (Ag) or silver palladium (AgPd) or the like.

[0051] FIG. 8 is a perspective view showing a state in which a connector 40 serving as a power supply member is connected to the heater 22. As shown in FIG.

[0052] 8, connector 40 has a resin housing 41, a plurality of contact terminals 42 provided in housing 41, and a power supply harness 43 connected to each of contact terminals 42. Each contact terminal 42 is formed of an elastically deformable member such as a leaf spring.

[0053] 8, the connector 40 is attached so as to sandwich the heater 22 and the heater holder 23 together. As a result, the heater 22 and the heater holder 23 are held together by the connector 40. In this state, the tips (contact portions 42a) of the contact terminals 42 of the connector 40 elastically contact (pressure-contact) with the corresponding electrode portions 58, thereby electrically connecting the contact terminals 42 and the electrode portions 58. As a result, power can be supplied to the heater 22 (each resistance heating element 56) from a power source provided in the image forming apparatus via the connector 40.

[0054] Incidentally, in the heater according to this embodiment, as shown in FIG. 9, the electrode portion 58 is provided only on one side of the substrate 55 in the longitudinal direction X, and the electrode portion 58 is not provided on the other side opposite thereto. For this reason, it is necessary to secure a space for arranging the electrode portion 58 on one side of the substrate 55, and if the space for arranging the electrode portion 58 is secured, the substrate 55 becomes longer on one side. That is, in this embodiment, since the electrode portion 58 is provided only on one side of the substrate 55, the length La between the end 60a on the electrode portion side of the heat generating region 60 in which each resistance heating element 56 is arranged and the end 55a on the electrode portion side of the substrate 55 is longer than the length Lb between the end 60b on the side opposite to the electrode portion side of the heat generating region 60 (hereinafter referred to as the "counter-electrode portion side") and the end 55b on the counter-electrode portion side of the substrate 55. Note that the "heat generating region" here does not mean the region in which one resistance heating element 56 is arranged, but means the region from end to end of all the resistance heating elements 56 on the substrate 55. The same applies to the "heat generating region" in the following description.

[0055] In this way, in a configuration in which the base material 55 of the heater 22 is formed long on one side of the longitudinal direction X, when the heater 22 is heated, the amount of heat transferred to the base material 55 is greater on the long end side of the base material 55 than on the short end side. That is, the amount of heat transferred to the end side where the electrode portion 58 is provided is greater. For this reason, the temperature of the heater tends to be relatively lower on the electrode portion side than on the counter-electrode portion side. In particular, when the fixing device is started up for the first time after the image forming apparatus is turned on, the temperature of the fixing device is low, so the temperature of the heater on the electrode portion side is difficult to increase. As a result, if the temperature of the fixing belt varies, there is a risk that the paper passing through the nip portion cannot be heated uniformly. Therefore, in this embodiment, the following measures are taken to suppress such temperature variation of the fixing device.

[0056] A fixing device equipped with a heater of the second embodiment is shown in Fig. 10. In Fig. 10, heater 22 and pressure roller 21 provided in the fixing device, and a maximum paper passing area (maximum sheet passing area) W through which a maximum width paper P passes are shown, and a fixing belt and the like are omitted. For convenience, this fixing device equipped with a heater of the second embodiment is referred to as fixing device 9A.

[0057] As shown in FIG. 10, the heating region 60 of the heater 22 is arranged symmetrically with respect to the widthwise center m of the maximum paper passing region W, in a range equal to or larger than the maximum paper passing region W, so that the heating region 60 can be uniformly heated across the widthwise direction (direction perpendicular to the paper passing direction along the paper surface) of any size of paper. That is, the length Ea from the widthwise center m of the maximum paper passing region W to the end 60a of the heating region 60 on the electrode side and the length Eb from the widthwise center m of the maximum paper passing region W to the end 60b of the heating region 60 on the counter-electrode side are set to the same length (Ea=Eb). In this embodiment, a so-called center-based transport method is adopted in which papers of various width sizes are transported based on their respective widthwise centers. Therefore, the widthwise center m of the maximum paper passing region W is also the widthwise center of the paper passing region of papers other than the maximum-width paper.

[0058] On the other hand, since the base material 55 of the heater 22 is formed long on the electrode portion side, it is arranged asymmetrically with respect to the center m in the width direction of the maximum paper feed area W. That is, the length Da from the center m in the width direction of the maximum paper feed area W to the end 55a on the electrode portion side of the base material 55 is set longer than the length Db from the center m in the width direction of the maximum paper feed area W to the end 55b on the counter electrode portion side of the base material 55 (Da>Db). For this reason, as described above, the amount of heat transferred from the heat generation region 60 to the electrode portion side of the base material 55 is larger than the amount of heat transferred to the counter electrode portion side.

[0059] Here, a part of the heat generated in the heat generation region 60 moves not only to the base material 55 but also to the pressure roller 21 via the fixing belt 20. Therefore, the amount of heat transferred to the pressure roller 21 affects the temperature distributions of the heater 22 and the fixing belt 20. Accordingly, if the amount of heat transferred to the pressure roller 21 can be adjusted on the electrode portion side and the counter electrode portion side, it is possible to adjust the temperature distributions of the heater 22 and the fixing belt 20. Focusing on this point, in the present embodiment, the pressure roller 21 is made shorter on the electrode portion side than on the counter electrode portion side.

[0060] That is, as shown in FIG. 10, the length Fa from the center m in the width direction of the maximum paper feed area W to the end 21d on the electrode portion side of the pressure roller 21 is made shorter than the length Fb from the center m in the width direction of the maximum paper feed area W to the end 21e on the counter electrode portion side of the pressure roller 21 (Fa<Fb). Note that this "end of the pressure roller" means the end of the roller portion 21g made of an elastic layer or the like, not the end of the core metal 21a which is the shaft portion of the pressure roller 21 supported by a bearing or the like.

[0061] As described above, in this embodiment, since the pressure roller 21 is formed shorter on the electrode portion side, as shown in FIG. 10, the length Ga between the end 60a on the electrode portion side of the heating region 60 and the end 21d on the electrode portion side of the pressure roller 21 is shorter than the length Gb between the end 60b on the counter electrode portion side of the heating region 60 and the end 21e on the counter electrode portion side of the pressure roller 21. For this reason, the amount of heat transferred from the heater 22 to the pressure roller 21 on the electrode side is less than that on the counter electrode portion side, and a temperature drop on the electrode portion side can be suppressed. That is, in this embodiment, while the amount of heat transferred to the electrode portion side of the base material 55 increases due to the base material 55 being formed longer on the electrode portion side (La > Lb), by reducing the protruding amount of the pressure roller 21 toward the electrode portion side with respect to the heating region 60 (Ga < Gb), the amount of heat transferred to the electrode portion side of the pressure roller 21 is reduced, and heat balance between the electrode portion side and the counter electrode portion side is achieved. As a result, in this embodiment, variations in temperature in the fixing device can be suppressed, temperature drop on the electrode portion side and excessive temperature rise on the counter electrode portion side can be suppressed, and thus fixing quality can be improved.

[0062] Further, according to this embodiment, variations in temperature in the fixing device can be suppressed without making the calorific value different between one end side and the other end side in the longitudinal direction of the heater. For this reason, adverse effects caused by making the calorific value different (temperature variations when the heating element generates heat to the maximum extent and damage to components due to local thermal expansion) can also be avoided. Therefore, according to this embodiment, the reliability of the device is also improved.

[0063] FIG. 11 is a diagram showing another fixing device equipped with the heater of the second embodiment, and this will be described. For convenience, another fixing device equipped with the heater of this second embodiment is referred to as the fixing device 9B.

[0064] In the configuration shown in FIG. 11, a high-friction portion 63 is provided on the counter-electrode portion side of the pressure roller 21. Thus, in the present embodiment, since the high-friction portion 21h is provided on the counter-electrode portion side of the pressure roller 21, the frictional force between the fixing belt 20 and the pressure roller 21 on the counter-electrode portion side (high-friction portion 21h side) with respect to the center m in the width direction of the maximum paper passage area W is greater than the frictional force between the fixing belt 20 and the pressure roller 21 on the electrode portion side with respect to the center m in the width direction of the maximum paper passage area W. In other words, the frictional force between the fixing belt 20 and the pressure roller 21 on the counter-electrode portion side (high-friction portion 21h side) with respect to the center of the fixing belt 20 in the longitudinal direction X of the base material 55 (the position of m in the figure) is greater than the frictional force between the fixing belt 20 and the pressure roller 21 on the electrode portion side with respect to the center of the fixing belt 20 in the longitudinal direction X of the base material 55. The fixing device 9B has the same configuration as the above-described fixing device 9A in other respects. The frictional force (F) between the fixing belt and the pressure roller is obtained by the following formula (1) using the coefficient of friction (μ) between the fixing belt and the pressure roller and the contact pressure (N) of the pressure roller against the fixing belt.

[0065] (Equation 1) F = μ × N ····· (1)

[0066] Also in the present embodiment (fixing device 9B), similar to the above-described fixing device 9A, by forming the base material 55 longer on the electrode portion side (La > Lb) and forming the pressure roller 21 shorter on the electrode portion side (Ga < Gb), the heat balance between the electrode portion side and the counter-electrode portion side is achieved. However, when the pressure roller 21 is made shorter on the electrode portion side, the contact area (contact range in the longitudinal direction) between the pressure roller 21 and the fixing belt 20 on the electrode portion side decreases, so the rotational transmission force between the pressure roller 21 and the fixing belt 20 decreases. As a result, the fixing belt 20 may not be able to rotate well in a driven manner with respect to the pressure roller 21, and there is a risk that the fixing belt 20 slips when the paper passes through the nip portion.

[0067] Therefore, in this embodiment, a high friction portion 21h having a large frictional force against the fixing belt 20 is provided on the counter-electrode portion side of the pressure roller 21 to improve the grip force between the fixing belt 20 and the pressure roller 21. This makes it possible to compensate for the decrease in the rotation transmission force caused by shortening the pressure roller 21 on the electrode portion side, and makes it possible to transmit the rotation from the pressure roller 21 to the fixing belt 20 well.

[0068] Specifically, in this embodiment, the release layer 222 is not provided as a surface layer on a part of the outer peripheral surface of the elastic layer 221 of the pressure roller 21, and a part of the elastic layer 221 is exposed to form the high friction portion 21h. The position of the high friction portion 21h is preferably on the outside (opposite electrode portion side) of the maximum paper passing area W so that the high friction portion 21h can contact the fixing belt 20 regardless of the size of the paper passed through (see FIG. 11). Also, the high friction portion 21h is not limited to being provided on the surface of the pressure roller 21, and may be provided on a part of the surface of the fixing belt 20.

[0069] [Third embodiment of the heater according to the present invention] Next, a third embodiment of the heater according to the present invention will be described. In the following description, the differences from the above-mentioned embodiment will be mainly described, and the other parts will be omitted as they are basically the same. For convenience, the heater of the third embodiment may also be referred to as a series type in this specification.

[0070] FIG. 12 is a plan view of a fixing device equipped with a heater of the third embodiment.

[0071] In this embodiment, as in the above-described embodiments, in order to balance the heat between the electrode side and the counter electrode side, the base material 55 is formed longer toward the electrode side (La>Lb), and the pressure roller 21 is formed shorter toward the electrode side (Ga <Gb)。

[0072] Furthermore, in the present embodiment, in order to raise the temperature of the electrode portion side where the temperature tends to decrease, the heat generation region 60 is made longer on the electrode portion side. Therefore, the heat generation region 60 is not arranged symmetrically with respect to the center m in the width direction of the maximum paper passage region W. That is, in the present embodiment, the length Ea from the center m in the width direction of the maximum paper passage region W to the end 60a on the electrode portion side of the heat generation region 60 is set to be longer than the length Eb from the center m in the width direction of the maximum paper passage region W to the end 60b on the counter electrode portion side of the heat generation region 60 (Ea > Eb). For this reason, the length Ha between the end Pa on the electrode portion side of the maximum paper passage region W and the end 60a on the electrode portion side of the heat generation region 60 is set to be longer than the length Hb between the end Pb on the counter electrode portion side of the maximum paper passage region W and the end 60b on the counter electrode portion side of the heat generation region 60 (Ha > Hb). Here, the relationship between the left and right lengths of the heat generation region 60 is described based on the maximum paper passage region W. However, in the present embodiment, since it is a center reference conveyance method, the relationship between the left and right lengths of the heat generation region 60 when based on a paper passage region of other width sizes is the same.

[0073] As described above, in the present embodiment, since the heat generation region 60 is formed longer on the electrode portion side, the temperature drop on the electrode portion side can be more effectively suppressed. Further, such a configuration is particularly suitable when, as in the above embodiments, even if the pressure roller 21 is made shorter on the electrode portion side, the temperature drop on the electrode portion side cannot be effectively suppressed. That is, according to the present embodiment, in addition to making the pressure roller 21 shorter on the electrode portion side (Ga < Gb), by making the heat generation region 60 longer on the electrode portion side (Ha > Hb), the temperature drop on the electrode portion side can be more effectively suppressed.

[0074] <Regarding the characteristic part according to the present invention> Next, the characteristic part of the present invention will be described in detail below with reference to the drawings. Also, before entering the description of the characteristic part, the problems will be described.

[0075] [Regarding the problem of the shape of the flange] An example of a fixing device is disclosed in JP 2020-052347 A. This publication discloses a fixing device in which a heating device having a pair of frames at both ends of a fixing belt in the longitudinal direction (rotation axis direction) is inserted in the thickness direction of the heater while being fitted into the frames in the short direction of the heater.

[0076] The frame is a device frame of the heating device and also a part of the device frame of the fixing device. The pair of frames have flanges that are inserted into the inner periphery of the fixing belt to support the fixing belt.

[0077] Here, the configuration of the flange will be described. As shown in Fig. 13, the flange 53 has a belt support part 53b having a substantially U-shape that is inserted into the inner circumference of the fixing belt 20 to support the fixing belt 20, a belt regulation part 53c that contacts the end face of the fixing belt 20 to regulate the movement (deviation) of the fixing belt in the rotation axis direction, and a support recess 53d into which both end sides of the heater holder 23 and the stay 24 are inserted to support them. The flange 53 is also provided with a guide groove 53a formed by a guide groove forming part 53f and a belt regulation part 53c. The flange 53 is assembled to the frame by inserting the guide groove 53a along the edge of the insertion groove of the frame.

[0078] 14 is a diagram for explaining the problems associated with the flange shape. The problems that arise due to the flange shape will be explained below using this diagram.

[0079] The flanges described above are often made of resin, and are often configured in a generally U-shape as described above when viewed from the direction of the rotation axis of the fixing belt (see the left diagram in FIG. 14(a)). Therefore, the flanges may deform so that the tip of the generally U-shape (the slit of the U-shape) closes due to shrinkage during molding or pressure applied from the pressure roller (see the right diagram in FIG. 14(a)).

[0080] At this time, the fixing device is configured so 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 flange, and the flange is positioned on the frame (see the left diagram in Figure 14(b)). Here, the heater rotates as the pressure roller rotates, and as a result, the flange hits the downstream side of the frame in the direction of rotation of the pressure roller. Therefore, if the flange deforms, the heater will be displaced from its designated position (see the right diagram in Figure 14(b)). If the heater is displaced, the heat from the heater will not be sufficiently transmitted to the fixing belt, which may result in poor fixing. Furthermore, if the heater is displaced, it may overheat in some areas, and the thermal stress caused by this overheating may damage the heater.

[0081] Here, Fig. 15 is a diagram for explaining a case where a bridging portion is provided on the flange. As shown in Fig. 15, to address the above-mentioned problem, a bridge that connects the U-shaped slit (see Fig. 15(a)) is provided at the tip, and the flange is configured to have an approximately square shape (see Fig. 15(b)), making it possible to prevent deformation of the flange.

[0082] On the other hand, if such a fixing device is provided with a bridging portion and the flange is configured to have an approximately square shape, the end of the heater is hidden by the heater connector or the bridging portion. The end of the heater may have marks or the like, such as identification symbols related to the characteristic values ​​of the heater. Therefore, the bridging portion hides the marks or the like, which creates a problem in that they cannot be seen.

[0083] [Configuration of the heater provided with protrusions according to the present invention] 16 is a diagram showing a fixing device equipped with a heater that is a characteristic feature of the present invention. Here, the characteristic feature of the present invention relates to the configuration of the heater. The characteristic feature of the present invention will be described in detail below. Note that the heater will be described as adopting a series heater configuration as shown in the second and third embodiments described above, but it is possible to apply it to the above embodiments.

[0084] 16, the fixing device 9 in this embodiment includes a heating device 200. The heating device 200 also includes a fixing belt 20 (an example of a cylindrical member, also called a heating belt), a heater 22 (an example of a heating body), and a flange 53 (an example of an end holding member).

[0085] The fixing belt 20 is a rotatable, endless cylindrical member having a rotation axis direction. The heater 22 has a plurality of resistance heating elements 56 and heats the fixing belt 20. In addition to the configuration described above, the flange 53 has a bridging portion 53h that holds the end of the fixing belt 20 in the rotation axis direction and the heater 22 and bridges the portion holding the heater 22 so as to open the portion. A detailed description of the bridging portion will be given later.

[0086] The fixing device 9 also includes a pressure roller 21, which is a pressure rotating body disposed opposite the fixing belt 20 and which forms a fixing nip portion by contacting the fixing belt 20, and a frame 80, which is a side plate that holds the flange 53 so that the flange 53 can move relatively. The frame 80 further includes a bearing 80b for receiving a core metal 21a, which is a rotation shaft of the pressure roller 21.

[0087] Here, FIG. 17 is a diagram showing the heater which is a characteristic part of the present invention. As shown in FIG. 17(a), the heater 22 according to the present invention has at least one end of both ends in the rotation axis direction of the fixing belt 20 protruding outward from the bridging portion 53h (opposite to the side where the resistance heating element 56 in the rotation axis direction is located). That is, the heater 22 according to the present invention has an end protruding outward from the bridging portion 53f in the longitudinal direction of the heater 22 (see FIG. 17(b)). Also, the protrusion protrudes beyond the core metal 21a of the pressure roller 21. The reason for this is to make the mark described below visible from the direction of the arrow γ shown in FIG. 17 even in the assembled state of the fixing device 9. Also, the heater 22 becomes easier to hold, which makes it easier to assemble the device. In this embodiment, the heater 22 is configured so that the side opposite to the side on which the connector 40 that connects to the electrode portion 58 of the heater 22 is located in the longitudinal direction X of the heater 22 protrudes, and this protruding portion is referred to as the protrusion 22p.

[0088] Here, the protruding portion 22p has a mark 22m that can identify a characteristic value of the heater 22. The characteristic value of the heater 22 may be, for example, a value that indicates the resistance value of the resistive heating element, or a value that indicates the power supply voltage or the like to confirm whether the heater has appropriate specifications. The mark 22m protrudes outward from the bridge portion 53h and the end of the fixing belt 20 in the rotation axis direction. The mark 22m may be, for example, a mark, a seal, an engraving, a letter, a sticker, or a mark written with a marker.

[0089] Furthermore, the size (width) of the protrusion of the protrusion 22p in the longitudinal direction X of the heater 22 is larger than the size (width) in the lateral direction Y (direction perpendicular to the rotation axis direction of the fixing belt 20) of the heater 22. This is because, for example, when the mark 22m is a character, by writing the character in an array in the longitudinal direction of the heater 22, it is possible to prevent the heater from becoming large in the lateral direction.

[0090] [Relationship between heater and temperature distribution in the comparative example] Next, the temperature distribution of the heater will be described in detail. FIG. 18 is a diagram for explaining the temperature distribution of the heater in the comparative example. The graph in FIG. 18(a) shows the relationship between the distance (mm) from the end 55b in the longitudinal direction (X direction) of the heater and the temperature (°C), and FIG. 18(b) shows the relationship between the heater configuration and the graph shown in FIG. 18(a). The paper P shown in these figures shows the corresponding relationship with the area where the paper passes through the heater. Using these, the temperature distribution of the heater in the comparative example will be described below.

[0091] First, the center line of the resistance heating element 56 extending in the longitudinal direction X of the heater 22 is taken as the center. In this case, as shown in FIG. 18(a), the portion from the center line to the electrode portion 58 side (end 55a side) of the heater 22 is generally made longer in the longitudinal direction of the heater 22 than the portion from the center line to the opposite side (end 55b side) of the electrode portion 58 for fitting with the connector 40. The length is set to 20 to 30 mm. In this way, if the electrode portion 58 side of the heater 22 is long in the longitudinal direction, the heat generated by the resistance heating element 56 is thermally conducted within the heater 22, and the temperature drops. Therefore, as shown in the temperature distribution shown in FIG. 18(a), the temperature deviation becomes large at both ends of the longitudinal direction of the heater 22.

[0092] [Temperature distribution of the heater according to the present invention] Fig. 19 is a diagram for explaining the relationship between the heater and temperature distribution in an embodiment of the present invention. The graph in Fig. 19(a) shows the relationship between the distance (mm) from the end 55b in the longitudinal direction X of the heater and the temperature (°C), and Fig. 19(b) shows the relationship between the heater configuration and the graph shown in Fig. 19(a). The paper P shown in these figures shows the corresponding relationship with the area where the paper passes through the heater. Using these, the temperature distribution of the heater according to the present invention will be described in detail below.

[0093] First, the heater 22 often has a temperature deviation between both ends in the longitudinal direction X. If the end of the heater 22 on the electrode part 58 side from the center line of the resistance heating element 56 is long, a temperature drop occurs on the long side, resulting in a large temperature deviation between both ends in the longitudinal direction X of the heater 22. The reason for this temperature deviation is that only one side of the heater 22 in the longitudinal direction X is long.

[0094] Therefore, in the present invention, as shown in Fig. 19(b), the protrusion 22p of the heater 22 in the embodiment according to the present invention is configured so that the end 55b on the opposite side to the position of the connector 40 (electrode portion 58) protrudes. That is, in the present invention, the protrusion 22p is provided on the side opposite to the electrode portion 58 side, thereby lengthening both sides in the longitudinal direction X of the heater 22. Therefore, in the present invention, the temperature distribution is as shown in Fig. 19(a), and the temperature deviation at both ends of the heater 22 in the longitudinal direction X can be suppressed to be small.

[0095] Here, the protrusion width (protrusion amount) of the protrusion 22p is 5 mm starting from the end of the flange 53, and is preferably 10 mm or more. Furthermore, taking into consideration that the temperature distribution is symmetrical, it is more preferable that the distance from the center line of the resistance heating element 56 of the heater 22 to both ends of the heater 22 is made equal (symmetrical about the center line of the heater 22).

[0096] The temperature distribution in the longitudinal direction of the heater is also affected by the resistance value of the resistive heating element. Therefore, in order to reduce the temperature deviation at both ends of the heater 22 in the longitudinal direction, which end of the heater in the longitudinal direction X should be made longer will be explained with reference to Fig. 20. Here, the protrusion of the heater 22 on the side of the connector 40 (electrode portion 58) is called the electrode side protrusion 22q.

[0097] First, when the resistance value of the resistance heating element 56 of the heater 22 is high (thermal conductivity is low), the temperature on the side of the connector 40 (electrode portion 58) of the heater 22 becomes high as shown in Fig. 20(a), so the electrode side protrusion 22q is made to protrude more than the protrusion 22p. On the other hand, when the resistance value of the resistance heating element 56 of the heater 22 is low (thermal conductivity is high), the temperature on the side of the connector 40 (electrode portion 58) of the heater 22 becomes low as shown in Fig. 20(b), so the protrusion 22p is made to protrude more than the electrode side protrusion 22q. In this way, it is possible to keep the temperature deviation at both ends of the heater 22 in the longitudinal direction small.

[0098] In addition, the temperature at both ends of the heater in the longitudinal direction is lower than that at the center of the heater in the longitudinal direction X, and the temperature distribution is such that the temperature at the ends sags (so-called end temperature sag occurs). In order to prevent this end temperature sag, the present invention can be applied to the following configuration. This embodiment will be described with reference to FIG.

[0099] First, as shown in FIG. 21(b), in this embodiment, end heating elements 56t are provided on both end sides of the resistance heating element 56 of the heater 22. FIG. 21(c) is a diagram showing the end heating element 56t by focusing on the area surrounded by a broken line circle in FIG. 21(b). Note that the paper P shown in these figures shows the correspondence relationship with the area where the paper passes through the heater. As shown in FIG. 21(c), the size (width) of the end heating element 56t in the short side direction Y (direction perpendicular to the rotation axis direction of the fixing belt 20) is larger than the size (width) of the heating element 56 in the short side direction Y at the center of the heater 22. In this way, as shown in FIG. 21(a), the heat generation amount of the heating elements at both end sides of the heater can be made larger than the heat generation amount of the heating element at the center of the heater. Therefore, the temperature in the longitudinal direction of the heater becomes uniform, which makes it possible to suppress the end temperature sagging.

[0100] The size of the end heating element can be changed according to the length of the heater in the longitudinal direction. This will be explained with reference to Fig. 22. Note that the paper P shown in this figure shows the correspondence with the area where the paper passes over the heater.

[0101] First, as shown in Fig. 22(b), for example, the length of the heater in the longitudinal direction X of the protruding portion 22p is longer than that of the configuration of Fig. 21(b) described above. Therefore, a temperature drop occurs in the protruding portion 22p. Therefore, in this embodiment, an end heating element 56t is provided on the side where the electrode portion 58 of the heating element 56 of the heater 22 is located, and an end heating element 56p having an area larger than that of the end heating element 56t is provided on the protruding portion 22p side.

[0102] 22(b), the size (width) of the end heating element 56p having this large area in the short side direction Y (the direction perpendicular to the rotational axis direction of the fixing belt 20) of the end heating element 56t is larger than the size (width) of the short side direction Y of the resistance heating element 56 in the center of the heater 22. Furthermore, the size of the end heating element 56p in the longitudinal direction X of the end heating element 56t is larger than the size of the longitudinal direction of the end heating element 56t.

[0103] In this way, as shown in Fig. 22(a), the amount of heat generated by the heating element at both ends of the heater can be made greater than the amount of heat generated by the heating element at the center of the heater. In addition, the end heating element 56p can increase the amount of heat generated on the protruding side of the heater, thereby preventing a drop in temperature. Therefore, the temperature in the longitudinal direction of the heater becomes uniform, which makes it possible to prevent the end temperature from dropping.

[0104] In the above embodiment, the heater 22 is described with the protruding portion 22p side being longer, but the present invention is also applicable to the heater 22 with the electrode portion 58 side being longer. In that case, the area of ​​the end heating element located on the electrode portion side should be made larger than that on the protruding portion side.

[0105] [Regarding the flange bridge portion according to the present invention] Next, the flange bridging portion according to the present invention will be described in detail. Although the flanges are provided on both ends of the fixing belt, the following description is the same for both cases.

[0106] First, the flange 53 according to the present invention is made of resin. This makes it possible to suppress molding shrinkage, creep deformation, etc. in the flange 53. In addition, because the flange 53 is made of resin, there is also an effect that the heat generated by the resistance heating element 56 of the heater 22 is less likely to transfer to the flange 53.

[0107] Next, the bridging portion of the flange will be described with reference to FIG. 23. As shown in FIG. 23(a), the flange according to the present invention has a bridging portion 53h that bridges the portion that holds the heater 22 so as to open it. The width of the bridging portion 53h of the flange 53 is greater than the thickness of the frame 80. Note that the width of the bridging portion 53h here refers to the size in the longitudinal direction X of the heater (the direction from the front of the paper to the back in FIG. 23(a)). This is because it makes it possible to prevent deformation of the flange. In this embodiment, the width of the bridging portion 53h is 3 to 4 mm.

[0108] The thickness of the bridging portion 53h of the flange 53 is greater than the thickness of the heater 22. This is because it is possible to prevent deformation of the flange. In this embodiment, the thickness of the bridging portion 53h is set to 1.5 to 2 mm. Note that the thickness of the bridging portion 53h here refers to the size in the thickness direction Z of the heater.

[0109] Furthermore, as shown in Fig. 23(b), the bridging portion 53h may have a facing portion 53t facing the pressure roller 21. The facing portion 53t has a smaller thickness than the other portions of the bridging portion 53h. This makes it possible to avoid interference with the core metal of the pressure roller and to reduce the size. In this embodiment, the thickness of the facing portion 53t is 0.5 mm.

[0110] The bridging portion 53h is positioned so as to overlap the frame 80, which is a side plate, in a direction perpendicular to the rotation axis direction of the fixing belt 20. This makes it possible to suppress deformation of the fitting portion of the frame 80 and to improve positional accuracy.

[0111] The present invention is also applicable to the following embodiments, which will now be described.

[0112] <Modifications of thermistor placement> In the fixing device described above, the thermistor may be disposed in the cross-arrangement direction as follows. For example, as shown in Fig. 24, in this embodiment, the thermistor 25 is provided upstream of the center position NA of the fixing nip N in the rotation direction of the fixing belt 20, in other words, on the entrance side of the fixing nip N, in the cross-arrangement direction. Since the entrance side of the fixing nip N is an area that is particularly susceptible to heat loss by the paper P, the thermistor 25 detects the temperature of this area, thereby ensuring the fixability of the fixing device 9 and effectively suppressing the fixing offset.

[0113] <Modifications of the fixing device> Further, in addition to the fixing device described above, the present invention can also be applied to fixing devices as shown in Figures 25 to 27. The configuration of each fixing device shown in Figures 25 to 27 will be briefly described below.

[0114] First, in the fixing device 9 shown in FIG. 25, a pressure roller 44 is disposed on the opposite side of the fixing belt 20 to the pressure roller 21 side. The pressure roller 44 is a counter rotating member that rotates opposite the fixing belt 20 as a rotating member. The pressure roller 44 and the heater 22 are configured to sandwich and heat the fixing belt 20. On the other hand, on the pressure roller 21 side, a nip forming member 45 is disposed on the inner periphery of the fixing belt 20. The nip forming member 45 is supported by the stay 24. The nip forming member 45 and the pressure roller 21 sandwich the fixing belt 20 to form a fixing nip N.

[0115] 26, the above-mentioned pressure 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 in accordance with the curvature of the fixing belt 20. The rest of the configuration is the same as that of the fixing device 9 shown in FIG.

[0116] Finally, the fixing device 9 shown in FIG. 27 will be described. The fixing device 9 is composed of a heating assembly 92, a fixing roller 93 as a fixing member, and a pressure assembly 94 as an opposing member. The heating assembly 92 has the heater 22, the heater holder 23, the stay 24, the heating belt 120 as a rotating member, and the like, which have been described in the previous embodiment. The fixing roller 93 is an opposing rotating member that rotates opposite to the heating belt 120 as a rotating member. The fixing roller 93 is composed of a solid iron core 93a, an elastic layer 93b formed on the surface of the core 93a, and a release layer 93c formed on the outside of the elastic layer 93b. A pressure assembly 94 is provided on the opposite side of the fixing roller 93 from the heating assembly 92 side. The pressure assembly 94 has a nip forming member 95 and a stay 96 arranged therein, and a pressure belt 97 arranged rotatably so as to include the nip forming member 95 and the stay 96. Then, the paper P is passed through the fixing nip N2 between the pressure belt 97 and the fixing roller 93, where it is heated and pressed to fix the image thereon.

[0117] <Modifications 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, but may be a monochrome image forming apparatus, a copying machine, a printer, a facsimile, or a combination machine of these.

[0118] 28, image forming apparatus 100 of this embodiment includes image forming means 50 including a photosensitive drum and the like, a paper transport section including a pair of timing rollers 15 and the like, paper feeder 7, fixing device 9, paper discharge device 10, and reading section 51. Paper feeder 7 includes multiple paper feed trays, each of which stores paper of a different size.

[0119] The reading unit 51 reads an image of the document J. The reading unit 51 generates image data from the read image. The paper feeder 7 stores a plurality of sheets of paper P and sends the sheets of paper P to a transport path. The timing rollers 15 transport the sheets of paper P on the transport path to the image forming means 50.

[0120] 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 charge removing device. The toner image represents, for example, an image of an original Q. The fixing device 9 applies heat and pressure to the toner image to fix the toner image to the paper P. The paper P on which the toner image has been fixed is transported to the paper discharge device 10 by a transport roller or the like. The paper discharge device 10 discharges the paper P outside the image forming apparatus 100.

[0121] <Further Modifications of the Fixing Device> Next, a further modified example of the fixing device of this embodiment will be described. Description of the configuration common to the fixing device of the above embodiment will be omitted as appropriate.

[0122] As shown in FIG. 29, 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, and the like.

[0123] 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.

[0124] The fixing belt 20 has a polyimide base and a release layer, and does not have an elastic layer. The release layer is made of a heat-resistant film material such as fluororesin. The outer diameter of the fixing belt 20 is about 24 mm.

[0125] The pressure roller 21 includes a core metal 21a, an elastic layer 21b, and a release layer 21c. The pressure roller 21 has an outer diameter of 24 to 30 mm, and the elastic layer 21b has a thickness of 3 to 4 mm.

[0126] The heater 22 includes a base material, a heat insulating layer, a conductor layer including a resistance heating element, and an insulating layer, and is formed with an overall thickness of 1 mm. The width Y of the heater 22 in the short side direction (array crossing direction) is 13 mm.

[0127] FIG. 30 is a plan view of a fixing device equipped with a heater of the fourth embodiment. The heater of the fourth embodiment is also configured to have divided regions in the longitudinal direction of the heater, in which a plurality of resistance heating elements 31 are divided in the arrangement direction, as in the heater of the first embodiment. As shown in FIG. 30, 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. In this embodiment, as shown in the enlarged view of FIG. 30, a divided region B is formed in which a plurality of resistance heating elements 31 are divided in the arrangement direction (however, in FIG. 30, the divided region B is illustrated only in the enlarged view range, but in reality, a divided region is provided between all of the resistance heating elements 31). The resistance heating elements 31 form three heat generating portions 35A to 35C. By passing electricity through the electrode portions 34A and 34B, the heat generating portions 35A and 35C generate heat. By passing electricity through the electrode portions 34A and 34C, the heat generating portion 35B generates heat. For example, when performing the fixing operation on small size paper, the heat generating section 35B can be made to generate heat, and when performing the fixing operation on large size paper, all the heat generating sections can be made to generate heat.

[0128] As shown in Fig. 31, 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 is composed of a surface 23b1 that is approximately parallel to the base material 30 and is recessed toward the stay 24 side more than the other surfaces of the heater 22, a wall portion 23b2 provided on the inside of the heater holder 23 on both sides in the arrangement direction of the heater holder 23 (or on one side), and a wall portion 23b3 provided on the inside of the heater holder 23 on both sides in the arrangement crossing direction. The heater holder 23 has a guide portion 26. The heater holder 23 is formed of LCP (liquid crystal polymer).

[0129] As shown in FIG. 32, a connector 70 includes a housing made of resin (for example, LCP), and a plurality of contact terminals provided inside the housing.

[0130] The connector 70 is attached so as to sandwich the heater 22 and the heater holder 23 from the front and back sides together. In this state, each contact terminal comes into contact (pressure-welded) with each electrode portion of the heater 22, electrically connecting the heat generating portion 35 and the power source provided in the image forming apparatus via the connector 70. This enables power to be supplied from the power source to the heat generating portion 35. Note that in order to ensure connection with the connector 70, at least a portion of each electrode portion 34 is not covered with an insulating layer and is exposed.

[0131] The flanges 53 are provided on both sides of the fixing belt 20 in the arrangement direction, and hold both ends of the fixing belt 20 from the inside of the belt. The flanges 53 are fixed to the housing of the fixing device 9. The flanges 53 are inserted into both ends of the stays 24 (see the arrow directions from the flanges 53 in FIG. 32).

[0132] The direction in which the connector 70 is attached to the heater 22 and the heater holder 23 is the direction that crosses the arrangement of the heaters (see the direction of the arrow from the connector 70 in FIG. 32). 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 move relatively within the concave portion. The connector 70 is attached to the heater 22 and the heater holder 23 on one side of the arrangement direction, opposite to the side on which the drive motor of the pressure roller 21 is provided.

[0133] 33, thermistors 25 are provided on the center side and end side of the arrangement direction of the fixing belt 20, facing the inner circumferential surface of the fixing belt 20. The heater 22 is controlled based on the temperatures of the center side and end side of the arrangement direction of the fixing belt 20 detected by the thermistor 25. Note that one of these thermistors 25 is provided at a position corresponding to a division area between the resistance heating elements of the heater 22, as in the above-mentioned embodiment.

[0134] Thermostats 27 are provided on the central side and end sides of the arrangement direction of fixing belt 20, facing the inner circumferential surface of fixing belt 20. When the temperature of fixing belt 20 detected by thermostat 27 exceeds a predetermined threshold value, power supply to heater 22 is stopped.

[0135] Flanges 53 are provided on both ends of the fixing belt 20 in the arrangement direction to hold the respective ends of the fixing belt 20. The flanges 53 are made of LCP (liquid crystal polymer).

[0136] 34, a slide groove 53a is provided in the flange 53. The slide groove 53a extends in the direction in which the fixing belt 20 approaches and separates from the pressure roller 21. An engagement portion of the housing of the fixing device 9 engages with the slide groove 53a. The engagement portion moves relatively within the slide groove 53a, so that the fixing belt 20 can move in the direction in which the fixing belt 20 approaches and separates from the pressure roller 21.

[0137] <Example of a fixing device having a highly heat conductive member> Next, a fixing device according to another embodiment will be described. Note that, for the sake of convenience, reference numerals will be given to the components in the fixing device according to the present embodiment.

[0138] 35 has a second high thermal conductivity member 90 between a heater holder 164 and a first high thermal conductivity member 89. The second high thermal conductivity member 90 is provided at a position different from that of the first high thermal conductivity member 89 in the stacking direction (left-right direction in FIG. 35) of members such as the heater holder 164, the stay 165, and the first high thermal conductivity member 89. More specifically, the second high thermal conductivity member 90 is provided overlapping the first high thermal conductivity member 89.

[0139] In this embodiment, similarly to the above embodiment, a temperature sensor (thermistor) 167 is provided, but FIG. 35 shows a cross section in which the temperature sensor 167 is not provided.

[0140] The second high thermal conductivity member 90 is made of a material having a higher thermal conductivity than the base material 155, such as graphene or graphite. In this embodiment, the second high thermal conductivity member 90 is made of a graphite sheet having a thickness of 1 mm. The second high thermal conductivity member 90 may also be made of a plate material such as aluminum, copper, or silver.

[0141] 36, a plurality of second high thermal conductive members 90 are arranged in recess 164b of heater holder 164, and a longitudinal gap is provided between each of the second high thermal conductive members 90. A recess that is one step deeper than the other portions is formed in the portion of heater holder 164 where second high thermal conductive member 90 is provided. A gap is provided between second high thermal conductive member 90 and heater holder 164 on both sides in the longitudinal direction. This suppresses heat transfer from second high thermal conductive member 90 to heater holder 164, and heater 163 efficiently heats fixing belt 161.

[0142] The heater shown in Fig. 37 is an example in which a plurality of resistance heating elements are divided in the longitudinal direction of the heater. As shown in Fig. 37, the second high thermal conductivity member 90 (see the hatched portion) is disposed in a position corresponding to the interval B1 in the longitudinal direction (arrow X direction) and at a position overlapping at least a part of the adjacent resistance heating elements 156. Particularly, in this embodiment, the second high thermal conductivity member 90 is disposed over the entire interval B1. Note that Fig. 37 (and Fig. 39 described later) shows a case in which the first high thermal conductivity member 89 is disposed over the entire longitudinal direction of the region in which all the resistance heating elements 156 are disposed, but the range of the arrangement of the first high thermal conductivity member 89 is not limited thereto.

[0143] In this embodiment, in addition to the first high thermal conductivity member 89, the second high thermal conductivity member 90 is disposed at a position corresponding to the interval B in the longitudinal direction so as to overlap at least a part of the adjacent resistance heating element 156. This further improves the heat transfer efficiency in the longitudinal direction at the interval B1, and more effectively suppresses temperature unevenness in the longitudinal direction of the heater 163. Most preferably, as shown in FIG. 38, the first high thermal conductivity member 89 and the second high thermal conductivity member 90 are provided only in the entire region at the position corresponding to the interval B. This makes it possible to particularly improve the heat transfer efficiency at the position corresponding to the interval B1 compared to other regions. Note that in FIG. 38, the resistance heating element 156, the first high thermal conductivity member 89, and the second high thermal conductivity member 90 are shown shifted in the vertical direction of the figure for convenience, but they are disposed at approximately the same position in the longitudinal cross direction (arrow Y direction). However, this is not limited to the above, and the first high thermal conductivity member 89 and the second high thermal conductivity member 90 may be arranged in a portion of the resistive heating element 156 in the longitudinal crossing direction, or may be arranged so as to cover the entire longitudinal crossing direction.

[0144] Furthermore, both the first high thermal conductivity member 89 and the second high thermal conductivity member 90 may be formed from the graphene sheet. In this case, the first high thermal conductivity member 89 and the second high thermal conductivity member 90 can be formed to have high thermal conductivity in a predetermined direction along the graphene surface, that is, in the longitudinal direction rather than the thickness direction. This makes it possible to effectively suppress temperature unevenness in the heater 163 and the fixing belt 161 in the longitudinal direction.

[0145] Graphene is a flaky powder. Graphene consists of a planar hexagonal lattice structure of carbon atoms, as shown in FIG. 41. A graphene sheet is a sheet of graphene, usually a single layer. A graphene sheet may contain impurities in a single layer of carbon, or may have a fullerene structure. A fullerene structure is generally recognized as a compound in which the same number of carbon atoms form a polycyclic ring in which five-membered and six-membered rings are condensed into a cage shape, such as C60, C70 and C80 fullerenes or other closed cage structures with three-coordinate carbon atoms.

[0146] Graphene sheets are man-made and can be made, for example, by chemical vapor deposition (CVD) methods.

[0147] The graphene sheet may be a commercially available product. The size and thickness of the graphene sheet, or the number of layers of the graphite sheet described below, may be measured, for example, by a transmission electron microscope (TEM).

[0148] Moreover, graphite, which is a multi-layered graphene, has a large thermal conductivity anisotropy. As shown in FIG. 42, graphite has a layer in which the condensed six-membered ring layer plane of carbon atoms spreads in a planar shape, and has a crystal structure in which these layers are stacked on top of each other. In this crystal structure, adjacent carbon atoms in a layer form a covalent bond, and carbon atoms between layers form a van der Waals bond. The covalent bond has a larger bond strength than the van der Waals bond, and has a large anisotropy between the bond within a layer and the bond between layers. In other words, by forming the first highly thermally conductive member 89 or the second highly thermally conductive member 90 from graphite, the heat transfer efficiency in the longitudinal direction of the first highly thermally conductive member 89 or the second highly thermally conductive member 90 is larger than that in the thickness direction (i.e., the stacking direction of the members), 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. Furthermore, by making the first high thermal conductivity member 89 or the second high thermal conductivity member 90 out of graphite, the first high thermal conductivity member 89 or the second high thermal conductivity member 90 can have excellent heat resistance and will not oxidize up to approximately 700 degrees.

[0149] The physical properties and dimensions of the graphite sheet can be appropriately changed depending on the function required of the first high thermal conductivity member 89 or the second high thermal conductivity member 90. For example, the anisotropy of the thermal conductivity can be increased by using high purity graphite or single crystal graphite, or 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 may be used to reduce the heat capacity of the fixing device. Also, when the width of the nip portion N and the heater 163 is large, the longitudinal width of the first high thermal conductivity member 89 or the second high thermal conductivity member 90 may be increased accordingly.

[0150] From the viewpoint of increasing mechanical strength, the number of layers of the graphite sheet is preferably equal to or greater than 11. The graphite sheet may partially include a single layer portion and a multilayer portion.

[0151] The second high thermal conductivity members 90 may be arranged in positions corresponding to the interval B1 (and further to the enlarged divided region C) in the longitudinal direction so as to overlap at least a portion of the adjacent resistance heating elements 156, and are not limited to the arrangement shown in FIG. 37. For example, as shown in the example shown in FIG. 39, the second high thermal conductivity members 90A may be arranged to protrude beyond the base material 155 on both sides in the longitudinal cross direction (short direction, arrow Y direction). The second high thermal conductivity members 90B may be arranged in a range in the longitudinal cross direction where the resistance heating elements 156 are arranged. The second high thermal conductivity members 90C may be arranged in a portion of the interval B1.

[0152] In another embodiment shown in FIG. 40, a gap is provided between the first highly heat-conductive member 89 and the heater holder 164 in the thickness direction (left-right direction in FIG. 40). That is, a relief portion 164c is provided as a heat insulating layer in a part of a region of the recess 164b (see FIG. 36) of the heater holder 164 in which the heater 163, the first highly heat-conductive member 89, and the second highly heat-conductive member 90 are arranged. The relief portion 164c is provided in a part of a region in the longitudinal direction other than the part in which the second highly heat-conductive member 90 (not shown in FIG. 40) is provided. The relief portion 164c is formed by making the depth of the recess 164b of the heater holder 164 deeper than the other parts. This can minimize the contact area between the heater holder 164 and the first highly heat-conductive member 89, so that the heat transfer from the first highly heat-conductive member 89 to the heater holder 164 is suppressed, and the fixing belt 161 can be efficiently heated by the heater 163. In addition, in the cross section in the longitudinal direction where second high thermal conductivity member 90 is provided, second high thermal conductivity member 90 abuts against heater holder 164 as in the embodiment shown in FIG.

[0153] In this embodiment, the relief portion 164c is provided in the longitudinal cross direction (the vertical direction in FIG. 40) over the entire area where the resistance heating element 156 is provided. This effectively suppresses heat transfer from the first highly thermally conductive member 89 to the heater holder 164, improving the heating efficiency of the fixing belt 161 by the heater 163. Note that, as the heat insulating layer, in addition to a configuration in which a space is provided like the relief portion 164c, a configuration in which a heat insulating member having a lower thermal conductivity than the heater holder 164 is provided may also be used.

[0154] In the present embodiment, second high thermal conductivity member 90 is provided as a member different from first high thermal conductivity member 89, but this is not limited thereto. For example, the first high thermal conductivity member 89 may also function as second high thermal conductivity member 90 by making the portion of first high thermal conductivity member 89 corresponding to interval B1 thicker than the other portions.

[0155] As described above, this embodiment comprises an endless tubular member 20 that is rotatable and has a rotational axis direction, a heating element 22 which has a plurality of heating elements 31, 56 and heats the tubular member, and an end holding member 53 which holds the end of the tubular member in the rotational axis direction and the heating element 22 and has a bridging portion 53h which bridges the portion holding the heating element so as to open, and at least one of the two ends of the heating element 22 in the rotational axis direction has a protrusion 22p which protrudes beyond the bridging portion 53h on the side opposite to the side on which the heating elements 31, 56 are located in the rotational axis direction.

[0156] This prevents the identifiable mark from becoming difficult to see.

[0157] As described above, in this embodiment, the protruding portion 22p has the mark 22m that allows the characteristic value of the heater 22 to be identified, and the mark 22m protrudes on the opposite side beyond the bridging portion 53h.

[0158] This makes it possible to improve the visibility of the mark and also improves the efficiency of the assembly process.

[0159] As described above, in this embodiment, the protruding width of the protruding portion 22p is larger than the width of the heater 22 in the direction perpendicular to the rotation axis direction.

[0160] This makes it possible to reduce the size of the heater in the short direction.

[0161] As described above, in this embodiment, the heating device 200 has the connector 40 that connects to the electrode 58 of the heating element 22, and the end of the protruding portion 22p opposite to the position of the connector 40 protrudes.

[0162] This makes it possible to reduce the size of the heater in the longitudinal direction and to keep the temperature deviation between both ends of the heater in the longitudinal direction small.

[0163] As described above, in this embodiment, the end holding member 53 is made of resin.

[0164] This makes it possible to prevent molding shrinkage, creep deformation, and the like.

[0165] As described above, in this embodiment, the pressure rotating body 21 has the core metal 21a, and the protruding portion 22p is the fixing device 9 that protrudes on the opposite side beyond the core metal 21a.

[0166] This allows the size of the heater in the short direction to be reduced, and the visibility of the mark to be improved.

[0167] As described above, in this embodiment, the thickness of the facing portion 53t of the bridging portion 53h that faces the pressurizing rotor 21 is smaller than the thickness of the portions other than the facing portion 53t.

[0168] This makes it possible to avoid interference with the core metal of the pressure roller, thereby realizing a compact device.

[0169] As described above, in this embodiment, the fixing device 9 has the heater holder 23 that holds the heating element 22 and the stay 24 that supports the heater holder 23, and the end holding member 53 and the stay 24 come into contact with each other.

[0170] This makes it possible to prevent deformation due to the load.

[0171] As described above, this embodiment is a fixing device 9 that has a heating device 200 and a side plate 80 that holds the end holding member 53 so that it can move relative to the heating device 200, and the bridging portion 53h is positioned so as to overlap the side plate 80 in a direction perpendicular to the rotation axis direction.

[0172] This makes it possible to suppress deformation of the side plate due to the fitting portion, and to improve positional accuracy.

[0173] As described above, this embodiment is a fixing device 9 that includes the heating device 200 and the 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 greater than the thickness of the side plate 80.

[0174] This makes it possible to suppress deformation of the flange.

[0175] As described above, this embodiment is a fixing device 9 having the heating device 200 and the side plate 80 that holds the end holding member 53 so as to be relatively movable.

[0176] This makes it possible to suppress deformation of the flange.

[0177] <Applicability to other areas> Regarding other applications, for example, the heating device according to the present invention may be applied as a drying device of an ink-jet image forming apparatus.

[0178] The fixing device according to the present invention may be a lamination processing device.

[0179] Although an embodiment of the present invention has been described above, the present invention is not limited to the above-described embodiment, and it goes without saying that various modifications can be made without departing from the gist of the present invention.

[0180] The above description is merely an example, and the present invention provides unique effects for each of the following aspects.

[0181] [First aspect] The first aspect comprises a rotatable, endless tubular member (e.g., fixing belt 20) having a rotational axis direction, a heating element (e.g., heater 22) having a plurality of heating elements (e.g., resistance heating elements 31, 56) and heating the tubular member, and an end holding member (e.g., flange 53) having a bridging portion (e.g., bridging portion 53h) that holds an end of the tubular member in the rotational axis direction and the heating element and bridges the portion that holds the heating element so as to open, and the heating element is characterized in that at least one of both ends in the rotational axis direction has a protrusion (e.g., protrusion 22p) that protrudes beyond the bridging portion toward the side opposite the side on which the heating element is located in the rotational axis direction.

[0182] [Second aspect] The second aspect is characterized in that, in the first aspect, the protrusion has a mark (e.g., mark 22m) that can identify a characteristic value of the heating element, and the mark protrudes on the opposite side beyond the bridging portion.

[0183] [Third aspect] A third aspect is characterized in that in the first or second aspect, a protruding width of the protrusion is larger than a width of the heating element in a direction perpendicular to the rotation axis direction.

[0184] [Fourth aspect] A fourth aspect is characterized in that, in any of the first to third aspects, the heating device has a connector that connects to an electrode of the heating body, and the protrusion has an end protruding on the opposite side to the position of the connector.

[0185] [Fifth aspect] A fifth aspect is characterized in that in any one of the first to fourth aspects, the end holding member is made of resin.

[0186] [Sixth aspect] A sixth aspect is a fixing device characterized by having a heating device described in any one of the first to fifth aspects, and a pressure rotating body (e.g., a pressure roller 21) arranged opposite the tubular member and forming a nip portion by abutting against the tubular member.

[0187] [Seventh aspect] A seventh aspect is the sixth aspect, characterized in that the pressurizing rotator has a core metal, and the protruding portion protrudes to the opposite side beyond the core metal.

[0188] [Eighth aspect] An eighth aspect is characterized in that in the sixth or seventh aspect, a thickness of a facing portion of the bridging portion facing the pressurizing rotor is smaller than a thickness of the portion other than the facing portion.

[0189] [Ninth aspect] A ninth aspect is characterized in that in any of the sixth to eighth aspects, the fixing device has a heater holder (e.g., heater holder 23) that holds the heating element, and a stay (e.g., stay 24) that supports the heater holder, and the end holding member and the stay are in contact with each other.

[0190] [Tenth aspect] A tenth aspect is a fixing device having a heating device described in any one of the first to fifth aspects, and a side plate (e.g., frame 80) that holds the end holding member so that it can move relative to the side plate, and the bridging portion is positioned so as to overlap the side plate in a direction perpendicular to the rotation axis direction.

[0191] [Eleventh aspect] An eleventh aspect is a fixing device having a heating device in any one of the first to fifth aspects and a side plate that holds the end holding member so that it can move relative to the other, and is characterized in that the width of the bridging portion is greater than the thickness of the side plate.

[0192] [12th aspect] A twelfth aspect is a fixing device having a heating device as in any one of the first to fifth aspects, and a side plate that holds the end holding member so that it can move relative to the heating device, and is characterized in that the thickness of the bridging portion is greater than the thickness of the heating body.

[0193] [13th aspect] A thirteenth aspect is an electrophotographic image forming apparatus including the fixing device according to any one of the sixth to twelfth aspects.

[0194] [14th aspect] A fourteenth aspect is a drying device including the heating device according to any one of the first to fifth aspects.

[0195] [15th aspect] A fifteenth aspect is an ink-jet type image forming apparatus including the drying device according to the fourteenth aspect.

[0196] [16th aspect] A sixteenth aspect is the image forming apparatus according to the thirteenth or fifteenth aspect, further comprising a covering device. [Explanation of symbols]

[0197] 1Y, 1M, 1C, 1Bk Imaging unit 2 Photoreceptor 3. Charging device 4. Developing device 5 Cleaning device 6 Exposure equipment 7 Paper feeder 8. Transcription device 9 Fixing device 10 Paper ejection device 11 Intermediate transfer belt 12 Primary transfer roller 13 Secondary transfer roller 14 Paper transport path 15 Pair of timing rollers 20 Fixing belt 21 Pressure roller 21a Core metal 21b Elastic layer 21c Release layer 21d Electrode side end 21e End opposite to electrode 221 Elastic layer 222 Release layer 22 Heater 22p protrusion 22q Electrode side protrusion 22m mark 23 Heater holder 23b Recess 23b2 Wall section 23b3 Wall section 24 Stay 25 Thermistor 26 Guide part 27 Thermostat 30, 55 base material 31, 56 Resistance heating element 34A, B, C electrode section 35A, B, C Heating parts 40, 70 Connectors 41 Housing 42 Multiple Contact Terminals 42a Contact part 43 Power supply harness 44 Pressure roller 45 Nip forming member 53 Flange 53a Slide groove 53b Belt support part 53c Belt regulation part 53d Support recess 53f Guide groove forming part 53h Bridging Section 53t Opposite section 56t End Heating Element 56p End heating element (large area) 57 Insulating layer 58 Electrode part (pair of electrodes) 59 Power line 60 Heating Area 60a Electrode side end 60b edge 89 First high thermal conductive material 90 Second high thermal conductive material 100 Image forming device [Prior art documents] [Patent documents]

[0198] [Patent Document 1] JP 2022-133736 A [Patent Document 2] JP 2013-117576 A

Claims

1. an endless cylindrical member that is rotatable and has a rotation axis direction; A heating element having a plurality of heating elements and configured to heat the cylindrical member; an end holding member that holds an end of the cylindrical member in the rotation axis direction and the heating body, and has a bridging portion that bridges the portion that holds the heating body so as to open the end holding member, A heating device characterized in that at least one of the two ends of the heating element in the direction of the rotation axis has a protrusion that protrudes further than the bridging portion on the side opposite to the side on which the heating element is located in the direction of the rotation axis.

2. the protrusion has a mark that allows a characteristic value of the heater to be identified, The heating device according to claim 1 , wherein the mark protrudes beyond the bridge portion to the opposite side.

3. 2. The heating device according to claim 1, wherein a protruding width of the protrusion is larger than a width of the heating body in a direction perpendicular to the rotation axis direction.

4. The heating device has a connector that is connected to an electrode of the heating body, 2. The heating device according to claim 1, wherein the protruding portion has an end protruding from a side opposite to the position of the connector.

5. 2. The heating device according to claim 1, wherein the end holding member is made of resin.

6. The heating device according to claim 1 ; a pressure rotating body disposed opposite the cylindrical member and contacting the cylindrical member to form a nip portion.

7. The pressurizing rotor has a core metal, The fixing device according to claim 6 , wherein the protruding portion protrudes beyond the core metal toward the opposite side.

8. 7. The fixing device according to claim 6, wherein a thickness of the bridge portion facing the pressure rotator is smaller than a thickness of the other portion.

9. The fixing device is A heater holder for holding the heating element; A stay that supports the heater holder, The fixing device according to claim 6 , wherein the end holding member and the stay are in contact with each other.

10. The heating device according to claim 1 ; a side plate that holds the end holding member so as to be relatively movable; The fixing device, wherein the bridge portion is positioned so as to overlap the side plate in a direction perpendicular to the rotation axis direction.

11. The heating device according to claim 1 ; a side plate that holds the end holding member so as to be relatively movable; The fixing device according to claim 1, wherein the width of the bridge portion is greater than the thickness of the side plate.

12. The heating device according to claim 1 ; a side plate that holds the end holding member so as to be relatively movable; The fixing device according to claim 1, wherein the bridge portion has a thickness greater than a thickness of the heating body.

13. 7. An electrophotographic image forming apparatus comprising the fixing device according to claim 6.

14. A drying device comprising the heating device according to claim 1.

15. An ink-jet type image forming apparatus comprising the drying device according to claim 14.

16. 16. The image forming apparatus according to claim 13, further comprising a coating device.

Images