Heating device, fixing device, and image forming device

Abstract

To secure fixed insulation distance between a high heat conduction member and a temperature detection member, and to suppress a decrease in temperature in a longitudinal end side of a heating element.SOLUTION: A soaking plate 28 and a thermistor 25 are disposed overlappingly in a thickness direction of a base material 30. The soaking plate 28 has a bending section 28a that is provided in the outside of one side in a longitudinal direction relative to the thermistor 25, and projects to the side of the thermistor 25 in the thickness direction of the base material 30 relative to the other parts of the soaking plate 28. A predetermined insulation distance H1 in the longitudinal direction is provided between the bending section 28a and the thermistor 25. In a fixing device 9, the soaking plate 28 has an arm section 28b in which the area of a section orthogonal to the longitudinal direction becomes smaller than the area of a part in which the area of the soaking plate 28 is maximized between the bending section 28a in the longitudinal direction, and a position closest to the bending section 28a of the thermistor 25.SELECTED DRAWING: Figure 13

Description

Technical Field

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

Background Art

[0002] There is a fixing device (heating device) having a planar heater (heating element) provided inside a fixing belt (rotating member), a heat sink plate (high heat conduction member) for promoting heat transfer in the longitudinal direction of the heater and suppressing temperature unevenness in the longitudinal direction, and a thermistor (temperature detection member) for detecting the temperature of the heater and the like.

[0003] As the above-mentioned high heat conduction member, there are various shapes. For example, in the fixing device of Patent Document 1 (Japanese Patent Application Laid-Open No. 2015-152752), the heat capacity per unit length of the portion corresponding to the non-paper-passing region in the longitudinal direction of the high heat conduction member is made larger than the heat capacity of the central portion. Thereby, overheating of the non-paper-passing region can be suppressed.

Summary of the Invention

Problems to be Solved by the Invention

[0004] In the heating device as described above, in order to prevent a short circuit caused by the electrical connection between the heating element side and the temperature detection member side, it is necessary to provide a certain insulation distance between the high heat conduction member and the temperature detection member.

[0005] However, if the length of the high heat conduction member is extended outward in the longitudinal direction to secure the insulation distance, the heat of the heating element is lost outward in the longitudinal direction, resulting in temperature unevenness in the longitudinal direction of the heating element and the rotating member.

[0006] An object of the present invention is to secure a certain insulation distance between the high heat conduction member and the temperature detection member and suppress a temperature drop on the longitudinal end side of the heating element.

Means for Solving the Problems

[0007] To solve the above problems, the present invention provides a heating device including a rotating member, a heating member having a base material and a heating element, at least the heating element being provided inside the rotating member, a holding member for holding the heating member, a high thermal conductivity member extending in the longitudinal direction of the rotating member and having a higher thermal conductivity than the base material, and a temperature detection member provided on one side of a main heating region which is a region in the longitudinal direction where the heating element is provided inside the rotating member. The high thermal conductivity member and the temperature detection member are arranged to overlap in the thickness direction of the base material. When the central side of the main heating region is the inner side in the longitudinal direction and one or the other end side of the main heating region with respect to the central side of the main heating region is the outer side in the longitudinal direction, the high thermal conductivity member is provided outside the temperature detection member on one side in the longitudinal direction, and has a protruding portion protruding toward the temperature detection member side in the thickness direction of the base material more than other portions of the high thermal conductivity member. A predetermined insulation distance in the longitudinal direction is provided between the protruding portion and the temperature detection member. The high thermal conductivity member has a first portion in the longitudinal direction between the protruding portion and the position closest to the protruding portion of the temperature detection member, and the cross-sectional area perpendicular to the longitudinal direction is smaller than the area of the portion where the cross-sectional area of the high thermal conductivity member is the largest.

Advantages of the Invention

[0008] A certain insulation distance can be ensured between the high thermal conductivity member and the temperature detection member, and the temperature drop on the longitudinal end side of the heating member can be suppressed.

Brief Description of the Drawings

[0009]

Figure 1

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Embodiments for Carrying Out the Invention

[0010] Hereinafter, embodiments of the present invention will be described with reference to the drawings. In each figure, the same or corresponding parts are denoted by the same reference numerals, and the redundant description thereof will be appropriately simplified or omitted. Hereinafter, as an example of the heating device of the present invention, a fixing device for fixing an image on a sheet as a recording medium will be described.

[0011] FIG. 1 is a schematic configuration diagram of an image forming apparatus according to an embodiment of the present invention.

[0012] The image forming apparatus 100 shown in FIG. 1 includes four image forming units 1Y, 1M, 1C, and 1Bk that are detachable from the image forming apparatus main body. Each of the image forming units 1Y, 1M, 1C, and 1Bk has the same configuration except that it contains different color developers of yellow, magenta, cyan, and black. These color developers correspond to the color separation components of a color image. Each of the image forming units 1Y, 1M, 1C, and 1Bk includes a drum-shaped photoreceptor 2 as an image carrier, a charging device 3, a developing device 4, and a cleaning device 5. The charging device 3 charges the surface of the photoreceptor 2. The developing device 4 supplies toner as a developer to the surface of the photoreceptor 2 to form a toner image. The cleaning device 5 cleans the surface of the photoreceptor 2.

[0013] As the photoreceptor 2, for example, an inorganic photoreceptor such as amorphous silicon or selenium, or an organic photoreceptor such as titanyl phthalocyanine can be used. As the organic photoreceptor, a layer (charge generation layer) in which a charge generation material such as metal-free phthalocyanine or titanyl phthalocyanine is dispersed in a binder resin and a layer (charge transport layer) in which a charge transport material is dispersed in a binder resin are stacked on a support such as an aluminum drum. Examples include a laminated photoreceptor having a laminated structure and a single-layer photoreceptor having a photosensitive layer with a single-layer structure in which both a charge generation material and a charge transport material are dispersed in a binder resin on a support. In the single-layer photoreceptor, a hole transport agent and an electron transport agent can also be added as charge transport materials to the photosensitive layer. Further, an undercoat layer may be provided between the support and the laminated charge generation layer or the single-layer photosensitive layer.

[0014] Further, the image forming apparatus 100 includes an exposure device 6, a paper feeding device 7 as a recording medium supply unit, a transfer device 8, a fixing device 9 as a heating device, and a paper discharging device 10. The exposure device 6 exposes the surface of each photoreceptor 2 to form an electrostatic latent image on the surface. The paper feeding device 7 has a paper feeding tray 16 and a paper feeding roller 17. The paper feeding device 7 supplies a sheet of paper P as a recording medium to a paper conveyance path 14 as a conveyance path for the recording medium. The transfer device 8 transfers the toner image formed on each photoreceptor 2 to the sheet of paper P. The fixing device 9 fixes the toner image transferred to the sheet of paper P on the surface of the sheet of paper P. The paper discharging device 10 discharges the sheet of paper P outside the apparatus. Each image forming unit 1, photoreceptor 2, charging device 3, exposure device 6, transfer device 8, etc. constitute an image forming means for forming an image on the paper.

[0015] The transfer device 8 includes an endless intermediate transfer belt 11 as an intermediate transfer member, four primary transfer rollers 12 as primary transfer members, and a secondary transfer roller 13 as a secondary transfer member. The intermediate transfer belt 11 is stretched by a plurality of rollers. The primary transfer roller 12 transfers the toner image on each photoreceptor 2 to the intermediate transfer belt 11. The secondary transfer roller 13 transfers the toner image transferred onto the intermediate transfer belt 11 to the paper P. The plurality of primary transfer rollers 12 are each in contact with the photoreceptor 2 via the intermediate transfer belt 11. As a result, the intermediate transfer belt 11 and each photoreceptor 2 are in contact with each other, and a primary transfer nip is formed therebetween. On the other hand, the secondary transfer roller 13 is in contact with one of the rollers that stretch the intermediate transfer belt 11 via the intermediate transfer belt 11. As a result, a secondary transfer nip is formed between the secondary transfer roller 13 and the intermediate transfer belt 11. As the intermediate transfer member, an elastic intermediate transfer belt can also be used. As the elastic intermediate transfer belt, for example, one in which a flexible elastic layer is laminated on a rigid base layer capable of obtaining relatively high flexibility can be used. Further, in order to prevent the intermediate transfer belt 11 from meandering, a centering guide member may be provided on the inner peripheral surface of the intermediate transfer belt 11.

[0016] Also, a pair of timing rollers 15 are provided in the middle of the paper conveyance path 14 from the paper feeding device 7 to the secondary transfer nip (secondary transfer roller 13). The pair of rollers provided on the paper conveyance path 14 such as the timing rollers 15 are conveyance members for conveying the paper P on the paper conveyance path 14.

[0017] Next, the printing operation of the above image forming apparatus will be described with reference to FIG. 1.

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

[0019] The toner image formed on each photosensitive member 2 rotates as the photosensitive member 2 rotates and reaches the primary transfer nip (the position of the primary transfer roller 12). Then, the toner image is transferred so as to sequentially overlap the intermediate transfer belt 11 that is rotationally driven counterclockwise in FIG. 1. And the toner image transferred onto the intermediate transfer belt 11 is conveyed to the secondary transfer nip (the position of the secondary transfer roller 13) as the intermediate transfer belt 11 rotates. The toner image is transferred to the sheet P conveyed to the secondary transfer nip. This sheet P is supplied from the paper feed tray 16. The sheet P supplied from the paper feeding device 7 is once stopped by the timing roller 15 and then conveyed to the secondary transfer nip at the timing when the toner image on the intermediate transfer belt 11 reaches the secondary transfer nip. Thus, a full-color toner image is carried on the sheet P. Also, after the toner image is transferred, the toner remaining on each photosensitive member 2 is removed by each cleaning device 5.

[0020] The sheet P onto which the toner image has been transferred is conveyed to the fixing device 9, and the toner image is fixed to the sheet P by the fixing device 9. Thereafter, the sheet P is discharged outside the device by the paper discharging device 10, and a series of printing operations is completed.

[0021] Subsequently, the configuration of the fixing device will be described with reference to FIG. 2.

[0022] As shown in FIG. 2, the fixing device 9 according to the present embodiment includes a fixing belt 20, a pressure roller 21 as a pressure member, a heater 22 as a heating element, a heater holder 23 as a holding member, a stay 24 as a support member, a thermistor 25 as a temperature detecting member, a heat sink 28 as a high thermal conductivity member, a thermostat, etc. The fixing belt 20 is formed of an endless belt. The pressure roller 21 contacts the outer peripheral surface of the fixing belt 20 to form a fixing nip N between the fixing belt 20. The heater 22 heats the fixing belt 20. The heater holder 23 holds the heater 22. The stay 24 supports the heater holder 23. The thermistor 25 abuts against the back surface of the base material 30 and detects its temperature. Further, the fixing member provided in the fixing device is an aspect of the rotating member provided in the heating device. In the fixing device 9 of the present embodiment, a fixing belt 20 is provided as a specific example of this fixing member.

[0023] The direction orthogonal to the plane of FIG. 2 (see direction X in FIG. 3) is the longitudinal direction of the fixing belt 20, the pressure roller 21, the heater 22, the heater holder 23, the stay 24, the heat sink 28, and the fixing device 9. Hereinafter, this direction will also be simply referred to as the longitudinal direction. Note that this longitudinal direction is also the belt width direction of the fixing belt 20 or the axial direction of the pressure roller 21, and is also the width direction of the paper being conveyed. The width direction of the paper is the direction orthogonal to the paper conveyance direction and the thickness direction. The vertical direction Y in FIG. 2 is the short-side direction of the heater 22 and the heat sink 28, and is also the paper conveyance direction and the opposite direction thereof. Further, the left-right direction Z in FIG. 2 is the thickness direction of the base material 30 and the heater 22, and is also the pressure application direction of the pressure roller 21 to the fixing belt 20 and the opposite direction thereof. The heater 22, the heat sink 28, and the thermistor 25 are arranged so as to overlap in the thickness direction of the base material 30. This overlapping arrangement includes not only the case where two members are directly overlapped and abutted in the thickness direction, but also the case where other members or spaces are interposed therebetween. The directions X, Y, and Z in the present embodiment are directions orthogonal to each other.

[0024] The fixing belt 20 has a base layer composed of, for example, a cylindrical substrate made of polyimide (PI) with an outer diameter of 25 mm and a thickness of 40 to 120 μm. On the outermost surface of the fixing belt 20, in order to enhance durability and ensure release properties, a release layer with a thickness of 5 to 50 μm made of a fluororesin such as PFA or PTFE is formed. An elastic layer made of rubber or the like with a thickness of 50 to 500 μm may be provided between the substrate and the release layer. The fixing belt 20 of the present embodiment is a rubberless belt without an elastic layer. Further, 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.

[0025] The pressure roller 21 is composed of, for example, a solid iron core 21a with an outer diameter of 25 mm, an elastic layer 21b formed on the surface of the core 21a, and a release layer 21c formed outside the elastic layer 21b. The elastic layer 21b is formed of silicone rubber and has a thickness of, for example, 3.5 mm. The release layer 21c is a conductive layer formed by adding a conductive material filler such as carbon to PFA.

[0026] When the pressure roller 21 is biased toward the fixing belt 20 by a biasing means, the pressure roller 21 is pressed against the heater 22 via the fixing belt 20. Thereby, a fixing nip N as a nip portion is formed between the fixing belt 20 and the pressure roller 21. Further, the pressure roller 21 is configured to be rotationally driven by a driving means. When the pressure roller 21 rotates in the direction of arrow A1 in FIG. 2, the fixing belt 20 is driven to rotate in the direction of arrow A2 accordingly. The directions of A1 and A2 are the rotation directions of the pressure roller 21 and the fixing belt 20 during the image forming operation or the fixing operation.

[0027] The heater 22 is arranged to contact the inner peripheral surface of the fixing belt 20. The heater 22 of the present embodiment contacts the pressure roller 21 via the fixing belt 20 and serves as a nip forming member that forms a fixing nip N therebetween. Further, the fixing belt 20 is a member to be heated that is heated by the heater 22. In other words, the heater 22 heats the paper P passed through the fixing nip N via the fixing belt 20.

[0028] The heater 22 is a planar heating element provided longitudinally across the width direction of the fixing belt 20. The heater 22 is composed of a plate-shaped base material 30, a resistive heating element 31 provided on the base material 30, an insulating layer 32 covering the resistive heating element 31, and the like. Further, the heater 22 is in contact with the inner peripheral surface of the fixing belt 20 on the insulating layer 32 side, and the heat generated from the resistive heating element 31 is transmitted to the fixing belt 20 through the insulating layer 32. In the present embodiment, the resistive heating element 31 and the insulating layer 32 are provided on the fixing belt 20 side (fixing nip N side) of the base material 30. Conversely, the resistive 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 resistive heating element 31 is transmitted to the fixing belt 20 through the base material 30, it is desirable that the base material 30 be made of a material with high thermal conductivity such as aluminum nitride. Also, by configuring the base material 30 with a material having high thermal conductivity, even if the resistive heating element 31 is arranged on the side opposite to the fixing belt 20 side of the base material 30, it is possible to sufficiently heat the fixing belt 20.

[0029] The heater holder 23 and the stay 24 are arranged on the inner peripheral side of the fixing belt 20. The stay 24 is composed of a metal channel material, and both end portions in its longitudinal direction are supported by both side plates of the fixing device 9. By supporting the heater holder 23 and the heater 22 by the stay 24, the heater 22 can surely receive the pressing force of the pressure roller 21 in a state where the pressure roller 21 presses the fixing belt 20. Thereby, the fixing nip N is stably formed between the fixing belt 20 and the pressure roller 21. In the present embodiment, the thermal conductivity of the heater holder 23 is provided to be smaller than that of the base material 30.

[0030] Since the heater holder 23 is likely to become hot due to the heat of the heater 22, it is preferably formed of a heat-resistant material. For example, when the heater holder 23 is formed of a low thermal conductivity heat-resistant resin such as LCP or PEEK, heat transfer from the heater 22 to the heater holder 23 is suppressed. Thereby, the heater 22 can efficiently heat the fixing belt 20.

[0031] The heater holder 23 has a holding recess 23b for holding the heater 22.

[0032] Also, as shown in FIG. 2, the heater holder 23 is integrally provided with guide ribs 26 for guiding the fixing belt 20. A plurality of guide ribs 26 are provided in the longitudinal direction on the upstream side and the downstream side of the heater holder 23 in the paper conveyance direction, respectively.

[0033] The guide rib 26 is formed in a substantially fan shape. The guide rib 26 is provided along the inner peripheral surface of the fixing belt 20 and has a guide surface 260 that extends in an arc shape or a convex curved surface shape in the belt circumferential direction.

[0034] The heater holder 23 has an insertion hole 23a that penetrates in the thickness direction within the recess 23b. A thermistor 25 is provided in the insertion hole 23a.

[0035] The heat sink 28 is composed of a member having a higher thermal conductivity than the base material 30. In the present embodiment, the heat sink 28 is formed of an aluminum alloy, steel, a graphite sheet, or other conductors. By forming the heat sink 28 in a plate shape, the positional accuracy of the heater 22 with respect to the heater holder 23 and the heat sink 28 can be improved. By arranging the heat sink 28, heat transfer in the longitudinal direction can be promoted, and the temperature in the longitudinal direction of the heater 22, and thus the fixing belt 20, can be made uniform. By forming the heat sink 28 of a metal material, workability is good and its dimensional accuracy can be increased.

[0036] Next, the method for calculating the thermal conductivity described above will be explained. When calculating the thermal conductivity, first, the thermal diffusivity of the target object is measured, and the thermal conductivity is calculated using this thermal diffusivity.

[0037] The measurement of the thermal diffusivity was performed using a thermal diffusivity / thermal conductivity measuring device (product name: ai-Phase Mobile 1u, manufactured by AI Phase Co., Ltd.).

[0038] In order to convert the above thermal diffusivity into thermal conductivity, the values of density and specific heat capacity are required. For the measurement of density, a dry-type automatic densitometer (product name: Accupyc 1330, manufactured by Shimadzu Corporation) was used. Also, for the measurement of specific heat capacity, a differential scanning calorimeter (product name: DSC-60, manufactured by Shimadzu Corporation) was used, and sapphire was used as a reference substance with a known specific heat capacity for measurement. In this example, the specific heat capacity was measured 5 times, and the average value at 50°C was used. Assuming the density and specific heat capacity are ρ and C respectively, the thermal conductivity λ can be obtained from the thermal diffusivity α obtained from the above thermal diffusivity measurement by the following formula (1). λ = ρ × C × α ···(1)

[0039] In the fixing device 9 according to this embodiment, when the printing operation is started, the pressure roller 21 is rotationally driven, and the fixing belt 20 starts to rotate passively. At this time, the inner peripheral surface of the fixing belt 20 contacts the guide surface 260 of the guide rib 26 and is guided, so that the fixing belt 20 rotates stably and smoothly. Also, when power is supplied to the resistance heating element 31 of the heater 22, the fixing belt 20 is heated. Then, in a state where the temperature of the fixing belt 20 reaches the fixing temperature which is a predetermined target temperature, as shown in FIG. 2, the sheet P carrying the unfixed toner image is conveyed in the direction of arrow A3 to the fixing nip N between the fixing belt 20 and the pressure roller 21, so that the unfixed toner image is heated and pressurized and fixed to the sheet P.

[0040] Next, a more detailed configuration of the heater provided in the above fixing device will be described with reference to FIG. 3. FIG. 3 is a plan view of the heater according to this embodiment.

[0041] As shown in FIG. 3, on the surface of the plate-shaped base material 30, a plurality (four) of resistance heating elements 31, power supply lines 33A and 33B as conductors, and a first electrode portion 34A and a second electrode portion 34B are provided. However, the number of the resistance heating elements 31 is not limited to this embodiment. Hereinafter, the power supply lines 33A and 33B are also referred to as the power supply line 33, and the first electrode portion 34A or the second electrode portion 34B is also referred to as the electrode portion 34.

[0042] Note that the longitudinal direction of the heater 22 or the like, which is the direction orthogonal to the plane of FIG. 2, and the left-right direction X in FIG. 3 are also the arrangement directions of the plurality of resistance heating elements 31. Hereinafter, this direction is also simply referred to as the arrangement direction. Further, the direction intersecting the arrangement direction, particularly the vertical direction in this embodiment and different from the thickness direction of the base material 30, the up-down direction Y in FIG. 3 is referred to as the direction intersecting the arrangement direction of the plurality of resistance heating elements 31, or simply the arrangement intersection direction. The arrangement intersection direction Y is the direction along the surface of the base material 30 provided with the resistance heating elements 31, and is also the short-side direction of the heater 22 or the conveyance direction of the paper passed through the fixing device 9.

[0043] The plurality of resistance heating elements 31 constitute a heat generation portion 35 divided into a plurality in the arrangement direction. Each resistance heating element 31 is electrically connected in parallel to the pair of electrode portions 34A and 34B via the power supply lines 33A and 33B. The pair of electrode portions 34A and 34B are provided at the left end in FIG. 3, which is one end on the arrangement direction side of the base material 30. The power supply lines 33A and 33B are composed of conductors having a resistance value smaller than that of the resistance heating elements 31.

[0044] The resistance heating element 31 is made of a material having PTC (positive temperature coefficient) characteristics, and has a feature that the resistance value increases and the heater output decreases as the temperature rises.

[0045] Since the resistance heating element 31 has PTC characteristics and due to the configuration of the heating section 35 divided in the array direction, it is possible to prevent the overheating of the fixing belt 20 when passing small-sized paper. That is, when passing paper with a width smaller than the overall width of the heating section 35, in the area outside the paper width, the heat of the fixing belt 20 is not taken away by the paper, 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, its resistance value increases. As a result, the output of the heater, that is, the calorific value, relatively decreases, and the rise in the end temperature is suppressed. Also, by electrically connecting a plurality of resistance heating elements 31 in parallel, it is possible to suppress the rise in temperature of the non-paper-passing part while maintaining the printing speed. Note that the heating element constituting the heating section 35 may be other than a resistance heating element having PTC characteristics. Also, the resistance heating elements may be arranged in a plurality of rows in the direction intersecting the arrangement of the heater 22.

[0046] The resistance heating element 31 can be formed, for example, by applying a paste prepared by mixing silver palladium (AgPd), glass powder, etc. to the base material 30 by screen printing or the like, and then firing the base material 30. In the present embodiment, the resistance value of the resistance heating element 31 is set to 80 Ω at normal temperature. As the material of the resistance heating element 31, in addition to the above-mentioned materials, a resistance material such as silver alloy (AgPt) or ruthenium oxide (RuO2) may be used. The materials of the power supply line 33 and the electrode portion 34 can be formed by screen printing or the like using silver (Ag) or silver palladium (AgPd). The power supply line 33 is composed of a conductor having a resistance value smaller than that of the resistance heating element 31.

[0047] As the material of the base material 30, ceramics such as alumina and aluminum nitride, which are excellent in heat resistance and insulation, or non-metallic materials such as glass and mica are preferable. In the present embodiment, an alumina base material having a width of 8 mm in the direction intersecting the array, a width of 270 mm in the array direction, and a thickness of 1.0 mm is used. Alternatively, a structure in which an insulating material is laminated on a conductive material such as metal may constitute the base material 30. As the metal material of the base material 30, aluminum, stainless steel, etc. are preferable because of their low cost.

[0048] The insulating layer 32 is made of, for example, heat-resistant glass with a thickness of 75 μm. The insulating layer 32 covers the resistance heating element 31 and the power supply line 33, insulates and protects them, and maintains the slidability with the fixing belt 20.

[0049] The region where the longitudinal resistance heating element 31 is provided is the main heating region D of the heater 22, and the region between the resistance heating elements 31 is also included in the main heating region D. In other words, from the longitudinal one-side end of the resistance heating element 31 arranged on the most one side in the longitudinal direction to the longitudinal other-side end of the resistance heating element 31 arranged on the most other side in the longitudinal direction is the main heating region D of the heater 22. The main heating region D is the main heating region by the heater 22, and the heater 22 also slightly generates heat in the region outside the main heating region D.

[0050] In this embodiment, the first electrode portion 34A and the second electrode portion 34B are provided on the same side in the arrangement direction, but they may be provided on different sides. Also, the resistance heating element 31 is not limited to the shape of this embodiment. For example, as shown in FIG. 4, the resistance heating element 31 may be rectangular, or as shown in FIG. 5, the resistance heating element 31 may be composed of a linear portion, and this linear portion may be folded back to form a substantially parallelogram shape. Also, as shown in FIG. 4, the portion extending from the block-shaped resistance heating element 31 to the side of the power supply line 33 (the portion extending in the arrangement intersection direction) may be a part of the resistance heating element 31, or may be composed of the same material as the power supply line 33.

[0051] Also, in the heater 22 shown in FIG. 6, two resistance heating elements 31 extending in the longitudinal direction are connected in series. The two resistance heating elements 31 are connected to the electrode portions 34A and 34B via the power supply lines 33A and 33B, respectively, on the left side of FIG. 6. Also, the two resistance heating elements 31 are connected in series via the power supply line 33C on the right side of FIG. 6.

[0052] In the heaters 22 of FIGS. 3 to 6, the length of the left side of the substrate 30 in each figure is longer than that of the right side with respect to the central position D1 of the main heating region D. This is because the left side of the figure has the electrode portions 34A and 34B arranged, so the length is increased by that amount. Due to the asymmetry of the length of the substrate 30, the heat of the heater 22 easily flows outward in the longitudinal direction on the left side portion of the substrate 30. Therefore, when looking at the heater 22 alone, the temperature of the left side portion in FIGS. 3 to 6 tends to be lower than that of the right side portion. Further, the thermistor 25 of the present embodiment is arranged on the end side on the side opposite to the electrode portions 34A and 34B, which is the side where the temperature in the longitudinal direction becomes high (see FIG. 13). By detecting the side with a high temperature by the thermistor 25, the rise in the end temperature can be effectively suppressed.

[0053] FIG. 7 is a diagram showing a power supply circuit for the heater shown in FIG. 3.

[0054] As shown in FIG. 7, in the present embodiment, a power supply circuit for supplying power to each resistance heating element 31 is configured by electrically connecting an AC power supply 200 and the electrode portions 34A and 34B of the heater 22. Further, a triac 210 for controlling the supplied power amount is provided in the power supply circuit. The power amount supplied to each resistance heating element 31 is controlled by the control unit 220 via the triac 210 based on the detected temperatures of the thermistors 25A and 25B. The control unit 220 is composed of a microcomputer including a CPU, ROM, RAM, I / O interface, etc. Note that the control unit 220 may be provided in the fixing device or may be provided in the main body of the image forming apparatus.

[0055] FIG. 8 is a perspective view showing each member such as a heater holder provided in the fixing belt 20. In the following figures, the thermistor 25A (see FIG. 7) arranged on the longitudinal end side of the main heating region D will be described as the thermistor 25, and the thermistor 25A will be simply referred to as the thermistor 25. The longitudinal end side of the main heating region D is, for example, the regions at both ends when the main heating region D is divided into three equal parts in the longitudinal direction. Also, in FIG. 8, the description of the thermistor 25B in FIG. 7 is omitted, and the same applies to the following figures.

[0056] As shown in FIG. 8, an insertion hole 23a and a soaking plate holding hole 23c are provided in the holding recess 23b of the heater holder 23. An AC connector 29 is attached to the other side in the longitudinal direction of the heater holder 23 (the right side in FIG. 8). The AC connector 29 can electrically connect the heater 22 and the power supply side by the contact terminals in the terminal holder 291 contacting the first electrode portion 34A and the second electrode portion 34B. The soaking plate 28 has bent portions 28a as protruding portions at both ends in its longitudinal direction.

[0057] When assembling these members, first, the soaking plate 28 is fitted into the holding recess 23b of the heater holder 23. At this time, the bent portion 28a of the soaking plate 28 is inserted into the soaking plate holding hole 23c, and the bent portion 28a is locked to the heater holder 23 (details will be described later). Then, the heater 22 is fitted into the holding recess 23b so as to be overlapped from above the soaking plate 28. In this state, the substantially U-shaped terminal holder 291 of the AC connector 29 sandwiches the other side in the longitudinal direction of the heater holder 23, the soaking plate 28, and the heater 22, so that the soaking plate 28 and the heater 22 are fixed to the heater holder 23. The thermistor 25 is inserted into the insertion hole 23a from the back side of the heater holder 23, that is, from the side opposite to the side of the heater 22.

[0058] FIG. 9 is a cross-sectional view showing the inside of the holding recess 23b of the heater holder 23 with the soaking plate 28 and the heater 22 attached to the heater holder 23. The cross-sectional view of FIG. 9 is a cross-sectional view perpendicular to the short side direction of the heater 22. In actuality, the heater 22, the soaking plate 28, the heater holder 23, and the thermistor 25 are laminated with substantially no gap in the thickness direction, but in FIG. 9, gaps are shown for convenience.

[0059] As shown in FIG. 9, the bent portion 28a of the heat pipe 28 is a portion formed by bending one side in the longitudinal direction of the plate member in two steps. More specifically, after bending a predetermined portion in the longitudinal direction of the plate member 90 degrees to one side in the thickness direction, the portion on the end side in the longitudinal direction from the bent portion is bent 90 degrees to the opposite surface side. However, it is not necessarily bent at an angle of 90 degrees.

[0060] The bent portion 28a is inserted into the heat pipe holding hole 23c of the heater holder 23. At this time, as shown in FIG. 8, the convex portion 23c1 forming the heat pipe holding hole 23c is inserted into the hole portion 28a2 provided at the center of the bent portion 28a. As shown in FIG. 9, when the heat pipe 28 moves in the direction of falling off from the heater holder 23, the upper surface of the tip portion 28a1 of the bent portion in FIG. 9 abuts against the back surface 23d of the heater holder 23 (see the arrow in FIG. 9). Thereby, the bent portion 28a can be locked to the heater holder 23, and the heat pipe 28 can be prevented from falling off from the heater holder 23.

[0061] The heat-sensitive element 251, which is the temperature detection portion of the thermistor 25, abuts against the heat pipe 28 via the insulating sheet 252. Thereby, the heat-sensitive element 251 can detect the temperature of the heat pipe 28.

[0062] As shown in FIG. 10(a), the thermistor 25 includes a heat-sensitive element 251 as a temperature detection portion, an insulating sheet 252 as an insulating portion, a holder 253, and a harness 254. As shown in FIG. 10(b), the harness 254 is fixed to the holder 253 by a soldering portion 255. The soldering portion 255 is a conductor portion.

[0063] As shown in FIG. 9, the heat-sensitive element 251 abuts on the heat pipe 28 via the insulating sheet 252. The bent portion 28a of the heat pipe 28 protrudes downward in FIG. 9, which is on the thermistor 25 side (particularly the solder portion 255 side) in the thickness direction of the base material 30 (the vertical direction in FIG. 9), rather than other portions of the heat pipe 28. A longitudinal insulation distance H1 is provided between the solder portion 255 and the bent portion 28a. That is, in this embodiment, by the bent portion 28a protruding downward on the thermistor 25 side in FIG. 9, a longitudinal insulation distance H1 is provided between the solder portion 255 and the bent portion 28a. However, in the heat pipe 28, the bent portion 28a does not necessarily need to be the portion that protrudes most on the thermistor 25 side in the thickness direction.

[0064] Next, the relationship between the insulation distance between the thermistor 25 and the heat pipe 28 and the longitudinal temperature distribution of the fixing device will be described with reference to FIGS. 11 to 13. FIGS. 11 to 13 show the longitudinal positional relationship between members such as the heat pipe and the thermistor and the paper passing area, as well as the longitudinal temperature distribution of the heater. FIGS. 11 and 12 are diagrams showing the temperature distribution in fixing devices respectively having different heat pipes 280 and 290 from this embodiment, and FIG. 13 is a diagram showing the temperature distribution in the fixing device having the heat pipe of this embodiment. Note that FIGS. 11 to 13 show the temperature on the left side of the longitudinal center position D1 of the heater 22 with a dashed line. Also, although FIGS. 11 to 13 show the temperature distribution of the heater, the fixing belt shows a similar tendency of temperature distribution.

[0065] As shown in FIG. 11, the longitudinal center position D1 of the main heat generation region D coincides with the longitudinal center position of the maximum paper passing region E, which is the longitudinal passing region of the paper P1 with the maximum width passed through the fixing device 9. However, the present invention is not limited to this, and they do not necessarily need to coincide. This maximum paper passing region E refers to the region when the paper P1 is conveyed without longitudinal misalignment.

[0066] The heat spreader 280 in FIG. 11 is provided over the entire region of the main heat generation region D in the longitudinal direction and extends outward beyond the main heat generation region D in both directions in the longitudinal direction. Thereby, in the entire region where the resistive heating element 31 in the longitudinal direction generates heat, heat transfer in the longitudinal direction can be promoted and temperature unevenness in the longitudinal direction can be suppressed.

[0067] The heat spreader 280 is configured such that there is no significant difference in the lengths on one side and the other side in the longitudinal direction with respect to the central position D1. For this reason, the distance between the bent portion 280a on one side in the longitudinal direction, which is the left side in FIG. 11, and the thermistor 25 provided at a position corresponding to the longitudinal end side of the heater 22 is short. For this reason, the insulation distance H2 cannot be sufficiently ensured.

[0068] On the other hand, the heat spreader 290 shown in FIG. 12 has a longer length on one side in the longitudinal direction compared to the heat spreader 280 in FIG. 11. Thereby, the longitudinal distance between the bent portion 290a and the solder portion 255 in FIG. 12 can be made larger, and a larger insulation distance H3 can be ensured.

[0069] However, on the other hand, as the distance on one side in the longitudinal direction of the heat spreader 290 increases, the heat of the heater 22 more easily flows outward on one side in the longitudinal direction. As a result, as shown by the dashed-dotted line on the lower side in FIG. 12, the temperature on one side in the longitudinal direction of the heater 22 significantly drops with respect to the temperature at the central position D1, and the temperature unevenness in the longitudinal direction of the heater 22 increases. Thereby, it has an adverse effect on the fixing property of the image on one side in the longitudinal direction. In particular, the temperature of the heater 22 decreases as it goes outward on one side in the longitudinal direction, and within the maximum paper feed region D, the temperature at one end in the longitudinal direction is the lowest.

[0070] Then, the heat pipe 28 of the present embodiment shown in FIG. 13 extends its length to one side in the longitudinal direction, similar to the heat pipe 290. Thereby, a sufficient insulation distance H1 can be provided between the heat pipe 28 and the thermistor 25. The bent portion 28a is provided outside the thermistor 25 on one side in the longitudinal direction. This outside in the longitudinal direction refers to the side of one or the other end of the main heat generation region D with respect to the central position D1 of the main heat generation region D when the side of the central position D1 of the main heat generation region D is taken as the inside. As the length of the sufficient insulation distance, it is preferable to set the insulation distance H1 to 2.5 mm or more, for example.

[0071] In addition to this, the heat pipe 28 of the present embodiment reduces the heat capacity of the portion extended to one side in the longitudinal direction. That is, the cross-sectional area of the arm portion 28b as the first portion, which is a part of the extended portion of the heat pipe 28, is made smaller than the portion where the cross-sectional area of the heat pipe 28 is the largest. This cross-sectional area refers to the area in the cross-section in the direction orthogonal to the longitudinal direction. The arm portion 28b is a part of the heat pipe 28 and is part or all of the portion between the bent portion 28a and the position closest to the bent portion 28a of the thermistor 25 (the left end position of the thermistor 25 in FIG. 13) in the longitudinal direction. In the present embodiment, it is particularly a part of the portion outside the main heat generation region D in the longitudinal direction. The portion where the cross-sectional area of the heat pipe 28 of the present embodiment is the largest is the portion within the maximum paper passing region D of the heat pipe 28. The cross-sectional area of the arm portion 28b may be smaller than not only the portion where the cross-sectional area of the heat pipe 28 is the largest as in the present embodiment, but also the cross-sectional area of the portion corresponding to the main heat generation region D of the heat pipe 28 or the cross-sectional area of the portion corresponding to the maximum paper passing region E, or smaller than the cross-sectional area of the region on the central side in the longitudinal direction, or smaller than the cross-sectional area of the position corresponding to the central position D1 of the heat pipe 28, etc.

[0072] By reducing the cross-sectional area of the arm portion 28b, the heat capacity of that portion of the vapor chamber 28 is reduced. As a result, the amount of heat flowing to the outside on one side in the longitudinal direction is suppressed, and as shown by the dashed-dotted line in FIG. 13, the temperature drop on one side in the longitudinal direction of the heater 22 can be suppressed. In other words, with respect to the length extending to one side in the longitudinal direction of the vapor chamber 28, the amount of temperature drop on one side in the longitudinal direction of the heater 22 can be suppressed. Thereby, for example, even at the position of the end on one side in the longitudinal direction of the maximum paper passage area D, the temperature difference from the central position D1 can be kept small, and the temperature drop of the heater 22 on one side in the longitudinal direction can be suppressed, and the adverse effect on the fixing property can be suppressed. In particular, in the present embodiment, the cross-sectional area is reduced by reducing the width in the short direction of the arm portion 28b. By forming the arm portion 28b by reducing the width in the short direction of the vapor chamber 28, processing is easy, and the arm portion 28b with a small heat capacity can be easily formed.

[0073] As described above, according to the present embodiment, by providing a longitudinal distance between the bent portion 28a and the soldering portion 255 of the thermistor 25 to secure an insulation distance, the temperature drop of the heater 22 on the thermistor 25 side can be suppressed, and the adverse effect on the fixing property can be suppressed.

[0074] In particular, in the present embodiment, the thermistor 25 and the arm portion 28b of the vapor chamber 28 are provided on the left side of FIG. 13, which is the side where the length of the base material 30 is shorter, out of one side and the other side in the longitudinal direction with respect to the central position D1. On the other side in the longitudinal direction where the length of the base material 30 is long, the temperature of the heater 22 easily flows to the outside in the longitudinal direction, and the temperature easily becomes low. On the contrary, by extending the length of the vapor chamber 28 on one side in the longitudinal direction opposite to the other side in the longitudinal direction, the temperature deviation in the longitudinal direction of the heater 22 due to the base material 30 can be suppressed.

[0075] Also, by extending the vapor chamber 28 to the outside in the longitudinal direction beyond the main heat generation region D, the temperature rise at the end in the non-paper passage region can be suppressed.

[0076] Also, by making the width in the short side direction of the bent portion 28a and the arm portion 28b on the side of the bent portion 28a smaller than other portions of the heat sink 28, the assemblability of the heat sink 28 with respect to the heater holder 23 can be improved. Different from this embodiment, the heat sink 300 shown in FIG. 14 has a bent portion 300a whose width is the same as that of other portions. And in the recessed portion 23b of the heater holder 23, a heat sink holding hole 23c having a large width in the short side direction corresponding to the bent portion 300a is provided. The margin of the width in the short side direction of the heat sink holding hole 23c is small with respect to the width in the short side direction of the bent portion 300a. In this case, as shown in FIG. 15(a), when the heat sink 300 is horizontally arranged and attached to the recessed portion 23b, the bent portion 300a does not interfere with the heater holder 23. On the other hand, as shown in FIG. 15(b), when the bent portion 300a is about to be inserted into the heat sink holding hole 23c with the heat sink 300 inclined with respect to the recessed portion 23b, the bent portion 300a is likely to interfere with the wall surface portion forming the recessed portion 23b of the heater holder 23. Thereby, it has an adverse effect on the assemblability of the heat sink 300 with respect to the heater holder 23. In contrast, in this embodiment, as described above, by making the width in the short side direction of the bent portion 28a and the arm portion 28b (see FIG. 8) on the side of the bent portion 28a smaller, as shown in FIG. 16(a), the width in the short side direction of the heat sink holding hole 23c can be set to be larger with a margin with respect to the width in the short side direction of the bent portion 28a. Thereby, as shown in FIG. 16(b), even when the bent portion 28a is about to be inserted into the heat sink holding hole 23c with the heat sink 28 inclined with respect to the recessed portion 23b, the bent portion 28a does not interfere with the heater holder 23. For this reason, the assemblability of the heat sink 28 with respect to the heater holder 23 can be improved. Also, as shown in FIG. 8, by making the width in the short side direction of the bent portion 28a and the arm portion 28b smaller, when the heat sink 28 is assembled to the heater holder 23, the bent portion 28a and the arm portion 28b are less likely to interfere with the corner portion 23e of the heater holder 23 and the like. Thereby, the assemblability of the heat sink 28 with respect to the heater holder 23 can be improved.

[0077] Also, the soaking plate 28 is preferably made of an aluminum alloy, steel, or graphite with high thermal conductivity. This can effectively suppress temperature unevenness in the longitudinal direction of the heater 22 and, consequently, the fixing belt, and can suppress an increase in the end temperature and temperature drop at the ends.

[0078] As shown in FIG. 13, by providing the heat-sensitive element 251 of the thermistor 25 on the longitudinal end side within the maximum paper passage area E, the temperature of the heater 22 can be detected at the position on the longitudinal end side of the paper, and the temperature of the heater 22 in this part, that is, the temperature of the fixing belt, can be surely raised to the temperature required for the fixing operation. Therefore, the fixability on the longitudinal end side of the paper can be ensured.

[0079] Also, as shown in FIG. 17, by providing the heat-sensitive element 251 of the thermistor 25 outside the maximum paper passage area and at a position overlapping the main heat generation area D, the thermistor 25 can detect the temperature of the longitudinal area where heat is least likely to be taken away from the paper and where the temperature is most likely to rise. This can suppress abnormal temperature rise of the heater 22 and improve the safety of the fixing device.

[0080] Also, as shown in FIGS. 18(a) and 18(b), a detection unit insertion hole 28c for fitting the thermistor 25 can be provided in the heat spreader 28. Thereby, the thermistor 25 can be directly brought into contact with the heater 22 without passing through the heat spreader 28. As a result, the responsiveness of the thermistor 25 to the temperature change of the heater 22, and thus the temperature change of the fixing belt, can be enhanced, and the safety of the fixing device is improved. Also, the heater 22 can be made to generate heat at a more appropriate timing, and the fixing device 9 can be made energy-efficient. Further, in the present embodiment, the detection unit insertion hole 28c is extended to the outside in the longitudinal direction from the portion where the thermistor 25 is fitted, and an arm portion 28b as a first portion is formed in this portion in the longitudinal direction. Thereby, similar to the above-described embodiment, it is possible to achieve both ensuring the insulation distance and suppressing the temperature drop on the longitudinal end portion side of the heater. The thermistor 25 can be positioned at the position shown in FIG. 18(a) or FIG. 18(b) in the detection unit insertion hole 28c by a predetermined positioning unit such as a fitting portion. Note that the arm portion 28b in FIG. 18(a) or FIG. 18(b) is provided with a smaller width in the lateral direction than the other portions of the heat spreader 28, and this width is the total width of the portions provided above and below in the lateral direction in the arm portion 28b, and the same applies to the cross-sectional area orthogonal to the longitudinal direction.

[0081] The above-described heat spreader 28 can be constituted by a graphene sheet. Thereby, a heat spreader 28 having a high thermal conductivity in a predetermined direction along the surface of graphene, that is, in the arrangement direction rather than the thickness direction, can be formed. Therefore, the temperature unevenness in the arrangement direction of the heater 22 and the fixing belt 20 can be effectively suppressed.

[0082] Graphene is a flaky powder. As shown in FIG. 19, graphene has a planar hexagonal lattice structure of carbon atoms. A graphene sheet is a sheet-like graphene, and is usually a single layer. It may contain impurities in a single layer of carbon. Also, graphene may have a fullerene structure. The fullerene structure is generally recognized as a compound formed by a polycyclic body in which the same number of carbon atoms are condensed in a cage shape by 5-membered rings and 6-membered rings. For example, C60, C70, and C80 fullerenes or other closed ones having 3-coordinate carbon atoms It has a cage-like structure.

[0083] The graphene sheet is an artificial product and can be produced, for example, by a chemical vapor deposition (CVD) method.

[0084] Commercially available products can be used for the graphene sheet. The size, thickness of the graphene sheet, or the number of layers of the graphite sheet described later, etc. are measured, for example, by a transmission electron microscope (TEM).

[0085] Also, graphite with multilayered graphene has large thermal conductivity anisotropy. As shown in FIG. 20, graphite has a layer in which the condensed six-membered ring planes of carbon atoms spread out flatly, and has a crystal structure in which these layers are stacked multiple times. Between carbon atoms in this crystal structure, adjacent carbon atoms within the layer form a covalent bond, and carbon atoms between layers form a van der Waals bond. And the covalent bond has a greater binding force compared to the van der Waals bond, and there is a large anisotropy between the bond within the layer and the bond between layers. That is, by forming the heat spreader 28 with graphite, the heat transfer efficiency in the arrangement direction in the heat spreader 28 becomes larger compared to the thickness direction (that is, the member stacking direction), and the heat transfer to the heater holder 23 can be suppressed. Therefore, the temperature unevenness in the arrangement direction of the heater 22 can be efficiently suppressed, and the heat flowing out to the heater holder 23 side can be minimized. Also, by forming the heat spreader 28 with graphite, the heat spreader 28 can be given excellent heat resistance that does not oxidize up to about 700 degrees.

[0086] The physical properties and dimensions of the graphite sheet can be appropriately changed according to the functions required for the heat spreader 28. For example, by using high-purity graphite or single-crystal graphite, or by increasing the thickness of the graphite sheet, the anisotropy of its thermal conductivity can be enhanced. Also, in order to increase the speed of the fixing device 9, a graphite sheet with a small thickness may be used to reduce the heat capacity of the fixing device 9. Also, when the width of the fixing nip N or the heater 22 is large, the width in the arrangement direction of the heat spreader 28 may be increased accordingly.

[0087] From the viewpoint of enhancing mechanical strength, the number of layers of the graphite sheet is preferably 11 or more. Further, the graphite sheet may partially include a single-layer portion and a multi-layer portion.

[0088] As described above, the embodiments of the present invention have been explained. However, the present invention is not limited to the above-described embodiments, and it goes without saying that various modifications can be made without departing from the gist of the present invention.

[0089] In addition to the above-described fixing device, the present invention is also applicable to a fixing device as shown in FIGS. 21 to 23. Hereinafter, the configurations of the respective fixing devices shown in FIGS. 21 to 23 will be briefly described.

[0090] First, in the fixing device 9 shown in FIG. 21, a pressing roller 39 is disposed on the side opposite to the pressure roller 21 side with respect to the fixing belt 20. The pressing roller 39 is an opposing rotating member that rotates facing the fixing belt 20 as a rotating member. The pressing roller 39 and the heater 22 are configured to heat the fixing belt 20 therebetween. On the other hand, on the pressure roller 21 side, a nip forming member 41 is disposed on the inner circumference of the fixing belt 20. The nip forming member 41 is supported by a stay 24. The nip forming member 41 and the pressure roller 21 form a fixing nip N by sandwiching the fixing belt 20.

[0091] Next, in the fixing device 9 shown in FIG. 22, the above-described pressing roller 39 is omitted, and in order to secure 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. Otherwise, the configuration is the same as that of the fixing device 9 shown in FIG. 21.

[0092] Finally, the fixing device 9 shown in FIG. 23 will be described. The fixing device 9 is composed of a heating assembly 42, a fixing roller 43 as a fixing member, and a pressure assembly 44 as an opposing member. The heating assembly 42 has the heater 22, the heat equalizing plate 28, the heater holder 23, the stay 24, and a heating belt 48 as a rotating member, which are described in the previous embodiment. The fixing roller 43 is an opposing rotating member that rotates opposite to the heating belt 48 as a rotating member. The fixing roller 43 is composed of a solid iron core 43a, an elastic layer 43b formed on the surface of the core 43a, and a release layer 43c formed on the outside of the elastic layer 43b. A pressure assembly 44 is provided on the opposite side of the fixing roller 43 from the heating assembly 42 side. The pressure assembly 44 has a nip forming member 45 and a stay 46 arranged therein, and a pressure belt 47 as a pressure member is rotatably arranged so as to include the nip forming member 45 and the stay 46. Then, the paper P is passed through the fixing nip N2 between the pressure belt 47 and the fixing roller 43, where it is heated and pressed to fix the image thereon.

[0093] 21 to 23, the configurations of the heat equalizer plate 28 and heater holder 23 of the above-described embodiment can be adopted. This ensures an insulation distance between the heat equalizer plate 28 and thermistor 25, and also suppresses a temperature drop on the longitudinal end side of the heater 22.

[0094] Furthermore, the heating device of the present invention is not limited to the fixing device as described in the above embodiment. In other words, it may be a heating device such as a drying device that dries ink applied to paper, a laminator that thermocompresses a film as a covering member onto the surface of a sheet such as paper, or a thermocompression device such as a heat sealer that thermocompresses a seal portion of a packaging material. By applying the present invention to such a heating device, a certain insulation distance can be secured between the high thermal conductivity member and the temperature detection member, and a temperature drop on the longitudinal end side of the heating body can be suppressed.

[0095] 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.

[0096] As the recording medium, in addition to paper P (plain paper), cardboard, postcards, envelopes, thin paper, coated paper (such as coated paper and art paper), tracing paper, OHP sheets, plastic films, prepregs, copper foils, etc. are included.

[0097] Aspects of the present invention are as follows, for example. <1> A rotating member, A heating member having a base material and a heating element, wherein at least the heating element is provided inside the rotating member, A holding member for holding the heating member, A high thermal conductivity member extending in the longitudinal direction of the rotating member and having a higher thermal conductivity than the base material, A temperature detection member provided on one side of a main heating region which is a region in the longitudinal direction where the heating element is provided inside the rotating member, and a heating device comprising: The high thermal conductivity member and the temperature detection member are arranged to overlap in the thickness direction of the base material, When the central side of the main heating region is the inner side in the longitudinal direction and one or the other end side in the longitudinal direction of the main heating region with respect to the central side of the main heating region is the outer side in the longitudinal direction, The high thermal conductivity member is provided on the outer side of one side in the longitudinal direction with respect to the temperature detection member, and has a protruding portion protruding toward the temperature detection member side in the thickness direction of the base material more than other portions of the high thermal conductivity member, A predetermined insulation distance in the longitudinal direction is provided between the protruding portion and the temperature detection member, The high thermal conductivity member has a first portion in the longitudinal direction between the protruding portion and the position closest to the protruding portion of the temperature detection member, and the area of a cross section perpendicular to the longitudinal direction is smaller than the area of the portion where the area of the high thermal conductivity member is the largest, and the heating device is characterized by this. <2> The base material has a shorter length on one side than on the other side with respect to the central position of the main heating region, and is the heating device according to <1>. <3> The first part is the heating device according to <1> or <2>, which extends to the outside on one side of the longitudinal direction from the main heat generation region. <4> The first part is the heating device according to any one of <1> to <3>, in which the width in the short-side direction, which is the direction orthogonal to the longitudinal direction, is smaller than the portion where the width of the high heat conduction member is the largest. <5> The high heat conduction member has a detection part insertion hole into which the temperature detection member is inserted. The heating device according to any one of <1> to <4>, in which the detection part insertion hole is extended to one side in the longitudinal direction from the portion where the temperature detection member is inserted, and the extended portion of the detection part insertion hole in the longitudinal direction is taken as the first part. <6> The heating device according to any one of <1> to <5>, in which the high heat conduction member is formed of any one of aluminum alloy, steel, and graphite. <7> The high heat conduction member is formed of a plate material. The protruding part is a bent part formed by bending one end side in the longitudinal direction of the high heat conduction member, and the heating device according to any one of <1> to <6>. <8> The bent part is formed by two-stage bending. The heating device according to <7>, in which the bent part of the high heat conduction member is inserted into a holding hole provided in the holding member, and the end of the bent part is locked to the holding member in the thickness direction of the base material. <9> The temperature detection member has a temperature detection part. The heating device according to any one of <1> to <8>, in which the temperature detection part is provided in the maximum passing region, which is the passing region of the recording medium having the maximum width corresponding to the heating device in the longitudinal direction. <10> The temperature detection member has a temperature detection part. When the passing region of the recording medium having the maximum width corresponding to the heating device in the longitudinal direction is taken as the maximum passing region, The heating device according to any one of <1> to <9>, wherein the temperature detection unit is provided inside the main heat generation region and outside the maximum passage region. <11> The heating device according to any one of <1> to <10>, wherein the insulation distance is 2.5 mm or more. <12> A rotating member, A heating body having a base material and a heating element, wherein at least the heating element is provided inside the rotating member, A holding member for holding the heating body, A high thermal conductivity member extending in the longitudinal direction of the rotating member and having a higher thermal conductivity than the base material, A temperature detection member provided on one side of a main heat generation region which is a region in the longitudinal direction where the heating element is provided inside the rotating member, the heating device comprising: The high thermal conductivity member and the temperature detection member are arranged to overlap in the thickness direction of the base material, When the central side of the main heat generation region is the inner side in the longitudinal direction and one or the other end side in the longitudinal direction of the main heat generation region with respect to the central side of the main heat generation region is the outer side in the longitudinal direction, The high thermal conductivity member is provided outside one side in the longitudinal direction of the temperature detection member, and has a protruding portion protruding toward the temperature detection member side in the thickness direction of the base material more than other portions of the high thermal conductivity member, A predetermined insulation distance in the longitudinal direction is provided between the protruding portion and the temperature detection member, The high thermal conductivity member has a first portion in the longitudinal direction between the protruding portion and the position closest to the protruding portion of the temperature detection member, the width in the short side direction which is the direction orthogonal to the longitudinal direction being smaller than the maximum width in the short side direction of the high thermal conductivity member. The heating device is characterized by this. <13> A fixing device that heats a recording medium using the heating device according to any one of <1> to <12> and fixes an image on the recording medium to the recording medium. <14> An image forming apparatus including the fixing device according to <13>.

Explanation of Signs

[0098] 1 Image forming apparatus 9 Fixing device (heating device) 20 Fixing belt (rotating member) 21 Pressing roller (pressing member) 22 Heater (heating element) 23 Heater holder (holding member) 23c Soaking plate holding hole (holding hole) 25 Thermistor (temperature detecting member) 251 Heat-sensitive element (temperature detecting part) 28 Soaking plate (high heat-conducting member) 28a Bending part (projecting part) 28b Arm part (first part) 28c Detection part insertion hole 30 Base material 31 Resistance heating element (heating element) D Main heating region of heater (main heating region of heating element) D1 Central position of main heating region E Maximum paper feed region (maximum passing region of recording medium) H1 Insulation distance P Paper (recording medium) X Longitudinal direction of fixing belt (longitudinal direction of rotating member) Z Thickness direction of base material

Prior art documents

Patent documents

[0099]

Patent Document 1

Claims

1. A rotating member, A heating member having a base material and a heating element, wherein at least the heating element is provided inside the rotating member, A holding member for holding the heating member, A high thermal conductivity member extending in the longitudinal direction of the rotating member and having a higher thermal conductivity than the base material, A heating device including a temperature detection member provided on one side of a main heating region which is a region in the longitudinal direction where the heating element is provided inside the rotating member, wherein The high thermal conductivity member and the temperature detection member are arranged to overlap in the thickness direction of the base material, When the central side of the main heating region is the inner side in the longitudinal direction and one end side or the other end side in the longitudinal direction of the main heating region with respect to the central side of the main heating region is the outer side in the longitudinal direction, The high thermal conductivity member is provided on the outer side of one side in the longitudinal direction with respect to the temperature detection member, and has a protruding portion protruding toward the temperature detection member side in the thickness direction of the base material more than other portions of the high thermal conductivity member, A predetermined insulation distance in the longitudinal direction is provided between the protruding portion and the temperature detection member, The high thermal conductivity member has a first portion between the protruding portion in the longitudinal direction and the position closest to the protruding portion of the temperature detection member, and the area of a cross section orthogonal to the longitudinal direction is smaller than the area of the portion where the area of the high thermal conductivity member is the largest. The heating device is characterized by this.

2. The heating device according to claim 1, wherein the length of one side of the base material is shorter than that of the other side with respect to one side and the other side with respect to the central position of the main heating region.

3. The heating device according to claim 1, wherein the first portion extends to the outer side of one side in the longitudinal direction with respect to the main heating region.

4. The heating device according to claim 1, wherein the width of the first portion in the short side direction, which is the direction orthogonal to the longitudinal direction, is smaller than the width of the portion where the width of the high thermal conductivity member is the largest.

5. The high thermal conductivity member has a detection part insertion hole into which the temperature detection member is inserted. The heating device according to claim 1, wherein the detection part insertion hole extends to one side in the longitudinal direction from a part where the temperature detection member is inserted, and a part of the detection part insertion hole extended in the longitudinal direction is defined as the first part. **Claim 6** The heating device according to claim 1, wherein the high thermal conductivity member is formed of any one of an aluminum alloy, steel, and graphite. **Claim 7** The high thermal conductivity member is formed of a plate material. The heating device according to claim 1, wherein the protruding part is a bent part formed by bending one end side in the longitudinal direction of the high thermal conductivity member. **Claim 8** The bent part is formed by two-stage bending. The heating device according to claim 7, wherein the bent part of the high thermal conductivity member is inserted into a holding hole provided in the holding member, and an end of the bent part is locked in the thickness direction of the base material with respect to the holding member. **Claim 9** The temperature detection member has a temperature detection part. The heating device according to claim 1, wherein the temperature detection part is provided in a maximum passing area which is a passing area of a recording medium having a maximum width corresponding to the heating device in the longitudinal direction. **Claim 10** The temperature detection member has a temperature detection part. When a passing area of a recording medium having a maximum width corresponding to the heating device in the longitudinal direction is defined as a maximum passing area, The heating device according to claim 1, wherein the temperature detection part is provided inside the maximum passing area and within the main heat generation area. **Claim 11** The heating device according to claim 1, wherein the insulation distance is 2.5 mm or more. **Claim 12** A rotating member, A heating body having a base material and a heating element, wherein at least the heating element is provided inside the rotating member. A holding member that holds the heating element, A high thermal conductivity member that extends in the longitudinal direction of the rotating member and has a higher thermal conductivity than the base material, A heating device including a temperature detection member provided on one side of a main heating region, which is a region in the longitudinal direction where the heating element is provided, inside the rotating member, The high thermal conductivity member and the temperature detection member are arranged to overlap in the thickness direction of the base material, When the central side of the main heating region is the inner side in the longitudinal direction and one or the other end side in the longitudinal direction of the main heating region with respect to the central side of the main heating region is the outer side in the longitudinal direction, The high thermal conductivity member is provided on the outer side of one side in the longitudinal direction with respect to the temperature detection member, and has a protruding portion that protrudes toward the temperature detection member side in the thickness direction of the base material more than other portions of the high thermal conductivity member, A predetermined insulation distance in the longitudinal direction is provided between the protruding portion and the temperature detection member, The high thermal conductivity member has a first portion in the longitudinal direction between the protruding portion and the position closest to the protruding portion of the temperature detection member, and the width in the short hand direction, which is a direction orthogonal to the longitudinal direction, is smaller than the maximum width in the short hand direction of the high thermal conductivity member. The heating device is characterized by this.

13. A fixing device that heats a recording medium using the heating device according to any one of Claims 1 to 12 and fixes an image on the recording medium to the recording medium.

14. An image forming apparatus including the fixing device according to Claim 13.

Images