Heating device, fixing device, image forming apparatus

Abstract

To prevent temperature unevenness of a rotary member in the arrangement direction of a plurality of resistance heating elements.SOLUTION: A fixing device 9 comprises: a fixing belt 20; a plane heater 22 that has a substrate 30 and a plurality of resistance heating elements 31; a heater holder 23 that holds the heater 22; and a first high thermal conduction member 28 that has a higher thermal conductivity than that of the substrate 30. The resistance heating elements 31 are divided into plurality and arranged on the substrate 30, and the first high thermal conduction member 28 is provided between the heater holder 23 and the heater 22 in the arrangement direction X of the plurality of resistance heating elements 31 at a position corresponding to division areas B of the resistance heating elements 31.SELECTED DRAWING: Figure 2

Description

[Technical Field]

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

[0002] The fixing device is provided with a planar heater having a resistance heating element on a substrate as a heating member for heating the fixing belt, which is a rotating member. In such a fixing device, it is important to make the temperature of the fixing belt uniform in its longitudinal direction (the direction in which the multiple resistance heating elements are arranged) and to heat the toner on the recording medium uniformly.

[0003] For example, in Patent Document 1 (JP 2019-164328 A), a resistive heating element is provided on a substrate, with multiple segments. The resistive heating element has a PTC characteristic. In this fixing device, when a small-sized recording medium is passed through and the temperature of the resistive heating element corresponding to the non-paper passing area rises, the resistance of the resistive heating element increases due to the PTC characteristic, and the amount of heat generated by this resistive heating element is suppressed. Therefore, the amount of heat generated by the heater in the non-paper passing area is suppressed, preventing excessive temperature rise in the non-paper passing area of ​​the fixing belt.

[0004] However, in this configuration where the resistance heating element is divided into multiple parts, the amount of heat generated by the heating element in the divided areas, which are the spaces between the resistance heating elements, is smaller than in other areas, which causes the temperature of the rotating element to be lower in these areas, resulting in uneven temperature distribution of the fixing belt. Summary of the Invention [Problem to be solved by the invention]

[0005] The object is to suppress temperature unevenness in the direction in which a plurality of resistance heating elements are arranged on a rotating member. [Means for solving the problem]

[0006] In order to solve the above problems, the present invention provides a heating device including a rotating member, a planar heating member having a base material and a plurality of resistance heating elements, a holding member for holding the heating member, and a first high thermal conductive member having a thermal conductivity higher than that of the base material, wherein the plurality of resistance heating elements are disposed on the base material. , in the longitudinal direction of the heating element The first high thermal conductivity member is disposed between the holding member and the heating member, and at least a part of the first high thermal conductivity member overlaps with the spacing between the resistance heating elements in the arrangement direction of the plurality of resistance heating elements. and a second high thermal conductivity member having a higher thermal conductivity than the base material is provided between the holding member and the first high thermal conductivity member, and a plurality of the second high thermal conductivity members are provided in the arrangement direction of the plurality of resistance heating elements, and each of the second high thermal conductivity members is provided at a position overlapping with the intervals between the resistance heating elements in the arrangement direction of the plurality of resistance heating elements. It is characterized by: [Effects of the Invention]

[0007] According to the heating device of the present invention, it is possible to suppress temperature unevenness in the direction in which the plurality of resistance heating elements are arranged on the rotating member. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 1 is a schematic diagram illustrating the configuration of an image forming apparatus. [Figure 2] 1 is a side cross-sectional view showing a schematic configuration of a fixing device according to an embodiment of the present invention. [Figure 3] FIG. [Figure 4] FIG. 10 is a diagram illustrating power supply to a heater. [Figure 5] FIG. 4 is a plan view of a heater having a different resistive heating element shape from that of FIG. 3. [Figure 6] FIG. 6 is a plan view of a heater having a resistance heating element with a different shape from those in FIGS. 3 and 5. [Figure 7] 1A and 1B are diagrams showing the temperature distribution in the arrangement direction of the fixing belt, in which FIG. 1A is a plan view of the heater, and FIG. 1B is a diagram showing the temperature distribution of the fixing belt. [Figure 8] FIG. 6 is a diagram showing divided regions of the heater in FIG. 5. [Figure 9] FIG. 9 is a diagram showing divided regions having a different shape from that in FIG. 8. [Figure 10] FIG. 7 is a diagram showing divided regions of the heater in FIG. 6. [Figure 11] FIG. 2 is a perspective view of a heater, a first high thermal conductive member, and a heater holder. [Figure 12] FIG. 2 is a plan view of the heater showing the arrangement of the first high thermal conductivity members. [Figure 13] 3 is a side cross-sectional view showing a schematic configuration of a fixing device according to an embodiment different from that shown in FIG. 2. [Figure 14] 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 15] FIG. 3 is a plan view of the heater showing the arrangement of the first and second high thermal conductive members. [Figure 16] 16 is a plan view showing a heater in which the arrangement of the second high thermal conductive members is different from that in FIG. 15. FIG. [Figure 17] 14 is a side cross-sectional view showing a schematic configuration of a fixing device according to an embodiment different from that shown in FIGS. 2 and 13. FIG. [Figure 18] FIG. 2 is a side cross-sectional view showing a schematic configuration of a fixing device different from the above. [Figure 19] FIG. 2 is a side cross-sectional view showing a schematic configuration of a fixing device different from the above. [Figure 20] FIG. 2 is a side cross-sectional view showing a schematic configuration of a fixing device different from the above. [Figure 21] FIG. 2 is a schematic diagram illustrating the configuration of an image forming apparatus different from that in FIG. [Figure 22] 1 is a side cross-sectional view showing a schematic configuration of a fixing device according to an embodiment of the present invention. [Figure 23] FIG. 23 is a plan view of a heater in the fixing device of FIG. 22. [Figure 24] FIG. 2 is a perspective view of a heater and a heater holder. [Figure 25] FIG. 4 is a perspective view showing a state in which a connector is attached to a heater. [Figure 26] FIG. 2 is a diagram showing the arrangement of a thermistor and a thermostat. [Figure 27] FIG. 10 is a view showing a groove portion of a flange. [Figure 28] 10A and 10B are plan views of a heater showing different examples of the arrangement of first high thermal conductivity members. [Figure 29] FIG. 10 is a plan view of a heater showing yet another example of the arrangement of first high thermal conductivity members. [Figure 30]3A to 3C are plan views of a heater showing examples of different arrangements of the first and second high thermal conductive members. [Figure 31] FIG. 1 illustrates the atomic crystal structure of graphene. [Figure 32] FIG. 1 illustrates the atomic crystal structure of graphite. DETAILED DESCRIPTION OF THE INVENTION

[0009] The present invention will be described below with reference to the accompanying drawings. In each drawing for explaining the present invention, components such as members and components having the same function or shape are designated by the same reference numerals as far as they can be distinguished, and descriptions thereof will be omitted once they have been described.

[0010] FIG. 1 is a schematic diagram of an image forming apparatus according to an embodiment of the present invention.

[0011] 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 different color developer: yellow, magenta, cyan, or black. These color developers correspond to the color separation components of a color image. Each imaging unit 1Y, 1M, 1C, and 1Bk includes a drum-shaped photoconductor 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 photoconductor 2. The developing device 4 supplies toner as a developer to the surface of the photoconductor 2 to form a toner image. The cleaning device 5 cleans the surface of the photoconductor 2.

[0012] The image forming apparatus 100 also includes an exposure device 6, a paper feed device 7, a transfer device 8, a fixing device 9 as a heating device, and a paper discharge device 10. The exposure device 6 exposes the surface of each photoconductor 2 to light and forms an electrostatic latent image on that surface. The paper feed device 7 supplies paper P as a recording medium to a paper transport path 14. The transfer device 8 transfers the toner image formed on each photoconductor 2 to the paper P. The fixing device 9 fixes the toner image transferred to the paper P to the surface of the paper P. The paper discharge device 10 discharges the paper P outside the apparatus. The imaging units 1, photoconductors 2, charging devices 3, exposure device 6, transfer device 8, etc. constitute image forming means for forming an image on paper.

[0013] The transfer device 8 has an endless intermediate transfer belt 11 as an intermediate transfer body, 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 multiple rollers. The primary transfer rollers 12 transfer the toner images on the photoconductors 2 to the intermediate transfer belt 11. The secondary transfer rollers 13 transfer the toner images transferred onto the intermediate transfer belt 11 to paper P. Each of the multiple primary transfer rollers 12 contacts the photoconductors 2 via the intermediate transfer belt 11. This brings the intermediate transfer belt 11 and each photoconductor 2 into contact with each other, forming a primary transfer nip between them. Meanwhile, the secondary transfer roller 13 contacts one of the rollers stretching the intermediate transfer belt 11 via the intermediate transfer belt 11. This forms a secondary transfer nip between the secondary transfer roller 13 and the intermediate transfer belt 11.

[0014] Further, a pair of timing rollers 15 is provided in the paper transport path 14 between the paper feeder 7 and the secondary transfer nip (secondary transfer roller 13).

[0015] Next, the printing operation of the image forming apparatus will be described with reference to FIG.

[0016] When a command to start a printing operation is issued, in each of the imaging units 1Y, 1M, 1C, and 1Bk, the photoconductor 2 is rotated clockwise in FIG. 1, and the charging device 3 charges the surface of the photoconductor 2 to a uniform high potential. Next, the exposure device 6 exposes the surface of each photoconductor 2 based on the image information of the original document read by the document reading device or the print information instructed to be printed from the terminal. This reduces the potential of the exposed area, forming an electrostatic latent image. Toner is then supplied from the developing device 4 to this electrostatic latent image, and a toner image is formed on each photoconductor 2.

[0017] The toner images formed on each photoconductor 2 rotate with the rotation of the photoconductor 2 and reach the primary transfer nip (the position of the primary transfer roller 12). The toner images are then transferred to the intermediate transfer belt 11, which rotates counterclockwise in FIG. 1, so that they overlap one another. The toner images transferred onto the intermediate transfer belt 11 are then transported to the secondary transfer nip (the position of the secondary transfer roller 13) with the rotation of the intermediate transfer belt 11. The toner images are then transferred to the paper P transported at the secondary transfer nip. This paper P is supplied from the paper feeder 7. The paper P supplied from the paper feeder 7 is temporarily stopped by timing roller 15 and then transported to the secondary transfer nip in time with the toner image on the intermediate transfer belt 11 reaching the secondary transfer nip. In this way, a full-color toner image is carried on the paper P. After the toner image is transferred, any toner remaining on each photoconductor 2 is removed by the cleaning devices 5.

[0018] 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. The paper P is then discharged outside the apparatus by a paper discharge device 10, completing the series of printing operations.

[0019] Next, the configuration of the fixing device will be described.

[0020] As shown in FIG. 2 , the fixing device 9 according to this embodiment includes a fixing belt 20 as a rotating or fixing member, a pressure roller 21 as a counter rotating or pressure member, a heater 22 as a heating member, a heater holder 23 as a holding member, a stay 24 as a support member, a thermistor 25 as a temperature detection member, and a first high thermal conductivity member 28. The fixing belt 20 is an endless belt. The pressure roller 21 contacts the outer surface of the fixing belt 20 and forms a fixing nip N between the fixing belt 20 and the pressure roller 21. 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 detects the temperature of the first high thermal conductivity member 28. The direction perpendicular to the plane of the paper in FIG. 2 is the longitudinal direction of the fixing belt 20, the pressure roller 21, the heater 22, the heater holder 23, the stay 24, the first high thermal conductivity member 28, etc., and hereinafter, this direction will be referred to simply as the longitudinal direction. This longitudinal direction also corresponds to the width direction of the paper being transported, the width direction of the fixing belt 20, and the axial direction of the pressure roller 21.

[0021] The fixing belt 20 has a cylindrical substrate made of polyimide (PI) with an outer diameter of 25 mm and a thickness of 40 to 120 μm. A release layer made of a fluorine-based resin 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 to enhance durability and ensure releasability. A 50 to 500 μm elastic layer made of rubber or the like 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 a sliding layer made of polyimide, PTFE, or the like.

[0022] 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. To improve release properties, it is desirable to form the release layer 21c, which is made of a fluororesin layer with a thickness of, for example, about 40 μm, on the surface of the elastic layer 21b.

[0023] 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 fixing nip N between the fixing belt 20 and the pressure roller 21. The pressure roller 21 is also 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.

[0024] 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 substrate 30, a resistance heating element 31 provided on the substrate 30, an insulating layer 32 covering the resistance heating element 31, and the like. The insulating layer 32 side of the heater 22 is in contact with the inner circumferential surface of the fixing belt 20, 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 (the fixing nip N side) of the substrate 30. However, the resistance heating element 31 and the insulating layer 32 may be provided on the heater holder 23 side of the substrate 30. In this case, the heat from the resistance heating element 31 is transferred to the fixing belt 20 via the substrate 30, so the substrate 30 is preferably made of a material with high thermal conductivity, such as aluminum nitride. Furthermore, by forming the base material 30 from a material with high thermal conductivity, it is possible to heat the fixing belt 20 sufficiently even if the resistance heating element 31 is placed on the opposite side of the base material 30 from the fixing belt 20 side.

[0025] 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. By supporting the heater holder 23 and the heater 22 by the stay 24, the heater 22 can reliably receive the pressing force of the pressure roller 21 while the pressure roller 21 is pressed against the fixing belt 20. This ensures that the fixing nip N is stably formed between the fixing belt 20 and the pressure roller 21. In this embodiment, the thermal conductivity of the heater holder 23 is set to be smaller than that of the base material 30.

[0026] Note that the stay 24 supporting the heater holder 23 means that the stay 24, which has a portion extending in the pressure direction of the pressure roller 21 (the left-right direction in the figure) or a portion with a thickness, abuts against the heater holder 23 from the side opposite the pressure roller 21 (the left side in the figure). This makes it possible to suppress deflection of the heater holder 23 due to the pressure from the pressure roller 21 (particularly deflection in the longitudinal direction in this embodiment). However, the above-mentioned abutment does not necessarily mean that the stay 24 abuts against the heater holder 23 directly, but also includes a case where the stay 24 abuts against the heater holder 23 via another member. "Abutment via another member" refers to a state where another member is sandwiched between the stay 24 and the heater holder 23 in the left-right direction in the figure, and the stay 24 abuts against the other member at a position where at least a portion of the other member corresponds to the other member, and the other member abuts against the heater holder 23. Furthermore, the term "extending in the pressure direction" mentioned above does not necessarily mean the same direction as the pressure direction of the pressure roller 21, but also includes the case of extending in a direction at a certain angle from the pressure direction of the pressure roller 21. Even in these cases, it goes without saying that the stay 24 can suppress the deflection of the heater holder 23 against the pressure force from the pressure roller 21.

[0027] The heater holder 23 is desirably made of a heat-resistant material because it is prone to becoming hot due to the heat from the heater 22. For example, if the heater holder 23 is made of a heat-resistant resin with low thermal conductivity such as LCP, heat transfer from the heater 22 to the heater holder 23 is suppressed. This allows the heater 22 to heat the fixing belt 20 efficiently.

[0028] The heater holder 23 is also provided with guide portions 26 that guide the fixing belt 20. The guide portions 26 are provided on the upstream side (below the heater 22 in FIG. 2) and downstream side (above the heater 22 in FIG. 2) of the heater 22 in the belt rotation direction. The upstream and downstream guide portions 26 are arranged at intervals along the longitudinal direction of the heater 22. Each guide portion 26 is formed in a roughly fan shape and has a belt-facing surface 260 that is arc-shaped or convexly curved and extends in the belt circumferential direction so as to face the inner circumferential surface of the fixing belt 20.

[0029] Heater holder 23 has a plurality of openings 23a in the longitudinal direction. Openings 23a are openings that penetrate heater holder 23 in the thickness direction. Thermistor 25 and a thermostat, which will be described later, are provided in these openings 23a. These thermistors 25 and thermostats are pressed against the back surface of first high thermal conductivity member 28 by spring 29. However, openings may also be similarly provided in first high thermal conductivity member 28 (and second high thermal conductivity member, which will be described later), so that thermistor 25 and thermostat are pressed against the back surface of base material 30.

[0030] The first high thermal conductivity member 28 is made of a material having a higher thermal conductivity than the base material. In this embodiment, the first high thermal conductivity member 28 is made of plate-shaped aluminum. Alternatively, the first high thermal conductivity member 28 may be made of, for example, copper, silver, graphene, or graphite. By making the first high thermal conductivity member 28 plate-shaped, the positional accuracy of the heater 22 with respect to the heater holder 23 and the first high thermal conductivity member 28 can be improved.

[0031] Next, a method for calculating the thermal conductivity will be described. When calculating the thermal conductivity, first, the thermal diffusivity of the object is measured, and then the thermal conductivity is calculated using the measured thermal diffusivity.

[0032] The thermal diffusivity was measured using a thermal diffusivity / thermal conductivity measuring device (trade name: ai-Phase Mobile 1u, ai-Phase Corporation).

[0033] To convert the thermal diffusivity to thermal conductivity, the density and specific heat capacity values ​​are required. A dry-type automatic densitometer (product name: Accupyc 1330, manufactured by Shimadzu Corporation) was used to measure the density. A differential scanning calorimeter (product name: DSC-60, manufactured by Shimadzu Corporation) was used to measure the specific heat capacity, using sapphire as a reference material with a known specific heat capacity. In this example, the specific heat capacity was measured five times, and the average value at 50°C was used. When the density and specific heat capacity are ρ and C, respectively, the thermal conductivity λ can be calculated from the thermal diffusivity α obtained from the thermal diffusivity measurement using the following equation (1):

[0034]

number

[0035] In the fixing device 9 according to this embodiment, when a printing operation is started, the pressure roller 21 is driven to rotate, and the fixing belt 20 starts to rotate driven by the pressure roller 21. 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, thereby allowing the fixing belt 20 to rotate stably and smoothly. Furthermore, power is supplied to the resistance heating element 31 of the heater 22, thereby heating the fixing belt 20. Then, when the temperature of the fixing belt 20 reaches a predetermined target temperature (fixing temperature), as shown in FIG. 2 , a sheet of paper P carrying an unfixed toner image is transported between the fixing belt 20 and the pressure roller 21 (fixing nip N), whereby the unfixed toner image is heated and pressurized to be fixed to the sheet of paper P. The fixing belt 20 is a heated member that is heated by the heater 22.

[0036] FIG. 3 is a plan view of the heater according to this embodiment.

[0037] 3, a plurality of (four) resistance heating elements 31, power supply lines 33A and 33B as conductors, a first electrode portion 34A, and a second electrode portion 34B are provided on the surface of a plate-shaped substrate 30. However, the number of resistance heating elements 31 is not limited to that in this embodiment.

[0038] In this embodiment, the longitudinal direction of the heater 22, etc. (the direction perpendicular to the plane of the paper in FIG. 2) is also the arrangement direction X of the multiple resistance heating elements 31, as shown in FIG. 3. Hereinafter, this direction will also be simply referred to as the arrangement direction. Furthermore, the up-down direction Y in FIG. 3, which is a direction intersecting the arrangement direction (a direction perpendicular to the plane of the paper in this embodiment) and different from the thickness direction of the base material 30, will also be referred to as the direction intersecting the arrangement direction of the multiple resistance heating elements 31, or simply as the intersecting arrangement direction. The intersecting arrangement direction Y is the direction along the surface of the base material 30 on which the resistance heating elements 31 are provided, and is also the widthwise direction of the heater 22 or the transport direction of paper passed through the fixing device 9.

[0039] The plurality of resistance heating elements 31 constitute a heating section 35 divided into a plurality of sections in the arrangement direction. Each resistance heating element 31 is electrically connected in parallel to a pair of electrode portions 34A, 34B provided at one end of the substrate 30 in the arrangement direction (the left end in FIG. 3 ) via power supply lines 33A, 33B. The power supply lines 33A, 33B are made of a conductor having a lower resistance value than the resistance heating elements 31. To ensure insulation between the resistance heating elements 31, the gap between adjacent resistance heating elements 31 is preferably 0.2 mm or more, more preferably 0.4 mm or more. Furthermore, if the gap between adjacent resistance heating elements 31 is too large, a temperature drop is likely to occur in the gap. Therefore, to suppress temperature unevenness across the arrangement direction, the gap is preferably 5 mm or less, more preferably 1 mm or less.

[0040] 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.

[0041] The PTC characteristics of the resistance heating element 31 and the divided heating section 35 configuration in the arrangement direction prevent excessive temperature rise of the fixing belt 20 when small-size paper is passed through. In other words, when paper narrower than the overall width of the heating section 35 is passed through, the paper does not absorb heat from the fixing belt 20 in the area outside the paper width, so the temperature of the resistance heating element 31 corresponding to that area rises. Because the voltage applied to the resistance heating element 31 is constant, the temperature of the resistance heating element 31 outside the paper width rises, and when its resistance value increases, the output (heat generation amount) decreases relatively, suppressing the temperature rise at the edge. Furthermore, by electrically connecting multiple resistance heating elements 31 in parallel, it is possible to suppress the temperature rise in non-paper passing areas while maintaining printing speed. The heating elements constituting the heating section 35 may be other than resistance heating elements having PTC characteristics. Furthermore, the resistance heating elements may be arranged in multiple rows in the direction crossing the arrangement of the heaters 22.

[0042] 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 80 Ω at room temperature. In addition to the materials mentioned above, the resistance heating element 31 may also be made of resistance materials such as silver alloy (AgPt) or 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. The power supply line 33 is made of a conductor with a lower resistance value than the resistance heating element 31.

[0043] The substrate 30 is preferably made of ceramics such as alumina or aluminum nitride, which have excellent heat resistance and insulation properties, or non-metallic materials such as glass or mica. In this embodiment, an alumina substrate is used, which is 8 mm wide in the cross-array direction, 270 mm wide in the array direction, and 1.0 mm thick. Alternatively, the substrate 30 may be made of a conductive material such as a metal laminated with an insulating material. Aluminum and stainless steel are preferred metal materials for the substrate 30, as they are low-cost. By constructing the substrate 30 from a stainless steel plate, cracks due to thermal stress can be suppressed. Furthermore, to improve the thermal uniformity of the heater 22 and enhance image quality, the substrate 30 may be made of a highly thermally conductive material such as copper, graphite, or graphene.

[0044] 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, insulating and protecting them and maintaining sliding properties with the fixing belt 20.

[0045] FIG. 4 is a diagram showing a power supply circuit to the heater according to this embodiment.

[0046] 4, 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 200 and the electrodes 34A, 34B of the heater 22. The power supply circuit is also provided with a triac 210 that controls the amount of power supplied. The amount of power supplied to each resistance heating element 31 is controlled by a control unit 220 via the triac 210 based on the temperature detected by the thermistor 25. The control unit 220 is configured by a microcomputer including a CPU, ROM, RAM, I / O interface, etc.

[0047] In this embodiment, thermistors 25 are disposed in a central region in the arrangement direction of heaters 22, which is within the minimum paper passing width, and at one end side in the arrangement direction of heaters 22. Furthermore, at one end side in the arrangement direction of heaters 22, a thermostat 27 is disposed as a power cut-off device that cuts off the supply of power to resistance heating elements 31 when the temperature of resistance heating elements 31 reaches or exceeds a predetermined temperature. Thermistors 25 and thermostat 27 contact first high thermal conductivity member 28 to detect its temperature.

[0048] 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. The shape of the resistance heating element 31 is not limited to that of this embodiment. For example, as shown in FIG. 5, the resistance heating element 31 may be rectangular. Alternatively, as shown in FIG. 6, the resistance heating element 31 may be formed of a linear portion that is folded back to form a substantially parallelogram shape. As shown in FIG. 5, the portion extending from the block-shaped portion of the resistance heating element 31 toward the power supply line 33 (the portion extending in the intersecting direction) may be part of the resistance heating element 31, or may be made of the same material as the power supply line 33.

[0049] 7A and 7B are diagrams showing the temperature distribution in the arrangement direction of the fixing belt 20. (a) shows the arrangement of the heaters 22. (b) shows the temperature T of the fixing belt 20 on the vertical axis, and the horizontal axis shows each position in the arrangement direction of the fixing belt 20.

[0050] As shown in FIGS. 7(a) and 7(b), the heater 22 has a plurality of resistance heating elements 31 divided in the arrangement direction, forming divided regions B between the resistance heating elements 31. In other words, the heater 22 has a plurality of resistance heating elements 31 arranged at intervals B. Hereinafter, the range B of the divided region will be referred to as interval B. In interval B, the area occupied by the resistance heating elements 31 is smaller than in other regions, resulting in a smaller amount of heat generation. As a result, the temperature of the fixing belt 20 in interval B is lower than in other regions, causing temperature unevenness in the arrangement direction of the fixing belt 20. Furthermore, in an expanded divided region C (hereinafter simply referred to as region C) including the region surrounding interval B, which is a divided region, the temperatures of the heater 22 and the fixing belt 20 are also lower. Note that the temperature of the heater 22 is also lower in interval B. Hereinafter, as shown in the enlarged view of FIG. 7(a), interval B refers to the arrangement direction region including all of the regions into which the resistance heating elements 31, which are the main heat-generating portions of the heater 22, are divided in the arrangement direction. Furthermore, an area including the interval B and a range corresponding to the connection portion 311 of the resistance heating element 31 is defined as an area C. The connection portion 311 refers to the portion of the resistance heating element 31 that extends in the cross-arrangement direction and is connected to each of the power supply lines 33A and 33B.

[0051] As shown in Fig. 8, the temperature in the interval B is lower than that in other parts in the heater 22 having the rectangular resistance heating element 31 shown in Fig. 5. Also, the temperature in the interval B is lower than that in other parts in the heater 22 having the resistance heating element 31 shaped as shown in Fig. 9. Furthermore, as shown in Fig. 10, the temperature in the interval B is lower than that in other parts in the heater 22 having the resistance heating element 31 shaped as shown in Fig. 6. However, by overlapping adjacent resistance heating elements 31 in the arrangement direction as shown in Figs. 7, 9 and 10, the temperature drop in the interval B relative to other parts can be suppressed.

[0052] In this embodiment, the above-described first high thermal conductivity member 28 is provided to suppress the temperature drop in the above-mentioned interval and to suppress temperature unevenness in the arrangement direction of the fixing belt 20. The first high thermal conductivity member 28 will be described in more detail below.

[0053] 2, first high thermal conductivity member 28 is disposed between heater 22 and stay 24 in the left-right direction of FIG. 2, and is particularly sandwiched between heater 22 and heater holder 23. That is, first high thermal conductivity member 28 has one surface abutting against the back surface of base material 30 and the other surface abutting against heater holder 23.

[0054] The stay 24 supports the heater holder 23, the first high thermal conductive member 28, and the heater 22 by bringing contact surfaces 24a1 of two vertical portions 24a, which extend in the thickness direction of the heater 22 and other components, into contact with the heater holder 23. In the cross-array direction (the vertical direction in FIG. 2), the contact surfaces 24a1 are provided outside the range in which the resistance heating elements 31 are provided. This makes it possible to suppress heat transfer from the heater 22 to the stay 24, and allows the heater 22 to heat the fixing belt 20 efficiently.

[0055] As shown in Fig. 11, first high thermal conductivity member 28 is made of a plate material having a thickness of 0.3 mm, a length in the arrangement direction of 222 mm, and a width in the direction crossing the arrangement of 10 mm. In this embodiment, first high thermal conductivity member 28 is made of a single plate material, but it may be made of multiple members. Note that illustration of guide portion 26 of Fig. 2 is omitted in Fig. 11.

[0056] The first high thermal conductive member 28 is fitted into the recess 23b of the heater holder 23, and the heater 22 is attached thereto, thereby sandwiching and holding the first high thermal conductive member 28 between the heater holder 23 and the heater 22. In this embodiment, the width of the first high thermal conductive member 28 in the arrangement direction is set to be substantially the same as the width of the heater 22 in the arrangement direction. Movement of the first high thermal conductive member 28 and the heater 22 in the arrangement direction is restricted by both side walls (arrangement direction restricting portions) 23b1 in the arrangement direction that form the recess 23b. In this manner, restricting misalignment of the first high thermal conductive member 28 in the arrangement direction within the fixing device 9 improves heat conduction efficiency within a target range in the arrangement direction. Movement of the first high thermal conductive member 28 and the heater 22 in the arrangement direction is restricted by both side walls (arrangement cross direction restricting portions) 23b2 in the arrangement cross direction that form the recess 23b.

[0057] The range in the arrangement direction in which the first high thermal conductivity members 28 are provided is not limited to the above. For example, as shown in FIG. 12, the first high thermal conductivity members 28 may be provided only in the range corresponding to the heat generating portions 35 in the arrangement direction (see the hatched area in FIG. 12). Alternatively, as shown in FIG. 28, the first high thermal conductivity members 28 may be provided only in the entire area at a position corresponding to the interval B in the arrangement direction. For convenience, FIG. 28 illustrates the resistance heating elements 31 and the first high thermal conductivity members 28 shifted vertically in FIG. 28, but they are actually disposed at approximately the same position in the cross-array direction. However, this is not a limitation. The first high thermal conductivity members 28 may be provided only in a portion of the resistance heating elements 31 in the cross-array direction, or may be provided so as to cover the entire cross-array direction as shown in FIG. 29 (described later). Furthermore, as shown in FIG. 29, the first high thermal conductivity members 28 may be provided in addition to the position corresponding to the interval B in the arrangement direction, straddling both resistance heating elements 31 on either side of the interval B. "Provided across the resistance heating elements 31 on both sides" here means that the first high thermal conductivity members 28 at least partially overlap with the resistance heating elements 31 on both sides in the arrangement direction. Note that the first high thermal conductivity members 28 may be provided to correspond to all of the intervals B of the heaters 22, or may be provided only at positions corresponding to some of the intervals B, such as by providing the first high thermal conductivity members 28 only at a position corresponding to one of the intervals B as shown in Figure 29. Here, "provided at a position corresponding to the interval B in the arrangement direction" means that the first high thermal conductivity members 28 at least partially overlap with the interval B in the arrangement direction.

[0058] Due to the pressure of the pressure roller 21, the first highly thermally conductive member 28 is sandwiched between the heaters 22 and the heater holder 23 and is in close contact with these members. The contact of the first highly thermally conductive member 28 with the heaters 22 improves the thermal conduction efficiency in the arrangement direction of the heaters 22. Furthermore, by providing the first highly thermally conductive member 28 at a position corresponding to the spacing B between the heaters 22 in the arrangement direction, the thermal conduction efficiency at the spacing B can be improved, increasing the amount of heat transferred to the position at the spacing B in the arrangement direction and raising the temperature at the spacing B in the arrangement direction. This reduces temperature unevenness in the arrangement direction of the heaters 22. This reduces temperature unevenness in the arrangement direction of the fixing belt 20. This reduces uneven fixing and glossiness of the image fixed to the paper. Alternatively, there is no need for excessive heating by the heaters 22 to ensure sufficient fixing performance at the spacing, thereby achieving energy savings in the fixing device 9. Furthermore, by providing the first high thermal conductivity member 28 over the entire heat generating section 35 in the arrangement direction, the heat transfer efficiency of the heater 22 can be improved over the entire main heating area (i.e., the image forming area of ​​the paper being passed through), thereby suppressing temperature unevenness in the arrangement direction of the heater 22 and, ultimately, the fixing belt 20.

[0059] In particular, in this embodiment, the combination of the configuration of the first high thermal conductivity member 28 and the resistance heating element 31 having the PTC characteristic described above can effectively suppress excessive temperature rise in the non-paper passing area when small size paper is passed. In other words, the PTC characteristic suppresses the amount of heat generated by the resistance heating element 31 in the non-paper passing area, and the heat of the non-paper passing area with an increased temperature can be efficiently transferred to the paper passing area, effectively suppressing excessive temperature rise in the non-paper passing area.

[0060] Furthermore, it is preferable to arrange first high thermal conductivity members 28 around gap B, since the temperature there is also low due to the small amount of heat generated in gap B. For example, in this embodiment, by providing first high thermal conductivity members 28 at positions corresponding to region C (see FIG. 8), the heat transfer efficiency in the arrangement direction in gap B and its periphery is particularly improved, and temperature unevenness in the arrangement direction of heaters 22 can be further suppressed. Particularly in this embodiment, first high thermal conductivity members 28 are provided over the entire area of ​​heat-generating section 35 in the arrangement direction. This makes it possible to further suppress temperature unevenness in the arrangement direction of heaters 22 (fixing belt 20).

[0061] Next, a different embodiment of the fixing device will be described.

[0062] 13, fixing device 9 of this embodiment has second high thermal conductivity member 36 between heater holder 23 and first high thermal conductivity member 28. Second high thermal conductivity member 36 is provided at a different position from first high thermal conductivity member 28 in the stacking direction (left-right direction in FIG. 13) of members such as heater holder 23, stay 24, and first high thermal conductivity member 28. More specifically, second high thermal conductivity member 36 is provided overlapping first high thermal conductivity member 28. Note that, unlike FIG. 2, FIG. 13 shows a cross section in which second high thermal conductivity member 36 is arranged in the arrangement direction and thermistor 25 is not arranged.

[0063] The second high thermal conductivity member 36 is made of a material having a higher thermal conductivity than the base material 30, such as graphene or graphite. In this embodiment, the second high thermal conductivity member 36 is formed of a graphite sheet having a thickness of 1 mm. However, the second high thermal conductivity member 36 may also be formed of a plate material such as aluminum, copper, or silver.

[0064] As shown in Fig. 14, a plurality of second high thermal conductive members 36 are arranged in the arrangement direction, each of which is partially provided in the arrangement direction. The portion of recess 23b of heater holder 23 where second high thermal conductive members 36 are provided is one level deeper than the remaining portion. A gap is provided between second high thermal conductive members 36 and heater holder 23 on both sides in the arrangement direction. This suppresses heat transfer from second high thermal conductive members 36 to heater holder 23, allowing heater 22 to efficiently heat fixing belt 20. Note that illustration of guide portion 26 of Fig. 2 is omitted in Fig. 14.

[0065] 15, second high thermal conductivity members 36 (see hatched areas) are provided in positions corresponding to interval B in the arrangement direction so as to overlap at least a portion of adjacent resistance heating elements 31, and in this embodiment in particular, are provided over the entire area of ​​interval B. However, although FIG. 15 (and FIG. 16 described below) shows a case where first high thermal conductivity members 28 are provided only in areas corresponding to heat generating portions 35 in the arrangement direction, as mentioned above, this is not limited to this.

[0066] In this embodiment, in addition to the first high thermal conductivity members 28, second high thermal conductivity members 36 are provided at positions corresponding to the interval B in the arrangement direction, overlapping at least a portion of adjacent resistance heating elements 31. This particularly improves the heat transfer efficiency in the arrangement direction at the interval B, thereby further suppressing temperature unevenness in the arrangement direction of the heaters 22. Most preferably, as shown in FIG. 30 , the first high thermal conductivity members 28 and the second high thermal conductivity members 36 are provided only over the entire area of ​​the position corresponding to the interval B. This particularly improves the heat transfer efficiency in the position corresponding to the interval B compared to other areas. For convenience, FIG. 30 illustrates the resistance heating elements 31, the first high thermal conductivity members 28, and the second high thermal conductivity members 36 offset from one another in the vertical direction, but they are actually positioned at approximately the same position in the cross-array direction. However, this is not a limitation, and the first high thermal conductivity members 28 and the second high thermal conductivity members 36 may be provided only over a portion of the resistance heating elements 31 in the cross-array direction, or may be provided so as to cover the entire resistance heating elements 31 in the cross-array direction.

[0067] In one embodiment of the present invention different from the above, first high thermal conductivity member 28 and second high thermal conductivity member 36 are formed from the graphene sheet. This allows first high thermal conductivity member 28 and second high thermal conductivity member 36 to be formed with high thermal conductivity in a predetermined direction along the graphene surface, that is, in the arrangement direction rather than the thickness direction. This makes it possible to effectively suppress temperature unevenness in the arrangement direction of heater 22 and fixing belt 20.

[0068] Graphene is a flaky powder. As shown in Figure 31, graphene is made of a planar hexagonal lattice structure of carbon atoms. A graphene sheet is a sheet of graphene, and is usually a single layer. The single layer of carbon may contain impurities. Graphene may also 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, and examples thereof include C 60 , C 70 and C 80 Fullerenes or other closed cage structures with three-coordinated carbon atoms.

[0069] Graphene sheets are man-made and can be produced, for example, by chemical vapor deposition (CVD).

[0070] 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 later), may be measured using, for example, a transmission electron microscope (TEM).

[0071] Furthermore, graphite, which is a multilayered graphene, has a large thermal conductivity anisotropy. As shown in FIG. 32, graphite has a crystalline structure in which layers of fused six-membered rings of carbon atoms are laid out in a planar fashion, and these layers are stacked on top of each other. In this crystalline structure, adjacent carbon atoms within a layer form covalent bonds, while carbon atoms between layers form van der Waals bonds. Covalent bonds have a stronger bonding strength than van der Waals bonds, resulting in a large anisotropy between intralayer and interlayer bonds. In other words, by constructing the first high thermal conductivity member 28 or the second high thermal conductivity member 36 from graphite, the heat transfer efficiency in the arrangement direction of the first high thermal conductivity member 28 or the second high thermal conductivity member 36 is greater than in the thickness direction (i.e., the stacking direction of the members), thereby suppressing heat transfer to the heater holder 23. This effectively suppresses temperature unevenness in the arrangement direction of the heater 22 and minimizes heat leakage toward the heater holder 23. Furthermore, by making the first high thermal conductivity member 28 or the second high thermal conductivity member 36 out of graphite, the first high thermal conductivity member 28 or the second high thermal conductivity member 36 can have excellent heat resistance, preventing oxidation up to approximately 700 degrees.

[0072] The physical properties and dimensions of the graphite sheet can be changed as appropriate depending on the functions required of first high thermal conductivity member 28 or second high thermal conductivity member 36. For example, the anisotropy of thermal conduction can be increased by using high-purity graphite or single-crystal graphite, or by increasing the thickness of the graphite sheet. Furthermore, in order to increase the speed of fixing device 9, a thin graphite sheet may be used to reduce the heat capacity of fixing device 9. Furthermore, if the width of fixing nip N or heater 22 is large, the width of first high thermal conductivity member 28 or second high thermal conductivity member 36 in the arrangement direction may be increased accordingly.

[0073] From the viewpoint of increasing the mechanical strength, the number of layers of the graphite sheet is preferably at least 11. The graphite sheet may partially include a single layer portion and a multi-layer portion.

[0074] The second high thermal conductivity members 36 may be arranged in positions corresponding to interval B (and further to region C) in the arrangement direction so as to overlap at least a portion of the adjacent resistance heating elements 31, and are not limited to the arrangement shown in Fig. 15. For example, as shown in Fig. 16, the second high thermal conductivity members 36A are arranged to protrude beyond the base material 30 on both sides in the cross-array direction. The second high thermal conductivity members 36B are arranged in the range in the cross-array direction where the resistance heating elements 31 are arranged. The second high thermal conductivity members 36C are arranged in a portion of interval B.

[0075] 17, in this embodiment, a gap is provided between the first high thermal conductivity member 28 and the heater holder 23 in the thickness direction (left-right direction in FIG. 17). That is, a recess 23c is provided as a heat insulating layer in a partial area of ​​the recess 23b (see FIG. 14) for accommodating the heater 22, the first high thermal conductivity member 28, and the second high thermal conductivity member 36 of the heater holder 23, except for the area where the second high thermal conductivity member 36 is provided in the arrangement direction. This recess 23c is located in the cross-arrangement direction and is deeper than the remaining area that accommodates the first high thermal conductivity member 28. This minimizes the contact area between the heater holder 23 and the first high thermal conductivity member 28. This suppresses heat transfer from the first high thermal conductivity member 28 to the heater holder 23, allowing the heater 22 to efficiently heat the fixing belt 20. In addition, in the cross section in the arrangement direction where second high thermal conductivity members 36 are provided, second high thermal conductivity members 36 abut against heater holder 23 as in FIG. 13 of the above-described embodiment.

[0076] Furthermore, particularly in this embodiment, relief portion 23c is provided over the entire area where resistance heating elements 31 are provided in the array cross direction (the vertical direction in FIG. 17). This particularly suppresses heat transfer from first high thermal conductivity member 28 to heater holder 23, allowing heater 22 to efficiently heat fixing belt 20. Note that, in addition to a configuration in which a space is provided like relief portion 23c as the heat insulating layer, a configuration in which a heat insulating member with a lower thermal conductivity than heater holder 23 is provided may also be used.

[0077] Furthermore, in the above description, second high thermal conductivity member 36 is provided as a member different from first high thermal conductivity member 28, but this is not limiting. For example, the portion of first high thermal conductivity member 28 corresponding to interval B may be made thicker than the other portions.

[0078] Although the embodiments of the present invention have been described above, 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 spirit of the present invention.

[0079] Furthermore, in addition to the fixing device described above, the present invention can also be applied to fixing devices such as those shown in Figures 18 to 20. The configuration of each fixing device shown in Figures 18 to 20 will be briefly described below.

[0080] First, in the fixing device 9 shown in Figure 18, a pressure roller 44 is disposed on the opposite side of the fixing belt 20 from the pressure roller 21 side. The pressure roller 44 is a counter rotating member that rotates opposite the fixing belt 20, which is a rotating member. This pressure roller 44 and heater 22 are configured to sandwich and heat the fixing belt 20. Meanwhile, 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 fixing nip N is formed by the nip forming member 45 and the pressure roller 21 sandwiching the fixing belt 20.

[0081] 19, 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 to match 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.

[0082] Finally, the fixing device 9 shown in FIG. 20 will be described. The fixing device 9 includes a heating assembly 92, a fixing roller 93 as a fixing member, and a pressure assembly 94 as an opposing member. The heating assembly 92 includes the heater 22, the first high thermal conductivity member 28, the heater holder 23, the stay 24, and the heating belt 120 as a rotating member, as described in the previous embodiment. The fixing roller 93 is an opposing rotating member that rotates opposite the heating belt 120 as a rotating member. The fixing roller 93 includes 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 outer surface of the elastic layer 93b. A pressure assembly 94 is provided on the side of the fixing roller 93 opposite the heating assembly 92. The pressure assembly 94 includes a nip forming member 95 and a stay 96, and a pressure belt 97 is rotatably disposed so as to enclose 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, and heat and pressure are applied to fix the image.

[0083] 18 to 20, the amount of heat generated by the heater 22 decreases at the interval B between the resistance heating elements 31 of the heater 22, resulting in temperature unevenness in the arrangement direction of the heater 22 and the fixing members. Therefore, as in the above-described embodiment, by providing the first high thermal conductive member 28 and the second high thermal conductive member at positions corresponding to the interval B between the resistance heating elements 31 of the heater 22, it is possible to suppress temperature unevenness in the heater 22 and the fixing members. This makes it possible to suppress uneven gloss and uneven fixing of images on paper sheets passed through the fixing device. Alternatively, there is no need for excessive heating by the heater 22 to ensure sufficient fixing performance at the intervals between the resistance heating elements 31, thereby realizing energy savings in the fixing device 9.

[0084] Furthermore, the present invention is not limited to the fixing device described in the above embodiment, but can also be applied to heating devices 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, and a heat sealer that thermocompresses the seal portion of a packaging material. By applying the present invention to such devices, temperature unevenness in the arrangement direction of the heating member or rotating member can be suppressed.

[0085] The image forming apparatus according to the present invention is not limited to the color image forming apparatus shown in FIG. 1, but may also be a monochrome image forming apparatus, a copying machine, a printer, a facsimile, or a combination machine of these.

[0086] 21, for example, image forming apparatus 100 of this embodiment includes image forming means 50 including a photosensitive drum and the like, a paper transport unit including a pair of timing rollers 15 and the like, a paper feeder 7, a fixing device 9, a paper discharge device 10, and a reading unit 51. Paper feeder 7 includes multiple paper feed trays, each of which stores paper of a different size.

[0087] The reading unit 51 reads an image of the document Q. 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 conveyance path. The timing rollers 15 convey the sheets of paper P on the conveyance path to the image forming means 50.

[0088] 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 replenishment device, a transfer roller, a cleaning device, and a discharging device. The toner image represents, for example, an image of the 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 with the fixed toner image 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.

[0089] Next, the fixing device 9 of this embodiment will be described. Descriptions of the configurations common to the fixing devices of the above-described embodiments will be omitted as appropriate.

[0090] As shown in FIG. 22, the fixing device 9 includes a fixing belt 20, a pressure roller 21, a heater 22, a heater holder 23, a stay 24, a thermistor 25, a first high heat conductive member 28, and the like.

[0091] 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.

[0092] The fixing belt 20 has a polyimide base and a release layer, but 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 approximately 24 mm.

[0093] 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.

[0094] 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 to a total thickness of 1 mm. The width Y of the heater 22 in the array crossing direction is 13 mm.

[0095] As shown in FIG. 23, the conductor layer of the heater 22 includes a plurality of resistance heating elements 31, power supply lines 33, and electrode portions 34A-34C. In this embodiment, as shown in the enlarged view of FIG. 23, the resistance heating elements 31 are divided into divided regions in the arrangement direction, with intervals B formed (although FIG. 23 only illustrates the intervals B within the enlarged view, in reality, intervals B are provided between all of the resistance heating elements 31). The resistance heating elements 31 form three heat generating portions 35A-35C. By applying electricity to the electrode portions 34A and 34B, the heat generating portions 35A and 35C generate heat. By applying electricity to the electrode portions 34A and 34C, the heat generating portion 35B generates heat. For example, when performing a fixing operation on small-sized paper, the heat generating portion 35B is made to generate heat, and when performing a fixing operation on large-sized paper, all of the heat generating portions are made to generate heat.

[0096] As shown in Figure 24, the heater holder 23 holds the heater 22 and the first high thermal conductivity member 28 in its recess 23d. The recess 23d is provided on the heater 22 side of the heater holder 23. The recess 23d is composed of a surface 23d1 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, wall portions 23d2 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 wall portions 23d3 provided on the inside of the heater holder 23 on both sides in the intersecting direction of the arrangement. The heater holder 23 has a guide portion 26. The heater holder 23 is made of LCP (liquid crystal polymer).

[0097] As shown in FIG. 25, the connector 60 includes a housing made of resin (for example, LCP), and a plurality of contact terminals provided inside the housing.

[0098] The connector 60 is attached so as to sandwich the heater 22 and heater holder 23 together from the front and back sides. 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 to a power supply provided in the image forming apparatus via the connector 60. This enables power to be supplied from the power supply to the heat generating portion 35. Note that, to ensure connection with the connector 60, at least a portion of each electrode portion 34 is not covered with an insulating layer and is exposed.

[0099] 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 Figure 25).

[0100] The direction in which the connector 60 is attached to the heater 22 and heater holder 23 is the direction that intersects the heater arrangement (see the direction of the arrow from the connector 60 in FIG. 25). When the connector 60 is attached to the heater holder 23, a convex portion on one of the connector 60 and the heater holder 23 may engage with a concave portion on the other, and the convex portion may move relatively within the concave portion. The connector 60 is attached to the heater 22 and heater holder 23 on one side in the arrangement direction, opposite the side on which the drive motor of the pressure roller 21 is provided.

[0101] 26, thermistors 25 are provided facing the inner circumferential surface of the fixing belt 20 on the central side and the end side in the arrangement direction of the fixing belt 20. The heater 22 is controlled based on the temperatures detected by the thermistors 25 on the central side and the end side in the arrangement direction of the fixing belt 20.

[0102] Thermostats 27 are provided facing the inner circumferential surface of the fixing belt 20, at the center and end sides in the arrangement direction of the fixing belt 20. When the temperature of the fixing belt 20 detected by the thermostat 27 exceeds a predetermined threshold, the supply of power to the heater 22 is stopped.

[0103] 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).

[0104] 27, 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, allowing the fixing belt 20 to move in the direction in which the fixing belt 20 approaches and separates from the pressure roller 21.

[0105] In the fixing device 9 described above, by providing the first and second high thermal conductive members at positions corresponding to the interval B between the resistance heating elements of the heater 22, it is possible to suppress temperature unevenness in the arrangement direction of the heater 22 and the fixing belt 20. This makes it possible to suppress uneven gloss and uneven fixing of images on paper sheets passed through the fixing device. Alternatively, there is no need to apply extra heat to ensure sufficient fixing performance in the interval between the resistance heating elements, which makes it possible to realize energy saving in the fixing device 9.

[0106] Recording media include paper P (plain paper), as well as cardboard, postcards, envelopes, thin paper, coated paper (coated paper, art paper, etc.), tracing paper, OHP sheets, plastic film, prepreg, copper foil, etc. [Explanation of symbols]

[0107] 1. Image forming device 9 Fixing device (heating device) 20 Fixing belt (rotating member or fixing member) 21 Pressure roller (opposing rotating member or pressure member) 22 heater (heating element) 23 Heater holder (holding member) 23b Recess 23b1 Side wall (arrangement direction control part) 23b2 Side wall (array cross direction regulation part) 23c Relief section (insulating layer) 24 Stay (support member) 25 Thermistor (temperature detection element) 28 First high thermal conductivity member 30 Base material 31 Resistance heating element 35 Heat generating part 36 Second high thermal conductivity member B Interval (split area) N Fixing nip (nip part) X: Arrangement direction of multiple resistance heating elements Y array cross direction [Prior art documents] [Patent documents]

[0108] [Patent Document 1] Japanese Patent Application Publication No. 2019-164328

Claims

1. A rotating member; a planar heating element having a base material and a plurality of resistance heating elements; a holding member for holding the heating member; a first high thermal conductive member having a thermal conductivity higher than that of the base material, the plurality of resistance heating elements are arranged on the base material at intervals in the longitudinal direction of the heating member, the first high thermal conductivity member is provided between the holding member and the heating member, and at a position where at least a part of the first high thermal conductivity member overlaps with the interval between the resistance heating elements in an arrangement direction of the plurality of resistance heating elements, a second high thermal conductive member having a higher thermal conductivity than the base material is further provided between the holding member and the first high thermal conductive member, a heating device characterized in that the second high thermal conductivity members are provided in multiple positions in the arrangement direction of the multiple resistance heating elements, and each of the second high thermal conductivity members is provided at a position in the arrangement direction of the multiple resistance heating elements that overlaps with the spacing between the resistance heating elements.

2. 2. The heating device according to claim 1, wherein the first highly thermally conductive member is disposed across the resistance heating elements on both sides of the gap.

3. 3. The heating device according to claim 1, wherein the first high thermal conductivity member is provided over the entire area of ​​the spacing between the resistance heating elements in the arrangement direction of the plurality of resistance heating elements.

4. The second high thermal conductivity member is provided at a position where at least a portion of the second high thermal conductivity member overlaps with the first high thermal conductivity member in the arrangement direction of the plurality of resistance heating elements, The heating device according to claim 1 , wherein the second high thermal conductivity member has a thermal conductivity in an arrangement direction of the plurality of resistance heating elements that is greater than a thermal conductivity in a thickness direction of the second high thermal conductivity member.

5. 5. The heating device according to claim 4, wherein the second highly thermally conductive member is a graphite sheet.

6. When a direction intersecting the arrangement direction of the plurality of resistance heating elements and along the surface of the base material on which the resistance heating elements are provided is defined as an arrangement intersecting direction, The heating device according to claim 1 , further comprising a heat insulating layer between the holding member and the first high thermal conductivity member at a position where the heat resistive heating element at least partially overlaps with the heat resistive heating element in the crossing direction.

7. The heating device according to claim 1 , wherein the first high thermal conductivity member is provided over an entire area in which the resistance heating elements are provided in an arrangement direction of the plurality of resistance heating elements.

8. The heating device according to claim 1 , wherein the first highly thermally conductive member is made of a metal material.

9. 9. The heating device according to claim 8, wherein the first highly thermally conductive member is made of aluminum.

10. 10. The heating device according to claim 1, wherein the substrate is stainless steel.

11. The heating device according to claim 1 , wherein the holding member has an arrangement direction restricting portion that restricts movement of the first high thermal conductivity member in the arrangement direction of the plurality of resistance heating elements.

12. The heating device according to claim 1 , wherein the resistive heating element has a PTC characteristic.

13. A fixing device that heats and fixes a recording medium by using the heating device according to claim 1 .

14. An image forming apparatus comprising the fixing device according to claim 13.

Images