Heating apparatus, fixation device and image formation device

Abstract

To inhibit the temperature unevenness of a rotary member in a longer direction.SOLUTION: A fixation device comprises: a heater 22 including a fixation belt, a base material 30 and a resistance heating element 31 for heating the fixation belt; and a first heat-equalizing plate 28 having higher heat conductivity than the base material 30. A region of the fixation belt where the resistance heating element 31 is provided in a longer direction is denoted by a main heating area D. On a first side, the projection amount of the main heating area D to the maximum paper passing region E in the longer direction is denoted by L1L and the projection amount of the heat-equalizing plate 28 to the maximum paper passing region E in the longer direction is denoted by L2L, and L2L-L1L=L3L is defined. On a second side, the projection amount of the main heating area D to the maximum paper passing region E in the longer direction is denoted by L1R, and the projection amount of the first heat-equalizing plate 28 to the maximum paper passing region E in the longer direction is denoted by L2R, and L2R-L1R=L3R is defined. In this case, the following formulae (1) and (2) are satisfied. L1R≤L2R≤L1R+1 ... (1) and 0≤L3R<L3L ... (2).SELECTED DRAWING: Figure 9

Description

[Technical field]

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

[0002] One example of a fixing device that is a heating device is one that is configured to heat the fixing belt using a planar heating element provided inside the fixing belt as a rotating member, and to heat and pressurize the recording medium between the fixing belt and a pressure roller as a pressure member.

[0003] In such a fixing device, in order to suppress uneven fixing of an image on a recording medium, it is important to reduce temperature unevenness in the longitudinal direction of the fixing belt. In this regard, there is a problem that the temperature of the longitudinal end side of the fixing belt is difficult to increase compared to the longitudinal center side because heat is taken away by members on the longitudinal outer side (hereinafter referred to as end temperature sagging). However, on the other hand, when the resistance heating element provided on the heating element is longer than the maximum width of the recording medium, there is a problem that the temperature of the recording medium does not pass through the longitudinal end side of the fixing belt becomes excessive (hereinafter referred to as end temperature rise) when the fixing operation is performed continuously on the recording medium. For this reason, it has been difficult to maintain a uniform temperature of the fixing belt, especially on the longitudinal end side.

[0004] For example, in Patent Document 1 (JP 2015-176085 A), the width in the short direction at the longitudinal end of the heater's resistance heating element is narrowed compared to the longitudinal center to increase the heat generation amount of the resistance heating element at the longitudinal end, and an aluminum plate with a higher thermal conductivity than the heater base material is provided in the region where the longitudinal resistance heating element is provided and beyond this region, extending to the outside in the longitudinal direction. The aluminum plate promotes heat transfer in the longitudinal direction to suppress the end temperature rise, while increasing the heat generation amount of the resistance heating element at the longitudinal end alleviates the problem of end temperature sagging. Summary of the Invention [Problem to be solved by the invention]

[0005] Increasing the amount of heat generated at the longitudinal end of the heater as in Patent Document 1 increases the power consumption of the heater, which in turn increases the energy consumption of the fixing device. In this way, the configuration in Patent Document 1 is not necessarily an effective solution.

[0006] An object of the present invention is to suppress temperature unevenness in the longitudinal direction of a rotating member. [Means for solving the problem]

[0007] In order to solve the above problems, the present invention provides a heating device comprising a rotating member, a substrate, and a resistance heating element, the heating element for heating the rotating member, and a highly heat-conductive member having a higher thermal conductivity than the substrate, the substrate and the highly heat-conductive member extending in the longitudinal direction of the rotating member, a region of the rotating member in the longitudinal direction where the resistance heating element is provided being defined as a main heating region, and of one and the other sides of the main heating region with respect to a central position in the longitudinal direction, a side with a smaller amount of protrusion of the substrate with respect to the main heating region being defined as a first side in the longitudinal direction, and a side with a larger amount of protrusion of the substrate with respect to the main heating region being defined as a second side in the longitudinal direction, the amount of protrusion of the main heating region with respect to a maximum passing region, which is a passing region in the longitudinal direction of a recording medium of a maximum width that the heating device can accommodate, on the first side, is L 1L [mm], the amount of protrusion of the high thermal conductivity member in the longitudinal direction with respect to the maximum passing area is L 2L [mm], L 2L -L 1L =L 3L [mm], and on the second side, the amount of protrusion of the main heat generating region with respect to the maximum passing region in the longitudinal direction is L 1R [mm], the amount of protrusion of the high thermal conductivity member in the longitudinal direction with respect to the maximum passing area is L 2R [mm] 、 L 2R -L 1R =L 3R [mm], the heating device is characterized by satisfying the following formulas (1) and (2). L 1R ≦L 2R ≦L 1R+1 ···(1) 0≦L 3R <L 3L (2) Effect of the Invention

[0008] According to the present invention, it is possible to suppress temperature unevenness in the longitudinal direction of the rotating member. [Brief description of the drawings]

[0009] [Figure 1] FIG. 1 is a schematic diagram of an image forming apparatus. [Diagram 2] 1 is a side cross-sectional view showing a schematic configuration of a fixing device according to an embodiment of the present invention. [Diagram 3] FIG. [Figure 4] FIG. 4 is a plan view of a heater having a resistive heating element with a different shape from that of FIG. 3. [Diagram 5] FIG. 5 is a plan view of a heater having a resistive heating element with a different shape from those in FIGS. 3 and 4. [Figure 6] FIG. 4 is a diagram showing power supply to a heater. [Figure 7] 7 is a diagram showing temperature deviations of a heater and a fixing belt in a fixing device different from the embodiment. [Figure 8] 7A and 7B are diagrams illustrating temperature rises at the ends of a heater and a fixing belt in a fixing device different from the embodiment. [Figure 9] 4A to 4C are diagrams illustrating the arrangement of a heater and a first heat equalizing plate in the longitudinal direction of the fixing device and the temperature distribution in the longitudinal direction of the fixing belt in the embodiment. [Figure 10] 6A and 6B are diagrams illustrating a state in which the temperature at the longitudinal end side of the fixing device according to the embodiment has increased. [Figure 11] 11A and 11B are diagrams for explaining a state in which a temperature deviation between the left and right sides of a heater occurs due to asymmetry between the left and right power supply lines; [Figure 12] 11A and 11B are diagrams illustrating a state in which a temperature deviation between the left and right of a heater occurs due to asymmetry between the left and right of an elastic layer of a pressure roller. [Figure 13]5A and 5B are diagrams showing temperature distribution in the arrangement direction of a fixing belt, in which FIG. 5A is a plan view of a heater, and FIG. 5B is a diagram showing temperature distribution in the fixing belt. [Figure 14] FIG. 6 is a diagram showing divided regions of the heater in FIG. 5. [Figure 15] FIG. 15 is a diagram showing divided regions having a different shape from those in FIG. 14. [Figure 16] FIG. 7 is a diagram showing divided regions of the heater in FIG. 6. [Figure 17] FIG. 2 is a perspective view of a heater, a first high thermal conductive member, and a heater holder. [Figure 18] FIG. 4 is a plan view of the heater showing the arrangement of the first high thermal conductive member. [Figure 19] 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 20] 2 is a perspective view of a heater, a first highly thermally conductive member, a second highly thermally conductive member, and a heater holder. FIG. [Figure 21] 4 is a plan view of the heater showing the arrangement of the first and second high thermal conductive members. FIG. [Figure 22] FIG. 1 illustrates the atomic crystal structure of graphene. [Figure 23] FIG. 1 illustrates the atomic crystal structure of graphite. [Figure 24] 22 is a plan view showing a heater in which the arrangement of the second high thermal conductive members is different from that in FIG. 21. [Diagram 25] 2 and 19. FIG. 20 is a side cross-sectional view showing a schematic configuration of a fixing device according to an embodiment different from that shown in FIG. [Figure 26] FIG. 4 is a side cross-sectional view showing a schematic configuration of a fixing device different from the above. [Figure 27] FIG. 4 is a side cross-sectional view showing a schematic configuration of a fixing device different from the above. [Figure 28] FIG. 4 is a side cross-sectional view showing a schematic configuration of a fixing device different from the above. [Figure 29] FIG. 2 is a schematic diagram illustrating a configuration of an image forming apparatus different from that in FIG. [Diagram 30] 1 is a side cross-sectional view showing a schematic configuration of a fixing device according to an embodiment of the present invention. [Diagram 31]31 is a plan view of a heater in the fixing device of FIG. 30. [Diagram 32] FIG. 2 is a perspective view of a heater and a heater holder. [Diagram 33] FIG. 4 is a perspective view showing a state in which a connector is attached to a heater. [Diagram 34] FIG. 2 is a diagram showing the arrangement of a thermistor and a thermostat. [Diagram 35] FIG. 4 is a diagram showing a groove portion of the flange. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

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

[0011] FIG. 1 is a schematic 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 imaging units 1Y, 1M, 1C, and 1Bk that are detachable from the image forming apparatus main body. The imaging units 1Y, 1M, 1C, and 1Bk have the same configuration except that they contain different color developers, namely, yellow, magenta, cyan, and 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.

[0013] The image forming apparatus 100 also includes an exposure device 6, a paper feeder 7 as a recording medium supply unit, 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 the surface. The paper feeder 7 has a paper feed tray 16 and a paper feed roller 17. The paper feeder 7 supplies paper P as a recording medium to a paper transport path 14 as a transport path for the recording medium. 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 on the surface of the paper P. The paper discharge device 10 discharges the paper P outside the apparatus. The imaging units 1, the photoconductor 2, the charging device 3, the exposure device 6, the transfer device 8, etc. constitute an image forming means for forming an image on paper.

[0014] 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 a plurality of 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 a sheet of paper P. Each of the primary transfer rollers 12 contacts the photoconductors 2 via the intermediate transfer belt 11. As a result, the intermediate transfer belt 11 and each photoconductor 2 come into contact with each other, and a primary transfer nip is formed 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. As a result, a secondary transfer nip is formed between the secondary transfer roller 13 and the intermediate transfer belt 11.

[0015] Further, a pair of timing rollers 15 are provided on the paper transport path 14 between the paper feeder 7 and the secondary transfer nip (secondary transfer roller 13). A pair of rollers such as the timing rollers 15 provided on the paper transport path 14 are transport members for transporting the paper P on the paper transport path 14.

[0016] Next, the printing operation of the image forming apparatus will be described with reference to FIG.

[0017] When an instruction to start a printing operation is given, in each of the imaging units 1Y, 1M, 1C, and 1Bk, the photoconductor 2 is rotated clockwise in FIG. 1, and the surface of the photoconductor 2 is charged to a uniform high potential by the charging device 3. Next, the exposure device 6 exposes the surface of each photoconductor 2 based on the image information of the original document read by the original reading device or the print information instructed to be printed from the terminal. This reduces the potential of the exposed portion, forming an electrostatic latent image. Then, toner is supplied from the developing device 4 to this electrostatic latent image, and a toner image is formed on each photoconductor 2.

[0018] The toner images formed on each photoconductor 2 rotate with the rotation of each 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 as to be superimposed one on the other. 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 transferred to the paper P transported at the secondary transfer nip. This paper P is supplied from the paper supply tray 16. The paper P supplied from the paper supply device 7 is stopped once by the timing roller 15, and then transported to the secondary transfer nip in accordance with the timing at which the toner image on the intermediate transfer belt 11 reaches the secondary transfer nip. Thus, a full-color toner image is carried on the paper P. After the toner images are transferred, the toner remaining on each photoconductor 2 is removed by each cleaning device 5.

[0019] The paper P onto which the toner image has been transferred is transported to a fixing device 9, which fixes the toner image onto the paper P. Thereafter, the paper P is discharged outside the apparatus by a paper discharge device 10, completing a series of printing operations.

[0020] Next, the configuration of the fixing device will be described with reference to FIG.

[0021] 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 body, a heater holder 23 as a holding member, a stay 24 as a support member, a thermistor 25 as a temperature detection member, a first heat equalizing plate 28 as a highly heat conductive member, a thermostat, and the like. The fixing belt 20 is 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 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 contacts the back surface of the base material 30 and detects its temperature. The fixing member provided in the fixing device is one aspect of a rotating member provided in a heating device. The fixing device 9 according to the present embodiment is provided with the fixing belt 20 as a specific example of the fixing member.

[0022] 2 is the longitudinal direction of the fixing belt 20, pressure roller 21, heater 22, heater holder 23, stay 24, first heat equalizing plate 28, separation plate, and fixing device 9, and hereinafter this direction will 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 transported. The width direction of the paper is the direction perpendicular to the paper transport direction and thickness direction.

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

[0024] The pressure roller 21 has an outer diameter of, for example, 25 mm, and is composed of a solid iron core 21a, an elastic layer 21b formed on the surface of the core 21a, and a release layer 21c formed on the outside of the elastic layer 21b. The elastic layer 21b is made of silicone rubber and has a thickness of, for example, 3.5 mm. The release layer 21c is a conductive layer formed by adding a conductive filler such as carbon to PFA.

[0025] The pressure roller 21 is urged toward the fixing belt 20 by the urging means, so that the pressure roller 21 is pressed against the heater 22 via the fixing belt 20. As a result, a fixing nip N is formed between the fixing belt 20 and the pressure roller 21. The pressure roller 21 is configured to be rotationally driven by a driving means, and when the pressure roller 21 rotates in the direction of arrow A1 in Fig. 2, the fixing belt 20 is accordingly rotated in the direction of arrow A2. The A1 and A2 directions are the rotation directions of the pressure roller 21 and the fixing belt 20 during the image forming operation or the fixing operation.

[0026] The heater 22 is disposed so as to be in contact with the inner circumferential surface of the fixing belt 20. The heater 22 in this embodiment comes into contact with the pressure roller 21 via the fixing belt 20, and serves as a nip forming member that forms a fixing nip N between the pressure roller 21 and the heater 22. The fixing belt 20 is also a member to be heated by the heater 22. In other words, the heater 22 heats the paper P passing through the fixing nip N via the fixing belt 20.

[0027] 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 resistance heating element 31 provided on the base material 30, an insulating layer 32 covering the resistance heating element 31, and the like. The heater 22 is in contact with the inner circumferential surface of the fixing belt 20 on the insulating layer 32 side, and heat generated from the resistance heating element 31 is transferred to the fixing belt 20 via the insulating layer 32. In this embodiment, the resistance heating element 31 and the insulating layer 32 are provided on the fixing belt 20 side (fixing nip N side) of the base material 30, but conversely, the resistance heating element 31 and the insulating layer 32 may be provided on the heater holder 23 side of the base material 30. In that case, since the heat of the resistance heating element 31 is transferred to the fixing belt 20 via the base material 30, it is desirable that the base material 30 be made of a material with high thermal conductivity such as aluminum nitride. Furthermore, by forming the base material 30 from a material with high thermal conductivity, even if the resistance heating element 31 is disposed on the opposite side of the base material 30 from the fixing belt 20 side, it is possible to sufficiently heat the fixing belt 20.

[0028] 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 longitudinal end portions thereof are supported by both side plates of the fixing device 9. The heater holder 23 and the heater 22 are supported by the stay 24, so that the heater 22 can reliably receive the pressing force of the pressure roller 21 in a state in which the pressure roller 21 is pressed against the fixing belt 20. This allows the fixing nip N to be 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.

[0029] The heater holder 23 is desirably made of a heat-resistant material because it is likely to become hot due to the heat of the heater 22. For example, when the heater holder 23 is made of a heat-resistant resin with low thermal conductivity such as LCP or PEEK, the 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.

[0030] The heater holder 23 has a holding recess 23 b for holding the heater 22 .

[0031] 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 both the upstream side and the downstream side of the heater holder 23 in the paper transport direction.

[0032] The guide rib 26 is formed in a substantially fan shape. The guide rib 26 is provided along the inner circumferential surface of the fixing belt 20, and has an arc-shaped or convex-curved guide surface 260 extending in the belt circumferential direction.

[0033] The heater holder 23 has a detection portion through-hole 23a1 penetrating in the thickness direction. A thermistor 25 is provided in the detection portion through-hole 23a1.

[0034] The first heat equalizing plate 28 is made of a material having a higher thermal conductivity than the base material 30. In this embodiment, the first heat equalizing plate 28 is made of a 0.3 mm plate-shaped aluminum. The first heat equalizing plate 28 may be made of other materials such as copper, silver, graphene, and graphite. By making the first heat equalizing plate 28 plate-shaped, the positional accuracy of the heater 22 with respect to the heater holder 23 and the first heat equalizing plate 28 can be improved. By arranging the first heat equalizing plate 28, heat transfer in the longitudinal direction can be promoted, and the temperature of the heater 22, and therefore the fixing belt 20, can be made uniform in the longitudinal direction. By forming the first heat equalizing plate 28 from a metal material, the workability is good and the dimensional accuracy can be improved.

[0035] 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.

[0036] The thermal diffusivity was measured using a thermal diffusivity / thermal conductivity measuring device (product name: ai-Phase Mobile 1u, ai-Phase Corporation).

[0037] In order to convert the thermal diffusivity to thermal conductivity, the values ​​of density and specific heat capacity are required. A dry-type automatic density meter (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, and sapphire was used as a reference material with a known specific heat capacity. In this embodiment, the specific heat capacity was measured five times, and the average value at 50°C was used. If the density and specific heat capacity are ρ and C, respectively, the thermal conductivity λ can be obtained from the thermal diffusivity α obtained by the thermal diffusivity measurement by the following formula (20). λ = ρ × C × α (20)

[0038] In the fixing device 9 according to the present embodiment, when a printing operation is started, the pressure roller 21 is driven to rotate, and the fixing belt 20 starts to rotate in a driven manner. At this time, the inner circumferential surface of the fixing belt 20 contacts and is guided by the guide surface 260 of the guide rib 26, so that the fixing belt 20 rotates stably and smoothly. In addition, the fixing belt 20 is heated by supplying power to the resistance heating element 31 of the heater 22. Then, in a state where the temperature of the fixing belt 20 reaches the fixing temperature, which is a predetermined target temperature, as shown in FIG. 2, the paper P carrying the unfixed toner image is conveyed in the direction of the 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 to be fixed to the paper P.

[0039] Next, a more detailed configuration of the heater provided in the fixing device will be described with reference to Fig. 3. Fig. 3 is a plan view of the heater according to this embodiment.

[0040] 3, a plurality of (four) 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 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. Hereinafter, the power supply lines 33A and 33B are also referred to as power supply lines 33, and the first electrode portion 34A or the second electrode portion 34B is also referred to as an electrode portion 34.

[0041] 2, which is the longitudinal direction of the heater 22, etc., and which is perpendicular to the paper surface of FIG. 2, and which is the left-right direction X in FIG. 3, is also the arrangement direction of the multiple resistance heating elements 31. Hereinafter, this direction will also be referred to simply as the arrangement direction. Also, a direction intersecting the arrangement direction, particularly a vertical direction in this embodiment, and a vertical direction Y in FIG. 3 which is a direction different from the thickness direction of the base material 30, will also be referred to as a direction intersecting the arrangement direction of the multiple resistance heating elements 31, or simply as the arrangement intersecting direction. The arrangement intersecting direction Y is a direction along the surface of the base material 30 on which the resistance heating elements 31 are provided, and is also the short-side direction of the heater 22, or the transport direction of the paper passed through the fixing device 9.

[0042] A heating section 35 divided into a plurality of parts in the arrangement direction is formed by a plurality of resistance heating elements 31. Each resistance heating element 31 is electrically connected in parallel to a pair of electrode parts 34A, 34B via power supply lines 33A, 33B. The pair of electrode parts 34A, 34B is provided at the left end of FIG. 3, which is one end of the substrate 30 in the arrangement direction. The power supply lines 33A, 33B are made of a conductor having a smaller resistance value than the resistance heating element 31. From the viewpoint of ensuring insulation between the resistance heating elements 31, the gap between the adjacent resistance heating elements 31 is preferably 0.2 mm or more, and more preferably 0.4 mm or more. In addition, if the gap between the adjacent resistance heating elements 31 is too large, a temperature drop is likely to occur in the gap. For this reason, from the viewpoint of suppressing temperature unevenness across the arrangement direction, the gap is preferably 5 mm or less, and more preferably 1 mm or less.

[0043] The resistance heating element 31 is made of a material having a PTC (positive temperature coefficient of resistance) characteristic, and is characterized in that as the temperature rises, the resistance value rises and the heater output falls.

[0044] The resistance heating element 31 has a PTC characteristic, and the heating section 35 is divided in the arrangement direction, so that the fixing belt 20 can be prevented from overheating when small-sized paper is passed through. In other words, when paper having a width smaller than the entire width of the heating section 35 is passed through, the paper does not take 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 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 rises. This relatively reduces the output of the heater, that is, the amount of heat generated, and suppresses the rise in the temperature at the end. In addition, by electrically connecting multiple resistance heating elements 31 in parallel, it is possible to suppress the temperature rise in the non-paper passing area while maintaining the printing speed. The heating element constituting the heating section 35 may be other than the resistance heating element having the PTC characteristic. In addition, the resistance heating elements may be arranged in multiple rows in the arrangement crossing direction of the heaters 22.

[0045] The resistance heating element 31 can be formed, for example, by applying a paste prepared by mixing silver palladium (AgPd) and glass powder to the substrate 30 by screen printing or the like, and then firing the substrate 30. In this embodiment, the resistance value of the resistance heating element 31 is set to 80Ω at room temperature. The material of the resistance heating element 31 may be a resistance material such as silver alloy (AgPt) or ruthenium oxide (RuO2) in addition to the above-mentioned materials. The material of the power supply line 33 and the electrode portion 34 may be silver (Ag) or silver palladium (AgPd) formed by screen printing or the like. The power supply line 33 is made of a conductor having a smaller resistance value than the resistance heating element 31.

[0046] As the material of the substrate 30, ceramics such as alumina and aluminum nitride, which have excellent heat resistance and insulation, and non-metallic materials such as glass and mica are preferable. In this embodiment, an alumina substrate having a width of 8 mm in the cross direction of the array, a width of 270 mm in the array direction, and a thickness of 1.0 mm is used. Alternatively, the substrate 30 may be formed by laminating an insulating material onto a conductive material such as a metal. As the metal material of the substrate 30, aluminum and stainless steel are preferable because they are low cost. By forming the substrate 30 from a stainless steel plate, cracks due to thermal stress can be suppressed. In addition, the substrate 30 may be formed from a material with high thermal conductivity such as copper, graphite, and graphene in order to improve the thermal uniformity of the heater 22 and increase the image quality.

[0047] 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 to insulate and protect them, and maintains the sliding property with the fixing belt 20.

[0048] The region in which the resistance heating elements 31 are provided in the longitudinal direction is the main heat generating region D of the heater 22, and the main heat generating region D also includes the region between the resistance heating elements 31. In other words, the main heat generating region D of the heater 22 is from one longitudinal end of the resistance heating element 31 arranged on the most one longitudinal side to the other longitudinal end of the resistance heating element 31 arranged on the most other longitudinal side. The main heat generating region D is the main heat generating region by the heater 22, and the heater 22 also generates heat slightly in regions outside the main heat generating region D.

[0049] 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 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. 4, the resistance heating element 31 may be rectangular, or as shown in FIG. 5, the resistance heating element 31 may be made of a linear portion that is folded back to form a substantially parallelogram shape. As shown in FIG. 4, a portion extending from the block-shaped resistance heating element 31 toward the power supply line 33 (a portion extending in the arrangement crossing direction) may be a part of the resistance heating element 31, or may be made of the same material as the power supply line 33.

[0050] FIG. 6 is a diagram showing a power supply circuit to the heater according to this embodiment.

[0051] As shown in Fig. 6, 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 electrodes 34A, 34B of the heater 22. The power supply circuit is provided with a triac 210 for controlling 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 a thermistor 25. The control unit 220 is configured with a microcomputer including a CPU, a ROM, a RAM, an I / O interface, etc. The control unit 220 may be provided in the fixing device or in the image forming apparatus body.

[0052] In this embodiment, a thermistor 25 serving as a temperature detection member is disposed in the central region in the longitudinal direction of the heater 22, which is within the minimum paper passing width. Furthermore, a thermostat 27 serving as a power cut-off member that cuts off the power supply to the resistance heating element 31 when the temperature of the heater 22 reaches or exceeds a predetermined temperature is disposed on the other longitudinal end side of the heater 22. However, the present invention is not limited to this, and an end side thermistor may be provided on the end side within the maximum paper passing region.

[0053] However, in such a heating device, the problem is to make the temperature of the rotating member uniform in the longitudinal direction and eliminate the temperature unevenness. In the fixing device of FIG. 7, which is different from the present embodiment in this respect, the resistance heating element 31 is arranged symmetrically with respect to the center position E1 of the maximum paper passing area E, which is the paper passing area of ​​the maximum width paper P1 that the fixing device 9 can handle. In other words, the longitudinal center position of the main heat generation area D of the heater 22 coincides with the longitudinal center position E1 of the paper. In other words, the length of the resistance heating element 31 on one side in the longitudinal direction and the other side in the longitudinal direction with respect to the longitudinal center position of the paper are set to be the same, and the width in the short side is also the same, so the heat generation amount is also approximately the same. In contrast, the side (left side in FIG. 7) of the base material 30 where the first electrode portion 34A and the second electrode portion 34B are provided is longer than the opposite side with respect to the longitudinal center position. In other words, the protrusion amount of the base material 30 with respect to the main heat generation area D is larger on the right side of FIG. 7 than on the left side of FIG. 7. Therefore, the heat of the heater 22 flows more easily outward in the longitudinal direction on the right side of FIG. 7 than on the left side of FIG. 7, and as shown by the dashed line, the temperature of the heater 22 on the left side of FIG. 7, and therefore the temperature of the fixing belt 20, is higher than that on the right side of FIG. 7. In this way, the base material of the heating body is asymmetrical, which causes a problem that the temperature of the rotating member is uneven in the longitudinal direction. Hereinafter, this will be referred to as problem 1. Note that the dashed line in FIG. 7 shows a schematic temperature distribution in the longitudinal direction of the heater 22, with the upper side of FIG. 7 being the high temperature side, the lower side being the low temperature side, and the left and right directions of FIG. 7 showing the temperature at each longitudinal position, and the same applies to the following figures. The fixing belt 20 also shows the same temperature tendency as the heater 22.

[0054] Another issue is how to properly control the temperature at the longitudinal end of the rotating member. In other words, heat is absorbed from the longitudinal end of the rotating member by the components arranged on the longitudinal outside of the rotating member. For this reason, the temperature at the longitudinal end of the rotating member tends to be lower than that at the center, especially when the heating device is in a cold state and electricity is applied to the heating element to heat the rotating member. Hereinafter, this is referred to as issue 2 or end temperature sagging.

[0055] In response to this, it is possible to eliminate the end temperature drop by extending the length of the main heating region D on the lower temperature side, that is, the length of the resistance heating element 31, as shown in FIG. 8. However, in this case, there is a problem that the heater 22 and the fixing belt 20 will overheat on the side where the main heating region D on the longitudinal end side is extended, when the fixing operation is performed continuously on the paper. In other words, when the main heating region D of the heater 22 is larger than the width of the paper P passing through the fixing device 9, a non-passage region where the paper P does not pass will be generated in the main heating region D. In this non-passage region, the heat is not absorbed by the paper P, and the heater 22 and the longitudinal end side of the fixing belt 20 will overheat. As shown by the dashed line in FIG. 8, during the fixing operation, the temperature of the heater 22 exceeds the damage temperature T1 corresponding to the temperature at which the fixing belt will be damaged. Hereinafter, this will be referred to as problem 3 or end temperature rise.

[0056] Furthermore, there is a problem that it is necessary to minimize the power consumption of the heater in order to save energy in the heating device. In particular, when there is a temperature deviation between the left and right sides of the rotating member, the heater heats the side with the lower temperature so that it can reach the target temperature, so the side with the higher temperature is heated excessively and power consumption increases. Hereinafter, saving energy in the heating device is referred to as problem 4. In addition, in order to solve problems 2 and 3, there is a measure to partially provide a different shape to the highly thermally conductive member, such as partially providing a notch in the circumferential direction at a specific position on the end side in the longitudinal direction. However, even in this case, there is a problem that the processing cost of the highly thermally conductive member increases. Hereinafter, this is referred to as problem 5.

[0057] Hereinafter, a configuration of the present embodiment that solves these problems and makes the temperature of fixing belt 20 uniform in the longitudinal direction will be described with reference to FIG.

[0058] As shown in FIG. 8, in this embodiment, the amount of protrusion of the substrate 30 with respect to the main heat generation region D is different between one side and the other side in the longitudinal direction. Specifically, the amount of protrusion of the substrate 30 is small on the left side of FIG. 9, and the amount of protrusion is large on the right side of FIG. 9. Therefore, when the heater 22 is generated alone, the temperature on the right side of FIG. 9 is lower than that on the left side, as in the heater 22 in FIG. 7 described above. Hereinafter, the left side of FIG. 9 where the amount of protrusion of the substrate 30 is large is referred to as the first side in the longitudinal direction, and the right side of FIG. 9 is referred to as the second side in the longitudinal direction. Note that, in this embodiment, the amount of protrusion of the main heat generation region D with respect to the maximum paper passing region E is larger on the right side of FIG. 9 than on the left side of FIG. In the following description, the side of the center position E1 of the maximum paper passing region E in the longitudinal direction is also referred to as the inside in the longitudinal direction, and the side from the center position E1 toward one side or the other side in the longitudinal direction is also referred to as the outside in the longitudinal direction. The amount of protrusion of the substrate 30 relative to the main heat generating region D means, for example, the length from the end position of the main heat generating region D to the end position of the substrate 30 in a configuration in which the substrate 30 protrudes longitudinally outward beyond the main heat generating region D, taking the first side as an example, and the same is true for the second side.

[0059] The first side may be the side where the heater 22 has a large heat distribution, and the second side may be the side where the heater 22 has a small heat distribution. In other words, the heater 22 is not incorporated into a heating device, but is energized alone at a low duty (for example, 50% or less), and each side in the longitudinal direction is measured with a temperature detection member, or the temperature distribution in the longitudinal direction is measured with a thermoviewer. In this case, the side where the temperature of the heater 22 is high may be the first side, and the side where the temperature is low may be the second side, among the one side and the other side relative to the center position of the main heat generation area in the longitudinal direction or the center position of the recording medium. Also, the first side may be the side where the length of the substrate 30 is short (the left side in FIG. 9), and the second side may be the side where the length of the substrate 30 is long (the right side in FIG. 9), on one side and the other side in the longitudinal direction relative to the center position D1 of the main heat generation area D or the center position E1 of the maximum paper passing area E.

[0060] The main heat generating region D of the heater 22 and the first heat equalizing plate 28 are provided so as to protrude on both sides in the longitudinal direction from the maximum paper passing region E. On the first side in the longitudinal direction, the amount of protrusion of the main heat generating region D from the maximum paper passing region E is a length L 1L[mm], the protrusion amount of the first heat equalizing plate 28 with respect to the maximum paper passing area E is the length L 2L [mm], L 2L -L 1L =L 3L [mm]. Also, on the second side in the longitudinal direction, the amount of protrusion of the main heat generation area D from the maximum paper passing area E is set to a length L 1R [mm], the protrusion amount of the first heat equalizing plate 28 with respect to the maximum paper passing area E is the length L 2R [mm], L 2R -L 1R =L 3R In the case of the first side, for example, this protrusion amount refers to the length from the end position of the first side of the maximum paper passing area E to the end position of the first side of the main heating area D or the first heat equalizing plate 28 in a configuration in which the main heating area D or the first heat equalizing plate 28 protrudes outward in the longitudinal direction of the first side beyond the maximum paper passing area E, and the same is true for the second side. In this embodiment, the lengths of the resistance heating element 31 and the first heat equalizing plate 28 are set so as to satisfy the following equations (21) and (22). In this embodiment, in particular, L 2R =L 1R The lengths of the first heat equalizing plate 28 and the main heating area D are set so that: L 1R ≦L 2R ≦L 1R +1 ···(21) 0≦L 3R <L 3L ···(twenty two)

[0061] L 3R <L 3L By doing so, the protrusion amount of the first heat equalizer 28 is set to be large on the first side where the temperature of the heater 22 is high. As a result, more heat flows to the first heat equalizer 28 on the first side than on the second side, and the heat tends to flow more outward in the longitudinal direction. This suppresses the temperature on the first side, and suppresses the temperature bias on the end sides of the first side and the second side, as shown by the dashed line in FIG. 9. In other words, the temperature bias of problem 1 can be suppressed.

[0062] In addition, in this embodiment, on the second side where the temperature of the heater 22 is low, the main heat generation area D is protruded from the maximum paper passing area E, and the formula (21) is satisfied, so that the main heat generation area D is provided with a length similar to that of the first heat equalizer 28, and the main heat generation area D can be secured with a necessary length. This allows the end side of the fixing belt 20 to be sufficiently heated on the second side, and the end temperature drop of the problem 2 can be suppressed. In other words, unlike this embodiment, if the first heat equalizer 28 is sufficiently longer than the main heat generation area D on the second side, the heat of the heater 22 and the fixing belt 20 will escape to the outside in the longitudinal direction by the first heat equalizer 28, which will promote the end temperature drop of the fixing belt 20, but this can be avoided in this embodiment.

[0063] Furthermore, by satisfying formula (22), the first heat equalizing plate 28 can be provided on the first and second sides with a length equal to or longer than the main heat generation area D, and the first heat equalizing plate 28 can be provided in a non-paper passing area outside the maximum paper passing area E within the main heat generation area D. This allows the first heat equalizing plate 28 to obtain a sufficient heat equalizing effect even if the temperature rises in the non-paper passing area due to heating by the heater 22 during the fixing operation. 3R <L 3L By doing so, the first heat equalizing plate 28 protrudes more from the main heat generating region D on the first side where the temperature is likely to become high. This effectively prevents the end temperature from rising in the non-paper passing region on the first side. As a result, as shown in FIG. 10, it is possible to prevent the heater 22, and in turn the fixing belt 20, from overheating in the maximum paper passing region E. In other words, problem 3 can be solved. In this embodiment, the main heat generating region D on the second side and the first heat equalizing plate 28 are set to have the same length, but taking into account dimensional errors and the like, even if the first heat equalizing plate 28 is 1 mm or less larger than the main heat generating region D, approximately the same effect can be obtained.

[0064] As described above, by satisfying formulas (21) and (22), problems 1 to 3 can be solved, and the left-right deviation of the heater 22 and therefore the fixing belt 20, the temperature drop at the ends, and the temperature rise at the ends can be suppressed. This makes it possible to set the target temperature of the heater 22 low, and the amount of heat generated by the heater 22 can be reduced, thereby suppressing the energy consumption of the heater 22. This solves problem 4. In addition, these problems can be solved simply by adjusting the lengths of the resistance heating element 31 and the first heat equalizing plate 28, and there is no increase in the processing costs of the first heat equalizing plate 28, etc. Therefore, problem 5 can be solved.

[0065] As described above, according to the fixing device 9 of the present embodiment, problems 1 to 5 can be solved, and temperature unevenness in the longitudinal direction of the fixing belt 20 can be suppressed with an inexpensive configuration.

[0066] As shown in FIG. 9, on the first side, the protrusion amount of the base material 30 with respect to the maximum paper passing area E is L 4L [mm], and on the second side, the protrusion amount of the base material 30 with respect to the maximum paper passing area E is L 4R [mm], the lengths of the base material 30 and the first heat equalizing plate 28 can be set so as to satisfy the following formulas (23) and (24). L 2L ≦L 4L ···(twenty three) L 2R ≦L 4R ···(twenty four)

[0067] As shown in the above formulas (23) and (24), the protrusion amount of the first heat equalizer 28 can be set smaller than the protrusion amount of the base material 30 on both sides in the longitudinal direction. This allows the first heat equalizer 28 to promote heat transfer in the longitudinal direction within the range in which the base material 30 is arranged in the longitudinal direction, and suppresses heat from flowing outward in the longitudinal direction. Therefore, the end temperature drop of problem 2 can be further suppressed.

[0068] The thermal conductivity of the base material 30 is λ1 [W / m K], and the thermal conductivity of the first heat equalizing plate 28 is λ2 [W / m K]. The volume of the protruding part of the base material 30 on the first side with respect to the main heat generation area D, that is, the length L in FIG.5L The volume of the part is V 1L [mm 3 ], the volume of the protruding portion of the first heat equalizing plate 28 relative to the main heat generating area D, i.e., the length L 3L The volume of the part is V 2L [mm 3 The volume of the protruding portion with respect to the main heat generating region D of the base material 30 on the second side, that is, the length L 5R The volume of the part is V 1R [mm 3 〕, the volume of the protruding part of the first heat equalizing plate 28 with respect to the main heat generation area D is V 2R [mm 3 In addition, in FIG. 10, the main heat generating region D and the first heat equalizing plate 28 are provided with the same length on the second side, so that the volume V 2R In other words, in Figure 10, there is no part that corresponds to V 2R is set to 0. The integrated value λ1×V of the volume and thermal conductivity of the protruding portion with respect to the main heat generating region D of the base material 30 on the first side 1L The integrated value λ2×V of the volume and thermal conductivity of the protruding portion of the first heat equalizing plate 28 on the first side with respect to the main heat generation area D 2L The sum of these values ​​A L = λ1 × V 1L +λ2×V 2L In addition, the integrated value λ1×V of the volume and thermal conductivity of the protruding portion of the base material 30 on the second side is 1R The integrated value λ2×V of the volume and thermal conductivity of the protruding portion of the first heat equalizing plate 28 on the second side with respect to the main heat generation area D 2R The sum of these values ​​A R = λ1 × V 1R +λ2×V 2R In this case, A is set so as to satisfy the following formula (25) or formula (26). L and A R can be set. 0.6≦A L / A R ≦1.4 ···(25) 0.8≦A L / A R ≦1.2 (26)

[0069] A aboveL , A R is used as an evaluation index for the heat quantity imbalance between the first side and the second side. By satisfying equation (25), that is, A L and A R By not setting a large difference between the values ​​of A and B, it is possible to maintain a heat balance between the first side and the second side, and to suppress temperature unevenness in the longitudinal direction of the fixing belt 20. This allows the target temperature of the heater 22 to be set lower, and the end temperature rise of problem 3 to be suppressed. In addition, the fixing device 9 can be made more energy efficient. Furthermore, by satisfying formula (26), it is possible to further suppress temperature unevenness in the longitudinal direction of the fixing belt 20, and to further save energy in the fixing device 9. Moreover, since these can be achieved by adjusting the lengths of the base material 30 and the first heat equalizing plate 28, there is no increase in processing costs as described in problem 5. A of this embodiment L、 A R The set values ​​for A are shown in Table 1. The lengths in Table 1 refer to the protruding amounts from the main heating area D on each side. In this embodiment, as shown in Table 1, each value is set to satisfy formula (26). That is, A L / A R =8248.4 / 6929.44 ≒ 1.19. [Table 1]

[0070] As described above, it is preferable to use aluminum, which has high thermal conductivity, as the material for the first heat equalizing plate 28. This promotes the transfer of heat in the longitudinal direction of the fixing belt 20, and can suppress the end temperature drop of problem 2 and the end temperature rise of problem 3.

[0071] It is preferable to interpose grease as a lubricant between the heater 22 and the fixing belt 20. This prevents the formation of a gap between the heater 22 and the fixing belt 20, and allows the heat of the heater 22 to be efficiently transferred to the fixing belt 20. In other words, the fixing belt 20 can be efficiently heated, the end temperature drop of problem 2 can be suppressed, and the energy saving of the fixing device of problem 4 can be achieved. In addition, because the heater 22 is unlikely to become too hot, the end temperature rise of problem 3 can be suppressed.

[0072] In the above description, a case where a temperature deviation occurs between the left and right sides of the heater 22 due to different lengths of the base material 30 has been exemplified in Problem 1, but the present invention is not limited to this. For example, the heater 22 shown in FIG. 11 has two resistance heating elements 31 extending in the longitudinal direction connected in series. The two resistance heating elements 31 are connected to electrode portions 34A and 34B via power supply lines 33A and 33B, respectively, on the right side of FIG. 11. The two resistance heating elements 31 are also connected in series via a power supply line 33C on the left side of FIG. 11. Here, with regard to the power supply lines 33A to 33C, which are conductors provided in the heater 22, the power supply line 33C has a length L 6L 11, the power supply line 33A and the power supply line 33B are provided with a length L 6R [mm]. The power supply lines 33A to 33C of this embodiment are made of metal material and have a higher thermal conductivity than the base material. Therefore, on the right side of FIG. 11 where the power supply lines 33A and 33B are provided longer, the heat of the heater 22 flows more easily outward in the longitudinal direction, and as shown by the dashed line in FIG. 11, the temperature of the heater 22 on the right side of FIG. 11 is lower than that on the left side of FIG. 11. That is, the left side of FIG. 11 where the conductor protrudes less from the main heat generating region is the first side in the longitudinal direction, and the right side of FIG. 11 where the conductor protrudes more from the main heat generating region is the second side in the longitudinal direction. This causes a temperature deviation between the left and right sides of the heater 22 of the problem 1. Note that in the heater 22 of FIG. 9, the length of the power supply line is longer on the right side of FIG. 9, and the conductor is provided asymmetrically on the left and right. That is, the left side of FIG. 9 is the first side, and the right side of FIG. 9 is the second side.

[0073] In the embodiment shown in FIG. 12, the length of the elastic layer 21b provided on the pressure roller is asymmetric. That is, the protruding amount of the elastic layer 21b protruding outward in the longitudinal direction from the main heat generation region D is different between the left side of FIG. 12 and the right side of FIG. 12. Specifically, the protruding amount on the right side of FIG. 12 is larger than that on the left side of FIG. 12. As a result, in the pressure roller, the heat flows more easily outward in the longitudinal direction on the right side of FIG. 12 than on the left side. Therefore, as shown by the dashed line in FIG. 12, the temperature of the pressure roller, and further the fixing belt and the heater, is lower on the right side of FIG. 12 than on the left side of FIG. 12. That is, the left side of FIG. 12, where the protruding amount of the elastic layer with respect to the main heat generation region is small, is the first side in the longitudinal direction, and the right side of FIG. 12, where the protruding amount of the elastic layer with respect to the main heat generation region is large, is the second side in the longitudinal direction. In other words, the left side of FIG. 12 where the length of the elastic layer is short with respect to the center position E1 of the maximum paper passing area E can be the first side in the longitudinal direction, and the right side of FIG. 12 where the length of the elastic layer is long can be the second side in the longitudinal direction. This difference in the length of the elastic layer causes the temperature deviation between the left and right of the heater 22 in the problem 1. In addition, the above-mentioned configuration of this embodiment can be applied when the temperature deviation between the left and right in the longitudinal direction occurs in the heating body or the rotating member (when the side with large heat distribution and the side with small heat distribution occur) due to the difference in the length of one side and the other side in the longitudinal direction with respect to the center position E1 or the center position D1 for other members in the fixing device, or the difference in the protrusion amount between one side and the other side in the longitudinal direction with respect to the main heat generation area D. Alternatively, the above-mentioned configuration of this embodiment can be applied when the temperature deviation between the left and right in the longitudinal direction occurs in the heating body or the rotating member due to the provision of a specific member such as a thermistor only on one side or the other side in the longitudinal direction.

[0074] 13A and 13B are diagrams showing temperature distribution in the arrangement direction of the fixing belt 20. FIG. 13A shows the arrangement of the heaters 22. FIG. 13B shows the temperature T of the fixing belt 20 on the vertical axis and the position of the fixing belt 20 on the horizontal axis in the arrangement direction.

[0075] 13(a) and 13(b), the multiple resistance heating elements 31 provided in the heater 22 are divided in the arrangement direction, and divided regions B are formed between the resistance heating elements 31. In other words, the multiple resistance heating elements 31 provided in the heater 22 are arranged with a gap B therebetween. Hereinafter, the range B as the divided region will be referred to as the gap B.

[0076] In the interval B, the area occupied by the resistance heating element 31 is smaller than the other parts, and the amount of heat generated is smaller. As a result, the temperature of the fixing belt 20 in the interval B is smaller than the other parts, which causes temperature unevenness in the arrangement direction of the fixing belt 20. The temperature of the heater 22 and the fixing belt 20 is also lower in an expanded divided area C (hereinafter simply referred to as area C) including the area around the interval B, which is a divided area. The temperature of the heater 22 is also lower in the interval B. Here, as shown in the enlarged view of FIG. 13(a), the interval B means an arrangement direction area including the entire part into which the resistance heating element 31, which is the main heat generating part of the heater 22, is divided in the arrangement direction. In addition to the interval B, an area including a range corresponding to the connection part 311 of the resistance heating element 31 is defined as area C. The connection part 311 refers to a part of the resistance heating element 31 that extends in the arrangement crossing direction and is connected to each of the power supply lines 33A and 33B.

[0077] As shown in Fig. 14, the temperature in the interval B is lower than the other portions in the heater 22 having the rectangular resistance heating element 31 shown in Fig. 4. The temperature in the interval B is also lower than the other portions in the heater 22 having the resistance heating element 31 shaped as shown in Fig. 15. Furthermore, as shown in Fig. 16, the temperature in the interval B is also lower than the other portions in the heater 22 having the resistance heating element 31 shaped as shown in Fig. 5. However, by overlapping adjacent resistance heating elements 31 in the arrangement direction as in Figs. 13, 15 and 16, the temperature drop in the other portions of the interval B can be suppressed.

[0078] In this embodiment, the above-mentioned first heat equalizing plate 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 heat equalizing plate 28 will be described in more detail below.

[0079] 2, the first heat equalizing plate 28 is disposed between the heater 22 and the stay 24 in the left-right direction of Fig. 2, and is particularly sandwiched between the heater 22 and the heater holder 23. That is, the first heat equalizing plate 28 has one surface in contact with the rear surface of the base material 30 and the other surface in contact with the heater holder 23.

[0080] The stay 24 supports the heater holder 23, the first heat equalizing plate 28, and the heater 22 by directly abutting the abutment surfaces of two vertical portions 24a extending in the thickness direction of the heater 22 etc. against the heater holder 23. In the array crossing direction (the up-down direction in FIG. 2), the abutment surfaces are provided outside the range in which the resistance heating element 31 is 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.

[0081] As shown in Fig. 17, the first heat equalizing plate 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, the first heat equalizing plate 28 is made of a single plate material, but it may be made of a plurality of members. Note that the illustration of the guide ribs 26 in Fig. 2 is omitted in Fig. 17.

[0082] The first heat equalizing plate 28 is fitted into the holding recess 23b of the heater holder 23, and the heater 22 is attached from above, so that the first heat equalizing plate 28 is sandwiched and held between the heater holder 23 and the heater 22. The movement of the first heat equalizing plate 28 and the heater 22 in the arrangement direction is restricted by both side walls (arrangement direction restricting parts) 23b1 in the arrangement direction that form the holding recess 23b. In this way, by restricting the positional deviation of the first heat equalizing plate 28 in the arrangement direction within the fixing device 9, it is possible to improve the heat conduction efficiency within a target range in the arrangement direction. In addition, the movement of the first heat equalizing plate 28 and the heater 22 in the arrangement cross direction is restricted by both side walls (arrangement cross direction restricting parts) 23b2 in the arrangement cross direction that form the holding recess 23b.

[0083] The range in the arrangement direction in which the first heat equalizing plate 28 is provided is not limited to the above. For example, as shown in Fig. 18, the first heat equalizing plate 28 may be provided only in the range in the arrangement direction corresponding to the heat generating portion 35 (see the hatched portion in Fig. 18).

[0084] The first heat equalizing plate 28 is sandwiched between the heater 22 and the heater holder 23 by the pressure of the pressure roller 21 and is in close contact with these members. The first heat equalizing plate 28 comes into contact with the heater 22, thereby improving the heat conduction efficiency in the arrangement direction of the heater 22. The first heat equalizing plate 28 is provided at a position corresponding to the interval B of the heater 22 in the arrangement direction, thereby improving the heat conduction efficiency in the interval B. This increases the amount of heat transferred to the area of ​​the interval B in the arrangement direction, and increases the temperature in the area of ​​the interval B in the arrangement direction. This makes it possible to suppress temperature unevenness in the arrangement direction of the heater 22. This makes it possible to suppress temperature unevenness in the arrangement direction of the fixing belt 20. This makes it possible to suppress uneven fixing and uneven gloss of the image fixed on the paper. Alternatively, in order to ensure sufficient fixing performance in the area of ​​the interval B, it is not necessary to apply extra heat by the heater 22, and energy saving of the fixing device 9 can be realized. In addition, by providing the first heat equalizing plate 28 over the entire area of ​​the heat generating section 35 in the arrangement direction, the heat transfer efficiency of the heater 22 can be improved over the entire area that is the main heating area by the heater 22, i.e., the image forming area of ​​the paper being passed through, and temperature unevenness in the arrangement direction of the heater 22 and therefore the fixing belt 20 can be suppressed.

[0085] Particularly in this embodiment, the combination of the configuration of the first heat equalizing plate 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.

[0086] Also, since the temperature around the gap B is low due to the small amount of heat generated in the gap B, it is preferable to place the first heat equalizing plate 28. For example, in this embodiment, the first heat equalizing plate 28 is provided at a position corresponding to the region C (see FIG. 14), thereby particularly improving the heat transfer efficiency in the arrangement direction in the gap B and its periphery, and further suppressing the temperature unevenness in the arrangement direction of the heaters 22. Particularly in this embodiment, the first heat equalizing plate 28 is provided over the entire area of ​​the heat generating section 35 in the arrangement direction. This makes it possible to further suppress the temperature unevenness in the arrangement direction of the heaters 22 (fixing belt 20).

[0087] Next, a different embodiment of the fixing device will be described.

[0088] As shown in Fig. 19, the fixing device 9 of this embodiment has a second heat equalizer plate 36 as a second high thermal conductive member between the heater holder 23 and the first heat equalizer plate 28. The second heat equalizer plate 36 is provided at a position different from that of the first heat equalizer plate 28 in the left-right direction of Fig. 19, which is the stacking direction of members such as the heater holder 23, the stay 24, and the first heat equalizer plate 28. More specifically, the second heat equalizer plate 36 is provided overlapping the first heat equalizer plate 28. Note that Fig. 19 shows a cross section in which the thermistor 25 is not arranged in the arrangement direction, unlike Fig. 2. In other words, Fig. 19 shows a cross section in which the second heat equalizer plate 36 is arranged.

[0089] The second heat equalizer 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 heat equalizer 36 is made of a graphite sheet having a thickness of 1 mm. However, the second heat equalizer 36 may be made of a plate material such as aluminum, copper, or silver.

[0090] As shown in Fig. 20, a plurality of second heat equalizing plates 36 are arranged in the arrangement direction, each of which is partially provided in the arrangement direction. The portion of the holding recess 23b of the heater holder 23 where the second heat equalizing plate 36 is provided is provided one step deeper than the other portion. A gap is provided between the second heat equalizing plate 36 and the heater holder 23 on both sides in the arrangement direction. This suppresses heat transfer from both ends of the second heat equalizing plate 36 in the arrangement direction to the heater holder 23, allowing the heater 22 to efficiently heat the fixing belt 20. Note that the guide rib 26 in Fig. 2 is omitted in Fig. 20.

[0091] 21, the second heat equalizing plate 36 (see hatched portion) is provided at a position in the arrangement direction corresponding to the interval B so as to overlap at least a portion of the adjacent resistance heating elements 31, and in this embodiment in particular, is provided over the entire area of ​​the interval B. The second heat equalizing plate 36 is provided at a position in the longitudinal direction where no thermistor or thermostat is provided.

[0092] In one embodiment of the present invention different from the above, the first heat equalizer plate 28 and the second heat equalizer plate 36 are formed from the graphene sheet. This makes it possible to form the first heat equalizer plate 28 and the second heat equalizer plate 36 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 the heater 22 and the fixing belt 20.

[0093] Graphene is a flaky powder. As shown in FIG. 22, graphene is composed 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 of such a compound include C 60 , C 70 and C 80 It is a fullerene or other closed cage structure with three coordinated carbon atoms.

[0094] Graphene sheets are man-made and can be produced, for example, by chemical vapor deposition (CVD) techniques.

[0095] The graphene sheet may be a commercially available product. The size and thickness of the graphene sheet, or the number of layers of the graphite sheet described below, may be measured, for example, by a transmission electron microscope (TEM).

[0096] Moreover, graphite, which is a multi-layered graphene, has a large thermal conduction anisotropy. As shown in FIG. 23, graphite has a layer in which the condensed six-membered ring layer plane of carbon atoms spreads in a planar shape, and has a crystal structure in which these layers are stacked on top of each other. In this crystal structure, adjacent carbon atoms in a layer form a covalent bond, and carbon atoms between layers form a van der Waals bond. The covalent bond has a larger bond strength than the van der Waals bond, and has a large anisotropy between the bond within the layer and the bond between the layers. In other words, by forming the first heat equalizer plate 28 or the second heat equalizer plate 36 from graphite, the heat transfer efficiency in the arrangement direction of the first heat equalizer plate 28 or the second heat equalizer plate 36 is larger than that in the thickness direction (i.e., the stacking direction of the members), 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. Furthermore, by forming the first heat equalizer plate 28 or the second heat equalizer plate 36 from graphite, the first heat equalizer plate 28 or the second heat equalizer plate 36 can have excellent heat resistance that prevents oxidation up to approximately 700 degrees.

[0097] The physical properties and dimensions of the graphite sheet can be appropriately changed depending on the function required for the first heat equalizer plate 28 or the second heat equalizer plate 36. For example, the anisotropy of the thermal conduction can be increased by using high-purity graphite or single crystal graphite, or by increasing the thickness of the graphite sheet. Also, in order to increase the speed of the fixing device 9, a graphite sheet with a small thickness may be used to reduce the thermal capacity of the fixing device 9. Also, when the width of the fixing nip N or the heater 22 is large, the width of the first heat equalizer plate 28 or the second heat equalizer plate 36 in the arrangement direction may be increased accordingly.

[0098] From the viewpoint of increasing mechanical strength, the number of layers of the graphite sheet is preferably equal to or greater than 11. The graphite sheet may partially include a single layer portion and a multilayer portion.

[0099] The second heat equalizer 36 is not limited to the arrangement shown in Fig. 21 as long as it is provided at a position corresponding to the interval B (and further to area C) in the arrangement direction and overlaps at least a portion of the adjacent resistance heating elements 31. For example, as shown in Fig. 24, the second heat equalizer 36A is provided protruding out from the base material 30 on both sides in the arrangement cross direction. The second heat equalizer 36B is provided in a range in the arrangement cross direction where the resistance heating elements 31 are provided. The second heat equalizer 36C is provided in a portion of the interval B.

[0100] As shown in FIG. 25, in this embodiment, a gap is provided between the first heat equalizing plate 28 and the heater holder 23 in the thickness direction, ie, the left-right direction in FIG. 25. That is, in a part of the holding recess 23b (see FIG. 20) for arranging the heater 22 of the heater holder 23, the first heat equalizing plate 28, and the second heat equalizing plate 36, a relief portion 23c is provided as a heat insulating layer that makes the depth of the holding recess 23b deeper than the other part that receives the first heat equalizing plate 28. This part is a part or the whole of the part other than the part where the second heat equalizing plate 36 is provided in the arrangement direction, and is a part of the arrangement cross direction. This makes it possible to minimize the contact area between the heater holder 23 and the first heat equalizing plate 28. Therefore, the heat transfer from the first heat equalizing plate 28 to the heater holder 23 is suppressed, and the heater 22 can efficiently heat the fixing belt 20. In addition, in the cross section in the arrangement direction where the second heat equalizing plate 36 is provided, the second heat equalizing plate 36 abuts against the heater holder 23 as in FIG. 19 of the above-mentioned embodiment.

[0101] 25, which is the array crossing direction, the relief portion 23c is provided over the entire area where the resistance heating element 31 is provided. This particularly suppresses heat transfer from the first heat equalizing plate 28 to the heater holder 23, allowing the heater 22 to efficiently heat the fixing belt 20. Note that, as the heat insulating layer, in addition to a configuration in which a space is provided like the relief portion 23c, a configuration in which a heat insulating member having a lower thermal conductivity than the heater holder 23 is provided may also be used.

[0102] Furthermore, in the above description, the second heat equalizing plate 36 is provided as a member different from the first heat equalizing plate 28, but this is not limited to the above. For example, the portion of the first heat equalizing plate 28 corresponding to the interval B may be made thicker than the other portions.

[0103] 19 and 25, the lengths of the main heat generating region D, the first heat equalizing plate 28, the base material 30 of the heater 22, etc. can be set as in the above-described embodiments. This makes it possible to suppress temperature unevenness in the longitudinal direction of the fixing belt 20 with an inexpensive configuration.

[0104] Although an embodiment of the present invention has been described above, the present invention is not limited to the above-described embodiment, and it goes without saying that various modifications can be made without departing from the gist of the present invention.

[0105] Further, in addition to the fixing device described above, the present invention is also applicable to fixing devices as shown in Figures 26 to 28. The configuration of each fixing device shown in Figures 26 to 28 will be briefly described below.

[0106] First, in the fixing device 9 shown in FIG. 26, a pressure roller 39 is disposed on the opposite side of the fixing belt 20 to the pressure roller 21 side. The pressure roller 39 is a counter rotating member that rotates opposite the fixing belt 20 as a rotating member. The pressure roller 39 and the heater 22 are configured to sandwich and heat the fixing belt 20. On the other hand, on the pressure roller 21 side, a nip forming member 41 is disposed on the inner periphery of the fixing belt 20. The nip forming member 41 is supported by the stay 24. The nip forming member 41 and the pressure roller 21 sandwich the fixing belt 20 to form a fixing nip N.

[0107] 27, the above-mentioned pressure roller 39 is omitted, and in order to ensure the circumferential contact length between the fixing belt 20 and the heater 22, the heater 22 is formed in an arc shape in accordance with the curvature of the fixing belt 20. The rest of the configuration is the same as that of the fixing device 9 shown in FIG.

[0108] Finally, the fixing device 9 shown in FIG. 28 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 first 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. The pressure assembly 44 is provided on the opposite side of the heating assembly 42 side with respect to the fixing roller 43. 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 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.

[0109] 26 to 28, the lengths of the main heat generation region D, the first heat equalizing plate 28, or the base material 30 of the heater 22 can be set as in the above-described embodiment. This makes it possible to suppress temperature unevenness in the longitudinal direction of the fixing belt 20 or the heating belt 48 with an inexpensive configuration.

[0110] 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.

[0111] 29, image forming apparatus 100 of this embodiment includes image forming means 50 including a photosensitive drum and the like, a paper transport section including a pair of timing rollers 15 and the like, paper feeder 7, fixing device 9, paper discharge device 10, and reading section 51. Paper feeder 7 includes a plurality of paper feed trays 16 and paper feed rollers 17, and each paper feed tray 16 stores paper of a different size.

[0112] 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 P and sends the sheets P to a conveying path. The timing rollers 15 convey the sheets P on the conveying path to the image forming means 50.

[0113] The image forming means 50 forms a toner image on the paper P. Specifically, the image forming means 50 includes a photosensitive drum, a charging roller, an exposure device, a developing device, a replenishing device, a transfer roller, a cleaning device, and a charge removing device. The toner image represents, for example, an image of an original Q. The fixing device 9 applies heat and pressure to the toner image to fix the toner image to the paper P. The paper P on which the toner image has been fixed is transported to the paper discharge device 10 by a transport roller or the like. The paper discharge device 10 discharges the paper P outside the image forming apparatus 100.

[0114] Next, a fixing device 9 of this embodiment will be described. Descriptions of configurations common to the fixing devices of the above-mentioned embodiments will be omitted as appropriate.

[0115] As shown in FIG. 30, 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 heat equalizing plate 28, and the like.

[0116] 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.

[0117] The fixing belt 20 has a polyimide base and a release layer, and does not have an elastic layer. The release layer is made of a heat-resistant film material such as fluororesin. The outer diameter of the fixing belt 20 is about 24 mm.

[0118] 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.

[0119] 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 have an overall thickness of 1 mm. The width Y of the heater 22 in the array crossing direction is 13 mm.

[0120] As shown in FIG. 31, the conductor layer of the heater 22 includes a plurality of resistance heating elements 31, a power supply line 33, and electrode portions 34A to 34C. In this embodiment, as shown in the enlarged view of FIG. 31, the resistance heating elements 31 are divided in the arrangement direction to form intervals B as divided regions (although the intervals B are illustrated only in the enlarged view in FIG. 31, the intervals B are actually provided between all of the resistance heating elements 31). The resistance heating elements 31 form three heat generating portions 35A to 35C. By passing a current through the electrode portions 34A and 34B, the heat generating portions 35A and 35C generate heat. By passing a current through the electrode portions 34A and 34C, the heat generating portion 35B generates heat. For example, when performing a fixing operation on a small size paper, the heat generating portion 35B is made to generate heat, and when performing a fixing operation on a large size paper, all of the heat generating portions are made to generate heat.

[0121] As shown in Fig. 32, the heater holder 23 holds the heater 22 and the first heat equalizing plate 28 in the 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, a wall portion 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 a wall portion 23d3 provided on the inside of the heater holder 23 on both sides in the arrangement crossing direction. The heater holder 23 has a guide rib 26. The heater holder 23 is formed of LCP (liquid crystal polymer).

[0122] As shown in FIG. 33, connector 55 includes a housing made of resin (for example, LCP), and a plurality of contact terminals provided in the housing.

[0123] The connector 55 is attached so as to sandwich the heater 22 and the heater holder 23 from the front and back sides together. In this state, each contact terminal comes into contact (pressure-welded) with each electrode portion of the heater 22, electrically connecting the heat generating portion 35 and the power source provided in the image forming apparatus via the connector 55. This enables power to be supplied from the power source to the heat generating portion 35. Note that in order to ensure connection with the connector 55, at least a portion of each electrode portion 34 is not covered with an insulating layer and is exposed.

[0124] The flanges 53 are provided on both sides of the fixing belt 20 in the arrangement direction, and hold both ends of the fixing belt 20 from the inside of the belt. The flanges 53 are fixed to the housing of the fixing device 9. The flanges 53 are inserted into both ends of the stays 24 (see the arrow directions from the flanges 53 in FIG. 33).

[0125] The attachment direction of the connector 55 to the heater 22 and the heater holder 23 is the direction that intersects the arrangement of the heaters (see the direction of the arrow from the connector 55 in FIG. 33). When the connector 55 is attached to the heater holder 23, a convex portion provided on one of the connector 55 and the heater holder 23 may be engaged with a concave portion provided on the other, and the convex portion may move relatively within the concave portion. The connector 55 is attached to the heater 22 and the heater holder 23 on one side of the arrangement direction, opposite to the side on which the drive motor of the pressure roller 21 is provided.

[0126] 34, thermistors 25 are provided on the center side and end side of the arrangement direction of fixing belt 20, facing the inner circumferential surface of fixing belt 20. Heater 22 is controlled based on the temperatures detected by the thermistors 25 on the center side and end side of the arrangement direction of fixing belt 20.

[0127] Thermostats 27 are provided on the central side and end sides of the arrangement direction of fixing belt 20, facing the inner circumferential surface of fixing belt 20. When the temperature of fixing belt 20 detected by thermostat 27 exceeds a predetermined threshold value, power supply to heater 22 is stopped.

[0128] 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).

[0129] 35, 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 inside the slide groove 53a, so that the fixing belt 20 can move in the direction in which the fixing belt 20 approaches and separates from the pressure roller 21.

[0130] In the fixing device 9 described above, the lengths of the main heat generating region D, the first heat equalizing plate 28, the base material 30 of the heater 22, etc. can be set as in the above-described embodiment. This makes it possible to suppress temperature unevenness in the longitudinal direction of the fixing belt 20 with an inexpensive configuration.

[0131] 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, it is possible to suppress temperature unevenness in the longitudinal direction of the rotating member with an inexpensive configuration.

[0132] Although an embodiment of the present invention has been described above, the present invention is not limited to the above-described embodiment, and it goes without saying that various modifications can be made without departing from the gist of the present invention.

[0133] 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.

[0134] Examples of 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, and the like.

[0135] For example, aspects of the present invention are as follows. <1> A rotating member; a heating element having a base material and a resistance heating element, the heating element heating the rotating member; A heating device comprising: a high thermal conductivity member having a thermal conductivity higher than that of the base material, the substrate and the highly thermally conductive member extend in a longitudinal direction of the rotating member; a region in the longitudinal direction of the rotating member where the resistance heating element is provided is defined as a main heating region, Of the two sides of the main heat generating region with respect to the central position in the longitudinal direction, the side on which the base material protrudes less with respect to the main heat generating region is defined as a first side in the longitudinal direction, and the side on which the base material protrudes more with respect to the main heat generating region is defined as a second side in the longitudinal direction. On the first side, the amount of protrusion of the main heating area in the longitudinal direction with respect to a maximum passing area, which is a passing area in the longitudinal direction of a recording medium with the maximum width that the heating device can accommodate, is L 1L [mm], the amount of protrusion of the high thermal conductivity member in the longitudinal direction with respect to the maximum passing area is L 2L [mm], L 2L -L 1L =L 3L [mm], On the second side, the amount of protrusion of the main heat generating region with respect to the maximum passing region in the longitudinal direction is L 1R [mm], the amount of protrusion of the high thermal conductivity member in the longitudinal direction with respect to the maximum passing area is L 2R [mm] 、 L 2R -L 1R =L 3R [mm], the heating device is characterized by satisfying the following formula (1) and formula (2). L 1R ≦L 2R ≦L 1R +1 ···(1) 0≦L 3R <L 3L (2) <2> A rotating member; a heating element having a base material and a resistance heating element, the heating element heating the rotating member; a pressure member having an elastic layer and pressing the rotating member; A heating device comprising: a high thermal conductivity member having a thermal conductivity higher than that of the base material, the substrate and the highly thermally conductive member extend in a longitudinal direction of the rotating member; a region in the longitudinal direction of the rotating member where the resistance heating element is provided is defined as a main heating region, Of the two sides of the main heat generating region with respect to the center position in the longitudinal direction, the side on which the elastic layer protrudes less with respect to the main heat generating region is defined as a first side in the longitudinal direction, and the side on which the elastic layer protrudes more with respect to the main heat generating region is defined as a second side in the longitudinal direction. On the first side, the amount of protrusion of the main heating area in the longitudinal direction with respect to a maximum passing area, which is a passing area in the longitudinal direction of a recording medium with the maximum width that the heating device can accommodate, is L 1L [mm], the amount of protrusion of the high thermal conductivity member in the longitudinal direction with respect to the maximum passing area is L 2L [mm], L 2L -L 1L =L 3L [mm], On the second side, the amount of protrusion of the main heat generating region with respect to the maximum passing region in the longitudinal direction is L 1R [mm], the amount of protrusion of the high thermal conductivity member in the longitudinal direction with respect to the maximum passing area is L 2R [mm] 、 L 2R -L 1R =L 3R [mm], the heating device is characterized by satisfying the following formula (3) and formula (4). L 1R ≦L 2R ≦L 1R +1 ···(3) 0≦L 3R <L 3L (4) <3> A rotating member; a heating element that includes a base material, a resistive heating element, and a conductor and heats the rotating member; A heating device comprising: a high thermal conductivity member having a thermal conductivity higher than that of the base material, the substrate and the highly thermally conductive member extend in a longitudinal direction of the rotating member; a region in the longitudinal direction of the rotating member where the resistance heating element is provided is defined as a main heating region, Of the two sides of the main heat generating region with respect to the center position in the longitudinal direction, the side on which the conductor protrudes less from the main heat generating region is defined as a first side in the longitudinal direction, and the side on which the conductor protrudes more from the main heat generating region is defined as a second side in the longitudinal direction. On the first side, the amount of protrusion of the main heating area in the longitudinal direction with respect to a maximum passing area, which is a passing area in the longitudinal direction of a recording medium with the maximum width that the heating device can accommodate, is L 1L [mm], the amount of protrusion of the high thermal conductivity member in the longitudinal direction with respect to the maximum passing area is L 2L [mm], L 2L -L 1L =L 3L [mm], On the second side, the amount of protrusion of the main heat generating region with respect to the maximum passing region in the longitudinal direction is L 1R [mm], the amount of protrusion of the high thermal conductivity member in the longitudinal direction with respect to the maximum passing area is L 2R [mm] 、 L 2R -L 1R =L 3R [mm], the heating device is characterized by satisfying the following formulas (5) and (6). L 1R ≦L 2R ≦L 1R +1 ···(5) 0≦L 3R <L 3L (6) <4> A rotating member; a heating element having a base material and a resistance heating element, the heating element heating the rotating member; A heating device comprising: a high thermal conductivity member having a thermal conductivity higher than that of the base material, the substrate and the highly thermally conductive member extend in a longitudinal direction of the rotating member; If the region in the longitudinal direction of the rotating member where the resistance heating element is provided is defined as a main heating region, Of the two sides of the rotating member in the longitudinal direction with respect to the center position of the main heat generating region, the side with the larger heat distribution of the heating body is defined as a first side in the longitudinal direction, and the side with the smaller heat distribution of the heating body is defined as a second side in the longitudinal direction. On the first side, the amount of protrusion of the main heating area in the longitudinal direction with respect to a maximum passing area, which is a passing area in the longitudinal direction of a recording medium with the maximum width that the heating device can accommodate, is L 1L [mm], the amount of protrusion of the high thermal conductivity member in the longitudinal direction with respect to the maximum passing area is L 2L [mm], L 2L -L 1L =L 3L [mm], On the second side, the amount of protrusion of the main heat generating region with respect to the maximum passing region in the longitudinal direction is L 1R [mm], the amount of protrusion of the high thermal conductivity member in the longitudinal direction with respect to the maximum passing area is L 2R [mm] 、 L 2R -L 1R =L 3R [mm], the heating device is characterized by satisfying the following formulas (7) and (8). L 1R ≦L 2R ≦L 1R +1 ···(7) 0≦L 3R <L 3L (8) <5> A rotating member; a heating element having a base material and a resistance heating element, the heating element heating the rotating member; A heating device comprising: a high thermal conductivity member having a thermal conductivity higher than that of the base material, the substrate and the highly thermally conductive member extend in a longitudinal direction of the rotating member; If the region in the longitudinal direction of the rotating member where the resistance heating element is provided is defined as a main heating region, Of the two sides of the maximum passing area, which is the passing area of ​​the recording medium with the maximum width that the heating device can accommodate, the side on which the length of the substrate is shorter is defined as a first side in the longitudinal direction, and the side on which the length of the substrate is longer is defined as a second side in the longitudinal direction. On the first side, the amount of protrusion of the main heat generating region with respect to the maximum passing region in the longitudinal direction is L 1L [mm], the amount of protrusion of the high thermal conductivity member in the longitudinal direction with respect to the maximum passing area is L 2L [mm], L 2L -L 1L =L 3L [mm], On the second side, the amount of protrusion of the main heat generating region with respect to the maximum passing region in the longitudinal direction is L 1R [mm], the amount of protrusion of the high thermal conductivity member in the longitudinal direction with respect to the maximum passing area is L 2R [mm] 、 L 2R -L 1R =L 3R [mm], the heating device is characterized by satisfying the following formulas (9) and (10). L 1R ≦L 2R ≦L 1R +1 ···(9) 0≦L 3R <L 3L (10) <6> The amount of protrusion of the substrate on the first side in the longitudinal direction relative to the maximum passing area is L 4L [mm], the amount of protrusion of the substrate on the second side in the longitudinal direction relative to the maximum passing area L 4R In mm, Satisfying the following formulas (11) and (12) <1> from <5> The heating device described herein is L 2L ≦L 4L (11) L 2R ≦L 4R (12) <7> The thermal conductivity of the base material is λ1, and the thermal conductivity of the high thermal conductivity member is λ2, The volume of the protruding portion of the first side relative to the main heat generating region of the substrate is defined as V 1L The volume of the protruding portion of the high thermal conductivity member relative to the main heat generation area is V 2L , The volume of the protruding portion of the second side relative to the main heat generating region of the substrate is defined as V 1R The volume of the protruding portion of the high thermal conductivity member relative to the main heat generation area is V 2R year, The integrated value λ1×V of the volume and thermal conductivity of the protruding portion with respect to the maximum passing area of ​​the substrate on the first side 1L and the integrated value λ2×V of the volume and thermal conductivity of the protruding portion of the high thermal conductivity member relative to the maximum passing area. 2L The sum of these values ​​is A L = λ1 × V 1L +λ2×V 2L and the integrated value λ1×V of the volume and thermal conductivity of the protruding portion with respect to the maximum passing area of ​​the substrate on the second side. 1R and the integrated value λ2×V of the volume and thermal conductivity of the protruding portion of the high thermal conductivity member relative to the maximum passing area. 2R The sum of these values ​​is A R = λ1 × V 1R +λ2×V 2R Then, the following equation (13) is satisfied. <1> from <6> The heating device according to any one of the preceding claims. 0.6≦A L / A R ≦1.4 (13) <8> The following formula (14) is satisfied <7> The heating device described herein is 0.8≦A L / A R ≦1.2 (14) <9> The high thermal conductivity member is made of aluminum. <1> from <8> The heating device according to any one of the preceding claims. <10> Grease is placed between the heating body and the rotating member. <1> from <9> The heating device according to any one of the preceding claims. <11> <1> from <10> The fixing device includes any one of the heating devices and fixes an image by heat. <12> <11> An image forming apparatus including the fixing device described above. [Explanation of symbols]

[0136] 1. Image forming device 9 Fixing device (heating device) 20 Fixing belt (rotating member) 21 Pressure roller (pressure member) 21b Elastic layer 22 Heater (heating element) 28 First heat equalizing plate (high thermal conductivity material) 30 Base material 31 Resistance heating element 33A, 33B, 33C feed line (conductor) D Main heating area D1 Center position of main heating area E Maximum paper passing area (area through which the widest recording medium can pass) E1 Center position of maximum paper passing area (center position of maximum width recording medium) X Longitudinal direction [Prior art documents] [Patent documents]

[0137] [Patent Document 1] JP 2015-176085 A

Claims

1. A rotating member; a heating element having a base material and a resistance heating element, the heating element heating the rotating member; A heating device comprising: a high thermal conductivity member having a thermal conductivity higher than that of the base material, the substrate and the highly thermally conductive member extend in a longitudinal direction of the rotating member; a region in the longitudinal direction of the rotating member where the resistance heating element is provided is defined as a main heating region, Of the two sides of the main heat generating region with respect to the central position in the longitudinal direction, the side on which the base material protrudes less with respect to the main heat generating region is defined as a first side in the longitudinal direction, and the side on which the base material protrudes more with respect to the main heat generating region is defined as a second side in the longitudinal direction. On the first side, the amount of protrusion of the main heat generating area in the longitudinal direction with respect to a maximum passing area, which is a passing area in the longitudinal direction of a recording medium with the maximum width that the heating device can accommodate, is L １Ｌ [mm], the amount of protrusion of the high thermal conductivity member in the longitudinal direction with respect to the maximum passing area is L ２Ｌ [mm], L ２Ｌ -L １Ｌ = L ３Ｌ [mm], On the second side, the amount of protrusion of the main heat generating region with respect to the maximum passing region in the longitudinal direction is L １Ｒ [mm], the amount of protrusion of the high thermal conductivity member in the longitudinal direction with respect to the maximum passing area is L ２Ｒ [mm] 、 L ２Ｒ -L １Ｒ = L ３Ｒ A heating device characterized in that, where x is the distance between the inner wall of the heating device and the outer wall of the heating device, and m is the distance between the inner wall of the heating device and the outer wall of the heating device, the heating device satisfies the following formulas (1) and (2): L １Ｒ ≦L ２Ｒ ≦L １Ｒ +1 ・・・(1) 0≦L ３Ｒ <L ３Ｌ ・・・(2)

2. A rotating member; a heating element having a base material and a resistance heating element, the heating element heating the rotating member; a pressure member having an elastic layer and pressing the rotating member; A heating device comprising: a high thermal conductivity member having a thermal conductivity higher than that of the base material, the substrate and the highly thermally conductive member extend in a longitudinal direction of the rotating member; a region in the longitudinal direction of the rotating member where the resistance heating element is provided is defined as a main heating region, Of the two sides of the main heat generating region with respect to the center position in the longitudinal direction, the side on which the elastic layer protrudes less with respect to the main heat generating region is defined as a first side in the longitudinal direction, and the side on which the elastic layer protrudes more with respect to the main heat generating region is defined as a second side in the longitudinal direction. On the first side, the amount of protrusion of the main heat generating area in the longitudinal direction with respect to a maximum passing area, which is a passing area in the longitudinal direction of a recording medium with the maximum width that the heating device can accommodate, is L １Ｌ [mm], the amount of protrusion of the high thermal conductivity member in the longitudinal direction with respect to the maximum passing area is L ２Ｌ [mm], L ２Ｌ -L １Ｌ = L ３Ｌ [mm], On the second side, the amount of protrusion of the main heat generating region with respect to the maximum passing region in the longitudinal direction is L １Ｒ [mm], the amount of protrusion of the high thermal conductivity member in the longitudinal direction with respect to the maximum passing area is L ２Ｒ [mm] 、 L ２Ｒ -L １Ｒ = L ３Ｒ A heating device characterized in that, when the distance between the inner wall and the outer wall is expressed in mm, the following formulas (3) and (4) are satisfied. L １Ｒ ≦L ２Ｒ ≦L １Ｒ +1 ・・・(3) 0≦L ３Ｒ <L ３Ｌ ・・・(4)

3. A rotating member; a heating element that includes a base material, a resistive heating element, and a conductor and heats the rotating member; A heating device comprising: a high thermal conductivity member having a thermal conductivity higher than that of the base material, the substrate and the highly thermally conductive member extend in a longitudinal direction of the rotating member; a region in the longitudinal direction of the rotating member where the resistance heating element is provided is defined as a main heating region, Of the two sides of the main heat generating region with respect to the center position in the longitudinal direction, the side on which the conductor protrudes less from the main heat generating region is defined as a first side in the longitudinal direction, and the side on which the conductor protrudes more from the main heat generating region is defined as a second side in the longitudinal direction. On the first side, the amount of protrusion of the main heat generating area in the longitudinal direction with respect to a maximum passing area, which is a passing area in the longitudinal direction of a recording medium with the maximum width that the heating device can accommodate, is L １Ｌ [mm], the amount of protrusion of the high thermal conductivity member in the longitudinal direction with respect to the maximum passing area is L ２Ｌ [mm], L ２Ｌ -L １Ｌ = L ３Ｌ [mm], On the second side, the amount of protrusion of the main heat generating region with respect to the maximum passing region in the longitudinal direction is L １Ｒ [mm], the amount of protrusion of the high thermal conductivity member in the longitudinal direction with respect to the maximum passing area is L ２Ｒ [mm] 、 L ２Ｒ -L １Ｒ = L ３Ｒ A heating device characterized in that, when the distance between the inner wall of the heating device and the outer wall of the heating device is [mm], the following formulas (5) and (6) are satisfied. L １Ｒ ≦L ２Ｒ ≦L １Ｒ +1 ・・・(5) 0≦L ３Ｒ <L ３Ｌ ・・・(6)

4. A rotating member; a heating element having a base material and a resistance heating element, the heating element heating the rotating member; A heating device comprising: a high thermal conductivity member having a thermal conductivity higher than that of the base material, the substrate and the highly thermally conductive member extend in a longitudinal direction of the rotating member; If the region in the longitudinal direction of the rotating member where the resistance heating element is provided is defined as a main heating region, Of the two sides of the rotating member in the longitudinal direction with respect to the center position of the main heat generating region, the side with the larger heat distribution of the heating body is defined as a first side in the longitudinal direction, and the side with the smaller heat distribution of the heating body is defined as a second side in the longitudinal direction. On the first side, the amount of protrusion of the main heat generating area in the longitudinal direction with respect to a maximum passing area, which is a passing area in the longitudinal direction of a recording medium with the maximum width that the heating device can accommodate, is L １Ｌ [mm], the amount of protrusion of the high thermal conductivity member in the longitudinal direction with respect to the maximum passing area is L ２Ｌ [mm], L ２Ｌ -L １Ｌ = L ３Ｌ [mm], On the second side, the amount of protrusion of the main heat generating region with respect to the maximum passing region in the longitudinal direction is L １Ｒ [mm], the amount of protrusion of the high thermal conductivity member in the longitudinal direction with respect to the maximum passing area is L ２Ｒ [mm] 、 L ２Ｒ -L １Ｒ = L ３Ｒ A heating device characterized in that, when the distance between the inner wall and the outer wall is [mm], the following formulas (7) and (8) are satisfied. L １Ｒ ≦L ２Ｒ ≦L １Ｒ +1 ・・・(7) 0≦L ３Ｒ <L ３Ｌ ・・・(8)

5. A rotating member; a heating element having a base material and a resistance heating element, the heating element heating the rotating member; A heating device comprising: a high thermal conductivity member having a thermal conductivity higher than that of the base material, the substrate and the highly thermally conductive member extend in a longitudinal direction of the rotating member; If the region in the longitudinal direction of the rotating member where the resistance heating element is provided is defined as a main heating region, Of the two sides of the maximum passing area, which is the passing area of ​​the recording medium with the maximum width that the heating device can accommodate, the side on which the length of the substrate is shorter is defined as a first side in the longitudinal direction, and the side on which the length of the substrate is longer is defined as a second side in the longitudinal direction. On the first side, the amount of protrusion of the main heat generating region with respect to the maximum passing region in the longitudinal direction is L １Ｌ [mm], the amount of protrusion of the high thermal conductivity member in the longitudinal direction with respect to the maximum passing area is L ２Ｌ [mm], L ２Ｌ -L １Ｌ = L ３Ｌ [mm], On the second side, the amount of protrusion of the main heat generating region with respect to the maximum passing region in the longitudinal direction is L １Ｒ [mm], the amount of protrusion of the high thermal conductivity member in the longitudinal direction with respect to the maximum passing area is L ２Ｒ [mm] 、 L ２Ｒ -L １Ｒ = L ３Ｒ A heating device characterized in that, when the distance between the inner wall of the heating device and the outer wall of the heating device is [mm], the following formulas (9) and (10) are satisfied. L １Ｒ ≦L ２Ｒ ≦L １Ｒ +1 ・・・(9) 0≦L ３Ｒ <L ３Ｌ ・・・(10)

6. The amount of protrusion of the substrate on the first side in the longitudinal direction relative to the maximum passing area is L ４Ｌ [mm], the amount of protrusion of the substrate on the second side in the longitudinal direction relative to the maximum passing area L ４Ｒ In [mm], The heating device according to claim 1 , which satisfies the following formulas (11) and (12). L ２Ｌ ≦L ４Ｌ ・・・(11) L ２Ｒ ≦L ４Ｒ ・・・(12)

7. The thermal conductivity of the substrate is λ １ , the thermal conductivity λ of the high thermal conductivity member ２ year, The volume of the protruding portion of the first side relative to the main heat generating region of the substrate is defined as V １Ｌ The volume of the protruding portion of the high thermal conductivity member relative to the main heat generation region is V ２Ｌ , The volume of the protruding portion of the second side relative to the main heat generating region of the substrate is defined as V １Ｒ The volume of the protruding portion of the high thermal conductivity member relative to the main heat generation region is V ２Ｒ year, The integrated value λ of the volume and thermal conductivity of the protruding portion with respect to the maximum passing area of ​​the substrate on the first side １ ×V １Ｌ and an integrated value λ of the volume and thermal conductivity of the protruding portion with respect to the maximum passing area of ​​the high thermal conductivity member. ２ ×V ２Ｌ The sum of these is A Ｌ = λ １ ×V １Ｌ +λ ２ ×V ２Ｌ and a cumulative value λ of the volume and thermal conductivity of the protruding portion with respect to the maximum passing area of ​​the substrate on the second side. １ ×V １Ｒ and an integrated value λ of the volume and thermal conductivity of the protruding portion with respect to the maximum passing area of ​​the high thermal conductivity member. ２ ×V ２Ｒ The sum of these is A Ｒ = λ １ ×V １Ｒ +λ ２ ×V ２Ｒ The heating device according to claim 1, which satisfies the following formula (13). 0.6≦A Ｌ / A Ｒ ≦1.4 ・・・(13)

8. The heating device according to claim 7, which satisfies the following formula (14). 0.8≦A Ｌ / A Ｒ ≦1.2 ・・・(14)

9. 2. The heating device according to claim 1, wherein said highly heat-conductive member is made of aluminum.

10. 2. The heating device according to claim 1, wherein grease is interposed between said heating body and said rotating member.

11. A fixing device comprising the heating device according to claim 1 , for fixing an image by heat.

12. An image forming apparatus comprising the fixing device according to claim 11.

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