Heating device, fixing device, image forming device

Abstract

To form an excellent sliding state between a rotary member and a heating body.SOLUTION: A fixation device 9 comprises: a fixation belt 20; a pressure roller 21 which forms a fixation nip N2 between the fixation belt 20 and itself; a heater 22; a heater holder 23; and a grease 90 which is applied to a sliding surface 30a with respect to the fixation belt 20 of the heater 22 or an inner surface of the fixation belt 20. When a nip part formed by the heater 22 and an inner surface of the fixation belt 20 is a sliding nip N1, a grease reservoir 40 holding the grease 90 is provided between the fixation belt 20 and the heater 22 on an outer side of the sliding nip N1 in a sheet conveyance direction. A resistance heating element 31 is provided on a rear surface 30b on a side opposite to the sliding nip N1 side of a base material 30. When an application amount of the grease 90 is P, an irregularity height of the inner surface of the fixation belt 20 is A, a width in a longitudinal direction of the fixation belt 20 is X1, a peripheral length of the fixation belt 20 is B, a specific gravity of the grease 90 is C and volume of the grease reservoir 40 is D, a following formula is satisfied: A×X1×B×C≤P≤D×C.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 Art

[0002] As a fixing device provided in an electrophotographic image forming apparatus, there is a configuration in which an endless fixing belt (rotating member) is heated by a planar heater (heating element) provided on the inner surface thereof. And, in such a fixing device, a lubricant for reducing the sliding resistance between the fixing belt and the heater is applied to the inner surface of the fixing belt.

[0003] In such a fixing device, it is required to interpose an appropriate amount of lubricant between the fixing belt and the heater to suppress wear of the fixing belt and maintain the driving torque of the pressure roller at an appropriate value.

[0004] For example, in the fixing device of Patent Document 1 (Japanese Patent Application Laid-Open No. 2010-204587), a rough surface portion is formed at the axial center portion of the inner peripheral surface of the fixing belt. Thereby, the ability of the fixing belt to hold the lubricant is improved.

[0005] However, even with the configuration as in Patent Document 1, depending on the amount of lubricant applied, the heating element, and the structure of the holding member that holds the heating element, it may not be possible to hold an appropriate lubricant between the rotating member and the heating element.

Summary of the Invention

Problems to be Solved by the Invention

[0006] It is an object to form a good sliding state between the rotating member and the heating element.

Means for Solving the Problems

[0007] To solve the above problems, the present invention provides a rotating member, a pressurizing member that forms an outer nip portion between itself and the rotating member, a heating element provided inside the rotating member and having a base material and a resistance heating element, a holding member having a recess for holding the heating element, and a lubricant applied to the sliding surface of the heating element with respect to the rotating member or to the inner surface of the rotating member. A high thermal conductivity member formed from a material with higher thermal conductivity than the aforementioned substrate, A heating device comprising the above, wherein the nip portion formed by the heating element and the inner surface of the rotating member is a sliding nip, Direction of media transport A lubricant holding region is provided on the outside of the sliding nip, between the rotating member and the heating element, the resistance heating element is provided on the surface of the base material opposite to the sliding nip side, the amount of lubricant applied is P, and the height of the unevenness on the inner surface of the rotating member average value If A is the length of the rotating member, X1 is the longitudinal width of the rotating member, B is the circumference of the rotating member, C is the specific gravity of the lubricant, and D is the volume of the lubricant holding area, then the following equation is satisfied. death, A × X1 × B × C ≤ P ≤ D × C The resistance heating elements are provided in multiple locations on the substrate in the longitudinal direction, and the high thermal conductivity member is provided across positions corresponding to the resistance heating elements in the longitudinal direction and positions corresponding to the spaces between the resistance heating elements, and contacts the heating element from the side opposite to the sliding nip side. It is characterized by the following: [Effects of the Invention]

[0008] According to the present invention, a good sliding state can be formed between the rotating member and the heating element. [Brief explanation of the drawing]

[0009] [Figure 1] This is a schematic diagram of the image forming apparatus. [Figure 2] This is a side cross-sectional view showing the schematic configuration of a fixing device according to one embodiment of the present invention. [Figure 3] This is a plan view of the heater. [Figure 4] This diagram shows the power supply to the heater. [Figure 5] Figure 3 is a plan view of a heater with a different shape of resistance heating element. [Figure 6] Figures 3 and 5 are plan views of heaters with different shapes of resistance heating elements. [Figure 7] Figures 3, 5, and 6 are plan views of heaters with different shapes of resistance heating elements. [Figure 8] It is a diagram showing the longitudinal width of the heater and the first high heat conductivity member. [Figure 9] It is a cross-sectional view of a fixing device showing a sliding nip and a fixing nip. [Figure 10] It is a diagram showing the relationship between the sliding nip and the fixing nip. [Figure 11] It is a diagram showing the temperature distribution in the arrangement direction of the fixing belt, where (a) is a plan view of the heater and (b) is a diagram showing the temperature distribution of the fixing belt. [Figure 12] It is a diagram showing the divided region of the heater in FIG. 5. [Figure 13] It is a diagram showing a divided region with a different shape from FIG. 12. [Figure 14] It is a diagram showing the divided region of the heater in FIG. 6. [Figure 15] It is a perspective view of the heater, the first high heat conductivity member, and the heater holder. [Figure 16] It is a plan view of the heater showing the arrangement of the first high heat conductivity member. [Figure 17] It is a plan view of the heater showing a different example of the arrangement of the first high heat conductivity member. [Figure 18] It is a plan view of the heater showing an even more different example of the arrangement of the first high heat conductivity member. [Figure 19] It is a side cross-sectional view showing the schematic configuration of a fixing device according to an embodiment different from FIG. 2. [Figure 20] It is a perspective view of the heater, the first high heat conductivity member, the second high heat conductivity member, and the heater holder. [Figure 21] It is a plan view of the heater showing the arrangement of the first high heat conductivity member and the second high heat conductivity member. [[ID=四十二]] [Figure 22] [[ID=四十三]]It is a plan view of the heater showing an example of a different arrangement of the first high heat conductivity member and the second high heat conductivity member. [[ID=四十四]] [[ID=四十五]] [Figure 23] [[ID=四十六]]It is a diagram showing the atomic crystal structure of graphene. [[ID=四十七]] [[ID=四十八]] [Figure 24] [[ID=四十九]]It is a diagram showing the atomic crystal structure of graphite. [[ID=五十]] [[ID=五十一]] [Figure 25] [[ID=五十二]]It is a plan view showing a heater with a different arrangement of the second high heat conductivity member from FIG. 21. [[ID=五十三]] [Figure 26] Figures 2 and 19 show a schematic side cross-sectional view of a fixing device in a different embodiment. [Figure 27] This is a side cross-sectional view showing a schematic configuration of a fixing device different from the one described above. [Figure 28] This is a schematic diagram of an image forming apparatus different from Figure 1. [Figure 29] This is a side cross-sectional view showing the schematic configuration of a fixing device according to one embodiment of the present invention. [Figure 30] Figure 29 is a plan view of the heater in the fixing device. [Figure 31] This is a perspective view of the heater and heater holder. [Figure 32] This is a perspective view showing the connector attached to the heater. [Figure 33] This diagram shows the arrangement of the thermistor and thermostat. [Figure 34] This is a diagram showing the groove portion of the flange. [Modes for carrying out the invention]

[0010] The present invention will be described below with reference to the attached drawings. In each drawing used to explain the present invention, components such as members and parts having the same function or shape will be given the same reference numerals to the extent possible so that they can be distinguished, and their description will be omitted after they have been described once.

[0011] Figure 1 is a schematic diagram of an image forming apparatus according to one embodiment of the present invention. The image forming apparatus of this embodiment includes a fixing device for fixing a toner image on paper to the paper, as one aspect of the heating device of the present invention.

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

[0013] The image forming apparatus 100 also includes an exposure device 6, a paper feed device 7, a transfer device 8, a fixing device 9 as a heating device, and a paper discharge device 10. The exposure device 6 exposes the surface of each photoreceptor 2 and forms an electrostatic latent image on its surface. The paper feed device 7 supplies paper P, which is a recording medium, to the paper transport path 14. The transfer device 8 transfers the toner image formed on each photoreceptor 2 to the paper P. The fixing device 9 fixes the toner image transferred to the paper P to the surface of the paper P. The paper discharge device 10 discharges the paper P outside the apparatus. Each image forming unit 1, photoreceptor 2, charging device 3, exposure device 6, transfer device 8, etc., constitutes an image forming means for forming an image on paper.

[0014] The transfer device 8 includes 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 image on each photoreceptor 2 to the intermediate transfer belt 11. The secondary transfer rollers 13 transfer the toner image transferred on the intermediate transfer belt 11 to the paper P. Each of the plurality of primary transfer rollers 12 is in contact with the photoreceptor 2 via the intermediate transfer belt 11. As a result, the intermediate transfer belt 11 and each photoreceptor 2 are in contact with each other, and a primary transfer nip is formed between them. On the other hand, the secondary transfer roller 13 is in contact with one of the rollers that stretches 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] Furthermore, a pair of timing rollers 15 are provided in the paper transport path 14, between the paper feed device 7 and the secondary transfer nip (secondary transfer roller 13).

[0016] Next, the printing operation of the image forming apparatus described above will be explained with reference to Figure 1.

[0017] When a print operation is initiated, in each image unit 1Y, 1M, 1C, and 1Bk, the photoreceptor 2 is driven to rotate clockwise as shown in Figure 1, and the surface of the photoreceptor 2 is charged to a uniform high potential by the charging device 3. Next, based on the image information of the original document read by the document reader or the print information instructed from the terminal, the exposure device 6 exposes the surface of each photoreceptor 2. As a result, the potential of the exposed area decreases, and an electrostatic latent image is formed. Then, toner is supplied from the developing device 4 to this electrostatic latent image, and a toner image is formed on each photoreceptor 2.

[0018] The toner images formed on each photoreceptor 2 rotate with the rotation of each photoreceptor 2 and reach the primary transfer nip (the position of the primary transfer roller 12). The toner images are then transferred sequentially onto the intermediate transfer belt 11, which rotates counterclockwise as shown in Figure 1. 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) as the intermediate transfer belt 11 rotates. At the secondary transfer nip, the toner images are transferred to the paper P that has been transported. This paper P is supplied from the paper feeder 7. The paper P supplied from the paper feeder 7 is stopped by the timing roller 15, and then transported to the secondary transfer nip in time with the toner images on the intermediate transfer belt 11 reaching the secondary transfer nip. Thus, a full-color toner image is carried on the paper P. After the toner image is transferred, any toner remaining on each photoreceptor 2 is removed by the cleaning devices 5.

[0019] The paper P onto which the toner image has been transferred is transported to the fuser unit 9, where the fuser unit 9 fixes the toner image onto the paper P. After that, the paper P is ejected from the device by the paper output unit 10, completing the series of printing operations.

[0020] Next, I will explain the configuration of the fixing device.

[0021] As shown in Figure 2, the fixing device 9 according to this embodiment includes a fixing belt 20, a pressure roller 21, a heater 22 as a heating element, a heater holder 23 as a holding member, a stay 24 as a support member, a thermistor 25 as a temperature sensing member, and a first high thermal conductivity member 28, etc. The fixing belt 20 is an endless belt. The pressure roller 21 contacts the outer circumferential surface of the fixing belt 20, forming a fixing nip N2 as an outer nip portion between the fixing belt 20 and the pressure roller 21. The heater 22 heats the fixing belt 20. The heater holder 23 holds the heater 22. The stay 24 supports the heater holder 23. The thermistor 25 detects the temperature of the first high thermal conductivity member 28.

[0022] The direction perpendicular to the plane of the paper in Figure 2 is the longitudinal direction of the fixing belt 20, the pressure roller 21 as a pressure member, the heater 22, the heater holder 23, the stay 24, the first high heat conductivity member 28, etc. Hereafter, this direction will simply be referred to as the longitudinal direction. This longitudinal direction is also the width direction of the paper being transported, the belt width direction of the fixing belt 20, and the axial direction of the pressure roller 21. The fixing member provided in the fixing device is one form of the rotating member provided in the heating device of the present invention. In the fixing device 9 of this embodiment, the fixing belt 20 is provided as a specific example of this fixing member. Arrow A in Figure 2 is the paper transport direction (recording medium transport direction).

[0023] The fixing belt 20 has, for example, a tubular base made of polyimide (PI) with an outer diameter of 25 mm and a thickness of 50 to 75 μm. A release layer with a thickness of 7 to 20 μm is formed on the outermost layer of the fixing belt 20 using a fluororesin such as PFA or PTFE to enhance durability and ensure release properties. An elastic layer made of rubber or the like with a thickness of 100 to 300 μm may be provided between the base and the release layer. Furthermore, the base of the fixing belt 20 is not limited to polyimide, but may also be a heat-resistant resin such as PEEK, or a metal base such as nickel (Ni) or SUS. The inner circumferential 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, for example, an outer diameter of 20 to 22 mm. The pressure roller 21 has, from the inside out, a core metal 21a, an elastic layer 21b, and a surface layer 21c. The solid core metal 21a is made of a conductive material, and in this embodiment, it is made of iron. The elastic layer 21b is made of a non-conductive material, and in this embodiment, it is made of silicone rubber with a thickness of 3.5 to 4.0 mm. By making the elastic layer 21b a non-conductive layer, it is not necessary to add materials such as fillers to impart conductivity to the elastic layer 21b, and its elasticity and stretchability can be ensured. The surface layer 21c is made of fluororesin with a thickness of 30 to 50 μm.

[0025] The pressure roller 21 is biased toward the fixing belt 20 by the biasing means, causing the pressure roller 21 to press against the heater 22 via the fixing belt 20. This forms a fixing nip N2 between the fixing belt 20 and the pressure roller 21. The pressure roller 21 is also configured to be rotationally driven by a driving means, and as the pressure roller 21 rotates in the direction of the arrow in Figure 2, the fixing belt 20 rotates in conjunction with it.

[0026] 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, and an insulating layer 32 covering the resistance heating element 31. The side of the base material 30 opposite to the side on which the resistance heating element 31 is provided is in contact with the inner circumferential surface of the fixing belt 20, and the heat generated from the resistance heating element 31 is transferred to the fixing belt 20 via the base material 30. In this embodiment, alumina is used for the base material 30. However, the contact of the heater 22 with the inner circumferential surface of the fixing belt 20 may be contact via a conductive member such as a sliding sheet. By applying an AC voltage to the heater 22 from a power supply 200 (see Figure 4), the resistance heating element 31 mainly generates heat.

[0027] The heater holder 23 and stay 24 are positioned on the inner circumference side of the fixing belt 20. The stay 24 is made of a metal channel material, and both ends are supported by the side plates of the fixing device 9. The heater holder 23 and heater 22 are supported by the stay 24, so that when the pressure roller 21 is pressed against the fixing belt 20, the heater 22 can reliably receive the pressing force of the pressure roller 21. This stably forms a fixing nip N2 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 lower than that of the base material 30.

[0028] Since the heater holder 23 is prone to becoming hot due to the heat from the heater 22, it is desirable that it be made of a heat-resistant material. For example, if the heater holder 23 is made of a heat-resistant resin with low thermal conductivity such as LCP, heat transfer from the heater 22 to the heater holder 23 is suppressed. This allows the heater 22 to efficiently heat the fixing belt 20.

[0029] Furthermore, the heater holder 23 is provided with guide sections 26 for guiding the fixing belt 20. The guide sections 26 are provided on the upstream side (below the heater 22 in Figure 2) and the downstream side (above the heater 22 in Figure 2) of the heater 22 in the direction of belt rotation. Multiple guide sections 26 on the upstream and downstream sides are arranged at intervals along the longitudinal direction of the heater 22. Each guide section 26 is formed in a substantially fan shape and has an arc-shaped or convex curved belt-facing surface 260 that extends in the circumferential direction of the belt so as to face the inner circumferential surface of the fixing belt 20.

[0030] The heater holder 23 has a plurality of openings 23a in the longitudinal direction. The openings 23a are openings that penetrate the heater holder 23 in the thickness direction. Thermistors 25 and thermostats described later are provided in these openings 23a. These thermistors 25 and thermostats are pressed against the back surface of the first high heat conductive member 28 by pressure from a spring 29. However, the first high heat conductive member 28 (and the second high heat conductive member described later) may also be provided with openings in a similar manner, so that the thermistors 25 and thermostats are pressed against the back surface of the insulating layer 32 of the heater 22.

[0031] The first high thermal conductivity member 28 is made of a material with a higher thermal conductivity than the base material 30. In this embodiment, the first high thermal conductivity member 28 is made of plate-shaped aluminum. Alternatively, the first high thermal conductivity member 28 may be made of other materials such as copper, silver, graphene, or graphite. By making the first high thermal conductivity member 28 plate-shaped, the positional accuracy of the heater 22 relative to the heater holder 23 and the first high thermal conductivity member 28 can be improved. The first high thermal conductivity member 28 is in contact with the insulating layer 32 of the heater 22.

[0032] Next, we will explain the method for calculating the thermal conductivity described above. When calculating thermal conductivity, first, the thermal diffusivity of the object in question is measured, and this thermal diffusivity is used to calculate the thermal conductivity.

[0033] Thermal diffusivity was measured using a thermal diffusivity / thermal conductivity measuring device (product name: ai-Phase Mobile 1u, manufactured by iPhase Co., Ltd.).

[0034] To convert the above thermal diffusivity to thermal conductivity, the values ​​of density and specific heat capacity are required. A dry automatic densimeter (product name: Accupyc 1330, manufactured by Shimadzu Corporation) was used to measure the density. A differential scanning calorimetry device (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 example, 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 in the above thermal diffusivity measurement by the following equation (1). λ = ρ × C × α ···(1)

[0035] In the fixing device 9 according to this embodiment, when the printing operation is started, the pressure roller 21 is driven to rotate, and the fixing belt 20 starts to rotate in response. At this time, the inner surface of the fixing belt 20 contacts and is guided by the belt-facing surface 260 of the guide part 26, so that the fixing belt 20 rotates stably and smoothly. Power is also supplied to the resistance heating element 31 of the heater 22, which heats the fixing belt 20. When the temperature of the fixing belt 20 reaches a predetermined target temperature (fixing temperature), as shown in Figure 2, the paper P carrying the unfixed toner image is transported between the fixing belt 20 and the pressure roller 21 (fixing nip N2), so that the unfixed toner image is heated and pressurized and fixed to the paper P. The fixing belt 20 is the heated member that is heated by the heater 22.

[0036] Next, the configuration of the heater installed in the fixing device will be described in detail.

[0037] Figure 3 is a plan view of the heater according to this embodiment, showing a conductor such as a resistance heating element 31 provided on the left side of the base material 30 as shown in Figure 2. In the following description, the left side of the base material 30 as shown in Figure 2, opposite to the sliding nip side of the base material 30 (described later), will also be referred to as the back surface 30b of the base material 30. The side of the base material 30 opposite to the back surface 30b, on the sliding nip side, will also be referred to as the front surface 30a of the base material 30.

[0038] As shown in Figure 3, the surface of the plate-shaped substrate 30 is provided with a plurality (four) of resistance heating elements 31, power supply lines 33A and 33B acting as conductors, and a first electrode section 34A and a second electrode section 34B. However, the number of resistance heating elements 31 is not limited to this embodiment.

[0039] In Figure 3, the left-right direction X is the longitudinal direction of the heater 22, etc., and is also the arrangement direction of the multiple resistance heating elements 31. This arrangement direction is the same as the longitudinal direction of the fixing belt 20 and the axial direction of the pressure roller 21. In Figure 3, the up-down direction Y is the paper transport direction (recording medium transport direction). The up-down direction Y is the short-side direction of the heater 22, and is a direction that intersects the arrangement direction of the resistance heating elements 31 (a perpendicular direction in this embodiment), and is different from the thickness direction of the base material 30. Hereafter, the left-right direction X will simply be referred to as the longitudinal direction, and the up-down direction Y will simply be referred to as the short-side direction.

[0040] The heating section 35 is divided into multiple sections in the longitudinal direction by multiple resistance heating elements 31. Each resistance heating element 31 is electrically connected in parallel to a pair of electrode sections 34A and 34B provided at one longitudinal end of the base material 30 (the left end in Figure 3) via power supply lines 33A and 33B. The power supply lines 33A and 33B are made of conductors with a lower resistance value than the resistance heating elements 31. The gap between adjacent resistance heating elements 31 is preferably 0.2 mm or more, and more preferably 0.4 mm or more, from the viewpoint of ensuring insulation between the resistance heating elements 31. If the gap between 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 along the longitudinal direction, the gap is preferably 5 mm or less, and more preferably 1 mm or less.

[0041] The resistive heating element 31 is made of a material with PTC (positive temperature resistance coefficient) characteristics, and has the characteristic that its resistance increases (heater output decreases) as the temperature rises. The temperature resistance coefficient of the resistive heating element 31 is set to, for example, 500 ppm.

[0042] The resistive heating element 31 has PTC characteristics, and the configuration of the heating section 35, which is divided in the longitudinal direction, prevents the fixing belt 20 from overheating when small-sized paper is fed through. In other words, when paper with a width smaller than the overall width of the heating section 35 is fed through, the heat from the fixing belt 20 is not absorbed by the paper in the area outside the paper width, so the temperature of the resistive heating element 31 in that area rises. Since the voltage applied to the resistive heating element 31 is constant, as the temperature of the resistive heating element 31 outside the paper width rises and its resistance value increases, the output (amount of heat generated) decreases relatively, and the temperature rise at the edges is suppressed. In addition, because multiple resistive heating elements 31 are electrically connected in parallel, the temperature rise of the non-feeding area can be suppressed while maintaining the printing speed. Note that the heating elements constituting the heating section 35 may be other than resistive heating elements with PTC characteristics. Also, the resistive heating elements may be arranged in multiple rows in the short direction of the heater 22.

[0043] The resistive heating element 31 can be formed by, for example, applying a paste made of silver palladium (AgPd) or glass powder to a substrate 30 by screen printing or the like, and then firing the substrate 30. In this embodiment, the resistance value of the resistive heating element 31 is set to 80Ω at room temperature. In addition to the materials mentioned above, the resistive material of the resistive heating element 31 may also be a silver alloy (AgPt) or ruthenium oxide (RuO2). The materials for the power supply line 33 and the electrode part 34 can be formed from silver (Ag) or silver palladium (AgPd) by screen printing or the like. The power supply line 33 is composed of a conductor with a resistance value smaller than that of the resistive heating element 31.

[0044] As the material for the base material 30, ceramics such as alumina and aluminum nitride, which have excellent heat resistance and insulation properties, or non-metallic materials such as glass and mica are preferred. In this embodiment, an alumina base material with a width of 8 mm in the short direction, a width of 270 mm in the long direction, and a thickness of 1.0 mm is used. Alternatively, the base material 30 may be constructed by laminating an insulating material onto a conductive material such as a metal. As the metallic material for the base material 30, aluminum and stainless steel are preferred due to their low cost. By constructing the base material 30 from a stainless steel plate, cracking due to thermal stress can be suppressed. Furthermore, in order to improve the uniformity of heating of the heater 22 and enhance image quality, the base material 30 may be constructed from a material with high thermal conductivity such as copper, graphite, or graphene.

[0045] The insulating layer 32 is made of, for example, heat-resistant glass with a thickness of 75 μm. The insulating layer 32 covers the resistive heating element 31 and the power supply line 33, insulating and protecting them.

[0046] Figure 4 shows the power supply circuit to the heater according to this embodiment.

[0047] As shown in Figure 4, in this embodiment, the power supply circuit for supplying power to each resistive heating element 31 is configured by electrically connecting the AC power supply 200 and the electrode portions 34A and 34B of the heater 22. The power supply circuit is also provided with a triac 210 for controlling the amount of power supplied. The amount of power supplied to each resistive heating element 31 is controlled by the control unit 220 via the triac 210 based on the temperature detected by the thermistor 25. The control unit 220 is composed of a microcomputer that includes a CPU, ROM, RAM, I / O interface, etc.

[0048] In this embodiment, thermistors 25 are positioned in the central region of the heater 22 in the longitudinal direction, which is within the minimum paper feed width, and at one end of the heater 22 in the longitudinal direction. Furthermore, a thermostat 27 is positioned at one end of the heater 22 in the longitudinal direction as a power interruption means that interrupts the power supply to the resistance heating element 31 when the temperature of the resistance heating element 31 exceeds a predetermined temperature. The thermistors 25 and thermostat 27 contact the first high thermal conductivity member 28 to detect its temperature.

[0049] In this embodiment, the first electrode portion 34A and the second electrode portion 34B are provided on the same side in the longitudinal direction, but they may be provided on different sides. Furthermore, the resistive heating element 31 is not limited to the shape of this embodiment. As shown in Figure 5, the resistive heating element 31 may be rectangular, or as shown in Figure 6, the resistive heating element 31 may consist of a linear portion, which may be folded to form a substantially parallelogram shape. Also, as shown in Figure 5, the portion extending from the block-shaped resistive heating element 31 towards the power supply line 33 (the portion extending in the short direction) may be part of the resistive heating element 31, or it may be made of the same material as the power supply line 33.

[0050] Alternatively, the heater 22 may have a configuration in which the resistive heating element 31 is not divided in the longitudinal direction. For example, as shown in Figure 7, there may be a configuration in which two resistive heating elements 31 extending in the longitudinal direction are connected in series. The two resistive heating elements 31 are connected to electrode sections 34A and 34B via power supply lines 33A and 33B on one side in the longitudinal direction, respectively. The two resistive heating elements 31 are also connected in series via power supply line 33C on the other side in the longitudinal direction.

[0051] In the following explanation, we will describe the case using the heater 22 shown in Figure 7 as an example. The dimensions of the heater 22 in the short direction Y are 8.0 mm for the base material 30, 1.5 mm for each resistance heating element 31 in the short direction, and 3.0 mm for the spacing between the resistance heating elements 31, so the width Y2 in the short direction of the heating area of ​​the heater 22 is set to 6.0 mm. The heating area of ​​the heater 22 is the main heat-generating area of ​​the heater 22, which is the area within the heater 22 where the resistance heating elements 31 are provided. However, this heating area also includes the gaps between the resistance heating elements 31.

[0052] As shown in Figure 8, the longitudinal width X2 of the heater's heating area is set to 216 mm. The first high-heat-conductivity member 28 has a thickness of 0.3 mm, a longitudinal length X3 of 222 mm, and a transverse width of 10 mm. The longitudinal width X3 of the first high-heat-conductivity member 28 is set to be larger than the longitudinal width X2 of the heater's heating area, so as to cover the entire heating area of ​​the heater. This prevents the resistance heating element 31 of the heater 22 from overheating locally and causing cracks in the heater 22.

[0053] As shown in Figure 9, the fixing belt 20 contacts the pressure roller 21 in the paper transport direction, which is the left-right direction in Figure 9, and forms a fixing nip N2. The inner circumferential surface of the fixing belt 20 also contacts the heater 22 in the paper transport direction, forming a sliding nip N1. The dashed line shown at the bottom of Figure 9 indicates the temperature distribution of the sliding surface 30a of the base material 30 in the paper transport direction.

[0054] The sliding nip N1 refers to the portion where the sliding surfaces of the heater 22 and the fixing belt 20 come into contact with each other at a constant nip pressure. Specifically, the sliding nip is measured by applying Shinmeitan N-RED (manufactured by Nakatani Co., Ltd.) to the surface of the heater 22 and pressurizing the fixing device 9. Then, the surface temperature of the fixing belt 20 is set to 190°C and the fixing device 9 is driven for 10 minutes. After that, the fixing device 9 is disassembled and the surface of the heater 22 is examined, and the portion where the Shinmeitan has peeled off can be observed. This is photographed, and the portion where the Shinmeitan has peeled off is measured using the known width of the heater 22 in the shorter direction, and this portion is defined as the sliding nip N1.

[0055] In a fixing device equipped with the heater 22 as described above, a lubricant is applied to the inner surface of the fixing belt 20 or to the sliding surface 30a of the base material 30, which is the sliding surface of the heater 22, in order to suppress the sliding resistance between the inner surface of the fixing belt 20 and the front surface 30a of the base material 30, which is the sliding surface of the heater 22, and to suppress wear of the fixing belt 20 due to this sliding. In this embodiment, fluorine grease (hereinafter also simply referred to as grease) is used as the lubricant.

[0056] In this embodiment, the heater 22 is held in the recess 23b of the heater holder 23. The heater holder 23 has protrusions 23e on both sides in the paper transport direction. The protrusions 23e protrude toward the fixing belt 20 side from the base material 30 of the heater 22 held in the recess 23b and are in sliding contact with the inner surface of the fixing belt 20.

[0057] The fixing belt 20, pressurized by the pressure roller 21, is pressed toward the sliding surface 30a of the base material 30. As a result, the inner surface of the fixing belt 20 comes into contact with the sliding surface 30a of the base material 30 at the center of the heater 22 in the short direction (left-right direction in Figure 9), forming a sliding nip N1. On the other hand, at both ends of the base material 30 in the short direction, a grease reservoir 40 is formed as a lubricant retention area, which is a space formed between the sliding surface 30a and the inner circumferential surface of the fixing belt 20. Grease is stored in this grease reservoir 40, and in this embodiment in particular, grease 90 is stored on the sliding nip N1 side of the grease reservoir 40. As the grease 90 stored in this grease reservoir 40 is gradually supplied to the sliding nip N1, good sliding performance between the sliding surface 30a of the base material 30 and the inner circumferential surface of the fixing belt 20 can be maintained for a long period of time.

[0058] In order to create a good sliding surface between the inner surface of the fixing belt 20 and the base material 30 of the heater 22, it is necessary to maintain the amount and viscosity of the grease interposed between the sliding surfaces of the fixing belt 20 and the heater 22 at appropriate values. In other words, if the amount of interposed grease is too small, a good sliding surface cannot be created, but if the amount of grease is too large, the grease film thickness will become too large, increasing the sliding load, or causing excessive grease leakage from the ends of the fixing belt 20. Thus, a good sliding surface cannot be created if the viscosity of the grease is too high or too low. Furthermore, the grease retention capacity of the sliding surfaces of the fixing belt 20 and the heater 22 also changes depending on the surface roughness of the sliding surfaces that hold the grease.

[0059] In this embodiment, the base material 30 is formed from a highly smooth ceramic material, and the surface roughness Ra of the sliding surface 30a is set to 0.2 μm or less. Alternatively, a thin film of polyimide or a glass layer may be coated on the sliding surface 30a. These measures suppress wear caused by sliding between the inner surface of the fixing belt 20 and the sliding surface 30a. Furthermore, when the sliding surface 30a is smooth as in this embodiment, the irregularities on the inner surface of the fixing belt 20 greatly affect the grease retention capacity. In particular, by retaining PTFE, which is a thickener for fluorine grease, in the recesses on the inner surface of the fixing belt 20, the base oil of the fluorine grease is supplied to the sliding nip N1 over time, preventing oil film breakdown.

[0060] Therefore, in this embodiment, enough grease is supplied to fill the recesses on the inner circumferential surface of the fixing belt 20. Specifically, if A is the height of the irregularities on the inner circumferential surface of the fixing belt 20, X1 is the width of the fixing belt 20 in the longitudinal direction, B is the circumference of the fixing belt 20, and C is the specific gravity of the grease, then the amount of grease applied P is set to satisfy the following equation (2), taking into account the grease wrapping around to the back side of the heater 22 and adhering to the heater holder 23. A × X1 × B × C ≤ P···(2)

[0061] Here, the surface irregularity height A of the inner circumferential surface of the fixing belt 20 is determined by measuring the surface profile using a laser microscope (Keyence VK series) and calculating the 10-point average of the peak-to-peak values. This 10-point average is calculated by measuring 10 points on the inner circumferential surface of the fixing belt 20, for example, two points each at the center position in the longitudinal direction of the fixing belt 20, ±50 mm from the center position, and ±100 mm from the center position, and averaging these 10 peak-to-peak values. Specifically in this embodiment, the surface irregularity height was 1.67 μm.

[0062] Furthermore, the fixing belt 20 in this embodiment has an outer diameter of 25 mm, a base material of 60 μm, an elastic layer made of silicone rubber of 250 μm, and a release layer made of PFA of 12 μm. The longitudinal width X1 of the fixing belt 20 is 234 mm, and the inner circumference B is 76.5 mm. The total area of ​​the inner surface of the fixing belt 20 is 234 × 76.5 = 17901 mm². 2 Furthermore, the specific gravity C of fluorine grease is 2.0 kg / m³. 3 That is the case.

[0063] Using the above values, equation (2) shows that the amount of grease applied P is approximately 0.06 g or more. This allows grease to be retained in the recesses on the inner surface of the fixing belt 20, especially in the grease reservoirs, and an appropriate amount of grease can be supplied over time between the sliding surface 30a of the base material 30 and the inner surface of the fixing belt 20, thereby preventing oil film breakdown.

[0064] Furthermore, the amount of grease applied, P, is set to be less than or equal to the volume of the grease reservoirs formed upstream and downstream of the sliding nip N1. Applying more grease than the volume of these reservoirs would cause problems such as grease leakage from the end of the anchoring belt 20 and increased sliding resistance due to excessive grease. These grease reservoirs are the space between the inner circumferential surface of the anchoring belt 20 and the sliding surface 30a, and are formed outside the sliding nip N1, as shown by the width Y1 in Figure 9.

[0065] If Y1 is the width of the grease reservoir on the outside of the sliding nip N1 in the paper transport direction, and Z1 is the amount of protrusion of the protrusion 23e of the heater holder 23 from the sliding surface 30a, then the amount of grease applied P is set to satisfy the following equation (3). The product of the width Y1 × 2, the protrusion amount Z1, and the longitudinal width X1 of the fixing belt 20 in equation (3) is the volume Dm of the grease reservoir. 3 That is the case. P ≤ Y1 × 2 × Z1 × X1 × C···(3)

[0066] As mentioned above, the width of the sliding nip N1 is 5.1 mm and the width of the heater 22 in the short direction is 8.0 mm, so the width Y1 × 2 is 2.9 mm. The height of the protrusion 23e is 1.57 mm, while the thickness of the first high heat conductive member 28 is 0.3 mm and the thickness of the heater 22 is 1.07 mm, so the protrusion amount Z1 is 0.2 mm. The longitudinal width X1 of the fixing belt 20 is 234 mm. Therefore, from equation (3), the volume D of the grease reservoir is 2.9 × 0.2 × 234 = 135.72 mm 3 This is the result. Multiplying this by the specific gravity of the grease gives 0.271g. By keeping the application amount P to 0.271g or less, it is possible to suppress grease leakage from the end of the fixing belt 20 and prevent slippage of the fixing belt 20 due to the increase in initial torque at the start of driving.

[0067] Here, we will explain an example of the calculation direction for height Z1. First, the heater 22 and the first high-heat-conducting member 28 are removed from the fixing device 9. With the pressure roller 21 applied, the height from the bottom surface of the recess 23b to the point where the protrusion 23e most protrudes toward the fixing belt 20 is measured using a height gauge. At this time, the measurement is performed with the bottom surface of the recess 23b positioned horizontally to the floor. The height is measured on both the upstream and downstream sides of the recess 23b in the paper transport direction, and the average value is calculated. The height Z1 can be calculated by subtracting the thickness of the heater 22 and the first high-heat-conducting member 28, which were also measured, from this value.

[0068] Furthermore, by providing the resistance heating element 31 on the back surface 30b side of the base material 30, the temperature rise on the front surface 30a side, which is the sliding surface of the base material 30, can be suppressed compared to a configuration in which the resistance heating element 31 is provided on the front surface 30a side of the base material 30. This suppresses the heating of the grease 90 stored in the grease reservoir 40, thereby suppressing the decrease in viscosity of the grease and the volatilization of the fluorine oil caused by this heating. Consequently, good quality grease can be maintained in the grease reservoir 40, and the base oil component of the grease can be supplied from the grease reservoir 40 to the sliding nip N1. Therefore, good sliding properties can be ensured between the inner circumferential surface of the fixing belt 20 and the heater 22.

[0069] As described above, by providing the resistance heating element 31 on the back surface 30b of the base material 30, and by setting the amount of fluorine grease applied within the aforementioned lower and upper limits, good sliding performance can be ensured between the inner surface of the fixing belt 20 and the heater 22 over a long period of time. Therefore, wear on the inner surface of the fixing belt 20 and the generation of abnormal noise due to sliding can be suppressed. In addition, slippage during rotational operation of the fixing belt 20 can be prevented.

[0070] Furthermore, by having the first high-heat-conductivity member 28 in contact with the back surface 30b of the base material 30, localized overheating in the portion of the heater 22 where the resistance heating element 31 is provided can be prevented. Therefore, heating of the grease stored in the grease reservoir by the heater 22 can be suppressed, and the decrease in viscosity of the grease and the volatilization of the fluorine oil due to this heating can be suppressed. As a result, grease in good condition can be supplied from the grease reservoir 40 to the sliding nip N1, and better sliding performance can be ensured between the inner circumferential surface of the fixing belt 20 and the heater 22.

[0071] Furthermore, the resistance heating element 31 can be housed within the sliding nip N1 in the paper transport direction. This suppresses the heating of the grease accumulated in the grease reservoir outside the sliding nip N1, thereby suppressing the decrease in grease viscosity and the volatilization of fluorine oil caused by this heating. Consequently, grease in good condition can be supplied from the grease reservoir 40 to the sliding nip N1, ensuring good sliding performance between the inner circumferential surface of the fixing belt 20 and the heater 22.

[0072] Furthermore, in this embodiment in particular, by setting the coating amount P to 0.15g, it is possible to keep the coating amount within the aforementioned lower and upper limits even if there is an error of approximately ±30% in the coating amount, which is preferable.

[0073] As a lubricant, it is preferable to use fluorine grease as in this embodiment. This ensures viscosity through the PTFE thickener, retains the lubricant without oil film breakdown between the fixing belt 20 and the heater 22, and ensures good sliding performance between the fixing belt 20 and the heater 22 over a long period of time.

[0074] Furthermore, in this embodiment, the fixing belt 20 can be configured to have an elastic layer. This increases the rigidity of the fixing belt 20 and narrows the sliding nip N1. Also, the outer diameter of the fixing belt 20 can be configured to be smaller than the outer diameter of the pressure roller 21. This also narrows the sliding nip N1.

[0075] Furthermore, it is preferable that the surface roughness of the sliding surface 30a, which is the sliding surface of the heater 22, be 0.2 μm or less. Since the sliding surface 30a has a small ability to hold grease, it is preferable that its surface roughness be small in order to suppress the sliding resistance between the sliding surface 30a and the inner surface of the fixing belt 20. Furthermore, it is preferable that the surface roughness of the inner circumferential surface of the fixing belt 20 be 0.5 μm or less. By reducing the surface roughness of the inner circumferential surface of the fixing belt 20, it is possible to prevent grease from being trapped in the irregularities of the inner circumferential surface of the fixing belt 20 and preventing it from being supplied between the inner circumferential surface of the fixing belt 20 and the heater 22.

[0076] These surface roughness measurements are performed using a Surfcom 1400A surface roughness meter (manufactured by Tokyo Seimitsu Co., Ltd.) in accordance with JIS B0601-2001, measuring the arithmetic mean roughness Ra under the following conditions: evaluation length Ln = 1.5 mm, reference length L = 0.25 mm, and cutoff value = 0.8 mm.

[0077] Incidentally, in order to improve the quality of the fixing operation and extend the lifespan of the fixing device, it is necessary to increase the rigidity of the fixing belt 20 by making the base of the fixing belt 20 thicker, using a metal base, or making the elastic layer thicker. However, on the other hand, if the rigidity of the fixing belt 20 is high, the amount of deformation of the fixing belt 20 due to the pressure of the pressure roller 21 will be small, and the sliding nip N1 will be small relative to the fixing nip N2. Also, if the outer diameter of the fixing belt 20 is small, or if the outer diameter of the fixing belt 20 is small relative to the outer diameter of the pressure roller 21, the sliding nip N1 will be small relative to the fixing nip N2.

[0078] This section describes experimental results showing the relationship between the sliding nip N1 and the fixing nip N2. Two types of fixing devices were used in the experiment.

[0079] The fixing device of configuration 1 has a fixing belt 20 with an outer diameter of 25 mm and a polyimide base with a thickness of 60 μm, an elastic layer of silicone rubber with a thickness of 250 μm, and a release layer of PFA with a thickness of 12 μm on the outermost layer. The pressure roller 21 has an outer diameter of 20 mm, a core metal, an elastic layer of silicone rubber with a thickness of 3.5 mm, and a release layer of PFA with a thickness of 50 μm on the outermost layer.

[0080] The fixing device of configuration 2 has a fixing belt 20 with an outer diameter of 25 mm and a nickel base with a thickness of 40 μm, an elastic layer of silicone rubber with a thickness of 120 μm, and a release layer of PFA with a thickness of 7 μm on the outermost layer. The pressure roller 21 is the same as in configuration 1.

[0081] In the fixing devices of configurations 1 and 2 described above, the width between the sliding nip N1 and the fixing nip N2 in the paper transport direction was measured by changing the on-axial hardness (Asker C) value of the pressure roller 21. The measurement results are shown in Figure 10. The solid line in Figure 10 shows the results for configuration 1, and the dotted line in Figure 10 shows the results for configuration 2.

[0082] The width of the fixing nip N2 is measured as follows: First, the surface temperature of the fixing belt 20 of the fixing device 9 is set to 190°C and driven for 5 minutes or more. Between the time the OHP sheet is passed through the fixing nip N2 and the fixing belt 20 completes one rotation, the fixing device 9 is stopped from the tip of the OHP sheet and the sheet is clamped by the fixing nip N2. After leaving it for 20 seconds, the OHP sheet is removed. The width of the fixing nip N2 of the fixing device 9 is measured accurately using calipers to determine the width of the nip width mark left on the OHP sheet.

[0083] As shown in Figure 10, in the region where the width of the fixing nip N2 is 6.5 to 8.0 mm, in configuration 1, the sliding nip N1 is approximately 1.4 mm to 2.0 mm smaller than the fixing nip N2. On the other hand, in configuration 2, the sliding nip N1 is approximately 2.4 mm to 3.0 mm smaller than the fixing nip N2. Thus, configuration 2, which employs a fixing belt 20 made of a highly rigid nickel base, results in a narrower width for the sliding nip N1.

[0084] If the resistance heating element 31 is positioned outside the range of the sliding nip N1, the temperature of the heater 22 rises particularly high outside the sliding nip N1, causing a decrease in the viscosity of the grease in the grease reservoir and volatilization of the fluorine oil. Therefore, the more rigid the fixing belt used, as in configuration 2, the larger the fixing nip N2 needs to be, and the larger the sliding nip N1 needs to be (that is, the fixing nip N2 needs to be positioned further to the upper right in Figure 10). For this reason, from the viewpoint of increasing the size of the device and suppressing the driving torque, it is preferable to use a fixing belt like that in configuration 1.

[0085] Figure 11 shows the temperature distribution along the longitudinal direction of the fixing belt 20. (a) shows the arrangement of the heaters 22. (b) shows the temperature T of the fixing belt 20 on the vertical axis and the position along the longitudinal direction of the fixing belt 20 on the horizontal axis.

[0086] As shown in Figures 11(a) and 11(b), the multiple resistance heating elements 31 provided on the heater 22 are divided in the longitudinal direction, forming a divided region B between the resistance heating elements 31. In other words, the multiple resistance heating elements 31 provided on the heater 22 are arranged with a gap B between them. Hereinafter, this divided region B will be referred to as gap B. In gap B, the area occupied by the resistance heating elements 31 is smaller than in other parts, resulting in less heat generation. As a result, the temperature of the fixing belt 20 in gap B is lower than in other parts, causing temperature unevenness in the longitudinal direction of the fixing belt 20. Furthermore, in the enlarged divided region C (hereinafter simply referred to as region C), which includes the area surrounding the divided region gap B, the temperatures of the heater 22 and the fixing belt 20 are also lower. Similarly, the temperature of the heater 22 is also lower in gap B. Here, as shown in the enlarged view of Figure 11(a), gap B refers to the longitudinal region that includes the entire portion in which the resistance heating elements 31, which are the main heat-generating parts of the heater 22, are divided in the longitudinal direction. In addition to interval B, region C includes the area corresponding to the connection portion 311 of the resistive heating element 31. This connection portion 311 refers to the portion of the resistive heating element 31 that extends in the shorter direction and is connected to each of the power supply lines 33A and 33B.

[0087] As shown in Figure 12, even in the heater 22 having the rectangular resistance heating element 31 shown in Figure 5, the temperature of the gap B is lower than that of the other parts. Similarly, in the heater 22 having the resistance heating element 31 with the shape shown in Figure 13, the temperature of the gap B is lower than that of the other parts. Furthermore, as shown in Figure 14, even in the heater 22 having the resistance heating element 31 with the shape shown in Figure 6, the temperature of the gap B is lower than that of the other parts. However, as shown in Figures 11, 13, and 14, by overlapping adjacent resistance heating elements 31 in the longitudinal direction, the temperature drop in the gap B relative to the other parts can be suppressed.

[0088] In this embodiment, the first high thermal conductivity member 28 described above is provided to suppress temperature drops in the above-mentioned intervals and to suppress temperature unevenness in the longitudinal direction of the fixing belt 20. The first high thermal conductivity member 28 will be described in more detail below.

[0089] As shown in Figure 2, the first high-heat-conductivity member 28 is positioned between the heater 22 and the stay 24 in the left-right direction of Figure 2, and is particularly sandwiched between the heater 22 and the heater holder 23. In other words, one side of the first high-heat-conductivity member 28 is in contact with the back surface of the base material 30, and the other side is in contact with the heater holder 23.

[0090] The stay 24 supports the heater holder 23, the first high heat conductive member 28, and the heater 22 by bringing the contact surfaces 24a1 of two vertical portions 24a extending in the thickness direction of the heater 22 into contact with the heater holder 23. In the short direction (up and down direction in Figure 2), the contact surfaces 24a1 are located outside the area where the resistance heating element 31 is provided. This suppresses heat transfer from the heater 22 to the stay 24, allowing the heater 22 to efficiently heat the fixing belt 20.

[0091] As shown in Figure 15, the first high-thermal-conductivity member 28 is made of a plate material. In this embodiment, the first high-thermal-conductivity member 28 is made of a single plate material, but it may consist of multiple members. Note that the guide portion 26 in Figure 2 is omitted from Figure 15.

[0092] The first high-heat-conductivity member 28 is fitted into the recess 23b of the heater holder 23, and the heater 22 is mounted on top of it, so that the first high-heat-conductivity member 28 is held in place by being sandwiched between the heater holder 23 and the heater 22. In this embodiment, the longitudinal width of the first high-heat-conductivity member 28 is set to be approximately the same as the longitudinal width of the heater 22. The longitudinal movement of the first high-heat-conductivity member 28 and the heater 22 is restricted by the longitudinal side walls (longitudinal direction restricting parts) 23b1 that form the recess 23b. In this way, by restricting the longitudinal displacement of the first high-heat-conductivity member 28 within the fixing device 9, the heat conduction efficiency can be improved over the target range in the longitudinal direction. Furthermore, the movement of the first high-heat-conductivity member 28 and the heater 22 is restricted by the short-side side walls (short-side direction restricting parts) 23b2 that form the recess 23b.

[0093] The longitudinal range in which the first high thermal conductivity member 28 is provided is not limited to the above. For example, as shown in Figure 16, the first high thermal conductivity member 28 may be provided only in the range corresponding to the longitudinal heating element 35 (see the hatched area in Figure 16). Also, as shown in Figure 17, the first high thermal conductivity member 28 may be provided only in the entire area at a position corresponding to the longitudinal spacing B. For convenience, in Figure 17, the resistance heating element 31 and the first high thermal conductivity member 28 are shown offset vertically in Figure 17, but they are arranged at approximately the same position in the short direction. However, this is not the only option, and the first high thermal conductivity member 28 may be provided in a part of the short direction of the resistance heating element 31, or it may be provided so as to cover the entire short direction as shown in Figure 18, which will be described later. Furthermore, as shown in Figure 18, the first high thermal conductivity member 28 may be provided not only at a position corresponding to the longitudinal spacing B, but also spanning the resistance heating elements 31 on both sides of the spacing B. To say that the first high-heat-conducting member 28 spans both resistance heating elements 31 means that the position of the first high-heat-conducting member 28 overlaps with the position of both resistance heating elements 31 in the longitudinal direction in at least a portion of the way. The first high-heat-conducting member 28 may be provided for all the intervals B of the heater 22, or it may be provided for only some of the intervals B, such as providing the first high-heat-conducting member 28 for only one location of the interval B as shown in Figure 18. Here, to say that the first high-heat-conducting member 28 is provided for the position of the interval B in the longitudinal direction means that at least a portion of it overlaps with the interval B in the longitudinal direction.

[0094] The pressure applied by the pressure roller 21 causes the first high-heat-conductivity member 28 to be sandwiched between the heater 22 and the heater holder 23, making close contact with these members. The contact of the first high-heat-conductivity member 28 with the heater 22 improves the thermal conductivity of the heater 22 in the longitudinal direction. Furthermore, by positioning the first high-heat-conductivity member 28 at a position corresponding to the interval B of the heater 22 in the longitudinal direction, the thermal conductivity at interval B can be improved, increasing the amount of heat transferred to the position of interval B in the longitudinal direction and raising the temperature at interval B in the longitudinal direction. Therefore, temperature unevenness in the longitudinal direction of the heater 22 can be suppressed. This also suppresses temperature unevenness in the longitudinal direction of the fixing belt 20. Consequently, uneven fixing and gloss unevenness of the image fixed to the paper can be suppressed. Alternatively, it becomes unnecessary to perform extra heating by the heater 22 to ensure sufficient fixing performance at interval B, thereby achieving energy savings for the fixing device 9. Furthermore, by providing the first high-heat-conducting member 28 over the entire lengthwise heating section 35, the heat transfer efficiency of the heater 22 can be improved throughout the main heating area (i.e., the image-forming area of ​​the paper being fed through), thereby suppressing temperature unevenness in the lengthwise direction of the heater 22 and, consequently, the fixing belt 20.

[0095] In particular, in this embodiment, the combination of the configuration of the first high thermal conductivity member 28 described above and the resistance heating element 31 having the PTC characteristics described above effectively suppresses overheating in the non-paper-feeding area when small-sized paper is fed. In other words, the PTC characteristics suppress the amount of heat generated by the resistance heating element 31 in the non-paper-feeding area, and the heat from the non-paper-feeding area, whose temperature has risen, can be efficiently transferred to the paper-feeding area, thereby effectively suppressing overheating in the non-paper-feeding area.

[0096] Furthermore, since the temperature around interval B is low due to the small amount of heat generated by interval B, it is preferable to place the first high-heat-conducting member 28 there. For example, in this embodiment, by providing the first high-heat-conducting member 28 at a position corresponding to region C (see Figure 12), the longitudinal heat transfer efficiency in and around interval B is particularly improved, and longitudinal temperature unevenness of the heater 22 can be further suppressed. In particular, in this embodiment, the first high-heat-conducting member 28 is provided over the entire area of ​​the heat-generating section 35 in the longitudinal direction. This further suppresses longitudinal temperature unevenness of the heater 22 (fixing belt 20).

[0097] Next, different embodiments of the fixing device will be described.

[0098] As shown in Figure 19, the fixing device 9 of this embodiment has a second high-temperature conductive member 36 between the heater holder 23 and the first high-temperature conductive member 28. The second high-temperature conductive member 36 is provided at a different position from the first high-temperature conductive member 28 in the stacking direction (left-right direction in Figure 19) of the members such as the heater holder 23, the stay 24, and the first high-temperature conductive member 28. More specifically, the second high-temperature conductive member 36 is provided superimposed on the first high-temperature conductive member 28. Note that Figure 19 differs from Figure 2 in that it shows a cross-section where the second high-temperature conductive member 36 is arranged in the longitudinal direction and the thermistor 25 is not arranged.

[0099] The second high thermal conductivity member 36 is made of a material with a higher thermal conductivity than the base material 30, such as graphene or graphite. In this embodiment, the second high thermal conductivity member 36 is formed from a graphite sheet with a thickness of 1 mm. However, the second high thermal conductivity member 36 may also be made from a plate material such as aluminum, copper, or silver.

[0100] As shown in Figure 20, multiple second high-heat-conducting members 36, each partially provided in the longitudinal direction, are arranged in the longitudinal direction. The portion of the recess 23b of the heater holder 23 where the second high-heat-conducting member 36 is provided is made one step deeper than the other portions. The second high-heat-conducting member 36 has a gap between it and the heater holder 23 on both sides in the longitudinal direction. This suppresses heat transfer from the second high-heat-conducting member 36 to the heater holder 23, allowing the heater 22 to efficiently heat the fixing belt 20. Note that the guide portion 26 shown in Figure 2 is omitted in Figure 20.

[0101] As shown in Figure 21, the second high-thermal-conductivity member 36 (see hatched area) is provided in the longitudinal direction at a position corresponding to the interval B, overlapping at least a portion of the adjacent resistance heating element 31, and in this embodiment in particular, it is provided over the entire interval B. However, although Figure 21 (and Figure 25 described later) shows a case in which the first high-thermal-conductivity member 28 is provided only in the region corresponding to the heating element 35 in the longitudinal direction, as mentioned above, it is not limited to this.

[0102] As in this embodiment, by providing a second high-heat-conducting member 36 in addition to the first high-heat-conducting member 28 at a position corresponding to the longitudinal spacing B, overlapping at least a portion of the adjacent resistance heating elements 31, the longitudinal heat transfer efficiency at spacing B can be particularly improved, and longitudinal temperature unevenness of the heater 22 can be further suppressed. Furthermore, most preferably, as shown in Figure 22, the first high-heat-conducting member 28 and the second high-heat-conducting member 36 are provided only in the entire area at the position corresponding to spacing B. This makes it possible to particularly improve the heat transfer efficiency at the position corresponding to spacing B compared to other areas. Note that in Figure 22, for convenience, the resistance heating elements 31, the first high-heat-conducting member 28, and the second high-heat-conducting member 36 are shown shifted vertically in Figure 22, but they are actually arranged at approximately the same position in the short direction. However, this is not limited to the above, and the first high heat conductive member 28 and the second high heat conductive member 36 may be provided on a part of the short side of the resistance heating element 31, or they may be provided so as to cover the entire short side.

[0103] In one embodiment of the present invention, which differs from the above, the first high thermal conductivity member 28 and the second high thermal conductivity member 36 are made of the graphene sheet. This makes it possible to form the first high thermal conductivity member 28 and the second high thermal conductivity member 36 with high thermal conductivity in a predetermined direction along the surface of the graphene, that is, in the longitudinal direction rather than the thickness direction. Therefore, temperature unevenness in the longitudinal direction of the heater 22 and the fixing belt 20 can be effectively suppressed.

[0104] Graphene is a flaky powder. As shown in Figure 23, graphene consists of a planar hexagonal lattice structure of carbon atoms. A graphene sheet is a sheet of graphene, 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 an equal number of carbon atoms form a polycyclic structure fused in a cage-like manner with 5-membered and 6-membered rings, for example, C 60 , C 70 and C 80 It is a fullerene or another closed cage-like structure having three-coordinate carbon atoms.

[0105] Graphene sheets are artificial materials and can be fabricated, for example, by chemical vapor deposition (CVD).

[0106] Commercially available graphene sheets can be used. The size and thickness of the graphene sheet, as well as the number of layers of the graphite sheet described later, can be measured, for example, by a transmission electron microscope (TEM).

[0107] Furthermore, graphite with multiple layers of graphene exhibits high thermal conductivity anisotropy. As shown in Figure 24, graphite has a crystalline structure in which layers of condensed six-membered rings of carbon atoms are spread out in a planar manner, and these layers are stacked multiple times. In this crystalline structure, adjacent carbon atoms within a layer form covalent bonds, while carbon atoms between layers form van der Waals bonds. The covalent bonds have a stronger bonding force than van der Waals bonds, and there is a large anisotropy between the bonds within a layer and the bonds between layers. In other words, by constructing the first high-thermal-conductivity member 28 or the second high-thermal-conductivity member 36 from graphite, the heat transfer efficiency in the longitudinal direction of the first high-thermal-conductivity member 28 or the second high-thermal-conductivity member 36 becomes larger than in the thickness direction (i.e., the stacking direction of the members), and heat transfer to the heater holder 23 can be suppressed. Therefore, temperature unevenness in the longitudinal direction of the heater 22 can be efficiently suppressed, and the heat flowing out to the heater holder 23 can be minimized. Furthermore, by constructing the first high-thermal-conductivity member 28 or the second high-thermal-conductivity member 36 from graphite, it is possible to provide the first high-thermal-conductivity member 28 or the second high-thermal-conductivity member 36 with excellent heat resistance that prevents oxidation up to approximately 700 degrees Celsius.

[0108] The physical properties and dimensions of the graphite sheet can be appropriately changed according to the function required of the first high-thermal-conductivity member 28 or the second high-thermal-conductivity member 36. For example, the anisotropy of its thermal conductivity can be increased by using high-purity graphite or single-crystal graphite, or by increasing the thickness of the graphite sheet. In addition, to increase the speed of the fixing device 9, a thinner graphite sheet may be used to reduce the heat capacity of the fixing device 9. Furthermore, if the width of the fixing nip N2 or heater 22 is large, the longitudinal width of the first high-thermal-conductivity member 28 or the second high-thermal-conductivity member 36 may be increased accordingly.

[0109] From the viewpoint of increasing mechanical strength, it is preferable that the graphite sheet has 11 or more layers. Furthermore, the graphite sheet may partially consist of single-layer and multi-layer sections.

[0110] The second high-heat-conductivity member 36 is provided in a position in the longitudinal direction corresponding to the interval B (and further to region C) and overlapping with at least a portion of the adjacent resistance heating element 31, and is not limited to the arrangement shown in Figure 21. For example, as shown in Figure 25, the second high-heat-conductivity member 36A is provided in the short direction, protruding from both sides of the base material 30 in the short direction. The second high-heat-conductivity member 36B is provided in the short direction within the range where the resistance heating element 31 is provided. The second high-heat-conductivity member 36C is provided in a portion of the interval B.

[0111] Furthermore, as shown in Figure 26, in this embodiment, a gap in the thickness direction (left-right direction in Figure 26) is provided between the first high heat conductive member 28 and the heater holder 23. In other words, in a part of the recess 23b (see Figure 20) of the heater holder 23 for arranging the heater 22, the first high heat conductive member 28, and the second high heat conductive member 36, a relief portion 23c as an insulating layer is provided in a part of the short direction, excluding the part in the longitudinal direction where the second high heat conductive member 36 is provided, making the depth of the recess 23b deeper than the other part that receives the first high heat conductive member 28. This minimizes the contact area between the heater holder 23 and the first high heat conductive member 28. Consequently, heat transfer from the first high heat conductive member 28 to the heater holder 23 is suppressed, and the heater 22 can efficiently heat the fixing belt 20. In the cross-section where the second high-heat-conducting member 36 in the longitudinal direction is provided, the second high-heat-conducting member 36 abuts against the heater holder 23, as shown in Figure 19 of the embodiment described above.

[0112] Furthermore, in this embodiment in particular, a relief portion 23c is provided over the entire area where the resistance heating element 31 is installed in the short direction (up and down direction in Figure 26). This suppresses heat transfer, especially from the first high thermal conductivity member 28 to the heater holder 23, allowing the heater 22 to efficiently heat the fixing belt 20. In addition to a configuration that provides a space as in the relief portion 23c, a configuration in which an insulating material with a lower thermal conductivity than the heater holder 23 is provided may also be used as the insulating layer.

[0113] Furthermore, although the above description describes the second high-temperature conductive member 36 as a different member from the first high-temperature conductive member 28, the explanation is not limited to this. For example, the portion of the first high-temperature conductive member 28 corresponding to the gap B may be made thicker than the other portions.

[0114] In these embodiments shown in Figure 19 or Figure 26, as in the embodiments described above, the resistance heating element 31 is placed on the back surface 30b of the base material 30 opposite to the sliding nip N1 side, and by appropriately setting the amount of lubricant applied, a good sliding state can be formed between the fixing belt 20 and the heater 22.

[0115] Furthermore, the present invention is applicable not only to the fixing device described above, but also to the fixing device shown in Figure 27. The fixing device 9 shown in Figure 27 will be described below.

[0116] As shown in Figure 27, the fixing device 9 consists of a heating assembly 92, a fixing roller 93 which is a fixing member, and a pressure assembly 94 which is an opposing member. The heating assembly 92 includes the heater 22, first high heat conductivity member 28, heater holder 23, stay 24, and heating belt 120 as a rotating member, as described in the previous embodiment. The fixing roller 93 is a pressure member that pressurizes the heating belt 120 to form a heating nip N3 between the heating belt 120 and the fixing roller 93. The fixing roller 93 is composed of a core metal 93a, an elastic layer 93b, and a surface layer 93c. The pressure assembly 94 is provided on the side opposite to the heating assembly 92 relative to the fixing roller 93. The pressure assembly 94 has a nip forming member 95 and a stay 96 arranged therein, and the pressure belt 97 is rotatably arranged to enclose these nip forming member 95 and stay 96. Then, the paper P is passed through the fixing nip N2 between the pressure belt 97 and the fixing roller 93, and the image is fixed by heating and pressurizing it.

[0117] In the embodiment shown in Figure 27, as in the previously described embodiment, by arranging the resistance heating element 31 on the back surface 30b of the base material 30 opposite to the sliding nip N1 side and appropriately setting the amount of lubricant applied, a good sliding state can be formed between the fixing belt 20 and the heater 22. Also in the embodiment shown in Figure 27, by arranging the resistance heating element 31 on the back surface 30b of the base material 30 opposite to the sliding nip N1 side and appropriately setting the amount of lubricant applied, a good sliding state can be formed between the heating belt 120 and the heater 22.

[0118] Furthermore, the present invention is not limited to fixing devices as described in the above embodiments, but can also be applied to drying devices for drying ink applied to paper, and even to heating devices such as laminators for heat-pressing a film as a covering member onto the surface of a sheet such as paper, and heat sealers for heat-pressing the sealing portion of packaging materials. By applying the present invention to such devices, a good sliding state can be formed between the rotating member and the heating member.

[0119] The image forming apparatus according to the present invention is not limited to the color image forming apparatus shown in Figure 1, but may also be a monochrome image forming apparatus, a copier, a printer, a facsimile, or a combination device thereof.

[0120] For example, as shown in Figure 28, the image forming apparatus 100 of this embodiment comprises an image forming means 50 consisting of a photosensitive drum, a paper transport unit consisting of a pair of timing rollers 15, a paper feed device 7, a fuser 9, a paper discharge device 10, and a reading unit 51. The paper feed device 7 is equipped with multiple paper trays, each of which accommodates paper of different sizes.

[0121] The reading unit 51 reads the image of the original document Q. The reading unit 51 generates image data from the read image. The paper feed device 7 receives multiple sheets of paper P and feeds the paper P to the transport path. The timing roller 15 transports the paper P on the transport path to the image forming means 50.

[0122] The image forming means 50 forms a toner image on the paper P. Specifically, the image forming means 50 includes a photoreceptor drum, a charging roller, an exposure device, a developing device, a replenishment device, a transfer roller, a cleaning device, and a static elimination device. The toner image represents, for example, the image of the original document Q. The fixing device 9 heats and pressurizes the toner image to fix it to the paper P. The paper P with the fixed toner image is transported to the paper discharge device 10 by a transport roller or the like. The paper discharge device 10 discharges the paper P to the outside of the image forming device 100.

[0123] Next, the fixing device 9 of this embodiment will be described. Configurations common to the fixing device of the previously described embodiment will be omitted from the description as appropriate.

[0124] As shown in Figure 29, the fixing device 9 includes a fixing belt 20, a pressure roller 21, a heater 22, a heater holder 23, a stay 24, a thermistor 25, a first high heat conductive member 28, and the like.

[0125] A fixing nip N2 is formed between the fixing belt 20 and the pressure roller 21. The nip width of the fixing nip N2 is 10 mm, and the linear speed of the fixing device 9 is 240 mm / s.

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

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

[0128] The heater 22 comprises a base material, a heat insulating layer, a conductor layer including a resistance heating element, and an insulating layer, and is formed with an overall thickness of 1 mm. The width Y in the short direction of the heater 22 is 13 mm.

[0129] As shown in Figure 30, the conductor layer of the heater 22 comprises a plurality of resistive heating elements 31, a power supply line 33, and electrode sections 34A to 34C. In this embodiment as well, as shown in the enlarged view of Figure 30, the plurality of resistive heating elements 31 are divided into intervals B as divided regions in the longitudinal direction (however, in Figure 30 only the interval B is shown in the enlarged view, in reality intervals B are provided between all resistive heating elements 31). The resistive heating elements 31 constitute three heating sections 35A to 35C. By energizing the electrode sections 34A and 34B, the heating sections 35A and 35C generate heat. By energizing the electrode sections 34A and 34C, the heating section 35B generates heat. For example, when performing a fixing operation on small-sized paper, the heating section 35B is heated, and when performing a fixing operation on large-sized paper, all heating sections are heated.

[0130] As shown in Figure 31, the heater holder 23 holds the heater 22 and the first high heat conductive member 28 in its recess 23d. The recess 23d is provided on the heater 22 side of the heater holder 23. The recess 23d is composed of a surface 23d1 that is substantially parallel to the base material 30 and recessed on the stay 24 side than the other surfaces of the heater 22, a wall portion 23d2 provided on the inside of the heater holder 23 on both sides (or one side) in the longitudinal direction of the heater holder 23, and a wall portion 23d3 provided on the inside of the heater holder 23 on both sides in the short direction. The heater holder 23 has a guide portion 26. The heater holder 23 is made of LCP (liquid crystal polymer).

[0131] As shown in Figure 32, the connector 60 comprises a housing made of resin (e.g., LCP) and a plurality of contact terminals provided inside the housing.

[0132] The connector 60 is attached by sandwiching the heater 22 and the heater holder 23 together from the front and back sides. In this state, each contact terminal makes contact (pressure contact) with each electrode portion of the heater 22, thereby electrically connecting the heating element 35 and the power supply provided in the image forming apparatus via the connector 60. This makes it possible to supply power from the power supply to the heating element 35. Note that each electrode portion 34 is exposed, at least a portion of which is not covered by the insulating layer, in order to ensure connection with the connector 60.

[0133] The flanges 53 are provided on both sides of the anchoring belt 20 in the longitudinal direction and hold both ends of the anchoring belt 20 from the inside of the belt. The flanges 53 are fixed to the housing of the anchoring device 9. The flanges 53 are inserted into both ends of the stay 24 (see the direction of the arrows from the flanges 53 in Figure 32).

[0134] The mounting direction of the connector 60 to the heater 22 and heater holder 23 is in the direction of the shorter side of the heater (see the direction of the arrow from the connector 60 in Figure 32). When the connector 60 is mounted to the heater holder 23, a protrusion on one side of the connector 60 and the heater holder 23 may engage with a recess on the other side, and the protrusion may move relative to the other within the recess. The connector 60 is mounted to the heater 22 and heater holder 23 on one side in the longitudinal direction, on the side opposite to the side where the drive motor for the pressure roller 21 is installed.

[0135] As shown in Figure 33, thermistors 25 are provided on the center and end sides of the fixing belt 20, facing the inner circumferential surface of the fixing belt 20. The heater 22 is controlled based on the temperatures of the center and end sides of the fixing belt 20 detected by the thermistors 25.

[0136] Thermostats 27 are provided on the center and end sides of the fixing belt 20, facing the inner circumferential surface of the fixing belt 20. If the temperature of the fixing belt 20 detected by the thermostats 27 exceeds a predetermined threshold, the power supply to the heater 22 is stopped.

[0137] Flanges 53 are provided at both longitudinal ends of the fixing belt 20 to hold each end of the fixing belt 20. The flanges 53 are made of LCP (liquid crystal polymer).

[0138] As shown in Figure 34, a slide groove 53a is provided in the flange 53. The slide groove 53a extends in the direction in which the fixing belt 20 moves toward and away from the pressure roller 21. An engaging portion of the housing of the fixing device 9 engages with the slide groove 53a. As this engaging portion moves relative to the slide groove 53a, the fixing belt 20 can move toward and away from the pressure roller 21.

[0139] In the fixing device 9 described above, as in the embodiment described above, the resistance heating element 31 is placed on the back surface 30b of the base material 30 opposite to the sliding nip N1 side, and the amount of lubricant applied is set appropriately to create a good sliding state between the fixing belt 20 and the heater 22.

[0140] Although embodiments of the present invention have been described above, the present invention is not limited to the embodiments described above, and various modifications can be made without departing from the spirit of the present invention.

[0141] The image forming apparatus according to the present invention is not limited to the color image forming apparatus shown in Figure 1, but may also be a monochrome image forming apparatus, a copier, a printer, a facsimile, or a combination device thereof.

[0142] Recording media include plain paper (P), as well as cardboard, postcards, envelopes, thin paper, coated paper (such as coated paper and art paper), tracing paper, OHP sheets, plastic film, prepreg, copper foil, and the like.

[0143] Examples of the present invention are as follows: <1> Rotating member and A pressurizing member that forms an outer nip portion between itself and the rotating member, A heating element provided inside the rotating member, having a base material and a resistance heating element, A retaining member having a recess for holding the heating element, A heating device comprising: a lubricant applied to the sliding surface of the heating element with respect to the rotating member or to the inner surface of the rotating member, If the nip portion formed by the heating element and the inner surface of the rotating member is defined as a sliding nip, A lubricant holding region is provided on the outside of the sliding nip in the recording medium transport direction, between the rotating member and the heating element, for holding the lubricant. The resistance heating element is provided on the surface of the substrate opposite to the sliding nip side, The heating device is characterized in that, if P is the amount of lubricant applied, A is the height of the irregularities on the inner surface of the rotating member, X1 is the longitudinal width of the rotating member, B is the circumference of the rotating member, C is the specific gravity of the lubricant, and D is the volume of the lubricant holding area, then the following equation is satisfied. A × X1 × B × C ≤ P ≤ D × C <2> The lubricant is fluorine grease. <1> This is the heating device described. <3> The device further comprises a high-heat-conducting member that contacts the heating element from the side opposite to the sliding nip side. <1> or <2> This is the heating device described. <4> The substrate is formed from highly smooth ceramic. <1> from <3> It is one of the heating devices described below. <5> The surface roughness of the sliding surface of the heating element with respect to the rotating member is 0.2 μm or less. <1> from <4> It is one of the heating devices described below. <6> The surface roughness of the inner surface of the rotating member is 0.5 μm or less. <1> from <5> It is one of the heating devices described below. <7> <1> from <6> This fixing device heats and fixes heat on a recording medium using one of the heating devices described above. <8> <7> This is an image forming apparatus equipped with the fixing device described above. [Explanation of Symbols]

[0144] 1. Image forming apparatus 9. Fixing device (heating device) 20 Fixing belt (rotating component) 21 Pressure roller (pressure component) 22 Heater (heating element) 23 Heater holder (holding member) 23b Recess 30 Base material 30a Sliding surface of the base material 30b Back surface of the substrate (the side of the substrate opposite to the sliding nip side) 31 Resistive heating element 32 Insulating layer 40. Grease reservoir (lubricant retention area) 90 Fluorine grease (lubricant) A. Paper transport direction (recording medium transport direction) N1 Sliding Nib N2 Fixing nip (outer nip portion) X Longitudinal direction Y-short direction (direction of media transport) [Prior art documents] [Patent Documents]

[0145] [Patent Document 1] Japanese Patent Publication No. 2010-204587

Claims

1. Rotating member and A pressurizing member that forms an outer nip portion between itself and the rotating member, A heating element provided inside the rotating member, having a base material and a resistance heating element, A retaining member having a recess for holding the heating element, A lubricant applied to the sliding surface of the heating element with respect to the rotating member or to the inner surface of the rotating member, A heating device comprising a high thermal conductivity member formed of a material with a higher thermal conductivity than the aforementioned base material, If the nip portion formed by the heating element and the inner surface of the rotating member is defined as a sliding nip, A lubricant holding region is provided on the outside of the sliding nip in the recording medium transport direction, between the rotating member and the heating element, for holding the lubricant. The resistance heating element is provided on the surface of the substrate opposite to the sliding nip side, If P is the amount of lubricant applied, A is the average height of the unevenness on the inner surface of the rotating member, X1 is the longitudinal width of the rotating member, B is the circumference of the rotating member, C is the specific gravity of the lubricant, and D is the volume of the lubricant holding area, then the following equation is satisfied: A × X1 × B × C ≤ P ≤ D × C The resistance heating element is provided in multiple locations on the substrate in the longitudinal direction. The heating device is characterized in that the high thermal conductivity member is provided across positions corresponding to the resistance heating elements in the longitudinal direction and positions corresponding to the spaces between the resistance heating elements, and contacts the heating element from the side opposite to the sliding nip side.

2. The heating apparatus according to claim 1, wherein the lubricant is fluorine grease.

3. The heating apparatus according to claim 1, wherein the substrate is formed of a highly smooth ceramic.

4. The heating apparatus according to claim 1, wherein the arithmetic mean roughness of the sliding surface of the heating element with respect to the rotating member is 0.2 μm or less.

5. The heating apparatus according to claim 1, wherein the arithmetic mean roughness of the inner surface of the rotating member is 0.5 μm or less.

6. A fixing device for heating and fixing heat on a recording medium using a heating device according to any one of claims 1 to 5.

7. An image forming apparatus comprising the fixing device described in claim 6.

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