Fixing device, image forming apparatus

Abstract

To remove electric charges of a first layer and a third layer of a first rotary member.SOLUTION: A fixation device 9 comprises: a pressure roller 21; a fixation belt 20 which forms a fixation nip N through which a sheet P carrying a toner image passes between the pressure roller 21 and itself; a heater 22 which is brought into contact with the inner side of the fixation belt 20 and heats the fixation belt 20; a charge elimination brush 37 which eliminates the charge from the pressure roller 21; and a conductive member 38. The pressure roller 21 includes a conductive core grid 21a, a non-conductive elastic layer 21b, and a conductive surface layer 21c in this order from the inner side thereof. The conductive member 38 is in contact with the surface layer 21c, and the charge elimination brush 37 is in contact with the conductive member 38 and the core grid 21a.SELECTED DRAWING: Figure 7

Description

[Technical Field]

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

[0002] The fixing device is provided with a pressure roller as a first rotating member. The pressure roller is made up of, for example, a core metal as a first layer, an elastic layer as a second layer, and a surface layer as a third layer, stacked from the inside.

[0003] The elastic layer of such a pressure roller is made of a non-conductive material to ensure its elasticity and extensibility. Therefore, the surface layer and the core metal are not electrically connected, and therefore each must be neutralized. In other words, if the surface layer of the pressure roller becomes charged, it can cause image defects due to electrostatic offset. Furthermore, if the core metal becomes charged, electrical noise can be generated.

[0004] For example, in the fixing device of Patent Document 1 (Japanese Patent Laid-Open Publication No. 2002-162857), earthed conductive members are in contact with the surface layer and the core of the pressure roller.

[0005] However, the configuration of Patent Document 1 requires multiple neutralizing members to neutralize the surface layer and core of the pressure roller, and there is room for further consideration in terms of a configuration for neutralizing the first and third layers of the first rotating member. Summary of the Invention [Problem to be solved by the invention]

[0006] The object is to remove the charge from the first and third layers of the first rotating member. [Means for solving the problem]

[0007] In order to solve the above problems, the present invention provides a fixing device comprising a first rotating member, a second rotating member that forms a nip portion between the first rotating member and the second rotating member and through which a recording medium carrying a toner image passes, a heating element that contacts the inside of the second rotating member and heats the second rotating member, a discharge member that discharges the first rotating member, and a conductive member, wherein the first rotating member has, from the inside, a conductive first layer, a non-conductive second layer, and a conductive third layer in that order, the conductive member contacts the third layer, and the discharge member contacts the conductive member and the first layer. [Effects of the Invention]

[0008] According to the present invention, the charges on the first and third layers of the first rotating member can be removed. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 is a schematic diagram illustrating the configuration of an image forming apparatus. [Figure 2] 1 is a side cross-sectional view showing a schematic configuration of a fixing device according to an embodiment of the present invention. [Figure 3] FIG. 2 is a plan view illustrating a configuration for eliminating static electricity from the fixing device according to the present embodiment. [Figure 4] FIG. 4 is a plan view showing the mounting structure of the discharging brush. [Figure 5] FIG. 10 is a plan view showing another mounting structure of the static eliminating brush. [Figure 6] FIG. 10 is a plan view showing a holding structure of the pressure roller by the side plates. [Figure 7] 10A and 10B are diagrams showing a modified example of the conductive member, in which FIG. 10A is a plan view and FIG. 10B is a cross-sectional view. [Figure 8] FIG. 10 is a plan view showing a modified example of the conductive member. [Figure 9] 10A and 10B are diagrams showing a modified example of the conductive member, in which FIG. 10A is a plan view and FIG. [Figure 10] FIG. 10 is a side view showing a modified example of the conductive member. [Figure 11] 10A and 10B are diagrams showing a modified example of the conductive member, in which FIG. 10A is a plan view and FIG. [Figure 12] FIG. 4 is a plan view showing the longitudinal arrangement of the conductive members. [Figure 13] FIG. 2 is a side view showing the configuration of a charge removal brush that comes into contact with the fixing belt. [Figure 14] FIG. 10 is a diagram illustrating the occurrence of a banding image. [Figure 15] FIG. [Figure 16] FIG. 10 is a diagram illustrating power supply to a heater. [Figure 17] FIG. 16 is a plan view of a heater having a different resistive heating element shape from that of FIG. [Figure 18] FIG. 18 is a plan view of a heater having a resistance heating element with a different shape from those in FIGS. 15 and 17. [Figure 19] 1A and 1B are diagrams showing the temperature distribution in the arrangement direction of the fixing belt, in which FIG. 1A is a plan view of the heater, and FIG. 1B is a diagram showing the temperature distribution of the fixing belt. [Figure 20] FIG. 18 is a diagram showing divided regions of the heater in FIG. 17. [Figure 21] FIG. 21 is a diagram showing divided regions having a different shape from that shown in FIG. 20. [Figure 22] FIG. 19 is a diagram showing divided regions of the heater in FIG. 18. [Figure 23] FIG. 2 is a perspective view of a heater, a first high thermal conductive member, and a heater holder. [Figure 24] 4 is a diagram showing the positional relationship in the longitudinal direction of a first highly thermally conductive member, a fixing belt, and a heater. FIG. [Figure 25] 10 is a side view showing how the static elimination brush contacts the conductive member, the surface layer of the fixing belt, and the first high-thermal-conductivity member. FIG. [Figure 26] FIG. 2 is a plan view of the heater showing the arrangement of the first high thermal conductivity members. [Figure 27] 10A and 10B are plan views of a heater showing different examples of the arrangement of first high thermal conductivity members. [Figure 28] FIG. 10 is a plan view of a heater showing yet another example of the arrangement of first high thermal conductivity members. [Figure 29] 3 is a side cross-sectional view showing a schematic configuration of a fixing device according to an embodiment different from that shown in FIG. 2. [Figure 30]FIG. 2 is a perspective view of a heater, a first highly thermally conductive member, a second highly thermally conductive member, and a heater holder. [Figure 31] FIG. 3 is a plan view of the heater showing the arrangement of the first and second high thermal conductive members. [Figure 32] 3A to 3C are plan views of a heater showing examples of different arrangements of the first and second high thermal conductive members. [Figure 33] FIG. 1 illustrates the atomic crystal structure of graphene. [Figure 34] FIG. 1 illustrates the atomic crystal structure of graphite. [Figure 35] 32 is a plan view showing a heater in which the arrangement of the second high thermal conductive members is different from that in FIG. 31. FIG. [Figure 36] 29. FIG. 30 is a side cross-sectional view showing a schematic configuration of a fixing device according to an embodiment different from that shown in FIGS. [Figure 37] FIG. 2 is a side cross-sectional view showing a schematic configuration of a fixing device different from the above. [Figure 38] FIG. 2 is a side cross-sectional view showing a schematic configuration of a fixing device different from the above. [Figure 39] FIG. 2 is a side cross-sectional view showing a schematic configuration of a fixing device different from the above. [Figure 40] FIG. 10 is a side cross-sectional view showing a schematic configuration of a fixing device that is different from the above. [Figure 41] 41A, 41B, and 41C are diagrams showing a support structure for an end portion of the fixing belt in FIG. 40, in which (a) is a perspective view, (b) is a plan view, and (c) is a cross-sectional view taken along line AA in (b). [Figure 42] FIG. 10 is a side cross-sectional view showing a schematic configuration of a fixing device that is different from the above. [Figure 43] FIG. 43 is a perspective cross-sectional view of the fixing device of FIG. 42. [Figure 44] FIG. 43 is a front cross-sectional view of the fixing device of FIG. 42. [Figure 45] FIG. 2 is a perspective view of a belt support member. [Figure 46] FIG. 10 is a perspective view showing a modified example of the belt support member. [Figure 47] 43 is a side cross-sectional view of the fixing device in FIG. 42, showing the reflecting surface of the reflecting member. FIG. [Figure 48]FIG. 2 is a schematic diagram illustrating the configuration of an image forming apparatus different from that in FIG. [Figure 49] 1 is a side cross-sectional view showing a schematic configuration of a fixing device according to an embodiment of the present invention. [Figure 50] FIG. 50 is a plan view of a heater in the fixing device of FIG. 49. [Figure 51] FIG. 2 is a perspective view of a heater and a heater holder. [Figure 52] FIG. 4 is a perspective view showing a state in which a connector is attached to a heater. [Figure 53] FIG. 2 is a diagram showing the arrangement of a thermistor and a thermostat. [Figure 54] FIG. 10 is a view showing a groove portion of the flange. DETAILED DESCRIPTION OF THE INVENTION

[0010] The present invention will be described below with reference to the accompanying drawings. In each drawing for explaining the present invention, components such as members and components having the same function or shape are designated by the same reference numerals as far as they can be distinguished, and descriptions thereof will be omitted once they have been described.

[0011] 1 is a schematic diagram of an image forming apparatus according to an embodiment of the present invention, which includes a fixing device that fixes a toner image on a sheet of paper to the sheet of paper, as an aspect of the heating device of the present invention.

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

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

[0014] The transfer device 8 has an endless intermediate transfer belt 11 as an intermediate transfer body, four primary transfer rollers 12 as primary transfer members, and a secondary transfer roller 13 as a secondary transfer member. The intermediate transfer belt 11 is stretched by multiple rollers. The primary transfer rollers 12 transfer the toner images on the photoconductors 2 to the intermediate transfer belt 11. The secondary transfer rollers 13 transfer the toner images transferred onto the intermediate transfer belt 11 to paper P. Each of the multiple primary transfer rollers 12 contacts the photoconductors 2 via the intermediate transfer belt 11. This brings the intermediate transfer belt 11 and each photoconductor 2 into contact with each other, forming a primary transfer nip between them. Meanwhile, the secondary transfer roller 13 contacts one of the rollers stretching the intermediate transfer belt 11 via the intermediate transfer belt 11. This forms a secondary transfer nip between the secondary transfer roller 13 and the intermediate transfer belt 11.

[0015] Further, a pair of timing rollers 15 is provided in the paper transport path 14 between the paper feeder 7 and the secondary transfer nip (secondary transfer roller 13).

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

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

[0018] The toner images formed on each photoconductor 2 rotate with the rotation of the photoconductor 2 and reach the primary transfer nip (the position of the primary transfer roller 12). The toner images are then transferred to the intermediate transfer belt 11, which rotates counterclockwise in FIG. 1, so that they overlap one another. The toner images transferred onto the intermediate transfer belt 11 are then transported to the secondary transfer nip (the position of the secondary transfer roller 13) with the rotation of the intermediate transfer belt 11. The toner images are then transferred to the paper P transported at the secondary transfer nip. This paper P is supplied from the paper feeder 7. The paper P supplied from the paper feeder 7 is temporarily stopped by timing roller 15 and then transported to the secondary transfer nip in time with the toner image on the intermediate transfer belt 11 reaching the secondary transfer nip. In this way, a full-color toner image is carried on the paper P. After the toner image is transferred, any toner remaining on each photoconductor 2 is removed by the cleaning devices 5.

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

[0020] Next, the configuration of the fixing device will be described.

[0021] As shown in FIG. 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 supporting member, a thermistor 25 as a temperature detection member, and a first high thermal conductivity member 28. The fixing belt 20 is an endless belt. The pressure roller 21 contacts the outer peripheral surface of the fixing belt 20 to form a fixing nip N between the pressure roller 21 and the fixing belt 20. The heater 22 heats the fixing belt 20. The heater holder 23 holds the heater 22. The stay 24 supports the heater holder 23. The thermistor 25 detects the temperature of the first high thermal conductivity member 28.

[0022] The direction perpendicular to the plane of FIG. 2 is the longitudinal direction of the fixing belt 20, pressure roller 21, heater 22, heater holder 23, stay 24, first high thermal conductivity member 28, etc., and hereinafter, this direction will be simply referred to as the longitudinal direction. This longitudinal direction also corresponds to the width direction of the paper being conveyed, the belt width direction of the fixing belt 20, and the axial direction of the pressure roller 21. The pressure member provided in the fixing device is one aspect of the first rotating member provided in the heating device of the present invention. The fixing device 9 of this embodiment is provided with the pressure roller 21 as a specific example of this pressure member. The fixing member provided in the fixing device is one aspect of the second rotating member provided in the heating device of the present invention. The fixing device 9 of this embodiment is provided with the fixing belt 20 as a specific example of this fixing member.

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

[0024] The pressure roller 21 has an outer diameter of, for example, 25 mm. From the inside, the pressure roller 21 has a core 21a as a first layer, an elastic layer 21b as a second layer, and a surface layer 21c as a third layer. The solid core 21a is made of a conductive material, which is made of iron in this embodiment. The elastic layer 21b is made of a non-conductive material, which is made of silicone rubber with a thickness of 3.5 mm in this embodiment. By making the elastic layer 21b a non-conductive layer, there is no need to add a material such as a filler to impart conductivity to the elastic layer 21b, and its elasticity and stretchability can be ensured.

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

[0026] The heater 22 is a planar heating element provided longitudinally across the width of the fixing belt 20. The heater 22 is composed of a plate-shaped substrate 30, a resistance heating element 31 provided on the substrate 30, and an insulating layer 32 covering the resistance heating element 31. The insulating layer 32 side of the heater 22 is in contact with the inner circumferential surface of the fixing belt 20, and heat generated by the resistance heating element 31 is transmitted to the fixing belt 20 via the insulating layer 32. However, the contact of the heater 22 with the inner circumferential surface of the fixing belt 20 may be via a conductive member such as a sliding sheet. When an AC voltage is applied to the heater 22 from a power source 200 (see FIG. 16 ), the resistance heating element 31 mainly generates heat. In this embodiment, the resistance heating element 31 and the insulating layer 32 are provided on the fixing belt 20 side (the fixing nip N side) of the substrate 30. However, the resistance heating element 31 and the insulating layer 32 may be provided on the heater holder 23 side of the substrate 30. In this case, since the heat from the resistance heating element 31 is transferred to the fixing belt 20 via the base material 30, it is desirable that the base material 30 be made of a material with high thermal conductivity, such as aluminum nitride. Also, by making the base material 30 out of a material with high thermal conductivity, it is possible to sufficiently heat the fixing belt 20 even if the resistance heating element 31 is placed on the opposite side of the base material 30 from the fixing belt 20 side.

[0027] The heater holder 23 and the stay 24 are disposed on the inner circumferential side of the fixing belt 20. The stay 24 is made of a metal channel material, and both ends thereof are supported by both side plates of the fixing device 9. By supporting the heater holder 23 and the heater 22 by the stay 24, the heater 22 can reliably receive the pressing force of the pressure roller 21 while the pressure roller 21 is pressed against the fixing belt 20. This ensures that the fixing nip N is stably formed between the fixing belt 20 and the pressure roller 21. In this embodiment, the thermal conductivity of the heater holder 23 is set to be smaller than that of the base material 30.

[0028] Note that the stay 24 supporting the heater holder 23 means that the stay 24, which has a portion extending in the pressure direction of the pressure roller 21 (the left-right direction in the figure) or a portion with a thickness, abuts against the heater holder 23 from the side opposite the pressure roller 21 (the left side in the figure). This makes it possible to suppress deflection of the heater holder 23 due to the pressure from the pressure roller 21 (particularly deflection in the longitudinal direction in this embodiment). However, the above-mentioned abutment does not necessarily mean that the stay 24 abuts against the heater holder 23 directly, but also includes a case where the stay 24 abuts against the heater holder 23 via another member. "Abutment via another member" refers to a state where another member is sandwiched between the stay 24 and the heater holder 23 in the left-right direction in the figure, and the stay 24 abuts against the other member at a position where at least a portion of the other member corresponds to the other member, and the other member abuts against the heater holder 23. Furthermore, the term "extending in the pressure direction" mentioned above does not necessarily mean the same direction as the pressure direction of the pressure roller 21, but also includes the case of extending in a direction at a certain angle from the pressure direction of the pressure roller 21. Even in these cases, it goes without saying that the stay 24 can suppress the deflection of the heater holder 23 against the pressure force from the pressure roller 21.

[0029] The heater holder 23 is desirably made of a heat-resistant material because it is prone to becoming hot due to the heat from the heater 22. For example, if the heater holder 23 is made of a heat-resistant resin with low thermal conductivity such as LCP, heat transfer from the heater 22 to the heater holder 23 is suppressed. This allows the heater 22 to heat the fixing belt 20 efficiently.

[0030] The heater holder 23 is also provided with guide portions 26 that guide the fixing belt 20. The guide portions 26 are provided on the upstream side (below the heater 22 in FIG. 2) and downstream side (above the heater 22 in FIG. 2) of the heater 22 in the belt rotation direction. The upstream and downstream guide portions 26 are arranged at intervals along the longitudinal direction of the heater 22. Each guide portion 26 is formed in a roughly fan shape and has a belt-facing surface 260 that is arc-shaped or convexly curved and extends in the belt circumferential direction so as to face the inner circumferential surface of the fixing belt 20.

[0031] Heater holder 23 has a plurality of openings 23a in the longitudinal direction. Openings 23a are openings that penetrate heater holder 23 in the thickness direction. Thermistor 25 and a thermostat, which will be described later, are provided in these openings 23a. These thermistors 25 and thermostats are pressed against the back surface of first high thermal conductivity member 28 by spring 29. However, openings may also be similarly provided in first high thermal conductivity member 28 (and second high thermal conductivity member, which will be described later), so that thermistor 25 and thermostat are pressed against the back surface of base material 30.

[0032] The first high thermal conductivity member 28 is made of a material having a higher thermal conductivity than the base material. In this embodiment, the first high thermal conductivity member 28 is made of plate-shaped aluminum. Alternatively, the first high thermal conductivity member 28 may be made of, for example, copper, silver, graphene, or graphite. By making the first high thermal conductivity member 28 plate-shaped, the positional accuracy of the heater 22 with respect to the heater holder 23 and the first high thermal conductivity member 28 can be improved.

[0033] Next, a method for calculating the thermal conductivity will be described. When calculating the thermal conductivity, first, the thermal diffusivity of the object is measured, and then the thermal conductivity is calculated using the measured thermal diffusivity.

[0034] The thermal diffusivity was measured using a thermal diffusivity / thermal conductivity measuring device (trade name: ai-Phase Mobile 1u, ai-Phase Corporation).

[0035] To convert the thermal diffusivity to thermal conductivity, the density and specific heat capacity values ​​are required. A dry-type automatic densitometer (product name: Accupyc 1330, manufactured by Shimadzu Corporation) was used to measure the density. A differential scanning calorimeter (product name: DSC-60, manufactured by Shimadzu Corporation) was used to measure the specific heat capacity, using sapphire as a reference material with a known specific heat capacity. In this example, the specific heat capacity was measured five times, and the average value at 50°C was used. When the density and specific heat capacity are ρ and C, respectively, the thermal conductivity λ can be calculated from the thermal diffusivity α obtained from the thermal diffusivity measurement using the following equation (1):

[0036]

number

[0037] In the fixing device 9 according to this embodiment, when a printing operation is started, the pressure roller 21 is driven to rotate, and the fixing belt 20 begins to rotate. At this time, the inner circumferential surface of the fixing belt 20 contacts and is guided by the belt-facing surface 260 of the guide portion 26, thereby allowing the fixing belt 20 to rotate stably and smoothly. Furthermore, power is supplied to the resistance heating element 31 of the heater 22, thereby heating the fixing belt 20. Then, when the temperature of the fixing belt 20 reaches a predetermined target temperature (fixing temperature), as shown in FIG. 2, a sheet of paper P carrying an unfixed toner image is transported between the fixing belt 20 and the pressure roller 21 (fixing nip N), whereby the unfixed toner image is heated and pressurized to be fixed to the sheet of paper P. The fixing belt 20 is a heated member that is heated by the heater 22.

[0038] Incidentally, the charge on the surface of the pressure roller 21 may transfer to the fixing belt 20. Then, when the pressure roller 21 is charged with a polarity opposite to that of the toner on the paper, some of the toner on the paper adheres to the surface of the fixing belt 20. This adhered toner then adheres to the paper P that is passed through the fixing nip N, causing a problem of image defects due to electrostatic offset.

[0039] Furthermore, in the pressure roller 21 of this embodiment, a non-conductive elastic layer 21b is provided between the conductive core 21a and the surface layer 21c, so that the core 21a and the surface layer 21c are not electrically connected. The core 21a is not in contact with other conductive members and is not electrically connected. This causes a problem of electrical noise being generated by electric charges accumulated in the core 21a.

[0040] For these reasons, it is necessary to neutralize the core metal 21a and the surface layer 21c, respectively. To address this issue, different neutralization members can be provided for the core metal 21a and the surface layer 21c. However, this increases the number of components in the fixing device, resulting in increased costs and a larger fixing device. Alternatively, a conductive filler or other material can be mixed into the intermediate elastic layer 21b to form a conductive layer, electrically connecting the core metal 21a and the surface layer 21c. By contacting a neutralization member with either the core metal 21a or the surface layer 21c, these layers can be neutralized. However, mixing the conductive filler into the elastic layer 21b reduces the elasticity and flexibility of the elastic layer 21b. This requires the pressure roller 21 to apply more pressure to the fixing belt 20 to form a fixing nip N of a predetermined width, which can lead to other problems, such as an increased size of the fixing device and damage to the fixing belt 20.

[0041] Next, the configuration of the fixing device of this embodiment that neutralizes the core metal 21a and the surface layer 21c will be described with reference to FIG.

[0042] 3, the metal core 21a of the pressure roller 21 protrudes in the axial direction beyond the surface layer 21c and the elastic layer, and has an exposed portion 21a1 where its outer circumferential surface is exposed to the outside. Hereinafter, the portions of the pressure roller 21 other than the exposed portion 21a1, that is, the portions of the pressure roller 21 other than the exposed portion 21a1 of the elastic layer, the surface layer 21c, and the metal core 21a, will be collectively referred to as the main body portion of the pressure roller 21 or the main body side of the pressure roller 21.

[0043] In this embodiment, the pressure roller 21 has a core metal 21a as a first layer, an elastic layer 21b (see FIG. 2) as a second layer, and a surface layer 21c as a third layer, in this order. However, "having in this order" does not limit the pressure roller 21 to being composed of only these three layers, and other layers may be provided between the layers. Also, other layers may be located inside the first layer or outside the third layer. Furthermore, the core metal 21a as the first layer may be a solid layer as in this embodiment, or may be a hollow layer.

[0044] The direction perpendicular to the axial direction of the pressure roller 21, which is the left-right direction in Fig. 3, is the radial direction of the pressure roller 21. This radial direction of the pressure roller 21 is the direction along the plane of the paper in Fig. 2, and is the direction from the center side, which is the circular center of the pressure roller 21, to the outer peripheral surface side. In the following explanation, the radial direction of the pressure roller 21 will also be simply referred to as the radial direction. Furthermore, in the following explanation, the center side of the pressure roller 21 in this radial direction will be referred to as the "inside" of the pressure roller 21 in the radial direction, and the outer peripheral surface side of the pressure roller 21 opposite to this inside will be referred to as the "outside" of the pressure roller 21 in the radial direction.

[0045] 3, a conductive member 38 is provided on the outer peripheral surface of exposed portion 21a1 near the main body side of pressure roller 21 of exposed portion 21a1. Conductive member 38 is made of a conductive material. Conductive member 38 is not in contact with the main body side of pressure roller 21. In the radial direction of pressure roller 21, which is a direction perpendicular to the axial direction of pressure roller 21, a contacted portion of the outer peripheral surface of conductive member 38 that comes into contact with discharging brush 37, which will be described later, is provided at approximately the same position as the outer peripheral surface of surface layer 21c of pressure roller 21.

[0046] The conductive member 38 is attached to the outer peripheral surface of the exposed portion 21a1, and is electrically connected to the core 21a. Therefore, by bringing a later-described charge-removing brush 37 into contact with the conductive member 38, the core 21a can be neutralized. In this embodiment, the conductive member 38 is an annular member, but this is not limiting. The conductive member 38 can also be formed integrally as part of the exposed portion 21a1 of the core 21a.

[0047] The conductive member 38 is preferably made of an elastic material. This allows the conductive member 38 to be fixed to the exposed portion 21a1 of the pressure roller 21 by the contraction force of the elastic material. Therefore, the conductive member 38 can be positioned relative to the pressure roller 21. This allows the charge removal brush 37 to stably contact the conductive member 38. Furthermore, there is no need to provide fixing members such as screws to fix the conductive member 38 to the pressure roller 21, which improves the ease of assembling the conductive member 38 to the pressure roller 21.

[0048] The core metal 21a has an exposed portion 21a1 that constitutes part of the shaft of the pressure roller 21, and is supported by a bearing 39. The bearing 39 is made of a non-conductive material. Note that the bearing 39 is omitted from the description of Figure 7 and subsequent figures.

[0049] The fixing device of this embodiment also has a charge-removing brush 37 as a charge-removing member. The charge-removing brush 37 has a contact portion 37a and a holding portion 37b. The contact portion 37a is made up of a plurality of hair-like portions, which contact the metal core 21a or the surface layer 21c. The holding portion 37b holds the root portion, which is one end of the hair-like portions of the contact portion 37a. This root portion is the end of the hair-like portions opposite the side that contacts the metal core 21a or the surface layer 21c. The charge-removing brush 37 is grounded via a resistor. By using a brush-like member as the charge-removing member in this embodiment, the charge-removing brush 37 can contact the metal core 21a or the surface layer 21c without damaging them, and can remove electricity from the conductive member 38 or the surface layer 21c.

[0050] The static elimination brush 37 is disposed in a position facing both the surface layer 21c and the exposed portion 21a1 of the pressure roller 21 in the axial direction of the pressure roller 21, which is the left-right direction in FIG. 3. The contact portion 37a of the static elimination brush 37 contacts both the surface layer 21c and the conductive member 38. This allows static elimination of both the core metal 21a and the surface layer 21c. The pressure roller 21 and the conductive member 38 are members to be neutralized by the static elimination brush 37.

[0051] As described above, according to the configuration of this embodiment, both the core metal 21 a and the surface layer 21 c can be neutralized using the common neutralization brush 37. This solves the electrical problems that arise in the core metal 21 a and the surface layer 21 c. Furthermore, the number of parts in the fixing device can be reduced, leading to cost reduction and miniaturization of the fixing device.

[0052] As shown in FIG. 4, the anti-static brush 37 has a held portion 37d on the side opposite the contact portion 37a. The held portion 37d is attached to a metal housing 42 of the fixing device. Alternatively, as shown in FIG. 5, it may be attached to a side plate 41. The held portion 37d can be attached, for example, by screwing. The side plate 41 already has holes for attaching the shaft portion of the pressure roller 21 and its bearing. Therefore, from the perspective of ensuring the strength of the side plate 41, it is preferable to attach the held portion 37d to the housing 42 as shown in FIG. 4, rather than providing additional holes in the side plate 41 for attaching the held portion 37d. Note that FIG. 4 is a plan view of the fixing device 9, and FIG. 5 is a front view of the fixing device 9.

[0053] 3, the outer peripheral surface of exposed portion 21a1 is located radially inward of surface layer 21c of pressure roller 21 and farther from charge removal brush 37 by the thickness of the elastic layer and surface layer 21c of pressure roller 21. Therefore, if contact portion 37a were to be in contact with exposed portion 21a1 without providing conductive member 38, the contact position of contact portion 37a with exposed portion 21a1 would be farther from surface layer 21c. This requires the length of the hair portion in contact with exposed portion 21a1 to be increased, which can cause problems such as unstable contact between contact portion 37a and exposed portion 21a1 if the hair portion of contact portion 37a in contact with exposed portion 21a1 bends or the brush rigidity decreases due to deterioration over time.

[0054] In contrast, in this embodiment, the conductive member 38 is provided, allowing the contact positions of the contact portion 37a with each component to be closer in the radial direction of the pressure roller 21. Specifically, in this embodiment, the outer peripheral surface of the conductive member 38, which is the contacted portion of the conductive member 38, is located radially outward of the pressure roller 21 relative to the outer peripheral surface of the exposed portion 21a1. Therefore, the contact position of the contact portion 37a with the conductive member 38 and the contact position of the contact portion 37a with the surface layer 21c can be located closer in the radial direction of the pressure roller 21. This allows the hair portions arranged in the axial direction of the contact portion 37a to contact the conductive member 38 and the surface layer 21c under more closely matched conditions. Furthermore, it is not necessary to lengthen the hair portions constituting the contact portion 37a to contact the exposed portion 21a1. Therefore, the contact portion 37a stably contacts the conductive member 38 and the surface layer 21c, allowing for stable de-electrification of the core metal 21a and the surface layer 21c. In particular, in this embodiment, the outer diameter of the conductive member 38 is set to be approximately the same as the outer diameter of the surface layer 21c of the pressure roller 21, so that the contact portion 37a can come into contact with the conductive member 38 and the surface layer 21c under conditions closer to those of the conductive member 38 and the surface layer 21c. This allows the contact portion 37a to come into contact with the conductive member 38 and the surface layer 21c more stably.

[0055] Furthermore, by providing the conductive member 38 on the exposed portion 21a1 as in this embodiment, the axial movement of the pressure roller 21 can be restricted. Specifically, as shown in FIG. 6 , the shaft of the pressure roller 21 is held by the side plate 41 via the bearing 39. When the pressure roller 21 shifts axially, the conductive member 38, which has a larger diameter than the shaft, contacts the bearing 39, thereby restricting the axial movement of the pressure roller 21. In other words, the side plate 41 can hold the pressure roller 21 in a predetermined axial position. Conventionally, to restrict the axial movement of the pressure roller 21, the bearing 39 is provided axially outside the side plate 41, and a restricting member such as a C-ring is provided further outside the bearing 39. The configuration of this embodiment eliminates the need for such a restricting member, simplifying the holding configuration of the pressure roller 21 by the side plate 41. The axial movement of the pressure roller 21 can also be similarly restricted by the enlarged diameter portion 21a2 (see FIG. 7 ), which will be described later.

[0056] Next, the conductive member 38 having a different configuration from the above embodiment will be described in order.

[0057] As shown in FIG. 7(a), in this embodiment, a conductive member 38 is attached so as to cover one axial side of the pressure roller 21 on the main body side. As shown in the cross-sectional view of FIG. 7(b), the conductive member 38 contacts the surface layer 21c. The conductive member 38 has a cylindrical portion 38a on one axial side that is smaller in diameter than the portion covering the main body side of the pressure roller 21. The outer peripheral surface of the cylindrical portion 38a is the contacted portion that comes into contact with the discharging brush 37. The outer diameter of the cylindrical portion 38a is smaller than the outer diameter of the surface layer 21c. An insertion hole 38a1 is provided inside the cylindrical portion 38a. The exposed portion 21a1 passes through the insertion hole 38a1 and protrudes outward from one axial side of the insertion hole 38a1.

[0058] The core metal 21a has an expanded diameter portion 21a2 in a part of the axial direction of the exposed portion 21a1. The expanded diameter portion 21a2 is a portion that is longer in the radial direction than the remaining portion of the exposed portion 21a1. In this embodiment, the outer peripheral surface of the expanded diameter portion 21a2 and the outer peripheral surface of the cylindrical portion 38a are located at approximately the same position in the radial direction.

[0059] 7(a), the contact portion 37a of the static elimination brush 37 of this embodiment contacts the outer circumferential surface of the cylindrical portion 38a of the conductive member 38 and the expanded diameter portion 21a2 of the exposed portion 21a1, thereby eliminating static electricity from the core metal 21a and the surface layer 21c.

[0060] Furthermore, by setting the outer diameter of the cylindrical portion 38a to be smaller than the outer diameter of the surface layer 21c, the radial contact position of the static elimination brush 37 with each component can be made closer. This allows the contact portion 37a to stably eliminate static electricity from the core metal 21a and the surface layer 21c. Furthermore, by having the contact portion 37a contact the expanded diameter portion 21a2 of the exposed portion 21a1, the radial contact position of the static elimination brush 37 with each component can be made closer. This allows the contact portion 37a to stably eliminate static electricity from the core metal 21a and the surface layer 21c. Particularly in this embodiment, the outer peripheral surface of the expanded diameter portion 21a2 and the outer peripheral surface of the cylindrical portion 38a are located at approximately the same radial position, which allows the radial contact conditions of the static elimination brush 37 with each component to be made approximately the same. This allows the contact portion 37a to more stably eliminate static electricity from the core metal 21a and the surface layer 21c. In this way, the positions of the contact portions 37a of the charge removal brush 37 can be made closer to each other in the radial direction of the pressure roller 21 on both sides of the surface layer 21c and the core metal 21a.

[0061] 8, the conductive member 38 contacts one axial side of the main body of the pressure roller 21. The conductive member 38 has approximately the same outer diameter as the surface layer 21c of the pressure roller 21, and the conductive member 38 contacts the axial end face of the surface layer 21c of the pressure roller 21. That is, in this embodiment, the conductive member 38 is provided on the outer peripheral surface of the exposed portion 21a1 and contacts the core metal 21a, as well as the surface layer 21c. This electrically connects the core metal 21a, the conductive member 38, and the surface layer 21c.

[0062] The charge-removing brush 37 contacts the conductive member 38 and the surface layer 21c. However, the charge-removing brush 37 may contact only one side of the conductive member 38. This allows the contact portion 37a to stably remove charge from the core metal 21a and the surface layer 21c.

[0063] 9(a), in the assembled state of the fixing device, the outer diameter of the conductive member 38 can be made smaller than the outer diameter of the surface layer 21c, that is, the outer diameter of the main body side of the pressure roller 21. In this embodiment as well, the static elimination brush 37 can be stably brought into contact with the surface layer 21c of the pressure roller 21 and the conductive member 38, and static elimination can be stably performed on the surface layer 21c and the core metal 21a.

[0064] As shown in FIG. 9(b), the outer surface of the conductive member 38 contacts the outer surface of the fixing belt 20. The conductive member 38 also contacts one axial end of the pressure roller 21 on the main body side. As a result, heat from the pressure roller 21 and the fixing belt 20 transfers to the conductive member 38, resulting in heat loss in the fixing device. In response to this, by reducing the outer diameter of the conductive member 38 as described above, the contact area of ​​the conductive member 38 with the fixing belt 20 and the pressure roller 21 is reduced, thereby suppressing the outflow of heat to the conductive member 38. However, the outer diameter of the conductive member 38 may be further reduced so that the conductive member 38 does not come into contact with the fixing belt 20.

[0065] Furthermore, as shown in FIG. 10 , the diameter of the conductive member 38 can be made non-uniform in the circumferential direction. In this embodiment, the conductive member 38 comes into contact with the fixing belt 20 only when the large-diameter portion 38c of the conductive member 38 moves to a position facing the fixing belt 20 due to the rotation of the pressure roller 21. This suppresses the heat leakage from the conductive member 38 to the fixing belt 20. Furthermore, the charge removal brush 37 can come into contact with the conductive member 38 when the large-diameter portion 38c of the conductive member 38 moves to a position facing the contact portion 37a due to the rotation of the pressure roller 21. This prevents the charge removal function of the charge removal brush 37 from being impaired. In this way, by making the diameter of the conductive member 38 non-uniform in the circumferential direction so that it comes into contact with the fixing belt 20 only in a partial region in the circumferential direction, the charge removal function of the charge removal brush 37 can be maintained while suppressing the heat leakage from the fixing belt 20 to the conductive member 38.

[0066] 11(a) and 11(b), the conductive member 38 has a protrusion 38d that protrudes in the axial direction of the pressure roller 21. Multiple protrusions 38d are provided in the circumferential direction of the conductive member 38. In this embodiment, the conductive member 38 contacts the main body side of the pressure roller 21 at the end of the protrusion 38d. This allows the conductive member 38 to be positioned relative to the main body side of the pressure roller 21. This allows the discharging brush 37 to stably contact the conductive member 38. Furthermore, compared to the embodiment shown in FIG. 9 and the like, the contact area of ​​the conductive member 38 with the pressure roller 21 can be made smaller. This therefore reduces the flow of heat from the pressure roller 21 to the conductive member 38.

[0067] The number of protrusions 38d is not limited to three as in the embodiment shown in FIG. 11, and any number of protrusions can be provided. The shape of the protrusions can also be modified as needed, such as by arranging them in a circumferential ring shape. It is particularly preferable that the contact area of ​​the conductive member 38 in the axial direction with the main body of the pressure roller 21 be one-third or less of the area of ​​the pressure roller 21. This effectively prevents heat from leaking from the pressure roller 21 to the conductive member 38. The one-third area of ​​the pressure roller 21 refers to one-third of the total area of ​​the cross section of the pressure roller 21 perpendicular to the axial direction at the position where the conductive member 38 contacts the pressure roller 21 in the axial direction.

[0068] As shown in FIG. 12 , the conductive member 38 of the pressure roller 21 is preferably located on the opposite side of the axial direction from the connector 40, which is the power supply member for the heater 22. In other words, the length of the connector 40 on the axial side of the pressure roller 21 is longer than on the opposite side, ensuring a contact point between the heater 22 and the connector 40. This reduces the temperature of the fixing belt 20 and other components. As mentioned above, heat is also transferred from the pressure roller 21 and fixing belt 20 to the conductive member 38. Therefore, by arranging the conductive member 38 and the connector 40 on opposite sides of the axial direction, the temperatures of the fixing belt 20 and pressure roller 21 can be balanced, preventing a drop in temperature on only one side of the axial direction. The opposite side of the connector 40 on the axial direction of the pressure roller 21 refers to the opposite side of the connector 40 relative to the center position in the horizontal direction of FIG. 12 , which is the longitudinal direction of the fixing device or fixing belt 20.

[0069] In the above embodiment, the static elimination brush is described as eliminating the first and third layers of the pressure roller, which is the first rotating member, but it may be configured to eliminate the surface layer of the second rotating member instead of the third layer of the first rotating member. In other words, since the surface layer 21c of the pressure roller 21 and the surface layer 20c of the fixing belt 20 are in contact with each other at the fixing nip N, the charge accumulated on the surface layer 21c of the pressure roller 21 or the surface layer 20c of the fixing belt 20 can be removed by eliminating the charge on either one of them.

[0070] For example, as shown in FIG. 13, a contact portion 37a of the discharging brush 37 contacts the core metal 21a of the pressure roller 21 and the surface layer 20c of the fixing belt 20 serving as a second rotating member.

[0071] 3, in this embodiment, a conductive member 38 is provided on the outer peripheral surface of the exposed portion 21a1. The outer diameter of the conductive member 38 is set to be approximately the same as the outer diameter of the surface layer 21c of the pressure roller 21. This allows the neutralization brush 37 to be closer to each part it comes into contact with than in a configuration in which the neutralization brush 37 contacts the core metal 21a. Specifically, the neutralization brush 37 can come into contact with the outer peripheral surface of the conductive member 38 and the surface layer 20c of the fixing belt 20 under closer conditions.

[0072] The contact portion 37a of the charge-removing brush 37 comes into contact with the surface layer 20c of the fixing belt 20 and the conductive member 38. This allows both the surface layer 20c of the fixing belt 20 and the core 21a of the pressure roller 21 to be neutralized by the common charge-removing brush 37. Furthermore, the contact portion 37a can come into contact with the surface layer 20c of the fixing belt 20 and the conductive member 38 at a position closer in the radial direction. This allows the contact portion 37a to stably neutralize the surface layer 20c of the fixing belt 20 and the core 21a of the pressure roller 21. This allows the charge on the core 21a and surface layer 21c of the pressure roller 21 to be removed. The fixing belt 20 and the conductive member 38 are members to be neutralized by the charge-removing brush 37.

[0073] Furthermore, the occurrence of banding images can be prevented by eliminating charge from the surface of the fixing belt 20 using the charge-removing brush 37 of this embodiment. In other words, in a fixing device 9 that applies an AC voltage to the heater 22, the insulating layer on the heater 22 and the surface layer of the fixing belt 20 are equivalent to a capacitor. When the heater 22 and the fixing belt 20 come into contact with each other, an AC voltage is applied to the fixing nip N via the fixing belt 20. As shown in FIG. 14 , when a sheet of paper P is in contact with both the secondary transfer nip NA and the fixing nip N, this AC voltage propagates through the sheet of paper P to the secondary transfer nip NA as indicated by the arrow in FIG. 14 . This AC voltage affects the transfer electric field, causing periodic density variations in the transferred image, resulting in so-called banding images. This problem is particularly pronounced when the sheet of paper P has low resistance, such as in a high-humidity environment or when thin paper is used as the sheet of paper P. The secondary transfer nip NA is the nip formed between the secondary transfer roller 13 and the secondary transfer counter roller 16.

[0074] In this embodiment, the AC voltage can be passed from the fixing nip N to the fixing belt 20 and then to the ground side via the charge removal brush 37. Alternatively, the AC voltage can be passed from the fixing nip N to the fixing belt 20, the conductive member 38, and then to the ground side via the charge removal brush 37. Therefore, the formation of the banding image can be suppressed.

[0075] In addition, in a configuration in which the conductive member 38 is in contact with the core metal 21a and surface layer 21c of the pressure roller 21 as shown in Figure 8, instead of contacting the discharging brush 37 with the pressure roller 21, the discharging brush 37 may be in contact with the surface layer 20c of the fixing belt 20.

[0076] Next, the configuration of the heater provided in the fixing device will be described in detail.

[0077] FIG. 15 is a plan view of the heater according to this embodiment.

[0078] 15, a plurality of (four) resistance heating elements 31, power supply lines 33A and 33B as conductors, a first electrode portion 34A, and a second electrode portion 34B are provided on the surface of a plate-shaped substrate 30. However, the number of resistance heating elements 31 is not limited to that in this embodiment.

[0079] In this embodiment, the longitudinal direction of the heater 22, etc. (the direction perpendicular to the plane of the paper in FIG. 2) is also the arrangement direction X of the multiple resistance heating elements 31, as shown in FIG. 15. The arrangement direction X is the same direction as the longitudinal direction of the fixing belt 20 and the axial direction of the pressure roller 21. Hereinafter, this direction will also be simply referred to as the arrangement direction. Furthermore, the up-down direction Y in FIG. 15, which is a direction intersecting the arrangement direction (a direction perpendicular to the arrangement direction in this embodiment) and different from the thickness direction of the base material 30, will also be referred to as the direction intersecting the arrangement direction of the multiple resistance heating elements 31, or simply as the intersecting arrangement direction. The intersecting arrangement direction Y is the direction along the surface of the base material 30 on which the resistance heating elements 31 are provided, and is also the short-side direction of the heater 22 or the transport direction of paper passed through the fixing device 9.

[0080] The plurality of resistance heating elements 31 constitute a heating section 35 divided into a plurality of sections in the arrangement direction. Each resistance heating element 31 is electrically connected in parallel to a pair of electrode portions 34A and 34B provided at one end of the substrate 30 in the arrangement direction (the left end in FIG. 15 ) via power supply lines 33A and 33B. The power supply lines 33A and 33B are made of a conductor having a lower resistance value than the resistance heating elements 31. To ensure insulation between the resistance heating elements 31, the gap between adjacent resistance heating elements 31 is preferably 0.2 mm or more, more preferably 0.4 mm or more. Furthermore, if the gap between adjacent resistance heating elements 31 is too large, a temperature drop is likely to occur in the gap. Therefore, to suppress temperature unevenness across the arrangement direction, the gap is preferably 5 mm or less, more preferably 1 mm or less.

[0081] The resistance heating element 31 is made of a material having a PTC (positive temperature coefficient of resistance) characteristic, and is characterized in that the resistance value increases (heater output decreases) as the temperature increases.

[0082] The PTC characteristics of the resistance heating element 31 and the divided heating section 35 configuration in the arrangement direction prevent excessive temperature rise of the fixing belt 20 when small-size paper is passed through. In other words, when paper narrower than the overall width of the heating section 35 is passed through, the paper does not absorb heat from the fixing belt 20 in the area outside the paper width, so the temperature of the resistance heating element 31 corresponding to that area rises. Because the voltage applied to the resistance heating element 31 is constant, the temperature of the resistance heating element 31 outside the paper width rises, and when its resistance value increases, the output (heat generation amount) decreases relatively, suppressing the temperature rise at the edge. Furthermore, by electrically connecting multiple resistance heating elements 31 in parallel, it is possible to suppress the temperature rise in non-paper passing areas while maintaining printing speed. The heating elements constituting the heating section 35 may be other than resistance heating elements having PTC characteristics. Furthermore, the resistance heating elements may be arranged in multiple rows in the direction crossing the arrangement of the heaters 22.

[0083] The resistance heating element 31 can be formed, for example, by applying a paste made of silver palladium (AgPd) and glass powder to the substrate 30 by screen printing or the like, and then firing the substrate 30. In this embodiment, the resistance value of the resistance heating element 31 is set to 80 Ω at room temperature. In addition to the materials mentioned above, the resistance heating element 31 may also be made of resistance materials such as silver alloy (AgPt) or ruthenium oxide (RuO2). The power supply line 33 and the electrode portion 34 can be made of silver (Ag) or silver palladium (AgPd) by screen printing or the like. The power supply line 33 is made of a conductor with a lower resistance value than the resistance heating element 31.

[0084] The substrate 30 is preferably made of ceramics such as alumina or aluminum nitride, which have excellent heat resistance and insulation properties, or non-metallic materials such as glass or mica. In this embodiment, an alumina substrate is used, which is 8 mm wide in the cross-array direction, 270 mm wide in the array direction, and 1.0 mm thick. Alternatively, the substrate 30 may be made of a conductive material such as a metal laminated with an insulating material. Aluminum and stainless steel are preferred metal materials for the substrate 30, as they are low-cost. By constructing the substrate 30 from a stainless steel plate, cracks due to thermal stress can be suppressed. Furthermore, to improve the thermal uniformity of the heater 22 and enhance image quality, the substrate 30 may be made of a highly thermally conductive material such as copper, graphite, or graphene.

[0085] The insulating layer 32 is made of heat-resistant glass having a thickness of, for example, 75 μm. The insulating layer 32 covers the resistance heating element 31 and the power supply line 33, insulating and protecting them and maintaining sliding properties with the fixing belt 20.

[0086] FIG. 16 is a diagram showing a power supply circuit to the heater according to this embodiment.

[0087] 16, in this embodiment, a power supply circuit for supplying power to each resistance heating element 31 is configured by electrically connecting an AC power supply 200 and the electrodes 34A, 34B of the heater 22. The power supply circuit is also provided with a triac 210 that controls the amount of power supplied. The amount of power supplied to each resistance heating element 31 is controlled by a control unit 220 via the triac 210 based on the temperature detected by the thermistor 25. The control unit 220 is configured by a microcomputer including a CPU, ROM, RAM, I / O interface, etc.

[0088] In this embodiment, thermistors 25 are disposed in a central region in the arrangement direction of heaters 22, which is within the minimum paper passing width, and at one end side in the arrangement direction of heaters 22. Furthermore, at one end side in the arrangement direction of heaters 22, a thermostat 27 is disposed as a power cut-off device that cuts off the supply of power to resistance heating elements 31 when the temperature of resistance heating elements 31 reaches or exceeds a predetermined temperature. Thermistors 25 and thermostat 27 contact first high thermal conductivity member 28 to detect its temperature.

[0089] In this embodiment, the first electrode portion 34A and the second electrode portion 34B are provided on the same side in the arrangement direction, but they may be provided on different sides. The shape of the resistance heating element 31 is not limited to that of this embodiment. For example, as shown in FIG. 17, the resistance heating element 31 may be rectangular. Alternatively, as shown in FIG. 18, the resistance heating element 31 may be formed of a linear portion that is folded back to form a substantially parallelogram shape. As shown in FIG. 17, the portion extending from the block-shaped portion of the resistance heating element 31 toward the power supply line 33 (the portion extending in the intersecting direction) may be part of the resistance heating element 31, or may be made of the same material as the power supply line 33.

[0090] 19A and 19B are diagrams showing the temperature distribution in the arrangement direction of the fixing belt 20. (a) shows the arrangement of the heaters 22. (b) shows the temperature T of the fixing belt 20 on the vertical axis and the position of the fixing belt 20 on the horizontal axis.

[0091] As shown in FIGS. 19(a) and 19(b), the heater 22 has a plurality of resistance heating elements 31 divided in the arrangement direction, forming divided regions B between the resistance heating elements 31. In other words, the heater 22 has a plurality of resistance heating elements 31 arranged at intervals B. Hereinafter, the range B of the divided region will be referred to as interval B. In interval B, the area occupied by the resistance heating elements 31 is smaller than in other regions, resulting in a smaller amount of heat generation. As a result, the temperature of the fixing belt 20 in interval B is lower than in other regions, causing temperature unevenness in the arrangement direction of the fixing belt 20. Furthermore, in an expanded divided region C (hereinafter simply referred to as region C) including the region surrounding interval B, which is a divided region, the temperatures of the heater 22 and the fixing belt 20 are also lower. Note that the temperature of the heater 22 is also lower in interval B. Here, as shown in the enlarged view of FIG. 19(a), interval B refers to the arrangement direction region including all of the regions into which the resistance heating elements 31, which are the main heat-generating portions of the heater 22, are divided in the arrangement direction. Furthermore, an area including the interval B and a range corresponding to the connection portion 311 of the resistance heating element 31 is defined as an area C. The connection portion 311 refers to the portion of the resistance heating element 31 that extends in the cross-arrangement direction and is connected to each of the power supply lines 33A and 33B.

[0092] As shown in Fig. 20, in heater 22 having rectangular resistance heating element 31 as shown in Fig. 17, the temperature in interval B is also lower than in other parts. In heater 22 having resistance heating element 31 shaped as shown in Fig. 21, the temperature in interval B is also lower than in other parts. Furthermore, as shown in Fig. 22, in heater 22 having resistance heating element 31 shaped as shown in Fig. 18, the temperature in interval B is also lower than in other parts. However, by overlapping adjacent resistance heating elements 31 in the arrangement direction as in Figs. 19, 21 and 22, the temperature drop in interval B relative to other parts can be suppressed.

[0093] In this embodiment, the above-described first high thermal conductivity member 28 is provided to suppress the temperature drop in the above-mentioned interval and to suppress temperature unevenness in the arrangement direction of the fixing belt 20. The first high thermal conductivity member 28 will be described in more detail below.

[0094] 2, first high thermal conductivity member 28 is disposed between heater 22 and stay 24 in the left-right direction of FIG. 2, and is particularly sandwiched between heater 22 and heater holder 23. That is, first high thermal conductivity member 28 has one surface abutting against the back surface of base material 30 and the other surface abutting against heater holder 23.

[0095] The stay 24 supports the heater holder 23, the first high thermal conductive member 28, and the heater 22 by bringing contact surfaces 24a1 of two vertical portions 24a, which extend in the thickness direction of the heater 22 and other components, into contact with the heater holder 23. In the cross-array direction (the vertical direction in FIG. 2), the contact surfaces 24a1 are provided outside the range in which the resistance heating elements 31 are provided. This makes it possible to suppress heat transfer from the heater 22 to the stay 24, and allows the heater 22 to heat the fixing belt 20 efficiently.

[0096] As shown in Fig. 23, first high thermal conductivity member 28 is made of a plate material having a thickness of 0.3 mm, a length in the arrangement direction of 222 mm, and a width in the direction crossing the arrangement of 10 mm. In this embodiment, first high thermal conductivity member 28 is made of a single plate material, but it may be made of multiple members. Note that illustration of guide portion 26 of Fig. 2 is omitted in Fig. 23.

[0097] The first high thermal conductive member 28 is fitted into the recess 23b of the heater holder 23, and the heater 22 is attached thereto, thereby sandwiching and holding the first high thermal conductive member 28 between the heater holder 23 and the heater 22. In this embodiment, the width of the first high thermal conductive member 28 in the arrangement direction is set to be substantially the same as the width of the heater 22 in the arrangement direction. Movement of the first high thermal conductive member 28 and the heater 22 in the arrangement direction is restricted by both side walls (arrangement direction restricting portions) 23b1 in the arrangement direction that form the recess 23b. In this manner, restricting misalignment of the first high thermal conductive member 28 in the arrangement direction within the fixing device 9 improves heat conduction efficiency within a target range in the arrangement direction. Movement of the first high thermal conductive member 28 and the heater 22 in the arrangement direction is restricted by both side walls (arrangement cross direction restricting portions) 23b2 in the arrangement cross direction that form the recess 23b.

[0098] Further, the above-mentioned discharging brush 37 may be configured to come into contact with the first high thermal conductivity member 28. For example, as shown in Fig. 24, the first high thermal conductivity member 28 has a contacted portion 28a at one end in the arrangement direction. The contacted portion 28a is provided outside one end in the width direction of the fixing belt 20 and is a bent portion bent in the direction crossing the arrangement. However, the shape of the contacted portion 28a is not limited to this.

[0099] As shown in FIG. 25, contact portion 37a of discharging brush 37 comes into contact with conductive member 38, the surface layer of fixing belt 20, and contacted portion 28a of first high heat conductive member 28, respectively, to dissipate electricity therefrom.

[0100] In this embodiment, by providing conductive member 38 on core metal 21a and providing contacted portion 28a on first high thermal conductivity member 28, the radial positions at which contact portion 37a comes into contact with each of the members to be neutralized can be made closer. Therefore, contact portion 37a can stably contact these members and neutralize them. Note that contacted portion 28a of first high thermal conductivity member 28 does not necessarily have to be provided integrally with first high thermal conductivity member 28, and may also be formed from another conductive member.

[0101] The range in the arrangement direction in which the first high thermal conductivity members 28 are provided is not limited to the above. For example, as shown in FIG. 26, the first high thermal conductivity members 28 may be provided only in the range corresponding to the heat generating portions 35 in the arrangement direction (see the hatched area in FIG. 26). Alternatively, as shown in FIG. 27, the first high thermal conductivity members 28 may be provided only in the entire area at a position corresponding to the interval B in the arrangement direction. Note that in FIG. 27, for convenience, the resistance heating elements 31 and the first high thermal conductivity members 28 are shown shifted in the vertical direction in FIG. 27, but they are actually disposed at approximately the same position in the cross-array direction. However, this is not a limitation, and the first high thermal conductivity members 28 may be provided only in part of the resistance heating elements 31 in the cross-array direction, or may be provided so as to cover the entire cross-array direction as shown in FIG. 28 described later. Furthermore, as shown in FIG. 28, the first high thermal conductivity members 28 may be provided in addition to the position corresponding to the interval B in the arrangement direction, straddling the resistance heating elements 31 on both sides of the interval B. "Provided across the resistance heating elements 31 on both sides" here means that the first high thermal conductivity members 28 at least partially overlap with the resistance heating elements 31 on both sides in the arrangement direction. Note that the first high thermal conductivity members 28 may be provided to correspond to all of the intervals B of the heaters 22, or may be provided only at positions corresponding to some of the intervals B, such as by providing the first high thermal conductivity members 28 only at a position corresponding to one of the intervals B as shown in Figure 28. Here, "provided at a position corresponding to the interval B in the arrangement direction" means that the first high thermal conductivity members 28 at least partially overlap with the interval B in the arrangement direction.

[0102] Due to the pressure of the pressure roller 21, the first highly thermally conductive member 28 is sandwiched between the heaters 22 and the heater holder 23 and is in close contact with these members. The contact of the first highly thermally conductive member 28 with the heaters 22 improves the thermal conduction efficiency in the arrangement direction of the heaters 22. Furthermore, by providing the first highly thermally conductive member 28 at a position corresponding to the spacing B between the heaters 22 in the arrangement direction, the thermal conduction efficiency at the spacing B can be improved, increasing the amount of heat transferred to the position at the spacing B in the arrangement direction and raising the temperature at the spacing B in the arrangement direction. This reduces temperature unevenness in the arrangement direction of the heaters 22. This reduces temperature unevenness in the arrangement direction of the fixing belt 20. This reduces uneven fixing and glossiness of the image fixed to the paper. Alternatively, there is no need for extra heating by the heaters 22 to ensure sufficient fixing performance at the spacing B, thereby achieving energy savings in the fixing device 9. Furthermore, by providing the first high thermal conductivity member 28 over the entire heat generating section 35 in the arrangement direction, the heat transfer efficiency of the heater 22 can be improved over the entire main heating area (i.e., the image forming area of ​​the paper being passed through), thereby suppressing temperature unevenness in the arrangement direction of the heater 22 and, ultimately, the fixing belt 20.

[0103] In particular, in this embodiment, the combination of the configuration of the first high thermal conductivity member 28 and the resistance heating element 31 having the PTC characteristic described above can effectively suppress excessive temperature rise in the non-paper passing area when small size paper is passed. In other words, the PTC characteristic suppresses the amount of heat generated by the resistance heating element 31 in the non-paper passing area, and the heat of the non-paper passing area with an increased temperature can be efficiently transferred to the paper passing area, effectively suppressing excessive temperature rise in the non-paper passing area.

[0104] Furthermore, it is preferable to arrange first high thermal conductivity members 28 around gap B, since the temperature there is also low due to the small amount of heat generated in gap B. For example, in this embodiment, by providing first high thermal conductivity members 28 at positions corresponding to region C (see FIG. 20), the heat transfer efficiency in the arrangement direction in gap B and its periphery is particularly improved, and temperature unevenness in the arrangement direction of heaters 22 can be further suppressed. Particularly in this embodiment, first high thermal conductivity members 28 are provided over the entire area of ​​heat-generating section 35 in the arrangement direction. This makes it possible to further suppress temperature unevenness in the arrangement direction of heaters 22 (fixing belt 20).

[0105] Next, a different embodiment of the fixing device will be described.

[0106] 29, fixing device 9 of the present embodiment has second high thermal conductivity member 36 between heater holder 23 and first high thermal conductivity member 28. Second high thermal conductivity member 36 is provided at a different position from first high thermal conductivity member 28 in the stacking direction (left-right direction in FIG. 29) of members such as heater holder 23, stay 24, and first high thermal conductivity member 28. More specifically, second high thermal conductivity member 36 is provided overlapping first high thermal conductivity member 28. Note that, unlike FIG. 2, FIG. 29 shows a cross section in which second high thermal conductivity member 36 is arranged in the arrangement direction and thermistor 25 is not arranged.

[0107] The second high thermal conductivity member 36 is made of a material having a higher thermal conductivity than the base material 30, such as graphene or graphite. In this embodiment, the second high thermal conductivity member 36 is formed of a graphite sheet having a thickness of 1 mm. However, the second high thermal conductivity member 36 may also be formed of a plate material such as aluminum, copper, or silver.

[0108] As shown in Figure 30, a plurality of second high thermal conductive members 36 are arranged in the arrangement direction, each of which is partially provided in the arrangement direction. The portion of recess 23b of heater holder 23 where second high thermal conductive members 36 are provided is one level deeper than the remaining portion. A gap is provided between second high thermal conductive members 36 and heater holder 23 on both sides in the arrangement direction. This suppresses heat transfer from second high thermal conductive members 36 to heater holder 23, allowing heater 22 to efficiently heat fixing belt 20. Note that illustration of guide portion 26 of Figure 2 is omitted in Figure 30.

[0109] 31, second high thermal conductivity members 36 (see hatched areas) are provided in positions corresponding to interval B in the arrangement direction so as to overlap at least a portion of adjacent resistance heating elements 31, and in this embodiment in particular, are provided over the entire area of ​​interval B. However, although FIG. 31 (and FIG. 35 described later) shows a case where first high thermal conductivity members 28 are provided only in areas corresponding to heat generating portions 35 in the arrangement direction, as mentioned above, this is not limited to this.

[0110] In this embodiment, in addition to the first high thermal conductivity members 28, second high thermal conductivity members 36 are provided at positions corresponding to the interval B in the arrangement direction, overlapping at least a portion of adjacent resistance heating elements 31. This particularly improves the heat transfer efficiency in the arrangement direction at the interval B, thereby further suppressing temperature unevenness in the arrangement direction of the heaters 22. Most preferably, as shown in FIG. 32, the first high thermal conductivity members 28 and the second high thermal conductivity members 36 are provided only over the entire area of ​​the position corresponding to the interval B. This particularly improves the heat transfer efficiency in the position corresponding to the interval B compared to other areas. For convenience, FIG. 32 illustrates the resistance heating elements 31, the first high thermal conductivity members 28, and the second high thermal conductivity members 36 offset from one another in the vertical direction, but they are actually positioned at approximately the same position in the cross-array direction. However, this is not a limitation, and the first high thermal conductivity members 28 and the second high thermal conductivity members 36 may be provided only over a portion of the resistance heating elements 31 in the cross-array direction, or may be provided so as to cover the entire resistance heating elements 31 in the cross-array direction.

[0111] In one embodiment of the present invention different from the above, first high thermal conductivity member 28 and second high thermal conductivity member 36 are formed from the graphene sheet. This allows first high thermal conductivity member 28 and second high thermal conductivity member 36 to be formed with high thermal conductivity in a predetermined direction along the graphene surface, that is, in the arrangement direction rather than the thickness direction. This makes it possible to effectively suppress temperature unevenness in the arrangement direction of heater 22 and fixing belt 20.

[0112] Graphene is a flaky powder. As shown in Figure 33, graphene is composed of a planar hexagonal lattice structure of carbon atoms. A graphene sheet is a sheet of graphene, and is usually a single layer. The single layer of carbon may contain impurities. Graphene may also have a fullerene structure. A fullerene structure is generally recognized as a compound in which the same number of carbon atoms form a polycyclic ring in which five-membered and six-membered rings are condensed into a cage shape, and examples thereof include C 60 , C 70 and C 80 Fullerenes or other closed cage structures with three-coordinated carbon atoms.

[0113] Graphene sheets are man-made and can be produced, for example, by chemical vapor deposition (CVD).

[0114] The graphene sheet may be a commercially available product. The size and thickness of the graphene sheet, or the number of layers of the graphite sheet (described later), may be measured using, for example, a transmission electron microscope (TEM).

[0115] Furthermore, graphite, which is a multilayered graphene, has a large thermal conductivity anisotropy. As shown in FIG. 34, graphite has layers in which the layer planes of condensed six-membered rings of carbon atoms extend in a planar fashion, forming a crystalline structure in which 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. Covalent bonds have a stronger bonding strength than van der Waals bonds, resulting in a large anisotropy between intralayer and interlayer bonds. In other words, by constructing the first high thermal conductivity member 28 or the second high thermal conductivity member 36 from graphite, the heat transfer efficiency in the arrangement direction of the first high thermal conductivity member 28 or the second high thermal conductivity member 36 is greater than in the thickness direction (i.e., the stacking direction of the members), thereby suppressing heat transfer to the heater holder 23. This effectively suppresses temperature unevenness in the arrangement direction of the heater 22 and minimizes heat leakage toward the heater holder 23. Furthermore, by making the first high thermal conductivity member 28 or the second high thermal conductivity member 36 out of graphite, the first high thermal conductivity member 28 or the second high thermal conductivity member 36 can have excellent heat resistance, preventing oxidation up to approximately 700 degrees.

[0116] The physical properties and dimensions of the graphite sheet can be changed as appropriate depending on the functions required of first high thermal conductivity member 28 or second high thermal conductivity member 36. For example, the anisotropy of thermal conduction can be increased by using high-purity graphite or single-crystal graphite, or by increasing the thickness of the graphite sheet. Furthermore, in order to increase the speed of fixing device 9, a thin graphite sheet may be used to reduce the heat capacity of fixing device 9. Furthermore, if the width of fixing nip N or heater 22 is large, the width of first high thermal conductivity member 28 or second high thermal conductivity member 36 in the arrangement direction may be increased accordingly.

[0117] From the viewpoint of increasing the mechanical strength, the number of layers of the graphite sheet is preferably at least 11. The graphite sheet may partially include a single layer portion and a multi-layer portion.

[0118] The second high thermal conductivity members 36 may be arranged in positions corresponding to intervals B (and further to regions C) in the arrangement direction so as to overlap at least a portion of adjacent resistance heating elements 31, and are not limited to the arrangement shown in Fig. 31. For example, as shown in Fig. 35, second high thermal conductivity members 36A are arranged to protrude beyond base material 30 on both sides in the cross-array direction. Second high thermal conductivity members 36B are arranged in an area in the cross-array direction where resistance heating elements 31 are arranged. Second high thermal conductivity members 36C are arranged in a portion of intervals B.

[0119] 36, in this embodiment, a gap is provided between the first high thermal conductivity member 28 and the heater holder 23 in the thickness direction (left-right direction in FIG. 36). That is, a recess 23c is provided as a heat insulating layer in a partial area of ​​the recess 23b (see FIG. 30) for arranging the heater 22, the first high thermal conductivity member 28, and the second high thermal conductivity member 36 of the heater holder 23, except for the area where the second high thermal conductivity member 36 is provided in the arrangement direction. This recess 23c is deeper than the remaining area that receives the first high thermal conductivity member 28. This minimizes the contact area between the heater holder 23 and the first high thermal conductivity member 28. This suppresses heat transfer from the first high thermal conductivity member 28 to the heater holder 23, allowing the heater 22 to efficiently heat the fixing belt 20. In addition, in the cross section in the arrangement direction where second high thermal conductivity members 36 are provided, second high thermal conductivity members 36 abut against heater holder 23 as in FIG. 29 of the above-described embodiment.

[0120] Furthermore, particularly in this embodiment, relief portions 23c are provided in the array cross direction (the vertical direction in FIG. 36) over the entire area where resistance heating elements 31 are provided. This particularly suppresses heat transfer from first high thermal conductivity member 28 to heater holder 23, allowing heater 22 to efficiently heat fixing belt 20. Note that, in addition to a configuration in which a space is provided like relief portions 23c as the heat insulating layer, a configuration in which a heat insulating member with a lower thermal conductivity than heater holder 23 is provided may also be used.

[0121] Furthermore, in the above description, second high thermal conductivity member 36 is provided as a member different from first high thermal conductivity member 28, but this is not limiting. For example, the portion of first high thermal conductivity member 28 corresponding to interval B may be made thicker than the other portions.

[0122] 29 or 36, similarly to the previously described embodiments, a conductive member 38 is provided on the pressure roller 21 as the first rotating member, and the static elimination brush 37 of the embodiment shown in FIG. 3 and the like can be brought into contact with the conductive member 38. This allows static elimination of both the core metal 21a and the surface layer 21c using the common static elimination brush 37. Furthermore, the static elimination brush 37 stably contacts the member to be neutralized, allowing stable removal of charges from the first and third layers of the first rotating member.

[0123] Furthermore, in addition to the fixing device described above, the present invention can also be applied to fixing devices such as those shown in Figures 37 to 39. The configuration of each fixing device shown in Figures 37 to 39 will be briefly described below.

[0124] First, in the fixing device 9 shown in FIG. 37, a pressure roller 44 is disposed on the opposite side of the fixing belt 20 from the pressure roller 21 side. The pressure roller 44 is a second rotating member that rotates opposite the fixing belt 20, which serves as a first rotating member. The pressure roller 44 and the heater 22 are configured to sandwich and heat the fixing belt 20. Meanwhile, on the pressure roller 21 side, a nip forming member 45 is disposed on the inner periphery of the fixing belt 20. The nip forming member 45 is supported by the stay 24. The fixing nip N is formed by the nip forming member 45 and the pressure roller 21 sandwiching the fixing belt 20.

[0125] 38, the above-mentioned pressure roller 44 is omitted, and in order to ensure the circumferential contact length between the fixing belt 20 and the heater 22, the heater 22 is formed in an arc shape to match the curvature of the fixing belt 20. The rest of the configuration is the same as that of the fixing device 9 shown in FIG.

[0126] In the embodiment shown in Figures 37 and 38, the conductive member 38 of the embodiment shown in Figure 3 and other figures can be provided on the pressure roller 21, which serves as the first rotating member, and the static elimination brush 37 can be brought into contact with it. This allows the common static elimination brush 37 to eliminate static electricity from both the core metal 21a and the surface layer 21c. This reduces the number of parts in the fixing device, thereby reducing the cost and size of the fixing device. Furthermore, the static elimination brush 37 stably contacts the member to be neutralized, stably removing charges from the first and third layers of the first rotating member. Note that in a configuration in which a non-conductive second layer, such as an elastic layer, is provided in the middle of the fixing belt 20 and the base layer serving as the first layer and the surface layer serving as the third layer are not electrically connected, a conductive member may be provided on the fixing belt 20 and the static elimination brush may be brought into contact with it.

[0127] Finally, the fixing device 9 shown in FIG. 39 will be described. The fixing device 9 includes a heating assembly 92, a fixing roller 93 as a fixing member, and a pressure assembly 94 as an opposing member. The heating assembly 92 includes the heater 22, the first high-thermal-conductivity member 28, the heater holder 23, the stay 24, and the heating belt 120 as a first rotating member, as described in the previous embodiment. The fixing roller 93 is a second rotating member that rotates opposite the heating belt 120 as the first rotating member. The fixing roller 93 is also composed of a conductive core metal 93a as a first layer, a non-conductive elastic layer 93b as a second layer, and a conductive surface layer 93c as a third layer. A pressure assembly 94 is provided on the side of the fixing roller 93 opposite the heating assembly 92. The pressure assembly 94 includes a nip forming member 95 and a stay 96, and a pressure belt 97 is rotatably disposed so as to enclose the nip forming member 95 and the stay 96. Then, the paper P is passed through the fixing nip N2 between the pressure belt 97 and the fixing roller 93, and heat and pressure are applied to fix the image.

[0128] In the embodiment of FIG. 39 , the aforementioned conductive member 38 and charge-removing brush 37 can also be applied to the fixing roller 93, which serves as the first rotating member. This allows the common charge-removing brush 37 to remove charge from both the core metal 93 a and the surface layer 93 c. This reduces the number of components in the fixing device, thereby reducing the cost and size of the fixing device. Furthermore, the charge-removing brush 37 stably contacts the member to be decharged, stably removing charge from the first and third layers of the first rotating member. Note that if the heating belt 120 or the pressure belt 97 has a non-conductive second layer, such as an elastic layer, and the first and third layers are not electrically connected, the conductive member 38 and charge-removing brush 37 may be applied to the heating belt 120 or the pressure belt 97.

[0129] Furthermore, the fixing device to which the present invention can be applied is not limited to the fixing device having the planar heater described above. For example, as shown in Fig. 40, the fixing device 9 of this embodiment has a halogen heater 61 as a heating element. The fixing device 9 also includes a fixing belt 20, a pressure roller 21 as a first rotating member, a nip forming member 62, a stay 24, a reflecting member 63, a temperature sensor 64, a separating member 65, etc.

[0130] The halogen heater 61 has both longitudinal ends fixed to the side plates. The heating element of the fixing device of this embodiment may be an induction heater or a carbon heater, in addition to a halogen heater. Furthermore, the fixing device 9 may have multiple halogen heaters with different heat generating regions in the longitudinal direction.

[0131] The nip forming member 62 has a base pad 621 and a sliding sheet 622 provided on the surface of the base pad 621. The base pad 621 is disposed in the longitudinal direction and determines the shape of the fixing nip N by receiving the pressure of the pressure roller 21. The base pad 621 is fixed and supported by the stay 24. This prevents the nip forming member 62 from being deflected by the pressure of the pressure roller 21, and ensures a uniform nip width along the axial direction of the pressure roller 21. In this embodiment, the surface of the base pad 621 facing the pressure roller 21 is formed flat, so that the fixing nip N has a straight shape. By forming the fixing nip N in a straight shape, the pressure of the pressure roller 21 can be reduced.

[0132] The base pad 621 is also made of a fairly hard material to ensure strength, and is also made of a heat-resistant material with a heat resistance temperature of 200°C or higher. This prevents deformation of the nip forming member 62 due to heat in the toner fixing temperature range, ensures a stable fixing nip N, and stabilizes the output image quality. The base pad 621 can be made of common heat-resistant resins such as polyethersulfone (PES), polyphenylene sulfide (PPS), liquid crystal polymer (LCP), polyethernitrile (PEN), polyamideimide (PAI), and polyetheretherketone (PEEK), as well as metals and ceramics.

[0133] The sliding sheet 622 is disposed on at least the surface of the base pad 621 that faces the fixing belt 20. This causes the base pad 621 to come into indirect contact with the fixing belt 20 via the sliding sheet 622. While the fixing belt 20 is rotating, the fixing belt 20 slides against the sliding sheet 622, thereby reducing the frictional force generated in the fixing belt 20 and the drive torque of the fixing belt 20. Note that it is also possible to configure the fixing belt 20 without the sliding sheet 622.

[0134] The reflecting member 63 is disposed between the stay 24 and the halogen heater 61. In this embodiment, the reflecting member 63 is fixed to the stay 24. The reflecting member 63 can be made of aluminum, stainless steel, or the like. By disposing the reflecting member 63 in this manner, light radiated from the halogen heater 61 toward the stay 24 is reflected toward the fixing belt 20. This increases the amount of light irradiated onto the fixing belt 20, making it possible to heat the fixing belt 20 efficiently. Furthermore, since the transfer of radiant heat from the halogen heater 61 to the stay 24 and the like can be suppressed, energy savings can be achieved.

[0135] The sheet passing through the fixing nip N is heated and pressed, and the image on the surface of the sheet is fixed. After passing through the fixing nip N, the sheet is separated from the fixing belt 20 by a separating member 65.

[0136] Next, a support structure for supporting both longitudinal ends of the fixing belt 20 will be described with reference to Figures 41(a) to (c). In this support structure, both ends of the fixing belt 20 are rotatably supported by belt holding members 66 inserted into the inner periphery thereof. The fixing device 9 is incorporated into the image forming apparatus by attaching the belt holding members 66 to the side plates. Note that although Figures 41(a) to (c) show only the belt holding member 66 on one side, the belt holding member on the other side has the same configuration, so only the belt holding member 66 on one side will be described below.

[0137] As shown in FIGS. 41(a) and 41(b), the belt holding member 66 has a cylindrical tubular portion 66a with a cylindrical outer peripheral surface and a flange portion 66b that protrudes from the outer diameter side of the tubular portion 66a and restricts longitudinal movement of the fixing belt 20. The belt holding member 66 is integrally formed, for example, by injection molding of resin. As shown in FIG. 41(c), the tubular portion 66a of the belt holding member 66 has a C-shaped cross section with a longitudinal notch at the position where the nip forming member 62, which is the position of the fixing nip N, is disposed. The tubular portion 66a of the belt holding member 66 is loosely fitted onto the inner peripheral surface of the fixing belt 20, and the end of the fixing belt 20 is rotatably held by the tubular portion 66a. The end of the stay 24 is fixed to the belt holding member 66 for positioning.

[0138] 41(a) and 41(b), a slip ring 69 is disposed as a protective member for protecting the end of the fixing belt 20 between the longitudinal end surface of the fixing belt 20 and the end surface 66b1 of the flange portion 66b, which is the opposing surface of the belt holding member 66. This prevents the end of the fixing belt 20 from directly contacting the end surface 401 of the flange portion 66b of the belt holding member 66 when the fixing belt 20 is shifted in the longitudinal direction, thereby preventing wear and damage to the end.

[0139] In the above support structure, only both ends of the fixing belt 20 are held by the belt holding members 66, and therefore the fixing belt 20 is in a deformable state between both ends except for the fixing nip N.

[0140] 41(b), the pressure roller 21 and the belt holding member 66 are arranged so as to be offset in the axial direction without overlapping in the axial direction. Specifically, the tip of the belt holding member 66 and the end 211 of the pressure roller 21 are spaced apart in the axial direction. This forms a longitudinal region J in the fixing belt 20 that is out of contact with both the pressure roller 21 and the belt holding member 66, thereby mitigating stress concentration near the tip edge of the fixing belt 20.

[0141] 42, a halogen heater 61 heats a nip forming member 62. The fixing device 9 also includes a fixing belt 20, a pressure roller 21 as a first rotating member, a nip forming member 62, a reflecting member 63, a guide member 67, and a temperature sensor 64.

[0142] The nip forming member 62 has a flat nip forming portion 62a that contacts the inner surface of the fixing belt 20, and a pair of bending portions 62b that bend from both ends of the nip forming portion 62a in the rotation direction of the fixing belt 20 toward the opposite side to the pressure roller 21.

[0143] The nip forming surface 62c of the nip forming portion 62a on the side of the fixing belt 20 is in direct contact with the inner circumferential surface of the fixing belt 20. Therefore, when the fixing belt 20 rotates, the fixing belt 20 slides against the nip forming surface 62c. To improve the wear resistance and sliding properties of the nip forming surface 62c, the nip forming surface 62c may be anodized or coated with a fluororesin-based material. Furthermore, to ensure sliding properties over time, the nip forming surface 62c may be coated with a lubricant such as fluorine-based grease. In this embodiment, the nip forming surface 62c is flat, but it may also be concave or have other shapes. For example, if the nip forming surface 62c has a concave shape that is recessed away from the pressure roller 21, the exit of the fixing nip N will be closer to the pressure roller 21, improving the separation of the paper from the fixing belt 20.

[0144] The reflecting member 63 is a member that reflects radiant heat (infrared light) from the halogen heater 61, and at least a portion of it is disposed between the fixing belt 20 and the halogen heater 61 in a cross section intersecting the longitudinal direction of the fixing belt 20. Similarly to the nip forming member 62, the reflecting member 63 is disposed inside the fixing belt 20 along the longitudinal direction. In this embodiment, the reflecting member 63 has a U-shaped cross section, consisting of a pair of side walls 63a and a bottom wall 63b connecting them. The nip forming member 62 is supported by the pair of side walls 63a of the reflecting member 63 at both ends in the rotational direction of the fixing belt 20. Furthermore, since each side wall 63a extends in the pressure direction of the pressure roller 21, rigidity in the pressure direction is increased, and deflection of the nip forming portion 62a due to the pressure force of the pressure roller 21 is suppressed, resulting in a fixing nip N of uniform width along the longitudinal direction. To ensure its rigidity, the reflecting member 63 is preferably made of an iron-based metal material such as SUS or SECC.

[0145] The guide member 67 is disposed inside the fixing belt 20 and guides the rotating fixing belt 20. In this embodiment, the guide members 67 are provided on both the upstream and downstream sides of the fixing nip N in the belt rotation direction. The guide member 67 has an attachment portion 67a that is fixed to the reflecting member 63 or the like, and a curved guide portion 67b that contacts the inner peripheral surface of the fixing belt 20. As shown in FIG. 43 , the guide surface of the guide portion 67b facing the fixing belt 20 has a plurality of ribs 67c that are evenly spaced across the belt width direction. The fixing belt 20 is guided along the guide surface having the plurality of ribs 67c, allowing the fixing belt 20 to rotate smoothly without significant deformation.

[0146] The temperature sensor 64 may be either a contact type or a non-contact type. As the temperature sensor 64, a known temperature sensor such as a thermopile, a thermostat, a thermistor, or an NC sensor can be used.

[0147] 44, the fixing belt 20 is rotatably supported by a pair of belt holding members 66 inserted at both ends thereof. The fixing belt 20 is fixed to a pair of side plates 68 which are a frame constituting the fixing device 9.

[0148] As shown in Fig. 45, the belt holding member 66 has a C-shaped tubular portion 66a and a flange portion 66b. The tubular portion 66a is inserted into the inner periphery of the fixing belt 20 to support the fixing belt 20. The belt holding member 66 also has an opening 66c, through which both ends of the halogen heater 61 and the reflecting member 63 are fixed to the side plates 68. The halogen heater 61 and the reflecting member 63 may be fixed to the belt holding member 66. The tubular portion 66a may be a continuous cylinder over the entire periphery, as in the example shown in Fig. 46.

[0149] 47, a reflective surface 63c that reflects radiant heat (infrared light) from the halogen heater 61 is formed on the inner surface of the reflective member 63, which is the surface of the reflective member 63 facing the halogen heater 61. In this embodiment, the reflective surface 63c is formed by applying a reflective material to a base material of the reflective member 63 made of an iron-based metal material. In addition to applying a reflective material, the reflective surface 63c may also be formed by polishing the surface of the base material of the reflective member 63 facing the halogen heater 61.

[0150] In the present invention, the term "reflective surface" refers to a reflective surface having a reflectance of 70% or more for infrared light from a heater. For example, reflective surface 63c has a reflectance of 70% or more for wavelengths of 900 to 1600 nm, or 70% or more for wavelengths of 1000 to 1300 nm, which are the wavelengths of infrared light from heaters generally used in fixing devices. The reflectance can be measured using a spectrophotometer (e.g., a UV-Vis-Infrared Spectrophotometer UH4150 manufactured by Hitachi High-Tech Science Corporation) using a known method (e.g., an incident angle of 5°).

[0151] By forming such a reflective surface 63c on the reflective member 63, the infrared light emitted from the halogen heater 61 is reflected by the reflective surface 63c, and the reflected light is emitted toward the nip forming member 62. As a result, the nip forming member 62 is irradiated with not only the infrared light directly emitted from the halogen heater 61 but also the infrared light reflected by the reflective surface 63c, and is therefore heated effectively. Furthermore, by reflecting the infrared light by the reflective surface 63c, it is possible to suppress the wasteful consumption of thermal energy caused by heating the reflective member 63.

[0152] Furthermore, in this embodiment, the reflective member 63 also functions as a support member for supporting the nip forming member 62, eliminating the need for a separate support member. If the support member were a separate member, the reflective member would have to be thin because it would be placed in the narrow space between the support member and the halogen heater 61. However, if the reflective member were thin, its thermal capacity would be small, making it more susceptible to temperature rise. As a result, the reflective member may become hot in a short time, discoloring the reflective member and reducing its reflectivity. In contrast, in this embodiment, the reflective member 63 functions as a support member, allowing the reflective member 63 to be thicker, increasing its thermal capacity and slowing the temperature rise due to radiant heat from the halogen heater 61. As a result, even when the halogen heater 61 is used for a long period of time, the decrease in reflectivity caused by high-temperature discoloration can be suppressed, and high heating efficiency can be maintained.

[0153] 40 or 42, by applying the conductive member 38 and the discharging brush 37 of the above-described embodiment, it is possible to discharge both the core metal and the surface layer with the common discharging brush 37. This reduces the number of parts in the fixing device, thereby reducing the cost and size of the fixing device. Furthermore, the discharging brush 37 stably contacts the member to be discharged, and the charges on the first and third layers of the first rotating member can be stably removed.

[0154] Furthermore, the present invention is not limited to the fixing device described in the above embodiment, but can also be applied to heating devices such as drying devices that dry ink applied to paper, laminators that thermocompression bond films as covering members to the surface of sheets such as paper, and thermocompression bonding devices such as heat sealers that thermocompression bond seal portions of packaging materials. By applying the present invention to such devices, the first and third layers of the first rotating member can be neutralized using a common neutralization member. Furthermore, the neutralization member can stably contact the member to be neutralized, thereby stably removing charges from the first and third layers of the first rotating member.

[0155] The image forming apparatus according to the present invention is not limited to the color image forming apparatus shown in FIG. 1, but may also be a monochrome image forming apparatus, a copying machine, a printer, a facsimile, or a combination machine of these.

[0156] 48, for example, image forming apparatus 100 of this embodiment includes image forming means 50 including a photosensitive drum and the like, a paper transport section including a pair of timing rollers 15 and the like, paper feeder 7, fixing device 9, paper discharge device 10, and reading section 51. Paper feeder 7 includes multiple paper feed trays, each of which stores paper of a different size.

[0157] The reading unit 51 reads an image of the document Q. The reading unit 51 generates image data from the read image. The paper feeder 7 stores a plurality of sheets of paper P and sends the sheets of paper P to a conveyance path. The timing rollers 15 convey the sheets of paper P on the conveyance path to the image forming means 50.

[0158] The image forming means 50 forms a toner image on the paper P. Specifically, the image forming means 50 includes a photosensitive drum, a charging roller, an exposure device, a developing device, a replenishment device, a transfer roller, a cleaning device, and a discharging device. The toner image represents, for example, an image of the original Q. The fixing device 9 applies heat and pressure to the toner image to fix the toner image to the paper P. The paper P with the fixed toner image is transported to the paper discharge device 10 by a transport roller or the like. The paper discharge device 10 discharges the paper P outside the image forming apparatus 100.

[0159] Next, the fixing device 9 of this embodiment will be described. Descriptions of the configurations common to the fixing devices of the above-described embodiments will be omitted as appropriate.

[0160] As shown in FIG. 49, 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.

[0161] A fixing nip N is formed between the fixing belt 20 and the pressure roller 21. The nip width of the fixing nip N is 10 mm, and the linear speed of the fixing device 9 is 240 mm / s.

[0162] The fixing belt 20 has a polyimide base and a release layer, but does not have an elastic layer. The release layer is made of a heat-resistant film material such as fluororesin. The outer diameter of the fixing belt 20 is approximately 24 mm.

[0163] The pressure roller 21 includes a core metal 21a, an elastic layer 21b, and a surface layer 21c. The pressure roller 21 has an outer diameter of 24 to 30 mm, and the elastic layer 21b has a thickness of 3 to 4 mm.

[0164] The heater 22 includes a base material, a heat insulating layer, a conductor layer including a resistance heating element, and an insulating layer, and is formed to a total thickness of 1 mm. The width Y of the heater 22 in the array crossing direction is 13 mm.

[0165] As shown in FIG. 50, the conductor layer of the heater 22 includes a plurality of resistance heating elements 31, power supply lines 33, and electrode portions 34A-34C. In this embodiment, as shown in the enlarged view of FIG. 50, the resistance heating elements 31 are divided in the arrangement direction to form intervals B as divided regions (although FIG. 50 only illustrates the intervals B within the enlarged view, in reality, intervals B are provided between all of the resistance heating elements 31). The resistance heating elements 31 form three heat generating portions 35A-35C. By applying electricity to the electrode portions 34A and 34B, the heat generating portions 35A and 35C generate heat. By applying electricity to the electrode portions 34A and 34C, the heat generating portion 35B generates heat. For example, when performing a fixing operation on small-sized paper, the heat generating portion 35B is made to generate heat, and when performing a fixing operation on large-sized paper, all of the heat generating portions are made to generate heat.

[0166] As shown in Figure 51, the heater holder 23 holds the heater 22 and the first high thermal conductivity member 28 in its recess 23d. The recess 23d is provided on the heater 22 side of the heater holder 23. The recess 23d is composed of a surface 23d1 that is approximately parallel to the base material 30 and is recessed toward the stay 24 side more than the other surfaces of the heater 22, wall portions 23d2 provided on the inside of the heater holder 23 on both sides in the arrangement direction of the heater holder 23 (or on one side), and wall portions 23d3 provided on the inside of the heater holder 23 on both sides in the intersecting direction of the arrangement. The heater holder 23 has a guide portion 26. The heater holder 23 is made of LCP (liquid crystal polymer).

[0167] As shown in FIG. 52, the connector 60 includes a housing made of resin (for example, LCP), and a plurality of contact terminals provided inside the housing.

[0168] The connector 60 is attached so as to sandwich the heater 22 and heater holder 23 together from the front and back sides. In this state, each contact terminal comes into contact (pressure-welded) with each electrode portion of the heater 22, electrically connecting the heat generating portion 35 to a power supply provided in the image forming apparatus via the connector 60. This enables power to be supplied from the power supply to the heat generating portion 35. Note that, to ensure connection with the connector 60, at least a portion of each electrode portion 34 is not covered with an insulating layer and is exposed.

[0169] The flanges 53 are provided on both sides of the fixing belt 20 in the arrangement direction, and hold both ends of the fixing belt 20 from the inside of the belt. The flanges 53 are fixed to the housing of the fixing device 9. The flanges 53 are inserted into both ends of the stays 24 (see the arrow directions from the flanges 53 in Figure 52).

[0170] The direction in which the connector 60 is attached to the heater 22 and heater holder 23 is the direction that intersects the heater arrangement (see the direction of the arrow from the connector 60 in Figure 52). When the connector 60 is attached to the heater holder 23, a convex portion on one of the connector 60 and the heater holder 23 may engage with a concave portion on the other, and the convex portion may move relatively within the concave portion. The connector 60 is attached to the heater 22 and heater holder 23 on one side in the arrangement direction, opposite the side on which the drive motor of the pressure roller 21 is provided.

[0171] 53, thermistors 25 are provided on the center side and end side of the fixing belt 20 in the arrangement direction, facing the inner circumferential surface of the fixing belt 20. The heater 22 is controlled based on the temperatures detected by the thermistors 25 on the center side and end side of the fixing belt 20 in the arrangement direction.

[0172] Thermostats 27 are provided facing the inner circumferential surface of the fixing belt 20, at the center and end sides in the arrangement direction of the fixing belt 20. When the temperature of the fixing belt 20 detected by the thermostat 27 exceeds a predetermined threshold, the supply of power to the heater 22 is stopped.

[0173] Flanges 53 are provided on both ends of the fixing belt 20 in the arrangement direction to hold the respective ends of the fixing belt 20. The flanges 53 are made of LCP (liquid crystal polymer).

[0174] 54, a slide groove 53a is provided in the flange 53. The slide groove 53a extends in the direction in which the fixing belt 20 approaches and separates from the pressure roller 21. An engagement portion of the housing of the fixing device 9 engages with the slide groove 53a. The engagement portion moves relatively within the slide groove 53a, allowing the fixing belt 20 to move in the direction in which the fixing belt 20 approaches and separates from the pressure roller 21.

[0175] In the fixing device 9 described above, the conductive member 38 and the charge-removing brush 37 of the embodiment shown in FIG. 3 and the like can be applied to the pressure roller 21, which serves as the first rotating member. This allows the common charge-removing brush 37 to remove charge from both the core metal 21a and the surface layer 21c. This reduces the number of parts in the fixing device, thereby reducing the cost and size of the fixing device. Furthermore, the charge-removing brush 37 stably contacts the member to be de-ionized, allowing stable removal of charges from the first and third layers of the first rotating member.

[0176] Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and it goes without saying that various modifications can be made without departing from the spirit of the present invention.

[0177] The image forming apparatus according to the present invention is not limited to the color image forming apparatus shown in FIG. 1, but may also be a monochrome image forming apparatus, a copying machine, a printer, a facsimile, or a combination machine of these.

[0178] Recording media include paper P (plain paper), as well as cardboard, postcards, envelopes, thin paper, coated paper (coated paper, art paper, etc.), tracing paper, OHP sheets, plastic film, prepreg, copper foil, etc.

[0179] In the above embodiment, a brush-like member has been described as the static eliminator, but the present invention is not limited to this. For example, a sheet-like static eliminator or other suitable configuration may be employed. [Explanation of symbols]

[0180] 1. Image forming device 9 Fixing device (heating device) 20 Fixing belt (second rotating member or fixing member) 21 Pressure roller (first rotating member or pressure member) 21a Core metal (first layer) 21a1 Exposed part 21a2 Expanded diameter part 21b Elastic layer (second layer) 21c Surface layer (third layer) 22 Heater (heating element) 37 Anti-static brush (anti-static material) 37a Contact part 37b Holding part 38 Conductive materials 38d protrusion 39 Bearings 40 Connector (power supply component) [Prior art documents] [Patent documents]

[0181] [Patent Document 1] Japanese Patent Application Laid-Open No. 2002-162857

Claims

1. a first rotating member; a second rotating member that forms a nip portion between the first rotating member and the second rotating member, through which a recording medium carrying a toner image passes; a heating element that contacts the inside of the second rotating member and heats the second rotating member; a static eliminator that eliminates static electricity from the first rotating member; A fixing device including a conductive member, the first rotating member has, from its inside, a conductive first layer, a non-conductive second layer, and a conductive third layer in this order; the conductive member contacts the third layer; The fixing device is characterized in that the charge removing member is in contact with the conductive member and the first layer.

2. 2. The fixing device according to claim 1, wherein the contacted portion of the conductive member that comes into contact with the charge removing member is provided radially inward of the outer surface of the third layer of the first rotary member.

3. the first layer has an exposed portion whose outer surface is exposed to the outside, the first layer has an expanded diameter portion in the exposed portion, the expanded diameter portion being partially larger in length in the radial direction of the first rotary member; 3. The fixing device according to claim 2, wherein the charge removing member contacts the enlarged diameter portion.

4. 4. The fixing device according to claim 3, wherein the outer surface of the enlarged diameter portion and the contacted portion of the conductive member are provided at the same position in the radial direction of the rotary member.

5. 5. The fixing device according to claim 1, wherein the second layer is an elastic layer.

6. a bearing for holding a shaft portion of the first rotating member; 6. The fixing device according to claim 1, wherein the bearing is made of a non-conductive material.

7. 7. The fixing device according to claim 1, wherein the conductive member is made of an elastic material.

8. Further provided is a power supply member that supplies power to the heating element, 8. The fixing device according to claim 1, wherein the power supply member and the conductive member are provided on opposite sides of a center position in the longitudinal direction of the fixing device.

9. the heating element includes a base material, a resistance heating element provided on the base material, and a high thermal conductivity member on a surface of the base material on which the resistance heating element is provided, 9. The fixing device according to claim 1, wherein the charge removing member is in contact with the high heat conductive member.

10. The fixing device according to claim 9 , wherein the highly heat-conductive member is graphene.

11. An image forming apparatus comprising the fixing device according to claim 1 .

Images