Fixing apparatus and image forming apparatus

Abstract

To achieve a configuration that grounds a separation member and a rotating body while ensuring certain insulating properties with a small number of components.SOLUTION: A fixing device 9 comprises: a first rotating body 20; a second rotating body 21 that is in contact with an outer peripheral surface of the first rotating body 20 to form a nip part N for passing a recording medium P carrying an unfixed image; a heating body 22 that has a resistance heating element and heats the first rotating body 20; and a separation member 41 that is in contact with the outer peripheral surface of the first rotating body 20 to separate the recording medium P passing through the nip part N from the first rotating body 20. The second rotating body 21 and the separation member 41 are grounded through the same resistor 39.SELECTED DRAWING: Figure 6

Description

Technical Field

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

Background Art

[0002] In electrophotographic image forming apparatuses such as copiers and printers, a fixing device for fixing a toner image on a recording medium such as paper is mounted.

[0003] The fixing device includes a pair of rotating bodies that fix the toner image on the recording medium by transporting the recording medium while heating and pressing it. However, when charges applied to the recording medium move to these rotating bodies and the surfaces of the rotating bodies become charged, abnormal images called electrostatic offset may occur where a part of the toner image on the recording medium adheres to the rotating bodies.

[0004] Therefore, in Patent Document 1 (Japanese Patent Laid-Open No. 2002-162857), grounded discharge brushes are brought into contact with both the fixing roller and the pressure roller, which are rotating bodies, so that charges do not accumulate on the surfaces of each roller.

[0005] By the way, in some fixing devices, a separating member for separating the recording medium passed through the nip portion from the surface of the rotating body is provided. Generally, the tip of the separating member is arranged at a predetermined interval from the surface of the rotating body, and it is preferable that this interval is maintained constant in order to ensure stable separability. Therefore, in the conventional configuration, a part of the separating member is brought into contact with the surface of the rotating body in a region where the recording medium does not pass, so that even if the surface position of the rotating body fluctuates with rotation, the tip of the separating member can follow the fluctuating surface of the rotating body.

[0006] However, in this configuration where the separating member contacts the surface of the rotating body, if the insulating layer of the heater in the fuser unit is damaged and current flows from the heater to the rotating body, the current may flow to the fuser unit's housing side via the separating member in contact with the rotating body, potentially affecting the heater's heat output or causing electrical damage to surrounding components. There is also the problem of abnormal images (electrostatic offset) due to the surface of the rotating body becoming charged. Furthermore, if toner adheres to the separating member due to its charge, the separation (transport) of the recording medium by the separating member may become unstable. Therefore, it is necessary to ground the separating member and the rotating body while ensuring a certain level of insulation, but grounding the separating member and the rotating body via separate resistors results in a problem of increasing the number of components. [Overview of the project] [Problems that the invention aims to solve]

[0007] Given the above circumstances, the objective of the present invention is to realize a configuration in which a separating member and a rotating body are grounded while ensuring a certain level of insulation with a small number of parts. [Means for solving the problem]

[0008] To solve the above problems, the present invention provides a fixing device comprising: a first rotating body; a second rotating body that contacts the outer circumferential surface of the first rotating body and forms a nip portion through which a recording medium carrying an unfixed image passes; a heating body having a resistance heating element that heats the first rotating body; and a separating member that contacts the outer circumferential surface of the first rotating body and separates the recording medium passing through the nip portion from the first rotating body, wherein the second rotating body and the separating member are grounded via the same resistor. [Effects of the Invention]

[0009] According to the present invention, a configuration can be realized in which a separating member and a rotating body are grounded while ensuring a certain level of insulation with a small number of parts. [Brief explanation of the drawing]

[0010] [Figure 1] This is a schematic diagram of an image forming apparatus according to one embodiment of the present invention. [Figure 2] This is a side cross-sectional view of the fixing device according to this embodiment. [Figure 3] This is a perspective cross-sectional view of the fixing device according to this embodiment. [Figure 4] This is a plan view of the heater according to this embodiment. [Figure 5] This diagram shows the power supply circuit to the heater according to this embodiment. [Figure 6] This is a side cross-sectional view of a fixing device according to a second embodiment of the present invention. [Figure 7] This is a perspective cross-sectional view of a fixing device according to a second embodiment of the present invention. [Figure 8] This is a side cross-sectional view of a fixing device according to a third embodiment of the present invention. [Figure 9] This is a perspective cross-sectional view of a fixing device according to a third embodiment of the present invention. [Figure 10] This is a side cross-sectional view of a fixing device according to a fourth embodiment of the present invention. [Figure 11] This is a perspective cross-sectional view of a fixing device according to a fourth embodiment of the present invention. [Figure 12] This is a side cross-sectional view of a fixing device according to the fifth embodiment of the present invention. [Figure 13] This is a perspective cross-sectional view of a fixing device according to the fifth embodiment of the present invention. [Figure 14] This is a plan view showing a modified example of the heater. [Figure 15] This figure shows yet another variation of the heater. [Figure 16] This figure shows the temperature distribution along the longitudinal direction of the fixing belt in a configuration where multiple resistance heating elements are arranged at intervals along the longitudinal direction of the heater. [Figure 17] This figure shows the divided regions of the heater as shown in Figure 14. [Figure 18] This figure shows a divided region with a different shape from the example shown in Figure 17. [Figure 19] This figure shows the divided regions of the heater as shown in Figure 15. [Figure 20] It is a diagram showing the configuration of a fixing device different from each of the above embodiments. [Figure 21] It is an exploded perspective view of the heater, the first high thermal conductivity member, and the heater holder shown in FIG. 20. [Figure 22] It is a plan view of the heater showing the arrangement of the first high thermal conductivity member. [Figure 23] It is a diagram showing another example of the arrangement of the first high thermal conductivity member. [Figure 24] It is a diagram showing yet another example of the arrangement of the first high thermal conductivity member. [Figure 25] It is a diagram showing the configuration of a fixing device different from each of the above embodiments. [Figure 26] It is an exploded perspective view of the heater, the first high thermal conductivity member, the second high thermal conductivity member, and the heater holder shown in FIG. 25. [Figure 27] It is a plan view of the heater showing the arrangement of the first high thermal conductivity member and the second high thermal conductivity member. [Figure 28] It is a diagram showing another example of the arrangement of the first high thermal conductivity member and the second high thermal conductivity member. [Figure 29] It is a diagram showing the atomic crystal structure of graphene. [Figure 30] It is a diagram showing the atomic crystal structure of graphite. [Figure 31] It is a diagram showing yet another example of the arrangement of the second high thermal conductivity member. [Figure 32] It is a diagram showing the configuration of a fixing device different from each of the above embodiments. [Figure 33] It is a diagram showing the configuration of a fixing device different from each of the above embodiments. [Figure 34] It is a diagram showing the configuration of a fixing device different from each of the above embodiments. [Figure 35] It is a diagram showing the configuration of a fixing device different from each of the above embodiments. [Figure 36] It is a diagram showing the configuration of an image forming apparatus different from the above embodiments. [Figure 37] It is a diagram showing the configuration of the fixing device shown in FIG. 36. [Figure 38]Figure 37 is a plan view of the heater shown. [Figure 39] Figure 37 is a perspective view of the heater and heater holder shown. [Figure 40] This figure shows the method of attaching a connector to the heater shown in Figure 37. [Figure 41] This figure shows the arrangement of the temperature sensor and thermostat in the fixing device shown in Figure 36. [Figure 42] This figure shows the groove portion of the flange shown in Figure 40. [Figure 43] This figure shows a configuration of a fixing device that differs from each of the embodiments described above. [Figure 44] This figure shows a configuration of a fixing device that differs from each of the embodiments described above. [Figure 45] This is a diagram showing the configuration of a halogen heater. [Figure 46] This figure shows a configuration of a fixing device that differs from each of the embodiments described above. [Modes for carrying out the invention]

[0011] The present invention will be described below with reference to the attached drawings. In each drawing used to explain the present invention, components such as members and parts having the same function or shape will be given the same reference numerals to the extent possible so that they can be distinguished, and their description will be omitted after they have been described once.

[0012] Figure 1 is a schematic diagram of an image forming apparatus according to one embodiment of the present invention. Here, "image forming apparatus" in this specification includes printers, copiers, facsimile machines, printing presses, or multifunction devices that combine two or more of these. Furthermore, "image forming" as used in the following description means not only forming images that have meaning, such as characters and figures, but also forming images that do not have meaning, such as patterns. First, the overall configuration and operation of the image forming apparatus according to this embodiment will be described with reference to Figure 1.

[0013] The image forming apparatus 100 shown in Figure 1 includes four detachable image forming units 1Y, 1M, 1C, and 1Bk attached to the main body of the image forming apparatus. Each image forming unit 1Y, 1M, 1C, and 1Bk has the same configuration except that it contains different colored developers: yellow, magenta, cyan, and black. These colored developers correspond to the color separation components of a color image. Each image forming unit 1Y, 1M, 1C, and 1Bk includes a drum-shaped photoreceptor 2 as an image carrier, a charging device 3, a developing device 4, and a cleaning device 5.

[0014] The image forming apparatus 100 also includes an exposure device 6, a paper feed device 7, a transfer device 8, a fixing device 9, and a paper discharge device 10. Each image forming unit 1, photoreceptor 2, charging device 3, exposure device 6, transfer device 8, etc., constitutes an image forming means for forming an image on paper.

[0015] The transfer device 8 includes an endless intermediate transfer belt 11 as an intermediate transfer body, four primary transfer rollers 12 as primary transfer members, and a secondary transfer roller 13 as a secondary transfer member. The intermediate transfer belt 11 is an endless belt member stretched by a plurality of rollers. The plurality of primary transfer rollers 12 contact each opposing photoreceptor 2 via the intermediate transfer belt 11, forming a primary transfer nip between the intermediate transfer belt 11 and each photoreceptor 2. On the other hand, the secondary transfer roller 13 contacts one of the rollers stretching the intermediate transfer belt 11 via the intermediate transfer belt 11, forming a secondary transfer nip between the secondary transfer roller 13 and the intermediate transfer belt 11.

[0016] Furthermore, a pair of timing rollers 15 are provided in the paper transport path 14, between the paper feed device 7 and the secondary transfer nip (secondary transfer roller 13).

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

[0018] When a print operation is initiated, in each image unit 1Y, 1M, 1C, and 1Bk, the photoreceptor 2 is driven to rotate clockwise as shown in Figure 1, and the surface of the photoreceptor 2 is charged to a uniform high potential by the charging device 3. Next, based on the image information of the original document read by the document reader or the print information instructed from the terminal, the exposure device 6 exposes the surface of each photoreceptor 2. As a result, the potential of the exposed area decreases, and an electrostatic latent image is formed. Then, toner is supplied as a developer from the developing device 4 to this electrostatic latent image, and a toner image is formed on each photoreceptor 2.

[0019] The toner image formed on each photoreceptor 2 rotates with the rotation of each photoreceptor 2 and reaches the primary transfer nip (the position of the primary transfer roller 12). The toner image is then transferred sequentially onto the intermediate transfer belt 11, which rotates counterclockwise as shown in Figure 1. Thus, a full-color toner image is supported on the intermediate transfer belt 11. After the image is transferred to the intermediate transfer belt 11, any toner and foreign matter such as paper dust remaining on each photoreceptor 2 is removed by the cleaning device 5.

[0020] The toner image transferred onto the intermediate transfer belt 11 is transported to the secondary transfer nip (the position of the secondary transfer roller 13) as the intermediate transfer belt 11 rotates. At the secondary transfer nip, the toner image is transferred to the paper P, which serves as the recording medium. This paper P is supplied from the paper feed device 7. In addition to paper P (plain paper), the recording medium may also be cardboard, postcards, envelopes, thin paper, coated paper (such as coated paper or art paper), tracing paper, OHP sheets, plastic film, prepreg, copper foil, etc.

[0021] The paper P supplied from the paper feeder 7 is temporarily stopped by the 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. This transfers the toner image onto the paper P.

[0022] The paper P onto which the toner image has been transferred is transported to the fuser unit 9, where the fuser unit 9 fixes the toner image onto the paper P. After that, the paper P is ejected from the device by the paper output unit 10, completing the series of printing operations.

[0023] Next, the configuration of the fixing device according to this embodiment will be described based on Figures 2 and 3. Figure 2 is a side cross-sectional view of the fixing device, and Figure 3 is a perspective cross-sectional view of the fixing device.

[0024] As shown in Figures 2 and 3, the fixing device 9 according to this embodiment includes a side plate 40, a fixing belt 20, a pressure roller 21, a belt holding member 19, a heater 22, a heater holder 23, a stay 24, a separation plate 41, and the like. The fixing device 9 is also configured to be detachable from the main body of the image forming apparatus.

[0025] The side plates 40 are components that constitute at least a part of the housing of the fixing device 9, and are provided on both sides in the direction of arrow X in Figure 3, which is the longitudinal direction of the fixing belt 20, heater 22, heater holder 23, stay 24, and separation plate 41. Note that these longitudinal directions are also the same direction as the rotation axis of the pressure roller 21 and the width direction of the paper. The side plates 40 are made of metal and are grounded.

[0026] The fixing belt 20 is a first rotating body positioned on the unfixed image-carrying surface side of the paper, and is a fixing member that contacts the unfixed image-carrying surface of the paper to fix the toner image to the paper. The fixing belt 20 is composed of an endless belt member having a cylindrical base made of polyimide (PI) with an outer diameter of 25 mm and a thickness of 40 to 120 μm. The base of the fixing belt 20 is not limited to polyimide, but may also be a heat-resistant resin such as PEEK, or a metal base such as nickel (Ni) or SUS. The outermost layer of the fixing belt 20 is provided with a release layer made of a fluororesin such as PFA or PTFE with a thickness of 5 to 50 μm to enhance durability and ensure release properties. An elastic layer made of rubber or the like with a thickness of 50 to 500 μm may be provided between the base and the release layer. In addition, a sliding layer made of polyimide or PTFE may be provided on the inner circumferential surface of the fixing belt 20.

[0027] The pressure roller 21 is a second rotating body separate from the fixing belt 20, and is an opposing member positioned opposite the outer circumferential surface of the fixing belt 20. The pressure roller 21 is composed of a roller member with an outer diameter of, for example, 25 mm. The pressure roller 21 has, from the inside out, a core metal 21a as the first layer, an elastic layer 21b as the second layer, and a release layer 21c as the third layer. The core metal 21a is made of a conductive material such as iron. The core metal 21a may be a hollow cylindrical shape or a solid shaft shape. The elastic layer 21b is made of a non-conductive material, for example, silicone rubber with a thickness of 3.5 mm. Some elastic layers 21b are made conductive, but if the elastic layer 21b is non-conductive, it does not contain conductive materials such as fillers, so its elasticity and stretchability can be ensured. The release layer 21c is made of, for example, a fluororesin with a thickness of about 40 μm.

[0028] The pressure roller 21 is biased toward the fixing belt 20 by a biasing means such as a spring. As a result, the pressure roller 21 is pressed against the heater 22 via the fixing belt 20, and a nip portion N (fixing nip) is formed 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 Figure 2, the fixing belt 20 rotates in conjunction with it.

[0029] The belt holding member 19 is a rotating body holding member that holds the anchoring belt 20. The belt holding member 19 is positioned on both ends in the longitudinal direction of the anchoring belt 20 and rotatably holds both ends in the longitudinal direction of the anchoring belt 20. Specifically, the belt holding member 19 has a cylindrical or C-shaped holding portion 19a (see Figure 2) that is inserted inside the anchoring belt 20, and a plate-shaped base portion 19b that holds the holding portion 19a. The holding portion 19a is inserted inside the longitudinal end of the anchoring belt 20, thereby rotatably holding the anchoring belt 20. On the other hand, the base portion 19b is positioned opposite the longitudinal end face of the anchoring belt 20 and functions as a restricting portion that restricts the longitudinal movement (shift) of the anchoring belt 20 by contacting the longitudinal end face of the anchoring belt 20 when the anchoring belt 20 shifts in the longitudinal direction.

[0030] The heater 22 is a planar heating element provided longitudinally along the longitudinal direction of the fixing belt 20 (direction of arrow X in Figure 3). As shown in the enlarged view in Figure 2, the heater 22 has a plate-shaped base material 30, a resistance heating element 31 provided on the base material 30, and an insulating layer 32 covering the resistance heating element 31. The heater 22 is in contact with the inner circumferential surface of the fixing belt 20 on the insulating layer 32 side, and the heat generated from the resistance heating element 31 is transferred to the fixing belt 20 via the insulating layer 32. In this embodiment, the resistance heating element 31 and the insulating layer 32 are provided on the fixing belt 20 side (nip portion N side) of the base material 30, but conversely, the resistance heating element 31 and the insulating layer 32 may be provided on the heater holder 23 side of the base material 30. In that case, since the heat from the resistance heating element 31 will be transferred to the fixing belt 20 via the base material 30, it is preferable that the base material 30 be made of a material with high thermal conductivity such as aluminum nitride.

[0031] When power is supplied to the resistive heating element 31 of the heater 22, the resistive heating element 31 generates heat, and the fixing belt 20 is heated. When the temperature of the fixing belt 20 reaches a predetermined target temperature (fixing temperature), the paper P carrying the unfixed toner image is transported between the rotating fixing belt 20 and the pressure roller 21 (nip section N), and the paper P is heated and pressurized by the fixing belt 20 and the pressure roller 21, fixing the unfixed toner image to the paper P.

[0032] The heater holder 23 is a heating element holding member that holds the heater 22. Since the heater holder 23 is prone to becoming hot due to the heat from the heater 22, it is preferable that it be made of a heat-resistant material. For example, if the heater holder 23 is made of a heat-resistant resin with low thermal conductivity such as LCP, heat transfer from the heater 22 to the heater holder 23 is suppressed, so that the heat from the heater 22 can be efficiently applied to the fixing belt 20.

[0033] The stay 24 is a support member that supports the heater holder 23. Here, "supporting" the heater holder 23 by the stay 24 means that the stay 24 contacts the heater holder 23 from the side opposite to the pressure roller 21 (the right side in Figure 2) and receives the pressure from the pressure roller 21. This suppresses the deflection of the heater holder 23 (especially the deflection in the longitudinal direction) caused by the pressure from the pressure roller 21, and a nip portion N is stably formed between the fixing belt 20 and the pressure roller 21. The stay 24 may also be in contact with the heater holder 23 via other members. For example, both ends of the stay 24 in the longitudinal direction are supported by a pair of side plates 40. As for the material of the stay 24, an iron-based metal material such as SUS or SECC is preferred in order to ensure rigidity.

[0034] The separation plate 41 is a separating member that separates the paper P after it has passed through the nip section N from the surface of the fixing belt 20. The separation plate 41 is made of a metal material such as rust-proofed iron, stainless steel, or aluminum, and is positioned downstream of the nip N in the paper transport direction. The separation plate 41 has a separation section 411, a stopper section 412, and a mounting section 413. The separation section 411 is positioned downstream of the nip section N in the paper transport direction and close to the surface (outer peripheral surface) of the fixing belt 20, and contacts the paper P after it has passed through the nip section N, separating the paper P from the surface of the fixing belt 20. The separation section 411 is positioned over a range larger than the maximum paper passage area (maximum recording medium passage area) through which the widest paper passes, so that it can separate paper of various widths. The stopper section 412 is a part that branches off from the main body of the separation plate 41, including the separation section 411, and is positioned downstream of the nip N in the paper transport direction and contacts the outer peripheral surface of the fixing belt 20. Furthermore, the abutment portion 412 contacts an area outside the maximum paper-feeding area of ​​the fixing belt 20 in order to avoid wear and damage to the outer surface of the fixing belt 20 within the paper-feeding area. The mounting portion 413 is provided at both longitudinal ends of the separation plate 41 and is attached to the support shafts 42 (see Figure 2) provided on the pair of belt-holding members 19. The mounting portion 413 is rotatably supported by the support shafts 42. For this reason, the separation plate 41 (the tip of the separation portion 411) is configured to be displaceable in the direction of approaching and moving away from the outer surface of the fixing belt 20. However, since the separation plate 41 is biased in the direction of approaching the outer surface of the fixing belt 20 by a biasing member such as a torsion spring, the abutment portion 412 is basically held in contact with the outer surface of the fixing belt 20.

[0035] Figure 4 is a plan view of the heater according to this embodiment.

[0036] As shown in Figure 4, the surface of the plate-shaped substrate 30 is provided with a plurality (four) of resistance heating elements 31, power supply lines 33A and 33B acting as conductors, and a first electrode portion 34A and a second electrode portion 34B. However, the number of resistance heating elements 31 is not limited to this embodiment.

[0037] Multiple resistance heating elements 31 are arranged at intervals along the longitudinal direction of the heater 22 (in the direction of arrow X in Figure 4). Therefore, in this embodiment, the longitudinal direction of the heater 22 is also the arrangement direction of the multiple resistance heating elements 31. Hereinafter, this direction will also be simply referred to as the arrangement direction. Furthermore, the vertical direction Y in Figure 4, which intersects the arrangement direction (a perpendicular direction in this embodiment) and is different from the thickness direction of the base material 30, will be referred to as the direction that intersects the arrangement direction of the multiple resistance heating elements 31, or simply the arrangement intersection direction. The arrangement intersection direction Y is the direction along the surface of the base material 30 on which the resistance heating elements 31 are provided, and is also the short-side direction of the heater 22, or the transport direction of the paper fed through the fixing device 9.

[0038] Multiple resistive heating elements 31 constitute a heating section 35 that is divided into multiple sections in the direction of arrangement. Each resistive heating element 31 is electrically connected in parallel to a pair of electrode sections 34A and 34B provided at one end of the base material 30 in the direction of arrangement (the left end in Figure 4) via power supply lines 33A and 33B. The power supply lines 33A and 33B are made of conductors with a lower resistance value than the resistive heating elements 31. From the viewpoint of ensuring insulation between adjacent resistive heating elements 31, the gap between them is preferably 0.2 mm or more, and more preferably 0.4 mm or more. Furthermore, if the gap between adjacent resistive heating elements 31 is too large, a temperature drop is likely to occur in the gap. For this reason, from the viewpoint of suppressing temperature unevenness across the direction of arrangement, the gap is preferably 5 mm or less, and more preferably 1 mm or less.

[0039] The resistive heating element 31 according to this embodiment is made of a material having PTC (positive temperature resistance coefficient) characteristics, and has the characteristic that the resistance value increases (heater output decreases) as the temperature rises. In this embodiment, the temperature resistance coefficient of the resistive heating element 31 is set to 500 ppm.

[0040] Thus, by having a resistive heating element 31 with PTC characteristics and by configuring a heating section 35 divided in the arrangement direction, it is possible to prevent overheating of the fixing belt 20 when continuously feeding small-sized paper. In other words, when paper with a width smaller than the overall width of the heating section 35 is fed, the heat of the fixing belt 20 is not absorbed by the paper in the area outside the paper width (non-feeding area), so the temperature of the resistive heating element 31 in that area tends to rise. Since the voltage applied to the resistive heating element 31 is constant, as the temperature of the resistive heating element 31 rises in the area outside the paper width, its resistance value increases, conversely, and the output (amount of heat generated) decreases relatively, suppressing the temperature rise. Furthermore, in this embodiment, since multiple resistive heating elements 31 are electrically connected in parallel, it is possible to suppress the temperature rise in the non-feeding area while maintaining the printing speed. Note that the heating elements constituting the heating section 35 may be other than resistive heating elements with PTC characteristics. Also, the resistive heating elements may be arranged in multiple rows in the direction of the arrangement intersection of the heaters 22.

[0041] The resistive heating element 31 can be formed, for example, by coating a paste made of silver palladium (AgPd) and glass powder onto a substrate 30 by screen printing, and then firing the substrate 30. In this embodiment, the resistance value of the resistive heating element 31 is set to 80Ω at room temperature. In addition to the materials mentioned above, the resistive material of the resistive heating element 31 may also be a silver alloy (AgPt) or ruthenium oxide (RuO2). The materials of the power supply lines 33A, 33B and the electrode parts 34A, 34B can be formed from silver (Ag) or silver palladium (AgPd) by screen printing, etc. The power supply lines 33A, 33B are composed of conductors with a resistance value smaller than that of the resistive heating element 31.

[0042] As the material for the base material 30, ceramics such as alumina or aluminum nitride, which have excellent heat resistance and insulation properties, or non-metallic materials such as glass or mica are preferred. In this embodiment, an alumina base material with a width of 8 mm in the direction of the array intersection, a width of 270 mm in the direction of the array, and a thickness of 1.0 mm is used. Alternatively, the base material 30 may be constructed by laminating an insulating material onto a conductive material such as a metal. As the metallic material for the base material 30, aluminum or stainless steel are preferred due to their low cost. If the base material 30 is constructed from a stainless steel plate, cracking due to thermal stress can be suppressed. Furthermore, in order to improve the uniformity of the heater 22 and enhance image quality, the base material 30 may be constructed from a material with high thermal conductivity such as copper, graphite, or graphene.

[0043] The insulating layer 32 is made of, for example, heat-resistant glass with a thickness of 75 μm. The insulating layer 32 covers the resistance heating element 31 and the power supply line 33, insulating and protecting them while maintaining sliding properties with the fixing belt 20.

[0044] Figure 5 shows the power supply circuit to the heater according to this embodiment.

[0045] As shown in Figure 5, in this embodiment, the power supply circuit for supplying power to each resistive heating element 31 is configured by electrically connecting the AC power supply 200 to the electrode portions 34A and 34B of the heater 22. The power supply circuit is also provided with a triac 210 for controlling the amount of power supplied. The amount of power supplied to each resistive heating element 31 is controlled by the control unit 220 via the triac 210 based on the temperature detected by the thermistor 25, which is a temperature sensing element. The control unit 220 is composed of a microcomputer that includes a CPU, ROM, RAM, I / O interface, etc.

[0046] In this embodiment, thermistors 25 are positioned in the central region of the heater 22 in the arrangement direction, which is within the minimum paper feed width, and at one end of the heater 22 in the arrangement direction. Furthermore, a thermostat 27 is positioned at one end of the heater 22 in the arrangement direction as a power shutoff means that shuts off the power supply to the resistance heating element 31 when the temperature of the resistance heating element 31 exceeds a predetermined temperature. The thermistors 25 and thermostat 27 contact the heater 22 to detect its temperature.

[0047] Incidentally, in order to ensure the separation performance of the paper P by the separation plate 41, it is preferable to position the tip of the separation plate 41 (separation section 411) close to the outer circumferential surface of the fixing belt 20 near the downstream end of the nip section N in the paper transport direction. In this regard, as in this embodiment, when the separation plate 41 is made of a metal material, the dimensional accuracy of the separation plate 41 can be improved, so that the tip of the separation plate 41 can be positioned close to the outer circumferential surface of the fixing belt 20.

[0048] However, since the fixing belt 20 is made of a flexible material, when the fixing belt 20 rotates, its rotational trajectory changes, and there is a risk that the distance between the surface of the fixing belt 20 and the tip of the separating plate 41 facing it will change. To address this problem, in this embodiment, the separating plate 41 has a butt portion 412 that contacts the surface of the fixing belt 20, so that even if the trajectory of the fixing belt 20 changes due to rotation, the separating plate 41 can follow the change. In other words, in this embodiment, even if the surface position of the fixing belt 20 changes, the tip of the separating plate 41 is displaced to follow that surface position, so that the distance between the surface of the fixing belt 20 and the tip of the separating plate 41 can be maintained at the desired distance. This ensures stable paper separation.

[0049] However, in a configuration where the metal separator plate 41 is in contact with the surface of the fixing belt 20, if the insulating layer 32 of the heater 22 is damaged, there is a risk that the current supplied to the heater 22 will flow from the fixing belt 20 through the conductive separator plate 41 to the side plate 40. When the current from the heater 22 flows to the side plate 40, the amount of heat generated by the heater 22 fluctuates, causing variations in the temperature at which the image on the paper is fixed, and degrading the fixing quality. In addition, if the components inside the image forming apparatus become charged by the current that flows through the side plate 40, toner may adhere to the charged components, causing them to become dirty, or the operator's hands may become contaminated with toner when touching the components during jam processing, etc.

[0050] Furthermore, the leakage current problem of the heater 22 described above is particularly likely to occur in a planar heater 22 like the one in this embodiment. This is because planar heaters 22 are generally formed with an insulating layer 32 that is thinner than 0.1 mm, making them susceptible to damage.

[0051] Therefore, in a configuration where a thin insulating layer is provided for the planar heater 22, and the separation plate 41 is in contact with the surface of the fixing belt 20, if the insulating layer is damaged, the current supplied to the heater 22 may flow through the separation plate 41 to the side plate 40, potentially affecting the amount of heat generated by the heater 22 or causing adverse electrical effects on surrounding components. Furthermore, if the current flows through the fixing belt 20 to the surface of the pressure roller 21, the surface of the pressure roller 21 may become charged, and if the potential difference between the fixing belt 20 and the pressure roller 21 changes, there is a risk that an abnormal image (electrostatic offset) may occur in which part of the toner image on the paper adheres to the fixing belt 20. For this reason, it is necessary to ground the separation plate 41 and the pressure roller 21 while ensuring a certain level of insulation, but if the separation plate 41 and the pressure roller 21 are each grounded via separate resistors, the number of parts increases, leading to problems such as a larger device and higher costs. Therefore, in this embodiment, in order to realize a configuration in which the separation plate 41 and the pressure roller 21 are grounded while ensuring a certain level of insulation with a small number of parts, the following structure is adopted.

[0052] The grounding structure of the separation plate 41 and pressure roller 21 according to this embodiment will be described below with reference to Figures 2 and 3.

[0053] As shown in Figures 2 and 3, the fixing device 9 according to this embodiment includes a static elimination brush 43 as a static elimination member and a resistor 39 that electrically connects the static elimination brush 43 and the side plate 40 as members constituting the grounding structure of the separation plate 41 and the pressure roller 21.

[0054] The static elimination brush 43 is made of a conductive material, and for example, stainless steel fibers or resin fibers such as acrylic or polyester with metal plating can be used. The static elimination brush 43 is positioned downstream of the nip section N in the paper transport direction, and its brush-like tip is in contact with the abutment section 412 of the separation plate 41 and the surface (release layer 21c) of the pressure roller 21. The static elimination brush 43 is attached to the side plate 40 via a resistor holding member 44 that holds the resistor 39.

[0055] The resistor 39 is composed of a wire that is partially wound around it and is held by the resistor holding member 44. Specifically, one end of the resistor 39 is held by being sandwiched between the head of the fixing screw 29A that secures the static elimination brush 43 to the resistor holding member 44 and the resistor holding member 44, and the other end of the resistor 39 is held by being sandwiched between the head of the fixing screw 29B that secures the resistor holding member 44 to the side plate 40 and the resistor holding member 44. Furthermore, the wound portion of the resistor 39 is positioned within a hole 44a provided in the resistor holding member 44 and is held non-contact with the resistor holding member 44.

[0056] In this way, the resistor 39 is fixed to the static elimination brush 43 and the resistor holding member 44 by two fixing screws 29A and 29B, so that the static elimination brush 43 is electrically connected to the grounded side plate 40 via the resistor 39 and the resistor holding member 44. Furthermore, since the static elimination brush 43 is in direct contact with both the separation plate 41 and the pressure roller 21, the charge accumulated on the separation plate 41 and the pressure roller 21 flows to the side plate 40 via the static elimination brush 43 and is removed.

[0057] Here, if the static elimination of the separation plate 41 and pressure roller 21 via the static elimination brush 43 becomes excessive, there is a risk that the amount of heat generated will fluctuate due to the current from the heater 22 flowing from the separation plate 41 to the side plate 40. Also, when the paper is sandwiched between both the fixing nip (nip section N) and the secondary transfer nip, if the transfer current flows to the static elimination brush 43 via the paper and pressure roller 21, there is a risk of transfer failure.

[0058] Therefore, in this embodiment, a resistor 39 with an electrical resistance value that allows an appropriate amount of electricity to flow is interposed between the static elimination brush 43 and the side plate 40, thereby ensuring a certain level of insulation between the separation plate 41 and the side plate 40, and between the pressure roller 21 and the side plate 40. That is, the electrical resistance value of the resistor 39 is set to be higher than the electrical resistance value of the side plate 40 and lower than the electrical resistance value of the resistor holding member 44. As a result, the current from the separation plate 41 and the pressure roller 21 can be appropriately supplied to the side plate 40 via the resistor 39, preventing charge buildup on the separation plate 41 and the pressure roller 21, while suppressing the current flowing from the separation plate 41 and the pressure roller 21 to the side plate 40. In this embodiment, the pressure roller 21 has a metal core 21a, but an elastic layer 21b with high electrical resistance is provided between the core 21a and the release layer 21c. Therefore, the current applied to the surface of the pressure roller 21 does not flow to the core 21a, but flows to the side plate 40 via the static elimination brush 43 and the resistor 39. In other words, the elastic layer 21b is made of a material with a higher electrical resistance than the resistor 39 and the static elimination brush 43. Furthermore, the separation plate 41 in this embodiment is not directly attached to the metal side plate 40, but is attached to the support shaft 42 of the resin belt holding member 19, which has a higher electrical resistance than the resistor 39 and the static elimination brush 43. Therefore, the current applied to the separation plate 41 does not flow directly to the side plate 40, but flows to the side plate 40 via the static elimination brush 43 and the resistor 39.

[0059] As a result, in this embodiment, the current supplied to the heater 22 can be prevented from flowing excessively to the side plate 40 side via the fuser belt 20, separation plate 41, and pressure roller 21. This improves the problem of fluctuations in the amount of heat generated by the heater 22 due to leakage current, and the problem of electricity flowing through and charging electronic components in the image forming apparatus. Furthermore, since it is possible to prevent the accumulation of charge on the separation plate 41 and pressure roller 21, the occurrence of abnormal images (electrostatic offset) in which a portion of the toner image on the paper adheres to the fuser belt 20 can also be suppressed.

[0060] Furthermore, in this embodiment, since both the separation plate 41 and the pressure roller 21 are grounded via the same (single) resistor 39, the number of parts can be reduced compared to the case where the resistor 39 is individually provided for each of the separation plate 41 and the pressure roller 21. In addition, in this embodiment, by connecting the separation plate 41 and the pressure roller 21 via a single static elimination brush 43, the grounding path from the separation plate 41 and the pressure roller 21 to the grounding point can be consolidated into a single path. As a result, the resistor 39 that constitutes the grounding path, as well as the static elimination brush 43 and the resistor holding member 44, can each be consolidated into one, further reducing the number of parts. Thus, in this embodiment, the number of parts for the various components constituting the grounding structure of the separation plate 41 and the pressure roller 21 can be reduced, making it possible to miniaturize and reduce the cost of the device.

[0061] Furthermore, as shown in Figures 2 and 3, in this embodiment, the static elimination brush 43 is positioned downstream of the nip section N in the paper transport direction, and is also positioned between the pressure roller 21 and the separation plate 41, thus enabling miniaturization of the device. In other words, in this embodiment, since the static elimination brush 43 is positioned close to the pressure roller 21 and the separation plate 41, which are the targets of static elimination, the installation space for the static elimination brush 43, the pressure roller 21, and the separation plate 41 is reduced, thus enabling miniaturization.

[0062] Furthermore, it is preferable to provide a creepage distance equivalent to foundation insulation between the separation plate 41 and the side plate 40, and between the pressure roller 21 and the side plate 40. Specifically, it is preferable that the creepage distance between the separation plate 41 and the side plate 40, and between the pressure roller 21 and the side plate 40 (the distance at the point where the pressure roller 21 and the side plate 40 are closest) be 2.5 mm or more. By setting the creepage distance between these points to 2.5 mm or more, insulation equivalent to foundation insulation can be ensured between the separation plate 41 and the side plate 40, and between the pressure roller 21 and the side plate 40.

[0063] Next, other embodiments of the present invention will be described, focusing on the parts that differ from the above-described embodiment (first embodiment). Since the other parts are basically the same as those of the above embodiment, their description will be omitted.

[0064] In the second embodiment of the present invention shown in Figures 6 and 7, in addition to the static elimination brush 43 and resistor 39, a flexible sheet-like conductive member 38 is used as a component constituting the grounding structure of the separation plate 41 and the pressure roller 21.

[0065] The sheet-like conductive member 38 is positioned to directly contact both the abutment portion 412 of the separation plate 41 and the outer circumferential surface of the pressure roller 21. Therefore, the separation plate 41 and the pressure roller 21 are electrically connected via the conductive member 38. Furthermore, since the static elimination brush 43 is in direct contact with the outer circumferential surface of the pressure roller 21, the pressure roller 21 is electrically connected to the side plate 40 via the static elimination brush 43 and the resistor 39. The separation plate 41 is also electrically connected to the side plate 40 via the conductive member 38, the static elimination brush 43, and the resistor 39. Otherwise, the configuration is the same as in the above embodiment (first embodiment).

[0066] Here, the conductive member 38 is made of a conductive material with an electrical resistance value smaller than the electrical resistance value of the support shaft 42 of the belt holding member 19 that supports the separation plate 41, and the electrical resistance value of the elastic layer 21b of the pressure roller 21. As a result, the current from the separation plate 41 flows appropriately to the side plate 40 via the conductive member 38, the static elimination brush 43, and the resistor 39. Similarly, the current from the pressure roller 21 also flows appropriately to the side plate 40 via the static elimination brush 43 and the resistor 39.

[0067] Thus, in the second embodiment of the present invention, the separator plate 41 and the pressure roller 21 can be grounded while ensuring a certain level of insulation between the separator plate 41 and the side plate 40, and between the pressure roller 21 and the side plate 40, by using the resistor 39. This makes it possible to suppress fluctuations in the amount of heat generated by the heater 22 due to leakage current, adverse effects caused by the charging of electronic components in the image forming apparatus, and the occurrence of abnormal images (electrostatic offset).

[0068] Furthermore, in this embodiment, by providing one of each component constituting the grounding structure—the conductive member 38, the static elimination brush 43, and the resistor 39—the device can be miniaturized and cost-effective, similar to the above embodiment (first embodiment). In other words, compared to the case where the conductive member 38, the static elimination brush 43, and the resistor 39 are individually provided on the separation plate 41 and the pressure roller 21, the number of parts can be reduced, resulting in miniaturization and cost reduction. Moreover, in this embodiment, as shown in Figures 6 and 7, the conductive member 38 is positioned downstream of the nip section N in the paper transport direction, between the pressure roller 21 and the separation plate 41, thereby bringing the conductive member 38 closer to the pressure roller 21 and the separation plate 41, which are the targets for static elimination, and thus achieving miniaturization.

[0069] Furthermore, it is preferable that the volume resistance of the conductive member 38 be 110 kΩ or more. By setting the volume resistance of the conductive member 38 to 110 kΩ or more, the current flowing from the separation plate 41 and the pressure roller 21 to the side plate 40 can be limited, thereby more effectively suppressing fluctuations in the amount of heat generated by the heater 22 due to leakage current, adverse effects caused by the charging of electronic components in the image forming apparatus, and the occurrence of abnormal images (electrostatic offset).

[0070] Next, in the third embodiment of the present invention shown in Figures 8 and 9, the conductive member 38 is in direct contact with the abutment portion 412 of the separation plate 41 and the outer circumferential surface of the pressure roller 21, as well as with the static elimination brush 43. Therefore, the separation plate 41 and the pressure roller 21 are electrically connected to the static elimination brush 43 via the conductive member 38.

[0071] As a result, in this embodiment, the separation plate 41 and the pressure roller 21 are electrically connected to the side plate 40 via the conductive member 38, the static elimination brush 43, and the resistor 39. That is, the separation plate 41 and the pressure roller 21 are grounded while ensuring a certain level of insulation between the separation plate 41 and the side plate 40, and between the pressure roller 21 and the side plate 40. Therefore, in this embodiment as well, the current from the separation plate 41 and the pressure roller 21 can be appropriately supplied to the side plate 40, thereby suppressing fluctuations in the amount of heat generated by the heater 22 due to leakage current, adverse effects caused by the charging of electronic components in the image forming apparatus, and the occurrence of abnormal images (electrostatic offset).

[0072] Furthermore, in this embodiment as well, by using one of each component—the conductive member 38, the static elimination brush 43, and the resistor 39—the number of parts can be reduced, resulting in miniaturization and cost reduction. Also, similar to the second embodiment described above, the conductive member 38 is positioned downstream of the nip section N in the paper transport direction, between the pressure roller 21 and the separation plate 41, thus enabling space-saving and miniaturization of the device.

[0073] Next, in the fourth embodiment of the present invention shown in Figures 10 and 11, the conductive member 38 is in direct contact with both the abutment portion 412 of the separation plate 41 and the outer circumferential surface of the pressure roller 21, and the static elimination brush 43 is in direct contact with the separation portion 411 of the separation plate 41. Thus, in this embodiment, the static elimination brush 43 is in direct contact with the separation plate 41, which is different from the second embodiment shown in Figures 6 and 7. That is, in the second embodiment, the static elimination brush 43 is in direct contact only with the pressure roller 21 of the separation plate 41 (see Figures 6 and 7), whereas in this embodiment, the static elimination brush 43 is in direct contact only with the separation plate 41 (see Figures 10 and 11).

[0074] In this case as well, just like in each of the embodiments described above, a grounding structure with a certain level of insulation can be configured between the separation plate 41 and the side plate 40, and between the pressure roller 21 and the side plate 40. Therefore, in this embodiment as well, the current from the separation plate 41 and the pressure roller 21 can be appropriately supplied to the side plate 40, thereby suppressing fluctuations in the amount of heat generated by the heater 22 due to leakage current, adverse effects caused by the charging of electronic components in the image forming apparatus, and the occurrence of abnormal images (electrostatic offset).

[0075] Furthermore, in this embodiment as well, by using only one of each component—the conductive member 38, the static elimination brush 43, and the resistor 39—the number of parts can be reduced, resulting in miniaturization and cost reduction. In addition, since the conductive member 38 is positioned downstream of the nip section N in the paper transport direction, between the pressure roller 21 and the separation plate 41, the device can be made smaller by saving space.

[0076] Next, in the fifth embodiment of the present invention shown in Figures 12 and 13, the conductive member 38 is arranged to be in direct contact with the separation portion 411 of the separation plate 41 and the brush-shaped portion of the static elimination brush 43. On the other hand, the static elimination brush 43 is in direct contact with the outer circumferential surface of the pressure roller 21 as well as the conductive member 38.

[0077] In this embodiment, since the conductive member 38 does not come into contact with the outer surface of the pressure roller 21, damage to the outer surface of the pressure roller 21 due to contact with the conductive member 38 can be avoided, and the lifespan of the pressure roller 21 can be extended. Furthermore, in this embodiment, it is possible to select a highly rigid (non-flexible) material as the conductive member 38. In the embodiments shown in Figures 6 to 11 above, in which the conductive member 38 comes into direct contact with the outer surface of the pressure roller 21, it is preferable that the conductive member 38 be made of a conductive resin rather than a metal material in order to suppress damage to the outer surface of the pressure roller 21 due to contact between the conductive member 38 and the outer surface of the pressure roller 21.

[0078] Furthermore, in this embodiment as well, since the separation plate 41 and the pressure roller 21 are electrically connected to the side plate 40 via the conductive member 38, the static elimination brush 43, and the resistor 39, a grounding structure with a certain level of insulation can be configured between the separation plate 41 and the side plate 40, and between the pressure roller 21 and the side plate 40. Therefore, in this embodiment as well, the current from the separation plate 41 and the pressure roller 21 can be appropriately supplied to the side plate 40, thereby suppressing fluctuations in the amount of heat generated by the heater 22 due to leakage current, adverse effects caused by the charging of electronic components in the image forming apparatus, and the occurrence of abnormal images (electrostatic offset).

[0079] Furthermore, in this embodiment as well, by using only one of each component—the conductive member 38, the static elimination brush 43, and the resistor 39—the number of parts can be reduced, resulting in miniaturization and cost reduction. In addition, since the conductive member 38 is positioned downstream of the nip section N in the paper transport direction, between the pressure roller 21 and the separation plate 41, the device can be made smaller by saving space.

[0080] Although embodiments of the present invention have been described above, the present invention is not limited to the configurations of the above embodiments. For example, the heater 22 may be one in which the resistive heating element 31 is rectangular, as shown in Figure 14, or it may be one in which the resistive heating element 31 consists of a linear portion, and this linear portion is folded back to form a substantially parallelogram shape, as shown in Figure 15. In Figure 14, the portion extending from the block-shaped resistive heating element 31 towards the power supply line 33 (the portion extending in the direction of array intersection Y) may be a part of the resistive heating element 31, or it may be made of the same material as the power supply line 33.

[0081] Figure 16 shows the temperature distribution in the longitudinal direction X of the fixing belt 20 in a configuration in which multiple resistance heating elements 31 are arranged at intervals along the longitudinal direction of the heater 22. In Figure 16, (a) shows the arrangement of each resistance heating element 31 on the heater 22, and (b) shows the temperature T of the fixing belt 20 on the vertical axis and the positions of the fixing belt 20 in the longitudinal direction X on the horizontal axis.

[0082] As shown in Figures 16(a) and 16(b), the multiple resistance heating elements 31 provided on the heater 22 are divided in the direction of arrangement (longitudinal direction X), forming a divided region B between the resistance heating elements 31. In other words, the multiple resistance heating elements 31 provided on the heater 22 are arranged with a gap B between them. Hereinafter, this divided region B will be referred to as gap B. In gap B, the area occupied by the resistance heating elements 31 is smaller than in other parts, resulting in less heat generation. As a result, the temperature of the fixing belt 20 in gap B is lower than in other parts, causing temperature unevenness in the direction of arrangement of the fixing belt 20. Furthermore, in the expanded divided region C (hereinafter simply referred to as region C), which includes the area surrounding the divided region of gap B, the temperatures of the heater 22 and the fixing belt 20 are also lower. Similarly, the temperature of the heater 22 is also lower in gap B. Here, as shown in the enlarged view of Figure 16(a), spacing B represents the region in the direction of the arrangement, which includes the entire portion of the resistive heating element 31, the main heat-generating part of the heater 22, that is divided in the direction of the arrangement. In addition to spacing B, region C includes the area corresponding to the connection portion 311 of the resistive heating element 31. This connection portion 311 refers to the portion of the resistive heating element 31 that extends in the direction of the arrangement crossing and is connected to each power supply line 33A, 33B.

[0083] As shown in Figure 17, even in the heater 22 having the rectangular resistance heating element 31 shown in Figure 14, the temperature of the gap B is lower than that of the other parts. Similarly, in the heater 22 having the resistance heating element 31 with the shape shown in Figure 18, the temperature of the gap B is lower than that of the other parts. Furthermore, as shown in Figure 19, even in the heater 22 having the resistance heating element 31 with the shape shown in Figure 15, the temperature of the gap B is lower than that of the other parts. However, as shown in Figures 16, 18, and 19, by overlapping adjacent resistance heating elements 31 in the direction of arrangement (arrow X direction), the temperature drop in the gap B relative to the other parts can be suppressed.

[0084] Furthermore, as shown in the example in Figure 20, the fixing device 9 according to the present invention may also include a first high heat conductive member 28 between the heater 22 and the heater holder 23.

[0085] The first high thermal conductivity member 28 is made of a material with a higher thermal conductivity than the base material 30 of the heater 22. The first high thermal conductivity member 28 is made of plate-shaped aluminum, copper, silver, graphene, or graphite. By making the first high thermal conductivity member 28 plate-shaped, the positional accuracy of the heater 22 relative to the heater holder 23 and the first high thermal conductivity member 28 can be improved.

[0086] As shown in Figure 20, the first high-heat-conductivity member 28 is positioned between the heater 22 and the stay 24 in the left-right direction of Figure 20, and is particularly sandwiched between the heater 22 and the heater holder 23. In other words, the first high-heat-conductivity member 28 is positioned so that one surface is in contact with the back surface of the heater 22 and the other surface is in contact with the heater holder 23.

[0087] Furthermore, the stay 24 supports the heater holder 23, the first high heat conductive member 28, and the heater 22 by bringing the contact surfaces 24a1 of two vertical portions 24a extending in the thickness direction of the heater 22 into contact with the heater holder 23. In the direction of the array intersection (up and down direction in Figure 2), the contact surfaces 24a1 are located outside the area where the resistance heating element 31 is provided. This suppresses heat transfer from the heater 22 to the stay 24, allowing the heater 22 to efficiently heat the fixing belt 20.

[0088] The method for calculating the thermal conductivity of the first high thermal conductivity component 28 involves measuring the thermal diffusivity of the object in question and using this thermal diffusivity to calculate the thermal conductivity. A thermal diffusivity / thermal conductivity measuring device (product name: ai-Phase Mobile 1u, manufactured by iPhase Co., Ltd.) is used to measure the thermal diffusivity.

[0089] Furthermore, to convert the above thermal diffusivity to thermal conductivity, the values ​​of density and specific heat capacity are required. A dry automatic densimeter (product name: Accupyc 1330, manufactured by Shimadzu Corporation) is used to measure density. A differential scanning calorimetry device (product name: DSC-60, manufactured by Shimadzu Corporation) is used to measure specific heat capacity, and sapphire is used as a reference material with a known specific heat capacity. For example, the specific heat capacity is measured five times, and the average value at 50°C is used. If the density and specific heat capacity are ρ and C, respectively, the thermal conductivity λ can be obtained from the thermal diffusivity α obtained in the above thermal diffusivity measurement by the following equation (1).

[0090]

number

[0091] The first high thermal conductivity member 28 will be described in more detail below.

[0092] As shown in Figure 21, the first high thermal conductivity member 28 is formed in the shape of a plate, for example, having a thickness of 0.3 mm, a length of 222 mm in the direction of arrangement, and a width of 10 mm in the direction of arrangement intersection. The first high thermal conductivity member 28 may be composed of a single plate material or of multiple members.

[0093] As shown in Figure 21, the first high-heat-conductivity member 28 is fitted into the recess 23b of the heater holder 23, and the heater 22 is mounted on top of it, so that it is held between the heater holder 23 and the heater 22. In the example shown in Figure 21, the width of the first high-heat-conductivity member 28 in the direction of arrangement is set to be approximately the same as the width of the heater 22 in the direction of arrangement. The movement of the first high-heat-conductivity member 28 and the heater 22 in the direction of arrangement intersection is restricted by the side walls (arrangement intersection direction restricting parts) 23b2 of the side walls forming the recess 23b, which are arranged apart in the direction of arrangement intersection of the recess 23b. Furthermore, the movement of the first high-heat-conductivity member 28 and the heater 22 in the direction of arrangement is restricted by the side walls (arrangement direction restricting parts) 23b1 of the side walls forming the recess 23b, which are arranged apart in the direction of arrangement intersection of the recess 23b. In this way, by restricting the positional displacement of the first high-heat-conductivity member 28 in the direction of arrangement within the fixing device 9, the heat conduction efficiency can be improved for the target range in the direction of arrangement.

[0094] The range in the arrangement direction in which the first high thermal conductivity member 28 can be provided is not limited to the above example. For example, as shown in Figure 22, the first high thermal conductivity member 28 may be provided only in the range corresponding to the heat-generating portion 35 in the arrangement direction (see the hatched area in Figure 22). Also, as shown in Figure 23, the first high thermal conductivity member 28 may be provided only in the entire area at a position corresponding to the spacing B in the arrangement direction. In Figure 23, for convenience, the resistance heating element 31 and the first high thermal conductivity member 28 are shown shifted vertically in Figure 23, but both are positioned at approximately the same location in the arrangement intersection direction Y. However, this is not the only option, and the first high thermal conductivity member 28 may be provided in a part of the arrangement intersection direction Y of the resistance heating element 31, or it may be provided so as to cover the entire arrangement intersection direction Y, as shown in Figure 24 described later.

[0095] Furthermore, as shown in the example in Figure 24, the first high-heat-conductivity member 28 may be provided not only at positions corresponding to the spacing B in the arrangement direction, but also spanning the resistance heating elements 31 on both sides that straddle the spacing B. Here, providing the first high-heat-conductivity member 28 spanning the resistance heating elements 31 on both sides means that the position of the first high-heat-conductivity member 28 in the arrangement direction overlaps with that of the resistance heating elements 31 on both sides in at least a portion of the arrangement direction. Note that the first high-heat-conductivity member 28 may be provided corresponding to all the spacing B of the heater 22, or it may be provided only at positions corresponding to some of the spacing B, such as providing the first high-heat-conductivity member 28 at a position corresponding to one of the spacing B, as shown in Figure 24. Here, providing the first high-heat-conductivity member 28 at a position corresponding to the spacing B in the arrangement direction means that at least a portion of it overlaps with the spacing B in the arrangement direction.

[0096] The pressure applied by the pressure roller 21 causes the first high-heat-conductivity member 28 to be sandwiched between the heater 22 and the heater holder 23, making close contact with these members. The contact of the first high-heat-conductivity member 28 with the heater 22 improves the heat conduction efficiency of the heater 22 in the arrangement direction. Furthermore, by positioning the first high-heat-conductivity member 28 at a position corresponding to the spacing B of the heater 22 in the arrangement direction, the heat 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. Therefore, temperature unevenness of the heater 22 in the arrangement direction can be suppressed. As a result, temperature unevenness of the fixing belt 20 in the arrangement direction can be suppressed, thus suppressing uneven fixing and gloss unevenness of the image fixed to the paper. Alternatively, it becomes unnecessary to perform extra heating by the heater 22 to ensure sufficient fixing performance at the spacing B, thereby achieving energy savings for the fixing device 9. Furthermore, by providing the first high thermal conductivity member 28 over the entire area of ​​the heating element 35 in the arrangement direction, the heat transfer efficiency of the heater 22 can be improved throughout the main heating area (i.e., the image forming area of ​​the paper being passed through), thereby suppressing temperature unevenness in the arrangement direction of the heater 22 and, consequently, the fixing belt 20.

[0097] In particular, by combining the configuration of the first high thermal conductivity member 28 with the resistance heating element 31 having the aforementioned PTC characteristics, overheating in the non-paper-feeding area during small-sized paper feeding can be effectively suppressed. In other words, the PTC characteristics suppress the amount of heat generated by the resistance heating element 31 in the non-paper-feeding area, and the heat from the heated non-paper-feeding area can be efficiently transferred to the paper-feeding area, thereby effectively suppressing overheating in the non-paper-feeding area.

[0098] Furthermore, since the temperature around interval B is low due to the small amount of heat generated by interval B, it is preferable to place the first high-heat-conducting member 28 there. For example, by providing the first high-heat-conducting member 28 at a position corresponding to region C (see Figure 16), the heat transfer efficiency in the arrangement direction around interval B is particularly improved, and temperature unevenness in the arrangement direction of the heater 22 can be further suppressed. In addition, by providing the first high-heat-conducting member 28 over the entire area of ​​the heat-generating section 35 in the arrangement direction, temperature unevenness in the arrangement direction of the heater 22 (fixing belt 20) can be further suppressed.

[0099] Next, yet another example of a fixing device to which the present invention can be applied will be described.

[0100] The example shown in Figure 25 is one in which the fixing device 9 is equipped with a second high heat conductive member 36 between the heater holder 23 and the first high heat conductive member 28. The second high heat conductive member 36 is provided superimposed on the first high heat conductive member 28 in the stacking direction of the members such as the heater holder 23, the stay 24, and the first high heat conductive member 28 (left-right direction in Figure 25).

[0101] The second high thermal conductivity member 36 is made of a material with a higher thermal conductivity than the base material 30 of the heater 22, such as graphene or graphite. For example, the second high thermal conductivity member 36 is made of a graphite sheet with a thickness of 1 mm. Alternatively, the second high thermal conductivity member 36 may be made of a plate material such as aluminum, copper, or silver.

[0102] As shown in Figure 26, multiple second high-heat-conductivity members 36, which are partially provided in the arrangement direction, are arranged in the arrangement direction (arrow X direction). The portion of the recess 23b of the heater holder 23 where the second high-heat-conductivity member 36 is provided is made one step deeper than the other portions. The second high-heat-conductivity member 36 has a gap between it and the heater holder 23 on both sides in the arrangement direction. This suppresses heat transfer from the second high-heat-conductivity member 36 to the heater holder 23, allowing the heater 22 to efficiently heat the fixing belt 20.

[0103] As shown in Figure 27, the second high thermal conductivity member 36 (see hatched area) is provided in the arrangement direction (arrow X direction) at a position corresponding to the interval B, overlapping at least a portion of the adjacent resistance heating element 31, and in particular, in this example, it is provided over the entire interval B. In the example shown in Figure 27 (and Figure 31 described later), the first high thermal conductivity member 28 is provided only in the region corresponding to the heating element 35 in the arrangement direction, but the arrangement of the first high thermal conductivity member 28 is not limited to this.

[0104] As shown in Figure 27, by providing a second high-heat-conductivity member 36 in addition to the first high-heat-conductivity member 28 at a position corresponding to the spacing B in the arrangement direction, overlapping at least a portion of the adjacent resistance heating elements 31, the heat transfer efficiency in the arrangement direction at the spacing B can be particularly improved, and temperature unevenness in the arrangement direction of the heater 22 can be further suppressed. Furthermore, most preferably, as shown in Figure 28, the first high-heat-conductivity member 28 and the second high-heat-conductivity member 36 are provided only in the entire area at the position corresponding to the spacing B. This makes it possible to particularly improve the heat transfer efficiency at the position corresponding to the spacing B compared to other areas. Note that in Figure 28, for convenience, the resistance heating elements 31, the first high-heat-conductivity member 28, and the second high-heat-conductivity member 36 are shown offset in the vertical direction of Figure 28, but they are actually arranged at approximately the same position in the direction of the arrangement intersection. However, this is not limited to the above, and the first high thermal conductivity member 28 and the second high thermal conductivity member 36 may be provided in a part of the arrangement crossing direction Y of the resistance heating element 31, or they may be provided so as to cover the entire arrangement crossing direction Y.

[0105] Furthermore, if the first high thermal conductivity member 28 and the second high thermal conductivity member 36 are made of the graphene sheet, the first high thermal conductivity member 28 and the second high thermal conductivity member 36 can be formed in a predetermined direction along the surface of the graphene, that is, in the arrangement direction rather than the thickness direction, with high thermal conductivity. Therefore, temperature unevenness in the longitudinal direction X (arrangement direction) of the heater 22 and the fixing belt 20 can be effectively suppressed.

[0106] Graphene is a flaky powder. As shown in Figure 29, graphene consists of a planar hexagonal lattice structure of carbon atoms. A graphene sheet is a sheet of graphene, usually a single layer. The single layer of carbon may contain impurities. Graphene may also have a fullerene structure. A fullerene structure is generally recognized as a compound in which an equal number of carbon atoms form a polycyclic structure fused in a cage-like manner with five-membered and six-membered rings, such as C60, C70, and C80 fullerenes or other closed cage-like structures with three-coordinate carbon atoms.

[0107] Graphene sheets are artificial materials and can be fabricated, for example, by chemical vapor deposition (CVD).

[0108] Commercially available graphene sheets can be used. The size and thickness of the graphene sheet, as well as the number of layers of the graphite sheet described later, can be measured, for example, by a transmission electron microscope (TEM).

[0109] Furthermore, graphite with multiple layers of graphene exhibits high thermal conductivity anisotropy. As shown in Figure 30, graphite has a crystalline structure in which layers of condensed six-membered rings of carbon atoms are spread out in a planar manner, and these layers are stacked multiple times. In this crystalline structure, adjacent carbon atoms within a layer form covalent bonds, while carbon atoms between layers form van der Waals bonds. The covalent bonds have a stronger bonding force than van der Waals bonds, and there is a large anisotropy between the bonds within a layer and the bonds between layers. In other words, by constructing the first high thermal conductivity member 28 or the second high thermal conductivity member 36 from graphite, the heat transfer efficiency in the arrangement direction of the first high thermal conductivity member 28 or the second high thermal conductivity member 36 becomes larger than in the thickness direction (i.e., the stacking direction of the members), and heat transfer to the heater holder 23 can be suppressed. Therefore, temperature unevenness in the arrangement direction of the heater 22 can be efficiently suppressed, and the heat flowing out to the heater holder 23 can be minimized. Furthermore, by constructing the first high-thermal-conductivity member 28 or the second high-thermal-conductivity member 36 from graphite, the first high-thermal-conductivity member 28 or the second high-thermal-conductivity member 36 can be given excellent heat resistance, such as not oxidizing up to about 700 degrees Celsius.

[0110] The physical properties and dimensions of the graphite sheet can be appropriately changed according to the function required of the first high-thermal-conductivity member 28 or the second high-thermal-conductivity member 36. For example, the anisotropy of its thermal conductivity can be increased by using high-purity graphite or single-crystal graphite, or by increasing the thickness of the graphite sheet. In addition, to increase the speed of the fixing device 9, a thinner graphite sheet may be used to reduce the heat capacity of the fixing device 9. Furthermore, if the width of the nip section N or the width of the heater 22 is large, the width of the first high-thermal-conductivity member 28 or the second high-thermal-conductivity member 36 in the arrangement direction may be increased accordingly.

[0111] From the viewpoint of increasing mechanical strength, it is preferable that the graphite sheet has 11 or more layers. Furthermore, the graphite sheet may partially consist of single-layer and multi-layer sections.

[0112] The second high thermal conductivity member 36 may be provided in a position corresponding to the spacing B (and further to region C) in the arrangement direction, overlapping at least a portion of the adjacent resistance heating element 31, and is not limited to the arrangement shown in Figure 27. For example, as shown in Figure 31, the second high thermal conductivity member 36A may be provided extending beyond the base material 30 in the arrangement crossing direction Y, and the second high thermal conductivity member 36B may be provided in the range where the resistance heating element 31 is provided in the arrangement crossing direction Y. Also, as shown in Figure 31, the second high thermal conductivity member 36C may be provided in a portion of the spacing B.

[0113] Furthermore, as shown in the example in Figure 32, a gap 23c in the thickness direction (left-right direction in Figure 32) may be provided between the first high heat conductive member 28 and the heater holder 23. In other words, in a part of the recess 23b (see Figure 26) for arranging the heater 22, the first high heat conductive member 28, and the second high heat conductive member 36 of the heater holder 23, in a part of the area other than the part where the second high heat conductive member 36 is provided in the arrangement direction, and in a part of the area in the arrangement intersection direction, the depth of the recess 23b is made deeper than the other part that receives the first high heat conductive member 28, and a relief portion 23c as an insulating layer is provided. This minimizes the contact area between the heater holder 23 and the first high heat conductive member 28. Therefore, heat transfer from the first high heat conductive member 28 to the heater holder 23 is suppressed, and the heater 22 can efficiently heat the fixing belt 20. In the cross-section where the second high-heat-conducting member 36 in the arrangement direction is provided, the second high-heat-conducting member 36 contacts the heater holder 23, as shown in Figure 25.

[0114] Furthermore, as shown in Figure 32, relief portions 23c are provided over the entire area where the resistance heating element 31 is installed in the direction of the array crossing (up and down direction in Figure 32). This suppresses heat transfer, particularly from the first high thermal conductivity member 28 to the heater holder 23, allowing the heater 22 to efficiently heat the fixing belt 20. In addition to the configuration of providing a space as in the relief portion 23c, a configuration in which an insulating material with a lower thermal conductivity than the heater holder 23 is provided may also be used as the insulating layer.

[0115] In each of the above examples, the second high-temperature conductive member 36 is provided as a separate member from the first high-temperature conductive member 28. However, the second high-temperature conductive member 36 may be formed integrally with the first high-temperature conductive member 28, and the portion of the first high-temperature conductive member 28 corresponding to the gap B may be made thicker than the other portions.

[0116] In each of the examples described above, as in the embodiments of the present invention described above, the separation plate 41 and the pressure roller 21 are grounded via the same resistor 39, thereby ensuring a certain level of insulation between the separation plate 41 and the side plate 40, and between the pressure roller 21 and the side plate 40, while also reducing the number of parts, thereby enabling miniaturization and cost reduction. In Figures 20, 25, and 32, the configuration of the fixing device 9 with these configurations is applied to the embodiment shown in Figure 2 (first embodiment), but the configurations of the other embodiments shown in Figures 6 to 13 are also applicable.

[0117] Furthermore, the present invention is also applicable to fixing devices with configurations as shown in Figures 33 to 35. The configurations of each fixing device shown in Figures 33 to 35 will be described below.

[0118] First, in the fixing device 9 shown in Figure 33, a heating nip section N1 that heats the fixing belt 20 with a heater 22 and a fixing nip section N2 that allows the paper P to pass through are formed at separate locations. Specifically, in this example, a nip forming member 65 is placed inside the fixing belt 20 in addition to the heater 22, and pressure rollers 64 and 21 are pressed against the heater 22 and the nip forming member 65, respectively, via the fixing belt 20, thereby forming the heating nip section N1 and the fixing nip section N2. In this case, the fixing belt 20 is heated in the heating nip section N1, and the heat from the fixing belt 20 is applied to the paper P in the fixing nip section N2, thereby fixing the unfixed image to the paper P.

[0119] Next, the fixing device 9 shown in Figure 34 is an example in which the pressure roller 64 on the heater 22 side is omitted from the fixing device shown in Figure 33, and the heater 22 is formed in an arc shape to match the curvature of the fixing belt 20. Otherwise, the configuration is the same as shown in Figure 33. In this case, because the heater 22 is formed in an arc shape, the contact length between the fixing belt 20 and the heater 22 in the belt rotation direction is secured, and the fixing belt 20 can be heated efficiently.

[0120] Next, the fixing device 9 shown in Figure 35 is an example in which a roller 93 is positioned between a pair of belts 97 and 120. In this example, a heater 22 is positioned in the left belt 120 in Figure 35, and a nip forming member 95 is positioned in the right belt 97. The heater 22 contacts the roller 93 via the conductive belt 120 (conductive member) on the left, and the nip forming member 95 contacts the roller 93 (first rotating body) via the right belt 97 (second rotating body), thereby forming a heating nip portion N1 and a fixing nip portion N2.

[0121] In the fixing device 9 shown in Figures 33 to 35 above, the same effects and advantages as in the embodiments of the present invention can be obtained by applying the configuration of the present invention. That is, a certain level of insulation can be ensured between the separation plate 41 and the side plate 40, and between the pressure roller 21 and the side plate 40, and the number of parts can be reduced, resulting in miniaturization and cost reduction. In Figures 32 to 35, the configuration of the embodiment shown in Figure 2 (first embodiment) is applied to the fixing device 9 with these configurations, but the configurations of other embodiments shown in Figures 6 to 13 can also be applied.

[0122] Furthermore, the image forming apparatus according to the present invention is not limited to the color image forming apparatus shown in Figure 1, but is also applicable to image forming apparatuses with configurations such as those shown in Figure 36. The configurations of other image forming apparatuses to which the present invention can be applied will be described below.

[0123] The image forming apparatus 100 shown in Figure 36 comprises an image forming means 50 consisting of a photosensitive drum and the like, a paper transport unit consisting of a pair of timing rollers 15 and the like, a paper feed device 7, a fuser 9, a paper discharge device 10, and a reading unit 51. The paper feed device 7 has multiple paper trays, each of which accommodates paper of a different size.

[0124] The reading unit 51 reads the image of the original document Q. The reading unit 51 generates image data from the read image. The paper feed device 7 receives multiple sheets of paper P and feeds the paper P to the transport path. The timing roller 15 transports the paper P on the transport path to the image forming means 50.

[0125] 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 static elimination device. The toner image shows, for example, the image of the original document Q. The fixing device 9 heats and pressurizes the toner image to fix it to the paper P. The paper P with the fixed toner image is transported to the paper discharge device 10 by a transport roller or the like. The paper discharge device 10 discharges the paper P to the outside of the image forming device 100.

[0126] Next, the fixing device 9 of this embodiment will be described based on Figure 37. In the configuration shown in Figure 37, parts that are common with the fixing device 9 of the above embodiment shown in Figure 2 are denoted by the same reference numerals, and their descriptions are omitted.

[0127] As shown in Figure 37, 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 thermal conductivity member 28, a separation plate 41, a static elimination brush 43, a resistor 39, a resistor holding member 44, a side plate 40, and the like.

[0128] A nip section N is formed between the fixing belt 20 and the pressure roller 21. The nip width of the nip section N is 10 mm, and the linear speed of the fixing device 9 is 240 mm / s.

[0129] The fixing belt 20 comprises a polyimide substrate and a release layer, and does not have an elastic layer. The release layer is made of a heat-resistant film material, for example, made of fluororesin. The outer diameter of the fixing belt 20 is approximately 24 mm.

[0130] The pressure roller 21 includes a core metal 21a, an elastic layer 21b, and a surface layer 21c. The outer diameter of the pressure roller 21 is formed to be 24-30 mm, and the thickness of the elastic layer 21b is formed to be 3-4 mm.

[0131] The heater 22 includes a base material, a heat insulating layer, a conductor layer containing a resistance heating element, and an insulating layer, and is formed with an overall thickness of 1 mm. The width of the heater 22 in the direction of the array intersection is 13 mm.

[0132] As shown in Figure 38, the conductor layer of the heater 22 comprises a plurality of resistive heating elements 31, a power supply line 33, and electrode sections 34A to 34C. In this example as well, as shown in the enlarged view of Figure 38, a gap B is formed as a divided region in which the plurality of resistive heating elements 31 are divided in the direction of arrangement (arrow X direction) (although in Figure 38 only the gap B is shown in the enlarged view, in reality a gap B is provided between all of the resistive heating elements 31).

[0133] Furthermore, multiple resistance heating elements 31 constitute a central heating element 35B and heating elements 35A and 35C at both ends that can generate heat independently of it. For example, when current is applied to the leftmost electrode 34A and the central electrode 34B of the three electrode elements 58A to 58C in Figure 38, the heating elements 35A and 35C at both ends will generate heat. Also, when current is applied to the electrode elements 34A and 34C at both ends, the central heating element 35B will generate heat. For example, when performing a fixing operation on small-sized paper, only the central heating element 35B is heated, and when performing a fixing operation on large-sized paper, all heating elements 35A to 35C are heated, allowing for heating according to the size of the paper.

[0134] Furthermore, as shown in Figure 39, the heater holder 23 holds the heater 22 and the first high heat conductive member 28 in its recess 23d. The recess 23d is provided on the heater 22 side of the heater holder 23. The recess 23d consists of a surface 23d1 that is substantially parallel to the base material 30 and recessed on the stay 24 side compared to the other surfaces of the heater 22, a wall portion 23d2 extending in the alignment direction Y on both sides (or one side) of the alignment direction of the heater holder 23, and a wall portion 23d3 extending in the alignment direction (arrow X direction) on both sides of the alignment direction Y. The heater holder 23 is made of LCP (liquid crystal polymer).

[0135] As shown in Figure 40, the heater 22 and the stay 24 are held by the connector 60. The connector 60 comprises a housing made of resin (e.g., LCP) and a plurality of contact terminals provided within the housing.

[0136] The connector 60 is attached by sandwiching the heater 22 and the heater holder 23 together from the front and back sides. In this state, each contact terminal makes contact (pressure contact) with each electrode portion of the heater 22, thereby electrically connecting each resistive heating element 31 of the heater 22 to the power supply provided in the image forming apparatus via the connector 60. This makes it possible to supply power from the power supply to each resistive heating element 31.

[0137] Furthermore, the flanges 53 shown in Figure 40 are belt retaining members provided on both sides in the arrangement direction of the fixing belt 20, and hold both ends of the fixing belt 20 from the inside of the belt. The flanges 53 are inserted into both ends of the stay 24 (see the direction of the arrows from the flanges 53 in Figure 37) and fixed to the housing of the fixing device 9. The flanges 53 are made of LCP (liquid crystal polymer) or the like.

[0138] The mounting direction of the connector 60 to the heater 22 and heater holder 23 is the array intersection direction Y (see the direction of the arrow extending from the connector 60 side in Figure 40). When the connector 60 is mounted to the heater holder 23, a protrusion on one of the connector 60 and heater holder 23 may engage with a recess on the other, and the protrusion may move relative to the other within the recess. The connector 60 is mounted to the heater 22 and heater holder 23 on one side in the array direction, on the side opposite to the side where the drive motor for the pressure roller 21 is installed.

[0139] As shown in Figure 41, thermistors 25 are provided opposite the inner circumferential surface of the fixing belt 20, on the central side and the end side in the direction of arrangement of the fixing belt 20. The heater 22 is controlled based on the temperatures of the central side and the end side of the fixing belt 20 detected by the thermistors 25.

[0140] Thermostats 27 are provided on the center side and end side of the fixing belt 20, facing the inner circumferential surface of the fixing belt 20. If the temperature of the fixing belt 20 detected by the thermostats 27 exceeds a predetermined threshold, the power supply to the heater 22 is stopped.

[0141] As shown in Figure 42, the flange 53 is provided with a slide groove 53a. The slide groove 53a extends in the direction in which the fixing belt 20 moves toward and toward the pressure roller 21. The engaging portion of the housing of the fixing device 9 engages with the slide groove 53a. As this engaging portion moves relative to the slide groove 53a, the fixing belt 20 can move toward and toward the pressure roller 21.

[0142] In the fixing device 9 configured as described above (see Figure 37), the same effects and advantages as those of the embodiments of the present invention can be obtained by applying the configuration of the present invention. Furthermore, although Figure 37 shows a configuration to which the configuration of the embodiment shown in Figure 2 (first embodiment) is applied, the configurations of the other embodiments shown in Figures 6 to 13 can also be applied.

[0143] Furthermore, the present invention is also applicable to a fixing device 9, as shown in Figure 43, which includes a heat equalization plate 37 as a heat transfer assisting member between the heater 22 and the inner circumferential surface of the fixing belt 20. The heat equalization plate 37 is made of a material with a higher thermal conductivity than the heater holder 23 (for example, copper, aluminum, silver, etc.) and is a member that transfers heat from the heater 22 in the longitudinal direction of the fixing belt 20 to equalize the heat. However, since the heat equalization plate 37 is made of a conductive material, current may flow from the heater 22 to the pressure roller 21 and the separation plate 41 through the heat equalization plate 37. Therefore, even in such a fixing device 9, by applying the present invention, a certain level of insulation can be ensured between the separation plate 41 and the side plate 40, and between the pressure roller 21 and the side plate 40, and the number of parts can be reduced, making it possible to miniaturize and reduce costs.

[0144] Furthermore, the present invention is also applicable to a fixing device 16 equipped with a halogen heater 45 as a heating element, as shown in Figure 44.

[0145] The fixing device 16 shown in Figure 44 includes a fixing belt 17, a pressure roller 18, a halogen heater 45, a nip forming member 46, a stay 47, a reflector 48, a shielding member 49, a temperature sensor 26, a heat equalizing plate 55, and the like.

[0146] The halogen heater 45 is a heating element that heats the fixing belt 17 and is positioned inside the fixing belt 17 in a non-contact manner. In the example shown in Figure 44, two halogen heaters 45 are provided, but the number of halogen heaters 45 may be one or three or more.

[0147] As shown in Figure 45, each halogen heater 45 is a filament lamp having a glass tube 71 made of quartz glass or the like, and a filament 72 housed inside the glass tube 71. The filament 72 has a straight section 72a and a tightly wound section 72b that is tightly wound in a coil shape, and this tightly wound section 72b is a resistive heating element (heating part or light-emitting part) that generates heat when power is supplied.

[0148] The nip-forming member 46 shown in Figure 44 is positioned on the opposite side of the pressure roller 18, across the fixing belt 17, and is a member that cooperates with the pressure roller 18 to form the nip portion N. When the pressure roller 18 pressurizes the nip-forming member 46 via the fixing belt 17, the nip portion N is formed at the point where the pressure roller 18 and the fixing belt 17 come into contact. The configuration of the pressure roller 18 and the fixing belt 17 is basically the same as that of the pressure roller 21 and fixing belt 20 in the embodiment shown in Figure 2 and other figures.

[0149] The stay 47 is a support member that supports the nip-forming member 46. By supporting the nip-forming member 46 with the stay 47, the deflection of the nip-forming member 46 due to the pressure of the pressure roller 18 is suppressed, and a nip portion N of uniform width is formed.

[0150] The reflective member 48 is a member that reflects the radiant heat emitted from each halogen heater 45 to the inner surface of the fixing belt 17. The reflective member 48 is fixed to the stay 47 so as to face each halogen heater 45. The reflective member 48 reflects the radiant heat from each halogen heater 45 to the fixing belt 17, thereby efficiently heating the fixing belt 17. In addition, because the reflective member 48 is interposed between each halogen heater 45 and the stay 47, the transfer of radiant heat from each halogen heater 45 to the stay 47 is suppressed, thus contributing to energy saving.

[0151] The shielding member 49 is movably provided on the inside of the fixing belt 17 and is a member that shields the radiant heat from each halogen heater 45 to the fixing belt 17. When the shielding member 49 is moved and positioned between each halogen heater 45 and the fixing belt 17, the radiant heat from each halogen heater 45 to the fixing belt 17 is shielded by the shielding member 49, and excessive heating of the fixing belt 17 can be suppressed. Also, when the shielding member 49 is positioned away from between each halogen heater 45 and the fixing belt 17 (the position shown in Figure 44), the heating of the fixing belt 17 by each halogen heater 45 is performed effectively.

[0152] The heat equalization plate 55 is a heat transfer assisting member made of a material with high thermal conductivity, similar to the heat equalization plate 37 shown in Figure 43 above. The heat equalization plate 55 is interposed between the nip forming member 46 and the fixing belt 17, and aims to equalize the heat by transferring the heat from the fixing belt 17 in the longitudinal direction.

[0153] The temperature sensor 26 is positioned opposite the outer circumferential surface of the fixing belt 17 and is a temperature sensing member that detects the temperature of the fixing belt 17 in a non-contact manner.

[0154] As shown in Figure 44, in this example as well, the static elimination brush 43 is brought into contact with both the separation plate 41 and the pressure roller 18, and the static elimination brush 43 is electrically connected to the side plate 40 via the resistor 39. This ensures a certain level of insulation between the separation plate 41 and the side plate 40, and between the pressure roller 18 and the side plate 40, while grounding the separation plate 41 and the pressure roller 18. This allows the current from the separation plate 41 and the pressure roller 18 to flow appropriately to the side plate 40 via the resistor 39, preventing charge buildup on the separation plate 41 and the pressure roller 18, while suppressing the current flowing from the separation plate 41 and the pressure roller 18 to the side plate 40. Furthermore, since the separation plate 41 and the pressure roller 18 are grounded via the same resistor 39, the number of components can be reduced, leading to miniaturization and cost reduction. Note that while Figure 44 applies the configuration of the embodiment shown in Figure 2 (first embodiment), the configurations of other embodiments shown in Figures 6 to 13 are also applicable.

[0155] Furthermore, the present invention is also applicable to a fixing device 80 as shown in Figure 46.

[0156] The fixing device 80 shown in Figure 46 includes a fixing belt 81, a pressure roller 82, a halogen heater 83, a nip forming member 84, a stay 85, a reflector member 86, a guide member 87, a temperature sensor 88, and the like.

[0157] Here, the fixing belt 81, pressure roller 82, halogen heater 83, nip forming member 84, stay 85, reflective member 86, and temperature sensor 88 have basically the same functions as the fixing belt 17, pressure roller 18, halogen heater 45, nip forming member 46, reflective member 48, and temperature sensor 26 shown in Figure 44.

[0158] However, the reflective member 86 shown in Figure 46 reflects the radiant heat emitted from the halogen heater 83 not to the fixing belt 81, but mainly to the nip-forming member 84. The reflective member 86 is formed in a U-shape in cross-section so as to cover the outside of the halogen heater 83, and the surface of the reflective member 86 facing the halogen heater 83 (inner surface) is a highly reflective surface. Therefore, when radiant heat is emitted from the halogen heater 83, the radiant heat is reflected to the nip-forming member 84 by the reflective surface of the reflective member 86. As a result, the nip-forming member 84 is heated by the radiant heat emitted from the halogen heater 83 toward the nip-forming member 84 and the radiant heat reflected to the nip-forming member 84 by the reflective member 86. Then, the heat of the nip-forming member 84 is transferred to the fixing belt 81 at the nip portion N. In other words, in this case, the nip-forming member 84 not only forms the nip portion N, but also functions as a heat transfer member that transfers heat to the fixing belt 81 at the nip portion N. Therefore, the nip-forming member 84 is made of a metal material such as copper or aluminum, which has good thermal conductivity.

[0159] The guide member 87 is positioned inside the anchoring belt 81 and guides the rotating anchoring belt 81 from the inside. By being guided by the guide member 87, the anchoring belt 81 rotates smoothly without significant deformation.

[0160] Even in such a fixing device 80, by applying the present invention, a grounding structure can be configured while ensuring a certain level of insulation, and moreover, the number of parts can be reduced, resulting in miniaturization and cost reduction. Specifically, as shown in the example in Figure 46, by making the static elimination brush 43 contact both the separation plate 41 and the pressure roller 82, and electrically connecting the static elimination brush 43 to the side plate 40 via the resistor 39, the separation plate 41 and the pressure roller 82 can be grounded while ensuring a certain level of insulation between the separation plate 41 and the side plate 40, and between the pressure roller 82 and the side plate 40. As a result, the current from the separation plate 41 and the pressure roller 82 can be appropriately directed to the side plate 40 via the resistor 39, preventing charge buildup on the separation plate 41 and the pressure roller 82, while suppressing the current flowing from the separation plate 41 and the pressure roller 82 to the side plate 40. Furthermore, since the separation plate 41 and the pressure roller 82 are grounded via the same resistor 39, the number of parts can be reduced, resulting in miniaturization and cost reduction. In Figure 46, the configuration of the embodiment shown in Figure 2 (the first embodiment) is applied, but the configurations of the other embodiments shown in Figures 6 to 13 are also applicable.

[0161] To summarize the embodiments of the present invention described above, the present invention includes a heating device, a fixing device, and an image forming apparatus having at least the following configurations.

[0162] [First Structure] The first configuration is a fixing device comprising: a first rotating body; a second rotating body that contacts the outer circumferential surface of the first rotating body and forms a nip portion through which a recording medium carrying an unfixed image passes; a heating body having a resistance heating element that heats the first rotating body; and a separating member that contacts the outer circumferential surface of the first rotating body and separates the recording medium passing through the nip portion from the first rotating body, wherein the second rotating body and the separating member are grounded via the same resistor.

[0163] [Second Structure] The second configuration is a fixing device that, in the first configuration, includes an anti-static member that is electrically connected to the resistor and makes direct contact with both the separating member and the second rotating body.

[0164] [The third structure] The third configuration is a fixing device comprising, in the first configuration, an antistatic member electrically connected to the resistor and in direct contact with either the separating member or the second rotating body, and a conductive member in direct contact with the separating member and the second rotating body.

[0165] [Fourth component] The fourth configuration is a fixing device comprising, in the first configuration, an anti-static member electrically connected to the resistor, and a conductive member that directly contacts the separating member, the second rotating body, and the anti-static member.

[0166] [Fifth Structure] The fifth configuration is a fixing device comprising, in the first configuration, an antistatic member electrically connected to the resistor and in direct contact with the second rotating body, and a conductive member in direct contact with the antistatic member and the separating member.

[0167] [The sixth component] The sixth configuration is a fixing device in which, in any one of the first to fifth configurations, the second rotating body and the separating member are electrically connected to a grounded housing via the resistor, and a creepage distance of 2.5 mm or more is provided between the second rotating body and the housing, and between the separating member and the housing.

[0168] [The seventh component] The seventh configuration is one of the first to sixth configurations, wherein the first rotating body is an endless belt member rotatably held by a resin belt holding member, and the separating member is a fixing device attached to the belt holding member.

[0169] [The eighth component] The eighth configuration is a fixing device in any one of the second to fifth configurations, wherein the static elimination member is positioned between the second rotating body and the separating member.

[0170] [The ninth structure] The ninth configuration is a fixing device in which, in any one of the second to fifth and eighth configurations, the static elimination member is positioned downstream of the nip portion in the transport direction of the recording medium.

[0171] [The 10th component] The tenth configuration is a fixing device in which, in any one of the first to ninth configurations, the heating element has an insulating layer between the resistance heating element and the first rotating body.

[0172] [Structure of the 11th] The eleventh configuration is a fixing device in which, in any one of the third to fifth configurations, the volume resistance of the conductive member is 110 kΩ or more.

[0173] [Structure 12] The twelfth configuration is a fixing device in which the conductive member is made of a conductive resin, in any one of the third to fifth and eleventh configurations.

[0174] [Structure 13] The thirteenth configuration is a fixing device in which, in any one of the first to twelfth configurations, the separating member contacts the first rotating body in a region outside the maximum recording medium passage region through which the maximum width of the recording medium passes.

[0175] [Structure 14] The fourteenth configuration is a fixing device in which the heating element is in contact with the first rotating body either directly or via a conductive member, in any one of the first to thirteen configurations.

[0176] [Structure of the 15th] The 15th configuration is an image forming apparatus comprising a fixing device of any one of the first to 14 configurations described above. [Explanation of Symbols]

[0177] 9. Fixing device 19 Belt holding member 20 Fixing belt (first rotating body) 21. Pressure roller (second rotating body) 22 Heater (heating element) 31 Resistive heating element 32 Insulating layer 37. Heat distribution plate (conductive material) 38 Conductive material 39 Resistors 40 Side panels (enclosure) 41 Separation plate (separation member) 43 Static elimination brush (static elimination component) 100 Image forming apparatus N Nip section P Paper (recording medium) [Prior art documents] [Patent Documents]

[0178] [Patent Document 1] Japanese Patent Publication No. 2002-162857

Claims

1. The first solid of revolution and, A second rotating body that contacts the outer circumferential surface of the first rotating body and forms a nip portion through which a recording medium carrying an unfixed image passes; A heating element having a resistance heating element, which heats the first rotating body, A separating member that contacts the outer circumferential surface of the first rotating body and separates the recording medium passing through the nip portion from the first rotating body, A fixing device comprising, A fixing device characterized in that the second rotating body and the separating member are grounded via the same resistor.

2. The fixing device according to claim 1, further comprising an antistatic member electrically connected to the resistor and in direct contact with both the separating member and the second rotating body.

3. A static elimination member is electrically connected to the resistor and directly contacts either the separating member or the second rotating body. The separating member and the conductive member that is in direct contact with the second rotating body, The fixing device according to claim 1, comprising:

4. A static elimination member electrically connected to the resistor, The separating member, the second rotating body, and the conductive member that directly contacts the static elimination member, The fixing device according to claim 1, comprising:

5. A static elimination member is electrically connected to the resistor and in direct contact with the second rotating body, The static elimination member and the conductive member that is in direct contact with the separation member, The fixing device according to claim 1, comprising:

6. The second rotating body and the separating member are electrically connected to the grounded housing via the resistor. The fixing device according to any one of claims 1 to 5, wherein a creepage distance of 2.5 mm or more is provided between the second rotating body and the housing, and between the separating member and the housing.

7. The first rotating body is an endless belt member that is rotatably held by a resin belt holding member. The fixing device according to any one of claims 1 to 5, wherein the separating member is attached to the belt holding member.

8. The fixing device according to any one of claims 2 to 5, wherein the static elimination member is disposed between the second rotating body and the separating member.

9. The fixing device according to any one of claims 2 to 5, wherein the static elimination member is arranged downstream of the nip portion in the transport direction of the recording medium.

10. The fixing device according to any one of claims 1 to 5, wherein the heating element has an insulating layer between the resistance heating element and the first rotating body.

11. The fixing device according to any one of claims 3 to 5, wherein the volume resistance of the conductive member is 110 kΩ or more.

12. The fixing device according to any one of claims 3 to 5, wherein the conductive member is made of a conductive resin.

13. The fixing device according to any one of claims 1 to 5, wherein the separating member contacts the first rotating body in a region outside the maximum recording medium passage region through which the maximum width of the recording medium passes.

14. The fixing device according to any one of claims 1 to 5, wherein the heating element is in contact with the first rotating body either directly or via a conductive member.

15. An image forming apparatus characterized by comprising a fixing device according to any one of claims 1 to 5.

Images