Rotating body driving device, heating device, fixing device and image forming apparatus

Abstract

To suppress a lubricant from penetrating between an edge face of a rotor and an edge face contact member that comes in contact with the edge face.SOLUTION: A rotor drive device comprises: an edge face contact member 29A that comes in contact with an edge face 21a of a rotor 21; a first helical gear 41 which is provided on the side of the edge face contact member 29A that is opposite the rotor edge face side; and a second helical gear 42 that engages with the first helical gear 41. The teeth of the first helical gear 41 are arranged in such a direction as to generate a force Fx in a direction in which the edge face contact member 29A is brought closer to the edge face 21a of the rotor 21 when the first helical gear 41 rotates. The outer diameter D1 of the first helical gear 41 is smaller than or equal to the outer diameter D2 of a belt 21.SELECTED DRAWING: Figure 8

Description

[Technical Field]

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

[0002] 2. Description of the Related Art As an example of a rotating body driving device mounted in an image forming apparatus such as a copying machine or a printer, a fixing device having an endless belt is known.

[0003] In such a belt-type fixing device, if the belt stops rotating during heating, the same part of the belt continues to be heated, which causes a problem of the temperature of the belt rising abnormally.

[0004] For this reason, Patent Document 1 (JP 2019-148618 A) below proposes a configuration in which an end surface contact member (cap member) is provided that contacts the end surface of the belt and the rotation of the end surface contact member that rotates together with the belt is detected. In other words, by detecting the rotation of the end surface contact member that rotates together with the belt, it is possible to determine whether the belt is rotating normally. Furthermore, Patent Document 1 also interposes an elastic member with a high friction coefficient between the belt and the end surface contact member so that the end surface contact member (cap member) rotates without slipping relative to the belt.

[0005] In a belt-type fixing device, when the belt rotates, it slides against a sliding member, such as a nip forming member, that contacts the inner circumferential surface of the belt. To reduce the sliding resistance associated with the belt rotation, a lubricant, such as grease or oil, is typically interposed between the belt and the sliding member. However, if the lubricant migrates to the end of the belt due to the belt's rotation and penetrates between the belt and the end contact member, there is a risk that the lubricant will adhere to the elastic member. If the lubricant adheres to the elastic member, the friction between the elastic member and the belt or between the elastic member and the end contact member will decrease, causing the elastic member to slip and preventing the belt and the end contact member from rotating together. For this reason, Patent Document 1 provides a groove in the end contact member to retain the lubricant. Summary of the Invention [Problem to be solved by the invention]

[0006] As described above, by providing grooves in the end surface contact member, lubricant leaking from the inner peripheral surface of the belt can be stored in the grooves. However, if the lubricant leaks from the grooves due to the rotation or vibration of the belt, the leaked lubricant may enter between the belt and the end surface contact member, causing slippage and preventing the belt and the end surface contact member from rotating together. Furthermore, Patent Document 1 does not disclose any measures to solve the problem of lubricant leaking from the inside to the outside of the belt. [Means for solving the problem]

[0007] In order to solve the above-mentioned problems, the rotating body drive device of the present invention includes a rotatable endless rotating body, a sliding member in contact with an inner peripheral surface of the rotating body, a lubricant interposed between the sliding member and the inner peripheral surface of the rotating body, an end face contact member in contact with an end face of the rotating body, a first helical gear provided on the side opposite to the end face side of the rotating body of the end face contact member, and a second helical gear meshing with the first helical gear, wherein the teeth of the first helical gear are oriented so as to generate a force in a direction that moves the end face contact member closer to the end face of the rotating body when the first helical gear rotates, and the outer diameter of the first helical gear is equal to or smaller than the outer diameter of the rotating body. [Effects of the Invention]

[0008] According to the present invention, it is possible to prevent the lubricant from entering between the end face of the rotating body and the end face contact member. [Brief explanation of the drawings]

[0009] [Figure 1] 1 is a schematic diagram illustrating the configuration of an image forming apparatus according to an embodiment of the present invention. [Figure 2] FIG. 2 is a schematic diagram illustrating the configuration of a fixing device according to the present embodiment. [Figure 3] FIG. 2 is a cross-sectional view of the fixing belt according to the embodiment. [Figure 4] 2A and 2B are diagrams illustrating the configuration of a support structure and a drive mechanism for a pressure roller and a fixing belt according to the embodiment. [Figure 5] FIG. 2 is a cross-sectional view of the fixing device according to the embodiment. [Figure 6] 3A and 3B are diagrams illustrating the end and end surface of a fixing belt. [Figure 7] 2A and 2B are diagrams illustrating the configuration and operation of a fixing device according to the present embodiment. [Figure 8] 6 is a diagram illustrating the relationship between the outer diameter of the first gear and the inner diameter of the fixing belt. [Figure 9] FIG. 10 is a diagram showing a configuration according to a comparative example. [Figure 10] FIG. 4 is a diagram showing the inclination angles of the teeth of the first gear and the second gear. [Figure 11] 10 is a diagram showing an example in which a positioning portion for positioning a fixing device relative to a main body of an image forming apparatus is provided. FIG. [Figure 12] 10A and 10B are diagrams illustrating an example in which the fixing belt and the pressure roller are rotated in opposite directions. [Figure 13] 10A and 10B are diagrams illustrating another example in which the fixing belt and the pressure roller are rotated in opposite directions. [Figure 14] FIG. 10 is a diagram illustrating a state in which the pressure of the pressure roller is released. [Figure 15] 10A and 10B are diagrams for explaining the adverse effects that occur when the fixing belt and the pressure roller are rotated in opposite directions. [Figure 16] FIG. 10 is a diagram showing an example in which a one-way clutch is provided on a first gear. [Figure 17] 10A and 10B are diagrams for explaining the operation of the one-way clutch during reverse rotation. [Figure 18] FIG. 10 is a diagram showing an example in which a one-way clutch is provided on a driving force transmission gear. [Figure 19] 10A and 10B are diagrams for explaining the operation of the one-way clutch during reverse rotation. [Figure 20] FIG. 10 is a diagram showing a configuration of a fixing device different from that of the above embodiment. [Figure 21] FIG. 21 is a plan view of the heater shown in FIG. 20. [Figure 22] FIG. 10 is a diagram showing a configuration of a fixing device different from that of the above embodiment. [Figure 23] FIG. 10 is a diagram showing a configuration of a fixing device different from that of the above embodiment. [Figure 24] FIG. 10 is a diagram showing a configuration of a fixing device different from that of the above embodiment. [Figure 25] FIG. 10 is a diagram showing a configuration of a fixing device different from that of the above embodiment. [Figure 26] FIG. 10 is a diagram showing a configuration of an image forming apparatus different from that of the above embodiment. [Figure 27] FIG. 27 is a diagram showing the configuration of the fixing device shown in FIG. 26. [Figure 28] FIG. 28 is a plan view of the heater shown in FIG. 27. [Figure 29]FIG. 28 is a perspective view of the heater and heater holder shown in FIG. 27. [Figure 30] 28 is a diagram showing a method of attaching a connector to the heater shown in FIG. 27. [Figure 31] 27 is a diagram showing the arrangement of temperature sensors and thermostats included in the fixing device shown in FIG. 26. FIG. [Figure 32] 31 is a view showing a groove portion of the flange shown in FIG. 30. FIG. [Figure 33] 10A and 10B are diagrams illustrating an example in which an elastic member between a cap member and an end of a fixing belt is omitted. [Figure 34] FIG. 10 is a diagram showing a configuration of a fixing device different from that of the above embodiment. [Figure 35] FIG. 35 is a perspective view of the heater, the first high thermal conductive member, and the heater holder shown in FIG. 34. [Figure 36] FIG. 2 is a plan view of the heater showing the arrangement of the first high thermal conductivity members. [Figure 37] 10 is a plan view of a heater showing another example of the arrangement of the first high thermal conductivity members. FIG. [Figure 38] FIG. 10 is a plan view of a heater showing yet another example of the arrangement of the first high thermal conductivity members. [Figure 39] FIG. 2 is a plan view of the heater showing enlarged divided regions. [Figure 40] FIG. 10 is a diagram showing a configuration of a fixing device different from that of the above embodiment. [Figure 41] 41 is a perspective view of the heater, the first highly thermally conductive member, the second highly thermally conductive member, and the heater holder shown in FIG. 40. FIG. [Figure 42] FIG. 3 is a plan view of the heater showing the arrangement of the first and second high thermal conductive members. [Figure 43] 10 is a plan view of a heater showing another example of the arrangement of the first and second high thermal conductive members. FIG. [Figure 44] FIG. 10 is a plan view of a heater showing yet another example of the arrangement of second high-thermal-conductivity members. [Figure 45] FIG. 10 is a diagram showing a configuration of a fixing device different from that of the above embodiment. [Figure 46] FIG. 1 illustrates the atomic crystal structure of graphene. [Figure 47] FIG. 1 illustrates the atomic crystal structure of graphite. DETAILED DESCRIPTION OF THE INVENTION

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

[0011] FIG. 1 is a schematic diagram of an image forming apparatus according to one embodiment of the present invention. In this specification, the term "image forming apparatus" includes a printer, a copier, a facsimile, a printing machine, or a multifunction machine that combines two or more of these. Furthermore, the term "image formation" used in the following description refers not only to the formation of meaningful images such as characters and figures, but also to the formation of meaningless images such as patterns. First, the overall configuration and operation of the image forming apparatus according to this embodiment will be described with reference to FIG. 1.

[0012] As shown in FIG. 1, the image forming apparatus 100 according to this embodiment includes an image forming unit 200 that forms an image on a sheet-like recording medium such as paper, a fixing unit 300 that fixes the image on the recording medium, a recording medium supply unit 400 that supplies the recording medium to the image forming unit 200, and a recording medium discharge unit 500 that discharges the recording medium outside the apparatus.

[0013] The image forming section 200 is provided with four process units 1Y, 1M, 1C, and 1Bk as image-forming units, an exposure device 6 that forms an electrostatic latent image on the photosensitive member 2 provided in each of the process units 1Y, 1M, 1C, and 1Bk, and a transfer device 8 that transfers the image onto a recording medium.

[0014] Each of the process units 1Y, 1M, 1C, and 1Bk has basically the same configuration, except that it contains toner (developer) of a different color: yellow, magenta, cyan, or black, which corresponds to the color separation components of a color image. Specifically, each of the process units 1Y, 1M, 1C, and 1Bk includes a photoconductor 2 as an image carrier that carries an image on its surface, a charging member 3 that charges the surface of the photoconductor 2, a developing device 4 that supplies toner as developer to the surface of the photoconductor 2 to form a toner image, and a cleaning member 5 that cleans the surface of the photoconductor 2.

[0015] The transfer device 8 includes an intermediate transfer belt 11, a primary transfer roller 12, and a secondary transfer roller 13. The intermediate transfer belt 11 is an endless belt member that is stretched by a plurality of support rollers. Four primary transfer rollers 12 are provided inside the intermediate transfer belt 11. Each primary transfer roller 12 contacts each photoconductor 2 via the intermediate transfer belt 11, thereby forming a primary transfer nip between the intermediate transfer belt 11 and each photoconductor 2. The secondary transfer roller 13 contacts the outer peripheral surface of the intermediate transfer belt 11, thereby forming a secondary transfer nip.

[0016] The fixing section 300 is provided with a fixing device 20. The fixing device 20 includes a fixing belt 21 made of an endless belt, and a pressure roller 22 as a counter rotating body facing the fixing belt 21. The fixing belt 21 and the pressure roller 22 come into contact with each other at their outer circumferential surfaces to form a nip portion (fixing nip).

[0017] The recording medium supply unit 400 is provided with a paper feed cassette 14 that stores paper P as a recording medium, and a paper feed roller 15 that feeds paper P from the paper feed cassette 14. Hereinafter, the "recording medium" will be described as "paper," but the "recording medium" is not limited to paper (paper). The "recording medium" includes not only paper (paper), but also transparencies, fabrics, metal sheets, plastic films, and prepreg sheets made of carbon fiber pre-impregnated with resin. Furthermore, "paper" includes not only plain paper, but also cardboard, postcards, envelopes, thin paper, coated paper (coated paper, art paper, etc.), tracing paper, and the like.

[0018] The recording medium discharge section 500 is provided with a pair of discharge rollers 17 that discharge the paper P outside the image forming apparatus, and a paper discharge tray 18 on which the paper P discharged by the discharge rollers 17 is placed.

[0019] Next, the printing operation of the image forming apparatus 100 according to this embodiment will be described with reference to FIG.

[0020] When a printing operation is started in the image forming apparatus 100, the photosensitive elements 2 of the process units 1Y, 1M, 1C, and 1Bk and the intermediate transfer belt 11 of the transfer device 8 start to rotate. Also, the paper feed roller 15 starts to rotate, and a sheet of paper P is fed out of the paper feed cassette 14. The fed sheet of paper P comes into contact with a pair of timing rollers 16 and stops, and the transport of the sheet of paper P is temporarily stopped until an image to be transferred onto the sheet of paper P is formed.

[0021] In each process unit 1Y, 1M, 1C, and 1Bk, the surface of the photoconductor 2 is first charged to a uniform high potential by the charging member 3. Next, the exposure device 6 exposes the surface (charged surface) of each photoconductor 2 based on the image information of the original document read by the document reader or the print image information instructed to be printed from a terminal. This reduces the potential of the exposed area, forming an electrostatic latent image on the surface of each photoconductor 2. The developing device 4 then supplies toner to this electrostatic latent image, forming a toner image on each photoconductor 2. As each photoconductor 2 rotates, the toner image formed on each photoconductor 2 reaches the primary transfer nip (the position of the primary transfer roller 12), where it is transferred sequentially onto the rotating intermediate transfer belt 11 so as to overlap one another. In this way, a full-color toner image is formed on the intermediate transfer belt 11. In the image forming apparatus 100, it is possible to form a monochrome image using any one of the process units 1Y, 1M, 1C, and 1Bk, or to form a two-color or three-color image using any two or three of the process units. After the toner image is transferred from the photoreceptor 2 to the intermediate transfer belt 11, the cleaning member 5 removes residual toner and the like from each photoreceptor 2.

[0022] The toner image transferred onto intermediate transfer belt 11 is transported to the secondary transfer nip (position of secondary transfer roller 13) as intermediate transfer belt 11 rotates, and is transferred onto the transported paper P by timing roller 16. Thereafter, paper P is transported to fixing device 20, where the toner image on paper P is heated and pressed by fixing belt 21 and pressure roller 22, thereby fixing the toner image to paper P. Paper P is then transported to recording medium discharge section 500, and is discharged onto paper discharge tray 18 by paper discharge roller 17. This completes the series of printing operations.

[0023] Next, the configuration of the fixing device according to this embodiment will be described in detail with reference to FIG.

[0024] As shown in FIG. 2, the fixing device 20 according to this embodiment includes, in addition to a fixing belt 21 and a pressure roller 22, an electromagnetic induction heating section 23, a nip forming member 24, a stay 25, a guide member 26, a temperature sensor 27, and the like.

[0025] The fixing belt 21 is a rotating body (fixing member) that comes into contact with the unfixed toner carrying surface of the paper P to fix the unfixed toner (unfixed image) to the paper P, and is made of a flexible endless belt. The diameter of the fixing belt 21 is set to, for example, 15 to 120 mm. In this embodiment, the inner diameter of the fixing belt 21 is set to 25 mm.

[0026] Specifically, the fixing belt 21 is formed by sequentially laminating a base material layer, an elastic layer, and a release layer from the inner circumferential surface side, with a total thickness of 1 mm or less. The base material layer is 30 to 50 μm thick and is made of a metal material such as nickel or stainless steel, or a resin material such as polyimide. The elastic layer is 100 to 300 μm thick and is made of a rubber material such as silicone rubber, foamed silicone rubber, or fluororubber. The fixing belt 21 has an elastic layer, which prevents minute irregularities from forming on the surface of the fixing belt 21 at the nip portion, facilitating uniform heat transfer to the toner image on the paper P. The release layer is 10 to 50 μm thick and is made of a material such as PFA (tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer), PTFE (polytetrafluoroethylene), polyimide, polyetherimide, or PES (polyether sulfide). The fixing belt 21 has a release layer, which ensures releasability (separability) from the toner (toner image).

[0027] In addition to the base layer, elastic layer, and release layer, fixing belt 21 also has a heat-generating layer that is electromagnetically induction heated by electromagnetic induction heating unit 23. Specifically, as shown in Fig. 3, fixing belt 21 has, in order from its inner circumferential surface side to its outer circumferential surface side, base layer 210, heat-generating layer 211, elastic layer 212, and release layer 213. Heat-generating layer 211 may be provided between elastic layer 212 and release layer 213, or base layer 210 may be used as the heat-generating layer. Examples of materials that can be used for heat-generating layer 211 include nickel, stainless steel, iron, copper, cobalt, chromium, aluminum, gold, platinum, silver, tin, palladium, and alloys of two or more of these metals.

[0028] The pressure roller 22 is a counter rotating body disposed opposite the fixing belt 21. The pressure roller 22 is a roller set to have an outer diameter of 25 mm, for example, and contacts the outer peripheral surface of the fixing belt 21 to form a nip portion N.

[0029] Specifically, pressure roller 22 has a solid iron core 220, an elastic layer 221 provided on the outer peripheral surface of core 220, and a release layer 222 provided on the outer peripheral surface of elastic layer 221. Elastic layer 221 has a thickness of, for example, 3.5 mm and is made of silicone rubber or the like. Release layer 222 has a thickness of, for example, about 40 μm and is made of fluororesin or the like.

[0030] The electromagnetic induction heating unit 23 is a heat source having an excitation coil 31, a core 32, and a coil guide 33. The excitation coil 31 is a Litz wire, which is a bundle of thin wires, extending in the longitudinal direction of the fixing belt 21 so as to cover a portion of the fixing belt 21. Note that the "longitudinal direction of the fixing belt" here refers to the direction perpendicular to the plane of the paper in FIG. 2, and is the same direction as the width direction of the paper passing through the nip portion (the direction perpendicular to the paper feed direction) or the direction of the rotation axis of the pressure roller. The "longitudinal direction of the fixing belt" in the following description also refers to the same direction. The coil guide 33 is made of a highly heat-resistant resin material and supports the excitation coil 31 and the core 32. The core 32 is a semi-cylindrical member made of a ferromagnetic material such as ferrite (with a relative permeability of approximately 1000 to 3000). The core 32 has a center core and a side core to generate an efficient magnetic flux toward the fixing belt 21. The core 32 is also positioned to face the excitation coil 31.

[0031] Nip forming member 24 is a member that contacts the inner circumferential surface of fixing belt 21 and forms nip portion N by being pressed against pressure roller 22 via fixing belt 21. Nip forming member 24 is made of a heat-resistant material that has high mechanical strength and can withstand temperatures of 200°C or higher. Heat-resistant resins such as polyimide and PEEK (polyether ether ketone) are preferred as materials for nip forming member 24. Alternatively, nip forming member 24 may be made of a metal material. By using such a material with excellent strength and heat resistance, deformation of nip forming member 24 due to heat can be prevented in the toner fixing temperature range, ensuring a stable state of nip portion N and stabilizing output image quality.

[0032] A sliding sheet 28 is provided on the surface of nip forming member 24 on the nip portion N side. Sliding sheet 28 is formed, for example, by impregnating a material made of PTFE thread with a lubricant such as silicone oil. Since nip forming member 24 contacts the inner circumferential surface of fixing belt 21 via such sliding sheet 28, sliding resistance when fixing belt 21 rotates is reduced, and wear of fixing belt 21 can be suppressed. Note that sliding sheet 28 may be omitted, and nip forming member 24 may directly contact the inner circumferential surface of fixing belt 21.

[0033] Stay 25 is a support member that supports nip forming member 24. Stay 25 supports the surface of nip forming member 24 opposite the surface on the nip portion N side across the longitudinal direction of fixing belt 21, thereby preventing nip forming member 24 from being deflected by the pressure of pressure roller 22, and forming nip portion N of uniform width between fixing belt 21 and pressure roller 22. Furthermore, stay 25 is preferably made of an iron-based metal material such as SUS or SECC to ensure its rigidity.

[0034] The guide member 26 is a member that guides the fixing belt 21 from the inside to ensure stable rotation of the fixing belt 21. The guide member 26 has an arc-shaped cross section that follows the inner circumferential surface of the fixing belt 21, and is fixed to the stay 25.

[0035] Temperature sensor 27 is a temperature detection member that detects the temperature of fixing belt 21. In this embodiment, a non-contact temperature sensor is used as the temperature detection member, which is arranged in a non-contact manner with respect to the outer peripheral surface of fixing belt 21 and detects the ambient temperature near the outer peripheral surface of fixing belt 21. Alternatively, the temperature detection member may be a contact temperature sensor that comes into contact with the surface of fixing belt 21 and detects the surface temperature.

[0036] The fixing device 20 configured in this manner operates as follows.

[0037] 2, the fixing belt 21 is heated at a position facing the electromagnetic induction heating unit 23. More specifically, when a high-frequency alternating current flows through the excitation coil 31, magnetic lines of force are formed around the fixing belt 21 so that they alternate in both directions. At this time, eddy currents are generated on the surface of the heat-generating layer of the fixing belt 21, and Joule heat is generated due to the electrical resistance of the heat-generating layer itself. This Joule heat electromagnetically heats the heat-generating layer, and the fixing belt 21 is heated.

[0038] Furthermore, the temperature of fixing belt 21 is detected by temperature sensor 27, and electromagnetic induction heating unit 23 is controlled based on the detected temperature, thereby maintaining the temperature of fixing belt 21 at a predetermined temperature (fixing temperature). In this state, as shown in Fig. 2, when paper P carrying unfixed toner (unfixed image) enters between fixing belt 21 and pressure roller 22 (nip portion N), paper P is transported by rotating fixing belt 21 and pressure roller 22. Then, as paper P passes through nip portion N, the unfixed toner on paper P is pressurized and heated, and the toner image is fixed to paper P.

[0039] Next, the configuration of the support structure and drive mechanism for the pressure roller and fixing belt according to this embodiment will be described with reference to FIGS.

[0040] 4, the fixing belt 21 and the pressure roller 22 are rotatably supported by a pair of side plates 30A and 30B, which are frame members of the fixing device 20. Specifically, the pressure roller 22 is supported by having both ends 22a and 22b of its rotation shaft (core metal 220) rotatably attached to the side plates 30A and 30B. Meanwhile, the fixing belt 21 is rotatably held by stays 25 attached to the side plates 30A and 30B, and by a guide member 26 and a nip forming member 24 supported by the stays 25.

[0041] As shown in FIG. 4, a driving force transmission gear 40 is provided on one end 22a (the left end in FIG. 4) of the rotation shaft (core metal 220) of the pressure roller 22, to which a rotational driving force is transmitted from a driving source of the image forming apparatus main body. When the fixing device 20 is mounted in the image forming apparatus main body, the driving force transmission gear 40 is coupled to a driving gear provided in the image forming apparatus main body, and is in a state in which a driving force can be transmitted. In this state, the pressure roller 22 is rotationally driven by the rotational driving force transmitted from the driving source of the image forming apparatus main body to the driving force transmission gear 40. When the pressure roller 22 is rotationally driven, the fixing belt 21 is rotated in accordance with the rotational driving of the pressure roller 22.

[0042] A pair of cap members 29A, 29B are provided on both end faces 21a, 21b of the fixing belt 21 in the longitudinal direction (the direction of the arrow X in FIG. 4) as end face contact members that contact the respective end faces 21a, 21b. As shown in FIG. 5, each of the cap members 29A, 29B has a cylindrical peripheral wall portion 291 and an end wall portion 292 provided at one end of the peripheral wall portion 291 in the axial direction. The end wall portion 292 of each of the cap members 29A, 29B is provided with a hole 293 for inserting the stay 25. When each of the cap members 29A, 29B is attached to both end faces of the fixing belt 21, the inner peripheral surface of each peripheral wall portion 291 is disposed to face the outer peripheral surfaces of both end faces of the fixing belt 21, and the end wall portions 292 are disposed to contact both end faces 21a, 21b of the fixing belt 21 in the longitudinal direction X (hereinafter simply referred to as "both end faces of the fixing belt"). The "ends" of the fixing belt 21 referred to here refer to regions E on both ends of a central region including the center C in the longitudinal direction X of the fixing belt 21 shown in Fig. 6. The "central region including the center C" refers to a region that is equal to or larger than one of three equal parts when the fixing belt 21 is divided into three equal parts in the longitudinal direction X, but is smaller than the entire length in the longitudinal direction. The "end faces" of the fixing belt 21 refer to surfaces 21a and 21b that are the extreme edges of the fixing belt 21 in the longitudinal direction X and intersect with the longitudinal direction X.

[0043] 5, elastic members 36A and 36B are disposed between the inner circumferential surface of each peripheral wall portion 291 and the outer circumferential surface of both ends of the fixing belt 21. Each elastic member 36A and 36B is an annular member made of a material with a high coefficient of friction, such as silicone rubber. Because these elastic members 36A and 36B are interposed between the inner circumferential surface of each peripheral wall portion 291 and the outer circumferential surface of the fixing belt 21 and are in contact with each peripheral wall portion 291 and the outer circumferential surface of the fixing belt 21, when the fixing belt 21 rotates, the rotational force is transmitted to the cap members 29A and 29B via the elastic members 36A and 36B. As a result, the cap members 29A and 29B rotate integrally with the fixing belt 21.

[0044] Furthermore, one of the pair of cap members 29A, 29B (the left one in FIG. 4) is provided with a first gear 41 for transmitting a rotational force to a rotating member 37, which will be described later. The first gear 41 is fixed to the surface of the cap member 29A opposite to the belt end surface (the left one in FIG. 4). Therefore, when the cap member 29A rotates, the first gear 41 rotates integrally with the cap member 29A. Furthermore, like the cap member 29A, the first gear 41 is provided with a hole 410 for inserting the stay 25 therethrough (see FIG. 5).

[0045] The rotating member 37 is a disk-shaped member and is rotatably mounted on one side plate 30A (the left side in FIG. 4). A second gear 42 that meshes with the first gear 41 is provided on one end (the end opposite the end provided on the side plate 30A) of the rotating shaft of the rotating member 37. The second gear 42 is fixed to the rotating shaft of the rotating member 37. Therefore, when the rotating member 37 rotates, the second gear 42 rotates integrally with the rotating member 37.

[0046] The fixing device 20 according to this embodiment also includes a photointerrupter 38 as a rotation detection member that detects the rotation of the rotating member 37. The photointerrupter 38 has a light-emitting section and a light-receiving section that are arranged to sandwich the rotating member 37. The rotating member 37 has a plurality of slits that are aligned in the rotation direction, and when the rotating member 37 rotates, light (e.g., infrared light) emitted from the light-emitting section passes through the slits and is received by the light-receiving section. The number of times that light passes through the slits is counted, thereby detecting the rotation of the rotating member 37 (the number of rotations per unit time or the rotation angle). The rotation detection member is not limited to an optical sensor having a light-emitting section and a light-receiving section, and may also be a magnetic sensor.

[0047] As described above, in this embodiment, the rotation of the rotating member 37 is detected by the photointerrupter 38, thereby making it possible to detect whether or not the fixing belt 21 is rotating and the number of rotations. More specifically, when the fixing belt 21 is rotated in accordance with the rotation of the pressure roller 22, the first gear 41 rotates together with the fixing belt 21, and the second gear 42 rotates in accordance with the rotation of the first gear 41, causing the rotating member 37 to rotate integrally with the second gear 42. That is, in this embodiment, when the fixing belt 21 rotates, the rotating member 37 rotates in conjunction with the fixing belt 21, so that the rotation of the rotating member 37 can be detected. As a result, even if the fixing belt 21 stops during heating, the stoppage can be detected, and an abnormal temperature rise in the fixing belt 21 can be avoided.

[0048] When the fixing belt rotates in accordance with the rotation of the pressure roller, the fixing belt slides against a sliding member, such as a nip forming member or a sliding sheet, disposed inside the fixing belt. Since sliding resistance occurs between the fixing belt and the sliding member, a lubricant, such as grease or oil, is generally interposed between the fixing belt and the sliding member. For the same purpose, a lubricant is interposed between the fixing belt 21 and the sliding sheet 28 shown in FIG. 2 in the fixing device according to this embodiment.

[0049] 5 between end surfaces 21a and 21b of fixing belt 21 and cap members 29A and 29B, and if the lubricant further moves to the outer circumferential surface of fixing belt 21 via end surfaces 21a and 21b of fixing belt 21, there is a risk that the lubricant will adhere to elastic members 36A and 36B. When lubricant adheres to elastic members 36A and 36B, the frictional force between fixing belt 21 and elastic members 36A and 36B or between elastic members 36A and 36B and cap members 29A and 29B decreases, causing elastic members 36A and 36B to slip, preventing cap members 29A and 29B from rotating integrally with the fixing belt. In this case, the rotation of the fixing belt 21 cannot be detected accurately by the photointerrupter 38, and if the fixing belt 21 stops during heating, the temperature of the fixing belt 21 may rise abnormally.

[0050] One way to prevent lubricant from penetrating between the fixing belt and the elastic member, and between the elastic member and the cap member, is to tightly fit each component along the entire rotational direction of the fixing belt, eliminating any gaps between them. However, tightly fitting each component along the entire rotational direction makes it difficult to attach the elastic member and the cap member to the end of the fixing belt. This is particularly difficult when the diameter of the fixing belt increases due to dimensional errors during manufacturing. Even if the elastic member and the cap member can be attached, thermal expansion of the elastic member and the cap member due to temperature increases during use of the fixing device can place a load on the fixing belt, potentially damaging it. Therefore, tightly fitting the fixing belt, the elastic member, and the cap member along the entire rotational direction is not a desirable way to prevent lubricant from penetrating.

[0051] Another solution is to lengthen the elastic member in the longitudinal direction of the fixing belt. In this case, even if lubricant adheres to the end of the elastic member, the frictional force of the elastic member can be maintained in other parts, preventing slippage of the elastic member. However, lengthening the elastic member increases the size of the fixing device, which is disadvantageous for miniaturization. Furthermore, the lubricant adhering to the end of the elastic member gradually spreads, ultimately reducing the frictional force of the elastic member, making it difficult to maintain the frictional force of the elastic member over a long period of time.

[0052] Furthermore, there is a problem that the elastic member may crack if it deteriorates due to the effects of heat. That is, if a crack occurs in the elastic member and the lubricant penetrates into the crack due to capillary action, the lubricant may adhere to the elastic member. In particular, when small-sized paper is passed through the end portion of the fixing belt where the elastic member is located, the paper is less likely to absorb heat from the fixing belt and the temperature tends to become high, so there is a risk of the elastic member cracking.

[0053] In consideration of the above circumstances, the fixing device according to this embodiment takes the following measures to prevent the adhesion of the lubricant to the elastic member. The configuration and operation of this embodiment to prevent the adhesion of the lubricant to the elastic member will now be described.

[0054] FIG. 7 is a diagram for explaining the configuration and operation of the fixing device according to this embodiment.

[0055] 7, in the fixing device 20 according to this embodiment, the first gear 41 provided on the cap member 29A and the second gear 42 meshing with the first gear 41 are both configured as helical gears. Unlike spur gears, helical gears are gears in which multiple teeth provided on the outer circumferential surface are inclined in a spiral shape relative to the rotation axis of the gear.

[0056] 7, at the meshing portion where the first gear 41 and the second gear 42 mesh with each other, a rotational force is transmitted from the first gear 41 to the second gear 42, and as the teeth of the first gear 41 push and move the teeth of the second gear 42, a reaction force F is generated in the first gear 41. This reaction force F is generated in a direction perpendicular to the tooth trace direction (the inclination direction of the teeth) of the first gear 41, and therefore the reaction force F is generated in a direction inclined with respect to the rotation axis 41x of the first gear 41.

[0057] Here, the reaction force F can be broken down into a component Fy perpendicular to the rotation axis 41x and a component Fx parallel to the rotation axis 41x, and the thrust force Fx, which is the component parallel to the rotation axis 41x, is generated toward the right in FIG. 7. Therefore, the first gear 41 is subjected to the thrust force Fx and is urged toward the right in FIG. 7 (in the direction toward the end surface 21a of the cap member 29A), and accordingly, the one cap member 29A is also urged toward the right. As a result, the end wall portion 292 of the one cap member 29A is pressed against the end surface 21a of the fixing belt 21 facing it.

[0058] Furthermore, when one cap member 29A is pressed against the end surface 21a of the fixing belt 21, the pressing force presses the fixing belt 21 toward the other cap member 29B. As a result, the other cap member 29B is pressed against the opposing side plate 30B. At this time, the movement of the other cap member 29B in the axial direction (to the right in FIG. 7) is restricted by contact with the opposing side plate 30B, so the end surface 21b of the fixing belt 21 is pressed against the end wall portion 292 of the other cap member 29B.

[0059] As described above, in this embodiment, the cap members 29A, 29B are pressed against both end faces 21a, 21b of the fixing belt 21 by the thrust force Fx generated by the meshing of the first gear (first helical gear) 41 and the second gear (second helical gear) 42, thereby maintaining good contact between the cap members 29A, 29B and the end faces 21a, 21b of the fixing belt 21. That is, the cap members 29A, 29B are not fixed to the side plates 30A, 30B and are attached so as to be movable in the longitudinal direction X relative to the fixing belt 21. However, the thrust force Fx generated by the rotation of the first gear 41 presses the cap member 29A on the left side in FIG. 7 against the end face 21a of the fixing belt 21 that faces it. As a result, the opposite end surface 21b of the fixing belt 21 is pressed against the opposing cap member 29B, thereby maintaining good contact between the cap members 29A and 29B and the end surfaces 21a and 21b of the fixing belt 21. Even after the rotation of the pressure roller 22 and the fixing belt 21 stops, the position of the cap member 29A to which the first gear 41 is attached (the position in the longitudinal direction X of the fixing belt 21) is maintained by the meshing of the first gear 41 and the second gear 42, so that the pressing state of the cap members 29A and 29B against the end surfaces 21a and 21b of the fixing belt 21 is maintained without being released. This prevents the lubricant inside the fixing belt 21 from leaking out of the fixing belt 21 through the end surfaces 21a and 21b, preventing the lubricant from entering between the outer circumferential surfaces of the ends of the fixing belt 21 and the cap members 29A and 29B. As a result, the lubricant can be prevented from adhering to the elastic members 36A and 36B, and the occurrence of slippage can be avoided, improving the reliability of rotation detection of the fixing belt 21.

[0060] Furthermore, with the configuration according to this embodiment, slippage can be avoided without tightly contacting the fixing belt and the elastic member, or the elastic member and the cap member, over the entire rotational direction, or without lengthening the elastic member in the longitudinal direction of the fixing belt. This prevents the problems of poor assembly due to tight contact between members, damage to the fixing belt due to thermal expansion, and an increase in the size of the device due to a longer elastic member, making it possible to provide a fixing device that is easy to assemble, compact, and highly reliable.

[0061] 8, the outer diameter D1 of the first gear 41 is set to be equal to or smaller than the outer diameter D2 of the fixing belt 21. Note that the "outer diameter of the first gear" here refers to the diameter (maximum outer diameter) of a tooth tip circle formed by continuously connecting the tips of multiple teeth of the first gear, and the "outer diameter of the fixing belt" refers to the diameter of the outer surface of the fixing belt in an unloaded state where the fixing belt is not subjected to pressure from a pressure roller or the like. In this way, in the present embodiment, the outer diameter D1 of the first gear 41 is set to be equal to or smaller than the outer diameter D2 of the fixing belt 21, so that the thrust force Fx of the reaction force F that the first gear 41 receives from the second gear 42 is generated on the inner diameter side of the outer surface of the fixing belt 21.

[0062] On the other hand, unlike the present embodiment, when the outer diameter D1 of the first gear 41 is larger than the outer diameter D2 of the fixing belt 21 (see FIG. 9), the thrust force Fx is generated on the outer diameter side of the outer peripheral surface of the fixing belt 21. In this case, as shown in FIG. 9, the load of the thrust force Fx cannot be stably received by the end surface 21a of the fixing belt 21, and the posture of the cap member 29A becomes unstable.

[0063] 9, the posture of the cap member 29A becomes unstable, which may result in a risk of not effectively preventing the lubricant from entering between the end surface 21a of the fixing belt 21 and the cap member 29A. In contrast, in this embodiment, unlike the example shown in FIG. 9, the thrust force Fx is generated on the inner diameter side of the outer circumferential surface of the fixing belt 21, which allows the cap member 29A to stably contact the end surface 21a of the fixing belt 21. This makes it possible to effectively prevent the lubricant from entering between the end surface 21a of the fixing belt 21 and the cap member 29A.

[0064] Furthermore, unlike the thin-walled fixing belt having a thickness of about 1 mm as in this embodiment, in the case of a thick rotating body such as a fixing roller, there is a difference between the inner and outer diameters of the rotating body, and therefore the outer diameter D1 of the first gear 41 may be larger than the inner diameter of the rotating body. Even in such a case, it is sufficient that the outer diameter D1 of the first gear 41 is equal to or smaller than the outer diameter D2 of the rotating body. By having the outer diameter D1 of the first gear 41 be equal to or smaller than the outer diameter D2 of the rotating body, the cap member can be stably brought into contact with the end surface of the fixing belt, as in this embodiment.

[0065] 10, the inclination angles (torsion angles) θ1 and θ2 of the teeth of the first gear 41 and the second gear 42 relative to the rotation axes 41x and 42x, respectively, are preferably 1 degree or more and 30 degrees or less (1°≦θ1, θ2≦30°). If the inclination angles θ1 and θ2 of the teeth are less than 1 degree, the thrust force Fx that presses the cap member 29A against the end surface 21a of the fixing belt 21 cannot be effectively obtained. Conversely, if the inclination angles θ1 and θ2 of the teeth are greater than 30 degrees, the thrust force Fx becomes too large, which may damage the fixing belt 21. Therefore, by setting the inclination angles θ1 and θ2 of the teeth to be 1 degree or more and 30 degrees or less, it is possible to bring the cap members 29A and 29B into contact with the end surfaces 21a and 21b of the fixing belt 21 while preventing damage to the fixing belt 21, and to effectively prevent the intrusion of lubricant. Furthermore, in order to effectively prevent the intrusion of the lubricant, it is preferable that the inclination angles θ1 and θ2 of the teeth are 10 degrees or more and 20 degrees or less (10°≦θ1, θ2≦20°).

[0066] 10. In other words, the direction of the thrust force Fx generated in the first gear 41 differs depending on the direction of rotation of the fixing belt 21 and the pressure roller 22 when feeding the paper P into the nip N. Therefore, in a configuration in which the fixing belt 21 and the pressure roller 22 rotate in the opposite direction to that of this embodiment, the directions of the teeth of the first gear 41 and the second gear 42 must be inclined in the opposite direction. Therefore, the directions of the teeth of the first gear 41 and the second gear 42 should be set appropriately depending on the direction of rotation of the fixing belt 21 and the pressure roller 22 when fixing an image on the paper.

[0067] Furthermore, when the fixing belt 21 has a base material (base material layer) containing a metal material, the strength of the fixing belt 21 is increased, making it less likely that the fixing belt 21 will be damaged by friction, etc. On the other hand, when the base material (base material layer) of the fixing belt 21 is formed from a resin material such as polyimide, the rigidity of the fixing belt 21 is lower than that of a fixing belt having a metal base material, so that the cap members 29A, 29B and the end faces 21a, 21b of the fixing belt 21 are more likely to come into contact with each other, thereby improving adhesion therebetween.

[0068] 11, when a positioning section 50 for positioning the fixing device 20 relative to the image forming apparatus main body in the longitudinal direction X of the fixing belt 21 is provided, it is preferable that the positioning section 50 be disposed on the opposite side of the first gear 41 with respect to the center C in the longitudinal direction X of the fixing belt 21. The positioning section 50 is configured, for example, by a positioning protrusion 51 provided on an exterior section (frame member) of the fixing device 20 and a positioning recess 52 on the image forming apparatus main body side that is provided so as to be engageable with the positioning protrusion 51. Note that the relationship between the protrusions and recesses that configure the positioning section 50 may be opposite to that in the example shown in FIG. 11. That is, the positioning section on the fixing device side may be a recess, and the positioning section on the image forming apparatus main body side may be a protrusion.

[0069] 11, as in the above embodiment, when the fixing belt 21 is rotated in accordance with the rotation of the pressure roller 22, a thrust force Fx is generated at the meshing portion between the first gear 41 and the second gear 42, and this thrust Fx presses one cap member 29A (left side in FIG. 11) against the end surface 21a of the fixing belt 21. In addition, this pressing force presses the other cap member 29B (right side in FIG. 11) against the opposing side plate 30B, and the fixing belt 21 is positioned closer to the other cap member 29B (right side in FIG. 11) than the center C in the longitudinal direction X.

[0070] 11, the first gear 41 is disposed on the opposite side of the positioning unit 50 across the center C of the fixing belt 21, so that the positioning location of the fixing belt 21 (the contact position between the other cap member 29B and the side plate 30B) is on the same side (to the right of the center C in FIG. 11) as the positioning location of the fixing device 20 (the position of the positioning unit 50). In this case, the positioning location of the fixing belt 21 and the positioning location of the fixing device 20 are close to each other, so that the relative positional deviation between these positioning locations is reduced. As a result, the positional deviation of the fixing belt 21 relative to the image forming apparatus main body is also reduced, improving the positioning accuracy of the fixing belt 21.

[0071] 11, it is preferable that the drive force transmission gear 40, the first gear 41, and the second gear 42 are all arranged on the same side of the center C in the longitudinal direction X of the fixing belt 21. When the drive force transmission gear 40, the first gear 41, and the second gear 42 are arranged on the same side, it is possible to arrange on the same side the gear on the image forming apparatus main body that meshes with the drive force transmission gear 40, the drive source, the rotating member 37 on which the second gear 42 is provided, and the photointerrupter 38 that detects the rotation of the rotating member 37. This allows for the installation space for wiring connected to the power source and the photointerrupter 38 to be consolidated, thereby enabling the device to be made more compact.

[0072] In some fixing devices, the fixing belt and pressure roller are configured to be rotatable in the direction opposite to the direction of rotation when fixing an image onto paper. For example, as shown in Figure 12, in order to make it easier to remove paper P caught in the nip portion N, the fixing belt 21 and pressure roller 22 are rotated in the reverse direction to move paper P upstream in the transport direction.

[0073] 13, the pressure applied by pressure roller 22 to fixing belt 21 may be released. If the fixing device is left unused for a long period of time, the elastic layer of the pressure roller will undergo plastic deformation at the point where the pressure roller presses against the fixing belt, causing noise and image defects. Therefore, the pressure of the pressure roller is released to prevent plastic deformation of the pressure roller. The pressure of the pressure roller may also be released to make it easier to remove paper caught in the nip.

[0074] 13, a cam member 45 is provided to release the pressure of the pressure roller 22 from the fixing belt 21, and the cam member 45 is provided with a cam gear 46 that meshes with the drive force transmission gear 40 provided on the pressure roller 22. When releasing the pressure of the pressure roller 22, the pressure roller 22 is rotated in the reverse direction, causing the cam member 45 to rotate as shown in FIG. 14. This causes the cam member 45 to push and move the lever 47, causing the pressure roller 22 to separate from the fixing belt 21 and release the pressure of the pressure roller 22. At this time, the rotation of the pressure roller 22 is transmitted to the fixing belt 21 until the pressure roller 22 is completely separated from the fixing belt 21, and therefore the fixing belt 21 also rotates in the reverse direction in accordance with the reverse rotation of the pressure roller 22.

[0075] As described above, in fixing devices, there are configurations in which the fixing belt and pressure roller are rotated in opposite directions for various purposes. However, in the above-described embodiment of the present invention, if the fixing belt and pressure roller are rotated in opposite directions, the following problem occurs.

[0076] In the embodiment of the present invention, since the first gear 41 and the second gear 42 are helical gears, when the pressure roller 22 and the fixing belt 21 rotate in the reverse direction, the direction of the thrust force Fx generated at the meshing portion between the first gear 41 and the second gear 42 is reversed. That is, as shown in Fig. 15, when the first gear 41 and the second gear 42 rotate in the reverse direction in conjunction with the reverse rotation of the pressure roller 22 and the fixing belt 21, a thrust force Fx is generated at the meshing portion in a direction that separates the cap member 29A from the end surface 21a of the fixing belt 21. Therefore, when the pressure roller 22 and the fixing belt 21 rotate in the reverse direction, there is a risk that the contact state between the cap members 29A and 29B and both end surfaces 21a and 21b of the fixing belt 21 cannot be maintained satisfactorily.

[0077] One method for suppressing such adverse effects of reverse rotation is to shorten the reverse rotation time. By shortening the reverse rotation time of the fixing belt 21 and the pressure roller 22, the thrust force Fx generated at the meshing portion between the first gear 41 and the second gear 42 is generated for a shorter time, making it difficult for the cap member 29A to separate from the end surface 21a of the fixing belt 21. The time for which the fixing belt 21 and the pressure roller 22 are reversely rotated is preferably shorter than the rotation time (forward rotation time) of the fixing belt 21 and the pressure roller 22 when fixing an image on one sheet of paper, for example.

[0078] Furthermore, the rotation speed of the fixing belt 21 and the pressure roller 22 during reverse rotation may be slower than the rotation speed (forward rotation speed) when fixing an image. In this case, the rotation torque of the fixing belt 21 and the pressure roller 22 generated during reverse rotation is smaller than the rotation torque during forward rotation, so the reaction force F that the first gear 41 receives is also smaller, and the thrust force Fx in the direction of separating the cap member 29A from the end surface 21a of the fixing belt 21 is also smaller. Therefore, by slowing down the rotation speed during reverse rotation, it becomes more difficult for the cap member 29A to separate from the end surface 21a of the fixing belt 21.

[0079] Furthermore, as a method for avoiding the adverse effects of reverse rotation, there is a method of using a one-way clutch as a one-way rotation transmission member that transmits rotation in only one direction (not rotation in the opposite direction).

[0080] 16 is an example in which the first gear 41 is provided with a one-way clutch 43 that transmits only the forward rotation of the cap member 29A to the first gear 41. In this case, as shown in FIG. 16, when the fixing belt 21 and the pressure roller 22 rotate in a direction to pass the paper P through the nip portion N in order to fix an image on the paper P, the one-way clutch 43 transmits the rotation (forward rotation) of the cap member 29A to the first gear 41. Therefore, during the forward rotation operation, the first gear 41 and the second gear 42 rotate, and a thrust force is generated at the meshing portion between the first gear 41 and the second gear 42 in a direction that moves the cap member 29A closer to the end face of the fixing belt 21.

[0081] 17, during the reverse rotation operation, the one-way clutch 43 does not transmit the rotation (reverse rotation) from the cap member 29A to the first gear 41, and therefore the first gear 41 and the second gear 42 do not rotate (reversely rotate). Therefore, during the reverse rotation operation, no thrust force in the direction of separating the cap member 29A from the end face of the fixing belt 21 is generated at the meshing portion between the first gear 41 and the second gear 42, and therefore, the cap member 29A can be prevented from separating from the end face of the fixing belt 21.

[0082] 18 shows an example in which the drive force transmission gear 40 is provided with a one-way clutch 44 that transmits only the forward rotation of the drive force transmission gear 40 to the pressure roller 22. In this case, as shown in FIG. 18, during forward rotation, the one-way clutch 44 transmits rotation (forward rotation) from the drive force transmission gear 40 to the pressure roller 22, causing the pressure roller 22 and the fixing belt 21 to rotate (forward rotation), passing the paper P through the nip N. Note that the cam gear 46 is provided with another one-way clutch that does not transmit forward rotation, so the cam member 45 does not rotate. At this time, the first gear 41 and the second gear 42 rotate in conjunction with the rotation of the fixing belt 21, and a thrust force is generated at the meshing portion between the first gear 41 and the second gear 42 in a direction that moves the cap member 29A toward the end face of the fixing belt 21.

[0083] 19, during the reverse rotation operation, the one-way clutch 44 does not transmit rotation (reverse rotation) from the drive force transmission gear 40 to the pressure roller 22, so the pressure roller 22 and the fixing belt 21 do not rotate (reversely rotate). Therefore, the first gear 41 and the second gear 42 do not rotate (reversely rotate), and no thrust force is generated in the direction of separating the cap member 29A from the end face of the fixing belt 21. Therefore, the cap member 29A can be prevented from separating from the end face of the fixing belt 21. Note that the cam member 45 rotates due to the reverse rotation of the drive force transmission gear 40, so the cam member 45 pushes and moves the lever 47, and the pressure on the pressure roller 22 is released.

[0084] 18 and 19, unlike the examples shown in Figures 16 and 17, the fixing belt 21 and the pressure roller 22 do not rotate in reverse during the reverse rotation operation. Therefore, if it is desired to rotate the fixing belt 21 and the pressure roller 22 in reverse to make it easier to remove paper caught in the nip portion N, it is preferable to adopt the configurations shown in Figures 16 and 17. Also, in the examples shown in Figures 18 and 19, the one-way clutch 44 may be provided on the first gear 41 instead of the driving force transmission gear 40, as in the examples shown in Figures 16 and 17.

[0085] Although the embodiments of the present invention have been described above, the present invention is not limited to the above embodiments, and various modifications can be made without departing from the spirit of the present invention.

[0086] For example, the present invention is also applicable to fixing devices having the configurations shown in Figures 20 to 25. The configurations of the fixing devices shown in Figures 20 to 25 will be described below.

[0087] The fixing device 60 shown in FIG. 20 does not use an electromagnetic induction heating source as in the above embodiment, but instead includes a planar or plate-shaped heater 63 having a resistance heating element 56 mounted on a substrate 55. The substrate 55 is formed of a heat-resistant and insulating material such as ceramics, such as alumina or aluminum nitride, or glass, mica, or polyimide. Alternatively, the substrate 55 may be formed by forming an insulating layer on a metal material, such as stainless steel, iron, or aluminum. The resistance heating element 56 is formed by applying a paste containing silver-palladium (AgPd) and glass powder to the surface of the substrate 55 by screen printing or the like, and then firing the substrate 55. The resistance heating element 56 is covered with an insulating layer 57. The insulating layer 57 is formed of a material, such as heat-resistant glass, ceramic, or polyimide.

[0088] As shown in FIG. 21 , the heater 63 is formed in the shape of a rectangular plate and is arranged so that its longitudinal direction coincides with the longitudinal direction of the fixing belt 61. A plurality of resistance heating elements 56 are arranged at intervals along the longitudinal direction of the substrate 55 (heater 63). A plurality of electrode portions 58 and a plurality of power supply lines 59 are provided on the surface of the substrate 55 on which each resistance heating element 56 is provided. Each resistance heating element 56 is connected in parallel via the power supply lines 59 to each of the electrode portions 58 provided on both longitudinal ends of the substrate 55. Each resistance heating element 56 and each power supply line 59 are covered with an insulating layer 57. Meanwhile, each electrode portion 58 is not covered by the insulating layer 57 and is exposed so that a connector serving as a power supply terminal can be connected.

[0089] As shown in Figure 20, heater 63 is held by heater holder 64 and is arranged so as to be in contact with the inner circumferential surface of fixing belt 61. Therefore, when heater 63 generates heat, fixing belt 61 is heated from the inside. Like the fixing belt in the above embodiment, fixing belt 61 is configured as an endless belt having a base layer, an elastic layer, and a release layer. However, fixing belt 61 does not have a heat-generating layer that is heated by electromagnetic induction. The same materials as those in the above embodiment can be used for the base layer, elastic layer, and release layer.

[0090] At the location where heater 63 contacts fixing belt 61, pressure roller 62 is pressed against heater 63 via fixing belt 61. This forms a nip N between fixing belt 61 and pressure roller 62. Pressure roller 62 has basically the same configuration as the pressure roller according to the above embodiment.

[0091] The heater holder 64 is disposed inside the fixing belt 61 and is a heat source holding member that holds the heater 63. The heater holder 64 is preferably made of a heat-resistant material because it is prone to becoming hot due to the heat from the heater 63. In particular, when the heater holder 64 is made of a heat-resistant resin with low thermal conductivity, such as LCP (liquid crystal polymer) or PEEK, the heat resistance of the heater holder 64 is ensured while heat transfer from the heater 63 to the heater holder 64 is suppressed, so that the fixing belt 61 can be heated efficiently.

[0092] The heater holder 64 is supported by a stay 65 serving as a support member. The stay 65 is disposed inside the fixing belt 61 and supports the surface of the heater holder 64 opposite to the surface on the nip portion N side. This prevents the heater holder 64 from bending in the longitudinal direction of the fixing belt 61 due to the pressure of the pressure roller 62, and forms a nip portion N of uniform width between the fixing belt 61 and the pressure roller 62. The stay 65 is preferably made of an iron-based metal material such as stainless steel or SECC (electro-galvanized steel sheet) to ensure its rigidity.

[0093] Guide members 66 are integrally provided with the heater holder 64. The guide members 66 are arranged on the upstream and downstream sides of the nip portion N in the rotation direction of the fixing belt 61. When the fixing belt 61 rotates, the guide members 66 come into contact with the inner circumferential surface of the fixing belt 61, thereby guiding the fixing belt 61 from the inside.

[0094] 20 is a contact-type temperature sensor that detects the temperature of the heater 63 by contacting the surface of the heater 63 opposite to the nip portion N side, but it may also be a non-contact-type temperature sensor that is disposed in a non-contact state with the heater 63 and detects the ambient temperature near the heater 63.

[0095] In the fixing device 60 according to this embodiment, power is supplied to the heater 63 from a power source provided in the image forming apparatus main body, causing the resistance heating element 56 to generate heat. This heats the fixing belt 61. The amount of heat generated by the heater 63 is controlled based on the temperature of the heater 63 detected by a temperature sensor 67, thereby maintaining the temperature of the fixing belt 61 at a predetermined temperature (fixing temperature). In this state, as shown in FIG. 20 , when a sheet of paper P carrying unfixed toner enters the nip N between the fixing belt 61 and the pressure roller 62, the unfixed toner on the sheet of paper P is pressurized and heated, and the toner image is fixed to the sheet of paper P.

[0096] The temperature sensor 67 may be located at the center M of the nip N in the paper transport direction as shown in Fig. 20, or may be located upstream of the center M of the nip N in the paper transport direction as shown in the embodiment shown in Fig. 22. In other words, the temperature sensor 67 may be located on the entrance side of the nip N. The entrance side of the nip N is an area where heat from the fixing belt 61 is particularly likely to be lost by the paper P entering the nip N. Therefore, by using the temperature sensor 67 to detect the temperature on the entrance side, it is possible to ensure image fixability and effectively prevent the occurrence of fixing offset, which is an insufficient heating of the toner image.

[0097] 23, a fixing nip N1 through which paper P passes and a heating nip N2 through which heater 63 heats fixing belt 61 are formed in separate positions. Specifically, in this embodiment, heater 63 and nip forming member 68 are disposed inside fixing belt 61, and pressure rollers 69 and 70 are pressed against heater 63 and nip forming member 68, respectively, via fixing belt 61, thereby forming fixing nip N1 and heating nip N2.

[0098] Next, the fixing device 60 shown in Fig. 24 is an example in which the pressure roller 69 on the heater 63 side of the fixing device shown in Fig. 23 is omitted, and the heater 63 is formed in an arc shape to match the curvature of the fixing belt 61. In other respects, it is the same as the configuration shown in Fig. 23. In this case, since the heater 63 is formed in an arc shape, the contact length between the fixing belt 61 and the heater 63 in the belt rotation direction is ensured, and the fixing belt 61 can be heated efficiently.

[0099] 25 shows an example of a fixing device 60 in which a roller 73 is disposed between a pair of belts 71 and 72. In this example, a heater 63 disposed in belt 71 on the left side in FIG. 25 contacts roller 73 via belt 71, and a nip forming member 74 disposed in belt 72 on the right side contacts roller 73 via belt 72, thereby forming a nip N1 for heating and a nip N2 for fixing.

[0100] Furthermore, the image forming apparatus according to the present invention is not limited to the color image forming apparatus shown in FIG. 1, but may also be a monochrome image forming apparatus, a copying machine, a printer, a facsimile, or a combination machine of these.

[0101] For example, the present invention can also be applied to an image forming apparatus configured as shown in Fig. 26. Image forming apparatus 100 shown in Fig. 26 includes image forming means 80 including a photosensitive drum and the like, a paper transport section including a pair of timing rollers 81 and the like, a paper feeder 82, a fixing device 83, a paper discharge device 84, and a reading section 85. Paper feeder 82 includes multiple paper feed trays, each of which stores paper of a different size.

[0102] The reading unit 85 reads an image of the document Q. The reading unit 85 generates image data from the read image. The paper feeder 82 stores a plurality of sheets of paper P and sends the sheets of paper P to a conveyance path. The timing rollers 81 convey the sheets of paper P on the conveyance path to the image forming means 80.

[0103] The image forming means 80 forms a toner image on the paper P. Specifically, the image forming means 80 includes a photosensitive drum, a charging roller, an exposure device, a developing device, a replenishment device, a transfer roller, a cleaning device, and a discharging device. The fixing device 83 applies heat and pressure to the toner image to fix the toner image to the paper P. The paper P with the fixed toner image is transported to the paper discharge device 84 by a transport roller or the like. The paper discharge device 84 discharges the paper P outside the image forming apparatus 100.

[0104] Next, a fixing device 83 according to this embodiment will be described with reference to Fig. 27. In the configuration shown in Fig. 27, components common to the fixing device 60 of the above embodiment shown in Fig. 20 are denoted by the same reference numerals, and description thereof will be omitted.

[0105] As shown in FIG. 27, the fixing device 83 includes a fixing belt 61, a pressure roller 62, a heater 63, a heater holder 64, a stay 65, a temperature sensor 67, and the like.

[0106] A nip portion N is formed between the fixing belt 61 and the pressure roller 62. The nip width of the nip portion N is 10 mm, and the linear speed of the fixing device 83 is 240 mm / s.

[0107] The fixing belt 61 has a polyimide base and a release layer, but does not have an elastic layer. The release layer is formed of a heat-resistant film material made of, for example, fluororesin. The outer diameter of the fixing belt 61 is approximately 24 mm.

[0108] The pressure roller 62 includes a core metal, an elastic layer, and a release layer. The pressure roller 62 has an outer diameter of 24 to 30 mm, and the elastic layer has a thickness of 3 to 4 mm.

[0109] The heater 63 includes a base material, a heat insulating layer, a conductive layer including a resistance heating element, and an insulating layer, and has an overall thickness of 1 mm. The width of the heater 63 in the paper transport direction is 13 mm.

[0110] 11, as in the above embodiment, when the fixing belt 21 is rotated in accordance with the rotation of the pressure roller 22, a thrust force Fx is generated at the meshing portion between the first gear 41 and the second gear 42, and this thrust Fx presses one cap member 29A (left side in FIG. 11) against the end surface 21a of the fixing belt 21. In addition, this pressing force presses the other cap member 29B (right side in FIG. 11) against the opposing side plate 30B, and the fixing belt 21 is positioned closer to the other cap member 29B (right side in FIG. 11) than the center C in the longitudinal direction X.

[0111] Furthermore, the multiple resistance heating elements 56 form a central heating section 35B and heating sections 35A and 35C on both ends that can generate heat independently. For example, of the three electrode sections 58A to 58C, when electricity is applied to the leftmost electrode section 58A and the central electrode section 58B in FIG. 28, the heating sections 35A and 35C on both ends generate heat. When electricity is applied to the electrode sections 58A and 58C on both ends, the central heating section 35B generates heat. For example, when fixing small-size paper, only the central heating section 35B generates heat, and when fixing large-size paper, all of the heating sections 35A to 35C generate heat, allowing heating according to the size of the paper.

[0112] 29, the heater holder 64 according to this embodiment has a recess 64b that accommodates and holds the heater 63. The recess 64b is formed on the heater 63 side of the heater holder 64. The recess 64b is composed of a surface (bottom surface) 64b1 formed in a rectangular shape having approximately the same size as the heater 63, and four wall portions (side surfaces) 64b2, 64b3 provided along four sides that form the outline of the surface 641b and intersect with the surface 641b. Of the pair of wall portions 64b2 arranged in a direction intersecting the longitudinal direction X of the heater 63 (the arrangement direction of the resistance heating elements 56), one wall portion 64b2 may be omitted, and the recess 64b may be configured to open at one end of the heater 63 in the longitudinal direction.

[0113] 30, the heater 63 and heater holder 64 according to this embodiment are held by a connector 86. The connector 86 has a housing made of resin (for example, LCP) and a plurality of contact terminals provided inside the housing.

[0114] The connector 86 is attached to the heater 63 and the heater holder 64 in a direction intersecting the longitudinal direction X of the heater 63 (the arrangement direction of the resistance heating elements 56) (see the direction of the arrow from the connector 86 in FIG. 30). The connector 86 is attached to the heater 63 and the heater holder 64 at one end side in the longitudinal direction X of the heater 63 (the arrangement direction of the resistance heating elements 56), on the side opposite to the side on which the drive motor of the pressure roller 62 is provided. Note that when the connector 86 is attached to the heater holder 64, a convex portion provided on one of the connector 86 and the heater holder 64 may be configured to engage with a concave portion provided on the other, and the convex portion may move relatively within the concave portion.

[0115] With the connector 86 attached, the heater 63 and heater holder 64 are held in place by being sandwiched between them from the front and back sides by the connector 86. In this state, the contact terminals come into contact (pressure-welded) with the electrodes of the heater 63, electrically connecting each resistance heating element 56 to a power supply provided in the image forming apparatus via the connector 86. This allows power to be supplied from the power supply to each resistance heating element 56.

[0116] 30 are belt holding members that are provided on both longitudinal ends of the fixing belt 61 and hold both ends of the fixing belt 61 from the inside. The flanges 87 are inserted into both ends of the stay 65 and fixed to a pair of side plates that are frame members of the fixing device.

[0117] FIG. 31 is a diagram showing the arrangement of the temperature sensor 67 and the thermostat 88, which is a current interrupting member, according to this embodiment.

[0118] 31, the temperature sensors 67 according to this embodiment are disposed so as to face the inner circumferential surfaces of the center C and end portions in the longitudinal direction X of the fixing belt 61. One of these temperature sensors 67 is disposed at a position corresponding to the divided region B (see FIG. 28) between the resistance heating elements of the heater 63.

[0119] Further, on the center C side and end sides of the fixing belt 61, thermostats 88 as current-cutting members are arranged to face the inner circumferential surface of the fixing belt 61. Each thermostat 88 detects the temperature of the inner circumferential surface of the fixing belt 61 or the ambient temperature near the inner circumferential surface. When the temperature detected by the thermostat 88 exceeds a preset threshold value, the current to the heater 63 is cut off.

[0120] 31 and 32, flanges 87 that hold both ends of the fixing belt 61 are provided with slide grooves 87a. The slide grooves 87a extend in the direction in which the fixing belt 61 approaches and separates from the pressure roller 62. An engagement portion of the housing of the fixing device engages with the slide grooves 87a. The engagement portion moves relatively within the slide grooves 87a, allowing the fixing belt 61 to move in the direction in which the fixing belt 61 approaches and separates from the pressure roller 62.

[0121] The above describes the configurations of other fixing devices and image forming apparatuses to which the present invention can be applied, but by applying the present invention to fixing devices and image forming apparatuses with such configurations, the same effects as those of the above-described embodiment can be obtained. That is, by applying the present invention, the contact state between the end surface of the fixing belt and the end surface contact member that contacts it can be maintained in a good condition, so that it is possible to effectively prevent the intrusion of lubricant between the end surface of the fixing belt and the end surface contact member.

[0122] In addition, in the fixing device according to the present invention, the sliding member that contacts the inner surface of the fixing belt and slides relative to the rotating fixing belt includes not only nip forming member 24 or sliding sheet 28 as shown in FIG. 2, but also heater 63 as shown in FIGS. 20 to 25, nip forming member 68 as shown in FIG. 23 or 24, and nip forming member 74 as shown in FIG. 25.

[0123] The lubricant interposed between the fixing belt and the sliding member may be grease or oil. Because grease has a higher viscosity than oil, when grease is used as the lubricant, it is less likely to penetrate between the end surface of the fixing belt and the end surface contact member that contacts it, making slippage even less likely to occur. On the other hand, when oil is used as the lubricant, frictional resistance between the fixing belt and the sliding member can be effectively reduced, making the fixing belt less likely to wear out.

[0124] In the above embodiment, the elastic members 36A and 36B (see FIG. 5) are interposed between the outer circumferential surface of the fixing belt 21 and the inner circumferential surfaces of the cap members 29A and 29B. However, a configuration without the elastic members 36A and 36B is also possible, as shown in the example of FIG. 33. That is, when the cap members 29A and 29B are made of a member with a high friction coefficient, and the cap members 29A and 29B are rotated by the rotation of the fixing belt 21, the elastic members 36A and 36B may be omitted, and the outer circumferential surfaces of the cap members 29A and 29B may be in direct contact with the outer circumferential surface of the fixing belt 21.

[0125] The present invention is also applicable to a fixing device having the following configuration.

[0126] FIG. 34 is a schematic diagram of a fixing device according to another embodiment to which the present invention can be applied.

[0127] As shown in FIG. 34 , the fixing device 60 according to this embodiment includes a fixing belt 61 as a rotating body or fixing member, a pressure roller 62 as an opposing rotating body or pressure member, a heater 63 as a heat source, a heater holder 64 as a heat source holding member, a stay 65 as a support member, a temperature sensor (thermistor) 67 as a temperature detection member, and a first high thermal conductivity member 89. The fixing belt 61 is an endless belt. The pressure roller 62 contacts the outer surface of the fixing belt 61 and forms a nip N between the fixing belt 61 and the pressure roller 62. The heater 63 heats the fixing belt 61. The heater holder 64 holds the heater 63. The stay 65 supports the heater holder 64. The temperature sensor 67 detects the temperature of the first high thermal conductivity member 89. That is, the fixing device 60 according to this embodiment has basically the same configuration as the fixing device shown in FIG. 20 above, except for the inclusion of the first high thermal conductivity member 89. 34 is the longitudinal direction of the fixing belt 61, pressure roller 62, heater 63, heater holder 64, stay 65, and first high thermal conductivity member 89, and hereinafter this direction will be simply referred to as the longitudinal direction. This longitudinal direction also corresponds to the width direction of the paper being transported, the belt width direction of the fixing belt 61, and the axial direction of the pressure roller 62.

[0128] 28, the heater 63 in this embodiment has a plurality of resistance heating elements 56 arranged at intervals in the longitudinal direction of the heater 63. However, in a configuration in which a plurality of resistance heating elements 56 are arranged at intervals, the temperature of the heater 63 in divided regions B, which are the spaces between the resistance heating elements 56, tends to be lower than in the portions where the resistance heating elements 56 are arranged. Therefore, the temperature of the fixing belt 61 also becomes lower in divided region B, and there is a risk that the temperature of the fixing belt 61 will become uneven along the longitudinal direction.

[0129] Therefore, in this embodiment, the first high thermal conductivity member 89 is provided to suppress the temperature drop in the divided region B and suppress temperature unevenness in the longitudinal direction of the fixing belt 61. The first high thermal conductivity member 89 will be described in more detail below.

[0130] 34, first high thermal conductivity member 89 is disposed between heater 63 and stay 65 in the left-right direction of the figure, and is particularly sandwiched between heater 63 and heater holder 64. In other words, one surface of first high thermal conductivity member 89 abuts against the back surface of base material 55 of heater 63, and the other surface of first high thermal conductivity member 89 (the surface opposite to the one surface) abuts against heater holder 64.

[0131] The stay 65 supports the heater holder 64, the first high thermal conductive member 89, and the heater 63 by bringing contact surfaces 65a1 of two vertical portions 65a extending in the thickness direction of the heater 63 and the like into contact with the heater holder 64. In the direction crossing the longitudinal axis (the up-down direction in FIG. 34), the contact surfaces 65a1 are provided outside the range in which the resistance heating element 56 is provided. This makes it possible to suppress heat transfer from the heater 63 to the stay 65, and allows the heater 63 to heat the fixing belt 61 efficiently.

[0132] As shown in Fig. 35, first high thermal conductivity member 89 is a plate-like member having a certain thickness, for example, a thickness of 0.3 mm, a length in the longitudinal direction of 222 mm, and a width in the direction transverse to the longitudinal direction of 10 mm. In this embodiment, first high thermal conductivity member 89 is formed from a single plate material, but it may also be formed from a plurality of members. Note that in Fig. 35, guide member 66 shown in Fig. 34 is omitted.

[0133] The first high thermal conductivity member 89 is fitted into the recess 64b of the heater holder 64, and the heater 63 is attached thereto, thereby sandwiching and holding the first high thermal conductivity member 89 between the heater holder 64 and the heater 63. In this embodiment, the longitudinal width of the first high thermal conductivity member 89 is set to be approximately the same as the longitudinal width of the heater 63. The longitudinal movement of the first high thermal conductivity member 89 and the heater 63 is restricted by both side walls (longitudinal direction restriction portions) 64b1 arranged in a direction intersecting the longitudinal direction of the recess 64b. In this manner, the longitudinal positional deviation of the first high thermal conductivity member 89 within the fixing device 9 is restricted, thereby improving the heat conduction efficiency within a target range in the longitudinal direction. Furthermore, the longitudinal movement of the first high thermal conductivity member 89 and the heater 63 is restricted by both side walls (arrangement intersecting direction restriction portions) 64b2 arranged in the longitudinal direction of the recess 64b.

[0134] The range in the longitudinal direction (arrow X direction) in which the first high thermal conductivity members 89 are arranged is not limited to the range shown in Fig. 35. For example, as shown in Fig. 36, the first high thermal conductivity members 89 may be arranged only in the longitudinal range in which the resistance heating elements 56 are arranged (see the hatched area in Fig. 36). Furthermore, as shown in the example in Fig. 37, the first high thermal conductivity members 89 may be arranged only in the entire area at positions corresponding to intervals (divided areas) B in the longitudinal direction (arrow X direction). Note that in Fig. 37, the resistance heating elements 56 and the first high thermal conductivity members 89 are shown shifted in the vertical direction in Fig. 37 for convenience, but they are arranged at approximately the same position in the direction intersecting the longitudinal direction (arrow Y direction). The first high thermal conductivity member 89 may be disposed across a portion of the resistance heating element 56 in the direction intersecting the longitudinal axis (direction of arrow Y), or, as in the example shown in FIG. 38 , the first high thermal conductivity member 89 may be disposed across the entire resistance heating element 56 in the direction intersecting the longitudinal axis (direction of arrow Y). Furthermore, as shown in FIG. 38 , the first high thermal conductivity member 89 may be disposed not only at a position corresponding to the longitudinal interval B but also across both resistance heating elements 56 on both sides of the interval B. This "disposing the first high thermal conductivity member 89 across the resistance heating elements 56 on both sides" means that the first high thermal conductivity member 89 at least partially overlaps with the resistance heating elements 56 on both sides in the longitudinal direction. The first high thermal conductivity member 89 may be disposed at a position corresponding to the entire interval B of the heater 63, or, as in the example shown in FIG. 38 , it may be disposed only at a position corresponding to a portion of the interval B (one location in this case). Here, "first high thermal conductivity member 89 is disposed at a position corresponding to interval B" means that interval B and first high thermal conductivity member 89 at least partially overlap in the longitudinal direction.

[0135] Due to the pressure of the pressure roller 62, the first highly thermally conductive member 89 is sandwiched between the heater 63 and the heater holder 64 and is in close contact with these members. The first highly thermally conductive member 89 comes into contact with the heater 63, thereby improving the thermal conductivity of the heater 63 in the longitudinal direction. Furthermore, by arranging the first highly thermally conductive member 89 at a position corresponding to the interval B between the heaters 63 in the longitudinal direction, the thermal conductivity in the interval B can be improved, increasing the amount of heat transferred to the interval B and raising the temperature in the interval B. This reduces temperature variations in the heater 63 in the longitudinal direction and in the fixing belt 61 in the longitudinal direction. As a result, uneven fixing and glossiness of the image fixed to the paper can be reduced. Furthermore, there is no need to increase the heat output of the heater 63 to ensure sufficient fixing performance in the interval B, thereby achieving energy savings in the fixing device. In particular, when the first high thermal conductivity member 89 is arranged over the entire longitudinal area in which the resistance heating element 56 is arranged, the heat transfer efficiency of the heater 63 is improved over the entire area of ​​the main heating area by the heater 63 (i.e., the image forming area of ​​the paper being passed through), and temperature unevenness in the longitudinal direction of the heater 63 and therefore the fixing belt 61 can be suppressed.

[0136] Furthermore, the combination of the first high thermal conductivity member 89 and the resistance heating element 56 having PTC characteristics can more effectively suppress excessive temperature rise in the non-paper passing area when small-size paper is passed. The PTC characteristics are such that the resistance value increases as the temperature increases (when a constant voltage is applied, the heater output decreases). In other words, the PTC characteristics of the resistance heating element 56 can effectively suppress the amount of heat generated by the resistance heating element 56 in the non-paper passing area, and the first high thermal conductivity member 89 can efficiently transfer the heat from the non-paper passing area, where the temperature has increased, to the paper passing area. Therefore, the synergistic effect of these factors can effectively suppress excessive temperature rise in the non-paper passing area.

[0137] Furthermore, since the amount of heat generated in the gap B is small, the temperature of the heater 63 is also low in the vicinity of the gap B, so it is preferable to place the first high thermal conductivity member 89. For example, by placing the first high thermal conductivity member 89 at a position corresponding to the expanded divided region C including the region around the gap B shown in Fig. 39, the heat transfer efficiency in the longitudinal direction in the gap B and its periphery can be improved, and temperature unevenness in the longitudinal direction of the heater 63 can be more effectively suppressed. Furthermore, if the first high thermal conductivity member 89 is placed over the entire longitudinal direction of the region in which all of the resistance heating elements 56 are placed, temperature unevenness in the longitudinal direction of the heater 63 (fixing belt 61) can be more reliably suppressed.

[0138] Next, still another embodiment of the fixing device will be described.

[0139] The fixing device 60 shown in FIG. 40 has a second high thermal conductivity member 90 between a heater holder 64 and a first high thermal conductivity member 89. The second high thermal conductivity member 90 is provided at a different position from the first high thermal conductivity member 89 in the stacking direction (left-right direction in FIG. 40) of members such as the heater holder 64, stay 65, and first high thermal conductivity member 89. More specifically, the second high thermal conductivity member 90 is provided overlapping the first high thermal conductivity member 89. In addition, in this embodiment, a temperature sensor (thermistor) 67 is provided as in the embodiment shown in FIG. 34 above, but FIG. 40 shows a cross section in which the temperature sensor 67 is not provided.

[0140] The second high thermal conductivity member 90 is made of a material having a higher thermal conductivity than the base material 55, such as graphene or graphite. In this embodiment, the second high thermal conductivity member 90 is made of a graphite sheet with a thickness of 1 mm. The second high thermal conductivity member 90 may also be made of a plate material such as aluminum, copper, or silver.

[0141] As shown in FIG. 41, a plurality of second high thermal conductive members 90 are arranged in the recess 64b of the heater holder 64, with longitudinal gaps between each of the second high thermal conductive members 90. A recess that is one level deeper than the remaining portions of the heater holder 64 is formed in the portion of the heater holder 64 where the second high thermal conductive member 90 is provided. A gap is provided between the second high thermal conductive member 90 and the heater holder 64 on both longitudinal sides. This suppresses heat transfer from the second high thermal conductive member 90 to the heater holder 64, allowing the heater 63 to efficiently heat the fixing belt 61. Note that the guide member 66 shown in FIG. 34 is omitted from FIG. 41.

[0142] 42, second high thermal conductivity members 90 (see hatched areas) are arranged in positions corresponding to interval B in the longitudinal direction (direction of arrow X) so as to overlap at least a portion of adjacent resistance heating elements 56. In particular, in this embodiment, second high thermal conductivity members 90 are arranged across the entire area of ​​interval B. Note that while FIG. 42 (and FIG. 44 described below) shows a case in which first high thermal conductivity members 89 are arranged across the entire longitudinal direction of the area in which all resistance heating elements 56 are arranged, the arrangement range of first high thermal conductivity members 89 is not limited to this.

[0143] In this embodiment, in addition to the first high thermal conductivity member 89, second high thermal conductivity members 90 are disposed at positions corresponding to the longitudinal interval B so as to overlap at least a portion of adjacent resistance heating elements 56. This further improves the longitudinal heat transfer efficiency at the interval B, thereby more effectively suppressing temperature unevenness in the heater 63 along the longitudinal direction. Most preferably, as shown in FIG. 43 , the first high thermal conductivity member 89 and the second high thermal conductivity member 90 are disposed only over the entire area of ​​the position corresponding to the interval B. This improves the heat transfer efficiency particularly at the position corresponding to the interval B compared to other areas. For convenience, in FIG. 43 , the resistance heating elements 56, the first high thermal conductivity member 89, and the second high thermal conductivity member 90 are shown shifted from one another in the vertical direction of the figure, but they are actually disposed at approximately the same position in the direction transverse to the longitudinal direction (the direction of the arrow Y). However, this is not limited to this, and the first high thermal conductivity member 89 and the second high thermal conductivity member 90 may be arranged in a part of the longitudinal direction of the resistance heating element 56, or may be arranged so as to cover the entire longitudinal direction.

[0144] Furthermore, both the first high thermal conductivity member 89 and the second high thermal conductivity member 90 may be formed from the graphene sheet. In this case, the first high thermal conductivity member 89 and the second high thermal conductivity member 90 can be formed with high thermal conductivity in a predetermined direction along the graphene surface, that is, in the longitudinal direction rather than the thickness direction. This makes it possible to effectively suppress temperature variations in the heater 63 and the fixing belt 61 in the longitudinal direction.

[0145] Graphene is a flake-like powder. Graphene consists of a planar hexagonal lattice structure of carbon atoms, as shown in Figure 46. Graphene sheets are sheet-like graphene, typically a single layer. Graphene sheets may contain impurities in the single carbon layer, or may have a fullerene structure. Fullerene structures are generally recognized as compounds consisting of polycyclic rings in which the same number of carbon atoms are fused together in a cage-like fashion by five- and six-membered rings, such as C60, C70, and C80 fullerenes, or other closed cage structures with three-coordinate carbon atoms.

[0146] Graphene sheets are man-made and can be produced, for example, by chemical vapor deposition (CVD).

[0147] The graphene sheet may be a commercially available product. The size and thickness of the graphene sheet, or the number of layers of the graphite sheet (described later), may be measured using, for example, a transmission electron microscope (TEM).

[0148] Furthermore, graphite, which is a multilayered graphene, has a large thermal conductivity anisotropy. As shown in FIG. 47, graphite has layers in which the layer planes of condensed six-membered rings of carbon atoms extend in a planar fashion, forming a crystal structure in which these layers are stacked multiple times. In this crystal structure, adjacent carbon atoms within a layer form covalent bonds, while carbon atoms between layers form van der Waals bonds. Covalent bonds have a stronger bonding strength than van der Waals bonds, resulting in a large anisotropy between intralayer and interlayer bonds. In other words, by constructing the first high thermal conductivity member 89 or the second high thermal conductivity member 90 from graphite, the heat transfer efficiency in the longitudinal direction of the first high thermal conductivity member 89 or the second high thermal conductivity member 90 is greater than that in the thickness direction (i.e., the stacking direction of the members), thereby suppressing heat transfer to the heater holder 64. This effectively suppresses temperature unevenness in the longitudinal direction of the heater 63 and minimizes heat leakage toward the heater holder 64. Furthermore, by making the first high thermal conductivity member 89 or the second high thermal conductivity member 90 out of graphite, the first high thermal conductivity member 89 or the second high thermal conductivity member 90 can be endowed with excellent heat resistance, i.e., not oxidizing up to approximately 700 degrees.

[0149] The physical properties and dimensions of the graphite sheet can be appropriately changed depending on the functions required of the first high thermal conductivity member 89 or the second high thermal conductivity member 90. For example, the anisotropy of the thermal conductivity can be increased by using high-purity graphite or single-crystal graphite, or by increasing the thickness of the graphite sheet. Furthermore, in order to increase the speed of the fixing device, a thin graphite sheet may be used to reduce the thermal capacity of the fixing device. Furthermore, if the widths of the nip portion N and the heater 63 are large, the longitudinal width of the first high thermal conductivity member 89 or the second high thermal conductivity member 90 may be increased accordingly.

[0150] From the viewpoint of increasing the mechanical strength, the number of layers of the graphite sheet is preferably at least 11. The graphite sheet may partially include a single layer portion and a multi-layer portion.

[0151] The second high thermal conductivity members 90 may be arranged in positions in the longitudinal direction corresponding to intervals B (and enlarged divided regions C) so as to overlap at least a portion of adjacent resistance heating elements 56, and are not limited to the arrangement shown in FIG. 42. For example, as shown in the example in FIG. 44, the second high thermal conductivity members 90A may be arranged to protrude beyond the base material 55 on both sides in the transverse direction (direction of arrow Y). Furthermore, the second high thermal conductivity members 90B may be arranged in a range in the transverse direction where the resistance heating elements 56 are arranged. Furthermore, the second high thermal conductivity members 90C may be arranged in a portion of intervals B.

[0152] In another embodiment shown in FIG. 45, a gap is provided between the first high thermal conductivity member 89 and the heater holder 64 in the thickness direction (left-right direction in FIG. 45). That is, a recess 64c serving as a heat insulating layer is provided in a partial region of the recess 64b (see FIG. 41) of the heater holder 64 where the heater 63, the first high thermal conductivity member 89, and the second high thermal conductivity member 90 are disposed. The recess 64c is provided in a partial region in the longitudinal direction other than the portion where the second high thermal conductivity member 90 (not shown in FIG. 45) is provided. The recess 64c is formed by making the recess 64b of the heater holder 64 deeper than the remaining portion. This minimizes the contact area between the heater holder 64 and the first high thermal conductivity member 89, thereby suppressing heat transfer from the first high thermal conductivity member 89 to the heater holder 64 and enabling the heater 63 to efficiently heat the fixing belt 61. In addition, in the cross section in the longitudinal direction where second high thermal conductivity member 90 is provided, second high thermal conductivity member 90 abuts against heater holder 64, as in the embodiment shown in FIG.

[0153] In this embodiment, the relief portion 64c is provided across the entire area where the resistance heating element 56 is provided in the transverse direction (the vertical direction in FIG. 45). This effectively suppresses heat transfer from the first high thermal conductivity member 89 to the heater holder 64, improving the heating efficiency of the heater 63 for the fixing belt 61. Note that, in addition to a configuration in which a space is provided like the relief portion 64c as the heat insulating layer, a configuration in which a heat insulating member having a lower thermal conductivity than the heater holder 64 is provided may also be used.

[0154] In addition, in the present embodiment, second high thermal conductivity member 90 is provided as a member different from first high thermal conductivity member 89, but this is not limiting. For example, first high thermal conductivity member 89 may also function as second high thermal conductivity member 90 by making the portion of first high thermal conductivity member 89 corresponding to interval B thicker than the other portions.

[0155] In the above description, the present invention has been described as being applied to a fixing device, which is an example of a belt-type heating device (rotating body driving device). However, the present invention is not limited to fixing devices, and may also be applied to heating devices such as a drying device that dries a liquid such as ink applied to paper, a laminator that thermocompresses a film as a covering member onto the surface of a sheet such as paper, or a heat sealer that thermocompresses a seal portion of a packaging material. The present invention can also be applied to a rotating body driving device that does not have a heat source such as a heater. [Explanation of symbols]

[0156] 20 Fixing device (heating device, rotating body driving device) 21 Fixing belt (rotating body) 22 Pressure roller (opposing rotating body) 23 Electromagnetic induction heating section (heating source) 24 Nip forming member (sliding member) 28 Sliding sheet (sliding member) 29A Cap member (end face contact member) 29B Cap member (end surface contact member) 36A Elastic member 36B Elastic member 37 Rotating member 38 Photointerrupter (rotation detection component) 40 Driving force transmission gear 41 First gear (first helical gear) 42 Second gear (second helical gear) 60 Fixing device (heating device, belt drive device) 61 Fixing belt 62 Pressure roller (opposing rotating body) 63 Heater (heat source, sliding member) 100 Image forming device N Nip section [Prior art documents] [Patent documents]

[0157] [Patent Document 1] Japanese Patent Application Publication No. 2019-148618

Claims

1. a rotatable endless rotor; a sliding member that contacts the inner circumferential surface of the rotating body; a lubricant interposed between the sliding member and the inner circumferential surface of the rotating body; an end surface contact member that contacts an end surface of the rotating body; a first helical gear provided on the side of the end surface contact member opposite to the end surface side of the rotor; a second helical gear that meshes with the first helical gear, the teeth of the first helical gear are arranged in an orientation such that, when the first helical gear rotates, a force is generated in a direction that moves the end surface contact member toward the end surface of the rotating body, The rotating body driving device, wherein an outer diameter of the first helical gear is equal to or smaller than an outer diameter of the rotating body.

2. 2. The rotary body driving device according to claim 1, wherein an inclination angle of the teeth of the first helical gear with respect to the rotation axis is equal to or greater than 1 degree and equal to or less than 30 degrees.

3. an opposing rotating body that contacts the outer circumferential surface of the rotating body and forms a nip portion; a driving force transmission gear that transmits a driving force that rotates the counter rotating body; Equipped with 3. The rotary body drive device according to claim 1, wherein the driving force transmission gear, the first helical gear, and the second helical gear are arranged on the same side of the center of the rotary body in the longitudinal direction of the rotary body.

4. The belt driving device according to claim 1 , wherein the lubricant is oil.

5. a rotating member that rotates due to rotation of the second helical gear; The rotating body driving device according to claim 1 , further comprising a rotation detection member that detects rotation of the rotating member.

6. The rotating body driving device according to claim 1 , wherein the rotating body has a base material containing a metal material.

7. The rotating body driving device according to claim 1 , wherein the end surface contact member contacts the outer peripheral surface of the rotating body via an elastic member.

8. The rotary body driving device according to any one of claims 1 to 7, a heat source that heats the rotating body; A heating device comprising:

9. The heating device according to claim 8 , wherein the heat source is the sliding member.

10. The heating device according to claim 8 , wherein the heat source is an electromagnetic induction heating type heat source.

11. A fixing device that fixes an image on a recording medium using the heating device according to any one of claims 8 to 10.

12. 12. An image forming apparatus comprising: the rotating body driving device according to claim 1; the heating device according to claim 8; or the fixing device according to claim 11.

Images