Heating device, fixing device, and image forming apparatus

Abstract

The present invention relates to a heating device, a fixing device, and an image forming apparatus capable of reducing the amount of heat generated at the end portions of a belt-shaped resistor without increasing the material of the belt-shaped resistor. The heating device is configured to pass a sheet-shaped heated member through a nip formed between a rotating pressure member and a heating member, the direction of passing the sheet in the nip is set as a short side direction, and the direction orthogonal to the short side direction is set as a long side direction, a belt-shaped resistor extending in the long side direction is disposed inside the heating member, and both end portions of the belt-shaped resistor are connected to electrodes for power supply via conductive bodies, the belt-shaped resistor has a central region having a certain width in the short side direction at the central portion in the long side direction, and an end portion region in which the width in the short side direction at the end portion in the long side direction adjacent to the central region decreases toward the end portion in the long side direction, and in the end portion region, the conductive bodies are connected to the end edges of the belt-shaped resistor whose width in the short side direction decreases.

Description

Technical Field

[0001] The present invention relates to a heating device having a strip resistive element, a fixing device, and an image forming device. Background Technology

[0002] As an example of a heating device mounted on an image forming apparatus such as a copier or printer, a fixing device is known that fixes an image onto a sheet-shaped heated component by passing paper through a clamping portion formed between a rotating pressure component and a heating component. The fixing belt, as the heating component, is heated by a strip-shaped resistor disposed inside it. However, the temperature decreases at the long side end of the fixing belt (end temperature sags), and excessive heating of the portion not passing through the paper becomes a problem. Therefore, the fixing device in Patent Document 1 (Japanese Patent Application Laid-Open No. 2010-107577) suppresses end heating and prevents excessive end heating by narrowing the short side width of the strip-shaped resistor at the center and widening it at the end to reduce the heat generation at the end compared to the central portion along the long side. Summary of the Invention

[0003] However, if the short side width of the strip resistor is increased at the end, more material of the strip resistor will be wasted, and the increase in material cost becomes a problem.

[0004] The present invention was made in view of the above circumstances, and its object is to reduce the heat generation at the end of the strip resistor without increasing the material of the strip resistor.

[0005] [Patent Document 1] Japanese Patent Application Publication No. 2010-107577 Summary of the Invention

[0006] The heating device of the present invention, which achieves the above-mentioned objective, is a heating device for passing paper through a sheet-shaped heating component in a clamping portion formed between a rotating pressure component and a heating component. Its characteristic feature is that, when the paper-passing direction in the clamping portion is set as the short-side direction and the direction orthogonal to the short-side direction is set as the long-side direction, a strip-shaped resistive element extending along the long-side direction is disposed inside the heating component, and both ends of the strip-shaped resistive element are connected to electrodes for power supply via conductors. The strip-shaped resistive element has a central region having a certain width in the short-side direction at the center of the long-side direction, and an end region where the width in the short-side direction decreases towards the end of the long-side direction at the end of the long-side direction adjacent to the central region. In the end region, the conductor is integrally connected to the end edge of the strip-shaped resistive element whose width decreases in the short-side direction.

[0007] According to the present invention, the heat generation at the end of the strip resistor can be reduced without increasing the material of the strip resistor. Attached Figure Description

[0008] Figure 1 The diagram shown is a schematic configuration diagram of an image forming apparatus according to an embodiment of the present invention.

[0009] Figure 2 The diagram shown is a basic structural schematic of the fixing device according to an embodiment of the present invention.

[0010] Figure 3 Figures (a)-(b) show top views of a heater as a heating device according to the first embodiment of the present invention.

[0011] Figure 4 The image shown is a cross-sectional view of the clamping part of the fixing device.

[0012] Figure 5 The diagram shown is a graph of the temperature distribution of the fixing zone.

[0013] Figure 6 The figures shown are (a) a top view of the end of the heater according to the second embodiment and (b) a cross-sectional view.

[0014] Figure 7A (a) is a top view of the heater, (b) is a top view of the third embodiment, and (c) is a top view of the fourth embodiment.

[0015] Figure 7B (d) is a top view of the heater, (e) is a top view of the sixth embodiment, (f) is a top view of the seventh embodiment, and (c) is a top view of the eighth embodiment. Detailed Implementation

[0016] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. Furthermore, in the drawings used to explain the present invention, components or constituent parts having the same function or shape are assigned the same symbol and are omitted from further description after being described once, as long as they can be identified.

[0017] ●The overall structure of the image forming apparatus

[0018] Figure 1 The diagram shown is a schematic configuration diagram of an image forming apparatus 1000 according to an embodiment of the present invention. Here, "image forming apparatus" in this specification includes printers, copiers, fax machines, printing presses, or multifunctional peripheral devices combining two or more of these.

[0019] Furthermore, the term "image formation" used in the following explanation refers not only to forming meaningful images with text and graphics, but also to forming images without pattern-like meaning. First, refer to... Figure 1 This will explain the overall structure and operation of the image forming apparatus according to embodiments of the present invention. For example... Figure 1 As shown, the image forming apparatus 1000 according to the embodiments of the present invention includes an image forming unit 100, a fixing unit 200, a sheet supply unit 300, and a sheet discharge unit 400.

[0020] ●Image Formation Section

[0021] The image forming unit 100 is the part that forms an image on a sheet that serves as a recording medium. The image forming unit 100 includes four imaging units 1Y, 1M, 1C, and 1Bk, an exposure device 6, and a transfer device 8. The four imaging units 1Y, 1M, 1C, and 1Bk each include an electrostatic latent image carrier 2, a charging component 3, a developing device 4, and a cleaning component 5.

[0022] The electrostatic latent image carrier 2 is a rotating body that carries an electrostatic latent image on a surface. For example, in addition to a photoreceptor drum, an annular photoreceptor belt or the like can be used as the electrostatic latent image carrier 2. For example, an inorganic photoreceptor such as amorphous silicon or selenium, or an organic photoreceptor such as titanium dioxide phthalocyanine, can be used as the photoreceptor drum.

[0023] Examples of organic photosensitive materials include laminated photosensitive materials with a stacked structure on a support such as an aluminum drum. This laminated structure consists of a layer (charge-generating layer) formed by dispersing charge-generating materials such as metal-free phthalocyanines or titanyl phthalocyanines in a binder resin, and a layer (charge-transporting layer) formed by dispersing charge-transporting materials in the binder resin. A single-layer photosensitive material has a single-layer photosensitive layer on the support, in which both charge-generating and charge-transporting materials are dispersed in the binder resin. In single-layer photosensitive materials, hole transporters and electron transporters can be added to the photosensitive layer as charge-transporting materials. Furthermore, an undercoat layer can be provided between the support and the laminated charge-generating layer or the single-layer photosensitive layer.

[0024] The charging component 3 is a component that charges the surface of the electrostatic latent image carrier 2. There are no particular limitations on the charging component 3, as long as it can uniformly charge the surface of the electrostatic latent image carrier 2 by applying a voltage, and it can be appropriately selected according to the purpose. Specifically, in addition to contact-type charging components such as conductive or semi-conductive charging rollers, magnetic brushes, bristle brushes, film materials, and rubber scrapers, non-contact charging components utilizing corona discharge can also be cited.

[0025] The developing apparatus 4 is a device that supplies toner as a developer to the electrostatic latent image in the electrostatic latent image carrier 2 to form a toner image. The developing apparatus 4 contains toners (developers) of different colors, such as yellow, magenta, cyan, and black, corresponding to the color decomposition components of the color image, according to the imaging units 1Y, 1M, 1C, and 1Bk.

[0026] The cleaning component 5 is used to remove residual toner and other foreign matter from the electrostatic latent image carrier 2. The cleaning component 5 may include a cleaning scraper or similar device configured to contact the surface of the electrostatic latent image carrier 2.

[0027] Exposure apparatus 6 is an apparatus for exposing the charged surface of the electrostatic latent image carrier 2 to form an electrostatic latent image. Exposure apparatus 6 is not particularly limited, as long as it can expose the charged surface of the electrostatic latent image carrier 2, and can be appropriately selected according to the purpose. Specifically, examples include various exposure apparatuses such as photocopying optical systems, rod lens array systems, laser optical systems, liquid crystal shutter optical systems, and LED optical systems.

[0028] The transfer device 8 is a device for transferring images onto a sheet. The transfer device 8 includes a transfer belt 11, a primary transfer roller 12, and a secondary transfer roller 13.

[0029] The intermediate transfer belt 11 is a ring-shaped belt component that is tensioned and mounted by multiple support rollers. Four primary transfer rollers 12 are provided on the inner side of the intermediate transfer belt 11.

[0030] Through the contact between each primary transfer roller 12 and the electrostatic latent image carrier 2 via the intermediate transfer belt 11, a primary transfer clamping portion is formed between the intermediate transfer belt 11 and each electrostatic latent image carrier 2. On the other hand, the secondary transfer roller 13 contacts the outer peripheral surface of the intermediate transfer belt 11. Therefore, a secondary transfer clamping portion is formed between the secondary transfer roller 13 and the intermediate transfer belt 11.

[0031] Alternatively, an elastic intermediate transfer tape can be used as the intermediate transfer tape 11. For example, an elastic intermediate transfer tape can be used that has a soft elastic layer laminated on a relatively rigid base layer that allows for bending. Furthermore, to prevent the intermediate transfer tape 11 from serpentinizing, anti-deviation guide members can be provided on the inner circumferential surface of the intermediate transfer tape 11.

[0032] ●Fixing Section

[0033] The fixing unit 200 has a fixing device 20 that heats the sheet and fixes the image onto the sheet. The fixing device 20 includes a pair of rotating bodies 19A and 19B that are in contact with each other and a heating source that heats at least one of the pair of rotating bodies 19A and 19B.

[0034] ●Sheet Supply Department

[0035] The sheet supply unit 300 is the part that supplies sheet material to the image forming unit 100. The supply unit 300 has a paper cassette 14 that holds the paper P, which serves as the heating element, and a paper feed roller 15 that feeds the paper P out of the paper cassette 14. Therefore, a secondary transfer clamping part is formed between the secondary transfer roller 13 and the intermediate transfer belt 11.

[0036] In addition to paper, the "heated component" also includes OHP sheets or cloth, metal sheets, plastic films, or semi-cured sheets pre-impregnated with resin in carbon fibers. Furthermore, "paper" includes not only ordinary paper but also thick paper, postcards, envelopes, thin paper, coated paper (such as art paper and tracing paper), and tracing paper.

[0037] ●Sheet ejection section

[0038] The sheet discharge section 400 is the part that discharges the paper P out of the device. The sheet media discharge section 400 has a pair of paper discharge rollers 17 for discharging the paper P, and a paper discharge tray 18 for holding the paper P discharged by the paper discharge rollers 17.

[0039] ●Image forming action

[0040] Next, refer to Figure 1 The operation of the image forming apparatus 1000 according to an embodiment of the present invention will be explained. When the image forming operation is started according to an instruction from an operation panel or an external terminal, the electrostatic latent image carrier 2 begins to rotate in each of the imaging units 1Y, 1M, 1C and 1Bk.

[0041] Next, each charging component 3 uniformly charges the surface of each electrostatic latent image carrier 2 to a high potential. Then, the exposure device 6 exposes the surface (charged surface) of each electrostatic latent image carrier 2 according to the image information of the original read by the original read device or the printed image information indicated by the external terminal.

[0042] As a result, the potential of the exposed portion decreases, forming an electrostatic latent image on the surface of each electrostatic latent image carrier 2. Then, by supplying toner from each developing apparatus 4 to each electrostatic latent image carrier 2, toner images of different colors are formed on each electrostatic latent image carrier 2.

[0043] As the electrostatic latent image carrier 2 rotates, the toner image on each carrier reaches the primary transfer clamping section (position of the primary transfer roller 12). Then, in the primary transfer clamping section, the toner image is sequentially superimposed and transferred from each electrostatic latent image carrier 2 onto the rotating intermediate transfer belt 11.

[0044] In this way, a full-color toner image is formed on the intermediate transfer belt 11. In addition, the image formation is not limited to the case of forming a full-color image using all four imaging units 1Y, 1M, 1C, and 1Bk. It is also possible to use any one of the imaging units 1Y, 1M, 1C, and 1Bk to form a monochrome image, or to use any two or three imaging units to form a two-color or three-color image.

[0045] Furthermore, after the toner image is transferred onto the intermediate transfer belt 11, the cleaning unit 5 performs a cleaning operation on the electrostatic latent image carrier 2. This removes residual toner and other foreign matter from the surface of each electrostatic latent image carrier 2.

[0046] The toner image transferred onto the intermediate transfer belt 11 is conveyed to the secondary transfer clamping section (position of the secondary transfer roller 13) as the intermediate transfer belt 11 rotates. Then, in the secondary transfer clamping section, the toner image is transferred from the intermediate transfer belt 11 onto the paper P.

[0047] The paper P is supplied from the sheet supply unit 300. After the image forming operation begins, the paper P is fed out from the paper supply cassette 14 by the rotation of the paper supply roller 15.

[0048] The paper P being fed out comes into contact with the timing roller pair 16 on its way to the secondary transfer clamping section, and the feeding stops temporarily. Then, by rotating the timing roller pair 16 at a predetermined time, the paper P is fed to the secondary transfer clamping section after the timing of the toner image on the intermediate transfer belt 11 is aligned, and the toner image is transferred onto the paper P.

[0049] Paper P, with a toner image transferred onto it, is conveyed to fixing unit 200. In fixing unit 200, paper P passes between a pair of rotating bodies 19A and 19B, whereby the toner image on paper P is heated and pressurized, thereby fixing the toner image onto paper P.

[0050] Then, the paper P is conveyed to the sheet discharge section 400 and discharged to the paper discharge tray 18 via the paper discharge roller 17. Thus, a series of image forming operations are completed.

[0051] ●Basic components of a fixing device

[0052] Figure 2 The diagram shown is a basic structural schematic of the fixing device 20 according to an embodiment of the present invention. Figure 2 As shown, the fixing device 20 includes a heater 23, a heater holder 24, a support member 25, etc., in addition to a pair of rotating bodies 19A and 19B.

[0053] Of the pair of rotating bodies 19A and 19B, the first rotating body 19A is a fixing belt 21 disposed on the side of the unfixed image-carrying surface of the paper P. The second rotating body 19B is a pressure roller 22 disposed opposite to the fixing belt 21.

[0054] The fixing belt 21 and the pressure roller 22 are pressurized by contacting each other through a pressure-applying component such as a spring. As a result, a clamping part N is formed between the fixing belt 21 and the pressure roller 22.

[0055] The fixing belt 21 is composed of an annular belt component having a cylindrical substrate material and a release layer or the like disposed on the outer peripheral surface of the substrate material. The substrate material is formed, for example, from a metallic material such as nickel or stainless steel, or from a resin material such as polyimide.

[0056] The release layer is formed, for example, from materials such as PFA (a copolymer of tetrafluoroethylene and perfluoroalkoxy vinyl acid), PTFE (polytetrafluoroethylene), polyimide, polyetherimide, PES (polyethersulfone), etc. By having a release layer, the separation of the toner image from the fixing belt 21 is improved, and the winding of the paper P relative to the fixing belt 21 is suppressed.

[0057] Alternatively, the fixing belt 21 may have an elastic layer between the substrate material and the release layer. Materials used for the elastic layer include, for example, rubber materials such as silicone rubber, foamed silicone rubber, and fluororubber. When the fixing belt 21 has an elastic layer, it becomes difficult to form minute irregularities on its surface, thus allowing heat to be easily and evenly transferred to the toner image on the paper P, improving fixing quality.

[0058] The pressure roller 22 is composed of a roller having a hollow or solid core material, an elastic layer disposed on the outer periphery of the core material, and a release layer disposed on the outer periphery of the elastic layer. The core material is formed of a metal material such as iron.

[0059] Materials used for the elastic layer include silicone rubber, foamed silicone rubber, and fluororubber. The release layer is formed from fluororesins such as PFA or PTFE.

[0060] The heating tube 23 is the heating source for heating the fixing belt 21. At this time, the heater 23 is composed of a planar or plate-shaped heater that contacts the inner circumferential surface of the fixing belt 21.

[0061] Furthermore, at the position where the fixing belt 21 and the pressure roller 22 face each other, a clamping portion N is formed between the fixing belt 21 and the pressure roller 22 through the contact between the heater 23 and the inner circumferential surface of the fixing belt 21. In addition to direct contact with the inner circumferential surface of the fixing belt 21, the heater 23 may also make indirect contact via a low-friction sliding piece. Furthermore, in this specification, "contact" includes not only direct contact without contact via other components, but also indirect contact via other components, unless otherwise explicitly stated.

[0062] Specifically, the heater 23 includes a substrate material 50, a strip resistor 51, an insulating layer 52, etc. The strip resistor 51 is disposed on the substrate material 50 and is covered by the insulating layer 52.

[0063] When the strip resistor 51 heats up due to energization, the heat is transferred through the insulating layer 52 to the inner peripheral surface of the fixing belt 21, thereby heating the fixing belt 21. Alternatively, the orientation of the heater 23 can be changed so that the substrate material 50 is in contact with the inner peripheral surface of the fixing belt 21. In this case, since the heat from the strip resistor 51 is transferred to the fixing belt 21 through the substrate material 50, the substrate material 50 is preferably formed of a material with high thermal conductivity.

[0064] The substrate material 50 may be formed from non-metallic materials such as ceramics, glass, or mica, which have excellent heat resistance and insulation properties, such as alumina or aluminum nitride. Alternatively, by providing an insulating layer between the substrate material 50 and the strip resistor 51, the substrate material 50 may also be formed from a conductive material such as a metal.

[0065] From a low-cost perspective, aluminum or stainless steel are preferred metallic materials. Furthermore, to suppress temperature unevenness in the heater 23 and improve image quality, the substrate material 50 can also be formed from materials with high thermal conductivity, such as copper, graphite, or graphene. Graphene is a sheet-like material formed by the bonding of carbon atoms.

[0066] The strip resistor 51 is formed by methods such as screen printing. For example, a paste mixed with silver palladium (AgPd) and glass powder is applied to the substrate material 50 by screen printing, and then the strip resistor 51 can be formed by firing the substrate material 50.

[0067] In addition to silver and palladium, other resistive materials such as silver alloy (AgPt) or ruthenium oxide (RuO2) can also be used as the material for the strip resistor 51. The insulating layer 52 is formed, for example, from heat-resistant glass.

[0068] The heater retainer 24 is a heat source retaining member that holds the heater 23. By housing the heater 23 within the recess 24a of the heater retainer 24, the direction of the heater 23 is restricted. Figure 2The movement in the vertical direction and in the direction perpendicular to the paper.

[0069] Since the heater holder 24 is prone to high temperatures due to the heat from the heater 23, it is preferable to form it from a heat-resistant material. In particular, when the heater holder 24 is formed from a heat-resistant resin with low thermal conductivity, such as LCP, the heating efficiency of the heater 23 is improved because unnecessary heat transfer from the heater 23 to the heater holder 24 is suppressed.

[0070] The support member 25 is a support component that supports the heater holder 24. By supporting the side of the heater holder 24 opposite to the side of the pressure roller 22, the support member 25 suppresses the deflection of the heater 23 caused by the pressure from the pressure roller 22, resulting in a clamping portion N of uniform width. As the material of the support member 25, in order to ensure rigidity, an ferrous metal material such as SUS or SECC is preferred.

[0071] ● Operation of the fixing device

[0072] The operation of the fixing apparatus 20 according to the embodiment of the present invention is as follows. When the image forming operation begins, the pressure roller 22 begins to press against the image. Figure 2 The fixing belt 21 rotates in response to the rotation driven by the arrow in the image. Furthermore, the fixing belt 21 is heated by starting to energize the heater 23.

[0073] Then, when the temperature of the fixing belt 21 reaches the predetermined target temperature, the paper P carrying the unfixed image is conveyed to the clamping section N between the fixing belt 21 and the pressure roller 22. Thereby, the toner image on the paper P is heated and pressurized, thus fixing it onto the paper P. The paper P is then discharged from the clamping section N and conveyed to the sheet discharge section 400.

[0074] ●Components of the heater

[0075] Figure 3 The image shown is a top view of the basic configuration of the heater 23 according to the first embodiment of the present invention. Furthermore, Figure 4 yes Figure 2 A cross-sectional view of the clamping part. (See example...) Figure 3 , Figure 4 As shown, the heater 23 according to the embodiment of the present invention, in addition to the substrate material 50, the strip resistor 51, and the insulating layer 52, also has a pair of end electrodes 55 and 56 for power supply and a plurality of conductors 57 and 58.

[0076] Here, the substrate material 50 is a strip-shaped plate arranged in a manner extending in the long side direction X of the fixing belt 21. The strip resistor 51 is formed in the long side direction (X direction) of the substrate material 50.

[0077] A pair of end electrodes 55 and 56 are disposed at the long side end of the substrate material 50. Furthermore, each end electrode 55 and 56 is connected to the strip resistor 51 via multiple conductors 57 and 58. Moreover, the arrangement, number, and shape of the strip resistor 51, end electrodes 55 and 56, and conductors 57 and 58 are not limited to specific configurations. Figure 3 The example shown can be modified appropriately.

[0078] To ensure insulation and durability, the conductors 57 and 58 are covered by the insulating layer 52, just like the strip resistor 51. On the other hand, the end electrodes 55 and 56 are connected to the connector, which serves as a power supply component, and are therefore exposed without being covered by the insulating layer 52. When the connector is connected to the end electrodes 55 and 56, power can be supplied to the strip resistor 51 from the power supply (AC power) provided in the main body of the image forming apparatus.

[0079] Here, the paper-passing direction in the clamping part N is defined as the short side direction, and the direction orthogonal to the short side direction is defined as the long side direction. The strip resistor 51 has: a central region L2, which has a certain width in the short side direction at its central portion in the long side direction, and an end region L1, which has a width in the short side direction that decreases towards the end in the long side direction at the end adjacent to the central region L2.

[0080] In the end region L1, the conductor 57 is integrally connected to the end edge 51c of the strip resistor 51, whose width decreases in the short side direction. Specifically, the width of the end region L1 in the short side direction is formed to decrease linearly towards the end in the long side direction.

[0081] exist Figure 3 In this design, the edge 51c of the strip resistor is formed as a central portion approaching the long side of the strip resistor 51 as it moves from the upstream side towards the downstream side in the paper-passing direction. Here, "conductor 57 and edge 51c are integrally connected" means that conductor 57 is continuously connected from the upstream end of edge 51c in the paper-passing direction to the downstream end. Furthermore, with... Figure 3 In contrast, the case in this invention also includes the case where the end edge 51c of the strip resistor is formed to be closer to the center of the long side of the strip resistor 51 as it moves from the downstream side to the upstream side in the direction of the paper.

[0082] Thus, by forming the end edge 51c of the strip resistor 51 at an angle and connecting the end edge 51c entirely to the conductor 57, the heat generation in the end region L1 gradually decreases towards the end side in the long side direction. Since the end edge 51c of the strip resistor 51 is entirely connected to the conductor 57, the resistance in the end region L1 does not increase. As a result, as... Figure 5 As shown, compared with the prior art, it is possible to suppress excessive heating of the non-paper-passing section of the fixing belt 21.

[0083] According to this embodiment, costs can be reduced without increasing the material of the strip resistor 51. Furthermore, damage to the components of the fixing device 20 and the lubricant (grease) can be prevented.

[0084] Furthermore, the short side width of the strip resistor 51 varies narrowly within a range that is further outward than the maximum image width and further inward than the maximum paper width. Therefore, the portion containing the image edge can be sufficiently heated even during the initial rise, thus preventing poor fixing while suppressing temperature rise in the non-paper-passing portion.

[0085] Normally, when the width of the strip resistor 51 narrows in the energizing direction (long side of the heater), the resistance per unit length increases, and the heat generation increases. However, since the conductor 57 is in complete contact with the portion of the strip resistor 51 where the short side width narrows (end edge 51c), the resistance value remains constant at any point along the long side of the energized strip resistor 51. Therefore, the heat generation does not change at any point along the long side of the strip resistor 51; instead, the heat generation is based on the cross-sectional area of ​​the short side of the strip resistor 51 at any point along the long side.

[0086] As the area (cross-sectional area) of the strip resistor 51 narrows in the end direction, the heat generation decreases. Since the heat generation at the end of the strip resistor 51 is less than that at the center, the temperature rise of the non-paper-passing section can be suppressed.

[0087] In contrast, such as Figure 3 As shown in (b), when the conductor 58 is only disposed at the end, and the width of the end of the strip resistor 51b varies narrowly at the position separated from the conductor 58, the heat generation in the narrow portion increases. If only the width (cross-sectional area) in the short side direction of the end region L1 of the strip resistor 51b is reduced, the resistance in this reduced portion increases, and the heat generation increases locally. Therefore, in Figure 3 In the configuration of (b), it is difficult to suppress the excessive heating of the non-paper-passing part of the fixing belt 21.

[0088] Figure 6 The figures shown are (a) a top view of the end of the heater according to the second embodiment and (b) a cross-sectional view. Figure 6 The cross-sectional view in (b) shows the connection between the end edge 51c of the strip resistor 51 and the conductor 57.

[0089] Furthermore, the strip resistor 51 and conductor 57 of the heater 23 are overlapped in the thickness direction to ensure stable current supply, and an insulating layer 52 is provided on the strip resistor 51 and conductor 57. Due to this structure, the contact portion between the strip resistor 51 and conductor 57 is formed in a convex shape.

[0090] That is, the end of the conductor 57, which is connected to the end edge 51c of the strip resistor 51, covers the end edge 51c of the strip resistor 51. This forms a protrusion 57a ​​that protrudes upwards (towards the pressure member 22) from the end of the conductor 57. Through this protrusion 57a, the insulating layer 52 also forms a protrusion 52a that protrudes upwards (towards the pressure member 22). This protrusion 52a is formed such that it approaches the center of the longitudinal side as it moves from the upstream side towards the downstream side in the direction of paper passage.

[0091] On the other hand, a lubricating material (grease) is applied to the inner surface of the fixing belt 21 to suppress the increase of sliding wear with the heater 23 or the increase of the driving torque of the fixing belt 21. When the fixing belt 21 moves from the upstream side to the downstream side, the grease applied to the inner surface of the fixing belt 21 is also transported to the downstream side.

[0092] Most of the grease delivered to the clamping part does not penetrate the clamping part and remains on the upstream side of the clamping part. The remaining portion of this retained grease sometimes flows outward along the long side of the clamping part and cannot be effectively utilized.

[0093] like Figure 6 As shown in (a), the protrusion 52a of the insulating layer 52 is formed at an incline from the upstream side in the paper direction toward the downstream side, approaching the central portion in the long side direction. The remaining portion of the retained grease is guided into the incline of the protrusion 52a and transported to the central side in the long side direction, thereby being effectively used as a lubricant. Therefore, wear suppression and torque rise suppression of the fixing belt 21 can be achieved for a long time by means of grease.

[0094] ●Other implementation methods

[0095] Figure 7A , Figure 7B The image shown is a top view of the heater according to the third to eighth embodiments of the present invention. Figure 7A The third embodiment of (a) is an embodiment in which two rows of strip resistors 51a and 51b are provided. The strip resistor 51a on the upstream side has an end region L1 and a central region L2.

[0096] The width of the downstream strip resistor 51b is constant in the short side direction while maintaining its length. Three or more rows of strip resistors can also be used.

[0097] By expanding the heating area using two rows of strip resistors 51a and 51b, the heating time of the fixing belt 21 can be increased, thereby improving heat transfer efficiency. In order to provide the same amount of heat through one row of strip resistors as through two rows of strip resistors, the width of one row of strip resistors needs to be narrowed. However, by setting multiple rows of strip resistors, the short side width of each strip resistor can be widened, which can extend the heating time and improve heat transfer efficiency.

[0098] The left ends of the strip resistors 51a and 51b are connected to the end electrodes 55 and 56 via conductors 57 and 58. In addition, the right ends of the strip resistors 51a and 51b are connected in series with each other via conductor 59.

[0099] The gap 70 formed between the two rows of strip resistors 51a and 51b has a constant width in the short side direction while maintaining its length. As a result, the heat generation in the central region L2 can be kept constant in the long side direction, resulting in stable fixing performance without unevenness.

[0100] From the viewpoint of ensuring insulation between the strip resistors 51a and 51b, the gap 70 is preferably 0.2 mm or more, more preferably 0.4 mm or more. However, if the gap 70 is too large, a temperature drop is likely to occur in the gap area. Therefore, from the viewpoint of suppressing temperature unevenness along the entire long side, it is preferably 5 mm or less, and more preferably 1 mm or less.

[0101] The gap 70 can be located at the center of the clamping width of the clamping part N (the pressure center of the pressure member 22) in the short side direction. As a result, equal fixing performance can be obtained on both sides of the clamping width.

[0102] Figure 7A The fourth embodiment of (b) is an embodiment in which the width of the end region L1 in the short side direction decreases in a stepped manner towards the end in the long side direction to form the end edge 51c of the upstream strip resistor 51a. Figure 7A The fifth embodiment of (c) is an embodiment in which the width of the end region L1 in the short side direction decreases in an arc shape as it approaches the end in the long side direction to form the end edge 51c of the upstream strip resistor 51a.

[0103] Figure 7BThe sixth embodiment (d) is an embodiment in which the width of the short side of the end region L1 decreases linearly towards the end in the long side, forming the edge 51c of the upstream strip resistor 51a. The width of the downstream strip resistor 51b in the short side is formed to be constant throughout the long side direction. Since the conductor 57 is located downstream of the end region L1, heat from the downstream strip resistor 51b is not transferred to this part. Therefore, heat in the end region L1 can be reduced.

[0104] Figure 7B The seventh embodiment of (e) is an embodiment in which the width of the end region L1 in the short side direction decreases linearly towards the end in the long side direction, forming the end edges 51c of the upstream and downstream strip resistors 51a, 51b. The inclination of the end edge 51c can be the same or different in the upstream strip resistor 51a and the downstream strip resistor 51b.

[0105] Figure 7B In the eighth embodiment (f), the width of the end region L1 in the short side direction is linearly reduced towards the end in the long side direction to form the end edge 51c of the upstream strip resistor 51a. Furthermore, the right ends of the upstream and downstream strip resistors 51a and 51b are connected to the end electrode 60 via a conductor 59. This allows for independent temperature control of the upstream and downstream strip resistors 51a and 51b.

[0106] In addition, Figure 7B In (f), the two ends of the long side of the downstream strip resistor 51b are located downstream of the conductor 59. This suppresses the temperature drop (end temperature decrease) of the fixing band 21 in a portion of the conductor 59.

[0107] While the present invention has been specifically described above with reference to the embodiments, the present invention is not limited to the embodiments described above. Needless to say, various modifications can be made within the scope of the technical concept described in the claims.

[0108] <Note> The preferred embodiments of the present invention are described below.

[0109] [First Method]

[0110] A heating device that allows a sheet-shaped heating element to pass paper through a clamping portion formed between a rotating pressure element and a heating element, characterized in that: when the paper-passing direction in the clamping portion is set as the short-side direction and the direction orthogonal to the short-side direction is set as the long-side direction, a strip-shaped resistive element extending along the long-side direction is disposed inside the heating element, and both ends of the strip-shaped resistive element are connected to electrodes for power supply via conductors. The strip-shaped resistive element has a central region with a certain width in the short-side direction at the center of the long-side direction, and an end region in the long-side direction adjacent to the central region where the width in the short-side direction decreases towards the end of the long-side direction. In the end region, the conductor is integrally connected to the end edge of the strip-shaped resistive element where the width in the short-side direction decreases.

[0111] [Second Method]

[0112] According to the heating device of the first embodiment, the edge of the strip resistor to which the conductor is connected is formed such that it approaches the central portion of the long side as it moves from the upstream side toward the downstream side in the direction of the paper.

[0113] [Third Method]

[0114] According to the heating device of the first or second method, the conductor connected to the end edge of the strip resistor has a protrusion that covers the end edge of the strip resistor and protrudes toward the pressure member.

[0115] [Fourth Method]

[0116] A heating device according to any one of the first to third methods, characterized in that the end region is formed inside the paper-passing area of ​​the heated component.

[0117] [Fifth Method]

[0118] According to any one of the first to fourth methods of the heating device, the heating device according to claim 1 is characterized in that: the strip resistor is arranged in multiple rows, and at least one of the multiple rows of strip resistors has the central region and the end region.

[0119] [Sixth Method]

[0120] According to the heating device of the fifth method, the electrode is connected to each of the multiple rows of strip resistors via the conductor at both ends.

[0121] [Seventh Method]

[0122] According to the heating device of the fifth or sixth method, a gap with a certain width is formed between the multiple rows of strip resistive elements in the central region.

[0123] [Eighth Method]

[0124] The heating device according to any one of the first to seventh methods is characterized in that the width of the end region in the short side direction decreases linearly, stepwise or arcwise towards the end in the long side direction.

[0125] [Ninth Method]

[0126] A fixing device, characterized in that it has a heating device of any one of the first to eighth modes.

[0127] [Tenth Method]

[0128] An image forming apparatus, characterized in that it has a fixing device of a ninth mode.

Claims

1. A heating device that allows a sheet-shaped heating element to pass paper through a clamping portion formed between a rotating pressure element and a heating element, characterized in that: When the direction through which the paper passes in the clamping part is set as the short side direction, and the direction orthogonal to the short side direction is set as the long side direction, A strip-shaped resistor extending along the long side is disposed on the inner side of the heating element, and both ends of the strip-shaped resistor are connected to electrodes for power supply via conductors. The strip resistor has a central region having a certain width in the short side direction at the center of the long side direction, and an end region in the short side direction at the end of the long side direction adjacent to the central region, where the width decreases towards the end of the long side direction. In the end region, the conductor is integrally connected to the end edge of the strip resistor whose width decreases in the short side direction.

2. The heating device according to claim 1, characterized in that: The edge of the strip resistor to which the conductor is connected is formed such that it approaches the center of the long side as it moves from the upstream side toward the downstream side in the direction of the paper.

3. The heating device according to claim 2, characterized in that: The end of the conductor connected to the edge of the strip resistor has a protrusion that covers the edge of the strip resistor and protrudes toward the pressure-applying component.

4. The heating device according to claim 1, characterized in that: The end region is formed inside the paper-passing area of ​​the heated component.

5. The heating device according to claim 1, characterized in that: The strip resistors are arranged in multiple rows, and at least one of the multiple rows of strip resistors has the central region and the end region.

6. The heating device according to claim 5, characterized in that: The electrodes are connected to both ends of each of the multiple rows of strip resistors via the conductor.

7. The heating device according to claim 5, characterized in that: Between the multiple rows of strip resistors in the central region, gaps with a certain width are formed in the direction of the short side.

8. The heating device according to claim 1, characterized in that: The width of the end region in the short side direction decreases linearly, stepwise, or arcwise towards the end in the long side direction.

9. A fixing device, characterized in that: The heating device having any one of claims 1 to 8.

10. An image forming apparatus, characterized in that: It has the fixing device as described in claim 9.

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