Heating device, fixing device, and image forming apparatus

Abstract

To prevent a reduction in temperature at both end sides in a longitudinal direction of a rotating body and positioning of a reflecting member.SOLUTION: A reflecting member 27 has a heat transfer part 29 that is applied with pressure between a base member 26 and a nip forming member 24. The heat transfer part 29 has hole parts 29a that are provided on both end sides in a longitudinal direction with respect to the longitudinal center M of the heat transfer part 29 so as to reduce the contact area of the heat transfer part 29 with the nip forming member 24, and a positioning part 29c that is provided at a position closer to the longitudinal center M than the hole parts 29a and determines the position of the reflecting member 27 relative to the base member 26.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present invention relates to 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 heating device installed in an image forming apparatus such as a copying machine or a printer, a fixing device is known that heats paper onto which an image has been transferred, thereby fixing the image onto the paper.

[0003] The fixing device has a pair of rotating bodies such as rollers or belts, a heat source for heating at least one of the pair of rotating bodies, etc. When a sheet of paper carrying an unfixed image enters the nip between the rotating bodies heated to a predetermined temperature, the sheet of paper is heated and pressurized by the pair of rotating bodies, and the image is fixed to the sheet of paper.

[0004] Furthermore, some fixing devices are configured to reflect heat radiated from the heat source back to the rotating body using a reflective member to improve the heating efficiency of the rotating body. Reflective members are generally made of a material that effectively reflects heat, such as aluminum. However, the reflective member gradually increases in temperature because it absorbs a portion of the heat radiated from the heat source. In particular, when a large number of sheets of paper are fixed continuously, the reflective member is exposed to the heat of the heat source for a long period of time, which can cause the reflective member to excessively increase in temperature. Furthermore, if the reflective member becomes excessively hot, its surface may discolor, reducing its reflective function.

[0005] To address this problem, Patent Document 1 (JP 2023-106335 A) proposes a configuration in which the heat from the reflective member is transferred to the rotating body (fixing belt) via a nip forming member (heat equalizing member) with high thermal conductivity, thereby suppressing the temperature rise of the reflective member.

[0006] However, in a configuration in which the reflecting member and the rotating body are in contact with each other via a nip forming member with high thermal conductivity, as in Patent Document 1, heat from the rotating body may be transferred to the reflecting member via the nip forming member. In this case, heat is removed from the rotating body, causing the temperature of the rotating body to drop. In particular, the temperature drop tends to be more pronounced at both ends of the rotating body in the longitudinal direction, where heat is more easily dissipated than at the center of the longitudinal direction.

[0007] Furthermore, in a configuration that includes a reflective member, if the reflective member thermally expands due to a temperature rise, the reflective member may interfere with surrounding components. For this reason, there is a demand for positioning the reflective member so that the reflective member does not interfere with surrounding components. Summary of the Invention [Problem to be solved by the invention]

[0008] Therefore, the present invention aims to suppress the temperature drop at both ends of the rotating body in the longitudinal direction and to position the reflecting member. [Means for solving the problem]

[0009] In order to solve the above-mentioned problems, the present invention provides a heating device including a first rotating body, a second rotating body arranged to face the outer circumferential surface of the first rotating body, a nip forming member that sandwiches the first rotating body between itself and the second rotating body to form a nip portion where the first rotating body and the second rotating body are in contact with each other, a heat source arranged inside the first rotating body, a reflecting member arranged inside the first rotating body, a support member that receives the pressure force of the second rotating body via the nip forming member, and a base member interposed between the support member and the nip forming member. The reflecting member has a reflecting portion that is arranged opposite the heat source and reflects the heat of the heat source to the inner surface of the first rotating body, and a heat transfer portion that is pressurized between the base member and the nip forming member, and the heat transfer portion has a hole or recess that is arranged so that the contact area of ​​the heat transfer portion with the nip forming member is smaller at both ends of the longitudinal direction than the longitudinal center of the heat transfer portion, and a positioning portion that is arranged at a position closer to the longitudinal center than the hole or recess and positions the reflecting member with respect to the base member. [Effects of the Invention]

[0010] According to the present invention, it is possible to suppress a temperature drop at both ends of the rotating body in the longitudinal direction, and to position the reflecting member. [Brief explanation of the drawings]

[0011] [Figure 1] 1 is a schematic diagram illustrating the configuration of an image forming apparatus according to a first embodiment of the present invention. [Figure 2] 1 is a schematic diagram of a fixing device according to a first embodiment of the present invention. [Figure 3] 1 is a perspective view of a fixing device according to a first embodiment of the present invention. [Figure 4] FIG. 2 is a perspective view of a heating unit disposed in a fixing belt of the fixing device according to the first embodiment of the present invention. [Figure 5] 1 is a cross-sectional view of a heating unit according to a first embodiment of the present invention, taken at one end in the longitudinal direction. [Figure 6]5A and 5B are diagrams showing the relationship between the positions of holes on both ends of the reflecting member and the paper passing width according to the first embodiment of the present invention. [Figure 7] FIG. 10 is a cross-sectional view showing a modified example of the present invention. [Figure 8] 1 is a cross-sectional view of a heating unit according to a first embodiment of the present invention, taken at the center in the longitudinal direction. [Figure 9] FIG. 10 is a perspective view showing another modified example of the present invention. [Figure 10] FIG. 10 is a cross-sectional view showing yet another modified example of the present invention. [Figure 11] FIG. 10 is a perspective view of a heating unit according to a second embodiment of the present invention. [Figure 12] FIG. 10 is a cross-sectional view of a heating unit according to a third embodiment of the present invention. [Figure 13] FIG. 10 is a view of a heating unit according to a third embodiment of the present invention, as viewed from the downstream side in the paper transport direction. [Figure 14] FIG. 10 is a view of a heating unit according to a third embodiment of the present invention, as viewed from the upstream side in the paper transport direction. DETAILED DESCRIPTION OF THE INVENTION

[0012] 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 once they have been described, their description will be omitted.

[0013] FIG. 1 is a schematic diagram of an image forming apparatus 1000 according to a first 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 the first embodiment of the present invention will be described with reference to FIG. 1.

[0014] <Overall configuration of image forming apparatus> As shown in FIG. 1, an image forming apparatus 1000 according to the first embodiment of the present invention includes an image forming section 100, a fixing section 200, a sheet supply section 300, and a sheet discharge section 400.

[0015] (Image forming section) The image forming section 100 is a section that forms an image on a sheet as a recording medium. The image forming section 100 is provided with four imaging units 1Y, 1M, 1C, and 1Bk, an exposure device 6, and a transfer device 8.

[0016] Each of the four imaging units 1Y, 1M, 1C, and 1Bk includes an electrostatic latent image carrier 2, a charging member 3, a developing device 4, and a cleaning member 5.

[0017] The electrostatic latent image carrier 2 is a rotating body that carries an electrostatic latent image on its surface. Examples of the electrostatic latent image carrier 2 include a photosensitive drum and an endless photosensitive belt.

[0018] The charging member 3 is a member that charges the surface of the electrostatic latent image carrier 2. There are no particular limitations on the charging member 3, and it can be appropriately selected depending on the purpose, as long as it can apply a voltage to the surface of the electrostatic latent image carrier 2 and uniformly charge it. Specific examples of the charging member 3 include contact-type charging members such as a conductive or semi-conductive charging roller, a magnetic brush, a fur brush, a film, and a rubber blade, as well as non-contact-type charging members that utilize corona discharge.

[0019] The developing device 4 is a device that supplies toner as a developer to the surface of the electrostatic latent image carrier 2. The developing device 4 contains toner of different colors, such as yellow, magenta, cyan, and black, corresponding to the color separation components of the color image for each of the imaging units 1Y, 1M, 1C, and 1Bk.

[0020] The cleaning member 5 is a member that removes toner and other foreign matter remaining on the electrostatic latent image carrier 2. An example of the cleaning member 5 is a cleaning blade that is arranged so as to come into contact with the surface of the electrostatic latent image carrier 2.

[0021] The exposure device 6 is a device that exposes the charged surface of the electrostatic latent image carrier 2 to light to form an electrostatic latent image. The exposure device 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 depending on the purpose. Specific examples of the exposure device 6 include various exposure devices such as a copying optical system, a rod lens array system, a laser optical system, a liquid crystal shutter optical system, and an LED optical system.

[0022] The transfer device 8 is a device that transfers an image onto a sheet. 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 a corresponding electrostatic latent image carrier 2 via the intermediate transfer belt 11, thereby forming a primary transfer nip between the intermediate transfer belt 11 and each electrostatic latent image carrier 2. Meanwhile, the secondary transfer roller 13 contacts the outer peripheral surface of the intermediate transfer belt 11. This forms a secondary transfer nip between the secondary transfer roller 13 and the intermediate transfer belt 11.

[0023] (fixing part) The fixing section 200 is provided with a fixing device 20 that heats a sheet to fix an image on the sheet. The fixing device 20 is an example of a heating device that heats a sheet. Specifically, the fixing device 20 includes a pair of rotating bodies 19A and 19B that contact each other, a heat source that heats at least one of the pair of rotating bodies 19A and 19B, and the like.

[0024] (sheet supply unit) The sheet supply unit 300 is provided with a paper feed cassette 14 that stores paper P, and a paper feed roller 15 that feeds paper P from the paper feed cassette 14. Hereinafter, a "sheet" as a recording medium used in image formation will be described as "paper," but the "sheet" is not limited to paper (paper), and may be an overhead projector sheet, fabric, metal sheet, plastic film, or a prepreg sheet made of carbon fiber pre-impregnated with resin. Furthermore, the "paper" may be plain paper, cardboard, postcards, envelopes, thin paper, coated paper (coated paper, art paper, etc.), tracing paper, etc.

[0025] (sheet discharge section) The sheet discharge section 400 is provided with a pair of discharge rollers 17 for discharging the paper P, and a paper discharge tray 18 on which the discharged paper P is placed.

[0026] <Image formation operation> Next, the operation of the image forming apparatus 1000 according to the first embodiment of the present invention will be described with reference to FIG.

[0027] When an image formation operation is initiated in response to an instruction from the operation panel or an external terminal, the electrostatic latent image carrier 2 in each of the imaging units 1Y, 1M, 1C, and 1Bk begins to rotate. The charging member 3 then charges the surface of the electrostatic latent image carrier 2. This causes the surface of each electrostatic latent image carrier 2 to be uniformly charged to a high potential. The exposure device 6 then exposes the surface (charged surface) of each electrostatic latent image carrier 2 to light based on the image information of the original document read by the document reader or the print image information instructed from the external terminal. This reduces the potential of the exposed portion, forming an electrostatic latent image on the surface of each electrostatic latent image carrier 2. Subsequently, toner is supplied from each developing device 4 to each electrostatic latent image carrier 2, forming a toner image of a different color on each electrostatic latent image carrier 2.

[0028] As the electrostatic latent image carriers 2 rotate, the toner images on each electrostatic latent image carrier 2 reach the primary transfer nip (the position of the primary transfer roller 12). At the primary transfer nip, the toner images are transferred from each electrostatic latent image carrier 2 to the rotating intermediate transfer belt 11, overlapping one another. Thus, a full-color toner image is formed on the intermediate transfer belt 11. Image formation is not limited to forming a full-color image using all four imaging units 1Y, 1M, 1C, and 1Bk. It is also possible to form a monochrome image using any one of the imaging units 1Y, 1M, 1C, and 1Bk, or to form a two- or three-color image using any two or three of the imaging units. After the toner images are transferred to the intermediate transfer belt 11, the electrostatic latent image carriers 2 are cleaned by the cleaning member 5. This removes residual toner and other foreign matter from the surface of each electrostatic latent image carrier 2.

[0029] The toner image transferred onto the intermediate transfer belt 11 is transported to the secondary transfer nip (the position of the secondary transfer roller 13) as the intermediate transfer belt 11 rotates. Then, the toner image on the intermediate transfer belt 11 is transferred to the paper P being transported to the secondary transfer nip. At this time, the paper P transported to the secondary transfer nip is supplied from the sheet supply unit 300. After the image forming operation starts, the paper P is sent out from the paper feed cassette 14 by the rotation of the paper feed roller 15. On the way to the secondary transfer nip, the sent paper P hits the pair of timing rollers 16 and its transport is temporarily stopped. Thereafter, the pair of timing rollers 16 rotates at a predetermined timing, and the paper P is transported to the secondary transfer nip in synchronization with the toner image on the intermediate transfer belt 11. Then, the toner image on the intermediate transfer belt 11 is transferred to the paper P.

[0030] The paper P onto which the toner image has been transferred is transported to the fixing unit 200. Then, the paper P passes between the pair of rotating rotors 19A and 19B, whereby the paper P is heated and pressurized, and the toner image on the paper P is fixed to the paper P. Thereafter, the paper P is transported to the sheet discharge unit 400 and discharged onto the paper discharge tray 18 by the paper discharge rollers 17. This completes the series of image forming operations.

[0031] <Basic structure of the fixing device> FIG. 2 is a schematic diagram of the fixing device 20 according to the first embodiment of the present invention.

[0032] As shown in FIG. 2, the fixing device 20 according to the first embodiment of the present invention includes a pair of rotating bodies 19A and 19B, a halogen heater 23, a nip forming member 24, a support member 25, a base member 26, a reflecting member 27, and the like.

[0033] The pair of rotating bodies 19A and 19B is composed of a fixing belt 21 as a first rotating body and a pressure roller 22 as a second rotating body.

[0034] The fixing belt 21 is disposed on the unfixed image bearing side (toner image T side) of the paper P. The fixing belt 21 is an endless belt having, from the inside out, a base material, an elastic layer, and a release layer. The base material has a thickness of, for example, 30 to 50 μm and is made of a metal material such as nickel or stainless steel, or a resin material such as polyimide. The elastic layer has a thickness of 100 to 300 μm 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, thereby facilitating uniform heat transfer to the toner image T on the paper P. The release layer has a thickness of 10 to 50 μm 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 the release properties of the toner image T on the paper P. In addition, when miniaturization and low heat capacity are desired, it is preferable that the overall thickness of the fixing belt 21 be 1 mm or less and the diameter be 30 mm or less.

[0035] The pressure roller 22 is disposed to face the outer peripheral surface of the fixing belt 21. The pressure roller 22 is configured as a roller having a core material, an elastic layer provided on the outer peripheral surface of the core material, and a release layer provided on the outer peripheral surface of the elastic layer. The core material is formed of a metal material such as iron. The core material may be a solid member or a hollow member. The cross-sectional shape of the core material may be circular, rectangular, or another cross-sectional shape. Examples of materials for the elastic layer include silicone rubber, foamed silicone rubber, and fluororubber. The silicone rubber may be solid rubber, but sponge rubber is also acceptable. Sponge rubber is preferred because it has higher heat insulation properties and is less likely to remove heat from the fixing belt 21 by the pressure roller 22. The release layer is formed of a fluororesin such as PFA or PTFE.

[0036] The pressure roller 22 is pressed against the fixing belt 21 by a pressure means such as a spring. As a result, the pressure roller 22 comes into contact with the outer peripheral surface of the fixing belt 21, and a nip portion N is formed at the point where the pressure roller 22 and the fixing belt 21 come into contact. As shown in FIG. 2 , when the pressure roller 22 rotates, the fixing belt 21 is rotated in accordance with the rotation of the pressure roller 22. Then, when the fixing belt 21 is heated to a predetermined target temperature and a sheet of paper P carrying a toner image (unfixed image) T enters the nip portion N, the fixing belt 21 and the pressure roller 22 heat and pressurize the sheet of paper P while rotating, thereby fixing the toner image T to the sheet of paper P.

[0037] The halogen heater 23 is a radiant heat source that radiates heat (infrared rays) to heat the fixing belt 21. When heat is radiated from the halogen heater 23, the fixing belt 21 is heated from the inside. The heat source is not limited to a halogen heater, and other radiant heat heaters such as a carbon heater may also be used. Furthermore, if the pressure roller 22 does not have an elastic layer made of sponge rubber, a heat source such as a halogen heater may be disposed inside the pressure roller 22.

[0038] Nip forming member 24 is a member that comes into contact with the inner circumferential surface of fixing belt 21 and forms nip portion N between fixing belt 21 and pressure roller 22. When pressure roller 22 presses fixing belt 21, pressure roller 22 is pressed against nip forming member 24 via fixing belt 21. At this time, fixing belt 21 is pressed by pressure roller 22 and nip forming member 24, and fixing belt 21 deforms to follow the shape of nip forming member 24, thereby forming nip portion N. In the example of FIG. 2, nip portion N is formed in a flat shape, but the shape of nip portion N may be a concave curved surface that is recessed toward fixing belt 21, or may be some other shape.

[0039] Furthermore, nip forming member 24 is made of a metal material such as aluminum or copper, which has a high thermal conductivity of 50 W / m K or more. Therefore, if temperature unevenness occurs in the longitudinal direction of fixing belt 21, heat is transferred from high-temperature areas of fixing belt 21 to low-temperature areas via nip forming member 24. This reduces temperature unevenness in fixing belt 21. In other words, nip forming member 24 also functions as a heat transfer assisting member that transfers heat from fixing belt 21 in its longitudinal direction.

[0040] Furthermore, in order to improve the sliding properties of the fixing belt 21 relative to the nip forming member 24, it is preferable to form a sliding layer with excellent sliding performance on the surface 24a of the nip forming member 24 that faces the inner peripheral surface of the fixing belt 21. Examples of materials for the sliding layer include resin-based materials such as polyimide resin, fluororesin, polyphenylene sulfide resin, and saturated polyester resin. Alternatively, such resin-based materials may be mixed with glass fiber, carbon, graphite, graphite fluoride, carbon fiber, molybdenum disulfide, fluororesin, etc.

[0041] Metal-based materials may also be used as the sliding layer material. Examples of metal-based materials include molybdenum disulfide, nickel, composite plating of nickel and fluororesin, alumite, and alumite impregnated with resin or metal. Ceramics may also be used as the sliding layer material. Examples of ceramics used for the sliding layer include silicon carbide ceramics, silicon carbide ceramics, alumina ceramics, and mixtures of these with molybdenum disulfide, fluororesin, etc.

[0042] Furthermore, when the nip forming member 24 is made of aluminum or an aluminum alloy, an anodized aluminum layer may be formed on the surface of the nip forming member 24, and the micropores of the anodized aluminum layer may be filled with molybdenum disulfide produced by secondary electrolysis from the deepest part of the micropores to the outermost surface.

[0043] Support member 25 supports nip forming member 24, base member 26, and reflecting member 27, and is a member that receives the pressure of pressure roller 22 via nip forming member 24 and the like. When support member 25 receives the pressure of pressure roller 22, bending of nip forming member 24 and the like is suppressed, and a nip portion N with a uniform width is obtained. As a material for support member 25, a metal material such as iron or stainless steel is preferred to ensure rigidity.

[0044] The base member 26 is a member interposed between the support member 25 and the nip forming member 24. The base member 26 is made of a heat-resistant resin such as polyethersulfone (PES), polyphenylene sulfide (PPS), liquid crystal polymer (LCP), polyethernitrile (PEN), polyamideimide (PAI), or polyetheretherketone (PEEK). When the base member 26 is made of resin, it functions as a heat insulating member that suppresses heat transfer from the fixing belt 21 to the support member 25.

[0045] Reflecting member 27 is a member that is disposed inside fixing belt 21 and reflects heat from halogen heater 23 to the inner circumferential surface of fixing belt 21. Reflecting member 27 has a reflecting portion 28 that is disposed so as to face halogen heater 23, and a heat transfer portion 29 that is interposed between base member 26 and nip forming member 24 so as to be pressed against it.

[0046] Reflecting section 28 is a section that reflects heat radiated from halogen heater 23 onto the inner circumferential surface of fixing belt 21. The heat reflected by reflecting section 28 is applied to the inner circumferential surface of fixing belt 21, and fixing belt 21 is effectively heated by the reflected heat and heat applied directly from halogen heater 23. In addition, because reflecting section 28 is disposed between halogen heater 23 and support member 25, application of unnecessary heat to support member 25 is also suppressed, thereby reducing energy consumption.

[0047] On the other hand, heat transfer section 29 is a section that comes into contact with nip forming member 24 and mainly transfers heat from reflecting member 27 (reflecting section 28) to nip forming member 24. Heat transfer section 29 may come into direct contact with nip forming member 24, or may come into indirect contact with nip forming member 24 via a heat conducting member or the like.

[0048] Reflective members used in fixing devices include those made of high-purity aluminum with multiple reflective coatings and protective coatings formed on the surface, as well as those with silver vapor-deposited on the aluminum plate to improve reflectivity. However, reflective members gradually increase in temperature due to exposure to heat from a heating source such as a halogen heater. In particular, when a large volume of paper is continuously fed, the reflective member is exposed to heat for a long period of time, and the temperature of the reflective member may rise to approximately 300 to 400°C. If the aluminum or silver vapor-deposited layer on the reflective member's surface discolors as a result of excessive temperature rise, the reflective member's thermal reflectivity may decrease, potentially preventing the desired heating effect. Furthermore, excessive temperature rise of the reflective member is undesirable from a safety standpoint. Therefore, conventional measures have been taken to adjust the productivity (image formation speed) of image forming devices to prevent excessive temperature rise of the reflective member. However, in such cases, productivity cannot be achieved beyond the reflective member's heat resistance, and the reflective member's heat resistance has limited productivity improvement.

[0049] To address this problem, in the first embodiment of the present invention, in order to suppress a temperature rise in the reflecting member, as shown in FIG. 2 , reflecting member 27 is extended so that a portion of reflecting member 27 (heat transfer portion 29) comes into contact with nip forming member 24. That is, because reflecting member 27 has heat transfer portion 29 in contact with nip forming member 24, when reflecting portion 28 receives heat from halogen heater 23 and its temperature rises, the heat of reflecting portion 28 is transferred to nip forming member 24 via heat transfer portion 29. Note that heat transfer portion 29 is in contact with not only nip forming member 24 but also base member 26. However, because base member 26 is made of a material with a lower thermal conductivity than nip forming member 24, heat from reflecting member 27 is preferentially transferred to nip forming member 24 rather than to base member 26. Furthermore, because heat transfer portion 29 is sandwiched and pressurized between nip forming member 24 and base member 26, the adhesion of heat transfer portion 29 to nip forming member 24 is improved, and heat is efficiently transferred from heat transfer portion 29 to nip forming member 24. This makes it possible to suppress a rise in temperature of reflective member 27 and prevent discoloration of reflective portion 28 due to heat.

[0050] As described above, in the first embodiment of the present invention, the heat of reflecting member 27 (reflecting portion 28) can be transferred to nip forming member 24, thereby suppressing the temperature rise of reflecting member 27 when continuous sheets are fed, thereby improving the productivity of the image forming apparatus. Furthermore, the heat transferred to nip forming member 24 via heat transfer portion 29 is further transferred to fixing belt 21 via nip forming member 24. Therefore, in the first embodiment of the present invention, the heat of reflecting member 27 can be effectively used as heat energy for heating fixing belt 21, and improved energy savings can also be expected.

[0051] <Issues with fixing devices equipped with reflective members> Next, another problem of the fixing device having a reflecting member will be described using the first embodiment of the present invention as an example.

[0052] In a configuration in which reflective member 27 is extended and a portion of reflective member 27 (heat transfer portion 29) is in contact with nip forming member 24, as in the first embodiment of the present invention, when the temperature of reflective member 27 rises, the heat of reflective member 27 can be transferred to nip forming member 24. On the other hand, when the temperature of fixing belt 21 rises, the heat of fixing belt 21 may be transferred to reflective member 27 via nip forming member 24.

[0053] For example, when the image forming apparatus is turned on or when the image forming apparatus is restored from a long sleep state, and the warm-up operation or restoration operation is started from a state in which the temperature of the fixing device is low, the temperature of fixing belt 21 rises faster than that of nip forming member 24 and reflecting member 27, and the temperature of fixing belt 21 may become higher than that of nip forming member 24 and reflecting member 27. In this case, heat is transferred from fixing belt 21 to nip forming member 24 and reflecting member 27, and the temperature of fixing belt 21 drops.

[0054] 3, at both longitudinal ends of the fixing belt 21, the fixing belt 21 is supported by a pair of rotator support members 30, and therefore the heat of the fixing belt 21 is likely to escape to the side plates or the like via the rotator support members 30, and the temperature tends to drop. Therefore, at both longitudinal ends of the fixing belt 21, the drop in temperature of the fixing belt 21 may cause a fixing failure known as cold offset, in which part of the image is not fixed to the paper and is missing.

[0055] Furthermore, since the reflecting member 27 thermally expands due to the heat from the halogen heater 23, there is a risk that the reflecting member 27 may interfere with surrounding components if the reflecting member 27 thermally expands. Therefore, it is preferable that the reflecting member 27 is positioned properly.

[0056] On the other hand, if the reflecting member 27 is fixed to the peripheral members in order to position the reflecting member 27, the reflecting member 27 may be constrained when the reflecting member 27 thermally expands, which may cause deformation of the reflecting member 27 and the peripheral members. Also, because heat from the reflecting member 27 is transferred to the peripheral members via the fixed points between the reflecting member 27 and the peripheral members, there is a concern that the amount of heat transferred from the reflecting member 27 to the fixing belt 21 may decrease, resulting in a loss of energy efficiency. For this reason, there is a demand to minimize the fixing (positioning) of the reflecting member 27 to the peripheral members.

[0057] Furthermore, when positioning the reflecting member 27, the following factors must be taken into consideration. For example, if double-sided adhesive tape is used as a positioning means, and the double-sided adhesive tape is interposed between the reflecting member 27 and the nip forming member 24, the double-sided adhesive tape, which has low thermal conductivity, may impede heat transfer from the reflecting member 27 to the nip forming member 24. Furthermore, because misalignment occurs at the bonding surfaces between the reflecting member 27 and the nip forming member 24 due to the difference in thermal expansion between the two members, adhesion using double-sided adhesive tape or the like is not suitable as a positioning means to be used in locations where such misalignment occurs. Therefore, a means for positioning the reflecting member 27 is required that does not impede heat transfer from the reflecting member 27 to the nip forming member 24 and is less susceptible to misalignment due to the difference in thermal expansion.

[0058] In consideration of the above circumstances, the fixing device according to the first embodiment of the present invention employs the following configuration to suppress the temperature drop at both ends of the fixing belt in the longitudinal direction and to achieve good positioning of the reflective member. The configuration of the characteristic parts according to the first embodiment of the present invention will be described below.

[0059] <Configuration of Characteristic Parts of the Fixing Device> First, a description will be given of a configuration for suppressing a temperature drop on both longitudinal end sides of the fixing belt in the fixing device according to the first embodiment of the present invention.

[0060] FIG. 4 is a perspective view of a heating unit disposed in the fixing belt of the fixing device according to the first embodiment of the present invention.

[0061] The heating unit 10 is a unit that includes a halogen heater 23, a reflecting member 27, a base member 26, a support member 25, and a nip forming member 24. In Fig. 4, the nip forming member 24 is indicated by a two-dot chain line.

[0062] 4, the halogen heater 23, reflecting member 27, base member 26, support member 25, and nip forming member 24 are all formed in a longitudinal shape extending in the direction of arrow X in the figure. In particular, the longitudinal centers M of the nip forming member 24 and heat transfer portion 29 of the reflecting member 27 are arranged to coincide with the longitudinal center of the fixing belt. As a result, when the temperature of the reflecting member 27 rises, the heat of the reflecting member 27 is transferred symmetrically to the fixing belt via the heat transfer portion 29 and nip forming member 24, with the longitudinal center of the fixing belt as the reference.

[0063] On the other hand, when the temperature of the fixing belt becomes higher than the temperatures of nip forming member 24 and reflecting member 27, the heat of the fixing belt is transferred to nip forming member 24 and reflecting member 27. At this time, the temperature tends to drop significantly at both longitudinal ends of the fixing belt due to the influence of heat transfer to rotator support member 30 (see FIG. 3).

[0064] Therefore, in the first embodiment of the present invention, in order to suppress a temperature drop at both longitudinal ends of the fixing belt, a pair of holes 29a is provided on both longitudinal ends of the heat transfer section 29 relative to the longitudinal center M, as shown in Fig. 4. In this case, the pair of holes 29a are provided symmetrically, one on each end, with the longitudinal center M of the heat transfer section 29 in between.

[0065] FIG. 5 is a cross-sectional view of the heating unit 10 according to the first embodiment of the present invention, taken at one end position in the longitudinal direction (the position of the hole 29a).

[0066] 5, at the location where hole 29a is provided, a gap (air layer) corresponding to the size of hole 29a is present between nip formation member 24 and base member 26. In other words, since heat transfer portion 29 does not exist at the location of hole 29a, heat transfer portion 29 does not come into contact with nip formation member 24.

[0067] In this way, by providing the holes 29a at both longitudinal ends of the heat transfer portion 29, the contact area of ​​the heat transfer portion 29 with the nip forming member 24 can be reduced compared to other regions including the longitudinal center M. In other words, when the heat transfer portion 29 is cut in a direction perpendicular to the longitudinal direction X, the contact area with the nip forming member 24 at the positions of the holes 29a can be reduced compared to other regions including the longitudinal center M. Therefore, heat transfer between the nip forming member 24 and the heat transfer portion 29 is suppressed at both longitudinal ends of the heat transfer portion 29. As a result, even if the temperature of the fixing belt becomes higher than the temperatures of the nip forming member 24 and the reflecting member 27, heat transfer from the fixing belt to the nip forming member 24 and the reflecting member 27 is suppressed. Therefore, according to the first embodiment of the present invention, it is possible to suppress a temperature drop at both longitudinal ends of the fixing belt, thereby preventing the occurrence of cold offset.

[0068] 4, the pair of holes 29a are arranged at symmetrical positions with respect to the longitudinal center M of the heat transfer section 29, but if the locations of the fixing belt where the temperature is likely to decrease are not actually symmetrical, the pair of holes 29a may be arranged at positions shifted from the symmetrical positions accordingly. Also, the shape of the holes 29a is not limited to the rectangular shape shown in FIG. 4, but may be a circle or another shape.

[0069] Furthermore, the holes 29a are preferably positioned according to the locations where the temperature of the fixing belt is likely to drop, and also according to the paper passing width (sheet passing width) of the paper passing through the nip N. For example, as shown in Fig. 6, the holes 29a may be positioned at or near both ends of the paper passing width (sheet passing width) W of a frequently used standard size paper P such as "A4". In this case, cold offset at both widthwise ends of frequently used paper can be prevented, and therefore poor fixing can be more effectively prevented.

[0070] 4 and 5, the pair of holes 29a are formed as through holes that penetrate heat transfer portion 29, but as in the modified example shown in Fig. 7, instead of through holes, recesses 29b (that do not penetrate heat transfer portion 29) may be provided on both longitudinal ends of heat transfer portion 29. In this case as well, the contact area of ​​heat transfer portion 29 with nip formation member 24 is reduced at the locations where recesses 29b are provided, making it possible to suppress the transfer of heat from the fixing belt to nip formation member 24 and reflecting member 27 when the temperature of the fixing belt becomes high.

[0071] Next, a configuration for positioning the reflecting member 27 in the fixing device according to the first embodiment of the present invention will be described.

[0072] 4, in the reflecting member 27 according to the first embodiment of the present invention, a positioning hole 29c for positioning the reflecting member 27 relative to the base member 26 is provided at the longitudinal center M of the heat transfer portion 29. The positioning hole 29c is an example of a positioning portion for positioning the reflecting member 27. Meanwhile, the base member 26 is provided with a positioning protrusion 26a as a mating positioning portion.

[0073] FIG. 8 is a cross-sectional view of the heating unit 10 according to the first embodiment of the present invention, cut at the center M in the longitudinal direction (the position of the positioning hole 29c).

[0074] 8, the positioning holes 29c are formed to penetrate the heat transfer portion 29. Therefore, when the heat transfer portion 29 is pressed between the nip forming member 24 and the base member 26, the positioning protrusions 26a of the base member 26 are inserted into the positioning holes 29c of the heat transfer portion 29. With the positioning protrusions 26a inserted into the positioning holes 29c, the positioning protrusions 26a are engaged with the edges of the positioning holes 29c in the longitudinal direction X or are capable of engaging with the edges in the longitudinal direction X. As a result, the reflecting member 27 is positioned relative to the base member 26 in the longitudinal direction X.

[0075] As described above, in the first embodiment of the present invention, the positioning protrusion 26a and the positioning hole 29c are engaged or engageable with each other, thereby enabling the positioning of the reflecting member 27 in the longitudinal direction X. In particular, in the first embodiment of the present invention, the positioning hole 29c is provided at the longitudinal center M of the heat transfer unit 29, as shown in FIG. 4 , thereby enabling the reflecting member 27 to be positioned with high precision. That is, the longitudinal center M of the heat transfer unit 29 is a portion through which various paper sheets of different widths pass and is also a range subject to temperature control. Therefore, there is little temperature change at the longitudinal center M of the heat transfer unit 29, and dimensional changes in the longitudinal direction X due to thermal expansion are also small. Therefore, by using the longitudinal center M as the reference position for positioning, the influence of dimensional changes due to thermal expansion can be reduced, thereby improving the positioning accuracy of the reflecting member 27. Therefore, according to the first embodiment of the present invention, interference between the reflecting member 27 and surrounding components due to thermal expansion can be effectively avoided.

[0076] The positioning hole 29c is not necessarily provided at the longitudinal center M of the heat transfer portion 29, and may be provided at a position shifted from the longitudinal center M to one side in the longitudinal direction X, as shown in Fig. 9. That is, the position of the positioning hole 29c is preferably the longitudinal center M, but may be at a position shifted from the longitudinal center M as long as it is closer to the longitudinal center M than the positions at which the pair of holes 29a are provided.

[0077] Furthermore, in the first embodiment of the present invention, the positioning of the reflecting member 27 in the longitudinal direction X is achieved by the engagement between the positioning protrusions 26a and the positioning holes 29c, and this engagement is maintained by the pressure applied to the reflecting member 27 by the base member 26 and the nip forming member 24. Therefore, in the first embodiment of the present invention, the number of fixing points can be reduced compared to when the reflecting member 27 is fixed to the support member 25 or the like to be positioned. This makes it possible to suppress deformation of the reflecting member 27 and surrounding components due to constraint of the reflecting member 27 during thermal expansion, and to suppress excess heat transfer from the reflecting member 27 to the surrounding components. Therefore, according to the first embodiment of the present invention, deformation of the reflecting member 27 and surrounding components can be suppressed, preventing damage, and heat transfer from the reflecting member 27 to the fixing belt can be ensured, improving energy efficiency.

[0078] Furthermore, in the first embodiment of the present invention, the mating member against which reflecting member 27 is positioned is not nip forming member 24 or support member 25, which have high thermal conductivity, but rather base member 26, which is made of resin and has lower thermal conductivity than nip forming member 24 and support member 25. This suppresses heat transfer from reflecting member 27 to surrounding members through the positioning location. This suppresses unnecessary heat transfer from reflecting member 27 to surrounding members, and improves heat transfer from reflecting member 27 to the fixing belt, thereby improving energy efficiency. Furthermore, in the first embodiment of the present invention, positioning hole 29c is formed with a smaller opening area than pair of holes 29a. This suppresses a decrease in thermal conductivity between heat transfer portion 29 and nip forming member 24 due to the provision of positioning hole 29c (due to a reduced contact area between heat transfer portion 29 and nip forming member 24).

[0079] Furthermore, in the first embodiment of the present invention, the positioning of reflecting member 27 is performed by engaging positioning protrusions 26a with positioning holes 29c rather than by adhesion using double-sided adhesive tape, which ensures good heat transfer from reflecting member 27 to nip forming member 24 and maintains good positioning of reflecting member 27. That is, according to the first embodiment of the present invention, it is possible to avoid problems such as impeded heat transfer from reflecting member 27 to nip forming member 24 and poor positioning due to misalignment of the bonding surfaces, which occur when double-sided adhesive tape is used to position reflecting member 27 and nip forming member 24, and therefore good heat transfer from reflecting member 27 to nip forming member 24 and good positioning of reflecting member 27 can be achieved.

[0080] 8, positioning protrusion 26a is preferably configured so as not to protrude from positioning hole 29c toward nip forming member 24. In other words, the protrusion amount (height) of positioning protrusion 26a is preferably equal to or less than the depth of positioning hole 29c or the thickness of heat transfer portion 29. By configuring positioning protrusion 26a so as not to protrude from positioning hole 29c toward nip forming member 24, interference between positioning protrusion 26a and nip forming member 24 can be avoided.

[0081] 10, the concave-convex relationship between the positioning portion of reflecting member 27 and the mating positioning portion of base member 26 may be reversed. That is, reflecting member 27 may be provided with positioning protrusion 29d, and base member 26 may be provided with positioning hole 26b.

[0082] Next, another embodiment of the present invention will be described. In the following description, differences from the first embodiment of the present invention will be mainly described, and descriptions of the same parts will be omitted as appropriate.

[0083] <Second embodiment of the present invention> FIG. 11 is a perspective view of a heating unit 10 according to a second embodiment of the present invention.

[0084] 11 , in the second embodiment of the present invention, hole 29a of heat transfer section 29 is arranged so as to be divided into two in a direction intersecting with the longitudinal direction X of heat transfer section 29. A heat transfer assistance section 29e extending in the longitudinal direction X of heat transfer section 29 is provided between the two divided hole sections 29a.

[0085] Heat transfer assistant portion 29e constitutes part of the surface (nip-side facing surface) of heat transfer portion 29 that faces nip formation member 24. Therefore, when heat transfer portion 29 is pressed between nip formation member 24 and base member 26, heat transfer assistant portion 29e comes into contact with nip formation member 24. In this way, in the second embodiment of the present invention, heat transfer between nip formation member 24 and heat transfer portion 29 is promoted via heat transfer assistant portion 29e by heat transfer assistant portion 29e coming into contact with nip formation member 24.

[0086] Incidentally, when hole 29a is provided in heat transfer unit 29, the transfer of heat from the fixing belt to reflecting member 27 can be suppressed when the temperature of the fixing belt rises, but the transfer of heat from heat transfer unit 29 to nip forming member 24 is hindered when the temperature of reflecting member 27 rises. Therefore, in the second embodiment of the present invention, heat transfer assisting portion 29e is provided between hole 29a to alleviate the hinderance of heat transfer from heat transfer unit 29 to nip forming member 24. In other words, the contact area of ​​heat transfer unit 29 with nip forming member 24 is increased by the provision of heat transfer assisting portion 29e, and therefore the transfer of heat from heat transfer unit 29 to nip forming member 24 can be promoted when the temperature of reflecting member 27 rises.

[0087] Like other parts of the heat transfer section 29, the heat transfer assistance section 29e may be in direct or indirect contact with the nip formation member 24. The sizes and shapes of the holes 29a arranged to sandwich the heat transfer assistance section 29e may be the same or different.

[0088] 11, the heat transfer portion 29 may be divided into a plurality of portions along the longitudinal direction X. In this case, gaps 29f are provided between the divided heat transfer portions 29, and the heat transfer portions 29 are spaced apart from each other in the longitudinal direction X.

[0089] In this way, by dividing the heat transfer portion 29 into multiple parts along the longitudinal direction X, it is possible to mitigate dimensional changes that occur when the heat transfer portion 29 thermally expands and deformation associated with the dimensional changes. That is, even if the heat transfer portion 29 thermally expands, the dimensional increase of the heat transfer portion 29 in the longitudinal direction X can be absorbed by the gaps 29f between the heat transfer portions 29, so it is possible to mitigate the overall dimensional changes from the heat transfer portion 29 located on one end side to the heat transfer portion 29 located on the opposite end side and deformation associated with the dimensional changes. This makes it possible to more reliably avoid interference between the reflecting member 27 and surrounding members.

[0090] The number of divisions and division locations of heat transfer section 29 can be changed as needed, but it is preferable that the division locations be at or near both ends of the paper passing width of the paper being used. By locating the division locations at or near both ends of the paper passing width, it is possible to prevent the influence of variations in heat transfer between gaps 29f between heat transfer sections 29 and other areas from affecting the image forming area of ​​the paper. This makes it possible to prevent fixing problems such as uneven gloss.

[0091] Third Embodiment of the Present Invention Next, a third embodiment of the present invention will be described with reference to FIGS.

[0092] Fig. 12 is a cross-sectional view of a heating unit 10 according to a third embodiment of the present invention. Fig. 13 is a view of the heating unit 10 according to the third embodiment of the present invention as seen from the downstream side in the paper transport direction. Meanwhile, Fig. 14 is a view of the heating unit 10 according to the third embodiment of the present invention as seen from the upstream side in the paper transport direction. In Fig. 12, the arrow Z direction is the paper transport direction. In Figs. 13 and 14, the halogen heater 23 is omitted.

[0093] 12 , in the third embodiment of the present invention, engagement protrusions 26c, 26d that engage with nip forming member 24 are provided at the upstream end and downstream end of base member 26 in paper transport direction Z. Meanwhile, engagement holes 24c, 24d that engage with the engagement protrusions 26c, 26d of base member 26 are provided at the upstream end and downstream end of nip forming member 24. Here, each of engagement holes 24c, 24d is configured as a through hole that passes through nip forming member 24, but each of engagement holes 24c, 24d may also be a recess (engagement recess) that does not pass through nip forming member 24.

[0094] 12 , when the engagement protrusions 26c, 26d of the base member 26 engage with the engagement holes 24c, 24d of the nip forming member 24, the nip forming member 24 is fixed to the base member 26. In this state, the reflecting member 27 is sandwiched between the base member 26 and the nip forming member 24, and the reflecting member 27 is held between the base member 26 and the nip forming member 24.

[0095] Some fixing devices are configured to release the pressure between the fixing belt and pressure roller to facilitate paper removal when a paper jam occurs in the nip. When the pressure is released, the pressure between base member 26 and nip forming member 24, which sandwich reflective member 27, is also released. This could cause reflective member 27 to fall off from between base member 26 and nip forming member 24. If reflective member 27 were to fall off and come into contact with the inner circumferential surface of the fixing belt, the coating layer provided on the inner circumferential surface to improve sliding properties and heat absorption efficiency could be damaged, reducing the sliding properties and heat absorption efficiency of the fixing belt and potentially preventing it from performing its intended function.

[0096] Therefore, in the third embodiment of the present invention, base member 26 and nip forming member 24 are configured to be engageable with each other, and reflective member 27 is sandwiched between base member 26 and nip forming member 24 when they are engaged. In this way, reflective member 27 is sandwiched between base member 26 and nip forming member 24, so that reflective member 27 is prevented from falling off even when the pressure between the fixing belt and the pressure roller is released. This makes it possible to prevent damage to the inner circumferential surface of the fixing belt due to reflective member 27 falling off, ensuring good fixing belt function and improving reliability.

[0097] 13, in the third embodiment of the present invention, engagement hole 24d and engagement protrusion 26d provided on the downstream side are disposed at longitudinal center M of nip forming member 24 and base member 26. In this manner, engagement hole 24d and engagement protrusion 26d provided on the downstream side are disposed at longitudinal center M, where dimensional change due to thermal expansion is small, thereby improving the positioning accuracy of base member 26 and nip forming member 24 at longitudinal center M. Furthermore, as in the first embodiment of the present invention, reflection member 27 and nip forming member 24 are also positioned at longitudinal center M (see FIG. 4), and therefore, the positioning accuracy of reflection member 27 and nip forming member 24 at longitudinal center M is also improved. In this way, the same longitudinal center M is used as a reference point between the reflecting member 27 and the nip forming member 24, and between the base member 26 and the nip forming member 24, respectively, improving the relative positioning accuracy between the reflecting member 27, the nip forming member 24 and the base member 26, and effectively avoiding interference between the members.

[0098] On the other hand, as shown in FIG. 14 , the upstream engagement hole 24c and engagement protrusion 26c are located at both longitudinal ends of the longitudinal center M of the nip forming member 24 and the base member 26. Because dimensional changes due to thermal expansion are more likely to occur at both longitudinal ends than at the longitudinal center M, it is preferable to form a gap between the upstream engagement hole 24c and engagement protrusion 26c to avoid interference during thermal expansion. Therefore, in the third embodiment of the present invention, the engagement hole 24c is configured as an elongated hole that is longer than the engagement protrusion 26c. In contrast, the downstream engagement hole 24d and engagement protrusion 26d are located at the longitudinal center M, where dimensional changes due to thermal expansion are less likely, and therefore are configured as a hole and protrusion of the same size.

[0099] The downstream side engagement hole 24d and engagement protrusion 26d are preferably disposed at the longitudinal center M, but may be disposed at a position shifted to one side in the longitudinal direction from the longitudinal center M. In other words, the downstream side engagement hole 24d and engagement protrusion 26d may be disposed at a position shifted from the longitudinal center M as long as they are closer to the longitudinal center M than the upstream side engagement hole 24c and engagement protrusion 26c.

[0100] Furthermore, in the third embodiment of the present invention, similarly to the first embodiment of the present invention, a pair of holes 29a are provided at both longitudinal ends of the heat transfer portion 29 (see FIG. 4). Therefore, in the third embodiment of the present invention, as shown in FIG. 12, the upstream engagement protrusions 26c arranged at both longitudinal ends protrude toward the nip forming member 24 (engagement holes 24c) through holes 29a of the heat transfer portion 29, which are also arranged at both longitudinal ends. In this manner, in the third embodiment of the present invention, by having the upstream engagement protrusions 26c protrude toward the nip forming member 24 through holes 29a of the heat transfer portion 29, it is not necessary to provide a separate hole in the heat transfer portion 29 specifically for protruding the upstream engagement protrusions 26c. This avoids a reduction in the contact area of ​​the heat transfer portion 29 with the nip forming member 24, which would otherwise be caused by providing a separate dedicated hole in the heat transfer portion 29. This prevents a reduction in the heat transfer efficiency from the heat transfer portion 29 to the nip forming member 24 due to a reduction in the contact area.

[0101] 12, in the third embodiment of the present invention, a fitting protrusion 26e for positioning the base member 26 on the support member 25 is provided on the base member 26. Meanwhile, the support member 25 is provided with a fitting hole 25e into which the fitting protrusion 26e of the base member 26 is inserted and fitted.

[0102] 12, if the insertion length of fitting protrusion 26e into fitting hole 25e is A and the distance in the approach direction between fitting protrusion 26e and support member 25 at a portion where reflecting member 27 moves to approach support member 25 when fitting protrusion 26e moves in the direction to be pulled out of fitting hole 25e (to the right in FIG. 12) is B, fitting protrusion 26e will be difficult to pull out if distance B in the approach direction is smaller than insertion length A. In other words, before fitting protrusion 26e is pulled out, reflecting member 27 comes into contact with support member 25, preventing fitting protrusion 26e from being pulled out.

[0103] By making the distance B in the approach direction smaller than the insertion length A, the fitting protrusion 26e is less likely to be pulled out, thereby preventing the base member 26 from accidentally falling off the support member 25. Furthermore, by preventing the base member 26 from falling off the support member 25, the base member 26, the reflecting member 27, and the nip forming member 24 are held together with the support member 25 as an integrated unit, preventing the base member 26, the reflecting member 27, and the nip forming member 24 from falling off when the pressure between the fixing belt and the pressure roller is released. This prevents damage to the fixing belt due to the base member 26, the reflecting member 27, and the nip forming member 24 falling off. Furthermore, because the base member 26, the reflecting member 27, and the nip forming member 24 can be handled as an integrated unit with the support member 25, the work of assembling the unit into the fixing belt becomes easier.

[0104] If there are multiple portions where reflective member 27 approaches support member 25 when fitting protrusion 26e is pulled out, it is sufficient that distance B in the approach direction of at least one of these approaching portions is smaller than insertion length A of fitting protrusion 26e. Furthermore, if distance B in the approach direction is made smaller than insertion length A, reflection member 27 and support member 25 will interfere with each other when a unit made up of base member 26, reflection member 27, and nip forming member 24 is assembled to support member 25. In this case, reflection member 27 can be elastically deformed to temporarily widen distance B in the approach direction before assembly.

[0105] Although the embodiments of the present invention have been described above, the present invention can also be applied to heating devices other than fixing 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.

[0106] Furthermore, to summarize aspects of the present invention, the present invention includes at least the following aspects.

[0107] [First aspect] A first aspect is a heating device including a first rotating body, a second rotating body arranged to face an outer peripheral surface of the first rotating body, a nip forming member that sandwiches the first rotating body between itself and the second rotating body to form a nip portion where the first rotating body and the second rotating body come into contact, a heat source arranged inside the first rotating body, a reflecting member arranged inside the first rotating body, a support member that receives the pressure force of the second rotating body via the nip forming member, and a base member interposed between the support member and the nip forming member, The reflecting member has a reflecting portion that is arranged opposite the heat source and reflects the heat of the heat source onto the inner surface of the first rotating body, and a heat transfer portion that is pressurized between the base member and the nip forming member, and the heat transfer portion has a hole or recess that is arranged so that the contact area of ​​the heat transfer portion with the nip forming member is smaller at both ends of the longitudinal direction than the longitudinal center of the heat transfer portion, and a positioning portion that is arranged at a position closer to the longitudinal center than the hole or recess and positions the reflecting member with respect to the base member, making this a heating device.

[0108] [Second aspect] In a second aspect, in the first aspect, the positioning portion is disposed at the center of the heat transfer portion in the longitudinal direction.

[0109] [Third aspect] In a third aspect, in the first or second aspect, the holes or recesses are arranged separately in a direction intersecting the longitudinal direction of the heat transfer section, and the heat transfer section has a heat transfer assisting section arranged so as to be in contact with the nip forming member between the holes or recesses arranged separately in a direction intersecting the longitudinal direction.

[0110] [Fourth aspect] A fourth aspect is any one of the first to third aspects, wherein the heat transfer portion is divided into a plurality of portions in the longitudinal direction of the heat transfer portion.

[0111] [Fifth aspect] A fifth aspect is any one of the first to fourth aspects, in which an engagement protrusion is provided at each of the upstream end and downstream end of the base member in the conveying direction of the sheet passing through the nip portion, and the nip forming member has an engagement hole portion that engages with the engagement protrusion.

[0112] [Sixth aspect] A sixth aspect is the fifth aspect, wherein the engaging projection is arranged so as to protrude toward the nip forming member through the hole of the heat transfer portion.

[0113] [Seventh aspect] A seventh aspect is any one of the first to sixth aspects, wherein the base member has an engaging protrusion that is inserted into and engages with an engaging hole in the support member, and when the engaging protrusion moves in a direction to be pulled out of the engaging hole, the distance in the approach direction between the support member and the part of the reflective member that moves to approach the support member is smaller than the insertion length of the engaging protrusion into the engaging hole.

[0114] [Eighth aspect] An eighth aspect is a fixing device that uses the heating device of any one of the first to seventh aspects to heat a recording medium bearing an unfixed image, and fixes the unfixed image to the recording medium.

[0115] [Ninth aspect] A ninth aspect is an image forming apparatus including the heating device according to any one of the first to seventh aspects or the fixing device according to the tenth aspect. [Explanation of symbols]

[0116] 20 Fixing device (heating device) 21 Fixing belt (first rotating body) 22 Pressure roller (second rotating body) 23 Halogen heater (heat source) 24 Nip forming member 25 Support member 25e fitting hole 26 Base material 26a Positioning protrusion (positioning part) 26b Positioning hole (positioning part) 26c Engagement protrusion 26d Engagement protrusion 26e mating protrusion 27 Reflective material 28 Reflector 29 Heat Transfer Section 29a hole 29b Recess 29c Positioning hole (positioning part) 29d Positioning protrusion (positioning part) 29e Heat transfer auxiliary part 1000 Image forming device A Insertion length of mating projection B. Distance between the nip forming member and the support member in the approach direction P Paper (recording media, sheets) [Prior art documents] [Patent documents]

[0117] [Patent Document 1] Japanese Patent Application Publication No. 2023-106335

Claims

1. a first rotating body; a second rotating body disposed opposite to an outer peripheral surface of the first rotating body; a nip forming member that sandwiches the first rotating body between itself and the second rotating body to form a nip portion where the first rotating body and the second rotating body are in contact with each other; a heat source disposed inside the first rotating body; a reflecting member disposed inside the first rotating body; a support member that receives the pressure of the second rotating body through the nip forming member; a base member interposed between the support member and the nip forming member; A heating device comprising: the reflecting member has a reflecting portion that is disposed to face the heat source and reflects heat from the heat source to an inner circumferential surface of the first rotating body, and a heat transfer portion that is pressed between the base member and the nip forming member, A heating device characterized in that the heat transfer section has a hole or recess that is arranged so that the contact area of ​​the heat transfer section with the nip forming member is smaller at both ends of the longitudinal direction of the heat transfer section than the longitudinal center of the heat transfer section, and a positioning section that is arranged at a position closer to the longitudinal center than the hole or recess and positions the reflective member with respect to the base member.

2. The heating device according to claim 1 , wherein the positioning portion is disposed at the center in the longitudinal direction of the heat transfer portion.

3. the holes or the recesses are arranged separately in a direction intersecting with the longitudinal direction of the heat transfer portion, The heating device according to claim 1 , wherein the heat transfer section has a heat transfer assisting section arranged so as to contact the nip forming member between the holes or between the recesses arranged in a direction intersecting the longitudinal direction.

4. The heating device according to claim 1 , wherein the heat transfer portion is divided into a plurality of portions along the longitudinal direction of the heat transfer portion.

5. an engaging projection is provided at each of an upstream end and a downstream end of the base member in a conveying direction of the sheet passing through the nip portion; The heating device according to claim 1 , wherein the nip forming member has an engagement hole that engages with the engagement protrusion.

6. The heating device according to claim 5 , wherein the engaging projection is disposed so as to protrude toward the nip forming member through the hole in the heat transfer portion.

7. the base member has a fitting protrusion that is inserted into and fitted into a fitting hole of the support member, 2. The heating device according to claim 1, wherein when the engagement protrusion moves in a direction to be pulled out of the engagement hole, the distance in the approach direction between the part of the reflective member that moves to approach the support member and the support member is smaller than the insertion length of the engagement protrusion into the engagement hole.

8. 10. A fixing device, comprising: a heating device according to claim 1, for heating a recording medium carrying an unfixed image thereon; and fixing the unfixed image on the recording medium.

9. An image forming apparatus comprising the heating device according to claim 1.

Images