Heating device, fixing device and image forming apparatus

Abstract

To prevent a variation in temperature in a heating device.SOLUTION: A length La between an end 55a on one side in a longitudinal direction X of a substrate 55 of a heater 23 and an end 60a on one side of a substrate of a heating area 60, is longer than a length Lb between an end 55b on the other side in the longitudinal direction X of the substrate 55 and an end 60b on the other side of the heating area 60. Heat transfer auxiliary members 28 are arranged on at least one side and the other side of the heating area 60 in the longitudinal direction X of the substrate 55. The volume of a portion 281 of the heat transfer auxiliary member 28 arranged on one side of the heating area 60 is smaller than the volume of a portion 282 of the heat transfer auxiliary member 28 arranged on the other side of the heating area 60.SELECTED DRAWING: Figure 7

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 mounted in an image forming apparatus such as a copying machine or a printer, a fixing device is known that heats a sheet carrying an unfixed image to fix the unfixed image on the sheet.

[0003] In a fixing device, a heating source such as a heater is arranged symmetrically with respect to the center of the sheet passage area through which the sheet passes so that the sheet can be heated uniformly. However, for various reasons, other components constituting the fixing device may not necessarily be arranged symmetrically with respect to the center of the sheet passage area. In such cases, the amount of heat transferred from the heat generating element of the heating source to the surrounding components is not the same on one end and the other end of the heating source with respect to the center of the sheet passage area. This results in a problem of insufficient heat to heat the sheet, particularly on the side with a large amount of heat transfer, and conversely, a significant temperature rise on the side with a small amount of heat transfer.

[0004] To address this issue, Patent Document 1 (JP 2008-76857 A) proposes a configuration in which the amount of heat generated per unit area of ​​the heat generating element is made different between one end and the other end of the heat source. In this case, the amount of heat generated on the higher temperature side is made lower than the amount of heat generated on the lower temperature side, thereby suppressing temperature variations in the fixing device. Summary of the Invention [Problem to be solved by the invention]

[0005] However, as described above, if the heat generation amount per unit area of ​​the heat generating element is different between one end and the other end of the heat source, temperature variations in the fixing device become significant when the heat generating element is operated at maximum heat generation. In particular, in areas where the heat generation amount is large, thermal expansion of the heat source and heated components becomes significant locally, which may result in damage to components. Therefore, this method of differentiating the heat generation amount per unit area of ​​the heat generating element between one end and the other end of the heat source is not desirable as a measure to suppress temperature variations in the heating device. Therefore, an alternative solution is required. [Means for solving the problem]

[0006] In order to solve the above problem, the present invention provides a heating device comprising a rotatable first rotating body, a rotatable second rotating body that contacts the outer peripheral surface of the first rotating body to form a nip portion, a heat source that heats the first rotating body, and a heat transfer auxiliary member that contacts the heat source, wherein the heat source has a base material and a heating element provided on the base material, the base material has a heating area in which the heating element is arranged, the length between one longitudinal end of the base material and the one end of the heating area is longer than the length between the other longitudinal end of the base material and the other end of the heating area, the heat transfer auxiliary member is arranged on at least the one side and the other side of the heating area in the longitudinal direction of the base material, and the volume of the portion of the heat transfer auxiliary member that is arranged on the one side of the heating area is smaller than the volume of the portion of the heat transfer auxiliary member that is arranged on the other side of the heating area. [Effects of the Invention]

[0007] According to the present invention, it is possible to suppress temperature variations in the heating device. [Brief explanation of the drawings]

[0008] [Figure 1] 1 is a schematic diagram illustrating the configuration of an image forming apparatus according to an embodiment of the present invention. [Figure 2] FIG. 2 is a schematic diagram illustrating the configuration of a fixing device according to the present embodiment. [Figure 3] FIG. 2 is a cross-sectional view of the fixing belt according to the embodiment. [Figure 4] FIG. 2 is a plan view of the heater according to the embodiment. [Figure 5] 1 is a perspective view showing a state in which a connector as a power supply member is connected to the heater according to the embodiment. FIG. [Figure 6] FIG. 2 is a plan view of the heater according to the embodiment. [Figure 7] 1 is a plan view showing a configuration according to a first embodiment of the present invention. [Figure 8] 1 is a side view showing a configuration according to a first embodiment of the present invention. [Figure 9] FIG. 10 is a plan view showing a configuration according to a second embodiment of the present invention. [Figure 10] 10A and 10B are plan views showing modified examples of the electrode portion-side protrusions. [Figure 11] FIG. 10 is a plan view showing a configuration according to a third embodiment of the present invention. [Figure 12] FIG. 10 is a side view showing a configuration according to a third embodiment of the present invention. [Figure 13] FIG. 10 is a diagram showing a configuration according to a fourth embodiment of the present invention. [Figure 14] 10A and 10B are diagrams showing modified examples of the hole portion; [Figure 15] FIG. 10 is a plan view showing a configuration according to a fifth embodiment of the present invention. [Figure 16] 10A and 10B are diagrams illustrating an example in which the hole portion is a through-hole. [Figure 17] 10A and 10B are diagrams illustrating an example in which the hole portion is a hole having a bottom portion. [Figure 18] FIG. 10 is a diagram showing an example in which two holes are provided and a thermistor and a thermostat are disposed in these holes. [Figure 19] FIG. 10 is a diagram showing an example in which electrode portions are provided on both ends of a substrate. [Figure 20] FIG. 10 is a diagram showing a configuration of a fixing device different from that of the above embodiment. [Figure 21] FIG. 10 is a diagram showing a configuration of a fixing device different from that of the above embodiment. [Figure 22]FIG. 10 is a diagram showing a configuration of a fixing device different from that of the above embodiment. [Figure 23] FIG. 10 is a diagram showing a configuration of a fixing device different from that of the above embodiment. [Figure 24] FIG. 10 is a diagram showing a configuration of an image forming apparatus different from that of the above embodiment. [Figure 25] 25 is a diagram showing the configuration of the fixing device shown in FIG. 24. FIG. [Figure 26] FIG. 26 is a plan view of the heater shown in FIG. 25. [Figure 27] FIG. 26 is a perspective view of the heater and heater holder shown in FIG. 25. [Figure 28] 26 is a diagram showing a method of attaching a connector to the heater shown in FIG. 25. [Figure 29] 25 is a diagram showing the arrangement of temperature sensors and thermostats included in the fixing device shown in FIG. 24. FIG. [Figure 30] FIG. 29 is a view showing a groove portion of the flange shown in FIG. 28. [Figure 31] FIG. 10 is a diagram showing a configuration of a fixing device different from that of the above embodiment. [Figure 32] 32 is a perspective view of the heater, the first high thermal conductive member, and the heater holder shown in FIG. 31. FIG. [Figure 33] FIG. 2 is a plan view of the heater showing the arrangement of the first high thermal conductivity members. [Figure 34] 10 is a plan view of a heater showing another example of the arrangement of the first high thermal conductivity members. FIG. [Figure 35] FIG. 10 is a plan view of a heater showing yet another example of the arrangement of the first high thermal conductivity members. [Figure 36] FIG. 2 is a plan view of the heater showing enlarged divided regions. [Figure 37] FIG. 10 is a diagram showing a configuration of a fixing device different from that of the above embodiment. [Figure 38] 38 is a perspective view of the heater, the first high thermal conductive member, the second high thermal conductive member, and the heater holder shown in FIG. 37. FIG. [Figure 39] FIG. 3 is a plan view of the heater showing the arrangement of the first and second high thermal conductive members. [Figure 40]10 is a plan view of a heater showing another example of the arrangement of the first and second high thermal conductive members. FIG. [Figure 41] FIG. 10 is a plan view of a heater showing yet another example of the arrangement of second high-thermal-conductivity members. [Figure 42] FIG. 10 is a diagram showing a configuration of a fixing device different from that of the above embodiment. [Figure 43] FIG. 1 illustrates the atomic crystal structure of graphene. [Figure 44] FIG. 1 illustrates the atomic crystal structure of graphite. DETAILED DESCRIPTION OF THE INVENTION

[0009] The present invention will be described below with reference to the accompanying drawings. In each drawing for explaining the present invention, components such as members and components having the same function or shape are designated by the same reference numerals as far as they can be distinguished, and descriptions thereof will be omitted once they have been described.

[0010] FIG. 1 is a schematic diagram of an image forming apparatus according to one embodiment of the present invention. In this specification, the term "image forming apparatus" includes a printer, a copier, a facsimile, a printing machine, or a multifunction machine that combines two or more of these. Furthermore, the term "image formation" used in the following description refers not only to the formation of meaningful images such as characters and figures, but also to the formation of meaningless images such as patterns. First, the overall configuration and operation of the image forming apparatus according to this embodiment will be described with reference to FIG. 1.

[0011] As shown in FIG. 1, the image forming apparatus 100 according to this embodiment includes an image forming unit 200 that forms an image on a sheet-like recording medium such as paper, a fixing unit 300 that fixes the image on the recording medium, a recording medium supply unit 400 that supplies the recording medium to the image forming unit 200, and a recording medium discharge unit 500 that discharges the recording medium outside the apparatus.

[0012] The image forming section 200 is provided with four process units 1Y, 1M, 1C, and 1Bk as image-forming units, an exposure device 6 that forms an electrostatic latent image on the photosensitive member 2 provided in each of the process units 1Y, 1M, 1C, and 1Bk, and a transfer device 8 that transfers the image onto a recording medium.

[0013] Each of the process units 1Y, 1M, 1C, and 1Bk has basically the same configuration, except that it contains toner (developer) of a different color: yellow, magenta, cyan, or black, which corresponds to the color separation components of a color image. Specifically, each of the process units 1Y, 1M, 1C, and 1Bk includes a photoconductor 2 as an image carrier that carries an image on its surface, a charging member 3 that charges the surface of the photoconductor 2, a developing device 4 that supplies toner as developer to the surface of the photoconductor 2 to form a toner image, and a cleaning member 5 that cleans the surface of the photoconductor 2.

[0014] The transfer device 8 includes an intermediate transfer belt 11, a primary transfer roller 12, and a secondary transfer roller 13. The intermediate transfer belt 11 is an endless belt member that is stretched by a plurality of support rollers. Four primary transfer rollers 12 are provided inside the intermediate transfer belt 11. Each primary transfer roller 12 contacts each photoconductor 2 via the intermediate transfer belt 11, thereby forming a primary transfer nip between the intermediate transfer belt 11 and each photoconductor 2. The secondary transfer roller 13 contacts the outer peripheral surface of the intermediate transfer belt 11, thereby forming a secondary transfer nip.

[0015] The fixing section 300 is provided with a fixing device 20. The fixing device 20 includes a fixing belt 21 made of an endless belt, and a pressure roller 22 as an opposing member facing the fixing belt 21. The fixing belt 21 and the pressure roller 22 come into contact with each other on their outer circumferential surfaces to form a nip portion (fixing nip).

[0016] The recording medium supply unit 400 is provided with a paper feed cassette 14 that stores paper P as a recording medium, and a paper feed roller 15 that feeds paper P from the paper feed cassette 14. Hereinafter, the "recording medium" will be described as "paper," but the "recording medium" is not limited to paper (paper). The "recording medium" includes not only paper (paper), but also transparencies, fabrics, metal sheets, plastic films, and prepreg sheets made of carbon fiber pre-impregnated with resin. Furthermore, "paper" includes not only plain paper, but also cardboard, postcards, envelopes, thin paper, coated paper (coated paper, art paper, etc.), tracing paper, and the like.

[0017] The recording medium ejection section 500 is provided with a pair of ejection rollers 17 for ejecting the paper P outside the image forming apparatus, and an ejection tray 18 on which the paper P ejected by the ejection rollers 17 is placed.

[0018] Next, the printing operation of the image forming apparatus 100 according to this embodiment will be described with reference to FIG.

[0019] When a printing operation is started in the image forming apparatus 100, the photosensitive elements 2 of the process units 1Y, 1M, 1C, and 1Bk and the intermediate transfer belt 11 of the transfer device 8 start to rotate. Also, the paper feed roller 15 starts to rotate, and a sheet of paper P is fed out of the paper feed cassette 14. The fed sheet of paper P comes into contact with a pair of timing rollers 16 and stops, and the transport of the sheet of paper P is temporarily stopped until an image to be transferred onto the sheet of paper P is formed.

[0020] In each process unit 1Y, 1M, 1C, and 1Bk, the surface of the photoconductor 2 is first charged to a uniform high potential by the charging member 3. Next, the exposure device 6 exposes the surface (charged surface) of each photoconductor 2 based on the image information of the original document read by the document reader or the print image information instructed to be printed from a terminal. This reduces the potential of the exposed area, forming an electrostatic latent image on the surface of each photoconductor 2. The developing device 4 then supplies toner to this electrostatic latent image, forming a toner image on each photoconductor 2. As each photoconductor 2 rotates, the toner image formed on each photoconductor 2 reaches the primary transfer nip (the position of the primary transfer roller 12), where it is transferred sequentially onto the rotating intermediate transfer belt 11 so as to overlap one another. In this way, a full-color toner image is formed on the intermediate transfer belt 11. In the image forming apparatus 100, it is possible to form a monochrome image using any one of the process units 1Y, 1M, 1C, and 1Bk, or to form a two-color or three-color image using any two or three of the process units. After the toner image is transferred from the photoreceptor 2 to the intermediate transfer belt 11, the cleaning member 5 removes residual toner and the like from each photoreceptor 2.

[0021] The toner image transferred onto intermediate transfer belt 11 is transported to the secondary transfer nip (position of secondary transfer roller 13) as intermediate transfer belt 11 rotates, and is transferred onto the transported paper P by timing roller 16. Thereafter, paper P is transported to fixing device 20, where the toner image on paper P is heated and pressed by fixing belt 21 and pressure roller 22, thereby fixing the toner image to paper P. Paper P is then transported to recording medium discharge section 500, and is discharged onto paper discharge tray 18 by paper discharge roller 17. This completes the series of printing operations.

[0022] Next, the configuration of the fixing device according to this embodiment will be described in detail with reference to FIG.

[0023] As shown in FIG. 2, the fixing device 20 according to this embodiment includes a fixing belt 21, a pressure roller 22, a heater 23, a heat equalizer plate 28, a heater holder 24, a stay 25, a guide member 26, a temperature sensor 27, and the like.

[0024] The fixing belt 21 is a rotating body (first rotating body or fixing member) that comes into contact with the unfixed toner carrying surface of the paper P to fix the unfixed toner (unfixed image) to the paper P, and is made of a flexible endless belt. The diameter of the fixing belt 21 is set to be, for example, 15 to 120 mm. In this embodiment, the inner diameter of the fixing belt 21 is set to be 25 mm.

[0025] As shown in FIG. 3, the fixing belt 21 is, for example, formed by laminating a substrate 210, an elastic layer 211, and a release layer 212 in this order from the inner circumferential surface to the outer circumferential surface, with the total thickness set to 1 mm or less. The substrate 210 has a thickness of 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 211 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 includes the elastic layer 211, which prevents minute irregularities from forming on the surface of the fixing belt 21 at the nip portion, thereby facilitating uniform heat transfer to the toner image on the paper P. The release layer 212 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 the release layer 212, so that the release properties (peelability) of the toner (toner image) are ensured.

[0026] 2, pressure roller 22 is a rotating body (second rotating body or opposing member) disposed opposite the outer circumferential surface of fixing belt 21. Pressure roller 22 contacts heater 23 via fixing belt 21, forming a nip N between pressure roller 22 and fixing belt 21.

[0027] Pressure roller 22 is a roller with an outer diameter set to, for example, 25 mm, and has a hollow iron core material 220, an elastic layer 221 provided on the outer peripheral surface of this core material 220, and a release layer 222 provided on the outer peripheral surface of elastic layer 221. Elastic layer 221 has a thickness of, for example, 3.5 mm and is made of silicone rubber or the like. Release layer 222 has a thickness of, for example, about 40 μm and is made of fluororesin or the like.

[0028] The heater 23 is a heat source that heats the inside of the fixing belt 21. The heater 23 is a planar or plate-shaped heater that extends longitudinally across the length of the fixing belt 21 (the paper width direction that intersects with the paper transport direction), and is disposed so as to contact the inner circumferential surface of the fixing belt 21. The heater 23 according to this embodiment includes a base material 55, a resistance heating element 56 provided on the base material 55, an insulating layer 57 that covers the resistance heating element 56, and the like.

[0029] 2, in this embodiment, the resistance heating elements 56 are provided on the surface of the base material 55 on the side of the nip portion N, but they may also be provided on the opposite surface. In this case, since the heat from each resistance heating element 56 is transferred to the fixing belt 21 via the base material 55, it is preferable that the base material 55 be made of a material with high thermal conductivity, such as aluminum nitride.

[0030] The heat equalizer 28 is a heat transfer assisting member that contacts the heater 23 and transfers the heat of the heater 23 in the longitudinal direction of the fixing belt 21 to achieve uniform heat transfer. In this embodiment, the heat equalizer 28 is disposed so as to contact the surface (base material 55) of the heater 23 opposite the surface on the nip portion N side. The heat equalizer 28 is made of a metal material with high thermal conductivity. Specifically, copper, aluminum, silver, or the like is used as the material for the heat equalizer 28. By providing such a heat equalizer 28, the heat from the high-temperature portion of the heater 23 is dispersed to the surrounding low-temperature portion, thereby suppressing the maximum temperature that the heater 23 can reach.

[0031] The heater holder 24 is disposed inside the fixing belt 21 and is a heat source holding member that holds the heater 23. The heater holder 24 also holds the heat equalizing plate 28 in addition to the heater 23. The heater holder 24 is preferably made of a heat-resistant material because it is prone to becoming hot due to the heat from the heater 23. For example, if the heater holder 24 is made of a heat-resistant resin with low thermal conductivity, such as LCP or PEEK, the heat resistance of the heater holder 24 is ensured while heat transfer from the heater 23 to the heater holder 24 is suppressed, allowing the fixing belt 21 to be heated efficiently.

[0032] The stay 25 is a support member that supports the heater holder 24. The stay 25 supports the surface of the heater holder 24 opposite to the surface on the pressure roller 22 side across the longitudinal direction of the fixing belt 21, thereby preventing the heater holder 24 from being deflected by the pressure force of the pressure roller 22 and forming a nip portion N of uniform width between the fixing belt 21 and the pressure roller 22. The stay 25 is preferably made of an iron-based metal material such as SUS or SECC to ensure its rigidity.

[0033] The guide members 26 are members that guide the fixing belt 21 from the inside. The guide members 26 have an arc-shaped cross section that follows the inner circumferential surface of the fixing belt 21, and are respectively disposed on the upstream side and downstream side of the heater 23 in the rotation direction (the direction of the arrow in FIG. 2) of the fixing belt 21. In this embodiment, each guide member 26 is configured integrally with the heater holder 24, but may be configured separately.

[0034] The temperature sensor 27 is a temperature detection member that detects the temperature of the heater 23. Known temperature sensors such as a thermopile, a thermistor, or an NC sensor can be used as the temperature sensor 27. In this embodiment, a contact-type temperature sensor that comes into contact with the heater 23 via the heat equalizer plate 28 is used. Alternatively, the temperature sensor 27 may be a non-contact-type temperature sensor.

[0035] The fixing device 20 according to this embodiment operates as follows.

[0036] 2, when pressure roller 22 is driven to rotate, the driving force is transmitted to fixing belt 21, causing fixing belt 21 to rotate. Then, fixing belt 21 is heated by heater 23, and fixing belt 21 is heated. The temperature of heater 23 at this time is detected by temperature sensor 27, and the amount of heat generated by heater 23 is controlled based on the detected temperature. This maintains the temperature of fixing belt 21 at a temperature at which an image can be fixed (fixing temperature). Then, when paper P carrying an unfixed image is transported between fixing belt 21 and pressure roller 22 (nip portion N), the toner image on paper P is heated and pressurized by fixing belt 21 and pressure roller 22, and the image is fixed to paper P.

[0037] FIG. 4 is a plan view of the heater according to this embodiment.

[0038] 4, the heater 23 according to this embodiment has a plate-shaped substrate 55 extending in one direction (the direction of the arrow X in FIG. 4). The substrate 55 is disposed so that its longitudinal direction X is oriented along the longitudinal direction of the fixing belt 21 or the axial direction of the pressure roller 22. Two resistance heating elements 56 extend in the longitudinal direction X of the substrate 55 on the surface thereof and are disposed side by side in the lateral direction Y of the substrate 55. Note that the "lateral direction" here refers to a direction perpendicular to the longitudinal direction X along the surface of the substrate 55 on which the resistance heating elements 56 are provided.

[0039] As shown in Fig. 4, a pair of electrode portions 58 are provided on one side of the base material 55 in the longitudinal direction X. Each electrode portion 58 is connected to a corresponding resistance heating element 56 via a power supply line 59. Furthermore, the ends of each resistance heating element 56 opposite to the end connected to the electrode portion 58 are connected to each other via another power supply line 59. Each resistance heating element 56 and each power supply line 59 are covered with an insulating layer 57 to ensure insulation. In contrast, each electrode portion 58 is not covered by the insulating layer 57 and is exposed so that a connector serving as a power supply terminal, which will be described later, can be connected thereto.

[0040] The substrate 55 is made of a material with excellent heat resistance and insulation, such as ceramics such as alumina or aluminum nitride, glass, mica, or polyimide. Alternatively, the substrate 55 may be made of a metal (conductive material) such as stainless steel (SUS), iron, or aluminum, on which an insulating layer is formed. In particular, when the substrate 55 is made of a highly thermally conductive material such as aluminum, copper, silver, graphite, or graphene, the heater 23 can be uniformly heated, thereby improving image quality. The insulating layer 57 is made of a material with excellent heat resistance and insulation, such as ceramics such as alumina or aluminum nitride, glass, mica, or polyimide. The resistance heating element 56 is formed, for example, by applying a paste containing silver palladium (AgPd) and glass powder to the surface of the substrate 55 by screen printing or the like, and then firing the substrate 55. Alternatively, a resistance material such as silver alloy (AgPt) or ruthenium oxide (RuO) can be used as the material for the resistance heating element 56. The electrode portion 58 and the power supply line 59 are formed by screen printing silver (Ag) or silver palladium (AgPd).

[0041] FIG. 5 is a perspective view showing a state in which a connector 40 serving as a power supply member is connected to the heater 23. As shown in FIG.

[0042] 5, connector 40 has a resin housing 41, a plurality of contact terminals 42 provided in housing 41, and a power supply harness 43 connected to each of contact terminals 42. Each contact terminal 42 is made of an elastically deformable member such as a leaf spring.

[0043] 5, the connector 40 is attached so as to sandwich the heater 23 and the heater holder 24 together. As a result, the heater 23 and the heater holder 24 are held together by the connector 40. In this state, the tips (contact portions 42a) of the contact terminals 42 of the connector 40 elastically contact (pressure-contact) with the corresponding electrode portions 58, thereby electrically connecting the contact terminals 42 and the electrode portions 58. As a result, power can be supplied to the heater 23 (each resistance heating element 56) from a power source provided in the image forming apparatus via the connector 40.

[0044] In the heater according to this embodiment, as shown in FIG. 6 , the electrode portion 58 is provided only on one side of the substrate 55 in the longitudinal direction X, and no electrode portion 58 is provided on the other side. Therefore, it is necessary to secure a space for arranging the electrode portion 58 on one side of the substrate 55. If the space for arranging the electrode portion 58 is secured, the substrate 55 becomes longer on one side. That is, in this embodiment, the electrode portion 58 is provided only on one side of the substrate 55. Therefore, the length La between the electrode portion-side end 60 a of the heat generating region 60 and the electrode portion-side end 55 a of the substrate 55 is longer than the length Lb between the end 60 b of the heat generating region 60 on the side opposite to the electrode portion side (hereinafter referred to as the “anti-electrode portion side”) and the anti-electrode portion-side end 55 b of the substrate 55. The “heat generating region” here refers to the region on the substrate 55 where each resistive heating element 56 is arranged. It does not refer to the region where one resistive heating element 56 is arranged, but rather refers to the region from end to end of all the resistive heating elements 56 on the substrate 55. The same applies to the "heat generating region" in the following description.

[0045] In this configuration in which the substrate 55 of the heater 23 is elongated on one side of the longitudinal direction X, when the heater 23 is activated, the amount of heat transferred to the substrate 55 is greater at the longer end of the substrate 55 than at the shorter end. In other words, more heat transfers to the end where the electrode portion 58 is provided. Therefore, the heater temperature tends to be relatively lower on the electrode portion side than on the opposite electrode portion side. In particular, when the fixing device is first started up after the image forming apparatus is turned on, the temperature of the fixing device is low, so the heater temperature on the electrode portion side does not rise easily. This can lead to temperature variations in the fixing belt, which can result in inconsistent heating of paper passing through the nip. Therefore, in this embodiment, the following measures are taken to suppress such temperature variations in the fixing device.

[0046] The configuration of the fixing device according to this embodiment is shown in Figures 7 and 8. Figure 7 is a plan view of the heater 23 and the heat equalizer plate 28 as viewed from a direction Z perpendicular to a contact surface 280 of the heat equalizer plate 28 that contacts the heater 23 (see Figure 8), and Figure 8 is a side view of the heater 23 and the heat equalizer plate 28 as viewed from the short-side direction Y of the substrate 55 (see Figure 7). The fixing belt, pressure roller, etc. are omitted from Figures 7 and 8.

[0047] As shown in FIG. 7 , the heating region 60 of the heater 23 is arranged symmetrically with respect to the widthwise center m of the maximum sheet-passing region W, extending beyond the maximum sheet-passing region W through which the widest sheet P passes, so that any size sheet can be uniformly heated across its width (the direction perpendicular to the sheet-passing direction along the sheet surface). That is, the length Ea from the widthwise center m of the maximum sheet-passing region W to the electrode-side edge 60a of the heating region 60 is the same as the length Eb from the widthwise center m of the maximum sheet-passing region W to the non-electrode-side edge 60b of the heating region 60 (Ea = Eb). Note that this embodiment employs a so-called center-based transport method, in which sheets of various widths are transported based on their respective widthwise centers. Therefore, the widthwise center m of the maximum sheet-passing region W is also the widthwise center of the sheet-passing region for sheets other than the widest sheet.

[0048] On the other hand, the substrate 55 of the heater 23 is formed longer on the electrode portion side, and is therefore arranged asymmetrically with respect to the widthwise center m of the maximum paper passing region W. That is, the length Da from the widthwise center m of the maximum paper passing region W to the electrode portion side edge 55a of the substrate 55 is set to be longer than the length Db from the widthwise center m of the maximum paper passing region W to the anti-electrode portion side edge 55b of the substrate 55 (Da>Db). Therefore, as described above, the amount of heat that moves from the heat generating region 60 to the electrode portion side of the substrate 55 is greater than the amount of heat that moves to the anti-electrode portion side.

[0049] In this embodiment, the heat equalizer 28, which transfers heat from the heater 23 in the longitudinal direction of the fixing belt 21, is provided continuously in the longitudinal direction X so as to include at least the heat-generating region H of the heater 23. Therefore, when the heat-generating region 60 (resistance heating element 56) generates heat, the heat from the heat-generating region 60 is transferred in the longitudinal direction X of the base material 55 by the heat equalizer 28. Furthermore, in this embodiment, the heat equalizer 28 is disposed so as to protrude toward the electrode portion side and the counter-electrode portion side from the heat-generating region 60 (resistance heating element 56). Therefore, the heat from the heat-generating region 60 transfers to both the electrode portion side and the counter-electrode portion side via the heat equalizer 28. At this time, the amount of heat transferred to the heat equalizer 28 affects the temperature distribution of the heater 23 and the fixing belt 21. Therefore, if the amount of heat transferred to the heat equalizer 28 can be adjusted on the electrode portion side and the counter-electrode portion side, the temperature distribution of the heater 23 and the fixing belt 21 can be adjusted. Taking this into consideration, in this embodiment, the heat capacity of the electrode portion side protrusion 281 that protrudes toward the electrode portion side from the heat generation area 60 of the heat equalizer 28 and the heat capacity of the counter-electrode portion side protrusion 282 that protrudes toward the counter-electrode portion side from the heat generation area 60 of the heat equalizer 28 are adjusted as follows.

[0050] Since the heat capacity of an object is proportional to the mass or volume of the object, in the present embodiment, the volume of the electrode portion side protrusion 281 of the heat spreader 28 is made smaller than the volume of the counter electrode portion side protrusion 282 of the heat spreader 28. Therefore, in the present embodiment, as shown in FIG. 7, the length Ra of the electrode portion side protrusion 281 is made shorter than the length Rb of the counter electrode portion side protrusion 282 (Ra < Rb). On the other hand, the widths Sa and Sb of the electrode portion side protrusion 281 and the counter electrode portion side protrusion 282 are set to the same size (Sa = Sb). Further, as shown in FIG. 8, the thicknesses Ta and Tb of the electrode portion side protrusion 281 and the counter electrode portion side protrusion 282 are also set to the same size (Ta = Tb).

[0051] Here, both the lengths Ra and Rb mean the lengths in the longitudinal direction X of the base material 55. That is, the length Ra of the electrode portion side protrusion 281 and the length Rb of the counter electrode portion side protrusion 282 are the length Ra from the end 60a on the electrode portion side of the heat generation region 60 to the end 28a on the electrode portion side of the heat spreader 28, and the length Rb from the end 60b on the counter electrode portion side of the heat generation region 60 to the end 28b on the counter electrode portion side of the heat spreader 28. Further, the widths Sa and Sb mean the widths in the lateral direction Y of the base material 55, and the thicknesses Ta and Tb mean the thicknesses in the direction Z orthogonal to both the longitudinal direction X and the lateral direction Y of the base material 55, in other words, the thickness in the direction Z orthogonal to the surface on which the resistive heating element 56 of the base material 55 is provided.

[0052] Thus, in the present embodiment, by making the electrode - side protrusion 281 of the heat - spreader 28 shorter than the counter - electrode - side protrusion 282, in a plan view of the heat - spreader 28 (in the state shown in FIG. 7), the area of the electrode - side protrusion 281 is made smaller than the area of the counter - electrode - side protrusion 282. As a result, in the present embodiment, since the volume (heat capacity) of the electrode - side protrusion 281 is smaller than the volume (heat capacity) of the counter - electrode - side protrusion 282, the amount of heat transferred from the heater 23 to the heat - spreader 28 on the electrode - side is less than that on the counter - electrode - side. Therefore, a temperature drop on the electrode - side can be suppressed. That is, in the present embodiment, for the part where the base material 55 is formed long on the electrode - side (La > Lb), the amount of heat transferred to the electrode - side of the base material 55 increases, while for the part where the electrode - side of the heat - spreader 28 is shortened (Ra < Rb), the amount of heat transferred to the electrode - side through the heat - spreader 28 decreases, so that heat balance between the electrode - side and the counter - electrode - side is achieved. As a result, in the present embodiment, the temperature variation in the fixing device can be suppressed, and the temperature drop on the electrode - side and the excessive temperature rise on the counter - electrode - side can be suppressed, so that the fixing quality can be improved.

[0053] Also, according to the present embodiment, by adjusting the length of the heat - spreader 28, the temperature variation in the fixing device can be suppressed. Therefore, unlike in Patent Document 1, it is not necessary to make the calorific value of the heater different between one end side and the other end side in the longitudinal direction. For this reason, the adverse effects (temperature variation when the heating element generates heat to the maximum and damage of parts due to local thermal expansion) caused by making the calorific value different can also be avoided. Therefore, according to the present embodiment, the reliability of the device is also improved.

[0054] In the examples shown in FIGS. 7 and 8, one heat spreader 28 is continuously provided in the longitudinal direction X so as to include at least the heat generating region H of the heater 23. However, the heat spreader 28 may be composed of a plurality of heat conduction members (heat transfer assisting members). In that case, there may be a gap between adjacent heat spreaders 28 in the longitudinal direction X of the base material 55. That is, as long as the heat spreader 28 has at least a portion (electrode portion side protruding portion 281) disposed on the electrode portion side and a portion (opposite electrode portion side protruding portion 282) disposed on the opposite electrode portion side with respect to the heat generating region H, in addition to the case where it is disposed entirely within the range including the heat generating region H, it may be partially disposed.

[0055] Next, an embodiment of the present invention different from the above-described embodiment (the first embodiment) will be described. In the following description, mainly the parts different from the above-described embodiment will be described, and the description of the other parts will be omitted as appropriate since they have basically the same configuration.

[0056] FIG. 9 is a diagram showing a configuration according to a second embodiment of the present invention.

[0057] In the second embodiment shown in FIG. 9, different from the above-described embodiment, the electrode portion side protruding portion 281 is formed in a triangular shape in plan view, and the width Sa of the electrode portion side protruding portion 281 is formed to gradually become smaller than the width Sb of the opposite electrode portion side protruding portion 282 (Sa < Sb). For this reason, in the present embodiment, the area of the electrode portion side protruding portion 281 in plan view is smaller than the area of the opposite electrode portion side protruding portion 282. On the other hand, the lengths Ra, Rb and the thicknesses Ta, Tb of the electrode portion side protruding portion 281 and the opposite electrode portion side protruding portion 282 in the present embodiment are all set to the same size (Ra = Rb, Ta = Tb).

[0058] As described above, in the second embodiment, the width Sa of the electrode portion-side protrusion 281 is reduced, and the area of ​​the electrode portion-side protrusion 281 is reduced, so that the volume (heat capacity) of the electrode portion-side protrusion 281 is smaller than the volume (heat capacity) of the counter-electrode portion-side protrusion 282. As a result, in this embodiment, as in the above-described embodiment, the amount of heat transferred to the electrode portion side via the heat equalizer plate 28 is reduced, thereby achieving thermal equilibrium between the electrode portion side and the counter-electrode portion side. Therefore, in this embodiment, temperature variations in the fixing device can be suppressed, and temperature drops on the electrode portion side and excessive temperature increases on the counter-electrode portion side can be suppressed, thereby improving fixing quality. Furthermore, in this embodiment, it is not necessary to differentiate the heat generation amounts between one end and the other end of the heater in the longitudinal direction, so that adverse effects resulting from different heat generation amounts (such as temperature variations when the heating element is maximized and damage to components due to local thermal expansion) can be avoided.

[0059] In the example shown in Figure 9, the width Sa of the electrode portion side protrusion 281 gradually becomes smaller toward the electrode portion 58, and the electrode portion side protrusion 281 is formed in a triangular shape when viewed in a plane, but the width Sa and shape of the electrode portion side protrusion 281 are not limited to this.

[0060] 10 , only the width Sa of a portion of the electrode part-side protrusion 281 may be smaller than the width Sb of the counter-electrode part-side protrusion 282. In short, as long as the area of ​​the electrode part-side protrusion 281 is smaller than the area of ​​the counter-electrode part-side protrusion 282 and the volume (heat capacity) of the electrode part-side protrusion 281 as a whole is smaller than the volume (heat capacity) of the counter-electrode part-side protrusion 282, it is not limited to the case where the entire width Sa of the electrode part-side protrusion 281 is smaller than the width Sb of the counter-electrode part-side protrusion 282, but the case where only the width Sa of the portion of the electrode part-side protrusion 281 is smaller than the width Sb of the counter-electrode part-side protrusion 282 may also be the case.

[0061] 11 and 12 show a configuration according to a third embodiment of the present invention.

[0062] In the third embodiment shown in FIGS. 11 and 12, the lengths Ra and Rb and widths Sa and Sb of the electrode portion side protrusion 281 and the counter electrode portion side protrusion 282 are all set to the same size (Ra = Rb, Sa = Sb), but the thicknesses Ta and Tb are different. That is, in the present embodiment, the thickness Ta of the electrode portion side protrusion 281 is made smaller than the thickness Tb of the counter electrode portion side protrusion 282 (Ta < Tb), so that the volume (heat capacity) of the electrode portion side protrusion 281 becomes smaller than the volume (heat capacity) of the counter electrode portion side protrusion 282.

[0063] Thereby, also in the present embodiment, the amount of heat transferred to the electrode portion side via the heat spreader 28 can be reduced, so that heat balance between the electrode portion side and the counter electrode portion side can be achieved. Therefore, as in the above-described embodiment, variations in temperature in the fixing device can be suppressed, and a temperature drop on the electrode portion side and an excessive temperature rise on the counter electrode portion side can be suppressed. Further, in the present embodiment, it is not necessary to make the calorific value different between one end side and the other end side in the longitudinal direction of the heater, so that adverse effects (temperature variations when the heating element generates heat to the maximum, and breakage of parts due to local thermal expansion) due to making the calorific value different can be avoided.

[0064] In each of the above embodiments, as a means for reducing the volume (heat capacity) of the electrode portion side protrusion 281, any one of the length Ra, width Sa, and thickness Ta of the electrode portion side protrusion 281 is adjusted, but any two or three of these may be adjusted. That is, any two or three of the length Ra, width Sa, and thickness Ta of the electrode portion side protrusion 281 may be made smaller than the length Rb, width Sb, and thickness Tb of the counter electrode portion side protrusion 282. Thereby, the options for the temperature balance adjustment means between the electrode portion side and the counter electrode portion side increase, and variations in temperature in the fixing device can be more effectively suppressed.

[0065] Subsequently, FIG. 13 is a diagram showing a configuration according to a fourth embodiment of the present invention.

[0066] In the fourth embodiment shown in FIG. 13, in the longitudinal direction X of the base material 55, a hole 29 is provided at a position shifted from the center c of the heat spreader 28 toward one side in the longitudinal direction X (in this embodiment, the anti-electrode part side). Therefore, in this embodiment, the shape of the heat spreader 28 is asymmetric with respect to its center c.

[0067] As described above, in the fourth embodiment, since the heat spreader 28 is formed in an asymmetric shape, it becomes easy to understand which end of the heat spreader 28 should be arranged on the electrode part side or the anti-electrode part side. Specifically, in the example shown in FIG. 13, it can be seen that among the two ends 28a and 28b of the heat spreader 28, the end 28b closer to the hole 29 (the left end in FIG. 13) is the end to be arranged on the anti-electrode part side. Therefore, in this embodiment, it is less likely to occur a mis-assembly where the two ends of the heat spreader 28 are assembled in the opposite direction, and the assembly work is also easier to perform.

[0068] Such a configuration is particularly applicable to a configuration in which, as shown in FIG. 13, the length Ra of the protruding part 281 on the electrode part side of the heat spreader 28 is different from the length Rb of the protruding part 282 on the anti-electrode part side (Ra < Rb), and the respective widths Sa, Sb and thicknesses Ta, Tb are the same (Sa = Sb, Ta = T). In this case, before the heat spreader 28 is assembled to the heater 23, it is not easy to tell at first glance which end of the heat spreader 28 should be arranged on the electrode part side or the anti-electrode part side. Therefore, it is preferable to provide the hole 29 as described above to form the heat spreader 28 in an asymmetric shape. Thereby, it is possible to expect suppression of mis-assembly and improvement of assembly workability.

[0069] The shape of the hole 29 may be a rectangle or other shapes in addition to the circular shape as shown in FIG. 13. Also, the hole 29 may be a shape (concave part) in which the long side of the heat spreader 28 as shown in FIG. 14 is cut out in the short side direction Y of the base material 55.

[0070] Subsequently, FIG. 15 shows a configuration according to the fifth embodiment of the present invention.

[0071] In the fifth embodiment shown in Figure 15, as in the above-mentioned embodiment (see Figure 13), a hole 29 is provided in the heat equalizer plate 28, and further, a thermistor 30 is arranged in this hole 29 as a temperature sensor 27 that detects the temperature of the heater 23.

[0072] In this way, by disposing the temperature sensor 27 in the hole 29, the thermistor 30 can be disposed close to the heater 23, and the detection accuracy and responsiveness of the thermistor 30 can be improved.

[0073] 16, when the holes 29 are formed so as to penetrate from the surface of the heat equalizer plate 28 facing the heater 23 to the opposite surface, the thermistor 30 can be placed in direct contact with the heater 23. In this case, the heat from the heater 23 is transferred directly to the thermistor 30, which is expected to effectively improve the detection accuracy and responsiveness of the thermistor 30.

[0074] 17, the hole 29 may have a shape with a bottom (a shape that does not penetrate the heat equalizer plate 28). In this case, the thermistor 30 is in indirect contact with the heater 23 via the bottom of the hole 29. However, even with such a hole 29, the thermistor 30 can be disposed close to the heater 23, improving the detection accuracy and responsiveness of the thermistor 30.

[0075] Furthermore, the temperature sensor (temperature detection member) placed inside hole 29 is not limited to temperature sensor 27 (thermistor 30) for temperature control to maintain the temperature of fixing belt 21 at a predetermined temperature, but may also be thermostat 31 as a safety device that stops heater 23 from generating heat when the temperature of heater 23 exceeds a predetermined temperature. In this case, too, by placing thermostat 31 inside hole 29, the detection accuracy and responsiveness of thermostat 31 can be improved.

[0076] 18, two holes 29 may be provided at positions shifted from the center c of the heat equalizer plate 28 in the longitudinal direction X of the substrate 55, with the thermistor 30 disposed in one of the holes 29 and the thermostat 31 disposed in the other hole 29. The shape of the holes 29 in which the thermistor 30 and thermostat 31 are disposed is not limited to a circle, and they may be rectangular or another shape, or may be a shape in which the long side of the heat equalizer plate 28 is cut out (see FIG. 14). The number of holes 29 may be three or more.

[0077] As described above, according to the present invention, even in a configuration in which the electrode portions are arranged on only one side in the longitudinal direction of the substrate and the substrate is formed longer on one side, it is possible to achieve heat balance in the fixing device by adjusting the heat capacity of the heat equalizer plates 28 on one side and the other side. Furthermore, the present invention is not limited to a configuration in which the electrode portions are arranged on only one side of the substrate, but can also be applied to a configuration in which the electrode portions 58 are arranged on both one side and the other side of the substrate 55 as shown in FIG.

[0078] 19, electrode portions 58 are arranged on both ends of the substrate 55 in the longitudinal direction X. That is, the electrode portions 58 are arranged between one end 55a of the substrate 55 and one end 60a of the heat generating region 60, and between the other end 55b of the substrate 55 and the other end 60b of the heat generating region 60. However, the number of electrode portions 58 arranged on one side of the substrate 55 is different from the number of electrode portions 58 arranged on the other side of the substrate 55. In this case, two electrode portions 58 are arranged on one side of the substrate 55 (the right side in FIG. 19), and one electrode portion 58 is arranged on the other side of the substrate 55 (the left side in FIG. 19).

[0079] 19, the number of electrode portions 58 arranged on one side and the other side of the base material 55 is different, and therefore, on one side of the base material 55 where relatively more electrode portions 58 are arranged, more space must be secured for arranging the electrode portions 58 than on the other side. For this reason, in the example shown in Fig. 19, the length La between the end 55a on one side of the base material 55 and the end 60a on one side of the heat generating region 60 is set longer than the length Lb between the end 55b on the other side of the base material 55 and the end 60b on the other side of the heat generating region 60.

[0080] 19 also has the same problem as the heaters according to the above embodiments: when the heater 23 is turned on, the amount of heat transferred to the substrate 55 is greater at the longer ends of the substrate 55 than at the shorter ends. For this reason, it is preferable to apply the present invention. By applying the present invention, it is possible to balance the heat between one side and the other in the longitudinal direction, thereby suppressing variations in the temperature of the heater and the fixing belt.

[0081] The present invention is also applicable to fixing devices having the configurations shown in Figures 20 to 23. The configurations of the fixing devices shown in Figures 20 to 23 will be described below.

[0082] The fixing device 20 shown in FIG. 20 differs from the fixing device 20 shown in FIG. 2 above in the location of the temperature sensor 27 that detects the temperature of the heater 23. The rest of the configuration is the same. In the fixing device 20 shown in FIG. 20, the temperature sensor 27 is disposed upstream of the center M of the nip N in the paper feed direction (the nip entrance side). On the other hand, in the fixing device 20 shown in FIG. 2, the temperature sensor 27 is disposed at the center M of the nip N. As shown in FIG. 20, when the temperature sensor 27 is disposed upstream of the center M of the nip N in the paper feed direction, the temperature sensor 27 can accurately detect the temperature at the nip entrance side. The nip entrance side is an area where heat from the fixing belt 21 is particularly likely to be lost by the paper P entering the nip N. Therefore, by accurately detecting the temperature at the nip entrance side using the temperature sensor 27, image fixability can be ensured and the occurrence of fixing offset (a state in which a toner image cannot be sufficiently heated) can be effectively suppressed.

[0083] 21 , a heating nip N1, in which the heater 23 heats the fixing belt 21, and a fixing nip N2, through which the paper P passes, are formed in separate positions. Specifically, in this embodiment, a nip forming member 68 as well as the heater 23 are disposed inside the fixing belt 21, and pressure rollers 69 and 70 are pressed against the heater 23 and the nip forming member 68 from the outside of the fixing belt 21. As a result, the heating nip N1 is formed between the heater 23 and one pressure roller 69, and the fixing nip N2 is formed between the nip forming member 68 and the other pressure roller 70. In this case, the fixing belt 21 is heated in the heating nip N1, and the heat of the fixing belt 21 is applied to the paper P in the fixing nip N2, thereby fixing an unfixed image to the paper P.

[0084] 22 is an example of the fixing device 20 shown in Fig. 21, in which the pressure roller 69 on the heater 23 side is omitted, and the heater 23 is formed in an arc shape to match the curvature of the fixing belt 21. Other than that, it is the same as the configuration shown in Fig. 21. In this case, since the heater 23 is formed in an arc shape, the contact length between the fixing belt 21 and the heater 23 in the belt rotation direction is ensured, and the fixing belt 21 can be heated efficiently.

[0085] 23 shows an example of a fixing device 20 in which a roller 73 is disposed between a pair of belts 71 and 72. In this example, a heater 23 is disposed in the left-hand belt 71 in FIG. 23, and a nip forming member 74 is disposed in the right-hand belt 72. The heater 23 comes into contact with the roller 73 via the left-hand belt 71, thereby forming a heating nip N1, and the nip forming member 74 comes into contact with the roller 73 via the right-hand belt 72, thereby forming a fixing nip N2.

[0086] Furthermore, the image forming apparatus according to the present invention is not limited to the color image forming apparatus shown in Fig. 1, but can also be applied to an image forming apparatus configured as shown in Fig. 24. Below, the configuration of an image forming apparatus according to another embodiment to which the present invention can be applied will be described.

[0087] 24 includes an image forming means 80 including a photosensitive drum and the like, a paper transport section including a pair of timing rollers 81 and the like, a paper feeder 82, a fixing device 83, a paper discharge device 84, and a reading section 85. The paper feeder 82 includes multiple paper feed trays, each of which stores paper of a different size.

[0088] The reading unit 85 reads an image of the document Q. The reading unit 85 generates image data from the read image. The paper feeder 82 stores a plurality of sheets of paper P and sends the sheets of paper P to a conveyance path. The timing rollers 81 convey the sheets of paper P on the conveyance path to the image forming means 80.

[0089] The image forming means 80 forms a toner image on the paper P. Specifically, the image forming means 80 includes a photosensitive drum, a charging roller, an exposure device, a developing device, a replenishment device, a transfer roller, a cleaning device, and a discharging device. The fixing device 83 applies heat and pressure to the toner image to fix the toner image to the paper P. The paper P with the fixed toner image is transported to the paper discharge device 84 by a transport roller or the like. The paper discharge device 84 discharges the paper P outside the image forming apparatus 100.

[0090] Next, the fixing device 83 according to this embodiment will be described with reference to Fig. 25. In the configuration shown in Fig. 25, components common to the fixing device 20 of the above embodiment shown in Fig. 2 are denoted by the same reference numerals and description thereof will be omitted.

[0091] As shown in FIG. 21, the fixing device 83 includes a fixing belt 21, a pressure roller 22, a heater 23, a heat equalizing plate 28, a heater holder 24, a stay 25, a temperature sensor 27, and the like.

[0092] A nip N is formed between the fixing belt 21 and the pressure roller 22. The nip width of the nip N is 10 mm, and the linear speed of the fixing device 83 is 240 mm / s.

[0093] The fixing belt 21 has a polyimide base and a release layer, but does not have an elastic layer. The release layer is formed of a heat-resistant film material made of, for example, fluororesin. The outer diameter of the fixing belt 21 is approximately 24 mm.

[0094] The pressure roller 22 includes a core metal, an elastic layer, and a release layer. The pressure roller 22 has an outer diameter of 24 to 30 mm, and the elastic layer has a thickness of 3 to 4 mm.

[0095] The heater 23 includes a base material, a heat insulating layer, a conductive layer including a resistance heating element, and an insulating layer, and has an overall thickness of 1 mm. The width of the heater 23 in the paper transport direction is 13 mm.

[0096] As shown in FIG. 26 , the conductor layer of the heater 23 includes a plurality of resistance heating elements 56, power supply lines 59, and electrode portions 58A to 58C. The plurality of resistance heating elements 56 are arranged at intervals in the longitudinal direction (arrow X direction) of the heater 23. Here, if the portions between the resistance heating elements 56 are referred to as "divided regions," then, as shown in the enlarged view of FIG. 26 , divided regions B are formed between the resistance heating elements 56 (although FIG. 26 only illustrates the divided regions B within the enlarged view, in reality, divided regions B are provided between all of the resistance heating elements 56). In addition, in FIG. 26 , the direction of arrow Y is a direction intersecting or perpendicular to the longitudinal direction X of the heater 23 (longitudinal intersecting direction) and different from the thickness direction of the substrate 55. In addition, the direction of arrow Y is a direction that intersects with the arrangement direction of the multiple resistance heating elements 56 (arrangement cross direction), or a direction along the surface of the substrate 55 on which the resistance heating elements 56 are provided, which is the same as the short side direction of the heater 23, or the transport direction of the paper passing through the fixing device.

[0097] Furthermore, the multiple resistance heating elements 56 form a central heating section 35B and heating sections 35A and 35C on both ends that can generate heat independently. For example, of the three electrode sections 58A to 58C, when electricity is applied to the leftmost electrode section 58A and the central electrode section 58B in FIG. 26, the heating sections 35A and 35C on both ends generate heat. When electricity is applied to the electrode sections 58A and 58C on both ends, the central heating section 35B generates heat. For example, when fixing small-size paper, only the central heating section 35B generates heat, and when fixing large-size paper, all of the heating sections 35A to 35C generate heat, allowing heating according to the size of the paper.

[0098] As shown in FIG. 27, the heater holder 24 according to this embodiment has a recess 24a that accommodates and holds the heater 23 and the heat equalizer plate 28 (see FIG. 25). The recess 24a is formed on the heater 23 side of the heater holder 24. The recess 24a is composed of a surface (bottom surface) 24f formed in a rectangular shape having approximately the same size as the heater 23, and four walls (side surfaces) 24b, 24c, 24d, and 24e that intersect with the surface 24f along the four sides that form the outline of the surface 24f. Note that the right wall 24e is not shown in FIG. 27. Alternatively, one of the pair of walls 24d and 24e (left and right) that intersect with the longitudinal direction X of the heater 23 (the direction in which the resistance heating elements 56 are arranged) may be omitted, and the recess 24a may be configured to open at one end of the heater 23 in the longitudinal direction.

[0099] 28, the heater 23 and heater holder 24 according to this embodiment are held by a connector 86. The connector 86 has a housing made of resin (for example, LCP) and a plurality of contact terminals provided inside the housing.

[0100] The connector 86 is attached to the heater 23 and the heater holder 24 in a direction intersecting the longitudinal direction X of the heater 23 (the arrangement direction of the resistance heating elements 56) (see the direction of the arrow from the connector 86 in FIG. 28). The connector 86 is attached to the heater 23 and the heater holder 24 at one end side in the longitudinal direction X of the heater 23 (the arrangement direction of the resistance heating elements 56), on the side opposite to the side on which the drive motor of the pressure roller 22 is provided. Note that when the connector 86 is attached to the heater holder 24, a convex portion provided on one of the connector 86 and the heater holder 24 may be configured to engage with a concave portion provided on the other, and the convex portion may move relatively within the concave portion.

[0101] With the connector 86 attached, the heater 23 and heater holder 24 are held by being sandwiched between them from the front and back sides by the connector 86. In this state, each contact terminal comes into contact (pressure-welded) with each electrode portion of the heater 23, electrically connecting each resistance heating element 56 to a power supply provided in the image forming apparatus via the connector 86. This enables power to be supplied from the power supply to each resistance heating element 56.

[0102] 28 are belt holding members that are provided on both longitudinal ends of the fixing belt 21 and hold both ends of the fixing belt 21 from the inside. The flanges 87 are inserted into both ends of the stay 25 and fixed to a pair of side plates that are frame members of the fixing device.

[0103] FIG. 29 is a diagram showing the arrangement of the temperature sensor 27 and the thermostat 88, which is a current interrupting member, according to this embodiment.

[0104] 29, the temperature sensors 27 according to this embodiment are disposed so as to face the inner circumferential surfaces of the center Xm side and the end side in the longitudinal direction X of the fixing belt 21. One of these temperature sensors 27 is disposed at a position corresponding to the divided region B (see FIG. 26) between the resistance heating elements of the heater 23.

[0105] Further, on the center Xm side and end sides of the fixing belt 21, thermostats 88 as current-cutting members are arranged to face the inner circumferential surface of the fixing belt 21. Each thermostat 88 detects the temperature of the inner circumferential surface of the fixing belt 21 or the ambient temperature near the inner circumferential surface. When the temperature detected by the thermostat 88 exceeds a preset threshold value, the current to the heater 23 is cut off.

[0106] 29 and 30 , flanges 87 that hold both ends of fixing belt 21 are provided with slide grooves 87a. Slide grooves 87a extend in the direction in which fixing belt 21 approaches and separates from pressure roller 22. An engagement portion of the housing of the fixing device engages with slide groove 87a. This engagement portion moves relatively within slide groove 87a, allowing fixing belt 21 to move in the direction in which fixing belt 21 approaches and separates from pressure roller 22.

[0107] The present invention is also applicable to a fixing device having the following configuration.

[0108] FIG. 31 is a schematic diagram of a fixing device according to another embodiment to which the present invention can be applied.

[0109] As shown in FIG. 31, the fixing device 20 according to this embodiment includes a fixing belt 21 as a rotating body or fixing member, a pressure roller 22 as an opposing rotating body or pressure member, a heater 23 as a heat source, a heater holder 24 as a heat source holding member, a stay 25 as a support member, a temperature sensor (thermistor) 27 as a temperature detection member, and a first high thermal conductivity member 89 as a heat equalization member (heat transfer assisting member). The fixing belt 21 is an endless belt. The pressure roller 22 contacts the outer peripheral surface of the fixing belt 21 and forms a nip N between the fixing belt 21 and the pressure roller 22. The heater 23 heats the fixing belt 21. The heater holder 24 holds the heater 23 and the first high thermal conductivity member 89. The stay 25 supports the heater holder 24. The temperature sensor 27 detects the temperature of the first high thermal conductivity member 89. 31 is the longitudinal direction of the fixing belt 21, pressure roller 22, heater 23, heater holder 24, stay 25, and first high thermal conductivity member 89, and hereinafter this direction will be simply referred to as the longitudinal direction. This longitudinal direction also corresponds to the width direction of the paper being transported, the belt width direction of the fixing belt 21, and the axial direction of the pressure roller 22.

[0110] 26, the heater 23 in this embodiment has a plurality of resistance heating elements 56 arranged at intervals in the longitudinal direction of the heater 23. However, in a configuration in which a plurality of resistance heating elements 56 are arranged at intervals, the temperature of the heater 23 in divided regions B, which are the spaces between the resistance heating elements 56, tends to be lower than in the portions where the resistance heating elements 56 are arranged. Therefore, the temperature of the fixing belt 21 also becomes lower in divided regions B, and there is a risk that the temperature of the fixing belt 21 will become uneven along the longitudinal direction.

[0111] Therefore, in this embodiment, the first high thermal conductive member 89 is provided to suppress the temperature drop in the divided region B and suppress temperature unevenness in the longitudinal direction of the fixing belt 21. The first high thermal conductive member 89 will be described in more detail below.

[0112] 31 , first high thermal conductivity member 89 is disposed between heater 23 and stay 25 in the left-right direction of the figure, and is particularly sandwiched between heater 23 and heater holder 24. In other words, one surface of first high thermal conductivity member 89 abuts against the back surface of base material 55 of heater 23, and the other surface of first high thermal conductivity member 89 (the surface opposite to the one surface) abuts against heater holder 24.

[0113] The stay 25 supports the heater holder 24, the first high thermal conductive member 89, and the heater 23 by bringing contact surfaces 25a1 of two vertical portions 25a extending in the thickness direction of the heater 23 and the like into contact with the heater holder 24. In the direction crossing the longitudinal axis (the up-down direction in FIG. 31 ), the contact surfaces 25a1 are provided outside the range in which the resistance heating element 56 is provided. This makes it possible to suppress heat transfer from the heater 23 to the stay 25, and allows the heater 23 to heat the fixing belt 21 efficiently.

[0114] As shown in Fig. 32, first high thermal conductivity member 89 is a plate-like member having a certain thickness, for example, a thickness of 0.3 mm, a length in the longitudinal direction of 222 mm, and a width in the direction transverse to the longitudinal direction of 10 mm. In this embodiment, first high thermal conductivity member 89 is formed from a single plate material, but it may also be formed from a plurality of members. Note that guide member 26 shown in Fig. 31 is omitted from Fig. 32.

[0115] The first high thermal conductivity member 89 is fitted into the recess 24a of the heater holder 24, and the heater 23 is attached thereto, thereby sandwiching and holding the first high thermal conductivity member 89 between the heater holder 24 and the heater 23. In this embodiment, the longitudinal width of the first high thermal conductivity member 89 is set to be approximately the same as the longitudinal width of the heater 23. The longitudinal movement of the first high thermal conductivity member 89 and the heater 23 is restricted by both side walls (longitudinal direction restriction portions) 24d, 24e arranged in a direction intersecting the longitudinal direction of the recess 24a. In this manner, the longitudinal positional deviation of the first high thermal conductivity member 89 within the fixing device is restricted, thereby improving the heat conduction efficiency within a target longitudinal range. Furthermore, the longitudinal movement of the first high thermal conductivity member 89 and the heater 23 is restricted by both side walls (arrangement intersecting direction restriction portions) 24b, 24c arranged in the longitudinal direction of the recess 24a.

[0116] As shown by the hatched area in FIG. 33 , the longitudinal range (direction of arrow X) in which the first high thermal conductivity member 89 is disposed includes the heat-generating region 60 and is set longer toward the electrode portion side and the counter-electrode portion side than the heat-generating region 60. In this configuration, as in the above-described embodiment, by making the length Ra from the electrode portion-side end 60a of the heat-generating region 60 to the electrode portion-side end 89a of the first high thermal conductivity member 89 shorter than the length Rb from the counter-electrode portion-side end 60b of the heat-generating region 60 to the counter-electrode portion-side end 89b of the first high thermal conductivity member 89, heat balance is achieved between the electrode portion side and the counter-electrode portion side, and temperature variation in the fixing device can be suppressed. Alternatively, instead of the length, the width or thickness of the first high thermal conductivity member 89 may be made different between the electrode portion side and the counter-electrode portion side. Alternatively, any two or three of the length, width, and thickness of the first high thermal conductivity member 89 may be made different between the electrode portion side and the counter-electrode portion side.

[0117] 34, some of the first high thermal conductivity members 89 may be arranged only over the entire area corresponding to the interval (divided area) B in the longitudinal direction (arrow X direction). In FIG. 34, for convenience, the resistance heating element 56 and the first high thermal conductivity members 89 are shown shifted in the vertical direction of FIG. 34, but they are actually arranged at approximately the same position in the direction transverse to the longitudinal direction (arrow Y direction). The first high thermal conductivity members 89 may be arranged over a portion of the resistance heating element 56 in the direction transverse to the longitudinal direction (arrow Y direction), or, as in the example shown in FIG. 35, the first high thermal conductivity members 89 may be arranged over the entire resistance heating element 56 in the direction transverse to the longitudinal direction (arrow Y direction). Furthermore, as shown in FIG. 35, the first high thermal conductivity members 89 may be arranged in addition to the position corresponding to the interval B in the longitudinal direction, so as to straddle both resistance heating elements 56 on both sides of the interval B. The phrase "the first high thermal conductivity member 89 is arranged across the resistance heating elements 56 on both sides" means that the first high thermal conductivity member 89 at least partially overlaps with the resistance heating elements 56 on both sides in the longitudinal direction. Furthermore, the first high thermal conductivity member 89 may be arranged at a position corresponding to all of the intervals B of the heater 23, or may be arranged at a position corresponding to only part of the intervals B (one location in this case), as in the example shown in FIG. 35. Here, the phrase "the first high thermal conductivity member 89 is arranged at a position corresponding to the intervals B" means that the intervals B and the first high thermal conductivity member 89 at least partially overlap in the longitudinal direction.

[0118] Due to the pressure of the pressure roller 22, the first highly thermally conductive member 89 is sandwiched between the heater 23 and the heater holder 24 and is in close contact with these members. The first highly thermally conductive member 89 comes into contact with the heater 23, thereby improving the thermal conductivity of the heater 23 in the longitudinal direction. Furthermore, by arranging the first highly thermally conductive member 89 at a position corresponding to the interval B between the heaters 23 in the longitudinal direction, the thermal conductivity in the interval B can be improved, increasing the amount of heat transferred to the interval B and raising the temperature in the interval B. This reduces temperature variations in the heater 23 in the longitudinal direction and in the fixing belt 21 in the longitudinal direction. As a result, uneven fixing and glossiness of the image fixed on the paper can be reduced. Furthermore, there is no need to increase the heat output of the heater 23 to ensure sufficient fixing performance in the interval B, thereby achieving energy savings in the fixing device. In particular, when the first high thermal conductivity member 89 is arranged over the entire longitudinal area where the resistance heating element 56 is arranged, the heat transfer efficiency of the heater 23 is improved over the entire area where the heater 23 is mainly heated (i.e., the image forming area of ​​the paper being passed through), and temperature unevenness in the longitudinal direction of the heater 23 and therefore the fixing belt 21 can be suppressed.

[0119] Furthermore, the combination of the first high thermal conductivity member 89 and the resistance heating element 56 having PTC characteristics can more effectively suppress excessive temperature rise in the non-paper passing area when small-size paper is passed. The PTC characteristics are such that the resistance value increases as the temperature increases (when a constant voltage is applied, the heater output decreases). In other words, the PTC characteristics of the resistance heating element 56 can effectively suppress the amount of heat generated by the resistance heating element 56 in the non-paper passing area, and the first high thermal conductivity member 89 can efficiently transfer the heat from the non-paper passing area, where the temperature has increased, to the paper passing area. Therefore, the synergistic effect of these factors can effectively suppress excessive temperature rise in the non-paper passing area.

[0120] Furthermore, since the amount of heat generated in the gap B is small, the temperature of the heater 23 is also low in the vicinity of the gap B, so it is preferable to place the first high thermal conductivity member 89. For example, by placing the first high thermal conductivity member 89 at a position corresponding to the expanded divided region C including the region around the gap B shown in FIG. 36, the heat transfer efficiency in the longitudinal direction in the gap B and its periphery can be improved, and temperature unevenness in the longitudinal direction of the heater 23 can be more effectively suppressed. Furthermore, if the first high thermal conductivity member 89 is placed over the entire longitudinal direction of the region in which all of the resistance heating elements 56 are placed, temperature unevenness in the longitudinal direction of the heater 23 (fixing belt 21) can be more reliably suppressed.

[0121] Next, still another embodiment of the fixing device will be described.

[0122] 37 has a second high thermal conductivity member 90 between heater holder 24 and first high thermal conductivity member 89. The second high thermal conductivity member 90 is provided at a different position from the first high thermal conductivity member 89 in the stacking direction (left-right direction in FIG. 37) of members such as heater holder 24, stay 25, and first high thermal conductivity member 89. More specifically, the second high thermal conductivity member 90 is provided overlapping the first high thermal conductivity member 89. In addition, in this embodiment, a temperature sensor (thermistor) 27 is provided as in the embodiment shown in FIG. 31 above, but FIG. 37 shows a cross section in which the temperature sensor 27 is not provided.

[0123] The second high thermal conductivity member 90 is made of a material having a higher thermal conductivity than the base material 55, such as graphene or graphite. In this embodiment, the second high thermal conductivity member 90 is made of a graphite sheet with a thickness of 1 mm. The second high thermal conductivity member 90 may also be made of a plate material such as aluminum, copper, or silver.

[0124] As shown in FIG. 38, a plurality of second high thermal conductive members 90 are arranged in recess 24a of heater holder 24, with longitudinal gaps between each of the second high thermal conductive members 90. A recess that is one level deeper than the remaining portions of heater holder 24 is formed in the portion of heater holder 24 where second high thermal conductive members 90 are provided. Gaps are provided between second high thermal conductive members 90 and heater holder 24 on both longitudinal sides. This suppresses heat transfer from second high thermal conductive members 90 to heater holder 24, allowing heater 23 to efficiently heat fixing belt 21. Note that guide member 26 shown in FIG. 37 is omitted from FIG. 38.

[0125] As shown in Fig. 39, second high thermal conductivity members 90 (see hatched areas) are arranged in positions corresponding to interval B in the longitudinal direction (direction of arrow X) so as to overlap at least a portion of adjacent resistance heating elements 56. In particular, in this embodiment, second high thermal conductivity members 90 are arranged across the entire area of ​​interval B. Note that Fig. 39 (and Fig. 41 described below) shows a case where first high thermal conductivity members 89 are arranged across the entire longitudinal direction of the area in which all resistance heating elements 56 are arranged, but the arrangement range of first high thermal conductivity members 89 is not limited to this.

[0126] In this embodiment, in addition to the first high thermal conductivity members 89, second high thermal conductivity members 90 are arranged at positions corresponding to the longitudinal interval B so as to overlap at least a portion of adjacent resistance heating elements 56. This further improves the longitudinal heat transfer efficiency at the interval B, thereby more effectively suppressing temperature unevenness in the heater 23 along the longitudinal direction. Most preferably, as shown in FIG. 40 , some of the first high thermal conductivity members 89 and second high thermal conductivity members 90 are provided only over the entire area at the position corresponding to the interval B. This improves the heat transfer efficiency particularly at the position corresponding to the interval B compared to other areas. Note that, for convenience, in FIG. 40 , the resistance heating elements 56, the first high thermal conductivity members 89, and the second high thermal conductivity members 90 are shown shifted from one another in the vertical direction of the figure, but they are actually arranged at approximately the same position in the direction transverse to the longitudinal direction (the direction of the arrow Y). However, this is not limited to this, and the first high thermal conductivity member 89 and the second high thermal conductivity member 90 may be arranged in a part of the longitudinal direction of the resistance heating element 56, or may be arranged so as to cover the entire longitudinal direction.

[0127] Furthermore, both the first high thermal conductivity member 89 and the second high thermal conductivity member 90 may be formed from the graphene sheet. In this case, the first high thermal conductivity member 89 and the second high thermal conductivity member 90 can be formed with high thermal conductivity in a predetermined direction along the graphene surface, that is, in the longitudinal direction rather than the thickness direction. This makes it possible to effectively suppress temperature variations in the heater 23 and the fixing belt 21 in the longitudinal direction.

[0128] Graphene is a flake-like powder. Graphene consists of a planar hexagonal lattice structure of carbon atoms, as shown in Figure 43. A graphene sheet is a sheet of graphene, typically a single layer. Graphene sheets may contain impurities in the single carbon layer, or may have a fullerene structure. Fullerene structures are generally recognized as compounds consisting of polycyclic rings in which the same number of carbon atoms are fused together in a cage-like fashion by five- and six-membered rings, such as C60, C70, and C80 fullerenes, or other closed cage structures with three-coordinate carbon atoms.

[0129] Graphene sheets are man-made and can be produced, for example, by chemical vapor deposition (CVD).

[0130] The graphene sheet may be a commercially available product. The size and thickness of the graphene sheet, or the number of layers of the graphite sheet (described later), may be measured using, for example, a transmission electron microscope (TEM).

[0131] Furthermore, graphite, which is a multilayered graphene, has a large thermal conductivity anisotropy. As shown in FIG. 44, graphite has layers in which the layer planes of condensed six-membered rings of carbon atoms extend in a planar fashion, forming a crystalline structure in which these layers are stacked multiple times. In this crystalline structure, adjacent carbon atoms within a layer form covalent bonds, while carbon atoms between layers form van der Waals bonds. Covalent bonds have a stronger bonding strength than van der Waals bonds, resulting in a large anisotropy between intralayer and interlayer bonds. In other words, by constructing the first high thermal conductivity member 89 or the second high thermal conductivity member 90 from graphite, the heat transfer efficiency in the longitudinal direction of the first high thermal conductivity member 89 or the second high thermal conductivity member 90 is greater than that in the thickness direction (i.e., the stacking direction of the members), thereby suppressing heat transfer to the heater holder 24. This effectively suppresses temperature unevenness in the longitudinal direction of the heater 23 and minimizes heat leakage toward the heater holder 24. Furthermore, by making the first high thermal conductivity member 89 or the second high thermal conductivity member 90 out of graphite, the first high thermal conductivity member 89 or the second high thermal conductivity member 90 can be endowed with excellent heat resistance, i.e., not oxidizing up to approximately 700 degrees.

[0132] The physical properties and dimensions of the graphite sheet can be appropriately changed depending on the functions required of the first high thermal conductivity member 89 or the second high thermal conductivity member 90. For example, the anisotropy of the thermal conductivity can be increased by using high-purity graphite or single-crystal graphite, or by increasing the thickness of the graphite sheet. Furthermore, in order to increase the speed of the fixing device, a thin graphite sheet may be used to reduce the thermal capacity of the fixing device. Furthermore, if the widths of the nip portion N and the heater 23 are large, the longitudinal width of the first high thermal conductivity member 89 or the second high thermal conductivity member 90 may be increased accordingly.

[0133] From the viewpoint of increasing the mechanical strength, the number of layers of the graphite sheet is preferably at least 11. The graphite sheet may partially include a single layer portion and a multi-layer portion.

[0134] The second high thermal conductivity members 90 may be arranged in positions in the longitudinal direction corresponding to intervals B (and further enlarged divided regions C) so as to overlap at least a portion of adjacent resistance heating elements 56, and are not limited to the arrangement shown in FIG. 39 . For example, as shown in the example in FIG. 41 , second high thermal conductivity members 90A may be arranged to protrude beyond base material 55 on both sides in the transverse direction (direction of arrow Y). Furthermore, second high thermal conductivity members 90B may be arranged in a range in the transverse direction where resistance heating elements 56 are arranged. Furthermore, second high thermal conductivity members 90C may be arranged in a portion of intervals B.

[0135] In another embodiment shown in FIG. 42, a gap is provided between the first high thermal conductivity member 89 and the heater holder 24 in the thickness direction (left-right direction in FIG. 42). That is, a recess 24g serving as a heat insulating layer is provided in a portion of the recess 24a (see FIG. 38) of the heater holder 24 where the heater 23, the first high thermal conductivity member 89, and the second high thermal conductivity member 90 are disposed. The recess 24g is provided in a portion of the longitudinal direction other than the portion where the second high thermal conductivity member 90 (not shown in FIG. 42) is provided. The recess 24g is formed by making the recess 24a of the heater holder 24 deeper than the remaining portion. This minimizes the contact area between the heater holder 24 and the first high thermal conductivity member 89, thereby suppressing heat transfer from the first high thermal conductivity member 89 to the heater holder 24 and enabling the heater 23 to efficiently heat the fixing belt 21. In addition, in the cross section in the longitudinal direction where second high thermal conductivity member 90 is provided, second high thermal conductivity member 90 abuts against heater holder 24, as in the embodiment shown in FIG.

[0136] In this embodiment, the relief portion 24g is provided across the entire area where the resistance heating element 56 is provided in the transverse direction (the vertical direction in FIG. 42). This effectively suppresses heat transfer from the first high thermal conductivity member 89 to the heater holder 24, improving the heating efficiency of the heater 23 for the fixing belt 21. Note that, in addition to a configuration in which a space is provided like the relief portion 24g as the heat insulating layer, a configuration in which a heat insulating member having a lower thermal conductivity than the heater holder 24 is provided may also be used.

[0137] In addition, in the present embodiment, second high thermal conductivity member 90 is provided as a member different from first high thermal conductivity member 89, but this is not limiting. For example, first high thermal conductivity member 89 may also function as second high thermal conductivity member 90 by making the portion of first high thermal conductivity member 89 corresponding to interval B thicker than the other portions.

[0138] The above describes the configurations of other fixing devices and image forming apparatuses to which the present invention can be applied, but by applying the present invention to fixing devices and image forming apparatuses with such configurations, the same effects as those of the above-described embodiment can be obtained. That is, by applying the present invention, it is possible to suppress variations in the heater and belt temperatures and improve fixing quality.

[0139] Although the above description has been given with reference to an example where the present invention is applied to a fixing device, which is an example of a heating device, the present invention is not limited to fixing devices and can also be applied to heating devices such as a drying device that dries a liquid such as ink applied to paper, a laminator that thermocompresses a film as a covering member onto the surface of a sheet such as paper, and a heat sealer that thermocompresses a seal portion of a packaging material. [Explanation of symbols]

[0140] 20 Fixing device (heating device) 21 Fixing belt (first rotating body) 22 Pressure roller (second rotating body) 23 Heater (heat source) 28 Heat equalizer (heat transfer auxiliary component) 29 Hole 30 Thermistor 31 Thermostat 55 Base material 55a One end 55b Other end 56 Resistance heating element 58 Electrode section 100 Image forming device 281 Electrode side protrusion 282 Anti-electrode side protrusion N Nip section X Longitudinal direction [Prior art documents] [Patent documents]

[0141] [Patent Document 1] Japanese Patent Application Laid-Open No. 2008-76857

Claims

1. a rotatable first rotor; a rotatable second rotor that contacts an outer peripheral surface of the first rotor to form a nip portion; a heat source that heats the first rotating body; A heating device comprising a heat transfer assisting member in contact with the heat source, the heat source has a base material and a heating element provided on the base material, the substrate has a heat generating region in which the heat generating element is disposed, a length between one end of the base material in the longitudinal direction and the one end of the heat generating region is longer than a length between the other end of the base material in the longitudinal direction and the other end of the heat generating region; the heat transfer assistance member is disposed on at least the one side and the other side of the heat generating region in the longitudinal direction of the base material, A heating device characterized in that the volume of the portion of the heat transfer assistance member that is located on one side of the heat generation area is smaller than the volume of the portion of the heat transfer assistance member that is located on the other side of the heat generation area.

2. A heating device as described in claim 1, wherein, when viewed from a direction perpendicular to the contact surface of the heat transfer auxiliary member that contacts the heat source, the area of ​​the portion of the heat transfer auxiliary member that is located on one side of the heat generation area is smaller than the area of ​​the portion of the heat transfer auxiliary member that is located on the other side of the heat generation area.

3. 3. The heating device according to claim 2, wherein the length of the portion of the heat transfer auxiliary member located on one side of the heat generating region in the longitudinal direction of the base material is shorter than the length of the portion of the heat transfer auxiliary member located on the other side of the heat generating region in the longitudinal direction of the base material.

4. A heating device as described in claim 2 or 3, wherein the width of the portion of the heat transfer auxiliary member located on one side of the heat generation area in a direction perpendicular to the longitudinal direction of the base material is smaller than the width of the portion of the heat transfer auxiliary member located on the other side of the heat generation area in a direction perpendicular to the longitudinal direction of the base material.

5. A heating device described in any one of claims 1 to 4, wherein the thickness in a direction perpendicular to the surface of the base material on which the heating element is provided of the portion of the heat transfer auxiliary member located on one side of the heat generation area is smaller than the thickness in a direction perpendicular to the surface of the base material on which the heating element is provided of the portion of the heat transfer auxiliary member located on the other side of the heat generation area.

6. 6. The heating device according to claim 1, wherein the heat transfer assistance member is formed in an asymmetric shape with respect to a center of the heat transfer assistance member in the longitudinal direction of the base material.

7. The heating device according to claim 6 , wherein the heat transfer assistance member has a hole at a position shifted from the center in the longitudinal direction of the base material.

8. a temperature detection member that detects the temperature of the heat source; The heating device according to claim 7 , wherein the temperature sensing member is disposed within the hole.

9. 9. The heating device according to claim 8, wherein the temperature detecting member is a thermostat.

10. 9. The heating device according to claim 8, wherein the temperature detecting member is a thermistor.

11. the heat transfer assistance member has two of the holes, 8. The heating device according to claim 7, wherein a thermostat is disposed in one of the holes and a thermistor is disposed in the other of the holes.

12. A fixing device, comprising: a heating device according to claim 1 ; and a fixing unit for fixing an unfixed image onto a sheet.

13. An image forming apparatus comprising the heating device according to any one of claims 1 to 11 or the fixing device according to claim 12.

Images