Heater, heating device, and image forming apparatus

Abstract

To prevent a warp in the shape of a substrate of a heater.SOLUTION: In a heater 22 having a metal slender substrate 221, an insulating layer 222 provided on the substrate 221, and a heating element 223 provided on the insulating layer 222, in a short direction orthogonal to a longitudinal direction of a surface of the substrate 221 on which the insulating layer 222 is provided, when an area including the center of the substrate 221 is defined as a first area, an area adjacent to the first area and on one end side of the substrate as a second area, and an area adjacent to the first area and on the other end side of the substrate as a third area, the first area is a flat surface, and in a thickness direction of the substrate 221 orthogonal to the longitudinal direction and short direction, the second area and the third area are bent from the first area.SELECTED DRAWING: Figure 6

Description

[Technical Field]

[0001] The present invention relates to a heater used in an image forming apparatus such as a copying machine or a printer that utilizes an electrophotographic system or an electrostatic recording system. The present invention also relates to a heating device such as a fixing device equipped with the heater, or a gloss applying device that improves the glossiness of a toner image by reheating a fixed toner image on a recording material. The present invention further relates to an image forming apparatus including the heating device. [Background Art]

[0002] As a heating device mounted in an electrophotographic printer or copying machine, a configuration including a heater having a heating resistor on a substrate, a film that moves while being in contact with the heater, and a pressure roller that forms a nip portion with the heater via the film is common. As a substrate used for a heater in such a device, a metal substrate is sometimes used from the viewpoint of strength against thermal stress.

[0003] In a heater constituted by a metal substrate, since the substrate has conductivity, an insulating layer for ensuring insulation withstand voltage is provided between the heating resistor and the substrate. Glass is mainly used as the main material for the insulating layer, however, since the coefficient of linear expansion of glass differs from that of metal, a heater in which an insulating layer is provided on a metal substrate is prone to warping during firing. In view of this, Patent Document 1 discloses a configuration that suppresses warping of the heater by providing an insulating layer also on the back surface of the substrate opposite to the surface on which the heating resistor is provided. [Prior Art Literature] [Patent Literature]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 10-275671 [Summary of the Invention] [Problem to be Solved by the Invention]

[0005] In the device with the configuration described above, in order to suppress warping, it was necessary to provide an insulating layer on the back surface of the substrate opposite to the surface on which the heat-generating resistor is located.

[0006] This invention was made in view of the above problems, and aims to suppress warping by changing the shape of the substrate. [Means for solving the problem]

[0007] To achieve the above objective, the heater of the present invention is A long, thin metal circuit board, An insulating layer provided on the substrate, A heater having a heating element provided in the insulating layer, In the short-side direction perpendicular to the longitudinal direction of the surface of the substrate on which the insulating layer is provided, if the region including the center of the substrate is defined as the first region, the region on one end side of the first region as the second region, and the region on the other end side of the first region as the third region, The first region described above is a plane, In the thickness direction of the substrate, which is perpendicular to the longitudinal direction and the transverse direction of the transverse direction, the second region and the third region are bent from the first region. Occasionally, The insulating layer on which the heating element is provided is designated as the first insulating layer. If the surface on which the first insulating layer is provided is referred to as the first surface, The substrate has a second insulating layer on the second surface opposite to the first surface in the thickness direction, on which no heating element is provided. In the thickness direction, the first insulating layer is thicker than the second insulating layer. It is characterized by the following: Furthermore, in order to achieve the above objective, the heating device of the present invention is The first solid of revolution and A heater provided in the internal space of the first rotating body, comprising a metal elongated substrate, an insulating layer provided on the substrate, and a heating element provided on the insulating layer, A second rotating body that forms the nip portion with the heater via the first rotating body, A temperature detection unit for detecting the temperature of the heater, In a heating device having, In the short-side direction perpendicular to the longitudinal direction of the surface of the substrate on which the insulating layer is provided, if the region including the center of the substrate is defined as the first region, the region on one end side of the first region as the second region, and the region on the other end side of the first region as the third region, The first region described above is a plane, In the thickness direction of the substrate, which is perpendicular to the longitudinal direction and the transverse direction of the transverse direction, the second region and the third region are bent from the first region. The temperature sensing unit is provided on the side opposite to the side on which the insulating layer on which the heating element is provided is provided, in the thickness direction. The second region and the third region are characterized by being in contact with the first rotating body. Furthermore, in order to achieve the above object, the heating device of the present invention is a first rotating body, an elongated metal substrate, an insulating layer provided on the substrate, and a heating element provided on the insulating layer, a heater provided in an inner space of the first rotating body, and a second rotating body that forms a nip portion with the heater via the first rotating body, the heating device comprising: in the short direction that is orthogonal to the longitudinal direction of the surface of the substrate on which the insulating layer is provided, ,before a region including a center of the substrate is defined as a first region, a region closer to one end than the first region is defined as a second region, and a region closer to the other end than the first region is defined as a third region, in a thickness direction of the substrate orthogonal to the longitudinal direction and the short direction, the second region and the third region are bent closer to the nip portion side than the first region, Occasionally, The second and third regions are bent from the first region over the entire longitudinal direction of the substrate. characterized in that. Furthermore, in order to achieve the above objective, the heating device of the present invention is The first solid of revolution and A heater comprising a metal, elongated substrate, an insulating layer provided on the substrate, and a heating element provided on the insulating layer, provided in the internal space of the first rotating body, A second rotating body that forms the nip portion with the heater via the first rotating body, In a heating device having, In the short-side direction perpendicular to the longitudinal direction of the surface of the substrate on which the insulating layer is provided, if the region including the center of the substrate is defined as the first region, the region on one end side of the first region as the second region, and the region on the other end side of the first region as the third region, In the thickness direction of the substrate, which is perpendicular to the longitudinal and transverse directions, the second and third regions are bent so as to be closer to the nip portion than the first region. The insulating layer on which the heating element is provided is designated as the first insulating layer. If the surface on which the first insulating layer is provided is referred to as the first surface, The substrate has a second insulating layer on the second surface opposite to the first surface in the thickness direction, on which no heating element is provided. In the thickness direction, the first insulating layer is characterized by being thicker than the second insulating layer. Effects of the Invention

[0008] As described above, according to the present invention, warping can be suppressed by the shape of the substrate. Brief Description of the Drawings

[0009] [Figure 1]This is a schematic diagram of the image forming apparatus according to Example 1. [Figure 2] This is a cross-sectional view of the fixing device according to Example 1. [Figure 3] This is an exploded perspective view of the film unit according to Example 1. [Figure 4] This is a front view of the fixing device according to Example 1. [Figure 5] This is a cross-sectional perspective view of the fixing device according to Example 1. [Figure 6] This is a perspective view of the substrate and a cross-sectional view of the fixing device according to Example 1. [Figure 7] This is a schematic diagram of a conventional heater. [Figure 8] This is a cross-sectional perspective view of the fixing device according to modified example 1. [Figure 9] This is a perspective view of the heater and a cross-sectional view of the fixing device according to Modification 1. [Figure 10] This is a cross-sectional perspective view of the fixing device according to modified example 2. [Figure 11] This is a perspective view of the heater and a cross-sectional view of the fixing device according to modified example 2. [Figure 12] This is a cross-sectional perspective view of the fixing device according to Example 2. [Figure 13] This is a perspective view of the substrate and a cross-sectional view of the fixing device according to Example 2. [Figure 14] This is a perspective view of the heater and a cross-sectional view of the fixing device according to Modification 3. [Figure 15] This is a perspective view of the heater and a cross-sectional view of the fixing device according to Modification 4. [Figure 16] This is a cross-sectional perspective view of the fixing device according to Example 3. [Figure 17] This is a schematic diagram of the heater according to Example 3 and a cross-sectional view of the fixing device near the heater. [Figure 18] This is a cross-sectional view of the fixing device near the heater according to modified example 5. [Figure 19] This is a cross-sectional perspective view of the fixing device according to Example 4. [Figure 20] This is a cross-sectional view of the fixing device according to Example 4. [Figure 21]This is a cross-sectional view of the fixing device according to modified example 6. [Modes for carrying out the invention]

[0010] The embodiments for carrying out this invention will be described in detail below with reference to the drawings, based on examples. However, the dimensions, materials, shapes, and relative arrangements of the components described in the examples should be appropriately modified depending on the configuration and various conditions of the apparatus to which the invention is applied. In other words, the scope of this invention is not intended to be limited to the following embodiments. Examples of image forming apparatus to which the present invention can be applied include printers and copiers using electrophotographic or electrostatic recording methods, and here we will describe the case in which it is applied to a laser printer.

[0011] <Example 1> (1) Image forming apparatus 100 Figure 1 is a schematic diagram of the image forming apparatus 100 using electrophotographic recording technology in Example 1. First, the configuration and operation of the image forming apparatus 100 will be explained.

[0012] The image forming operation in the image forming section of the image forming apparatus 100 will be described. When the unit 100 receives a print command from an external device, the scanner unit 3 emits a laser beam L corresponding to the image information toward the photoreceptor 1. The photoreceptor 1, which has been charged to a predetermined polarity by the charging roller 2, is scanned by the laser beam L, and an electrostatic latent image corresponding to the image information is formed on the surface of the photoreceptor 1. Subsequently, the developer unit 4 supplies toner to the photoreceptor 1, and a toner image corresponding to the image information is formed on the photoreceptor 1. The toner image on the photoreceptor 1 moves to a transfer position formed by the photoreceptor 1 and the transfer roller 5 as the photoreceptor 1 rotates in the direction of arrow R, and is transferred to the recording material P fed from the cassette 6 by the pickup roller 7. The surface of the photoreceptor 1 that has passed through the transfer position is cleaned by the cleaner 8.

[0013] The recording material P onto which the toner image has been transferred is fixed by heat and pressure in the fixing unit 9. After that, the recording material P is discharged into the output tray 11 by the output roller 10.

[0014] (2) Fixing device 9 Next, the configuration and operation of the fixing device 9 will be described. In this embodiment, a tensionless type film heating fixing device 9 is used as an example of a heating device. The fixing device 9 in this embodiment uses an endless belt-shaped (or cylindrical) heat-resistant film, and at least a portion of the circumference of the film is always tension-free (no tension is applied), and the film is rotated by the rotational driving force of the pressurizing member.

[0015] Figure 2 is a schematic cross-sectional view of the fixing device 9 in this embodiment, showing how the recording material P having a toner image is transported to the fixing device 9. Figure 3 is an exploded perspective view of the film unit 20 used in the fixing device 9. Figure 4 is a schematic diagram of the fixing device 9 with a portion of the film 23 obscured to show the internal structure of the film unit 20.

[0016] Referring to Figure 2, the configuration of the fixing device 9 will be described. The fixing device 9 of this embodiment includes a cylindrical film 23 as a first rotating body, a heater 22 that heats the film 23 in the internal space of the film 23, and a pressure roller 30 as a second rotating body that forms a nip portion N with the heater 22 via the film 23. The fixing device 9 further includes a heater holder 21 that supports the heater 22 and guides the rotation of the film 23, and a reinforcing member 24 that reinforces the heater holder 21. The pressure roller 30 receives power from a motor (not shown) and rotates in the direction of arrow b, causing the film 23 to move and rotate in the direction of arrow a.

[0017] The film 23 is a cylindrical rotating body. The thickness of the film 23 is preferably 20 μm to 100 μm in order to ensure good thermal conductivity. If the film 23 is a single-layer film, it is preferable to use a material such as PTFE (polytetrafluoroethylene), PFA (tetrafluoroethylene-perfluoroalkyl vinyl ether), or PPS as the base layer. If it is a composite layer film, it is preferable to use a material such as PI (polyimide), PAI (polyamide-imide), PEEK (polyetheretherketone), or PES (polyethersulfone) as the base layer. Furthermore, it is preferable to construct a composite layer film using a material such as PTFE, PFA, or FEP (tetrafluoroethylene-perfluoroalkyl vinyl ether) as the release layer coated on the surface of the base layer. It is also preferable to use a base layer made of pure metals or alloys such as SUS, Al, Ni, Cu, or Zn, which have high thermal conductivity, and to apply the aforementioned coating treatment or a fluororesin tube coating to the release layer.

[0018] The film 23 in this embodiment is a composite layer film in which a base layer of PI with a thickness of 60 μm is coated with a release layer made of PFA with a thickness of 12 μm to achieve both abrasion resistance due to paper passage of the release layer and thermal conductivity. The longitudinal length of the film 23 is 240 mm. The axial direction of the cylindrical shape of the film 23 will henceforth be referred to as the longitudinal direction.

[0019] The heater holder 21 is a support member provided in the internal space of the film 23 and supports the heater 22. The heater holder 21 has the function of guiding the rotation of the film 23 while sliding in contact with the inner circumferential surface of the film 23, with the film 23 loosely fitted to the outside of the heater holder 21. Since the heater holder 21 is required to have heat resistance and rigidity, it is preferable to use a material such as a liquid crystal polymer resin that has high heat resistance and excellent strength as the material of the heater holder 21. For example, molded products of heat-resistant resins such as PPS (polyphenylene sulfite) or liquid crystal polymer can be used as the heater holder 21.

[0020] The heater 22 includes at least an elongated plate-shaped substrate mainly made of metal, a resistive heating element that generates heat when electricity is applied, an insulating layer that insulates the resistive heating element from the substrate, and a glass coating layer that protects the heating element. The detailed configuration of the heater 22 will be described later.

[0021] The thermistor 25, which is a temperature sensing unit, is in contact with a second surface of the substrate opposite to the first surface on which the resistive heating element is provided, in the thickness direction perpendicular to the longitudinal and transverse directions of the heater 22. The current supplied to the heating resistor is controlled according to the temperature detected by the thermistor 25, and the temperatures of the heater 22 and the film 23 are managed. In other words, in this embodiment, the temperature change of the film 23 is detected by the thermistor 25 via the heater 22.

[0022] The pressure roller 30 has a core made of a material such as iron or aluminum, an elastic layer made of a material such as silicone rubber, and a release layer made of a material such as PFA. A drive gear 33 (see Figure 4) is attached to one end of the core of the pressure roller 30 in the longitudinal direction, and the drive gear 33 receives rotational driving force from a driving means (not shown) to rotate the pressure roller 30.

[0023] The reinforcing member 24 is made of a metal such as iron and is a member that maintains its strength so as not to deform significantly even under the pressure applied to press the heater holder 21 toward the pressure roller 30 side (the second rotating body side). The heater 22 is pressed toward the pressure roller 30 side via the heater holder 21 and the reinforcing member 24 by the pressing means described later. The area where the pressure roller 30 and the film 23 are in close contact due to the pressure is the nip portion N (as a pressure contact area).

[0024] Next, with reference to the perspective view in Figure 3, the details of the film unit 20, which is composed of parts such as the film 23, will be described. First, the heater holder 21 has a roughly trough-shaped cross-section perpendicular to the longitudinal direction, and a reinforcing member 24 is fitted inside the barrel shape. A heater receiving groove is provided on the side of the heater holder 21 facing the pressure roller 30, and the heater 22 is fitted into the heater receiving groove and positioned as desired. The film 23 is fitted onto the outside of the heater holder 21, to which the above-mentioned parts are assembled, with some circumferential clearance.

[0025] The longitudinal ends of the reinforcing member 24 protrude outward from both ends of the film 23, and the film unit 20 is assembled by fitting flanges 26 to each end of the reinforcing member 24.

[0026] The power supply terminal of the heater 22 also protrudes outward from one end of the film 23 in the longitudinal direction, and the power supply connector 27 is fitted to it. The power supply connector 27 makes contact with the electrode portion of the heater 22 with contact pressure, creating a power supply path. The heater clip 28 is formed from a metal plate bent into a C shape, and its springiness holds the end of the heater 22 to the heater holder 21.

[0027] Next, the configuration of the fixing device 9 will be described in more detail with reference to Figure 4. In Figure 4, a portion of the film 23 is not shown so that the heater holder 21 and heater 22 provided in the internal space of the film 23 can be seen. The flanges 26 located at both ends of the film 23 restrict the longitudinal movement of the rotating film 23.

[0028] The film unit 20 is positioned opposite the pressure roller 30 and is supported by the top plate side housing 41. The film unit 20 is supported by the top plate side housing 41 so as to be able to move freely in the pressurizing direction, but its movement in the longitudinal direction is restricted. A pressure spring 45 is attached to the top plate side housing 41 of the fixing device 9 in a compressed state. The pressing force of the pressure spring 45 is received by both longitudinal ends of the reinforcing member 24 via the flange 26. Due to the pressing force of the pressure spring 45, the reinforcing member 24 is pressed toward the pressure roller 30, and the entire film unit 20 is pressed toward the pressure roller 30, forming the nip portion N.

[0029] The bearing member 31 is provided to pivotally support the core metal of the pressure roller 30 and receives the pressing force from the film unit 20 via the pressure roller 30. In order to rotatably support the core metal of the pressure roller 30, which becomes relatively hot, the bearing member 31 is made of a material that is heat resistant and has excellent sliding properties. The bearing member 31 is attached to the bottom housing 43 of the fixing device 9.

[0030] (3) Heater 22 Next, the materials and manufacturing method of the heater 22 in this embodiment will be described using Figures 5 and 6. Figure 5 is a perspective view showing a cross-section of the fixing device 9 in which the heater 22 of this embodiment is provided. Figure 6(a) is a perspective view showing the substrate 221 of the heater 22, and Figure 6(b) is a cross-sectional view of the fixing device 9 showing the vicinity of the heater 22.

[0031] The heater 22 comprises an elongated, plate-shaped substrate 221 made primarily of metal, a heating element 223 that generates heat when electricity is applied, an insulating layer 222 that insulates the heating element 223 from the substrate 221, and a protective layer 224 that protects the heating element 223. Of the surfaces of the substrate 221, the surface on which the insulating layer 222 and the heating element 223 are provided and which faces the pressure roller 30 via the film 23 is conveniently referred to as the first surface 221g (front surface), and the surface opposite to the first surface is conveniently referred to as the second surface 221h (back surface).

[0032] (3-1) Substrate 221 Suitable materials for the substrate 221 include stainless steel, nickel, copper, aluminum, and alloys primarily composed of these materials. Of these, stainless steel is most preferred in terms of strength, heat resistance, and corrosion resistance. The type of stainless steel is not particularly limited and should be selected appropriately considering the required mechanical strength, the coefficient of thermal expansion suitable for forming the insulating layer 222 and heating element 223, and the availability of sheet metal in the market. For example, martensitic and ferritic types of chromium-based stainless steel (400 series) have relatively low coefficients of thermal expansion among stainless steels, making them suitable for forming the insulating layer and heating element.

[0033] The thickness of the substrate 221 should be determined considering strength, heat capacity, and heat dissipation performance. A thin substrate 221 is advantageous for quick start-ups due to its low heat capacity, but if it is too thin, problems such as distortion are likely to occur during the heat molding of the heating element. In particular, since the heater is a long, narrow plate shape, it is prone to deformation into an arc shape with the longitudinal center on the heating element forming surface being a convex apex. Conversely, a thick substrate 221 is advantageous in terms of distortion during the heat molding of the heating element, but if it is too thick, the high heat capacity is disadvantageous for quick start-ups. The preferable substrate thickness, considering the balance between mass productionability, cost, and performance, is approximately 0.1 mm to 2.0 mm.

[0034] In this embodiment, the substrate 221 was made from a ferritic stainless steel plate (SUS430:18Cr stainless steel) with a width of 10 mm, a length of 300 mm, and a thickness of 0.1 mm. The characteristic shape of the substrate 221 of the present invention and its molding method will be described in detail later.

[0035] (3-2) Insulating layer 222 The material of the insulating layer 222 is not particularly limited, but a heat-resistant material should be used considering the actual operating temperature. The material needs to be selected. Glass and PI (polyimide) are preferred as materials from the viewpoint of heat resistance, and in the case of glass, the specific powder material should be selected appropriately within a range that does not impair the properties of the present invention. If necessary, insulating thermal conductive fillers may be mixed in.

[0036] Generally, heaters used in image forming apparatuses are preferably provided with an dielectric strength of around 1.5kV. Therefore, to obtain a dielectric strength of 1.5kV between the heating element 223 and the substrate 221, the thickness of the insulating layer 222 should be ensured according to the material.

[0037] The method for forming the insulating layer 222 is not particularly limited, but one example is that it can be smoothly formed by screen printing. When forming an insulating layer of glass or PI (polyimide) on a substrate, it is necessary to appropriately adjust the coefficients of thermal expansion of the substrate and the insulating layer material so that cracks or peeling occur in the insulating layer due to the difference in coefficients of thermal expansion between the materials. In this embodiment, an insulating layer glass paste was applied to a stainless steel substrate 221 by screen printing, and then the insulating layer 222 was formed by drying at 180°C and firing at 850°C. In this embodiment, an insulating layer 222 with a layer thickness of 50 μm is formed on the first surface 221g of the substrate 221.

[0038] (3-3) Heating element 223 The heating element 223 is connected to a power supply electrode (not shown), and when the power supply connector 27 supplies power to the power supply electrode, the heating element 223 is energized and generates heat. The heating element 223 is formed by printing a heat-resistant paste, which is a mixture of (A) a conductive component, (B) a glass component, and (C) an organic binder component, onto an insulating layer 222, and then firing it. When the heat-resistant paste is fired, the organic binder component (C) burns off, leaving components (A) and (B), thus forming a heating element 223 containing the conductive component and the glass component. Here, the conductive component (A) can be silver-palladium (Ag-Pd), ruthenium oxide (RuO2), etc., either alone or in combination, and it is preferable to have a sheet resistance value of 0.1 [Ω / □] to 100 [kΩ / □]. In addition, it is not a problem if other materials are included in trace amounts other than (A) to (C) above, as long as it does not impair the characteristics of the present invention. Here, the aforementioned heat-retaining resistor paste must be made of a material that softens and melts at a temperature lower than the melting point of the substrate 221, and a heat-resistant material must be selected considering the actual operating temperature.

[0039] The heating element 223 in this embodiment is formed from a heating element paste containing silver-palladium (Ag-Pd) as the conductive component, along with other glass components and organic binder components. The heating element paste is applied to a substrate 221, which has an insulating layer 222, by screen printing. After drying at 180°C and firing at 850°C, the heating element 223 is formed on the first surface 221g side of the substrate 221. After firing, the heating element 223 has a thickness of 15 μm, a length of 220 mm, and a width of 1.1 mm.

[0040] (3-4) Power supply electrodes and conductive patterns The power supply electrodes and conductive patterns are provided for the purpose of supplying power to the heating element 223. The power supply electrodes and conductive patterns (not shown) are mainly made of silver (Ag), platinum (Pt), gold (Au), silver-platinum (Ag-Pt) alloy, silver-palladium (Ag-Pd) alloy, etc. The power supply electrodes and conductive patterns are formed by printing a paste, which is a mixture of (A) conductive components, (B) glass components, and (C) organic binder components, onto a substrate 221 on which an insulating layer 222 is provided, and then firing it, similar to the heating element paste.

[0041] (3-5) Protective layer 224 The protective layer 224 is provided on the insulating layer 222 so as to cover the heating element 223, and is a layer that protects the heating element 223 and ensures sliding properties with respect to the film 23. As for the material, glass or PI (polyimide) is preferred from the viewpoint of heat resistance, and if necessary, a heat conductive filler with insulating properties may be mixed in.

[0042] The protective layer 224 is formed on the insulating layer after the protective layer glass paste is screen printed onto the heating element 223, followed by drying at 180°C and firing at 850°C. The thickness of the protective layer 224 in this embodiment is 50 μm.

[0043] (4) Shape of the substrate 221 As shown in Figure 6(a), the substrate 221 in this embodiment is a long metal member in the longitudinal direction, with an insulating layer 222 and a heating element 223 provided on the central flat portion 221a. In this embodiment, the substrate 221 is long in the same direction as the longitudinal direction of the film 23. Furthermore, the substrate 221 has a curved shape throughout its entire longitudinal direction. The shape of the substrate 221 of the heater 22 will be described in detail below.

[0044] The substrate 221 is bent such that the end in the short direction perpendicular to the longitudinal direction approaches the pressure roller 30 side in the thickness direction of the central flat portion 221a of the substrate 221. At both ends of the short direction of the substrate 221, there are end flat portions 221b which are substantially parallel to the central flat portion 221a and are located closer to the pressure roller 30 (heating element 223 side) than the central flat portion 221a. In this embodiment, the substrate 221 is formed by deep drawing press processing, and the drawing depth d1 of the substrate 221, which is the difference in step between the central flat portion 221a and the end flat portions 221b, is 50 μm.

[0045] The shape of the substrate 221 will now be described in more detail. The substrate 221 has four bends that bend along its entire longitudinal direction. The substrate 221 has a first bend 221c on one end in the short direction, located upstream in the transport direction of the recording material P, which bends toward the pressure roller 30, and a second bend 221d on the other end, one end further than the first bend, which bends toward the upstream in the transport direction. The substrate 221 further has a third bend 221e on the other end opposite to the one end located downstream in the transport direction of the recording material P, which bends toward the pressure roller 30, and a fourth bend 221f on the other end, one end further than the third bend, which bends toward the downstream in the transport direction. In this embodiment, the end-side flat portion 221b includes a second bent portion 221d and a fourth bent portion 221f, and the second bent portion 221d and the fourth bent portion 221f have planes parallel to the central-side flat portion 221a. That is, since the substrate is formed by bending a flat plate material multiple times, the central-side flat portion 221a and the end-side flat portion 221b are provided substantially parallel to each other with a certain amount of step difference.

[0046] In the short-side direction of the substrate 221, the central region including the central flat portion 221a of the first surface 221g on which the insulating layer 222 is provided is defined as the first region R1, the region on one end side of the first region R1 is defined as the second region R2, and the region on the other end side of the first region R1 is defined as the third region R3. In this embodiment, it can also be said that the second region R2 includes the first bent portion 221c and the second bent portion 222d, and the third region R3 includes the third bent portion 221e and the fourth bent portion 221f. That is, the first region R1 of the substrate 221 is flat, and the second region R2 and the third region R3 are bent from the first region R1. Furthermore, the second region R2 and the third region R3 each include a part of the end-side flat portion 221b. By providing multiple bends in this manner, the bending strength of the substrate 221 in the thickness direction is improved compared to a simple flat plate shape.

[0047] It should be noted that the bending described above does not necessarily mean forming a substrate by bending a sheet material through processes such as deep drawing press. For example, even if a substrate with a similar shape is formed by means of casting or cutting, the effects of reducing warping and improving the responsiveness of the film to temperature changes, as described later, can still be obtained. In other words, in this embodiment, deep drawing press was used to form the substrate as a processing method that offers ease of processing and the expected effect of improving the strength of the substrate through plastic deformation, but the method of forming the substrate is not limited to plastic deformation.

[0048] (5) Effects To confirm the effects of the present invention, evaluation tests were conducted, including comparative examples. The amount of heater warping, the temperature control temperature at which it can be fixed, and the load capacity were evaluated under each condition of this embodiment and comparative example.

[0049] The evaluation test was conducted using three types of heaters: this embodiment and two comparative examples. Figure 7(a) is a schematic diagram showing the configuration of heater 52 of Comparative Example 1, and Figure 7(b) is a schematic diagram showing the configuration of heater 62 of Comparative Example 2. Comparative Example 1 has a flat, unmolded plate-shaped substrate 521, with an insulating layer 522, a heating element 523, and a protective layer 524 provided on the surface side of the substrate 521, and an insulating layer 525 made of the same material as the insulating layer 522 provided on the back side. Comparative Example 2 has a flat, unmolded plate-shaped substrate 621, similar to Comparative Example 1. Similar to this embodiment, Comparative Example 2 has an insulating layer 622 only on the surface side of the substrate, with a heating element 623 and a protective layer 624 provided on top of it. Other configurations of Comparative Example 1 and Comparative Example 2, such as the thickness of the substrate and the length in the longitudinal direction, are the same as in Embodiment 1.

[0050] The amount of warping of the heater was measured by placing the heater on a horizontal surface plate with the surface of the substrate on which the heating element is mounted facing upwards, and defining the amount of warping as the height from the surface plate to the convex apex at the center of the longitudinal side of the heater on the back side. When assembling the heater into the heater holder, if the amount of warping is 3 mm or less, it is possible to assemble it along the heater holder with good workability, so a warping amount within the range of 0 to 3 mm was evaluated as acceptable (OK).

[0051] As an evaluation test of temperature control, the machine was left in a stopped state without standby temperature control for about an hour, and then 250 sheets were fed through using single-sided paper from a cold state. Xerox was used as the recording material for this test. Vitality (75g / m²) 2 A LTR (Laser Timer) was used. For calculating the temperature control temperature, a solid black pattern with toner printed across the entire surface was used as the print density pattern. From an energy-saving and power-saving perspective, a lower temperature control temperature is desirable for the fuser unit.

[0052] As part of the load capacity evaluation test, the machine was left in a stopped state without standby temperature control for about an hour, and then 250 sheets were fed through using double-sided paper from a cold state. In this test, Xerox Vitality (75g / m²) was used as the recording material. 2A (LTR) was used. Load capacity was evaluated by the number of sheets of recording material that could be loaded onto the output tray 11 after feeding. The amount of curl of the recording material affects the number of sheets that can be loaded; heaters and fusers that apply excessive heat to the recording material increase the amount of curl and decrease the number of sheets that can be loaded.

[0053] Table 1 shows the main configurations of this embodiment and comparative examples, as well as the evaluation results of warpage during heater molding, assembly ease, and fixing / loading performance. Assembly ease is indicated in the table as OK if the warpage is 3 mm or less, and NG if it is otherwise.

[0054] [Table 1]

[0055] In Example 1, the heater 22 had a warp of 2.8 mm, and there were no problems with assembly. The temperature control temperature was 190°C, and the number of recording materials that could be stacked was 200.

[0056] Comparative Example 1 showed a warp of 0.1 mm in the heater 52. This result indicates that warping is suppressed because the insulating layer 525 is also provided on the surface opposite to the surface on which the heating element 223 is formed.

[0057] However, the temperature control temperature in Comparative Example 1 was 200°C, which was higher than in Example 1, and the number of recording materials that could be stacked was also lower at 50 sheets. In Comparative Example 1, the sensitivity of the thermistor 25 to detecting temperature changes in the film 23 was reduced due to the thermal resistance of the insulating layer 525, resulting in a higher temperature control temperature and increased curling of the recording material, which further reduced the number of stackable sheets. In other words, Comparative Example 1 could not achieve both suppression of heater warping and detection through good responsiveness to temperature changes in the film.

[0058] Comparative Example 2 had a heater 62 warp of 11 mm, which made assembly difficult. In Example 1, the substrate is bent, which strengthens the bending strength in the thickness direction of the substrate. As a result, the amount of warp in Example 1 was significantly reduced compared to Comparative Example 2, which had the same layer configuration.

[0059] Furthermore, the temperature control temperature for Comparative Example 2 was 195°C, and the number of recording materials that could be stacked was 100. In both Comparative Example 2 and Example 1, the insulating layer is provided on only one side of the substrate, but the substrate of Example 1 is formed with a diaphragm depth d1 of 50 μm, and the short edge of the substrate is closer to the inner surface of the film compared to the substrate of Comparative Example 2. In other words, in Example 1, not only is the heat of the film 23 transferred to the substrate 221 via the protective layer 224, but heat is also more easily transferred directly from the film 23 to the substrate 221. Consequently, Example 1 can sense temperature changes of the film 23 more sensitively than Comparative Example 2, so Example 1 has a lower temperature control temperature and an increased number of stackable materials than Comparative Example 2.

[0060] As described above, the present invention suppresses the warping that occurs during heater molding to an extent that does not hinder assembly, while detecting temperature changes in the film with good responsiveness, thereby suppressing a decrease in temperature control temperature and curling of the recording material, and increasing the number of sheets that can be stacked. In other words, by bending the substrate so that the short edge of the substrate is closer to the pressure roller side (heating element side) in the thickness direction, heater warping can be suppressed without providing insulating layers on both sides of the substrate. Furthermore, since an insulating layer is not provided on one side of the substrate, it is possible to detect temperature changes in the film with good responsiveness.

[0061] The above-mentioned effects of the present invention are particularly useful in high-speed machines. For example, when the toner printing rate is high, such as for graphic patterns, the temperature of the film drops significantly when the recording material passes through the nip. In this case, if the film's responsiveness to temperature changes is poor, the recording material will pass through the nip before the temperature drop of the film can be fed back into the heater's power supply control. Therefore, if the film's responsiveness to temperature changes is poor, it is necessary to set a high temperature control temperature that satisfies the fixing requirements even under conditions of large film temperature drops. On the other hand, in double-sided printing, when printing the second side after the first side has passed through the nip and been heated, the amount of temperature drop of the film is smaller compared to the first side. Therefore, if the temperature control temperature is high, the amount of heat supplied to the recording material at the nip becomes excessive (overheating of the recording material), raising concerns about deterioration of stackability due to increased curling of the recording material. According to the present invention, since temperature changes of the film can be detected with good responsiveness, it is possible to reduce the temperature control temperature and suppress curling of the recording material.

[0062] Next, with reference to Figures 8 and 9, Modification 1 will be described as a modification of Example 1. Figure 8 is a perspective view showing a cross-section of the fixing device 39 equipped with a heater 32 according to Modification 1. Figure 9(a) is a perspective view showing the substrate 321 of the heater 32, and Figure 9(b) is a cross-sectional view of the fixing device 39 near the heater 32. For Modification 1, components similar to those in Example 1 are denoted by the same reference numerals and their descriptions are omitted. Modification 1 is characterized by the fact that the amount of warping of the heater 32 is suppressed compared to the configuration of Example 1, by providing an insulating layer 325 on the second surface 321h side of the substrate 321 to the extent that the temperature responsiveness of the thermistor 25 is not impaired. That is, in Modification 1, an insulating layer 322 is provided as a first insulating layer on the first surface 321g of the substrate 321, and an insulating layer 325 is provided as a second insulating layer on the second surface 321h.

[0063] In the modified example 1, the thickness of the insulating layer 325 on the second surface 321h side was set to 50 μm, and the tapering depth d3 of the substrate 321, which is the difference in height between the central flat portion 321a and the edge flat portion 321b, was set to 50 μm. The total thickness of the insulating layer 322 and protective layer 324 formed on the first surface 321g side was set to 100 μm, the same as in Example 1.

[0064] Table 2 shows the main components of this embodiment, comparative example, and modified example 1, as well as the evaluation results of warpage during heater molding, assembly ease, and fixing / loading performance. For assembly ease, those with a warpage of 3 mm or less are marked as OK, and all others are marked as NG.

[0065] [Table 2]

[0066] As shown in Table 2, in this modified example, the temperature control temperature became 195°C due to the provision of an insulating layer 325 on the second surface 321h side, resulting in a 5°C deterioration in adhesion compared to the configuration of Example 1, which reduced the number of stacked sheets from 200 to 100. On the other hand, the amount of warpage of the heater 32 in Modified Example 1 was 1.4 mm, which is a reduction in warpage during heater molding compared to Example 1. This is because, in Example 1, the insulating layer was provided on only one side of the substrate, whereas in Modified Example 1, the insulating layer 325 was provided on the second surface 321h side, so that insulating layers were provided on both the first surface 321g and the second surface 321h of the substrate 321. In other words, a configuration in which insulating layers are provided on both sides of the substrate, as in Modified Example 1, is effective in achieving both adhesion and heater warpage, especially in configurations where assembly accuracy is required.

[0067] Furthermore, as another variation, in this embodiment, both the upstream and downstream sides in the transport direction of the substrate are bent to approach the inner surface of the film. However, even if only one side is bent, a warping suppression effect can be obtained compared to a conventional flat substrate. Moreover, in this embodiment, end-side flat sections are provided at both ends in the short direction of the substrate. However, in order to save space in the device, a variation can be considered in which there are no end-side flat sections, and only two bent sections are provided on the substrate so that both ends in the short direction of the substrate extend substantially parallel to the thickness direction.

[0068] Next, with reference to Figures 10 and 11, Modification 2 will be described as a modification of Example 1. Figure 10 is a perspective view showing a cross-section of the fixing device 49 equipped with a heater 42 according to Modification 2. Yes. Figure 11(a) is a perspective view showing the substrate 421 of the heater 42, and Figure 11(b) is a cross-sectional view of the fixing device 49 near the heater 42. For Modification 2, the same reference numerals are used for components similar to those in Embodiment 1, and their explanation is omitted. The fixing device 49 of Modification 2 differs from Embodiment 1 in that the bending direction of the substrate 421 of the heater in the short direction perpendicular to the longitudinal direction is opposite to that of Embodiment 1, and the substrate 421 is bent toward the thermistor 25. That is, in Modification 2, the substrate 421 is bent so that the short end of the substrate 421 is separated from the pressure roller 30.

[0069] As shown in Figure 11(a), the substrate 421 is bent at its short-side edge in the thickness direction away from the side with the heating element 423. In other words, the short-side edge of the substrate 421 is bent away from the insulating layer 422 and the protective layer 424. Furthermore, the substrate 421 does not have a flat edge portion, and has only two bent sections on the substrate such that both ends in the short direction of the substrate extend substantially parallel to the thickness direction, thereby achieving space saving for the fixing device 49. The bent sections extend over the entire length of the substrate 421, and in this embodiment, the substrate 421 is formed by deep drawing press processing. For the second modification, the assembly and fixing / loading performance of the heater were evaluated for cases where the bending depth d4 of the substrate 421 was 50 μm and 150 μm, respectively.

[0070] Furthermore, as shown in Figure 11(b), the bent portion of the substrate 421 toward the thermistor 25 is positioned in a notched groove 211 provided in the heater holder 21. The notched groove 211 of the heater holder 21 is formed over the entire lengthwise region, and the groove depth d4h was set considering tolerances and the effect of thermal expansion of the bent portion of the substrate 421. Specifically, when the bending depth d4 of the substrate 421 is 50 μm, the groove depth d4h is set to 150 μm, and when the bending depth d4 is 150 μm, the groove depth d4h is set to 250 μm. The groove depth d4h of the notched groove is set to be reliably larger than the bending depth d4, taking into account manufacturing tolerances, etc., so that the heater 42 reliably contacts the holding surface of the heater holder 21. Furthermore, the groove depth d4h of the notch groove is set within a range that is not affected by deflection or other factors that occur when the heater holder 21 is pressurized by the pressure roller 30.

[0071] Table 3 shows the main components of this embodiment, comparative example, and modified example 2, as well as the evaluation results of warpage during heater molding, assembly ease, and fixing / loading performance. For assembly ease, those with a warpage of 3 mm or less are marked as OK, and all others are marked as NG.

[0072] [Table 3]

[0073] As shown in Table 3, in Modification 2, when the bending depth d4 of the substrate 421 is 50 μm, the heater warp is 2.8 mm, and when the bending depth d4 of the substrate 421 is 150 μm, the heater warp is 0.8 mm. In other words, the heater warp decreases as the bending depth d4 of the substrate 421 increases. Furthermore, regarding the fixing and loading performance evaluation results, The temperature control temperature was 195°C regardless of the bending depth d4 of the substrate 421, and the number of stacked sheets was 100, resulting in a 5°C improvement compared to Comparative Example 1. On the other hand, in Modification Example 2, the reason why the temperature control was 5°C higher than in the configuration of Example 1 is that the bending direction of the substrate 321 was on the thermistor 25 side, which reduced the effect of the temperature change of the film 23 being more easily transmitted to the substrate 421.

[0074] As explained above, increasing the bending depth d4 of the substrate 421 makes it possible to reduce the amount of heater warping during heater 42 molding, which is expected to improve ease of assembly. Also, similar to Example 1, the absence of an insulating glass layer on the opposite side of the heating element 423 allows for detection of temperature changes in the film with good responsiveness, thereby suppressing a decrease in temperature control temperature and curling of the recording material.

[0075] <Example 2> Next, Embodiment 2 of the present invention will be described. The fixing device 79 of Embodiment 2 differs from that of Embodiment 1 in that both ends of the heater substrate in the short direction are in contact with the inner circumferential surface of the film. As for the other configurations of the image forming apparatus and fixing device in Embodiment 2, the same configuration as in Embodiment 1 is adopted, so the same reference numerals are used and their description is omitted. The characteristic configuration of Embodiment 2 will be described in detail below.

[0076] Figure 12 is a perspective view showing a cross-section of the fixing device 79 equipped with the heater 72 of this embodiment. Figure 13(a) is a perspective view showing the substrate 721 of the heater 72, and Figure 13(b) is a cross-sectional view of the fixing device 9 showing the vicinity of the heater 72.

[0077] In this embodiment as well, the heater 72 includes an elongated plate-shaped substrate 721 made mainly of metal, a heating element 723 that generates heat when electricity is applied, an insulating layer 722 that insulates the heating element 723 from the substrate 721, and a protective layer 724 that protects the heating element 723.

[0078] As shown in Figure 13(a), the substrate 721 in this embodiment is a long metal member in the longitudinal direction, with an insulating layer 722 and a heating element 723 provided on the central flat portion 721a. The substrate 721 is bent such that the ends in the short direction, perpendicular to the longitudinal direction, approach the pressure roller 30 side in the thickness direction of the substrate 721. At both ends of the short direction of the substrate 721, end-side flat portions 721b, which are substantially parallel to the central flat portion 721a, are provided so as to be located on the pressure roller 30 side (heating element 723 side). The substrate 721 also has a plurality of bent portions 721c to 721f formed over the entire length. In this embodiment, the substrate 721 is formed by deep drawing press processing, and the drawing depth d2 of the substrate 721, which is the difference in step between the central flat portion 721a and the end-side flat portion 721b, is 150 μm.

[0079] In the short-side direction of the substrate 721, the central region including the central flat portion 721a of the first surface 721g on which the insulating layer 722 is provided is defined as the first region R1, the region on one end side of the first region R1 is defined as the second region R2, and the region on the other end side of the first region R1 is defined as the third region R3. In this embodiment, it can also be said that the second region R2 includes the first bent portion 721c and the second bent portion 722d, and the third region R3 includes the third bent portion 721e and the fourth bent portion 721f. That is, the first region R1 of the substrate 721 is flat, and the second region R2 and the third region R3 are bent from the first region R1. Furthermore, the second region R2 and the third region R3 each include a part of the end-side flat portion 721b.

[0080] As described above, this embodiment has a greater throttling depth than Embodiment 1, and its throttling depth d2 is greater than the combined thickness of the insulating layer 722 and the protective layer 724. Therefore, the flat end portion 721b of the substrate 721 of the heater 72 is configured to protrude toward the pressure roller 30 side from the protective layer 724 in the thickness direction. In other words, the fixing device 79 of this embodiment has the substrate 7 on the inner surface of the film 23. This differs from Embodiment 1 in that the end-side flat portion 721b provided at the short end of 21 makes contact. In the fixing device 79, the film 23 slides against the protective layer 724 of the heater 72, the substrate 721, and the heater holder 21.

[0081] In this embodiment as well, evaluation tests were conducted on the amount of heater warpage and fixing / loading performance, as performed in Example 1 and the comparative example. Furthermore, in order to compare Example 1 and Example 2, the lifespan of the fixing device was additionally evaluated for each. The lifespan of the fixing device was determined using Xerox Vitality (75g / m²). 2 The LTR (Long-Term Relay) was subjected to a paper feed durability test in an ambient temperature of 33°C and humidity of 80%, and was evaluated by the number of sheets that could be fed until a jam occurred due to a feeding malfunction when intermittently fed.

[0082] Table 2 shows the main configurations of this embodiment and Embodiment 1, the evaluation results of warpage during heater molding, assembly ease, fixing and loading performance, and the lifespan of the fixing device. For assembly ease, those with a warpage of 3 mm or less are marked as OK, and all others are marked as NG.

[0083] [Table 4]

[0084] In Example 2, the heater 72 had a warp of 0.8 mm, and there were no problems with assembly. The temperature control temperature was 180°C, the number of recording materials that could be loaded was 250, and the fixing device life was 100,000 sheets.

[0085] In Example 2, the amount of heater warpage is significantly reduced compared to Example 1. This is because Example 2 has a greater drawing depth for the substrate, resulting in superior bending strength. In other words, a greater drawing depth for the substrate is better for suppressing heater warpage.

[0086] Furthermore, in Example 2, the temperature control temperature was lower and the number of recording materials that could be stacked was increased compared to Example 1. This is because, in Example 2, the substrate 721 is in contact with the inner surface of the film 23 at the edge flat portion 721b, allowing Example 2 to sense temperature changes of the film 23 more sensitively than Example 1. In other words, to reduce the temperature control temperature and increase the number of recording materials that can be stacked, it is better for the heater substrate to be located closer to the inner surface of the film.

[0087] On the other hand, in Example 2, the lifespan of the fixing device was inferior to that of Example 1. This is because, in the fixing device 79 of Example 2, the film 23 rotates while sliding against the substrate 721. When paper is repeatedly fed while the film is sliding against the substrate, the inner surface of the film is gradually worn down, and this wear on the inner surface of the film increases the rotational resistance of the film. In other words, in Example 2, the rotational resistance of the film 23 increased, reducing its ability to transport the recording material. As a result, jams due to transport failures occurred with fewer sheets compared to Example 1, and the lifespan of the fixing device was reduced. In short, to improve the lifespan of the fixing device, it is better to have a configuration in which the heater substrate does not come into contact with the film.

[0088] As described above, the heater substrate is in contact with the inner surface of the film, as in Example 2. Compared to a configuration without contact, this approach results in a shorter fuser lifespan, but offers advantages such as improved heater warping suppression, reduced temperature control requirements, and increased storage capacity. Such a fuser configuration is suitable for consumer printers where long product lifespan is not a critical concern.

[0089] Modify 3 will be described as a modification of Example 2 with reference to Figures 14(a) and (b). Figure 14(a) is a perspective view showing the substrate 821 of the heater 82 according to Modify 3, and Figure 14(b) is a cross-sectional view of the fixing device 89 near the heater 82. For Modify 3, components similar to those in Example 2 are denoted by the same reference numerals and their description is omitted.

[0090] In the modified example 3, the tapering depth d5 ​​of the substrate 821, which is the difference in height between the central flat portion 821a and the edge flat portion 821b, is set to 100 μm. Furthermore, the protective layer 824 is formed to cover not only the central flat portion 821a of the substrate 821 but also the edge flat portion 821b, thereby improving the sliding properties between the heater 82 and the film 23. At the edge flat portion 821b of the substrate 821, the protective layer 824 is directly provided on the substrate 821, and the insulating layer 822 is not interposed between the substrate 821 and the protective layer 824. In other words, the central portion 824a of the protective layer 824 is in contact with the insulating layer 822, and the edge portion 824b is in contact with the substrate 821. In the configuration of Modified Example 3, the thickness of the end portion 824b of the protective layer 824 covering the edge flat portion 821b of the substrate 821 is set to 50 μm, and the height from the central flat portion 821a to the end portion 824b is set to the same value as the substrate drawing depth in Example 2.

[0091] Table 5 shows the main configurations of Examples 1 and 2 and Modification 3, the evaluation results of warpage during heater molding, assembly ease, fixing and loading performance, and the lifespan of the fixing device. For assembly ease, those with a warpage of 3 mm or less are marked as OK, and all others are marked as NG.

[0092] [Table 5]

[0093] The heater warp in Modification 3 was 1.4 mm. In Modification 3, the aperture depth d5 ​​was 100 μm, which was 50 μm less than the configuration in Example 2. As a result, although the amount of warp increased slightly compared to the configuration in Example 2, the assembly was not affected. In addition, a protective layer 824 was provided on the edge flat portion 821b of the substrate 821, and the sliding effect between the heater 82 and the film 23 improved the lifespan of the fixing device from 100,000 sheets in Example 2 to 200,000 sheets. On the other hand, regarding the temperature control temperature, the protective layer 824 provided on the edge flat portion 821b hindered heat transfer, resulting in a temperature of 185°C, which was 5°C higher than the 180°C in Example 2, and the number of recording materials that could be stacked slightly worsened from 250 sheets to 225 sheets.

[0094] As described above, by using a heater configuration like that in Modification 3, it is possible to suppress the warping effect of the heater, and although the number of recording materials that can be stacked is slightly reduced compared to Example 2, an improvement in the lifespan of the fixing device can be expected.

[0095] Next, with reference to Figures 15(a) and (b), Modification 4 will be described as a modification of Example 2. Figure 15(a) is a perspective view showing the substrate 921 of the heater 92 according to Modification 4. 15(b) is a cross-sectional view of the fixing device 99 near the heater 92. For Modification 4, the same reference numerals are used for components similar to those in Example 2, and their descriptions are omitted. Modification 4 is a configuration in which the thickness of the insulating layer 922 and the protective layer 924 are changed compared to Modification 3.

[0096] Modification 4 involves adjusting the thickness of the insulating layer 922 and protective layer 924 formed on the central flat portion 921a and the edge flat portion 921b of the substrate 921 so that the surface shape of the protective layer 924 that contacts the inner surface of the film 23 becomes a single plane. That is, in Modification 4, the thickness of the protective layer 924 is substantially the same in the central portion 924a and the edge portion 924b. By shaping the heater so that the protective layer 924 is substantially flat, the present invention can also be applied to fixing configurations that require a wider nip width, such as those for high-speed machines.

[0097] Furthermore, as a further variation of the configuration in which the heater substrate is in contact with the inner surface of the film, processing to improve sliding properties, such as anodizing or applying a release agent, may be performed on the substrate surface to improve the lifespan of the fixing device.

[0098] <Example 3> Next, Embodiment 3 of the present invention will be described with reference to Figures 16 and 17. This embodiment is characterized in that a heat diffusion member 81 is provided between the heater 102 and the film 23 to diffuse and homogenize the temperature distribution of the heat generated by the heating element of the heater 102. The configuration of the image forming apparatus and fixing apparatus in other parts of Embodiment 3 is the same as in Embodiment 1, so the same reference numerals are used and their description is omitted. The characteristic configuration of Embodiment 3 will be described in detail below.

[0099] Figure 16 is a perspective view showing a cross-section of the fixing device 109 equipped with the heater 102 of this embodiment. Figure 17(a) is a schematic diagram showing the configuration of the heater 102, and Figure 17(b) is a cross-sectional view of the fixing device 109 near the heater 102. In this embodiment, a heat diffusion member 81, which is long in the same direction as the heater 102, is provided between the heater 102 and the film 23.

[0100] In this embodiment as well, the heater 102 includes an elongated plate-shaped substrate 1021 made mainly of metal, a heating element 1023 that generates heat when electricity is applied, an insulating layer 1022 that insulates the heating element 1023 from the substrate 1021, and a protective layer 1024 that protects the heating element 1023.

[0101] As shown in Figure 17(a), the substrate 1021 in this embodiment is a long metal member in the longitudinal direction, with an insulating layer 1022 and a heating element 1023 provided on the central flat portion 1021a. The substrate 1021 is bent so that the ends in the short direction, perpendicular to the longitudinal direction, approach the pressure roller 30 side in the thickness direction of the substrate 1021. At both ends of the substrate 1021 in the short direction, end-side flat portions 1021b, which are substantially parallel to the central flat portion 1021a, are provided so as to be located on the pressure roller 30 side (heating element 1023 side). The substrate 1021 also has multiple bent portions formed over its entire length.

[0102] In the short-side direction of the substrate 1021, the central region of the surface on which the insulating layer 1022 is provided is defined as the first region R1, the region on one end side of the first region R1 is defined as the second region R2, and the region on the other end side of the first region R1 is defined as the third region R3. In this embodiment, the second region R2 and the third region R3 each contain two bends. That is, the first region R1 of the substrate 221 is a plane, and the second region R2 and the third region R3 are bent from the first region R1.

[0103] In this embodiment, the substrate 1021 is formed by deep drawing press processing, and the drawing depth d6 of the substrate 1021, which is the difference in step between the central flat portion 1021a and the edge flat portion 1021b, is 100 μm. The thickness of the substrate 1021 is 0.5 mm, and the length L1 in the short direction of the central flat portion is 6 For heater 102, the short-side length L2 was set to 8 mm.

[0104] In this embodiment, the heater 102 has a tapered depth d6 of the substrate 1021 that is approximately the same as the combined thickness of the insulating layer 1022 and the protective layer 1024 on the central flat portion 1021a, and is configured so that the surface of the protective layer 1024 and the edge flat portion 1021b are on approximately the same plane. With this configuration, as shown in Figure 17(b), both the edge flat portion 1021b and the protective layer 1024 are in contact with the heat diffusion member 81.

[0105] The heat diffusion member 81 is a metal plate with a roughly C-shaped cross-section, with both ends in the shorter direction bent toward the thermistor 25. Preferably, the heat diffusion member 81 is a metal plate with a thickness in the range of 0.2 mm to 1.0 mm. For example, a thin metal plate such as stainless steel, aluminum alloy, or iron can be used as the heat diffusion member 81. Furthermore, it is desirable that the sliding surface of the heat diffusion member 81 with the film 23 be treated (for example, glass coating or hard chrome coating) to reduce the coefficient of friction and increase wear resistance.

[0106] In this embodiment, a stainless steel sheet with a thickness of 0.5 mm was used as the heat diffusion member 81. The heat diffusion member 81 was formed by bending a thin stainless steel sheet at its short-side end, with the length of the bent portion being 0.6 mm. The length of the heat diffusion member 81 in the short-side direction after bending was 9.0 mm, and a glass coating with a thickness of 50 μm was applied to the sliding portion with the film 23.

[0107] Furthermore, grease is applied between the heater 102 and the heat diffusion member 81 to improve heat transfer. In this embodiment, thermal conductive grease is applied as the grease, and the heater 102 is held in the heater holder 21 with the heater 102 and the heat diffusion member 81 in close contact.

[0108] By making the cross-section of the heat diffusion member 81 roughly C-shaped as described above, some of the grease applied between the heater 102 and the heat diffusion member 81 is displaced from the heat diffusion member 81 by the pressurization and heating of the fuser, preventing it from adhering to the film 23.

[0109] The thermistor 25, which is a temperature sensing unit, is in contact with a second surface of the substrate opposite to the first surface on which the resistive heating element is provided, in the thickness direction perpendicular to the longitudinal and transverse directions of the heater 102. The current supplied to the heating resistor is controlled according to the temperature detected by the thermistor 25, and the temperatures of the heater 102 and the film 23 are managed. In other words, in this embodiment, the temperature change of the film 23 is detected by the thermistor 25 via the heat diffusion member 81 and the heater 102.

[0110] To confirm the effects of the present invention, evaluation tests including comparative examples will be described. In the evaluation tests, the amount of heater warping, the fixed temperature control temperature, and the load capacity were evaluated for this embodiment and Comparative Examples 3 and 4, in the same manner as in the evaluation test for Example 1.

[0111] The evaluation test was conducted using three types of heaters: this embodiment and two comparative examples. The heater configuration of Comparative Example 3 is the same as heater 52 of Comparative Example 1, which was used for comparison with Example 1. The heater configuration of Comparative Example 4 is the same as heater 62 of Comparative Example 2, which was used for comparison with Example 1. The other configurations of Comparative Examples 3 and 4 are the same as those of Example 3, and Comparative Examples 3 and 4 are also provided with the same heat diffusion members as in Example 3.

[0112] Table 6 shows the main components of this embodiment and Comparative Examples 3 and 4, as well as the evaluation results of warpage during heater molding, assembly ease, and fixing / loading ease. For assembly ease, those with a warpage of 3 mm or less are marked as OK, and all others are marked as NG.

[0113] [Table 6]

[0114] In Example 3, the heater 22 had a warp of 2.8 mm, and there were no problems with assembly. The temperature control temperature was 190°C, and the number of recording materials that could be stacked was 200.

[0115] In Comparative Example 3, the amount of warping of the heater 52 was 0.1 mm. From this result, it can be seen that warping is suppressed because the insulating layer 525 is also provided on the surface opposite to the surface on which the heating element 523 is formed.

[0116] However, the temperature control temperature in Comparative Example 3 was 200°C, which was higher than in Example 3, and the number of recording materials that could be stacked was 50, which was also lower than in Example 3. In Comparative Example 3, the sensitivity of the thermistor 25 to detecting temperature changes in the film 23 was reduced due to the thermal resistance of the insulating layer 525, resulting in a higher temperature control temperature and increased curling of the recording material, which further reduced the number of stackable materials. In other words, in Comparative Example 3, it is not possible to achieve both suppression of heater warping and detection through good responsiveness of temperature changes in the heat diffusion member 81.

[0117] Comparative Example 4 had a heater 62 warp of 11 mm, which made assembly difficult. In Example 3, the substrate is bent, which strengthens the bending strength in the thickness direction of the substrate. Therefore, compared to Comparative Example 4, which has the same layer configuration, the amount of heater warp in Example 3 was significantly reduced.

[0118] Furthermore, the temperature control temperature of Comparative Example 4 was 195°C, and the number of recording materials that could be stacked was 100. In both Comparative Example 4 and Example 3, the insulating layer is provided on only one side of the substrate, but in Example 3, the substrate 1021 is formed with a condensation depth d6 of 100 μm, and the short edge of the substrate 1021 is in contact with the heat diffusion member 81. In other words, in Example 3, not only is the heat from the heat diffusion member 81 transferred to the substrate 1021 via the protective layer 1024, but the heat is also transferred directly from the heat diffusion member 81 to the substrate 1021, so the heat from the heat diffusion member 81 is transferred to the substrate 1021 more easily compared to Comparative Example 4. Consequently, Example 3 can sense the temperature change of the heat diffusion member 81 more sensitively than Comparative Example 4, and therefore, the temperature control temperature is lower and the number of stackable materials is increased according to the configuration of Example 3.

[0119] As described above, according to the present invention, the warping of the heater that occurs during the molding of the heater can be suppressed to an extent that does not hinder assembly. Furthermore, by detecting the temperature change of the heat diffusion member 81 with good responsiveness, the temperature control temperature is reduced and curling of the recording material is suppressed, thereby increasing the number of recording materials that can be stacked. In other words, by bending the substrate so that the short edge of the substrate is closer to the pressure roller side (heating element side) in the thickness direction, the warping of the heater can be suppressed without providing insulating layers on both sides of the substrate. Also, since the heat of the heat diffusion member is transferred to the short edge of the substrate, the temperature change of the heat diffusion member can be detected with good responsiveness. Furthermore, since an insulating layer is not provided on one side of the substrate, it is possible to detect the temperature change of the film with good responsiveness.

[0120] In this embodiment, the fold depth d6 of the substrate was set to 100 μm, so that it was approximately flush with the protective layer 1024. However, the embodiment is not limited to this, and the depth of the fold of the substrate may be set to a value lower than the total thickness of the insulating layer and the protective layer. Even with such a configuration, temperature changes of the film 23 and the heat diffusion member 81 can be sensed more sensitively compared to a configuration without a fold in the substrate.

[0121] Referring to Figure 18, Modification 5 will be described as a modification of Example 3. Figure 18 is a cross-sectional view of the fixing device near the heater 112 according to Modification 5. For Modification 5, components similar to those in Example 3 are denoted by the same reference numerals and their descriptions are omitted.

[0122] As shown in Figure 18, in Modification 5, the substrate of the heater 112 does not have a flat end portion, and the substrate is formed so that both ends in the short direction of the substrate extend substantially parallel to the thickness direction, resulting in only two bent portions of the substrate. The short ends of the substrate then contact the bent portions of the short ends of the heat diffusion member. Even with this configuration, the bending of the heater is suppressed by providing bent portions in the substrate, and because the bent portions of the substrate are in contact with the heat diffusion member 81, temperature changes of the heat diffusion member 81 are sensitively detected. Consequently, in Modification 5, as in Example 3, it is possible to achieve both suppression of heater warping and detection through good responsiveness of temperature changes of the heat diffusion member 81.

[0123] Furthermore, as another variation, the heater may not have a flat end portion, and both ends of the substrate in the short direction may be bent in the direction opposite to the side with the heating element, resulting in a configuration with only two bent portions of the substrate so that both ends of the substrate extend substantially parallel to the thickness direction. Even with such a configuration, the same effect as in Example 3 can be obtained by bringing both ends of the substrate in the short direction into contact with the bent portions of the short ends of the heat diffusion member.

[0124] <Example 4> Next, Embodiment 4 of the present invention will be described with reference to Figures 19 and 20. Figure 19 is a perspective view showing a cross-section of a fixing device 129 equipped with a heater 122 according to Embodiment 4, and Figure 20 is a cross-sectional view of the fixing device 129. The fixing configuration of this embodiment is characterized in that a heat transfer member 85, which is located in a place other than the nip portion N, the area in which the film 83 and the pressure roller 90 are in close contact, is heated by the heater 122, and the film 83 is heated via the heat transfer member 85. This fixing configuration is excellent in that, since there is no heater in the nip portion N, the degree of design freedom of the nip portion is high, and the nip N can be made larger, thus enabling high throughput.

[0125] In this embodiment, the heater according to the present invention is applied as a heating means for heating the heat transfer member 85 described above. The characteristic features of the configuration of the image forming apparatus and fixing apparatus in Embodiment 4 will be described in detail. Furthermore, in Embodiment 4, components similar to those in Embodiment 1 are denoted by the same reference numerals and their description is omitted.

[0126] Referring to Figure 20, the configuration of the fixing device 129 of this embodiment will be described. The fixing device 129 of this embodiment has a cylindrical film 83 as a first rotating body and a pressure roller 90 as a second rotating body for transporting the recording material. The fixing device 129 further has a nip roller 86 and a nip forming member 87 which are arranged in the internal space of the film and form a nip portion N with the pressure roller 90 via the film 83, and a heater 122 which is arranged in the internal space of the film 83 at a location other than the nip portion N. The fixing device 129 further has a heater support member 84 which holds the heater 122 and is arranged in the internal space of the film, and a heat transfer member 85 which is in contact with the film 83 in the internal space of the film 83 and uniformly diffuses and transfers the heat generated from the heater 122. The nip forming member 87 and the heater support member 84 are arranged in the internal space of the film 83. The stay 91 is pressurized by a pressure spring (not shown) located at its longitudinal end.

[0127] In this embodiment, among the above-mentioned members provided in the internal space of the film 83, the heat transfer member 85, the nip roller 86, and the nip forming member 87 are arranged to be in contact with the inner surface of the film 83. In the direction adjacent to the film 83 and the pressure roller 90, the nip roller 86 and the nip forming member 87 are in contact with the film 83 on the side closer to the pressure roller 90, while the heat transfer member 85 is in contact with the film 83 on the side further away from the pressure roller 90.

[0128] Film 83 is a composite film with a base layer of 100 μm thick PI and a 12 μm thick release layer made of PFA to balance abrasion resistance due to paper passage in the release layer with thermal conductivity. The outer diameter is Φ45 mm.

[0129] The pressure roller 90 consists of a core metal and an elastic layer. The elastic layer is made of 1.5 mm thick silicone rubber, and the release layer is made of 30 μm thick PFA tubing. To ensure sufficient nip width, the outer diameter of the pressure roller 90 is Φ36 mm.

[0130] The nip roller 86, positioned within the internal space of the film 83, is composed of a core metal and an elastic layer. The elastic layer of the nip roller 86 is made of 2.0 mm thick silicone rubber and has an outer diameter of Φ25 mm.

[0131] The nip-forming member 87 is pressed to adhere closely to the film 83 by a pressure spring positioned on the inner surface of the film. In this embodiment, the nip roller 86 and the nip-forming member 87 form a nip portion with the pressure roller 90 via the film 83, making it possible to increase the nip width compared to a configuration in which the nip portion is formed by a heater and a pressure roller. The shape of the portion of the nip-forming member 87 that contacts the film 83, which also has the function of guiding the rotation of the film, consists of a composite curve of a substantially flat portion and a substantially curved portion, and aluminum extruded material was used for the nip-forming member 87 to improve dimensional accuracy. The substantially flat portion of the nip-forming member 87 forms a nip portion with the pressure roller 90 via the film 83.

[0132] The thermistor 25, which is a temperature sensing unit, is in contact with a second surface of the substrate opposite to the first surface on which the resistive heating element is provided, in the thickness direction perpendicular to the longitudinal and transverse directions of the heater 122, via a through hole provided in the heater support member 84. The current supplied to the heating resistor is controlled according to the temperature detected by the thermistor 25, and the temperatures of the heater 122 and the film 83 are managed. In other words, in this embodiment, the temperature change of the film 83 is detected by the thermistor 25 via the heat transfer member 85 and the heater 122.

[0133] The heater support member 84 is made of PPS, which has high heat resistance and heat insulation properties, and the side opposite to the side on which the heater 122 is supported is configured to receive pressure from pressure springs (not shown) located at two locations on the longitudinal end of the stay 91.

[0134] The heat transfer member 85 is made of aluminum, which has high thermal conductivity, in order to efficiently transfer heat from the heater 122 to the film 83. The contact surface with the film 83 is roughly arc-shaped to ensure a wide contact area with the film 83. In addition, a grease (not shown) is applied between the heater 122 and the heat transfer member 85 to improve the adhesion between the heater 122 and the heat transfer member 85 and to ensure heat transfer performance.

[0135] In this embodiment as well, the heater 122 includes an elongated plate-shaped substrate 1221 made mainly of metal, a heating element 1223 that generates heat when electricity is applied, an insulating layer 1222 that insulates the heating element 1223 from the substrate 1121, and a protective layer 1224 that protects the heating element 1223. The shape of the heater 122 in this embodiment is the same as that of the heater 102 in Embodiment 3, so a description is omitted.

[0136] In this embodiment, the heater 122 has a tapered depth of the substrate 1221 that is approximately the same as the combined thickness of the insulating layer 1222 and the protective layer 1224 on the central flat portion 1221a, and is configured so that the surface of the protective layer 1224 and the edge flat portion 1221b are on approximately the same plane. With this configuration, as shown in Figure 20, both the edge flat portion 1221b and the protective layer 1224 are in contact with the heat transfer member 85, so the thermistor 25 can detect temperature changes of the film 83 and the heat transfer member 85 with good responsiveness.

[0137] To confirm the effects of the present invention, evaluation tests including comparative examples will be described. In the evaluation tests, the amount of heater warping, the fixed temperature control temperature, and the load capacity were evaluated for this embodiment and Comparative Examples 5 and 6, in the same manner as in the evaluation test for Example 1.

[0138] The evaluation test was conducted using three types of heaters: this embodiment and two comparative examples. The heater configuration of Comparative Example 5 is the same as heater 52 of Comparative Example 1, which was used for comparison with Example 1. Similarly, the heater configuration of Comparative Example 6 is the same as heater 62 of Comparative Example 2, which was used for comparison with Example 1. The other configurations of Comparative Examples 5 and 6 are the same as those of Example 4, and Comparative Examples 5 and 6 are also provided with heat transfer members 85 and nip forming members 87, etc., as in Example 4.

[0139] Table 7 shows the main components of this embodiment and Comparative Examples 5 and 6, as well as the evaluation results for warpage during heater molding, assembly ease, and fixing / loading performance. Assembly ease is indicated in the table as OK if the warpage is 3 mm or less, and NG if it is otherwise.

[0140] [Table 7]

[0141] In Example 4, the heater 22 had a warp of 1.4 mm, and there were no problems with assembly. The temperature control temperature was 190°C, and the number of recording materials that could be stacked was 200.

[0142] In Comparative Example 5, the amount of warping of the heater 52 was 0.1 mm. From this result, it can be seen that warping was suppressed because the insulating layer 525 was also provided on the surface opposite to the surface on which the heating element 523 was formed.

[0143] However, the temperature control temperature in Comparative Example 5 was 200°C, which was higher than in Example 4, and the number of recording materials that could be stacked was 50, which was also lower than in Example 4. In Comparative Example 5, the sensitivity of the thermistor 25 to detecting temperature changes in the film 83 was reduced due to the thermal resistance of the insulating layer 525, resulting in a higher temperature control temperature and increased curling of the recording material, which further reduced the number of stackable sheets. In other words, in Comparative Example 5, it is not possible to achieve both suppression of heater warping and detection through good responsiveness of temperature changes in the heat transfer member 85.

[0144] Comparative Example 6 had a heater 62 warp of 11 mm, which made assembly difficult. Example 4 had the same bending strength in the thickness direction of the substrate because the substrate was bent. Compared to Comparative Example 6, which has a layered structure, the amount of heater warping was significantly reduced in Example 4.

[0145] Furthermore, the temperature control temperature of Comparative Example 6 was 195°C, and the number of recording materials that could be stacked was 100. In both Comparative Example 6 and Example 4, the insulating layer is provided on only one side of the substrate, but the substrate 1221 of Example 4 is formed with a diaphragm depth of 100 μm, and the short edge of the substrate 1221 is in contact with the heat transfer member 85. In other words, in Example 4, not only is the heat from the heat transfer member 85 transferred to the substrate 1221 via the protective layer 1224, but the heat is also transferred directly from the heat transfer member 85 to the substrate 1221, so the heat from the heat transfer member 85 is transferred to the substrate 1221 more easily compared to Comparative Example 6. Consequently, Example 4 can sense the temperature change of the heat transfer member 85 more sensitively than Comparative Example 6, and therefore, the temperature control temperature is lower and the number of stackable materials is increased according to the configuration of Example 4.

[0146] As described above, according to the present invention, the warping of the heater that occurs during the molding of the heater can be suppressed to an extent that does not hinder assembly. Furthermore, by detecting the temperature change of the heat transfer member 85 with good responsiveness, the temperature control temperature is reduced and curling of the recording material is suppressed, thereby increasing the number of recording materials that can be stacked. In other words, by bending the substrate so that the short edge of the substrate approaches the opposite side of the heater support member (heat transfer member side) in the thickness direction, the warping of the heater can be suppressed without providing insulating layers on both sides of the substrate. And, since heat from the heat transfer member is also transferred to the short edge of the substrate, the temperature change of the heat diffusion member can be detected with good responsiveness. Furthermore, since an insulating layer is not provided on one side of the substrate, it is possible to detect the temperature change of the film with good responsiveness.

[0147] Furthermore, in this embodiment, the depth of the folded portion of the substrate is set to 100 μm, and the height is set so that it is approximately flat with the protective layer 1224. However, the embodiment is not limited to this, and the depth of the folded portion of the substrate may be set to a value lower than the total thickness of the insulating layer and the protective layer. Even with such a configuration, temperature changes of the film 83 and the heat transfer member 85 can be sensed.

[0148] Referring to Figure 21, Modification 6 will be described as a modification of Example 4. Figure 21 is a cross-sectional view of the fixing device near the heater 132 according to Modification 6. For Modification 6, components similar to those in Example 4 are denoted by the same reference numerals and their descriptions are omitted.

[0149] As shown in Figure 21, in Modification 6, the substrate of the heater 132 does not have a flat end portion, and the substrate is formed so that both ends in the short direction of the substrate extend substantially parallel to the thickness direction, resulting in only two bent portions of the substrate. The ends in the short direction of the substrate are in contact with the heat transfer member. Even with this configuration, the bending of the substrate suppresses the warping of the heater, and because the bending of the substrate is in contact with the heat transfer member 85, temperature changes of the heat transfer member 85 are sensitively detected. Consequently, in Modification 6, as in Example 4, it is possible to achieve both suppression of heater warping and detection of temperature changes of the heat transfer member 85 with good responsiveness.

[0150] Furthermore, as another modification, the heater may not have a flat end portion, and both ends of the substrate in the short direction may be bent in the direction opposite to the side with the heating element, so that both ends of the substrate extend substantially parallel to the thickness direction, resulting in only two bent portions of the substrate, which may also be porous. Even with this configuration, the same effect as in Example 4 can be obtained by bringing both ends of the substrate in the short direction into contact with the heat transfer member.

[0151] This embodiment includes the following configuration (and method). (Composition 1) A long, thin metal circuit board, An insulating layer provided on the substrate, A heater having a heating element provided in the insulating layer, In the short-side direction perpendicular to the longitudinal direction of the surface of the substrate on which the insulating layer is provided, if the region including the center of the substrate is defined as the first region, the region on one end side of the first region as the second region, and the region on the other end side of the first region as the third region, The first region described above is a plane, A heater characterized in that, in the thickness direction of the substrate perpendicular to the longitudinal direction and the short direction, the second region and the third region are bent from the first region. (Configuration 2) The heater according to configuration 1, characterized in that the second region has a first bent portion that bends in the thickness direction so as to move toward the heating element side from the first region. (Composition 3) The heater according to configuration 2, characterized in that the second region has a second bent portion that bends in the shorter direction from the first bent portion. (Composition 4) The heater according to configuration 3, characterized in that the second bent portion includes a plane parallel to the first region. (Composition 5) The heater according to configuration 4, characterized in that, in the thickness direction, the distance from the plane of the first region to the plane of the second bent portion is greater than the thickness of the insulating layer. (Composition 6) The heater according to any one of configurations 1 to 5, characterized in that the third region has a third bent portion that bends in the thickness direction so as to move toward the heating element side from the first region. (Composition 7) The heater according to configuration 6, characterized in that the third region has a fourth bend that bends in the shorter direction from the third bend. (Composition 8) The heater according to configuration 7, characterized in that the fourth bent portion includes a plane parallel to the first region. (Composition 9) The heater according to configuration 8, characterized in that, in the thickness direction, the distance from the plane of the first region to the plane of the fourth bent portion is greater than the thickness of the insulating layer. (Composition 10) A heater according to any one of configurations 1 to 9, characterized in that the insulating layer is not formed in the second region and the third region. (Composition 11) The heater according to any one of configurations 1 to 10, characterized in that the second region and the third region are bent from the first region over the entire longitudinal direction of the substrate. (Composition 12) If the surface on which the insulating layer is provided is referred to as the first surface, The heater according to any one of configurations 1 to 11, characterized in that the substrate does not have an insulating layer on the second surface opposite to the first surface in the thickness direction. (Composition 13) The insulating layer on which the heating element is provided is designated as the first insulating layer. If the surface on which the first insulating layer is provided is referred to as the first surface, The substrate has a second insulating layer on the second surface opposite to the first surface in the thickness direction, on which no heating element is provided. A heater according to any one of configurations 1 to 11, characterized in that, in the thickness direction, the first insulating layer is thicker than the second insulating layer. (Composition 14) The first solid of revolution and A heater according to claim 1, provided in the internal space of the first rotating body, A second rotating body that forms the nip portion with the heater via the first rotating body, A temperature detection unit for detecting the temperature of the heater, In a heating device having, The heating device is characterized in that the temperature sensing unit is provided on the side opposite to the side on which the insulating layer on which the heating element is provided is provided, in the thickness direction. (Composition 15) The heating device according to configuration 14, characterized in that the second region and the third region are in contact with the first rotating body. (Composition 16) The first rotating body is a cylindrical film, The heating device according to configuration 14 or 15, characterized in that the second rotating body is a roller. (Composition 17) The first solid of revolution and A heater comprising a metal, elongated substrate, an insulating layer provided on the substrate, and a heating element provided on the insulating layer, provided in the internal space of the first rotating body, A second rotating body that forms the nip portion with the heater via the first rotating body, In a heating device having, In the short-side direction perpendicular to the longitudinal direction of the surface of the substrate on which the insulating layer is provided, if the region including the center of the substrate is defined as the first region, the region on one end side of the first region as the second region, and the region on the other end side of the first region as the third region, A heating device characterized in that, in the thickness direction of the substrate perpendicular to the longitudinal direction and the transverse direction of the transverse direction, the second region and the third region are bent so as to be closer to the nip portion than the first region. (Composition 18) The heating device according to configuration 17, characterized in that the second region has a first bent portion that bends in the thickness direction so as to move toward the nip portion side from the first region. (Composition 19) The heating device according to configuration 18, characterized in that the second region has a second bend that bends in the shorter direction from the first bend. (Composition 20) The first region described above includes a plane, The heating device according to configuration 19, characterized in that the second bent portion includes a plane parallel to the first region. (Composition 21) The heating device according to configuration 20, characterized in that, in the thickness direction, the distance from the plane of the first region to the plane of the second bent portion is greater than the thickness of the insulating layer. (Composition 22) The heating device according to any one of the configurations 17 to 21, characterized in that the third region has a third bent portion that bends in the thickness direction so as to move toward the heating element side from the first region. (Composition 23) The heating device according to configuration 22, characterized in that the third region has a fourth bend that bends in the shorter direction from the third bend. (Composition 24) The first region described above includes a plane, The heating device according to configuration 23, characterized in that the fourth bent portion includes a plane parallel to the first region. (Composition 25) The heating device according to configuration 24, characterized in that, in the thickness direction, the distance from the plane of the first region to the plane of the fourth bent portion is greater than the thickness of the insulating layer. (Composition 26) A heating device according to any one of the configurations 17 to 25, characterized in that the insulating layer is not formed in the second region and the third region. (Composition 27) The heating device according to any one of the configurations 17 to 26, characterized in that the second region and the third region are bent from the first region over the entire longitudinal direction of the substrate. (Composition 28) If the surface on which the insulating layer is provided is referred to as the first surface, The heating device according to any one of the configurations 17 to 27, characterized in that the substrate does not have an insulating layer on the second surface opposite to the first surface in the thickness direction. (Composition 29) The insulating layer on which the heating element is provided is designated as the first insulating layer. If the surface on which the first insulating layer is provided is referred to as the first surface, The substrate has a second insulating layer on the second surface opposite to the first surface in the thickness direction, on which no heating element is provided. A heating device according to any one of the configurations 17 to 27, characterized in that, in the thickness direction, the first insulating layer is thicker than the second insulating layer. (Composition 30) An image forming unit that forms an image on the recording material, An image forming apparatus comprising a heating device according to any one of claims 14 to 29 for fixing an image formed on a recording material to the recording material. [Explanation of Symbols]

[0152] 22...Heater, 221...Substrate, 222...Insulating layer, 223...Heating element, R1...First region, R2...Second region, R3...Third region

Claims

1. A long, thin metal circuit board, An insulating layer provided on the substrate, A heater having a heating element provided in the insulating layer, In the short-side direction perpendicular to the longitudinal direction of the surface of the substrate on which the insulating layer is provided, if the region including the center of the substrate is defined as the first region, the region on one end side of the first region as the second region, and the region on the other end side of the first region as the third region, The first region is a plane, In the thickness direction of the substrate, which is perpendicular to the longitudinal direction and the transverse direction of the transverse direction, the second region and the third region are bent from the first region. The insulating layer on which the heating element is provided is designated as the first insulating layer. If the surface on which the first insulating layer is provided is referred to as the first surface, The substrate has a second insulating layer on the second surface opposite to the first surface in the thickness direction, on which no heating element is provided. A heater characterized in that, in the thickness direction, the first insulating layer is thicker than the second insulating layer.

2. The heater according to claim 1, characterized in that the second region has a first bent portion that bends in the thickness direction so as to move toward the heating element side from the first region.

3. The heater according to claim 2, characterized in that the second region has a second bent portion that bends in the shorter direction from the first bent portion.

4. The heater according to claim 3, characterized in that the second bent portion includes a plane parallel to the first region.

5. The heater according to claim 4, characterized in that, in the thickness direction, the distance from the plane of the first region to the plane of the second bent portion is greater than the thickness of the insulating layer.

6. The heater according to claim 2, characterized in that the third region has a third bent portion that bends in the thickness direction so as to move toward the heating element side from the first region.

7. The heater according to claim 6, characterized in that the third region has a fourth bend that bends in the shorter direction from the third bend.

8. The heater according to claim 7, characterized in that the fourth bent portion includes a plane parallel to the first region.

9. The heater according to claim 8, characterized in that, in the thickness direction, the distance from the plane of the first region to the plane of the fourth bent portion is greater than the thickness of the insulating layer.

10. The heater according to any one of claims 1 to 9, characterized in that the insulating layer is not formed in the second region and the third region.

11. The heater according to any one of claims 1 to 9, characterized in that the second region and the third region are bent from the first region over the entire longitudinal direction of the substrate.

12. The first solid of revolution and A heater provided in the internal space of the first rotating body, comprising a metal elongated substrate, an insulating layer provided on the substrate, and a heating element provided on the insulating layer, A second rotating body that forms the nip portion with the heater via the first rotating body, A temperature detection unit for detecting the temperature of the heater, In a heating device having, In the short-side direction perpendicular to the longitudinal direction of the surface of the substrate on which the insulating layer is provided, if the region including the center of the substrate is defined as the first region, the region on one end side of the first region as the second region, and the region on the other end side of the first region as the third region, The first region is a plane, In the thickness direction of the substrate, which is perpendicular to the longitudinal direction and the transverse direction of the transverse direction, the second region and the third region are bent from the first region. The temperature sensing unit is provided on the side opposite to the side on which the insulating layer on which the heating element is provided is provided, in the thickness direction. A heating device characterized in that the second region and the third region are in contact with the first rotating body.

13. The first rotating body is a cylindrical film, The heating device according to claim 12, characterized in that the second rotating body is a roller.

14. The first solid of revolution and A heater comprising a long, narrow metal substrate, an insulating layer provided on the substrate, and a heating element provided on the insulating layer, provided in the internal space of the first rotating body, A second rotating body that forms the nip portion with the heater via the first rotating body, In a heating device having, In the short-side direction perpendicular to the longitudinal direction of the surface of the substrate on which the insulating layer is provided, if the region including the center of the substrate is defined as the first region, the region on one end side of the first region as the second region, and the region on the other end side of the first region as the third region, In the thickness direction of the substrate, which is perpendicular to the longitudinal and transverse directions, the second and third regions are bent so as to be closer to the nip portion than the first region. A heating device characterized in that the second region and the third region are bent from the first region over the entire longitudinal direction of the substrate.

15. The heating device according to claim 14, characterized in that the second region has a first bent portion that bends in the thickness direction so as to move toward the nip portion side from the first region.

16. The heating device according to claim 15, characterized in that the second region has a second bend that bends in the shorter direction from the first bend.

17. The first region includes a plane, The heating apparatus according to claim 16, characterized in that the second bent portion includes a plane parallel to the first region.

18. The heating device according to claim 17, characterized in that, in the thickness direction, the distance from the plane of the first region to the plane of the second bent portion is greater than the thickness of the insulating layer.

19. The heating device according to claim 15, characterized in that the third region has a third bent portion that bends in the thickness direction so as to move toward the heating element side from the first region.

20. The heating device according to claim 19, characterized in that the third region has a fourth bend that bends in the shorter direction from the third bend.

21. The first region includes a plane, The heating apparatus according to claim 20, characterized in that the fourth bent portion includes a plane parallel to the first region.

22. The heating device according to claim 21, characterized in that, in the thickness direction, the distance from the plane of the first region to the plane of the fourth bent portion is greater than the thickness of the insulating layer.

23. The heating device according to any one of claims 14 to 22, characterized in that the insulating layer is not formed in the second region and the third region.

24. If the surface on which the insulating layer is provided is referred to as the first surface, The heating device according to any one of claims 14 to 22, characterized in that the substrate does not have an insulating layer on the second surface opposite to the first surface in the thickness direction.

25. A first rotating body, A heater comprising a long, narrow metal substrate, an insulating layer provided on the substrate, and a heating element provided on the insulating layer, provided in the internal space of the first rotating body, A second rotating body that forms the nip portion with the heater via the first rotating body, In a heating device having, In the short-side direction perpendicular to the longitudinal direction of the surface of the substrate on which the insulating layer is provided, if the region including the center of the substrate is defined as the first region, the region on one end side of the first region as the second region, and the region on the other end side of the first region as the third region, In the thickness direction of the substrate, which is perpendicular to the longitudinal and transverse directions, the second and third regions are bent so as to be closer to the nip portion than the first region. The insulating layer on which the heating element is provided is designated as the first insulating layer. If the surface on which the first insulating layer is provided is referred to as the first surface, The substrate is provided with a heating element on the second surface opposite to the first surface in the thickness direction. A second insulating layer is provided, which is not formed. A heating device characterized in that, in the thickness direction, the first insulating layer is thicker than the second insulating layer.

26. An image forming unit that forms an image on the recording material, An image forming apparatus comprising a heating device according to claim 12 or 14 for fixing an image formed on a recording material to the recording material.

Images