Heater and image heating device including the same

Abstract

To provide a technique that prevents heat of heating elements from being transferred to the ends of a heater to improve fixability at the ends.SOLUTION: A heater is used for heating an image formed on a recording material, and comprises: a substrate; heating elements that are provided on the substrate and generate heat upon energization; and power supply electrode units that are provided on one side in a longitudinal direction of the substrate with respect to the heating elements on the substrate and are electrically connected with the heating elements. The substrate has an area with no substrate between the heating elements and the power supply electrode units in the longitudinal direction of the substrate.SELECTED DRAWING: Figure 7

Description

Technical Field

[0001] The present invention relates to an image heating device such as a fixing device mounted on an image forming apparatus such as an electrophotographic copying machine or an electrophotographic printer, or a gloss imparting device that improves the glossiness of an image by reheating a fixed toner image on a recording material, and a heater suitable for use in the image heating device.

Background Art

[0002] As an image heating device (fixing device) mounted on an electrophotographic printer or copying machine, there is one having a heater having a heating resistor on a ceramic substrate, a flexible member movable while contacting the heater, and a pressure roller that presses against the heater via the flexible member to form a nip portion. A recording material carrying an unfixed toner image is heated using the heat of the heater while being nipped and conveyed at the nip portion of the fixing device, whereby the toner image on the recording material is heat-fixed to the recording material. Also, a metal substrate heater using a metal superior to ceramics in terms of strength against thermal stress has been proposed for the substrate of the heater. (Patent Document 1)

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, in the above conventional example, since the heat of the heating element at the longitudinal end of the heater is transferred outside the end of the heating element through the metal substrate, there is a problem that the heater temperature near the end of the heating element drops compared to the vicinity of the central portion (hereinafter referred to as end temperature drop).

[0005] Therefore, an object of the invention according to the present application is to provide an image heating device that can improve end temperature drop in an image heating device using a metal substrate heater.

Means for Solving the Problem

[0006] In order to achieve the above object, the present invention provides a heater comprising: a substrate; a heating element provided on the substrate and generating heat upon energization; a power supply electrode portion provided on one side of the heating element in the longitudinal direction of the substrate and electrically connected to the heating element; and wherein there is a region on the substrate where there is no substrate between the heating element and the power supply electrode portion in the longitudinal direction, and the region where there is no substrate is a notch overlapping a virtual line extended from the heating element along the longitudinal direction.

[0007] Also, in order to achieve the above object, the present invention provides a heater comprising: a substrate; a heating element provided on the substrate and generating heat upon energization; and wherein there are regions on the substrate where there is no substrate on one side and the other side of the heating element in the longitudinal direction of the substrate.

[0008] Also, in order to achieve the above invention, the present invention provides a heater comprising: a substrate; a heating element provided on the substrate and generating heat upon energization; and wherein the thickness of at least one of the regions on one side and the other side of the substrate in the longitudinal direction of the region where the heating element is placed is thinner than the thickness of the region where the heating element is placed.

Advantages of the Invention

[0009] According to the present invention, the notch provided at the end of the heater substrate suppresses the heat of the heating element from being transferred to the end of the heater substrate, and it becomes possible to obtain good end fixing property with respect to the recording material.

Brief Description of Drawings

[0010]

Figure 1

Figure 2

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Figure 7

Figure 8

Figure 9

Figure 10

Figure 11

Figure 12

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Figure 16

Figure 17

Mode for Carrying Out the Invention

[0011] Hereinafter, with reference to the drawings, modes for carrying out the present invention will be exemplarily and detailedly described based on examples. However, dimensions, materials, shapes, relative arrangements, etc. of the components described in this embodiment should be appropriately changed according to the configuration of the apparatus to which the invention is applied and various conditions. That is, it is not intended to limit the scope of the present invention to the following embodiments.

[0012] <Embodiment 1> (1) Image forming apparatus FIG. 1 is a cross-sectional view of a laser printer (image forming apparatus) 100 using electrophotographic recording technology. Hereinafter, its operation will be briefly described. When a print instruction is received, the scanner unit 3 emits a laser beam L corresponding to the image information. The photoreceptor 1 charged to a predetermined polarity by the charging roller 2 is scanned by the laser beam L, and thereby an electrostatic latent image corresponding to the image information is formed on the surface of the photoreceptor 1. Thereafter, the developing device 4 supplies toner to the photoreceptor 1 to form a toner image corresponding to the image information on the photoreceptor 1. The toner image that has reached the transfer position formed by the photoreceptor 1 and the transfer roller 5 due to the rotation of the photoreceptor 1 in the direction of arrow R1 is transferred to the recording material P fed by the pickup roller 7 from the cassette 6. 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 subjected to a fixing process by applying heat and pressure with the heat fixing device 9. Thereafter, the recording material P is discharged to the tray 11 by the paper discharge roller 10. The heat fixing device 9 will be described in detail in the following item (2).

[0014] (2) Heat fixing device The heating and fixing device 9 will be described. The heating and fixing device 9 is a film heating method of the tensionless type. The heating and fixing device 9 of the tensionless type film heating method uses an endless belt-shaped (or cylindrical) one as the heat-resistant film. At least a part of the circumference of the film is always in a tension-free state (a state where no tension is applied), and the film is a device that is rotationally driven by the rotational driving force of the pressure member. Hereinafter, the heating and fixing device (image heating device) of the film heating method will be described in detail.

[0015] Referring to the cross-sectional view of FIG. 2, the configuration of the heating and fixing device 9 will be described. The heating and fixing device 9 of the present embodiment includes a cylindrical fixing film 23, a heater 22 which is a heating body in the internal space of the fixing film 23, and a pressure roller 30 which is a pressure member that presses against the outer peripheral surface of the fixing film 23 to form a fixing nip portion N. The reinforcing member 24 is made of a metal such as iron, and presses the heater 22 for utilizing heat toward the pressure roller 30 side via a film guide 21 which is a support member for supporting the heater. The reinforcing member 24 is a member that maintains its strength so as not to be greatly deformed even by the pressure that presses against the pressure roller 30 to form the fixing nip portion N. The film guide 21 also has a function of guiding the rotation of the fixing film 23. The pressure roller 30 receives power from the motor M via a gear (not shown) and rotates in the direction of arrow b. When the pressure roller 30 rotates, the fixing film 23 becomes movable and rotates in the direction of arrow a in a driven manner. The film guide 21 is, for example, a molded product of a heat-resistant resin such as PPS (polyphenylene sulfite) or liquid crystal polymer.

[0016] The heater 22 uses a metal substrate 22a, which is superior to ceramics, from the viewpoints of ease of processing the substrate shape, strength against thermal stress, and cracking of the substrate against bending stress. The substrate 22a has an elongated plate shape, a resistive heating element 22c that generates heat when energized, and a glass coating layer 22d that protects the surface of the resistive heating element 22c. When using a metal substrate 22a, it has an insulating layer 22b that insulates the resistive heating element 22c and the substrate 22a. Further, in order to prevent warping of the substrate during manufacturing, an insulating layer 22e, which is a second insulating layer, may be used on the surface opposite to the surface having the heating element. Details of the heater 22 will be described later.

[0017] A thermistor 25, which is a temperature sensing member, is in contact with the surface of the heater substrate 22a on the side opposite to the contact surface with the fixing film 23. The energization of the heating resistor 22c is controlled according to the detected temperature of the thermistor 25.

[0018] The thickness of the fixing film 23 is preferably about 20 μm or more and 100 μm or less in order to ensure good thermal conductivity. The fixing film 23 has, as a film base layer 23a, a single-layer film made of a material such as PTFE (polytetrafluoroethylene), PFA (tetrafluoroethylene-perfluoroalkyl vinyl ether), PPS, or a composite layer film in which the surface of a material such as PI (polyimide), PAI (polyamideimide), PEEK (polyetheretherketone), PES (polyethersulfone) is coated with PTFE, PFA, FEP (tetrafluoroethylene-perfluoroalkyl vinyl ether), etc. as a release layer 23b. Further, a pure metal, alloy, etc. such as SUS, Al, Ni, Cu, Zn having high thermal conductivity is used as the base layer, and the release layer is subjected to the above-described coating treatment and coating with a fluororesin tube, which is also suitable. In the present embodiment, PI with a thickness of 60 μm is used as the film base layer 23a, and a film in which PFA with a thickness of 12 μm is coated on the film release layer 23b is used in consideration of both wear of the release layer 23b due to paper passage and thermal conductivity. The longitudinal length of the fixing film 23 is 240 mm.

[0019] ​

[0020] The pressure roller 30 as a pressure rotating body has a core metal 30a made of a material such as iron or aluminum, an elastic layer 30b made of a material such as silicone rubber, and a release layer 30c made of a material such as PFA. The pressure roller 30 receives power from the motor M via gears (not shown) and rotates in the direction of arrow b. When the recording material P is nipped and conveyed at the nip portion N, the toner image on the recording material P is heat-fixed to the recording material P. The recording material P that has passed through the nip portion N is conveyed to the paper discharge tray 11.

[0021] Next, an explanation will be given with reference to the exploded perspective view of FIG. 3. After the film guide 21 and the reinforcing member 24 are fitted together, the fixing film 23 is externally fitted around the outer peripheries of the film guide 21 and the reinforcing member 24 with a margin in the circumferential length. The axial direction of the cylindrical shape of the fixing film 23 will hereinafter be referred to as the longitudinal direction.

[0022] Both ends of the reinforcing member 24 protrude from both ends of the fixing film 23, and flange members 26 are fitted to both ends respectively, and the whole is assembled as a film assembly unit 20. The power supply terminal of the heater 22 also protrudes from one side end of the film 23, and the power supply connector 27 is fitted. The power supply connector 27 contacts the power supply electrode portion of the heater 22 with a contact pressure and is electrically connected to form a power supply path. Also, the heater clip 28 is formed from a metal plate bent in a U-shape, and holds the end of the heater 22 against the film guide 21 by its spring property. Furthermore, with reference to the perspective view of FIG. 4, the state of assembling the heater 22 to the film guide 21 will be described in detail. FIG. 4(a) shows the state before assembly, and FIG. 4(b) shows the state where the heater 22 is assembled to the film guide 21 and the power supply connector 27 and the heater clip 28 are attached.

[0023] Next, an explanation will be given with reference to the front view of FIG. 5. The flange member 26 restricts the longitudinal movement of the rotating film 23 and regulates the position of the film while the heat fixing device is in operation. The film assembly unit 20 is provided facing the pressure roller 30, and its movement in the left - right direction in the figure is restricted, and it is supported by the top - plate - side housing 41 of the fixing device so as to be movable in the up - down direction. A pressure spring 45 is attached to the top - plate - side housing 41 of the fixing device in a compressed state. The pressing force of the pressure spring 45 is received at both ends of the reinforcing member 24 via the flange member 26, the reinforcing member 24 is pressed toward the pressure roller 30 side, and the entire film assembly unit 20 is pressed toward the pressure roller 30 side.

[0024] A bearing member 31 is provided to pivotally support the shaft of the pressure roller 30. The bearing member 31 receives the pressing force from the film assembly unit 20 via the pressure roller 30. In order to rotatably support the shaft of the pressure roller, which becomes relatively hot, a bearing material having heat resistance and excellent slidability is used. The bearing member 31 is attached to the bottom - side housing 43 of the fixing device.

[0025] (3) Heater 22 Next, materials, manufacturing methods, etc. of the heater 22 of this embodiment will be described with reference to FIGS. 6 to 7. FIG. 6 is a cross - sectional view in the short - hand direction near the center of the heater 22 of this embodiment. FIG. 7 is a diagram showing the configuration of the heater 22 of this embodiment in the order of manufacturing processes.

[0026] (3 - 1) Substrate The heater 22 of this embodiment uses a metal substrate. FIG. 6 is a cross - sectional view of the heater 22. It has at least an elongated plate - shaped substrate 22a mainly made of a metal alloy, a heating element 22c that generates heat when energized, an insulating layer 22b which is the first insulating layer that insulates the heating element 22c from the substrate 22a, and a protective layer 22d that protects the heating element. Also, in order to prevent warping of the substrate during manufacturing, an insulating layer 22e, which is the second insulating layer, is also provided on the surface opposite to the surface where the heating element is located.

[0027] As materials used for the substrate 22a, stainless steel, nickel, copper, aluminum, and alloys mainly composed of these are preferably used. Among these, stainless steel is most preferable from the viewpoints of strength, heat resistance, and corrosion. The type of stainless steel is not particularly limited, and it may be appropriately selected in consideration of the required mechanical strength, the coefficient of linear expansion suitable for forming the insulating layer and the heating element described in the next section, the ease of obtaining sheet materials in the market, and the like.

[0028] For example, martensitic and ferritic chromium-based stainless steels (400 series) have a relatively low coefficient of linear expansion among stainless steels, and are preferably used because the insulating layer and the heating element are easily formed.

[0029] The thickness of the substrate 22a may be determined in consideration of strength, heat capacity, and heat dissipation performance. When the thickness of the substrate 22a is thin, the heat capacity is small, which is advantageous for quick start-up. However, if it is too thin, problems with distortion are likely to occur during the hot forming of the heating element. Conversely, when the thickness of the substrate 22a is thick, it is advantageous in terms of distortion during the hot forming of the heating element. However, if it is too thick, the heat capacity is large, which is disadvantageous for quick start-up. The preferable thickness of the substrate 22a is 0.3 mm to 2.0 mm in consideration of mass productivity, cost, and performance balance. In this embodiment, a ferritic stainless steel substrate (SUS430: 18Cr stainless steel) having a width of 10 mm, a length of 300 mm, and a thickness of 0.5 mm was prepared as the substrate 22a.

[0030] (3-2) Insulating layer The materials of the insulating layers 22b and 22e are not particularly limited, but it is necessary to select a heat-resistant material in view of the actual use temperature. As the material, glass and PI (polyimide) are preferable from the viewpoint of heat resistance. The specific selection of the powder material in the case of glass may be appropriately selected as long as the characteristics of the present invention are not impaired. If necessary, a heat-conductive filler having insulating properties may be mixed.

[0031] There is no problem even if the insulating layers 22b and 22e use the same material or different materials. Similarly, the thicknesses of the insulating layers 22b and 22e may be the same, or may be changed as necessary without any problem.

[0032] Generally, as a heater used in an image forming apparatus, it is preferable to have a dielectric breakdown voltage of about 1.5 kV. Therefore, in order to obtain a dielectric breakdown voltage performance of 1.5 kV between the heating element 22c and the substrate 22a, the film thickness of the insulating layer 22b may be ensured according to the material.

[0033] The forming method of the insulating layers 22b and 22e is not particularly limited. As an example, it can be smoothly formed by a screen printing method or the like. When forming an insulating layer of glass or PI (polyimide) on the substrate 22a, it is necessary to appropriately adjust the linear expansion coefficients of the substrate and the insulating layer material so that cracks or peeling do not occur in the insulating layer due to the difference in linear expansion coefficients between the materials.

[0034] In this embodiment, an insulating layer glass paste is applied to the aforementioned stainless steel substrate by screen printing. After that, an insulating layer 22b with a film thickness of 60 μm and an insulating layer 22e with a film thickness of 120 μm are formed on both sides of the stainless steel substrate through drying at 180°C and firing at 850°C. This state is designated as stainless steel substrate A.

[0035] (3-3) Heating element The heating element 22c is obtained by printing a heating resistor paste in which (A) a conductive component, (B) a glass component, and (C) an organic binder component are mixed on the insulating layer 22b and then firing it. When the heating resistor paste is fired, the organic binder component (C) burns out and the components (A) and (B) remain, so that the heating element 22c containing the conductive component and the glass component is formed. Here, as the conductive component (A), silver-palladium (Ag·Pd), ruthenium oxide (RuO 2 ) and the like are used alone or in combination, and a sheet resistance value of 0.1 [Ω / □] to 100 [kΩ / □] is preferably used.

[0036] Also, as long as the amount is trace and does not impair the characteristics of the present invention other than the above (A) to (C), it is not a problem that other materials are included. In this example, a heating resistor paste in which silver and palladium (Ag·Pd) are used as conductive components and other glass components and organic binder components are mixed is used. After being applied to the stainless steel substrate A by screen printing, it is dried at 180°C and fired at 850°C to form the heating element 22c. The thickness of the heating element 22c after firing was 15 μm, the length was 220 mm, and the width was 1.1 mm.

[0037] (3-4) Power supply electrode part and conductive pattern The power supply electrode part 22f and the conductive pattern 22g shown in FIG. 7 mainly consist of silver (Ag), platinum (Pt), gold (Au), silver-platinum (Ag·Pt) alloy, silver-palladium (Ag·Pd) alloy, etc. Also, the power supply electrode part 22f and the conductive pattern 22g are formed by printing a paste in which (A) a conductive component, (B) a glass component, and (C) an organic binder component are mixed on the insulating layer 22b in the same manner as the heating resistor paste and then firing.

[0038] The power supply electrode part 22f and the conductive pattern 22g are provided for the purpose of supplying power to the heating element 22c, and the resistance is made sufficiently low with respect to the heating element 22c. Here, it is necessary to select a material that softens and melts at a temperature lower than the melting point of the substrate 22a for the above-mentioned heating resistor paste, power supply electrode part, and conductive pattern paste, and to select a heat-resistant material in view of the actual use temperature. In this example, the power supply electrode part 22f and the conductive pattern 22g were formed in the following manufacturing process. First, a paste for the power supply electrode part and the conductive pattern in which silver is used as the conductive component and other glass components and organic binder components are mixed is prepared. Next, after being applied to the stainless steel substrate A by screen printing, it is dried at 180°C and fired at 850°C.

[0039] (3-5) Protective layer The protective layer 22d shown in Fig. 7 is provided for the purpose of protecting the heating element 22c and the conductive pattern 22g. As the material, glass or PI (polyimide) is preferable from the viewpoint of heat resistance, and a heat-conductive filler having insulating properties may be mixed as necessary. In this embodiment, a protective layer glass paste was prepared, and after the protective layer glass paste was applied by screen printing on the heating element 22c and the conductive pattern 22g, it was dried at 180°C and fired at 850°C to form a protective layer 22d with a film thickness of 60 μm.

[0040] Hereinafter, the notch 22h which is a feature of the heater 22 of this embodiment will be described with reference to Fig. 7. Fig. 7(a) shows the planar shape of the heater substrate 22a. As shown by the notch 22h, the heater substrate 22a has a shape in which a part is cut out. Fig. 7(b) shows a state in which the first insulating layer 22b is provided on the heater substrate 22a. Fig. 7(c) shows a state in which the heating element 22c, the conductive pattern 22g, and the power supply electrode portion 22f are provided on the first insulating layer 22b. In the longitudinal direction of the heater substrate 22a (the left-right direction in the figure), the notch 22h is located between the power supply electrode portion 22f and the heating element 22c. Also, the notch 22h is provided so as to overlap with a virtual line extended along the longitudinal direction of the heater substrate 22a from the heating element 22c. Fig. 7(d) shows a state in which the protective layer 22d is provided. Fig. 7(e) is a cross-sectional view of the heater 22 on the line x shown in Fig. 7(d). The region of the notch 22h shows that, in addition to the heater substrate 22a, the insulating layers 22b, 22e, and the protective layer 22d do not exist. In this embodiment, as an example of the "region without a substrate" in the present invention, a configuration in which a "notch" is provided will be described, but the scope of the "region without a substrate" in the present invention is not limited to the "notch" shown in this embodiment. For example, forms such as "partially recessed concave-shaped portions (holes)" and "through-holes" are also included in the specific forms of the "region without a substrate" in the present invention. electric electrode portion 22f and the heating element 22c. Also, the notch 22h is provided so as to overlap with a virtual line extended along the longitudinal direction of the heater substrate 22a from the heating element 22c. Fig. 7(d) shows a state in which the protective layer 22d is provided. Fig. 7(e) is a cross-sectional view of the heater 22 on the line x shown in Fig. 7(d). The region of the notch 22h shows that, in addition to the heater substrate 22a, the insulating layers 22b, 22e, and the protective layer 22d do not exist. In this embodiment, as an example of the "region without a substrate" in the present invention, a configuration in which a "notch" is provided will be described, but the scope of the "region without a substrate" in the present invention is not limited to the "notch" shown in this embodiment. For example, forms such as "partially recessed concave-shaped portions (holes)" and "through-holes" are also included in the specific forms of the "region without a substrate" in the present invention.

[0041] (4) Operational effects The operation and effect of the present invention will be described by comparing with a comparative example. FIG. 8 is a plan view showing the heater 22 of the comparative example. Different from this embodiment, the notch portion 22h does not exist. In order to verify the operation and effect of this embodiment, the fixing property evaluation was performed under each condition, and the temperature control temperature at which the image of the end temperature drop region can be fixed was confirmed. As the printed image, a pattern in which toner is printed on the entire surface within 5 mm from the ends of the longitudinal and lateral directions of the paper was used. For the fixing property evaluation, the heating and fixing device 9 was left for about 1 hour in a stopped state without standby temperature control until it adapted to room temperature (hereinafter referred to as the Cold state), and then 10 sheets of recording material P were continuously passed through at a conveyance speed of 200 mm / s.

[0042] FIG. 9 is a perspective view showing the state of the above fixing property evaluation, and shows a state in which the recording material P is sandwiched and conveyed between the film assembly unit 20 and the pressure roller 30, and the toner image is heat-fixed on the recording material P. In addition, a part of the heating and fixing device 9 is omitted, and only the parts necessary for the explanation are shown. In FIG. 9, the dotted line A indicates the position of the image end, and the dotted line B indicates the end of the heating element 22c. Also, immediately before the tip of the 10th sheet of paper enters the fixing nip portion N at the same time as the fixing property evaluation, the longitudinal temperature profile of the film 23 at the position indicated by the dotted line C in FIG. 9 was measured with a thermoviewer, and the temperature of the film 23 in the end temperature drop region was compared with the fixing property of the printed image.

[0043]

Table 1

[0044] This effect will be described in more detail with reference to FIG. 11. FIG. 11 is a diagram showing the temperature distribution of the heater 22 near the notch 22h. As shown in FIG. 11(a), in the heater of this embodiment, due to the notch 22h provided in the heater substrate 22a outside the end of the heating element 22c (the left side in FIG. 11), the heat of the heating element 22c is transferred in the direction of the end of the heater substrate 22a indicated by the arrow D is suppressed. Thus, it is considered that the effect of keeping the heat of the heating element 22c near the image end is obtained. That is, in order to obtain this effect, the effect can be obtained by cutting out at least a part of the heater substrate 22a on the virtual line along the longitudinal direction of the heating element 22c, and a greater effect can be obtained by cutting out the heater substrate 22a on the extension line of one heating element 22c as in this embodiment. Incidentally, if a conductive pattern 22g can be formed to connect between the power supply electrode portion 22f and the heating element 22c, a greater effect can be obtained by providing a large notch 22h that exceeds the extension line of the heating element 22c from both ends in the short direction of the heater 22 toward the center portion

[0045] On the other hand, regarding the configuration of Condition 1 of the comparative example shown in Table 1, when the temperature control temperature similar to that of Example 1 was set to 185° C. and heat fixing was performed, as shown in FIG. 9(b), image loss occurred at the image end. According to the longitudinal temperature profile of the film 23 in FIG. 10, it was confirmed that in the configuration of Condition 1 of the comparative example, the temperature of the film 23 was lower than the fixing target temperature at the image end position (dotted line A). Therefore, it is considered that image loss occurred at the image end. This is because, as shown in FIG. 11(b), since the notch 22h is not provided in the heater substrate 22a of the comparative example, the heat of the heating element 22c is transferred in the direction of the end of the heater substrate 22a indicated by the arrow D, resulting in end temperature drop

[0046] Therefore, as shown in Condition 2 of the comparative example in Table 1, when the temperature control temperature was set to 205°C, which is 20°C higher than that in Example 1, and heat fixation was performed, good fixability similar to that in Example 1 could be obtained. According to the longitudinal temperature profile of the film 23 in FIG. 10, the film temperature can exceed the target temperature at which good fixability can be obtained at the position of the dotted line A at the end of the image. As a result, it is considered that good fixability was obtained.

[0047] However, in the central part of the image (the right side in FIG. 10), the temperature of the film 23 became about 25°C higher than the target temperature. As a result, a high-temperature offset image due to excessive fixability occurred in the central part of the image.

[0048] As described above, according to this embodiment, the notch portion 22h provided in the heater substrate 22a suppresses the heat of the heating element 22c from being transferred to the end of the heater substrate 22a, and it becomes possible to obtain good end fixability. In the heaters 22 of this embodiment and the comparative example, the length of the heater substrate 22a on the side where the power supply electrode portion 22f is not provided (the right side in FIGS. 7 and 8) is set within a range where the end temperature drop is acceptable. Therefore, for the end image on the side where the power supply electrode portion 22f is not provided, good fixability was obtained despite the absence of the notch portion 22h.

[0049] <Example 2> Regarding the image forming apparatus and the fixing apparatus in Example 2, since the same configuration as that in Example 1 is adopted, the description is omitted, and only the configuration of the notch portion 22h provided in the heater substrate 22a will be described.

[0050] FIG. 12 is a diagram showing step by step the manufacturing process of the heater 22 of the present embodiment. Since the detailed description is the same as that of the first embodiment, it is omitted. As shown in FIG. 12(a), the heater 22 of the present embodiment is provided with notches 22h on one side of the power supply electrode portion in the longitudinal direction of the heater substrate 22a and on the other side. The reason for this will be explained. For example, when a large amount of the recording material P is continuously fed, there is a problem that the heating element 22 outside the paper feed area of the recording material P overheats and exceeds the heat resistance temperature of the pressure roller 30, causing the pressure roller 30 to be damaged.

[0051] As a countermeasure against this problem, a means such as adding a carbon filler or the like to the elastic layer 30b of the pressure roller 30 to enhance heat conduction and suppressing the temperature of the pressure roller 30 below the heat resistance temperature by equalizing the temperature of the pressure roller 30 may be taken. However, when this countermeasure is taken, when paper feeding is performed from the Cold state, poor fixing of the image end portion may occur. This is because the temperatures of the film 23 and the pressure roller 30 in the vicinity of the image end portion position are equalized in the direction of the end portion of the pressure roller 30 by the pressure roller 30 with enhanced heat conduction and do not reach the fixing target temperature. Therefore, by providing the notches 22h at both ends in the longitudinal direction of the heater substrate 22a as in the present embodiment, it is possible to suppress the temperature drop at the end portion of the heater 22 and obtain good fixing property of the image end portion even when paper feeding is performed from the Cold state. The length of the heater substrate 22a of the present embodiment is 310 mm, which is 10 mm longer than that of the first embodiment at the end portion on the side where the power supply electrode portion 22f of the heater 22 is not provided (the right side in FIG. 12), and the other configurations are the same as those of the first embodiment. The state of assembling the heater 22 of the present embodiment to the film guide 21 is shown in the perspective view of FIG. 13. Further, as shown in FIG. 14, as the heater 22 of the comparative example, a heater having the length of the heater substrate 22a set to 310 mm as in the present embodiment and not provided with the notches 22h at both ends in the longitudinal direction of the heater substrate 22a was prepared. The same fixing property evaluation as in the first embodiment was performed using the heater of the present embodiment and the heater of the comparative example. Table 2 shows a list of the fixing property evaluation results, and the end portion fixing property is the result of confirming the fixing property of both end portions.

[0052] ​

[0053]

Table 2

[0054] As described above, according to this embodiment, the notch portions 22h provided at both ends of the heater substrate 22a made it possible to obtain good fixing properties at both ends of the image. Further, the notch portions 22h are not limited to the notch shape that extends from both ends in the short direction of the heater 22 toward the central part as in Example 1 and Example 2, and the heater substrate 22a may be notched in a hole shape at least in part on the virtual line in the longitudinal direction of the heating element 22c as shown in FIG. 15(a). Also, as shown in FIG. 15(b), it may be notched in a large hole shape that straddles at least a part of the virtual lines in the longitudinal direction of a plurality of heating elements 22c at the same time. Further, as shown in FIG. 15(c), the notch shape that extends from both ends in the short direction of the heater 22 toward the central part may be provided up to the end of the heater substrate 22a.

[0055] <Example 3> Regarding the image forming apparatus and the fixing apparatus in Example 3, since the same configuration as in Example 1 is adopted, the description is omitted, and only the configuration of the reduced thickness portion 22h provided on the heater substrate 22a will be described.

[0056] FIG. 16(a) is a plan view in the longitudinal direction of the heater 22 of this embodiment, and FIG. 16(b) is a sectional view. As shown in the reduced thickness portion 22h of FIG. 16(b), the heater 22 of this embodiment is Outside the end of the heating element 22c, the thickness of the heater substrate 22a is made thinner. As a result, the heat capacity of the heater substrate 22a outside the end of the heating element 22c can be reduced, so that the end temperature drop can be reduced. When a notch 22h is provided on the surface that rubs against the fixing film 23 as in the heaters 22 of Example 1 and Example 2, in the latter half of the life of a high-life machine, a scratch may occur on the inner surface of the fixing film 23 corresponding to the position of the notch 22h. Therefore, by using the configuration of this embodiment, the above problems and the end temperature drop can be made compatible.

[0057] The length of the heater substrate 22a of this embodiment is 310 mm, the same as in Example 2, and other configurations are the same as in Example 1. A perspective view of assembling the heater 22 of this embodiment to the film guide 21 is shown in Fig. 17. As shown in Fig. 17(a), corresponding to the portions where the thickness of the heater substrate 22a at both longitudinal ends of the heater 22 is made thinner, the portion indicated by 21a of the film guide 21 is set higher than the portion indicated by 21b. The heater 22 of the comparative example is the same heater with a heater substrate 22a having a length of 310 mm shown in Fig. 14 used in Example 2.

[0058] Using the heater of this embodiment and the heater of the comparative example, the same fixability evaluation as in Example 1 was performed. Regarding Condition 1 and Condition 2 of the comparative example, since the results are the same as those obtained in Example 2, detailed description is omitted. Table 3 shows a list of fixability evaluation results, and the end fixability is the result of confirming the fixability at both ends.

Table 3

[0059] In the configuration of this embodiment, good fixability is obtained at both ends of the image at a temperature control temperature of 185°C, and the effect of suppressing the end temperature drop by reducing the heat capacity of the heater substrate 22a outside the end of the heating element 22c was confirmed.

[0060] As described above, according to the present embodiment, it is possible to suppress the end temperature drop by thinning the thickness of the heater substrate 22a outside the end of the heating element 22c and reducing the heat capacity of the heater substrate 22a. In the present embodiment, the surface opposite to the surface on which the heating element is placed is cut out.

[0061] In addition, as in the first embodiment, when the length of the heater substrate 22a is set within a range where the end temperature drop can be tolerated on the other side (the right side in FIG. 16) of the power supply electrode portion 22f, the thickness of the substrate 22a may be thinned only on the power supply electrode portion 22f side (the left side in FIG. 16).

Explanation of Reference Numerals

[0062] 1... Image forming apparatus, 9... Fixing device, 20... Film assembly, 21... Film guide, 22... Heater, 23... Fixing film, 24... Reinforcing member, 25... Thermistor, 26... Flange, 27... Power supply connector, 28... Heater clip, 30... Pressing roller, 31... Bearing member, 33... Pressing roller drive gear, 41... Top plate side housing, 42... Frame side plate, 43... Bottom side housing, 45... Pressing spring

Claims

1. A heater, A substrate; A heating element that is provided on the substrate and generates heat when electricity is applied; a power supply electrode portion provided on one side of the substrate in a longitudinal direction with respect to the heating element and electrically connected to the heating element; Equipped with the substrate has a region between the heating element and the power supply electrode portion in the longitudinal direction where the substrate is not present, A heater characterized in that the region without the substrate is a cutout portion that overlaps with an imaginary line extending from the heating element along the longitudinal direction.

2. 2. The heater according to claim 1, wherein the substrate is made of a metal, and the heating element is provided via an insulating layer.

3. A heater according to claim 1 or 2; A cylindrical film; a pressure member that contacts an outer peripheral surface of the film; having an image heating device characterized in that the heater is disposed in an internal space of the film, the film is sandwiched between the heater and the pressure member, and an image on a recording material is heated via the film in a nip portion formed between the film and the pressure member.

Images