Heater and fixing device

Abstract

The present invention discloses a heater and a fixing device. In the heater according to the present invention, one of the conductive wires is arranged to extend from a temperature detection element toward one end of a substrate in the length direction of the substrate, and the other conductive wire is arranged to extend from the temperature detection element toward the other end of the substrate in the length direction of the substrate, and at least one of the two conductive wires has an area inclined in both the length direction and the width direction of the substrate.

Description

[0001] This application is a divisional application of the invention patent application with application number 201811284172.0 filed on October 31, 2018 and invention name “Heater and fixing device”. Technical Field

[0002] The present invention relates to a fixing device mounted on an image forming apparatus such as an electrophotographic recording type copying machine or a printer, and a heater mounted on the fixing device. Background Art

[0003] Known fixing devices using films include fixing devices to be mounted on an electrophotographic recording type image forming apparatus. The fixing device includes a tubular film and a heater in contact with the inner surface of the film. Since the fixing device using a film has a low heat capacity, it is advantageous that the device can be operated with a short warm-up time and low power consumption.

[0004] The heater includes a substrate made of a material such as ceramic and a heating resistor (heating element) arranged on the substrate. The temperature of the heater is detected by a temperature detection element such as a thermistor, and the control unit controls the power supplied to the heating resistor according to the output of the temperature detection element.

[0005] The temperature detection element is configured to be installed independently of the heater, and the temperature detection element is pushed toward the heater via an insulating sheet. In addition, a heater-integrated configuration is provided in which the temperature detection element and the conductive wire electrically connected to the temperature detection element are arranged on a substrate of the heater by a coating method such as screen printing. In the above heater-integrated configuration, for insulation, the temperature detection element, the conductive wire and the heating element are protected by a glass film. The heater-integrated configuration is advantageous because the change in responsiveness is small and the temperature detection accuracy is high because the temperature detection element is printed on the substrate.

[0006] In addition, in order to accurately detect the temperature at the fixing nip portion, a configuration in which a temperature detection element is arranged on the sliding surface of the heater in contact with the film is discussed (Japanese Patent Application Publication No. 10-240357). In addition, in order to reduce the size of the heater, a heating resistor may be arranged on the surface opposite to the surface of the substrate on which the temperature detection element is arranged.

[0007] However, in the configuration of the above-mentioned heater, at the portion where the temperature detection element or the conductive wire is arranged, its thickness from the surface of the substrate becomes thicker than other portions, so that irregularities may appear on the surface of the heater. According to an inspection conducted by the inventors, when the conductive wire is formed on the substrate of the heater in parallel with the conveying direction of the recording material, sometimes fixing failure or gloss streak occurs. This is because the heat and pressure applied to the toner image become uneven due to the step portion generated by the conductive wire on the surface of the heater.

[0008] The present invention is directed to a heater and a fixing device capable of suppressing the occurrence of image defects such as fixing failure or gloss streaks. Summary of the invention

[0009] According to an aspect of the present invention, a heater for a fixing device includes a substrate having a length direction and a width direction, a heating element, a temperature detection element, two conductive wires, the heating element being arranged on the substrate, the temperature detection element being arranged on a surface opposite to a surface of the substrate on which the heating element is arranged, the two conductive wires being electrically connected to the temperature detection element, the two conductive wires being arranged on a surface opposite to a surface of the substrate on which the heating element is arranged, and a protective layer covering the temperature detection element and the two conductive wires, wherein one of the conductive wires is arranged to extend from the temperature detection element toward one end of the substrate in the length direction of the substrate, and the other conductive wire is arranged to extend from the temperature detection element toward the other end of the substrate in the length direction of the substrate, and wherein at least one of the two conductive wires has an area inclined in both the length direction and the width direction of the substrate in an area covered by the protective layer.

[0010] From the following description of exemplary embodiments with reference to the accompanying drawings, further features of the present invention will become clear. Each embodiment of the present invention described below can be implemented separately or as a combination of multiple embodiments. Moreover, features from different embodiments can be combined when necessary, or a combination of elements or features from various embodiments in a single embodiment is beneficial. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Figure 1 is a cross-sectional view of the image forming apparatus.

[0012] Figure 2 is a cross-sectional view of a fixing device.

[0013] Figure 3A and Figure 3B is a diagram showing a configuration of a heater according to a first exemplary embodiment.

[0014] Figure 4 is a diagram showing a configuration of a heater according to a comparative example.

[0015] Figure 5 It is a diagram showing the position where image defects occur.

[0016] Figure 6 is a diagram showing a configuration of a heater according to Modification Example 1 of the first exemplary embodiment.

[0017] Figure 7 is a diagram showing a configuration of a heater according to Modification Example 2 of the first exemplary embodiment.

[0018] Figure 8 is a diagram showing a configuration of a heater according to Modification Example 3 of the first exemplary embodiment.

[0019] Fig. 9A and Fig. 9B is a diagram showing a configuration of a heater according to a second exemplary embodiment.

[0020] Fig.10 is a diagram showing a configuration of a heater according to another example of the second exemplary embodiment.

[0021] Fig.11A , Fig. 11B and Fig. 11C are diagrams each showing an enlarged view of the vicinity of a conductive line of a heater according to a second exemplary embodiment.

[0022] Fig.12 is a diagram showing the configuration of a sliding surface of a heater according to a modified example of the second exemplary embodiment.

[0023] Fig.13 is a diagram showing a configuration of a rear surface of a heater according to a modified example of the second exemplary embodiment.

[0024] Fig.14A and Fig. 14B is a diagram illustrating a heater according to a third exemplary embodiment.

[0025] Fig.15A , Fig. 15B and Fig. 15C is a diagram showing a connection portion of a thermistor and a conductive wire according to a third exemplary embodiment.

[0026] Fig.16 is a diagram showing a heater according to a comparative example.

[0027] Fig.17A , Fig. 17B and Fig. 17Cis a diagram showing a connection portion of a thermistor and a conductive wire according to a comparative example.

[0028] Fig.18 is a diagram showing the occurrence of image defects in the comparative example.

[0029] Fig.19A and Fig.19B : is a diagram showing a connection portion of a thermistor and a conductive wire according to a modified example of the third exemplary embodiment.

[0030] Fig. 20A and Fig. 20B is a diagram illustrating a heater according to a fourth exemplary embodiment.

[0031] Fig.21A , Fig. 21B and Fig. 21C is a diagram showing a connection portion of a thermistor and a conductive wire according to a fourth exemplary embodiment.

[0032] Fig.22A and Fig. 22B : is a diagram showing a connection portion of a thermistor and a conductive wire according to a modified example of the fourth exemplary embodiment. DETAILED DESCRIPTION

[0033] Figure 1 is a cross-sectional view of an electrophotographic recording type image forming apparatus. The photosensitive drum 1 is driven and rotated in the direction indicated by the arrow, and its surface is uniformly charged by the charging roller 2. Then, the laser scanner 3 scans the charged surface of the photosensitive drum 1 with a laser beam L according to image information. Through this process, an electrostatic latent image is formed on the surface of the photosensitive drum 1. The electrostatic latent image is developed with the toner supplied from the developing unit 4. The toner image formed on the photosensitive drum 1 is transferred to the recording material P fed from the sheet feeding box 6 at the transfer nip portion formed by the transfer roller 5 and the photosensitive drum 1 as a pressure-contact portion. The recording material P to which the toner image has been transferred is conveyed to the fixing device 7, so that the toner image is heated and fixed to the recording material P by the fixing device 7. Thereafter, the recording material P is discharged onto the discharge tray. The toner remaining on the photosensitive drum 1 after the transfer process is collected by the cleaning unit 8.

[0034] <Configuration of Fixing Device 7>

[0035] Next, we will refer to Figure 2 The fixing device 7 is described. Figure 2: is a cross-sectional view of the fixing device 7. The fixing device 7 includes a film unit 10 and a pressure roller 20, and a fixing nip portion N for clamping and conveying a recording material P is formed at a space between the film unit 10 and the pressure roller 20. The film unit 10 includes a tubular film 11 and a heater 12 in contact with the inner surface of the film 11. The fixing device 7 also includes a heater holder 13 for holding the heater 12 and a metal support 14 urged by a pressure spring (not shown) to press the heater holder 13 against the pressure roller 20.

[0036] The film 11 includes a base layer and a release layer formed on the outside of the base layer. The base layer is formed by a heat-resistant resin such as polyimide, polyamide-imide or polyether-ether-ketone (PEEK) or a metal such as stainless steel (SUS). The release layer is a mixed layer or a single layer of a heat-resistant resin (such as a fluororesin, for example, polytetrafluoroethylene (PTFE), tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA) or tetrafluoroethylene-hexafluoropropylene copolymer (FEP), and a silicone resin) having good release properties. In addition, an intermediate layer formed by a heat-resistant rubber such as silicone rubber can be arranged between the base layer and the release layer. The film 11 of this exemplary embodiment includes a SUS base layer with a thickness of 30 μm, a silicone rubber layer (elastic layer) with a thickness of 200 μm, and a release layer composed of PFA with a thickness of 20 μm. The outer diameter and the length in the length direction of the film 11 (i.e., the length in the width direction of the recording material P) are 24 mm and 240 mm, respectively.

[0037] The heater holder 13 holds the heater 12, and serves as a guide for guiding the rotation of the film 11. The heater holder 13 is formed of a heat-resistant resin such as a liquid crystal polymer.

[0038] The metal support 14 is a member for reinforcing the heater holder 13. A metal material such as SUS having high rigidity is used for the metal support 14 so that a load applied thereto when the heater holder 13 is pressed against the pressure roller 20 can be endured.

[0039] The pressure roller 20 includes a core metal 21 and an elastic layer 22 formed on the outside of the core metal 21. A release layer formed of PFA or PTFE may be arranged on the outside of the elastic layer 22. The core metal 21 receives a driving force from a motor (not shown) to rotate the pressure roller 20 in the direction indicated by the arrow. When the pressure roller 20 rotates, the film 11 rotates accordingly. The pressure roller 20 according to the present exemplary embodiment includes an elastic layer 22 formed of silicone rubber having a thickness of 3.5 mm and a release layer formed of PFA having a thickness of 70 μm. The outer diameter and the length in the length direction of the pressure roller 20 are 25 mm and 230 mm, respectively.

[0040] The fixing device 7 fixes the image formed on the recording material P onto the recording material P using heat applied from the heater 12 via the rotating film 11 .

[0041] <Configuration of Heater 12>

[0042] Next, we will refer to Figure 3A and Figure 3B The configuration of the heater 12 of the first exemplary embodiment is described. The heater 12 includes a substrate 30 and a heating element 31 arranged on the substrate 30. The heater 12 also includes a temperature detection element 33 arranged on a surface opposite to the surface of the substrate 30 on which the heating element 31 is arranged, and a conductive wire 34 electrically connected to the temperature detection element 33, the temperature detection element 33 being arranged on a surface opposite to the surface of the substrate 30 on which the heating element 31 is arranged, and the conductive wire 34 being arranged on a surface opposite to the surface of the substrate 30 on which the heating element 31 is arranged.

[0043] Figure 3A 1 is a diagram showing the back side of the heater 12 (i.e., the surface of the heater 12 on the opposite side of the sliding surface on which the film 11 slides). A heating resistor (heating element) 31 and an electrode 32 are formed on an alumina substrate 30 by screen printing, and the heating resistor 31 is covered with a back protective layer 35 made of a glass material. A connector (not shown) is connected to the electrode 32, and the heating resistor 31 receives power supplied from a power source to generate heat. In addition, a ceramic material such as aluminum nitride or a metal material whose surface is covered with an insulating layer can be used as the material of the substrate 30.

[0044] Figure 3B is a diagram showing the sliding surface side of the heater 12. A thermistor 33 as a temperature detection element and a conductive wire 34 are formed on the sliding surface of the heater 12 by screen printing. Since the conductive wire 34 is connected to the control circuit 9 in the image forming device via a connector (not shown), the temperature detected by the thermistor 33 can be sent to the control circuit 9. The present exemplary embodiment is characterized in that the conductive wire 34 includes an area 34a that is inclined relative to both the length direction D1 and the width direction D2 of the substrate 30. Although the details will be described below, by forming the conductive wire 34 in an inclined direction, the occurrence of image defects can be suppressed. In addition, line X represents the center of the heater 12 in the width direction D2.

[0045] The thermistor 33 and the conductive wire 34 are also covered with a sliding side protective layer 36 made of a glass material arranged on the sliding surface side. Since the protective layer 36 arranged on the sliding surface side also plays a role in protecting the thermistor 33 and the conductive wire 34 from wear caused by friction relative to the film 11, a glass material having higher wear resistance than the protective layer on the back side is used. In addition, silver / palladium (Ag / Pd) is used as the material of the heating resistor 31, and silver (Ag) is used as the material of the electrode 32 and the conductive wire 34. In addition, although the heater 12 according to the present exemplary embodiment includes a total of three thermistors 33 arranged in the center and both ends in the length direction D1, respectively, the number of thermistors may be one or more.

[0046] <Effects of the Present Exemplary Embodiment>

[0047] A comparative example serving as a comparison target of the present exemplary embodiment will be described. Figure 4 3 is a diagram showing the sliding surface side of the heater 120. Since the conductive wire 34 includes the region 34b parallel to the width direction D2, a local step is generated on a portion of the surface of the heater 120 (i.e., the surface of the protective layer 36) in the length direction D1. The height of the step in the comparative example (i.e., the step in the thickness direction of the heater 120) is 20 μm. In addition, the back side of the heater 120 of the comparative example is similar to that of the first exemplary embodiment. Figure 3A The back side shown in .

[0048] The effect of the present exemplary embodiment is verified under the following conditions. First, plain paper and glossy paper are prepared as recording materials P. Plain paper "HP Laser Jet 90g" and glossy paper "HPBrochure Paper 200g" are used. Then, unfixed colorant images are formed on the plain paper and glossy paper, respectively. Then, a fixing process is performed on these recording materials P by a fixing device 7 on which the heater 12 of the present exemplary embodiment is installed. Similarly, a fixing process is performed on these recording materials P by a fixing device on which the heater 120 of the comparative example is installed. The toner image fixed by the fixing device 7 of the present exemplary embodiment and the toner image fixed by the fixing device of the comparative example are compared with each other. In addition, when the fixing process is performed on plain paper, the conveying speed is set to 300 mm / s, and when the fixing process is performed on glossy paper, the conveying speed is set to 75 mm / s. The control target temperatures of the heaters 12 and 120 are both set to 160°C.

[0049] The results are shown in Table 1. Although image defects occurred in both plain paper and glossy paper when the heater 120 of the comparative example was used, a good fixed image was obtained over the entire length area when the heater 12 of the present exemplary embodiment was used. Figure 5 As shown in FIG. 1 , in the region 34b parallel to the width direction of the conductive line 34 (see FIG. Figure 4 ) at a position corresponding to the above-mentioned portion, a negative influence that the toner image T is not sufficiently fixed or a gloss streak Td is generated due to a decrease in glossiness.

[0050] Table 1

[0051] Heater Configuration Image on plain paper Image on glossy paper Configuration of this exemplary embodiment good good Configuration of traditional examples Fusing failure Glossy Stripes

[0052] As described above, by using the heater according to the present exemplary embodiment, the occurrence of image defects can be suppressed. The reason for the above result will be described below.

[0053] The reason why the image defect occurs in the comparative example is that the heater locally has an area where the heat and pressure applied to the toner image become insufficient at the step portion generated by the conductive wire 34 on the heater sliding surface (the surface of the protective layer). In the present exemplary embodiment, since the conductive wire 34 is formed in an inclined direction, the step will not be concentrated on a part of the sliding surface side length area, so that the insufficient heat and pressure in the local area described in the comparative example does not occur. As a result, since the fixability of the toner becomes substantially uniform throughout the length area, the image defect does not occur.

[0054] In addition, in order to confirm the scope of the effect of the present exemplary embodiment, an experiment was conducted by changing the arrangement of the conductive wires 34. Figure 3B As shown in , with respect to a parallel line drawn in parallel with the length direction of the heater at the center position X in the width direction of the substrate 30, an angle formed between the parallel line and the conductive line 34 formed in an inclined manner is defined as angle A, and images fixed by changing angle A are compared with each other. With respect to the “Configuration of the present exemplary embodiment” in Table 1 above, angle A is set to 45° (angle A=45°).

[0055] Table 2

[0056] Angle A Image on plain paper Image on glossy paper A＝45° good good A＝60° good good A＝75° Minor fixing failure Slight glossy streaks

[0057] As shown in Table 2, when the angle A is 45° or 60°, no image defect occurs. When the angle A increases to 75°, the configuration becomes similar to that of the heater 120 described in the comparative example. Therefore, although the image defect is not as severe as that of the comparative example, a slight image defect occurs.

[0058] According to the results obtained in the present exemplary embodiment, it was found that if the conductive wire 34 is formed and arranged at an angle A of 60° or less, image defects are less likely to occur. However, conditions such as "angle A = 60°" depend on the type of film, the thickness of the conductive wire 34, and the type of recording material or the conveying speed, so the condition cannot be determined uniformly. However, as described above, if the angle A is set to be less than 90°, the steps on the sliding surface side may not be concentrated in a part of the length region. Thus, providing an area inclined in both the length direction and the width direction of the substrate 30 without providing an area parallel to its width direction is effective in suppressing the occurrence of image defects.

[0059] <Modification Example 1>

[0060] Figure 6 is a diagram showing a heater as a modification example 1 of the present exemplary embodiment. Figure 6 In the embodiment, although there is also an area parallel to the width direction, if the length of the area is small, image defects are less likely to occur. In the present exemplary embodiment, when the length of the area parallel to the width direction is 1.5 mm or less, image defects do not occur. Similar to the conditions of angle A, although the above conditions are not uniformly determined, it is preferred that the length of the conductive line 34 formed in the width direction is shorter.

[0061] <Modification Example 2>

[0062] Now, a modification example 2 of the present exemplary embodiment will be described. Figure 7 As shown in , the conductive line 34 of the heater in Modified Example 2 includes a region parallel to the length direction of the substrate 30 and a region parallel to the width direction of the substrate 30. Then, the respective regions parallel to the length direction and the width direction are alternately connected to each other, so that the conductive line 34 is formed into a step-like shape. In this modified example, if the length of the region parallel to the width direction is short (i.e., 1.5 mm or less in the present exemplary embodiment), image defects are less likely to occur.

[0063] <Modification Example 3>

[0064] like Figure 8 As shown in , the thermistor 33 as the temperature detection element may have a shape that is not parallel to the length direction and the width direction. If the thermistor 33 has an area parallel to the width direction, there is a possibility that image defects occur similarly to the case where the conductive line 34 extends parallel to the width direction. This modification is more preferred because it is possible to prevent steps from being concentrated on a portion of the length region including the portion of the thermistor 33, so that the occurrence of image defects can be suppressed.

[0065] A second exemplary embodiment of the present invention will be described. This exemplary embodiment is characterized in that image defects are suppressed by reducing the step itself generated by the conductive line.

[0066] The basic configuration and operation of the fixing device 7 are similar to those described in the first exemplary embodiment. Only the shape of one side of the sliding surface of the heater 12 mounted on the fixing device 7 is different from that of the first exemplary embodiment.

[0067] < Heater Configuration >

[0068] Reference Fig. 9A and Fig. 9B The configuration of the heater of the present exemplary embodiment is described. Fig. 9A is a diagram showing the back side of the substrate 30 , which has a shape similar to that described in the first exemplary embodiment. Fig. 9B is a diagram showing the sliding surface side thereof, where the sliding surface side is Figure 4 The thermistor 33 and the conductive wire 34 are formed similarly to the configuration shown in . However, in the present exemplary embodiment, a convex portion 37 electrically insulated from the conductive wire 34 is arranged on the side of the substrate 30 where the conductive wire 34 is arranged. The material of the convex portion 37 of the present exemplary embodiment is Ag. The thermistor 33, the conductive wire 34 and the convex portion 37 are covered with a protective layer 36 made of a glass material.

[0069] The step generated in the comparative example of the first exemplary embodiment is reduced by the convex portion 37. In the present exemplary embodiment, the convex portion 37 is formed at a position where the step has a height of 10 μm or less. The reason for this will be described below.

[0070] <Effects of the Present Exemplary Embodiment>

[0071] The effect of the present exemplary embodiment will be described. An experiment was conducted by using the heater according to the present exemplary embodiment as a heater to be mounted on a fixing device under the same conditions as those of the first exemplary embodiment, and the present exemplary embodiment was compared with a comparative example. In addition, the distance D between the conductive line and the convex portion was changed to confirm the range of the effect of the present exemplary embodiment, and the fixed image was evaluated. FIG. 11A to FIG. 11C As shown in the enlarged view of the sliding surface of the heater in , a step with a height of 20 μm is produced in the comparative example, a step with a height of 15 μm is produced when the distance D between the conductive wire and the raised portion is 0.75 mm (D=0.75 mm), and a step with a height of 10 μm is produced when the distance D between the conductive wire and the raised portion is 0.50 mm (D=0.50 mm).

[0072] The results are shown in Table 3. The results of the comparative example are the same as those obtained in the first exemplary embodiment. When the step is reduced to 15 μm, although slight gloss streaks are generated, no fixing failure occurs in plain paper. On the other hand, if the step is reduced to 10 μm, image defects do not occur. If the step is 10 μm or less, the area where the applied heat and pressure are insufficient is reduced, so that the fixing property is sufficiently obtained.

[0073] Table 3

[0074] Heater Configuration Image on plain paper Image on glossy paper Configuration of step size 10μm good good Configuration of step 15μm good Slight glossy streaks Configuration of traditional examples Fusing failure Glossy Stripes

[0075] According to the above results, if the convex portion is formed to reduce the step on the surface of the protective layer to 10 μm or less, image defects can be suppressed. In other words, by setting the step generated by the protective layer on the conductive wire 34, the protective layer on the convex portion 37, and the protective layer between the conductive wire 34 and the convex portion 37 to 10 μm or less, image defects can be suppressed. Since the conductive wire 34 or the convex portion 37 exists in a wide area on the heater, it is advantageous that the thermal resistance becomes substantially uniform. Therefore, the present exemplary embodiment is more preferable than the first exemplary embodiment.

[0076] In addition, in the present exemplary embodiment, although the same material (Ag) is used for the conductive wire 34 and the convex portion 37, different materials may be used therefor. However, by using the same material, as described above, since the thermal resistance of the conductive wire 34 and the convex portion 37 becomes substantially uniform, the occurrence of image defects can be more easily suppressed.

[0077] In addition, Fig. 9B In the embodiment, the convex portion 37 is formed parallel to the length direction of the heater. Fig.10 Also in the case where the heater is formed in parallel with the width direction as shown in , an effect similar to that obtained in the above exemplary embodiment can be obtained by reducing the step.

[0078] <Variation Example>

[0079] As a modified example of this exemplary embodiment, Fig.12As shown in , the configuration may be such that the conductive wire 34 is formed on the substrate 30 in an inclined direction, and a convex portion 37 insulated from the conductive wire 34 may be formed thereon. This modified example is more preferable because the step itself can be reduced by the convex portion 37, while the state in which the step is concentratedly generated on a part of the length region can be prevented by the conductive wire 34 formed in an inclined direction as described in the first exemplary embodiment. In addition, the convex portion 37 may be formed on a heater having a conductive wire formed in the shape shown in the modified example of the first exemplary embodiment.

[0080] In addition, the shape of the heating resistor 31 is not limited to the shape adopted in the present exemplary embodiment or the modified example. Fig.13 As shown in , a plurality of heating resistors 31 may be arranged in the length direction, and the temperatures thereof may be independently controlled. Fig.13 The heating resistor 31 shown in is divided into five areas, and each of the areas can be controlled independently. In the case where the temperature at each area is controlled independently, it is necessary to arrange thermistors at each of the areas, and the number of conductive wires connected to thermistors must be increased. Therefore, the effect of the present invention can be obtained more efficiently.

[0081] Next, a heater according to a third exemplary embodiment will be described.

[0082] <Configuration of Heater 12>

[0083] Reference Fig.14A and Fig. 14B The configuration of the heater according to the third exemplary embodiment is described. The heater 12 includes a substrate 30 and a heating element 31 arranged on the substrate 30. The heater 12 also includes temperature detection elements 331 to 333, which are arranged on the surface opposite to the surface of the substrate 30 on which the heating element 31 is arranged, and a conductive wire 34 electrically connected to the temperature detection elements 331 to 333, and the conductive wire 34 is arranged on the surface opposite to the surface of the substrate 30 on which the heating element 31 is arranged.

[0084] Fig.14A 1 is a diagram showing the back side of the heater 12 (i.e., the surface of the heater 12 on the opposite side of the sliding surface on which the film 11 slides). A heating resistor (heating element) 31 and an electrode 32 are formed on an alumina substrate 30 by screen printing, and the heating resistor 31 is covered with a first protective layer 35 made of a glass material. A connector (not shown) is connected to the electrode 32, and the heating resistor 31 receives power supplied from a power source to generate heat. In addition, a ceramic material such as aluminum nitride or a metal material whose surface is covered with an insulating layer can be used as the material of the substrate 30.

[0085] Fig. 14B 3 is a diagram showing the sliding surface side of the heater 12. Thermistors 331 to 333 as temperature detection elements and conductive wires 34 are formed on the sliding surface of the heater 12 by screen printing. Since the conductive wires 34 are connected to the control circuit 9 in the image forming device via a connector (not shown), the temperature detected by the thermistors 331 to 333 can be sent to the control circuit 9. The conductive wires 34 include an area 34a that is inclined in both the length direction D1 (i.e., the length direction of the heater 12) and the width direction D2 (i.e., the width direction of the heater 12) of the substrate 30. By forming the conductive wires 34 in the inclined direction, the occurrence of image defects can be suppressed. In addition, line X represents the center in the width direction D2 of the heater 12. Angle A is the inclination angle of the area 34a relative to the direction D1. In addition, the direction D2 is the conveying direction of the recording material in the fixing device.

[0086] In the middle of the region 34a of the conductive line 34 arranged in the inclined direction, each of the thermistors 331, 332, and 333 is arranged in parallel with the direction D1 so that the length direction of the thermistor is parallel to the direction D1. The reason for arranging the thermistors 331 to 333 in the above state is to prevent the occurrence of image defects caused by steps generated at the connection parts of the thermistors 331, 332, and 333 and the conductive line 34. The details will be described below. In addition, as Fig.15A As shown in , each of the thermistors 331 to 333 is formed in a shape having a long side and a short side when the heater 12 is viewed in a direction perpendicular to the sliding surface.

[0087] The thermistors 331 to 333 and the conductive wire 34 are also covered with a second protective layer 36 made of glass. The second protective layer 36 also plays a role in protecting the thermistors 331 to 333 and the conductive wire 34 from wear caused by friction relative to the film 11. Therefore, a glass material having a higher wear resistance than that of the first protective layer 35 is used. In addition, Ag / Pd is used as a material for the heat generating resistor 31, and Ag is used as a material for the electrode 32 and the conductive wire 34.

[0088] Reference FIG. 15A to FIG. 15C The connection portion of the thermistor 332 and the conductive wire 34 is described. Fig.15A332 is an enlarged view showing the vicinity of the thermistor 332, and the width of both the thermistor 332 and the conductive wire 34 is width W1. Width W1 is 0.5 mm. However, the width of the conductive wire 34 at the portion connected to the thermistor 332 is width W2, and width W2 is wider than width W1. With this configuration, the occurrence of image defects caused by steps generated at each connection portion of the thermistor 332 and the conductive wire 34 can be prevented. The details will be described below. Width W2 is 0.7 mm. In the present exemplary embodiment, the thermistor 332 is connected to the conductive wire 34 so as to overlap with the conductive wire 34 from above. Fig.15A The shaded portion in φ represents an overlapping portion OLP of the conductive line 34 and the thermistor 332 .

[0089] Fig. 15B It is along Fig.15A Symbol "h0" represents the height of the substrate 30, symbol "h1" represents the height of the overlapping portion OLP of the conductive line 34 and the thermistor 332 (ie, the first height), and symbol "h2" represents the height of the conductive line 34 (ie, the second height).

[0090] In addition, the symbol "g0" represents the height of the second protective layer 36 at the portion where nothing is arranged on the substrate 30, the symbol "g1" represents the height of the second protective layer 36 on the overlapping portion OLP, and the symbol "g2" represents the height of the second protective layer 36 on the conductive line 34. In addition, the thermistor 332 and the conductive line 34 are set to have the same thickness of 7μm. Therefore, the respective heights satisfy the conditions of "h1-h0=14μm" and "h2-h0=7μm". In addition, the difference in height g0 to g2 of the second protective layer 36 (the height of the step) is substantially the same as the difference in height h0 to h2 (the height of the step).

[0091] exist Fig. 15B In the cross section L1 in FIG. 1 , the conductive line 34 as the gradient relaxation portion having a height (second height) h2 exists at a position between the substrate 30 having a height h0 and the overlapping portion OLP having a height (first height) h1. Therefore, the change in height from the surface of the substrate 30 to the surface of the overlapping portion OLP becomes gentle, so that the change in height of the surface of the second protective layer 36 in the direction D1 also becomes gentle. In addition, the thickness of the second protective layer 36 is set to 20 μm.

[0092] like Fig. 15BAs shown in, in the cross section at line L1, there is no region in the vicinity of the thermistor 332 where the height changes from height h0 to height h1 without passing through height h2. In the case where the height changes from height h0 to height h1, the conductive wire 34 having the second height h2 always exists in the space between the substrate 30 and the thermistor 332 as a gradient relaxation portion. In the heater 12 according to the present exemplary embodiment, the structure of the cross section at line L1 in the region near the thermistors 331 and 333 is similar to the structure in the region near the thermistor 332. In addition, not all structures of the cross section at line L1 near the thermistors 331 to 333 must be the above-mentioned structure. Only the structure near at least one thermistor in which the change in the height of the surface of the second protective layer 36 must be suppressed needs to have the above-mentioned structure. In addition, in the present exemplary embodiment, the length L34 in the direction D1 of the portion of the conductive wire 34 used as the gradient relaxation portion (the portion does not include the portion corresponding to the overlapping portion OLP) is 0.5 mm or longer.

[0093] Fig. 15C It is along Fig.15A . As described above, the width W2 of the connection portion between the conductive wire 34 and the thermistor 332 is wider than the width W1. Therefore, at the cross section at the line F1, there is no region near the thermistor 332 where the height changes from the height h0 to the height h1 without passing through the height h2. In the case where the height changes from the height h0 to the height h1, as a gradient relaxation portion, the conductive wire 34 having the second height h2 always exists in the space between the substrate 30 and the thermistor 332. Therefore, the change in the height of the surface of the second protective layer 36 in the D2 direction also becomes moderate.

[0094] In the heater 12 according to the present exemplary embodiment, the structure of the cross section at the midline F1 in the region near the thermistors 331 and 333 is similar to the structure at the midline F1 in the region near the thermistor 332. In addition, not all structures of the cross section at the midline F1 in the thermistors 331 to 333 need to be the above-mentioned structure. Only the structure in the vicinity of at least one thermistor in which the change in the height of the surface of the second protective layer 36 must be suppressed needs to have the above-mentioned structure. In addition, in the present exemplary embodiment, the length F34 in the direction D2 of the conductive wire 34 (excluding the portion corresponding to the overlapping portion OLP) serving as the gradient relaxation portion is 0.1 mm or longer.

[0095] In the present exemplary embodiment, the heater 12 having a total of three thermistors has been described. However, even if the number of thermistors included in the heater is one, or four or more, the variation in the height of the surface of the second protective layer 36 can be mitigated by arranging the above-mentioned gradient mitigation portion.

[0096] Next, we will refer to Fig.16 A heater according to a comparative example is described. Fig.16 The heater of Comparative Example 1 shown in FIG. 1 also includes three thermistors. The three thermistors are arranged at the same positions as those in the heater 12 according to the third exemplary embodiment, and the thickness of the thermistors and the thickness of the conductive wires are also the same as those in the third exemplary embodiment, respectively.

[0097] Fig.16 Thermistors 334, 335, and 336 shown in the figure are arranged so that their long sides are placed parallel to the direction D2. In addition, each of thermistors 334 to 336 is connected to the conductive wire 34 so that each of thermistors 334 to 336 and two connection positions of the conductive wire 34 are connected and arranged in a direction parallel to the direction D2.

[0098] Next, we will refer to Fig.17A , Fig. 17B and Fig. 17C The connection portion of the thermistor 335 and the conductive wire 34 in Comparative Example 1 is described. Fig.17A is an enlarged view showing the vicinity of the thermistor 335 of the heater in Comparative Example 1, Fig. 17B It is along Fig.17A A cross-sectional view taken along line L2 in FIG. Fig. 17C It is along Fig.17A The width of both thermistor 335 and the conductive line 34 is width W1.

[0099] The path PH1 and the path PH2 show paths through which the height changes from the height h0 of the substrate 30 to the height h1 of the overlapping portion OLP. Since the conductive line 34 as the gradient relaxation portion having the second height h2 exists in the path PH1, the height changes gently from the height h0 of the substrate 30 to the height h1 of the overlapping portion OLP. However, in the path PH2, since there is no gradient relaxation portion, the height changes directly from the height h0 of the substrate 30 to the height h1 of the overlapping portion OLP. Therefore, the height changes with a steep gradient. Therefore, on the surface of the second protective layer 36 corresponding to the path PH2, the height changes steeply from the height g0 corresponding to the height h0 of the substrate 30 to the height g1 corresponding to the height h1 of the overlapping portion OLP. Therefore, there is a possibility that fixing failure or gloss streaks caused by the size of the concave-convex on the surface of the second protective layer 36 may occur.

[0100] The paths PH3 and PH4 also show paths through which the height changes from the height h0 of the substrate 30 to the height h1 of the overlapping portion OLP. Since there is no gradient relaxation portion in each of the paths PH3 and PH4, the height changes directly from the height h0 of the substrate 30 to the height h1 of the overlapping portion OLP, so that the height changes with a steep gradient. According to the size of the gradient, on the surface of the second protective layer 36 corresponding to the paths PH3 and PH4, the height changes steeply from the height g0 corresponding to the height h0 of the substrate 30 to the height g1 corresponding to the height h1 of the overlapping portion OLP. Therefore, there is a possibility that fixing failure or gloss streaks caused by the size of the concavo-convex on the surface of the second protective layer 36 may occur.

[0101] As described above, in Comparative Example 1, there is a region where the height changes from height h0 to height h1 in both directions D1 and D2 without having a height h2. In addition, in the heater of Comparative Example 1, there is a region where the height changes from height h0 to height h1 in both directions D1 and D2 on the face where the thermistor and the conductive wire are arranged (for example, Fig.17A On the other hand, in the region between the region with height h0 and the region with height h1 of the heater 12 of the third exemplary embodiment, the gradient relaxation portion as the region with height h2 exists in all directions except the directions D1 and D2 on the face where the thermistor and the conductive wire are arranged.

[0102] The effect of the heater according to the present exemplary embodiment was verified under the following conditions. Plain paper "HP LaserJet 90g" and glossy paper "HP Brochure Paper 200g" were used as recording material P. The toner images formed on the recording material P were heated and fixed to the recording material P by using the heaters according to the present exemplary embodiment and the comparative example, respectively. And the fixed images were compared with each other. When plain paper was used as recording material P, the conveying speed was set to 300 mm / s, and when glossy paper was used as recording material P, the conveying speed was set to 75 mm / s.

[0103] The results are shown in Table 4. Although image defects occurred in both plain paper and glossy paper when the heater of Comparative Example 1 was used, a good image was obtained over the entire area of ​​the recording medium P when the heater of the present exemplary embodiment was used.

[0104] In Comparative Example 1, Fig.18 As shown in FIG. 1 , a negative influence that the toner image T is not sufficiently fixed or generation of gloss streaks caused by a decrease in glossiness occurs in regions Y1 , Y2 , and Y3 corresponding to the arrangement portions of the thermistors 334 , 335 , and 336 .

[0105] Table 4

[0106] Heater Configuration Image on plain paper Image on glossy paper Configuration of the Third Exemplary Embodiment good good Configuration of Comparative Example 1 Fusing failure Glossy Stripes

[0107] As described above, by adopting the configuration of the heater according to the present exemplary embodiment, the occurrence of image defects can be suppressed. The reason for the above result will be described below.

[0108] The reason why image defects occur in the comparative example is that the heater locally has an area where heat and pressure applied to the toner image become insufficient due to a large step on the sliding surface of the heater generated at the overlapping portion OLP of the conductive wires of the thermistor.

[0109] As described above, in the present exemplary embodiment, the gradient relaxation portion is always arranged in the directions D1 and D2 so that a large step is not generated around the overlapping portion OLP of the conductive wire and the thermistor. Therefore, as described above, the generation of a region where the heat and pressure applied to the toner image locally become insufficient can be suppressed. As a result, the effect of suppressing the occurrence of image defects can be obtained.

[0110] In addition, in the configuration of the device of the present exemplary embodiment, it was confirmed that the frequency of occurrence of image defects increased when the height of one step exceeded about 10 μm. In the first exemplary embodiment, since the height of one step (h1-h2) was about 7 μm, the effect of suppressing image defects could be obtained. Therefore, it is preferable that the gradient relaxation portion is arranged so that the step becomes 10 μm or less.

[0111] Next, modified examples of the present exemplary embodiment will be described. Fig.19A and Fig.19B are diagrams showing two examples in each of which a thermistor and a conductive wire are connected to each other in a direction different by 90 degrees from that of the first exemplary embodiment.

[0112] <Modification Example 1>

[0113] Fig.19A Modification example 1 in FIG. 1 shows a configuration in which the periphery of the connection portion of the thermistor 332 and the conductive wire 34 in the first exemplary embodiment is rotated by 90 degrees.

[0114] The cross sections in the directions D1 and D2 including the overlapping portion OLP are reversed from those of the first exemplary embodiment, and effects obtained from the respective cross sections are similar to those described in the third exemplary embodiment.

[0115] <Modification Example 2>

[0116] Fig.19BThe relationship between the thermistor 332 and the width of the conductive line 34 at the connection portion in Modification Example 2 shown in FIG. 1 is different from that in the third exemplary embodiment or Modification Example 1.

[0117] In Modified Example 2, the width of the thermistor 332 is set to a width W3 wider than the width W1 of the conductive wire 34. In this configuration, similar to the first exemplary embodiment and Modified Example 1, the conductive wire 34 is used as a gradient relaxation portion in the conveying direction. However, unlike the third exemplary embodiment and Modified Example 1, the thermistor 332 is used as a gradient relaxation portion in the direction D1. Because the thermistor 332 and the conductive wire 34 have the same thickness, an effect similar to that obtained in the third exemplary embodiment and Modified Example 1 can be obtained.

[0118] In the above exemplary embodiment, a portion of the conductive wire 34 or thermistor 332 is used as the gradient relaxing portion. However, for example, an insulating member having the second height may be used as the gradient relaxing portion.

[0119] As described above, the heater according to the present exemplary embodiment includes a substrate, a heating element arranged on the substrate, a temperature detection element arranged on the substrate, a conductive wire connected to the temperature detection element, and a protective layer covering the temperature detection element and the conductive wire. The heater is used for a fixing device, which is used to fix the toner image formed on the recording material to the recording material. Then, the overlapping portion where the temperature detection element and the conductive wire overlap each other is arranged at the connection portion of the temperature detection element and the conductive wire. In the cross section of the heater parallel to the length direction and cut along the surface through the temperature detection element, a gradient relaxation portion having a step smaller than the step from the surface of the substrate to the surface of the overlapping portion is arranged at a position adjacent to the overlapping portion. In addition, in the cross section of the heater parallel to the width direction and cut along the surface through the temperature detection element, a gradient relaxation portion having a step smaller than the step from the surface of the substrate to the surface of the overlapping portion is arranged at a position adjacent to the overlapping portion.

[0120] Next, a fourth exemplary embodiment will be described. This exemplary embodiment is characterized in that the gradient relaxation portion is necessarily provided only in the direction D1. Unlike the third exemplary embodiment, the gradient relaxation portion does not exist in all or part of the region in the direction D2.

[0121] The basic configuration and operation of the image forming apparatus 100 and the fixing device 7 are similar to those described in the third exemplary embodiment. Only the shape of the sliding surface side of the heater 12 mounted on the fixing device 7 is different.

[0122] <Features of Heater>

[0123] Features of the heater used in the fourth exemplary embodiment will be described. Fig. 20A is shown with Fig.14A The shape of the third exemplary embodiment is similar to the shape of the back side of the substrate 30 in FIG. Fig. 20B is a diagram showing the sliding surface side thereof, and except for the parts described below, the configuration is similar to Fig. 14B The configuration of the third exemplary embodiment in FIG. Fig.21A , Fig. 21B and Fig. 21C A configuration different from that of the third exemplary embodiment is described.

[0124] Fig.21A 3 is an enlarged view of the thermistor 338, and the width of both the thermistor 338 and the conductive wire 34 is a width W1. In the present exemplary embodiment, the width W1 is also set to 0.5 mm, and unlike the third exemplary embodiment, the conductive wire 34 at the portion connected to the thermistor 338 also has a width W1. Configurations other than the above configuration are similar to those described in the third exemplary embodiment. Fig. 21B It is along Fig.21A The cross-sectional view taken along line L3 in FIG. 1 is similar to the cross-sectional view taken along line L3 in FIG. Fig. 15B The cross-section diagrams in are exactly the same. Fig. 21C It is along Fig.21A A cross-sectional view taken along line F3.

[0125] As described above, in the present exemplary embodiment, the widths of both the thermistor 338 and the conductive line 34 are the same width W1, so that the thermistor 338 and the conductive line 34 precisely overlap each other. Fig. 15C Unlike the cross section at line F1 in the third exemplary embodiment, there is no gradient relaxation portion in the cross section at line F3. Therefore, in this exemplary embodiment, the change in the height of the surface of the second protective layer 36 in the cross section at line F3 becomes steeper than that in the third exemplary embodiment.

[0126] When verification was performed under the same conditions as those used to verify the effect of the third exemplary embodiment, no fixing failure and gloss streaks occurred in the present exemplary embodiment. This result indicates that image defects can be prevented if the gradient relaxation portion exists in the direction D1. This is due to the following reasons.

[0127] In the present exemplary embodiment, although there is a steep step in the direction D2, the contact pressure with respect to the inner peripheral surface of the film is reduced only for a short period of time, the pressure becomes lower than the pressure in other parts, and the heat transfer efficiency becomes lower. Therefore, the influence with respect to the image is small, and thus image defects such as fixing failure or gloss streaks do not occur.

[0128] As described above, it is preferable that the conductive wire 34 is arranged so that the gradient relaxation portion appears at least in the cross-sectional structure at the line L3.

[0129] Next, configurations of modified examples of the present exemplary embodiment will be described. In these configurations, the gradient relaxation portion necessarily exists in the direction D1, but the gradient relaxation portion does not exist in a part of the region in the direction D2. Fig.22A and Fig. 22B , two modification examples, ie, modification examples 3 and 4, will be described as modification examples of the present exemplary embodiment.

[0130] <Modification Example 3>

[0131] exist Fig.22A In the configuration of the modification example 3 shown in , the thermistor 338 is arranged in an inclined state, and the two portions thereof connected to the conductive wire 34 are also arranged in an inclined state. Fig.22A As shown in , the thermistor 338 does have a parallelogram shape, not a rectangular shape. In addition, the conductive line 34 near the connection portion and the overlapping portion OLP also have a parallelogram shape. With this configuration, a portion of the conductive line 34 necessarily exists as a gradient relaxation portion in the direction D1.

[0132] On the other hand, in the direction D2, although the conductive wire 34 or thermistor 338 exists as a gradient relaxation portion in most parts, Fig.22A There is no gradient relaxation portion in points PA and PB in . However, since the gradient relaxation portion does not exist only in two points PA and PB, the influence exerted on the image is smaller than that in the second exemplary embodiment, so that no image defect occurs in the verification performed under the same conditions.

[0133] <Variation Example 4>

[0134] exist Fig. 22B In the configuration of the modified example 4 shown in , the relationship between the thermistor 338 and the width of the conductive line 34 at the connection portion described in the third exemplary embodiment is reversed. Therefore, a portion of the thermistor 338 always exists as a gradient relaxation portion in the D1 direction.

[0135] On the other hand, in the direction D2, although the conductive wire 34 or thermistor 338 exists as a gradient relaxation portion in most areas, Fig. 22B There is no gradient relaxation portion in the points PC and PD in . However, since the gradient relaxation portion does not exist only in the above two points PC and PD, the influence exerted on the image is smaller than that in the second exemplary embodiment, so that no image defects occur in the verification performed under the same conditions.

[0136] Furthermore, the configurations described in the third and fourth exemplary embodiments can also be applied to devices capable of independently controlling Fig.12 A heater with multiple heating resistors as shown.

[0137] While the present invention has been described with reference to exemplary embodiments, it is to be understood that the invention is not limited to the disclosed exemplary embodiments.

Claims

1. A heater for a fixing device, comprising: A substrate having a length direction and a width direction; a heating element, the heating element being arranged on the substrate; a temperature detection element disposed on the substrate; two conductive lines, the two conductive lines being used to extract a signal corresponding to the temperature and being electrically connected to the temperature detection element, the two conductive lines being arranged on the same surface of the substrate on which the temperature detection element is arranged; and a protective layer, the protective layer covering the temperature detection element and the two conductive wires, wherein the first conductive line is one of the conductive lines, the first conductive line being arranged to extend from the temperature detection element toward one end of the substrate in the length direction of the substrate, and the second conductive line is another of the conductive lines, the second conductive line being arranged to extend from the temperature detection element toward the other end of the substrate in the length direction of the substrate, wherein the first conductive line is arranged in a region extending from a first position where the temperature detection element is arranged in the width direction of the substrate to a second position in the width direction of the substrate that is different from the first position, and In the protective layer covered area, the first conductive line has an area inclined in both the length direction and the width direction of the substrate and does not have an area extending only in a direction parallel to the width direction of the substrate.

2. The heater according to claim 1, wherein if the temperature detection element is referred to as a first temperature detection element, the heater further comprises a second temperature detection element arranged on the same surface of the substrate on which the first temperature detection element is arranged and a first conductive wire and a second conductive wire of the second temperature detection element, wherein the second conductive line of the second temperature detection element is arranged to extend from the second temperature detection element toward one end of the substrate in the length direction of the substrate; the first conductive line of the second temperature detection element is arranged to extend from the second temperature detection element toward the other end of the substrate in the length direction of the substrate, and The second conductive wire of the first temperature detection element and the second conductive wire of the second temperature detection element are the same conductive wire. 3 . The heater according to claim 1 , wherein the heater comprises a plurality of independently controllable heating elements arranged in a length direction of the substrate.

4. A fixing device for fixing an image formed on a recording material onto the recording material, the fixing device comprising: tubular membrane; as well as A heater according to claim 1, arranged in contact with the inner face of the film, wherein the heater is arranged in contact with the inner face of the film on the side of the face where the temperature detection element is arranged. 5 . The fixing device according to claim 4 , further comprising a pressure roller configured to form a fixing nip portion for pinching and conveying a recording material with the heater via the film.

6. A heater for a fixing device, comprising: A substrate having a length direction and a width direction; a heating element, the heating element being arranged on the substrate; a plurality of temperature detection elements, the plurality of temperature detection elements being arranged on the substrate; a plurality of conductive lines, including a plurality of two conductive lines for extracting a signal corresponding to temperature, electrically connected to one temperature detection element of the plurality of temperature detection elements, the plurality of conductive lines being arranged on the same surface of the substrate on which the plurality of temperature detection elements are arranged; and a protective layer, the protective layer covering the plurality of temperature detection elements and the plurality of conductive wire groups, wherein a first conductive line as one of the two conductive lines is arranged to extend from the temperature detection element to which it is electrically connected toward one end of the substrate in the length direction of the substrate, and a second conductive line as the other of the two conductive lines is arranged to extend from the temperature detection element to which it is electrically connected toward the other end of the substrate in the length direction of the substrate, wherein the first conductive line is arranged in a region extending from a first position where the temperature detection element is arranged in the width direction of the substrate to a second position in the width direction of the substrate that is different from the first position, and In the protective layer covered area, the first conductive line has an area inclined in both the length direction and the width direction of the substrate and does not have an area extending only in a direction parallel to the width direction of the substrate. 7 . The heater according to claim 6 , wherein the heater comprises a plurality of independently controllable heating elements arranged in a length direction of the substrate.

8. A fixing device for fixing an image formed on a recording material onto the recording material, the fixing device comprising: tubular membrane; as well as A heater according to claim 6, arranged in contact with the inner face of the film, wherein the heater is arranged in contact with the inner face of the film on the side of the face where the temperature detection element is arranged. 9 . The fixing device according to claim 8 , further comprising a pressure roller configured to form a fixing nip portion for pinching and conveying a recording material with the heater via the film.

Images