Heating device, fixing device, and image forming apparatus

Abstract

To prevent an increase in the temperature of a conductive member in an area where temperature is likely to increase compared with the other area.SOLUTION: A heating device comprises: a pair of rotating bodies 21, 22; a heat source 23 that heats at least one of the pair of rotating bodies 21, 22; a temperature detection member 27 that detects the temperature of the heat source 23; a heat source holding member 24 that holds the heat source 23; and a conductive member 44 that is connected with the temperature detection member 27 and has flexibility. The heating device has a first member 50 different from the heat source holding member 24 between the heat source holding member 24 and the conductive member 44. The first member 50 has a conductive member support part 30 that supports the conductive member 44 on a side of a surface 510 opposite to a side of the heat source. The conductive member support part 30 supports the conductive member 44 in an at least partial area outside a predetermined width W2 so as to increase the distance from the conductive member 44 to the heat source 23 compared with an area inside the predetermined width W2.SELECTED DRAWING: Figure 6

Description

Technical Field

[0001] The present invention relates to a heating device, a fixing device, and an image forming apparatus.

Background Art

[0002] As an example of a heating device mounted in an image forming apparatus such as a copying machine or a printer, a fixing device is known that fixes an unfixed image on a sheet by heating the sheet carrying the unfixed image.

[0003] In a fixing device, there is a case where a temperature detection member such as a thermistor or a thermostat is provided on a heat source holding member that holds a heat source. The temperature control member is connected to a control unit via a conduction member such as a lead wire, and the control unit controls heat generation based on the temperature of the heat source detected by the temperature detection member, thereby maintaining the temperature of the heat source at an appropriate temperature.

[0004] Since the conduction member connected to the temperature detection member is arranged near the heat source that becomes high temperature, it is preferably made of a material having heat resistance or protected by a coating material having heat resistance. However, since there are problems such as an increase in manufacturing cost in selecting a material with excellent heat resistance, in Patent Document 1 (Japanese Patent Application Laid-Open No. 2011-118246), a plurality of protrusions are provided on the surface side opposite to the surface of the heat source holding member that holds the heat source, and a configuration in which a conductive member is supported through each protrusion is proposed. According to this configuration, since the contact area of the conduction member with respect to the heat source holding member decreases, the heat transmitted from the heat source holding member to the conduction member decreases, and it is said that the temperature rise of the conduction member can be suppressed.

[0005] Incidentally, the temperature of the heating source does not always remain uniform throughout; variations occur, for example, when sheets are continuously transported through the fixing device. In other words, when a sheet narrower than the heating area of ​​the heating source is transported, the heat from the heating source is not absorbed by the sheet in the areas that the sheet does not pass through. As a result, heat accumulates and the temperature rises in these areas compared to the areas that the sheet does pass through. Consequently, variations in the temperature of the heating source occur between the areas that the sheet passes through and the areas that the sheet does not.

[0006] In the above-mentioned Patent Document 1, multiple protrusions are provided to make it difficult for heat to be transferred to the conductive member, but the influence of heat on the conductive member from parts of the heating source that are prone to temperature rise and parts that are not has not been considered at all. [Overview of the project] [Problems that the invention aims to solve]

[0007] It is necessary to suppress the temperature rise of conductive components in regions where the temperature may rise compared to other regions. [Means for solving the problem]

[0008] To solve the above problems, the present invention provides A heating device comprising: a pair of rotating bodies that come into contact with each other to form a nip portion through which a sheet passes; a heating source for heating at least one of the pair of rotating bodies; a temperature sensing member for sensing the temperature of the heating source; a heating source holding member for holding the heating source; and a flexible conductive member connected to the temperature sensing member, wherein a first member separate from the heating source holding member is located between the heating source holding member and the conductive member, the first member having a plurality of conductive member support portions that protrude toward the opposite side from the heating source and support the conductive member, and at least some of the conductive member support portions located beyond a predetermined width have a greater height in the protruding direction from the first member than the other conductive member support portions. It is characterized by the following: [Effects of the Invention]

[0009] According to the present invention, it is possible to suppress the temperature rise of a conductive member in a region where the temperature may rise compared to other regions. [Brief explanation of the drawing]

[0010] [Figure 1] This is a schematic diagram of an image forming apparatus according to one embodiment of the present invention. [Figure 2] This is a schematic diagram of the fixing device according to this embodiment. [Figure 3] This is a cross-sectional view of the fixing belt according to this embodiment. [Figure 4] This is a plan view of the heater according to this embodiment. [Figure 5] It is a perspective view showing a state where a connector as a power supply member is connected to the heater according to this embodiment. [Figure 6] In the fixing device according to this embodiment, it is a diagram showing a support structure of a lead wire connected to a temperature sensor. [Figure 7] It is a diagram showing a modification example of the present invention. [Figure 8] It is a diagram showing another modification example of the present invention. [Figure 9] It is a diagram showing yet another modification example of the present invention. [Figure 10] It is a diagram showing yet another modification example of the present invention. [Figure 11] It is a diagram showing yet another modification example of the present invention. [Figure 12] It is a diagram showing yet another modification example of the present invention. [Figure 13] It is a diagram showing an example of a protrusion that is not a comparison target for height. [Figure 14] It is a diagram showing an example of a protrusion that is not a comparison target for height. [Figure 15] It is a diagram showing yet another modification example of the present invention. [Figure 16] It is a diagram showing yet another modification example of the present invention. [Figure 17] It is a diagram showing yet another modification example of the present invention. [Figure 18] It is a diagram for explaining the arrangement of protrusions. [Figure 19] It is a diagram for explaining the shape of protrusions. [Figure 20] It is a diagram showing a modification example of protrusions. [Figure 21] It is a diagram for explaining the shape of protrusions. [Figure 22] It is a diagram showing a modification example of protrusions. [Figure 23] It is a diagram showing yet another modification example of the present invention. [Figure 24] It is a diagram showing yet another modification example of the present invention. [Figure 25]It is a diagram showing yet another modification of the present invention. [Figure 26] It is a diagram showing an example where a protrusion is provided on a flange. [Figure 27] It is a diagram showing an example where a protrusion is provided on a heater holder. [Figure 28] It is a diagram showing a thermistor with lead wires protruding from both ends. [Figure 29] It is a diagram showing a thermistor with a lead wire protruding from one end. [Figure 30] It is a diagram showing an example of applying the present invention to an end-reference conveyance system. [Figure 31] It is a diagram showing the configuration of a fixing device different from the above-described embodiment. [Figure 32] It is a diagram showing the configuration of a fixing device different from the above-described embodiment. [Figure 33] It is a diagram showing the configuration of a fixing device different from the above-described embodiment. [Figure 34] It is a diagram showing the configuration of a fixing device different from the above-described embodiment. [Figure 35] It is a diagram showing the configuration of an image forming apparatus different from the above-described embodiment. [Figure 36] It is a diagram showing the configuration of the fixing device shown in FIG. 35. [Figure 37] It is a plan view of the heater shown in FIG. 36. [Figure 38] It is a perspective view of the heater and the heater holder shown in FIG. 36. [Figure 39] It is a diagram showing a method of attaching a connector to the heater shown in FIG. 36. [Figure 40] It is a diagram showing the arrangement of the temperature sensor and the thermostat provided in the fixing device shown in FIG. 35. [Figure 41] It is a diagram showing the groove portion of the flange shown in FIG. 39. [Figure 42] It is a diagram showing the configuration of a fixing device different from the above-described embodiment. [Figure 43] It is a perspective view of the heater, the first high thermal conductivity member, and the heater holder shown in FIG. 42. [Figure 44]This is a plan view of the heater showing the arrangement of the first high-heat-conductivity member. [Figure 45] This is a plan view of a heater showing another example of the arrangement of the first high-heat-conductivity member. [Figure 46] This is a plan view of a heater showing yet another example of the arrangement of the first high-heat-conductivity member. [Figure 47] This is a plan view of the heater showing the enlarged division area. [Figure 48] This figure shows a configuration of a fixing device that differs from the embodiment described above. [Figure 49] Figure 48 is a perspective view of the heater, first high-thermal-conductivity member, second high-thermal-conductivity member, and heater holder shown. [Figure 50] This is a plan view of the heater showing the arrangement of the first high-heat-conductivity member and the second high-heat-conductivity member. [Figure 51] This is a plan view of a heater showing another example of the arrangement of the first and second high-heat-conductivity members. [Figure 52] This is a plan view of a heater showing yet another example of the arrangement of the second high-heat-conductivity member. [Figure 53] This figure shows a configuration of a fixing device that differs from the embodiment described above. [Figure 54] This is a diagram showing the atomic crystal structure of graphene. [Figure 55] This is a diagram showing the atomic crystal structure of graphite. [Modes for carrying out the invention]

[0011] The present invention will be described below with reference to the attached drawings. In each drawing used to explain the present invention, components such as members and parts having the same function or shape will be given the same reference numerals to the extent possible so that they can be distinguished, and their description will be omitted after they have been described once.

[0012] Figure 1 is a schematic diagram of an image forming apparatus according to one embodiment of the present invention. Here, "image forming apparatus" in this specification includes printers, copiers, facsimile machines, printing presses, or multifunction devices that combine two or more of these. Furthermore, "image forming" as used in the following description means not only forming images that have meaning, such as characters and figures, but also forming images that do not have meaning, such as patterns. First, the overall configuration and operation of the image forming apparatus according to this embodiment will be described with reference to Figure 1.

[0013] As shown in Figure 1, the image forming apparatus 100 according to this embodiment includes an image forming unit 200 for forming an image on a sheet-like recording medium such as paper, a fixing unit 300 for fixing the image on the recording medium, a recording medium supply unit 400 for supplying the recording medium to the image forming unit 200, and a recording medium discharge unit 500 for discharging the recording medium outside the apparatus.

[0014] The image forming unit 200 includes four process units 1Y, 1M, 1C, and 1Bk as image forming units, an exposure apparatus 6 that forms an electrostatic latent image on the photoreceptor 2 provided in each process unit 1Y, 1M, 1C, and 1Bk, and a transfer apparatus 8 that transfers the image to a recording medium.

[0015] Each process unit 1Y, 1M, 1C, and 1Bk has essentially the same configuration, except that they contain toners (developers) of different colors: yellow, magenta, cyan, and black, which correspond to the color separation components of a color image. Specifically, each process unit 1Y, 1M, 1C, and 1Bk includes a photoreceptor 2 as an image carrier that carries an image on its surface, a charging member 3 that charges the surface of the photoreceptor 2, a developing device 4 that supplies toner as a developer to the surface of the photoreceptor 2 to form a toner image, and a cleaning member 5 that cleans the surface of the photoreceptor 2.

[0016] The transfer device 8 comprises an intermediate transfer belt 11, a primary transfer roller 12, and a secondary transfer roller 13. The intermediate transfer belt 11 is an endless belt member and is stretched by a plurality of support rollers. Four primary transfer rollers 12 are provided inside the intermediate transfer belt 11. Each primary transfer roller 12 contacts each photoreceptor 2 via the intermediate transfer belt 11, thereby forming a primary transfer nip between the intermediate transfer belt 11 and each photoreceptor 2. The secondary transfer rollers 13 contact the outer circumferential surface of the intermediate transfer belt 11, forming a secondary transfer nip.

[0017] In the fixing section 300, a fixing device 20 is provided. The fixing device 20 includes a fixing belt 21 made of an endless belt, and a pressure roller 22 as an opposing member facing the fixing belt 21. The fixing belt 21 and the pressure roller 22 contact each other on their respective outer surfaces, forming a nip section (fixing nip).

[0018] The recording medium supply unit 400 is provided with a paper feed cassette 14 for storing paper P as a recording medium, and a paper feed roller 15 for feeding paper P from the paper feed cassette 14. Hereinafter, "recording medium" will be described as "paper," but "recording medium" is not limited to paper. "Recording medium" includes not only paper but also OHP sheets or fabrics, metal sheets, plastic films, or prepreg sheets made by pre-impregnating carbon fibers with resin. Furthermore, "paper" includes not only plain paper but also cardboard, postcards, envelopes, thin paper, coated paper (such as coated paper and art paper), tracing paper, etc.

[0019] The recording medium discharge unit 500 is provided with a pair of paper discharge rollers 17 for discharging the paper P to the outside of the image forming apparatus, and a paper discharge tray 18 for placing the paper P discharged by the paper discharge rollers 17.

[0020] Next, the printing operation of the image forming apparatus 100 according to this embodiment will be described with reference to Figure 1.

[0021] When printing is started in the image forming apparatus 100, the photoreceptors 2 of each process unit 1Y, 1M, 1C, 1Bk and the intermediate transfer belt 11 of the transfer device 8 begin to rotate. At the same time, the paper feed roller 15 begins to rotate, and paper P is fed out from the paper feed cassette 14. The fed paper P comes to rest upon contact with a pair of timing rollers 16, and the transport of paper P is temporarily stopped until the image to be transferred to paper P is formed.

[0022] In each process unit 1Y, 1M, 1C, and 1Bk, first, the surface of the photoreceptor 2 is charged to a uniform high potential by the charging member 3. Next, based on the image information of the original document read by the document reader or the print image information instructed to print from the terminal, the exposure unit 6 exposes the surface (charged surface) of each photoreceptor 2. As a result, the potential of the exposed area decreases, and an electrostatic latent image is formed on the surface of each photoreceptor 2. Then, the developing unit 4 supplies toner to this electrostatic latent image, and a toner image is formed on each photoreceptor 2. As the toner image formed on each photoreceptor 2 reaches the primary transfer nip (position of the primary transfer roller 12) as the photoreceptor 2 rotates, it is transferred sequentially onto the rotating intermediate transfer belt 11. Thus, a full-color toner image is formed on the intermediate transfer belt 11. Furthermore, in the image forming apparatus 100, a monochrome image can be formed using any one of the process units 1Y, 1M, 1C, or 1Bk, or a two-color or three-color image can be formed using any two or three of the process units. After the toner image is transferred from the photoreceptor 2 to the intermediate transfer belt 11, residual toner and other contaminants on each photoreceptor 2 are removed by the cleaning member 5.

[0023] The toner image transferred onto the intermediate transfer belt 11 is transported to the secondary transfer nip (the position of the secondary transfer roller 13) as the intermediate transfer belt 11 rotates, and is transferred onto the paper P that has been transported by the timing roller 16. The paper P is then transported to the fuser unit 20, where the toner image on the paper P is heated and pressurized by the fuser belt 21 and the pressure roller 22, thereby fixing the toner image to the paper P. The paper P is then transported to the recording medium discharge unit 500 and discharged into the paper discharge tray 18 by the paper discharge roller 17. This completes the series of printing operations.

[0024] Next, the configuration of the fixing device according to this embodiment will be described in detail based on Figure 2.

[0025] As shown in Figure 2, the fixing device 20 according to this embodiment includes a fixing belt 21 and a pressure roller 22, as well as a heater 23, a heater holder 24, a stay 25, a guide member 26, a temperature sensor 27, and the like.

[0026] The fixing belt 21 is a rotating body (first rotating body or fixing member) that contacts the unfixed toner-carrying surface of the paper P to fix the unfixed toner (unfixed image) to the paper P, and is composed of a flexible, endless belt. The diameter of the fixing belt 21 is set to, for example, 15 to 120 mm. In this embodiment, the inner diameter of the fixing belt 21 is set to 25 mm.

[0027] As shown in Figure 3, the fixing belt 21 is constructed by laminating a base material 210, an elastic layer 211, and a release layer 212 in order from the inner circumferential surface to the outer circumferential surface, with an overall thickness of 1 mm or less. The base material 210 has a layer thickness of 30 to 50 μm and is made of a metal material such as nickel or stainless steel, or a resin material such as polyimide. The elastic layer 211 has a layer thickness of 100 to 300 μm and is made of a rubber material such as silicone rubber, foamed silicone rubber, or fluororubber. Because the fixing belt 21 has an elastic layer 211, minute irregularities are not formed on the surface of the fixing belt 21 in the nip portion, making it easier for heat to be uniformly transferred to the toner image on the paper P. The release layer 212 has a layer thickness of 10 to 50 μm and is made of materials such as PFA (tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer), PTFE (polytetrafluoroethylene), polyimide, polyetherimide, or PES (polyether sulfide). The fixing belt 21 has a release layer 212, which ensures release properties (peelability) from the toner (toner image).

[0028] As shown in Figure 2, the pressure roller 22 is a rotating body (second rotating body or opposing member) positioned opposite the outer circumferential surface of the fixing belt 21. The pressure roller 22 contacts the heater 23 via the fixing belt 21 and forms a nip portion N between itself and the fixing belt 21.

[0029] The pressure roller 22 is, for example, a roller with an outer diameter set to 25 mm, and has a hollow iron core material 220, an elastic layer 221 provided on the outer surface of the core material 220, and a release layer 222 provided on the outer surface of the elastic layer 221. The elastic layer 221 has a thickness of, for example, 3.5 mm and is made of silicone rubber or the like. The release layer 222 has a thickness of, for example, about 40 μm and is made of fluororesin or the like.

[0030] The heater 23 is a heating source that heats the fixing belt 21 from the inside. The heater 23 is a planar or plate-shaped heater that extends longitudinally along the longitudinal direction of the fixing belt 21 (the paper width direction intersecting the paper transport direction), and is positioned to contact the inner circumferential surface of the fixing belt 21. The heater 23 according to this embodiment includes a base material 55, a resistance heating element 56 provided on the base material 55, and an insulating layer 57 covering the resistance heating element 56.

[0031] As shown in Figure 2, in this embodiment, the resistance heating element 56 is provided on the surface of the base material 55 on the pressure roller 22 side (nip portion N side), but it may also be provided on the opposite side. In that case, since the heat from each resistance heating element 56 is transferred to the fixing belt 21 via the base material 55, it is preferable that the base material 55 be made of a material with high thermal conductivity, such as aluminum nitride.

[0032] The heater holder 24 is a heating source holding member positioned inside the fixing belt 21 and holding the heater 23. Since the heater holder 24 is prone to becoming hot due to the heat from the heater 23, it is preferable that it be made of a heat-resistant material. For example, if the heater holder 24 is made of a heat-resistant resin with low thermal conductivity such as LCP or PEEK, the heat resistance of the heater holder 24 is ensured while suppressing heat transfer from the heater 23 to the heater holder 24, thereby efficiently heating the fixing belt 21.

[0033] The stay 25 is a support member that supports the heater holder 24. The stay 25 supports the side of the heater holder 24 opposite to the side facing the pressure roller 22 along the longitudinal direction of the fixing belt 21, thereby suppressing the bending of the heater holder 24 due to the pressure applied by the pressure roller 22, and forming a nip portion N of uniform width between the fixing belt 21 and the pressure roller 22. To ensure its rigidity, the stay 25 is preferably made of an iron-based metal material such as SUS or SECC.

[0034] The guide member 26 is a member that guides the anchoring belt 21 from the inside. The guide member 26 has an arc-shaped cross-section that follows the inner circumferential surface of the anchoring belt 21 and is positioned on the upstream and downstream sides of the heater 23 in the rotational direction of the anchoring belt 21 (direction of the arrow in Figure 2), respectively. In this embodiment, each guide member 26 is configured integrally with the heater holder 24, but they may be configured as separate parts.

[0035] The temperature sensor 27 is a temperature sensing member that detects the temperature of the heater 23. Known temperature sensors such as thermopiles, thermostats, thermistors, or NC sensors can be used as the temperature sensor 27. In this embodiment, a contact-type temperature sensor is used that detects the temperature by contacting the side of the heater 23 opposite to the pressure roller 22 side. Furthermore, the temperature sensor 27 is not limited to a contact-type temperature sensor; it may also be a non-contact type temperature sensor that is positioned without contact with the heater 23 and detects the ambient temperature near the heater 23.

[0036] The fixing device 20 according to this embodiment operates as follows.

[0037] As shown in Figure 2, when the pressure roller 22 is driven to rotate, the driving force is transmitted to the fixing belt 21, causing the fixing belt 21 to rotate in response. The fixing belt 21 is then heated by the heater 23. The temperature of the heater 23 at this time is detected by the temperature sensor 27, and the amount of heat generated by the heater 23 is controlled based on the detected temperature. This maintains the temperature of the fixing belt 21 at a temperature at which the image can be fixed (fixing temperature). When the paper P carrying the unfixed image is transported between the fixing belt 21 and the pressure roller 22 (nip section N), the toner image on the paper P is heated and pressurized by the fixing belt 21 and the pressure roller 22, and the image is fixed to the paper P.

[0038] Figure 4 is a plan view of the heater according to this embodiment.

[0039] As shown in Figure 4, the heater 23 according to this embodiment has a plate-shaped base material 55 extending in one direction (in the direction of arrow X in Figure 4). The base material 55 is arranged such that its longitudinal direction X is oriented in the longitudinal direction of the fixing belt 21 or in the axial direction of the pressure roller 22. On the surface of the base material 55, two resistance heating elements 56 are arranged side by side in the longitudinal direction Y of the base material 55, extending in the longitudinal direction X of the base material 55. The "short direction" refers to the direction perpendicular to the longitudinal direction X along the surface of the base material 55 on which the resistance heating elements 56 are provided, and is the same direction as the paper transport direction in which the paper is transported.

[0040] As shown in Figure 4, a pair of electrode portions 58 are provided on one end of the base material 55 in the longitudinal direction X. Each electrode portion 58 is connected to each resistance heating element 56 via a power supply line 59. The ends of each resistance heating element 56 opposite to the ends connected to the electrode portions 58 are connected to each other via another power supply line 59. Each resistance heating element 56 and each power supply line 59 are covered with an insulating layer 57 to ensure insulation. In contrast, each electrode portion 58 is exposed and not covered by the insulating layer 57 so that a connector, which will be used as a power supply terminal as described later, can be connected to it.

[0041] The base material 55 is made of a material with excellent heat resistance and insulation properties, such as ceramics like alumina or aluminum nitride, glass, mica, or polyimide. Alternatively, the base material 55 may be a metal material (conductive material) such as stainless steel (SUS), iron, or aluminum, with an insulating layer formed on top. In particular, if the base material 55 is a highly thermally conductive material such as aluminum, copper, silver, graphite, or graphene, the uniformity of heating the heater 23 can be improved, enhancing image quality. The insulating layer 57 is made of a material with excellent heat resistance and insulation properties, such as ceramics like alumina or aluminum nitride, glass, mica, or polyimide. The resistive heating element 56 is formed, for example, by coating the surface of the base material 55 with a paste made of silver palladium (AgPd) and glass powder by screen printing, and then firing the base material 55. It is also possible to use a resistive material such as silver alloy (AgPt) or ruthenium oxide (RuO2) as the material for the resistive heating element 56. Furthermore, the electrode portion 58 and the power supply line 59 are formed by screen printing silver (Ag) or silver-palladium (AgPd).

[0042] Figure 5 is a perspective view showing the state in which the connector 40, which serves as a power supply component, is connected to the heater 23.

[0043] As shown in Figure 5, the connector 40 has a resin housing 41, a plurality of contact terminals 42 provided on the housing 41, and a power supply harness 43 connected to each contact terminal 42. Each contact terminal 42 is made of an elastically deformable member such as a leaf spring.

[0044] As shown in Figure 5, the connector 40 is attached so as to sandwich the heater 23 and the heater holder 24 together. In this way, the heater 23 and the heater holder 24 are held together by the connector 40. In this state, the tip (contact portion 42a) of each contact terminal 42 of the connector 40 elastically contacts (pressure contact) the corresponding electrode portion 58, thereby electrically connecting each contact terminal 42 and each electrode portion 58. This makes it possible to supply power to the heater 23 (each resistance heating element 56) from the power supply of the image forming apparatus via the connector 40.

[0045] Figure 6 shows the support structure for the lead wire 44 connected to the temperature sensor 27 in the fixing device according to this embodiment.

[0046] As shown in Figure 6, a flexible lead wire 44, which acts as a conductive member, is connected to the temperature sensor 27. The end of the lead wire 44 opposite to the end connected to the temperature sensor 27 is connected to a control unit provided in the main body of the image forming apparatus. The lead wire 44 is composed of a conductor and an insulator covering the conductor in order to ensure insulation and heat resistance. In addition, a sensor holder 50 is provided on the surface 240 (the upper surface of the heater holder 24 in Figure 6) of the heater holder 24 opposite to the surface 241 that holds the heater 23, as a temperature sensing member holding member that holds the temperature sensor 27. The sensor holder 50 has a main body portion 50a that is placed on the heater holder 24 and a spring 50b that acts as a biasing member provided on the main body portion 50a. The temperature sensor 27 is held in contact with the heater 23 by the pressure applied to the temperature sensor 27 toward the heater 23 by the spring 50b.

[0047] To avoid direct heat exposure from the heater 23, the lead wire 44 is positioned on the opposite side of the heater 23, sandwiching the heater holder 24 and the sensor holder 50. Specifically, the lead wire 44 is routed along the side 510 (the upper surface of the main body 50a in Figure 6) of the sensor holder 50's main body 50a that is opposite to the heater 23. In addition, the surface 510 of the sensor holder 50 on the lead wire 44 side is provided with multiple protrusions 30 that serve as conductive member support parts to support the lead wire 44.

[0048] Multiple protrusions 30 are provided so as to project from the main body 50a of the sensor holder 50 toward the side opposite to the heater 23, and are spaced apart along the longitudinal direction X of the heater 23. The lead wires 44 are supported by the tips of each protrusion 30, so that the lead wires 44 are positioned non-contact with the main body 50a of the sensor holder 50, where each protrusion 30 is provided, with a gap between them. That is, the sensor holder 50 has a main body 50a having a first surface 520 that faces the heater 23 via the heater holder 24, and multiple protrusions 30 provided on a second surface 510 of the main body 50a opposite to the first surface 520. In this way, by supporting the lead wires 44 with the multiple protrusions 30, contact between the lead wires 44 and the main body 50a can be avoided, and the contact area of ​​the lead wires 44 with the sensor holder 50 can be reduced. In the first place, the lead wire 44 has lower rigidity compared to sheet metal or jumper wires, so in order to be held at a position away from the sensor holder 50, it is necessary to support it with other components. For this reason, in this embodiment, a plurality of protrusions 30 are provided to support the lead wire 44, reducing the contact area of ​​the lead wire 44 with the sensor holder 50, and thereby suppressing heat transfer from the heater 23, heater holder 24 and sensor holder 50 to the lead wire 44.

[0049] Furthermore, since the projection 30 is provided on the sensor holder 50, which does not directly contact the heater 23 and the fixing belt 21, rather than on the heater holder 24, which directly contacts the heater 23 and the fixing belt 21, the temperature rise of the projection 30 can be suppressed. In other words, the sensor holder 50 is less prone to temperature rise than the heater holder 24, so by providing the projection 30 on the sensor holder 50, which is less prone to temperature rise, the temperature rise of the projection 30 can be effectively suppressed. Moreover, since the sensor holder 50 is separate from the heater holder 24, a temperature difference is generated between the heater holder 24 and the sensor holder 50 due to contact thermal resistance, so the temperature rise of the projection 30 is even less likely to occur. Thus, in this embodiment, the projection 30 is interposed between the heater holder 24 and the lead wire 44, rather than on the heater holder 24, and is provided on the sensor holder 50, which is a separate first component from the heater holder 24. As a result, the temperature rise of the projection 30 is effectively suppressed, and the temperature rise of the lead wire 44 supported by the projection 30 is also effectively suppressed.

[0050] Furthermore, the lead wire 44 is not necessarily in contact with the tip of the projection 30; it may not be in contact. In other words, "supporting" the lead wire 44 by the projection 30 means supporting the lead wire 44 so that it does not come into contact with the main body 50a of the sensor holder 50. This includes not only cases where the lead wire 44 and the projection 30 are in contact, but also cases such as the projection 30A2 shown in Figure 8, which will be described later, where the projection 30A2 does not actually come into contact with the lead wire 44, but supports the lead wire 44 in a way that avoids contact with the main body 50a when it approaches the main body 50a.

[0051] Here, among the multiple protrusions 30, the protrusion 30A located at the outermost end (rightmost end in Figure 6) in the longitudinal direction of the sensor holder 50, which is also the longitudinal direction X of the heater 23, is set to have a higher height in the direction of protrusion from the sensor holder 50 (main body 50a) compared to the other protrusions 30B (t1>t2). This taller protrusion 30A is positioned to correspond to the part of the heater 23 where the temperature becomes high, and reduces the influence of the heater 23's heat on the lead wire 44.

[0052] Specifically, in this embodiment, the portion of the heater 23 where the temperature becomes high refers to the portion inside the heating region 60 where the resistance heating element 56 of the heater 23 is located, and outside the maximum paper width W1 (maximum sheet passage width) through which the widest sheet of paper P1 can pass (the region indicated by the symbol H in Figure 6). Furthermore, in this specification, "heating region" refers to the region in the longitudinal direction X of the heater 23 where the resistance heating element 56 is located, and in the case where multiple resistance heating elements 56 are located, as shown in the example described later (see Figure 18), it refers to the range from one end to the other of the region where all the resistance heating elements 56 are located. Furthermore, in this specification, "maximum paper passage width" refers to a predetermined region through which the widest sheet of paper is assumed to pass, regardless of whether the widest sheet of paper actually passes through. In this embodiment, a so-called central reference transport method is employed, in which paper of various widths is transported with its width center as the reference point. Therefore, the maximum paper transport width is the range from the longitudinal center m of the heating area 60 of the heater 23 toward both ends at a distance of half the maximum width of the paper, or half the maximum width plus 5 mm. For example, if the maximum width of the paper is A4 size (width: 210 mm), the maximum paper transport width is the range from the longitudinal center m of the heating area 60 toward both ends at a distance of 105 mm (half the width of A4), or 110 mm (105 mm plus 5 mm). Also, in Figure 6, the area indicated by the symbol W2 is the minimum paper transport width (minimum sheet transport width) through which the minimum width of paper P2 passes. This minimum paper transport width, like the maximum paper transport width, refers to a pre-set area through which the minimum width of paper is assumed to pass, regardless of whether the minimum width of paper actually passes through or not. In other words, the minimum paper width is the range from the longitudinal center m of the heating area 60 of the heater 23 toward both ends, at a distance of half the minimum width of the paper, or half the minimum width plus 5 mm.

[0053] Basically, to heat the paper, it is sufficient to maintain the temperature of the fixing belt 21 within the maximum paper feed width W1 at a predetermined temperature. However, immediately after the temperature of the fixing belt 21 rises to the predetermined temperature, the amount of heat stored is small, so when paper passes through, the temperature of the fixing belt 21 tends to drop easily at both ends of the heat-generating area 60. Therefore, in this embodiment, the heat-generating area 60 of the heater 23 is extended beyond the maximum paper feed width W1 to suppress the temperature drop of the fixing belt 21 associated with paper feeding. However, when the heat-generating area 60 is extended beyond the maximum paper feed width W1, the fixing belt 21 and heater 23 may accumulate heat in the non-paper-feeding area where the maximum width of paper P1 does not pass, especially when multiple sheets of paper are fed continuously, causing an excessive temperature rise. Temperature rise in the non-paper-feeding area associated with paper feeding can occur not only when feeding the widest paper P1, but also when feeding paper smaller than the heating area 60 of the heater 23. However, for small-sized paper which is not used frequently, a reduction in productivity (printing speed) is adopted to suppress the temperature rise in the non-paper-feeding area. In contrast, for the widest paper P1 which is used frequently, there is a tendency to print without reducing productivity, so temperature rise in the non-paper-feeding area is more likely to occur when paper is fed continuously. Furthermore, in recent years, with the increase in the amount of heat generated by the heater due to the increased speed of image forming machines, the problem of excessive temperature rise outside the maximum paper width W1 has become more pronounced.

[0054] Therefore, in the embodiment of the present invention, as shown in Figure 6, the protrusion 30A located inside the heating region 60 of the heater 23 and outside the maximum paper feed width W1 region H (hereinafter, this region is conveniently referred to as the "overheating region") is made higher (t1>t2) than the protrusions 30B located in other regions, so that the distance of the lead wire 44 to the heater 23 in the overheating region H is greater than in other regions.

[0055] As a result, heat is less likely to be transferred from the heater 23 to the lead wire 44. Therefore, even if the heater 23 overheats excessively in the overheating region H when continuously feeding the widest paper P1, the temperature rise of the lead wire 44 can be suppressed, thereby suppressing deterioration and damage to the lead wire 44. Furthermore, since deterioration and damage to the lead wire 44 can be suppressed, the widest paper P1 can be continuously fed without reducing productivity.

[0056] The tall protrusion 30A described above may not only be located within the overheating region H shown in Figure 6, but may also be located outside the overheating region H.

[0057] For example, as shown in Figure 7, tall protrusions 30A may be placed on both outer sides of the overheating region H. In this case as well, in the overheating region H, a greater distance between the lead wire 44 and the heater 23 can be secured compared to other regions, thus suppressing the temperature rise of the lead wire 44. Furthermore, in the example shown in Figure 7, since the protrusions 30A are not provided within the overheating region H, the temperature rise of the protrusions 30A themselves can also be suppressed. As a result, the amount of heat transferred from the protrusions 30A to the lead wire 44 can also be reduced, effectively suppressing the temperature rise of the lead wire 44. In addition, because the temperature rise of the lead wire 44 can be effectively suppressed, it becomes possible to select inexpensive materials (materials with not very high heat resistance) as the material for the lead wire 44 or the insulator covering the lead wire 44, thereby reducing costs. On the other hand, as shown in the example in Figure 6, when the protrusion 30A is positioned in the overheating region H, the protrusion 30A is not positioned on the longitudinal end of the sensor holder 50 beyond the overheating region H. This eliminates the need for the installation space of the protrusion 30A, which has the advantage of reducing the longitudinal size of the sensor holder 50.

[0058] Also, as in the example shown in FIG. 8, among the high protrusions 30A, the right protrusion 30A1 may be made higher than the left protrusion 30A2 (t3>t4). In the case of this example, the lead wire 44 is mainly supported by the higher protrusion 30A1. Further, since the higher protrusion 30A1 is arranged outside the heat generation region 60, it is less affected by the heat of the heater 23 than the protrusion 30A2 arranged in the heat generation region 60. Therefore, the amount of heat transmitted from the higher protrusion 30A1 to the lead wire 44 also decreases, and the temperature rise of the lead wire 44 can be effectively suppressed.

[0059] Conversely, as in the example shown in FIG. 9, among the high protrusions 30A, the left protrusion 30A2 may be made higher than the right protrusion 30A1 (t3<t4). In this case, since an increase in the height of the protrusion 30A1 on the longitudinal end side of the sensor holder 50 is suppressed, the freedom of movement of the lead wire 44 is improved.

[0060] Subsequently, in the example shown in FIG. 10, the protrusion 30A1 arranged on the longitudinal end side of the sensor holder 50 rather than in the over-temperature region H is arranged further on the longitudinal end side (the right side in FIG. 10) of the sensor holder 50 than the end 620 of the roller portion 62 (the portion having an elastic layer) of the pressure roller 22. In this way, when the protrusion 30A1 on the longitudinal outer side is on the longitudinal outer side of the roller portion 62 of the pressure roller 22, the heat of the pressure roller 22 can be suppressed from being transmitted to the protrusion 30A1 on the longitudinal outer side through the heater holder 24 and the sensor holder 50, and the temperature rise of the protrusion 30A1 can be suppressed. Therefore, the amount of heat transmitted from the protrusion 30A1 to the lead wire 44 can be reduced, and the temperature rise of the lead wire 44 can be effectively suppressed.

[0061] Furthermore, as shown in the example in Figure 10, if there is a heat equalization plate 28 as a heat transfer assisting member between the heater 23 and the heater holder 24, it is preferable to suppress the influence of heat from this heat equalization plate 28 on the protrusion 30A1. The heat equalization plate 28 is made of a material with a higher thermal conductivity than the heater holder 24 (for example, copper, aluminum, silver, etc.) and is a member that transfers the heat from the heater 23 in the longitudinal direction of the fixing belt 21 to equalize the heat. As shown in Figure 10, the protrusion 30A1, which is located on the longitudinal end side of the heater holder 24 beyond the overheating region H, is positioned even further towards the longitudinal end side of the sensor holder 50 (right side in Figure 10) than the longitudinal end 280 of the heat equalization plate 28. This suppresses the transfer of heat from the heat equalization plate 28 to the longitudinally outer protrusion 30A1, thereby effectively suppressing the temperature rise of the protrusion 30A1.

[0062] As described above, in each embodiment of the present invention, the height of some of the protrusions 30 is increased to increase the distance of the lead wires 44 to the heater 23 in the overheating region H when feeding paper of the maximum width. However, the temperature rise in the non-feeding region during continuous feeding can occur not only when feeding paper of the maximum width P1, but also when feeding paper of any size smaller than the heating region 60 of the heater 23.

[0063] Therefore, as shown in the example in Figure 11, not only the protrusions 30A located outside the maximum paper feeding width W1, but also the protrusions 30A located inside the maximum paper feeding width W1 may be made higher than the protrusions 30B located in other areas. Specifically, in the example shown in Figure 11, the protrusions 30A located outside the minimum paper feeding width W2 are made higher than the protrusions 30B located inside the minimum paper feeding width W2 (t6>t5). In this case, the distance of the lead wire 44 to the heater 23 can be increased outside the minimum paper feeding width W2 (compared to inside the minimum paper feeding width W2), so the temperature rise of the lead wire 44 can be suppressed in the non-paper feeding area of ​​any size paper.

[0064] Furthermore, as shown in the example in Figure 12, the heights of the protrusions 30A1 and 30A2 may be different on the outside and inside of the maximum paper feeding width W1. Specifically, in the example shown in Figure 12, the height t7 of the protrusion 30A2 that is inside the maximum paper feeding width W1 and outside the minimum paper feeding width W2 is lower than the height t8 of the protrusion 30A1 that is outside the maximum paper feeding width W1. Therefore, in the example shown in Figure 12, the protrusion 30A1 that is outside the maximum paper feeding width W1 is the highest, followed by the protrusion 30A2 that is inside the maximum paper feeding width W1 and outside the minimum paper feeding width W2, and the protrusion 30B within the minimum paper feeding width W2 is the lowest (t8>t7>t5).

[0065] In this way, by making the height t7 of the protrusion 30A2, which is outside the minimum paper feeding width W2 and within the maximum paper feeding width W1, lower than the height t8 of the protrusion 30A1, which is outside the maximum paper feeding width W1, the degree of freedom in layout can be increased. Furthermore, outside the minimum paper feeding width W2 and within the maximum paper feeding width W1, the effect of suppressing heat transfer to the lead wire 44 is slightly reduced by lowering the height of the protrusion 30A2. However, by reducing the productivity when feeding small-sized paper (paper smaller than the maximum width) as needed, the temperature rise in the non-paper feeding area can be suppressed, and the temperature rise of the lead wire 44 can be controlled within an acceptable range.

[0066] In each of the above examples of the present invention, the projections 30A (30A1, 30A2) that increase the height only need to be higher than the projections 30B that are positioned in the minimum paper width W2. However, the projections 30B within the minimum paper width W2 that are used for comparison are assumed to be located in the area where the lead wires 44 are positioned. Even if a projection 32 is positioned in an area without lead wires 44, as shown in Figure 13, even if it is within the minimum paper width W2, it will not be used for height comparison. This is because such a projection 32 is not a conductive member support member (projection 30) that supports the lead wires 44 in the first place.

[0067] Furthermore, in the cross-section in the paper feeding direction Y (sheet transport direction) as shown in Figure 14, the projection 33 provided in the portion where the lead wire 44 of the sensor holder 50 is not located is not a conductive member support member (projection 30) that supports the lead wire 44, and therefore cannot be used for height comparison. Accordingly, the projections that can be used for height comparison are those located within the region where the lead wire 44 may be present in the paper feeding direction Y (sheet transport direction) as shown in Figure 14.

[0068] Furthermore, the projection 30 supporting the lead wire 44 is not necessarily located within the minimum paper width W2; it is also possible that the projection 30 supporting the lead wire 44 is not located within the minimum paper width W2. In that case, for example, a projection 30 (30B) located inside the maximum paper width W1 shown in Figure 6 and outside the minimum paper width W2 may be used as the comparison target for height. Therefore, in the present invention, the objects for height comparison are not limited to projections located within the minimum paper width W2 and projections located outside the minimum paper width W2, but may also be projections within a predetermined width other than the minimum paper width W2 and projections located outside the predetermined width. In other words, the objects for height comparison may be projections 30 within a predetermined width arbitrarily set from the minimum paper width W2, maximum paper width W1, etc., and projections 30 outside that predetermined width. Also, at least some of the projections 30 located outside the predetermined width may be taller than the other projections 30 outside the predetermined width. Furthermore, the tall protrusions 30 support the lead wires 44 located outside the predetermined width such that the distance between the lead wires 44 and the heater 23 is greater compared to the lead wires 44 located within the predetermined width, thereby suppressing the temperature rise of the lead wires 44 outside the predetermined width.

[0069] In the above examples, a configuration was described in which the temperature rise of the lead wire 44 is suppressed by increasing the height of some of the protrusions 30. However, the present invention also includes the following examples in addition to the configuration in which the height of the protrusions 30 is increased.

[0070] Unlike the above examples, the example shown in FIG. 15 is an example in which the distance d1 between some of the protrusions 30 is made smaller than the distance d2 between the other protrusions 30 (d1 < d2). Specifically, in this example, outside the maximum paper passing width W1, the distance d1 between the protrusions 30 arranged within the heat generation region 60 of the heater 23 is made smaller than the distance d2 between the protrusions 30 arranged within the maximum paper passing width W1. In this case, at the location where the distance between the protrusions 30 is large (the location with the distance d2), the lead wire 44 deflects downward between the protrusions 30, and the height s2 of the lead wire 44 with respect to the sensor holder 50 becomes low. On the other hand, at the location where the distance between the protrusions 30 is small (the location with the distance d1), it becomes difficult for the lead wire 44 to deflect downward between the protrusions 30, so the height of the lead wire 44 with respect to the sensor holder 50 can be kept high (s1 > s2). Here, the heights s1 and s2 of the lead wire 44 with respect to the sensor holder 50, and the height s3 described later, mean the shortest distance of the lead wire 44 with respect to the surface on the lead wire 44 side (the surface facing the lead wire 44) in the main body portion 50a of the sensor holder 50. Thus, by making the distance between the protrusions 30 small, in the region where the distance is small (the location with the distance d1), the height s1 of the lead wire 44 with respect to the sensor holder 50 can be kept high, and it becomes difficult for the lead wire 44 to approach the main body portion 50a of the sensor holder 50. Therefore, in the overheating region H where the temperature can rise when the paper P1 with the maximum width is continuously passed, compared with other regions, the approach of the lead wire 44 to the heater 23 is suppressed, and it becomes easier to secure the distance between the heater 23 and the lead wire 44, so that the temperature rise of the lead wire 44 can be suppressed.

[0071] Also, the protrusions 30 whose intervals are set to be narrow are not limited to only the protrusions 30 arranged outside the maximum paper passing width W1. For example, as in the example shown in FIG. 16, the distance d1 between the protrusions 30 outside the maximum paper passing width W1 and the distance d3 between the protrusions 30 within the maximum paper passing width W1 and outside the minimum paper passing width W2 may be made narrower than the distance d2 between the protrusions 30 in other regions (d1, d3 < d2).

[0072] Thus, by making the intervals d1 and d3 between the protrusions 30 outside the minimum paper passing width W2 smaller than the interval d2 between the protrusions 30 within the minimum paper passing width W2 (d1, d3 < d2), in the region outside the minimum paper passing width W2 (where the intervals are d1 and d3), the height of the lead wire 44 with respect to the sensor holder 50 can be kept higher than in the region within the minimum paper passing width W2 (where the interval is d2) (s1, s3 > s2). In this case, not limited to the case where the paper P1 with the maximum width is passed, it is possible to cope with the temperature rise in the non-paper passing region when papers of all sizes are passed. That is, regardless of the size of the paper passed, in the non-paper passing region where the temperature can rise (the region outside the minimum paper passing width W2), the approach of the lead wire 44 to the heater 23 and the sensor holder 50 (main body portion 50a) can be blocked, so that the temperature rise of the lead wire 44 can be effectively suppressed.

[0073] Furthermore, when the temperature rise outside the maximum paper passing width W1 is likely to be significant, as in the example shown in FIG. 16, by making the interval d1 between the protrusions 30 outside the maximum paper passing width W1 smaller than the interval d3 between the protrusions 30 within the maximum paper passing width W1 and outside the minimum paper passing width W2 (d1 < d3), it becomes possible to more reliably suppress the temperature rise of the lead wire 44 disposed particularly in the location where the temperature is likely to rise (the location of the interval d1). That is, in the present embodiment, the closer the region is to the longitudinal end side of the heater 23 where the temperature rise is likely to be significant, the smaller the interval between the protrusions 30 (d1 < d3 < d2), making it difficult for the lead wire 44 to bend downward and keeping the height of the lead wire 44 with respect to the sensor holder 50 high (s1 > s3 > s2), so that the temperature rise of the lead wire 44 is less likely to occur.

[0074] The objects for comparing the relative sizes of the spacing between the protrusions 30 are determined using the same criteria as for comparing the heights of the protrusions 30. That is, it is sufficient that the spacing between any of the protrusions 30 located outside the minimum paper feed width W2 is smaller than the spacing between the protrusions 30 located within the minimum paper feed width W2. However, the protrusions 30 within the minimum paper feed width W2 are located within the area where the lead wires 44 are located. Furthermore, the protrusions 30 within the minimum paper feed width W2 are located within the area where the lead wires 44 may exist in the paper feed direction Y (sheet transport direction) (see Figure 14). In addition, the objects for comparing the relative sizes of the spacing between the protrusions 30 are not limited to the protrusions located within the minimum paper feed width W2 and the protrusions located outside the minimum paper feed width W2, but may also be the protrusions within a predetermined width other than the minimum paper feed width W2 and the protrusions located outside the predetermined width. Furthermore, it is acceptable that the spacing between at least some of the protrusions 30 located outside the predetermined width is smaller than the spacing between other protrusions 30 located outside the predetermined width. The term "specified width" as used herein includes not only the minimum paper feed width or the maximum paper feed width, but also any other width that can be arbitrarily set.

[0075] In the above example, a configuration was described in which the height of some of the multiple protrusions 30 is increased or the spacing between some of the protrusions 30 is reduced. However, it is also possible to increase the height of some of the protrusions 30 and further reduce the spacing between those protrusions 30. In addition, the protrusions 30 that support the lead wires 44 are not limited to multiple protrusions 30, but may consist of only one.

[0076] For example, as shown in the example in Figure 17, only one protrusion 30 may be provided outside the maximum paper feeding width W1 and within the heating region 60 of the heater 23. Furthermore, the height t of the protrusion 30 is preferably higher than the position (height) z where the lead wire 44 is connected to the temperature sensor 27 (t>z). In this example, since the lead wire 44 is supported by the protrusion 30 outside the maximum paper feeding width W1 where the temperature tends to rise, the lead wire 44 can be moved further away from the heater 23 and sensor holder 50 (main body 50a) compared to within the maximum paper feeding width W1. This suppresses heat transfer from the heater 23 to the lead wire 44 in the region where the temperature tends to rise. Note that the position of the single protrusion 30 is not limited to outside the maximum paper feeding width W1; it can be appropriately changed as long as it is outside the minimum paper feeding width W2, which is the region where the temperature tends to rise, depending on the size of paper used most frequently.

[0077] Next, the arrangement and shape of the projections 30 will be further explained. The arrangement and shape of the projections 30 described below are applicable to any of the projections 30 in the above examples.

[0078] Figure 18 is a plan view of the sensor holder 50 as seen from the heater 23 side. As shown in Figure 18, when the heater 23 has a plurality of resistance heating elements 56 arranged at intervals in the longitudinal direction X (paper width direction), it is preferable that at least a part of the projection 30 on the right side in the figure is positioned so as to overlap with the region E between the resistance heating elements 56 in the longitudinal direction X (paper width direction) of the heater 23, or at a position offset from the resistance heating elements 56. Here, "overlapping" means that when the heater 23 is viewed from a direction perpendicular to the surface on which the resistance heating elements 56 are provided (viewed from the direction perpendicular to the plane of the paper in Figure 18), at least a part of the projection 30 overlaps with the region E between the resistance heating elements 56.

[0079] In this way, by arranging the protrusions 30 to overlap with the region E between the resistance heating elements 56, the temperature rise of the protrusions 30 can be suppressed. That is, the region E between the resistance heating elements 56 tends to experience less temperature rise compared to the region where the resistance heating elements 56 are arranged, so by arranging the protrusions 30 to overlap with this region E, the temperature rise of the protrusions 30 can be suppressed. As a result, the amount of heat transferred from the protrusions 30 to the lead wires 44 can also be reduced, and the temperature rise of the lead wires 44 can also be suppressed. Furthermore, if multiple temperature sensors are provided and it is necessary to route the lead wires 44 on the left side in addition to the right side in Figure 18, the protrusions 30 may also be arranged to overlap with the region E between the resistance heating elements 56 on the left side (see the dashed line in Figure 18).

[0080] Furthermore, as shown in the example in Figure 18, when multiple guide members 26 are provided at intervals along the longitudinal direction X (paper width direction) of the heater 23, it is preferable that at least a portion of the protrusions 30 be positioned offset from the guide members 26 in the longitudinal direction X (paper width direction) of the heater 23 (the range indicated by the symbol F in Figure 18). In this case, the influence of heat stored in the guide members 26 on the protrusions 30 can be suppressed, thereby suppressing the temperature rise of the protrusions 30 and, consequently, the temperature rise of the lead wires 44. Also, as shown by the dashed line in Figure 18, on the left side of the figure, at least a portion of the protrusions 30 may be positioned offset from the guide members 26 in the longitudinal direction X (paper width direction) of the heater 23.

[0081] Furthermore, as shown in the example in Figure 19, if the heater 23 has a resistance heating element 56 at the center M of the heater 23 or the nip portion N in the paper transport direction U, it is preferable that the central portion 30m of the projection 30 in the paper transport direction (center portion in the sheet transport direction) is formed higher than the portions on either side. This allows for a larger distance between the lead wire 44 and the heater 23 when the lead wire 44 is positioned at the central portion 30m of the projection 30 in the paper transport direction, making it easier to suppress the temperature rise of the lead wire 44. Also, because the central portion 30m of the projection 30 in the paper transport direction is formed higher, if the lead wire 44 is shifted away from the central portion 30m of the projection 30 in the paper transport direction towards either side due to gravity, the lead wire 44 is moved away from the resistance heating element 56, thus also suppressing the temperature rise of the lead wire 44.

[0082] The shape of the projection 30 is not limited to the case shown in Figure 19, where the tip surface of the projection 30 gradually rises towards the center 30m in the paper transport direction, but may also be a convex stepped shape, where the tip surface rises sharply in the center 30m and its vicinity in the paper transport direction, as shown in Figure 20.

[0083] Furthermore, as shown in the example in Figure 21, when the resistance heating element 56 is positioned on either side of the center M of the heater 23 or the nip portion N in the paper transport direction, it is preferable that the central portion 30m of the projection 30 in the paper transport direction is formed lower than the portions on either side. In this case, the lead wires 44 are positioned to converge toward the central portion 30m of the projection 30 in the paper transport direction due to gravity, so that the lead wires 44 can be positioned away from the resistance heating element 56, thereby suppressing the temperature rise of the lead wires 44.

[0084] Furthermore, the shape of the projection 30 is not limited to the concave curved surface shown in Figure 21, where the tip surface of the projection 30 gradually slopes downward toward the center 30m in the paper transport direction, but may also be a concave stepped shape, as shown in Figure 22, where the tip surface slopes sharply downward toward the center 30m in the paper transport direction and its vicinity.

[0085] Furthermore, the following configurations can also be adopted as additional variations of each of the above examples of the present invention.

[0086] The example shown in Figure 23 is one in which a low thermal conductivity member 63 is provided on the inside of the stay 25 (lead wire 44 side). In a configuration in which the heater holder 24 is supported by the stay 25, deformation of the heater holder 24 is suppressed, and the nip portion N can be formed into a desired shape. Furthermore, if the stay 25 has a U-shaped cross-section as shown in Figure 23, the second moment of area of ​​the stay 25 (resistance to bending force) can be greatly increased, allowing for miniaturization of the stay 25 while ensuring rigidity, and also making interference between the stay 25 and the protrusions of the fixing belt 21 and the heater holder 24 less likely to occur.

[0087] However, if the stay 25 is in contact with the heater holder 24, heat from the heater 23 is transferred to the stay 25 via the heater holder 24, causing the stay 25 to rise in temperature. In particular, if the stay 25 is made of a metal material, its good thermal conductivity makes it more likely for the stay 25 to rise in temperature. Therefore, in order to suppress the temperature rise of the lead wire 44, it is preferable to prevent the lead wire 44 from coming into contact with the stay 25.

[0088] Therefore, in the example shown in Figure 23, a low thermal conductivity member 63, which has lower thermal conductivity than the stay 25, is placed between the inner surface of the stay 25 and the lead wire 44. This prevents the lead wire 44 from directly contacting the stay 25. Furthermore, even if the lead wire 44 does come into contact with the low thermal conductivity member 63, the transfer of heat to the lead wire 44 is suppressed compared to when the lead wire 44 is in direct contact with the stay 25, thus suppressing the temperature rise of the lead wire 44. The low thermal conductivity member 63 may be fixed to the inner surface of the stay 25 via screws or a snap-fit ​​mechanism, or it may be provided on the sensor holder 50 or the belt retaining member described later.

[0089] Furthermore, as a measure to suppress the temperature rise of the stay 25 itself, multiple recesses 250 may be provided at the end of the stay 25 on the heater holder 24 side, as shown in Figure 24. In this case, the contact area of ​​the stay 25 with respect to the heater holder 24 is reduced, so the transfer of heat from the heater holder 24 to the stay 25 is suppressed, and the temperature rise of the lead wire 44 via the stay 25 is less likely to occur. Also, the spacing between the recesses 250 of the stay 25 is not limited to being uniform; as shown in Figure 24, it may be smaller than the minimum paper feed width W2 in the region where the temperature rise of the heater 23 is likely to occur, that is, in the region outside the minimum paper feed width W2 within the heat-generating region 60 (g1 <g2)。

[0090] In the above example, the case was described in which a projection 30 for supporting the lead wire 44 is provided on a sensor holder 50 that holds a temperature sensor 27 within the minimum paper feed width W2. However, the sensor holder 50 on which the projection 30 is provided is not limited to one that holds a temperature sensor 27 located within the minimum paper feed width W2. For example, as shown in the example in Figure 25, a projection 30 may be provided on a sensor holder 50 (50B) that holds a temperature sensor 27B located outside the maximum paper feed width W1, and this projection 30 may support the lead wire 44 extending from a temperature sensor 27A located within the minimum paper feed width W2.

[0091] Next, another example shown in Figure 26 is one in which projections 30 supporting the lead wires 44 are provided on flanges 70 (belt holding members) that hold both longitudinal ends of the anchoring belt 21. The flanges 70 have a C-shaped or cylindrical holding portion 70a that is inserted inside the anchoring belt 21 and a restricting portion 70b that restricts the movement of the anchoring belt 21 in the longitudinal direction (direction of arrow X). The holding portion 70a has an outer circumferential surface with a diameter smaller than the inner diameter of the anchoring belt 21, and by being inserted into the anchoring belt 21, the anchoring belt 21 is held in a so-called free belt manner in which basically no circumferential tension is applied when the anchoring belt 21 is stationary (not rotating). On the other hand, the restricting portion 70b is formed with an outer diameter larger than the inner diameter of the anchoring belt 21, and if movement (shifting) occurs in the longitudinal direction X of the anchoring belt 21, the restricting portion 70b restricts further movement of the anchoring belt 21. The projection 30 is provided so as to protrude from the inner circumferential surface of the holding portion 70a toward the side opposite to the heater 23.

[0092] Furthermore, although not included in the present invention, an example in which the projection 30 is provided on the heater holder 24 will be described.

[0093] As shown in Figure 27, in this example, the projections 30 that support the lead wires 44 are provided on the heater holder 24 that holds the heater 23, rather than on the sensor holder 50. The projections 30 are provided on the surface 240 (the upper surface of the heater holder 24 in Figure 27) of the heater holder 24 opposite to the surface 241 that holds the heater 23. That is, the heater holder 24 has a plate-shaped base portion 31 with a recess 24a for holding the heater 23 formed on its first surface 241, and a plurality of projections 30 provided on the second surface 240 of the base portion 31 opposite to the first surface 241.

[0094] As described above, even when the projection 30 is provided on the heater holder 24 or the flange 70, the lead wire 44 is supported by the projection 30, which allows for a larger distance between the lead wire 44 and the heater 23 in the region where the heater 23 is prone to temperature rise, i.e., the region outside the minimum paper feed width W2 within the heat-generating region 60. Therefore, in these examples as well, the temperature rise of the lead wire 44 can be suppressed. However, since the heater holder 24 is more prone to temperature rise than the flange 70, the effect when the projection 30 is provided on the heater holder 24 is not as significant as when the projection 30 is provided on the flange 70. In other words, the temperature rise of the projection 30 can be more effectively suppressed when it is provided on the flange 70, which is interposed between the heater holder 24 and the lead wire 44 and is a separate first component from the heater holder 24, rather than when the projection 30 is provided on the heater holder 24. Therefore, when the projection 30 is provided on the flange 70, the temperature rise of the lead wire 44 can be suppressed more effectively. Furthermore, the number of projections 30 shown in Figures 26 and 27 is not limited to just one; there may be multiple projections, as in the examples of the present invention described above. The arrangement and shape of the projections 30 can also be the same as in the examples of the present invention described above.

[0095] Although the present invention has been described above, the present invention is not limited to the above embodiments and examples, and the design can be modified as appropriate without departing from the spirit of the invention. In the above example of the present invention, the case in which the first member interposed between the heater holder 24 and the lead wire 44 and which is separate from the heater holder 24 is a sensor holder 50 or a flange 70 has been described, but the first member may be a member other than the sensor holder 50 and flange 70, as long as it is a member separate from the heater holder 24. For example, the first member may be a projection separate from the heater holder 24.

[0096] As an example of the thermistor which is the temperature sensor 27 used in the fixing device, generally, there are those in which the lead wires 44 protrude from both ends on the opposite sides of the thermistor 39 as shown in FIG. 28, and those in which the lead wires 44 protrude from only one end of the thermistor 39 as shown in FIG. 29. In the present invention, any thermistor can be adopted. In particular, the type in which the lead wires 44 protrude from both ends (FIG. 28) has a smaller size in the paper conveyance direction U than the type in which the lead wires 44 protrude from only one end (FIG. 29) (i1 < i2). By adopting the former thermistor 39, miniaturization in the paper conveyance direction U can be achieved. Further, when the thermistor 39 in which the lead wires 44 protrude from both ends is used, as shown in FIG. 28, by bending and winding one of the lead wires 44, each lead wire 44 can be gathered and arranged on one side of the thermistor 39. Also, according to the present invention, since the temperature rise of the lead wires 44 can be suppressed, a lead wire with a low heat-resistant temperature and excellent flexibility can be adopted as the lead wire 44, and the layout of bending and winding the lead wires 44 also becomes easy.

[0097] Further, the present invention is not limited to the case where it is applied to an image forming apparatus of the center reference conveyance method in which papers of various width sizes are conveyed with reference to the center in each width direction. It is also applicable to an image forming apparatus of the so-called end conveyance reference method in which papers of various sizes are conveyed with reference to one end in the width direction. In that case, as shown in FIG. 30, the range from the position r which is the conveyance reference of various papers P1, P2 to the distances of the maximum width W1 and the minimum width W2 of the paper, or to the position at a distance of 5 mm added to these widths W1, W2 becomes the maximum paper passing width W1 and the minimum paper passing width W2. Therefore, also in the case of such an end conveyance reference method, by providing the protrusion 30 that can ensure a large distance of the lead wire 44 with respect to the heater 23 outside the minimum paper passing width W2 and within the heat generation region 60 of the heater 23, the temperature rise of the lead wire 44 can be suppressed in the same manner as in the above embodiment.

[0098] Furthermore, a heater having PTC characteristics may be used as the heating source in the fixing device according to the present invention. PTC characteristics refer to the characteristic that the resistance value increases as the temperature increases (the heater output decreases when a constant voltage is applied). By using a heater with PTC characteristics as the resistance heating element, it is possible to achieve high output and rapid rise at low temperatures, and low output and suppress overheating at high temperatures. Therefore, by using such a heater with PTC characteristics, the heat generation of the resistance heating element in the non-paper-feeding area can be effectively suppressed, and the temperature rise of the lead wires can be further suppressed. For example, if the TCR coefficient of the PTC characteristics is set to about 300 to 4000 ppm / degree, the cost can be reduced while ensuring the necessary resistance value for the heater. More preferably, the TCR coefficient should be set to 500 to 2000 ppm / degree. The TCR coefficient can be calculated by measuring the resistance value at 25 degrees and 125 degrees. For example, if the resistance value increases by 10% when the temperature rises by 100 degrees, the TCR coefficient is 1000 ppm / degree.

[0099] Furthermore, the present invention is also applicable to fixing devices with configurations as shown in Figures 31 to 34. The configurations of each fixing device shown in Figures 31 to 34 will be described below.

[0100] The fuser 20 shown in Figure 31 differs from the fuser 20 shown in Figure 2 in the position of the temperature sensor 27 that detects the temperature of the heater 23. Other than that, the configuration is the same. In the fuser 20 shown in Figure 31, the temperature sensor 27 is positioned upstream of the center M of the nip section N in the paper feeding direction (nip inlet side). On the other hand, in the fuser 20 shown in Figure 2, the temperature sensor 27 is positioned at the center M of the nip section N. As shown in Figure 31, when the temperature sensor 27 is positioned upstream of the center M of the nip section N in the paper feeding direction, the temperature sensor 27 can accurately detect the temperature on the nip inlet side. Since the nip inlet side is a region where heat from the fuser belt 21 is particularly easily lost by the paper P entering the nip section N, accurately detecting the temperature on the nip inlet side with the temperature sensor 27 ensures image fixation and effectively suppresses the occurrence of fixation offset (a state where the toner image cannot be sufficiently heated).

[0101] Next, in the embodiment shown in Figure 32, a heating nip section N1 that heats the fixing belt 21 with a heater 23 and a fixing nip section N2 that allows the paper P to pass through are formed at separate locations. Specifically, in this embodiment, a nip forming member 68 is placed inside the fixing belt 21 in addition to the heater 23, and pressure rollers 69 and 70 are pressed against the heater 23 and the nip forming member 68, respectively, via the fixing belt 21, thereby forming the heating nip section N1 and the fixing nip section N2. In this case, the fixing belt 21 is heated at the heating nip section N1, and the heat from the fixing belt 21 is applied to the paper P at the fixing nip section N2, thereby fixing the unfixed image to the paper P.

[0102] Next, the fixing device 20 shown in Figure 33 is an example in which the pressure roller 69 on the heater 23 side is omitted from the fixing device shown in Figure 32, and the heater 23 is formed in an arc shape to match the curvature of the fixing belt 21. Otherwise, the configuration is the same as shown in Figure 32. In this case, because the heater 23 is formed in an arc shape, the contact length between the fixing belt 21 and the heater 23 in the belt rotation direction is secured, and the fixing belt 21 can be heated efficiently.

[0103] Next, the fixing device 20 shown in Figure 34 is an example in which a roller 73, as another rotating body, is positioned between a pair of rotating bodies, belts 71 and 72. In this example, a heater 23 is positioned in the left belt 71 in Figure 34, and a nip forming member 74 is positioned in the right belt 72. The heater 23 contacts the roller 73 via the left belt 71, and the nip forming member 74 contacts the roller 73 via the right belt 72, thereby forming a heating nip portion N1 and a fixing nip portion N2. In this case, the heater 23 heats the roller 73 via the left belt 71.

[0104] Furthermore, the image forming apparatus according to the present invention is not limited to the color image forming apparatus shown in Figure 1, but is also applicable to image forming apparatuses with configurations such as those shown in Figure 35. The configurations of other image forming apparatuses to which the present invention can be applied will be described below.

[0105] The image forming apparatus 100 shown in Figure 35 comprises an image forming means 80 consisting of a photosensitive drum and the like, a paper transport unit consisting of a pair of timing rollers 81 and the like, a paper feeder 82, a fuser 83, a paper discharger 84, and a reading unit 85. The paper feeder 82 has multiple paper trays, each of which accommodates paper of a different size.

[0106] The reading unit 85 reads the image of the original document Q. The reading unit 85 generates image data from the read image. The paper feeder 82 receives multiple sheets of paper P and feeds the paper P to the transport path. The timing roller 81 transports the paper P on the transport path to the image forming means 80.

[0107] The image forming means 80 forms a toner image on the paper P. Specifically, the image forming means 80 includes a photoreceptor drum, a charging roller, an exposure device, a developing device, a replenishment device, a transfer roller, a cleaning device, and a static elimination device. The fixing device 83 heats and pressurizes the toner image to fix it to the paper P. The paper P with the fixed toner image is transported to the paper discharge device 84 by a transport roller or the like. The paper discharge device 84 discharges the paper P to the outside of the image forming device 100.

[0108] Next, the fixing device 83 according to this embodiment will be described with reference to Figure 36. In the configuration shown in Figure 36, parts that are common with the fixing device 20 of the above embodiment shown in Figure 2 are denoted by the same reference numerals, and their descriptions are omitted.

[0109] As shown in Figure 36, the fixing device 83 includes a fixing belt 21, a pressure roller 22, a heater 23, a heater holder 24, a stay 25, a temperature sensor 27, and the like.

[0110] A nip section N is formed between the fixing belt 21 and the pressure roller 22. The nip width of the nip section N is 10 mm, and the linear speed of the fixing device 83 is 240 mm / s.

[0111] The fixing belt 21 comprises a polyimide substrate and a release layer, and does not have an elastic layer. The release layer is formed from a heat-resistant film material, for example, a fluororesin. The outer diameter of the fixing belt 21 is approximately 24 mm.

[0112] The pressure roller 22 includes a core metal, an elastic layer, and a release layer. The outer diameter of the pressure roller 22 is 24-30 mm, and the thickness of the elastic layer is 3-4 mm.

[0113] The heater 23 includes a base material, an insulating layer, a conductor layer containing a resistive heating element, and an insulating layer, with an overall thickness set to 1 mm. The width of the heater 23 in the paper transport direction is 13 mm.

[0114] As shown in Figure 37, the conductor layer of the heater 23 comprises a plurality of resistive heating elements 56, a power supply line 59, and electrode sections 58A to 58C. The plurality of resistive heating elements 56 are arranged at intervals from each other in the longitudinal direction (arrow X direction) of the heater 23. Here, the portion between each resistive heating element 56 is called a "divided region," and as shown in the enlarged view of Figure 37, a divided region B is formed between each resistive heating element 56 (in Figure 37, divided region B is only shown in the enlarged view, but in reality, divided region B is provided between all resistive heating elements 56). Also, in Figure 37, the direction of arrow Y is a direction that intersects or is perpendicular to the longitudinal direction X of the heater 23 (longitudinal intersection direction), and is a different direction from the thickness direction of the base material 55. Furthermore, the direction of arrow Y is the same as the direction that intersects the arrangement direction of the multiple resistance heating elements 56 (arrangement intersection direction), or the direction that follows the surface of the base material 55 on which the resistance heating elements 56 are provided, which is the short-side direction of the heater 23, or the same direction as the transport direction of the paper fed through the fixing device.

[0115] Furthermore, multiple resistive heating elements 56 constitute a central heating element 35B and heating elements 35A and 35C at both ends that can generate heat independently of it. For example, when current is applied to the leftmost electrode 58A and the central electrode 58B of the three electrode elements 58A to 58C in Figure 37, the heating elements 35A and 35C at both ends will generate heat. Also, when current is applied to the electrode elements 58A and 58C at both ends, the central heating element 35B will generate heat. For example, when performing a fixing operation on small-sized paper, only the central heating element 35B is heated, and when performing a fixing operation on large-sized paper, all heating elements 35A to 35C are heated, allowing for heating according to the size of the paper.

[0116] Furthermore, as shown in Figure 38, the heater holder 24 according to this embodiment has a recess 24a for housing and holding the heater 23. The recess 24a is formed on the heater 23 side of the heater holder 24. The recess 24a is composed of a rectangular surface (bottom surface) 24f formed in the shape of approximately the same size as the heater 23, and four wall portions (sides) 24b, 24c, 24d, and 24e provided along the four sides forming the outer perimeter of the surface 24f so as to intersect with the surface 24f. Note that in Figure 38, the right-side wall portion 24e is omitted from the illustration. Alternatively, one of the pair of wall portions 24d and 24e that intersect with the longitudinal direction X of the heater 23 (the arrangement direction of the resistance heating elements 56) may be omitted, and the recess 24a may be configured to open at one end of the heater 23 in the longitudinal direction.

[0117] As shown in Figure 39, the heater 23 and heater holder 24 according to this embodiment are held by a connector 86. The connector 86 has a housing made of resin (e.g., LCP) and a plurality of contact terminals provided inside the housing.

[0118] The connector 86 is attached to the heater 23 and heater holder 24 in a direction intersecting the longitudinal direction X of the heater 23 (the direction of arrangement of the resistance heating elements 56) (see the direction of the arrow from the connector 86 in Figure 39). The connector 86 is attached to the heater 23 and heater holder 24 on one end side of the heater 23 in the longitudinal direction X (the direction of arrangement of the resistance heating elements 56), on the side opposite to the side where the drive motor for the pressure roller 22 is provided. When attaching the connector 86 to the heater holder 24, a protrusion provided on one of the connector 86 or heater holder 24 may engage with a recess provided on the other, and the protrusion may move relative to the other within the recess.

[0119] With the connector 86 attached, the heater 23 and heater holder 24 are held in place by the connector 86 from both their front and back sides. In this state, each contact terminal makes contact (pressure contact) with each electrode portion of the heater 23, thereby electrically connecting each resistive heating element 56 to the power supply provided in the image forming apparatus via the connector 86. This makes it possible to supply power from the power supply to each resistive heating element 56.

[0120] Furthermore, the flanges 87 shown in Figure 39 are belt retaining members provided at both ends in the longitudinal direction of the anchoring belt 21, and hold both ends of the anchoring belt 21 from the inside. The flanges 87 are inserted into both ends of the stay 25 and fixed to a pair of side plates which are frame members of the anchoring device.

[0121] Figure 40 shows the arrangement of the temperature sensor 27 and the thermostat 88, which is a power cut-off member, according to this embodiment.

[0122] As shown in Figure 40, the temperature sensor 27 according to this embodiment is positioned to face the inner circumferential surfaces of the central Xm side and the end side of the fixing belt 21 in the longitudinal direction (arrow X direction). In addition, one of these temperature sensors 27 is positioned in a location corresponding to the divided region B (see Figure 37) between the resistance heating elements of the heater 23.

[0123] Furthermore, thermostats 88, which act as power-cutting members, are positioned at the central Xm side and the end side of the fixing belt 21 so as to face the inner circumferential surface of the fixing belt 21. Each thermostat 88 detects the temperature of the inner circumferential surface of the fixing belt 21 or the ambient temperature near the inner circumferential surface. If the temperature detected by the thermostat 88 exceeds a preset threshold, the power supply to the heater 23 is cut off.

[0124] Furthermore, as shown in Figures 40 and 41, the flanges 87 that hold both ends of the fixing belt 21 are provided with slide grooves 87a. The slide grooves 87a extend in the direction in which the fixing belt 21 moves toward and toward the pressure roller 22. The engaging portion of the fixing device housing engages with the slide grooves 87a. By the relative movement of these engaging portions within the slide grooves 87a, the fixing belt 21 is configured to move toward and toward the pressure roller 22.

[0125] Furthermore, the present invention is also applicable to fixing devices having the following configuration.

[0126] Figure 42 is a schematic diagram of a fixing device according to another embodiment to which the present invention can be applied.

[0127] As shown in Figure 42, the fixing device 20 according to this embodiment comprises a fixing belt 21 as a rotating body or fixing member, a pressure roller 22 as an opposing rotating body or pressure member, a heater 23 as a heat source, a heater holder 24 as a heat source holding member, a stay 25 as a support member, a temperature sensor (thermistor) 27 as a temperature sensing member, and a first high thermal conductivity member 89. The fixing belt 21 consists of an endless belt. The pressure roller 22 contacts the outer circumferential surface of the fixing belt 21, forming a nip portion N between it and the fixing belt 21. The heater 23 heats the fixing belt 21. The heater holder 24 holds the heater 23. The stay 25 supports the heater holder 24. The temperature sensor 27 detects the temperature of the first high thermal conductivity member 89. In other words, the fixing device 20 according to this embodiment has basically the same configuration as the fixing device shown in Figure 2, except that it is equipped with a first high thermal conductivity member 89. In Figure 42, the direction perpendicular to the plane of the paper is the longitudinal direction of the fixing belt 21, pressure roller 22, heater 23, heater holder 24, stay 25, and first high heat conductive member 89. Hereafter, this direction will simply be referred to as the longitudinal direction. This longitudinal direction is also the width direction of the conveyed paper, the belt width direction of the fixing belt 21, and the axial direction of the pressure roller 22.

[0128] In this embodiment, the heater 23, like the heater shown in Figure 37, has a plurality of resistance heating elements 56 arranged at intervals from each other in the longitudinal direction of the heater 23. However, in a configuration where a plurality of resistance heating elements 56 are arranged at intervals from each other, the temperature of the heater 23 in the divided region B, which is the space between the resistance heating elements 56, tends to be lower than in the part where the resistance heating elements 56 are arranged. As a result, the temperature of the fixing belt 21 also becomes lower in the divided region B, and there is a risk that the temperature of the fixing belt 21 will become uneven over the longitudinal direction.

[0129] Therefore, in this embodiment, the first high thermal conductivity member 89 is provided to suppress temperature drops in the divided region B and to suppress temperature unevenness in the longitudinal direction of the fixing belt 21. The first high thermal conductivity member 89 will be described in more detail below.

[0130] As shown in Figure 42, the first high-heat-conductivity member 89 is positioned between the heater 23 and the stay 25 in the left-right direction of the figure, and is particularly sandwiched between the heater 23 and the heater holder 24. That is, one surface of the first high-heat-conductivity member 89 is in contact with the back surface of the base material 55 of the heater 23, and the other surface of the first high-heat-conductivity member 89 (the surface opposite to the one surface) is in contact with the heater holder 24.

[0131] The stay 25 supports the heater holder 24, the first high heat conductive member 89, and the heater 23 by bringing the contact surfaces 25a1 of two vertical portions 25a extending in the thickness direction of the heater 23 into contact with the heater holder 24. In the longitudinal direction (up and down direction in Figure 42), the contact surfaces 25a1 are located outside the area where the resistance heating element 56 is provided. This suppresses heat transfer from the heater 23 to the stay 25, allowing the heater 23 to efficiently heat the fixing belt 21.

[0132] As shown in Figure 43, the first high-thermal-conductivity member 89 is a plate-shaped member having a certain thickness, for example, its thickness is set to 0.3 mm, its length in the longitudinal direction to 222 mm, and its width in the longitudinal intersection direction to 10 mm. In this embodiment, the first high-thermal-conductivity member 89 is made of a single plate material, but it may be made of multiple members. Note that in Figure 43, the guide member 26 shown in Figure 42 is omitted.

[0133] The first high-heat-conductivity member 89 is fitted into the recess 24a of the heater holder 24, and the heater 23 is mounted on top of it, so that the first high-heat-conductivity member 89 is held in place by being sandwiched between the heater holder 24 and the heater 23. In this embodiment, the longitudinal width of the first high-heat-conductivity member 89 is set to be approximately the same as the longitudinal width of the heater 23. The longitudinal movement of the first high-heat-conductivity member 89 and the heater 23 is restricted by the side walls (longitudinal direction restricting parts) 24d and 24e, which are arranged in a direction intersecting the longitudinal direction of the recess 24a. In this way, the longitudinal displacement of the first high-heat-conductivity member 89 within the fixing device is restricted, thereby improving the heat conduction efficiency over the target range in the longitudinal direction. Furthermore, the longitudinal movement of the first high-heat-conductivity member 89 and the heater 23 is restricted by the side walls (arrangement crossing direction restricting parts) 24b and 24c, which are arranged in the longitudinal direction of the recess 24a.

[0134] The range in the longitudinal direction (arrow X direction) in which the first high heat conductive member 89 is placed is not limited to the range shown in Figure 43. For example, as shown in Figure 44, the first high heat conductive member 89 may be placed only in the longitudinal range in which the resistance heating element 56 is placed (see hatched area in Figure 44). Also, as shown in the example in Figure 45, the first high heat conductive member 89 may be placed only in the entire area at a position corresponding to the interval (divided region) B in the longitudinal direction (arrow X direction). Note that in Figure 45, for convenience, the resistance heating element 56 and the first high heat conductive member 89 are shown offset vertically in Figure 45, but they are placed at approximately the same position in the longitudinal intersection direction (arrow Y direction). Furthermore, the first high-heat-conductivity member 89 may be positioned over a portion of the longitudinal direction (arrow Y direction) of the resistance heating element 56, or, as shown in the example in Figure 46, the first high-heat-conductivity member 89 may be positioned over the entire longitudinal direction (arrow Y direction) of the resistance heating element 56. Moreover, as shown in Figure 46, the first high-heat-conductivity member 89 may be positioned not only at a position corresponding to the longitudinal spacing B, but also across the resistance heating elements 56 on both sides that straddle the spacing B. "Positioning the first high-heat-conductivity member 89 across the resistance heating elements 56 on both sides" means that the longitudinal position of the first high-heat-conductivity member 89 overlaps with the resistance heating elements 56 on both sides in at least a portion of the way. Furthermore, the first high-heat-conductivity member 89 may be positioned at a position corresponding to all of the spacing B of the heater 23, or, as shown in the example in Figure 46, it may be positioned only at a position corresponding to a portion of the spacing B (in this case, one location). Here, "the first high heat-conducting member 89 is positioned at a location corresponding to the interval B" means that at least a portion of the interval B and the first high heat-conducting member 89 overlap in the longitudinal direction.

[0135] The pressure applied by the pressure roller 22 causes the first high-heat-conductivity member 89 to be sandwiched between the heater 23 and the heater holder 24, causing it to adhere closely to these members. The contact of the first high-heat-conductivity member 89 with the heater 23 improves the heat conduction efficiency of the heater 23 in the longitudinal direction. Furthermore, by positioning the first high-heat-conductivity member 89 at a location corresponding to the interval B of the heater 23 in the longitudinal direction, the heat conduction efficiency at interval B can be improved, increasing the amount of heat transferred to interval B and raising the temperature at interval B. This suppresses temperature unevenness in the longitudinal direction of the heater 23 and also suppresses temperature unevenness in the longitudinal direction of the fixing belt 21. As a result, uneven fixing and gloss unevenness of the image fixed to the paper can be suppressed. Additionally, it becomes unnecessary to increase the heat output of the heater 23 to ensure sufficient fixing performance at interval B, thus achieving energy savings in the fixing device. In particular, when the first high heat conductive member 89 is arranged over the entire longitudinal area where the resistance heating element 56 is located, the heat transfer efficiency of the heater 23 can be improved over the entire main heating area of ​​the heater 23 (i.e., the image forming area of ​​the paper being fed through), and temperature unevenness in the longitudinal direction of the heater 23 and, consequently, the fixing belt 21 can be suppressed.

[0136] Furthermore, the combination of the first high thermal conductivity member 89 and the resistance heating element 56 having PTC characteristics can more effectively suppress overheating in the non-paper-feeding area when small-sized paper is fed. PTC characteristics refer to the characteristic that the resistance value increases as the temperature rises (when a constant voltage is applied, the heater output decreases). In other words, because the resistance heating element 56 has PTC characteristics, the amount of heat generated by the resistance heating element 56 in the non-paper-feeding area can be effectively suppressed, and the first high thermal conductivity member 89 can efficiently transfer the heat from the non-paper-feeding area, where the temperature has risen, to the paper-feeding area. As a result of these synergistic effects, overheating in the non-paper-feeding area can be effectively suppressed.

[0137] Furthermore, in the vicinity of interval B, the temperature of the heater 23 is lower due to the small amount of heat generated in interval B, so it is preferable to place the first high heat conductive member 89. For example, by placing the first high heat conductive member 89 at a position corresponding to the enlarged division region C, which includes the area around interval B shown in Figure 47, the longitudinal heat transfer efficiency in and around interval B can be improved, and longitudinal temperature unevenness of the heater 23 can be suppressed more effectively. In addition, if the first high heat conductive member 89 is placed over the entire longitudinal direction of the region where all resistance heating elements 56 are arranged, longitudinal temperature unevenness of the heater 23 (fixing belt 21) can be suppressed more reliably.

[0138] Next, we will describe yet another embodiment of the fixing device.

[0139] The fixing device 20 shown in Figure 48 has a second high-temperature conductive member 90 between the heater holder 24 and the first high-temperature conductive member 89. The second high-temperature conductive member 90 is provided at a different position from the first high-temperature conductive member 89 in the stacking direction (left-right direction in Figure 48) of the components such as the heater holder 24, the stay 25, and the first high-temperature conductive member 89. More specifically, the second high-temperature conductive member 90 is provided superimposed on the first high-temperature conductive member 89. In this embodiment, a temperature sensor (thermistor) 27 is provided, as in the embodiment shown in Figure 42, but Figure 48 shows a cross-section where the temperature sensor 27 is not located.

[0140] The second high thermal conductivity member 90 is made of a material with a higher thermal conductivity than the base material 55, such as graphene or graphite. In this embodiment, the second high thermal conductivity member 90 is made of a graphite sheet with a thickness of 1 mm. Alternatively, the second high thermal conductivity member 90 may be made of a plate material such as aluminum, copper, or silver.

[0141] As shown in Figure 49, multiple second high-heat-conductivity members 90 are arranged in the recess 24a of the heater holder 24, with longitudinal spacing between each second high-heat-conductivity member 90. The portion of the heater holder 24 where the second high-heat-conductivity members 90 are provided has a recess that is deeper than the rest of the heater holder 24. The second high-heat-conductivity members 90 have gaps between them and the heater holder 24 on both longitudinal sides. This suppresses heat transfer from the second high-heat-conductivity members 90 to the heater holder 24, allowing the heater 23 to efficiently heat the fixing belt 21. Note that in Figure 49, the guide member 26 shown in Figure 48 is omitted.

[0142] As shown in Figure 50, the second high-heat-conductivity member 90 (see hatched area) is positioned in the longitudinal direction (arrow X direction) at a location corresponding to the interval B, overlapping at least a portion of the adjacent resistance heating elements 56. In particular, in this embodiment, the second high-heat-conductivity member 90 is positioned over the entire interval B. Note that Figure 50 (and Figure 52 described later) shows the case where the first high-heat-conductivity member 89 is positioned over the entire longitudinal direction of the area where all the resistance heating elements 56 are arranged, but the arrangement range of the first high-heat-conductivity member 89 is not limited to this.

[0143] As in this embodiment, in addition to the first high heat conductive member 89, the second high heat conductive member 90 is positioned at a location corresponding to the longitudinal spacing B, overlapping at least a portion of the adjacent resistance heating elements 56. This further improves the longitudinal heat transfer efficiency at spacing B, and more effectively suppresses longitudinal temperature unevenness of the heater 23. Furthermore, most preferably, as shown in Figure 51, the first high heat conductive member 89 and the second high heat conductive member 90 are provided only in the entire area at the location corresponding to spacing B. This makes it possible to particularly improve the heat transfer efficiency at the location corresponding to spacing B compared to other areas. Note that in Figure 51, for convenience, the resistance heating elements 56, the first high heat conductive member 89, and the second high heat conductive member 90 are shown offset in the vertical direction of the figure, but they are actually positioned at approximately the same location in the longitudinal intersection direction (arrow Y direction). However, the first high thermal conductivity member 89 and the second high thermal conductivity member 90 may be arranged in a part of the longitudinal direction of the resistance heating element 56, or they may be arranged to cover the entire longitudinal direction.

[0144] Furthermore, both the first high thermal conductivity member 89 and the second high thermal conductivity member 90 may be made of the graphene sheet. In this case, the first high thermal conductivity member 89 and the second high thermal conductivity member 90 can be formed in a predetermined direction along the surface of the graphene, that is, in the longitudinal direction rather than the thickness direction. This effectively suppresses temperature unevenness in the longitudinal direction of the heater 23 and the fixing belt 21.

[0145] Graphene is a flaky powder. As shown in Figure 54, graphene consists of a planar hexagonal lattice structure of carbon atoms. A graphene sheet is a sheet of graphene, usually a single layer. A graphene sheet may also contain impurities in the single layer of carbon, or it may have a fullerene structure. A fullerene structure is generally recognized as a compound in which an equal number of carbon atoms form a polycyclic structure fused in a cage-like manner with 5-membered and 6-membered rings, such as C60, C70, and C80 fullerenes, or other closed cage-like structures with 3-coordinate carbon atoms.

[0146] Graphene sheets are artificial materials and can be fabricated, for example, by chemical vapor deposition (CVD).

[0147] Commercially available graphene sheets can be used. The size and thickness of the graphene sheet, as well as the number of layers of the graphite sheet described later, can be measured, for example, by a transmission electron microscope (TEM).

[0148] Furthermore, graphite with multiple layers of graphene exhibits high thermal conductivity anisotropy. As shown in Figure 55, graphite has a crystalline structure in which layers of condensed six-membered rings of carbon atoms are spread out in a planar manner, and these layers are stacked multiple times. In this crystalline structure, adjacent carbon atoms within a layer form covalent bonds, while carbon atoms between layers form van der Waals bonds. The covalent bonds have a stronger bonding force than van der Waals bonds, and there is a large anisotropy between the bonds within a layer and the bonds between layers. In other words, by constructing the first high thermal conductivity member 89 or the second high thermal conductivity member 90 from graphite, the heat transfer efficiency in the longitudinal direction of the first high thermal conductivity member 89 or the second high thermal conductivity member 90 becomes larger than in the thickness direction (i.e., the stacking direction of the members), and heat transfer to the heater holder 24 can be suppressed. Therefore, temperature unevenness in the longitudinal direction of the heater 23 can be efficiently suppressed, and the heat flowing out to the heater holder 24 can be minimized. Furthermore, by constructing the first high-temperature conductive member 89 or the second high-temperature conductive member 90 from graphite, the first high-temperature conductive member 89 or the second high-temperature conductive member 90 can be given excellent heat resistance, such as not oxidizing up to about 700 degrees Celsius.

[0149] The physical properties and dimensions of the graphite sheet can be appropriately changed according to the function required of the first high-thermal-conductivity member 89 or the second high-thermal-conductivity member 90. For example, the anisotropy of its thermal conductivity can be increased by using high-purity graphite or single-crystal graphite, or by increasing the thickness of the graphite sheet. In addition, to increase the speed of the fixing device, a thinner graphite sheet may be used to reduce the heat capacity of the fixing device. Furthermore, if the width of the nip portion N and the heater 23 is large, the longitudinal width of the first high-thermal-conductivity member 89 or the second high-thermal-conductivity member 90 may be increased accordingly.

[0150] From the viewpoint of increasing mechanical strength, it is preferable that the graphite sheet has 11 or more layers. Furthermore, the graphite sheet may partially consist of single-layer and multi-layer sections.

[0151] The second high-heat-conductivity member 90 may be provided in the longitudinal direction at a position corresponding to the interval B (further expanded division region C) and overlapping with at least a portion of the adjacent resistance heating element 56, and is not limited to the arrangement shown in Figure 50. For example, as shown in the example in Figure 52, the second high-heat-conductivity member 90A may be provided extending outwards on both sides of the base material 55 in the longitudinal intersection direction (arrow Y direction). The second high-heat-conductivity member 90B may be provided in the longitudinal intersection direction within the range where the resistance heating element 56 is provided. The second high-heat-conductivity member 90C may be provided in a portion of the interval B.

[0152] In another embodiment shown in Figure 53, a gap in the thickness direction (left-right direction in Figure 53) is provided between the first high heat conductive member 89 and the heater holder 24. That is, a relief portion 24g acting as an insulating layer is provided in a part of the recess 24a (see Figure 49) of the heater holder 24 where the heater 23, the first high heat conductive member 89, and the second high heat conductive member 90 are arranged. The relief portion 24g is provided in a part of the longitudinal direction other than the part where the second high heat conductive member 90 (not shown in Figure 53) is provided. Furthermore, the relief portion 24g is formed by making the depth of the recess 24a of the heater holder 24 deeper than the other parts. As a result, the contact area between the heater holder 24 and the first high heat conductive member 89 can be minimized, so that heat transfer from the first high heat conductive member 89 to the heater holder 24 is suppressed, and the heater 23 can efficiently heat the fixing belt 21. In the cross-section where the second high-heat-conducting member 90 in the longitudinal direction is provided, the second high-heat-conducting member 90 abuts against the heater holder 24, as shown in the embodiment in Figure 48.

[0153] Furthermore, in this embodiment, the relief portion 24g is provided over the entire area where the resistance heating element 56 is installed in the longitudinal direction (vertical direction in Figure 53). This effectively suppresses heat transfer from the first high thermal conductivity member 89 to the heater holder 24, improving the heating efficiency of the fixing belt 21 by the heater 23. In addition to the configuration of providing a space as in the relief portion 24g, the insulating layer may also be configured with an insulating material having a lower thermal conductivity than the heater holder 24.

[0154] Furthermore, in this embodiment, the second high-temperature conductive member 90 is provided as a different member from the first high-temperature conductive member 89, but this is not limited to this. For example, the portion of the first high-temperature conductive member 89 corresponding to the gap B may be made thicker than the other portions so that the first high-temperature conductive member 89 also functions as the second high-temperature conductive member 90.

[0155] Although the configurations of other fixing devices and image forming devices to which the present invention can be applied have been described above, the same effects as in the above embodiments can be obtained by applying the present invention to fixing devices and image forming devices with such configurations. That is, by applying the present invention, the temperature rise of the lead wires in the non-paper-feeding area can be suppressed and the durability of the lead wires can be improved.

[0156] Furthermore, in the above description, the present invention has been explained using the case of application to a fixing device, which is an example of a heating device. However, the present invention is not limited to fixing devices, but can also be applied to heating devices such as drying devices for drying liquids such as ink applied to paper, laminators for heat-pressing a film as a covering member onto the surface of a sheet such as paper, and heat sealers for heat-pressing the sealing portion of packaging materials.

[0157] To summarize the embodiments of the present invention described above, the present invention includes a heating device, a fixing device, and an image forming apparatus having at least the following configurations.

[0158] [First Structure] The first configuration is a heating device comprising: a pair of rotating bodies that contact each other to form a nip portion through which a sheet passes; a heating source that heats at least one of the pair of rotating bodies; a temperature sensing member that detects the temperature of the heating source; a heating source holding member that holds the heating source; and a flexible conductive member connected to the temperature sensing member, wherein a first member separate from the heating source holding member is located between the heating source holding member and the conductive member, the first member having a conductive member support portion that supports the conductive member on the side opposite to the heating source, and the conductive member support portion supports the conductive member such that the distance of the conductive member to the heating source is larger in at least a portion of the area outside a predetermined width compared to the area within the predetermined width.

[0159] [Second Structure] The second configuration is a heating device comprising: a pair of rotating bodies that come into contact with each other to form a nip portion through which a sheet passes; a heating source that heats at least one of the pair of rotating bodies; a temperature sensing member that detects the temperature of the heating source; a heating source holding member that holds the heating source; and a flexible conductive member connected to the temperature sensing member, wherein a first member separate from the heating source holding member is located between the heating source holding member and the conductive member, the first member having a plurality of conductive member support portions that protrude toward the opposite side from the heating source and support the conductive member, and at least some of the conductive member support portions that are located beyond a predetermined width have a greater height in the protruding direction from the first member than the other conductive member support portions.

[0160] [The third structure] The third configuration is a heating device comprising: a pair of rotating bodies that contact each other to form a nip portion through which a sheet passes; a heating source that heats at least one of the pair of rotating bodies; a temperature sensing member that detects the temperature of the heating source; a heating source holding member that holds the heating source; and a flexible conductive member connected to the temperature sensing member, wherein a first member separate from the heating source holding member is located between the heating source holding member and the conductive member, and the first member has a plurality of conductive member support portions that protrude on the side opposite to the heating source and support the conductive member, and the spacing in the sheet width direction between at least some of the conductive member support portions that are located outside a predetermined width is smaller than the spacing in the sheet width direction between the other conductive member support portions.

[0161] [Fourth component] The fourth configuration is a heating device in which, in any one of the first to third configurations, the first member is a temperature sensing member holding member that holds the temperature sensing member.

[0162] [Fifth Structure] The fifth configuration is a heating device in any one of the first to fourth configurations, wherein the predetermined width is the minimum sheet passage width.

[0163] [The sixth component] The sixth configuration is a heating device in which, in any one of the first to fifth configurations, the heating source has a plurality of heating elements arranged at intervals in the sheet width direction, and the conductive member support is arranged to overlap the areas between the heating elements in the sheet width direction.

[0164] [The seventh component] The seventh configuration is a heating device in which, in any one of the first to sixth configurations, the conductive member support portion protrudes from the side of the first member opposite to the heating source side, and the height of the conductive member support portion in the direction protruding from the first member is higher than the position where the conductive member is connected to the temperature sensing member.

[0165] [The eighth component] The eighth configuration is a heating device in which, in any one of the first to seventh configurations, the heating source has a heating element at the center of the heating source in the sheet conveying direction, and the conductive member support part supports the conductive member at a position offset from the center of the heating source in the sheet conveying direction.

[0166] [The ninth structure] The ninth configuration is a heating device in which, in the eighth configuration, the conductive member support portion protrudes on the side opposite to the heating source side of the first member, and the height of the conductive member support portion in the protruding direction from the first member is higher at the center of the conductive member support portion in the sheet conveying direction than at both ends in the sheet conveying direction.

[0167] [The 10th component] The tenth configuration is a heating device that, in any one of the first to ninth configurations, includes a support member for supporting the heating source holding member, and a low thermal conductivity member with a lower thermal conductivity than the support member is placed between the support member and the conductive member.

[0168] [Structure of the 11th] The eleventh configuration is a heating device in any one of the first to ten configurations, wherein the temperature sensing member is positioned within the minimum sheet passage width.

[0169] [Structure 12] The twelfth configuration is a fixing device that fixes an unfixed image onto a sheet using a heating device of any one of the first to eleventh configurations.

[0170] [Structure 13] The 13th configuration is an image forming apparatus comprising a heating device according to any one of the first to 11 configurations, or a fixing device according to the 12th configuration. [Explanation of Symbols]

[0171] 20 Fixing device (heating device) 21 Fixing belt (first rotating body) 22 Pressure roller (second rotating body) 23 Heater (heat source) 24 Heater holder (heat source holding member) 25. Stay (support member) 27 Temperature sensor (temperature sensing component) 30. Protrusion (support part for conductive member) 30m Center of paper transport direction (center of sheet transport direction) 44. Lead wires (conductive components) 50 Sensor holder (temperature sensing element holding member) 56. Resistive heating element (heating element) 63 Low thermal conductivity material 100 Image forming apparatus N Nip section P Paper (sheet) W1 Maximum paper feed width (maximum sheet passage width) W2 Minimum paper feed width (minimum sheet passage width) X Longitudinal direction [Prior art documents] [Patent Documents]

[0172] [Patent Document 1] Japanese Patent Publication No. 2011-118246

Claims

1. A pair of rotating bodies that come into contact with each other to form a nip portion through which the sheet passes, A heating source for heating at least one of the pair of rotating bodies, A temperature sensing member for detecting the temperature of the heating source, A heat source holding member that holds the aforementioned heat source, A flexible conductive member connected to the temperature sensing member, A heating device comprising, Between the heating source holding member and the conductive member, there is a first member separate from the heating source holding member, The first member has a plurality of conductive member support portions that protrude on the side opposite to the heating source and support the conductive member, A heating device characterized in that, of the plurality of conductive member support portions, at least some of the conductive member support portions that are located outside a predetermined width have a greater height in the protruding direction from the first member than the other conductive member support portions.

2. A pair of rotating bodies that come into contact with each other to form a nip portion through which the sheet passes, A heating source for heating at least one of the pair of rotating bodies, A temperature sensing member for detecting the temperature of the heating source, A heat source holding member that holds the aforementioned heat source, A flexible conductive member connected to the temperature sensing member, A heating device comprising, Between the heating source holding member and the conductive member, there is a first member separate from the heating source holding member, The first member has a plurality of conductive member support portions that protrude on the side opposite to the heating source and support the conductive member, A heating device characterized in that, among the plurality of conductive member support portions, the spacing in the sheet width direction between at least some of the conductive member support portions that are arranged outside a predetermined width is smaller than the spacing in the sheet width direction between the other conductive member support portions.

3. The heating device according to claim 1 or 2, wherein the first member is a temperature sensing member holding member that holds the temperature sensing member.

4. The heating device according to claim 1 or 2, wherein the predetermined width is the minimum sheet passage width.

5. The heating source has a plurality of heating elements arranged at intervals in the sheet width direction, The heating device according to claim 1 or 2, wherein the conductive member support portion is arranged to overlap the region between the heating elements in the sheet width direction.

6. The conductive member support portion protrudes from the side of the first member opposite to the heating source side, The heating device according to claim 1 or 2, wherein the height of the conductive member support portion in the direction protruding from the first member is higher than the position where the conductive member is connected to the temperature sensing member.

7. The heating source has a heating element in the center of the heating source in the sheet conveying direction, The heating device according to claim 1 or 2, wherein the conductive member support portion supports the conductive member at a position offset from the center of the heating source in the sheet conveying direction.

8. The conductive member support portion protrudes from the side of the first member opposite to the heating source side, The heating device according to claim 7, wherein the height of the conductive member support portion in the protruding direction from the first member is higher at the center of the conductive member support portion in the sheet conveying direction than at both ends in the sheet conveying direction.

9. comprising a support member that supports the heating source holding member, The heating device according to claim 1 or 2, wherein a low thermal conductivity member having a lower thermal conductivity than the support member is arranged between the support member and the conductive member.

10. The heating device according to claim 1 or 2, wherein the temperature sensing member is arranged within the minimum sheet passage width.

11. A fixing device characterized by fixing an unfixed image onto a sheet using the heating device described in Claim 1 or 2.

12. An image forming apparatus characterized by comprising the heating device described in claim 1 or 2.

Images