JP2023167195A - Heating device, fixing device, and image forming apparatus - Google Patents

Abstract

To prevent an increase in the temperature of a conductive member in an area where the temperature is likely to increase compared with the other area.SOLUTION: A heating device comprises: a pair of rotating bodies 21, 22 that are in contact with each other to form a nip part for passing a sheet; a heat source 23 that heats at least one of the pair of rotating bodies 21, 22; a heat source holding member 24 that holds the heat source 23; a temperature detection member 27 that detects the temperature of the heat source 23; and a conductive member 44 that has flexibility and is connected to the temperature detection member 27. The heat source holding member 24 has a conductive member support part 30 that supports the conductive member 44 on a surface 240 opposite to a surface 241 holding the heat source 23. The conductive member support part 30 supports the conductive member 44 in at least partial area outside a predetermined width W2 of the heat source holding member 24 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

The present invention relates to a heating device, a fixing device, and an image forming device.

2. Description of the Related Art As an example of a heating device installed in an image forming apparatus such as a copying machine or a printer, a fixing device is known that fixes an unfixed image onto a sheet by heating the sheet carrying the unfixed image.

In some fixing devices, 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 the control unit via a conductive member such as a lead wire, and the control unit controls the temperature of the heat source by controlling heat generation based on the temperature of the heat source detected by the temperature detection member. is maintained at the appropriate temperature.

Since the conductive member connected to the temperature sensing member is disposed near a heating source that becomes high temperature, it is preferably made of a heat-resistant material or protected by a heat-resistant covering material. However, selecting a material with excellent heat resistance leads to problems such as an increase in manufacturing costs. A configuration has been proposed in which a plurality of protrusions are provided on the side opposite to the above, and a conductive member is supported via each protrusion. According to this configuration, since the contact area of the conductive member with the heat source holding member is reduced, less heat is transmitted from the heat source holding member to the conductive member, and it is possible to suppress a rise in temperature of the conductive member.

Incidentally, the temperature of the heat source does not necessarily have to be uniform throughout; variations occur, for example, when sheets are continuously conveyed to a fixing device. In other words, when a sheet with a width smaller than the heat generating area of the heating source is conveyed, the heat from the heating source is not absorbed by the sheet in the area where the sheet does not pass, so heat accumulates and the temperature rises compared to the area where the sheet passes. do. Therefore, variations occur in the temperature of the heat source between the region through which the sheet passes and the region through which the sheet does not pass.

In Patent Document 1, heat is made difficult to transfer to the conductive member by providing a plurality of protrusions, but the effect of heat on the conductive member from parts of the heating source that are likely to rise in temperature and parts that are not Nothing has been considered.

In order to solve the above problems, the present invention provides a pair of rotating bodies that contact each other to form a nip through which a sheet passes, a heat source that heats at least one of the pair of rotating bodies, and a heating source that heats at least one of the pair of rotating bodies. A heating device comprising: a heat source holding member for holding the heat source; a temperature detecting member for detecting the temperature of the heat source; and a conductive member having flexibility connected to the temperature detecting member, the heating device comprising: a heat source holding member for holding the heat source; The holding member has a conductive member support portion that supports the conductive member on a side opposite to the surface side that holds the heat source, and the conductive member support portion has a width that is wider than a predetermined width of the heat source holding member. The conductive member is supported so that the distance of the conductive member from the heat source is greater in at least a part of the outer region than in the region within the predetermined width.

According to the present invention, it is possible to suppress the temperature rise of the conductive member in a region where the temperature may rise more than in other regions.

1 is a schematic configuration diagram of an image forming apparatus according to an embodiment of the present invention. FIG. 1 is a schematic configuration diagram of a fixing device according to an embodiment. FIG. 2 is a cross-sectional view of the fixing belt according to the present embodiment. FIG. 2 is a plan view of a heater according to the present embodiment. FIG. 2 is a perspective view showing a state in which a connector serving as a power supply member is connected to the heater according to the present embodiment. FIG. 3 is a diagram showing a support structure for a lead wire connected to a temperature sensor in the fixing device according to the present embodiment. It is a figure which shows the modification of this invention. It is a figure which shows the other modification of this invention. It is a figure which shows yet another modification of this invention. It is a figure which shows yet another modification of this invention. It is a figure which shows yet another modification of this invention. It is a figure which shows yet another modification of this invention. FIG. 7 is a diagram illustrating an example of a protrusion whose height is not to be compared. FIG. 7 is a diagram illustrating an example of a protrusion whose height is not to be compared. It is a figure which shows yet another modification of this invention. It is a figure which shows yet another modification of this invention. It is a figure which shows yet another modification of this invention. FIG. 3 is a diagram for explaining the arrangement of protrusions. It is a figure for explaining the shape of a protrusion. It is a figure which shows the modification of a protrusion. It is a figure for explaining the shape of a protrusion. It is a figure which shows the modification of a protrusion. It is a figure which shows yet another modification of this invention. It is a figure which shows yet another modification of this invention. It is a figure which shows the example in which a protrusion is provided in a sensor holder. It is a figure which shows the example which a protrusion is provided in a flange. FIG. 3 is a diagram showing a thermistor with lead wires protruding from both ends. FIG. 3 is a diagram showing a thermistor with a lead wire protruding from one end. FIG. 3 is a diagram showing an example in which the present invention is applied to an end-based conveyance method. FIG. 3 is a diagram showing a configuration of a fixing device different from the above embodiment. FIG. 3 is a diagram showing a configuration of a fixing device different from the above embodiment. FIG. 3 is a diagram showing a configuration of a fixing device different from the above embodiment. FIG. 3 is a diagram showing a configuration of a fixing device different from the above embodiment. FIG. 2 is a diagram showing a configuration of an image forming apparatus different from the above embodiment. 35 is a diagram showing the configuration of the fixing device shown in FIG. 34. FIG. 36 is a plan view of the heater shown in FIG. 35. FIG. 36 is a perspective view of the heater and heater holder shown in FIG. 35. FIG. 36 is a diagram showing a method of attaching a connector to the heater shown in FIG. 35. FIG. 35 is a diagram showing the arrangement of a temperature sensor and a thermostat included in the fixing device shown in FIG. 34. FIG. FIG. 39 is a diagram showing a groove of the flange shown in FIG. 38; FIG. 3 is a diagram showing a configuration of a fixing device different from the above embodiment. FIG. 42 is a perspective view of the heater, the first high heat conductive member, and the heater holder shown in FIG. 41. FIG. FIG. 3 is a plan view of the heater showing the arrangement of the first high heat conductive member. It is a top view of the heater which shows another example of arrangement|positioning of a 1st high thermal conductivity member. FIG. 7 is a plan view of the heater showing still another example of the arrangement of the first high heat conductive member. FIG. 3 is a plan view of the heater showing enlarged divided regions. FIG. 3 is a diagram showing a configuration of a fixing device different from the above embodiment. 48 is a perspective view of the heater, the first high heat conduction member, the second high heat conduction member, and the heater holder shown in FIG. 47. FIG. FIG. 3 is a plan view of the heater showing the arrangement of a first high heat conduction member and a second high heat conduction member. It is a top view of the heater which shows another example of arrangement|positioning of a 1st high heat conduction member and a 2nd high heat conduction member. It is a top view of the heater which shows yet another example of arrangement|positioning of a 2nd high thermal conductivity member. FIG. 3 is a diagram showing a configuration of a fixing device different from the above embodiment. FIG. 2 is a diagram showing the atomic crystal structure of graphene. FIG. 2 is a diagram showing the atomic crystal structure of graphite.

Hereinafter, the present invention will be explained based on the accompanying drawings. In addition, in each drawing for explaining the present invention, components such as members and components having the same function or shape are given the same reference numerals as much as possible so that they can be distinguished. Omitted.

FIG. 1 is a schematic configuration diagram of an image forming apparatus according to an embodiment of the present invention. Here, the "image forming apparatus" in this specification includes a printer, a copying machine, a facsimile machine, a printing machine, or a multifunction machine that combines two or more of these. Furthermore, "image formation" used in the following description means not only forming images with meaning such as characters and figures, but also forming images without meaning such as patterns. First, with reference to FIG. 1, the overall configuration and operation of an image forming apparatus according to this embodiment will be described.

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

The image forming section 200 includes four process units 1Y, 1M, 1C, and 1Bk as image forming units, and an exposure device that forms an electrostatic latent image on the photoreceptor 2 provided in each process unit 1Y, 1M, 1C, and 1Bk. 6, and a transfer device 8 for transferring an image onto a recording medium.

Each process unit 1Y, 1M, 1C, and 1Bk has basically the same configuration except that it contains toner (developer) of different colors of yellow, magenta, cyan, and black corresponding to the color separation components of a color image. be. Specifically, each of the process units 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, and a charging member 3 that charges the surface of the photoreceptor 2. The photoreceptor 2 includes a developing device 4 that supplies toner as a developer to form a toner image, and a cleaning member 5 that cleans the surface of the photoreceptor 2.

The transfer device 8 includes an intermediate transfer belt 11, a primary transfer roller 12, and a secondary transfer roller 13. The intermediate transfer belt 11 is an endless belt member, 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 roller 13 contacts the outer peripheral surface of the intermediate transfer belt 11 to form a secondary transfer nip.

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, a pressure roller 22 as a facing member facing the fixing belt 21, and the like. The fixing belt 21 and the pressure roller 22 are in contact with each other on their respective outer peripheral surfaces to form a nip portion (fixing nip).

The recording medium supply section 400 is provided with a paper feed cassette 14 that accommodates paper P as a recording medium, and a paper feed roller 15 that feeds the paper P from the paper feed cassette 14. Hereinafter, the "recording medium" will be explained as "paper," but the "recording medium" is not limited to paper. The "recording medium" includes not only paper but also an OHP sheet or cloth, a metal sheet, a plastic film, a prepreg sheet in which carbon fiber is pre-impregnated with a resin, and the like. In addition to plain paper, "paper" also includes cardboard, postcards, envelopes, thin paper, coated paper (coated paper, art paper, etc.), tracing paper, and the like.

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

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

When a printing operation is started in the image forming apparatus 100, the photoreceptors 2 of each process unit 1Y, 1M, 1C, and 1Bk and the intermediate transfer belt 11 of the transfer device 8 start rotating. Further, the paper feed roller 15 starts rotating, and the paper P is sent out from the paper feed cassette 14. The fed paper P comes into contact with the pair of timing rollers 16 and comes to rest, and the conveyance of the paper P is temporarily stopped until an image to be transferred to the paper P is formed.

In each of the process units 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, the exposure device 6 exposes the surface (charged surface) of each photoreceptor 2 based on the image information of the document read by the document reading device or the print image information instructed to print from the terminal. As a result, the potential of the exposed portion decreases, and an electrostatic latent image is formed on the surface of each photoreceptor 2. The developing device 4 supplies toner to this electrostatic latent image, and a toner image is formed on each photoreceptor 2. When the toner images formed on each photoreceptor 2 reach the primary transfer nip (the position of the primary transfer roller 12) as each photoreceptor 2 rotates, they are transferred onto the rotating intermediate transfer belt 11 so as to overlap one another. be done. In this way, a full-color toner image is formed on the intermediate transfer belt 11. In the image forming apparatus 100, one of the process units 1Y, 1M, 1C, and 1Bk is used to form a single-color image, or two or three process units are used to form a two-color or It is also possible to form a three-color image. Further, after the toner image is transferred from the photoreceptor 2 to the intermediate transfer belt 11, residual toner and the like on each photoreceptor 2 is removed by the cleaning member 5.

The toner image transferred onto the intermediate transfer belt 11 is conveyed to the secondary transfer nip (the position of the secondary transfer roller 13) as the intermediate transfer belt 11 rotates, and onto the paper P conveyed by the timing roller 16. transcribed into. After that, the paper P is conveyed to the fixing device 20, and the toner image on the paper P is heated and pressed by the fixing belt 21 and the pressure roller 22, so that the toner image is fixed on the paper P. Then, the paper P is conveyed to the recording medium discharge section 500 and discharged to the paper discharge tray 18 by the paper discharge roller 17. This completes the series of printing operations.

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

As shown in FIG. 2, the fixing device 20 according to the present embodiment includes a fixing belt 21, a pressure roller 22, a heater 23, a heater holder 24, a stay 25, a guide member 26, a temperature sensor 27, and the like. We are prepared.

The fixing belt 21 is a rotating body (first rotating body or fixing member) that contacts the unfixed toner bearing surface of the paper P and fixes the unfixed toner (unfixed image) to the paper P, and has flexibility. Consists of an endless belt. The diameter of the fixing belt 21 is set to be, for example, 15 to 120 mm. In this embodiment, the inner diameter of the fixing belt 21 is set to 25 mm.

As shown in FIG. 3, the fixing belt 21 has, for example, a base material 210, an elastic layer 211, and a release layer 212 laminated in this order from the inner peripheral surface side to the outer peripheral surface side, and the total thickness of the fixing belt 21 is It is set to 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, foamable silicone rubber, or fluororubber. Since the fixing belt 21 has the elastic layer 211, minute irregularities are not formed on the surface of the fixing belt 21 at the nip portion, so that heat is easily transmitted to the toner image on the paper P evenly. The release layer 212 has a layer thickness of 10 to 50 μm and is made of PFA (tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer), PTFE (polytetrafluoroethylene), polyimide, polyetherimide, PES (polyether sulfide). ) and other materials. Since the fixing belt 21 has the release layer 212, release properties (releasability) for the toner (toner image) are ensured.

As shown in FIG. 2, the pressure roller 22 is a rotating body (second rotating body or opposing member) that is arranged to face 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 the pressure roller 22 and the fixing belt 21 .

The pressure roller 22 is, for example, a roller whose outer diameter is set to 25 mm, and includes a hollow iron core material 220, an elastic layer 221 provided on the outer circumferential surface of the core material 220, and an elastic layer 221 provided on the outer circumferential surface of the elastic layer 221. A release layer 222 is provided. 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.

The heater 23 is a heat source that heats the fixing belt 21 from inside. The heater 23 is a planar or plate-shaped heater that extends longitudinally in the longitudinal direction of the fixing belt 21 (paper width direction intersecting the paper conveyance direction), and contacts the inner circumferential surface of the fixing belt 21. It is arranged like this. The heater 23 according to this embodiment includes a base material 55, a resistance heating element 56 provided on the base material 55, an insulating layer 57 covering the resistance heating element 56, and the like.

As shown in FIG. 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 on the opposite side. It may be provided on the surface. In that case, since the heat of each resistance heating element 56 is transmitted to the fixing belt 21 via the base material 55, the base material 55 is preferably made of a material with high thermal conductivity such as aluminum nitride.

The heater holder 24 is a heat source holding member that is disposed inside the fixing belt 21 and holds the heater 23 . Since the heater holder 24 tends to reach a high temperature due to the heat of the heater 23, it is preferable that the heater holder 24 is made of a heat-resistant material. For example, when the heater holder 24 is made of a heat-resistant resin with low thermal conductivity such as LCP or PEEK, heat transfer from the heater 23 to the heater holder 24 is suppressed while ensuring the heat resistance of the heater holder 24. The fixing belt 21 can be heated efficiently.

The stay 25 is a support member that supports the heater holder 24. By supporting the surface of the heater holder 24 opposite to the surface on the pressure roller 22 side in the longitudinal direction of the fixing belt 21 by the stay 25, bending of the heater holder 24 due to the pressing force of the pressure roller 22 is suppressed. As a result, a nip portion N having a uniform width is formed between the fixing belt 21 and the pressure roller 22. In order to ensure its rigidity, the stay 25 is preferably made of a ferrous metal material such as SUS or SECC.

The guide member 26 is a member that guides the fixing belt 21 from inside. The guide member 26 has an arcuate cross-sectional shape that follows the inner circumferential surface of the fixing belt 21, and is disposed on the upstream and downstream sides of the heater 23 in the rotation direction of the fixing belt 21 (in the direction of the arrow in FIG. 2), respectively. has been done. In this embodiment, each guide member 26 is configured integrally with the heater holder 24, but may be configured separately.

The temperature sensor 27 is a temperature detection member that detects the temperature of the heater 23. As the temperature sensor 27, a known temperature sensor such as a thermopile, thermostat, thermistor, or NC sensor can be applied. In this embodiment, a contact temperature sensor is used that detects the temperature by contacting the surface of the heater 23 on the side opposite to the pressure roller 22 side. Further, the temperature sensor 27 is not limited to a contact type temperature sensor, and may be a non-contact type temperature sensor that is arranged in a non-contact manner with respect to the heater 23 and detects the ambient temperature in the vicinity of the heater 23.

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

As shown in FIG. 2, when the pressure roller 22 is driven to rotate, the driving force is transmitted to the fixing belt 21, so that the fixing belt 21 is driven to rotate. Then, the fixing belt 21 is heated by the heater 23, and the fixing belt 21 is heated. Further, 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. Thereby, the temperature of the fixing belt 21 is maintained at a temperature at which the image can be fixed (fixing temperature). Then, when the paper P carrying the unfixed image is conveyed between the fixing belt 21 and the pressure roller 22 (nip portion N), the toner image on the paper P is fixed by the fixing belt 21 and the pressure roller 22. The image is fixed on the paper P by heating and pressure.

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

As shown in FIG. 4, the heater 23 according to this embodiment has a plate-shaped base material 55 extending in one direction (the direction of the arrow X in FIG. 4). The base material 55 is arranged so that its longitudinal direction X faces the longitudinal direction of the fixing belt 21 or the axial direction of the pressure roller 22. On the surface of the base material 55, two resistance heating elements 56 extend in the longitudinal direction X of the base material 55 and are arranged side by side in the transverse direction Y of the base material 55. Note that this "lateral direction" means a direction perpendicular to the longitudinal direction be.

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

The base material 55 is made of a material with excellent heat resistance and insulation properties, such as ceramics such as alumina or aluminum nitride, glass, mica, and polyimide. Further, the base material 55 may be formed by forming an insulating layer on a metal material (conductive material) such as stainless steel (SUS), iron, or aluminum. In particular, when the material of the base material 55 is a highly thermally conductive material such as aluminum, copper, silver, graphite, graphene, etc., the heat uniformity of the heater 23 is improved and image quality can be improved. The insulating layer 57 is made of a material with excellent heat resistance and insulation properties, such as ceramics such as alumina or aluminum nitride, glass, mica, and polyimide. The resistance heating element 56 is formed, for example, by applying a paste prepared by mixing silver palladium (AgPd), glass powder, etc. onto the surface of the base material 55 by screen printing, and then firing the base material 55. Further, as the material of the resistance heating element 56, it is also possible to use a resistance material such as a silver alloy (AgPt) or ruthenium oxide (RuO ₂ ). Further, the electrode portion 58 and the power supply line 59 are formed by screen printing silver (Ag) or silver palladium (AgPd).

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

As shown in FIG. 5, the connector 40 includes a housing 41 made of resin, a plurality of contact terminals 42 provided in the housing 41, and a power supply harness 43 connected to each contact terminal 42. . Each contact terminal 42 is constituted by an elastically deformable member such as a leaf spring.

As shown in FIG. 5, the connector 40 is attached so as to sandwich the heater 23 and heater holder 24 together. The heater 23 and heater holder 24 are thereby held together by the connector 40. In addition, in this state, the tips (contact portions 42a) of each contact terminal 42 of the connector 40 are elastically contacted (press-contacted) with the corresponding electrode portions 58, so that each contact terminal 42 and each electrode portion 58 are connected to each other. are electrically connected. This allows power to be supplied to the heater 23 (each resistance heating element 56) from the power supply of the image forming apparatus main body via the connector 40.

FIG. 6 is a diagram showing a support structure for the lead wire 44 connected to the temperature sensor 27 in the fixing device according to the present embodiment.

As shown in FIG. 6, a flexible lead wire 44 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 section provided in the main body of the image forming apparatus. The lead wire 44 is composed of a conducting wire and an insulator covering the conducting wire in order to ensure insulation and heat resistance. Furthermore, the lead wire 44 is placed on the opposite side of the heater 23 with the heater holder 24 in between to avoid being directly affected by the heat of the heater 23 . That is, the lead wire 44 is routed around a surface 240 (the upper surface of the heater holder 24 in FIG. 6) opposite to the surface 241 side of the heater holder 24 that holds the heater 23. A plurality of protrusions 30 are provided on a surface 240 of the heater holder 24 on the lead wire 44 side as a conductive member support portion that supports the lead wire 44.

The plurality of protrusions 30 are arranged at intervals in the longitudinal direction of the heater holder 24, which is also the longitudinal direction X of the heater 23. By supporting the lead wire 44 by the tip of each protrusion 30, the lead wire 44 is arranged without contacting the base portion 31 of the heater holder 24 provided with each protrusion 30 at a distance. That is, the heater holder 24 includes a plate-shaped base portion 31 in which a recess 24a for holding the heater 23 is formed on a first surface 241, and a second surface 240 of the base portion 31 opposite to the first surface 241. It has a plurality of protrusions 30. By supporting the lead wire 44 by the plurality of protrusions 30 in this manner, contact between the lead wire 44 and the base portion 31 can be avoided, and the contact area of the lead wire 44 with the heater holder 24 can be reduced. In the first place, the lead wire 44 has lower rigidity than a sheet metal or a jumper wire, and therefore requires support by another member in order to be held at a position away from the heater holder 24. Therefore, in this embodiment, a plurality of protrusions 30 are provided to support the lead wires 44, thereby reducing the contact area of the lead wires 44 with the heater holder 24, and suppressing heat transfer from the heater 23 and the heater holder 24 to the lead wires 44. That's what I do.

Note that the lead wire 44 does not necessarily have to be in contact with the tip of the protrusion 30, but may not be in contact with it. That is, when the protrusion 30 "supports" the lead wire 44, it means that the lead wire 44 is supported so as not to contact the base portion 31 of the heater holder 24, and when the lead wire 44 and the protrusion 30 are in contact with each other, For example, when the lead wire 44 approaches the base portion 31 even if the projection 30A2 is not actually in contact with the lead wire 44, as in the case of a projection 30A2 shown in FIG. This also includes the case where the base portion 31 is supported so as to avoid contact with the base portion 31.

Here, among the plurality of protrusions 30, the protrusion 30A located at the farthest end in the longitudinal direction of the heater holder 24 (the right end side in FIG. 6) protrudes from the heater holder 24 (base portion 31) more than the other protrusions 30B. The height in the direction is set high (t1>t2). The protrusion 30A having a high height is a protrusion 30 disposed corresponding to a portion where the temperature of the heater 23 becomes high, and makes it difficult for the heat of the heater 23 to affect the lead wire 44.

Specifically, in this embodiment, the portion where the temperature of the heater 23 becomes high is inside the heat generating area 60 where the resistance heating element 56 of the heater 23 is arranged, and is located at the maximum passage through which the paper P1 of the maximum width passes. This refers to the area outside the paper width W1 (maximum sheet passing width) (the area indicated by the symbol H in FIG. 6). Further, the term "heat generating area" in this specification means an area in which the resistance heating element 56 is arranged in the longitudinal direction When the resistance heating elements 56 are arranged, it means the range from one end to the other end of the area where all the resistance heating elements 56 are arranged. Further, the term "maximum paper passing width" in this specification means a preset area through which the maximum width paper is assumed to pass, regardless of whether or not the maximum width paper actually passes. In the case of the present embodiment, a so-called center-based conveyance method is adopted in which paper sheets of various width sizes are conveyed with the center of each width direction as a reference. The maximum sheet passing width is the range from 1 to 5 mm toward both ends of the sheet, or a distance equal to half the maximum width plus 5 mm. For example, if the maximum width paper is A4 size (width: 210 mm), the position is 105 mm away from the longitudinal center m of the heat generating area 60 toward both ends, which is half the distance of A4 size, or The maximum paper passing width is the range up to a position separated by 110 mm, which is 105 mm plus 5 mm. In addition, in FIG. 6, the area indicated by the symbol W2 is the minimum paper passing width (minimum sheet passing width) through which the paper P2 of the minimum width passes, and this minimum paper passing width is also the same as the maximum paper passing width. refers to a preset area through which a sheet of minimum width is assumed to pass, regardless of whether or not a sheet of paper actually passes through it. In other words, the range from the center m in the longitudinal direction of the heat generating area 60 of the heater 23 toward both ends to a distance equal to half the minimum width of the paper, or a distance equal to half the minimum width plus 5 mm is the minimum passing distance. It is the width of the paper.

Basically, in order to heat the paper, it is sufficient that the temperature of the fixing belt 21 within the maximum paper passing width W1 is maintained at a predetermined temperature, but immediately after the temperature of the fixing belt 21 rises to a predetermined temperature Since the amount is small, the temperature of the fixing belt 21 tends to drop at both ends of the heat generating area 60 when the paper passes through. Therefore, in the present embodiment, the heat generating region 60 of the heater 23 is extended to the outside of the maximum paper passing width W1 to suppress a decrease in temperature of the fixing belt 21 due to paper passing. However, if the heat generating area 60 is extended to the outside of the maximum paper passing width W1, the fixing belt 21 and the heater 23 will accumulate heat in the non-paper passing area where the largest width paper P1 does not pass, especially when a plurality of sheets are passed continuously. However, the temperature may rise excessively. The temperature increase in the non-paper passing area due to paper passing may occur not only when the maximum width paper P1 is passed, but also when paper having a size smaller than the heat generating area 60 of the heater 23 is passed. In the case of small-sized paper that is generally used infrequently, measures are taken to reduce productivity (printing speed) in order to suppress temperature rise in non-sheet passing areas. On the other hand, in the case of the maximum width paper P1 that is frequently used, there is a tendency for printing to be performed without reducing productivity, and therefore, when the paper is continuously passed, the temperature tends to rise in the non-paper passing area. Furthermore, in recent years, as the amount of heat generated by heaters increases due to higher speeds of image forming apparatuses, the problem of excessive temperature rise outside the maximum paper passing width W1 is becoming more prominent.

Therefore, in the embodiment of the present invention, as shown in FIG. 6, a region H (hereinafter, this region is conveniently referred to as " The protrusions 30A arranged in the "overheating region" are made higher than the protrusions 30B arranged in other regions (t1>t2), and the distance of the lead wire 44 from the heater 23 in the overheating region H is set. , so that it is larger than other areas.

This makes it difficult for heat to be transferred from the heater 23 to the lead wire 44, so even if the temperature of the heater 23 rises excessively in the overheating region H when the largest width paper P1 is continuously passed, the lead wire 44 temperature rise can be suppressed, and deterioration and damage to the lead wire 44 can be suppressed. Further, since deterioration and damage to the lead wire 44 can be suppressed, it becomes possible to continuously pass the maximum width paper P1 without reducing productivity.

The protrusion 30A having a high height as described above is not limited to being disposed within the overheating region H shown in FIG. 6, but may be disposed outside the overheating region H.

For example, as in the example shown in FIG. 7, tall protrusions 30A may be arranged on both sides of the overheated region H, respectively. In this case as well, the distance of the lead wire 44 from the heater 23 can be secured to be larger in the overheating region H than in other regions, so that the temperature rise of the lead wire 44 can be suppressed. Furthermore, in the case of the example shown in FIG. 7, since the protrusion 30A is not provided within the overheating region H, the temperature rise of the protrusion 30A itself can also be suppressed. As a result, the amount of heat transmitted from the protrusion 30A to the lead wire 44 can be reduced, so that a rise in temperature of the lead wire 44 can be effectively suppressed. Furthermore, since the temperature rise of the lead wire 44 can be effectively suppressed, an inexpensive material (a material whose heat resistance is not so high) can be selected as the material of the lead wire 44 or the insulator covering the lead wire 44. , cost reduction can also be achieved. On the other hand, as in the example shown in FIG. 6, when the protrusion 30A is disposed in the overheating region H, the protrusion 30A is not disposed closer to the longitudinal end of the heater holder 24 than the overtemperature raising region H. There is an advantage that the installation space for the projection 30A can be omitted and the size of the heater holder 24 in the longitudinal direction can be reduced.

Further, as in the example shown in FIG. 8, among the taller protrusions 30A, the right protrusion 30A1 may be higher than the left protrusion 30A2 (t3>t4). In this example, the lead wire 44 is mainly supported by the higher protrusion 30A1. Furthermore, since the higher protrusion 30A1 is disposed outside the heat generating area 60, it is less susceptible to the heat of the heater 23 than the protrusion 30A2 disposed within the heat generating area 60. Therefore, the amount of heat transmitted from the higher protrusion 30A1 to the lead wire 44 is reduced, and the temperature rise of the lead wire 44 can be effectively suppressed.

Conversely, as in the example shown in FIG. 9, among the taller protrusions 30A, the left protrusion 30A2 may be higher than the right protrusion 30A1 (t3<t4). In this case, an increase in the height of the protrusion 30A1 on the longitudinal end side of the heater holder 24 is suppressed, so that the degree of freedom of the lead wire 44 in moving around is improved.

Next, in the example shown in FIG. 10, the protrusion 30A1 disposed closer to the longitudinal end of the heater holder 24 than the overheating region H is located on the roller portion 62 (the portion having the elastic layer) of the pressure roller 22. This is an example in which the heater holder 24 is disposed further toward the longitudinal end of the heater holder 24 (on the right side in FIG. 10) than the end 620. In this way, when the longitudinally outer protrusion 30A1 is longitudinally outer than the roller portion 62 of the pressure roller 22, the heat of the pressure roller 22 is transmitted to the longitudinally outer protrusion 30A1 via the heater holder 24. can be suppressed, and an increase in temperature 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 rise in temperature of the lead wire 44 can be effectively suppressed.

Further, as in the example shown in FIG. 10, when there is a heat equalizing plate 28 as a heat transfer assisting member between the heater 23 and the heater holder 24, heat is transferred from the heat equalizing plate 28 to the protrusion 30A1. It is preferable to also suppress the influence. The heat equalizing plate 28 is made of a material having higher thermal conductivity than the heater holder 24 (for example, copper, aluminum, silver, etc.), and moves the heat of the heater 23 in the longitudinal direction of the fixing belt 21 to equalize the heat. It is a member. As shown in FIG. 10, the protrusion 30A1 disposed closer to the longitudinal end of the heater holder 24 than the overheating region H is located further to the longitudinal end of the heater holder 24 than the longitudinal end 280 of the heat equalizing plate 28. By being arranged on the side (right side in FIG. 10), it is possible to suppress the heat of the heat equalizing plate 28 from being transmitted to the projection 30A1 on the outside in the longitudinal direction, and it is possible to effectively suppress the temperature rise of the projection 30A1.

As described above, in each example that is an embodiment of the present invention, by increasing the height of some of the protrusions 30, the lead wire 44 relative to the heater 23 is I'm trying to increase the distance. However, the temperature rise in the non-paper passing area during continuous paper passing is not limited to the case where the largest width paper P1 is passed, but any paper size smaller than the heat generating area 60 of the heater 23 will increase the temperature. This can occur even when passing paper.

Therefore, as in the example shown in FIG. 11, not only the protrusions 30A arranged outside the maximum paper passing width W1 but also the protrusions 30A arranged inside the maximum paper passing width W1 are arranged in other areas. It may be higher than the protrusion 30B. Specifically, in the example shown in FIG. 11, the protrusion 30A located outside the minimum paper passing width W2 is made higher than the protrusion 30B located within the minimum paper passing width W2 (t6>t5). In this case, since the distance of the lead wire 44 to the heater 23 can be increased outside the minimum paper passing width W2 (compared to within the minimum paper passing width W2), the lead wire 44 can be temperature rise can be suppressed.

Furthermore, as in the example shown in FIG. 12, the heights of the protrusions 30A1 and 30A2 may be made different on the outside and inside of the maximum paper passing width W1. Specifically, in the example shown in FIG. 12, the height t7 of the protrusion 30A2 located inside the maximum paper passing width W1 and outside the minimum paper passing width W2 is set to the height t7 of the protrusion 30A2 located outside the maximum paper passing width W1. The height is set lower than the height t8 of 30A1. Therefore, in the example shown in FIG. 12, the protrusion 30A1 located outside the maximum paper passing width W1 is the highest, followed by the protrusion 30A2 located inside the maximum paper passing width W1 and outside the minimum paper passing width W2. , the protrusion 30B within the minimum paper passing width W2 is formed the lowest (t8>t7>t5).

In this way, the height t7 of the protrusion 30A2 located outside the minimum paper passing width W2 and within the maximum paper passing width W1 is made lower than the height t8 of the protrusion 30A1 located outside the maximum paper passing width W1. This increases the degree of freedom in layout. Further, outside the minimum paper passing width W2 and within the maximum paper passing width W1, the effect of suppressing heat transfer to the lead wire 44 is somewhat reduced as the height of the protrusion 30A2 is reduced. By reducing the productivity when passing small size paper (paper of a size smaller than the maximum width), the temperature rise in the non-paper passing area can be suppressed, so the temperature rise of the lead wire 44 can be controlled within the allowable range. can.

Here, in each example of the present invention described above, the protrusions 30A (30A1, 30A2) that increase the height need only be higher than the protrusions 30B arranged at least in the minimum paper passing width W2. However, it is assumed that the protrusion 30B within the minimum paper passing width W2 to be compared is within the area where the lead wire 44 is arranged. Even if the width is within the minimum paper passing width W2, the height of the protrusion 32 disposed in an area without a lead wire 44 as shown in FIG. 13 is not included in the height comparison. This is because such a protrusion 32 is not a conductive member support member (protrusion 30) that supports the lead wire 44 in the first place.

Furthermore, the protrusions such as the guide member 26 that protrudes from the heater holder 24 as shown in FIG. 14 are not conductive member support members (protrusions 30) that support the lead wires 44, and therefore are not subject to height comparison. Therefore, the protrusions whose heights are to be compared are arranged in a region J where the lead wire 44 can exist, that is, a region J where the temperature sensor 27 exists in the paper passing direction Y (sheet conveyance direction) shown in FIG. It is assumed that the protrusion is

Further, the protrusion 30 supporting the lead wire 44 is not necessarily present within the minimum paper passing width W2, but may be a case in which the protrusion 30 supporting the lead wire 44 does not exist within the minimum paper passing width W2. In that case, for example, the protrusion 30 (30B) that is inside the maximum sheet passing width W1 and outside the minimum sheet passing width W2 shown in FIG. 6 may be used as a height comparison target. Therefore, in the present invention, the objects whose heights are compared are not limited to protrusions arranged within the minimum paper passing width W2 and protrusions arranged outside the minimum paper passing width W2, but also to predetermined widths other than the minimum paper passing width W2. The inner protrusion may be an inner protrusion, and the protrusion may be disposed on the outer side of the predetermined width. That is, the objects whose heights are compared may be the protrusions 30 within a predetermined width arbitrarily set from among the minimum paper passing width W2, the maximum paper passing width W1, etc., and the protrusions 30 outside the predetermined width. Further, at least some of the protrusions 30 arranged outside the predetermined width may be higher than other protrusions 30 outside the predetermined width. Due to the protrusion 30 having a high height, the distance of the lead wire 44 disposed outside the predetermined width from the heater 23 is greater than that of the lead wire 44 disposed within the predetermined width. By being supported in this manner, it becomes possible to suppress the temperature rise of the lead wire 44 outside the predetermined width.

In each of the above examples, a configuration has been described in which the temperature rise of the lead wire 44 is suppressed by increasing the height of some of the protrusions 30, but the present invention includes a configuration in which the height of the protrusions 30 is increased. , including examples such as:

The example shown in FIG. 15 is different from the above examples in that the distance d1 between some of the projections 30 is smaller than the distance d2 between other projections 30 (d1<d2). Specifically, in this example, the distance d1 between the protrusions 30 disposed outside the maximum paper passing width W1 and within the heat generating area 60 of the heater 23 is set as the distance d1 between the protrusions 30 disposed within the maximum paper passing width W1. The distance is smaller than the distance d2. In this case, at a location where the distance between the protrusions 30 is the largest (a location where the distance is d2), the lead wire 44 is bent downward between the protrusions 30, and the height s2 of the lead wire 44 relative to the heater holder 24 becomes lower. On the other hand, in places where the distance between the protrusions 30 is small (the place where the distance is d1), the lead wire 44 is less likely to bend downward between the protrusions 30, so the height of the lead wire 44 relative to the heater holder 24 is increased. (s1>s2). Note that the heights s1 and s2 of the lead wires 44 relative to the heater holder 24 and the height s3 described below refer to the surface of the heater holder 24 on the lead wire 44 side (the surface opposite to the surface holding the heater 23). ) means the shortest distance of the lead wire 44 with respect to In this way, by reducing the distance between the protrusions 30, the height s1 of the lead wire 44 relative to the heater holder 24 can be kept high in the area where the distance is small (the location of the distance d1), and the lead wire 44 is connected to the heater holder. It becomes difficult to approach the base portion 31 of 24. Therefore, in the overheating region H where the temperature may rise when the maximum width paper P1 is continuously passed, the approach of the lead wire 44 to the heater 23 is suppressed compared to other regions, and the heater 23 and the lead Since it becomes easier to secure a distance between the lead wire 44 and the lead wire 44, a rise in temperature of the lead wire 44 can be suppressed.

Further, the protrusions 30 whose intervals are set to be narrow are not limited to 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 that are outside the maximum paper passing width W1, and the distance d1 between the protrusions 30 that are within the maximum paper passing width W1 and outside the minimum paper passing width W2. The distance d3 may be narrower than the distance d2 between the protrusions 30 in other areas (d1, d3<d2).

In this way, by making the distances d1 and d3 between the protrusions 30 located outside the minimum paper passing width W2 smaller than the distance d2 between the protrusions 30 located within the minimum paper passing width W2 (d1, d3<d2), The height of the lead wire 44 relative to the heater holder 24 can be maintained higher in the area outside the minimum sheet passing width W2 (at the intervals d1 and d3) compared to the area within the minimum sheet passing width W2 (at the interval d2) ( s1, s3>s2). In this case, it is possible to cope with the temperature rise in the non-paper passing region when paper of all sizes is passed, not only when the maximum width paper P1 is passed. That is, when paper of any size is passed, the lead wire 44 is connected to the heater 23 and the heater holder 24 (base part 31) in the non-paper passing area (area outside the minimum paper passing width W2) where the temperature may rise. Since the approach can be prevented, the temperature rise of the lead wire 44 can be effectively suppressed.

Furthermore, if the temperature rise is likely to be noticeable outside the maximum paper passing width W1, as in the example shown in FIG. By making the distance between the protrusions 30 within W1 and outside the minimum paper passing width W2 smaller than the distance d3 (d1<d3), the leads are arranged in areas where the temperature is particularly likely to rise (the area with the distance d1). The temperature rise of the wire 44 can be suppressed more reliably. That is, in the present embodiment, the distance between the protrusions 30 is made smaller (d1<d3<d2) in the region closer to the longitudinal end of the heater 23 where the temperature rise tends to be more pronounced, thereby allowing the lead wire 44 to move downward. Since the lead wire 44 is less likely to bend and the height of the lead wire 44 relative to the heater holder 24 can be maintained high (s1>s3>s2), the temperature of the lead wire 44 is less likely to rise.

It should be noted that the target for comparing the size relationship of the intervals between the protrusions 30 is determined based on the same criteria as the comparison target for the heights of the protrusions 30 described above. That is, any distance between the protrusions 30 arranged outside the minimum paper passing width W2 may be smaller than the interval between the protrusions 30 arranged within the minimum paper passing width W2. However, it is assumed that the protrusion 30 within the minimum paper passing width W2 is within the area where the lead wire 44 is arranged. Further, the protrusion 30 within the minimum paper passing width W2 is arranged in the paper passing direction Y (sheet conveyance direction) in a region where the lead wire 44 can exist, that is, in a region J where the temperature sensor 27 exists (see FIG. 14). shall be carried out. In addition, the targets for comparing the size relationship between the intervals between the protrusions 30 are not limited to protrusions disposed within the minimum paper passing width W2 and protrusions disposed outside the minimum paper passing width W2, but also protrusions disposed outside the minimum paper passing width W2. The protrusion may be within a predetermined width and the protrusion may be disposed outside the predetermined width. Further, the distance between at least some of the protrusions 30 arranged outside the predetermined width may be smaller than the distance between other protrusions 30 outside the predetermined width. Note that the "predetermined width" herein includes the minimum paper passing width, the maximum paper passing width, and other arbitrarily set widths.

In the above example, a configuration has been described in which the height of some of the protrusions 30 among the plurality of protrusions 30 is increased or the interval between some of the protrusions 30 is reduced. The height of the protrusions 30 may be increased and the distance between the protrusions 30 may be further reduced. Furthermore, the number of protrusions 30 that support the lead wires 44 is not limited to the case where a plurality of protrusions 30 are provided, and the case where only one protrusion 30 is provided may be provided.

For example, as in the example shown in FIG. 17, only one protrusion 30 may be provided outside the maximum paper passing width W1 and within the heat generating area 60 of the heater 23. Further, 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 passing width W1 where the temperature tends to rise, the lead wire 44 is supported by the heater 23 and the heater holder 24 (base part) compared to inside the maximum paper passing width W1. 31). This makes it possible to suppress heat transfer from the heater 23 to the lead wire 44 in a region where the temperature is likely to rise. Note that the position where one protrusion 30 is arranged is not limited to the case where the position is outside the maximum paper passing width W1, but may be outside the minimum paper passing width W2, which is an area where the temperature is likely to rise, depending on the size of frequently used paper, etc. As long as it is outside, it can be changed as appropriate.

Next, the arrangement and shape of the protrusion 30 will be further explained. The arrangement and shape of the protrusion 30 described below can be applied to any of the protrusions 30 in each of the above examples.

FIG. 18 is a plan view of the heater holder 24 viewed from the heater 23 side. As shown in FIG. 18, when the heater 23 has a plurality of resistance heating elements 56 arranged at intervals in the longitudinal direction X (paper width direction), at least a part of the right protrusion 30 in FIG. It is preferable that the heater 23 be arranged so as to overlap the region E between the resistance heating elements 56 in the longitudinal direction X (paper width direction), or be arranged at a position shifted from the resistance heating elements 56. Here, "overlapping" means that at least a portion of the protrusion 30 is This refers to a state in which the resistive heating elements 56 overlap with each other in the region E between them.

In this way, by arranging the protrusions 30 so as to overlap the region E between the resistance heating elements 56, the temperature rise of the protrusions 30 can be suppressed. That is, in the area E between the resistance heating elements 56, the temperature tends to rise more easily than in the area where the resistance heating elements 56 are arranged, so the protrusion 30 is arranged so as to overlap this area E. Therefore, the temperature rise of the protrusion 30 can be suppressed. As a result, the amount of heat transmitted from the protrusion 30 to the lead wire 44 can be reduced, and the rise in temperature of the lead wire 44 can also be suppressed. In addition, if it is necessary to run the lead wire 44 on the left side in addition to the right side in FIG. 18, such as when a plurality of temperature sensors are provided, the protrusion 30 is also placed in the area E between the resistance heating elements 56 on the left side. may be arranged so that they overlap (see the two-dot chain line in FIG. 18).

Further, as in the example shown in FIG. 18, when a plurality of guide members 26 are provided at intervals in the longitudinal direction X (paper width direction) of the heater 23, at least a part of the protrusion 30 It is preferable that the guide member 26 be disposed at a position offset from the guide member 26 in the longitudinal direction X (paper width direction) (in the range indicated by the symbol F in FIG. 18). In this case, since the influence of the heat stored in the guide member 26 can be suppressed from reaching the protrusion 30, the temperature rise of the protrusion 30 can be suppressed, and in turn, the temperature rise of the lead wire 44 can be suppressed. Furthermore, as shown by the two-dot chain line in FIG. 18, on the left side of the figure as well, at least a portion of the protrusion 30 is misaligned with the guide member 26 in the longitudinal direction X (paper width direction) of the heater 23. It may be placed in any position.

Further, as in the example shown in FIG. 19, when the heater 23 has a resistance heating element 56 at the center M of the heater 23 or the nip portion N in the sheet conveyance direction U, the central portion 30m of the protrusion 30 in the sheet conveyance direction ( It is preferable that the central portion (in the sheet conveyance direction) is formed higher than the portions on both end sides. As a result, when the lead wire 44 is disposed at the central portion 30m of the protrusion 30 in the sheet conveyance direction, a large distance between the lead wire 44 and the heater 23 can be ensured, and a rise in temperature of the lead wire 44 can be easily suppressed. In addition, if the lead wire 44 is disposed to be shifted from the center portion 30m of the projection 30 in the paper transport direction toward both ends due to gravity because the central portion 30m of the projection 30 in the paper transport direction is formed high, the lead wire 44 Since the lead wire 44 is kept away from the resistance heating element 56, the temperature rise of the lead wire 44 can also be suppressed in this case.

The shape of the protrusion 30 is not limited to the case where the tip end surface of the protrusion 30 is a convex curved shape that gradually becomes higher toward the central portion 30m in the paper transport direction as shown in FIG. It may have a convex stepped shape in which the tip end surface is suddenly raised at the central portion 30m in the direction and the vicinity thereof.

Further, as in the example shown in FIG. 21, when the resistance heating element 56 is disposed on both end sides of the heater 23 or the center M of the nip portion N in the paper transport direction, the central part of the protrusion 30 in the paper transport direction It is preferable that 30 m be formed lower than that in comparison with the portions on both end sides. In this case, the lead wires 44 are arranged so as to gather toward the center 30m side of the protrusion 30 in the paper conveyance direction according to gravity, so the lead wires 44 can be arranged away from the resistance heating element 56, thereby suppressing the temperature rise of the lead wires 44. can.

Further, the shape of the protrusion 30 is not limited to the case where the tip end surface of the protrusion 30 is a concave curved shape that gradually becomes lower toward the central portion 30m in the paper conveyance direction as shown in FIG. 21, but also the shape as shown in FIG. It may be a concave stepped shape in which the leading end surface is suddenly lowered at the central portion 30m in the sheet conveyance direction and its vicinity.

Moreover, the following configuration can also be adopted as an additional modification of each example of the present invention described above.

The example shown in FIG. 23 is an example in which a low thermal conductive member 63 is provided inside the stay 25 (on the lead wire 44 side). In the 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, when the stay 25 has a U-shaped cross section as shown in FIG. 23, a large moment of inertia (resistance to bending force) of the stay 25 can be ensured, and the stay 25 can be made smaller while increasing its rigidity. In addition, it is possible to prevent the stay 25 from interfering with the protrusions of the fixing belt 21 and the heater holder 24.

However, when the stay 25 is in contact with the heater holder 24, the heat of the heater 23 is transmitted to the stay 25 via the heater holder 24, and the temperature of the stay 25 increases. In particular, when the stay 25 is made of a metal material, the temperature of the stay 25 tends to rise because of good thermal conductivity. 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.

Therefore, in the example shown in FIG. 23, a low thermal conductivity member 63 having lower thermal conductivity than the stay 25 is disposed between the inner surface of the stay 25 and the lead wire 44. Thereby, the lead wire 44 can be prevented from coming into direct contact with the stay 25. Furthermore, even if the lead wire 44 contacts the low thermal conductivity member 63, the temperature of the lead wire 44 increases because heat transfer to the lead wire 44 is suppressed compared to when the lead wire 44 directly contacts the stay 25. can be suppressed. The low thermal conductivity member 63 may be fixed to the inner surface of the stay 25 via a screw or a snap fit mechanism, or may be provided on a temperature sensor holding member or a belt holding member, which will be described later.

Moreover, as a measure to suppress the temperature rise of the stay 25 itself, as shown in FIG. 24, a plurality of recesses 250 may be provided at the end of the stay 25 on the heater holder 24 side. In this case, since the contact area of the stay 25 with the heater holder 24 is reduced, heat transfer from the heater holder 24 to the stay 25 is suppressed, and the temperature of the lead wire 44 via the stay 25 is less likely to rise. Furthermore, the spacing between the recesses 250 of the stay 25 is not limited to being uniform, but as shown in FIG. may also be smaller than the minimum paper passing width W2 in the outer region (g1<g2).

Next, although not included in the present invention, another example of suppressing the temperature rise of the lead wire 44 will be described.

The example shown in FIG. 25 is an example in which the protrusion 30 that supports the lead wire 44 is provided not on the heater holder 24 but on the sensor holder 50 (temperature sensing member holding member) that holds the temperature sensor 27. The sensor holder 50 includes a main body 50a that is attached to the heater holder 24 or the like, and a spring 50b that serves as a biasing member provided on the main body 50a. By pressurizing the temperature sensor 27 toward the heater 23 by the spring 50b, the temperature sensor 27 is held in contact with the heater 23. The protrusion 30 is provided so as to protrude from the main body 50a of the sensor holder 50 toward the side opposite to the heater 23 side.

Next, another example shown in FIG. 26 is an example in which the protrusion 30 that supports the lead wire 44 is provided on a flange 70 (belt holding member) that holds both ends of the fixing belt 21 in the longitudinal direction. The flange 70 has a C-shaped or cylindrical holding part 70a that is inserted inside the fixing belt 21, and a regulating part 70b that regulates movement of the fixing belt 21 in the longitudinal direction (in the direction of the arrow X). The holding portion 70a has an outer circumferential surface with a smaller diameter than the inner diameter of the fixing belt 21, and when inserted into the fixing belt 21, the holding portion 70a basically maintains the circumference when the fixing belt 21 is stationary (non-rotating). It is held by a so-called free belt method in which no directional tension is applied. On the other hand, the regulating part 70b is formed to have an outer diameter larger than the inner diameter of the fixing belt 21, and when the fixing belt 21 moves (shifts to one side) in the longitudinal direction X, the regulating part 70b prevents further fixing. Movement of the belt 21 is restricted. The protrusion 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 side.

As described above, even when the protrusion 30 is provided on the sensor holder 50 or the flange 70, the lead wire 44 is supported by the protrusion 30, so that the temperature of the heater 23 is easily increased in the area where the temperature of the heater 23 tends to rise, that is, in the heat generating area 60. Therefore, a large distance between the lead wire 44 and the heater 23 can be ensured in the area outside the minimum paper passing width W2. Therefore, also in these examples, the temperature rise of the lead wire 44 can be suppressed. Note that the number of protrusions 30 is not limited to one, and may be plural as in each example of the present invention described above. Further, regarding the arrangement and shape of the protrusion 30, the same configuration as in each example of the present invention described above can be applied.

Although the present invention has been described above, the present invention is not limited to the above-described embodiments and examples, and design changes can be made as appropriate within the scope of the invention.

Generally, a thermistor, which is an example of a temperature sensor 27 used in a fixing device, has lead wires 44 protruding from opposite ends of a thermistor 39 as shown in FIG. 27, and a thermistor as shown in FIG. 28. In some cases, the lead wire 44 protrudes from only one end of the thermistor 39. In the present invention, it is possible to employ any type of thermistor, but in particular, the type in which the lead wire 44 protrudes from both ends (FIG. 27) is replaced by the type in which the lead wire 44 protrudes from only one end (FIG. 28). In comparison, the size in the paper transport direction U is smaller (i1<i2), so by employing the former thermistor 39, size reduction in the paper transport direction U can be achieved. Furthermore, when using a thermistor 39 in which the lead wires 44 protrude from both ends, each lead wire 44 is concentrated on one side of the thermistor 39 by bending one lead wire 44 and running it around, as shown in FIG. and can be placed. Further, according to the present invention, since the temperature rise of the lead wire 44 can be suppressed, a lead wire with low heat resistance and excellent flexibility can be used as the lead wire 44, and the lead wire 44 can be bent and The layout for turning is also easier.

Further, the present invention is not limited to being applied to an image forming apparatus using a center reference conveyance method in which sheets of various width sizes are conveyed with the center of each width direction as a reference. It is also applicable to an image forming apparatus using a so-called edge conveyance reference method in which the image forming apparatus is conveyed with one end aligned with a reference. In that case, as shown in FIG. 29, the distance from the position r that serves as the transport reference for each type of paper P1 and P2 is the distance of the maximum width W1 and minimum width W2 of the paper, or a distance of 5 mm added to these widths W1 and W2. The range up to the position becomes the maximum paper passing width W1 and the minimum paper passing width W2. Therefore, even in the case of such an edge conveyance reference method, a protrusion 30 that can secure a large distance between the lead wire 44 and the heater 23 is provided outside the minimum paper passing width W2 and within the heat generating area 60 of the heater 23. This makes it possible to suppress the temperature rise of the lead wire 44, as in the above embodiment.

Furthermore, a heater having PTC characteristics may be used as the heat source used in the fixing device according to the present invention. The PTC characteristic is a characteristic in which the resistance value increases as the temperature increases (when a constant voltage is applied, the heater output decreases). By using a heater whose resistance heating element has PTC characteristics, it is possible to start up quickly at low temperatures with high output, and to suppress excessive temperature rise at high temperatures with low output. Therefore, by using a heater having such a PTC characteristic, it is possible to effectively suppress the heat generation of the resistance heating element in the non-sheet passing area, and therefore it is possible to further suppress the temperature rise of the lead wire. For example, by setting the TCR coefficient of the PTC characteristic to about 300 to 4000 ppm/degree, it is possible to reduce the cost while ensuring the resistance value necessary for the heater. More preferably, the TCR coefficient is 500 to 2000 ppm/degree. The TCR coefficient can be calculated by measuring resistance values at 25 degrees and 125 degrees. For example, if the temperature increases by 100 degrees and the resistance value increases by 10%, the TCR coefficient is 1000 ppm/degree.

Furthermore, the present invention is also applicable to fixing devices configured as shown in FIGS. 30 to 33. The configuration of each fixing device shown in FIGS. 30 to 33 will be described below.

The fixing device 20 shown in FIG. 30 differs from the fixing device 20 shown in FIG. 2 in the position of the temperature sensor 27 that detects the temperature of the heater 23. The other parts have the same configuration. In the fixing device 20 shown in FIG. 30, the fixing device 20 is disposed upstream in the paper passing direction (nip entrance side) from the center M of the nip portion N in the paper passing direction. On the other hand, in the fixing device 20 shown in FIG. 2, a temperature sensor 27 is arranged at the center M of the nip portion N. As shown in FIG. 30, when the temperature sensor 27 is disposed upstream of the center M of the nip portion N in the paper passing direction, the temperature at the nip entrance side can be accurately detected by the temperature sensor 27. On the nip entrance side, the heat of the fixing belt 21 is particularly easily absorbed by the paper P entering the nip portion N. Therefore, by accurately detecting the temperature on the nip entrance side with the temperature sensor 27, the image is fixed. It is possible to effectively suppress the occurrence of fixing offset (a state in which the toner image cannot be heated sufficiently).

Next, in the embodiment shown in FIG. 31, a heating nip N1 in which the fixing belt 21 is heated by the heater 23 and a fixing nip N2 through which the paper P passes are formed at different positions. ing. Specifically, in this embodiment, in addition to the heater 23, a nip forming member 68 is arranged inside the fixing belt 21, and pressure rollers 69 and 70 are used to press the fixing belt 21 against the heater 23 and the nip forming member 68, respectively. A nip portion N1 for heating and a nip portion N2 for fixing are formed by being pressed against each other. In this case, the fixing belt 21 is heated in the heating nip N1, and the heat of the fixing belt 21 is applied to the paper P in the fixing nip N2, thereby fixing the unfixed image to the paper P.

Next, in the fixing device 20 shown in FIG. 32, the pressure roller 69 on the heater 23 side is omitted from the fixing device shown in FIG. This is an example. Other than that, the configuration is the same as that shown in FIG. 31. In this case, since the heater 23 is formed in an arc shape, a contact length between the fixing belt 21 and the heater 23 in the belt rotation direction can be ensured, and the fixing belt 21 can be heated efficiently.

Next, the fixing device 20 shown in FIG. 33 is an example in which a roller 73 as another rotating body is disposed between belts 71 and 72 as a pair of rotating bodies. In this example, the heater 23 is disposed within the belt 71 on the left side in FIG. 33, and the nip forming member 74 is disposed within the belt 72 on the right side. 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, so that the heating nip N1 and the fixing nip N2 are separated. It is formed. In this case, the heater 23 heats the roller 73 via the left belt 71.

Further, the image forming apparatus according to the present invention is applicable not only to the color image forming apparatus shown in FIG. 1 but also to an image forming apparatus having a configuration as shown in FIG. 34. The configuration of an image forming apparatus according to another embodiment to which the present invention is applicable will be described below.

The image forming apparatus 100 shown in FIG. 34 includes an image forming means 80 including a photosensitive drum, a paper transport section including a pair of timing rollers 81, a paper feeding device 82, a fixing device 83, and a paper ejecting device. 84 and a reading section 85. The paper feed device 82 includes a plurality of paper feed trays, each of which accommodates sheets of different sizes.

The reading unit 85 reads the image of the document Q. The reading unit 85 generates image data from the read image. The paper feed device 82 accommodates a plurality of sheets P and sends out the sheets P to a conveyance path. Timing roller 81 transports paper P on the transport path to image forming means 80 .

Image forming means 80 forms a toner image on paper P. Specifically, the image forming means 80 includes a photosensitive drum, a charging roller, an exposure device, a developing device, a replenishing device, a transfer roller, a cleaning device, and a static eliminator. The fixing device 83 heats and pressurizes the toner image to fix the toner image on the paper P. The paper P with the toner image fixed thereon is transported to the paper ejecting device 84 by a transport roller or the like. Paper ejection device 84 ejects paper P to the outside of image forming apparatus 100 .

Next, the fixing device 83 according to this embodiment will be explained based on FIG. 35. Note that in the configuration shown in FIG. 35, the same reference numerals are given to the parts that are common to the fixing device 20 of the above embodiment shown in FIG. 2, and the explanation thereof will be omitted.

As shown in FIG. 35, 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.

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

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

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

The heater 23 includes a base material, a heat insulating layer, a conductor layer including a resistance heating element, and an insulating layer, and has a total thickness of 1 mm. Further, the width of the heater 23 in the paper conveyance direction is 13 mm.

As shown in FIG. 36, the conductor layer of the heater 23 includes a plurality of resistance heating elements 56, a power supply line 59, and electrode portions 58A to 58C. The plurality of resistance heating elements 56 are arranged at intervals in the longitudinal direction of the heater 23 (arrow X direction). Here, if the portion between each resistance heating element 56 is referred to as a "divided area," then as shown in the enlarged view of FIG. 36, a divided area B is formed between each resistance heating element 56. (In FIG. 36, the divided region B is illustrated only in the enlarged view, but in reality, the divided region B is provided between all the resistance heating elements 56.) Further, in FIG. 36, the direction of the arrow Y is a direction that intersects or perpendicularly intersects with the longitudinal direction X of the heater 23 (longitudinal cross direction), and is a direction different from the thickness direction of the base material 55. Further, the arrow Y direction is a direction that intersects the arrangement direction of the plurality of resistance heating elements 56 (arrangement crossing direction), or a direction along the surface of the base material 55 on which the resistance heating elements 56 are provided, which is the short side of the heater 23. direction, or the same direction as the conveyance direction of the paper that is passed through the fixing device.

Furthermore, the plurality of resistance heating elements 56 constitute a central heating section 35B and heating sections 35A and 35C at both ends that can generate heat independently of the central heating section 35B. For example, among the three electrode sections 58A to 58C, when the leftmost electrode section 58A and the center electrode section 58B in FIG. 36 are energized, the heat generating sections 35A and 35C at both ends generate heat. Moreover, when electricity is applied to the electrode parts 58A and 58C at both ends, the heat generating part 35B in the center generates heat. For example, when performing a fixing operation on small-sized paper, only the central heating section 35B generates heat, and when performing a fixing operation on large-sized paper, all the heating sections 35A to 35C generate heat, thereby adjusting the size of the paper. It is possible to heat according to the

Further, as shown in FIG. 37, the heater holder 24 according to this embodiment has a recess 24a that accommodates and holds the heater 23. The recess 24a is formed on the heater 23 side of the heater holder 24. Further, the recess 24a is provided with a surface (bottom surface) 24f formed in a rectangular shape having approximately the same size as the heater 23, and along four sides forming the outline of the surface 24f so as to intersect with the surface 24f. It is composed of four wall portions (side surfaces) 24b, 24c, 24d, and 24e. Note that in FIG. 37, the right wall portion 24e is omitted from illustration. Also, one of the pair of (left and right) walls 24d and 24e intersecting with the longitudinal direction X of the heater 23 (the arrangement direction of the resistance heating elements 56) is omitted, and the recess 24a is It may be configured to open at one end in the direction.

As shown in FIG. 38, the heater 23 and heater holder 24 according to this embodiment are held by a connector 86. The connector 86 includes a housing made of resin (for example, LCP) and a plurality of contact terminals provided within the housing.

The connector 86 is attached to the heater 23 and the heater holder 24 in a direction that intersects the longitudinal direction X of the heater 23 (the direction in which the resistance heating elements 56 are arranged) (see the arrow direction from the connector 86 in FIG. 38). Further, the connector 86 is located at one end side of the heater 23 in the longitudinal direction It is attached to the heater 23 and heater holder 24. Note that when the connector 86 is attached to the heater holder 24, a convex portion provided on one of the connector 86 and the heater holder 24 engages with a concave portion provided on the other, and the convex portion moves relatively within the concave portion. Good too.

When the connector 86 is attached, the heater 23 and the heater holder 24 are held between the front and back sides of the heater 23 by the connector 86. In this state, each contact terminal is brought into contact (pressure contact) with each electrode portion of the heater 23, so that each resistance heating element 56 and the power supply provided in the image forming apparatus are electrically connected via the connector 86. Ru. This allows power to be supplied from the power source to each resistance heating element 56.

Further, flanges 87 shown in FIG. 38 are belt holding members that are provided at both ends of the fixing belt 21 in the longitudinal direction and hold both ends of the fixing belt 21 from inside. The flanges 87 are inserted into both ends of the stay 25 and fixed to a pair of side plates that are frame members of the fixing device.

FIG. 39 is a diagram showing the arrangement of the temperature sensor 27 and the thermostat 88, which is a current cutoff member, according to this embodiment.

As shown in FIG. 39, the temperature sensor 27 according to the present embodiment is arranged to face the inner circumferential surface of the fixing belt 21 on the center Xm side and the end side in the longitudinal direction (arrow X direction). ing. Further, one of these temperature sensors 27 is arranged at a position corresponding to the divided region B (see FIG. 36) between the resistance heating elements of the heater 23.

Further, on the center Xm side and the end side of the fixing belt 21, a thermostat 88 as a current cutoff member is arranged so as to face the inner circumferential surface of the fixing belt 21. Each thermostat 88 detects the temperature of the inner peripheral surface of the fixing belt 21 or the ambient temperature near the inner peripheral surface. When the temperature detected by the thermostat 88 exceeds a preset threshold value, power to the heater 23 is cut off.

Further, as shown in FIGS. 39 and 40, the flange 87 that holds both ends of the fixing belt 21 is provided with a slide groove 87a. The slide groove 87a extends in the direction in which the fixing belt 21 approaches and separates from the pressure roller 22. An engaging portion of the housing of the fixing device engages with the slide groove 87a. By relatively moving this engaging portion within the slide groove 87a, the fixing belt 21 is configured to be movable in the direction toward and away from the pressure roller 22.

Further, the present invention is also applicable to a fixing device having the following configuration.

FIG. 41 is a schematic configuration diagram of a fixing device according to another embodiment to which the present invention is applicable.

As shown in FIG. 41, the fixing device 20 according to the present embodiment includes a fixing belt 21 as a rotating body or a fixing member, a pressure roller 22 as a counter rotating body or a pressure member, and a heater 23 as a heat source. A heater holder 24 as a heating source holding member, a stay 25 as a supporting member, a temperature sensor (thermistor) 27 as a temperature detecting member, and a first high heat conductive member 89 are provided. The fixing belt 21 is an endless belt. The pressure roller 22 contacts the outer peripheral surface of the fixing belt 21 and forms a nip portion N between the pressure roller 22 and the fixing belt 21 . Heater 23 heats fixing belt 21 . Heater holder 24 holds heater 23. The stay 25 supports the heater holder 24. The temperature sensor 27 detects the temperature of the first highly heat conductive member 89 . That is, the fixing device 20 according to this embodiment has basically the same configuration as the fixing device shown in FIG. 2 above, except that it includes the first high heat conductive member 89. Note that the direction perpendicular to the paper surface of FIG. 41 is the longitudinal direction of the fixing belt 21, the pressure roller 22, the heater 23, the heater holder 24, the stay 25, and the first high heat conductive member 89, and hereinafter this direction will simply be referred to as the longitudinal direction. It is called. Further, this longitudinal direction is also the width direction of the paper being conveyed, the belt width direction of the fixing belt 21, and the axial direction of the pressure roller 22.

Here, in the heater 23 in this embodiment, a plurality of resistance heating elements 56 are arranged at intervals from each other in the longitudinal direction of the heater 23, similarly to the heater shown in FIG. 36 above. However, in a configuration in which a plurality of resistance heating elements 56 are arranged at intervals, the temperature of the heater 23 in the divided region B, which is the interval between the resistance heating elements 56, is different from the part where the resistance heating elements 56 are arranged. It tends to be lower than that. Therefore, in the divided region B, the temperature of the fixing belt 21 also becomes low, and there is a possibility that the temperature of the fixing belt 21 becomes non-uniform in the longitudinal direction.

Therefore, in this embodiment, the first high heat conductive member 89 is provided in order to suppress the temperature drop in the divided region B and to suppress temperature unevenness in the longitudinal direction of the fixing belt 21. Hereinafter, the first high heat conductive member 89 will be explained in more detail.

As shown in FIG. 41, the first high thermal conductivity member 89 is disposed 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 conduction member 89 is in contact with the back surface of the base material 55 of the heater 23, and the other surface (the surface opposite to the one surface) of the first high heat conduction member 89 is in contact with the back surface of the base material 55 of the heater 23. It is in contact with 24.

The stay 25 supports the heater holder 24, the first high thermal conductivity member 89, and the heater 23 by bringing contact surfaces 25a1 of two vertical portions 25a of the heater 23, etc., extending in the thickness direction into contact with the heater holder 24. In the longitudinal cross direction (vertical direction in FIG. 41), the contact surface 25a1 is provided outside the range where the resistance heating element 56 is provided. Thereby, heat transfer from the heater 23 to the stay 25 can be suppressed, and the heater 23 can efficiently heat the fixing belt 21.

As shown in FIG. 42, the first high thermal conductivity member 89 is a plate-shaped member having a certain thickness, for example, the thickness is 0.3 mm, the length in the longitudinal direction is 222 mm, and the length in the longitudinal direction is 222 mm. The width is set to 10 mm. In this embodiment, the first high thermal conductivity member 89 is made of a single plate, but it may be made of a plurality of members. Note that in FIG. 42, the guide member 26 shown in FIG. 41 is omitted.

The first highly thermally conductive member 89 is fitted into the recess 24a of the heater holder 24, and the heater 23 is attached from above, thereby being held between the heater holder 24 and the heater 23. In this embodiment, the longitudinal width of the first high heat conductive member 89 is set to be approximately the same as the longitudinal width of the heater 23 . The movement of the first high thermal conductivity member 89 and the heater 23 in the longitudinal direction is regulated by both side walls (longitudinal direction regulating portions) 24d and 24e arranged in a direction intersecting the longitudinal direction of the recess 24a. In this way, by restricting the displacement of the first highly heat conductive member 89 in the longitudinal direction within the fixing device, it is possible to improve the heat conduction efficiency within the targeted range in the longitudinal direction. Further, the movement of the first high thermal conductivity member 89 and the heater 23 in the longitudinal direction is regulated by both side walls (array transverse direction regulating portions) 24b and 24c arranged in the longitudinal direction of the recess 24a.

The range in the longitudinal direction (arrow X direction) in which the first high thermal conductivity member 89 is arranged is not limited to the range shown in FIG. 42. For example, as shown in FIG. 43, the first highly thermally conductive member 89 may be disposed only in the longitudinal range where the resistance heating element 56 is disposed (see the hatched portion in FIG. 43). Further, as in the example shown in FIG. 44, the first high thermal conductivity member 89 can be arranged only in the entire area at a position corresponding to the interval (divided area) B in the longitudinal direction (arrow X direction). In addition, in FIG. 44, for convenience, the resistance heating element 56 and the first high heat conductive member 89 are shown shifted in the vertical direction of FIG. Placed. Further, the first high heat conductive member 89 may be disposed over a part of the longitudinal direction (arrow Y direction) of the resistance heating element 56, or as in the example shown in FIG. The member 89 may be arranged over the entire length of the resistance heating element 56 in the longitudinal direction (arrow Y direction). Furthermore, as shown in FIG. 45, the first high thermal conductivity member 89 is disposed in addition to the position corresponding to the distance B in the longitudinal direction, and straddles the resistance heating elements 56 on both sides with the distance B in between. You can also do it. The phrase "the first high heat conductive member 89 is disposed astride the resistance heating elements 56 on both sides" means that the first high heat conductive member 89 at least partially overlaps the resistance heating elements 56 on both sides in the longitudinal direction. do. Further, the first high thermal conductivity member 89 may be arranged at a position corresponding to all the intervals B of the heaters 23, or as in the example shown in FIG. may be placed only at positions corresponding to . Here, "the first high heat conductive member 89 is arranged at a position corresponding to the interval B" means that the interval B and at least a portion of the first high heat conductive member 89 overlap in the longitudinal direction.

Due to the pressing force of the pressing roller 22, the first high heat conductive member 89 is sandwiched between the heater 23 and the heater holder 24 and comes into close contact with these members. The contact of the first highly heat conductive member 89 with the heater 23 improves the heat conduction efficiency of the heater 23 in the longitudinal direction. By arranging the first high thermal conductivity member 89 at a position corresponding to the interval B between the heaters 23 in the longitudinal direction, the heat conduction efficiency in the interval B can be improved, and the amount of heat transferred to the interval B. can be increased to increase the temperature in interval B. Thereby, temperature unevenness in the longitudinal direction of the heater 23 can be suppressed, and temperature unevenness in the longitudinal direction of the fixing belt 21 can be suppressed. As a result, it is possible to suppress uneven fixing and uneven gloss of images fixed on paper. Further, in order to ensure sufficient fixing performance at the interval B, it is no longer necessary to increase the amount of heat generated by the heater 23, and energy saving of the fixing device can be realized. In particular, when the first high heat conductive member 89 is arranged over the entire lengthwise area where the resistance heating element 56 is arranged, the entire main heating area by the heater 23 (that is, the image forming area of the paper being passed) In this case, the heat transfer efficiency of the heater 23 can be improved, and temperature unevenness in the longitudinal direction of the heater 23 and thus the fixing belt 21 can be suppressed.

Furthermore, the combination of the first high thermal conductivity member 89 and the resistance heating element 56 having PTC characteristics can more effectively suppress excessive temperature rise in the non-sheet passing area when small size paper is passed. This PTC characteristic is a characteristic in which the resistance value increases as the temperature increases (when a constant voltage is applied, the heater output decreases). That is, since the resistance heating element 56 has the PTC characteristic, the amount of heat generated by the resistance heating element 56 in the non-sheet passing area can be effectively suppressed, and the first high heat conduction member 89 prevents the non-paper whose temperature has increased. Since the amount of heat in the paper passing area can be efficiently transferred to the paper passing area, the synergistic effect of these effects can effectively suppress excessive temperature rise in the paper non-passing area.

Further, it is preferable to arrange the first high heat conductive member 89 also around the interval B, since the temperature of the heater 23 is lowered due to the small amount of heat generated at the interval B. For example, by arranging the first highly thermally conductive member 89 at a position corresponding to the enlarged divided area C including the area around the interval B shown in FIG. This makes it possible to more effectively suppress temperature unevenness in the longitudinal direction of the heater 23. In addition, when the first high heat conductive member 89 is arranged over the entire lengthwise region where all the resistance heating elements 56 are arranged, temperature unevenness in the longitudinal direction of the heater 23 (fixing belt 21) can be further reduced. It can definitely be suppressed.

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

The fixing device 20 shown in FIG. 47 includes a second high heat conduction member 90 between the heater holder 24 and the first high heat conduction member 89. The second high heat conduction member 90 is provided at a different position from the first high heat conduction member 89 in the stacking direction (left-right direction in FIG. 47) of members such as the heater holder 24, the stay 25, and the first high heat conduction member 89. More specifically, the second high heat conductive member 90 is provided to overlap the first high heat conductive member 89. Further, in this embodiment, a temperature sensor (thermistor) 27 is provided as in the embodiment shown in FIG. 41 above, but FIG. There is.

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

As shown in FIG. 48, a plurality of second high heat conduction members 90 are arranged in the recess 24a of the heater holder 24, and a longitudinal interval is provided between each second high heat conduction member 90. A recess is formed in a portion of the heater holder 24 where the second high heat conductive member 90 is provided, which is deeper than other portions. A gap is provided between the second high heat conductive member 90 and the heater holder 24 on both sides in the longitudinal direction. As a result, heat transfer from the second highly heat conductive member 90 to the heater holder 24 is suppressed, and the fixing belt 21 is efficiently heated by the heater 23. Note that in FIG. 48, the guide member 26 shown in FIG. 41 is omitted.

As shown in FIG. 49, the second high thermal conductivity member 90 (see the hatched part) overlaps at least a portion of the adjacent resistance heating element 56 at a position corresponding to the interval B in the longitudinal direction (arrow X direction). placed in position. In particular, in this embodiment, the second high thermal conductivity member 90 is arranged over the entire interval B. Note that FIG. 49 (and FIG. 51 described later) shows a case in which the first high thermal conductivity member 89 is arranged over the entire lengthwise region where all the resistance heating elements 56 are arranged. , the arrangement range of the first high heat conductive member 89 is not limited to this.

As in the present embodiment, in addition to the first high heat conduction member 89, a second high heat conduction member 90 is arranged at a position corresponding to the longitudinal interval B and overlapping at least a portion of the adjacent resistance heating elements 56. By doing so, the heat transfer efficiency in the longitudinal direction in the interval B can be further improved, and temperature unevenness in the longitudinal direction of the heater 23 can be suppressed more effectively. Furthermore, most preferably, as shown in FIG. 50, the first high heat conduction member 89 and the second high heat conduction member 90 are provided only in the entire area at a position corresponding to the interval B. Thereby, the heat transfer efficiency can be particularly improved at the position corresponding to the interval B compared to other regions. In addition, in FIG. 50, for convenience, the resistance heating element 56, the first high heat conduction member 89, and the second high heat conduction member 90 are shown shifted in the vertical direction of the figure, but these are shown in the longitudinal cross direction (arrows are arranged at approximately the same position in the Y direction). However, the present invention is not limited to this, and the first high heat conductive member 89 and the second high heat conductive member 90 may be disposed in a part of the resistance heating element 56 in the longitudinal direction, or may cover the entire length in the longitudinal direction. It may be placed so as to cover it.

Further, both the first high heat conduction member 89 and the second high heat conduction member 90 may be made of the graphene sheet. In this case, the first highly thermally conductive member 89 and the second highly thermally conductive member 90 having high thermal conductivity can be formed in a predetermined direction along the plane of graphene, that is, not in the thickness direction but in the longitudinal direction. Therefore, temperature unevenness in the longitudinal direction of the heater 23 and the fixing belt 21 can be effectively suppressed.

Graphene is a flaky powder. Graphene consists of a planar hexagonal lattice structure of carbon atoms, as shown in FIG. A graphene sheet is a sheet of graphene, and is usually a single layer. Further, the graphene sheet may contain impurities in a single layer of carbon, or may have a fullerene structure. The fullerene structure is generally recognized as a compound consisting of a polycyclic ring in which the same number of carbon atoms are fused into a 5-membered ring and a 6-membered ring in the form of a cage, such as C60, C70 and C80 fullerenes. or other closed cage-like structures with three-coordinated carbon atoms.

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

A commercially available graphene sheet can be used. The size and thickness of the graphene sheet, the number of layers of the graphite sheet described below, etc. are measured using, for example, a transmission electron microscope (TEM).

Additionally, graphite, which is made by layering graphene, has large thermal conduction anisotropy. As shown in FIG. 54, graphite has a layer in which the surface of the condensed six-membered ring layer of carbon atoms spreads out in a planar shape, and has a crystal structure in which these layers are stacked in many layers. In this crystal structure, adjacent carbon atoms within a layer form covalent bonds, and carbon atoms between layers form van der Waals bonds. Covalent bonds have a stronger bonding force than van der Waals bonds, and have a large anisotropy between bonds within layers and bonds between layers. In other words, by configuring the first high heat conductive member 89 or the second high heat conductive member 90 from graphite, the heat transfer efficiency in the longitudinal direction of the first high heat conductive member 89 or the second high heat conductive member 90 is increased in the thickness direction (that is, in the thickness direction of the member). (laminated direction), 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 toward the heater holder 24 side can be suppressed to a minimum. Furthermore, by configuring the first high heat conductive member 89 or the second high heat conductive member 90 with graphite, the first high heat conductive member 89 or the second high heat conductive member 90 can have excellent heat resistance that does not oxidize up to about 700 degrees. I can do it.

The physical properties and dimensions of the graphite sheet can be changed as appropriate depending on the function required of the first high heat conduction member 89 or the second high heat conduction member 90. For example, by using high-purity graphite or single crystal graphite, or by increasing the thickness of the graphite sheet, the anisotropy of thermal conduction can be enhanced. Furthermore, in order to increase the speed of the fixing device, a thin graphite sheet may be used to reduce the heat capacity of the fixing device. Further, when the width of the nip portion N and the heater 23 is large, the width in the longitudinal direction of the first high heat conduction member 89 or the second high heat conduction member 90 may be increased accordingly.

From the viewpoint of increasing mechanical strength, the number of layers of the graphite sheet is preferably 11 or more. Further, the graphite sheet may partially include a single layer and a multilayer portion.

The second high thermal conductivity member 90 may be provided at a position corresponding to the interval B (furthermore, the enlarged divided region C) in the longitudinal direction and at a position overlapping at least a portion of the adjacent resistance heating elements 56, and the arrangement shown in FIG. Not limited to. For example, as in the example shown in FIG. 51, the second highly thermally conductive member 90A may be provided so as to protrude from the base material 55 to both sides in the longitudinal direction (arrow Y direction). Further, the second high thermal conductivity member 90B may be provided in the range where the resistance heating element 56 is provided in the longitudinal direction. Further, the second high heat conductive member 90C may be provided in a part of the interval B.

Further, in another embodiment shown in FIG. 52, a gap is provided between the first high thermal conductivity member 89 and the heater holder 24 in the thickness direction (left-right direction in FIG. 52). That is, a relief portion 24g as a heat insulating layer is provided in a part of the recess 24a (see FIG. 48) of the heater holder 24 where the heater 23, the first high heat conduction member 89, and the second high heat conduction member 90 are arranged. ing. The relief portion 24g is provided in a partial region in the longitudinal direction other than the portion where the second high heat conductive member 90 (not shown in FIG. 52) is provided. Further, the relief portion 24g is formed by making the depth of the recessed portion 24a of the heater holder 24 deeper than other portions. As a result, the contact area between the heater holder 24 and the first high heat conduction member 89 can be minimized, so heat transfer from the first high heat conduction member 89 to the heater holder 24 is suppressed, and the fixing belt 21 is Allows for efficient heating. Note that in the cross section where the second high heat conduction member 90 in the longitudinal direction is provided, the second high heat conduction member 90 contacts the heater holder 24, as in the embodiment shown in FIG. 47 above.

Further, in this embodiment, the relief portion 24g is provided over the entire range in which the resistance heating element 56 is provided in the longitudinal cross direction (vertical direction in FIG. 52). As a result, heat transfer from the first high thermal conductivity member 89 to the heater holder 24 is effectively suppressed, and the heating efficiency of the fixing belt 21 by the heater 23 is improved. In addition to the configuration in which a space is provided as the escape portion 24g, a configuration in which a heat insulating member having a lower thermal conductivity than the heater holder 24 is provided may be used as the heat insulating layer.

Further, in this embodiment, the second high heat conduction member 90 is provided as a member different from the first high heat conduction member 89, but the present invention is not limited to this. For example, the first high heat conductive member 89 may also function as the second high heat conductive member 90 by making the part of the first high heat conductive member 89 corresponding to the interval B thicker than the other parts. good.

The configurations of other fixing devices and image forming apparatuses to which the present invention can be applied have been described above. By applying the present invention to fixing devices and image forming apparatuses with such configurations, the same effects as in the above embodiments can be obtained. You can get . That is, by applying the present invention, it is possible to suppress the temperature rise of the lead wire in the non-sheet passing area, and it is possible to improve the durability of the lead wire.

Furthermore, in the above description, the present invention is applied to a fixing device, which is an example of a heating device. However, the present invention is not limited to the fixing device, but also includes a drying device that dries liquid such as ink applied to paper, a laminator that thermocompresses a film as a covering member onto the surface of a sheet such as paper, and a sealing part of a packaging material. It can also be applied to heating devices such as heat sealers for thermocompression bonding.

To summarize the aspects 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.

[First configuration]
A first configuration includes a pair of rotating bodies that contact each other to form a nip portion through which the sheet passes, a heat source that heats at least one of the pair of rotating bodies, and a heat source that holds the heat source. A heating device comprising a holding member, a temperature sensing member that detects the temperature of the heat source, and a flexible conductive member connected to the temperature sensing member, wherein the heating source holding member is connected to the temperature of the heating source. It has a conductive member support part that supports the conductive member on the side opposite to the surface side that holds the heat source, and the conductive member support part has at least a part outside a predetermined width of the heat source holding member. In the heating device, the conductive member support is supported such that the distance of the conductive member from the heat source is increased in the region within the predetermined width.

[Second configuration]
The second configuration includes a pair of rotating bodies that contact each other to form a nip portion through which the sheet passes, a heat source that heats at least one of the pair of rotating bodies, and a heat source that holds the heat source. A heating device comprising a holding member, a temperature sensing member that detects the temperature of the heat source, and a flexible conductive member connected to the temperature sensing member, wherein the heating source holding member is connected to the temperature of the heating source. It has a plurality of conductive member support parts that protrude on the side opposite to the side that holds the heat source and supports the conductive member, and at least some of the plurality of conductive member support parts are arranged outside a predetermined width. The conduction member supporting portion is a heating device having a height in a protruding direction that protrudes from the heat source holding member than the other conduction member support portions.

[Third configuration]
A third configuration includes a pair of rotating bodies that contact each other to form a nip portion through which the sheet passes, a heating source that heats at least one of the pair of rotating bodies, and a heating source that holds the heating source. A heating device comprising a holding member, a temperature sensing member that detects the temperature of the heat source, and a flexible conductive member connected to the temperature sensing member, wherein the heating source holding member is connected to the temperature of the heating source. It has a plurality of conductive member support parts that protrude on the side opposite to the side that holds the heat source and supports the conductive member, and at least some of the plurality of conductive member support parts are arranged outside a predetermined width. In the heating device, the distance between the conductive member supporting portions in the sheet width direction is smaller than the distance between the other conductive member supporting portions in the sheet width direction.

[Fourth configuration]
In a fourth configuration, in any one of the first to third configurations, the predetermined width is a heating device having a sheet passing width of a minimum size.

[Fifth configuration]
In a fifth configuration, in any one of the first to fourth configurations, the heat source has a plurality of heating elements arranged at intervals in the sheet width direction, and the conductive member support part is , a heating device arranged so as to overlap a region between the heating elements in the sheet width direction.

[Sixth configuration]
In a sixth configuration, in any one of the first to fifth configurations, the conductive member support portion protrudes to a side opposite to a side of the heat source holding member that holds the heat source, and The height of the member supporting portion in the direction in which it projects from the heating source holding member is higher than the position where the electrically conductive member is connected to the temperature sensing member.

[Seventh configuration]
In a seventh configuration, in any one of the first to sixth configurations, the conductive member support portion protrudes on a side opposite to a side of the heating source holding member that holds the heating source, and The source has a heating element at the center of the heat source in the sheet conveyance direction, and the conductive member support part is a heating device that supports the conductive member at a position offset from the center of the heat source in the sheet conveyance direction. .

[Eighth configuration]
In an eighth configuration, in the seventh configuration, the conductive member supporting portion protrudes on a side opposite to a side of the heating source holding member that holds the heating source, and The height of the heating device protruding from the holding member in the protruding direction is higher at the center of the conductive member supporting portion in the sheet conveying direction than at both ends in the sheet conveying direction.

[Ninth configuration]
A ninth configuration, in any one of the first to eighth configurations, includes a support member that supports the heat source holding member, and a position between the support member and the conductive member that is larger than the support member. This is a heating device in which a low thermal conductive member with low thermal conductivity is arranged.

[Tenth configuration]
A tenth configuration is a fixing device that fixes an unfixed image onto a sheet using the heating device of any one of the first to ninth configurations.

[Eleventh configuration]
An eleventh configuration is an image forming apparatus including the heating device of any one of the first to ninth configurations or the fixing device of the tenth configuration.

20 Fixing device (heating device)
21 Fixing belt (first rotating body)
22 Pressure roller (second rotating body)
23 Heater (heating source)
24 Heater holder (heating source holding member)
25 Stay (support member)
27 Temperature sensor (temperature detection member)
30 Protrusion (conducting member support part)
30m Center part in paper transport direction (Center part in sheet transport direction)
44 Lead wire (conducting member)
56 Resistance heating element (heating element)
63 Low thermal conductivity member 100 Image forming device N Nip section P Paper (sheet)
W1 Maximum sheet passing width (maximum sheet passing width)
W2 Minimum sheet passing width (minimum sheet passing width)
X Longitudinal direction

JP2011-118246A

Claims (11)

a pair of rotating bodies that contact each other to form a nip portion through which the sheet passes;
a heating source that heats at least one of the pair of rotating bodies;
a heating source holding member that holds the heating source;
a temperature detection member that detects the temperature of the heating source;
a flexible conductive member connected to the temperature sensing member;
A heating device comprising:
The heat source holding member has a conductive member support portion that supports the conductive member on a side opposite to a side that holds the heat source,
The conductive member supporting portion is configured to increase the distance of the conductive member from the heat source in at least a part of the region outside the predetermined width of the heat source holding member compared to the region within the predetermined width. A heating device characterized by supporting a conductive member. a pair of rotating bodies that contact each other to form a nip portion through which the sheet passes;
a heating source that heats at least one of the pair of rotating bodies;
a heating source holding member that holds the heating source;
a temperature detection member that detects the temperature of the heating source;
a flexible conductive member connected to the temperature sensing member;
A heating device comprising:
The heat source holding member has a plurality of conductive member support portions that protrude on a side opposite to the surface holding the heat source and support the conductive member,
Among the plurality of conduction member support parts, at least some of the conduction member support parts disposed outside a predetermined width protrude from the heat source holding member more than the other conduction member support parts in the protrusion direction. A heating device characterized by its high height. a pair of rotating bodies that contact each other to form a nip portion through which the sheet passes;
a heating source that heats at least one of the pair of rotating bodies;
a heating source holding member that holds the heating source;
a temperature detection member that detects the temperature of the heating source;
a flexible conductive member connected to the temperature sensing member;
A heating device comprising:
The heat source holding member has a plurality of conductive member support portions that protrude on a side opposite to the surface holding the heat source and support the conductive member,
Among the plurality of conductive member supporting parts, the distance in the sheet width direction between at least some of the conductive member supporting parts arranged outside a predetermined width is the same as the distance in the sheet width direction between the other conductive member supporting parts. A heating device characterized in that the spacing is smaller than the spacing. The heating device according to any one of claims 1 to 3, wherein the predetermined width is a minimum size sheet passing width. The heat source has a plurality of heating elements arranged at intervals in the sheet width direction,
The heating device according to any one of claims 1 to 3, wherein the conductive member support portion is arranged so as to overlap a region between the heating elements in the sheet width direction. The conductive member supporting portion protrudes on a side opposite to a side of the heating source holding member that holds the heating source,
The heating device according to any one of claims 1 to 3, wherein the height of the conductive member supporting portion in a direction in which it projects from the heating source holding member is higher than a position where the conductive member is connected to the temperature sensing member. Device. The conductive member supporting portion protrudes on a side opposite to a side of the heating source holding member that holds the heating source,
The heat source has a heating element at the center of the heat source in the sheet conveyance direction,
The heating device according to any one of claims 1 to 3, wherein the conductive member support section supports the conductive member at a position offset from the center of the heating source in the sheet conveyance direction. The conductive member supporting portion protrudes on a side opposite to a side of the heating source holding member that holds the heating source,
8. The heating device according to claim 7, wherein the height of the conductive member support in the protruding direction from the heat source holding member is higher at the center of the conductive member support in the sheet conveyance direction than at both ends of the conductive member support in the sheet conveyance direction. comprising a support member that supports the heat source holding member,
The heating device according to any one of claims 1 to 3, 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. A fixing device, characterized in that the heating device according to claim 1 is used to fix an unfixed image on a sheet. An image forming apparatus comprising the heating device according to claim 1 .

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