Image heating device and image forming apparatus

An image heating device is provided that includes: a film; a heater with a heat generator; a support member; a roller; and an electrical wire that is joined to the heater using a joining material; and a thermal conductive member that is in contact with the heater and the support member. The heater includes a first region in which the heat generator is provided, a second region in which the joining material is provided, and a third region between the first region and the second region. A surface of the third region of the heater that faces a seat of the support member includes a region that is not in contact with the support member. The thermal conductive member is in contact with the heater and the support member in at least one of the second region and the third region of the heater.

BACKGROUND OF THE INVENTION

Field of the Invention

The present invention relates to an image heating device such as a fixing apparatus that is installed in an image forming apparatus such as a photocopier or printer using an electrophotographic method or an electrostatic recording method, or a glossing apparatus that reheats a toner image fixed on a recording material to improve the glossiness of the toner image. The present invention further relates to an image forming apparatus including an image heating device.

Description of the Related Art

Conventionally, as an image heating device that is installed in an image forming apparatus such as a photocopier or a printer, there is a fixing apparatus including a film that transfers heat to a recording material, a heater that is in contact with an inner surface of the film, and a roller that forms a nip portion together with the film. Japanese Patent Application Publication No. 2017-054071 discloses, as an example of such an image heating device, a heater that includes a plurality of heat generating blocks lined up in a longitudinal direction of the heater on a substrate of the heater, each heat generating block including a temperature detection element.

SUMMARY OF THE INVENTION

In the configuration disclosed in Japanese Patent Application Publication No. 2017-054071, it is conceivable that a flexible sheet such as a Flexible Printed Circuit (FPC) or a Flexible Flat Cable (FFC) is used as an electrical wire that connects the heater and a control substrate. It is also conceivable that an electrical connection between the flexible sheet and the heater is soldered. In this case, when the heater generates heat and stops generating heat, the temperature of the soldered joint portion that is in contact with the heater increases and decreases in a repeated manner. Particularly, when the heater has a structure with a high temperature ramp rate such as a configuration in which a heater seat of a heater support member has a region that is not in contact with the heater, the temperature of the joint portion is also ramped up rapidly and thus thermal fatigue is likely to accumulate in the joint portion. If the joint portion cracks due to cumulative thermal fatigue, a problem may occur in which the electrical connection is interrupted, or the flexible sheet is detached.

It is an object of the present invention to provide an image heating device in which heat transfer to a joint portion between a heater and an electrical wire is suppressed.

In order to solve the above-described problem, an image heating device of the present invention includes:a film that is tubular;a heater with a heat generator, the heater being elongated in a generatrix direction of the film, and being arranged in an inner space of the film along the generatrix direction of the film;a support member that is arranged in the inner space of the film, and supports the heater;a roller that is in contact with an outer circumferential surface of the film, and forms a nip portion between the roller and the film, the nip portion being configured to hold the recording material between the roller and the film; andan electrical wire that is joined to the heater using a joining material, and is electrically connected to the heater,wherein the image heating device further includes, between the heater and the support member, a thermal conductive member that is in contact with the heater and the support member,wherein the heater includes, in the generatrix direction, a first region in which the heat generator is provided, a second region in which the joining material is provided, and a third region between the first region and the second region,wherein a surface of the third region of the heater that faces a seat of the support member includes a region that is not in contact with the support member, andwherein the thermal conductive member is in contact with the heater and the support member in at least one of the second region and the third region of the heater.

With this configuration, according to the present invention, it is possible to provide an image heating device in which heat transfer to a joint portion between a heater and an electrical wire is suppressed.

DESCRIPTION OF THE EMBODIMENTS

Hereinafter, a description will be given, with reference to the drawings, of embodiments (examples) of the present invention. However, the sizes, materials, shapes, their relative arrangements, or the like of constituents described in the embodiments may be appropriately changed according to the configurations, various conditions, or the like of apparatuses to which the invention is applied. Therefore, the sizes, materials, shapes, their relative arrangements, or the like of the constituents described in the embodiments do not intend to limit the scope of the invention to the following embodiments.

Image Forming Apparatus100

The following will first describe a schematic configuration of an image forming apparatus100according to the present embodiment with reference toFIG.1.FIG.1is a schematic cross-sectional view of the image forming apparatus100, which is a laser printer using an electrophotographic recording technique. When the image forming apparatus100receives a print signal, a scanner unit21emits laser light modulated according to image information, and scans a photo conductor19electrically charged to a predetermined polarity by a charging roller16. With this, an electrostatic latent image is formed on the photo conductor19. A tonner is supplied from a development roller17to this electrostatic latent image, and a toner image that corresponds to the image information is formed on the photo conductor19. The toner image is transferred to a recording material P, and then the photo conductor19is cleaned up by a cleaner18.

The recording material P stacked on a paper cassette (paper feed unit)11is fed one by one by a pick-up roller12, and is conveyed by a roller13toward a registration roller14. Furthermore, the recording material P is conveyed from the registration roller14to a transfer position formed by the photo conductor19and a transfer roller20at a timing at which the toner image on the photo conductor19reaches the transfer position. While the recording material P passes through the transfer position, the toner image on the photo conductor19is transferred to the recording material P. Then, the recording material P is heated by a fixing apparatus200, and the toner image is thermally fixed to the recording material P. The fixing apparatus200, which serves as an image heating device, is supplied with power from a control circuit40, which serves as a control unit connected to a commercially available AC source41. The recording material P carrying the fixed toner image is discharged by rollers26and27to a tray provided in an upper portion of the image forming apparatus100.

The above-described photo conductor19, charging roller16, scanner unit21, development roller17, and transfer roller20constitute an image forming unit for forming an unfixed image on the recording material P. Also, a cartridge15including the photo conductor19, the charging roller16, the development roller17, and the cleaner18serves as a replacement unit, and is detachable from the image forming apparatus100.

The following will describe a schematic configuration of the fixing apparatus200, which serves as a fixing unit configured to fix an image formed on the recording material P to the recording material P, with reference toFIGS.2A and2B.FIG.2Ais a schematic cross-sectional view of the fixing apparatus200according to the present embodiment. The fixing apparatus200includes: a fixing film210serving as a heating rotation member; a heater300having a contact surface S1that faces and is in contact with an inner surface of the fixing film210; and a pressure roller220serving as a pressure rotation member that forms a fixing nip portion N between the pressure roller220and the fixing film210. The fixing nip portion N of the present embodiment is formed by the heater300and the pressure roller220via the fixing film210, and the contact surface S1of the heater300serves as a nip portion forming surface. Also, on a side opposite to the contact surface S1in contact with the inner surface of the fixing film210, a heater support member240is provided that serves as a support member for supporting the heater300. A metal stay250is provided on, while being in contact with, a surface of the heater support member240that is opposite to the seat on which the heater300is supported. The metal stay250is biased toward the pressure roller220by a not-shown pressure mechanism. With this biasing force, the fixing nip portion N is formed.

The fixing film210is a tubular multi-layer film, and as a base layer of the fixing film210, a heat-resistant resin such as polyimide with a thickness of about 50 to 100 μm, or metal such as stainless steel with a thickness of about 20 to 50 μm can be used. The surface of the fixing film210is covered with a heat-resistant resin in order to prevent a toner from adhering to the fixing film210or ensure that a toner is separated from the recording material P, and thus releasability is realized. An example of the heat-resistant resin may be tetrafluoroethylene perfluoroalkyl vinyl ether copolymer (PFA) with a thickness of about 10 to 50 μm. Furthermore, particularly in an apparatus for forming a color image, heat-resistant rubber serving as an elastic layer may be provided between the base layer and a release layer to improve image quality. An example of the heat-resistant rubber is silicone rubber with a thickness of about 100 to 400 μm and a thermal conductivity of about 0.2 to 3.0 W/m·K.

In the present embodiment, polyimide with a thickness of 60 μm is used as the base layer of the fixing film210, silicone rubber with a thickness of 300 μm and a thermal conductivity of 1.6 W/m·K is used as the elastic layer, and PFA with a thickness of 30 μm is used as the release layer, in view of thermal responsiveness, image quality, durability, and the like.

The pressure roller220includes: a core metal221made of a material such as iron or aluminum; and an elastic layer222made of a material such as silicone rubber. The heater support member240also has a guide function of guiding the rotation of the fixing film210by contact with the inner surface of the fixing film210. The pressure roller220is powered by a motor30and is rotated in a direction indicated by an arrow R1. In response to the rotation of the pressure roller220, the fixing film210is driven and is rotated in a direction indicated by an arrow R2, since the pressure roller220is in contact with an outer circumferential surface of the fixing film210. Then, the recording material P interposed between the pressure roller220and the fixing film210is conveyed in a conveying direction in accordance with the rotations of the pressure roller220and fixing film210. When, in the fixing nip portion N, the recording material P is conveyed while being interposed between pressure roller220and fixing film210and is heated by the fixing film210, the unfixed toner image T on the recording material P is fixed.

The heater300is a ceramic heater that includes a ceramic substrate305and at least one heat generator302on the substrate305, and heats the fixing film210with heat generated by the heat generator302. The heater300of the present embodiment is a member that is elongated in a direction parallel to the width direction of the recording material P and to a rotation axis direction (generatrix direction) of the pressure roller220or the fixing film210, and the heater300is arranged on an inner space of the fixing film210. The heater300includes a surface protection layer308provided on the fixing nip portion N side, and a surface protection layer307provided on a side opposite to the fixing nip portion N side. Although details will be described later, a plurality of electrodes E electrically connected to a plurality of heat generators302are provided on a side of the heater300opposite to a side facing the fixing nip portion N, and the fixing apparatus200includes a plurality of electrical contacts C that are respectively in contact with the plurality of electrodes E of the heater300. As representative examples of them, an electrode E4and an electrical contact C4are shown inFIG.2A.

FIG.2Bis an enlarged view showing the vicinity of the heater300in theFIG.2A. The heater300includes contact regions S2that are in contact with the heater support member240on a side opposite to the contact surface S1in contact with the fixing film210. The heater300also includes a non-contact region S3that is not in contact with the heater support member240. Although details will be described later, in the non-contact region S3, there is no component in contact with the heater300, except for an adhesive and the electrodes, and heat is unlikely to be transferred from the heater300to the heater support member240.

The following will describe a configuration of the heater300in detail with reference toFIGS.3A and3B.FIG.3Ais a schematic cross-sectional view of a layer configuration of the heater300according to the present embodiment, andFIG.3Bis a diagram showing configurations of layers of the heater300. InFIG.3A, a cross section of a portion in the vicinity of a conveying reference position X shown inFIG.3Bis shown. The conveying reference position X is defined as a reference position used when the recording material P is conveyed. In the present embodiment, the recording material P is conveyed in a manner such that the central portion of the recording material P in the width direction of the recording material P orthogonal to the conveying direction conforms to the conveying reference position X.

The surface protection layer308that is provided on the substrate305and slides with respect to the fixing film210can be broadly divided into a sliding surface layer1and a sliding surface layer2in this order from the substrate305based on a layer configuration of the surface protection layer308. Similarly, the surface protection layer307that is provided on the substrate305on a side opposite to the surface protection layer308can be broadly divided into a back surface layer1and a back surface layer2in this order from the substrate305based on a layer configuration of the surface protection layer307. The layer configurations will be described in detail later.

The heater300includes a first conductor301and a second conductor303that are provided on the surface on the back surface layer side, that is, on the back surface layer1. The first conductor301(301aand301b) extends in the longitudinal direction of the heater300. The first conductor301includes a conductor301aarranged on the upstream side in the conveying direction of the recording material P, and a conductor301barranged on the downstream side. The second conductor303(303-4in the vicinity of the conveying reference position X) is provided at a position different from the first conductor301in a short-side direction of the heater300that is orthogonal to the longitudinal direction thereof, and extends in the longitudinal direction of the heater300.

Between the first conductor301and the second conductor303, the heat generator302is provided that generates heat upon being supplied with power via the first conductor301and the second conductor303. The heat generator302includes a heat generator302a(302a-4in the vicinity of the conveying reference position X) arranged on the upstream side in the conveying direction of the recording material P in the present embodiment, and a heat generator302b(302b-4in the vicinity of the conveying reference position X) arranged on the downstream side.

Also, the insulating surface protection layer307(glass in the present embodiment) of the back surface layer2of the heater300covers the heat generator302, the first conductor301, and the second conductor303(303-4in the vicinity of the conveying reference position X) without covering the electrode portions (E4in the vicinity of the conveying reference position X).

FIG.3Bshows the layers (the back surface layer2, the back surface layer1, the sliding surface layer1, and the sliding surface layer2) of the heater300in a plane view. The back surface layer1of the heater300includes a plurality of heat generating blocks provided in the longitudinal direction of the heater300, each heat generating block being constituted by a pair of first conductor301, second conductor303, and heat generator302. The heater300of the present embodiment includes, in the longitudinal direction of the heater300, heat generating blocks HB1to HB7, which correspond to seven heating regions in total. The heat generating blocks HB1to HB7respectively include the heat generators302a-1to302a-7and the heat generators302b-1to302b-7that are formed symmetrically in the short-side direction of the heater300. The first conductor301is constituted by the conductors301aconnected to the heat generators (302a-1to302a-7), and the conductors301bconnected to the heat generators (302b-1to302b-7). Similarly, the second conductor303is divided into seven conductors303-1to303-7that correspond to the seven heat generating blocks HB1to HB7.

In the present embodiment, the conveying reference position X is located in the center of the heat generating block HB4, and the width of the heat generating block HB4in the longitudinal direction of the heater300is set to 150 mm in order to cover the paper width (148 mm) of the recording material P of the A5 size. Also, the heat generating blocks HB3and HB5each have a width of 17 mm in the longitudinal direction. This is because, in order for a heat generating region of the heat generating blocks HB3to HB5to cover the paper width (182 mm) of the B5 size, the width of the heat generating region in the longitudinal direction is set to 184 mm, which is slightly larger than the paper width. The heat generating blocks HB2and HB6each have a width of 14 mm in the longitudinal direction. This is because, in order for a heat generating region of the heat generating blocks HB2to HB6to cover the paper width (210 mm) of the A4 size, the width of the heat generating region in the longitudinal direction is set to 212 mm, which is slightly larger than the paper width. The heat generating blocks HB1and HB7each have a width of 4 mm in the longitudinal direction. This is because, in order for the heat generating blocks HB1to HB7to cover the paper width (215.9 mm) of the LTR size, the total width of the heat generating blocks HB1to HB7is set to 220 mm, which is larger than the paper width. Hereinafter, a description is given assuming that the region of the heat generating blocks HB1to HB7having the width of 220 mm in the longitudinal direction of the heater300is defined as a heat generating region L1of the heater (seeFIG.3B).

To supply the heater300with power from the control circuit40, electrical contacts C1to C7, C8-1, and C8-2are respectively connected to the electrodes E1to E7, E8-1, and E8-2. The electrodes E1to E7are electrodes for supplying power to the heat generating blocks HB1to HB7via the conductors303-1to303-7. The electrodes E8-1and E8-2are common electrodes that are used to supply power to the seven heat generating blocks HB1to HB7via the conductors301aand the conductor301b, and to which common electrical contacts are connected. Note that although, in the present embodiment, the electrodes E8-1and E8-2are provided at two ends of the heater300in the longitudinal direction, a configuration is also possible in which, for example, only the electrode E8-1is provided at one of the two ends, or different electrodes are provided between the upstream side and the downstream side in the conveying direction of the recording material P.

Also, the surface protection layer307of the back surface layer2of the heater300is formed without covering the positions of the electrodes E1to E7, E8-1, and E8-2, so that it is possible to connect the electrical contacts C1to C7, C8-1, and C8-2for power supply, which will be described in detail layer, to the electrodes from the back surface layer side of the heater300. That is to say, the configuration is such that power can be supplied from the back surface layer side of the heater300. Also, the heater300is configured to independently control power to be supplied to at least one heat generating block among the plurality of heat generating blocks, and power to be supplied to the remaining heat generating blocks. That is to say, with the control circuit40, the temperatures of the heat generating blocks HB1to HB7are respectively detected, and temperature control of the heat generators302a-1to302a-7and302b-1to302b-7is independently performed.

The sliding surface layer1on the sliding surface side of the heater300includes thermistors Th1to Th7serving as temperature detection elements for respectively detecting the temperature of the heat generating blocks HB1to HB7of the heater300. The thermistors Th1to Th7of the present embodiment are made of a thin material having NTC (Negative Temperature Coefficient) characteristics laid on the substrate. Note that the material may also have PTC (Positive Temperature Coefficient) characteristics. Since all of the heat generating blocks HB1to HB7include the thermistor Th, it is possible to detect the temperatures of all of the heat generating blocks HB by detecting resistance values of the thermistors Th.

The sliding surface layer1includes, as electrical contacts for electrifying the four thermistors Th1to Th4, conductors ET1-1to ET1-4for detecting resistance values of the thermistors Th1to Th4, and a common conductor EG1that is used in common for the thermistors Th1to Th4. The thermistors Th1to Th4, the conductors ET1-1to ET1-4, and the common conductor EG1constitute a thermistor block TB1.

Similarly, for electrifying the three thermistors Th5to Th7, the sliding surface layer1includes conductors ET2-5to ET2-7for detecting resistance values of the thermistors Th5to Th7, and a conductor EG2that is used in common for the thermistors Th5to Th7. The thermistors Th5to Th7, the conductors ET2-5to ET2-7, and the common conductor EG2constitute a thermistor block TB2.

The sliding surface layer2on the sliding surface side of the heater300includes the slidable surface protection layer308(glass in the present embodiment). Note however that the surface protection layer308does not cover the conductors ET1-1to ET1-4, ET2-5to ET2-7and the common conductors EG1and EG2, which are electrical contacts provided at both ends of the heater300in the longitudinal direction. This is because an FPC (Flexible Printed Circuits) is joined to the conductors ET1-1to ET1-4, ET2-5to ET2-7and the common conductors EG1and EG2, which are provided at both ends of the heater300in the longitudinal direction. In the present embodiment, an FPC601and an FPC602are provided as electrical wires for connecting the thermistors Th of the heater300and the control circuit40. The FPC601and the FPC602have the same conductor patterns as those of the conductors ET1-1to ET1-4, ET2-5to ET2-7and the common conductor EG1connected to the thermistors Th. The FPC601is joined to the conductors ET1-1to ET1-4and the common conductor EG1, and the FPC602is joined to the conductor ET2-5to ET2-7and the common conductor RG2, so that the FPC601and the FPC602function as the electrical wires.

As in the present embodiment, if a heat generating region with heat generators is divided into a plurality of regions, the number of temperature detection elements increases, and the number of electrical contacts at the ends of the heater also increases. There is also a limitation in the area at the ends of the heater in which electrical contacts are provided, and if, as described above, a large number of electrical contacts are to be provided at the ends of the heater, the electrical contacts need to be minimized. To do so, the electrical wires to be connected to the electrical contacts at the ends of the heater also need to be minimized. Therefore, it is preferable to use, as the electrical wire to be connected to the electrical contacts, a flexible sheet such as an FPC or an FFC (Flexible Flat Cable) that enables minimization of a connection to the electrical contact or a conduction path.

The FPC601and the FPC602are conductor pattern protection members that serve also as terminal connecting connectors. Here, at the ends of the heater300in the longitudinal direction, the conductors ET1-1to ET1-4and the common conductor EG1are aligned at equal interval in the short-side direction of the heater300. Similarly, at the ends of the heater300in the longitudinal direction, the conductors ET2-5to ET2-7, and the common conductor EG2are aligned at equal interval in the short-side direction of the heater300. The conductors ET1-1to ET1-4, and the common conductor EG1are arranged so as to overlap with a conductive wire connection portion of the FPC601, and the conductor ET2-5to ET2-7and the common conductor EG2are arranged so as to overlap with a conductive wire connection portion of the FPC602.

The FPC601and the FPC602of the present embodiment have a configuration in which a copper foil pattern serving as a conductive wire is interposed between polyimide films via an adhesive layer, and the copper foil pattern is exposed from the conductive wire connection portion. By joining the conductive wire-exposed portions of the FPC601and the FPC602to the conductors (ET1-1to ET1-4and ET2-5to ET2-7) and the common conductors (EG1and EG2) of the heater300using a solder serving as an adhesive, the FPCs and the conductors are connected.

Joint Configuration of Heater300and Heater Support Member240

The following will describe a joint configuration of the heater300and the heater support member240with reference toFIGS.4A to4D.FIG.4Ais a diagram showing the heater support member240where the heater300is removed, and showing a portion of the heater support member240that faces the back surface layer2of the heater300.FIG.4Bis a diagram showing a state in which the heater300, and the FPC601and FPC602are provided on the heater support member240.FIG.4Cis a cross-sectional view of a portion in the vicinity of the heater300, taken along a position Z in the longitudinal direction of the heater300inFIG.4A.FIG.4Dis a cross-sectional view of a portion in the vicinity of the longitudinal end of the heater300on the FPC601side, viewed at a central position Y in the short-side direction of the heater300.

The electrical contacts C1to C7, C8-1, and C8-2are connected to the electrodes E1to E7, E8-1, and E8-2of the heater300. As shown inFIG.4A, the heater support member240is open at positions at which the electrical contacts C1to C7, C8-1, and C8-2are arranged. With such a configuration, the electrodes E1to E7, E8-1, and E8-2can be electrically connected to the electrical contacts C1to C7, C8-1, and C8-2. Note that inFIG.4A, for clear illustration of the openings, the portions of the heater support member240other than the openings are filled or hatched.

In the present embodiment, an adhesive500is used to adhere the heater300to the heater support member240. This is because if the position of the heater is changed during image formation, a problem such as a defect in toner image fixation will occur. As in the present embodiment, in a configuration in which the heat generator is divided, and temperature adjustment is possible for each of the divided areas, a conveying region for the recording material P that is defined in the longitudinal direction of the heater300is determined based on information relating to the size of the recording material P, and a heat generation distribution that corresponds to the conveying region is formed. Accordingly, if the position of the heater300is changed in the longitudinal direction of the heater300, an area that generates an insufficient amount of heat will be located in the conveying region for the recording material P, the toner image on the recording material P cannot be heated, and thus the toner image cannot be fixed to the recording material P. In order to prevent such a situation, the heater300is adhered to the heater support member240. InFIG.4A, twelve positions on the heater support member240at which the adhesive500is arranged are defined as adhesion positions G1to G12, and are hatched.

In the present embodiment, the adhesion positions G1to G12of the heater support member240at which the adhesive500is arranged are aligned in the longitudinal direction of the heater300. By arranging adhesives500-1to500-12at the respective adhesion positions G1to G12, the heater300is adhered to the heater support member240. The adhesive500of the present embodiment is heat-resistant adhesive made of silicone rubber. Also, the amount of the adhesive that is applied to the adhesion positions G1to G12is about 13 mg.

InFIG.4A, the region of the heater support member240with which the contact regions S2of the heater300are in contact when the heater300is arranged on the heater support member240is hatched. The contact regions S2of the heater300are located at both ends of the heater300in the short-side direction as shown inFIG.2B, and extend over almost entire region of the heater300in the longitudinal direction as shown inFIG.4A. The contact regions S2are the smallest area required to sufficiently support the heater300with the heater support member240when the heater300is pressed by the pressure roller220with the fixing film210and the like interposed therebetween.

Of the surface of the heater300that is opposite to the contact surface S1in contact with the fixing film210, the portion except for the contact regions S2is defined as a non-contact region S3, which is not in contact with the heater support member240and in which there is no component in contact with the heater300, except for the adhesive500and the electrodes. This is because, by reducing the contact area between the heater300and the heater support member240, heat transfer from the heat generating region L1to the heater support member240is reduced and heat of the heater is efficiently transferred to the fixing film210. The non-contact region S3is located between the contact regions S2at both ends of the heater300in the short-side direction, and extends over the entire longitudinal region of the heater300. Note that in the present embodiment, the non-contact region S3extends to the ends of the heater300in the longitudinal direction, but it is sufficient that the non-contact region S3extends at least to positions at which the heat generator302is located.

Furthermore,FIG.4Ashows a region of the non-contact region S3excluding openings for the electrical contacts C and the adhesive arrangement positions G1to G12, as a non-contact surface H3of the heater support member240that is not in contact with the heater300. The non-contact surface H3is retracted from and is depressed with respect to the regions of the heater support member240with which the contact regions S2of the heater are in contact, in order to avoid contact with the heater300.

As shown inFIG.4C, a counter sinking is provided at each of the adhesion positions G1to G12of the heater support member240to prevent the adhesive500from running out and flowing to an unintended region. That is to say, the positions of the heater support member240at which the adhesive500is provided are retracted from the non-contact surface H3, and are depressed in a direction apart from the heater300.

The following will describe a joining material400, which is a joint portion of the heater300and the FPC601shown inFIG.4D. The joining material400of the present embodiment is solder that joins a conductive wire-exposed portion of the FPC601and a conductor ET1-2of the heater300. Note that the joining material400is not limited to solder, and any material can be used as long as it is conductive, is disposed between the heater300and the FPC601, and joins them together. Also, inFIG.4D, a heat generator end HE1, which is an end position in the heat generating region L1(first region) of the heater300on the FPC601side in the longitudinal direction of the heater300, is denoted by a dotted line. The heat generator end HE1serves as an end of the heat generator302a-1and an end of the heat generator302b-1in the longitudinal direction of the heater300. The heater300includes, in addition to the above-described heat generating region L1, a joint region L2(second region) with which the joining material400is in contact, and an intermediate region L3(third region) between the heat generating region L1and the joint region L2, in the longitudinal direction of the heater300. That is to say, the intermediate region L3is a region between the heat generator302and the joining material400in the longitudinal direction of the heater300.

As shown inFIG.4D, the adhesive500-2provided at the adhesion position G2is located in the intermediate region L3in the longitudinal direction of the heater300. On the other hand, the adhesive500-1provided at the adhesion position G1extends over the boundary between the joint region L2and the intermediate region L3in the longitudinal direction of the heater300.

The present embodiment of the present invention is characterized by a configuration in which the adhesives500-1and500-2are respectively arranged in the joint region L2and the intermediate region L3of the heater300. It is sufficient that the adhesive is provided in at least one of the joint region L2and the intermediate region L3. With this layout configuration of the adhesive500, when the heat generator302is supplied with power and generates heat, heat transferred from the heat generator end HE1via the substrate305of the heater300can be transferred to the heater support member240via the adhesives500-1and500-2. Accordingly, it is possible to reduce the heat transferred to the joining material400. Note that a cross section of a portion in the vicinity of the longitudinal end on the FPC602side has a symmetric structure with respect to that inFIG.4D. That is to say, in the present embodiment, the joining materials400are provided on both sides of the heat generating region L1in the longitudinal direction of the heater300, and the joint region L2and the intermediate region L3are located on both sides of the heat generating region L1.

Thus, according to the configuration of the present embodiment, if the heater300generates heat, heat transferred to the joining material from an end of the heat generator302in the longitudinal direction of the heater300is dispersed to the adhesive500, and thus it is possible to reduce the temperature ramp rate of the joining material. Therefore, it is possible to reduce cumulative thermal fatigue of the joining material, and prevent cracks or detachment of the flexible sheet.

Effects of Present Embodiment

The following will describe effects of reduction of the temperature ramp rate of the joint portion according to the present embodiment, in comparison with a comparative example. The comparative example has a configuration in which the adhesives500-1,500-2,500-11, and500-12of the present embodiment that are provided at longitudinal ends of the heater300are omitted.

The inventors of the present application conducted verification tests for the present embodiment and the comparative example to check effects of reduction of the temperature ramp rate. In the verification tests, the fixing apparatus200was set under the room temperature of 23° C., the thermistors Th1to Th7were turned on and were heated to 230° C. for about 7.0 seconds, and the temperatures of the thermistors Th1to Th7were adjusted to 230° C.FIG.5shows a temperature transition of the thermistor Th1at this time and temperature transitions of the joining material. Note that the temperature transitions of the joining material are substantially the same between the comparative example and the present embodiment, because the heater300has a left-right symmetric structure in the longitudinal direction, and the same positional relationship between the joining material and the peripheral components thereof.

As shown inFIG.5, the increase in temperature of the joining material is steeper in the comparative example, and the increase in temperature of the joining material is gentler in the present embodiment. Specifically, in the comparative example, it took 7.0 seconds until the temperature of the joining material reached 130° C., but in the present embodiment, it took 10.0 seconds until the temperature reached 130°, and the temperature ramp rate is low. It was considered because by providing the adhesives500-1and500-2, which are the thermal conductive members, heat was transferred also to the adhesives500-1and500-2, and was dispersed before transferred to the joining material400. Note that, in order to achieve sufficient effects of reduction of the temperature ramp rate, it is desirable that the contact thermal resistance of the thermal conductive member that is in contact with the heater is low. Therefore, as in the present embodiment, an adhesive with high adhesiveness at a contact portion with the heater is particularly effective.

Therefore, according to the configuration of the present embodiment, since the adhesive functions as the thermal conductive member and heat to be transferred to the joining material is dispersed, it is possible to reduce the temperature ramp rate of the joining material that connects the FPC and the electrical contacts of the heater. Accordingly, it is possible to suppress cumulative thermal fatigue of the joining material, thereby preventing occurrence of problems such as cracks in the joint portion or detachment of the flexible sheet. According to the configuration of the present embodiment, neither cracks in the solder nor detachment of the FPC occurred during the product lifetime.

The preferred embodiment of the present invention has been described so far, but the present invention is not limited to the embodiment, and various modifications and changes are possible without departing from the spirit of the invention. Although, in the present embodiment, a plurality of thermal conductive members (adhesive500) is provided between the heat generator end HE1and the joining material400to achieve sufficient effects of reduction of the temperature ramp rate, the same effects of reduction of the temperature ramp rate can be achieved even when, for example, only one thermal conductive member is provided. In such a configuration, the thermal conductive member may be provided only in the joint region L2or may be provided only in the intermediate region L3, but larger effects of reduction of increase in temperature of the joining material400can be achieved when the thermal conductive member is provided in the intermediate region L3.

Also, in the present embodiment, adhesive is used as the thermal conductive member that is in contact with the heater300and extends from the heat generator ends HE1and HE2to the joining material, but the configuration for realizing the same effects is not limited to this. For example, instead of the adhesives500-1,500-2,500-11, and500-12provided at two outer ends of the heat generator, heat conductive grease may be provided as the thermal conductive member on the heater. Alternatively, instead of the adhesives500-1,500-2,500-11, and500-12provided at two outer ends of the heat generator, the heater support member240may be in contact with the heater300, so that part of the heater support member240functions as the thermal conductive member.

This application claims the benefit of Japanese Patent Application No. 2022-091287, filed on Jun. 6, 2022, which is hereby incorporated by reference herein in its entirety.