JP2019179150A - Fixing device, image forming apparatus, and heat transfer device - Google Patents

Abstract

To provide a fixing device, an image forming apparatus, and a heat transfer device with which a function of heat transfer with a graphite sheet is sufficiently exhibited.SOLUTION: A fixing device comprises: an endless fixing belt 61; a heat source that heats the fixing belt 61; a pad member 63 that is arranged on an inner peripheral side of the fixing belt 61; a pressure rotating member 64 that is arranged opposite to the pad member 63 with the fixing belt 61 therebetween and presses the fixing belt 61 toward the pad member 63; and a heat transfer sheet 65 that is arranged between the pad member 63 and fixing belt 61. The heat transfer sheet 65 has a graphite sheet and a first adhesion layer that attaches the graphite sheet to the pad member 63. The heat transfer sheet 65 is provided with holes that at least penetrate the graphite sheet in its thickness direction.SELECTED DRAWING: Figure 3

Description

  The present invention relates to a fixing device, an image forming apparatus, and a heat transfer device.

  Regarding a conventional fixing device, for example, Japanese Patent Laying-Open No. 2015-64561 (Patent Document 1) discloses a fixing rotator and a counter rotator, a heating source for heating the fixing rotator, and an inner side of the fixing rotator. And a nip forming member. The nip forming member includes a base material and a first heat conductive member that is disposed on the nip portion side of the base material and has a thermal conductivity larger than that of the base material. A protruding portion protruding downward is formed on the nip outlet side of the first heat conducting member.

  Japanese Patent Laid-Open No. 2006-267410 (Patent Document 2) passes between a rotating member, a planar member having a heat conductive layer pressed against the rotating member, and the rotating member and the planar member. A fixing device is disclosed that includes heating means for applying heat to an unfixed toner image carried on a recording sheet. The heat conduction layer is made of a heat conduction anisotropic material having higher heat conductivity in the plane direction than in the thickness direction.

  Japanese Patent Laying-Open No. 2015-132722 (Patent Document 3) discloses a rotatable fixing roll, an endless belt that can move while contacting the fixing roll, and a fixing roll that faces the fixing roll via the endless belt. Disclosed is a fixing device including a pressure pad that is formed and a sliding sheet that is disposed over the nip portion and at least the downstream side in the sheet passing direction from the nip portion and reduces the frictional resistance between the pressure pad and the endless belt. Yes. The sliding sheet includes a nip portion corresponding portion provided corresponding to the nip portion, and a nip portion non-corresponding portion provided corresponding to a portion other than the nip portion and having a higher thermal conductivity than the nip portion corresponding portion.

Japanese Patent Laying-Open No. 2015-64561 JP 2006-267410 A Japanese Patent Laying-Open No. 2015-132722

  As disclosed in Patent Documents 1 to 3 above, a fixing device is known in which a recording medium such as paper is heated and pressed by a fixing belt to fix a toner image on the recording medium.

  In such a fixing device, assuming that a small size paper such as A6 or A5 is continuously passed through the fixing device, heat transfer from the fixing belt to the paper is not performed in the non-sheet passing region of the fixing belt. Since it does not advance, the temperature of the fixing belt locally increases. This causes a problem in that the fixing property of the toner image on the recording medium varies and the uniformity of the image quality is impaired.

  As a method for solving the above-mentioned problem, a method of adhering a highly heat conductive graphite sheet to a pad member against which the fixing belt is pressed can be considered. However, in such a measure, moisture contained in the adhesive evaporates due to heating during the fixing process, or air entrained between the pad member and the graphite sheet during bonding of the graphite sheet causes There is a possibility of thermal expansion due to heating. In these cases, there is a concern that the graphite sheet is damaged and the function of heat transfer by the graphite sheet is greatly impaired.

  SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to solve the above-described problems, and to provide a fixing device, an image forming apparatus, and a heat transfer device that can sufficiently perform a heat transfer function using a graphite sheet.

  A fixing device according to the present invention is arranged to face an endless fixing belt, a heat source for heating the fixing belt, a pad member disposed on the inner peripheral side of the fixing belt, and the pad member via the fixing belt. A pressure rotating member that presses the fixing belt toward the pad member, and a heat transfer sheet disposed between the pad member and the fixing belt. The heat transfer sheet includes a graphite sheet and a first adhesive layer that bonds the graphite sheet to the pad member. The heat transfer sheet is provided with a hole penetrating at least the graphite sheet in the thickness direction.

  According to the fixing device configured as described above, even if gas is generated from the first adhesive layer, the gas can be discharged to the outside through the hole. Thereby, the heat transfer function of the graphite sheet can be sufficiently exerted in the heat transfer sheet, and the local temperature rise of the fixing belt can be suppressed.

Preferably, the hole further penetrates the first adhesive layer.
According to the fixing device configured as described above, even if the gas entrained between the pad member and the first adhesive layer may thermally expand, the gas can be discharged to the outside through the hole.

Preferably, the heat transfer sheet is provided with a plurality of holes.
According to the fixing device configured as described above, the gas can be more reliably discharged to the outside through the plurality of holes.

  Preferably, when the first region where the first adhesive layer is provided and the second region where the first adhesive layer is not provided are defined on the surface of the graphite sheet, the hole is defined as the first region and the first region. It is provided only in the first region of the two regions.

  According to the fixing device configured as described above, since the hole is provided only in the first region where the gas may be present, the gas is suppressed while suppressing the strength reduction of the graphite sheet due to the provision of the hole. Can be discharged to the outside.

Preferably, the first adhesive layer is made of an acrylic or silicone adhesive.
According to the fixing device configured as described above, the adhesive force of the first adhesive layer can be maintained even in a high temperature environment.

  Preferably, the heat transfer sheet includes a plurality of graphite sheets stacked on each other in the thickness direction, and a second adhesive layer that bonds between adjacent graphite sheets. The holes are provided so as to penetrate the plurality of graphite sheets and the second adhesive layer in the stacking direction of the graphite sheets.

  According to the fixing device configured as described above, even if gas is generated from the second adhesive layer, the gas can be discharged to the outside through the hole.

  Preferably, the holes are provided so that the opening surfaces of the holes partially overlap between adjacent graphite sheets in the stacking direction.

  According to the fixing device configured as described above, the gas can be discharged to the outside while suppressing the strength reduction of the graphite sheet laminate due to the provision of the holes.

  Preferably, the graphite sheet is provided with a plurality of holes. A fixing nip portion is formed between the fixing belt and the pressure rotating member. When a third region facing the recording medium passing through the fixing nip portion and a fourth region not facing the recording medium passing through the fixing nip portion are defined on the surface of the graphite sheet, the plurality of holes are It is provided more densely in the fourth region than in the third region.

  According to the fixing device configured as described above, in the fourth region that does not face the recording medium that passes through the fixing nip portion, heat transfer from the fixing belt to the recording medium does not proceed, so the temperature of the fixing belt locally increases. Thus, it tends to lead to a phenomenon in which gas is inherent. For this reason, gas can be discharged | emitted more smoothly outside by providing a some hole relatively densely in the 4th area | region.

  Preferably, the graphite sheet is provided with a plurality of holes. A fixing nip portion is formed between the fixing belt and the pressure rotating member. The plurality of holes are provided side by side along a direction orthogonal to the passing direction of the recording medium in the fixing nip portion.

  According to the fixing device configured as described above, the hole can be a break point of heat transfer in the graphite sheet. For this reason, the plurality of holes are provided side by side along the direction orthogonal to the passing direction of the recording medium, so that heat can be smoothly moved along the direction orthogonal to the passing direction of the recording medium.

  Preferably, a fixing nip portion is formed between the fixing belt and the pressure rotating member. When the fifth region facing the fixing nip portion and the sixth region not facing the fixing nip portion are defined on the surface of the graphite sheet, the hole is the sixth of the fifth region and the sixth region. It is provided only in the area.

  According to the fixing device configured as described above, a large pressure acts on the graphite sheet from the pressure rotating member in the fifth region facing the fixing nip portion. For this reason, by avoiding the fifth region and providing a hole in the sixth region that does not face the fixing nip portion, it is possible to avoid damage to the graphite sheet starting from the hole.

  Preferably, the sixth area is located on the upstream side in the passing direction of the recording medium in the fixing nip portion as viewed from the fifth area.

  According to the fixing device configured as described above, the hole can be provided without affecting the separation property of the recording medium when discharged from the fixing nip portion.

  Preferably, the sixth area is located on the downstream side in the passing direction of the recording medium in the fixing nip portion as viewed from the fifth area.

  According to the fixing device configured as described above, the gas present in the fifth region facing the fixing nip portion is pushed out toward the sixth region as the recording medium passes. For this reason, gas can be discharged | emitted outside by providing a hole in the 6th area | region.

  Preferably, the heat transfer sheet is provided with a plurality of holes. When the graphite sheet has a thickness t, the interval L between adjacent holes satisfies the relationship 2t ≦ L ≦ 30 mm.

  According to the fixing device configured as described above, the breakage of the graphite sheet due to the provision of the holes can be effectively prevented when the distance L between the adjacent holes satisfies the relationship of 2t ≦ L. . Moreover, gas can be more reliably discharged | emitted outside by the space | interval L of the mutually adjacent hole satisfy | filling the relationship of L <= 30mm.

  An image forming apparatus according to the present invention includes a base member and a heat transfer sheet attached to the base member. The heat transfer sheet includes a graphite sheet and an adhesive layer that bonds the graphite sheet to the base member. The heat transfer sheet is provided with a hole penetrating at least the graphite sheet in the thickness direction.

  According to the image forming apparatus configured as described above, the gas generated inside the heat transfer sheet can be discharged to the outside through the holes. Thereby, the heat transfer function by the graphite sheet can be sufficiently exhibited in the heat transfer sheet.

  The heat transfer device according to the present invention includes a base member and a heat transfer sheet attached to the base member. The heat transfer sheet includes a graphite sheet and an adhesive layer that bonds the graphite sheet to the base member. The heat transfer sheet is provided with a hole penetrating at least the graphite sheet in the thickness direction.

  According to the heat transfer device configured as described above, the gas generated inside the heat transfer sheet can be discharged to the outside through the holes. Thereby, the heat transfer function by the graphite sheet can be sufficiently exhibited in the heat transfer sheet.

  As described above, according to the present invention, it is possible to provide a fixing device, an image forming apparatus, and a heat transfer device that can sufficiently exhibit the heat transfer function of the graphite sheet.

1 is a diagram schematically illustrating an overall configuration of an image forming apparatus. It is a figure which shows the fixing device in Embodiment 1 of this invention. FIG. 3 is a diagram illustrating a fixing device in a range surrounded by a two-dot chain line III in FIG. 2. It is sectional drawing which expands and shows the surface layer of the pad member in FIG. It is a perspective view which shows the process of sticking a heat-transfer sheet | seat on a pad member. It is sectional drawing which shows the modification of the heat-transfer sheet | seat shown in FIG. FIG. 3 is a diagram for explaining how heat is transmitted in the fixing device in FIG. 2. It is a top view which shows the heat-transfer sheet | seat in FIG. It is sectional drawing which shows a pad member and a heat-transfer sheet | seat (single layer type). It is sectional drawing which shows a pad member and a heat-transfer sheet | seat (lamination type). It is sectional drawing which shows the form from which gas is discharged | emitted from the inside of the heat-transfer sheet | seat in FIG. It is sectional drawing which shows another form from which gas is discharged | emitted from the inside of the heat-transfer sheet | seat in FIG. It is a top view which shows the 1st modification of the form with which a some hole is provided in a heat-transfer sheet | seat. It is a perspective view showing typically the 2nd modification of the form by which a plurality of holes are provided in a heat transfer sheet (lamination type). It is a top view which shows the 3rd modification of the form by which a some hole is provided in a heat exchanger sheet. It is a top view which shows the 3rd modification of the form by which a some hole is provided in a heat exchanger sheet. It is a top view which shows the 4th modification of the form by which a some hole is provided in a heat exchanger sheet. It is a top view which shows the 5th modification of the form by which a some hole is provided in a heat exchanger sheet. It is a top view which shows the 5th modification of the form by which a some hole is provided in a heat exchanger sheet. It is sectional drawing which shows the image forming apparatus and heat-transfer apparatus in Embodiment 3 of this invention. It is a photograph which shows the heat-transfer apparatus in an Example. It is a photograph which shows the heat-transfer apparatus for a comparison.

  Embodiments of the present invention will be described with reference to the drawings. In the drawings referred to below, the same or corresponding members are denoted by the same reference numerals.

(Embodiment 1)
FIG. 1 is a diagram schematically showing an overall configuration of an image forming apparatus. First, the overall configuration of the image forming apparatus will be described.

  Referring to FIG. 1, an image forming apparatus 1 is an intermediate transfer type color image forming apparatus using an electrophotographic process technology. The image forming apparatus 1 primarily transfers Y (yellow), M (magenta), C (cyan), and K (black) toner images formed on the photosensitive drum 413 to the intermediate transfer belt 21. The image forming apparatus 1 forms an image by superimposing four color toner images on the intermediate transfer belt 21 and then secondary-transferring them onto a transported recording medium. The recording medium is, for example, plain paper.

  The image forming apparatus 1 employs a tandem method. In the tandem method, the photosensitive drums 413 corresponding to the four colors of YMCK are arranged along the traveling direction of the intermediate transfer belt 21 (direction indicated by arrow A in FIG. 1). In the tandem system, four color toner images of YMCK are sequentially transferred onto the intermediate transfer belt 21 in a single procedure.

  The image forming apparatus 1 includes an image reading unit 10, an image processing unit 30, an image forming unit 40, a transport unit 50, and a fixing device 60.

  The image reading unit 10 includes an automatic document feeder 11 called an ADF (Auto Document Feeder) and a document image scanning device 12 (scanner). The automatic document feeder 11 transports a document J placed on a document tray by a transport mechanism and sends it out to a document image scanning device 12. The automatic document feeder 11 can continuously read images (including both sides) of a large number of documents J placed on the document tray all at once.

  The document image scanning device 12 optically scans a document conveyed on the contact glass from the automatic document feeder 11 or a document placed on the contact glass. The document image scanning device 12 forms an image of reflected light from the document on a light receiving surface of a CCD (Charge Coupled Device) sensor 12a, and reads the document image. The image reading unit 10 generates input image data based on the reading result by the document image scanning device 12. The input image data is subjected to predetermined image processing in the image processing unit 30.

  The image processing unit 30 includes a circuit that performs digital image processing according to initial settings or user settings on the input image data generated by the image reading unit 10. For example, the image processing unit 30 performs tone correction based on tone correction data (tone correction table).

  The image processing unit 30 performs various correction processing such as color correction and shading correction, compression processing, and the like on the input image data in addition to gradation correction. The image forming unit 40 is controlled based on the image data subjected to these processes.

  The image forming unit 40 includes image forming units 41Y, 41M, 41C, and 41K, and an intermediate transfer unit 42. The image forming units 41Y, 41M, 41C, and 41K and the intermediate transfer unit 42 are toners of each color of Y component, M component, C component, and K component based on the image data processed by the image processing unit 30. To form an image.

  The image forming units 41Y, 41M, 41C, and 41K have the same configuration. For convenience of illustration and explanation, common constituent elements are denoted by the same reference numerals, and Y, M, C, and K are added to the reference numerals when distinguished from each other. In FIG. 1, only the components of the image forming unit 41Y for the Y component are denoted by reference numerals, and the symbols of the other image forming units 41M, 41C, and 41K are omitted.

  The image forming unit 41 includes an exposure device 411, a developing device 412, a photosensitive drum 413, a charging device 414, and a drum cleaning device 415. The photoreceptor drum 413 is a negatively charged organic photoreceptor (OPC: Organic Photo-conductor) having an aluminum conductive cylinder (aluminum base tube). The drum diameter of the photosensitive drum 413 is, for example, 80 [mm]. An undercoat layer (UCL), a charge generation layer (CGL) and a charge transport layer (CTL) are sequentially stacked on the outer peripheral surface of the photosensitive drum 413. The photosensitive drum 413 rotates when power is transmitted from a drive motor (not shown).

  The charge generation layer is an organic semiconductor in which a charge generation material (for example, phthalocyanine pigment) is dispersed in a resin binder (for example, polycarbonate). The charge generation layer is exposed by the exposure device 411 to generate a pair of positive charges and negative charges.

  The charge transport layer is formed by dispersing a hole transport material (electron donating nitrogen-containing compound) in a resin binder (for example, polycarbonate). The charge transport layer transports positive charges generated in the charge generation layer to the surface of the charge transport layer.

  The charging device 414 uniformly charges the surface of the photoconductive drum 413 to a negative polarity. The exposure apparatus 411 is composed of, for example, a semiconductor laser. The exposure device 411 irradiates the photosensitive drum 413 with laser light corresponding to the image of each color component.

  A positive charge is generated in the charge generation layer of the photosensitive drum 413 and is transported to the surface of the charge transport layer, whereby the surface charge (negative charge) of the photosensitive drum 413 is neutralized. An electrostatic latent image of each color component is formed on the surface of the photosensitive drum 413 due to a potential difference from the surroundings.

  The developing device 412 is a two-component developing type developing device. The developing device 412 visualizes the electrostatic latent image by depositing toner of each color component on the surface of the photosensitive drum 413 to form a toner image.

  The drum cleaning device 415 includes a drum cleaning blade that is in sliding contact with the surface of the photosensitive drum 413. The drum cleaning device 415 removes toner remaining on the surface of the photosensitive drum 413 after the primary transfer.

  The intermediate transfer unit 42 includes an intermediate transfer belt 21, a primary transfer roller 422, a plurality of support rollers 423, a secondary transfer unit 23, and a belt cleaning device 426. The intermediate transfer belt 21 is endless. The intermediate transfer belt 21 is looped around a plurality of support rollers 423. At least one of the plurality of support rollers 423 is configured by a driving roller, and the other is configured by a driven roller.

  For example, it is preferable that the roller 423A disposed on the downstream side in the traveling direction of the intermediate transfer belt 21 with respect to the primary transfer roller 422K for the K component is a drive roller. This makes it easy to keep the running speed of the intermediate transfer belt 21 constant. As the roller 423A rotates, the intermediate transfer belt 21 travels in the direction of arrow A at a constant speed.

  The intermediate transfer belt 21 has conductivity and elasticity. The intermediate transfer belt 21 has a high resistance layer having a volume resistivity of, for example, 8 to 11 [log Ω · cm] on the surface. The intermediate transfer belt 21 is not limited in material, thickness and hardness as long as it has conductivity and elasticity.

  The primary transfer roller 422 is disposed on the inner peripheral surface side of the intermediate transfer belt 21. The primary transfer roller 422 is disposed to face the photosensitive drum 413. The primary transfer roller 422 is pressed against the photosensitive drum 413 with the intermediate transfer belt 21 interposed therebetween. Thereby, the primary transfer nip portion N1 is formed.

  When the intermediate transfer belt 21 passes through the primary transfer nip portion N <b> 1, the toner images on the photoconductive drum 413 are primarily transferred onto the intermediate transfer belt 21 in order. Specifically, a primary transfer bias is applied to the primary transfer roller 422, and a charge having a polarity opposite to that of the toner is applied to the back surface side of the intermediate transfer belt 21 (the side in contact with the primary transfer roller 422). As a result, the toner image is electrostatically transferred to the intermediate transfer belt 21.

  The toner image electrostatically transferred onto the intermediate transfer belt 21 is then conveyed to the secondary transfer unit 23. When the recording medium passes through the secondary transfer portion 23, the toner image on the intermediate transfer belt 21 is secondarily transferred to the recording medium. Specifically, a secondary transfer bias is applied to the secondary transfer roller 33, and a charge having a polarity opposite to that of the toner is applied to the side of the recording medium that contacts the secondary transfer roller 33. Thereby, the toner image is electrostatically transferred to the recording medium.

  The belt cleaning device 426 contacts the outer peripheral surface of the intermediate transfer belt 21. The belt cleaning device 426 removes toner remaining on the surface of the intermediate transfer belt 21 after the secondary transfer.

  The recording medium onto which the toner image has been transferred passes through the secondary transfer unit 23 and is then conveyed to the fixing device 60. The fixing device 60 fixes the toner image on the recording medium by heating and pressing the recording medium on which the toner image is secondarily transferred. Details of the fixing device 60 will be described later.

  The transport unit 50 transports a recording medium. The transport unit 50 includes a paper feed unit 51, a paper discharge unit 52, and a transport path unit 53. The paper feed unit 51 includes paper feed tray units 51a, 51b, and 51c. In the paper feed tray units 51a, 51b, 51c, paper S (standard paper, special paper) identified based on basis weight, size, or the like is stored for each preset type.

  The sheets S accommodated in the sheet feed tray units 51 a, 51 b, 51 c are sent one by one from the top and are conveyed to the conveyance path unit 53. The conveyance path unit 53 includes a plurality of conveyance roller pairs including a registration roller pair 53a. The registration roller portion in which the registration roller pair 53a is arranged corrects the tilt and deviation of the recording medium. The recording medium is conveyed to the secondary transfer unit 23 through the conveyance path unit 53. In the secondary transfer unit 23, the toner image on the intermediate transfer belt 21 is secondarily transferred to one side of the sheet S at a time, and a fixing process is performed in the subsequent fixing device 60.

  The recording medium that has passed through the fixing device 60 is conveyed to the paper discharge unit 52. The paper discharge unit 52 includes a transport roller pair (paper discharge roller pair) 52a. The recording medium on which the image has been formed is discharged to the outside through the transport roller pair 52a.

  Next, the structure of the fixing device 60 will be described in detail. FIG. 2 is a diagram showing a fixing device according to Embodiment 1 of the present invention.

  Referring to FIGS. 1 and 2, fixing device 60 in the present embodiment includes endless fixing belt 61, heat source 62, pad member 63, pressure rotating member 64, support member 66, and reflection. Member 111. The fixing device 60 is a direct heating (heating roller-less) method in which heat generated from the heat source 62 is directly transmitted to the fixing belt 61.

  The heat source 62 is composed of, for example, a halogen heater. The heat source 62 is disposed on the inner peripheral side of the fixing belt 61. The heat source 62 emits light to heat the fixing belt 61 from the inside. The fixing belt 61 is held by holding members at both ends. A temperature sensor (not shown) is provided on the outer peripheral side of the fixing belt 61 so that the heat source 62 can achieve a predetermined temperature target (for example, a fixing temperature within a range of 150 ° C. to 180 ° C.). Be controlled.

  The heat source 62 includes a long heater 62A and a short heater 62B. The length (heat source length) of the long heater 62 </ b> A in the axial direction of the pressure rotating member 64 is larger than the length (heat source length) of the short heater 62 </ b> B in the axial direction of the pressure rotating member 64. The heat source 62 is controlled so that the long heater 62A generates heat in a fixing process for a large size sheet, and the short heater 62B generates heat in a fixing process for a small size sheet (for example, A6 and A5 size sheets). .

  The pad member 63 is disposed on the inner peripheral side of the fixing belt 61. The pad member 63 is formed from a resin material. The pad member 63 is made of, for example, PPS (polyphenylene sulfide).

  The pressure rotating member 64 is made of a pressure roller, for example. The pressure rotating member 64 has an elastic layer formed of silicon rubber on the outer peripheral surface. The pressure rotating member 64 is disposed on the outer peripheral side of the fixing belt 61. The pressure rotating member 64 is disposed to face the pad member 63 with the fixing belt 61 interposed therebetween. The pressure rotating member 64 presses the fixing belt 61 toward the pad member 63. The pressure rotating member 64 is driven to rotate by a driving source (not shown). The pressure rotating member 64 conveys the recording medium 110 by following the rotation of the fixing belt 61.

  The support member 66 is disposed on the inner peripheral side of the fixing belt 61. The support member 66 extends in the direction of the rotation axis of the pressure rotation member 64 while having an L-shaped cross section. The support member 66 supports the pad member 63.

  The reflection member 111 is attached to the support member 66. The reflection member 111 is provided on the opposite side of the fixing belt 61 with respect to the heat source 62. The reflection member 111 is configured to reflect the radiant heat from the heat source 62 toward the fixing belt 61.

  The fixing belt 61 heated by the heat source 62 heats and pressurizes the recording medium 110 while conveying the recording medium 110 together with the pressure rotating member 64. As a result, the fixing device 60 fixes the toner image on the recording medium 110 to the recording medium 110.

  FIG. 3 is a diagram illustrating the fixing device in a range surrounded by a two-dot chain line III in FIG. 2. 4 is an enlarged cross-sectional view of the surface layer of the pad member in FIG.

  Referring to FIGS. 3 and 4, a fixing nip portion N is formed between the fixing belt 61 and the pressure rotating member 64. The fixing belt 61 and the pressure rotating member 64 are in pressure contact with each other at the fixing nip portion N.

  The fixing device 60 further includes a heat transfer sheet 65 and a sliding sheet 68. The heat transfer sheet 65 is provided between the pad member 63 and the fixing belt 61. The heat transfer sheet 65 is fixed to the pad member 63. The heat transfer sheet 65 is provided so as to cover the surface of the pad member 63 on the side where the pad member 63 faces the pressure rotating member 64.

  The sliding sheet 68 is provided between the heat transfer sheet 65 and the fixing belt 61. The sliding sheet 68 is fixed to the pad member 63. The sliding sheet 68 is provided to reduce the frictional force between the heat transfer sheet 65 and the fixing belt 61.

  The heat transfer sheet 65 includes a graphite sheet 121 and a first adhesive layer 131. The graphite sheet 121 has a higher thermal conductivity than aluminum or copper. The graphite sheet 121 has a characteristic that the thermal conductivity in the surface direction increases as the thickness (sheet thickness) decreases.

  The first adhesive layer 131 is provided between the pad member 63 and the graphite sheet 121. The first adhesive layer 131 bonds the graphite sheet 121 to the pad member 63. The 1st contact bonding layer 131 consists of a double-sided tape which has heat resistance, for example.

  The first adhesive layer 131 is preferably made of a silicone or acrylic adhesive. Depending on the temperature of the part to which the graphite sheet 121 is bonded, the silicone type and the acrylic type may be properly used.

  With such a configuration, the adhesive force of the first adhesive layer 131 can be maintained high even under a high temperature environment. A characteristic of acrylic adhesives is that they are excellent in weather resistance, heat resistance, solvent resistance, and the like. As a feature of the silicone-based adhesive, it is excellent in cold resistance and heat resistance, so that the use temperature range is wide.

  FIG. 5 is a perspective view showing a process of attaching a heat transfer sheet to the pad member. Referring to FIGS. 3 to 5, heat transfer sheet 65 has a first region 141 and a second region 142 on the surface thereof.

  The first region 141 is a region where the first adhesive layer 131 is provided on the surface of the graphite sheet 121. The second region 142 is a region where the first adhesive layer 131 is not provided on the surface of the graphite sheet 121. When the first adhesive layer 131 is made of double-sided tape, one side of the double-sided tape is stuck to the surface of the graphite sheet 121 corresponding to the first region 141 during the step of sticking the heat transfer sheet 65 to the pad member 63.

  The first area 141 is located on the downstream side in the passing direction of the recording medium 110 in the fixing nip portion N. The first region 141 includes a region (fifth region 156 in FIGS. 18 and 19 described later) facing the fixing nip N on the surface of the graphite sheet 121. The second region 142 is located on the upstream side in the passing direction of the recording medium 110 in the fixing nip portion N.

  Note that the arrangement of the first region 141 and the second region 142 is not limited to the above. For example, the second region 142 where the first adhesive layer 131 is not provided is upstream in the passing direction of the recording medium 110 in the fixing nip N. In addition to the end of the graphite sheet 121 on the side, it may also exist at the end of the graphite sheet 121 on the downstream side.

  An example of a specific configuration of the fixing device 60 will be described. In consideration of heat resistance, strength, and surface smoothness, the fixing belt 61 includes a PI base material (base material) having a thickness of 60 μm, a rubber layer (elastic layer) having a thickness of 200 μm, and a PFA tube (release layer) having a thickness of 30 μm. ) And three layers (diameter 30 mm).

  The pressure rotating member 64 is a pressure roller having a diameter of 25 mm. The pressure rotating member 64 has a rubber layer (thickness 3 mm) disposed on the outer peripheral surface thereof and a graphite layer.

  The heat source 62 is composed of a halogen heater having a tube diameter of 5.5 mm. The heat source 62 includes a long heater that emits full width light and a short heater that emits light at the center. The support member 66 is made of a SECC plate (thickness: 2 mm). The reflecting member 111 is made of an aluminum reflecting plate having a thickness of 0.5 mm.

  The pad member 63 is made of a liquid crystal polymer. The heat transfer sheet 65 includes a graphite sheet 121 having a thickness of 40 μm and a first adhesive layer 131 made of a double-sided tape. For the first adhesive layer 131, a silicone-based adhesive is used.

  FIG. 6 is a cross-sectional view showing a modification of the heat transfer sheet shown in FIG. With reference to FIG. 6, in this modification, the heat transfer sheet 65 includes a plurality of graphite sheets 121, a first adhesive layer 131, and a second adhesive layer 132.

  The plurality of graphite sheets 121 are stacked on each other in the thickness direction indicated by the arrow 101. The first adhesive layer 131 is provided between the pad member 63 and the graphite sheet 121 located at the lowest layer in the stacking direction of the graphite sheets 121. The second adhesive layer 132 is provided between the graphite sheets 121 adjacent to each other in the stacking direction. The second adhesive layer 132 bonds the graphite sheets 121 adjacent to each other in the stacking direction.

  In the following, the heat transfer sheet 65 having one graphite sheet 121 shown in FIG. 4 is referred to as a “single layer type”, and the heat transfer sheet 65 having a plurality of graphite sheets 121 shown in FIG. It is called “stacked type”.

  FIG. 7 is a diagram for explaining how heat is transmitted in the fixing device in FIG. 2. In FIG. 7, an endless fixing belt 61 and a heat source 62, a support member 66, a pad member 63, and a heat transfer sheet 65 disposed inside the fixing belt 61 at both ends are schematically shown. ing. DR1 indicates the rotational axis direction of the pressure rotating member 64, and is hereinafter referred to as “axial direction DR1”.

  Referring to FIG. 7, heat source 62 has a length H (hereinafter referred to as “heat source length H”) in axial direction DR1. The heat source 62 heats the fixing belt 61 from the inner peripheral side over the heat source length H (arrow Z in FIG. 7).

  The width of a recording medium such as a sheet passing through the fixing nip N is defined as D (hereinafter referred to as “sheet width D”). A dotted line shown in FIG. 7 is an area through which the sheet passes through the fixing nip N (hereinafter referred to as “sheet passing area”). In the paper passing area, the heat of the fixing belt 61 is transmitted to the paper, and therefore the temperature of the fixing belt 61 (area F in FIG. 7) in the paper passing area does not increase greatly even if the paper is continuously passed. .

  However, the heat source length H needs to be larger than the paper width D so that the entire maximum paper width can be heated during the fixing process. In this case, a region of the fixing belt 61 that is heated over the heat source length H (hereinafter referred to as “heating region”) and is also a non-sheet passing region (hereinafter referred to as “end region R”). Will exist). Even if the temperature of the end region R rises greatly due to continuous paper passing, the heat is not transferred to the paper, so the temperature of the end region R rises greatly. Such a temperature rise in the end region R is likely to occur when printing on a sheet having a small sheet width such as A5 or A6.

  In the fixing device 60 in the present embodiment, a heat transfer sheet 65 having a highly heat conductive graphite sheet 121 is disposed between the pad member 63 and the fixing belt 61 in order to suppress a temperature rise in the end region R. Has been.

  The heat of the fixing belt 61 in the end region R is transmitted to the heat transfer sheet 65 (arrow C in FIG. 7). The heat transmitted to the heat transfer sheet 65 is diffused throughout the heat transfer sheet 65 in the axial direction DR1 (arrow E in FIG. 7). The diffused heat is transmitted to the low temperature portion I (the non-sheet passing area and the non-heated area) of the fixing belt 61 (arrow G in FIG. 7).

  As described above, the heat transfer function by the graphite sheet 121 is exhibited, so that the heat in the end region R is dispersed throughout the fixing belt 61, and as a result, the fixing belt 61 has a soaking effect.

  In addition, when the laminated type heat transfer sheet 65 shown in FIG. 6 is used, the graphite sheet 121 has a characteristic that the thermal conductivity in the surface direction increases as the thickness decreases, so the thickness of the heat transfer sheet 65 ( High thermal conductivity can be obtained in the heat transfer sheet 65 while keeping the heat capacity) small. Thereby, the soaking effect of the fixing belt 61 by the heat transfer sheet 65 can be enhanced.

  FIG. 8 is a plan view showing the heat transfer sheet in FIG. 5. FIG. 9 is a cross-sectional view showing a pad member and a heat transfer sheet (single layer type). FIG. 10 is a cross-sectional view showing a pad member and a heat transfer sheet (laminated type).

  With reference to FIGS. 8 to 10, the heat transfer sheet 65 is provided with holes 146. The hole 146 is provided so as to penetrate the graphite sheet 121 in the thickness direction. The hole 146 is further provided so as to penetrate the first adhesive layer 131.

  The holes 146 are provided so as to reach from the outer surface of the heat transfer sheet 65 facing the fixing belt 61 to the inner surface of the heat transfer sheet 65 facing the pad member 63. The hole 146 continuously extends between the outer surface of the heat transfer sheet 65 facing the fixing belt 61 and the inner surface of the heat transfer sheet 65 facing the pad member 63.

  The hole 146 is not a hole existing in the molecular structure of the graphite sheet 121, but is a hole obtained by drilling the graphite sheet 121. Although the kind of process is not specifically limited, For example, the machining using the various tools for drilling may be sufficient, and laser processing may be sufficient.

  A plurality of holes 146 are provided in the heat transfer sheet 65. The plurality of holes 146 are provided to be spaced from each other. The plurality of holes 146 are provided over the entire region on the surface of the heat transfer sheet 65. The plurality of holes 146 are provided over both the first region 141 and the second region 142.

  Further, in the laminated type heat transfer sheet 65 shown in FIG. 10, the holes 146 are provided in the lamination direction of the graphite sheet 121, the first adhesive layer 131, the plurality of graphite sheets 121, and the (multiple) second adhesion. It is provided so as to penetrate the layer 132.

  In the drawings of the present application, a plurality of holes 146 are drawn larger than the actual size for the purpose of illustration.

  FIG. 11 is a cross-sectional view showing a form in which gas is discharged from the inside of the heat transfer sheet in FIG. 9. FIG. 12 is a cross-sectional view showing another embodiment in which gas is discharged from the inside of the heat transfer sheet in FIG. 9.

  Referring to FIGS. 5 and 11, during the process of attaching heat transfer sheet 65 to pad member 63, there is a possibility that gas (air) may be caught between pad member 63 and first adhesive layer 131. In particular, when the step of attaching the heat transfer sheet 65 is performed manually, there is a high possibility that gas (air) is involved. If the gas entrained between the pad member 63 and the first adhesive layer 131 is thermally expanded by heating in the fixing process, the graphite sheet 121 may be wrinkled, which may lead to peeling of the graphite sheet 121. When the graphite sheet 121 is peeled off from the pad member 63, the graphite sheet 121 is broken from the portion, and there is a problem that the graphite sheet 121 does not sufficiently exhibit the heat transfer function.

  On the other hand, in the present embodiment, since the plurality of holes 146 are provided in the heat transfer sheet 65, the thermally expanded gas can be discharged to the outside through the plurality of holes 146. For this reason, it is possible to prevent the graphite sheet 121 from being peeled off from the pad member 63. Thereby, the heat transfer function by the graphite sheet 121 can be sufficiently exhibited in the heat transfer sheet 65, and a local temperature increase of the fixing belt 61 can be suppressed.

  Referring to FIG. 12, with the heating in the fixing process, moisture contained in first adhesive layer 131 may evaporate, and gas (water vapor) may accumulate between first adhesive layer 131 and graphite sheet 121. There is. Such a phenomenon becomes remarkable under a temperature condition of 100 ° C. or higher. In this case as well, the graphite sheet 121 may be peeled off as before.

  On the other hand, in the present embodiment, since the plurality of holes 146 are provided in the heat transfer sheet 65, the gas generated from the first adhesive layer 131 can be discharged to the outside through the plurality of holes 146. .

  In the present embodiment, the configuration in which the hole 146 penetrates both the first adhesive layer 131 and the graphite sheet 121 has been described. However, the present invention is not limited to this, and the hole 146 has the first adhesive layer 131 and the graphite sheet 121. It is good also as a structure which penetrates only the graphite sheet 121 of them. In this case, the gas generated from the first adhesive layer 131 and accumulated between the first adhesive layer 131 and the graphite sheet 121 can be discharged to the outside through the plurality of holes 146.

  Referring to FIGS. 8 and 9, hole 146 has an opening area that allows gas to pass therethrough. For example, the diameter of the hole 146 is 0.01 μm or more.

  When the graphite sheet 121 has a thickness t (in the case of a laminated type, the thickness of the graphite sheet 121 that is the thinnest among the plurality of graphite sheets 121), the diameter R of the hole 146 satisfies the relationship t ≦ R <2 mm. It is preferable. When the diameter R of the hole 146 satisfies the relationship of t ≦ R, the hole 146 can be provided in the graphite sheet 121 at low cost without using special processing such as laser processing. When the diameter R of the hole 146 satisfies the relationship R <2 mm, the graphite sheet 121 can be effectively prevented from being damaged starting from the hole 146.

  When the graphite sheet 121 has a thickness t (in the case of a laminated type, the thickness of the graphite sheet 121 that is the thinnest among the plurality of graphite sheets 121), the interval L between the adjacent holes 146 is 2t ≦ L ≦ 30 mm. It is preferable to satisfy the relationship. When the distance L between the adjacent holes 146 satisfies the relationship of 2t ≦ L, it is possible to effectively prevent the graphite sheet 121 from being damaged due to the provision of the plurality of holes 146. Further, when the interval L between the adjacent holes 146 satisfies the relationship of L ≦ 30 mm, the gas can be more reliably discharged to the outside through the plurality of holes 146.

  The plurality of holes 146 are provided over both the first region 141 and the second region 142. According to such a configuration, since it is not necessary to selectively provide the plurality of holes 146 in a specific region of the heat transfer sheet 65, the heat transfer sheet 65 can be manufactured at low cost.

  In the above description, the effect of exhausting the gas from the inside of the single-layer type heat transfer sheet 65 shown in FIG. 9 has been described. However, the same effect can be obtained in the stacked-type heat transfer sheet 65 shown in FIG. Is done.

  In addition, in the laminated heat transfer sheet 65, there is a possibility that gas (water vapor) is also generated from the second adhesive layer 132 disposed between the layers of the graphite sheet 121. By providing a hole 146 so as to pass through the plurality of graphite sheets 121 and the second adhesive layer 132 between adjacent graphite sheets 121, the gas (water vapor) generated from the second adhesive layer 132 is discharged to the outside. be able to.

  The structure of the fixing device 60 according to the first embodiment of the present invention described above will be described together. The fixing device 60 according to the present embodiment is a fixing device that fixes a toner image on a recording medium. The fixing device 60 has an endless fixing belt 61, a heat source 62 for heating the fixing belt 61, a pad member 63 disposed on the inner peripheral side of the fixing belt 61, and the pad member 63 via the fixing belt 61. A pressure rotating member 64 that presses the fixing belt 61 toward the pad member 63, and a heat transfer sheet 65 that is disposed between the pad member 63 and the fixing belt 61. The heat transfer sheet 65 includes a graphite sheet 121 and a first adhesive layer 131 that bonds the graphite sheet 121 to the pad member 63. The heat transfer sheet 65 is provided with a hole 146 that penetrates at least the graphite sheet 121 in the thickness direction.

  According to the fixing device 60 configured as described above in the first embodiment of the present invention, the heat transfer sheet 65 sufficiently exhibits the function of heat transfer by the graphite sheet 121, and the local temperature of the fixing belt 61. The rise can be suppressed.

(Embodiment 2)
In the present embodiment, various modifications of the embodiment in which a plurality of holes 146 are provided in the heat transfer sheet 65 will be described.

  FIG. 13: is a top view which shows the 1st modification of the form by which a some hole is provided in a heat-transfer sheet | seat. FIG. 13 and FIGS. 15 to 19 described later correspond to FIG. 8 in the first embodiment.

  Referring to FIG. 13, in the present modification, a plurality of holes 146 are provided only in first region 141 of first region 141 and second region 142.

  In the second region 142, since the first adhesive layer 131 is not provided, a gas (air) is entrained between the pad member 63 and the first adhesive layer 131 during the step of attaching the heat transfer sheet 65, There is no possibility that gas (water vapor) generated from the first adhesive layer 131 is accumulated between the first adhesive layer 131 and the graphite sheet 121. For this reason, by providing a plurality of holes 146 only in the first region 141 where the first adhesive layer 131 is provided, gas is suppressed while suppressing a decrease in strength of the graphite sheet 121 due to the provision of the plurality of holes 146. It can be discharged to the outside.

  FIG. 14 is a perspective view schematically showing a second modification example in which a plurality of holes are provided in a heat transfer sheet (laminated type).

  Referring to FIG. 14, in this modification, hole 146 is provided such that the opening surface of hole 146 partially overlaps between graphite sheets 121 adjacent to each other in the stacking direction.

  FIG. 14 schematically shows a plurality of graphite sheets 121A, 121B, and 121C stacked on each other. The hole 146 forms an opening surface 147A in the graphite sheet 121A, forms an opening surface 147B in the graphite sheet 121B, and forms an opening surface 147C in the graphite sheet 121C. The hole 146 is provided so that the opening surface 147A and the opening surface 147B partially overlap and the opening surface 147B and the opening surface 147C partially overlap as viewed from the stacking direction of the plurality of graphite sheets 121.

  According to such a configuration, it is possible to suppress a decrease in strength of the laminate of the graphite sheets 121 due to the provision of the holes 146. Further, in the manufacturing process of the heat transfer sheet 65, when the holes 146 are provided in each of the plurality of graphite sheets 121, and then the plurality of graphite sheets 121 are laminated and bonded together, Mutual positioning accuracy is not required. For this reason, the manufacturing process of the heat transfer sheet 65 can be easily performed.

  As shown in FIG. 14, the hole 146 provided so that the opening surface of the hole 146 partially overlaps between the graphite sheets 121 adjacent to each other in the stacking direction, and the opening surface of the hole 146 includes a plurality of sheets. The holes 146 provided so as to be aligned between the graphite sheets 121 may be mixed and provided.

  FIG. 15 and FIG. 16 are plan views showing a third modification example in which a plurality of holes are provided in the heat transfer sheet.

  Referring to FIGS. 15 and 16, on the surface of the graphite sheet 121, a third region 151 facing the recording medium passing through the fixing nip portion N and a fourth region not facing the recording medium passing through the fixing nip portion N are shown. A region 152 is defined.

  The recording medium that serves as a reference when defining the third area 151 and the fourth area 152 is a minimum-size recording medium among the recording media applied to the fixing device 60, for example, A6 size paper. In this case, the third region 151 has the same length as the width of the A6 size paper in the direction perpendicular to the passing direction of the recording medium (paper) in the fixing nip portion N (the rotational axis direction of the pressure rotating member 64). The fourth area 152 is defined on both sides of the third area 151 in a direction perpendicular to the recording medium (paper) passing direction in the fixing nip portion N.

  In this modification, the plurality of holes 146 are provided more densely in the fourth region 152 than in the third region 151. The number of holes 146 per unit area in the fourth region 152 is larger than the number of holes 146 per unit area in the third region 151. As shown in FIG. 16, the third region 151 may not be provided with the hole 146.

  In such a configuration, in the fourth region 152 that does not face the recording medium that passes through the fixing nip portion N, heat transfer from the fixing belt 61 to the recording medium does not proceed, so that a phenomenon in which the temperature of the fixing belt 61 rises easily occurs. . For this reason, by providing the plurality of holes 146 relatively densely in the fourth region 152, the gas can be smoothly discharged to the outside.

  FIG. 17 is a plan view showing a fourth modification example in which a plurality of holes are provided in the heat transfer sheet. Referring to FIG. 17, in the present modification, a plurality of holes 146 are provided side by side along a direction orthogonal to the recording medium passing direction in fixing nip portion N indicated by arrow 201.

  In FIG. 17, a configuration in which a plurality of holes 146 are provided in two rows is shown, but the present invention is not limited to this, and the plurality of holes 146 may be provided in a row, or three or more. May be provided in a plurality of rows.

  In such a configuration, the hole 146 penetrating the graphite sheet 121 can be a break point of heat transfer in the graphite sheet 121. For this reason, by providing a plurality of holes 146 along the direction perpendicular to the recording medium passing direction in the fixing nip portion N, the chance of the heat transfer in the graphite sheet 121 being divided along the holes 146 is reduced. Can do. Thereby, the function of heat transfer by the graphite sheet 121 can be further enhanced.

  FIG. 18 and FIG. 19 are plan views showing a fifth modification example in which a plurality of holes are provided in the heat transfer sheet.

  With reference to FIGS. 3, 18 and 19, a fifth region 156 facing the fixing nip portion N and a sixth region 157 not facing the fixing nip portion N are defined on the surface of the graphite sheet 121. Yes. In the present modification, the plurality of holes 146 are provided only in the sixth region 157 of the fifth region 156 and the sixth region 157.

  According to such a configuration, a large pressure acts on the surface of the graphite sheet 121 from the pressure rotating member 64 in the fifth region 156 facing the fixing nip portion N. For this reason, by avoiding the fifth region 156 and providing the plurality of holes 146 in the sixth region 157 that does not face the fixing nip portion N, damage to the graphite sheet 121 starting from the holes 146 can be avoided.

  In the heat transfer sheet 65 shown in FIG. 18, the sixth region 157 is located upstream of the fixing nip portion N in the recording medium passing direction when viewed from the fifth region 156. According to such a configuration, the plurality of holes 146 can be provided without affecting the separability of the recording medium when the recording medium is discharged from the fixing nip portion N.

  In the heat transfer sheet 65 shown in FIG. 19, the sixth region 157 is located on the downstream side of the fixing nip portion N in the recording medium passing direction when viewed from the fifth region 156. According to such a configuration, the gas generated in the fifth region 156 facing the fixing nip N is pushed out toward the sixth region 157 on the downstream side as the recording medium passes. For this reason, by providing the plurality of holes 146 in the sixth region 157, the gas can be discharged to the outside.

  In addition, you may combine suitably the various modifications of the form provided with the some hole 146 in the heat-transfer sheet | seat 65 demonstrated above.

  According to the fixing device in the second embodiment of the present invention described above, the effects described in the first embodiment can be similarly obtained.

(Embodiment 3)
In the present embodiment, an embodiment of an image forming apparatus and a heat transfer device will be described. FIG. 20 is a cross-sectional view showing an image forming apparatus and a heat transfer device according to Embodiment 3 of the present invention.

  Image forming apparatus 200 </ b> A and heat transfer apparatus 200 </ b> B in the present embodiment include base member 240 and heat transfer sheet 230 attached to base member 240. The heat transfer sheet 230 includes a graphite sheet 220 and an adhesive layer 210 that bonds the graphite sheet 220 to the base member 240. The heat transfer sheet 230 is provided with (a plurality of) holes 250 penetrating at least the graphite sheet 220 in the thickness direction.

  Base member 240 corresponds to pad member 63 in the first and second embodiments. The heat transfer sheet 230 corresponds to the heat transfer sheet 65 in the first embodiment and the second embodiment, and various modifications of the heat transfer sheet 65 described above can be applied. The graphite sheet 220 in the heat transfer sheet 230 has a function of transferring heat from the high temperature side to the low temperature side.

  A specific example of the configuration of the image forming apparatus 200 </ b> A will be described. A sheet guide unit provided before and after the fixing device 60 in FIG. 1 or a sheet from the secondary transfer unit 23 in FIG. 1 toward the fixing device 60. A heat transfer sheet 230 for dissipating heat received from the heat source 62 of the fixing device 60 may be affixed to the base member 240 using the guide portion of the sheet for feeding out the base member 240. Further, the support member 66 in the fixing device 60 or the power supply mounting plate provided in the image forming apparatus 200 </ b> A may be used as the base member 240, and the heat transfer sheet 230 for heat dissipation may be attached to the base member 240.

  A specific example of the configuration of the heat transfer device 200B will be described. In addition to the example in the image forming apparatus 200A described above, the case of the smartphone is used as the base member 240, and the heat transfer sheet 230 for heat dissipation is attached to the base member 240. May be.

  According to the image forming apparatus 200A and the heat transfer apparatus 200B according to the third embodiment of the present invention configured as described above, the gas generated inside the heat transfer sheet 230 can be discharged to the outside through the holes 250. Thereby, in the heat transfer sheet 230, the function of heat transfer by the graphite sheet 220 can be sufficiently exhibited.

  FIG. 21 is a photograph showing the heat transfer device in the example. FIG. 22 is a photograph showing a heat transfer device for comparison.

  In the heat transfer device in the example shown in FIG. 21, the graphite sheet 220 having been subjected to hole processing was attached to a glass plate (base member 240) via a double-sided tape (adhesive layer 210). In the heat transfer device for comparison shown in FIG. 22, an unprocessed graphite sheet was attached to a glass plate via a double-sided tape. The glass plate with the graphite sheet attached was left in an oven at 250 ° C. for 24 hours. Thereafter, the glass plate was taken out of the oven into a room temperature laboratory and photographed.

  In the heat transfer device for comparison shown in FIG. 22, the graphite sheet floated due to the expansion of air, and wrinkles due to the float were also observed. On the other hand, in the heat transfer device in the example shown in FIG. 21, the graphite sheet did not float.

  The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

  The present invention is applied to a fixing device, an image forming apparatus, and a heat transfer device.

  1,200A image forming apparatus, 10 image reading unit, 11 automatic document feeder, 12 document image scanning device, 12a CCD sensor, 21 intermediate transfer belt, 23 secondary transfer unit, 30 image processing unit, 33 secondary transfer roller 40, image forming unit, 41, 41C, 41K, 41M, 41Y image forming unit, 42 intermediate transfer unit, 50 transport unit, 51 paper feed unit, 51a, 51b, 51c paper feed tray unit, 52 paper discharge unit, 52a transport Roller pair, 53 Conveyance path section, 53a Registration roller pair, 60 Fixing device, 61 Fixing belt, 62 Heat source, 62A Long heater, 62B Short heater, 63 Pad member, 64 Pressure rotating member, 65, 230 Heat transfer sheet, 66 Support member, 68 sliding sheet, 110 recording medium, 111 reflecting member, 121, 21A, 121B, 121C, 220 Graphite sheet, 131 1st adhesive layer, 132 2nd adhesive layer, 141 1st region, 142 2nd region, 146,250 hole, 147A, 147B, 147C Opening surface, 151 3rd region, 152 4th area, 156 5th area, 157 6th area, 200B Heat transfer device, 210 Adhesive layer, 240 Base member, 411 Exposure device, 412 Development device, 413 Photosensitive drum, 414 Charging device, 415 Drum cleaning device, 422 Primary transfer roller, 423 Support roller, 426 Belt cleaning device.

Claims (15)

An endless fixing belt,
A heat source for heating the fixing belt;
A pad member disposed on the inner peripheral side of the fixing belt;
A pressure rotating member that is disposed to face the pad member via the fixing belt and presses the fixing belt toward the pad member;
A heat transfer sheet disposed between the pad member and the fixing belt,
The heat transfer sheet has a graphite sheet and a first adhesive layer that bonds the graphite sheet to the pad member,
The fixing device, wherein the heat transfer sheet is provided with a hole penetrating at least the graphite sheet in a thickness direction thereof.   The fixing device according to claim 1, wherein the hole further penetrates the first adhesive layer.   The fixing device according to claim 1, wherein the heat transfer sheet is provided with a plurality of the holes.   When the first region where the first adhesive layer is provided and the second region where the first adhesive layer is not provided are defined on the surface of the graphite sheet, the hole is defined as the first region and The fixing device according to claim 1, wherein the fixing device is provided only in the first area of the second area.   The fixing device according to claim 1, wherein the first adhesive layer is made of an acrylic or silicone adhesive. The heat transfer sheet has a plurality of the graphite sheets stacked on each other in the thickness direction, and a second adhesive layer that bonds between the adjacent graphite sheets,
6. The fixing device according to claim 1, wherein the hole is provided so as to penetrate a plurality of the graphite sheets and the second adhesive layer in a stacking direction of the graphite sheets.   The fixing device according to claim 6, wherein the hole is provided such that an opening surface of the hole partially overlaps between the graphite sheets adjacent to each other in the stacking direction. The graphite sheet is provided with a plurality of the holes,
A fixing nip portion is formed between the fixing belt and the pressure rotating member,
When a third region facing the recording medium passing through the fixing nip portion and a fourth region not facing the recording medium passing through the fixing nip portion are defined on the surface of the graphite sheet, a plurality of regions are defined. The fixing device according to claim 1, wherein the holes are provided more densely in the fourth region than in the third region. The graphite sheet is provided with a plurality of the holes,
A fixing nip portion is formed between the fixing belt and the pressure rotating member,
The fixing device according to claim 1, wherein the plurality of holes are provided side by side along a direction orthogonal to a passing direction of the recording medium in the fixing nip portion. A fixing nip portion is formed between the fixing belt and the pressure rotating member,
In the case where a fifth region facing the fixing nip portion and a sixth region not facing the fixing nip portion are defined on the surface of the graphite sheet, the hole includes the fifth region and the sixth region. The fixing device according to claim 1, wherein the fixing device is provided only in the sixth region of the regions.   The fixing device according to claim 10, wherein the sixth area is located upstream of the fixing nip portion in the recording medium passing direction when viewed from the fifth area.   The fixing device according to claim 10, wherein the sixth area is located downstream of the fixing nip portion in the recording medium passing direction when viewed from the fifth area. The heat transfer sheet is provided with a plurality of the holes,
13. The fixing device according to claim 1, wherein when the graphite sheet has a thickness t, an interval L between the adjacent holes satisfies a relationship of 2t ≦ L ≦ 30 mm. A base member;
A heat transfer sheet attached to the base member,
The heat transfer sheet has a graphite sheet, and an adhesive layer that bonds the graphite sheet to the base member,
The image forming apparatus, wherein the heat transfer sheet is provided with a hole penetrating at least the graphite sheet in a thickness direction thereof. A base member;
A heat transfer sheet attached to the base member,
The heat transfer sheet has a graphite sheet, and an adhesive layer that bonds the graphite sheet to the base member,
The heat transfer device is provided with a hole penetrating at least the graphite sheet in a thickness direction thereof.