Fixing device

Abstract

To provide a fixing device capable of stabilizing behavior of a sheet.SOLUTION: A fixing device 1 includes: a tubular belt 10; a plate-like heater 20 disposed inside the belt 10; a pressure roller 50 forming a nip part NP between the belt 10 and itself, the pressure roller 50 for conveying a sheet S between the belt 10 and itself in a conveyance direction orthogonal to both a longitudinal direction of the heater 20 and the thickness direction of the heater 20; and a heat conductive plate 30 disposed between an inner peripheral face 10A of the belt 10 and the heater 20, where the heat conductive plate 30 clamps the belt 10 between the pressure roller 50 and itself. The heat conductive plate 30 includes a recess 33 formed on a first contact surface 30A that comes into contact with the inner peripheral surface 10A of the belt 10. The recess 33 is located within a range of the nip part NP in the conveyance direction.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a fixing device. [Background technology]

[0002] Conventionally, a fixing device is known that includes a cylindrical film, a plate-shaped heater arranged inside the film, a pressure roller that forms a nip between the film and the pressure roller, and a heat conductive member arranged between the inner surface of the film and the heater (Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2022-029694 A Summary of the Invention [Problem to be solved by the invention]

[0004] However, if the behavior of the sheet is not stable in the fixing device, the sheet may become jammed or wrinkled. Therefore, it is desirable that the behavior of the sheet in the fixing device be stable. [Means for solving the problem]

[0005] The fixing device includes a cylindrical heating rotor, a plate-shaped heater, a pressure rotor, and a heat-conductive plate. The heater is disposed inside the heating rotor. The pressure rotating body forms a nip portion between itself and the heating rotating body, and conveys the sheet between itself and the heating rotating body in a conveying direction perpendicular to both the longitudinal direction of the heater and the thickness direction of the heater. The heat conductive plate is a heat conductive plate disposed between the inner circumferential surface of the heating rotor and the heater, and sandwiches the heating rotor between itself and the pressure rotor. The heat conducting plate has a recess formed on the surface that comes into contact with the inner circumferential surface of the heating rotor. The recess is located within the range of the nip portion in the transport direction.

[0006] The recess formed on the surface that contacts the inner circumferential surface of the heating rotor is located within the range of the nip in the conveying direction, so that the sheet can enter the nip upstream of the nip in the conveying direction while being aligned with the heating rotor, thereby stabilizing the behavior of the sheet in the fixing device.

[0007] The recess may be formed symmetrically with respect to a plane perpendicular to the conveying direction and passing through the center of the pressure rotating body in the conveying direction.

[0008] By forming the recess symmetrically with respect to a plane passing through the center of the pressure rotating body in the transport direction, it is possible to achieve a balanced pressure distribution upstream and downstream of the nip portion with the center of the recess in the transport direction as a reference.

[0009] The recess may be formed symmetrically with respect to a plane perpendicular to the transport direction and passing through the center of the heater in the transport direction.

[0010] By forming the recess symmetrically with respect to a plane passing through the center of the heater in the transport direction, it is possible to achieve a good balance in heat distribution upstream and downstream of the nip portion with the center of the recess in the transport direction as a reference.

[0011] The recess may be formed symmetrically with respect to a plane perpendicular to the conveying direction and passing through the center of the heat conducting plate in the conveying direction.

[0012] By forming the recess symmetrically with respect to a plane passing through the center of the thermal conduction plate in the transport direction, it is possible to achieve a balanced heat distribution upstream and downstream of the nip portion with the center of the recess in the transport direction as a reference.

[0013] The heater may include a substrate and a resistive heating element supported by the substrate. In this case, the recessed portion may be configured to be formed symmetrically with respect to a plane perpendicular to the transport direction and passing through the center of the region in the transport direction where the resistance heating element is disposed.

[0014] By forming the recess symmetrically with respect to a plane passing through the center of the area in which the resistive heating element is located in the transport direction, it is possible to balance the heat distribution upstream and downstream of the nip portion based on the center of the recess in the transport direction.

[0015] The heater may have a substrate and a resistive heating element supported by the substrate, and the resistive heating element may include a first resistive heating element and a second resistive heating element. The first resistive heating element extends in the longitudinal direction and is located at one end in the transport direction of the area in which the resistive heating elements are arranged. The second resistive heating element extends in the longitudinal direction and is located at the other end in the transport direction of the region in which the resistive heating elements are arranged. In this case, the first resistive heating element and the second resistive heating element can be configured to be located within the range of the recess in the transport direction.

[0016] By positioning the first and second resistive heating elements within the recessed portion in the transport direction, the recessed portion in the transport direction can be effectively heated, and the amount of heat escaping from the nip portion to the upstream and downstream of the nip portion in the transport direction can be reduced.

[0017] In the transport direction, the upstream end of the heat conduction plate may be located upstream of the upstream end of the heater, and the downstream end of the heat conduction plate may be located downstream of the downstream end of the heater.

[0018] In the conveying direction, the upstream end of the heat conduction plate is located upstream of the upstream end of the heater, and the downstream end of the heat conduction plate is located downstream of the downstream end of the heater, so that contact between the edge of the heater and the heating rotor in the conveying direction can be suppressed. Also, the contact area between the heat conduction plate heated by the heater and the heating rotor can be increased. This allows the heating rotor to be heated effectively. Also, the area of ​​the nip portion can be increased.

[0019] In the transport direction, the upstream end of the heat conduction plate may be located upstream of the upstream end of the nip portion, and the downstream end of the heat conduction plate may be located downstream of the downstream end of the nip portion.

[0020] In the conveying direction, the upstream end of the heat conduction plate is located upstream of the upstream end of the nip portion, and the downstream end of the heat conduction plate is located downstream of the downstream end of the nip portion, thereby suppressing wear of the heating rotor.

[0021] The heater may include a substrate and a resistive heating element supported by the substrate. In this case, in the conveying direction, the upstream end of the nip portion can be located at the same position as the upstream end of the area in which the resistive heating element is arranged, or further upstream than the upstream end of the area in which the resistive heating element is arranged, and the downstream end of the nip portion can be located at the same position as the downstream end of the area in which the resistive heating element is arranged, or further downstream than the downstream end of the area in which the resistive heating element is arranged.

[0022] In the transport direction, the region in which the resistance heating element is disposed is positioned within the range of the nip portion, so that the nip portion can be effectively heated.

[0023] The edge of the heat conducting plate that can come into contact with the inner circumferential surface of the heating rotor may be rounded.

[0024] By rounding the edges of the heat conducting plate that can come into contact with the inner circumferential surface of the heating rotor, wear of the heating rotor can be suppressed.

[0025] In the longitudinal direction, one end of the heat conduction plate may be located farther from the center of the pressurizing rotor than one end of the pressurizing rotor, and the other end of the heat conduction plate may be located farther from the center of the pressurizing rotor than the other end of the pressurizing rotor.

[0026] In the longitudinal direction, one end of the heat conduction plate is located farther from the center of the pressurizing rotor than one end of the pressurizing rotor, and the other end of the heat conduction plate is located farther from the center of the pressurizing rotor than the other end of the pressurizing rotor, thereby suppressing wear of the pressurizing rotor.

[0027] Furthermore, in the longitudinal direction, one end of the heating rotor may be located farther from the center of the heat conduction plate than one end of the heat conduction plate, and the other end of the heating rotor may be located farther from the center of the heat conduction plate than the other end of the heat conduction plate.

[0028] In the longitudinal direction, one end of the heat conduction plate is positioned between one end of the heating rotor and one end of the pressure applying rotor, and the other end of the heat conduction plate is positioned between the other end of the heating rotor and the other end of the pressure applying rotor, thereby suppressing wear of the heating rotor.

[0029] The thermally conductive plate may include a base material and a coating layer. The layer covers at least a portion of the surface of the base material and is in contact with the inner circumferential surface of the heating rotor. In this case, the covering layer can be made of a material having higher slidability than the base material.

[0030] The coating layer of the heat conductive plate is made of a material having a higher sliding property than the base material, so that wear of the heating rotor can be suppressed and slippage of the heating rotor between the heat conductive plate and the pressure rotor can be suppressed. Effect of the Invention

[0031] The behavior of the sheet in the fixing device can be stabilized. [Brief description of the drawings]

[0032] [Figure 1]2 is a cross-sectional view of the fixing device according to the embodiment, seen from the longitudinal direction of the heater. [Diagram 2] FIG. 2 is a view of the heater as viewed from the first surface side. [Diagram 3] 2 is an enlarged cross-sectional view showing the vicinity of a heat conductive plate of the fixing device; [Figure 4] 2 is a cross-sectional view of the fixing device as viewed from the sheet transport direction. [Diagram 5] 6 is an enlarged cross-sectional view showing the vicinity of a heat conductive plate of a fixing device according to a first modified example. FIG. [Figure 6] 13A is an enlarged cross-sectional view showing the vicinity of a heat conductive plate of a fixing device according to a second modified example, and FIG. 13B is a view of a heater as seen from the first surface side. [Figure 7] 13A is an enlarged cross-sectional view showing the vicinity of a heat conduction plate of a fixing device according to a third modified example, and FIG. 13B is an enlarged cross-sectional view showing the vicinity of a heat conduction plate of a fixing device according to a fourth modified example. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0033] Next, an embodiment will be described. 1, the fixing device 1 is a fixing device used in an electrophotographic image forming apparatus, a foil transfer device that transfers foil by heat, etc. The fixing device 1 includes a heating unit 2 and a pressure unit 3.

[0034] When used in an image forming apparatus, the fixing device 1 fixes a toner image onto a sheet S, such as paper, by transporting the sheet S between the heating unit 2 and the pressure unit 3. When used in a foil transfer apparatus, the fixing device 1 transfers foil onto the sheet S by transporting the sheet S between the heating unit 2 and the pressure unit 3.

[0035] The heating unit 2 includes a belt 10 as a heating rotatable body, a heater 20, a heat conductive plate 30, and a holder 40. The pressure unit 3 includes a pressure roller 50 as a pressure rotating body.

[0036] The belt 10 is a cylindrical belt that rotates around the heater 20. The belt 10 has an inner circumferential surface 10A and an outer circumferential surface 10B. The inner circumferential surface 10A of the belt 10 contacts the heat conductive plate 30. The outer circumferential surface 10B of the belt 10 contacts the pressure roller 50. In addition, the outer circumferential surface 10B of the belt 10 also contacts the sheet S transported between the heating unit 2 and the pressure unit 3.

[0037] The heater 20 is a plate-shaped heater that heats the sheet S transported between the heating unit 2 and the pressurizing unit 3. The heater 20 is disposed inside the belt 10. The heater 20 has a first surface 20A and a second surface 20B. The first surface 20A is a surface that contacts the thermally conductive plate 30. The second surface 20B is a surface opposite to the first surface 20A in the thickness direction of the heater 20.

[0038] The pressure roller 50 is a roller that forms a nip portion NP between itself and the belt 10. The pressure roller 50 rotates to transport the sheet S between itself and the belt 10 in a predetermined transport direction. The transport direction is a direction perpendicular to both the longitudinal direction of the heater 20 (see FIG. 2) and the thickness direction of the heater 20. Hereinafter, the longitudinal direction of the heater 20 is also simply referred to as the "longitudinal direction," and the thickness direction of the heater 20 is also simply referred to as the "thickness direction."

[0039] The pressure roller 50 has a shaft 51 and a roller body 52. ​​The shaft 51 is made of, for example, metal. The roller body 52 is made of, for example, rubber, and is provided so as to cover the periphery of the shaft 51. In the fixing device 1, one of the heating unit 2 and the pressure unit 3 is biased toward the other. As a result, a nip portion NP is formed between the belt 10 and the pressure roller 50.

[0040] The heat conductive plate 30 is a member for conducting heat from the heater 20 in the longitudinal direction and the transport direction to make the temperature of the nip portion NP uniform in the longitudinal direction and the transport direction. The heat conductive plate 30 is a plate-shaped member. The heat conductive plate 30 is disposed between the inner circumferential surface 10A of the belt 10 and the first surface 20A of the heater 20 in the thickness direction. The heat conductive plate 30 sandwiches the belt 10 between itself and the pressure roller 50.

[0041] The heat conductive plate 30 has a first contact surface 30A and a second contact surface 30B. The first contact surface 30A is a surface that contacts the inner circumferential surface 10A of the belt 10. The second contact surface 30B is a surface that contacts the first surface 20A of the heater 20.

[0042] The holder 40 is a member that supports the heater 20. The holder 40 supports the second surface 20B of the heater 20. The holder 40 is disposed on the inner side of the belt 10. In this embodiment, the holder 40 is made of resin. The holder 40 has a support wall 41 and a guide 42.

[0043] The support wall 41 has a first arrangement groove 43 and a second arrangement groove 44. The first arrangement groove 43 is a groove in which the heater 20 is arranged. The second arrangement groove 44 is a groove in which the heat conduction plate 30 is arranged. The first arrangement groove 43 and the second arrangement groove 44 extend in the longitudinal direction.

[0044] The second arrangement groove 44 has a shape that is recessed in the thickness direction away from the pressure roller 50. The first arrangement groove 43 has a shape that is recessed in the thickness direction from the bottom surface of the second arrangement groove 44 in the direction away from the pressure roller 50. The holder 40 supports the second surface 20B of the heater 20 at the bottom surface of the first arrangement groove 43 of the support wall 41.

[0045] The guides 42 are provided on both sides of the support wall 41 in the conveying direction. The guide 42 has a guide rib 42A. A plurality of guides 42 and guide ribs 42A are provided side by side in the longitudinal direction. The guide rib 42A has a shape that follows the inner circumferential surface 10A of the belt 10. The inner circumferential surface 10A of the belt 10 contacts the guide 42. The belt 10 can rotate around the heater 20 while being guided by the guide 42.

[0046] The heater 20 includes a substrate 21, a resistive heating element 22, and a cover 23. 2, the substrate 21 is a rectangular plate extending in the longitudinal direction. In this embodiment, the substrate 21 is made of ceramic, and the heater 20 is a so-called ceramic heater.

[0047] The resistive heating element 22 is supported by the substrate 21. The resistive heating element 22 is provided on the first surface 20A of the heater 20. The resistive heating element 22 is formed by printing. The resistive heating element 22 includes a first resistive heating element 22A and a second resistive heating element 22B. The first resistive heating element 22A and the second resistive heating element 22B each extend in the longitudinal direction.

[0048] The first resistive heating element 22A and the second resistive heating element 22B are arranged parallel to each other and spaced apart in the transport direction. The first resistive heating element 22A is located at one end of the transport direction area A1 in which the resistive heating element 22 is arranged. The second resistive heating element 22B is located at the other end of the transport direction area A1 in which the resistive heating element 22 is arranged.

[0049] One longitudinal end of the first resistive heating element 22A and one longitudinal end of the second resistive heating element 22B are connected to each other by a conductor 24A. The other longitudinal end of the first resistive heating element 22A and the other longitudinal end of the second resistive heating element 22B are connected to conductors 24B, respectively, and a power supply terminal 25 is provided at the end of each conductor 24B. The power supply terminal 25 is electrically connected to the resistive heating element 22 via the conductor 24B. A connector 60 (see FIG. 4) for supplying power to the resistive heating element 22 is connected to the power supply terminal 25.

[0050] 3, the cover 23 covers the resistance heating element 22. The cover 23 is made of, for example, glass.

[0051] The thermally conductive plate 30 includes a substrate 31 and a covering layer 32 . The base material 31 is a member having a thermal conductivity greater than that of the substrate 21. The thermal conductivity of the base material 31 is also greater than that of the cover 23. The material of the base material 31 is not particularly limited, but may be a metal having a high thermal conductivity, such as aluminum, an aluminum alloy, or copper.

[0052] The covering layer 32 is a layer that comes into contact with the inner circumferential surface 10A of the belt 10. The covering layer 32 covers at least a part of the surface of the base material 31. In this embodiment, the covering layer 32 covers, of the surface of the base material 31, a surface close to the pressure roller 50 in the thickness direction, a side surface in the conveying direction, and a side surface in the longitudinal direction. The covering layer 32 may cover the entire surface of the base material 31.

[0053] The coating layer 32 is made of a material having higher slidability than the base material 31. Examples of the material that can be used for the coating layer 32 include nickel phosphorus (NiP), chromium nitride (CrN), titanium nitride (TiN), titanium aluminum nitride (TiAlN), intrinsic carbon film (ICF), and diamond-like carbon (DLC). That is, the coating layer 32 is, for example, an electroless nickel plating layer, a CrN coating layer, a TiN coating layer, a TiAlN coating layer, an ICF coating layer, and a DLC coating layer.

[0054] The heat conducting plate 30 has an edge 30E. The edge 30E can come into contact with the inner peripheral surface 10A of the belt 10. The edge 30E of the heat conducting plate 30 is rounded. Specifically, the edge 30E of the heat conducting plate 30 has a cross-sectional shape that is rounded in a substantially arc shape. The radius of curvature of the edge 30E is, for example, 0.3 mm or more.

[0055] The heat conductive plate 30 has a recess 33 formed on the first contact surface 30A. The recess 33 has a shape recessed toward the heater 20 in the thickness direction. In this embodiment, the recess 33 has a shape recessed to form a curved surface approaching the heater 20 as it approaches the center from the end in the transport direction. Specifically, the recess 33 has a shape recessed in a substantially arc shape when viewed in the longitudinal direction.

[0056] The curvature of the recess 33 is, for example, half or more of the curvature of the roller body 52 of the pressure roller 50. The curvature of the roller body 52 is the curvature before the roller body 52 is deformed. Note that in the reference drawings, the size of the recess 33 is exaggerated.

[0057] The recess 33 extends in the longitudinal direction. The recess 33 is formed over the longitudinal direction of the heat conduction plate 30.

[0058] The recess 33 is formed symmetrically with respect to the plane PL. The plane PL is a plane perpendicular to the transport direction. In this embodiment, the plane PL is a plane passing through the center of the pressure roller 50 in the transport direction. The plane PL is also a plane passing through the center of the heater 20 in the transport direction. The plane PL is also a plane passing through the center of the heat conduction plate 30 in the transport direction. The plane PL is also a plane passing through the center of the area A1 in which the resistance heating element 22 is arranged in the transport direction.

[0059] The recessed portion 33 is located within the range of the nip portion NP in the transport direction. More specifically, the region A2 in which the recessed portion 33 of the heat conductive plate 30 is formed is located within the range of the nip portion NP in the transport direction.

[0060] The first contact surface 30A of the heat conduction plate 30 has at least a first portion P1 and a second portion P2 that are in contact with a reference plane PR, which is a virtual plane. The first portion P1 is the portion of the first contact surface 30A that is in contact with the reference plane PR and is located most upstream in the conveying direction. The second portion P2 is the portion of the first contact surface 30A that is in contact with the reference plane PR and is located most downstream in the conveying direction.

[0061] In the transport direction, the upstream end of the region A2 where the recesses 33 of the heat conduction plate 30 are formed is a point where the first contact surface 30A starts to move away from the reference plane PR from the first portion P1 toward the downstream in the transport direction. In the transport direction, the downstream end of the region A2 where the recesses 33 of the heat conduction plate 30 are formed is a point where the first contact surface 30A starts to move away from the reference plane PR from the second portion P2 toward the upstream in the transport direction.

[0062] A dimension DNP of the nip portion NP in the transport direction is larger than a dimension D33 of the region A2 in which the recesses 33 of the heat conduction plate 30 are formed in the transport direction. In the transport direction, the upstream end of the nip portion NP is located upstream of the upstream end of the region A2 in which the recesses 33 of the heat conduction plate 30 are formed. In the transport direction, the downstream end of the nip portion NP is located downstream of the downstream end of the region A2 in which the recesses 33 of the heat conduction plate 30 are formed.

[0063] In this embodiment, the dimension DNP of the nip portion NP in the transport direction is larger than the dimension D33 of the recessed portion 33 in the transport direction. In the transport direction, the upstream end of the nip portion NP is located upstream of the upstream end of the recessed portion 33. In the transport direction, the downstream end of the nip portion NP is located downstream of the downstream end of the recessed portion 33.

[0064] The heat conductive plate 30 further has flat planar portions 34 formed on the first contact surface 30A. The planar portions 34 are provided on both sides of the recess 33 in the transport direction. More specifically, the planar portions 34 include a first planar portion 34A and a second planar portion 34B.

[0065] The first flat surface portion 34A extends straight along the conveying direction from the upstream end of the region A2 in which the recesses 33 are formed in the conveying direction toward the upstream in the conveying direction. The second flat surface portion 34B extends straight along the conveying direction from the downstream end of the region A2 in which the recesses 33 are formed in the conveying direction toward the downstream in the conveying direction.

[0066] In this embodiment, the first flat surface portion 34A extends straight along the conveying direction from the upstream end of the recessed portion 33 in the conveying direction toward the upstream side in the conveying direction. The second flat surface portion 34B extends straight along the conveying direction from the downstream end of the recessed portion 33 in the conveying direction toward the downstream side in the conveying direction.

[0067] Within the range of the nip portion NP in the conveying direction, the belt 10 is in close contact with the surface of the recessed portion 33 and the surface of the flat portion 34. Within the range of the nip portion NP in the conveying direction, the belt 10 is in close contact with the surface of the region A2 of the first contact surface 30A where the recessed portion 33 is formed, and the surface of the flat portion 34. In this embodiment, the first flat portion 34A corresponds to the first portion P1, and the second flat portion 34B corresponds to the second portion P2.

[0068] It is desirable that the boundary between the first flat surface portion 34A and the recess 33, and the boundary between the recess 33 and the second flat surface portion 34B, are each rounded.

[0069] A dimension D30 of the heat conduction plate 30 in the transport direction is larger than a dimension D20 of the heater 20 in the transport direction. In the transport direction, the upstream end of the heat conduction plate 30 is located upstream of the upstream end of the heater 20. In the transport direction, the downstream end of the heat conduction plate 30 is located downstream of the downstream end of the heater 20.

[0070] The dimension D30 of the heat conductive plate 30 in the transport direction is larger than the dimension DNP of the nip portion NP in the transport direction. In the transport direction, the upstream end of the heat conductive plate 30 is located upstream of the upstream end of the nip portion NP. In the transport direction, the downstream end of the heat conductive plate 30 is located downstream of the downstream end of the nip portion NP.

[0071] A dimension DNP of the nip portion NP in the transport direction is larger than a dimension DA1 of the area A1 in which the resistance heating element 22 is disposed in the transport direction. In the transport direction, the upstream end of the nip portion NP is located upstream of the upstream end of the area A1 in which the resistance heating element 22 is disposed. In the transport direction, the downstream end of the nip portion NP is located downstream of the downstream end of the area A1 in which the resistance heating element 22 is disposed.

[0072] A dimension D33 in the transport direction of the region A2 where the recess 33 of the thermally conductive plate 30 is formed is larger than a dimension DA1 in the transport direction of the region A1 where the resistance heating element 22 is arranged. In this embodiment, a dimension DNP in the transport direction of the nip portion NP is larger than the dimension DA1 in the transport direction of the region A1 where the resistance heating element 22 is arranged.

[0073] The first resistive heating element 22A and the second resistive heating element 22B are located within the range of the recess 33 in the transport direction. In other words, the first resistive heating element 22A and the second resistive heating element 22B are located between one end and the other end of the recess 33 in the transport direction.

[0074] 4, the dimension L30 of the heat conductive plate 30 in the longitudinal direction is larger than the dimension L50 of the pressure roller 50 in the longitudinal direction. In the longitudinal direction, one end of the heat conductive plate 30 is located farther from the center of the pressure roller 50 than one end of the pressure roller 50. In the longitudinal direction, the other end of the heat conductive plate 30 is located farther from the center of the pressure roller 50 than the other end of the pressure roller 50.

[0075] Specifically, the dimension L50 is the dimension of the roller body 52 of the pressure roller 50 in the longitudinal direction. In the longitudinal direction, one end of the heat conductive plate 30 is located farther from the center of the pressure roller 50 than one end of the roller body 52. ​​In the longitudinal direction, the other end of the heat conductive plate 30 is located farther from the center of the pressure roller 50 than the other end of the roller body 52.

[0076] In this embodiment, in the longitudinal direction, one end of the heat conduction plate 30 is located farther from the center of the roller body 52 than one end of the roller body 52. ​​In the longitudinal direction, the other end of the heat conduction plate 30 is located farther from the center of the roller body 52 than the other end of the roller body 52.

[0077] Furthermore, the dimension L10 of the belt 10 in the longitudinal direction is larger than the dimension L30 of the heat conduction plate 30 in the longitudinal direction. In the longitudinal direction, one end of the belt 10 is located farther from the center of the heat conduction plate 30 than one end of the heat conduction plate 30. In the longitudinal direction, the other end of the belt 10 is located farther from the center of the heat conduction plate 30 than the other end of the heat conduction plate 30.

[0078] In the longitudinal direction, one end of the heat conductive plate 30 is located between one end of the belt 10 and one end of the roller body 52 of the pressure roller 50. In the longitudinal direction, the other end of the heat conductive plate 30 is located between the other end of the belt 10 and the other end of the roller body 52 of the pressure roller 50.

[0079] Next, the effects of the fixing device 1 according to the embodiment will be described. The recess 33 formed on the first contact surface 30A of the heat conductive plate 30 is positioned within the range of the nip portion NP in the transport direction, so that the sheet S can enter the nip portion NP upstream of the nip portion NP in the transport direction while being aligned with the belt 10. This makes it possible to stabilize the behavior of the sheet S in the fixing device 1.

[0080] By forming the recesses 33 on the first contact surface 30A of the heat conductive plate 30, the area of ​​the nip portion NP can be made larger than when the entire first contact surface is a flat surface (see the reference plane PR in FIG. 3). This allows the sheet S transported between the belt 10 and the pressure roller 50 to be effectively heated, improving fixability.

[0081] The recess 33 is formed symmetrically with respect to the plane PL passing through the center of the pressure roller 50 in the conveying direction, so that the pressure distribution upstream and downstream of the nip portion NP can be well balanced with respect to the center of the recess 33 in the conveying direction. This makes it possible to stabilize the behavior of the sheet S and the belt 10.

[0082] By forming the recess 33 symmetrically with respect to the plane PL passing through the center of the heater 20 in the transport direction, the heat distribution upstream and downstream of the nip portion NP can be balanced based on the center of the recess 33 in the transport direction.

[0083] Since the recess 33 is formed symmetrically with respect to the plane PL passing through the center of the thermal conduction plate 30 in the conveying direction, the heat distribution upstream and downstream of the nip portion NP can be balanced based on the center of the recess 33 in the conveying direction.

[0084] Since the recess 33 is formed symmetrically with respect to the plane PL passing through the center of the area A1 in which the resistive heating element 22 is arranged in the transport direction, the heat distribution upstream and downstream of the nip portion NP can be balanced based on the center of the recess 33 in the transport direction.

[0085] By achieving a good balance in the heat distribution upstream and downstream of the nip portion NP in the transport direction, it is possible to stabilize the temperature control of the nip portion NP and to stabilize the supply of heat to the sheet S.

[0086] By positioning the first resistive heating element 22A and the second resistive heating element 22B within the range of the recessed portion 33 in the transport direction, the range of the recessed portion 33 in the transport direction can be heated more effectively than when the first resistive heating element and the second resistive heating element are positioned outside the range of the recessed portion 33. Also, the amount of heat escaping from the nip portion NP to the upstream and downstream of the nip portion NP in the transport direction can be reduced.

[0087] In the conveying direction, the upstream end of the heat conductive plate 30 is located upstream of the upstream end of the heater 20, and the downstream end of the heat conductive plate 30 is located downstream of the downstream end of the heater 20, thereby making it possible to suppress contact between the edge of the heater 20 and the belt 10 in the conveying direction. In addition, the contact area between the heat conductive plate 30 heated by the heater 20 and the belt 10 can be increased. This allows the belt 10 to be heated effectively. In addition, the area of ​​the nip portion NP can be increased.

[0088] In the conveying direction, the upstream end of the heat conduction plate 30 is located upstream of the upstream end of the nip portion NP, and the downstream end of the heat conduction plate 30 is located downstream of the downstream end of the nip portion NP. This prevents the belt 10 from being pressed against the edge 30E of the heat conduction plate 30 by the pressure roller 50 at the end of the nip portion NP in the conveying direction, thereby suppressing wear of the belt 10.

[0089] In the transport direction, the region A1 where the resistance heating element 22 is arranged is located within the range of the nip portion NP, so that the nip portion NP can be heated more effectively by the heater 20 compared to a case where the resistance heating element is arranged outside the range of the nip portion NP in the transport direction. In other words, the heater 20 does not unnecessarily heat the upstream and downstream of the nip portion NP in the transport direction.

[0090] By having the edge 30E of the heat conducting plate 30 be rounded, wear of the belt 10 can be suppressed.

[0091] In the longitudinal direction, one end of the heat conduction plate 30 is located at a position farther from the center of the roller body 52 of the pressure roller 50 than one end of the roller body 52, and the other end of the heat conduction plate 30 is located at a position farther from the center of the roller body 52 than the other end of the roller body 52. ​​As a result, the pressure roller 50 (roller body 52) is not pressed against the edge 30E of the heat conduction plate 30 in the longitudinal direction, so that wear of the pressure roller 50 (roller body 52) can be suppressed.

[0092] In the longitudinal direction, one end of the heat conduction plate 30 is located between one end of the belt 10 and one end of the roller body 52, and the other end of the heat conduction plate 30 is located between the other end of the belt 10 and the other end of the roller body 52, so that the belt 10 is not sandwiched between the edge 30E of the heat conduction plate 30 and the pressure roller 50 in the longitudinal direction. This makes it possible to suppress wear of the belt 10.

[0093] The covering layer 32 of the heat conductive plate 30, which comes into contact with the inner circumferential surface 10A of the belt 10, is made of a material having higher sliding properties than the base material 31, thereby making it possible to suppress wear of the belt 10. In addition, it is possible to suppress slippage of the belt 10 between the heat conductive plate 30 and the pressure roller 50.

[0094] Although the embodiment has been described above, the fixing device can be modified as appropriate as shown in the following examples. The following description will focus on the differences from the above embodiment. Members and parts having the same functions as those in the above embodiment will be given the same reference numerals and will not be described.

[0095] For example, as in a first modified example shown in Fig. 5, the heat conduction plate 30 may have a different thickness on the upstream side and the downstream side in the transport direction. In the first modified example, the heat conduction plate 30 has a thickness T1 on the upstream side in the transport direction that is greater than a thickness T2 on the downstream side. Furthermore, in the first modified example, the heat conduction plate 30 has a shape in which the thickness gradually decreases overall from the upstream side to the downstream side in the transport direction, as shown by the imaginary line.

[0096] The thermally conductive plate may have a smaller thickness on the upstream side in the conveying direction than on the downstream side.The thermally conductive plate may have a shape such that the thickness gradually increases overall from the upstream side to the downstream side in the conveying direction.

[0097] 6(a) and 6(b), the heater 20 may include a first resistive heating element 22A, a second resistive heating element 22B, a third resistive heating element 22C, and a fourth resistive heating element 22D as the resistive heating element 22. The resistive heating elements 22A to 22D each extend in the longitudinal direction. The resistive heating elements 22A to 22D are arranged in the following order from upstream to downstream in the conveying direction: the first resistive heating element 22A, the third resistive heating element 22C, the fourth resistive heating element 22D, and the second resistive heating element 22B.

[0098] The first resistive heating element 22A and the third resistive heating element 22C are arranged parallel to each other and spaced apart from each other in the transport direction. The third resistive heating element 22C and the fourth resistive heating element 22D are arranged parallel to each other and spaced apart from each other in the transport direction. The fourth resistive heating element 22D and the second resistive heating element 22B are arranged parallel to each other and spaced apart from each other in the transport direction.

[0099] One longitudinal end of the first resistive heating body 22A and one longitudinal end of the third resistive heating body 22C are connected to each other by a conductor 24C. One longitudinal end of the second resistive heating body 22B and one longitudinal end of the fourth resistive heating body 22D are connected to each other by a conductor 24C.

[0100] The other end in the longitudinal direction of the third resistive heating element 22C and the other end in the longitudinal direction of the fourth resistive heating element 22D are connected to each other by a conductor 24C. The other end in the longitudinal direction of the first resistive heating element 22A and the other end in the longitudinal direction of the second resistive heating element 22B are connected to conductors 24B, respectively, and power supply terminals 25 are provided at the ends of the conductors 24B.

[0101] In the second modified example, in the transport direction, the upstream end of the nip portion NP is located at the same position as the upstream end of the area A1 in which the resistance heating element 22 is arranged, and the downstream end of the nip portion NP is located at the same position as the downstream end of the area A1 in which the resistance heating element 22 is arranged. Specifically, in the transport direction, the upstream end of the nip portion NP is located at the same position as the upstream end of the first resistance heating element 22A, and the downstream end of the nip portion NP is located at the same position as the downstream end of the second resistance heating element 22B.

[0102] In the transport direction, the area A1 in which the resistance heating element 22 is arranged is located at the same position as the range of the nip portion NP, so that the heater 20 can effectively heat the nip portion NP.

[0103] In the heater, the number, arrangement, etc. of the resistive heating elements are not particularly limited. Also, for example, a resistive heating element having a larger heat generation amount at the longitudinal center than at the longitudinal end portions, and a resistive heating element having a larger heat generation amount at the longitudinal end portions than at the longitudinal center portion may be provided, and the heat generation distribution in the longitudinal direction may be adjusted by individually controlling each resistive heating element.

[0104] In the embodiment described above, the first resistive heating element 22A and the second resistive heating element 22B are located within the range of the recessed portion 33 in the transport direction, but this is not limiting. For example, as in a second modified example shown in Fig. 6(a), at least a portion of the first resistive heating element 22A and the second resistive heating element 22B may be located outside the range of the recessed portion 33 in the transport direction.

[0105] Specifically, in the second modified example, in the transport direction, the upstream end of the first resistive heating element 22A is located upstream of the upstream end of the recessed portion 33. Meanwhile, in the transport direction, the downstream end of the first resistive heating element 22A is located within the range of the recessed portion 33. Also, in the transport direction, the downstream end of the second resistive heating element 22B is located downstream of the downstream end of the recessed portion 33. Meanwhile, in the transport direction, the upstream end of the second resistive heating element 22B is located within the range of the recessed portion 33.

[0106] In the second modified example, the third resistive heating element 22C and the fourth resistive heating element 22D are located within the range of the recessed portion 33 in the transport direction.

[0107] In the embodiment, as shown in Fig. 1, the heat conduction plate 30 has one recess 33 formed on the first contact surface 30A, but for example, as in a third modified example shown in Fig. 7(a), the heat conduction plate 30 may have a plurality of recesses 33A to 33C formed on the first contact surface 30A. In the third modified example, the heat conduction plate 30 has a first recess 33A, a second recess 33B, and a third recess 33C formed on the first contact surface 30A.

[0108] The recesses 33A to 33C are arranged in the order of the first recess 33A, the second recess 33B, and the third recess 33C from the upstream to the downstream in the transport direction. The second recess 33B is formed symmetrically with respect to the plane PL. The first recess 33A and the third recess 33C are formed symmetrically with respect to the plane PL. In the third modified example, the multiple recesses 33A to 33C are formed symmetrically with respect to the plane PL as a whole.

[0109] The recesses 33A to 33C are located within the range of the nip portion NP in the transport direction. More specifically, the area A3 of the heat conductive plate 30 in which the recesses 33A to 33C are formed is located within the range of the nip portion NP in the transport direction.

[0110] A dimension DNP of the nip portion NP in the transport direction is larger than a dimension DA3 of the region A3 in which the recesses 33A-33C of the heat conductive plate 30 are formed in the transport direction. In the transport direction, the upstream end of the nip portion NP is located upstream of the upstream end of the region A3 in which the recesses 33A-33C of the heat conductive plate 30 are formed. In the transport direction, the other downstream end of the nip portion NP is located downstream of the downstream end of the region A3 in which the recesses 33A-33C of the heat conductive plate 30 are formed.

[0111] The belt 10 is in close contact with the surfaces of the recesses 33A-33C and the surfaces of the flat portions 34A, 34B within the range of the nip portion NP in the transport direction. The belt 10 is in close contact with the surface of the region A3 of the first contact surface 30A where the recesses 33A-33C are formed and the surfaces of the flat portions 34A, 34B within the range of the nip portion NP in the transport direction.

[0112] The boundary between the first flat surface portion 34A and the first recess 33A is preferably rounded. The boundary between the first recess 33A and the second recess 33B is preferably rounded. The boundary between the second recess 33B and the third recess 33C is preferably rounded. The boundary between the third recess 33C and the second flat surface portion 34B is preferably rounded.

[0113] 7(b), the heat conducting plate 30 may have a first recess 33D, a second recess 33E, and a flat surface 35 formed on the first contact surface 30A. The first recess 33D, the second recess 33E, and the flat surface 35 are arranged in the order of the first recess 33D, the flat surface 35, and the second recess 33E from the upstream to the downstream in the conveying direction. The first recess 33D and the second recess 33E are formed symmetrically with respect to the plane PL. In the fourth modification, the first recess 33D, the flat surface 35, and the second recess 33E are formed symmetrically with respect to the plane PL as a whole.

[0114] The recesses 33D, 33E are located within the range of the nip portion NP in the transport direction. More specifically, the region A4 in which the recesses 33D, 33E of the heat conduction plate 30 are formed is located within the range of the nip portion NP in the transport direction. In the fourth modification, the region A4 in which the recesses 33D, 33E of the heat conduction plate 30 are formed in the transport direction includes a flat portion 35 formed between the recesses 33D, 33E.

[0115] A dimension DNP of the nip portion NP in the transport direction is larger than a dimension DA4 of the region A4 in which the recesses 33D, 33E of the heat conduction plate 30 are formed in the transport direction. In the transport direction, the upstream end of the nip portion NP is located upstream of the upstream end of the region A4 in which the recesses 33D, 33E of the heat conduction plate 30 are formed. In the transport direction, the downstream end of the nip portion NP is located downstream of the downstream end of the region A4 in which the recesses 33D, 33E of the heat conduction plate 30 are formed.

[0116] Within the range of the nip portion NP in the transport direction, the belt 10 is in close contact with the surfaces of the recesses 33D and 33E and the surfaces of the flat portions 34A, 34B, and 35. Within the range of the nip portion NP in the transport direction, the belt 10 is in close contact with the surface of the region A4 (including the flat portion 35) where the recesses 33D and 33E of the first contact surface 30A are formed, and the surfaces of the flat portions 34A and 34B.

[0117] The boundary between the first flat surface portion 34A and the first recess 33D is desirably rounded. The boundary between the first recess 33D and the flat surface portion 35 is desirably rounded. The boundary between the flat surface portion 35 and the second recess 33E is desirably rounded. The boundary between the second recess 33E and the second flat surface portion 34B is desirably rounded.

[0118] In addition, in FIGS. 7(a) and 7(b), the sizes of the recesses 33A to 33E are exaggerated.

[0119] In the above embodiment, the heat conductive plate 30 includes the covering layer 32. However, for example, the heat conductive plate may not include the covering layer.

[0120] In the above embodiment, the recess 33 of the heat conducting plate 30 is formed symmetrically with respect to the plane PL. However, for example, the recess may be formed asymmetrically with respect to the plane PL.

[0121] In the above embodiment, in the transport direction, the upstream end of the nip portion NP is located upstream of the upstream end of the region A2 in which the recess 33 is formed, and the downstream end of the nip portion NP is located downstream of the downstream end of the region A2 in which the recess 33 is formed, but this is not limited to this. For example, in the transport direction, the upstream end of the nip portion may be located at the same position as the upstream end of the region in which the recess is formed. Also, in the transport direction, the downstream end of the nip portion may be located at the same position as the downstream end of the region in which the recess is formed.

[0122] In the above embodiment, in the transport direction, the upstream end of the heat conduction plate 30 is located upstream of the upstream end of the nip portion NP, and the downstream end of the heat conduction plate 30 is located downstream of the downstream end of the nip portion NP, but this is not limited thereto. For example, in the transport direction, the upstream end of the heat conduction plate may be located at the same position as the upstream end of the nip portion. Also, in the transport direction, the downstream end of the heat conduction plate may be located at the same position as the downstream end of the nip portion.

[0123] In the above embodiment, in the transport direction, the upstream end of the heat conduction plate 30 is located upstream of the upstream end of the heater 20, and the downstream end of the heat conduction plate 30 is located downstream of the downstream end of the heater 20, but this is not limited to the above. For example, in the transport direction, the upstream end of the heat conduction plate may be located at the same position as the upstream end of the heater. Also, in the transport direction, the downstream end of the heat conduction plate may be located at the same position as the downstream end of the heater.

[0124] In the above embodiment, the heater 20 has a configuration in which the resistance heating element 22 is disposed on the first surface 20A. However, for example, the heater may have a configuration in which the resistance heating element is disposed on the second surface.

[0125] In the above embodiment, the cylindrical belt 10 is exemplified as the heating rotator, but the heating rotator may be, for example, a cylindrical film, etc. Also, in the above embodiment, the pressure roller 50 is exemplified as the pressure rotator, but the pressure rotator may be, for example, a cylindrical belt sandwiched between the heating rotator and an elastic pad disposed inside the pressure roller 50.

[0126] The elements described in the above embodiment and modified examples may be implemented in any combination. [Explanation of symbols]

[0127] 1 Fixing device 10 Belt 10A inner surface 20 Heater 30 Heat Conduction Plate 30A 1st contact surface 33 Recess 50 Pressure roller NP Nip S Seat

Claims

1. A cylindrical heating rotor; A plate-shaped heater disposed inside the heating rotator; a pressure rotating body that forms a nip portion between itself and the heating rotating body, and that conveys a sheet between itself and the heating rotating body in a conveying direction perpendicular to both a longitudinal direction of the heater and a thickness direction of the heater; a heat conductive plate disposed between an inner circumferential surface of the heating rotor and the heater, the heat conductive plate sandwiching the heating rotor between the heating rotor and the pressurizing rotor; The heat conductive plate has a recess formed on a surface that contacts the inner circumferential surface of the heating rotor, The fixing device, wherein the recess is located within a range of the nip portion in the transport direction.

2. 2. The fixing device according to claim 1, wherein the recess is formed symmetrically with respect to a plane perpendicular to the transport direction and passing through a center of the pressure rotating body in the transport direction.

3. 2. The fixing device according to claim 1, wherein the recess is formed symmetrically with respect to a plane perpendicular to the transport direction and passing through a center of the heater in the transport direction.

4. 2. The fixing device according to claim 1, wherein the recess is formed symmetrically with respect to a plane perpendicular to the transport direction and passing through a center of the heat conductive plate in the transport direction.

5. The heater includes a substrate and a resistive heating element supported by the substrate. The fixing device according to claim 1 , wherein the recess is formed symmetrically with respect to a plane perpendicular to the transport direction and passing through a center of an area in the transport direction in which the resistance heating element is disposed.

6. The heater includes a substrate and a resistive heating element supported by the substrate. The resistance heating element is a first resistance heating element extending in the longitudinal direction and positioned at one end of a region in which the resistance heating elements are arranged in the transport direction; a second resistance heating element extending in the longitudinal direction and located at the other end of the region in the transport direction in which the resistance heating elements are arranged; Including, The fixing device according to claim 1 , wherein the first resistance heating element and the second resistance heating element are located within a range of the recess in the transport direction.

7. In the conveying direction, an upstream end of the heat conductive plate is located upstream of an upstream end of the heater; 2. The fixing device according to claim 1, wherein a downstream end of the heat conductive plate is located downstream of a downstream end of the heater.

8. In the conveying direction, an upstream end of the heat conductive plate is located upstream of an upstream end of the nip portion; 2. The fixing device according to claim 1, wherein a downstream end of the heat conductive plate is located downstream of a downstream end of the nip portion.

9. The heater includes a substrate and a resistive heating element supported by the substrate. In the conveying direction, an upstream end of the nip portion is located at the same position as an upstream end of the region in which the resistance heating element is disposed, or is located upstream of the upstream end of the region in which the resistance heating element is disposed; 2. The fixing device according to claim 1, wherein the downstream end of the nip portion is located at the same position as the downstream end of the area in which the resistive heating element is arranged, or downstream of the downstream end of the area in which the resistive heating element is arranged.

10. 2. The fixing device according to claim 1, wherein an edge of the heat conductive plate capable of coming into contact with the inner circumferential surface of the heating rotary member is rounded.

11. In the longitudinal direction, one end of the heat conductive plate is located farther from the center of the pressurizing rotor than one end of the pressurizing rotor; 2. The fixing device according to claim 1, wherein the other end of the heat conductive plate is located farther from the center of the pressure rotating body than the other end of the pressure rotating body.

12. In the longitudinal direction, one end of the heating rotator is located farther from the center of the heat conductive plate than one end of the heat conductive plate, 12. The fixing device according to claim 11, wherein the other end of the heating rotator is located farther from the center of the heat conductive plate than the other end of the heat conductive plate.

13. The heat conductive plate is A substrate; a coating layer covering at least a part of a surface of the base material and contacting an inner circumferential surface of the heating rotator; Including, The fixing device according to claim 1 , wherein the covering layer is made of a material having a higher sliding property than the base material.

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