Fixing device

Abstract

To provide a fixing device capable of preventing a lubricant interposed between a heater and a belt from flowing to a back side of a sheet member.SOLUTION: A fixing device F conveys a recording material S by a heating unit 1 and a pressing unit (pressing roller 2). The heating unit 1 has a heater 10 having a substrate 11 and a resistance heat generating body supported on the substrate 11, an endless belt 3 which has an inner peripheral surface 3B brought into contact with a front-side surface 15 of the heater 10 through a lubricant and rotates around the heater 10, a holder 20 for holding the heater 10, a sheet member 70 which is positioned between a back-side surface 16 of the heater 10 and the holder 20 and has a coefficient of thermal conductivity smaller than that of the substrate 11, and a temperature detection member 50 which detects the temperature of the heater 10 and is positioned opposite to the back-side surface 16 of the heater 10 with respect to the sheet member 70. A length L170 in the conveyance direction of the sheet member 70 is longer than a length L110 in the conveyance direction of the heater 10.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a fixing device that conveys a recording material with a heating unit and a pressure unit. [Background technology]

[0002] Conventionally, a known heating unit for a fixing device includes a heater having a resistance heating element formed on a substrate, an endless belt rotating around the heater, and a holder supporting the heater (Patent Document 1). In this technology, the heater has a first surface that contacts the inner circumferential surface of the belt and a second surface opposite to the first surface, and a heat insulating sheet is disposed between the second surface and the holder. The heat insulating sheet is also disposed between the second surface of the heater and a temperature detection member such as a thermistor or a temperature fuse. Heat-resistant grease (lubricant) is also applied to the inner circumferential surface of the belt, thereby ensuring the sliding properties between the heater and the holder and the inner circumferential surface of the belt. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2019-194649 A Summary of the Invention [Problem to be solved by the invention]

[0004] In the conventional configuration, the length of the heat insulating sheet in the recording material conveying direction was the same as the length of the heater in the conveying direction, so there was a possibility that the lubricant between the heater and the belt would flow to the back side of the heat insulating sheet, i.e., to the temperature detection member side. If the lubricant that has flowed into the temperature detection member side adheres to the temperature detection surface of the temperature detection member, for example, it may impair the function of the temperature detection member.

[0005] SUMMARY OF THE PRESENT DISCLOSURE An object of the present invention is to provide a fixing device that can prevent a lubricant present between a heater and a belt from flowing to the rear side of a sheet member. [Means for solving the problem]

[0006] The fixing device for achieving the above-mentioned object is a fixing device that transports a recording material with a heating unit and a pressure unit, and the heating unit includes a heater having a substrate and a resistive heating element supported by the substrate, an endless belt having an inner surface that contacts the front side of the heater via a lubricant and rotates around the heater, a holder that holds the heater, a sheet member that is located between the holder and the back side opposite the front side of the heater and has a thermal conductivity lower than that of the substrate, and a temperature detection member for detecting the temperature of the heater, the temperature detection member being located on the opposite side of the back side of the heater with respect to the sheet member. The length of the sheet member in the recording material transport direction is longer than the length of the heater in the transport direction.

[0007] With this configuration, the sheet member can prevent the lubricant present between the heater and the belt from flowing to the back side of the sheet member, i.e., to the temperature detection member side.

[0008] In addition, the sheet member can have an extension portion at at least one end in the conveying direction that extends in a direction away from the front side in the opposing direction in which the back side of the heater and the sheet member face each other, and the holder can be configured to have an insertion portion into which the extension portion is inserted.

[0009] According to this, it is possible to further prevent the lubricant from flowing into the temperature detection member, and also to prevent the sheet member from moving in the conveying direction.

[0010] The extension portion may be provided at least at a downstream end in the conveying direction of the sheet member.

[0011] According to this, the lubricant easily flows to the downstream side of the heater in the transport direction as the belt rotates, so that the lubricant can be effectively prevented from flowing toward the temperature detection member on the downstream side in the transport direction.

[0012] The insertion portion may be a groove having a bottom.

[0013] According to this, even if the lubricant flows down the sheet member into the insertion portion, the insertion portion is a groove having a bottom, so that the lubricant can be prevented from entering further, thereby further preventing the lubricant from flowing into the temperature detection member.

[0014] The temperature detection member may have a contact surface that comes into contact with the temperature detection target, and the extension portion may extend in the facing direction to a position farther from the front side surface than the contact surface.

[0015] This can further prevent the lubricant from flowing into the temperature detection member.

[0016] In addition, the fixing device can be configured so that it is located between the rear side of the heater and the sheet member and includes a heat conductive member having a thermal conductivity greater than that of the substrate, the length of the sheet member in the transport direction is longer than the length of the heat conductive member in the transport direction, and the temperature detection member has a contact surface that contacts the temperature detection target and is in contact with the sheet member.

[0017] This can further prevent the lubricant from flowing into the temperature detection member. Also, at the beginning of printing, the heat conductive member can make the temperature distribution of the heater more uniform, and the sheet member can prevent heat from moving to the temperature detection member. This can prevent the temperature drop of the belt at the beginning of printing, and therefore prevent insufficient fixing strength.

[0018] The contact area between the sheet member and the heat conducting member may be equal to or larger than the contact area between the heater and the heat conducting member.

[0019] This can further prevent heat from being transferred by the sheet member toward the temperature detection member at the beginning of printing.

[0020] In addition, the sheet member contacts the back side of the heater, and the fixing device is located between the holder and the surface of the sheet member opposite the surface that contacts the back side of the heater, and includes a heat conductive member having a higher thermal conductivity than the substrate, and the length of the sheet member in the transport direction is longer than the length of the heat conductive member in the transport direction.

[0021] According to this, in the initial stage of heating by the heater, the sheet member can prevent heat from being transferred to the heat conductive member. Also, during printing, the heat conductive member can make the temperature distribution of the heater more uniform, so that the temperature of the end portion of the heater in the direction perpendicular to the conveying direction can be prevented from rising too high.

[0022] Also, the heater may be configured not to be in contact with the heat conducting member.

[0023] This can further suppress the transfer of heat to the heat conductive member in the initial stage of heating by the heater.

[0024] The temperature detection member may be configured so that a contact surface thereof that contacts the temperature detection target is in contact with a heat conductive member.

[0025] This makes it possible to detect the temperature of the heater via the thermally conductive member.

[0026] The heat conducting member may have a through hole or a notch, and the temperature detecting member may pass through the through hole or the notch and have a contact surface that contacts the temperature detection target and contacts the sheet member.

[0027] This makes it possible to detect the temperature of the heater through the sheet member.

[0028] The holder can also be configured to have a first surface that supports the sheet member and the heat conductive member, and a second surface that is located outside the first surface in the width direction of the recording material perpendicular to the transport direction and is closer to the heater than the first surface, and supports the back side of the heater.

[0029] With this, even if the sheet member tries to move in a direction perpendicular to the conveying direction, the step between the first surface and the second surface can restrict the movement of the sheet member in the direction perpendicular to the conveying direction.

[0030] Further, the step between the first surface and the second surface may be configured to be equal to or smaller than the sum of the thickness of the sheet member and the thickness of the heat conducting member.

[0031] According to this, when the heating unit is pressed by the pressure unit, it is possible to prevent a gap from being generated between the heater and the sheet member or the heat conductive member.

[0032] In addition, the pressure unit forms a nip portion by sandwiching the belt between itself and the heater, and the length of the sheet member in the width direction of the recording material perpendicular to the conveying direction can be configured to be longer than the length of the nip portion in the width direction.

[0033] This can prevent the lubricant from flowing along the widthwise ends of the sheet member toward the temperature detection member.

[0034] In addition, multiple temperature detection members may be provided, and the multiple temperature detection members may be configured to be arranged inside the outline of the same sheet member when viewed from the opposing direction in which the back side of the heater and the sheet member face each other.

[0035] According to this, even when there are a plurality of temperature detection members, one sheet member can prevent the lubricant from flowing into the temperature detection members.

[0036] The sheet member may be a film containing polyimide.

[0037] This allows the thickness of the sheet member to be reduced. Effect of the Invention

[0038] According to the present invention, it is possible to prevent the lubricant present between the heater and the belt from flowing to the back side of the sheet member. [Brief description of the drawings]

[0039] [Figure 1] 2 is a cross-sectional view of the fixing device according to the first embodiment. FIG. [Diagram 2] 1A is a diagram showing the heater as viewed from the front side, and FIG. 1B is a diagram showing the temperature detection member and the sheet member as viewed from the back side of the heater. [Diagram 3] 2 is an enlarged cross-sectional view of the vicinity of a sheet member of the fixing device according to the first embodiment. FIG. [Figure 4] 1 is a cross-sectional view of a fixing device according to a first embodiment, taken along a plane perpendicular to a conveying direction of a recording paper. [Diagram 5] 11 is an enlarged cross-sectional view of the vicinity of a sheet member of a fixing device according to a second embodiment. FIG. [Figure 6] 11 is a cross-sectional view of a fixing device according to a second embodiment, taken along a plane perpendicular to the conveying direction of a recording paper. FIG. [Figure 7] 13 is an enlarged cross-sectional view of the vicinity of a sheet member of a fixing device according to a third embodiment. FIG. [Figure 8] FIG. 11 is a perspective view of a heat conduction member according to a third embodiment. [Figure 9] 13A and 13B are perspective views of a heat conducting member according to a modified example. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0040] Next, a first embodiment will be described. As shown in Fig. 1, fixing device F is used in electrophotographic image forming devices, foil transfer devices that transfer foil by heat, etc., and includes a heating unit 1 and a pressure roller 2 as an example of a pressure unit. Fixing device F is configured to transport recording material S such as paper in a predetermined direction by heating unit 1 and pressure roller 2. Hereinafter, the transport direction of recording material S in fixing device F will be referred to simply as the "transport direction", and the width direction of recording material S perpendicular to the transport direction will be referred to simply as the "width direction" (see Fig. 2).

[0041] The pressure roller 2 is a member that forms a nip portion NP by sandwiching the belt 3 between itself and a heater 10, which will be described later. The pressure roller 2 has a shaft 2A and a roller portion 2B that is provided so as to cover a part of the outer periphery of the shaft 2A. The shaft 2A is made of, for example, metal, and the roller portion 2B is made of, for example, rubber that has high heat resistance. In the fixing device F, one of the heating unit 1 and the pressure roller 2 is biased toward the other.

[0042] The heating unit 1 is a device for heating the recording material S, and includes a belt 3, a heater 10, a holder 20, a heat conductive member 30, a stay 40, a temperature detection member 50, and a sheet member 70. Note that the above-mentioned "width direction" corresponds to the longitudinal direction of the heater 10, the holder 20, the heat conductive member 30, the sheet member 70, etc., and the "conveyance direction" corresponds to the short direction perpendicular to the longitudinal direction of the heater 10, the holder 20, the heat conductive member 30, the sheet member 70, etc.

[0043] The belt 3 is an endless belt made of metal, resin, or the like. The belt 3 rotates around the heater 10 while being guided by the holder 20. The belt 3 has an outer peripheral surface 3A and an inner peripheral surface 3B. The outer peripheral surface 3A contacts the recording material S to be heated. The inner peripheral surface 3B contacts the front side surface 15 of the heater 10 via a lubricant. The lubricant is a heat-resistant grease. The belt 3 rotates counterclockwise in FIG. 1 as the pressure roller 2 is driven to rotate clockwise in FIG. 1.

[0044] As shown in FIG. 2( a ), the heater 10 has a substrate 11 and a resistance heating element 12 supported by the substrate 11 . The substrate 11 is made of a long and narrow rectangular ceramic plate. The heater 10 is a so-called ceramic heater.

[0045] The resistance heating element 12 is formed by printing on one surface of the substrate 11. In this embodiment, two resistance heating elements 12 are provided. The two resistance heating elements 12 are each long in the width direction and are arranged parallel to each other and spaced apart in the transport direction perpendicular to the width direction.

[0046] A conductor 19A is connected to one end 12A of each resistance heating element 12, and a terminal 18 for supplying power is provided at each end of the conductor 19A. The other ends 12B of each resistance heating element 12 are connected to each other by the conductor 19B. In the width direction, the one end 12A and the other end 12B of the resistance heating element 12 are located outside a range W1 through which a recording material S of the maximum width usable in the fixing device F can pass.

[0047] The resistance heating element 12 and one surface of the substrate 11 on which the resistance heating element 12 is provided are covered with a cover (not shown) made of glass or the like.

[0048] The number of the resistance heating elements 12 is not particularly limited. Alternatively, a resistance heating element having a larger heat generation amount at the widthwise center than at the widthwise end portions and a resistance heating element having a larger heat generation amount at the widthwise end portions than at the widthwise center portion may be provided, and the heat generation distribution in the width direction may be adjusted by individually controlling each resistance heating element.

[0049] Returning to FIG. 1, the heater 10 has a front side surface 15 that contacts the inner circumferential surface 3B of the belt 3 and a back side surface 16 opposite the front side surface 15.

[0050] The holder 20 is a member that holds the heater 10, the thermally conductive member 30, etc. The holder 20 is made of a material such as resin, and has a support portion 21 and a guide portion 22. The support portion 21 is a portion that supports the heater 10, the heat conductive member 30, and the sheet member 70, and has a shape that is elongated in the width direction corresponding to the shape of the heater 10. The guide portions 22 are provided on both sides in the conveying direction of the support portion 21. Each guide portion 22 has a guide surface 22G along the inner circumferential surface 3B of the belt 3. The guide portion 22 has a plurality of guide ribs 22A aligned in the width direction.

[0051] The stay 40 is a member that supports the holder 20, and is made of a material, such as metal, that has greater rigidity than the holder 20. As one example, the stay 40 is formed by bending a steel plate or the like into a U-shape.

[0052] 3, the heat conductive member 30 is a member for conducting heat in the width direction to make the temperature of the heater 10 uniform in the width direction. The heat conductive member 30 is a sheet-like member, and is located between the back side surface 16 of the heater 10 and the support portion 21 of the holder 20. When the heating unit 1 sandwiches the recording material S, which is the object to be heated, between the pressure roller 2 and the heat conductive member 30, the heat conductive member 30 is sandwiched between the heater 10 and the support portion 21. The heat conductive member 30 has a heater side surface 31 that contacts the back side surface 16 of the heater 10, and an opposite surface 32 opposite the heater side surface 31.

[0053] The heat conducting member 30 is a member whose thermal conductivity in a direction parallel to the heater side surface 31 (hereinafter simply referred to as the "planar direction") is greater than that in the planar direction of the substrate 11. The material of the heat conducting member 30 is not particularly limited, but for example, metals with high thermal conductivity such as aluminum, aluminum alloys, and copper can be used. In addition, the heat conducting member 30 is desirably an anisotropic heat conducting member whose thermal conductivity in the planar direction is greater than that in a direction perpendicular to the heater side surface 31. For example, a graphite sheet can be used as the anisotropic heat conducting member. In addition, the thickness of the heat conducting member 30 is not particularly limited, and for example, it may be a film-like member thinner than 0.1 mm, or a plate-like member thicker than 1 mm.

[0054] The sheet member 70 is a member for suppressing the transfer of heat toward the temperature detection member 50 in the initial stage of heating by the heater 10. The sheet member 70 is located between the rear surface 16 of the heater 10 and the support portion 21 of the holder 20. When the heating unit 1 sandwiches the recording material S between itself and the pressure roller 2, the sheet member 70, together with the heat conductive member 30, is sandwiched between the heater 10 and the support portion 21.

[0055] The sheet member 70 is located on the opposite side of the heat conductive member 30 to the rear side 16 of the heater 10. In other words, the heat conductive member 30 is located between the rear side 16 of the heater 10 and the sheet member 70. The sheet member 70 is located between the opposite surface 32 of the heat conductive member 30 and the support portion 21 of the holder 20. Hereinafter, the direction in which the rear side 16 of the heater 10 and the sheet member 70 face each other is referred to as the "facing direction." The facing direction is a direction perpendicular to the transport direction and the width direction.

[0056] The sheet member 70 is a member whose thermal conductivity in a planar direction is smaller than that of the substrate 11 in the planar direction. The material of the sheet member 70 is not particularly limited, and for example, a resin having a lower thermal conductivity and higher heat resistance than ceramics can be used. The thickness of the sheet member 70 is also not particularly limited, and for example, the sheet member 70 may be thinner or thicker than the heat conducting member 30. As an example, the sheet member 70 is a film containing polyimide and is thinner than the heat conducting member 30. That is, the thickness of the sheet member 70 is thinner than the heat conducting member 30.

[0057] The sheet member 70 has a U-shape when viewed in the width direction, and has a main body portion 71 and extension portions 72 provided on both ends in the conveying direction. The main body portion 71 is a portion extending along the conveyance direction. The main body portion 71 of the sheet member 70 is located between the rear side surface 16 of the heater 10 and the support portion 21 of the holder 20. The main body portion 71 is located between the opposite surface 32 of the heat conductive member 30 and the support portion 21 of the holder 20. The heat conductive member 30 is located between the rear side surface 16 of the heater 10 and the main body portion 71.

[0058] The extension portion 72 is a portion extending in the facing direction from an end of the main body portion 71 in the transport direction. More specifically, the extension portion 72 is provided so as to extend in a direction away from the front side surface 15 of the heater 10 in the facing direction. Also, the extension portion 72 extends in the facing direction to a position farther from the front side surface 15 of the heater 10 than a contact surface 51 (described later) of the temperature detection member 50. More specifically, the extension portion 72 is provided so as to extend from an end of the main body portion 71 in the transport direction toward the upper side of FIG. 3 to a position above the contact surface 51.

[0059] The extension portion 72 includes a downstream extension portion 72A provided at a downstream end in the conveying direction of the sheet member 70, and an upstream extension portion 72B provided at an upstream end in the conveying direction of the sheet member 70. The downstream extension portion 72A extends from a downstream end in the conveying direction of the main body portion 71 toward the temperature detection member 50 in the opposing direction, and the upstream extension portion 72B extends from an upstream end in the conveying direction of the main body portion 71 toward the temperature detection member 50 in the opposing direction. The length of the downstream extension portion 72A in the opposing direction and the length of the upstream extension portion 72B in the opposing direction may be the same or different.

[0060] The support portion 21 of the holder 20 has an insertion portion 23. The insertion portion 23 is a groove having a bottom. More specifically, the insertion portion 23 is a groove that is open at a lower end in FIG. 3 that is closer to the heater 10 in the facing direction and closed at an upper end in FIG. 3 that is farther from the heater 10, and extends long in the width direction. The extension portion 72 of the sheet member 70 is inserted into the insertion portion 23.

[0061] The insertion section 23 includes a downstream insertion section 23A into which the downstream extending section 72A is inserted, and an upstream insertion section 23B into which the upstream extending section 72B is inserted. The length in the opposing direction of the downstream insertion section 23A (groove depth) is longer than the length in the opposing direction of the downstream extending section 72A, and the length in the opposing direction of the upstream insertion section 23B (groove depth) is longer than the length in the opposing direction of the upstream extending section 72B. The length in the opposing direction of the downstream insertion section 23A and the length in the opposing direction of the upstream insertion section 23B may be the same or different.

[0062] The temperature detection member 50 is a member for detecting the temperature of the heater 10. The temperature detection member 50 is located on the opposite side of the sheet member 70 to the back side 16 of the heater 10. The temperature detection member 50 is also located on the opposite side of the sheet member 70 to the opposite surface 32 of the heat conduction member 30. The temperature detection member 50 is disposed so as to sandwich the main body 71 of the sheet member 70 between itself and the heat conduction member 30. The temperature detection member 50 has a contact surface 51 that contacts the temperature detection target. The temperature detection member 50 detects the temperature of the temperature detection target via the contact surface 51.

[0063] The temperature detection member 50 has a contact surface 51 in contact with the sheet member 70. More specifically, a second sheet member 52 is attached so as to be wrapped around the temperature detection member 50, and the contact surface 51 is in contact with a main body portion 71 of the sheet member 70 via the second sheet member 52. The sheet member 70 is located between the opposite surface 32 of the heat conduction member 30 and the temperature detection member 50. The second sheet member 52 is made of, for example, a resin having high heat resistance. As an example, the sheet member 70 is a film containing polyimide.

[0064] As shown in Fig. 2(b), a plurality of temperature detection members 50 are provided. More specifically, the temperature detection members 50 include a first temperature detection member 50A, a second temperature detection member 50B, and a third temperature detection member 50C. As an example, the first temperature detection member 50A and the second temperature detection member 50B are thermistors and are used to control the temperature of the heater 10 to a predetermined target temperature. The third temperature detection member 50C is a thermostat and is used to cut off the power supply to the resistance heating element 12 when the temperature of the heater 10 rises abnormally.

[0065] As shown in FIG. 2(b), the temperature detection members 50 (50A-50C) are arranged inside the contour of the same sheet member 70 when viewed from the opposing direction. More specifically, the temperature detection members 50 (50A-50C) are arranged inside the contour of the sheet member 70 with the same contact surface 51 when viewed from the opposing direction. The above-mentioned second sheet member 52 is attached to each of the first temperature detection member 50A, the second temperature detection member 50B, and the third temperature detection member 50C. Therefore, the temperature detection members 50 (50A-50C) are arranged inside the contour of the second sheet member 52 with different contact surfaces 51 when viewed from the opposing direction.

[0066] 3, the length L170 of the sheet member 70 in the transport direction is longer than the length L110 of the heater 10 (substrate 11) in the transport direction. In the transport direction, one end 70A of the sheet member 70 is located outside one end 10A of the heater 10 (substrate 11), and the other end 70B of the sheet member 70 is located outside the other end 10B of the heater 10 (substrate 11).

[0067] Furthermore, length L170 of sheet member 70 in the transport direction is longer than length L130 of heat conduction member 30 in the transport direction. In the transport direction, one end 70A of sheet member 70 is located outside one end 30A of heat conduction member 30, and the other end 70B of sheet member 70 is located outside the other end 30B of heat conduction member 30.

[0068] In this embodiment, the length L110 of the heater 10 in the transport direction is the same as the length L130 of the heat conductive member 30 in the transport direction. In the transport direction, one end 10A of the heater 10 and one end 30A of the heat conductive member 30 are located at the same position, and the other end 10B of the heater 10 and the other end 30B of the heat conductive member 30 are located at the same position.

[0069] 4, the length L270 of the sheet member 70 in the width direction is longer than the length L2 of the nip portion NP in the width direction. More specifically, the length L270 of the sheet member 70 in the width direction is longer than the length L2 of the roller portion 2B of the pressure roller 2 in the width direction. In the width direction, one end 70C of the sheet member 70 is located outside one end 2C of the roller portion 2B, and the other end 70D of the sheet member 70 is located outside the other end 2D of the roller portion 2B. Note that the belt 3 is not shown in FIG. 4.

[0070] Furthermore, length L270 of sheet member 70 in the width direction is longer than length L230 of heat conduction member 30 in the width direction. In the width direction, one end 70C of sheet member 70 is located outside one end 30C of heat conduction member 30, and the other end 70D of sheet member 70 is located outside the other end 30D of heat conduction member 30.

[0071] Furthermore, the length L230 of the heat conductive member 30 in the width direction is longer than the length L2 of the roller portion 2B in the width direction. In the width direction, one end 30C of the heat conductive member 30 is located outside one end 2C of the roller portion 2B, and the other end 30D of the heat conductive member 30 is located outside the other end 2D of the roller portion 2B. The roller portion 2B is located within the range of the sheet member 70 and the heat conductive member 30 in the width direction.

[0072] Furthermore, length L210 of heater 10 (substrate 11) in the width direction is longer than lengths L270, L230, and L2. In the width direction, one end 10C of heater 10 (substrate 11) is located outside one end 70C of sheet member 70, one end 30C of heat conductive member 30, and one end 2C of roller portion 2B, and the other end 10D of heater 10 (substrate 11) is located outside the other end 70D of sheet member 70, the other end 30D of heat conductive member 30, and the other end 2D of roller portion 2B.

[0073] In this embodiment, the entire opposite surface 32 of the heat conduction member 30 is in contact with the main body portion 71 of the sheet member 70, and the entire heater side surface 31 of the heat conduction member 30 is in contact with the back side surface 16 of the heater 10. As a result, the contact area between the main body portion 71 of the sheet member 70 and the opposite surface 32 of the heat conduction member 30 is the same as the contact area between the back side surface 16 of the heater 10 and the heater side surface 31 of the heat conduction member 30.

[0074] Support portion 21 of holder 20 has first surface 21A, second surface 21B, and third surface 21C which are surfaces on the heater 10 side, a first step surface 21D connecting first surface 21A and second surface 21B, and a second step surface 21E connecting first surface 21A and third surface 21C. First surface 21A, second surface 21B, and third surface 21C are surfaces perpendicular to the opposing direction, and first step surface 21D and second step surface 21E are surfaces perpendicular to the width direction.

[0075] The first surface 21A is a surface that supports the sheet member 70 and the heat conduction member 30. More specifically, the first surface 21A supports the sheet member 70 by contacting the main body portion 71 of the sheet member 70, and supports the heat conduction member 30 via the main body portion 71 of the sheet member 70. The length in the width direction of the first surface 21A is longer than the length L230 in the width direction of the heat conduction member 30 and longer than the length L270 in the width direction of the sheet member 70. The heat conduction member 30 and the sheet member 70 are located within the range of the first surface 21A in the width direction.

[0076] The second surface 21B and the third surface 21C are surfaces that support the rear side surface 16 of the heater 10, and are located outside the first surface 21A in the width direction. More specifically, the second surface 21B is located on one side of the first surface 21A in the width direction, and supports the rear side surface 16 of the heater 10 by contacting one end of the rear side surface 16 of the heater 10 in the width direction. The third surface 21C is located on the other side of the first surface 21A in the width direction, and supports the rear side surface 16 of the heater 10 by contacting the other end of the rear side surface 16 of the heater 10 in the width direction.

[0077] The second surface 21B and the third surface 21C are located closer to the heater 10 than the first surface 21A in the opposing direction. The second surface 21B and the third surface 21C are located at the same position in the opposing direction. In the support portion 21, a recess is formed by the first surface 21A, the first step surface 21D, and the second step surface 21E, which is recessed toward the second surface 21B and the third surface 21C, and the main body portion 71 of the sheet member 70 and the heat conductive member 30 are disposed in this recess.

[0078] The length of first step surface 21D in the opposing direction, i.e., the step D1 between first surface 21A and second surface 21B, is equal to or less than the sum of the thickness T70 of sheet member 70 and the thickness T30 of heat conductive member 30. Similarly, the length of second step surface 21E in the opposing direction, i.e., the step D2 between first surface 21A and third surface 21C, is equal to or less than the sum of the thickness T70 of sheet member 70 and the thickness T30 of heat conductive member 30. It is desirable that the steps D1 and D2 are the same as the sum of the thickness T70 of sheet member 70 and the thickness T30 of heat conductive member 30.

[0079] 3, according to the first embodiment described above, the length L170 of the sheet member 70 in the conveying direction is longer than the length L110 of the heater 10 in the conveying direction, so that the sheet member 70 can prevent the lubricant present between the heater 10 and the belt 3 from flowing to the back side of the sheet member 70, i.e., to the temperature detection member 50 side. This can prevent the lubricant from adhering to, for example, the contact surface 51 of the temperature detection member 50, so that the temperature detection member 50 can exhibit its function well.

[0080] In addition, since the sheet member 70 has the extension portion 72 and the holder 20 has the insertion portion 23 into which the extension portion 72 is inserted, it is possible to further prevent the lubricant from flowing into the temperature detection member 50. In addition, it is possible to prevent the sheet member 70 from moving in the conveying direction following, for example, the thermal expansion of the heater 10.

[0081] In addition, since the lubricant tends to flow downstream of the heater 10 in the conveying direction as the belt 3 rotates, the extension portion 72 includes a downstream extension portion 72A provided at the downstream end of the sheet member 70 in the conveying direction, so that the lubricant can be effectively prevented from flowing toward the temperature detection member 50 on the downstream side in the conveying direction.

[0082] Even if the lubricant flows down the sheet member 70 into the insertion portion 23, the insertion portion 23 is a groove having a bottom, so that the lubricant can be prevented from entering further. This makes it possible to further prevent the lubricant from flowing into the temperature detection member 50.

[0083] Furthermore, since the extension portion 72 extends in the opposing direction to a position farther from the front side surface 15 of the heater 10 than the contact surface 51 of the temperature detection member 50, the lubricant can be further prevented from flowing into the temperature detection member 50 side compared to when the length of the extension portion in the opposing direction is short.

[0084] Furthermore, since the heat conductive member 30 is disposed between the heater 10 and the sheet member 70, it is possible to further suppress the lubricant from flowing into the temperature detection member 50. Furthermore, at the beginning of printing, the heat conductive member 30 can make the temperature distribution of the heater 10 more uniform, and the sheet member 70 can suppress the transfer of heat to the temperature detection member 50. This makes it possible to suppress a drop in the temperature of the belt 3 at the beginning of printing, thereby suppressing a lack of fixing strength.

[0085] Furthermore, since the contact area between the sheet member 70 and the heat conduction member 30 is the same as the contact area between the heater 10 and the heat conduction member 30, the transfer of heat by the sheet member 70 toward the temperature detection member 50 can be further suppressed at the beginning of printing.

[0086] Furthermore, even if the sheet member 70 attempts to move in the width direction, for example, following the thermal expansion of the heater 10, the movement of the sheet member 70 in the width direction can be restricted by the step (first step surface 21D) between the first surface 21A and the second surface 21B and the step (second step surface 21E) between the first surface 21A and the third surface 21C, as shown in FIG. 4.

[0087] Furthermore, since the steps D1, D2 are less than the sum of the thickness T70 of the sheet member 70 and the thickness T30 of the heat conductive member 30, when the heating unit 1 is pressed by the pressure roller 2, it is possible to prevent gaps from being formed between the heater 10 and the heat conductive member 30, between the heat conductive member 30 and the sheet member 70, and between the sheet member 70 and the first surface 21A of the holder 20.

[0088] Furthermore, since the length L270 of the sheet member 70 in the width direction is longer than the length L2 of the nip portion NP in the width direction, the lubricant can be prevented from flowing along the width direction edge of the sheet member 70 toward the temperature detection member 50.

[0089] 2(b), since multiple temperature detection members 50 (50A-50C) are arranged inside the contour of the same sheet member 70 when viewed from the opposing direction, even when there are multiple temperature detection members 50, one sheet member 70 can prevent the lubricant from flowing into the temperature detection members 50. This makes it possible to reduce the number of parts in the fixing device F compared to, for example, a case in which a sheet member is provided for each temperature detection member, and also makes it possible to prevent the lubricant from flowing into the temperature detection members through gaps between adjacent sheet members.

[0090] Furthermore, since the sheet member 70 is a film containing polyimide, the thickness of the sheet member 70 can be reduced.

[0091] In the first embodiment, the contact area between the sheet member 70 and the heat conductive member 30 is the same as the contact area between the heater 10 and the heat conductive member 30, but the contact area between the sheet member and the heat conductive member may be larger than the contact area between the heater and the heat conductive member. This also makes it possible to further suppress the transfer of heat by the sheet member to the temperature detection member at the beginning of printing.

[0092] Next, a second embodiment will be described. In the following, differences from the previously described embodiment will be described in detail, and the same elements will be denoted by the same reference numerals, and the description thereof will be omitted as appropriate.

[0093] 5, the heating unit 1 includes a belt 3, a heater 10, a holder 20, a heat conductive member 30, a stay 40, a temperature detection member 50, and a sheet member 70. The second embodiment differs from the first embodiment in the arrangement of the heat conductive member 30 and the sheet member 70.

[0094] The main body portion 71 of the sheet member 70 has a sheet front side surface 71A and a sheet back side surface 71B opposite to the sheet front side surface 71A. The sheet member 70 is disposed in a state in which the sheet front side surface 71A is in contact with the back side surface 16 of the heater 10 and the sheet back side surface 71B is in contact with the heater side surface 31 of the heat conductive member 30. That is, in the second embodiment, the sheet member 70 (main body portion 71) is located between the back side surface 16 of the heater 10 and the heater side surface 31 of the heat conductive member 30. In addition, the heat conductive member 30 is located between the sheet back side surface 71B of the sheet member 70 and the support portion 21 of the holder 20.

[0095] Also in the second embodiment, the length L170 of the sheet member 70 in the transport direction is longer than the length L110 of the heater 10 in the transport direction, and one end 70A and the other end 70B of the sheet member 70 in the transport direction are located outside one end 10A and the other end 10B of the heater 10. Also, the length L170 of the sheet member 70 in the transport direction is longer than the length L130 of the heat conduction member 30 in the transport direction, and one end 70A and the other end 70B of the sheet member 70 are located outside one end 30A and the other end 30B of the heat conduction member 30 in the transport direction.

[0096] Also, as shown in FIG. 6, the length L270 of the sheet member 70 in the width direction is longer than the length L230 of the heat conduction member 30 in the width direction, and one end 70C and the other end 70D of the sheet member 70 are located outside one end 30C and the other end 30D of the heat conduction member 30 in the width direction.

[0097] As a result, the sheet member 70 is disposed so as to cover and conceal the heat conducting member 30 when viewed from the heater 10 side in the opposing direction. As a result, in the second embodiment, the heater 10 is not in contact with the heat conducting member 30.

[0098] 5, the temperature detection member 50 has a contact surface 51 in contact with the heat conduction member 30. More specifically, the contact surface 51 is in contact with the opposite surface 32 of the heat conduction member 30 with a second sheet member 52 interposed therebetween.

[0099] According to the above-described second embodiment, similarly to the first embodiment, the length L170 of the sheet member 70 in the conveying direction is longer than the length L110 of the heater 10 in the conveying direction, so that the sheet member 70 can prevent the lubricant interposed between the heater 10 and the belt 3 from flowing toward the temperature detection member 50.

[0100] Furthermore, since the sheet member 70 is disposed between the heater 10 and the heat conductive member 30, in the initial stage of heating by the heater 10, the sheet member 70 can suppress the transfer of heat to the heat conductive member 30. Furthermore, during printing, the heat conductive member 30 can make the temperature distribution of the heater 10 more uniform, so that the temperature of the ends of the heater 10 in the width direction can be suppressed from rising too high.

[0101] Furthermore, since the heater 10 is not in contact with the heat conducting member 30, the transfer of heat to the heat conducting member 30 can be further suppressed in the initial stage of heating by the heater 10.

[0102] Furthermore, since the contact surface 51 of the temperature detection member 50 is in contact with the heat conducting member 30 , the temperature of the heater 10 can be detected via the heat conducting member 30 .

[0103] Also, as shown in FIG. 6, in the second embodiment, the steps D1, D2 are less than the sum of the thickness T70 of the sheet member 70 and the thickness T30 of the heat conduction member 30, so that when the heating unit 1 is pressed by the pressure roller 2, it is possible to prevent gaps from being formed between the heater 10 and the sheet member 70, between the sheet member 70 and the heat conduction member 30, and between the heat conduction member 30 and the first surface 21A of the holder 20.

[0104] Next, a third embodiment will be described. 7, in the third embodiment, the heat conduction member 30 has a through hole 33 penetrating in the opposing direction. The temperature detection member 50 passes through the through hole 33 and has a contact surface 51 in contact with the sheet member 70. More specifically, the contact surface 51 is in contact with the sheet back surface 71B of the sheet member 70 (main body portion 71) via the second sheet member 52.

[0105] As shown in FIG. 8, three through holes 33 are provided corresponding to the three temperature detection members 50, that is, the first temperature detection member 50A, the second temperature detection member 50B and the third temperature detection member 50C (see FIG. 2).

[0106] According to the above-described third embodiment, similarly to the first and second embodiments, the sheet member 70 can prevent the lubricant interposed between the heater 10 and the belt 3 from flowing toward the temperature detection member 50.

[0107] Furthermore, since the temperature detection member 50 passes through the through hole 33 provided in the heat conducting member 30 and the contact surface 51 is in contact with the sheet member 70 , the temperature of the heater 10 can be detected via the sheet member 70 .

[0108] In the third embodiment, the heat conducting member 30 has a through hole 33, and the temperature detection member 50 passes through the through hole 33 so that the contact surface 51 of the temperature detection member 50 comes into contact with the sheet member 70. However, as shown in FIG. 9(a), the heat conducting member 30 may have a notch 34, and the temperature detection member 50 (not shown) may pass through the notch 34 so that the contact surface 51 comes into contact with the sheet member 70. This also makes it possible to detect the temperature of the heater 10 via the sheet member 70. Furthermore, as shown in FIG. 9(b), the heat conducting member 30 may have both the through hole 33 and the notch 34.

[0109] Although the embodiment has been described above, the fixing device is not limited to the above embodiment, and can be modified as appropriate as exemplified below.

[0110] In the above embodiment, the length L130 of the heat conductive member 30 in the transport direction is the same as the length L110 of the heater 10 in the transport direction, but the length of the heat conductive member in the transport direction may be longer than the length of the heater in the transport direction. When the length of the heat conductive member in the transport direction is longer than the length of the heater in the transport direction, the length of the sheet member in the transport direction may be the same as the length of the heat conductive member in the transport direction.

[0111] In the above embodiment, the sheet member 70 has the extending portions 72 at both ends in the conveying direction, but the sheet member may have an extending portion only at one end in the conveying direction. In this case, the one end may be the downstream end in the conveying direction of the sheet member. In other words, the sheet member may have an extending portion only at the downstream end in the conveying direction of the sheet member.

[0112] In the embodiment described above, the extension portion 72 of the sheet member 70 extends in the facing direction to a position farther from the front side surface 15 of the heater 10 than the contact surface 51 of the temperature detection member 50, but referring to Fig. 5, the extension portion may be long enough to be located between the contact surface 51 of the temperature detection member 50 and the heater side surface 31 of the heat conduction member 30 in the facing direction. Also, the sheet member may be configured without an extension portion.

[0113] In the above embodiment, the insertion portion 23 is a groove having a bottom, but the insertion portion may be a slit-like hole penetrating in the opposing direction.

[0114] In the above embodiment, three temperature detection members 50 are provided, but the number of temperature detection members is arbitrary. Also, in the above embodiment, a plurality of temperature detection members 50 are provided, but a configuration in which only one temperature detection member is provided may be used.

[0115] In the above embodiment, the contact surface 51 of the temperature detection member 50 contacts the sheet member 70 or the heat conductive member 30 via the second sheet member 52, but the contact surface of the temperature detection member may directly contact the sheet member or the heat conductive member in a configuration without the second sheet member. Also, the contact surface of the temperature detection member may contact the sheet member or the heat conductive member via an amorphous member such as grease instead of the second sheet member.

[0116] In the above embodiment, the step between the first surface 21A and the second surface 21B (first step surface 21D) is a surface perpendicular to the width direction, but the step between the first surface and the second surface may be a surface that is inclined perpendicular to the width direction. The same applies to the step between the first surface and the third surface.

[0117] In the above embodiment, the sheet member 70 and the heat conductive member 30 are each made of a single sheet-like member, but the sheet member and the heat conductive member may be made of a combination of multiple sheet-like members. In this case, the multiple sheet-like members may be different from each other in terms of material, thermal conductivity, shape, etc., or may be the same as each other. In addition, the fixing device may be configured without including a heat conductive member.

[0118] In the above embodiment, the substrate 11 of the heater 10 is made of a long and narrow rectangular ceramic plate, but the heater substrate may be made of a long and narrow rectangular metal plate such as stainless steel.

[0119] In the above embodiment, a pressure roller 2 is exemplified as the pressure unit, but the pressure unit may also be a device including an endless second belt, a pressure pad that sandwiches the second belt between the heating unit, and a second holder that holds the pressure pad.

[0120] The elements described in the above embodiment and modified examples may be implemented in any combination. [Explanation of symbols]

[0121] 1 Heating unit 2 Pressure roller 3 Belt 3B Inner surface 10 Heater 11 Substrate 12 Resistance heating element 15 Front side 16 Back side 20 Holder 21A 1st page 21B 2nd side 23 Insertion section 30 Thermal Conductive Materials 50 Temperature sensing member 51 Contact surface 70 Sheet material 72 Extension part F Fixing unit NP Nip S recording material

Claims

1. A fixing device that conveys a recording material using a heating unit and a pressure unit, The heating unit includes: a heater having a substrate and a resistive heating element supported by the substrate; an endless belt having an inner circumferential surface that contacts the front surface of the heater via a lubricant and rotates around the heater; A holder for holding the heater; a sheet member that is located between the holder and a back surface of the heater opposite to the front surface, the sheet member having a thermal conductivity lower than that of the substrate; a temperature detection member for detecting a temperature of the heater, the temperature detection member being located on an opposite side of the sheet member to the rear side of the heater; a length of the sheet member in a recording material conveying direction is longer than a length of the heater in the recording material conveying direction; the sheet member has an extension portion at at least one end in the transport direction, the extension portion extending in a direction away from the front side surface in a facing direction in which the back side surface of the heater and the sheet member face each other, The fixing device, wherein the holder has an insertion portion into which the extension portion is inserted.

2. The fixing device according to claim 1 , wherein the extension portion is provided at least at an end portion of the sheet member on a downstream side in the transport direction.

3. 3. The fixing device according to claim 1, wherein the insertion portion is a groove having a bottom.

4. The temperature detection member has a contact surface that contacts a temperature detection target, 4. The fixing device according to claim 1, wherein the extension portion extends in the facing direction to a position farther from the front side surface than the contact surface.

5. A fixing device that conveys a recording material using a heating unit and a pressure unit, The heating unit includes: a heater having a substrate and a resistive heating element supported by the substrate; an endless belt having an inner circumferential surface that contacts the front surface of the heater via a lubricant and rotates around the heater; A holder for holding the heater; a sheet member that is located between the holder and a back surface of the heater opposite to the front surface, the sheet member having a thermal conductivity lower than that of the substrate; a temperature detection member for detecting a temperature of the heater, the temperature detection member being located on an opposite side of the sheet member to the rear side of the heater; a heat conductive member located between the back surface of the heater and the sheet member, the heat conductive member having a higher thermal conductivity than the substrate; a length of the sheet member in a recording material transport direction is longer than a length of the heater in the transport direction and is also longer than a length of the heat conductive member in the transport direction; The fixing device, wherein the temperature detection member has a contact surface that contacts a temperature detection target and is in contact with the sheet member.

6. 6. The fixing device according to claim 5, wherein a contact area between said sheet member and said heat conducting member is equal to or larger than a contact area between said heater and said heat conducting member.

7. the sheet member contacts the back side of the heater, the fixing device includes a heat conductive member having a higher thermal conductivity than the substrate, the heat conductive member being located between the holder and a surface of the sheet member opposite to a surface that contacts the rear side surface of the heater; 5. The fixing device according to claim 1, wherein the length of the sheet member in the transport direction is longer than the length of the heat conductive member in the transport direction.

8. 8. The fixing device according to claim 7, wherein the heater is not in contact with the heat conductive member.

9. 9. The fixing device according to claim 7, wherein the temperature detection member has a contact surface that contacts a temperature detection target and is in contact with the heat conductive member.

10. A fixing device that conveys a recording material using a heating unit and a pressure unit, The heating unit includes: a heater having a substrate and a resistive heating element supported by the substrate; an endless belt having an inner circumferential surface that contacts the front surface of the heater via a lubricant and rotates around the heater; A holder for holding the heater; a sheet member that is located between the holder and a back surface of the heater opposite to the front surface, the sheet member having a thermal conductivity lower than that of the substrate; a temperature detection member for detecting a temperature of the heater, the temperature detection member being located on an opposite side of the sheet member to the rear side of the heater; a heat conductive member having a higher thermal conductivity than the substrate, the heat conductive member being located between the holder and a surface of the sheet member opposite to a surface that contacts the back side of the heater, the sheet member contacts the back side of the heater, a length of the sheet member in a recording material transport direction is longer than a length of the heater in the transport direction and is also longer than a length of the heat conductive member in the transport direction; the heat conducting member has a through hole or a notch; The fixing device, wherein the temperature detection member has a contact surface that contacts a temperature detection target through the through hole or the notch and contacts the sheet member.

11. The holder includes: a first surface supporting the sheet member and the thermally conductive member; 11. The fixing device according to claim 5, further comprising a second surface located outside the first surface in a width direction of the recording material perpendicular to the transport direction and closer to the heater than the first surface, the second surface supporting the back side of the heater.

12. 12. The fixing device according to claim 11, wherein a step between the first surface and the second surface is equal to or smaller than a sum of a thickness of the sheet member and a thickness of the heat conductive member.

13. A fixing device that conveys a recording material using a heating unit and a pressure unit, The heating unit includes: a heater having a substrate and a resistive heating element supported by the substrate; an endless belt having an inner circumferential surface that contacts the front surface of the heater via a lubricant and rotates around the heater; A holder for holding the heater; a sheet member that is located between the holder and a back surface of the heater opposite to the front surface, the sheet member having a thermal conductivity lower than that of the substrate; a temperature detection member for detecting a temperature of the heater, the temperature detection member being located on an opposite side of the sheet member to the rear side of the heater; the pressure unit forms a nip portion by sandwiching the belt between the pressure unit and the heater, a length of the sheet member in a recording material conveying direction is longer than a length of the heater in the recording material conveying direction; a length of the sheet member in a width direction of the recording material perpendicular to the conveying direction is longer than a length of the nip portion in the width direction.

14. A fixing device that conveys a recording material using a heating unit and a pressure unit, The heating unit includes: a heater having a substrate and a resistive heating element supported by the substrate; an endless belt having an inner circumferential surface that contacts the front surface of the heater via a lubricant and rotates around the heater; A holder for holding the heater; a sheet member that is located between the holder and a back surface of the heater opposite to the front surface, the sheet member having a thermal conductivity lower than that of the substrate; a temperature detection member for detecting a temperature of the heater, the temperature detection member being located on an opposite side of the sheet member to the rear side of the heater; a length of the sheet member in a recording material conveying direction is longer than a length of the heater in the recording material conveying direction; The temperature detection member is provided in plurality, a fixing device, wherein the plurality of temperature detection members are arranged inside the outline of the same sheet member when viewed from a direction in which the back side of the heater and the sheet member face each other;

15. 15. The fixing device according to claim 1, wherein the sheet member is a film containing polyimide.

Images