Heating unit

Abstract

To detect an accurate temperature with a temperature detection member.SOLUTION: A heating unit 1 comprises: a heater 10; a temperature detection member (thermistor 50) that detects the temperature of the heater 10; an endless belt 3 that has an inner peripheral surface in contact with a nip surface 15 and rotates around the heater 10; a holder 20 that supports the heater 10; a sheet-like first heat conduction member 30 that is located between the heater 10 and the holder 20, the first heat conduction member 30 having a first heater side surface 31 in contact with a back side surface 16 of the heater 10 and a first opposite surface 32 on the opposite side of the first heater side surface 31; and a sheet-like second heat conduction member 45 that is smaller than the first heat conduction member 30 when seen from an orthogonal direction orthogonal to the first opposite surface 32, the second heat conduction member 45 having a second heater side surface 45F in contact with the first opposite surface 32 and a second opposite surface 45R on the opposite side of the second heater side surface 45F. The temperature detection member is in contact with the second opposite surface 45R.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a heating unit used in a fixing device of an electrophotographic image forming apparatus. [Background technology]

[0002] Conventionally, a fixing device in which a rotating belt is sandwiched between a ceramic heater and a pressure roller is known (Patent Document 1). In this fixing device, the ceramic heater has a substrate and a resistance heating element, and a sheet-like heat conductive member is arranged in contact with the back surface opposite to the nip surface that contacts the belt. The temperature detection member is in contact with the heat conductive member. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2015-99190 A Summary of the Invention [Problem to be solved by the invention]

[0004] However, when a heater has a resistance heating element provided on a substrate, there is a difference in temperature between the area close to the resistance heating element and the area far from the resistance heating element. Therefore, if the temperature detection element is brought into contact with a single heat conducting member arranged between the temperature detection element and the heater, as in the conventional technology, the heat conducting member may be affected by the uneven temperature caused by the arrangement of the resistance heating element, and the temperature detection element may not be able to detect the temperature accurately.

[0005] SUMMARY OF THE PRESENT EMBODIMENT An object of the present invention is to detect temperature accurately using a temperature detection member. [Means for solving the problem]

[0006] The heating unit for solving the above-mentioned problems includes a substrate, a resistive heating element supported on the substrate, a heater having a nip surface and a back side opposite the nip surface, a temperature detection member for detecting the temperature of the heater, an endless belt having an inner surface in contact with the nip surface and rotating around the heater, a holder for supporting the heater, a sheet-like first heat conduction member located between the heater and the holder and having a thermal conductivity higher than that of the substrate, the first heat conduction member having a first heater side surface in contact with the back side surface of the heater and a first opposite side opposite the first heater side surface, and a sheet-like second heat conduction member smaller than the first heat conduction member when viewed from an orthogonal direction perpendicular to the first opposite side, the second heat conduction member having a second heater side surface in contact with the first opposite side and a second opposite side opposite the second heater side surface. The temperature sensing member then contacts the second opposite surface.

[0007] According to this configuration, the temperature detection member does not directly contact the first opposite surface of the first thermal conductive member, but contacts the second opposite surface of the second thermal conductive member that is smaller than the first thermal conductive member and contacts the first opposite surface of the first thermal conductive member, so that the second thermal conductive member can average out temperature unevenness caused by the arrangement of the heating resistors, thereby allowing the temperature detection member to detect an accurate temperature.

[0008] In the longitudinal direction of the heater, the length of the first thermally conductive member may be longer than the length of the resistive heating element.

[0009] With this configuration, the temperature of the heater can be made uniform over the entire area in the longitudinal direction of the heater where the resistance heating element is disposed.

[0010] When viewed from a direction perpendicular to the first opposite surface, the size of the heater of the second heat conduction member in the longitudinal direction may be within twice the size of the contact portion where the temperature detection member contacts the second opposite surface, and the size of the second heat conduction member in a short direction perpendicular to the orthogonal direction and the longitudinal direction may be within twice the size of the contact portion in the short direction.

[0011] In this manner, by making the size of the second thermal conductive member appropriately small, the range of objects whose temperatures are detected by the temperature detection member can be limited to a predetermined range.

[0012] The temperature detection member may be positioned in the longitudinal direction of the heater so as to detect the temperature at a position within a range through which a recording material of a maximum width that can be used with the heating unit can pass, and outside a range through which a recording material of a minimum width that can be used with the heating unit can pass.

[0013] According to this configuration, the temperature rise in the portion where the minimum-width sheet does not pass can be detected by the temperature detection member.

[0014] The first thermally conductive member may be made of aluminum or an aluminum alloy.

[0015] The first heat conducting member may be an anisotropic heat conducting member having a higher thermal conductivity in a direction parallel to the first heater side surface than in a direction perpendicular to the first heater side surface. The anisotropic heat conducting member is, for example, a graphite sheet.

[0016] The second thermally conductive member may be made of aluminum or an aluminum alloy.

[0017] The temperature sensing member may have a protrusion, and the second thermally conductive member may be positioned relative to the temperature sensing member by engaging the protrusion.

[0018] With this configuration, the second thermal conductive member can be appropriately positioned with respect to the temperature detection member.

[0019] The second thermally conductive member may have a protrusion, and the protrusion may be engaged with the temperature detection member, thereby positioning the second thermally conductive member with respect to the temperature detection member.

[0020] With this configuration, the second thermal conductive member can be appropriately positioned with respect to the temperature detection member.

[0021] The second thermally conductive member may have a positioning portion that is positioned relative to the first thermally conductive member.

[0022] With this configuration, the second thermal conductive member can be appropriately positioned with respect to the first thermal conductive member.

[0023] The temperature detection member may be a thermistor or a current interrupting member that cuts off the current to the resistance heating element when the heater becomes abnormally hot. Effect of the Invention

[0024] According to the present invention, the temperature can be accurately detected by the temperature detection member. [Brief description of the drawings]

[0025] [Figure 1] FIG. 2 is a cross-sectional view of the heating unit at the location of the thermistor. [Diagram 2] FIG. 3A shows the surface on which the resistive heating element of the heater is arranged, FIG. 3B shows the heater, the first thermal conductive member and the second thermal conductive member as viewed from the rear surface side of the heater, and FIG. 3C shows the holder as viewed from the opposite side to the heater. [Diagram 3] 1A is a perspective view of a thermistor, and FIG. 1B is a perspective view of a current interrupting member. [Figure 4] 4 is a cross-sectional view of the heating unit at the position of the current interrupting member. FIG. [Diagram 5] FIG. 1A is a cross-sectional view along the longitudinal direction of the heating unit, explaining the positioning of the second heat conductive member and thermistor, and FIG. 1B is a cross-sectional view along the longitudinal direction of the heating unit, explaining the positioning of the second heat conductive member and the current interruption member. [Figure 6] 11 is a cross-sectional view of a heating unit at the position of a thermistor when the first thermally conductive member is a graphite sheet. FIG. [Figure 7]FIG. 1A is a cross-sectional view along the longitudinal direction of the heating unit illustrating another embodiment of the positioning of the second heat conductive member and thermistor; FIG. 1B is a cross-sectional view along the longitudinal direction of the heating unit illustrating another embodiment of the positioning of the second heat conductive member and the current-blocking member; and FIG. 1C is an enlarged cross-sectional view along the longitudinal direction of the heating unit illustrating yet another embodiment of the positioning of the second heat conductive member and thermistor. [Figure 8] FIG. 1A is a longitudinal cross-sectional view of a configuration in which the second thermal conduction member has a convex portion to position the second thermal conduction member relative to the first thermal conduction member, and FIG. 1B is a longitudinal cross-sectional view of a configuration in which the first thermal conduction member has a convex portion to position the second thermal conduction member relative to the first thermal conduction member. [Figure 9] FIG. 1(a) shows the surface on which the resistive heating element of a modified heater is arranged, FIG. 1(b) shows the heater, the first thermal conductive member and the second thermal conductive member as viewed from the back side of the heater, and FIG. 1(c) shows the holder as viewed from the opposite side to the heater. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0026] The heating unit 1 according to the embodiment is used in a fixing device of an image forming apparatus, a device for transferring foil by heat, etc. As shown in Fig. 1, the heating unit 1 includes a belt 3, a heater 10, a holder 20, a first heat conductive member 30, second heat conductive members 45, 46 (see Fig. 4), a thermistor 50 as an example of a temperature detection member, and a current interrupting member 60 as another example of a temperature detection member (see Fig. 4).

[0027] The belt 3 is endless and made of metal or resin. The belt 3 rotates around the heater 10 while being guided by the holder 20. The belt 3 has an outer circumferential surface and an inner circumferential surface. The outer circumferential surface comes into contact with the sheet to be heated. The inner circumferential surface comes into contact with the heater 10.

[0028] The heater 10 includes a substrate 11, a resistance heating element 12 supported by the substrate 11, and a cover 13. The substrate 11 is made of a long and narrow rectangular ceramic plate. The heater 10 is a so-called ceramic heater. The resistance heating element 12 is formed on one surface of the substrate 11 by printing. As shown in FIG. 2(a), in this embodiment, two resistance heating elements 12 are provided. The two resistance heating elements 12 are each long in the longitudinal direction of the heater 10 (hereinafter, the longitudinal direction of the heater 10 is simply referred to as the "longitudinal direction") and are arranged in parallel and spaced apart from each other in a lateral direction perpendicular to the longitudinal direction. 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. The number of resistance heating elements 12 is not particularly limited. In addition, a resistive heating element having a greater heat generation amount at the longitudinal center than at the longitudinal ends, and a resistive heating element having a greater heat generation amount at the longitudinal ends than at the longitudinal center may be provided, and by controlling each resistive heating element individually, the heat generation distribution in the longitudinal direction can be adjusted.

[0029] The cover 13 covers the resistance heating element 12. The cover 13 is made of, for example, glass. The heater 10 has a nip surface 15 that contacts the inner circumferential surface of the belt 3 and a back surface 16 opposite to the nip surface 15.

[0030] The holder 20 is a member that supports the heater 10. The holder 20 has a support portion 21 and a guide portion 22. The support portion 21 has a plate shape corresponding to the shape of the heater 10. The support portion 21 has a support surface 21A that faces the side where the heater 10 is arranged, and an inner surface 21B opposite to the support surface 21A. As shown in FIG. 2(c), the support portion 21 has holder openings 25A, 25B, and 26 that penetrate the support portion 21. The holder opening 25A is disposed in the center of the support portion 21 in the longitudinal direction, and is a rectangle that is long in the longitudinal direction. The holder opening 26 is disposed at one end of the support portion 21 in the longitudinal direction, and is a rectangle that is long in the longitudinal direction. The holder opening 25B is disposed at the other end of the support portion 21 in the longitudinal direction, and is a rectangle that is long in the longitudinal direction.

[0031] The thermistor 50 includes two thermistors, a first thermistor 50A and a second thermistor 50B. The first thermistor 50A and the second thermistor 50B are the same component. The first thermistor 50A detects the temperature of the center of the heater 10 in the longitudinal direction. The first thermistor 50A is used to control the temperature of the heater 10 to a target temperature based on the temperature detected by the first thermistor 50A. The second thermistor 50B detects the temperature of the heater 10 at a position closer to the end of the heater 10 than the position detected by the first thermistor 50A in the longitudinal direction of the heater 10. The second thermistor 50B is used to detect an increase in temperature at a position closer to the end of the heater 10. The holder opening 25A is disposed at a position corresponding to the first thermistor 50A. The first thermistor 50A and the second thermistor 50B do not have to be the same component. In this case, it is desirable that the first thermistor 50A is a member that has higher temperature detection accuracy than the second thermistor 50B within the temperature range during the printing operation.

[0032] The current interrupting member 60 is a member that interrupts the flow of electricity to the resistance heating element 12 when the temperature of the heater 10 increases abnormally. The holder opening 26 is disposed at a position corresponding to the current interrupting member 60.

[0033] Returning to Fig. 1, the guide portions 22 are provided on both ends in the short direction of the support portion 21. Each guide portion 22 has a guide surface 22G along the inner peripheral surface of the belt 3. As shown in Fig. 1 and Fig. 2(c), the guide portion 22 has a plurality of guide ribs 22A aligned in the longitudinal direction.

[0034] The first heat conducting member 30 is a member for conducting heat in the longitudinal direction of the heater 10 to make the temperature of the heater 10 uniform in the longitudinal direction. The first heat conducting member 30 is a sheet-like member and is located between the heater 10 and the support part 21 of the holder 20. When the heating unit 1 sandwiches a sheet, which is an object to be heated, between itself and another pressing member, the first heat conducting member 30 is sandwiched between the heater 10 and the support part 21. The first heat conducting member 30 has a first heater side surface 31 that contacts the back side surface 16 of the heater 10 and a first opposite surface 32 that is opposite to the first heater side surface 31. The first opposite surface 32 is in contact with the support surface 21A of the support part 21.

[0035] First thermal conduction member 30 is a member whose thermal conductivity in a direction parallel to first heater side surface 31 (hereinafter simply referred to as the “planar direction”) is greater than its thermal conductivity in the planar direction of substrate 11. The material of first thermal conduction member 30 is not particularly limited, and for example, metals with high thermal conductivity such as aluminum, aluminum alloys, and copper can be used. First thermal conduction member 30 may also be an anisotropic thermal conduction member whose thermal conductivity in the planar direction is greater than its thermal conductivity in the thickness direction perpendicular to first heater side surface 31. As the anisotropic thermal conduction member, for example, a thin graphite sheet as shown in FIG. 6 can be used. The thickness of first thermal conduction 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.

[0036] Second heat conducting members 45, 46 are intended to conduct heat in the planar direction and make the temperature of the portions where second heat conducting members 45, 46 are in contact with first heat conducting member 30 uniform. The second thermally conductive member 45 is a sheet-like member and has a second heater side surface 45F facing the heater 10 and a second opposite surface 45R opposite the second heater side surface 45F. The second heater side surface 45F contacts the first opposite surface 32. 4, the second thermal conductive member 46 also has a second heater side surface 46F facing the heater 10 and a second opposite surface 46R opposite to the second heater side surface 46F. The second heater side surface 46F is in contact with the first opposite surface 32.

[0037] 1 and 4, second heat conduction members 45A, 45B, and 46 are disposed at positions corresponding to holder openings 25A, 25B, and 26, respectively, when viewed from a direction perpendicular to first opposite surface 32 of first heat conduction member 30. Second heat conduction member 45 includes second heat conduction member 45A and second heat conduction member 45B. In this embodiment, second heat conduction member 45A and second heat conduction member 45B are the same component, except that they are disposed at different positions. In this embodiment, the size of second thermally conductive members 45A, 45B, 46 is smaller than first thermally conductive member 30 when viewed in a direction perpendicular to first opposite surface 32. Small in size here refers to a case where second thermally conductive member 45A, second thermally conductive member 45, or second thermally conductive member 46 is included inside the outline of first thermally conductive member 30 when first thermally conductive member 30 and second thermally conductive member 45A, second thermally conductive member 45, or second thermally conductive member 46 are overlapped.

[0038] The second heat conductive members 45, 46 are members whose thermal conductivity in a planar direction is greater than that of the substrate 11 in the planar direction. The material of the second heat conductive members 45, 46 is not particularly limited, but may be, for example, a metal with a high thermal conductivity, such as aluminum, an aluminum alloy, or copper. The thickness of the second heat conductive members 45, 46 is not particularly limited, and may be, for example, a film-like member thinner than 0.1 mm, or a plate-like member thicker than 1 mm.

[0039] The size of the second thermal conductive members 45, 46 in a short side direction perpendicular to the longitudinal direction is larger than the size of the short side direction of the resistance heating body 12. In this embodiment, the second thermal conductive members 45, 46 are located between the two resistance heating bodies 12 in the short side direction.

[0040] 5(b), second heat conductive member 46 has protrusions 46B that protrude in the thickness direction toward current interruption member 60. Protrusions 46B protrude from ends of second heat conductive member 46 in the longitudinal direction.

[0041] As shown in FIG. 3(b), thermistor 50 (50A, 50B) has a support plate 51, a biasing member 52, a film 53, and a temperature detection element 55. The biasing member 52 is a member having sponge-like elasticity, and is supported by the support plate 51. The biasing member 52 has a D-shaped cross section. The temperature detection element 55 is disposed so as to be located at the most protruding portion of the biasing member 52, and is connected to wiring (not shown). The film 53 is disposed so that the temperature detection element 55 is located at the most protruding portion of the biasing member 52, and is attached to the support plate 51 by being wrapped around the biasing member 52 and the support plate 51.

[0042] As shown in Fig. 3(a), film 53 has slits 53X at both ends in the longitudinal direction, extending in a direction perpendicular to the longitudinal direction. Thus, film 53 has central portion 53A located at the longitudinal center and in contact with biasing member 52, and protruding portions 53B located at both ends in the longitudinal direction. As shown in Fig. 5(a), when the thermistor 50 is attached to holder 20 and pressed against second heat conductive members 45A and 45B, biasing member 52 is crushed, and protruding portions 53B are portions that protrude relative to central portion 53A. Both ends in the longitudinal direction of second heat conductive members 45A and 45B engage with protruding portions 53B, and the second heat conductive members 45A and 45B are positioned relative to thermistor 50.

[0043] 3(b), current interrupting member 60 is a thermostat having an internal bimetallic interrupting mechanism, and has a case 61 that houses the interrupting mechanism, and a detection portion 62 that detects temperature and protrudes from case 61. As shown in FIG. 5(b), second heat conducting member 46 is positioned with respect to current interrupting member 60 by convex portions 46B engaging with both longitudinal ends of detection portion 62.

[0044] 1, the portion of first thermistor 50A protruding from support plate 51 enters holder opening 25A and contacts second opposite surface 45R of second heat conductive member 45A through holder opening 25A. Biasing member 52 of first thermistor 50A is crushed and temperature detection element 55 is pressed toward second opposite surface 45R of second heat conductive member 45A. The configuration in which second thermistor 50B contacts second opposite surface 45R is the same as the configuration in which first thermistor 50A contacts second opposite surface 45R, so a description thereof will be omitted.

[0045] As shown in FIG. 4, in the current interrupting member 60, the detection portion 62 protruding from the case 61 fits into the holder opening 26 and contacts the second opposite surface 46R of the second heat conducting member 46 through the holder opening 26.

[0046] When viewed from the orthogonal direction perpendicular to first opposite surface 32, the size of second heat conducting member 45 in the longitudinal direction is within twice the size of the contact portion of thermistor 50 in contact with second opposite surface 45R in the longitudinal direction. Moreover, the size of second heat conducting member 45 in the lateral direction perpendicular to the orthogonal direction and the longitudinal direction is within twice the size of the contact portion of thermistor 50 in contact with second opposite surface 45R in the lateral direction. Desirably, second heat conducting member 45 is larger in the lateral direction than the width of one resistance heating element 12 and larger than the interval between adjacent resistance heating elements 12.

[0047] When viewed from the orthogonal direction, the size of second heat conducting member 46 in the longitudinal direction is within twice the size of the contact portion where current interrupting member 60 contacts second opposite surface 46R in the longitudinal direction. Moreover, the size of second heat conducting member 46 in the lateral direction perpendicular to the orthogonal direction and the longitudinal direction is within twice the size of the contact portion where current interrupting member 60 contacts second opposite surface 46R in the lateral direction. Desirably, second heat conducting member 46 is larger in the lateral direction than the width of one resistance heating element 12 and larger than the interval between adjacent resistance heating elements 12.

[0048] As shown in Fig. 2, the first thermistor 50A is disposed so as to detect the temperature at a position within a range through which a sheet of the minimum width W2 usable in the heating unit 1 can pass. The second thermistor 50B is disposed so as to detect the temperature at a position within a range through which a sheet of the maximum width W1 usable in the heating unit 1 can pass, and outside the range through which a sheet of the minimum width W2 usable in the heating unit 1 can pass (the range on the other end side where the second thermistor 50B can be disposed is shown as an end range AE1 in Fig. 2). The current interrupting member 60 is disposed so as to detect the temperature at a position within a range through which a sheet of the maximum width W1 usable in the heating unit 1 can pass, and outside the range through which a sheet of the minimum width W2 usable in the heating unit 1 can pass (the range on one end side where the current interrupting member 60 can be disposed is shown as an end range AE2 in Fig. 2).

[0049] One end 12A and the other end 12B of resistance heating element 12 are located outside maximum width W1 in the longitudinal direction and inside one end 38A and the other end 38B of first thermal conductive member 30. That is, the length of first thermal conductive member 30 is longer than the length of resistance heating element 12 in the longitudinal direction. Furthermore, one end 38A and the other end 38B of first thermal conductive member 30 are located, in the longitudinal direction, outside one end 12A and the other end 12B of resistance heating element 12 and inside one end 11A and the other end 11B of substrate 11. That is, in the longitudinal direction, the length of substrate 11 is longer than the length of first thermal conductive member 30.

[0050] The effects of the heating unit 1 described above will now be described. The thermistor 50 contacts the second opposite surface 45R of the second heat conducting member 45, and the current interrupting member 60 contacts the second opposite surface 46R of the second heat conducting member 46. If the thermistor 50 and the current interrupting member 60 were to directly contact the first opposite surface 32 of the first heat conducting member 30, they may be affected by temperature unevenness due to the arrangement of the resistance heating body 12. For example, if the thermistor 50 and the current interrupting member 60 contact a portion of the first opposite surface 32 that corresponds to between the two resistance heating bodies 12 in the short direction, there is a possibility that the temperature cannot be detected accurately. However, in this embodiment, the thermistor 50 and the current interrupting member 60 do not directly contact the first opposite surface 32 of the first heat conducting member 30, but contact the second opposite surfaces 45R, 46R of the second heat conducting members 45, 46, so that the temperature unevenness due to the arrangement of the resistance heating body 12 can be averaged by the second heat conducting members 45, 46. This allows the thermistor 50 and the current interruption member 60 to detect the temperature accurately.

[0051] When a sheet with a minimum width W2 is heated, the end ranges AE1 and AE2 are portions where the temperature is likely to rise because the sheet with a minimum width W2 does not take away heat. When the temperature of the end ranges AE1 and AE2 rises, the heat of the heater 10 flows from the end ranges AE1 and AE2 toward the inner range of the minimum width W2 through the first thermal conductive member 30 and the second thermal conductive members 45B and 46. In this embodiment, the presence of the second thermal conductive members 45B and 46 in addition to the first thermal conductive member 30 improves the thermal conductivity performance of the end ranges AE1 and AE2. Therefore, the temperature rise at the longitudinal ends of the heater 10 can be suppressed.

[0052] Furthermore, since the length of first thermally conductive member 30 is longer than the length of resistance heating element 12, the temperature of heater 10 can be made uniform over the entire area in the longitudinal direction of heater 10 where resistance heating element 12 is disposed.

[0053] Second heat conductive members 45, 46 are appropriately small because their longitudinal and lateral sizes are within twice the size of the contact areas of thermistor 50 and current interruption member 60 with second heat conductive members 45, 46. Therefore, the range of objects whose temperatures are detected by second heat conductive members 45, 46 can be limited to a predetermined range.

[0054] The second thermistor 50B is disposed so as to detect the temperature at the position of the end area AE1, and therefore the rise in temperature in the end area AE1 can be detected by the second thermistor 50B.

[0055] Since the current interrupting member 60 is disposed so as to detect the temperature at the position of the end area AE2, the current interrupting member 60 can detect the rise in temperature of the end area AE2.

[0056] Since second thermal conductive member 45 engages with protrusion 53B of thermistor 50, second thermal conductive member 45 can be appropriately positioned with respect to thermistor 50.

[0057] Since protrusion 46B of second heat conducting member 46 engages with current interrupting member 60, second heat conducting member 46 can be appropriately positioned with respect to current interrupting member 60.

[0058] Although the embodiment of the present invention has been described above, the present invention is not limited to the above embodiment and can be appropriately modified and carried out.

[0059] The method for positioning the second thermally conductive member may be different from that in the above embodiment. For example, instead of thermistor 50 having a protrusion, second thermal conductive member 245 may have protrusions 245B at both ends in the longitudinal direction, and protrusions 245B may engage with both ends of film 53 of thermistor 50, as shown in FIG. 7(a). In addition, instead of the second thermal conductive member having a protrusion, as shown in Figure 7 (b), the current interruption member 60 may have a protrusion 61A at both ends in the longitudinal direction, and the protrusion 61A may engage with both ends of the second thermal conductive member 246. 7(a), second thermally conductive member 245 may not only have protrusion 245B protruding toward thermistor 50, but also may have locking portion 345C protruding inward in the longitudinal direction from protrusion 345B, as in the embodiment shown in Fig. 7(c). Locking portion 345C engages with film 53, so that after film 53 and second thermally conductive member 345 are combined, the second thermally conductive member will not come off unnecessarily.

[0060] The second heat conducting member may have a positioning portion that is positioned relative to the first heat conducting member. For example, as shown in FIG. 8(a), the second heat conducting member 45 may have a protrusion 45P protruding toward the heater 10 at both ends in the longitudinal direction, and the first heat conducting member 30 may have a hole 30P with which the protrusion 45P engages. Alternatively, as shown in FIG. 8(b), the first heat conducting member 30 may have a protrusion 30Q protruding toward the side opposite the heater 10, and the second heat conducting member 45 may have a hole 45Q with which the protrusion 30Q engages. With this configuration, the second heat conducting member 45 can be appropriately positioned relative to the first heat conducting member 30.

[0061] 9, the current interrupting member 60 may be arranged so as to detect the temperature at a position within a range through which a sheet of the minimum width W2 usable by the heating unit 1 can pass. In such a case, the temperature can be accurately detected by the thermistor 50 and the current interrupting member 60. Furthermore, since the current interrupting member 60 is arranged within a range through which a sheet of the minimum width W2 usable by the heating unit 1 can pass, an abnormal temperature rise in the heater 10 can be detected regardless of the width of the sheet.

[0062] Furthermore, the number of temperature detection members and current interruption members is not limited, and the number of temperature detection members may be one or three or more, and the number of current interruption members may be two or more or none at all.

[0063] In the above embodiment, first thermally conductive member 30 and second thermally conductive members 45, 46 are each made of a single sheet-like member, but may be made of a combination of multiple sheet-like members. In this case, the multiple sheet-like members may be different from one another in terms of material, thermal conductivity, shape, etc., or may be the same as one another.

[0064] In addition, in the above embodiment, the substrate 11 of the heater 10 is made of a long, narrow rectangular plate made of ceramic, but it may be made of a long, narrow rectangular plate made of a metal such as stainless steel as long as it has a lower thermal conductivity than the heat conduction member 30.

[0065] Furthermore, the elements described in the above embodiment and modified examples can be implemented in appropriate combinations. [Explanation of symbols]

[0066] 1 Heating unit 3 Belt 10 Heater 11 Substrate 12 Resistance heating element 15 Nip surface 16 Back side 20 Holder 30 First heat conductive member 31 First heater side 32 1st opposite side 45 (45A, 45B) Second heat conductive member 45F Second heater side 45R 2nd opposite side 46 Second heat conductive member 46F Second heater side 46R 2nd opposite side 50 Thermistor 60 Current interrupting member

Claims

1. a heater having a substrate, a resistance heating element supported by the substrate, a nip surface, and a back surface opposite the nip surface; a temperature detection member for detecting the temperature of the heater; an endless belt having an inner circumferential surface in contact with the nip surface and rotating around the heater; A holder for supporting the heater; a first thermally conductive member having a sheet-like shape and a thermal conductivity higher than that of the substrate, the first thermally conductive member being located between the heater and the holder, the first thermally conductive member having a first heater side surface in contact with the back surface of the heater and a first opposite surface opposite to the first heater side surface; a sheet-like second thermal conduction member that is smaller than the first thermal conduction member when viewed in a direction perpendicular to the first opposite surface, the second thermal conduction member having a second heater side surface in contact with the first opposite surface and a second opposite surface opposite to the second heater side surface; The temperature sensing member contacts the second opposite surface, The temperature detection member has a protrusion, The heating unit according to claim 1, wherein the second heat conducting member is engaged with the protrusion and positioned relative to the temperature detecting member.

2. a heater having a substrate, a resistance heating element supported by the substrate, a nip surface, and a back surface opposite the nip surface; a temperature detection member for detecting the temperature of the heater; an endless belt having an inner circumferential surface in contact with the nip surface and rotating around the heater; A holder for supporting the heater; a first thermally conductive member having a sheet-like shape and a thermal conductivity higher than that of the substrate, the first thermally conductive member being located between the heater and the holder, the first thermally conductive member having a first heater side surface in contact with the back surface of the heater and a first opposite surface opposite to the first heater side surface; a sheet-like second thermal conduction member that is smaller than the first thermal conduction member when viewed in a direction perpendicular to the first opposite surface, the second thermal conduction member having a second heater side surface in contact with the first opposite surface and a second opposite surface opposite to the second heater side surface; The temperature sensing member contacts the second opposite surface, The heating unit according to claim 1, wherein the second thermal conductive member has a protrusion, and the protrusion engages with the temperature detection member to thereby position the second thermal conductive member relative to the temperature detection member.

3. a heater having a substrate, a resistance heating element supported by the substrate, a nip surface, and a back surface opposite the nip surface; a temperature detection member for detecting the temperature of the heater; an endless belt having an inner circumferential surface in contact with the nip surface and rotating around the heater; A holder for supporting the heater; a first thermally conductive member having a sheet-like shape and a thermal conductivity higher than that of the substrate, the first thermally conductive member being located between the heater and the holder, the first thermally conductive member having a first heater side surface in contact with the back surface of the heater and a first opposite surface opposite to the first heater side surface; a sheet-like second thermal conduction member that is smaller than the first thermal conduction member when viewed in a direction perpendicular to the first opposite surface, the second thermal conduction member having a second heater side surface in contact with the first opposite surface and a second opposite surface opposite to the second heater side surface; The temperature sensing member contacts the second opposite surface, A heating unit, wherein the second heat conducting member has a positioning portion that is positioned relative to the first heat conducting member.

4. 4. The heating unit according to claim 1, wherein a length of the first thermally conductive member in a longitudinal direction of the heater is longer than a length of the resistive heating element.

5. When viewed from a direction perpendicular to the first opposite surface, a size of the second thermally conductive member in a longitudinal direction of the heater is within twice the size of a contact portion of the temperature detection member in contact with the second opposite surface in the longitudinal direction; The heating unit according to any one of claims 1 to 4, characterized in that the size of the second thermal conductive member in a short direction perpendicular to the orthogonal direction and the longitudinal direction is within twice the size of the contact portion in the short direction.

6. A heating unit as described in any one of claims 1 to 5, characterized in that the temperature detection member detects the temperature at a position in the longitudinal direction of the heater, within a range through which a recording material of a maximum width that can be used with the heating unit can pass, and outside a range through which a recording material of a minimum width that can be used with the heating unit can pass.

7. 7. The heating unit according to claim 1, wherein the first heat conducting member is made of aluminum or an aluminum alloy.

8. 8. The heating unit according to claim 1, wherein the first thermal conduction member is an anisotropic thermal conduction member having a thermal conductivity in a direction parallel to the first heater side surface greater than a thermal conductivity in a direction perpendicular to the first heater side surface.

9. 9. The heating unit according to claim 8, wherein the anisotropic heat conductive member is a graphite sheet.

10. 10. The heating unit according to claim 1, wherein the second heat conducting member is made of aluminum or an aluminum alloy.

11. 11. The heating unit according to claim 1, wherein the temperature detection member is a thermistor or a current interrupting member that interrupts current flow to the resistance heating element when the heater becomes abnormally hot.

Images