Heating unit

Abstract

To suppress the intrusion of a lubricant disposed on an inner circumferential surface of a belt into a thermostat.SOLUTION: A fixing device 1 includes a heater 10, a belt 20, a thermostat 60, a cable 70, a thermostat holder 80, and a film 100. A lubricant is disposed on an inner circumferential surface of the belt. The thermostat 60 includes a case 61 and a heat-sensitive member 62 having a heat-sensitive surface 62A. The thermostat holder 80 holds the case 61 and the cable 70. The film 100 covers the thermostat 60 and the thermostat holder 80. The film 100 includes a first cover section 110 that covers the heat-sensitive surface 62A, a second cover section 120, and a third cover section 130. The second cover section 120 covers the heat-sensitive member 62 and the thermostat holder 80 from one side in the short side direction. The third cover section 130 covers the heat-sensitive member 62 and the thermostat holder 80 from the other side in the short side direction.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a fixing device used in an image forming apparatus or the like.

Background Art

[0002] Conventionally, as a fixing device used in an image forming apparatus or the like, there is known one including a planar heater, an endless belt rotating around the heater, and a thermostat (Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] By the way, in order to reduce the friction between the heater and the endless belt, a lubricant may be disposed on the inner peripheral surface of the belt. When the lubricant is disposed on the inner peripheral surface of the belt, there is a risk that the lubricant may enter the thermostat.

[0005] Therefore, an object is to suppress the lubricant disposed on the inner peripheral surface of the belt from entering the thermostat.

Means for Solving the Problems

[0006] The fixing device for solving the above-described problems includes a heater, a belt, a thermostat, a thermostat holder, and a film. The heater extends in the longitudinal direction and the short-side direction orthogonal to the longitudinal direction. The heater is plate-shaped. The belt rotates around the heater. The belt is endless. A lubricant is disposed on the inner peripheral surface of the belt. The thermostat has a case and a heat-sensitive member. The case houses therein a cutoff mechanism that cuts off energization when the temperature rises to a predetermined temperature or higher. The heat-sensitive member protrudes from the case. The heat-sensitive member has a heat-sensitive surface that detects the temperature of the heater. The thermostat holder holds the case. The film covers the thermostat and the thermostat holder. The film has a first cover portion, a second cover portion, and a third cover portion. The first cover portion covers the heat-sensitive surface. The second cover portion extends from the first cover portion. The second cover portion covers the heat-sensitive member and the thermostat holder from one side in the short-side direction. The third cover portion extends from the first cover portion. The third cover portion covers the heat-sensitive member and the thermostat holder from the other side in the short-side direction.

[0007] Since the film covers the thermostat and the thermostat holder, it is possible to suppress the lubricant disposed on the inner peripheral surface of the belt from entering the thermostat.

[0008] Also, the second cover portion and the third cover portion may be in contact with the thermostat holder.

[0009] The fixing device for solving the above-described problems includes a heater, a belt, a thermostat, and a film. The heater extends in the longitudinal direction and the short-side direction orthogonal to the longitudinal direction. The heater is plate-shaped. The belt is endless and rotates around the heater. A lubricant is disposed on the inner peripheral surface of the belt. The thermostat has a case and a heat-sensitive member. The case houses therein a cutoff mechanism that cuts off energization when the temperature rises to a predetermined temperature or higher. The heat-sensitive member protrudes from the case. The heat-sensitive member has a heat-sensitive surface that detects the temperature of the heater. The film covers the thermostat. The film has a first cover portion, a second cover portion, and a second cover portion. The first cover part covers the heat-sensitive surface. The second cover part extends from the first cover part. The second cover part covers the boundary between the heat-sensitive member on one side surface in the short direction of the thermostat and the case. The second cover part has a first edge extending in the longitudinal direction. The third cover part extends from the first cover part. The third cover part covers the boundary between the heat-sensitive member on the other side surface in the short direction of the thermostat and the case. The third cover part has a second edge extending in the longitudinal direction. The first edge is located farther from the heater than the boundary between the case and the heat-sensitive member in the orthogonal direction orthogonal to the longitudinal direction and the short direction. The second edge is located farther from the heater than the boundary between the case and the heat-sensitive member in the orthogonal direction.

[0010] Since the first edge and the second edge are located farther from the heater than the boundary between the case and the heat-sensitive member in the orthogonal direction orthogonal to the longitudinal direction and the short direction, it is possible to suppress the lubricant disposed on the inner peripheral surface of the belt from entering the thermostat.

[0011] Further, it may further include a cable extending from the thermostat and a thermostat holder for holding the case and the cable. And the second cover part and the third cover part may be in contact with the thermostat holder.

[0012] Also, when viewed in the longitudinal direction, the film may cover the thermostat at least one full turn or more.

[0013] Since the film covers the thermostat at least one full turn or more, it is difficult for the lubricant to enter the thermostat.

[0014] Also, in the longitudinal direction, the dimension of the film may be larger than the dimension of the case.

[0015] In the longitudinal direction, since the dimension of the film is larger than the dimension of the case, it is difficult for the lubricant to enter the thermostat.

[0016] Further, it may include a heater holder that holds the heater and has a first opening through which the heat-sensitive member passes. And in the longitudinal direction, the dimension of the film may be larger than the dimension of the first opening.

[0017] In the longitudinal direction, since the dimension of the film is larger than the dimension of the first opening, it is difficult for the lubricant to penetrate into the heat-sensitive member.

[0018] Further, the heater holder may have a rib that protrudes toward the case at a position a predetermined distance away from the first opening in the longitudinal direction. And the tip of the rib may be in contact with the film.

[0019] Since the tip of the rib protruding toward the case is in contact with the film, it is difficult for the lubricant to penetrate into the thermostat.

[0020] Further, the thermostat holder may have a boss that protrudes in a direction away from the heater. And the film may have a first extension portion extending from the second cover portion and a second extension portion extending from the third cover portion. And the first extension portion may be a first hole into which the boss enters and may have a first hole for locking the second cover portion to the thermostat holder. And the second extension portion may be a second hole into which the boss enters and may have a second hole for locking the third cover portion to the thermostat holder.

[0021] By the first hole of the first extension portion and the second hole of the second extension portion entering the boss, the film can be locked to the thermostat holder.

[0022] Further, the boss may have a recess for holding a spring that biases the case so that the heat-sensitive surface is pressed toward the heater.

[0023] Since the boss holds the spring, the heat-sensitive surface is pressed toward the heater, so that the heat-sensitive surface can stably detect the temperature of the heater.

[0024] Further, the fixing device may further include a stay that supports the heater holder, the stay having a first wall orthogonal to the short side direction, a second wall extending parallel to the first wall, and a third wall connecting the first wall and the second wall. And the first wall may have a through hole at a position corresponding to the thermostat in the longitudinal direction.

[0025] Since the first wall of the stay has a through hole at a position corresponding to the thermostat in the longitudinal direction, the lubricant can escape to the outside of the stay.

[0026] Also, in the conveying direction of the belt at the position where the heater and the belt face each other, the first wall may be located upstream of the thermostat.

[0027] Since the first wall is located upstream of the thermostat, the lubricant upstream of the thermostat can be escaped from the through hole to the outside of the stay.

[0028] Also, the second cover portion may extend to a position farther from the heater than the through hole in the orthogonal direction orthogonal to the longitudinal direction and the short side direction.

[0029] Since the second cover portion extends to a position farther from the heater than the through hole in the orthogonal direction, it is difficult for the lubricant to enter the thermostat.

[0030] Also, the heater holder may be a wall located between the first wall and the case in the conveying direction, and may have a wall extending in the longitudinal direction. And the wall may have a second opening at a position corresponding to the thermostat in the longitudinal direction.

[0031] Since the wall located between the first wall and the case has a second opening at a position corresponding to the thermostat in the longitudinal direction, the movement of the lubricant along the wall is suppressed and it is difficult for the lubricant to enter the thermostat.

[0032] The fixing device may further include a cable extending from the thermostat, and the thermostat holder may hold the cable.

[0033] Further, the film may be configured to have a lower thermal conductivity than the heat-sensitive member.

[0034] Further, the film may be made of polyimide.

Advantages of the Invention

[0035] According to the present invention, it is possible to suppress the lubricant disposed on the inner peripheral surface of the belt from entering the thermostat.

Brief Description of the Drawings

[0036]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Figure 10

Best Mode for Carrying Out the Invention

[0037] Next, embodiments will be described. As shown in FIG. 1, the fixing device 1 is a fixing device used in an electrophotographic image forming device, a foil transfer device that transfers a foil by heat, and the like. The fixing device 1 includes a heating unit 2 and a pressure roller 3.

[0038] When the fixing device 1 is used in an image forming device, the toner image is fixed on the recording material by transporting the recording material such as paper between the heating unit 2 and the pressure roller 3. Further, when the fixing device 1 is used in a foil transfer device, the foil is transferred to the recording material by transporting the recording material between the heating unit 2 and the pressure roller 3.

[0039] The heating unit 2 includes a heater 10, a belt 20, a heater holder 30, a stay 40, and a thermostat 60.

[0040] The heater 10 is a heater that heats the recording material transported between the heating unit 2 and the pressure roller 3. The heater 10 is a so-called ceramic heater. The heater 10 is plate-shaped. The heater 10 extends in the longitudinal direction and the short-side direction orthogonal to the longitudinal direction. In the present embodiment, the short-side direction is the transport direction of the recording material in the heater 10.

[0041] Hereinafter, the longitudinal direction of the heater 10 will be simply referred to as the "longitudinal direction". Also, the short-side direction of the heater 10 will be simply referred to as the "short-side direction". The short-side direction is orthogonal to the longitudinal direction. Also, the direction orthogonal to the longitudinal direction and the short-side direction is referred to as the "orthogonal direction". Also, in the figure, the arrow indicating the direction shall point to one side of that direction.

[0042] The heater 10 has a first surface 10A and a second surface 10B. The first surface 10A is a surface that contacts the inner peripheral surface 21 of the belt 20, and the second surface 10B is a surface on the side opposite to the first surface 10A. The heater 10 has a power supply terminal 14 disposed at the other end in the longitudinal direction (see FIG. 2).

[0043] The belt 20 rotates around the heater 10. The belt 20 is an endless belt. The belt 20 has an inner peripheral surface 21 and an outer peripheral surface 22. The inner peripheral surface 21 of the belt 20 contacts the first surface 10A of the heater 10, and the outer peripheral surface 22 contacts the pressure roller 3. Further, the outer peripheral surface 22 of the belt 20 also contacts the recording material conveyed between the heating unit 2 and the pressure roller 3.

[0044] A lubricant is disposed on the inner peripheral surface 21 of the belt 20. The type of the lubricant is not particularly limited, but in the present embodiment, a grease containing a fluorine oil as a base oil, a thickener, and an additive is used.

[0045] The heater holder 30 is a member that holds the heater 10 and guides the belt 20. Specifically, the heater holder 30 supports the second surface 10B side of the heater 10. In the present embodiment, the heater holder 30 is made of resin. The heater holder 30 has a support wall 31 and a belt guide 32.

[0046] As shown in FIGS. 3 and 4, the support wall 31 has a heater placement groove 31A, a first opening 31B, a first wall portion 31C, a second wall portion 31D, a first notch 31E, a second notch 31F as an example of the second opening, and a rib 31G.

[0047] As shown in FIG. 4, the heater placement groove 31A extends in the longitudinal direction. The heater placement groove 31A is a groove in which the heater 10 is disposed.

[0048] The first opening 31B is an opening that penetrates the support wall 31. The first opening 31B is a rectangular hole. In the present embodiment, the heat-sensitive member 62 of the thermostat 60 described later penetrates the first opening 31B.

[0049] As shown in FIG. 3, the first wall portion 31C is a wall that protrudes from the support wall 31 in a direction away from the heater 10 and extends in the longitudinal direction.

[0050] The second wall portion 31D is a wall that protrudes from the support wall 31 in a direction away from the heater 10 and extends in the longitudinal direction. The second wall portion 31D is disposed at a predetermined distance from one side in the short direction with respect to the first wall portion 31C. The second wall portion 31D is an example of a wall located between the first wall 41 of the stay 40, which will be described later, and the case 61 in the conveyance direction (see FIG. 8).

[0051] The first notch 31E is a notch formed in the first wall portion 31C. The first notch 31E is disposed at a position corresponding to the first opening 31B in the longitudinal direction. That is, the first notch 31E is disposed at a position corresponding to the heat-sensitive member 62 of the thermostat 60 in the longitudinal direction.

[0052] The second notch 31F is a notch formed in the second wall portion 31D. The second notch 31F is disposed at a position corresponding to the first opening 31B in the longitudinal direction. That is, the second notch 31F is disposed at a position corresponding to the heat-sensitive member 62 of the thermostat 60 in the longitudinal direction.

[0053] The rib 31G protrudes from the support wall 31 in a direction away from the heater 10 and extends in the short direction. The rib 31G connects the first wall portion 31C and the second wall portion 31D. Further, the rib 31G protrudes toward the case 61 of the thermostat 60, which will be described later. The rib 31G is disposed at a position a predetermined distance away from the first opening 31B in the longitudinal direction. In the present embodiment, the rib 31G is disposed on both sides of the first opening 31B in the longitudinal direction.

[0054] The belt guides 32 are respectively provided on one side and the other side of the support wall 31 in the short side direction. The belt guide 32 has a guide rib 32A protruding in the short side direction. A plurality of belt guides 32 and guide ribs 32A are provided side by side in the longitudinal direction (see also Fig. 2). The guide rib 32A has a shape along the inner peripheral surface 21 of the belt 20. The inner peripheral surface 21 of the belt 20 is in contact with the guide rib 32A. The belt 20 is rotatable around the heater 10 and the heater holder 30 while being guided by the guide rib 32A.

[0055] The stay 40 is a member that supports the heater holder 30. The stay 40 has a first wall 41, a second wall 42, and a third wall 43.

[0056] As shown in Fig. 1, the first wall 41 is a wall orthogonal to the short side direction. In the conveyance direction of the belt 20 at the position where the heater 10 and the belt 20 face each other, the first wall 41 is located upstream of the thermostat 60. The first wall 41 has a through hole 41H.

[0057] The through hole 41H has a rectangular shape extending in the longitudinal direction. The through hole 41H is disposed at the center of the first wall 41 in the orthogonal direction. Also, as shown in Fig. 2, the through hole 41H is disposed at a position corresponding to the thermostat 60 in the longitudinal direction. Specifically, the through hole 41H is disposed at a position overlapping the thermostat 60 when viewed from the short side direction.

[0058] As shown in Fig. 1, the second wall 42 is a wall extending parallel to the first wall 41. In the conveyance direction of the belt 20 at the position where the heater 10 and the belt 20 face each other, the second wall 42 is located downstream of the thermostat 60. The second wall 42 is disposed on the other side of the first wall 41 in the short side direction, spaced apart from the first wall 41.

[0059] The third wall 43 connects the other end of the first wall 41 in the orthogonal direction and the other end of the second wall 42 in the orthogonal direction.

[0060] Stay 40 supports the heater holder 30 from the side opposite to the side where the heater 10 is located. Specifically, one end side in the orthogonal direction of the first wall 41 and one end side in the orthogonal direction of the second wall 42 of the stay 40 are in contact with the surfaces of the support wall 31 on the side opposite to the side where the heater 10 is located, respectively. The stay 40 is a member having higher rigidity than the resin-made heater holder 30. In the present embodiment, the stay 40 is made of metal. Specifically, the stay 40 is formed by bending a steel plate into a U shape.

[0061] The pressure roller 3 has a shaft 3A and a roller body 3B. The shaft 3A is made of, for example, metal. The roller body 3B is made of, for example, rubber and is provided so as to cover the periphery of the shaft 3A. The pressure roller 3 sandwiches the belt 20 with the heater 10. In the fixing device 1, one of the heating unit 2 and the pressure roller 3 is biased toward the other.

[0062] As shown in FIG. 3, the thermostat 60 has a case 61, a heat-sensitive member 62, a first terminal 63, and a second terminal 64.

[0063] The case 61 houses an interruption mechanism inside that interrupts energization when the temperature rises to a predetermined temperature or higher.

[0064] The heat-sensitive member 62 protrudes from the case 61 to one side in the orthogonal direction. The heat-sensitive member 62 includes a bimetal disposed inside and a cap covering the bimetal. As shown in FIG. 7, the heat-sensitive member 62 passes through the first opening 31B of the heater holder 30. The heat-sensitive member 62 has a heat-sensitive surface 62A for detecting the temperature of the heater 10 on the outer surface of the cap covering the bimetal. The heat-sensitive surface 62A is a flat surface and faces the second surface 10B of the heater 10. When the temperature of the heat-sensitive surface 62A rises to a predetermined temperature or higher, the bimetal disposed inside the heat-sensitive member 62 deforms and the interruption mechanism interrupts energization.

[0065] The first terminal 63 is disposed on one side in the longitudinal direction of the case 61. The second terminal 64 is disposed on the other side in the longitudinal direction of the case 61.

[0066] As shown in FIG. 2, the heating unit 2 further includes a connector 50, a cable 70, a thermostat holder 80, a cable guide 90, a spring SP, and a film 100.

[0067] The cable 70 extends from the thermostat 60. Specifically, the cable 70 electrically connects the connector 50 and the thermostat 60. The cable 70 has a first cable 71 and a second cable 72. The first cable 71 connects the connector 50 and the first terminal 63 of the thermostat 60. The second cable 72 connects the connector 50 and the second terminal 64 of the thermostat 60. The connector 50 supplies power to the heater 10 by contacting the power supply terminal of the heater 10.

[0068] The thermostat holder 80 is a member that holds the thermostat 60. Specifically, the thermostat holder 80 is a member that holds the case 61 of the thermostat 60 and a part of the cable 70.

[0069] As shown in FIG. 8, the thermostat holder 80 is supported by the heater holder 30. Specifically, the thermostat holder 80 is disposed between the first wall portion 31C and the second wall portion 31D of the heater holder 30.

[0070] As shown in FIG. 3, the thermostat holder 80 has a first cover wall 81, a second cover wall 82, and a boss 83. The first cover wall 81 and the second cover wall 82 face each other in the short side direction. As shown in FIG. 8, the thermostat 60 is disposed between the first cover wall 81 and the second cover wall 82. That is, the first cover wall 81 and the second cover wall 82 face the thermostat 60 in the short side direction.

[0071] The boss 83 is a member that holds the spring SP and the cable 70 and locks the film 100. The boss 83 protrudes from the first cover wall 81 to the other side in the direction away from the heater 10, that is, in the orthogonal direction. Also, the boss 83 protrudes from the center in the longitudinal direction of the first cover wall 81 to one side in the short direction. As shown in FIG. 7, the cable 70 passes through in the longitudinal direction on one side in the orthogonal direction of the boss 83. For this reason, the cable 70 is held by the thermostat holder 80 by the boss 83 so as not to come out to the other side in the orthogonal direction.

[0072] The boss 83 has a recess 83A for holding the spring SP and an engaging protrusion 83B. One end of the spring SP enters the recess 83A. The engaging protrusion 83B is disposed within the recess 83A and protrudes to the other side in the direction away from the heater 10, that is, in the orthogonal direction. The engaging protrusion 83B engages with one end of the spring SP.

[0073] As shown in FIG. 2, the cable guide 90 is disposed between the heater holder 30 and the stay 40. The cable guide 90 is a member that holds the cable 70 and the thermostat holder 80.

[0074] The spring SP is a spring that biases the case 61 of the thermostat 60 so that the heat-sensitive surface 62A is pressed toward the heater 10. In the present embodiment, the spring SP is a compression coil spring. The spring SP is disposed between the stay 40 and the thermostat 60. Specifically, one end of the spring SP enters the recess 83A and is in contact with the thermostat holder 80 in a state of being engaged with the engaging protrusion 83B, and the other end is in contact with the stay 40.

[0075] The film 100 is made of a material having a lower thermal conductivity than the heat-sensitive member 62. In the present embodiment, the film 100 is made of polyimide. The film 100 covers the thermostat 60 and the thermostat holder 80. In the present embodiment, as shown in FIG. 8, when viewed from the longitudinal direction, the film 100 covers the thermostat 60 more than once.

[0076] As shown in FIG. 7, in the longitudinal direction, the dimension L1 of the film 100 is larger than the dimension K1 of the first opening 31B. Also, in the longitudinal direction, the dimension L1 of the film 100 is larger than the dimension C1 of the case 61.

[0077] As shown in FIG. 8(b), the film 100 has a first cover portion 110, a second cover portion 120, a third cover portion 130, a first extension portion 140, and a second extension portion 150.

[0078] The first cover portion 110 is a portion that covers the heat-sensitive surface 62A of the thermostat 60. In FIG. 8(b), the portion in contact with the heat-sensitive surface 62A is shown by dot hatching. Note that the scales of FIGS. 8(a) and 8(b) are not the same. As shown in FIG. 7, the tip of the rib 31G of the heater holder 30 is in contact with the film 100 (see also FIG. 4).

[0079] As shown in FIG. 8(b), the second cover portion 120 extends from the first cover portion 110. The dimension of the second cover portion 120 in the longitudinal direction is the same as the dimension L1 of the first cover portion 110. As shown in FIG. 8(a), the second cover portion 120 is a portion that covers the heat-sensitive member 62 and the thermostat holder 80 from one side in the short direction. The second cover portion 120 is in contact with the first cover wall 81 of the thermostat holder 80. Also, the second cover portion 120 covers the boundary BD between the heat-sensitive member 62 on one side surface of the thermostat 60 in the short direction and the case 61.

[0080] As shown in FIG. 8(b), the second cover portion 120 has a first edge 121 that extends in the longitudinal direction. In the present embodiment, the first edge 121 extends substantially along the longitudinal direction, but in the longitudinal direction, it is slightly inclined with respect to the longitudinal direction so as to approach the first cover portion 110 as it moves away from the portion in contact with the heat-sensitive surface 62A shown by dot hatching.

[0081] As shown in FIG. 6, the second cover portion 120 extends in the orthogonal direction to a position farther from the heater 10 than the through hole 41H of the stay 40. Further, as shown in FIG. 7, the first edge 121 is located farther from the heater 10 than the boundary BD between the case 61 and the heat-sensitive member 62 in the orthogonal direction (see also FIG. 6).

[0082] As shown in FIG. 8(b), the third cover portion 130 extends from the first cover portion 110. The dimension of the third cover portion 130 in the longitudinal direction is the same as the dimension L1 of the first cover portion 110. As shown in FIG. 8(a), the third cover portion 130 is a portion that covers the heat-sensitive member 62 and the thermostat holder 80 from the other side in the short direction. The third cover portion 130 is in contact with the second cover wall 82 of the thermostat holder 80. Further, the third cover portion 130 covers the boundary BD between the heat-sensitive member 62 and the case 61 on the other side in the short direction of the thermostat 60.

[0083] As shown in FIG. 8(b), the third cover portion 130 has a second edge 131 that extends in the longitudinal direction. In the present embodiment, the second edge 131 extends substantially along the longitudinal direction, but is slightly inclined with respect to the longitudinal direction so as to approach the first cover portion 110 as it moves away from the portion in contact with the heat-sensitive surface 62A indicated by dot hatching in the longitudinal direction.

[0084] As shown in FIG. 8(b), the first extension portion 140 extends from the second cover portion 120. The dimension L2 of the first extension portion 140 in the longitudinal direction is smaller than the dimension L1 of the second cover portion 120. The first extension portion 140 has a third edge 141 and a first hole 142.

[0085] The third edge 141 extends in the longitudinal direction. The first hole 142 is a rectangular hole formed at the center of the first extension portion 140 in the longitudinal direction. As shown in FIG. 5(a), the boss 83 fits into the first hole 142. The first hole 142 is adapted to lock the second cover portion 120 to the thermostat holder 80.

[0086] As shown in FIG. 8(b), the second extending portion 150 extends from the third cover portion 130. The dimension L2 in the longitudinal direction of the second extending portion 150 is smaller than the dimension L1 of the third cover portion 130. The second extending portion 150 has a fourth edge 151 and a second hole 152.

[0087] The fourth edge 151 extends in the longitudinal direction. The second hole 152 is a rectangular hole formed at the center in the longitudinal direction of the second extending portion 150. As shown in FIG. 5(a), the boss 83 fits into the second hole 152. The second hole 152 is adapted to lock the third cover portion 130 to the thermostat holder 80.

[0088] Here, the procedure for assembling the thermostat 60 to the fixing device 1 will be described. As shown in FIG. 3, when assembling the thermostat 60 to the fixing device 1, first, the thermostat 60 is placed in the thermostat holder 80. Then, the cable 70 is held at a predetermined position of the thermostat holder 80. Next, as shown in FIGS. 5(a) and 5(b), the film 100 is attached to the thermostat 60 and the thermostat holder 80. In this case, first, the boss 83 is inserted into the second hole 152 of the second extending portion 150. Then, the film 100 is wound around the thermostat 60 and the thermostat holder 80 so that the first cover portion 110 contacts the heat-sensitive surface 62A, and the boss 83 is inserted into the first hole 142 of the first extending portion 140. Thereby, the film 100 is attached to the thermostat 60 and the thermostat holder 80. Next, as shown in FIG. 7, the thermostat 60 and the thermostat holder 80 to which the film 100 is attached are placed in the heater holder 30. The heater 10 may be pre-assembled in the heater holder 30 or assembled later. Next, attach the stay 40 to the heater holder 30. When the stay 40 is attached to the heater holder 30, the spring SP disposed between the stay 40 and the thermostat 60 biases the thermostat 60 toward the heater 10. Then, the heat-sensitive surface 62A of the thermostat 60 is pressed against the second surface 10B of the heater 10, and the tip of the rib 31G is pressed against the film 100.

[0089] Next, the effects exhibited by the fixing device 1 of the present embodiment will be described. In the fixing device 1 of the present embodiment, a lubricant is disposed on the inner peripheral surface 21 of the belt 20. If this lubricant enters the thermostat 60, the thermostat 60 may not operate properly. However, according to the fixing device 1, since the film 100 covers the thermostat 60 and the thermostat holder 80, it is possible to suppress the lubricant disposed on the inner peripheral surface 21 of the belt 20 from entering the thermostat 60.

[0090] Also, as shown in FIG. 7, the first edge 121 and the second edge 131 of the film 100 are located farther from the heater 10 than the boundary BD between the case 61 and the heat-sensitive member 62 of the thermostat 60 in the orthogonal direction. For this reason, it is possible to suppress the lubricant disposed on the inner peripheral surface 21 of the belt 20 from entering the thermostat 60.

[0091] Also, as shown in FIG. 8, since the film 100 covers the thermostat 60 at least one full turn or more, it is difficult for the lubricant to enter the thermostat 60.

[0092] Also, in the longitudinal direction, since the dimension L1 of the film 100 is larger than the dimension C1 of the case 61, it is difficult for the lubricant to enter the thermostat 60.

[0093] Also, as shown in FIG. 4, in the longitudinal direction, since the dimension L1 of the film 100 is larger than the dimension K1 of the first opening 31B, it is difficult for the lubricant to enter the heat-sensitive member 62 of the thermostat 60.

[0094] Also, as shown in FIG. 7, since the tip of the rib 31G protruding toward the case 61 of the thermostat 60 contacts the film 100, it is difficult for the lubricant to enter the thermostat 60.

[0095] Further, by the first hole 142 of the first extending portion 140 of the film 100 and the second hole 152 of the second extending portion 150 entering the boss 83 of the thermostat holder 80, the film 100 can be locked to the thermostat holder 80 without using an adhesive or a double-sided tape.

[0096] Also, since the boss 83 of the thermostat holder 80 holds the spring SP, the heat-sensitive surface 62A of the thermostat 60 is pressed toward the heater 10. Therefore, the heat-sensitive surface 62A can stably detect the temperature of the heater 10.

[0097] Also, since the first wall 41 of the stay 40 has a through hole 41H at a position corresponding to the thermostat 60 in the longitudinal direction, the lubricant can escape to the outside of the stay 40. Therefore, it is possible to suppress the lubricant from entering the thermostat 60.

[0098] Also, since the first wall 41 of the stay 40 is located upstream of the thermostat 60, the lubricant upstream of the thermostat 60 can be escaped from the through hole 41H to the outside of the stay 40.

[0099] Also, the second cover portion 120 of the film 100 extends in the orthogonal direction to a position farther from the heater 10 than the through hole 41H of the stay 40. Therefore, it is difficult for the lubricant to enter the thermostat 60.

[0100] Also, the second wall portion 31D located between the first wall 41 of the stay 40 and the case 61 of the thermostat 60 has a second notch 31F at a position corresponding to the thermostat 60 in the longitudinal direction. Therefore, the movement of the lubricant along the second wall portion 31D to the other side in the orthogonal direction is suppressed, and it is difficult for the lubricant to enter the thermostat 60.

[0101] Although the embodiments have been described above, the fixing device can be appropriately modified and implemented as exemplified below.

[0102] In the above-described embodiment, when viewed in the longitudinal direction, the film 100 covered the thermostat 60 for one or more turns, but the film may not cover the thermostat 60 for one or more turns.

[0103] For example, the film 200 shown in FIG. 9 does not cover the thermostat 60 for one or more turns. As shown in FIG. 9, the film 200 has a first cover portion 210, a second cover portion 220, a third cover portion 230, and a first extension portion 240. The second cover portion 220 has a first edge 221 extending in the longitudinal direction. The third cover portion 230 has a first edge 231 extending in the longitudinal direction. The first extension portion 240 has a third edge 241 and a first hole 242. The film 200 locks the second cover portion 220 to the thermostat holder 80 by the first hole 242 entering the boss 83. The third cover portion 230 is attached to the second cover wall 82 with an adhesive. Even with this film 200, since it covers the thermostat 60 and the thermostat holder 80, it is possible to suppress the lubricant disposed on the inner peripheral surface 21 of the belt 20 from entering the thermostat 60.

[0104] For example, the film 300 shown in FIG. 10 does not cover the thermostat 60 for one or more turns. As shown in FIG. 10, the film 300 has a first cover portion 310, a second cover portion 320, and a third cover portion 330. The second cover portion 320 has a first edge 321 extending in the longitudinal direction. The third cover portion 230 has a first edge 331 extending in the longitudinal direction. The second cover portion 320 and the third cover portion 330 are attached to the first cover wall 81 and the second cover wall 82 with an adhesive. Even with this film 300, since it covers the thermostat 60 and the thermostat holder 80, it is possible to suppress the lubricant disposed on the inner peripheral surface 21 of the belt 20 from entering the thermostat 60.

[0105] In the above-described embodiment, the heat-sensitive member 62 passed through the first opening 31B of the heater holder 30. However, as long as the heat-sensitive member 62 can detect the temperature of the heater 10, it does not have to pass through the first opening 31B. For example, even if the heat-sensitive member 62 enters the first opening 31B and the heat-sensitive surface 62A does not reach the heater 10. Also, a temperature transmission member that easily transmits heat may be disposed between the heat-sensitive member 62 and the heater 10.

[0106] In the above-described embodiment, the thermostat 60 has a bimetal inside, and when the heat-sensitive surface 62A is heated to a predetermined temperature or higher, the bimetal deforms and the cutoff mechanism cuts off the power supply. However, the thermostat may have a fuse inside. In this configuration, when the temperature rises to a predetermined temperature or higher, the metal melts and the power supply is cut off.

[0107] In the above-described embodiment, the thermostat holder 80 holds a part of the case 61 of the thermostat 60 and the cable 70. However, the thermostat holder may be configured to hold only the case 61 of the thermostat 60.

[0108] In the above-described embodiment, when viewed from the longitudinal direction, the film 100 covered the thermostat 60 one or more times, but it may cover it two or more times.

[0109] In the above-described embodiment, as an example of the second opening, the second notch 31F was illustrated, but the second opening may be a through hole or a groove.

[0110] In the above-described embodiment, the biasing member that biases the thermostat 60 toward the heater 10 was the spring SP. However, for example, the biasing member may be a torsion coil spring or a leaf spring. In the above-described embodiment, the film 100 was made of polyimide. However, the film 100 may be made of other resins such as fluororesin or PET, or may be made of a material other than resin.

[0111] Each element described in the above-described embodiments and modified examples may be implemented in any combination.

Description of Reference Numerals

[0112] 1 Fixing device 2 Heating unit 10 Heater 10A First surface 10B Second surface 20 Belt 21 Inner peripheral surface 30 Heater holder 40 Stay 60 Thermostat 61 Case 62 Heat-sensitive member 62A Heat-sensitive surface 70 Cable 80 Thermostat holder 81 First cover wall 82 Second cover wall 83 Boss 100 Film 110 First cover portion 120 Second cover portion 130 Third cover portion 140 First extending portion 150 Second extending portion SP Spring

Claims

1. A plate-shaped heater extending in a longitudinal direction and a short-side direction orthogonal to the longitudinal direction, An endless belt that rotates around the heater, the belt having a lubricant disposed on its inner peripheral surface, A case in which a cutoff mechanism for cutting off energization is housed when the temperature rises above a predetermined temperature, and a heat-sensitive member protruding from the case, the heat-sensitive member having a heat-sensitive surface for detecting the temperature of the heater, and a thermostat having the same, A thermostat holder for holding the case, A film covering the thermostat and the thermostat holder, The film, A first cover portion covering the heat-sensitive surface, A second cover portion extending from the first cover portion and covering the heat-sensitive member and the thermostat holder from one side in the short-side direction, A third cover portion extending from the first cover portion and covering the heat-sensitive member and the thermostat holder from the other side in the short-side direction, and a fixing device characterized by having the same.

2. The fixing device according to claim 1, wherein the second cover portion and the third cover portion are in contact with the thermostat holder.

3. A plate-shaped heater extending in a longitudinal direction and a short-side direction orthogonal to the longitudinal direction, An endless belt that rotates around the heater, the belt having a lubricant disposed on its inner peripheral surface, A case in which a cutoff mechanism for cutting off energization is housed when the temperature rises above a predetermined temperature, and a heat-sensitive member protruding from the case, the heat-sensitive member having a heat-sensitive surface for detecting the temperature of the heater, and a thermostat having the same, A film covering the thermostat, The film, A first cover portion covering the heat-sensitive surface, A second cover portion extending from the first cover portion and covering the boundary between the heat-sensitive member and the case on one side surface of the thermostat in the short-side direction, the second cover portion having a first edge extending in the longitudinal direction, A third cover portion extending from the first cover portion and covering the boundary between the heat-sensitive member and the case on the other side surface of the thermostat in the short-side direction, the third cover portion having a second edge extending in the longitudinal direction, The first edge is located farther from the heater than the boundary between the case and the heat-sensitive member in a direction orthogonal to the longitudinal direction and the short-side direction. The fixing device is characterized in that the second edge is located farther from the heater than the boundary between the case and the heat-sensitive member in the orthogonal direction. **Claim 4** a cable extending from the thermostat; and a thermostat holder that holds the case and the cable, and the fixing device according to claim 3, wherein the second cover portion and the third cover portion are in contact with the thermostat holder. **Claim 5** The fixing device according to claim 1 or claim 3, wherein the film covers the thermostat at least once or more when viewed from the longitudinal direction. **Claim 6** The fixing device according to claim 1 or claim 3, wherein the dimension of the film in the longitudinal direction is larger than the dimension of the case. **Claim 7** a heater holder that holds the heater, the heater holder having a first opening through which the heat-sensitive member passes, and the fixing device according to claim 1 or claim 3, wherein the dimension of the film in the longitudinal direction is larger than the dimension of the first opening. **Claim 8** The heater holder has a rib protruding toward the case at a position a predetermined distance away from the first opening in the longitudinal direction, and the fixing device according to claim 7, wherein the tip of the rib contacts the film. **Claim 9** The thermostat holder has a boss protruding in a direction away from the heater, the film has a first extension portion extending from the second cover portion and a second extension portion extending from the third cover portion, and the first extension portion has a first hole into which the boss fits and is a first hole for locking the second cover portion to the thermostat holder. The second extension portion has a second hole into which the boss fits and is a second hole for locking the third cover portion to the thermostat holder, and the fixing device according to claim 1 or claim 4. **Claim 10** The fixing device according to claim 9, wherein the boss has a recess for holding a spring that biases the case so that the heat-sensitive surface is pressed toward the heater. **Claim 11** a stay that supports the heater holder, the stay having a first wall orthogonal to the short-side direction, a second wall extending parallel to the first wall, and a third wall connecting the first wall and the second wall. ​ ​ ​ ​ ​ The fixing device according to claim 7, wherein the first wall has a through hole at a position corresponding to the thermostat in the longitudinal direction.

12. The fixing device according to claim 11, wherein the first wall is located upstream of the thermostat in the conveying direction of the belt at a position where the heater and the belt face each other.

13. The fixing device according to claim 11, wherein the second cover portion extends to a position farther from the heater than the through hole in a direction orthogonal to the longitudinal direction and the short-side direction.

14. The heater holder is a wall located between the first wall and the case in the conveying direction, and has a wall extending in the longitudinal direction. The fixing device according to claim 12, wherein the wall has a second opening at a position corresponding to the thermostat in the longitudinal direction.

15. Further comprising a cable extending from the thermostat. The fixing device according to claim 1, wherein the thermostat holder holds the cable.

16. The fixing device according to claim 1 or claim 3, wherein the film has a lower thermal conductivity than the heat-sensitive member.

17. The fixing device according to claim 1 or claim 3, wherein the film is made of polyimide.

Images