Fixing device

Abstract

To provide a fixing device that can suppress reduction in a fixing temperature at ends of an area through which the largest sheet on which an image forming apparatus can perform printing passes.SOLUTION: A fixing device comprises: a belt; a heater 112; a holder; and a heat conduction member 114. The heater 112 has a substrate 1121, and a heating element 1122. The heat conduction member 114 is located between the heater 112 and the holder, and has a main body part 1141, a first opposite part 1142A, and a second opposite part 1142B. The first opposite part 1142A faces an area where the heating element 1122 has one end E21 on the substrate 1121. The second opposite part 1142B faces an area where the heating element 1122 has the other end E22 on the substrate 1121. A cross-sectional area of the first opposite part 1142A and a cross-sectional area of the second opposite part 1142B are smaller than a cross-sectional area of the main body part 1141.SELECTED DRAWING: Figure 3

Description

[Technical field]

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

[0002] A heating device including a fixing film and a heater for heating the fixing film is known. The heating device has a metal plate, which is a highly thermally conductive member, between a heat insulating support member and the heater (see Patent Document 1 below). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 11-84919 Summary of the Invention [Problem to be solved by the invention]

[0004] In the heating device described in Patent Document 1 mentioned above, a metal plate is provided over the entire area of ​​the heating heater, so the heat from the heating heater is transmitted by the metal plate to outside the area through which the largest sheet that the image forming device can print passes.

[0005] Therefore, the fixing temperature may drop at the end of the area through which the largest sheet that the image forming apparatus can print passes.

[0006] Therefore, an object of the present disclosure is to provide a fixing device that can suppress a drop in fixing temperature at the end of an area through which the largest sheet that can be printed by an image forming apparatus passes. [Means for solving the problem]

[0007] (1) A fixing device according to the present disclosure includes a cylindrical belt, a heater, a holder, and a heat conductive member. The heater contacts an inner peripheral surface of the belt. The heater heats the belt. The heater includes a plate-shaped substrate and a heating element. The substrate extends in a first direction. The first direction is parallel to a rotation axis direction of the belt. The heating element is located on the substrate. The holder is located inside the belt. The holder supports the heater. The heat conductive member is located between the heater and the holder. The thermal conductivity of the heat conductive member is higher than the thermal conductivity of the substrate.

[0008] The thermally conductive member has a main body portion, a first opposing portion, and a second opposing portion. The main body portion is located between one end of the heating element and the other end of the heating element in a first direction. The first opposing portion faces an area of ​​the substrate where one end of the heating element is located. The cross-sectional area of ​​the first opposing portion is smaller than the cross-sectional area of ​​the main body portion. The second opposing portion faces an area of ​​the substrate where the other end of the heating element is located. The cross-sectional area of ​​the second opposing portion is smaller than the cross-sectional area of ​​the main body portion.

[0009] According to this configuration, in the heat conducting member, the cross-sectional area of ​​the first opposing portion and the cross-sectional area of ​​the second opposing portion are smaller than the cross-sectional area of ​​the main body portion.

[0010] Therefore, in the heat conducting member, the heat conduction in the first opposing portion and the heat conduction in the second opposing portion are suppressed as compared to the heat conduction in the main body portion.

[0011] The first opposing portion of the heat conducting member faces an area on the substrate where one end of the heat generating element is located, and the second opposing portion of the heat conducting member faces an area on the substrate where the other end of the heat generating element is located.

[0012] This allows the first opposing portion to prevent the heat from the heater from being transmitted to one side of the heating element rather than to one end thereof, and the second opposing portion to prevent the heat from the heater from being transmitted to the other side of the heating element rather than to the other end thereof.

[0013] Therefore, a drop in the fixing temperature can be suppressed near one end of the heat generating element and near the other end of the heat generating element.

[0014] As a result, a drop in the fixing temperature can be suppressed at both ends of the area through which the largest sheet that the image forming apparatus can print passes.

[0015] (2) The end portion of the first opposing portion on the side of the main body portion and the end portion of the second opposing portion on the side of the main body portion may be located within an area in the first direction through which the largest sheet that the image forming apparatus can print passes.

[0016] According to this configuration, the first opposing portion can further prevent the heat of the heater from being transmitted to one side of the area through which the largest sheet that can be printed by the image forming apparatus passes.

[0017] In addition, the second opposing portion can further prevent the heat of the heater from being transmitted to the other side of the area through which the maximum sheet that can be printed by the image forming apparatus passes.

[0018] As a result, the drop in the fixing temperature can be further suppressed at both ends of the area through which the largest sheet that the image forming apparatus can print passes.

[0019] (3) The heating element has a first portion, a second portion, and a third portion. The first portion is a central portion of the heating element in the first direction. The second portion is located on one end side of the first portion in the first direction. The resistance value per unit length of the second portion is lower than the resistance value per unit length of the first portion. The third portion is located on the other end side of the first portion in the first direction. The resistance value per unit length of the third portion is lower than the resistance value per unit length of the first portion. The end portion on the main body side of the first opposing portion faces one end of the first portion of the heating element. The end portion on the main body side of the second opposing portion faces the other end of the first portion of the heating element.

[0020] According to this configuration, the end portion on the main body side of the first opposing portion and the end portion on the main body side of the second opposing portion do not face the center of the first portion of the heat generating element.

[0021] This makes it possible to prevent the first opposing portion and the second opposing portion from impeding the conduction of heat from the first portion of the heat generating element.

[0022] Therefore, the fixing temperature can be made uniform in the area through which the largest sheet that the image forming apparatus can print passes.

[0023] (4) The heat conducting member may have a first end and a second end. The first end is located in the first direction between one end of the heat conducting member and an end of the first opposing portion opposite the main body portion. The cross-sectional area of ​​the first end is larger than the cross-sectional area of ​​the first opposing portion. The second end is located in the first direction between the other end of the heat conducting member and an end of the second opposing portion opposite the main body portion. The cross-sectional area of ​​the second end is larger than the cross-sectional area of ​​the second opposing portion.

[0024] With this configuration, when the image forming device prints sheets continuously, the first end and the second end can prevent the temperature of the belt in areas where the sheets do not pass from becoming too high.

[0025] (5) The heater further has a terminal. The terminal is located between one end of the heater and the heating element in the first direction. The terminal is electrically connected to the heating element by a wiring. The thermally conductive member may extend from a position between the terminal and the heating element to the other end of the heater in the first direction.

[0026] (6) The thermally conductive member may extend in the first direction from one end of the heater to the other end of the heater.

[0027] (7) Each of the first opposed portion and the second opposed portion may have a rectangular hole. Effect of the Invention

[0028] According to the fixing device of the present disclosure, it is possible to suppress a drop in the fixing temperature at the end of the area through which the largest sheet that the image forming apparatus can print passes. [Brief description of the drawings]

[0029] [Figure 1] FIG. 1 is a schematic diagram of an image forming apparatus. [Diagram 2] FIG. 2 is a cross-sectional view of the fixing device. [Diagram 3] FIG. 3 is an explanatory diagram for explaining the positional relationship between the heater and the heat conductive member. [Figure 4] FIG. 4 is an explanatory diagram for explaining the first modified example. [Diagram 5] FIG. 5 is an explanatory diagram for explaining the second modified example. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0030] 1. Overview of image forming apparatus 1 An outline of an image forming apparatus 1 will be described with reference to FIG.

[0031] The image forming apparatus 1 includes a main body housing 2, a sheet storage section 3, a photosensitive drum 4, a charging device 5, an exposure device 6, a developing device 7, a transfer device 8, and a fixing device 9.

[0032] 1.1 Main unit 2 The main body housing 2 accommodates a sheet storage section 3, a photosensitive drum 4, a charging device 5, an exposure device 6, a developing device 7, a transfer device 8, and a fixing device 9.

[0033] 1.2 Sheet storage section 3 The sheet storage unit 3 is capable of storing a sheet S. The sheet S is, for example, a printing paper. The sheet S is transported from the sheet storage unit 3 toward the photosensitive drum 4.

[0034] 1.3 Photosensitive drum 4 The photosensitive drum 4 is rotatable about a drum axis A1. The drum axis A1 extends in a first direction. The photosensitive drum 4 extends in the first direction.

[0035] 1.4 Charging device 5 The charging device 5 charges the surface of the photosensitive drum 4. In this embodiment, the charging device 5 is a charging roller. The charging device 5 may be a scorotron charger.

[0036] 1.5 Exposure Equipment 6 The exposure device 6 exposes the surface of the photosensitive drum 4 that has been charged by the charging device 5. Specifically, the exposure device 6 is a laser scanning unit. The exposure device 6 may be an LED array.

[0037] 1.6 Developing device 7 The developing device 7 supplies toner onto the photosensitive drum 4. More specifically, the developing device 7 supplies toner onto the surface of the photosensitive drum 4 exposed by the exposure device 6. The developing device 7 has a developing housing 71 and a developing roller 72.

[0038] 1.6.1 Developer box 71 The developing housing 71 is capable of containing toner.

[0039] 1.6.2 Developing roller 72 The developing roller 72 can supply toner in the developing housing 71 to the surface of the photosensitive drum 4. In this embodiment, the developing roller 72 contacts the photosensitive drum 4. The developing roller 72 may be spaced apart from the photosensitive drum 4 by a predetermined interval. The developing roller 72 can rotate about a developing axis A2. The developing axis A2 extends in a first direction. The developing roller 72 extends in the first direction.

[0040] 1.7 Transfer device 8 The transfer device 8 transfers the toner on the photosensitive drum 4 to the sheet S. In this embodiment, the transfer device 8 has a transfer roller 81. The transfer roller 81 contacts the photosensitive drum 4. The transfer roller 81 may be spaced apart from the photosensitive drum 4 at a predetermined interval. The sheet S in the sheet storage unit 3 passes between the photosensitive drum 4 and the transfer roller 81 and is transported to the fixing device 9. The transfer roller 81 transfers the toner on the photosensitive drum 4 to the sheet S passing between the photosensitive drum 4 and the transfer roller 81. The transfer roller 81 is rotatable about a transfer axis A3. The transfer axis A3 extends in a first direction. The transfer roller 81 extends in the first direction. The transfer device 8 may have a transfer belt.

[0041] 1.8 Fixing device 9 The fixing device 9 applies heat and pressure to the sheet S onto which the toner has been transferred, thereby fixing the toner to the sheet S. The sheet S that has passed through the fixing device 9 is discharged onto the top surface of the main body housing 2.

[0042] 2. Details of Fixing Device 9 Next, the fixing device 9 will be described in detail with reference to FIGS.

[0043] As shown in FIG. 2, the fixing device 9 includes a heating unit 11 and a pressure roller 12.

[0044] 2.1 Heating unit 11 The heating unit 11 heats the sheet S onto which the toner has been transferred. The heating unit 11 includes a belt 111, a heater 112, a holder 113, and a heat conductive member 114. In other words, the fixing device 9 includes the belt 111, the heater 112, the holder 113, and the heat conductive member 114.

[0045] 2.1.1 Belt 111 The belt 111 heats the sheet S onto which the toner has been transferred. The belt 111 is cylindrical. In other words, the belt 111 is an endless belt. The belt 111 extends in a first direction. The belt 111 is rotatable about a rotation axis A4. The rotation axis A4 extends in the first direction. In other words, the first direction is parallel to the rotation axis direction of the belt 111. The belt 111 has an inner circumferential surface S1 and an outer circumferential surface S2.

[0046] 2.1.2 Heater 112 The heater 112 heats the belt 111. The heater 112 is located inside the belt 111. The heater 112 contacts the inner circumferential surface S1 of the belt 111. The heater 112 extends in a first direction. The heater 112 has an elongated plate shape.

[0047] As shown in FIG. 3, the heater 112 includes a substrate 1121 , a heating element 1122 , a terminal 1123 , and a wiring 1124 .

[0048] 2.1.2.1 Substrate 1121 The substrate 1121 has a long and narrow plate shape. The substrate 1121 extends in a first direction. The substrate 1121 is made of a metal such as stainless steel. The surface of the substrate 1121 is covered with an insulating layer. The substrate 1121 may be made of a heat-resistant insulating material such as ceramic.

[0049] 2.1.2.2 Heating Element 1122 The heating element 1122 is located on the substrate 1121. More specifically, the heating element 1122 is patterned on an insulating layer of the substrate 1121. The heating element 1122 is a resistive heating element made of a silver-palladium alloy or the like. The heating element 1122 generates heat when electricity is applied. The heating element 1122 extends in a first direction. The heating element 1122 is plate-shaped. The heating element 1122 is located between one end E1 of the heater 112 and the other end E2 of the heater 112 in the first direction. One end E21 of the heating element 1122 is located at one end of an area A through which the largest sheet S that the image forming apparatus 1 can print passes in the first direction. The other end E22 of the heating element 1122 is located at the other end of the area A in the first direction. The heating element 1122 has a first portion 1122A, a second portion 1122B, and a third portion 1122C.

[0050] The first portion 1122A is a central portion in the first direction of the heating element 1122. The first portion 1122A extends in the first direction.

[0051] The second portion 1122B is located on one end side of the first portion 1122A in the first direction. The second portion 1122B is located on one end E21 of the heating element 1122 in the first direction. The size in the width direction of the second portion 1122B is larger than the size in the width direction of the first portion 1122A. In other words, the cross-sectional area of ​​the second portion 1122B is larger than the cross-sectional area of ​​the first portion 1122A. Therefore, the resistance value per unit length of the second portion 1122B is lower than the resistance value per unit length of the first portion 1122A. Therefore, the amount of heat generated by the second portion 1122B is lower than the amount of heat generated by the first portion 1122A.

[0052] The third portion 1122C is located on the other end side of the first portion 1122A in the first direction. The third portion 1122C is located at the other end E22 of the heating element 1122 in the first direction. The size in the width direction of the third portion 1122C is larger than the size in the width direction of the first portion 1122A. In other words, the cross-sectional area of ​​the third portion 1122C is larger than the cross-sectional area of ​​the first portion 1122A. Therefore, the resistance value per unit length of the third portion 1122C is lower than the resistance value per unit length of the first portion 1122A. Therefore, the amount of heat generated by the third portion 1122C is lower than the amount of heat generated by the first portion 1122A.

[0053] 2.1.2.3 Terminal 1123 The terminal 1123 is located between one end E1 of the heater 112 and the heating element 1122 in the first direction. The terminal 1123 is located away from the heating element 1122 in the first direction. The terminal 1123 is a terminal for supplying electricity to the heating element 1122, and is connected to a power source in the main body housing 2 via a connector (not shown).

[0054] 2.1.2.4 Wiring 1124 The wiring 1124 is located between the terminal 1123 and the heating element 1122 in the first direction. One end of the wiring 1124 is connected to the terminal 1123. The other end of the wiring 1124 is connected to the heating element 1122. The wiring 1124 is made of silver or the like. The wiring 1124 electrically connects the terminal 1123 and the heating element 1122. In other words, the terminal 1123 is electrically connected to the heating element 1122 by the wiring 1124.

[0055] 2.1.3 Holder 113 2, the holder 113 supports the heater 112. The holder 113 is located inside the belt 111. The holder 113 extends in a first direction. The holder 113 is made of resin. The holder 113 has a support portion 1131 and two belt guides 1132A and 1132B.

[0056] 2.1.3.1 Support part 1131 The support portion 1131 supports the heater 112 and the heat conductive member 114. The support portion 1131 is located at the center of the holder 113 in the width direction of the heater 112. The width direction of the heater 112 intersects with the first direction and the thickness direction of the heater 112. Preferably, the width direction of the heater 112 is perpendicular to the first direction and the thickness direction of the heater 112. The support portion 1131 is located between the belt guide 1132A and the belt guide 1132B in the width direction of the heater 112. The support portion 1131 has a support surface 1131A and side surfaces 1131B and 1131C.

[0057] The support surface 1131A is located on the opposite side of the heater 112 from the pressure roller 12 in the thickness direction of the heater 112. The support surface 1131A supports the heater 112 and the heat conductive member 114. The support surface 1131A extends in the width direction of the heater 112 and in the first direction.

[0058] The side surface 1131B is located at one end of the support portion 1131 in the width direction of the heater 112. The side surface 1131B faces one edge E11 of the heater 112 in the width direction of the heater 112. The side surface 1131B extends in the thickness direction of the heater 112 and in the first direction.

[0059] The side surface 1131C is located at the other end of the support portion 1131 in the width direction of the heater 112. The side surface 1131C is located away from the side surface 1131B in the width direction of the heater 112. The side surface 1131C is located on the opposite side of the heater 112 to the side surface 1131B in the width direction of the heater 112. The side surface 1131C faces the other edge E12 of the heater 112 in the width direction of the heater 112. The side surface 1131C extends in the thickness direction of the heater 112 and in the first direction.

[0060] 2.1.3.2 Belt guides 1132A, 1132B The belt guide 1132A is located at one end of the holder 113 in the width direction of the heater 112. The belt guide 1132A contacts the inner circumferential surface S1 of the belt 111. The belt guide 1132A guides the rotation of the belt 111.

[0061] The belt guide 1132B is located at the other end of the holder 113 in the width direction of the heater 112. The belt guide 1132B is located on the opposite side of the heater 112 to the belt guide 1132A in the width direction of the heater 112. The belt guide 1132B contacts the inner circumferential surface S1 of the belt 111. The belt guide 1132B guides the rotation of the belt 111.

[0062] 2.1.4 Thermal Conductive Materials 114 The heat conducting member 114 conducts heat from the heater 112 in a first direction. The heat conducting member 114 is located between the heater 112 and the holder 113. More specifically, the heat conducting member 114 is located between the rear surface of the heater 112 and the support surface 1131A of the holder 113. The heat conducting member 114 contacts the heater 112. The heat conducting member 114 has a higher thermal conductivity than the thermal conductivity of the substrate 1121 of the heater 112 (see FIG. 3). The heat conducting member 114 is made of a metal such as aluminum.

[0063] 3, the heat conducting member 114 extends in a first direction. The heat conducting member 114 extends in the first direction from a position between the terminal 1123 and the heating element 1122 to the other end E2 of the heater 112. One end E31 of the heat conducting member 114 is located between the terminal 1123 and the heating element 1122 in the first direction. The other end E32 of the heat conducting member 114 is located near the other end E2 of the heater 112 in the first direction. The heat conducting member 114 has a main body 1141, a first opposing portion 1142A, a second opposing portion 1142B, a first end 1143A, and a second end 1143B.

[0064] 2.1.4.1 Main body 1141 The main body 1141 is a central portion of the heat conducting member 114 in the first direction. The main body 1141 is located between one end E21 of the heat generating element 1122 and the other end E22 of the heat generating element 1122 in the first direction. The main body 1141 contacts the heater 112. The main body 1141 extends in the first direction.

[0065] 2.1.4.2 First opposing part 1142A The first facing portion 1142A is located between one end E31 of the heat conducting member 114 and the main body portion 1141 in the first direction. The first facing portion 1142A contacts the heater 112. In this embodiment, the first facing portion 1142A has a rectangular hole H1. Therefore, the cross-sectional area of ​​the first facing portion 1142A is smaller than the cross-sectional area of ​​the main body portion 1141. Therefore, the thermal conduction in the first facing portion 1142A is suppressed compared to the thermal conduction in the main body portion 1141.

[0066] The first opposing portion 1142A extends in a first direction. The first opposing portion 1142A has an outer end E41 and an inner end E42 in the first direction. The outer end E41 is an end of the first opposing portion 1142A opposite to the main body portion 1141. The outer end E41 is located away from the main body portion 1141 in the first direction. The inner end E42 is an end of the first opposing portion 1142A on the main body portion 1141 side. The inner end E42 is located between the outer end E41 and the main body portion 1141 in the first direction.

[0067] The first facing portion 1142A faces an area of ​​the substrate 1121 where one end E21 of the heating element 1122 is located. This allows the first facing portion 1142A to suppress the heat of the heater 112 from being transferred to one side beyond the one end E21 of the heating element 1122. As a result, the drop in the fixing temperature can be suppressed near the one end E21 of the heating element 1122. The inner end E42 of the first facing portion 1142A is located in the area A in the first direction through which the maximum sheet S that the image forming apparatus 1 can print passes. This allows the first facing portion 1142A to further suppress the heat of the heater 112 from being transferred to one side beyond the area A. As a result, the drop in the fixing temperature can be further suppressed at one end of the area A. The inner end E42 of the first facing portion 1142A faces one end of the first portion 1122A of the heating element 1122. In other words, the inner end E42 of the first facing portion 1142A does not face the center of the first portion 1122A of the heat generating element 1122. This makes it possible to prevent the first facing portion 1142A from blocking the conduction of heat from the first portion 1122A of the heat generating element 1122. Therefore, it is possible to make the fixing temperature uniform in the first direction within the region A.

[0068] The outer end E41 of the first facing portion 1142A is located between the terminal 1123 and the heating element 1122 in the first direction. The outer end E41 of the first facing portion 1142A is located on one side of the region A in the first direction.

[0069] 2.1.4.3 Second opposing part 1142B The second facing portion 1142B is located between the other end E32 of the heat conducting member 114 and the main body portion 1141 in the first direction. The second facing portion 1142B contacts the heater 112. In the present embodiment, the second facing portion 1142B has a rectangular hole H2. Therefore, the cross-sectional area of ​​the second facing portion 1142B is smaller than the cross-sectional area of ​​the main body portion 1141. Therefore, the thermal conduction in the second facing portion 1142B is suppressed compared to the thermal conduction in the main body portion 1141.

[0070] The second opposing portion 1142B extends in the first direction. The second opposing portion 1142B has an outer end E51 and an inner end E52 in the first direction. The outer end E51 is an end of the second opposing portion 1142B opposite the main body portion 1141. The outer end E51 is located away from the main body portion 1141 in the first direction. The inner end E52 is an end of the second opposing portion 1142B on the main body portion 1141 side. The inner end E52 is located between the outer end E51 and the main body portion 1141 in the first direction.

[0071] The second facing portion 1142B faces the region of the substrate 1121 where the other end E22 of the heating element 1122 is located. This allows the second facing portion 1142B to suppress the heat of the heater 112 from being transmitted to the other side of the other end E22 of the heating element 1122. As a result, a drop in the fixing temperature can be suppressed near the other end E22 of the heating element 1122. The inner end E52 of the second facing portion 1142B is located within the region A in the first direction. This allows the second facing portion 1142B to further suppress the heat of the heater 112 from being transmitted to the other side of the other end of the region A. As a result, a drop in the fixing temperature can be further suppressed at the other end of the region A. The inner end E52 of the second facing portion 1142B faces the other end of the first portion 1122A of the heating element 1122. In other words, the inner end E52 of the second opposing portion 1142B does not face the center of the first portion 1122A of the heat generating element 1122. This makes it possible to prevent the second opposing portion 1142B from blocking the conduction of heat from the first portion 1122A of the heat generating element 1122. Therefore, it is possible to make the fixing temperature uniform in the first direction within the region A.

[0072] The outer end E51 of the second facing portion 1142B is located between the other end E2 of the heater 112 and the heat generating element 1122 in the first direction. The outer end E51 of the second facing portion 1142B is located on the other side of the region A in the first direction.

[0073] 2.1.4.4 First end 1143A The first end 1143A is located between one end E31 of the heat conducting member 114 and the outer end E41 of the first opposing portion 1142A in the first direction. That is, the first end 1143A is located on one side of the region A in the first direction. The first end 1143A contacts the heater 112. In this embodiment, the size in the width direction of the first end 1143A is the same as the size in the width direction of the main body 1141. Therefore, the cross-sectional area of ​​the first end 1143A is larger than the cross-sectional area of ​​the first opposing portion 1142A. Therefore, the first end 1143A conducts heat more than the first opposing portion 1142A. The sheet S does not pass through the one side of the region A during printing. Therefore, when the image forming apparatus 1 prints the sheets S continuously, the one side of the belt 111 from the region A is likely to become high temperature due to the heat of the heater 112. In this embodiment, the first end 1143A conducts heat from the heater 112 on one side of the region A to the other side in the first direction. This makes it possible to prevent the temperature of the belt 111 from becoming too high in the region where the sheet S does not pass.

[0074] 2.1.4.5 Second end 1143B The second end 1143B is located between the other end E32 of the heat conducting member 114 and the outer end E51 of the second opposing portion 1142B in the first direction. That is, the second end 1143B is located on the other side of the region A in the first direction. The second end 1143B contacts the heater 112. In this embodiment, the size in the width direction of the second end 1143B is the same as the size in the width direction of the main body 1141. Therefore, the cross-sectional area of ​​the second end 1143B is larger than the cross-sectional area of ​​the second opposing portion 1142B. Therefore, the second end 1143B conducts heat more than the second opposing portion 1142B. The sheet S does not pass through the other side of the region A during printing. Therefore, when the image forming apparatus 1 prints the sheets S continuously, the other side of the belt 111 from the region A is likely to become hot due to the heat of the heater 112. In this embodiment, the second end 1143B conducts heat from the heater 112 on the other side of the region A to one side in the first direction. This makes it possible to prevent the temperature of the belt 111 in the region where the sheet S does not pass from becoming too high.

[0075] 2.2 Pressure roller 12 2, the pressure roller 12 contacts the outer peripheral surface S2 of the belt 111. The pressure roller 12 sandwiches the belt 111 between itself and the heater 112 to form a nip portion for applying heat and pressure to the sheet S onto which the toner has been transferred.

[0076] 3. Effects (1) In fixing device 9, in heat conductive member 114, the cross-sectional area of ​​first opposing portion 1142A and the cross-sectional area of ​​second opposing portion 1142B are smaller than the cross-sectional area of ​​main body portion 1141, as shown in FIG.

[0077] Therefore, in the heat conducting member 114, the heat conduction in the first opposing portion 1142A and the heat conduction in the second opposing portion 1142B are suppressed as compared to the heat conduction in the main body portion 1141.

[0078] The first opposing portion 1142A of the heat conducting member 114 faces the area of ​​the substrate 1121 where one end E21 of the heating element 1122 is located, and the second opposing portion 1142B of the heat conducting member 114 faces the area of ​​the substrate 1121 where the other end E22 of the heating element 1122 is located.

[0079] As a result, the first opposing portion 1142A can prevent the heat from the heater 112 from being transmitted to one side of the one end E21 of the heating element 1122, and the second opposing portion 1142B can prevent the heat from the heater 112 from being transmitted to the other side of the other end E22 of the heating element 1122.

[0080] Therefore, near one end E21 of the heat generating element 1122 and near the other end E22 of the heat generating element 1122, a drop in the fixing temperature can be suppressed.

[0081] As a result, a drop in the fixing temperature can be suppressed at one end and the other end of the area A through which the maximum sheet S printable by the image forming apparatus 1 passes.

[0082] (2) According to the fixing device 9, as shown in FIG. 3, the inner end E42 of the first opposing portion 1142A and the inner end E52 of the second opposing portion 1142B are located within an area A in the first direction through which the largest sheet S that the image forming device 1 can print passes.

[0083] Therefore, the first opposing portion 1142A can further suppress the heat of the heater 112 from being transmitted to one side of the area A through which the maximum sheet S that the image forming apparatus 1 can print passes.

[0084] In addition, the second opposing portion 1142B can further prevent the heat of the heater 112 from being transmitted to the other side of the area A through which the maximum sheet S that the image forming apparatus 1 can print passes.

[0085] As a result, the drop in the fixing temperature can be further suppressed at one end and the other end of the area A through which the maximum sheet S printable by the image forming apparatus 1 passes.

[0086] (3) According to the fixing device 9, as shown in Fig. 3, the inner end E42 of the first facing portion 1142A faces one end of the first portion 1122A of the heat generating element 1122. The inner end E52 of the second facing portion 1142B faces the other end of the first portion 1122A of the heat generating element 1122.

[0087] In other words, the inner end E42 of the first facing portion 1142A and the inner end E52 of the second facing portion 1142B do not face the center of the first portion 1122A of the heat generating element 1122.

[0088] This makes it possible to prevent the first opposing portion 1142A and the second opposing portion 1142B from impeding the conduction of heat from the first portion 1122A of the heat generating element 1122.

[0089] Therefore, in the area A through which the maximum sheet S printable by the image forming apparatus 1 passes, the fixing temperature can be made uniform.

[0090] 4. Variations Next, a modified example will be described with reference to Figures 4 and 5. In the modified example, the same members as those in the above-described embodiment are given the same reference numerals, and the description thereof will be omitted.

[0091] (1) As shown in FIG. 4, the heat conducting member 114 may extend from one end E1 of the heater 112 to the other end E2 of the heater 112 in the first direction.

[0092] (2) As shown in Fig. 5, the first opposing portion 1142A of the heat conductive member 114 may have a notch C1 instead of the hole H1 (see Fig. 3). The second opposing portion 1142B of the heat conductive member 114 may have a notch C2 instead of the hole H2 (see Fig. 3).

[0093] The first opposing portion 1142A of the heat conduction member 114 may have a notch C1, and the second opposing portion 1142B of the heat conduction member 114 may have a hole H2. The first opposing portion 1142A of the heat conduction member 114 may have a hole H1, and the second opposing portion 1142B of the heat conduction member 114 may have a notch C2. [Explanation of symbols]

[0094] 9 Fixing device 111 Belt 112 Heater 113 Holder 114 Thermal Conductive Materials 1121 Board 1122 Heating element 1122A Part 1 1122B 2nd part 1122C 3rd part 1123 Terminal 1124 Wiring 1141 Main body 1142A 1st opposing part 1142B 2nd opposing part 1143A 1st end 1143B 2nd end Area A A4 Rotation Axis H1 hole H2 hole S Seat S1 Inner Surface

Claims

1. Cylindrical belt and a heater that contacts an inner circumferential surface of the belt and heats the belt, the heater including a plate-shaped substrate extending in a first direction parallel to a rotation axis direction of the belt and a heating element located on the substrate; a holder positioned inside the belt and supporting the heater; a heat conductive member located between the heater and the holder and having a thermal conductivity higher than that of the substrate; Equipped with The heat conductive member is a main body portion located between one end of the heating element and the other end of the heating element in the first direction; a first opposing portion that faces a region of the substrate where one end of the heat generating element is located and has a cross-sectional area smaller than that of the main body portion; a second opposing portion that faces a region of the substrate where the other end of the heating element is located and has a cross-sectional area smaller than that of the main body portion; A fixing device, wherein an end portion of the first opposing portion opposite the main body portion and an end portion of the second opposing portion opposite the main body portion are located outside an area in the first direction through which the largest sheet that the image forming device can print passes.

2. The fixing device according to claim 1 , wherein the end of the first opposing portion on the side of the main body portion and the end of the second opposing portion on the side of the main body portion are located within an area in the first direction through which the largest sheet that the image forming device can print passes.

3. The heating element is a first portion that is a center portion in the first direction; a second portion located on one end side of the first portion in the first direction and having a resistance value per unit length lower than that of the first portion; a third portion located on the other end side of the first portion in the first direction and having a resistance value per unit length lower than that of the first portion; having an end portion of the first opposing portion on the side of the main body portion faces the one end portion of the first portion of the heat generating element; 3. The fixing device according to claim 1, wherein an end portion of the second opposing portion on the side of the main body portion faces the other end portion of the first portion of the heat generating element.

4. The heat conductive member is a first end portion located between one end of the heat conductive member and an end portion of the first opposing portion opposite the main body portion in the first direction, the first end portion having a cross-sectional area larger than that of the first opposing portion; 4. The fixing device according to claim 1, further comprising a second end portion located between the other end of the heat conductive member and the end portion of the second opposing portion opposite the main body portion in the first direction, the second end portion having a cross-sectional area larger than that of the second opposing portion.

5. The heater is a terminal located between one end of the heater and the heating element in the first direction and electrically connected to the heating element by a wiring; The fixing device according to claim 1 , wherein the heat conductive member extends in the first direction from a position between the terminal and the heat generating element to the other end of the heater.

6. The fixing device according to claim 1 , wherein the heat conductive member extends in the first direction from one end of the heater to the other end of the heater.

7. The fixing device according to claim 1 , wherein each of the first opposing portion and the second opposing portion has a rectangular hole.

Images