JP7604864B2 - Fixing device - Google Patents

Description

This disclosure relates to a fixing device.

Conventionally, a heating device is known that includes a fixing film and a heater for heating the fixing film. The heating device has a metal plate, which is a highly thermally conductive member, between the heat-insulating support member and the heater (see Patent Document 1 below).

Japanese Patent Application Publication No. 11-84919

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

As a result, the fixing temperature may drop at the ends of the area through which the largest sheet that the image forming device can print passes.

The objective of this disclosure is to provide a fixing device that can suppress a drop in fixing temperature at the end of the area through which the largest sheet that the image forming device can print passes.

(1) The fixing device of the present disclosure includes a cylindrical belt, a heater, a holder, and a heat conductive member. The heater contacts the inner peripheral surface of the belt. The heater heats the belt. The heater has a plate-shaped substrate and a heating element. The substrate extends in a first direction. The first direction is parallel to the 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.

The thermally conductive member has a contact portion, a first non-contact portion, and a second non-contact portion. The contact portion is located in the first direction between one end of the heating element and the other end of the heating element. The contact portion contacts the heater. The first non-contact portion faces an area on the substrate where one end of the heating element is located. The first non-contact portion does not contact the heater. The second non-contact portion faces an area on the substrate where the other end of the heating element is located. The second non-contact portion does not contact the heater.

With this configuration, the first non-contact portion and the second non-contact portion of the heat conducting member do not come into contact with the heater.

Therefore, in the thermally conductive member, the thermal conduction between the heater and the first non-contact portion and between the heater and the second non-contact portion is suppressed compared to the thermal conduction between the heater and the contact portion.

The first non-contact portion of the heat conducting member faces an area on the substrate where one end of the heating element is located, and the second non-contact portion of the heat conducting member faces an area on the substrate where the other end of the heating element is located.

As a result, the first non-contact portion prevents the heat from the heater from being transmitted to one side of the heating element rather than to one end, and the second non-contact portion prevents the heat from the heater from being transmitted to the other side of the heating element rather than to the other end.

As a result, the drop in fixing temperature can be suppressed near one end of the heating element and near the other end of the heating element.

As a result, the drop in fixing temperature can be suppressed at one end and the other end of the area through which the largest sheet that the image forming device can print passes.

(2) Each of the first non-contact portion and the second non-contact portion may face the substrate with a gap therebetween.

With this configuration, the first non-contact portion and the second non-contact portion of the thermally conductive member each have a gap between them and the substrate, thereby preventing them from coming into contact with the heater.

(3) The end of the first non-contact portion on the contact side and the end of the second non-contact portion on the contact side may be located within an area in the first direction through which the largest sheet that the image forming device can print passes.

With this configuration, the first non-contact portion can further prevent the heat from the heater from being transmitted to one side of the area through which the largest sheet that the image forming device can print passes.

The second non-contact portion also further prevents the heat from the heater from being transmitted to the other side of the area through which the largest sheet that the image forming device can print passes.

As a result, the drop in fixing temperature can be further suppressed at one end and the other end of the area through which the largest sheet that the image forming device can print passes.

(4) 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 of the first non-contact portion on the contact side faces one end of the first portion of the heating element. The end portion of the second non-contact portion on the contact side faces the other end of the first portion of the heating element.

With this configuration, the end of the first non-contact portion on the contact side and the end of the second non-contact portion on the contact side do not face the center of the first portion of the heating element.

This prevents the first non-contact portion and the second non-contact portion from impeding the conduction of heat from the first portion of the heat generating element.

This allows for uniform fixing temperature in the area where the largest sheet that the image forming device can print passes.

(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 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.

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

(7) The heat conducting member may further have a second contact portion and a third contact portion. The second contact portion is located at one end of the heat conducting member in the first direction. The second contact portion is in contact with the heater. The third contact portion is located at the other end of the heat conducting member in the first direction. The third contact portion is in contact with the heater. The first non-contact portion is located between the contact portion and the second contact portion in the first direction. The second non-contact portion is located between the contact portion and the third contact portion in the first direction.

With this configuration, when the image forming device prints sheets continuously, the second contact portion and the third contact portion can prevent the temperature of the belt in areas where the sheets do not pass from becoming too high.

The fixing device disclosed herein can suppress a drop in fixing temperature at the ends of the area through which the largest sheet that the image forming device can print passes.

FIG. 1 is a schematic diagram of an image forming apparatus. FIG. 2 is a cross-sectional view of the fixing device. FIG. 3 is an explanatory diagram for explaining the positional relationship between the heater and the heat conductive member. FIG. 4 is an explanatory diagram for explaining contact between the heater and the heat conductive member. FIG. 5 is an explanatory diagram for explaining the modified example.

1. Overview of Image Forming Apparatus 1 The overview of the image forming apparatus 1 will be described with reference to FIG.

The image forming device 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.

1.1 Main body housing 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 .

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.

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.

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.

1.5 Exposure device 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.

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.

1.6.1 Developing case 71
The developing housing 71 is capable of containing toner.

1.6.2 Developing Roller 72
The developing roller 72 is capable of supplying 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 is rotatable about a developing axis A2. The developing axis A2 extends in a first direction. The developing roller 72 extends in the first direction.

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 separated from the photosensitive drum 4 with 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.

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.

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

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

2.1 Heating Unit 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.

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.

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 an inner circumferential surface S1 of the belt 111. The heater 112 extends in a first direction. The heater 112 has an elongated plate shape.

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

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 is made of a heat-resistant insulating material such as ceramic.

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.

The first portion 1122A is the center of the heating element 1122 in the first direction. The first portion 1122A extends in the first direction.

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 side of the heating element 1122 in the first direction. The size in the width direction of the second portion 1122B is wider 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.

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 on the other end side of the heating element 1122 in the first direction. The width direction size of the third portion 1122C is wider than the width direction size 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.

2.1.2.3 Terminal 1123
The terminal 1123 is located in the first direction between one end E1 of the heater 112 and the heating element 1122. 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).

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.

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.

2.1.3.1 Support part 1131
The support portion 1131 supports the heater 112 and the thermal 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 is the first direction , and intersects with 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 disposed in the width direction of the heater 112 such that the support portion 1131 is perpendicular to the first direction and the thickness direction of the heater 112. The support portion 1131 is located between the guide 1132A and the belt guide 1132B. The support portion 1131 has a support surface 1131A and side surfaces 1131B and 1131C.

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.

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.

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

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.

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 from the belt guide 1132A in the width direction of the heater 112. The belt guide 1132B contacts the inner surface S1 of the belt 111. The belt guide 1132B guides the rotation of the belt 111.

2.1.4 Thermally conductive member 114
The thermally conductive member 114 transfers heat from the heater 112 in a first direction. The thermally conductive member 114 is located between the heater 112 and the holder 113. More specifically, the thermally conductive member 114 is located between the rear surface of the heater 112 and the support surface 1131A of the holder 113. The thermal conductivity of the thermally conductive member 114 is higher than the thermal conductivity of the substrate 1121 (see FIG. 3 ) of the heater 112. The thermally conductive member 114 is made of a metal such as aluminum.

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 contact portion 1141, a first non-contact portion 1142A, a second non-contact portion 1142B, a second contact portion 1143A, and a third contact portion 1143B.

2.1.4.1 Contact portion 1141
The contact portion 1141 is a central portion of the heat conducting member 114 in the first direction. The contact portion 1141 is located between one end E21 of the heating element 1122 and the other end E22 of the heating element 1122 in the first direction. The contact portion 1141 extends in the first direction. As shown in FIG. 4 , the contact portion 1141 contacts the heater 112.

2.1.4.2 First non-contact part 1142A
The first non-contact portion 1142A is located between one end E31 of the heat conducting member 114 and the contact portion 1141 in the first direction. It is located between the second contact portion 1143A.

As shown in FIG. 4, the first non-contact portion 1142A does not contact the heater 112. The first non-contact portion 1142A has a gap between it and the substrate 1121 of the heater 112 in the thickness direction of the heater 112. Therefore, the thermal conduction between the first non-contact portion 1142A and the heater 112 is suppressed compared to the thermal conduction between the contact portion 1141 and the heater.

As shown in FIG. 3, the first non-contact portion 1142A extends in a first direction. The first non-contact portion 1142A has an outer end E41 and an inner end E42 in the first direction. The outer end E41 is the end of the first non-contact portion 1142A opposite the contact portion 1141. The outer end E41 is located away from the contact portion 1141 in the first direction. The inner end E42 is the end of the first non-contact portion 1142A on the contact portion 1141 side. The inner end E42 is located between the outer end E41 and the contact portion 1141 in the first direction.

The first non-contact portion 1142A faces the region of the substrate 1121 where one end E21 of the heating element 1122 is located. This allows the first non-contact portion 1142A to suppress the heat of the heater 112 from being transmitted 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 non-contact portion 1142A is located in the region A in the first direction through which the largest sheet S that the image forming device 1 can print passes. This allows the first non-contact portion 1142A to further suppress the heat of the heater 112 from being transmitted to one side beyond the region A. As a result, the drop in the fixing temperature can be further suppressed at one end of the region A. The inner end E42 of the first non-contact 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 non-contact portion 1142A does not face the center of the first portion 1122A of the heating element 1122. This makes it possible to prevent the first non-contact portion 1142A from impeding the conduction of heat from the first portion 1122A of the heating element 1122. Therefore, it is possible to make the fixing temperature uniform in the first direction within the region A.

The outer end E41 of the first non-contact portion 1142A is located between the terminal 1123 and the heating element 1122 in the first direction. The outer end E41 of the first non-contact portion 1142A is located on one side of the region A in the first direction.

2.1.4.3 Second non-contact part 1142B
The second non-contact portion 1142B is located between the other end E32 of the heat conducting member 114 and the contact portion 1141 in the first direction. and the third contact portion 1143B.

As shown in FIG. 4, the second non-contact portion 1142B does not contact the heater 112. The second non-contact portion 1142B has a gap between it and the substrate 1121 of the heater 112 in the thickness direction of the heater 112. Therefore, the thermal conduction between the second non-contact portion 1142B and the heater 112 is suppressed compared to the thermal conduction between the contact portion 1141 and the heater 112.

As shown in FIG. 3, the second non-contact portion 1142B extends in the first direction. The second non-contact portion 1142B has an outer end E51 and an inner end E52 in the first direction. The outer end E51 is the end of the second non-contact portion 1142B opposite the contact portion 1141. The outer end E51 is located away from the contact portion 1141 in the first direction. The inner end E52 is the end of the second non-contact portion 1142B on the contact portion 1141 side. The inner end E52 is located between the outer end E51 and the contact portion 1141 in the first direction.

The second non-contact 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 non-contact portion 1142B to prevent the heat of the heater 112 from being transmitted to the other side beyond 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 non-contact portion 1142B is located within the region A in the first direction. This allows the second non-contact portion 1142B to further prevent the heat of the heater 112 from being transmitted to the other side beyond 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 non-contact 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 non-contact portion 1142B does not face the center of the first portion 1122A of the heating element 1122. This makes it possible to prevent the second non-contact portion 1142B from impeding the conduction of heat from the first portion 1122A of the heating element 1122. Therefore, it is possible to make the fixing temperature uniform in the first direction within the region A.

The outer end E51 of the second non-contact portion 1142B is located between the other end E2 of the heater 112 and the heating element 1122 in the first direction. The outer end E51 of the second non-contact portion 1142B is located on the other side of the region A in the first direction.

2.1.4.4 Second contact part 1143A
4, the second contact portion 1143A is located at one end E31 of the heat conducting member 114 in the first direction. The second contact portion 1143A contacts the heater 112. The second contact portion 1143A is In the first direction, the belt 1 is located on one side of the area A. The sheet S does not pass through the area A during printing. Therefore, when the image forming apparatus 1 continuously prints the sheet S, the belt 1 The second contact portion 1143A is arranged to transfer the heat of the heater 112 to the one side of the region A of the heat source 114. This makes it possible to prevent the temperature of the belt 111 in the area where the sheet S does not pass from becoming too high.

2.1.4.5 Third contact part 1143B
The third contact portion 1143B is located at the other end E32 of the heat conducting member 114 in the first direction. The third contact portion 1143B is in contact with the heater 112. The third contact portion 1143B has a region The sheet S does not pass through the other side of the area A during printing. Therefore, when the image forming apparatus 1 continuously prints the sheet S, the area A of the belt 111 is located on the other side of the area A. The other side is likely to become hot due to the heat from the heater 112. In this embodiment, the third contact portion 1143B conducts the heat from the heater 112 on the other side of the region A to one side in the first direction. This can prevent the temperature of the belt 111 in the area where the sheet S does not pass from becoming too high.

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 to which the toner has been transferred.

3. Effects (1) According to the fixing device 9, the first non-contact portion 1142A and the second non-contact portion 1142B of the heat conductive member 114 are not in contact with the heater 112, as shown in FIG.

Therefore, in the thermally conductive member 114, the thermal conduction between the first non-contact portion 1142A and the heater 112, and the thermal conduction between the second non-contact portion 1142B and the heater 112 are suppressed compared to the thermal conduction between the contact portion 1141 and the heater.

As shown in FIG. 3, the first non-contact portion 1142A of the heat conducting member 114 faces one end E21 of the heating element 1122, and the second non-contact portion 1142B of the heat conducting member 114 faces the other end E22 of the heating element 1122.

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

As a result, the drop in fixing temperature can be suppressed at one end and the other end of the area A through which the largest sheet S that the image forming device 1 can print passes.

(2) According to the fixing device 9, as shown in FIG. 4, each of the first non-contact portion 1142A and the second non-contact portion 1142B has a gap between them and the substrate 1121 and faces the substrate 1121.

Therefore, in the thermal conduction member 114, the first non-contact portion 1142A and the second non-contact portion 1142B each have a gap between them and the substrate 1121, thereby preventing them from coming into contact with the heater 112.

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

Therefore, the first non-contact portion 1142A can further prevent the heat of the heater 112 from being transmitted to one side of the area A through which the largest sheet S that the image forming device 1 can print passes.

In addition, the second non-contact 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 largest sheet S that the image forming device 1 can print passes.

As a result, the drop in fixing temperature can be further suppressed at one end and the other end of the area A through which the largest sheet S that the image forming device 1 can print passes.

(4) According to the fixing device 9, as shown in FIG. 3, the inner end E42 of the first non-contact portion 1142A faces one end of the first portion 1122A of the heating element 1122. The inner end E52 of the second non-contact portion 1142B faces the other end of the first portion 1122A of the heating element 1122.

In other words, the inner end E42 of the first non-contact portion 1142A and the inner end E52 of the second non-contact portion 1142B do not face the center of the first portion 1122A of the heating element 1122.

This prevents the first non-contact portion 1142A and the second non-contact portion 1142B from impeding the conduction of heat from the first portion 1122A of the heating element 1122.

As a result, the fixing temperature can be made uniform in the area A through which the largest sheet S that the image forming device 1 can print passes.

(5) According to the fixing device 9, as shown in FIG. 4, the second contact portion 1143A and the third contact portion 1143B come into contact with the heater 112.

Therefore, when the image forming device 1 prints the sheets S continuously, the second contact portion 1143A and the third contact portion 1143B can prevent the temperature of the belt 111 in the areas where the sheets S do not pass from becoming too high.

4. Modifications Next, a modification will be described with reference to Fig. 5. In the modification, the same members as those in the above-described embodiment are denoted by the same reference numerals, and the description thereof will be omitted.

As shown in FIG. 5, the thermal conduction member 114 may extend in the first direction from one end E1 of the heater 112 to the other end E2 of the heater 112.

9 Fixing device 111 Belt 112 Heater 113 Holder 114 Heat conductive member 1121 Substrate 1122 Heat generating element 1122A First portion 1122B Second portion 1122C Third portion 1123 Terminal 1124 Wiring 1141 Contact portion 1142A First non-contact portion 1142B Second non-contact portion 1143A Second contact portion 1143B Third contact portion A Area A4 Rotating shaft S Sheet S1 Inner peripheral surface

Claims (6)

a heater that contacts an inner peripheral surface of the belt and heats the belt, the heater having 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 contact portion located between one end of the heating element and the other end of the heating element in the first direction and in contact with the heater;
a first non-contact portion that faces a region of the substrate where one end of the heating element is located and does not contact the heater;
a second non-contact portion that faces a region of the substrate where the other end of the heating element is located and does not contact the heater ;
The fixing device, wherein each of the first non-contact portion and the second non-contact portion faces the substrate with a gap therebetween . The fixing device according to claim 1 , wherein an end portion of the first non-contact portion on the contact portion side and an end portion of the second non-contact portion on the contact portion side are located within an area in the first direction through which a maximum sheet that can be printed by an image forming device passes. 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 non-contact portion on the contact portion side faces the one end portion of the first portion of the heating element;
3. The fixing device according to claim 1, wherein an end portion of the second non-contact portion on the contact portion side faces the other end portion of the first portion of the heat generating element. 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. 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. The heat conductive member is
a second contact portion located at one end of the heat conducting member in the first direction and in contact with the heater;
a third contact portion located at the other end of the heat conducting member in the first direction and in contact with the heater;
and
the first non-contact portion is located between the contact portion and the second contact portion in the first direction,
The fixing device according to claim 1 , wherein the second non-contact portion is located between the contact portion and the third contact portion in the first direction.

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