JP2022163871A - heating unit - Google Patents

Abstract

To prevent an excessive increase in temperature at the ends of a heater through which a sheet does not pass.SOLUTION: A heating unit 1 comprises: a substrate 11; a heater 10 that has a resistance heating element 12 supported by the substrate 11; an endless belt 3 that has an inner peripheral surface in contact with a nip surface of the heater 10 and rotates around the heater 10; a pressure member (pressure roller 40) that sandwiches the belt 3 with the heater 10 to form a nip part NP; a holder 20 that supports the heater 10; and a heat conduction member 30 that is located between the holder 20 and a rear side surface on the opposite side of the nip surface of the heater 10 and has a larger thermal conductivity than that of the substrate 11. The ends 38A, 38B of the heat conduction member 30 in a longitudinal direction of the substrate 11 are located, in the longitudinal direction, on the outside of the ends NP1, NP2 in the longitudinal direction of the nip part NP.SELECTED DRAWING: Figure 3

Description

The present invention relates to a heating unit used in a fixing device of an image forming apparatus.

Conventionally, as a heating unit, the belt is sandwiched between an endless belt, a plate-shaped heater that contacts the inner peripheral surface of the belt, a heat-conducting member that makes the temperature distribution in the longitudinal direction of the heater nearly uniform, and the heater. and a pressurizing roller that forms a nip portion (see Patent Document 1). In this technique, the longitudinal ends of the heat-conducting member are located inside the longitudinal ends of the nip portion.

JP 2015-43075 A

However, in the prior art, the longitudinal ends of the heat-conducting member are located inside the longitudinal ends of the nip portion, so that the longitudinal ends of the heat-conducting member are located inside and outside the nip portion. Due to the difference in heat flow between the nip portion and the nip portion, excessive temperature rise may occur at the longitudinal end portion of the nip portion, and the excessive temperature rise at the end portion of the heater through which the sheet does not pass may not be mitigated.

SUMMARY OF THE INVENTION Accordingly, it is an object of the present invention to prevent the end portion of a heater, through which a sheet does not pass, from being excessively heated.

In order to solve the above-described problems, a heating unit according to the present invention includes a heater having a substrate and a resistance heating element supported by the substrate, an inner peripheral surface in contact with a nip surface of the heater, and the heater. an endless belt that rotates around the heater, a pressing member that forms a nip portion by pinching the belt with the heater, a holder that supports the heater, and a side opposite to the nip surface of the heater. and a thermally conductive member located between the back side of the holder and the holder, the thermally conductive member having a higher thermal conductivity than the substrate.
An end portion of the thermally conductive member in the longitudinal direction of the substrate is located outside the longitudinal end portion of the nip portion in the longitudinal direction.

According to this configuration, it is possible to suppress excessive temperature rise of the ends of the nip portion in the longitudinal direction by means of the heat conducting member, so that it is possible to suppress excessive temperature rise of the ends of the heater through which the sheet does not pass. .

Further, the longitudinal end of the nip portion may be located outside the longitudinal end of the resistance heating element in the longitudinal direction.

According to this structure, the end portion of the heater, through which the sheet does not pass, is prevented from being excessively heated compared to the structure in which the longitudinal end portion of the resistance heating element is positioned outside the longitudinal end portion of the nip portion. can be suppressed.

In addition, the heating unit further includes a guide member having a guide surface that guides the longitudinal end portion of the inner peripheral surface of the belt, and a part of the heat conducting member It may be located at the same position as at least part of the guide surface.

According to this configuration, at least part of the guide surface that guides the end of the inner peripheral surface of the belt and part of the heat conducting member are positioned at the same position, thereby preventing the end of the belt from being excessively heated. It can be suppressed by a heat-conducting member.

Further, the heat conducting member has a first portion located at a position corresponding to the resistance heating element in the longitudinal direction and in contact with the back surface of the heater, and a first portion located outside the first portion in the longitudinal direction. and a second portion that does not contact the back surface of the heater, and a third portion that is located outside the second portion in the longitudinal direction and contacts the back surface of the heater. good.

According to this configuration, heat conduction from the first portion to the third portion can be dulled, so that the ends of the heater can be prevented from overheating.

Further, the second portion may face the rear side surface of the heater with a gap therebetween.

With this configuration, the second portion can be kept out of contact with the back side surface of the heater.

Further, the heat conducting member has a first portion located at a position corresponding to the resistance heating element in the longitudinal direction and in contact with the back surface of the heater, and a first portion located outside the first portion in the longitudinal direction. a second portion contacting the back surface of the heater, the second portion having a cross-sectional area perpendicular to the longitudinal direction smaller than that of the first portion; and a third portion located on the outside and in contact with the back side of the heater.

According to this configuration, heat conduction from the first portion to the third portion can be dulled, so that the ends of the heater can be prevented from overheating.

Also, the second portion may have a hole.

According to this configuration, the second portion having a small cross-sectional area can be easily formed in the heat conducting member.

Further, the longitudinal end of the resistance heating element may be positioned within the range of the second portion in the longitudinal direction.

According to this configuration, it is possible to suppress the heat of the resistance heating element from being transferred to the outside from the ends of the resistance heating element, and to suppress the temperature drop near the ends of the resistance heating element.

According to the present invention, it is possible to suppress excessive temperature rise of the end portion of the heater through which the sheet does not pass.

FIG. 4 is a cross-sectional view showing the configuration of a heating unit; FIG. 2A is a vertical cross-sectional view showing the configuration of the heating unit according to the first embodiment, and FIG. It is a figure which expands and shows the both ends of the longitudinal direction of a heating unit. FIG. 6 is a vertical cross-sectional view showing the configuration of a heating unit according to a second embodiment; FIG. 7 is a perspective view showing the configuration of a heat conducting member according to a second embodiment; FIG. 10 is an enlarged view showing both ends in the longitudinal direction of a heating unit according to a third embodiment;

Next, the first embodiment will be described in detail with appropriate reference to the drawings.
As shown in FIG. 1, the heating unit 1 is used for a fixing device of an electrophotographic image forming apparatus, a foil transfer device for transferring foil by heat, and the like. The heating unit 1 includes a belt 3 , a heater 10 , a holder 20 , a stay 25 , a heat conducting member 30 , a pressure roller 40 as an example of a pressure member, and a guide member 50 .

The belt 3 is an endless belt made of metal, resin, or the like. Belt 3 rotates around heater 10 . The belt 3 has an outer peripheral surface 3A and an inner peripheral surface 3B. The outer peripheral surface 3A contacts the sheet to be heated or the pressure roller 40 . The inner peripheral surface 3</b>B contacts the nip surface 15 of the heater 10 .

The heater 10 has a substrate 11 , a resistance heating element 12 supported by the substrate 11 , and a cover 13 . The heater 10 also has a nip surface 15 that contacts the inner peripheral surface 3B of the belt 3 and a back surface 16 opposite to the nip surface 15 .

The substrate 11 consists of an elongated rectangular plate of ceramic. The heater 10 is a so-called ceramic heater.

The resistance heating element 12 is formed on one surface of the substrate 11 by printing. As shown in FIG. 2B, in this embodiment, two resistance heating elements 12 are provided. The two resistance heating elements 12 are long in the longitudinal direction of the heater 10 (hereinafter, the longitudinal direction of the heater 10 is simply referred to as the "longitudinal direction"), and are spaced apart from each other in the short direction perpendicular to the longitudinal direction. are placed. A conductor 19A is connected to one end 12A of each resistance heating element 12 in the longitudinal direction, and a terminal 18 for supplying electric power to the resistance heating element 12 is provided at each end of the conductor 19A. Further, the other longitudinal ends 12B of the resistance heating elements 12 are connected to each other by a conductor 19B.

The number of resistance heating elements 12 is not particularly limited. In addition, there is a resistance heating element in which the amount of heat generated at the central portion in the longitudinal direction is greater than that at the ends in the longitudinal direction, and a resistance heating element in which the amount of heat generated at the ends in the longitudinal direction is greater than the amount of heat generated at the central portion in the longitudinal direction. and individually controlling each resistance heating element to adjust the heat generation distribution in the longitudinal direction.

Returning to FIG. 1 , the cover 13 covers the resistance heating element 12 . The cover 13 is made of, for example, glass.

The holder 20 is a member that supports the heater 10 . The holder 20 has a support portion 21 and a guide portion 22 .
The support portion 21 has a plate shape corresponding to the shape of the heater 10 . The support portion 21 has a support surface 21A that faces the side where the heater 10 is arranged, and an inner surface 21B on the side opposite to the support surface 21A.

The guide portions 22 are provided at both ends of the support portion 21 in the lateral direction. Each guide portion 22 has a guide surface 22G along the inner peripheral surface 3B of the belt 3. As shown in FIG.

The stay 25 is a member that is provided on the inner surface 21</b>B side of the support portion 21 of the holder 20 and supports the holder 20 . The stay 25 extends in the longitudinal direction and is formed by bending a plate material, such as a steel plate, having greater rigidity than the holder 20 into a substantially U shape when viewed in the longitudinal direction.

The pressure roller 40 and the heater 10 sandwich the belt 3 to form a nip portion NP. The pressure roller 40 has a cylindrical shaft 41 and a cylindrical roller portion 42 . The shaft 41 is made of metal, for example. The roller portion 42 is made of, for example, rubber. The roller portion 42 covers a portion of the shaft 41 . The roller portion 42 contacts the belt 3 . One of holder 20 and pressure roller 40 is biased toward the other.

The guide member 50 is a member that guides the ends of the belt 3 in the longitudinal direction. The guide members 50 are provided at both ends of the stay 25 in the longitudinal direction. As shown in FIG. 2A, the guide members 50 are arranged at one end and the other end of the belt 3 in the longitudinal direction. In addition, in FIG. 2A and the like, illustration of the stay 25 is omitted for the sake of convenience.

The guide member 50 has a guide surface 51 and a regulation surface 52 . The guide surface 51 is a surface that guides the longitudinal ends of the inner peripheral surface of the belt 3 . The guide surface 51 is an arc-shaped surface along the inner peripheral surface 3B of the belt 3 (see FIG. 1). The guide surface 51 extends inward in the longitudinal direction from the regulation surface 52 . The belt 3 is guided by the guide surface 51 and the guide surface 22</b>G of the guide portion 22 and rotates around the heater 10 , the holder 20 and the stay 25 .

The restricting surface 52 is a surface that restricts movement of the belt 3 in the longitudinal direction. The restricting surface 52 is a surface extending in a direction perpendicular to the longitudinal direction. The restricting surface 52 faces the ends of the belt 3 in the longitudinal direction. The restricting surface 52 protrudes outside the belt 3 beyond the guide surface 51 .

As shown in FIG. 1, the heat conducting member 30 is a member for conducting heat in the longitudinal direction of the heater 10 to make the temperature of the heater 10 uniform in the longitudinal direction. The heat-conducting member 30 is a sheet-like member and is positioned between the back surface 16 of the heater 10 and the support portion 21 of the holder 20 . When the heating unit 1 sandwiches the sheet to be heated between the heating unit 1 and the pressure roller 40 , the heat conducting member 30 is sandwiched between the heater 10 and the support portion 21 . The heat conducting member 30 has a heater side surface 30A that contacts the back side surface 16 of the heater 10, and an opposite surface 30B opposite to the heater side surface 30A. The opposite surface 30B is in contact with the support surface 21A of the support portion 21. As shown in FIG.

The thermally conductive member 30 is a member whose thermal conductivity in a direction parallel to the heater side surface 30A (hereinafter simply referred to as “plane direction”) is higher than that in the plane direction of the substrate 11 . Although the material of the thermally conductive member 30 is not particularly limited, for example, metals with high thermal conductivity such as aluminum, aluminum alloys, and copper can be used. Moreover, it is desirable that the thermally conductive member 30 is an anisotropic thermally conductive member whose thermal conductivity in the planar direction is greater than that in the thickness direction perpendicular to the heater side surface 30A. A graphite sheet, for example, can be used as the anisotropic thermally conductive member. Also, the thickness of the heat conducting member 30 is not particularly limited.

As shown in FIG. 2( a ), the heat conducting member 30 has a first portion 31 , two second portions 32 and two third portions 33 .

The first portion 31 is a portion located at a position corresponding to the resistance heating element 12 in the longitudinal direction. The first portion 31 is positioned inside the one end portion 12A and the other end portion 12B of the resistance heating element 12 in the longitudinal direction. The first portion 31 is in contact with the back side 16 of the heater 10 .

The second portion 32 is a portion located outside the first portion 31 in the longitudinal direction. Second portion 32 does not contact backside surface 16 of heater 10 . Specifically, the second portion 32 is formed by bending a part of the sheet-like member that constitutes the heat conducting member 30 into a substantially U-shape so as to protrude away from the back surface 16 of the heater 10. It is The second portion 32 faces the rear side surface 16 of the heater 10 with a gap therebetween.

The third portion 33 is a portion located outside the second portion 32 in the longitudinal direction. The third portion 33 is in contact with the back side 16 of the heater 10 .

The relationship of the longitudinal length of each member is as follows.
Holder 20>Substrate 11>Heat conduction member 30>Longitudinal distance between two regulation surfaces 52>Belt 3>Roller portion 42 (nip portion NP) of pressure roller 40>Resistive heating element 12>Usable in heating unit 1 maximum sheet width W1

One end portion 12A and the other end portion 12B of the resistance heating element 12 are positioned outside the range in which the sheet having the maximum width W1 can pass in the longitudinal direction. One end portion 12A and the other end portion 12B of the resistance heating element 12 are each positioned within the range of the second portion 32 in the longitudinal direction. The first portion 31 and the second portion 32 are positioned within the range of the nip portion NP in the longitudinal direction.

The resistance heating element 12 is positioned within the range of the nip portion NP in the longitudinal direction. In other words, as shown in FIG. 3, one longitudinal end NP1 of the nip portion NP is located outside the one end 12A of the resistance heating element 12 in the longitudinal direction. The other end NP2 of the nip portion NP in the longitudinal direction is located outside the other end 12B of the resistance heating element 12 in the longitudinal direction.

One end portion 38A in the longitudinal direction of the heat conducting member 30 is located outside the one end portion NP1 of the nip portion NP in the longitudinal direction. Specifically, the one end portion 38A of the heat conducting member 30 is positioned outside in the longitudinal direction of the longitudinal center C1 of the guide surface 51 on the one end side. More specifically, the one end portion 38A of the heat conducting member 30 is positioned outside the one end side regulation surface 52 in the longitudinal direction.

The other longitudinal end portion 38B of the heat conducting member 30 is located outside the other end portion NP2 of the nip portion NP in the longitudinal direction. Specifically, the other end portion 38B of the heat conducting member 30 is positioned outside in the longitudinal direction of the longitudinal center C2 of the guide surface 51 on the other end side. More specifically, the other end portion 38B of the heat conducting member 30 is located outside the regulation surface 52 on the other end side in the longitudinal direction.

A portion of the heat-conducting member 30 is located at the same position as the entire guide surface 51 in the longitudinal direction. In other words, the guide surface 51 is located within the range of the heat conducting member 30 in the longitudinal direction. Specifically, a portion of the third portion 33 is located at the same position as a portion of the guide surface 51 in the longitudinal direction, and a portion of the second portion 32 is located at the same position as the other portion of the guide surface 51 in the longitudinal direction. located in position.

According to the above, the following effects can be obtained in this embodiment.
Since the ends 38A and 38B of the heat conducting member 30 are positioned outside the ends NP1 and NP2 of the nip portion NP in the longitudinal direction, excessive temperature rise at the ends NP1 and NP2 of the nip portion NP is prevented by heat conduction. Since it can be suppressed by the member 30, it is possible to suppress excessive temperature rise of the end portion of the heater 10 through which the sheet does not pass.

By positioning the ends NP1 and NP2 of the nip portion NP outside the ends 12A and 12B of the resistance heating element 12 in the longitudinal direction, for example, the ends of the resistance heating element are longer than the ends of the nip portion. Compared to the configuration located outside the direction, it is possible to suppress excessive temperature rise at the end of the heater 10 through which the sheet does not pass.

Since a part of the heat-conducting member 30 is positioned at the same position as the entire guide surface 51 in the longitudinal direction, the end of the belt 3 is positioned within the range of the heat-conducting member 30 in the longitudinal direction. can be diffused by the heat conducting member 30 via the heater 10 . Therefore, the heat-conducting member 30 can prevent the ends of the belt 3 from being excessively heated.

By interposing the second portion 32 not in contact with the heater 10 between the first portion 31 and the third portion 33 in contact with the heater 10, heat conduction from the first portion 31 to the third portion 33 is reduced. Therefore, it is possible to prevent the ends of the heater 10 from being excessively heated.

Since the second portion 32 faces the rear side surface 16 of the heater 10 with a gap therebetween, the second portion 32 can be prevented from coming into contact with the rear side surface 16 of the heater 10 .

Since the ends 12A and 12B of the resistance heating element 12 are positioned within the range of the second portion 32 in the longitudinal direction, the heat of the resistance heating element 12 is transmitted outside the ends 12A and 12B of the resistance heating element 12. can be suppressed, and a drop in temperature near the ends 12A and 12B of the resistance heating element 12 can be suppressed.

By positioning the ends 38A and 38B of the heat conducting member 30 outside the centers C1 and C2 of the guide surface 51 in the longitudinal direction, a part of the heat conducting member 30 is located near the ends of the belt 3 in the longitudinal direction. , the heat from the end of the belt 3 can be diffused by the heat conducting member 30 via the heater 10 . Therefore, the heat-conducting member 30 can prevent the ends of the belt 3 from being excessively heated.

Since the ends 38A and 38B of the heat conducting member 30 are positioned outside the regulation surface 52 in the longitudinal direction, the ends of the belt 3 are positioned within the range of the heat conducting member 30 in the longitudinal direction. 3 can be diffused by the heat conducting member 30 via the heater 10 . Therefore, it is possible to more reliably prevent the ends of the belt 3 from being excessively heated.

Next, a second embodiment will be described. In the following, differences from the above-described embodiment will be described in detail, and points that are similar to the above-described embodiment will be appropriately described by, for example, assigning the same reference numerals to the same components. omitted.

As shown in FIGS. 4 and 5 , the heat conducting member 30 has a first portion 31 , two second portions 34 and two third portions 33 . As shown in FIG. 5, the thermally conductive member 30 is in the form of a flat sheet without bending, and the length in the short direction orthogonal to the longitudinal direction of the thermally conductive member 30 is substantially constant over the longitudinal direction. Also, the length in the longitudinal direction of the first portion 31 is longer than the length in the longitudinal direction of the second portion 34 . The first portion 31 is a portion located at a position corresponding to the resistance heating element 12 in the longitudinal direction.

The second portion 34 is a portion located outside the first portion 31 in the longitudinal direction. The second portion 34 has a rectangular hole 34H therethrough. Hole 34H is longitudinally adjacent to the outer end of first portion 31 and the inner end of third portion 33 . The second portion 34 is in contact with the back surface 16 of the heater 10 on both sides of the hole 34</b>H in the lateral direction of the heat conducting member 30 . One end 12A and the other end 12B of the resistance heating element 12 are each positioned within the range of the hole 34H in the longitudinal direction.

A cross-sectional area S34 of the second portion 34 orthogonal to the longitudinal direction is smaller than a cross-sectional area S31 of the first portion 31 orthogonal to the longitudinal direction. That is, the contact area between the second portion 34 and the back side surface 16 of the heater 10 per unit length in the longitudinal direction is the contact area between the first portion 31 and the back side surface 16 of the heater 10 per unit length in the longitudinal direction. is smaller than

Note that the cross section of the first portion 31 perpendicular to the longitudinal direction is obtained when the first portion 31 is provided with a through hole or notch (not shown) for arranging a temperature detection member such as a thermistor or thermostat. is a cross section orthogonal to the longitudinal direction at a position where such a through hole or notch is not provided in the longitudinal direction.

The third portion 33 is a portion located outside the second portion 34 in the longitudinal direction. A cross-sectional area S33 of the third portion 33 perpendicular to the longitudinal direction is the same as the cross-sectional area S31 of the first portion 31 perpendicular to the longitudinal direction. That is, the contact area per unit length between the third portion 33 and the back side surface 16 of the heater 10 in the longitudinal direction is the contact area per unit length between the first portion 31 and the back side surface 16 of the heater 10 in the longitudinal direction. is the same as

Further, in the second embodiment, part of the third portion 33 is positioned at the same position as the entire guide surface 51 in the longitudinal direction. In other words, the guide surface 51 is located within the range of the third portion 33 in the longitudinal direction. The second portion 34 is located inside the guide surface 51 in the longitudinal direction.

According to the second embodiment described above, it is possible to obtain the same effects as those of the first embodiment.

In addition, in the second embodiment, unlike the first embodiment, the second portion 34 is in contact with the heater 10 . Movement to the member 30 can be suppressed. Thereby, the transfer of heat between the heater 10 and the heat conducting member 30 can be promoted in the region where the first portion 31 with a large contact area is located.

Further, by configuring the second portion 34 to have the hole 34H, the second portion 34 having a small cross-sectional area can be easily formed in the heat conducting member 30 .

In addition, in the second embodiment, one hole 34H is formed in each second portion 34, but the present invention is not limited to this, and a plurality of holes 34H may be formed. Moreover, the shape of the hole 34H is arbitrary and is not limited to a rectangle, and may be, for example, a circle. Also, the hole 34</b>H may be a non-penetrating hole (concave portion) that opens toward the heater 10 instead of a penetrating hole. Also, the second portion 34 may be formed with a notch (recess) formed by notching one end in the short direction instead of the hole 34H.

By making the cross-sectional area S34 of the second portion 34 smaller than the cross-sectional areas S31 and S33 of the first portion 31 and the third portion 33, heat conduction from the first portion 31 to the third portion 33 can be reduced. Therefore, it is possible to prevent the ends of the belt 3 from being excessively heated.

Next, a third embodiment will be described. In the following, differences from the above-described embodiment will be described in detail, and points that are similar to the above-described embodiment will be appropriately described by, for example, assigning the same reference numerals to the same components. omitted.

As shown in FIG. 6, the heat conducting member 30 according to the third embodiment has a flat sheet shape without bending. That is, the heat conducting member 30 according to the third embodiment has a structure obtained by removing the holes 34H from the heat conducting member 30 according to the second embodiment. In the third embodiment, the one end portion 38A of the heat conducting member 30 is positioned outside the center C1 of the guide surface 51 on the one end side and inside the regulation surface 52 on the one end side in the longitudinal direction. . Further, the other end portion 38B of the heat conducting member 30 is positioned outside the center C2 of the guide surface 51 on the other end side and inside the regulation surface 52 on the other end side in the longitudinal direction. That is, in the third embodiment, part of the heat conducting member 30 is located at the same position as part of the guide surface 51 in the longitudinal direction. In addition, the one end portion 38A of the heat conducting member 30 is located outside the one end portion NP1 of the nip portion NP in the longitudinal direction. The other end portion 38B of the heat conducting member 30 is positioned outside the other end portion NP2 of the nip portion NP in the longitudinal direction.

In the third embodiment, the longitudinal length relationship of each member is as follows.
Holder 20>Substrate 11>Longitudinal distance between two regulation surfaces 52>Belt 3>Heat conduction member 30>Roller portion 42 (nip portion NP) of pressure roller 40>Resistive heating element 12>Usable in heating unit 1 maximum sheet width W1

Also in the third embodiment described above, the ends 38A and 38B of the heat conducting member 30 are positioned outside the ends NP1 and NP2 of the nip portion NP in the longitudinal direction, so that the ends 38A and 38B of the nip portion NP Since excessive temperature rise of NP1 and NP2 can be suppressed by the heat conduction member 30, excessive temperature rise of the end portion of the heater 10 through which the sheet does not pass can be suppressed.

Although the embodiments have been described above, the present invention is not limited to the above-described embodiments, and can be implemented with appropriate modifications as exemplified below.

Moreover, in the above-described embodiment, the heat conducting member 30 is made of one sheet-like member, but the present invention is not limited to this. For example, the heat-conducting member may be composed of a combination of a plurality of sheet-like members. In this case, the plurality of sheet-shaped members may be different from each other in material, thermal conductivity, shape, etc., or may be the same as each other.

Further, in the above-described embodiment, the heat conducting member 30 is sheet-like (including film-like and plate-like), but is not limited to this. For example, the heat conducting member may be thicker than a plate.

Moreover, in the above embodiment, the ends 12A and 12B of the resistance heating element 12 are positioned within the range of the second portion 32 in the longitudinal direction, but the present invention is not limited to this. For example, the ends 12A and 12B of the resistance heating element 12 may be positioned within the range of the first portion 31 in the longitudinal direction.

Further, in the above-described embodiment, the substrate 11 of the heater 10 is made of an elongated rectangular ceramic plate, but it is not limited to this as long as the heat conductivity is lower than that of the heat-conducting member. For example, the substrate of the heater may consist of an elongated rectangular plate of metal such as stainless steel.

Moreover, each element described in the above-described embodiment and modifications may be implemented in any combination.

REFERENCE SIGNS LIST 1 heating unit 3 belt 3B inner peripheral surface 10 heater 11 substrate 12 resistance heating element 15 nip surface 16 back surface 20 holder 30 heat conducting member 38A one end 38B other end 40 pressure roller NP nip NP1 one end NP2 other end

Claims (8)

a heater having a substrate and a resistive heating element supported by the substrate;
an endless belt that rotates around the heater and has an inner peripheral surface that contacts the nip surface of the heater;
a pressing member that forms a nip portion by sandwiching the belt between itself and the heater;
a holder that supports the heater;
a thermally conductive member located between the holder and the back surface of the heater opposite to the nip surface, and having a thermal conductivity greater than that of the substrate;
The heating unit, wherein an end portion of the thermally conductive member in the longitudinal direction of the substrate is located outside an end portion of the nip portion in the longitudinal direction in the longitudinal direction. 2. The heating unit according to claim 1, wherein the longitudinal end of the nip portion is located outside the longitudinal end of the resistance heating element in the longitudinal direction. further comprising a guide member having a guide surface that guides the longitudinal ends of the inner peripheral surface of the belt;
3. The heating unit according to claim 1, wherein a portion of the heat-conducting member is located at the same position as at least a portion of the guide surface in the longitudinal direction. The thermally conductive member is
a first portion located at a position corresponding to the resistance heating element in the longitudinal direction and in contact with the back surface of the heater;
a second portion located outside the first portion in the longitudinal direction and not in contact with the back surface of the heater;
4. The heater according to any one of claims 1 to 3, further comprising a third portion positioned outside the second portion in the longitudinal direction and in contact with the back side surface of the heater. heating unit. 5. The heating unit according to claim 4, wherein the second portion faces the back surface of the heater with a gap therebetween. The thermally conductive member is
a first portion located at a position corresponding to the resistance heating element in the longitudinal direction and in contact with the back surface of the heater;
A second portion located outside the first portion in the longitudinal direction and in contact with the back side surface of the heater, the second portion having a cross-sectional area orthogonal to the longitudinal direction smaller than that of the first portion. part and
4. The heater according to any one of claims 1 to 3, further comprising a third portion positioned outside the second portion in the longitudinal direction and in contact with the back side surface of the heater. heating unit. 7. Heating unit according to claim 6, characterized in that the second part has a hole. 8. The heating unit according to any one of claims 4 to 7, wherein the longitudinal end of the resistance heating element is located within the range of the second portion in the longitudinal direction. .

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