Fixing device, image forming apparatus, and heat- conducting multilayer body

1. A fixing device comprising:

a contact portion that comes into contact with a recording material transported;

a heat source that heats the contact portion and includes

a heat generator extending in a width direction intersecting a transport direction in which the recording material is transported, and

a support portion supporting the heat generator,

the heat source having a counter surface that faces the contact portion, and an opposite surface; and

a high-thermal-conductivity portion provided on the opposite surface of the heat source and extending continuously in the width direction such that at least a part of the high-thermal-conductivity portion overlaps the heat generator of the heat source, the high-thermal-conductivity portion having a higher thermal conductivity than at least one of materials forming the support portion and the contact portion,

wherein a length of an area of overlap between the high-thermal-conductivity portion and the heat generator of the heat source in the transport direction is shorter in a width-direction central portion than in two width-direction end portions,

wherein the heat generator is disposed in the heat source at an opposite side from the counter surface.

2. The fixing device according to claim 1 ,

wherein the high-thermal-conductivity portion and the heat generator of the heat source do not overlap each other in the width-direction central portion.

3. The fixing device according to claim 1 ,

wherein a length of the high-thermal-conductivity portion in the transport direction is shorter in the width-direction central portion than in the width-direction end portions.

4. The fixing device according to claim 3 ,

wherein the heat generator of the heat source overlaps the high-thermal-conductivity portion over an entirety of the heat generator in the transport direction in the width-direction end portions.

5. The fixing device according to claim 4 ,

wherein the heat generator of the heat source generates a greater amount of heat in the width-direction end portions than in the width-direction central portion.

6. The fixing device according to claim 1 ,

wherein the high-thermal-conductivity portion does not overlap an entirety of the heat generator in the width direction.

7. The fixing device according to claim 6 ,

wherein the region of the high-thermal-conductivity portion that does not overlap the heat generator is positioned on an upstream side with respect to the heat generator in the transport direction.

8. The fixing device according to claim 6 ,

wherein the heat source includes an electrode portion extending in the width direction and that supplies electric power to the heat generator, and

wherein the region of the high-thermal-conductivity portion that does not overlap the heat generator overlaps the electrode portion.

9. The fixing device according to claim 1 , further comprising:

a low-thermal-conductivity portion provided in contact with the opposite surface of the heat source and extending in the width direction such that at least a part of the low-thermal-conductivity portion overlaps the heat generator of the heat source, the low-thermal-conductivity portion having a lower thermal conductivity than the high-thermal-conductivity portion,

wherein the high-thermal-conductivity portion is provided on the opposite surface of the heat source with the low-thermal-conductivity portion provided in between.

10. The fixing device according to claim 9 ,

wherein the low-thermal-conductivity portion has a same shape as the high-thermal-conductivity portion.

11. The fixing device according to claim 1 ,

wherein the high-thermal-conductivity portion includes

a plurality of plate-like members stacked one on top of another and each having a plate-like shape extending in the width direction; and

heat-conducting viscous liquid provided between adjoining ones of the plate-like members, and

wherein a length of an area of overlap between each of the plate-like members and the heat generator in the transport direction is shorter in the width-direction central portion than in the width-direction end portions.

12. An image forming apparatus comprising:

an image forming device that forms an image on a recording material; and

a fixing device that fixes the image formed by the image forming device to the recording material,

wherein the fixing device is the fixing device according to claim 1 .

13. A fixing device comprising:

a contact portion that comes into contact with a recording material transported;

a heat source that heats the contact portion and includes

a heat generator extending in a width direction intersecting a transport direction in which the recording material is transported, and

a support portion supporting the heat generator,

the heat source having a counter surface that faces the contact portion, and an opposite surface; and

a high-thermal-conductivity portion provided on the opposite surface of the heat source and extending in the width direction such that at least a part of the high-thermal-conductivity portion overlaps the heat generator of the heat source, the high-thermal-conductivity portion having a higher thermal conductivity than at least one of materials forming the support portion and the contact portion,

wherein a length of an area of overlap between the high-thermal-conductivity portion and the heat generator of the heat source in the transport direction is shorter in a width-direction central portion than in two width-direction end portions,

wherein a length of the heat generator of the heat source in the transport direction is shorter in the width-direction central portion than in the width-direction end portions, and

wherein a length of the high-thermal-conductivity portion in the transport direction is equal between the width-direction end portions and the width-direction central portion.

14. A fixing device comprising:

a contact portion that comes into contact with a recording material transported;

a heat source that heats the contact portion and includes

a heat generator extending in a width direction intersecting a transport direction in which the recording material is transported, and

a support portion supporting the heat generator,

the heat source having a counter surface that faces the contact portion, and an opposite surface; and

a high-thermal-conductivity portion provided on the opposite surface of the heat source and extending in the width direction such that at least a part of the high-thermal-conductivity portion overlaps the heat generator of the heat source, the high-thermal-conductivity portion having a higher thermal conductivity than at least one of materials forming the support portion and the contact portion,

wherein a length of an area of overlap between the high-thermal-conductivity portion and the heat generator of the heat source in the transport direction is shorter in a width-direction central portion than in two width-direction end portions,

wherein the high-thermal-conductivity portion includes,

a narrow portion positioned in the width-direction central portion; and

two wide portions positioned at two respective width-direction ends of the narrow portion, and being wider than the narrow portion in a moving direction,

wherein a length of the narrow portion in the moving direction gradually increases toward each of the wide portions at the two respective width-direction ends of the narrow portion.