Cylindrical heating rotator for heating a developer, fixing device using said heating rotator and image forming device using said heating rotator

1. A heating rotator that is used for heating a developer on a recording medium, the heating rotator comprising a cylindrical body that is made of a metal and both end portions of the cylindrical body being rotatably supported, the cylindrical body having a thick-walled portion on at least one of both end portions that is thicker than a center portion in an axial direction of the cylindrical body, and a cross-sectional shape of the heating rotator changing from the end portions toward the center portion in a pressure area of an outer peripheral surface to which pressure is applied by a pressure roll.

2. The heating rotator of claim 1 , wherein the thick-walled portion is provided only on one of the end portions in the axial direction of the cylindrical body.

3. A fixing device comprising:

the heating rotator of claim 1 ;

a supporting structure that rotatably supports both end portions of the heating rotator;

a heating device that heats the heating rotator; and

the pressure roll that, both end portions of the pressure roll being rotatably supported, applies pressure to the outer peripheral surface of the heating rotator, in which a member that contacts the heating rotator and receives pressure from the pressure roll is not present inside the heating rotator.

4. The fixing device of claim 3 , wherein a driving force transmitting member that transmits a driving force is attached to the supporting structure.

5. The fixing device of claim 3 , wherein the pressure roll has a foamed sponge elastic layer.

6. The fixing device of claim 3 , wherein the pressure roll has an endless rotating member, and a pressure member provided inside the rotating member for, through the rotating member, applying pressure to the outer peripheral surface of the heating rotator and changing a cross-sectional shape of the heating rotator in an axial direction.

7. The fixing device of claim 3 , wherein the heating device has a magnetic field generating unit that generates a magnetic field, and the heating rotator has a heat generating layer that generates heat by electromagnetic induction of the magnetic field.

8. The fixing device of claim 7 , wherein the heating rotator has a supporting layer, comprising a temperature-sensitive magnetic metal, that supports the heat generating layer.

9. The fixing device of claim 7 , wherein the heating rotator has a protecting layer that protects the heat generating layer from oxidation.

10. An image forming device comprising:

the fixing device of claim 3 ;

an exposure unit that emits exposure light;

a developing unit that develops a latent image formed by the exposure light by using a developer to form a developer image;

a transferring unit that transfers the developer image onto a recording medium; and

a conveyance unit that conveys the recording medium, to which the developer image has been transferred, to the fixing device.

11. The heating rotator of claim 1 , wherein the thick-walled portion is provided on both ends in the axial direction of the cylindrical body.

12. The heating rotator of claim 1 , wherein the thick-walled portion is formed such that an outer surface of the cylindrical body is raised outwardly.

13. The heating rotator of claim 1 , wherein the thick-walled portion is formed such that an inner surface of the cylindrical body protrudes inwardly.

14. A fixing device comprising:

a heating rotator that is used for heating a developer on a recording medium, the heating rotator including a cylindrical body that is made of a metal and both end portions of the cylindrical body being rotatably supported, the cylindrical body having a thick-walled portion on at least one of both end portions that is thicker than a center portion in an axial direction of the cylindrical body, and a cross-sectional shape perpendicular to the axial direction of the heating rotator changes from the end portions toward the center portion;

a supporting structure that rotatably supports both end portions of the heating rotator;

a heating device that heats the heating rotator; and

a pressure roll that applies pressure to an outer peripheral surface of the heating rotator, both end portions of the pressure roll being rotatably supported.

15. The fixing device of claim 14 , wherein the pressure roll applies pressure to the outer peripheral surface of the heating rotator, and wherein a member that contacts an inner surface of the heating rotator and receives pressure from the pressure roll is not present inside the heating rotator.

16. The fixing device of claim 14 , wherein the supporting structure rotatably supports the cylindrical body through a supporting member that fits inside the thick-walled portion.