FIXING DEVICE AND IMAGE FORMING APPARATUS PROVIDED WITH FIXING DEVICE

Abstract

A disclosed fixing device includes: a heat roller unit having a rotatable roller having an elastic body on a surface thereof and a heating unit heating the roller; a pad disposed along a circumference of the elastic body of the heat roller; a belt member disposed on a curved surface of the pad, the belt member rotating by following a rotation of the heat roller; and a pressure member pressing the belt member to the heat roller using the pad, the fixing device causing a conveyed recording medium carrying a visualized image to pass through a space between the heat roller and the pressure member so as to fix the visualized image on the recording medium, wherein a curvature of the curved surface of the pad is changed in a central portion and end portions in an axial direction of the heat roller.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side elevational view showing an example of a structure of a fixing device according to the present invention;

FIG. 2 is a diagram showing an example of a structure of a fixing device when viewed from an insertion direction of a recording medium;

FIG. 3A is a cross-sectional view of a pressure pad in example 1;

FIG. 3B is a diagram showing a contact face of a pressure pad in example 1;

FIG. 4A is a side elevational view showing a holder in example 2;

FIG. 4B is a top view showing a holder in example 2;

FIG. 5 is a diagram showing the holder of FIGS. 4A and 4B when a pressure pad is fitted therein; and

FIG. 6 is a side elevational view showing an image forming apparatus using an example of a fixing device according to the present invention.

Claims

1. A fixing device comprising: a heat roller unit having a rotatable roller having an elastic body on a surface thereof and a heating unit heating the roller;a pad disposed along a circumference of the elastic body of the heat roller;a belt member disposed on a curved surface of the pad, the belt member rotating by following a rotation of the heat roller; anda pressure member pressing the belt member to the heat roller using the pad, the fixing device causing a conveyed recording medium carrying a visualized image to pass through a space between the heat roller and the pressure member so as to fix the visualized image on the recording medium, whereina curvature of the curved surface of the pad is changed in a central portion and end portions in an axial direction of the heat roller.

2. The fixing device according to claim 1, wherein the curvature of the curved surface of the pad is formed such that the curvature of the end portions of the pad is larger than the curvature of the heat roller which is larger than the curvature of the central portion of the pad.

3. The fixing device according to claim 1, wherein the curvature of the curved surface of the pad is gradually changed from predetermined positions between the central portion of the pad and the end portions of the pad to the end portions of the pad.

4. The fixing device according to claim 2, wherein the curvature of the curved surface of the pad is gradually changed from predetermined positions between the central portion of the pad and the end portions of the pad to the end portions of the pad.

5. The fixing device according to claim 1, including: a pad fixing unit supporting and fixing the pad, whereina contact face of the pad fixing unit in contact with the pad has an end portion supporting shape for gradually deforming the curved surface of the pad from predetermined positions to the end portions.

6. A fixing device comprising: a heat roller unit having a rotatable roller having an elastic body on a surface thereof and a heating unit heating the roller;a pad disposed along a circumference of the elastic body of the heat roller;a belt member disposed on a curved surface of the pad, the belt member rotating by following a rotation of the heat roller;a pressure member pressing the belt member to the heat roller using the pad, the fixing device causing a conveyed recording medium carrying a visualized image to pass through a space between the heat roller and the pressure member so as to fix the visualized image on the recording medium; anda pad fixing unit supporting and fixing the pad, whereina contact face of the pad fixing unit in contact with the pad has an end portion supporting shape for gradually deforming the curved surface of the pad from predetermined positions to end portions.

7. An image forming apparatus comprising: a fixing device including:a heat roller unit having a rotatable roller having an elastic body on a surface thereof and a heating unit heating the roller;a pad disposed along a circumference of the elastic body of the heat roller;a belt member disposed on a curved surface of the pad, the belt member rotating by following a rotation of the heat roller; anda pressure member pressing the belt member to the heat roller using the pad, the fixing device causing a conveyed recording medium carrying a visualized image to pass through a space between the heat roller and the pressure member so as to fix the visualized image on the recording medium, whereina curvature of the curved surface of the pad is changed in a central portion and end portions in an axial direction of the heat roller.

8. The image forming apparatus according to claim 7, wherein the curvature of the curved surface of the pad is formed such that the curvature of the end portions of the pad is larger than the curvature of the heat roller which is larger than the curvature of the central portion of the pad.

9. The image forming apparatus according to claim 7, wherein the curvature of the curved surface of the pad is gradually changed from predetermined positions between the central portion of the pad and the end portions of the pad to the end portions of the pad.

10. The image forming apparatus according to claim 8, wherein the curvature of the curved surface of the pad is gradually changed from predetermined positions between the central portion of the pad and the end portions of the pad to the end portions of the pad.

11. The image forming apparatus according to claim 7, including: a pad fixing unit supporting and fixing the pad, whereina contact face of the pad fixing unit in contact with the pad has an end portion supporting shape for gradually deforming the curved surface of the pad from predetermined positions to the end portions.

12. An image forming apparatus comprising: a fixing device including:a heat roller unit having a rotatable roller having an elastic body on a surface thereof and a heating unit heating the roller;a pad disposed along a circumference of the elastic body of the heat roller;a belt member disposed on a curved surface of the pad, the belt member rotating by following a rotation of the heat roller;a pressure member pressing the belt member to the heat roller using the pad, the fixing device causing a conveyed recording medium carrying a visualized image to pass through a space between the heat roller and the pressure member so as to fix the visualized image on the recording medium; anda pad fixing unit supporting and fixing the pad, whereina contact face of the pad fixing unit in contact with the pad has an end portion supporting shape for gradually deforming the curved surface of the pad from predetermined positions to end portions.