IMAGE HEATING DEVICE CAPABLE OF CHANGING PRESSURE APPLIED TO HEATING NIP

Abstract

An image heating device includes a pressure-changing mechanism configured to change pressure applied to a heating nip. A cam of the pressure-changing mechanism acting on a pressure-applying mechanism is attached to a rotating shaft of a conveying roller that conveys recording materials. With this, an increase in the cost of the device can be regulated.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a power transmission channel from a motor to a fixing unit according to a first exemplary embodiment of the present invention.

FIG. 2 illustrates gears that constitute the power transmission channel shown in FIG. 1.

FIG. 3 illustrates the fixing unit without a side plate thereof viewed from one end of the unit in the longitudinal direction thereof, where a pressure that is the same as that during fixing is applied to a heating nip.

FIG. 4 illustrates the fixing unit without the side plate thereof viewed from one end of the unit in the longitudinal direction thereof, where the pressure is removed.

FIG. 5 illustrates the relationship between the pressure applied to the heating nip (pressure-contact nip) and the phase (rotational angle) of a cam member.

FIG. 6 is a schematic cross-sectional view of an electrophotographic image forming apparatus including the fixing unit.

FIG. 7 is a cross-sectional view of the fixing unit adjacent to an end of a fixing film in the longitudinal direction of the fixing unit.

FIG. 8 is a perspective view of a power transmission channel from a motor to a fixing unit according to a second exemplary embodiment of the present invention.

FIG. 9 illustrates gears that constitute the power transmission channel shown in FIG. 8.

FIG. 10A illustrates the fixing unit viewed from the side during image formation where the pressure-contact nip is formed, and FIG. 10B illustrates the pressure-contact nip N in the non-released state.

FIG. 11A illustrates the fixing unit where the pressure-contact nip is released, and FIG. 11B illustrates the pressure-contact nip N in the released state.

Claims

1. An image heating device for heating an image formed on a recording material, comprising: a nip-forming member;a pressure-applying mechanism configured to apply pressure to the nip-forming member so as to form a heating nip where the recording material is heated; anda pressure-changing mechanism including a rotatable cam member acting on the pressure-applying mechanism so as to change the pressure applied to the nip-forming member by the pressure-applying mechanism,wherein the cam member is attached to a rotating shaft of a rotating body that can be brought into contact with the recording material.

2. The image heating device according to claim 1, further comprising a one-way clutch mechanism, wherein the cam member is attached to the rotating shaft via the one-way clutch mechanism, andwherein the cam member is not substantially rotated when the rotating body is rotated in a direction in which the recording material is conveyed, and the cam member is rotated when the rotating body is rotated in a direction opposite to the conveying direction of the recording material.

3. The image heating device according to claim 2, wherein the rotating body is disposed at a position remote from the heating nip in the conveying direction of the recording material.

4. The image heating device according to claim 3, wherein the rotating body is disposed downstream of the heating nip in the conveying direction of the recording material.

5. The image heating device according to claim 4, wherein the rotating body includes a conveying roller disposed immediately downstream of the heating nip in the conveying direction of the recording material.

6. The image heating device according to claim 3, further comprising a power source configured to rotate the rotating body and the cam member and to drive the nip-forming member.

7. The image heating device according to claim 6, wherein the nip-forming member includes a flexible sleeve and a pressurizing roller that is brought into contact with an outer periphery of the flexible sleeve.

8. The image heating device according to claim 2, wherein the rotating body forms the heating nip.

9. The image heating device according to claim 8, further comprising a driving source configured to rotate the cam member and drive the rotating body.

10. An image forming apparatus for forming images on recording materials, comprising: an image forming unit forming unfixed images on the recording materials; anda fixing unit configured to fix the unfixed images on the recording materials, the fixing unit including the image heating unit according to claim 1.