Transferring and fixing apparatus and image forming apparatus including the same

Abstract

The subject invention provides a transferring and fixing apparatus in which a transferring and fixing member and a pressure member are in close and pressing contact with each other, forming a transferring and fixing region therebetween, and a fused toner image held and heated by the transferring and fixing member is transferred and fixed into in the transferring and fixing region onto a recording paper fed to the transferring and fixing region, either of an end portion of the transferring and fixing region where the recording paper is fed or an end portion of the transferring and fixing region where the recording paper is discharged is set to have a highest pressure in the transferring and fixing region. With this arrangement the present invention prevents micro offset phenomenon in a transferring and fixing process of toner into a recording paper in a simultaneous transferring and fixing mode, thereby achieving high picture quality.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a vertical cross-sectional view schematically showing a main part of an image forming apparatus including a transferring and fixing apparatus according to one embodiment of the present invention.

FIG. 2 is a vertical cross-sectional view showing a magnified view of the transferring and fixing unit of FIG. 1.

FIG. 3 is a vertical cross-sectional view showing a lamination structure of the transferring and fixing roller of FIG. 1.

FIG. 4 is a vertical cross-sectional view showing a conventional transferring and fixing unit.

FIG. 5( a) is a graph showing temperature change of the toner layer and pressure distribution in the transferring and fixing region of the conventional transferring and fixing unit of FIG. 4; and FIG. 5(b) is a graph showing temperature change of the toner layer and pressure distribution in the transferring and fixing region of the transferring and fixing unit of FIG. 2 according to the present embodiment.

FIG. 6 is a vertical cross-sectional view showing another example of the transferring and fixing unit of FIG. 2.

FIG. 7 is a vertical cross-sectional view showing still another example of the transferring and fixing unit of FIG. 2.

FIG. 8 is a vertical cross-sectional view showing a structure of the transferring and fixing unit of FIG. 7 in which only the pressure in the insertion-end of the transferring and fixing region increases.

FIG. 9 is a vertical cross-sectional view showing another structure of the transferring and fixing unit of FIG. 7 in which only the pressure in the discharge-end of the transferring and fixing region increases.

Claims

1. A transferring and fixing apparatus in which a transferring and fixing member and a pressure member are in close and pressing contact with each other, forming a transferring and fixing region therebetween, and a fused toner image held and heated by the transferring and fixing member is transferred and fixed into the transferring and fixing region onto a recording paper fed to the transferring and fixing region, either of an end portion of the transferring and fixing region where the recording paper is fed or an end portion of the transferring and fixing region where the recording paper is discharged being set to have a highest pressure in the transferring and fixing region.

2. The transferring and fixing apparatus as set forth in claim 1, wherein the pressure member includes a belt member and two pressure rollers, each of two pressure rollers is in close and pressing contact with the transferring and fixing member via the belt member, and the belt member is set around the two pressure rollers.

3. The transferring and fixing apparatus as set forth in claim 1, wherein the pressure member includes two pressure rollers, which are disposed with a certain distance and are in close and pressing contact with the transferring and fixing member.

4. The transferring and fixing apparatus as set forth in claim 1, wherein the pressure member has a belt member, a hard pad and a soft pad softer than the hard pad, the hard pad and the soft pad are in close and pressing contact with the transferring and fixing member via the belt member, the belt member is rotated while sliding on the hard pad and the soft pad.

5. The transferring and fixing apparatus as set forth in claim 4, wherein the hard pad and the soft pad are adjacently provided in the transferring and fixing region in a direction from a paper feed portion to a paper discharge portion, the soft pad has a wider width than the hard pad in terms of this direction.

6. An image forming apparatus including the transferring and fixing apparatus of claim 1.

7. A transferring and fixing apparatus in which a transferring and fixing member and a pressure member are in close and pressing contact with each other, forming a transferring and fixing region therebetween, and a fused toner image held and heated by the transferring and fixing member is transferred and fixed into the transferring and fixing region onto a recording paper fed to the transferring and fixing region, a portion of the highest temperature of the toner image in the transferring and fixing region being a portion having a highest pressure in the transferring and fixing region.

8. The transferring and fixing apparatus as set forth in claim 7 wherein the pressure member includes a plurality of pressure rollers in close and pressing contact with the transferring and fixing member so as to form the transferring and fixing region.

9. An image forming apparatus including the transferring and fixing apparatus of claim 7.

10. A transferring and fixing apparatus in which a transferring and fixing member and a pressure member are in close and pressing contact with each other, forming a transferring and fixing region therebetween, and a fused toner image held and heated by the transferring and fixing member is transferred and fixed into the transferring and fixing region onto a recording paper fed to the transferring and fixing region, the transferring and fixing member and the pressure member rotating in the same direction, and the peripheries of the transferring and fixing member and the pressure member in close and pressing contact with each other moving at different speeds.

11. The transferring and fixing apparatus as set forth in claim 10, wherein the speeds of the peripheries of the transferring and fixing member and the pressure member are determined on condition that: V1>V2where V1 denotes a speed at which the periphery of the transferring and fixing member moves and V2 denotes a speed at which the periphery of the pressure member moves.

12. An image forming apparatus including the transferring and fixing apparatus of claim 10.