Belt drive apparatus and image forming apparatus

1. A belt drive apparatus comprising:

a rotatable first roller;

a rotatable second roller;

a belt member stretched by the first and the second rollers so as to be capable of being conveyed by the first and the second rollers; and

a restraint member provided on at least one of two ends of the second roller and including a belt receiving surface to be brought into contact with an edge portion of the belt member,

wherein the belt receiving surface includes a first receiving surface and a second receiving surface located in a radial direction away from the center of the first receiving surface, and

the first belt surface and the axis of the second roller make an angle that is not smaller than 93° but not larger than 115°, and

a second angle made by the second receiving surface and the axis of the second roller is larger than a first angle made by the first receiving surface and the axis of the second roller.

2. A belt drive apparatus comprising:

a rotatable first roller;

a rotatable second roller including: a roller main body; and a supporting shaft protruding from each end, in an axial direction, of the roller main body;

a belt member stretched by the first and the second rollers so as to be capable of being conveyed by the first and the second rollers; and

a restraint member provided on at least one of two ends of the second roller and including a belt receiving surface to be brought into contact with an edge portion of the belt member,

wherein the belt receiving surface and the axis of the second roller make an angle that is not smaller than 93° but not larger than 115°, and

the restraint member is provided on at least one end, in the axial direction, of the supporting shaft and movable relative to the supporting shaft in the axial direction of the supporting shaft,

a shaft-end-position changing apparatus provided adjacent to the restraint member and configured to tilt the axis of the second roller by changing a position of one end of the second roller.

3. The belt drive apparatus according to claim 1 , wherein

the restraint member is movable with respect to the second roller in the axial direction of the second roller,

wherein belt drive apparatus further comprising

a shaft-end-position changing apparatus provided adjacent to the restraint member and configured to tilt the axis of the second roller by changing a position of the at least one end of the second roller in response to movements of the restraint member in the axial direction of the second roller.

4. The belt drive apparatus according to claim 2 , wherein the angle made by the belt receiving surface and the axis of the second roller increases in an axial direction away from the center of the second roller.

5. The belt drive apparatus according to claim 2 ,

wherein the second roller includes:

a roller main body; and

a supporting shaft protruding from each end, in an axial direction, of the roller main body, and

the restraint member is provided on at least one end, in the axial direction, of the supporting shaft.

6. The belt drive apparatus according to claim 5 , wherein the restraint member is provided movable relative to the supporting shaft in the axial direction of the supporting shaft.

7. The belt drive apparatus according to claim 2 , wherein the belt receiving surface includes a sliding-friction reducing film thereon.

8. An image forming apparatus comprising the belt drive apparatus of claim 2 .

9. The image forming apparatus according to claim 8 , further comprising:

a media conveyance path through which a medium is conveyed;

a developer image forming unit configured to form a developer image;

a transferring unit configured to transfer the developer image formed by the developer image forming unit onto the medium conveyed along the media conveyance path; and

a fixing unit provided downstream of the transferring unit in the media conveyance path, and configured to fix the developer image on the medium by heating the medium with the developer image formed thereon.

10. The image forming apparatus according to claim 9 , wherein the belt drive apparatus is provided in a portion of the media conveyance path.

11. The image forming apparatus according to claim 9 , wherein the belt drive apparatus is provided in the transferring unit.

12. The belt drive apparatus according to claim 2 , wherein

a gap is provided between the roller and the restraint member in the axial direction of the roller.

13. The belt drive apparatus according to claim 2 , further comprising

a cleaning blade being in contact with the belt member at a position corresponding to an outer circumferential surface of the second roller, to thereby clean the surface of the belt member as the belt is conveyed.