Image forming apparatus having rollers, belt and a tension applying unit

1. An image forming apparatus comprising:

a plurality of rollers including

a first roller rotated by receiving rotation from a drive unit, and

a second roller rotated with the rotation of the first roller;

a belt stretched around the plurality of rollers, the belt having an inner surface; and

a tension applying unit that applies tension to the belt,

wherein the inner surface of the belt has an uneven shape,

wherein each respective roller of at least one roller of the plurality of rollers satisfies conditions expressed by μkmax≦0.73 and Δμk=(μkmax−μkmin)≦0.51, where μkmax is a maximum dynamic friction coefficient between the inner surface of the belt and the respective roller, and μkmin is a minimum dynamic friction coefficient between the inner surface of the belt and the respective roller, and

wherein each respective roller of the at least one roller satisfies said conditions when a speed of the belt relative to the respective roller is 0.2 mm/s.

2. The image forming apparatus of claim 1 , wherein each respective roller of the at least one roller further satisfies μkmax≧0.12 when a speed of the belt relative to the respective roller is 0.2 mm/s.

3. The image forming apparatus of claim 1 , wherein the tension applying unit urges the second roller to apply the tension to the belt.

4. The image forming apparatus of claim 1 , wherein the plurality of rollers further include a third roller rotated with the rotation of the first roller.

5. The image forming apparatus of claim 4 , wherein the tension applying unit urges the third roller to apply the tension to the belt.

6. The image forming apparatus of claim 1 , further comprising at least one restriction member that is disposed at at least one end of a predetermined one of the plurality of rollers and abuts against the belt to restrict movement of the belt.

7. The image forming apparatus of claim 6 , wherein the predetermined roller is provided with an inclination mechanism that inclines the predetermined roller.

8. The image forming apparatus of claim 1 , wherein the belt has a single layer structure.

9. The image forming apparatus of claim 1 , wherein each respective roller of the at least one roller satisfies Δμk≦0.45 when a speed of the belt relative to the respective roller is 0.2 mm/s.

10. The image forming apparatus of claim 1 , wherein the tension applying unit urges the second roller with a stretching force of 2 kg±0.2 kg or more and 8 kg±0.8 kg or less.

11. The image forming apparatus of claim 1 , wherein a surface of the belt has a specularity of 60 or more and 200 or less.

12. The image forming apparatus of claim 1 , wherein a surface of the belt has, with respect to stainless steel, a static friction coefficient μe of 0.1 or more and 1.0 or less.

13. An image forming apparatus comprising:

a plurality of rollers including

a first roller rotated by receiving rotation from a drive unit, and

a second roller rotated with the rotation of the first roller;

a belt stretched around the plurality of rollers, the belt having an inner surface; and

a tension applying unit that applies tension to the belt,

wherein the inner surface of the belt has an uneven shape,

wherein each respective roller of at least one roller of the plurality of rollers satisfies conditions expressed by μkmax≦0.54 and Δμk=(μkmax−μkmin)≦0.23, where μkmax is a maximum dynamic friction coefficient between the inner surface of the belt and the respective roller, and μkmin is a minimum dynamic friction coefficient between the inner surface of the belt and the respective roller, and

wherein each respective roller of the at least one roller satisfies said conditions when a speed of the belt relative to the respective roller is 3.54 mm/s.

14. The image forming apparatus of claim 13 , wherein each respective roller of the at least one roller further satisfies μkmax≧0.10 when a speed of the belt relative to the respective roller is 3.54 mm/s.

15. The image forming apparatus of claim 13 , wherein the tension applying unit urges the second roller to apply the tension to the belt.

16. The image forming apparatus of claim 13 , wherein the plurality of rollers further include a third roller rotated with the rotation of the first roller.

17. The image forming apparatus of claim 16 , wherein the tension applying unit urges the third roller to apply the tension to the belt.

18. The image forming apparatus of claim 13 , further comprising at least one restriction member that is disposed at at least one end of a predetermined one of the plurality of rollers and abuts against the belt to restrict movement of the belt.

19. The image forming apparatus of claim 18 , wherein the predetermined roller is provided with an inclination mechanism that inclines the predetermined roller.

20. The image forming apparatus of claim 13 , wherein the belt has a single layer structure.

21. The image forming apparatus of claim 13 , wherein each respective roller of the at least one roller satisfies Δμk≦0.22 when a speed of the belt relative to the respective roller is 3.54 mm/s.

22. The image forming apparatus of claim 13 , wherein the tension applying unit urges the second roller with a stretching force of 2 kg±0.2 kg or more and 8 kg±0.8 kg or less.

23. The image forming apparatus of claim 13 , wherein a surface of the belt has a specularity of 60 or more and 200 or less.

24. The image forming apparatus of claim 13 , wherein a surface of the belt has, with respect to stainless steel, a static friction coefficient μe of 0.1 or more and 1.0 or less.