Belt transporting apparatus, image forming apparatus and belt member transporting method with obilqueness mitigation

1. A belt transporting apparatus comprising:

a belt member that is rotated;

a first roll member that holds the belt member;

a second roll member that is provided apart from the first roll member by a first distance, holds the belt member together with the first roll member and is movable toward the first roll member; and

a third roll member that is provided apart from the second roll member by a second distance and holds the belt member together with the second roll member, the second distance being longer than the first distance,

wherein the first roll member is a drive roll that rotatable drives the belt member.

2. The belt transporting apparatus according to claim 1 , wherein the second roll member is arranged on an upstream side in a rotating direction of the belt member relative to the first roll member.

3. The belt transporting apparatus according to claim 1 , wherein the second roll member is a tension-adjusting roll that adjusts tension applied to the belt member.

4. The belt transporting apparatus according to claim 1 , further comprising a cleaning member that is arranged to be brought in contact with the belt member at a position opposed to the first roll member while the belt member is sandwiched therebetween, and removes adhesion material on the belt member.

5. An image forming apparatus comprising:

a plurality of image forming units;

an intermediate transfer belt that holds and transports images formed by the plurality of image forming units;

a first roll member that holds the intermediate transfer belt;

a second roll member that holds the intermediate transfer belt together with the first roll member, forms a first face on the intermediate transfer belt between the first roll member and the second roll member, and is movable along the first face; and

a third roll member that forms a second face on the intermediate transfer belt together with the second roll member, the second face having a longer distance in a rotating direction of the intermediate transfer belt than the first face,

wherein the plurality of image forming units respectively include:

an image carrier that the image is formed thereon; and

a primary transfer member that transfers the image formed on the image carrier to the intermediate transfer belt, and

the second roll member is a path change roll that changes the number of the image carriers being in contact with the intermediate transfer belt by changing a rotation path of the intermediate transfer belt.

6. A belt member transporting method for use in an image forming apparatus, the belt member transporting method comprising:

rotating a belt member by driving a first roll member in a state where the belt member is held by the first roll member, a second roll member that is provided apart from the first roll member by a first distance and is movable toward the first roll member, and a third roll member that is provided apart from the second roll member by a second distance longer than the first distance; and

adjusting tensile force of the belt member by moving the second roll member toward the first roll member,

wherein the first roll member is a drive roll that rotatable drives the belt member.

7. The belt member transporting method according to claim 6 , wherein the second roll member is arranged on an upstream side in a rotating direction of the belt member relative to the first roll member.

8. The belt member transporting method according to claim 6 , wherein the second roll member is a tension-adjusting roll that adjusts tension applied to the belt member.