Medium conveyance device and image formation apparatus

1. A medium conveyance device, comprising:

a pressed member;

a first retention member retaining the pressed member and including a first bias-member retention portion;

a press member provided facing the pressed member;

a second retention member being provided movable relative to the first retention member and retaining the press member, the second retention member including a second bias-member retention portion; and

a bias member provided between the first bias-member retention portion and the second bias-member retention portion and supported at one end thereof by the first bias-member retention portion and at another end thereof by the second bias-member retention portion, thereby pressing the press member against the pressed member, wherein

the first retention member includes a pressed-member support portion supporting the pressed member,

the second retention member includes a press-member support portion supporting the press member, and

the pressed-member support portion is located between the press-member support portion and the first bias-member retention portion.

2. The medium conveyance device according to claim 1 , wherein

the pressed member is a roller.

3. The medium conveyance device according to claim 1 , wherein

the press member is a roller.

4. The medium conveyance device according to claim 1 , wherein

the pressed member is a drive roller.

5. The medium conveyance device according to claim 4 , wherein

the press member is a driven roller.

6. The medium conveyance device according to claim 1 , wherein

the bias member is provided in a compressed state between the first and second bias-member retention portions.

7. The medium conveyance device according to claim 1 , wherein

the pressed member is supported by the pressed-member support portion of the first retention member via a first support member, and

the press member is supported by the press-member support portion of the second retention member via a second support member.

8. The medium conveyance device according to claim 7 , wherein

the device further comprises a conductive member and a fixture member,

the press member and the second support member are made of a conductive material,

the conductive member has one end in contact with the second support member and another end fixed by the fixture member, and

the press member is grounded via the second support member, the conductive member, and the fixture member.

9. The medium conveyance device according to claim 8 , wherein

the conductive member is attached to a conductive-member support portion formed in the second retention member.

10. The medium conveyance device according to claim 9 , wherein

the conductive member is a torsion spring having a coil portion,

the torsion spring is attached to the conductive-member support portion by fitting a boss portion of the conductive-member support portion into the coil portion of the torsion spring, and

a center of the boss portion is located at a predetermined distance away from a straight line connecting a shaft center of the press member and a center of the fixture member.

11. The medium conveyance device according to claim 1 , wherein

the pressed member is in contact with the press member at a contact portion,

a distance between the contact portion and the second retention member is greater than a distance between the contact portion and the first retention member, and

the bias member is a compressed spring.

12. An image formation apparatus comprising the medium conveyance device according to claim 1 .

13. A medium conveyance device, comprising:

a pressed member;

a first retention member retaining the pressed member and including a first bias-member retention portion;

a press member provided facing the pressed member;

a second retention member being provided movable relative to the first retention member and retaining the press member, the second retention member including a second bias-member retention portion; and

a bias member is provided in a compressed state between the first bias-member retention portion and the second bias-member retention portion and supported at one end thereof by the first bias-member retention portion and at another end thereof by the second bias-member retention portion, thereby pressing the press member against the pressed member in a first direction, wherein

the second bias-member retention portion is provided downstream of the first bias-member retention portion in a second direction substantially parallel to the first direction.

14. The medium conveyance device according to claim 13 , wherein the pressed member comprises a first roller having a first axis,

wherein the press member comprises a second roller having a second axis, and

wherein the first axis is provided between the second axis and the bias member.

15. The medium conveyance device according to claim 13 , further comprising:

a conductive member; and

a fixture member,

wherein the press member is made of a conductive material,

wherein the conductive member has one end electrically connected with the press member and another end electrically connected with the fixture member, and

wherein the press member is grounded via the conductive member and the fixture member.

16. The medium conveyance device according to claim 13 , wherein the pressed member is a roller.

17. The medium conveyance device according to claim 13 , wherein the press member is a roller.

18. The medium conveyance device according to claim 13 , wherein the pressed member is a drive roller.

19. The medium conveyance device according to claim 18 , wherein the press member is a driven roller.

20. An image formation apparatus comprising the medium conveyance device according to claim 13 .