Roll supporting mechanism, image forming apparatus and assembly body

1. A roll supporting mechanism rotatably supporting an electrically-conductive roll, the roll supporting mechanism comprising:

an electrically-conductive portion that contacts with one circumferential portion of an outer periphery of the electrically-conductive roll to conduct electricity to the electrically-conductive roll,

an insulating portion that contacts with another circumferential portion of the outer periphery of the electrically-conductive roll at a contact portion smaller than a contact portion of the electrically-conductive portion and that is formed by an insulating material, and

a pressing member that presses the electrically-conductive portion against the electrically-conductive roll,

wherein the pressing member presses the electrically-conductive portion against the electrically-conductive roll further toward the outer side in the rotation-axis direction of the electrically-conductive roll than the contact portion at which the electrically-conductive roll and the electrically-conductive portion contact with each other.

2. The roll supporting mechanism according to claim 1 , wherein the pressing member conducts electricity to the electrically-conductive portion.

3. An image forming apparatus comprising:

an image holding body that holds an image;

a transfer body to which the image is transferred;

a transfer roll serving as an electrically-conductive roll, that transfers the image from the image holding body to the transfer body by application of a voltage;

the roll supporting mechanism according to claim 1 , that rotatably supports the transfer roll by the electrically-conductive portion and the insulating portion and that applies the voltage to the transfer roll via the electrically-conductive portion.

4. An image forming apparatus comprising:

a charging roll serving as an electrically-conductive roll, that charges a charged body by application of a voltage;

an exposure device that exposes the charged body charged by the charging roll so as to form a latent image;

a developing device that develops the latent image formed by the exposure device;

the roll supporting mechanism according to claim 1 , that rotatably supports the charging roll by the electrically-conductive portion and the insulating portion and that applies the voltage to the charging roll via the electrically-conductive portion.

5. An assembly body being assembled integrally and removably with an apparatus main body, the assembly body comprising:

an image holding body that holds an image,

a transfer body to which the image is transferred,

a transfer roll serving as the electrically-conductive roll, that transfers the image from the image holding body to the transfer body by application of a voltage, and

the roll supporting mechanism according to claim 1 that rotatably supports the transfer roll by the electrically-conductive portion and the insulating portion and that applies the voltage to the transfer roll via the electrically-conductive portion.

6. An assembly body being assembled integrally and removably with an apparatus main body, the assembly body comprising:

a charging roll serving as the electrically-conductive roll, that charges a charged body by application of a voltage, and

the roll supporting mechanism according to claim 1 , that rotatably supports the charging roll by the electrically-conductive portion and the insulating portion and that applies the voltage to the charging roll via the electrically-conductive portion.

7. A roll supporting mechanism rotatably supporting an electrically-conductive roll, the roll supporting mechanism comprising:

an electrically-conductive portion that contacts with one circumferential portion of an outer periphery of the electrically-conductive roll to conduct electricity to the electrically-conductive roll,

an insulating portion that contacts with another circumferential portion of the outer periphery of the electrically-conductive roll at a contact portion smaller than a contact portion of the electrically-conductive portion and that is formed by an insulating material, wherein

the electrically-conductive portion has a curved surface portion that contacts with the outer periphery of the electrically-conductive roll, and

the insulating portion has a pair of contact portions, each of which contacts with the outer periphery of the electrically-conductive roll, and a curved surface portion whose curvature changes from one of the contact portions to the other of the contact portions along the outer periphery of the electrically-conductive roll and that does not contact with the outer periphery of the electrically-conductive roll.

8. The roll supporting mechanism according to claim 7 , wherein the curved surface portion of the insulating portion has a curvature larger than that of the outer periphery of the electrically-conductive roll.

9. The roll supporting mechanism according to claim 7 , wherein each contact portion of the insulating portion is a planar surface portion that is formed in a linear shape and is connected to the curved surface portion of the insulating portion.

10. The roll supporting mechanism according to claim 7 , wherein each contact portion of the insulating portion has a curved surface whose curvature is smaller than that of the outer periphery of the electrically-conductive roll.

11. The roll supporting mechanism according to claim 7 , wherein the contact portion of the electrically-conductive portion is plurally formed along the axial direction of the electrically-conductive roll.