Roller component with non-constant size of cells and image forming apparatus

1. A roller component comprising:

a layer composed of a foamed rubber material including a plurality of cells formed by gas, the layer being formed into a substantially cylindrical body,

wherein a volume of the cells decreases from an inner side of the substantially cylindrical body toward an outside.

2. The roller component according to claim 1 , wherein a ratio of the volume of the cells to a volume of the foamed rubber material per unit volume decreases from the inner side of the substantially cylindrical body toward the outside.

3. The roller component according to claim 2 , wherein when a thickness of the layer is divided into three portions, and a density of an outermost portion is represented by A, a density of an intermediate portion is represented by B, and a density of an innermost portion is represented by C, a relationship A>B>C is satisfied, a difference between A and B is larger than about 0.15 g/cm 3 , and a difference between B and C is larger than about 0.15 g/cm 3 .

4. The roller component according to claim 1 , wherein the layer has a density of about 0.35 g/cm 3 or more and about 0.55 g/cm 3 or less, and a hardness of about 30° or more and about 40° or less measured with an Asker-C hardness meter.

5. An image forming apparatus comprising:

a first roller component formed of the roller component according to claim 1 ;

a second roller component; and

a transfer belt onto which a toner is transferred,

wherein the first roller component includes a shaft as a first electrode for applying a transfer bias voltage, and faces the second roller component with the transfer belt therebetween,

the layer rotates around the shaft while contacting the transfer belt, and

the second roller component includes a second electrode for applying the transfer bias voltage.

6. The image forming apparatus according to claim 5 , wherein a ratio of the volume of the cells to a volume of the foamed rubber material per unit volume decreases from the inner side of the substantially cylindrical body toward the outside.

7. The image forming apparatus according to claim 5 , wherein the layer has a density of about 0.35 g/cm 3 or more and about 0.55 g/cm 3 or less, and a hardness of about 30° or more and about 40° or less measured with an Asker-C hardness meter.

8. The image forming apparatus according to claim 7 , wherein when a thickness of the layer is divided into three portions, and a density of an outermost portion is represented by A, a density of an intermediate portion is represented by B, and a density of an innermost portion is represented by C, a relationship A>B>C is satisfied, a difference between A and B is larger than about 0.15 g/cm 3 , and a difference between B and C is larger than about 0.15 g/cm 3 .

9. The image forming apparatus according to claim 5 ,

wherein the transfer belt includes a first layer and a second layer, the first layer containing a resin and an electrically conductive agent, and the second layer being disposed on an inner peripheral side of the transfer belt with respect to the first layer and containing the resin and the electrically conductive agent, and

a content of the electrically conductive agent in the second layer is higher than a content of the electrically conductive agent in the first layer.

10. The image forming apparatus according to claim 9 ,

wherein the second layer includes a first region, a second region, and a third region that are sequentially layered on a boundary surface between the first layer and the second layer in a thickness direction of a second layer side,

the first region and the second region are layered in a range up to about 15 μm from the boundary surface in a thickness direction of the second layer,

the first region does not contain the electrically conductive agent, and

an electrical conductivity of the second region is about 5 times an electrical conductivity of the third region or more.