Image forming apparatus or transfer roller used in image forming apparatus

A transfer roller for use in an image forming apparatus, the image forming apparatus including an image bearing member configured to bear a toner image and the transfer roller configured to face the image bearing member and form a transfer nip portion together with the image bearing member, the transfer roller transferring a toner image from the image bearing member onto a transfer medium conveyed to the transfer nip, the transfer roller comprising:

• a metal core bar;
• and
• an elastic layer disposed on the metal core bar, the elastic layer being formed of solid rubber which does not foam by a foaming process;
• wherein the elastic layer includes, on a surface thereof, a plurality of convex portions each extending in a line in an axis direction of the transfer roller, and
• wherein a convex portion positioned at the transfer nip, among the plurality of convex portions, tilts such that a leading end of convex portion comes into contact with a neighboring convex portion when the toner image is transferred onto the transfer medium.

An image forming apparatus comprising:

• an image bearing member configured to bear a toner image;
• and
• a transfer roller configured to face the image bearing member and form a transfer nip portion together with the image bearing member,
• wherein the image forming apparatus transfers the toner image from the image bearing member onto a transfer medium conveyed into the transfer nip portion, and wherein the transfer roller includes a metal core bar and an elastic layer disposed on the metal core bar, the elastic layer is formed of solid rubber which does not foam by a foaming process, and the elastic layer includes, on a surface thereof, a plurality of convex portions each extending in a line in an axis direction of the transfer roller,
• wherein the following condition is satisfied:
• D/W≧0.7
• where W denotes a center-to-center distance of the neighboring convex portions, and D denotes a length between a tangential line of the vertex of any one of the convex portions and a bottom of a concave portion, and
• wherein W is larger than or equal to 100 μm, and D is larger than or equal to 100 μm.

A transfer roller for use in an image forming apparatus, the image forming apparatus including an image bearing member configured to bear a toner image and the transfer roller configured to face the image bearing member and form a transfer nip portion together with the image bearing member, the transfer roller transferring a toner image from the image bearing member onto a transfer medium conveyed to the transfer nip, the transfer roller comprising:

• a metal core bar;
• and
• an elastic layer disposed on the metal core bar, the elastic layer being formed of solid rubber which does not foam by a foaming process,
• wherein the elastic layer includes, on a surface thereof, a plurality of convex portions each extending in a line in an axis direction of the transfer roller.
• wherein the following condition is satisfied:
• D/W≧0.7
• where W denotes a center-to-center distance of the neighboring convex portions, and D denotes a length between a tangential line of the vertex of any one of the convex portions and a bottom of a concave portion, and wherein W is larger than or equal to 100 μm, and D is larger than or equal to 100 μm.