Roller for use with image forming apparatus

A developing device to be incorporated within an electrophotographic image forming apparatus, comprising:

• a first roller and a second roller disposed in a peripheral contact with the first roller to define a contact region therebetween so that the first roller is capable of supplying and collecting a toner to and from the second roller in the contact region, the second roller being disposed adjacent a photosensitive member of the electrophotographic image forming apparatus to provide the toner from the second roller to the photosensitive member to visualize an electrostatic latent image supported on the photosensitive member,
• wherein the first roller has a core, and a polyurethane foam layer made of polyurethane foam including cells therein and covering the core to form a peripheral surface of the first roller;
• wherein
• the polyurethane foam has an open ratio of cells of 2% or more and 50% or less and a hardness of 1 gf/mm or more and 6 gf/mm or less, the hardness being defined by a load per unit length in a longitudinal direction of the first roller, the load being determined by forcing the peripheral surface of the polyurethane foam layer against a substrate, measuring a load necessary for the polyurethane foam layer to be compressed by 30% in thickness, and dividing the load by a length of the polyurethane foam layer in the longitudinal direction;
• and
• wherein
• the first and second rollers are disposed so that the contact region has a peripheral width of 3 mm or more and 8 mm or less.

An electrophotographic image forming apparatus, comprising:

• a photosensitive member;
• and
• a developing device, the developing device having a first roller and a second roller disposed in a peripheral contact with the first roller to define a contact region therebetween so that the first roller is capable of supplying and collecting a toner to and from the second roller in the contact region, the second roller being disposed adjacent the photosensitive member to provide the toner from the second roller to the photosensitive member to visualize an electrostatic latent image supported on the photosensitive member,
• wherein the first roller has a core, and a polyurethane foam layer made of polyurethane foam including cells therein and covering the core to form a peripheral surface of the first roller;
• wherein
• the polyurethane foam has an open ratio of cells of 2% or more and 50% or less and a hardness of 1 gf/mm or more and 6 gf/mm or less, the hardness being defined by a load per unit length in a longitudinal direction of the first roller, the load being determined by forcing the peripheral surface of the polyurethane foam layer against a substrate, measuring a load necessary for the polyurethane foam layer to be compressed by 30% in thickness, and dividing the load by a length of the polyurethane foam layer in the longitudinal direction;
• and
• wherein
• the first and second rollers are disposed so that the contact region has a peripheral width of 3 mm or more and 8 mm or less.