Developing device, process cartridge, and image forming apparatus

A process cartridge detachably attachable to an apparatus main body of an image forming apparatus, the process cartridge comprising:

• an image bearing member on which at least a latent image is formed;
• a frame member configured to accommodate a developer;
• a developer bearing member rotatably supported in an opening of the frame member and configured to bear and convey the developer;
• a regulation member configured to make contact with the developer bearing member and regulate the developer to a predetermined layer thickness;
• and
• an end seal fixed to a longitudinal end of the opening of the frame member and configured to seal a gap between the frame member, the developer bearing member, and the regulation member,
• wherein the regulation member includes an opposed surface and a contact surface contacting with the developer bearing member at least in a portion corresponding to an image forming area, the opposed surface being opposed to the developer bearing member, the contact surface protruding from the opposed surface and having a height different from that of the opposed surface,
• wherein the regulation member includes an area not having the contact surface between the image forming area and a sealing area in which the regulation member and the end seal overlap, and
• wherein in the sealing area, a step between the opposed surface and the contact surface has a height of greater than or equal to 0 mm and not greater than 0.10 mm.

An image forming apparatus for forming an image on a recording material, the image forming apparatus comprising:

• an image bearing member on which at least a latent image is formed;
• a frame member configured to accommodate a developer;
• a developer bearing member rotatably supported in an opening of the frame member and configured to bear and convey the developer;
• a regulation member configured to make contact with the developer bearing member and regulate the developer to a predetermined layer thickness;
• and
• an end seal fixed to a longitudinal end of the opening of the frame member and configured to seal a gap between the frame member, the developer bearing member, and the regulation member,
• wherein the regulation member includes an opposed surface and a contact surface contacting with the developer bearing member at least in a portion corresponding to an image forming area, the opposed surface being opposed to the developer bearing member, the contact surface protruding from the opposed surface and having a height different from that of the opposed surface,
• wherein the regulation member includes an area not having the contact surface between the image forming area and a sealing area in which the regulation member and the end seal overlap, and
• wherein in the sealing area, a step between the opposed surface and the contact surface has a height of greater than or equal to 0 mm and not greater than 0.10 mm.