Patent ID: 7899375

Claim:
A developing apparatus comprising: a developer carrier having concave portions regularly arranged on the surface thereof and being rotatable with a developer thereon; and a contact member being made of an elastic rubber material, being in contact with the surface of the developer carrier, and vibrating with the rotation of the developer carrier, wherein the developing apparatus can be mounted on and demounted from an image forming apparatus body of an image forming apparatus; wherein an operating temperature range is set in the image forming apparatus; and wherein a value obtained by dividing a movement speed of the surface at the time of rotation of the developer carrier at a constant speed by a pitch of the concave portions in a peripheral direction of the developer carrier is smaller than a peak vibrational frequency of the contact member when a loss tangent obtained by dividing a loss elastic modulus of the contact member by a storage elastic modulus is the greatest at all temperatures in the operating temperature range.