Patent ID: 8909110

Claim:
A developing device used in an image forming apparatus, comprising: a developer carrying member that carries a developer to develop an electrostatic latent image formed on an image carrying member; a developer regulating member that includes a plate-shaped elastic member, is rotatably supported, and brings the elastic member into contact with the developer carrying member such that a leading edge of the elastic member faces an upstream side, in a rotation direction, of the developer carrying member to regulate a amount of developer held in the developer carrying member; and an urging portion that applies a moment to the developer regulating member to bring the developer regulating member into pressure contact with the developer carrying member, wherein a distance from a rotation center of the developer regulating member to a center of the developer carrying member is set to be more than a distance from the rotation center of the developer regulating member to the leading edge of the elastic member, and when a load received by the developer regulating member due to contact between the developer carrying member is P (N), a free length of the developer regulating member is L (m), a Young's modulus of the developer regulating member is E (Pa), a second moment of area of the developer regulating member is I (m 4 ), and an angle formed between the elastic member and a tangent line to the developer carrying member in a contact portion between the leading edge of the developer regulating member and the developer regulating member at a time when the elastic member comes into contact with the developer carrying member without receiving the load is a set angle α (rad), a bending angle β of the elastic member calculated from the following Expression 1 is less than the set angle α: β= PL 2 /2 EI.