Image forming apparatus

An image forming apparatus, comprising:

• a developing device including a rotatable developer carrying member for carrying a developer, a developer supplying member for supplying the developer to said developer carrying member, and a regulating member for regulating an amount of the developer carried by said developer carrying member in contact with said developer carrying member;
• a first power source for applying a bias to said developer carrying member;
• a second power source for applying a bias to said regulating member;
• and
• a controller for controlling said first and second power sources,
• wherein in a period from a start of a developing operation to an end of the developing operation for printing an image on a single recording material, said controller effects control of a potential difference between said developer carrying member and said regulating member so that a force for urging the developer from said regulating member toward said developer carrying member acts on the developer at a contact portion between said regulating member and said developer carrying member, with the potential difference being controlled so that the force acting on the developer is stronger at the end of the developing operation than at the start of the developing operation on the single recording material.