Patent ID: 7912390

Claim:
An image forming apparatus having a plurality of image forming speeds, the image forming apparatus comprising: an image bearing member on which an electrostatic image is formed: a developing container that receives a developer; a developer carrying member that is arranged to be rotatable and conveys the developer so as to develop said electrostatic image; a developer feed member that is arranged in contact with said developer carrying member and to be rotatable, wherein said developer feed member feeds the developer to said developer carrying member; a detection device that detects an amount of developer in said developing container by detecting an electrostatic capacitance between said developer carrying member and said developer feed member; and a control unit that changes a rotational speed of said developer feed member into a plurality of developer feed member rotational speeds corresponding to the plurality of image forming speeds, wherein said control unit controls the rotational speed of said developer feed member prior to an execution of a detection operation of said detection device so as to be faster than the slowest speed of the plurality of developer feed member rotational speeds, and wherein said control unit decides a timing at which said detection operation is carried out, based on historical information of image formation.