Patent ID: 7257338

Claim:
An image forming apparatus comprising: a rotary driven photoreceptor; a charging device that charges a surface of the photoreceptor; an exposing device that exposes the photoreceptor charged by the charging device to form an electrostatic latent image; and a developing device that develops, using developer, the electrostatic latent image formed on the photoreceptor by the exposing device to form a developer image, wherein the image forming apparatus transfers the developer image on a recording material to form an image on the recording material, the image forming apparatus further comprising: a charged amount detection device that detects a charged amount per unit mass of the developer used by the developing device, based on a current value of the electric current flowing between a part of the photoreceptor charged by the charging device but not exposed by the exposing device and the developing device, so that the charged amount per unit mass of the developer is detected in an indirect manner; and a developing bias adjustment device that adjusts a developing bias to regulate a ratio of the charged amount per unit mass detected by the charged amount detection device to an electric current which flows between the developing device and the photoreceptor at the time of developing the electrostatic latent image representing a reference image.