Patent ID: 8233811

Claim:
An image stabilizing apparatus, comprising: a developing apparatus which stores two-component developer including toner and carrier, for developing an electrostatic latent image formed on an image bearing member; a magnetic permeability sensor for detecting a toner concentration in two-component developer in the developing apparatus; a print coverage detecting portion for detecting a print coverage of a plurality of documents; a toner replenishing apparatus for replenishing toner to the developing apparatus; and a control portion for controlling a toner replenishment operation of the toner replenishing apparatus depending on the toner concentration detected by the magnetic permeability sensor and the print coverage of documents as detected by the print coverage detecting portion, wherein when an average print coverage for a predetermined number of documents as detected by the print coverage detecting portion is less than a predetermined threshold value, the control portion causes a predetermined amount of toner to be forcibly developed onto the image bearing member, and wherein the control portion also causes the same predetermined amount of toner to be replenished into the developing apparatus by the toner replenishing apparatus.