Patent ID: 7003235

Claim:
A developing device, comprising: a developer comprising toner including a coloring agent dispersed in a first binder resin, and carrier including a core material, and a coating layer covering the core material and containing a second binder resin and a powder; a developer carrier configured to carry and transfer the developer to an image carrier disposed opposite to the developer carrier; a developer conveying member disposed opposite to the developer carrier and configured to convey the developer to the developer carrier; a toner density detecting device disposed opposite to the developer conveying member and configured to detect a toner density of the developer by use of a bulk density sensor; and a control device configured to control the toner density based on a detection result of the toner density detecting device, the toner density being controlled to satisfy the following relationship: 1< D/h< 10, where (D) is an average particle diameter of the powder, and (h) is a thickness of the coating layer.