Patent ID: 7995934

Claim:
A developing device comprising: a developer container that contains developer including toner and carrier; a toner-concentration detecting unit that detects toner concentration of the developer in the developer container; a developer carrier that carries the developer in the developer container on its surface and develops a latent image on a latent-image carrier with the developer, wherein at least one of an information attaching unit and a density-information storage unit is provided in the developing device before shipment of the developing device, the information attaching unit attaches either one of carrier density information of initial developer, which is new developer set in the developing device, and loose apparent density information of toner in the initial developer, to a housing of the developing device, the density-information storage unit stores therein either one of the carrier density information and the loose apparent density information as electronic data, the toner-concentration detecting unit is a bulk-density sensor for detecting toner concentration in two component developer containing toner and carrier, and the developing device further comprises a development controller that controls upper and lower limits of the toner concentration in the developer by an output value of the toner-concentration detecting unit and that corrects control values for the upper and lower limits of the toner concentration by changing an amount of shift of the control values of the upper and lower limits of toner concentration from an appropriate value for the toner concentration, based on either one of the carrier density information and the loose apparent density information, wherein the upper limit is higher than the lower limit.