Patent ID: 7512348

Claim:
An image forming apparatus comprising: a developing device for developing an electrostatic image on an image bearing member using a developer containing a toner and a carrier; a detection device for detecting a density of a detection toner image; and a controller for controlling a toner replenishment operation to said developing device on the basis of a result detected by said detection device, wherein, when a result detected by said detection device becomes equal to or smaller than a predetermined value, said controller performs a residual toner amount detection mode while interrupting an imaging forming operation, wherein, in the residual toner amount detection mode, there are performed: a first step of performing the toner replenishment operation; and a second step of, after said first step, forming a toner patch by said developing device, and detecting said toner patch by said detection device; wherein said controller performs said residual toner amount detection mode again if the result detected by said detection device in said second step is equal to or smaller than the predetermined value, and terminates said residual toner amount detection mode if the result detected by said detection device in said second step is larger than the predetermined value, and wherein, when the residual toner amount detection mode is performed a plurality of times, said controller performs a replenishment control in such a manner that a period of time for the toner replenishment operation during an early phase mode of the plurality of residual toner amount detection modes is longer than a period of time for the toner replenishment operation during a late phase mode, of the plurality of residual toner amount detection modes, after the early phase mode.