Patent ID: 6381421
Filing Date: 2002-04-30
Classification: G03G

Abstract:
An image forming apparatus comprising:a plurality of developing means containing a developer inside and used for supplying the developer to an image bearer; a plurality of detectors for detecting developer densities of said plurality of developing means; replenishment means for replenishing said plurality of developing means with a developer based on detection results output from said plurality of detectors; first control means for executing a replenishment operation from the replenishment means to a developing means when detection by the plurality of detectors shows that at least one of the developing means has a developer density that is not more than a density value C; second control means for executing a replenishment operation from the replenishment means to all developing means whose developer densities are not more than a density value B, which is between the density value C and a density value A, until the developer densities exceed the density value C, when detection by the plurality of detectors shows that at least one of the developing means has a developer density that is not more than the density value A, which is lower than the density value C; and developer-empty state detecting means for detecting a developer-empty state of the replenishment means if the developer density of the developing means for which the replenishment operation is performed does not exceed the density value C even after the replenishment operation by the second control means is executed for more than a predetermined period of time.