Toner concentration control method

摘要

A toner density control method senses the concentration of a toner image for control formed on a photoconductive element by an optical sensor and, based on the output of the sensor, corrects a target target toner concentration for toner supplement control to be effected in response to an output of a toner concentration sensor mounted on a developing device. When the output Vs of the optical sensor is determined to be greater than a reference value Vs0 (short toner deposition), the reference value Vt0 is corrected to smaller one. When Vs determined to be smaller than Vs0 (excessive toner deposition), Vt0 is corrected to greater one. In each of such cases, a predetermined amount nx DELTA VT is subtracted from or added to the output Vt of the toner concentration sensor of that instant.