| 摘要 |
PROBLEM TO BE SOLVED: To improve responsiveness to the secular changes of the characteristics of a photoreceptor and developer characteristics, as for a toner concentration control method for correcting a target concentration value for a toner replenishing control based on the output of a toner concentration sensor installed in a developing device, based on the output of the density of a detection image formed on a photoreceptor and detected by an optical sensor. SOLUTION: In the case of judging that the optical sensor output Vs is larger than a reference value Vs0 (insufficient in toner sticking quantity) and correcting a control reference value Vt0 to a smaller value (steps 5, 7 and 8), on the other hand, in the case of judging that the optical sensor output Vs is smaller than the reference value Vs0 and correcting the control reference value Vt0 to a larger value (steps 6, 9 and 10), instead of a conventional practice of subtracting/ adding a prescribed amount with reference to the control reference value Vt0 at the point of time and taking the value as a new control reference value Vt0, a value obtained by subtracting/adding only a prescribed amount n.ΔVT from/to the output Vt of a permeability sensor at the point of time is regarded as a new control reference value Vt0 (steps 7 and 8 or 14 and 15). |
