TONER CONCENTRATION CONTROL SYSTEM AND IMAGE FORMING DEVICE USING THE SAME

PROBLEM TO BE SOLVED: To provide a toner concentration control system capable of accurately correcting an output value from a toner concentration sensor, and an image forming device using the system. SOLUTION: This control system is equipped with the toner concentration sensor 13 detecting toner concentration in a developing part 11, a reflection type photosensor 5 detecting toner adhesive amount on a photoreceptor 1, and a control means 21 controlling so that the developing part 11 is replenished with toner from a toner replenishing part 12 based on the detected result by both sensors. In the case of judging from the output values from both sensors that the toner concentration is low and the toner adhesive amount is large, the control means 21 corrects the reference value of the toner concentration while successively reducing correction amount, and also judges from the output value from both sensors that such correction must be performed again when the correction is finished.