| 摘要 |
PROBLEM TO BE SOLVED: To make an error generated in toner density control of an inductance detection sensor of a developing device as small as possible even when an electrified carrier from a magnetic brush electrification device side in magnetic brush contact electrification method, two component developing method, transfer method and cleanerless system is mixed into two component developer. SOLUTION: In developer density control devices 50 to 57 and M, outward magnetic permeability of the two component developer 47 of the developing device 4 is detected and a toner replenishing means is activated based on a standard value of toner replenishing control derived from a compared result of a detecting signal based on that detected result and the detecting signal of the standard value. These developer concentration control devices 50 to 57 and M are provided with a detection signal standard value compensating means (74 to 79) where the standard value for the detection signal is set again from the amount of mixture of the electrified magnetic carrier to the developing device that can be predicted from the time for an image forming operation or the number of times it is carried out, and/or the number of video count of a concentration signal of an image information signal are provided. |
