PURPOSE: To stabillize printing quality in a printing density, to environmental condition and in the properties of developer by providing plural reference levels for controlling the magnetic permeability of the developer to be constant one, on a comparator circuit and comparing plural reference levels with the detection level for a magnetic permeability so as to change the quantity of toner.
CONSTITUTION: The printing density is pasped by the relation of the quantity of the toner 1 to be replenished from a toner hopper 9, the detection level of the magnetic permeability of the developer 3 and the plural reference levels provided on the comparator circuit 8 and the reference level of the comparator circuit 8 is changed o make the concentration of the toner 1 fluctuated in accordance with the printing density constant. Moreover, the reference level of the comparator circuit 8 is varied with respect to the influence of the environmental humidity on the magnetic permeability of the developer and th influence of the number of printing pages on the properties of the developer, to optimize them. Thus, the concentration of the toner 1 fluctuated in accordance with the printing density, etc., can be stabilized by the change in the reference level of the comparator circuit 8.
NAKAJIMA ISAO
AKAI MUNEYOSHI
ONOSE TSUKASA
SHINOHARA KATSUHIRO
OGURA YOSHIO
KOMODA KATSUHITO
