| 摘要 |
PURPOSE:To maintain the specified toner concn. by detecting the magnetic permeability of a developer consisting of a toner and carrier and to display warning, etc. to prevent the carrier spending by detecting the toner concn. region where the carrier spending does not arise. CONSTITUTION:This device detects the change of the toner concn. of the developer 2 as a change of the magnetic permeability thereof by means of a sensor 20. The output from a smoothing circuit 25 when the developer 2 having the reference toner concn. is contained in a developing tank is compared with the reference voltage of a voltage comparator 26. The sensor 20 is so adjusted as to increase the toner concn. when the toner concn. decreases down to the level at which the toner is replenished after the execution of copying. The toner supply is thereupon controlled by the output of the comparator 26 until the reference toner concn. is attained when the toner concn. decreases. The signal from the smoothing circuit 26 which is the detection output from the sensor 20 is also inputted to the 2nd voltage comparator 28, by which the warning is displayed and the copying machine is stopped if there is the possibility of the carrier spending, etc. |
