Abstract: A toner cleaning device for a toner detecting sensor for cleaning toner without scratching the surface of area to be detected. Two sheets of blades in two different length, one being shorter than the other, are atached to a rotating shaft for cleaning toner. A first blade does not reach the surface of the sensor but removes most of the toner accumulated on the surface to be detected except the toner in the area closely contacted with the surface, while a second blade contacts slidably and softly with the surface to be detected thereby removeing the toner accumulated thereon.

Abstract: A method of controlling toner concentration for an electrophotographic copying apparatus in which voltage to be impressed on a toner collecting or recovering roller disposed to contact a flow of a developing material after developing is arranged to vary so that a voltage lower than that for a reference density image is applied thereto for an image having a high density requiring a large toner consumption, while a voltage higher than that for the reference density image is applied thereto for an image having a low density requiring a small toner consumption.