| 摘要 |
PURPOSE:To keep developer concentration constant and to perform satisfactory development by surely and readily preventing carriers contained in a two- component developer from sticking to the detection surface of the detecting window of a developer concentration detecting device. CONSTITUTION:A developer regulating member 54 provided on the detecting window 33 of the detecting device detecting the concentration of the developer containing toner of a 10mum or less volume average grain size and carriers of a 30 to 80mum weight average grain size regulates the toner electrifying quantity when the developer rubs against the detection surface 33a of the detecting window 33 to 200 to 500V in terms of absolute value with polarity the same as that of toner electrification. The vertical component of force which is generated by the magnetic field of a magnet 22 in a developing sleeve 21 and affects the developer facing the detection surface is set to 2.0 X 10<-8> Newton or below. Consequently, the adhesion of carriers in the developer to the detection surface is readily and surely prevented, whereby the detecting device can detect the developer concentration with high accuracy. Thus, toner supply of a toner supply device can keep the developer concentration constant, thereby performing satisfactory development. |
