| 摘要 |
PURPOSE:To make possible long-term stable concentration controlling by hermetically forming the optical paths for detecting the quantity of developer irradiating light and the quantity of the light reflected from the developer in a flow pipe transmission window which is prevented of sticking of the developer. CONSTITUTION:The developer formed by carrier and toner flows down a flow passage pipe 42 on the way of falling from a developing roller. By the sliding removal by this flow-down, the sticking of the developer on the transparent window 43 of the pipe 42 is prevented. On the other hand, the irradiating light path by a light source 5 as well as the optical path for detecting the quantity of reflected light according to the toner concentrations of the developer and the optical path for detecting the quantity of irradiated light of the light source 5 by the 1st and 2nd photodetectors 6, 7 are formed by the supporting member 44 mounted to the window 43 in a hermetic state. Hence, the scattering toner etc. do not stick on the light source 5 and the elements 6, 7. These make it possible to control the developer toner concentration stably for a long time by the comparative operations of the detected value of the reflected light corresponding to the toner concentration and the detected value of the quantity of the irradiated light without the effect of outside ambient conditions. |
