| 摘要 |
PROBLEM TO BE SOLVED: To surely detect the ends of not only a black toner but also the other color toners, in a developing device provided with plural developing units housing the black toner and the other color toners. SOLUTION: The device 30 is provided with the developing units 31Bk, 31Y, 31M and 31C housing the toners of black, yellow, magenta and cyan respectively. Each developing unit is turned by 90 deg. and set in a developing position D facing a photoreceptor 10. The inside of the hopper 33 of the developing unit set in the developing position D is irradiated with light from a light emitting element 81 and when the developing unit is nearly empty or empty of the toner, the light reflected from a reflection surface 36 is made incident on a light receiving element 82, to decide the residual toner, based on the light receiving output voltage of the light receiving element 82. Diaphragm members 85 are installed for the color developing units except black, to prevent the interface reflected light of translucent window members 35 from being made incident on the light receiving element 82. |
