| 摘要 |
PURPOSE:To reduce the number of parts and costs by displaying a message prompting the feed of toner to hoppers when the time required for detection signals from toner concentration sensors to reach a reference level continues to exceed a previously set time. CONSTITUTION:When the time required for the detection signals from the toner concentration sensors 51a to 51d to reach a reference level continues to exceed the previously set time, a toner concentration control part 52 sends a lighting signal to a display 54 to prompt the feed of toner to hoppers 31a to 34a. In this case, a time setting means 53 can set for each of developing units 31c to 34c to attain a set time according to consumption of toner in each color. Consequently, toner of different colors can be charged to all hoppers 31a to 34a. Thus, toner quantity sensors detecting the quantity of toner in the hopper can be eliminated. Namely, the number of parts and costs can be reduced. |
