| 摘要 |
PURPOSE:To detect accurately supplied toner decreasing below a specific amount and to simplify the structure of a toner hopper by digitizing the output signal of a density detecting means into multistage toner density data and comparing it with reference data, and thus detecting toner empty state. CONSTITUTION:The multistage toner density data B obtained by converting the output voltage of a magnetic sensor 23 as a density detecting means into digital data by an A/D converting circuit 35 is compared with the reference data read out of a RAM 41; when A<=B (namely, when toner density is low or reference density), the density data is compared with toner empty data C in a ROM 40. Then when C>B, a solenoid 39 is turned on to supply toner and when C<=B, it is judged that the toner in a toner hopper 25 decreases below a specific amount and a toner empty display 43 is turned on to indicate that. Consequently, toner empty detection is performed accurately and a mechanical mechanism is eliminated to simplify the structure of the toner hopper. |
