| 摘要 |
PURPOSE:To detect the residual quantity of toner and the existence of a developing device by simple and inexpensive constitution. CONSTITUTION:In a toner residual quantity detection device which detects the residual quantity of the toner being developer in a developing device 1 loaded in an electrophotographic copying device, a piezoelectric toner sensor 2 provided in the developing device 1, a comparison circuit 11 which compares the output of the sensor 2 with a reference voltage which is previously set, a monostable multivibrator circuit 12 triggered by the output of the comparator circuit 11 and an arithmetic and logic circuit 13 which calculates the AND of the output of the comparator circuit 11 and the output of the vibrator circuit 12 are provided. Then, the residual quantity of the toner is detected by the output of the vibrator circuit 12 and the existence of the developing device 1 is detected by the output of the arithmetic and logic circuit 13. |
