| 摘要 |
PROBLEM TO BE SOLVED: To accurately detect the toner concentration so that the toner concentration can be stably controlled by removing output fluctuation part having a large time constant without the occurrence of the attenuation of output, etc., from the output of a magnetic sensor detecting the toner concentration and set on a developing device. SOLUTION: As to this image forming device, a noise component having a comparatively high frequency is removed from the detection output VS of the magnetic sensor by an LPF(low-pass filter) 60, a minimum signal L61 which becomes high for a specified time when a sensor signal L60 is a minimum value by a peak detector 61 is outputted, a maximum signal L63 which becomes high when the sensor signal L60 is a maximum value by the a peak detector 63 is outputted, the signal respectively pass through S/H(sample hold) circuits 62 and 64 and are inputted to an analog adder 65 as an L62 and an L64, the L62 is added to the L64, an average signal L66 is generated by the amplifier 66 of 1/2 gain, passes through an S/H circuit 68, is inputted to an A/D converter (analog/digital) 69 as a sensor signal L68, read in a CPU part 70 by a CPU bus L69, and used for the replenishment control of toner. |
