| 摘要 |
PURPOSE:To regenerate a filter according to the decrease in the activity of the filter by removing harmful gases with the filter, detecting the gases to be detected with a gas sensor and subjecting the filter to heat cleaning when the output thereof rises higher than a prescribed value. CONSTITUTION:The output of a gas sensor 2 of a gas detecting circuit 1 is inputted to a comparator 12 of a buzzer driving circuit 11, which compares the same with a reference voltage and actuates a buzzer 15. The output of the circuit 1 is inputted via a diode 22 to a heat cleaning circuit 21. The potential of a capacitor 23 is compared with the reference value in a comparator 26. The output thereof is inputted via a diode 30 to the negative terminal of the comparator 31. The potential of the positive terminal of the comparator 31 is made equal to the reference potential of the negative terminal of the comparator 26. The outputs of the comparators 26 and 31 are inputted to an AND element 32, and a heater 34 for heat cleaning is operated by the output thereof via an SCR 33 to generate heat. Thus the filter is regenerated in accordance with the decrease in the activity of the filter (the increase in the output of the sensor 2). |
