| 摘要 |
PURPOSE:To prevent the chattering phenomenon of a smoke removing means in the case that smoke intermittently flows into a smoke sensor, by comparing a reference value stored in memory with a detected value after a predetermined time set by a timer circuit elapses to control the smoke removing means. CONSTITUTION:A detected value corresponding to the concentration of smoke in the passenger's compartment of a vehicle, which is detected by a smoke sensor 1, is subjected to voltage-division by resistors R1, R2 and is delivered to a comparator 3 after being amplified by an amplifier 2. Further, thus amplified detected value is also delivered to a reference setting section 4 including a temperature drift countermeasure circuit 4a for correcting the reference value in accordance with a drift in the temperature of the passenger's compartment and a memory means 4b for storing the reference value when the detected value exceeds the reference value. Further, the comparator 3 compares the detected value with the reference value, and if the detected value is higher than the reference value due to smoke existing in the passenger's compartment in some degree, a smoke removing means 5 is operated for a predetermined time set by a timer circuit 5 to purify air in the passenger's compartment. |
