| 摘要 |
PURPOSE:To aim at enhancing the quality, performance and reliability of a vehicle air-conditioning system, by utilizing a frequency comparing and determining section to count pulses proportional to the speeds of an engine and a compressor so that the lowering of rotational speed of the compressor is detected to eliminate the dispersions of discrete characteristics. CONSTITUTION:A counter 14 does not normally have a chance to count 10 of IG pulses indicating the rotational speed of an engine so that a determining circuit 15 does not issue its determination output. Accordingly, an electromagnetic clutch 2 is maintained to be turned on by means of a switch circuit 12 and a relay 13. When the rotational speed of a compressor lowers due to locking etc., estimating that the frequency of a CP signal indicating the rotational speed of the compressor is less than the frequency of the IG signal by 50%, IG pulses and CP pulses delivered into the counters 14, 16 are such that the counter 14 counts 10 of IG pulses until the counter 16 counts 5 of pulses, and therefore, the determining circuit detects the output of the counter 14 and delivers a stopping signal as a determination signal to the counters 14, 16, simultaneously with the deliveration of the signal to the switch circuit 12 which therefore energizes a relay 13 to turn off the electromagnetic clutch 2. |
