| 摘要 |
<p>PURPOSE:To determine the rate of air flow accurately and a low cost without use of plurality of heat emitting resistances by sensing a signal which bases itself upon the change in the resistance value of heat emitting resistance in the suction path, and judging correctly the signal of counterflow by a counterflow judging means. CONSTITUTION:A sensor circuit 22 senses the resistance value of a heat emitting resistance 11 installed on an air flow sensor 10, and then an electric signal is emitted in accordance with the rate air flow, and a CPU 25 converts the electric signal into rate of air flow. Three max. values of the rate of flow and two min. values between them are sensed, and when a counterflow judging means judges that it is a rippled flow including counterflow, a correction is made for the portion of counterflow, and the rate of air flow within a certain period of time is calculated. This eliminates necessity for provision of plurality of heat emitting resistances 11, and a signal resulting from counterflow in the suction passage can be judged accurately and at a low cost, which enables determining the rate of air flow with high precision.</p> |
