| 摘要 |
<p>PURPOSE:To prevent the deterioration of a hot-wire resistor by operating burn- off control means when a condition wherein an intake air flow rate from the time when an ignition switch is turned off is below a prescribed value continues for a prescribed time. CONSTITUTION:Reading a voltage signal corresponding to the intake air flow rate of a hot-wire flowmeter when an ignition switch 7 is turned off, a read value is compared with a prescribed voltage value and, when this voltage value is larger than (and equal to) the read value, the intake air flow rate is approximately equal to zero. When above-described condition continues for a prescribed time (for example, 0.6sec) or more, a hot-wire resistor Rh is heated to satisfactorily burn off an attachment. Burn-off signals output high level signals to the base terminal of a transistor 5 for a prescribed time (for example, 0.3sec), reduces the output of a differential amplifier 2 during the output of the high level signals and accordingly increases a power supply to a bridge circuit, that is, the power supply to the hot-wire resistor Rh to heat it up to about 1,000 deg.C, burning off the attachment.</p> |
