| 摘要 |
PURPOSE:To prevent any abnormal heating of an engine and make it possible to take a necessary emergency measure, by arranging such that a disconnection trouble can be effectively detected only when a transistor for controlling a solenoid is not conducting. CONSTITUTION:In the case where a transistor Q is not conducting, when a solenoid valve VA energizing line is normal, the voltage at a node J is equal to a supply voltage value V, and a voltage substantially equivalent to the voltage value is applied to a second input of a comparator CMP, and the output OUT thereof is at a low level. If the solenoid energizing line has a disconnection failure, the line voltage value shows almost zero, and the output OUT of the comparator CMP takes a high level to actuate a lamp and an alarm such as a buzzer. When the transistor Q is conducting, the solenoid valve VA is not energized but being urged by a spring SP, and a cooling fan is rotating. Therefore, any disconnection trouble will not stop the rotation of the cooling fan. |
