Overheating protection device for rotational control apparatus

摘要

A device (10) is disclosed for intercepting the input of a system (23) of an internal combustion engine (12) normally provided to a solenoid valve (22) for actuating a fan clutch (20). A pressure switch (24) is provided in the pressure line between the solenoid valve (22) and the fan clutch (20). The input is received by terminals (27, 28) and is passed on to a transistor (53) which turns on and allows current flow to the solenoid valve (22) during a first period of time. If a second transistor (48) turns on because the pressure switch (24) remains open as a set point is not sensed in the pressure line and does not discharge a time delay circuit formed by a combination of a resistor (44) and a capacitor (46), then the voltage of the gate of the first transistor (53) is pulled down to turn the transistor (53) off and interrupt the current flow to the solenoid valve (22). When the current flow to the solenoid valve (22) is interrupted, the solenoid valve (22) exhausts the fluid pressure, and actuation of the fan clutch (20) is interrupted.