Image Number 4 for United States Patent #5979373.
A cooling control system by which an internal combustion engine is prevented from overheating, and a fail-safe function exerts its effect. A butterfly valve 34b for regulating the flow of cooling water is rotated by a motor 31, a clutch mechanism 32, and a speed reduction mechanism 33, thereby cooling the engine to be at the most suitable temperature for driving. The aforesaid butterfly valve 34b is given momentum in a direction to open the valve 34b by a return spring 34e. For example, an angle sensor 34g for detecting the rotational angle of the butterfly valve 34b is included. In a computing unit, when it is determined that an abnormality occurs from the relationship between the data from an encode 34g and the temperature of the cooling water, the clutch mechanism 32 is released, and the butterfly valve 34b is automatically opened. Accordingly the engine is prevented form overheating.