Temperature control system for internal combustion engine

A temperature control system for an internal combustion engine having a radiator for cooling engine coolant, which flows around the engine jacket, and having first and second heat exchangers, in front of or within the radiator, for cooling first and second fluids, respectively, used in the engine, the coolant and the two fluids each having a different desired operating temperature range to achieve optimum engine performance, said temperature control system comprising:

• first temperature sensing means for sensing the coolant temperature and producing a first temperature signal having an amplitude which is directly proportional to and representative of the relative level of the sensed coolant temperature within the coolant's operating temperature range;
• second temperature sensing means for sensing the temperature of the first fluid and producing a second temperature signal having an amplitude which is directly proportional to and representative of the relative level of the sensed fluid temperature within the fluid's operating temperature range;
• third temperature sensing means for sensing the temperature of the second fluid and producing a third temperature signal having an amplitude which is directly proportional to and representaive of the relative level of the sensed fluid within the fluid's operating temperature range;
• a coolant flow control valve for controlling the amount of coolant diverted from the engine jacket and circulated through the radiator;
• controllable radiator shutters for adjusting the amount of ram air impinging on the radiator and the two heat exchangers;
• a variable speed fan drive for blowing a controlled amount of air through the radiator and the first and second heat exchangers;
• means coupled to said first temperature sensing means for controlling said coolant flow control valve in response to said first temperature signal in order to maintain the coolant temperature within the desired operating temperature range;
• means coupled to said first, second and third temperature sensing means for effectively selecting the particular one of the three temperature signals having the highest amplitude;
• and means responsive to the selected temperature signal, when the signal's amplitude is within a predetermined relatively low amplitude range, for controlling said radiator shutters to adjust the amount of ram air striking the radiator and the first and second heat exchangers, and responsive to the selected temperature signal, when the signal's amplitude is within a predetermined relatively high amplitude range, for controlling said variable speed fan drive to vary the amount of air pulled in through the radiator and the first and second heat exchangers.