Dual coolant engine cooling system

A temperature control apparatus for an air breathing internal combustion engine having a cylinder block, a recirculating lubrication oil circuit containing lubrication oil, a compressor for pressurizing engine intake air, and an aftercooler for modifying the temperature of the pressurized intake air as it passes into the engine, said temperature control apparatus comprising:

• (a) first fluid circuit means for passing the lubrication oil in heat exchange relationship with one or more engine cylinders to provide the primary coolant for the engine cylinders, said first circuit means including first control means for maintaining the temperature of the lubrication oil at a first level which is relatively constant for substantially all engine operating conditions, wherein said first control means includes a heat exchanger means for linking said first and second fluid circuit means in heat exchange relationship and oil by-pass means for controlling the flow of lubrication oil around said heat exchanger means for causing heat to flow only from the lubrication oil into the secondary coolant as necessary to maintain a desired temperature;
• and
• (b) second fluid circuit means for passing secondary coolant distinct from the lubrication oil through the aftercooler in heat exchange relationship with the pressurized intake air, said second circuit means including second control means for controlling the temperature of the pressurized intake air supplied to the engine by modulating the temperature of the secondary coolant supplied to the aftercooler in proportion to engine output torque to cause the intake air to be at its lowest temperature at maximum engine output torque and to be at its highest temperature at minimum engine output torque, said second control means includes a radiator means for transferring heat out of the secondary coolant into the ambient environment and secondary coolant by-pass means for controlling the flow of secondary coolant around said radiator means to achieve the desired temperature modulation of the secondary coolant supplied to the aftercooler, said secondary coolant by-pass means includes a secondary coolant flow control valve operated in response to engine output torque to control the flow of secondary coolant around said radiator means and pressure means for sensing the intake air pressure and for controlling said secondary coolant flow control valve in accordance with a predetermined response curve which relates sensed pressure to engine torque in a manner to cause said flow control valve to adjust the temperature of the secondary coolant supplied to the aftercooler to cause the intake air to be at its lowest temperature at maximum engine output torque and to be at its highest temperature at minimum engine output torque.

A temperature control apparatus for an air breathing internal combustion engine having a cylinder block, a compressor for pressurizing engine intake air, and an aftercooler for modifying the temperature of the pressurized intake air as it passes into the engine, said temperature control apparatus comprising:

• (a) first fluid circuit means for passing first coolant in heat exchange relationship with one or more engine cylinders to provide the primary coolant for the engine cylinders, said first circuit means including first control means for maintaining the temperature of the first coolant at a first level which is relatively constant for substantially all engine operating conditions;
• and
• (b) second fluid circuit means for passing secondary coolant distinct from the first coolant through the aftercooler in heat exchange relationship with the pressurized intake air, said second circuit means including second control means responsive to a control signal for controlling the temperature of the pressurized intake air supplied to the engine by modulating the temperature of the secondary coolant supplied to the aftercooler in proportion to engine output torque, said second control means including signal generating means for producing said control signal in response to an operating condition of the engine indicative of engine output torque to cause the intake air to be cooled by the aftercooler to its lowest temperature at maximum engine output torque and to be heated by the aftercooler to its highest temperature at minimum engine output torque.