Low flow cooling system and apparatus

A logic control system for an internal combustion engine having a cooling system including a combination of a heat exchanger and a bypass passage in parallel connection, an aftercooler serially connected to the combination and disposed immediately downstream thereof and pumping means for circulating a heat exchange medium through said cooling system, said logic control system comprising:

• temperature sensing means for sensing the temperature of the heat exchange medium at one or more locations in the cooling system;
• bypass logic control means for effecting control of the flow of heat exchange medium through said bypass passage whereby maximum flow through the bypass passage is effected when the temperature sensed by said temperature sensing means at a first predetermined location in the cooling system is equal to or below a first setpoint temperature, and whereby no flow through the bypass passage is effected when the temperature sensed by said temperature sensing means at the first location is equal to or greater than a second setpoint temperature greater than said first setpoint temperature;
• cooling logic control means for effecting control of the flow of heat exchange medium through the heat exchanger whereby no flow through the heat exchanger is effected when the temperature sensed by said temperature sensing means at a second predetermined location is equal to or below a third setpoint temperature, and whereby maximum flow through the heat exchanger is effected when the temperature sensed by said temperature sensing means at the second location is equal to or greater than a fourth setpoint temperature greater than said third setpoint temperature;
• and
• wherein said third setpoint temperature is independent of said first setpoint temperature and said fourth setpoint temperature is independent of said second setpoint temperature.

A dual valve thermostat for an internal combustion engine having a cooling system including a combination of a heat exchanger and a bypass passage in parallel connection and pumping means for circulating a heat exchange medium through said cooling system, said dual valve thermostat comprising:

• a housing defining upper and lower bypass control chambers and upper and lower cooling control chambers;
• a bypass control valve engaging said upper and lower bypass control chambers, said bypass control valve allowing maximum communication between said upper and lower bypass control chambers when the temperature of the heat exchange medium in said lower bypass chamber is less than a first setpoint temperature, and selectively allowing communication between said upper and lower bypass control chambers only when the temperature of the heat exchange fluid is less than a second setpoint temperature;
• and
• a cooling control valve engaging said upper and lower cooling control chambers, said cooling control valve selectively allowing communication between said upper and lower cooling control chambers only when the temperature of the heat exchange medium in said lower cooling control chamber is greater than a third setpoint temperature, and allowing maximum communication between said upper and lower cooling control chambers when the temperature of the heat exchanger medium in said lower cooling chamber is greater than a fourth setpoint temperature.