Patent Publication Number: US-6712028-B1

Title: Engine cooling system with water pump recirculation bypass control

Description:
TECHNICAL FIELD 
     This invention relates to a cooling system for a liquid cooled internal combustion engine and more particularly to a system including a bypass for controlling coolant flow through the system. 
     BACKGROUND OF THE INVENTION 
     Commonly, a pressurized cooling system employs a circulating liquid coolant for cooling an internal combustion engine, including both gasoline and diesel fueled engines. Engine heat is transferred from the engine to the coolant through a coolant jacket surrounding certain parts of the engine. The heat absorbed by the circulated coolant is dissipated by a heat exchanger, generally by a radiator, into the air. 
     Under most normal operating conditions, an engine only requires nominal coolant flow to maintain proper temperature of internal components. However, under severe conditions, an engine requires increased coolant flow to maintain proper temperature of internal components. If a high flow rate water pump is used to provide a high coolant flow rate under severe conditions to prevent engine overheating, the amount of coolant flow will be excessive under normal operating conditions. Parasitic losses occur in a cooling system having excessive coolant flow through the engine. 
     SUMMARY OF THE INVENTION 
     The present invention minimizes parasitic losses in a cooling system by using a system bypass to reduce coolant flow through the coolant jacket of an engine. The system bypass allows coolant to bypass the engine and flow directly from the outlet of the water pump in to the inlet of the water pump, thereby forming a recirculating loop. A diverter valve in the system bypass can selectively increase or decrease coolant flow through engine coolant jacket without changing the output of the water pump. 
     A control module detects coolant temperature, fuel flow rate, air flow rate, and engine knock information. As these values change, the control module adjusts the diverter valve accordingly to maintain proper engine cooling. The control module actuates the diverter to recirculate a greater amount of coolant flow to the water pump, when the engine is operating below optimal temperature. As the engine reaches optimal operating temperature, a conventional thermostat directs engine coolant flow to a radiator to maintain a desired coolant temperature. The control module actuates the diverter to control coolant flow between the system bypass and the coolant jacket of the engine to maintain needed coolant flow. 
     Under severe conditions such as high speed driving, rapid acceleration, or towing, additional engine heat is produced. As a result of the additional heat production, the control module actuates the diverter valve to increase coolant flow to the coolant jacket to maintain optimal engine operating conditions. As conditions change where engine heat production is reduced, the control module actuates the diverter valve to divert additional coolant to the system bypass instead of the coolant jacket to increase cooling system efficiency and thereby reduce parasitic losses in the system. 
    
    
     These and other features and advantages of the invention will be more fully understood from the following description of certain specific embodiments of the invention taken together with the accompanying drawings. 
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The single drawing FIGURE is a diagrammatic view of an engine cooling system according to the present invention. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring to the single drawing FIGURE in detail, numeral  10  generally indicates a cooling system for an internal combustion engine. System  10  includes an engine  12  having a coolant jacket  14 . The coolant jacket  14  includes an inlet  16  and an outlet  18 . The inlet  16  is connected to receive coolant from an engine driven water pump  20  which operates at a rotational speed that varies with engine rpm. The outlet  18  is connected through a thermostat with a radiator or ambient air heat exchanger  24  for removing excess heat from the coolant heated in the engine. Coolant discharged from the radiator  24  is conducted back to the water pump to be recirculated through the system  10  for cooling the engine  12 . 
     To maintain a desired engine coolant temperature, the thermostat  22  regulates the amount of coolant flow to the radiator  24  by directing excess coolant flow back to the water pump  20  through a radiator bypass line  26  to avoid over cooling the engine. During engine warm-up, coolant flow through the radiator is completely cut off until a desired engine out coolant temperature is reached. 
     Because the water pump  20  is engine driven, it must be designed to provide adequate coolant flow at idle as well as at maximum engine loads over the engine speed range. As a result, the coolant flow at higher speeds and lower loads is generally greater than is needed to cool the engine  12 . Thus, a large amount of coolant is caused to bypass the radiator  24  in order to maintain the desired coolant temperature out of the engine  12 . The excess coolant flow in the system  10  and through the engine results in parasitic power losses that reduce system efficiency. 
     In accordance with the present invention, the system  10  includes a system bypass line  28  that connects the water pump outlet  30  directly to the water pump inlet  32 . A diverter valve  34  is connected to the system bypass line  28  between the water pump outlet  30  and the engine coolant jacket inlet  16  to selectively regulate the amount of coolant flow recirculated back to the water pump  20 . 
     The system bypass  28  allows the water pump  20  to operate at a reduced pressure differential by reducing the flow of coolant through the engine coolant jacket  14 , which has a higher flow resistance than the system bypass  28 . Thus, as the amount of coolant pumped through the coolant jacket  14  decreases, the energy required to drive the water pump decreases and efficiency of the cooling system increases. 
     A control module  48  detects coolant temperature, fuel flow rate, air flow rate, and engine knock information. The control module uses this information to adjust the position of the diverter valve  44  to provide adequate coolant flow to the coolant jacket  14  of the engine  12 . 
     In operation, engine coolant flows from the water pump  20  to the coolant jacket  14  of the engine  12 . The diverter valve  34  diverts some of the coolant through the system bypass line  28  to the inlet of the water pump. This reduces the flow of coolant through the engine coolant jacket  14  without reducing the speed of the water pump  20 . 
     The coolant not diverted into the system bypass  28  flows through the engine coolant jacket  14 . Coolant from the engine  12  is directed to the thermostat  22  which directs the coolant to the radiator  24  or through the radiator bypass  26  back to the water pump  20 . 
     Under start up and other low temperature conditions, the thermostat  26  stops coolant flow to the radiator  24 , causing the coolant to flow through the radiator bypass  26  to the water pump  20 . When the coolant reaches its optimal engine out temperature, the thermostat  26  opens, modulating coolant flow through the radiator  24  to maintain the desired temperature. 
     The control module  36  monitors coolant temperature, fuel flow rate, air flow rate, and engine knock information. Based upon these factors, the control module  36  determines the appropriate amount of coolant the engine needs to maintain optimal operation temperatures. As the engine develops more heat, the control module  36  actuates the diverter valve  34  to direct more coolant from the water pump  20  to the coolant jacket  14  to increase cooling of the engine  12 . As the engine  12  develops less heat, typically under low load conditions, the control module  36  actuates the diverter valve  34  to direct more coolant into the system bypass  46  to increase system efficiency. 
     While the invention has been described by reference to certain preferred embodiments, it should be understood that numerous changes could be made within the spirit and scope of the inventive concepts described. Accordingly, it is intended that the invention not be limited to the disclosed embodiments, but that it have the full scope permitted by the language of the following claims.