Abstract:
A charge air management system for an automotive engine provides air charge densification and cooling during periods of operation at higher load. Two air ducts are provided, with a first for furnishing uncooled and unboosted air, and with a second duct for furnishing chilled and boosted air, with the second duct being chilled during operation with air flowing through the first duct.

Description:
BACKGROUND OF INVENTION  
         [0001]    The present invention relates to a system for providing chilled and super-atmospheric air charge to an engine on a preferential basis.  
           [0002]    Engine designers have devised a potpourri of systems for increasing the density and decreasing the temperature of the air charge entering an internal combustion engine.  
           [0003]    For ordinary driving, it is desirable, on only a very infrequent basis, to operate the engine at its highest possible output. Thus, it is not desirable or necessary, from the standpoint of cost, fuel consumption, or weight, to have a system, which is capable of providing densified and chilled air to the engine on a continuous basis in a quantity sufficient to support the engine&#39;s maximum output.  
           [0004]    It is known to provide densifying and even chilling on a basis in which the densification and chilling will operate on a continued basis, but such systems, alluded to above, are hampered by excess cost, weight, and power consumption.  
           [0005]    A system according to the present invention overcomes the disadvantages of prior densification and chilling systems while providing excellent throttle response for infrequent accelerations by providing alternative pathways for air to enter the engine&#39;s air supply plenum. Thus, during normal operation, the air will enter into the unchilled passageway, allowing the chilling apparatus to be pulled down to a very low temperature so as to provide a transient but very high level of densification and charge cooling. Because the densification apparatus does not operate continuously, power consumption of the apparatus is low. Moreover, because chilling is not required to operate continuously, a very high level of chilling is available on an intermittent basis, which is consistent with usage of such system for normal driving.  
         SUMMARY OF INVENTION  
         [0006]    A charge air management system for an automotive engine includes an air intake plenum for furnishing air to the engine, a first duct for furnishing air to the intake plenum, and a second duct for furnishing air to the intake plenum. A charge booster increases the quantity of air entering the plenum from the second duct. An intercooler removes heat from air flowing through at least the second duct. Finally, a splitter valve controls the relative proportion of air flowing into the plenum from the first and second ducts.  
           [0007]    According to the present invention, a charge booster may comprise a supercharger or an exhaust driven turbocharger. If a supercharger is used, it may be driven by a clutched drive.  
           [0008]    According to another aspect of the present invention, the splitter valve is preferably operated such that the plenum is furnished with air flowing through the first duct at relatively lower loads and with air flowing through the second duct at relatively higher loads.  
           [0009]    The intercooler is preferably cooled with liquid coolant, which is chilled by an air-to-liquid heat exchanger exposed to ambient air. Liquid coolant may also be chilled by a liquid-to-liquid heat exchanger, which is exposed to a refrigerated fluid. Liquid coolant is chilled by the air-to-liquid heat exchanger only if the temperature of the liquid coolant leaving the inner cooler exceeds the ambient air temperature by an amount greater than a predetermined threshold. If the temperature of the liquid coolant leaving the intercooler is less than a predetermined threshold temperature, a heat exchanger bypass valve will be closed so as to allow the liquid coolant to circulate only through the liquid-to-liquid heat exchanger.  
           [0010]    The refrigerated fluid, which chills the liquid coolant in the liquid-to-liquid heat exchanger, comprises refrigerant fluid flowing in a vehicle air conditioning system. The air conditioning system is called upon to furnish the refrigerant fluid only if the demand placed upon the air conditioning system is less than a predetermined threshold. In other words, if the vehicle occupants demand a high level of air conditioning service, refrigerant fluid will not be allowed to flow to the liquid-to-liquid heat exchanger.  
           [0011]    As noted above, the flow of charge air through the first and second ducts is controlled by a splitter valve, which is itself controlled so as to send most of the air into the plenum through the second duct in the event that the throttle associated with the engine is opened at a rate exceeding a threshold opening rate. Similarly, the splitter valve is controlled so as to send most of the air into the plenum through the second duct in the event that the airflow through the engine exceeds a threshold airflow rate.  
           [0012]    According to another aspect of the present invention, a method for operating an automotive engine having a charge air management system for furnishing air to an air intake plenum associated with the engine includes the steps of providing air to the plenum through an uncooled duct during normal operation at lower power levels, providing coolant to a cooled duct during normal operation so as to chill the cooled duct when air is being provided to the plenum through the uncooled duct, and providing air to the plenum through the cooled duct during operation of the engine at higher power levels. 
       
    
    
     BRIEF DESCRIPTION OF DRAWINGS  
       [0013]    [0013]FIG. 1 is a schematic representation of an engine having a charge air management system according to the present invention.  
         [0014]    [0014]FIG. 2 is a schematic representation of the various control elements of the system according to the present invention. 
     
    
     DETAILED DESCRIPTION  
       [0015]    As shown in FIG. 1, engine  8 , having air intake plenum  10 , is furnished with intake air by means of first duct  12 , which is uncooled, and second duct  14 , which is cooled by means of intercooler  18 . Splitter valve  20  determines whether air flows into plenum  10  by means of first duct  12  or second duct  14 .  
         [0016]    Air flowing to plenum  10  through duct  14  is subject to densification by means of supercharger  16  and chilling by means of intercooler  18 . Those skilled in the art will appreciate in view of this disclosure that supercharger  16  could comprise either a mechanically driven supercharger, or an exhaust driven turbocharger, or other types of screw or vane compressors, or other types of devices known to those skilled in the art and suggested by this disclosure.  
         [0017]    In the normal course of events, air enters plenum  10  via first duct  12  without any additional densification or cooling. If, however, the vehicle driver demands high power output from the engine, the splitter valve will close and thereby allow air to enter plenum  10  primarily through second duct  14 .  
         [0018]    During operation wherein air is being allowed to enter plenum  10  only through first duct  12 , intercooler  18  will be pulled down to a lower temperature level by means of liquid coolant which circulates through coolant lines  15  from intercooler  18  through air-to-liquid heat exchanger  22 .  
         [0019]    If the ambient temperature within which the vehicle is being operated is sufficiently great, heat exchanger bypass control valve  26  will be closed so as to allow liquid coolant to circulate only through liquid-to-liquid heat exchanger  24  and not through air-to-liquid heat exchanger  22 .  
         [0020]    The rate of circulation of liquid coolant through lines  15  is determined by the operation of coolant pump  34 . Coolant pump  34  operates at a speed which is determined by controller  40  (FIG. 2) as a function of one or more engine operating parameters. For example, the speed of coolant pump  34  may be determined by controller  40  as a function of temperature of liquid coolant leaving intercooler  18  as determined by intercooler temperature sensor  30 . In this case, if the temperature of the liquid exceeds a predetermined threshold, pump  34  will be operated at a higher speed. Alternatively, pump  34  may be operated by controller  40  at a speed which is determined by controller  40  as a function of the intake vacuum or, in other words, the air pressure within plenum  10 . In this case, if air pressure within plenum  10  is at a higher level, indicating that throttle  28  is in an open position, pump  34  may be operated at a higher speed. Alternatively, the speed of pump  34  may be determined in the event that the throttle  28  is opened at very high rate, in which case pump  34  is preferably set at a higher rate of speed. Finally, valves  38  and  39 , which control the flow of refrigerant circulated by compressor  36  through condenser  37 , through liquid-to-liquid heat exchanger  24 , and through air conditioning evaporator  32 , will be set to bypass evaporator  32  if the present system is trimmed for maximum performance and if such is sought by the vehicle&#39;s driver. Alternatively, valves  38  and  39  may be controlled by controller  40  to bypass liquid-to-liquid heat exchanger  24  in the event that the present system is trimmed for maximum passenger comfort, and in the further event that maximum cooling is called for by the vehicle&#39;s passengers.  
         [0021]    The operation of splitter valve  12  is handled by controller  40 , with the position of valve  12  depending upon the value of one or more engine operating parameters. For example, splitter valve  12  may be opened based upon the rate of throttle opening of throttle  28 , or in the event that airflow through the engine is measured by a mass airflow meter, which is one of sensors  42  of FIG. 2, exceeds a threshold airflow rate. In the case of throttle opening control, if throttle  28  opens at a rate exceeding a predetermined threshold, splitter valve  12  will direct air through second duct  14 . Similarly, if engine airflow exceeds a predetermined threshold, this indicates that the driver is demanding higher power output, and second duct  14  will be chosen.  
         [0022]    In the event that controller  40  determines that engine load, as determined in conventional fashion through the manipulation of data from its various sensors  42 , exceeds its threshold, splitter valve  20  may be positioned so as to cause air to flow into plenum  10  primarily through second duct  14 .  
         [0023]    Finally, according to another aspect of the present invention, a present method for operating an automotive engine having a charge air management system for furnishing air to an air intake plenum associated with the engine operates as alluded to above by providing air to the engine&#39;s air intake plenum primarily through an uncooled duct during operation at lower power levels, and providing coolant to a second cooled duct during normal operation so as to chill the cooled duct when air is being provided to the plenum primarily through the uncooled duct. Air is provided to the plenum primarily through the cooled duct during operation of the engine at higher power levels. This cooling is combined as noted above with the use of a charge booster such as a supercharger or turbocharger, or other type of densification apparatus.  
         [0024]    While the invention has been shown and described in its preferred embodiments, it will be clear to those skilled in the art to which it pertains that many changes and modifications may be made thereto without departing from the spirit and scope of the invention.