Abstract:
A method of powertrain thermal control in a vehicle having grille airflow shutters. The method comprises the steps of: detecting vehicle operating conditions including at least a temperature condition for an engine cooling loop and engine load; pumping engine coolant through the engine cooling loop including pumping the engine coolant through a radiator under all temperature conditions of the engine cooling loop; and adjusting the grille airflow shutters relative to a grille to selectively block a portion, none or all airflow through the grille to thereby control airflow through the radiator based upon the detected vehicle operating conditions.

Description:
BACKGROUND OF INVENTION 
       [0001]    The present invention relates generally to front grilles on vehicles and more particularly to front grilles where the airflow through the grilles can be selectively blocked. 
         [0002]    Grille airflow shutters have traditionally been used for the purpose of assuring that the airflow through the grille is reduced to an amount that minimizes the aerodynamic drag coefficient penalty for the vehicle. This is accomplished by managing airflow to the minimum required to meet air conditioning, powertrain cooling and under-hood thermal requirements. Adding this system to a vehicle, though, adds to the vehicle cost without removing other costs to the vehicle, so a cost penalty is incurred to improve the vehicle fuel economy, making grille airflow shutters less desirable to include on some vehicles. 
       SUMMARY OF INVENTION 
       [0003]    An embodiment contemplates a method of powertrain thermal control in a vehicle having grille airflow shutters, the method comprising the steps of: detecting vehicle operating conditions including at least a temperature condition for an engine cooling loop and engine load; pumping engine coolant through the engine cooling loop including pumping the engine coolant through a radiator under all temperature conditions of the engine cooling loop; and adjusting the grille airflow shutters relative to a grille to selectively block a portion, none or all airflow through the grille to thereby control airflow through the radiator based upon the detected vehicle operating conditions. 
         [0004]    An embodiment contemplates a method of powertrain thermal control in a vehicle having upper grille airflow shutters and lower grille airflow shutters, the method comprising the steps of: detecting vehicle operating conditions including at least a temperature condition for an engine cooling loop and engine load; pumping engine coolant through the engine cooling loop including pumping the engine coolant through a radiator under all temperature conditions of the engine cooling loop; and adjusting the lower grille airflow shutters relative to a lower grille to selectively block a portion, none or all airflow through the lower grille to thereby control airflow through the radiator based upon the detected vehicle operating conditions; detecting if an air conditioning system is operating; if the air conditioning system is operating, actuating the upper grille airflow shutters to allow most or all airflow through an upper grille; and if the air conditioning system is not operating, actuating the upper grille airflow shutters to block most or all airflow through the upper grille. 
         [0005]    An advantage of an embodiment is that the grille airflow shutters can be employed not only to improve the vehicle fuel economy but also allow for the elimination of a thermostat valve in the engine cooling loop and a bypass valve in the transmission cooling loop thus reducing costs. The elimination of these devices also reduces the complexity of those cooling loops. Moreover, the shutters can be controlled to respond quickly to changes in vehicle operating conditions. The grille airflow shutters allow for transmission warming under light load, moderate ambient temperature conditions, while also allowing for adequate cooling under maximum load, high ambient temperature conditions. A second set of grille airflow shutters may be employed to improve the control of airflow through the grilles based on use or non-use of a vehicle air conditioning system. 
     
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         [0006]      FIG. 1  is a schematic view of a portion of a vehicle having grille airflow shutters. 
           [0007]      FIG. 2  is a flow chart showing a method of using grille airflow shutters for powertrain thermal control. 
       
    
    
     DETAILED DESCRIPTION 
       [0008]    Referring to  FIG. 1 , a vehicle, indicated generally at  20 , is shown. The vehicle  20  includes a front end  22  with a lower grill  24  and an upper grille  26  proximate the front end  22 . Alternatively, the vehicle  20  may have only one grille, depending upon the particular styling of the vehicle. The lower grille  24  has openings  28  that allow airflow through, and the upper grille  26  also has openings  30  that allow airflow through. 
         [0009]    Lower grille airflow shutters  32  are mounted adjacent to the lower grille  24  and include openings  34  sized and spaced to align with the openings  28  in the lower grille  24  to allow for maximum airflow in a first position of the lower shutters  32  and blocking members  36  that are sized and spaced to align with the openings  28  and block all or almost all of the airflow through the lower shutters  32  in a second position of the lower shutters  32 . The movement of the lower shutters  32  between the first and second positions allow for partial blockage of the airflow. A lower actuator  38  is connected to a lower motor  40  via a lower gear box  42 . The actuation of the lower motor  40  causes the lower actuator  38  to move the lower grille airflow shutters  32  relative to the lower grill  24  to precisely control the airflow blockage through the lower grill  24 . 
         [0010]    Upper grille airflow shutters  44  are mounted adjacent to the upper grille  26  and include openings  46  sized and spaced to align with the openings  30  in the upper grille  26  to allow for maximum airflow in a first position of the upper shutters  44  and blocking members  48  that are sized and spaced to align with the openings  30  and block all or almost all of the airflow through the upper shutters  44  in a second position of the upper shutters  44 . The movement of the upper shutters  44  between the first and second positions allow for partial blockage of the airflow. An upper actuator  50  is connected to an upper motor  52  via an upper gear box  54 . The actuation of the upper motor  52  causes the upper actuator  50  to move the upper grille airflow shutters  44  relative to the upper grill  26  to precisely control the airflow blockage through the upper grill  26 . 
         [0011]    In  FIG. 1 , the shutters  32 ,  44  are not shown directly behind the grilles  24 ,  26 , respectively, for clarity in showing the shutters  32 ,  44 . Also, while the shutters shown as move up and down linearly to selectively allow and block airflow, other types of shutter mechanisms may be employed instead if so desired. For example, the shutters may be configured to pivot or rotate relative to openings in the grilles. The shutters employed just need to be movable so that precise control of blockage of grille openings can be achieved in order to control airflow. 
         [0012]    A condenser, radiator, fan module (CRFM)  56  is located behind the lower and upper grilles  24 ,  26  in order to receive airflow coming through the grille openings  28 ,  30 . The CRFM  56  may include a radiator  58 , another heat exchanger  60 , a condenser  62  and an engine fan  64 . The condenser  62  connects to and is part of an air conditioning system  66 . The engine fan  64  may be driven by a fan motor  68 . The other heat exchanger  60  may be, for example, a transmission oil cooler, a charge air cooler for a turbocharger/supercharger system or a powertrain electronics heat exchanger, In the particular example shown in  FIG. 1 , the heat exchanger shown is the transmission oil cooler. 
         [0013]    The transmission oil cooler  60  is part of a transmission cooling loop  70  that includes transmission oil lines  72  that direct transmission oil between the transmission oil cooler  60  and a transmission  74 . The term “transmission cooling loop” as used herein does not include a transmission oil cooler bypass or valve for bypassing the transmission oil cooler as the transmission oil flows through the transmission cooling loop. 
         [0014]    The radiator  58  is part of an engine cooling loop  76  that includes engine coolant lines  78  that direct engine coolant between the radiator  58  and an engine  80 . An engine coolant pump  82  pumps the engine coolant through the engine cooling loop  76 . The pump  82  may be, for example, a pump with an electromagnetic clutch that is pulse controlled. This allows for significant control over the rate of engine coolant flow through the engine cooling loop. The term “engine cooling loop” as used herein does not include a thermostat valve for selectively bypassing the radiator as the engine coolant flows through the engine cooling loop. 
         [0015]    An engine control module  84  interacts with and controls the lower motor  40 , upper motor  52 , fan motor  68 , transmission  74 , and engine  80 . The engine control module  84  may be made up of a single controller or multiple interacting controllers, and may be any combination of hardware and software as is known to those skilled in the art. The engine control module  84  may also be in communication with other vehicle sensors, which may include, for example, a transmission oil temperature sensor  86 , an engine coolant temperature sensor  88 , an ambient air temperature sensor  90  and a vehicle speed sensor  92 . The location and operation of these sensors are known to those skilled in the art and so will not be discussed herein. Other sensors and inputs to the engine control module  84  may be employed to determine the control of the shutters  32 ,  44  as well, if so desired. 
         [0016]      FIG. 2  illustrates a method of powertrain thermal control in the vehicle of  FIG. 1 . Vehicle operating conditions are detected, block  100 . The operating conditions that may be monitored to determine the actuation of the grille airflow shutters  32 ,  44  may include a temperature reading from the engine cooling loop  76 , the engine load, a temperature reading from the transmission cooling loop  70 , the vehicle speed, ambient air temperature, operation of the air conditioning system. The engine load may be determined based on, for example, a throttle position, engine vacuum, or other conventional means of determining an engine load. Also, other operating conditions may be monitored and used to determine the actuation of the grille airflow shutters  32 ,  44 , if so desired. 
         [0017]    The engine coolant is pumped through the engine cooling loop  76 , including pumping the engine coolant through the radiator  58 , block  102 . With a thermostat valve not present in the engine cooling loop  76 , the engine coolant does not bypass the radiator  58  as it flows through the engine cooling loop  76 . The rate of coolant flow through the system may be controlled by employing an engine coolant pump  82  that allows for variable flow, thus further improving the control over the engine cooling. 
         [0018]    One or both of the grille airflow shutters  32 ,  44  are adjusted to selectively block a portion, none or all of the airflow through the grilles  24 , 26 , block  104 . The adjustment is based upon the vehicle operating conditions that were detected. The engine control module  84  receives the inputs from the various vehicle systems and determines the amount of desired airflow through the grilles  24 ,  26 . The control module  84  then actuates the motors  40 ,  52  to cause the airflow shutters  32 ,  44  to move relative to the grilles  24 ,  26 . The amount of overlap between the grille openings  34 ,  46  and their respective blocking members  36 ,  48  determines the amount of airflow that is blocked. 
         [0019]    If the vehicle  20  is equipped with an air conditioning system  66  and has both the lower grille  24  and the upper grille  26 , then the control of the upper grille airflow shutters  44  may be based primarily on whether the air conditioning system is operating or not. 
         [0020]    As an example of the operation of this system, the vehicle  20  may be started in cool ambient temperature conditions where the engine coolant and the transmission fluid are both below their respective desired operating temperature ranges and the engine is operating under light load, such as when it is idling. Under this operating condition, the engine control module  84  may actuate the motors  40 ,  52  to move the grille airflow shutters  32 ,  44  so that all or almost all of the airflow is blocked from flowing through the grilles  24 , 26 . Thus, both the engine coolant and the transmission fluid will warm faster to reach their desired operating temperatures without the need for a thermostat for radiator bypass or a bypass valve for the transmission oil cooler  60 . 
         [0021]    Under heavy load when the engine coolant and transmission fluid are within their desired temperature ranges, one or both of the grille airflow shutters  32 ,  44  may be adjusted to allow for a high rate of airflow through the grilles  24 ,  26 . The engine fan  64  speed may also be controlled to coordinate with the adjustments of the grille airflow shutters  32 ,  44  to allow for greater precision and a wider range of airflow through the CRFM  56 . 
         [0022]    While certain embodiments of the present invention have been described in detail, those familiar with the art to which this invention relates will recognize various alternative designs and embodiments for practicing the invention as defined by the following claims.