Abstract:
A control system for minimizing the flow rate and energy consumption of a water pump in a vehicle. The control system and method correlate a climate thermal load value with the temperature of the coolant in a climate control cooling circuit. A correlation is performed by mapping the inputs to a desired pump flow rate that is determined to be necessary at a minimum to provide adequate cooling for the engine and for air conditioning or heating the vehicle.

Description:
TECHNICAL FIELD 
       [0001]    This disclosure relates to a system for controlling a water pump in a vehicle to minimize the flow rate and reduce power consumption. 
       BACKGROUND 
       [0002]    Conventional internal combustion engines have a water pump that is driven by an accessory belt. Water pump flow varies with engine speed and is calibrated to provide ample cooling at maximum power. Accessory belt drive systems add weight that reduces fuel economy. 
         [0003]    Current hybrid engines use water pumps that are driven by accessory belt drives on the battery charging internal combustion engine. An auxiliary water pump is required to heat the passenger compartment when the battery charging internal combustion engine is not operating. Auxiliary water pumps add weight to the vehicle that also reduces fuel economy. 
       SUMMARY 
       [0004]    This disclosure proposes a control system for a hybrid vehicle having a primary water pump that is driven by an electric motor. This disclosure may also relate to other types of vehicle drives that are driven by an electric motor instead of an accessory belt, such as an all-electric vehicle. The cooling system integrates a climate thermal load value that is provided by the vehicle bus and a heater coolant temperature value. Data from these values is mapped to generate a heater core flow request value that sets the pump flow rate. 
         [0005]    Accessory belt drives may be eliminated by providing air conditioning systems and power steering systems that are driven by electric motors. Further power savings are achieved by minimizing the water pump flow rate to a rate that is sufficient to meet climate thermal load requirements. As vehicles become more efficient, the effects of parasitic losses become more important. 
         [0006]    The climate thermal load value is a composite calculated value that is provided by the climate module on the vehicle electrical control system bus. The climate thermal load value may be based upon the temperature set point of the passenger compartment heating, ventilation and air conditioning (HVAC) control in the passenger compartment, the outside or ambient air temperature, the coolant temperature, and other factors such as sun load. 
         [0007]    According to one aspect of the disclosed system for controlling a water pump in a vehicle, an electric motor is provided that operates the water pump. A controller generates a heater core flow request signal as a function of a climate thermal load value and a heater coolant temperature value. The controller determines whether the heater core flow request is greater than zero and provides a signal to the motor to set the pump flow rate to satisfy the heater core flow request. 
         [0008]    According to other aspects of the system, the determining step may include selecting a pump flow rate based upon the table of values corresponding to a plurality of climate thermal load values and a plurality of heater coolant temperature values. The climate thermal load value is based, in part, upon the cabin set point and ambient air temperature. The heater coolant temperature may be obtained from a thermal sensor that senses the temperature of the coolant, for example, at an inlet to the heater core. Alternatively, the coolant temperature may be inferred from a cylinder head temperature sensor. The pump flow rate is selected to minimize power consumption by the electric motor and increase fuel economy. The controller determines whether a HVAC selector is set at a maximum defrost setting that causes the pump flow rate to be set at a maximum value. The controller also determines whether an HVAC selector is requesting cabin temperature modification. 
         [0009]    According to another aspect of this disclosure, a method is provided for controlling an electric water pump in a vehicle. The method includes the steps of determining whether a maximum defrost input is actuated and setting the water pump at maximum flow. Next, the HVAC input may be actuated if the maximum defrost input is not actuated and setting the water pump is set to “no flow” if the HVAC input is not actuated. If the HVAC input is actuated, a climate thermal load value and a heater coolant temperature value are obtained. The climate thermal load value and heater coolant temperature value are integrated in a multiple variable table to develop a heater core flow rate. The heater core flow rate is mapped to a pump speed if the heater core flow rate is greater than the threshold value. 
         [0010]    According to other aspects of the method, the threshold value for the heater core flow rate may be zero. The HVAC input includes a thermistor for sensing cabin temperature and a variable temperature selector switch for controlling the temperature of the passenger compartment. 
         [0011]    According to another aspect of the method, the integrating step may include selecting a heater core flow rate based upon a table of values corresponding to a plurality of climate thermal load values and a plurality of heater coolant temperature values. The climate thermal load value is based, in part, upon the cabin temperature set point and ambient air temperature. The heater core flow rate is selected to minimize power consumption by the electric motor and increase fuel economy. 
         [0012]    According to another aspect of the disclosure, a heating, ventilation and air conditioning system is provided for a vehicle having an electric motor driven water pump. The system comprises a heater core, an HVAC selector having a heat request seating, an air cooling request setting, a defrost setting, and a maximum defrost setting. The climate control module provides a thermal load value. A coolant temperature sensor measures the temperature of a coolant. A controller provides a coolant flow request value to the water pump. When the maximum defrost setting is actuated, the coolant flow request is set at maximum. When the heat request setting is off and the air cooling request setting is zero, the heater cool flow rate is set based upon the thermal load value and the coolant temperature value. If the heater core flow rate is greater than zero, the heater core flow is mapped to the water pump speed. 
         [0013]    According to another aspect of the HVAC system, the controller may select the coolant flow request based upon a table of values corresponding to a plurality of climate thermal load values and a plurality of coolant temperature values. The heat request setting and the air cooling request setting are compared to a passenger compartment thermistor signal for controlling the temperature of a passenger compartment. The controller integrates a table of values corresponding to a plurality of climate thermal load values and a plurality of heater coolant temperature values. 
         [0014]    These and other aspects of the present invention will be better understood in view of the attached drawings and the following detailed description of the illustrated embodiments. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0015]      FIG. 1  is a diagrammatic view of a cooling circuit for a vehicle; 
           [0016]      FIG. 2  is a flowchart illustrating the steps of the method and operation of a water pump control system; and 
           [0017]      FIG. 3  is a table for integrating the plurality of thermal load values with a plurality of engine coolant temperature values to select a minimum heater core flow request. 
       
    
    
     DETAILED DESCRIPTION 
       [0018]    Detailed descriptions of the illustrated embodiments of the present invention are provided below. The disclosed embodiments are examples of the invention that may be embodied in various and alternative forms. The figures are not necessarily to scale. Some features may be exaggerated or minimized to show details of particular components. The specific structural and functional details disclosed in this application are not to be interpreted as limiting, but merely as a representative basis for teaching one skilled in the art how to practice the invention. 
         [0019]    Referring to  FIG. 1 , a combustion engine  10  is shown with a water pump  12  that is driven by an electric motor  14 . The engine  10  may be a battery charging engine for a hybrid electric vehicle. The engine  10  and water pump  12  are part of a radiator cooling circuit generally indicated by reference numeral  16  that circulates water and antifreeze through a radiator  18  to cool the engine  10 . Prior to reaching a predetermined temperature, the water may flow through a bypass  20  to a thermostat  22 . Upon reaching the predetermined temperature, the coolant is directed to the radiator  18 . Gas is separated from the coolant in a de-gas reservoir  24 . The fluid recirculates through the radiator coolant return  26  from either the radiator  18  or the de-gas reservoir  24  and returns it to the thermostat  22 . 
         [0020]    The engine  10  and water pump  12  are also connected to a climate control circuit generally indicated by reference numeral  28  that provides the coolant to an exhaust heat recovery/coolant preheat apparatus  30  and a heater core  32 . The exhaust heat recovery/coolant preheat apparatus  30  may circulate coolant around exhaust system components to recover heat from the exhaust system. The heater core  32  provides warm air for heating a passenger compartment  33  through air ducts represented by the dashed line in  FIG. 1 . A heater core inlet coolant temperature sensor  34  senses the temperature of the coolant in the climate control cooling circuit  28 . The coolant in the climate control cooling circuit  28  returns the coolant to the thermostat  22  in a closed loop. 
         [0021]    Referring to  FIG. 2 , a control system and method are shown as a flowchart. The control system and method start at  42 . In a first step, at  44 , the system determines whether a maximum defrost request has been selected by a vehicle occupant at a selector control panel  43 . If the user has requested a maximum defrost request, the coolant flow for maximum defrost is requested at  46 . If the maximum defrost request is not selected at  44 , the system looks for a climate modification request at  48 . The climate modification request is made by a vehicle occupant operating an HVAC selector control panel  43  having selector switches that may be provided in many forms. The selector switch may be a digital temperature selection, a knob on a potentiometer, or the like. If a climate modification request is not made by a vehicle occupant, no coolant flow is requested at  50 . 
         [0022]    If there is a climate modification request, at  48 , the coolant system controller  49  reads the thermal load value from the climate module at  52 . The thermal load value is obtained from an electrical bus  53  in the vehicle. The thermal load value is a composite value based upon the selector control panel  43 , thermistor input  45  and ambient air temperature sensor  55 . Other inputs to the thermal load value may be a sun sensor  57 , a temperature setting, or other inputs. The heater coolant temperature is obtained, for example, from a thermal sensor  34  (shown in  FIG. 1 ) that senses the temperature of the coolant at an inlet to the heater core  32 , or may sense the temperature of the cylinder head temperature (CHT) from which the coolant temperature may be inferred. The coolant temperature may also be sensed at other locations in the climate control cooling circuit  28  (shown in  FIG. 1 ). The controller  49  also reads the engine coolant temperature (ECT), at  54 . The ECT is obtained from the heater core inlet coolant temperature sensor  34  (shown in  FIG. 1 ). The ECT may be inferred from another sensor, such as the CHT. 
         [0023]    The heater core flow request is determined as a function of the thermal load value and the engine coolant temperature. A heater core flow request is generated by the controller  49  at  56 . At  58 , the heater core flow request is compared to zero to determine if the flow is greater than zero. If the flow is not greater than zero, the system returns to start. However, if the flow is greater than zero, a signal is provided in the controller  49  to map the heater core flow to a pump flow value at  60 . 
         [0024]    Referring to  FIG. 3 , a multi-variable map, or “look-up table”, is shown in which the ECT is mapped against the thermal load value. Depending upon the thermal load and engine coolant temperature, one of 16 flow rates may be selected that is provided to the electric motor  14  (shown in  FIG. 1 ) to control the flow rate of the water pump  12  (shown in  FIG. 1 ). 
         [0025]    While exemplary embodiments are described above, it is not intended that these embodiments describe all possible forms of the invention. Rather, the words used in the specification are words of description rather than limitation, and it is understood that various changes may be made without departing from the spirit and scope of the invention. Additionally, the features of various implementing embodiments may be combined to form further embodiments of the invention.