Climate Thermal Load Based Minimum Flow Rate Water Pump Control

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.

What is claimed is: 
     
         1 . A system for controlling a water pump in a vehicle comprising:
 an electric motor operating the water pump;   a controller generating a heater core flow request signal as a function of a climate thermal load and a heater coolant temperature; and   providing a signal to the motor to set the pump flow rate to satisfy the heater core flow request.   
     
     
         2 . The system of  claim 1  wherein the determining step includes selecting a pump 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. 
     
     
         3 . The system of  claim 1  wherein the climate thermal load value is based upon the cabin temperature set point, and ambient air temperature. 
     
     
         4 . The system of  claim 1  wherein the heater coolant temperature is obtained from a thermal sensor that senses the temperature of the coolant at an inlet to a heater core. 
     
     
         5 . The system of  claim 1  wherein the pump flow rate is selected to minimize power consumption by the electric motor and increase fuel economy. 
     
     
         6 . The system of  claim 1  wherein the controller determines whether a heating ventilation and air conditioning (HVAC) selector is set to a maximum defrost setting and wherein the pump flow rate is at a maximum value. 
     
     
         7 . The system of  claim 1  wherein the controller determines whether an HVAC selector is requesting cabin temperature change. 
     
     
         8 . The system of  claim 1  wherein the climate thermal load value is obtained from a vehicle bus. 
     
     
         9 . A method of controlling a water pump in a vehicle comprising:
 setting the water pump at maximum flow if a maximum defrost input is actuated;   if the maximum defrost input is not actuated, setting the water pump to no flow if the HVAC input is not actuated;   if the HVAC input is actuated, integrating a climate thermal load value and a heater coolant temperature value using a multiple variable table to select a heater core flow rate, and if the heater core flow rate is greater than a threshold value, providing a signal to an electric motor that controls the flow rate of the water pump.   
     
     
         10 . The method of  claim 9  wherein the threshold value is zero. 
     
     
         11 . The method of  claim 9  wherein the HVAC input includes a thermistor and a variable temperature selector switch for controlling the temperature of a passenger compartment. 
     
     
         12 . The method of  claim 9  wherein the integrating step includes 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. 
     
     
         13 . The method of  claim 9  wherein the climate thermal load value is based upon the cabin temperature set point, and ambient air temperature. 
     
     
         14 . The method of  claim 9  wherein the heater core flow rate is selected to minimize power consumption by the electric motor and increase fuel economy. 
     
     
         15 . A heating ventilation and air conditioning (HVAC) system for a vehicle having an electric motor driven water pump, the system comprising:
 a heater core;   an HVAC selector having a heat request setting, an air cooling request setting and a maximum defrost setting;   a climate module that provides a thermal load value;   a coolant temperature sensor that determines the temperature of a coolant;   a controller that provides a coolant flow request value to the water pump, wherein the coolant flow request is set to a maximum if the maximum defrost setting is actuated, wherein the coolant flow request is set at zero if the heat request setting is off, and a heater core flow rate is set based upon the thermal load value and coolant temperature value; and   wherein if the heater core flow rate is greater than zero, the heater core flow is mapped to the water pump speed.   
     
     
         16 . The system of  claim 15  wherein the controller selects 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. 
     
     
         17 . The system of  claim 15  wherein the heat request setting and the air cooling request setting is compared to a passenger compartment temperature signal for controlling the temperature of a passenger compartment. 
     
     
         18 . The system of  claim 15  wherein the controller integrates a table of values corresponding to a plurality of climate thermal load values and a plurality of heater coolant temperature values. 
     
     
         19 . The system of  claim 15  wherein the coolant temperature sensor is a cylinder head temperature sensor from which the temperature of the coolant is inferred. 
     
     
         20 . The system of  claim 15  wherein the thermal load value is based upon a cabin temperature sensor signal, a cabin temperature set point, an ambient temperature signal, and a sun load sensor signal.