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.

Description

TECHNICAL FIELD

This disclosure relates to a system for controlling a water pump in a vehicle to minimize the flow rate and reduce power consumption.

BACKGROUND

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.

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

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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

FIG. 1 is a diagrammatic view of a cooling circuit for a vehicle;

FIG. 2 is a flowchart illustrating the steps of the method and operation of a water pump control system; and

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

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.

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.

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.

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.

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.

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.

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).

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.

Claims

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.