US20080034767A1

US20080034767A1 - Methods of Optimizing Vehicular Air Conditioning Control Systems

Info

Publication number: US20080034767A1
Application number: US11/464,216
Authority: US
Inventors: Lawrence P. Ziehr; Peter A. Donis; Gregory A. Major; Mark D. Nemesh
Original assignee: GM Global Technology Operations LLC
Current assignee: GM Global Technology Operations LLC
Priority date: 2006-08-14
Filing date: 2006-08-14
Publication date: 2008-02-14
Also published as: KR20080015361A; DE102007037626A1; KR100881885B1

Abstract

Air conditioning system controls are optimized for an air conditioning system having a compressor in IC engine vehicles and in hybrid or fuel cell vehicles having electric drive motors by first determining the operating temperature of at least one of the following vehicle components: engine coolant and transmission oil for all types of vehicles, and for hybrid or fuel cell vehicles also determining the operating temperature of inverter coolant and the electric drive motors. At least one operating temperature is then compared to lower and upper temperature limits. If the operating temperature is outside of the temperature limits air conditioner heat load is reduced by at least one of the following steps: increasing cabin air recirculation, reducing cabin blower speed and reducing air conditioner compressor capacity. Subsequent to reducing air conditioner heat load, selected operating temperature or temperatures are monitored to determine if the operating temperature exceeds the upper temperature limit or limits. If the operating temperature or temperatures exceed the upper limit or limits the compressor is shut off.

Description

FIELD OF THE INVENTION

The present invention is directed to methods of optimizing vehicular air conditioning control systems. More particularly, the present invention is directed to such methods which result in reduced propulsion cooling system size in non-hybrid vehicles and lower operating temperature for coolant loops in hybrid and fuel cell vehicles.

BACKGROUND OF THE INVENTION

Conventional vehicle propulsion cooling systems include heat exchangers and fans, the size of which is based on propulsion system losses. Losses are absorbed by engine coolant, engine oil and transmission oil. Those losses typically are momentarily exacerbated when the vehicle operates on a steep gradient and/or is towing a trailer, especially when the ambient air temperature is high. With respect to hybrid and fuel cell vehicles, propulsion cooling loops require lower operating temperatures than conventional power train vehicles.
Air conditioning condensers are typically the first heat exchangers in the CRFM (Condenser Radiator Fan Module) air stream. Propulsion cooling system heat exchangers typically include engine radiators and transmission oil coolers. Hybrid and fuel cell vehicles also include inverter radiators and electric motor radiators. These heat exchangers are typically disposed downstream of the A/C (Air Conditioning) condenser, and are therefore affected by A/C condenser heat load.
In current production vehicles having power train controls, when propulsion cooling systems approach maximum temperature limits, A/C system control is typically limited to A/C compressor interrupt. A/C compressor interrupt results in a complete loss of cabin cooling because the A/C system simply shuts off when propulsion system thermal limits are reached.

SUMMARY OF THE INVENTION

In view of the aforementioned considerations, the present invention optimizes air conditioning systems for vehicles by momentarily reducing A/C condenser heat load during transient, high ambient temperature/high propulsion system load events, thereby allowing an overall reduction in propulsion cooling system size.
Reducing the required propulsion cooling system size includes at least one of the following possibilities:
1) reducing radiator cooling size, e.g., by core thickness reduction, fin density reduction, and/or core face area reduction;
2) reducing electric cooling fan size, e.g., by reduced fan motor power;
3) for hybrid and fuel cell vehicles the possibilities also include:

- 3a) reducing power electronics radiator size, e.g., by core thickness reduction, fin density reduction, and/or by reducing core face area reduction, and/or
- 3b) reducing electric motor cooler size, e.g., by reduced core thickness, fin density reduction, and/or core face area reduction.

In another aspect, there is a reduction of mass and cost of propulsion cooling systems for the following vehicles: hybrid vehicles that have either an electric A/C compressor or an external capacity control A/C compressor; fuel cell vehicles that have either an electric A/C compressor or an external capacity control A/C compressor; and conventional power train vehicles that have an external capacity control A/C compressor; as well as conventional power train vehicles that have a fixed displacement A/C compressor.
In a further aspect, the realization of cabin air conditioning is maintained during propulsion system thermal excursions and improved fuel economy is realized due to, for example, reduced CRFM (Condenser Radiator Fan Module) electric fan power and CRFM mass.

BRIEF DESCRIPTION OF THE DRAWINGS

Various other features and attendant advantages of the present invention will be more fully appreciated as the same becomes better understood when considered in conjunction with the accompanying drawings, in which like reference characters designate the same or similar parts throughout the several views, and wherein:

FIG. 1 is a perspective view of a controller according to the invention in combination with an automotive vehicle, wherein in the illustrated example the vehicle is a hybrid vehicle;

FIG. 2 is a flow chart outlining operation of the controller of FIG. 1;

FIG. 3 is a diagrammatical illustration of the controller used with a strong-hybrid arrangement;

FIG. 4 is a diagram illustrating results for a specific simulation in a hybrid or non-hybrid vehicle;

FIG. 5 is a graph of theoretical eThermal simulation results for an A/C system optimization of a propulsion cooling system of reduced size in a non-hybrid vehicle;

FIG. 6 is a graph of eThermal simulation results for a model of an A/C system optimization in a propulsion cooling system of reduced size used in a non-hybrid vehicle;

FIG. 7 is a tabulation of results for examples of amounts of condenser heat load reduction showing positive impacts to the vehicles, and

FIG. 8 is a graph of eThermal simulation results for an A/C system optimization of reduced propulsion cooling system size in a non-hybrid example.

DETAILED DESCRIPTION

Referring now to FIG. 1, a controller 10 in a hybrid vehicle 11 selectively connects an IC engine 13 or an electric traction motor 14 to the drive wheels 15 of the hybrid vehicle. The controller 10 is mounted at any convenient location in the vehicle 11, but typically is mounted in an engine compartment 16. Controllers such as cabin temperature controllers and controllers for HVAC systems including a compressor 17 and a condenser 18 are preferably installed in the cabin, for example, within the instrument panel, or under the seats, or maybe installed in the trunk.
FIG. 2 is a flow chart outlining the step-by-step operation of a controller 10 according to the invention. In the “initial step,” the controller 10 checks a first truth table 21 to determine if any of the following conditions are true:

- 1) whether the operating temperature of the engine coolant is higher than a temperature limit T1A and lower than a temperature limit T2A, or
- 2) whether the operating temperature of the transmission oil is higher than a temperature limit T1B and lower than a temperature limit T2B, or
- 3) whether the operating temperature of the inverter coolant is higher than a temperature limit T1C and lower than a temperature limit T2C, or
- 4) whether the operating temperature of the electric motor is higher than a temperature limit T1D and lower than a temperature limit T2D.

Information on various other parameters applicable to a given system may also be checked by the controller in its decision making process. The temperature limits T1A, T2A, T1B, T2B, T1C, T2C, T1D and T2D, are predetermined based on design choices for a given vehicle 12. Temperature limits T1C, T2C, T1D and T2D apply only to hybrid and fuel cell vehicles.
If the answer to all of the parameters checked in the initial step by the truth table 21 is “YES,” then the A/C system operation is within normal ranges and the controller 10 periodically repeats the same initial step of checking the parameters.
If the answer to any of the parameters in the initial step 21 is “NO,” then the controller 10 responds in step 22 by:
1) increasing cabin recirculation of air by X %,
2) reducing cabin blower speed by Y %, and/or
3) reducing compressor capacity by Z %.
These adjustments achieve a reduction of A/C condenser heat load. Preferably, all three, i.e., increasing cabin recirculation of air by X %, reducing cabin blower speed Y %, and reducing compressor capacity Z % are performed to achieve optimization according to the invention. Alternatively, any one or more, or preferably two of the three procedures in step 22 are performed. The percent values for X, Y, Z are predetermined based on design choices for a given vehicle 12. Alternatively, the X, Y, Z values are based on a calculation in the controller 10 based on various data, such as vehicle operating parameters/conditions.
Following the above steps 21 and 22 which achieve a reduction of A/C condenser heat load, the controller 10 checks a second truth table 23 to determine whether any of the following conditions are true:
1) the operating temperature of the engine coolant is higher than the high temperature limit T2A, or
2) the operating temperature of the transmission oil is higher than the high temperature limit T2B, or
3) the operating temperature of the inverter coolant is higher than the high temperature limit T2C, or
4) the operating temperature of the electric motor is higher than the high temperature limit T2D.
The controller 10 may also check information on various other parameters not in the illustrated truth table 23 applicable to a given system. The values the high temperature limits T2A-T2D can be the same as the temperature limits in pre-corresponding order listed in the initial step 21 of the controller 10, or alternatively the values can be different. For example, the temperature values of the first predetermined values T2A-T2D, other than the values in the first step 21, can be a function of the temperature values of the first step.
If the answer to any of the parameters is “YES in the second truth table 23, the A/C compressor is shut off and a Flag AA is set in step 24. Then the controller 10 repeats checking the parameters discussed above. If the answer to all of the parameters that have been checked is “NO,” then the controller 10 checks as to whether Flag AA in an A/C restart mode.
If the Flag AA is present, the A/C system is restarted by the A/C restart step 24 to perform cabin recirculation at limited cabin blower speed and reduced compressor capacity. Preferably, all three, i.e., cabin recirculation plus limited cabin blower speed and reduced compressor capacity are performed to achieve optimization according to the invention. Alternatively, any one or more preferably two of the three may be performed. The cabin recirculation, limited cabin blower speed and reduced compressor capacity is limited and/or reduced by predetermined amounts, or alternatively are a function of full capacity values, e.g., a percentage of the same or are based on various changing vehicle performance parameters/conditions, for example, a calculation based on data provided to the controller 10. Following the check of the Flag AA 25, the controller 10 rechecks the truth table 21.
FIG. 3 depicts a hybrid air conditioning system, in which an air stream 30 enters the system from the front end of the vehicle 12 and passes through an A/C condenser 31. Downstream of the A/C condenser 31, the air stream 30 passes through a transmission oil cooler 32 and a power electronics heat exchanger 33. Transmission oil 35 circulates between the transmission oil cooler 32 and transmission 36. Fluid 39 circulates from the power electronics heat exchanger 33 to a power train power electronics and/or electric traction motor 40 followed by vehicle power electronics 41. Further downstream, the air stream 30 passes through an engine radiator 43 positioned in front of an electric fan package 44, which engine radiator cools coolant fluid from the IC engine 13 of FIG. 1.
FIG. 4 illustrates a hybrid simulation in which the air conditioning load is decreased according to the previously discussed arrangement illustrated in FIG. 2. In FIG. 4, there is heat rejection in front of the engine radiator 43 due to the conditioned air 30 passing through both the auxiliary transmission oil cooler 32 and the AC condenser 31. When the load on the AC condenser 31 is reduced using the method of FIG. 2, there is a reduction of less than 10% in the air available to cool coolant in the engine radiator 43 due to heat rejection by both the AC condenser 31 and the auxiliary transmission oil cooler 32. This results in approximately 10% reduction in the temperature of the coolant from the internal combustion engine 13 (FIG. 1) to the engine radiator 43, which reduces power train cooling content, i.e., the mass, dimensions and thus cost of the heat exchanger (the engine radiator 43) and the cooling fan package 44 (FIG. 2). This feature is available for both hybrid and non-hybrid vehicles as well as fuel cell vehicles in which the internal combustion engine 13 is replaced by a fuel cell.
FIG. 5 is a graph of results using data for an A/C system optimization for a propulsion cooling system of reduced size in a non-hybrid vehicle. Conditioned air results in KW and Temperature T (C) are graphed as a function of time and include condenser outside air (OSA) 51 introduced into the cabin; condenser recirculated air 52; condenser air out temperature 53; conditioner recirculated air out temperature 54 and engine rpm/100 55. As is seen in FIG. 5, by using the method of FIG. 2, there is an approximately 50% reduction in conditioner heat load 51 from heat load of the cabin OSA 51 compared with the heat load of cabin recirculation air 52. There is also about a 10% reduction in conditioner air out temperature 54 when using the method of FIG. 2.
FIG. 6 is a graph similar to FIG. 5, but also plotting the temperature 57 of coolant into the engine radiator 43 during cooling of outside air, as well as the temperature 59 of coolant into the engine radiator 43 during cooling of recirculating air from the cabin of the vehicle. It is seen from FIG. 6 that by employing the method of FIG. 2, wherein cabin recirculation air is increased, while cabin blower speed and compressor capacity are reduced during recirculation, the temperature 59 of coolant into the engine radiator 43 is substantially lower than the temperature 57 of coolant into the engine radiator when outside air is being cooled. This difference allows for a smaller radiator size, as well as fan package size in non-hybrid vehicles. In hybrid or fuel cell powered vehicles, condensers run by electric motors consume less power by increasing cabin recirculation while reducing cabin blower speed and compressor capacity.
FIG. 7 is a chart tabulating examples of condenser heat load reduction resulting improvements to the vehicle efficiency. The chart shows that for hybrid/fuel cell vehicles with electric A/C compressor, the average A/C condenser heat load reduction by forcing cabin recirculation and having reduced compressor capacity is about 11%, which impacts the vehicle by a reduction in transmission sump temperature and a reduction in engine radiator inlet coolant temperature.
For non-hybrid vehicles with a belt driven compressor, where cycling is fixed if using a displacement compressor, displacement can be reduced if using a variable capacity compressor. There are also improvements in efficiency. As is set forth in the chart of FIG. 7, the average A/C condenser heat load reduction by forcing cabin recirculation and having reduced compressor capacity is about 50%. This results in a reduction in engine radiator inlet coolant temperature or a reduction in Engine Radiator Core Thickness. This provides a potential production cost option in designing and/or manufacturing an automotive vehicle.
FIG. 8 illustrates results in a graph for an A/C system optimization for reduced propulsion cooling system size in a non-hybrid example. Condenser heat load 81 in watts (w) and engine rpm 82, as well as vehicle speed 83 in kph and condenser air out temperature 84 in ° C. are plotted as a function of time with cabin HVAC in a recirculation mode 92 versus an outside air (OSA) mode 94 with the vehicle on 0% grade. The data shows that when the system is in a cabin recirculation mode, the condenser load 92 is lower than when the system is in cabin in OSA mode 94. The method of FIG. 8 is carried out by a controller operated in accordance with the method of FIG. 2. While the data plotted is for a non-hybrid vehicle, the same principles apply for hybrid and fuel cell vehicles.
From the foregoing description, one skilled in the art can easily ascertain the essential characteristics of this invention, and without departing form the spirit and scope thereof, can make various changes and modifications of the invention to adapt it to various usages and conditions.

Claims

1) A method of optimizing an air conditioning system control in a vehicle comprising momentarily reducing air conditioner condenser heat load via electric compressor speed control, forced cabin recirculation, and/or reduced cabin blower speed during transient, high ambient and high propulsion system load events.

2) A method according to claim 1, wherein all three of electric compressor speed control, forced cabin recirculation, and reduced cabin blower speed are performed.

3) A method of optimizing an air conditioning system control in an air conditioning system for a vehicle, comprising the steps of:

I) checking:

1) whether the temperature of the engine coolant is higher than a first engine coolant temperature limit and lower than a second engine coolant temperature limit,

2) whether the temperature of the transmission oil is higher than a first transmission oil temperature limit and lower than a second transmission oil temperature limit,

Ia) if the answer to 1 or 2 is yes, then repeating I),

Ib) if the answer to 1 or 2 is no, then proceeding to step II),

II) reducing air conditioner heat load by:

1) increasing cabin recirculation of air

2) reducing cabin blower speed

3) reducing air conditioner compression

III) after step II), checking

1) whether the engine coolant temperature is higher than the second engine coolant temperature limit; and

2) whether the transmission oil temperature of the transmission oil is higher than the second temperature limit;

IIIa) if the answer to 1 or 2 is yes, then shutting off the A/C compressor, setting a flag and then repeating step III),

IIIb) if the answer is no, then checking for the presence of the flag,

IIIbi) if the flag is present, performing cabin recirculation, limiting cabin blower speed and reducing compressor capacity followed by repeating step I),

IIIbii) if no flag is present, repeating step I).

4) The method according to claim 3, wherein the temperature limits are predetermined values.

5) The method according to claim 3, wherein in step II) cabin recirculation of air is increased by X %, cabin blower speed is increased by Y %, and compressor capacity is reduced by Z %.

6) The method according to claim 3, wherein X, Y and Z are predetermined values.

7) The method according to claim 3, wherein X, Y and Z are calculated values.

8) A method of designing vehicles comprising determining propulsion cooling system size which achieves predetermined performance while performing the method according to claim 3.

9) The method according to claim 8, wherein the cooling system size is reduced from a size the cooling system would have been without the vehicles performing a method according to claim 3 while having the same predetermined performance, comprising:

reducing radiator cooling size by core thickness reduction, fin density reduction, or core face area reduction; and

reducing fan motor power.

10) A method of optimizing an air conditioning system control in an air conditioning system for a hybrid or fuel cell vehicle, comprising the steps of:

I) checking:

3) whether the temperature of the inverter coolant is higher than a first inverter coolant temperature limit and lower than a second electric motor temperature limit, and

4) whether the temperature of the electric motor is higher than a first electric motor temperature limit and lower than a second electric motor temperature limit,

Ia) if the answer to all of 1), 2) 3) and 4) checked is yes, then repeating I),

Ib) if the answer to any of 1), 2) 3) or 4) is no, then proceeding to step II),

II) reducing air conditioner heat load by:

1) increasing cabin recirculation of air, or

2) reducing cabin blower speed, or

3) reducing air conditioner compressor capacity,

III) after step II), checking

1) whether the engine coolant temperature is higher than the second engine coolant temperature limit;

3) whether the inverter coolant temperature of the inverter coolant is higher than the second inverter coolant temperature limit;

4) whether the electric motor temperature of the electric motor is higher than the second electric motor temperature limit;

IIIa) if the answer to any of 1), 2) 3) or 4) is yes, then shutting off the A/C compressor, setting a flag and then repeating step II),

IIIb) if the answer to all of the parameters that have been checked is no, then checking for the presence of the flag,

IIIbii) if no flag is present, repeating step I).

11) The method according to claim 3, wherein the temperature limits are predetermined values.

12) The method according to claim 3, wherein the temperature limits are calculated values.

13) A method of designing vehicles comprising determining propulsion cooling system size which achieves predetermined performance while performing the method according to claim 10.

14) The method according to claim 13, wherein the cooling system size is reduced from a size having the same predetermined performance, comprising:

reducing fan motor power.

15) The method of claim 14 wherein the vehicle is a hybrid or fuel cell vehicle and the method further comprises:

reducing power electronics radiator size by core thickness reduction, fin density reduction, and core face area reduction, and

reducing electric motor cooler size by reduced core thickness, fin density reduction, and core face area reduction.

16) A method of optimizing an air conditioning system control for an air conditioning system having a compressor in hybrid or fuel cell having an electric drive motor, the method comprising:

determining the operating temperature of at least one of the following vehicle components: engine coolant, transmission oil, inverter coolant and the electric drive motor;

comparing the at least one operating temperature to lower and upper temperature limits;

if the operating temperature is outside of the temperature limits reducing air conditioner heat load by at least one fo the following steps: increasing cabin air recirculation, reducing cabin blower speed and reducing air conditioner compressor capacity;

subsequent to reducing air conditioner heat load, monitoring the operating temperature to determine if the operating temperature exceeds the upper temperature limit,

shutting off the compressor if the operating temperature exceeds the upper limit;

repeating the step of determining the operating temperature, and

restarting the compressor once the operating temperature is below the upper temperature limit to recirculate conditioned air a limited blower speed on reduced compressor capacity.

17) The method of claim 16 wherein the operating temperatures of at least two of the vehicular components are determined.

18) The method of claim 16 wherein the operating temperatures of three of the vehicular, components are determined.

19) The method of claim 16 wherein the operating temperatures of four of the vehicular components are determined.