Abstract:
A method of increasing a range of a vehicle by decreasing trapped HVAC energy at an end of a trip. The method may include the steps of: determining a destination list based on locations where the vehicle may be parked in the future, the destination list accessible by a control module in the vehicle; determining HVAC reduction regions around each of the locations on the destination list, the HVAC reduction regions accessible by the control module; operating a HVAC system while the vehicle is moving; tracking the location of the vehicle relative to the locations on the destination list; and the control module automatically reducing the energy usage of the HVAC system when the vehicle enters one of the HVAC reduction regions.

Description:
BACKGROUND OF INVENTION 
     The present invention relates generally to controlling heating, ventilation and air conditioning (HVAC) systems for vehicles. 
     Many modern automotive vehicles now operate at times on battery power, either fully or partially. Since the range of a vehicle on battery power is generally much less than a conventional vehicle operated with a gasoline or diesel engine, the drain on the battery from particular vehicle systems becomes more significant. For example, in battery electric vehicles, extended range electric vehicles and some types of hybrid electric vehicles, the HVAC system can consume as much power as the average load on the traction motor on cold days. The HVAC cooling load can also be quite high on hot days. Either way, the drain on the battery from the HVAC load can significantly shorten the range the vehicle can travel on battery power. Thus, it is desirable to increase the electric driving range by decreasing the vehicle electrical loads where possible, without sacrificing occupant comfort and conveniences. 
     SUMMARY OF INVENTION 
     An embodiment contemplates a method of increasing a range of a vehicle by decreasing trapped HVAC energy at an end of a trip, the method comprising the steps of: determining a destination list based on locations where the vehicle may be parked in the future, the destination list accessible by a control module in the vehicle; determining HVAC reduction regions around each of the locations on the destination list, the HVAC reduction regions accessible by the control module; operating a HVAC system while the vehicle is moving; tracking the location of the vehicle relative to the locations on the destination list; and the control module automatically reducing the energy usage of the HVAC system when the vehicle enters one of the HVAC reduction regions. 
     An advantage of an embodiment is that the range of a vehicle operating on battery power can be extended by reducing power consumed by the HVAC system, while preserving thermal comfort for the vehicle occupants. Energy already in the HVAC system can be used near the end of a trip to provide heating or cooling, thus minimizing thermal energy trapped in the HVAC system when the vehicle arrives at a destination. This can also be applied to a more conventional vehicle using a gasoline or diesel engine, where the refrigerant compressor operation may be terminated before arriving at a destination. The slight decrease in HVAC performance near the end of a trip may be minimal on the vehicle occupants since the vehicle will have already been conditioned during the most of the trip. The HVAC operation can be modified with respect to programmed destinations, learned destinations or both. The destinations and vehicle location can be tracked via a navigation system, OnStar™, or other types of systems that can be employed to track the particular location of the vehicle. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a schematic view of a portion of a vehicle. 
         FIG. 2  is a schematic view of possible roads and points of significance relative to HVAC operation. 
         FIG. 3  is a flow chart illustrating a method for operating the HVAC system to reduce energy used by the HVAC system. 
         FIG. 4  is a flow chart illustrating the addition of destination locations where HVAC energy reduction may be employed. 
     
    
    
     DETAILED DESCRIPTION 
     Referring to  FIG. 1 , a portion of a vehicle  20  is shown schematically. The vehicle  20  may include an electric motor  22  that may provide torque to vehicle wheels  24  and be powered by a battery  26 . The vehicle may also include a power plant  28  that provides torque to the vehicle wheels or charges the battery  26  or both. The power plant  28  may be, for example, an internal combustion engine or a fuel cell. Alternatively, the vehicle  20  may not include a power plant  28 , or may include a power plant such as an internal combustion engine without employing a motor to provide torque to the wheels  24 . 
     One or more control module(s)  30  may be employed to communicate with and control the various vehicle systems. The control modules may be made up of various types of electronic hardware and software as is known to those skilled in the art. The control module  30  is in communication with a heating, ventilation and air conditioning (HVAC) system  32  and can control the operation of this system  32 . The control module  30  may also be in communication with a navigation system  34  and/or another type of electronic system, such as, for example, an OnStar™ system  36 . Generally, the control module  30  is in communication with some type of system that can track the location of the vehicle  20 . This may use, for example, Global Positioning System (GPS), cell towers and/or some other means to determine the location of the vehicle. The control module  30  may also be in communication with various sensors. Such sensors may include, for example, an odometer  38  for measuring the distance the vehicle  20  travels, an external temperature sensor  40  for measuring ambient temperature around the vehicle  20 , a sun load sensor  42  for measuring the sun load on the vehicle  20 , and an internal temperature sensor  44  for measuring temperature inside a passenger compartment, among others known to those skilled in the art. 
       FIG. 2  illustrates a schematic view of a road system  100 , with various roadways that one may travel in the vehicle. The control module stores the locations that may be significant relative to the HVAC control. Alternatively, the locations may be stored remotely, but with a communication system that allows the control module to access the information. For example, recent battery charging locations  102 , indicated by a star shape on the map, may be sites that are stored in the control module on a destination list. Recent parking locations  104 , indicated by an octagonal shape on the map, may be sites that are stored in the control module on the destination list. Rules may be set for when a vehicle stopping is considered a parking location  104 . For example, the vehicle may have to be turned off for a minimum amount of time (measured in minutes or hours) for the vehicle stoppage to be considered a parking location  104 . Long term parking locations  106 , indicated by a triangle on the map, may be sites that are stored in the control module on the destination list. The long term parking location  106  may be set only when the vehicle has remained at that location for a long time, for example at least several days, before it is considered long term parking. In addition, programmed addresses  108 , indicated by diamond shapes on the map, may be sites that are programmed onto the destination list by the vehicle operator. This allows the vehicle operator to set locations where reduced HVAC use is acceptable without having to remember to adjust the HVAC system while one is operating the vehicle. The destination list may be set up such that some sites drop off the list after a certain amount of time. That way sites that are not visited regularly (or ever again) may be eliminated from the list, leaving the most relevant on the list. Although, programmed addresses may stay on the list, while only learned destinations are those that drop off the list. 
     The dashed, generally circular regions  110  in  FIG. 2  are regions for reduced HVAC use. That is, when the vehicle enters in these regions  110 , the energy used for heating (or air conditioning) is substantially reduced or eliminated (under certain circumstances). The diameter of the circle for these regions  110  may be a predetermined distance—for example, a radius of about three kilometers. In addition, the predetermined distance may be varied based on various factors related to the climate around and in the vehicle. For example, if the air conditioning is running and the ambient temperature is quite high and/or the sun load is quite high, then the predetermined distance may be reduced since the vehicle interior will heat up much more rapidly. Of course, if the opposite is true, then the predetermined distance may be increased in order to achieve even greater energy savings. In addition, the difference between the actual passenger compartment temperature and the temperature requested by the vehicle occupants (the set point), may be a factor in adjusting the predetermined distance for the particular HVAC reduction region  110 . Rather than adjusting the predetermined distance, or in addition to this, the amount of reduction in the HVAC operation may be adjusted to account for the different ambient conditions. In addition, the HVAC reduction region size may be based on expected travel time to the location rather than distance from the location. 
       FIG. 3  will now be discussed with reference to  FIGS. 1 and 2 . After the vehicle  20  and HVAC system  32  are started, block  200 , a trip odometer is started, block  202 . Alternatively, a timer may be started for block  202 . A determination is made whether the trip odometer has passed an enable distance, block  204 . Alternatively, a determination is made whether the timer has passed an enable time, block  204 . This distance or time may be predetermined based on a distance or time that is needed to heat or cool the vehicle interior. This predetermined distance or time may also be increased or decreased based on ambient conditions around the vehicle  20 , with very high or very low temperatures increasing the predetermined time/distance. 
     If the vehicle has not passed the enable distance (or time), then the check is repeated. If it has, then a determination is made whether the vehicle  20  is within a HVAC reduction region  110 , block  208 . If not, then the HVAC system continues with normal HVAC operation, block  206 . If it is, then the control module  30  changes the HVAC system  32  into a power saving (or off) mode. Thus, with the vehicle  20  within a predetermined distance/time of a possible stopping site, the energy used for HVAC operation is reduced. The operation then checks again to determine if the vehicle  20  is still within one of the HVAC reduction regions, block  208 . If it is not still in one of the regions  110 , then normal HVAC operation is resumed, block  206 . 
       FIG. 4 , which will now be discussed with reference to  FIGS. 1 and 2 , illustrates a method for learning destinations  102 ,  104 ,  106  that may be added to a destination list, creating new (or replacing old) HVAC reduction regions  110 . When the vehicle  20  is started, block  248 , a determination is made as to whether the vehicle has been stationary sufficiently long to be considered a parking location  104 , block  250 . This determination may also take into account if the vehicle  20  was charged at this location. Alternatively, there may be no minimum amount of time and the location may be considered a parking location  104  if, for example, the vehicle is turned off, the driver&#39;s door is opened, or the driver&#39;s seat is unoccupied. 
     If not, then the location is not added to the destination list. If it is stationary for at least a predetermined time or meets other criteria sufficient to be considered a parking location  104  (or is a charging location  102 ), then a determination is made whether this location is currently on the destination list, block  252 . If it is, then no addition is needed. Alternatively, this location may be moved up the list to show that it was a recent HVAC reduction location so that it does not drop from the destination list as new locations are added. If the location is not on the destination list, then it is added to the list, block  254 . A HVAC reduction region  110  is then added around this new destination location. 
     For block  250 , the determination may also include other criteria for determining when a parking location  104  should be added to the destination list. For example, the particular location may be added to the list only after the vehicle  20  has been parked at this location two or more times. There may also be a general error factor, so that the vehicle does not have to be parked in exactly the same parking space to be considered the same parking location  104 . For example, different parking spaces in a mall parking lot. Other criteria can be set for determining when a particular site should be added to the destination list, which determines where HVAC reduction regions  110  will be located. Of course these learned locations may be in addition to locations programmed onto the destination list by the vehicle operator. 
     As an alternative, for sites on the destination list, the route taken to get to the destination and the time of day and day of week the vehicle went to that particular site may be tracked as well. The probability of going to a particular destination on the list may be calculated based on not only the distance to that particular site but also on the route taken, time of day and day of the week. If the probability of going to a particular site on the destination list is below a predetermined threshold, then, even though the vehicle enters the HVAC reduction region for that site, the control module may not switch the HVAC system to a power reduction mode. 
     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.