Abstract:
A HVAC system for a vehicle has a condenser, an evaporator, a compressor, a variable accumulator comprising a piston and an actuator, and a control system operatively connected to the actuator. Fluid flows in a circuit from the condenser, to the evaporator, to the compressor, and to the condenser. The variable accumulator is arranged between the evaporator and the compressor. The control system operates the actuator to displace the piston to alter at least one characteristic of the HVAC system.

Description:
RELATED APPLICATIONS 
       [0001]    This application (Attorney&#39;s Ref. No. P218764) claims benefit of U.S. Provisional Application Serial No. X62/117,824 filed Feb. 18, 2016, the contents of which are incorporated herein by reference. 
     
    
     TECHNICAL FIELD 
       [0002]    The present invention relates to heating and cooling systems and methods that operate on DC power. 
       BACKGROUND 
       [0003]    Utility power is typically made available as an AC power signal distributed from one or more centralized sources to end users over a power distribution network. However, utility power is unavailable for certain structures. For example, movable structures such vehicles do not have access to utility power when moving and can be connected to power distribution network when parked only with difficulty. Similarly, remote structures such as cabins and military installations not near the utility power distribution network often cannot be practically powered using utility power. 
         [0004]    DC power systems including batteries are often employed to provide power when utility power is unavailable. For example, trucks and boats typically employ a DC power system including a battery array to provide power at least to secondary vehicle electronics systems such as communications systems, navigation systems, ignition systems, heating and cooling systems, and the like. Shipping containers and remote cabins that operate using alternative primary power sources such as solar panels or generators also may include DC power systems including a battery or array of batteries to operate electronics systems when primary power is unavailable. Accordingly, most modern vehicles and remote structures use battery power sufficient to operate, at least for a limited period of time, electronics systems such as secondary vehicle electronics systems. 
         [0005]    The capacity of a battery system used by a vehicle or remote structure is typically limited by factors such as size, weight, and cost. For example, a vehicle with an internal combustion engine may include a relatively small battery for use when the engine is not operating; a large battery array is impractical for vehicles with an internal combustion engine because the size of the batteries takes up valuable space and the weight of the batteries reduces vehicle efficiency when the vehicle is being moved by the engine. All electric vehicles have significantly greater battery capacity, but that battery capacity is often considered essential for the primary purpose of moving the vehicle, so the amount of battery capacity that can be dedicated to secondary vehicle electronics systems is limited. Battery systems employed by remote structures must be capable of providing power when the alternative power source is unavailable, but factors such as cost, size, and weight reduce the overall power storage capacity of such systems. 
         [0006]    Heating and cooling systems have substantial energy requirements. Vehicles such as trucks or boats typically rely on the availability of the internal combustion engine when heating or cooling is required. When heating or cooling is required when the vehicle is parked or the boat is moored for more than a couple of minutes, the internal combustion engine will be operated in an idle mode solely to provide power to the heating and cooling system. Engine idling is inefficient and creates unnecessary pollution, and anti-idling laws are being enacted to prevent the use of idling engines, especially in congested environments like cities, truck stops, and harbors. For remote structures such as cabins or shipping containers, heating and cooling systems can be a major draw on battery power. Typically, an alternative or inferior heating or cooling source such as a wood burning stove, fans, or the like are used instead of a DC powered heating and cooling system. 
         [0007]    The need thus exists for heating and cooling systems that operate using DC power having improved efficiency to optimize the use of battery power. 
       SUMMARY 
       [0008]    As one example, a HVAC system for a vehicle has a condenser, an evaporator, a compressor, a variable accumulator comprising a piston and an actuator, and a control system operatively connected to the actuator. Fluid flows in a circuit from the condenser, to the evaporator, to the compressor, and to the condenser. The variable accumulator is arranged between the evaporator and the compressor. The control system operates the actuator to displace the piston to alter at least one characteristic of the HVAC system. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0009]      FIG. 1  is a highly schematic view of a conventional heating and cooling system adapted for use in a structure system such as a vehicle or remote structure; 
           [0010]      FIG. 2  is a schematic view of a first example of a heating and cooling system of the present invention; 
           [0011]      FIG. 3  is a schematic view of a second example of a heating and cooling system of the present invention; 
           [0012]      FIG. 4  is a schematic view of a third example of a heating and cooling system of the present invention; 
       
    
    
     DETAILED DESCRIPTION 
       [0013]    The present invention may be embodied in a number of different example configurations, and several examples of vehicle heating and cooling systems constructed in accordance with, and embodying, the principles of the present invention will be described separately below. 
         [0014]    i. Conventional DC Heating and Cooling System 
         [0015]    Referring initially to  FIG. 1  of the drawing, depicted at  20  therein is an example DC heating and cooling system  20  adapted to operate in conjunction with a structure system  22 . The structure system  22  comprises a cabin  30 , ducting  32 , and a DC power system  34  having one or more batteries  36 . The structure system  20  may be, as examples, a vehicle such as a car, truck, or boat or a remote structure such as a cabin or shipping container. 
         [0016]    The cabin  30  defines the area of the structure system  22  to be heated and/or cooled. The ducting  32  allows the flow of heated and/or cooled air through the cabin  30 . The cabin  30  and the ducting  32  will be defined by the characteristics of the structure system  22 , are not per se part of the present invention, and will not be described herein in detail. 
         [0017]    The DC power system  34  will take many forms and will be defined by the nature of the structure system  22 . For example, if the structure system  22  is a car, truck, or boat, the DC power system  34  will typically include a conventional alternator connected to an internal combustion engine, and the alternator is configured to charge the battery or batteries  36  when the internal combustion engine is operating. If the structure is a remote cabin or possibly a shipping container, the DC power system  34  may include or be connected to a solar power system and/or generator, and the solar power system and/or generator are configured to charge the battery or batteries  36 . 
         [0018]    In any case, the DC power system  34  will typically be the sole source of power to the structure system  22 , and the present invention is of particular significance when utility AC power is not available to the structure system  22 . While the principles of the present invention may be used when a utility AC power signal is available to the structure system  22 , AC power powered heating and cooling systems may be more effective in the event that utility AC power is available. 
         [0019]      FIG. 1  further shows that the example heating and cooling system  20  depicted therein conventionally comprises a compressor  40 , a condenser  42 , an evaporator  44 , and an accumulator  46  connected by a conduit system  48  to define a conventional refrigeration system. In addition, the example heating and cooling system  20  further comprises a drier  50 , a metering device  52 , a condenser fan  54 , and an evaporator blower  56 . The conduit system  48  defines a liquid line  60  extending between the condenser  42  and the evaporator  44 , a suction line  62  extending between the evaporator  44  and compressor  40 , and a discharge line  64  extending between the compressor  40  and the condenser  42 . The drier  50  and metering device  52  are arranged in the liquid line  60 . The accumulator  46  is arranged in the suction line  62 . 
         [0020]    When the system operates, the DC power supply  34  is connected to the compressor  40 , the condenser fan  54 , and the evaporator blower  56 . The compressor  40  forces refrigerant through the conduit system  48  in a conventional refrigeration cycle. At the same time, the condenser fan  54  forces air to flow over the condenser  42 , resulting in warm air  70  flowing into the ducting  32 . The evaporator blower  56  causes air to flow over the evaporator  44 , resulting in cold air  72  flowing into the ducting  32 . The ducting  32  operates in a conventional manner to allow the warm air  70  or the cold air  72  to flow into the cabin  30  as desired. 
         [0021]    Because the example DC heating and cooling system  22  operates based on a DC voltage supplied by the battery  36  of the power supply  34 , the size and operating characteristics of the compressor  40  are typically limited and the compressor  40  may not operate effectively over the entire range of operating parameters of the example DC heating and cooling system  22 . Because the characteristics of the example DC heating and cooling system  22  are typically fixed, the compressor  40  will not operate with optimum efficiency under at least some of the operating parameters of the example DC heating and cooling system  22 . 
         [0022]    II. First Example DC Heating and Cooling System 
         [0023]    Turning now to  FIG. 2  of the drawing, depicted therein is a first example DC heating and cooling system  20   a  that may be used in place of the DC heating and cooling system  20  with the structure system  22  as depicted in  FIG. 1  and described above. 
         [0024]    The first example DC heating and cooling system  20   a  comprises a compressor  120 , a condenser  122 , an evaporator system  124 , and a variable accumulator  126 . A conduit system  128  is configured such that refrigerant fluid flows from the compressor  120  to the condenser  122 , from the condenser  122  to the evaporator system  124 , from the evaporator system  124  to the variable accumulator  126 , and back to the compressor  120 . The example compressor  220  and condenser  222  are or may be conventional. 
         [0025]      FIG. 2  illustrates that the evaporator system  124  comprises a primary coil  130 , a secondary coil  132 , a primary metering device  134 , a secondary metering device  136 , a first valve  140 , and, optionally, a second valve  142 . A drier  144  is arranged upstream of the evaporator system  124 . The valves  140  and  142  are operable to allow or prevent refrigerant fluid from flowing from the condenser  122  through the secondary metering device  136  and secondary coil  132 . The evaporator system  124  may thus be operated in a first configuration in which the valves  140  and  142  are configured to allow refrigerant fluid to flow only through the primary coil  130  and in a second configuration in which the valves  140  and  142  are configured to allow refrigerant fluid to flow through both the primary coil  130  and the secondary coil  132 . 
         [0026]      FIG. 2  further illustrates that the example variable accumulator  126  comprises an accumulator assembly  150  and an actuator assembly  152 . The accumulator assembly  150  comprises a housing  160  and a piston  162  comprising a head portion  164  and a shaft portion  166 . The head portion  164  is arranged within the housing  160  to define a sealed accumulator chamber  168 . The shaft portion  166  extends from the housing  160  and engages the actuator assembly  152 . The actuator assembly  152  is capable of moving the piston  162  relative to the housing  160  such that a volume of the actuator chamber  168  may be varied between a first volume (solid lines in  FIG. 2 ) and a second volume (broken lines in  FIG. 2 ). The actuator assembly  162  may be a screw actuator, pneumatic or hydraulic actuator, or any other actuator cable of causing linear displacement of the piston  162  as shown by a comparison of the solid and dotted lines in  FIG. 2 . 
         [0027]    The first example DC heating and cooling system  20   a  further optionally comprises a control system comprising a controller  170  and first and second sensors  172  and  174 . The first and second sensors  172  and  174  measure and/or quantify characteristics of the refrigerant fluid, and the example first and second sensors  172  and  174  measure the temperature and pressure, respectively, of the refrigerant fluid. Additional sensors such may be connected to the controller  170  to measure ancillary characteristics of the DC heating and cooling system  20   a  such as outside temperature and cabin temperature. Further, the controller  170  may optionally be connected to user input devices such as a control panel or thermostat. The example conduit system  128  defines a liquid line  180 , a suction line  182 , and a discharge line  184 . The example sensor  172  and  174  are arranged in the suction line  182  but may be arranged at other locations as appropriate. 
         [0028]    The use of the example evaporator system  124  and the example variable accumulator  126  effectively allow the characteristics of the first example DC heating and cooling system  20   a  to be varied during operation thereof. In the first example DC heating and cooling system  20   a,  the example controller  170  implements logic that operates the valves  140  and/or  142  and actuator  152  to alter the characteristics of the first example DC heating and cooling system  20   a  to optimize the performance of the compressor  120  and thus the entire DC heating and cooling system  20   a.    
         [0029]    III. Second Example DC Heating and Cooling System 
         [0030]    Turning now to  FIG. 3  of the drawing, depicted therein is a second example DC heating and cooling system  20   b  that may be used in place of the DC heating and cooling system  20  with the structure system  22  as depicted in  FIG. 2  and described above. 
         [0031]    The second example DC heating and cooling system  20   a  comprises a compressor  220 , a condenser  222 , an evaporator system  224 , and an accumulator  226 . A conduit system  228  is configured such that refrigerant fluid flows from the compressor  220  to the condenser  222 , from the condenser  222  to the evaporator system  224 , from the evaporator system  224  to the variable accumulator  226 , and back to the compressor  220 . The example compressor  220 , condenser  222 , and accumulator  226  are or may be conventional. 
         [0032]      FIG. 3  illustrates that the evaporator system  224  comprises a primary coil  230 , a secondary coil  232 , a primary metering device  234 , a secondary metering device  236 , a first valve  240 , and, optionally, a second valve  242 . A drier  244  is arranged upstream of the evaporator system  224 . The valves  240  and  242  are operable to allow or prevent refrigerant fluid from flowing from the condenser  222  through the secondary metering device  236  and secondary coil  232 . The evaporator system  224  may thus be operated in a first configuration in which the valves  240  and  242  are configured to allow refrigerant fluid to flow only through the primary coil  230  and in a second configuration in which the valves  240  and  242  are configured to allow refrigerant fluid to flow through both the primary coil  230  and the secondary coil  232 . 
         [0033]    The second example DC heating and cooling system  20   b  further optionally comprises a control system comprising a controller  270  and first and second sensors  272  and  274 . The first and second sensors  272  and  274  measure and/or quantify characteristics of the refrigerant fluid, and the example first and second sensors  272  and  274  measure the temperature and pressure, respectively, of the refrigerant fluid. Additional sensors such may be connected to the controller  270  to measure ancillary characteristics of the DC heating and cooling system  20   b  such as outside temperature and cabin temperature. Further, the controller  270  may optionally be connected to user input devices such as a control panel or thermostat. The example conduit system  228  defines a liquid line  280 , a suction line  282 , and a discharge line  284 . The example sensor  272  and  274  are arranged in the suction line  282  but may be arranged at other locations as appropriate. 
         [0034]    The use of the example evaporator system  224  effectively allow the characteristics of the second example DC heating and cooling system  20   b  to be varied during operation thereof. In the second example DC heating and cooling system  20   b,  the example controller  270  implements logic that operates the valves  240  and/or  242  to alter the characteristics of the second example DC heating and cooling system  20   b  to optimize the performance of the compressor  220  and thus the entire DC heating and cooling system  20   b.    
         [0035]    IV. Third Example DC Heating and Cooling System 
         [0036]    Turning now to  FIG. 4  of the drawing, depicted therein is a third example DC heating and cooling system  20   c  that may be used in place of the DC heating and cooling system  20  with the structure system  22  as depicted in  FIG. 4  and described above. 
         [0037]    The third example DC heating and cooling system  20   c  comprises a compressor  320 , a condenser  322 , an evaporator  324 , and a variable accumulator  326 . A conduit system  328  is configured such that refrigerant fluid flows from the compressor  320  to the condenser  322 , from the condenser  322  to the evaporator system  324 , from the evaporator system  324  to the variable accumulator  326 , and back to the compressor  320 . The example compressor  220 , condenser  222  and evaporator  324  are or may be conventional.  FIG. 4  illustrates that the evaporator  324  comprises a coil  330  and is connected to a metering device  332  and a drier  340 . 
         [0038]      FIG. 4  further illustrates that the example variable accumulator  326  comprises an accumulator assembly  350  and an actuator assembly  352 . The accumulator assembly  350  comprises a housing  360  and a piston  362  comprising a head portion  364  and a shaft portion  366 . The head portion  364  is arranged within the housing  360  to define a sealed accumulator chamber  368 . The shaft portion  366  extends from the housing  360  and engages the actuator assembly  352 . The actuator assembly  352  is capable of moving the piston  362  relative to the housing  360  such that a volume of the actuator chamber  368  may be varied between a first volume (solid lines in  FIG. 4 ) and a second volume (broken lines in  FIG. 4 ). The actuator assembly  362  may be a screw actuator, pneumatic or hydraulic actuator, or any other actuator cable of causing linear displacement of the piston  362  as shown by a comparison of the solid and dotted lines in  FIG. 4 . 
         [0039]    The third example DC heating and cooling system  20   c  further optionally comprises a control system comprising a controller  370  and first and second sensors  372  and  374 . The first and second sensors  372  and  374  measure and/or quantify characteristics of the refrigerant fluid, and the example first and second sensors  372  and  374  measure the temperature and pressure, respectively, of the refrigerant fluid. Additional sensors such may be connected to the controller  370  to measure ancillary characteristics of the DC heating and cooling system  20   c  such as outside temperature and cabin temperature. Further, the controller  370  may optionally be connected to user input devices such as a control panel or thermostat. The example conduit system  328  defines a liquid line  380 , a suction line  382 , and a discharge line  384 . The example sensor  372  and  374  are arranged in the suction line  382  but may be arranged at other locations as appropriate. 
         [0040]    The use of the evaporator system  324  and variable accumulator effectively allow the characteristics of the third example DC heating and cooling system  20   c  to be varied during operation thereof. In the third example DC heating and cooling system  20   c,  the example controller  370  implements logic that operates the valves  340  and/or  342  and actuator  352  to alter the characteristics of the third example DC heating and cooling system  20   c  to optimize the performance of the compressor  320  and thus the entire DC heating and cooling system  20   c.    
         [0041]    V. Summary 
         [0042]    A multi-mode evaporator system such as the example evaporator systems  124  and  224  and/or the variable accumulator such as the example variable accumulator systems  126  and  326  may be used as part of any heating and cooling system configured to operate using DC power. As examples, the multi-mode evaporator and variable accumulator of the present invention may be used as the evaporator and/or accumulator of the DC heating and cooling systems depicted and described in the Applicant&#39;s co-pending U.S. Provisional Patent Application Ser. No. 61/950,719, and the contents of the &#39;719 provisional application are incorporated herein by reference.