Abstract:
A hybrid air conditioning system for a combustion engine vehicle. When the combustion engine is running and a rechargeable battery unit is not at full charge, an electric machine is configured by an MCU control unit as mechanically coupled to the combustion engine, and a battery charger is configured as electrically connected to the rechargeable battery unit such that the electric machine generates electric power to recharge the rechargeable battery unit. When the combustion engine stops and air conditioning is required, the rechargeable battery unit is configured by the MCU control unit as electrically connected to a motor drive, and the electric machine is configured as mechanically coupled to the compressor to provide mechanical power to drive the compressor. This allows the automobile air conditioning system to operate for a limited period of time after the combustion engine stops.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    The invention is related to air conditioning systems for vehicles, and particularly related to air conditioning systems for vehicles powered by internal combustion engine. 
         [0003]    2. Description of Related Art 
         [0004]    An air conditioning system provides a human comfort environment by controlling a suitable range of air temperature and humidity in the living environment. The history of air conditioning systems is over one century old. In 1939, an air conditioning system for an automobile was developed by Packard Motor Car Company. By 1969 more than 50% of the automobiles sold in the United States were equipped with automobile air conditioning systems. Nowadays, automobile air conditioning systems have become one of the necessary items of equipments in automobiles. 
         [0005]    In the conventional art, the long standing dilemma of vehicle air-conditioning faced by vehicles powered solely by internal combustion engines is that, when they are stopped for a short period, keeping the air-conditioning running requires continuous operation of the engine and hence increases fuel consumption and exhaust gas emission. Switching off the engine and hence the air-conditioning results in a temperature rise. In tropical and subtropical geographical areas such as South China, cabin temperatures can rise rapidly beyond a bearable level shortly after the air-conditioning is switched off. The advent of the hybrid electric vehicle provides an ideal platform to address this problem. Examples of such systems are disclosed in U.S. Pat. Nos. 6,840,055 and 6,516,621. However, these systems are not suitable for conventional internal engine powered vehicles. 
         [0006]      FIG. 1  shows the basic structure of a conventional automobile air conditioning (A/C) system. In this system the A/C compressor  3  is driven by the engine  1  of the vehicle. The clutch  2  is an electromagnetic clutch which is integrated in most A/C compressors. A/C temperature control relies on switching the clutch off and on. This structure is simple and easy for maintenance. However, the speed of the engine changes frequently in a wide range of speeds when the vehicle is running on the road. The speed of the compressor changes independently of the A/C temperature and hence the A/C temperature fluctuates. Another disadvantage of the conventional air conditioning system is that the air conditioning system has to be shut down when the engine is shut down (vehicle off). 
         [0007]    Accordingly, a need exists for an improved automobile air conditioning system to provide air-conditioning when the operation of the combustion engine is off, and to drive the speed of the compressor in such a manner as to provide a steady A/C temperature. 
       SUMMARY 
       [0008]    Several aspects of the presently claimed invention have been developed with a view to substantially reduce or eliminate the drawbacks described hereinbefore and known to those skilled in the art and to provide an automobile hybrid air conditioning system that may be adopted to offer air-conditioning without the need to keep the vehicle combustion engine running, thus reducing fuel consumption and exhaust gas emission. Some embodiments of the invention provide steady temperature irrespective of speed changes in the combustion engine. The compressor of this system is driven by the internal combustion engine when the engine is running as a conventional automobile air conditioning system. When the engine is shut down, the A/C compressor of this system is driven by an electric machine, in some embodiments a brushless DC (BLDC) machine, powered by a rechargeable battery unit, in some embodiments a 24-volt lead acid battery. When the battery voltage level is low, resulting from partial discharge, the battery is recharged with electric power generated from the same electric machine driven by the engine. The A/C temperature may be controlled by varying the speed of the electric machine. 
         [0009]    According to an aspect of the presently claimed invention, there is provided a hybrid air conditioning system for a combustion engine vehicle. The system includes a combustion engine mechanically coupled to the transmission system of the vehicle; a rechargeable battery unit selectively connected to a battery charger and a motor drive electrically; and an electric machine electrically connected to the battery charger and the motor drive. The electric machine is further selectively coupled to the combustion engine mechanically. A compressor for air conditioning is selectively coupled to the combustion engine and the electric machine mechanically. When the combustion engine is running and the rechargeable battery unit is low, the electric machine is configured by an MCU control unit as mechanically coupled to the combustion engine, and the battery charger is configured as electrically connected to the rechargeable battery unit such that the electric machine generates electric power to recharge the rechargeable battery unit. When the combustion engine stops and air conditioning is required, the rechargeable battery unit is configured by the MCU control unit as electrically connected to the motor drive, and the electric machine is configured as mechanically coupled to the compressor to provide mechanical power to drive the compressor. 
         [0010]    In some embodiments the hybrid air conditioning system further includes a first clutch, a second clutch and a third clutch. The clutches are mechanically coupled with each other by pulleys and belt. The first clutch is mechanically coupled to the combustion engine, for example by pulleys and belt; the second clutch is mechanically coupled to the compressor; and the third clutch is mechanically coupled to the DC electric machine. 
         [0011]    In some embodiments the hybrid air conditioning system further includes a first relay and a second relay. The first relay electrically connects the output of the battery charger to the rechargeable battery unit and the second relay electrically connects the motor drive to the rechargeable battery unit. In some embodiments the first relay and the second relay have normally-open switch contacts which provide electrical connection when the relay is energized. 
         [0012]    In some embodiment, when the combustion engine is running and air conditioning is required, the compressor is configured as mechanically coupled to the combustion engine such that the combustion engine produces mechanical power for driving the compressor. 
         [0013]    In some embodiments, the hybrid air conditioning system further includes a battery charger controller, for example in the MCU control unit, for monitoring both the rechargeable battery voltage and the speed of the electric machine. When the electric machine is generating electric power for charging the rechargeable battery unit, the charging current applied to the rechargeable battery unit is controlled by the battery charger controller to be directly proportional to the speed of the electric machine. 
         [0014]    According to another aspect of the presently claimed invention, there is provided a hybrid air conditioning controller for a combustion engine vehicle. The combustion engine vehicle has a combustion engine, a rechargeable battery unit, a battery charger, a electric machine, and a compressor for air conditioning. When the combustion engine is running and the rechargeable battery unit is partly discharged, the hybrid air conditioning controller configures the electric machine as mechanically coupled to the combustion engine, and the hybrid air conditioning controller configures the battery charger as electrically connected to the rechargeable battery unit such that the electric machine generates electric power to recharge the rechargeable battery unit. When the combustion engine stops and air conditioning is required, the hybrid air conditioning controller configures the rechargeable battery unit as electrically connected to the motor drive and the electric machine as mechanically coupled to the compressor to provide mechanical power to drive the compressor. 
         [0015]    In some embodiments, when the combustion engine is running and air conditioning is required, the hybrid air conditioning controller configures the compressor as mechanically coupled to the combustion engine such that the combustion engine produces mechanical power for driving the compressor. 
         [0016]    In another embodiment, the hybrid air conditioning controller further includes a battery charger controller for monitoring both the rechargeable battery voltage and the speed of the electric machine. When the electric machine is generating electric power for charging the rechargeable battery unit, the charging current applied to the rechargeable battery unit is controlled by the battery charger controller to be directly proportional to the speed of the electric machine. 
         [0017]    According to a further aspect of the presently claimed invention, there is provided a method of hybrid air conditioning for combustion engine vehicle, the combustion engine vehicle having a combustion engine, a rechargeable battery unit, a battery charger, a electric machine, and a compressor for air conditioning. The method includes, when the combustion engine is running and the rechargeable battery unit is low, configuring the electric machine as mechanically coupled to the combustion engine and the battery charger as electrically connected to the rechargeable battery unit such that the electric machine generates electric power to recharge the rechargeable battery unit. When the combustion engine stops and air conditioning is required, the method includes configuring the rechargeable battery unit as electrically connected to the motor drive, and the electric machine is configured as mechanically coupled to the compressor to provide mechanical power to drive the compressor. 
         [0018]    In some embodiments the method further includes, when the combustion engine is running and air conditioning is required, configuring the compressor as mechanically coupled to the combustion engine such that the combustion engine produces mechanical power for driving the compressor. 
         [0019]    In some embodiments the method also includes monitoring both the rechargeable battery voltage and the speed of the electric machine. When the electric machine is generating electric power for charging the rechargeable battery unit, the charging current applied to the rechargeable battery unit is controlled to be directly proportional to the speed of the electric machine. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0020]      FIG. 1  is a system diagram of a conventional automobile air conditioning system according to the prior art. 
           [0021]      FIG. 2  is a system diagram in accordance with an embodiment of the present invention. 
           [0022]      FIG. 3  is an equivalent system diagram in accordance with an embodiment of the present invention in mode 1 operation. 
           [0023]      FIG. 4  is an equivalent system diagram in accordance with an embodiment of the present invention in mode 2 operation. 
           [0024]      FIG. 5  is an equivalent system diagram in accordance with an embodiment of the present invention in mode 3 operation. 
           [0025]      FIG. 6  is an equivalent system diagram in accordance with an embodiment of the present invention in mode 4 operation. 
           [0026]      FIG. 7  is an equivalent system diagram in accordance with an embodiment of the present invention in mode 5 operation. 
           [0027]      FIG. 8  is a bi-directional drive in accordance with a further embodiment of the present invention. 
           [0028]      FIG. 9  is a state diagram of the control flow in accordance with an embodiment of the present invention. 
       
    
    
     DESCRIPTION OF EMBODIMENTS 
       [0029]    An automobile hybrid air conditioning system is described hereinafter. In the following description, numerous specific details, including electrical components, mechanical components, and the like are set forth. However, from this disclosure, it will be apparent to those skilled in the art that modifications and substitutions may be made without departing from the scope of the invention. In other circumstances, specific details may be omitted so as not to obscure the invention. 
         [0030]    Where reference is made in any one or more of the accompanying drawings to steps and features which have the same reference numerals, those steps and features have for the purposes of this description the same function(s) or operation(s), unless the contrary intention appears. 
         [0031]    The embodiments of the present invention provide automobile air conditioning systems that are capable of operating for a limited time period when the combustion engine vehicle stops.  FIG. 2  shows an automobile air conditioning system diagram in accordance with an embodiment of the present invention. The system comprises an A/C compressor  18  integrated with an electromagnetic clutch  16 , two further electromagnetic clutches  16 ,  17 , a valve  21 , a condenser  27 , an evaporator  22 , belts  11 ,  12  and belt pulleys  27 ,  28 ,  29 ,  30 ,  31 , a brushless DC electric machine  19 , a motor drive  20 , a rechargeable battery  26 , a battery charger  25 , tubes in high pressure  14 , tubes in low pressure  13 , two relays  23 ,  24 , and an MCU control unit  32 . 
         [0032]    According to  FIG. 2 , the clutches  15 ,  16 ,  17  are used for switching the mechanical power sources to the A/C compressor  18  between the combustion engine  10  and the electric machine  19 . Mechanical power is transmitted by the belt pulleys  27 ,  28 ,  29 ,  30 ,  31  and the belts  11 ,  12 . 
         [0033]    The rechargeable battery  26  is a deep cycle battery so that it is suitable for providing high current in long duration with long life cycles. It powers the motor drive  23 , the controller of the battery charger  24  and the MCU control unit  32 . 
         [0034]    According to an embodiment of the present invention, the electric machine  19  is a brushless DC (BLDC) machine. This type of machine has fast response, high power density, robustness and high reliability. The electric machine  19  can serve as an electric motor as well as an electric generator. It is both for driving the compressor  18  and for generating electric power for charging the rechargeable battery  26 . When the BLDC machine  19  drives the A/C compressor  18 , it is driven by the motor drive  20 . The electric power for driving the BLDC machine is provided by the rechargeable battery  26 . The battery charger  25  is responsible for recharging the rechargeable battery  26 . The relay  23  is for switching the motor drive  20  on and off. The relay  24  is for connecting and disconnecting the rechargeable battery  26  and the battery charger  25 . In an exemplary embodiment of the present invention, the relays  23  and  24  are normally-open type relays. The relay  23  and the relay  24  should not be closed at the same moment. 
         [0035]    The MCU control unit  32  is powered by the rechargeable battery  26 . It controls on/off states of the relays  23 ,  24  and closed/open states of the clutches  15 ,  16 ,  17 . Relay drivers and clutch drivers are built into the MCU control unit  32 . It is also responsible for controlling the speed of the electric machine  19  with the motor drive  20  when the machine  19  is in motoring operation. It monitors the speed of the electric machine  19  by a Hall effect position sensor built in the machine  19  and the A/C temperature by a thermal sensor so that the speed of the electric machine  19  and the A/C temperature are under closed-loop control. It also monitors the rechargeable battery  26  voltage and the angular speed of the combustion engine  10 . When the speed of the combustion engine  10  is too high while the electric machine  19  is generating power for recharging the rechargeable battery  26 , the MCU control unit  32  opens clutch  3   17  in order to avoid damaging the electric machine  19  by over speed and the battery charger  25  by over input voltage. 
         [0036]    The controller of the battery charger  25  monitors both the voltage of the rechargeable battery  26  and the speed of the electric machine  19 . When the electric machine  19  is generating electric power for recharging the rechargeable battery  26 , its output voltage of the electric machine  19  is substantially in direct proportion relationship with its angular speed. The charging current of the rechargeable battery  26  is controlled by the controller of the battery charger  25 . It is proportional to the speed of the electric machine  19  and hence, over input current of the battery charger  25  is prevented. The rechargeable battery  26  can be rechargeable even when the combustion engine is at low speed. 
         [0037]    The operation of the automobile hybrid air conditioning system of the present invention shown in  FIG. 1  is considered as 5 modes of operation. The equivalent system diagrams of the modes of operation of the present invention are shown in  FIG. 3 ,  FIG. 4 ,  FIG. 5 ,  FIG. 6  and  FIG. 7 . The modes of operation are described in the following: 
       Mode 1 
       [0038]      FIG. 3  shows an equivalent system diagram in accordance with an embodiment in Mode 1 operation. In this mode of operation, the vehicle is on and the air conditioning system is on. The combustion engine  10  is running in Mode 1. The rechargeable battery  26  is fully charged. Clutch  1   15  is closed. Relay  1   23 , Relay  2   24  and Clutch  3   17  are open. The combustion engine  10  drives the A/C compressor  18 . The electric machine  19  is not operated. The rechargeable battery  26  is not recharged. The room temperature is controlled by switching on and off Clutch  2   16 , i.e., switching on and off of the A/C compressor  18 . 
       Mode 2 
       [0039]      FIG. 4  shows an equivalent system diagram in accordance with an embodiment in Mode 2 operation. The vehicle stops in Mode 2. The air conditioning system of the present invention is on. The combustion engine  10  is not running in this moment. Clutch  1   15  and Relay  2   24  are open. Clutch  2   16 , Clutch  3   17  and Relay  1   23  are closed. The rechargeable battery  26  produces electric power to the motor drive  20  to drive the electric machine  19 , and the electric machine  19  drives the A/C compressor  18 . The room temperature is controlled by controlling the speed of the electric machine  19  by the motor drive  20  and the MCU control unit  32 . This obtains stable temperature and saves compressor starting energy. The electric machine  19  stops when the voltage of the rechargeable battery  26  reaches its minimum discharge voltage. 
       Mode 3 
       [0040]      FIG. 5  shows an equivalent system diagram in accordance with an embodiment in Mode 3 operation. The vehicle is running in Mode 3 so that the combustion engine  10  is running in this moment. The rechargeable battery  26  voltage reaches its minimum battery voltage. The air conditioning system of the present invention is on. The rechargeable battery  26  is recharged by the battery charger  25 . Clutch  1   15 , Clutch  3   17  and Relay  2   24  are all closed. Relay  1   23  is open. The combustion engine  10  drives both the A/C compressor  18  and the electric machine  19 . The electric machine  19  generates electric power to the battery charger  25  to recharge the rechargeable battery  25 . The A/C temperature is controlled by switching on and off Clutch  2   16 . 
       Mode 4 
       [0041]      FIG. 6  shows an equivalent system diagram in accordance with an embodiment in Mode 4 operation. The air conditioning system of the present invention is off in Mode 4. The combustion engine  10  is running. The rechargeable battery  26  is recharged because its voltage level is low. Clutch  1   15 , Clutch  3   17  and Relay  2   24  are closed. Clutch  2   16  and Relay  1   23  are open. The combustion engine  10  drives only the electric machine to generate electric power to the battery charger  25  and to recharge the rechargeable battery  26 . 
       Mode 5 
       [0042]      FIG. 7  shows an equivalent system diagram in accordance with an embodiment in Mode 5 operation. The air conditioning system of the present invention is off in Mode 5. The combustion engine  10  is either running or stop. The rechargeable battery  26  is fully charged. The electric machine  19  neither drives the A/C compressor  18  nor generates electric power. Clutch  1   15 , Clutch  2   16 , Clutch  3   17 , Relay  1   23  and Relay  2   24  are all open. 
         [0043]    According to another embodiment, the electric drive in  FIG. 1  can be replaced by a bi-directional drive as depicted in  FIG. 8 . The integration of motor drive and battery charger shares certain components of the power electronic circuitry and it eliminates the use of power relays. Thus, it can be made smaller with longer life cycle. 
         [0044]    The status of the combustion engine, the air conditioning, and rechargeable battery under different modes are summarized in Table 1 below: 
         [0000]    
       
         
               
               
               
               
             
           
               
                 TABLE 1 
               
               
                   
               
               
                 Mode 
                 Engine 
                 A/C 
                 Batt 
               
               
                   
               
             
             
               
                 5 
                 OFF 
                 OFF 
                 / 
               
               
                   
                 RUNS 
                 OFF 
                 FULL 
               
               
                 1 
                 RUNS 
                 ON 
                 FULL 
               
               
                 2 
                 OFF 
                 ON 
                 / 
               
               
                 3 
                 RUNS 
                 ON 
                 LOW 
               
               
                 4 
                 RUNS 
                 OFF 
                 LOW 
               
               
                   
               
             
          
         
       
     
         [0045]      FIG. 8  shows a bi-directional drive which replaces the electric drive in  FIG. 2  according to a further embodiment of the present invention. The integration of motor drive and battery charger shares certain components of the power electronic circuitry and it eliminates the use of power relays. Thus, it can be made smaller with longer life cycle. 
         [0046]      FIG. 9  is a state diagram of the control flow of the automobile hybrid air conditioning system in accordance with an embodiment. The control flow begins at Mode 5, state  901  when the system is started up, both the combustion engine and A/C are turned off in this mode. If the engine is then started to run and the A/C is switched on with full battery level, the state changes to Mode 1, state  902 . If the engine is started to run while the battery level is low, the state changes to Mode 4, state  905 . If the A/C is turned on while the engine remains off, then the state changes to Mode 2, state  903 . 
         [0047]    At Mode 1, state  902  where both the engine and A/C are running, if the A/C is then turned off, the state changes to Mode 2, state  903 . If the battery level becomes low, the state changes to Mode 3, state  904 . 
         [0048]    At Mode 2, state  903  where the engine is off and the A/C is running, if the engine is then started to run, the state changes to Mode 3, state  904 . If the A/C is turned off, the state changes back to Mode 5, state  901 . 
         [0049]    At Mode 3, state  904  where both the engine and A/C are running with the battery being charged, if the A/C is then turned off, the state changes to Mode 4, state  905 . If the battery level becomes full, the state changes to Mode 1, state  902 . If the engine is stopped, the state returns to Mode 5, state  901 . 
         [0050]    At Mode 4, state  905  where the engine is running, the battery is being charged and the A/C is off, if the A/C is then turned on, the state changes to Mode 3, state  904 . If the engine is turned off or the battery level becomes full, the state returns to Mode 5, state  901 . 
         [0051]    Embodiments described hereinbefore provide air-conditioning when the operation of the vehicle combustion engine is off, and drive the speed of the compressor in such a manner as to provide steady A/C temperature. 
         [0052]    The foregoing description provides exemplary embodiments only, and is not intended to limit the scope, applicability or configurations of the present invention. Rather, the description of the exemplary embodiments provides those skilled in the art with enabling descriptions for implementing embodiments of the invention. Various changes may be made in the function and arrangement of elements without departing from the scope of the invention as set forth in the claims hereinafter. 
         [0053]    Where specific features, elements and steps referred to herein have known equivalents in the art to which the invention relates, such known equivalents are deemed to be incorporated herein as if individually set forth. Furthermore, features, elements and steps referred to in respect of particular embodiments may optionally form part of any of the other embodiments unless stated to the contrary. 
         [0054]    The term “comprising”, as used herein, is intended to have an open-ended, non-exclusive meaning. For example, the term is intended to mean: “including principally, but not necessarily solely” and not to mean “consisting essentially of” or “consisting only of”. Variations of the term “comprising”, such as “comprise”, “comprises” and “is comprised of”, have corresponding meanings.