Patent Abstract:
A motor-driven compressor according to the present invention is formed with a housing that contains a compression portion and a motor for compressing refrigerant. The compressor housing further is provided with a suction housing for introducing the refrigerant. A capacitor is provided for smoothing a current that is supplied from a power source to the motor. The capacitor is in contact with the suction housing. In such motor-driven compressors, because the capacitor is in contact with the suction housing, heat transfer from the capacitor to the housing may effectively be facilitated. In further embodiments of the present invention, the capacitors may be disposed on various portions of the suction housing and in various orientations relative to an axial direction of the motor-driven compressor. These selected orientations reduce the dimensions of the motor-driven compressor.

Full Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to motor-driven compressors used in vehicle air conditioning systems to compress refrigerant, and more particularly, to motor-driven compressors having a motor driven by a power supply, such as a battery. 
     2. Description of Related Art 
     Motor-driven compressors are known in the art. For example, Japanese Unexamined Patent Publication No. 2000-291557 describes a motor-driven compressor formed with a housing containing a compression portion and a motor for driving the compression portion to compress refrigerant. In this known motor-driven compressor, a drive circuit for controlling the operation of the motor is disposed adjacent to a suction port for refrigerant gas. In the drive circuit, a capacitor is included as one of the components of an inverter. The capacitor is provided to smooth, i.e., to reduce or eliminate, the alternating current component or ripple current of current supplied from a direct-current (DC) power supply to the motor. According to this known motor-driven compressor, a cooling device, such as a radiator, fan, water cooling radiator or water circulating pipes, is no longer necessary for cooling the drive circuit. 
     In the known motor-driven compressor, however, a high-frequency, ripple current flows through the capacitor, thereby increasing the heat generated in the capacitor. Moreover, the increase in heat generated in the capacitor by the ripple current may require an increase in the size of a capacitor used to handle the increased heat generated by such high-frequency, ripple current. The increased size of the capacitor may increase the cost of the capacitor. In addition, because the drive circuit may be manufactured separately and attached to the motor-driven compressor, the capacitor may extend from a housing of the motor-driven compressor. As a result, the size of the known motor-driven compressor with a built-in inverter may increase due to any increase in the size of the capacitor. 
     SUMMARY OF THE INVENTION 
     A need has arisen in motor-driven compressors that use capacitors for smoothing current supplied to the motor, to reduce the overall size of the motors. Further needs have arisen to reduce the manufacturing cost of such motor-driven compressors and to facilitate heat transfer from the capacitors. 
     In an embodiment of this invention, a motor-driven compressor comprises a housing containing a compression portion and a motor for driving the compression portion to compress refrigerant. The compressor housing further comprises a suction housing for introducing the refrigerant. A capacitor is provided for smoothing current supplied from a power source to the motor. The capacitor is disposed in contact with the suction housing. In further embodiments of this invention, the capacitor may be disposed on various portions of the suction housing and in one of a plurality of orientations relative to an axial direction of the motor-driven compressor. The selected orientations facilitate heat transfer and reduce the overall dimensions of the motor-driven compressor. 
    
    
     Other objects, features, and advantages of embodiments of this invention will be apparent to, and understood by, persons of ordinary skill in the art from the following detailed description of the invention and the accompanying drawings. 
     BRIEF DESCRIPTION OF DRAWINGS 
     The present invention may be more readily understood with reference to the following drawings. 
     FIG. 1 is a vertical, cross-sectional view of a motor-driven compressor, according to a first embodiment of the present invention. 
     FIG. 2 is a vertical, cross-sectional view of a motor-driven compressor, according to a second embodiment of the present invention. 
     FIG. 3 is a vertical, cross-sectional view of a motor-driven compressor, according to a third embodiment of the present invention. 
     FIG. 4 is a circuit diagram of a drive circuit for use in the motor-driven compressors depicted in FIGS. 1-3. 
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
     Referring to FIG. 1, a motor-driven compressor according to a first embodiment of the present invention is shown. A motor-driven compressor  10  has a discharge housing  11 , an intermediate housing  12 , and a suction housing  13 . Housings  11 ,  12 , and  13  may be made from a metal or a metal alloy, including aluminum or an aluminum alloy. Intermediate housing  12  and discharge housing  11  are connected by a plurality of fasteners, such as bolts  14   a.  Suction housing  13  and intermediate housing  12  are connected by a plurality of fasteners, such as bolts  14   b.  Thus, a common housing  15  comprises discharge housing  11 , intermediate housing  12 , and suction housing  13 . Discharge housing  11  has a discharge port  16  formed through an axial end surface. The compression portion comprises a fixed scroll member  17  and an orbiting scroll member  18 . Fixed scroll member  17  and orbiting scroll member  18  are provided in discharge housing  11 , so that both scroll members  17  and  18  interfit to form a refrigerant compression area  19 . 
     Fixed scroll member  17  includes an end plate  21 , a spiral element  22  provided on one surface of end plate  21 , and a securing portion  23  formed on another surface of end plate  21 . Securing portion  23  is fixed to an inner surface of a side wall of discharge housing  11  by a plurality of bolts  24 . Orbiting scroll member  18  includes an end plate  26 , a spiral element  27  provided on one surface of end plate  26 , and a cylindrical boss portion  28  projecting from another surface of end plate  26 . A rotation prevention mechanism  29  comprises a plurality of balls, each of which travels in a pair of rolling ball grooves formed in opposing ring-shaped races and is provided between a surface of end plate  26  and an axial end surface of intermediate housing  12 . Rotation prevention mechanism  29  prevents the rotation of orbiting scroll member  18 , but allows an orbital motion of orbiting scroll member  18  at a predetermined orbital radius with respect to a center of fixed scroll member  17 . Alternatively, an Oldham coupling may be used as the rotation prevention mechanism. 
     As shown in FIG. 1, a drive shaft  31  is disposed within intermediate housing  12  and suction housing  13 . One end portion of drive shaft  31  has a first portion  31  a with a diameter that is less than a diameter of a central portion of drive shaft  31 . Another end portion of drive shaft  31  has a second portion  31   b  with a diameter that is greater than the diameter of the central portion of drive shaft  31 . Suction housing  13  has a partition wall  32  at its axial middle portion. Partition wall  32  extends across a width of suction housing  13 . A cylindrical projecting portion  33  is provided on one surface of partition wall  32  to extend toward the compression area  19 . Reduced diameter first portion  31   a  is rotatably supported by projecting portion  33  via a bearing  34 . Increased diameter second portion  31   b  is rotatably supported by intermediate housing  12  via a bearing  39 . An eccentric pin  31   c  projects from an end surface of increased diameter second portion  31   b  in a direction along an axis of drive shaft  31 . Eccentric pin  31   c  is inserted into an eccentric bushing  42 , which is rotatably supported by boss portion  28  of orbiting scroll member  18  via a bearing  41 . 
     A motor  35  is disposed within intermediate housing  12  and suction housing  13 . Motor  35  comprises a stator  36 , a coil  37 , and a rotor  38 . Stator  36  is fixed on an inner surface of intermediate housing  12  and suction housing  13 . Coil  37  is provided around stator  36 . Rotor  38  is fixed on drive shaft  31 . 
     In motor-driven compressor  10 , a plurality of sealed terminals  43  are provided on an upper or left portion of partition wall  32  in suction housing  13 , as depicted in FIG. 1. A refrigerant suction port  44  is provided through an outer surface of a side wall of suction housing  13 . Suction housing  13  also includes an opening, which is located at an end of suction housing  13  away from intermediate housing  12 . The opening of suction housing  13  is covered by a lid  45 . Lid  45  is fixed to an axial end of suction housing  13  via a plurality of fasteners, such as bolts  49 . Lid  45  may be formed from a metal or a metal alloy, including aluminum or an aluminum alloy, as is used to form suction housing  13 . In addition, lid  45  may be formed from materials such as iron or magnetic materials. Preferably, lid  45  is made from a material capable of providing shielding against electromagnetic radiation. In addition, lid  45  protects electrical circuits provided within motor-driven compressor  10  from damage due to water and foreign materials. 
     A drive circuit  46  includes a control circuit  47  and an inverter  48 . Drive circuit  46  is provided on, and fixed to, a surface of partition wall  32  within suction housing  13 . Inverter  48  is connected to output terminals  43 . A capacitor chamber  50  for receiving a capacitor  51  is provided on an upper exterior wall of suction housing  13 . Capacitor  51 , which smoothes current sent or supplied to motor  35 , is inserted into capacitor chamber  50 . Thus, capacitor  51  is in contact, e.g., direct contact, with suction housing  13 . Capacitor  51  is connected to an external power source (not shown), such as a battery mounted on the vehicle, via a connector  52 , which is provided on an upper wall of suction housing  13 . Electric power is supplied to drive circuit  46  and other electrical components, via connector  52 . In this embodiment of motor-driven compressor  10 , because capacitor  51  is in contact with suction housing  13 , heat transfer from capacitor  51  to suction housing  13  may effectively be facilitated. 
     Referring to FIG. 2, a motor-driven compressor according to a second embodiment of the present invention is shown. In this embodiment, parts that are the same or substantially similar to those disclosed in the first embodiment of the motor compressor are designated by like numerals, and explanations thereof are omitted hereinafter. In this embodiment of motor-driven compressor  10 , a capacitor chamber  53  for receiving a capacitor  51  is formed at a lower portion of suction housing  13 , as depicted in FIG. 2, and opens along an axial direction of motor-driven compressor  10 . Capacitor  51  is inserted into capacitor chamber  53  along an axial direction of motor-driven compressor  10 . Thus, capacitor  51  is in contact, e.g., direct contact, with suction housing  13 . As a result, because capacitor  51  is in contact with suction housing  13 , heat transfer from capacitor  51  to suction housing  13  may effectively be facilitated. Moreover, because capacitor  51  is inserted into capacitor chamber  53  formed in an interior portion of suction housing  13 , a reduction of the dimensions of motor-driven compressor  10  may be achieved. Consequently, the manufacturing cost of motor-driven compressor  10  may be reduced, as well. 
     Referring to FIG. 3, a motor-driven compressor according to a third embodiment of the present invention is shown. In this embodiment of the present invention, parts that are the same or substantially similar as those disclosed in the first embodiment of the motor-driven compressor are designated by like numerals and explanations thereof are omitted hereinafter. In this embodiment of motor-driven compressor  10 , a capacitor chamber  54  for receiving a capacitor  51  is formed at a lower portion of suction housing  13 , as depicted in FIG. 3, and opens in a direction substantially transverse to an axial direction of motor-driven compressor  10 . Capacitor  51  is inserted into capacitor chamber  54 . Thus, capacitor  51  is in contact, e.g., direct contact, with suction housing  13 . As a result, because capacitor  51  is in contact with suction housing  13 , heat transfer from capacitor  51  to suction housing  13  may effectively be facilitated. Moreover, because capacitor  51  is inserted into capacitor chamber  54  formed in suction housing  13 , a reduction of the dimensions of motor-driven compressor  10  may be achieved. Consequently, the manufacturing cost of motor-driven compressor  10  may be reduced, as well. 
     FIG. 4 depicts the circuit structure of drive circuit  46  of motor-driven compressor  10 . Drive circuit  46  has a circuit structure similar to that disclosed in Japanese Unexamined Patent Publication No. H9-163791. Motor  35  may be a three-phase current motor and may comprise three coils  64   a,    64   b,  and  64   c  coupled to one another. Motor  35  may be, for example, a brushless motor. Motor  35  also may include a rotor  38  comprised of a permanent magnet and a stator  36  having coils  64   a,    64   b,  and  64   c.  In inverter  48 , a plurality of transistors  61   a,    61   b,    61   c ,  63   a,    63   b,  and  63   c  are provided. Transistors  61   a,    61   b,    61   c,    63   a,    63   b,  and  63   c  are coupled to control circuit  47 . Control circuit  47  controls a switching operation of transistors  61   a,    61   b,    61   c ,  63   a,    63   b,  and  63   c.    
     In inverter  48 , transistors  61   a ,  61   b ,  61   c ,  63   a ,  63   b , and  63   c  are divided into positive-side transistors  61   a ,  61   b , and  61   c , and negative-side transistors  63   a ,  63   b , and  63   c . Positive-side transistors  61   a ,  61   b , and  61   c  form upper arms, while negative-side transistors  63   a ,  63   b , and  63   c  form lower arms in inverter  48 . Both positive-side transistors  61   a ,  61   b , and  61   c  and negative-side transistors  63   a ,  63   b , and  63   c  are coupled to an external DC power source  65 , which may comprise a battery, via a capacitor  51 . 
     Further, diodes  66   a ,  66   b ,  66   c ,  67   a ,  67   b , and  67   c  are coupled between the emitters and the collectors of transistors  61   a ,  61   b ,  61   c ,  63   a ,  63   b , and  63   c , respectively. Diodes  66   a ,  66   b ,  66   c ,  67   a ,  67   b , and  67   c  return a counter-current generated by three-phase motor  35  to DC power source  65 . Specifically, when the operation of motor  35  is stopped, or when the chopping (i.e., cutting a peak or a bottom of a wave, or both) of the pulse code modulation is deactivated, diodes  66   a ,  66   b ,  66   c ,  67   a ,  67   b , and  67   c  cause a counter-electromotive force, generated from coils  64   a ,  64   b , and  64   c  of motor  35 , to be applied to DC power source  65 . Usually, the internal capacitance of each of diodes  66   a ,  66   b ,  66   c ,  67   a ,  67   b , and  67   c  is set at the same internal capacitance as each of corresponding transistors  61   a ,  61   b ,  61   c ,  63   a ,  63   b , and  63   c.  Moreover, diodes  66   a ,  66   b ,  66   c ,  67   a ,  67   b , and  67   c  protect transistors  61   a ,  61   b ,  61   c ,  63   a ,  63   b , and  63   c  from damage due to counter-electromotive forces. 
     Moreover, each of the base sides of transistors  61   a ,  61   b ,  61   c ,  63   a ,  63   b , and  63   c  is coupled to control circuit  47 . The collector sides of upper arms (i.e., transistors  61   a ,  61   b , and  61   c ) and the emitter sides of lower arms (i.e., transistors  63   a ,  63   b , and  63   c ) are coupled to DC power source  65  for supplying power to the transistors. Capacitor  51  is coupled between the poles of DC power source  65  for smoothing the current supplied to motor  35 . 
     In operation, control circuit  47  sends control signals to transistors  61   a ,  61   b ,  61   c ,  63   a ,  63   b , and  63   c.  When motor-driven compressor  10  is to be stopped, the switching operations of transistors  61   a ,  61   b ,  61   c ,  63   a ,  63   b , and  63   c  first are briefly deactivated. After that, while the upper arms (i.e., transistors  61   a ,  61   b , and  61   c ) are maintained in a deactivated condition, the lower arms (i.e., transistors  63   a ,  63   b , and  63   c ) are activated for a time period that is not less than a predetermined period. By this procedure, operation of motor-driven compressor  10  is stopped completely and smoothly. 
     In inverter  48 , when motor-driven compressor  10  is operated under normal operating conditions, the transistors  61   a ,  61   b ,  61   c ,  63   a ,  63   b , and  63   c  receive control signals from control circuit  47 , and inverter  48  converts the DC current supplied by DC power source  65  into a three-phase current at a suitable phase differentiation for operating motor  35 . The three-phase current is supplied to motor  35 . 
     As described above, in a motor-driven compressor according to various embodiments of the present invention, because a capacitor is in contact with a suction housing, heat transfer from the capacitor may effectively be facilitated. Moreover, the overall dimensions of the motor-driven compressor may be reduced. In addition, the manufacturing cost of the motor-driven compressor may be reduced. 
     Although the present invention has been described in connection with preferred embodiments, the invention is not limited thereto. It will be understood by those skilled in the art that other embodiments, variations, and modifications of the invention will be apparent to those skilled in the art from a consideration of this specification or practice of the invention disclosed herein, and may be made within the scope and spirit of this invention, as defined by the following claims.

Technology Classification (CPC): 5