Patent Publication Number: US-2011058962-A1

Title: Compressor for use in a vehicle

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates to a compressor for use in a vehicle. 
     In vehicle air conditioners, mechanically driven compressors are widely used. Such compressor includes a casing having therein a suction chamber and a discharge chamber and rotatably supporting a drive shaft. The drive shaft is rotated by a drive source such as an engine, and the piston of the compressor is reciprocated to compress refrigerant. 
     However, when such type of compressor is used in a vehicle equipped with an idling stop function that automatically stops the drive source while the vehicle is at a stop so as to meet the recent requirement of carbon dioxide emission regulations, no compression is performed by the compressor, resulting in reduced air conditioning performance. To solve this problem, a vehicle air conditioner including not only a mechanical compressor but also with an electric compressor is proposed in Japanese Unexamined Patent Application Publications No. 9-295510, No. 2003-341334 and No. 2004-237907. In the air conditioner, the electric compressor is operated while the drive source is stopped, which prevents reduction of air conditioning performance. 
     However, such use of the plural compressors makes it difficult to install the air conditioner in the vehicle. Specifically, in conventional vehicles, particularly in small vehicles that are intended to be equipped with a single compressor for air conditioning, the provision of an installation space for plural compressors is quite difficult. 
     The present invention is directed to providing a compressor that allows air conditioning while a drive source is at a stop and also easy installation in a vehicle. 
     SUMMARY OF THE INVENTION 
     In accordance with an aspect of the present invention, a compressor for use in a vehicle includes a mechanical compression mechanism including a first casing and a drive shaft. The first casing has therein a first suction chamber and a first discharge chamber. The drive shaft is rotatably supported by the first casing and mechanically driven by a drive source for compression of refrigerant. The compressor further includes a linear electric compression mechanism including a second casing and a piston. The second, casing has therein a second suction chamber and a second discharge chamber. The piston is reciprocally movable in the second casing and driven by electromagnetic force for compression of refrigerant. The first casing is integrated with the second casing so as to allow at least one of fluid communication between the first suction chamber and the second suction chamber and between the first discharge chamber and the second discharge chamber. 
     Other aspects and advantages of the invention will become apparent from the following description, taken in conjunction with the accompanying drawings, illustrating by way of example the principles of the invention. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a longitudinal sectional view of a compressor according to a first embodiment of the present invention; 
         FIG. 2  is a schematic view of a vehicle air conditioner using the compressor of  FIG. 1 ; 
         FIG. 3  is an enlarged sectional view of a linear electric compression mechanism of the compressor of  FIG. 1 ; 
         FIG. 4  is an enlarged fragmentary sectional view of the linear compression mechanism of  FIG. 3 ; 
         FIG. 5  is a schematic view of an arrangement of coils and permanent magnets of the linear electric compression mechanism of  FIGS. 3 and 4 ; 
         FIG. 6  is a longitudinal sectional view of a compressor according to a second embodiment of the present invention; and 
         FIG. 7  is an enlarged fragmentary sectional view of a linear electric compression mechanism of the compressor of  FIG. 6 . 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The following will describe the embodiments of the compressor according to the present invention with reference to the accompanying drawings. In the embodiments, the compressor is intended to be used in a vehicle air conditioner for a hybrid vehicle or electric vehicle equipped with an idling stop system. 
     Referring to  FIGS. 1 and 2 , the compressor of the first embodiment includes a mechanical compression mechanism  200  and a linear electric compression mechanism  100 . The mechanical compression mechanism  200  is of a swash plate type and driven by an engine  212  (drive source) to compress refrigerant. The linear electric compression mechanism  100  is driven by an electric power supply  110  to compress refrigerant. 
     As shown in  FIG. 1 , the mechanical compression mechanism  200  has a first cylinder block  201  formed with plural cylinder bores  201 A (only one is shown) extending parallel to one another and arranged circularly around the axis of the first cylinder block  201  at regular intervals. The first cylinder block  201  is disposed between a front housing  203  and a rear housing  205  and fastened thereto. The first cylinder block  201  cooperates with the front housing  203  to form therebetween a crank chamber  209 . 
     The rear housing  205  is formed with a shell  5  that is a component of the linear electric compression mechanism  100 . The rear housing  205  has a first suction chamber  205 A and an annular first discharge chamber  206  formed therein. The first suction chamber  205 A is located in the center of the rear housing  205 , and the first discharge chamber  206  is located radially outward of the first suction chamber  205 A. The rear housing  205  is formed therethrough with an outlet port  208 , a first discharge passage  205 B and a second discharge passage  205 C each communicating with the first discharge chamber  206 . 
     The first suction chamber  205 A is connected through an inlet port  5 A to a pipe  102  (see  FIG. 2 ). The first discharge chamber  206  is connected through the outlet port  208  to a pipe  101  (see  FIG. 2 ). The rear housing  205  serves as the first housing of the present invention. The first cylinder block  201  cooperates with the front housing  203  and the rear housing  205  to form a first casing  250 . 
     As shown in  FIG. 1 , the front housing  203  and the first cylinder block  201  have shaft holes  203 A and  201 B, respectively, by which a drive shaft  211  is rotatably supported through a shaft seal  209 A and bearings  209 B and  209 C. The drive shaft  211  is connected to a pulley  210  engaged over a belt  212 A that is driven by the engine  212  (see  FIG. 2 ). The pulley  210  may be replaced with an electromagnetic clutch. 
     In the crank chamber  209 , the drive shaft  211  is fixed to a lug plate  213  by press fitting, and a bearing  215  is provided between the lug plate  213  and the front housing  203 . The drive shaft  211  is inserted in a swash plate  217 . The lug plate  213  is connected to the swash plate  217  through a link mechanism  219  that allows the swash plate  217  to be inclined relative to the drive shaft  211 . 
     Each cylinder bore  201 A of the first cylinder block  201  receives a piston  221  reciprocally movable therein. A valve unit  223  is provided between the first cylinder block  210  and the rear housing  205 . The piston  221  in each cylinder bore  201 A cooperates with the valve unit  223  to form a compression chamber  222  therebetween. When the piston  221  is in the suction stroke, refrigerant is introduced from the first suction chamber  205 A through the valve unit  223  into the compression chamber  222 . The refrigerant is compressed in the compression chamber  222  when the piston  221  is in the compression stroke, and then discharged through the valve unit  223  into the first discharge chamber  206  when the piston  221  is in the discharge stroke. 
     Each piston  221  is connected to the swash plate  217  through a pair of shoes  233  by which oscillating motion of the swash plate  217  is converted into reciprocating motion of the piston  221 . 
     Although not shown in the drawings, the crank chamber  209  and the first suction chamber  205 A are connected through a bleed passage, and the crank chamber  209  and the first discharge chamber  206  are connected through a supply passage provided with a control valve for controlling the displacement of the mechanical compression mechanism  200 . 
     Referring to  FIG. 3 , the linear electric compression mechanism  100  includes second cylinder blocks  1 ,  3 , the shell  5  and a center housing  7 , which cooperate to form a second housing  9  of the linear electric compression mechanism  100 . The second cylinder blocks  1 ,  3  have a first cylinder bore  1 A and a second cylinder bore  3 A formed therethrough, respectively. The first and second cylinder bores  1 A,  3 A are substantially concentric with each other and have substantially the same diameter. The shell  5  is formed therethrough with the inlet port  5 A described above. 
     The second cylinder blocks  1 ,  3  have flanges  1 B,  3 B around the first and second cylinder bores  1 A,  3 A, respectively. The second cylinder blocks  1 ,  3  are accommodated in the shell  5  so that the flanges  1 B,  3 B are located at opposite ends of the shell  5 . The center housing  7  is provided in the shell  5  between the second cylinder blocks  1 ,  3 . The center housing  7  has a bore  7 A (cylinder bore) which is substantially concentric with the first and second cylinder bores  1 A,  3 A and whose diameter is substantially the same as those of the first and second cylinder bores  1 A,  3 A. 
     A first and a second end plates  11 ,  13  are mounted to the opposite ends of the shell  5  through a first and a second gaskets  10 ,  12 , respectively. The first and second end plates  11 ,  13  cooperate with the second housing  9  to form the second casing of the present invention. The first and second end plates  11 ,  13  have recesses formed therein. A first valve plate  15  is held between the first gasket  10  and the first end plate  11 , and a second valve plate  17  is held between the second gasket  12  and the second end plate  13 . The first and second end plates  11 ,  13  cooperate with the first and second valve plates  15 ,  17  to form therebetween second discharge chambers  14 ,  16 , respectively. As shown in  FIG. 1 , the second discharge chamber  14  communicates with the first discharge chamber  206  in facing relation to each other through the second discharge passage  205 C, and the second discharge chamber  16  communicates with the first discharge passage  206  in facing relation to each other through the first discharge passage  205 B. 
     Referring to  FIGS. 3 and 4 , the first valve plate  15  is formed therethrough with a discharge port  15 A. A reed type discharge valve  19  for the discharge port  15 A and a retainer  21  for restricting the opening of the discharge valve  19  are fixed by a rivet  23  to the first valve plate  15  on the side of the second discharge chamber  14 . The first valve plate  15 , the discharge valve  19 , the retainer  21  and the rivet  23  cooperate to form a first valve unit  25 . A valve unit for the second valve plate  17  is formed similarly. 
     As shown in  FIG. 3 , the first and second cylinder bores  1 A,  3 A and the bore  7 A receive a piston  27  reciprocally movable therein. The piston  27  includes a piston rod  29 , a first piston head  31  provided at one end of the piston rod  29  so as to slide in the first cylinder bore  1 A, and a second piston head  33  provided at the other end of the piston rod  29  so as to slide in the second cylinder bore  3 A. 
     As shown in  FIGS. 4 and 5 , the first piston head  31  includes a head  39 , a first spacer  41 , and a second spacer  43 . Permanent magnets  35 ,  37  are mounted on the outer surface of the head  39 . The first and second spacers  41 ,  43  are provided on the head  39  so as to space the outer surfaces of the permanent magnets  35 ,  37  from the inner surface of the first cylinder bore  1 A. 
     As shown in  FIG. 5 , the permanent magnets  35 ,  37  are ring shaped and provided by a rare-earth magnet. The permanent magnet  35  has the north pole and the south poles on the outer peripheral side and inner peripheral side of the ring-shaped magnet, respectively, while the permanent magnet  37  has the south pole and the north poles on the outer peripheral side and inner peripheral side of the ring-shaped magnet, respectively. The polar character of the permanent magnets  35 ,  37  may be reversed. 
     In installing the permanent magnets  37 ,  35 , firstly the second spacer  43  is press fit on the head  39 , the permanent magnets  37 ,  35  are press fit on the outer surface of the head  39 , and then the first spacer  41  is press fit on the outer surface of the head  39 , as shown in  FIG. 4 . The permanent magnets  35 ,  37  are thus held securely on the outer surface of the head  39  between the first and second spacers  41 ,  43 . The piston head  31  cooperates with the first valve unit  25  to form a compression chamber  45  therebetween. 
     The head  39  is formed therethrough with a suction port  39 A. The first spacer  41  is formed therethrough with a valve hole  41 A that is communicable with the suction port  39 A and receives therein a float type suction valve  47 . The valve hole  41 A has a stop  41 B on the side of the compression chamber  45 . The suction valve  47  has on the outer periphery thereof plural engaging portions  47 A that are brought into contact with the stop  41 B when the suction port  39 A is opened. A cutout  47 B is formed between any two adjacent engaging portions  47 A. 
     As shown in  FIG. 3 , the first and second piston heads  31 ,  33  are press fit on the opposite ends of the piston rod  29 . The piston rod  29  has a diameter that is smaller than those of the first and second piston heads  31 ,  33 . The piston rod  29  is formed therethrough with a suction passage  29 A. The suction passage  29 A includes also radially extending passages in the center of the piston rod  29  so as to open at the outer peripheral surface of the piston rod  29 . As shown in  FIG. 4 , the suction passage  29 A communicates with the suction port  39 A of the first piston head  31 . The suction passage  29 A, the suction port  39 A, the suction valve  47  and the first spacer  41  cooperate to form a suction valve mechanism  50 . A suction valve mechanism for the second piston head  33  is formed similarly. 
     As shown in  FIG. 3 , the center housing  7  has a spring seat  7 B in the bore  7 A. The spring seat  7 B projects radially inward from the inner surface of the bore  7 A at the center between the opposite end surfaces of the second cylinder blocks  1 ,  3 . The space between the inner surface of the bore  7 A and the outer surface of the piston rod  29  forms a spring space  7 C where a first coil spring  41  and a second coil spring  51  are accommodated. 
     The first coil spring  49  is preloaded with one end thereof in contact with the spring seat  7 B and the other end thereof in contact with the second spacer  43  of the first piston head  31 . The second coil spring  51  is preloaded with one end thereof in contact with the spring seat  7 B and the other end thereof in contact with the second spacer of the second piston head  33 . 
     The center housing  7  and the shell  5  form an intermediate chamber  53  therebetween. The center housing  7  is formed therethrough with a communication hole  7 D through which the intermediate chamber  53  communicates with the spring space  7 C. The intermediate chamber  53  and the spring space  7 C cooperate to form a second suction chamber  55  that communicates with the first suction chamber  205 A (see  FIG. 1 ) in facing relation to each other through the communication hole  7 D. Although not shown in the drawings, terminals connected to coils  63 A,  63 B,  65 A,  65 B, which will be described later, are mounted in the second suction chamber  55 . 
     The coils  63 A,  63 B are provided between the shell  5  and the second cylinder block  1 . The coils  63 A,  63 B are held by a first holder  59  so as to surround the first piston head  31 . Similarly, the coils  65 A,  65 B are provided between the shell  5  and the second cylinder block  3 . The coils  65 A,  65 B are held by a second holder  61  so as to surround the second piston head  33 . The second cylinder blocks  1 ,  3  and the first and second holders  59 ,  61  are made of a magnetic material. The second cylinder blocks  1 ,  3  may be made of a nonmagnetic material. 
     As shown in  FIG. 2 , the linear electric compression mechanism  100  is connected through the pipes  101 ,  103  to a condenser  105 . The condenser  105  is connected through an expansion valve  107  and an evaporator  108  to a pipe  102  that is connected to the inlet port  5 A (see  FIG. 3 ). The terminals in the intermediate chamber  53  are connected to the electric power supply  110  through a lead wire  109 . The electric power supply  110  is electrically controlled by a controller (not shown). 
     In the above-described compressor, when the engine  212  is operating and vehicle is running, the drive shaft  211  of the mechanical compression mechanism  200  is rotated, and the lug plate  213  and the swash plate  217  are rotated integrally with the drive shaft  211 . The pistons  221  are reciprocated in the respective cylinder bores  201 A at a stroke depending on the inclination angle of the swash plate  217 , and refrigerant in the first suction chamber  205 A is introduced into the compression chambers  222  and compressed therein. After being discharged into the first discharge chamber  206 , the refrigerant is delivered out of the compressor and then through the pipes  101 ,  103  to the condenser  105 , the expansion valve  107  and the evaporator  108 . Thus air conditioning of the vehicle compartment by the mechanical compression mechanism  200  is accomplished. 
     When the vehicle is stopped at a traffic light, the engine speed is reduced to an idling speed and then the engine  212  is stopped. In this case, the electric power supply  110  periodically supplies electric power to the coils  63 A,  63 B,  65 A,  65 B of the linear electric compression mechanism  100  thereby to generate periodically variable electromagnetic force around the coils  63 A,  63 B,  65 A,  65 B. Referring to  FIG. 5 , when the coil  63 A attracts the permanent magnet  35  of the first piston head  31 , magnetic repulsion is produced between the coil  63 B and the permanent magnet  37  of the first piston head  31 . On the other hand, when magnetic repulsion is produced between the coil  63 A and the permanent magnet  35  of the first piston head  31 , the coil  63 B attracts the permanent magnet  37  of the first piston head  31 . Thus, the linear electric compression mechanism  100  can provide a large thrust force to reciprocate the piston  27 . 
     Thus, the permanent magnets  35 ,  37  of the piston  27  are attracted and repelled by electromagnetic force generated by the coils  63 A,  63 B,  65 A,  65 B, so that the piston  27  is reciprocated in the first and second cylinder bores  1 A,  3 A. In this case, the resonance of the first and second coil springs  49 ,  51  oscillating at the natural frequency serves to reciprocate the piston  27 . 
     Strokes of suction, compression and discharge of refrigerant are accomplished by the reciprocating movement of the piston  27 . As shown in  FIG. 4 , when the first piston head  31  is in the suction stroke, the pressure in the compression chamber  45  is reduced and, accordingly, the suction valve  47  is moved within the valve hole  41 A so as to open the suction port  39 A. Refrigerant in the second suction chamber  55  (see  FIG. 3 ) is introduced from the suction port  39 A into the compression chamber  45  through the clearances between the cutouts  47 B of the suction valve  47  and the stop  41 B. The discharge port  15 A is closed by the discharge valve  19 . 
     When the first piston head  31  begins the compression stroke, the suction valve  47  is moved within the valve hole  41 A so as to close the suction port  39 A, and the pressure in the compression chamber  45  is increased thereby to open the discharge valve  19 . That is, the first piston head  31  begins the discharge stroke and the compressed refrigerant is discharged through the discharge port  15 A into the second discharge chamber  14 . Though the temperature of refrigerant in the second discharge chamber  14  is high, the first gasket  10  provided between the first end plate  11  and the second cylinder block  1  prevents the piston  27  from being exposed directly to the second discharge chamber  14 . Thus, the piston  27  is hardly affected by the heat of the refrigerant in the second discharge chamber  14 . The same is true of the second piston head  33  side 
     Referring to  FIG. 2 , refrigerant flowing out from the evaporator  108  into the pipe  102  is introduced through the second suction chamber  55  into the compression chamber  45  of the linear electric compression mechanism  100 . Refrigerant is compressed in the compression chamber  45 , discharged into the second discharge chambers  14 ,  16 , and then delivered through the pipes  101 ,  103  to the condenser  105 . Thus air conditioning of the vehicle compartment by the linear electric compression mechanism  100  is accomplished. 
     The linear electric compression mechanism  100  in which the compression chambers  45  are formed at the opposite ends of the piston  27  can compress refrigerant twice by a single reciprocating movement of the piston  27 , which increases the efficiency of compression of refrigerant per unit time while reducing the size of the compressor. Thus, the compressor according to the present embodiment allows easy installation in a vehicle while achieving high air conditioning performance. 
     In addition, the rear housing  205  is integrated with the shell  5  so as to allow fluid communication between the first suction chamber  205 A and the second suction chamber  55  and between the first discharge chamber  206  and the second discharge chambers  14 ,  16 . In this case, the interior space of the compressor is shared by the mechanical compression mechanism  200  and the linear electric compression mechanism  100 , which allows reduction in the size of the compressor and easy installation of the compressor in a vehicle, as compared to the case where the interior space of the compressor is not shared by the compression mechanisms  200  and  100 . 
     Thus, the compressor according the present embodiment allows air conditioning while a drive source is at a stop and also easy installation in a vehicle. 
     The integration of the rear housing  205  with the shell  5  allows easier management of compressor parts and components and results in reduced manufacturing cost. 
     Particularly in the present embodiment, the inlet port  5 A through which the first and second suction chambers  205 A,  55  communicate with the outside, that is, the inlet port  5 A for introducing refrigerant into the compressor is shared by the mechanical compression mechanism  200  and the linear electric compression mechanism  100 . Similarly, the outlet port  208  through which the first and second discharge chambers  206 ,  14 ,  16  communicate with the outside, that is, the outlet port  208  for discharging refrigerant out of the compressor is also shared by the mechanisms  100 ,  200 . In such a case, since the inlet port  5 A communicates with the first and second suction chambers  205 A,  55  and the outlet port  208  communicates with the first and second discharge chambers  206 ,  14 ,  16 , refrigerant is introduced though the common inlet port  5 A into the first and second suction chambers  205 A,  55  and discharged from the first and second discharge chambers  206 ,  14 ,  16  through the common outlet port  208  out of the compressor. The connection of the pipes  101 ,  102  to the compressor can be simplified, thereby allowing easier installation of the compressor in a vehicle. 
     In the present embodiment, the rear housing  205  has the first suction chamber  205 A in the center thereof, that is, in a position axially extended from the end of the drive shaft  211 , and the first discharge chamber  206  in a position radially outward of the first suction chamber  205 A. The second discharge chambers  14 ,  16  are located at the opposite ends of the second housing  9 . The rear housing  205  is integrated with the shell  5  so that the axis of the drive shaft  211  is perpendicular to the axis of the piston rod  29 . In such a case, the components of the linear electric compression mechanism  100  are aligned in the radial direction of the mechanical compression mechanism  200 , so that the mechanisms  100  and  200  are integrated neatly. 
     In the linear electric compression mechanism  100 , the intermediate chamber  53  is formed between the shell  5  and the second cylinder blocks  1 ,  3 . The first valve units  25  cooperate with the first and second end plates  11 ,  13  to form therebetween the second discharge chambers  14 ,  16 , respectively, and the suction valve mechanisms  50  are provided in the respective first and second piston heads  31 ,  33 . The spring space  7 C, which is a part of the second suction chamber  55 , and the suction passage  29 A are formed in the piston  27 . In such a case, the piston  27  can be made lighter, and the linear electric compression mechanism  100  can be made smaller while achieving high efficiency of compression of refrigerant. 
     The diameter of the piston rod  29  is smaller than that of the first and second piston heads  31 ,  33 . The center housing  7  has the spring seat  7 B, and the first and second coil springs  49 ,  51  are provided between the spring seat  7 B and the respective piston heads  31 ,  33 . This allows the linear electric compression mechanism  100  to dispense with a means such as a spring in the compression chamber  45 , thereby increasing the volume of the compression chamber  45 . Further, the diameter of the first and second coil springs  49 ,  51  does not become larger than that of the first and second piston heads  31 ,  33  and, therefore, the linear electric compression mechanism  100  can be made smaller while achieving high efficiency of compression of refrigerant. 
     The linear electric compression mechanism  100 , in which the second housing  9  is formed by the second cylinder blocks  1 ,  3  and the shell  5 , allows easy installation of the coils  63 A,  63 B,  65 A,  65 B between the second cylinder blocks  1 ,  3  and the shell  5 , which facilitates assembling of the linear electric compression mechanism  100 . 
       FIGS. 6 and 7  show the second embodiment of the present invention. In the drawings, same reference numerals are used for the common elements or components in the first and second embodiments, and the description of such elements or components for the second embodiment will be omitted. 
     As shown in  FIG. 7 , the linear electric compression mechanism  150  includes a second cylinder block  71  and a shell  73  which cooperate to form a second housing  70  of the linear electric compression mechanism  150 . The second cylinder block  71  has a cylinder bore  71 A formed therethrough. 
     The shell  73  is located radially outward of the second cylinder block  71 . A first and a second end plates  75 ,  77  are mounted to the opposite ends of the shell  73  and the second cylinder block  71 . The first and second end plates  75 ,  77  cooperate with the second housing  70  to form the second casing of the present invention. The first and second end plates  75 ,  77  have recesses formed therein. A first valve unit  79  is held between the second cylinder block  71  and the first end plate  75 , and a second valve unit  81  is held between the second cylinder block  71  and the second end plate  77 . The first and second end plates  75 ,  77  cooperate with the first and second valve units  79 ,  81  to form therebetween second discharge chambers  76 ,  78 , respectively. The second discharge chambers  76 ,  78  are connected through a discharge passage (not shown). 
     The first valve unit  79  includes a first valve plate  79 A and a reed type discharge valve  79 B. The first valve plate  79 A is formed therethrough with a discharge port  79 C that is opened and closed by the discharge valve  79 B. The structure of the second valve unit  81  is similar to that of the first valve unit  79 . 
     The cylinder bore  71 A receives a piston  83  reciprocally movable therein. The piston  83  includes a piston rod  83 A, a first piston head  83 B provided at one end of the piston rod  83 A so as to slide in the cylinder bore  71 A, and a second piston head  83 C provided at the other end of the piston rod  83 A so as to slide in the cylinder bore  71 A. 
     The piston rod  83 A has a diameter that is smaller than those of the first and second piston heads  83 B,  83 C. The piston rod  83 A is a permanent magnet provided by a rare-earth magnet and having the north pole on one end and the south pole on the other end. The piston rod  83 A may have the south pole on one end and the north pole on the other end. The first piston head  83 B cooperates with the first valve unit  79  to form a compression chamber  85  therebetween, and similarly the second piston head  83 C cooperates with the second valve unit  81  to form a compression chamber  85  therebetween 
     The first piston head  83 B is formed therethrough with plural suction ports  83 D, and a reed type suction valve  83 E for the suction ports  83 D is mounted to the first piston head  83 B on the side of the compression chamber  85 . The suction ports  83 D and the suction valve  83 E cooperate to form a suction valve mechanism  80 . A suction valve mechanism of the second piston head  83 C is formed similarly. 
     The second cylinder block  71  has a spring seat  71 B in the cylinder bore. The spring seat  71 B projects radially inward from the inner surface of the cylinder bore  71 A at the center between the opposite end surfaces. The space between the inner surface of the cylinder bore  71 A and the outer surface of the piston rod  83 A forms an intermediate chamber  86  where a first and a second coil springs  87 ,  89  are accommodated. 
     The first coil spring  87  is preloaded with one end thereof in contact with the spring seat  71 B and the other end thereof in contact with the first piston head  83 B. The second coil spring  89  is preloaded with one end thereof in contact with the spring seat  71 B and the other end thereof in contact with the second piston head  83 C. 
     The space between the second cylinder block  71  and the shell  73  forms a suction passage  73 A in which a coil  91  is provided. Although not shown in the drawings, the coil  91  is connected through the terminal and the lead wire to the electric power supply. The second cylinder block  71  is formed therethrough with plural suction ports  71 C through which the intermediate chamber  86  in the cylinder bore  71 A communicates with the suction passage  73 A. The intermediate chamber  86  and the suction passage  73 A cooperate to form a second suction chamber  93 . The shell  73  is formed therethrough with an inlet port  73 B communicating with the suction passage  73 A. 
     As shown in  FIG. 6 , the shell  73  of the linear electric compression mechanism  150  is formed by part of the first cylinder block  202  of the mechanical compression mechanism  200 . The second end plate  77  of the linear electric compression mechanism  150  is formed by part of the front housing  204  of the mechanical compression mechanism  200 , and the first end plate  75  of the linear electric compression mechanism  150  is formed by part of the rear housing  207  of the mechanical compression mechanism  200 . The second housing  70  is located radially outward of the first cylinder block  202  (cylinder block), the second end plate  77  is integrated with the front housing  204  (first casing), and the first end plate  75  is integrated with the rear housing  207  (first housing). 
     The inlet port  205 D of the mechanical compression mechanism  200  and the inlet port  73 B of the linear electric compression mechanism  150  are connected to the evaporator  108  through a pipe (not shown). The second discharge chamber  76  of the linear electric compression mechanism  150  is connected through the discharge passage  75 C to the first discharge chamber  206  of the mechanical compression mechanism  200 . The outlet port  208 B is connected to the condenser  105  through a pipe (not shown). In the second embodiment, the first cylinder block  202  is integrated with the shell  73  so as to allow fluid communication between the first discharge chamber  206  and the second discharge chambers  76 ,  78 . The outlet port  208 B communicates with the first and second discharge chambers  206 ,  76 ,  78  so that the outlet port  208 B is shared by the mechanical compression mechanism  200  and the linear electric compression mechanism  150 . 
     According to the second embodiment, the first cylinder block  202  is integrated with the shell  73  so that the axis of the drive shaft  211  is parallel to the axis of the piston rod  83 A. In such a case, the components of the linear electric compression mechanism  150  are aligned in the axial direction of the mechanical compression mechanism  200 , so that the mechanisms  150  and  200  are integrated neatly. In addition, the integration of components such as the first cylinder block  202 , the shell  73 , the front and rear housings  204 ,  207 , and the first and second end plates  75 ,  77  allows easier management of compressor parts and components and results in reduced manufacturing cost. The second embodiment also offers the advantages similar to those of the first embodiment. 
     The above embodiments may be modified in various ways as exemplified below. 
     The mechanical compression mechanism  200  may be of a vane type or a scroll type. The drive source includes not only a general internal combustion engine but also a hybrid engine or an electric motor. 
     The present invention is applicable not only to a hybrid vehicle or an electric vehicle with electric motor but also an engine powered vehicle.