Patent Publication Number: US-2009238698-A1

Title: Reciprocal Compressor

Description:
TECHNICAL FIELD 
     The present invention relates to a reciprocal compressor. 
     BACKGROUND ART 
     Patent document 1 discloses a reciprocal compressor comprising a rotation shaft, a motion converter for converting rotation to reciprocal motion, pistons driven by the rotation shaft through the motion converter to move reciprocally, a cylinder block provided with cylinder bores in which the pistons are inserted and a center bore in which one end of the rotation shaft is inserted, a valve plate provided with suction holes, discharge holes, suction valves for closing the suction holes and discharge valves for closing the discharge holes and disposed opposite one end of the cylinder block, and a rear housing provided with a suction chamber communicating with the cylinder bores through the suction holes and the suction valves and a discharge chamber communicating with the cylinder bores through the discharge valves and the discharge holes, wherein the cylinder bores are circumferentially distanced from each other, and the cylinder block is provided with a secondary discharge chamber which is located closer to the valve plate than the center bore to communicate with the discharge chamber through an opening formed in the valve plate. 
     In accordance with the reciprocal compressor of patent document 1, the volume of the discharge chamber increases to decrease pulsation of discharge pressure caused by refrigerant gas discharging from the cylinder bores to the discharge chamber, thereby decreasing noise of the compressor. 
     Patent document 1: Japanese Patent Laid-Open Publication No. 7-77157 
     DISCLOSURE OF INVENTION 
     Problems to be Solved 
     The reciprocal compressor of patent document 1 has a problem in that the secondary discharge chamber is complicated in structure and troublesome to produce because it is formed by a center cylindrical portion coaxial to the center bore and radial arm portions extending from the center cylindrical portion and located between the cylinder bores. 
     The center bore of the reciprocal compressor of patent document 1 extends only to the longitudinal middle of the cylinder block. However, such kind of reciprocal compressor also has been used, wherein the center bore extends to one end of the cylinder block adjacent the valve plate and an adjust member is screwed in the center bore to adjust the longitudinal position of the rotation shaft. When the technical concept of the cylinder block being provided with the secondary discharge chamber, which is the technical concept of patent document 1, is applied to the aforementioned reciprocal compressor, the portion of the center bore closer to the valve plate than the adjust member is communicated with the discharge chamber through the opening formed in the valve plate to increase the volume of the discharge chamber. However, if the portion of the center bore closer to the valve plate than the adjust member is communicated with the discharge chamber through the opening formed in the valve plate, a crank chamber accommodating the rotation shaft and the motion converter communicates with the discharge chamber through the center bore because the portion of the center bore more distant from the valve plate than the adjust member communicates with the portion of the center bore closer to the valve plate than the adjust member through threaded portion of the adjust member. As a result, operation of the reciprocal compressor is impaired. 
     An object of the present invention is to provide a reciprocal compressor wherein a cylinder block is provided with a void space communicating with a discharge chamber to increase the volume of the discharge chamber and which can resolve the problem of the reciprocal compressor of patent document 1. 
     Means for Solving the Problems 
     In accordance with the present invention, there is provided a reciprocal compressor comprising a rotation shaft, a motion converter for converting rotation to reciprocal motion, pistons driven by the rotation shaft through the motion converter to move reciprocally, a cylinder block provided with cylinder bores in which the pistons are inserted and a center bore in which one end of the rotation shaft is inserted, a valve plate provided with suction holes, discharge holes, suction valves for closing the suction holes and discharge valves for closing the discharge holes and disposed opposite one end of the cylinder block, and a rear housing provided with a suction chamber communicating with the cylinder bores through the suction holes and the suction valves and a discharge chamber communicating with the cylinder bores through the discharge valves and the discharge holes and disposed opposite the valve plate, wherein the cylinder bores are circumferentially distanced from each other, and the cylinder block is provided with a group of secondary discharge chambers which are located closer to the valve plate than the center bore to communicate with the discharge chamber through openings formed in the valve plate, and wherein the group of secondary discharge chambers comprises a center secondary discharge chamber adjacent the center bore, and a plurality of satellite secondary discharge chambers located radially outside the center secondary discharge chamber, circumferentially distanced from each other, and located between the cylinder bores, and each of the secondary discharge chambers communicates with the discharge chamber through the opening formed in the valve plate. 
     In the reciprocal compressor of the present invention, the secondary discharge chamber is formed not by a center cylindrical portion coaxial to the center bore and radial arm portions extending from the center cylindrical portion and located between the cylinder bores but by a center secondary discharge chamber adjacent the center bore and a plurality of satellite discharge chambers located radially outside the center secondary discharge chamber, circumferentially distanced from each other and located between the cylinder bores. A secondary discharge chamber formed by a center secondary discharge chamber and satellite secondary discharge chambers independent of the center secondary discharge chamber is simpler in structure and easier to produce than a secondary discharge chamber formed by a center cylindrical portion and radial arms continuously extending from the center cylindrical portion. 
     In accordance with the present invention, there is provided a reciprocal compressor comprising a rotation shaft, a motion converter for converting rotation to reciprocal motion, pistons driven by the rotation shaft through the motion converter to move reciprocally, a cylinder block provided with cylinder bores in which the pistons are inserted and a center bore in which one end of the rotation shaft is inserted, a valve plate provided with suction holes, discharge holes, suction valves for closing the suction holes and discharge valves for closing the discharge holes and disposed opposite one end of the cylinder block, and a rear housing provided with a suction chamber communicating with the cylinder bores through the suction holes and the suction valves and a discharge chamber communicating with the cylinder bores through the discharge valves and the discharge holes and disposed opposite the valve plate, wherein an adjust member is screwed in the center bore to locate the rotation shaft in the longitudinal direction, the center bore communicates with the discharge chamber at a portion closer to the valve plate than the adjust member through an opening formed in the valve plate, and the contact part between the adjust member and the center bore is sealed by a seal member. 
     In the reciprocal compressor of the present invention, the center bore communicates with the discharge chamber at a portion closer to the valve plate than the adjust member through an opening formed in the valve plate, and the contact part between the adjust member and the center bore is sealed by a seal member. Therefore, volume of the discharge chamber is increased, pulsation of discharge pressure caused by the refrigerant gas discharging from the cylinder bores to the discharge chamber is decreased, and the compressor noise is decreased, with the portion of the center bore more distanced from the valve plate than the adjust member being prevented from communicating with the portion of the center bore closer to the valve plate than the adjust member through the threaded portion of the adjust member, and with the crank chamber accommodating the rotation shaft and the motion converter being prevented from communicating with the discharge chamber through the center bore. 
     In accordance with a preferred embodiment of the present invention, the cylinder block is provided with a plurality of satellite bores located radially outside the center bore, circumferentially distanced from each other and located between the cylinder bores, and each of the satellite bores communicates with the discharge chamber through an opening formed in the valve plate. 
     In this embodiment, the volume of the discharge chamber further increases, pulsation of discharge pressure caused by the refrigerant gas discharging from the cylinder bores to the discharge chamber further decreases, and the compressor noise further decreases. 
     In accordance with a preferred embodiment of the present invention, not only a bulkhead for separating the discharge chamber from the suction chamber but also legs provided in the discharge chamber clamp the valve plate in cooperation with the cylinder block. 
     When the secondary discharge chamber or the portion of the center bore closer to the valve plate than the adjust member communicates with the discharge chamber through the opening formed in the valve plate, the balance of the pressure acting on the valve plate is liable to change, the force acting on the valve plate to push it in the direction of the rear housing is liable to become larger than the force acting on the valve plate to push it in the reverse direction, and the valve plate is liable to deform toward the discharge chamber at the center portion. When the legs provided in the discharge chamber as well as the bulkhead for separating the discharge chamber from the suction chamber clamp the valve plate in cooperation with the cylinder block, the deformation of the valve plate is prevented. 
     Effect of the Invention 
     In accordance with the present invention, there is provided a reciprocal compressor wherein a cylinder block is provided with a void space communicating with a discharge chamber to increase the volume of the discharge chamber and which can resolve the problem of the reciprocal compressor of patent document  1 . 
     BEST MODE FOR CARRYING OUT THE INVENTION 
     Preferred embodiments of the present invention will be described. 
     First Embodiment 
     As shown in  FIG. 1 , a variable displacement swash plate compressor A comprises a rotation shaft  10 , a rotor  11  fixed to the rotation shaft  10 , a swash plate  12  supported by the rotation shaft  10  to be variable in inclination relative to the rotation shaft  10 . The swash plate  12  is connected to the rotor  11  by a linkage  13 , which allows the inclination of the swash plate  12  to vary, so as to rotate synchronously with the rotor  11  or the rotation shaft  10 . 
     Pistons  15  are anchored to the swash plate  12  through pairs of shoes  14  slidably engaging the outer circumferential portion of the swash plate  12 . 
     The rotor  11 , the linkage  13 , the swash plate  12  and the shoes  14  form a motion converter for converting rotation of the rotation shaft  10  to reciprocal motion of the pistons  15 . 
     The pistons  15  are inserted in cylinder bores  16   a  formed in a cylinder block  16 . 
     The cylinder bores  16   a  are circumferentially distanced from each other. 
     A front housing  18  forms a crank chamber  17  for accommodating the rotation shaft  10 , the rotor  11 , the linkage  13 , the swash plate  12  and the shoes  14 . The front housing  18  has a cylindrical form closed at one end. 
     One end of the rotation shaft  10  passes through the closed end of the front housing  18  to extend out of the front housing  18 . A seal member  19  is disposed between the front hosing  18  and the portion of the rotation shaft  10  passing through the front housing  18 . 
     The rotation shaft  10  is rotatably supported by a radial bearing  20  pressed in and fixed to the portion of the front housing through which the rotation shaft passes and a radial bearing  21  pressed in and fixed to a center bore  16   b  formed in the cylinder block  16 . The center bore  16   b  extends to the longitudinal middle of the cylinder block  16 . 
     Driving power is transmitted from an external power source to the said one end of the rotation shaft  10  through an electromagnetic clutch  26  mounted on the front housing  18 . The external power source is not shown in  FIG. 1 . 
     A valve plate  27  is disposed opposite one end of the cylinder block  16 . The valve plate  27  is provided with suction holes  27   a,  discharge holes  27   b,  suction valves for closing the suction holes  27   a  and discharge valves for closing the discharge holes  27   b.    
     A rear housing  28  is disposed opposite the valve plate  27 . The rear housing  28  is provided with a suction chamber  28   a  communicating with the cylinder bores  16   a  through the suction holes  27   a  and the suction valves, and a discharge chamber  28   b  communicating with the cylinder bores  16   a  through the discharge valves and the discharge holes  27   b.  The suction chamber  28   a  connects to an evaporator of a car air conditioner through a suction port  29  and the discharge chamber  28   b  connects to a condenser of the car air conditioner through a discharge port  30 . The car air conditioner, the evaporator and the condenser are not shown in  FIG. 1 . 
     A center secondary discharge chamber  16   c  of cylindrical shape is formed in the cylinder block  16 . The center secondary discharge chamber  16   c  is disposed adjacent the center bore  16   b  and located closer to the valve plate  27  than the center bore  16   b.  The center secondary discharge chamber  16   c  extends to the aforementioned one end of the cylinder block  16  to communicate with the discharge chamber  28   b  through an opening  27   c  formed in the valve plate  27 . As shown in  FIGS. 1 and 2 , a plurality of satellite secondary discharge chambers  16   d  of cylindrical shape with small diameter are formed in the cylinder block  16 . The satellite secondary discharge chambers  16   d  are located radially outside the center secondary discharge chamber  16   c,  circumferentially distanced from each other and located between the cylinder bores  16   a.  The satellite secondary discharge chambers  16   d  extend to the aforementioned one end of the cylinder block  16  to communicate with the discharge chamber  28   b  through openings  27   d  formed in the valve plate  27 . 
     Legs  28   d  are disposed in the discharge chamber  28   b  in addition to the bulkhead  28   c  for separating the discharge chamber  28   b  from the suction chamber  28   a  to clamp the valve plate  27  in cooperation with the cylinder block  16 . 
     The front housing  18 , the cylinder block  16 , the valve plate  27  and the rear housing  28  are assembled as a unitary body by through bolts  31 . 
     The variable displacement swash plate compressor A is provided with an air supply passage communicating the discharge chamber  28   b  with the crank chamber  17  and a displacement control valve for closing the air supply passage. The variable displacement swash plate compressor A is provided with an air exhaust passage communicating the crank chamber  17  with the suction chamber  28   a  and a restriction disposed in the air exhaust passage. The air supply passage, the displacement control valve, the air exhaust passage and the restriction are not shown in  FIGS. 1 and 2 . 
     In the variable displacement swash plate compressor A, driving power of the external power source not shown in  FIGS. 1 and 2  is transmitted to the rotation shaft  10  through the electromagnetic clutch  26  and the rotation of the rotation shaft  10  is transmitted to the swash plate  12  through the rotor  11  and the linkage  13 . Rotation of the swash plate  12  causes reciprocal motion of the outer circumferential portion thereof in the direction of the longitudinal axis of the rotation shaft  10 . The reciprocal motion of the outer circumferential portion of the swash plate  12  is transmitted to the pistons  15  through the shoes  14  to cause reciprocal motion of the pistons  15  in the cylinder bores  16   a.  Refrigerant gas returned from the evaporator of the car air conditioner is sucked into the cylinder bores  16   a  through the suction port  29 , the suction chamber  28   a,  the suction holes  27   a  and the suction valves. The refrigerant gas is compressed in the cylinder bores  16   a  and passes out of the compressor to the condenser of the car air conditioner through the discharge holes  27   b,  the discharge valves, the discharge chamber  28   b  and the discharge port  30 . 
     The displacement control valve opens and closes the air supply passage between the discharge chamber  28   b  and the crank chamber  17  to start and stop the introduction of the discharge pressure to the crank chamber  17 . Thus, the pressure in the crank chamber  17  is controlled to control the inclination angle of the swash plate  12 , thereby variably controlling the displacement of the compressor A. 
     When the compressed refrigerant gas discharges from the cylinder bores  16   a  to the discharge chamber  28   b,  the refrigerant gas causes pulsation of discharge pressure. The pulsation of the discharge pressure propagates outside the compressor through the discharge port  30  to resonate with various members close to the compressor, thereby causing compressor noise. However, in the variable displacement swash plate compressor A, the operation of the discharge chamber  28   b  as an expansion muffler is enhanced to restrict the propagation of the pulsation of the discharge pressure outside the compressor because the center secondary discharge chamber  16   c  and the plurality of the satellite secondary discharge chambers  16   d  formed in the cylinder block  16  communicate with the discharge chamber  28   b  through the opening  27   c  and the openings  27   d  formed in the valve plate  27  to increase the volume of the discharge chamber  28   b.  As a result, the compressor noise decreases. 
     In the variable displacement swash plate compressor A, the secondary discharge chamber is not formed by a center cylindrical portion coaxial to the center bore and radial arm portions extending from the center cylindrical portion and located between the cylinder bores but by a center secondary discharge chamber  16   c  adjacent the center bore  16   b  and a plurality of satellite secondary discharge chambers  16   d  located radially outside the center secondary discharge chamber  16   c,  circumferentially distanced from each other and located between the cylinder bores  16   a.  The secondary discharge chamber formed by the center secondary discharge chamber  16   c  and the satellite secondary discharge chambers  16   d  independent of the center secondary discharge chamber  16   c  is simpler in structure and easier to produce than the secondary discharge chamber formed by the center cylindrical portion and the radial arm portions continuously extending from the center cylindrical portion. 
     When the secondary discharge chambers  16   c  and  16   d  communicate with the discharge chamber  28   b  through the openings  27   c  and  27   d  formed in the valve plate  27 , the balance of the pressure acting on the valve plate  27  is liable to change, the force acting on the valve plate  27  to push it in the direction of the rear housing  28  is liable to become larger than the force acting on the valve plate  27  to push it in the reverse direction, and the valve plate  27  is liable to deform toward the discharge chamber  28   b  at the center portion. When the legs  28   d  provided in the discharge chamber  28   b  as well as the bulkhead  28   c  for separating the discharge chamber  28   b  from the suction chamber  28   a  clamp the valve plate  27  in cooperation with the cylinder block  16 , the deformation of the valve plate  27  is prevented. 
     Second Embodiment 
     In the following description, the same structures as in the first embodiment will be allotted the same reference numerals as in the first embodiment. 
     As shown in  FIG. 3 , a variable displacement swash plate compressor A′ comprises a rotation shaft  10 , a rotor  11  fixed to the rotation shaft  10 , a swash plate  12  supported by the rotation shaft  10  to be variable in inclination relative to the rotation shaft  10 . The swash plate  12  is connected to the rotor  11  by a linkage  13 , which allows the inclination of the swash plate  12  to vary, so as to rotate synchronously with the rotor  11  or the rotation shaft  10 . 
     Pistons  15  are anchored to the swash plate  12  through pairs of shoes  14  slidably engaging the outer circumferential portion of the swash plate  12 . 
     The rotor  11 , the linkage  13 , the swash plate  12  and the shoes  14  form a motion converter for converting rotation of the rotation shaft  10  to reciprocal motion of the pistons  15 . 
     The pistons  15  are inserted in cylinder bores  16   a  formed in a cylinder block  16 . The cylinder bores  16   a  extend through the cylinder block  16 . 
     A front housing  18  forms a crank chamber  17  for accommodating the rotation shaft  10 , the rotor  11 , the linkage  13 , the swash plate  12  and the shoes  14 . The front housing  18  has a cylindrical shape closed at one end. 
     One end of the rotation shaft  10  passes through the closed end of the front housing  18  to extend out of the front housing  18 . A seal member  19  is disposed between the front hosing  18  and the portion of the rotation shaft  10  passing through the front housing  18 . 
     The rotation shaft  10  is rotatably supported by a radial bearing  20  pressed in and fixed to the portion of the front housing through which the rotation shaft passing and a radial bearing  21  pressed in and fixed to a center bore  16   b  formed in the cylinder block  16 . The center bore  16   b  passes through the cylinder block  16 . 
     The rotation shaft  10  is clamped by a thrust bearing  22  disposed between the rotor  11  and the front housing  18  and a support member  23  disposed adjacent the other end of the rotation shaft  10 . The space between the other end of the rotation shaft  10  and the support member  23  is controlled to a predetermined value by an adjust member  24  screwed in the center bore  16   b  to locate the rotation shaft  10  in the longitudinal direction. 
     The contact part between the head of the adjust member  24  and the center bore  16   b  is sealed by an O-ring  25 . 
     Driving power is transmitted from an external power source not shown in  FIG. 3  to the said one end of the rotation shaft  10  through an electromagnetic clutch  26  mounted on the front housing  18 . 
     A valve plate  27  is disposed opposite one end of the cylinder block  27 . The valve plate  27  is provided with suction holes  27   a,  discharge holes  27   b,  suction valves for closing the suction holes  27   a  and discharge valves for closing the discharge holes  27   b.    
     A rear housing  28  is disposed opposite the valve plate  27 . The rear housing  28  is provided with a suction chamber  28   a  communicating with the cylinder bores  16   a  through the suction holes  27   a  and the suction valves and a discharge chamber  28   b  communicating with the cylinder bores  16   a  through the discharge valves and the discharge holes  27   b.  The suction chamber  28   a  connects to an evaporator of a car air conditioner through a suction port  29  and the discharge chamber  28   b  connects to a condenser of the car air conditioner through a discharge port  30 . The car air conditioner, the evaporator and the condenser are not shown in  FIG. 3 . 
     The portion of the center bore  16   b  closer to the valve plate  27  than the adjust member  24  communicates with the discharge chamber  28  through an opening  27   c  formed in the valve plate  27 . 
     Legs  28   d  are disposed in the discharge chamber  28   b  in addition to the bulkhead  28   c  for separating the discharge chamber  28   b  from the suction chamber  28   a  to clamp the valve plate  27  in cooperation with the cylinder block  16 . 
     The front housing  18 , the cylinder block  16 , the valve plate  27  and the rear housing  28  are assembled as a unitary body by through bolts  31 . 
     The variable displacement swash plate compressor A′ is provided with an air supply passage communicating the discharge chamber  28   b  with the crank chamber  17  and a displacement control valve for closing the air supply passage. The variable displacement swash plate compressor A′ is provided with an air exhaust passage communicating the crank chamber  17  with the suction chamber  28   a  and a restriction disposed in the air exhaust passage. The air supply passage, the displacement control valve, the air exhaust passage and the restriction are not shown in  FIG. 3 . 
     In the variable displacement swash plate compressor A′, driving power of the external power source not shown in  FIG. 3  is transmitted to the rotation shaft  10  through the electromagnetic clutch  26  and the rotation of the rotation shaft  10  is transmitted to the swash plate  12  through the rotor  11  and the linkage  13 . Rotation of the swash plate  12  causes reciprocal motion of the outer circumferential portion thereof in the direction of the longitudinal axis of the rotation shaft  10 . The reciprocal motion of the outer circumferential portion of the swash plate  12  is transmitted to the pistons  15  through the shoes  14  to cause reciprocal motions of the pistons  15  in the cylinder bores  16   a.  Refrigerant gas returned from the evaporator of the car air conditioner is sucked into the cylinder bores  16   a  through the suction port  29 , the suction chamber  28   a,  the suction holes  27   a  and the suction valves. The refrigerant gas is compressed in the cylinder bores  16   a  and passes out of the compressor to the condenser of the car air conditioner through the discharge holes  27   b,  the discharge valves, the discharge chamber  28   b  and the discharge port  30 . 
     The displacement control valve opens and closes the air supply passage between the discharge chamber  28   b  and the crank chamber  17  to start and stop the introduction of the discharge pressure to the crank chamber  17 . Thus, the pressure in the crank chamber  17  is controlled to control the inclination angle of the swash plate  12 , thereby variably controlling the displacement of the compressor. 
     When the compressed refrigerant gas discharges from the cylinder bores  16   a  to the discharge chamber  28   b,  the refrigerant gas causes pulsation of discharge pressure. The pulsation of the discharge pressure propagates outside the compressor through the discharge port  30  to resonate with various members disposed close to the compressor, thereby causing compressor noise. However, in the variable displacement swash plate compressor A′, the operation of the discharge chamber  28   b  as an expansion muffler is enhanced to restrict the propagation of the pulsation of the discharge pressure outside the compressor because the portion of the center bore  16   b  closer to the valve plate  27  than the adjust member  24  communicates with the discharge chamber  28   b  through the opening  27   c  to increase the volume of the discharge chamber  28   b.  As a result, the compressor noise decreases. 
     In the variable displacement swash plate compressor A′, the contact part between the head of the adjust member  24  and the center bore  16   b  is sealed by the O-ring  25 . Therefore, the portion of the center bore  16   b  more distanced from the valve plate  27  than the adjust member  24  is prevented from communicating with the portion of the center bore  16   b  closer to valve plate  27  than the adjust member  24  through the threaded portion of the adjust member  24 , and the crank chamber  17  does not communicate with the discharge chamber  28   b  through the center bore  16   b.  Therefore, the displacement of the compressor A′ is reliably controlled by opening and closing the air supply passage between the discharge chamber and the crank chamber. 
     When the portion of the center bore  16   b  closer to the valve plate  27  than the adjust member  24  communicates with the discharge chamber  28   b  through the openings  27   c  formed in the valve plate  27 , the balance of the pressure acting on the valve plate  27  is liable to change, the force acting on the valve plate  27  to push it in the direction of the rear housing  28  is liable to become larger than the force acting on the valve plate  27  to push it in the reverse direction, and the valve plate  27  is liable to deform toward the discharge chamber  28   b  at the center portion. When the legs  28   d  provided in the discharge chamber  28   b  as well as the bulkhead  28   c  for separating the discharge chamber  28   b  from the suction chamber  28   a  clamp the valve plate  27  in cooperation with the cylinder block  16 , the deformation of the valve plate  27  is prevented. 
     It is possible to form a plurality of satellite bores like the satellite secondary discharge chambers  16   d  in the first embodiment, which are located radially outside the center bore  16   b,  circumferentially distanced from each other and located between the cylinder bores  16   a,  in the cylinder block  16  and form openings like the openings  27   d  in the first embodiment in the valve plate  27  to communicate the satellite bores to the discharge chamber  28   b  through the openings in the valve plate, in addition to communicating the portion of the center bore  16   b  closer to the valve plate  27  than the adjust member  24  with the discharge chamber  28   b  through the opening  27   c  formed in the valve plate  27 . 
     In the aforementioned case, the volume of the discharge chamber  28   b  further increases, the pulsation of the discharge pressure caused by the refrigerant gas discharging from the cylinder bores  16   a  to the discharge chamber  28   b  further decreases and the compressor noise further decreases. 
     INDUSTRIAL APPLICABILITY 
     The present invention can be widely used in reciprocal compressors such as swash plate compressors, wobble plate compressors, etc. 
    
    
     BRIEF EXPLANATION OF DRAWINGS 
       FIG. 1  is a sectional view of a reciprocal compressor in accordance with the first preferred embodiment of the present invention. 
       FIG. 2  is a view in the direction of arrows II-II in  FIG. 1 . 
       FIG. 3  is a sectional view of a reciprocal compressor in accordance with the second preferred embodiment of the present invention.