Patent Publication Number: US-2009232669-A1

Title: Refrigerant Compressor

Description:
TECHNICAL FIELD 
     The present invention relates to a refrigerant compressor used for a fridge-freezer. 
     BACKGROUND ART 
     Hitherto, as a refrigerant compressor, there is a compressor provided with a discharge valve system for improving energy efficiency by reducing fluctuation in noise during an operation and reducing a loss at the time of opening and closing a discharge reed as a refrigerant compressor, which is disclosed in Japanese Patent Unexamined Publication No. 2004-218537 (hereinafter referred to as Document 1). 
     Referring now to the drawings, a refrigerant compressor in the related art will be described below. 
       FIG. 9  is a vertical cross sectional view of a refrigerant compressor in the related art described in Document 1,  FIG. 10  is a cross-sectional plan view of the refrigerant compressor in the related art disclosed in the Document 1, and  FIG. 11  is an enlarged drawing of a principal portion of the refrigerant compressor in the related art disclosed in the Document 1. 
     In  FIGS. 9 to 11 , the refrigerant compressor includes oil  2  stored in airtight container  1 , suction pipe  3  opening into airtight container  1  and discharge pipe  15  mounted to airtight container  1 . Airtight container  1  accommodates electric motor  4  and compressing element  5  driven thereby. 
     Compressing element  5  includes piston  8 , cylinder  9 , valve plate  12 , suction muffler  13 , cylinder head  14  for tightly sealing discharge valve system  10 , and discharge communicating pipe  16  for communicating cylinder head  14  and discharge pipe  15 . 
     Piston  8  in this case is connected to shaft  7  via connecting rod  6  and reciprocates in cylinder  9 . Valve plate  12  is provided with discharge valve system  10  and suction valve  11  which communicates to the interior of cylinder  9 . The discharge valve system  10  is disposed at an opening end of cylinder  9 , and is provided on an outer surface of cylinder  9 . An end of sound-muffling portion  17  of suction muffler  13  is communicated with suction valve  11 , and the other end thereof is opened toward suction pipe  3  mounted to airtight container  1  in the vicinity thereof. Here, sound-muffling portion  17  is a portion which constitutes a sound-muffling space of suction muffler  13 . 
     Subsequently, referring now to  FIG. 11 , discharge valve system  10  will be described in detail. Discharge valve system  10  includes discharge valve seat  20 , pedestal  21  formed on recess  19  on the opposite side from discharge valve seat  20 , discharge reed  23 , and stopper  25 . 
     Discharge valve seat  20  is provided in recess  19  on the outer side of cylinder  9  of valve plate  12  (OUT side in  FIG. 11 ) as a projection surrounding the outer periphery of a suction port  18  formed on the valve plate  12 . Discharge reed  23  is fixed at one end to pedestal  21  and includes opening/closing portion  22  for opening and closing discharge valve seat  20 . Stopper  25  is fixed to pedestal  21  so that spring reed  24  and discharge reed  23  are held between stopper  25  and pedestal  21 . 
     Spring reed  24  is fixed while keeping a predetermined space with respect to stopper  25  and discharge reed  23  respectively by bending portion  27  in the vicinity of spring reed fixing portion  26 . Stopper  25  is fixed at one end to pedestal  21  and is in contact at the other end against contact portion  28  of valve plate  12 , and a predetermined space is kept with respect to spring reed  24 . 
     Movement of refrigerant compressor configured as described above will be described below. 
     When electric motor  4  rotates, shaft  7  rotates, and the rotation of shaft  7  is transmitted to connecting rod  6 , and hence piston  8  is reciprocated. Refrigerant flowed from external cooling circuit (not shown) is released once in airtight container  1  via suction pipe  3 , and when piston  8  is reciprocated, the refrigerant is sucked from airtight container  1  into suction muffler  13 , and is sucked into cylinder  9  intermittently via suction valve  11 . 
     The refrigerant sucked into cylinder  9  is compressed by piston  8 , and released once into cylinder head  14  by pushing and opening opening/closing portion  22  of discharge reed  23  toward ‘OUT’ side via discharge hole  18  of valve plate  12 . The refrigerant released to cylinder head  14  is discharged again to the external cooling circuit (not shown) via discharge communication pipe  16  and discharge pipe  15 . 
     Stopper  25  comes into contact with contact portion  28  of valve plate  12  at an end opposite from fixed valve seat  21 . Stopper  25  keeps spaces among spring reed  24 , stopper  25  and discharge reed  23  to be constant with high degree of accuracy by controlling a bending angle of bending portion  27  of spring reed  24 . 
     In the configuration in the related art as described above, the end of stopper  25  is caused to come into contact with contact portion  28  of valve plate  12 , when stopper  25 , spring reed  24 , and discharge reed  23  are fixed to pedestal  21  of valve plate  12 . It is configured in such a manner that a space is not generated between the end of stopper  25  and contact portion  28  by deforming stopper  25  when the end of stopper  25  and contact portion  28  come into interference. In this configuration, since a component force of a holding force generated by being fixed, which causes the above described deformation of stopper  25 , is applied from stopper  25  to contact portion  28  of valve plate  12 , discharge reed  23  is not pressed uniformly against pedestal  21 . 
     Consequently, there is a problem such that lifting of discharge reed  23  occurs and a space is generated between opening/closing portion  22  of discharge reed  23  and discharge valve  20 , and hence lowering of compression efficiency due to reverse flow of refrigerant gas is resulted. 
     DISCLOSURE OF INVENTION 
     A refrigerant compressor of the present invention includes a valve plate provided with a discharge valve system and the discharge valve system includes a recess having a discharge hole which is communicated with a compression chamber of a cylinder opened at a bottom surface thereof, a discharge reed for covering the discharge hole, and a stopper formed of plate spring arranged above the discharge reed. The discharge reed and one end of the stopper is fixed to the bottom surface of the recess, and the other end of the stopper comes into contact with the contact portion provided on the valve plate, so that the stopper and the bottom surface of the recess have a space from each other, and the discharge reed is arranged in the space. A refrigerant compressor with high accuracy of assembly, high compression efficiency and low fluctuation of noise level can be provided. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a vertical cross-section of a refrigerant compressor according to a first embodiment of the invention. 
         FIG. 2  is a cross-sectional plan view of the refrigerant compressor according to the first embodiment of the invention. 
         FIG. 3  is an enlarged cross-sectional view showing a principal portion of the refrigerant compressor according to the first embodiment of the invention. 
         FIG. 4  is an exploded perspective view of the refrigerant compressor according to the first embodiment of the invention. 
         FIG. 5  is a vertical cross-sectional view of the refrigerant compressor according to a second embodiment of the invention. 
         FIG. 6  is a cross-sectional plan view of the refrigerant compressor according to the second embodiment of the invention. 
         FIG. 7  is an enlarged cross-sectional view showing a principal portion of the refrigerant compressor according to the second embodiment of the invention. 
         FIG. 8  is an exploded perspective view of the refrigerant compressor according to the second embodiment of the invention. 
         FIG. 9  is a vertical cross-sectional view of the conventional refrigerant compressor. 
         FIG. 10  is a cross-sectional plan view of the conventional refrigerant compressor. 
         FIG. 11  is an enlarged cross-sectional view showing a principal portion of the conventional refrigerant compressor. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The invention is a refrigerant compressor including an electric motor, a compressing element driven by the electric motor, and an airtight container for accommodating the electric motor and the compressing element and storing oil therein. The compressing element includes a cylinder accommodating a piston, and a valve plate sealing an opened end of the cylinder and provided with a discharge valve system on the outer side of the cylinder. The discharge valve system includes a discharge hole formed on the valve plate, a discharge valve seat formed on the valve plate on the outer side of the cylinder so as to surround the discharge hole, a pedestal formed on the valve plate on the outer side of the cylinder, a discharge reed having an opening/closing portion fixed at one end to the pedestal for opening and closing the discharge valve seat, and a stopper for retaining a predetermined space with respect to an opening/closing portion of the discharge reed. The stopper, being formed of a plate spring, is fixed at one end to the pedestal of the valve plate with a discharge reed fixing end portion, and is brought at the other end into contact with the contact portion formed on the valve plate. 
     When the stopper and the discharge reed are fixed to the pedestal of the valve plate, an end of the stopper comes into contact with the contact portion of the valve plate, so that a predetermined space is secured with high degree of accuracy between the stopper and the discharge reed. 
     The stopper is made of a plate spring. As materials for the plate spring, stainless-steel plate spring (JIS G4313), or spring steel (JIS G4810) is suitable, for example. And the thickness of the plate spring for the stopper is preferably 0.2 mm-1.5 mm. Such a plate spring as described above can perform as a good stopper of the present invention. 
     Since the stopper has the spring property, a component force of a fixing force applied from the stopper to the contact portion can be absorbed by a fine deformation of the stopper. Accordingly, since the fixing force with respect to the pedestal becomes uniform, the discharge reed is prevented from lifting upward from the discharge valve seat, and reverse flow of refrigerant gas discharged from the cylinder does not occur. In this configuration, a refrigerant compressor with high compression efficiency can be provided. 
     In the invention, the stopper may be fixed with the intermediary of a spacer with respect to the discharge reed. Then, the spacer is placed between the stopper and the discharge reed. Accordingly, since the stopper without being applied with bending process can be brought into contact with the contact portion of the valve plate, the predetermined space with respect to the discharge reed can be secured with high degree of accuracy, and, in addition, bending process can be omitted. Therefore, the refrigerant compressor which has less fluctuation in compressing efficiency and noise, and furthermore, which is inexpensive, can be provided. 
     In the invention, it is also possible to form the valve plate of sintered metal and the contact portion and the pedestal provided on the valve plate by a material surface of the sintered metal. Accordingly, the shape of a metal mold with high degree of accuracy can be reflected as a step between the pedestal and the contact portion, and hence the predetermined space between the discharge reed and the stopper can be secured with high degree of accuracy. Therefore, the refrigerant compressor with further less fluctuation of compressing efficiency and noise can be provided. 
     In the invention, the compressing element may include a suction muffler provided with the sound-muffling portion which communicates with the cylinder and make a suction port provided on the suction muffler opposite and open to an opening end of the suction pipe mounted to the airtight container, or bring the same into communication with an opening end of the suction pipe. Accordingly, refrigerant flowed from the external cooling circuit (not shown) is sucked into the cylinder without receiving heat. Therefore, the compression efficiency is further increased. On the other hand, although it is a structure in which compression of liquid refrigerant which is returned back from the external cooling circuit is liable to occur, the stopper which is deformed once by the liquid refrigerant injected from the discharge hole is restored to its initial shape immediately by the spring property thereof. Therefore, the refrigerant compressor without malfunction and with high reliability can be provided. 
     In the invention, hydrocarbon can be used as the refrigerant to be compressed, and mineral oil or alkyl benzene can be used as oil. Normally, even in the case in which the liquid compression occurs very often due to the combination of the oil and the refrigerant which is liable to cause a forming phenomenon, the stopper which is deformed once by mixture of the liquid refrigerant and the oil injected with great force from the discharge hole is restored to its initial shape by the spring property thereof, and therefore the refrigerant compressor without malfunction and with high reliability can be provided. 
     Referring now to the drawings, the embodiment of the refrigerant compressor according to the invention will be described. The invention is not limited to the embodiments. 
     First Embodiment 
       FIG. 1  is a vertical cross-sectional view of a refrigerant compressor according to a first embodiment of the invention;  FIG. 2  is a cross-sectional plan view of the refrigerant compressor in the first embodiment;  FIG. 3  is an enlarged cross-sectional view of a principal portion of the refrigerant compressor according to the first embodiment; and  FIG. 4  is an exploded perspective view of the refrigerant compressor in the first embodiment. 
     In  FIG. 1  to  FIG. 4 , airtight container  101  includes discharge pipe  102  and suction pipe  103  connected to an external cooling circuit, (not shown). Oil  104  formed of mineral oil is stored in a bottom portion of airtight container  101 , and the interior of airtight container  101  is filled with refrigerant  105  formed of hydrocarbon such as R600a. Airtight container  101  accommodates electric motor  108  including stator  106  and rotor  107  and compressing element  109  driven thereby. 
     Subsequently, a configuration of compressing element  109  will be described. 
     Compressing element  109  includes shaft  110  to be inserted and fixed to rotor  107  of electric motor  108 , and cylinder block  113 . Cylinder block  113  includes cylinder  112  which rotatably supports shaft  110  and forms compression chamber  111 . Piston  114  is inserted into cylinder  112 , and shaft  110  and piston  114  are connected by connecting rod  115 . 
     Valve plate  116  formed of sintered metal to be disposed at an opening end of cylinder  112  includes suction valve  117  which communicates with the interior of cylinder  112  and discharge valve system  119 . Discharge valve system  119  is provided on valve plate  116  on the outer side of cylinder  112  (right side in  FIG. 1 ), and is sealed by cylinder head  118 . 
     An end of sound-muffling portion  121  communicates with suction valve  117  via suction muffler  120  formed of resin. Suction port  122  in communication with sound-muffling portion  121  is opened toward opening end  123  of suction pipe  103  mounted to airtight container  101  in the vicinity thereof. 
     Subsequently, a configuration of discharge valve system  119  will be described in detail using  FIGS. 3 and 4 . “OUT” in  FIGS. 3 and 4  shows the outer side of cylinder  112  with respect to compression chamber  111 , and “In” shows the inner side of the cylinder. 
     Valve plate  116  includes recess  124  which constitutes discharge valve system  119  on the outer side of cylinder  112 . Recess  124  is formed with discharge hole  125  on the bottom thereof, and is formed with discharge valve seat  126  formed of projection which surrounds discharge hole  125 . Recess  124  is formed with pedestal  127  having the same height as discharge valve seat  126  on the bottom of recess  124 . Contact portion  128  is formed on the opposite side of pedestal  127  with the intermediary of discharge hole  125 . When comparing with the height from the bottom of recess  124 , contact portion  128  is formed to be higher than pedestal  127 . 
     Pedestal  127  and contact portion  128  which constitute discharge valve system  119  are formed of the same sintered metal mold, and the surface is not additionally processed and is remained as a material surface of the sintered metal. Pedestal  127  is formed with projected pin hole  129 . Discharge reed  130 , spring reed  131 , and stopper  132  are piled on pedestal  127  in this order, and are fixed to pin hole  129  with caulking pin  133 . 
     Discharge reed  130  formed of plate spring includes opening/closing portion  134 , and opening/closing portion  134  opens and closes discharge valve seat  126 . Spring reed  131  is also formed of the plate spring material. Spring reed  131  is bent and formed at spring reed bent portion  136  in the vicinity of spring reed fixing portion  135 , and predetermined spaces are secured between spring reed  131  and discharge reed  130  and between spring reed  131  and stopper  132 , respectively. 
     Stopper  132  manufactured of the plate spring material includes stopper bending portion  137  formed by being bent and formed into substantially a crank shape, stopper fixing portion  138  and regulation portion  139 . By fixing stopper  132  to pedestal  127  at stopper fixing portion  138  by use of caulking pin  133 , the end of regulation portion  139  comes into contact with contact portion  128  and the predetermined space between the stopper  132  and the bottom surface of the recess  124  is secured. 
     Subsequently, movement and mechanism of the refrigerant compressor configured as described above will be described. 
     When compressing element  109  is driven by electric motor  108 , shaft  110  rotates with rotor  107  of electric motor  108 . The rotation of shaft  110  reciprocates piston  114  via connecting rod  115 . When piston  114  reciprocates in the interior of cylinder  112 , refrigerant  105  formed of hydrocarbon flowed from the external cooling circuit (not shown) is sucked directly into suction muffler  120  via suction pipe  103 , and is flowed from sound-muffling portion  121  via suction valve  117  into compression chamber  111  of cylinder  112 . 
     Refrigerant  105  flowed into compression chamber  111  is compressed by piston  114  which reciprocates in the interior of cylinder  112 , passed through discharge valve system  119 , released once into cylinder head  118  and then is discharged again into the external cooling circuit (not shown) from discharge pipe  102 . In this case, since refrigerant  105  flowed from suction pipe  103  is adapted to be directly sucked into suction muffler  102 . In other words, these steps are subject to a direct suction system, and hence the refrigerant reaches compression chamber  111  without receiving heat too much from electric motor  108 , whereby the compression efficiency can be increased. 
     Refrigerant  105  is discharged from compression chamber  111  to cylinder head  118 . In other words, with increase in pressure in the interior of compression chamber  111 , refrigerant  105  presses and opens discharge reed  130  in OUT direction, and refrigerant  105  flows into cylinder head  118  intermittently. 
     In the initial period of the compressing process in which discharge reed  130  starts to open, since a predetermined space is secured between discharge reed  130  and spring reed  131 , only discharge reed  130  is opened. In this movement, it can be opened with a lower pressure in the compression chamber  111 , and hence input loss in association with the compression can be reduced. 
     In the middle range of the compressing process, discharge reed  130  and spring reed  131  are deformed in OUT direction in an adhered state by refrigerant  105  injected from compression chamber  111 , and comes into contact with stopper  132 . By discharge reed  130  and spring reed  131  coming in contact with stopper  132  in an adhered state, the opening area of discharge hole  125  is maximized and, simultaneously, bending damage of discharge reed  130  and spring reed  131  can be prevented. 
     When the compressing process is terminated, and discharge reed  130  is closed, a restoring force of spring reed  131  is added to a restoring force of discharge reed  130 , so that discharge reed  130  is restored to IN direction and comes into contact with discharge valve seat  126 , thereby closing discharge hole  125 . Therefore, by alleviating closing time lag of discharge reed  130 , refrigerant  105  discharged to cylinder head  118  is prevented from flowing reversely to compression chamber  111 . 
     Subsequently, the mechanism of discharge valve system  119  will be described. 
     When assembling discharge valve system  119 , an end of stopper  132  is fixed to valve plate  116  by caulking pin  133  and the other end of stopper  132  comes into contact with contact portion  128  of valve plate  116 . In this configuration, a predetermined space between spring reed  131  and regulation portion  139  of stopper  132  is secured. 
     The space is defined at a position between pedestal  127  and contact portion  128 . Pedestal  127  and contact portion  128  are formed of the same sintered metal mold and the surface is not additionally processed and is remained as a material surface of the sintered metal. Therefore, since dimensions of sintered metal mold at high degree of accuracy is reflected as a space between stopper  132  and valve plate  116 , variation in dimension is small and extremely high dimensional accuracy is ensured. 
     Consequently, variations of the opening, amount or closing time lag of discharge reed  130  are extremely reduced, and hence optimum amount of opening amount or closing time lag can be achieved. Therefore, not only enhancement of compression efficiency, but also minimization of variation in noise level can be achieved. 
     On the other hand, stopper  132  is fixed at one end to pedestal  127  by caulking pin  133 , and interferes with contact portion  128  at the other end, so that the space with respect to contact portion  128  can be eliminated while deforming stopper  132 . In this case, since stopper  132  is formed of plate spring, rigidity is low. Therefore, even though a component force of the caulking force which deforms stopper  132  generated by caulking pin  133  is applied to contact portion  128 , a minute resilient deformation is generated in stopper  132 , so that the component force of the caulking force applied to contact portion  128  of the valve plate  116  is alleviated. Consequently, a pressing force of caulking pin  133 , acts uniformly on stopper fixing portion  138 , whereby lifting of caulking pin  133  upward or lifting of discharge reed  130  or spring reed  131  upward can be substantially eliminated. 
     Since discharge reed  130  is not lifted upward from discharge valve seat  126 , reverse flow of refrigerant  105  from cylinder head  118  is prevented, and hence the refrigerant compressor of high performance can be provided. Since lifting of spring reed  131  upward can be substantially eliminated, and the predetermined space set between spring reed  131  and regulation portion  139  of stopper  132  can be secured, the compression efficiency is enhanced, and variation in noise level can be minimized. 
     Subsequently, a case in which the refrigerant compressor causes liquid compression in this embodiment will be described. 
     Suction port  122  of suction muffler  120 , which is communicated with sound-muffling portion  121 , is opened toward opening end  123  of suction pipe  103  mounted to airtight container  101  in the vicinity thereof. Therefore, when refrigerant  105  is returned from a freezing cycle system in an unvaporized liquid state, there may be a case such that refrigerant  105  in the liquid state is sucked into compression chamber  111  and compressed. 
     Refrigerant  105  such as hydrocarbon has a high compatibility with oil  104  such as mineral oil. Therefore, there may be a phenomenon such that refrigerant  105 , which is blended into oil  104  when the refrigerant compressor is stopped, abruptly generates bubble in the initial stage of activation of the refrigerant compressor. The bubbled oil  104  is sucked directly into suction muffler  120  together with refrigerant  105 , and is flowed from sound-muffling portion  121  through suction valve  117  into compression chamber  111  of cylinder  112  to be compressed. 
     Consequently, refrigerant  105  in the state of liquid or refrigerant  105  containing oil  104  is injected with strong force from discharge hole  125  and significantly deforms stopper  132  toward OUT side. 
     However, since stopper  132  is formed of plate spring, deformation of stopper  132  is resilient deformation. Therefore, when compression of liquid is terminated and a normal state of compressing gas refrigerant is restored, stopper  132  is restored to an initial shape simultaneously. Accordingly, the refrigerant compressor which can hardly be broken down even when liquid compression is occurred and hence has a high reliability is provided. 
     In this embodiment, a structure in which suction muffler  120  has suction port  122  in communication with sound-muffling portion  121  being opened toward opening end  123  of suction pipe  103  mounted to airtight container  101  in the vicinity thereof is shown as an example. However, the invention is not limited thereto, and the same effect can be obtained also in a structure in which suction port  122  and opening end  123  of suction pipe  103  are directly in communication. 
     Second Embodiment 
       FIG. 5  is a vertical cross-sectional view of a refrigerant compressor according to a second embodiment of the invention;  FIG. 6  is a cross-sectional plan view of the refrigerant compressor according to the second embodiment;  FIG. 7  is an enlarged cross-sectional view showing a principal portion of the refrigerant compressor according to the second embodiment; and  FIG. 8  is an enlarged perspective view of the refrigerant compressor according to the second embodiment. 
     In  FIG. 5  to  FIG. 8 , airtight container  201  is provided with discharge pipe  202  and suction pipe  203  connected to the external cooling circuit (not shown). Airtight container  201  stores oil  204  formed of mineral oil in the bottom portion thereof and the interior of airtight container  201  is filled with refrigerant  205  formed of hydrocarbon such as R600a. Airtight container  201  accommodates electric motor  208  including stator  206  and rotor  207 , and compressing element  209  driven thereby. 
     Subsequently, main configuration of compressing element  209  will be described. 
     Compressing element  209  includes shaft  210  to be inserted and fixed to rotor  207  of electric motor  208  and cylinder block  213 . Cylinder block  213  rotatably supports shaft  210 , and includes cylinder  212  which defines compression chamber  211 . Piston  214  is inserted into the interior of cylinder  212 , and shaft  210  and piston  214  are connected by connecting rod  215 . 
     Valve plate  216  disposed at an opening end of cylinder  212  and formed of sintered metal has suction valve  217  which communicates with the interior of cylinder  212  and discharge valve system  219 . Discharge valve system  219  is provided on valve plate  216  on the outer side of cylinder  212  (OUT side), and is sealed by cylinder head  218 . 
     An end of sound muffling portion  221 , which constitute a muffling space, communicates with suction valve  217  via suction muffler  220  formed of resin. Suction port  222  in communication with sound-muffling portion  221  is opened toward opening end  223  of suction pipe  203  mounted to airtight container  201  in the vicinity thereof. 
     Subsequently, a configuration of discharge valve system  219  will be described in detail using mainly  FIGS. 7 and 8 . “OUT” in  FIGS. 7 and 8  shows the outer side of cylinder  212  and “In” shows the inner side of the cylinder. 
     Valve plate  216  includes recess  224  on the outer side of cylinder  212 . Recess  224  is formed with discharge hole  225  on the bottom thereof, and is formed with discharge valve seat  226  in the state of a projection which surrounds discharge hole  225 . Recess  224  is formed with pedestal  227  having the same height as discharge valve seat  226  on the bottom thereof. Contact portion  228  shallower than pedestal  227  is formed on the opposite side of pedestal  227  with the intermediary of discharge hole  225 . In other words, when comparing with the height from the bottom of recess  224 , contact portion  228  is formed to be higher than pedestal  227 . 
     Pedestal  227  and contact portion  228  which constitute discharge valve system  229  are formed of the same sintered metal mold, and the surface is not additionally processed and is remained as a material surface of the sintered metal. Pedestal  227  is formed with pin hole  229 . Discharge reed  230 , spring reed  231 , spacer  232  and stopper  234  are piled on pedestal  227  in this order, and are fixed to pin hole  229  with caulking pin  235 . 
     Discharge reed  230  formed of plate spring includes opening/closing portion  236  for opening and closing discharge valve seat  226 . Spring reed  231  is also formed of the plate spring material. Spring reed  231  is bent and formed at spring reed bending portion  238  in the vicinity of spring reed fixing portion  237 , and predetermined spaces are secured for discharge reed  230  and stopper  234 , respectively. 
     Stopper  234  manufactured of the plate spring material includes stopper fixing portion  239  and regulation portion  240 . Stopper  234  is fixed to pedestal  227  by caulking pin  235  at stopper fixing portion  239 . At this time, spacer  232  is placed between stopper fixing portion  239  and spring reed fixing portion  237  so as to be interposed therebetween. Spacer  232  can secure a predetermined space between stopper  234  and the bottom surface of recess  224 . An end of regulation portion  240  of stopper  234  comes into contact with contact portion  228 . 
     Movement and mechanism of the refrigerant compressor configured as described above will be described. 
     When compressing element  209  is driven by electric motor  208 , shaft  210  rotates with rotor  207  of electric motor  208 . The rotation of shaft  210  reciprocates piston  214  via connecting rod  215 . When piston  214  reciprocates in the interior of cylinder  212 , refrigerant  205  formed of hydrocarbon flowed from the external cooling circuit (not shown) is sucked directly into suction muffler  220  via suction pipe  203 , and is flowed from sound-muffling portion  221  via suction valve  217  into compression chamber  211  of cylinder  212 . 
     Refrigerant  205  flowed into compression chamber  211  is compressed by piston  214  which reciprocates in the interior of cylinder  212 , passed through discharge valve system  219 , released once into cylinder head  218  and then is discharged again into the external cooling circuit (not shown) from discharge pipe  202 . In this case, since refrigerant  205  flowed from suction pipe  203  is adapted to be directly sucked into suction muffler  220 . In other words, these steps are subject to a direct suction system, and hence reaches compression chamber  211  without receiving heat too much from electric motor  208 , whereby the compression efficiency can be increased. 
     Refrigerant  205  is discharged from compression chamber  211  to cylinder head  218 . In other words, increase in pressure in the interior of the compression chamber  211  presses and opens discharge reed  230  in OUT direction by refrigerant  205 , and refrigerant  205  flows into cylinder head  218  intermittently. 
     In the initial period of the compressing process in which discharge reed  230  starts to open, since a predetermined space is secured between discharge reed  230  and spring reed  231 , only discharge reed  230  is opened. In this movement, it can be opened with a lower pressure in the compression chamber  211 , and hence input loss in association with the compression can be reduced. 
     In the middle range of the compressing process, with refrigerant  205  injected from compression chamber  211 , discharge reed  230  and spring reed  231  come into contact with stopper  234  in an adhered state. By discharge reed  230  and spring reed  231  coming in contact with stopper  234  in an adhered state, the opening area of discharge hole  225  is maximized and, simultaneously, bending damage of discharge reed  230  and spring reed  231  can be prevented. 
     When the compressing process is terminated, and discharge reed  230  is closed, a restoring force of discharge reed  230  and a restoring force of spring reed  231  are added to close discharge reed  230 . Therefore, by alleviating closing time lag of discharge reed  230 , refrigerant  205  discharged to cylinder head  218  is prevented from flowing reversely to compression chamber  211 . 
     Subsequently, the mechanism of discharge valve system  219  will be described. 
     When assembling discharge valve system  219 , an end of stopper  234  is fixed to valve plate  216  by caulking pin  235  via spacer  232  and the other end of stopper  234  comes into contact with contact portion  228  of valve plate  216 . In this configuration, a predetermined space between spring reed  231  and regulation portion  240  of stopper  234  is secured. 
     The space is defined at a position between pedestal  227  and contact portion  228 . Pedestal  227  and contact portion  228  are formed of the same sintered metal mold and the surface is not additionally processed and is remained as a material surface of the sintered metal. Therefore, since dimensions of sintered metal mold at high degree of accuracy is reflected as a space between stopper  234  and valve plate  216 , variation in dimension is small and extremely high dimensional accuracy is ensured. By placing spacer  232  between stopper  234  and spring reed  231  so as to be interposed therebetween, a predetermined space between stopper  234  and the bottom surface of recess  224  can be secured. Since a flat plate spring material can be used, bending formation of the plate spring material which is difficult to control dimensions can be omitted, and hence a high degree of accuracy can be maintained when assembling discharge valve system  219 . 
     Consequently, variations of the opening amount or closing time lag of discharge reed  230  are extremely reduced, and hence optimum amount of opening amount or closing time lag can be achieved. Therefore, not only enhancement of compression efficiency, but also minimization of variation in noise level can be achieved. 
     On the other hand, stopper  234  is fixed at one end to pedestal  227  by caulking pin  235 , and contacts with contact portion  228  at the other end, so that the space with respect to contact portion  228  can be eliminated while deforming stopper  234 . In this case, since stopper  234  is formed of plate spring, rigidity is low. Therefore, even though a component force of the caulking force which deforms stopper  234  generated by caulking pin  235  is applied to contact portion  228 , a minute resilient deformation is generated in stopper  234 , so that the component force of the caulking force applied to contact portion  228  of the valve plate  216  is alleviated. Consequently, a pressing force of caulking pin  235  acts uniformly on stopper fixing portion  239 , whereby lifting of caulking pin  235  upward or lifting of discharge reed  230  or spring reed  231  upward can be substantially eliminated. 
     Since discharge reed  230  is not lifted upward from discharge valve seat  226 , reverse flow of refrigerant  205  from cylinder head  218  is prevented, and hence the refrigerant compressor of high performance can be provided. Since lifting of spring reed  231  upward can be substantially eliminated, and the predetermined space set between spring reed  231  and regulation portion  240  of stopper  234  can be secured, the compression efficiency is enhanced, and variation in noise level can be minimized. 
     Next, a case in which the refrigerant compressor causes liquid compression in this embodiment will be described. 
     Suction port  222  of suction muffler  220 , which is communicated with sound-muffling portion  221 , is opened toward opening end  223  of suction pipe  203  mounted to airtight container  201  in the vicinity thereof. Therefore, when refrigerant  205  is returned from a freezing cycle system in an unvaporized liquid state, there may be a case such that refrigerant  205  in the liquid state is sucked into compression chamber  211  and compressed. 
     Refrigerant  205  such as hydrocarbon has a high compatibility with oil  204  such as mineral oil. Therefore, there may be a phenomenon such that refrigerant  205 , which is solved into oil  204  when the refrigerant compressor is stopped, abruptly generates bubble in the initial stage of activation of the refrigerant compressor. The bubbled oil  204  is sucked directly into suction muffler  220  together with refrigerant  205 , and is flowed from sound-muffling portion  221  through suction valve  217  into compression chamber  211  of cylinder  212  to be compressed. 
     Consequently, refrigerant  205  in the state of liquid or refrigerant  205  containing oil  204  is injected with strong force from discharge hole  225  and significantly deforms stopper  234  toward OUT side. 
     However, since stopper  234  is formed of plate spring, deformation of stopper  234  is resilient deformation. Therefore, when compression of liquid is terminated and a normal state of compressing gas refrigerant is restored, stopper  234  is restored to an initial shape simultaneously. Accordingly, the refrigerant compressor which can hardly be broken down even when liquid compression is occurred and hence has a high reliability is provided. 
     In this embodiment, a structure in which suction muffler  220  has suction port  222  in communication with sound-muffling portion  221  being opened toward opening end  223  of suction pipe  203  mounted to airtight container  201  in the vicinity thereof is shown as an example. However, the invention is not limited thereto, and the same effect can be obtained also in a structure in which suction port  222  and opening end  223  of suction pipe  203  are directly in communication. 
     INDUSTRIAL APPLICABILITY 
     As described above, according to the refrigerant compressor in the present invention, since the refrigerant compressor having high reliability without malfunction can be provided even when the returned amount of liquid refrigerant or oil from the external cooling circuit is large, or even when the amount of liquid refrigerant dissolved in oil when the refrigerant compressor is stopped, it can be applied to a large fridge-freezer for air conditioning or industrial use.