Abstract:
A hermetic compressor includes a compressing chamber and a valve plate forming suction and discharge ports communicating with the chamber. A discharge valve has one end fixed to the valve plae and a free end that is flexible to open and close the discharge port. A discharge backer has one end fixed to the valve plate and is positioned to limit the opening movement of the discharge valve. The discharge backer includes integral protrusions projecting toward the discharge valve. One of the projections is in constant contact with the discharge valve and forms a fulcrum therefor.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a hermetic compressor, more particularly, a valve apparatus for a hermetic compressor, which drives facilely a refrigerant discharge valve so as to improve a refrigerant discharge efficiency. 
     2. Description of the Related Art 
     Generally, there are various kinds of hermetic compressors such as a reciprocating compressor, a linear compressor and a rotary compressor. Most compressors are provided with a valve apparatus which controls an entrance of a refrigerant into a compressing chamber. 
     As shown in FIG. 6, a valve apparatus of the conventional reciprocating compressor comprises a cylinder head  11  which is coupled to a side of a cylinder block (not shown) of the compressor, and a valve plate  12  which is interposed between the cylinder head  11  and the cylinder block. A discharge valve  13  and a discharge backer  14  are riveted to the valve plate  12 . 
     Here, the discharge backer  14  is curved from a fixed end riveted to the valve plate  12  toward a free end thereof, i.e., the cylinder head  11 . This prevents the discharge valve  13  from having an unnecessary operating width, when the discharge valve  13  is operated, so that the discharge valve  13  properly performs an open-and-shut action. 
     However, in the conventional discharge backer  14 , since a surface, which is contacted wish the discharge valve  13 , is formed into a plane, an oil film is formed on the surface of the discharge backer  14  by oil which is discharged together with refrigerant gas during the open-and-shut action of the discharge valve  13 . Frequently, the discharge valve  13  to be contacted with the discharge backer  14  is closely contacted with the surface of the discharge backer  14  due to an oil viscosity. Therefore, there is a problem that the discharge valve  13  can not secure its own equal driving property. As disclosed above, if the discharge valve  13  can not show the equal driving property, a part of the discharged refrigerant flows backward into a compressing chamber during a suction stroke by the delay of a returning action of the discharge valve  13 . Therefore, there is other problem that a compressing efficiency of the refrigerant is lowered. 
     SUMMARY OF THE INVENTION 
     It is therefore an object of the present invention to improve the discharge backer which restricts and supports the operating width of the discharge valve so as to secure the equal and stable driving property of the discharge valve, thereby improving the compressing efficiency of the refrigerant. 
     To achieve the above objects and other advantages, there is provided an valve apparatus of a hermetic compressor, comprising a cylinder block in which a compressing chamber is formed; a valve plate which is disposed between the cylinder block and the a cylinder head coupled to a side of the cylinder block, and which is formed with a suction port and a discharge port; a discharge valve of which one end is fixed to the valve plate and the other end opens/closes the discharge port; and a discharge backer which is outwardly curved from its clamping end toward its free end so as to restrict an operating width of the discharge valve, characterized in that the discharge backer is provided with a protrusion which is projected toward the discharge backer so as to prevent the discharge valve from being closely contacted with the discharge backer. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The above object and other advantages of the present invention will become more apparent by describing in detail the preferred embodiments thereof with reference to the accompanying drawings, in which: 
     FIG. 1 is a cross-sectional view of a hermetic compressor with a valve apparatus according to the present invention; 
     FIG. 2 is an exploded perspective view of the valve apparatus according to the present invention; 
     FIG. 3 is an exploded perspective view of a part of the valve apparatus according to the present invention; 
     FIG. 4 is an enlarged perspective view of a discharge backer according to the present invention; 
     FIG. 5 a  is a view showing a state of the valve apparatus prior to discharging of refrigerant; 
     FIG. 5 b  is a view showing a state of the valve apparatus in which the refrigerant is discharged; and 
     FIG. 6 is an exploded perspective view of a valve apparatus in a conventional hermetic compressor. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The present invention now will be described more fully hereinafter with reference to the accompanying drawings, in which preferred embodiments of the invention are shown. 
     As shown in FIG. 1, a hermetic compressor with a valve apparatus according to the present invention is provided with a sealed housing  100  which has a sealed space therein. In the sealed housing  100 , there are disposed a driving portion  110  and a compressing portion  120 . 
     The driving portion  110  comprises a stator  111  which receives an electric current from the outside and forms a magnetic field, and a rotor  112  which is disposed at an inner side of the stator  111  and rotated by an electromagnetic force with the stator  111  and supported by a supporting bearing  113 . And at a center portion of the rotor  112 , there is mounted a rotational shaft  114 . A lower part of the rotational shaft  114  forms an eccentric shaft  115  which is biased against a rotational center of the rotational shaft  114 . At a lower end of the eccentric shaft  115 , there is mounted an oil pickup device  116  for picking up oil stored at a lower portion of the sealed housing  100 . 
     The compressing portion  120  supports the above construction elements of the driving portions, and comprises a cylinder block  121  which has a compressing chamber  125  therein and a piston  122  which is mounted in the compressing chamber in a vertical direction with respect to the eccentric shift  115  so as to perform a reciprocal rectilinear motion. A cylinder head  123  is mounted at a side of the compressing chamber  125 . Between the cylinder block  121  and the cylinder head  123 , there is disposed a valve apparatus  130  comprising a plurality of construction elements. A suction muffler  124  is disposed at an upper portion of the cylinder head  123 . 
     Meanwhile, as shown in FIGS. 2 and 3, the valve apparatus  130  comprises a suction valve  131  which is adjacent to the cylinder block  121  and a valve plate  132  which is formed with a suction port  132   b  and a discharge port  132   a . A discharge valve  133  is mounted on an outer side of the valve plate  132 . A discharge backer  200  is riveted along with the discharge valve  133 . At an outer face of the valve plate  132 , there is formed a mounting groove  132   d  for mounting the discharge valve  133  and the discharge backer  200 . Further, there are provided a plurality of gaskets  138  among the construction elements of the valve apparatus  130 . 
     Here, as shown in FIG. 4, the discharge backer  200  is formed with a clamping portion  210  having two holes  211  through which rivets are respectively inserted, and a supporting portion  220  which is extended from the clamping portion  210  so as to support an operating part of the discharge valve  133 . The supporting portion  220  is curved from the clamping portion  210  toward the cylinder head  123 . The curved width(W: a space between a free end of the supporting portion  220  and a surface of the valve plate  132 , FIG. 5 b ) is about 0.6˜1.2 mm. Further, the supporting portion  220  of the discharge backer ( 200 ) is formed with two protrusions  221 ,  222  which prevent the discharge valve  133  from being closely contacted with a bottom face of the discharge backer  200  by an oil viscosity. 
     The protrusions  221 ,  222  are a first protrusion  221  which is formed to be adjacent to the clamping portion  210  and is projected in a thickness (T 1 ) of 0.1˜0.3 mm toward the discharge valve  133 , and a second protrusion  222  which is projected in a thickness (T 2 ) of 0.1˜0.5 mm from the bottom face of the discharge backer  200  toward the discharge valve  133  and extended from a center of the free end of the supporting portion  220  to a portion which is below the half length of the supporting portion  220 . Further, at each opposite side of the first and second protrusions  221 ,  222 , there are respectively formed a first recess  223  and a second recess  224  corresponding to the first and second protrusions  221 ,  222 . 
     In addition, the supporting portion  220  of the discharge backer  200  is bent at an angle with the second protrusion  222  in the center so as to schematically form a V-shape. This also prevents the discharge valve  133  from being closely contacted with the discharge backer  200 . 
     Hereinafter, the operating state of the hermetic compressor according to the present invention will be disclosed more fully. 
     According to the hermetic compressor according to the present invention, if an electric current is applied from the outside to the stator  111 , the rotor  112  is rotated by an interaction due to the electromagnetic force between the stator  111  and the rotor  112 . The rotational shaft and the eccentric shaft  115  are rotated by the rotation of the rotor  112 . And due to the rotation of the eccentric shaft  115 , the piston  122  is linearly reciprocated within the compressing chamber  125  so that the refrigerant is sucked and discharged. 
     At this time, during the suction stroke, the piston  122  is moved to a bottom dead point in the compressing chamber  125 . Therefore, a pressure in the compressing chamber  125  is lowered. The suction valve  131  is opened so that the refrigerant passed through the suction muffler  124  is introduced into the compressing chamber  125 . In this situation, the discharge valve  133  is sealingly contacted to the discharge port  132   a , as shown in FIG. 5 a.    
     And during the exhaust stroke, the discharge valve  133  is pushed away by a pressure of the refrigerant compressed to the side of the discharge backer  200 , as shown in FIG. 5 b . At this time, the discharge valve  133  which opens the discharge port  132   a  is moved to the bottom face of the discharge backer  200  so that the operating width of the discharge valve  133  is restricted. Further, the discharge valve  133  is prevented from making close contact with discharge backer  200  by the first and second protrusions  221 ,  222 . As is apparent from FIGS. 5 a  and  5   b , the inner protrusion  221  is in constant contact with the discharge valve in both the open position (FIG. 5 b ) and the closed position (FIG. 5 a ) and forms a fulcrum therefor. 
     Further, since the supporting portion  220  of the discharge backer  200  is formed into the almost V-shape, the edge portion of the discharge valve except for the contacted portion with the second protrusion  222  is hardly contacted with the discharge backer  200 , thereby minimizing the contact surface between the discharge valve  133  and the discharge backer  200 . 
     If the discharge operating of the refrigerant is completed by the compressor, the discharge valve  133  is returned to the discharge port  132   a  by a restoring force and a suction due to a pressure reduction in the compressing chamber  125  so as to close the discharge port  132   a . Then, the suction, compression and exhaust stokes are continuously repeated. 
     In the discharge valve of the hermetic compressor according to the present invention, as described above, the plurality of protrusions are provided on the contacting face of the discharge backer which restricts the operating width of the discharge valve so as to minimize the contacting surface between the discharge backer and the discharge valve, thereby preventing the discharge valve from being closely contacted with the discharge backer by the oil viscosity, and preventing the unequal operating of the discharge valve. Ultimately, the compressing efficiency of the compressor is improved. 
     It will be apparent to those skilled in the art that various modifications and variations of the present invention can be made without departing from the spirit or scope of the invention. Thus, it is intended that the present invention cover the modifications and variations of this invention provided they come within the scope of the appended claims and their equivalents.