Patent Publication Number: US-6905318-B2

Title: Compressor including tapered discharged valve and valve seat

Description:
BACKGROUND OF THE INVENTION 
   The present invention relates to a compressor for use, mainly, in a cooling, refrigeration and/or air-conditioning apparatuses. 
   Conventionally, as a valve for opening and/or closing a passage, through which coolant or refrigerant flows into and/or out in a reciprocating compressor and/or a rotary compressor for use in cooling, refrigeration and/or air-condition, in particular, the valve which is applied into a discharge port for discharging the refrigerant therefrom, it is common to use a valve of so-called a reed-type, in which a thin plate-like valve opens and/or close the port therewith. 
   With such the valve mentioned above, an end of the plate-like valve is disposed so that it closes an outlet portion of the discharge valve, through which the refrigerant flows out, while the other end thereof is fixed on a side of compressing element of the compressor (i.e., on the port side thereof), wherein the opening/closing of the valve is conducted automatically through pressure difference between an inside and an outside of the discharge port. Also, there is one, in which the valve is fixed onto the compressing element through a stopper. 
   Considering an improvement on performances of the compressor, working fluid (i.e., the refrigerant) lying within the volume of a part of the discharge port, i.e., a gap or clearance volume, will not be discharged when the compressor completes the discharge cycle or stroke thereof, therefore it remains therein. Namely, the refrigerant remaining in this part comes to be discharged by the compressor operation but does not effect the heat exchange, therefore an efficiency in the compressor operation is lowered down if such the refrigerant increases in the volume thereof. 
   The working fluid of high temperature and high pressure remaining in this clearance volume, after all, expands within a suction chamber of low pressure, and in particular, in a case of the reciprocating compressor, this expansion reduces the suction volume thereof, thereby bringing about the decreasing of volume efficiency. Also, since energy of this expansion cannot be recovered or collected in the case of the rotary compressor, it comes to be power loss (hereinafter, being called by “re-expansion loss”), therefore it brings about lowering of the performances in the compressor. The greater the loss due to this re-expansion loss, the larger the ratio of the clearance volume occupying within the stroke volume of the compressor. For example, according to studies made by the inventors of the present invention, it is found that adiabatic efficiency is reduced down by about 5% due to this re-expansion, in particular in the case of the rotary compressor that is used in a home-use refrigerator. 
   For dissolving such the problem of the reed valve, for example, U.S. Pat. Nos. 4,543,989 and 5,346,373 disclose discharge valve apparatuses, in which a discharge valve of a poppet-type is applied so as to bring the clearance volume to be almost zero (0). 
   In the above-mentioned U.S. Pat. No. 4,543,989 (prior art 1) is disclosed a compressor of the reciprocating-type, which comprises a discharge port having a valve of a conical-shape and a spherical shape, and a valve seat recessed in a conical-shape, wherein the valve bodies are engaged within the recess of the valve seat, so as to remove that clearance volume therein. With the structure according to this prior art, the valve and the valve seat, both in the conical shape, are in contact with each other upon contacting surfaces thereof, thereby enclosing the spaces in front and rear of the port. Further, the valve is restricted on displacement in the vertical direction and decentering in the horizontal direction, within a cylindrical vacant cavity of a retainer engaged with or fitted to a bridge member, being provided over an opening of the port, so that it cover the discharge port on a down-stream side thereof, and the valve is biased toward the valve seat by means of a wound leaf spring which is inserted into this cavity. 
   Further in the above-mentioned Pat. No. 5,346,373 (prior art 2), a discharge valve apparatus is disclosed, in which both the valve and the valve seat are formed in the spherical shapes, so that they enable to close up even if the valve are inclined to the valve seat, and further the valve is biased toward the valve seat by means of the thin plate-like spring. 
   In the above-mentioned prior art 1, the retainer is fixed onto the compressing element (a cylinder side) by screwing the bridge member, on which is engaged or fitted the retainer, however when the retainer is attached onto the valve seat in eccentric or decentering therefrom, i.e., in a case where the valve is assembled into the valve seat in decentering therefrom, the valve declines when seating, so that it is unable to fully contact with upon the surface thereof, thereby disabling the enclosure, and therefore the working liquid of high temperature and high pressure flows back into the suction chamber, thereby decreasing volume efficiency. For this reason, the retainer and the valve seat must be fixed in concentric with each other, at high accuracy, therefore it causes a problem that the number of processes in assembling increases up, as well as the cost thereof. Further, the discharge valve apparatus is large in the number of constituent parts and complex in the structure thereof, therefore the productivity thereof is decreased down. 
   Also, though it is easy for a large compressor, it is more difficult to make an adjustment on the compressor, if it comes to be smaller in the sizes thereof, and also the higher accuracy is needed for it, therefore it causes a problem of bringing about the cost-up, however this prior art never pay considerations onto such the problems. 
   Also, in this prior art, since the valve is pushed or projected into the operation chamber of the compressor, so that it collides on a piston, if a bottom surface of the valve lies on the same plane to that of a valve plate and if the valve declines, during the closure of the valve, there occurs a problem that both collide with each other, in particular in the case of the rotary compressor, in which the moving direction of the valve for opening/closing, as well as that of a roller thereof, lie in the vertical direction. No consideration was paid, however, on those problems in this prior art. 
   In the prior art 2 mentioned above, since no bias is applied onto the valve due to the spring force under the condition when the valve is closed, and further no means is provided for restricting the movement of the valve in the horizontal direction, a delay is caused in the closing operation thereof due to rebounding when the valve is seated on the valve seat and/or the inclination of the valve when it is seated in greatly eccentric or decentering to the valve seat, therefore it causes a problem that the working fluid of high temperature and high pressure flows back into the suction chamber, thereby decreasing the volume efficiency down. 
   Also, with the retainer, the spring and the valve, etc., the constituent parts of the discharge valve apparatus, since they must be treated separately when they are assembled, it is difficult to handle or deal with them if they become small in sizes thereof, for example, in case of being applied into the compressor of small capacity, such as the compressor of a refrigerator or an air-conditioner for home-use, thereby bringing about a problem of decreasing down workability in assembling, as well as the productivity thereof. 
   Also, since the valve projects into the operation chamber of the compressor while providing a gap or clearance for escaping at the top portion of the piston, the clearance volume comes to be large, and this cannot be applied to such the rotary compressor, in which the moving direction of the valve for opening/closing, as well as that of the roller thereof, lie in the vertical direction. No consideration was paid, however, on such the problem in this prior art 2. 
   SUMMARY OF THE INVENTION 
   An object according to the present invention, therefore, is to provide a compressor, which can be assembled with ease, improving compression efficiency or adiabatic efficiency, as well as performances thereof. 
   The object mentioned above, according to the present invention, is accomplished by a compressor, comprising: a compression chamber for compressing working fluid within an inside thereof; a discharge port, through which said working fluid flows out from said compression chamber; a valve means for opening or closing said discharge port; a valve seat portion being provided in said discharge port and having a shape of curved surfaces, so that a cross-section area of said discharge port comes to be large from a side of the compression chamber; a valve having a projection portion having a curved surface in contact with said curved surface of the valve seat portion; and a means being provided on a member formed in one body with said valve seat portion, for positioning said valve to said valve seat portion. 
   Or alternatively, it is also accomplished by a compressor, comprising: a compression chamber for compressing working fluid within an inside thereof; a discharge port, through which said working fluid flows out from said compression chamber; a valve means for opening or closing said discharge port; a valve seat portion being provided in said discharge port and having a shape of curved surfaces, so that a cross-section area of said discharge port comes to be large from a side of the compression chamber; a valve having a projection portion having a curved surface in contact with said curved surface of the valve seat portion; a bore being provided on a member formed in one body with said valve seat portion, and connecting to said valve seat portion; and a holding means being inserted into an inside of said bore to be positioned, for holding said valve opposing to said valve seat. 
   Further, it is also accomplished by the compressor as defined in the above, further comprising: a biasing means for supporting said valve, so that said valve is freely contact on or separate from a sheet surface of said valve seat portion. Furthermore, it is also accomplished by the compressor as defined in the above, wherein said biasing means is a coiled spring, which is engaged with said valve and formed nearly into a conical shape. Or alternatively, it is also accomplished with the compressor as defined in the above, wherein said biasing means is a leaf spring, being formed with slits therein and biasing said valve with a central portion thereof. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIGS.  1 ( a ) and  1 ( b ) are the vertical and the horizontal cross-section views of a portion of a compressor according to the present invention; 
       FIG. 2  is an enlarged view of the compressor which is shown in the FIGS.  1 ( a ) and  1 ( b ), in particular for explaining a condition where a discharge valve thereof is closed; 
       FIG. 3  is an enlarged view of the compressor which is shown in the FIGS.  1 ( a ) and  1 ( b ), in particular for explaining a condition where a discharge valve thereof is opened; 
       FIG. 4  is an enlarged view of the compressor which is shown in the FIGS.  1 ( a ) and  1 ( b ), in particular for explaining curved surface configure of a valve of the discharge valve thereof; 
       FIG. 5  is an exploded perspective view of parts which constitute the discharge valve of the compressor shown in the FIGS.  1 ( a ) and  1 ( b ); 
     FIGS.  6 ( a ) through  6 ( c ) are views for explaining an assembling method of the discharge valve of the compressor shown in the FIGS.  1 ( a ) and  1 ( b ); 
       FIG. 7  is a plan view for showing a condition where a coiled spring is engaged within the discharge valve of the compressor shown in the FIGS.  1 ( a ) and  1 ( b ); 
     FIGS.  8 ( a ) and  8 ( b ) are views for explaining inclination of the valve of the discharge valve shown in the FIGS.  1 ( a ) and  1 ( b ), in particular when it is seated; 
     FIGS.  9 ( a ) and  9 ( b ) are the vertical cross-section views for showing machining processes of a valve seat, on which the discharge valve is seated, in the compressor shown in the FIGS.  1 ( a ) and  1 ( b ); 
     FIGS.  10 ( a ) and  10 ( b ) are also the vertical cross-section views for showing machining processes of a valve seat, on which the discharge valve is seated, in the compressor shown in the FIGS.  1 ( a ) and  1 ( b ); 
       FIG. 11  is a graph of showing performances of the compressor according to the present invention and that to the prior art, in comparison therebetween; 
       FIG. 12  is a graph of showing performances of the compressor according to the present, in comparison between cases where the discharge valve is biased by spring and where it is not; 
       FIG. 13  is an enlarged cross-section view for showing another embodiment of the compressor, according to the present invention; 
       FIG. 14  is a top plane view of the compressor shown in the  FIG. 13 ; 
       FIG. 15  is an enlarged cross-section view for showing other embodiment of the compressor, according to the present invention; 
       FIG. 16  is a top plane view of the compressor shown in the  FIG. 15 ; 
       FIG. 17  is an enlarged cross-section view for showing further other embodiment of the compressor, according to the present invention; 
     FIGS.  18 ( a ) through  18 ( c ) are view for explaining the assembling method of the compressor according to the present invention; 
       FIG. 19  is an enlarged cross-section view for showing further other embodiment of the compressor, according to the present invention; 
       FIG. 20  is a B—B cross-section view of the compressor shown in the  FIG. 19 ; 
       FIG. 21  is a vertical cross-section view of further other compressor, according to the present invention; 
       FIG. 22  is an enlarged view of the discharge valve of the compressor shown in the  FIG. 21 ; and 
       FIG. 23  is an enlarged cross-section view of a reed valve, which is widely applied as the discharge valve in the conventional art. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   Hereinafter, embodiments according to the present invention will be fully explained by referring to the attached drawings. 
   FIG.  1 ( a ) is the vertical cross-section view for showing the structure of a horizontal-type oscillating piston compressor, as one embodiment of the compressor comprising a discharge valve according to the present invention, and FIG.  1 ( b ) the horizontal cross-section view corresponding to a A—A cross-section in the FIG.  1 ( a ).  FIGS. 2 and 3  are enlarged views of the discharge valve shown in the FIGS.  1 ( a ) and  1 ( b ), and in particular, the  FIG. 2  shows the condition where the discharge valve is closed, while the  FIG. 3  where the discharge valve is fully opened.  FIG. 4  is an enlarged view of the compressor shown in the FIGS.  1 ( a ) and  1 ( b ), for explaining curved surface configure of a valve of the discharge valve thereof.  FIG. 5  is an exploded perspective view of parts which constitute the discharge valve of the compressor shown in the FIGS.  1 ( a ) and  1 ( b ). And, FIGS.  6 ( a ) through  6 ( c ) are views for explaining an assembling method of the discharge valve of the compressor shown in the FIGS.  1 ( a ) and  1 ( b ). 
   First of all, explanation will be given by referring to the FIGS.  1 ( a ) through  3 . 
   A reference numeral  1  indicates a hermetic container, in which are stored an electromotive element (i.e., a motor)  2  having a stator  2   a  and a rotor  2   b , and a compression element  3  driven by that electromotive element  2 . The compression element  3  comprises a cylinder  4 , a main bearing  5  and a sub- or auxiliary bearing  6  blocking the cylinder  4  at both end openings thereof, and a retainer insertion portion  6   a  formed in the sub-bearing  6 . This retainer insertion portion or bore  6   a , as will be mentioned later, constitutes a portion, into which is inserted a retainer for positioning a discharge valve of the compressor to a discharge port. 
   It further comprises an oscillating piston  8 , which is rotatably engaged with an eccentric portion  7   a  of a crank shaft  7  connected to the electromotive element  2  mentioned above, and a shoe  9  having a plane portion slidably abutting on a vane portion  8   a  of the oscillating piston  8  and a cylindrical surface portion slidably abutting on a cylindrical opening portion  4   a  of the cylinder  4  mentioned above. A reference numeral  10  indicates lubrication oil stored on the bottom of the hermetic container,  11  a suction pipe, through which refrigerant is sucked into,  12  a discharge pipe through which the refrigerant is discharged,  13  a discharge valve disposed on an end plate  6   b  of the sub-bearing  6 ,  14  a discharge port, and  15  a discharge cover for defining a discharge chamber therewith. 
   Also, the discharge valve  13  is constructed from a valve  17 , a valve seat  18 , a coiled spring  19  for biasing the valve  17  toward the valve seat  18 , and a retainer  20  for restricting the valve  17  from displacement thereof and positioning the valve to the valve seat or the discharge port. The valve  17  is made of a heat-resistive synthetic resin, such as, polyimide, polyamideimide, polyether-etherketone, polyetherimide, etc., or alloy material of relatively light-weight, such as, an alloy of titanium group, etc., and has a seal portion  17   a  in a spherical shape, so that it enters into inside of the discharge port  14 , to contact the valve seat  18  on the surface thereof, thereby closing or blocking the discharge port  14 . 
   The valve seat  18  is formed around the discharge port  14  in one body, and has an almost conical and trapezoidal shape. Also, the coiled spring  19  is made from a line-like material (wire) of same diameter, and is formed, for example, in a conical shape, and/or wound at an equal pitch, so that the line-like material does not contact with by itself even when the coiled spring  19  is compressed. 
   In the example of this embodiment, the oscillating piston compressor performs the compression operation as below. Upon rotation of the rotor  2   b  of the electromotive element  2 , the crank shaft  7  is driven, and the oscillating piston  8  engaged with the eccentric portion  7   a  on the crank shaft  7  performs wobbling movement within the cylinder  4 . An operation chamber  21  defined within the cylinder  4  is divided into a suction chamber and a compression chamber by the vane portion  8   a , therefore working fluid sucked from the suction pipe  11  into the suction chamber is compressed in the compression chamber. The compressed working fluid (i.e., the refrigerant) enters into the discharge chamber  16  from the discharge port  14  through the discharge valve  13 , and thereafter is discharged within the hermetic container  1 , to be discharged into an outside therefrom. 
   Next, explanation will be given on the operation of the discharge valve  13  according to the present embodiment.  FIG. 2  shows the condition where the discharge valve is closed, i.e., the condition of the discharge valve on suction stroke and on compression stroke. In this instance, the discharge chamber  16  in an upper portion of the valve  17  is communicated with, therefore it is filled with an atmosphere of the refrigerant discharged, i.e., at the high pressure of the discharge gas. On a while, since the discharge port  14  is communicated with the working chamber  21  on the suction stroke and/or the compression stroke, the pressure therein is lower than the discharge pressure at a lower portion of the valve  17 . 
   Accordingly, force acts upon the valve  17  due to the difference in pressures between those two, so that the valve  17  is suppressed downward. With this force, the seal portion  17   a  having the curved-surface shape of the valve  17  is pushed down toward the valve seat  18 , and they form a line-like contact portion forming just a circuit shape or the like, i.e., forming a so-called line contact, thereby maintaining the sealing therebetween. 
   The pressure increases up within the operation chamber  21  as the compression stroke proceeds, and when it comes to be larger than the discharge pressure, the force acting upon the valve  17  then pushes it down toward an outlet side (an upper side in the figure) of the discharge port due to the pressure difference. Explanation will be given on this condition by referring to FIG.  3 . 
   With the force due to the pressure difference in the refrigerant (i.e., the working fluid), the valve  17  is pushed up towards the outlet side (the upper side) of the discharge port as shown in the  FIG. 3 , and in this instance, a gap or clearance occurs between the valve  17  and the valve seat  18 . The working fluid compressed within the operation chamber  21  is discharged from the discharge port  14  after passing through the clearance mentioned above, a space defined between the line of the coiled spring  19  and a discharge gas passage  22  defined in the retainer  20  into the discharge chamber  16 . Namely, the insertion portion  6   a , into which the retainer is inserted, forms a part of the discharge port or the discharge passage for the working fluid. 
   The retainer  20  restricts the position of the valve  17 , so that the surface of the retainer  20  on the valve  17  side abuts on the surface of the valve  17  on the retainer  20  side, under the condition where the valve  17  is pushed upwards and then the coiled spring  19  is compressed. When the discharge stroke is completed, the valve  17  is pushed back by means of elastic force of the coiled spring  19 , so as to be seated on the valve seat  18 , i.e., in the condition shown in the  FIG. 2 , where the discharge valve is closed, again. 
   Next, explanation will be given on the configuration of curved surfaces of the valve, by referring to FIG.  4 . 
   The valve according to the present embodiment has a curved surface formed on the surface thereof, within a range so that it is able to contact the valve on all around the periphery surface thereof, even if it is eccentric from. Namely, on the valve  17 , as shown in the  FIG. 4 , a section “a-b” of curved surface is provided within a range of ε (≧δ 1 +δ 2 +δ 3 ) at a center of the seal portion  17  when the valve  17  is in no eccentric (i.e., concentric) condition, to be contact with the valve seat  18 , so that the valve  17  can contact the valve seat  18  on all around the periphery surfaces thereof, even in the condition where it is inclined, i.e., if the valve  17  comes in eccentric from the valve seat  18  due to mounting (or assembling) clearances, for example, clearance δ 1  defined between the insertion portion  6   a  of the sub-bearing  6  and the retainer  20  in the direction of diameter, clearance δ 2  between the retainer  20  and the coiled spring  19 , and clearance δ 3  between the coiled spring  19  and the valve  17 . 
   Next, explanation will be given on the configuration of the valve  17 , in more details thereof. In the  FIG. 4 , a side surface of the valve  17  has a spherical portion (the section “a-b”) and a conical portion (a section “b-c”). The valve  17  is provided as was mentioned in the above, for reducing the clearance volume within the discharge port  14  through an entire body thereof, and in particular, the spherical portion (the section “a-b”) mentioned above is a portion that is provided for sealing between the cylinder  4  side and the discharge chamber  16  side of the compressor mechanism portion within the discharge port  14 , by contacting with the surface of the valve seat  18 , while the conical shaped portion (the section “b-c”) is a portion provided for reducing the clearance volume by fitting to the shape of the valve seat  18  within the discharge port  14 . Length in the horizontal direction of the spherical portion (the section “a-b”) can be expressed by the following equation:
 
ε= SR (sin α−sin β 1 )= SR (sin β 1 −sin β 2 )
 
where, “α” is an angle defined by a central axis of the valve  17  being almost axial-symmetric in the shape and a straight line connecting between a center “O” of the spherical portion and a point “a”, “β 1 ” an angle defined by the central axis of the valve  17  and a straight line connecting between the center “O” of the spherical portion and a contact point of the valve  17  when it is seated on the valve seat  18  in concentric therewith, “β 2 ” an angle defined by the central axis of the valve  17  and a straight line connecting between the center “O” of the spherical portion and a point “b”, and “SR” a radius of the spherical portion.
 
   Further, among arc angles (α−β 1 ) and (β 1 −β 2 ) of the spherical portion, an angle  01  of the conical portion and an angle θ 2  of the valve seat  18 , the following relationships can be founded:
 
(α−β 2 )≧(β 1 −β 2 )
 
(β 1 −β 2 )≧(θ 1 −θ 2 )/2
 
   With such the construction as mentioned in the above, the valve can contact the valve seat  18  at the spherical portion (the section a-b) on a line all around thereof even when the valve  17  is inclined with respect to the valve seat  18  due to the clearances δ 1  through δ 3 , therefore it is possible to obtain sealing by means of the valve  17 , as well as reduction in the clearance volume. 
   Next, explanation will be given on assembling of the discharge valve  13  according to the present invention, by ref erring to  FIGS. 5  to  7 . The  FIG. 5  is an exploded perspective view of parts constructing the discharge valve of the present embodiment. A sequence for assembling each of the parts, which are shown in the  FIG. 5 , is shown in the FIGS.  6 ( a ) through  6 ( c ). As shown in the FIG.  6 ( a ), the retainer  20  and the coiled spring  19  and the valve  17  are fixed to one another, in such the condition that an end turn portion  19   c  on one end of the coiled spring  19  is tightly fitted into a bottom surface  20   a  of the retainer  20  where the wire material thereof is wound around on the maximum radius, while an end turn portion  19   b  on the other end thereof onto the valve  17  where the wire material is wound on the minimum one, by tying them with remaining to be tighten. In the present embodiment, as is shown in this figure, the retainer  20  and the valve  17  are fitted to or engaged with the coiled spring  19  each other, respectively, and then they are treated with as if being a one part, to be assembled into the discharge port  14 . 
   This coiled spring  19  mentioned above is in one body, together with the retainer  20  and the valve  17 , under the condition as shown by two-dotted chain lines in FIG.  7 . The portions treated with hatching lines indicate the end turn portions  19   a , wherein they are wound about by 0.6 turn at the minimum and the maximum radius, respectively, and further, each one of the end turn portion  19   b  of the minimum radius and the end turn portion  19   c  of the maximum radius is axial-symmetric in the region thereof. Fitting the end turn portion  19   b  of the minimum radius onto the valve  17  by tying up changes the radius from “R 1 ” to “R 1 ′”, and the center thereof from “O” to “O′”. 
   Next, fitting the end turn portion  19   c  of the maximum diameter onto the retainer  20  by tying up also changes the radius thereof from “R 2 ” to “R 2 ′”, however since both the end turn portions of the maximum radius and the minimum radius are tied up with the same remaining, the center of that radius “R 2 ” comes to “O′”, and then it comes to be coincident with the center of the above-mentioned “R 1 ′”. As a result of this, the retainer  20  and the valve  17  can be formed in one body with the coiled spring, concentrically. Also, due to the change in shape into a conical one by making the effective turn number thereof small (for example, 1.5 turn in the present embodiment), rigidity of the coiled spring  19  can be strengthen, thereby enabling to suppress the decentering of the valve when moving. 
   And, this part assembled in one body, as shown in FIG.  6 ( b ), is inserted into an insertion portion  6   a  of the sub-bearing  6  by means of a press-fitting jig  23 , in concentric with the valve seat  18 , thereby to be fixed thereto. Also, as shown in FIG.  6 ( c ), the coiled spring  19  is attached under the condition of being suppressed to be shorter than the free length thereof, therefore it applies spring force upon the valve  17  to be biased even under the condition that the valve is closed. Application of the spring force upon the valve  17  even under the closing condition of the valve, in this manner, suppresses rebounding of the valve  17  due to collision when the valve  17  is seated on the valve seat  18 , thereby effecting to prevent the valve from being delayed when it is closed. 
   Next, explanation will be given on movement of the valve, by referring to FIGS.  8 ( a ) and  8 ( b ). As be shown in those figures, in a case where the valve  17  is seated on the valve seat  18  in an eccentric condition, first the valve  17  contacts the valve seat  18  at a point “c” thereof, and thereafter at a point “d” on the opposing side with time-delay. This time difference comes to be a cause to delay inclosing of the valve, however such the application of the spring force under the condition where the valve is closed enables quick seating of the valve from the point “c” to the point “d”, thereby preventing the valve from delay in closing. 
   Further, since the bottom surface  17   b  of the valve  17  is formed, so that the valve  17  does not protrude or project into the compression chamber even when it is seated with inclination, it also can be applied into a compressor, such as an oscillating piston compressor shown in the present embodiment, in which the valve and the piston move in the directions being orthogonal to each other. 
   Next, explanation will be given on a machining method of the valve seat  18 , by referring to FIGS.  9 ( a ) through  10 ( b ). Those FIGS.  9 ( a ) through  10 ( b ) are vertical cross-section views of showing steps for machining the valve seat portion, on which is seated the discharge valve of the compressor according to the present invention. 
   As was mentioned in the above, the reed valve which was used as the discharge valve widely in the conventional art, has the structure that, as shown in the  FIG. 23 , the discharge port is covered by a thin plate-like valve seat  35 . With this reed valve, since the plate-like valve seat  35  is able to cover the port outlet as a whole even if it is shifted a little bit to the valve seat  18  in position, the valve  35  can seal the port  14 , therefore chance is small for it to have an important influence upon the performance of compression in the compressor. On the contrary to this, with the compressor having such the structure, in which the valve of the discharge valve has such the configuration that it fills up the inside of the discharge port, as in the present embodiment, the valve deteriorates the sealing capacity and/or causes delay in closing, thereby lowering the performances of the compressor, in particular when the valve  17  is seated on the valve seat  18  in such the eccentric or decentering manner therewith. 
   Then, it is preferable that the valve  17  and the valve seat  18  are disposed as in concentric with as possible. 
   According to the present embodiment, the valve  17  and the coiled spring  19  and the retainer  20  are assembled in one body, and are inserted into the insertion portion  6   a . Namely, the discharge valve  13  in the present embodiment has such the structure that the positional relationship between the insertion portion  6   a  and the retainer  20  is restricted by the positional relationship of the valve  17  to the valve seat  18 . Then, as was mentioned in the above, it is very important to dispose the insertion portion  6   a  and the valve seat  18 , concentrically, for the purpose of disposing the valve  17  and the valve seat  18 , concentrically. 
   In the present embodiment, as shown in FIGS.  9 ( a ) and  9 ( b ), the valve seat  18  and the retainer insertion portion  6   a  are machined by means of a cutting tool  36 . In those FIGS.  9 ( a ) and  9 ( b ), the cutting tool  36  has a first portion  36   a  for cutting the sub-bearing  6 , so as to form the insertion portion  6   a  and an inner side surface thereof, and a second portion  36   b , provided on tip side of the first portion  36   a , for cutting the sub-bearing  6 , so as to form an inclined surface on the valve seat  18 . In this cutting tool  36  according to the present embodiment, the first and the second portions are formed in concentric with the axial center thereof, therefore cutting-through of the cutting tool  36  to the sub-bearing  6  forms the insertion portion  6   a  and the valve seat  18 , concentrically. 
   With the cutting tool  36  of such the structure, it is possible to achieve work of forming, not only the insertion portion  6   a , but also the valve seat  18 , at the same time. With this, the work can be lessened in steps thereof, comparing to the case of performing it by steps separately, thereby reducing production cost thereof. Further, since there is no necessity of steps for positioning to fit with the configure, which was made up in a previous step, in a step following thereafter, an accuracy in the work step depends upon that of the configure obtained by the cutting tool  36 , therefore it is possible to form the configure with high accuracy, comparing to the case where the steps are performed separately, as was mentioned above. 
   Also, with the configure of the valve seat  18  shown in those FIGS.  9 ( a ) and  9 ( b ), since a member of the sub-bearing in the vicinity of the edge portion  6   c  is thin in the thickness, there is a possibility that the thin portion is deformed, like in a shape of an edge portion  6   d  shown by broken lines, when being machined. If such the edge portion  6   c  projects into the inside of the cylinder, it comes contact with the piston, the rotor and the scroll, thereby injuring or damaging them. While, if trying to make the piston to escape from the projecting portion of the edge portion  6   c , the volume efficiency of the compressor is reduced. 
   Also, if such the deformation occurs, the inclination is changed on the surface of the valve seat  18 , being made up by cutting until then. If the surface of the valve seat  18  is cut out by means of the cutting tool  36  in this condition, it is impossible to form the valve seat  18  with an appropriate angle of the inclination. 
   Then, it is necessary to make the deformation in the edge portion  6   c  of the valve seat  18  as small as possible. According to the present embodiment, as shown in FIGS.  10 ( a ) and  10 ( b ), a cylindrical portion  6   d ′ is provided on the valve seat  18  provided within the sub-bearing  6  at the cylinder  4  side. In this instance, on the cutting tool  36  is further provided a third portion  36   c  for cutting out the above-mentioned cylindrical portion  6   d , at a tip of the second portion  36   b . With such the cutting tool  36 , the cylindrical portion  6   d ′ can be formed on the valve seat  18  at the cylinder  4  side, at the same time when the insertion portion  6   a  or the valve seat  18  is formed with. 
   With such the structure, it is possible to ensure the thickness of the member corresponding to the edge portion  6   c  of the sheet member, by height of the cylindrical surface of the cylindrical portion  6   d ′, when forming the valve seat  18 , and due to this, it is possible to reduce the deformation of the sheet member, thereby lowering the protrusion of the edge portion  6   c  into the inside of the cylinder. Furthermore, it is also possible to form the valve seat  18  with an appropriate inclination, therefore it is possible to improve the sealing characteristic between the valve seat  18  and the valve  17 . 
   As was mentioned in the above, the discharge valve  13 , according to the present embodiment, is formed, so that it can be fit into the discharge port formed by the valve seat  18 , while forming the surface configuration of the valve  17 , which comes contact with the valve seat  18 , in a curved surface, therefore it is possible to reduce the clearance volume in the discharge port portion. Further, by making the valve  17  and the valve seat  18  have curved surfaces being different each other in the shapes thereof, the contact region between them comes to be in a circle, and further be nearly in such the condition that they contact each other on a line between them. With this, it is possible to reduce the clearance volume greatly, at the discharge port portion while maintaining the sealing between the valve  17  and the valve seat  18 , as well as to reduce the loss due to re-expansion. 
   Also, since the section, on which sealing is obtained through contacting between the valve  17  and the valve seat  18 , is defined on a region, so that the sealing can be obtained all around thereof even if the valve  17  is eccentrically seated on the valve seat  18  with inclining thereto, there is no need of fine adjustment for assembling the valve  17  and the valve seat  18  concentrically, thereby achieving easiness in assembling. Further, the valve  17  is biased so that the spring force is applied on it under the condition where the valve is closed, it is possible to suppress the rebounding of the valve  17 , which is caused due to the collision when it is seated on the valve seat  18 , as well as the delay in closing, which is caused due to the inclination of the valve  17  when it is seated on the on the valve seat  18  eccentrically therefrom. 
   Also, since the retainer  20  and the coiled spring  19  and the valve  17  are unified in one body, and since the retainer  20  mentioned above is fixed into the insertion portion  6   a  of the sub-bearing  6 , which is formed in concentric with the valve seat  18 , through press-fitting, it is possible to make the assembling further easy, as well as to suppress the delay in closing due to the inclination of the valve when it is seated, since the valve  17  and the valve seat  18  can be assembled to be in almost concentric with each other. 
   Next, the performances of the compressor according to the embodiments shown in the  FIGS. 1  to  7  are compared with those of the example of applying the reed valve as the discharge valve according to the conventional art. The compressor of this example is same to the oscillating piston compressor shown in the FIGS.  1 ( a ) and  1 ( b ), except for that the reed valve of the conventional art is applied as the discharge valve. 
   An example of experimental results is shown in FIG.  11 . This figure is a graph of showing a relationship between rotating speed and coefficient of performance “COP” (=refrigeration capacity/electric power consumption) for comparing the performances between the discharge valve according to the present embodiment and that of the conventional art. Herein, refrigerant is R134a, and the condition of experiments is that, suction pressure is Ps=0.101 MPa and discharge pressure Pd=0.837 MPa, corresponding to actual operating condition of refrigerators. The coefficient of performance “COP” is indicated by ratio, being set to 1.0 for the COP of the reed valve. Form the figure, with the discharge valve according to the present invention, it is apparent that the COP ration increases up by about 3% to 6%, and that the performance is improved by making the clearance volume almost to zero (0), so as to reduce the loss due to the re-expansion, comparing to that of the reed valve. 
   Next, a result of comparison is shown in  FIG. 12 , which is made on the performances of the compressors, in particular, between a case of applying the spring force on the valve when it is closed and a case of applying no such the force thereon, under the experimental condition that is shown in the FIG.  11 . The COP of the compressor is indicated by ratio, being set to 1.0 when no spring force is applied onto the valve when it is closed. From the figure, it is apparent that the COP ratio is improved by about 3% to 5%, comparing the case of biasing the valve with the spring force when it is closed to the case of biasing with no such the spring force. Biasing the valve with the spring force may be considered to be a cause of increasing the excessive compression loss, thereby lowering the performances of the compressor. However, from this experimental result, in case of applying a poppet type discharge valve, which is likely to be thick in the thickness of the valve and therefore heavy in the weight, it becomes clear that suppression of the delay inclosing of the valve due to the rebounding and/or the inclination of the valve when it is seated is more important than reduction of such the excessive compression loss. 
   From the above, according to the present embodiment, the loss can be reduced, which is caused from the clearance volume at the discharge port portion, thereby improving the efficiency of the compressor. Also, the compressor can be improved in assembling workability and productively. According to the present embodiment, the valve is formed in the spherical shape while the valve seat in the conical one, however those should not be restricted only thereto, and the same effect may be obtained if they are formed in such the shapes that the sealing can be obtained all around the periphery surfaces thereof even if the valve is inclined, such as, in the spherical shapes both. Also, though the discharge valve  13  is disposed on an end plate of the sub-bearing  6 , in the present embodiment, it is also possible to obtain the same effect to the present embodiment, if it is disposed on the end plate of the main bearing  5  or a side wall of the cylinder  4 . 
   Also, the explanation was given on the example of the compressor having only one cylinder, for example, listing up such as the oscillating piston compressor, however it is also possible to apply the present embodiment to an oscillating piston compressor having two (2) or more cylinders or to a rotary compressor having two (2) or more cylinders other than that mentioned above. 
   Explanation will be given on other embodiment according to the present invention, by referring to  FIGS. 13 and 14 . The  FIG. 13  is the enlarged vertical cross-section view for showing, in particular in the vicinity of the discharge valve of the other embodiment of the compressor having the discharge valve according to the present invention. The  FIG. 14  is a top plane view of the compressor shown in the FIG.  11 . The valve according to this embodiment is same to that of the discharge valve shown in those  FIGS. 2 and 3 , in the operation thereof, however it differs from that in the manner of fixing the retainer thereof. 
   In those  FIGS. 13 and 14 , the retainer  20   b  is inserted, so that an outer periphery portion  20   d  of a receiving portion  20   c  for receiving the coiled spring  19  therein keeps a fine clearance of about 50 μm from an inner side surface of an insertion portion  6   a , which is defined by a bore of the sub-bearing for insertion of the retainer, and is fixed onto the sub-bearing  6  through a screw  6   s . With this, the valve  17  and the valve seat  18  can be assembled almost in concentric with each other, but without rotating the retainer  20   b  accompanying with squeezing-up of the screw  6   s  when being screwed. 
   According to this, since the valve  17  can be prevented from the inclination when it is seated onto the valve seat  18 , it is possible to suppress the delay in closing of the valve. Further, the discharge port  14  and the valve seat  18  are free from the deformations due to the press-fitting of the retainer  20   b  and the sub-bearing  6 , therefore it is possible to provide the discharge valve for the compressor, being high in the assembling workability as well as the productivity thereof, and furthermore being superior in sealing property thereof. 
   Next, explanation will be given on further other embodiment according to the present invention, by referring to  FIGS. 15 and 16 . 
   The  FIG. 15  is the enlarged vertical cross-section view for showing, in the vicinity of the discharge valve of the further other embodiment of the compressor having the discharge valve according to the present invention. The  FIG. 16  is a top plane view of the compressor shown in the FIG.  15 . The discharge valve according to this embodiment differs from that shown in those  FIGS. 13 and 14 , in particular in the configuration of the discharge passage defined between the discharge valve and the retainer. 
   In those  FIGS. 15 and 16 , on the retainer  20   e  are formed plural numbers of guide portions  20   f , which are radially projecting from the spring receiving portion  20   c . A tip (outer peripheral) portion of this guide portion  20   f  is inserted, while keeping a fine clearance of about 50 μm from the side-wall surface of the insertion portion  6 , which is defined by the insertion bore of the sub-bearing  6 , being formed in concentric with the valve seat  18  to be inserted with the retainer therein. Herein, the working fluid (the refrigerant) passing by the valve  17  is discharged through a cutting portion  20   g  formed in an outside of the spring receiving portion  20   c.    
   With this, since it is possible to enlarge the area of the discharge passage for the working fluid after passing by the valve  17 , and further it is possible to discharge the working fluid, being discharged toward an outer direction from the valve  17 , smoothly from the cutting portion  20   g  formed on an outside of the spring receiving portion  20   c , then the pressure loss can be reduced, thereby providing the discharge valve being suitable for the compressor having a large flow-rate, too. 
   Explanation will be given on further other embodiment according to the present invention, by referring to FIG.  17 . The  FIG. 17  is the enlarged vertical cross-section view for showing, in particular in the vicinity of the discharge valve of the further other embodiment of the compressor, which has the discharge valve according to the present invention. 
   The valve according to this embodiment is same to that of the discharge valve shown in those  FIGS. 2 and 3  mentioned above, in the operation thereof, however it differs from in the manner of fixing the retainer thereof. In the  FIG. 17 , the retainer  20  is inserted while keeping the fine clearance of about 50 μm from the inner wall surface of the insertion portion  6   a , which is formed in concentric with the valve seat  18  and is defined by the bore on the sub-bearing to be inserted with the retainer therein, and then a collar  24  is pressed from above into the insertion portion  6   a  thereof, thereby press-fitting the retainer  20  into the insertion portion of the sub-bearing  6  through the collar  24  mentioned above. 
   According to this, since the valve  17  and the valve seat  18  are assembled in almost concentric with each other, so that the delay in closing of the valve due to the inclination of the valve can be suppressed when it is seated, and since the retainer  20  is not press-fitted by itself, it is possible to prevent the retainer  20  or the discharge port  14  and the valve seat  18  from the deformation thereon. With such the construction, good assembling workability and productivity can be obtained, and also the property of sealing between the valve and the valve seat can be improved, therefore it is possible to provide the compressor being superior in efficiency thereof. 
   Next, another method for assembling the retainer  20 , the coiled spring  19  and the valve  17  is shown in FIGS.  18 ( a ) through  18 ( c ), with the structures of those which are shown in the FIGS.  6 ( a ) through  6 ( c ). 
   With the structure of the discharge valve according to the present embodiment, as shown in FIG.  18 ( a ), a penetrating bore  20   i  is formed at a central portion of the retainer  20  while a recessed portion  17   d  at a central portion of the valve  17 . Insertion of an assembling assist member  23   a  of elasticity, such as robber, resin material, etc., into those penetrating bore  20   i  and recessed portion  17   d  mentioned above brings them to be in a form of one body. Those parts assembled in one body, as shown in FIG.  18 ( b ), are fixed through press-fitting of the retainer  20  into the insertion portion  6   a  of the sub-bearing  6 , which is formed in concentric with the valve seat  18 , by means of a press-fitting tool  23 . After the press-fitting, as shown in FIG.  18 ( c ), the assembling assist member  23   a  is removed out, and the discharge valve is provided or positioned. 
   With doing so, the retainer  20  and the coiled spring  19  and the valve  17  can be formed in one body with the force due to elastic deformation of the assembling assist member  23   a , thereby enabling easy assembling thereof. 
   Next, explanation will be given on further other embodiment according to the present invention, by referring to  FIGS. 19 and 20 . The  FIG. 19  is the enlarged vertical cross-section view for showing, in the vicinity of the discharge valve of the further other embodiment of the compressor, which has the discharge valve according to the present invention. The  FIG. 20  is a B—B cross-section view of the compressor shown in the  FIG. 19 , in the vicinity of the discharge valve thereof. The operation of the discharge valve according to this embodiment is similar to that in the case of the discharge valve shown in those  FIGS. 2 and 3  mentioned above, however the spring for giving the bias onto the valve  17  is in a form of a plate-like spring. 
   According to the present embodiment, as shown in the  FIGS. 19 and 20 , the valve  17  is biased toward the valve seat by means of the leaf spring  19   d . This leaf spring  19   d , being provided with slits on a flat plate-like sheet member thereof in symmetry with respect to the central portion where the valve  17  is held thereon, as shown in the  FIG. 18 , is movable in parallel to an upper surface  17   c  of the valve  17 , at a central portion  19   f  thereof. Also, this leaf spring  19   d  is fixed with an outer peripheral portion thereof, within the insertion portion, by means of the retainer, which is press-fitted into the insertion bore, i.e., the insertion portion  6   a.    
   With this, the space volume can be reduced, in which the spring is disposed, thereby enabling small-sizing of the discharge valve as a whole. 
   Also, since it is possible to make the rigidity in the horizontal direction stronger than the coiled spring, as well as light-weighting of the valve  17 , it is possible to make the decentration of the valve  17  to the valve seat  18  much smaller, thereby suppressing the delay in closing of the valve  17  due to the inclination much shorter. 
   Next, explanation will be given on a reciprocating type compressor installing the discharge valve therein, which is explained in the embodiment mentioned above, by referring to  FIGS. 21 and 22 . 
     FIG. 21  is the vertical cross-section view for showing the structure of a so-called Scotch yoke type reciprocating compressor having the discharge valve according to the embodiment mentioned above.  FIG. 22  is the cross-section view for showing the compressor shown in the  FIG. 21 , in particular in the vicinity of the discharge valve thereof, enlargedly. The compression element  3   a  of the Scotch yoke type reciprocating compressor comprises a cylinder block  25 , a frame on which the cylinder block  25  is fixed, a piston  27  which is inserted into a bore portion  25   a  of the cylinder block  25 , and a cylinder head which closes one opening of the cylinder block  25 . Onto a cylinder head  28  is attached a retainer  20   h , on which the coiled spring  19  is attached, and on the retainer  20   h  is attached a head cover  29  forming the discharge chamber  16  therewith. It also comprises a slider  30  which is engaged with an eccentric portion  7   c  of a crank shaft  7   b . And, the discharge valve  13  according to the present embodiment of the present invention mentioned above is provided on a cylinder head  28 . 
   Compression operation of the Scotch yoke type reciprocating compressor is performed as follows. When electricity is conducted through the electromotive element  2   c , rotation of the rotor  2   b  drives the crank shaft  7   b , and the piston  27  conducts reciprocating movement within the bore portion  25   a , following the revolution of the slider  30  accompanying therewith, thereby repeating increase and decrease in volume of the operation chamber  21 . Accompanying with the reciprocating movement of this piston  27 , the working fluid (the refrigerant) sucked into from the suction pipe  11  flows into a silencer  31 , and after passing through the suction valve  32  of a thin plate, it is compressed within the above-mentioned operation chamber  21 . Next, the working fluid compressed passes from the discharge port  14  through the discharge valve  13  into the discharge chamber  16 , and is discharged outside the compressor from the discharge pipe  12 . 
   Herein, the retainer  20   h  and the coiled spring  19  and the valve  17  are assembled in one body, in such the method as shown in those  FIGS. 5  to  7 . The retainer  20   h  mentioned above is positioned with respect to the cylinder head  28 , so that the valve  17  mentioned above and the valve seat  18  are concentric with each other, through guide pins  34 , which are inserted into the guide bores  33  provided on the retainer  20   h  and the cylinder head  28  at least two (2) or more with keeping a fine clearance of about 50 μm therebetween. 
   With this, the discharge valve can be assembled easily, as well as the valve  17  and the valve seat  18  in almost concentric with, and the valve can be protected from the inclination thereof when it is seated, thereby suppressing the delay in closing thereof. Also, an escape portion is provided with a flat surface portion on the bottom of the bottom surface  17   b  of the valve  17 , so that the valve  17  does not project into the operation chamber of the bore portion  25   a  when it is inclined, therefore it is possible to reduce the clearance volume comparing to the case where the escaping portion for the valve  17  is provided at the top of the piston  27 . 
   From the above, since the reciprocating compressor of the present embodiment has the discharge valve  13  according to the present embodiment, it is possible to reduce the suction volume due to the re-expansion of the gas within the clearance volume of the discharge port, thereby to improve the volume efficiency thereof. It is also possible to improve the assembling workability and productivity of the compressor, or improve the sealing property of the valve, thereby to improve the adiabatic efficiency of the compressor. 
   In the embodiments mentioned above, the explanation was given only on the case where the discharge valve is applied to the oscillating piston compressor and the reciprocating compressor, however the present invention should not be restricted only thereto, but it may be applied to a scroll compressor, with obtaining the following effects therefrom. 
   With the scroll compressor having the discharge valve  13  according to the present invention, shortage compression loss is small even when the design pressure ratio (being proportional to the turn number of wrap winding) of wrapping is made smaller than the operating pressure ratio, therefore it is possible to remove the re-expansion loss caused due to the clearance volume of the discharge port. Accordingly, it is possible to reduce the turn number of the wrap winding, greatly, thereby greatly reducing the manufacturing steps, as well as improving the assembling workability thereof; therefore it is possible to provide the compressor being greatly reduced in the manufacturing const thereof. Then, the scroll having pressure ratio of about four (4) for use in the air-conditioning also can be used as the scroll for use in the refrigerator of the pressure ratio, being as two times large as that, i.e., with high efficiency. It is possible to achieve common use of the parts between both of them, thereby realizing great cost reduction thereof. It is also possible to improve the assembling workability and the productivity of the compressor, thereby providing the compressor having improvement on the sealing property between the valve and the valve seat. 
   As was fully explained in the above, according to the present invention, it is possible to provide the compressor, being easy in assembling and improved in the performances thereof. 
   While we have shown and described several embodiments in accordance with our invention, it should be understood that the disclosed embodiments are susceptible of changes and modifications without departing from the scope of the invention. Therefore, we do not intend to be bound by the details shown and described herein but intend to cover all such changes and modifications falling within the ambit of the appended claims.