Abstract:
A scroll compressor has a pair of scroll members which compress a fluid as the fluid moves through pockets created by the scroll members. The fluid moves from a suction pressure zone to a discharge pressure zone. A chamber is defined by one of the scroll members. The chamber is in communication with a pocket located between the suction and discharge pressure zone such that an intermediate pressurized fluid is supplied to the chamber through a fluid passageway. The fluid passageway is designed to allow a large flow from the pocket to the chamber and a small flow from the chamber to the pocket. This dual flow capability reduces the pressure pulsation in the chamber. In one embodiment, a capacity control mechanism is associated with the compressor to vary the capacity of the compressor.

Description:
FIELD OF INVENTION 
     The present invention relates to scroll machines. More particularly, the present invention relates to asymmetrically located bleed holes located in one of the scroll members which provide pressurized fluid for scroll biasing and can also be utilized for a capacity modulation system of the delayed suction type for scroll compressors. 
     BACKGROUND AND SUMMARY OF THE INVENTION 
     Scroll type machines are becoming more and more popular for use as compressors in both refrigeration as well as air conditioning applications due primarily to their capability for extremely efficient operation. Generally, these machines incorporate a pair of intermeshed spiral wraps, one of which is caused to orbit relative to the other so as to define one or more moving chambers which progressively decrease in size as they travel from an outer suction port toward a center discharge port. An electric motor is provided which operates to drive the orbiting scroll member via a suitable drive shaft affixed to the motor rotor. In a hermetic compressor, the bottom of the hermetic shell normally contains an oil sump for lubricating and cooling purposes. 
     In order to expand the use of scroll type machines and to increase the efficiency of these machines, capacity modulation systems have been developed to vary the capacity of these machines. A wide variety of systems have been developed in order to accomplish capacity modulation most of which delay the initial sealing point of the moving fluid pockets defined by the scroll members. In one form, such systems commonly employ a pair of vent passages communicating between suction pressure and the outermost pair of moving fluid pockets. Typically these passages open into the moving fluid pockets at a position normally within 360° of the sealing point of the outer ends of the wraps. Some systems employ a separate valve member for each such vent passage. These valves are intended to be operated simultaneously so as to ensure a pressure balance between the two fluid pockets. Other systems employ additional passages to place the two vent passages in fluid communication thereby enabling use of a single valve to control capacity modulation. 
     More recently a capacity modulation system for scroll compressors of the delayed suction type has been developed in which a valving ring is movably supported on the non-orbiting scroll member. An actuating piston is provided which operates to rotate the valving ring relative to the non-orbiting scroll member to thereby selectively open and close one or more vent passages which communicate with selective ones of the moving fluid pockets to thereby vent the pockets to suction. A scroll-type compressor incorporating this type of capacity modulation system is disclosed in U.S. Pat. No. 5,678,985 the disclosure of which is hereby incorporated by reference. In this capacity modulation system, the actuating piston is operated by fluid pressure controlled by a solenoid valve. 
     This capacity modulation system utilizes a pair of axially extending passages in the non-orbiting scroll that place a pair of the moving pockets in fluid communication with the suction pressure zone of the compressor in order to delay the sealing of the moving pockets and thus reduce the capacity of the scroll machine. The delay in the sealing for the pockets reduces the capacity of the scroll machine and therefore reduces the fluid pressure within the pockets when compared with the pressure within the fluid pockets when the compressor is operating in the full load mode. In a scroll compressor which utilizes compressed fluid from the moving pockets to bias the two scroll members together, the reduced pressure within the pockets reduces the fluid pressure biasing the scroll members together which then potentially creates the problem of the scroll members unloading. 
     In compressors which utilize a floating seal which is biased to close a leakage path between discharge and suction, a similar problem could be created. A lower fluid pressure lowers the biasing load for the seal which potentially creates the problem of the seal falling to open the leakage path between discharge and suction thus unloading the compressor. 
     In order to prevent unloading of the scroll compressor when the capacity modulation system is actuated, the bleed hole which supplies the biasing fluid for the biasing chamber needs to be moved closer to the discharge port of the compressor. This movement of the bleed hole closer to the discharge port will increase the biasing fluid pressure in both the modulation mode as well as in the full capacity mode. While moving the bleed hole closer to discharge may help resolve the problems associated with compressor unloading during modulated operation, the increase biasing pressurized fluid during full load operation can create other problems with the operation of the compressor. These problems include but are not limited to an increase in the pressure pulsation in the intermediate chamber and an increase in the compression power required. 
     The present invention provides the art with a bleed hole which allows a relatively large flow of pressurized fluid from the fluid pockets to the intermediate chamber while limiting the flow of pressurized fluid from the intermediate chamber back to the fluid pockets. In one embodiment, this bleed hole is used in conjunction with a capacity modulation system which then allows for the normal placement for the bleed hole. In another embodiment of the present invention, this bleed hole is used in a non-modulated compressor in order to decrease the pressure pulsation in the intermediate chamber. 
     Other advantages and objects of the present invention will become apparent to those skilled in the art from the subsequent detailed description, appended claims and drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     In the drawings which illustrate the best mode presently contemplated for carrying out the present invention: 
     FIG. 1 is a vertical cross-sectional view through the center of a scroll type refrigerant compressor incorporating a capacity modulation system which include the unique bleed hole in accordance with the present invention; 
     FIG. 2 is a fragmentary view of the compressor shown in FIG. 1 showing the valve ring in a closed or unmodulated position; 
     FIG. 3 is a plan view of the compressor shown in FIG. 1 with the top portion of the outer shell removed; 
     FIG. 4 is a fragmentary view of the compressor shown in FIG. 1 showing the valve ring in an open or modulated position; 
     FIG. 5 is a perspective view of the valving ring incorporated in the compressor shown in FIG. 1; 
     FIG. 6 is an enlarged detail view of the actuating assembly incorporating into the compressor of FIG. 1; 
     FIG. 7 is a perspective view of the compressor of FIG. 1 with portions of the outer shell broken away; 
     FIG. 8 is a fragmentary section view of the compressor of FIG. 1 showing the pressurized fluid supply passages provided in the non-orbiting scroll; 
     FIG. 9 is an enlarged section view of the solenoid valve assembly incorporated in the compressor of FIG. 1; 
     FIG. 10 is an enlarged view of the bleed hole in the non-orbiting scroll shown in FIG. 1; 
     FIG. 11 is a fragmentary view of a compressor incorporating the bleed hole in accordance with the present invention but without a capacity modulation system; and 
     FIG. 12 is an enlarged view of a bleed hole in a non-orbiting scroll in accordance with another embodiment of the present invention. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring now to the drawings in which like reference numerals designate like or corresponding parts throughout the several views, there is shown in FIG. 1 a scroll compressor which incorporates a bleed hole designed in accordance with the present invention which is designated generally by reference numeral  10 . Compressor  10  is generally of the type disclosed in U.S. Pat. No. 4,767,293 issued Aug. 30, 1988 and assigned to the same assignee as the present application, the disclosure of which is hereby incorporated herein by reference. Compressor  10  comprises a generally cylindrical hermetic shell  12  having welded at the upper end thereof a cap  14  and at the lower end thereof a base  16  having a plurality of mounting feet (not shown) integrally formed therewith. Cap  14  is provided with a refrigerant discharge fitting  18  which may have the usual discharge valve therein. Other major elements affixed to the shell include a transversely extending partition  22  which is welded about its periphery at the same point that cap  14  is welded to shell  12 , a main bearing housing  24  which is suitably secured to shell  12  and a lower bearing housing  26  having a plurality of radially outwardly extending legs each of which is also suitably secured to shell  12 . A motor stator  28  which is generally square in cross-section but with the corners rounded off is press fitted into shell  12 . The flats between the rounded corners on the stator provide passageways between the stator and shell, which facilitate the return flow of lubricant from the top of the shell to the bottom. 
     A drive shaft or crankshaft  30  having an eccentric crank pin  32  at the upper end thereof is rotatably journaled in a bearing  34  in main bearing housing  24  and a second bearing  36  in lower bearing housing  26 . Crankshaft  30  has at the lower end a relatively large diameter concentric bore  38  which communicates with a radially outwardly inclined smaller diameter bore  40  extending upwardly therefrom to the top of crankshaft  30 . The lower portion of the interior shell  12  defines an oil sump  44  which is filled with lubricating oil to a level slightly above the lower end of a rotor  46 , and bore  38  acts as a pump to pump lubricating fluid up the crankshaft  30  and into bore  40  and ultimately to all of the various portions of the compressor which require lubrication. 
     Crankshaft  30  is rotatively driven by an electric motor including stator  28 , windings  48  passing therethrough and rotor  46  press fitted on the crankshaft  30  and having upper and lower counterweights  50  and  52 , respectively. 
     The upper surface of main bearing housing  24  is provided with a flat thrust bearing surface  54  on which is disposed an orbiting scroll member  56  having the usual spiral vane or wrap  58  extending upward from an end plate  60 . Projecting downwardly from the lower surface of end plate  60  of orbiting scroll member  56  is a cylindrical hub having a journal bearing  62  therein and in which is rotatively disposed a drive bushing  64  having an inner bore  66  in which crank pin  32  is drivingly disposed. Crank pin  32  has a flat on one surface which drivingly engages a flat surface (not shown) formed in a portion of bore  66  to provide a radially compliant driving arrangement, such as shown in assignee&#39;s U.S. Pat. No. 4,877,382, the disclosure of which is hereby incorporated herein by reference. An Oldham coupling  68  is also provided positioned between orbiting scroll member  56  and bearing housing  24  and keyed to orbiting scroll member  56  and a non-orbiting scroll member  70  to prevent rotational movement of orbiting scroll member  56 . Oldham coupling  68  is preferably of the type disclosed in assignee&#39;s co-pending U.S. Pat. No. 5,320,506, the disclosure of which is hereby incorporated herein by reference. 
     Non-orbiting scroll member  70  is also provided having a wrap  72  extending downwardly from an end plate  74  which is positioned in meshing engagement with wrap  58  of orbiting scroll member  56  to define moving pockets  76  and  78  which progressively decrease in size as they move inwardly from the outer periphery of scroll members  56  and  70 . Non-orbiting scroll member  70  has a centrally disposed discharge passage  80  which communicates with an upwardly open recess  82  which in turn is in fluid communication with a discharge muffler chamber  84  defined by cap  14  and partition  22 . An annular recess  86  is also formed in non-orbiting scroll member  70  within which is disposed a seal assembly  88 . Recesses  82  and  86  and seal assembly  88  cooperate to define axial pressure biasing chambers which receive pressurized fluid being compressed by wraps  58  and  72  so as to exert an axial biasing force on non-orbiting scroll member  70  to thereby urge the tips of respective wraps  58 ,  72  into sealing engagement with the opposed end plate surfaces of end plates  74  and  60 , respectively. Seal assembly  88  is preferably of the type described in greater detail in U.S. Pat. No. 5,156,539, the disclosure of which is hereby incorporated herein by reference. Non-orbiting scroll member  70  is designed to be mounted to bearing housing  24  in a suitable manner such as disclosed in the aforementioned U.S. Pat. No. 4,877,382 or U.S. Pat. No. 5,407,335, the disclosure of which is hereby incorporated herein by reference. 
     As thus far described, scroll compressor  10  is typical of such scroll-type refrigeration compressors. In operation, suction gas directed to a lower suction chamber  90  via a suction inlet  92  is drawn into the moving fluid pockets  76  and  78  as orbiting scroll member  56  orbits with respect to non-orbiting scroll member  70 . As the moving fluid pockets  76  and  78  move inwardly, this suction gas is compressed and subsequently discharged into discharge chamber  84  via center discharge passage  80  in non-orbiting scroll member  70  and a discharge opening  94  in partition  22 . Compressed refrigerant is then supplied to the refrigeration system via discharge fitting  18 . 
     In selecting a refrigeration compressor for a particular application, one would normally choose a compressor having sufficient capacity to provide adequate refrigerant flow for the most adverse operating conditions to be anticipated for that application and may select a slightly larger capacity to provide an extra margin of safety. However, such “worst case” adverse conditions are rarely encountered during actual operation and thus this excess capacity of the compressor results in operation of the compressor under lightly loaded conditions for a high percentage of its operating time. Such operation results in reducing overall operating efficiency of the system. Accordingly, in order to improve the overall operating efficiency under generally encountered operating conditions while still enabling the refrigeration compressor to accommodate the “worst case” operating conditions, compressor  10  is provided with a capacity modulation system. 
     The capacity modulation system includes an annular valving ring  100  movably mounted on non-orbiting scroll member  70 , an actuating assembly  102  supported within shell  12  and a control system  104  for controlling operation of the actuating assembly. 
     As best seen with reference to FIGS. 2,  4  and  5 , valving ring  100  comprises a generally circularly shaped main body  106  having a pair of substantially diametrically opposed radially inwardly extending protrusions  108  provided thereon of substantially identical predetermined axial and circumferential dimensions. Suitable substantially identical circumferentially extending guide surfaces  112  and  116  are provided adjacent axially opposite sides of each of protrusions  108 . Additionally, two pairs of substantially identical circumferentially extending axially spaced guide surfaces  120  and  124  are provided on main body  106 , each being positioned in substantially diametrically opposed relationship to each other and spaced circumferentially approximately 90° from each protrusions  108 . As shown, guide surfaces  124  project radially inwardly slightly from main body  106  as do guide surfaces  112 . Preferably, guide surfaces  124  and  112  are all axially aligned and lie along the periphery of a circle of a radius slightly less than the radius of main body  106 . Similarly, guide surfaces  120  project radially inwardly slightly from main body  106  as do guide surfaces  116  with which they are preferably axially aligned. Also surfaces  120  and  116  lie along the periphery of a circle of a radius slightly less than the radius of main body  106  and preferably substantially equal to the radius of the circle along which surfaces  124  and  112  lie. Main body  106  also includes a circumferentially extending stepped portion  126  which includes an axially extending circumferentially facing stop surface  128  at one end. Step portion  126  is positioned between protrusion  108  and guide surfaces  120 ,  124 . A pin member  130  is also provided extending axially upwardly adjacent one end of stepped portion  126 . Valving ring  100  may be fabricated from a suitable metal such as aluminum or alternatively may be formed from a suitable polymeric composition and pin member  130  may be either pressed into a suitable opening provided therein or integrally formed therewith. 
     As previously mentioned, valving ring  100  is designed to be movably mounted on non-orbiting scroll member  70 . In order to accommodate valving ring  100 , non-orbiting scroll member  70  includes a radially outwardly facing cylindrical sidewall portion  132  thereon having an annular groove  134  formed therein adjacent the upper end thereof. In order to enable valving ring  100  to be assembled to non-orbiting scroll member  70 , a pair of diametrically opposed substantially identical radially inwardly extending notches  136  and  138  are provided in non-orbiting scroll member  70  each opening into groove  134  as best seen with reference to FIG.  3 . Notches  136  and  138  have a circumferentially extending dimension slightly larger than the circumferential extent of protrusions  108  on valving ring  100 . 
     Groove  134  is sized to movably accommodate protrusions  108  when valving ring is assembled thereto and notches  136  and  138  are sized to enable protrusions  108  to be moved into groove  134 . Additionally, cylindrical sidewall portion  132  will have a diameter such that guide surfaces  112 ,  116 ,  120  and  124  will slidingly support rotary movement of valving ring  100  with respect to non-orbiting scroll member  70 . 
     Non-orbiting scroll member  70  also includes a pair of generally diametrically opposed radially extending passages  140  and  142  opening into the inner surface of groove  134  and extending generally radially inwardly through the end plate of non-orbiting scroll member  70 . An axially extending passage  144  places the inner end of passage  140  in fluid communication with moving fluid pocket  76  while a second axially extending passage  146  places the inner end of passage  142  in fluid communication with moving fluid pocket  78 . Preferably, passages  144  and  146  will be oval in shape so as to maximize the size of the opening thereof without having a width greater than the width of the wrap of the orbiting scroll member  56 . Passage  144  is positioned adjacent an inner sidewall surface of scroll wrap  72  and passage  146  is positioned adjacent an outer sidewall surface of wrap  72 . Alternatively passages  144  and  146  may be round if desired however the diameter thereof should be such that the opening does not extend to the radially inner side of the orbiting scroll member  56  as it passes thereover. 
     As best seen with reference to FIG. 6, actuating assembly  102  includes a piston and cylinder assembly  148  and a return spring assembly  150 . Piston and cylinder assembly  148  includes a housing  152  having a bore defining a cylinder  154  extending inwardly from one end thereof and within which a piston  156  is movably disposed. An outer end  158  of piston  156  projects axially outwardly from one end of housing  152  and includes an elongated or oval-shaped opening  160  therein adapted to receive pin  130  forming a part of valving ring  100 . Elongated or oval opening  160  is designed to accommodate the arcuate movement of pin  130  relative to the linear movement of piston end  158  during operation. A depending portion  162  of housing  152  has secured thereto a suitably sized mounting flange  164  which is adapted to enable housing  152  to be secured to a suitable flange member  166  by bolts  168 . Flange  166  is in turn suitably supported within outer shell  12  such as by bearing housing  24 . 
     A passage  170  is provided in depending portion  162  extending upwardly from the lower end thereof and opening into a laterally extending passage  172  which in turn opens into the inner end of cylinder  154 . A second laterally extending passage  174  provided in depending portion  162  opens outwardly through the sidewall thereof and communicates at its inner end with passage  170 . A second relatively small laterally extending passage  178  extends from fluid passage  170  in the opposite direction of fluid passage  172  and opens outwardly through an end wall  180  of housing  152 . 
     A pin member  182  is provided upstanding from housing  152  to which is connected one end of a return spring  184  the other end of which is connected to an extended portion of pin  130 . Return spring  184  will be of such a length and strength as to urge ring  100  and piston  156  into the position shown in FIG. 7 when cylinder  154  is fully vented via passage  178 . 
     As best seen with reference to FIGS. 7 and 9, control system  104  includes a valve body  186  having a radially outwardly extending flange  188  including a conical surface  190  on one side thereof. Valve body  186  is inserted into an opening  192  in outer shell  12  and positioned with conical surface  190  abutting the peripheral edge of opening  192  and then welded to shell  12  with a cylindrical portion  194  projecting outwardly therefrom. Cylindrical portion  194  of valve body  186  includes an enlarged diameter threaded bore  196  extending axially inwardly and opening into a recessed area  198 . 
     Valve body  186  includes a housing  200  having a first passage  202  extending downwardly from a substantially flat upper surface  204  and intersecting a second laterally extending passage  206  which opens outwardly into the area of opening  192  in shell  12 . A third passage  208  also extends downwardly from surface  204  and intersects a fourth laterally extending passage  210  which also opens outwardly into a recessed area  212  provided in the end portion of body  186 . 
     A manifold  214  is sealingly secured to surface  204  by means of suitable fasteners and includes fittings for connection of one end of each of fluid lines  216  and  218  so as to place them in sealed fluid communication with respective passages  202  and  208 . 
     A solenoid coil assembly  220  is designed to be sealingly secured to valve body  186  and includes an elongated tubular member  222  having a threaded fitting  224  sealingly secured to the open end thereof. Threaded fitting  224  is adapted to be threadedly received within bore  196  and sealed thereto by means of an O-ring  226 . A plunger  228  is movably disposed within tubular member  222  and is biased outwardly therefrom by a spring  230  which bears against a closed end  232  of tubular member  222 . A valve member  234  is provided on the outer end of plunger  228  and cooperates with a valve seat  236  to selectively close off passage  206 . A solenoid coil  238  is positioned on tubular member  222  and secured thereto by means of a nut  240  threaded on the outer end of tubular member  222 . 
     In order to supply pressurized fluid to actuating assembly  102 , an axially extending passage  242  extends downwardly from recess  82  and connects to a generally radially extending passage  244  in non-orbiting scroll member  70 . Passage  244  extends radially and opens outwardly through the circumferential sidewall of non-orbiting scroll  70  as best seen with reference to FIG.  8 . The other end of fluid line  216  is sealingly connected to passage  244  whereby a supply of compressed fluid may be supplied from annular recess  86  to valve body  186 . A circumferentially elongated opening  246  is provided in valving ring  100  suitably positioned so as to enable fluid line  216  to pass therethrough while accommodating the rotational movement of ring  100  with respect to non-orbiting scroll member  70 . 
     In order to supply pressurized fluid from valve body  186  to actuating piston  156  and cylinder assembly  148 , fluid line  218  extends from valve body  186  and is connected to passage  174  provided in depending portion  162  of housing  152 . 
     Valving ring  100  may be easily assembled to non-orbiting scroll member  70  by merely aligning protrusions  108  with respective notches  136  and  138  and moving protrusions  108  into annular groove  134 . Thereafter valving ring  100  is rotated into the desired position with the axially upper and lower surfaces of protrusions  108  cooperating with guide surfaces  112 ,  116 ,  120  and  124  to movably support valving ring  100  on non-orbiting scroll member  70 . Thereafter, housing  152  of actuating assembly  102  may be positioned on mounting flange  166  with piston end  158  receiving pin  130 . One end of spring  184  may then be connected to pin member  182 . Thereafter, the other end of spring  184  may be connected to pin  130  thus completing the assembly process. 
     While non-orbiting scroll member  70  is typically secured to main bearing housing  24  by suitable bolts  248  prior to assembly of valving ring  100 , it may in some cases be preferable to assemble this capacity modulation component to non-orbiting scroll member  70  prior to assembly of non-orbiting scroll member  70  to main bearing housing  24 . This may be easily accomplished by merely providing a plurality of suitably positioned arcuate cutouts along the periphery of valving ring  100 . These cutouts will afford access to securing bolts  248  with valving ring assembled to non-orbiting scroll member  70 . 
     In operation, when system operating conditions as sensed by one or more sensors  250  indicate that full capacity of compressor is required, controller  252  will operate in response to a signal from sensor  250  to energize solenoid coil  238  of solenoid assembly  220  thereby causing plunger  228  to be moved out of engagement with valve seat  236  thereby placing passages  206  and  210  in fluid communication. Pressurized fluid at substantially discharge pressure will then be allowed to flow from recess  82  to cylinder  154  via passages  242 ,  244 , fluid line  216 , passages  208 ,  210 ,  206 ,  202 , fluid line  218  and passages  174 ,  170  and  172 . This fluid pressure will then cause piston  156  to move outwardly with respect to cylinder  154  thereby rotating valving ring so as to move protrusions  108  into sealing overlying relationship to passages  140  and  142 . This will then prevent suction gas drawn into the moving fluid pockets defined by interengaging scroll members  56  and  70  from being exhausted or vented through passages  140  and  142 . 
     When the load conditions change to the point that the full capacity of compressor  10  is not required, sensor  250  will provide a signal indicative thereof to controller  252  which in turn will deenergize coil  238  of solenoid assembly  220 . Plunger  228  will then move outwardly from tubular member  222  under the biasing action of spring  230  thereby moving valve member  234  into sealing engagement with seat  236  thus closing off passage  206  and the flow of pressurized fluid therethrough. It is noted that recessed area  212  will be in continuous fluid communication with recess  82  and hence continuously subject to discharge pressure. This discharge pressure will aid in biasing valve member  234  into fluid tight sealing engagement with valve seat  236  as well as retaining same in such relationship. 
     The pressurized gas contained in cylinder  154  will bleed back into chamber  90  via vent passage  178  thereby enabling spring  184  to rotate valving ring  100  back to a position in which passages  140  and  142  are no longer closed off by protrusions  108 . Spring  184  will also move piston  156  inwardly with respect to cylinder  154 . In this position a portion of the suction gas being drawn into the moving fluid pockets defined by the interengaging scroll members  56  and  70  will be exhausted or vented through passages  140  and  142  until such time as the moving fluid pockets have moved out of communication with passages  144  and  146  thus reducing the volume of the suction gas being compressed and hence the capacity of the compressor. It should be noted that by arranging the modulation system such that compressor  10  is normally in a reduced capacity mode of operation (i.e., solenoid coil is deenergized and hence no fluid pressure is being supplied to the actuating piston cylinder assembly), this system offers the advantage that the compressor will be started in a reduced capacity mode thus requiring a lower starting torque. This enables use of a less costly lower starting torque motor if desired. 
     It should be noted that the speed with which the valving ring may be moved between the modulated position of FIG.  4  and the unmodulated position of FIG. 2 will be directly related to the relative size of vent passage  178  and the size of the supply lines. In other words, because passage  178  is continuously open to chamber  90  which is at suction pressure, a portion of the pressurized fluid flowing from annular recess  86  will be continuously vented to suction pressure. The volume of this fluid will be controlled by the relative sizing of passage  178 . However, as passage  178  is reduced in size, the time required to vent cylinder  154  will increase thus increasing the time required to switch from reduced capacity to full capacity. 
     While the above embodiment has been described utilizing a passage  178  provided in housing  152  to vent actuating pressure from cylinder  154  to thereby enable compressor  10  to return to reduced capacity, it is also possible to delete passage  178  and incorporate a vent passage in valve body  186  in place thereof. 
     Referring now to FIG. 10, the unique bleed hole in accordance with the present invention is illustrated. Annular recess  86  is designed to receive pressurized fluid from at least one of pockets  76  and  78  in order to bias seal assembly  88  against partition  22  to separate discharge chamber  84  from suction chamber  90 . A bleed hole  300  extends through non-orbiting scroll member  70  for this purpose. Bleed hole  300  comprises a first smaller bleed hole  302  opening into one of pockets  76  or  78  and a second larger bleed hole  304  in communication with bleed hole  302  and opening into annular recess  86 . A shoulder or seal surface  306  is defined by bleed holes  302  and  304 . Disposed for axial movement within bleed hole  304  is a valve member  308 . Valve member  308  defines a flow orifice  310  which extends through valve member  308 . Valve member  308  controls the flow of pressurized lubricant through bleed hole  300 . When the fluid pressure within pocket  76  or  78  is greater than the fluid pressure within annular recess  86 , valve member  308  is lifted off of seal surface  306  due to fluid pressure to allow a relatively large flow of refrigerant around valve member  308 . The large flow of refrigerant around valve member  308  is permitted because the diameter of bleed hole  304  is greater than the diameter of valve member  308 . When the fluid pressure within annular recess  86  is greater than the fluid pressure within pocket  76  or  78 , valve member  308  is urged against seal surface  306  due to fluid pressure. When valve member  308  is urged against seal surface  306  the flow of refrigerant is reduced to a relatively small amount due to flow orifice  310 . 
     Thus, by allowing a large flow of pressurized lubricant into annular recess  86  from pockets  76  or  78  and limiting the amount of flow of pressurized fluid from annular recess  86  to pockets  76  or  78 , bleed hole  300  is able to prevent the unloading of the scroll compress, decrease the pressure pulsations in annular recess  86  and decrease the compression power required. 
     Referring now to FIG. 11, bleed hole  300  is shown disposed within a non-orbiting scroll  70 ′ which does not include the capacity control modulation system shown in FIGS. 1-9. In a non-capacity modulated or a fixed capacity scroll machine, the incorporation of bleed hole  300  will help to reduce the pressure pulsations within annular recess  86  due to the continued movement of pocket  76  or  78  from suction chamber  90  to discharge chamber  84 . The decrease in the pressure pulsations will again help to decrease the compression power required. 
     Referring now to FIG. 12, a bleed hole  300 ′ is disclosed. Bleed hole  300 ′ can replace bleed hole  300  in either a capacity modulated scroll machine or a fixed capacity (non-capacity modulated) machine if desired. Bleed hole  300 ′ defines a first smaller bleed hole  302 ′ opening into pocket  76  or  78  and a second frusto-conical shaped diffuser passage  304 ′ in communication with bleed hole  302 ′ opening into annular recess  86 . Smaller bleed hole  302 ′ forms a flow orifice  310 ′. Frusto-conical shaped diffuser passage  304 ′ will provide less of a flow restriction and thus an increase in flow when the flow is from pocket  76  or  78  to annular recess  86  and more of a flow restriction and thus a decrease in flow when the flow is from annular recess  86  to pocket  76  or  78 . Thus, bleed hole  300 ′ provides the same effect and advantages as those described above for bleed hole  300 . 
     While the above detailed description describes the preferred embodiment of the present invention, it should be understood that the present invention is susceptible to modification, variation and alteration without deviating from the scope and fair meaning of the subjoined claims.