Abstract:
A scroll compressor for compressible fluids includes a fixed housing having a spiral-shaped feed chamber which contains a working fluid. A displacement member interacts with the feed chamber and includes a driveshaft which is supported in the housing and has an eccentric disk, a carrier disk which is mounted on the driveshaft, and spiral blades which extend out from both sides of the carrier disk. The displacement member is supported by a bearing on the eccentric disk. A lubricant supply system feeds lubricant to the bearing via the driveshaft and the eccentric disk, with a seal assembly sealing a lubricant chamber against the feed chamber. A pressure regulating valve substantially maintains during operation a differential between a pressure in the feed chamber acting on one side of the seal assembly and a pressure in the lubricant chamber acting on another side of the seal assembly, with the pressure regulating valve being acted upon by the pressure in the feed chamber and by the pressure in the lubricant chamber.

Description:
CROSS-REFERENCES TO RELATED APPLICATIONS 
     This application is a continuation of prior filed copending PCT International Appl. No. PCT/CH2007/000275, filed Jun. 1, 2007, which designated the United States and has been published as International Publication No. WO 2008/124950 and on which priority is claimed under 35 U.S.C. §120, and which claims the priority of Swiss Patent Application, Serial No. 629/07, filed Apr. 17, 2007, pursuant to 35 U.S.C. 119(a)-(d). 
     The contents of PCT/CH2007/000275 and CH 629/07 are incorporated herein by reference in its entirety as if fully set forth herein. 
    
    
     BACKGROUND OF THE INVENTION 
     The present invention relates to a scroll compressor with two scrolls for compressible fluids. 
     The following discussion of related art is provided to assist the reader in understanding the advantages of the invention, and is not to be construed as an admission that this related art is prior art to this invention. 
     Scroll compressors with two scrolls operate at virtually pulsation-free feeding of gaseous working fluid, e.g. air, and may find application for supercharging internal combustion engines, among other purposes. During operation of this type of compressor, a plurality of approximately crescent-shaped work chambers are enclosed in the displacement chamber or feed chamber between a spiral displacement member and two peripheral walls of the displacement chamber and move from an inlet through the displacement chamber toward the outlet, whereby the volume of the displacement chamber steadily decreases while the pressure of the working fluid correspondingly increases. An example of such a scroll compressor is disclosed in German patent document DE 33 47 081 A1. The displacement member is driven by an eccentric shaft and is held by a bearing upon the eccentric of the eccentric shaft. This bearing requires lubrication, using a lubricant, e.g. oil, contained in a lubricant chamber. To seal the lubricant chamber against the feed chamber, shaft sealing rings are typically used which are provided at the bearings of the driveshaft in a housing as well as at the bearings of the displacement member. In certain load situations, the pressure in the feed chamber can exceed the pressure in the lubricant chamber so that there is a risk that the shaft sealing rings become detached from the shaft and thus from the eccentric during operation. As a result, working fluid, e.g. air, may migrate to the lubricant side of the shaft sealing rings and escape through a lubricant recirculation line. A loss of working fluid adversely affects operation of the scroll compressor, in particular when operating at low speed. 
     It would be desirable and advantageous to provide an improved scroll compressor to obviate prior art shortcomings. 
     SUMMARY OF THE INVENTION 
     According to one aspect of the present invention, a scroll compressor for compressible fluids includes a fixed housing having a spiral-shaped feed chamber which contains a working fluid, a driveshaft supported in the housing and having an eccentric disk, a displacement member interacting with the feed chamber and including, a carrier disk, and spiral blades extending out from both sides of the carrier disk, a bearing supporting the carrier disk of the displacement member on the eccentric disk of the driveshaft, a lubricant supply system having a lubricant chamber which contains lubricant and feeding lubricant to the bearing via the driveshaft and the eccentric disk, a seal assembly sealing the lubricant chamber against the feed chamber, and a pressure regulating valve constructed to substantially maintain during operation a differential between a pressure in the feed chamber acting on one side of the seal assembly and a pressure in the lubricant chamber acting on another side of the seal assembly, with the pressure regulating valve being acted upon by the pressure in the feed chamber and by the pressure in the lubricant chamber. 
     The present invention resolves prior art problems by keeping the differential between the pressure in the feed chamber acting on one side of the seal assembly and the pressure in the lubricant chamber acting on the other side of the seal assembly during operation substantially constant, so that a detachment of the sealing assembly is effectively prevented. This is true at any working pressure in the feed chamber. 
     According to another advantageous feature of the present invention, the lubricant supply system may include a lubricant recirculation connected to the lubricant chamber, with the pressure regulating valve being arranged in the lubricant recirculation. 
     According to yet another advantageous feature of the present invention, the pressure regulating valve may be constructed in the form of a diaphragm valve. 
     According to still another advantageous feature of the present invention, the lubricant recirculation can have a lubricant recirculation line in communication with the lubricant chamber, wherein the pressure regulating valve has a flexible diaphragm which includes a control member having one side placed in opposition to an exit opening of the lubricant recirculation line, and another side subjected to the force in the feed chamber, wherein the control member can be constructed to control a lubricant outflow from the exit opening of the lubricant recirculation line in dependence on the differential between the pressure in the feed chamber and the pressure in the lubricant chamber. 
     According to yet another advantageous feature of the present invention, the lubricant chamber can have a first compartment on one side of the bearing and a second compartment on another side of the bearing, wherein a tubular guide sleeve is placed in a length bore in the driveshaft and has formed therein a lubricant feed passageway which is in communication with a lubricant source and in communication with one of the first and second compartments of the lubricant chamber, wherein the guide sleeve is defined by a first outer diameter and has a section extending over part of the guide sleeve and defined by a second outer diameter which is smaller than the first outer diameter to form with a wall of the length bore a lubricant recirculation passageway which is in communication with the other one of the first and second compartments of the lubricant chamber and in communication with the lubricant recirculation passageway. 
     According to yet another advantageous feature of the present invention, the lubricant supply system may include a flow limiter. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWING 
       Other features and advantages of the present invention will be more readily apparent upon reading the following description of currently preferred exemplified embodiments of the invention with reference to the accompanying drawing, in which: 
         FIG. 1  is a front elevation in a direction of arrow A in  FIG. 2  of a drive-side housing part of a scroll compressor according to the present invention; 
         FIG. 2  is a longitudinal section of the scroll compressor of  FIG. 1 , taken along the line II-II in  FIG. 1 ; 
         FIG. 3  is an enlarged detailed view of a section of the scroll compressor; and 
         FIG. 4  is an enlarged detailed view of a section similar to  FIG. 3  of another embodiment of a scroll compressor according to the present invention. 
     
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
     Throughout all the figures, same or corresponding elements may generally be indicated by same reference numerals. These depicted embodiments are to be understood as illustrative of the invention and not as limiting in any way. It should also be understood that the figures are not necessarily to scale and that the embodiments are sometimes illustrated by graphic symbols, phantom lines, diagrammatic representations and fragmentary views. In certain instances, details which are not necessary for an understanding of the present invention or which render other details difficult to perceive may have been omitted. 
     Turning now to the drawing, and in particular to  FIG. 1 , there is shown a front elevation in a direction of arrow A in  FIG. 2  of a drive-side housing part of a scroll compressor according to the present invention. The scroll compressor includes a housing, generally designated by reference numeral  1  and including two housing parts  1   a ,  1   b  ( FIG. 2 ) for support of a displacement member  2 . Both housing parts  1   a ,  1   b  are bolted together in a manner not shown in detail. In the illustration of  FIG. 1 , housing part  1   a  has been removed. 
     The displacement member  2  includes a carrier disk  3  which carries on one side thereof a spirally extending displacement element or scroll  4  and on the other side thereof a spirally extending displacement element or scroll  5 . The displacement elements  4 ,  5 , are configured as ribs in the form of spiral blades which project out from the disk  3 . The disk  3  is supported by a driveshaft  6  which rotates about a rotation axis  6   a . The driveshaft  6  is supported in the housing parts  1   a ,  1   b  by bearings  7  and  8 , respectively, and includes an eccentric disk  9  which defines a symmetry axis  9   a . The distance between the rotation axis  6   a  of the driveshaft  6  and the symmetry axis  9   a  of the eccentric disk  9  (eccentricity) is designated with “e” in  FIG. 1 . A screw fastener  10  secures a driving belt pulley  11  to the driveshaft  6 . 
     The carrier disk  3  has a hub  13  which is supported on the eccentric disk  9  by a bearing  12 , e.g. a rolling-contact bearing. The disk  3  and thus the displacement body  2  is driven via the driveshaft  6  and the eccentric disk  9 . The driving force is hereby transmitted via the bearing  12  onto the hub  13  of the disk  3 . The displacement member  2  is guided by a rocker  14  which has one end rotatably supported on a shaft  15  ( FIG. 1 ). The other end of the rocker  14  carries a bolt  16  which is rotatably supported in an eye  17  of the disk  3 . 
     The housing  1  has an inlet  18  and an outlet  19  for the feed medium, e.g. air, as well as two feed chambers  20 ,  20 ′. The disk  3  has an opening  21  (or several openings) to enable the feed medium to flow from the feed chamber  20  into the feed chamber  20 ′. 
     Counterweights  22 ,  23  are disposed on the driveshaft  6  in order to compensate forces of mass, when the displacement body  2  is driven eccentrically. 
     The bearing  12 , disposed between the eccentric disk  9  and the hub  13  of the disk  3 , is lubricated by a lubricant supply system  24  shown in greater detail in  FIG. 2  which is a longitudinal section of the scroll compressor of  FIG. 1 , taken along the line II-II in  FIG. 1 , for supplying the bearing  12  with lubricant  30 , e.g. lubricating oil. 
     The lubricant supply system  24  includes a supply line  25  which is connected to the housing  1  and connected with the pressure side of a pressure-controlled feed pump  26 . This type of pump with pressure control is used in internal combustion engines and generates a lubricant delivery pressure which remains within certain limits at operation. On the suction side, the feed pump  26  is connected via a suction line  27  with a lubricant reservoir  28  which is in fluid communication with the surroundings via a connection line  29 . As a result, ambient pressure acts constantly on the surface of the lubricant  30  in the lubricant reservoir  28 . A flow limiter  31 , e.g. a flow limiting valve, may be disposed in the supply line  25  and is indicated in  FIGS. 2 to 4  by a broken line. 
     The driveshaft  6  has a lubricant feed channel  32  and a lubricant recirculation channel  33  in coaxial relationship to the rotation axis  6   a  of the driveshaft  6  ( FIGS. 2 and 3 ). The two channels  32 ,  33  are formed by placing in a length bore  34  in the driveshaft  6  a tubular guide sleeve  35  which has on its outside a section of smaller outer diameter along a portion of the length of the guide sleeve  35  so as to define the lubricant recirculation channel  33  with the wall of the length bore  34 . The lubricant feed channel  32  inside the guide sleeve  35  is fluidly connected with the feed channel  36  which extends in radial direction in the eccentric disk  9  and feeds into a first lubricant compartment  37  on the one side of the bearing  12 , as shown in  FIG. 3 . The first lubricant compartment  37  is sealed against the feed chamber  20  by a ring-shaped sealing element  38  which bears upon the eccentric disk  9 . A second lubricant compartment  39  is located on the other side of the bearing  12  and sealed against the feed chamber  20 ′ by a ring-shaped sealing element  40  which also bears upon the eccentric disk  9 . The second lubricant compartment  39  is fluidly connected with the lubricant recirculation channel  33  via a radial outflow channel  41  in the eccentric disk  9 . 
     A radial connection channel  42  in the driveshaft  6  connects the lubricant recirculation channel  33  with a lubricant recirculation line  43  which is part of a lubricant recirculation system, generally designated in  FIGS. 2 to 4  by reference numeral  44 . The lubricant recirculation line  43  is connected with the inlet of a pressure regulating valve  45  having an outlet which is fluidly connected with the lubricant reservoir  28  via a return line  46 . The pressure regulating valve  45  is constructed in the form of a diaphragm valve and has a diaphragm  47  to divide the interior space of the pressure regulating valve  45  into two chambers  45   a ,  45   b . The diaphragm  47  has a control member  48  approximately in midsection of the diaphragm  47  in opposition to an exit opening  43   a  of the lubricant recirculation line  43  for controlling the lubricant outflow from the lubricant recirculation line  43  into the chamber  45   a . The chamber  45   b  of the pressure regulating valve  45  in opposition to the chamber  45   a  is fluidly connected with the feed chamber  20 ′ via a connection line  49 . As a result, the pressure in the chamber  45   b  corresponds to the working pressure in the feed chamber  20 ′. The feed chamber  20 ′ is sealed off to the outside by a ring-shaped sealing element  50  which bears upon the driveshaft  6 . 
     Lubricant conveyed from the feed pump  26  flows via the supply line  25 , the lubricant feed channel  32 , and the feed channel  36  to the first lubricant compartment  37 . From the first lubricant compartment  37 , lubricant passes through the bearing  12  into the second lubricant compartment  39 . From the second lubricant compartment  39 , lubricant flows to the chamber  45   a  of the pressure limiting valve  45  via the outflow channel  41 , the lubricant recirculation channel  33 , the connection channel  42 , and the lubricant recirculation line  43 . From the chamber  45   a , lubricant flows back into the lubricant reservoir  28  via the return line  46 . 
     The diaphragm  27  is deflected more or less downwards in the direction of the exit opening  43   a  of the lubricant recirculation line  43  in dependence on the magnitude of the delivery or working pressure prevailing in the feed chamber  20 ′, which pressure is present also in the chamber  45   b  of the pressure limiting valve  45 . As a result, the distance between the control member  48  and the exit opening  43   a  of the lubricant recirculation line  43  increases or decreases in dependence on the difference of the pressures in the chambers  45   a ,  45   b , so that the amount of lubricant flowing out of the lubricant recirculation line  43  into the chamber  45   a  is correspondingly adjusted. In this way, the pressure in the lubricant recirculation line  43  and thus also in the lubricant compartments  37 ,  39  is changed in dependence on the delivery or working pressure in the feed compartment  20 ′. In the event the pressure in the feed chamber  20 ′ rises, the distance between the control member  48  and the exit opening  43   a  decreases, causing a backup of returning lubricant and thus to a pressure increase in the lubricant recirculation system  44  and in the lubricant compartments  37 ,  39 . As a consequence, a pressure rise in the feed chamber  20 ′ is necessarily accompanied by a pressure rise in the lubricant compartments  37 ,  39 . In this way, it is attained that the pressure differential between the pressures on both sides of the sealing elements  38 ,  40  remains approximately the same at any time, regardless whether the delivery pressure in the feed chamber  20 ′ is higher or lower during operation of the scroll compressor. As the difference between the pressure acting in the feed chambers  20 ,  20 ′ on the one side of the sealing elements  38 ,  40  and the pressure acting in the lubricant chambers  37 ,  39  on the other side of the sealing elements  38 ,  40  remains substantially constant, a detachment of the sealing elements  38 ,  40  from the eccentric disk  9  is prevented during operation. 
     Referring now to  FIG. 4 , there is shown an enlarged detailed view of another embodiment of a scroll compressor according to the present invention. Parts corresponding with those in  FIGS. 1-3  are denoted by identical reference numerals and not explained again. The description below will center on the differences between the embodiments. In this embodiment, provision is made for a direct securement of the housing  51   a  and the diaphragm  47  with the control member  48  of the pressure regulating valve  51  upon the housing part  1   a , e.g. by means of a snap ring  52 . A chamber  51 ′ is formed by the housing  51   a  and the diaphragm  47  and is in fluid communication with the feed chamber  20 ′ via the connection line  49 . The lubricant recirculation line  43  feeds with its exit opening  43   a  into a chamber  53  which is formed in the housing part  1   a  and is part of the pressure regulating valve  51  and which is closed by the diaphragm  47  and connected to the return line  46 . The control member  48  of the diaphragm  47  is positioned, like in the embodiment of  FIG. 3 , in opposition to the exit opening  43   a  of the lubricant recirculation line  43  and provided to control the amount of lubricant flowing out of the exit opening  43   a.    
     The mode of operation of the pressure regulating valve  51  is the same as the afore-described mode of operation of the pressure regulating valve  45  of  FIG. 3 . 
     While the invention has been illustrated and described in connection with currently preferred embodiments shown and described in detail, it is not intended to be limited to the details shown since various modifications and structural changes may be made without departing in any way from the spirit and scope of the present invention. The embodiments were chosen and described in order to explain the principles of the invention and practical application to thereby enable a person skilled in the art to best utilize the invention and various embodiments with various modifications as are suited to the particular use contemplated.