Patent Publication Number: US-10774833-B2

Title: Scroll-type machine

Description:
This Application claims priority of U.S. Provisional Application No. 60/444,962, Jan. 11, 2017. 
    
    
     This invention was made with government support under DE-AR0000562 awarded by DOE. The government may have certain rights in this invention. 
    
    
     FIELD OF THE INVENTION 
     The present invention generally relates to scroll-type displacement machines adapted as a compressor, expander (pneumatic motor), liquid pump, or hydraulic motor. More particularly, according to one aspect, the present invention relates to a so-called high-side machine, where the compressor mechanism within the casing is surrounded by high-pressure working fluid. According to another aspect, the present invention relates to a unique arrangement of the internal drive system which simplifies the manufacture of the scroll-type machine and which allows for easy adaptation to various motor types (ie. compressor or pump) or various power transfer devices (i.e. expander or motor). According to a further aspect, the present invention relates to such a machine which uses an Oldham coupling (or ring) to prevent rotation of the orbiting scroll relative to the fixed scroll. According to yet another aspect, the present invention relates to hermetic or semi-hermetic compressors where the motor and compressor are sealed within an enclosure which contains the working fluid to be compressed. 
     BACKGROUND OF THE INVENTION 
     Scroll-type displacement machines are commonly employed as a compressor for various gases, including air and refrigerants. However, they are readily adapted for use as a compressed vapor expander (e.g. pneumatic motor), a liquid pump, or a hydraulic motor. In normal operation, scroll-type machines have high pressure in the center region of the scroll pair and low pressure around the outside periphery. Fluid flows from the outside to the inside for compressors and pumps and from the inside to the outside for expanders and motors. 
     In the case of so-called low-side machines, where the housing containing the scroll mechanism contains working fluid at the low-pressure level, means are provided to isolate the high pressure fluid passing through the high pressure port in the fixed scroll, sometimes through a simple discharge tube attached to the fixed scroll and more commonly through a high pressure manifold or pulse volume integrated into the external housing and further communicating externally through a high-pressure tube or fitting. 
     For so-called high-side machines the low-pressure flow is connected directly to the scroll pair at the periphery and the high-pressure flow exits at the center of the scroll pair and passes through an external housing which contains the pressurized flow. The high pressure flow serves to cool the bearings and any other heat-generating components such as motors or sliding mechanisms. The orbiting scroll typically has a drive bearing located at the center of the scroll on the opposite side from the spiral vanes. In order to isolate this drive system from the direct fluid flow, the high pressure port is typically located at the center of the fixed scroll, on the opposite side of the scroll set from the drive bearing. The high-pressure port in the fixed scroll communicates directly with the interior of the external housing. In such an arrangement means are provided for flow to pass around the scroll set to communicate between the discharge port on one side of the scroll set and the rest of the external housing on the other side. This may take the form of an enlarged external housing or special gas passage means to carry the fluid. These options represent some degree of increased size and weight for the overall compressor assembly along with associated complications in manufacture. 
     Accordingly, an aspect of the invention is directed towards improvements over the state of the art as it relates to routing high pressure fluid in a high-side machine to avoid the disadvantages associated with conducting high pressure working fluid between a fixed scroll high pressure port and the external compressor housing. 
     In all these configurations a drive shaft, used either to input or to extract mechanical power, is provided with support bearing means to support radial loads and to allow free rotation of the drive shaft. Interposed between the drive shaft and the orbiting scroll is an eccentric drive bearing which may take the form of an eccentric bearing, a so-called slider block, or an eccentric bushing, all serving to provide an eccentric drive to connect between the drive shaft and the orbiting scroll and to drive the orbiting scroll in a circular path, i.e., a circular non-rotating orbit. The eccentric drive bearing may take the form of a bearing rigidly attached to the drive shaft and which drives the orbiting scroll through a fixed orbital radius or it may take the form of a so-called radially compliant drive where the radial position of the orbiting scroll relative to the drive shaft center is permitted to vary in response to misalignment and tolerance variations so as to maintain positive contact at all times between the vane walls of the orbiting scroll and the fixed scroll. 
     Additionally, a counterweight arrangement is provided to achieve a dynamic balance among the various orbiting, rotating, and translating masses within the machine. Typically, a primary counterweight nearest the orbiting scroll provides a static balance for the machine. However, the axial spacing between the planes of unbalance of the moving components and the plane of action of the primary counterweight results in an overturning moment which tends to impose a wobbling-type load onto the shaft and consequently onto compressor frame which results in undesirable vibration. To counteract this dynamic unbalance, a secondary counterweight is provided toward the end of the shaft opposite the orbiting scroll (on the other side of said primary counterweight) to create a counteracting overturning moment. An equivalent mass unbalance may also be added to the primary counterweight to maintain static balance. In a way, the scroll-type machine may be said to have three counterweights: one larger counterweight to provide a static balance and two smaller counterweights of identical unbalance phased 180 degrees from each other and axially separated to provide a dynamic balance with one of the smaller counterweights at the same location as the larger counterweight. The primary counterweight may thus consist of the combination of the larger counterweight and one of the smaller counterweights while the secondary counterweight is simply the other smaller counterweight. 
     The offset between the drive shaft center and the center of said eccentric drive bearing defines an angular reference which rotationally orients the drive shaft. The moving masses within the machine may all be defined by their axial position along the axis of the drive shaft and by their angular orientation relative to the eccentric drive bearing angular reference. Likewise, the locations of the primary counterweight and the secondary counterweight are also defined by axial positions along the drive shaft axis and their angular positions relative to the eccentric drive bearing angular reference. The mass unbalances of these counterweights are chosen to counter the mass unbalances of all the moving masses. 
     In typical scroll machines, the drive means, the primary counterweight, and the secondary counterweight are all separate components located at separate axial locations along the drive shaft. Typically the primary counterweight is interposed between the support bearing and the drive means and said secondary counterweight is placed at the opposite end of the drive shaft. During manufacture, locating means must be provided to position these counterweights properly both axially and angularly onto the drive shaft. Such locating means may consist of locating features between the counterweights and the drive shaft, they may consist of external fixturing, or they may consist of a combination of locating features and fixturing. This construction requires fabrication, alignment, and assembly of a number of components during manufacture of the scroll machine, all of which adds to the cost of manufacture. In some designs, the drive shaft and primary counterweight may be combined into a single component but with the same general overall layout. 
     The support bearing means typically includes two bearings supporting the main drive shaft which are in turn supported by a structure, frame or shell. In scroll-type machines where a motor (for compressors or pumps) or a power transfer device (e.g. a generator for expanders or hydraulic motors) is integrated into the scroll-type machine, the motor or power transfer device is supported by the structure or frame and is located between the two bearings or just outboard of the two bearings. The rotor component of the motor or power transfer device is affixed onto the drive-shaft. The result of such close integration is that drive shaft, counterweights, and structure or frame are to a large extent custom designed for a single motor or power transfer device. This has advantages in reducing material content in high volume production of larger machinery but is relatively inflexible or difficult to change if variations in the design of motor or power transfer device are desired. 
     One requirement for proper operation for scroll-type machines is that the two scrolls must be constrained from any relative rotation between them. The orbiting scroll follows a circular path or orbit with respect to the fixed scroll but relative rotation is not permitted. In some designs, both scrolls are adapted to rotate together on offset axes (as opposed to the conventional fixed-orbiting arrangement) but they both rotate at the same speed and the angular phasing between the two scrolls remains the same, which is to say they do not rotate relative to one another. 
     Several different mechanisms may be used to prevent the relative rotation between the two scrolls, but an Oldham coupling (comprising an Oldham ring and mating features on the two respective scrolls) is in common use today. A typical Oldham ring comprises a solid body, more or less ring-shaped. The body may be an oblong or irregular shape to fit around other features in the machine but it will generally follow the pattern of a closed ring. Axial or radial projections from the Oldham ring body are provided with axially extending surfaces or keyways which engage matching surfaces on the respective scrolls to complete the coupling assembly and to prevent relative rotation between the scrolls while permitting orbiting action. 
     The ring-shaped portion of the Oldham ring is typically flat and of a more or less uniform thickness, being generally distributed about a radial plane at all points around the ring. A radial plane which passes through the centroid of the Oldham ring will divide the Oldham ring into two continuous ring-shaped portions. Thus the main body of the Oldham ring will have a space set aside specifically to contain it and allow free motion during operation. This dedicated space adds to the overall height (i.e. axial length) of the scroll-type machine and thereby increases the size and weight of the scroll machine. 
     Thus an aspect of this invention is directed towards improvements over the state of the art as it relates to the design of an Oldham coupling to avoid the need for a dedicated axial space for the coupling and thereby to reduce the overall size of the displacement machine. 
     In some applications where the working fluid (vapor) must be isolated from the outside air (such as in a refrigeration circuit) the compressor and drive motor are contained within a sealed housing which isolates the working fluid from the outside environment. The vapor flows around the compressor and motor and provides cooling, especially for the motor. 
     The drive motor, typically an electric motor, is normally integrated into the overall compressor assembly. The motor stator is integrated into the compressor frame and the motor rotor is mounted directly onto the compressor shaft, which also incorporates the compressor drive means (e.g. eccentric bearing) and counterweights which may be placed on both sides of the motor or even attached directly to the rotor. This arrangement provides acceptable economy and simplicity by minimizing the number of separate components that make up the motor and compressor combination. However, a given compressor is then dedicated to a particular motor size and design. Physical changes to the motor often require extensive changes to the compressor frame and drive shaft to accommodate the new motor. 
     In larger compressors the motor lineup is typically standardized with common motor sizes and configurations found across a relatively limited selection of motor suppliers. There is seldom a need to change to a different size motor and the compressor design can be relatively stable with regard to motor selection. 
     But in smaller compressors, there is a very wide variety of motor types and manufacturers to choose from. These motors are normally available as prepackaged modules with motor housing, shaft, and bearings integrated together into a single product intended for a wide array of applications, a small scroll compressor being only one of them. 
     So another aspect of this invention is directed towards a general compressor design which allows use of a range of prepackaged motors of various sizes with minimal if any changes to the compressor or to the motor. 
     OBJECTS AND SUMMARY OF THE INVENTION 
     Accordingly, it is an object of this invention to locate the high-pressure port in a high-side scroll-type machine at the center of the orbiting scroll. The inlet or low pressure port may then be located in a radially outer portion of the fixed scroll which may have a solid baseplate thus avoiding any need to provide means for fluid communication between the fixed scroll and the compressor housing (which is at high pressure). 
     It is a related object greatly to simplify the structure around the scroll set and in some cases to provide the option of the fixed scroll itself forming an exterior end wall of the compressor housing. 
     In an embodiment of this invention, high-pressure fluid passes directly from the center of the orbiting scroll over the drive bearing means that engages the orbiting scroll and thus through a path directly between the high pressure port and the interior of the compressor housing. Lubricant which is entrained in the vapor flow serves to lubricate the drive bearing means and other mechanical components in the displacement machine. This arrangement is well to systems where the fluid flow is contained within a closed loop and a fixed quantity of recirculating lubricant is present. However, this may be easily adapted to open-cycle systems, where the fluid passes through the displacement machine once and does not recirculate, by providing means to inject lubricant into the inlet flow and optionally to extract it from the outlet flow. 
     As a result, the high-side scroll machine is simpler, more compact, and easier to manufacture than an equivalent high side machine with the high pressure port at the center of the fixed scroll. 
     In accordance with another aspect of the present invention, the scroll machine combines the eccentric drive bearing means, the primary counterweight, and the secondary counterweight into a single component or module (referred to in the description as a widget) which may be affixed to the end of the drive shaft adjacent the orbiting scroll. This module is designed as a single, unitary piece suitable for casting, molding, forming, or machining operations so that the necessary counterweight sizes and locations relative to said eccentric drive bearing means are integral to the as-formed part and no subassembly, alignment operations, or alignment features are required. Since all angular relationships are built into the drive module there is no need for angular alignment of the drive module with the drive shaft. The module or widget is preferably designed to be fitted on to the end of a drive shaft although the module could also be formed integrally with the drive shaft. 
     According to another aspect of this invention, the drive module may be standardized in terms of the interface with the motor or the power transfer device so that a wide variety of motors or power transfer devices may be readily adapted to a particular scroll machine model. 
     The drive shaft and shaft support bearing means may be packaged as part of the motor or power transfer device assembly. This allows ready access to a wide range of commercially produced motors or other drive devices with no significant design change required to integrate a variety of different devices into a scroll-type machine. Only details of device attachment, alignment, and the attachment of the drive module to the drive shaft need be considered. The rated bearing life of said device when applied to the scroll machine would simply be one of the product specifications along with other performance specifications. 
     A still further aspect of the present invention is to improve the Oldham coupling for the scroll machine. In an embodiment of this invention, the main body of the Oldham ring may be considered as being divided into four arc-shaped segments. A first pair of diametrically opposed segments bridges between and slidingly engages with the corresponding Oldham coupling surfaces on the orbiting scroll. The first segment pair occupies around the same level, i.e. the same axial position, as the orbiting scroll baseplate but not extending beyond the orbiting scroll floor surface. The space between the ends of the segment pairs is occupied by the Oldham key tabs on the orbiting scroll. The first segment pair occupies otherwise unused space in the machine. The second pair of diametrically opposed segments (oriented generally at 90 degrees to the first pair) bridges between and slidingly engages with the corresponding Oldham coupling surfaces on the fixed scroll. The second segment pair occupies a level starting at around the floor of the orbiting scroll baseplate (also the fixed scroll tip surface) and extends away from the orbiting scroll floor but does not extend across the plane defined by the orbiting scroll floor. This makes the coupling arrangement more compact. The symmetry of the Oldham ring of this design eliminates any polarity or handedness, so that it is impossible to install improperly. 
     The ends of the segment pairs can favorably be extended so that they overlap some reasonable distance in a common radial or lateral plane. With the segment pairs fused together at the overlap zones, the Oldham ring becomes a single solid object which may be fabricated by a number of methods. 
     No particular axial space specifically needs to be provided to house the Oldham ring. The spaces it inhabits, with the first segment pair extending between the key tabs of the orbiting scroll and with the second segment pair bridging over the key tabs, is space already present in the compressor layout and otherwise unused. There is no need to provide clear space along a single axial plane such as is required to house the conventional flat ring of prior-art Oldham couplings. A still further aspect of the present invention is to design the scroll machine to permit incorporation of a prepackaged motor unit including stator, rotor, housing, bearings, and shaft, as is typical of commercially available motors. The motor unit can be attached to the compressor frame and a drive module may then be attached to the end of the motor shaft. The motor shaft and bearings serve as the main compressor shaft and bearings. Design changes, if any, accompanying a motor change are limited to details of the motor unit attachment to the compressor frame, and of the drive module attachment to the motor shaft. 
     Other aspects, objectives and advantages of the invention are disclosed in the following detailed description, the appended claims, and the accompanying figures. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWING 
         FIG. 1  is an exploded isometric view of a scroll-type machine, here a compressor according to one embodiment of this invention, viewed from the scroll end. 
         FIG. 2  is an exploded isometric view of the same compressor viewed from the motor end. 
         FIG. 3  depicts a cross-sectional isometric view of the same compressor. 
         FIG. 4  depicts a cross-sectional orthographic view of the same compressor. 
         FIG. 5  is an isometric view of a fixed scroll according to the present invention. 
         FIG. 6  is an orthographic plan view of the same fixed scroll. 
         FIG. 7  is an isometric view of an orbiting scroll seen from the front or vane side according to the present invention. 
         FIG. 8  is an isometric view of the orbiting scroll seen from the back or opposite of the vane side according to the present invention. 
         FIG. 9  is a cross-sectional orthographic side view of the same orbiting scroll. 
         FIG. 10  is an isometric view of an Oldham ring as used in the present invention. 
         FIG. 11  is an isometric view of an Oldham ring divided into sections showing a dividing plane. 
         FIG. 12  is a cross-sectional orthographic side view of the drive housing. 
         FIG. 13  is an orthographic representation of a motor as used in the present invention. 
         FIG. 14  is an isometric view of the drive widget as used in the present invention. 
         FIG. 15  is an orthographic plan view of the drive widget. 
         FIG. 16  is a cross-sectional orthographic side view of the drive widget. 
         FIG. 17  is a schematic representation of the drive system including the drive bearing and orbiting scroll drive hub. 
         FIG. 18  is a cross-sectional orthographic side view of the motor-compressor module. 
         FIG. 19  is a cross-sectional isometric view of the compressor housing. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT(S) 
     The scroll machine of an embodiment of this invention is illustrated in the accompanying Drawing Figures, which illustrate the component parts thereof. Generally, the scroll compressor  10  of this embodiment includes a motor-compressor module  11  with a drive gallery  12 . A motor chamber  14  is defined between the module  11  and a main compressor housing  80 . The scroll pair is here shown as a fixed scroll  20  and a mating orbiting scroll  30 , wherein the fixed scroll has an inlet (low-pressure) port  21  located on a radially outward portion, a fixed scroll spiral vane  22  having a tip surface  23 . The fixed scroll  20  also has a flat face  24 , shoulder  25 , pilot floor  26 , with an outside diameter  27  and pilot diameter  28 . At the center of the scroll vane is a blind recess or mirror port  29 , which will be explained later. 
     The orbiting scroll  30 , which has a defined orbiting path  31  relative to the fixed scroll  20  has a scroll vane  32 , a number of anti-thrust pads  33 , a plurality of flat faces  34 , a drive hub  35  on the side opposite the vane  32 , with the drive hub having an inside diameter  36  defining a drive bearing contact point  37 , a drive hub center  38  and a discharge port  39  that penetrates the scroll  30  more-or-less at the axis or center. 
     A drive widget  40  for achieving the orbital motion of the scroll  30  is comprised of a shaft bore  41 , an eccentric crankpin  42  having a crankpin center  43 , and a drive bearing  45  that has a predetermined drive bearing outside diameter  46 . The shaft bore  41  has a shaft bore center  47  located at the main drive axis for the compressor. To prevent wobble or vibration caused by the eccentric motion of the orbiting scroll, the drive widget  40  also includes a primary counterweight  48  and a secondary counterweight  49 . 
     Restraining the orbiting scroll  30  from any rotation relative to the fixed scroll is accomplished by an Oldham ring  50 , here shown in the form of four arcuate segments, and whose shape defines key surfaces  54  that slidably engage the flat faces  24  and  34  of the fixed and orbiting scrolls  20  and  30 , with the ring comprising a lateral dividing plane  56 , a first segment pair  57  and a second segment pair  58 . 
     A drive housing  60  that houses the aforementioned components is shown with a back-flange surface  61 , a flat motor-engaging surface  62 , and a pilot bore  63 ; a flat face  66  for engaging the fixed scroll pilot floor  26 , and having an outside diameter  68 . An outlet port  69  permits the compressed working fluid vapor to pass through. 
     Motive power for the orbiting scroll is provided here by an electric motor  70 , having a motor shaft  71  with a shaft center or axis  77 , a flat surface  72 , and having pilot diameter  73 . A set of motor bolts  74  or similar fasteners are provided to attach the motor to the drive housing. 
     The compressor housing  80  is shown with a flat surface or flange  81 , an O-ring seal  83  and an annular O-ring groove  84 , a retaining ring  85  and annular retaining ring groove  86 , a bore  87 , electrical feedthrough passage  88 , and a discharge passage  89 . 
     Referring first to  FIGS. 1-4  of the Drawing, scroll compressor  10  includes fixed scroll  20  and orbiting scroll  30 . Fixed scroll  20  and orbiting scroll  30  comprise a conventional scroll pair, each having involute shaped vanes  22  and  32  respectively which interfit to form pairs of moveable sealed crescent-shaped pockets. The scroll-type principle is well-known in the art and may be employed to transport, compress, or expand various fluids and gases. 
     Further referring to  FIGS. 5-9  the orbiting scroll  30  is driven through a circular path by means of drive widget  40  which includes eccentric crankpin  42  and drive bearing  45  which together urge orbiting scroll  30  into contact with fixed scroll  20 . Orbiting scroll  30  and fixed scroll  20  contact each other through orbiting scroll vane  32  and fixed scroll vane  22 . Drive widget  40  including drive bearing  45  further urges orbiting scroll  30  to move in a circular path which is defined by the geometry of orbiting scroll vane  32  and fixed scroll vane  22 . The orbiting scroll  30  is constrained to move in a lateral plane without rotation by means of Oldham ring  50 . Four of eight key surfaces  54  of Oldham ring  50  slidingly engage fixed scroll  20  through a set of four flat faces  24  and the other four key surfaces  54  of Oldham ring  50  slidingly engage orbiting scroll  30  through a set of four flat faces  34 . 
     Within the art, the Oldham ring is typically keyed between the scrolls as in the present invention or between the orbiting scroll and a fixed structure within the compressor such as a crankcase or bearing housing (e.g. drive housing  60 ). Keying to a fixed structure requires the additional step of angularly aligning the fixed scroll to the structure to provide the proper angular orientation between the orbiting scroll and the fixed scroll. Keying to a fixed structure offers the option to allow the Oldham ring to fit behind the orbiting scroll, i.e. between the orbiting scroll and the structure, which can offer advantages in (smaller) diametric size of the ring which may further facilitate a smaller diameter of the overall compressor. However, keying to a fixed structure requires the addition of precision machined surfaces to the structure (e.g. to drive housing  60 ) to engage the Oldham ring and precision alignment features to both the structure and to the fixed scroll to facilitate the scroll alignment operation, whether they are self-aligning or fixture-aligned. Keying between the two scrolls provides direct, built-in angular alignment with no need for additional alignment features or operations. The scrolls become self-aligning Keying between the scrolls also tends to concentrate the number ofprecision features into the two scroll parts and allows simpler and less precise (and thus less expensive) manufacture of non-scroll components. 
     In conventional prior-art scroll machines with the Oldham ring keyed between the scrolls, the body of the ring is typically a solid ring of a generally constant thickness evenly distributed about a lateral plane. Posts which extend axially from the body of the ring engage key-slots or flat faces on the two scroll components. The body of the ring maybe located between the two scrolls with posts extending from both sides of the body of the Oldham ring, or the body maybe located beneath the orbiting scroll with posts extending from one side of the body of the Oldham ring and with some features keying directly into the adjacent orbiting scroll and some features extending beyond the orbiting scroll to key into the fixed scroll. In both cases, a specific axial space must be set aside for the body of the ring, all at a single level. 
     Referring to  FIGS. 10 and 11 , in the present invention, while Oldham ring  50  is a single, solid component, it is conceptually made up of four segments placed at two different axial locations. Segment pair  57  extends between the four flat surfaces  34  or  24  of orbiting scroll  30  or fixed scroll  20 , respectively, and segment pair  58  extends between the four flat surfaces  24  or  34  of the other scroll, i.e. fixed scroll  20  or orbiting scroll  30 , respectively. Segment pairs  57  and  58  are joined together at their ends at a single plane of symmetry  56 . As a general rule, portions of segment pair  57  do not cross over the plane into the side occupied by segment pair  58  and likewise portions of segment pair  58  do not cross over the plane into the side occupied by segment pair  57 . As a result, Oldham ring  50  does not require a dedicated axial space to be set aside for it. Instead each segment pair extends only between their respective set of flat surfaces  24  or  34  and occupies axial space which would otherwise be unused within the compressor. If desired, segment pairs  57  and  58  may be even further removed from plane  56  with axially extending segments joining the segment pairs  57  and  58  at the four pairs of segment ends. 
     Oldham ring  50  has been designed to be fully symmetric in that segment pair  57  is identical to segment pair  58  and Oldham ring  50  may be installed in any of four possible orientations in the compressor, i.e. it is not possible to mis-assemble it. It may be desirable in some cases to allow the ring to be non-symmetric across plane  56 , such as having different spacing between the flat surfaces  24  on fixed scroll  20  and  34  on orbiting scroll  30 . Segment pair  57  or segment pair  58  may also be non-symmetric, in that segment pair  57  may comprise two different shaped segments or segment pair  58  may comprise two different shaped segments. But whether the ring is designed symmetrically or non-symmetrically there will still be two segments operating on one side of a lateral plane  56  and two segments operating on the other side of plane  56 . 
     Referring to  FIG. 12  in addition to  FIGS. 1-4 , drive housing  60  nests within fixed scroll  20 . Flat face  66  engages fixed scroll pilot floor  26  to establish axial position and perpendicularity between drive housing  60  and fixed scroll  20 . Outside diameter  68  engages fixed scroll pilot diameter  28  to establish centerline concentricity between drive housing  60  and fixed scroll  20 . In this example, the components are self-aligning through this engagement between features  66  and  26  and between features  68  and  28 . Alternately, some or all of this alignment between the fixed scroll  20  and drive housing  60  may be provided through external fixturing for some or all alignment attributes with means provided to maintain alignment after the fixturing is removed. 
     Additionally referring to  FIG. 13 , motor  70  is attached to drive housing  60  and motor shaft  71  extends into the scroll side of the drive housing. In this example motor  70  is secured to drive housing  60  by three bolts  74  although other attachment means may be used. Motor  70  is aligned axially and perpendicularly to drive housing  60  through flat surface  72  which engages flat surface  62  of drive housing  60 . Motor  70  is aligned concentrically with drive housing  60  through pilot diameter  73  which engages pilot bore  63  of drive housing  60 . Alternately, some or all alignment between motor  70  and drive housing  60  may be provided through external fixturing with means provided to maintain alignment after the fixturing is removed. In the present invention, motor  60  is an electric motor but it is understood that motor  60  could be a hydraulic motor, pneumatic motor, or any other prime mover which provides a rotary output. 
     Now, referring to  FIGS. 14-16 , drive widget  40  is attached to motor shaft  71 . In this example the drive widget  40  is pressed onto the shaft  71  through an interference fit between shaft bore  41  and shaft  71  but it is understood that any of a wide variety of attachment methods may be used, including combining drive widget  40  and shaft  71  into a single component. Drive widget  40  is aligned to the shaft  71  concentrically and perpendicularly through the press fit on the shaft  71 . The axial position of drive widget  40  with respect to motor  70  may be determined by physical features in or adjacent the shaft bore  41  and motor shaft  71  or by external fixturing during manufacture or assembly. 
     Drive bearing  45  is fitted over eccentric crankpin  42 . In this example drive bearing  45  is a ball bearing pressed on to the crankpin  42 ; however a number of other bearing types may be used including a solid disk with a smooth bore running directly against the eccentric crankpin  42 . Drive bearing  45  is aligned to the drive widget  40  through the fit between drive bearing  45  and crankpin  42  and through axial locating features such as a mechanical stop or through external fixturing. 
     The axial, perpendicular, and concentric alignment chain between the fixed scroll  20 , drive housing  60 , motor  70 , and drive widget  40  including drive bearing  45  all combine to determine the position of the drive bearing  45  relative to the fixed scroll  20  in the compressor assembly. Orbiting scroll  30  is interposed between fixed scroll  20  and drive bearing  45 . The orbiting scroll  30  is not rigidly constrained to be in any one particular position or orientation relative to any other compressor components. Orbiting scroll  30  may freely move laterally or radially within the limits of the geometry of fixed and orbiting scroll vanes  22  and  32  and also within the limits of the radial clearance space between drive bearing  45  and drive hub inside diameter  36 . Orbiting scroll  30  is free to move axially inside the clearance allowed within the space defined between the fixed scroll tip surface  23  and the flat face  66  of drive housing  60 . In this way, when the compressor is not in operation, orbiting scroll  30  may be said to be “rattling loose” in the assembly with no particular position or orientation imposed upon it. 
     In the assembly, drive bearing  45  is positioned within the orbiting scroll drive hub inside diameter  36  and, when driven by motor  70  through the drive widget  40 , drive bearing outside diameter  46  acts against the drive hub inside diameter  36  at contact point  37  to urge the orbiting scroll vane  32  against the fixed scroll vane  22  in the lateral or radial plane and to follow a circular orbit path as defined by the resulting contact between fixed scroll vane  22  and orbiting scroll vane  32 . 
       FIG. 17  shows a schematic representation of the drive bearing  45  with an outside diameter  46  and a drive bearing center  43  situated inside the drive hub  35  which has an inside diameter  36  and a center  38 . Motor shaft center  77  is coincident with the center of fixed scroll  20  and defines the center of rotation for drive widget  40 . During normal operation, when orbiting scroll vane  32  is in contact with fixed scroll vane  22  and drive bearing outside diameter  46  is pushing against drive hub inside diameter  36 , the orbiting scroll is constrained through pressure and inertial loads to move in a circular orbit path  31  which is centered on fixed scroll  20  and which is defined by the respective geometries of fixed scroll vane  22  and orbiting scroll vane  32 . In  FIG. 17 , the motor shaft  71  and thus also the drive widget  40  are rotating in a clockwise direction and drive bearing center  43  is also moving in a clockwise direction in a circular path centered on shaft center  77 . 
     Drive bearing outside diameter  46  contacts the drive hub inside diameter  36  at contact point  37  and the instantaneous direction of motion of the orbiting scroll  30  is to the right as indicated in  FIG. 17  even though drive bearing center  43  is moving down and to the right as also indicated in  FIG. 17 . Assuming there is no slippage between drive bearing outside diameter  46  and drive hub inside diameter  36  at contact point  37  the difference in velocity vectors between the orbiting scroll center  38  and drive bearing center  43  results in a rolling action between drive bearing  40  and drive hub inside diameter  36 . As a result of the rolling action, drive bearing outside diameter  46  will rotate in a counterclockwise direction as viewed in  FIG. 17  even though the drive system is rotating in a clockwise direction. The total rotational speed of drive bearing  45  relative to crankpin  42  will be the sum of the rotation induced by this reverse rolling action plus the rotational speed of the motor shaft  71 . Thus it is necessary to design drive bearing  45  to run at a somewhat higher rotational speed than that of the motor shaft  71 . 
     The contact force Fc between drive bearing outside diameter  46  and drive hub inside diameter  36  is applied at contact point  37  and is directed normal to the two surfaces  46  and  36  at the point of contact. This contact force Fc will have a component Ft which acts in the instantaneous direction of motion of the orbiting scroll  30 . This force balances a gas compression force generated within the scroll pair which resists the action of drive bearing  45  and represents the force against which the work of compression is accomplished. 
     In this example, the drive bearing center  43  is positioned so that the line of action of the contact force Fc acts at an angle α to the instantaneous direction of orbiting scroll motion. In this manner, in addition to contact force Fc generating a tangential force component Ft in the direction of orbiting scroll motion to accomplish the work of compression, contact force Fc also generates a radial force component Fr which acts to push the orbiting scroll  30  radially outward to increase the loading between the orbiting scroll vane  32  and the fixed scroll vane  22 . This may be done to counteract a radially inward-acting gas force generated by the scroll set which tends to separate the orbiting and fixed scroll vanes  32  and  22 . In larger compressors, where the centrifugal inertial action of a larger, heavier orbiting scroll is sufficient to counteract the radial gas force, the drive bearing center  43  may be repositioned to reduce or eliminate the outward-acting radial force component Fr of the contact force Fc or even to reverse the radial force component Fr to act radially inward against the centrifugal inertial action of the orbiting scroll  30  and thus to reduce the load between orbiting and fixed scroll vanes  32  and  22 . 
     The advantage of this drive system, as opposed to simply rigidly mounting drive bearing  45  in drive hub  35 , where the orbiting scroll  30  is driven in a fixed circular path centered on motor shaft  71  as opposed to the path defined by scroll vanes  22  and  32 , is in its tolerance for deviations in the actual orbit path  31  from the ideal circle centered on motor shaft  71 . Normal manufacturing dimensional and alignment tolerances result in a vane-generated orbit path which deviates significantly from the ideal, shaft-centered orbit path. In the drive arrangement of  FIG. 17  the orbiting scroll  30  is able to move radially inward and outward in response to deviations in the vane-generated orbit path. The orbiting scroll vane  32  and fixed scroll vane  22  are thus able to remain in continuous sealing contact. As orbiting scroll  30  moves radially inward and outward, orbiting scroll center  38  in the Figure moves down or up, respectively, and contact point  37  moves in a direction to increase or decrease contact angle α, also respectively. 
     If orbiting scroll  30  were constrained to rigidly follow a circular path centered on shaft center  77 , it would be necessary to reduce the radius of orbit path  31  in order to avoid mechanical interference between scroll vanes  32  and  22  resulting from manufacturing and assembly alignment tolerances. The radially compliant drive system defined by drive widget  40  and drive hub  35  as illustrated in  FIG. 17  allows the scroll vanes to remain in sealing contact in spite of necessary deviations imposed by manufacturing variations. It also allows transient deviations from the ideal orbit path in the presence of contaminants or liquid in the scroll set which would otherwise result in interference or hydraulic lock. 
     In addition to providing the function of the eccentric crankpin  42  and drive bearing  45 , drive widget  40  also provides two counterweights, primary counterweight  48  and secondary counterweight  49 . The size, location, and orientation of the two counterweights  48  and  49  are selected and calibrated so that the entire rotodynamic system defined by drive widget  40  including drive bearing  45 , orbiting scroll  30 , and Oldham ring  50  is in both static and dynamic balance. In conventional scroll machine designs the three functions of the drive system, i.e. the mechanical drive, primary counterweight, and secondary counterweight, are normally carried out by separate components distributed at separate locations along a drive-shaft which also includes an integrated motor. 
     The present invention decouples the mechanical drive function from the motor  70  and allows either the drive system (drive widget  40  and orbiting scroll drive hub  35 ) or the motor  70  to be modified with little if any impact on the other. Additionally, the specific geometric relationships between the eccentric crankpin  42  and the two counterweights  48  and  49  are “locked in” to a single component instead of requiring assembly and alignment of various components in various operations. Any prime mover, whether electrical, hydraulic, pneumatic, or otherwise need only meet requirements of shaft output, radial shaft loading, and mechanical interface in order to be applied to this compressor. No significant redesign or retooling is needed to change from one motor type or design to another. 
     The combined assembly of fixed scroll  20 , orbiting scroll  30 , the drive widget  40  (including drive bearing  45 ), Oldham ring  50 , drive housing  60 , and motor  70  together form an integrated motor-compressor module  11  which may be packaged and applied in a number of different ways. Motor-compressor module  11  is illustrated in  FIG. 18 . In the present invention, motor-compressor module  11  is mounted within a semi-hermetic compressor housing  80 . In addition to appearing in  FIGS. 1-4 , compressor housing  80  is illustrated in detail in  FIG. 19 . The back-flange surface  61  of drive housing  60  seats against flat surface  81  of compressor housing  80  which establishes the axial position of motor-compressor module  11  within compressor housing  80 . The fixed scroll outside diameter  27  matches the compressor housing bore  87  closely enough for a snug fit, which establishes the radial position (concentricity) of the fixed scroll  20  and thus the concentricity of the motor-compressor module  11  within compressor housing  80 . A sealing element  83  fits within seal groove  84  in the side wall of bore  87  and seals against fixed scroll outside diameter  27 . Beveled retaining ring  85  fits within retaining ring groove  86  of compressor housing  80  and seats against fixed scroll shoulder  25 . The bevel-spring action of the retaining ring  85  loads and clamps drive module  11  within compressor housing  80 . In this manner the motor-compressor module  11  is located and sealingly secured within compressor housing  80 . Electrical feed-through  88  is/are provided to conduct motor power leads into the sealed space within compressor housing  80 , and a discharge passage  89  is provided for compressed vapor to exit the compressor housing. 
     This design concept may be easily converted to a hermetic-type compressor by eliminating the retaining ring  85  and joining the compressor housing  80  to the fixed scroll outside diameter  27  with some sort of vapor-tight seal such as welding, swaging, brazing, soldering, roll forming, crimping, bonding, or other suitable joining process. A ring type seal  83  or an applied sealant may optionally be used in addition to the joining process to assure gas-tightness of the joint. Suitable hermetic power terminals and piping connections would replace the corresponding threaded and gasketed components in this design example. 
     When motor  70  is energized, causing motor shaft  71  and drive widget  40  to rotate, orbiting scroll  30 , as described above, is driven in a circular path with orbiting scroll vane  32  bearing radially against fixed scroll vane  22 . The orbiting scroll  30  is prevented from any rotational motion by the action of Oldham ring  50  between orbiting scroll  30  and fixed scroll  20 . The scroll vanes interact in the conventional manner, vapor is transported from the inlet port  21 , compressed within sealed crescent-shaped chambers, and discharged into the drive housing  60  through discharge port  39 . Fixed scroll  20  also has a “mirror port” blind recess  29  which aids in the discharge flow process. 
     The high-pressure discharge port  39  through the orbiting scroll floor directs the full discharge flow into the drive bearing system, which is unusual if not unique in current scroll practice. The normal arrangement has the discharge flowing through the fixed scroll  20  (with an open, through port in place of blind mirror port recess  29 ) with the space behind orbiting scroll  30  reserved for bearing, drive, and lubrication systems which are intentionally kept separate from the direct flow through the compressor. 
     In a conventional closed-loop refrigeration or air conditioning circuit some percentage of the compressor lubricant is circulating throughout the system at any given time. This is due in large part to the inherent difficulty of fully separating the lubricant from the refrigerant flow. Conventional compressor designs capture as much of the returning lubricant as practical and return it to an internal sump to replenish lubricant which is lost to the discharge flow from the compression mechanism. When applied in a closed-loop system the present invention directs all returning lubricant directly into the compression chambers and discharges the full combined refrigerant and lubricant flow into drive gallery  12  which is the space defined by the combination of the fixed scroll  20 , drive housing  60 , and motor  70 . Drive gallery  12  contains or is adjacent to all critical moving parts in the compressor, including drive widget  40  with drive bearing  45 , Oldham ring  50 , the sliding tip-to-floor interface between the fixed scroll  20  and orbiting scroll  30 , and the motor shaft bearings. 
     So-called high-side compressor designs, both scroll and non-scroll, where all returning flow passes through the compression mechanism and discharges into the mechanical drive space which operates in the discharge pressure environment, are well-known in the art. However, conventional designs direct the flow through a discharge port in the fixed scroll and along a path separated from direct exposure to the mechanical drive and lubricant sump. These provide means to separate the lubricant flow from the compressed vapor flow, and return the lubricant to an isolated, managed sump from which a lubricant pumping system delivers lubricant to the bearings and scroll drive. Conventional (i.e. commercially produced) low-side compressor layouts are very similar in that the lubricant flow is separated and returned to the sump where pumping and distribution means deliver the lubricant to the bearing and drive system. The most significant difference is the suction pressure environment in the mechanical drive space and that the lubricant separation process takes place upstream, i.e. before the compression device instead of after. 
     Mist-lubricated compressors, including scroll-types as well as others, are also well in the art. They are most commonly applied in automotive air conditioning applications or other small transport air conditioning and refrigeration applications. However, as a rule they are low side designs with the discharge flow exiting the compressor from a fitting connected directly to a discharge port in the fixed scroll. 
     Any and all lubricant and vapor passing through compressor  10  will be discharged through port  39 , through and around drive bearing  45 , and into drive gallery  12 . The compressed vapor exits drive gallery  12  through outlet port  69  along with whatever lubricant remains entrained in the vapor flow. In this embodiment port  69  is at the top of drive gallery  12  in an effort to allow gravity to collect lubricant on the opposite side at the bottom of drive gallery  12 . Other means, such as baffles or deflectors within drive gallery  12  or around port  69  may be added to further separate the lubricant flow and to tend to retain lubricant within drive gallery  12 . In this way drive gallery  12  tends to act as a lubricant sump, but one which is not managed. There are no means for lubricant pumping or distribution. Any lubricant delivery from the bottom of drive gallery  12  will be through splashing action of the moving parts and the turbulent vortex flow driven by the rotating drive widget  40 . As long as lubricant is returning from the system to compressor  10  through the suction flow there is no need for a lubricant reserve in drive gallery  12 . However, if more lubricant remains resident in drive gallery  12 , that will permit for a lower percentage of lubricant circulation in the system, which is generally desirable. This also provides a lubricant reserve for critical moving parts in the event of a transient loss of lubricant return. 
     The discharge pressure acting on the drive hub side of orbiting scroll  30  serves to load it against the fixed scroll  20  in opposition to the internally pressure-generated axial force which tends to separate the scrolls. In this way the scrolls are pressure-loaded together for effective contact sealing between tip and floor surfaces. 
     During the startup phase of the compressor the discharge and suction sides are at equal pressure and so there is no force to push the scrolls together. However on startup there is almost immediately an internally-generated pressure from the compression action within the scroll set which tends to push the orbiting scroll  30  away from fixed scroll  20 . During this startup phase anti-thrust pads  33  adjacent flat faces  34  on orbiting scroll  30  bear against flat face  62  of drive housing  60 . This necessarily results in axial clearance between orbiting scroll  30  and fixed scroll  20  which allows leakage between adjacent compression volumes. This leakage results in degraded performance and flow through compressor  10 . However if the axial clearance is controlled within reasonable limits the compressor  10  will generate enough flow to create back pressure against the system restriction or load until enough pressure is developed to overcome the axial separating gas force and to axially load the orbiting scroll  30  against the fixed scroll  20 . In this way the compressor “bootstraps” itselfup from a balanced-pressure start. 
     After exiting drive gallery  12  through port  69  the compressed vapor flows into motor chamber  14  where the vapor absorbs heat rejected by the motor, i.e. the motor is cooled by the vapor flow. After flowing around the motor, the vapor exits the compressor through discharge passage  89 . In the present invention, discharge passage  89  is placed at the bottom of motor chamber  14  to avoid creating “traps” or pockets where lubricant could collect away from the main vapor flow. Any carryover lubricant in the discharge vapor flow will be carried along by the flow and the force of gravity to discharge passage  89  and flows back to the system to be returned again to the compressor the next time around. 
     The above-described embodiment(s) are given as examples of implementing the invention. The invention is not to be limited to the foregoing illustrative embodiments thereof. Rather many modifications and variations thereof are possible within the scope of this invention which is to be measured by the appended claims.