Abstract:
Co-orbiting scroll members are maintained in a fixed angular relationship. An anti-rotation structure limits one of the scroll members to orbiting motion with respect to the separator plate. In a first embodiment the scroll members coact with a common anti-rotation structure while in a second embodiment the other scroll coacts with an anti-rotation structure which coacts with the crankcase. The scroll members orbit in orbits of different radii.

Description:
This application is a continuation-in-part of commonly assigned application Ser. No. 808,820 filed Dec. 17, 1991, and now U.S. Pat. No. 5,141,417. 
    
    
     BACKGROUND OF THE INVENTION 
     In a scroll machine such as a pump, compressor or expander there is one basic coaction between the scroll elements in that one must orbit with respect to the other. The scroll element orbiting with respect to the other scroll element is generally called the orbiting scroll. In known designs both scroll elements are rotating, both are orbiting, one is fixed or is only capable of axial movement. A design where both scroll elements orbit, but at different radii, is exemplified by U.S. Pat. No. 3,874,827 which discloses a number of embodiments. Specifically, in FIG. 15, a version of a co-orbiting scroll design is disclosed in which two Oldham couplings are used. One is keyed between the scrolls but is located within the scroll elements. Basically, however, the disclosed embodiments have a driving major/orbiting scroll which has a fixed orbit and which drives a driven scroll which is able to move in a minor/smaller orbit as well as axially. The driven scroll is acted on by discharge pressure which forces the driven scroll into axial engagement with the driving scroll as well as a resilient material member which tends to locate the driven scroll at a position corresponding to the center of the minor orbit. The driven scroll moves in an orbiting motion subject to the bias of the resilient material which may make the orbit non-circular. In the disclosed embodiments, the compressor is of the open drive type with the motor above the scrolls. 
     In parent application Ser. No. 808,820, a method for dynamically balancing nested coupling mechanisms is disclosed. Basically, one coupling is keyed between the two scrolls and the other coupling is keyed between the driven or major scroll and the crankcase or fixed housing. The couplings can be arranged to provide a resultant centrifugal or inertial force which is easily balanced by a rotating counterweight. 
     SUMMARY OF THE INVENTION 
     The present invention is directed to a scroll machine having two orbiting scrolls. One Oldham coupling is keyed between the scrolls in a first embodiment and between the major/orbiting scroll and the crankcase in the second embodiment. The second coupling in each embodiment is keyed between the minor/free scroll and the pilot housing or fixed structure. The second coupling reciprocates through the smaller minor orbit so that it is made somewhat more massive than the first coupling so that the mass-displacement product of each coupling is the same. The minor scroll coacts with the inner surface of a pilot ring which guides and supports the minor scroll in its movement through its minor orbit to thereby provide radial compliance. Intermediate and discharge pressure acts on the minor scroll to provide an axial compliance force to maintain the minor and major/orbiting scrolls in engagement. The major/orbiting scroll rides on the crankcase. The crankcase and the separator plate with its integral pilot ring are bolted together and hold the major and minor scroll as well as the anti-rotation structure therebetween. 
     In scroll compressors having an Oldham coupling or some other reciprocating anti-rotation device, the reciprocating unbalance can, at best, be counterbalanced by only one half by using rotating counterweights. In the case of the co-orbiting scroll design of the present invention, there are two separately reciprocating Oldham couplings to balance. 
     It is an object of this invention to couple two components in a fixed angular relationship while allowing one component, the minor scroll, to orbit with respect to the other member, the major scroll. 
     It is a further object of this invention to counteract most, if not all, of the reciprocating unbalance of the anti-rotation structure through the use of rotating counterweights. 
     It is another object of this invention to provide a co-orbiting scroll machine which maintains a fixed angular relationship between the two orbiting members. These objects, and others as will become apparent hereinafter, are accomplished by the present invention. 
     Basically, a scroll machine is provided with co-orbiting scroll members which are maintained in a fixed angular relationship. Each of the scroll members coacts with an anti-rotation structure and is located within an assembly defined by a separator plate, pilot ring and crankcase which are secured together. The anti-rotation structure includes two Oldham-type couplings. One coupling is keyed between the minor/free scroll and the pilot housing or fixed structure. In one embodiment, the second coupling is keyed between the scrolls and, in a second embodiment, it is keyed between the major/orbiting scroll and the crankcase or fixed structure. 
     The coactions of the two couplings is such as to produce the effect of a rotating unbalance. The rotating unbalance may be fully balanced with conventional rotational counterweights. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     For a fuller understanding of the present invention, reference should now be made to the following detailed description thereof taken in conjunction with the accompanying drawings wherein: 
     FIG. 1 is a partial, vertical sectional view of a scroll compressor employing the present invention; 
     FIG. 2 is a top view of a first coupling member; 
     FIG. 3 is a sectional view taken along line 3--3 of FIG. 2; 
     FIG. 4 is a top view of a second coupling member; 
     FIG. 5 is a mass displacement diagram for the anti-rotation couplings of the present invention; 
     FIG. 6 is a combination of a rotating mass unbalance and sinusoidally reciprocating masses according to the teachings of the present invention; 
     FIG. 7 is a partial, vertical sectional view of a modified scroll compressor employing a second embodiment of the present invention; 
     FIG. 8 is a top view of a first coupling member of the FIG. 7 embodiment; and 
     FIG. 9 is a mass displacement diagram for the anti-rotation couplings of the FIG. 7 embodiment. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     In FIG. 1, the numeral 10 generally designates a low side hermetic scroll compressor. Compressor 10 has a shell or casing 12 having a main body 12-1 with an upper cover 12-2. Separator plate 32 divides the shell 12 into a suction plenum 16 and a discharge plenum 17. A crankcase 20 is welded or otherwise suitably secured within main body 12-1 and supports crankshaft 22 in a conventional manner while slidably supporting the flat side of Oldham coupling 30 which has all of its keys on the opposite side. Crankshaft 22 receives hub 26-3 of major or driving scroll 26 in eccentrically located recess 22-1. Crankshaft 22 has a counterweight 22-2 thereon which may be integral therewith, as shown, or a separate piece. Major or driving scroll 26 is supported by crankcase 20 and coacts with Oldham coupling 30. Crankshaft 22 drives major or driving scroll 26 at a fixed radius. Major or driving scroll 26 has a wrap 26-1 which coacts with wrap 28-1 of minor or driven scroll 28. Minor or driven scroll 28 also coacts with Oldham coupling 30 so that relative orbital motion is possible between scrolls 26 and 28. A second Oldham coupling 24 is located between separator plate 32 and minor/free scroll 28. It should be noted that in FIG. 1, the Oldham couplings 24 and 30 are illustrated to show a single key and adjacent keys rather than the paired keys. 
     Referring now to FIGS. 2 and 3, it will be noted that Oldham coupling 30 differs from conventional designs in that it is asymmetrical, all of the keys are on the same side of coupling 30 and the pairs of keys are of different heights. Specifically, coupling 30 has a bore 30-1, opposed short keys 30-2 and 30-3, and opposed tall keys 30-4 and 30-5. 
     Referring to FIG. 4, it will be noted that Oldham coupling 24 is of a generally conventional design. Specifically, there are two pairs of keys generally diametrically located with respect to bore 24-1. In order to reduce dimensional requirements, a pair of keys may be located other than on a diameter of bore 24-1. One pair of keys is located on each side of coupling 24 with the diameters of the respective pairs being located at right angles. As viewed in FIG. 4, only keys 24-2 and 24-3 are visible. Keys 24-4 and 24-5 appear in phantom. 
     Major scroll 26, minor scroll 28 and Oldham couplings 24 and 30 are held in place between crankcase 20 and separator plate 32. Specifically, as illustrated, separator plate 32 has a discharge passage 32-1 extending between discharge port 28-3 and discharge plenum 17. Annular surface 32-2 surrounds the entrance to discharge passage 32-1 and is engaged by annular O-rings or other suitable seals 36 and 37 carried by minor scroll 28. Bore 32-3 has an axial extent corresponding to the major portion of the axial extent of minor scroll 28 whereby bore 32-3 defines a pilot ring or surface. Shoulder 32-4 surrounds bore 32-3. Circumferentially spaced legs 32-5 extend from shoulder 32-4 and their inner surfaces 32-6 provide a greater diametrical clearance than bore 32-3. Pilot ring 32-3 surrounds minor scroll 28. Minor scroll 28 has a base 28-2 and inner and outer annular recesses are formed in the surface of base 28-2 and receive O-rings or other suitable seals 36 and 37, respectively. One or more restricted fluid passages 28-4 extend through base 28-2 from a point located between seals 36 and 37 and a point located between adjacent turns of wrap 28-1. 
     In assembling compressor 10, starting with crankcase 20, coupling 30 is placed over central annular projection 20-1 such that there is a clearance between bore 30-1 and projection 20-1. Referring specifically to FIG. 3, it will be noted that keys 30-4 and 30-5 are taller than keys 30-2 and 30-3. Major/orbiting scroll 26 is set in place such that key 30-2 is received in slot 26-4 and key 30-3 is received in a diametrically located slot (not illustrated). 
     As noted, when major/orbiting scroll 26 is set in place, short keys 30-2 and 30-3 are located in corresponding slots on the back of base 26-2, while keys 30-4 and 30-5 extend axially above base 26-2. Minor scroll 28 is then set in place with wrap 28-1 being operatively located with respect to wrap 26-1. Also, corresponding slots formed in minor scroll 28 are located so as to operatively receive tall keys 30-4 and 30-5, with only slot 28-5 which receives key 30-4 being illustrated. Seals 36 and 37 are located in corresponding grooves formed in the back of base 28-2. Oldham coupling 24 is set in place such that key 24-4 is received in slot 28-6 and diametrically located key 24-5 is received in a corresponding slot (not illustrated). Separator plate 32 is placed such that key 24-2 is received in slot 32-8 and key 24-3 is received in a diametrically located slot (not illustrated), minor scroll 28 is received in bore 32-3, and coupling 30 is received within the space defined by legs 32-5. Corresponding sets of bores 32-7 and 20-2 are aligned and bolts 42 are threaded thereinto. The resultant pump structure may then be secured in main casing 12-1. When so assembled, major scroll 26 is capable of orbital movement in a circle having a radius equal to the distance between A-A the axis of crankshaft 22 and B-B the axis of hub 26-3. Scroll 28 is capable of orbital movement through a circle having a diameter equal to the difference in diameters of bore 32-3 and base 28-2. 
     In operation, a motor 60 drives crankshaft 22 causing it to rotate about its axis A--A carrying eccentrically located hub 26-3 of major scroll 26. Because major scroll 26 coacts with Oldham coupling 30, major scroll 26 is held to an orbiting motion when driven by crankshaft 22 with the radius of the orbit being equal to the distance between axes A--A and B--B. Wrap 26-1 of major scroll 26 coacts with wrap 28-1 of minor scroll 28 to trap volumes of gas from suction plenum 16 and compress the gas with the resultant compressed gas passing serially through discharge port 28-3 and discharge passage 32-1 into discharge plenum 17 from which the compressed gas passes to the refrigeration system via an outlet (not illustrated). As the gas is being compressed the resultant pressure results in a force acting on scrolls 26 and 28 tending to separate them axially and radially. Radial movement of minor scroll 28 is limited by base 28-2 coacting with the inner annular surface of bore 32-3 which acts as a pilot ring. Additionally, coupling 30 coacts with both major scroll 26 and minor scroll 28 while coupling 24 coacts with separator plate 32 and minor scroll 28 to limit radial movement of minor scroll 28 to an orbiting motion relative to major scroll 26. Because the difference in diameters of base 28-2 and bore 32-3 determines the diameter of the orbit of minor scroll 28, it is possible for the diameter of orbit of scroll 28 to be designed to be increased and made equal to or greater than the orbit of scroll 26, if necessary or desired. However, if the orbit of scroll 28 is so increased, the mass-displacement product of coupling 24 will have to be adjusted to equal that of coupling 30. Axial separation of scrolls 26 and 28 is limited by annular surface 32-2 of separator plate 32 which is bolted to crankcase 20 by bolts 42 or otherwise suitably secured. Axial separation of scrolls 26 and 28 is opposed by intermediate fluid pressure in annular chamber 50 and by discharge pressure acting on base 28-2 between seal 36 and discharge port 28-3. Annular chamber 50 is located between separator plate 32 and minor scroll 28 with its inner boundary defined by seal 36 and its outer boundary defined by seal 37. Chamber 50 is in fluid communication with a location at an intermediate pressure in the compression process via one or more fluid passages 28-4. As a result, the intermediate pressure in chamber 50 and the discharge pressure acting on base 28-2 axially force minor scroll 28 into axial engagement with major scroll 26. 
     To summarize the operation, major scroll 26 is driven in a fixed orbiting motion. Responsive to the fluid pressure of the compression process, base 28-2 of minor scroll 28 is forced into engagement with pilot surface 32-3 and maintains engagement thereby being limited in radial movement while being held to an orbiting motion relative to major scroll 26 by the coaction of coupling 30 with major scroll 26 and minor scroll 28 and is held to an orbiting motion with respect to separator plate 32 by Oldham coupling 24. Minor scroll 28 is held in axial engagement with major scroll 26 by fluid pressure acting on base 28-2 and in chamber 50. 
     From the foregoing description it should be readily evident that Oldham coupling 24 undergoes a reciprocating motion with respect to the separator plate 32 which is fixed with respect to crankcase 20. Because Oldham coupling 24 only reciprocates while the scroll 28 orbits, there is an unbalance. However, Oldham coupling 30 undergoes a reciprocating motion with respect to scroll 26 which is orbiting and the mass-displacement path of Oldham coupling 30 between scrolls 26 and 28 is shown in FIG. 5. It will be noted that the mass-displacement path of Oldham coupling 30 between scrolls 26 and 28 is essentially an ellipse with a major axis approximately equal to the major orbit diameter and a minor axis approximately equal to the minor orbit diameter. If the difference in diameter between bore 32-3 and base 28-2 is changed, as noted above, the shape of the ellipse defining the mass-displacement path of Oldham coupling 30 can be changed. 
     The displacement of coupling 30 may be approximated as a combination of a rotating mass unbalance and a sinusoidally reciprocating mass as shown in FIG. 6. The displacement of coupling 24 is purely linear with a sinusoidal motion. The key slots, of which only 32-8, 28-5, 28-6 and 26-4 are illustrated in FIG. 1, are placed such that the two reciprocating components of motion are essentially at right angles and moving 90° out of phase. The masses of the respective Oldham elements 24 and 30 are sized in inverse proportion to their reciprocating displacement components so that the total mass-displacements of each coupling are the same. As a result, the two components combine to produce the equivalent of a rotating mass unbalance which may be fully balanced with conventional rotational counterweights. Also, the pairs of aligned keys of the couplings 24 and/or 30 may intersect at an angle other than 90°. Specifically, an alignment of up to 10° from perpendicular could be made to also work effectively with only a small residual unbalance. 
     Referring now to FIG. 7, a modified compressor 110 is illustrated. All modified details of the structure have been labeled one hundred higher than the corresponding structure in FIG. 1. The main structural difference is in Oldham coupling 130 which now couples major or orbiting scroll 26 to crankcase 20 rather than to minor scroll 28, as in the FIG. 1 embodiment. Thus, the FIG. 7 embodiment has each of the scrolls coupled to a fixed element, but not to each other. As shown in FIG. 8, coupling 130 is generally conventional with keys 130-2 and 130-3 being visible and keys 130-4 and 130-5 being shown in phantom. Key 130-2 is received in slot 26-4 and key 130-3 is received in a diametrically located slot (not illustrated). Key 130-4 is received in slot 120-3 in crankcase 20 while key 130-5 is received in a diametrically located slot (not illustrated). 
     In operation, motor 60 drives crankshaft 22 causing it to rotate about its axis A--A carrying eccentrically located hub 26-3 of major or orbiting scroll 26. Because Oldham coupling 130 coacts with both scroll 26 and crankcase 20, major or orbiting scroll 26 is held to an orbiting motion when driven by crankshaft 22 with the radius of the orbiting motion being equal to the distance between axes A--A and B--B. Oldham coupling 24 coacts with minor scroll 26 and separator plate 32 such that minor scroll 26 can orbit with respect to separator plate 32 with the orbit diameter being determined by the difference in diameters between bore 32-3 and base 28-2. Wrap 26-1 of major scroll 26 coacts with wrap 28-1 of minor scroll 28 but they are not directly coupled and, as noted, minor scroll 28 is capable of orbiting motion. Wrap 26-1 of major scroll 26 coacts with wrap 28-1 of minor scroll 28 which is caused to orbit as a result of the coaction. As a result of the coaction between wraps 26-1 and 28-1, volumes of gas from the suction plenum 16 are trapped and compressed with the resultant compressed gas passing serially through discharge port 28-3, and discharge passage 32-1 into discharge plenum 17 from which the compressed gas passes to the refrigeration system via an outlet (not illustrated). While both scrolls are capable of movement, each is held to orbiting motion by a separate Oldham coupling coacting with a fixed member and contact is maintained between the scroll wraps during the compression process as in a conventional scroll compressor. 
     From the foregoing description it should be readily evident that Oldham couplings 24 and 130 each undergoes a reciprocating motion with respect to the fixed separator plate 32 and crankcase 20 while scrolls 26 and 28 orbit. The mass-displacement paths of Oldham couplings 24 and 130 are shown in FIG. 9. 
     Although preferred embodiments of the present invention have been illustrated and described, other changes will occur to those skilled in the art. It is therefore intended that the scope of the present invention is to be limited only by the scope of the appended claims.