Oldham coupling for scroll compressor

Abstract: A scroll-type machine is disclosed which incorporates a unique Oldham coupling for preventing relative rotation between the two scroll members while allowing relative orbital motion therebetween. The Oldham coupling is positioned below the end plate of the orbiting scroll member and includes a first pair of keys slidingly engaging slots in the orbiting scroll and a second pair of keys slidingly engaging slots in the non-orbiting scroll. An optional third key may be provided to slidingly engage a slot in the non-rotating bearing housing.

Description: Background And Summary Of The Invention The present invention relates generally to scroll machines and more specifically to unique Oldham couplings for use in such scroll-type machines. Scroll-type machines typically employ a crankshaft operative to drive one of a pair of scroll members in orbital motion with respect to a second interleaved scroll member. In order to prevent relative rotation between the scroll members, Oldham couplings have normally been employed. These Oldham couplings have taken various forms but generally incorporate two or more pairs of keys, each pair projecting in opposite directions from an annular ring member with one pair engaging slots in the orbiting scroll member and the other pair engaging either slots in the non-orbiting scroll member or a stationary body or bearing housing. While such Oldham couplings which are operative between the respective scroll members are effective to prevent relative rotation between these respective scroll members, they present design and/or assembly problems in regards to positioning of the coupling between the scroll members. Alternatively, in other applications, additional support structure and/or increased shell size may be required to support the Oldham coupling radially outwardly of the scroll members. The use of an Oldham coupling acting between the stationary body and one of the scroll members with the other scroll member being mounted to the stationary body simplifies the above design problems but such an arrangement tends to be more costly in that both scrolls must now be accurately positioned with respect to a third element. This third element must then be provided with precise locating and alignment surfaces for each of the two scroll members in order to insure that the two scroll members are accurately rotationally positioned with respect to each other. The present invention, however, provides an Oldham coupling which is capable of directly inter-connecting the two scroll members so as to effectively prevent relative rotation therebetween while avoiding the potential design problems presented by prior designs and also reducing the number of locating and positioning surfaces required. The present invention provides an Oldham coupling positioned in underlying relationship to the orbiting scroll member with first and second pairs of keys all projecting upwardly therefrom into engagement with the respective scroll members. JP-A-191488 discloses an Oldham coupling for use in a scroll-type machine as defined in the prior art portion of claim 1. With this prior coupling, first and second pairs of keys are provided projecting upwardly in the same direction from a ring into engagement with respective scroll members. However, with the prior construction, as with the construction illustrated in our earlier US-A-4 877 382 which does not have an Oldham coupling having two pairs of upwardly projecting keys, there is a limitation in the size of thrust surface which may be used with a given size Oldham coupling. With the present invention as defined in claim 1, the offset of one of the lines of abutment surfaces from the axis of the machine enables a larger size of thrust surface to be used for a given sized Oldham coupling ring without overriding interference with the location and extent of the wrap of the orbiting scroll member. The invention also relates to scroll-type machines embodying the improved Oldham coupling. The positioning of the keys and shape of the coupling combines to enable the two scroll members to be directly interconnected so as to both ensure positive precise rotational positioning therebetween and to thereafter prevent relative rotation therebetween in an efficient manner without the need to add additional supporting structure therefor nor the need to increase the overall size of the compressor. Additional advantages and features of the present invention will become apparent from the subsequent description and the appended claims taken in conjunction with the accompanying drawings. Brief Description of the Drawings Figure 1 is a vertical section view of a scroll-type refrigeration compressor in accordance with the present invention; Figure 2 is a fragmentary section view similar to that of Figure 1 but with the section being taken along a plane passing through the non-orbiting scroll mounting arrangement, all in accordance with the present invention; Figure 3 is a section view of the refrigeration compressor of Figure 1, the section being taken along the line 3-3 thereof; Figure 4 is a plan view of the Oldham coupling incorporated in the refrigeration compressor shown in Figures 1-3, all in accordance with the present invention; Figure 5 is an elevational view of the Oldham coupling of Figure 4; Figure 6 is a view similar to that of Figure 5, but showing a modified embodiment of the Oldham coupling in accordance with the present invention; and Figure 7 is a fragmentary section view of the Oldham coupling of Figure 6 shown in operative relationship with a scroll-type refrigeration compressor. Description of the Preferred Embodiment Referring now to the drawings and in particular to Figure 1, a compressor 10 is shown which comprises a generally cylindrical hermetic shell 12 having welded at the upper end thereof a cap 14 and at the lower end thereof a base 16 having a plurality of mounting feet (not shown) integrally formed therewith. Cap 14 is provided with a refrigerant discharge fitting 18 which may have the usual discharge valve therein (not shown). Other major elements affixed to the shell include a transversely extending partition 22 which is welded about its periphery at the same point that cap 14 is welded to shell 12, a main bearing housing 24 which is suitably secured to shell 12 and a lower bearing housing 26 also having a plurality of radially outwardly extending legs each of which is also suitably secured to shell 12. A motor stator 28 which is generally square in cross section but with the corners rounded off is pressfitted into shell 12. The flats between the rounded corners on the stator provide passageways between the stator and shell, which facilitate the flow of lubricant from the top of the shell to the bottom. A drive shaft or crankshaft 30 having an eccentric crank pin 32 at the upper end thereof is rotatably journaled in a bearing 34 in main bearing housing 24 and a second bearing 36 in lower bearing housing 26. Crankshaft 30 has at the lower end a relatively large diameter concentric bore 38 which communicates with a radially outwardly inclined smaller diameter bore 40 extending upwardly therefrom to the top of the crankshaft. Disposed within bore 38 is a stirrer 42. The lower portion of the interior shell 12 is filled with lubricating oil, and bore 38 acts as a pump to pump lubricating fluid up the crankshaft 30 and into passageway 40 and ultimately to all of the various portions of the compressor which require lubrication. Crankshaft 30 is rotatively driven by an electric motor including stator 32, windings 44 passing therethrough and a rotor 46 pressfitted on the crankshaft 30 and having upper and lower counterweights 48 and 50 respectively. A counterweight shield 52 may be provided to reduce the work loss caused by counterweight 50 spinning in the oil in the sump. A generally cylindrical upper portion 51 of main bearing housing 24 defines a flat thrust bearing surface 53 on which is supported an orbiting scroll 54 having the usual end plate and spiral vane or wrap 56 projecting from the upper surface thereof. Projecting downwardly from the lower surface of the end plate of orbiting scroll 54 is a cylindrical hub having a journal bearing 58 therein and in which is rotatively disposed a drive bushing 60 having an inner bore 62 in which crank pin 32 is drivingly disposed. Crank pin 32 has a flat on one surface which drivingly engages a flat surface (not shown) formed in a portion of bore 62 to provide a radially compliant driving arrangement, such as disclosed in assignee's U.S. Letters Patent 4,877,382, the disclosure of which is herein incorporated by reference. A non-orbiting scroll member 64 is also provided having an end plate and wrap 66 projecting therefrom which is positioned in meshing engagement with wrap 56 of scroll 54. Non-orbiting scroll 64 has a centrally disposed discharge passage 75 which communicates with an upwardly open recess 77 which in turn is in fluid communication with a discharge muffler chamber 79 defined by cap 14 and partition 22. An annular recess 81 is also formed in non-orbiting scroll 64 within which is disposed a seal assembly 83. Recesses 77 and 81 and seal assembly 83 cooperate to define axial pressure basing chambers which receive pressurized fluid being compressed by wraps 56 and 66 so as to exert an axial biasing force on non-orbiting scroll member 64 to thereby urge the tips of respective wraps 56, 66 into sealing engagement with the opposed end plate surfaces. As best seen with reference to Figure 2, non-orbiting scroll member 64 is designed to be mounted to bearing housing 24 by means of a plurality of circumferentially spaced bolts 68 extending through respective bushings 70 which are slidably fitted within bores 72 provided in radially outwardly projecting flange portions 74 integrally formed on non-orbiting scroll member 64. Preferably, the length of bushings 70 will be such as to provide a slight clearance between the lower surface of the head of bolts 68 and the upper surface of flange portion 74 so as to allow a slight axial movement of scroll member 64 in a direction away from scroll member 54. Alternative mounting arrangements are disclosed in the assignee's above referenced U.S. Letters Patent No. 4,877,382. In order to prevent relative rotation between scroll members 54 and 64, a unique Oldham coupling 76 is provided being positioned in surrounding relationship to cylindrical portion 51 of main bearing housing 24 and immediately below the end plate of scroll member 54. As best seen with reference to Figures 4 and 5, Oldham coupling 76 includes an annular ring portion 78, the inner periphery of which is non-circular in shape being defined by two generally circular arc segments 80, 82 each of a substantially constant radius R the opposed ends of which are interconnected by substantially straight segments 84, 86 of a length L. Preferably, the radius R of arcs 80 and 82 will be approximately equal to the radius of cylindrical portion 51 provided on main bearing housing 24 plus a small clearance. The length L of straight segments 84, 86 will preferably be approximately equal to twice the radius of the orbit traveled by orbiting scroll member 54 plus a slight clearance. A pair of keys 88, 90 are provided on annular ring 78 in diametrically aligned relationship and projecting axially upwardly from surface 92 thereof. A second pair of keys 94, 96 are also provided on annular ring 78 also projecting axially upwardly from surface 92 thereof. Keys 94, 96 are also aligned along a line extending parallel to a radius of arc 82 which radius is substantially perpendicular to the diameter along which keys 88 and 90 are aligned but shifted radially toward key 90. Additionally, keys 94 and 96 are positioned on outwardly projecting flange portions. Both the radial shifting and outward positioning of keys 94 and 96 cooperate to enable the size of Oldham coupling 76 to be kept to a minimum for a given size compressor and associated shell diameter while enabling the size of thrust surface 53 to be maximized for this same compressor as well as to avoid interference with the location and extent of wrap 56 of orbiting scroll member 54. As shown in Figure 3, the end plate of orbiting scroll member 54 is provided with a pair of outwardly projecting flange portions 98, 100 each of which is provided with an outwardly opening slot 102. Slots 102 are sized to slidingly receive respective keys 94, 96. Keys 94, 96 will, of course, have an axial length or height so as to avoid projecting above the upper surface of the end plate of orbiting scroll member 54. Referring once again to Figure 1, non-orbiting scroll 64 is similarly provided with a pair of radially extending aligned slots 104, 106 which are designed to receive respective keys 88, 90. Of course, keys 88 and 90 will be substantially longer than keys 94, 96 and of sufficient length to project above the end plate of scroll 54 and remain in engagement with slots 104, 106 throughout the limited axial movement of non-orbiting scroll 64 noted above. It should be noted, however, that preferably a slight clearance will be provided between the end of respective keys 88 and 90 and the overlying surfaces of respective slots 104 and 106 when scroll member 64 is fully seated against scroll member 54 thereby avoiding any possibility of interference with the tip sealing between the respective scroll members. As may now be appreciated, Oldham coupling 76 serves to directly interconnect and prevent any relative rotation between scroll members 54 and 64 through the cooperative action of the abutment surfaces provided by respective slots 102, 104 106 and associated keys 94, 96, 88, and 90. Similarly, the mounting arrangement of scroll 64 to bearing housing 24 will operate to effectively prevent relative rotation of scroll member 64 with respect to bearing housing 24 and hence also prevent relative rotation of scroll member 54 with respect to bearing housing 24. An alternative embodiment 108 of Oldham coupling 76 is shown in Figures 6 and 7. Oldham coupling 108 is substantially identical to Oldham coupling 76 with the exception that a fifth key 110 is provided thereon projecting axially from surface 112 thereof in a direction opposite from that of keys 88', 90', 94', 96'. Key 110 is preferably axially aligned with key 90' and is designed to be received within a slot 114 provided in main bearing housing 24'. As such, key 110 will cooperate with the abutment surfaces defined by slot 114 provided in main bearing housing 24' to thereby prevent relative rotation of both scroll members 54 and 64 with respect thereto without regard to reliance upon the non-orbiting scroll mounting arrangement. While, as described above, only a single key 110 is provided for engagement with slot 114 in bearing housing 24', if desired, a sixth key could also be added diametrically aligned with key 110 and adapted to be received within a similarly aligned second slot provided in bearing housing 24'.

Claims: An Oldham coupling (76), having an annular ring (78) with a first face (92) and an axis centre, for use in a scroll machine (10) to assist in maintaining a relatively fixed angular relationship between first and second scroll members (64 and 54), a first pair of aligned abutment surfaces (88 and 90) being provided on said first face (92) for operative association with said first scroll member (64) to prevent relative rotation between said coupling (76) and said first scroll member (64), and a second pair of aligned abutment surfaces (94 and 96) being provided on said first face (92) for operative association with said second scroll member (54) to prevent relative rotation between said coupling (76) and said second scroll member (54), said first pair of aligned abutment surfaces (88,90) being aligned along a first line which is at right angles to the line of alignment of the second pair of aligned abutment surfaces, characterised in that said second line is offset from the axis centre. An Oldham coupling according to claim 1, wherein said second pair of aligned abutment surfaces (94 and 96) are positioned on radially outwardly projecting flange portions of said ring (78). An Oldham coupling according to claim 1 or 2, wherein said ring portion (78) further comprises a non-circular inner periphery, generally defined by first and second circular arc segments (80 and 82) interconnected by substantially straight segments (84 and 86) of length L. An Oldham coupling according to claim 3, wherein said first line passes through the centre of said ring (78). An Oldham coupling according to any preceding claim, wherein said first pair of abutment surfaces are provided on a first pair of keys (88,90) each of which is centred on said first line. An Oldham coupling according to any preceding claim, wherein said second pair of abutment surfaces are provided on a second pair of keys (94,96) each of which is centred on said second line. A scroll-type machine having: a first scroll member (64) having a first spiral wrap (66) projecting outwardly from an end plate; a second scroll member (54) having a second spiral wrap (56) projecting outwardly from an end plate and interleaved with said first spiral wrap (66) to define a plurality of moving fluid chambers therebetween when said second scroll member (54) and said first scroll member (64) orbit with respect to one another; fixed support means (24) for supporting both said scroll members (64 and 54); drive means (30, 32, 44 and 46) for causing said first and second scroll members (64 and 54) to orbit with respect to one another and an Oldham coupling (76) according to any preceding claim, for preventing relative rotational movement between said first and second scroll members (64 and 54). A scroll-type machine as claimed in claim 7, wherein said Oldham coupling (76) is positioned in surrounding relationship to an axial thrust surface (53). A scroll-type machine as claimed in claim 7 or 8, when appendant to claim 5, wherein said first pair of keys project axially beyond said end plate of said second scroll member (54) in radially outwardly spaced relationship to said end plate. A scroll-type machine as claimed in claim 7, 8 or 9, further comprising means (110 and 114) for preventing relative rotation between said first scroll member (64) and a bearing housing (24') comprising said fixed support means. A scroll-type machine as claimed in claim 10, wherein said rotation preventing mean (110 and 114) comprise axially compliant mounting means (68, 70, 72 and 74) for mounting said first scroll member (64) to said bearing housing (24'), said axially compliant mounting means (68, 70, 72 and 74) permitting limited axial movement of said first scroll member (64). A scroll-type machine as claimed in any one of claims 7 to 11, when appendant to claim 3, wherein the radius of the arc segments is equal to that of said bearing housing (24 or 24') plus a predetermined minimal clearance. A scroll-type machine as claimed in claim 12, wherein said first pair of aligned abutment surfaces (88 and 90) engage a pair of radial slots (104 and 106) in said first scroll member (64) disposed on diametrically opposite sides of the centre axis of said machine (10). A scroll-type machine as claimed in any one of claims 7 to 13, wherein said second pair of aligned abutment surfaces (94 and 96) engage a pair of slots (102) in said second scroll member (64) disposed on opposite sides of the centre axis of said machine (10). A scroll-type machine as claimed in any one of claims 7 to 13, further comprising a third key (110) on the opposite face of said annular ring (78), said third key (110) being in linear sliding engagement with a third abutment surface (114) on said fixed support means (24') thereby to prevent relative rotation of said Oldham coupling (76) with respect to said fixed support means (24'). A scroll-type machine as claimed in claim 15, wherein said third key (110) is aligned in an axial direction with one of a first pair of keys providing the first pair of abutment surfaces.

Inventors: FOGT JAMES FRANKLIN, FOGT, JAMES FRANKLIN
Applicants: COPELAND CORP, COPELAND CORPORATION
Application year: 1991
Main classification: F01C17
IPC codes: F01C17, F16D3, F04C23, F04C18, F01C1