EP0479421A1

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Info

Publication number: EP0479421A1
Application number: EP91307172A
Authority: EP
Inventors: Gary Justin Anderson; James William Bush
Original assignee: Copeland Corp LLC
Current assignee: Copeland Corp LLC
Priority date: 1990-10-01
Filing date: 1991-08-05
Publication date: 1992-04-08
Anticipated expiration: 2011-08-05
Also published as: BR9103456A; DE69115422T2; AU8153991A; CN1028379C; KR920008353A; CA2046548C; KR100188324B1; JPH06341387A; EP0479421B1; DE69115422D1; CA2046548A1; AU651606B2; MX9100629A; CN1060699A; JP2922343B2

Abstract

A scroll machine utilizing working fluid under pressure to enhance axial sealing, including several embodiments of a multi-function floating seal to isolate the axial biasing fluid, and provide vacuum protection and a degree of high pressure ratio protection.

Description

The present invention relates to seals for scroll- type machinery, and more particularly to a multi-function floating seal for axially compliant scroll compressors.

BACKGROUND AND SUMMARY OF THE INVENTION

A typical scroll machine has an orbiting scroll member having a spiral wrap on one face thereof, a non-orbiting scroll member having a spiral wrap on one face thereof, said wraps being entermeshed with one another, and means for causing said orbiting scroll member to orbit about an axis with respect to said non-orbiting scroll member, whereby said wraps will create pockets of progressively changing volume.

To maximize efficiency, it is important for the wrap tips of each scroll member to sealingly engage the end plate of the other scroll member so that there is minimum leakage therebetween. One way this has been accomplished, other than by using tip seals (which are very difficult to assemble and which often present reliability problems) is by using fluid under pressure to axially bias one of the scroll members against the other scroll member. This, of course, requires seals in order to isolate the biasing fluid at the desired pressure. Accordingly, there is a continuing need in the field of scroll machines for improved axial biasing techniques, including improved seals to facilitate same.

The seals of the present invention are embodied in a compressor and suited for use in machines which use discharge pressure alone, discharge and an independent intermediate pressure, or solely an Intermediate pressure only, in order to provide the necessary axial biasing forces to enhance tip sealing. In addition, the seals of the present invention, which in most embodiments are three seals in one, are suitable for use in applications which bias the non-orbiting scroll or those which bias the orbiting scroll, although they are particularly suited for the former.

It is therefore one of the primary objects of the present invention to provide an improved seal which is relatively simple in construction, easy to install and inspect, and which effectively provides the complex sealing functions desired. The seals of the present invention provide significant additional advantages. For example, the seal has been discovered to be particularly sensitive to the pressure ratio of the scroll machine and consequently provides particularly good protection against vacuum conditions such as caused by reverse rotation or a blocked suction condition. In this condition, the seal will become ineffective and thus permit discharge gas to be bypassed directly into a zone of suction gas at suction gas pressure. This prevents the creation of a high vacuum on the inlet side of the compressor which might otherwise occur and which could cause excessive and damaging forces pulling the scroll members together. Even more importantly, it prevents the arcing or burning of the motor protector connector pins which has been observed to occur under some vacuum conditions.

The seals of the present invention also, in some applications, provide a degree of temperature protection, particularly in motor-compressors where suction gas is used to cool the motor. This is because the seal will leak from the high side to the low side at pressure differentials which are significantly higher than those for which the machine was designed. This leakage of discharge fluid to the suction side of the compressor will cause the machine to have a reduced output and the resulting heat build-up within the compressor enclosure due to the reduced flow of cooling gas will cause the standard motor protector to trip and shut the machine down. This characteristic of the seals of the present invention therefore provides a degree of protection in certain applications from excessive discharge temperatures which could result from loss of working fluid charge, or from a blocked condensor fan In a refrigeration system, or from an excessive discharge pressure (for whatever reason). All of these undesirable conditions will cause a scroll machine to function at a pressure ratio is greater than that which is designed into the machine in terms of its predetermined fixed volume ratio.

These and other advantages of the present invention will become more apparent when viewed in light of the accompanying drawings and following detailed description.

BRIEF DESCRIPTION OF THE DRAWING FIGURES

Figure 1 is a partial vertical sectional view through a scroll machine in which fluid pressure is used to bias the non-orbiting scroll member axially against the orbiting scroll member, and which embodies the principles of the present invention;
Figure 2 is an enlarged vertical sectional view of a floating seal forming a part of the Figure 1 first embodiment of the invention, shown in its relaxed state;
Figure 3 is a sectional view taken along line 3-3 of Figure 2 and having line 2-2 showing where the section of Figure 2 is taken;
Figure 4 is a view similar to Figure 1 showing a second embodiment of the floating seal of the present invention;
Figure 5 is an enlarged vertical sectional view of a portion of the seal shown in Figure 4;
Figure 6 is an enlarged vertical sectional view of the floating seal of the embodiment of Figure 4, shown in its relaxed state;
Figure 7 is a sectional view taken along line 8-8 in Figure 6 and having line 6-6 showing where the section of Figure 6 is taken;
Figure 8 is a fragmentary view similar to Figure 1 showing a third embodiment of the floating seal of the present invention;
Figure 9 is an enlarged vertical cross-sectional view of the floating seal of Figure 8, shown in its relaxed state;
Figure 10 is a sectional view taken along line 10-10 in Figure 9.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

While the present invention is suitable for incorporation in many different types of scroll machines, for exemplary purposes it will be described herein incorporated in a scroll refrigerant compressor of the general structure illustrated in vertical section in Figure 1. Generally speaking, the compressor comprises a cylindricalhermetic shell 10 having welded at the upper end thereof acap 12, which is provided with a refrigerant discharge fitting 14 optionally having the usual discharge valve therein (not shown). Other elements affixed to the shell include a transversely extendingpartition 16 which is welded about its periphery at the same point thatcap 12 is welded toshell 10, a main bearinghousing 18 which is affixed toshell 10 at a plurality of points in any desirable manner, and a suction gas inlet fitting 17 having agas deflector 19 disposed in communication therewith inside the shell.

Amotor stator 20 which is generally square in cross-section but with the corners rounded off is press fit intoshell 10. The flats between the rounded corners on the stator provide passageways between the stator and shell, indicated at 22, which facilitate the flow of lubricant from the top of the shell to the bottom. Acrankshaft 24 having aneccentric crank pin 26 at the upper end thereof is rotatably journaled in abearing 28 in main bearinghousing 18 and a second bearing in a lower bearing housing (not shown).Crankshaft 24 has at the lower end the usual relatively large diameter oil- pumping concentric bore (not shown) which communicates with a radially outwardly inclined smaller diameter bore 30 extending upwardly therefrom to the top of the crankshaft. The lower portion of theinterior shell 10 is filled with lubricating oil in the usual manner and the pump at the bottom of the crankshaft is the primary pump acting in conjunction withbore 30, which acts as a secondary pump, to pump lubricating fluid to all of the various portions of the compressor which require lubrication.

Crankshaft 24 is rotatively driven by an electricmotor including stator 20,windings 32 passing therethrough, and a rotor 34 press fit on the crankshaft and having one or more counterweights 36. Amotor protector 35, of the usual type, is provided in close proximity tomotor windings 32 so that if the motor exceeds its normal temperature range the protector will deenergize the motor.

The upper surface of main bearinghousing 18 is provided with an annular flatthrust bearing surface 38 on which is disposed an orbiting scroll member 40 comprising anend plate 42 having the usual spiral vane or wrap 44 on the upper surface thereof, an annular flat thrust surface 46 on the lower surface, and projecting downwardly therefrom acylindrical hub 48 having a journal bearing 50 therein and in which is rotatively disposed a drive bushing 52 having an inner bore 54 in whichcrank pin 26 is drivingly disposed.Crank pin 26 has a flat on one surface (not shown) which drivingly engages a flat surface in a portion of bore 54 (not shown) to provide a radially compliant driving arrangement, such as shown in assignee's U.S. Letters Patent No. 4,877,382, the disclosure of which is herein incorporated by reference.

Wrap 44 meshes with a non-orbitingspiral wrap 56 forming a part ofnon-orbiting scroll member 58 which is mounted to main bearinghousing 18 in any desired manner which will provide limited axial movement ofscroll member 58. The specific manner of such mounting 15 not relevant to the present invention, however, in the present embodiment, for exemplary purposes, non-orbitingscroll member 58 has a plurality of circumferentially spaced mountingbosses 60, one of which is shown, each having a flatupper surface 62 and an axial bore 64 in which is slidably disposed asleeve 66 which is bolted to main bearinghousing 18 by a bolt 68 in the manner shown. Bolt 68 has an enlarged head having a flat lower surface 70 which engagessurface 62 to limit the axially upper or separating movement of non-orbiting scroll member, movement in the opposite direction being limited by axial engagement of the lower tip surface ofwrap 56 and the flat upper surface of orbiting scroll member 40.

Non-orbiting scroll member 58 has a centrally disposeddischarge passageway 72 communicating with an upwardlyopen recess 74 which is in fluid communication via anopening 75 inpartition 16 with thedischarge muffler chamber 76 defined bycap 12 andpartition 16.Non-orbiting scroll member 58 has in the upper surface thereof anannular recess 78 having parallel coaxial side walls in which is sealingly disposed for relative axial movement an annular floatingseal 80 which serves to isolate the bottom ofrecess 78 from the presence of gas under suction and discharge pressure so that it can be placed in fluid communication with a source of intermediate fluid pressure by means of apassageway 82. The non-orbiting scroll member is thus axially biased against the orbiting scroll member by the forces created by discharge pressure acting on the central portion ofscroll member 58 and those created by intermediate fluid pressure acting on the bottom ofrecess 78. This axial pressure biasing, as well as various techniques for supportingscroll member 58 for limited axial movement, are disclosed in much greater detail in assignee's aforesaid U.S. Letters Patent No. 4,877,328.

Relative rotation of the scroll members is prevented by the usual Oldham coupling comprising a ring 83 having a first pair of keys 84 (one of which is shown) slidably disposed in diametrically opposed slots 86 (one of which is shown) inscroll member 58 and a second pair of keys (not shown) slidably disposed in diametrically opposed slots (not shown) in scroll member 40.

The compressor is preferably of the "low side" type in which suction gas entering viadeflector 19 is allowed, in part, to escape into the shell and assist in cooling the motor. So long as there is an adequate flow of returning suction gas the motor will remain within desired temperature limits. When this flow ceases, however, the loss of cooling will causemotor protector 35 to trip and shut the machine down.

The scroll compressor as thus far broadly described is either now known in the art or is the subject matter of other pending applications for patent by applicants' assignee. The details of construction which incorporate the principles of the present invention are those which deal with several embodiments of a novel multi-function floating seal.

With reference to Figures 1-5, the floating seal of the first embodiment is of a coaxial sandwiched construction and comprises anannular base plate 100, cast out of aluminum or the like, having a plurality of equally spaced upstandingintegral projections 102 each having an enlargedbase portion 104. Disposed onplate 100 is anannular gasket 106 formed of epoxy coated fiber gasket material having a plurality of equally spaced holes which receivebase portions 104, on top of which is disposed a pair of normally flat identicallower lip seals 108 formed of glass filled PTFE (approximately 5%) and optionally including 5% MoS2, by weight.Seals 108 have a plurality of equally spaced holes which receivebase portions 104. On top ofseals 108 is disposed anannular spacer plate 110, which can be a simple steel stamping, havingannular recesses 112 and 114 on the top and bottom surfaces thereof and a plurality of equally spaced holes which receivebase portions 104, and on top ofplate 110 are a pair of normally flat identical annularupper lip seals 116 formed of the same material aslip seals 108 and maintained in coaxial position by means of an annularupper seal plate 118 having a plurality of equally spacedholes receiving projections 102 and an annular rim 120 disposed inrecess 112.Seal plate 118, which may be formed of grey cast iron, has disposed about the inner periphery thereof an upwardly projectingplanar sealing lip 122. The assembly is secured together by swaging the ends of each of theprojections 102, as indicated at 123.

The overall seal assembly therefore provides three distinct seals; namely, an inside diameter seal at 124 and 126, an outside diameter seal at 128 and a top seal at 130, as best seen in Figure 1. Seal 124 is between the inner periphery of lip seals 108 and the inside wall ofrecess 78, and seal 126 is between the inner periphery of lip seals 116 and the inside wall ofrecess 78.Seals 124 and 126 isolate fluid under intermediate pressure in the bottom ofrecess 78 from fluid under discharge pressure inrecess 74.Seal 128 is between the outer periphery of lip seals 108 and the outer wall ofrecess 78, and isolates fluid under intermediate pressure in the bottom ofrecess 78 from fluid at suction pressure withinshell 10.Seal 130 is be-twen lip seal 122 and anannular wear ring 132, formed of cast iron or the like and affixed to partition 16 by a suitable adhesive in aposition surrounding opening 75, and isolates fluid at suction pressure from fluid at discharge pressure across the top of the seal assembly. In lieu of aseparate wear ring 132 for the upper seal the lower surface ofpartition 16 surroundingopening 75 can be locally hardened, by nitriding, carbo-nitriding or the like.

The diameter ofseal 130 is chosen so that there is a positive upward sealing force onseal 80 under normal operating conditions, i.e., at normal pressure differentials. Therefore, when excessive pressure differentials are encountered, the seal will be forced downwardly by discharge pressure, thereby permitting a leak of high side discharge gas directly across the seal to a zone of low side suction gas. If this leakage is great enough, then the resultant loss of flow of motor-cooling suction gas (aggravated by the excessive temperature of the leaking discharge gas) will cause the motor protector to trip, thereby deenergizing the motor. The width ofseal 130 is chosen so that the unit pressure on the seal itself (i.e., betweenseal 122 and seat 132) is greater than normally encountered discharge pressure, thus insuring consistant sealing.

With reference to Figures 4-7, the floating seal of the second embodiment is also of a coaxial sandwiched construction and comprises anannular base plate 200, cast out of aluminum or the like and having an annular upstandingintegral rib 202. Disposed onplate 200 is a lowerinner lip seal 204 formed of 5% glass and 5% molydisulfide filled PTFE and having a conical resilient sealinglip 206; and anouter lip seal 208 of the same material having a resilientconical sealing lip 210. Disposed on top ofinner seal 204 and insiderib 202 is an annularmetal separator plate 212 having minutely ribbed upper and lower surfaces to increase mechanical contact with the seals. On top ofplate 110 are a pair of identical annular upper lip seals 214 formed of the same material as lip seals 206 and 208, also maintained in coaxial position by means of anannular rib 202, and anupper seal element 216 having disposed about the inner periphery thereof an upwardly projectingplanar sealing lip 218.Seals 214 have resilient conical inner sealinglips 220.Seal plate 118 is preferably formed of cast iron.Outer seal 208 is retained in place by anannular metal ring 222, and the entire assembly is secured together by swaging the top ofrib 202 at spaced locations, as indicated at 224.

This seal assembly also provides three distinct seals; namely, an inside diameter seal at 226 and 228, an outside diameter seal at 230 and a top seal at 232, as best seen in Figure 4.Seal 226 is between the inner periphery oflip seal 204 and the inside wall ofrecess 78, and seal 228 is between the inner periphery of lip seals 214 and the inside wall ofrecess 78.

Seals

226 and 228 isolate fluid under intermediate pressure in the bottom ofrecess 78 from fluid under discharge pressure inrecess 74.Seal 230 is between the outer periphery oflip seal 208 and the outer wall ofrecess 78, and isolates fluid under intermediate pressure in the bottom ofrecess 78 from fluid at suction pressure withinshell 10. Seal 232 is betweenlip seal 218 andannular wear ring 132 surroundingopening 75 inpartition 16, and isolates fluid at suction pressure from fluid at discharge pressure across the top of the seal assembly. The diameter and width of the top seal are chosen in the same manner as for the first embodiment.

With reference to Figure 8-10, the floating seal of the third embodiment is also of a coaxial sandwiched construction and comprises anannular base plate 300, cast out of alumminum or the like, having a plurality of equally spaced upstandingintegral projections 302 projecting from a shallowannular rib 304. Disposed on the inner periphery ofplate 300 insiderib 304 are a pair of normally flat identical inner lip seals 306 formed of suitably filled PTFE. Disposed on top of the outer periphery ofplate 300, outsiderib 304, are a pair of normally flat identical annular outer lip seals 308 formed of the same material as lip seals 306. Both pairs of seals are maintained in coaxial position by means ofrib 304, and are clamped in place by an annularupper seal plate 310 having a plurality of equally spacedholes receiving projections 302.Seal plate 118, which is preferably formed of grey cast iron, stamped steel or powered metal, has disposed about the inner periphery thereof an upwardly projectingplanar sealing lip 312. The assembly is secured together by swaging the ends of each of theprojections 302, as indicated at 314.

Again, the overall seal assembly therefor provides three distinct seals; namely, an inside diameter seal at 316, an outside diameter seal at 318 and a top seal at 320, as best seen in Figure 8.Seal 316 is between the inner periphery of lip seals 306 and the inside wall ofrecess 78.Seal 316 isolates fluid under intermediate pressure in the bottom ofrecess 78 from fluid under discharge pressure inrecess 74.Seal 318 is between the outer periphery of lip seals 308 and the outer wall ofrecess 78, and isolates fluid under intermediate pressure in the bottom ofrecess 78 from fluid at suction pressure withinshell 10.Seal 320 is betweenlip seal 312 andannular wear ring 132 surroundingopening 75 inpartition 16, and isolates fluid at suction pressure from fluid at discharge pressure across the top of the seal assembly. The diameter and width of the top seal are chosen in the same manner as for the first embodiment.

In order to prevent excessive intermediate pressure from building up between the inner and outer seals, which would occur in a liquid slugging situation and could blow out the high-side seal, a suitable vent can be provided, such as at 125 in Figure 2 and at 316 in Figure 8.

While this invention has been described in connection with these particular examples, no limitation is intended except as defined by the following claims. The skilled practitioner will realize that other modifications may be made without departing from the scope of this invention after studying the specification and drawings.