The embodiments described herein relate generally to scroll compressors. More particularly, the embodiments described herein relate to a technique for using thrust pads and/or a back pressure valve to stabilize an orbiting scroll in a scroll compressor.
One increasingly popular type of compressor is a scroll compressor. In a scroll compressor, a pair of scroll members orbits relative to each other to compress an entrapped refrigerant.
In typical scroll compressors, a first, stationary, scroll member has a base and a generally spiral wrap extending from its base. A second, orbiting, scroll member has a base and a generally spiral wrap extending from its base. The second, orbiting, scroll member is driven to orbit by a rotating shaft. Some scroll compressors employ an eccentric pin on the rotating shaft that drives the second, orbiting, scroll member.
In a two-stage scroll compressor, there can be circumstances where there is a moment on one or more orbiting scrolls tending to tip the scroll. This moment can result for example from inertia, gas, friction and bearing forces acting on the scroll at different axial locations. This moment can be offset by a stabilizing moment provided by the thrust surface. The stabilizing moment can be a function of the axial gas force acting on the scroll and thrust bearing geometry. Stable operation occurs for example when there is a positive scroll stability, e.g., when the stabilizing moment is greater than the tipping moment.
Orbiting scroll stability can be an issue in compressor designs that result in higher destabilizing loads, such as for example high speed operation, high drive loads and/or high axial distances between loads, or that result in lower stabilizing loads such as for example at low volume ratios including for example multiple stage compressor designs that may result in relatively lower axial gas forces.
Operational conditions can also affect stability due to their effect of both stabilizing and destabilizing loads. Because of this, a design that is stable at normal operating conditions, for example, can become unstable at extreme conditions such as low discharge pressure conditions.
In view of the foregoing, there is a need to provide a structure that stabilizes an orbiting scroll during its operation, such as in a low volume ratio, and in multiple-stage scroll compressor designs. Orbiting scroll destabilization can be overcome according to one embodiment by some combination of running the scroll compressor at artificially high discharge pressures at unstable conditions caused by insufficient discharge pressure and/or stabilizing pads positioned between the orbiting scroll and a stationary component.
More specifically, a backpressure valve is employed according to one embodiment that ensures for example, that a minimum axial pressure differential across the orbiting scroll is achieved by artificially increasing discharge port pressure.
According to another embodiment, an active discharge pressure control system is employed. The active discharge pressure control system is controlled for example by a combination of suction pressure and compressor speed to ensure for example a minimum axial pressure differential across the orbiting scroll is achieved by artificially increasing discharge port pressure.
According to yet another embodiment, stabilizing pads can be positioned between the orbiting scroll and a stationary component such as for example the fixed scroll with a controlled gap in such a way as to limit orbiting scroll tipping at unstable conditions without measurably increasing power input due to shear losses at stable conditions. In this way, stability can be maintained at conditions that would normally be unstable without affecting compressor performance at stable operating conditions.
These and other features, aspects, and advantages of the apparatuses, systems, and methods of using thrust pads and/or a back pressure valve to stabilize an orbiting scroll in a scroll compressor will become better understood when the following detailed description is read with reference to the accompanying drawing, wherein:
While the above-identified drawing figures set forth particular embodiments to the apparatuses, systems, and methods of using thrust pads and/or a back pressure valve to stabilize an orbiting scroll in a scroll compressor, other embodiments are also contemplated, as noted in the discussion. In all cases, this disclosure presents illustrated embodiments by way of representation and not limitation. Numerous other modifications and embodiments can be devised by those skilled in the art which fall within the scope and spirit of the principles described herein.
In a two-stage scroll compressor, there can be circumstances where there is a moment on one or more orbiting scrolls tending to tip the scroll. This moment can result for example from inertia, gas, friction and bearing forces that act on the scroll, for example not being applied in the same axial location. This moment can be offset by a stabilizing moment provided by the thrust surface. The stabilizing moment can be a function of the axial gas force acting on the scroll and thrust bearing geometry. Stable operation occurs for example when there is a positive scroll stability, e.g., when the stabilizing moment is greater than the tipping moment. Keeping the foregoing principles in mind,
The two-stage horizontal scroll compressor 30 comprises a first, input stage 34 and a second, output stage 36. The first, input stage 34 comprises a fixed, non-orbiting scroll member 38 and an orbiting scroll member 40. The non-orbiting scroll member 38 is positioned in meshing engagement with the orbiting scroll member 40.
The second, output stage 36 also comprises a fixed, non-orbiting scroll member 42 and an orbiting scroll member 44. The second stage non-orbiting scroll member 42 is positioned in meshing engagement with the second stage orbiting scroll member 44.
Scroll compressor 30 further comprises a compressor drive shaft 58 or crankshaft extending between the first, input stage 34 and the second, output stage 36. The crankshaft 58 may be rotatably driven, by way of example and not limitation, via an electric motor comprising a wound stator 46 and a rotor 48 which may be in an interference type fit on the compressor crankshaft 58. The crankshaft 58 may be rotatably journaled within one or more main bearings 50, 52. Each crankshaft main bearing 50, 52 may comprise, by way of example and not limitation, a rolling element bearing having a generally cylindrical portion.
According to one embodiment, the first stage 34 further comprises a conventional hydrodynamic type orbiting scroll thrust bearing 54; while the second stage of compression 36 further comprises a hydrostatic type orbiting scroll thrust bearing 56.
In a practical two-stage scroll compressor, one of the orbiting scrolls may operate with an axial pressure differential across the orbiting scroll base plate. An orbiting scroll that is stable at normal operating conditions can become unstable at extreme conditions such as low discharge pressure conditions. This problem can be overcome by some combination of running the scroll compressor at artificially high discharge pressures at unstable conditions caused by insufficient discharge pressure and/or stabilizing pads positioned between the orbiting scroll and a stationary component, such as described herein with reference to
With continued reference to
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The second, output stage 36 also comprises a fixed, non-orbiting scroll member 42 and an orbiting scroll member 44. The second stage non-orbiting scroll member 42 is positioned in meshing engagement with the second stage orbiting scroll member 44.
The first, input stage 34 may further comprise an Oldham coupling enumerated as 70 in
According to one embodiment, scroll compressor 30 may further comprise orbiting scroll stabilizing pads 64 protruding from the second stage orbiting scroll 44 in some circumstances. The scroll compressor 30 may further comprise stationary pads 66 protruding from the output stage non-orbiting scroll member 42 in some circumstances. In some embodiments, the scroll compressor 30 further may comprise a pad 60 protruding from the Oldham coupling 72 in the space between the Oldham coupling 72 and the orbiting scroll 44 in some circumstances. A pad 62 may further protrude from the Oldham coupling 72 in the space between the Oldham coupling 72 and the second stage non-orbiting scroll member 42 in some circumstances. The Oldham coupling pads 60, 62 can advantageously provide additional stabilization from axial/thrust forces associated with the Oldham coupling(s) 70, 72.
The stabilizing pads 60, 62, 64, 66 are positioned between the orbiting scroll 44 and a stationary component such as the fixed scroll 42 with a controlled gap in such a way as to limit orbiting scroll tipping at unstable conditions without measurably increasing power input due to shear losses at stable conditions. In this way, stability can be maintained for example at conditions that would normally be unstable without affecting compressor performance at stable operating conditions, as stated herein.
Earlier attempts at improving the stability of orbiting scrolls have focused primarily on limiting orbiting scroll inertia forces by limiting orbiting scroll weight, compressor speed or compressor orbit radius thereby reducing the number of design options that could be considered. The embodiments described herein can advantageously employ stabilization pads and/or back pressure allowing stability to be controlled for example at conditions that would normally be unstable in a structure that can be optimized at targeted design points. It will be appreciated that stabilizing pads and back pressure valves may be used individually or in combination depending upon the particular application to increase orbiting scroll stability and/or limit orbiting scroll tipping.
In summary explanation, a backpressure valve is employed in a scroll compressor according to one embodiment that ensures a suitable or a minimum axial pressure differential across an orbiting scroll is achieved by artificially increasing the scroll compressor discharge pressure. Stabilizing pads may also be positioned between the orbiting scroll and a stationary component such as the fixed scroll with a controlled gap in such a way as to limit orbiting scroll tipping at unstable conditions without measurably increasing power input due to shear losses at stable conditions. In this way, stability can be maintained for example at conditions that would normally be unstable without affecting compressor performance at stable operating conditions.
It will be appreciated that, while horizontal orientation of a scroll compressors are discussed and shown, the stabilizing structures described herein can apply to and be suitable for vertically oriented scroll compressors.
Any aspects 1 to 9 can be combined with any aspects 10-22.
Aspect 1. A scroll compressor, comprising: a compressor housing; an output stage of compression disposed within the compressor housing, the output stage comprising: a first, stationary, scroll member comprising a base and a generally spiral wrap extending from the base of the first, stationary, scroll member; and a second, orbiting, scroll member comprising a substantially circular base and a generally spiral wrap extending from the base of the second, orbiting scroll member; a coupling disposed between the first scroll member base and the second scroll member base and in surrounding relationship to the first and second scroll member spiral wraps; one or more stabilizing pads disposed on the base of the first scroll member and configured to at least partially stabilize an axial thrust force between the coupling and the base of the first scroll member to at least partially prevent tipping of the second scroll member; one or more stabilizing pads disposed on the base of the second scroll member and configured to at least partially stabilize an axial thrust force between the coupling and the base of the second scroll member to at least partially prevent tipping of the second scroll member; one or more stabilizing pads disposed on the first scroll member base side of the coupling and configured to at least partially stabilize an axial thrust force between the coupling and the base of the first scroll member to at least partially prevent tipping of the second scroll member; and one or more stabilizing pads disposed on the second scroll member base side of the coupling and configured to at least partially stabilize an axial thrust force between the coupling and the base of the second scroll member to at least partially prevent tipping of the second scroll member.
Aspect 2. The scroll compressor according to aspect 1, further comprising: an input stage of compression disposed within the compressor housing, the input stage comprising: a third, stationary, scroll member comprising a base and a generally spiral wrap extending from the base of the third, stationary, scroll member; and a fourth, orbiting, scroll member comprising a substantially circular base and a generally spiral wrap extending from the base of the fourth, orbiting scroll member; another coupling disposed between the third scroll member base and the fourth scroll member base and in surrounding relationship to the third and fourth scroll member spiral wraps; one or more stabilizing pads disposed on the base of the third scroll member and configured to at least partially stabilize an axial thrust force between the another coupling and the base of the third scroll member to at least partially prevent tipping of the fourth scroll member; one or more stabilizing pads disposed on the base of the fourth scroll member and configured to at least partially stabilize an axial thrust force between the another coupling and the base of the fourth scroll member to at least partially prevent tipping of the fourth scroll member; one or more stabilizing pads disposed on the third scroll member base side of the another coupling and configured to at least partially stabilize an axial thrust force between the another coupling and the base of the third scroll member to at least partially prevent tipping of the fourth scroll member; and one or more stabilizing pads disposed on the fourth scroll member base side of the another coupling and configured to at least partially stabilize an axial thrust force between the another coupling and the base of the fourth scroll member to at least partially prevent tipping of the fourth scroll member.
Aspect 3. The scroll compressor according to aspect 2, wherein the input stage of compression further comprises a backpressure valve configured to create a predetermined minimum axial thrust pressure differential across the fourth, orbiting scroll member.
Aspect 4. The scroll compressor according to any of aspects 1 to 3, wherein the scroll compressor is a single-stage scroll compressor.
Aspect 5. The scroll compressor according to any of aspects 1 to 4, wherein the scroll compressor is a double-ended two-stage scroll compressor.
Aspect 6. The scroll compressor according to any of aspects 1 to 5, wherein the scroll compressor comprises more than two sets of single stage compression.
Aspect 7. The scroll compressor according to any of aspects 1 to 6, wherein the scroll compressor is a horizontal scroll compressor.
Aspect 8. The scroll compressor according to any of aspects 1 to 7, further comprising an orbiting scroll hydrostatic thrust bearing configured to limit thrust loading on the substantially circular base of the second, orbiting, scroll member.
Aspect 9. The scroll compressor according to any of aspects 1 to 8, wherein the output stage further comprises a backpressure valve configured to create a predetermined minimum axial thrust pressure differential across the second, orbiting scroll member.
Aspect 10. A scroll compressor, comprising: an output stage of compression disposed within a compressor housing, the output stage comprising: a first, stationary scroll member comprising a base and a generally spiral wrap extending from the base of the stationary scroll member; and a second, orbiting, scroll member comprising a substantially circular base and a substantially spiral wrap extending from the base of the orbiting scroll member; an coupling disposed between the first scroll member base and the second scroll member base and in surrounding relationship to the first and second scroll member spiral wraps; and at least one stabilizing pad disposed between the first scroll member base and the second scroll member base and in axial thrust force relationship with the coupling to at least partially prevent tipping of the second scroll member.
Aspect 11. The scroll compressor according to aspect 10, wherein at least one stabilizing pad protrudes from the base of the first scroll member and is configured to at least partially stabilize an axial thrust force between the coupling and the base of the first scroll member to at least partially prevent tipping of the second scroll member.
Aspect 12. The scroll compressor according to any of aspects 10 or 11, wherein at least one stabilizing pad protrudes from the base of the second scroll member and is configured to at least partially stabilize an axial thrust force between the coupling and the base of the second scroll member to at least partially prevent tipping of the second scroll member.
Aspect 13. The scroll compressor according to any of aspects 10 to 12, wherein at least one stabilizing pad protrudes from the first scroll member base side of the coupling and is configured to at least partially stabilize an axial thrust force between the coupling and the base of the first scroll member to at least partially prevent tipping of the second scroll member.
Aspect 14. The scroll compressor according to any of aspects 10 to 13, wherein at least one stabilizing pad protrudes from the second scroll member base side of the coupling and is configured to at least partially stabilize an axial thrust force between the coupling and the base of the second scroll member to at least partially prevent tipping of the second scroll member.
Aspect 15. The scroll compressor according to any of aspects 10 to 14, wherein the output stage of compression further comprises a backpressure valve configured to create a predetermined minimum axial thrust pressure differential across the second, orbiting scroll member.
Aspect 16. The scroll compressor according to any of aspects 10 to 15, further comprising: an input stage of compression disposed within the compressor housing, the input stage comprising: a third, stationary, scroll member comprising a base and a generally spiral wrap extending from the base of the third, stationary, scroll member; and a fourth, orbiting, scroll member comprising a substantially circular base and a generally spiral wrap extending from the base of the fourth, orbiting scroll member; another coupling disposed between the third scroll member base and the fourth scroll member base and in surrounding relationship to the third and fourth scroll member spiral wraps; and at least one stabilizing pad disposed between the third scroll member base and the fourth scroll member base and in axial thrust force relationship with the another coupling.
Aspect 17. The scroll compressor according to aspect 16, wherein the input stage of compression further comprises a backpressure valve configured to create a predetermined minimum axial thrust pressure differential across the fourth, orbiting scroll member.
Aspect 18. The scroll compressor according to any of aspects 10 to 17, wherein the scroll compressor is a single-stage scroll compressor.
Aspect 19. The scroll compressor according to any of aspects 10 to 18, wherein the scroll compressor is a double-ended two-stage scroll compressor.
Aspect 20. The scroll compressor according to any of aspects 10 to 19, wherein the scroll compressor comprises more than two sets of single stage compression.
Aspect 21. The scroll compressor according to any of aspects 10 to 20, wherein the scroll compressor is a horizontal scroll compressor.
Aspect 22. The scroll compressor according to any of aspects 10 to 21, further comprising an orbiting scroll hydrostatic thrust bearing configured to limit thrust loading on the substantially circular base of the orbiting scroll member.
While the embodiments have been described in terms of various specific embodiments, those skilled in the art will recognize that the embodiments can be practiced with modification within the spirit and scope of the claims.
Number | Date | Country | |
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61860308 | Jul 2013 | US |