Liquid refrigerant pump having single fixed scroll and two non-contacting orbiting scrolls to pump fluid and provide pressurized fluid to thrust bearing area

Abstract

A pump as provided includes an inlet, an outlet, and a scroll pumping element. The scroll pumping element includes a fixed scroll component having one or more fixed scrolls and orbiting scroll component having one or more orbiting scrolls for fluid pumping. The fixed scroll component and the orbiting scroll component are arranged so as to be capable of providing pressurized fluid to a thrust bearing and prevent contact between the fixed scroll component and the orbiting scroll component.

Claims

1. A pump, comprising: an inlet, an outlet, and a scroll pumping element, wherein said scroll pumping element comprises: a fixed scroll component having a single fixed scroll formed thereon, the single fixed scroll includes two fixed scroll portions and an orbiting scroll component having an orbiting base plane containing two distinct, non-contacting orbiting scrolls projecting therefrom, wherein the two fixed scroll portions include a first fixed scroll portion and a second fixed scroll portion and the two distinct, non-contacting orbiting scrolls including a first orbiting scroll and a second orbiting scroll; and a thrust bearing area formed by an arrangement of said fixed scroll component and said orbiting scroll component, wherein: the first fixed scroll portion of said single fixed scroll and the first orbiting scroll of said two orbiting scrolls are arranged to pump a fluid from said inlet to said outlet, and the second fixed scroll portion of said single fixed scroll and the second orbiting scroll of said two distinct, non-contacting orbiting scrolls are arranged to provide a pressurized fluid to the thrust bearing area and prevent contact between said fixed scroll component and said orbiting scroll component.

2. The pump of claim 1 wherein a wrap length of at least one of said two orbiting scrolls is 0.75 wraps to 1.25 wraps long, and a wrap length of the single fixed scroll is 1.75 wraps to 2.25 wraps long.

3. The pump of claim 1 wherein a wrap length of at least one of said two orbiting scrolls is one wrap long and a wrap length of the single fixed scroll is two wraps long.

4. The pump of claim 1, further comprising an Oldham coupling associated with said orbiting scroll component.

5. The pump of claim 4, wherein said Oldham coupling comprises a wear-resistant coating.

6. The pump of claim 5, wherein said wear-resistant coating is hard anodized aluminum.

7. The pump of claim 1, further comprising an orbital drive mechanism in fluid communication with said outlet, said orbital drive mechanism comprising a drive shaft, two drive shaft bearings that support said drive shaft, and a radially compliant crank mechanism associated with said drive shaft.

8. The pump of claim 7, wherein said drive shaft bearings are radial ball bearings with ceramic balls.

9. The pump of claim 7 further comprising an orbital scroll bearing between said radially compliant crank mechanism and said orbiting scroll component.

10. The pump of claim 9, wherein said orbital scroll bearing is a radial ball bearing with ceramic balls.

11. The pump of claim 7, further comprising an electric drive motor mechanically coupled to said orbital drive mechanism.

12. The pump of claim 11, wherein said electric drive motor is hermetically enclosed within a fluid space.

13. The pump of claim 11, further comprising a second fluid outlet allowing fluid flow through said electric drive motor.

14. The pump of claim 1, wherein said fixed scroll component and said orbiting scroll component each have wear-resistant surfaces.

15. The pump of claim 14, wherein said wear resistant surfaces comprise or consist of hard anodized aluminum.

16. The pump of claim 1, wherein said pressurized fluid is the same fluid being pumped from said inlet to said outlet.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The aspects set forth in the drawings are illustrative and exemplary in nature and not intended to limit the subject matter defined by the claims. The following detailed description of the illustrative aspects can be understood when read in conjunction with the following drawings, where like structure is indicated with like reference numerals and in which:

(2) FIG. 1 illustrates a plan view of an orbiting scroll component according to some aspects as provided herein;

(3) FIG. 2 illustrates a plan view of a fixed scroll component according to some aspects as provided herein;

(4) FIG. 3 illustrates fixed and orbiting scroll components meshed together according to some aspects as provided herein;

(5) FIG. 4 illustrates exemplary axial pressure balance on the orbiting scroll component according to some aspects as provided herein; and

(6) FIG. 5 illustrates an exemplary cross section of a pump assembly according to some aspects as provided herein.

DETAILED DESCRIPTION

(7) Provided in this disclosure are scroll type pumps capable of meeting the need for a pump that can handle minimally subcooled liquid refrigerants and similar heat transfer fluids. Scroll machines, particularly scroll refrigerant compressors, have a well-established track record of easily handling two-phase flows, for example, in the form of slugs of liquid refrigerant ingested into a scroll refrigerant compressor. These pass harmlessly through the scroll elements. The scroll pumps as provided herein capitalize on the relative motion between a meshed pair of scrolls that move in an orbital motion, with one scroll orbiting in a small circle and at low velocity relative to the other scroll. At these low relative velocities, it was found that there is minimal susceptibility to damage due to cavitation.

(8) The basic advantages of scroll type pumps as provided herein include a self porting at the inlet and outlet, so intake and discharge valves are not needed. In addition, the circular orbital motion of the moving scroll can be dynamically balanced. The pumps are capable of providing continuous fluid flow. Within the provided pumps, the fluid pockets formed by the scroll form a trailing hydrodynamic wedge, providing robust hydrodynamic lubrication, despite the low viscosity of the liquid that may be typically used with the provided pump designs. Also, the scroll machinery used in aspects of the provided pumps is scalable over a wide range of flow capacities, so a scroll pump family developed for this purpose will be able to meet a wide range of needs.

(9) The scroll type pump design as provided in this disclosure can operate reliably and for a long life under the aforementioned conditions. The disclosed scroll-type pump is capable of pumping fluids with minimal subcooling (NPSH). In prototype tests, fluid flows did not decrease as the inlet subcooling of fluorocarbon fluid R-134a was reduced from 20° F. to 2° F. Even with only 1° F. of subcooling, the pump mass flow was only reduced by 20%.

(10) The essence of the mechanical design challenge is to drive the orbital motion of the orbiting scroll component in a manner that keeps close clearance between the active fluid pumping surfaces of the two scroll elements while avoiding or minimizing contact that leads to friction and wear. There are five sets of surfaces having mechanically loaded relative motion within a scroll pumping device according to some aspects: The axially facing surfaces of the scroll elements (involving large fluid pressure forces) The radially oriented contact between the sidewall (i.e., flanks) of the scrolls (involving modest pressure and inertial forces) The sliding contact between the keys and slots of the Oldham coupling, assuming an Oldham coupling is used to maintain the correct angular alignment of one scroll with respect to the other (involving modest pressure and inertial forces). The rotating bearing that translates the rotational motion of the drive shaft to orbital motion of the orbiting scroll component (the “scroll drive bearing”, heavily loaded) The rotating bearings that support the drive shaft (heavily loaded)

(11) The axial (tip) clearances between the two scroll elements are minimized by applying the pump discharge pressure to the space containing the orbital drive mechanism, resulting in this same pressure being applied to back side of the orbiting scroll component, pushing it against the fixed scroll component. The tip clearances are then reduced to those resulting from the dimensional tolerances to which the axially facing surfaces of the two scrolls have been manufactured. However this results in a large contact force between the two scroll elements that would cause excessive friction loss and wear. A thin film of the liquid being pumped is provided by incorporating a second pair of scroll elements on the two scroll parts that has the sole purpose of pumping enough fluid into the thrust bearing area of the two scroll parts to provide that thin film. The fluid film thickness is generally less than 0.001 inch (25 microns) and the average axial clearances between the two pumping scrolls are similar.

(12) The modest radial contact forces between the two scrolls are managed by the aforementioned hydrodynamic wedge that exists at each flank contact point between the two scrolls.

(13) The fluid film resulting from the sliding motion and load reversals are sufficient to handle the modest loads on the Oldham keys.

(14) The shaft bearings and the scroll drive bearing are heavily loaded. In the non-lubricating, low viscosity fluid environment of the orbital drive mechanism, ceramic ball bearing with hardened steel races and silicon nitride ceramic balls are used. Metal balls in standard non-lubricated bearings tend to fail by chips falling off the balls as wear occurs and welding to the races, whereas the silicon nitrite ceramic balls do not have this failure mechanism.

(15) To minimize the disruption of occasional breakdown of fluid films, the critical parts optionally have a wear resistant, optionally self-lubricating coating or surface treatment. Optionally, the two scroll elements and the Oldham ring have been fabricated from an aluminum alloy and the surfaces have been hard anodized and impregnated with polytetrafluoroethylene (PTFE).

(16) FIG. 1 shows a plan view of the orbiting scroll component 1, comprising inner pumping scroll 2 and outer thrust bearing scroll 3. Orbiting scrolls 2 and 3 project from base plane 4 (e.g., also referred to as an orbiting base plate) that also acts as one surface of the fluid film thrust bearing. Through hole 5 provides fluid communication between the liquid being pumped and the space enclosing the orbital drive mechanism (FIG. 5).

(17) FIG. 2 shows a plan view of the fixed scroll component 11, comprising inner pumping scroll 12 and outer thrust bearing scroll 13. The tips of scrolls 12 and 13 are coplanar with each other and with thrust bearing surface 14. Hole (inlet) 15 is the liquid inlet and hole (outlet) 16 is the liquid outlet. Groove 17 distributes pressurized fluid uniformly over the thrust bearing surface 14.

(18) Referring to both FIGS. 1 and 2, the inner pumping scroll set includes the inner pumping scroll 2 of the orbiting scroll component 1 (FIG. 1) and the inner pumping scroll 12 of the fixed scroll component 11 (FIG. 2) and the outer thrust bearing scroll set includes the outer thrust bearing scroll 3 of the orbiting scroll component 1 (FIG. 1) and the outer thrust bearing scroll 13 of the fixed scroll component 11 (FIG. 2). The inner pumping scroll 2 and/or the outer thrust bearing scroll 3 of the orbiting scroll component 1 (FIG. 1) is optionally one wrap in length. The inner pumping scroll 12 and/or the outer thrust bearing scroll 13 of the mating fixed scroll component 11 is optionally 2 wraps in length. The inner pumping scroll 2 and/or the outer thrust bearing scroll 3 of the orbiting scroll component 1 may be generally referred to as “one or more orbiting scrolls.” Similarly, the inner pumping scroll 12 and/or the outer thrust bearing scroll 13 of the fixed scroll component 11 may be generally referred to as “one or more fixed scrolls.”

(19) This asymmetric configuration results in minimal flow variation with orbital position and minimal variation in the axial pressure forces carried by the thrust bearing. In some aspects the wrap length of the inner pumping scroll 2 and/or the outer thrust bearing scroll 3 of the orbiting scroll component 1 (FIG. 1) is from 0.75 wraps to 1.25 wraps in length and the wrap length of the inner pumping scroll 12 and/or the outer thrust bearing scroll 13 of the fixed scroll component 11 (FIG. 2) is from 1.75 to 2.25 wraps in length.

(20) FIG. 3 shows a plan section of the orbiting scroll component 1 (FIG. 1) as assembled with the fixed scroll component 11 (FIG. 2) in one exemplary representative orbital position. Orbiting scroll component 1 (not shown in FIG. 3) orbits in a counterclockwise direction. This orbital motion of inner pumping scroll 2, which moves in response to the motion of the orbiting scroll component 1, within the inner pumping scroll 12 of the fixed scroll component 11 transfers fluid from inlet 15 to outlet 16. The coincident orbital motion of the outer orbiting scroll 3 of the orbiting scroll component 1 (FIG. 1) within the outer thrust bearing scroll 13 of the fixed scroll component 11 causes fluid to be pumped onto thrust bearing surface 14 (FIG. 2), providing a thin fluid film separating the base plane 4 (FIG. 1) of the orbiting scroll component 1 (FIG. 1) and the fixed scroll surface 14 by approximately 0.0005 inches (12 microns), preventing wear and minimizing friction.

(21) FIG. 4 illustrates a cross-sectional view of the orbiting scroll component 1 as depicted in FIG. 1. The illustration in FIG. 4 depicts the resulting axial pressure force balance on the orbiting scroll component 1 according to some aspects as provided herein. The orbiting scroll component 1 is positioned by the net effect of the fluid pressures acting on the first side 51 facing the orbital drive mechanism and the second side 52 facing the scroll pumping elements. Pump outlet pressure is admitted to the orbital drive unit via hole 5 (FIG. 1) and acts on all of side 51. Force lines 110 depict the forces due to the pump outlet pressure acting on the first side 51 of the orbiting scroll component 1. On side 52 of the orbiting scroll component 1, the fluid pumping region formed by the inner pumping scroll set which includes the inner pumping scroll 2 of the orbiting scroll component 1 and the inner pumping scroll 12 of the fixed scroll component 11 (FIGS. 2 and 5) generates a pump inlet pressure depicted by force lines 103 that acts on a portion of the orbiting scroll component 1 and pump outlet pressure acts on the remaining area defined by the force lines 103. Outside of the pumping scrolls, the outer thrust bearing scroll set that includes the outer thrust bearing scroll 3 of the orbiting scroll component 1 and the outer thrust bearing scroll 13 of the fixed scroll component 11 (FIGS. 2 and 5) pump enough fluid into the thrust bearing gap between the surfaces of base plane 4 (FIG. 1) and the thrust bearing surface 14 (FIG. 2) to generate a pressure (i.e., depicted by force lines 102 and 104) sufficient to counterbalance the outlet pressure force 110 acting on side 51.

(22) FIG. 5 shows a horizontal cross section of a pump 30 according to some aspects as provided herein. The pump 30 is configured to pump liquid, for example without limitation, low viscosity, non-lubricating liquids, such as fluorocarbon refrigerants. The pump 30 is not limited to pumping refrigerants. In some embodiments, the pump 30 may be described by way of three general components: a scroll pumping element, an orbital drive mechanism, and an electric drive motor. Each of the components, the scroll pumping element, the orbital drive mechanism, and the electric drive motor are mechanically, rotationally, and/or fluidly coupled to each other.

(23) The scroll pumping element is coupled to an inlet 15 and an outlet 16 formed with a scroll end cover 33. The scroll pumping element is further coupled to an orbital drive housing 31. The orbital drive housing 31 may be configured as a pressure-tight housing coupled to the scroll end cover 33 and the fixed scroll component 11. The scroll pumping element includes the fixed scroll component 11 and the orbiting scroll component 1 for fluid pumping. The fixed scroll component 11 and the orbiting scroll component 1 are arranged so as to be capable of providing pressurized fluid to a thrust bearing and prevent contact between surfaces of the fixed scroll component 11 and the orbiting scroll component 1. In some embodiments, the orbiting scroll component 1 and the fixed scroll component 11 are disposed within a liquid tight housing that includes the orbital drive housing 31, the motor housing 32, the scroll end cover 33, and motor end cover 34. A second outlet 35, which, for example, is configured with the motor end cover 34, provides means for a portion of the pumped liquid flow to pass around the motor stator 41 and through the gap between the motor stator 41 and the motor rotor 42, cooling the electric drive motor.

(24) The orbital drive mechanism is in fluid communication with the outlet 16 of the scroll pumping element. The orbital drive mechanism includes a drive shaft 21, one or more drive shaft bearings 25 and 26 that support the drive shaft 21. The orbital drive mechanism may further include a radially compliant crank mechanism 23 coupled to the drive shaft 21 via a pivot pin 27, which in turn drives the orbital motion of the orbiting scroll component 1 via orbital scroll bearing 24. An Oldham coupling 22 may also be included in the orbital drive mechanism. The Oldham coupling 22 maintains the correct angular alignment of orbiting scroll component 1 with respect to fixed scroll component 11.

(25) As discussed above the Oldham coupling may have a wear-resistant coating such as a hard anodized aluminum. Additionally, the drive shaft bearings 25 and 26 and/or the orbital scroll bearing 24 may be radial ball bearings. The radial ball bearings may be ceramic balls, for example silicon nitride ceramic balls, or the like that are configured within hardened steel races. In some embodiments, the fixed scroll component 11 and/or the orbiting scroll component 1 may each have wear-resistant surfaces. The wear resistant surfaces may include hard anodized aluminum.

(26) Still referring to the pump in FIG. 5, the electric drive motor includes a motor stator 41 and a motor rotor 42. The motor rotor 42 may be coupled to the drive shaft 21. That is, as the motor stator 41 induces an electro-magnetic field the motor rotor 42 is driven to rotate thereby rotating the drive shaft 21. The electric drive motor is mechanically coupled to the orbital drive mechanism. In some embodiments, the motor housing is fluidly coupled to the orbital drive mechanism and/or the scroll pumping element. For example, the electric drive motor may be hermetically enclosed with a fluid space. The second outlet 35 may dispense (i.e., output) fluid from the orbital drive mechanism and/or the scroll pumping element that flows through the motor housing 32 and/or the electric drive motor. This may provide cooling to the electric drive motor and components within the motor housing 32.

(27) It should now be understood that the present disclosure is directed to scroll type pumps capable of meeting the need for a pump that can handle minimally subcooled liquid refrigerants and similar heat transfer fluids. The scroll pumps as provided herein capitalize on the relative motion between a meshed pair of scrolls that move in an orbital motion, with one scroll orbiting in a small circle and at low velocity relative to the other scroll. For example, and without limitation, a liquid pump of the present disclosure includes a pressure-tight housing, an inlet, an outlet, a scroll pumping element and an orbital drive mechanism. The scroll pumping element includes a fixed scroll component having one or more fixed scrolls and orbiting scroll component having one or more orbiting scrolls for fluid pumping. The fixed scroll component and the orbiting scroll component are arranged so as to be capable of providing pressurized fluid to a thrust bearing and prevent contact between the fixed scroll component and the orbiting scrolls component, and where the orbital drive mechanism is in fluid communication with the outlet.

(28) The disclosed embodiments may be embodied in many different forms, and this disclosure should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. Like reference numerals refer to like elements throughout.

(29) It will be understood that, although the terms “first,” “second,” “third” etc. may be used herein to describe various elements, components, regions, layers and/or sections, these elements, components, regions, layers and/or sections should not be limited by these terms. These terms are only used to distinguish one element, component, region, layer or section from another element, component, region, layer or section. Thus, “a first element,” “component,” “region,” “layer” or “section” discussed below could be termed a second element, component, region, layer or section without departing from the teachings herein.

(30) The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting. As used herein, the singular forms “a,” “an,” and “the” are intended to include the plural forms, including “at least one,” unless the content clearly indicates otherwise. “Or” means “and/or.” As used herein, the term “and/or” includes any and all combinations of one or more of the associated listed items. It will be further understood that the terms “comprises” and/or “comprising,” or “includes” and/or “including” when used in this specification, specify the presence of stated features, regions, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, regions, integers, steps, operations, elements, components, and/or groups thereof.

(31) Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure belongs. It will be further understood that terms, such as those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of the relevant art and the present disclosure, and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein.

(32) While the invention has been described with reference to an exemplary embodiment, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from the essential scope thereof. Therefore, it is intended that the invention not be limited to the particular embodiment disclosed as the best mode contemplated for carrying out this invention.