EP4269800A1 - Scroll pump with axial load control system - Google Patents

Abstract

A scroll pump includes a first scroll member (12) and a second scroll member (14). An electromagnet (112) is fixedly connected to one of the first scroll member and a second scroll member, and a magnetic target (116) is fixedly connected to the other of the first scroll member and the second scroll member. The electromagnet is operable to generate a magnetic field between the electromagnet and the magnetic target, thereby establishing an axially-directed magnetic biasing force between the first scroll member and the second scroll member.

Description

BACKGROUND AND SUMMARY OF THE DISCLOSURE
• A scroll pump includes a fixed scroll member operably associated with a moving scroll member. The fixed scroll member includes a fixed scroll extending axially from a fixed end plate to a fixed tip. Similarly, the moving scroll member includes a moving scroll extending from a moving end plate to a moving tip. The moving scroll is interleaved with the fixed scroll and configured to orbit with respect to the fixed scroll, so that the fixed tip engages with the moving end plate (either directly or through an intervening tip seal or gasket), and the moving tip engages with the fixed end plate (either directly or through an intervening tip seal or gasket). The fixed and moving scrolls thereby define a variable working volume therebetween. A fluid inlet port is provided in a peripheral region of the fixed and moving scrolls. A fluid discharge port is provided in a central region of the fixed and moving scrolls.
• In operation, the moving scroll is driven by a motor or other prime mover so that the moving scroll orbits with respect to the fixed scroll. This orbiting causes fluid to be drawn through the fluid inlet port at a fluid inlet pressure, compressed to a discharge pressure, and discharged through the discharge port.
• One skilled in the art would recognize that the increase in fluid pressure between the fixed and moving scrolls places an axial force on the fixed and moving scrolls, which axial force tends to force the moving scroll away from the fixed scroll. Consequently, this pressure tends to displace the tips of the fixed and moving scrolls away from the corresponding end plates of the moving and fixed scrolls. This phenomenon can result in undesired separation of the scroll tips from the corresponding end plates can result in the working fluid leaking between the scroll tips and the corresponding end plates. Such leakage can adversely affect the efficiency of the pump.
• In some applications, it may be desirable to operate a scroll pump to provide a variable pressure output. Typically, varying the pressure output of a scroll pump is accomplished by varying the speed of the motor driving the scroll pump. One consequence of varying motor speed is variation in motor noise, which can be undesirable.
• The present disclosure is directed to a system configured to control the axial force between the fixed and moving scroll members of a scroll pump. The system may use one or more of a preload force control system using a spring or other biasing member to permanently preload the moving scroll member axially toward the fixed scroll member, a fluid pressure-based axial force control system configured to bias the moving scroll member axially toward the fixed scroll member during operation of the scroll pump, and an electromagnetic axial force control system configured to selectively bias the moving scroll member axially toward or away from the fixed scroll member.
• An electromagnetic axial force control system according to the present disclosure includes an electromagnet associated with one of the fixed scroll member and the moving scroll member and a magnetic target associated with the other of the fixed scroll member and the moving scroll member. The magnetic target could be a ferrous target made of ferromagnetic material. Alternatively, the magnetic target could be a permanent magnet. In embodiments wherein the ferrous target is a ferromagnetic material, the electromagnet is operable to selectively generate a force tending to bias the fixed and moving scrolls toward each other or away from each other. In embodiments wherein the ferrous target is a permanent magnet, the electromagnet is operable to selectively generate a force tending to bias the fixed and moving scrolls toward each other, away from each other, or both.
BRIEF DESCRIPTION OF THE DRAWINGS

Fig. 1

is an upper perspective view of an illustrative scroll pump having a preload and fluid pressure-based axial force control systems according to the pre-sent disclosure;

Fig. 2

is a top plan view of the scroll pump ofFig. 1;

Fig. 3

is a front cross-sectional elevation view of the scroll pump ofFig. 1 taken through section A-A;

Fig. 4

is an enlarged cross-sectional front elevation view of a portion of the scroll pump ofFig. 1 taken through section B-B;

Fig. 5A

is a perspective view of a first side of an orbiting scroll member of the scroll pump ofFig. 1;

Fig. 5B

is a perspective view of a second side of an orbiting scroll member of the scroll pump ofFig. 1;

Fig. 6

is a perspective view of a first side of a fixed scroll member of the scroll pump ofFig. 1;

Fig. 7

is a first exploded perspective view of the scroll pump ofFig. 1;

Fig. 8

is a second exploded perspective view of the scroll pump ofFig. 1;

Fig. 9

is a schematic representation of forces acting on fixed and moving scroll members of the scroll pump ofFig. 1 during operation thereof.

Fig. 10

is a front cross-sectional view of the scroll pump ofFig. 1 further including an electromagnetic axial force control system according to the present disclosure;

Fig. 11

is a schematic representation of forces acting on fixed and moving scroll members of the scroll pump ofFig. 10 during operation thereof;

Fig. 12

is a front cross-sectional view of the scroll pump ofFig. 10 with an alternative electromagnetic axial force control system according to the present disclosure;

Fig. 13

is a schematic representation of forces acting on fixed and moving scroll members of the scroll pump ofFig. 12 during operation thereof;

Fig. 14

is a front cross-sectional view of an illustrative scroll pump according to the present disclosure, which is similar to the scroll pump ofFig. 10 with the fluid pressure-based axial force control system omitted;

Fig. 15

is an upper perspective view of the scroll pump ofFig. 14;

Fig. 16

is a top plan view of the scroll pump ofFig. 14;

Fig. 17

is a first exploded perspective view of the scroll pump ofFig. 14;

Fig. 18

is a second exploded perspective view of the scroll pump ofFig. 14; and

Fig. 19

is a schematic representation of forces acting on fixed and moving scroll members of the scroll pump ofFig. 14 during operation thereof.

DETAILED DESCRIPTION OF THE DRAWINGS
• Figs. 1-8 show an illustrative embodiment of ascroll pump 10 having a preload axial force control system and a fluid-pressure-based axial force control system according to the present disclosure. Thescroll pump 10 includes: a first (or fixed)scroll member 12; a second (or orbiting)scroll member 14; acamshaft 16 having afirst shaft portion 16A and asecond shaft portion 16B connected to, spaced from, and parallel to thefirst shaft portion 16A; alink 18; and aprime mover 20, for example, an electric motor. Thefirst scroll member 12 is in orbiting engagement with thesecond scroll member 14. Thefirst shaft portion 16A of thecamshaft 16 is rotatably connected to thefirst scroll member 12. Thesecond shaft portion 16B of thecamshaft 16 is rotatably connected to thesecond scroll member 14. Afirst end 18A of thelink 18 is pivotably connected to thefirst scroll member 12, and asecond end 18B of thelink 18 is pivotably connected to thesecond scroll member 14. Themotor 20 is configured to rotate thecamshaft 16 with respect to thefirst scroll member 12 and thesecond scroll member 14. Thelink 18 substantially precludes rotation of thesecond scroll member 14 with respect to thefirst scroll member 12 when thecamshaft 16 is rotating, so that rotation of thecamshaft 16 causes thesecond scroll member 14 to orbit with respect to thefirst scroll member 12.
• Thefirst scroll member 12 includes afirst end plate 22 and afirst involute 24 extending axially from a first side of thefirst end plate 22. Thefirst end plate 22 defines a first shaft-receivingaperture 26 configured to receive thefirst shaft portion 16A of thecamshaft 16. Thefirst end plate 22 also defines a bearingpocket 28 extending into thefirst end plate 22. In the embodiment shown, the bearingpocket 28 extends toward the first side of thefirst end plate 22 from a second side of thefirst end plate 22 opposite the first side of thefirst end plate 22. Afirst bearing 30 is received within thefirst bearing pocket 28, for example, in press-fit engagement. Aland 32 at the bottom of the bearing pocket precludes the bearing 30 from being inserted into and removed from the bearingpocket 28 from the first side of thefirst end plate 22. Thefirst bearing 30 may abut theland 32.
• Alternatively, the bearingpocket 28 may extend into thefirst end plate 22 from the first side of thefirst end plate 22 toward the second side of thefirst end plate 22. In such an embodiment (not shown), theland 32 would preclude the bearing 30 from being inserted into and removed from the bearingpocket 28 from the second side of thefirst end plate 22.
• In other embodiments, thefirst aperture 26 and the bearingpocket 28 may be combined into a single feature and theland 32 may be omitted. In such embodiments, thefirst bearing 32 could be inserted into and removed from the bearingpocket 28 from the first side of thefirst end plate 22 or the second side of thefirst end plate 22.
• Thefirst bearing 30 is configured to receive thefirst shaft portion 16A of thecamshaft 16 in rotating, bearing engagement. Thefirst bearing 30 may be a sealed bearing, and the interfaces among thefirst end plate 22, thefirst bearing 30, and thefirst shaft portion 16A of thecamshaft 16 may be substantially sealed interfaces so that thefirst bearing 32 and the foregoing interfaces are substantially airtight.
• As suggested above, thefirst involute 24 extends axially from the first side of thefirst end plate 22 in a direction perpendicular to thefirst end plate 22. Afirst end 24A of thefirst involute 24 proximate a periphery of thefirst involute 24 closes upon an intermediate portion of thefirst involute 24. Asecond end 24B of thefirst involute 24 proximate a center of thefirst involute 24 is free. As such, thefirst end plate 22 and thefirst involute 24 cooperate to define a space configured to receive a second involute, as will be discussed further below. Afirst tip seal 24S is provided at a free surface of thefirst involute 24 opposite thefirst end plate 22. The free end of thefirst involute 24 may define a recess or groove 24G configured to receive and retain thetip seal 24S.
• Thefirst scroll member 12 defines a fluid inlet aperture orport 34 proximate a periphery of thefirst end 24A of thefirst involute 24. Thefluid inlet aperture 34 is configured to admit air or another fluid into thescroll pump 10 for pressurizing thereby. Thefluid inlet port 34 may extend through one or both of thefirst end plate 22 and thefirst involute 24. Thefirst scroll member 12 also defines a fluid outlet aperture orport 36 extending through thefirst end plate 22 proximate thesecond end 24B of thefirst involute 24. Thefluid outlet port 36 is configured to discharge fluid pressurized by thescroll pump 10.
• Thefirst scroll member 12 further defines afirst pivot point 38 configured to receive an axle or pin 40 connecting thefirst end 18A of thelink 18 to thefirst scroll member 12 in pivoting engagement therewith. As shown, thefirst pivot point 38 may be embodied as a boss proximate the periphery of thefirst end plate 22 and/or radially outboard of thefirst involute 24.
• Thefirst scroll member 12 also may include one or mountingbosses 42 configured to receive fasteners (not shown) for connecting thefirst scroll member 12 to another structure (not shown).
• Asidewall 44 extends axially from the second side of thefirst end plate 22. Thesidewall 44 cooperates with thefirst end plate 22 to define a housing configured to receive theprime mover 20, in this case an electric motor. As shown, thesidewall 44 is monolithically formed or integral with thefirst end plate 22. Anend cap 46 covers the open end of thesidewall 44. Aseal 48, for example, an O-ring, may be provided between the housing wall and the end cap so that the interior of the housing is substantially air-tight.
• Thesecond scroll member 14 includes asecond end plate 52 and asecond involute 54 extending from a first side of thesecond end plate 52. Thesecond end plate 52 defines a second shaft-receivingaperture 56 extending from the first side thereof to a second side thereof opposite the first side. The second shaft-receivingaperture 56 is configured to receive asecond bearing 58 therein, for example, in press-fit engagement. Thesecond end plate 52 also defines one or more vent holes 60 extending therethrough, proximate the center of thesecond end plate 52, as will be discussed further below. Anannular sidewall 62 extends axially from the second side of thesecond end plate 52, thereby defining acavity 64 extending axially from the second side of the second end plate. Thecavity 64 is configured to receive apiston 66, as will be discussed further below. Thecavity 64 may be cylindrical.
• As suggested above, thesecond involute 54 extends from a first side of thesecond end plate 52 in a direction perpendicular thereto. Asecond tip seal 54S is provided at a free end of thesecond involute 54. The free end of thesecond involute 54 may define a recess or groove 54G configured to receive and retain thesecond tip seal 54S.
• Thesecond scroll member 52 further defines asecond pivot point 68 configured to receive a second axle or pin 70 connecting thesecond end 18B of thelink 18 to thesecond scroll member 14 in pivoting engagement therewith. As shown, thesecond pivot point 68 may be embodied as a boss proximate the periphery of thesecond end plate 52.
• As mentioned above, thecamshaft 16 includes afirst shaft portion 16A and asecond shaft portion 16B. Thefirst shaft portion 16A defines a first axis of rotation. The first axis of rotation is perpendicular to thefirst end plate 22 and parallel to thefirst involute 24. Thesecond shaft portion 16B defines a second axis of rotation. The second axis of rotation is perpendicular to thesecond end plate 52 and parallel to thesecond involute 54. The second axis of rotation is radially offset from and parallel to the first axis of rotation. Thefirst shaft portion 16A is configured for connection to a drive shaft of theprime mover 20 for rotation therewith. In embodiments, thecamshaft 16 may be integrated and/or monolithically formed with the drive shaft of theprime mover 20.
• Thesecond shaft portion 16B defines acircumferential groove 72 configured to receive ashaft seal 74, for example, an O-ring. Theshaft seal 74 is engaged between thesecond shaft portion 16B and an inner race of thesecond bearing 58. A free end of thesecond shaft portion 16B may define a threadedbore 76 configured to receive afastener 78, as will be discussed further below.
• Thefirst shaft portion 16A is received within thefirst bearing 30 in rotating bearing engagement therewith. Thesecond shaft portion 16B is received within thesecond bearing 58 in rotating bearing engagement therewith. Thefirst scroll member 12 is axially fixed to thefirst shaft portion 16A. Thesecond scroll member 14 axially floats with respect to thesecond shaft portion 16B.
• Thefirst scroll member 12 is engaged with thesecond scroll member 14 so that thefirst involute 24 is interleaved with thesecond involute 54. Thefirst tip seal 24S of thefirst scroll member 12 engages with the first side of thesecond end plate 52 of thesecond scroll member 14 in sealing engagement therewith. Similarly, thesecond tip seal 54S of thesecond scroll member 14 engages with the first side of thefirst end plate 22 of thefirst scroll member 12 in sealing engagement therewith. So assembled, the first andsecond scroll members 12, 14 define a working volume V substantially bounded by the first andsecond end plates 22, 52 and the first andsecond involutes 24, 54.
• With the first andsecond scroll members 12, 14 so assembled together, a first exposed surface area of thesecond end plate 52 is exposed to fluid pressure within the working volume V. The first exposed surface area is defined by the surface area of the first side of thesecond end plate 52 normal to the second axis of rotation and radially inboard of thefirst involute 24, minus the surface area of the first side of thesecond end plate 52 normal to the second axis of rotation occupied by thesecond involute 54 and covered by thefirst involute 24/first tip seal 24S. Put another way, the first exposed surface area is the surface area of the first side of thesecond end plate 52 that projects against the first side of thefirst end plate 22, minus the surface area of the free end of thesecond involute 54 engaging the first side of the first end plate. A second exposed surface area of thesecond end plate 52 is exposed to fluid pressure within thecavity 64. The second exposed surface area is defined by the surface area of the second side of thesecond end plate 52 normal to the second axis of rotation within the confines of thecavity 64. The second exposed surface area is greater than the first exposed surface area so that when both sides of thesecond end plate 52 are subjected to the same fluid pressure, the net force on thesecond end plate 52 parallel to the second axis of rotation tends to bias thesecond scroll member 14 toward thefirst scroll member 12, thereby compressing the first and second tip seals 24S, 54S against the respective second andfirst end plates 52, 22.
• As mentioned above, thelink 18 is pivotably connected to both the first andsecond scroll members 12, 14. More specifically, a first portion of thelink 18, which may be proximate afirst end 18A thereof, is pivotably connected to thefirst scroll member 12. Similarly, a second portion of thelink 18, which may be proximate asecond end 18B thereof, is pivotably connected to thesecond scroll member 14. So connected to the first andsecond scroll members 12, 14, thelink 18 allows thesecond scroll member 14 to orbit with respect to thefirst scroll member 12, while substantially precluding rotation of thesecond scroll member 14 with respect to thefirst scroll member 12. As shown in the drawings, thecamshaft 16 and thelink 18 are the only structures constraining the radial position of thesecond scroll member 14 with respect to thefirst scroll member 12.
• As suggested above, thepiston 66 is received within thecavity 64 defined by thesecond scroll member 14. Thepiston 66 defines a third bearing-receivingaperture 80 at the center thereof. Athird bearing 82 is received in the third bearing-receivingaperture 80. Thethird bearing 82 is shown as a flanged bearing received in the third bearing-receiving aperture from a side of thepiston 66 facing away from thesecond scroll member 14. Thethird bearing 82 may be a sealed bearing that substantially precludes fluid flow therethrough. Thepiston 66 also defines agroove 84 about the perimeter thereof. Thegroove 84 is configured to receive apiston seal 86, for example, an O-ring. Thepiston seal 86 substantially precludes fluid flow between thepiston 66 and thecavity 64.
• As shown, thepiston 66 is axially retained to thecamshaft 16 by asnap ring 50 received within asnap ring groove 51 defined by thecam shaft 16. More specifically, thepiston 66 and thethird bearing 82 received therein are disposed between thesnap ring 50 and thesecond scroll member 14. As such, thesnap ring 50 limits the axial travel of thethird bearing 82 and, therefore, thepiston 66, in a direction away from thesecond scroll member 14. The free end of thesecond shaft portion 16B of thecamshaft 16 may be received within the center of thethird bearing 82. Thethird bearing 82 is configured to allow thecamshaft 16 to rotate with respect to thesecond scroll member 14, while thepiston 66 remains rotationally fixed with respect to thesecond scroll member 14.
• As shown, afirst counter weight 88 may be proximate the base of thesecond shaft portion 16B of thecamshaft 16, where thefirst shaft portion 16A of the camshaft is connected to thesecond portion 16B of thecamshaft 16. As shown, thefirst counterweight 88 is disposed within the interior confines of thefirst involute 24. Asecond counterweight 90 may be provided proximate the free end of thesecond shaft portion 16B of thecamshaft 16. Thesecond counterweight 90 may be connected to the end of thecamshaft 16 by afastener 78, for example, a threaded fastener, extending into the threaded bore 76 defined by the free end of thesecond shaft portion 16B of thecamshaft 16. As shown, thesecond counterweight 90 is disposed within the confines of acavity 67 defined by thepiston 66 on the side of thepiston 66 opposite thesecond end plate 52. Each of the first andsecond counterweights 88, 90 is rotationally fixed to thecamshaft 16 and may axially fixed thereto, as well.
• A biasingspring 92 is disposed between the second side of thesecond end plate 52 and thepiston 66. As shown, the biasingspring 92 is an assembly of a plurality of wave washers. In embodiments, the biasingspring 92 could be a plurality of distinct wave washers, a single wave washer, an elastomer, or any other suitable biasing member. The biasingspring 92 preloads thesecond scroll member 14 away from thepiston 66 and toward thefirst scroll member 12, thereby engaging the first and second tip seals 24S, 54S with the respective, opposing second andfirst end plates 52, 22. As shown, the biasingspring 92 is disposed between thesecond end plate 52 and thesecond counterweight 90. In embodiments, the biasingspring 92 could be disposed between thepiston 66 and thesecond counterweight 90.
• Anend cap 94 covers thecavity 67 and thepiston 66 andsecond counterweight 90 received therein. Anend cap seal 96, for example, an O-ring, may be provided between theend cap 94 and thesecond scroll member 14.
• In use, the biasingspring 92 preloads thesecond scroll member 14 toward thefirst scroll member 12, thereby engaging the first and second tip seals 24S, 54S with the respective, opposing second andfirst end plates 52, 22. Theprime mover 20 rotates thecamshaft 16. The rotatingcamshaft 16 causes thesecond scroll member 14 to orbit with respect to thefirst scroll member 12. The orbiting of thesecond scroll member 14 with respect to thefirst scroll member 12 causes the air or another fluid to be drawn into the working volume V through thefluid inlet port 34 and pumped toward thefluid outlet port 36, thereby increasing the pressure of the fluid from thefluid inlet port 34 to thefluid outlet port 36.
• In the absence of the vent holes 60 defined by thesecond end plate 52, the foregoing increase in fluid pressure acting against thefirst end plate 22 and the first exposed surface of thesecond end plate 52 would tend to force the first andsecond scroll members 12, 14 apart from each other axially. Axial displacement of thesecond scroll member 14 away from thefirst scroll member 12 resulting from such force could lessen the effect of the first and second tip seals 24S, 54S, thereby decreasing the efficiency of thescroll pump 10.
• The vent holes 60 mitigate this phenomenon by equalizing the fluid pressure on the first and second opposed sides of thesecond end plate 52 and by applying this equalized pressure to the surface of thepiston 66 facing the second end plate 52 (and to the piston seal 86) in a first embodiment or to the end cap 94 (and to the end cap seal 96) in a second embodiment.
• In the first embodiment, the equalized pressure is applied against thepiston 66. Because force equals pressure times area, because the second exposed surface area on the second side of thesecond end plate 52 is greater than the first exposed surface area on the first side of thesecond end plate 52, and because thepiston 66 is fixed axially with respect to thefirst scroll member 12, the net axial force acting on thesecond end plate 52 due to the fluid pressure within the working volume V and thecavity 64 tends to bias thesecond end plate 52, and therefore thesecond scroll member 14, toward thefirst scroll member 12. This net axial force tends to increase as a function of increasing fluid pressure within the working volume V and thecavity 64. Also, because thesecond scroll member 14 floats on thesecond shaft portion 16B of thecamshaft 16, thesecond scroll member 14 may be displaced slightly toward thefirst scroll member 12 in response to the foregoing axial biasing force, thereby compressing the first and second tip seals 24S, 54S against the respective, opposing second andfirst end plates 52, 22, and thereby promoting operational efficiency of thescroll pump 10.
• In the second embodiment, as shown inFig. 7, thepiston 66 may be provided with anoptional vent hole 98 similar to vent hole(s) 60 (theoptional vent hole 98 is absent in the first embodiment). This may be desirable where thethird bearing 82 is not a sealed a bearing. In applications where thethird bearing 82 is not a sealed bearing, pressure differential across first and second sides of thethird bearing 82 could force grease out of thethird bearing 82, potentially leading to premature wear and failure of thethird bearing 82. Providing thevent hole 98 in thepiston 66 allows for pressure equalization across thepiston 66, thereby mitigating against forcing grease out of thethird bearing 82 due to pressure differential across thethird bearing 82. In such embodiments, the equalized pressure across thesecond end plate 52 and thepiston 66 bears against theend cap 94 and theend cap seal 96. In such embodiments, in use, thesecond scroll member 14 is biased toward thefirst scroll member 12 in a manner similar to that described above.
• In any of the foregoing embodiments, cooperation of thepiston 66 with thecavity 64 may provide radial support for thesecond shaft portion 16B of the camshaft.
• Fig. 9 is a schematic representation of forces acting on fixed and movingscroll members 12, 14 of thescroll pump 10 during operation thereof. InFig. 9, F_PI represents the axial force applied between thefixed end plate 22 and the movingend plate 52 by the fluid being pumped or compressed by thescroll pump 10 and tending to bias the movingscroll member 14 away from the fixedscroll member 12, as discussed above. Fs represents the axial preload force applied between the fixed and movingscroll members 12, 14 and tending to bias the movingscroll member 14 toward the fixedscroll member 12, as discussed above. F_PE represents the axial force applied between thepiston 66 or theend cap 94 and the movingend plate 52 and tending to bias the movingscroll member 14 toward the fixedscroll member 12, as discussed above. F_NET represents the net axial force acting between thefixed scroll member 12 and the movingscroll member 14 as a result of the forces F_PI, F_S, and F_PE. That is, F_NET represents the algebraic sum of the forces F_PI, Fs, and F_PE. The symbol + represents a force direction tending to bias the movingscroll member 14 away from the fixedscroll member 12, and the symbol - represents a force direction tending to bias the movingscroll member 14 toward the fixedscroll member 12. As suggested inFig. 9, F_NET may be neutral, tending to bias the movingscroll member 14 toward the fixedscroll member 12, or tending to bias the movingscroll member 14 away from the fixedscroll member 12.
• In embodiments, the preload axial force control system including thespring 92 may be eliminated fromscroll pump 10. In such embodiments, the axial preload force Fs would be absent from the schematic representation of forces shown inFig. 9.
• Fig. 10 shows an illustrative embodiment of ascroll pump 100 generally identical to thescroll pump 10 but further including an electromagnetic axialforce control system 110 according to the present disclosure. The electromagnetic axialforce control system 110 of thescroll pump 100 includes anelectromagnet 112 fixedly connected to the fixedscroll member 12 via a mountingbracket 114, and a magnetic target in the form of apermanent magnet 116 fixedly connected to the movingscroll member 14 via a mountingbracket 118.Fig. 10 shows theelectromagnet 112 as a coil 120 (wound about a bobbin, not shown) surrounding aferromagnetic core 122.Fig. 10 shows thecoil 120 and thepermanent magnet 116 as having respective outer diameters. In embodiments, the outer diameter of thepermanent magnet 116 is sufficiently larger than the outer diameter of thecoil 120 so that the radial bounds of thepermanent magnet 116 overlap the radial bounds of thecoil 120 at all times as thesecond scroll member 14 orbits with respect to thefirst scroll member 14 during operation of thescroll pump 100. This arrangement of relative diameters promotes consistent magnetic coupling between theelectromagnet 112 and thepermanent magnet 116 during operation of thescroll pump 100.
• Awiring harness 124 connects theelectromagnet 112 to a source of electrical current (not shown). A controller (not shown), for example, an electronic controller, may be provided to selectively control the supply of electrical current to theelectromagnet 112 and thereby control a magnetic electric field generated by theelectromagnet 112. The controller (not shown) may be configured to vary the magnitude of electrical current provided to theelectromagnet 112 to thereby vary the strength of the magnetic field generated by theelectromagnet 112.
• In use, the biasingspring 92 preloads thesecond scroll member 14 toward thefirst scroll member 12, thereby engaging the first and second tip seals 24S, 54S with the respective, opposing second andfirst end plates 52, 22. Also, thepermanent magnet 116 magnetically couples with the fixedscroll member 12 and thereby biases thesecond scroll member 14 away from thefirst scroll member 12.
• Theelectromagnet 112 may be selectively energized and thereby generate a magnetic force that couples to thepermanent magnet 116. As would be understood by one skilled in the art, theelectromagnet 112 may be selectively energized to generate an attractive magnetic force between theelectromagnet 112 and thepermanent magnet 116, thereby biasing the movingscroll member 14 away from the fixedscroll member 12. As also would be understood by one skilled in the art, theelectromagnet 112 also may be selectively energized to generate a repulsive magnetic force between theelectromagnet 112 and thepermanent magnet 116, thereby biasing the movingscroll member 14 toward the fixedscroll member 12.
• During operation of thescroll pump 100, a net axial biasing force axially biasing the movingscroll member 14 away from the fixedscroll member 12 may lessen the seal between the fixed and movingscroll tips 24, 54 and/or between the fixed and movingtip seals 24S, 54S and thecorresponding end plates 52, 22. The lessening of the foregoing seal may induce fluid leakage between the fixed and movingscroll tips 24, 54 and/or between the fixed and movingtip seals 24S, 54S and thecorresponding end plates 52, 22. Such induced fluid leakage may be used to control the output flow rate and/or output pressure of thescroll pump 10 without varying its speed. Controlling the output flow rate and/or output pressure of thescroll pump 10 by inducing leakage in this manner may allow the scroll pump to operate within a predetermined range of output flow rate and/or output pressure with less noise or variation in noise than operating thescroll pump 10 at varying speeds to accomplish similar variation in output flow rate and/or output pressure.
• Fig. 11 is a schematic representation of forces acting on the fixed and movingscroll members 12, 14 of thescroll pump 100 during operation thereof. InFig. 11, F_PI represents the axial force applied between thefixed end plate 22 and the movingend plate 52 by the fluid being pumped or compressed by thescroll pump 100 and tending to bias the movingscroll member 14 away from the fixedscroll member 12, as discussed above. F_PE represents the axial force applied between thepiston 66 or theend cap 94 and the movingend plate 52 and tending to bias the movingscroll member 14 toward the fixedscroll member 12, as discussed above. Fs represents the axial preload force applied between the fixed and movingscroll members 12, 14 and tending to bias the movingscroll member 14 toward the fixedscroll member 12, as discussed above. F_M represents the axial magnetic force applied by thepermanent magnet 116 of the magnetic target between the permanent magnet of the magnetic target and the fixed scroll member and tending to bias the movingscroll member 14 away from the fixedscroll member 12. F_E represents the magnetic force selectively applied by theelectromagnet 112 between theelectromagnet 112 and thepermanent magnet 116 of the magnetic target and tending to selectively bias the movingscroll member 14 toward or away from the fixedscroll member 12. F_NET represents the net axial force acting between thefixed scroll member 12 and the movingscroll member 14 as a result of the forces F_PI, F_PE, Fs, F_M, and F_E. That is, F_NET represents the algebraic sum of the forces F_PI, F_PE, Fs, F_M, and F_E. The symbol + represents a force direction tending to bias the movingscroll member 14 away from the fixedscroll member 12, and the symbol - represents a force direction tending to bias the movingscroll member 14 toward the fixedscroll member 12. As suggested inFig. 9, F_NET may be neutral, tending to bias the movingscroll member 14 toward the fixedscroll member 12, or tending to bias the movingscroll member 14 away from the fixedscroll member 12.
• In the foregoing embodiment of thescroll pump 100, theelectromagnet 112 is located opposite the movingscroll member 14 from the fixedscroll member 12. In an alternative embodiment, theelectromagnet 112 could be located on the same side of the movingscroll member 14 as the fixedscroll member 12. For example, theelectromagnet 112 may be integrated into the fixedscroll member 12. In such an embodiment, the magnetic force vector F_M shown inFig. 11 would point in the opposite direction, and the magnetic force applied by thepermanent magnet 116 of the magnetic target would tend to bias the movingscroll member 14 toward the fixedscroll member 12, rather than away from the fixedscroll member 12. In such an embodiment, the preload axial force control system could be configured to bias the movingscroll member 14 away from the fixedscroll member 12, rather than toward the fixedscroll member 12. In such an embodiment, the axial preload force vector Fs shown inFig. 11 would point in the opposite direction.
• In embodiments, the axial preload system including thespring 92 could be omitted from thescroll pump 100. In such embodiments, axial force Fs would be omitted from the force diagram ofFig. 11.
• Fig. 12 shows an alternative embodiment of the scroll pump 100' wherein thepermanent magnet 116 is omitted and aferrous element 117 is provided in its place. Functionally, the scroll pump 100' is similar to thescroll pump 100. Functionally, the scroll pump 100' differs from thescroll pump 100 in that theelectromagnet 112 of the scroll pump 100' is operable only to generate an attractive force between itself and theferrous element 117, whereas theelectromagnet 112 of thescroll pump 100 is operable to generate both attractive and repulsive forces between itself and thepermanent magnet 116. As such, theelectromagnet 112 of the scroll pump 100' is operable to effect an attractive axial biasing force between thefixed scroll member 12 and the movingscroll member 14, but not a repulsive biasing force between thefixed scroll member 12 and the movingscroll member 14. Accordingly, theelectromagnet 112 of the scroll pump 100' is operable to bias the fixedscroll member 12 and the movingscroll member 14 away from each other, but not toward each other.
• Fig. 13 is a schematic representation of forces acting on fixed and movingscroll members 12, 14 of the scroll pump 100' during operation thereof. InFig. 13, F_PI represents the axial force applied between thefixed end plate 22 and the movingend plate 52 by the fluid being pumped or compressed by the scroll pump 100' and tending to bias the movingscroll member 14 away from the fixedscroll member 12, as discussed above. F_PE represents the axial force applied between thepiston 66 or theend cap 94 and the movingend plate 52 and tending to bias the movingscroll member 14 toward the fixedscroll member 12, as discussed above. Fs represents the axial preload force applied between the fixed and movingscroll members 12, 14 and tending to bias the movingscroll member 14 toward the fixedscroll member 12, as discussed above. F_E represents the magnetic force selectively applied by theelectromagnet 112 between theelectromagnet 112 and theferrous element 117 of the magnetic target and tending to selectively bias the movingscroll member 14 toward or away from the fixedscroll member 12. F_NET represents the net axial force acting between thefixed scroll member 12 and the movingscroll member 14 as a result of the forces F_PI, F_PE, F_S, and F_E. That is, F_NET represents the algebraic sum of the forces F_PI, F_PE, F_S, and F_E. The symbol + represents a force direction tending to bias the movingscroll member 14 away from the fixedscroll member 12, and the symbol - represents a force direction tending to bias the movingscroll member 14 toward the fixedscroll member 12. As suggested inFig. 9, F_NET may be neutral, tending to bias the movingscroll member 14 toward the fixedscroll member 12, or tending to bias the movingscroll member 14 away from the fixedscroll member 12.
• In the foregoing embodiment of the scroll pump 100', theelectromagnet 112 is located opposite the movingscroll member 14 from the fixedscroll member 12. In an alternative embodiment, theelectromagnet 112 could be located on the same side of the movingscroll member 14 as the fixedscroll member 12. For example, theelectromagnet 112 may be integrated into the fixedscroll member 12.
• In embodiments, the axial preload system including thespring 92 could be omitted from the scroll pump 100'. In such embodiments, axial force Fs would be omitted from the force diagram ofFig. 11.
• Figs. 14-18 show an illustrative embodiment of ascroll pump 200 including an electromagnetic axial force control system according to the present disclosure. Thescroll pump 200 is in most respects similar to thescroll pump 100. Thescroll pump 200 differs from thescroll pump 100 primarily in that the preload-based axial force control system and the fluid pressure-based axial force control system of thescroll pump 100 are omitted from thescroll pump 200.
• As such, the electromagnetic axialforce control system 110 of thescroll pump 200 as shown inFigs. 14-18 includes theelectromagnet 112 fixedly connected to the fixedscroll member 12 via theintervening mounting bracket 114, and the magnetic target in the form of thepermanent magnet 116 fixedly connected to the movingscroll member 14.Figs. 14-18 show the electromagnet as the coil 120 (wound about a bobbin, not shown) surrounding theferromagnetic core 122.Fig. 14 shows thecoil 120 and thepermanent magnet 116 as having respective outer diameters. In embodiments, the outer diameter of thepermanent magnet 116 is sufficiently larger than the outer diameter of thecoil 120 so that the radial bounds of thepermanent magnet 116 overlap the radial bounds of thecoil 120 at all times as thesecond scroll member 14 orbits with respect to thefirst scroll member 14 during operation of thescroll pump 200. This arrangement of relative diameters promotes consistent magnetic coupling between theelectromagnet 112 and thepermanent magnet 116 during operation of thescroll pump 200.
• Thewiring harness 124 connects theelectromagnet 112 to a source of electrical current (not shown). A controller (not shown), for example, an electronic controller, may be provided to selectively control the supply of electrical current to theelectromagnet 112 and thereby control a magnetic electric field generated by theelectromagnet 112. The controller (not shown) may be configured to vary the magnitude of electrical current provided to theelectromagnet 112 to thereby vary the strength of the magnetic field generated by theelectromagnet 112.
• In use, theelectromagnet 112 may be selectively energized and thereby generate a magnetic force that couples to thepermanent magnet 116. As would be understood by one skilled in the art, theelectromagnet 112 may be selectively energized to generate an attractive magnetic force between theelectromagnet 112 and thepermanent magnet 116, thereby biasing the movingscroll member 14 away from the fixedscroll member 12. As also would be understood by one skilled in the art, theelectromagnet 112 also may be selectively energized to generate a repulsive magnetic force between theelectromagnet 112 and thepermanent magnet 116, thereby biasing the movingscroll member 14 toward the fixedscroll member 12.
• During operation of thescroll pump 200, a net axial biasing force axially biasing the movingscroll member 14 away from the fixedscroll member 12 may lessen the seal between the fixed and movingscroll tips 24, 54 and/or between the fixed and movingtip seals 24S, 54S and thecorresponding end plates 52, 22. The lessening of the foregoing seal may induce fluid leakage between the fixed and movingscroll tips 24, 54 and/or between the fixed and movingtip seals 24S, 54S and thecorresponding end plates 52, 22. Such induced fluid leakage may be used to control the output flow rate and/or output pressure of thescroll pump 200 without varying its speed. Controlling the output flow rate and/or output pressure of thescroll pump 200 by inducing leakage in this manner may allow the scroll pump to operate within a predetermined range of output flow rate and/or output pressure with less noise or variation in noise than operating thescroll pump 200 at varying speeds to accomplish similar variation in output flow rate and/or output pressure.
• Fig. 19 is a schematic representation of forces acting on fixed and movingscroll members 12, 14 of thescroll pump 200 during operation thereof. InFig. 19, F_PI represents the axial force applied between thefixed end plate 22 and the movingend plate 52 by the fluid being pumped or compressed by thescroll pump 200 and tending to bias the movingscroll member 14 away from the fixedscroll member 12, as discussed above. F_M represents the axial magnetic force applied by thepermanent magnet 116 of the magnetic target between thepermanent magnet 116 of the magnetic target and the fixedscroll member 12 and tending to bias the movingscroll member 14 toward the fixedscroll member 12. F_E represents the magnetic force selectively applied by theelectromagnet 112 between theelectromagnet 112 and thepermanent magnet 116 of the magnetic target and tending to selectively bias the movingscroll member 14 toward or away from the fixedscroll member 12. F_NET represents the net axial force acting between thefixed scroll member 12 and the movingscroll member 14 as a result of the forces F_PI, F_M, and F_E. That is, F_NET represents the algebraic sum of the forces F_PI, F_M, and F_E. The symbol + represents a force direction tending to bias the movingscroll member 14 away from the fixedscroll member 12, and the symbol - represents a force direction tending to bias the movingscroll member 14 toward the fixedscroll member 12. As suggested inFig. 19, F_NET may be neutral, tending to bias the movingscroll member 14 toward the fixedscroll member 12, or tending to bias the movingscroll member 14 away from the fixedscroll member 12.
• In embodiments, thepermanent magnet 116 of thescroll pump 200 could be replaced with theferrous target 117 of the scroll pump 100'. In such embodiments, theelectromagnet 112 would be operable to generate an attractive force, but not a repulsive force, between thefixed scroll member 12 and the movingscroll member 14. As such, the axial force F_E- would be absent from the force diagram ofFig. 19.
• In the foregoing embodiment of thescroll pump 200, theelectromagnet 112 is located opposite the movingscroll member 14 from the fixedscroll member 12. In an alternative embodiment, theelectromagnet 112 could be located on the same side of the movingscroll member 14 as the fixedscroll member 12. For example, theelectromagnet 112 may be integrated into the fixedscroll member 12. In such an embodiment, the magnetic force vector F_M shown inFig. 11 would point in the opposite direction, and the magnetic force applied by thepermanent magnet 116 of the magnetic target would tend to bias the movingscroll member 14 toward the fixedscroll member 12, rather than away from the fixedscroll member 12.
• In embodiments, the axial preload system including thespring 92 could be added to thescroll pump 200. In such embodiments, the axial force Fs would be added to the force diagram ofFig. 19 in a manner similar to the force Fs shown inFigs. 9,11, and13.
• In all of the foregoing embodiments, the axial control forces F_PE, Fs, and F_M may be predetermined and the axial control force F_E may be predetermined or adjusted as desired to achieve the desired net axial force F_NET tending to bias the movingscroll member 14 toward or away from the fixedscroll member 12, as desired.
• The embodiments shown and described herein are illustrative and may be modified as would be understood by one skilled in the art without departing from the scope of the appended claims.

Claims (12)

1. A scroll pump comprising:

   a first scroll member, the first scroll member comprising:

   a first end plate; and

   a first scroll extending in an axial direction from the first end plate to a first scroll tip;

   a second scroll member, the second scroll member comprising:

   a second end plate; and

   a second scroll extending in the axial direction from the second end plate to a second scroll tip, wherein the second scroll is intermeshed with the first scroll, wherein the first scroll member and the second scroll member define a working volume therebetween, and wherein the second scroll is movable in the axial direction with the respect to the first scroll; and

   an electromagnet fixedly connected to the fixed scroll member, wherein the electromagnet is operable to selectively bias the second scroll member axially with respect to the first scroll member.
2. The scroll pump of claim 1 wherein the electromagnet comprises a coil.
3. The scroll pump of claim 2 wherein the electromagnet further comprises a ferromagnetic core.
4. The scroll pump of any preceding claim further comprising a magnetic target fixed to the other of the first scroll member and the second scroll member.
5. The scroll pump of claim 4 wherein the magnetic target comprises a ferrous target made of ferromagnetic material.
6. The scroll pump of claim 4 wherein the magnetic target comprises a permanent magnet.
7. The scroll pump of any preceding claim further comprising a spring associated with the first scroll member and the second scroll member and operable to bias the second scroll member toward the first scroll member.
8. The scroll pump of any of any preceding claim further comprising a controller operable to selectively energize and de-energize the coil and thereby selectively cause the electromagnet to bias the second scroll member axially with respect to the first scroll member.
9. The scroll pump of claim 8 wherein the controller is operable to selectively cause the electromagnet to bias the second scroll member away from the first scroll member.
10. The scroll pump of claim 8 wherein the controller is operable to selectively cause the electromagnet to bias the second scroll member toward the first scroll member.
11. The scroll pump of claim 8 wherein the controller is operable to selectively cause the electromagnet to bias the second scroll member toward the first scroll member to mitigate leakage of a working fluid between the first scroll and the second scroll.
12. The scroll pump of claim 8 wherein the controller is operable to selectively cause the electromagnet to bias the second scroll member away from the first scroll member to induce leakage of a working fluid between the first scroll and the second scroll.

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