Scroll Pump

Abstract

The non-contact scroll pump (100) comprises a housing (110), an orbiting scroll (130) disposed within the housing, and a thrust bearing assembly (170) disposed within the housing for axially supporting the orbiting scroll. The thrust bearing assembly comprises a first plate (171) secured to the orbiting scroll, a second plate (172) spaced apart from the first plate, and a ball bearing (174) disposed between the first plate and the second plate, the ball bearing configured to roll relative to the first and second plates during orbiting of the orbiting scroll. The thrust bearing assembly further comprises a coupling structure extending between the housing and the second plate and coupling the housing to the second plate, the coupling structure comprising a thermal break for reducing heat transfer from the second plate to the coupling structure during operation of the non-contact scroll pump.

Description

[Technical field]

[0001] The present invention relates to a scroll pump. [Background technology]

[0002] Scroll pumps are a known type of pump used in a variety of different industries to pump fluids. Scroll pumps work by utilizing the relative motion of two intermeshing scrolls, known as a fixed scroll and an orbiting scroll, to pump a fluid. The fixed scroll and the orbiting scroll each include a spiral wall extending from a base.

[0003] One type of scroll pump is a non-contact scroll pump. In a non-contact scroll pump, the tips (i.e., the ends of the spiral walls) of the fixed and orbiting scrolls do not contact the other scroll. Furthermore, in a non-contact scroll pump, there is no tip seal between the tips of the fixed and orbiting scrolls and the other scroll. Thus, in a non-contact scroll pump, there is a small gap (or clearance), e.g., 10-20 microns, between the tips of the fixed and orbiting scrolls and the other scroll. To maintain this clearance, a non-contact scroll pump typically includes a thrust bearing assembly that engages one of the scrolls to maintain the scroll in the correct axial position relative to the other scroll. Summary of the Invention [Means for solving the problem]

[0004] In one aspect of the invention, a non-contact scroll pump is provided, the non-contact scroll pump comprising: a housing; an orbiting scroll disposed within the housing; and a thrust bearing assembly disposed within the housing for axially supporting the orbiting scroll. The thrust bearing assembly comprises a first plate secured to the orbiting scroll, a second plate spaced apart from the first plate, and a ball bearing disposed between the first plate and the second plate, the ball bearing configured to roll relative to the first and second plates during orbiting of the orbiting scroll. The thrust bearing assembly further comprises a coupling structure extending between the housing and the second plate and coupling the housing to the second plate, the coupling structure comprising a thermal break for reducing heat transfer from the second plate to the coupling structure during operation of the non-contact scroll pump.

[0005] The coupling structure can include a pin including a hollow section. The hollow section can extend axially from near an end of the pin that contacts the second plate. The thermal break can be provided, at least in part, by the hollow section.

[0006] The pin may have the same coefficient of thermal expansion as the section of the housing through which it extends.

[0007] The bonded structure may include one or more inserts disposed between the second plate and the remainder of the bonded structure, the thermal break being provided at least in part by the one or more inserts.

[0008] The non-contact scroll pump may further include a first ball bearing cage sandwiched between the first plate and the second plate and a second ball bearing cage sandwiched between the first plate and the second plate, the first and second ball bearing cages housing the ball bearings and limiting movement of the ball bearings.

[0009] The first ball bearing cage may be secured to the first plate and the second ball bearing cage may be secured to the second plate.

[0010] The first and second ball bearing cages each have a hole, the hole of the first ball bearing cage overlaps with the hole of the second ball bearing cage, and the ball bearings are received within the overlapping holes of the ball bearing cages.

[0011] The non-contact scroll pump may include three thrust bearing assemblies, each of which includes a first plate fixed to the orbiting scroll, a second plate spaced apart from the first plate, and a ball bearing disposed between the first plate and the second plate, the ball bearing configured to roll relative to the first and second plates during orbiting of the orbiting scroll. Each of the three thrust bearing assemblies further includes a coupling structure extending axially between the housing and the second plate and coupling the housing to the second plate, the coupling structure including a thermal break for reducing heat transfer from the second plate to the coupling structure during operation of the non-contact scroll pump. The three thrust bearing assemblies may be evenly angularly distributed in a triangular configuration about the axis of rotation of the orbiting scroll.

[0012] The coupling structure may be for adjusting the axial position of the orbiting scroll.

[0013] In another aspect of the present invention, a vacuum pump system is provided that includes a plurality of vacuum pumps, one of the vacuum pumps being the non-contact scroll pump of the above aspect.

[0014] In yet another aspect of the present invention, there is provided a use of the non-contact scroll pump of any of the above aspects for pumping a fluid. [Brief description of the drawings]

[0015] [Figure 1]FIG. 1 is a schematic diagram (not to scale) showing a cross-sectional view of a non-contact scroll pump. [Diagram 2] FIG. 2 is a schematic diagram (not to scale) showing an enlarged cross-sectional view of a thrust bearing assembly of a non-contact scroll pump. [Diagram 3] FIG. 1 is a schematic diagram (not to scale) showing a perspective view of multiple thrust bearing assemblies of a non-contact scroll pump. [Figure 4] FIG. 2 is a schematic diagram (not to scale) showing an enlarged perspective view of a portion of a thrust bearing assembly of a non-contact scroll pump. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0016] FIG. 1 is a schematic diagram (not to scale) showing a cross-sectional view of a non-contact scroll pump 100.

[0017] The scroll pump 100 includes a housing portion 110 , a fixed scroll 120 , an orbiting scroll 130 , a drive shaft 140 , an actuator 150 , a main bearing assembly 160 , and a number of thrust bearing assemblies 170 .

[0018] In this embodiment, the housing portion 110 and the fixed scroll 120 together define an overall housing for the scroll pump 100 within which the other components of the scroll pump 100 are disposed. However, it should be understood that in other embodiments, the fixed scroll 120 does not define any of the overall housing for the scroll pump 100, but instead can be disposed entirely within the overall housing. In this embodiment, the orbiting scroll 130 is disposed within the overall housing for the scroll pump 100.

[0019] The orbiting scroll 130 is intermeshed with the fixed scroll 120 to define a space (or flow path) through which the scroll pump 100 pumps a fluid (e.g., gas) during operation. The orbiting scroll 130 is configured to orbit relative to the fixed scroll 120 to pump a fluid from an inlet (not shown) of the scroll pump 100 to an outlet (not shown) of the scroll pump 100. The exact physical mechanisms by which fluid is pumped by the orbiting scroll 130 relative to the fixed scroll 120 are well understood and will not be described herein for the sake of brevity.

[0020] The fixed scroll 120 includes a first base 122 and a first spiral wall 124. The orbiting scroll 130 includes a second base 132 and a second spiral wall 134. The first spiral wall 124 and the second spiral wall 134 are interdigitated with each other. Furthermore, the first spiral wall 124 extends vertically from the first base 122 to the second base 132, and an end face (also called a tip) of the first spiral wall 124 is adjacent to but does not contact (e.g., 10-20 microns away) the opposing surface of the second base 132. The second spiral wall 134 extends vertically from the second base 132 to the first base 122, and an end face (or tip) of the second spiral wall 134 is adjacent to but does not contact (e.g., 10-20 microns away) the opposing surface of the first base 122. Thus, a gap or clearance (e.g., 10-20 microns) exists between the end faces of the first and second spiral walls 124, 134 and the opposing faces of the first and second bases 122, 132, respectively. The distance between the end face of the first spiral wall 124 and the opposing face of the second base 132 is the same as the distance between the second spiral wall 134 and the opposing face of the first base 122. The clearance is empty in the sense that no object or other scroll pump component is disposed within the clearance. For example, no tip seal is present within the clearance. Thus, the end faces of the first and second spiral walls 124, 134 do not come into contact with any object or other scroll pump component.

[0021] In this embodiment, the first base 122 and the first helical wall 124 are integrally formed with one another, and the second base 132 and the second helical wall 134 are integrally formed with one another. However, in other embodiments, one or both of the helical walls 124, 134 are not integrally formed with their respective bases 122, 132.

[0022] The drive shaft 140 is coupled to the orbiting scroll 130 and is configured to rotate to orbitally drive the orbiting scroll 130. The drive shaft 140 is disposed within the overall housing of the scroll pump 100 and is mounted via a main bearing assembly 160 that aids in the rotation of the drive shaft 140. In this embodiment, the drive shaft 140 extends through both the fixed scroll 120 and the orbiting scroll 130, with the orbiting scroll 130 attached to the end of the drive shaft 140.

[0023] An actuator 150 (e.g., an electric motor) is coupled to the drive shaft 140 and configured to actuate the drive shaft 140, causing the drive shaft 140 to rotate and drive the orbiting scroll 130. The actuator 150 is disposed within the overall housing of the scroll pump 100 and is mounted about the drive shaft 140.

[0024] The main bearing assembly 160 mechanically couples the drive shaft 140 to the orbiting scroll 130 and the overall housing of the scroll pump 100 such that the drive shaft 140 can rotate within the scroll pump 100 to drive the orbiting scroll 130. In this embodiment, the main bearing assembly 160 includes a bearing disposed (mechanically coupled) between a first end of the drive shaft 140 and the overall housing of the scroll pump 100, a bearing disposed (mechanically coupled) between the orbiting scroll 130 and a second end of the drive shaft 140 opposite the first end, and a bearing disposed (mechanically coupled) between the fixed scroll 120 and the drive shaft 140.

[0025] Each of the plurality of thrust bearing assemblies 170 is disposed between the orbiting scroll 130 and the housing portion 110 axially spaced from the orbiting scroll 130. Each thrust bearing assembly 170 is coupled to (and engaged with) the orbiting scroll 130 to limit and / or control the axial position of the orbiting scroll 130 relative to the fixed scroll 120. In this embodiment, three thrust bearing assemblies 170 are evenly angularly distributed in a triangular configuration about the central axis of rotation of the orbiting scroll 130 (as further shown in FIG. 3) to provide a steady axial force to the orbiting scroll 130. The exact structure of each thrust bearing assembly is described in more detail below with reference to FIG. 2.

[0026] FIG. 2 is a schematic diagram (not to scale) showing an enlarged cross-sectional view of thrust bearing assembly 170 of non-contact scroll pump 100.

[0027] Thrust bearing assembly 170 includes a first plate 171, a second plate 172, a first ball bearing cage 173a, a second ball bearing cage 173b, a plurality of ball bearings 174, an adjustment pin 175, and a casing 176. These structures enable thrust bearing assembly 170 to provide axial support to orbiting scroll 130 while also assisting orbiting scroll 130 during operation, as described in more detail below.

[0028] Each of the first and second plates 171, 172 has a first side facing the orbiting scroll 130 and a second side opposite the first side facing away from the orbiting scroll 130. Similarly, each of the first and second ball bearing cages 173a, 173b has a first side facing the orbiting scroll 130 and a second side opposite the first side facing away from the orbiting scroll 130. The first side of the first plate 171 is fixed to the back surface of the orbiting scroll 130 and the second side of the first plate 171 is fixed to the first side of the first ball bearing cage 173a. The second side of the first ball bearing cage 173a is spaced from the first side of the second ball bearing cage 173b by ball bearings 174, thereby allowing relative movement of the first and second ball bearing cages 173a, 173b. A second side of the second ball bearing cage 173b is fixed to a first side of the second plate 172. A second side of the second plate 172 engages an end of an adjustment pin 175.

[0029] Each of the first and second ball bearing cages 173a, 173b includes a plurality of holes within which a plurality of ball bearings 174 are disposed. Each hole of the first ball bearing cage 173a overlaps a corresponding hole of the second ball bearing cage 173b to form a plurality of hole pairs. Each hole pair accommodates a single ball bearing 174. The hole overlap allows the first and second bearing cages 173a, 173b to accommodate the orbiting movement of the orbiting scroll 130 during operation while limiting the movement of the ball bearings 174. This is further shown in FIG.

[0030] The plurality of ball bearings 174 are sandwiched between the first and second plates 171, 172 such that each of the first and second plates 171, 172 contacts a ball bearing 174. Each of the plurality of ball bearings 174 is received within a respective pair of holes in the first and second ball bearing cages 173a, 173b. The plurality of ball bearings 174 may be formed from steel or ceramic.

[0031] During operation, the plurality of ball bearings 174 roll against the first and second plates 171, 172 in pairs of holes in the first and second ball bearing cages 173a, 173b to assist in the orbiting scroll 130 orbiting. During operation of the scroll pump 100, the first plate 171 and the first ball bearing cage 173a are fixed to each other and to the orbiting scroll 130 and move together with the orbiting scroll 130. Thus, during operation, the first plate 171, the first ball bearing cage 173a, and the orbiting scroll 130 all move together against the second plate 172 and the second ball bearing cage 173b on the plurality of ball bearings 174.

[0032] The adjustment pin 175 extends axially between the housing portion 110 and the second plate 172 of the scroll pump 100. A first end 175a of the adjustment pin 175 is attached to the housing portion 110, and a second end 175b of the adjustment pin 175 opposite the first end 175a is engaged to a second side of the second plate 172. The first end 175a of the adjustment pin 175 is threaded and coupled to the housing portion 110 via a corresponding threaded nut 175c. The threaded nut 175c is on the first end 175a of the adjustment pin 175 and is rotatable on the threads of the first end 175a to adjust the axial position of the adjustment pin 175, thereby facilitating control of the axial position of the orbiting scroll 130 via the remainder of the thrust bearing assembly 170.

[0033] The second end 175b of the adjustment pin 175 is located in a tapered recess 172a provided in the second side of the second plate 172. The tapered recess 172a has a generally conical shape. More specifically, the second end 175b of the adjustment pin 175 includes a rounded surface that engages with a surface of the second side of the second plate 172 that defines the tapered recess 172a. In this manner, the rounded surface of the second end 175b of the adjustment pin 175 and the surface that defines the tapered recess 172a together form a ball and socket joint, which allows the second plate 172 and the second ball bearing cage 173b to articulate / rotate on the first end 175b of the adjustment pin 175.

[0034] The adjusting pin 175 has the same coefficient of thermal expansion as the housing portion 110 to prevent changes in ambient temperature from causing the housing portion and the adjusting pin 175 to expand at different rates, which would cause an undesirable offset in the axial position of the orbiting scroll 130. During operation of the scroll pump 100, the orbiting scroll 130, the first plate 171, the second plate 172, the ball bearing cages 173a, 173b, and the ball bearings 174 all heat up at a rate significantly greater than the rate at which the housing portion 110 heats up. The adjusting pin 175 is in thermal contact with the second plate 172, and therefore in thermal contact with the hotter components of the scroll pump 100. It is desirable for the adjusting pin 175 to heat up at substantially the same rate (i.e., slower than the second pad 172) in the housing portion 110 so that the thermal expansion of the adjusting pin 175 can be matched to the thermal expansion of the housing portion 110. Again, this is to prevent undesirable offset of the axial position of orbiting scroll 130 during operation of scroll pump 100.

[0035] To match the thermal expansion rate of the adjustment pin 175 to that of the housing portion 110 during operation, the adjustment pin 175 further comprises a hollow section 300. The hollow section 300 extends axially from the second end 175b such that the second end 175b has enough material remaining (e.g., at least 1 mm thick) to withstand the axial force from contact with the second plate 172. The hollow section 300 acts as an insulating thermal break that reduces the transfer of heat from the second plate 172 to the adjustment pin 175 as a whole. This tends to help thermally insulate the adjustment pin 175 from the second pad 172, so that the adjustment pin 175 remains at substantially the same temperature as the housing portion 110. Because the adjustment pin 175 and the housing portion 110 have the same thermal expansion rate, they expand at substantially the same rate.

[0036] In this embodiment, the hollow section 300 is cylindrical, however, it should be understood that other shapes may be used so long as the hollow section 300 functions as an adequate thermal break.

[0037] As an alternative or additional thermal break for the hollow section 300, the thrust bearing assembly 170 may include one or more inserts (not shown) disposed between the second end 175b of the adjustment pin 175 and the second plate 172. The one or more inserts act as a physical barrier, thereby providing a thermal break and helping to reduce heat transfer from the second plate 172 to the adjustment pin 175. The one or more inserts may be formed from a steel or a ceramic material.

[0038] The casing 176 surrounds the adjustment pin 175 and acts as a barrier to prevent escape of the lubricant (e.g., oil or grease) used in the ball bearing 174, the first and second bearing cages 173a, 173b, and the first and second plates 171, 172. In this embodiment, the casing 176 has a bellows shape.

[0039] 3 is a schematic diagram (not to scale) illustrating a perspective view of multiple thrust bearing assemblies 170 of non-contact scroll pump 100. As shown, in this embodiment, scroll pump 100 includes three thrust bearing assemblies 170 that are evenly angularly distributed in a triangular configuration about the central axis of rotation of orbiting scroll 130 to provide a steady axial force to orbiting scroll 130.

[0040] FIG. 4 is a schematic diagram (not to scale) illustrating an enlarged perspective view of a portion of the thrust bearing assembly 170 of the non-contact scroll pump 100. Specifically, FIG. 4 illustrates an enlarged view of the first and second ball bearing cages 173a, 173b of the thrust bearing assembly 170. As shown, each hole in the first ball bearing cage 173a overlaps with a corresponding hole in the second ball bearing cage 173b to form a plurality of hole pairs. Each of the ball bearings 174 is disposed within a respective hole pair (only one ball bearing 174 is depicted in FIG. 4).

[0041] The non-contact scroll pump 100 described above can be used as part of a vacuum pumping system that may include multiple pumps and / or other components.

[0042] It will be appreciated that various modifications / variations can be made to the above-described embodiments without departing from the scope of the present invention.

[0043] In the embodiment described above, the scroll pump includes three separate thrust bearing assemblies, however, in other embodiments, the scroll pump includes a different number of thrust bearing assemblies, for example, only one, only two, or four or more thrust bearing assemblies.

[0044] In the above described embodiment, the thrust bearing assembly comprises multiple ball bearings, however, in other embodiments, the thrust bearing assembly comprises only one ball bearing.

[0045] In the embodiment described above, the thrust bearing assembly includes a ball bearing cage that restricts the movement of the ball bearings. However, in other embodiments, the ball bearing cage is omitted.

[0046] In the embodiment described above, elongated alignment pins are used to couple the housing to the second plate, however, in other embodiments, different types of coupling structures, for example, different types of elongated members, can be used. [Explanation of symbols]

[0047] 100 Non-contact scroll pump 110 Housing 120 Fixed Scroll 122 Base of fixed scroll 124 Fixed Scroll Spiral Wall 130 Swivel Scroll 132 Rotating Scroll Base 134 Spiral Wall of the Rotating Scroll 140 Drive shaft 150 Actuator 160 Main bearing assembly 170 Thrust bearing assembly 171 First Plate 172 Second Plate 172a Recess 173a first ball bearing cage 173b Second ball bearing cage 174 Ball Bearings 175 Adjustment pin 175a first end of adjustment pin 175b second end of adjustment pin 175c nut 176 Casing 300 Hollow Section

Claims

1. A non-contact scroll pump, Housing and an orbiting scroll disposed within the housing; a thrust bearing assembly disposed within the housing for axially supporting the orbiting scroll; The thrust bearing assembly comprises: a first plate fixed to the orbiting scroll; a second plate spaced from the first plate; and a ball bearing disposed between the first plate and the second plate, the ball bearing configured to roll relative to the first and second plates during orbiting of the orbiting scroll; and a coupling structure extending between the housing and the second plate and coupling the housing to the second plate; Equipped with The coupling structure includes a thermal break for reducing heat transfer from the second plate to the coupling structure during operation of the non-contact scroll pump.

2. 2. The non-contact scroll pump of claim 1, wherein the coupling structure comprises a pin including a hollow section, the hollow section extending axially from near an end of the pin that contacts the second plate, and the thermal break is provided at least in part by the hollow section.

3. 3. The non-contact scroll pump of claim 2, wherein the pins have the same coefficient of thermal expansion as the section of the housing through which they extend.

4. 4. The non-contact scroll pump of claim 1, wherein the coupling structure comprises one or more inserts disposed between the second plate and a remainder of the coupling structure, and the thermal break is provided at least in part by the one or more inserts.

5. a first ball bearing cage sandwiched between the first plate and the second plate; a second ball bearing cage sandwiched between the first plate and the second plate; Further equipped with 5. The non-contact scroll pump of claim 1, wherein the first and second ball bearing cages contain the ball bearings and limit movement of the ball bearings.

6. 6. The non-contact scroll pump of claim 5, wherein said first ball bearing cage is fixed to said first plate and said second ball bearing cage is fixed to said second plate.

7. each of the first and second ball bearing cages has a hole, the hole of the first ball bearing cage overlapping with the hole of the second ball bearing cage; 7. A non-contact scroll pump as claimed in claim 5 or 6, wherein the ball bearings are housed within the overlapping bores of the ball bearing cage.

8. The non-contact scroll pump comprises three thrust bearing assemblies; Each of the three thrust bearing assemblies comprises: a first plate fixed to the orbiting scroll; a second plate spaced from the first plate; and a ball bearing disposed between the first plate and the second plate, the ball bearing configured to roll relative to the first and second plates during orbiting of the orbiting scroll; and a coupling structure extending between the housing and the second plate and coupling the housing to the second plate; Equipped with the coupling structure includes a thermal break for reducing heat transfer from the second plate to the coupling structure during operation of the non-contact scroll pump; 8. The non-contact scroll pump of claim 1, wherein the three thrust bearing assemblies are evenly angularly distributed in a triangular configuration about the axis of rotation of the orbiting scroll.

9. 9. The non-contact scroll pump according to claim 1, wherein the coupling structure is for adjusting the axial position of the orbiting scroll.

10. 10. A vacuum pumping system comprising a plurality of vacuum pumps, one of which is a non-contact scroll pump according to any one of claims 1 to 9.

11. Use of the non-contact scroll pump according to any one of claims 1 to 9 for pumping a fluid.

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