Compliant foil thrust bearing

Abstract

The compliant foil thrust bearing subassembly includes a fluid plate including an annular mating ring and a plurality of fluid foil elements arranged radially inward from the fluid plate mating ring, a force transfer plate including an annular mating ring and a plurality of force transfer elements arranged radially inward from the force transfer plate mating ring, and a spring plate including an annular mating ring and a plurality of flexure elements arranged radially inward from the spring plate mating ring, the fluid plate, force transfer plate, and spring plate being stacked such that each fluid foil element is axially supported by a corresponding set of overlapping force transfer elements and flexure elements.

Description

Technical Field

[0001] The subject matter disclosed herein generally relates to compliant foil thrust bearings.

Background Art

[0002] Microturbines are used as distributed energy sources and can convert fuel into a local power source by being utilized in compressors, combustors, turbines, and generators. Since microturbines operate at high temperatures, bearings such as conventional oil-hydrostatic bearings are not practical, but air bearings can be used because of their high rotational speeds. Also, by not using oil, simplification of the design and reduction of maintenance are achieved.

[0003] While a radial bearing supports a radial load, a thrust bearing supports an axial load. A compliant fluid foil thrust bearing utilizes a fluid plate having a thrust plate, a compliant spring foil member axially supported by the thrust plate, and a fluid foil element for axially supporting a thrust disk that is axially supported by the spring foil member and rotates through the remaining plate.

[0004] After spin-up, the rotating thrust disk is axially supported by a thin layer of fluid formed between the non-rotating fluid plate and the rotating thrust disk, generating a low-friction hydrodynamic air bearing, and furthermore, heat conduction is promoted by the movement of the fluid.

[0005] While the thrust disk is generally flat, the fluid foil elements are generally circumferentially inclined and stepped, and this circumferential surface inclination results in the generation of a fluid film and an axial lifting effect on the thrust disk. Thus, the axial load applied from the rotating thrust disk is transmitted to the thrust plate through the fluid film, fluid plate, and compliant spring foil member, giving an axial force in the opposite direction equivalent to the axial load applied to the bearing. The presence of the fluid film in this force transmission path can significantly reduce the frictional losses that may occur due to relative rotation between the surfaces.

[0006] By adopting the compliant fluid foil thrust bearing in a microturbine, problems that cannot be solved by conventional bearings with high rotational speeds and operating temperatures can be solved.

[0007] Existing designs of fluid foil thrust bearings generally use a series of independent plates and sometimes non-planar features to provide a resilient spring effect. Such existing designs not only make manufacturing overly complex but also have problems in terms of performance, such as excessive frictional force occurring especially at low revolutions per minute.

[0008] Therefore, it is desirable to provide a fluid foil thrust bearing that solves one or more of the above-mentioned deficiencies in existing designs.

Brief Description of the Drawings

[0009] The disclosed mechanism is further described below by way of example and with reference to the accompanying drawings. Figure 1 is an exploded perspective view showing an example of a compliant thrust bearing including a compliant thrust bearing subassembly and a thrust plate. Figure 2 shows an example of a fluid plate including fluid foil elements. Figure 3 shows an example of a force transmission plate including a force transmission element extending radially inward. Figure 4 shows an example of a spring plate with a flexure element extending radially inward. Figure 5 shows an example of a thrust plate including an axially recessed concave surface. Figure 6a shows an example of a compliant thrust bearing, and Figure 6b is a perspective view of the same through the plate. Figures 7a and 7b are another view of the compliant thrust bearing, showing a state in which a cut is made in the fluid foil plate to expose the lower plate. Figures 8a and 8b are an example of the lower surface of a compliant foil thrust bearing subassembly, showing the states in which the retaining tabs are respectively in the extended position and the folded position. Figures 9A and 9B are exaggerated views showing an example of the interaction between the support of the thrust plate and the flexure element of the spring plate. **DETAILED DESCRIPTION OF THE INVENTION**

[0010] Figure 1 shows an example of a compliant foil thrust bearing including a compliant foil thrust bearing subassembly 100 and a thrust plate 200.

[0011] The compliant foil thrust bearing subassembly 100 includes a fluid plate 110, a force transfer plate 120, and a spring plate 130.

[0012] As shown in Figure 1, the force transfer plate 120 and the spring plate 130 are at least substantially planar. While the fluid foil plate 110 may include out-of-plane features, the force transfer plate 120 and the spring plate 130 may be planar. In the illustrated example, the force transfer plate 120 and the spring plate 130 are formed with a fixed cross-sectional shape. The provision of planar and axially uniform plates in the compliant foil thrust bearing provides a significant simplification in manufacturing. In particular, the plates may be formed as cutouts from sheet metal.

[0013] In the example shown, the plates of the compliant foil thrust bearing assembly 100 are arranged to share a common axis passing through their centers. In the example of FIG. 1, this common axis extends vertically through the center of the plate. The thrust plate 200 is arranged to share this common axis.

[0014] The fluid foil elements 114 may be evenly arranged on the circumference of the annular fitting ring 112. The fluid foil elements 114 may be formed in pairs that are radially opposed, as shown in FIG. 2. Such a symmetric distribution, in particular in combination with the correspondingly distributed force transmission elements 124 and deflection elements 134, facilitates uniform circumferential load distribution and helps prevent any local stress concentrations that would otherwise increase losses and wear.

[0015] FIG. 2 shows a fluid plate 110 suitable for receiving a rotating thrust disk. The fluid plate 110 includes an annular fitting ring 112 and fluid foil elements 114 arranged radially inward from the fitting ring 112 of the fluid plate. The fluid foil elements 114 are arranged to provide an axial undulation in the circumferential direction. This circumferential undulation serves to generate a fluid film during the rotation of an adjacent thrust disk, and this fluid film is for axially supporting the rotating thrust disk.

[0016] The axial force applied to the upper surface of the fluid plate by the rotating thrust disk is not constant both during startup and normal operation. In response to such load fluctuations, the thrust bearing responds by providing compliance, i.e., a restoring force, in the form of a spring mechanism coupled to the lower surface of the fluid plate.

[0017] The fluid plate 110 may include notches 118 for receiving tabs provided at its radially outer end. Alternatively, the fluid plate 110 may include tabs (not shown) received by corresponding notches provided at the radially outer ends of one or more underlying plates. This notch and tab arrangement facilitates retention between one or more plates of the thrust bearing subassembly 100.

[0018] FIG. 3 shows a force transmission plate 120 comprising an annular fitting ring 122 and a force transmission element 124 disposed radially inward of the annular fitting ring 122. The force transmission element 124 may extend radially inward from the annular fitting ring 122.

[0019] As will be described in detail below, each force transmission element 124 may include a through hole 126. As shown in this example, each force transmission element 124 may be configured by a grid forming open 126a and / or closed 126b through holes.

[0020] As shown, the force transmission plate 120 may include notches 128 provided at its radially outer end for receiving tabs.

[0021] FIG. 4 shows a spring plate 130 comprising an annular fitting ring 132 and a flexure element 134 disposed radially inward of the annular fitting ring 132. The flexure element 134 may extend radially inward from the annular fitting ring 132.

[0022] The force transmission plate 120 and the spring plate 130 of the thrust bearing sub-assembly 100 together facilitate the transmission of the axial load generated by the fluid foil elements 114 of the fluid plate 110. In particular, each of the circumferentially spaced fluid foil elements 114 may be supported by a corresponding set of axially overlapping force transmission elements 124 and flexure elements 134. As shown in FIG. 7a, the overlapping sets of force transmission elements and flexure elements may be composed of offset circumferential and / or radial portions, i.e., the offset circumferential and / or radial portions of the force transmission elements are offset from or do not overlap those of the flexure elements.

[0023] In the specific example of FIG. 7a, the force transmission element 124 comprises circumferential and radial portions connected to each other, and the corresponding flexure element 134 comprises a radial portion connected to each other. The radial portion 4 of the force transmission element 12 is circumferentially offset with respect to the radial portion of the flexure element 134, and the circumferential portion of the force transmission element 124 is arranged to contact the radial portion of the flexure element 134. This overlapping contact supports the axial load applied by the circumferentially spaced fluid foil elements 114 of the fluid plate 110, thereby facilitating the transmission of the axial force through the force transmission and spring plates 120 and 130 of the sub-assembly 100 in a circumferentially spaced region. It will be recognized that other forms of overlapping contact between the force transmission element 124 and the flexure element 134 are possible.

[0024] The force transmission element 124 and the flexure element 134 may be circumferentially separated, thereby facilitating the provision of axially spaced axial support channels within the thrust bearing during lamination.

[0025] As will be described in more detail below, each flexure element 134 may include a radially extending portion 135. These radially extending portions may be arranged to overlap with the axial through holes 126 provided in the force transmission element 124, and the axial through holes 126 may be arranged to overlap with the radially extending portions 135. This facilitates the resilient deflection of the flexure element.

[0026] Each flexure element 134 and / or each force transmission element 124 may be composed of a grid that forms open and / or closed through holes 126, 136. In the illustrated example, only closed through holes exist in the flexure element 124, but it will be recognized that it is also possible to provide further open through holes as shown with respect to the force transmission element 124 of the force transmission plate 120.

[0027] The spring plate 130 is composed of a notch 138 provided at its radially outer end and can receive tabs from the upper or lower plate.

[0028] In the illustrated example, the spring plate 130 includes tabs 138. The tabs 138 are arranged to wrap around the notches of the stacked force transmission plate 120 and the fluid plate 110, firmly holding the plates of the thrust bearing subassembly 100 together.

[0029] Also, the fluid plate 110 may be composed of tabs arranged to wrap around the notches of the force transmission plate and the spring plate.

[0030] FIG. 5 shows a thrust plate 200 having an annular mating surface 242 and a concave surface 244 disposed radially inwardly of the annular mating surface 242. The concave surface 244 is axially recessed from the annular mating surface 242. In the illustrated example, the annular mating surface 242 extends axially further than the concave surface 244. Thus, the thickness of the thrust plate 140 is radially non-uniform in that the thickness of the radially outer portion constituting the annular mating surface 242 is greater than the thickness of the radially inner portion including the concave surface 244.

[0031] This is in contrast to prior art arrangements where a substantially flat thrust plate 140 is provided.

[0032] Providing the concave surface 244 axially provides an opportunity for the upper flexure element 134 to extend axially beyond the annular mating surface 242 towards the thrust plate 140.

[0033] By facilitating such axial deflection of the flexure element 134, compliance can be provided by the spring plate. In this way, the flexure element 134 is considered to act as a cantilever beam extending radially inwardly.

[0034] Each fluid foil element 114 may be axially supported by a set underlying the overlapping force transmission element 124 and flexure element 134. Thus, a load applied via a fluid film from a rotating thrust disk (not shown) may be transmitted via the fluid foil element 114, through the corresponding force transmission element 124, to the corresponding flexure element 134, which is elastically deflected axially towards the thrust plate 140 and may be adapted to enter a recess space formed by a recess provided in the thrust plate.

[0035] In the illustrated example, the thrust plate 140 includes a support 246 disposed radially inward from the annular mating surface 242. The support may have the same height as the height of the annular mating surface, that is, the support may terminate at an axial position substantially located within the plane defined by the annular mating surface 242.

[0036] The support 246 may include a convex surface for contacting the upper flexure element 134. By providing such a convex surface, the bending of the flexure element 134 about one or both sides of each support is facilitated.

[0037] The depth of the recess 244 and / or the support 246 serves to limit the deflection of the axial flexure element 134. In this case, the flexure element 134 is arranged to deflect on one or both sides of each support 246. For example, if the support 246 is provided radially outside the radially inner end of the flexure element 134, the flexure element may bend both outside and inside the support 246, while if the support 246 is substantially arranged at the radially inner end of the flexure element 134, the flexure element 134 may bend outside the support 246. Axially, the concave surface 244 may serve to limit the deflection of the flexure element 134 by contact therebetween after sufficient deflection of the flexure element 134.

[0038] In the example of the figure, the support 246 is annular and concentric. However, the support 246 may be in other forms. For example, the support 246 may extend annularly under each flexure element 134 and may optionally have an annular discontinuity between the supports. Alternatively, the support 246 may take the form of other shapes such as rods. Providing an annular support facilitates manufacturing.

[0039] Supports 346 may be provided disposed under each flexure element 124.

[0040] One or more supports 246 may be arranged to be disposed radially outside the radially inner end of each flexure element 134. One or more supports 246 may be disposed radially inside the mating surface 132 of the spring plate 130 and radially outside the radially inner end of the spring plate 130.

[0041] As shown in FIG. 7A, the force transmission element 124 may have circumferential and radial portions connected to each other. The corresponding underlying flexure element 134 may include a radial portion arranged to extend between the radial portions of the force transmission element 124. The circumferential portion of the force transmission element 124 may be arranged to contact the radial portion of the flexure element 134. The support 246 may include a circumferential portion arranged to extend between the circumferential portions of the force transmission element 124 and to contact the radial portion of the flexure element 134. In this way, force transmission is performed by overlapping circumferential / radial contacts.

[0042] The downward axial load applied to the force transmission element 124 may be transmitted to the flexure element 134 via the circumferential portion of the force transmission element 124, contact the radial portion of the flexure element 134, contact the circumferential portion of the support 134, and be arranged to deflect axially in the axially recessed region 244 of the thrust plate 200.

[0043] FIGS. 9a and 9b are exaggerated radial cross-sectional views showing the layer structure of a compliant foil thrust bearing including the compliant foil thrust bearing subassembly 100 and the thrust plate 200.

[0044] From bottom to top in the Z direction shown in FIGS. 9a and 9b, the concave surface 244, the support 246, the flexure element 134, the force transmission element 124, and the fluid foil element 114 are shown.

[0045] In this example, the load applied via the fluid film formed on the fluid foil element 114 by the rotating thrust disk is transmitted from the fluid foil element 114, via the corresponding force transmission element 124, to the corresponding flexure element 134, one or more portions of which flex on the support 246 so as to enter the axial through-hole 126, such axial flexure being shown in the change from FIG. 9a to FIG. 9b.

[0046] FIGS. 6a and 6b are perspective views of a compliant foil thrust bearing 300 and its plate, respectively.

[0047] Similarly, FIGS. 7a and 7b show the compliant foil thrust bearing 300, which has a cutout portion 310 showing the concave surface 244, the support 246, the flexure element 134, the force transmission element 124, and the fluid foil element 114.

[0048] The cutout portion 310 shows the relative interaction between the compliant foil thrust bearing subassembly 100 and the plate of the thrust plate 200 in this example of the compliant foil thrust bearing 300.

[0049] As is apparent from considering FIGS. 6a, 6b, 7a, and 7b, the fluid plate 110, the force transmission plate 120, and the spring plate 130 may be vertically stacked such that the fluid foil element 114, the force transmission element 124, and the flexure element 134 are circumferentially aligned with each other in an axially overlapping relationship.

[0050] Thus, the plates of the subassembly 100 may be stacked such that each fluid foil element 114 is axially supported by a set of corresponding axially overlapping force transmission elements 124 and flexure elements 134.

[0051] In the example shown in FIG. 1, the fluid plate 110 overlaps the force transmission plate 120, and the force transmission plate 120 overlaps the spring plate 130. Also, when the subassembly 100 and the thrust plate 200 are combined, the spring plate overlaps the thrust plate 200.

[0052] The expected stacking order in the example of FIG. 1 is that the spring plate 130 is disposed on the thrust plate 200, the force transmission plate 120 is disposed on the spring plate 130, and finally the fluid plate 110 is disposed on the force transmission plate 120. During or after stacking, the plates can be oriented such that the fluid foil element 114 is axially supported by corresponding pairs of overlapping force transmission elements 124 and flexure elements 134.

[0053] The plates can be oriented such that each fluid foil element 114 overlaps the corresponding force transmission element 124, and the force transmission element 124 overlaps the corresponding flexure element 134. In this way, the force transmitted from each fluid foil element 114 may be transmitted to the corresponding flexure element 134 via the corresponding force transmission element 124. The force applied to the flexure element 134 may axially displace the flexure element 134 relative to the spring plate fitting ring 132. The direction of displacement is away from the fluid plate 110 axially.

[0054] Among the prior arts, there are those in which a corrugated foil is implemented to promote compliance that tends to undergo plastic deformation during use. According to the example described herein, the force transmission mechanism disclosed herein promotes the possibility of preventing such plastic deformation.

[0055] In the examples disclosed herein, a compliant foil thrust bearing subassembly 100 is provided for direct positioning on a thrust plate 200 that provides a minimum number of plates, thus reducing manufacturing complexity and performance variability compared to cases where a greater number of plates are employed.

[0056] In particular, attention should be paid to the interaction between the force transmission element 124 and the corresponding flexure element 134.

[0057] In particular, as shown in these figures, the force transmission element 124 and / or the flexure element 134 may include axial through-holes 126, 136. These axial through-holes may be open and / or closed axial through-holes. The force transmission element 124 and / or the flexure element 134 may constitute a grid including axial through-holes. For example, each force transmission element 124 may include a grid defining an axial through-hole 126.

[0058] The flexure element 134, or at least a part thereof, may be disposed extendably within the axial through-hole 126 of the force transmission element 124.

[0059] Referring to FIGS. 9a and 9b, the axial through-hole 126 provided in the force transmission element 124 facilitates the axial displacement of the flexure element 314 into the through-hole 126 formed in the force transmission element 124.

[0060] Each force transmission element 124 may include a force transmission element grid, and each corresponding flexure element 134 may include an overlapping and offset flexure element grid. By overlapping and offsetting the force transmission element and flexure element grids in this way, relative displacement between them in the axial direction is promoted for the purpose of elastically transmitting loads and providing compliance in a compliant foil thrust bearing.

[0061] The examples provided herein show the shapes of the specific force transmission element 124 and the flexure element 134, but it will be recognized that the overall principle is applicable to a wide variety of variations in shape.

[0062] The support 246 of the thrust plate 200 may be arranged to axially overlap with the axial through-hole 126 of the force transmission plate 120 and / or the axial through-hole 136 of the spring plate 130, as particularly seen in FIGS. 7a and 7b.

[0063] The radial portion of the flexure element 134 may be arranged to axially overlap with the axial through-hole 125 of the force transmission plate 120, as shown in FIGS. 7a and 7b.

[0064] Thus, the support 246 of the thrust plate 200 and / or a part of the flexure element 134 and a part of the force transmission element 124 may axially engage to provide a gap through which a part of the flexure element 134 can extend. Such an extension facilitates relative movement between the plates and provides a restoring force.

[0065] In the examples shown in FIGS. 7a and 7b, the force transmission element 124 comprises radially extending portions interconnected by circumferentially extending portions. The force transmission element 124 overlaps the underlying flexure element 134. The flexure element 134 comprises a radially extending portion arranged to extend between the radially extending portions of the corresponding force transmission element 124. The circumferentially extending portion of the force transmission element 124 contacts the radially extending portion of the underlying corresponding flexure element 134. The annular support 246 of the underlying thrust plate 200 extends between the circumferential portions of the force transmission element 124. Such an interconnected configuration promotes excellent restoring characteristics that are highly configurable for individual applications.

[0066] Figures 8a and 8b show the tab 138 of the spring plate 130 in an extended state and a folded state. In this way, the plates can be stacked together, and the tab 138 is folded over the remaining plates to hold its position.

[0067] As shown in FIGS. 9a and 9b, the force transmission plate 120 may have a thickness greater than that of the spring plate 130 and optionally greater than that of the fluid plate 110. It has been confirmed that by providing a force transmission plate with a thickness greater than that of the spring plate, it is possible to prevent a performance degradation associated with the distortion of the force transmission plate. The force transmission plate with increased thickness helps to evenly distribute the force transmitted to a wider working area of the fluid plate.

[0068] The fluid plate may be configured with a thickness between 0.076 and 0.127 mm. The force transmission plate 120 may be configured with a thickness of 0.1 - 0.25 mm, or 0.127 - 0.25 mm. The spring plate 130 may be configured with a thickness of 0.076 - 0.127 mm.

[0069] Each example disclosed herein, including the claimed examples, may be provided in a gas turbine system, such as a microturbine system, that includes a compliant foil thrust bearing according to any one of the examples. By employing such a compliant foil thrust bearing in a gas turbine system, friction loss and heat management can be improved, and manufacturing can be simplified, thereby providing a gas turbine system with improved performance characteristics.

[0070] It will be recognized that the examples disclosed herein are not limiting and that numerous changes and substitutions are possible.

Claims

1. A compliant foil thrust bearing subassembly, and a thrust plate coupled to the compliant foil thrust bearing subassembly, comprising a compliant foil thrust bearing, wherein the compliant foil thrust bearing subassembly comprises a fluid plate having an annular mating ring and a plurality of fluid foil elements disposed radially inwardly of the fluid plate mating ring, a force transmission plate having an annular mating ring and a plurality of force transmission elements disposed radially inwardly of the force transmission plate mating ring, and a spring plate having an annular mating ring and a plurality of flexure elements disposed radially inwardly of the spring plate mating ring, wherein the fluid plate, the force transmission plate, and the spring plate are stackable such that each fluid foil element is axially supported by a corresponding pair of overlapping force transmission elements and flexure elements, the thrust plate comprises an annular mating surface, and a concave surface disposed radially inwardly of the annular mating surface, wherein the flexure elements include a radially extending portion, the force transmission elements include a radially extending portion disposed between the radially extending portions of the corresponding flexure elements, and the force transmission elements include a circumferentially extending portion disposed to contact the radially extending portion of the flexure element, a compliant foil thrust bearing.

2. The force transmission element comprises an axial through hole, the compliant foil thrust bearing according to claim 1.

3. The flexure element comprises a portion disposed to overlap the axial through hole of the corresponding force transmission element, the compliant foil thrust bearing according to claim 2.

4. The force transmission plate is substantially planar and / or the spring plate is substantially planar, the compliant foil thrust bearing according to any one of claims 1 to 3.

5. The thrust plate comprises one or more supports extending axially from the concave surface the compliant foil thrust bearing according to claim 1.

6. Each support extends in an annular direction, the compliant foil thrust bearing according to claim 5.

7. Each support includes a convex surface, ​ ​ The compliant foil thrust bearing according to claim 5 or 6.

8. Each support extends in the axial direction from the concave surface to a position substantially lying in a plane defined by the annular fitting surface. The compliant foil thrust bearing according to any one of claims 5 to 7.

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