MXPA01007362A - Foil thrust bearing with varying circumferential and radial stiffness - Google Patents

Abstract

An improved foil thrust bearing having a thrust runner and a thrust plate includes an underspring element positioned adjacent to the thrust plate. The underspring element comprises, in one embodiment, a plurality of alternating first apertures and spring portions, with at least one spring portion having a periodic configuration and comprising a leading edge and a trailing edge. The periodic configuration is defined by a plurality of pitches that vary between the leading and trailing edges. Also defining the periodic configuration is a plurality of periodic elements that vary in longitudinal length between the leading and trailing edges. A thrust bearing disk is disposed intermediate the underspring element and the thrust runner. The disk comprises a plurality of transition areas that provide a stepped configuration to the disk. The transition areas match a plurality of circumferential positions of the first apertures in the underspring.

Description

LEAF PUSH BEARING, WITH RIGIDECES CIRCUNFERENTIAL AND RADIAL VARIANTS BACKGROUND OF THE INVENTION The present invention relates, generally, to bearings and, more particularly, to leaf thrust bearings. The easy availability of the ambient atmosphere, such as a bearing fluid, makes the fluid bearings particularly attractive for high-speed rotating machinery. Some applications may include, for example, a turbo-alternator-generator and turbocharger. The fluid bearings generally comprise two relatively mobile elements (i.e., a bearing and a runner). A predetermined spacing, between the bearing and the runner, is filled with a fluid, such as air. The sheets (or thin sheets of a docile material) disposed in the spacing are deflected by hydrodynamic film forces between the adjacent surfaces of the bearing. These sheets thus increase the hydrodynamic characteristics of the fluid bearing and also provide improved operation under extreme load conditions, when the normal bearing failure could otherwise occur. Additionally, these sheets provide the added advantage of accommodating the eccentricity of the relatively mobile elements and also providing a cushioning and cushioning effect. In order to properly place the sheets between the movable bearing elements, it has been common to mount a plurality of sheets, spaced individually, on a blade bearing disc and to place this disk in one of the bearing elements. Another common practice has been to provide rigid, docile, separate elements, or springs, under the leaves to provide the required elasticity. Examples of these typical leaf thrust bearings are shown in U.S. Patent Nos. 5,547,286; 4,871,257; 4,682,900; 4,666,106; 4,624,583; 4,621,930; 4,597,677; 4,459,047; 4,331,365; 4,315,359; 4,300,606; 4,277,113; 4,277,111 and 4,247,155. Notwithstanding the inclusion of the above design features, the load capacity of a blade thrust bearing depends on the elasticity of the bearing with the pressure exerted by a fluid film, developed between the bearing and the runner. The pressure profile for the thrust bearing varies and, in order to accommodate the optimum pressure profile and the thickness of the corresponding fluid film, associated with the maximum load capacity, the thrust bearing must be designed to provide rigidity which varies in a manner similar to the pressure profile.

The current leaf thrust bearings have a limited load capacity. This limitation results from spring designs that indicate only a limited appreciation of the variance in the pressure profile and its effect on load capacity. Some spring designs have been aimed at providing variable stiffness in the radial directions. Examples of designs for varying radial stiffness are shown in U.S. Patent Nos. 5,110,220; 4,558,106 and 4,277.12. However, they tend to provide a limited load capacity, due to excess deflection of the cushion on the spring support points. In an effort to address the foregoing limitations in the design of the spring, U.S. Patent No. 5,248,205 provides a plurality of sets of arched springs having a corrugated configuration. Rectangular slits are supplied in the individual springs, with the number, size and position of the slits being altered. Such alteration is attempted to change the radial and circumferential stiffness of the springs. However, the need for the slits with such variation makes the manufacture of the springs difficult. Another attempt to vary the rigidity, both radial and circumferential, of the spring in a blade thrust bearing is found in U.S. Patent No. ,318,366. In it, a plurality of corrugated springs are supplied in assemblies. Within any set, the springs have increasing widths towards the outer edge of the leaf. And each spring, within a set, has a width that decreases towards the guide edge of the blade. But the change configurations within each set of springs and within each individual spring make manufacturing heavy. As can be seen, there is a need for an improved blade thrust bearing. In particular, there is a need for a blade thrust bearing that provides a variable, circumferential and / or radial stiffness. A further need is for an improved blade thrust bearing that allows a circumferential stiffness that can be correlated to a variable pressure of the fluid film, developed by the bearing. Another need is for a blade thrust bearing that includes a lower spring element that can be manufactured by fewer manufacturing steps, when compared to current technology, but still provides variable stiffness. SUMMARY OF THE INVENTION In an improved blade thrust bearing, having a thrust runner and a thrust bearing disc, the present invention provides a lower spring element, operatively coupled to the disc, and this lower spring element comprises at least one spring portion, having a periodic configuration, with the spring portion comprising a guide edge and a trailing edge, and this periodic configuration being defined by a plurality of steps, varying in size, between the edges of guide and drag. Also in an improved blade thrust bearing, which carries a thrust runner and a thrust bearing disc, the present invention supplies a lower spring element, operatively coupled with the disk, and this lower spring element comprises at least one spring portion, having a periodic configuration, with the spring portion comprising a guide edge and a trailing edge, and the periodic configuration defined by a plurality of periodic elements, which vary in longitudinal size between the guide edges and of drag. These and other features, aspects and advantages of the present invention will come to be better understood with reference to the following drawings, description and claims. BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a view, with separate parts, of a blade thrust bearing, according to an embodiment of the present invention; Figure 2 is a plan view of a thrust bearing disc, which can be used in the leaf thrust bearing shown in Figure 1; Figure 3 is a plan view of a lower spring element, operatively coupled to the bearing disk shown in Figure 2; Figure 4 is a cross-sectional view of the thrust bearing, taken through line 4-4 of Figure 1, and Figure 5 is a projection of the thickness of the fluid film and the pressure versus the circumferential distance over the blade thrust bearing, shown in Figure 1. DETAILED DESCRIPTION OF THE INVENTION Figure 1 shows a blade thrust bearing 10, according to one embodiment of the present invention. This bearing 10 generally comprises the components of a thrust runner 11, a thrust bearing disc 14, a lower spring element or a stiffening element 22 of the thrust bearing, and a thrust plate 28. The above components are typically constructed of nickel-based alloys. While various applications for the bearing 10 are within the scope of the present invention, the bearing 10 is considered to have the particular benefit of a high-speed rotating machinery, such as a turbo-generator-generator and turbochargers. In more particularly describing a first embodiment of the present invention, it can be seen in Figure 1 that the thrust runner 11 engages a rotating shaft 12, whereby it causes this runner 11 to rotate in a direction of the arrow shown in FIG. Figure 1. This corridor 11 includes a runner surface 13, which faces opposite the bearing surface 15 of the push plate 28. Intermediate of the runner 11 and the push plate 28, is the thrust bearing disc 14. In this embodiment of the present invention and as shown in Figure 1, the bearing disk 14 is of the type shown in U.S. Patent No. 4,624,583. This bearing disk is annularly shaped and comprises a plurality of thrust pads or blades 16. These cushions 16 are opposite to or face the surface of the runner 13, when the components of the blade thrust bearing 10 are operatively coupled together. As illustrated in Figure 2, each of the cushions is substantially in the configuration of an annular sector, although other configurations, such as trapezoidal, may be employed. The cushions 16 are placed circumferentially around the entire surface of the bearing disc 14, which faces the surface 13 of the corridor. Therefore, each cushion 16 is described by a guide edge 17 and a trailing edge 19, as this runner 11 rotates in the direction shown in Figure 1. While the present embodiment shows the cushions 16 as being substantially equidistant from each other in a circumferential direction, the present invention considers that unequal spacing can be used. Further, although Figure 2 illustrates ten (10) cushions 16 employed, the present invention considers that more or less than ten cushions 16 may be used. The cushions or sheets 16 are alternately placed with a plurality of endures 18, as also seen in Figure 2. Therefore, and for this particular embodiment of the invention, a cushion 16 is alternately positioned with a slit 18. The function of the slits 18 is to allow the substantially unrestricted flow of the fluid (i.e. the air). which passes through the bearing disk 14 and from a fluid film between the surface 13 of the runner and the surface 15 of the bearing. In this particular embodiment, all the slits 18 are of an L-shaped configuration. It can still be seen that all the slits 18 can be of other configurations, such as those shown in U.S. Patent No. 4,624,583. Also, the slits do not need to be of the same configuration and may vary from each other. Additionally, the slits 18 can be completely suppressed and the bearing 10 can still provide acceptable performance. As best seen in Figures 2 and 4, adjacent to each slit 18 is a pair of transition areas 20, which create a stepped configuration between adjacent cushions 16 and thus, a stepped configuration over the entire bearing disk 14. Such a configuration is also further described in U.S. Patent No. 4,624,583. The bearing disk 14, in this embodiment, further includes a plurality of notches 21, positioned around the outer or circumferential edge of the bearing disk 14 and adjacent the slots 18. These notches 21 may be aligned with a plurality of notches 30 in the groove. lower spring element 22, for fixing the rotational position of the disk 14 to the lower spring 22, as described below below. This bearing disk 14 also includes a plurality of holes, which allow the pins to retain the bearing disk 14 to a bearing thrust plate or bearing housing (not shown). Figure 2 also shows the bearing disk 14 operatively coupled to the lower spring or stiffening element 22 of the thrust bearing, while Figure 3 shows the lower spring 22 in greater detail. This lower spring 22 is configured to substantially correspond to the configuration and dimensions of the bearing disk 14. In this embodiment, the lower spring element 22 comprises a plurality of spring portions 23, with each portion 23 being positioned under a respective cushion 16. As shown in Figure 3, all spring portions 23 have substantially the same configuration and dimensions, with the configuration resembling something to a parallelogram from a plan view. However, it is considered by the present invention that all spring portions 23 need not be of the same configuration and dimensions. Regardless of the particular configuration, each spring portion 23 comprises a guide edge 24 and a trailing edge 25, as determined by the direction of rotation of the runner 11. The circumferential positioning of the guide and trawl bodes, 24, 25, of any spring portion 23, are substantially the same as the locations of the guide edge 17 and the trailing edge 19 of the cushion 16, which respectively overlap the spring 23. Furthermore, although different spacings may be employed, the present embodiment has the spring portions 23 substantially equidistant from each other in their circumferential positions. This preferred embodiment of the spring portions 23 incorporates a cross-sectional configuration that is periodic, as best seen in Figure 4. While the cross-sectional configuration in Figure 4 is corrugated, other cross-sectional configurations may be used. The periodic configuration is described by a plurality of variable steps, Px to Px. In general, and as further described below, the steps are varied in size to correlate with a variable fluid film pressure that develops between the surface 13 of the runner and the bearing surface 15. In particular, the steps in any spring portion 23 decrease from the guide edge 24 and towards the drive edge 25. More specifically, with each spring portion 23 having a circumferential mid-point or, in other words, a mid-point between the guide and trailing edges, 24, 25, the step sizes decrease in a staggered manner from the edge 24 of guidance and substantially to the midpoint. From this mid-point, the sizes of the passages remain substantially equal to the trailing edge 25. For purposes of illustration, Figure 4 illustrates the stepwise decrease in step size for a single spring portion 23. A circumferential midpoint is designated as "M". The various steps have a size or distance in which Pi >; P2 P3, where P3 = P4 = P6. As noted above, the steps are varied to correlate with a variable fluid film pressure. This correlation can be explained with reference to Figure 5. The projection in Figure 5 illustrates typical operating characteristics for a blade thrust bearing in the current art. The thickness of the fluid film that develops between a thrust runner and a thrust disc typically decreases in thickness from the leading edge of the lower spring to approximately its circumferential center point. Next, the thickness of the fluid film tends to remain the same. Conversely, in the typical bearing, the pressure of the fluid film increases from the guide edge to around the midpoint and then tends to remain the same. Thus, a correlation between the force of the lower spring and the fluid pressure - requires that the spring force generally increases from the guide edge and to the circumferential mid point then, the force of the spring must remain substantially the same. To alter the force in a spring at any given point, the present invention alters the pitch around that point. Again, referring to Figure 3, the lower spring element or the stiffening element 22 of the thrust bearing is described by a center C from which a radial line R extends to the outer or circumferential edge of the lower spring 22 It can be seen that a directional line D describes an address along which the longitudinal axes of the corrugations for the spring portions 2 are placed. The direction D, in this embodiment, intersects the radial line R. From the existence of such an intersection, it can be appreciated that the spring portions 23 are placed obliquely to the actual radial lines of the lower spring 22. At the same time, the portions 2 of spring have their longitudinal axes generally perpendicular to the direction of travel of the corridor 11. The perpendicular orientation enables the rigidity of the lower spring element 22 to vary in the circumferential direction. The lower spring or stiffening element 22 further includes a plurality of first connecting elements 27, which are positioned circumferentially around an inner edge of the lower spring 22, to provide a physical connection between the adjacent spring portions 223. A pair of second connecting elements 36 is fixed between each spring portion 23 and an outer or circumferential edge area of the lower spring 22. The second connection elements 35 provide a means for securing the spring portions 23 to the remaining part of the lower spring 22. Intermediate arrangements of each pair of second connection elements 35 are a second opening 29 which is intended to allow an area finish the shape of the spring portion 23. A total of four joints (i.e., two connecting elements 27 and two connecting elements 35) are shown in Figure 3, to maintain the spring portions 23 in the proper orientation with respect to the bearing 10. However, two or three unions can also provide a sufficient restriction. Alternatively, the spring portions 23 may be welded to a separate plate, as shown in U.S. Patent No. 5,498,082. Also included in the stiffening element 22 is a plurality of first openings 26, disposed between the spring portions 23. In this way, a single opening 26 is alternately positioned with a single spring portion 23 in a circumferential manner. For this embodiment, all the first openings 26 are substantially of the same configuration and dimension, although the configurations and dimensions can be changed. The first openings 26, shown in Figure 3, are somewhat triangular and have a leg 26a extending under a portion of the spring portion 23., in order to allow an area to terminate the shape of the spring portion 23. The first openings 26 provide the physical separation between each spring portion 23. As with the bearing disk 14, the lower spring 22 includes a plurality of notches 30, located above the outer edge. These notches 30 are shaped, dimensioned and positioned circumferentially, preferably in order to coincide with the notches 21 of the bearing disk 14. Various means, such as spike pins, can then be used to rotationally secure the relative positions of the bearing disk 14 and the lower spring 22. Then, the disk 14 and the lower spring 22 can be fixed to the push plate 28. In manufacturing the lower spring or stiffening element 22 of the present invention, conventional methods may be employed. For example, most of the lower springs 22, which include the spring portions 23, can be stamped. The first and second openings 26, 31 can be formed by photochemical machining or mechanical puncture. However, it can be appreciated that, in accordance with the prior art, the present invention eliminates certain manufacturing steps. For example, to create multiple openings of multiple sizes in U.S. Patent No. 5,248,205, a relatively large number of process steps is required. On the other hand, the lower spring 22 of the present invention has a relatively small number of different openings and sizes, which can be created in a relatively small number of process steps. When the blade pushing bearing 10 is operative, the shaft 12 rotates and the runner 11 rotates similarly. As the runner 11 rotates, a fluid film is formed between the surface 13 of the runner and the bearing surface 15. For each of the cushions or sheets 16, the pressure of the fluid film increases from the guide edge 19 and the drive edge 17. At the same time, each spring portion 23 supplies the load support to its respective cushions 16. In particular, the spring portions 23 provide variable support by virtue of having elements of variable spring stiffness in a circumferential direction, the additional variance in the circumferential direction it can be accompanied by varying the direction D with respect to a radial line R. The typical design has increasing rigidity from the inside diameter to the outside diameter. Due to the particular variable stiffness, the spring portions 23 and, consequently, the cushions 16, may coincide with the variable fluid film pressure profile. In addition to varying the circumferential stiffness, the embodiment shown in Figures 3 and 4, provides variable radial stiffness. The variance in the radial direction is achieved by a plurality of notches 36, which vary the number of corrugations (i.e., the periodic elements) of different radii. As best seen in Figure 3, the notches 36 essentially represent the gap of space from a periodic element sized to the next dimensionally dimensioned element. Thus, the longitudinal sections of the corrugations by direction D are varied. Also, the periodic elements are formed in the groups of periodic elements, with each group being of different radius from the lower spring element 22. As can be understood, a greater number of corrugations in each group of periodic elements will tend to increase the rigidity, while a smaller number of corrugations in each group of periodic elements will tend to decrease the rigidity. For example purposes, in Figure 3, each spring portion 23 is shown with two notches 36. However, it should be understood that the present invention considers that the number of notches in each spring portion 23 need not be the same. Similarly, although the embodiment of Figure 3 illustrates notches 36 in each spring portion 23, it is considered that not all spring portions 23 will have notches 36. Even more, the present invention considers that the variation of the radial stiffness and the variation of the circumferential stiffness do not need to be provided simultaneously, and that only one type of stiffness can be provided. Those skilled in the art can appreciate that the present invention provides an improved blade thrust bearing and, specifically, a lower spring or stiffening element of the thrust bearing. An improved blade thrust bearing, in accordance with the present invention, provides variable circumferential rigidity, this variance can be optimized for a given application. Additionally, the present invention provides variable radial stiffness. In addition, the present invention provides the variable circumferential stiffness by a manufacturing method that eliminates the need for a large number of manufacturing steps to make several sized openings, for example in each spring portion of the lower spring or stiffening element. Also provided by the present invention is an improved combination of a bearing disk and a lower spring, which can reduce the overall manufacturing cost of the blade thrust bearing, while providing an element for variable, circumferential and radial stiffness. Of course, it should be understood that the foregoing refers to the preferred embodiments of the invention and that modifications can be made without departing from the spirit and scope of the invention, as set forth in the following claims.

Claims (25)

1. CLAIMS 1. In an improved blade thrust bearing, having a thrust runner and a thrust bearing disc, where the improvement comprises: a lower spring element, operatively coupled to the disk, this lower spring element comprises the less a spring portion, having a periodic configuration, this spring portion includes a guide edge and a trailing edge, said periodic configuration is defined by a plurality of steps, which vary in size between said guide and trailing edges .
2. 2. The improvement of claim 1, wherein the steps decrease in size from the guide edge and towards the trailing edge.
3. 3. The improvement of claim 1, wherein the steps decrease in size for the correlation with a variable fluid pressure, capable of being developed between the disc and the runner.
4. 4. The improvement of claim 1, further comprising a plurality of spring portions.
5. 5. The improvement of claim 4, further comprising a plurality of first openings, disposed between the spring portions.
6. 6. In an improved blade thrust bearing, having a thrust runner and a thrust bearing disc, where the improvement comprises: a lower spring element, operatively coupled to the disk, this lower spring element comprises at least a portion spring, having a periodic configuration, this spring portion comprises a guide edge and a trailing edge, said periodic configuration being defined by a plurality of periodic elements that vary in longitudinal size between the guide and trailing edges.
7. 7. The improvement of claim 6, wherein the periodic elements increase in longitudinal size from the guide edge and towards the trailing edge.
8. 8. The improvement of claim 6, in which the periodic elements decrease in size to correlate with the variable fluid pressure, capable of being developed between the disc and the runner.
9. 9. The improvement of claim 6, further comprising a plurality of spring portions.
10. 10. The improvement of claim 9, further comprising a plurality of first openings, disposed between said spring portions.
11. 11. In an improved blade thrust bearing, having a thrust runner and a thrust bearing disc, where the improvement comprises: a lower spring element, operatively coupled to the disk, this lower spring element comprises at least a portion of spring, having a periodic configuration, this spring portion includes a guide edge and a trailing edge, said configuration is defined by a plurality of steps, which decrease in size from the guide edge and towards the trailing edge.
12. 12. The improvement of claim 11, in which the steps decrease in size for their correlation with a variable fluid pressure, capable of being developed between the disc and the runner.
13. 13. The improvement of claim 11, wherein the steps decrease in size in a staggered manner.
14. 14. The improvement of claim 11, wherein the spring portion further comprises a circumferential mid-point and the steps decrease in size between the guide edge and said mid-point.
15. 15. The improvement of claim 14, wherein the steps are substantially equal in size, between the midpoint and the trailing edge.
16. 16. In an improved blade thrust bearing, having a thrust runner and a thrust bearing disc, the improvement comprising: a lower spring element, operatively coupled to the disk, this lower spring element comprises a plurality of portions spring, having a corrugated configuration, the spring portions each comprise a guide edge and a trailing edge, this configuration being defined by a plurality of periodic elements, which vary in longitudinal dimension, and a plurality of steps that they vary in size for their correlation with a variable fluid pressure, capable of being developed between the disc and the runner.
17. 17. The improvement of claim 16, wherein the periodic elements increase in length from the guide edge and towards the trailing edge.
18. 18. The improvement of claim 17, wherein the periodic elements are grouped into a plurality of groups of periodic elements with different radii of these lower spring elements.
19. 19. The improvement of claim 16, wherein the passages of at least one of the spring portions, decrease in size from the guide edge and substantially to a circumferential midpoint of said spring portion.
20. 20. The improvement of claim 19, wherein the passages are substantially equal in size, between the mid-point and the trailing edge of a spring portion.
21. 21. The improvement of claim 16, further comprising a plurality of first connecting elements, connecting the spring portions together.
22. 22. The improvement of claim 16, further comprising a plurality of first openings, arranged in an alternative manner with the spring portions.
23. 23. In an improved blade thrust bearing, having a thrust runner and a thrust plate, where the better comprises: a lower spring element, positioned adjacent to the thrust plate, this lower spring element comprises a plurality of first alternative openings and spring portions, at least one spring portion has a periodic configuration and includes a guide edge and a trailing edge, this periodic configuration is defined by a plurality of groups of periodic elements of variable radii of the elements of lower spring, and a plurality of steps, which vary between the guide and trailing edges; and a thrust bearing disc, intermediate intermediate the lower spring element and the thrust runner, this disc comprises a plurality of transition areas, which provide a staggered configuration to the disk. these transition areas are positioned to correspond substantially with a plurality of circumferential positions of the first openings.
24. 24. The improvement of claim 23, wherein the transition areas comprise a plurality of slits.
25. 25. A blade thrust bearing, for a rotary machine, this bearing comprises: a thrust runner; a push plate, which looks opposite the corridor; a lower spring element, operatively coupled to the thrust plate, and comprising a plurality of first alternative openings and spring portions, each spring portion having a corrugated configuration and including a guide edge and a trailing edge, this configuration being defined by a plurality of periodic elements, increasing in length from the guide edge to the trailing edge, and a step decreasing from the guide edge and substantially at a circumferential center point of each spring portion, said step is substantially constant from the midpoint to the trailing edge; and a thrust bearing disc, coupled to the lower spring element, this disc has a plurality of transition areas, which provide a stepped configuration to the disc, said transition areas being positioned to substantially correspond to a plurality of circumferential positions of the discs. first openings. SUMMARY OF THE INVENTION An improved blade thrust bearing, having a thrust runner and a thrust plate, includes a lower spring element, adjacent to the thrust plate. This lower spring element comprises, in one embodiment, a plurality of first openings and alternative spring portions, with at least one spring portion having a periodic configuration and comprising a guide edge and a trailing edge. This periodic configuration is defined by a plurality of steps, which vary between the guide and trailing edges. Also defining the periodic configuration is a plurality of periodic elements that vary longitudinally between the guide and trailing edges. A thrust bearing disc is intermediate to the lower spring element and the thrust runner. The disk comprises a plurality of transition areas, which provide a stepped configuration to the disk. The transition areas coincide with a plurality of circumferential positions of the first openings in the lower spring. 1/3 FIG. 1 FIG. J / J FIG 4 G 5