Not applicable.
This invention relates to bearing assemblies. In particular, this invention relates to bearing assemblies for aerospace applications.
Conventionally, bearing assemblies include an inner race and an outer race which is rotatable relative to the inner race. To minimize the frictional resistance to rotation, a number of rolling elements are positioned between the inner and outer races.
The rolling elements in such bearing assemblies accommodate the controlled rotation of the races relative to one another as well as any connected components to the races. For example, the inner race is often mounted to or received on a shaft and the outer race is often mounted into or received in a housing. When the shaft and housing move relative to one another, the bearing assembly provides bearing surfaces which facilitate smooth rotation and reduce frictional resistance to rotation.
Such bearing assemblies must be able to perform reliably under increasingly demanding application requirements. Traditional bearing assemblies which utilize steel components, while strong, are less than ideal for many applications. Hence, a need exists for improved bearing assemblies.
To provide an improved bearing assembly for aerospace applications, a lightweight hybrid bearing assembly has been designed which also has a structure that allows the bearing to be operated in a non-aligned condition.
According to one aspect of the invention, a lightweight hybrid bearing assembly includes an inner race and an outer race that is radially spaced from the inner race. One or both of the inner race and the outer race have a convex bearing surface. A plurality of ceramic roller elements are positioned between the inner race and the outer race. The ceramic roller elements have a concave bearing surface that engages the convex bearing surface.
The lightweight hybrid bearing assembly may be configured to be operable in a misaligned condition in which an axis of the inner race is not aligned with an axis of the outer race. Even within a range of misalignment, the bearing surfaces will remain in contact with one another.
In one form, the inner race may include an outwardly-facing convex bearing surface and the outer race may include one or more inwardly-facing convex bearing surfaces. In this form, the concave bearing surfaces of the plurality of roller elements may engage both the inwardly-facing convex bearing surface(s) of the outer race and the outwardly-facing convex bearing surface of the inner race.
The plurality of ceramic roller elements may have an hourglass shape and may be fabricated from, but not limited to, one or more of Yttria Tetragonal Zirconia Polycrystal (TZP), Yttria Tetragonal Zirconia Polycrystal H [Y-TZP(H)], silicon nitride, and silicon carbide. The plurality of ceramic roller elements may be formed from a sintered ceramic cylinder into which the concave bearing surface has been ground. The ceramic roller elements may be porous.
The inner race and the outer race may comprise titanium, titanium alloy, ceramic, or alloy steel.
Further, the ceramic roller bearings may be in various configurations. The ceramic roller elements may be in a double row annular configuration, single row annular configuration, and/or assembled as part of an assembly including a structure/housing.
In one form, the plurality of ceramic roller elements may include a pair of radially outward facing cylindrical bearing surfaces on either side of the concave bearing surface. The pair of radially outward facing cylindrical bearing surfaces may engage a pair of radially inward facing cylindrical bearing surfaces on the outer race.
According to another aspect of the invention, a method of making a lightweight hybrid bearing assembly of the type described above is also disclosed. The method includes pressing a ceramic powder into a cylindrically-shaped preform, sintering the cylindrically-shaped preform, followed by a hot iso-static process option, and then grinding a concave bearing surface into the cylindrically-shaped preform to thereby form a ceramic roller element. Once the ceramic roller element is formed, a plurality of the ceramic roller elements are positioned between an inner race and an outer race in which at least one of the inner race and the outer race has a convex bearing surface. This convex bearing surface engages the concave bearing surface of the ceramic roller elements.
Again, the ceramic roller elements may have an hourglass shape and may be fabricated from at least one of Yttria Tetragonal Zirconia Polycrystal (TZP), Yttria Tetragonal Zirconia Polycrystal H [Y-TZP(H)], silicon nitride and silicon carbide. The inner race and the outer race may comprise titanium, titanium alloy, ceramic, or alloy steel.
The plurality of ceramic roller elements made by this method may include a pair of radially outward facing cylindrical bearing surfaces on either side of the concave bearing surface. The pair of radially outward facing cylindrical bearing surfaces may engage a pair of radially inward facing cylindrical bearing surfaces on the outer race.
Thus, a lightweight hybrid bearing assembly and a related method of making the bearing assembly are disclosed. This lightweight hybrid bearing assembly provides a low weight component in contrast to traditional steel-based bearing assemblies. Further, as the ceramic roller elements have a concave surface, this allows the inner race to become misaligned with the outer race within a predetermined range of angles and still be operable. As the bearing assembly is operable over a range of misalignment angles, the bearing assembly and attached components are less likely to fail.
These and still other advantages of the invention will be apparent from the detailed description and the drawings. What follows is merely a description of some preferred embodiments of the present invention. To assess the full scope of the invention the claims should be looked to as the preferred embodiments are not intended to be the only embodiments within the scope of the claims.
The various aspects of the disclosure are now described with reference to the annexed drawings, wherein like numerals refer to like or corresponding elements throughout. It should be understood, however, that the drawings and the detailed description relating thereto are not intended to limit the claimed subject matter to the particular form disclosed. Rather, the intention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the claimed subject matter.
Referring first to
In a direction perpendicular to the direction of extension of the body 114, the head 116 has a circular opening or eye 122 into which the bearing assembly 110 is inserted. Preferably, the bearing assembly 110 will be dimensioned to have a diameter that is slightly less than the diameter of the eye 122 into which the bearing assembly 110 is received such that the bearing assembly 110 may be swaged into place in the bearing housing 112. Alternatively, the bearing assembly 110 might be lightly press fit into the eye 122 of the bearing housing 112. However, one having ordinary skill in the art will appreciate that even small amounts of deformation to the bearing assembly 110 can, in some instances, have adverse effects on the operation or life of the bearing assembly 110 and, thus, swaging is generally preferred.
As best illustrated in
A pair of shields 134 and a pair of elastomeric seals 135 are attached to the races and help to isolate the inner chamber or volume containing the roller elements 128 from the external environment. The pair of shields 134 are attached at the axial ends of the outer race 126 and are generally annularly-shaped. Each of these shields 134 are fixed with respect to the outer race 126 about their outer circumference 136. Likewise, each of the pair of elastomeric seals 135 are attached or connected to one of the collars 132. Each of the pair of elastomeric seals 135 contact one of the pair of shields 134 to form a sealing interface there between. This sealing interface performs the function of preventing the ingress of debris and other particulate matter into the volume between the inner race 124 and the outer race 126 containing the plurality of roller elements 128. Because the shields 134 are not connected to the elastomeric seals 135, the sealing interface is sliding and accommodates the movement of the inner race 124 relative to the outer race 126 while maintaining the seal. Although specific shield/seal combinations are shown, it will be appreciated that other shield/seal arrangements and improvements might be utilized in a bearing of the type disclosed.
A radial lubrication channel 140 is formed in the outer race 126 of the bearing assembly 110 which is in fluid communication with an inner chamber or volume defined by the inner race 124, the outer race 126, the pair of shields 134, and the pair of elastomeric seals 135. This radial lubrication channel 140 is aligned with a separate radially-extending lubrication channel 142 formed in the bearing housing 112, such that when a plug 144 is removed from the radially-extending lubrication channel 142, then a lubricant may be supplied to the inner chamber and bearing surfaces.
Notably, each of the roller elements 128 are formed to have a concave bearing surface 146 such that the roller elements 128 may be said to have an hourglass shape in which the diameter of the roller element 128 is smaller in the center than on either of the axial ends. As the particular bearing assembly 110 shown in
In the embodiment shown, the roller elements 128 are formed of s ceramic material. Preferably, the ceramic material may be one of Yttria Tetragonal Zirconia Polycrystal (TZP), Yttria Tetragonal Zirconia Polycrystal H [Y-TZP(H)], silicon nitride, or silicon carbide. With additional reference to
The inner race 124 and the outer race 126 are formed of a lightweight, but high strength metallic material such as titanium, titanium alloy, or alloy steel. A titanium alloy housing, in combination with the ceramic roller elements, offers a significant weight reduction over a standard steel bearing assembly. Alternatively, one or both of the races might be made of a ceramic material or coated therewith.
Referring now to
Now with reference to
Unlike the previously described bearing assemblies, the bearing assembly 310 has an outer race 326 with an outer periphery 356 which is convexly curved along the axial direction. The flanged housing 312 includes a convexly shaped inner periphery 358 which partially matches this curvature. By mounting the back side of the flanged housing 312 to a flat surface (not shown), the outer periphery 356 of the outer race 326 of the bearing assembly 310 contacts the inner periphery 358 such that upon contacting one, another their curvature holds or captures the bearing assembly 310 in place relative to the bearing housing 312 and the flat surface.
With particular reference to
Thus, a lightweight hybrid bearing assembly is disclosed. This lightweight hybrid bearing assembly provides a low weight component in contrast to traditional steel-based bearing assemblies which are comparatively heavy. Further, as the ceramic roller elements have a concave surface, this allows the inner race to become misaligned with the outer race within a predetermined range of angles and still be operable. As the bearing assembly is operable over a range of axial misalignment, the bearing assembly and attached components are less likely to fail. The rolling elements are fabricated in a unique manner from a ceramic material to have a concave bearing surface. A bearing assembly of this type with these stated advantages is heretofor unknown.
It should be appreciated that various other modifications and variations to the preferred embodiments can be made within the spirit and scope of the invention. Therefore, the invention should not be limited to the described embodiments. To ascertain the full scope of the invention, the following claims should be referenced.
This application claims the benefit of provisional patent application Ser. No. 61/331,562 entitled “Lightweight Hybrid Bearing Assembly and a Method of Making Thereof” filed on May 5, 2010. The content of that application is hereby incorporated by reference as if set forth in its entirety herein.
Number | Date | Country | |
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61331562 | May 2010 | US |