Patent Description:
Gas turbine engines include various rotating components such as shafts, rotors, fans, and the like. In various situations, it may be desirable to couple components together in such a way as to allow relative rotation of the components. In that regard, a roller bearing may be used as the coupling feature. The roller bearing may include an inner ring coupled to a first component, and outer ring coupled to a second component, and rollers located between the inner ring and the outer ring that allow relative rotation between the inner ring and the outer ring. One or both of the inner ring or the outer ring may include side walls that define a cavity for receiving the rollers. The side walls may have an outer edge that contacts the rollers. Contact between the outer edge and the rollers may undesirably cause wear of the outer edge of the sidewalls.

<CIT> discloses a cylindrical roller bearing suited for higher rotation speeds.

<CIT> discloses an antifriction roller bearing assembly.

<CIT> discloses a bearing device for a wheel with improved durability.

<CIT> discloses a taper roller bearing where the rollers are guided by a contact at two spaced points.

<CIT> discloses a roller bearing comprising inner and outer members each having a circular raceway, and a plurality of bearing rollers arranged between the raceways, at least one of the inner and outer members having at least one circumferential flange beside its raceway, the flange having a convex surface arranged to engage an end face of each bearing roller to restrain the bearing rollers against axial movement.

According to a first aspect of the invention, a roller bearing as claimed in claim <NUM> is provided.

In any of the foregoing embodiments, the radius is between <NUM> inches (about <NUM> millimeters) and <NUM>,<NUM> inches (about <NUM>,<NUM> millimeters).

In any of the foregoing embodiments, the roller bearing is configured for use in a gas turbine engine, the inner ring is configured to rotate at a rotor speed of a rotor of the gas turbine engine, and the at least one roller is configured to rotate at a roller speed that is less than the rotor speed.

In any of the foregoing embodiments, the second curved crown includes two curved crowns each extending inward from a respective one of the two side walls.

In any of the foregoing embodiments, the inner ring comprises a steel.

In any of the foregoing embodiments, the outer wall surrounds the axis, and the two side walls extend away from the outer wall in a direction away from the axis.

In any of the foregoing embodiments, the second curved crown extends from the outer wall to the outer edge.

The foregoing features and elements are to be combined in various combinations without exclusivity, unless expressly indicated otherwise.

A more complete understanding of the present disclosure, however, is best obtained by referring to the detailed description and claims when considered in connection with the drawing figures, wherein like numerals denote like elements.

The detailed description of exemplary embodiments herein makes reference to the accompanying drawings, which show exemplary embodiments by way of illustration and their best mode. While these exemplary embodiments are described in sufficient detail to enable those skilled in the art to practice the inventions, it should be understood that other embodiments may be realized and that logical, chemical and mechanical changes may be made without departing from the scope of the invention which is defined by the appended claims only.

For example, the steps recited in any of the method or process descriptions may be executed in any order and are not necessarily limited to the order presented. Also, any reference to attached, fixed, connected or the like may include permanent, removable, temporary, partial, full and/or any other possible attachment option. Where used herein, the phrase "at least one of A or B" can include any of "A" only, "B" only, or "A and B.

With reference to <FIG>, a gas turbine engine <NUM> is provided. As used herein, "aft" refers to the direction associated with the tail (e.g., the back end) of an aircraft, or generally, to the direction of exhaust of the gas turbine engine. As used herein, "forward" refers to the direction associated with the nose (e.g., the front end) of an aircraft, or generally, to the direction of flight or motion. As utilized herein, radially inward refers to the negative R direction and radially outward refers to the R direction.

The gas turbine engine <NUM> may be a two-spool turbofan that generally incorporates a fan section <NUM>, a compressor section <NUM>, a combustor section <NUM> and a turbine section <NUM>. In operation, the fan section <NUM> drives air along a bypass flow-path B while the compressor section <NUM> drives air along a core flow-path C for compression and communication into the combustor section <NUM> then expansion through the turbine section <NUM>. Although depicted as a turbofan gas turbine engine <NUM> herein, it should be understood that the concepts described herein are not limited to use with turbofans as the teachings may be applied to other types of turbine engines including three-spool architectures, geared turbofan architectures, and turboshaft or industrial gas turbines with one or more spools.

The gas turbine engine <NUM> generally comprises a low speed spool <NUM> and a high speed spool <NUM> mounted for rotation about an engine central longitudinal axis X-X' relative to an engine static structure <NUM> via several bearing systems <NUM>, <NUM>-<NUM>, and <NUM>-<NUM>. It should be understood that various bearing systems <NUM> at various locations may alternatively or additionally be provided, including for example, the bearing system <NUM>, the bearing system <NUM>-<NUM>, and the bearing system <NUM>-<NUM>.

The low speed spool <NUM> generally includes an inner shaft <NUM> that interconnects a fan <NUM>, a low pressure (or first) compressor section <NUM> and a low pressure (or second) turbine section <NUM>. The inner shaft <NUM> is connected to the fan <NUM> through a geared architecture <NUM> that can drive the fan shaft <NUM>, and thus the fan <NUM>, at a lower speed than the low speed spool <NUM>. The geared architecture <NUM> includes a gear assembly <NUM> enclosed within a gear diffuser case <NUM>. The gear assembly <NUM> couples the inner shaft <NUM> to a rotating fan structure.

The high speed spool <NUM> includes an outer shaft <NUM> that interconnects a high pressure (or second) compressor section <NUM> and the high pressure (or first) turbine section <NUM>. A combustor <NUM> is located between the high pressure compressor <NUM> and the high pressure turbine <NUM>. A mid-turbine frame <NUM> of the engine static structure <NUM> is located generally between the high pressure turbine <NUM> and the low pressure turbine <NUM>. The mid-turbine frame <NUM> supports one or more bearing systems <NUM> in the turbine section <NUM>. The inner shaft <NUM> and the outer shaft <NUM> are concentric and rotate via the bearing systems <NUM> about the engine central longitudinal axis X-X', which is collinear with their longitudinal axes. As used herein, a "high pressure" compressor or turbine experiences a higher pressure than a corresponding "low pressure" compressor or turbine.

The core airflow C is compressed by the low pressure compressor section <NUM> then the high pressure compressor <NUM>, mixed and burned with fuel in the combustor <NUM>, then expanded over the high pressure turbine <NUM> and the low pressure turbine <NUM>. The mid-turbine frame <NUM> includes airfoils <NUM> which are in the core airflow path.

The gas turbine engine <NUM> is a high-bypass ratio geared aircraft engine. The bypass ratio of the gas turbine engine <NUM> may be greater than about six (<NUM>). The bypass ratio of the gas turbine engine <NUM> may also be greater than ten (<NUM>:<NUM>). The geared architecture <NUM> may be an epicyclic gear train, such as a star gear system (sun gear in meshing engagement with a plurality of star gears supported by a carrier and in meshing engagement with a ring gear) or other gear system. The geared architecture <NUM> may have a gear reduction ratio of greater than about <NUM> and the low pressure turbine <NUM> may have a pressure ratio that is greater than about five (<NUM>). The diameter of the fan <NUM> may be significantly larger than that of the low pressure compressor section <NUM>, and the low pressure turbine <NUM> may have a pressure ratio that is greater than about five (<NUM>:<NUM>). The pressure ratio of the low pressure turbine <NUM> is measured prior to an inlet of the low pressure turbine <NUM> as related to the pressure at the outlet of the low pressure turbine <NUM>. It should be understood, however, that the above parameters are exemplary of various embodiments of a suitable geared architecture engine and that the present disclosure contemplates other turbine engines including direct drive turbofans.

The next generation turbofan engines are designed for higher efficiency and use higher pressure ratios and higher temperatures in the high pressure compressor <NUM> than are conventionally experienced. These higher operating temperatures and pressure ratios create operating environments that cause thermal loads that are higher than the thermal loads conventionally experienced, which may shorten the operational life of current components.

In various embodiments and referring to <FIG> and <FIG>, the gas turbine engine <NUM> may include one or more roller bearings <NUM>. The roller bearing <NUM> includes an inner ring <NUM>, and outer ring <NUM>, at least one roller <NUM>, and a cage <NUM>. The inner ring <NUM>, the outer ring <NUM>, and the cage <NUM> surround an axis <NUM>, such as the axis X-X' of <FIG>. The inner ring <NUM> may be coupled to a first rotating component (such as a rotor, the inner shaft <NUM>, or the outer shaft <NUM>), and may rotate along with the first rotating component. The outer ring <NUM> may be coupled to a stationary component (such as a case) or to a second rotating component that is rotating at a radial velocity that is different than that of the first rotating component. The at least one roller <NUM> may facilitate rotation of the outer ring <NUM> relative to the inner ring <NUM>. The cage <NUM> at least partially houses the at least one roller <NUM> and may resist separation of the at least one roller <NUM> from the other components of the roller bearing <NUM>.

Turning now to <FIG>, additional details of the roller bearing <NUM> are shown. As shown, the at least one roller <NUM> is retained in place by the cage <NUM> and housed between the inner ring <NUM> and the outer ring <NUM>.

The inner ring <NUM> includes an outer wall <NUM> and two side walls <NUM>, or shoulders <NUM>, that extend towards the outer ring <NUM> from the outer wall <NUM> and, thus, extend away from the outer wall <NUM> and the axis <NUM>. The outer wall <NUM> and the two side walls <NUM> define a cavity <NUM> therebetween that receives the at least one roller <NUM>. The outer wall <NUM> may define an inner ring raceway <NUM> on which the at least one roller <NUM> makes contact.

The side walls <NUM> have an outer edge <NUM> that faces the cavity <NUM> and is located on the side walls <NUM> at a location farthest from the outer wall <NUM>. The outer edge <NUM> is located at an intersection of an axially-extending surface <NUM> and a radially-extending surface <NUM>. Contact between the at least one roller <NUM> and the outer edge <NUM> may cause undesirable stress at the outer edge <NUM>, which may undesirably result in wear of the inner ring <NUM> at the outer edge <NUM>. Such contact may result from a flat inner face of the two side walls <NUM> contacting the at least one roller <NUM>.

In order to reduce contact between the outer edge <NUM> and the at least one roller <NUM>, the roller bearing <NUM> includes a curved crown <NUM> extending inward (i.e., towards the at least one roller <NUM>) from at least one of the two side walls <NUM>. In various embodiments, the roller bearing <NUM> may include a curved crown <NUM> extending inward from each of the two side walls <NUM>. The curved crown <NUM> may be formed monolithically with the side walls <NUM> or may be formed separately and later coupled to the side walls <NUM>.

The curved crown <NUM> has a shape that resembles or comprises a portion of a circle and has a radius <NUM>. In various embodiments, the radius <NUM> may be between <NUM> inches (about <NUM> millimeters (mm)) and <NUM>,<NUM> inches (about <NUM>,<NUM>), between <NUM> inches (about <NUM>) and <NUM> inches (about <NUM>,<NUM>), or between <NUM> inches (about <NUM>) and <NUM> inches (about <NUM>,<NUM>).

The curved crown <NUM> has an apex <NUM> facing the at least one roller <NUM>. The apex <NUM> may be located anywhere along a height <NUM> of the two side walls <NUM>. The shape of the curved crown <NUM> causes the at least one roller <NUM> to contact the curved crown <NUM> along an area <NUM> referred to as a "contact ellipse. " As shown, the contact ellipse is located at a mid-section of the two side walls <NUM> and thus away from the outer edge <NUM>. Inclusion of the curved crown <NUM> results in the contact ellipse being closer to the outer wall <NUM> relative to an inner ring that lacks a curved crown. The curved crown <NUM> thus reduces contact between the at least one roller <NUM> and the outer edge <NUM> of the two sidewalls <NUM>, reducing wear experienced by the components of the roller bearing <NUM>.

Although the inner ring <NUM> is shown as having the side walls <NUM>, in various embodiments the outer ring <NUM> may include similar features as the inner ring <NUM> including the curved crown <NUM>. In various embodiments that do not form part of the invention, only one of the inner ring <NUM> or the outer ring <NUM> may include curved crowns, and according to the invention, both of the inner ring <NUM> and the outer ring <NUM> include curved crowns.

Any one or more of the inner ring <NUM>, the outer ring <NUM>, the at least one roller <NUM>, and the cage <NUM> may include a metal alloy such as a steel. For example, one or more of these components may include a tool steel with a relatively high percentage by volume of molybdenum available as M50 Tool Steel or M50NIL Tool Steel (conforming to the AMS <NUM>), available from Universal Stainless of Bridgeville, PA; a steel with a relatively high percentage by volume of carbon and chromium available as <NUM> Steel, available from Continental Steel & Tube of Fort Lauderdale, FL; a carburizing gear steel that resists softening at elevated service temperatures available as Pyrowear®, available from Carpenter Technology Corporation of Philadelphia, PA; or a stainless steel with a relatively high percentage by volume of chromium available as 440C Stainless Steel, available from Penn Stainless Products of Quakertown, PA.

However, the benefits, advantages, solutions to problems, and any elements that may cause any benefit, advantage, or solution to occur or become more pronounced are not to be construed as critical, required, or essential features or elements of the inventions. The scope of the invention is accordingly to be limited by nothing other than the appended claims, in which reference to an element in the singular is not intended to mean "one and only one" unless explicitly so stated, but rather "one or more.

In the detailed description herein, references to "one embodiment", "an embodiment", "various embodiments", etc., indicate that the embodiment described may include a particular feature, structure, or characteristic, but every embodiment may not necessarily include the particular feature, structure, or characteristic.

Claim 1:
A roller bearing (<NUM>), comprising:
at least one roller (<NUM>);
an outer ring (<NUM>) surrounding an axis (<NUM>) and comprising an outer wall; two side walls extending away from the outer wall, defining a cavity therebetween for receiving the at least one roller (<NUM>), and each of the two side walls having an outer edge located at an intersection of an axially-extending surface and a radially-extending surface at a location facing the cavity and farthest from the outer wall; and a first curved crown extending inward from at least one of the two side walls contacting the at least one roller (<NUM>) to reduce wear to the outer edge, wherein the first curved crown comprises a portion of a circle having a radius and an apex facing the at least one roller (<NUM>); and
an inner ring (<NUM>) surrounding the axis (<NUM>), located radially inward from the outer ring (<NUM>), wherein the inner ring comprises:
an outer wall (<NUM>);
two side walls (<NUM>) extending away from the outer wall (<NUM>), defining a cavity (<NUM>) therebetween for receiving the at least one roller (<NUM>), and each of the two side walls (<NUM>) having an outer edge (<NUM>) located at an intersection of an axially-extending surface (<NUM>) and a radially-extending surface (<NUM>) at a location facing the cavity (<NUM>) and farthest from the outer wall (<NUM>); and
a second curved crown (<NUM>) extending inward from at least one of the two side walls (<NUM>) contacting the at least one roller (<NUM>) to reduce wear of the outer edge (<NUM>), wherein
the second curved crown (<NUM>) comprises a portion of a circle having a radius (<NUM>) and an apex (<NUM>) facing the at least one roller (<NUM>);
the at least one roller being (<NUM>) at least partially housed by a cage (<NUM>), wherein the cage (<NUM>) houses the at least one roller (<NUM>) between the outer ring (<NUM>) and the inner ring (<NUM>);
the second curved crown (<NUM>) contacts the at least one roller (<NUM>) at a contact ellipse, wherein the contact ellipse is an area located at a midsection of the two side walls (<NUM>) and away from the outer edge (<NUM>).