Patent Description:
Certain aircraft engines include a main rotor shaft drivingly engaged to a compressor and supported by a number of bearing assemblies that are disposed at different axial locations along the shaft. As the engine operates, the shaft and at least some of the bearing assemblies become loaded axially due to operating loads developed by the compressor. As such operating loads may vary in magnitude and axial direction, considerations must be taken into account to ensure that the shaft remains suitably supported across a range of power outputs.

In accordance with an aspect of the present disclosure, there is provided a shaft assembly for an aircraft powerplant, comprising: a shaft extending along an axis from a first shaft end to a second shaft end; a bearing assembly extending about the axis and supporting the first shaft end of the shaft, the bearing assembly including an inner race secured to the shaft and an outer race radially outward of the inner race relative to the axis; a seal extending about the axis and located radially outward of the shaft, the seal disposed axially between the bearing assembly and the second shaft end; a housing having a housing wall located between the bearing assembly and the seal; and a washer extending about the axis and located axially between the bearing assembly and the seal, the washer extending axially from the outer race to the housing wall.

The shaft assembly for an aircraft powerplant as defined above and described herein may also include any one or more of the following features, in whole or in part, and in any combination.

In certain aspects, an annular bearing seal about the axis extending radially from the outer race to an annular housing surface of the housing facing radially inwardly relative to the axis, the washer extending radially from inward of the annular bearing seal to the annular housing surface.

In certain aspects, the housing includes a seal support having the housing wall, the housing wall having a first wall surface adjacent to the washer and a second wall surface facing away from the washer and located adjacent to the seal.

In certain aspects, the washer has a radially inner washer surface, a radially outer washer surface, and at least one washer channel in fluid communication between the radially inner washer surface and the radially outer washer surface.

In certain aspects, the housing defines a venting channel in register with the washer channel.

In certain aspects, the washer and the housing wall respectively have complementary anti-rotational shapes.

In certain aspects, a resilient element is received in an annular recess defined in a first surface of the washer facing toward the bearing assembly.

In certain aspects, the annular recess is axially retentive and the resilient element is a toric joint.

In certain aspects, the annular recess and the resilient element extends radially inwardly from outward of the outer race to inward of the outer race, and the resilient element is a flat gasket.

In certain aspects, the resilient element is one of a wave spring and a helicoidal spring.

In accordance with another aspect, there is provided an aircraft powerplant comprising: a shaft extending along an axis of the powerplant from a first shaft end to a second shaft end; a gearbox operatively connected to the first shaft end; a compressor rotor secured to the shaft at an axial location between the first shaft end and the second shaft end; a bearing assembly supporting the first shaft end, the bearing assembly including an inner race secured to the shaft and axially bound between the first shaft end and the compressor rotor, and an outer race radially outward of the inner race; a seal located radially outward of the shaft, the seal located axially between the bearing assembly and the second shaft end; a housing having a housing wall located between the bearing assembly and the seal, and an annular housing surface facing radially inwardly and surrounding the outer race; an annular bearing seal extending radially from the outer race to the annular housing surface; and a washer about the axis located axially between the bearing assembly and the seal relative to the axis, the washer extending axially from the outer race to the housing wall and radially from inward of the annular bearing seal to the annular housing surface.

The aircraft powerplant as defined above and described herein may also include any one or more of the preceding and/or following features, in whole or in part, and in any combination.

In certain aspects, the housing includes a bearing support having a flange portion located next to the outer race and a sleeve portion projecting axially from the flange portion and extending radially between the outer race and the annular housing surface, the flange portion defining an oil supply path in fluid communication with an annular gap defined radially between the sleeve portion and the outer race.

In certain aspects, the washer is axially compressed between the housing wall and the outer race to axially hold the outer race against the flange portion.

In certain aspects, the housing defines a cavity receiving the seal support and the bearing support, the housing defining at least one venting channel in fluid communication with the cavity between the seal support and the bearing support.

In certain aspects, the washer has a radially inner washer surface, a radially outer washer surface, and at least one washer channel in fluid communication between the radially inner washer surface and the radially outer washer surface, the at least one washer channel in register with the at least one venting channel.

In certain aspects, the resilient element is one of a flat gasket, a wave spring and a helicoidal spring.

<FIG> illustrates a powerplant <NUM> that may be used in an aircraft. In addition to airborne applications, the powerplant <NUM> may also be used in marine or industrial applications depending on the embodiment. The forthcoming description pertains to an exemplary powerplant <NUM> of a type commonly referred to as an auxiliary power unit (hereinafter APU <NUM>). The APU <NUM> comprises a casing <NUM>, an inlet <NUM> connected to the casing <NUM> through which ambient air is drawn, a load (or first) compressor 14A to compress some of the drawn air upstream of aircraft pneumatic system(s), a power (or second) compressor 14B to compress some of the drawn air upstream of a combustor <NUM> in which the compressed air is mixed with fuel and ignited for generating an annular stream of hot combustion gases, and a turbine <NUM> for extracting energy from the combustion gases. A shaft <NUM> extends along an axis A of the APU <NUM> from a first shaft end 20A, which may be connected to an aircraft load (e.g., a gearbox or an electric AC generator), to a second shaft end 20B connected to the turbine <NUM>. The shaft <NUM> is rotationally driven about the axis A by the turbine <NUM> and rotates with the compressors 14A, 14B. A first and a second bearing assembly <NUM>, <NUM>' disposed proximate to the first 14A and the second 14B compressors respectively support the shaft <NUM> about the axis A relative to the casing <NUM>.

During operation of the APU <NUM>, the first bearing assembly <NUM> (hereinafter the bearing <NUM>) is subjected to an internal load oriented axially relative to the axis A and originating from the compressor(s) 14A, 14B and/or the turbine <NUM>, as schematically shown by arrow L. The internal load L corresponds to a compound of all axial loads imposed by the compressors 14A, 14B and the turbine <NUM> as borne by the bearing system <NUM>. As the APU <NUM> operates, the internal load L may vary in magnitude and/or direction. For instance, the internal load L is generally directed toward the first shaft end 20A (i.e., forward) when the APU <NUM> operates under normal conditions. Under certain circumstances however, the internal load L may be directed toward the second shaft end 20B (i.e., aft), for example upon the compressor(s) 14A, 14B undergoing a surge. As will become apparent from the forthcoming, the APU <NUM> is provided with features that palliate undesirable effects that such variations of the internal load L may otherwise have on spatial relationship and lubrication of components of the bearing <NUM>.

Exemplary embodiments of a shaft assembly of the APU <NUM> will now be described. Referring particularly to <FIG>, the shaft assembly generally comprises the shaft <NUM>, the bearing <NUM>, a housing <NUM> secured to the casing <NUM> and defining a cavity C about the axis A, the bearing <NUM> being located inside the cavity C, a seal <NUM> about the axis A inside the cavity C, and a washer <NUM> about the axis A between the bearing <NUM> and the seal <NUM>.

The bearing <NUM> includes an inner race <NUM> extending circumferentially about the axis A and mounted to the shaft <NUM>, a series of rolling elements <NUM> disposed circumferentially about the axis A around the inner race <NUM>, an annular cage <NUM> shaped for maintaining each rolling element of the series of rolling elements <NUM> in a suitable spatial relationship relative to one another, and an outer race <NUM> extending circumferentially about the axis A and around the series of rolling elements <NUM>. The bearing <NUM> is an axial bearing, i.e., a bearing that can withstand axial loads and transfer such loads internally to and from its components. For instance, imparting an axial load to the inner rate <NUM> can axially load the rolling elements <NUM>, the annular cage <NUM> and the outer race <NUM>, and vice versa. Several types of suitable axial bearings exist, such as ball bearings (as depicted), tapered roller bearings or the like. It should be noted that the inner race <NUM> is axially bound, or held in place, relative to the shaft <NUM> between two axial abutments <NUM>, <NUM> of the shaft <NUM> axially spaced from one another relative to the axis A. In this case, the inner race <NUM> is bound by a nut <NUM> and a spacer <NUM> on either side thereof. Hence, the shaft <NUM> may transmit the internal load L to the inner race <NUM> either forward via the spacer <NUM> or aft via the nut <NUM>. The outer race <NUM> however is axially free relative to the shaft <NUM>, and some axial movement of the inner race <NUM> relative to the outer race <NUM> may occur as the shaft <NUM> transmits the internal load L to the bearing <NUM> in either direction.

The housing <NUM> has first and second axial surfaces 40A, 40B defining axial boundaries of the cavity C and respectively facing toward first and second axial surfaces 38A, 38B of the outer race <NUM>. The second axial surface 40B of the housing <NUM> may be referred to as a side of a housing wall extending radially relative to the axis A inside the cavity C between the bearing <NUM> and the seal <NUM> facing toward the bearing <NUM>.

Still referring to <FIG>, the housing <NUM> also has a first radially inner surface 40C (i.e., a first annular surface of the housing <NUM> facing radially inwardly relative to the axis A) circumscribing the cavity C and surrounding a portion of a radially outer surface 38C of the outer race <NUM> that is located proximate to the first axial surface 38A. In the depicted embodiment, the first radially inner surface 40C extends axially relative to the first axial surface 38A along a majority (i.e., more than half) of an axial length of the radially outer surface 38C. The radially outer surface 38C and the first radially inner surface 40C are sized relative to one another so as to define a first annular gap therebetween provided that the outer race <NUM> is held about the axis A. The housing <NUM> has an oil supply path shown schematically at O in <FIG> that is fluidly connected to the cavity C proximate to a junction between the first axial surface 40A and the first radially inner surface 40C. The oil supply path O pressurizes oil into the cavity C so as to provide a film of oil between the radially outer surface 38C and the first radially inner surface 40C that maintains the first annular gap therebetween, holding the outer race <NUM> about the axis A.

Proximate to the second axial surface 38B of the outer race <NUM>, the housing <NUM> has a second radially inner surface 40D (i.e., a second annular surface of the housing <NUM> facing radially inwardly relative to the axis A) circumscribing the cavity C at a location spaced radially outward from a remainder of the radially outer surface 38C. The radially outer surface 38C of the outer race <NUM> and the second radially inner surface 40D may be said to respectively define radially inner and radially outer boundaries of a second annular gap surrounding an end of the outer race <NUM> having the second axial surface 38B. An annular seal <NUM> is provided in the second annular gap to sealingly engage the second radially inner surface 40D and the radially outer surface 38C, thereby assisting the building of oil pressure in the first annular gap and hindering leakage of oil axially away from the outer race <NUM> past the second axial end 38B. The annular seal <NUM> is in this case a C-seal, although other static or dynamic types of seals are contemplated, such as toric seals, o-rings, Garlock seals, lip seals, metal C-seals, spring energized rubber seals, dual cone seals and piston seals, among other examples.

The housing <NUM> in this case is a multi-structure component including a body <NUM> secured to the casing <NUM>, and a bearing support <NUM> and a seal support <NUM> respectively secured to the casing <NUM> via the body <NUM>. Depending on the embodiment, the body <NUM> may be an integral part of the casing <NUM>, or may be separate. The bearing support <NUM> and the seal support <NUM> together define the cavity C. The bearing support <NUM> includes a flange portion defining the first axial surface 40A of the housing <NUM> next to the outer race <NUM>, and a sleeve portion projecting from the flange portion and extending radially between the outer race <NUM> and the second radially inner surface 40D of the housing <NUM>. The flange portion in this case defines the oil supply path O. The seal support <NUM> defines the housing wall having the second axial surface 40B, which may be referred to as a first wall surface. The housing wall may be said to partition the cavity C in a first cavity portion C1 and a second cavity portion C2 inside which are respectively disposed the bearing <NUM> and the seal <NUM>. A second wall surface of the housing wall opposite to the first wall surface, thus facing away from the washer <NUM>, is located adjacent to the seal <NUM>. It is contemplated that in some embodiments, the housing <NUM> may comprise fewer components, e.g., the body <NUM> and one or more of the bearing support <NUM> and the seal support <NUM> may be together form a unitary component. In this case, the bearing support <NUM> defines the first and second axial surfaces 40A, 40B as well as the first radially inner surface 40C, whereas the seal support <NUM> defines the second radially inner surface 40D. Inside the first cavity portion C1, the outer race <NUM> and the housing wall are axially spaced from one another so as to define an axial gap G. The axial gap G extends axially from the second axial surface 38B of the outer race 38B to the second axial surface 40B of the housing <NUM>. The housing <NUM> may define a venting passage P that is fluidly connected to the cavity C, namely to the first cavity portion C1 in the axial gap G, via which heat emanating from the bearing <NUM> may be evacuated away therefrom. The washer <NUM> is disposed inside the axial gap G.

Referring to <FIG>, the washer <NUM> will now be described in further detail. The washer <NUM> has a first axial surface 60A and a second axial surface 60B facing away from one another. The first and second axial surfaces 60A, 60B are both generally annular in shape and are spaced from one another so as to define an axial width, or thickness, of the washer <NUM>. The washer <NUM> is sized such that the axial width substantially spans a maximum axial dimension of the axial gap G, i.e., an axial dimension of the gap G resulting from the first axial surface 38A of the outer race <NUM> being held against the first axial surface 40A of the housing <NUM>, for example when the internal load L is exerted forward onto the first axial surface 40A via the shaft <NUM> and ultimately by the outer race <NUM>. A nominal (i.e., uncompressed) axial width and/or a rigidity of the washer <NUM> may be selected for the washer <NUM> to substantially span the maximum dimension of the axial gap G when the internal load L of a given magnitude (for example corresponding to a known surge condition of the APU <NUM> as discussed hereinabove) is exerted aft onto the washer <NUM> via the shaft <NUM> and ultimately by the outer race <NUM>. In some embodiments, the nominal axial width of the washer <NUM> is greater than the maximum axial dimension of the axial gap G. In such embodiments, the outer race <NUM> may be said to be pre-loaded by the washer <NUM>, i.e., being biased toward the first axial surface 40A of the housing <NUM> regardless of the magnitude and direction of the internal load L. Conveniently, a plurality of washers <NUM> having different nominal axial widths and/or rigidities may be provided, each suitable to provide a pre-load of a given magnitude for opposing a corresponding magnitude of the internal load L being exerted aft. It will be appreciated that by opposing such aft internal loads L via the washer <NUM>, leakage of oil from the oil supply path O to between the first axial surface 40A of the housing <NUM> and the first axial surface 38A of the outer race <NUM>, which may be detrimental to the pressurization of the first annular gap, may be mitigated.

Radially, the washer <NUM> extends from a radially inner surface 60C to a radially outer surface 60D, from radially inward of the radially outer surface 38C to radially outward thereof adjacent to the second annular gap. By virtue of this arrangement, the washer <NUM> defines an axial abutment that hinders axial displacement of the outer race <NUM> and of the annular seal <NUM> toward the second axial surface 40B of the housing <NUM>. In the depicted embodiments, the washer <NUM> is sized such that upon being located about the axis A inside the axial gap G, the radially inner surface 60C is radially inward of the outer race <NUM>, and the radially outer surface 60D is adjacent to the second radially inner surface 40D of the housing <NUM>, although other arrangements are possible.

In embodiments, the washer <NUM> may be provided with at least one channel <NUM> in fluid communication between inside the washer <NUM> (i.e., radially inward of the radially inner surface 60C) and outside the washer <NUM> (i.e., radially outward of the radially outer surface 60D). The at least one channel <NUM> is routed through the washer <NUM> so as to be in register with the venting passage P upon the washer <NUM> being disposed inside the axial gap G. As such, heat generated by the bearing <NUM>, for example due to friction occurring at interfaces between the rolling elements <NUM> and the inner and/or outer races <NUM>, <NUM> may be evacuated away from the bearing <NUM> via the at least one channel <NUM> and away from the cavity C via the venting passage P. The housing <NUM> may define more than one venting passage P, for example a pair of diametrically-opposed passages P as shown in <FIG>. Conversely, the at least one channel <NUM> may in some embodiments include two diametrically-opposed channels <NUM> (best seen in <FIG>) defined inward of the second axial surface 60B that may respectively and simultaneously be positioned in register with a corresponding one of the venting passages P.

In embodiments, the washer <NUM> is provided with at least one anti-rotational shape <NUM> defined adjacent to the second axial surface 60B that is complementary to an anti-rotational shape 40B' of the housing <NUM> defined in the second axial surface 40B. By way of this anti-rotational arrangement, wear of the washer <NUM> that may otherwise occur due to fretting thereof against the housing <NUM> and/or the outer race <NUM> may be mitigated. For example, in an exemplary embodiment shown in <FIG>, the at least one anti-rotational shape <NUM> may be a pair of protrusions projecting from the second axial surface 60B on either side of one of the channels <NUM>. Optionally, anti-rotational shapes 40B', <NUM> may be defined by the second axial surface 38B of the outer race <NUM> (for example one or more slot(s)) and by the first axial surface 60A (for example one or more protrusion(s)) of the washer <NUM>.

With reference to <FIG>, other non-limiting embodiments of the washer <NUM> are shown, each having a different implementation of the at least one anti-rotational shape <NUM>. In <FIG>, a sole protrusion <NUM> is provided, in this case projecting from inside a channel <NUM>. In <FIG>, two pairs of parallel protrusions <NUM> are provided on the second axial surface 60B for engagement with the housing <NUM>, whereas the channels <NUM> are provided on the first axial surface 60A. In <FIG>, the at least one anti-rotational shape <NUM> is provided in the form of two diametrically-opposite notches defined inward of the radially outer surface 60D. Depending on the embodiment, different arrangements of protrusions and/or notches may be provided, on the first axial surface 60A, the second axial surface 60B or the radially outer surface 60D.

With reference to <FIG>, yet other non-limiting embodiments of the washer <NUM> are shown, each having a different implementation of the at least one channel <NUM>. In <FIG>, the at least one channel <NUM> is provided in the form of a plurality of radial holes spaced circumferentially from one another and extending from the radially inner surface 60C to the radially outer surface 60D. In <FIG>, the at least one channel <NUM> is provided in the form of a plurality of radial slots spaced circumferentially from one another and extending from the radially inner surface 60C to the radially outer surface 60D, in this case inward of the first axial surface 60A. In <FIG>, the at least one channel <NUM> includes a network of at least one first channel <NUM>' and at least one second channel <NUM>" extending inward of the first axial surface 60A for example, the first and second channels <NUM>', <NUM>" extending in this case linearly and at an angle relative to one another. Depending on the embodiment, different arrangements of channels <NUM> may be provided, so long as they provide fluid communication from inside the washer <NUM> to outside thereof.

With reference to <FIG>, in some embodiments, the washer <NUM> has an annular recess <NUM> defined inward of its first axial surface 60A, and the shaft assembly of the APU <NUM> further comprises a resilient element <NUM> received inside the annular recess <NUM>. The washer <NUM> and the resilient element <NUM> may be structured and arranged relative to one another to achieve a desired pre-load magnitude onto the outer race <NUM>. In the embodiment depicted in <FIG>, the resilient element <NUM> is a flat gasket that may be less rigid than the washer <NUM>. The annular recess <NUM> and the resilient element <NUM> extend radially outwardly from radially inward of the outer race <NUM> to radially outward thereof, such that the resilient element <NUM> spans a radial height of the outer race <NUM> while being suitably supported by the washer <NUM>. In embodiments, the resilient element <NUM> only covers a portion of the radial height outer race <NUM>. Also of note with regard to <FIG>, the at least one channel <NUM> includes a network of first and second channels <NUM>', <NUM>" in the form of holes in fluid communication with one another and extending with respect to the axis A in orientations other than radial. In <FIG>, the resilient element <NUM> is provided in the form of a toric joint which may be less rigid than the washer <NUM>, and the annular recess <NUM> is shaped so as to be axially retentive of the resilient element <NUM>. In this example, the resilient element <NUM> and the annular recess <NUM> are sized relative to one another such that a radial height of the annular recess <NUM> is smaller than a radial height (or diameter of a cross-section) of the resilient element <NUM>, whereas an axial depth of the annular recess <NUM> is greater than half of the radial height (or diameter of the cross-section) of the resilient element <NUM>. In <FIG>, the resilient element <NUM> is provided in the form of a wave spring. Other types of springs are contemplated, for example helicoidal springs. It is contemplated that in some embodiments, an annular member (or second washer, not shown) may be provided in the axial gap G between the outer race <NUM> and the first axial surface 60A over the annular recess <NUM> such that the resilient element <NUM> is axially bound between the washer <NUM> and the annular member in a compressed state. In such cases, the axial dimension of the washer <NUM>, the resilient element <NUM> and the annular member being axially stacked as described hereinabove are sized to amount to the maximum axial dimension of the axial gap G.

Claim 1:
A shaft assembly for an aircraft powerplant, comprising:
a shaft (<NUM>) extending along an axis (A) from a first shaft end (20A) to a second shaft end (20B);
a bearing assembly (<NUM>) extending about the axis (A) and supporting the first shaft end (20A) of the shaft (<NUM>), the bearing assembly (<NUM>) including an inner race (<NUM>) secured to the shaft (<NUM>) and an outer race (<NUM>) radially outward of the inner race (<NUM>) relative to the axis (A);
a seal (<NUM>) extending about the axis (A) and located radially outward of the shaft (<NUM>), the seal (<NUM>) disposed axially between the bearing assembly (<NUM>) and the second shaft end (20B);
a housing (<NUM>) having a housing wall located between the bearing assembly (<NUM>) and the seal (<NUM>); characterised by
a washer (<NUM>) extending about the axis (A) and located axially between the bearing assembly (<NUM>) and the seal (<NUM>), the washer (<NUM>) extending axially from the outer race (<NUM>) to the housing wall.