KR20090033241A - Centrifugal bearing with stable pitching moment - Google Patents

Abstract

Disclosed are centrifugal bearings having means for providing a stable pitching moment. Centrifugal bearings may optionally have corning means. A rotor system with centrifugal bearings is disclosed. A rotorcraft is disclosed having a centrifugal bearing.

Description

Centrifugal force bearing with stable pitching moment {CF BEARING WITH STEADY PITCHING MOMENT}

The present invention relates generally to the field of rotorcraft aircraft, and more particularly to the field of rotor systems for rotorcraft aircraft.

Rotary wing aircraft lasted a very long time. Several designs of rotary wing aircraft include means for changing the pitch of the rotor blades or airfoils around the pitch change axis in an effort to change the amount of thrust generated when the rotor blades or airfoils are rotated about the center mast. . Common components among the various known means for changing the pitch of the blades are generally vertical pitch links and generally horizontal pitch horns.

Pitch links are generally rod-shaped structures with one end attached to a control device (usually a swash plate) and the other end attached to a pitch horn. The pitch horn is also attached to the blade. The pitch link is attached to the pitch horn so that the pitch horn perturbs when the pitch link is translated along the longitudinal axis of the pitch link. Perturbation of the pitch horn causes the blades attached to the pitch horn to rotate about the pitch change axis of the blade. Unfortunately, when the pitch horn rotates the blade, an undesired reaction moment resulting from the blade's inherent mass / inertia is applied to the pitch horn and also the pitch link. Most blades can be generalized to have a large inertial axis and an inertial axis, which are associated with the directionality of the cord length. In general, blades generally tend to lie flat with cord lengths parallel to the ground. In operation, as the pitch horn rotates the blade at a larger angle of attack to produce thrust, the blade simultaneously counteracts a rotation that deviates from the initial lower angle of attack position.

When the pitch link and pitch horn are deliberately exposed to the force needed to rotate the blade about the pitch change axis, the pitch link and pitch horn must also withstand the forces transmitted due to unintended recoil moments. Because these forces are known to rotorcraft aircraft designers, pitch links, rich horns and related components must be designed to withstand at least the sum of the intended and unintended forces described above.

Usually, pitch links, pitch horns and related components are simply sized, formed, and consist of a material that can handle the expected sum of forces. In order to adapt to the unintentional recoil moment delivered by the blades, the pitch link, pitch horn and associated components are inevitably large, medium and inconveniently formed and / or for recoil moments where the components are not intended. If it did not have to withstand exposure, it would consist of more expensive materials than required.

In addition, without additional hardware, unintended kickback moments caused by multiple blades are generally transmitted all the way through the control system to the pilot input device. Recoil moment is experienced by the pilot as additional resistance as the pilot attempts to increase thrust by pitching the blades. The resistance experienced by pilots is often significant, causing the hydraulic compensator to be incorporated into the control system when attempting to invalidate the pilot's perception of the total number of unintentional kickback moments. Similar to the foregoing, the addition of a hydraulic system capable of correcting the total amount of unintended kickback moments adds undesirable weight, cost and package constraints to the overall control system design.

Finally, some higher performance airfoils tend to have undesirably higher recoil pitching moments. The use of high performance airfoils continues to be less attractive until the negative effects of undesired larger recoil pitching moments are advantageously addressed and resolved.

The blade pitch change mechanism described above represents a significant advance in rotary wing aircraft, but significant drawbacks remain.

There is a need for centrifugal bearings that provide a constant pitching moment.

It is therefore an object of the present invention to provide a centrifugal bearing that provides a constant pitching moment.

This object is achieved by providing a centrifugal force bearing with a pitching means that provides a constant pitching moment.

The present invention is directed to providing a low cost and lightweight means for reducing the recoil pitching moment of undesired blades, and reducing the transfer of undesirable forces to the pilot input device. It offers significant advantages, including the use of high performance airfoils without the need to significantly increase the strength of control system components.

Further objects, features and advantages will be apparent from the description set forth below.

Features which are believed to be novel features of the invention are set forth in the appended claims. However, the preferred mode of use, as well as its further objects and advantages, as well as the invention itself, will be best understood with reference to the following detailed description when read in conjunction with the accompanying drawings.

1 is a perspective view of a tilt rotor aircraft having a centrifugal bearing in accordance with the present invention.

2 is a partial perspective view of a rotor hub assembly with centrifugal bearings in accordance with a preferred embodiment of the present invention.

3 is a perspective view of the centrifugal bearing of FIG. 2 oriented for use with the yoke.

4 is an exploded perspective view of the centrifugal bearing of FIG. 2 oriented to show inwardly facing component surfaces;

5 is an exploded perspective view of the centrifugal force bearing of FIG. 2 oriented to show outwardly facing component surfaces.

The present invention shows the discovery that centrifugal force bearings (hereinafter referred to as CF bearings) for the rotor hub pitch change mechanism of a rotorcraft aircraft can be made to favor the effects of undesirable pitching moments. While specific reference is made to the use of the present invention in a tilt rotor rotorcraft, the present invention may alternatively be used in any other rotorcraft vehicle / aircraft.

1 shows a tilt rotor rotorcraft incorporating the CF bearing of the present invention. 1 shows a tiltrotor aircraft 101 in flight operation in helicopter mode. Aircraft 101 has a fuselage 103 to which wing 105 is attached. Nacelle 107 is generally supported at the outer end of wing 105. The nacelle 107 may be rotated between the generally shown helicopter mode position and forward facing airplane mode position (not shown). The nacelle 107 is equipped with an engine and a transmission that power the rotor system 109 during rotation. Each rotor system 109 has a rotor hub pitch change mechanism 111 that selectively rotates the rotor blades 113 about respective pitch change axes (not shown). Each rotor system 109 is shown having three blades 113. Spinning cover 115 and nacelle 107 substantially surround rotor hub pitch change mechanism 111 such that rotor hub pitch change mechanism 111 is blocked from the field of view of FIG. 1.

Referring now to FIG. 2 of the drawings, a perspective view of a rotor hub pitch change mechanism in accordance with the present invention is shown. The rotor hub pitch change mechanism 111 generally controls the bearings that connect the grips to the yokes to allow relative movement between the grips and the yokes, and the control that affects the movement of the grips and attached blades 113 (not shown in FIG. 2). A link device (not shown) is provided. The rotor hub pitch change mechanism 111 has an inner and outer shear bearing 116 and a CF bearing 117. The CF bearing 117 includes a mounting means 119 for firmly connecting the rotor hub yoke 121, a pitching moment means 123 for selectively generating a pitching moment about the pitch change shaft 124, and a grip ( Grip connection means 125 for transmitting (at least rotational and compression) forces between the CF bearing 117 and the grip and yoke 121, which allows for a relatively small coning movement between the grip and the yoke 121. Corning means 127 is provided. Although not shown, the grip is used to couple the blade 113 to the CF bearing 117.

The yoke 121 is configured to rotate about the mast shaft 129. Yoke 121 generally includes a plurality of arms 131 (only one is shown), each arm 131 for connecting to blade 113. Yoke 121 also has an inner hole 133 (only one shown) associated with each arm 131. The inner hole 133 is sized and formed to provide a convenient interface between the yoke 121 and the mounting means 119. The inner hole 133 is preferably sized and formed to have a forked portion 135 disposed in a portion of the hole 133 disposed generally furthest away from the mast shaft 129. The fork 135 is provided with mounting means 119 to minimize the relative movement between the yoke 121 and the mounting means 119 when the yoke 121 and the CF bearing 117 are rotated about the mast shaft 129. ) Is specially sized and shaped to connect

3 to 5, a preferred embodiment of the CF bearing 117 according to the present invention is shown in more detail alone. The mounting means 119, the pitching moment means 123, the grip connecting means 125 and the Corning differential means 127 will each be described in detail below as having specific practical characteristics. However, it will be appreciated that the scope of the present invention extends beyond the specific and preferred practical embodiments.

The mounting means 119 is arranged farther from the mast shaft 129 than the rest of the CF bearing 117. The mounting means 119 has an upper wall 137, a lower wall 139, and an inner wall 141. The walls 137, 139, 141 are preferably formed of a single piece of steel. However, the walls 137, 139, 141 are formed of any other material having appropriate strength and can all be joined together by welding or any other suitable means. The inner wall 141 is formed to connect with the forked portion 135, the upper wall 137 is formed to connect with the top surface of the yoke 121, and the lower wall 139 is formed with the bottom surface of the yoke 121. It is formed to connect. The upper wall 137 and the lower wall 139 have holes 143, respectively. The hole 143 is formed to receive a retaining fastener such as a bolt or a pin (not shown in any of these) for fixing the mounting means 119 to the yoke 121. The inner surface 145 (see FIG. 4) is formed to have a substantially cylindrical curvature, where the directionality and radius of the cylindrical curvature intersect the inner shear bearing 116 with the longitudinal axis of the coincidence cylinder and the pitch change axis 124. It is intended to lie vertically on the same plane. The radius of the coinciding cylinder is approximately equal to the distance from the intersection of the inner shear bearing 116 and the pitch changing shaft 124 to the intersection of the pitch changing shaft 124 and the inner surface 145. The inner side 145 abuts the generally parallel retainer wall 147 extending generally parallel to the pitch change axis 124 and facing the mast axis 129.

The grip connecting means 125 is arranged closer to the mast shaft 129 than to the rest of the CF bearing 117. The grip connecting means 125 is generally disc shaped and has an inward wall 149 (mostly facing the mast axis 129) and an outward wall 151 (mostly facing the opposite side of the mast axis 129). The stud 153 protrudes from the inward wall 149 generally parallel to the pitch change axis 124 and generally towards the mast axis 129. The stud 153 is generally formed as a cylinder. However, the stud may be formed as the grip connecting means 125 and any other suitable mutual locking means for connecting the grip. The grip (not shown) includes a structure complementary to the stud 153 to receive the stud 153. The rotational force exchange between the grip (about the pitch change shaft 124) and the grip connecting means 125 occurs mainly through the interface between the stud 153 and the grip.

The grip also has a structure complementary to the inward wall 149 to primarily transmit the centrifugal compression force to the inward wall 149 (along the pitch change shaft 124). The outward wall 151 has a plurality of helical inclined portions 155, where the helical shape has a central axis coinciding with the pitch change axis 124, and the helical inclination angle is about 2-3 degrees. However, variations of CF bearings may have spiral shafts that are arranged to incorporate different inclination angles or not coincide with the pitch change shaft 124. More specifically, each inclined portion 155 follows a separate helical sweep about the pitch change axis 124, where each helical sweep has substantially the same inclination angle, but the individual helical sweeps do not coincide but rather the pitch change. It is offset evenly about the axis 124 at a predetermined angle. The jaw portion 157 at a predetermined angle connects the adjacent inclined portion 155.

Inward wall 149, outward wall 151, stud 153, inclined portion 155 and jaw portion 157 are preferably formed of a single member of steel. However, inward wall 149, outward wall 151, stud 153, inclined portion 155 and jaw portion 157 may be formed of any other material having suitable strength and may be welded or any other suitable. All can be joined together by means.

In general, the pitching moment means 123 and the corning means 127 are sandwiched between the mounting means 119 and the grip connection means 125. More specifically, the pitching moment means 123 is sandwiched between the corning means 127 and the grip connecting means 125, and the corning means 127 is sandwiched between the pitching moment means 123 and the mounting means 119. .

Pitching moment means 123 comprises a laminated structure of rubber insert 159 and shim 161. Each shim 161 is generally disc-shaped with an inner side 163 formed generally to provide an outline of the outer side wall 151 (in a manner that enables offset matching of the inner side 163 and the outward side wall 151). Although structured, the outer surface 165 is generally formed to have the same contour as the outward wall 151. Shims 161 are each preferably a single thin member of metal, but may alternatively be composed of any other suitable material in any other suitable manner. The rubber insert 159 is preferably formed to completely cover the inclined portion 155, respectively. Accordingly, the rubber insert 159 is appropriately formed equally so as to completely cover the portion of the shim 161 formed similarly to the inclined portion 155. Each rubber insert 159 is preferably a thin rubber sheet having a constant thickness. The rubber insert 159 is preferably formed of a mixed natural rubber. However, in the alternative, it is possible to incorporate inserts formed from mixed natural rubber and other materials.

The corning means 127 has a structure in which the moment reaction plate 163, the rubber sheet 165, and the curved shim 167 are alternately stacked. The moment reaction plate 163 has an inwardly rotating interface wall 169 and an outwardly corning interface wall 171. The rotary interface wall 169 is generally formed to provide an outline of the outward wall 151 to enable offset matching of the wall 169 and the adjacent shim 161. The Corning interface wall 171 is generally formed to provide an outline of the inner side 145 of the mounting means 119. Sheet 165 is sandwiched between wall 171 and curved shim 167. The plurality of sheets 165 and shims 167 are stacked in an alternating arrangement, and the outermost end of the stacked structure consists of a rubber sheet 165 that connects with the inner side 145 of the mounting means. Each shim 167 is preferably a thin curved member having a constant thickness. Each sheet 165 is preferably a thin rubber sheet having a constant thickness. The sheet 165 is preferably formed of a mixed natural rubber. However, in the alternative, it is possible to incorporate sheets formed of mixed natural rubber and other materials.

When fully constructed, the CF bearing 117 is a unitary structure composed of the aforementioned components. Although the natural rubber insert 159 and the seat 165 have been described above as separate members, injection / vulcanization which spatially arranges the metal components of the CF bearing 117 and injects rubber to fill the gaps between the metal components. It is preferable to introduce the CF bearing 117 through the process. The vulcanization process ensures that the metal and rubber components of the CF bearing 117 are attached together to form a single structure.

In operation, the CF bearing 117 is rotated with the yoke 121 about the mast shaft 129. The centrifugal compression force is from grip to grip connecting means 125, from grip connection end 125 to pitching moment means 123, from pitching moment means to corning means 127, and from corning means 127 to mounting means 119. Finally, it is transmitted from the mounting means 119 to the yoke 121. Centrifugal compression can be very large. For example, CF bearing 117 may experience compression forces as high as 130,000 lbf during normal use in Bell Helicopter V-22 tiltrotor aircraft. Under considerable compression, the rubber insert 159 and the seat 165 are virtually devoid of shear friction. Thus, conventional centrifugal bearings neither hinder nor assist the rotation of the grips and associated blades 113 about the pitch change axis.

However, CF bearing 117 is not common. Even under significant compression, adjacent shims 161 of the pitching moment means 123 are compressed towards each other to allow the spirally inclined faces of the adjacent shims 161 to interact. This interaction causes each shim 161 to rotate slightly from the uncompressed seated state, so that the CF bearing 117 exerts a stable moment about the pitch change shaft 124.

As described above, when the rotor hub pitch change mechanism such as the mechanism 111 acts to rotate the blade such as the blade 113 to a more drastic or higher pitch position, an undesirable rebound pitching moment is caused by the blade 113. From to the mechanism 111. The geometry and material of the CF bearing 117 is preferably adjusted so that the stable moment exerted about the pitch change axis 124 by the CF bearing fights and invalidates a substantially undesirable rebound pitching moment. Although the preferred embodiment of the CF bearing 117 is configured to exert a stable moment whose magnitude is approximately equal to the value of the undesirable recoil pitching moment, variations of the invention may be configured to exert a larger or smaller stable moment. have. The CF bearing 117 is configured such that the grip connecting means 125 is rotated by ± 45 degrees or more about the pitch change shaft 124 with respect to the mounting means 119.

In addition, when the grip and associated blades experience a Corning motion, the Corning motion is from grip to grip connecting means 125, from grip connecting means 125 to pitching moment means 123, and from pitching moment means to corning means 127. May be delivered at least partially. The corning means 127 is configured to allow at least 2-3 degrees of corning motion between the reaction plate 163 and the mounting means 119. As most clearly shown in FIG. 3, the reaction plate 163 is prevented from moving too much in the corning direction by the retainer wall 147.

Of course, a variation of the CF bearing according to the invention is substantially similar to the CF bearing 117 but does not include corning means. This modification is easily configured by allowing the mounting means 119 to directly connect with the pitching moment means 123. Other variations of the present invention may include both corning means and substantially similarly configured lead-lag means adapted to enable small relative lead-lag motion. Of course, another variation may include only lead-lag means and no corning means.

It is apparent that the invention has been described and illustrated with significant advantages. While the invention has been shown in a limited number of forms, it is not intended to be limited to these forms and various changes and modifications can be made without departing from the spirit of the invention.

Claims (23)

As centrifugal bearing for rotor hub, Mounting means adapted for attachment to the yoke, Grip connecting means adapted to pitch-rotate by the blade grip and to receive centrifugal compressive force from the grip, Pitching moment means connected to said mounting means and grip connecting means And the pitching moment means is configured to exert a pitching moment when the pitching moment means is compressed by a centrifugal compression force. The method of claim 1 wherein the pitching moment means has a plurality of shims and inserts disposed between adjacent shims, the shims and inserts cooperating to generate a pitching moment when the pitching moment means are compressed by centrifugal compression forces. Centrifugal force bearing. 3. The centrifugal bearing of claim 2 wherein the shim and insert are disposed along a pitch change axis and the centrifugal compression force acts along a pitch change axis. The centrifugal bearing of claim 2, wherein at least one of the shims is formed to have one or more helical slopes. The centrifugal bearing of claim 2, wherein the insert is at least partially composed of an elastomeric material. The centrifugal force bearing according to claim 1, further comprising angular differential means for allowing relative angular movement between the grip connecting means and the mounting means. The centrifugal bearing of claim 1 wherein said pitching moment is approximately constant. As centrifugal bearing for rotor hub, A first end rigidly coupled to the yoke, A second end facing the first end, A plurality of stacked shims supported between the first and second ends, One or more inserts supported between adjacent shims Wherein the second end is pivoted by a blade grip, and is configured to receive centrifugal compressive force from the grip, generally along the longitudinal bearing axis, and is configured to rotate about the longitudinal bearing axis relative to the first end, The shim and insert cooperate to produce a pitching moment about the longitudinal bearing axis when the centrifugal compression force moves the second end towards the first end. The centrifugal bearing of claim 8, wherein the second end has a first surface and a stud projecting from the first surface, the stud being adapted to receive rotational force from the grip. 9. The method of claim 8, wherein the second end further comprises a second surface and at least one inclined portion projecting from the second surface, wherein each inclined portion is helically spirally towards the first end substantially coaxially with the longitudinal bearing axis. Moving forward, Each shim having a first shim face formed to substantially coincide with the shape of the second face of the second end, and a second shim face formed substantially similar to the second face of the second end. bearing. The centrifugal force bearing of claim 8, wherein the insert separates the outermost shim from the first end and the innermost face of the first end is formed to coincide with the shape of the second shim face of the outermost shim. The method of claim 8, wherein the second end further includes a second surface and at least one inclined portion protruding from the second surface. Each inclined portion is spirally inclined, and each inclined portion is spirally advanced toward the first end substantially coaxially with the longitudinal bearing axis, Each shim has a first shim face that is formed to substantially match the shape of the second face of the second end, and a second shim face that is formed substantially similar to the second face of the second end, The insert separates the outermost shim from the first end and the innermost face of the first end is formed to coincide with the shape of the second shim face of the outermost shim. The centrifugal bearing of claim 8, wherein the insert is at least partially composed of an elastomeric material. 9. The apparatus of claim 8 further comprising angular differential means for enabling relative angular motion between the first and second ends, wherein the angular differential means comprises: A moment plate having an inner surface and an outer surface, the inner surface is formed to connect with an adjacent seam, the outer surface is formed as a cylindrical curved portion having a longitudinal axis, the longitudinal axis being generally in contact with the mast axis and on the same plane as the longitudinal bearing axis. That moment plate, A plurality of stacked cylindrically curved shims supported between the moment plate and the first end, One or more cylindrically curved inserts supported between adjacent shims and between the outermost cylindrically curved shim and the first end And an inward surface of the first end is curved in a cylindrical shape to facilitate relative angular motion. 15. The centrifugal bearing of claim 14, wherein the first end further comprises a retainer wall that is bounded by an inward surface to limit relative corning motion between the moment plate and the first end. 15. The centrifugal bearing of claim 14, wherein the cylindrically curved insert is at least partially composed of an elastomeric material. A rotorcraft having one or more rotors, the rotor comprising: York, Two or more blades coupled with the yoke, One or more blade grips coupling the blade to the yoke, And a centrifugal force bearing, wherein the centrifugal force bearing, Mounting means adapted for attachment to the yoke, Grip connecting means adapted to rotate by one of the blade grips and to receive a centrifugal compressive force from the grip, Pitching moment means connected to said mounting means and grip connecting means Wherein the pitching moment means is configured to exert a pitching moment with respect to the associated grip when the pitching moment means is compressed by centrifugal compression. 18. The method of claim 17, wherein the pitching moment means have a plurality of shims and inserts disposed between adjacent shims, the shims and inserts cooperating to generate a pitching moment when the pitching moment means are compressed by centrifugal compressive forces. Rotorcraft. 19. The rotorcraft of claim 18 wherein the shim and insert are disposed along a pitch change axis and the centrifugal compression force acts along a pitch change axis. 19. The rotorcraft of claim 18, wherein at least one of the shims is formed to have one or more spiral slopes. 19. The rotorcraft of claim 18, wherein the insert is at least partially composed of elastomeric material. 18. The rotorcraft of claim 17, further comprising angular differential means for enabling relative angular motion between the grip connecting means and the mounting means. 18. The rotorcraft of claim 17, wherein the pitching moment is approximately constant.

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