WO2000027698A1

WO2000027698A1 - Rotor hub for rotating wing aircraft

Info

Publication number: WO2000027698A1
Application number: PCT/GB1999/003647
Authority: WO
Inventors: Nigel Howard Mckrill; Stephen Anthony Sherwood-Rogers
Original assignee: Nigel Howard Mckrill; Sherwood Rogers Stephen Anthon
Priority date: 1998-11-05
Filing date: 1999-11-04
Publication date: 2000-05-18
Also published as: GB9824075D0; AU1058100A

Abstract

A rotor hub for a rotating wing aircraft includes a mechanism for controlling blade pitch. The blade pitch controlling mechanism includes a rotatable disc (560) having an axis of rotation which is pivotable and a pitch control shaft (520) mounted at a location spaced from the axis of rotation of the rotatable disc (560). The pitch control shaft (520) is connected to at least a part of the blade (340) for controlling its pitch.

Description

ROTOR HUB FOR ROTATING WING AIRCRAFT

This invention relates to a rotor hub for a rotating wing aircraft.

Rotating wing aircraft, such as helicopters and autogyros, are well known and typically comprise a fixed component, including a fuselage, and a rotating component including an overhead rotor blade assembly, known as a rotor head, including a rotor hub and rotating blades mounted on the hub.

One function of the rotor hub is to control the pitch of the rotating blades, not only to control the amount of lift generated, but also to maintain stability of the aircraft as each blade rotates by varying the pitch during rotation.

Conventional mechanisms for controlling blade pitch are coupled between the fixed component and the rotating component utilise a swash-plate (or tilt-plate) mechanism or the like which exerts a force in the axial direction of the main rotor shaft in order to vary the pitch of the rotating blades. Such mechanisms are interactive and suffer oscillatory feedback, in the form of vibration, as a result of the pivoting movement of each blade of the rotor head to generate lift, maintain stability and directional control. This vibratory interaction is variable, being proportional to torque and pitch. In addition, conventional rotor hubs and their control systems inhibit rotation of the main rotor shaft and therefore waste engine power and degrade autorotational performance. This is because of the mechanical interaction of conventional mechanisms between the fixed component and the rotating component.

It is therefore an object of the present invention to provide a rotor hub for a rotating wing aircraft which overcomes, or at least ameliorates, the above-described disadvantages of conventional mechanisms.

According to the present invention there is provided a rotor hub for a rotating wing aircraft including means for controlling blade pitch, wherein the blade pitch controlling means comprises a rotatable member having an axis of rotation which is pivotable and pitch control means mounted at a location spaced from the axis of rotation of the rotatable member and connected to at least a part of the blade for controlling the pitch thereof.

The axis of rotation of the rotatable member may be generally perpendicular to an axis of rotation of the rotor hub.

The rotatable member may be connected to or may form part of a motor which is rotated in variable synchronism with the rotor hub. The rotatable member may be connected to the motor by way of a constant velocity joint.

Means may be provided for moving the rotatable member in an axial direction. The means for axial movement may comprise a pair of cam plates. Each of the cam plates may be provided with a generally circumferentially extending cam means, one end of which is at a greater radial distance from the axis of rotation of the hub than the other.

The rotatable member may be pivotable in a plane which includes the axis of rotation of the rotor hub.

Pivoting of the rotatable member may be effected by a pair of cam plates. Each of the cam plates may be provided with a generally circumferentially extending cam means, one end of which is at a greater radial distance from the axis of rotation of the rotor hub that the other.

Alternatively, pivoting of the rotatable member may be effected by lever arm and push-rod assemblies operating on opposing sides of the rotating member.

As a further alternative, pivoting of the rotatable member may be effected by controlling movement of a member extending axially therefrom. Movement of the axially extending member may be controlled in a two-dimensional space by means of a control matrix or by a plurality of extensible arms.

The invention also relates to a rotating wing aircraft including a rotor shaft and a rotor hub as hereinbefore defined, wherein the rotor hub is pivotably mounted on the rotor shaft.

For a better understanding of the present invention and to show more clearly how it may be carried into effect reference will now be made, by way of example, to the accompanying drawings in which:

Figure 1 is a perspective view of a rotating wing aircraft in the form of a helicopter which is provided with one embodiment of a rotor hub according to the present invention;

Figure 2 is a schematic layout of a control system for the helicopter shown in Figure 1;

Figure 3 is an exploded perspective view the rotor hub of the helicopter of Figures 1 and 2 with wiring omitted for clarity;

Figures 4A to 4C show schematically a pitch control actuator of the rotor hub and various modes of pitch control provided thereby; Figure 5 is a perspective view of a pitch control actuator, mechanism forming part of the rotor hub of Figure 3 ;

Figures 6A to 6D illustrate schematically a phased output position of each pitch control actuator;

Figure 7 is a diagrammatic illustration of the operation of the pitch control mechanism shown in Figure 5;

Figure 8 is an exploded perspective view of a second embodiment of a rotor hub according to the present invention;

Figures 9 and 10 are perspective views of parts of a twin- bladed rotor hub;

Figures 11 and 12 are respectively an exploded view and a partial view of parts of a further embodiment of a pitch control actuator mechanism in a rotor hub according to the present invention.

The helicopter shown in Figures 1 to 6 includes a fixed component in the form of a fuselage 1 with rotating component in the form of an overhead rotor blade assembly 3. A main rotor shaft 10 is mounted within the fuselage 1 and is driven by a combined engine and transmission unit 30 by way of a belt drive 20. A rotor hub 100 is mounted at the upper end of the main shaft 10 and is provide with electrical power by means of an annular generator 110, such, as a brushless induction generator, mounted around the main shaft 10. As indicated in Figure 2, power from the generator 110 is fed by way of a power supply line 310 extending within the shaft 10 to a battery 300 within the rotor hub 100.

Control signals for the helicopter originate from a cockpit control unit shown diagram atically as 230 and pass by way of a signal line 235 to a processor or computer 220. In response to signals from the cockpit control unit 230, control signals are generated by the processor 220 and are transmitted to the rotor hub 100 along signal lines 240 and 250, control rings 200 and 210, respectively, and signal lines 320 and 330, respectively, within the main shaft 10. Further control signals are transmitted by the processor 220 through signal lines 260 and 270 to an engine control actuator 280 and to a tail rotor control actuator 290 respectively.

As can be seen most clearly from Figure 3 , the rotor hub 100 is in two parts. A main body 420 may be flexibly attached to the main rotor shaft 10 to provide a 360 degree teeter action and a cover assembly 430. The manner of the flexible attachment of the main body 420 to the rotor shaft 10, for example using a constant velocity joint, is readily apparent to the skilled person and requires no further description herein. Three rotor blades 340 are pivotably secured between the main body 420 and the cover assembly 430 by means of pivot assemblies 350 which accommodate the lead/lag pivotal movement (shown at 451) required. The pivot assemblies 350 are provided with damping in known manner.

Blades 340 are additionally provided with pivotal movement for pitch (shown at 452), whilst vertical flapping actions of the blade 340 are achieved by their spanwise flexion in known manner.

As can be seen from Figures 2 and 3, contained within the rotor hub 100 are upper and lower collective pitch adjustment cam plates 370 and 380 respectively. The cam plates 370 and 380 are circular and coaxial in configuration and are rotatable about their common axis by gearwheel output on each of two (upper and lower) actuators 375. The actuators 375 receive control signal input by way of a collective controller 800, to provide collective blade pitch output to each actuator assembly 500 which is described in more detail with reference to Figure 5. Control horns 540 of the actuator assembly 500 are engaged with cam slots 371 and 381 provided in the upper and lower cam plates 370 and 380, respectively. The cam slots extend generally in the circumferential direction of the cam plates but are angled relative thereto such that one end of each cam slot is radially inward of the other end thereof. For convenience that end of the cam slot in the upper cam plate that is radially inward corresponds to that end of the cam slot in the lower cam plate that is radially outward and vice versa. The cam slots are able to variably and synchronously adjust the radial position of each actuator assembly 500 as shown in Figure 4.

In Figure 4, Figures 4A and 4B illustrate COLLECTIVE pitch adjustment and Figure 4C shows the superimposition of CYCLIC pitch on a COLLECTIVE setting. Thus, Figure 4A shows a neutral pitch output position 600, Figure 4B shows a collective pitch output position 700, and Figure 4C shows a positive 750 and negative cycling pitch output 650 superimposed on collective pitch output position 700.

Referring to Figures 3 and 5, the cycling actuator assembly 500 is attached to, and located by, a scissor link assembly 510. The scissor link assembly 510 is attached to main body 420 at the radially outer end thereof to permit radial position and tilt adjustment of the cycling actuator assembly 500 along an axis substantially perpendicular to the axis of rotation of the rotor hub 100 with respect to a tilt centre 925 (see Figure 4C) , whilst preventing rotation and sideways deflection of a cycling actuator motor 565 which is attached to and drives an output disc 560.

A pitch control shaft 520 is connected to output disc 560 in the peripheral region thereof to provide a phased pitch control output by way of output centre 975 to each rotor blade 340 through a pitch control rod 525 (see Figure 3) according to the positional setting of the cycling actuator assembly 500, the actuator motor 565 rotating at substantially the same speed as the rotor shaft 10. The pitch control rod 525 can be used in known manner to control the pitch of the rotor blade 340 as a whole at the root thereof or can be used to control a servo-flap aerodynamic control device (tab) 526 (see Figure 1) provided on, or inset into, the rotor blade.

Figures 6A to 6D show the phased pitch control for the three rotor blades 340 showing the angular position of the point of connection of the pitch control shaft 520 to the output disc 560 in dependence on the angular position of the rotor blade 340 as it rotates about the axis of the rotor shaft 10.

Power for the rotor hub control system can be generated by utilising the rotation of the rotor hub itself. Thus, power may be generated using a variety of media, either singly or in combination, such as electrical, hydraulic, pneumatic and/or electro/hydraulic.

Thus, in use, the rotor hub according to the present invention provides both collective and cyclic output. COLLECTIVE control is provided by adjusting the radial position of each actuator assembly 500 relative to the axis of rotation of the rotor hub. This is effected by rotating the upper and lower cam plates 370 and 380 in opposite directions by means of the actuators 375. Thus, as illustrated in Figure 3, movement of the upper cam plate in a clockwise direction when viewed from above simultaneously with movement of the lower cam plate in a counter clockwise direction moves the actuator assemblies radially outwards, while movement of the upper cam plate in a counter clockwise direction when viewed from above simultaneously with movement of the lower cam plate in a clockwise direction moves the actuator assemblies radially inwards. As indicated in Figure 4B this has the effect of moving the output centre 975 along an axis substantially perpendicular to the axis of rotation of the hub either radially outwards or radially inwards.

CYCLIC pitch angle is determined by adjusting the tilt angle of the output disc 560 of each actuator assembly 500, the greater the angle of tilt the greater the cyclic variation in pitch angle. This is effected by relative movement of the upper and lower cam plates 370 and 380. Either one of the cam plates may be moved alone, either clockwise or counter clockwise, or more complex simultaneous movements of the cam plates may be effect if desired. By way of example, movement of the upper cam plate 370 in a clockwise direction when viewed from above in Figure 3 moves the upper control horn 540 radially outwardly thereby adjusting the radial extent of movement at the point where the pitch control shaft 520 is connected to the output disc 560. Conversely, movement of the upper cam plate 370 in a counter clockwise direction moves the upper control horn 540 radially inwardly. Alternatively, or additionally, movement of the lower cam plate 380 in a counter clockwise direction when viewed from above in Figure 3 moves the lower control horn 540 radially outwardly thereby adjusting the radial extent of movement at the point where the pitch control shaft is connected to the output disc 560. Conversely, movement of the lower cam plate 380 in a clockwise direction moves the lower control horn 540 radially inwardly.

Angular control of the CYCLIC pitch angle is effected by varying the rotational speed of the actuator motors 565 relative to the rotational speed of the rotor hub 100 in order to advance or retard the phase of the pitch control.

CYCLIC pitch angle and the angular control thereof are illustrated in Figure 7 which is a diagrammatic side view of the actuator mechanism for explanatory purposes only. Motor 565, such as a flux motor, is rotated in synchronism with the rotor hub 100 and the output shaft is connected to output disc 560 by a flexible coupling 561 in the form of a constant velocity joint and by a splined shaft or the like to permit axial movement of the disc relative to the motor. The output disc 560 is shown in solid line having its axis coaxial with the axis of the motor 565 and is shown in dashed line having its axis at an angle to the axis of the motor 565. In each case the axis of rotation of the output disc 560 is in the same plane as the axis of rotation of the hub. When the axis of the output disc 560 is coaxial with the axis of the motor 565 the output disc rotates in a plane perpendicular to the axis of the motor and there is no relative axial movement of the pitch control shaft 520 which is mounted in the peripheral region of the disc. However, when the axis of the output disc is tilted as shown in dashed lines the pitch control shaft is moved forwards and backwards depending on the angular position of the output disc 560 and serves to impose a cyclic backwards and forwards movement on the pitch control rod 525.

Thus the helicopter flight system will provide directional flight control by variably adjusting the rotational speed of the actuator motors above or below rotational speed of the rotor head through synchronised adjustment to the rotational speed of each cycling actuator motor 565, either momentarily or for a more prolonged period, to suit flight pattern demands.

Referring to Figure 2 , the underlying speed of rotation of the three actuator motors is controlled by referencing datum 950 interconnected by signal line 330 to control ring 210 and computer 220, for control of cycling and rotor tilt plane angle. Therefore, main rotor positional flight (thrust angle/vector) is controlled by adjusting referencing datum 950 and, consequently, actuator motors 565 linked thereto.

Thus, movement of referencing datum 950 relative to the rotating system, will cause actuator motors 565 to accelerate or decelerate to maintain position with datum point 950, causing a change to cycled output angle.

Tail rotor and engine power commands are mixed and adjusted by processor 220 to suit system requirements.

Output from actuator assembly 500 may be configured to provide variable pitch control output greater or less than 1/rev, either in linear or non-linear form.

The control signals for the rotor hub may be, for example, electrical, optical or remote radio signals. For example, control signal transmission may include a fibre-optic rotating joint comprising first and second components that are rotatable relative to each other about a common axis. Each component is provided with a plurality of coupling lenses positioned to form a circle having the common axis as the centre thereof, each lens being connected to an optical coupler by a respective pigtail optical fibre. The optical coupler is in turn connected to a wavelength division multiplexer which is connected to an optical, transmitter and an optical receiver. This results in a transmission path between the two rotating components by way of the rotating optical joint without mechanical contact.

Because control of rotor blade pitch is effected solely by movements in a direction substantially perpendicular to the axis of rotation of the rotor head, the invention eliminates the reaction-derived vibration and shaft drag of conventional rotor hubs with consequent improvements in safety from improved autorotation performance and reduced cost of manufacture and maintenance.

Further, because control of rotor blade pitch is effected solely by movements in a direction substantially perpendicular to the axis of rotation of the rotor head, it is possible to incorporate more radical modifications to a rotating wing aircraft than have hitherto been possible. For example, it is possible to increase the amount of kinetic energy stored in the rotor hub, such as by increasing the mass of the hub. In contrast to conventional such aircraft, the increase in mass would further reduce vibration and would increase safety by improving autorotation performance. Because the fixed component of the aircraft (the gondola) does not have to withstand the vibration previously imposed on it, the structural strength, and hence weight, of the fixed component can be reduced.

The rotor hub shown in Figure 8 is a modification of that shown in Figures 3 and 5 and the same references are used to denote the same or similar parts. The major feature of the rotor hub shown in Figure 8 is that the scissor link assembly has been replaced by a slot guide 995 which further simplifies manufacture of the hub. In addition, Figure 8 illustrates diagrammatically a pivotal coupling 997 to the upper end of the main rotor shaft 10.

The twin-bladed rotor hub shown in Figures 9 and 10 is relatively simple as compared with a rotor hub for three blades in that the upper and lower cam plates can be dispensed with a replaced with relatively simple lever arm 545 and push-rod 526 assemblies. As shown in Figures 9 and 10 a lever arm and push-rod assembly is provided on opposing sides of an output disc housing such that joint movement of the two assemblies to extend the push-rods moves the output disc outwardly or inwardly as a whole for COLLECTIVE control, while movement of the assemblies in opposing directions causes the output disc to pivot for CYCLIC control as described above in relation to Figure 7.

For all of the above embodiments of the invention it should be noted the motor 565, instead of being a separate component to the output disc 560, could be designed to incorporate the output disc as, for example, part of the armature of the motor with the output disc being rotatable about a pivotable axis.

The above embodiments of the rotor hub according to the present invention provide CYCLIC control by tilting the axis of the output disc in a single plane which is in the same plane as the axis of rotation of the rotor hub. The embodiment shown in Figures 11 and 12 allows full pivoting movement of the axis of rotation of the output disc 560 which can, in turn, significantly increase the degree of sophistication of CYCLIC control of the blades 340.

As shown in Figure 11 the output disc 560 is mounted within a cylindrical housing 115 in a manner which provides a constant velocity joint as described hereinabove. The housing 115 is externally splined and is mounted in a further cylindrical housing in a manner which permits relative axial movement for COLLECTIVE control. The output disc 560 is provided with an axially extending member 125, such as in the form of a cone, the free end of which is positionally controlled by a control matrix 145. Shown in Figure 12 is an alternative positional control mechanism 120 comprising three equispaced extensible arms 170 which are capable of adjusting the position of the free end of the axially extending member within a two-dimensional space thereby providing full angular control over the axis of tilt of the output disc and correspondingly providing full control over the operation of the pitch control shaft 520 and pitch control rod (not shown) for CYCLIC control.

Claims

1. A rotor hub for a rotating wing aircraft including means for controlling blade pitch, characterised in that the blade pitch controlling means comprises a rotatable member (560) having an axis of rotation which is pivotable and pitch control means (520) mounted at a location spaced from the axis of rotation of the rotatable member (560) and connected to at least a part of the blade (340) for controlling the pitch thereof.

2. A rotor hub as claimed in claim 1, characterised in that the axis of rotation of the rotatable member (560) is generally perpendicular to an axis of rotation of the rotor hub (100) .

3. A rotor hub as claimed in claim 1 or 2 , characterised in that the rotatable member (560) is connected to or forms part of a motor (565) which is rotated in variable synchronism with the rotor hub (100) .

4. A rotor hub as claimed in claim 3, characterised in that the rotatable member (560) is connected to the motor (565) by way of a constant velocity joint.

5. A rotor hub as claimed in any preceding claim, characterised in that means (370, 380) is provided for moving the rotatable member (560) in an axial direction.

6. A rotor hub as claimed in claim 5, characterised in that the means for axial movement comprises a pair of cam plates (370, 380).

7. A rotor hub as claimed in claim 6, characterised in that each of the cam plates is provided with a generally circumferentially extending cam means (371,

381) one end of which is at a greater radial distance from the axis of rotation of the hub than the other.

8. A rotor hub as claimed in any preceding claim, characterised in that the rotatable member (560) is pivotable in a plane which includes the axis of rotation of the rotor hub (100) .

9. A rotor hub as claimed in any preceding claim, characterised in that pivoting of the rotatable member is effected by a pair of cam plates (370, 380).

10. A rotor hub as claimed in claim 9, characterised in that each of the cam plates (370, 380) is provided with a generally circumferentially extending cam means

(371, 381) one erid of which is at a greater radial distance from the axis of rotation of the rotor hub that the other.

11. A rotor hub as claimed in any one of claims 1 to 8, characterised in that pivoting of the rotatable member (560) is effected by lever arm and push-rod assemblies (545, 526) operating on opposing sides of the rotating member (560) .

12. A rotor hub as claimed in any one of claims 1 to 8, characterised in that pivoting of the rotatable member (560) is effected by controlling movement of a member

(125) extending axially therefrom.

13. A rotor hub as claimed in claim 12, characterised in that movement of the axially extending member (125) is controlled in a two-dimensional space by means of a control matrix (145) .

14. A rotor hub as claimed in claim 12, characterised in that movement of the axially extending member (125) is controlled in a two-dimensional space by means of a plurality of extensible arms (170) .

15. A rotating wing aircraft including a rotor shaft (10) and a rotor hub (100) as claimed in any preceding claim, characterised in that the rotor hub (100) is pivotably mounted on the rotor shaft (10) .