JPS62286896A - Tunable vibration absorber - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

3. Detailed Description of the Invention Technical Field The present invention relates to a vibration absorber, and particularly to a vibration absorber used in a rotor hub of a helicopter.

1 NIR Technology During the flight of a helicopter, when the helicopter's rotor hub rotates its blades, the air supporting the helicopter exerts a liter dynamic load on the main rotor's blades,
This generates a force at the blade pass frequency.

three reference directions, namely a longitudinal direction extending substantially in the longitudinal direction of the helicopter in the plane of rotation of the tip of the blade, and perpendicular to said longitudinal direction in the plane of rotation of the tip of the blade to the side of the helicopter; The forces along the lateral and vertical directions are combined at the rotor hub.

One type of vibration absorber for helicopters is called a single-hanging plate shaker for rotating hubs. This vibration absorber is r(n-1
)/rotation'' and r(n+1>/rotation).However, this vibration absorber has been found to be not ineffective, and in practice ineffective.

Single-hung plate shakers act on in-plane forces in the longitudinal and lateral directions, but not on vertical forces. The absorber is also subjected to an undesirable amount of drag during forward flight of the helicopter.

Another type of vibration absorber is called a double-suspended absorber for rotor hubs. In this type of vibration absorber, centrifugal force is used to maintain the necessary stiffness to counter the imaging forces. In the case of a double-hanging type plate ritual vessel, a force in the vertical direction at a multiple of the number of rotations of the blades, i.e., r n/rotation, or a force r(n-
The absorber can be tuned and oriented to act on an in-plane force of 1)/revolution or r(n+1)/revolution. The latter two forces combine with each other to establish a lateral and longitudinal force of r n/rotation relative to a constant reference axis.

However, the double-hung plate device acts only on one of the forces in each of the above directions. Additionally, the shape and serrations of this type of absorber impose significant drag on the helicopter during flight. Furthermore, in the case of a two-hung plate ritual vessel, it is necessary to use a considerable amount of mass which is not actually effective. Moreover, in the case of two-hung plastic vibrators, manufacturing tolerances must be strictly adhered to, and the absorbers are susceptible to undesirable dynamic effects.

There are also vibration absorbers for rotor hubs that act against lateral and longitudinal forces of rn/revolution. One such vibration absorber is constructed by attaching a mass to the rotor hub. The attached mass is connected to the hub by a set of springs that provides symmetrical stiffness in any in-plane direction, such as the horizontal direction, between the hub and the vibration absorber mass.

There are still other rotor hub vibration absorbers that act only on in-plane forces. Such absorbers are limited to constant frequency, non-tuning applications. Therefore, such a vibration absorber should maintain the shared absorption and absorption function even under conditions where the blade passing frequency rn/rotation changes (its characteristics do not change depending on the rotational speed of the rotor).

Thus, a common drawback of all the vibration absorbers mentioned above is that they do not act on excitation forces along all three reference axes, but only on one or two reference axes. This means that it only works.

Furthermore, any previously known vibration absorber is a variably tunable vibration absorber for a rotor hub of a helicopter, which requires less mass storage to be mounted and which satisfies all three criteria to be applied to a rotating helicopter hub. It is not a vibration absorber that can effectively act on force components in any direction.

DISCLOSURE OF THE INVENTION According to the present invention, a vibration absorber for a helicopter including a suspended mass is provided for absorbing force components along three reference directions, which are applied along the vertical direction, the lateral direction, and the longitudinal direction. attached to the main rotor hub. The mass is suspended by air springs of variably selected stiffness arranged such that the absorbers are tunably aligned at or near the blade passing frequency. The vibration absorber may include an air spring or a mechanical spring to three-dimensionally support the central mass according to embodiments of the invention.

The net vibrational force transmitted to the gas is thus greatly reduced.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The invention will be explained in detail below by way of example embodiments with reference to the accompanying figures.

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows a vibration absorber 13 for a rotor hub 14 supporting the blades 15 of a helicopter. Vessel 13
Donut-shaped rubber that can be expanded by popping.

It includes an air spring 19 such as a bag and a central mass 21. The hub 14 is connected to the mast 1 which extends into the gearbox 17.
6 is supported. The air pressure within spring 19 is adjustable to vary the stiffness of the spring. Instead of one donut-shaped air spring 19, several air spring pouches arranged circumferentially and spaced from each other may be used as shown in FIG. Also, other compressible fluids, preferably non-volatile gases, may be used instead of air.

The centrum 21 may, for example, be cylindrical and rest against the air spring 19. The material of the solid body 21 may be, for example, steel, lead, or even tungsten. The air spring 19 is held in a metal housing 23, preferably of aerodynamic or symmetrical shape, which is attached to the rotor hub 14, for example by bolts. The housing 23 acts as a cover to smooth the flow of air over the absorber during helicopter flight. The housing 23 is removable allowing access to the body 21. Contains 23'. The housing 23 is secured to the bolt II! by means of a bolt (not shown), for example. It may be attached to the mast 16 along 16'.

As shown, in the preferred embodiment of the present invention, the flange portion 66 of the air spring 19 is attached to the adjacent portion 21 of the spring body 21.
' and 21''. This allows vibration absorption to be performed three-dimensionally as a function of the air pressure within the spring 19. Air is introduced into the spring 19 through the passageway 25 so that the air introduced into the spring 19 can have any level of air pressure that effectively provides the required degree of spring stiffness to the spring 19. It is becoming established.

Air to conduit 25 is supplied through flexible tube 41 and fitting 44 from an air supply controlled by a pressure control valve (not shown).

Additional air springs 19' may be installed above or below the mass 21 to provide additional variable vertical stiffness. The air pressure in such an additional air spring 19' may be controlled, for example, via an additional passage in the mass 21 (not shown). In addition to or instead of the additional air spring 19', several mechanical springs 88 (for example, a centrally located One spring is shown in FIG. 1). Alternatively, several symmetrically spaced vertical springs 19'' above and below the suspension 21 about the vertical axis may be used.

Additionally, an in-brain mechanical spring 88', as shown in FIG. 2, may be employed in conjunction with the bladders of spaced air springs 19. Tunable air spring 19
By using a mechanical spring in conjunction with the air spring 19, it is possible to establish a basic level of stiffness such that a fine tuning can be achieved in the air spring 19, thereby reducing the volume of the enclosed air space as a whole. can.

The air pressure in the spring 19 or 19' can be adjusted directly or even more as a function of the rotor rotational speed in order to vary the air pressure and thereby control the shooting of the helicopter in response to changes in the rotor rotational speed and flight conditions. It can be varied to vary the tuning in response to the output of a complex known i-first detection feedback system (not shown).

Although the present invention has been described in detail with respect to specific embodiments above, the present invention is not limited to such embodiments, and various other embodiments are possible within the scope of the present invention. This will be clear to those skilled in the art.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal sectional view of one preferred embodiment of the vibration absorber of the present invention in which an air spring or a mechanical spring acts to tunably absorb vibrations in a helicopter hub. FIG. 2 is a plan sectional view of another embodiment of the vibration absorber according to the invention, which is provided with an additional mechanical spring effective in the in-plane reference direction. 13... Vibration absorber, 14... Rotor hub, 15...
Blade, 16... Mast, 17... Gear box, 19... Air spring, 21... Central mass body, 23...
...Housing, 23'...Lid, 25...Conduit, 4
1...Tube. 44...Mounting tool, 66...Flange part, 88.8
8'...Mechanical spring patent applicant United Chiknoloshes Corporation Agent Patent attorney Akira
Ishimasa Tsuyoshi's drawing of the drawing
, Name of the invention Tunable vibration absorber 3, Relationship to the case of the person making the amendment Patent applicant address Financial Brother, Hartford, Connecticut, U.S.A. 1 Name United Chiknoroses Corporation 4, Agent

Claims (1)

[Claims] A tunable vibration absorber for a helicopter rotor hub that includes a central mass suspended in an outer casing fixedly mounted to the rotor hub to maintain the central mass suspended in three dimensions. 1. A tunable vibration absorber, characterized in that it has spring means for