WO2011026873A2

WO2011026873A2 - Oscillation damper for oscillations superimposing a rotating movement about a rotational axis

Info

Publication number: WO2011026873A2
Application number: PCT/EP2010/062828
Authority: WO
Inventors: Elmar Breitbach
Original assignee: B.E.C. Breitbach Engineering Consulting Gmbh
Priority date: 2009-09-01
Filing date: 2010-09-01
Publication date: 2011-03-10
Also published as: DE102009029071A1; WO2011026873A3; DE102009029071B4

Abstract

The invention relates to an oscillation damper (1) for oscillations superimposing a rotating movement about a rotational axis (3). Said damper comprises at least one rigid pendulum (4) mounted in such a way that it swings about a pendulum axis (5), the pendulum axis (5) swinging about the rotational axis (3) with the rotating movement, at a fixed distance (R) from the rotational axis (3). The mass distribution of the pendulum (4) about the pendulum axis (5) is such that the inherent frequency of the movement of the pendulum (4) about the pendulum axis (5) in the centrifugal field is the same as the rotational frequency (2) of the rotating movement (2) about the rotational axis (3) as a result of the rotating movement (2) about the rotational axis (3).

Description

RHP Ref .: 18413PCT TS

Patent application: file number not yet assigned

Title: Vibration absorber for vibrations superimposed on a rotation about a rotation axis

Applicant: b.e.c. Breitbach Engineering Consulting GmbH

Priority: DE 10 2009 029 071.0 (01.09.2009)

TECHNICAL FIELD OF THE INVENTION

The invention relates to a vibration damper for a rotational movement about a rotational axis superimposed vibrations having the features of the preamble of independent claim 1.

A rotational movement superimposed on a rotational axis, if the superimposed vibrations have the same direction as the rotational movement, also referred to as torsional vibrations. However, the present invention relates not only to the suppression of such torsional vibrations with a vibration absorber but also to vibrations having a direction perpendicular to the circumferential direction about the rotation axis.

STATE OF THE ART

A vibration absorber having the features of the preamble of independent claim 1 is known in the field of helicopter technology. At each of a plurality of rotor blades of a helicopter a pendulum about a tangential to the rotor axis aligned pendulum pendulum pendulum is arranged, the reduced pendulum length of the pendulum, which takes into account the deviations of a physical pendulum of a mathematical pendulum, is so much smaller than the distance of its pendulum axis of the rotor axis that the natural frequency of the pendulum movements of the pendulum about the pendulum axis in the centrifugal field due to the rotational movement of the rotor about the rotor axis n times the Rotational frequency of the rotational movement about the axis of rotation, where n is the number of rotor blades of the rotor.

Frequently, however, vibrations which are superimposed on a rotational movement about a rotational axis do not occur with an n-fold higher frequency than the rotational frequency of the rotational movement, but with this rotational frequency itself. Such oscillations are currently suppressed with vibration absorbers whose absorber masses are elastically coupled to a rotating base the elastic coupling causes a fixed Tilgereigenfrequenz, so that such vibration absorbers are effective only at a fixed rotational frequency of the rotational movement. By damping the elastic coupling of the absorber masses of the effective frequency range of such a vibration absorber can indeed be extended, but this is at the expense of the effectiveness of the vibration absorber at its natural frequency.

OBJECT OF THE INVENTION

The invention has for its object to provide a vibration absorber with the features of the preamble of claim 1, which also suppresses vibrations that have the rotational frequency of the rotational movement or are dependent on the rotational frequency and have an even lower frequency.

SOLUTION

According to the invention this object is achieved by a vibration damper with the features of independent claim 1. Preferred embodiments of the new vibration absorber are described in the dependent claims 2 to 15.

DESCRIPTION OF THE INVENTION

In the new vibration absorber, the pendulum has such a mass distribution about its pendulum axis, that the natural frequency of the pendulum motion of the pendulum about the pendulum axis in the centrifugal field due to the rotation about the rotation axis is equal to or smaller than the rotational frequency of the rotational movement about the rotation axis. This is synonymous with the fact that the reduced pendulum length for the pendulum movement of the pendulum around the pendulum axis at least as much greater than the distance of the pendulum axis to the axis of rotation is that in the centrifugal force field due to the rotational movement as large as the distance of the center of gravity of the pendulum from the axis of rotation. In the case that the reduced length in the centrifugal force field is the same as the distance of the center of gravity of the pendulum from the rotation axis, the effective restoring force on the deflected pendulum increases with the rotation frequency of the rotation just so that the natural frequency of pendulum pendulum movement always increases is just as big as the rotational frequency of the rotary motion.

Particularly preferred natural frequencies of the new vibration absorber, d. H. Natural frequencies of the pendulum motion of the pendulum about the pendulum axis in the centrifugal force field due to the rotational movement about the axis of rotation, are equal to the rotational frequency of the rotational movement about the axis of rotation or the same as half the rotational frequency of the rotational movement about the axis of rotation. In this case, the natural frequency of half the rotational frequency is a particularly important case in two respects. Firstly, in a four-stroke engine, it corresponds to the ignition frequency of each cylinder relative to the rotational frequency of the crankshaft. On the other hand, this is based on the rotational frequency very low natural frequency in a pendulum-based vibration absorber to achieve only with the inventive measures.

In the reduced pendulum length for pendulum motion of the pendulum around the pendulum axis, the moment of inertia around the pendulum axis as a factor and the distance of the center of gravity of the pendulum from the pendulum axis and the physical mass of the entire pendulum as a quotient. By a very large moment of inertia at a relatively small distance of the pendulum axis of the center of gravity of the pendulum a large reduced pendulum length is reached, which goes well beyond the maximum distance of the pendulum from the pendulum axis, which is a prerequisite for the formation of the new vibration absorber. The pendulum of the new vibration absorber can be essentially formed of two absorber masses whose centers of mass lie opposite each other across the pendulum axis. This mass distribution of the pendulum is particularly preferred in view of the effectiveness of the total mass used, ie the vibration-damping effectiveness of the total mass. In addition, based on this mass distribution, the operation of the new vibration absorber can also be explained by the fact that in her a pendulum on the pendulum mass acts a positive restoring force, one of the natural frequency increasing corresponds to positive stiffness, is rigidly coupled to a pendulum on the pendulum mass acts a negative restoring force, which corresponds to a natural frequency degrading negative stiffness. The pendulum with the negative rigidity is formed by the absorber mass of the pendulum lying in its zero position between the axis of rotation and the pendulum axis. By determining the relative magnitudes of these two "stiffnesses", their sum, which is due to the different signs the difference of their amounts, and thus the natural frequency of the rigidly coupled pendulum, can be determined largely independently of the actual pendulum length of the pendulum with the positive stiffness is formed by the absorber mass of the pendulum, which is in its zero position further away from the axis of rotation. Moreover, taking into account that the pendulum mass acted upon by the negative restoring force is the one closer to the axis of rotation in the new vibration absorber, and is thus particularly exposed to the inhomogeneity of the centrifugal force field, it becomes clear that the natural frequency is lower negative stiffness in the new vibration absorber can be provided with relatively small masses. Due to the inhomogeneity of the centrifugal force field due to the rotational movement about the axis of rotation omitted in the new vibration absorber, the fundamental independence of the natural frequency of a pendulum of his pendulum mass, as a result, a different weighting of the two pendulum masses that form the absorber masses of the pendulum of the vibration absorber according to the invention. As has already been indicated, this different weighting can be used to provide the negative stiffness in the centrifugal force field required for tuning the natural frequency of the pendulum movement of the entire pendulum due to the rotational movement about the axis of rotation with comparatively low actual mass.

As far as the axis of rotation and the pendulum axis of the new vibration absorber are not aligned vertically, the gravitational field of the earth affects the pendulum motion of the pendulum. However, this effect, which leads to a variation of the natural frequency of the pendulum movement of the pendulum about the pendulum axis over each rotation around the rotation axis, is only relevant with small rotation frequencies of the rotation movement about the rotation axis. At higher frequencies of rotation, their influence on the pendulum movement of the pendulum and its natural frequency diminishes. Nevertheless, it is preferred if the axis of rotation and the pendulum axis are aligned vertically in the new vibration absorber, so that even at lower rotational frequencies no influence of the gravitational field of the earth is given to the natural frequency of the pendulum motion of the pendulum. In the new vibration absorber, the pendulum can be damped with respect to its rotational movement about the pendulum axis. This is preferably an ideal damping as possible, which causes only a movement occurring opposing forces, ie no dependent of the pure deflection of the pendulum forces, because the latter forces to a shift of the natural frequency of the pendulum motion of the pendulum against the rotational frequency of the rotary motion to lead.

To limit the amplitude of the deflection of the pendulum, but soft stops can be provided for this. Such attacks are especially in a quick start of the rotary motion or strong speed fluctuations of the rotary motion, which is not meant to be suppressed vibrations but quasi static speed changes, makes sense.

In the new vibration absorber, the pendulum axis of the pendulum preferably has an orientation that is constant over the rotational movement relative to the axis of rotation. In this case, the pendulum axis parallel to the axis of rotation, tangential to the axis of rotation or at an angle to a tangent to the axis of rotation. In principle, the pendulum can also be mounted in a pivot bearing with a rotational degree of freedom for the pendulum axis, so that the pendulum axis can align perpendicular to the main direction of the occurring and suppressing vibrations.

Preferably, the new vibration absorber has a plurality of pendulum-mounted rigid pendulum whose pendulum axes are arranged symmetrically to the axis of rotation. In this case, the pendulum, in particular when their pendulum axes are parallel to each other, be coupled together. This can be done by elastic forces, for example by means of elastic bands.

Concretely, the pendulums in the new pacemaker can be mounted on a flange which can be fastened to a shaft having a rotary motion. The pendulum are preferably mounted within a closed housing at its periphery.

Advantageous developments of the invention will become apparent from the claims, the description and the drawings. The advantages of features and combinations of several features mentioned in the introduction to the description are merely exemplary and can take effect alternatively or cumulatively, without the advantages of compelling embodiments of the invention must be achieved. Further features are the drawings - in particular the illustrated geometries and the relative dimensions of several components to each other and their relative arrangement and operative connection - refer. The combination of features of different embodiments of the invention or of features of different claims is also possible deviating from the chosen relationships of the claims and is hereby stimulated. This also applies to those features which are shown in separate drawings or are mentioned in their description. These features can also be combined with features of different claims. Likewise, in the claims listed features for further embodiments of the invention can be omitted.

BRIEF DESCRIPTION OF THE FIGURES

The invention is explained in more detail below with reference to embodiments with reference to the accompanying figures and described. Fig. 1 outlines the principle of the vibration absorber according to the invention.

FIG. 2 outlines the geometric relationships with respect to one of two tiger masses in the vibratory tiger of FIG. 1; FIG. and

Fig. 3 outlines the geometric relationships with respect to the other of the two

Tigermassen in the Schwingungstiger of FIG. 1.

DESCRIPTION OF THE FIGURES

The sketched in Fig. 1 vibration damper 1 is provided for suppressing torsional vibrations that occur at a rotational movement 2 about a rotation axis 3. In this case, the vibration damper 1 on a rigid pendulum 4, which is mounted freely oscillating about a pendulum axis 5 to a here indicated only flange 8 and is shown in Fig. 1 in two pivot positions about this pendulum axis 5. The pendulum axis 5 extends in the rotational movement 2 at a fixed distance R parallel to the axis of rotation 3. The pendulum 4 comprises two absorber masses 6 and 7, wherein the absorber mass 7 is closer to the pendulum axis 5 than the absorber mass 6. The physical mass m, the absorber mass 7 may be smaller than the physical mass m _{P of} the absorber mass 6. The center of gravity of the entire pendulum 4 thus has a distance from the pendulum axis 5, which is smaller than the distance r _{p of} the absorber mass 6 of the pendulum axis 5. By suitable tuning of the physical masses m, and m _P and the distances r _p and η the Ti lgermassen 6 and 7 of the pendulum axis 5 in view of the distance R of the pendulum axis 5 of the rotation axis 3 is the natural frequency coo of the pendulum motion of the pendulum 4 about the pendulum axis 5 in the centrifugal force field due to the rotational movement 2 about the axis of rotation 3 always the same size as the rotational frequency Ω of the rotary motion 2.

That this is possible, the two following considerations prove.

1 . In the first consideration, the pendulum 4 is considered to be a rigid coupling of second mathematical pendulums whose pendulum masses are the physical masses m, and m _P and their pendulum lengths are the distances r _p and η of the absorber masses 6 and 7 from the pendulum axis 5. If these two mathematical pendulums are deflected by the same angle φ as the pendulum 4 in Fig. 1 from its zero position in which they lie in the plane defined by the axis of rotation 3 and the pendulum axis 5 extending parallel thereto, resulting in Fig. 2nd and Fig. 3 shown geometric relationships for the pendulum with the pendulum mass m _p and the inverse pendulum with the pendulum mass m ,. This results in the equation of motion of the coupled pendulum 4 to:

In this case, Θ is the moment of inertia of the entire pendulum 4 about the pendulum axis 5, for which, in this consideration, Θ = m _p r _p ² + m. /.

Thus, the above equation of motion can be transformed into:

small φ sin φ «φ holds, it follows that for is the pendulum natural frequency coo of the pendulum 4

R (m ^ - m ^)

and thus: Cö ₀ oc Ω as well as a suitable tuning of m _p , m ,, r _p and η to R: coo = Ω.

2. In the second consideration, the pendulum 4 as a whole, d. H. considered as a physical pendulum with a specific mass distribution. For the natural frequency coo of a physical pendulum in a gravitational field with gravity g, in the case of small deflections of the mgd

Pendulum ω _ρ where m is the total mass of the pendulum, d is the distance of the pendulum

Θ

Mass center of the pendulum from the pendulum axis and Θ the moment of inertia of the pendulum around the pendulum axis. If, for the application of this formula to pendulum 4, gravity g is replaced by centrifugal acceleration at the center of gravity of the pendulum, and at the small deflections considered, it depends only on the pendulum

Turning frequency sets with Ω ² (R + d), this results in ω _Ρ = Ω χ

also referred to as reduced pendulum length, which detects the deviations of a physical pendulum from a mathematical pendulum. That is, when the reduced pendulum length over the mass distribution of the pendulum 4 is set to be equal to the sum of the distance R of the pendulum axis 5 from the rotation axis 3 and the distance d of the pendulum 4 of the pendulum 4 Pendulum 5 are the natural frequency coo of the pendulum motion of the pendulum 4 about the pendulum axis 5 and the rotational frequency Ω of the rotational movement 2 about the rotation axis 3 regardless of the absolute magnitude of the rotational frequency Ω the same size.

It should be noted, however, that the above considerations are only roughly qualitative and the peculiarities of the radial centrifugal force field due to the rotational movement 2 to the D re ver ach se 3, d. H . Do not consider deviating from a homo genous force field. Nevertheless, they allow the conclusion that it is the mass distribution of the Pendulum 4 about the pendulum axis 5 allows to form a Tilger 1 according to Figure 1, which has a natural frequency, ie a Tilgereigenfrequenz at all rotational frequencies of the rotational movement 2, which is the same size as the current rotational frequency. The vibration damper 1 is thus effective at all rotational frequencies of the rotary motion 2. In specific embodiments of the vibration absorber 1, a plurality of pendulum 4 are mounted on the flange 9 of FIG. 1 in a rotationally symmetrical arrangement about the axis of rotation 3 about a pendulum axis 5 oscillating. In this case, the flange 9 typically has a central opening about the axis of rotation and mounting holes in a symmetrical arrangement about the axis of rotation 3. He can also form a pendulum 4 enclosing housing. In addition, the pendulum 4 can be elastically coupled to each other via elastic bands.

REFERENCE LIST Vibration absorber

rotary motion

axis of rotation

pendulum

swing axle

absorber mass

flange

Claims

1 . Vibration damper (1) for a rotary movement (2) about a rotation axis (3) superimposed vibrations, with at least one about a pendulum axis (5) oscillating mounted rigid pendulum (4), wherein the pendulum axis (5) with the rotational movement (2) in one fixed distance (R) to the axis of rotation (3) revolves around the axis of rotation (3), characterized in that the pendulum (4) has such a mass distribution about the pendulum axis (5) that the E igenfreq uenz d the Pend el mo and ung in the centrifugal force field due to the rotational movement (2) about the axis of rotation (3) is smaller than the rotational frequency (Ω) of the rotational movement about the axis of rotation (3).

2. Vibration damper according to claim 1, characterized in that the natural frequency of the pendulum movement of the pendulum (4) about the pendulum axis (5) in the centrifugal force field due to the rotational movement (2) about the axis of rotation (3) is the same as the rotational frequency of the rotational movement about the Rotary axis (3) or as half the rotational frequency of the rotational movement about the axis of rotation (3).

3. vibration damper according to claim 1 or 2, characterized in that the pendulum (4) for its oscillations about the pendulum axis (5) in the centrifugal force field due to the rotational movement (2) about the axis of rotation (3) has a reduced pendulum length, which is greater than that Distance (R) of the pendulum axis (5) to the axis of rotation (3).

4. Vibration damper according to one of claims 1 to 3, characterized in that the pendulum (4) has two absorber masses (6, 7) whose centers of mass lie opposite each other via the pendulum axis (5).

5. Vibration damper according to one of claims 1 to 4, characterized in that the pendulum (4) is damped with respect to its pendulum motion about the pendulum axis (5).

6. Vibration damper according to one of claims 1 to 5, characterized in that soft stops for the pendulum (4) are provided.

7. Vibration damper according to one of claims 1 to 6, characterized in that the pendulum axis (5) over the rotational movement (2) has a constant orientation to the axis of rotation (3).

8. Vibration damper according to claim 7, characterized in that the pendulum axis (5) parallel to the axis of rotation (3).

9. vibration damper according to claim 7, characterized in that the pendulum axis (5) tangent to the axis of rotation (3).

10. Vibration damper according to one of claims 1 to 6, characterized in that the pendulum (4) is mounted in a pivot bearing with a rotational degree of freedom for the pendulum axis (5).

1 1. Vibration damper according to one of claims 1 to 10, characterized in that a plurality of pendulum-mounted rigid pendulum (4) are provided, the pendulum axes (5) are arranged symmetrically to the axis of rotation (3).

12. Vibration damper according to claim 1 1, characterized in that the pendulum (4) are coupled together.

13. Vibration damper according to claim 12, characterized in that the pendulum (4) are elastically coupled.

14. Vibration damper according to one of claims 1 1 to 13, characterized in that the pendulum (4) are mounted on a fastened to a shaft flange (9).

15. Vibration damper according to claim 12, characterized in that the pendulum (4) are mounted within a closed housing at its periphery (12).