GB2121914A

GB2121914A - A damped rotary-oscillation or torsional vibration eradicator

Info

Publication number: GB2121914A
Application number: GB08315460A
Authority: GB
Inventors: Klaus Federn
Original assignee: Individual
Current assignee: Individual
Priority date: 1982-06-09
Filing date: 1983-06-06
Publication date: 1984-01-04
Also published as: GB2121914B; DE3222258A1; DE3222258C2; JPS596449A; GB8315460D0

Abstract

The damped rotary-oscillation eradicator has annular secondary rotary masses 1, 2 which engage the one around the other and which are connected to the primary mass by sleeve-shaped parallel-acting visco- elastic spring elements 5, 6 which engage around one another in a cascade-like manner from two sides. At the two-sided free surfaces of the spring elements, 5, 6 these are freely accessible, during production, for shaping tool or mould parts, so that the edge cross-sections of the spring elements 5, 6 are relieved of (or do not provide) connection surfaces between the spring elements 5, 6 and the metal parts 1, 2. Such a construction achieves a space-saving highly-effective construction having a long useful life. <IMAGE>

Description

SPECIFICATION A damped rotary-oscillation or torsional vibration eradicator This invention relates to a damped rotaryoscillation (or torsional vibration) eradicator having a rotary eradicator mass which is designed as a co-oscillating or resonant annular two-part housing for a damping fluid, a flange/hub element for connection to the rotor that is to be damped in its rotary oscillations, and visco-elastic spring elements which couple the rotary eradicator mass to the flange hub element with a determinable resonance frequency.

Such rotary-oscillation dampers (or torsionalvibration balancers) and damped rotaryoscillation eradicators usually consist of a rotary mass, capable of rotary oscillations, of a secondary system, which mass is coupled by way of a damping system element or by way of a damping and a resilient system element, both belonging to this secondary system, to a rotaryoscillating primary rotor mass in such a way and in attuned manner such that resonance rotary oscillations of the primarily mass are damped or suppressed to the desired degree.Such rotaryoscillation dampers or damped rotary-oscillation eradicators have to be used very frequently in conjunction with piston engines, so that impermissible resonant oscillations occurring upon the coincidence of the speed-dependent oscillation-exciting frequencies, stemming from mass forces and for example from gas forces, with a rotary inherent-oscillation frequency of the primary system, are avoided. Often, therefore, rotary-oscillation dampers or damped rotaryoscillation eradicators are connected to the free crankshaft end of an internal combustion engine.

The laws according to which such oscillation dampers or damped eradicators are to be calculated and be coordinated in optimum manner in any particular practical need are known as a result of research and development work over several decades. Difficulties still arise, however in achieving a cost-favourable design, or a design which utilises the available space as well as possible, or absolutely operationally-reliable design of such dampers or damped eradicators.

So-called viscous rotary-oscillation dampers are known in which the secondary mass, designed as a ring, can move within a closed annular housing which is connected to the primary mass, in which connection the gap remaining all around the secondary mass is filled with a damping medium in the form of silicone oil or fluid. Since this damping medium, upon alternating shear action, also develops alternating restoring moments, these viscous rotary-oscillation dampers work, basically, already with an eradicator action based on the spring action of the silicone oil; in other words they are no longer pure dampers in the basic sense of the words and belong, strictly speaking, to the known group of damped rotary-oscillation eradicators. What is disadvantageous is that these dampers do not, as originally assumed, work in a maintenance-free manner.Their useful life is limited to a degree which is not precisely foreseeable. Wear cannot be avoided in the sliding bearing of the ring in the housing. Also, the comparatively large rotary mass, co-oscillating with the primary mass part, of the housing has a disadvantageous effect.

Recent embodiments are known in which the housing represents a part of or even the entire secondary mass. Then, however, in order to be able to enclose the silicone oil reliably in the gap, an elastic seal made of a visco-elastic material has to be mounted between a flange on the primary mass and the housing. In such embodiments, the visco-elastic sealing element has to be widened in its dimensions in such a way that it contributes considerably to the resilient coupling of the secondary mass to the primary mass. In one known embodiment, such viscoelastic spring elements are accommodated as rotary-shear-stressed disc springs between the housing halves and a central web designed as a continuation of the fastening flange.

The problem underlying the invention is to provide a damped rotary-oscillation eradicator which, with the largest possible secondary rotary mass, has a connection of primary and secondary rotary mass by particularly wide visco-elastic springs elements which have, besides the sealing action, also a decisive spring action.

In accordance with the invention, this problem is solved in that the visco-elastic spring elements, which are thin-walled in relation to their width, are designed substantially not as discs in radial planes, but as axial hollow cylinders or sleeves engaging around one another from two sides in a cascade-like manner, so that the existing damper width, usually restricted for reasons of space, is approximately doubled and is utilised on the smallest possible radius by the visco-elastic spring elements which are aligned axially with their substantially rectangular cross-section, and there is reserved to the annular rotary masses the largest possible share of the mass action, increasing outwardly to the 3rd power, of crosssectional area or surface elements within the available space.

The damped rotary-oscillation eradicator in accordance with the invention obviates the disadvantages, discussed above, of the known viscous rotary-oscillation damper. With a preset construction space it is particularly important for a damped eradicator (or else already for a rotaryoscillation damper) for this construction space to be utilised as widely as possible for the accommodation of the secondary rotary mass. It determines primarily how far the oscillation deflection (or amplitude) in the resonance passage or range of the primary mass can be reduced by a damped eradicator. (This is also the reason why, in the case of new developments, one strives to avoid a dead housing mass which co-oscillates with the primary mass).A surface (or areal) element of specific size, for example a unit surface element in a cross-sectional area which is restricted for reasons of space, contributes with the third power of its radius to the overall moment of inertia fff r2 pdV of the secondary mass. With a given design and a given material, on the other hand, the energy absorptive capacity of a spring depends only upon the spring volume. It is therefore advantageous, with a view to a largest possible secondary rotary mass, to accommodate the spring element or the spring-element parts with a suitable design as close as possible to the axis (insofar as the flange dimensions preset by the rotor to be damped so allow). Shear-stressed, visco-elastic spring elements which have, besides the sealing action, also a decisive spring action, have a width which is large in relation to their thickness.The invention puts this circumstances to use.

The invention will be described further, by way of example, with reference to an exemplified embodiment, as shown in the drawing, of the damped rotary-oscillation eradicator of the invention. In the drawing: Figure 1 is a side view, sectioned in the lower half, of the eradicator; and Figure 2 is an enlarged sectional view of the upper half of the eradicator of Figure 1.

As illustrated in Figures 1 and 2, the eradicator comprises parallel-acting, visco-elastic sleeveshaped spring elements 5, 6 which engage around one another. The outer spring element 6 is, in this respect, larger in its wall thickness to the extent that its mean radius is greater, so that the alternating shear'stresses as a result of a relative oscillation between secondary masses 1, 2 and primary mass 3 in both spring elements 5, 6 remain at the same value, the value considered as permissible with safety.

The hollow-cylinder-like or generally axiallyelongated sleeve-like design of the visco-elastic spring elements, in accordance with the invention, additionally affords the advantage that their stiffness relative to radial displacements of the secondary masses 1, 2 relative to the flange 3 on the primary mass is higher than their stiffness in the axial direction (thin-walled "rubber elements" or "metal-rubber composite elements" have, as is known, a considerably higher compression-tension stiffness than shear stiffness). In the case of disc-shaped rubber elements the ratio of radial transverse stiffness to axial stiffness would be reversed. The same goes also for the centring accuracy of the secondary masses 1, 2 relative to the primary mass 3, which depends upon the production tolerances of the visco-elastic spring elements 5, 6 therebetween.

A high stiffness in the radial direction is necessary, so that the resonant rotary speed at which the annular secondary mass 1, 2 performs transverse oscillations relative to the primary mass 3 or shifts radially impermissibly imbalanceoccasioned and imbalance-reinforcing lies as high as possible above the highest operational speed of the rotor that is to be damped.

In order to be able to connect visco-elastic elements, such as for example rubber (natural rubber) or Viton (Trade Mark), in a fatigue-fast manner and tightly to the adjacent metal parts, it is advantageous for their free or unbound surfaces to be accessible from the outside in an unimpeded manner for shaping tool or mould parts during production. Therefore, in accordance with the invention provision is made for dividing the secondary system into constructional elements or components in such a way that the visco-elastic elements are accessible in an unimpeded manner from both sides at their free surfaces for the purposes of facilitating production for example by vulcanising connection to the adjacent metal parts. In the design shown in Figures 1 and 2, during the connection of the ring parts still not connected on the outside in Figure 2 a bias, reinforced by wedging or keying action, perpendicularly to the bounding surfaces of the visco-elastic shape or form or spring elements can also be applied in the case of their engaging around one another in a cascade-like manner.

For ease of reference the following is a schedule of the components of the embodiment above described with reference to the drawing: Reference Component numeral Rotary mass of the eradicator 1 Rotary mass of the eradicator 2 Flange/hub element 3 Connecting ring 4 Visco-elastic spring element 5 Visco-elastic spring element 6 Damper mass 7

Claims

1. A damped rotary-oscillation or torsional vibration eradicator having a rotary eradicator mass which is designed as a co-oscillating or resonant annular two-part housing for a damping fluid, a flange/hub element for connection to the rotor that is to be damped in its rotary oscillations and visco-elastic spring elements which couple the rotary eradicator mass to the flange/hub element with a determinable resonance frequency, characterised in that the visco-elastic spring elements, which are thin-walled in relation to their width, are designed substantially not as discs in radial planes, but as axial hollow cylinders or sleeves engaging around one another in a cascade-like manner from two sides, so that the existing damper width, generally restricted for reasons of space, is approximately doubled and is utilised on the smallest possible radius by the visco-elastic spring elements which are aligned axially with their substantially rectangular crosssection, and there is reserved to the annular rotary masses the largest possible proportion or share of the mass action, increasing outwardly to the 3rd power, of cross-sectional areal or surface elements within the available space.

2. A rotary-oscillation eradicator as claimed in claim 1, characterised in that it is composed of individual components or constructional elements, of which two, being respectively a rotary-mass part and a visco-elastic spring element, impart the mass and spring action, whilst a further component or constructional element, or a further subassembly, impart the primarily damping action, the division into the components or elements being untertaken in such a way that in each individual one of the two firstmentioned components the visco-elastic elements are shaped to be accessible for shaping tool parts in an unimpeded manner at their free surfaces during production.

3. A rotary-oscillation eradicator as claimed in claim 1 or 2, characterised in that the viscoelastic spring elements engaging around one another are designed as two individual components in such a way that, upon the connection of these components during the fitting of the damped rotary-oscillation eradicator they are given a bias, reinforced by wedging or keying action, perpendicularly to the bounding surfaces of the visco-elastic elements.