DE8418913U1 - Viscoelastically damped torsional vibration absorber with spring-coupled flywheel ring - Google Patents

Description

Prof. Dr.-Ing. Klaus Federn · · ·· · '

Vlskoelastfsch damped torsional vibration anti-lger with spring-coupled flywheel

Description of the invention:

So-called torsional vibration dampers have been used for decades to reduce the torsional vibration amplitudes of the engine system of diesel engines and other drive systems. In terms of vibration technology, they are more correctly referred to as damped torsional vibration dampers when a highly viscous damping medium is used for damping in the gap between a flywheel ring and a housing that encloses it. In addition to the viscosity characterized by its loss modulus G" ^e 11<(l (with T| as dynamic viscosity and Ω as oscillation frequency), this medium also has a shear stiffness characterized by the storage modulus G' [1, p. 29 ... 37]. Increasingly, additional spring elements are also being used to couple the flywheel (the so-called secondary mass) and the flanged housing (as the primary mass) [2, 2], because the shear stiffness of the highly viscous medium is usually not sufficient for the optimal tuning of a torsional vibration damper [4]. The optimal tuning of a damped torsional vibration damper is particularly necessary when the power per unit of piston area of diesel engines is increased by up to three times due to the high turbocharging. This is because the alternating torque components that cause the torsional vibrations are also significantly increased in higher orders.

Additional spring elements are also used to replace the previously predominant plain bearing of a silicone oil-damped flywheel with an elastically centering bearing without wear and thus without abrasion that could potentially destroy the damping medium [5]. It should be noted that in torsional vibration damping, mechanical energy is converted into heat by dissipotion and that the temperature in a damped torsional vibration damper can therefore practically fluctuate within the range of 40 °C to 120 °C. This has a significant impact on the loss modulus G" of the medium, for example, in the ratio 3:2 for the limits given for polymethylsiloxane AK 200000; the storage modulus G' is even more affected, for example, in the ratio 7:3 for the limits given [1, p. 37]. On the other hand, the high spatial thermal expansion coefficient of the highly viscous medium can cause problems due to pressure increases (up to 30000 hPa), not only due to additional loads on the screw connections and seals in the housing, but also due to the change in the

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Width of the damping space filtered with the metal housing, efforts have therefore always been made to keep the volume of the damping space small. This is no longer possible, although the spring coupling of the flywheel is only used for elastically centering support of the flywheel in the housing. With steel springs, only the change in shape with the displacement of individual spring sections can be utilized, but not the shape-preserving shear elasticity (as with rubber springs, for example, [o]) or even the volume elasticity as with gas springs.

Compared to springs made of elastomers and also compared to the shear elasticity of a highly viscous damping medium, steel springs have the advantage that their spring stiffness is practically independent of temperature. However, this temperature independence can only be exploited if the steel springs and their changes in shape do not lead to the displacement of the highly viscous medium, because the high shear rates that occur in the highly viscous medium, which can far exceed the shear rates in the damping gap, lead to high values of the speed-dependent parameters G" and in particular G' and to an increased temperature dependence of these values. But it is precisely a high temperature dependence of the storage modulus G' that is a hindrance, because it only allows optimal adjustment of the coupling spring stiffness between the flywheel and the housing for a single temperature or, in practice, a very narrow temperature range [4].

According to the invention, to solve this problem, i.e. to avoid these difficulties, it is therefore proposed to keep the space around the elastically centering or coupling spring elements, which improve the tuning, free from the highly viscous medium by installing additional elastically dynamically deformable elastomer seals inside the housing, which separate the gap with the highly viscous medium from the space around the spring elements. If the flywheel is assembled from parts or if screws are used to attach spring elements to the flywheel, additional seals that are not subject to dynamic stress are required to hermetically seal the space around the spring elements.

One of the advantages of the inventive addition of elastically deformable, dynamically stressable sealing elements in the housing is that the housing with its only statically stressed seals is retained to securely seal the gap with the highly viscous medium, thus fulfilling a requirement that can be raised for environmental protection. The separation of the space by the additional elastically deformable

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Springs, preferably rigid ^springs , allow for a more flexible opening of the spring elasticity by avoiding the displacement damping and displacement stiffness around the spring elements, and there is no need to worry about minimizing the unavoidable, unusable space around the deformable support elements. This leads to an optimal solution to the task set at the beginning of keeping the space filled with a highly viscous medium, e.g. silicone oil, as small as necessary and possible. Finally, the additional dynamic stress caused by changing medium displacement is also eliminated for the additional supporting or coupling spring elements in the subspace hermetically sealed from the highly viscous medium.

In Figure 1, (01) is the flange part of the housing, with which a damped torsional vibration absorber or torsional vibration damper is connected to the engine part whose torsional vibrations are to be counteracted, e.g. a crankshaft of an internal combustion engine, usually by screws. (02) and (03) are the housing enclosing the flywheel ring ^and the associated housing cover. In Figure 1, both are connected to the flange part by screws (04) and (05) and to each other by screws (06), with sealing rings (07a), (07b) and (08) in circumferential grooves hermetically sealing the interior of the housing from the outside in a known manner.

Spring elements, preferably steel spring elements, in this case vertically bent bending springs (10) or (10a) and (10b) in Figure 3', are connected to the additional flanges (09a) and (09b) belonging to the so-called primary mass (01), (02) ... (08), by means of screws arranged several times along the circumference, with screw bolts (11) and the symmetrically arranged nuts (12a) and (12b) and washers (13a) and (13b). (In Figure 1, only (12b) and (13b) are shown in the right-hand side of the figure.) In order to separate spring elements that do not vibrate in the same direction, additional washers (14) may be necessary between them, as in Figure 3. The springs are each connected to the ring parts (20a) and (20b) with their second clamping head using screw bolts (15), symmetrically arranged nuts (16a) and (16b) and washers (17a) and (17b). (This time only (15), (16a) and (17a) are shown in the left half of Figure 1.) The space around the ring parts is sealed against the space around the springs by elastomer springs (21 a) and (21 b) that are elastically deformed by shear. These sealing,

&diams;) e.g. according to DE 2818296 A 1, Figure 1

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Elastomer elements subject to alternating deformations within the closed housing can be bonded to the ring parts by vulcanization in one non-free surface or in both non-free surfaces, !^ for example at points (22a) and (22b).

[|. However, they can also be subject to shifts under the influence of

centrifugal forces or an overpressure in a gap with the highly viscous medium.'■ ...

I wanted to generate overpressure in the air or gas-filled space around the springs to elastic

|; Sealing elements (21 a) and (21 b) against centrifugal forces or against temperature

I ture-dependent overpressure in the outer gap space with the highly viscous medium*

To seal the space around the springs, sealing rings (24a) and, symmetrically to this, but not shown, (24b) and also (25) are fitted in matching, finely machined grooves; the sealing elastomer rings (24a) and (24b) around the screw bolts can be inserted into grooves on the bolts (15) or in grooves on the holes, as shown in Figure 3 with (24b").

5{ Assembly or occasional disassembly is not hindered if, instead of a nut , e.g. the one not shown (lob), a screw head (18) is arranged as shown in Figure 2 _, which is hermetically sealed against the gap (26) by a cap (19), but at the same time is positively secured against loosening by surfaces in the cap. I It is also possible to weld a sleeve (27") on one side as shown in Figure 3,

j which then replaces the fitting bolt with a normal head screw screwed into a blind hole.

I be (28"). To prevent rotation of locking screw heads (28")

* To be able to use it, a collar washer (29") is required, which is against the sleeve

I is positively secured against rotation by claws (30").

% If leaf springs clamped radially on both sides in a wedge shape are used as shown in Figure 4,

js den, then the screws for fastening the additional springs can be avoided. Such leaf springs (10') can be reversible or corrugated, as shown in Figure 4, in order to mitigate constraining stresses in the radial direction in the event of larger bending deformations.

In Figure 4 , parts already shown in Figure 1 are marked with the same symbols. These are marked with a comma ' if the parts had to be readjusted in their shape. The inner clamping head of the leaf spring (10'), (40), is clamped in the circumferential direction by circular ring sections (41 a) and (41 b), for example by radial screws (42a) and (42b) _t Figure 5.

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The heads (43 a) and (43 b) of a spring (10') or of two springs (10a') and (10b') are also clamped in the circumferential direction by circular ring sections, the latter resting pre-tensioned in circumferential grooves (with the profile of the heads (43o) and (43b)) in the ring part (20a') without additional screws. This pre-tensioning can be kept in balance by a shrink ring (45) around the slotted part of ring (20a') with slots (44).

The space around the springs (10') or (10' a) and (10' b) arranged three or more times around the circumference is in turn separated according to the invention by dynamically deformable elastomers (21 a') and (21 b') and the statically stressed sealing element (25').

&Ggr; ⁸ &Ggr; Prof. Dr.-Ing. Klaus Federn !··* «f.. ·&iacgr;· *··"*··* *·»

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{1 ] HARTMANN, R.: Calculation of the dynamic behavior of viscous torsional vibration dampers. Dr.-lng. Diss. TU Berlin.

[2] DE 2818290 Al.

&iacgr; 31 DE 32 21 987, Carl Hasse & Wrede GmbH, 11.6.1982 (F 16 F 15/16, 15.12.1983).

[4] FEDERN, K.: Generalized Criteria for the Evaluation of Torsional Vibration

Dampers. Third Intern. Conf. "Vibrating in Rotating Machinery", 11-13 Sept. 1984, Univ. of York (manuscript enclosed).

15] DE 2818295 Al.

[&oacgr;] DE 3222258, FEDERN, K., 9.6.1982 (F 16 F 15/14, 15.12.1983).

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Claims (1)

Prof. Dr.»Ing. Klaus Federn Viscous elastically damped torsional vibration absorber with spring-coupled flywheel fr/Sjnsp rüche: T. Torsional vibration damper with a flywheel damped by a highly viscous medium and coupled by the viscoelasticity of this medium and by one or more additional springs, consisting of this ring-shaped flywheel mass, a housing enclosing it with a flange part, the highly viscous medium in a gap between the flywheel and the housing, one or more additional spring coupling elements between the flywheel and the flange part and sealing elements made of elastomers, characterized in that the space around the additional spring coupling elements or elastically centering spring elements is not filled with the highly viscous liquid, but is separated from the gap with the highly viscous liquid by sealing elements made of a rubber-like elastomer that are elastically dynamically deformed in the operating state, in addition to the non-dynamically deformed sealing elements that may still be required for complete separation in the installation space of the flywheel that torsional vibrates under operating conditions. 2. Torsional vibration damper according to claim 1, characterized in that the additional spring elements are spiral springs which are bent edgewise in their free lengths and which enclose the axis and which are connected on the one hand to the housing or its flange part and on the other hand to the flywheel ring in an adhesive, positive or materially bonded manner. 3. Wire vibration damper according to claim 1, characterized in that the additional spring elements are bending-stressed, preferably substantially radially directed, flat or corrugated, flat bending-stressed leaf springs. 4. Torsional vibration damper according to claim 1, characterized in that the additional spring elements in their free lengths are each vertically bent disc springs, which each only partially enclose the axle. 5· Torsional vibration damper according to claim t and one or more further claims, characterized in that the screws which connect the flywheel ring parts and the additional spring elements to one another preferably in a frictionally locking manner. &bull; ■ · · ·#···*· f ff t which are simultaneously used to preload the elastically dynamically loaded sealing elements, which separate the gap space with the highly viscous medium and the space around the additional spring elements. 6. Torsional vibration damper according to claim 1, 2 or 4 and optionally also 5, characterized in that sealing rings are arranged between the screws for the adhesive connection according to claim 2 and optionally claim 5 and the associated screw shaft bores in the flywheel ring, either in grooves around the screw bolts, or in grooves in the bores for the screw bolts, or for the sleeves enclosing them. 7. Torsional vibration damper according to claim 1 and optionally further claims, characterized in that the screw bolts for connecting the additional spring elements to flywheel ring parts are screwed into sleeves which, through weld seams between them and ring parts, form a hermetic seal between the gap filled with the highly viscous medium and the space around the additional spring elements. 8» Torsional vibration damper according to claim 1 and optionally further claims, characterized in that the space around the additional springs is filled with air or an inert gas such as nitrogen, optionally under excess pressure. 9. Torsional vibration damper according to claim 1 and optionally further claims, characterized in that the elastically dynamically deformed sealing elements are connected to a flywheel part or a housing or flange part or on both sides by vulcanization or suitable adhesive. 10. Torsional vibration damper according to claim 1 and optionally further claims, characterized in that the space ur, the additional springs H and its pressure can be influenced from the outside as required.