GB2354055A

GB2354055A - Speed-adaptive vibration damper

Info

Publication number: GB2354055A
Application number: GB0025338A
Authority: GB
Inventors: Wolfgang Prestel; Hans-Gerd Eckel
Original assignee: Carl Freudenberg KG
Current assignee: Carl Freudenberg KG
Priority date: 1998-07-11
Filing date: 1999-07-08
Publication date: 2001-03-14
Anticipated expiration: 2019-07-08
Also published as: GB2354055B; GB0025338D0

Abstract

A speed-adaptive vibration damper for a shaft rotatable about an axis (15) comprises a hub part (17), on which a number of inertia masses (19) adjacent in the peripheral direction are in each case mounted in two holders (21), which are adjacent in the peripheral direction and which comprise pins (1) which can roll on curved tracks (27, 29), curved in opposite directions, of the inertia masses (19) and the hub part (17) in such a way that, when torsional vibrations superimposed on a rotational movement are initiated, the distance of the inertia masses (19) from the axis (15) is reduced in the course of curved paths of movement. The curved tracks (27, 29) are lubricated with a traction fluid.

Description

2354055 Speed-adaptive vibration damper The invention relates to a

speed-adaptive vibration damper for a shaft rotatable about an axis, comprising a hub part, on which a number of inertia masses adjacent in the peripheral direction are in each case mounted in two holders, which are adjacent in the peripheral direction and which comprise pins which can roll on curved tracks, curved in opposite directions, of the inertia-mass elements and the hub part in such a way that, when torsional vibrations superimposed on a rotational movement are initiated, the distance of the inertia-mass elements from the axis is reduced in the course of curved paths of movement.

DE 196 31 989 Cl discloses such a speed-adaptive vibration damper.

On shafts of machines working in a periodic manner, for example on the crankshaft of an internal combustion engine, torsional vibrations superimposed on the rotational movement occur, and the frequency of these torsional vibrations varies with the speed of the shaft. Vibration dampers may be provided in order to reduce these torsional vibrations. These vibration dampers are designated as speed adaptive if they can dampen torsional vibrations over a larger speed range, ideally over the entire speed range of the machine.

The principle underlying the torsional-vibration dampers is that the inertia masses,, due to centrifugal force, attempt to revolve around the axis at the greatest possible distance when a rotary movement is initiated.

Torsional vibrations which are superimposed on the rotary movement lead to a relative movement of the inertia-mass elements inwards in the radial direction, which leads to a vibration-damping effect. The vibration damper has a natural frequency proportional to the speed, so that torsional vibrations which have frequencies which are proportional to the speed can be damped over a large speed range. A disadvantage of the known speed-adaptive vibration damper, however, is that the desired long service life is not reached on account of wear on the rolling combination of pin/curved tracks.

one aim of the invention is to develop a known 5 speed-adaptive damper in such a way that an especially long service life and operational reliability can be achieved.

The present invention provides a speed-adaptive vibration damper according to claim 1.

The pins can roll on rolling tracks which are lubricated with a traction fluid. The use of traction fluids is known in friction drives. By the use of such a lubricant in a vibration damper, the service life of the vibration damper is increased in a surprising manner. on the one hand, it provides for sufficient lubrication of the rolling combination of pin/curved track, yet sliding of the pin on the curved tracks is reliably avoided.

A further improvement is achieved owing to the fact that the viscosity of the traction fluid increases sharply under pressure. As a result, a coefficient of friction which ensures that the pin performs a rolling movement is achieved at the rolling combination of pin/curved track, where a high pressure prevails during operation.

It has proved to be especially advantageous if the traction fluid contains a synthetic oil of the cycloaliphatic hydrocarbon type.

An especially advantageous refinement of the invention may also be achieved by the pins being provided with first auxiliary means, which can be brought into engagement with appropriately shaped second auxiliary means of the curved tracks in order to prevent peripheral slip and/or axially directed relative displacements. The interengaging auxiliary means ensure that the pin performs a rotary movement.

The first and second auxiliary means may be formed by the interengaging of the projections and grooves. These may be designed, for example, as a tooth system between pin and curved tracks.

An especially advantageous refinement is achieved by the projections contacting the grooves in the region of conical surfaces.

A distinctly longer service life and operational reliability of the speedadaptive vibration damper are achieved by a design in which the pins each have a shell, which encloses a cavity, whichis empty or is filled with a material having a density which is lower than that of the shell. During relative movement of the inertia mass with respect to the hub part, the pin rolls on the curved tracks of hub part and inertia mass. The applied pressure on the rolling combination of pin/curved track is essentially determined by the speed of the rotating shaft. Due to the design according to the invention, the pin is able to follow the relative movement of inertia mass and hub mass more easily, so that a situation in which the pin performs a sliding movement, instead of a rolling movement, relative to the curved tracks is avoided. A surprising advantage is that this design makes it possible to use lubricants between pin and curved tracks in order to further increase the service life, which lubricants reduce the coefficient of friction at the rolling combination of pin/curved tracks. Such a low coefficient of friction in principle increases the risk of the pin sliding, since the tangential force at the contact points of pin/curved tracks is reduced by the use of the lubricant. However, this can be compensated for in an advantageous manner by the present invention.

The durability of the speed-adaptive vibration damper is further increased if the shell is enclosed by a wear-resistant coating.

30. The manufacture of the pin is simplified in particular if the shell of the pin is formed by a tube.

In a further advantageous refinement, provision is made for stiffening ribs projecting into the cavity to be provided. The stability of the pin, with a low pin weight at the same time ', is increased by these stiffening ribs.

In a development of this idea, provision may be made for the stiffening ribs to extend parallel to the longitudinal direction of the pin. Such a pin can be manufactured in an especially simple and cost-effective manner.

On the other hand, especially high stability is achieved by the stiffening ribs extending transversely to 5 the longitudinal direction of the pin.

In particular, the manufacture is further simplified if the stiffening ribs form a component of at least one stiffening element fitted into the cavity. In this refinement, a further increase in the stability of the pin can be achieved by the stiffening element being arranged under prestress in the cavity of the pin, so that the stiffening element exerts a force directed radially outwards on the shell of the pin.

In an advantageous refinement, provision is made for the stiffening element to be formed by at least one ring or a helix.

Especially high stability, with low pin weight at the same time, is also achieved by the ring or the helix, in at least one section, having a rectangular profile arranged transversely to the longitudinal direction of the pin.

The resistance of the pin to pressure loading is further improved if the material in the cavity is essentially non-deformable. Suitable materials are, in particular, epoxy resin, a sintered body of metal, expanded aluminium, phenolic resin, porcelain and industrial ceramics. Compared with the shell, which may be made of high-strength steel, for example, these materials have a low density and, due to their high dimensional stability, increase the strength of the pin. Materials having similar coefficients of thermal expansion are preferably used, so that stresses in the pin which are induced by temperature fluctuations are reduced.

Embodiments of the invention will now be described in more detail, by way of example only, with reference to the accompanying drawings, in which:

Fig. 1-i's a plan view of a pin which may be used with the present invention, Fig. 2 is a longitudinal section through the pin shown in Fig. 1, Fig. 3 is a plan view of a further embodiment of a pin which may be used with the invention, Fig. 4 is a longitudinal section through a further 5 embodiment of a pin which may be used with the invention, Fig. 5 is a front view of a speed-adaptive vibration damper, Fig. 6 is a cross section through the speed-adaptive vibration damper shown in Fig. 5, and Fig. 7 is a cross section through a pin which may be used with the invention in a further embodiment.

Shown in Figures 1 and 2 is a pin 1 having a shell 3, which encloses a cavity 5.

The shell 3 is a tube made of high-strength steel and having a circular cross section. The interior of the tubular shell 3, which is open on both sides, defines the cavity 5.

Placed in the cavity 5 is a material 7 which has a lower density than the shell 3. The material 7 used in the cavity 5 is an essentially non-deformable material. According to the invention, in particular epoxy resin, a sintered body of metal, expanded aluminium, phenolic resin, porcelain and industrial ceramics are suitable. The shell 3 of the pin 1 can be supported in the radial direction of the pin 1 by these materials, as a result of which the stability of the pin 1 can be increased. At the same time, the weight of the pin 1 is reduced owing to the fact that the material 7 has a lower density than the shell 3.

The pin 1 filled with the incompressible material 7 can be produced by the material 7, for example epoxy resin, being poured into the cavity 5. However, it is also possible to shrink the tubular shell 3 of the pin 1 onto a prepared piece of material, for example made of porcelain or ceramic. In this way, a prestress, which has a positive effect on the service life of the pin 1, can be produced in the pin 1.

A wdar-resistant coating 9 is provided on the outside of the shell 3. Wear on the pin 1 can be reduced to a minimum by this coating 9. The coating may comprise for - 6 example, a hardness layer.

In the embodiment of a pin 1 shown in Figure 3, stiffening ribs 110, which project into the cavity 5, are provided on the inside of the tubular shell 3. The stiffening ribs 1 increase the loading capacity of the pin 1 under compression and bending stress. The stiffening pins 11 extend parallel to the longitudinal direction of the pin 1 over its entire length. However, the stiffening ribs 11 may also be oriented transversely to the longitudinal direction of the pin 1.

In the semilateral longitudinal section through a pin I shown in Figure 4, the shell 3 is likewise of tubular design. A number of stiffening ribs 13, which increase the loading capacity of the shell 3 in the radial direction, are fitted in the cavity 5. Like the cavity 5, the stiffening ribs 13 have a circular cross section and are of pot-shaped design. The stiffening elements 13 are held in the cavity 5 by virtue of the fact that they bear against the shell 3 in an elastically deformed manner. However, they may also be designed as a ring or as a helix. Such a ring or helix, in at least one section, advantageously has a rectangular profile arranged transversely to the longitudinal direction of the pin 1.

Figure 5 shows a speed-adaptive vibration damper for a shaft (not shown) rotatable about an axis 15, the vibration damper having a hub part 17 and a number of inertia masses 19 adjacent in the peripheral direction. For each inertia mass 19, the hub part 17 has in each case two holders 21, adjacent in the peripheral direction, in order to mount the inertia masses 19 on the hub part 17.

Each holder 21 is formed by a recess 23 in the hub part 17 and a pin 1 accommodated therein. In this case, the pin 1, whose longitudinal axis runs parallel to the axis 15 of the hub part 17, extends into a recess 25, formed as an aperture, in the inertia mass 19.

The hub part 17-has a curved track 27 defining the recess 23, and the inertia-mass element 19 has a curved track 29 defining the recess 25. The curved tracks 27, 29 and the pin 1 are designed and arranged in such a way that the inertia masses 19 can move relative to the hub part 17 while performing a pendulum motion. In the process, the pins 1 roll on the curved tracks 27, 29, which are curved in opposite directions. In this case, the curved track 27 in the hub part 17 points in the direction of the axis 15, whereas the curved track 29 in the inertia mass 19 points outwards away from the axis 15.

When a torsional vibration superimposed on a rotational movement of the shaft occurs, the inertia masses 19 are moved out of their centre position shown in Figure 5 relative to the hub part 17 along a curved path of movement, which is determined by the curved tracks 27, 29 and the pin 1. In this way, the distance of the centre of gravity of the inertia masses 19 from the axis 15 is reduced. The forces exerted in the process on the hub part 17 by the inertia masses 19 via the curved tracks 27, 29 dampen the vibrations. This vibration damping is optimal if the exciting frequency at a given speed corresponds to the natural frequency of the damper. In this case, the natural frequency of the damper changes in proportion to the speed of the shaft.

In addition, the inertia masses 19 have guide tracks 31 opposite the curved tracks 29 in the recess 25, so that the recess 25 is given the shape of a U, which is directed away from the axis 15. Corresponding guide tracks 33 opposite the curved tracks 27 are also formed in the holder 21 of the hub part 17 (cf. Fig. 6).

The curved tracks 27, 29 and the guide tracks 31, 33 form components of insert parts 41, 43, which are captively accommodated in the hub part 17 and the inertia masses 19 respectively. The insert parts 41, 43 may also be inserted loosely to begin with and, by subsequent shaping of the layer 45, 47 carrying the guide tracks 31, 33, may be adhesively bonded to the hub part 17 and the inertia masses 19 respectively.

The cross section along the axis 15 shown in Figure 6 illustrates the arrangement and mounting of the inertia masses 19 on the hub part 17. In the embodiment shown in Figure 6, the inertia masses 19 are arranged in an axially adjacent position in pairs on both sides in the hub part. However, it is also possible to arrange the inertia masses 19 in such a way that the hub part 17 axially encloses the inertia masses 19 on both sides.

The outer hub part 17 forming the holders 21 is enclosed by caps 35 sealed off from the hub part 17, so that a chamber 37 is obtained.

A lubricant is accommodated in the chamber 37. This lubricant passes in particular through the passages 39 formed in the inertia masses 19 to the pins 1 and the curved tracks 27 and 29, on which the pin 1 rolls. Only a small amount of lubricant is contained in the chamber 37 in order not to hinder the pendulum movement of the inertia masses 19 relative to the hub part 17 to such an extent that the vibration-damping effect would be considerably impaired as a result.

The lubricant used for the curved tracks 27, 29 is a traction fluid, the viscosity of which increases sharply under pressure. This ensures that the pin performs no sliding movement, which leads to premature wear, on the curved tracks. The traction fluid used may be a synthetic oil of the cyclo-aliphatic hydrocarbon type. The service life of the speed-adaptive vibration damper is considerably increased by this use, according to the invention, of the lubricant.

Figure 7 schematically shows a further embodiment of a pin 1 according to the invention with a detail of the curved track 29. The pin 1 is provided with first auxiliary means 49, which can be brought into engagement with appropriately shaped second auxiliary means 51 of the curved tracks 27, 29 in order to prevent peripheral slip and/or axially directed relative displacements. The first and second auxiliary means 49, 51 are designed as interengaging projections'- and grooves. These may be designed, for example, as an interengaging tooth system of curved tracks 27, 29 and pin 1, this tooth system being shown by chain-dotted lines in Figure 7. In this case, the pins I and the curved tracks 27, 29 may be designed in such a way that the projections contact the grooves in the region of conical surfaces.

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Claims

1. A speed-adaptive vibration damper for a shaft rotatable about an axis, comprising a hub part, on which a number of inertia masses adjacent in the peripheral direction are in each case mounted in two holders, which are adjacent in the peripheral direction and which comprise pins which can roll on curved tracks, curved in opposite directions, of the inertia masse and the hub part in such a way that, when torsional vibrations superimposed on a rotational movement are initiated, the distance of the inertia masses from the axis is reduced in the course of curved paths of movement, wherein the pins can roll on curved tracks which are lubricated with a traction fluid.

2. A speed-adaptive vibration damper according to claim 1, wherein the viscosity of the traction fluid increases sharply under pressure.

3. A speed-adaptive vibration damper according to claim 1 or 2, wherein the traction fluid contains a synthetic oil of the cyclo-aliphatic hydrocarbon type.

4. A speed-adaptive vibration damper according to claim 1, 2 or 3, wherein the pins are provided with first auxiliary means, which can be brought into engagement with appropriately shaped second auxiliary means of the curved tracks in order to prevent peripheral slip and/or axially directed relative displacements.

5. A speed-adaptive vibration damper according to claim 4, wherein the first and second auxiliary means are formed by interengaging projections and grooves.

6. A speed-adaptive vibration damper according to claim 5, wherein the projections contact the grooves in the region of conical surfaces.

7. A speed-adaptive vibration damper substantially as described herein with reference to Figures 5 and 6 of the accompanying drawings.

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