GB2108239A - Torsionally resilient hydraulically damped coupling - Google Patents

Abstract

Two flanges (1, 2) secured to shafts are provided with drivers which are embraced by a rubber element (8) present between the flanges, the element for its part having chambers (12) between the drivers filled with damping fluid. The chambers (12) present respectively on opposite sides of a driver are connected together through a throttle opening (7). In order to retain accurately defined chamber relationships and as large as possible a specific displacement volume, which determines the damping, whilst retaining simple manufacture and assembly, the rubber element (8) has on its end faces mutually offset axially extending blind holes (11) for receiving the drivers and sheet metal discs (16, 17) bonded to it to form a unit, by means of which discs the rubber element (8) is connected and sealed to the flanges (1, 2). The chambers (12) extend both through the element (8) and also through the discs (16, 17) and are closed off by the flanges (1, 2). <IMAGE>

Description

SPECIFICATION Torsionally resilient hydraulically damped coupling The invention relates to a torsionally resilient hydraulically damped coupling comprising two flanges designed to be secured to respective shafts, each carrying at least three interengaging drivers, and a one-piece rubber element engaging and fitting around the drivers, with chambers formed between the drivers and filled with damping fluid, and throttled openings formed in the drivers of at least one of the flanges, through which the chambers present on opposite sides of these drivers are in communication.

From DE-AS 2717170 there is known atorsionally resilient hydraulically damped coupling in which, on each of two hubs arranged spaced apart and each provided with a flange there are secured four cropped spokes acting as drivers, and which interengage one another but are spaced apart. In the clearance between two spokes, which are associated with a respective one of the opposed hubs, there are inserted pre-loaded rubber elements of matching shape and the elements are connected to the spokes and have two chambers separated by a supporting wall and open towards the spokes for receiving damping fluids. The rubber elements are vulcanised to the supporting walls.The chambers present on opposite sides of a spoke are in fluid communication with one another through a throttled opening in the spoke. in the event of elastic deformations of the rubber elements associated with torsional oscillations of the coupling, the volume of the chamber on one side of the spoke is increased whilst that of the other chamber is correspondingly reduced. Accordingly a transfer of the damping fluid takes place through the throttled opening. The dimensions of the throttling openings can be chosen as desired to produce damping forces which, for example, ensure smooth running of an engine and prevent resonant vibrations. Unfortunately, because of the multiplicity of rubber-metal components this coupling requires a high outlay in manufacture and assembly.The fact that each two rubber elements can be vulcanised rigidly to one spoke only reduces this outlay to a negligible extent.

In DE-OS 29 30 244 there is disclosed a torsionally resilient hydraulically damped coupling comprising an inner body capable of being secured to the one shaft and an outer component enclosing it but spaced radially from it and connected to the other shaft through a cover member. The inner body carries four radially outwardly directed driving projections which lie midway between driving webs that project inwards from the outer component. The projections are connected to the webs by a rubber spring element with the simultaneous formation of chambers between the adjacent drivers. Again, the chambers are filled with damping fluid and connected together through transfer passages.It is true that this coupling has a simple form of construction and is easy to assemble but it has the drawback that the specific volume of fluid displaced per unit of angle is relatively small and moreover not capable of accurate determination, as a consequence of the chamber relationships of the chambers on angular displacement being difficult to define which cannot be accurately defined on accurately - the rubber element is vulcanised not only to the drivers but also to the inner body and to the outer component; losses of volume arise which are not capable of being employed for damping - relatively small and furthermore cannot be accurately ascertained.

Moreover compression and tension stresses can arise in the rubber spring element.

Accordingly the aim of the invention is to provide a coupling of the kind described in the introduction, which, despite simple manufacture and low assembly costs, allows accurately defined chamber relationships and a large specific displacement volume.

This is achieved according to the invention in that the cylindrical rubber element is provided on its two end faces with relatively offset axially extending blind holes for receiving the inserted drivers, the chambers present between the blind holes are formed to extend axially right through, and the rubber element carries on its end faces sheet metal discs connected to it, these discs having openings alligned with the blind holes and the chambers and forming means by which the rubber element is capable of being sealed to the flanges.

A coupling constructed in this way has a freely deformable rubber element which produces accurately determinable chamber relationships without loss of volume and a large specific displacement volume, and ensures a consequent high degree of damping. Compression and tension stresses are largely eliminated. Assembly can be carried out in a simple manner and without large outlay.

The blind holes that receive the drivers are preferably clad with sheet metal or the like, eliminating friction between the drivers and the rubber element. Preferably that the blind holes and the drivers have at their radially outwardly directed ends a trapezium-shaped end cross section, as a result of which the pumping effect and thereby also the damping are further improved. This is also assisted by arranging that the outer wall of the rubber element is bulged inwards in the region of the chambers.

A central opening passing right through the rubber element ensures that stresses arising on cardan loading of the coupling can be reduced.

The connection of the sheet metal discs to the flanges is achieved either by means of screws or by seaming or bending over, which does not require any high outlay on assembly. In order to seal off the blind holes and the chambers with respect to the flanges, either the sheet metal discs are provided at their outer surfaces with a seal which surrounds them or the rubber element has sealing lips in the region of the blind holes and the chambers, which project through the corresponding openings in the sheet metal discs.

The invention is further explained in the following in conjunction with an embodiment by way of example illustrated in the accompanying drawings, in which: Figure 1 shows one flange of a coupling according to the invention, Figure 2 shows a rubber element of the coupling and Figure 3 is a section through the rubber element of Figure 2 along the line Ill-Ill, with the flanges connected to it.

The coupling illustrated in its assembled condition in Figure 3 comprises two disc-shaped flanges 1,2 as shown in Figure 1,which in this embodiment are provided on their outer faces with hub 3. The coupling is secured to the ends of two shafts, not shown, by means of these hubs 3. A central bore 4 extends both through the flanges 1,2 and also through the hubs 3 to receive the ends of the shafts.

Each flange 1,2 carries on its inner face four axially extending drivers 5, uniformly spaced circumferentially, and for example integral with the respective flange 1 or 2. The cross-section of the driver 5 is normally in the form of a flat radially extending rectangle. In the present example the drivers 5 have at their radially ends an enlarged trapezium-shaped cross section 6. In each driver 5, at least on the one flange 1, there is formed a respective throttled bore 7 spaced a small distance from the flange 1,2.

Between the two flanges 1, 2 in Figure 3 there is disposed a rubber element 8 as shown in Figure 2.

This element 8 is of substantially cylindrical shape, with a central bore 9. Four blind holes 10, 11 are fromed in the element 8, extending from each end face and, as can be seen in Figure 3, they each end at a point short of the opposite end face and are again uniformly spaced. The arrangement and cross section of the blind holes 10, 11 corresponds to the arrangement and cross section of the drivers 5 so that the drivers 5 can be recieved by the holes 10 and 11. In order to avoid friction between the walls of the blind holes 10, 11 and the drivers 5 during operation, the holes 10, 11 are clad at least at their inner end faces and the side faces, with a sheet metal component, not shown, which is bonded to the element 8 by vulcanisation.

Between adjacent holes 10 and 11 there are respective chambers 12 which pass right through and open into the end faces of the element, these chambers all being of the same shape and having a substantially triangular cross section. Between these chambers 12 and the blind holes 10,11 there remain walls 13 of the material of the element 8. Recesses 14 are formed in these walls 13 and, when the drivers 5 are inserted, these recesses are aligned with the throttled bores 7. In the embodiment illustrated the outer wall 15 of the element is bulged inwards so that in this case the outer surface is not round but is of wavy form.

Vulcanised to the end faces of the rubber element 8 are sheet metal discs 16, 17 of which the nearer disc 16 is illustrated in Figure 2 only on the left hand side of the Figure, in order to show better the form of the rubber element 8. These discs 16, 17 have openings 18, 19 aligned with the blind holes 10 and 11 and the chambers 12 in the corresponding end face of the rubber element 8, so they do not interfere with the insertion of the drivers 5 into the holes 10, 11.

In the embodiment illustrated byway of example the diameter of the sheet metal discs 16, 17 is greater than the outside dimension of the rubber element 8 and the diameter of the flanges 1, 2. In this way it is possible, on assembly of the coupling, which takes place in a container filled with damping fluid, to deform the edge that projects beyond the flanges 1, 2, over a collar 20 provided on each of the flanges 1, 2, to form a bead 21, and thereby to connect the rubber element 8 to the flanges 1,2 (Figure 3). In order to seal off the openings 18, 19 in the discs 16, 17 with respect to the flanges 1,2, the discs 16, 17 have on their outer surfaces a thin rubber layer, not shown, or sealing lips surrounding the openings 18, 19.These sealing lips could also be formed directly by the rubber element 8, in which case the openings 18, 19in the discs 16, 17 are made very slightly larger than the cross section of the blind holes 10, 11 and the chambers 12, so that the sealing lips can penetrate through the openings 18, 19.

It is of advantage to keep the radial spacing between opposed pairs of the drivers 5 somewhat smaller than the radial distance between opposed pairs of the holes 10 and 11 so that when the drivers 5 are inserted into the blind holes 10, 11 the rubber element is slightly pre-loaded under the radially innermost corners of the holes.

On relative angular movement between the flanges 1,2 there is a reduction in the size of alternate chambers 12 in relation to the adjacent chambers, which are enlarged. This causes a displacement of fluid through the restricted bores 7, influenced in an advantageous manner by the outermost trapezium-shaped portions of the blind holes 10, 11 and the drivers 5, and by the inwardly bulged outer wall, causiny an increase in the pumping or displacement effect for a given relative angular movement.

Claims (11)

1. Atorsionally resilient hydraulically damped coupling comprising two flanges designed to be secured to respective shafts, each carrying at least three interengaging drivers, and a one piece rubber element engaging and fitting around the drivers, with chambers formed between the drivers and filled with damping fluid, and throttled openings formed in the drivers of at least one of the flanges, through which the chambers present respectively on opposite sides of these drivers are in communication, in which the cylindrical rubber element is provided on its two end faces with mutually offset axially extending blind holes for receiving the drivers, the chambers extend axially right through and the rubber element carries on its end faces sheet metal discs secured to form a unit with it, these discs having openings aligned with the blind holes and the chambers, and through which the rubber element is capable of being connected in a sealing manner to the flanges.

2. A coupling according to claim 1, in which the blind holes are at least partially clad in sheet metal or the like.

3. A coupling according to claim 1 or claim 2, the blind holes and if necessary the drivers have at their radially outermost ends a trapezium-shaped cross section.

4. A coupling according to one of claims 1 to 3, in which the radial spacing between opposed pairs the drivers is smaller than the radial distance between the radially innermost corners of the blind holes.

5. A coupling according to any one of claims 1 to 4, in which the rubber element has a central opening right through it.

6. A coupling according to any one of claims 1 to 5, in which the sheet metal discs are secured to the flange by screws.

7. A coupling according to any one of claims 1 to 5, in which the sheet metal discs are connected to the flanges by beading orflanging over.

8. A coupling according to any one of claims 1 to 7, in which the sheet metal discs are provided on their free outer surfaces with a seals surrounding the blind holes and the chambers.

9. A coupling according to any one of claims 1 to 7, in which the rubber element has sealing lips in the region of the blind holes and the chambers which project through the corresponding openings in the sheet metal discs.

10. A coupling according to any one of claims 1 to 9, in which the outer cylindrical wall of the rubber element is bulged inwards in the region of the chambers.

11. Atorsionally resilient hydraulically damped coupling substantially as described with reference to the accompanying drawings.