WO2019110810A1

WO2019110810A1 - Flex coupling for a vehicle drive train, vehicle drive train and method of assembly

Info

Publication number: WO2019110810A1
Application number: PCT/EP2018/084000
Authority: WO
Inventors: Dong Ming LIU; Jan Wucherpfennig
Original assignee: BASF Polyurethanes GmbH
Current assignee: BASF Polyurethanes GmbH
Priority date: 2017-12-07
Filing date: 2018-12-07
Publication date: 2019-06-13
Anticipated expiration: 2020-06-07

Abstract

The invention suggests a flex coupling (1) for a vehicle drive train, the flex coupling (1) being configured to couple a first part of the vehicle drive train to a second part of the vehicle drive train for torque transmission about a rotational axis (X) between the first part and the second part, and comprising: a first, inner coupling body (3, 3') comprising a number of coupling teeth (9; 9a, b), a second, outer coupling body (5) comprising a number of coupling recesses (27a, b) corresponding to the number of coupling teeth (9; 9a, b), and an elastically deformable dampening element (7) interposed between the first and second coupling bodies (3, 5); the elastically deformable dampening element (7) comprising a meandering shape in a cross-sectional plane perpendicular to the rotational axis (X).

Description

Flex coupling for a vehicle drive train, vehicle drive train and method

of assembly

The invention relates to a flex coupling for a vehicle drive train, the coupling being configured to couple a first part of the vehicle drive train to a second part of the vehicle drive train for torque transmission about a rotational axis between the first part and the second part. Flex couplings of the aforementioned type are typically used in the automotive industry to transmit torque from at least one of a motor or an engine of the vehicle to at least wheel. In most instances, torque will be transmitted to a set or rear wheels (RWD), front wheels or both in cases of all wheel drive (AWD) systems. RWD and AWD vehicles typically comprise a drive shaft with a cardan joint for which the flex couplings are specifically relevant.

For example, CN 201679878 U shows a flex coupling having a first, inner coupling body and a second, out coupling body, both of which engage an intermediate elastically deformable dampening element. One of the coupling bodies comprises a number of axially protruding coupling teeth, while the other coupling body comprises an axially extending recess for receiving the coupling teeth. The dampening element is formed as a cap which sits inside the recess.

When transmitting torque in the aforementioned manner, certain the drive train is under the influence of torque, vibration and force peaks stemming from the drive train itself or from the environment of the vehicle. These act upon the drive train in the axial, radial and circumferential direction and may cause irregularities in the torque transmission to the wheel or wheels. In order to improve the reliability of the drive system and to increase the longevity of the drive train and the vehicle in general, flex couplings are used. A key feature of flex couplings is an elastically deformable element which is operative to absorb undesired forces and vibrations in an attempt to smoothen the torque profile transmitted through the flex coupling.

The dampening element within the drive train is susceptible to wear. Regardless of the operating parameters, at some point in time the dampening element will be worn to an extent that requires maintenance, and in most cases replacement of the dampening element.

The flex couplings known in the prior art allow for replacement of the dampening elements. This, however, requires significant maintenance time and corresponding costs. Also, the point at which the dampening element requires replacement is normally reached during operation of the vehicle, i.e. when the vehicle is moving and away from a workshop or other controlled environment. Sudden failure of the dampening element may cause increased wear of the drive train if operation is continued without functioning dampening element. Continued operation of the vehicle is however necessary to allow for the coupling to be serviced. In extreme cases, the defect of the dampening element may lead to a malfunction of the drive train which does not allow for continued operation of the vehicle, necessitating roadside assistance.

In light of the disadvantages observed and described hereinabove, it was therefore an object of the invention to provide a flex coupling of the initially mentioned type which overcomes the disadvantages in the best manner possible. In particular, it was an object of the invention to provide a flex coupling which is easy to service and allows for safe operation even in cases when the dampening element is defect.

To achieve this object a flex coupling is suggested having the features of claim 1. In particular, a flex coupling for a vehicle drive drain is suggested, the coupling being configured to couple a first part of the vehicle drive train to a second part of the vehicle drive train for torque transmission about a rotational axis between the first part and the second part, and comprising a first, inner coupling body comprising a number of coupling teeth, a second, outer coupling body comprising a number of coupling recesses corresponding to the number of coupling teeth, each coupling recess being associated to one coupling tooth, and elastically deformable dampening element interpose between the first and second coupling body in a positive connection, wherein the coupling teeth of the first coupling body extend radially outwards from at least one inner circumferential baseline, the second coupling body comprises a number of protrusions corresponding to the number of recesses, wherein the protrusions extend radially inverts from at least one outer circumferential baseline and are positioned alternatingly with respect to the recesses, and the elastically deformable dampening element comprises a meandering shape in a cross-sectional plane perpendicular to the rotational axis.

The invention is based upon the realization that upon interposing the dampening element in a meandering shape between the inner and outer baselines (that constitute the radial limits of the dampening element) defined by the protrusions of the first coupling body and recesses of the second coupling body, the dampening element provides a dampening cushion in the radial direction as well as the circumferential direction along the entire circumference of the coupling cross- section.

Forces acting upon the coupling in a direction perpendicular to the rotational axis are distributed much more uniformly due to the meandering shape, leading to reduced wear.

Also, the operation of the drive train is still ensured even if the dampening element is completely worn: Due to its meandering shape, the dampening element precisely lies against the coupling teeth and corresponding recesses in a positive fit along the entire circumference of the flex coupling. Also, each coupling tooth is very similarly shaped to its associated recess, leaving in between those two parts a gap having the same meandering shape as the dampening element. If in a worst case scenario the dampening element is worn so much that there is no longer a positive fit with respect to the first and second coupling bodies, there will be a certain amount of rotational play between the first and second coupling bodies. There is however no risk of the first and second coupling bodies disengaging from one another at any time due to the engagement of the coupling teeth with their associated recesses, so that even when the dampening element is defect, the vehicle is able to reach a controlled environment such as a workshop where the dampening element can be replaced. The circumferential baselines respectively are preferably circular baselines, polygonal baselines or a combination of both.

In its meandering shape, the dampening element preferably meanders back and forth between the at least one outer base line and the at least one inner base line such that in the cross-sectional plane perpendicular to the rotational axis, the dampening element is substantially star-shaped.

In a preferred embodiment, each coupling tooth and its respectively associated recess comprise a pair of mutually facing parallel side flanks, and the elastically deformable dampening element comprises for each pair of side flanks a cross web extending between the at least one outer and inner base lines. The dampening element is comprised of a number of first circumferentially oriented sections extending alone the first circumferential baseline, a number of second circumferentially oriented sections extending along the second circumferential baseline, and the cross webs connect adjacent first and second circumferential sections with one another.

Further preferably, the flex coupling has a first axial end face and a second axial end face opposite and facing away from the first axial end face, wherein the first coupling body and the second coupling body extend from the first axial end face to the second axial end face, respectively, such that the second coupling body is positioned radially outwards of the first coupling body. In a further preferred embodiment, the second coupling body is segmented axially in a plane perpendicular to the rotational axis. Particularly preferred, the second coupling body is symmetrically segmented with one half of the second coupling body and the second part of the second coupling body comprising the second axial end face. In a further preferred embodiment, the coupling teeth of the first coupling body taper towards the first axial end face and towards the second axial end face. The taper can be linear, progressive or regressive. By tapering towards the respective axial end faces, the material thickness of the coupling teeth decreases towards the respective end faces. The side flanks of the coupling teeth are therefore slightly inclined with respect to the rotational axis, and non-parallel with respect to the rotational axis such that longitudinal forces acting upon the flex coupling can be absorbed by the cross webs of the dampening element. By segmenting the second coupling body axially, it becomes possible to mount and unmount the flex coupling very quickly and easily. For mounting, it is preferred if the dampening element is attached to and aligned with the first coupling body, before attaching the second coupling body segments from both axial ends to the flex coupling assembly. Preferably, the first and second segments of the second coupling body are attached to one another with fastening means such as tensioning bolts.

In a further preferred embodiment, the recesses of the second coupling body taper towards the first axial end face and towards the second axial end face.

It is particularly preferred if both the coupling teeth and the recesses of the first coupling body and second body respectively, taper towards their first and second axial end faces such that despite the taper, a substantially constant gap width is maintained in between the first and second coupling bodies (when the two bodies are correctly aligned coaxially to the rotational axis and as in their mounted position).

In a further preferred embodiment, the elastically deformable dampening element is in a partially compressed state when interposed between the first coupling body and the second coupling body. Preferably, this is achieved by designing the dampening element with a material thickness in a cross-sectional plane perpendicular to the rotational axis that exceeds the width of the gap formed between the first and second coupling bodies when they are aligned with each other and aligned coaxially with respect to the rotational axis. The rate of compression is then defined by how much the thickness of the dampening element exceeds the gap width in the direction across the gap from the first coupling body to the second coupling body. The thicker the dampening element, the more compression is necessary to interpose the dampening element between the first and second coupling bodies. Accordingly, with the design of the dampening element and the meandering shape as the combination of radially protruding coupling teeth and recesses, it becomes possible to very easily fine-tune the desired rate of compression of the elastically deformable dampening element. In systems where a higher torque needs to be transmitted or higher vibrations are to be expected, the pre-load of the dampening element which is already present in the absence of drive torque and vibrations can be increased by selecting a thicker dampening element. There is no need to modify the material formula or other parameters. The material thickness can very easily be modified during production of the dampening element already, and a kit of dampening elements with varying thicknesses can be provided at ease. Increasing the material thickness of the dampening element essentially has the effect of pre-loading the dampening element in its mounted state without operational loads acting upon it. In a further preferred embodiment, the coupling teeth of the first coupling body are uniformly shaped with respect to one another. In other words, all coupling teeth of the first coupling body have the same shape. Particularly preferred, the coupling teeth are distributed and spaced apart from one another evenly along the circumference of the first coupling body.

Preferentially, the protrusions of the second coupling body are also uniformly shaped with respect to one another, which means that also the protrusions of the second coupling body a preferably evenly distributed along of this preconference of the second coupling body, corresponding to the spacing of the coupling teeth on the first coupling body.

By providing a symmetrical positioning of the coupling teeth and protrusions, respectively, it becomes possible to distribute the load incurred by the drive train and the vibrations and disturbance forces acting upon the drive train very evenly over the entire flex coupling. The invention has herein above been described in a first aspect with regard to the flex coupling per se.

In a second aspect of the invention, the invention relates to a vehicle drive train comprising a drive shaft for transmitting torque from at least one of a motor or an engine to at least one wheel, the drive train comprising a first part and a second part, wherein the first and second parts are connected by a flex coupling.

To achieve the initially mentioned object for such a vehicle drive train, the invention suggests that the flex coupling is formed according to one of the preferred embodiments described hereinabove.

The vehicle drive train and the flex coupling share the same advantages and preferred embodiments. Accordingly, in order to avoid redundancies, it is referred to the description of the preferred embodiments of the first aspect herein above.

In a third aspect, the invention relates to a method of assembling of a flex coupling of a vehicle drive shaft, in particular a flex coupling of anyone of the preferred embodiments described herein above, the method comprising the steps of: - providing a first coupling body,

- providing a second coupling body,

- providing an elastically deformable dampening element, and

interposing the elastically deformable dampening element between the first coupling body and the second coupling body.

In preferred embodiments, it has been considered beneficial to mount the dampening element to either the first coupling body or the second coupling body, and then additionally adding the respective other coupling body subsequently.

In embodiments where the second coupling body is segmented axially, the step of interposing the elastically deformable dampening element between the first coupling body and the second coupling body preferably encompasses attaching the elastically deformable dampening element to the first coupling body, and subsequently adding the first and second segments of the segmented second coupling body around the elastically deformable dampening element. In a further preferred embodiment of the method, the first and second coupling bodies are dimensioned such that a gap remains having a gap between the first coupling body and the second coupling body for accommodating the dampening element, and wherein the dampening element has a thickness in a direction across the gap from the first to the second coupling body that exceeds the gap width, and wherein the step of interposing the dampening element comprises partially compressing the dampening element. As has been described herein above, the partial compression of the dampening element has the effect of pre-loading the dampening element to account for a certain expected torque level or a certain level of disturbance forces acting upon the coupling during operation of the drive train. In other words, by changing the pre-load applied to the elastically deformable dampening element, the load-deflection curve of the flex-coupling can easily be adjusted. Additionally, the load-deflection curve could also be adjusted by changing the material density or the effective contact surface between the first and second coupling bodies. However, an adjustment of the compression rate of the dampening element is advantageous to those two alternatives with respect to flexibility, ease of operation and precision. In a further preferred embodiment, the method comprises the step of determining a required thickness for the dampening element as a function of a desired rate of compression for the dampening element in its interposed position, wherein the step of providing the dampening element comprises selecting a dampening element having the required thickness.

The elastically deformable dampening element is preferably based on generally known elastomers, for example rubber or polyisocyanate polyaddition products.

It is preferably based on cellular, in particular microcellular polyurethane elastomers, which may optionally comprise polyurea structures, particularly preferably on the basis of cellular polyurethane elastomers which preferably have a density in accordance with DIN EN ISO 845 of between 200 and 1 100 kg/m³, preferably 300 and 800 kg/m³, a tensile strength in accordance with DIN EN ISO 1798 of 2 N/mm² or higher, preferably 4 N/mm² or higher, particularly preferably between 2 and 8 N/mm², an elongation at breakage in accordance with DIN EN ISO 1798 of 200% or higher, preferably 230% or higher, particularly preferably between 300% and 700%, and a tear propagation resistance in accordance with DIN ISO 34-1 B(b) of 6 N/mm or higher, preferably 10 N/mm or higher.

The elastomers are preferably microcellular elastomers on the basis of polyisocyanate polyaddition products, preferably having cells with a diameter of 0.01 mm to 0.5 mm, particularly preferably 0.01 to 0.15 mm.

Elastomers on the basis of polyisocyanate polyaddition products and their preparation are generally known and have been widely described, for example in EP-A 62 835, EP-A 36 994, EP-A 250 969, DE-A 195 48 770 and DE-A 195 48 771.

The preparation usually takes place by reacting isocyanates with compounds that are reactive to isocyanates.

The elastomers on the basis of cellular polyisocyanate polyaddition products are usually prepared in a mold in which the reactive starting components are reacted with one another. Suitable molds here are generally customary molds, for example metal molds, which, on account of their form, ensure the three-dimensional form of the dampening element according to the invention. The preparation of the polyisocyanate polyaddition products may take place on the basis of generally known methods, for example by using the following starting materials in a one-stage or two-stage process:

(a) isocyanate, (b) compounds reactive to isocyanates,

(c) water and optionally

(d) catalysts,

(e) blowing agents and/or

(f) auxiliaries and/or additives, for example polysiloxanes and/or fatty acid sulfonates.

The surface temperature of the inner wall of the mold is usually 40° to 95° C., preferably 50° to 90° C.

The production of the molded parts is advantageously carried out using an NCO/OH ratio of from 0.85 to 1.20, the heated starting components being mixed and introduced into a heated, preferably tightly closing, and mold in an amount corresponding to the desired density of the molded part.

The molded parts are cured, and can consequently be removed from the mold, after up to 60 minutes.

The amount of reaction mixture introduced into the mold is usually set such that the moldings obtained have the density already described.

The starting components are usually introduced into the mold at a temperature of from 15 to 120° C., preferably from 30° to 110° C. The degrees of compaction for the production of the moldings lie between 1.1 and 8, preferably between 2 and 6.

The cellular polyisocyanate polyaddition products are expediently prepared by the one-shot process with the aid of the low-pressure technique or in particular the reaction injection-molding technique (RIM) in open or preferably closed molds. The reaction is carried out in particular with compaction in a closed mold. The reaction injection-molding technique is described, for example, by H. Piechota and H. Rohr in "Integralschaumstoffe" [integral foams], Carl Hanser-Verlag, Munich, Vienna, 1975; D. J. Prepelka and J. L. Wharton in Journal of Cellular Plastics, March/April

1975, pages 87 to 98, and U. Knipp in Journal of Cellular Plastics, March/April 1973, pages 76-84.

The invention will herein after be described with respect to preferred embodiments and with reference to the accompanying drawings. Herein: Fig. 1 shows a schematic three dimensional view of a flex coupling according to a first embodiment,

Fig. 2 shows a schematic exploded view of the flex coupling of Fig. 1 ,

Figs. 3, 4 show schematic views of a first coupling body of the flex coupling of Fig.

1 and 2, Figs. 5, 6 show schematic views of a second coupling body segment for the flex coupling of Fig. 1 and 2,

Fig. 7 shows a schematic plan view of an elastically deformable dampening element of the flex coupling of Fig. 1 and 2,

Fig. 8 shows a schematic detail view of a first coupling body for a flex coupling according to a second preferred embodiment, and

Fig. 9 shows a schematic partial view of a second coupling body for the flex coupling according to Fig. 8.

Fig.1 shows a flex coupling 1 for a vehicle drive train which is configured to transmit torque from a first drive train part to a second drive train part (not shown). The flex coupling 1 comprises an inner first coupling body 3 and an outer second coupling body 5 which are coaxially aligned along a rotational axis X. Interposed between the first and second coupling bodies 3, 5 is an elastically deformable dampening element 7 which has a meandering shape. Details of the shapes of each of these arts 3, 5, 7 are commented on with respect to figures 3 through 9. In the interposed position shown in fig. 1 , the dampening element 7 fills a gap having a width G between the first and second coupling bodies 3, 5 such that the dampening element is in a positive fitting relationship with the first and second coupling bodies 3, 5.

The second coupling body 5 is segmented axially in a plane perpendicular to the rotational axis X and comprises a first segment 5a and a second segment 5b. As can be seen from fig. 2, the flex coupling can easily be mounted and unmounted by for example mounting the elastically deformable dampening element 7 over the first coupling body 3 and then attaching from both sides, the segments 5a, b of the second coupling body 5. Due to the meandering shape of the elastically deformable dampening element 7, the entire circumference of the first and second coupling bodies 5, 7 is provided with an elastic cushion to absorb torque variations, radial and tangential forces.

Preferably, the dampening element 7 has substantially the length in the direction of rotational axis X as the first coupling body 3. Particularly preferred, the summary length of the segments 5a, b of the second coupling body 5 in the direction of the rotational axis is equal or less than the length of the first coupling body 3. Having a small decrease in length with respect to the first coupling body 3, e.g. 5 to 10%, makes it possible to establish a rate of compression of the dampening element 7 in the mounted, i.e. interposed, state by increasing the mounting tension on the second coupling body 5. Fig.3 shows the first coupling body 3 of the flex coupling 1 in more detail. The first coupling body 3 comprises a plurality of coupling teeth 9 which are distributed along the circumference of the coupling body 3 and extend radially outwards with respect to the rotation axis X. The coupling teeth 9 are comprised of a first set of coupling teeth 9a and a second set of coupling teeth 9b, wherein the second set of coupling teeth 9b have a higher thickness in the circumferential direction as compared to the first set of coupling teeth 9a. The increased thickness is makes the teeth 9b suitable for accommodating mounting holes 19. The mounting holes 19 extend through the first coupling body 3 from a first an axial end face 11 to a second axial end face 13. Each of the coupling teeth 9a, b comprises a first side flank 15a, oppositely located second side flank 17. The first and second side flanks 15, 17 are substantially parallel to a radial plane extending through the coupling teeth and the rotational axis X or alternatively oriented radially themselves or at an angle to that radial plane. Preferably, the angle of the side flanks 15, 17 to that plane is in the range of 30° or less, particularly preferred 10° or less.

The coupling teeth 9a, b are tapered towards the first axial end face 11 and the second axial end face 13. More particularly, the side flanks 15,17 are respectively inclined towards the end faces 11 ,13, making the coupling teeth thicker towards their center and thinner towards the respective end faces 11 ,13. When axial forces act upon the flex coupling 1 , the tapered side flanks together with the dampening element provide for absorption of axial forces. The recesses 27a, b are preferably tapered towards one of their axial end faces. The tapering angle preferably matches the tapering angle of the first coupling body’s coupling teeth 9a, b. As can further be seen from fig.4, the plurality of coupling teeth 9a, b extend radially outwards from a first, inner circumferential, in this example circular, base line 21.

The first coupling body 3 comprises a through-bore 23 oriented coaxially to axis X.

Each of the coupling teeth 9b of the second set is spaced apart from the adjacent tooth of its set at an angle a of 120°. Due to their increased thickness, the coupling teeth 9b of the second set of coupling teeth are configured to accommodate the mounting holes 29 having a diameter 25.

In fig.5, one of the segments 5a, b of the second coupling body 5 is shown in more detail.

The segments 5a, b are symmetrical to one another which is why only one of the segments is shown in detail. Following comments are made with respect to the second coupling body segments 5a. 5b and coupling body 5 in general. The second coupling body 5 comprises a plurality of recesses that are comprised of a first set of recesses 27a and a second set of recesses 27b. Each of the recesses 27a, b is configured to accommodate one of the coupling teeth 9a, b. In particular, the first recesses 27a are configured to each accommodate one coupling tooth 9a, while the second recesses 27b are configured to each accommodate one coupling tooth 9b.

The recesses extend radially outwards with respect to the rotational axis X. The recesses 27a, b are spaced apart from one another by protrusions 31 ,33 which extend radially inwards towards the rotation axis X. The protrusions extend inwardly from an outer circumferential baseline 35, which in this example is a circular baseline and is shown in fig.6.

The distribution of the recesses and protrusions of the first and second coupling bodies 3,5 along their circumference is typically chosen depending on the mounting requirements for the drive train. The distribution may be symmetrical or asymmetrical, depending on the customer-specific requirements.

In fig.7, the elastically deformable dampening element 7 is shown in more detail. In particular, the meandering shape of the dampening element 7 is shown. The dampening element 7 is comprised of a plurality of first, outer, circumferential sections 37a, 37b that extend along the outer circumferential baseline 35’, a second set of circumferential sections 39a, 39b extending along the second, inner, circular baseline 2T, and a plurality of cross webs 41a, 41 b that connect the first and second circumferential sections to one another. The first and second baselines 2T, 35’ are designated with a (‘) because while in the interposed state, these baselines will coincide with the baselines 21 , 35 shown in figs. 4+6, they may slightly deviate therefrom as long as the dampening element is a) not mounted, and b) uncompressed and in the uncompressed state thicker than the width of gap G, cf. fig. 1 and herein below.

Preferably, the cross webs 41a, b are extending linearly in between the circumferential sections 37a, b and 39a, b. Alternatively if the side flanks of the coupling teeth and recesses of the coupling bodies 3, 5 do so as well, the cross webs might also comprise a curvature.

The shape and inclination angles of the cross webs preferably match the tapering angles of the side flanks 15, 17 of the coupling teeth 9a, b and the side flanks 28, 30 of the recesses 27a, b of the second coupling body 5. By choosing this shape for the dampening element 7, the dampening element 7 is in positive fit across the entire contact surface with the first coupling body 3 and the second coupling body 5, provided that the dampening element 7 entirely fills the gap which is provided between the first and second coupling bodies 3, 5 when they are coaxially aligned with respect to the rotational axis X.

The dampening element 7 has a thickness T which preferably exceeds the width of the aforementioned gap G (fig.1 ). This has the effect that when mounted in its interposed position between the first and second coupling bodies 3, 5, the dampening element 7 is slightly compressed even in the absence of operational torque or forces on the drive train. The extent by which the thickness T exceeds the gap width G determines the pre-load and thus initial stiffness of the flex coupling 1. Together with the preferred material characteristics described hereinabove, this makes it possible to provide a system which is comparatively stiff for lower torque and force loads while still being resilient and sensitive to higher torques and forces.

The particular shape of the coupling teeth, recesses and dampening element also ensures that even if the dampening element is defect, torque transmission can still occur between the coupling teeth 9a, b and the recesses 27a, b such that the vehicle can still be operated until it reaches a controlled environment for maintenance.

The aforementioned figures 1 through 7 have shown a flex coupling with asymmetrical coupling teeth and recesses adapted to a more or less conventional mounting interface for a vehicle drive train. With the invention, it however becomes possible to deviate from these conventional mounting interface constellations towards symmetrical constellations. Instead of providing mounting holes in only some of the coupling teeth, the first coupling body 3’ shown in fig.8 comprises an inner groove 43 in its through-bore 23 which allows for a conventional shaft-hub joint. Now, since the mounting interface has been transferred radially inwards away from the teeth, all coupling teeth 9 are preferably shaped and distributed along the circumference symmetrically. The number of teeth can be increased which in turn increases the dampening surface in the circumferential direction and thus improves the absorption capabilities of the flex coupling even more. Likewise, the protrusions 31 adjacent to the recesses 27 of the second coupling body 5a, b are preferably rendered symmetrical by moving the mounting interface radially outwards, away from the protrusions 31.

Claims

Claims:

1. A flex coupling (1) for a vehicle drive train, the flex coupling (1) being configured to couple a first part of the vehicle drive train to a second part of the vehicle drive train for torque transmission about a rotational axis (X) between the first part and the second part, and comprising:

a first, inner coupling body (3, 3’) comprising a number of coupling teeth (9; 9a, b), a second, outer coupling body (5) comprising a number of coupling recesses (27a, b) corresponding to the number of coupling teeth (9; 9a, b), each coupling recess (27a, b) being associated to one coupling tooth (9; 9a, b), and

an elastically deformable dampening element (7) interposed between the first and second coupling bodies (3,5) and engaging the first coupling body (3) and the second coupling body (5) in a positive connection,

wherein the coupling teeth (9;9a,b) of the first coupling body (3) extend radially outwards from at least one first, inner circumferential baseline (21 ),

the second coupling body (5) comprises a number of protrusions (31 , 33) corresponding to the number of recesses (27a, b), wherein the protrusions (31 , 33) extend radially inwards from at least one second, outer circumferential baseline (35) and are positioned alternatingly with respect to the recesses (27a, b), and the elastically deformable dampening element (7) comprising a meandering shape in a cross-sectional plane perpendicular to the rotational axis (X).

2. The flex coupling (1 ) of claim 1 , wherein the dampening element (7) meanders back and forth between the at least one outer baseline (35) and the at least one inner baseline (21 ).

3. The flex coupling (1 ) of claim 1 or 2,

wherein each coupling tooth (9; 9a, b) and its respectively associated recess (27; 27a, b) comprise a pair of mutually facing parallel side flanks (15,17; 28,30), and the elastically deformable dampening element (7) comprises for each pair of side flanks (15,17; 28,30) a cross web (41a, b) extending between the at least one outer and inner baselines (21 ,35).

4. The flex coupling (1 ) of any one of the preceding claims,

having a first axial end face (11 ) and a second axial end face (13) opposite and facing away from the first axial end face (11 ), wherein the first coupling body (3) and the second coupling body (5) extend from the first axial end face (11 ) all the way through to the second axial end face (11 ), respectively, such that the second coupling body (5) is positioned radially outwards of the first coupling body (3).

5. The flex coupling (1 ) according to any one of the preceding claims, wherein the dampening element (7) extends all the way from the first axial end face (11 ) through to the second axial end face (13).

6. The flex coupling (1 ) of any one of the preceding claims,

wherein the second coupling body (5) is segmented axially in a plane perpendicular to the rotational axis (X).

7. The flex coupling (1 ) of any one of claims 4 to 6,

wherein the coupling teeth (9;9a,b) of the first coupling body (3) taper towards the first axial end face (11 ) and towards the second axial end face (13).

8. The flex coupling (1 ) of any one of claims 4 to 7,

wherein the recesses (27a, b) of the second coupling body (5) taper towards the first axial end face (1 1 ) and towards the second axial end face (13).

9. The flex coupling (1 ) of any one of the preceding claims,

wherein the elastically deformable dampening element (7) is in a partially compressed state when interposed between the first coupling body (3) and the second coupling body (5).

10. The flex coupling (1 ) of any one of the preceding claims,

wherein the coupling teeth (9) of the first coupling body (3’) are uniformly shaped with respect to one another.

11. The flex coupling (1 ) of claim 10,

wherein the protrusions (27) of the second coupling body (5) are uniformly shaped with respect to one another.

12. A vehicle drive train,

comprising a drive shaft for transmitting torque from at least one of a motor or an engine to at least one wheel, the drive train comprising a first part and a second part, wherein the first and second parts are connected by a flex coupling (1 ), characterized in that the flex coupling (1 ) is formed according to any one of the preceding claims.

13. A method of assembling a flex coupling (1 ) of a vehicle drive shaft, in particular a flex coupling (1 ) of any one of claims 1 to 10, the method comprising the steps of: - providing a first coupling body (3),

- providing a second coupling body (5),

- providing an elastically deformable dampening element (7), and

interposing the elastically deformable dampening element (7) between the first coupling body (3) and the second coupling body (5).

14. The method of claim 13, wherein the step of interposing the deformable dampening element comprises mounting the dampening element (7) to either the first coupling body (3) or the second coupling body (5), and then additionally adding the respective other coupling body subsequently.

15. The method of claim 13, wherein the second coupling body (5) is segmented axially, and the step of interposing the elastically deformable dampening element between the first coupling body and the second coupling body comprises attaching the elastically deformable dampening element (7) to the first coupling body (3), and subsequently adding the first and second segments of the segmented second coupling body around the elastically deformable dampening element (7).

16. The method of any one of claims 13 to 15,

wherein the first and second couplings bodies (3, 5) are dimensioned such that a gap (G) remains having a gap width between the first coupling body (3) and the second coupling body (5) for accommodating the dampening element (7), and wherein the dampening element (7) has a thickness (T) in a direction across the gap (G) from the first to the second coupling body (3,5) that exceeds the gap width, and wherein the step of interposing the dampening element (7) comprises partially compressing the dampening element (7).

17. The method of any one of claims 13 to 16,

comprising the step of determining a required thickness for the dampening element (7) as a function of a desired rate of compression for the dampening element (7) in its interposed position, wherein the step of providing the dampening element (7) comprises selecting a dampening element having the required thickness.