GB2242959A

GB2242959A - Drive shaft for a motor vehicle

Info

Publication number: GB2242959A
Application number: GB9107033A
Authority: GB
Inventors: Peter Amborn; Klaus Greulich
Original assignee: GKN Automotive GmbH
Current assignee: GKN Driveline International GmbH
Priority date: 1990-04-04
Filing date: 1991-04-04
Publication date: 1991-10-16
Anticipated expiration: 2011-04-04
Also published as: FR2660713A1; ITMI910869A0; IT1247848B; FR2660713B1; GB2242959B; ITMI910869A1; GB9107033D0

Abstract

A drive shaft for a motor vehicle, comprising a tubular central portion (Rm) disposal between, and of larger outside diameter than, two end portions (13, 14), is axially asymmetric with the centre of symmetry of its central portion or its centre of gravity axially offset from the centre of the shaft. The cross-sectional area may thus be optimised and the natural frequency of vibration displaced to a value subject to minimum external excitation in use, to reduce noise. Surface formations may be provided on the shaft central portion or damping sleeves fitted thereto. <IMAGE>

Description

Title: Drive Shaft Description of the Invention This invention relates to a tubular drive shaft produced in one piece by a forming operation, comprising a central tube portion disposed between, and having a larger outside diameter than, two end portions which have parts, e.g.

toothed, for torque transmitting connection to universal joints. Such a drive shaft, which is particularly, but not exclusively, usable in the drive lines of motor vehicles, will hereafter be referred to as a drive shaft of the kind specified.

DE-PS3009277 discloses a drive shaft of the kind specified which is usable as a half shaft in a motor rehidtt drive line. The drive shaft is tubular with two stepped ends provided with receiving regions for universal joints. The entire central portion of the tubular shaft is cylindrical, with a constant inside diameter.

To achieve a uniform mechanical strength along the entire length of the shaft, the wall thickness is deceased in the part of larger outside diameter. Conventional hollow shafts have a smooth cylindrical, part conical, or part parabolic (in longitudinal section) surface and are dimensioned to suit the torque required to be transmitted and meet the various strength requirements. Adjustment of the natural resonant frequency of the shaft in bending and torsion to suit particular vehicles can be achieved to a limited extent only, because the theoretically ideal drive shaft for a particular installation cannot be accommodated in the space available in the vehicle, cannot be manufactured, or is too heavy after measures to optimise its vibration performance have been carried out.The torsional characteristics of the shaft, which experience has shown are just as important as the bending characteristics, involve the maximum permissable angle of torsion in use and the natural frequency of torsional vibration. Existing designs of shaft generally have all their design attention focused on the mechanical strength of the shaft, and the natural frequency of the shaft with respect to bending vibration is only able to be varied to a limited extent. Generally, the natural frequency may be within the range of an excitation frequency of the engine/transmission system so that vibration and noise cannot be avoided.

It is the object of the present invention to provide a drive shaft whose vibration behaviour is improved by ensuring that its natural frequencies of vibration are kept within a frequency range which is subject to minimal external excitation, thereby enabling vibration and noise to be reduced.

According to one aspect of the invention, there is provided a drive shaft of the kind specified wherein the shaft is rotationally symmetrical and is asymmetrical in the longitudinal direction in respect of its resistance to deflection.

The asymmetrical design in the longitudinal direction of the drive shaft, in respect of its resistance to deflection, which may be expressed as its moment of resistance or section modulus, enables the natural frequency of the shaft to be moved into a range which is subject to a minimum external excitation.

The asymmetry may be provided by offsetting the centre of symmetry of the central portion of the shaft from the axial centre of the shaft as a whole, or by offsetting the centre of gravity of the shaft from the axial centre thereof.

Experience has shown that, for example, by offsetting the centre of gravity towards one end of the shaft (which end, when the shaft is in use in a vehicle, lies closest to the input or output part having the greatest mass, especially the gearbox) vibration and noise are clearly reduced while the symmetry of rotation of the drive shaft can be maintained.

In a first embodiment of the invention, one end of the central portion of the shaft may be stepped and provided with a cylindrical projection with a smaller outside diameter than the central portion, or one end of the central portion may be provided with a part-conical projection.

By either of these expedients, the centre of symmetry of the central portion of the shaft is displaced relative to the axial centre of the shaft of the whole. The position of the centre of symmetry of the central portion may be varied within a wide range by changing the length of the projection, which also makes it possible correspondingly to move the natural frequency of the shaft into a particularly advantageous range. In the central portion of the shaft wherein the outside diameter is constant over at least the largest part, the wall thickness may be kept approximately constant. The position of the centre of gravity may then be maintained by providing the projection with a different wall thickness.

Alternatively, the centre of gravity may be displaced by providing the central portion of the shaft with a substantially constant wall thickness but with an outside diameter which changes along its length, or by providing that the inside and/or outside diameter of the central portion of the shaft changes at least partially continuously and asymmetrically relative to the centre of the shaft.

By maintaining a constant wall thickness while providing a uniform or variable outside and/or inside diameter, it is possible to achieve a distribution of cross-sectional area which is functionally optimised and which meets the basic strength requirements of the shaft, with the required torsional stiffness being adjusted and with a natural resonant frequency in respect of both bending and torsional vibrations being adapted to the respective requirements. This means that while rotational stiffness and acoustic behaviour can be optimised, the load bearing capacity of the individual cross-sections of the shaft may greatly exceed minimum requirements.

The asymmetrically stepped cross-section of the tubular shaft results in a change in the bending stiffness towards the centre of the shaft, which permits a shift in the natural frequency of the bending vibration. The areas of transition between the regions of different diameter may have an inside or outside diameter which changes conically. The inside diameter of the central portion of the shaft may be kept constant while the outside diameter changes, to obtain the asymmetrical shaft.

The central portion of the shaft may have a maximum outside diameter in the vicinity of an end region of the shaft. The central portion of the shaft, between the second end portion and the location of the maximum outside diameter, may be of part-conical configuration, or may be part-parabolic in longitudinal section.

Alternatively, the maximum outside diameter may be provided in the vicinity of the centre of the shaft, or in the vicinity of both end portions. Again, the central portion of the shaft, between the positions of maximum and minimum outside diameter, may be part-conical, or part-parabolic in longitudinal section, thereby achieving the change in cross-sectional area.

In all the cases described so far, it is possible to achieve an asymmetrical drive shaft which permits a displacement of the centre of symmetry of the central portion of the shaft and/or of the centre of gravity from the axial centre of the shaft as a whole, and thus change the natural frequency of vibration of the shaft in bending. Additionally, in an embodiment where the maximum outside diameter is provided in the vicinity of the centre of the shaft, it is possible, approximately, to copy the form of the first basic mode of vibration of the shaft, and achieve a continuously increasing deformation resistance of the drive shaft towards the maximum outside diameter.

The natural frequency of bending vibration may also be varied by providing two different outside diameters in the centre of each half of the tubular shaft, or by moving identical or different outside diameters away from the centre of the respective halves of the shaft.

According to another aspect of the invention, the surface of the central portion of the shaft may be associated with surface formations distributed over at least a limited area, the internal diameter of the central portion of the shaft remaining constant.

By providing surface formations in the central portion of the shaft, which do not serve to fix other parts or act as aids to assembly, it is possible to obtain a drive shaft in which the values of the natural bending and torsional frequencies are changed in such a way that they are within the range of minimum external excitation. Furthermore, in a special embodiment of the drive shaft, it is possible to achieve a shaft stiffening which, while maintaining the bending characteristics, permits changing the torsional characteristics within a wide range.

Equally, it is possible to change the bending characteristics while maintaining the torsional characteristics, or change both characteristics jointly. There is a further advantage in that structure-borne sound vibrations extending along the shaft wall are interfered with or blocked by the impedance changes provided by such formations on the outer surface of the shaft.

The surface formations may be provided on at least one damping sleeve which is fitted onto the central portion of the shaft and is non-rotatingly connected to the shaft.

As a result of the provision of at least one damping sleeve it is possible to achieve the above described changes in the natural bending and/or torsional vibration frequencies, so that they are subject to the minimum external excitation.

The damping sleeve is preferably made of a material with a high modulus of elasticity and a low specific gravity, thereby achieving high stiffness values and a low weight. The damping sleeve may at least partially cover the central portion of the shaft. Damping sleeves may be arranged symmetrically or asymmetrically in the axial direction on the central portion of the shaft, an asymmetrical arrangement permitting an additional displacement of the centre of gravity or centre of symmetry of the shaft.

The or each damping sleeve may comprise a tubular portion or several part-tubular segments, and in a first embodiment they may be formed so as to be rotationally and axially symmetrical. In a further embodiment the damping sleeve (s) may comprise raised portions and/or indentations on its or their surface.

In a further embodiment of the invention, it is proposed that the surface formations, comprising raised portions or indentations, may be provided directly on the surface of the central portion of the shaft.

By providing raised portions or indentations on the surface of a damping sleeve or on the surface of the central portion of the shaft, it is possible to achieve a shaft stiffening which, while maintaining the bending characteristics of the shaft, permits changing the torsional characteristics within a wide range.

The raised portions may be provided in the form of ribs or naps, and the indentations in the form of grooves extending axially, circumferentially, or at an angle (helically). In the case of helical ribs, grooves or naps it is possible to arrange them in the form of a single or multiple helices on the surface of the damping sleeve or central portion of the shaft. Ribs or grooves may be combined in single or multiple rows in closely adjoining groups. Helical ribs or grooves may be arranged on the surface of the shaft of sleeve so as to extend anti-clockwise or clockwise or so as to intersect each other, thereby achieving an increase in the torsional and bending stiffness in a certain ratio. A combination of differently extending ribs, grooves or naps is also conceivable.

Tubular damping sleeves may be pressed onto the shaft's central portion, while individual part tubular segments may be welded on. A combination of different damping sleeves on the central portion of the shaft is conceivable.

In the case of an asymmetrical drive shaft featuring a displacement of the centre of symmetry of the central portion of the shaft and/or of the centre of gravity, from the axial centre of the shaft as a whole, it is possible to achieve individual adaptation of the shaft to each individual vehicle type. It is possible to use a drive shaft from current production runs and change its characteristics by the fitting of a damping sleeve or sleeves.

According to another aspect of the invention, we provide a drive shaft produced in one piece by a forming operation, comprising a central portion disposed between two end portions, wherein the central portion is provided on its surface with at least one damping sleeve non-rotatingly connected to the drive shaft. The or each damping sleeve may have any of the features above referred to.

The invention also proposes a method for producing a drive shaft featuring the above described raised portions or indentations, either directly on the surface of the central portion of the shaft or on the surface of the damping sleeve. According to this method, the ribs, grooves or naps are produced on the surface by hammering or drawing.

By means of the surface formations produced by hammering or drawing, it is possible to improve or specifically change the natural bending and/or torsional frequency of the shaft.

The invention will now be described in respect of certain of its abovementioned features, by way of example, with reference to the accompanying drawings, in which: FIGURE 1 shows diagrammatically the drive line arrangement of a motor vehicle having a drive shaft in accordance with the invention; FIGURE 2 is a longitudinal section through a first embodiment of drive shaft according to the invention; FIGURES 3 to 8 are respective longitudinal sections through further embodiments of drive shaft according to the invention; FIGURE 9 is a longitudinal section through a further embodiment of drive shaft according to the invention; FIGURES 10 to 12 are longitudinal sections through further embodiments of a drive shaft having surface formations; FIGURE 13 is an elevation of a first embodiment of a drive shaft with damping sleeves.

FIGURE 14 is an elevation of a further embodiment of a shaft with damping sleeves.

FIGURES 15a and 15b are respective sections on the lines A-A and B-B of Figure 14.

In all the Figures of drawings, the same reference numerals are used for parts corresponding to one another.

Referring firstly to Figure 1 the motor vehicle indicated generally a 1 comprises a front engine 2, gearbox 3, and front axle differential 4 from which the front wheels 5 are driven by respective drive shafts 6. The differential 4 also provides an output of driving torque for the rear wheels, which is transmitted by a two-part propeller shaft 8, 9 to a rear axle differential 10, from which the rear wheels 7 are driven by respective drive shafts 11. The front and rear drive shafts 11, and the parts 8, 9 of the divided propeller shaft may all be shafts in accordance with the present invention.

Referring now to Figures 2 to 8 of the drawings, these show embodiments of shaft 6, 8, 9 or 11. Each embodiment of shaft comprises end portions 13, 14 which are adapted, e.g. by the provision of axially extending spline teeth 12, to be torque-transmittingly connected to the inner members of respective universal joints. Each shaft further comprises a central portion whose length is indicated by Rm, in which the wall thickness D1 remains constant. It is also conceivable for the wall thickness D1 to change continuously in the central portion Rm of the shaft, and for it to be designed asymmetrically relative to the axial centre M of the shaft as a whole.Figures 2, 3 and 5 show a symmetrical central portion Rm, with the centre of symmetry thereof being displaced axially from the axial centre M of the shaft, whereas in Figures 4 and 6 to 8, the centre of gravity is displaced from the centre M of the shaft. Thus, in all embodiments, the shaft 6, 8, 9 or 11 is asymmetrical.

Figure 2 shows a shaft which, as above referred to has a constant wall thickness D1 in the central portion Rm. At one end, following a transition region, and leading to the end portion 13, there is a projection 15 which is cylindrical and has a different wall thickness D2 from the wall thickness D1 in the central portion Rm . The projection 15 has a smaller outer diameter than the outside diameter Da of the central portion. As a result of the projection 15, the centre of symmetry of the central portion Rm is displaced axially from the shaft centre M. Instead of a cylindrical projection 15, it is conceivable to provide a conical projection, with a conical transition area between the different outside diameters Da.

Figure 3 shows a drive shaft in which the central portion Rm has a maximum outside diameter Dmax and a uniform wall thickness. The maximum outside diameter is displaced axially away from the centre M of the shaft, and thus a displacement of the centre of symmetry of the central portion Rm away from the shaft centre M is achieved by providing different lengths of cylindrical projection 15 at opposite ends of the central portion Rm. The projection 15 at the end adjacent the end portion 13 is longer than that adjacent the other end, both cylindrical projections 15 having the same outside diameter Da. The regions between the position of maximum diameter and each of the projections 15 taper conically.

Referring now to Figure 4, this shows a drive shaft in which the maximum outside diameter Dmax is provided adjacent one of the end portions 13. Between the part of maximum outside diameter and the corresponding end portion 13 there is a cylindrical projection 15 of smaller diameter, and wall thickness D2 greater than the wall thickness D1 which applied over the central portion of the shaft. From the position of maximum outside diameter Dmax to the other end portion 14 of the shaft, the central portion of the shaft tapers conically.

Figure 5 shows a drive shaft which has a maximum outside diameter Dmax at each end of its central portion Rm There are respective part-conical projection 15 leading from the positions of maximum diameter Dmax to each of the end portions 13, 14 of the shaft. Between the positions of maximum outside diameter, the central portion of the shaft tapers conically to an outside diameter Da which is axially offset from the centre M of the shaft.

Figures 6 and 7 each illustrate a drive shaft having a maximum outer diameter Dmax in the vicinity of one of the end portions thereof, with the central portion Rm of the shaft tapering conically to the opposite end portion 14.

Adjacent the position of maximum outside diameter Dmax, there is a short partconical transition area leading into a cylindrical projection 15 which in turn leads into the end portion 13. The wall thickness D2 in the region of each projection is 15 is different from the wall thickness D1 of the central portion R The shaft of Figures 6 and 7 differ from one another in respect of the maximum outside diameter Dmax and its distance from the end portion 13.

Figure 8 shows a shaft which has a different maximum outside diameter Dmax in each half 16, 17 of the shaft. The minimum outside diameter Da is axially offset from the shaft centre M. A cylindrical projection 15 is provided adjacent the end portion 13, and in each case the central portion of the shaft tapers conically from its respective maximum outside diameter Dmax to its minimum outside diameter Da.

Figure 9 shows a drive shaft wherein the central portion Rm is provided with rectangular projections or naps 20 on its external surface 18. These naps or projections 20 extend in rows both axially and circumferentially, and each has its longer side edge extending in the longitudinal direction of the shaft.

Figure 10 shows a shaft whose central portion has its surface 18 provided with ribs 19 extending in two left hand helices. In modifications, ribs 19 may alternatively be provided in multiple rows in closely adjoining groups or helical configuration or they may be designed to intersect each other or extend in opposite directions. The rib 19 achieves an increase the torsion or bending stiffness of the shaft while the mass remains unchanged. It is conceivable to combine the raised portions of Figures 9 and 10 to provide, for example narrow ribs and wide naps 20.

Figure 11, as an example, shows ribs 19 which extend in the axial direction of the drive shaft and merely increase the bending stiffness thereof.

Figure 12 shows an embodiment wherein the surface 18 of the central portion of the shaft is provided with intersecting ribs 19 extending axially and circumferentially, to achieve a high bending stiffness and slight improvement in the torsional stiffness while the mass remains unaltered.

Figures 13 and 14 show further embodiments of a shaft according to the invention wherein the central portion Rm of the shaft has a cylindrical surface 18, with transition regions 21 leading therefrom to end portions 13, 14 by way of annular grooves 22 which provide for a sealing connection of a rubber sleeve.

Two damping sleeves 23, for example, are slid onto the central portion Rm and non-rotatingly connected to the surface 18 thereof. The damping sleeves 23 are each of cylindrical shape and comprise a surface 24 and bore 25 which is adapted to fit on the outside diameter Da of the central portion 18 of the shaft.

Sleeves 23 are of a material of high modulus of elasticity and low specific gravity, compared with that of the shaft. They may be pressed onto the shaft, or part tubular segments may be welded to the shaft. In Figure 13, the sleeves 23 are each provided with a smooth outside surface 24, whilst in Figure 14 the surface 24 of the lefthand damping sleeve 23 is provided with axially extending ribs 26.

The surface 24 of the right hand damping sleeve comprises ribs 27 which extend at an angle to the axis of the sleeve.

Figure 15a shows a section along a line A-A of Figure 14, whilst Figure 15b is a section on the line B-B. This clearly shows the ribs 26 with spaces 28 therebetween, and the ribs 27 with spaces 29 therebetween. Damping sleeves as Figures 13 or 14 can be provided on both hollow and solid shafts.

The features disclosed in the foregoing description, or the following claims, or the accompanying drawings, expressed in their specific forms or in terms of a means for performing the disclosed function, or a method or process for attaining the disclosed result, as appropriate, may, separately or in any combination of such features, be utilised for realising the invention in diverse forms thereof.

Claims

CLAIMS:

1. A drive shaft produced in one piece by a forming operation comprising a central tube portion disposed between, and with larger outside diameter than, two end portions which have parts for torque transmitting connection to universal joints, wherein the drive shaft is rotationally symmetrical and is asymmetrical in the longitudinal direction in respect of its resistance to deflection.

2. A drive shaft according to Claim 1, wherein the central portion thereof is symmetrical in the longitudinal direction, the centre of symmetry of the central portion being offset from the axial centre of the shaft.

3. A drive shaft according to Claim 1 wherein the centre of gravity of the shaft is offset from the axial centre of the shaft.

4. A drive shaft according to any one of Claims 1 to 3, wherein one end of the central portion thereof is stepped and provided with a cylindrical projection with a smaller outside diameter than the central portion.

5. A drive shaft according to any one of Claims 1 to 4, wherein one end of the central portion thereof is provided with a part-conical projection.

6. A drive shaft according to any one of Claims 1 to 5, wherein the central portion thereof, over at least its largest part, has a uniform outer diameter and substantially constant wall thickness.

7. A drive shaft according to any one of Claims 1 to 5, wherein the central portion thereof has a substantially constant wall thickness and an outside diameter which changes along its length.

8. A drive shaft according to any one of Claims 1 to 7 wherein the inside diameter and/or the outside diameter of the central portion thereof changes at least partially continuously and asymmetrically relative to the centre of the shaft.

9. A drive shaft according to any one of Claims 1 to 8, wherein the outside diameter of the central portion of the shaft is stepped asymmetrically, with transition regions between the regions of different diameter having an inside diameter and/or outside diameter which changes conically.

10. A drive shaft according to any one of Claims 1 to 9, wherein the inside diameter of the central portion of the shaft is constant.

11. A drive shaft according to any one of Claims 1 to 10 wherein the central portion of the shaft has a maximum outside diameter in the vicinity of an end region thereof.

12. A drive shaft according to any one of Claims 1 to 11 wherein the central portion of the shaft at least between an end and the location of the maximum outside diameter is of part-conical configuration, or part-parabolic in longitudinal section.

13. A drive shaft according to any one of Claims 1 to 12, wherein the maximum outside diameter of the central portion of the shaft is located in the vicinity of the centre of the shaft.

14. A drive shaft according to any one of Claims 1 to 12, wherein the maximum outside diameter of the central portion of the shaft, in each case, is located in the vicinity of each of the two end portions of the shaft.

15. A drive shaft according to any one of Claims 1 to 14, wherein the central portion of the shaft, between the maximum and minimum outside diameter in each case, is of part-conical configuration or part-parabolic longitudinal section.

16. A drive shaft according to any one of Claims 1 to 15, wherein the centre of each half of the shaft has a different maximum outside diameter.

17. A drive shaft according to any one of Claims 1 to 16, wherein in the vicinity of the centre of each half of the shaft, the shaft has the same or a different maximum outside diameter.

18. A motor vehicle including a drive shaft according to any one of Claims 1 to 17, wherein the centre of gravity of the drive shaft lies closest to the input or output part with the greatest mass, especially the gearbox.

19. A motor vehicle including a drive shaft according to any one of Claims 1 to 17, wherein the centre of symmetry of the central portion of the shaft, offset from the centre of the shaft, lies closest to the input or output part with the greatest mass, especially the gearbox.

20. A tubular drive shaft produced in one piece by a forming operation, comprising a central tube portion disposed between, and with a larger outside diameter than, two end portions which have parts for torque transmitting connection to universal joints, wherein the surface of the central portion of the shaft is associated with surface formations distributed over at least a limited area, the internal diameter of the central portion remaining constant.

21. A drive shaft according to Claim 20, wherein the surface formations are provided on at least one damping sleeve which is fitted on to the central portion of the shaft and which is non-rotatingly connected to the drive shaft.

22. A drive shaft according to Claim 20, wherein the surface formations comprise raised portions and/or indentations provided directly on the surface of the central portion of the drive shaft.

23. A drive shaft produced in one piece by a forming operation, comprising a central portion disposed between two end portions, wherein the central portion is provided on its surface with at least one damping sleeve nonrotatingly connected to the drive shaft.

24. A drive shaft according to Claim 21 or Claim 23, wherein the damping sleeve(s) is of a material with high modulus of elasticity and a low specific gravity.

25. A drive shaft according to Claim 21, Claim 23 or Claim 24 wherein the central portion of the shaft is at least partially covered by the damping sleeve(s).

26. A drive shaft according to Claim 21 or any one of Claims 23 to 25, wherein there are two or more damping sleeves arranged asymmetrically, in the axial direction, on the central portion of the shaft.

27. A drive shaft according to Claim 21 or any one of Claims 23 to 26 wherein the or each damping sleeve comprises one tubular portion or several tubular segments.

28. A drive shaft according to Claim 21 or any one of Claims 23 to 27 wherein the or each damping sleeve is rotationally and axially symmetrical.

29. A drive shaft according to Claim 21 or any one of Claims 23 to 28 wherein the or each damping sleeve comprises raised portions and/or indentations on its surface.

30. A drive shaft according to Claims 22 or 29, wherein the raised portions comprise ribs or naps and/or the indentations comprise grooves.

31. A drive shaft according to Claim 29, wherein the ribs, grooves, or naps are arranged in the axial direction, circumferential direction and/or at an angle on the surface of the central portion of the shaft or the damping sleeve(s).

32. A drive shaft according to Claim 30 or Claim 31 wherein the ribs, grooves, or naps are arranged in one or several helices on the surface of the central portion of the shaft or of the damping sleeve(s).

33. A drive shaft according to any one of Claims 30 to 32, wherein the ribs or grooves are arranged in intersecting helices on the surface of the central portion of the shaft or damping sleeve(s).

34. A drive shaft according to any one of Claims 30 to 33, wherein the ribs or grooves are arranged in combination in the axial and/or circumferential direction with helical-like ribs or grooves.

35. A drive shaft according to any one of Claims 30 to 34 wherein the ribs or grooves are arranged in a plurality of rows in closely adjoining groups, and several groups are provided on the surface of the central portion of the shaft or of the damping sleeve.

36. A drive shaft according to Claim 27 or any claim appendant thereto wherein the tubular portions of the or each damping sleeve are pressed onto the shaft.

37. A drive shaft according to Claim 27 or any claim appendant thereto, wherein the tubular segments of the or each damping sleeve are welded onto the shaft.

38. A drive shaft according to Claim 21 or Claim 23 or any claim appendant thereto wherein at least two different damping sleeves are provided on the central portion of the shaft.

39. A process for producing a drive shaft or damping sleeve according to any one of Claims 20 to 22, or any claim appendant thereto, wherein the ribs, grooves or naps are produced on the surface of the central portion of the tube shaft or on the damping sleeve(s) by hammering or drawing.

40. A drive shaft substantially as hereinbefore described with reference to any one of Figures 2 to 15 of the accompanying drawings.

41. Any novel feature or novel combination of features described herein and/or in the accompanying drawings.