SE1551513A1 - Driveshaft assembly and method for its production - Google Patents

Abstract

A driveshaft assembly is disclosed comprising a first and a second torque transmitting member, and a tube. A connecting member is arranged between the first torque transmitting member and the tube. The connecting member is designed to fail in case of unintended overload of the driveshaft assembly as regard to torque.(Fig.3)

Description

DRIVESHAFT ASSEMBLY AND METHOD FOR ITS PRODUCTION TECHNICAL FIELD The present disclosure relates in general to a driveshaft assembly comprising a tube, a first torquetransmitting member and a second torque transmitting member. The present disclosure also relates to a method for producing such a driveshaft assembly.

BACKGROUND A driveshaft, also known as a propeller shaft or a cardan shaft, is used for transmitting torque androtation power from a source of rotational power (a driving component) to a rotatably drivenmechanism or component. The driveshaft assembly generally comprises a tube with torquetransmitting members arranged at and attached to each respective end of the tube. A driveshaftassembly may also comprise additional components, such as various joints or couplings, toaccommodate for variations in alignment and distance between the driving component and driven mechanism or component.

A driveshaft assembly can be manufactured by various welding processes. For example, gas metal arcwelding is frequently used. During gas metal welding, the components of the driveshaft assemblymay however be subjected to a significant amount of heat, which in turn may lead to undesireddistortion and hence imbalance between the components. Thus, gas metal arc welding has the disadvantage of requiring balancing after welding.

A driveshaft assembly may also for example be manufactured by friction welding. Friction welding isa process suffering from the disadvantage of difficulties to change with respect to geometries andwelding parameters after selection of tool and machine. Friction welding also has the disadvantageof requiring balancing and straightening after welding due to misalignment and distortion of the driveshaft assembly resulting from the welding process. |mbalance in the driveshaft assembly results in problems with vibration and unacceptable noise bothinside and outside of the vehicle. Balancing of a driveshaft assembly is performed by spot weldingweights (such as weighted strips) to the tube of the driveshaft assembly and is performed manually.Balancing is thus time consuming and based on the experience of the operator. Furthermore, the spot welds may serve as initiation points for cracks and thus reduce the strength of the tube of the driveshaft assembly. Thus, there is a desire to minimise the need for balancing and straightening of a driveshaft assembly both from a cost perspective and from a quality perspective.

Laser welding is a method which today is commonly known and frequently used in the vehicleindustry. Laser welding has the ability of creating considerably better welds than gas metal weldingand friction welding, does not suffer from the risk of considerable misalignment of the componentswelded, and further minimises the heat introduced into the components welded together.Therefore, laser welding minimises the need for balancing and straightening and therefore reduces the overall production cost for the driveshaft assembly.

Additionally, compared to for example friction welded components, laser welded components canoften be made with thinner walls as there is less requirement of the depth of the weld. A thinner wallthickness of the components inter alia reduces the weight of driveshaft assembly and thereby theoverall weight of for example a vehicle comprising the driveshaft assembly, thus also improving the fuel economy of such a vehicle.

Examples of laser welded driveshaft assemblies are disclosed in GB 2383550 A, US 2010/0022317 A1,US 2004/0162150 A1 and EP 1350975 A2. ln each case, the driveshaft assembly comprises a tube andtwo torque transmitting members each partially inserted into the respective ends of the tube and laser welded to the tube.

A driveshaft assembly is subject to torsion and shear stress resulting from the difference betweenthe input torque and the load. The driveshaft assembly must be strong enough to bear the stress whilst avoiding too much weight in order not to unduly increase the inertia. ln case of an undesired overload of the torque, there is a risk for failure of the driveshaft assembly oradjacent components connected thereto. There are numerous solutions to overcome the problemwith torque overload, for example by compensating devices. Furthermore, the material and thedimensions of the tube of the driveshaft assembly may be designed such as to break in case ofundesired overload which has the advantage of decreasing the risk of failure of adjacent componentsfor example in a drive train. ln the latter case, this requires many different strength classes of thetubes in order to accommodate for each and every configuration of a driveshaft assembly needed forexample for a manufacturer of heavy vehicles. This also increases the overall costs for the manufacturing of driveshaft assemblies having different configurations.

There is a large variety in configurations of driveshaft assemblies. This is for example due to the needfor different lengths thereof resulting from the various constructions of the vehicles, and/or the fieldof use of the driveshaft assembly. The large variety of driveshaft assemblies requires a large varietyof constituent components, such as different tubes having different strengths (strength classes)depending on the use of the driveshaft. Thus, over-all production costs for driveshaft assembliestoday may be unduly high. Costs would be considerably decreased if production of differentdriveshaft assembly configurations could be achieved with a lower number of different types ofconstituent components, i.e. if the different constituent components could be standardized to a higher degree.

SUMMARY The object of the present disclosure is to enable cost effective driveshaft assemblies of differentconfigurations having predetermined torque strengths, for example depending on the intended use of the respective driveshaft assembly.

The object is achieved by means of a driveshaft assembly according to claim 1 and a method for producing a drive shaft assembly according to claim 11.

More specifically, the object is achieved by means of use of a connecting member in the driveshaftassembly. The connecting member is designed to have a predetermined torque strengthcorresponding to the intended torque strength of the driveshaft assembly, and hence has lowertorque strength than the torque strength of the tube of the driveshaft assembly. ln other words, theconnecting member is the decisive component for the torque strength of the driveshaft assembly. lncase of an undesired overload of the driveshaft assembly, the driveshaft assembly will fail due to theconnecting member breaking or, in another way, failing. Thereby, a fracture of the driveshaftassembly will occur at a predetermined point of the driveshaft assembly selected such as to cause the lowest possible risk for additional damages of adjacent components or the like.

Furthermore, the fact that the driveshaft assembly comprises a connecting member enables morestandardised components of a driveshaft assembly for the reason that the connecting member isdesigned to provide the lowest torque strength of the driveshaft assembly and hence constitutes thedecisive component for the torque strength of the driveshaft assembly as such. Thereby, the torquestrength of the tubes and the torque transmitting members can be overdesigned such as to enable using only one or a few grades of material and/or inner and outer diameters for the tubes for production of a large variety of different driveshaft assembly configurations. Thereby, theconstituent components can be standardised to a greater extent while still providing the possibilityof production of a large variety of driveshaft assembly configurations. Standardisation of constituentcomponents reduces the costs of the constituent components of the driveshaft assemblies since larger batches of each component can be produced or bought.

The driveshaft assembly according to the present disclosure comprises a tube having an innersurface, an outer surface, a first axial end, an opposing second axial end, and an axis of rotation. ltfurther comprises a first torque transmitting member and a second torque transmitting member. Aconnecting member is attached to the first axial end of the tube and to the first torque transmittingmember such that the connecting member is interposed between the tube and the first torquetransmitting member. The connecting member has a predetermined torque strength which is lowerthan the torque strength of the tube. Attachment of the connecting member to the tube and the first torque transmitting member can be performed by any previously known method.

The fact that the connecting member is arranged between the tube and a torque transmittingmember (compared to for example somewhere along the longitudinal extension of the tube) reducesthe number of interfaces between the different components of the driveshaft assembly, and hencethe number of welds needed, and also controls where a failure of the driveshaft assembly will takeplace in the case of overload such as to ensure minimal risk for causing additional damages to surrounding components or the like as mentioned above. ln accordance with one aspect, the connecting member is welded to the first axial end of the tube aswell as welded to the first torque transmitting member. Welding results in a firm and strongattachment of the connecting member to the directly adjacent components of the driveshaft assembly.

The use of a connecting member in accordance with the present invention enables use of laserwelding for attachment and would in such a case further reduce the costs for production in view ofminimising the need for balancing and straightening. Furthermore, the quality of the driveshaftassemblies increases as a result of minimising the number of spot welds associated with thebalancing step. Moreover, the wall thickness of the tube and portion of the torque transmittingmember attached to the connecting member can be reduced, if desired, when utilising laser welding compared to when friction welding is used, and hence enables a reduction of weight.

The connecting member may suitably be substantially rotational symmetrical and comprising acircumferential inner wall surface, such that it at least partly has an essentially tubular form. Thisensures a low weight of the connecting member and thus of the driveshaft assembly as such.Furthermore, the connecting member does not impart any imbalance to the driveshaft assembly since it is substantially rotational symmetrical.

According to one aspect, the connecting member may further comprise a first circumferential outerwall surface adapted to abut the inside surface of the tube, a second circumferential outer wallsurface forming a radially extending flange of the connecting member, and a third circumferentialouter wall surface intended to abut an inside portion of the first torque transmitting member. Theradially extending flange may comprise a first radial surface intended to abut an axial end surface ofthe tube, and a second radial surface intended to abut an axial end surface of the first torquetransmitting member. When constructed in this way, the connecting member can be partiallyinserted into the tube as well as the first torque transmitting member and properly aligned therewithbefore attachment. Preferably, the connecting member may be press fit to the tube and to the first torque transmitting member before it is attached, such as by welding, thereto.

As mentioned above, the connecting member has a predetermined torque strength which is lowerthan the torque strength of the tube. This may be achieved in different ways including selection ofthe geometrical configuration of the connecting member and/or selection of material with intended property as regard to torque strength.

For example, the connecting member may comprise a radially extending kerf or notch formed in theinner wall surface of the connecting member. Preferably, the kerf or notch extends radially from theinner wall surface to a depth having a diameter equal to or greater than the diameter of the innersurface of the tube at the first axial end of the tube. Such a kerf or notch, reduces the torquestrength of the connecting member and by selecting the size thereof, including the axial as well asthe radial extension, the intended torque strength of the connecting member can easily be achieved.ln order to be able to have a limited axial extension of the connecting member while still providingsufficient axial extension for proper attachment to the tube and the first torque transmittingmember, the kerf or notch may suitably be arranged at equal distances from the first axial endsurface and the second axial end surface of the connecting member, i.e. arranged essentially in the middle of the axial extension of the connecting member.

Alternatively, the connecting member may comprise a circumferential portion having an increasedinner diameter such that the inner wall surface of the connecting member in said circumferentialportion has a diameter equal to or greater than the diameter of the inner surface of the tube at thefirst axial end thereof. Thereby, the torque strength of the connecting member is reduced. Thecircumferential portion having an increased inner diameter may preferably be arranged essentiallymidway the axial extension of the connecting member, thereby enabling a low total axial extensionof the connecting member while still providing sufficient axial extension for proper attachment to the tube and the first torque transmitting member.

Alternatively, or in addition, the connecting member may be made of a material having lower torque strength than the torque strength of the material of the tube.

A process for manufacturing the driveshaft assembly as disclosed above may preferably compriseassembling the tube and the connecting member at the first axial end of the tube, suitably bypartially inserting the connecting member into the tube, and laser welding the connecting memberto the tube. Before or after assembly and attachment of the connecting member and the tube, theprocess further comprises assembling the first torque transmitting member and the connectingmember, suitably by partially inserting the connecting member into the first torque transmittingmember, and laser welding the connecting member to the first torque transmitting member. Other processes for manufacturing the driveshaft assembly are however also plausible.

The present disclosure also relates to a vehicle comprising a driveshaft assembly as disclosed above.

The vehicle may for example be a heavy vehicle such as a truck or a bus, but may also be a passenger car, a watercraft, a locomotive or any other vehicle which may include a driveshaft assembly.

BRIEF DESCRIPTION OF DRAWINGS Fig. 1 schematically illustrates a side view of a vehicle.

Fig. 2 schematically illustrates a side view of a driveshaft assembly.

Fig. 3 schematically illustrates a side view of the driveshaft assembly illustrated in figure 2 with a partial cut out along line A-A of figure 2.

Fig. 4 schematically illustrates a cross sectional view of a part of a driveshaft assembly in accordance with the box B shown in figure 3 according to one exemplifying embodiment.

Fig. 5 schematically illustrates a cross sectional view of a part of a driveshaft assembly according to another exemplifying embodiment wherein the connecting member comprises a kerf or notch.

Fig. 6 schematically illustrates a cross sectional view of a part of a driveshaft assembly according toyet another exemplifying embodiment wherein the connecting member comprises a rounded cut-out portion.

Fig. 7 schematically illustrates a cross sectional view of a part of a driveshaft assembly according toyet another exemplifying embodiment wherein the connecting member comprises a circumferential portion with increased inner diameter.

Fig. 8 schematically illustrates a cross sectional view of a part of a driveshaft assembly according toyet another exemplifying embodiment wherein the connecting member comprises a V-shaped groove.

DETAILED DESCRIPTION ln the following, the invention will be described in more detail with reference to certain exemplifyingembodiments and the drawings. However, the invention is not limited to the exemplifyingembodiments discussed and shown in the drawings but may be varied within the scope of theappended claims. Furthermore, the drawings shall not be considered drawn to scale as some features may be exaggerated in order to more clearly illustrate certain features. ln the present disclosure, the term ”attached” shall be considered to mean securely connected.Furthermore, the term ”attached” means that such components/members/devices or the like are indirect contact with each other without any separate mechanical components or the like providedbetween. ln this definition, a mechanical component is considered to mean a physical component having a geometry and does thus not encompass for example an adhesive, a coating or the like.

Moreover, the term "adjacent" in the present disclosure is considered to mean both directly adjacent(such as directly connected), or in proximity wherein other mechanical components may interconnect.

Figure 1 illustrates a vehicle 1, here in the form of a truck, in a schematic side view. The vehicle neednot necessarily be a truck but may also be any other motor driven vehicle, such as a bus, a passengercar or a watercraft, as long as it comprises a driveshaft assembly. The vehicle shown in Figure 1comprises an engine 2 which powers the vehicle's tractive wheels 3 via a gearbox 6 and a driveshaftassembly 5. While the driveshaft assembly in Figure 1 is illustrated for the drive of the wheels, a driveshaft may be used for transmitting torque for any purpose, not only for the drive of the wheels.

The driveshaft assembly according to the present disclosure is primarily intended for use in vehiclesto replace or substitute previously known driveshaft assemblies therein. However, it should be notedthat the driveshaft assembly according to the present disclosure may also be used in any otherpreviously known application for a driveshaft assembly, for example in industrial machines or the like.

Figure 2 schematically illustrates a side view of a driveshaft assembly 5 according to one exemplifyingembodiment. The driveshaft assembly comprises a first torque transmitting member 7 and a secondtorque transmitting member 8, which are arranged at the respective ends of the driveshaft assemblyand adapted to transmit torque to and from the driveshaft assembly to and from, respectively,adjacent components (not shown) to which the torque transmitting members 7, 8 are to beconnected. ln the figure, the torque transmitting members 7, 8 are illustrated to have a splinedportion 9 adapted from transmitting torque to a corresponding splined surface of a directly adjacentcomponent. The present disclosure is however not limited to torque transmitting members havingsplines and any previously known torque transmitting member known for use in a driveshaftassembly, for example a yoke or the like, may be used without departing from the scope of the present disclosure.

The driveshaft assembly furthermore comprises a tube 10 which is adapted to rotate around arotational axis thereof and hence transmitting the rotational power from one torque transmittingmember to the other. The tube comprises a first axial end 11, a second axial end 12, an inner surface13 (as shown in Figure 3), an outer surface 14, and an axis of rotation. While not illustrated in thefigure, the driveshaft assembly may comprise additional components if desired, for example toaccommodate for misalignment between driving source and driven component. Thus, the driveshaftassembly may comprise previously known joints or connections, and/or a plurality of tubes, as necessary for the intended use of the driveshaft assembly.

The driveshaft assembly 5 according to the present disclosure further comprises a connectingmember 16 arranged between and connecting the tube 10 and the first torque transmitting member7. The connecting member is thus attached to both the tube and to the first torque transmittingmember. The axial extension, i.e. the length, of the connecting member is considerably less than the axial extension of the tube.

The connecting member 16 is purposively selected to have lower torque strength than the torquestrength of the tube 10 such that in case of unintended torque overload of the driveshaft assembly,the connecting member will fail. Naturally, the first torque transmitting member and the secondtorque transmitting member both have a torque strength exceeding the torque strength of theconnecting member, and usually also the torque strength of the tube. Since the connecting memberhas lower torque strength than the tube, the tube will not break as a result of overload of torque,thereby ensuring that a potential break of the driveshaft assembly will always occur at a predetermined location (i.e. the connecting member).

The fact that the connecting member is designed to break in case of an undesired overload of torquealso has the advantage of avoiding failure of adjacent components, such as a component associatedwith the gearbox the like. By assuring that the driveshaft assembly as such suffers the failure, onlythe driveshaft assembly has to be replaced in case of torque overload. This is usually a considerablyeasier task compared to repairing components adjacent the driveshaft assembly, and could for example be made in field without having to transport a vehicle to a repair shop or the like.

Figure 3 schematically illustrates the driveshaft assembly according to Figure 2 partly cut out to showa cross section according to the line A-A in Figure 2. As shown in the figure, the connecting member16 is a substantially rotational symmetrical member interposed between the tube 10 and the firsttorque transmitting member 7 of the driveshaft assembly 5. Furthermore, it has an axis of rotation coinciding with the axis of rotation 15 of the tube and the first torque transmitting member.

Figure 4 illustrates a cross sectional view of a part, as illustrated by box B in Figure 3, of a driveshaftassembly wherein the axial end of the tube 10, the connecting member 16 and an axial end of the first torque transmitting member can be more clearly seen.

As shown for example in Figures 3 and 4, the connecting member 16 is suitably a substantiallytubular member having a circumferential inner wall surface 19, a first axial end surface 17 and a second axial end surface 18 opposite the first axial end surface. The outer surface of the connecting member comprises a first circumferential outer wall surface 20a intended to abut an inside surface13 of the tube of the driveshaft assembly, a second circumferential outer wall surface 20b having adiameter greater than the diameter of the first circumferential outer surface 20a and thus forming aradially extending flange 21 of the connecting member, and a third circumferential outer wall surface20c intended to abut a portion of the first torque transmitting member 7. The third circumferentialouter wall surface 20c may suitably have a diameter which is less than the diameter of the secondcircumferential outer wall surface 20b. ln fact, in order to be able to standardize the constituentcomponents of the driveshaft assembly to the greatest extent, it is preferred that the diameters ofthe first circumferential outer wall surface 20a and the third circumferential outer wall surface 20care the same thereby enabling the same inner diameters of the tube and the torque transmittingmembers such that these can be connected via a connecting member or directly to each other (such as in the case of at the second axial end of the tube). ln order to facilitate welding of the connecting member 16 to the tube 10, it is preferred that thediameter of the second circumferential outer wall surface 20b of the connecting member isessentially the same as the outer diameter of the tube 10 at the axial end 11 thereof welded to theconnecting member 16. Similarly, it is preferred that the diameter of the second circumferentialouter wall surface 20b of the connecting member is essentially the same as the outer diameter of the first torque transmitting member 7 at the end thereof to be welded to the connecting member.

The radially extending flange 21 of the connecting member 16 comprises a first radial surface 22intended to abut an axial end surface 11a of the tube 10, and an opposing second radial surface 23intended to abut an axial end surface 7a of a torque transmitting means. More specifically, the firstradial surface 22 of the connecting member is intended to be welded to an axial end surface 11a ofthe tube 10 by means of welding, preferably laser welding, and the second radial surface 23 of theconnecting member is intended to be welded to an axial end surface 7a of a torque transmittingmeans, preferably by means of laser welding. Thus, the first and second radial surfaces 22, 23 are configured to serve as welding surfaces.

During production of the driveshaft assembly, the connecting member is introduced into the tubesuch that the axial end surface of the tube abuts or at least is very close to the radial surface 22 ofthe flange 21 of the connecting member. The first circumferential outer surface 20a of theconnecting member abuts the inner surface of the tube 10 as shown in the figure and thus aid in thealignment of the connecting member and the tube. While not illustrated in the figures, it is also plausible that the tube comprises a portion at the first axial end where the inner diameter is greater 11 than the inner diameter of the inner wall surface of the majority of the tube. ln such a case, the innerwall surface of such a portion abuts the first circumferential outer wall surface 20a. Preferably, theconnecting member and the tube may be press fit coupled such as to secure the alignment betweenthem. Then, the connecting member may be welded to the tube in the interface between the first radial surface 22 of the flange 21 and the axial end surface 11a of the tube.

Furthermore, during production of the driveshaft assembly, the connecting member 16 is introducedinto an axial end the first torque transmitting member such that the axial end surface of the firsttorque transmitting member abuts or at least is very close to the second radial surface 23 of theflange 21 of the connecting member 16. The third circumferential outer wall surface abuts an innersurface of the first torque transmitting member such that they are duly aligned. Preferably, theconnecting member and the first torque transmitting member will be press fit coupled. Then, theconnecting member may be welded to the first torque transmitting member 7 in the interfacebetween the second radial surface 23 of the flange and the axial end surface 7a of the first torque transmitting member.

Welding of the connecting member to the tube and to the first torque transmitting member maypreferably be performed by laser welding as previously mentioned in order to minimize distortionand misalignment. Laser welding may be performed in accordance with previously known techniques and will therefore not be further discussed in detail in the present disclosure. ln order to facilitate evacuation of gas and thereby prevent formation of pores in the welds duringwelding, a circumferential recess 24 forming a space or cavity between the connecting member 16and the tube 10 and/or torque transmitting member 7 welded thereto may suitably be providedwhere the first radial or the second radial surface 22, 23, respectively, connects to the first outer wall surface 20a or third outer wall surface 20c, respectively.

The connecting member according to the present disclosure is constructed such as to have apredetermined torque strength which is lower than the torque strength of the tube of the driveshaftassembly. This may be achieved in different ways. For example, the connecting member may bemanufactured from a material which has lower torque strength than the material of the tube.Alternatively, or additionally, the connecting member may have a geometrical configuration which ensures the predetermined torque strength thereof. 12 Figure 5 illustrates one exemplifying embodiment of the connecting member which differs from theconnecting member shown in Figure 4 in that it comprises a kerf or notch 25 formed in the inner wallsurface 19 and extending radially towards the second circumferential outer wall surface 20b. Theradia| extension (i.e. depth) and axial extension (i.e. width) of the kerf or notch is selected such as toachieve the desired torque strength of the connecting member. Preferably, the depth of the kerf ornotch is selected such that the kerf or notch 25 extends slightly deeper than the diameter of the firstcircumferential outer wall surface 20a of the connecting member 16 such that the kerf or notchextends radially into the radially extending flange 21 of the connecting member. ln order not todecrease the strength of the connecting member too much, it is however important that the kerf ornotch does not extend too deep into the flange 21. Therefore, the kerf or notch should preferablynot be deeper than such as extending into a maximum of 30 % of the radia| extension of the flange21 of the connecting member 16. The radia| extension of the flange 21 is the difference in diameterbetween the first circumferential outer wall surface 20a and the second circumferential outer wall surface 20b.

The connecting member 16 may, when the geometrical configuration is altered with the purpose ofachieving the desired torque strength of the connecting member, be made of a material of the samegrade as the tube or of a different material, such as a material with lower torque strength than the tube.

Figure 6 illustrates one alternative exemplifying embodiment wherein the connecting membercomprises a rounded cut-out portion 26 formed in the inner wall surface 19 of the connectingmember. The cut-out portion reduces the wall thickness of the connecting member at the axialextension thereof comprising the radially extending flange. The dimensions and the shape of the cut-out portion are selected such as to give the connecting member the desired torque strength. Thediameter of the depth of the rounded cut-out portion is preferably greater than the diameter of thefirst circumferential outer wall surface 20a, such that the rounded cut-out portion slightly extendsinto the flange 21. Compared to the kerf or notch 25 as illustrated in Figure 5, the rounded cut-out portion 26 shown in Figure 6 may have a greater axial extension.

Yet another exemplifying embodiment is illustrated in Figure 7 wherein the inner wall surface 19 ofthe connecting member 16 comprises a circumferential portion 27 wherein the inner surface of theconnecting member has a diameter equal to or greater than the diameter of the first circumferentialouter wall surface 20a of the connecting member. Thus, the circumferential portion reduces the wall thickness of the connecting member in a similar manner as illustrated in Figure 6, but is essentially 13 not rounded as the cut-out portion 26 of Figure 6. The circumferential portion 27 is suitablyconnected to the inner surface of the connecting member having the smallest diameter via a chamfer 28 or the like.

Figure 8 i||ustrates yet another exemplifying embodiment, similar to the exemplifying embodiment asillustrated in figure 5. According to this exemplifying embodiment, the kerf or notch extending fromthe inner surface of the connecting member is in the form of a V-shaped groove 29. The V-shapedgroove is arranged at an axial extension of the connecting member where the radia| f|ange is. The V-shaped groove preferably has a depth such that it extends a small distance into the radia| f|ange inthe same manner as disclosed above with regard to the kerf or notch as illustrated in figure 5. Thepurpose of the V-shaped groove 29 is to ensure that the connecting member 16 achieves the desired torque strength.

While the Figures 4 to 8 illustrate exemplifying embodiments wherein the radially extending f|ange21 is arranged essentially in the middle of the axial extension of the connecting member such thatthe axial extension of the portions intended to be inserted into the tube and the first torquetransmitting member essentially have the same axial extension, it is also plausible that the axialextension of the first circumferential outer wall surface 20a is different from the axial extension ofthe third circumferential outer wall surface 20c if desired. However, from the perspective ofstandardisation of components and in the interest of seeking to avoid consideration by an operatoron how to insert and attach the connecting member to the tube and first torque transmittingmember, the first and third circumferential outer wall surfaces preferably have essentially the same axial extension.

As shown in Figures 2 and 3, the second torque transmitting member may be attached to the secondaxial end of the tube. lt is however also plausible to include additional components between the tube and the second torque transmitting member as previously discussed.

The axial extension of the connecting member is intended to be considerably less than the axialextension of the tube. The purpose of the connecting member is to ensure that it is the firstcomponent or part of the driveshaft assembly to fail in case of an unintended overload of thedriveshaft assembly as regards to torque. Therefore, the connecting member only has to have anaxial extension sufficient for this purpose and does not need to be designed for the intended axial extension of the driveshaft assembly as such. 14 ln view of the fact that the driveshaft assembly comprises the connecting member having lowertorque strength than the tube, the components can be standardised to a higher degree. To allow forthe various configurations of driveshaft assemblies needed, for example for a manufacturer ofvarious vehicles, all other components of the driveshaft assembly configurations could be essentiallystandardised, where needed by using over-dimensioned strength classes in some cases, and only theconnecting member need to have a preselected torque strength adapted for the intended use of aspecific driveshaft assembly configuration. Thus, the overall production costs different driveshaft assembly configurations can be reduced.

The driveshaft assembly according to the present invention is not limited to the specific exemplifyingembodiments discussed above and illustrated in the drawings, but can be modified in any mannerwithin the scope of the appended claims. For example, lower torque strength of the connectingmember compared to the tube may be achieved by altering the geometry of the connecting memberat the second outer circumferential surface 20b instead of at the inner wall surface 19. Furthermore,the connecting member need not necessarily be inserted into the tube or the first torquetransmitting member, even though this is preferred from the perspective of proper alignment of thecomponents. Furthermore, attachment of the connecting member to the tube and to the first torquetransmitting member can be performed by any means providing a firm attachment between saidcomponents, even though laser welding is preferred. Moreover, the tube of the driveshaft assemblymay have a constant diameter or a slightly tapering diameter from one axial end to the other without departing from the scope of the present invention.

Claims (1)

1. Driveshaft assembly (5) comprising: a tube (10) having an inner surface (13), and outer surface (14), a first axial end (11), asecond axial end (12), and an axis of rotation (15); a first torque transmitting member (7); and a second torque transmitting member (8), characterised in further comprising a connecting member (16) attached to the first axial endof the tube and attached to the first torque transmitting member, and wherein theconnecting member has predetermined torque strength which is lower than the torque strength of the tube. Driveshaft assembly (5) according to claim 1, wherein the connecting member (16) is welded to the first axial end (11) of the tube (10) and to the first torque transmitting member (7). Driveshaft assembly (5) according to any of claims 1 or 2, wherein the connecting member(16) is substantially rotational symmetrical and comprises a circumferential inner wall surface (19). Driveshaft assembly according to claim 3, wherein the connecting member (16) furthercomprises a first circumferential outer wall surface (20a) adapted to abut the inside surface(13) of the tube (10), a second circumferential outer wall surface (20b) forming a radiallyextending flange (21) of the connecting member, and a third circumferential outer wallsurface (20c) intended to abut an inside portion of the first torque transmitting member (7),and wherein the radially extending flange comprises a first radial surface (22) intended toabut an axial end surface (11a) of the tube, and a second radial surface (23) intended to abut an axial end surface (7a) of the first torque transmitting member. Driveshaft assembly according to any of claims 3 or 4, wherein the connecting member (16)comprises a radially extending kerf or notch (25) formed in the inner wall surface (19) of theconnecting member, preferably wherein the kerf or notch extends radially from the inner wall surface to a depth having a diameter equal to or greater than the diameter of the inner surface (13) of the tube (10) at the first axial end (11) of the tube. 10. 11. 16 Driveshaft assembly (5) according to claim 5, wherein the kerf or notch (25) is arrangedessentially at equal distances from the first axial end surface and the second axial end surface of the connecting member. Driveshaft assembly according to claim 3 or 4, wherein the connecting member (16)comprises a circumferential portion having an increased inner diameter such that the innerwall surface (19) of connecting member in said circumferential portion has a diameter equalto or greater than the diameter of the inner surface (13) of the tube (10) at the first axial end (11) of the tube. Driveshaft assembly according to claim 7, wherein the circumferential portion having anincreased inner diameter is arranged midway of the axial extension of the connecting member. Driveshaft assembly according to any of the preceding claims, wherein the connectingmember (16) is formed of a material having lower torque strength than the material of the tube (10). Vehicle (1) comprising a driveshaft assembly (5) according to any of the preceding claims. Process for manufacturing a drive shaft assembly according to any of claims 1 to 8,comprising assembling the tube and the connecting member at a first axial end of the tube,followed by laser welding the connecting member to the tube, and assembling the firsttorque transmitting member and the connecting member, followed by laser welding the connecting member to the first torque transmitting member.