DE4416725A1 - Road vehicle rear axle - has tubular cross brace with both ends having non=torsional cross=section and that of centre being torsionally weak, with double walled profile arm - Google Patents

Abstract

The road vehicle axle has two wheel-bearing longitudinal guides (2) elastically linked to the superstructure, which pivot about an axis transverse to the direction of travel. The longitudinal guides are welded to one another by a cross brace parallel to and spaced away from the pivot axis which is non-bendable but torsionally weak. The cross brace (5) over its total length comprises a tube profile (12), which at both ends has a non-torsional cross-section and in the central area a torsionally weak U,V,L,X or similar cross-section with at least one double-walled profile arm. The cross section of the connection point of the guides and the brace has a rotationally symmetrical shape which allows an axial turning of the cross brace before welding.

Description

The invention relates to a motor vehicle rear axle two wheel-bearing rigid rigidly hinged to the body Trailing arms, which are at least one transverse to the driving line device arranged swing axis and swing using a arranged parallel and spaced from the pivot axis rigid but torsionally soft cross strut with each other are welded.

Such motor vehicle rear axles are relative simple production requires a small space on and can with motor vehicles with different requirements the driving characteristics and the load capacity, like this different with family sedans or with sporty motor vehicles occur be built.

The driving characteristics and the carrying capacity of such Rear axles essentially depend on the selection of the the transverse link connecting the two trailing arms, and from the selected cross section of the profile in the torsion bar rich, which is usually a U, V, L, X or similar Chen cross section. The spatial out is direction of the individual profile legs of the cross section in Torsion area, especially the position dependent on it the shear center of the profile, decisive for the Determination of the kinematic properties of the rear axis, such as changing the camber and toe-in  with mutual deflection or self-steering behavior tens of the rear axle when cornering.

For example, with a cross strut with a V-shaped one Cross-section, the center of thrust lies approximately at the spit where the center lines of the angle profile intersect. When reciprocating or rebounding or in one When cornering, the wheels swivel (like on an incline kerachse) approximately around a swivel axis which is defined by the Bearing eyes of the trailing arms on the body and through the thrust center of the profile approximately in the middle of the torsion bar rich the cross strut runs.

So if you have the situation with such a rear axle of the thrust center changes, for example by axia les twisting of the profile (before welding) a little higher or lower, so will the kinematic Properties, in particular the self-steering behavior of the Rear axle, change when cornering.

In known motor vehicle rear axles of this type a change in the position of the thrust center in space constructively and technically very complex, because the trailing arms a certain at the junctions Form for connection to the corresponding cross strut must have. In addition, the verbin Special shaped knots and reinforcements parts to increase the strength and reduce the chip welded tips. Therefore, a change is required change in the position of the shear center of the profile (axial rotation by a certain angle) always one new constructive solution as well as a new welded one Assembly with customized reinforcement parts.

DE 43 30 192 AI is a motor vehicle rear axis known, in which the wheel-bearing bending and torsion  on stiff trailing arm by means of a rigid, for Torsional stress, however, compliant cross strut are interconnected. This cross strut has the entire length of a U-profile, whose profile leg at both ends of the cross strut parallel to the wall area trailing arms (with the plane of symmetry I). As a result, the cross strut can weld well the trailing arms are connected.

Specific kinematic properties around this rear axle regarding the camber and toe-in change when changing deflection or self-steering behavior lend is the U-profile of the cross strut in the torsion bar range by a certain angle with respect to the location of the U-profiles at both ends of the cross strut (with the Symme drive level I) rotated, the transition area between between the two cross sections of the fluids is designed.

In this construction, the trailing arms are specially designed for Connected to the U-profile of the cross strut. However, this has the disadvantage that when using a other cross brace that has a greater distance between the parallel profile legs or another profile has cross-section, the trailing arms, especially their Connection point with the cross strut, changed and to the new cross strut must be adjusted.

For example, the use of a low-warping V-profile due to the geometric shape of this cross cut problematic because the joints with the trailing arms, welding is no longer as good design constantly. There can thus be strength problems the connection points occur.  

The object of the invention is a generic force vehicle rear axle to create the reduced Manufacturing requirements regarding various requirements the driving characteristics that can be achieved, in particular the Camber and toe-in change when reciprocating and / or the self-steering behavior of the rear axle during a cure ven trips, as well as a higher durability and has load capacity.

This problem is solved in that the cross strut over the entire length of a tube profile that a torsionally rigid cross-section at both ends and in middle area a torsionally soft U-, V-, L-, X- or similar cross-section with at least one double has walled profile leg, the transition be rich from torsionally rigid to torsionally soft cross-section is fluently designed.

This allows for a reduced weight of the rear axle the torsional properties of the cross strut and its hold availability can be significantly improved, since such Deformation of the pipe profile a better distribution of the Forces in the cross strut (reduced or no chip peaks along the entire length of the tube profile) possible. The bending and torsional forces that occur can NEN are also well received by the trailing arms, because the tube profile at both ends to a torsionally rigid Profile cross section is deformed.

This torsionally rigid profile cross section can, for example wise have a round or polygonal shape that technically good for connection to the trailing arms is suitable. Since no additional reinforcement parts on the Liaison needed, the number of Welds are significantly reduced.  

A particularly advantageous connection between the cross strive and the trailing arms is achieved in that the cross-section of the connection point between longitudinal lines core and the cross strut have a rotationally symmetrical shape has an axial rotation of the cross strut before allowed to weld the joint. Through this rota The cross-symmetrical shape of the cross-section can strive with the trailing arms before welding be rotated axially, regardless of the cross sectional shape of the cross strut in the torsion area. The location the thrust center in the torsion area can thus be whoever changes during series production the.

To achieve sufficient torsional and flexural rigidity The trailing arms can be used as box sections or tubes be shaped. With these versions, the cross strut connecting the two trailing arms (tubular profile) at the appropriately designed connection points di be welded directly to the trailing arms. To Her position of this trailing arm is particularly suitable for the hy drastic hydroforming process, in which the Trailing arm inexpensive and weight-optimized from tube material can be manufactured.

According to a preferred embodiment, the longitudinal handlebars as cast and torsionally rigid castings det. This enables all necessary parts such as Radträ plate, spring seat, eye for fastening the shock absorber heel, socket for the lying or standing arrangement Damping bushing and other chassis parts in the trailing arm integrate. To increase the strength and / or for re The trailing arms can also reduce the weight Steel or light metal can be cast.  

For connection to the cross strut is according to the invention the trailing arms each have an approach that ent speaking of the shape of the tube profile end round or vielec kig can be trained. A particularly beneficial one Training is that the approach is tubular is formed and its wall thickness at the connection cross-section about the wall thickness of the Rohrpro filendes corresponds. This kind of training the Ansat zes is particularly suitable for welding using the magnetic Arc welding process. The necessary, about the same Wall thickness from the tube profile end and neck can either by mechanical post-processing of the batch or by Deformation of the pipe profile end to a ge for welding suitable wall thickness can be achieved.

As an alternative to this version, the outer circumference or -diameter of the approach equal to or slightly less than the inner circumference or diameter of the pipe profile end be trained. Can be connected to the trailing arm simply put the pipe profile end over the shoulder and be positioned so precisely before it is on his forehead side is welded to the approach.

According to another embodiment of the connection point the approach is provided with a recess in which the Pipe profile end inserted and on the face of the Ansat zes can be welded to it.

The load capacity of the rear axle according to the invention can can be increased relatively easily by adding a stiffer cross strive with a larger cross in the torsion area cutting surface or shape is used. Such Cross strut can by known methods, for example according to the hydroforming process, who manufactured the. Only the diameter of the pipe material in the Torsion area before deformation to U-, V-, L-, X-  or similar cross section expanded. So it can be done without Change in the connection points to the trailing arms in particular the rigidity and the torsion rate of the Pipe profile can be influenced.

For even distribution of forces and Torsional stresses in the tube profile are the transition area surface from torsionally rigid to torsionally soft cross-section deformed so that the torsional moment of resistance from torsion stiffness to the torsionally soft cross section continuous diminishes. Since the torsional moment of resistance of the Cross-sectional area and geometry depends on flowing deformation of the tube profile with defined Cross-sectional change such a course of the torso resistance moment in the transition areas become.

Depending on the cross-sectional geometry in the torso the pipe profile in the transition areas also with a progressively decreasing torsional resistance stationary torque can be designed. This advantageous execution tion allows for the same length of the cross strut Shorten transition areas.

A preferred embodiment of the motor vehicle rear axis provides that the torsion area of the cross strut an approximately open V-shaped profile with double has walled profile legs, in which the symmetry plane at an angle relative to the vehicle dimensions is facing downwards. In this version is it ensured that the free ends of the Profilschen under the influence of lateral forces on the wheels on the train be claimed.

The production of the tube profile according to the invention is right relatively simple and inexpensive, as the starting material  an ordinary pipe can be used. Before Ver special fittings for inserted the torsion area and the transition areas, to achieve the desired profile cross section. After that can the pipe mechanically with an appropriate stamp be shaped to the specified cross section. After The pipe profile can be removed with the Trailing arms welded in a welding device the.

The invention permits numerous embodiments. For Some further clarify their basic principle thereof shown in the drawing and below be wrote. The drawing shows in

Figure 1 is a perspective view of a motor vehicle rear axle according to the invention, in which the wheel-carrying trailing arms are connected to one another by means of a torsionally soft cross strut made of tubular profile;

FIG. 2 shows a plan view of the left half of the motor vehicle rear axle according to FIG. 1;

Fig. 3 is a section along line BB in Fig. 2;

Fig. 4 is a section along line AA in Fig. 2;

Figure 5 is an axial section through the connec tion point between the trailing arm and the cross strut of FIG. 2.

. FIG. 6 through FIG 11 show alternative embodiments of the connection point between the trailing arm and the cross strut;

Fig. 12 is an axial section through the fertigge turned transverse strut 5 in FIG. 2.

The motor vehicle rear axle partially shown in FIG. 1 consists essentially of two wheel-guiding trailing arms 2 and one of the two trailing arms 2 connecting cross strut 5 . The trailing arms 2 are formed as castings and at their front end with a La gerauge 3 articulated on the vehicle body, not shown. With 6 the shock absorbers and 7 with the Fe are designated, which are arranged between the trailing arms 2 and the vehicle body. At the rear end of the trailing arm 2 , receptacles 4 are provided for connection to a wheel carrier for mounting a wheel.

The cross strut 5 consists of a tubular profile 12 , which is deformed in its central region, the torsion region 13 , to a torsionally soft cross section and at both ends to a torsionally rigid cross section, the transition region from the torsionally rigid to the torsionally soft cross section (the region between the cutting guides A - A and BB in Fig. 2) is designed to flow with a progressively decreasing torsional moment of resistance. As shown in Fig. 3, the torsionally soft cross-section has a V-shaped profile 16 open to the front with double-walled legs 14 , 15 , in which the plane of symmetry 17 is directed obliquely downwards in relation to the vehicle dimensions. The center of thrust of this profile lies on the plane of symmetry 17 approximately in the point denoted by S. With 18 about the outer circumference at the end of the tube profile 12 is indicated.

For connection to the cross strut 5 , an extension 10 is provided on the trailing arm 2 , which, as shown in FIG. 2, is welded at the connection point 11 to one end of the cross strut 5 by the magnet-arc welding method. Since the cross strut 5 at the junction 11 egg nen torsionally rigid circular cross-section ( Fig. 4). The approach 10 is also circular and tubular. Whose wall thickness at the connection point 11 corresponds approximately to the wall thickness of the tubular profile 12 in this area.

With simultaneous deflection of the wheels, both trailing arms 2 pivot about the pivot axis 8 , which runs through the two bearing eyes 3 transversely to the direction of travel. With alternate deflection of the wheels, the trailing arms 2 pivot, as shown in Fig. 2, about a pivot axis 9 , which wa through the bearing eyes 3 of the trailing arms 2 on the structure and through the thrust center S of the profile approximately in the middle of the torsion area 13 of the Cross strut 5 runs.

The connection point 11 between the cross strut 5 and the trailing arms 2 can be designed differently. Fig. 5 shows an axial section through the connec tion point 11 , the cross section of which has a rotationally symmetrical shape. The diameter and the wall thickness of the tubular profile end 19 corresponds approximately to the diameter water and the wall thickness of the neck 10 , so that both parts 10 , 19 in a device, not shown, which can accommodate the cross strut 5 rotatably, on the end faces 20 , 21 after can be welded using the Magnet-Arc welding process. The wall thickness of the approach 10 at the junction 11 is adapted by mechanical processing to the wall thickness of the pipe profile end 19 .

In Fig. 6, an alternative embodiment of the connec tion point is shown, in which the inner diameter of the tubular profile end 19 is the same or slightly larger than the outer diameter of the extension 10 . To connect approach 10 and pipe profile end 19 , the pipe profile end 19 is placed over the approach 10 and welded to the face 10 with the approach 10 by known welding methods.

In the formation of the connection point 11 according to FIG. 7, a circular recess 22 is provided at the extension 10 , the inside diameter of which is approximately the same or slightly larger than the outside diameter of the tube profile end 19 . To connect the two parts 10 , 19 , the tubular profile end 19 is inserted into the recess 22 and welded to the shoulder 10 on the end face 21 . In this embodiment, the recess 22 can also be arranged directly on the trailing arm 2 .

In order to increase the rigidity of the cross strut 5 , according to FIG. 8, the diameter of the tubular profile 12 in the torsion area 13 before the deformation to the V-shaped profile 16 can be greater than the diameter at the tubular profile end 19 . In Fig. 8, the trailing arm 2 with the set 10 only for comparison of the diameter at the connec tion point 11 is shown. In this embodiment, the wall thickness of the tube profile end 19 is adapted to the wall thickness of the extension 10 according to known manufacturing methods, for example by compressing the length of the tube profile 12 .

As an alternative to the design of the cross strut 5 according to FIG. 8, as shown in FIG. 9, the diameter of the tubular profile 12 in the torsion region 13 before the deformation to the V-shaped profile 16 can be made smaller than the diameter at the tube profile end 19 . This training may be necessary if the torsional rigidity in the torsion on area 13 is to be reduced or the rigidity of the Rohrpro filendes 19 in the area of the connection point 11 is to be increased.

The FIG. 8 and 9 are cross struts 5 formed to the 6 or 7 ge shown in Fig. Embodiments of the junction 11 are connected to the longitudinal control arm 2 of course accordingly.

At the connecting points 11 and the cross struts 5 , which are designed according to FIGS. 1 to 9, the cross struts 5 can be rotated axially as desired to change the position of the thrust center S before welding with the trailing arms 2 . In the embodiment of the cross strut 5 according to FIG. 10, this rotatability of the cross strut 5 to change the position of the thrust center S is not necessary, since the thrust center S is located exactly in the torsion region 13 on the central axis 23 of the three-legged tubular profile 12 . Therefore, the connection point 11 can be designed according to the local conditions of the trailing arm 2 and the cross strut 5 .

Since the cross strut 5 at the connection point 11 has a torsionally rigid triangular profile, favorable conditions for welding with the trailing arms 2 are given, the cross strut 5 to increase the strength of the welded joint to the shape of the trailing arm 2 , as shown in FIG. 10 shown, can be adjusted.

The tube profile end 19 can also, as can be seen in FIG. 11, be formed, if necessary, into a very rigid profile cross section 24 which can be welded in a technically advantageous manner with a box-shaped trailing arm 2 . In this embodiment, the cross strut 5 in the torsion region 13 has a double-walled V-shaped profile cross section, the plane of symmetry 25 of which is vertical and the tip of the V-shaped cross section is directed upwards. However, the plane of symmetry 25 can also be arranged horizontally, obliquely towards the bottom below, obliquely towards the bottom or in any other direction.

For the production of the cross strut 5 consisting of a tubular profile 12 , which can be designed according to FIGS. 1 to 9, a circular tube 26 can be used, for example, which is indicated in FIG . Before the deformation to the U, V, L, X or similar cross section, speci elle shaped pieces 27 for the transition areas from torsionally rigid to torsionally soft cross section and, if necessary, in the torsion area 13 can be inserted into the tube 26 at both ends Special fitting 28 are inserted, which are formed in accordance with the desired profile shape in the transition and Torsionsberei Chen. The fitting 28 is then required if the individual profile legs 14 , 15 of the cross strut 5 are to be formed with a gap between the walls 30 , 31 ( FIG. 3) in order to increase the rigidity and / or reduce the friction and noise.

With a stamp 29 designed as a "negative" to the desired profile shape, the tube 26 can finally be formed into the predetermined profile shape.

Claims (14)

1. Motor vehicle rear axle with two wheel-supporting ela stically articulated rigid control arms that swing about at least one transverse pivot axis arranged and are welded together by means of a parallel and spaced to the pivot axis th rigid but torsionally soft cross strut, characterized in that the cross strut ( 5 ) over the entire length of a tubular profile ( 12 ), which has a torsionally rigid cross section at both ends and a torsionally soft U, V, L, X or similar cross section with at least one dop in the central region has fur-walled profile legs ( 14 , 15 ), the transition region from torsionally rigid to torsionally soft cross section being designed to be fluid. 2. Motor vehicle rear axle according to claim 1, characterized in that the cross section of the connection point ( 11 ) between the trailing arms ( 2 ) and the cross strut ( 5 ) has a rotationally symmetrical shape, which axially rotates the cross strut ( 5 ) before welding connection allowed. 3. Motor vehicle rear axle according to claim 1 or 2, characterized in that the trailing arms ( 2 ) are designed as flexurally and torsionally rigid cast parts and each have a shoulder ( 10 ) for connection to an end of the cross strut ( 5 ). 4. Motor vehicle rear axle according to claim 3, characterized in that the projection ( 10 ) is round or polygonal in cross section. 5. Motor vehicle rear axle according to claim 3 or 4, characterized in that the approach ( 10 ) is designed rohrför mig and its wall thickness at the Ver connection point ( 11 ) is approximately equal to the wall thickness of the tube profile end ( 19 ). 6. Motor vehicle rear axle according to one of claims 3 to 5, characterized in that the projection ( 10 ) with the tube profile end ( 19 ) is welded by the magnet-arc welding process. 7. Motor vehicle rear axle according to one of claims 3 to 5, characterized in that for connection to the trailing arm ( 2 ), the tubular profile end ( 19 ) is inserted over the neck ( 10 ) and on the end face ( 20 ) of the tubular profile ( 12 ) with the approach ( 10 ) is welded. 8. Motor vehicle rear axle according to one of claims 3 to 5, characterized in that for connection to the trailing arm ( 2 ), the tubular profile end ( 19 ) in a recess ( 22 ) in the neck ( 10 ) and on the front side ( 21 ) of the Approach ( 10 ) is welded to this. 9. Motor vehicle rear axle according to one of claims 1 to 8, characterized in that the wall thickness of the tubular profile ( 12 ) is enlarged at both ends compared to the wall thickness in the torsion region ( 13 ) by deformation. 10. Motor vehicle rear axle according to one of claims 1 to 9, characterized in that the tubular profile ( 12 ) in the torsion area ( 13 ) prior to the deformation to a U-, V-, L-, X- or similar cross-section egg nen larger diameter than points at both ends. 11. Motor vehicle rear axle according to one of claims 1 to 9, characterized in that the tubular profile ( 12 ) in the torsion area ( 13 ) prior to the deformation to a U, V, L, X or similar cross section egg nen smaller diameter than points at both ends. 12. Motor vehicle rear axle according to one of claims 1 to 11, characterized in that the tubular profile ( 12 ) is deformed at the transition areas from torsionally rigid to torsionally soft cross section such that the torsional moment of resistance decreases continuously from torsionally rigid to torsionally soft cross section. 13. Motor vehicle rear axle according to one of claims 1 to 11, characterized in that the tubular profile ( 12 ) is deformed at the transition regions from torsionally rigid to torsionally soft cross section such that the torsional moment of resistance progressively decreases from torsionally rigid to torsionally soft cross section. 14. Motor vehicle rear axle according to one of claims 1 to 13, characterized in that the torsionswei che cross-section has an approximately open V-shaped profile ( 16 ) with double-walled profile legs ( 14 , 15 ), in which the plane of symmetry ( 17th ) is directed approximately obliquely towards the bottom in relation to the vehicle dimensions.