FORM 2
THE PATENT ACT 1970 (39 of 1970)
The Patents Rules, 2003 COMPLETE SPECIFICATION See Section 10, and rule 13
1. TITLE OF INVENTION
WHEEL-GUIDING STRUT FOR AN ACTIVE CHASSIS

APPLICANT(S)
a) Name
b) Nationality
c) Address

ZF FRIEDRICHSHAFEN AG
GERMAN Company
8803 8 FRIEDRICHSHAFEN
GERMANY

PREAMBLE TO THE DESCRIPTION
The following specification particularly describes the invention and the manner in which it is to be performed : -

2021

2008

The invention relates to a wheel-guiding strut for an axle of a motor vehicle, according to the preamble of claim 1.
Wheel-guiding struts such as, for example, transverse control arms, longitudinal control arms or tension rods, are used on practically all wheel suspensions and axles of motor vehicles and serve for movably connecting or limiting the degrees of freedom of movement of the wheel with respect to the vehicle chassis. Conventional wheel-guiding struts are generally attached in a non-elastic but articulated manner in the region of the wheel, for example to the wheel carrier, while the chassis-side attachment of known wheel-guiding struts usually takes place in the form of elastomeric joints or rubber bearings.
The chassis-side attachment by means of elastomeric bearings serves on the one hand to absorb tolerances or deformations which occur in the axle system as a result of the static and dynamic wheel loads, and on the other hand within the context of a comfort bearing serves the purpose of damping and decoupling microvibrations and for reducing the transmission of structure-borne sound from the wheel carrier to the vehicle chassis.
For an effective comfort bearing with effective noise decoupling, it is thus desirable to use the softest possible elastomeric bearings in the region of the chassis-side attachment of the wheel-guiding strut. However, this results in a conflict of aims with regard to the exact wheel guidance desirable in the context of driving dynamics and with regard to maintaining the structurally intended axle kinematics such as toe, camber, splay, trail and the like, under as far as possible all the driving conditions which occur.
In other words, in the context of axle kinematics and driving dynamics, it is desirable to provide an attachment of the wheel-guiding strut which is as hard or as non-elastic as possible not only on the wheel side but rather also on the chassis side, whereas the aim of a comfort bearing demands quite the opposite requirement of an
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attachment of the wheel-guiding strut to the vehicle chassis in as soft and as elastic a manner as possible. These two opposite requirements have to date been met only in the form of a structural compromise settled more or less in the middle.
Added to this is the fact that elastomeric bearings arranged on the chassis side of a wheel-guiding strut are not only acted upon by the entire wheel forces but rather, due to the lever arm formed by the wheel-guiding strut, these bearings are in some circumstances additionally exposed to considerable torque loads. This additional torque loading furthermore leads to undesirable deformations of the chassis-side elastomeric bearing and thus tends to result in load-dependent errors in the axle geometry or in an imprecise road guidance of the motor vehicle.
The elastomeric bearings of the wheel-guiding struts known from the prior art furthermore lead to considerable structural conflicts of aim in applications involving the so-called active chassis. In the case of the active chassis, such as for example but in no way exclusively in the case of active roll stabilisation, considerable forces and/ or torques generated by an actuator are introduced into the wheel suspension of individual wheels or axles, in order thus to counteract a defined jounce or rebound movement of the wheel. In this case, however, due to the forces, considerable deformations of any chassis-side elastomeric bearings of wheel-guiding struts may still occur, which on the one hand lead to the described, undesirable changes in axle geometry but on the other hand also make it difficult or impossible to actively influence the jounce movements of the wheel in the desired manner.
Against this background, the object of the present invention is to provide a wheel-guiding strut for use inter alia on the active chassis, by means of which the aforementioned disadvantages to be found in the prior art can be overcome. The wheel-guiding strut is intended in particular to help to resolve the conflict of aims between a comfort bearing on the one hand and the precision of wheel guidance on the other hand. When used on the active chassis, the wheel-guiding strut is also intended to allow a reliable introduction of actuator forces into the wheel
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suspension, without appreciable or undesirably large elastic deformations being induced in the process between the individual components of the wheel suspension.
This object is achieved by a wheel-guiding strut having the features of claim 1.
Preferred embodiments form the subject matter of the dependent claims.
In a manner initially known per se, the wheel-guiding strut according to the present invention has two end regions, wherein each of the end regions carries at least one bearing arrangement. In this case, the bearing arrangement of at least one end region of the wheel-guiding strut comprises an elastomeric bearing in a manner known per se.
According to the invention, however, the wheel-guiding strut is characterised in that the wheel-side bearing arrangement comprises an elastomeric bearing.
The wheel-guiding strut according to the invention is thus firstly advantageous since, due to the elastomeric bearing arranged on the wheel side or on the wheel carrier side according to the invention - even in the case of a particularly hard or non-elastic chassis-side attachment - it is still possible for the decoupling with regard to noise and vibration to take place, which is desired in the context of a comfort bearing. At the same time, the elastomeric bearing arranged on the wheel side brings the advantage that, due to the fact that it is arranged directly at the force introduction point in the region of the wheel carrier, an optimal force introduction can take place without the secondary torques and corresponding deformations which exist in the prior art due to the lever arm of the wheel-guiding strut.
Finally, the wheel-guiding strut according to the invention is also predestined for use on the active chassis since, due to the possibility of providing a relatively hard articulated attachment of the wheel-guiding strut on the chassis side without any loss of comfort, a low-loss introduction of actuator forces and actuator torques can
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ideally take place, Along with the desired precisely controllable influencing of the jounce movements of the wheel.
Particularly against this background, it is provided according to one particularly preferred embodiment of the invention that the bearing at the chassis-side end region of the wheel-guiding strut is designed in a non-elastic manner.
In this way, firstly 3 particularly precise wheel guidance with the smallest possible deformations in the wheel suspension can be achieved, since the considerable deformations which exist in some circumstances in the prior art due to secondary torques in the chassis-side bearing which is necessarily soft are completely omitted. Furthermore, when using the wheel-guiding strut on the active chassis, it is even possible in this way for a practically lossless introduction of actuator forces and actuator torques to take place.
According to a further preferred embodiment of the invention, the wheel-side bearing arrangement comprises a ball joint. In this case, the ball joint is connected to the wheel-side end of the wheel-guiding strut by means of an elastomeric bearing. A ball joint at this location is firstly advantageous since ball joints have widely proven useful in wheel suspensions of motor vehicles. Furthermore, in this way a functional separation can be obtained between the absorption of steering movements or jounce movements of the wheel by the ball joint on the one hand, while on the other hand micromovements or undesirable vibrations can be absorbed by the elastomeric bearing.
Preferably in this case, the elastomeric bearing and the ball joint are arranged in such a way that the elastomer of the elastomeric bearing surrounds the ball joint at least in some regions. Such a substantially concentric arrangement of elastomeric bearing and ball joint proves to be particularly space-saving and robust, which is a definite advantage in the region of the wheel carrier of motor vehicles. Moreover, according to this embodiment of the invention, the elastomeric bearing may optionally be
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designed in such a way that the ball joint is additionally protected by the elastomer against harmful effects or against foreign substances.
Against this background, it is provided according to further embodiments of the invention that the elastomeric bearing surrounding the ball joint exists in the form of an elastomeric layer, which is arranged substantially radially between the bearing shell and the joint housing of the ball joint; or that the ball joint comprises an inner and an outer joint housing, wherein the elastomeric layer is arranged radially between the inner and outer joint housing of the ball joint. In particular these embodiments have the advantage of being particularly compact and robust and moreover of connecting a modular structure with great ease of assembly. Here, the last-mentioned embodiment is particularly useful in the case of ball joints with plastic bearing shells, in which a metal housing which directly surrounds the bearing shell is required for supporting the shape of the plastic bearing shell.
A further embodiment of the invention provides that the elastomeric layer surrounding the ball joint has different-sized cross-sectional surface areas in two directions which are perpendicular to one another and radial to the joint housing. This is advantageous since the elastomeric bearing surrounding the ball joint can in this way be provided with different spring stiffnesses for different radial directions. An improved structural control of the flexibilities of the elastomeric bearing as a function of the force introduction direction is thus provided.
According to a further embodiment of the invention, it is provided that, in the case of a joint housing comprising two shells with an elastomeric layer positioned therebetween, an axial stop is arranged on the inner joint housing, wherein the axial stop is surrounded by the outer joint housing. Preferably in this case, the axial stop is sheathed with elastomer at least in some regions. In this way, an additional, separate control of the spring travel and optionally also of the specific spring stiffness between the outer and inner joint housing in the third spatial direction axial to the joint housing is possible. In this case, the axial stop is preferably of annular shape
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and is preferably pressed against the inner joint housing in the region of the inner joint housing cover.
According to a further, particularly preferred embodiment of the invention, the ball joint is arranged in a cutout in the wheel-side end region of the wheel-guiding strut. In this way, a space-saving and compact arrangement composed of the wheel-guiding strut and the ball joint is achieved, along with a uniform force flow from the wheel-guiding strut to the ball joint. The joint housing or, in the case of a two-shell joint housing, the outer joint housing of the ball joint is preferably formed by the cutout in the wheel-side end region of the wheel-guiding strut. The combining of functions achieved as a result is advantageous in particular with regard to reducing the weight and space requirement of the arrangement consisting of wheel-guiding strut and ball joint.
Against the background of introducing and transmitting actuating forces and actuating torques - in the context of the active chassis - through the wheel-guiding strut into the wheel suspension, it is provided according to another preferred embodiment of the invention that the chassis-side bearing arrangement comprises two ball joints arranged at a distance from one another. In this way, forces and torques can be introduced into the wheel-guiding strut in a simple and effective manner for example in order to influence the jounce movement of the wheel, wherein the distance between the two ball joints arranged at the chassis-side end of the wheel-guiding strut serves as a lever arm for introducing the required forces and torques into the wheel-guiding strut.
The invention will be explained in more detail below with reference to drawings which show merely examples of embodiments. In the drawings:
Fig. 1 shows an isometric view of an embodiment of a wheel-guiding strut according to the present invention;
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Fig. 2 shows a detail view/ on an enlarged scale compared to Fig. 1, of the wheel-side ball joint of the wheel-guiding strut according to Fig. 1;
Fig. 3 shows an isometric detail view, again on an enlarged scale, of the ball joint according to Fig. 2 in a view of the underside;
Fig. 4 shows a schematic view of the ball joint of the wheel-guiding strut according to Figs. 1 to 3 in longitudinal section through the wheel-guiding strut and the ball joint;
Fig. 5 shows an isometric view of the assembly of the joint housing of a ball joint for a wheel-guiding strut according to Figs. 1 to 4;
Fig. 6 shows the joint housing according to Fig. 5 in plan view;
Fig. 7 shows the joint housing according to Figs. 5 and 6 along the longitudinal section line A-A shown in Fig. 6; and
Fig. 8 shows the joint housing according to Figs. 5 to 7 along the longitudinal section line B-B shown in Fig. 6.
Fig. 1 shows an isometric view of an embodiment of a wheel-guiding strut according to the present invention.
There can be seen firstly the configuration of the wheel-guiding strut 1, which in this embodiment is fork-shaped and of which the chassis-side end 2 on the left-hand side of the drawing is equipped with two ball joints 3,4, while the wheel-side end 5 of the illustrated wheel-guiding strut 1 on the right-hand side of the drawing carries a further individual ball joint 6.
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Here, the chassis-side ball joints 3, 4 are held non-elastically in the two fork ends 2 of the wheel-guiding strut 1, while the wheel-side ball joint 6 is connected to the corresponding end 5 of the wheel-guiding strut 1 by means of an elastomeric bearing arranged therebetween. The arrangement of the elastomeric layer 7 surrounding the wheel-side ball joint 6 can already be seen from the enlarged detail views in Figs. 2 and 3 and will be described in more detail below with reference to Figs. 4 to 8.
The illustrated wheel-guiding strut 1 is a strut which is provided for use in the context of the active chassis, for example for the active roll stabilisation of a motor vehicle. For the purpose of introducing the corresponding actuating forces and actuating torques into the wheel-guiding strut 1 and thus into the wheel suspension of the wheel that is to be influenced, the wheel-guiding strut 1 shown in Fig. 1 has on the chassis side not just one suspension means but rather two ball joints 3, 4 arranged at a distance from one another. In this way, the intended forces and torques can be introduced into the wheel suspension using the distance between the two chassis-side ball joints 3, 4 as a lever arm and - thanks to the chassis-side bearing points 3, 4 which are non-elastic unlike in the prior art - can be transmitted effectively and with low losses to the wheel carrier (not shown) at the wheel-side end 5 of the wheel-guiding strut 1.
Nevertheless, in the context of the comfort bearing, thanks to the invention there is still effective vibration damping between the wheel carrier and the vehicle chassis due to the fact that the wheel-side ball joint 6 according to the invention is connected via the interposition of an elastomeric bearing 7 to the wheel-side end 5 of the wheel-guiding strut 1.
It can clearly be seen in particular in the diagram in Fig. 3 that the elastomeric bearing 7 surrounds the ball joint 6 around its entire circumference, as a result of which a complete, effective decoupling is provided with regard to microvibrations and structure-borne sound transmission between the ball joint 6 and the wheel-side end 5 of the wheel-guiding strut 1.
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Fig. 4 shows a longitudinal section through the wheel^guiding strut 1 in the region of its wheel-side end and also through the ball joint 6 provided there. Fig. 4 also shows in particular the complete decoupling between the wheel-guiding strut 1 and the ball joint 6 by means of the elastomeric bearing 7.
In the direction of the section line, which in Fig. 4 coincides with the longitudinal axis of the wheel-guiding strut - and which thus also coincides with the section line A-A in Figs. 6 and 7 - the elastomeric bearing 7 has a particularly small cross section. The elastomeric bearing 7 therefore also has a particularly soft spring characteristic in the direction of the section line shown in Figs. 4 and 7.
It can moreover be seen from Fig. 4 that the illustrated ball joint 6 has a joint housing comprising two shells. In this case, the inner shell 8 of the joint housing accommodates the plastic bearing shell 9 of the ball joint 6, and furthermore serves to fix the sealing bellows 10 and the housing cover 11. The outer shell of the joint housing 12 serves to accommodate the ball joint 6 in a corresponding cylindrical recess in the wheel-side end of the wheel-guiding strut 1. Finally, the elastomeric bearing 7 is arranged between, preferably vulcanised onto, the two shells 8,12 of the joint housing.
Figs. 5 to 8 in each case again show assembled views of the joint housing of the ball joint 6 attached elastically to the wheel-side end 5 of the wheel-guiding strut 1. The sectional views in Figs, 7 and 8 show with particular clarity the cross section of the elastomeric layer 7 arranged between the outer 12 and inner joint housing shell 8, which cross section differs in size depending on the direction of section and is responsible for the accordingly different spring hardnesses in the two directions A-A and B-B perpendicular to one another as shown in the section line profile in Fig. 6.
The design of an axial stop 13 of the ball joint which is additionally present in this embodiment can also be seen by jointly considering Figs. 7 and 8 in particular. The axial stop 13 is formed by a substantially annular plate 13 which is pressed against
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the inner joint housing 8 of the ball joint in the region of the inner housing cover 11. The annular plate 13 has elastomer 14 injected around it and thus serves as a stop in the event of relative movements between the inner 8 and outer joint housing 12 in the direction axial to the joint housing. In this case, the axial stop 13 formed by the annular plate with elastomer injected around it butts against an annular circumferential protrusion 15 of the outer joint housing 12 in the event of relative movements of the inner joint housing 8 in the downward direction as seen in the drawing, while the axial stop 13 butts against the plate-like cover 16 of the outer joint housing 12 in the event of relative movements of the inner joint housing 8 in the upward direction as seen in the drawing.
Another advantageous function of the axial stop 13 lies in a certain additional protection of the ball joint against external influences by means of a sealing lip 17, the shape of which can be seen in particular from the sectional view in Fig. 7.
As a result, it is thus clear that the invention provides a wheel-guiding strut for use for example on the active chassis, which has critical advantages over the prior art with regard to managing the conflict of aims between a comfort bearing and the precision of wheel guidance. In particular, the wheel-guiding strut according to the invention allows the effective introduction of actuator forces and torques into the wheel-guiding strut or into the wheel suspension without inducing appreciable elastic deformations in the wheel suspension.
The invention thus makes an important contribution with regard to improving both the comfort properties of the chassis and the improved control of the driving dynamics of wheel suspensions, particularly when used on challenging axle systems and in the new field of the active chassis.
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LIST OF REFERENCES

1 wheel-guiding strut
2 chassis-side strut end
3,4 ball joint
5 wheel-side strut end
6 ball joint
7 elastomeric bearing
8 inner joint housing shell
9 bearing shell
10 sealing bellows
11 joint housing cover
12 outer joint housing shell
13 axial stop
14 overinjected elastomer
15 annular protrusion
16 plate-like cover
17 sealing lip

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CLAIM:
1. Wheel-guiding strut (1) for an axle of a motor vehicle, the wheel-guiding strut (1) having two end regions (2, 5) which in each case comprise at least one bearing arrangement (3, 4, 6, 7), wherein the bearing arrangement of at least one end region comprises an elastomeric bearing, characterised in that the wheel-side bearing arrangement (6, 7) comprises an elastomeric bearing (7).
2. Wheel-guiding strut according to claim 1, characterised in that the bearing (3, 4) at the chassis-side end region (2) of the wheel-guiding strut (1) is designed in a non-elastic manner.
3. Wheel-guiding strut according to claim 1 or 2, characterised in that the wheel-side bearing arrangement (6, 7) comprises a ball joint (6), wherein the ball joint (6) is connected to the wheel-side end (5) of the wheel-guiding strut (1) by means of an elastomeric bearing (7).
4. Wheel-guiding strut according to claim 3, characterised in that the
elastomeric bearing (7) surrounds the ball joint (6) at least in some regions as an elastomeric layer.
5. Wheel-guiding strut according to claim 3 or 4, characterised in that an
elastomeric layer (7) is arranged substantially radially between the bearing
shell (9) and the joint housing of the ball joint.
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6. Wheel-guiding strut according to claim 3 or 4, characterised in that the ball joint comprises an inner (8) and an outer joint housing (12), wherein an elastomeric layer (7) is arranged substantially radially between the inner (8) and outer (12) joint housing of the ball joint (6).
7. Wheel-guiding strut according to one of claims 4 to 6, characterised in that the elastomeric layer (7) has different-sized cross-sectional surface areas in two directions (A-A, B-B) which are perpendicular to one another and radial to the joint housing.
8. Wheel-guiding strut according to claim 6, characterised in that an axial stop (13, 14) is arranged on the inner joint housing (8) and is surrounded by the outer joint housing (12,15,16).
9. Wheel-guiding strut according to claim 8, characterised in that the axial stop (13,14) is sheathed with elastomer (14) at least in some regions.
10. Wheel-guiding strut according to claim 8 or 9, characterised in that the axial stop (13,14) is of annular shape and is pressed against the inner joint housing (8) in the region of the inner joint housing cover (11).
11. Wheel-guiding strut according to one of claims 3 to 10, characterised in that the ball joint (6) is arranged in a cutout in the wheel-side end region (5) of the wheel-guiding strut (1).
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12. Wheel-guiding strut according to one of claims 3 to 11, characterised in that the joint housing or the outer joint housing of the ball joint (6) is formed by the cutout in the wheel-side end region (5) of the wheel-guiding strut.
13. Wheel-guiding strut according to one of claims 1 to 12, characterised in that the chassis-side bearing arrangement comprises two ball joints (3, 4).
Dated this 19th day of September, 2008

HIRAL CHANDRAKANT JOSHI AGENT FOR ZF FRIEDRICHSHAFEN AG.
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