Independent wheel suspension having a wheel carrier supported by way of a coupling rod on an individual control arm

An independent wheel suspension for front wheels of a motor vehicle, having a wheel carrier which can be swivelled for steering purposes. A lower end of the wheel carrier is disposed on a lower control arm. An upper area of the wheel carrier is supported, on the one hand, by way of a coupling rod, on this lower control arm and, on the other hand, by way of an upper control arm, on the vehicle body. Instead of the semi-trailing arm known from the prior art, the independent wheel suspension has two separate individual control arms. At least in the projection onto the road (i.e., a horizontal plane), the lines of influence of these two control arms form a triangle corresponding to a transverse link or semi-trailing arm. The theoretical steering axis is either intersected or crossed by the lines of influence. The two control arms end spatially in front of the theoretical steering axis in two separate adjacent hinge points on the wheel carrier. The independent wheel suspension minimizes the number of vehicle-body-side linking points while leaving sufficient space for a large-dimensioned wheel-side braking system.

This application claims the priority of German patent 197 56 064.4, filed 
Dec. 17, 1997, the disclosure of which is expressly incorporated by 
reference herein. 
BACKGROUND AND SUMMARY OF THE INVENTION 
The invention relates to an independent wheel suspension for front wheels 
of a motor vehicle, having a wheel carrier which can be swivelled for 
steering purposes. A lower end of the wheel carrier is disposed on a lower 
control arm. An upper area of the wheel carrier is supported, on the one 
hand, by a coupling rod, on the lower control arm and, on the other hand, 
by an upper control arm, on the vehicle body. 
From German Patent Document DE 26 42 939, a space-saving independent wheel 
suspension is known for a steerable motor vehicle wheel, in the case of 
which the wheel carrier is linked at three points to the vehicle body by 
way of a lower semi-trailing arm and an upper bar-type control arm. The 
wheel carrier is supported by way of a coupling rod on the semi-trailing 
arm. The hinge points between the wheel carrier and the two control arms 
are situated on the steering or spreading axis. This limits the space for 
the wheel-side braking device. 
An object of the present invention is to provide an independent wheel 
suspension which, while the number of linking points on the vehicle body 
side is as low as possible, leaves sufficient space for a 
large-dimensioned wheel-side braking device. 
This and other objects have been achieved by providing an independent wheel 
suspension for a motor vehicle, comprising: a steerable wheel carrier 
swivellable with respect to a theoretical steering axis; a pair of lower 
control arms coupled to a lower area of said wheel carrier at separate 
hinge points; an upper control arm coupled to an upper portion of said 
wheel carrier; and a coupling rod extending between an upper area of said 
wheel carrier and one of the lower control arms, said pair of lower 
control arms defining lines of influence which when projected onto a 
horizontal plane form a triangle, each of said lines of influence 
intersectingsaid theoretical steering axis or crossing proximate thereto, 
said lower control arms ending at a distance from said theoretical 
steering axis at said separate hinge points on said wheel carrier. 
Instead of the semi-trailing arm known from the prior art, this new 
independent wheel suspension contains two separate, for example, 
bar-shaped, control arms. At least in the projection onto the road, the 
lines of influence of these two control arms form a triangle corresponding 
to a transverse link or semi-trailing arm. The theoretical steering axis 
is either intersected or crossed by the lines of influence. The two 
control arms end spatially in front of the theoretical steering axis in 
two separate adjacent hinge points on the wheel carrier. 
In the case of this further development of the known "antisquat rear 
suspension principle" for a four-control-arm axis, the steering axis on 
the wheel can be selected freely so that a large-dimensioned braking 
device also has sufficient space in the rim area. The important 
axis-kinematic parameters, such as the steering offset, the gap radius or 
the caster offset can be selected freely despite the limited space 
conditions. By dividing the lower control arm into two individual control 
arms and the linking of the coupling rod to or close to the line of 
influence of a lower control arm, a momentary steering axis is obtained 
for the wheel which extends at least approximately through the 
intersecting point or crossing point of the lines of influence of the 
lower individual control arms. 
Since at least the lower control arms end spatially in front of the 
steering axis, a large clearance is obtained between the rim bowl of the 
steered wheel and the wheel carrier, which clearance can be utilized, for 
example, for a wheel-side braking device. 
Other objects, advantages and novel features of the present invention will 
become apparent from the following detailed description of the invention 
when considered in conjunction with the accompanying drawings.

DETAILED DESCRIPTION OF THE DRAWINGS 
FIGS. 1 to 3 are three views of an independent wheel suspension for a motor 
vehicle wheel 1 which can, for example, be driven and steered. The wheel 
1, which has a rim 3 and a tire 2, is disposed on a swivellable wheel 
carrier 40. A drive shaft stub 4 is disposed by way of a roller bearing in 
the wheel carrier 40 and, as a rule, is part of a constant-10 velocity 
slide joint which is not shown here. A wheel hub 5, which carries a brake 
disk 6 and the wheel 1, is disposed in a non-rotatable manner on the drive 
shaft stub 4. 
The wheel carrier 40, which is generally star-shaped, is shown here in a 
simplified manner as a flat five-cornered plate 41 with a molded-on 
cylindrical axle journal tube 42. The corners of the plate 41 are the 
hinge points (21-24, U). 
The wheel carrier 40 is linked to the vehicle body via four control arms 
11-13, 16 at the linking points (D.sub.1 -D.sub.3) The linking point for 
the fourth control arm--the tie rod section 16--is not shown. 
The two lower control arms 11 and 12, which end on the wheel carrier 40 in 
the hinge points 21 and 22, are situated, for example, in a plane which is 
parallel to the road. In this case, the lines of influence 31 and 32 of 
the control arms 11, 12 form the legs of a triangle 9 whose wheel-side 
point (i.e., vertex defined by projections of control arms 11, 12) is 
ideally located on or in the proximity of the momentary steering axis 35. 
The projections of the lower individual control arms 11, 12 and the 
steering axis 35 intersect in the figures at point (G), as shown in FIG. 
2. Dependent on the constructive embodiment, the lines of influence 31 and 
32 intersect the momentary steering axis 35 in the area of point (G). In 
this case, instead of intersecting, the lines of influence 31 and 32 may 
only cross one another. 
In the illustrated embodiment, the monentary steering axis 35 intersects 
the wheel contact area outside its center at point 38, as shown in FIG. 2. 
Viewed in the driving direction 10, this point is situated by the caster 
offset "n" in front of the center. In addition, it is offset by the 
negative steering offset "r.sub.L " with respect to the center. Reference 
character "a" in FIG. 1 denotes the gap radius of the steering force lever 
arm. 
A coupling rod 14 is arranged between the rearward control arm 11 and the 
wheel carrier 40 in a hinged manner. For this purpose, the coupling rod 14 
is disposed on the control arm 11 at a linking point (D.sub.4) and on the 
wheel carrier 40 at the hinge point 24. It supports the wheel carrier 40 
with respect to the control arm 12. The hinge point 24 and the linking 
point (D.sub.4), together with the hinge point 22 situated on the wheel 
carrier 40, form a triangle which is part of a plane in which, at least in 
this embodiment of FIGS. 1 to 3, the theoretical steering axis 35 is 
situated. 
Above the horizontal wheel center plane, a third control arm 13 is arranged 
between the vehicle body and the wheel carrier 40. The upper control arm 
13 is supported on the vehicle body side at the linking point (D.sub.3). 
On the wheel carrier 40, the upper control arm 13 is disposed at the hinge 
point 23. For supporting the positive and negative acceleration forces, 
the linking point (D.sub.3) is offset with respect to the hinge point 23 
toward the front (i.e., toward the vehicle front). 
The line of influence 33 of the, for example, approximately horizontally 
aligned control arm 13 intersects or crosses the theoretical steering axis 
35 in the area of point (E). In FIGS. 1 to 5, the control arm 13 spatially 
ends in front of point (E). However, since sufficient space is available 
here, the wheel suspension may also be constructed such that the control 
arm 13 ends on the steering axis 35. Irrespective thereof, the line of 
influence 33 intersects the plane established by the points or the hinge 
points or linking points 22, 24 and (D.sub.4). Optionally, the 
intersection point, as for example, point (E) in FIG. 2, is situated on 
the theoretical steering axis 35. 
The hinge point (U) is arranged on the wheel carrier 40, for example, in 
the area in front of the wheel center line 37. The hinge point (U) 
represents the end of the steering arm which is integrated here in the 
plate 41. For example, an axially parallel tie rod section 16 is disposed 
at hinge point (U) in a hinged manner. 
FIGS. 4 and 5 illustrate an independent wheel suspension, in the case of 
which the lines of influence 31 and 32 of the lower control arms 11 and 12 
are situated in different, mutually intersecting planes. As shown in FIG. 
4, the forward control arm 11 is situated higher than the rearward control 
arm 12 and is sloped downward toward the wheel. Its line of influence 31 
intersects the theoretical steering axis 35 at point (G'). 
The planes, in which the lines of influence 31 and 32 are situated, may 
optionally also be aligned in parallel. 
FIG. 6 illustrates an independent wheel suspension in the case of which the 
line of influence 33 of the upper control arm 13 and the line of influence 
34 of the coupling rod 14 intersect the steering axis 35 in different 
points (E) and (E'). Here, point (E') is situated below point (E). 
The independent wheel suspension is supported on the vehicle body with a 
conventional vehicle spring, and a known shock absorber or a spring strut, 
not shown. The support of the spring and the shock absorber or the spring 
strut on the independent wheel suspension takes place, for example, on the 
forward lower control arm 11. In an independent wheel suspension with a 
driven vehicle wheel, the linking points on the control arm 11 are 
selected such that the driving drive shaft has the required moving space. 
Optionally, an intermediate element is arranged between the control arm 
and the spring elements and/or shock absorber elements, which intermediate 
element the moving space of the drive shaft is bypassed. 
The foregoing disclosure has been set forth merely to illustrate the 
invention and is not intended to be limiting. Since modifications of the 
disclosed embodiments incorporating the spirit and substance of the 
invention may occur to persons skilled in the art, the invention should be 
construed to include everything within the scope of the appended claims 
and equivalents thereof.