Abstract:
A wheel suspension for a two-track motor vehicle includes a multi-link assembly having control arms that are articulated on a vehicle body and on a wheel carrier, a rotary actuator for an active suspension control system, with a motor-gear-unit constructed to transfer torques as actuating forces to the multi-link assembly via a torsion rod, and at least one reinforcing brace independent of the multi-link assembly and disposed on a side of the vehicle body and extending below the multi-link assembly, as viewed in a vertical direction of the vehicle body. The reinforcing brace delimits downwardly in the vehicle&#39;s vertical direction a free space, in which the rotary actuator is at least partially arranged.

Description:
CROSS-REFERENCES TO RELATED APPLICATIONS 
     This application claims the priority of German Patent Application, Serial No. 10 2013 007 355.3, filed Apr. 27, 2013, pursuant to 35 U.S.C. 119(a)-(d), the content of which is incorporated herein by reference in its entirety as if fully set forth herein. 
     BACKGROUND OF THE INVENTION 
     The present invention relates to a wheel suspension for a motor vehicle, especially for a vehicle rear axle with non-steered vehicle wheels. 
     In an active suspension control, each wheel suspension of a vehicle axle, in particular a rear axle, may each have a rotary actuator. With the two rotary actuators of the vehicle axle, the vehicle level and/or pitch and roll of the vehicle of the vehicle can be compensated depending on the control. 
     It would be desirable and advantageous to obviate prior art shortcomings and to provide an improved wheel suspension for a motor vehicle, which reduces packaging problems in the vehicle axle in spite of the use of an active suspension control. 
     SUMMARY OF THE INVENTION 
     According to one aspect of the present invention, a wheel suspension for a two-track motor vehicle includes a multi-link assembly having control arms which are articulated on a vehicle body and on a wheel carrier, a rotary actuator for an active suspension control system, with a motor-gear-unit constructed to transfer torques as actuating forces to the multi-link assembly via a torsion rod, and at least one reinforcing brace independent of the multi-link assembly and disposed on a side of the vehicle body and extending below the multi-link assembly, as viewed in a vertical direction of the vehicle body, wherein the at least one reinforcing brace delimits downwardly in the vehicle&#39;s vertical direction a free space, in which the rotary actuator is at least partially arranged. 
     The invention is based on the recognition that for increasing the connection or bending rigidity of the rear section of the vehicle reinforcing braces are provided, which extend in the vehicle&#39;s vertical direction on the bottom side below the multi-link arrangement. So as not to impair the vehicle&#39;s ground clearance and to save space, the reinforcing braces are arranged in brace channels that are open toward the bottom. In other words, the reinforcing braces extend in the brace channels without impairing the vehicle&#39;s ground clearance. Advantageously, diagonal and mirror-symmetrically arranged reinforcing braces may be provided with reference to the vehicle&#39;s longitudinal center plane. These may each extend, for example, in the interior from a respective side rocker panel rearward to the spare-wheel well. 
     According to the present invention, these already provided brace channels will be used in the arrangement of the rotary actuator. The rotary actuator is at least partially disposed in a free space above the reinforcement brace. The torsion rod and/or the motor-gearbox unit of the rotary actuator may advantageously be arranged with an axial orientation, i.e. in alignment with the reinforcement brace. The existing brace channel which is open toward the bottom may be expanded to a torsion rod channel having an enlarged cross-section that provides a large enough space for placement of the torsion rod. This means that the fuel tank and/or the spare-wheel well both have at the bottom side a downwardly open torsion rod channel as free space, as well as a brace channel which optionally extends the torsion rod channel and in which the reinforcement brace extends. 
     The torsion rod may advantageously substantially extend over the entire length of the reinforcement brace. This significantly increases the effective spring length of the rotary actuator, so that a soft torsion rod can be provided with simple means. 
     Advantageously, the space-intensive motor-gearbox unit of the rotary actuator may project into another free space which is delimited by the control arms of the multi-link assembly in the vehicle longitudinal direction toward the front and/or toward the rear. 
     Advantageously, the free space for the motor-gearbox unit of the rotary actuator is delimited in the vehicle&#39;s longitudinal direction toward the front and/or toward the rear between a first control arm and a second control arm. The first and second control arms may each be the lower control arms of a five-link assembly. In such a multi-link assembly, the control arms may be arranged in a respective upper control arm plane and in a lower control arm plane. Accordingly, the free space for the motor-gearbox unit may advantageously be disposed between two control arms in the lower control arm plane. 
     The torsion rod which can be actuated by the motor-gearbox-unit may support an output lever, which is connected in an articulated manner via a tie rod on one of the control arms. In this way, the torques generated in the motor-gearbox-unit can ultimately be transferred to the vehicle wheel as linear actuating forces via the load path motor/gearbox/torsion rod/drive lever/tie rod/control arm/vehicle wheel. In the case of the above-mentioned five-link assembly, the output lever and the tie rod may engage on a control arm of the upper control arm plane and may be located below this upper control arm. 
     The free space for the motor-gearbox-unit may be delimited toward the top by at least one upper control arm, to which actuating forces are applied, for example, via the rotary actuator. As viewed in the vehicle&#39;s longitudinal direction, this upper control arm may be disposed between the first lower control arm and the second lower control arm. 
     To conserve space, the motor-gearbox-unit of the rotary actuator, at least its reduction gearbox, may advantageously be arranged coaxially with the torsion rod. The torsion rod may also, together with the motor-gearbox-unit, be aligned in the vehicle&#39;s longitudinal direction. In this case, the output lever projecting at a right angle from the torsion rod may protrude into the free space for the motor-gearbox-unit. 
     In another embodiment, the motor of the rotary actuator may not be arranged coaxially, but instead with a radial distance from the torsion rod. The motor may also drive the reducing gear that is coaxial with the torsion rod via an intermediate gearbox. In this way, the motor, in particular an electric motor, can be positioned regardless of the reducing gear, depending on the space requirements. Especially a motor that spatially separated from the reducing gear can advantageously be arranged in the above-mentioned free space of the multi-link assembly. 
     In a particularly compact design of the multi-link assembly, the tie rod can run vertically upwards and be connected with the upper arm of the multi-link assembly by an articulated joint. The articulated joint between the tie rod and the upper control arm can be arranged, in particular in the compressed state of the vehicle, in the vehicle&#39;s transverse direction outside of a vehicle&#39;s longitudinal rail with a transverse clearance. The upper control arm may extend in the vertical direction below the vehicle&#39;s longitudinal rail. To provide a vertical clearance for the vehicle&#39;s longitudinal rail, the upper control arm may be curved downwards, with arc sections converging at a lower apex point. The apex point may be spaced from the vehicle&#39;s longitudinal rail in the compressed state of the vehicle by a vertical clearance. 
     The intermediate gearbox stage may furthermore provide a larger overall gear ratio between the electric motor and to the torsion rod. The electric motors can therefore be designed to be smaller and have less weight. Advantageously, the reduction gear coaxial with the gearbox and the spaced-apart motor of the motor-gearbox-unit may each be arranged in individual housings. The intermediate gearbox may be, for example, a belt drive or a spur gear in order to produce the necessary radial offset between the motor and the torsion rod. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWING 
       Other features and advantages of the present invention will be more readily apparent upon reading the following description of currently preferred exemplified embodiments of the invention with reference to the accompanying drawing, in which: 
         FIG. 1  shows a partial view from below of the multi-link assembly of the wheel suspension according to the present invention; 
         FIG. 2  shows a partial view from above of the multi-link assembly of the wheel suspension according to the present invention; 
         FIG. 3  shows a sectional view taken along the section plane I-I of  FIG. 1 ; 
         FIG. 4  shows a partial front view of the multi-link assembly of the wheel suspension according to the present invention; and 
         FIG. 5  shows a sectional view along the section plane II-II of  FIG. 3 . 
     
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
     Throughout all the figures, same or corresponding elements may generally be indicated by same reference numerals. These depicted embodiments are to be understood as illustrative of the invention and not as limiting in any way. It should also be understood that the figures are not necessarily to scale and that the embodiments are sometimes illustrated by graphic symbols, phantom lines, diagrammatic representations and fragmentary views. In certain instances, details which are not necessary for an understanding of the present invention or which render other details difficult to perceive may have been omitted. 
     Turning now to the drawing, and in particular to  FIG. 1 , there is shown in a partial view from below a rear axle  1  for a two-track motor vehicle, which is described only to the extent necessary for an understanding of the invention. The rear axle  1  is designed mirror-symmetrically with respect to a longitudinal center plane  3  of the vehicle ( FIG. 1 ). The rear axle  1  has a subframe  5 , which is composed of longitudinal rails  7  as well as of front and rear transverse beams  9 . The subframe  5  is connected on a vehicle body shell in a conventional manner. Lower control arms  14 ,  16 ,  18 , and upper control arms  20 ,  22  for the wheel suspension are articulated in spaced offset arrangement on the longitudinal rail  7  of the subframe  5  by way of on control arm bearings (not illustrated in detail). The control arms  14  to  22  extend in the vehicle&#39;s transverse direction y outwardly to the wheel carrier  23 , which supports an unillustrated rear wheel of the motor vehicle. In the present exemplary embodiment, the rear wheel is driven by a propeller shaft  25 , which is guided to a rear-axle differential  26  suspended on the subframe  5 . A cardan shaft is connected at the rear-axle differential  26 . 
     As further shown in  FIG. 1 , a vehicle fuel tank  28  is provided before the rear axle  1 , as viewed in the vehicle&#39;s longitudinal direction x, which is abutted by an outwardly oriented side door rocker panel  30  in the vehicle&#39;s transverse direction y. The door rocker panel  30  extends rearward in the vehicle&#39;s longitudinal direction x to a wheel housing  32 , in which the unillustrated rear wheel is arranged. An end muffler  34  of an exhaust system is connected farther rearward. According to  FIG. 1 , a spare-wheel well  36  is arranged directly behind the rear axle  1  is provided at the center of the vehicle at approximately the same height. 
     To increase the rigidity of the vehicle rear carriage, a reinforcing brace  38  is provided in  FIG. 1  which is attached to attachment points  40  on the side rocker panel  30  and on the bottom side on the spare-wheel well  36 . The reinforcing brace  38  extends from the side door rocker panel  30  diagonally inwardly to the rear in the vehicle&#39;s transverse direction y. 
     As is further evident from  FIG. 1 , a rotary actuator  27  for an active suspension control is provided on the longitudinal subframe rail  7 . The rotary actuator  27  has a motor-gearbox unit  29 , which is drivingly connected with a torsion rod  31 . The torsion rod  31  is connected for force transmission with an output lever  33  which is connected via a tie rod  35  ( FIG. 4 ) in an articulated joint  37  with an upper lever  20  of the multi-link assembly  21 . 
     The lower first control arm  14  which is in front in the direction of travel FR and the lower second control arm  16  arranged behind the first control arm  14  converge in the vehicle&#39;s transverse direction y inwardly in form of a wedge, namely by forming a free space  39  ( FIG. 2 ), into which the motor-gearbox unit  29  of the rotary actuator  27  partially protrudes. According to  FIGS. 1 and 2 , a schematically shown support spring  41  and a schematically shown telescopic shock absorber  43  are each supported on the second lower control arm  16 . 
     The motor-gearbox-unit  29  has according to the Figures a reduction gear  45  arranged coaxially with the torsion rod  31  provided and an electric motor  47  which has a radial axis offset r ( FIG. 4 ) from the torsion rod  31  and which is in driving connection with the reduction gear  45  via an intermediate gearbox  49  ( FIG. 2 ). The housing of the reduction gear  45  of the rotary actuator  27  is rigidly attached in an unillustrated manner on the rigid longitudinal subframe rail  7  such that the torsion rod  31  of the rotary actuator  27  is aligned with the course of the reinforcement path  38 . The entire rotary actuator  27  is positioned below the longitudinal subframe rail  7  and below the articulated shaft  25 . Starting from the reduction gear  45 , the intermediate gear stage  49  together with the electric motor  47  thereby extends completely into the free space  39  between the two lower control arms  14 ,  16 . 
     The free space  39  between the two lower control arms  14 ,  16  is delimited in the vertical direction z toward the top by the upper control arm  20  of the multi-link assembly  21 . The two upper control arms  20 ,  22  of the multi-link assembly  21  are each arranged in an upper control arm level, whereas the three lower control arms  14 ,  16 ,  18  are positioned in a lower control arm level. The output lever  33  and the tie rod  35  are in this case approximately aligned below the upper control arm  20 , wherein the tie rod  35  is oriented substantially vertically upwards. 
       FIG. 4  shows the wheel suspension in a compressed state of the motor vehicle. Accordingly, the articulated joint  37  between the tie rod  35  and the front upper control arm  20  is arranged in the vehicle&#39;s lateral direction y outside the vehicle&#39;s longitudinal rail  51  by a transverse clearance Δy. The control arm  20  extending below the vehicle&#39;s longitudinal rail  51  is curved downward in approximately a V-shape so as to provide a large enough vertical clearance Δz. The V-shaped curvature has according to  FIG. 4  two arc portions  53 ,  55  converging at a lower apex point S. The lower apex point S of the control arm  20  is hereby spaced apart by the aforementioned vertical clearance Δz from the bottom side of the vehicle&#39;s longitudinal rail  51 . 
     As is evident from the Figures, the rotary actuator  27  is aligned with its torsion rod  31  with the reinforcement brace  38 . The torsion rod  31  together with the motor-gear-unit  29  extend along in the vehicle&#39;s vertical direction z above the reinforcement brace  38 , which extends according to  FIGS. 3 and 5  in a brace channel  57  which is formed in both in the fuel tank  28  and in the spare-wheel well  36  and which is open downwardly on the bottom side. The braces channel  57  forms a free space in which the reinforcing brace  38  is largely arranged so that a ground clearance  59  of the vehicle is not impaired. According to  FIGS. 3 and 5 , the brace channel  57  is expanded in the region of the torsion rod  31  to a likewise downwardly open torsion rod channel  61 . The cross section of the torsion rod channel  61  is designed so that the torsion rod  31  is completely disposed therein. 
     While the invention has been illustrated and described in connection with currently preferred embodiments shown and described in detail, it is not intended to be limited to the details shown since various modifications and structural changes may be made without departing in any way from the spirit and scope of the present invention. The embodiments were chosen and described in order to explain the principles of the invention and practical application to thereby enable a person skilled in the art to best utilize the invention and various embodiments with various modifications as are suited to the particular use contemplated.