Abstract:
A vehicle suspension wheel strut, includes a first bushing; a wheel carrier journaled onto the first bushing; a first bracket at a first end of the first bushing; a second bracket at a second end of the first bushing; and identical damping elements positioned between the first bracket and wheel carrier at the first end of the first bushing and the second bracket and the wheel carrier at the second end of the first bushing.

Description:
CROSS-REFERENCE TO RELATED APPLICATION(S) 
     This application claims priority to German Patent Application No. DE 102012200001.1 titled “Rubber metal bearing for motor vehicle suspension, trapezoidal strut and wheel suspension” filed Jan. 2, 2012, which is hereby incorporated by reference in its entirety. 
     TECHNICAL FIELD 
     The present disclosure relates to rubber metal bearings for a wheel suspension of a motor vehicle. 
     BACKGROUND 
     Rubber metal bearings come in many different forms and are used in different technical fields when a first component is pivotably fastened to a second component and, at the same time, the transmission of loads or noise caused thereby is to be avoided. Rubber metal bearings can be used as guide joints on axle suspensions and wheel suspensions of motor vehicles. Rubber metal bearings are generally required to carry out the pivoting movements of the wheel guiding members and to absorb the vibrations produced on the axle suspension and/or wheel suspension. 
     Rubber metal bearings can be used in steering applications as well. For example, in order to counteract a tendency to over steer, it is known to use rubber metal bearings of variable flexibility for the linkage on the vehicle body side. 
     It is still desirable, however, to have a rubber metal bearing which is suitable for use as a connecting joint between wheel guiding struts of a wheel suspension, in particular an independent wheel suspension, of the unarticulated wheels of a motor vehicle, such that the bearing permits a specific influence of toe behavior and/or individual steering behavior of the wheel articulated by the wheel suspension. 
     SUMMARY 
     The present disclosure addresses one or more of the above-mentioned issues. Other features and/or advantages will become apparent from the description which follows. 
     One advantage of the present disclosure is that it provides a rubber metal bearing which is suitable for use as a connecting joint between wheel guiding struts of a wheel suspension, in particular an independent wheel suspension, of the unarticulated wheels of a motor vehicle such that the bearing permits a specific influence of the toe behavior and/or individual steering behavior of the wheel articulated by the wheel suspension under the action of the forces acting on the wheel and/or the wheel suspension during cornering or load changes. 
     Additionally the present disclosure teaches a trapezoidal strut and a wheel suspension, in particular an independent wheel suspension, for the unarticulated wheels of a motor vehicle, which permits a desired individual steering behavior of the vehicle wheel articulated by the trapezoidal strut and/or the wheel suspension, both during cornering and load changes, in particular during braking of the motor vehicle. The trapezoidal strut and the wheel suspension are intended to achieve improved stability of the motor vehicle as well as better reaction to steering inputs and to be able to be produced more cost-effectively. 
     One exemplary embodiment of the present disclosure relates to a rubber metal bearing for a wheel suspension of a motor vehicle including: an elastic rubber body arranged between an outer bushing and an inner bushing and aligned coaxially therewith and fastened thereto. The outer bushing has a front frontal surface to which at least one front elastic rubber damping element is attached and a rear frontal surface to which at least one rear elastic rubber damping element is attached. The front and rear rubber damping elements are arranged asymmetrically with respect to one another. 
     Another exemplary embodiment of the present disclosure relates to a trapezoidal strut for a wheel suspension of a motor vehicle, having: two connecting points on a vehicle body side for connecting to a vehicle body; two connecting points on a wheel carrier side for connecting to a wheel carrier; and a rear bearing at the wheel side carrier having an elastic rubber body arranged between an outer bushing and an inner bushing and aligned coaxially therewith and fastened thereto. The outer bushing has a front frontal surface to which at least one front elastic rubber damping element is attached and a rear frontal surface to which at least one rear elastic rubber damping element is attached. The front and rear rubber damping elements are arranged asymmetrically with respect to one another. 
     Another exemplary embodiment of the present disclosure relates to an independent vehicle wheel suspension for unarticulated wheels of a motor vehicle, including: a wheel carrier articulated via a wheel guiding strut to a vehicle body; and a rubber metal bearing for attaching the wheel carrier to the wheel guiding strut. The rubber metal bearing has an elastic rubber body arranged between an outer bushing and an inner bushing and aligned coaxially therewith and fastened thereto. The outer bushing has a front frontal surface to which at least one front elastic rubber damping element is attached and a rear frontal surface to which at least one rear elastic rubber damping element is attached. The front and rear rubber damping elements are arranged asymmetrically with respect to one another. 
     Yet another exemplary embodiment of the present disclosure relates to a vehicle suspension wheel strut, having: a first bushing; a wheel carrier journaled onto the first busing; a first bracket at a first end of the first bushing; a second bracket at a second end of the first bushing; and identical damping elements positioned between the first bracket and wheel carrier at the first end of the first bushing and the second bracket and the wheel carrier at the second end of the first bushing. 
     Another exemplary embodiment of the present disclosure relates to a vehicle suspension wheel strut, having a first bushing; a wheel carrier journaled onto the first busing; a first bracket at a first end of the first bushing; a second bracket at a second end of the first bushing; and damping elements arranged as a ring, positioned between the first bracket and wheel carrier at the first end of the first bushing and the second bracket and the wheel carrier at the second end of the first bushing. 
     The invention will be explained in greater detail below by way of example with reference to the figures, in which the same reference numbers are used in the figures for identical or essentially identical elements. The above features and advantages and other features and advantages of the present teachings are readily apparent from the following detailed description of the best modes for carrying out the invention when taken in connection with the accompanying drawings. In the figures: 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is side view of a wheel guide carrier compatible with rubber metal bearings according to exemplary embodiments of the present invention. 
         FIGS. 2   a - b  are cross-sectional views of an exemplary embodiment of a rubber metal bearing. 
         FIG. 3  is a cross-sectional view of another exemplary embodiment of a rubber metal bearing. 
         FIG. 4  is a cross-sectional view of another embodiment of a rubber metal bearing. 
         FIG. 5  is a front view of a rubber damping element in the rubber metal bearing of  FIG. 4 . 
         FIG. 6  is a graphical illustration of torque path versus rotation for an exemplary rubber metal bearing in the toe-in and toe-out directions. 
     
    
    
     DETAILED DESCRIPTION 
     Referring to the drawings, wherein like characters represent examples of the same or corresponding parts throughout the several views, there are shown exemplary rubber metal bearings for a vehicle wheel guiding strut. 
     Illustrated examples of a rubber metal bearing, according to the invention, for a wheel suspension of a motor vehicle include an elastic rubber body arranged between an outer bushing and an inner bushing aligned coaxially therewith and fastened thereto (for example by being vulcanized thereto). The outer bushing has a front frontal surface to which at least one front elastic rubber damping element is attached and a rear frontal surface to which at least one rear elastic rubber damping element is attached. The front and rear rubber damping elements are arranged asymmetrically to one another. 
     According to an embodiment, in each case a plurality of front and rear rubber damping elements are arranged spaced apart from one another on the front frontal surface and on the rear frontal surface. As a result, an accurate elasticity and/or rigidity of the rubber metal bearing is specifically adapted to the desired individual steering behavior. The total elasticity and/or rigidity effective in the axial direction of the front and rear rubber damping elements can be set in a simple manner by the number of elements and the spacing thereof relative to one another. 
     A further simple possibility for setting the total elasticity and/or rigidity in the axial direction of the rubber damping elements arranged on a frontal surface is to provide the front and rear rubber damping elements with different lengths, widths and/or heights. Due to the variable heights of the rubber damping elements, for example, the spring constant of each individual rubber damping element that acts during compression as a spring can be set according to a current degree of compression. Such a path-dependent spring constant can also be advantageously achieved by the rubber damping elements having a conical profile. By the choice of suitable spacings of the rubber damping elements relative to one another and the lengths, widths and/or heights of the elements, the elasticity or rigidity acting in the axial direction can be varied both independent and dependent on the path, i.e. taking account of the actual degree of compression. 
     According to a further advantageous embodiment of the invention, the front rubber damping elements are arranged in a front peripheral portion of the front frontal surface and the rear rubber damping elements are arranged in a rear peripheral portion of the rear frontal surface. The front peripheral portion and the rear peripheral portion in each case form a maximum of half of the corresponding total frontal surface and the front peripheral portion, arranged diametrically to the rear peripheral portion. As a result, it is ensured that the rubber metal bearing, as described above, can rotate under the action of the torque by a specific angle transversely to the longitudinal axis of the bearing as, for example, the region exactly opposing the front peripheral portion (not the diametrically opposing region) of the rear frontal surface has no rubber damping elements and thus sufficient free space remains between this region of the frontal surface and a bearing bracket for a rotation of the rubber metal bearing. The rotation, however, requires a certain elastic compressibility of the rubber body in the radial direction. 
     For particularly simple and cost-effective manufacture, the front and rear rubber damping elements are configured integrally with the rubber body, according to one embodiment. Expediently, in this case the front and rear rubber damping elements are connected to the rubber body via a relatively narrow rubber web, so that, the damping elements can be folded over for easier insertion of the rubber body into the outer bushing. 
     A further advantageous embodiment of the present invention provides that the front and rear frontal surfaces are in each case of flange-like configuration and extend approximately at right-angles to the longitudinal axis of the rubber metal bearing. Thus, the front and rear frontal surfaces can be designed according to the axial forces to be received thereby when used in a wheel suspension and/or a wheel guiding strut. 
     The wheel suspension according to the present invention permits specific influence on the toe behavior and/or individual steering behavior of the wheel articulated by the wheel suspension, under the action of forces acting on the wheel and/or the wheel suspension during cornering or load changes. Also, excellent cornering stability is provided as well as better reaction to steering inputs produced via more cost-effective means. 
       FIG. 1  shows a schematic plan view of a wheel guide strut  1  according to an exemplary embodiment the invention. An installation position is illustrated by an arrow  2  in the direction of travel of a vehicle. In the exemplary embodiment shown, the wheel guide strut  1  is a torsionally rigid transverse strut and/or trapezoidal strut that has two connecting points  3  on the body side for connecting the trapezoidal strut  1  to a vehicle body or an auxiliary frame connected to the vehicle body. The connecting point  3  on the left-hand side of the body, shown in  FIG. 1 , is a front internal connecting point  3  viewed in the direction of travel  2 , whilst the right-hand connecting point  3  represents a rear internal connecting point  3 . 
     The wheel guiding and/or trapezoidal strut  1  also includes two connecting points  4  on the wheel carrier side, for connecting a wheel carrier  5 . Similar to the connecting points  3  on the body side, the connecting points  4  on the wheel carrier side can also be differentiated as a front outer connecting point  4  on the wheel carrier side viewed in the direction of travel  2  (left connecting point  4  with respect to  FIG. 1 ) and a rear outer connecting point  4  on the wheel carrier side (right connecting point  4  with respect to  FIG. 1 ). In the exemplary embodiment shown in  FIG. 1 , at least the rear connecting point  4  on the wheel carrier side comprises a rubber metal bearing  6  as described herein. A first exemplary embodiment of the rubber metal bearing  6  is described hereinafter with reference to  FIGS. 2   a - b.    
     In  FIGS. 2   a - b , two cross-sectional views of a first exemplary embodiment are shown of a rubber metal bearing  6 . The  FIG. 2   a  shows a section through the rubber metal bearing  6  along its longitudinal axis  7 , which coincides with an X-axis of the three coordinate axes.  FIG. 2   b  shows the rubber metal bearing  6  in a cross-sectional view perpendicular to the X-axis and/or longitudinal axis  7  along a cutting line A-A shown in  FIG. 2   a.    
     In the longitudinal section of the rubber metal bearing  6 , an outer bushing  8  and an inner bushing  9  are aligned coaxially therewith. Between the outer bushing  8  and the inner bushing  9  an elastic rubber body  10  is fastened, for example the rubber body  10  is vulcanized to the outer bushing  8  and the inner bushing  9 . The outer bushing  8  includes both a front frontal surface  11  as well as a rear frontal surface  12  which, as shown in  FIGS. 2   a - b , are of flange-like configuration and extend substantially approximately at right-angles to the longitudinal axis  7  of the rubber metal bearing  6 . As shown in  FIGS. 2   a - b , at least one elastic front rubber damping element  13  is attached to the front frontal surface  11  and at least one elastic rear rubber damping element  13  is also attached to the rear frontal surface  12 . The front and rear rubber damping elements  13  are arranged asymmetrically relative to one another. In the first exemplary embodiment shown, the front and rear rubber damping elements  13  are arranged diametrically to one another so that the rubber metal bearing  6  on its frontal surfaces  11  and  12  has an asymmetrical construction. 
     In  FIG. 2   b  a front peripheral portion of the front frontal surface  11  can be clearly seen, in which a plurality of elastic front rubber damping elements  13  are arranged. The front peripheral portion extends in the half of the front frontal surface  11  extending to the left from the Z-axis shown. The front peripheral portion extends approximately half of the entire frontal surface  11 . Thus, the left-hand half of the front frontal surface  11  shown forms the front peripheral portion in which the elastic front rubber damping elements  13  are arranged. The right-hand half of the front frontal surface  11  does not contain any front rubber damping elements  13 . 
     As shown in  FIG. 2   b , a total of four individual rubber damping elements  13  spaced apart from one another are arranged in the front peripheral portion of the front frontal surface  11 . The damping properties, in particular the total elasticity and/or rigidity effective in the axial direction of the front rubber damping elements  13  arranged in the front peripheral portion of the front frontal surface  11 , can be accurately set by the number of front rubber damping elements  13  and their spacing from one another. 
     The rear frontal surface  12  includes a rear peripheral portion in which the rear rubber damping elements  13  are arranged. The rear peripheral portion is arranged diametrically to the front peripheral portion. The diametric arrangement of the front peripheral portion of the front frontal surface  11  to the rear peripheral portion of the rear frontal surface  12  means that the rear frontal surface  12  has a mirror-inverted arrangement of the rubber damping elements  13  of the frontal surface  11  relative to the Z-axis. Accordingly, the rear peripheral portion of the rear frontal surface  12  in which the rubber damping elements  13  are arranged makes up approximately half of the entire rear frontal surface  12 . The rear peripheral portion is arranged in  FIG. 2   b  to the right of the Z-axis. The diametric asymmetrical arrangement is visible in  FIG. 2   a , in which a front rubber damping element  13  of the front frontal surface  11  is shown top left and a further rear rubber damping element  13  of the rear frontal surface  12  is shown bottom right. 
     As shown in  FIG. 2   a , the rubber damping elements  13  exhibits a conical profile. Due to the steepness of the profile flanks and the size of the cross-sectional surface of the individual rubber damping elements  13 , additionally the spring constant of each individual rubber damping element  13  acting as a spring during compression can be substantially set. A desired response behavior of the rubber metal bearing  6  can be set according to axial forces. It is generally the case that the more pointed the conical shape of each individual rubber damping element  13 , the lower the spring constant, in particular at the start of the compression. The lower the spring constant of the rubber damping elements  13 , the more flexibly the rubber metal bearing  6  according to the invention reacts to axial forces, i.e. the smaller the torque  14  initially produced about the Z-axis by the axial force acting, for example, in the direction of travel  2 , and the asymmetrical arrangement of the front and rear rubber damping elements  13 . 
     Also as shown in  FIG. 2   a  are a left-hand, front bearing bracket  15  viewed in the direction of travel  2 , and a right-hand, rear bearing bracket  16  viewed in the direction of travel  2  of the trapezoidal strut  1  (shown in  FIG. 1 ). By means of the bearing brackets  15 ,  16 , the rubber metal bearing  6  is retained and fastened to the trapezoidal strut  1  in a manner, for example by means of a bolt or a screw which is inserted through the inner bushing  9  and is retained by the bearing brackets  15 ,  16 . In the exemplary embodiment shown in  FIGS. 2   a - b , the front and rear rubber damping elements  13  are mounted and in an unloaded state are arranged substantially without clearance between the frontal surfaces  11 ,  12  and the corresponding bearing brackets  15  and/or  16 . As a result, an immediate response behavior of the rubber metal bearing  6  is achieved with an alteration to the direction of the vehicle, an acceleration and/or deceleration/braking procedure. 
     Now turning to  FIG. 3 , a cross-sectional view of another exemplary rubber metal bearing  17  is shown. The rubber metal bearing  17  has at least two front rubber damping elements  13 ,  18  of different heights in the axial direction of the rubber metal bearing  17  are attached to the front frontal surface  11 , and at least two rear rubber damping elements  13 ,  18  of different heights in the axial direction of the rubber metal bearing  17  attached to the rear frontal surface  12 . The front and rear rubber damping elements  13  and the front and rear rubber damping elements  18  have the same height. The rubber damping elements  13  and  18  have the same height and are arranged asymmetrically to one another on the front and rear frontal faces  11  and  12 . The front and rear rubber damping elements  18  have, in comparison with the front and rear rubber damping elements  13 , a shorter height in the axial direction of the rubber metal bearing  17 . The front and rear rubber damping elements  13  have a height such that, in the installed state of the rubber metal bearing  17 , damping elements bear substantially without clearance on the respective front and rear bearing brackets  15  and/or  16 . The front and rear rubber damping elements  18  have certain spacing from the corresponding bearing brackets  15  and/or  16 , in the installed state of the rubber metal bearing  17 . Thus, the rubber metal bearing  17  will behave in a similar manner to the rubber metal bearing  6  with the application of an axial force on the rubber metal bearing  17 , i.e. rotate in the direction denoted by  14 . 
     The variable spacing of the front and rear rubber damping elements  13 ,  18  from the bearing brackets  15  and  16  can alternatively or additionally also be produced by the bearing brackets  15  and  16 , as indicated in  FIG. 3 , having different spacings from the front and rear rubber damping elements  13  and  18 . To this end, the bearing brackets  15  and  16  in the region of the front and rear rubber damping elements  13  are accordingly closer to the rubber damping elements  13  than to the front and rear rubber damping elements  18 , from which they have certain spacing. 
     Regarding  FIG. 4 , a cross-sectional view is shown of another exemplary embodiment of a rubber metal bearing  19 . In the rubber metal bearing  19 , both the front and the rear rubber damping elements  13  are configured in each case as a rubber ring  20 . The rubber ring  20  has an asymmetrical axial rigidity. As may be seen in  FIG. 5 , in which the rubber ring  20  of the rubber metal bearing  19  of  FIG. 4  is shown in front view, the asymmetrical axial rigidity in the exemplary embodiment of  FIG. 4  is achieved by a width of the rubber ring not being constant along its periphery. As may be derived further from  FIG. 4 , the front rubber damping element  20  and the rear rubber damping element  20  of the rubber metal bearing  19  are also arranged asymmetrically with respect to one another. In  FIG. 4 , the front (left) rubber damping element  20  is arranged such that in  FIG. 4  it has a substantially greater width at the top than at the bottom. The rear (right) rubber damping element  20  has a substantially greater width at the bottom than at the top. In this manner, the rubber metal bearing  19  behaves in a similar manner to the already-described rubber metal bearings in the presence of a force acting in the axial direction on the rubber metal bearing  19 , i.e. rotation in the direction denoted by  14  will occur. 
       FIG. 6  shows a graphical representation for illustrating z torque path, depending on a rotation of an exemplary rubber metal bearing according to the present invention in the toe-in and toe-out directions. The abscissa  24  of the Cartesian coordinate system, the horizontal or x-axis, shown represents in a positive direction. I.e., in  FIG. 6  to the right, the amount of cardanic rotation of a rubber metal bearing is effective for a toe-in movement and in the negative direction (left) the amount of cardanic rotation of the rubber metal bearing is effective for a toe-out movement. The ordinate  21 , vertical or y-axis, represents the effective torque produced by the rubber metal bearing, depending on the rotation of the rubber metal bearing. As seen in  FIG. 6 , both the curve  22  for asymmetrical rigidity and the curve  23  for asymmetrical pretensioning provide less torque for toe-in than for toe-out. In other words, the rubber metal bearing is displaced more easily in the toe-in direction than the toe-out direction when an axial force is applied, which produces a torque on the rubber metal bearing. The curve  22  corresponds to a rubber metal bearing with one respective front and rear rubber damping element that in each case have an asymmetrical axial rigidity, as has been described herein, with reference to the rubber metal bearing  19  of  FIGS. 4 and 5 . The curve  23  corresponds to a rubber damping element that, in addition to the asymmetrical arrangement of the front and rear rubber damping elements, is also pretensioned in the toe-in direction. This can be achieved by the front and rear rubber damping elements  13  of the rubber metal bearing  6  and/or  17  in contact with the bearing brackets  15  and  16  in the installed state already being slightly compressed and/or pretensioned by the bearing brackets  15 ,  16 . 
     The rubber metal bearing according to the invention and disclosed herein, the trapezoidal strut and the wheel suspension are not limited to the embodiments disclosed herein but in each case also encompass further embodiments which act in the same manner. Thus the rubber body may also be bonded, pressed or positively inserted between the inner and outer bushings. Similarly, the rubber damping elements of a peripheral portion of the front and/or rear frontal surface can also have different lengths, widths and/or heights as well as different conical profiles or cross sections. 
     In an embodiment, the rubber metal bearing according to the invention is used in a trapezoidal strut having two connecting points on the vehicle body side for connecting the trapezoidal strut to a vehicle body or an auxiliary frame connected to the vehicle body and having two connecting points on the wheel carrier side for connecting a wheel carrier. The rubber metal bearing according to the invention, at least on the rear connecting point on the wheel carrier side, produces the articulated connection between the trapezoidal strut and a bearing of the wheel carrier. Such a trapezoidal strut is preferably used in an independent wheel suspension for the unarticulated wheels of a motor vehicle for connecting a wheel carrier. 
     The term “rubber metal bearing” does not constitute a limitation in the sense of the invention relative to an exclusive use of rubber as the rubber body and metal as the inner and outer bushing. On the contrary, the term “rubber” also encompasses any other rubber-like elastic material, for example dimensionally stable but elastically deformable plastics (elastomers). In a similar manner, the inner and/or outer bushing of the rubber metal bearing, as known per se, may be produced from a metal material but may also comprise any other material, for example plastics, provided the material is suitable for the function as the inner and outer bushings of the rubber metal bearing according to the invention. 
     A diametric arrangement is to be understood as an asymmetrical arrangement of the front and rear rubber damping elements, for example. Within the meaning of the present invention, “diametric” means any point of the front rubber damping element connected to a corresponding opposing point of the rear rubber damping element via a spatial diagonal. The spatial diagonal extends through the central point of the body of the rubber metal bearing. The central point of the body of the rubber metal bearing will generally correspond approximately to a center of gravity of the vehicle body. 
     The asymmetrical arrangement of the front and rear rubber damping elements provides a rubber metal bearing with an asymmetrical behavior where forces, in particular axial forces, act on the front and rear frontal surfaces, for example by a bearing bracket retaining the rubber metal bearing. In a conventional fastening of the rubber metal bearing, for example, to a wheel guiding strut, such as a transverse strut, the rubber metal bearing is retained by means of a fastening means which may be inserted through the inner bushing, e.g., with a bolt or screw. The bearing brackets generally define the mobility of the rubber metal bearing in the axial direction and can transmit axial forces to the front and/or rear frontal surface of the outer bushing via the corresponding front and/or rear rubber damping element. 
     The force acting in the axial direction and axially compressing the rubber metal bearing according to the invention in one direction thus produces a torque on the rubber metal bearing due to the asymmetrical arrangement of the front and rear rubber damping elements relative to one another, i.e. with sufficient elastic compressibility of the rubber bodies in the radial direction the torque results in a rotation of the rubber metal bearing about a spatial axis located perpendicular to the axial and/or longitudinal axis of the rubber metal bearing. This rotatability of the rubber metal bearing can be used for specific control of the toe behavior and individual steering behavior of the wheel connected to the rubber metal bearing via the wheel carrier. The asymmetrical arrangement of the front and rear rubber damping elements of the rubber metal bearing, relative to an arrangement between the wheel guiding strut and the wheel carrier, is selected such that both during cornering and load changes an adjustment of the wheel track generally takes place in the toe-in direction, in particular during braking of the motor vehicle, which generally acts in a stabilizing manner on the driving behavior of the motor vehicle. 
     Those familiar with the art to which this invention relates will recognize various alternative designs and embodiments for practicing the invention within the scope of the appended claims.