Abstract:
A wheel suspension arm comprises a link opening ( 12 ) for pivotably securing the wheel suspension arm to a vehicle frame and an axle opening ( 11 ) for securing an axle element ( 2 ) to the wheel suspension arm. A peripheral edge ( 11   a ) of the axle opening includes at least one discontinuation, such as a slot ( 13 ). A screw ( 17 ) can be tightened to clamp the axle element ( 2 ) in the axle opening ( 11 ). The invention also relates to a method for producing the inventive wheel suspension arm and to a wheel suspension comprising said wheel suspension arm.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    (1) Field of the Invention 
         [0002]    The present invention concerns a wheel suspension arm, especially a trailing arm for a vehicle, as well as a wheel suspension with such a wheel suspension arm. 
         [0003]    (2) Description of the Related Art 
         [0004]    In the prior art, according to utility model number DE 296 16 257 U1, a rigid axle consisting of an axle tube is led through a pair of boxlike trailing arms and welded to the trailing arms. In order to make possible a welding of the trailing arms to the axle tube, they must be fabricated of a material that lends itself to welding with the material of the axle tube, such as steel. Furthermore, any after treatment, such as rust prevention and painting, can only be applied after the welding. 
         [0005]    One can avoid a welding of the trailing arms to the rigid axle if the trailing arms are each clamped by a pair of U-shaped steel shackles to the rigid axle, as is shown in  FIG. 4 . This type of axle fixation is especially suitable when using leaf springs. But when using air springing, this type of fixation requires a plurality of individual parts and a relatively high cost of assembly/disassembly of the trailing arm, since each trailing arm is provided with additional positioning parts, and one has to tighten up four screws for each trailing arm. 
       SUMMARY OF THE INVENTION 
       [0006]    The present invention provides a wheel suspension arm for a vehicle, which can be fabricated cheaply and can be mounted/dismounted in simple fashion. Another aspect of the present invention is a corresponding method and a wheel suspension with such a wheel suspension arm. 
         [0007]    According to one aspect of the present invention, a wheel suspension arm is created, especially a trailing arm for a vehicle, with: a link opening for the pivoting fixation of the wheel suspension arm to a vehicle frame and an axle opening for the fixation of an axle element to the wheel suspension arm, wherein the axle opening has at its peripheral edge at least one interruption or recess, such as a slot. 
         [0008]    Since the wheel suspension arm is simply clamped onto an axle tube, it can be easily mounted and dismounted. Furthermore, a wheel suspension with such a wheel suspension arm has a minimal number of structural parts. The axle tube and the wheel suspension arm can receive a rust preventative, a coat of paint or the like prior to the mounting, since welding is no longer necessary. Since the axle opening has essentially the same diameter as the corresponding segment of the axle element, a clamping is produced which can transmit a high torque. The axle opening preferably has a transition fit. However, it is also possible to provide a clearance fit with a slight play of around 0.05 mm to 0.5 mm, or a press fit, in which the axle opening has a slightly smaller diameter than the axle element. In this case, the trailing arm can be heated for installation, so as to widen the diameter, or the wheel suspension arm can be pressed onto the axle element. Furthermore, the peripheral edge of the axle opening can be spread open at the interruption, in order to widen the diameter. 
         [0009]    Preferably, a fastening means is arranged in order to decrease the interruption or a dimension/distance of the interruption so that the wheel suspension arm can be clamped on the axle element. 
         [0010]    Furthermore, the axle opening may be generally round, with the axle opening having about the same diameter as a corresponding segment of the axle element. But the axle opening can also have other configurations, for example, if the axle element has a square cross section, an oval cross section, or other cross section configurations which are technically feasible, as long as the cross section configurations used have a largely closed cross section. In place of axle elements, it is also possible to insert steering knuckle holders outwardly, or torsion elements, such as those in the form of a transverse strut, connecting the two wheel suspension arms, of appropriate cross sectional configurations, inwardly into the axle opening of the wheel suspension arm, and then corresponding axle elements are arranged on them. It is also conceivable to divide up the functions, in which case the steering knuckle holders and the torsion element do not lie in the same axial line, but rather on axes running parallel to each other. In this case, if the distance is suitably chosen, both the torsion element and the steering knuckle holder can then be fastened in two axle openings by clamping. 
         [0011]    Advisedly, the axle opening is essentially adapted to the configuration of the corresponding axle element. 
         [0012]    The interruption may be formed by a slot, which ends in a recess formed in the wall region of the wheel suspension arm, such as in the form of a round or oval opening, or it is taken as far as the outer edge of the wheel suspension arm. In this way, the formation of stress cracks at one end of the interruption or slot is avoided. 
         [0013]    Preferably the wheel suspension arm is cast from spherulitic graphite iron GGG, gray cast iron GG, or vermicular graphite cast iron GGV, so that is can be produced in economical manner. 
         [0014]    Furthermore, a receiving element for a spring of the vehicle axle and fastening means for a shock absorber are arranged on the wheel suspension arm. 
         [0015]    Moreover, it is also preferable that at least one engaging means is arranged for a form-fitted engagement of the axle opening with an axle element, so that the axle element can be easily positioned in the trailing arm. Furthermore, the engaging means can form a fail-safe function in event of failure of the clamping and/or an indicator function to detect an undesirable twisting of the axle element. 
         [0016]    The wheel suspension arm of the invention preferably has a T-profile or an essentially open double-T profile, so that the wheel suspension arm has high torsional and bending strength. 
         [0017]    Furthermore, a method is created for the production of a wheel suspension arm for a vehicle, with the following steps: production, for example, by casting, of a wheel suspension arm with an axle opening to receive an axle element and providing of an interruption, such as in the form of a slot, at the peripheral edge of the axle opening. 
         [0018]    Advantageously, a fastening means can be provided in the region of the interruption, in order to provide an additional clamping if necessary. 
         [0019]    Preferably, at least one engaging means is configured for a form-fitting engagement of the axle opening with an axle element. 
         [0020]    Finally, a wheel suspension is created with a tube axle as an axle element and a pair of wheel suspension arms according to the invention, wherein the wheel suspension is moreover preferably provided with a clamped brake holder, so that the trailing arm or the axle tube can be dismounted from the axle tube after the clamped brake holder has first been dismounted. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS  
         [0021]      FIG. 1  is a partially fragmentary isometric view of a wheel suspension with a trailing arm  1 , and axle tube  2  and a clamped brake holder  3  according to the present invention; 
           [0022]      FIG. 2  is a side view of the trailing arm  1  with a shock absorber  4  arranged thereon; 
           [0023]      FIG. 3  is an isometric view of the trailing arm  1  with a shock absorber  4  arranged thereon; and 
           [0024]      FIG. 4  is an isometric view of a prior art wheel suspension with a pair of trailing arms and a rigid axle. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0025]    As is shown in  FIG. 1 , an axle tube  2  of a rigid axle extends through an axle opening  11  of a trailing arm  1  and a clamped brake holder  3  is arranged at one end of the axle tube  2 . Furthermore, a shock absorber  4  is arranged on the trailing arm  1  and the trailing arm  1  has a spring receptacle  15  as well as a link opening  12 . The trailing arm  1  is pivoted via the link opening  12  on a vehicle frame (not shown), for example, via a rubber-metal element. Furthermore, a spring element (not shown) is installed between a vehicle frame and the spring receptacle  15  of the trailing arm  1 . The spring element preferably comprises an air spring (not shown). The axle tube  2  likewise has a trailing arm  1  on the other side of the vehicle (not shown), so that the wheel suspension is formed by a pair of trailing arms  1  and an axle tube  2 . 
         [0026]    The trailing arm  1  is preferably made from gray cast iron, such as GG-60, spherical graphite cast iron (spherulitic cast iron GGG) or vermicular graphitic cast iron (GGV) and has a double-T profile with an opening  18 , as is best seen from  FIG. 3 . A trailing arm  1  of gray cast iron is especially cheap to produce, while a trailing arm  1  of spherical graphite cast iron GGG or vermicular graphite cast iron GGV has greater strength. 
         [0027]    The link opening  12  and the axle opening  11  can be worked further after being produced, in order to form an even better snug fit. The diameter of the axle opening  11  essentially corresponds to the diameter of the axle element or axle tube  2  on which the trailing arm  1  is seated. Furthermore, a peripheral edge  11   a  of the axle opening  11  has a recess or interruption  13 , for example, in the form of a slot, so as to make possible a clamping of the axle opening  11  on the axle element via a fastening means, such as a clamping screw  17 . In other words, a width of the interruption  13  is decreased by tightening the clamping screw  17 , thereby making possible a clamping of the trailing arm  1  on an axle element. However, other clamping devices can also be used in order to decrease the interruption, or the distance produced by the interruption in this region, to achieve a clamping. 
         [0028]    The snug fit of the axle opening  11  is preferably designed as a transition fit, i.e., the diameter of the axle opening  11  essentially corresponds to the diameter of the axle element on which the trailing arm  1  is mounted. In other words, the diameter of the axle opening  11  has both an upward tolerance (play) and a downward tolerance (pressing). Due to the transition fit, a fastening of the trailing arm  1  on the axle element is achieved, which can transmit a high torque and can prevent a shifting of the axle element in the sideways direction in reliable manner, while at the same time the production costs can be kept low, since the tolerance of the snug fit is not very narrow. Furthermore, a high yield can be achieved, since the relatively large tolerance of the snug fit reduces the number of rejects in the fabrication of the trailing arm. The tolerance should lie in the range of +/−0.05 to 0.5 mm, best of all in the range of 0.2 to 0.4 mm. 
         [0029]    For an easy installation, the trailing arm  1  can be heated and/or spread apart. 
         [0030]    For applications with lower strength requirements, the snug fit can contain a clearance fit with a play of 0.05 to 0.5 mm, in order to make possible an especially easy installation. Alternately, when particularly high requirements are placed on the strength, a press fit can be chosen. 
         [0031]    The trailing arm  1  of the invention can receive a surface treatment, such as rust prevention and painting, prior to being installed. This offers the benefit that no special rust prevention is needed during storage as a replacement part and the applying of a rust prevention and/or a coat of paint after installation on a vehicle can be dispensed with. In other words, a trailing arm  1  according to the invention is taken out of the warehouse and simply screwed onto the wheel suspension of a vehicle. Other processing steps such as applying of rust prevention and painting, as are necessary in the prior art, can be dispensed with. 
         [0032]    In order to further improve the clamping of the axle opening  11  on an axle element, the axle opening  11  can be further glued together with the axle element by means of suitable adhesive or provided with friction-increasing treatments. 
         [0033]    Furthermore, an additional engaging means such as one in the form of a projection (not shown) or a groove (not shown) can be provided at the peripheral edge  11   a  of the axle opening  11 . This engaging means allows for an easy positioning during the installation and it can also make possible a fail-safe function, i.e., if the frictional connection of the clamp fails, the axle tube is held securely by a form fitting due to this additional engaging means. Moreover, the engaging means can in addition or solely take on an indicator function in regard to an unwanted twisting of the axle element. 
         [0034]    Furthermore, the trailing arm  1  of the invention has a spring receptacle  15  at a rear end segment as well as fastening means  16 , for example, in the form of a screw opening for a shock absorber  4 . The link opening  12  is preferably braced by a plurality of ribs  19  against the body of the trailing arm  1 , in order to increase the flexural and torsional strength in a transverse direction. These ribs  19  are formed, for example, during a casting process. 
         [0035]    The invented trailing arm  1  is produced by casting from gray cast iron, spherulitic cast iron, or vermicular graphite cast iron, with all of the elements being cast on the unit. In other words, the trailing arm  1  of the invention is made as a single piece by casting and only the axle opening  11  and the link opening  12  may require further machining. 
         [0036]    Preferably, a pair of such trailing arms  1  is used for a wheel suspension, and preferably a rigid steel tube axle is pushed through the axle openings  11  of the pair of trailing arms  1  and clamped to them by the clamping screw  17 . However, it is also possible in the case of a single wheel suspension to only push one short axle element through the axle opening  11  of a single trailing arm  1 . In the case of the rigid axle, the wheel suspension can have a clamped brake holder  3 , as is best seen in  FIG. 3 , so that the trailing arm  1  can be dismounted in easy fashion by removing the link at the link opening  12 , taking off the clamped brake holder  3 , and then opening the axle opening  11  by means of the clamping screw  17  so as to pull the trailing arm  1  out from the axle tube  2 . In this way, a trailing arm  1  can be easily replaced on a vehicle. 
         [0037]    However, the trailing arm  1  can also consist of several parts which are screwed together. Although it is not depicted here, the trailing arm  1  can be divided roughly at the middle of the axle opening  11  and then be screwed together with a pair of clamping screws  17 . In order to achieve a high flexural and torsional strength of the trailing arm  1 , it has a double-T profile with a large opening  18  in a central middle segment, in order to economize on weight. The weight savings due to the large opening  18  results in a reduction in nonsuspended masses of the vehicle provided with this wheel suspension, so that the road quality can be improved. The fastening means  16  for the shock absorber  4  are preferably arranged in a cast cavity in order to reduce an installation space for a shock absorber  4  of the wheel suspension. 
         [0038]    However, the invention is not limited to the sample embodiment shown here. In particular, the following modifications of the sample embodiment are possible: 
         [0039]    1) The trailing arm can also be made from another material, such as aluminum or an aluminum alloy or another suitable light metal, for example, by casting. 
         [0040]    2) The spring receptacle  15  and the fastening means  16  for the shock absorber  4  of the vehicle axle can be arranged on the axle itself, so that these are not arranged on the trailing arm  1 . 
         [0041]    3) The trailing arm can have a profile different from the double-T profile shown here. For example, the trailing arm  1  can have a square profile or a T-profile. But any other profile is also conceivable, as long as the profile has high torsional and flexural strength. 
         [0042]    4) Although the sample embodiment shown shows a trailing arm for a pulled rigid axle, the wheel suspension arm of the invention can also be configured as a pushed trailing arm, a transverse link, tilted link, or space link. 
         [0043]    5) Although the sample embodiment shown here shows a nonlinked rigid rear axle, the wheel suspension arm of the invention can also be used for a front axle and/or a linkable axle, if the axle opening  11  encloses a corresponding axle element of such an axle. 
         [0044]    6) Although the use of a steel tube axle is proposed, other materials with suitable geometry and material characteristics can also be used, such as fiber-reinforced metals or plastics.