Abstract:
A rear suspension having an axle with a generally U-shaped or V-shaped twist beam is provided. The twist beam on its extreme ends is penetrated by the corresponding control arms. The control arms of the present invention penetrate through apertures provided into the twist beam. The first and second walls of the twist beam are brought toward one another to allow the control arm to penetrate through the respective first and second apertures provided in the walls of the twist beam. After insertion through the walls of the twist axle, the twist axle is allowed to angularly expand again to its free state wherein it locks the twist beam to the control arm. A slight weld may be added to further ensure the connection of the control arm to the twist beam.

Description:
FIELD OF THE INVENTION 
     The present invention is in the field of axle assemblies for rear suspensions of front wheel drive motor vehicles. More particularly, the invention relates to an inventive connection of a rear suspension axle assembly twist beam to a control arm and a method of manufacture thereof. 
     BACKGROUND OF THE INVENTION 
     One type of axle assembly commonly used in the rear suspension of front wheel drive vehicles is commonly referred to as a trailing twist axle or simply a twist axle. Twist axles are mounted to the underside of a vehicle at a pair of bushings. The bushings are typically disposed at extreme ends of an axle arm. The axle arms are also commonly referred to as the control arms. The control arms typically extend rearward from the bushings. The bushings define an axle pivot axis about which the rear axle assembly pivots after being mounted to the vehicle. A transverse beam connects the two parallel spaced control arms. 
     The transverse beam is commonly referred to as a twist beam. The twist beam is resistant to bending but resilient relative to torsional stress. Many twist beams are profiled in the shape of an inverted U having first and second sides. The inverted U design raises the torsional deflection axis of the twist beam relative to a closed tube. 
     The control arms along their rearward ends typically have connected thereto a spring seat. The spring seat is provided on the control arm to support a suspension coil spring which is disposed between the vehicle body and the control arm. A shock absorber having one end attached to the control arm and a second end attached to the vehicle body is usually mounted near the coil spring. Depending upon the structure of the control arms, a transversely oriented track bar may or may not be placed between the control arm and the vehicle body to laterally stabilize the axle assembly. Depending on the desired torsional stiffness of the axle assembly, the axle assembly may or may not have a transversely extending stabilizer bar disposed within or in close proximity to the twist beam. 
     Each control arm has connected thereto a spindle mounting plate. The spindle mounting plate can be part of the spring seat or can be optionally located elsewhere, separate from the spring seat. A spindle assembly is mounted to each of the spindle mounting plates. Each spindle assembly typically includes a spindle and a unitary flange for mounting to the spindle mounting plates. The spindle is fixed relative to the spindle mounting plate. A wheel bearing is disposed over the spindle. A rotating brake element such as a brake drum or brake disk turns on a wheel bearing mounted on the spindle by way of the wheel bearing. A wheel is mounted to the rotative brake elements for unitary rotation therewith. 
     Typically the control arms are welded to the extreme ends of the twist beam. The weld between the twist beam and the control arm is one of, if not the, most critical welds of the axle assembly. Typically, each end of the twist beam is stamped to mate around a respective control arm on the end board surface of the control arm only. The above noted construction requires a constant fit-up and nearly perfect weld. Any weld deficiencies or fit-up gap variation can dramatically impact the fatigue life of the axle assembly. In addition, if the twist beam/control arm weld should fail, the control arm may separate from the twist beam. It is desired to provide a rear axle assembly having a twist beam and control arm connection which lowers the cost of fabrication and achieves a high strength reliable joint between the twist beam and control arm. It is further desirable to provide a method of connecting the twist beam to the control arm wherein the control arm is retained to the twist beam even if there has been a failure in a connective weld between the twist beam and control arm. It is also a desire to provide a twist beam control arm connection which is more forgiving in fit-up variation. 
     SUMMARY OF THE INVENTION 
     To satisfy the above-noted and other desires, the revelation of the present invention is brought forth. In a preferred embodiment the present invention provides a rear suspension having an axle with a generally U-shaped or V-shaped twist beam. The twist beam on its extreme ends is penetrated by the corresponding control arms. The control arms of the present invention penetrate through apertures provided into the twist beam. The first and second walls of the twist beam are brought toward one another to allow the control arm to penetrate through the respective first and second apertures provided in the walls of the twist beam. After insertion through the walls of the twist axle, the twist axle is allowed to angularly expand again to its free state wherein it locks the twist beam to the control arm. A slight weld may be added to further ensure the connection of the control arm to the twist beam. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a perspective view of a preferred embodiment rear axle assembly according to the present invention. 
     FIG. 2 is an enlargement of a portion of the rear axle assembly shown in FIG. 1 illustrating the connection of a control arm with a twist beam. 
     FIG. 3 is a side elevational view of the portion of the rear axle assembly shown on FIGS. 1 and 2. 
     FIG. 4 is a front sectional view illustrating the connection between the control arm and the twist beam as shown in FIGS. 1 through 3 in the direction of arrow  4  in FIG.  3 . 
     FIG. 5 is an alternate preferred embodiment axle assembly with a view similar to that of FIG. 4 illustrating a control arm which has a non-constant radius tubular member. 
     FIG. 6 is a view similar to that of FIG. 4, illustrating an alternate preferred method of ensuring connection between the twist beam and the control arm. 
     FIG. 7 is a side elevational view of the twist beam control arm connection shown in FIG. 6 with the twist axle. 
     FIG. 8 is a view similar to that of FIG. 4, illustrating an alternate preferred embodiment control arm of a vertical plate control arm. 
     FIG. 9 is a side view of the axle assembly shown in FIG.  8 . 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     FIG. 1 illustrates a twist axle assembly  10 . The axle assembly  10  is mounted to the underbody of a vehicle body (not shown) at a pair of pivot points defined by bushings (not shown). The bushings are typically disposed at a forward or leading end  11  of control arms  12  in tubular bushing sleeves  14 . The control arms  12  typically extend rearward from the bushing sleeves  14 . The control arms  12  extend generally parallel to the longitudinal axis of the vehicle and are parallel spaced from one another. The bushings define an axle assembly pivot axis  13  about which the axle assembly pivots after being mounted in the vehicle body. A transverse twist beam  20  connects the control arms  12 . The twist beam  20  extends generally parallel to axis  13  and transverse to the longitudinal axis of the vehicle. A spring seat  15  is commonly provided on a rearward end  16  of control arm  12  support a suspension coil spring (not shown) disposed between the vehicle body and the spring seat  15 . A spring mount  17  laterally stabilizes the coil spring. A shock absorber (not shown) has one end attached to the control arms  12  and a second end attached to the vehicle body. Depending on the structure of the control arms  12 , a transversely oriented track bar may or may not be placed between the axle assembly and the vehicle body to laterally stabilize the axle assembly  10 . Depending on the desired torsional stiffness of the axle assembly  10 , the axle assembly  10  may or may not have a transversely extending stabilizer bar disposed within or in close proximity to the twist beam  20 . The stabilizer bar, if employed, can be of a desired torsional stiffness established by vehicle design criteria. 
     Each side of the axle  10  has a spindle mounting plate  18 . Although the spindle mounting plates  18  are shown in the accompanying figures as forming part of the spring seats  15 , they can be located elsewhere, such as at the ends of a transverse beam, separate from the spring seats. A spindle assembly (not shown), which includes a spindle, a spindle axis and a wheel bearing, is mounted to each of the spindle plates  18 . A rotative brake element (not shown), such as a brake drum or brake disc, is in turn rotatably mounted to the spindle through the wheel bearing. A wheel (not shown) is also mounted to the rotative brake element for rotation about the spindle. Because the wheels are mounted, albeit indirectly, to the spindle plates  18 , the spindle plates  18  must be made at the desired alignment angles for the vehicle rear suspension. Also, features on the spindle plates  18  which locate the spindle assemblies thereon must be aligned so that, when mounted, the spindles are axially aligned with each other. The location of the axis of alignment between the spindles is virtually parallel to the pivot axis  13  of the axle assembly as defined by the sleeves  14  of the bushings, so as to aid in ensuring wheel alignment. The axle assembly  10  has V-shaped notches  20 , or more simply put, V notches in a lower side which are beneficial in achieving a desired axle assembly to vehicle body alignment. 
     Referring additionally to FIGS. 2 and 3, the twist beam  20  is generally shaped as an inverted V, having a first or front wall  22  and a second or rear wall  24 . Adjacent its extreme ends  26 , the twist beam first wall has an aperture  28  which extends therethrough. Generally aligned with the aperture  28  is an aperture  32  which extends through the second wall  24  of the twist beam. The twist beam  20  is made from 980 HSLA 9 mm gauge or similar sheet steel which has been stamped or pressed to assume its inverted V-shape. A series of apertures  21  in the twist beam  20  are provided to decrease the weight of the axle  10  assembly while maintaining very high bending strength characteristics in the twist beam  20 . An angle between the first and second walls  22  and  24  is typically in the neighborhood of 45 to 90 degrees. 
     Referring additionally to FIG. 4, the control arm  12  which is inserted into apertures  28  and  32  is a constant radius tubular member typically having a wall thickness of ⅜ inch made from 950 HSLA or similar steel. A typical outside radius will be 3 inches diameter. To assemble the control arm  12  to the twist beam, the first and second walls  22  and  24  of the twist beam are folded or urged toward each other to a more nearly parallel position as shown in phantom in FIG.  3 . The control arm  12  is then passed through the apertures  28  and  32  of the first and second walls  22  and  24 , respectively, of the twist beam  20 . Apertures  28  and  30  are approximately equal in width to the control arms  12 . However, with the V-shaped twist beam  20 , apertures  28  and  30  must be more elongated in height H than the control arms  12  are high, as walls  22  and  24  are not at right angles with control arms  12 . It should be appreciated that the values of height H for walls  22  and  24  are the same only if both walls  22  and  24  are at the same angle to control arms  12 . By making the height H slightly smaller than that needed to accommodate control arms  12  when walls  22  and  24  are in their undeflected condition, walls  22  and  24  lockingly engage control arms  12  when walls  22  and  24  are released from the positions shown in phantom in FIG.  3 . Walls  22  and  24  engage control arms  12 , preventing them from completely returning to their undeflected positions. The locking effect can be supplemented by providing bulges in the control arms  12  fore and aft of the walls  22  and  24 , or alternatively necking down control arms  12  proximate to where arms  12  are engaged by walls  22  and  24 . As will be obvious to those skilled in the art, this procedure must occur before the bushing sleeve  14  is welded to the control arm  12 . After the aforementioned insertion of the control arm  12  into the apertures  28 ,  32  in the twist beam  20 , the twist beam  20  is released allowing the walls  22  and  24  to radially extend outward from one another causing the control arm to be mechanically locked to the twist beam. Partial weld seams  40  and  42  weldably connect the control arm  12  to the twist beam  20  to ensure connection and to prevent any possible rattling between the parts. 
     Referring to FIG. 5, an alternate preferred embodiment connective arrangement of the present invention is brought forth. The control arm  112  of FIG. 5 has a semi-oval or non-constant radius cross-sectional shape. The control arm  112  shape is connected with the twist beam  20  through corresponding shaped apertures through walls  22  and  24 . An additional advantage of the control arm  112  shape is that the control arm  112  is further restrained from any torsional movement with respect to the twist beam  20 . Although a semi-oval shape is illustrated in FIG. 5, it will be apparent to those skilled in the art that other non-constant radius shapes can also be utilized to take advantage of this aspect of added torsional rigidity of the control arm. 
     FIGS. 6 and 7 illustrate an alternate preferred embodiment of the present invention wherein a weld bead  202  is added to both sides of a control arm  212 . In one embodiment, the weld bead is added after the control arm  212  is inserted within the apertures  28  and  32  provided in the twist beam  20 . In another embodiment, slots or notches in wall  20  or  24  of twist beam  20  receive beads  202 , enabling arm  112  to be received by aperture  28  or  32 . Once beads  202  have been received, the control arms  212  are rotatively indexed so that beads  202  are no longer in alignment with the notches. Weld bead  202  prevents any axial slippage of the control arm within the twist beam by contact with its extreme ends  204  and  206  with the first  22  or second  24  wall of the twist beam. It should be appreciated that this arrangement would be most effective if the walls  22  and  24  are parallel, as with a U-shaped twist beam instead of the V-shaped twist beam  212 . 
     FIGS. 8 and 9 illustrate yet another alternate preferred embodiment connective arrangement of the present invention. In the embodiment of the present invention shown in FIGS. 8 and 9, the control arm  312  is a blade type control arm, and is fabricated from a generally flat plate of steel which is generally oriented in a vertical plane in the twist beam  20 . A fillet weld  314  is utilized to connect the control arm  312  to the twist beam  20 , after the control arm  312  has been inserted through matching apertures or slots in the first and second walls of the twist beam. 
     Yet alternatively, the twist beam  20  is provided with axially extending peripheral lips surrounding apertures  28  and  32 . The lips are crimped around the control arms  12  to fix the parts together. 
     As will be apparent to all those skilled in the art, the failures of the weld mounts in any of the embodiments shown in FIGS. 1 through 9 will still cause the control arms  12 ,  112 ,  212 , or  312  to be captured with the twist beam  20 . 
     Although preferred embodiments of this invention have been disclosed, it should be understood that a worker of ordinary skill in the art would recognize certain modifications which would come within the scope of this invention. For that reason, the following claims should be studied in order to determine the true scope and content of this invention.