Abstract:
A method for forming a stabilizer bar includes providing a metal bar having first and second ends, and die casting first and second receptacles over the respective first and second ends.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     The present invention relates generally to a vehicle suspension system and, more particularly, to a stabilizer bar for dampening the roll of a vehicle.  
         [0002]     Vehicles are commonly equipped with suspension systems having a stabilizer bar that increases roll rigidity and improves steering stability of the vehicle. Typically, the stabilizer bar is a rod-shaped member that extends laterally across the vehicle. The stabilizer bar includes a central section and an arm segment that extends longitudinally at each end of the central section. An end link couples the end of each arm segment to a control arm of the suspension system.  
         [0003]     Typically, a connection feature is used to secure the arm segments to the end links. One type of connection feature includes a ball stud and socket that are commonly manufactured as separate units from the stabilizer bar. The ball stud is secured with a fastener, such as a bolt, through an eye of a mounting portion of the arm segment. The socket is secured to a portion of the end link and receives the ball stud to secure the arm segment to the end link.  
         [0004]     There are several disadvantages with such an arrangement. For one, the fasteners can interfere with movement of the end link. Further, the mounting portions and eyes of the arm segments are typically formed in a forging process and secondarily forged or machined to meet dimensional requirements. The secondary forming process adds complexity and expense to the manufacturing process. Additionally, because the ball studs are typically manufactured independently and are fastened to the stabilizer bar, multiple machine operations are necessary and substantial weight is added to the suspension system.  
         [0005]     Accordingly, there is a need for a simplified stabilizer bar that can be manufactured economically. This invention addresses those needs and provides enhanced capabilities while avoiding the shortcomings and drawbacks of the prior art.  
       SUMMARY OF THE INVENTION  
       [0006]     One example method for forming a stabilizer bar includes the steps of providing a metal bar having first and second ends, and die casting first and second receptacles over the respective first and second ends.  
         [0007]     One example stabilizer bar for use in a vehicle suspension system includes a metal bar having first and second ends, and first and second die cast receptacles that are respectively formed over the first and second ends. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0008]     The various features and advantages of this invention will become apparent to those skilled in the art from the following detailed description of the currently preferred embodiment. The drawings that accompany the detailed description can be briefly described as follows.  
         [0009]      FIG. 1  illustrates an example vehicle suspension system.  
         [0010]      FIG. 2  illustrates one example method for manufacturing a stabilizer bar within the vehicle suspension system.  
         [0011]      FIG. 3  illustrates an example cross-sectional shape of a stabilizer bar.  
         [0012]      FIG. 4  illustrates an example stabilizer bar with a roughened surface to promote bonding with a receptacle.  
         [0013]      FIG. 5  illustrates one example receptacle having an opening for securing a link.  
         [0014]      FIG. 6  illustrates the receptacle of  FIG. 5  assembled with a ball stud.  
         [0015]      FIG. 7  illustrates an example receptacle in the shape of a ball.  
         [0016]      FIG. 8  illustrates an example receptacle in the shape of a socket. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0017]      FIG. 1  illustrates selected portions of an example vehicle suspension system  10 . In this example, a double transverse link suspension system is illustrated wherein two vehicle wheels  12  are each articulatably connected to a vehicle chassis (schematically illustrated at  14 ) by transverse links  16 . A stabilizer bar  18  is supported at a mounting bracket  20  by the vehicle chassis  14  in a conventional manner. The stabilizer bar  18  includes two arms  22  extending in a generally longitudinal direction relative to the vehicle. The arms  22  are articulatably joined to lower transverse links  16  on each side by an end link  24 . In this example, the stabilizer bar  18  includes a metal bar  26 . A receptacle  28  is die cast onto each end of the metal bar  26  for connection with the end link  24 . In this example, the receptacle  28  and arm  22  are integrally die cast onto the metal bar  26 .  
         [0018]     Referring to  FIG. 2 , the stabilizer bar  18  of this example is manufactured in several steps. The metal bar  26  is provided at step  38 , such as by hot forming in a known manner. Optionally, a bond promotion step  40  is performed to promote bonding between the die cast receptacle  28  and the metal bar  26 . In one example, the ends of the metal bar  26  are formed with an elliptical cross-section ( FIG. 3 ) during hot forming of the metal bar  26 . The elliptical cross-section provides the advantage of rotationally locking the metal bar  26  relative to the receptacles  28 . Alternatively, or in addition to forming the elliptical shape, the ends of the metal bar  26  are roughened to form a rough surface  44  ( FIG. 4 ). Shot-peening, abrasion, or other known methods may be used to produce the roughened surface  44 . The rough surface  44  provides mechanical interlocking between the metal bar  26  and the receptacles  28 .  
         [0019]     Referring again to  FIG. 2 , the receptacles  28  are die cast over the ends of the metal bar  26  in a die casting step  42 . Die casting the receptacles  28  provides the benefit of achieving relatively tight dimensional tolerances for the receptacles  28  without having to conduct secondary forming processes, such as forging, grinding, etc.  
         [0020]     In one example, the metal bar  26  is manufactured from spring steel and the receptacle  28  is also made of steel, but not necessarily spring steel. In one example, using similar materials for the metal bar  26  and the receptacle  28  promotes bonding therebetween because the similar materials form a strong bond. However, in another example, the receptacles  28  and metal bar  26  are made of dissimilar metals. In one example, the receptacles  28  are made of a non-ferrous metal, such as a zinc alloy, an aluminum alloy, or other non-ferrous material. These materials provide the advantage of lighter weight compared to steel.  
         [0021]      FIG. 5  illustrates one example receptacle  28  that has been die cast over the ends of the metal bar  26 . In this example, the receptacle  28  includes a base section  46   a  die cast directly over the end of the metal bar  26 , and a flat end section  46   b  that extends from the base section  46   a . The end section  46   b  includes an opening  48  that extends between two surfaces  50   a  and  50   b.    
         [0022]      FIG. 6  illustrates a modified version of the receptacle  28  shown in  FIG. 5 , in an assembled arrangement. In this example, a fastener  52  extends through the opening  48  to secure a ball stud  54  to the receptacle  28 . The fastener  52  is secured to the receptacle  28  with a nut  56  and a pair of washers  58 .  
         [0023]     In the illustrated example, the end section  46   b  forms an angle α with the base section  46   a . The angle α, other desired angles, curvatures or the like, can be pre-designed into the receptacle  28 . This allows bends or curves near the ends of the metal bar  26  to be eliminated, thereby eliminating additional steps and expense in forming the metal bar  26 .  
         [0024]     In the illustrated example, die casting the receptacle  28  over the ends of the metal bar  26  provides the benefit of forming the surfaces  50   a  and  50   b  parallel to each other within a desired tolerance. Parallel surfaces  50   a  and  50   b  allow uniform distribution of the stress exerted on the receptacle  28  from tightening of the nut  56  and washers  58  on the fastener  52 . Prior assemblies having receptacles that are, for example, formed by forging are unable to achieve the degree of tolerance that is possible with die casting without utilizing a secondary forming process. Thus, the die cast receptacle  28  provides flatter surfaces  50   a  and  50   b  for enhanced stress distribution without the need for a secondary forming process.  
         [0025]     The metal bar  26  in the illustrated embodiment is hollow such that a passage  60  extends through the metal bar  26 . Before the die casting step  42 , a plug  62  is inserted within the passage  60  at each end of the metal bar  26  to prevent molten die cast material from flowing through the passage  60  during formation of the receptacles  28 . The plug  62  also provides the benefit of sealing the metal bar  26  (in addition to the receptacles  28 ) to prevent environmental elements, such as road water, from infiltrating the passage  60  and corroding the metal bar  26  from the inside.  
         [0026]      FIG. 7  illustrates an example receptacle  28  in the shape of a ball. The ball has been die cast over the end of the metal bar  26  similar to as described above. In this example, the ball is received into a socket  72  that is part of the end link  24  for securing the stabilizer bar  18  to the lower transverse link  16 .  
         [0027]      FIG. 8  illustrates an example die cast receptacle  28  wherein the end section  46   b  includes a socket  74  that extends from the base section  46   a . In this example, the socket  74  receives a ball  76 , which is part of the end link  24 , to secure the stabilizer bar  18  to the lower transverse link  16 .  
         [0028]     The disclosed examples illustrate receptacles  28  that are die cast over the ends of the metal bar  26 . Die casting the receptacles  28  provides the benefit of achieving dimensional tolerances that are difficult or impossible to achieve with previously used methods, such as forging. Thus, with die casting, secondary machining operations may be eliminated in many cases. Furthermore, die casting provides a stabilizer bar  18  having integral receptacles  28 . This eliminates the need for fasteners or the like in some examples, which reduces cost and the number of parts in the assembly.  
         [0029]     Although a preferred embodiment of this invention has been disclosed, a worker of ordinary skill in this art would recognize that certain modifications would come within the scope of this invention. For that reason, the following claims should be studied to determine the true scope and content of this invention.