Patent Publication Number: US-2013234499-A1

Title: Torsion beam axle having ring member friction-welded to trailing arm

Description:
TECHNICAL FIELD 
     The present invention relates to a torsion beam axle, and more particularly to a torsion beam axle having a ring member which is provided between a torsion beam and a trailing arm to be friction-welded to the trailing arm. 
     BACKGROUND ART 
     A torsion beam axle (refer to  10  in  FIG. 1 ) is a suspension system for supporting vehicle wheels to a chassis and comprises a plurality of trailing arms (refer to  11  in  FIG. 1 ) each of which is coupled to a front (rear) lateral wheel and to the chassis respectively, and a torsion beam (refer to  12  in  FIG. 1 ) which is connected between the trailing arms. 
     Such a torsion beam axle realizes a torsion beam which has characteristics of twisting accordingly as there arises a twist between a left lateral wheel and a right lateral wheel. The torsion beam axle has its principal technological problems in that it has to have excellence in securing a trunk room and competitive price and in that it has to accomplish a light weight of the chassis through an optimized design of the torsion beam. 
     As for the material of the torsion beam axle, aluminum alloy casting is used for the trailing arm to enhance a supporting force of the lateral wheels and steel is used for the torsion beam to have elastic torsional deformation in order to easily absorb the torsion between the right and left lateral wheels which is generated when traveling. 
     Therefore, as the trailing arm and the torsion beam use different materials as described above, there is raised an important issue of coupling method between different materials in that a coupling strength between the trailing arm and the torsion beam has to be guaranteed in the manufacturing process enough to satisfy a predetermined load condition required to the torsion beam axle. 
     Although there were conventional cases where coupling elements such as bolt, nut and etc. were used as coupling means between such a trailing arm and a torsion beam, they have a problem of easy breakdown due to weak coupling strength. 
     Also, friction welding method may be introduced where the trailing arm and the torsion beam can be joined together through rotational surface contact therebetweeen. However, to adopt such method, not only an expensive and large-sized apparatus is required due to a comparably large-sized and heavy-weight torsion beam but also it is hard to meet the accuracy of the joining position. Therefore, the friction welding was not considered as a proper alternative method. 
     DISCLOSURE 
     Technical Problem 
     Accordingly, it is an object of the present invention to provide a torsion beam axle which can maintain an enhanced coupling force between a trailing arm and a torsion beam that are of different materials therebetween. 
     Technical Solution 
     In order to accomplish the above object, the present invention provides a torsion beam axle comprising a torsion beam whose both end parts have a cross section of a circular shape and a pair of trailing arms which are perpendicularly and integrally coupled to the both end parts of the torsion beam, wherein each of the trailing arms is formed with a circular joining surface which has at least a predetermined width in a radial direction to correspond to the end part of the torsion beam, and the torsion beam axle further comprises a ring member having in an axial direction one end surface which is correspondingly contacted to the circular joining surface and coupled thereto by friction welding to be integrally coupled to the trailing arm, and the other end surface which is correspondingly contacted to the end part of the torsion beam and welded thereto to be integrally coupled to the torsion beam. 
     According to an aspect of the present invention, the torsion beam and a pair of the trailing arm are made of different materials therebetween, and the ring member is made of a material whose weldability to the torsion beam is better than that of the trailing arm. 
     According to an aspect of the present invention, the trailing arm is made of aluminum alloy, and the torsion beam and the ring member are made of steel. 
     According to an aspect of the present invention, the ring member is made of the same material as the torsion beam. 
     Advantageous Effects 
     According to the torsion beam axle of the present invention as described above, a ring member is provided between a torsion beam and a trailing arm and integrally coupled to the trailing arm through the friction welding, then the torsion beam and the ring member can be integrally coupled together through a conventional welding. Therefore, coupling force between the trailing arm and the torsion beam can be enhanced. Also, as the friction welding method can be adopted by using a very small-sized ring member compared to the torsion beam, miniaturization of the required apparatus and high accuracy of the joining position can be accomplished. 
    
    
     
       DESCRIPTION OF DRAWINGS 
         FIG. 1  is a perspective view of a torsion beam axle according to an exemplary embodiment of the present invention; 
         FIG. 2  is a perspective view of a trailing arm which is one of the elements constituting the torsion beam axle of  FIG. 1 ; 
         FIG. 3  is a perspective view to explain a process of coupling a ring member to the trailing arm of  FIG. 2  through friction welding; 
         FIG. 4  is a perspective view of a torsion beam which is one of the elements constituting the torsion beam axle of  FIG. 1 ; and 
         FIG. 5  is a partially expanded perspective view to explain a process of coupling the torsion beam of  FIG. 4  to the trailing arm of  FIG. 3 . 
     
    
    
     BEST MODE 
     As shown in  FIG. 1 , a torsion beam axle  10  according to an exemplary embodiment of the present invention has a structure where a pair of trailing arms  11  are coupled perpendicularly and integrally to both ends of a torsion beam  12 . 
     The trailing arm  11  is formed with parts to be coupled to a chassis part and a wheel part, and coupled to a torsion beam  110  integrally through a ring member  13  (refer to  FIG. 3 ) as will be described later. 
     Different from the torsion beam  12 , it is preferable that the trailing arm  11  be made of a material of high strength in order not to be easily deformed by an outer force through the chassis or the wheels. Usually, aluminum alloy of high strength is used for the material. 
     The torsion beam  12  has a shape of a continuous tube with its center part having a cross section of ‘U’ or ‘V’ shaped curve to easily have elastic and torsional deformation. As a material of such a torsion beam  110 , steel may be used. 
     The torsion beam  12  may be manufactured by a method of pressing and deforming a hollow tube of a circular cross section by hydro-forming. 
     With such a structure of the torsion beam axle  10 , different outer forces acting from both lateral wheels can be absorbed through the torsional deformation of the torsion beam  12 , and the wheels and the chassis can be strongly supported by the trailing arms  11  at both ends. 
     In this embodiment, the trailing arms  11  are formed with a protruded circular joining surface  11   a , as shown in  FIG. 2 , at a part corresponding to both ends of the torsion beam  12 . 
     It is preferable that the circular joining surface  11   a  is formed to have at least predetermined with W in a radial direction so that an axially end surface of the ring member  13  can be contacted to the circular joining surface  11   a  and accommodated therein as shown in  FIG. 3 . 
     The ring member  13  whose axially end surface is contacted to the trailing arm  11  through the circular joining surface  11   a  is then rotated to an high speed in a state that it is pressed together with the trailing arm  11  in the axial direction, so that the ring member  13  and the trailing arm  11  are integrally coupled to each other by the friction welding therebetween (refer to a right-side drawing of  FIG. 3 ). 
     The other end surface of the ring member  13  which has been integrally coupled to the trailing arm  11  by the friction welding as described above is coupled to an end part of the torsion beam  12  (refer to  FIG. 1 ). 
     To this end, as shown in  FIG. 4 , both end parts  12   a  in a longitudinal direction of the torsion beam  12  has a cross section of a circular shape to correspond to the other end surface of the ring member  13 . 
     As shown in  FIG. 5 , the coupling between the torsion beam  12  and the trailing arm  11  can be accomplished by surface contacting the end part  12   a  of the torsion beam  12  to the axially end part of the ring member  13  and integrally coupling together by welding. 
     In this case, the welding needs not to be the friction welding but may be a conventional welding such as gas welding, arc welding and etc. in this embodiment, magnetic welding among the conventional welding methods is used. 
     Although the friction welding described above is adopted for joining between different materials, it is preferable that a conventional welding be made between materials of the same kind that can show a good weldability. 
     That is, as the torsion beam  12  is usually made of steel, it is preferable that the ring member  13  described above be made of a material whose weldability to the torsion beam  12  is better than that of the trailing arm  11 , especially steel which is the same material of the torsion beam  12 . 
     Although the torsion beam axle  10  according to the exemplary embodiment of the present invention has been disclosed, various modifications, additions and substitutions are possible, without departing from the scope and spirit of the invention. Therefore, the above embodiment must be regarded as one example provided for description of the present invention, rather than to limit the present invention.