Patent Publication Number: US-2013247380-A1

Title: Ball joint assembly for vehicle and manufacturing method thereof

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application is a Divisional Application of U.S. patent application Ser. No. 12/581,315, which was filed on Oct. 19, 2009, which claims priority to Korean Patent Application No. 10-2009-0073220 filed in the Korean Intellectual Property Office on Aug. 10, 2009, the entire contents of which are incorporated herein by reference. 
    
    
     BACKGROUND OF THE INVENTION 
     (a) Field of the Invention 
     The present invention relates to a suspension for a vehicle. More particularly, the present invention relates to a cross axes ball joint (or busing ball joint) assembly mounted at arms or other components connected to the arms, and to a method of manufacturing the ball joint assembly. 
     (b) Description of the Related Art 
     Generally, a suspension absorbs vibration or impact transmitted from a road to a vehicle body. The suspension is provided with a rubber bushing or a ball joint assembly so as to connect an arm or a link to the vehicle body. 
     According to the rubber bushing, anti-vibration rubber is interposed between an inner tube and an outer tube so as to absorb the vibration or the impact. 
     In addition, the ball joint assembly is applied to a connecting portion between an upper arm and a lower arm or to a connecting portion between the lower arm and a side arm in the suspension. 
     One type of ball joint assembly is a cross axes ball joint assembly. A conventional cross axes ball joint assembly is shown in  FIG. 3 . 
     The conventional cross axes ball joint assembly includes a hollow ball stud  110  formed of a ball at a middle portion thereof, a bearing  120  roll-contacted with an outer surface of the ball of the ball stud  110 , an outer case  130  enclosing the bearing  120 , a metal seat  140  mounted at an inner surface of the outer case  130 , and a dust cover  150  fitted at both sides of the outer case  130 . 
     According to the conventional ball joint assembly, roll-contact between the outer surface of the ball of the ball stud  110  and the bearing  20  occurs. That is, since the ball stud  110  rotates to a circumferential direction of the shaft and the bearing  120  is stopped, the ball stud  110  rolls with reference to an inner surface of the bearing  120 . 
     According to the conventional ball joint assembly, the bearing  120  is press-fitted in the outer case  130 , and the seat  140  is closely contacted to one end of the bearing  120  and is press-fitted in the outer case  130 . At this time, since the conventional ball joint assembly is assembled by bending one end portion of the outer case  130  to the seat  140  (this process is called caulking), more components may be required than a conventional rubber bushing and manufacturing processes may be complex. Thus, manufacturing cost may be high and weight may be increased. 
     Since the manufacturing cost of the conventional ball joint assembly is higher than that of the rubber bushing, it is mainly applied to expensive vehicles and the rubber bushing is mainly applied to inexpensive vehicles. 
     Meanwhile, when the ball of the ball stud  110  is roll-contacted with the inner surface of the bearing  120 , the bearing  120  should be stopped such that the conventional ball joint assembly displays its target performance. Since the conventional ball joint assembly is manufactured by the caulking process as described above, the bearing  120  may tumble or rotate with the ball stud  110  when the ball stud  110  rolls. 
     In addition, the caulking processes are performed by bending one end portion of the outer case  130  toward the seat  140  with high pressure and pushing the outer case  130  and the seat  140  strongly. The outer case  130  and the seat  140  are made of a metal material, and thus can endure high pressure. On the contrary, the bearing  120  is made of synthetic resin material, and thus cannot endure high pressure. 
     Therefore, performance may be deteriorated, and the bearing  120  and the outer case  130  may be damaged according to the conventional ball joint assembly. 
     The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art. 
     SUMMARY OF THE INVENTION 
     The present invention has been made in an effort to provide a ball joint assembly for a vehicle and a method of the same having advantages of reducing manufacturing cost and enhancing performance by improving manufacturing processes of the ball joint assembly. 
     A ball joint assembly for a vehicle according to an exemplary embodiment of the present invention may include: a ball stud having a ball on a shaft; a pair of bearing members roll-contacted with the ball of the ball stud; a seat member supporting an exterior circumference of the bearing members; and an outer case enclosing the seat member, wherein the outer case, the seat member, and the bearing members are integrally formed with each other. 
     A ball joint assembly for a vehicle according to another exemplary embodiment of the present invention may include a ball stud having a ball on a shaft; a pair of bearing members roll-contacted with the ball of the ball stud; a seat member supporting an exterior circumference of the bearing members; and an outer case enclosing the seat member, wherein the outer case and the bearing members are separately provided, and the seat member is formed of a molding portion that is insert-molded between the outer case and the bearing members. 
     The outer case and the bearing members may be integrally assembled through the molding portion. 
     The outer case may be made of a metal material and may be formed of a knurling portion at an interior circumference thereof. 
     Each bearing member may be made of a synthetic resin material, and may be formed of a plurality of protrusions at the exterior circumference thereof along a circumferential direction. 
     The seat member may be made of a synthetic resin material, and may be formed of grooves corresponding to the protrusions at an interior circumference thereof. 
     The pair of bearing members may be inserted into both sides of the shaft with reference to the ball. 
     One bearing member may be provided with a coupling groove at one end facing the other bearing member, and the other bearing member may be provided with a coupling protrusion corresponding to the coupling groove at one end facing the one bearing member. 
     The one bearing member may further include a coupling clip axially protruded from the coupling protrusion, and the other bearing member may further include a receiving recess into which the coupling clip snaps. 
     The ball joint assembly for a vehicle may further include dust covers mounted at both sides of the outer case. 
     A method of manufacturing a ball joint assembly including a ball stud having a ball on a shaft, a pair of bearing members roll-contacted with the ball of the ball stud, a seat member supporting an exterior circumference of the bearing members, and an outer case enclosing the seat member, may include: mounting the pair of bearing members on the ball; setting the outer case at an exterior circumferential side of the bearing members; and forming the seat member by insert-molding, in a state in which a predetermined molding region is set between the bearing members and the outer case apart from the bearing members, a molten synthetic resin material into the predetermined molding region. 
     The method may further include mounting a dust cover at both sides of the outer case. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The drawings are included so as to explain an exemplary embodiment of the present invention, and the spirit of the present invention is not limited to the accompanying drawings. 
         FIG. 1A  to  FIG. 1D  are perspective views showing a ball joint assembly for a vehicle and manufacturing processes of the same according to an exemplary embodiment of the present invention. 
         FIG. 2  is a cross-sectional view of a ball joint assembly for a vehicle according to an exemplary embodiment of the present invention. 
         FIG. 3  is a cross-sectional view of a conventional ball joint assembly for a vehicle. 
     
    
    
     DESCRIPTION OF REFERENCE NUMERALS INDICATING PRIMARY ELEMENTS IN THE DRAWINGS   
       
     
       
         
           
               
               
               
               
             
               
                   
               
             
            
               
                 10 
                 ball stud 
                   
                   
               
               
                 11 
                 hollow shaft 
               
               
                 13 
                 ball 
               
               
                 30 
                 bearing member 
               
               
                 33 
                 protrusions 
                 35 
                 coupling groove 
               
               
                 37 
                 coupling protrusion 
                 50 
                 seat member 
               
               
                 51 
                 molding portion 
                 53 
                 groove 
               
               
                 70 
                 outer case 
                 71 
                 knurling portion 
               
               
                 90 
                 dust cover 
               
               
                   
               
            
           
         
       
     
     DETAILED DESCRIPTION OF THE EMBODIMENTS 
     The present invention will be described more fully hereinafter with reference to the accompanying drawings, in which exemplary embodiments of the invention are shown. As those skilled in the art would realize, the described embodiments may be modified in various different ways, all without departing from the spirit or scope of the present invention. 
     The present invention relates to a cross axes ball joint (or busing ball joint) assembly. 
       FIG. 1A  to  FIG. 1D  are perspective views showing a ball joint assembly for a vehicle and manufacturing processes of the same according to an exemplary embodiment of the present invention, and  FIG. 2  is a cross-sectional view of a ball joint assembly for a vehicle according to an exemplary embodiment of the present invention. 
     Referring to the accompanying drawings, a ball joint assembly  100  according to an exemplary embodiment of the present invention is applied to a suspension for a vehicle that connects an axle to a vehicle body so as to alleviate vibration or impact transmitted from a road when driving and to enhance ride comfort. 
     Such a ball joint assembly  100  is mounted at a connecting portion between an upper arm and a lower arm or between the lower arm and a side arm in the suspension. In this embodiment, the cross axes ball joint assembly for connecting the arms to the vehicle body is shown as the ball joint assembly  100 . 
     According to the exemplary embodiment of the present invention, processes for manufacturing the ball joint assembly  100  may be simplified, and fewer components may be used for manufacturing the same. Therefore, manufacturing cost and weight can be reduced. 
     For theses purposes, the ball joint assembly  100  according to an exemplary embodiment of the present invention basically includes a ball stud  10 , bearing members  30 , a seat member  50 , an outer case  70 , and dust covers  90 . 
     According to an exemplary embodiment of the present invention, the outer case  70 , the seat member  50 , and the bearing members  30  are integrally formed, different from the conventional arts. 
     Referring to  FIG. 1A  to  FIG. 1D  and  FIG. 2 , constituent elements and coupling structures of the ball joint assembly  100  according to the exemplary embodiment of the present invention will be described in detail. 
     According to the present exemplary embodiment, the ball stud  10  is a rotating shaft connected to a vehicle body by means of a mount bolt (not shown). As shown in  FIG. 1A , the ball stud  10  includes a hollow shaft  11  having a hollow space therein, and a ball  13  integrally formed with the hollow shaft  11 . 
     Here, the ball  13  formed on a middle portion of the hollow shaft  11  has a spherical shape, and thus the ball stud  10  can rotate in a circumferential direction of the hollow shaft  11  and can move axially with reference to the hollow shaft  11  by means of the ball  13 . 
     According to the present exemplary embodiment, the bearing members  30 , as shown in  FIG. 1A  and  FIG. 1B , support circumferential rotation and axial movement of the hollow shaft  11 . A pair of bearing members  30  are provided so as to be assembled or disassembled, and are mounted on an outer surface of the ball  13  so as to roll with reference to the ball  13 . If the pair of bearing members  30  are mounted on the ball  13 , the bearing members  30  enclose the ball  13 . 
     That is, the pair of bearing members  30  are inserted axially into both sides of the hollow shaft  11  with reference to the ball  13  of the ball stud  10 , and are roll-contactedly mounted on the outer surface of the ball  13 . 
     Here, each bearing member  30  is made of a synthetic resin material such as plastic, and has an annular shape, both ends of which are opened. In addition, each bearing member  30  has a spherical inner surface  31  that is roll-contacted with the outer surface of the ball  13 . 
     Further, each bearing member  30  is provided with a plurality of protrusions  33  formed at an exterior circumference thereof. The protrusions  33  are evenly protruded from the bearing members  30  along a circumferential direction thereof. 
     In this case, each bearing member  30  is roll-contacted with the ball  13  and has one end facing the other bearing member  30 . The one end of one bearing member  30  is coupled with the one end of the other bearing member  30 . 
     Accordingly, a coupling groove  35  and a coupling protrusion  37  are formed at the one end of each bearing member  30 . 
     That is, the coupling groove  35  is formed at the one bearing member  30  (the left one in the drawings) by protruding at an inner circumference of the one end thereof, and the coupling protrusion  37  is formed at an outer circumference of the one bearing member  30  by forming the coupling groove  35 . 
     In addition, the coupling groove  35  is formed at the other bearing member  30  (the right one in the drawings) by protruding at an outer circumference of the one end thereof, and the coupling protrusion  37  is formed at an inner circumference of the other bearing member  30  by forming the coupling groove  35 . 
     When the pair of bearing members  30  are inserted axially into both ends of the hollow shaft  11  with reference to the ball  13  of the ball stud  10 , the coupling groove  35  and the coupling protrusion  37  facing each other are coupled. Accordingly, the pair of bearing members  30  are roll-contacted with the outer surface of the ball  13 . 
     In addition, a coupling clip  38  protruded axially from the coupling protrusion  37  is formed at the other bearing member  30 , and a receiving recess  36  coupled with the coupling clip  38  is formed at the one bearing member  30 . The coupling clip  38  and the receiving recess  36  as well as the coupling protrusion  37  and the coupling groove  35  prevent inflow of molten synthetic resin material into the bearing members  30  in a case of insert-molding. 
     According to the present exemplary embodiment, the seat member  50 , as shown in  FIG. 1C , supports the exterior circumference of the bearing members  30  such that the bearing members  30  are closely contacted with the ball  13  of the ball stud  10 . 
     The seat member  50  is made of a synthetic resin material, and is insert-molded between the outer case  70  and the bearing members  30 . 
     That is, the seat member  50  is formed of a molding portion  51  that is interposed between an interior circumference of the outer case  70  and the exterior circumference of the bearing members  30 , and integrally supports the outer case  70  and the bearing members  30 . 
     In other words, the outer case  70  and the bearing members  30  are integrally assembled through the molding portion  51  according to the present exemplary embodiment. 
     The molding portion  51  is formed by insert-molding the molten synthetic resin material between the outer case  70  and the bearing members  30  in a state in which the bearing members  30  are roll-contactedly mounted on the ball  13  of the ball stud  10 , and the outer case  70  is disposed apart from the exterior circumference of the bearing members  30 . 
     Formation of the molding portion  51  is performed by well-known insert-molding processes, and thus a detailed description thereof will be omitted in this specification. 
     Since the seat member  50  is insert-molded between the interior circumference of the outer case  70  and the exterior circumference of the bearing members  30 , a plurality of grooves  53  corresponding to the protrusions  33  of the bearing members  30  are formed at an interior circumference of the seat member  50 . 
     The seat member  50  is insert-molded between the outer case  70  and the bearing members  30 , and the grooves  53  are formed at the interior circumference of the seat member  50  by the protrusions  33  of the bearing members  30 . Therefore, the exterior circumference of the bearing members  30  and the interior circumference of the seat member  50  may be strongly assembled. 
     In order to show the plurality of grooves  53  at the interior circumference of the seat member  50 , the seat member  50  is drawn to be separated from the outer case  70  and the bearing members  30  in the drawings. 
     However, it is understood that the seat member  50  is integrally assembled to the outer case  70  and the bearing members  30  when the seat member  50  is insert-molded between the outer case  70  and the bearing members  30 . 
     According to the present exemplary embodiment, the outer case  70  is an outer surface of the ball joint assembly  100 , and is formed of an outer pipe enclosing the exterior circumference of the seat member  50 . 
     The outer case  70 , as shown in  FIG. 1B  and  FIG. 1C , has a cylindrical shape, both ends of which are opened, and is made of metal material. The outer case  70  is integrally assembled with the seat member  50  through the molding portion  51 . 
     A knurling portion  71  is formed at an interior circumference of the outer case  70  corresponding to the exterior circumference of the seat member  50  by a knurling process. 
     Since the seat member  50  is inset-molded between the interior circumference of the outer case  70  and the exterior circumference of the bearing members  30 , the knurling portion  71  enhances coupling strength between the interior circumference of the outer case  70  and the exterior circumference of the seat member  50 . 
     In the drawings, the exterior circumference of the seat member  50  is flat, but it is understood that a knurling portion corresponding to the knurling portion  71  of the outer case  70  is formed at the exterior circumference of the seat member  50  when the seat member  50  is insert-molded between the interior circumference of the outer case  70  and the exterior circumference of the bearing members  30 . 
     According to the present exemplary embodiment, the dust covers  90 , as shown in  FIG. 1D , cover between both ends of the outer case  70  and both ends of the ball stud  10 . 
     The dust covers  90  are mounted at both ends of the outer case  70  by pushing the dust covers  90  into both ends of the seat member  50  and both ends of the ball stud  10 . 
     Instead of mounting the dust cover  90  at both ends of the outer case  70  and both ends of the ball stud  10 , sealing members (not shown) may be mounted between both ends of the outer case  70  and both ends of the ball stud  10 . 
     A manufacturing method of ball joint assembly  100  for a vehicle according to an exemplary embodiment of the present invention will hereinafter be described in detail with reference to  FIG. 1A  to  FIG. 1D . 
     Firstly, the ball stud  10  having the ball  13  at the middle portion of the hollow shaft  11  is prepared, and the bearing members  30  are axially inserted into both sides of the hollow shaft  11  with reference to the ball  13  as shown in  FIG. 1A . 
     Then, in a state in which the bearing members  30  are roll-contactedly mounted on the outer surface of the ball  13 , the coupling groove  35  and the coupling protrusion  37  facing each other are coupled as shown in  FIG. 1B . At this time, the coupling clip  38  snaps into the receiving recess  36  so as to strengthen the coupling between the bearing members  30 . 
     After that, the ball stud  10  coupled with the bearing members  30  is set in an insert mold (not shown), and the outer case  70  is disposed apart from the exterior circumference of the bearing members  30  as shown in  FIG. 1B . 
     That is, the ball stud  10  is disposed in the outer case  70 , and the exterior circumference of the bearing members  30  is disposed apart from the interior circumference of the outer case  70  by a predetermined distance. 
     That is, a predetermined insert-molding region is set between the outer case  70  and the bearing members  30 . Then, the molten synthetic resin material is inserted into the insert-molding region, and the molding portion  51  of the seat member  50  is formed as shown in  FIG. 1C . 
     At this stage, since the bearing members  30  are coupled with each other through the coupling groove  35  and the coupling protrusion  37  on the outer surface of the ball  13 , the molten synthetic resin material cannot flow in a gap between the bearing members  30 . Since the coupling clip  38  snaps into the receiving recess  36 , the coupling between the bearing members  30  is strengthened and flow of the molten synthetic resin material into the gap between the bearing members  30  is further prevented. 
     In addition, since the plurality of protrusions  33  are formed at the exterior circumference of the bearing members  30 , the plurality of grooves  53  corresponding to the protrusions  33  is formed at the interior circumference of the seat member  50  when insert-molding proceeds. Therefore, the bearing members  30  and the seat member  50  are integrally assembled by the plurality of protrusions  33  and grooves  53 . 
     Also, since the knurling portion  71  is formed at the interior circumference of the outer case  70 , the outer case  70  and the seat member  50  are integrally assembled by the knurling portion  71 . 
     Finally, the dust covers  90  are pushed into both ends of the ball stud  10  so as to be closely contacted to both ends of the seat member  50  as shown in  FIG. 1D . Thereby, the ball joint assembly  100  according to the exemplary embodiment of the present invention is completely manufactured. 
     Since the seat member  50  formed of the molding portion  51  is integrally insert-molded between the outer case  70  and the bearing members  30  according to the exemplary embodiment of the present invention, the outer case  70  and the bearing members  30  are integrally assembled through the molding portion  51 . 
     Therefore, manufacturing processes and components used for manufacturing the ball joint assembly  100  may be reduced, different from the conventional art in which the ball joint assembly is assembled through a caulking processes. According to the exemplary embodiment of the present invention, manufacturing cost and weight may be reduced. 
     That is, the ball joint assembly  100  according to the present exemplary embodiment can be manufactured with a similar cost to a conventional rubber bushing. Therefore, the ball joint assembly  100  according to the present exemplary embodiment may be applied to an inexpensive vehicle as well as an expensive vehicle. 
     In addition, since the plurality of protrusions  33  are formed at the exterior circumference of the bearing members  30  according to the present exemplary embodiment, the plurality of grooves  53  corresponding to the protrusions  33  are formed at the interior circumference of the seat member  50  when the seat member  50  is insert-molded between the outer case  70  and the bearing members  30 , and thus, the bearing members  30  and the seat member  50  may be strongly coupled. 
     Further, since the knurling portion  71  is formed at the interior circumference of the outer case  70  according to the present exemplary embodiment, the outer case  70  and the seat member  50  may be strongly coupled when the seat member  50  is insert-molded between the outer case  70  and the bearing members  30 . 
     Since the bearing members  30 , the seat member  50 , and the outer case  70  are integrally and strongly assembled through the molding portion  51  according to the present exemplary embodiment, separation, rotation, or axial movement of the seat member  50  or the bearing members  30  may be prevented. Therefore, strength of the bearing members  30  may be improved. 
     Finally, since the outer case  70  is not bent toward the seat member  50 , breakage of the bearing members  30  may be prevented. 
     According to an exemplary embodiment of the present invention, the outer case and the bearing members are integrally assembled by insert-molding the seat member therebetween. Therefore, manufacturing processes, components used for manufacturing the ball joint assembly, manufacturing cost, and weight may be reduced, and performance may be improved. 
     While this invention has been described in connection with what is presently considered to be practical exemplary embodiments, it is to be understood that the invention is not limited to the disclosed embodiments, but, on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims.