Patent Publication Number: US-11649852-B2

Title: Ball joint with injection molded bearing

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a Divisional of U.S. patent application Ser. No. 16/638,843 filed Feb. 13, 2020, which is a United States National Phase Application of PCT Application No. PCT/CA2018/050999 filed Aug. 16, 2018, which claims priority to Untied States Provisional Application No. 62/546,091, which was filed on Aug. 16, 2017, and U.S. Provisional Application No. 62/681,990, which was filed on Jun. 7, 2018. 
    
    
     BACKGROUND 
     This disclosure relates to a ball joint for a vehicle suspension or steering member, for example. 
     Ball joints are commonly used in vehicles for suspension or steering elements such as control arms or tie rod ends. The ball joint provides a connection that permits rotation of one element with respect to another while permitting articulation during a range of motion experienced during vehicle operation. 
     One example ball joint configuration provides a pre-molded plastic bearing cup to which the ball is inserted in a snap-fit relationship. The sub assembly is then inserted into a bore of a housing, and a cover is arranged over the bearing. 
     Providing a consistent torque between the ball and its support structure is important so as to not provide any undesired free play or too stiff of a joint. To this end, one approach over-crimps a lip of the housing onto the cover, which forces the bearing into further engagement with the housing and ball. This type of method is disclosed in U.S. Pat. No. 6,592,284 to Rechtien. Any surface imperfections in the housing are accommodated by the bearing flowing into any gaps. This assembly method is challenging in that it is difficult to provide a consistent operational torque. Another internal tolerance compensation feature is disclosed in U.S. Pat. No. 2,993,717 to Gottschald, which uses a spring to apply a load to the ball. 
     U.S. Pat. No. 6,941,656 to Michioka discloses a ball joint that has the outer housing cast over a resin bearing. This method eliminates any gaps between the housing and the bearing but limits the housing material to relatively low strength zinc or aluminum die cast material so as not to melt the resin bearing during the casting process. Typically high load suspension applications require the housing to be made from a high strength steel. 
     SUMMARY 
     In one exemplary embodiment, a method of manufacturing a ball joint includes arranging a ball in a bore of a housing, enclosing an end of the bore, injecting plastic into a space between the housing and the ball to form a bearing that has a bearing surface that engages the ball, shrinking the bearing to form a recess in the bearing surface, and filling the recess with a grease. 
     In a further embodiment of any of the above, the arranging step includes a ball that has a stud that extends from the ball. The ball and stud includes a hole therethrough. The filling step includes injecting grease through the hole and into the recess. 
     In a further embodiment of any of the above, the method includes the step of sealing the hole subsequent to performing the filling step. 
     In a further embodiment of any of the above, the enclosing step includes securing a cover over the ball. The injecting step includes the bearing surface that engages around the cover to form a cap that is integrally connected to the bearing to provide a monolithic plastic structure. 
     In a further embodiment of any of the above, the cover securing step includes one of welding or swaging. 
     In a further embodiment of any of the above, the enclosing step includes swaging the housing toward the ball. 
     In a further embodiment of any of the above, the plastic injecting step includes overmolding a cap over the cover and connected to the bearing to provide a monolithic plastic structure. 
     In a further embodiment of any of the above, the cover includes an opening. The plastic injecting step includes molding the cap and the bearing as a monolithic structure with a connector that is arranged in the opening and joins the bearing and the cap. 
     In a further embodiment of any of the above, the arranging step includes a ball that has a stud that extends from the ball. The ball and stud includes a hole therethrough, and includes the step of plugging the hole prior to performing the plastic injecting step. 
     In a further embodiment of any of the above, the cover includes an elongate cavity. The injecting step includes filling the elongate cavity with plastic. The shrinking step includes shrinking the bearing at a location opposite the elongate cavity to create the recess. 
     In a further embodiment of any of the above, the injecting step includes forming a bearing with a perimeter lip that is arranged about a circumference of the ball at the housing. The grease filling step includes deforming the bearing to pull the perimeter lip into the housing and provide an enhanced seal between the ball and housing. 
     In a further embodiment of any of the above, the grease is a first grease, and includes a step of installing a boot onto the housing with a second grease that is different than the first grease that is arranged between the boot and the ball. The perimeter lip separates the first and second greases. 
     In a further embodiment of any of the above, the housing includes a hole on a side opposite the stud, and the hole is in fluid communication with the recess that is formed on a side of the bearing facing the ball stud and aligned with the elongate cavity. The hole is filled with grease. 
     In a further embodiment of any of the above, the arranging step includes the ball that has a stud that extends from the ball. The ball and stud include a hole therethrough, and includes the step of plugging the hole prior to performing the plastic injecting step. 
     In a further embodiment of any of the above, the arranging step includes the ball that has a stud that extends from the ball. The ball and stud include a hole therethrough. The filling step includes injecting grease through the hole and into the recess. 
     In a further embodiment of any of the above, the method includes the step of sealing the hole subsequent to performing the filling step. 
     In a further embodiment of any of the above, the bearing has first and second sides opposite one another to provide a thickness. The first side provides the bearing surface that forms a spherical surface. The second side has a protrusion opposite the spherical surface that is received in and fills an elongate cavity in the housing. A recess is provided in the spherical surface directly opposite the protrusion relative to the thickness. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The disclosure can be further understood by reference to the following detailed description when considered in connection with the accompanying drawings wherein: 
         FIG.  1    is a cross-sectional view through a ball joint arranged in a suspension element to provide a suspension member. 
         FIG.  2    is an exploded view of the ball joint shown in  FIG.  1   . 
         FIG.  3 A  illustrates a ball joint inserted into a bore of a housing. 
         FIG.  3 B  illustrates a cover welded to the housing over the ball. 
         FIG.  4    schematically depicts an injection molding process that forms the bearing and a cap arranged over the cover. 
         FIG.  5    is a partial cross-sectional view through a portion of the ball joint. 
         FIG.  6    illustrates grease injected into the ball joint. 
         FIG.  7 A  illustrates a bearing surface and a recess provided therein to accommodate the grease. 
         FIG.  7 B  is an enlarged view of the portion of the ball joint shown in  FIG.  7 A . 
         FIGS.  8 A and  8 B  are partial cross-sectional views of a portion of the bearing arranged between the ball and the housing as molded. 
         FIGS.  8 C and  8 D  illustrate the deflection of the bearing in an exaggerated fashion subsequent to grease being injected into the ball joint. 
         FIG.  9    is a cross-sectional view through the ball joint illustrating the first and second greases. 
         FIGS.  10 A and  10 B  are cross-sectional views respectively of one-piece housing and two-piece housing alternative ball joint embodiments. 
         FIGS.  11  and  12    illustrate partial cross-sectional views of the one-piece housing prior and subsequent to swaging. 
         FIGS.  13 A and  13 B  depict grooves in the one-piece and two-piece housings. 
         FIG.  13 C  illustrates grooves in the two-piece housing misaligned. 
         FIGS.  14 A and  14 B  are respectively cross-sectional exploded views of portions of the one-piece housing and two-piece housing ball joints. 
         FIG.  15    schematically depicts the injection molding process wherein a plastic is injected from a side of the housing adjacent the ball. 
         FIGS.  16 A and  16 B  are respectively cross-sectional views through the one-piece housing and two-piece housing ball joints with grease in the bearing and without the boots installed. 
         FIG.  17    illustrates a plug installed over the hole used to supply the bearing with grease. 
         FIG.  18    illustrates a bearing without a lip. 
     
    
    
     The embodiments, examples and alternatives of the preceding paragraphs, the claims, or the following description and drawings, including any of their various aspects or respective individual features, may be taken independently or in any combination. Features described in connection with one embodiment are applicable to all embodiments, unless such features are incompatible. 
     DETAILED DESCRIPTION 
     Referring to  FIGS.  1  and  2   , a ball joint  14  is provided in a suspension element  12  to provide a suspension member  10 , such as a control arm or tie rod end. A ball joint  14  includes a housing  16 , which may be constructed from steel. A ball  18  has a stud  20  extending therefrom, which typically includes a threaded end for securing the ball joint  14  to another suspension component, such as a steering knuckle. In the example, a single, linear hole  28  extends through the ball  18  and stud  20  and is blocked by a plug  68 . The exterior surface of the ball  18  is spherical in shape to permit the ball  18  to pivot and articulate in a bore  52  of the housing  16 . 
     In a two-piece housing configuration, a cover  24  forms another portion of the housing structure and is secured to one end of the bore  52 , such as by welding, to enclose and capture the ball  18  within the housing  16 . A bearing  22 , constructed from a material such as acetyl, is injection-molded into the space between the ball  18  and the housing  16 . A boot  26  with a seal rim  30  is provided over the stud  20  and is secured to the housing  16  opposite the cover  24  to seal the ball  18  from the elements and prevent corrosion. 
     Referring to  FIGS.  3 A- 5   , the ball joint  14  is manufactured by arranging the ball  18  in the bore  52 . The bore  52  is provided by a tapered wall  54 , which captures the ball  18  at an end of the housing  16  opposite the cover  24 . The cover  24  includes a domed portion  32  having a perimeter flange  34  providing a ridge  36 . The ridge  36  abuts a ledge  48  at a perimeter of the bore  52 . An edge  46  of the flange  34  is welded to the housing  16 , for example, by laser welding, to provide a weld  50  securing the cover  24  to the housing  16 . 
     One side of the domed portion  32  provides a spherical surface  38  having circumferentially spaced apart grooves  42  adjoining and radiating outwardly from an opening  44  in the cover  24 . The grooves  42  may be formed by coining, for example. 
     A plastic injection molding process is shown in  FIG.  4   . Molding equipment  56  is used to inject a molten plastic, such as acetyl, into the space between the housing  16 , the cover  24  and the ball  18  to provide the bearing  22 . 
     Multiple mold portions engage various components of the ball joint  14  to maintain a space provided by first and second cavities  70 ,  72  on opposite sides of the cover  24  and that are in fluid communication with one another. In one example, a first mold portion  58  abuts the housing  16  to create a second cavity  72  between the first mold portion  58  and a bottom portion of the housing  16  and the cover  24 . A second mold portion  60 , such as a pin, is inserted into the hole  28  to plug and block any molten plastic from entering the hole  28 . A third mold portion  62  includes first and second chamfers  64 ,  66  that respectively abut the housing  16  and the ball  18  to prevent molten plastic from escaping the first cavity  70  during molding. 
     A plastic injector  63  injects molten plastic through an outlet in the first mold portion  58  into the second cavity  72 , through the opening  44  in the cover  24  and into the first cavity  70 . 
     The opening  44  is aligned with the hole  28 . During injection, plastic flows through the opening  44  forming protrusions  77  that fill the grooves  42  in the cover  24  on a side facing the ball  18 . A spherical surface is formed on a first side  82  of the bearing  22  that engages the corresponding spherical surface of the ball  18 . A depression  69  is provided in the bearing surface at the first side  82  of the bearing  22  and is formed by an end of the second mold portion  60 , such that the depression  69  is beneath the hole  28  and aligned with the opening  44 . 
     An end of the housing  16  includes an annular projection  73  circumscribing the bore  52 . A cap  74  is over-molded over the cover  24 , the weld  50  and a portion of the annular projection  73  (with extension  71 ) to provide a water-tight seal and prevent corrosive elements from entering the ball joint  14 . A monolithic plastic structure is thus formed including the bearing  22  joined to the cap  74  by a connector  75 . 
     As the plastic cools, it shrinks slightly, approximately 2%. The wall thickness of the bearing  22  varies due to the presence of the grooves  42  in the cover. Thus, a first thickness  76  of the bearing  22  in the area of the grooves  42  is larger than that of a second thickness  78  provided by the adjacent bearing structure, as shown in  FIG.  7 A . As a result of the plastic shrinking, a recess  80  will form next to the ball  18  in the spherical bearing surface on the first side  82  at a location opposite each groove  42 , as best shown in  FIG.  7 B . 
     As shown in  FIGS.  6 - 7 B and  9   , grease  84  is injected through the hole  28  into the depression  69  left by the second mold portion  60 , permitting the grease  84  to travel into the recesses  80  that adjoin the depression  69 . A plug  68  is inserted into the hole  28  to retain the grease  84  and prevent entry of debris. 
     As shown in  FIGS.  8 A- 8 B , a slight perimeter lip  88  is provided at the end  86  of the bearing  22 . As grease  84  fills the depressions, the bearing  22  deforms, pulling the lip  88  a distance  90  into the space between the ball  18  and the housing  16  (exaggerated in  FIGS.  8 C- 8 D ) creating an interference fit and an enhanced seal between the ball  18  and the housing  16 . A second grease  94 , which is different than the first grease  84 , is provided between the boot  26  and the ball  18 . The lip  88  separates the first and second greases  84 ,  94 , as shown schematically in  FIG.  9   . 
     Variations of the ball joint  14  described above may also be used. Like numerals (e.g.,  14 ,  114 ,  214  for “ball joints”) are used to describe similar elements between the various embodiments. A one-piece housing ball joint  114  is shown in  FIG.  10 A , and another two-piece housing ball joint  214  is shown in  FIG.  10 B . The one-piece housing ball joint  114  uses thicker walls, which may be more suitable in particular for higher axial loads. Grease is injected through the housing  116 ,  216  rather than the stud  120 ,  220  in both example ball joints  114 ,  214 . 
     Referring to  FIGS.  10 A,  11  and  12   , the ball joint  114  has a housing  116  that includes an annular wall  116   a  on a side by the stud  120  and opposite a base  116   b  of the housing  116 . After the ball  118  has been placed into the bore  152  and prior to injecting the bearing  122 , the annular wall  116   a  is deformed inward toward the ball  118 , e.g., swaged, to enclose the ball  118  within the bore, as shown in  FIG.  12   . However, the annular wall  116   a  remains spaced from the ball  118  to provide the first cavity  170  that receives the bearing  122  during molding. 
     As described in connection with the ball joint  14  shown in  FIG.  7 B , the plastic bearing  22  shrinks as it cools, which forms the recesses  80  next to the ball  18  in the spherical bearing surface on the first side  82  at a location opposite each groove  42 . It may be desirable to provide the grease farther up toward the stud for improved lubrication. To this end, as shown in  FIGS.  13 A- 14 B , the housings  116 ,  216  each have grooves  142 ,  242  that extend to an end  117 ,  217  of the housing  116 ,  216  to provide corresponding recesses  180 ,  280 . However, it should be understood that the grooves  142 ,  242  need not extend all the way through to the terminal end of the housings  116 ,  216  as shown in the example embodiments. For the two-piece housing  216 , a portion of the groove  242  is provided in the cover  224 , which is preferably circumferentially aligned with the grooves in the other housing portion. Even if the grooves  242  are not circumferentially aligned with the grooves in the other housing portion ( FIG.  13 C ), grease will still flow into the recess  283  ( FIG.  14 B ) formed from the bearing  222  shrinking at a junction  281  between the cover  224  and the other housing portion. 
     As shown in  FIG.  13 B , the annular projection  273  may be folded over, or swaged, onto the cover  224  as an alternative to welding thereby reducing the likelihood of corrosion. 
     The bearing  122 ,  222  of each of the ball joints  114 ,  214  is injected through the base of the housing  116 ,  216  opposite the stud  120 ,  220 . The plastic injection molding process for the ball joint  214  is shown in  FIG.  15   . First and third mold portions  258 ,  262  are arranged about the ball joint  214  in a manner similar to that described in connection with  FIG.  4   . A second mold portion  259  includes an end  261  that is inserted into the opening  244  in the cover  224  and into abutment with the ball  218 . A fluid passage  261   a  that is connected to a plastic injector  263  is in communication with radially extending first and second passageways  261   b ,  261   c.    
     A first cavity  270  is provided between the ball  218  and the cover  224 , and a second cavity  272  is provided between the cover  224  and the first mold portion. The first and second passageways  261   b  and  261   c  are aligned respectively with the first and second cavities  270 ,  272 , which correspondingly provide the bearing  222  and the cap  274 . The lip  88  described in  FIGS.  8 A- 8 D  may be omitted, as shown in  FIG.  18   . 
     The ball joints  114 ,  214  are shown in  FIGS.  16 A and  16 B  subsequent to molding the bearings  122 ,  222 . The second mold portion  259  is withdrawn from the ball joint  214  subsequent to molding, leaving a hole  269  that adjoins the recesses  280  ( FIG.  14 B ). Grease  284  is injected through the hole  269  and into the recesses  280  where it lubricates the ball  218 . The injected grease  284  causes the bearing  222  to balloon slightly and achieve the desired lubrication of and load characteristic on the ball  218 . The hole  169  ( FIG.  16 A ),  269  ( FIG.  16 B ) acts as a reservoir for the grease  184 ,  284 . Referring to  FIG.  17   , a plug  268  is installed onto the cap  274  to cover the hole  269  and retain the grease  284  within the ball joint  114 . The plug  268  may be snapped and/or ultrasonically welded onto the cap  274 . 
     It should also be understood that although a particular component arrangement is disclosed in the illustrated embodiment, other arrangements will benefit herefrom. Although particular step sequences are shown, described, and claimed, it should be understood that steps may be performed in any order, separated or combined unless otherwise indicated and will still benefit from the present invention. 
     Although the different examples have specific components shown in the illustrations, embodiments of this invention are not limited to those particular combinations. It is possible to use some of the components or features from one of the examples in combination with features or components from another one of the examples. 
     Although an example embodiment has been disclosed, a worker of ordinary skill in this art would recognize that certain modifications would come within the scope of the claims. For that reason, the following claims should be studied to determine their true scope and content.