Patent Abstract:
A method for manufacturing a bearing shell assembly for a ball joint includes the following steps: a) a bearing shell having a plastic extension is produced; b) a spring element is arranged in a region of the plastic extension; and c) the spring element is fastened to the bearing shell by deformation of the plastic extension. The invention further relates to a bearing shell assembly for a ball joint, including a bearing shell and a spring element, the spring element being non-detachably connected with the bearing shell.

Full Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims priority to German Patent Application No. 10 2008 003 463.0 filed Jan. 8, 2008, the disclosures of which are incorporated herein by reference in their entirety. 
     BACKGROUND OF THE INVENTION 
     The invention relates to a bearing shell assembly for a ball joint and a method for manufacturing a bearing shell assembly. 
     Ball joints are generally known from the prior art and are employed, inter alia, in vehicle construction. For example, they are used as radial ball joints and, in that case, must be able to withstand high radial forces along with low axial forces and large tilting angles. The wear occurring over the lifespan of a radial ball joint can lead to the ball joint causing noises during travel, caused by free play in the joint. 
     In order to prevent the occurrence of this free play, ball joints already exist in which a pre-stressed spring element is arranged between a joint housing and a bearing shell in the composed state of the joint. Through the pre-stressing of the spring element, the bearing shell is acted upon against the ball head of the ball pin, so that even if wear occurs to the bearing shell, a permanent contact exists between the bearing shell and the ball pin, and no free play occurs between the ball head and the bearing shell. 
     In addition, it is known to provide an extension on the bearing shell, on which the spring element can be pre-mounted. On the one hand, this facilitates a simple and exact positioning of the spring element in the joint housing and, on the other hand, simplifies the assembly of the ball joint. 
     In the prior art, for example a bearing shell is disclosed (cf.  FIG. 1 ), in which the extension is constructed as a latching element, in order to enter into a snap-on connection with the spring element (not shown). However, specifically in the case of a preferred production of the bearing shell as an integral injection molded plastic part, the construction of the extension as a latching element involves considerable effort. In particular, the provision of notches for the formation of radially movable detent arms and also the forming of an undercut on the detent arms for the formation of radial detent noses at the free end of the extension is complex with regard to injection-molding technique. 
     It is a feature of the invention to produce a favorably priced, pre-mounted assembly of a bearing shell and a spring element with as little effort as possible. 
     BRIEF SUMMARY OF THE INVENTION 
     According to the invention, this feature is achieved by a method for manufacturing a bearing shell assembly for a ball joint, the method including the following steps:
         a) a bearing shell having a plastic extension is produced;   b) a spring element is arranged in a region of the plastic extension; and   c) the spring element is fastened to the bearing shell by deformation of the plastic extension.       

     The connection between the spring element and the bearing shell therefore takes place by a simple deformation of the plastic extension, which can be carried out mechanically with little effort. In return, with regard to injection-molding technique, the complex manufacture of alternative connecting means, such as latching elements for example, is dispensed with. 
     In a method variant, the bearing shell and the plastic extension are produced as an integral injection-molded part. This integral embodiment permits a particularly favorably priced production of the bearing shell, in particular owing to the fashioning of the plastic extension which is simplified with regard to injection-molding technique. 
     In step a) the plastic extension is preferably produced as a substantially hollow cylindrical extension having a free axial end. This technical design of the extension makes possible a particularly simple and reliable mechanical deformation at the free axial end. 
     In a preferred method variant, the spring element is fastened to the bearing shell by cold deformation of the plastic extension. “Cold deformation” in this context designates a deformation which takes place approximately at room temperature, so that a special heating of the plastic extension before deformation is superfluous. This contributes to a production of the bearing shell assembly which is energetic favorable and hence is particularly favorably priced. 
     The spring element may have an opening for the plastic extension and may be placed onto the bearing shell in step b), such that the spring element surrounds the plastic extension. In this case, a particularly simple and reliable positioning of the spring element on the bearing shell is achieved. 
     Preferably, with the deformation in step c), an external diameter of the substantially hollow cylindrical plastic extension is widened. A spring element being formed in a suitable manner can be fastened captively, in particular non-releasably, on the bearing shell owing to this widening of the external diameter. 
     In particular, the spring element may be a plate spring or an assembly of several plate springs. 
     The invention further relates to a bearing shell assembly for a ball joint, which is preferably produced by the previously described method, with a bearing shell and a spring element, the spring element being non-releasably connected to the bearing shell. 
     Other advantages of this invention will become apparent to those skilled in the art from the following detailed description of the preferred embodiments, when read in light of the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  shows the perspective view of a bearing shell according to the prior art; 
         FIG. 2  shows the perspective view of a bearing shell for a bearing shell assembly according to the invention; 
         FIG. 3  shows a diagrammatic section through the bearing shell according to  FIG. 2  with a spring element fitted in place, the bearing shell being clamped into a deformation tool; 
         FIG. 4  shows a perspective view of the bearing shell according to  FIG. 2  with a spring element fitted in place, the bearing shell being clamped into a deformation tool; 
         FIG. 5  shows a perspective view of a bearing shell assembly according to the invention; 
         FIG. 6  shows a longitudinal section through a ball joint with a bearing shell assembly according to the invention; and 
         FIG. 7  shows a detail section through the ball joint according to  FIG. 6  in the region of a plastic extension of the bearing shell assembly according to the invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       FIG. 1  shows a known bearing shell  10 ′ for a ball joint, with a shape which is substantially rotationally symmetrical to a longitudinal axis A′. The bearing shell  10 ′ has an axial extension  12 ′, on which latching elements  14 ′ are formed. The latching elements  14 ′ can enter into a snap-on connection with a spring element (not shown) in order to fasten the spring element to the bearing shell  10 ′, so that a pre-mounted bearing shell assembly is produced. According to  FIG. 1 , the axial extension  12 ′ is subdivided by notches  16 ′ into four radially movable latching elements  14 ′. At a free, axial end  18 ′ of the extension  12 ′, each latching element  14 ′ has a formed-on build-up or undercut, which respectively forms a detent nose  20 ′ of the associated latching element  14 ′. 
     If a spring element, such as for example a plate spring with a suitable opening, is pressed in the axial direction onto the extension  12 ′, then the latching elements  14 ′ deform radially inwards until the plate spring has passed the detent noses  20 ′. Thereafter, the elastic latching elements  14 ′ snap radially outwards again, so that the detent noses  20 ′ engage behind an edge of the opening of the plate spring and therefore fasten the plate spring to the bearing shell  10 ′. Depending on the construction of the latching elements  14 ′, the plate spring can be detached again from the extension  12 ′ by a suitable tool or an axial force, without the bearing shell  10 ′ being damaged or destroyed. 
     According to  FIG. 1 , the bearing shell  10 ′ and the extension  12 ′ are produced integrally as a single plastic part, in which the forming-on of the notches  16 ′ and the detent noses  20 ′ involves considerable effort with regard to injection-molding technology. 
       FIG. 2  shows a bearing shell  10  which is likewise substantially rotationally symmetrical to a longitudinal axis A, but has an altered axial plastic extension  12 , in which this plastic extension  12 , compared with the extension  12 ′ according to  FIG. 1 , is able to be produced in a substantially simpler manner with regard to injection-molding technique. Preferably, the bearing shell  10  and the plastic extension  12  according to  FIG. 2  are also produced in a single process step as an integral, favorably priced injection-molded part. The plastic extension  12  is preferably formed as a substantially hollow cylindrical extension having a free axial end  18 . In some variant embodiments, an outer side of the extension  12  is not exactly cylindrical, but rather is constructed so as to be slightly conical, such that the extension  20  narrows slightly towards the free end  18 . This conical embodiment facilitates the placement of a spring element  22  (cf.  FIGS. 3 to 7 ) and, moreover, simplifies the material deformation in this region owing to the smaller wall thickness at the free end  18  of the extension  12 . 
     The bearing shell  10  according to  FIG. 2  constitutes a suitable blank for the production of a bearing shell assembly  23  according to  FIG. 5 , with the production process of this bearing shell assembly  23  being described in detail below with the aid of  FIGS. 3 and 4 . 
     After a manufacture of the bearing shell  10  shown in  FIG. 2  in a first process step, the spring element  22  is arranged in the region of the plastic extension  12  in a second process step. Preferably, a plate spring or a plate spring set is used as spring element  22 . Basically however, any desired spring element  22  can be used which acts upon the bearing shell  10  in the desired manner when subsequently employed in a ball joint  34  (cf.  FIGS. 6 and 7 ). 
     In the present example, the spring element  22  includes two plate springs with respectively a central, approximately circular opening  24 , a diameter of the opening  24  being slightly larger than an external diameter d 1  of the substantially hollow cylindrical plastic extension  12  (cf.  FIGS. 2 and 3 ). Accordingly, the spring element  22  can be placed onto the plastic extension  12  and is thereby already largely fixed in a radial direction. 
     In a further, third process step, the spring element  22  is fastened on the bearing shell  10  by deforming the plastic extension  12 . This process step is illustrated diagrammatically in  FIG. 3 . In actual terms, firstly the bearing shell  10  on its side facing away from the extension  12  is turned over a form  26  which serves as an abutment. Then a pressure stamp  28  is supplied in the axial direction, the pressure stamp  28  engaging at the free end  18  of the plastic extension  12 . The shape of the pressure stamp  28  in the contact region with the plastic extension  12  is illustrated precisely on the left-hand side of  FIG. 3  by means of a section detail X. A stamp extension  30 , which narrows conically towards a free end of the pressure stamp  28 , engages into the hollow cylindrical plastic extension  12  of the bearing shell  10  and widens the extension slightly by applying axial pressure. Finally, the free end  18  of the extension  12  abuts onto a rounded, encircling guide channel  32  of the pressure stamp  28 , which deforms the plastic material at the free end  18  of the extension  12  radially outwards such that an encircling build-up  33  is formed. In other words, the external diameter of the substantially hollow cylindrical plastic extension  12  is widened during the deformation by the pressure stamp  28 . In the present example, the external diameter is increased in the region of the free end  18  from a value d 1  to a value d 2  (cf.  FIGS. 2 and 6 ). 
     With the deformation of the plastic extension  12  in this third process step, it is particularly important that the longitudinal axes of the form  26 , the pressure stamp  28  and the bearing shell  10  are precisely in alignment, so that a uniform deformation takes place, viewed in a peripheral direction. 
       FIG. 4  shows a perspective view during the process which is illustrated according to  FIG. 3  in a diagrammatic longitudinal section. Here, the bearing shell  10  is turned over the form  26  and the spring element  22  is placed onto the extension  12  of the bearing shell  10 . Furthermore, the pressure stamp  28  is already placed onto the free end  18  of the extension  12  and is acted upon against the form  26 . After the deformation of the free end  18 , the pressure stamp  28  moves away again in the axial direction and the bearing shell assembly  23  can be taken from the form  26 . Through the deformation of the free end  18 , the spring element  22  is now fastened both in radial and axial direction on the bearing shell  10 . In addition to the spring element  22 , of course further components such as for example a washer  35  (cf.  FIG. 6 ) can also be fastened on the bearing shell  10  by the described method. 
     Depending on the boundary conditions during the manufacturing process, in the finished bearing shell assembly  23  the spring element  22  is possibly rotatable relative to the bearing shell  10  about the axis A and/or has a slight axial play. However, as the objective was the (in particular radial) positioning of the spring element  22  relative to the bearing shell  10  and the non-releasable fastening of the spring element  22  on the bearing shell  10 , these movement possibilities in no way restrict the operability of the bearing shell assembly  23  and are therefore negligible. 
       FIG. 5  shows a perspective view of the pre-mounted bearing shell assembly  23 , which has been manufactured by the method described above. The bearing shell assembly  23  includes the bearing shell  10  and the spring element  22 , the spring element  22  being non-releasably connected with the bearing shell  10 . In this case, the connection is defined as being non-releasable because the spring element  22  can not be detached from the bearing shell  10  without destroying or at least damaging the extension  12 . 
     To produce at least the extension  12 , preferably the entire bearing shell  10 , plastics (in particular thermoplastics) are used, which are suitable for a permanent plastic deformation. In a variant embodiment, the deformation takes place at raised temperatures, which is designated as so-called hot deformation. However, in particularly preferred variant embodiments, the spring element  22  is fastened to the bearing shell  10  by so-called cold deformation, i.e. cold overstretching of the plastic extension  12 . During cold deformation, the plastic material is deformed beyond the linear-elastic range, up to close to the yield point. The deformation in this so-called entropy-elastic or plastic range is maintained substantially permanently, so that the spring element  22  is reliably fastened on the bearing shell  10 . 
       FIG. 6  shows a ball joint  34  with a ball pin  36 , a joint housing  38  and the bearing shell assembly  23  described above. In the present case, the joint housing  38  includes a housing cover  40  and a peripheral wall  42  on which the housing cover  40  is fastened. The bearing shell assembly  23  is accommodated inside the joint housing  38  and surrounds a ball head  44  of the ball pin  36 , which likewise extends into the interior of the housing. In this assembled state of the ball joint  34 , it becomes clear that the spring element  22  can be pre-stressed by the placement of the housing cover  40 . Through the pre-stressing of the spring element  22 , the bearing shell  10  is pressed against the ball head  44  of the ball pin  36 , so that even when wear occurs to the bearing shell  10 , a permanent contact exists between the bearing shell  10  and the ball pin  36  and no free play occurs between the ball head  44  and the bearing shell  10 . 
       FIG. 7  shows a detail of the ball joint  34  according to  FIG. 8  in the region of the axial plastic extension  12 . The widened external cross-section d 2  at the free end  18  of the plastic extension  12 , which provides for a captive, in particular non-releasable connection between the bearing shell  10  and the spring element  22  can be readily seen here. 
     In accordance with the provisions of the patent statutes, the principle and mode of operation of this invention have been explained and illustrated in its preferred embodiments. However, it must be understood that this invention may be practiced otherwise than as specifically explained and illustrated without departing from its spirit or scope.

Technology Classification (CPC): 1