Ball joint and control arm for a motor vehicle

A ball joint includes a base body, a ball socket formed in the base body, and a ball pivot having a joint ball which is received in the ball socket. The joint ball is held in the ball socket by a locking ring which has a flange portion bearing upon the base body. The flange portion has an outer periphery formed with a circumferential groove, with a groove flank of the groove providing a welding area. A welding seam running about the flange portion connects the locking ring to the base body.

CROSS-REFERENCES TO RELATED APPLICATIONS

This application claims the priority of German Patent Application, Serial No, 10 2013 105 091.3, filed May 17, 2013, pursuant to 35 U.S.C. 119(a)-(d), the disclosure of which is incorporated herein by reference in its entirety as if fully set forth herein.

BACKGROUND OF THE INVENTION

The present invention relates to a ball joint and to a control arm for a motor vehicle provided with such a ball joint.

Motor vehicle control arms, such as transverse members or side rails, are part of the wheel suspension of a motor vehicle and provided to control and steer the wheels and to absorb longitudinal and/or transverse forces. The kinematic linkage of the control arm is implemented via bearings or bearing assemblies. Ball joints find hereby application to enable the connection of the control arms with other components or the chassis with several rotational degrees of freedom.

It would be desirable and advantageous to obviate prior art shortcomings.

SUMMARY OF THE INVENTION

According to one aspect of the present invention, a ball joint includes a base body, a ball socket formed in the base body, a ball pivot having a joint ball which is received in the ball socket, a locking ring configured to hold the joint ball in the ball socket and having a flange portion bearing upon the base body, the flange portion having an outer periphery formed with a circumferential groove, with a groove flank of the groove providing a welding area, and a welding seam running about the flange portion for connecting the locking ring to the base body.

According to another advantageous feature of the present invention, the base body can be made, e.g. as pressed part, from a sheet metal blank, e.g. of a steel material such as high strength steel. Currently preferred is the use of a high strength multiphase steel with a tensile strength of 800 MPa and a yield point of 680 MPa or higher. The ball socket may be formed in one piece with the base body and can have a receptacle on an opening side of the ball socket for receiving the locking ring. The receptacle can be produced during shaping of the base body in a forming process, e.g. a deep-drawing process or pressing process.

According to another advantageous feature of the present invention, the joint ball of the ball pivot can be received in the ball socket through intervention of a bearing cup. The bearing cup can be made of thermoplastic material, e.g. polyoxymethylene (POM). The bearing cup may also be made of polyether ether ketone (PEEK). The locking ring is hereby used to maintain and positionally secure the joint ball in the ball socket. The locking ring can have a through opening through which a pivot body of the ball joint is guided. The locking ring mounted to the base body forms an upper closure of the ball joint.

The flange portion of the locking ring bears upon the base body in a proximate area of the opening of the ball socket. The attachment of the locking ring upon the base body is realized by a welding process, e.g. laser welding or electron beam welding.

According to another advantageous feature of the present invention, the groove may have a concave configuration on the outer periphery of the flange portion. During welding, the welding beam is directed onto the welding area. The clearing on the outside of the locking ring as a result of the presence of the groove enables a targeted alignment of the welding beam onto the welding area. The welding area broadens the impact zone of the welding beam. In this way, component tolerances or adverse effects can be compensated by the motion of the welding beam. A firm connection is ensured so long as the welding beam strikes the welding area. A circumferential welding seam is created in the contact zone between the locking ring and the base body below the contact zone and extends in the plane of the contact zone.

A ball joint according to the present invention is beneficial in terms of manufacture and is highly stress-resistant. The novel design improves quality of the ball joint with respect to strength and stress resistance as well as service life. The ball joint, in particular the connection between base body and locking ring, can be manufactured effectively and at shorter production time. An expanded tolerance range in particular is provided because the joint between base body and locking ring in accordance with the present invention is of high quality, even in the presence of fluctuating component tolerances.

According to another advantageous feature of the present invention, the welding area may be bound by a nose-shaped or wedge-shaped welding zone. The groove may hereby be configured in such a way that the welding beam is incident on the welding area at a predefined angle. Advantageously, the groove flank can be configured to have a lower groove flank, which can form the welding area, and an upper groove flank. The upper groove flank extends hereby at an angle of greater than or equal to 10° in relation to a vertical. Currently preferred is an angle of greater than or equal to 20° in relation to the vertical.

The groove is configured such that the welding beam can be guided relatively steep. Advantageously, the welding beam can be inclined at an angle of less than 20° in relation to the vertical or central longitudinal axis of the ball joint.

As a result of the novel configuration of the locking ring with the welding area on the outer circumference thereof, the connection zone in the contact zone between the base body and the bottom side of the locking ring or flange portion is widened or increased. A broad welding zone increases tensile strength and compressive resistance of the connection so that an increased pushing force of the ball pivot is realized.

According to another advantageous feature of the present invention, the locking ring can have a neck portion defined by an outer diameter, wherein the flange portion has an outer diameter which is greater than the outer diameter of the neck portion. The flange portion can bear upon the base body with an annular region situated below the flange portion.

The ball pivot can be secured in the ball socket by inserting the locking ring with its neck portion in the receptacle. The neck portion engages in the receptacle and urges hereby an upper circumferential wall section of the bearing cup against the joint ball. For this purpose, the neck portion has an inner circumferential surface of a shape which complements the geometry of the joint ball. The locking ring bears upon the base body via an annular surface at the bottom side of the flange portion. Joining is realized by the afore-described welding process using a welding beam which impinges from outside upon the welding area. The welding area, upon which the welding beam is directed and acts, and the created connection zone are sized sufficient to reliably compensate component tolerances or inaccuracies during motion of the welding beam, without adversely affecting the quality of the welded joint.

According to another advantageous feature of the present invention, a sealing bellows may be provided for protection of the ball joint. The sealing bellows may be made of rubber-elastic material, such as an elastomer, e.g. a CR elastomer (chloroprene rubber elastomer). A first clamping element can secure the sealing bellows on an outside of the flange portion at a clamping zone formed above the groove on the flange portion. The size of the clamping zone above the groove is sufficient to enable a reliable clamping of the sealing bellows by the clamping element. In addition, a second clamping element can be provided to secure the sealing bellows on a pivot body of the ball pivot. Examples of clamping elements include in particular clamping rings made of spring steel wire.

According to another aspect of the present invention, a control arm for a motor vehicle includes a ball joint which includes a base body, a ball socket formed in the base body, a ball pivot having a joint ball which is received in the ball socket, a locking ring configured to hold the joint ball in the ball socket and having a flange portion bearing upon the base body, said flange portion having an outer periphery formed with a circumferential groove and a groove flank to provide a welding area, and a welding seam running about the flange portion for connecting the locking ring to the base body.

The present invention thus enables an efficient production of lightweight control arms for motor vehicles, in particular transverse members or side rails. The ball socket can be made in one piece with the base body of the control arm and is formed as the base body is shaped from the sheet metal blank. The ball socket forms a single-part housing receptacle in the base body for receiving the joint ball of the pivot body. As the locking ring is circumferentially joined to the base body in a stable manner, the pivot body is held in the ball socket to enable a rotational motion or sliding motion. The novel design creates a connection between the locking ring and the base body which can be subjected to high stress and reliably absorbs tensile, compressive and shear forces during operation.

According to another advantageous feature of the present invention, the base body has a joining zone which is formed around the opening of the ball socket and upon which the flange portion of the locking ring rests via the annular surface on the bottom side of the flange portion. The joining zone is formed as the base body is shaped, and the joining zone may be configured to project in the direction of the locking ring in relation to the plane of the adjacent bottom region of the base body. Thus, the joining process can be further improved between the locking ring and the base body.

Bending and torsional resistances of a motor vehicle control arm can be further improved by using a ball joint according to the invention, when the base body has a cup-shaped configuration and includes a bottom with border-side legs. The bottom may further have stiffness-increasing depressions or eyelets with circumferentially closed or breached collars. The presence of such eyelets provide increase in stiffness and saves weight.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

Turning now to the drawing, and in particular toFIG. 1, there is shown a top and side perspective view of a motor vehicle control arm in the form of a transverse member, generally designated by reference numeral1and having integrated therein a ball joint according to the present invention, generally designated by reference numeral2. The transverse member1may find application within the wheel control or wheel suspension of the motor vehicle.

The transverse member1includes a base body3which has a cup-shaped configuration and can be made of steel, e.g. produced from a steel sheet blank using a pressforming process. The base body3has two length portions4,5which are aligned transversely to one another at an angle. A connection zone6forms a transition between the length portions4,5. The base body3is produced from a steel sheet blank through pressforming. The ball joint2is arranged at a free end7of the length portion4in the end zone thereof. A bearing mount in the form of an eyelet9is provided at a free end8of the length portion5in the end zone thereof for accommodating a rubber-metal bearing10.

The base body3has a bottom11with border-side legs12,13. The legs12,13are arranged at a right angle in relation to the bottom11. The bottom11of the base body3is formed with depressions14,15in the length portions4and5, respectively. The depressions14,15project out in the direction of the border-side legs12,13, respectively. Furthermore, the bottom11has an eyelet16which is formed in the connection zone6between the depressions14,15and points in the direction of the depressions14,15. A protrusion17extends from the outer periphery of the connection zone6to form a bearing mount18at a free end thereof. A sleeve19is joined here for a rubber-metal bearing20.

FIGS. 2 and 3show vertical sections through the transverse member1in the area of the ball joint2, depicting two assembly situations of the ball joint2. The ball joint2includes a ball pivot21having a joint ball22and a pivot body23. The joint ball22of the ball pivot21is received in a ball socket26through intervention of a bearing cup24and aligned by a locking ring26. The locking ring26involved here is a turned part. The bearing cup24is made of thermoplastic material.

The ball socket25is formed in one piece with the base body3and formed from the sheet metal blank as the base body3is produced by pressforming. Arranged at the side of the opening of the ball socket25is a receptacle27for the locking ring26. The locking ring26has a neck portion28and a flange portion29. The locking ring26has furthermore a central opening30for passage of the pivot body23. The neck portion28of the locking ring26is defined by an outer diameter D1 which corresponds to an inner diameter D2 of the receptacle27for the locking ring26. The flange portion29of the locking ring26is defined by an outer diameter D3 which is greater than the outer diameter D1 of the neck portion28. An annular surface31is formed at the underside of the flange portion on a side of the base body3.

When the ball joint2is assembled, the bearing cup24, greased beforehand on the inside, is placed into the ball socket25. The ball pivot21is positioned with its joint ball22in the bearing cup24, and the locking ring26is then guided with its opening30over the pivot body23and placed and press-fitted with the neck portion28into the locking ring receptacle27. As a result, an upper circumferential wall section32of the bearing cup24is pressed by the inner contour of the locking ring26against the joint ball22so that the bearing cup24conforms to the ball shape of the joint ball22. For that purpose, the locking ring26has at its inner circumference an inner wall33which has a spherical configuration which complements the shape of the joint ball22.

FIG. 2shows the ball pivot21in the bearing cup24before mounting the locking ring26, whereasFIG. 3shows the assembly situation in which the locking ring26has been press-fitted into place. The locking ring26, positioned in the receptacle27, rests with its annular surface31upon a joining zone35which is formed circumferentially about the opening34of the ball socket25. The joining zone35is formed as the base body3is shaped and slightly projects by a measure a in relation to the plane of the adjacent bottom region36of the base body3in the direction of the annular surface31, as shown in particular inFIG. 4a. The joining zone35is realized by material displacement during the pressing process of the base body3.

The locking ring26is welded to the base body3by laser beam welding or electron beam welding. The locking ring26and the base body3are hereby connected to one another by a circumferential welding seam37which extends along the annular surface31on the underside of the flange portion29and the joining zone35of the base body3.

The flange portion29has an outer periphery38provided with a circumferential groove39, as shown inFIGS. 4aand4b. The groove39has a lower groove flank40and an upper groove flank41. The lower groove flank40is configured as welding area42. A welding beam S is directed upon the welding area42during the joining process. The groove39is hereby configured such that the welding beam S is reliably incident on the welding area42, even when component tolerances of the locking ring26and/or base body3cause inaccuracies in assembly and position. Also, unevenness in the welding motion has no adverse effect because the welding area42is sized sufficiently large as target zone for the welding beam S. A nose-shaped or wedge-shaped welding zone43is provided below the welding area42and is bounded upwards by the welding area42. The underside of the welding zone43is formed by the annular surface31. A firm and high-quality welding seam37is realized as long as the welding beam S impacts the welding area42. The joined connection is formed in the contact zone between the locking ring26and the base body3at the annular surface31and the joining zone35in the form of the circumferential welding seam37which extends in the plane of the contact zone. The presence of the welding area42, which extends at an angle to the plane of the contact zone, enlarges the joining zone or connection zone. The width of the connection zone is designated inFIG. 4aby reference sign x. The width x of the connection zone is enlarged compared to conventional joining. This greater material coverage at the connection site results in an increase in strength of the connection. This results advantageously also in an increase of the pushing force against the ball pivot21.

The welding beam S may be guided steeply in relation to the vertical V. Welding angles between 0° and 20° are possible. The geometry of the groove39is configured such that the welding beam S impacts the welding area42. The groove39may be concavely shaped. The upper groove flank41extends in relation to the vertical V at an angle α which is greater than or equal to 10°. Currently preferred is an angle α of greater than or equal to 20°. In this way, the clearance on the outer circumference38of the flange portion29by the groove39can be suited to the welding beam position and the welding motion. The upper groove flank41and the lower groove flank40meet in the groove base at an obtuse angle.

The ball joint2and the joint ball22, rotatably mounted in the ball socket25, can be protected from environmental impacts by a sealing bellows44, as shown inFIG. 5. The sealing bellows44is secured in place on the locking ring26by a first clamping element45on a clamping zone46above the groove39on the outer circumference38of the flange portion29. The first clamping element45is integrated, e.g. vulcanized, in a lower annular collar47of the sealing bellows44. Moreover, the sealing bellows44is secured by a second clamping element48on the pivot body23. During assembly, the sealing bellows44is secured initially to the pivot body23by the upper second clamping element48in the form of a spring steel ring. Subsequently, the lower socket-proximal end of the sealing bellows44is secured by the lower first clamping element45to the outside on the locking ring26. The clamping element45may advantageously cooperate with the groove39for securement.

FIGS. 2,3,5further show that the joint ball22of the ball pivot21has an underside formed with recess49. The recess49may be used as lubricant reservoir.