FORM 2
THE PATENT ACT 1970 (39 of 1970)
The Patents Rules, 2003 COMPLETE SPECIFICATION See Section 10, and rule 13)
TITLE OF INVENTION
BALL JOINT COMPRISING WELDED HOUSING PARTS

APPLICANT (S)
a) Name
b) Nationality
c) Address

ZF FRIEDRICHSHAFEN AG GERMAN Company 88038 FRIEDRICHSHAFEN GERMANY

3. PREAMBLE TO THE DESCRIPTION
The following specification particularly describes the invention and the manner in which it is to be berformed : -


The invention relates to a ball joint for a vehicle, having a housing, a joint inner part, which is seated in and extends out of the housing and which with a bearing region having a spherical or part-spherical surface is mounted with the interposition of a bearing shell movably in the housing, which comprises two housing parts that engage one into the other and are connected in a fixed manner to one another by means of at least one welded joint. The invention further relates to a method of manufacturing such a ball joint.
Such ball joints are prior art. DE 197 56 984 Al discloses for example a ball joint comprising a bearing shell, which inside accommodates a ball head of a pivot pin and is supported in a housing, and a closing element, which rests on the outside of the bearing shell and by means of which the bearing shell is preloadable relative to the housing and the ball head. The closing element is guidable displaceably in an axial preloading direction on the housing, while acting upon the bearing shell, and is fixable in any desired position by welding. The closing element may be designed at its outer peripheral surface with saw-tooth or triangular projections.
From DE 10 2004 040 412 Al a ball sleeve joint is known, comprising a joint housing consisting of two joint housing halves as well as a ball sleeve provided with a rounded bearing surface, wherein the bearing surface is accommodated in a bearing shell, which is manufactured from flexible plastics material and fixed in a recess of the joint housing. The two housing halves are pressed together in the direction of the central longitudinal axis of the ball sleeve joint by defined pressing forces and held against one another by means of a welded connection. In particular, one of the housing halves is pushed partially into the other housing half. The bearing shell may have on its outer surface a protruding retaining projection that engages into a corresponding indentation of the housing. Furthermore, the centres of the sphere radii of the bearing surface and of the recess of the joint housing may be displaced relative to one another in the direction of the central longitudinal axis before application of the pressing forces.

In the known ball joints there is a risk of thermal overloading of the bearing shell as a result of the welding operation, which may lead to a reduction of the useful life of the ball joint.
Against this background art the underlying object of the invention is to reduce the risk of thermal overloading of the bearing shell.
This object is achieved according to the invention by a ball joint according to claim 1 and by a method according to claim 9. Preferred developments are indicated in the sub-claims.
The ball joint according to the invention for a vehicle, in particular a motor vehicle, has a housing and a joint inner part, which is seated in and extends out of the housing and which with a bearing region comprising a spherical or part-spherical surface is mounted with the interposition of a bearing shell movably, in particular rotatably and/ or pivotably, in the housing, which comprises two housing parts that engage one into the other and are connected in a fixed manner to one another by means of at least one welded joint. In this case, the two housing parts prior to formation of the at least one welded joint are braced against one another in radial direction, with simultaneous formation of an interference fit.
With the ball joint according to the invention it is easily possible to carry out a condenser discharge welding process for forming the at least one welded joint, wherein the process temperature at the welding point owing to the rapid rise of the welding current may be reached before any damaging heating of the surrounding material occurs. Condenser discharge welding is based in particular on the parameters: welding force and energy and/or electric current, wherein according to the invention the welding force is applied by virtue of the radial bracing or preloading between the two housing parts.

A first one of the housing parts preferably has a recess, into which a second one of the housing parts engages with an engagement region. The bracing may be realized for example in that the outside diameter of the engagement region of the second housing part prior to the engagement of the two housing parts one into the other is larger than the inside diameter of the recess of the first housing part. The at least one welded joint is then formed in particular between the outer lateral surface of the engagement region and the inner wall of the recess. The recess and/or the engagement region are in this case preferably of a cylindrical design.
In order to define the position of the at least one welding point at the site of the engagement of both housing parts one into the other at least one projection may extend radially from an outer lateral surface of one of the housing parts to an inner lateral surface of another of the housing parts, at which projection the interference fit is formed. During welding the at least one welded joint is then formed at the at least one projection. In particular, the at least one projection and/or the at least one welded joint is disposed between the axial ends of the inner lateral surface and may have an axial spacing relative to these ends.
The at least one projection is in particular continuously circumferential and/or is of an annular design, so that the at least one welded joint is likewise of a circumferential design and preferably forms a seal that prevents the penetration of dirt and moisture.
The inner wall of the recess may form the inner lateral surface and the outer lateral surface of the engagement region may form the outer lateral surface. Furthermore, a plurality of - preferably two - projections may extend radially from the outer lateral surface to the inner lateral surface and be disposed with spacing, in particular axial spacing, relative to one another. The projections are in particular of an identical type and may be continuously circumferential. Preferably, there is then formed during the welding process at each of the projections an in particular circumferential welded joint between the two housing parts. The projections and/or the welded

joints are moreover preferably disposed between the axial ends of the inner lateral surface and may have an axial spacing relative to these ends.
The housing parts are made for example of a weldable metal, preferably of steel or high-grade steel. As there is the possibility of welding corrosion-protected individual parts, one of the housing parts or both housing parts may, in particular already prior to the welding operation, be provided or coated entirely or partially with a corrosion protection, so that the joint after the welding operation is protected from corrosion. Suitable corrosion protection is for example a ZnNi and/or ZnFe coating, which may be applied in particular by electroplating onto the individual parts and/or housing parts.
The projection or the projections may moreover, in particular already prior to the welding operation, be formed integrally with the engagement region and may in the assembled state of the joint adjoin the inner wall of the recess, so that the second housing part is manufactured in particular by a cutting operation/ such as for example turning. The first housing part, on the other hand, may take the form of an extruded part. It is alternatively or additionally possible for the projection or the projections or some of the projections, in particular already prior to the welding operation, to be formed integrally with the first housing part, wherein this projection or these projections in the assembled state of the joint adjoin the lateral surface of the engagement region. The projection or the projections may result in the engagement region and/or the recess being no longer perfectly cylindrical. However, as the radial extent of each projection is preferably very much smaller than the outside diameter of the engagement region and/or than the inside diameter of the recess, it is still possible to speak of a cylindrical shape or a substantially cylindrical shape of the engagement region and/or the recess. The radial extent of the individual projections may in this case be of a different design in the non-assembled state of the housing parts.

Axially alongside the projection or the projections the inner wall of the recess and the outer lateral surface of the engagement region preferably have a radial spacing relative to one another, so that a direct contact between the two housing parts occurs in particular only by means of the projection or the projections. Since preferably a resistance welding method, such as for example condenser discharge welding, is used to form the welded joint, each projection forms an electrical resistance for the welding current and is heated up in such a way as to form a welded joint between the housing parts at the respective projection.
The bearing shell may be made of plastics material, such as for example POM (polyoxymethylene) or PEEK (polyetherether-ketone), and is in particular of an integral or one-piece design. In particular, the bearing shell has at the inside a hollow spherical surface or hollow part-spherical surface, which rests slidingly against the spherical surface or part-spherical surface of the bearing region. In this case, the hollow spherical surface or hollow part-spherical surface of the bearing shell may extend in axial direction across a great circle or equator lying on the spherical surface or part-spherical surface of the bearing region and in particular rests axially on both sides of the great circle or equator against the spherical surface or part-spherical surface of the bearing region.
The bearing shell preferably has on the outer circumference at least one radially outwardly extending collar, which is pressed axially between the housing parts. In this way, it is possible to realize for the bearing shell an anti-tilt and anti-rotation element, which prevents the bearing shell from tilting or twisting relative to the housing. The collar in this case is preferably of a circumferential, in particular continuously circumferential design.
Furthermore, the bearing shell at the outside may have at least one spherical surface or part-spherical surface, which in particular rests against at least one inner hollow spherical surface or hollow part-spherical surface of the housing. Preferably, the

housing has two inner hollow part-spherical surfaces, which rest against the bearing shell and are provided at the inside of the housing parts.
For low friction torque requirements, the housing parts (housing halves) may be manufactured with spherical eccentricity. Thus, defined by partially increased initial stresses small friction radii are possible. The spherical eccentricity may be realized for example in that the inner hollow part-spherical surfaces of the housing parts at least prior to assembly of the joint have a different curvature to the at least one outer spherical surface or part-spherical surface of the bearing shell.
The bearing shell is preferably under initial stress via the two housing halves, with it being possible to realize this in particular by virtue of axial pressing (e.g. hydraulically, or pneumatically) of the two housing parts towards one another. During this pressing operation the housing halves may be tightly connected and/or welded to one another, for example by condenser discharge welding (CD welding). The joint stiffness and torques may be produced with very low dispersions by means of the introduced force-controlled initial stress.
The bearing region of the joint inner part is preferably mounted slidingly in the bearing shell. Furthermore, the joint inner part may take the form of a ball pin, which has a connection region and extends at one end out of the housing. In this case, one of the housing parts may take the form of a cover or cover ring of the ball joint. Preferably, however, the joint inner part has two connection regions and extends at mutually opposite ends out of the housing, wherein the joint inner part is provided with a through-recess, which extends through the two connection regions and through the bearing region, which is disposed between the two connection regions, with the result that a ball sleeve joint is formed by the ball joint.
Between the housing and the connection region or the connection regions there may be provided in each case a bellows-type seal to prevent dirt and moisture from penetrating into the interior of the joint. In this case, the attachment of the bellows-

type seal or seals to the housing may be realized by vulcanizing one or more sheet metal rings in the respective bellows-type seal, with the result that inexpensive cold-pressed parts without additional machining are possible as a housing.
The invention further relates to a method of manufacturing a ball joint having a housing, a joint inner part, which is seated in and extends out of the housing and which with a bearing region having a spherical surface or part-spherical surface is mounted with the interposition of a bearing shell movably, in particular rotatabiy and/or pivotably, in the housing, which comprises two housing parts that are brought into engagement with one another and then welded to one another. In this case, the housing parts prior to the welding operation are braced against one another in radial direction, with simultaneous formation of an interference fit, this preferably occurring simultaneously with the bringing of the two housing parts into engagement with one another. As this ball joint is in particular a ball joint according to the invention, it may be developed in accordance with all of the described developments.
Preferably a first one of the housing parts has a recess, into which a second one of the housing parts is pressed with an engagement region, the outside diameter of which prior to the pressing-in operation is larger than the inside diameter of the recess. Furthermore, the two housing parts before and during the welding operation may be braced axially against one another so that a desired initial stress may develop in the joint and/or the bearing shell. In particular, the two housing parts are welded to one another by means of a resistance welding method, such as for example condenser discharge welding.
Conventionally the welding force is applied by a welding machine for condenser discharge welding (CD welding machine) (in plunger direction) onto the parts that are to be welded to one another, wherein the CD welding machine for applying the force may have a plunger movable in plunger direction. With the method according to the invention, however, it is possible to use the CD welding machine merely to

apply the defined initial stress in the joint and/or the initial stress of the bearing shell, wherein the welding force results in particular from the engagement factor (interference fit) of the two housing parts and/or parts being joined. Here, by the term "engagement factor" is meant in particular that, prior to the engagement of the two housing parts one into the other, the recess of the first housing part has a smaller diameter than the engagement region of the second housing part. The engaging and/or second housing part, which may also take the form of a cover or cover ring, is then pressed with an engagement factor into the receiving housing part and/or first housing part, with the strength of the connection arising as a function of the engagement factor.
The invention offers an alternative manufacturing concept with cost benefits. Functional values of the joint are moreover adjustable (for example initial stress in the joint). It is also a case of a rugged and reliable process, wherein the housing parts may be manufactured with relatively large step tolerances.
There now follows a description of a preferred embodiment of the invention with reference to the drawings. The drawings show:
Fig. 1 a cross-sectional view of an embodiment of the ball joint according to the invention,
Fig. 2 an isolated and enlarged representation of a first housing part according to Fig. 1 prior to assembly of the joint and
Fig. 3 an isolated and enlarged representation of a second housing part according to Fig. 1 prior to assembly of the joint.
Fig. 1 shows a sectional view of an embodiment of the ball joint 1 according to the invention, which takes the form of a ball sleeve joint and comprises a joint inner part in the form of a ball sleeve 2 having a first connection region 3, a bearing region 4, a

second connection region 5 and a through-recess 6. The bearing region 4 is disposed between the two substantially cylindrical connection regions 3 and 5 and is formed integrally therewith. The bearing region 4 further has a part-spherical outer bearing surface 7, by which it is mounted slidingly in a bearing shell 8, which is seated in a housing 9. The housing 9 is of a two-part construction and comprises a first housing part 10 with a cylindrical recess 11 (see Fig. 2) and a second housing part 12, which engages into the recess 11 of the first housing part 10.
The housing parts 10 and 12 each have a hollow part-spherical housing inner surface 13, 14 (see Figs. 2 and 3), against which a part-spherical outer surface 15 of the bearing shell 8 rests. The housing inner surfaces 13, 14 in this case each define a hollow part-spherical recess 17, 25 (see Figs. 2 and 3) in the housing 9. In the direction of the central longitudinal axis 16 of the ball joint 1 the two housing parts 10 and 12 have a spacing A relative to one another, into which a radially outwardly extending collar 18 of the bearing shell 8 engages, which is of a circumferential design and is axially pressed between the two housing parts 10, 12. The second housing part 12 is fastened to the first housing part 10 by two annular welded joints 19, 20, which connect the outer lateral surface 21 (see fig- 3) of the second housing part 12 to the inner wall 22 (see Fig. 2) of the recess 11.
Figs. 2 and 3 show sectional views of the first housing part 10 and the second housing part 12 prior to assembly, there being provided on the outer lateral surface 21 of the second housing part 12 two radially outwardly extending projections or elevations 23, 24 that are of a continuously circumferential, i.e. annular design. Prior to the insertion of the second housing part 12 into the cylindrical recess 11 of the first housing part 10, the outside diameter D2 of the projections 23, 24 is larger than the inside diameter Dl of the recess 11. Outside and/or axially alongside of the projections 23, 24 the outer lateral surface 21 of the second housing part 12 is of a cylindrical design and has a diameter D3 that is smaller than or equal to the inside diameter Dl of the cylindrical recess 11. The projections or elevations 23, 24 are formed integrally with the second housing part 12.

To assemble the ball joint 1, the second housing part 12 is pressed into the recess 11 with simultaneous deformation of the projections 23, 24, which consequently rest under radial initial stress against the inner wall 22 of the recess 11. Apart from the projections 23, 24 there is in particular no direct contact between the two housing parts 10, 12. After the pressing-in operation, the welding operation by means of condenser discharge welding is carried out, wherein the radial projections 23, 24 form resistors for the welding current and are heated up in such a way as to form at the radial projections 23, 24 the welded joints 19, 20 that connect the two housing parts 10,12 in a fixed manner to one another.
In a preferred construction, the outside diameter D2 of the projections 23 and 24 is not identical. To achieve a uniform application force between the first housing part 10 and the second housing part 12, the outside diameter of the inner projection 23 is designed slightly smaller than the outside diameter of the axially outer projection 24. In this way, a uniform widening of the cylindrical recess 11 in the first housing part 10 is achieved during the pressing-in operation, thereby resulting in a uniform application force at both projections 23,24.

List of reference characters

1 ball joint
2 ball sleeve
3 connection region
4 bearing region
5 connection region
6 through-recess in ball sleeve
7 bearing surface of bearing region
8 bearing shell
9 housing
10 first housing part
11 cylindrical recess in first "housing part
12 second housing part
13 housing inner surface
14 housing inner surface
15 outer surface of bearing shell
16 longitudinal axis of ball joint
17 hollow part-spherical recess of first housing part
18 collar on bearing shell
19 welded joint
20 welded joint
21 outer lateral surface of second housing part
22 inner wall of cylindrical recess
23 Projection
24 Projection
25 hollow part-spherical recess of second housing part
A spacing between housing parts
Dl inside diameter of cylindrical recess
D2 outside diameter of projections
D3 diameter of outer lateral surface

WE CLAIM:
1. Ball joint for a vehicle, having a housing (9), a joint inner part (2), which is
seated in and extends out of the housing (9) and which with a bearing region
(4) having a spherical or part-spherical surface (7) is mounted with the
interposition of a bearing shell (8) movably in the housing (9), which comprises
two housing parts (10,12) that engage one into the other and are connected in a
fixed manner to one another by means of at least one welded joint (19, 20),
characterized in that
the two housing parts (10,12) prior to formation of the at least one welded joint (19, 20) are braced against one another in radial direction, with simultaneous formation of an interference fit.
2. Ball joint according to claim 1, characterized in that at the site of the engagement of the two housing parts (10, 12) one into the other at least one projection (23) extends radially from an outer lateral surface (21) of one oi the housing parts (12) to an inner lateral surface (22) of another of the housing parts (10), at which projection the at least one welded joint (19) is formed.
3. Ball joint according to claim 2, characterized in that at the site of the engagement of the two housing parts (10, 12) one into the other at least one second projection (24) extends radially from the outer lateral surface (21) to the inner lateral surface (22), at which projection at least one second welded joint (19, 20) is formed, wherein both welded joints (19, 20) have an axial spacing relative to one another.
4. Ball joint according to claim 2 or 3, characterized in that the at least one welded joint (19) or the welded joints (19, 20) are of a continuously circumferential design.

5. Ball joint according to one of claims 2 to 4, characterized in that the at least one welded joint (19) or the welded joints (19, 20) are disposed between the axial ends of the inner lateral surface (22) and have an axial spacing relative to these ends.
6. Ball joint according to one of the preceding claims, characterized in that the integrally formed bearing shell (8) has on the outer circumference a radially outwardly extending collar (18), which is axially pressed between the housing parts (10,12).
7. Ball joint according to one of the preceding claims, characterized in that the housing (9) at the inside has a hollow spherical surface or hollow part-spherical surface (13,14) and the bearing shell (8) at the outside has a spherical surface or part-spherical surface (15), which rests against the hollow spherical surface or hollow part-spherical surface (13,14) of the housing (9).
8. Ball joint according to one of the preceding claims, characterized in that the joint inner part (2) has two connection regions (3, 5) and extends at mutually opposite ends out of the housing (9), wherein the joint inner part (2) is provided with a through-recess (6), which extends through the two connection regions (3, 5) and through the bearing region (4) that is disposed between the two connection regions (3, 5).
9. Method of manufacturing a ball joint (1) having a housing (9), a joint inner part (2), which is seated in and extends out of the housing (9) and which with a bearing region (4) having a spherical or part-spherical surface (7) is mounted with the interposition of a bearing shell (8) movably in the housing (9), which comprises two housing parts (10, 12) that are brought into engagement with one another and are then welded to one another, characterized in that

the housing parts (10, 12) prior to the welding operation are braced against one another in radial direction, with simultaneous formation of an interference fit.
10. Method according to claim 9, characterized in that the housing parts (10,12) are braced against one another in radial direction while being brought into engagement with one another.
11. Method according to claim 9 or 10, characterized in that a first one of the housing parts (10) has a recess (11), into which a second one of the housing parts (12) is pressed by an engagement region, the outside diameter of which prior to the pressing-in operation is larger than the inside diameter of the recess
(11).
12. Method according to one of claims 9 to 11, characterized in that the two housing parts (10, 12) before and during the welding operation are braced axially against one another.
13. Method according to one of claims 9 to 12, characterized in that the two housing parts (10, 12) are welded to one another by condenser discharge welding.
Dated this 24th day of February, 2009