FORM 2
THE PATENT ACT 1970 (39 of 1970)
&
The Patents Rules, 2003 COMPLETE SPECIFICATION See Section 10, and rule 13
TITLE OF INVENTION
RADIAL JOINT, AND METHOD FOR THE PRODUCTION OF SUCH A RADIAL
JOINT FOR A MOTOR VEHICLE

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

ZF FRIEDRICHSHAFEN AG GERMAN Company
88038 FRIEDRICHSHAFEN GERMANY

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


ENGLISH TRANSLATION VERIFICATION
CERTIFICATE u/r. 20(3)(b)
I, Mr. HIRAL CHANDRAKANT JOSHI, an authorized agent for the applicant, ZF FRIEDRICHSHAFEN AG do hereby verify that the content of English translated complete specification filed in pursuance of PCT International application No. PCT/ DE2007/ 000443 thereof is correct and complete.


The invention relates to a radial joint for a motor vehicle according to the preamble of claim 1 and to a method for the production of such a radial joint.
In the case ot ball joints, a distinction is drawn between axial joints and radial joints. This distinction is determined by the respective direction of engagement of the forces acting on the ball journal. The position of the non-deflected ball journal serves as a reference for this definition of the differing ball joints. Accordingly, the main loading of an axial joint lies in the direction of the longitudinal centre axis of the ball journal, whereas the main loading in the case of a radial joint acts transversely to the longitudinal centre axis of the ball journal. These types of joint thus differ fundamentally from one another with regard to the loads acting on them and thus also in terms of construction. In particular, the embodiment of the housing and the material which can be used for the housing are different.
Thus, a special feature in the case of axial joints is to mount the ball journal with its joint ball in the housing in such a way that said ball journal cannot become detached from the housing in the event of loading along its longitudinal centre axis, i.e. in the axial direction. This "pull-out" force" of the axial joint is a decisive variable and a basic quality criterion of an axial joint. In the case of radial joints, the ball journal is loaded via forces acting on said ball journal radially to its longitudinal centre axis. As a result, the pull-out force.of the ball journal is lower than in the case of axial joints, and this decisively influences the embodiment of the housing.
Irrespective of the design of the ball joint in question, considerable efforts are made to allow these joints to be produced cost-effectively. Costly machining processes to be carried out on the joint to be produced should in this regard be avoided wherever possible.
For the aforementioned reason, DE 197 55 020 Al specifies an axial joint and also a method for mounting an axial joint of this type. The axial joint consists of a one-piece metallic housing which is open on one side and through the opening of which a ball
-2-

journal can be inserted into an interior of the housing, the joint ball of the ball journal being pivotably and rotatably mounted in a bearing region of the interior. A journal portion, which is connected to the joint ball, of the ball journal protrudes from the housing through the opening of the housing. The ball journal is fixed within the housing by cold forming of the edge region of the opening of the housing in the direction toward the ball journal. A bearing shell, which is preferably made of a plastics material/metal composite material, is arranged between the joint ball of the ball journal and the interior of the housing. As a result of the forming of the edge region of the opening of the housing, the bearing shell, which prior to the forming of the housing has a circularly cylindrical opening cross section for insertion of the joint ball, is also formed in such a way that this opening-side edge region of the bearing shell rests against the joint ball. Owing tp the simple configuration of the housing, it is possible to produce the housing for this axial joint overall by a cold forming method. As a result, this axial joint can be manufactured very cost-effectively.
In addition, a radial joint which is produced overall by a cold forming method is known from DE 195 36 035 Al. However, this radial joint has a housing which is open on both sides, thus necessitating machining of the contact region of the lid. In addition, the radial joint has a straight and very simply shaped shaft. If, however, for example the housing has a shaft with an offset bend or if the other geometrical formations of the housing are required, the cold forming method quickly reaches its limits. In addition, the cold forming method requires a relatively soft material, for which reason for example a low-strength steel material such as C45 is used in order to produce the housing therefrom. This relatively low strength of the housing material has to be compensated for in terms of design. However, this means an increased use of material and accordingly also an increased weight of joints of this type.
For radial joints, a cold forming process cannot be used when said joints have a very complicated housing geometry and, owing to the installation conditions in the motor vehicle, a shaft having marked radii of curvature. For the aforementioned reason,
-3-

radial joints of this type have to date been produced by means of a hot forming method and have subsequently to be machined at great cost in order for example to produce the interior for the introduction of the ball journal, to attach the connection region for fastening the lid which is required to close the housing, or a groove for receiving a sealing bellows edge on the joint housing. Owing to the fact that the manufacture of a housing blank, produced by a hot forming method, for a radial joint requires a plurality of machining operations and in addition a plurality of clamping processes in the machining system, this gives rise to considerable costs which overall make the production process unnecessarily expensive. This basic drawback has already been described for the hot forming method in DE 195 36 035 Al. As the material for radial joint housings produced by means of a hot forming method, use is made of steels such as 30MnSiV6 which have a much higher strength (for example 950 N/mm2) compared to the aforementioned material C45.
As previously used radial joints, including that disclosed in DE 195 36 035 Al, conventionally have a housing which is open on both sides, the side of the housing that opposes the opening must subsequently be closed by a lid. During the use of a radial joint of this type, for example mechanical damage to the lid region can lead, in operation of the motor vehicle in winter, to aggressive media such as brines producing a formation of rust in the region of the lid. However, this can cause non-tightness and thus falling-out of the radial joint. For this reason, although the housings which are open on both sides have in the past been required in the case of radial joints, they are not without drawbacks. In addition, there is the circumstance that the machining of the lid bearing surface and the machining of the opposing opening for using the ball journal and also of the region for resting the sealing bellows edge against the housing require a plurality of successive clamping processes for machining the radial joint housing. This time-consuming clasping of the workpiece is also associated with corresponding production costs which are not desirable.
-4-

The invention is based on the object of providing a radial joint and a method for the production of a radial joint of this type which has a simple construction and can thus be produced cost-effectively.
The invention achieves this object set by the features of independent claims 1 and 15. Further configurations of the invention are represented in the ensuing sub-claims.
A radial joint for a motor vehicle with a one-piece metallic housing, through the opening on one side of which a ball journal can be inserted into an interior of the housing, the joint ball of the ball journal being pivotably and rotatably mounted in a bearing region of the interior and a journal portion, which is connected to the joint ball, of the ball journal protruding from the housing through the opening of the housing, is according to the invention developed in such a way that the housing has in the region of its opening a portion which is produced by machining and can be shaped by a cold forming method.
A basic aspect of the present invention consists in the fact that the housing has merely one portion in the region of the opening of the housing, the cross section of which portion is altered once by machining in such a way as to allow a subsequent cold forming process of this portion for the manufacture of the housing.
The radial joint can thus be produced simply and very cost-effectively. The machining of the outer portion of the joint housing in the case of a radial joint according to the invention permits likewise the attachment of the edge region of sealing bellows sealing the radial joint without a further operation being required for this purpose. Thus, the radial joint housing according to the invention can be machined overall with only one machining operation. Complex and cost-intensive clasping of the workpiece is no longer required. The previously required lid may be dispensed with, whereby at least one additional component could be saved.
-5-

The radial joints according to the invention are suitable for use in the region of the wheel suspension of motor vehicles. Preferred however is a use as a radial joint for a track rod.
Furthermore, a first development of the invention provides a radial joint which has a simple construction and can thus be produced and mounted cost-effectively. A basic advantage of this radial joint consists in the fact that the housing can be produced overall by a hot forming method. Complex housing geometries thus no longer present a problem.
In addition, a further advantage of the invention consists in the fact that, as a result of the hot forming method, the housing has high strength stemming on the one hand from the more high-strength material which is used and on the other hand from the method itself, as the structure of the steel changes during the machining of the material. However, this again enables the housing to be configured for example with smaller cross sections than in the case of previously known radial joints.
As a result of the higher strength of the material of the housing of the radial joint, with a substantially smaller metallic cover, comparatively high pull-out forces of the ball journal are achieved as in embodiments of joints according to the prior art. The metallic cover between the outer diameter of the joint ball and the inner diameter of the opening of the housing is in this case a measure of the ball journal pull-out force to be achieved.
In accordance with one configuration of the invention, the hot forming method can be a forging process. This forging process allows radial joint housings of any desired cross section and any desired configuration to be produced, i.e. even complex geometries are thus achievable.
In order to close the housing, the portion, the cross section of which has been reduced once by machining, in the edge region of the opening of the housing is
-6-

shaped by cold forming. Prior to forming thereof, the portion has a circularly cylindrical cross section.
After the forming, an opening remains in the housing, through which the ball journal protrudes from the housing. This opening has a circularly annular cross section. Thus, a radial joint of this type allows maximum angles of deflection to be achieved in each direction of deflection of the ball journal, i.e. the ball journal can be swivelled in any desired manner about the centre point of the joint ball. Accordingly, the pivoting range of the ball journal is maximised in the case of a radial joint according to the invention.
In addition, the shape of the opening can also have an oval geometry after forming, thus allowing differing angles of deflection to be achieved in various directions of alignment of the ball journal. Oval geometry can for example be achieved if there are already provided in the region of the housing opening on the housing unmachined part accumulations of material which after forming allow a non-round cross section of the opening.
In order to ensure a sufficient pull-out force, i.e. sufficient securing of the ball journal within the formed housing, the diameter oi the joint ball is larger after the joint mounting than the diameter of the remaining opening of the housing. The metallic cover between the outer diameter of the joint ball and the inner diameter of the opening of the housing is a measure of the ball journal pull-out force to be achieved.
In addition, it is of considerable advantage if a radial joint according to the invention has in the interior of the housing a movably mounting bearing shell which receives the joint ball. A bearing shell of this type allows the properties of the radial joint to be decisively influenced. For example/ this allows vibration dampening to be achieved. In accordance with one configuration of the invention, the bearing shell can be made of differing materials. The selection of the suitable material depends on the intended property of the bearings of the ball journal. Thus, the bearing shell can
._7-

for example be made of plastics material, a plastics composite material, a multicomponent material or at least partly of a plastics material/metal composite material.
In addition, depending on the geometry of the joint and the parameters to be achieved, it is beneficial if'the bearing shell has a support flange which is supported on a flange which is present in the interior of the housing and corresponds to the support flange. This allows the bearing forces acting via the housing or the journal to be optimally supported. The properties of the radial joint according to the invention can thus be optimised.
As previously stated, a housing according to the invention, produced by a hot forming method, [or a radial joint can also have complex geometries. In many cases, a shaft is formed integrally with a housing of this type. According to one configuration of the invention, this shaft can also have an offset bend or a plurality of offset bends. The term "an offset bend" refers in this case to a formation deviating from the rectilinear longitudinal centre axis of the shaft. In addition, it is important in terms of production if the housing and the shaft are produced jointly by means of a hot forming method, such as for example a forging method. This considerably reduces the costs oi producing a housing of a radial joint according to the invention.
However, in order to produce for example a modular system, it can also be beneficial to produce the shaft and the housing separately. The shaft and the housing are then joined together for example by means of a material-uniting connection. It is thus possible to produce a system of uniform, standardised components which can be combined with one another in accordance with the demands placed on the radial joint. Such a measure also allows the production costs to be reduced considerably.
In accordance with one configuration of the invention, a cold extrusion method is preferably used for the cold forming method. Corresponding manufacturing plants are available for this purpose.
-8-

The method according to the invention for the production of a radial joint of the embodiment described hereinbefore includes the following method steps:
producing the housing blank,
machining the portion close to the opening of the housing,
inserting the joint ball of the ball journal into the interior of the housing,
cold forming the opening-side portion of the housing until there is provided between the joint ball and the housing a metallic cover which ensures sufficient pull-out resistance for the joint to be produced and a positive connection is provided between the mutually contacting components.
The specified method for the production of a radial joint allows the radial joint to be produced in just a few operating steps. It is crucial in this regard that a controlled metallic cover can be produced for achieving a predefined pull-out resistance and a secure positive connection of the contacting components can be produced. The quality of the radial joints produced by means of such a method is significantly improved over known embodiments from the prior art. The reductions in cost already mentioned at the outset are considerable.
In order to achieve the specified metallic cover, the diameter of the joint ball after the joint mounting should be larger than the remaining opening of the housing. This very easily checkable quality criterion is measurable during the production process. During the production of the radial joint according to the invention, the housing is shaped with periodic or permanent force and/or pressure measurement. As a result of this periodic or permanent force and/or pressure measurement, the parameters of the radial joint according to the invention can be adjusted exactly and ensured at all times. This produces low frictional moments between the components which are able to move relative to one another.
-9-

This can also be achieved by a further configuration of the specified method, which configuration can consist in the housing being closed with periodic or permanent measurement of the torque required for deflection and/or rotation of the ball journal. As a result, the friction values of the radial joint are optimally set after manufacture thereof, so that the required quality criteria can be met by a method of this type for a radial joint and in cases of doubt can also be demonstrated. This demonstrability is increasingly being demanded by persons purchasing radial joints of this type. The radial joints of the design in question are safety components in a motor vehicle, so that the quality control described hereinbefore is highly important. It is therefore also not immaterial that the radial joint can be closed in a monitorable manner in accordance with the method steps mentioned hereinbefore.
In accordance with one development of the specified method according to the invention, the joint ball can be inserted, together with a bearing shell receiving said joint ball, into the interior of the housing. The forming of the opening-side portion of the housing is in this case accompanied by the forming of the opening-side portion of the bearing shell. The opening-side region of the bearing shell has, prior to forming thereof, a predominantly circularly cylindrical geometry. This allows the bearing shell to rest optimally against the surface of the joint ball during the closure of the housing. If this procedure is combined with the measuring method mentioned hereinbefore, a radial joint manufactured in this way is optimised, both with regard to its tolerances and with regard to the movability of the components and satisfies the most stringent requirements for convenience, despite the fact that it wTas produced cost-effectively by simple manufacture.
The invention will be described hereinafter in greater detail with reference to the appended drawings. However, the exemplary embodiment shown does not entail restriction to the illustrated variant, but rather serves merely to explain a principle of the invention. In this case, identical or similar components are denoted by the same reference numerals. In order to be able to illustrate the mode of operation according to the invention, the figures also show merely highly simplified schematic diagrams
-10-

from which components which are not essential to the invention have been omitted. However, this does not mean that such components are not present in a solution according to the invention.
In the drawings:
Figure 1 is a cross section through a detail oi a radial joint according to the invention;
Figure 2 is a simplified sequence plan for the production of a radial joint according to the invention;
Figure 3 is a cross section through a first variant embodiment of a housing for a radial joint according to the invention; and
Figure 4 shows a further variant embodiment of a housing for a radial joint-according to the invention.
The view showed in Figure 1 of a partial cross section through a radial joint according to the invention displays a housing 1 which in the present case was produced overall, i.e. together with the shaft 11, by means of a hot forming method. In the present case, the housing was produced by a forging method. The cup-shaped housing is provided with an opening 2 on one side. On the side opposing the opening 2, the housing is configured so as to be closed. As no opening is provided in this region, the introduction of a lid, which' is complex to produce and to mount, on the side opposing the opening 2 may be dispensed with. A ball journal 3 is introduced into the interior 4 of the housing through the opening 2 of the housing 1. A bearing shell 8 made oi plastics material is present between the wall of the interior 4 and the joint ball 5 of the ball journal 3. This bearing shell 8, which is equipped with damping properties, surrounds the joint ball 5 of the ball journal 3 almost completely. The bearing shell has in the region of the opening 2 of the housing 1 also an opening through which the journal 6 of the ball journal 3 protrudes. In addition,
- 11 -

the opening 2 of the housing 1 determines the swivelling range of the ball journal 3, i.e. the measure of the possible deflection of the ball journal 3 around the centre point of the joint ball 5. A portion 7, which is present on the outside of the housing 1, was brought in advance by means of machining to the required dimension in preparation for the carrying-out of the cold forming method. This portion 7 of the housing 1, which prior to the forming is circular cylindrical, is formed in the direction toward the ball journal 3 during the production process of the housing. The forming is carried out by means of a cold forming method. Sealing bellows 14, into the housing-side edge region of which a clamping ring 15 is vulcanised, are arranged on the outside of the housing in the region of the portion 7. The sealing bellows 14, which are made of elastomer material, preferably of rubber, rest at their other end, opposing the clamping ring 15, in the region of the journal 6 against the ball journal 3 as to produce a direct seal.
The ball journal 3 also has a journal neck 16 formed roughly in the region of the opening 2 of the housing. In the lower region, opposing the opening 2 of the housing 1, the housing has a flange 10 which is inclined toward the longitudinal centre axis of the non-deflected ball journal 3. A support flange 9 of the bearing shell 8 is supported on this flange 10 of the housing 1.
Figure 2 is a sequence plan which is intended to illustrate in a simplified manner the production process for producing a radial joint according to the invention. In this case, a housing blank 1 is first produced by means of a forging process. This housing blank 1 has an interior 4 and an opening 2 and possesses tolerance-related dimensions, compared to the manufactured housing.
In the subsequent step, a portion 7 is produced by a single machining operation carried out on the opening-side portion of the housing 1. It is possible to carry out in this machining operation also surface machining of the interior 4 of the housing 1, although this operation is not absolutely necessary.
-12-

The subsequent method step consists in attaching the bearing shell 8, which on the opening side initially has a circular cylindrical geometry, to the joint ball 5 of the ball journal 3. The resulting constructional unit, consisting of the ball journal 3 and bearing shell 8, is inserted into the interior 4 through the opening 2 of the housing 1.
In the next operation, the edge region 7 of the housing 1 is shaped by a cold forming method. The portion 7 of the housing 1 is in this case moved toward the ball journal 3 in the direction of arrows A and B as indicated in Figure 2. During this cold forming method of the portion 7 of the housing 1, the corresponding, opening-side portion of the bearing shell 8 is formed at the same time, so that the bearing shell rests against the joint ball 5. This closure process of the housing is assisted by a measurement of the forces which are applied to the portion 7 of the housing 1, which measurement is taken during the forming. Furthermore, the moment required for deflecting the ball journal 3 around the centre point of the joint ball 5 is periodically detected. Thus, the predetermined joint parameters can be adapted during the closure of the housing very precisely to the demands placed on the joint.
In a concluding operating step, the opening 2 of the housing 1 is closed by sealing bellows 14 which in the present case have a vulcanised-on clamping ring 15 only on one side in the region of the portion 7 of the housing 1. The clamping ring 15 causes the sealing bellows 14 to be pressed against the housing 1, thus producing an optimised seal at this location. The opposing end of the sealing bellows 14 rests against the ball journal 3 so as to produce a seal. As may be seen from the view in Figure 2, the shaft 11 of the housing 1 has an offset bend 12. This offset bend is produced together with the housing blank by the hot forming method (forging process).
Figure 3 is a cross section of a first variant embodiment of a housing 1 of a radial joint according to the invention. This shows the shaft 11 which is formed in one piece with the housing 1, the interior 4 provided within the cup-shaped housing 1 for subsequently receiving the bearing shell 8 with the ball journal 3, and also the
- 13-

opening 2 provided for this purpose in the housing 1. On the opening-side outer surface of the housing 1, the housing has a portion 7 which is produced by machining and, owing to the machining, is suitable to be shaped by a cold forming method in order thus to allow the joint to be closed as described hereinbefore.
In addition, Figure 4 shows a further, very simple embodiment of a housing 1 for a radial joint according to the invention. The housing is in the" present case not formed in one piece, but rather consists of a plurality of individual parts which can be joined together in the sense of a module. Thus, this housing 1 has a separate shaft 11 with an offset bend 12. The housing 1 and the shaft 11 are connected by means of a weld seam 17. As also in the case of the exemplary embodiments described hereinbefore, the housing 1 is equipped with the portion 7, which was produced by machining, and possesses an interior 4 and also an opening 2 which is suitable for introducing the ball journal 3. Furthermore, this view shows the flange 10 of the housing 1 on which a corresponding support flange 9 of the bearing shell 8 (not shown in this case) rests.
- 14-

List of reference numerals
1. Housing
2. Opening
3. Ball journal
4. Interior
5. Joint ball
6. Journal
7. Portion of the housing
8. Bearing shell
9. Support flange
10. Flange
11. Shaft
12. Offset bend
13. Cover
14. Sealing bellows
15. Clamping ring
16. Journal neck
17. Weld seam

-15-

CLAIM:
1. Radial joint for a motor vehicle with a one-piece metallic housing (1) which is open on one side and through the opening (2) of which a ball journal (3) can be inserted into an interior (4) of the housing (1), the joint ball (5) of the ball journal (3) being pivotably and rotatably mounted in a bearing region of the interior (4) and a journal portion (6), which is connected to the joint ball (5), of the ball journal (3) protruding from the housing (1) through the opening (2) of the housing (1), characterised in that the housing (1) has in the region of its opening (2) a portion (7) which is produced by machining and can be shaped by a cold forming method.
2. Radial joint according to claim 1, characterised in that the housing is produced by means of a hot forming method.
3. Radial joint according to claim 2, characterised in that the hot forming method is a forging process.
4. Radial joint according to any one of the aforementioned claims, characterised in that the housing (1) can be closed by cold forming of the initially circularly cylindrical portion (7) which is present in the region of the opening (2) of the housing (1).
5. Radial joint according to any one of the aforementioned claims, characterised in that the opening (2) of the housing (1) has a circular or oval geometry once said housing is closed.
- 16-

6. Radial joint according to any one of the aforementioned claims, characterised in that the diameter of the joint ball (5) is larger after the joint mounting than the remaining opening (2) of the housing (1).
7. Radial joint according to any one of the aforementioned claims, characterised in that a movably mounting bearing shell (8) which receives the joint ball (5) is inserted into the interior (4) of the housing (1).
8. Radial joint according to claim 7, characterised in that the bearing shell (8) is made of plastics material, a plastics composite material, a multicomponent material or at least partly of a plastics material/metal composite material.
9. Radial joint according to either claim 7 or claim 8, characterised in that the bearing shell (8) has a support flange (9) which is supported on a flange (10) which is present in the interior (4) of the housing (1) and corresponds to the support flange (9).
10. Radial joint according to any one of the aforementioned claims, characterised in that a shaft (11) is present on the housing (1).
11. Radial joint according to claim 10, characterised in that the shaft (11) has an offset bend (12).
12. Radial joint according to either claim 10 or claim 11, characterised in that the housing (1) and the shaft (11) are jointly produced by means of a hot forming method.
13. Radial joint according to either claim 10 or claim 11, characterised in that the shaft (11) is welded onto the housing (12).
- 17-

14. Radial joint according to any one of the aforementioned claims, characterised in that the cold shaping method is a cold extrusion method.
15. Method for the production of a radial joint according to any one of the aforementioned claims, characterised by the methods steps:
producing the housing blank,
machining the portion (7) close to the opening (2) of the housing (1),
inserting the joint ball (5) of the ball journal (3) into the interior (4) of the housing (1),
cold forming the opening-side edge portion of the housing (1) until there is provided between the joint ball (5) and the housing (1) a metallic cover (13) which ensures sufficient pull-out resistance for the joint to be produced and thus allows a positive connection between the mutually contacting components.
16. Method according to claim 15, characterised in that the housing (1) is closed with periodic or permanent force and/or pressure measurement.
17. Method according to either claim 15 or claim 16, characterised in that the housing (1) is closed with periodic or permanent measurement of the torque required for deflection and/ or rotation of the ball journal (3).
18. Method according to any one of claims 15 to 17, characterised in that the joint ball (5) is inserted, together with a bearing shell (8) receiving said joint ball, into the interior (4) of the housing (1) and the forming of the edge portion of the opening (2) of the housing (1) also causes forming of the opening-side
-18-

portion of the previously predominantly circularly cylindrically shaped bearing shell opening.
19. Method according to claim 18, characterised in that the bearing shell (8) rests against the surface of the joint ball (5) during the closure of the housing (1).
-19-
Dated this 11th day of August, 2008