FORM 2
THE PATENT ACT 1970 (39 of 1970)
&
The Patents Rules, 2003 COMPLETE SPECIFICATION
(See Section 10, and rule 13)
1. TITLE OF INVENTION
ARTICULATION AND/OR BEARING SYSTEM

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

ZF FRIEDRICHSHAFEN AG
GERMAN Company
8803 8 FRIEDRICHSHAFEN
GERMANY

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

Description
The invention relates to a joint and/or bearing arrangement of the type outlined in the introductory part of claim 1 and claim 12, and a motor vehicle fitted with one or more such joint and/or bearing arrangements, in particular in the chassis and/or steering system parts.
Patent specification DE 44 03 584 C2 discloses a ball and socket joint for use in steering system or chassis regions of motor vehicles, for example, and the ball and socket joint has a continuous bore by means of which it is fitted on a pin stub and secured from falling off by a crimped edge of the pin end. The parts are prevented from turning with respect to one another in this instance by a longitudinal profiling of the pin outer surface and ball inner surface. The fact of providing means to prevent turning and providing crimping involves a considerable amount of production work. The fact that it is necessary to use chromium-free corrosion protection due to requirements governing disposal, which are becoming ever more stringent, gives rise to a problem with regard to the resultant need to improve the quality of the joint ball and use an appropriate, more viscous lubricant when assembling the joint because an over-pressure occurs in the region between the joint ball and the joint shell, which can cause the joint shell, which is often made from plastic, to deform or even break.
The underlying objective of the invention is to propose joints which can specifically be made with efficient and environmentally friendly corrosion protection, which can be easily and reliably assembled.
This objective is achieved by the invention on the" basis of the joint arrangement incorporating the characterising features defined in claim 1 and by a joint arrangement incorporating the characterising features defined in claim 12, and the subject matter defined in said claims may be implemented individually or, in a particularly advantageous manner, in combination with one another, and on the basis of a motor vehicle incorporating the characterising features defined in claim 14. Advantageous
2

embodiments of the invention are defined in dependent claims 2 to 11 and 13.
The embodiment defined in claim 1 ensures that no over-pressure occurs in the space at the side opposite the axial extension of the pin and joint head or any over-pressure which does occur is reduced, so that damage to the joint shell or another component enclosing the joint head, which might occur during assembly in particular but also during subsequent operation, is reliably avoided.
If the space at the side opposite the axial extension of the pin and joint head, which is illustrated at the top in the drawings, is bounded by only the joint shell outside of these parts, the latter can be produced as a cheap, complete component, for instance as an integral injection moulded part with a uniform internal radius. Alternatively, it would also be possible to use an essentially annular-shaped joint shell, in which case it would be accommodated in a holder bounding the space.
The compensating duct or compensating ducts may advantageously serve as a means of both conveying air and conveying lubricant. This also enables the use of greases which are much less runny, which do not flow completely through the compensating ducts, even during operation over longer periods, and are therefore available for the space between the joint head and joint shell, which are subjected to high mechanical stress.
If the joint head is made from a steel with a high surface quality, in particular is treated by a nitration process, good protection against corrosion is guaranteed. In spite of the fact that additional hardness is imparted to the surface of the joint head as a result, assembly can be simplified by dispensing with means to prevent turning which would deform due to the harder joint head, and instead the joint head is secured in a press-fit seating on non-structured, round-cylindrical surface portions of the pin without further fixing means. This being the case, the surface portions may be interrupted by one or in particular several, for example four, compensating ducts, even if they are only very slim, with a radius of less than one millimetre in each case, for example.
3

In this respect, it is possible to obtain optimum adaptation to mechanical requirements and reduce the cost of the production process if the pin is made from a material subjected to a different treatment from that of the joint head, for example a high quality steel requiring no further surface treatment.
Providing the compensating duct or ducts in the pin ensures that the joint head, which is in a friction contact with the joint shell during operation and is therefore subjected to mechanical stress, is not weakened.
In particular, a plurality of compensating ducts may be recessed into the circumferential surface of the pin in the form of grooves. If the grooves are formed axially, it is also possible to make the pin by an extrusion process, which does not require finishing work involving the removal of material. Alternatively or in addition, depending on requirements, ducts may also be provided in the joint head or the joint shell, although this would mean weakening the actual joint surface if plastic shells were used.
Such a joint can be rendered better able to withstand rotation about the pin axis in the manner of a bearing as well as bending and may therefore be employed in a versatile and tolerance-compensating way, for example within chassis and/or steering system parts of motor vehicles, for example as a means of supporting pull rods and drag links connecting a respective transverse control arm to a torque arm lying transversely to the vehicle, such as needed with a so-called McPherson axle.
Other advantages and features of the invention will become apparent from an example of an embodiment of the subject matter of the invention, illustrated in the drawings and described below.
Of the drawings:
Fig. 1 is a section in elevation illustrating the joint proposed by the invention,
4

Fig. 2 is a view similar to that of Fig. 1 but showing only the pin in partial section,
Fig. 3 shows the pin illustrated in Fig. 1 with the joint head pressed on,
Fig. 4 is a view similar to that of Fig. 3 but showing only the pin in partial section,
Fig. 5 is a section along line VI-VI indicated in Fig. 4.
The joint 1 illustrated as a whole in Figures 1 and 2 comprises a pin 2, onto which a joint head 4, in this instance a joint ball, is pressed in an essentially round-cylindrical neck region 3.
The pin 2 may be made by an extrusion process requiting no removal of material and is made from a high-quality steel, for example, in this instance 32CrB4 steel, requiring no separate treatment to improve surface quality. The joint head 4, which is separate prior to assembly, may likewise be produced easily and inexpensively without processes
involving the removal of material and in this instance has a flattened spherical shape at two oppositely lying surfaces with a continuous bore extending transversely to the flattened regions by means of which it engages round the pin 2 in the assembled position. Other external shapes of the joint head would also be possible to meet different requirements, for example a round-cylindrical or frustoconical shape. The joint head 4 may be subjected to a surface treatment to render it better able to withstand stress caused by the friction contact with the surrounding joint shell 5 over longer periods of operation and in particular impart good resistance to corrosion. It is made from a 38MnB5 steel, for example, and in this instance is also subjected to an additional
salt bath nitration process. A different nitration process or any other surface treatment
would also be possible. As a result of the very good corrosion protection of the surface of the joint head 4 obtained due to nitration, its surface is made harder, and a means for preventing turning of the type used in the prior art when assembling the joint head and
pin would deform, if the pin were not also hardened, thereby incurring additional costs.
Consequently, in one embodiment of the invention, the harder joint head 4 is retained in
5

a press-fit seating on round-cylindrical surface portions 16 of the pin 2, and the pressure applied to produce the press-fit is high enough to obviate the need for additional fixing means, such as crimping the pin end.
For typical applications in the chassis and steering system region of motor vehicles, the diameter of the pin 2 in its neck region 3 retaining the joint head 4 is from nine to approximately fifteen millimetres in the embodiment illustrated as an example and may diverge in a conical arrangement in its shoulder region 6 remote from the joint head 4 in order to increase strength, for example.
When the parts are in the assembled state, the joint head 4 is held on the neck region 3 of the pin 2 in the press-fit seating so that it can not be dislodged and can move relative to a surrounding joint shell 5, which is made from plastic to minimise weight and costs, and the movement may be both a pivoting movement in the direction indicated by arrows 7 or 8 or also a rotation about the axis 9 of the pin 2. Consequently, such a joint arrangement acts in a manner akin to a type of bearing and, this being the case, is also generally referred to as a joint and/or bearing arrangement. The joint shell 5 is enclosed by a steel ring 10 in order to impart strength and provide a connection to other parts, for
example steering rods, pull rods and/ or drag links or similar. The joint 1 as a whole is encased by a seal 11 so that the pin 2 is also not accessible from outside with the exception of an accessible fixing end 12, for example a screw head, and lubricant is not able to escape. As an alternative to a closed joint shell 5, another option is to use an essentially annular-shaped joint shell, in which case it would not only be accommodated in an annular holder (steel ring 10) but also in a holder completely bounding the space 13 outside the axial extension of the pin 2 and the joint head 4.
The space 13 between the joint head 4 and the joint shell 5 is at least partially filled with a lubricant, the purpose of which is to reduce friction between contact surfaces of the joint head 4 and joint shell 5. The lubricant may be specifically provided for the entire anticipated service life of the joint 1. To this end, a viscid and only slightly free-flowing lubricant is used.
6

The space 13 disposed between the joint head 4 and the joint shell 5 surrounding it communicates with a space 14 on the other side of the joint head 4 by reference to the axial extension of the pin 2 by means of a - or as illustrated here - several compensating ducts 15. In the embodiment illustrated as an example, four identical compensating ducts 15 are provided as a means of connecting the spaces 13 and 14, uniformly distributed around the external circumference of the neck region 3. They are grooves in the circumferential surface of the pin 2, recessed into its neck region 3, and respectively extend axially in a straight line, with a radius of slightly less than one millimetre in this instance, whilst the total diameter of the neck region 3 is approximately nine
millimetres. Another layout such as a spiral or waved pattern would also be possible.
The number of ducts 15 is likewise variable - depending on the viscosity of the lubricant and the cross-sectional surface of the respective duct 15. The ducts 15 may accommodate an additional quantity of lubricant and/or direct an over-pressure occurring between the shell 5 and joint head 4 during assembly away to the space 14. The low flow capacity of the grease ensures that it cannot simply run completely through the ducts 15 and get into the space 14.
As an alternative to ducts 15 distributed about the circumference, it would also be possible to provide an axial central bore in the pin 2 with ducts leading transversely outwards into the space 14. As an alternative or in addition, one or more ducts could also be provided in the joint head 4, for example. As a rule, however, the latter is subjected to high stress in a small area and it is therefore more practical for the material of the pin 2 to be weakened than that of the joint head 4. In any event, damage to the thin-walled bearing shell 5 during assembly or subsequent operation, for example due to a temperature increase, causing an over-pressure of lubricant or air is prevented by the at least one compensating duct 15.
With the exception of the grooves 15, the neck region 3 has a totally round-cylindrical external circumference 16, as may be seen from the view in cross-section shown in Fig. 5, for example. The joint head 4 can therefore be retained in a press-fit seating on the
7

non-structured surface portions 16 between the grooves 15, as mentioned above, without having to provide any profiling here. This also means that a joint head 4 that is significantly harder than the pin 2 can be fitted.
If, as illustrated here, the grooves 15 extend axially on the pin 2 and extend into the region where the parallel-walled neck region 3 merges with the conically diverging shoulder region 6, the strength of the pin 2 is higher than a pin that is otherwise of the same type but without grooves 15 on exposure to bending stress about its axis 9, as may be demonstrated by FEM calculations. The improvement obtained using the materials and dimensions specified here is in the order of just short of ten percent.
8

List of reference numbers

1. Joint
2. Pin
3. Neck region
4. Joint head
5. Joint shell
6. Shoulder region
7. Pivot direction
8. Pivot direction
9. Axis
10. Steel ring
11. Seal
12. Fixing end
13. Space
14. Space
15. Compensating duct
16. Surface portions
9

WE CLAIM:
1. Joint and/or bearing arrangement (1) comprising a pin (2) and a separate joint
head (4) which can be retained thereon and engages around certain regions of
the pin (2) at least close to its axial end,
characterised by
at least one compensating duct (15) which links a space (13) disposed at least essentially outside the axial extension of the pin (2) and the joint head (4) to a space (14) disposed on the opposite side of the joint head (4) by reference to the axial extension of the pin (2).
2. Joint and/or bearing arrangement as claimed in claim 1,
characterised in that
the space (13) disposed at least essentially outside the axial extension of the pin
(2) and the joint head (4) is completely bounded by the surrounding joint shell (5) outside of the joint head (4) and the pin (2).
3. Joint and/or bearing arrangement as claimed in one of claims 1 or 2,
characterised in that
the joint head (4) is made from a steel with a high surface quality.
4. Joint and/or bearing arrangement as claimed in claim 3,
characterised in that
the joint head (4) is treated by means of a nitration process.
5. Joint and/or bearing arrangement as claimed in one of claims 3 or 4,
characterised in that
the pin (2) is made from a material that is treated differently from that of the joint head (4).
6. Joint and/or bearing arrangement as claimed in one of claims 1 to 5,
10

characterised in that
the at least one compensating duct (15) serves as a pressure compensating means.
Joint and/ or bearing arrangement as claimed in one of claims 1 to 6,
characterised in that
the at least one compensating duct (15) serves as a means of directing lubricant.
Joint and/or bearing arrangement as claimed in one of claims 1 to 7,
characterised in that
at least one compensating duct (15) is provided in the pin (2).
Joint and/or bearing arrangement as claimed in one of claims 1 to 8, characterised in that
a plurality of compensating ducts (15) is recessed into the circumferential surface (16) in the neck region (3) of the pin (2) in the form of grooves.
Joint and/or bearing arrangement as claimed in claim 9,
characterised in that
the grooves (15) extend axially.
Joint and/or bearing arrangement as claimed in one of claims 1 to 10,
characterised in that
it is able to withstand stress both due to rotation about the pin axis and due to bending.
Joint and/ or bearing arrangement (1) comprising a pin (2) and a separate joint head (4) which can be retained thereon and engages around certain regions of the pin (2), in particular as claimed in one of claims 1 to 11,
characterised in that
at least the surface of the joint head (4) is made from a harder material than the
11

pin surface and the joint head (4) is retained in the press-fit seating on non-structured, round-cylindrical surface portions (16) of the pin (2) without further fixing means.
13. Joint and/or bearing arrangement as claimed in one of claims 1 to 12,
characterised in that
it is sealed by means of a seal (11) enclosing the two spaces (13; 14) linking the at least one compensating duct (15) and is lubricated for a calculated service life.
14. Motor vehicle fitted with at least one joint and/or bearing arrangement (1) as
claimed in one of claims 1 to 12, in particular within chassis and/or steering
system parts.
Dated this 2nd day of March, 2007

12

ABSTRACT
In a joint and/or bearing arrangement (1) comprising a pin (2) and a separate joint head (4) which can be retained thereon and engages round certain regions of the pin (2), at least one compensating duct (15) links a space (13) disposed between the joint head (4) and a surrounding joint shell (5) to a space (14) disposed on the opposite side of the joint head (4) by reference to the axial extension of the pin (2).
To,
The Controller of Patents,
The Patent Office,
Mumbai
13
Figure 1