FORM 2
THE PATENT ACT 197 0 (39 of 1970)
&
The Patents Rules, 2003 COMPLETE SPECIFICATION (See Section 10, and rule 13)
1. TITLE OF INVENTION
AXIAL BALL JOINT WITH IMPACT DAMPING MECHANISM
2. APPLICANT(S)
a) Name : ZF FRIEDRICHSHAFEN AG
b) Nationality : GERMAN Company
c) Address : 8 8 038 FRIEDRICHSHAFEN
GERMANY
3. PREAMBLE TO THE DESCRIPTION
The following specification particularly describes the invention and the manner in which it is to be performed : -

The invention relates to an axial ball joint, in particular for use on a steering gear, consisting of a housing open on one side, with a housing pin arranged at the front, a joint ball with a joint pin and a bearing shell arranged between housing and joint ball.
Similar axial ball joints are generally known and are used in particular in the area of vehicle steering systems, such vehicle steering systems each having a limit stop in the region of the maximum deflection. If the steering is brought in each case into the region of the limit stop, the mechanical limitation of the steering excursion leads to a hard impact of the steering in the stop region. This problem has been known for quite a long time and attempts have therefore being made to develop an impact damping of such steering systems. By way of example, reference is made in this regard to the documents EP1122 149 Al, US 5,788,009, DE 600 01 626 T2, DE 697 25 931 T2, EP 1 429 951 Bl and JP 08-133102 A. All of these documents describe steering drives having damping systems for impact damping of the steering drives. However, the damping systems described therein are in each case arranged on the propeller-shaft side and/or on the steering-gear housing in a relatively complicated manner.
It is therefore the object of the invention to find an impact damping for an axial ball joint, which damping is to be integrated into a vehicle steering system in a simple manner.
This object is achieved by the features of the independent claim. Advantageous configurations are set out in the subclaims and the description.
The inventors have discovered that the design of a vehicle steering system with impact damping can be considerably simplified if the damping element required for this is arranged on the axial ball joint itself, in particular if an elastic damping element for impact damping is integrated on the housing side of the housing of the axial ball joint provided with a housing pin.

According to this basic idea, the inventors propose an axial ball joint, in particular for use on a steering gear, consisting of a housing open on one side, with a housing pin arranged at the front, a joint ball with a joint pin and a bearing shell arranged between housing and joint ball, the improvement according to the invention lying in the fact that the housing has at least one elastic damping element for impact damping on the housing side of the housing provided with a housing pin.
By virtue of this embodiment of the axial ball joint, it is possible to avoid a complex construction of a steering gear or a relatively complex assembly of a vehicle steering system, since the damping of the vehicle steering system or the steering gear is achieved merely by using an appropriately configured axial ball joint.
In an advantageous configuration of the invention, the inventors propose that the damping element is of annular configuration, a housing surface unprotected and set back rearwards in relation to the at least one annular damping element preferably being formed between the annular damping element and the housing pin. The result of this is that, in the event of impact of the steering at the maximum deflection or some other sudden heavy loading of the steering, first of all the damping element responds, but in the event oi too great a loading a metal stop surface, namely the unprotected housing surface, is again available. The result of this is that the elastic damping element cannot be destroyed by excessive compression.
Advantageously, such an annular damping element can be inserted in a step on the housing side of the housing provided with a housing pin, or there is also the possibility of providing a groove on the housing side of the housing provided with a housing pin and inserting the annular damping element therein.
The damping element can consist at least partly of an elastomer. For example, the annular damping element can be produced from a plastic ring and an elastomer injection-moulded onto it. In this case, it is advantageous if the plastic ring contributes to the dimensional stability of the damping element and simple

clamping of the plastic ring onto the housing is achieved, while the moulded-on elastic elastomer performs the actual damping work.
The annular damping element can, for example, be vulcanised directly onto the housing. However, there is also the possibility of adhesively bonding or pressing this annular damping element directly onto the housing,
Sufficient elasticity of the damping element can also be achieved by a plastic ring being of spring design, that is to say, for example, when the plastic ring is seen in axial section, a kind of v-shaped configuration or V-shaped configuration of the plastic ring can be produced, so that a pressing-together with elastic deformation of the plastic ring is possible. The plastic ring then acts in the manner of a spring.
In addition, the annular damping element can also receive a metal insert which, on the one hand, ensures firmer seating of the annular damping element in a groove or on a step on the housing. On the other hand, this nietal insert can also act as an additional spring component which ensures a two-stage elasticity of the damping element if desired.
With regard to better and firmer seating of the annular elastic damping element, the step or the groove can additionally have an undercut, for example in the form of a further groove or in the form of a conical course of the shoulder, so that the elastic damping element can be clipped into this groove or with appropriate vulcanisation a form fit is obtained which avoids simple detachment of the damping element.
It should be pointed out that the above-described dai-nping element of rotationally symmetrical construction can be used not only as a single damping element in the region of the housing side of the housing provided with a housing pin, but that, given sufficient space, i.e. a suitable size of the axial ball joint, a plurality of annular damping elements arranged concentrically with respect to one another are attached, these elements having the aforementioned properties.

A further possibility for the configuration of the axial ball joint according to the invention consists in that a plurality of damping elements are placed on the housing side of the housing of the axial ball joint provided with a housing pin, the damping elements then no longer being configured rotationally symmetrically with respect to the rotational axis of the housing, but arranged around the rotational axis in a plurality of elements.
A wide variety of shapes of such damping elements are possible, with circular-segment-like or circularly configured/ possibly also elliptically configured, damping elements being preferred.
To mount these damping elements on the housing side of the housing provided with a housing pin, it is proposed to provide, in the housing, recesses into which these damping elements can be let. These damping elements can consist at least partly of an elastomer or else of a combination of plastic and elastomer injection-moulded onto it.
Furthermore, the damping elements can be vulcanised or adhesively bonded directly onto the housing.
A further possibility consists in pressing the damping elements in each case into a recess on the housing side of the housing provided with a housing pin, and here too a metal insert providing the damping elements with additional dimensional stability may be advantageous. Furthermore, the recesses can in turn have undercuts which produce better seating of the inserted damping elements.
The invention is described in more detail below with the aid of the figures, in which only the features required for understanding the invention are illustrated and in which:

Figure 1 shows a side view of an axial ball joint with impact damping;
Figure 2 shows a longitudinal section through the axial ball joint from FIG. 1;
Figure 3 shows a longitudinal section through the housing with a damping element of spring design;
Figure 4 shows a longitudinal section through the housing with a damping element consisting of a combination of a plastic ring and vulcanised-on elastomer;
Figure 5 shows a plan view of a housing with vulcanised-on segment-like damping elements;
Figure 6 shows a plan view of a housing with a large number of inserted round damping elements;
Figure 7 shows a longitudinal section through the housing from FIG. 6.
Figure 1 shows a lateral view of a preferred exemplary embodiment of the axial ball joint 1 according to the invention. This joint consists first of all of a housing 2 which has a housing pin 3 at the lower side. Situated in the housing 2 is a bearing shell, not visible in the lateral view, in which an only partly visible joint ball 4 with a joint pin 5 is inserted. The joint pin 5 projects out of the housing 2 through an opening of the housing 2. At the lower side of the housing 2 lying opposite the opening of the housing 2 through which the joint pin 5 projects, an annular damping element 7 is inserted, on the outside, in a step or shoulder (not visible here).
If the axial ball joint 1 designed in accordance with the invention is used in a steering gear, the maximum excursion can be limited by a mechanical stop of the housing 2. In this case, the damping element 7 prevents a hard impact. As a rule, the steering-

gear housing is used as the mechanical stop here. The mechanical loading of the components of the entire steering system is greatly reduced by the use of the damping element, and the noise generation is reduced as well. The simple construction, in accordance with the invention, of the axial ball joint 1 with the integrated damping by using one or more damping elements on the housing of the axial ball joint thus enables an effective impact damping to be achieved in a simple and inexpensive manner.
Figure 2 shows the axial ball joint 1 from Figure 1 in longitudinal section. In this sectional drawing, the construction of the axial ball joint 1 can be seen more clearly. Figure 2 shows a housing 2 with attached housing pin 3. Situated in the housing 2 is the ball joint 4, which merges into a joint pin 5. Situated between housing 2 and joint ball 4 is a bearing shell 6, which ensures perfect seating of the joint ball 4 in the housing 2. In principle, a certain amount of damping is also produced by the bearing shell 6, but this damping cannot completely assume the function of the damping element 7. This damping element 7 is configured as an annular bead, with better seating of the damping element 7 on the step 12 of the housing 2 being additionally ensured by a metal insert 11 which is firmly pressed onto the step 12.
In this section through the housing 2, it can be additionally seen that there is provided between the housing pin 3 and the damping element 7 an additional surface 8 which can serve as an additional stop surface in the event of excessive compression of the damping element.
In Figures 3 and 4, two different embodiments of annular damping elements 7 are illustrated in section.
Figure 3 shows an embodiment of the damping element 7 as a plastic ring of v-shaped configuration. This configuration enables an elastic deformation of the damping element without the use of an elastomer. In principle, there is the possibility of producing such damping elements, for example, from plastic.

However, with greater loading, there is also the possibility of forming such a damping element from a spring steel or the like.
In Figure 4, a combination between a plastic ring 9 and an elastomer 10 vulcanised onto it is illustrated as the damping element 7. The plastic ring 9 here serves for firm seating on the step on the housing 2, while the elastomer part 10 performs the actual damping work, i.e. the elastic deformation during impact. In this configuration, it is further shown that the step has a conical shape 14 which additionally ensures improved seating of the entire damping element, in particular the plastic ring 9.
It should be pointed out that it is also within the scope of the invention for a plurality of concentrically arranged annular damping elements to be used on the housing of an axial ball joint.
While in Figures 1 to 4 damping elements of annular configuration have been illustrated in each case, Figures 5 to 7 show two variant embodiments of a plurality of damping elements not of annular configuration which are arranged on the pin-side housing surface 8 of the housing 2.
Figure 5 shows an embodiment of a housing 2 with three damping elements 13 of circular-segment-like configuration which are arranged on a housing surface 8 concentrically around the housing pin and vulcanised on the housing surface. Such an embodiment can be produced particularly simply and inexpensively.
Figure 6 likewise shows a housing 2 in axial plan view seen from the side of the housing pin 3, a large number of damping elements 13 of circular appearance being inserted in respective recesses. These recesses can be seen more clearly in Figure 7 which illustrates a cross-section of the housing of Figure 6. Here, the individual recesses 15 in which the damping elements 13 are inserted can be clearly seen. In addition, these recesses 15 have undercuts 14 in which the inserted damping

elements 13 can additionally engage and very firm seating in the recess is thereby achieved.
It should be pointed out that such undercuts are also easily possible in connection with the damping elements of annular configuration, as shown in Figures 1 to 4, and improved seating of the damping elements of annular configuration can thereby also be achieved.
Although the damping elements in the preferred examples illustrated all consist at least partly of an elastomer, the subject-matter of the invention is not to be limited to this. For instance, it is also within the scope of the invention to form both the damping element arranged annularly around the housing pin and the plurality of individual damping elements arranged around the housing pin as exclusively metal spring elements, for example cup springs, other inserts of spring design or annular spring elements.
It goes without saying that the above-mentioned features of the invention can be used not only in the combination specified in each case, but also in other combinations or alone, without departing from the scope of the invention. It is also within the scope of the invention to effect a mechanical reversal of the functions of the individual mechanical elements of the invention.

List of reference symbols
1 axial ball joint
2 housing
3 housing pin
4 joint ball
5 joint pin
6 bearing shell
7 damping element
8 housing surface

9 plastic ring
10 elastomer
11 metal insert
12 step
13 damping elements
14 undercut
15 recess

WE CLAIM:
1. Axial ball joint (1), in particular for use on a steering gear, consisting of a
housing (2) open on one side, with a housing pin (3) arranged on the housing
(2), a joint ball (4) with a joint pin (5) and a bearing shell (6) arranged between
housing (2) and joint ball (4),
characterised in that the housing (2) has at least one elastic damping element (7) for impact damping on the housing side of the housing (2) provided with the housing pin (3).
2. Axial ball joint (1) according to the preceding Claim 1, characterised in that the damping element (7) is of annular configuration.
3. Axial ball joint (1) according to the preceding Claim 2,
characterised in that a housing surface (8) unprotected and set back rearwards in relation to the at least one annular damping element (7) is formed between the annular damping element (7) and the housing pin (3).
4. Axial ball joint (1) according to one of the preceding Claims 2 to 3, characterised in that the annular damping element (7) is inserted in a step (12) on the housing side of the housing (2) provided with the housing pin (3).
5. Axial ball joint (1) according to one of the preceding Claims 2 to 3, characterised in that the annular damping element (7) is inserted in a groove on the housing side of the housing (2) provided with the housing pin (3).
6. Axial ball joint (1) according to one of the preceding Claims 2 to 5, characterised in that the annular damping element (7) consis least partly of an elastomer.

7. Axial ball joint (1) according to one of the preceding Claims 2 to 5, characterised in that the annular damping element (7) consists of a plastic ring (9) and an elastomer (10) injection-moulded onto it.
8. Axial ball joint (1) according to one of the preceding Claims 2 to 6, characterised in that the annular damping element (7) is vulcanised directly onto the housing (2).
9. Axial ball joint (1) according to one of the preceding Claims 2 to 7, characterised in that the annular damping element (7) is adhesively bonded directly onto the housing (2).
10. Axial ball joint (1) according to one of the preceding Claims 2 to 7, characterised in that the annular damping element (7) is pressed onto the housing (2).
11. Axial ball joint (1) according to one of the preceding Claims 2 to 10, characterised in that the annular damping element (7) consists of a plastic ring of spring design.
12. Axial ball joint (1) according to one of the preceding Claims 2 to 11, characterised in that the annular damping element (7) has a metal insert (11).
13. Axial ball joint (1) according to one of the preceding Claims 4 to 12, characterised in that the step (12) or the groove has an undercut (14).
14. Axial ball joint (1) according to one of the preceding Claims 2 to 5, characterised in that the annular damping element (7) consists exclusively of metal.

15. Axial ball joint (1) according to the preceding Claim 1,
characterised in that a plurality of damping elements (13) are placed on the housing side of the housing (2) provided with the housing pin (3).
16. Axial ball joint (1) according to the preceding Claim 15,
characterised in that the damping elements (13) are of circular-segment-like configuration.
17. Axial ball joint (1) according to the preceding Claim 15,
characterised in that the damping elements (13) are of circular configuration.
18. Axial ball joint (1) according to one of the preceding Claims 15 to 17, characterised in that the damping elements (13) are let into recesses (15) on the housing side provided with the housing pin (3).
19. Axial ball joint (1) according to one of the preceding Claims 15 to 18, characterised in that the damping elements (13) consist at least partly of elastomer.
20. Axial ball joint (1) according to one of the preceding Claims 15 to 19, characterised in that the damping element (13) consist of a combination of plastic and elastomer injection-moulded onto it.
21. Axial ball joint (1) according to one of the preceding Claims 15 to 20, characterised in that the damping elements (13) is vulcanised directly onto the housing (2).
22. Axial ball joint (1) according to one of the preceding Claims 15 to 20, characterised in that the damping elements (13) are adhesively bonded directly onto the housing (2).

23. Axial ball joint (1) according to one of the preceding Claims 15 to 20,
characterised in that the damping elements (13) are pressed in each case into
a recess on the housing side of the housing (2) provided with the housing pin
(3).
24. Axial ball joint (1) according to one of the preceding Claims 15 to 23, characterised in that the damping elements (13) have a metal insert (11).
25. Axial ball joint (1) according to one of the preceding Claims 18 to 24, characterised in that the recesses (15) have undercuts (14) which produce better seating of the damping elements (13).
26. Axial ball joint (1) according to one of the preceding Claims 15 to 18, characterised in that the damping elements (13) consist exclusively of metal.