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
FOUR-POINT LINK
APPLICANT(S)
a) Name
b) Nationality
c) Address
ZF FRIEDRICHSHAFEN AG
GERMAN Company
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 : -

region. The hollow housing may take the form of a moulded sheet-metal part or a casting, wherein the four-point link is made for example of austempered cast iron.
In practice, two shapes have hitherto proved particularly efficient for reasons of manufacture, cost, strength and weight. These are on the one hand the X shape, which up till now has been manufactured mainly by forging. For reasons of manufacture, this produces as an arm cross section a golid rectangular cross section that may be adjusted relatively easily to the required characteristic- and strength properties. The drawback of a more economical manufacture, for example by casting, of a hollow geometry according to EP 0 776 275 B1 is that this geometry is completely closed. Consequently an, in terms of processing, reliable support of the cavity-forming core is not possible or possible only to a very limited extent. The result may be non-uniform wall thicknesses and hence negative strength properties as a result of the core floating upwards during casting. The drawback of the X geometry hitherto manufactured by forging is its rectangular cross section, which is predefined by the method of manufacture and entails a high component weight and hence high costs. In the case of a torsionally flexible forged four-point link, the arms are generally of a very flat design. This may give rise to the problem that the housing tops are not completely filled during the forging operation. An X geometry with an I-shaped arm cross section requires, for casting purposes, a plurality of cores that add to the cost of the component. The I-section is moreover disadvantageous for lateral loads.
On the other hand, the cast structure open at both ends according to DE 10 2004 014 610 A1 has proved successful. This shape is distinguished by an inexpensive lightweight unmachined part as well as by the hollow design and therefore offers several advantages over the forged four-point link. The limiting factor of this design is however the flexible torsion characteristics. To make the characteristic more flexible, for example either the wall thickness or the core height is reduced. Both measures however have manufacturing bounds. The wall thickness should have a minimum dimension to allow casting of the component, and the core should have a

minimum height to prevent its breaking as a result of the buoyancy of the molten cast iron. This makes this shape less suitable for the case of application of a torsionally flexible characteristic. A reduction of the torsion characteristic by means of a narrower component is possible only to a very limited extent for reasons of structural durability.
In the case of the four-point link according to DE 100 50 772 Al, which substantially comprises a tube having small arms for connection purposes, the torsion characteristic is determined almost exclusively by the tube. The drawbacks of this structure lie firstly in the manufacturing technology. The geometry of the four-point link is as a rule impossible to forge as a result of the tubular section. The four-point link is also suitable only to a limited extent for manufacture by casting because the inside diameter should not fall below a minimum value owing to the required stability of the long core. As the arms take the form of a rectangular section, there is a risk of piping if the arms are not of a very thin design. Secondly, this geometry is unable to cope under load. The tubular section in the middle, given a flexible torsion characteristic, has to be either very thin or of a small cross section and therefore offers only low resistance to lateral load. The arms too, in the form of a thin rectangular section, offer only little resistance to lateral load. Furthermore, the control arm at the transition of the arms to the tube presents a sudden change of rigidity that is disadvantageous for structural durability.
Proceeding from this background art, the underlying object of the invention is to provide a four-point link that is torsionally flexible and at the same time capable of taking up high lateral loads.
This object is achieved according to the invention by a four-point link according to claim 1. Preferred developments are indicated in the sub-claims.
The four-point link according to the invention for the suspension of a vehicle axle on a vehicle frame of a vehicle, in particular a commercial vehicle, comprises four

control arms, which are connected in a fixed manner to one another in a central region and extend away from the central region to form a cross and of which two first control arms may be coupled to the vehicle frame and two second control arms may be coupled to the vehicle axle, wherein the control arms comprise in each case an H-section that is open transversely or vertically relative to the cross plane.
Each of the H-sections is formed preferably by two limbs and a web extending between the limbs, wherein the limbs and the web delimit two recesses, which are separated from one another by the web and are open towards mutually opposite sides. In particular the recesses in this case are opert only at one side. Here, the expression "H-section that is open transversely or vertically relative to the cross plane" is to be interpreted in particular in such a way that the recesses of each of the H-sections are open transversely or vertically relative to the cross plane. In the case of the I-section of prior art, on the other hand, the recesses are delimited and hence closed transversely of and/or at right angles to the cross plane by the limbs of the I- section. The two limbs of each H-section are oriented preferably parallel or substantially parallel to one another. Furthermore, the web of each H-section extends in particular transversely of or at right angles to the respective limbs.
By virtue of the fact that the control arms comprise an H-section that is open transversely or vertically relative to the cross plane, the four-point link is on the one hand torsionally flexible and on the other hand capable of taking up high lateral loads. In particular, the four-point link according to the invention is capable of taking up higher lateral loads than if its arms comprised an I-section according to EP 0 776 275 B1. The H-section that is open transversely or vertically relative to the cross plane moreover offers advantages in terms of manufacture because, unlike the I-section according to EP 0 776 275 Bl or the C-section known from DE 10 2004 014 610 Al, it may be cast without a core. The term "transversely" preferably stands for "at right angles", "substantially at right angles" or "obliquely". Thus, the term "transversely relative to the cross plane" means for example "at right angles to the

cross plane", "substantially at right angles to the cross plane" or "obliquely relative to the cross plane".
Preferably the control arms verge into one another in the central region, wherein this transition occurs in particular homogeneously in terms of material. The four-point link may moreover form a cross or X-shaped cross and/or be of an X-shaped configuration.
The cross plane preferably forms a centre plane of the four-point link. In particular the control arms, and preferably also the central region, lie in the cross plane of the four-point link. Thus, the expression "H-section that is open transversely or vertically relative to the cross plane" may be interpreted in particular also in such a way that the webs of the H-sections lie in the cross plane.
The control arms may extend in a straight manner. Preferably however the control arms are curved, so that the terms "cross-shaped", "cross", X-shaped cross" or "X- shaped configuration" include such a curved course of the control arms. The control arms are in particular curved in the cross plane.
The H-sections of the control arms may taper with increasing distance from the central region. In particular, the height of the limbs of the H-sections of the control arms and/or the width of the webs of the H-sections of the control arms and/or the width of the H-sections of the control arms decreases with increasing distance from the central region.
According to a development, the central region comprises a tubular section. In particular the central region comprises two H-sections, which are open in each case transversely or vertically relative to the cross plane and are connected to one another and/or verge into one another to form the tubular section.

Each of the H-sections of the central region is formed preferably by two limbs and a web extending between the limbs, wherein the limbs and the web delimit two recesses, which are separated from one another by the web and are open towards mutually opposite sides. In particular, the recesses in this case are open only at one side. The expression "H-sections that are open transversely or vertically relative to the plane of the cross" is therefore to be interpreted in particular in such a way that the recesses of each of the H-sections of the central region are open transversely or vertically relative to the cross plane. Preferably this expression may be interpreted also in such a way that the webs of the H-sections of the central region lie in the cross plane. The two limbs of each H-section of the central region are oriented preferably parallel or substantially parallel to one another. The web of each H- section of the central region moreover extends in particular transversely of or at right angles to the respective limbs.
The mutually opposing limbs of the H-sections of the central region are preferably connected to one another so as to form the tubular section that is disposed in particular between the webs of the two H-sections of the central region. In this case, the H-sections of the control arms preferably verge into the H-sections of the central region. The tubular section is preferably of an O-shaped design. In particular, the two mutually opposing limbs of the H-sections of the central region may be curved towards one another in order to form the tubular section.
The tubular section is in particular open at both sides. Furthermore, the tubular profile extends preferably in a longitudinal direction of the cross and/or of the four- point link that runs in particular centrally between the two first control arms and centrally between the two second control arms. In particular, the longitudinal direction runs also through the central region.
The control arms at their ends remote from the central region preferably comprise in each case a joint receiver, at or in which a joint is or may be disposed. In this case, the two first control arms may be coupled by means of the joints to the vehicle frame

and the two second control arms may be coupled by means of the joints to the vehicle axle. The bearing receivers are preferably of a hollow-cylindrical design. Furthermore, the joints in particular take the form of ball joints and/or molecular joints.
The four-point link is made preferably of metal, in particular of iron or an iron alloy. The four-point link may further be manufactured as a forging or as a casting. Preferably the four-point link is a casting and is made in particular from a cast material based on iron with spheroidal graphite. Such a casting material may after casting be subjected to a heat treatment so that the four-point link is made for example from an ADI (austempered ductile iron) casting material.
In particular the four-point link according to the invention forms a deformable cross, by means of which, in addition to the suspension of the vehicle axle on the vehicle frame, the function of a roll stabilizer may also be achieved. Preferably the four- point link for this purpose forms a reversibly and/or spring-elastically deformable cross.
The invention further relates to a vehicle, in particular a commercial vehicle, comprising at least one vehicle axle, a vehicle frame and one or at least one four- point link according to the invention, wherein the two first control arms are coupled to the vehicle frame and the two second control arms are coupled to the vehicle axle. In this case, the four-point link may be developed in accordance with all of the described refinements. In particular, the two first control arms and the two second control arms are coupled by means of the joints to the vehicle frame and to the vehicle axle respectively. The vehicle axle is moreover preferably a rigid axle.
The four-point link geometry according to the invention is specially designed for flexible torsion characteristics. The deformation is taken up by the torsionally flexible arms, by the special geometry in the centre of the link and by the molecular joints, wherein the component of the molecular joints is preferably low. Because of

the flexible characteristic, a low torsional moment and hence low vertical loads act upon the four-point link. Nevertheless, relatively high lateral loads may act upon the four-point link. In particular, the planar moment of inertia of the H-section used for the control arms is more suitable than the I-section according to EP 0 776 275 Bl.
The control arms of the four-point link converge in a cross. For the central region of the cross and/or of the four-point link a geometry that is formed by a combination of H-sections and a tubular section is advantageous. In particular, with this geometry the possibility of avoiding material accumulations and complying with specific wall thicknesses is already taken into account, so that piping in the four-point link may be avoided and a subsequent heat treatment of the four-point link influences the total cross section thereof.
The four-point link according to the invention has a high load capability in the central region. These loads arise on the one hand from the torsion, which may be optimally taken up by the tubular section, and on the other hand from the lateral load, which may additionally be taken up by the lateral webs of the H-sections of the central region. These advantages do not exist for example in a four-point link according to DE 100 50 772 Al. In the four-point link according to the invention there is preferably a homogeneous transition of the control arms to the central region, this having a positive influence on the structural durability of the four-point link according to the invention.
The core for the central region of the four-point link according to the invention owing to its relatively large cross section and its comparatively short length is very stable, this no longer being the case in a core for a cast link according to DE 10 2004 014 610 Al if this cast link is of a torsionally flexible and hence flat design.
The four-point link according to the invention offers the following advantages in particular:

- Its geometry is particularly suitable for a four-point link having a torsionally flexible characteristic.
- By virtue of the H-section of the control arms, the control arms may be cast without cores. The H-section is torsionally flexible but stable under lateral load and hence ideal for the intended application.
- The combination of H-section and tubular section and/or tubular cross section in the central region of the four-point link allows constant wall thicknesses corresponding to manufacture as well as a geometry without sudden changes of rigidity that can cope with load.
- A core need be used only in the middle for the central region. The core because of its compact nature may be of a very stable design, with the result that there is no limitation of the geometry with regard to core stability. If the hollow- cylindrical bearing receivers and/or housing tops are provided, then in addition to the core for the central region one core for each bearing receiver may be required.
There now follows a description of a preferred embodiment of the invention with
reference to the drawings. The drawings show:
Fig. 1: a perspective view of an embodiment of the four-point link according
to the invention,
Fig. 2: a cross section through one of the control arms of the four-point link
according to Fig. 1,
Fig. 3: a cross section through the central region of the four-point link
according to Fig. 1 and
Fig. 4: a partial side view of a vehicle with the four-point link according to
Fig. 1 in the fitted state.

Fig. 1 shows a perspective view of an embodiment of the four-point link 1 according to the invention, which comprises four control arms 2, 3, 4 and 5 arranged in the shape of a cross and connected in a fixed manner to one another in a central region 6 of the cross. The four-point link 1 takes the form of an integral casting, with the result that the control arms 2, 3, 4 and 5 verge into one another in particular homogeneously in terms of material in the central region 6. The control arms 2, 3, 4 and 5 at their ends remote from the central region 6 further comprise in each case a hollow-cylindrical bearing receiver 7, 8, 9 and 10, wherein each of the bearing receivers 7, 8, 9 and 10 is formed integrally with the respective associated control arm 2, 3, 4 or 5. The bearing receivers 7, 8, 9 and 10 are in particular part of the integral casting. For fitting the four-point link 1 in a vehicle 11 a molecular joint 12 is inserted into each of the bearing receivers 7, 8, 9 and 10 (see Fig. 4).
As is evident from Fig. 2, which shows a cross section of the control arm 5 along the cutting line 14 of Fig, 1, the control arms 2, 3, 4 and 5 each comprise an H-section 13. Each H-section 13 comprises two limbs 15 and 16, which are parallel to one another and connected at the middle to one another by means of a web 17. The limbs 15 and 16 as well as the web 17 delimit two recesses 18 and 19, which at mutually opposite sides are open at right angles to (and/or transversely of) the cross plane 20. The cross plane 20 in this case forms a centre plane of the four-point link 1 and cuts the four-point link 1 at the lines 21 shown in Fig. 1. In particular, the cross plane 20 extends through the webs 17 of the H-sections 13. In the webs 17 of each H-section 13 holes 24 are further provided, which are used to remove water and dirt (see Fig. 1).
As Fig. 2 reveals, the thicknesses 22 and 23 of the two limbs 15 and 16 of the H- section 13 differ. The heights 40 and 41 of the two limbs 15 and 16 of the H-section 13 also differ. The width of the H-section 13 and/or of the control arm is denoted by the reference character 42.


Fig. 3 shows a sectional view of the central region 6 along the cutting line 25 of Fig. 1, the central region 6 comprising two H-sections 26, each comprising two limbs 27 and 28 that extend parallel to one another as well as a web 29 that connects the two limbs 27 and 28 of the respective H-section 26 to one another at the middle. Each of the H-sections 26 comprises two recesses 30 and 31, which are delimited by the respective limbs 27 and 28 and by the respective web 29 and which at mutually opposite sides are open at right angles to (and/or transversely of) the cross plane 20. As is evident from Fig. 3, the webs 29 of the H-sectioris 26 lie on the cross plane 20. The two mutually opposing limbs 28 of the two H-sedtions 26 are connected to one another to form a tubular section 32, which extends in longitudinal direction 33 (see Fig. 1) of the four-point link 1 and has a through cavity 34 that is open at both sides in longitudinal direction 33. The H-sections 13 of the control arms 2 and 4 in this case verge into one of the H-sections 26 of the central region 6, and the two H- sections of the control arms 3 and 5 verge into the other H-section 26 of the central region 6.
Fig. 4 shows a partial side view of the vehicle 11 with a vehicle frame 35, to which the control arms 2 and 3 are coupled by means of two of the molecular joints 12. The control arms 4 and 5 are further coupled by means of another two of the molecular joints 12 to a vehicle axle 36 in the form of a rigid axle. The dashed line 37 in this case represents both the cross plane 20 and the longitudinal direction 33. Although in Fig. 4 the line 37 runs also in vehicle longitudinal direction, during spring deflection or rebound travel of the vehicle axle 36 relative to the vehicle frame 35 the cross plane 20 and the longitudinal direction 33 may incline relative to the vehicle longitudinal direction.
The vehicle axle 36 is further coupled by means of two longitudinal control arms 38 to the vehicle frame 35 and/or to beams 39 that are connected in a fixed manner to the vehicle frame 35, wherein only one of the longitudinal control arms 38 and one of the beams 39 is visible in Fig. 4.

List of reference characters
1 four-point link
2 control arm
3 control arm
4 control arm
5 control arm
6 central region
7 bearing receiver
8 bearing receiver
9 bearing receiver
10 bearing receiver
11 vehicle
12 molecular joint
13 H-section
14 cutting line
15 limb
16 limb
17 web
18 recess
19 recess
20 cross plane
21 line
22 thickness
23 thickness
24 hole
25 cutting line
26 H-section
27 limb
28 limb
29 web
" 1!F4 NOV 2009

30 recess
31 recess
32 tubular section
33 longitudinal direction
34 cavity
35 vehicle frame
36 vehicle axle
37 line
38 longitudinal control arm
39 beam
40 height
41 height
42 width

WE CLAIM:
1. Four-point link for the suspension of a vehicle axle (36) on a vehicle frame (35) of a vehicle (11), comprising four control arms (2, 3, 4, 5), which are connected in a fixed manner to one another in a central region (6) and extend away from the central region (6) to form a cross and of which two first control arms (2, 3) may be coupled to the vehicle frame (35) and two second control arms (4, 5) may be coupled to the vehicle axle (36), characterized in that the control arms (2, 3, 4, 5) comprise in each case an H-section (13) that is open transversely or vertically relative to the cross plane (20).
2. Four-point link according to claim 1, characterized in that the cross plane (20) forms a centre plane of the four-point link (1).
3. Four-point link according to claim 1 or 2, characterized in that the control arms (2, 3, 4, 5) verge into one another homogeneously in terms of material in the central region (6).
4. Four-point link according to one of the preceding claims, characterized in that the central region (6) comprises a tubular section (32).
5. Four-point link according to claim 4, characterized in that the central region (6) comprises two H-sections (26), which are open in each case transversely or vertically relative to the cross plane (20) and of which the mutually opposing limbs (28) are connected to one another to form the tubular section (32).
6. Four-point link according to claim 5, characterized in that the H-sections (13) of the control arms (2, 3, 4, 5) verge into the H-sections (26) of the central region (6).
7. Four-point link according to one of claims 4 to 6, characterized in that the tubular section (32) is open at both sides.

8. Four-point link according to one of claims 4 to 7, characterized in that the tubular section (32) extends in a longitudinal direction (33) of the cross that runs centrally between the two first control arms (2, 3), through the central region (6) and centrally between the two second control arms (4, 5).
9. Four-point link according to one of the preceding claims, characterized in that the control arms (2, 3, 4, 5) at their ends remote from the central region (6) each comprise a hollow-cylindrical joint receiver (7, 8, 9,10).
10. Four-point link according to one of the preceding claims, characterized in that each of the H-sections (13; 26) is formed by two limbs (15, 16; 27, 28) and a web (17; 29), which extends between the limbs (15, 16; 27, 28) and lies in the cross plane (20).
11. Vehicle having at least one vehicle axle (36), a vehicle frame (35) and at least one four-point link (1) according to one of the preceding claims, wherein the two first control arms (2, 3) are coupled by means of in each case one joint (12) to the vehicle frame (35) and the two second control arms (3, 4) are coupled by means of in each case one joint (12) to the vehicle axle (36).
12. Vehicle according to claim 11, characterized in that the joints (12) are molecular joints.
13. Vehicle according to claim 11 or 12, characterized in that the vehicle axle (36) is a rigid axle.
Dated this 4thday of November, 2009