GB2564963A

GB2564963A - Method for producing a bearing bush, bearing bush and control arm for a wheel suspension of a motor vehicle

Info

Publication number: GB2564963A
Application number: GB1810445.5A
Authority: GB
Inventors: Lobo Casanova Ignacio
Original assignee: ZF Friedrichshafen AG
Current assignee: ZF Friedrichshafen AG
Priority date: 2017-07-07
Filing date: 2018-06-26
Publication date: 2019-01-30
Anticipated expiration: 2038-06-26
Also published as: KR20190005754A; GB201810445D0; DE102017211625B4; DE102017211625A1; GB2564963B

Abstract

A method for producing a bearing bush, bearing bush for a control arm for a wheel suspension of a motor vehicle is provided. The invention relates to a method for producing a bearing bush 7 for a control arm of a wheel suspension, whereby a main body of the bearing bush 7 is produced from a fibre-reinforced plastic composite and defines a mount for a joint in a cut-out of the control arm. The main body of the bearing bush 7 is produced via a pultrusion process. The invention further relates to a bearing bush 7 and a control arm for a wheel suspension of a motor vehicle.

Description

Method for producing a bearing bush, bearing bush and control arm for a wheel suspension of a motor vehicle

The invention relates to a method for producing a bearing bush for a control arm of a wheel suspension, whereby a main body of the bearing bush is produced from a fibre-plastic composite and defines a mount for a joint in a cut-out. The invention further relates to a bearing bush and a control arm for a wheel suspension of a motor vehicle.

Control arms for wheel suspensions are conventionally produced as metal parts, but this comes with the major disadvantages of a high weight, the need for an additional finishing process as part of the production process and the provision of additional features to combat corrosion. For this reason, control arms are increasingly also being produced as hybrid components, in

which case the	respective control arm is made partly from a
metal material	and partly from a plastic. A significant reduc-
tion in weight	is achieved as a result compared with a design

based on pure metal and the risk of corrosion is also reduced.

However, control arms based on a hybrid construction also have disadvantages. For example, due to the different electronic potentials, contact corrosion often occurs between the metal components and the components made from plastic, which makes the additional use of a bonding agent or incorporation of an additional barrier layer necessary. Furthermore, an adequate bond between parts to be joined made from metal and plastic can only be achieved by expensive pre-treatment processes or additional positive joining on the surface is necessary which makes the production process correspondingly expensive. In addition, the parts to be joined usually have different high expansion coefficients which can lead to residual stresses in the component under thermal load and on cooling during the production process or also subsequently during operation. Fi-2nally, jumps in stiffness and strength can occur in the component due to different E-moduli and/or tensile/compressive strengths of the materials. Control arms for wheel suspensions are therefore also partially or also entirely produced from a fibre-plastic composite.

DE 10 2015 222 297 Al discloses a method for producing a bearing bush for a control arm of a wheel suspension, this bearing bush being produced from a fibre-plastic composite by extruding or hot pressing a fibre preform. To this end, a fibrematrix semi-finished product with a thermosetting matrix is firstly placed in a compression mould and pressed to create a main body, and the main body has a cut-out which defines a mount for a joint of the subsequent control arm.

Against the background of the prior art described above, the objective of this invention is to propose a method for producing a bearing bush, it being possible to produce a bearing bush capable of withstanding load by this method with little expense and effort.

This objective is achieved as specified in the preamble of claim 1 in conjunction with the characterising features thereof. The following dependent claims respectively specify advantageous embodiments of the invention. A bearing bush produced as proposed by the invention also constitutes the subject matter of claims 10 and 11. Finally, a control arm having at least one bearing bush produced as proposed by the invention is also claimed in claim 12.

Based on the invention, during the course of the method for producing a bearing bush, a main body of the bearing bush is produced from a fibre-plastic composite and thus defines a mount for a joint in a cut-out. In the finished state, therefore, the main body has at least one cut-out extending through

-3it which serves as a mount for a joint of the control arm. It is particularly preferable if the cut-out is of a cylindrical shape so that a ball joint, cross-axis joint, rubber mounting or similar can be accommodated in the bearing bush.

Apart from the cut-out, the main body of the bearing bush may be a solid body. However, the main body preferably has holes extending through it at appropriate points in order to save on material and also to reduce weight. These holes should be disposed in such a way that the bearing bush is able to absorb the forces and moments transmitted via the respective joint and direct them into the remaining part of the respective control arm.

As proposed by the invention, the main body of the bearing bush is made from a fibre-plastic composite and therefore comprises a material made up of reinforcing fibres and a plastic matrix .

The invention also comprises the technical teaching that the main body of the bearing bush is produced by a pultrusion process. In other words, the main body of the bearing bush is therefore produced from the fibre-plastic composite during the course of a pultrusion process.

The advantage of using such a method to produce a bearing bush is that because production takes place during the course of a pultrusion process, production complexity can be kept to a minimum but at the same time, this offers the possibility of being able to obtain degrees of stiffness of the main body to be produced that are akin to the degrees of stiffness of a metal component. In addition, more complicated geometries of the main body can also be produced as a result. For example, in addition to the cut-out, other holes can also be provided without any problem. At the same time, the use of fibre-4plastic composite means that the weight can be kept low and the problem of corrosion avoided.

Although the bearing bush in the case of DE 10 2015 222 297 Al is also made from a fibre-plastic composite, producing it by extrusion or hot pressing is correspondingly complex.

A pultrusion process within the meaning of the invention should be construed as the method known in principle to the skilled person, whereby fibres and/or semi-finished products (weaves/bundles/fibre mats) are formed, impregnated and cured as part of a continuous process. This is then followed by a process of cutting to the desired length. The advantage of this process, also known as pultruding, is that with little complexity in terms of production, it enables elongate fibrereinforced plastic profiles to be produced that are cut to the desired length at the end of the process.

Based on one embodiment of the invention, the main body is produced from a continuous fibre-reinforced fibre-plastic composite. The advantage of using continuous fibre reinforcements is that high degrees of stiffness can be obtained in the main body to be produced. By adapting the orientation of the continuous fibres in the plastic composite to the loads to be anticipated, a bearing bush can be produced which is capable of withstanding the same loads as a metal bearing bush.

Based on another possible embodiment of the invention, the main body is formed from at least one semi-finished product during the course of the pultrusion process. In this respect, a textile semi-finished product, in the form of a weave, a bundle or in the form of fibre mats, is used in particular, which is or are formed during the course of the pultrusion process to obtain the main body.

-5Based on a variant of the aforementioned possible embodiment, the at least one semi-finished product is formed, impregnated and cured during the course of the pultrusion process to obtain a contour forming the main body or a part of the main body. During the course of the pultrusion process, therefore, the initially two-dimensional semi-finished product is reshaped so as to produce either the main body or a part of the main body. This is followed by impregnation with a matrix and after that, the resultant profile is cured. In the simplest case, a single semi-finished product is used to produce the main body, i.e. the complete main body is formed from this semi-finished product during the course of the pultrusion process .

However, it is particularly preferable to use several semifinished products having different fibre orientations for the pultrusion process. The advantage of this is that due to the different orientations of the fibres, it is also possible to adapt to different requirements in terms of the ability of the bearing bush to withstand load. In this respect, it is particularly preferable to use two semi-finished products, in which case one semi-finished product has a fibre orientation of 0 and 90° whereas the fibre orientation of the other semifinished product is +/-45°. Apart from semi-finished products, it is also conceivable within the meaning of the invention to feed in fibres during the course of the pultrusion process and to obtain specific properties of the bearing bush by orienting them accordingly.

Another option in the context of the invention is to prefabricate one or more semi-finished products during the course of the pultrusion process by means of the so-called pultrusion winding method or by means of the so-called pultrusion braiding method. In particular, this enables tubular parts to be

-6prefabricated from fibres and then encased with the matrix and optionally other layers of semi-finished products.

Based on another embodiment of the invention, carbon, glass, aramid and/or basalt are used as the fibre type for the fibreplastic composite. In this context, several of the aforementioned fibre types may also be combined with one another in order to obtain different properties of the bearing bush. Particularly preferred however is the use of glass or carbon fibres .

Alternatively or also in addition to the above, a thermoplastic and/or a thermosetting material is used as the matrix for the fibre-plastic composite. Here too, the matrix may be produced from a mixture of these two material types. An epoxy resin, a polyester resin or also a vinyl ester resin may be used as a thermosetting material. On the other hand, polyamide, polypropylene or polyethylene may be used in the case of a thermoplastic material.

Based on another embodiment of the invention, the main body is provided with grooves on an external face. This enables the contact surface to be made larger and a connection to an adjoining part of the respective control arm also rendered capable of withstanding higher loads because this enables a positive connection to be obtained. Providing grooves enables a grooved structure to be obtained on the main body which makes a movement of the main body and hence also the bearing bush relative to the respective surrounding part of the control arm difficult.

Based on a variant of the aforementioned embodiment, a connecting device with elements projecting out from the connecting body may be provided in the individual groove in each case. By means of these projecting elements, which are prefer-7 ably of a pin-type design and applied to a base material, the connection to the surrounding part can be further improved during the process of producing the control arm. The projecting elements may be provided in one or more rows so that in the latter case, a three-dimensional connecting device is provided. Furthermore, the individual projecting elements may be different from one another in terms of their inclination and hence orientation.

As proposed by the invention, the connecting devices can be fitted or placed in the grooves immediately before or also after the pultrusion process for producing the main body and the connecting devices are respectively preferably glued in. However, it is particularly preferable if fitting takes place immediately after curing during the course of the pultrusion process so that the connecting devices are jointly cut to the desired length with the rest.

Another object of the invention is a bearing bush for a control arm of a wheel suspension, which bearing bush comprises a main body which is produced from a fibre-plastic composite and defines a mount for a joint in a cut-out. This joint within the wheel suspension is used to provide a connection to an adjacent component. As proposed by the invention, the main body is produced by a pultrusion process. Furthermore, the bearing bush may also be based on one of the aforementioned variants.

In particular, a bearing bush produced as proposed by the invention is part of a control arm for a wheel suspension of a motor vehicle. Accordingly, this control arm preferably comprises a connecting part which connects joints provided at articulation points to one another. At least one of the joints is accommodated in a bearing bush produced as proposed by the invention which is connected to the connecting part. Specifically, the control arm may be configured as a 2, 3 or also 4

-8point control arm and a bearing bush produced as proposed by the invention may be provided at each of the articulation points. Furthermore, the connecting part is also preferably produced as a fibre-plastic composite and the connecting part and also the one or more bearing bushes are connected to one another by positive bonding during the course of producing the control arm.

The invention is not restricted to the specified combination of features of the independent or dependent claims. There are also options whereby individual features disclosed in the claims, the following description of preferred embodiments of the invention or directly from the drawings may be combined with one another. Any reference of the claims to the drawings due to the use of reference numbers is not intended to restrict the protective scope of the claims.

Advantageous embodiments of the invention, which will be explained below, are illustrated in the drawings. Of these:

Fig. 1 is a perspective view of a control arm for a wheel suspension;

Fig. 2 is a view in section of a bearing bush, such as may be used with the control arm illustrated in Fig. 1;

Fig. 3 is a schematic diagram of a method for producing the bearing bush illustrated in Fig. 2;

Fig. 4 is another schematic diagram of the method for producing the bearing bush illustrated in Fig. 2;

Fig. 5 is a schematic diagram of an alternative method for producing the bearing bush illustrated in Fig. 2;

-9Fig. 6 is a view in section of a bearing bush, such as may likewise be used with the control arm illustrated in

Fig. 1;

Fig. 7 is a view of a bearing bush, which may be used as an alternative with the control arm illustrated in Fig. 1;

Fig. 8 is a view of a bearing bush which may also be used as an alternative with the control arm illustrated in Fig. 1;

Fig. 9 is a schematic diagram of a part of a method for producing the bearing bush illustrated in Fig. 7;

Fig. 10 is a schematic diagram of a part of a method for producing the bearing bush illustrated in Fig. 8; and

Fig. 11 shows the bearing bush from Fig. 8 during the process of assembling a control arm and subsequent use.

Fig. 1 is a perspective view illustrating a control arm 1 for a wheel suspension of a motor vehicle, said control arm 1 in this instance being a 2-point control arm. Accordingly, the control arm 1 comprises two articulation points 2 and 3, at which a connection to adjacently lying components of the wheel suspension is established respectively and at which a joint 4 respectively 5 is provided respectively when the control arm 1 is in the fitted state. The joints 4 and 5 are respectively provided in the form of rubber bearings.

The control arm 1, apart from the joints 4 and 5, is made entirely from a fibre-plastic composite in this instance. The control arm 1 comprises a connecting part 6 which extends between the joints 4 and 5. A respective connection of the respective joint 4 respectively 5 to the connecting part 6 is

-10established via a bearing bush 7 and/or 8 in each case. Furthermore, in order to stiffen the control arm 1, an insert 9 is also provided in the region between the articulation points und 3.

The bearing bushes 7 and 8 are respectively also produced from a fibre-plastic composite and the production will be described in more detail below taking bearing bush 7 as an example. In this context, the same reference numbers are used for components of the same name, although the components may differ slightly .

Fig. 2 is a view in section illustrating a bearing bush 7 such as may be used with the control arm 1 illustrated in Fig. 1. This bearing bush 7 comprises a main body 10 made from a continuous fibre-reinforced fibre-plastic composite. The main body 10 defines, in a cylindrical cut-out 11, a mount on which the corresponding joint 4 is to be provided in the control arm 1 in Fig. 1. The main body 10 also has several holes 12 extending through it. Individual fibres 13 of the fibre-plastic composite, which extend into the plane of the drawing, are indicated in Fig. 2. In terms of their orientation, however, the fibres of the fibre-plastic composite are disposed so that they extend in the directions in which forces and moments are also to be absorbed by the bearing bush 7 during subsequent use of the control arm 1.

Figs. 3 and 4 are schematic views respectively illustrating a method for producing the bearing bush 7 illustrated in Fig. 2. Production takes place during the course of a pultrusion process, the principle of which is known to the skilled person. Accordingly, in a first step, semi-finished products 14 and 15 are fed to a preform station 16 and are respectively moulded to a contour forming a part of the main body 10 and impregnated in this preform station 16. As may be seen in particular

-11from Fig. 4, a tubular portion 17 is thus formed from the semi-finished product 15 which defines the cut-out 11 of the subsequent main body 10. From the semi-finished product 14, on the other hand, a portion 18 is formed that constitutes an external face of the subsequent main body 10.

Forming of the semi-finished products 14 and 15 takes place progressively and an impregnation process is undertaken at the same time, preferably with a thermosetting and/or thermoplastic matrix. The semi-finished products 14 and 15 are provided in the form of rolls and have fibre mats. The fibre mat of the semi-finished product 14 preferably has a fibre orientation of 0 and 90° whilst that in the case of the semifinished product 15 is +/- 45° in particular.

After the preform station 16, the formed and impregnated semifinished products 14 and 15 are fed to a curing tool 19 in which the formed shape is cured. After that, the process of cutting to length to obtain the bearing bushes 7 takes place by means of a saw 20, as may be seen in particular from Fig.

4. This then constitutes the finished bearing bush 7.

As fibres, different plastic fibres may be used, which may also optionally be combined with one another. For example, the use of carbon, glass, aramid, basalt or similar fibres would be conceivable.

Fig. 5 is another schematic view illustrating an alternative manufacturing method for producing a bearing bush 7. The sole difference compared with the description above is that the tubular portion 17 is produced from fibres beforehand in a winding or braiding process so that production is ultimately based on a pultrusion-winding method or a pultrusion-braiding method.

-12Fig. 6 illustrates an alternative design of a bearing bush 7 such as may be used with the control arm 1 illustrated in Fig.

1. This design largely corresponds to the variant illustrated in Fig. 2, the difference being that a main body 10 is provided with a number of grooves 22 on an external face 21. Accordingly, these grooves 22 define a grooved structure of the bearing bush 7, thereby improving the connection to the surrounding connecting part 6 in its assembled state in the control arm 1. Shaping of the external face 21 of the main body 10 likewise takes place as part of the pultrusion process.

Another alternative design of a bearing bush 7 largely corresponding to the previous variant in Fig. 6 is illustrated in Fig. 7. The difference in this instance is that a connecting device 23 is provided respectively in the grooves 22 in each case which has elements 24 projecting out from the main body 10 of the bearing bush 7. As may be seen from the detail shown in Fig. 7, the elements are provided on a base material of the connecting device 23 arranged in a row. In addition, the elements 24 are inclined and hence oriented differently from one another. A positive connection to the surrounding connecting part 6 is therefore improved by the elements 24 during the process of producing the control arm 1.

Fig. 8 illustrates another design of a bearing bush 7, such as may likewise be used with the control arm 1 illustrated in Fig. 1. As with the variant illustrated in Fig. 7, grooves 22 are provided on the external face 21 of the main body 10 but compared with the variant illustrated in Fig. 6 and also Fig. 7, there are fewer of these grooves 22 in number so that they are of a bigger extension. Furthermore, as is the case with the variant illustrated in Fig. 7, a connecting device 23 having projecting elements 24 is provided respectively in each groove 22. By contrast with the variant illustrated in Fig. 7, however, the elements 24 are arranged in a number of rows. As

-13a result, a positive connection to the surrounding connecting part 6 can also be improved during production of the control arm 1 .

Figs. 9 and 10 then illustrate the point at which fitting of the connecting devices 23 respectively takes place during the process of producing the respective bearing bush 7. As may be seen from Fig. 9 and also from Fig. 10, fitting of the connecting device 23 in the grooves - not illustrated here takes place after curing and before cutting to length, the connecting devices 23 being respectively glued in.

Finally, Fig. 11 then illustrates the bearing bush 7 from Fig. 8 in the process of being connected to the connecting part not illustrated here - of the control arm 1 and the subsequent use of the control arm 1. In this instance, a connection is established with the connecting part by means of a matrix 25 and the projecting elements 24 thus form a positive connection. During subsequent use and when the control arm 1 is placed under stress by a load 26 indicated by an arrow, the elements 24 prevent the matrix 25 from becoming detached and hence any movement of the components of the control arm 1 apart from one another.

The method for producing a bearing bush proposed by the invention enables the latter to be manufactured with little cost and effort.

-14Reference numbers

1	control arm
2	articulation point
3	articulation point
4	joint
5	joint
6	connecting part
7	bearing bush
8	bearing bush
9	insert
10	main body
11	cut-out
12	holes
13	fibres
14	semi-finished product
15	semi-finished product
16	preform station
17	portion
18	portion
19	curing tool
20	saw
21	external face
22	grooves
23	connecting device
24	elements
25	matrix
26	load

Claims

1. Method for producing a bearing bush (7; 8) for a control arm (1) of a wheel suspension, whereby a main body (10) of the bearing bush (7; 8) is produced from a fibre-plastic composite and defines a mount for a joint (4; 5) in a cut-out (11), characterised in that the main body (10) is produced in a pultrusion process.

2. Method as claimed in claim 1, characterised in that the main body (10) is produced from a continuous fibre-reinforced fibre-plastic composite.

3. Method as claimed in claim 1 or 2, characterised in that the main body (10) is formed from at least one semi-finished product (14, 15) in the pultrusion process.

4. Method as claimed in claim 3, characterised in that the at least one semi-finished product (14, 15) is shaped to a contour forming the main body (10) or a part of the main body (10), impregnated and cured during the course of the pultrusion process .

5. Method as claimed in claim 3 or 4, characterised in that several semi-finished products (14, 15) with different fibre orientations are used for the pultrusion process.

6. Method as claimed in one of the preceding claims, characterised in that carbon, glass, aramid and/or basalt are used as the fibre type for the fibre-plastic composite.

7. Method as claimed in one of the preceding claims, characterised in that a thermoplastic and/or a thermosetting material is used as a matrix for the fibre-plastic composite.

8. Method as claimed in one of the preceding claims, characterised in that the main body (10) is provided with grooves (22) on an external face (21).

9. Method as claimed in claim 8, characterised in that a connecting device (23) having elements (24) projecting out from the external face (21) is inserted respectively in the individual groove (22).

10. Bearing bush (7; 8) for a control arm (1) of a wheel sus- pension of a motor vehicle, comprising a main body (10) which is produced from a fibre-plastic composite and defines a mount for a joint (4; 5) in a cut-out (11), characterised in that the main body (10) is produced in a pultrusion process.

11. Bearing bush (7; 8) as claimed in claim 10, further char- acterised by a production process as claimed in one or more of claims 2 to 9.

12. Control arm (1) for a wheel suspension of a motor vehicle, comprising a connecting part (6) which connects joints (4, 5) provided at articulation points (2, 3) to one another, at least one of the joints (4, 5) being mounted in a bearing bush (7, 8) as claimed in claim 10 or 11 which is connected to the connecting part (6).