EP3504458A1

EP3504458A1 - Method for producing a leaf spring from fibre-reinforced composite material with inserts, leaf spring, and chassis for a motor vehicle

Info

Publication number: EP3504458A1
Application number: EP17751284.5A
Authority: EP
Inventors: Stefan Krahn; Thomas RUPFLIN; Mathias SCHRAMM; Ignacio Lobo Casanova
Original assignee: ZF Friedrichshafen AG
Current assignee: ZF Friedrichshafen AG
Priority date: 2016-08-25
Filing date: 2017-07-24
Publication date: 2019-07-03
Also published as: KR20190039298A; CN109642630A; DE102016215938A1; JP2019528408A; DE102016215938B4; WO2018036733A1

Abstract

The invention relates to a method for producing a leaf spring (1) from a fibre-reinforced composite material, the leaf spring (1) being fabricated from a plurality of fibre layers with at least one thickened portion (2, 3) lying between ends (4, 5) in the longitudinal direction. To reduce outlay on production, the at least one thickened portion (2, 3) is in each case defined by at least one insert (8), which is prefabricated as a unit and is then arranged between an upper covering layer (6) and a lower covering layer (7) in the region of the thickened portion (2, 3) to be defined.

Description

METHOD FOR PRODUCING A LEAF SPRING

FIBER COMPOSITE WITH INSERTER, SHEET SPRING AND CHASSIS FOR A MOTOR VEHICLE

The invention relates to a method for producing a leaf spring made of a fiber composite material, wherein the leaf spring is made of several fiber layers with at least one lying in the longitudinal direction between the ends thickening. Furthermore, the invention relates to a leaf spring and a chassis for a motor vehicle.

In chassis of motor vehicles leaf springs can be used as suspension springs, which support the construction of the vehicle resiliently with respect to the wheels provided on the wheel carriers. A significant advantage of a leaf spring is that it also act as a construction element for connecting structure and axle and can take over Radführungsfunktionen compared to other types of spring simultaneously. If a plurality of leaf springs are then used, a certain degree of damping can still be achieved due to the frictional forces between the individual spring leaves, so that the leaf springs can support the work of a vibration damper.

Leaf springs are now increasingly made of a fiber composite material, which can realize the advantages mentioned above with low weight. Usually, the leaf spring is composed of several fiber layers, which are positioned according to the desired design of the leaf spring to each other, compacted and then bonded together by a plastic matrix materially. Depending on the geometry and choice of material of this ultimately formed leaf spring can thereby realize different properties of the leaf spring.

From DE 10 2010 050 065 B4, a method for producing a leaf spring from a fiber composite material is apparent, wherein the leaf spring is made of several fiber layers. In this case, between the ends of the leaf spring, a thickening is formed with a greater thickness compared to the remaining part of the leaf spring, wherein this thickening is produced by fiber layers with different lengths alternately from the ends to the desired area. overlap and overlap here. This targeted overlap of the fiber layers in the desired area then causes the thickening there.

Starting from the above-described prior art, it is now the object of the present invention to provide a method for producing a leaf spring made of a fiber composite material, wherein it should be possible to produce at least one thickening with low production costs.

This object is achieved on the basis of the preamble of claim 1 in conjunction with its characterizing features. The following dependent claims give each advantageous embodiments of the invention. A leaf spring according to the invention is also the subject of claim 9, while a leaf spring having a landing gear claimed in claim 10.

According to the invention, in a method for producing a leaf spring made of a fiber composite material, the leaf spring is manufactured from a plurality of fiber layers with at least one longitudinal thickening between the ends. According to the invention, the leaf spring is thus made of a plurality of individual fiber layers, which form a fiber-plastic composite in combination with a plastic. For the purposes of the invention, the fibers are reinforcing fibers, in particular in the form of glass fibers, which are surrounded by a plastic matrix. The plastic matrix is preferably formed by a thermosetting plastic, which may be in the form of epoxy resin.

In the case of the leaf spring to be produced, at least one thickening is formed in the course of production between the ends. Here, a "thickening" is to be understood as meaning a section of the leaf spring which has a significantly greater thickness, ie a greater extent in the springing direction, compared to other sections of the leaf spring Thickened areas may be provided, which may be designed according to their thickness in accordance with or deviating. The invention now includes the technical teaching that the at least one thickening is defined in each case by at least one insert, which is prefabricated as a unit and subsequently arranged in the region of the respectively defined thickening between an upper cover layer and a lower cover layer. In other words, in the method according to the invention, at least one insert is already manufactured in advance, wherein this prefabricated insert is then placed between a lower and an upper cover layer in the area to be thickened in the further production process of the actual leaf spring and, after connection with the cover layers there, the desired one Thickening defined.

Such a design of a method has the advantage that the production costs can be reduced by the upstream production of the at least one insert. Because the actual leaf spring is thus divided into several components, which are merged only at the end of the manufacturing process. In this way, positioning and connection of the individual fiber layers can be made simpler in the inserter than would be the case if fiber layer for fiber layer were laid one on top of the other in an expiration to the final leaf spring. As a further advantage, a production of leaf springs can thereby be designed in a modular manner, in that different combination possibilities of prefabricated embodiments of inserts with different cover layers exist and thus also different properties of leaf springs can be realized. In addition, different prefabricated inserts could be combined with each other. Overall, the manufacture of a leaf spring can be made simple by arranging one or more prefabricated inserts between the cover layers at or the respective points and thereby one or more thickened areas are realized.

On the other hand, in the case of DE 10 2010 050 065 B4, a respective thickening of a leaf spring to be manufactured is achieved by realizing a corresponding overlap of fiber layers, which in each case extend alternately from axial ends of the leaf spring into the corresponding region. This is correspondingly complex, since layered layer by layer for fiber layer for manufacturing must be and prevent slippage of the individual layers before the final joining is.

For the purposes of the invention, the fact that the at least one insert is prefabricated as a unit means that the insert has already been produced in the course of an upstream production process as fiber-plastic composite a plastic matrix integrated.

In principle, depending on the properties of the final leaf spring to be achieved, the insert can be made of the same fiber composite material as the cover layers or also of a material to be deviated. Likewise, the cover layers may consist of one and the same material or be formed by different materials.

According to one embodiment of the invention, the at least one insert is in advance composed of a plurality of fiber layers, which are connected in overlapping manner in at least one section and thereby define a greater thickness in the respective section. In a further development of this embodiment, fiber layers of different lengths are connected to one another. The at least one insert is thus composed according to a predefined pattern of the different fiber layers, wherein the thickness to be achieved is realized by targeted overlapping of the different fiber layers.

According to an alternative or supplementary embodiment of the invention, the at least one insert is previously composed of several fiber layers, wherein at least one section is made of greater thickness by attaching at least one shorter fiber layer to at least one longer fiber layer. In this case, therefore, the desired thickness of the at least one inserter is realized in that one or more shorter fiber layers are placed on one or more longer fiber layers. The fibers are thus stacked on top of each other. According to a further embodiment of the invention, the upper cover layer and / or the lower cover layer are each formed by a plurality of fiber layers. According to the invention, therefore, the upper cover layer or the lower cover layer or also both the upper and the lower cover layer are each composed of a plurality of fiber layers. As a result, depending on the choice of the number of fiber layers, the property of the leaf spring to be ultimately produced can be influenced. It is also within the meaning of the invention also conceivable to prefabricate the upper cover layer and the lower cover layer also in the context of an upstream process. Alternatively, however, the individual fiber layers can also be joined together only as part of the connection with the at least one intermediate insert.

In a further development of the aforementioned embodiment, the plurality of fiber layers each have the same lengths. Particularly preferably, the fiber layers of the upper cover layer and / or the lower cover layer extend in the longitudinal direction of the leaf spring from the axial end to the other end of the final leaf spring.

It is a further advantageous embodiment of the invention that the at least one thickening is formed in each case by a plurality of intermediate inserts. The individual thickening is thus formed by interaction of several depositors, these depositors more preferably corresponding to each other and are mirrored to each other between the upper cover layer and the lower cover layer are arranged. Through this interaction can be realized by the run as a common parts inserts significantly higher thickening.

A leaf spring produced by means of the method according to the invention is characterized in that at least one thickening is formed in the longitudinal direction between ends, wherein at least one insert is provided in the respective region of the at least one thickening between an upper cover layer and a lower cover layer, which as a prefabricated unit with the cover layers is connected. Such a leaf spring is then in particular part of a chassis for a motor vehicle, wherein the leaf spring used can be further made according to the further, previously described variants. The invention is not limited to the specified combination of the features of the independent or the dependent claims. There are also opportunities to combine individual features, even if they emerge from the claims, the following description of preferred embodiments of the invention o- directly from the drawings. The reference of the claims to the drawings by use of reference numerals is not intended to limit the scope of the claims.

Advantageous embodiments of the invention, which are explained below, are shown in the drawings. It shows:

Fig. 1 is a schematic representation of a leaf spring according to the invention according to a first embodiment of the invention, shown in the finished state;

Fig. 2 is a schematic representation of the leaf spring of Fig. 1, disassembled into their

components;

Fig. 3 is a schematic detail view of an insert of Fig. 2, shown before its completion;

4 shows a schematic single view of the insert in the finished state;

Fig. 5 is a schematic detail view of an upper cover layer of Figure 2, shown before its completion.

Fig. 6 is a schematic detail view of a lower cover layer of Figure 2, shown before its completion.

Fig. 7 is a schematic illustration of a leaf spring according to a second embodiment of the invention, shown before its completion; and Fig. 8 is a schematic view of a leaf spring according to a third embodiment of the invention, shown before its completion

From Fig. 1 shows a schematic view of a leaf spring 1, which is designed according to a first embodiment of the invention. As can be seen in Fig. 1, the leaf spring 1 has two thickenings 2 and 3, which lie in the longitudinal direction between the ends 4 and 5 to each other. In this case, the leaf spring 1 is designed in the region of the thickenings 2 and 3 in comparison to end-side sections and an intermediate central region with a significantly greater thickness. 1 shows the leaf spring 1 in a finished state, in which a plurality of fiber layers, in particular in the form of glass fibers, are surrounded by a plastic matrix and form a fiber-plastic composite. The plastic is formed in particular by a thermosetting plastic and is preferably present as an epoxy resin.

As a special feature, the leaf spring 1 modular-like composed of several prefabricated components, which are apparent from Fig. 2. Thus, it can be seen in FIG. 2 that the leaf spring 1 is formed by an upper cover layer 6, a lower cover layer 7 and a total of four inserts 8, which each have the same construction and are arranged between the upper cover layer 6 and the lower cover layer 7 , Specifically, the depositors 8 are each paired mirrored to each other at the locations between the upper cover layer 6 and the lower cover layer 7, where the later leaf spring 1 should have the thickenings 2 and 3.

The cover layers 6 and 7 and also the inserts 8 are each prefabricated in upstream process steps of several fiber layers, this being shown for the insert 8 in FIGS. 3 and 4, while FIG. 5 shows the prefabrication of the upper cover layer 6 and FIG the prefabrication of the lower cover layer 7 shows. With regard to the inserts 8, it can be seen in FIG. 3 that a plurality of fiber layers 9 to 13 are arranged one above the other, which have different lengths. In this case, the fiber layers 10 to 13 are arranged on the longest fiber layer 9 such that the fiber layer 10 overlaps with the layer layers of fiber layers 11 and 12 arranged one above the other and in turn, is overlapped by the uppermost fiber layer 13. In this way, the desired contour of the insert 8 is imaged, wherein the fiber layers 9 to 13 are subsequently precompacted in a furnace process to the wedge-shaped contour shown in FIG. 4, in order ultimately to be surrounded by a plastic matrix.

By contrast, as can be seen from FIGS. 5 and 6, both the upper cover layer 6 and the lower cover layer 7 are each formed from a plurality of equally long fiber layers 14. In this case, the fiber layers 14 each have a length which corresponds to a defined at the later leaf spring 1 between the ends 4 and 5 length. As can also be seen in FIGS. 5 and 6, the upper cover layer 6 is composed of two fiber layers 14, while the lower cover layer 7 is formed by a total of four fiber layers 14. Both the upper cover layer 6, and the lower cover layer 7 are also pre-compacted and incorporated in a plastic matrix. In a final process is then made of the upper cover layer 6, the intermediate, four inserts 8 and the lower cover layer 7, the final leaf spring 1.

Furthermore, in Fig. 7, the components of a leaf spring 15 are shown according to a second embodiment of the invention. In contrast to the previous variant, an upper cover layer 16 and a lower cover layer 17 are identical in that they are composed of the same number of fiber layers, in each case four fiber layers. The same is also the case with the components of a leaf spring 18 of FIG. 8, in which also the upper cover layer 19 and the lower cover layer 20 have the same construction, that is to say corresponding components are realized. Unlike the previous variant, however, the upper cover layer 19 and the lower cover layer 20 are each formed by two fiber layers each.

By means of the method according to the invention, a leaf spring can be produced with a low production cost, wherein at the same time different thickness profiles can be realized without difficulty. Bezuaszeichen leaf spring

thickening

The End

upper cover layer

lower cover layer

depositors

fiber layer

leaf spring

upper cover layer

lower cover layer

leaf spring

upper cover layer

lower cover layer

Claims

claims

A method of producing a leaf spring (1; 15; 18) from a fiber composite material, wherein the leaf spring (1; 15; 18) consists of several fiber layers (9 to 14) with at least one longitudinal thickening between ends (4, 5) (2, 3), characterized in that the at least one thickening (2, 3) is defined in each case by at least one insert (8), which is prefabricated as a unit and subsequently in the region of the respectively to be defined thickening (2, 3 ) between an upper cover layer (6; 16; 19) and a lower cover layer (7; 17; 20) is arranged.

2. The method according to claim 1, characterized in that the at least one insert (8) in advance from a plurality of fiber layers (10 to 13) is composed, which are connected in at least one portion overlapping each other and thereby define a greater thickness in the respective section ,

3. The method according to claim 2, characterized in that fiber layers (11 to 13) of different lengths are interconnected.

4. The method according to claim 1, characterized in that the at least one insert (8) is assembled in advance from a plurality of fiber layers (9 to 13), wherein at least one section is made of greater thickness by at least one shorter fiber layer (10 to 13 ) is fastened on at least one longer fiber layer (9).

5. The method according to claim 1, characterized in that the upper cover layer (6; 16; 19) and / or the lower cover layer (7; 17; 20) is formed in each case by a plurality of fiber layers (14).

6. The method according to claim 5, characterized in that the plurality of fiber layers (14) of the upper cover layer (6; 16; 19) and the lower cover layer (7; 17; 20) have the same lengths.

7. The method according to claim 1, characterized in that the at least one thickening (2, 3) in each case by a plurality of intermediate insert (8) is formed.

8. The method according to claim 7, characterized in that corresponding inserts (8) are arranged mirrored to each other.

9. leaf spring (1; 15; 18) made of a fiber composite material, in which longitudinally between the ends (4, 5) at least one thickening (2, 3) is formed, characterized in that in the respective region of the at least one thickening (2, 3) at least one insert (8) is provided between an upper cover layer (6; 16; 19) and a lower cover layer (7; 17; 20), the at least one insert (8) being provided as a prefabricated unit with the cover layers (6; 7, 16, 17, 19, 20).

10. Suspension for a motor vehicle, comprising a leaf spring according to claim 9.