DE102010049563A1 - Method for manufacturing torsion bar spring of motor car, involves thermally melting matrix material during and/or after braiding and/or wrapping of core, and connecting component to torsion bar spring - Google Patents

Abstract

The method involves manufacturing a component i.e. tubular component, with a tubular cross-section by braiding and/or taping a core with fiber bundles, which are pre-impregnated with a thermoplastic matrix material. The matrix material is thermally melted during and/or after braiding and/or wrapping of the core, and the component is connected to a torsion bar spring (1). The component is flexed after removal of the core into a near net shape, or the final form, where a blow-molded part is used as the core. The torsion bar spring is made of fiber reinforced plastic. The fiber bundles include glass fibers, aramid fibers, Kevlar(RTM: para-aramid synthetic fiber) fibers or carbon fibers.

Description

The invention relates to a method for producing a torsion spring for a motor vehicle with a substantially tubular cross-section.

Trunnions or torsion bars are known from the general state of the art. These are torsion springs intended to reduce the rolling motion of a vehicle. These components are made of a high strength spring steel due to the high material requirements in terms of stiffness and strength, especially in the torsional load, and typically designed as a tube or solid material. In particular, in the embodiment as a hollow structure (as a tubular member) while the high notch sensitivity of the highly resilient spring steel used is particularly critical and can significantly contribute to a potential failure of the component. In addition, the use of a metallic hollow profile leads to a technically difficult to implement anticorrosive treatment. In order to ensure this nevertheless, corresponding additional costs and an increase of the cycle time in the manufacturing process of the component are necessary. Finally, such torsion springs also have due to the high forces and the necessary spring rate comparatively large component diameters and thus high weights, which result in a movement of the vehicle to correspondingly high energy consumption.

Likewise, fiber-reinforced plastics are known as lightweight materials from the general state of the art. These are due to the usual training with thermoset matrix systems in a mass production difficult to integrate and significantly extending the previous cycle times. The load-oriented arrangement of the fibers is also a significant problem for mass production of such components. Finally, the problem of post-processing, for example, by bending or similar manufacturing steps is a major problem due to the thermoset matrix materials typically used. Since the curing then only then can be done When the component has reached its final contour, the manufacturing cost is thereby significantly increased.

From the DE 102 011 582 A1 For example, a method of manufacturing a fiber composite leaf spring utilizing a braided tube and a mandrel is known. In particular, in terms of the geometry, this obviously has a very high variability and also allows a reduction in weight by up to 60 percent. As a fiber-reinforced plastic in this case a Glasfaserepoxidmaterial is used, which has very long curing times and so, as already set out above in the general design for fiber reinforced plastic, not suitable for use in a mass production, especially not in a series production. Thus, for the construction of composite leaf springs according to the DE 102 011 582 A1 be assumed from a correspondingly costly individual production.

For further general state of the art describes the EP 1 242 229 B1 a method for non-contact bending of thermoplastic pipes. The local introduction of radiation energy, for example via a laser, the tube is heated or fused in a localized zone, so that low degrees of deformation are possible. The problem is that when producing a torsion bar or a torsion spring significantly higher degrees of deformation are required, as they are known for example in the field of metallic pipes. In addition, the local melting of the matrix material results in a deterioration of the fiber impregnation and thus a deterioration of the fiber adhesion to the matrix, which can lead to undefined stress notches or microcracks and thus correspondingly weakens a component formed in this way.

The DE 10 2007 003 596 A1 again relates to a method for producing a leaf spring from the vehicle sector using a composite thermoplastic fiber with thermoplastic matrix. For this purpose, thermoplastic prepregs, ie pre-impregnated with thermoplastic matrix material, flat fiber bundles or rovings are used, which are assembled by means of conventional textile technology measures and then pressed into a concave mold. Again, it is a discontinuous manufacturing process, which is unsuitable for mass production and thus correspondingly complex and expensive.

From the DE 10 2008 010 228 A1 and the DE 10 2007 051 517 A1 In addition, the so-called braided pultrusion is known, with which in particular bending and torsion-resistant raw profiles can be produced. In this case, a tubular fabric, in which a thermoplastic matrix material is already arranged, pulled by a pultrusion plant with one or more braiding eyes, consolidated by heat input and deburred at the outlet from the tool and then cut to length. In this case, almost any predetermined, but for the respective tool constant profile shapes and fiber orientations are feasible.

The object of the present invention is to provide a method for producing a torsion spring for a motor vehicle with a in the To provide a substantial tubular cross-section, which avoids the disadvantages mentioned and provides a suitable method for a continuous series production with short cycle times method, which also allows a lightweight, stable and functional torsion spring.

According to the invention, this method is achieved by the features mentioned in the characterizing part of claim 1. Further advantageous embodiments of the method result from the dependent therefrom dependent claims.

The method according to the invention provides that a component with a substantially tubular cross section is produced by braiding and / or wrapping a core with fiber bundles which are preimpregnated with a thermoplastic matrix material or are preferably flat as homogeneous hybrid rovings. During and / or after braiding and / or wrapping, thermal melting of the matrix material takes place.

The method according to the invention thus provides a base component for the torsion bar spring, which is produced in the form of a tubular component, in which a core is wrapped and / or braided with pre-impregnated fiber bundles or rovings, which are provided with a thermoplastic matrix material. When wrapping and / or braiding and / or thereafter, a thermal melting of this matrix material, so that ultimately a tubular member is formed, which can then be further processed to the torsion spring. Through the use of suitable fiber types, fiber amounts and directions of the individual fiber bundles, for example, when braiding and / or wrapping, so can be individually suitable over the length of the tubular member and the later torsion spring at the respective point strength, so that a sufficiently strong torsion spring with appropriate Damping properties can be realized. This is compared to steel springs significantly lighter and not or only slightly susceptible to corrosion with a suitable choice of material of the matrix material. For example, can be used as thermoplastic matrix materials PA, PPA or PEEK, which in addition to excellent chemical resistance additionally low water absorption and high impact strength. In addition, they are correspondingly temperature stable, so that they can be used both on the rear axle and on the front axle, in which the torsion bar must be passed through the relatively warm area of the engine compartment. In addition to these matrix materials, other thermoplastic matrix materials are also conceivable, in particular those having a high (≥ 125 ° C.) glass transition temperature, since these have constant spring characteristics over virtually the entire temperature range. These matrix materials may be combined with various types of fibers, for example, glass fibers, aramid fibers, Kevlar fibers, or more particularly carbon fibers, and combinations thereof.

• – Drastische Reduzierung des Bauteilsgewichtes
• – Verbesserte Medien- und Chemikalienbeständigkeit vgl. mit Stahl
• – Kein zusätzlicher Korrosionsschutz des Bauteils notwendig
• – Verbessertes Dämpfungsverhalten des Werkstoffs, erhöht Fahrkomfort und Emissionsverhalten
• – Reduzierte Fertigungszeiten, höhere Effizienz der Fertigung
• – Geringere Herstellkosten
• – Fasergerechte leichtbauende Lasteinleitung
• – hohe Dauerschwingfestigkeit (insbesondere durch geringe Ondulation bei geflochtenen flachen Hybridrovings wird die Schwingfestigkeit erhöht)
• – Einsetzbarkeit des Bauteils an Vorder- und Hinterachse
• – Federcharakteristik durch Variation des Laminataufbaus in weiten Bereichen beeinflussbar
• – Ideal torsionssteifes geschlossenes Hohlprofil bei gleichzeitiger Verwendung von Materialen mit höchster Leichtbaugüte
• – Senkung des Energieverbrauchs des Fahrzeugs pro gefahrenem Kilometer und Verkleinerung des Schadstoffausstoßes
• – Senkung des Energieverbrauchs bei der Herstellung des Drehstabs aus faserverstärktem Kunststoff bezogen auf einen vergleichbaren Drehstabs aus Stahl
• – Kleiner bauend (geringerer Hebelarm) durch höhere zulässige innere Spannung bei Faserverbundstrukturen

The construction of a torsion bar made of a fiber-reinforced plastic has the following advantages:

• - Drastic reduction of the component weight
• - Improved media and chemical resistance cf. with steel
• - No additional corrosion protection of the component necessary
• - Improved damping behavior of the material, increases ride comfort and emission behavior
• - Reduced production times, higher production efficiency
• - Lower manufacturing costs
• - Fiber-friendly lightweight load introduction
• - high fatigue strength (in particular due to low ondulation in braided flat hybrid rovings, the fatigue strength is increased)
• - Applicability of the component on the front and rear axles
• - Spring characteristic influenced by variation of the laminate structure in a wide range
• - Ideal torsionally rigid closed hollow profile with simultaneous use of materials with the highest level of lightweight construction
• - Reducing the energy consumption of the vehicle per kilometer driven and reducing pollutant emissions
• - Reduction of energy consumption during the production of the torsion bar made of fiber-reinforced plastic based on a comparable torsion bar made of steel
• - Smaller construction (lower lever arm) due to higher permissible internal stress in fiber composite structures

According to a particularly favorable and advantageous development of the method according to the invention, it is additionally provided that the core is braided by braided pultrusion by means of at least one braiding eye. The use of the braiding pultrusion makes it possible to realize different storage angles between ± 5 ° and ± 80 °, so as to realize an ideal for the expected force curve adapted fiber profile.

In a particularly favorable and advantageous development of the method according to the invention, it is further provided that the core is braided, wherein unidirectional fibers are interwoven with. The introduction of unidirectional fibers allows reinforcement specifically in the Direction in which unidirectional fibers are inserted. This process, which is also called undirectional braiding or UD braiding, enables a further increase of the strength by an ideal adaptation of the fiber flow to the expected forces or the expected force course.

In a particularly favorable and advantageous embodiment of the method according to the invention, it is further provided that the core is removed after braiding and / or wrapping. The core is therefore used only as a basis for braiding or wrapping the resulting on this core tubular component can then be deducted from this core and otherwise processed. Such further processing includes, for example, bending into the later shape or bending into a shape very close to the later shape as well as cutting to length.

In an alternative embodiment of the method, it may also be provided that the core remains in the component. In this case, the core may be, for example, a foam core, a blow molding or the like. In particular, however, the core may be a component produced by one of the above-mentioned methods, which has been produced, for example, on a core, which is later removed from the component, by braiding and / or wrapping. This core can then either bent or unbent serve as a core for further processing and can be wrapped again and / or braided until the desired material thickness is applied. In the case that the core has a near-net shape and is already bent, regardless of whether it is designed as a foam core, as a blow-molded part or as a braided and / or wound component, this can be used for re-braiding and / or wrapping, in particular by a multi-axis robot be guided by suitable braiding and / or winding machines, so as to be provided with further layers of the fiber-reinforced material.

In principle, a subsequent consolidation of the component, for example in an injection mold or by hydroforming is possible. In particular, as part of a Nachkonsolidierung in an injection mold and other functional elements such as bearing eyes, receptacles or similar fasteners can be attached to the final contour bent semifinished product. For example, by a two-component injection molding process, the required mounting of the torsion bar can be applied during the reconsolidation of the component.

Further advantageous embodiments of the invention will become apparent from the following embodiment, which shows with reference to the figures, various possible embodiments of the method for producing a torsion spring of a fiber-reinforced plastic. The description of the possible manufacturing methods refers to the figures, which show in principle schematically process sequences and structures for carrying out the method according to the invention.

In detail:

1 a three-dimensional view of a torsion spring according to the invention;

2 various preimpregnated fiber bundles;

3 a device arrangement for producing a tube by braiding pultrusion;

4 various possible variants for the production of the starting semifinished product;

5 an arrangement for wrapping a core with fiber bundles;

6 the process of braiding a blow-molded core;

7 the apparatus and process of bending the tubular semi-finished product;

8th a first possibility for introducing a bush into an end portion of the torsion bar spring;

9 a second possibility for introducing a bush in an end portion of the torsion bar spring;

10 a possibility for deformation of the braid when inserting a socket, in particular according to 9 ; and

11 the attachment of an attachment via a thread.

In the presentation of the 1 is purely an example of a finished torsion bar 1 to recognize in a three-dimensional representation. The torsion bar spring 1 or the torsion bar has two bearings 2 . 3 on, which in particular by a two-component injection molding process to the torsion bar 1 have been attached, as will be described later. At the two ends, the torsion bar spring 1 also recording elements 3 on, which in later also described in more detail manner on the torsion bar spring 1 to get integrated. These recording elements 3 can have other sockets, receiving openings or the like and serve together with the camps 2 for fastening the torsion bar spring 1 on the vehicle or the necessary functional elements and levers.

Hereinafter, various embodiments and aspects are described, which in a series production of such a torsion spring 1 are relevant and which different examples of a manufacturing method in the context of the present invention, without limiting the invention to such procedures or aspects.

For serial production of the torsion bar 1 With automotive quantities, it is first necessary to produce a starting semi-finished product to be manufactured continuously. When using fiber-reinforced plastic (FRP), thermoplastic matrix materials, in particular PA, PPA and PEEK, offer a wide range of applications, in addition to their very low water absorption, excellent chemical resistance and high notched impact strength, especially due to their high temperature stability the thermal requirements for a plastic in the engine compartment of a vehicle, distinguished. The reinforcing fiber used may be glass, aramid and, in particular, carbon fiber and combinations thereof. In order to achieve a good fiber impregnation as well as an excellent fiber matrix adhesion, the production of the FRP starting semifinished product, in particular those in 2 hybrid yarns (a), prepreg tapes (b) tow-preps (c) or d) (not shown, preferably flat) hybrid rovings made of reinforcing and matrix fibers used. In the presentation of the 2 In this case, the reinforcing fibers are shown in dark, while the matrix material is shown in light Their application leads in the further process to an improved consolidation of the semifinished product and prevents the formation of imperfections, such as air bubbles (pores, voids).

The production of the tubular starting semi-finished product for the torsion bar 1 takes place according to a first possible variant continuously according to the principle of braiding pultrusion. A suitable plant for braiding pultrusion is in the representation of 3 to recognize. Starting from a creel 4 , which is occupied in this case with unidirectional hybrid roving, follow three successive switched wicker or braiding wheels 5 followed by preheating 6 and a heated mold 7 , The by the preheating 6 heated preimpregnated fiber bundles reach at the latest in the heated mold a temperature at which the matrix material melts accordingly and thus forms a solid composite of the matrix material and the fiber bundles. In a subsequent cooling 8th The semi-finished tube then solidifies before it subsequently by means of a caterpillar take-off 9 is deducted. The feeding of the fiber matrix material is fully automated. It comes with several braiding wheels in a row 5 worked, with the number of braided pulp plants used or the system structure (number braiding wheels, number Pultrusionsanlagen) is determined by the achievable wall thickness per overall system. This arrangement makes it possible to deposit a plurality of braid layers one above the other on a mandrel made of metal, in particular in the case of very thick braids and correspondingly high thread tensions, or plastic in thinner braid structures, which is advantageous in particular with high wall thicknesses s (> 5 mm) and a corresponding number of layers to ensure the dimensional stability of the braided hose. When braiding reinforcement angles of about ± 5 ° to ± 80 ° are possible, for a reinforcement in 0 ° direction, which is particularly advantageous in bending stress, can be at the braiding 5 additional Stehfäden be supplied. These run stretched into the network and thus have virtually no ondulation. One speaks of so-called unidirectional lichen or UD lichen. Following every braiding process, the braided hose is made with the help of preheating 6 , in particular an IR emitter, (preheating) are heated, which facilitates the entry into the pultrusion, since the matrix already melts and first adhesions between matrix and reinforcing fiber occur, which in turn stabilizes the braided hose and slipping or upsetting of the braid before heated mold, which helps to prevent the Pultrusionmatrize. After being passed through the pultrusion tool, the resulting hollow profile is separated by a cutting device according to the desired length and transferred by an industrial robot to further processing. This process is in 4 (a) shown.

Especially with very complex component geometries, it is advantageous to vary the sequence of the process steps described above. Instead of producing a thick-walled semi-finished product, which is subsequently fed to shaping by CNC bending, the shaping process is preferred and combined with a subsequent 3D winding process; alternatively, the braiding of the preform is also possible, in which case preferably a subsequent consolidation in an injection-molded tool requirement. This is in 4 (b) indicated accordingly. The background is the significantly increased shape-changing capability of a thin-walled component. A semi-finished product having only a few (one to three) layers, which is produced by means of braiding pultrusion and subsequently assembled, is given its shape by CNC bending and serves as the core. Then done the application of further layers on the molded core formed by a movable in several axes laser-assisted winding robot. In this way, depending on the component geometry, a load-compatible fiber composite structure is achieved.

As a further variant for the production of the preformed component semifinished product, the fully integrated process of braiding pultrusion with bending "on the fly", ie the bending process takes place simultaneously with the pultrusion process by means of a movable bending tool, can be considered. This in 4 (c) indicated variant is characterized by a particularly high process integration. Lichening, pultrusion, bending and final cutting are integrated into a production line. However, in contrast to the variants a) and b), the preforming takes place only after shaping. The bending process is realized by a movable in Pultrusionsrichtung (on slide) bending unit. The traversing speed is adapted to the pultrusion process, so that during the bending process itself, a slightly reduced movement speed of the bending slit causes the material to be repressed analogously to conventional bending. The bending unit is designed so that the bending range of the semifinished product can be tempered down to its dimensional stability (depending on the plastic used) during a cycle time. After a bending point is formed, the bending unit moves to the next still heated by the pultrusion point and the molding process is continued.

As an alternative to the method described above in a first variant, in which the starting semifinished product is produced by the braided pultrusion, the semi-finished profiled product can also be produced by laser-assisted thermoplastic winding. A corresponding structure is in principle in 5 shown. From a yarn package 10 A fiber bundle runs over a thread tensioner 11 and suitable guides through a preheating zone 12 in which preheating of the matrix material takes place by means of infrared, ultrasound and / or microwaves. About a thread eye 13 and a pinch roller 14 then the fiber bundle enters the area of the later component. In this method, prepreg bands are preferably used, since a higher Ablegeleistung is achieved. That from the yarn package 11 supplied ribbon is on a winding core 15 wound. When the material hits the profile shape, a laser melts 16 by concentrated heat input at the point of impact, the matrix material. As a result, the fiber strand is optimally embedded in the matrix. The consolidation of the stored tapes takes place by means of one or more staggered pressure rollers 14 , In addition, several winding heads are used to achieve high lay-off rates, which enables production speeds of FRP pipes of up to 7 m / min. By means of thermoplastic winding variable fiber angle combinations and variable wall thicknesses can be represented. This creates the possibility of realizing a variable wall thickness over the course of the component with a constant inner tube cross-section, thus creating a load-compatible component structure. In order to improve the forming behavior, in particular for CNC bending, in addition to a fiber composite system with optimum fiber-matrix adhesion, the layer structure also has to be varied, in particular in the area of bending points, so that high degrees of deformation can be achieved despite relatively low fiber elasticity. By reducing the thread tension when braiding in the area of the bends also smaller bending radii and larger bending angles can be made possible. A separating device then cuts the wound semi-finished products to the desired length.

In a third variant serves as a starting semifinished a pultudiertes plastic tube in particular matched to the matrix material used z. B. from PA, PPA, PPS, PEEK, which may already have an endless fiber reinforcement depending on the load of the component or consists of several layers. For low loaded structural components an unreinforced profile is sufficient. Multilayer pipes offer the advantage that, in particular, the inner layer has a special plastic which improves adhesion to attachment parts, while the outer layer has special properties with regard to improving the adhesion to the matrix material of the reinforcement layer. The tube is preformed in the first step by means of bending in its near net shape and then metallic load introduction elements, in particular made of stainless steel or coated steel, which is particularly well suited because of the low potential difference introduced. Fiber and metal inserts are insulated by a dense matrix layer. Machining that could violate this isolation does not occur. In order to further increase the lightweight quality, aluminum inserts can also be used, in which case a primer should be used due to the high electrochemical potential difference in order to avoid corrosion. After the load introduction elements have been integrated into the bent pipe, it serves as a braiding core for generating the "outer reinforcement". After the reinforcement, in particular as a braid, has been applied in multiple layers and thus also an optimal transfer of force from the insert into the fiber composite, the component is placed in an injection mold and here on the one hand through the use of hybrid yarn (plastic Carbon fiber) melted the already contained in the semi-finished matrix and on the other hand, the semi-finished product is additionally encapsulated with matrix material.

As an alternative to the variant just described, a semi-finished production with core can also be realized in such a way that for the production of the fiber-reinforced torsion bar 1 a plastic liner is used and braided or wrapped. As a semifinished product ideally no pipe is used, which still has to be bent, but a blasformtechnisch- produced liner, which may also be constructed as the pipe described above multi-layered. This is already according to the contour of the torsion bar 1 formed. In the presentation of the 6 Such an arrangement can be recognized by way of example. In a blow mold 17 a suitable material is introduced and inflated in the next step with hot air. It then creates the described liner 18 , which is then guided by a robot 19 in the wicker eye 5 braided according to or in an arrangement according to 5 can be wrapped.

Analogous to the two variants described, a lost foam core, which already has the contour of the torsion bar, can also be used as the core material 1 having. The advantage of this variant is the additional supporting effect of the foam in the interior of the fiber composite structure.

Instead of a core remaining in the component, it is also possible to use a so-called lost core, which is in particular melted out or washed out before the attachment parts are introduced. Bonded sand, bismuth, foam or meltable resins can be used as the core material.

After a suitable tubular semi-finished product is produced according to one or a variation of the abovementioned method sequences, this is fed to a CNC mandrel bending system in a further processing by an industrial robot and bent here near net shape. For the preforming of the tubular semifinished product, alternatively, the stretch bending as well as the die bending can be used. For bending, the section semi-finished product in the region of the bending point under an infrared radiator (heating section) to the forming temperature, which is below the melting temperature and above the glass transition temperature, in the case of PA at about 145 ° C, heated. It should be noted that the semi-finished product is kept as cold as possible in the region of the clamping in the bending tool in order to prevent an escape from the tool holder and a cross-sectional deformation. In the presentation of the 7 this process is shown in principle in three steps. In 7 (a) is the semi-finished to recognize, which specifically by two infrared radiators 20 is heated at the later bending points. The intermediate areas and the right and left lying therefrom clamping areas remain correspondingly cold. In 7 (b) is shown to be a bending mandrel 22 , in particular a cooled mandrel 22 , is introduced into the preheated hollow profile. In the area of the bending point, with the help of variotherm heated bending jaws 23 and the tempered bending mandrel 22 , Which is designed as slender as possible to bead formation and thus to prevent stress notches, concentrated heat introduced into the forming zone and deformed the bending point. The jaws of a bending head 24 grasp the semi-finished product in a cold area, which also has a filler 25 is refilled to avoid deformation. The completed bending process is in 7 (c) shown. The variothermal cooling / heating to be recognized in this figure 26 the bending bakery 23 allows cooling of the bending zone after the bending process, so that a springback of the material (shape-memory effect) is avoided or reduced, as a result of the cooling of the semi-finished a non-deformable material state is achieved. The better it is possible here to cool the bending tool, the faster the thermal energy can be removed from the semifinished product, which in turn significantly reduces the cycle times.

Thereafter, the transfer of the bent semifinished product to an injection molding plant. Here, metallic attachments / inserts are first introduced for load introduction into the component by heating the semifinished product. Metallic inserts offer the advantage of a defined load introduction, whereas the semi-finished fiber composite takes over the task of remote load transmission. Subsequently, the injection mold tool is closed, the bent semifinished product in the end region to the corresponding contour of the load introduction element (LEE) formed (possibly undercuts formed) and with a plastic, in particular PPA, encapsulated. Optionally, the 2K injection molding process (compatible thermoplastics) can be used here to improve the bond strength. In order to prevent a collapse of the component, it is preferable to work with an internal support pressure, which is generated by a (preferably hot) gas. This requires two connection openings in the component, which can be realized via the LEE. After completion of the injection molding process, the finished torsion bar 1 are removed from the tool and the gas inlet holes z. B. to be sealed by gluing plastic plugs.

The encapsulation of the component after shaping and consolidation, depending on the manufacturing variant of the functional integration, the subsequent consolidation of the component and the protection of the LEE against corrosive media, such as road salt, inter alia during operation. In addition, for example, cable guides can be molded. By using the 2-component injection molding process, a "rubber insert", ie a sprayable elastomer in the area of the bearing points, could also be used, including connecting elements (clamps) of the torsion bar inserted in the tool 1 be integrated directly into the component.

When considering power transmission on and in fiber composite structures, a distinction is typically made between load application and remote transmission. For the remote transmission, the pipe structure is largely responsible, while the load introduction into the component is accomplished by so-called load introduction elements (LEE) (eg bolt, rivet, adhesive, press connections). The reason for this lies in the lower resilience of fiber composite plastics in terms of shear and the often not possible fiber composite design (fiber structure, fiber assembly) in the field of load application point, which makes it to Lochleibung u. a. failure-critical damage can occur. For this reason, as well as the better calculability / design and also the absence of creep under load, LEE are carried out metallic. However, special care must be taken to ensure that electrochemical corrosion can not occur due to the potential difference of the materials used. Therefore, the metallic LEE are provided with a primer / adhesive layer before they come into contact with the fiber composite. On the one hand the primer has the task of corrosion protection and on the other hand it improves the bond between the thermoplastic matrix and the metal.

In the following, some variants of the integration of load introduction elements in fiber composite structures will be described.

In 8th is the introduction of a self-piercing socket 27 in the formed, in particular compressed, end cross-section 28 represented the fiber composite tube. No inserter is used. The insertion of the bush takes care of the fiber. To increase the contact surface of the bolt connection washers 29 used. These have rounded edges in order to minimize the notch effect by the support of the discs on the fiber composite component. A connecting bolt 30 can then, for example, via a mother 31 bolted accordingly and with the end section 28 be connected to the fiber composite tube.

As an extension to this variant is before the compression of the end cross-section 28 of the torsion bar 1 one depositor each 32 in the form of a metal plate, in particular made of stainless steel, titanium or aluminum, introduced into the tube cross-section and then pressed under the action of heat with the fiber composite component, as in 9 to recognize. For radial support of the interference fit the torsion bars are wrapped again. In the precisely placed deposit 32 there is a hole for receiving a socket 33 , By means of a thorn 34 is the receptacle for the socket in the final cross-section 28 Pre-perforated fiber-friendly, ie the mandrel is designed so that the fibers are not penetrated, but only displaced. This is through the in 10 shown plan views, once before the penetration of the mandrel 34 and once after the intrusion of the thorn 34 analogous to the sectional views of 10 to recognize. Due to the formation of the fibers as a braid this is additionally favored, as in 10 to recognize. The thorn 34 can be designed to be heated, as in 10 through the indicated heating channels 35 is shown.

Alternatively, the preformed end 28 of the torsion bar 1 also be inserted into a combined punching / pressing tool. First, the introduction of the insert takes place 32 from the front of the torsion bar 1 , The coated with a primer LEE is pressed positively under pressure and temperature with the fiber composite. Thereafter, the punching tool is closed and punched through the end cross-section 28 and the depositor 32 simultaneously. The last step is from both sides of the torsion bar 1 a two-piece socket used and pressed. As an alternative to the punching process, the cutting out of the bushing hole can take place via a cutting laser whose advantage is a cleaner cutting edge with at the same time less fiber damage.

Another possibility consists of gluing / pressing in the coated with primer attachments / inserter in the tube and the subsequent encapsulation with fiber reinforced plastic with inner support pressure or in introducing the attachment / insert in the braided tube, forming the tube in an injection molding machine to a positive connection with insert to reach.

A special form of the attachment / insert with suitable undercuts, which are formed in the material of the tube, thereby creating the possibility of easy integration and a connection by positive engagement. The attachments with suitable undercuts can then be inserted during manufacture in the open ends of the tube. By suitable heating and deformation, the material of the tube is pressed into the region of the undercuts, thus creating a positive fastening between the insert and the material of the tube. The entire structure can be used to seal against corrosive media be encapsulated with a total, as already explained in more detail above.

Another possibility is the end section 28 with a suitable fiber-composite thread 36 to provide, in which a suitable attachment 37 can be screwed. This is in the presentation of 11 indicated in principle.

If necessary, necessary cross-sectional changes of the torsion bar 1 , So a change in the round cross-section of the substantially tubular torsion bar in certain areas, are of course possible. For this purpose, the round cross-section of the FRP material can be heated at certain points and deformed for example by stamp. In order to avoid an incidence of the material, for example, in the one-sided or two-sided Abplatten the tubular starting cross-section, the material can be held according to needle gripper or vacuum gripper to prevent such an idea. Another possibility is of course also in the above-described variant of hydroforming, in which in a hot gas, a pressure in the interior of the tubular body is constructed and incidents can be prevented in this way, since the pressure of the hot gas, the deformed area against the Stamp, which carries out the deformation, presses and thus can image the contour of the punch in the formed area accordingly.

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• DE 102011582 A1 [0004, 0004]
• EP 1242229 B1 [0005]
• DE 102007003596 A1 [0006]
• DE 102008010228 A1 [0007]
• DE 102007051517 A1 [0007]

Claims (11)

A method of producing a torsion bar for a motor vehicle having a substantially tubular cross-section, characterized in that a component of substantially tubular cross-section is produced by braiding and / or wrapping a core with fiber bundles preimpregnated with a thermoplastic matrix material, during and / or after braiding and / or wrapping the core, thermally melting the matrix material, and then completing the component to the torsion bar spring. A method according to claim 1, characterized in that the core is braided by braided pultrusion by means of a Flechtauges. A method according to claim 1 or 2, characterized in that the core is braided, wherein unidirectional fibers are braided with. A method according to claim 1, 2 or 3, characterized in that the core is removed after braiding and / or wrapping. A method according to claim 4, characterized in that the component is bent after removal of the core in a near net shape or the final shape. A method according to claim 1, 2 or 3, characterized in that the core remains in the component. A method according to claim 6, characterized in that a component produced according to one of claims 1 to 5 is used as the core. A method according to claim 6, characterized in that a blow molding is used as the core. Method according to one of claims 1 to 8, characterized in that after wrapping and / or braiding and optionally after the removal of the core, a subsequent consolidation of the component takes place in an injection mold. Method according to one of claims 1 to 9, characterized in that over 2K injection molded bearing elements for functional integration are molded. Method according to one of claims 1 to 8, characterized in that after the wrapping and / or braiding and optionally after the removal of the core, a post-processing of the component by means of hydroforming takes place.

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