Vehicle Rim with Turned-Over NCF Subpreforms at the Ends and Method for the production Thereof

The invention refers to a vehicle rim (1) with a rim body (2) made of fiber composite material, comprising a first subpreform (3) at a first axial end and a third subpreform (5) at the opposite second axial end, wherein a second subpreform (4) is arranged between the first subpreform (3) and the third subpreform (5), wherein the second subpreform (3) engages into a front connecting cavity (6) formed by the first subpreform (3) as well as also into a rear connecting cavity (7) being formed by the third subpreform (5). The invention also refers to a method for the production of a vehicle rim (1) with a rim body (2) made of fiber composite material, wherein an NCF material (19) comprising carbon fibers, glass fibers and/or aramid fibers is created respectively for the formation of a first subpreform (3) for a first axial end of the rim body (2) and of a third subpreform (5) for the opposite axial end of the rim body (2) with a connecting cavity (6, 7), respectively, wherein a second subpreform (4) made of a same or a similar NCF material (19) is inserted into the connecting cavity (6 and/or 7) and is fixed thereat.

The invention refers to a vehicle rim with a generally hollow, preferably (rotationally) symmetrical rim body made of fiber composite material.

From prior art there are basically known vehicle rims with a rim body made of fiber composite material. Said rim bodies normally comprise woven fabrics, non-crimp fabrics or braidings comprising carbon fibers, glass fibers or aramid fibers, preimpregnated with resin or subsequently injected with resin. After a curing process, a vehicle rim comprising said rim body is provided.

It is also known that the rim body made out of fiber composite material can be connected with another element which is provided for a fastening at the wheel hub of a vehicle, as for instance a car, a truck or another utility vehicle, but also for instance of two-wheeled motorized vehicles. Very often said element is formed as a star and is usually made of metal or a metal alloy like an aluminum alloy.

Up to now it has, however, been quite complex and cost-intensive to produce said (CFRP) rim bodies. Until now, such rim bodies have also not been capable of withstanding high loads and stresses to such a degree as desired. In particular it is necessary that they are still more robust against thermal stresses, pressures but also centripetal forces. And such a rim body shall be extremely rigid and lightweight.

Said object is solved by a vehicle rim according to the features of claim1, namely by a vehicle rim with a generally hollow, preferably (rotationally) symmetrical rim body made of fiber composite material, comprising a first subpreform at a first axial end and a third subpreform at the opposite second axial end, wherein a second subpreform is arranged between the first subpreform and the third subpreform, wherein the second subpreform engages into a front connecting cavity being formed by the first subpreform or being formed or being present in the first subpreform as well as also into a rear connecting cavity being formed by the third subpreform or being formed or being present in the third subpreform.

On account of having the possibilities to use three different subpreforms, the work steps can be carried out in parallel which saves a lot of time. Such a vehicle rim also enables a continuous production process as well as a discontinuous production process. The vehicle rims thus created are particularly lightweight, rigid and capable of bearing high loads and stresses.

The invention also has the object to make available a particularly fast, cost-intensive and reliable, i.e. fail-safe method for the production of a vehicle rim with a rim body made of fiber composite material.

Said object is solved according to the invention by a method comprising the features of claim10.

Such a method for the production of a vehicle rim with a rim body made of fiber composite material is characterized by the fact that an NCF (non-crimp fabric) comprising carbon fibers, glass fibers and/or aramid fibers is created respectively for the formation of a first subpreform for a first axial end of the rim body and of a third subpreform for the opposite axial end of the rim body with a connecting cavity, respectively, wherein a second subpreform made of the same or a similar NCF material is inserted into the connecting cavity and is fixed thereat, for instance by means of the activation of a (preferably thermal) binder and/or by means of the provision of a (3D) seam.

Advantageous further developments of the vehicle rim are claimed in the subclaims. Advantageous further developments of the method are also claimed in the subclaims. Said advantageous further developments will be explained in more detail in the following.

It is of advantage if the second subpreform is fixed or mounted in the two connecting cavities at the first subpreform and the third subpreform in particular in a one piece manner or in an integral manner. Then a good durability is guaranteed.

When all three subpreforms are penetrated by the same resin or resin mixture, a coherent, rigid but also particularly lightweight component is facilitated.

In order to keep costs low while still having a high load-bearing or stress-bearing capacity it has turned out to be advantageous if the first subpreform and/or the second subpreform and/or the third subpreform comprise an NCF or are made predominantly or completely made out of an NCF.

NCF is understood to mean “non-crimp fabric” (non-woven fabric). This is a flat structure that consists of one or more layers of parallel, stretched threads. The threads are usually fixed at the crossing points. The fixation takes place either by material connection or mechanically by friction and/or form fit.

The following types of thread arrangements exist:monoaxial or unidirectional thread arrangements, which are created by fixing a set of parallel threads;biaxial thread arrangements, in which two sets of parallel threads are fixed in the direction of two axes;multiaxial thread arrangements, wherein several sets of parallel threads are fixed in the direction of different axes.

The thread layers in multi-layer non-crimp fabrics can all have different orientations, and they can also consist of different thread densities and different thread counts. Compared to woven fabrics, non-crimp fabrics have, as is well known, better mechanical properties as reinforcement structures in fiber-plastic composites—which is the basic technical field to which the invention belongs—since the threads are in a stretched form and therefore there is no additional structural stretch and the orientation of the threads can be specifically defined for the respective application.

In order to be able to produce rims with a corresponding rim body which are particularly highly resistant to stresses and loads it has turned out to be of advantage if the NCF is a monoaxial/unidirectional or biaxial (e.g. +/−45° fibers-containing) non-crimp fabric or a multiaxial non-crimp fabric, preferably made of carbon fibers, glass fibers or aramid fibers.

The rim body will be able to bear particularly high forces with a low weight when the first subpreform and/or the second subpreform and/or the third subpreform comprises/comprise several, for instance 3, 4, 5, 6, 7, 8 or more layers consisting of NCF, wherein preferably the first subpreform and the third subpreform have the same number of or a different number of layers and the second subpreform has various numbers of layers, in relative terms preferably more layers than the first subpreform and/or the third subpreform. Exactly said different distribution of layers will also have a positive influence on the later running characteristics of the vehicle using said vehicle rim. The adaptation of the layers and of the number for each preform increases the optimization possibilities and, thus, the lightweight construction potential. It is, however, not necessary that it is different.

It is useful if the first subpreform and/or the third subpreform have an NCF on which a roving bundle is fixed, wherein for instance said combination is preferably wound up in multiple layers. By the use of a roving bundle, the later rim edge can be worked out in a better way. Then the high tensile forces occurring thereat can be coped with satisfactorily.

“Rovings” are understood to mean fiber filaments, in particular chemical fiber filaments. Here a “roving” is understood as a bundle, strand or multifilament yarn made of filaments/continuous fibers arranged in parallel. The cross-section of a “roving” is often elliptical or rectangular. Those ravings that have a slight protective twist, for instance five or ten twists per meter, which makes the cross-section more rounded, shall be comprised herein. In this connection, in particular filaments made of glass, aramid, or carbon form a roving.

When the roving bundle includes several, for instance 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15 or more rovings which are preferably twisted with each other, for instance 5, 6, 7, 8, 9 or 10 twists per meter +/−2 to 3, or which run in parallel to each other, and/or are entwined or wrapped by a positioning thread, like a glass fiber thread or a carbon fiber thread, even the roving bundle itself brings along an excellent rigidity for the processing as well as also for the later use of the entire rim body.

In order that the production can take place rapidly and that a machine-based production can be utilized, it is advantageous if the roving bundle is sewn on the NCF, for instance by means of a zigzag seam following the longitudinal direction of the roving bundle and of the NCF. In this connection it has turned out to be advantageous if a change of direction of the thread of the zigzag seam will occur every 15 mm and if the width of the seam as measured at right angles to the longitudinal direction of the roving bundle is 7 mm. Here it is favorable if the zigzag seam is spaced apart from the edge of the roving extending in the longitudinal direction of the NCF for instance 1/10 of the width. Here it is of advantage if the width of the entire roving bundle is approximately 10 mm+/−2 mm.

The ratio of rigidity to weight is particularly advantageous if the first subpreform and/or the third subpreforrn is/are wound up/structured with 4, 5, or 6 layers, and/or if the second subpreform is wound up/structured with 5, 6 or 7 layers. Also more layers, for instance 8, 9, 10, etc., are possible.

At present there are only three subpreforms. In future, however, there can be added further subpreforms (top layers, local thickenings, etc.). The three subpreforms can be supplemented by further “sub-subpreforms”. In practice this means additional visible layers also because of the visual appearance, because of the thermal protection and in order to achieve local additional reinforcements.

The three subpreforms can be additionally supplemented by the simultaneous winding up of rovings or strips together therewith. As a result thereof there are obtained areas in the circumferential direction which comprise additionally also fibers in the circumferential direction.

It is also possible to wind additional 0° rovings in the circumferential direction onto the second subpreform in the area of the connection and to further reinforce said area thereby.

When that part of the NCF layers of the first subpreform and/or of the third subpreform that adjoins the roving bundles, completely or partially, but the region comprising all layers, are fixed at each other via a preferably thermally activated binder such that they cannot slip. In this way, the area on one side of the roving bundle that is not provided with a binder can later on easily be turned over (turned inwards or outwards)/everted or inverted/folded over/flipped over, whereas the area on the other side of the roving bundle that is provided with the binder remains hard and cannot slip. This is advantageous for the production. The precision of the rim body will be particularly good and high.

When said area on which the binder is applied is (only) present on the outside of the vehicle rim, i.e. radially outward of the respective connecting cavity, the turning over/flipping over of the remaining part of the rim body defining the shape of the vehicle rim is easily possible beginning in the section of the incorporated roving bundle, even by hand force. It shall be noted that the turning over (turning inwards or outwards) can also be designated as everting or inverting, folding over or flipping over.

One advantageous embodiment is also characterized in that the second subpreform is fixed at the first subpreform and/or at the third subpreform (also) by means of a (3D) seam penetrating the respective connecting cavity. Thereby the coherence of the individual parts is increased.

A further embodiment refers to such a rim body configuration in which the roving bundle is spaced apart from a longitudinal edge of the NCF by between 5/12 to 6/13+/−10% of the width of the NCF. In this manner, the roving bundle is positioned eccentrically which accounts for more material for the turning over/flipping over/folding over/inverting or everting.

It is also advantageous if the roving bundle, with the section of the NCF at which it is attached, across several layers, forms a rim flange for the mounting of a tire. In this connection, winding and crimping or turning processes are suitable.

It is particularly suitable to evert or invert or turn over a part of the rim body on one side of the roving bundle in order to achieve this.

When an NCF section lies on the outside or on the inside of the rim in the area of the rim flange or a roving bundle lies on the inside or outside thereof, said area can be efficiently used for a later introduction of the forces of the tire.

The method can advantageously also be improved by the fact that one Roving bundle (respectively) will be sewed on the NCF of the first subpreform and/or of the third subpreform in the longitudinal direction (respectively).

When a section of the NFC of the first subpreform and/or of the third subpreform that preferably lies on the outside in the final product and covers all layers, adjoining the roving bundle, will be provided or sprinkled, brushed or sprayed with a thermal binder and (then) cured/hardened, a particularly precise component can be obtained,

In this connection it is favorable if the area of the roving bundle and only the directly adjoining area will be compressed and/or cooled prior to the curing/hardening of the binder.

Furthermore it is advantageous if, after the activation of the for instance thermal binder, the, when viewed from the roving bundle, other, binder-free part of the first subpreform and/or of the third subpreform is turned inwards/inverted inwards in order to bind a cavity/(front and/or rear) connecting cavity revolving into the rotational axis of the rim body between the portion comprising the binder and the binder-free portion.

In this way, a coupling area is created which can be used for the connection of two subpreforms, respectively.

When, after the turning over of the layers of the first subpreform and/or of the third subpreform, the second subpreform will be inserted into the respective cavity/connecting cavity, then the basis for a compact, integral, one-piece rim body is created.

In this connection it is favorable if the first subpreform, the second subpreform and the third subpreform are infiltrated simultaneously with resin and that these three components are cured together. It is useful to charge the three subpreforms with resin by means of an RTM (Resin Transfer Molding) injection. A roller or two rollers for pressing on are used, wherein at least one roller is coolable/is cooled/will be cooled. Principally, all areas of the NCF can be charged with a thermal binder. Then it is, however, sensible to cure only one area on the one side of the roving bundle, i.e. to “activate” a binder (which means for instance to heat it up and/or to cool it down, so that it will glue the fibers together), and to cure, i.e. to activate the other area on the other side of the roving bundle only after the turning over/inverting or everting/folding over and flipping over of the other area (i.e. offset in time). As a matter of course it is advantageous if the beginning and the end of an NCF is present at the same location or with a possible (smaller) overlapping when viewed in the circumferential direction of a winding core. For the application of pressure and heat preferably on one side of the roving bundle there can be used pressure rams or press rollers.

Alternatively it is also possible to use at least/only one steel roll for the pressing on and the cooling and to use additionally a plastic roller with a groove for the positioning of the area with the sewed-on roving bundle. Said device can be incorporated into a wind-up unit.

The figures are merely of a schematical character and only contribute to a better understanding of the invention. The same elements are provided with the same reference numerals.

InFIG. 1there is indicated a vehicle rim1. It comprises a rim body2. The rim body2is constructed with a fiber composite material cured in the final state, the fiber composite material comprising reinforcement threads, for instance carbon fiber threads, glass fiber threads and/or aramid fiber threads, embedded in a resin matrix. Also mixtures of the different threads are possible. The rim body2is composed of a plurality of individual parts comprising a first subpreform3, a second subpreform4and a third subpreform5.

The first subpreform3and the third subpreform5are inverted or everted/turned over/flipped over in such a manner that a front connecting cavity6or respectively a rear connecting cavity7is formed in its interior. Said two connecting cavities6and7are also cavities which are formed by the material of the respective first subpreform3or respectively the third subpreform5. The two connecting cavities6and7comprise ends of the second subpreform4, wherein said ends are provided with the reference numerals8and9.

Between end8of the second subpreform4and the material of the first subpreform3, respectively between end9of the second subpreform4and the material of the third subpreform5, there is located a resin/a resin mixture10. Said resin10can/shall be the same or even the identical resin/resin mixture which infuses/penetrates all three subpreforms3,4and5. It can, however, be different thereto. In particular it can be replaced by a binder11, for instance a thermal binder, which is present in the binder area12. The binder area12is present axially within a roving bundle area13. More precisely, for the production of the preform and for the connection of the subpreforms a binder powder is used. The resin will be added only during the injection of the entire, already assembled preform during the RTM injection. Then the binder powder will dissolve itself in the resin mixture during the injection,

The roving bundle section13is that section of the first subpreform3or respectively of the third subpreform5in which one roving bundle14is incorporated per subpreform3or5. The roving bundle14is composed of eleven ravings which have five or ten twists per meter. For an attaching incorporation thereof there can be used a seam14which is indicated with a dot-and-dash line.

The ends8and/or9can be inserted at the respective first subpreform3or third subpreform5with a (3D) seam16additionally or alternatively to the resin contained in the connecting cavities6or7. A tire17to be mounted later on the rim body2is indicated with a dashed line. In the course of this, the tire17engages into the area of rim flanges18which is formed by the roving bundle area13.

InFIG. 2there is shown the first subpreform3in more detail. It becomes obvious that several layers of a (single) NCF material19with (just one) applied roving bundle14are used. For simplification purposes, the seam15which is for instance formed as a zigzag seam is not represented.

The engagement of the second subpreform4into the front connecting cavity6by interposing the resin/resin mixture10can be clearly recognized.

In a particular embodiment, however, the ends/edges of the NCF19are not turned over, i.e. inwards or outwards, but simply lie on top of each other or with an offset at the same location. The assembly of the three subpreforms3,4and5can be carried out simultaneously with the eversion or inversion. When the eversion or inversion is carried out first, then they can no longer be plugged together.

There are formed for instance six layers, wherein, in the end, an approximately 9 m long continuous NCF material piece19comprising the sewed-on roving bundle14is wound up several times such that those six layers are obtained. Also five layers are conceivable, as well as more or less layers, depending on the load or stress to be expected. While on the one side of the front connecting cavity6the binder area12is present, a binder-free area20is present on the other side. Said binder-free area20eventually extends up to the roving bundle14.

The fact that also the second subpreform4is formed of several layers of an NCF material19can be inferred fromFIG. 3. Here seven layers of a 600 gr/m2material with +45° threads are used.

Between the winding layers there are inserted additional rovings26. The same is true for the second subpreform4in a further embodiment.

InFIG. 4there is represented the basic material, namely the NCF material19, for the first subpreform3, the second subpreform4and the third subpreform5. The first subpreform3uses NCF material that is approximately twice as heavy per square meter than the third subpreform5. Both subpreforms are based on a biaxial non-crimp fabric with +1-45° threads. The first subpreform3is broader by approximately 8%+/−3 than the third subpreform5. The length of the sections of the NCF material19are of equal size, for instance 9 m. With a width of 14 cm of the basic material of the first subpreform3, conveniently said five layers can be wound, respectively. Prior to the winding, however, the respective roving bundle14will be sewed on the NCF material19of the first subpreform3and of the third subpreform5by means of the (zigzag) seam15.

The winding up of the NCF material19, for instance comprising the sewn-on roving bundle14, is visualized inFIG. 5. In this connection there is a winding roll21, preferably made of wood. Wood has proved to be successful as it provides an almost optimal elastic modulus. Here, two rollers22press the NCF material19and indirectly also the roving bundle14in the direction of the winding roll21.

The application of pressure (P) is also indicated inFIG. 6, wherein inFIG. 6it is recognizable that the two rollers22are spaced apart from each other by the width of the roving bundle14. The rollers22are preferable made out of steel.

In a synopsis ofFIG. 5andFIG. 6it becomes dear that, at a location positioned before the rollers22, heat will be supplied which will then be discharged again subsequently by at least one of the two rollers22. The application of heat takes place via a heat gun/a heat flow, for instance by means of a blower, a laser, an infrared lamp or a hot air gun.

InFIG. 7there is indicated the thickened collar23at the first subpreform3which is created by the incorporated roving bundle14. The direction of turning over is indicated with the arrows24.

InFIG. 8there is shown the direction of the assembling or putting together of the three subpreforms3,4and5by means of the arrows25. When the three subpreforms3,4,5have been assembled, then resin will be injected into said subpreforms and then they will be cured by applying heat and pressure.

Where appropriate, thereafter still the coupling of a wheel center made of a light metal alloy will take place in order to obtain the finished vehicle rim.

LIST OF REFERENCE NUMERALS

8end of the second subpreform

9end of the second subpreform

13roving bundle area

24arrow/direction of turning over

25arrow/direction of the assembling or putting together