Gear element and method for producing a gear element

Abstract

The invention relates to a gear element (1) made of fiber-reinforced plastic, wherein the fiber-reinforced plastic comprises a thermoplastic matrix (11) with reinforcing fibers (12) embedded therein. The gear element (1) comprises at least one toothed region (2) with a plurality of teeth (3), with which the gear element (1) can be brought into positive engagement with a tooth section of another gear part that is designed to be substantially complementary to the toothed region (2). The gear element according to the invention is characterized in that reinforcing fibers (12) with an individual length of more than 5 mm are homogeneously embedded in the thermoplastic matrix (11), wherein these reinforcing fibers (12) have an average fiber length of more than 10 mm and up to 500 mm and are aligned in a relative order to one another in the gear element (1), including in the teeth of the at least one toothed region (2).The invention also relates to a transmission with such a transmission element and to a method for producing such a transmission element.

Description

The present invention relates to a transmission element made of fiber-reinforced plastic, wherein the fiber-reinforced plastic comprises a thermoplastic matrix with reinforcing fibers embedded therein, wherein the transmission element has at least one tooth region having a plurality of teeth, with which the transmission element can be positively brought into engagement with a tooth section of a further transmission part, which is substantially formed in a complementary manner to the tooth region.Fiber-reinforced plastics (FRP) belong to the subgroup of composite materials and consist of two or more components. For example, the use of LCVs is known in aircraft construction, in industrial components and in sports (Formula 1 racing cars, racing bicycles). Also known are injection-molded screws made of a thermoplastic material with short fibers present therein in random position in the length range of a few millimeters, i.e. ≤5 mm.The main disadvantages of present-day short-fiber-reinforced transmission elements, in particular of gear drives, are the low mechanical properties, in particular of the gear teeth, in comparison with metallic gear drives. In addition, manufacturing costs are higher compared to metal gear drives. The high costs of fiber-reinforced drive elements result, among other things, from the large amount of energy required for production and the high material prices.Overall, transmission elements made of short-fiber-reinforced plastic, which are produced using the previously known methods of injection molding or else additive manufacturing, have relatively poor mechanical properties, a frequently poor processing efficiency (in particular in the case of short fibers, which often agglomerate, which makes uniform distribution in the plastic difficult), and a non-uniform surface, which leads to visible defects. The transmittable loads in gear drives made of known short-fiber-reinforced plastics can also be implemented in many cases only by the use of expensive methods (injection-molding technique, etc.).Furthermore, gear elements made of plastics reinforced with continuous fibres are known which, although generally have good mechanical properties, impose design restrictions on the basis of the limited moldability of the continuous fibres. Rather, complex textile structures according to geometry with in particular narrow radii or sharp edges can only be implemented by means of a complex semi-finished product production with multistage longer production process stages. This makes the manufacturing process very time-consuming and the manufacturing costs are high.It is the object of the present invention to provide gear elements according to the preamble of claim 1, which can be subjected to high load while overall having good mechanical properties and which are also relatively simple and cost-effective to produce.This object is achieved by the features of the independent claims.According to claim 1, a transmission element made of fiber-reinforced plastic is proposed, the material of which comprises a thermoplastic matrix with embedded reinforcing fibers (also referred to as high-performance fibers) having an individual length of more than 5 mm - according to preferred embodiments of at least 10 mm -. Although reinforcing fibers with a smaller individual length may also be present, if such are present, they are not part of the invention and are therefore not taken into account in the following. Therefore, when reference is made hereinafter to reinforcing fibers, these are meant to have an individual length of more than 5 mm, preferably of at least 10 mm.According to the invention, the gear element has at least one tooth region, with which the gear element can be brought into positive engagement with a receiving section of another gear part, which receiving section is substantially formed in a complementary manner to the tooth region. Those reinforcing fibers which have an individual length of more than 5, preferably of at least 10 mm, have an average length or fiber length of more than 10 mm and up to 500 mm and are also aligned relative to one another in the transmission element. This relative order to each other also comprises reinforcing fibers which are present in the teeth of the at least one tooth region of the gear element.The formulation "reinforcing fibers are oriented in relative order to one another" means that the reinforcing fibers are not present in a random position in the thermoplastic, but rather have an at least coarse relative orientation to one another in their predominant majority-but not necessarily over their respective entire length-in particular in one or more preferred directions. When oriented in a preferred direction, at least longer sections of individual reinforcing fibers then run next to one another, namely linearly or curved, with, for example, a deviation in a direction of up to 5-20°. In particular in the case of reinforcing fibers which are arranged in the teeth of the gear element according to the invention, it is possible for these reinforcing fibers to have two or more preferred directions. Reinforcing fibers which lie between reinforcing fibers aligned in these two preferred directions can, in particular, successively transition from one preferred direction to the other preferred direction. In particular, the said relative order is not restricted to (linear) directions, but can also have curved profiles, in particular in the teeth of the at least one tooth region and in transition sections to and in the at least one tooth region. In particular, it is possible for a plurality of adjacent reinforcing fibers to have a similarly convex profile. Due to a relative arrangement of the reinforcing fibers with respect to one another and their homogeneous distribution, i.e. a distribution substantially uniform over the cross section, these can be aligned in the thermoplastic matrix in a load path-appropriate manner in order to also be able to transmit large torques by means of the transmission element. In this case, the transmission of the forces acting during operation, i.e. in particular the gravitational forces at the interface between the thermoplastic matrix and the reinforcing fibers, must be ensured. The reinforcing fibers are in this case aligned optimally in the load direction.As is known to those skilled in the art, the average fiber length is a statistical measure that quantitates the average length of the fibers in a material. The mean fiber length is calculated by measuring the lengths of individual fibers from a representative sample of fibers, then summing them and dividing them by the number of samples measured.The average fiber length of the reinforcing fibers having an individual length of more than 5 mm, preferably of at least 10 mm, is advantageously at least 20 mm, for example at least 30 mm or at least 40 mm. The average fiber length to be selected depends in particular on the respective requirements for the transmission element and its use.The proportion by volume of the reinforcing fibers can be, for example, between 20% and 70%, preferably between 40% and 60%. An exemplary volume fraction of the reinforcing fibers is about 50%. Good to optimum flowability is desired when the thermo-pressing method described below is used.Preferably, the transmission element is produced in a thermo-pressing process. Other common terms for this method are, for example, compression molding and extrusion molding. Such a method is described, for example, in DE 10 2018 117 883 A1. The thermo-pressing process, in which a thermoplastic that melts by temperature, for example in the form of thermoplastic fibers, presses reinforcing fibers embedded in the thermoplastic into desired regions of a pressing tool by applying pressure, makes it possible to produce reinforcing structures with adjustable properties on the basis of the variety of fiber materials that can be processed. For example, highly rigid structures can be realized with carbon fibers (CF), while high-impact structures can be produced with aramid fibers. Further details of the thermo-pressing process can be found further below in the description of the process according to the invention.As already noted above, particularly preferably a plurality of reinforcing fibers each run convexly in teeth of the tooth region in relative order to one another. In this case, the reinforcing fibers near the tooth edges are on average more convexly curved than the reinforcing fibers which run further away from the tooth edges. Such a course is obtained in particular when using the above-mentioned thermo-pressing method. The reinforcing fibers, which are pressed against the tooth edges from the inside due to the entrainment by the thermoplastic, cover a greater distance than reinforcing fibers located further inside, wherein the reinforcing fibers located further outside in the region of the tooth edges substantially assume the curvature of these tooth edges.The tooth region of the transmission element according to the invention can be part of a gearwheel or can represent the entire gearwheel, for example. The tooth region is preferably designed as a spur gear, toothed rack, elliptical gear, bevel gear, crown gear, worm wheel or worm.The tooth region can represent, for example, the entire transmission element according to the invention, for example in the form of a gearwheel. Alternatively or additionally, the transmission element comprises at least one shaft (as a solid shaft or hollow shaft) and / or at least one axle which is connected integrally to the tooth region or the gearwheel. In this case, some of the reinforcing fibers preferably run in sections in the region of the shaft or axle and in sections in the tooth region. As a result, the tooth region or the gearwheel is integrally connected to the shaft or axle. The generation of such a connection or connection does not require a discrete process step.In a configuration in this respect, that portion of said reinforcing fibers which runs in the region of the shaft or axis is aligned substantially in the direction of the shaft or axis, while that portion which runs in the tooth region is aligned substantially perpendicularly to the shaft or axis. Such reinforcing fibers reinforce the attachment of the tooth region to the shaft or axle.Preferably, the reinforcing fibers consist of staple fibers, e.g. glass fibers, carbon fibers and / or aramid fibers. The reinforcing fibers can be present here as virgin fibers, but also as recycled high-performance fibers, for example as recycled glass fibers (rGF), recycled carbon fibers (rCF) or recycled aramid fibers (rAR). Mixtures of virgin and recycled fibers may also be used. In general, the term "reinforcing fibers" is understood here as meaning preferably artificially produced fibers; however, it is also possible to use, for example, mixtures of synthetic fibers and natural fibers or else exclusively natural fibers, provided they meet the thermal and mechanical requirements for use.While a transmission element according to the invention has been described above, which can be brought into engagement with a transmission part, according to a further development of the invention this transmission part also consists of a fiber-reinforced plastic with one or more of the features mentioned above.The invention also comprises a method for producing a transmission element as described above according to the features of claim 12.In an advantageous thermo-pressing process, which is also described above. DE 10 2018 117 883 A1, a flat, preferably planar, textile semi-finished product, which contains at least reinforcing fibers and thermoplastic fibers, is introduced, preferably inserted, into the interior of a pressing tool. In this case, said interior space is bounded by surfaces of at least a first and a second pressing part of the pressing tool. Furthermore, at least one cavity is formed in at least one of said surfaces, which cavity is first not filled by the introduced at least one semi-finished textile product. The semi-finished textile product is heated in the pressing tool above the melting temperature or the melting temperature range of the thermoplastic fibers. As a result, the thermoplastic fibers melt, wherein the first and / or the second pressing part are adjusted in such a way that the thermoplastic begins to flow and penetrates into the at least one cavity. During this movement, the thermoplastic carries along reinforcing fibers, so that a thermoplastic matrix and reinforcing fibers embedded therein are now present in the at least one cavity and, according to a particularly preferred embodiment, are distributed homogeneously in cross section in the matrix. The semi-finished textile product is then consolidated in the pressing tool by cooling the semi-finished textile product below the solidification temperature of the thermoplastic in order finally to remove the fiber plastic composite from the pressing tool.In this flow or thermo-pressing method, the press parts are adjusted relative to one another according to the melting of the thermoplastic fibers, so that the reinforcing fibers can penetrate together with the molten thermoplastic into the cavity by this tool-side displacement process, in order to realize the desired gear element in this cavity. In addition to the displacement realized by the pressing, further measures, such as, for example, an air flow, can also assist the flow process of the thermoplastic. The air displaced in the at least one cavity is preferably discharged through a so-called riser. As a result, a continuous fiber composite structure in the form of a FRP transmission element is obtained, in which reinforcing fibers are homogeneously distributed in the cross section in the thermoplastic matrix.The thermo-pressing process is very suitable for the production of transmission elements based on fiber-reinforced composite structures for several reasons. Since the method is suitable for processing long fibers, in particular those having a length of 10 mm, composite structures having high strength and rigidity can be produced. Due to the high pressure exerted on the material, the fibers can be well embedded in the resin and an optimum bond can be produced. This leads to components with a high load-bearing capacity and durability. Furthermore, the setting of a controlled fiber orientation can be achieved, since the fibers are aligned in the desired direction in the composite structure in a targeted manner during the thermo-pressing process. This enables a load path-appropriate arrangement of the fibers in order to optimize the mechanical properties of the component. Also, the thermo-pressing process allows a great design flexibility, since complex shapes and geometries can be realized. By using specially manufactured pressing tools, components with different shapes and dimensions can be produced. Finally, the thermo-pressing method allows efficient series production of gear elements such as gear drives, because it is possible to press several components simultaneously, which increases the production speed and reduces the costs per component.According to an advantageous embodiment, a semi-finished textile product is used for the production of the transmission element according to the invention, which consists at least partially of thermoplastic fibers and reinforcing fibers, for example in the form of a pre-grpg or organo-sheet. During this heating, at least a part of the thermoplastic fibers melts. During the composite production, these then form at least a part of the thermoplastic matrix or completely the thermoplastic matrix if, in addition to the thermoplastic fibers, no further thermoplastic structures are present in the textile semi-finished product on the output side.Furthermore, the reinforcing fibers can be aligned in the desired direction by the thermo-pressing process and placed in the desired region when the molten thermoplastic, in particular in the form of molten thermoplastic fibers, flows into the mold. This allows transformation of 2D fiber structures into 3D composite structures with an aligned arrangement of the reinforcing fibers along the load paths.Preferably, the thermoplastic, for example in the form of thermoplastic fibers, contains a polyethylene, a polypropylene, polyphenylene sulfide (PPS), polyetheretherketone (PEEK) and / or a polyamide.In advantageous embodiments, a textile semi-finished product is used for the method according to the invention, in which thermoplastic fibers and reinforcing fibers, preferably all reinforcing fibers and thermoplastic fibers, are present in a hybrid yarn or a hybrid structure, for example a hybrid tape (the width of which can be from 1 cm to more than one meter). The thermoplastic fibers preferably have an adjustable dissolution behavior, so that the heating and forming of the semi-finished product can be precisely controlled.A wide variety of types of hybrid yarns or hybrid structures can be used. For example, the individual fibers of the reinforcing fibers and the thermoplastic fibers can run substantially side by side without being specifically connected to one another. Alternatively, for example, thermoplastic fibers may be spirally wound around reinforcing fibers, with windings being possible with or without leaving exposed surface areas of the reinforcing fibers. In a further alternative, yarns of reinforcing fibers and thermoplastic fibers are twisted together. Or the thermoplastic fibers are present, for example, as filament yarn and form, for example, a first core of a core yarn. A second core of the core yarn is formed, for example, from homogeneously dispersed thermoplastic fibers, for example in the form of staple fibers, and reinforcing fibers as staple fibers in the range of average fiber lengths from 10 mm to 500 mm, for example in the range of 20 mm to 120 mm average fiber length. These two cores are sheathed, for example, by thermoplastic fibers in the form of staple fibers of the same type.Other arrangements of the reinforcing fibers and the thermoplastic fibers relative to each other to form hybrid yarns or hybrid structures are readily possible.Alternatively or additionally, a textile semi-finished product can be used in which reinforcing fibers are connected to thermoplastic binding or adhesive fibers, wherein at least a part of the thermoplastic binding or adhesive fibers melts during said heating. By means of such binding or adhesive fibers, with a corresponding structural construction of the semi-finished textile product, a targeted detachment of reinforcing fibers is possible.It is also possible to use a semi-finished textile product in which - additionally or alternatively to said thermoplastic fibers - a part of the reinforcing fibers is embedded in a thermoplastic matrix which then melts at a correspondingly high temperature and also pulls reinforcing fibers into the at least one cavity.When using the thermo-pressing method, at least one semi-finished textile product can be used in which-in relation to the reinforcing fibers and / or the thermoplastic fibers-at least one of the following criteria applies (logical contradictions are excluded here): the same mean fiber length; homogeneous distribution of reinforcing fibers and thermoplastic fibers; different mean fiber lengths in different sections of the at least one semi-finished textile product; different fiber length distributions in different sections of the at least one semi-finished textile product; different fiber types in different sections of the at least one semi-finished textile product; different thermoplastics in different sections of the at least one semi-finished textile product; different thicknesses in different sections of the at least one semi-finished textile product. Depending on the desired requirement profile of the finished fiber plastic composite or FRP transmission element, different parameters can thus be varied.The at least one semi-finished textile product is preferably in the form of a woven fabric, laid scrim, knitted fabric, embroidered knit, knitted fabric, in the form of unidirectional (UD) hybrid fiber structures, definedly laid threads or rovings, or a mixed form of the aforementioned textile planar structures.In order to allow a targeted flow of the thermoplastic material and the reinforcing fibers floating therein during the pressing operation, the pressing tool is correspondingly designed. The following matching steps are advantageously carried out here: 1. belt production: the textile semi-finished product is produced from fiber structures with thermoplastic- and staple-fiber-based reinforcing fibers with a specific flowability, taking into account the pressing tool and the geometry of the gear element. 2. production and forming (optional): For very complex geometries, a preceding production and a pre-forming can be carried out. 3. shaping: The pressing tool has a specific shape which enables the desired geometry and structure of the final product. It may include cavities, channels or depressions, for example, to direct the material in the desired direction. 4. guide elements: The tool may include guide elements that control and influence the flow of material. These elements may be, for example, grooves, grooves or depressions which direct the material into particular webs and maintain the reinforcing fibers in the desired orientation. 5. pressure and temperature control: The pressing tool enables precise control of pressure and temperature during the pressing process. As a result, the material can flow uniformly and the fibers can be distributed and aligned optimally in the composite material.Preferably, the position of the reinforcing fibers in the semi-finished textile product is adapted to the aforementioned cavities in such a way that the thermopressing in the form of heating and pressing realizes an arrangement of the reinforcing fibers in the finished transmission element that is appropriate for the load path. In particular, the convex embedding of the reinforcing fibers in the teeth of the at least one tooth region, i.e. the curvature of the reinforcing fibers directed outwards towards the tooth edges, creates such a mounting appropriate for the load path. The fibers are therefore preferably arranged with a customized fiber placement such that the geometry of the teeth can be mapped exactly fiber-wise during extrusion.The semi-finished textile product used for the method according to the invention preferably has at least two sections, wherein the reinforcing fibers in the one section have a different orientation than the reinforcing fibers in the other section. The relative order of the reinforcing fibers in the respective section is maintained. These alignments of the reinforcing fibers in the respective section are adapted to the configuration of said cavities in order to realize load path-appropriate arrangements of the reinforcing fibers relative to one another in the finished transmission element. The reinforcing fibers in the at least two sections can assume different angular positions with respect to one another, for example 90° or +45° or +45° or, of course, also other angular positions.In certain embodiments, it is preferred that the reinforcing fibers in one section are oriented substantially perpendicular to the reinforcing fibers in the other section. If, for example, a planar textile semi-finished product is used for the integral production of a gearwheel on a shaft, reinforcing fibers can be aligned along the shaft in one section of the textile semi-finished product and reinforcing fibers can be aligned perpendicular to the first-mentioned reinforcing fibers in another section, namely in the section of the gearwheel to be produced. The latter reinforcing fibers can then be placed in the negative form in such a way that they follow the contour of one or more teeth in the circumferential direction of the gearwheel.According to one exemplary embodiment, the textile semi-finished product is laid, for example wound, around a tool before being inserted into at least one of the press moulds. This tool is then enveloped by the thermoplastic and the reinforcing fibers embedded therein. After consolidation of the transmission part, it is preferably removed from the latter, for example by pulling out or pressing on one of the end faces of the transmission element. Alternatively, the tool remains on or in the gear element.In a corresponding embodiment, the tool is rod-shaped. After removal of the tool, the gear element then has a cylindrical cavity into which a shaft for driving the gear element can be inserted. The hollow shaft produced in this way makes it possible to transmit torques effectively and, in addition, to axially support rotating parts.When thermoplastic fibers are used for the thermoplastic matrix, these are advantageously aligned in substantially the same direction as the reinforcing fibers in the semi-finished textile product. As a result, the melting and almost completely molten thermoplastic fibers can already carry along the reinforcing fibers during extrusion.Further advantages of the invention are described in the exemplary embodiment below. The following are shown: FIG. 1 shows a sequence of steps for producing a transmission element according to the invention; FIG. 2 shows a side view of the transmission element of FIG. 1 and an enlarged detail, and FIG. 3 shows a perspective view of the transmission element of FIGS. 1 and 2 with two enlarged details.FIG. 1 shows successive steps F 1 to F 5 for producing a transmission element 1 according to the invention. First, a plurality of fiber bundles 9 (only one is shown) are provided in a method step F 1, which comprise endless thermoplastic fibers 11 alocated next to one another and reinforcing fibers 12 distributed or mixed between them, wherein the reinforcing fibers 12 are oriented in the same direction as the thermoplastic fibers 11 a. The reinforcing fibers 12 have an average fiber length of more than 10 mm, and the average fiber length is not more than 500 mm. The thermoplastic fibers can consist, for example, of polyethylene, polypropylene, polyphenylene sulfide (PPS), polyetheretherketone (PEEK) and / or polyamide. The reinforcing fibers consist, for example, of glass fibers, carbon fibers and / or aramid fibers, either virgin and / or recycled. In general, the term "reinforcing fibers" is understood here to mean preferably synthetically produced fibers. However, mixtures of synthetic fibers and natural fibers can also be used, or else exclusively suitable natural fibers.The fiber bundles 9 are assembled in a method step F 2 to form a planar textile semi-finished product 10. In this case, a wide variety of surface formation methods can be used, for example weaving, knitting, knitting, winding and / or customized fiber placement (so-called tailored fiber placement). The requirements for the transmission element 1 to be produced are thereby taken into account, in particular by an arrangement of the fibers in the semi-finished textile product in accordance with the load path for the later use of the transmission element 1. It is thus shown in FIG. 1 that the semi-finished textile product 10 has two sections 13 and a section 14 between these two sections 13, wherein the thermoplastic fibers 11 aand the reinforcing fibers 12 in the section 14 are arranged substantially perpendicular to the thermoplastic fibers 11 aand the reinforcing fibers 12 in the two sections 13. The reinforcing fibers 12 in the section 14 are those which are to be arranged in the teeth 3 of the transmission element 1 (see FIG. 3 ), while the reinforcing fibers 12 in the sections 13 are to come to lie in a shaft 7 of the finished transmission element 1 (see FIGS. 2 and 3 ).In method step F 3, the semi-finished textile product 10 is laid or wound over its entire circumference around a rod-shaped tool 20, which consists, for example, of metal. The length of the rod-shaped tool 20 corresponds to the length of the semi-finished textile product 10 This structure of tool 20 and semi-finished textile product 10 is then inserted into a lower press mold 26 of a pressing tool 25, which in the present case has a cavity 28. Together with an upper press mold 27 of the pressing tool 25, which likewise has an identically shaped cavity (not visible in FIG. 1 ), the two press molds 26, 27, when placed one on top of the other, form the negative mold of the gear element 1 to be produced.The cavities 28 essentially each have two different sections 28 aand 28 b, wherein the sections 28 atogether form the negative shape of the shaft 7 of the transmission element 1 to be produced and the sections 28 btogether form the negative shape for a tooth region 2 (see FIGS. 2 and 3 ) of a gearwheel.The step F4 also comprises gradually relatively compressing the two dies 26, 27 (here, the upper die 27 is slowly lowered onto the lower die 26 as indicated by arrow c1), in addition supplying sufficient heat to the interior of the die 25 to melt the thermoplastic fibers 11a. During this melting and the tracking of the upper press mold 27 (exact mechanism not shown, see for general explanations the disclosure of DE 10 2018 117 883 A1), the molten thermoplastic flows by the relative pressing together of the press molds 26, 27 into the still unfilled sections of the cavities 28 of the press molds 26, 27.Method step F 5 comprises allowing the semi-finished textile product 10 to solidify, which has now assumed the shape of the transmission element 1. For consolidation, the temperature acting on the transmission element 1 is reduced considerably below the melting temperature of the thermoplastic until the latter has cured and now forms a homogeneous thermoplastic matrix 11. Subsequently, the gear element 1 is separated from the press moulds 26, 27, wherein the removal of the upper press mould 27 upward (arrow u 1) and of the lower press mould 26 downward (arrow u 2) is illustrated here. It is also shown that the rod-shaped tool 20 is pulled axially out of the gear element 1 (arrow z 1).Due to the original arrangement of the reinforcing fibers 12 in the semi-finished textile product 10, these fibers also have a relative order to one another in the consolidated thermoplastic matrix 11.FIGS. 2 and 3 show the transmission element 1 according to the invention and produced according to the invention in a side view and in a perspective view, wherein corresponding details are also shown in respective specifically emphasized magnifications.The side view of FIG. 2 shows the one-piece transmission element 1 with its multi-stepped shaft 7 with its longitudinal axis L and its tooth region 2 with a plurality of teeth 3 which is arranged on the shaft 7 and is designed as a gearwheel. In the enlarged detail of FIG. 2, which shows a partial section through the shaft 7 and the tooth region 2, a plurality of reinforcing fibers 12 are mounted in the thermoplastic matrix 11, wherein only relatively few reinforcing fibers 12 are depicted for the sake of clarity. The proportion by volume of fiber in the transmission element 1 is preferably more than 20%, preferably between 40% and 70%, the reinforcing fibers 12 also being distributed homogeneously in cross section in the thermoplastic matrix 11.As can be seen from the enlarged section of FIG. 2, some reinforcing fibers 12 are located in the shaft 7 and some reinforcing fibers 12 are located in the tooth region 2; other reinforcing fibers 12, on the other hand, have a section 12 aextending in the region of the shaft 7 and a section 12 bextending into the tooth region 2. By means of such extending reinforcing fibers 12 with sections 12 aand 12 b, an integral, high-loadable connection of the tooth region 2, which is embodied as a gearwheel in the present case, to the shaft 7 is achieved. For such a connection, it is advantageous if the corresponding reinforcing fibers 12 have a sufficient length, for example of more than 20 mm.The perspective illustration of FIG. 3 shows the configuration of the shaft 7 as a hollow shaft, wherein the hollow shaft forms a cylindrical cavity 8.The first enlarged representation of FIG. 3 shows a section of the tooth region 2, while the second enlarged representation shows a cross section of a fully represented tooth 3. According to this illustration, reinforcing fibers 12 are stored in the thermoplastic matrix 11 filling the tooth 3. In this tooth 3, a plurality of reinforcing fibers 12 run in relative order to one another, namely with a respectively convex profile with respect to the tooth edge 4 of the tooth 3; in this case, the reinforcing fibers 12 close to the tooth edge 4 have an on average more convex profile than the reinforcing fibers 12 which run further away from the tooth edge 4. This arrangement is due to the convex course of the tooth edge 4 and to the initial planar alignment of the reinforcing fibers 12 in the thermoplastic or between the thermoplastic fibers 11 ain the semi-finished textile product 10. Since the path from the surface of the semi-finished textile product 10 into the interior of the tooth 3 and to its tooth edge 4 is longer than, for example, the path from the semi-finished textile product 10 only up to the tooth root and, in addition, the tooth edge 4 represents a convex curvature and thus a corresponding positive guidance for the reinforcing fibers 12, the greater convex curvature of the reinforcing fibers 12 is produced in the vicinity of the tooth edge 4. When the teeth 3 roll on complementary tooth sections of a corresponding gear part (not shown), the load acting on the tooth edge 4 is oriented substantially tangentially to the reinforcing fibers 12. This is advantageous since this ensures optimum transmission of the forces acting during operation between the thermoplastic matrix 11 and the reinforcing fibers 12. More specifically, this transmission of force is effected by shear forces at the interface of thermoplastic matrix 11 and reinforcing fibers 12, wherein these shear forces can be maximum when the reinforcing fibers 12 are oriented in the load direction, are distributed homogeneously in cross section, the reinforcing fibers 12 have a certain average length (advantageously of more than 20 mm) and a relatively high fiber volume fraction (advantageously more than 20%, preferably more than 30%, for example more than 40%) is present. Overall, optimum load paths are thus achieved in the teeth 3 of the gear element 1.The transmission part-not shown-which interacts with the transmission element 1 can advantageously likewise be designed as a fiber-reinforced component having one or more of the features of the transmission element 1 described above.The transmission element according to the invention can comprise, for example, a spur gear, a toothed rack, an elliptical gear, a bevel gear, a crown gear, a worm wheel or a worm. For example, in a worm, the tooth area consists of the very obliquely arranged teeth which are wound helically around a cylinder, wherein one winding corresponds to one tooth.List of reference characters1 Gear element 2 tooth region 3 tooth 4 tooth edge 7 shaft 8 cylindrical cavity 9 fiber bundle 10 textile semi-finished product 11 thermoplastic matrix 11 armoplastically reinforced fibers 12 asegment of the reinforced fibers 12 bsegment of the reinforced fibers 13 region of the textile semi-finished product 14 region of the textile semi-finished product 20 tool 25 pressing tool 26 press mold 27 press mold 28 cavity F 1-F 5 method steps c 1 lowering the upper press mold u 1, u 2 moving the upper and the lower press mold z 1 removing the tool A integral connection L longitudinal axis of the gear elementReferences included in the specificationThis list of documents cited by the applicant has been produced in an automated manner and is only included for the better information of the reader. The list is not part of the German patent application or utility model application. The DPMA does not take any adhesion for any faults or omissions.Patent Literature citedDE 10 2018 117 883 A1 [0014, 0022, 0047]

Claims

Transmission element (1) made of fibre-reinforced plastic, wherein the fibre-reinforced plastic comprises a thermoplastic matrix (11) with reinforcement fibres (12) embedded therein, wherein the transmission element (1) has at least one tooth region (2) with a plurality of teeth (3), with which the transmission element (1) can be positively brought into engagement with a tooth section of a further transmission part which is substantially formed in a complementary manner to the tooth region (2), characterized in that reinforcement fibres (12) with an individual length of more than 5 mm are homogeneously embedded in the thermoplastic matrix (11), wherein these reinforcement fibres (12) have an average fibre length of more than 10 mm and up to 500 mm and are aligned with one another in the transmission element (1) in relative order, including in the teeth of the at least one tooth region (2).Transmission element (1) according to claim 1, characterized in that the average fiber length of said reinforcing fibers (12) is at least 20 mm, for example more than 30 mm or 40 mm.Transmission element (1) according to claim 1 or 2, characterised in that the proportion by volume of reinforcing fibre in the transmission element (1) is more than 20%, preferably between 40% and 70%.Transmission element (1) according to at least one of the preceding claims, characterized in that it is produced in a thermo-pressing process.Gear element (1) according to at least one of the preceding claims, characterized in that respectively defined number of the reinforcing fibres (12) are arranged in teeth (3) of the tooth region (2) so as to extend convexly in relative order to one another, wherein the reinforcing fibres (12) near the tooth edges (4) extend on average more convexly than the reinforcing fibres (12) which extend further away from tooth edges (4).Gear element (1) according to at least one of the preceding claims, characterized in that the tooth region (2) is designed as a spur gear, toothed rack, elliptical gear, bevel gear, crown gear, worm wheel or worm.Transmission element (1) according to at least one of the preceding claims, characterized in that it comprises a shaft (7) or axle integrally connected to the toothed zone (2), some of the reinforcing fibres (12) having both a portion (12a) running in the zone of the shaft (7) or axle and a portion (12b) running in the toothed zone (2).Transmission element (1) according to the preceding claim, characterized in that the portion (12a) of said reinforcing fibres (12) running in the region of the shaft (7) or axis is aligned substantially in the direction of the shaft (7) or axis, while the portion (12b) running in the tooth region (2) is aligned substantially perpendicular to the shaft (7) or axis.Transmission element (1) according to at least one of the two preceding claims, characterized in that it has a hollow shaft.Transmission element (1) according to at least one of the preceding claims, characterized in that the reinforcing fibers (12) comprise staple fibers, for example in the form of virgin and / or recycled glass fibers, virgin and / or recycled carbon fibers, virgin and / or recycled aramid fibers, cut continuous fibers and / or virgin natural staple fibers.Transmission having at least one transmission element (1) according to at least one of the preceding claims, characterized in that the transmission part which is to be or is brought into engagement with the transmission element (1) likewise consists of a fibre-reinforced plastic having the features of at least one of the preceding claims.Method for producing a transmission element (1) according to at least one of Claims 1 to 10, comprising the steps of: - providing a flowable, preferably flatly extending, semi-finished textile product (10) comprising reinforcing fibres (12) having an individual fibre length of more than 5 mm and an average fibre length of these reinforcing fibres (12) of more than 10 mm and up to 500 mm and a thermoplastic, the latter being present as a thermoplastic matrix (11) and / or as thermoplastic fibres (11a), wherein the reinforcing fibres (12) are distributed homogeneously in the thermoplastic, - providing a pressing tool (25) comprising at least two press moulds (26, 27), wherein at least one of the press moulds comprises a cavity (28), and wherein the press moulds (26, 27), when the pressing tool (25) is closed, form at least the negative shape of the transmission element (1) according to one of the preceding Claims 1 to 10, inserting the semi-finished textile product (10) into at least one of the press molds (26, 27); using elevated temperature at which the thermoplastic melts, pressing the semi-finished textile product (10) with the aid of the at least two press molds (26, 27), so that the thermoplastic flows into the negative mold together with the reinforcing fibers (12); consolidating the semi-finished textile product (10); removing the consolidated semi-finished product (10), which has formed a gear element (1) as a result of the shaping in the pressing tool (25); and, before or after this removal, if necessary, separating the gear element (1) from the remaining protrusions of the semi-finished textile product (10).Method according to the preceding claim, characterized in that the position of the reinforcing fibers (12) in the semi-finished textile product (10) is adapted to the said negative shape in such a way that the thermopressing in the form of heating and pressing realizes an arrangement of the reinforcing fibers (12) in the finished transmission element (1) in accordance with the load path.Method according to the preceding claim, characterized in that the semi-finished textile product (10) has at least two sections (13, 14) in which the reinforcing fibers (12) have different alignments, wherein these relative alignments of the reinforcing fibers (12) are adapted to the configuration of said negative shape in order to realize arrangements of the reinforcing fibers (12) relative to one another in the finished transmission element (1) that are appropriate for the load path.Method according to the preceding claim, characterized in that the reinforcing fibres (12) in the one section (13) are aligned substantially perpendicularly to the reinforcing fibres (12) in the other section (14).Method according to at least one of the preceding method claims, characterized in that the semi-finished textile product (10) is laid around a tool (20) before being inserted into at least one of the press moulds (26, 27), wherein the tool (20) is preferably separated from the transmission part (1) after consolidation of the latter.Method according to the preceding claim, characterized in that the tool (20) is rod-shaped, so that after removal of the tool (20), the transmission element (1) has a hollow shaft into which a drive shaft or output shaft of the transmission element (1) can be inserted.Method according to at least one of the preceding method claims, characterized in that, when using thermoplastic fibres (11a) for the thermoplastic matrix (11), these thermoplastic fibres (11a) are aligned like the reinforcing fibres (12) in the semi-finished textile product (10).

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