Method and assembly kit

Abstract

A method for manufacturing a leaf spring device (1) made of fiber composite plastic, comprising: a) a step (S1) of preparing an assembly kit (11) including a leaf spring unit (2) made of fiber composite plastic and a plurality of stiffening elements (8, 8A, 8A', 8A'', 8B, 8B', 8B'', 8C, 8C') for locally stiffening the leaf spring unit (2); and b) a step of designing the leaf spring device (1) according to a desired application. c) a step (S3) of selecting stiffening elements (8, 8A, 8A', 8A'', 8B, 8B', 8B'', 8C, 8C') from an assembly kit (11) according to the design of the leaf spring device (1); and d) a step (S4) of combining the selected stiffening elements (8, 8A, 8A', 8A'', 8B, 8B', 8B'', 8C, 8C') with the leaf spring unit (2) to form the spring device (1).

Description

[Technical field]

[0001] The present invention relates to a method for manufacturing a leaf spring arrangement made of fiber-composite plastic, and to an assembly kit for manufacturing such a leaf spring arrangement. [Background technology]

[0002] In motor vehicles, springs may be provided in the chassis for spring mounting of the motor vehicle. Such springs are usually made of metallic materials and are therefore heavy and prone to corrosion. Springs made of fiber composite plastics are lighter and less prone to corrosion, but their design and manufacture are more complex. In particular, composite leaf springs are gradually replacing steel leaf springs in the automotive field, since their design is easier compared to steel coil springs, and they are a more innovative technology than steel leaf springs, which can be rapidly built using mastered manufacturing processes. One attractive concept to replace steel coil springs is bending springs made of fiber composite plastics. Manufacturing concepts for such bending springs already exist. However, they are very expensive and therefore economically unattractive.

[0003] Specifically in the field of vehicle chassis, especially in the case of high volume vehicle platforms, for example in the order of millions of motor vehicles, a large number of different spring variants are required, since the vehicle platforms are intended to be served by different vehicle models and configurations, i.e. suspensions differ for different weight classes, for example due to different motorizations, body heights, intended uses, such as sports or comfort type, etc. Thus, different spring variants are required. In the case of steel springs, these variants can be produced without significant additional costs, since their shaping is performed in a freehand manner, i.e. they are not tied to tools.

[0004] Coil springs made of fiber composite plastics have too low performance due to the anisotropic material properties of fiber composite plastics, which have too low a lightweight effect and too complicated manufacturing process. On the other hand, bending springs made of fiber composite plastics have too high stress loads, especially at the inner diameter of the flexures of zigzag-shaped bending springs, which limits their performance or may even cause breakage. The applicant is aware of in-house prior art in which these above-mentioned flexures are stabilized, where the spring action is only performed by leaf spring parts that are rigidly connected to each other at the flexures. (Prior art document) (Patent Documents) (Patent Document 1) German Patent Application Publication No. 102016215938

[0005] However, the above concepts have manufacturing processes that are too complex to be economically attractive for mass production. With regard to the production of variants, steel springs are advantageous since they do not require tooling, and the manufacturing process is mastered, so they can be easily designed and economically produced even in small quantities. On the other hand, springs made of fiber composites are tool-bound. This means that separate tools must be made for each spring size or load capacity to enable the production of said springs. Due to the high production volume per vehicle platform, the tooling costs per spring are high, despite the high total number of units. In addition, the batch size decreases and the complexity and number of configurations increase. The economic efficiency decreases significantly with the number of variants.

[0006] In view of this background, one object of the present invention is to provide an improved method for manufacturing leaf springs made of fiber composite plastic. Summary of the Invention

[0007] Therefore, a method for manufacturing a leaf spring device made of fiber-composite plastic is proposed, which comprises the steps of: a) preparing an assembly kit with a leaf spring unit made of fiber-composite plastic and a number of stiffening elements for locally stiffening the leaf spring unit, b) designing the leaf spring device according to a desired application, c) selecting stiffening elements from the assembly kit according to the design of the leaf spring device, and d) combining the selected stiffening elements with the leaf spring unit to form the leaf spring device.

[0008] Since the leaf spring arrangement can be manufactured based on an assembly kit requiring only a limited number of different stiffening elements, a large number of different leaf spring arrangements can be produced at low cost and with little effort. Even small series can be produced at low cost.

[0009] Fiber-reinforced plastics (FRP) may also be referred to as fiber-reinforced plastic materials. Fiber-reinforced plastics include a plastic material, in particular a plastic matrix in which fibers, such as natural fibers, glass fibers, carbon fibers, aramid fibers, etc., are embedded. The plastic material may be a thermosetting resin, such as an epoxy resin. The fibers may be continuous. However, they may also be short or medium length fibers, with a fiber length of a few millimeters to a few centimeters. The fibers may be arranged directional or non-directional in the plastic material. The leaf spring unit may have a layered or laminated structure. For this purpose, for example, the plastic material is impregnated into a layer of a fiber fabric or a fiber scrim. Alternatively, however, the leaf spring unit may be manufactured using so-called prepregs, i.e. pre-impregnated fibers, fiber fabrics or fiber scrims.

[0010] In the present context, a "leaf spring unit" is understood to be a spring or spring element consisting of a plurality of leaf spring elements or leaf spring sections connected to one another and thereby forming a preferably zigzag or meandered geometric shape. The individual leaf spring sections may have a leaf-like or plate-like geometric shape. However, "leaf-like" or "leaf-like" does not exclude the leaf spring sections being curved or having any three-dimensional shape. In contrast to a leaf spring unit, a cylindrical or coil spring has a continuous wire formed in a helix such that the coil spring has a cylindrical geometric shape. Preferably, the leaf spring device is a compression spring. However, the leaf spring device may also be a tension spring.

[0011] The leaf spring unit may preferably be or be designed as a bending spring or bending spring unit. "Bending spring" or "bending spring unit" in this context means a part, in the simplest case a rod-like bending beam, which deforms elastically and therefore reversibly under load. The material properties of the materials used and the geometry of the leaf spring unit influence the deformation behavior of the leaf spring unit.

[0012] A leaf spring device differs from a leaf spring unit in that the leaf spring device comprises both a leaf spring unit and a stiffening element, i.e. the leaf spring unit and the stiffening element are part of the leaf spring device, whereas the stiffening element is not part of the leaf spring unit, however this does not exclude the stiffening element being attached or fixed to the leaf spring unit. The leaf spring device may comprise several leaf spring units.

[0013] The fact that in this example the leaf spring arrangement consists of a fiber composite plastic does not exclude that the leaf spring arrangement also comprises other materials. In this context, "stiffness" is to be understood as the resistance of the leaf spring unit to elastic deformation. That is to say, the stiffening element is configured to influence the leaf spring unit in such a way that its resistance to elastic deformation is changed, in particular increased. "Locally" in this context means that the leaf spring unit is stiffened only in a specific portion, i.e. only in the portion where the stiffening element is provided.

[0014] In the process of preparing the assembly kit, preferably a number of leaf spring units are manufactured. These leaf spring units are preferably identical. Thus, a number of stiffening elements are also manufactured. The assembly kit may comprise a number of different stiffening elements. The design of the leaf spring arrangement may, for example, be carried out with the aid of a computer program. However, this is not necessary. The desired application may, for example, be a specific type of vehicle that is manufactured in different configurations. For each of these configurations of the motor vehicle, a separate leaf spring arrangement may be manufactured with the assembly kit.

[0015] The stiffening elements are selected based on the design, i.e. when designing the leaf spring device, for example its geometry, its spring deflection and / or its spring constant are determined or calculated. Based on this data, suitable stiffening elements are selected from the assembly kit and subsequently combined with the leaf spring unit to form the leaf spring device. In this context, "combining" should be understood as attaching the stiffening elements to a specific area of ​​the leaf spring unit. For this purpose, the stiffening elements may for example be glued to the leaf spring unit.

[0016] According to one embodiment, in step d) the selected stiffening element is attached to the flexure of the leaf spring unit.

[0017] As mentioned above, the leaf spring unit preferably comprises a plurality of elastically deformable leaf spring parts, which are connected to one another by flexures, i.e. the leaf spring unit is flexed at the flexures, in particular by 180° in each case. This results in a zigzag or bent structure of the leaf spring unit. In particular, the stiffening element stiffens the flexures, which thus have a higher stiffness than the leaf spring parts, so that when the leaf spring device is loaded, only the leaf spring parts, and not the flexures, are deformed. In particular, this avoids the occurrence of critical compressive stresses at the flexures, in particular at the inner diameter of the flexures, which could cause the leaf spring unit to break.

[0018] According to a further embodiment, in step d) selected stiffening elements are attached to the inner diameter of each of the flexures.

[0019] Specifically, each flexure has an outer diameter and an inner diameter. Each of the inner diameters is provided with a stiffening element. In this regard, the flexures of the leaf spring unit may be provided with stiffening elements, or alternatively, only selected flexures of the leaf spring unit may be provided with stiffening elements.

[0020] According to a further embodiment, in step d) the selected stiffening element is form-fittingly and / or material-fittingly connected to the flexure.

[0021] A form-fit connection is formed by at least two connection partners that interlock or engage with each other back and forth. In the case of a material-bonded connection, the connection partners are connected by atomic or molecular forces. A material-bonded connection is an inseparable connection that can only be separated by destroying the connection means and / or the connection partners. A material-bonded connection can be connected, for example, by adhesive bonding. That is, the stiffening element can be glued into the flexure. Alternatively, the stiffening element can be inserted or sandwiched into the flexure. The stiffening element can also be completely non-positively connected to the flexure. A frictional connection requires a normal force of the surfaces that are connected to each other. A non-positively connected connection can be realized by a frictional connection.

[0022] According to a further embodiment, step a) comprises forming the leaf spring unit as a continuous strand of constant cross section.

[0023] This allows the leaf spring units to be produced in large quantities and cost-effectively. Preferably, the leaf spring unit is a one-piece part, in particular it is materially one-piece. In this case "one-piece" or "one" means that the leaf spring unit is a continuous part and is not made up of different parts. In this case "materially one-piece" means that the whole leaf spring unit is made of the same material, i.e. fiber composite plastic. In this context, the cross section of the leaf spring unit being "constant" means that the cross section does not have any bulges, constrictions, etc. In particular, the deflection part is not reinforced or thickened with respect to the leaf spring part.

[0024] According to a further embodiment, step a) comprises forming types of stiffening elements which differ from one another in their properties.

[0025] For example, "characteristics" may be understood in the present context to be the shape or geometry of the stiffening element, the stiffness, the modulus of elasticity, the material, the spring constant, etc. In particular, the assembly kit comprises at least two different types of stiffening elements.

[0026] According to a further embodiment, in step c) the stiffening elements are selected such that all of the selected stiffening elements belong to the same type of stiffening elements.

[0027] That is, identical stiffening elements are attached to the flexures of the leaf spring units, or the stiffening elements may be selected such that different types of stiffening elements are attached to the leaf spring units, which allows for further diversification in the manufacture of leaf spring devices.

[0028] According to a further embodiment, in step a) the stiffening element is formed such that it has a greater stiffness than the leaf spring unit.

[0029] As mentioned above, "rigidity" is to be understood as the resistance, in particular of the respective flexure, to elastic deformation. In particular, with regard to the stiffening element, its stiffness is to be understood as being relative to the stiffness of the respective flexure. This stiffness can be influenced, for example, by the geometry of the stiffening element or the corresponding material selection. For example, the stiffening element consists of a so-called bulk molding compound (BMC). BMC is a semi-finished product of a fiber matrix. However, the stiffening element may also consist, for example, of a metallic material or a ceramic material. If the stiffening element has a stiffness greater than that of the leaf spring unit, the leaf spring section will bend around the stiffening element when the leaf spring device is loaded. Preferably, the flexure is not deformed in this process.

[0030] According to a further embodiment, in step a) the stiffening element is formed such that the stiffening element undergoes elastic deformation when a load is applied to the leaf spring arrangement.

[0031] For example, the stiffening elements may consist of a resin elastomer or rubber, in which case, when the leaf spring device is loaded, the stiffening elements are elastically deformed and are at least partially pushed out of the respective flexures, in which case the stiffening elements ensure a uniform stress distribution in the flexures, so that no compressive stress peaks occur at the inner diameter of the flexures.

[0032] According to a further embodiment, in step a) the stiffening element is formed from an elastomer.

[0033] Resin elastomers or rubbers may have applications, but as mentioned above the stiffening elements may also consist of metallic or ceramic materials, but in this case the stiffening elements do not deform.

[0034] According to a further embodiment, in step a) the stiffening element is formed such that it comprises a core having a stiffness higher than the leaf spring unit and a shell surrounding the core at least in parts and having a stiffness lower than the core.

[0035] For example, the core may be made of a BMC as described above, while the shell may be made of an elastomer. The core is disposed within the shell. Preferably, the shell completely surrounds the core. When a small load is applied to the leaf spring device, initially only the shell elastically deforms, resulting in equal stress distribution in each flexure. In contrast, when a high load is applied to the leaf spring device, the leaf spring sections bend around the non-deformable core.

[0036] Furthermore, an assembly kit for manufacturing a leaf spring device made of fiber-reinforced plastic is proposed, which comprises a leaf spring unit made of fiber-reinforced plastic and a number of stiffening elements for localized stiffening of the leaf spring unit, whereby the leaf spring unit and selected stiffening elements can be combined to form the leaf spring device.

[0037] The assembly kit is particularly suitable for carrying out the method described above. The assembly kit may comprise a plurality of leaf spring units. The leaf spring units may all be identical. However, leaf spring units of different types may also be provided, which increases the number of possible variations in the manufacture of the leaf spring device. In particular, the assembly kit comprises a plurality of stiffening elements of different types. All embodiments relating to the assembly kit are also applicable to the method described above and vice versa.

[0038] According to one embodiment, the assembly kit comprises types of stiffening elements which differ from each other in their characteristics.

[0039] As mentioned above, the stiffening elements may differ from one another, for example, in their geometry or shape, but they may also differ from one another in the material used and thus in their material properties.

[0040] According to a further embodiment, the stiffening element has a stiffness greater than that of the leaf spring unit.

[0041] If the stiffening elements have a stiffness greater than the stiffness of the leaf spring units, the leaf spring sections will bend around the respective stiffening elements when the leaf spring device is loaded. However, the stiffening elements may also be elastically deformable. In this case, the stiffening elements will initially deform until the leaf spring sections then bend around the stiffening elements.

[0042] According to a further embodiment, the stiffening element comprises a core having a higher stiffness than the leaf spring unit and a shell surrounding at least in parts the core and having a lower stiffness than the core.

[0043] As mentioned above, the shell may completely surround the core. The core is preferably made of BMC, whereas the shell may be made of, for example, an elastomer. In particular, the core may be non-deformable, whereas the shell is elastically deformable.

[0044] As used herein, "a" should not be understood to be limited to exactly one element. Rather, there may be a number of elements, such as two, three, or more. Additionally, other numerical terms used herein should not be understood to limit the number of elements to that exact number. Rather, upward and downward numerical variations are contemplated unless otherwise indicated.

[0045] Further possible examples of the above methods and / or assembly kits include combinations of features or embodiments not expressly described above or below with respect to the embodiments. In this respect, the skilled person will also add individual aspects as improvements or additions to the respective basic forms of the above methods and / or assembly kits.

[0046] Further advantageous embodiments and aspects of said method and / or assembly kit are the subject matter of the subclaims and the embodiments of said method and / or assembly kit described below. Moreover, said method and / or assembly kit are explained in more detail by preferred embodiments with reference to the attached drawings. [Brief description of the drawings]

[0047] [Figure 1] 1 shows a schematic diagram of an embodiment of a leaf spring device. [Diagram 2] 2 shows another schematic view of the leaf spring device according to FIG. 1; [Diagram 3] FIG. 2 shows a schematic diagram of an embodiment of an assembly kit for manufacturing the leaf spring device according to FIG. 1; [Figure 4] 2 shows a schematic partial view of the leaf spring device according to FIG. 1; [Diagram 5] 2 shows a further schematic partial view of the leaf spring arrangement according to FIG. 1; [Figure 6] 2 shows a further schematic partial view of the leaf spring arrangement according to FIG. 1; [Figure 7] 2 shows a further schematic partial view of the leaf spring arrangement according to FIG. 1; [Figure 8] 2 shows a further schematic partial view of the leaf spring arrangement according to FIG. 1; [Figure 9] 2 shows a further schematic partial view of the leaf spring arrangement according to FIG. 1; [Figure 10] 2 shows a further schematic partial view of the leaf spring arrangement according to FIG. 1; [Figure 11] 2 shows a further schematic partial view of the leaf spring arrangement according to FIG. 1; [Figure 12] 2 shows a further schematic partial view of the leaf spring arrangement according to FIG. 1; [Figure 13] 2 shows a schematic block diagram of an embodiment of a method for manufacturing the leaf spring device according to FIG. 1;

[0048] In the drawings, identical or functionally identical elements are designated by the same reference numbers unless otherwise indicated. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0049] 1 shows a schematic diagram of a leaf spring arrangement 1. The leaf spring arrangement 1 is suitable for use in motor vehicles, in particular wheeled vehicles. The leaf spring arrangement 1 can be used in the area of ​​the wheel suspension of the motor vehicle.

[0050] The leaf spring device 1 comprises a leaf spring unit 2. The leaf spring unit 2 consists of a fiber-reinforced plastic material or a fiber-reinforced composite plastic (FRP) or a fiber composite plastic. The fiber-reinforced plastic material comprises a plastic material, in particular a plastic matrix in which fibers, such as for example natural fibers, glass fibers, carbon fibers, aramid fibers, are embedded. The plastic material may be a thermosetting resin, such as an epoxy resin. However, the plastic material may also be a thermoplastic resin. The fibers may be continuous fibers. However, the fibers may also be short or medium length fibers, with a fiber length of a few millimeters to a few centimeters. The leaf spring unit 2 may have a layered or laminated structure. For this purpose, for example, the plastic matrix is ​​impregnated into a layer of a fiber fabric or a fiber scrim. However, alternatively, the leaf spring unit 2 can also be manufactured using so-called prepregs, i.e. pre-impregnated fibers, fiber fabrics or fiber webs.

[0051] The leaf spring unit 2 has a curved geometric shape. It has a number of leaf spring sections 3 connected to each other at flexures 4. The number of leaf spring sections 3 is arbitrary. In FIG. 1, in each case only two leaf spring sections 3 and one flexure 4 are referenced. The individual leaf spring sections 3 each have an S-shaped geometric shape or may have an S-shaped path in side view. Each flexure 4 has an inner diameter 5 and an outer diameter 6.

[0052] The leaf spring portions 3 may be integrally connected to one another, in particular formed integrally from one material by the flexures 4. In this example, "integrally" or "one piece" means that the leaf spring portions 3 and the flexures 4 form a common part and are not constructed from different parts. In this example, "integrally formed from one material" means that the entire leaf spring portions 3 and the flexures 4 are made of the same material. The leaf spring unit 2 is a continuous strand or strip.

[0053] The leaf spring device 1 is designed so that when a load is applied to the leaf spring device 1, the flexures 4 do not deform at all, or at least do not deform appreciably. On the other hand, each leaf spring portion 3 deforms in its central region 7, generating a spring force that counteracts the load acting from the outside.

[0054] Fig. 1 shows the leaf spring device 1 in an unloaded or deflected state, whereas Fig. 2 shows the leaf spring device 1 in a loaded or compressed state. In the compressed state, the leaf spring portion 3, which is S-shaped in the unloaded state, has a planar shape.

[0055] In order that the flexures 4 deform and the leaf spring unit 3 deforms substantially only in the region 7, the leaf spring device 1 has stiffening elements 8, only one of which is referenced in Fig. 1. The stiffening elements 8 may also be referred to as insert elements or inserts. The stiffening elements 8 locally stiffen the leaf spring unit 2 at the flexures 4, so that the leaf spring unit 2 elastically deforms substantially only in the region 7.

[0056] The stiffening elements 8 are inserted into selected or all of the flexures 4, in particular into the inner diameter 5 of each of the flexures 4. In this respect, the stiffening elements 8 may be connected to the leaf spring unit 2, for example, in a material-locking, force-locking and / or form-locking manner. In the case of a material-locking connection, the connection partners are held together by atomic or molecular forces. A material-locking connection is an inseparable connection that can only be separated by destroying the connection means and / or the connection partners. A material-bonded connection can be formed, for example, by adhesive bonding or vulcanization.

[0057] A friction connection requires a normal force of the surfaces to be connected. A non-positive operating connection can be realized by friction locking. Misalignment of the surfaces relative to one another is prevented as long as the reaction force caused by static friction is not exceeded. A form-fit connection is formed by at least two connection partners that engage with one another or engage one behind the other. In other words, the stiffening element 8 is connected to the leaf spring unit 2 releasably or non-releasably.

[0058] By using the stiffening elements 8, the stressability of the leaf spring unit 2 can be increased by realizing an optimized distribution of the compressive stresses. The geometry-related shortcomings of the leaf spring concept, specifically the inner diameter 5 of the flexure 4, which may result in material limit compressive stresses at the inner diameter 5, are compensated for. In this way, the potential of the fiber-composite plastic material in terms of supporting the deformation energy in the less stress-critical leaf spring parts 3 can also be fully exploited.

[0059] For this purpose, several actions are utilized: On the one hand, the leaf spring parts 3 roll on the respective stiffening elements 8, which results in a controlled relative deformation of the flexures 4 and a controlled accumulation of compressive stresses in the flexures 4. This rolling is indicated by the arrows 9 in Figure 2. This allows the operating mode of the stiffening elements 8 to be compared with that of a flexure pulley.

[0060] Additionally or alternatively, one or more respective stiffening elements 8 are compressed. This compression or deformation is indicated by arrows 10 in FIG. 2. In this case, the stiffening elements 8 consist, for example, of an elastomer. This compression generates stresses which reduce the deformation of the leaf spring unit 2 in the flexures 4, which also results in a more uniform distribution of the compressive stresses. In particular, the stiffening elements 8 distribute the stresses uniformly, such that stress peaks are prevented or at least reduced. Thus, critical compressive stress peaks in the respective inner diameter 5 of the flexures 4 are prevented by means of the stiffening elements 8.

[0061] The material-specific advantages of anisotropic fiber composite plastics can be fully exploited by the concept of combining the leaf spring unit 2 with the stiffening element 8, since the total possible load of the leaf spring device 1 can be increased by the energy displacement into the leaf spring section 3, specifically into the area 7 by design.

[0062] Furthermore, by implementing the stiffening elements 8 in or on the prefabricated leaf spring unit 2, an economical manufacturing process can be performed. Unlike springs with laminated cores, a continuous draping process can be performed during the manufacture of the leaf spring unit 2. The laminating-in of the stiffening elements 8 can be omitted. A quality improvement can be realized by avoiding process interruptions and reducing the introduced porosity, which can cause air pockets during overdraping, either by the laminated core itself or by discontinuous areas.

[0063] Furthermore, by omitting the core in the form of stiffening elements 8, a more regular fibre profile can be achieved, since no pressing and curing of the core takes place in the pressing process, which could lead to deviations in the fibre profile, in particular to an increased build-up of resin at the outer diameter 6 of the flexure 4. This improves quality and reproducibility.

[0064] Furthermore, the concept of combining the leaf spring unit 2 with stiffening elements 8 also opens up the possibility of adapting the spring properties of the leaf spring device 1. This can be done downstream in the manufacturing process of the leaf spring unit 2 by easily and adaptively stiffening the flexures 4 with the insertion of the stiffening elements 8.

[0065] For example, by inserting the most diverse stiffening elements 8, which differ from one another, for example in their shape, size, material, etc., independently of the always identical hardened strand-like unidirectional leaf spring unit 2, which can always be produced using the same tool, leaf spring devices having approximately the same cross-section can now be easily produced with the most diverse properties. Since a stiffening element 8 or stiffening elements 8 can be inserted later from the outside, independently of the production process of the leaf spring unit 2, the draping and hardening process is decoupled from the properties of the leaf spring device 1 to be set. This allows a high degree of freedom in the production of the leaf spring device 1.

[0066] The combination of the prefabricated leaf spring unit 2 with the subsequently inserted stiffening element 8 allows the material-specific performance of fiber composite plastics to be fully utilized, according to the above concept, because the special structure and design of the leaf spring device 1, in particular the stiffening element 8, as well as its physical working principle, compensates for the material-specific weaknesses in the flexures 4, and thus the energy absorption of the leaf spring device 1 is highly optimized.

[0067] 3 shows a schematic diagram of an assembly kit 11 that can be used to manufacture a leaf spring device 1 as described above. The assembly kit 11 comprises at least one leaf spring unit 2 as described above and a number of stiffening elements 8. In this respect, the assembly kit 11 comprises any number of different types or kinds of stiffening elements 8. The types of stiffening elements 8 may differ, for example, in their stiffness, shape, size, material, etc.

[0068] 4 and 5 respectively show schematic partial views of a leaf spring device 1 with a further embodiment of a stiffening element 8A. The stiffening element 8A consists of an incompressible material, such as a so-called bulk molding compound (BMC). BMC is a semi-finished product of a fiber matrix. BMC most commonly contains short glass fibers and polyester or vinylester resin, although other reinforcing fiber or resin systems are also conceivable. However, the stiffening element 8A may also consist of a metallic or ceramic material.

[0069] FIG. 4 shows the leaf spring device 1 under high load. Here, in FIG. 4, the leaf spring part 3 is shown in dashed lines in the deflected or unloaded state of the leaf spring device 1. In the compressed or loaded state, the leaf spring part 3 is shown in solid lines. When the leaf spring device 1 is loaded, the leaf spring part 3 bends around the stiffening element 8A. In contrast, FIG. 5 shows the leaf spring device 1 in a low load state. In the light load state, the leaf spring part 3 is slightly deformed and slightly bends around the stiffening element 8A.

[0070] 6 shows how the properties of the leaf spring device 1 are influenced. For this purpose, different types of stiffening elements 8A, 8A', 8A'', each differing from one another in their shape and geometry, are provided. For example, the stiffening of the flexure 4 obtained with stiffening element 8A'' is greater than that obtained with stiffening element 8A.

[0071] 7 to 9 each show a schematic partial view of the leaf spring device 1 with a further embodiment of a stiffening element 8B. Unlike the stiffening element 8A, the stiffening element 8B is elastically deformable. For example, the stiffening element 8B may be made of an elastomer, in particular a resin elastomer. For example, the stiffening element 8B may be made of rubber.

[0072] Fig. 7 shows the leaf spring device 1 under high load. Here, in Fig. 7, the leaf spring part 3 is shown in dashed lines in the deflected or unloaded state of the leaf spring device 1. In the compressed or loaded state, the leaf spring part 3 is shown in solid lines. When the leaf spring device 1 is loaded, the leaf spring part 3 elastically deforms but does not bend around the deformable stiffening element 8B. However, the stiffening element 8B itself elastically deforms.

[0073] The deformed stiffening elements 8B result in a uniform stress distribution in the respective flexures 4. In the flexed state of the leaf spring device 1, the outer contour of the stiffening elements 8B is shown in dashed lines in FIG. 7. In the compressed state, the outer contour of the stiffening elements 8B is shown in solid lines. In contrast, FIG. 8 shows the leaf spring device 1 in a low-load state. In the low-load state, the leaf spring sections 3 are slightly deformed. The stiffening elements 8B themselves are elastically deformed.

[0074] 9 shows how the properties of the leaf spring device 1 are influenced. For this purpose, different types of stiffening elements 8B, 8B', 8B'', differing from one another in their shape and geometry, are provided. For example, the stiffening of the flexures 4 obtained with stiffening element 8B'' is greater than that obtained with stiffening element 8B.

[0075] 10 to 12 each show a schematic partial view of a leaf spring device 1 with a further embodiment of a stiffening element 8C. The properties of the stiffening element 8C result from the combination of the above-mentioned stiffening elements 8A, 8A', 8A'', 8B, 8B', 8B''. The stiffening element 8C is a composite or multi-material element. It comprises an incompressible core 12, for example made of BMC, and a shell 13 that encapsulates the core 12. The shell 13 may be made of an elastomer.

[0076] Figure 10 shows the leaf spring device 1 under high load. Here, in Figure 10, the leaf spring part 3 is shown in dashed lines in the deflected or unloaded state of the leaf spring device 1. In the compressed or loaded state, the leaf spring part 3 is shown in solid lines. When the leaf spring device 1 is loaded, the leaf spring part 3 bends around the stiffening element 8C, in particular around the core 12. At the same time, the shell 13 undergoes elastic deformation.

[0077] In the deflected state of the leaf spring device 1, the outer contour of the shell 13 is shown in dashed lines in Fig. 10. In the compressed state, the outer contour of the shell 13 is shown in solid lines. In contrast, Fig. 11 shows the leaf spring device 1 in a lightly loaded state. In the lightly loaded state, the leaf spring part 3 is slightly deformed and slightly bent around the core 12. At the same time, the shell 13 is also elastically deformed.

[0078] 12 shows how the properties of the leaf spring device 1 are influenced. For this purpose, different types of stiffening elements 8C, 8C' are provided, which differ from each other in that their shells 13 have different geometric shapes and / or material properties. For example, the stiffening of the flexures 4 obtained with the stiffening element 8C' is greater than that obtained with the stiffening element 8C.

[0079] 13 shows a schematic block diagram of an embodiment of a method for manufacturing a leaf spring device 1. In this method, in step S1, an assembly kit 11 is prepared, which comprises a leaf spring unit 2 made of a fiber composite plastic and a number of stiffening elements 8, 8A, 8A', 8A'', 8B, 8B', 8B'', 8C, 8C' for locally stiffening the leaf spring unit 2.

[0080] The step of preparing the assembly kit 11 may include the step of producing the leaf spring units 2 and stiffening elements 8, 8A, 8A', 8A'', 8B, 8B', 8B'', 8C, 8C'. In this respect, different types or kinds of leaf spring units 2 and / or stiffening elements 8, 8A, 8A', 8A'', 8B, 8B', 8B'', 8C, 8C' may be manufactured.

[0081] In step S2, the leaf spring device 1 is designed according to a desired use case. The use case may be, for example, a specific configuration of a vehicle platform. The design may be performed using a computer program. During the design, for example, the spring constant and / or dimensions of the leaf spring device 1 are determined.

[0082] In step S3, the stiffening elements 8, 8A, 8A', 8A'', 8B, 8B', 8B'', 8C, 8C' are selected from the assembly kit 11 according to the design of the leaf spring device 1. In the following step S4, the selected stiffening elements 8, 8A, 8A', 8A'', 8B, 8B', 8B'', 8C, 8C' and the leaf spring unit 2 are assembled or combined to form the leaf spring device 1. In this respect, the stiffening elements 8, 8A, 8A', 8A'', 8B, 8B', 8B'', 8C, 8C' may for example be joined to the leaf spring unit 2.

[0083] Although the present invention has been described with reference to exemplary embodiments, the present invention is susceptible to various modifications. [Explanation of symbols]

[0084] 1 Leaf spring device 2 Leaf spring unit 3 Leaf spring part 4 Flexure 5 Inner diameter 6 Outer diameter part 7 areas 8 Stiffening elements 8A Stiffening elements 8A' Stiffening element 8A'' stiffening element 8B Stiffening elements 8B' Stiffening element 8B'' stiffening element 8C Stiffening elements 8C' Stiffening element 9 Arrows 10 Arrows 11 Assembly kit 12 cores 13. Shell S1 process S2 process S3 process S4 process

Claims

1. A method for manufacturing a leaf spring device made of fiber composite plastic, comprising the steps of: a) preparing an assembly kit comprising the leaf spring unit made of the fiber composite plastic and a number of stiffening elements for locally stiffening the leaf spring unit; b) designing the leaf spring device according to a desired application; c) selecting stiffening elements from the assembly kit according to a design of the leaf spring device; d) combining the selected stiffening elements with the leaf spring unit to form the leaf spring device; Including, Step a) comprises forming types of stiffening elements which differ from one another in their properties, 4. The method according to claim 3, wherein in step a) the stiffening element is formed such that the stiffening element has a greater stiffness than the leaf spring unit.

2. 2. The method of claim 1, wherein in step d) the selected stiffening element is attached to a flexure of the leaf spring unit.

3. 3. The method of claim 2, wherein in step d), the selected stiffening elements are attached to an inner diameter of each of the flexures.

4. 4. The method according to claim 2 or 3, characterized in that in step d) the selected stiffening elements are form-fittingly and / or material-fittingly connected to the flexures.

5. 5. The method according to claim 1, wherein step a) comprises forming the leaf spring unit as a continuous strand of constant cross-section.

6. 6. The method according to any one of claims 1 to 5, characterized in that in step c) the stiffening elements are selected such that all of the selected stiffening elements belong to the same type of stiffening element.

7. 7. The method according to claim 1, wherein in step a) the stiffening element is formed such that the stiffening element undergoes elastic deformation when a load is applied to the leaf spring device.

8. 8. The method according to claim 7, wherein in step a) the stiffening element is made of an elastomer.

9. 7. The method according to claim 1, wherein in step a) the stiffening element is formed such that it comprises a core having a stiffness higher than that of the leaf spring unit and a shell surrounding at least in part the core and having a stiffness lower than that of the core.

10. An assembly kit for manufacturing a leaf spring device made of fiber composite plastic, comprising: A leaf spring unit made of the fiber composite plastic; a plurality of stiffening elements for locally stiffening the leaf spring unit; the leaf spring unit and selected stiffening elements are combinable to form the leaf spring device; 11. An assembly kit, comprising: a stiffening element having a stiffness greater than that of the leaf spring unit.

11. 11. An assembly kit according to claim 10, characterized in that the stiffening elements are of different types in their characteristics.

12. 12. The assembly kit according to claim 10 or 11, wherein the stiffening element comprises a core having a stiffness higher than that of the leaf spring unit, and a shell surrounding the core at least in part and having a stiffness lower than that of the core.

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