DE102018129549B9 - Shaping the ends of coil springs - Google Patents

Abstract

Helical spring (100, 100'), which has several turns of a helically wound spring wire (10, 10', 10'') made of fiber-reinforced plastic material, having a fiber reinforcement and a matrix material, the fiber reinforcement being distributed over the entire length of the spring wire (10 , 10', 10") as continuous fiber material with a constant number of fibers, the helical spring (100, 100') having two spring ends and at least one of the spring ends in a last coil (1) of the helical spring (100, 100') a transition area (B ) and then has an end region (E) in the direction of the end of the spring wire (10, 10', 10"), characterized in that a cross-sectional area of the spring wire (10, 10', 10") in the transition region (B) from a The cross-sectional area (A0) of the spring wire (10, 10', 10") in a central part of the spring (100, 100') transitions into a smaller cross-sectional area (A1) of the end region (E), in that the fiber volume content in the spring wire (10, 10' , 10") in Ve is continuously increased over the course of the transition region (B).

Description

The subject matter of the present application is a method for producing helical springs with specially shaped ends, a device for producing such helical springs, and the helical springs produced in this way.

Coil springs are springs that have a spring wire that extends in a helically wound manner from a first spring end to a second spring end. The helical spring has a longitudinal axis around which the windings of the spring wire run. The outside diameter of the helical spring is determined by the surface sections of the spring wire that are radially furthest away from this longitudinal axis. The inside diameter through the surface portions of the spring wire radially closest to the longitudinal axis. The spring wires often have a constant cross-section over the entire length. This is mostly circular. However, elliptical cross sections or polygonal shapes are also known.

The axis of the spring wire (spring wire axis) runs around the longitudinal axis of the helical spring in the helical coils mentioned.

Coil springs are used in a variety of technical fields. A particularly important area of application is vehicle construction. Here the springs often serve as a shock-reducing element in the chassis. In this field of application, the springs are often designed as steel springs. This enables a good spring action with a limited size, but has the disadvantage that the springs are very heavy. Based on this, attempts have been made to replace steel springs with springs made from fiber composites. The problem here is that the springs in fiber composite construction are to be used in the installation space that is provided for steel springs. The base materials used for fiber composite springs are generally less rigid than the isotropic metal alloys of steel springs. The spring wires of the fiber composite coil springs may therefore have to be designed with a larger diameter. This reduces the available spring deflection while keeping the installation space constant. Therefore, with helical springs in fiber composite construction, the individual spring coils can come together - so-called blocking.

There are now a number of efforts to make the springs as compact as possible and to prevent the problem of blocking, which is also known with coil springs made of other materials, or without undefined force distributions, as occurs when spring coils made of spring wire with a circular cross-section meet are expected to expire.

the EP 2 461 066 A1 suggests flattening the spring wire at the coils lying one above the other in the longitudinal direction of the spring. In this way, contact surfaces are formed on which the abutting turns rest in a defined manner. The disadvantage of this design is that the cross-section of the spring wire is reduced, thereby reducing the load-bearing capacity and rigidity of the spring.

A similar approach suggests the DE 44 06 826 B4 before. Here a coil spring is used in a torsional vibration damper. The longitudinal axis of the helical spring is curved. It is proposed to provide at least one flat area on the spring wire, on which the adjacent coil can rest. Due to the curvature of the longitudinal axis of the helical spring, the bearing surfaces of adjacent coils are not parallel to one another, but inclined towards one another at an angle. Here, too, a reduction in the load capacity of the spring is accepted.

The subject matter of JP H07-113 389 B2 is a helical spring which is subjected to a torsional load about its longitudinal axis. The pressure is applied via a clamping mechanism. A problem with previous constructions was that the spring ends rubbed against the clamping mechanism under load and were subject to heavy wear. This is to be avoided by making the spring ends conical. The figures 1 and 2 show the corresponding embodiment. The spring wire is flatter, but has a greater radial expansion.

Another approach to extending the available spring travel is to vary the coil radii, ie the distance between the axis of the spring wire in one coil and the longitudinal axis. However, this leads to an uneven stress on the spring over its length. Failure is more likely that way.

An example of this approach is the DE 10 2015 221 126 A1 called. This coil spring should be better stabilized against lateral forces. For this purpose, the spring ends are arranged in special spring seats, which engage in the spring at the ends of the latter. The last turn of the coil spring that rests on the spring seat is narrowed. This prevents it from slipping sideways Spring end in seat, but allows spring center section to move laterally.

the DE 10 2013 208 270 A1 also relates to a solution for the spring end of a coil spring. Known helical springs have ground ends of the spring wire. The grinding preferably takes place in a plane perpendicular to the central axis of the spring (longitudinal axis of the spring). The spring wire then rests with the ground area on the spring seat. The pitch of the windings of the spring wire remains the same in this area (in the relaxed state) as that of the central part of the spring. However, the force-absorbing cross-section of the spring wire is becoming smaller and smaller, so that failure in this area is likely. the DE 10 2013 208 270 A1 tries to counteract this by drawing in the ground end elliptically, i.e. deforming it in the direction of the longitudinal axis of the spring. However, grinding is unsuitable for springs made of fiber composite material, since damage to the fiber reinforcement, which would be unavoidable when grinding the spring ends, would damage the load-bearing capacity of the entire spring. The ground area has reduced mechanical properties and reduced resistance properties to corrosive influences due to the interrupted fiber routing.

The prior art offers a variety of solutions for steel springs. However, only very few are suitable for springs made of fiber composite material.

The object is therefore to propose a way of advantageously designing helical springs made of fiber composite material, particularly in the end regions, in such a way that the greatest possible spring deflection is achieved while maintaining the most uniform stiffness possible over the entire spring length. In addition, a method for producing such a helical spring and a device for producing such a helical spring are to be shown.

According to the invention, the object is achieved with a helical spring according to claim 1. Production methods are disclosed in claims 13-15. An apparatus for manufacturing a coil spring is defined in claim 16. Advantageous embodiments and procedures are presented in the dependent claims.

The helical spring according to the invention has a plurality of windings made of a helically wound spring wire made of fiber-reinforced plastic material. The spring wire thus has fiber reinforcement and a matrix material. The fiber reinforcement of the plastic material runs as a continuous fiber material with a constant number of fibers over the entire length of the spring wire. "Continuous fiber material" is understood to mean a material whose fibers run essentially without interruption, with technologically caused breaks in individual filaments being disregarded. The fiber reinforcement runs inside the spring wire.

The helical spring has two spring ends as well as a transition area on at least one of the spring ends in the last turn of the helical spring and an end area adjoining this in the direction of the end of the spring wire.

According to the invention, the helical spring has a cross-sectional area at one or both ends, but the number of fibers in the fiber reinforcement remains constant.

Optionally, the helical spring also has a cross-sectional shape at one or both ends that differs from the cross-sectional shape of the spring wire in the central part, but the number of fibers in the reinforcement remains constant.

The cross-sectional shape of the spring wire is preferably circular, at least in the central part. However, elliptical cross-sectional shapes (with the orientation of the major semi-axis perpendicular or vertical to the longitudinal axis of the spring) or rectangular shapes (with rounded corners) are also possible.

The spring wire consists of one or more layers of braided or wound fiber layers. These can differ in fiber orientation (angle to the spring wire axis) or in the manufacturing method (e.g. braided, wound, taped, unidirectional individual rovings laid). The spring wire has endless fibers that extend essentially without interruption over the entire length of the spring wire. Optionally, the use of unreinforced, short-fiber-reinforced and/or long-fiber-reinforced intermediate layers is also possible.

The spring optionally has a core. This consists preferably of fiber composite material in which the fibers run unidirectionally or slightly twisted parallel to the spring wire axis. Further preferred embodiments provide a hollow core in which an axial cavity is surrounded by a fiber composite material or an unreinforced plastic sheath. Also preferred is a core that consists entirely of plastic or a core that is formed exclusively by a cavity. The core material can be meltable.

The fiber reinforcement of the spring wire is surrounded by a matrix material that has also penetrated between the reinforcement fibers. The known fiber materials of fiber composite lightweight construction are preferably used as the material for the fiber reinforcement. These are, for example, glass fibers, carbon fibers, metal fibers, rock fibers, natural fibers, etc. Thermosetting materials, preferably resin systems (epoxy resins, polyester resins, phenolic resins, etc.) are used as matrix materials. Thermoplastics are also conceivable if the requirements permit. For example, the spring is mainly in the unloaded state and is rarely loaded for a short time, or the thermoplastic meets the necessary creep requirements.

The last turn of the spring wire of the coil spring is called the end of the spring. The transition area begins no earlier than half a turn before the beginning of the end of the spring. The transition region preferably begins with the end of the spring, that is to say it begins at the beginning of the last turn. The transition area preferably includes an eighth, particularly preferably a quarter of a turn, but can also include the entire last turn, so that the final cross-sectional shape of the spring wire is achieved with the end of the spring wire. The transition region particularly preferably begins within the end of the spring, preferably half a turn before the end of the spring wire. The transition area preferably includes an eighth, particularly preferably a quarter of a turn, but can also include the entire available range of turns to the end of the spring wire, so that the final cross-sectional shape of the spring wire is achieved with the end of the spring wire. However, the transition area can also begin in such a way that the final cross-sectional shape is just reached at the end of the spring wire without introducing cross-sectional changes that lead to a mechanical impairment of the spring. For example, there must be no sharp-edged notches with fiber breaks in the transition area if this endangers the functioning of the spring.

The helical spring according to the invention has at one end or at both ends a cross-sectional area that is the same as that of the spring wire in the central part, but the fiber reinforcement remains constant in terms of the number of fibers. This is preferably implemented using one of the three embodiments described below.

Preferably, the distribution of the fiber reinforcement and the matrix material in the spring ends is modified compared to the central part of the coil spring in such a way that the coil lying over the spring end is given a greater distance than would be the case with an unchanged cross section and the same gradient distribution of the spring wire axis, and thus a longer spring deflection arises. The pitch of the helical spring (winding pitch) designates the component of the spatial gradient of the spring wire axis, which points in the direction of the longitudinal axis of the spring. The distance between the spring wire axis and the respective axes of the adjacent coils in the longitudinal direction of the spring results when integrated. The longitudinal axis of the spring can be in the form of a continuously straight line, linear in sections along the longitudinal direction of the spring, curvilinear (e.g. banana-shaped) or of a combination of the aforementioned possibilities.

The first embodiment provides that the content of the cross-sectional area of the spring wire is constant over the entire length of the spring. The transition from the cross-sectional shape of the spring wire in the central part of the spring takes place in a transition area in the cross-section of the spring wire in the end area of the spring wire in a continuous manner. This includes the smooth transition from the cross-sectional shape in the middle part of the spring to the cross-sectional shape at the spring end or ends. In particular, this is achieved in that the fiber reinforcement and the matrix material in the spring wire have a different distribution than in the central part of the spring. The spring wire axis shifts accordingly in order to take account of the constant geometry of the spring supports. The core also deforms from its cross-sectional shape in the central part to the cross-sectional shape at the spring end. The core preferably deforms in a mathematically similar manner. Optionally, the spring core remains undeformed in the transition area.

If the cross-sectional shape in the central part and in the end area is superimposed so that there is the greatest possible overlap, the non-overlapping area of the cross-sectional area of the end area is at least a value of at least 2%, preferably at least 5% and particularly preferably at least 10% based on the total cross-sectional area of the end area . The non-overlapping area of the cross-sectional area of the end region is at most 70% based on the total cross-sectional area of the end region, preferably at most 60%.

The second embodiment provides that the cross-sectional area of the spring wire is smaller in the end area than in the central part of the spring. Here, too, the transition from the cross-sectional area of the spring wire in the central part of the spring takes place in a transition area into the cross-sectional area of the spring wire in the end area of the spring wire in a continuous manner. It is characteristic of this embodiment that the fiber reinforcement mat rial in the end area is identical to that in the middle part of the spring and in the transition area. This applies to the type of fiber, the number of fibers and all other properties that characterize fiber reinforcement, with the exception of the fiber density in the matrix material. All continuous fibers preferably run through the entire spring wire. In the end area, the fibers are just closer together and are surrounded by less matrix material. The cross-sectional area in the end area is smaller than the cross-sectional area in the middle area. For example, the surface area of the cross-sectional area in the end region is at least 2%, preferably at least 4% and particularly preferably at least 8% lower, based on the cross-sectional area in the central part. The reduction in cross-sectional area is limited in such a way that a maximum fiber volume content cannot technically be exceeded.

A third embodiment and a combination of the first and second embodiments is a spring end in which, in addition to a reduced cross-sectional area, the cross-sectional shape of the spring end is also different compared to the central part of the spring. Here, too, a transition area is provided, which transforms the cross-sectional shape and/or cross-sectional area from the central part of the spring into a smooth transition into the cross-sectional shape and area of the end area.

In a further preferred embodiment, which can be combined with those mentioned above, the cross-sectional shape at the end area of the spring wire, adjoining the transition area, remains preferably over a quarter, particularly preferably over a third and very particularly preferably over two thirds of the last turn of the spring wire constant.

The wire cross section of the helical spring is preferably constant at least in the central area between the two spring ends. At this point, this means that both the cross-sectional shape and the cross-sectional area remain unchanged, apart from production-related influences (different winding tension, mandrel tolerances, etc.).

First embodiment

In the first embodiment, the cross-sectional shape of the spring wire at the spring ends is preferably modified in such a way that it changes from the cross-sectional shape in the central part of the spring to a cross-sectional shape in the end region of the spring wire, which results in a smaller diameter of the spring wire in the longitudinal direction of the spring or a distribution of the fiber reinforcement and of the matrix material in such a way that in the direction of movement of the penultimate turn, a groove of the spring wire of the spring end is achieved. Furthermore, it is possible to give the spring wire a cross-section at the spring ends which is less opposed to the movement of the penultimate turn. This can be achieved, for example, by shifting the geometric center of gravity of the cross-sectional shape of the spring wire radially inwards or outwards, as viewed from the longitudinal axis of the spring. A characteristic of the first embodiment of the spring ends according to the invention is that the surface area of the cross-sectional area of the spring wire remains the same in the central part of the spring, in the transition area and also in the end area of the spring wire. Only the shape of the cross-sectional area changes.

In particular, the spring wire, which preferably has a circular cross-section in the middle part of the spring, transitions into an elliptical cross-section, with the semi-minor axis of the ellipse being aligned in the longitudinal direction of the spring. Another embodiment provides for a transition to a flattened cross-section with a groove opposite the penultimate turn. Also preferred is an irregular cross-section that exhibits a displacement of the curvature of the originally round cross-section radially inwards or outwards.

These changed cross-sectional shapes at the end of the spring are optionally accompanied by a flattening of the spring wire in the direction of the end of the longitudinal direction of the spring. This advantageously leads to an enlarged contact surface of the spring end in the spring seat.

Optionally, an irregular cross section of the end area of the spring wire, which has a radially inward or outward displacement of the curvature of the originally round cross section, is combined with a retraction or extension of the end area of the spring wire. The end area of the spring wire is pulled in when the curvature is directed towards the longitudinal axis of the spring and is deployed when the curvature is directed away from the longitudinal axis of the spring.

Second embodiment

In the second embodiment, the cross-sectional area of the spring wire at the spring ends is preferably modified in such a way that it changes from the cross-sectional area in the central part of the spring to a smaller cross-sectional area in the end area of the spring wire.

A characteristic of the second embodiment of the spring ends according to the invention is that in the transition area the cross-sectional area of the spring wire in the central part of the spring, which has a first surface area, transitions into a cross-sectional area in the end region of the spring wire, which has a second surface area that is smaller than the first surface area. However, the cross-sectional shape preferably remains unchanged, ie, geometrically similar in the mathematical sense. This means that a cross-sectional area in the central part, a cross-sectional area in the transition area and a cross-sectional area in the end area are geometrically similar to one another in a mathematical sense. This is the case if the cross-sectional areas can be converted into one another by means of a geometric similarity mapping. This means that there is a geometric mapping that can be composed of centric stretching and congruence mappings (i.e. displacements, rotations, reflections) and that maps one cross-sectional area onto the other. For example, the spring wire thus has a circular cross-section in the central part, in the transition area and in the end area. Only the area of the cross-sectional area changes. This is preferably achieved by guiding the fiber reinforcement from the middle part without interruption through the transition area into the end area of the spring wire. However, less matrix material is contained in the end area. The fiber density (fiber volume content) thus increases from the central part through the transition area to the end area. The end area then has a higher fiber density (fiber volume content) than the middle part and the transition area. The value of the fiber volume content of the end area is, for example, 10% higher than the value of the fiber volume content of the middle part. However, it can also assume other differences with a value greater than zero and the fiber volume content of the end region can be increased to just under the theoretical maximum of 80%. The reduced cross-sectional area of the spring wire results in an increased spring deflection in the end area of the spring.

Third embodiment

The third embodiment is a combination of the first and second embodiments. The cross-sectional shape and also the cross-sectional area change from the central part of the spring via the transition section to the end area. In particular, the cross-sectional area decreases as the fiber volume content of the spring wire increases, i.e. the fiber reinforcement material extends uninterruptedly from the central part of the spring through the transition region into the end region as the matrix material content decreases. Only less matrix material is used while the distribution of the fiber reinforcement material is changed. The reduced cross-sectional area of the spring wire results in an increased spring deflection in the end area of the spring. Parallel to the reduction in the cross-sectional area, the cross-sectional shape is also adapted in such a way that the compression travel that occurs is further increased analogously to the first embodiment.

Optionally, the second and the third embodiment can also be combined with a retraction or extension of the end area of the spring wire.

Optionally, the spring wire is completely or partially surrounded by a sheath. This can be arranged detachably or permanently on the surface of the consolidated spring wire. The shell preferably consists of an elastomer (e.g. silicone), thermoplastic elastomer (e.g. TPU (thermoplastic polyurethane)) or a thermoplastic synthetic material (e.g. PA (polyamide) or Teflon). The sheath may be formed on the spring wire as part of the manufacturing process or may be post applied to protect the surface thereof.

Since the load-bearing capacity of the spring is essentially determined by the reinforcing fibers, and in all three embodiments of the coil spring according to the invention only the distribution of the fibers and the matrix material and not the continuous course or length or number of fibers are changed, the load-bearing capacity of the spring remains the entire length essentially constant.

In embodiments of the helical spring, a first spring end of the helical spring is designed according to a first variant of the previously described embodiments and a second spring end of the helical spring is designed according to a second variant of the previously described embodiments. The first and the second variant can differ from one another in terms of the embodiment used, or the first and the second variant belong to the same embodiment described so far, but differ in the cross-sectional shape of the two spring ends and/or in the cross-sectional area of the two spring ends. Both ends of the spring are thus deformed in relation to the spring wire in the central part, but differently.

Various procedures are known for producing helical springs from fiber-reinforced material. That's how she beats U.S. 4,434,121A proposed to wind the resin-impregnated fiber reinforcement into the helically circumferential groove of a cylindrical mold core and then to surround it with a mold that has a corresponding groove. More resin of the matrix material should be fed through the groove to fill it. Mold and mold core should be heated in order to to harden resin. It is provided that the matrix material is only heated to below the glass transition temperature and the spring ends are heated again after being cut to length and drawn in or flattened into the shape of a loop.

the DE 10 2012 112 937 A1 proposes to produce a spring wire by forming a laminate strand of fiber reinforcement material, which is impregnated with curable matrix material, into a spring geometry. Before the laminate strand is shaped, a strand-like preliminary product is formed by applying a malleable protective jacket enclosing the laminate strand in a continuous application process. The spring ends can optionally be provided with protective caps, which can also be part of the finished spring after consolidation.

The basic features of the method according to the invention are based on the procedures known from the prior art. However, the different design of the spring ends is essential to the invention.

The method provides that the spring wire is wound onto a cylindrical mandrel in the unconsolidated state. This mandrel optionally has a helical groove running around the mandrel, into which the spring wire is inserted. The fiber reinforcement of the spring wire is dry or already impregnated with resin.

Optionally, an outer mold is provided, which surrounds the mold core with the spring wire inserted into the groove. The mold core and/or the mold can be heated. If the fiber reinforcement of the spring wire is not yet or not sufficiently soaked with resin, this is done by introducing resin into the groove.

The resin of the spring wire can now be fully or partially cured by heating the mold or the mold core or both. In the case of a complete curing, the adaptation of the cross-sectional shape and/or the cross-sectional area of the spring ends takes place before curing. A special forming tool for the spring ends is preferably provided for this purpose, which brings the transition area and the end of the spring wire into the desired shape and only then hardens (heating). With a corresponding shape of the mold, this leads to a change in cross-sectional shape and/or to a reduction in the cross-sectional area while maintaining all fiber orientations from the central part of the spring. The change in the cross-sectional area, or more precisely the content of the cross-sectional area, takes place in that unconsolidated matrix material is pressed out of the reinforcing fiber material through the mold or through a special shaping tool that acts on the ends of the unconsolidated spring wire.

The special mold is preferably part of the mold core and/or the mold surrounding it. It is therefore preferable to use the change in cross-sectional area or

Produce cross-sectional shape change from the cross-section in the middle of the spring between the spring ends, the transition region and the cross-sectional shape/area of the end of the spring wire in one process step. However, this approach is less suitable when the cross-sectional shape of the end of the spring wire includes an undercut configuration within the mold or core.

An alternative procedure provides that the spring ends are excluded in the case of complete curing. These are hardened at most to above the gel point. After the spring has been removed from the mold or removed from the mold core, the spring ends are treated with a special mold, e.g. a pressing tool, which brings the transition area and the end area of the spring wire into the desired cross-sectional shape. For this purpose, the tool can be heatable. By heating above the glass transition temperature, the spring wire becomes plastically deformable again. Further heating then leads to the complete consolidation of the matrix material. This procedure is suitable for the production of springs according to the first embodiment. In combination with a previous cross-sectional reduction using a special mold, it can also be used for the third embodiment.

A further preferred procedure is particularly suitable for the production of the first embodiment. It provides for encasing the fiber reinforcement of the spring wire with a hose. Matrix material is then fed into this tube in an unconsolidated state. The matrix material is then crosslinked (e.g. by heating) to above the gel point of the matrix material. The hose can now be removed or left on the preformed spring wire and then become part of the spring. The spring wire can then be heated above the glass transition temperature and brought into the desired helical shape. This is preferably done by winding onto a heatable mandrel. The ends of the springs can also be formed in this step. Suitable molds, e.g. clamping devices, can be used for this. The matrix material is fully cured by further heating.

A further alternative procedure involves cutting the spring wire, more precisely the fiber reinforcement of the spring wire, in the unconsolidated state. The fiber reinforcement of the spring wire is then soaked in resin and clamped at the ends in clamping devices. Optionally, these clamping devices act as special shaping tools to reduce the cross-sectional area in the end region. This is followed by winding onto a cylindrical mandrel, which optionally has a groove for guiding the spring wire. Optionally, the mold core with coiled spring wire is placed in a mold that can also be heated. The clamping devices comprise at least the transition area of the spring wire and the end of the spring. By heating the mold core and the clamping devices and optionally the mold, the matrix material is hardened and the coil spring is consolidated. Finally, the clamping devices and mold core and optionally also the mold are removed. The clamping devices can be designed in two parts or in several parts.

A further preferred procedure provides that the fiber reinforcement of the spring wire impregnated with resin is arranged in a flexible sheath in the unconsolidated state. This consists, for example, of a thermoplastic material or silicone. The unconsolidated spring wire is then applied to a heatable mold core with an optional groove and optional outer shape using one of the aforementioned methods and consolidated or partially consolidated as shown above. The design of the spring ends can also be carried out according to one of the procedures described above. After consolidation, the sleeve can remain on the spring as surface protection or, if it does not bond with the matrix material (e.g. Teflon sleeve or silicone sleeve), it can be removed. For spring ends that exhibit a reduction in cross-sectional area, the sleeve can optionally be severed and then removed. Further preferred procedures provide for multi-part casings, with the casing having a constant cross-section in the central part and casings adapted in each case for the transition and end regions. These can, for example, be tapered in the direction of the ends in order to follow a reduction in the cross-sectional area of the spring wire in the end region.

Optionally, shrink tubing can be used to cover the transition and end areas.

A device according to the invention for producing a helical spring according to the invention contains at least one molding tool, which has a cavity in its interior, into which an end region to be deformed or an end region to be deformed and a transition region to be deformed of the spring wire, which is unconsolidated at least in these regions, can be inserted, the cavity depicts the desired cross-sectional shape and/or cross-sectional area of the end region or of the end region and the transition region. The end area of the spring wire or the end area and the transition area of the spring wire is thus formed as desired and as described above.

The mold preferably has a temperature control device for heating or cooling the mold, so that the material of the spring wire can be heated inside the mold and, if necessary, consolidated and/or cooled again.

The mold preferably has a two-part or multi-part design for easier insertion of the spring wire areas to be deformed into the cavity and for easier demolding of the deformed spring wire areas.

The invention is not limited to the illustrated and described embodiments, but also includes all embodiments that have the same effect within the meaning of the invention. Furthermore, the invention is not limited to the combinations of features specifically described, but can also be defined by any other combination of specific features of all individual features disclosed overall, provided that the individual features are not mutually exclusive, or a specific combination of individual features is not explicitly excluded.

character list

• 1a shows a schematic sectional view of a first embodiment 100 of the spring according to the invention. One end of the spring has a transition region B and an end region E. The other end of the spring remains undeformed with the same support geometry.
• 1b until 1d show schematically the internal structure of various embodiments of the spring wire forming the spring. In a first embodiment 10 of the spring wire, shown in 1b , a sheath 11, e.g. The core 13 also consists of fiber material in which the fibers are arranged unidirectionally parallel to one another or are slightly twisted with one another. At least in the consolidated state is in the area of the fiber layers 12 and the core 13 next to the Fibers before matrix material. The matrix material can also already be contained in the spring wire 10 in the unconsolidated state.

In another embodiment, the core can also consist only of plastic, for example matrix material, and have no fibers. In addition, the cover 11 is only optionally available.

For example, the 1c an embodiment 10' of the spring wire in which there is no sheath. In addition, there is also no core, but instead a hollow space 13' is present inside the spring wire. The fiber layers 12 are designed, for example, in the form of a braided hose.

1d shows a further embodiment 10" of the spring wire, in which the fiber layers 12 are applied to a tube core 14, which is in the form of a hollow, flexible tube or tube and is made of plastic, and - again optionally - are closed to the outside with a sleeve 11.

If no specific statements are made below about the structure of the spring wire, the spring wire can be designed according to any of the embodiments listed here.

2 shows schematically a further embodiment 100' of the spring according to the invention. Both end areas are deformed here and realized as end cross section A1. The transition area B transitions from the cross-sectional area A0 to the elliptical end area A1.

3 Figure 12 shows schematically a spring end of a prior art construction. Here there is a distance q1 between the penultimate winding and the last winding.

4a until 4e show schematically spring ends of the construction according to the invention according to the first embodiment. The distances q2 to q6 of the individual figures are each greater than the distance q1 in the prior art. A longer spring deflection has therefore been achieved by the solution according to the invention. The reference numbers beginning with one refer to the last winding 1, the reference numbers beginning with two to the penultimate winding 2. The spring wires have a fiber reinforcement 15, 25 which is enclosed in matrix material 16, 26. The specific arrangement of the fiber reinforcement in the with reference to 1b until 1d Fiber layers described and possibly in a with respect to the 1b until 1d The core described here is neglected and not shown for better illustration of the deformation. The spring wires are each surrounded by a sheath 11, 21. The fiber reinforcement 25 transitions into the fiber reinforcement 15 in the transition area (not shown).

In 4a the end region of the last turn 1 has been brought into an elliptical cross-sectional shape, with the short axis of the ellipse, ie the minor axis, lying parallel to the longitudinal axis of the spring. The distance q2 to the penultimate turn 2 is therefore greater than if the circular cross-section had been retained.

In 4b the end region of the last coil 1 has been brought into a cross-sectional shape in which part of the material of the spring wire is shifted towards the longitudinal axis of the spring. The centroid of the cross-sectional area is thus shifted radially inwards. The distance q3 to the penultimate turn 2 is greater than if the circular cross-section had been retained, since a lower height of the spring wire cross-section has been obtained in the central area of the cross-section.

In 4c the end portion of the last coil 1 has been brought into a cross-sectional shape in which part of the material of the spring wire is displaced towards the longitudinal axis of the spring and part radially away from it. As a result, a groove-like indentation is formed in the spring wire, which increases the distance q4 from the penultimate turn 2.

In 4d the end portion of the last coil 1 has been brought into a cross-sectional shape in which part of the material of the spring wire is displaced towards the longitudinal axis of the spring and part radially away from it. As a result, a groove-like indentation is formed in the spring wire, which increases the distance q5 from the penultimate coil 2. Opposite of 4c the underside of the spring wire has been further flattened to provide a smoother contact surface for the spring wire in the spring seat.

In 4e the end portion of the last coil 1 has been brought into a cross-sectional shape in which part of the material of the spring wire is displaced radially away from the longitudinal axis of the spring. The centroid of the cross-sectional area is thus shifted radially outwards. The distance q6 to the penultimate turn 2 is greater than if the circular cross-section had been retained, since a lower height of the spring wire cross-section was obtained in the central region thereof.

The shapes of the end portions of the last turns 1 in the figures 4a until 4e were achieved by forming the spring ends during manufacture.

In 5a is a spring construction analogous to that shown in 4b shown. Here, however, the end of the spring is drawn in compared to the last but one coil (dashed line for orientation). The distance q7 is even greater than the distance q3 out 4b .

In 5b is a spring construction analogous to that shown in 4e shown. Here, however, the end of the spring is exposed opposite the penultimate coil (dashed line for orientation). The distance q8 is even larger than the distance q6 out 4e .

5c shows another spring construction. Here, too, the cross-sectional shape of the end of the spring is deformed into an ellipse, but the long axis of the ellipse, ie the main axis, is now arranged parallel to the longitudinal axis of the spring. The end of the spring is drawn in so far towards the center of the spring that the end of the spring dips into the interior of the spring under load. In order to avoid a collision with the coil above, there must be a minimum distance q9 between the outer edge of the last coil 1 and the inner edge of the penultimate coil 2. In addition, in 5c a spring wire according to the training 1b 1, ie the spring wire contains a core 13, 23 with fiber reinforcement, several fiber layers 12, 22 arranged around it and an outer sheath 11, 21, the reference numerals starting with one referring to the last turn 1 and the reference numerals starting with two referring to the penultimate turn 2 refer. As can be seen, in the last turn 1 the spring wire has not only been deformed externally, but the core 13 has also been deformed. However, this is not necessarily the case: there can also be deformations of the spring end where the core is not deformed.

6 shows schematically a spring construction according to the invention according to the second embodiment. Here, too, the specific arrangement of the fiber reinforcement in the with reference to 1b until 1d Fiber layers described and possibly in a with respect to the 1b until 1d described core is neglected to better illustrate the deformation and not shown. The spring wire has a circular cross-section. The area of this circular cross-section reduces from the penultimate turn 2 to the end region of the last turn 1. This can be seen from the fact that the diameter d2 of the spring wire of the penultimate turn 2 is reduced to a diameter d1 of the last turn 1. The distance q10 between the last coil and the penultimate coil of the spring wire is increased due to the reduced cross-section of the end area of the spring. The number of reinforcing fibers 15, 25 is identical in the penultimate turn 2 and the last turn 1. Due to the reduction in cross-section, the density of the fibers 15 is increased and the matrix material 16 has a smaller proportion of the cross-sectional area. The fiber volume content is thus increased in the end area of the spring.

7 shows schematically details of the last two turns of a spring construction according to the invention according to the third embodiment. Here, too, the specific arrangement of the fiber reinforcement in the with reference to 1b until 1d Fiber layers described and possibly in a with respect to the 1b until 1d described core is neglected to better illustrate the deformation and not shown. The third embodiment combines the adjustment of the cross-sectional shape according to the first embodiment with the reduction of the cross-sectional area while maintaining the fiber reinforcement material according to the second embodiment. Thus, in the end area of the spring, the cross-sectional shape is changed compared to the cross-sectional shape in the middle part, and the cross-sectional area is reduced compared to the cross-sectional area in the middle part. The distance q11 between the last coil and the penultimate coil of the spring wire is increased due to the changed shape and the reduced cross-section of the end region of the spring.

the 8a until 10e serve to illustrate the forming tools with which the spring ends are deformed and represent various embodiments of these forming tools, partly in connection with the spring wire to be deformed.

the 8a until 8e show a first example in which a spring 100 is deformed in the region of one of its spring ends by a first forming tool 210. The first mold consists of an upper part 211 and a lower part 212, the upper part 211 enclosing an upper part of the last coil of the spring 100 and the lower part 212 a lower part of the last coil of the spring 100. The top of the last coil faces outward, away from the other coils of the spring 100, while the bottom of the last coil faces the penultimate coil. The upper part 211 and the lower part 212 each have a recess 213, 214 into which the end area E and/or the transition area B of the spring 100 are inserted. The depressions 213, 214 thus form a cavity in the closed state of the mold 210, into which the end and/or transition region E or B of the spring wire can be inserted. The spring end is in the 8b and 8c already deformed and has a cross-sectional area at its end which is opposite to the cross-sectional area in the central part of the spring has a different shape. In 8b a lower part A11 of the cross-sectional area of the end portion of the spring is shown, while in 8c an upper part A12 of the cross-sectional area of the end portion of the spring can be seen. Due to its horizontal division into the upper part 211 and the lower part 212, the first forming tool 210 can be easily removed from the deformed end of the spring.

the 9a until 9e show a second example in which a spring 100 is deformed in the region of one of its spring ends by a second forming tool 220. The second mold consists of an outer part 221 and an inner part 222, the outer part 221 enclosing an outer part of the last coil of the spring 100 and the inner part 222 an inner part of the last coil of the spring 100. The outer portion of the last coil faces outward, away from the spring interior of the spring 100, while the inner portion of the last coil faces the spring interior and the spring longitudinal axis. The outer part 221 and the inner part 222 each consist of two parts 221a, 221b or 222a, 222b, whereby the part marked “a” accommodates the end area of the spring, while the part marked “b” attaches to the middle part of the spring adjacent. The vertical division is particularly advantageous for the inner part 222 for problem-free removal from the spring 100. The outer part 221 and the inner part 222 each have a recess 223, 224 into which the end area E and/or the transition area B of the spring 100 is inserted are. The end of the spring is already deformed and has a cross-sectional area at its end that has a different shape from the cross-sectional area in the central part of the spring. In 9b an inner part A13 of the cross-sectional area of the end portion of the spring is shown, while in 9c an outer part A14 of the cross-sectional area of the end portion of the spring can be seen. It can be seen that the cross-sectional area of the spring end is unevenly shaped and that the spring end is drawn inwards compared to the penultimate coil.

the 10a until 10e show a third example in which a spring 100 is deformed in the region of one of its spring ends by a third forming tool 230. The third mold is similar to the second mold in 9a until 9e , an outer part 231 and an inner part 232, the outer part 231 enclosing an outer part of the last turn of the spring 100 and the inner part 232 an inner part of the last turn of the spring 100. The outer part 231 and the inner part 232 each consist of two parts 231a, 231b or 232a, 232b, whereby the part marked “a” accommodates the end area of the spring, while the part marked “b” attaches to the middle part of the spring adjacent. The outer part 231 and the inner part 232 each have a depression 233, 234 into which the end area E and/or the transition area B of the spring 100 are inserted. Furthermore, in at least the outer part 231 or at least the inner part 232 there is a cavity 235, ie a hollow space, which is connected to the depression 233 or 234 via a channel with a small diameter. In 10d the cavity 235 for the outer part 231 is shown. In contrast to the first and second dies, the third die 230 serves to reduce the cross-sectional area of the end portion of the spring from the cross-sectional area of the middle portion of the spring. This is for example in the 10b and 10d can be seen in the different diameters of the spring 100 and the depression 233 at the beginning of the mold 230, ie at the border to the central part of the spring, and at the end of the spring. In 10b the inner part A13 of the cross-sectional area in the end area of the spring can be seen. The excess matrix material escaping as a result of the reduction in the cross-sectional area passes through the channel into the cavity 235 and is collected there.

exemplary embodiments

In a first embodiment ( 1a combined with 1b) the spring has a length h of 180mm. The diameter X is 75mm. The spring wire has a circular cross-section of area A0 with a diameter of 16mm in the middle of the spring. The spring wire consists of carbon fibers that are aligned unidirectionally along the spring wire axis F in the core. The core is surrounded by layers of carbon fibers. The layers of carbon fibers are surrounded by a tube so that the impregnated fibers are encased during the manufacturing process. In the central part of the spring, the distance q between the coils is 15mm. At a first spring end, the lower one in the figure, the cross-sectional area remains undeformed and at the other, second spring end, the upper one in the figure, the circular cross-sectional area of the spring wire becomes elliptical over the length of the transition region B, which is a quarter of a turn here Cross-sectional area of the end region E transferred to the area A1. This is done by pressing (pressing) the fibers into the desired shape during manufacture in a suitable mold that forms the transition and end areas. No fibers are broken or damaged. The transition area also means that there are no abrupt changes in the direction of the fibers, which could otherwise lead to stresses in the fiber reinforcement and potential breakage points. It is characteristic that the cross-sectional area A1 of the end region E is equal to the cross-sectional area A0 in the central part of the feather is. The end area of the spring wire has an elliptical cross-sectional area, in which the semi-minor axis of the ellipse runs parallel to the longitudinal axis L of the spring. However, due to the elliptical deformation of the end area of the spring wire at the second spring end, the distance qx- between the last coil and the penultimate coil on the second spring end is greater than the distance qy between the undeformed last coil and the penultimate coil on the first spring end. Here the distance qx is 12mm, while the distance qy is 7mm. In embodiments, the pitch qx may be less than, equal to, or greater than the pitch q of the coils in the central portion of the spring, but is always greater than the pitch qy.

In the second embodiment ( 2 ) are the data of the spring with the after 1 identical. However, here the transition area B extends over half a turn and the end area of the spring wire is only reached at the end. The cross-sectional area A1 reached at the end of the spring wire is again the same size as the cross-sectional area A0 in the middle part of the spring.

Reference List

1

last coil of the spring

10, 10', 10"

spring wire

11

Wrap the last turn around the spring wire

12

fiber layers

13

core

13'

cavity

14

tube core

15

Reinforcement fibers of the last turn of the spring wire

16

Matrix material of the last turn of the spring wire

2

penultimate turn of the spring before the end of the spring

21

Wrap the penultimate turn around the spring wire

25

Reinforcement fibers of the penultimate turn of the spring wire

26

Matrix material of the penultimate turn of the spring wire

100, 100'

coil spring

210, 220, 230

molding tool

211

upper part of the mold

212

lower part of the mold

221, 231

outer part of the mold

222, 232

Inner part of the mold

213, 214, 223, 224, 233, 234

Deepening in the mold

235

cavity in the mold

q

Distance between two coils in the central part of the spring

qx,qy,q1...q11

Distance between the last coil and the penultimate coil of the spring wire

A0

Cross-sectional area of the spring wire in the central part of the spring

A1

Cross-sectional area of the spring wire of the end portion of the spring wire

A11

lower part of A1

A12

upper part of A1

A13

inner part of A1

A14

outer part of A1

B

Transition area of the spring wire (dashed box)

i.e

Diameter of the spring wire in the middle part of the spring

f

spring wire axle

E

End area of the spring wire (dashed box)

H

length of the spring

L

spring longitudinal axis

X

diameter of the spring

Claims (18)

Helical spring (100, 100'), which has several turns of a helically wound spring wire (10, 10', 10'') made of fiber-reinforced plastic material, having a fiber reinforcement and a matrix material, the fiber reinforcement being distributed over the entire length of the spring wire (10 , 10', 10") as a continuous fiber material with a constant number of fibers, the helical spring (100, 100') having two spring ends and at least one of the spring ends in a last coil (1) of the helical spring (100, 100') a transition area (B ) and then has an end region (E) in the direction of the end of the spring wire (10, 10', 10"), characterized in that a cross-sectional area of the spring wire (10, 10', 10") in the transition region (B) from a The cross-sectional area (A0) of the spring wire (10, 10', 10") in a central part of the spring (100, 100') transitions into a smaller cross-sectional area (A1) of the end area (E), in that the fiber volume content in the spring wire (10, 10' , 10") in v is continuously increased during the transition region (B). coil spring (100, 100'). claim 1 , characterized in that the cross-sectional shape of the spring wire (10, 10', 10") in the transition area (B) changes from a cross-sectional shape of the spring wire (10, 10', 10") in a central part of the coil spring (100, 100') to a Cross-sectional shape of the end area (E) transitions by continuously changing the distribution of the fiber reinforcement and the matrix material in the spring wire (10, 10', 10") in the course of the transition area (B) in such a way that a coil lying above the end of the spring has a larger compression travel to the last turn (1) than would be the case with an unchanged cross-sectional shape. coil spring (100, 100'). claim 2 , characterized in that the cross-sectional shape in the end region (E) of the spring wire (10, 10', 10") has a smaller diameter of the spring wire (10, 10', 10") in the longitudinal direction of the helical spring (100, 100') or the Fiber reinforcement and the matrix material are distributed in such a way that the spring wire (10, 10', 10") has a groove-like depression that increases the distance to the penultimate turn (2). coil spring (100, 100'). claim 2 , characterized in that in the end region (E) a geometric center of gravity of the cross-sectional shape of the spring wire (10, 10', 10'') is shifted radially inwards or outwards, viewed from the longitudinal axis (L) of the spring (100, 100'). is. coil spring (100, 100'). claim 4 , characterized in that the shifting of the geometric center of gravity is realized by shifting a curvature of the originally round cross-section of the spring wire (10, 10', 10") radially inwards or outwards. Coil spring (100, 100') according to one of the preceding claims, characterized in that the spring wire (10, 10', 10") in the end area (E) or in the end area (E) and in the transition area (B) in the direction of the end of the Longitudinal direction (L) of the spring is flattened. coil spring (100, 100'). claim 1 , characterized in that the cross-sectional shape is geometrically similar over the entire length of the spring wire (10, 10', 10"). Helical spring (100, 100') according to one of the preceding claims, characterized in that the spring wire (10, 10', 10") has a sheath (11, 21) over its entire length or a portion of its length. coil spring (100, 100'). claim 8 , characterized in that the casing (11, 21) consists of an elastomer, a thermoplastic elastomer or a thermoplastic material. Helical spring (100, 100') according to one of the preceding claims, characterized in that the fiber reinforcement consists of unidirectional endless fibers which extend without interruption between the two ends of the spring wire (10, 10', 10"). Coil spring (100, 100') according to one of Claims 1 until 9 , characterized in that the fiber reinforcement consists of unidirectional continuous fibers which are surrounded by one or more layers of wound or braided fibers and the entire fiber reinforcement extends without interruption between the two ends of the spring wire (10, 10', 10"). Coil spring (100, 100') according to one of the preceding claims, characterized in that a first spring end of the coil spring (100'). claim 1 is formed and a second spring end of the coil spring (100 ') additionally has the feature of claim 2 comprises, wherein the first spring end and the second spring end differ. A method of manufacturing a helical spring (100, 100') according to any one of Claims 1 until 12 , having at least the following steps: - providing the spring wire (10, 10', 10"), - winding the spring wire (10, 10', 10") into the desired spring shape, - further processing of the coiled spring wire (10, 10', 10") in the unconsolidated or partially consolidated state, with the spring wire (10, 10', 10") being brought into a different cross-sectional area (A1) and possibly also a different cross-sectional shape than the spring wire in the unconsolidated or re-softened state at the end pieces (10, 10', 10") between the end pieces, - complete consolidation of the fiber-reinforced plastic material of the spring wire (10, 10', 10") after further processing. Method for producing a helical spring (100, 100') according to one of Claims 1 until 12 , having at least the following steps: - providing the spring wire (10, 10', 10"), - winding the spring wire (10, 10', 10") into the desired spring shape, - further processing of the coiled spring wire (10, 10', 10"), whereby the spring wire (10, 10', 10") is consolidated in the central part of the helical spring (100, 100') and the end pieces remain in the unconsolidated or partially consolidated state, - forming the end pieces into a different cross-sectional area (A1) and possibly .also other cross-sectional shape, - complete consolidation of the formed end pieces. A method of manufacturing a helical spring (100, 100') according to any one of Claims 1 until 12 , wherein - the fiber reinforcement material is introduced into a tubular sleeve (11, 21), - the matrix material is then introduced into this tubular sleeve (11, 21), - the matrix material is then crosslinked to above a gel point of the matrix material, - the tubular Cover (11, 21) is removed or remains on the spring wire (10, 10', 10"), - the spring wire (10, 10', 10") is heated and wound onto a mandrel, characterized in that - the Cross-sectional area (A1) and possibly also the cross-sectional shape of the transition (B) and the end area (E) at one or both ends of the spring wire (10, 10', 10") using a special forming tool (210, 220, 230) as above is changed so that a greater deflection occurs, - the matrix material is hardened by further heating. Device for producing a helical spring (100, 100') according to one of Claims 1 until 12 , containing at least one molding tool (210, 220, 230), characterized in that the molding tool (210, 220, 230) has a cavity in its interior, in which an end region (E) to be shaped or an end region (E) to be shaped and a transition area (B) to be deformed of the spring wire (10, 10', 10") that is unconsolidated at least in these areas can be inserted, the cavity having the desired cross-sectional area (A1) and possibly also the desired cross-sectional shape of the end area (E) or of the end area (E) and the transition area (B). device after Claim 16 , characterized in that the mold (210, 220, 230) has a temperature control device for heating or cooling the mold (210, 220, 230). device after Claim 16 or 17 , characterized in that the mold (230) has a cavity (235) for receiving the excess matrix material.

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