Spring wire for producing a coil spring, coil spring and method for producing a coil spring

Abstract

The invention relates to a spring wire (4) for producing helical springs (2), comprising a spring wire core with a martensitic structure and a jacket surface that outwardly delimits the spring wire core, a carrier layer formed on the entire jacket surface of the spring wire core with a jacket surface that outwardly delimits the carrier layer, wherein a spring wire corrosion protection layer (6) is applied to the entire jacket surface of the carrier layer. The invention further relates to a helical spring (2) and a method for producing a helical spring (2).

Description

[0001] The invention relates to a spring wire for producing coil springs, comprising a spring wire core with a martensitic structure and a jacket surface that outwardly defines the spring wire core, a carrier layer formed over the entire jacket surface of the spring wire core, the carrier layer having a jacket surface that outwardly defines the carrier layer. Furthermore, the invention relates to a coil spring and a method for its production.

[0002] A large number of embodiments of such spring wires, coil springs made of a spring wire and the production of coil springs are already known from the prior art.

[0003] The object of the present invention is to improve a spring wire for producing a coil spring, a coil spring and a method for producing a coil spring.

[0004] To achieve this object, the invention, in conjunction with the preamble of claim 1, is characterized in that a spring wire corrosion protection layer is applied to the entire surface of the carrier layer. Furthermore, this object is achieved by a coil spring according to claim 7 and a method according to claim 13.

[0005] The particular advantage of the invention is that a spring wire for producing a coil spring, a coil spring, and a method for producing a coil spring are improved. Due to the inventive design of the spring wire, the coil spring, and the method for producing the coil spring, a coil spring can be produced cost-effectively. This applies in particular to use of the coil spring according to the invention in the automotive sector, and here in particular to use of the coil spring according to the invention as a compression spring in a drive for opening or closing a tailgate or the like, wherein corrosion protection of the coil spring, namely of the spring wire used for this purpose, is essential for correct long-term function of the coil spring.In contrast to conventional methods, the coating of the spring wire core according to the invention prior to the production of the helical spring according to the invention from the spring wire formed therefrom is significantly easier in terms of manufacturing technology. The inventive design of the helical spring produced from the spring wire according to the invention also has the further advantage that, due to the use of an end cap as the force-transmitting end face of the helical spring, post-processing of the spring wire according to the invention after production of the helical spring is not absolutely necessary.For example, the spring wire of the coil spring does not need to be ground at least at one end of the coil spring in order to form a flat support surface running essentially perpendicular to a longitudinal axis of the coil spring for force-transmitting support of the coil spring against an abutment at this end of the coil spring. Accordingly, the carrier layer and the applied coating of the spring wire according to the invention, for example the zinc-aluminum layer, remain intact at this end of the coil spring according to the invention, so that subsequent application of a corrosion protection layer to a grinding surface of the spring wire created by grinding in order to ensure corrosion protection of the spring wire of the coil spring according to the invention can be omitted.The spring wire according to the invention therefore essentially has only a single and uniform spring wire corrosion protection layer on the entire sheath surface of the carrier layer of the spring wire core.

[0006] In principle, the spring wire can be freely selected within wide, suitable limits in terms of its type, material, dimensions, and geometry, particularly the geometry of its cross-section. For example, the spring wire can be a steel wire. However, this is not necessarily the case; it depends on the specific application. Furthermore, the application of the spring wire according to the invention is not limited to the use of the spring wire according to the invention on springs, particularly coil springs. The carrier layer and the spring wire corrosion protection layer of the spring wire according to the invention can be produced in a manner known per se to those skilled in the art.

[0007] A particularly advantageous development of the spring wire according to the invention provides that the spring wire core is designed as an alloyed and tempered spring wire core, preferably as a SiCr-alloyed and tempered spring wire core, particularly preferably as a SiCrV-alloyed and tempered spring wire core. In this way, the spring wire core of the spring wire according to the invention is particularly well suited for most applications, in particular in the automotive sector. This applies particularly to the preferred and in particular to the particularly preferred embodiment of this development. The spring wire core has a martensitic structure. Accordingly, this results in a pretreatment of the spring wire core that is known per se to those skilled in the art. SiCr-alloyed stands for an alloy with silicon and chromium; SiCrV-alloyed stands for an alloy with silicon, chromium, and vanadium.A SiCr alloy, particularly a SiCrV alloy, for the spring wire core ensures its very high strength. The SiCr-alloyed and SiCrV-alloyed spring wire core can contain other alloy components in addition to the aforementioned alloy components. Of course, other materials for the spring wire core, for example, other alloys, are also conceivable. Accordingly, the expert can select the appropriate material for the spring wire core depending on the requirements of the individual case.

[0008] The specialist knows about the pre-treatment of the spring wire core that needs to be carried out.

[0009] Analogous to the spring wire core, the spring wire corrosion protection layer can also be freely selected in terms of type, material and dimensions within wide, suitable limits.

[0010] Advantageously, the spring wire corrosion protection layer is formed as a zinc-aluminum layer, or ZnAl layer for short. Preferably, the zinc-aluminum layer has an aluminum content of up to 15%, particularly preferably from 3% to 7%, for example 5%, or Zn95Al5 layer for short. This results in a particularly suitable selection of the material for the spring wire corrosion protection layer for the production of the coil spring according to the invention and for most applications. This applies in particular to applications in the automotive sector. See the above explanations.

[0011] A particularly advantageous development of the spring wire according to the invention provides that the spring wire has a spring wire cross-section that deviates from a circular cross-section over substantially its entire length before the coil spring is manufactured, and preferably that the spring wire does not have opposing and parallel boundary surfaces on the casing side. In this way, it is possible, for example, to specifically design the geometry of the cross-section of the spring wire according to the invention of the coil spring according to the invention even before the actual manufacture of the coil spring according to the invention from this spring wire.For example, the geometry of the cross section of the spring wire according to the invention could be designed before the production of the helical spring in such a way that after the production of the helical spring according to the invention from this spring wire a cross section of the spring wire desired for the helical spring results, for example a substantially circular spring wire cross section of the helical spring.

[0012] It is also conceivable, for example, that the spring wire has a spring wire cross-section over substantially its entire length such that the spring core of a helical spring made from this spring wire has two opposing and parallel casing-side boundary surfaces. Preferably, the mutually parallel casing-side boundary surfaces of the helical spring made from the spring wire are oriented perpendicularly or substantially perpendicularly to a longitudinal axis of the helical spring.

[0013] When assessing whether a casing-side boundary surface is oriented perpendicular to the longitudinal axis of the coil spring and / or whether two opposing casing-side boundary surfaces are parallel to each other, the typical accuracy of the relevant production steps in the manufacture of such a coil spring, and in particular the accuracy in stamping the spring wire and winding the coil spring, must be taken into account. Typically, a manufacturing tolerance of ± 2 to 3° must be taken into account for the vertical or parallel orientation of the casing-side boundary surfaces.

[0014] For example, the spring wire may have a circular cross-section before the coil spring is manufactured. The coil spring produced from the spring wire then has a cross-section that deviates from the circular geometry, for example, an elliptical one.

[0015] An advantageous development of the helical spring according to the invention provides that the end cap is connected to the spring wire at the associated front end of the helical spring by means of frictional engagement, preferably that the end cap and the spring wire are connected to the spring wire by means of a press fit. This provides a very simple mechanical connection between the end cap on the one side and the spring wire of the front end of the helical spring according to the invention assigned to this end cap on the other side. This applies in particular to the preferred embodiment of this development. Accordingly, additional components or aids for connecting this end cap to the spring wire in a force-transmitting manner are omitted.

[0016] An alternative or additional advantageous development of the helical spring according to the invention provides that the end cap is connected to the spring wire at the associated front end of the helical spring by means of a positive fit in a force-transmitting manner, preferably that the end cap engages in a space between adjacent sections of the spring wire by means of an external thread of the end cap corresponding to the pitch of the spring wire. In this way, a very secure and therefore robust mechanical connection is possible between the end cap and the spring wire of the corresponding front end of the helical spring according to the invention. This applies in particular to the preferred embodiment of this development in which the end cap is not pushed onto the spring wire, but screwed on. For this purpose, the external thread of the end cap is designed to be complementary to the spring wire wound through the coil spring.

[0017] Furthermore, an alternative or additional development of the helical spring according to the invention to the last two mentioned developments provides that the end cap is connected to the spring wire at the associated front end of the helical spring by means of a frictional connection in a force-transmitting manner, preferably that the end cap and the spring wire are bonded to one another in a force-transmitting manner by means of an adhesive layer arranged between the end cap and the spring wire. This provides a tolerance-compensating connection technique between the end cap and the spring wire of the corresponding front end of the helical spring according to the invention, so that the production of both the spring wire and the helical spring blank produced therefrom, as well as the associated end cap, is significantly simplified. This applies in particular to the preferred embodiment of this development.Furthermore, the adhesive layer provides an additional corrosion protection layer for the spring wire in the area of the end cap.

[0018] According to a further development of the invention, measures are provided to reduce the tendency of the coil spring according to the invention to vibrate. For example, the diameter of the spring wire can be varied to reduce the tendency of the coil spring to vibrate. For example, flocking the outer surface of the spring wire or the coil spring with plastic fibers can be provided. To apply the flocking, it is preferably provided to statically charge the coil spring and apply an adhesive, followed by applying the plastic fibers.

[0019] Further advantages, features, and details of the invention can be derived from the further subclaims and the following description. Features mentioned therein may be essential to the invention individually or in any combination. Features and details of the spring wire and the coil spring described according to the invention naturally also apply in connection with the method according to the invention, and vice versa. Thus, reference can always be made to the disclosure relating to the individual aspects of the invention. The drawings serve merely as examples to clarify the invention and are not limiting in nature.

[0020] They show: Fig. 1a shows a first embodiment of the helical spring according to the invention made of the spring wire according to the invention in a perspective view of the helical spring, Fig. 1b the first embodiment in a partial longitudinal section in the area of an end cap, Fig. 1c the end cap of the first embodiment in two perspective individual views, Fig. 2a a second embodiment of the helical spring according to the invention made of the spring wire according to the invention in a perspective view of the helical spring, Fig. 2b the second embodiment in a partial longitudinal section in the area of an end cap, Fig. 2c the end cap of the second embodiment in two perspective individual views, Fig. 3a a third embodiment of the coil spring according to the invention made of the spring wire according to the invention in a perspective view of the coil spring, Fig. 3b the third embodiment in a partial longitudinal section in the area of an end cap, Fig. 3c the end cap of the third embodiment in two perspective individual views, Fig. 4a a fourth embodiment of the coil spring according to the invention made of the spring wire according to the invention in a perspective view of the coil spring, Fig. 4b the fourth embodiment in a partial longitudinal section in the area of an end cap, Fig. 4c the end cap of the fourth embodiment in a perspective individual view, with the adhesive layer and Fig. 4d the end cap of the fourth embodiment in a perspective individual view, without the adhesive layer.

[0021] In the Fig. 1a to 1c show a first embodiment of the helical spring according to the invention purely by way of example.

[0022] The coil spring 2 is designed for use in the automotive sector, namely as a compression spring in a drive for opening and closing a tailgate of a motor vehicle. The motor vehicle with the tailgate and drive is not explicitly shown.

[0023] The coil spring 2 is made of a spring wire 4, wherein the spring wire 4 comprises a spring wire core (not explicitly shown) with a martensitic structure and a jacket surface that outwardly delimits the spring wire core, as well as a carrier layer formed on the entire jacket surface of the spring wire core and also not explicitly shown, with a jacket surface that outwardly delimits the carrier layer. According to the invention, a spring wire corrosion protection layer 6 is applied to the entire jacket surface of the carrier layer.

[0024] In the present embodiment, the spring wire core is designed as an alloyed and tempered spring wire core, namely as a SiCrV-alloyed and tempered spring wire core.

[0025] The spring wire corrosion protection layer 6 applied to the outer surface of the carrier layer is formed as a zinc-aluminum layer, with the zinc-aluminum layer here having an aluminum content of approximately 5%. In principle, the aluminum content can be up to 15%, preferably between 3% and 7%.

[0026] Furthermore, in the present embodiment, the spring wire 4 has a spring wire cross-section that deviates from a circular cross-section over substantially its entire length, namely such that the spring wire 4 has no opposing and parallel boundary surfaces on the casing side. This spring wire cross-section of the spring wire 4 that deviates from a circular cross-section is evident from the Fig. 1 a to 1c. The spring wire cross-section of the spring wire 4 is shown in the aforementioned figures in a simplified manner as a circular cross-section.

[0027] For the purpose of producing the helical spring 2, the spring wire 4 of the helical spring 2 is connected at at least one end 8 of the helical spring 2, namely at both end 8 of the helical spring 2, to a force-transmitting end cap 10 of the helical spring 2, wherein this end cap 10 and the spring wire 4 are designed and arranged in such a way that, in a position of use of the helical spring 2, only a free surface of the end cap 10 forms a support surface of the helical spring 2 for force-transmitting support of the helical spring 2 at this end 8 of the helical spring 2 against an abutment (not shown), wherein the support surface extends substantially perpendicular to a longitudinal axis of the helical spring 2. The longitudinal axis of the helical spring 2 runs in the image plane of the Fig. 1b from top to bottom. In the image plane of the Fig. In Figure 1b, the longitudinal axis is symbolized by a dashed line 12. However, it is also conceivable in principle that only one of the two front ends of the helical spring according to the invention is formed by an end cap connected to the spring wire according to the invention.

[0028] In the present first embodiment, the respective end cap 10 is connected to the associated front end 8 of the coil spring 2 by means of frictional engagement with the spring wire 4 in a force-transmitting manner, wherein the end cap 10 and the spring wire 4 are connected here by means of a press fit. The two end caps 10 are designed analogously to one another, so that the detailed representations of one of the two end caps 10 according to the Fig. 1b and Fig. 1c applies mutatis mutandis to the other end cap 10, which is not shown in detail. The respective end cap 10 can be made of any material suitable for the specific application. For example, plastic or metal are examples.

[0029] In the Fig. Figures 2a to 4d show three further embodiments of the helical spring according to the invention purely by way of example. Identical or equivalent components are provided with the same reference numerals as in the first embodiment. Furthermore, only the differences, particularly from the first embodiment, will be explained below. Otherwise, reference is made to the above explanations regarding the first embodiment.

[0030] In the Fig. 2a to 2c show a second embodiment of the helical spring according to the invention. In contrast to the first embodiment, a total of three compression ribs 14 are arranged circumferentially on the respective end cap 10 of this second embodiment, which are in force-transmitting contact with the spring wire 4. See Fig. 2b and Fig. 2c in summary. Otherwise, the second embodiment corresponds to the first embodiment.

[0031] In the Fig. 3a to 3c show a third embodiment of the helical spring according to the invention. In contrast to the first and second embodiments, the respective end cap 10 is connected to the associated front end 8 of the helical spring 2 by means of a positive connection with the spring wire 4 in a force-transmitting manner, wherein the respective end cap 10 engages in a force-transmitting manner in a space between adjacent sections of the spring wire 4 by means of an external thread 16 of this end cap 10 corresponding to the pitch of the spring wire 4. See Fig. 3a to 3c in a summary.

[0032] Furthermore, in the Fig. 4a to 4d illustrate a fourth embodiment of the helical spring according to the invention. In contrast to the three aforementioned embodiments, the respective end cap 10 is connected to the spring wire 4 at the associated front end 8 of the helical spring 2 by means of a force-transmitting connection. The respective end cap 10 and the spring wire 4 are bonded to one another in a force-transmitting manner by means of an adhesive layer 18 arranged between this end cap 10 and the spring wire 4.

[0033] In the following, the production of the spring wire according to the invention and the method according to the invention for producing the helical spring according to the invention according to the present embodiments are described with reference to Fig. 1a to 4d are explained in more detail.

[0034] The process for manufacturing the coil spring 2 comprises the following process steps in the specified order: First, the spring wire core is cleaned, for example, by pickling. Then, zinc is applied to the jacket surface of the spring wire core, for example, using a liquid zinc bath (also not shown). This creates a diffusion layer of zinc and iron with an intermetallic phase on the jacket surface of the spring wire core. The diffusion layer with the intermetallic phase is shown in the Fig. 1a to 4d are also not shown. The spring wire corrosion protection layer 6, formed as a zinc-aluminum layer, is then applied to the outer surface of the carrier layer, for example, using a liquid zinc-aluminum bath (not shown). The spring wire 4 is now present with the overall coating of the carrier layer and the zinc-aluminum layer 6.

[0035] In the present exemplary embodiment, the spring wire 4 is shaped at least once during production of the spring wire 4 in such a way that, before winding the spring wire 4 to produce a helical spring blank of the helical spring 2, the spring wire 4 has a spring wire cross-section that deviates from a circular cross-section over substantially its entire length, namely in such a way that, before the aforementioned winding of the spring wire 4, the spring wire 4 has no opposing and parallel boundary surfaces on the casing side. The aforementioned shaping can, for example, be carried out in such a way that the spring wire 4 has a spring wire cross-section that, during the subsequent production of the helical spring 2 from the spring wire 4, forms a substantially circular cross-section of the spring wire 4 and thus of the helical spring 2 over the entire length of the spring wire 4.The aforementioned shaping can be carried out in any suitable manner known to those skilled in the art. Rolling and stamping are purely exemplary. However, such deformation of the spring wire is not mandatory. Accordingly, embodiments of the spring wire according to the invention are also conceivable in which the spring wire is used undeformed, i.e., with a circular spring wire cross-section, to produce a coil spring.

[0036] To produce the coil spring 2 from the spring wire 4 now present, the spring wire 4 produced in the aforementioned manner is wound in a manner known per se to those skilled in the art. The spring wire 4 is then wound and severed using a winding machine (also not shown) to produce the coil spring blank.Now the spring wire 4 is connected to one of the two end caps 10 at at least one end face 8 of the coil spring blank, namely both end faces 8 of the coil spring blank, in a manner known per se to those skilled in the art, namely in such a way that in the position of use of the coil spring 2, i.e. in the aforementioned installation position of the coil spring 2 in the motor vehicle, only the free surface of the respective end cap 10 forms a support surface of the coil spring 2 for the force-transmitting support of the coil spring 2 at this end face 10 of the coil spring 2 against the abutment of the motor vehicle (not shown), wherein the support surface extends substantially perpendicular to the longitudinal axis 12 of the coil spring 2.Depending on the selected embodiment, the respective end cap 10 is connected to the spring wire 4 at the corresponding front end 8 of the helical spring 2 by means of frictional engagement and / or positive engagement and / or force engagement, namely in such a way that the respective end cap 10 is connected to the spring wire 4 by means of a press fit and / or that the respective end cap 10 is brought into force-transmitting engagement with a gap between adjacent sections of the spring wire 4 by means of an external thread 16 of this end cap 10 corresponding to the pitch of the spring wire 4 and / or that the respective end cap 10 and the spring wire 4 are glued to one another in a force-transmitting manner by means of an adhesive layer 18 arranged between this end cap 10 and the spring wire 4.

[0037] After the coil spring 2 is manufactured, it is preferably subjected to a heat treatment. For example, the coil spring 2 is stress-relieved and / or tempered, and / or the coating is baked on, and / or the coil spring 2 is heat-set, i.e., heated and then brought to a block in the heated state.

[0038] Due to the inventive design of the spring wire 4, the coil spring 2, and the method for producing the coil spring 2, a coil spring 2 can be produced cost-effectively. This applies in particular to the use of the coil spring 2 in the automotive sector, and here in particular to the use of the coil spring 2 as a compression spring for the drive for opening and closing the tailgate of the motor vehicle, wherein the corrosion protection of the coil spring 2, namely of the spring wire 4 used for this purpose, is essential for the correct functioning of the coil spring 2 in the long term. In contrast to conventional methods, the coating of the spring wire core according to the invention prior to the production of the coil spring 2 from the spring wire 4 formed therefrom is significantly easier in terms of manufacturing technology.The inventive design of the helical spring 2 produced from the spring wire 4 has the further advantage that, due to the use of end caps 10 as force-transmitting end terminations of the helical spring 2, post-processing of the inventive spring wire 4 after production of the helical spring 2 is not absolutely necessary. Accordingly, the carrier layer and the applied coating of the inventive spring wire, for example the zinc-aluminum layer, remain intact at this end of the inventive helical spring, so that subsequent application of a corrosion protection layer to a grinding surface of the spring wire created by grinding to ensure corrosion protection of the spring wire of the helical spring 2 can be omitted.The spring wire 4 thus essentially has only a single, uniform spring wire corrosion protection layer, namely the zinc flake coating 6, on the entire surface of the carrier layer of the spring wire core. Of course, other spring wire corrosion protection layers suitable for the specific application are also conceivable. The method according to the invention for producing the helical spring according to the invention can be adapted accordingly to other requirements.

[0039] The invention is not limited to the present exemplary embodiments. For example, the invention can also be advantageously used for other applications, not only in the automotive sector. The spring wire can, as already explained in the introduction to the description, be designed, for example, as a spring steel wire. The aforementioned terms "winding" and "winding machine" are to be interpreted generally here and include all types of winding and coiling as well as all types of winding machines or winding machines used for this purpose. Furthermore, the method according to the invention can comprise further method steps in addition to the method steps explicitly mentioned above. This applies both to the production of the spring wire core and to the production of the spring wire according to the invention and the helical spring according to the invention. Furthermore, it should be added that the coating can be applied in any suitable manner familiar to a person skilled in the art.Purely examples include immersion, electrochemical coating methods such as cathodic dipping, spraying, printing, rolling, and brushing. To increase the durability of the coating, subsequent heat treatment, such as baking, curing, or drying, can be performed. As an alternative to the coating methods already mentioned, such as cathodic dipping and zinc flake coatings, other coating types, such as the application of a single- or multi-component paint, are also possible.

[0040] However, not only springs, in particular not only coil springs, can be produced from the spring wire according to the invention. The production of other bent wire parts is also advantageously possible from the spring wire according to the invention.

Claims

[1] Spring wire (4) for producing helical springs (2), comprising a spring wire core with a martensitic structure and with a jacket surface delimiting the spring wire core to the outside, a carrier layer formed on the entire jacket surface of the spring wire core with a jacket surface delimiting the carrier layer to the outside, characterized by that a spring wire corrosion protection layer (6) is applied to the entire surface of the carrier layer. [2] Spring wire (4) according to claim 1, characterized by that the spring wire core is designed as an alloyed and tempered spring wire core, preferably as a SiCr-alloyed and tempered spring wire core, particularly preferably as a SiCrV-alloyed and tempered spring wire core (6). [3] Spring wire (4) according to claim 1 or 2, characterized bythat the spring wire corrosion protection layer (6) is formed as a zinc-aluminum layer, preferably that the zinc-aluminum layer has an aluminum content of up to 15%, particularly preferably from 3% to 7%. [4] Spring wire according to one of claims 1 to 3, characterized by that the spring wire has a circular spring wire cross-section over substantially its entire length, preferably that the spring wire of a helical spring made from this spring wire does not have two opposing and mutually parallel boundary surfaces on the casing side. [5] Spring wire (4) according to one of claims 1 to 3, characterized by that the spring wire (4) has a spring wire cross-section deviating from a circular cross-section over substantially its entire length, preferably that the spring wire (4) has no opposing and mutually parallel boundary surfaces on the casing side. [6] Spring wire according to claim 5, characterized by that the spring wire has a spring wire cross-section over substantially its entire length such that the spring wire of a helical spring produced from this spring wire has two opposing and mutually parallel boundary surfaces on the casing side, wherein preferably the two opposing and mutually parallel boundary surfaces of the spring wire are oriented perpendicular to a longitudinal axis of the helical spring produced from this spring wire. [7] Coil spring (2) made of a spring wire (4), characterized bythat the spring wire (4) is designed according to one of claims 1 to 6 and that the spring wire (4) is connected at least at one end face (8) of the helical spring (2) to a force-transmitting end cap (10) of the helical spring (2), wherein this end cap (10) and the spring wire (4) are designed and arranged in such a way that, in a position of use of the helical spring (2), only a free surface of the end cap (10) forms a support surface of the helical spring (2) for the force-transmitting support of the helical spring (2) at this end face (8) of the helical spring (2) against an abutment, wherein the support surface extends substantially perpendicular to a longitudinal axis (12) of the helical spring (2). [8] Coil spring (2) according to claim 7, characterized bythat the end cap (10) is connected to the associated front end (8) of the helical spring (2) by means of frictional engagement with the spring wire (4) in a force-transmitting manner, preferably that the end cap (10) and the spring wire (4) are connected to the force-transmitting manner by means of a press fit. [9] Coil spring (2) according to claim 7 or 8, characterized by that the end cap (10) is connected to the associated front end (8) of the helical spring (2) by means of a positive connection with the spring wire (4) in a force-transmitting manner, preferably that the end cap (10) engages in a force-transmitting manner in a space between adjacent sections of the spring wire (4) by means of an external thread (16) of the end cap (10) corresponding to the pitch of the spring wire (4). [10] Coil spring (2) according to one of claims 7 to 9, characterized bythat the end cap (10) is connected to the associated front end (8) of the helical spring (2) by means of frictional engagement with the spring wire (4) in a force-transmitting manner, preferably that the end cap (10) and the spring wire (4) are glued to one another in a force-transmitting manner by means of an adhesive layer (18) arranged between the end cap (10) and the spring wire (4). [11] Coil spring (2) according to one of claims 7 to 10, characterized by that the spring wire (4) of a helical spring (2) made from the spring wire (4) does not have two opposing and mutually parallel boundary surfaces on the casing side. [12] Coil spring according to one of claims 7 to 10, characterized bythat the spring wire in the manufactured helical spring has two opposing and mutually parallel casing-side boundary surfaces, wherein the mutually parallel casing-side boundary surfaces are preferably oriented perpendicular to a longitudinal axis of the helical spring. [13] A method for producing a coil spring (2) according to any one of claims 7 to 12, wherein the method comprises the following method steps in the specified order: - Cleaning the spring wire core; - Creating the carrier layer on the entire sheath surface of the spring wire core; - applying the spring wire corrosion protection layer (6) to the entire surface of the carrier layer; - winding up the spring wire (4) produced in the above-mentioned manner; - winding the spring wire (4) by means of an automatic winding machine and cutting the spring wire (4) to produce a coil spring blank; - connecting the spring wire (4) at at least one end face (8) of the coil spring blank to an end cap (10) such that, in a position of use of the coil spring (2), only a free surface of the end cap (10) forms a support surface of the coil spring (2) for force-transmitting support of the coil spring (2) at this end face (8) of the coil spring (2) against an abutment, wherein the support surface extends substantially perpendicular to a longitudinal axis (12) of the coil spring (2). [14] Method according to claim 13, characterized bythat the end cap (10) is connected to the spring wire (4) at the aforementioned front end (8) of the helical spring (2) by means of frictional engagement and / or positive engagement and / or force engagement, preferably that the end cap (10) is connected to the spring wire (4) by means of a press fit and / or that the end cap (10) is brought into force-transmitting engagement with a gap between adjacent sections of the spring wire (4) by means of an external thread (16) of the end cap (10) corresponding to the pitch of the spring wire (4) and / or that the end cap (10) and the spring wire (4) are glued to one another in a force-transmitting manner by means of an adhesive layer (18) arranged between the end cap (10) and the spring wire (4). [15] Method according to claim 13 or 14, characterized bythat the spring wire (4) is shaped at least once during the production of the spring wire (4) according to one of claims 1 to 6 in such a way that the spring wire (4) has a spring wire cross-section deviating from a circular cross-section over substantially its entire length before the spring wire (4) is wound to produce the helical spring blank, preferably that the spring wire (4) has no opposing and mutually parallel boundary surfaces on the casing side before the aforementioned winding of the spring wire (4). [16] Method according to one of claims 13 to 15, characterized by that the coil spring blank (1) and / or the coil spring (2) are subjected to a heat treatment and are preferably stress-relieved and / or tempered and / or hot-set and / or that the coating is baked.

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