Spring device for a motor vehicle wheel suspension

Abstract

Spring device (1) for a motor vehicle wheel suspension, comprising: a coil spring (2) and a spring support (5) for supporting the coil spring (2) against a spring plate, wherein the spring support (5) is made of a casting compound (6) into which an end section (4) of the helical spring (2) is cast, characterized in that the casting compound (6) is a polyurethane based on diphenylmethane diisocyanate.

Description

[0001] The invention relates to a spring device for a motor vehicle wheel suspension, comprising a coil spring and a spring support for supporting the coil spring against a spring plate according to the preamble of patent claim 1, and further to a method for producing the same.

[0002] Known spring devices for motor vehicle wheel suspensions essentially comprise a coil spring and an upper and lower spring support. The lower spring support often contains an insert that serves to attach the spring device to a wheel-guiding component, such as a wishbone or wheel carrier. Furthermore, such a spring device can also include a stop buffer.

[0003] The coil spring is typically made of wound steel, while the spring pads are usually made of a natural rubber-based elastomer. Any inserts are usually made of plastic, with or without a corrosion-compensating metal disc.

[0004] The coil spring and spring seat are usually joined by clipping or clamping. In exceptional cases, the coil spring and spring seats are also glued together.

[0005] Corrosion on the coil spring can lead to component failure. In practice, spring fractures often occur in rear axle components in the lower area of ​​the spring coil, as dirt and corrosive media can accumulate there, causing tribo-oxidative attack on the component. The mechanical stress during operation ultimately leads to fatigue failure.

[0006] As corrosion protection, the coil spring is typically coated with a protective coating. However, stone chips and friction can permanently damage this paint protection system. Increasing the paint layer thickness only provides temporary protection and incurs additional costs.

[0007] In some cases, plastic deflectors are mounted around the wheel-guiding component, on which the spring assembly rests, to protect the coil spring from stone impact. However, this does not provide permanent protection against corrosive media.

[0008] Protective measures such as a plastic or rubber cover pulled or glued onto the coil spring have also proven unsatisfactory in practice, as there is a risk of infiltration by corrosive media.

[0009] In this context, DE 10 2009 052 030 A1 proposes a special spring support between the coil spring and a spring plate. DE 10 2009 052 030 A1 assumes that when the coil spring compresses and rebounds during driving, solid particles damage the protective coating of the coil spring, causing corrosion of the coil spring. Such damage to the coil spring coating caused by abrasive solid particles is to be avoided by preventing the penetration and deposition of solid particles in the space between the coil spring and the spring plate.For this purpose, according to DE 10 2009 052 030 A1, a spring pad is to be arranged between the coil spring and a spring plate supporting the coil spring. The pad has a base body made of a first material, the surface of which facing the coil spring is at least partially laminated with at least one elastic layer made of a second material. This elastic layer is to have a thickness adapted to the pitch of the coil spring so that any free space existing between the spring pad and the coil spring when installed is filled by the elastic layer. Dirt, sharp-edged stones or other foreign objects can no longer penetrate the free space filled by the elastic layer. At the same time, due to its elasticity, the elastic layer allows the relative movements between the spring end and the spring plate that occur during driving.This relative movement should prevent damage to the spring coating from abrasive particles. The elastic layer should be made of an elastomer such as rubber or polyurethane.

[0010] Another spring device with a helical spring and a spring pad for support against a spring plate with the aim of preventing corrosion formation at the spring end is known from DE 10 2007 003 782 A1. According to DE 10 2007 003 782 A1, the end coil of the spring intended for direct support on the spring plate ends with a full cross-section, and at least one end section of the end coil bears a vulcanized spring pad made of an elastomer on the outer side facing the spring plate. The pad is designed as an incompletely vulcanized molded part that is designed to receive the spring end coil in surface contact. The spring end coil is pretreated with an adhesive system in the surface area to be bonded.The spring end is then placed onto the molded part under moderate preload, and finally, the molded part is fully vulcanized in the assembled composite using a tempering furnace at temperatures between 140 and 150°C. The spring support is adapted to the curvature of the lower spring end. However, the preparation of the molded part and the subsequent steps for vulcanization to the coil spring are very complex in terms of handling.

[0011] Alternatively, DE 10 2007 003 782 A1 teaches covering at least one end section of the end turn with a shrink-treated heat-shrink tubing. However, the problem of infiltration by corrosive media, as already explained above, persists.

[0012] A spring device according to the preamble of patent claim 1 is known from EP 1 191 249 A2. To achieve tolerance compensation in steel springs, it is proposed to mold insulators of different heights onto the spring ends.

[0013] Furthermore, it is known from DE 26 33 739 A1 to arrange spring plate cores at the ends of a steel spring and to overmold these ends and spring plate cores with metal, in particular zinc-beryllium steel.

[0014] The invention is based on the object of providing a highly effective and at the same time easily attachable corrosion protection in a spring device of the type with a coil spring and a spring support for supporting the coil spring against a spring plate in the region of the spring ends of the coil spring.

[0015] This object is achieved by a spring device having the features of patent claim 1 and further by a method for its production according to patent claim 10.

[0016] It has been shown that this allows for very good corrosion protection with low manufacturing costs and low material usage.

[0017] Casting the end section of the coil spring provides good protection for the spring coils, which are particularly prone to breakage due to stone chipping and corrosion.

[0018] In addition, the casting process allows for a largely free choice of geometry for the shape of the spring base.

[0019] A polyurethane based on diphenylmethane diisocyanate is used as the casting compound, which is easy to process and, for example, has better damping and insulating properties compared to natural rubber due to lower dynamic hardening.

[0020] Polyurethane based on diphenylmethane diisocyanate is also hydrolysis and microbe-resistant and thus permanently environmentally resistant, ensuring high durability.

[0021] It is also highly flexible so that there is no need to worry about the material shearing or coming loose due to spring movements.

[0022] A chemical bonding agent system is used to bond the coil spring to the casting compound. This creates a particularly tight bond between the coil spring and the casting compound. This further improves corrosion protection, as the strong adhesion prevents any penetration or infiltration by corrosive media.

[0023] Particular embodiments of the invention are the subject of further patent claims.

[0024] Furthermore, one or more inserts can be embedded in the casting compound of the spring support, via which any necessary stiffening, defined connection and / or position determination can be carried out.

[0025] For example, the casting compound or an insert can be provided with a contour which can be brought into engagement with a corresponding contour of a spring plate in order to position the spring device.

[0026] Furthermore, an insert can form a fastening device, for example an opening, a projection or the like, for fastening to the spring plate.

[0027] In this context, a spring plate is understood to be any surface on which the spring device is supported via its spring support. In the simplest case, such a spring plate can be formed, for example, by a flat surface section of a wheel control arm or wheel carrier.

[0028] According to a further advantageous embodiment of the invention, the coil spring is cast into the casting compound with at least one complete turn. However, depending on requirements, the cast-in section can also be smaller or larger to provide a sufficient protective function of the type described above.

[0029] In one design variant, the spring support has a hat-shaped cross-sectional profile, the central elevation of which, accommodating the end section of the coil spring, serves as a damping mass. This allows for a targeted frequency shift of the spring's natural frequency without the need to attach additional components to the spring assembly. Frequency tuning of the damping mass can be achieved, for example, via the height and thickness of the central elevation of the spring support.

[0030] In a further design variant, the spring support has a spring protection section into which the end section of the coil spring is cast, as well as an adjoining support section that extends axially beyond the coil spring and allows the coil spring to be elastically supported on the spring plate. The various functions—namely, support against the spring plate on the one hand, and protection against stone chipping and corrosion in the area most prone to breakage on the other—are integrated into a single component with minimal manufacturing effort.

[0031] A spring device of the type described above can be produced, for example, by inserting the helical spring with an end section into a casting mold, then introducing the casting compound in liquid form into the casting mold and curing it there, including the end section of the helical spring.

[0032] The potting compound is preferably processed at a temperature below 100 °C. This ensures that no changes occur in the structure of the coil spring. Furthermore, the protective coating of the coil spring remains unaffected by the potting compound.

[0033] The invention is explained in more detail below with reference to exemplary embodiments illustrated in the drawing. The drawing shows: Fig. 1 shows a first embodiment of a spring device according to the invention, Fig. 2 a second embodiment of a spring device according to the invention, and in Fig. 3 is a diagram illustrating an example of the manufacture of a spring device according to the invention.

[0034] The Fig. The first embodiment shown in Figure 1 shows a spring device 1 for a motor vehicle wheel suspension. The spring device 1 can be used on both a front axle and a rear axle.

[0035] The spring device 1 comprises a helical spring 2, which is made of steel in a conventional manner and is provided with a protective coating 3.

[0036] At an end section 4 of the coil spring 2, a spring support 5 is arranged, via which the coil spring 2 can be supported against a suitable support surface, referred to below as a spring plate. The support surface can be located, for example, on a wheel guide, wheel carrier, or a structure fixed to the vehicle body. In the simplest case, this can be designed as a flat or planar wall section. However, it is also possible to configure it with a contour adapted to the spring device 1.

[0037] The spring support 5 serves primarily for sound insulation and vibration damping. In particular, it prevents direct contact between the coil spring 2 and the corresponding support surface on the vehicle.

[0038] According to the invention, the spring support 5, which serves to support the coil spring 2 against a spring plate, is made of a potting compound 6 into which the coil spring 2 is cast with its end section 4. The potting compound 6 encloses approximately one entire turn of the coil spring 2. However, the cast-in area can also be reduced to approximately half a turn. Furthermore, it is possible to embed more than one turn in the potting compound 6. Preferably, the potting compound 6 extends over the section of the coil spring 2 that is usually most at risk of breakage, i.e. in particular areas close to the wheel, which are particularly at risk from stone chips and / or exposed to corrosive media.

[0039] The potting compound 6 is a polyurethane based on diphenylmethane diisocyanate. This can be cast at relatively low temperatures, ranging from room temperature to below 100 °C. This prevents any impairment of the microstructure of the coil spring 2 and the protective coating 3.

[0040] In addition, this material offers better damping and insulation properties compared to natural rubber, as it exhibits less dynamic hardening. Furthermore, polyurethane based on diphenylmethane diisocyanate is hydrolysis- and microbe-resistant, ensuring high durability. Due to its high flexibility, there is no risk of the material shearing or detaching from the coil spring 2 due to spring movements.

[0041] The casting also ensures good adhesion of the material of the spring support 5 to the coil spring 2, which practically eliminates the possibility of infiltration by corrosive media.

[0042] Instead of polyurethane based on diphenylmethane diisocyanate, other casting elastomers can also be used which can be processed by casting within the temperature range mentioned.

[0043] To further improve the adhesion of the spring support 5 to the coil spring, a chemical bonding agent system 13 can be provided between the coil spring 2 and the potting compound 6 to bond them. This enables a significantly more intimate connection compared to glued or plugged connections, so that no corrosive medium can penetrate between the potting compound 6 and the coil spring 2.

[0044] In the illustrated embodiment, the spring support 5 has a spring protection section 5a and a support section 5b. In this case, the spring protection section 5a refers to the area of ​​the spring support 5 into which the end section 4 of the coil spring 2 is cast. It primarily serves to protect against stone chips and increase corrosion protection. The axially adjacent support section 5b projects axially beyond the coil spring 2 and serves to provide insulating support for the spring plate. Both sections 5a and 5b are manufactured in one step from the same material during the casting or injection molding of the spring support 5.

[0045] If necessary, the support section 5b can extend radially beyond the spring protection section. This may result in a hat-shaped cross-sectional profile for the spring support 5, whose central elevation 5c, which accommodates the end section 4 of the coil spring 2, serves as a damping mass. The height and thickness of the central elevation 5c can be used to adjust the frequency of this damping mass in order to achieve a targeted frequency shift of the spring's natural frequency.

[0046] Furthermore, one or more inserts 7 can be cast into the spring support 5. The insert(s) 7 are preferably arranged on the support section 5b. Such an insert 7 can, for example, be used to secure the spring plate. Fig. In the embodiment shown in Figure 2, an insert 7 is provided for this purpose, which has a corresponding fastening device 8 in the form of a recess. Instead of a recess or opening, a corresponding projection or the like can also be provided.

[0047] Furthermore, the spring device 1 can be positioned relative to a spring plate via such an insert 7, for example, by appropriately contouring it. For this purpose, the spring plate can optionally be provided with a corresponding contour that can be brought into engagement with the contour of the insert 7.

[0048] Alternatively or additionally, a corresponding contour 9 can also be formed directly on the casting compound 6 to facilitate correct installation of the spring device 1 in the wheel suspension. The casting mold 10 used to manufacture the spring support 5 can be designed with a corresponding negative contour for this purpose.

[0049] In the illustrated embodiments, only one end section 4 of the coil spring 2 is provided with a cast-on spring support 5. However, it is possible to cast spring supports 5 onto both end sections of a coil spring 2, wherein each spring support 5 can be designed with a geometry adapted to the respective installation situation. If only one end section 4 of the coil spring 2 is cast into a spring support, this can be done either, as shown, at the lower end section 4 or at the upper end section of the coil spring 2, relative to the installation position on the vehicle.

[0050] As explained above, according to the invention an end section 4 of the coil spring 2 is cast into the spring support 5.

[0051] Fig. 3 shows, by way of example, a casting mold 10 for the production of the spring support 5. This casting mold 10 can be provided with a division so that its casting mold parts 10a and 10b can be opened in a direction Q, preferably transverse to the axial direction A of the spring device 1. Furthermore, Fig. 3 a pouring channel 11 can be seen, through which the liquid casting compound is introduced into the casting mold 10.

[0052] The casting mold 10 shown in the exemplary embodiment has support projections 12 for supporting the coil spring 2. After the end section 4 of the coil spring 2 has been introduced into the casting mold 10, which may optionally have been previously provided with a chemical bonding agent system 13, the casting compound 6 is introduced in liquid form into the casting mold 10 and cured there, enclosing the end section 4 of the coil spring 2.

[0053] The casting compound is preferably processed at a temperature below 100°C. The support projections 12 ensure that a support section 5b of the spring support 5 is created during casting, projecting axially beyond the coil spring 2. As already indicated above, a desired contour 8 of the contact surface 13 of the spring support 5 toward the spring plate can be achieved by appropriately negatively contouring the casting mold 10. Furthermore, due to the fact that the spring support 5 is cast onto the coil spring 2, a flexible design of the geometry of the spring support 5 is possible.

[0054] Instead of the Fig. However, in accordance with the casting process shown in Figure 3, a spring support 5 can also be cast or injection-molded onto the coil spring 2 in a different manner.

[0055] The invention has been explained in more detail above with reference to exemplary embodiments and further modifications. In particular, individual technical features explained above in the context of further individual features can be implemented independently of these and in combination with other individual features, even if not expressly described, as long as this is technically feasible. The invention is expressly not limited to the described exemplary embodiment, but encompasses all configurations defined by the patent claims. List of reference symbols 1 spring device 2 coil springs 3 Protective coating 4 End section of the coil spring 5 spring rest 5a Spring protection section of the spring support 5b Support section of the spring support 5c central survey 6 Potting compound 7 inserts 8 Fastening device 9 Contouring 10 Casting mold 10a Cast part 10b Cast part 11 Pouring channel 12 Support projection 13 chemical adhesion promoter system A axial direction F spring plate Q Opening direction of the mold

Claims

[1] Spring device (1) for a motor vehicle wheel suspension, comprising: a coil spring (2) and a spring support (5) for supporting the coil spring (2) against a spring plate, wherein the spring support (5) is made of a casting compound (6) into which an end section (4) of the helical spring (2) is cast, characterized by that the casting compound (6) is a polyurethane based on diphenylmethane diisocyanate. [2] Spring device (1) according to claim 1, characterized by that a chemical bonding agent system (13) is provided between the helical spring (2) and the casting compound (6) to connect them. [3] Spring device (1) according to claim 1 or 2, characterized by that one or more inserts (7) are embedded in the casting compound (6) of the spring support (5). [4] Spring device (1) according to claim 3, characterized bythat an insert (7) forms a fastening device (8) for fastening to the spring plate. [5] Spring device (1) according to one of claims 1 to 4, characterized by that the casting compound (6) or an insert (7) is provided with a contour (8) which can be brought into engagement with a corresponding contour of the spring plate for positioning the spring device (1). [6] Spring device (1) according to one of claims 1 to 5, characterized by that the helical spring (2) is cast into the casting compound (6) with at least one complete turn. [7] Spring device (1) according to one of claims 1 to 6, characterized by that the spring support (5) has a hat-shaped cross-sectional profile, the central elevation (5c) of which, which receives the end section (4) of the helical spring (2), serves as a damping mass. [8] Spring device (1) according to one of claims 1 to 7, characterized bythat the spring support (5) has a spring protection section (5a) into which the end section (4) of the helical spring (2) is cast, as well as an adjoining support section (5b) which projects axially beyond the helical spring (2) and via which the helical spring (2) can be elastically supported on the spring plate. [9] Spring device (1) according to one of claims 1 to 8, characterized by that the coil spring (2) has a protective coating that is unaffected by the casting compound (6). [10] Method for producing a spring device (1) according to one of the preceding claims, characterized bythat the helical spring (2) is introduced with the end section (4) into a casting mold (10), then the casting compound (6) made of polyurethane based on diphenylmethane diisocyanate is introduced in liquid form into the casting mold (10) and is cured there with the end section (4) of the helical spring (2) included, wherein the processing of the casting compound (6) takes place at a temperature below 100 °C.

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