Shock absorber device for vehicle suspension and use of lubricant therefor

Abstract

The present invention relates to a shock absorber device (1) for a vehicle suspension, comprising: a shock absorber (3) having a damper cap (7) and a piston rod (5); and an auxiliary spring (9) arranged on the piston rod (5) opposite the shock absorber (3), the auxiliary spring having an outer surface (13) facing the damper cap (7) and an inner surface (21) facing the piston rod (5), and configured to dampen the movement of the shock absorber (3) in the direction of the piston rod (5) upon contact with the damper cap (7), wherein the outer surface (13) and / or the inner surface (21) are at least partially coated with a lubricant (17). According to the present invention, the lubricant (17) comprises a modified or unmodified polyether polyol. The present invention further relates to an auxiliary spring, a method, and corresponding uses.

Description

[Technical Field]

[0001] The present invention relates to a shock absorber device for a vehicle suspension, comprising: a shock absorber having a damper cap, a piston rod; and an auxiliary spring arranged on the piston rod opposite the shock absorber, the auxiliary spring having an outer surface facing the damper cap and an inner surface facing the piston rod, and configured to dampen movement of the shock absorber in the direction of the piston rod when in contact with the damper cap, the outer surface and / or the inner surface being at least partially coated with a lubricant.

[0002] Shock absorber devices of the type shown above are generally known. During vehicle operation, the bouncing motion of the vehicle's wheel suspension typically results in the damper cap of the shock absorber moving toward the piston rod. To prevent damage to the shock absorber and possibly other components of the suspension when the vehicle's suspension bottoms out, shock absorber devices often have an auxiliary spring that contacts the damper cap and damps further compression after a certain degree of suspension compression and a corresponding degree of shock absorber movement. For this purpose, volume-compressible materials are advantageously used, which provide material damping through geometric and / or volume compression.

[0003] It has been observed that the shock absorber system described above generates a squealing noise during operation, which does not impair the function of the shock absorber system itself, but which is perceived as unpleasant.

[0004] To produce the molded body that forms the auxiliary spring, the surface of the mold is often, and indeed usually, pretreated with a release agent. Release agents based on oil, wax, silicone, and / or solid inorganic or organic additives (e.g., Teflon powder), or other products that reduce adhesion of polyurethane to the mold surface, are known to those skilled in the art. It is known that certain release agents, especially certain silicone-containing release agents, can reduce or even prevent noise generation by themselves. However, for reasons of health and environmental protection, these variations are not preferred.

[0005] When moldings are produced, release agent residues often remain on the surface of the moldings. The type of residue can be influenced by the choice of release agent, but the amount of residue depends on many factors during production. Residues can sometimes change the noise emission. Since release agents are often an essential component of the production process, when referring to moldings made of microcellular polyurethane in the following in the context of the present invention, this always refers to both pure polyurethane moldings and moldings with release agent residues still attached to their surface. When referring to "dry" moldings below, this is intended to refer to both moldings without release agent and moldings with release agent residues attached.

[0006] To address the aforementioned noise emissions, attempts have been made in the past to use silicone-containing mold release agents in the manufacturing process. However, this solution is undesirable due to the potential health hazards associated with some silicone-containing compounds. International Publication No. WO 2016 / 5247 discloses the use of lubricants to at least partially coat the outer and / or inner surfaces of shock absorber springs. However, it has been found that the lubricants proposed therein can cause hydrolysis of polyurethane components, which is highly undesirable and shortens the lifespan of such polyurethane components.

[0007] It was therefore an object of the present invention to provide an alternative solution for reducing the noise during operation of shock absorber devices, in particular a solution that does not adversely affect the service life of the parts to be coated.

[0008] The object of the present invention is achieved by providing a shock absorber device of the above-mentioned type, in which the lubricant contains a modified or unmodified polyether polyol.

[0009] Polyether polyols have been found to not only reduce noise during operation of shock absorber systems, but also to provide high compatibility with the polyurethane auxiliary springs typically utilized in such systems.

[0010] The use of polyether polyols has been found to be particularly suitable due to their relatively low proportion of primary hydroxy groups among the terminal hydroxy groups. This has been found to be beneficial in terms of compatibility with polyurethane components, such as polyurethane auxiliary springs, because primary hydroxy groups are known to cause hydrolysis. A high content of primary hydroxy groups can decompose polyurethanes, which is highly undesirable. The polyether polyols may be unmodified or modified with respect to the terminal hydroxy groups.

[0011] Modified polyether polyols contain terminal hydroxy groups that have been at least partially reacted to replace the hydrogen with an organic substituent, such as an alkyl group, an aromatic group, or an acyl group. Such modification is not present in unmodified polyether polyols. Therefore, the OH number of modified polyether polyols can be lower than the OH number of unmodified polyether polyols.

[0012] Suitable polyether polyols have a number-average molecular weight of 62 g / mol to 30,000 g / mol. Suitable polyether polyols are based on propylene oxide, ethylene oxide, butylene oxide, or a combination of propylene oxide and ethylene oxide, or a combination of other alkylene oxides. Suitable polyether polyols are prepared by known methods of polymerizing ethylene oxide and / or propylene oxide from initiator molecules containing 1 to 6 reactive hydrogen atoms in bonded form. The polymerization can be carried out as an anionic polymerization using an alkali metal hydroxide or alkali metal alkoxide as a catalyst, or as a cationic polymerization using a Lewis acid, such as antimony pentachloride or boron trifluoride etherate. Additionally, complex metal cyanide compounds, known as DMC catalysts, can also be used as catalysts. Tertiary amines, such as triethylamine, tributylamine, trimethylamine, dimethylethanolamine, or dimethylcyclohexylamine, can also be used as catalysts. Ethylene oxide, butylene oxide, and propylene oxide can be polymerized singly, alternately, sequentially, or in a mixed state. Suitable initiator molecules having 1 to 6 reactive hydrogen atoms include, for example, water, and dihydric or trihydric alcohols, such as acetic acid, methanol, ethanol, aliphatic alcohols, ethylene glycol, 1,2- and 1,3-propanediol, diethylene glycol, dipropylene glycol, 1,4-butanediol, glycerol, trimethylolpropane, as well as pentaerythritol, sorbitol, and sucrose. Further suitable initiator molecules are amine initiators, such as triethanolamine, diethanolamine, ethylenediamine, and toluenediamine. The polyether polyol preferably has an OH value ranging from 1 mg KOH / g to 1,825 mg KOH / g.Particularly preferred polyether polyols are prepared from monohydric, dihydric, or trihydric alcohols, especially methanol, ethanol, aliphatic alcohols, ethylene glycol, trimethylolpropane, or glycerol, and are ethylene oxide homopolymers, propylene oxide homopolymers, or ethylene oxide-propylene oxide copolymers. Further preferred polyether polyols are α-hydro-ω-hydroxypoly(oxybutane-1,4-diyl), also known as PTHF. These particularly preferred polyether polyols have molecular weights of 62 g / mol to 10,000 g / mol and OH values ​​of 5 mg KOH / g to 1,825 mg KOH / g, preferably 5 mg KOH / g to 500 mg KOH / g, and more preferably 5 mg KOH / g to 100 mg KOH / g.

[0013] In one embodiment, the polyether polyol comprises polypropylene glycol, which has been found to be beneficial due to its low proportion of primary hydroxy groups, particularly about 4% to 6% of terminal hydroxy groups, and is preferably based on propylene oxide.

[0014] In one embodiment, the polyether polyol contains terminal hydroxy groups containing hydrogen, and in the modified polyether polyol, the terminal hydroxy groups are at least partially reacted to replace the hydrogen with organic substituents, particularly alkyl, aromatic, or acyl groups. The OH value of the modified polyether polyol is preferably lower than the OH value of the unmodified polyether polyol. The OH value is defined as the number of milligrams of potassium hydroxide (KOH) required to neutralize the acetic acid incorporated during the acetylation of one gram of a chemical containing free hydroxy groups. The OH value provides information about the average molecular weight of molecules per OH group. The OH value is measured in accordance with DIN 53240. By modifying the polyether polyol, the proportion of hydroxy groups, especially primary hydroxy groups, can be reduced.

[0015] In one embodiment, the assist spring comprises or consists of polyurethane. In a preferred embodiment, the polyurethane comprises or consists of microcellular polyurethane. Microcellular polyurethane is a volume-compressible material that has unique advantages over other materials, such as rubber, including high durability and an extremely high capacity for elastic shape change.

[0016] In one embodiment, the polyether polyol comprises terminal hydroxy groups, and less than 50% of the terminal hydroxy groups are primary hydroxy groups. In a preferred embodiment, less than 25% of the terminal hydroxy groups are primary hydroxy groups, and preferably, especially less than 10% of the terminal hydroxy groups are primary hydroxy groups.

[0017] A low proportion of primary hydroxy groups is beneficial in avoiding hydrolysis of polyurethane parts. Methods for determining the content of primary or secondary hydroxy groups (also called OH groups) are described, for example, in the following literature: Goodlett, VW, “Use of In Situ Reactions for Characterization of Alcohols and Glycols by Nuclear Magnetic Resonance”, Analytical Chemistry, 1965, Vol.37, p.431-432 Hirama Masahiro, Tohru Oishi, “Trichloroacetyl Isocyanate”, Encyclopedia of Reagents for Organic Synthesis (Trichloroacetyl Isocyanate - Hirama - Major Reference Works - Wiley Online Library) Meyer zur Heyde, Manfred, “Neuere Anwendungen von Trichloracetylisocyanat in der 1H-NMR-Spektroskopie”, Fresenius' Zeitschrift fuer analytische Chemie, 1979, Vol.295, p.125-142 Bose, AK, PR Srinivasan, “NMR spectral studies ― XII: Trichloroacetyl isocyanate as an in situ derivatizing reagent for 13C NMR spectroscopy of alcohols, phenols and amines”, Tetrahedron, 1975, Vol.31, p.3025-3029 known to those skilled in the art by either

[0018] Polymers prepared by polymerization of propylene oxide with the initiators mentioned above may be found to have a low content of primary hydroxy groups, and the products are called polypropylene ether polyols or polypropylene glycols.

[0019] In a preferred embodiment, the OH functional groups of the modified polyether polyol are at least partially reacted to result in a product with a lower OH value than the OH value of the original polyether polyol. In a more preferred embodiment, the modified polyether polyol is reacted with acetic anhydride, acetic acid chloride, or oxalic acid dichloride to form acetate or oxalate esters. The reaction by-product (acetic acid or HCl from the reaction) is removed from the product.

[0020] In another preferred embodiment, the polyether polyol is at least partially reacted with other products capable of reacting with alcoholic OH functional groups, namely dimethyl sulfate, methyl iodide, or phenyl isocyanate, resulting in an OH number lower than that of the original polyether polyol.

[0021] In a preferred embodiment, the lubricant coating is 0.8 mg / cm 2 areal density greater than 1.5 mg / cm 2 ~50mg / cm 2 , more preferably 1.5 mg / cm 2 ~10mg / cm 2 , very preferably 3 mg / cm 2 ~4mg / cm 2 This areal density of lubricant has been found to be beneficial in providing sufficient damping characteristics while keeping the total amount of lubricant applied to the component to a reasonable minimum.

[0022] In a first aspect, the present invention has been described with respect to the shock absorber device of the present invention. In a further aspect, the present invention also relates to an auxiliary spring having an outer surface facing a damper cap of a shock absorber and an inner surface configured to receive a piston rod of the shock absorber, the outer surface and / or the inner surface being at least partially coated with a lubricant.

[0023] The object underlying the present invention is achieved in that the lubricant in the auxiliary spring contains or consists of a modified or unmodified polyether polyol. The auxiliary spring according to the present invention utilizes the same advantages as the shock absorber device according to the present invention. Therefore, preferred embodiments of the shock absorber device are also preferred embodiments of the auxiliary spring according to the present invention, and vice versa.

[0024] In one embodiment, the polyether polyol comprises or consists of polypropylene glycol. In one embodiment, the polyether polyol comprises terminal hydroxy groups containing hydrogen, and in the modified polyether polyol, the terminal hydroxy groups are at least partially reacted to replace the hydrogen with organic substituents, particularly alkyl, aromatic, or acyl groups. Preferably, the OH value of the modified polyether polyol is lower than the OH value of conventional polyether polyols.

[0025] In a preferred embodiment, the assist spring comprises or consists of polyurethane. Preferably, the polyurethane is a microcellular polyurethane. In a preferred embodiment, the lubricant coating is 0.8 mg / cm 2 areal density greater than 1.5 mg / cm 2 ~50mg / cm 2 , more preferably 1.5 mg / cm 2 ~10mg / cm 2 , very preferably 3 mg / cm 2 ~4mg / cm 2 It has an areal density of

[0026] In a further aspect, the present invention relates to a method for manufacturing an auxiliary spring having an outer surface facing a damper cap of a shock absorber and an inner surface facing a piston rod of the shock absorber, the object of which is achieved in a step of at least partially coating the outer and / or inner surface with a lubricant, said lubricant comprising or consisting of a modified or unmodified polyether polyol.

[0027] In a further aspect, the present invention relates to a method for manufacturing an assist spring, the method comprising the steps of providing a mold for foam molding an assist spring therein, applying a release agent to the mold, foam molding the assist spring in the mold, and applying a lubricant comprising a modified or unmodified polyether polyol, the lubricant being applied to the mold together with, and / or after, and / or as part of the release agent formulation.

[0028] The method according to the invention uses the same advantages and preferred embodiments as the shock absorber device and auxiliary spring according to the invention, and therefore preferred embodiments of the shock absorber device and auxiliary spring are simultaneously preferred embodiments of the method according to the invention and vice versa.

[0029] In a further aspect, the present invention relates to the use of a lubricant for reducing noise in a shock absorber arrangement, the shock absorber arrangement comprising a shock absorber having a damper cap, a piston rod, and an auxiliary spring disposed opposite the shock absorber, the auxiliary spring having an outer surface facing the damper cap and an inner surface facing the piston rod, and configured to dampen movement of the shock absorber in the direction of the piston rod when in contact with the damper cap, the outer surface and / or the inner surface being at least partially coated with a lubricant. The object underlying the present invention is achieved in the use of a lubricant in that the lubricant comprises or consists of a modified or unmodified polyether polyol.

[0030] In one embodiment, the polyether polyol comprises or consists of polypropylene glycol. In one embodiment, the polyether polyol comprises terminal hydroxy groups containing hydrogen, and in the modified polyether polyol, the terminal hydroxy groups are at least partially reacted to replace the hydrogen with organic substituents, particularly alkyl, aromatic, or acyl groups. Preferably, the OH value of the modified polyether polyol is lower than the OH value of the unmodified polyether polyol. In a preferred embodiment, the auxiliary spring comprises or consists of polyurethane. Preferably, the polyurethane is microcellular polyurethane.

[0031] In yet another embodiment, the polyether polyol comprises terminal hydroxy groups, and less than 50% of the terminal hydroxy groups are primary hydroxy groups. In a preferred embodiment, less than 25% of the terminal hydroxy groups are primary hydroxy groups, and preferably, especially less than 10% of the terminal hydroxy groups are primary hydroxy groups.

[0032] In a preferred embodiment, 200 kg / m according to DIN 53420 3 ~1,100kg / m 3 , preferably 300 kg / m 3 ~800kg / m 3 Particularly preferred is a microcellular polyurethane elastomer having a density of 1000 MPa (1000 MPa). Such microcellular polyurethane elastomers are also called volume-compressible materials (or volume-compressible structural materials). Such volume-compressible materials have unique advantages over other materials, such as rubber, including high durability and an extremely high ability to elastically change shape.

[0033] The manufacturing process is usually carried out via the reaction of an isocyanate with a compound reactive with the isocyanate. Microcellular polyurethane is usually produced in a mold in which reactive starting components are reacted with each other. The molds that can be used here are generally conventional molds, for example, metal molds, and the shape of the mold ensures that the spring element has the three-dimensional shape of the present invention. In one embodiment, a foam mold is used to manufacture the profile element. In another embodiment, the profile element is then incorporated into a concentric main element. Another possible method is to use a part manufactured from a semi-finished product. The manufacturing process can be, for example, a water jet cutting process.

[0034] Microcellular polyurethane products can be produced by known processes, for example from the following starting materials: (a) Isocyanate (b) Compounds reactive with isocyanates (c) water, and optionally (d) Catalyst (e) a blowing agent, and / or (f) auxiliary agents and / or additives (e.g., polysiloxanes and / or fatty acid sulfonates) It can be prepared in a one-step or two-step process by using

[0035] The temperature of the inner surface of the mold is usually 30°C to 110°C, preferably 50°C to 100°C. Molded articles are advantageously produced at an NCO / OH ratio of 0.85 to 1.20 by mixing the heated starting components and injecting an amount of the mixture corresponding to the desired density of the molded article into a heated, preferably closed, mold. The molded article hardens and can be removed from the mold after 1 to 60 minutes. The amount of reaction mixture injected into the mold is usually calculated so that the resulting molded article has the above-mentioned density. The starting components are usually injected into the mold at a temperature of 15°C to 120°C, preferably 30°C to 110°C. The degree of compression during the production of molded articles is in the range of 1.1 to 8, preferably 2 to 6. Microcellular polyurethane products are advantageously produced by the "one-shot" method in an open or preferably closed mold using high-pressure, low-pressure, or, in particular, reaction injection molding (RIM) techniques. Alternatively, a prepolymer method is used. The reaction is carried out in a closed mold under compression. The reaction injection molding technique is, for example, H. Piechota, H. Roehr, “Integralschaumstoffe” (English translation: Integral foams), Carl Hanser-Verlag, Munich, Vienna, 1975; DJ Prepelka, JL Wharton, Journal of Cellular Plastics, March / April 1975, p.87-98; U. Knipp, Journal of Cellular Plastics, March / April 1973, p.76-84 is described in.

[0036] According to the present invention, it has been determined that the simultaneous use of a "dry" shock absorber device and a volume-compressible material, such as microcellular polyurethane foam (see above), results in no noise emissions, or at least only insignificantly unpleasant noise emissions. It has also been determined that, despite the inherent anti-friction properties of damper fluids, often mineral oils, noise emissions can occur, for example, when the damper fluid leaks from the shock absorber and spreads onto the damper cap and / or piston rod. Surprisingly, it has been found that undesirable noise can be significantly reduced by adding an additional lubricant that is different from the damper fluid but preferably has a similar anti-friction effect. This solves the seemingly contradictory problem of damper fluid leakage itself causing unpleasant noise. Water, or a combination of water and damper fluid, can also have a similar effect.

[0037] There are two approaches to applying lubricant to the surface of the auxiliary spring: (1) during the foam molding process, or (2) after the foam molding process.

[0038] (1) During the manufacture of assist springs, the mold surface is often pretreated with a release agent. In other cases, the mold surface is modified to provide a non-polar, permanent or semi-permanent surface to which polyurethane will not stick. A lubricant can be applied along with the release agent: (a) before the release agent is applied, and / or (b) after the release agent is applied, and / or (c) as part of the release agent formulation. A lubricant can be applied to modified mold surfaces as well.

[0039] In other words, in one embodiment, the lubricant is applied along with the mold release agent applied to the mold surfaces during the manufacture of the assist spring, prior to application of the mold release agent, and / or after application of the mold release agent, and / or as part of the mold release agent formulation.

[0040] (2) Alternatively, the lubricant can be applied to the surface of the auxiliary spring after the foaming process. In the method or use according to the invention, the lubricant can be applied to the auxiliary spring, for example, by spraying and / or brushing or painting, or alternatively or additionally, by dipping. The lubricant can thus be applied multiple times as needed, or renewed after a given period of time.

[0041] The present invention will now be described by way of preferred embodiments with reference to the accompanying drawings. [Brief explanation of the drawings]

[0042] [Figure 1a] 1 shows a shock absorber device according to a preferred embodiment. [Figure 1b] 1a-1c show a shock absorber device according to a preferred embodiment in different operating states than in FIG. 1a; [Figure 2] FIG. 2 is a detailed view of the shock absorber arrangement of FIGS. 1a and 1b. [Figure 3a] FIG. 3 is a more detailed view of the shock absorber arrangement of FIGS. 1a, 1b and 2; [Figure 3b] 3a and 3b show more detailed views of the shock absorber arrangement of FIGS. 1a, 1b and 2 in different operating states than FIG. 3a; [Figure 3c] 3a and 3b, in different operating states;

[0023] FIG. 4 is a more detailed view of the shock absorber arrangement of FIGS.

[0043] 1 shows a shock absorber device 1. The shock absorber device 1 includes a shock absorber 3 having a damper cap 7 and a piston rod 5 extending through the damper cap 7.

[0044] An auxiliary spring 9 is disposed on the opposite side of the damper cap 7 along the piston rod 5. The auxiliary spring 9 is housed by a base 11.

[0045] The auxiliary spring 9 has an outer surface 13 facing the outer surface 15 of the damper cap 7 .

[0046] During operation of the shock absorber device 1, the operation of the damper may result in a state such as that shown in Figure 1B. In this state, the outer surface 13 of the auxiliary spring 9 is in contact with the end surface 15 of the damper cap. As the shock absorber 3 continues to operate, the auxiliary spring 9 performs a retraction movement, resulting in the outer surface 13 moving relatively along the end surface 15. The operating principle of the present invention that acts in this case will be explained in more detail with reference to Figures 2 and 3a to 3c.

[0047] 2, firstly, the auxiliary spring 9 is shown in a partial cross section, and in the state shown in FIG.

[0048] The auxiliary spring 9 is at least partially coated on its outer surface 13 with a lubricant 17, which contains or consists of a polyether polyol. In the illustrated embodiment, by way of example, the lubricant 17 is additionally applied at least partially along an inner surface 21 of the auxiliary spring 9, which inner surface 21 faces the piston rod 5. A gap 19 exists between the inner surface 21 and the piston rod 5.

[0049] When compression of the auxiliary spring occurs, as shown by way of example in Figure 1b, the auxiliary spring 9 expands radially, i.e. laterally relative to the piston rod 5, outwards and inwards, so that the inner surface 21 contacts the piston rod 5. Here too, the lubricant 17 provides the benefits of the present invention. Although not as pronounced as when the lubricant 17 is applied to the outer surface 13, there is still a noise-reducing effect, which is advantageous in accordance with the present invention.

[0050] The example of FIG. 2 should be considered exemplary insofar as coating (at least partially) only the inner surface 21 and coating (at least partially) only the outer surface 13 should also be construed as separately encompassed preferred embodiments.

[0051] Figures 3a-3c show the behaviour of the lubricant 17 under different operating conditions. For simplicity, only the coating on the outer surface 13 is shown in the figures. However, the concepts can be applied equally to the behaviour of the coated inner surface 21 on the piston rod 5 (see Figure 2).

[0052] FIG. 3a shows the auxiliary spring 9 initially coated with lubricant 17 on its outer surface 13, but before it has contacted the damper cap 7. Damper fluid 23 has accumulated on the end surface 15 of the damper cap 7 as a result of shock absorber operation. As the auxiliary spring 9 contacts the damper cap 7 from the state shown in FIG. 3a, the outer surface 13 absorbs some of the damper fluid 23. Thus, both the damper fluid 23 and the lubricant 17 are present on the outer surface 13.

[0053] The additional presence of lubricant 17 ensures that undesirable stick-slip phenomena are reduced during continued operation.

[0054] Figure 3c shows the condition after extended operation, or when the exterior surface 13 is only slightly wetted by the lubricant 17. The amount of damper fluid 23 and lubricant 17 on the exterior surface 13 is generally much less than in the condition shown in Figure 3b. Nevertheless, with this configuration, a significant noise reduction is still achieved compared to the condition where the exterior surface 13 has the damper fluid 23 but no additional lubricant 17 of different nature from the damper fluid 23.

[0055] A particular advantage of the present invention is that it can also be retrofitted to existing damper systems at low cost: a partial and / or very thin coating of the auxiliary spring 9 with lubricant 17 is sufficient for reliable noise reduction, so that the expected maintenance intervals for renewing the coating can be extended accordingly.

[0056] In an embodiment, the auxiliary spring 9 comprises or consists of microcellular polyurethane.

[0057] The polyether polyol comprises terminal hydroxy groups, of which less than 50% are primary hydroxy groups. In a preferred embodiment, less than 25% of the terminal hydroxy groups are primary hydroxy groups, and preferably, in particular, less than 10% of the terminal hydroxy groups are primary hydroxy groups.

[0058] The lubricant coating is 0.8 mg / cm 2 areal density greater than 1.5 mg / cm 2 ~50mg / cm 2 , more preferably 1.5 mg / cm 2 ~10mg / cm 2 , very preferably 3 mg / cm 2 ~4mg / cm 2 The surface density may be

[0059] The present invention will now be further illustrated by the following examples.

[0060] To identify a suitable lubricant to prevent noise generated when microcellular polyurethane auxiliary springs rub against solid surfaces (e.g., plastic or metal), certain types of auxiliary springs were sprayed or coated with an additive on the upper flexure lip, using 0.04 g to 0.06 g of the additive.

[0061] Hard PVC or ABS was used as the surface material. Screening tests showed that the type of plastic used had little effect on noise generation. PC, POM, and various types of PA were tested.

[0062] First, a drop of shock absorber oil was applied to the end surface 15 (see FIG. 1a).

[0063] The auxiliary spring 9 was then repeatedly pressed against the end surface 15 and rotated about the piston rod 5, causing lateral movement along the piston rod 5 and rotational movement on the end surface 15 of the damper cap 7. This caused the untreated sub-spring to squeak. For comparison, a similar test was then performed on an auxiliary spring that had been treated with an additive on its outer surface 13.

[0064] To perform repeated measurements, a drop of shock absorber oil was applied to the end face 15 of a new damper cap 7 each time, and the same auxiliary spring was tested again until noise was observed.

[0065] Whereas unsuitable additives showed noise generation already during the first or second measurement and were directly rejected, effective additives were only rejected after 10 or more measurements.

[0066] A suitable additive was identified: polypropylene glycol with a molecular weight of 7,200 g / mol to 9,000 g / mol ("polypropylene glycol 8000"). With the above configuration, the number of measurements before the first noise was 21.

[0067] The compatibility of the additives with microcellular polyurethane was then tested by comparing the tensile strength and elongation of treated and untreated materials in accordance with DIN EN ISO 1798. The purpose of the test was to identify possible damage to the substrate caused by the product acting on it. The substrate in this case was microcellular polyurethane (Chelast®).

[0068] In a first step, at least eight test specimens PK1 were prepared from the same batch of substrate. Tensile tests were carried out on at least four of the test specimens within 10 days of preparation ("initial tensile strength"). Another set of test specimens (at least four) was stored in the test medium at 100°C for three days.

[0069] The specimens were then removed from the test medium. The specimens were drained and wiped dry. After cooling for 30 to 60 minutes, tensile tests were performed on the stored specimens (stored materials) to compare the tensile strength or elongation at break. In particular, the results were compared with the initial values ​​of untreated specimens.

[0070] A decrease in tensile strength of more than 10% indicates incompatibility or accelerated material degradation, while a nearly constant value can be considered an indication of compatibility. For reference, a value of 4.6 (standard deviation 0.3) N / mm 2 The tensile strength of the lubricant, polypropylene glycol 8000, was measured at 5.2 (standard deviation 0.5) N / mm 2 Tensile strength was measured and no decrease in tensile strength was observed when polypropylene glycol 8000 was applied to the test material.

Claims

1. A shock absorber device (1) for a vehicle suspension, comprising: a shock absorber (3) having a damper cap (7) and a piston rod (5); an auxiliary spring (9) arranged on the piston rod (5) opposite the shock absorber (3), the auxiliary spring having an outer surface (13) facing the damper cap (7) and an inner surface (21) facing the piston rod (5), and configured to dampen the movement of the shock absorber (3) in the direction of the piston rod (5) when contacting the damper cap (7); Equipped with The outer surface (13) and / or the inner surface (21) are at least partially coated with a lubricant (17). In a shock absorber device (1), A shock absorber device (1) characterized in that the lubricant (17) comprises a modified or unmodified polyether polyol.

2. The shock absorber device (1) according to claim 1, wherein the polyether polyol comprises polypropylene glycol.

3. 3. The shock absorber device (1) according to claim 1 or 2, wherein the polyether polyol comprises terminal hydroxy groups, and in the modified polyether polyol, the terminal hydroxy groups have at least partially reacted to replace the hydrogen with organic substituents, in particular alkyl, aromatic or acyl groups.

4. 4. The shock absorber device (1) according to any one of claims 1 to 3, wherein the polyether polyol comprises terminal hydroxy groups, less than 50% of which are primary hydroxy groups, preferably less than 25% of which are primary hydroxy groups, in particular less than 10% of which are primary hydroxy groups.

5. 5. The shock absorber device (1) according to any one of claims 1 to 4, wherein the auxiliary spring (9) comprises polyurethane, in particular microcellular polyurethane.

6. The lubricant coating has a thickness of 0.8 mg / cm ２ areal density of greater than 1.5 mg / cm ２ ~50 mg / cm ２ , more preferably 1.5 mg / cm ２ ~10 mg / cm ２ , very preferably 3 mg / cm ２ ~4 mg / cm ２ 6. The shock absorber device (1) according to claim 1, having an areal density of 0.015 .mu.m.sup.-1.0001 ...

7. An auxiliary spring (9) having an outer surface (13) facing the damper cap (7) of the shock absorber (3) and an inner surface configured to accommodate a piston rod of the shock absorber (3), The outer surface (13) and / or the inner surface (21) are at least partially coated with a lubricant (17). In the auxiliary spring (9), Auxiliary spring (9) characterized in that the lubricant (17) comprises a modified or unmodified polyether polyol.

8. 8. The assist spring (9) of claim 7, wherein the polyether polyol comprises terminal hydroxy groups, and wherein the modified polyether polyol has the terminal hydroxy groups at least partially reacted to replace the hydrogen with organic substituents, in particular, the organic substituents being alkyl, aromatic, or acyl groups.

9. Auxiliary spring (9) according to claim 8, characterized in that the auxiliary spring (9) comprises polyurethane, in particular microcellular polyurethane.

10. 10. An auxiliary spring (9) according to any one of claims 7 to 9, wherein the polyether polyol comprises terminal hydroxy groups, less than 50% of which are primary hydroxy groups, preferably less than 25% of which are primary hydroxy groups, in particular less than 10% of which are primary hydroxy groups.

11. 1. A method for manufacturing an auxiliary spring (9) having an outer surface (13) facing a damper cap (7) of a shock absorber (3) and an inner surface (21) facing a piston rod (5) of the shock absorber (3), comprising: - coating said outer surface (13) and / or said inner surface (21) at least partially with a lubricant (17), said lubricant (17) comprising a modified or unmodified polyether polyol. A method comprising:

12. A method for manufacturing an auxiliary spring (9), comprising the steps of: - preparing a mould in which said auxiliary spring (9) is foam moulded; - applying a release agent to the mould; - foaming said auxiliary spring (9) in said mould; - applying a lubricant (17), said lubricant (17) comprising a modified or unmodified polyether polyol, said lubricant being applied to the mould together with the release agent and / or after application of the release agent and / or as part of the formulation of the release agent; A method comprising:

13. 1. Use of a lubricant (17) for reducing noise in a shock absorber device (1), the shock absorber device (1) comprising a shock absorber (3) having a damper cap (7) and a piston rod (5), and an auxiliary spring arranged opposite the shock absorber (3), the auxiliary spring having an outer surface (13) facing the damper cap (7) and an inner surface (21) facing the piston rod (5), and configured to dampen movement of the shock absorber (3) in the direction of the piston rod (5) when contacting the damper cap (7), the outer surface (13) and / or the inner surface (21) being at least partially coated with a lubricant (17).

10. The use of claim 1, wherein the lubricant (17) comprises a modified or unmodified polyether polyol.

14. 14. The use according to claim 13, wherein the polyether polyol comprises terminal hydroxy groups containing hydrogen, and in the modified polyether polyol, the terminal hydroxy groups have at least partially reacted to replace the hydrogen with organic substituents, in particular, the organic substituents are alkyl, aromatic, or acyl groups.

15. 15. Use according to claim 13 or 14, wherein the auxiliary spring comprises polyurethane, in particular microcellular polyurethane.

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