Shock absorber arrangement for vehicle suspension and use of lubricant therefor

Abstract

The invention relates to a shock absorber arrangement (1) for a vehicle suspension, comprising a shock absorber (3) having a damper cover (7) and a piston rod (5), and an auxiliary spring (9) which is arranged on the piston rod (5) opposite the shock absorber (3) and has an outer surface (13) facing the damper cover (7) and an inner surface (21) facing the piston rod (5), the auxiliary spring is designed to damp a movement of the shock absorber (3) in the direction of the piston rod (5) when in contact with the damper cover (7), the outer surface (13) and / or the inner surface (21) being at least partially coated with a lubricant (17). According to the invention, the lubricant (17) comprises a modified or unmodified polyether polyol. The invention also relates to an auxiliary spring, a method and a corresponding use.

Description

[0001] The invention relates to a shock absorber arrangement for a vehicle suspension, comprising a shock absorber having a damper cover, a piston rod, and an auxiliary spring, which is arranged on the piston rod opposite the shock absorber and has an outer surface facing the damper cover and an inner surface facing the piston rod, and is configured to dampen movements of the shock absorber in the direction of the piston rod when in contact with the damper cover, wherein the outer surface and / or the inner surface are at least partially coated with a lubricant.

[0002] Shock absorber arrangements of the type indicated above are generally known. During vehicle operation, elastic movements of the vehicle's wheel suspension typically cause the shock absorber and its damper cover to move in the direction of the piston rod. To prevent damage to the shock absorber and potentially other suspension components when the vehicle suspension bottoms out, these shock absorber arrangements typically include an auxiliary spring that, after a certain degree of suspension compression and a corresponding degree of shock absorber movement, comes into contact with the damper cover and damps further compression. For this purpose, a volumetrically compressible material is advantageously used, which induces material damping due to its geometry and / or volume compression.

[0003] It has been observed that during operation of the above-described shock absorber arrangement squeaking noises occur which, although not detrimental to the function of the shock absorber arrangement itself, are nevertheless very annoying.

[0004] To produce the molded body that forms the auxiliary spring, the mold surface is often pretreated with a release agent. Release agents based on oils, waxes, silicones, and / or solid inorganic or organic additives (e.g., Teflon powder), or other products that reduce the adhesion of polyurethane to the mold surface, are known to those skilled in the art. Certain release agents, in particular certain types of silicone-containing release agents, are known to reduce or even prevent noise emissions. However, these variants are not preferred for health and environmental reasons.

[0005] During the production of molded parts, residues of release agent almost always remain on the surface of the molded product. The type of residue can be influenced by the choice of release agent, but the amount of residue depends on many factors during the manufacturing process. These residues can alter noise emissions when placed in the appropriate locations. Since release agents are generally an indispensable component of the manufacturing process, when reference is made to molded parts made of microporous polyurethane in the following text in conjunction with the present invention, this always refers to pure polyurethane molded parts as well as molded parts to which residues of release agent still adhere. If reference is made to "dry" molded parts below, this is intended to refer to molded parts that do not contain release agent as well as molded parts to which residues of release agent still adhere.

[0006] To combat this noise emission, attempts have been made in the past to use silicone-containing mold release agents during the manufacturing process. However, this solution is not desirable due to the potential health hazards posed by certain silicone-containing compounds. WO 2016 5247 A1 discloses at least partially coating the outer and / or inner surfaces of a shock absorber spring with a lubricant. However, it has been found that the lubricant proposed there can cause hydrolysis of the polyurethane component, which is highly undesirable and can shorten the service life of such a polyurethane component.

[0007] Therefore, the object of the present invention is to provide an alternative solution for reducing noise during operation of a shock absorber arrangement. In particular, the object of the present invention is also to provide such a solution which does not adversely affect the service life of the coated components.

[0008] The invention achieves this object in a shock absorber arrangement of the aforementioned type, in which the lubricant contains a modified or unmodified polyether polyol.

[0009] It has been found that polyether polyols not only reduce noise during operation of shock absorber arrangements, but are also highly compatible with the polyurethane helper springs frequently used in such shock absorber arrangements.

[0010] The use of polyether polyols has been determined to be particularly suitable because the proportion of primary hydroxyl groups in the terminal hydroxyl groups is relatively low. This has been found to be beneficial with respect to compatibility with polyurethane components, such as polyurethane auxiliary springs, since primary hydroxyl groups have been found to induce hydrolysis. Excessively high levels of primary hydroxyl groups can decompose the polyurethane, which is highly undesirable. The polyether polyols can be unmodified or modified with respect to the terminal hydroxyl groups.

[0011] Modified polyether polyols contain terminal hydroxyl groups that are at least partially reacted so that the hydrogen is replaced by an organic substituent (such as an alkyl, aryl, or acyl group). For unmodified polyether polyols, no such modification is performed. Therefore, the OH value of the modified polyether polyol may be lower than the OH value of the unmodified polyether polyol.

[0012] Suitable polyether polyols have a number-average molecular weight of 62 g / mol to 30,000 g / mol. They are based on propylene oxide, ethylene oxide, butylene oxide, or a combination of propylene oxide and ethylene oxide or other alkylene oxides. Suitable polyether polyols are prepared by polymerizing ethylene oxide and / or propylene oxide using initiator molecules containing 1 to 6 reactive hydrogen atoms in bonded form by known methods. This polymerization can be carried out as anionic polymerization using alkali metal hydroxides or alkali metal alkoxides as catalysts, or as cationic polymerization using Lewis acids such as antimony pentachloride or boron fluoride etherate. In addition, multimetal cyanide compounds (referred to 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 in pure form, alternating continuously, or as a mixture. Suitable starter molecules with 1 to 6 reactive hydrogen atoms are, for example, water and diols or triols such as acetic acid, methanol, ethanol, fatty alcohols, ethylene glycol, 1,2-propylene glycol and 1,3-propylene glycol, diethylene glycol, dipropylene glycol, 1,4-butanediol, glycerol, trimethylolpropane, as well as pentaerythritol, sorbitol and sucrose. Other suitable starter molecules are amine starters such as triethanolamine, diethanolamine, ethylenediamine and toluenediamine. The polyether polyols preferably have an OH number in the range of 1 mg KOH / g to 1,825 mg KOH / g. Particularly preferred polyether polyols are prepared from mono-, di- or triols, in particular methanol, ethanol, fatty alcohols, ethylene glycol, trimethylolpropane or glycerol, and are ethylene oxide homopolymers, propylene oxide homopolymers or ethylene oxide-propylene oxide copolymers. Another preferred class of polyether polyols is α-hydro-ω-hydroxypoly(oxy-1,4-butanediyl), also known as PTHF. These particularly preferred polyether polyols have a molecular weight of 62 g / mol to 10,000 g / mol and an OH number 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. Polypropylene glycol has been found to be beneficial because it has a low percentage of primary hydroxyl groups, particularly terminal hydroxyl groups of about 4% to 6%. The polypropylene glycol is preferably based on propylene oxide.

[0014] In one embodiment, the polyether polyol comprises terminal hydroxyl groups containing hydrogen, and wherein, in the case of the modified polyether polyol, the terminal hydroxyl groups are at least partially reacted so that the hydrogen is replaced by an organic substituent, in particular wherein the organic substituent is an alkyl, aryl or acyl group. Preferably, the OH value of the modified polyether polyol is 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 absorbed during the acetylation of 1 gram of a chemical substance containing free hydroxyl groups. The OH value provides information on the average molecular weight of each molecule per OH group. It is measured according to DIN 53240. By modifying the polyether polyol, the proportion of hydroxyl groups, in particular primary hydroxyl groups, can be reduced.

[0015] In one embodiment, the auxiliary spring comprises or consists of polyurethane. In a preferred embodiment, the polyurethane comprises or consists of microporous polyurethane. Microporous polyurethane is a volumetrically compressible material. Compared to other materials such as rubber, such volumetrically compressible materials have particular advantages, such as extremely high elastic deformation capacity and high durability.

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

[0017] A low percentage of primary hydroxyl groups is advantageous in preventing hydrolysis of the polyurethane component. Methods for determining the content of primary or secondary hydroxyl groups (also referred to as OH-groups) are known to those skilled in the art, for example from any of the following references:

[0018] Goodlett, VW 1965. 'Use of In Situ Reactions for Characterization of Alcohols and Glycols by Nuclear Magnetic Resonance', Analytical Chemistry, 37: 431-32. Hirama, Masahiro, and Tohru Oishi. 'Trichloroacetyl Isocyanate.' in, Encyclopedia of Reagents for Organic Synthesis. (Trichloroacetyl Isocyanate-Hirama-Major Refer-ence Works-Wiley Online Library). Meyer zur Heyde, Manfred. 1979. 'Neuere Anwendungen von Trichloracetylisocyanat in der 1H-NMR-Spektroskopie', Fresenius' Zeitschrift für analytische Chemie, 295: 125-42. Bose, AK, and PRSrinivasan. 1975. 'NMR spectral studies—XII: Trichloroacetylisocyanate as an in situ derivatizing reagent for 13C NMR spectroscopy ofalcohols,phenols and amines', Tetrahedron, 31: 3025-29.

[0019] In polymers produced by initiating the polymerization of propylene oxide with initiators such as those described above, the proportion of primary hydroxyl groups is low. These products are known as polypropylene ether polyols or polypropylene glycols.

[0020] In a preferred embodiment, the OH functional groups of the modified polyether polyol are at least partially reacted so that the OH number of the product is lower than that of the original polyether polyol. In a more preferred embodiment, the modified polyether polyol is reacted with acetic anhydride, acetyl chloride or oxalic acid dichloride to form an acetate or oxalic acid ester. The reaction by-products (acetic acid or HCl, respectively) are removed from the product.

[0021] In another preferred embodiment, the polyether polyol is at least partially reacted with other products which react with the alcoholic OH functions, ie dimethyl sulfate, methyl iodide or phenyl isocyanate, to a lower OH value than that of the original polyether polyol.

[0022] In a preferred embodiment, the lubricant coating has a viscosity greater than 0.8 mg / cm 2 , preferably between 1.5mg / cm 2 With 50mg / cm 2 between, more preferably between 1.5 mg / cm 2 With 10mg / cm 2 between, very preferably between 3 mg / cm 2 Up to 4 mg / cm 2 It has been found that such an area density of lubricant is advantageous for providing adequate damping performance while keeping the total amount of lubricant to be applied to the component to a suitable minimum.

[0023] In a first aspect, the present invention has been described with respect to a shock absorber arrangement according to the present invention. In another aspect, the present invention also relates to an auxiliary spring having an outer surface facing a damper cover of a shock absorber and an inner surface configured to receive a piston rod of the shock absorber, wherein the outer surface and / or the inner surface are at least partially coated with a lubricant.

[0024] The present invention achieves its underlying object in a helper spring, wherein the lubricant comprises or consists of a modified or unmodified polyether polyol. The helper spring according to the invention utilizes the same advantages as the shock absorber arrangement according to the invention. Therefore, preferred embodiments of the shock absorber arrangement are also preferred embodiments of the helper spring according to the invention, and vice versa.

[0025] In one embodiment, the polyether polyol comprises or consists of polypropylene glycol. In one embodiment, the polyether polyol comprises terminal hydroxyl groups containing hydrogen, and wherein, for the modified polyether polyol, the terminal hydroxyl groups are at least partially reacted such that the hydrogen is replaced by an organic substituent, in particular wherein the organic substituent is an alkyl, aryl or acyl group. Preferably, the OH value of the modified polyether polyol is lower than the OH value of conventional polyether polyols.

[0026] In a preferred embodiment, the auxiliary spring comprises or consists of polyurethane. Preferably, the polyurethane is a microporous polyurethane. In a preferred embodiment, the lubricant coating has a viscosity greater than 0.8 mg / cm 2 , preferably between 1.5mg / cm 2 With 50mg / cm 2between, more preferably between 1.5 mg / cm 2 With 10mg / cm 2 between, very preferably between 3 mg / cm 2 Up to 4 mg / cm 2 The area density between .

[0027] In another aspect, the present invention relates to a method for producing an auxiliary spring having an outer surface facing a damper cover of a shock absorber and an inner surface facing a piston rod of the shock absorber. The method achieves its underlying object by at least partially coating the outer surface and / or the inner surface with a lubricant, wherein the lubricant comprises or consists of a modified or unmodified polyether polyol.

[0028] In another aspect, the present invention relates to a method for manufacturing an auxiliary spring, comprising the steps of providing a mold for foaming the auxiliary spring therein; applying a release agent to the mold; foaming the auxiliary spring in the mold; applying a lubricant, wherein the lubricant comprises a modified or unmodified polyether polyol, and wherein the lubricant is applied to the mold together with the release agent and / or after applying the release agent and / or as part of a release agent formulation.

[0029] The method according to the invention utilizes the same advantages and preferred embodiments as the shock absorber arrangement and auxiliary spring according to the invention. Therefore, the preferred embodiments of the shock absorber arrangement and auxiliary spring are also preferred embodiments of the method according to the invention, and vice versa.

[0030] In another aspect, the present invention also relates to the use of a lubricant for reducing noise in a shock absorber arrangement comprising a shock absorber having a damper cover, a piston rod, and an auxiliary spring, the auxiliary spring being arranged opposite the shock absorber and having an outer surface facing the damper cover and an inner surface facing the piston rod, the auxiliary spring being configured to dampen movements of the shock absorber in the direction of the piston rod when in contact with the damper cover, wherein the outer surface and / or the inner surface are at least partially coated with the lubricant. The present invention achieves its underlying object in the use of a lubricant containing or consisting of a modified or unmodified polyether polyol.

[0031] In one embodiment, the polyether polyol comprises or consists of polypropylene glycol. In one embodiment, the polyether polyol comprises a terminal hydroxyl group containing hydrogen, and wherein, in the case of the modified polyether polyol, the terminal hydroxyl group is at least partially reacted such that the hydrogen is replaced by an organic substituent, in particular wherein the organic substituent is an alkyl, aryl, or acyl group. 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 a microporous polyurethane.

[0032] In yet another embodiment, the polyether polyol comprises terminal hydroxyl groups, and wherein less than 50% of the terminal hydroxyl groups are primary hydroxyl groups. In a preferred embodiment, less than 25% of the terminal hydroxyl groups are primary hydroxyl groups, preferably wherein in particular less than 10% of the terminal hydroxyl groups are primary hydroxyl groups.

[0033] Particularly preferred are microcellular polyurethane elastomers which, in a preferred embodiment, have a density of 200 kg / m 3 Up to 1,100kg / m 3 , preferably 300kg / m 3 Up to 800kg / m 3 This type of microporous polyurethane

[0034] Elastomers are also called volume compressible materials (also called volume compressible structural materials). Compared with other materials such as rubber, such volume compressible materials have particular advantages such as extremely high elastic deformation capacity and high durability.

[0035] The production process typically involves a reaction between an isocyanate and an isocyanate-reactive compound. Microcellular polyurethanes are typically produced in a mold, where the reactive starting components react with one another. The molds that can be used here are typically conventional molds, such as metal molds, whose shape ensures that the spring element has the three-dimensional shape of the present invention. In one embodiment, a foaming mold is used to produce the profile elements. In another embodiment, these are subsequently incorporated into a concentric main element. Another possible method is to use parts manufactured from semi-finished products. The production process can, for example, be water jet cutting.

[0036] Microcellular polyurethane products can be produced by well-known processes, for example by using the following starting materials in a single-stage or two-stage process:

[0037] (a) isocyanates,

[0038] (b) isocyanate-reactive compounds,

[0039] (c) water and optionally

[0040] (d) a catalyst,

[0041] (e) foaming agent and / or

[0042] (f) auxiliaries and / or additives, for example silicones and / or fatty acid sulfonates.

[0043] The surface temperature of the mold inner wall is typically 30°C to 110°C, preferably 50°C to 100°C. Advantageously, the molded article is produced by mixing the heated starting components at an NCO / OH ratio of 0.85 to 1.20 and introducing them into a heated mold, which is preferably tightly sealed, in an amount corresponding to the desired density of the molded article. After 1 to 60 minutes, the molded article has solidified and can therefore be removed from the mold. The reaction amount for the mixture introduced into the mold is typically calculated so that the resulting molded article has the aforementioned density. The starting components are typically introduced into the mold at a temperature of 15°C to 120°C, preferably 30°C to 110°C. The degree of compaction used to produce the molded article is in the range of 1.1 to 8, preferably 2 to 6. Advantageously, the microcellular polyurethane product is produced in an open or preferably closed mold using a "one-step" process, using high-pressure technology, low-pressure technology, or, in particular, reaction injection molding (RIM). Alternatively, a prepolymer process is used. The reaction is typically carried out by compaction in a closed mold. The reaction injection molding technology is described, for example, in H. Piechota and H. Rohr, “Integralschaumstoffe” [Integral foams], Carl Hanser-Verlag, Munich, Vienna 1975; D.J. Prepelka and J.L. Wharton, Journal of Cellular Plastics, March / April 1975, pp. 87-98; and U. Knipp, Journal of Cellular Plastics, March / April 1973, pp. 76-84.

[0044] According to the present invention, it has been recognized that, with a "dry" shock absorber arrangement and the simultaneous use of a volume-compressible material, such as microcellular polyurethane foam (see above), no or at least no very annoying noise emissions occur. It has also been recognized that, for example, noise emissions occur when the damper fluid flows out of the shock absorber and is distributed over the damper cover and / or piston rod, despite the fact that the damper fluid (typically mineral oil) generally has inherent friction-reducing properties. It has therefore surprisingly been found that the unwanted noise can be significantly reduced by adding a different lubricant than the damper fluid, which preferably also has a friction-reducing effect. In this way, the so-called paradox of the damper fluid itself causing annoying noise can be resolved. Water or a combination of water and damper fluid can have the same effect.

[0045] There are two ways to apply lubricant to the surface of the auxiliary spring: (1) during the foaming process, or (2) after the foaming process.

[0046] (1) During the manufacture of auxiliary springs, the mold surface is often pretreated with a release agent. In other cases, the mold surface is modified to provide a permanent or semi-permanent surface that is non-polar so that polyurethane does not adhere to it. A lubricant can be applied along with the release agent: (a) before applying the release agent, and / or (b) after applying the release agent, and / or (c) as part of the release agent formulation. It can also be applied to the modified mold surface.

[0047] In other words, in one embodiment, the lubricant is applied with the release agent applied to the mold surface during the manufacture of the auxiliary spring, before the release agent is applied, and / or after the release agent is applied, and / or as part of the release agent formulation.

[0048] (2) Alternatively, a lubricant may be applied to the surface of the auxiliary spring after the foaming process. In the method or use according to the invention, the lubricant may, for example, be sprayed and / or brushed or painted onto the auxiliary spring, or alternatively or additionally applied by dipping. If necessary, the lubricant may also be applied multiple times in this manner, or may be renewed after a predetermined period of time.

[0049] The present invention will be described below with reference to the accompanying drawings and by means of preferred working examples.

[0050] Figure 1a 、 Figure 1b is a shock absorber arrangement according to a preferred working example in different operating states,

[0051] Figure 2 Yes Figure 1a 、 Figure 1bA detailed description of the shock absorber arrangement, and

[0052] Figures 3a to 3c Is in different operating states based on Figure 1a 、 Figure 1b and Figure 2 Further detailed description of the shock absorber arrangement structure.

[0053] Fig. 1 shows a shock absorber arrangement 1. The shock absorber arrangement 1 comprises a shock absorber 3 having a damper cover 7 and a piston rod 5 extending through the damper cover 7.

[0054] Opposite to the damper cover 7, an auxiliary spring 9 is arranged along the piston rod 5. The auxiliary spring 9 is accommodated by a base 11.

[0055] The auxiliary spring 9 has an outer surface 13 which faces an outer surface 15 of the damper cover 7 .

[0056] During operation of the shock absorber arrangement 1, the movement of the damper may lead to the situation shown in FIG1B . In this situation, the outer surface 13 of the auxiliary spring 9 contacts the end surface 15 of the damper cover. If the shock absorber 3 continues to move, the auxiliary spring 9 performs an evasive movement, thereby causing the outer surface 13 to move relative to the end surface 15. Figure 2 and Figures 3a to 3c The functioning principle according to the invention which comes into effect subsequently is explained in more detail.

[0057] exist Figure 2 In FIG, the auxiliary spring 9 is first depicted in a partially broken away state. Figure 2 In the state shown, the auxiliary spring 9 is not compressed.

[0058] On the outer surface 13, the auxiliary spring 9 is at least partially coated with a lubricant 17, wherein the lubricant 17 contains or consists of a polyether polyol. In the working example shown, the lubricant 17 is also applied, for example, at least partially along the inner surface 21 of the auxiliary spring 9, wherein the inner surface 21 faces the piston rod 5. A gap 19 is present between the inner surface 21 and the piston rod 5.

[0059] When the auxiliary spring is compressed, Figure 1b As shown by way of example in FIG, auxiliary spring 9 expands radially (i.e., transversely to piston rod 5) in both outward and inward directions. Inner surface 21 then comes into contact with piston rod 5. Here, too, lubricant 17 offers advantages according to the present invention. Although the noise reduction effect is not as pronounced as when lubricant 17 is applied to outer surface 13, it still exists and is advantageous according to the present invention.

[0060] Figure 2The working examples should be considered illustrative, as the exclusive coating of the inner surface 21 (at least partially) and the exclusive coating of only the outer surface 13 (at least partially) are considered to be separately encompassed preferred embodiments.

[0061] Figures 3a to 3c The behavior of the lubricant 17 in different operating conditions is shown. To simplify the description, only the coating on the outer surface 13 is shown here. However, the concept can be roughly analogized to the behavior of the coated inner surface 21 relative to the piston rod 5 (see Figure 2 ).

[0062] exist Figure 3a In FIG. 1 , the auxiliary spring 9 is first shown in a state where the lubricant 17 is applied to the outer surface 13 but the auxiliary spring 9 has not yet come into contact with the damper cover 7. Due to the operation of the shock absorber, the damper fluid 23 has already accumulated on the end surface 15 of the damper cover 7. Figure 3a Initially, the auxiliary spring 9 is in contact with the damper cover 7 and the outer surface 13 will absorb some of the damper fluid 23. Subsequently, both the damper fluid 23 and the lubricant 17 are present on the outer surface 13.

[0063] Due to the additional presence of lubricant 17 , undesirable stick-slip effects are reliably reduced during ongoing operation.

[0064] Figure 3c The state after long-term operation or the state in which the outer surface 13 is only very slightly wetted by the lubricant 17 is shown. The amount of damper fluid 23 and lubricant 17 on the outer surface 13 is generally less than Figure 3b However, compared to a situation where the damper fluid 23 is present on the outer surface 13 but no additional lubricant 17 having properties different from the damper fluid 23 is present, a significant noise reduction can still be achieved with this arrangement.

[0065] A particular advantage of the present invention is that it can also be retroactively implemented in existing damper systems at little expense. Since a partial and / or very thin coating of the auxiliary spring 9 with lubricant 17 is sufficient for reliable noise reduction, any envisaged maintenance intervals for renewing the coating can be extended accordingly.

[0066] In this embodiment, the auxiliary spring 9 comprises or consists of microcellular polyurethane.

[0067] The polyether polyol comprises terminal hydroxyl groups, and less than 50% of the terminal hydroxyl groups are primary hydroxyl groups. In a preferred embodiment, less than 25% of the terminal hydroxyl groups are primary hydroxyl groups, preferably less than 10% of the terminal hydroxyl groups are primary hydroxyl groups.

[0068] The lubricant coating may have a viscosity greater than 0.8 mg / cm 2 , preferably between 1.5mg / cm 2 With 50mg / cm 2 between, more preferably between 1.5 mg / cm 2 With 10mg / cm 2 between, very preferably between 3 mg / cm 2 Up to 4 mg / cm 2 The area density between .

[0069] Next, the present invention will be further described through the following examples.

[0070] To determine the appropriate lubricant to prevent microporous polyurethane helper springs from making noise when rubbing against solid surfaces (such as plastic or metal), the additive was sprayed or coated onto the upper curved lip of a specific type of helper spring. In this case, 0.04g to 0.06g of the additive was used.

[0071] Use hard PVC or ABS as the surface. Screening tests have shown that the type of plastic used has virtually no influence on the noise generation. Tests were conducted on PC, POM and different PA types.

[0072] First, apply a drop of shock absorber oil to the end face 15 ( Figure 1a ).

[0073] Subsequently, the auxiliary spring 9 was repeatedly pressed against the end surface 15 and rotated about the piston rod 5, resulting in lateral movement along the piston rod 5 and rotational movement on the end surface 15 of the damper cover 7. This caused a squeaking noise in the untreated auxiliary spring. For comparison, an auxiliary spring whose outer surface 13 was treated with the additive was then tested in the same manner.

[0074] When repeating the measurement, one drop of shock absorber oil is applied each time to a new end face 15 of the damper cover 7 and the same auxiliary spring is tested again until the noise is observed.

[0075] Unsuitable additives already show noise development during the first or second measurement and are directly excluded, whereas effective additives fail only after 10 or more measurements.

[0076] Polypropylene glycol with a molecular weight between 7,200 g / mol and 9,000 g / mol ("polypropylene glycol 8,000") was identified as a suitable additive. In the above-described setup, the number of measurements until the first noise appeared was 21.

[0077] The compatibility of the additives with the microcellular polyurethane is then tested by comparing the tensile strength and elongation of the treated and untreated materials according to DIN EN ISO 1798. The purpose of the test is to determine the possible damage to the substrate caused by the action of the product on the substrate. In this case, the substrate is microcellular polyurethane.

[0078]

[0079] In a first step, at least eight test specimens PK1 were produced from a batch of substrates. A portion (at least four) of the test specimens was subjected to a tensile test ("original tensile strength") within ten days of production. Another portion (at least four) of the test specimens was stored in a test medium at 100°C for three days.

[0080] Afterwards, remove the specimen from the test medium. Drain and blot dry. After cooling for 30 to 60 minutes, perform a tensile test on the stored specimen (stored material) and compare the tensile strength or elongation at break. Specifically, compare the results with the initial values ​​of the untreated specimen.

[0081] A drop in tensile strength of more than 10% indicates incompatibility or accelerated material degradation, whereas an almost constant value can be considered a sign of compatibility. For reference, the tensile strength was determined to be 4.6 (standard deviation 0.3) N / mm 2 For the lubricant polypropylene glycol 8,000, the tensile strength was measured to be 5.2 (standard deviation 0.5) N / mm 2 When polypropylene glycol 8,000 was added to the test material, there was no decrease in its tensile strength.

Claims

1. A shock absorber arrangement (1) for a vehicle suspension, comprising a shock absorber (3) having a damper cover (7), a piston rod (5), and an auxiliary spring (9), which is arranged on the piston rod (5) opposite the shock absorber (3) and has an outer surface (13) facing the damper cover (7) and an inner surface (21) facing the piston rod (5), and is configured to dampen the movement of the shock absorber (3) in the direction of the piston rod (5) when in contact with the damper cover (7), wherein the outer surface (13) and / or the inner surface (21) are at least partially coated with a lubricant (17), It is characterized by: The lubricant (17) comprises modified or unmodified polyether polyol.

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

3. The shock absorber arrangement (1) according to claim 1 or 2, wherein the polyether polyol comprises terminal hydroxyl groups, and wherein for the modified polyether polyol, the terminal hydroxyl groups are at least partially reacted such that hydrogen is replaced by an organic substituent, in particular wherein the organic substituent is an alkyl, aryl or acyl group.

4. A shock absorber arrangement (1) according to any one of the preceding claims, wherein the polyether polyol comprises terminal hydroxyl groups, and wherein less than 50% of the terminal hydroxyl groups are primary hydroxyl groups, preferably wherein less than 25% of the terminal hydroxyl groups are primary hydroxyl groups, in particular wherein less than 10% of the terminal hydroxyl groups are primary hydroxyl groups.

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

6. The shock absorber arrangement (1) according to any one of the preceding claims, wherein the lubricant coating has a viscosity greater than 0.8 mg / cm 2 , preferably between 1.5mg / cm 2 With 50mg / cm 2 between, more preferably between 1.5 mg / cm 2 With 10mg / cm 2 between, very preferably between 3 mg / cm 2 Up to 4 mg / cm 2 The area density between .

7. An auxiliary spring (9) having an outer surface (13) facing the damper cover (7) of the shock absorber (3) and an inner surface configured to receive the piston rod of the shock absorber (3), wherein the outer surface (13) and / or the inner surface (21) are at least partially coated with a lubricant (17), It is characterized by: The lubricant (17) comprises modified or unmodified polyether polyol.

8. The auxiliary spring (9) according to claim 7, wherein the polyether polyol comprises terminal hydroxyl groups, and wherein for the modified polyether polyol, the terminal hydroxyl groups are at least partially reacted such that hydrogen is replaced by an organic substituent, in particular wherein the organic substituent is an alkyl, aryl or acyl group.

9. The auxiliary spring (9) according to claim 8, The auxiliary spring (9) comprises polyurethane, in particular microcellular polyurethane.

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

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

12. A method for manufacturing an auxiliary spring (9), comprising the steps of: - providing a mold for foaming the auxiliary spring (9) therein; - applying a release agent to the mold; - Foaming the auxiliary spring (9) in the mold; - applying a lubricant (17), wherein the lubricant (17) comprises a modified or unmodified polyether polyol, and wherein the lubricant is applied to the mold together with the release agent and / or after applying the release agent and / or as part of a release agent formulation.

13. Use of a lubricant (17) for reducing the noise of a shock absorber arrangement (1), the shock absorber arrangement comprising a shock absorber (3) having a damper cover (7) and a piston rod (5), and an auxiliary spring, the auxiliary spring being arranged opposite the shock absorber (3) and having an outer surface (13) facing the damper cover (7) and an inner surface (21) facing the piston rod (5), and the auxiliary spring being configured to dampen movements of the shock absorber (3) in the direction of the piston rod (5) when in contact with the damper cover (7), wherein the outer surface (13) and / or the inner surface (21) are at least partially coated with the lubricant (17), It is characterized by: The lubricant (17) comprises modified or unmodified polyether polyol.

14. The use according to claim 13, wherein the polyether polyol comprises terminal hydroxyl groups containing hydrogen, and wherein, for the modified polyether polyol, the terminal hydroxyl groups are at least partially reacted such that the hydrogen is replaced by an organic substituent, in particular wherein the organic substituent is an alkyl, aryl or acyl group.

15. The use according to claim 13 or 14, The auxiliary spring comprises polyurethane, in particular microcellular polyurethane.

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