DE3042350A1 - Reducing noise level from tyres - lining interior with foam of specified youngs modulus density and thickness range - Google Patents

Abstract

A tyre has a sound-reducing layer of open-cell foam on part or all of its internal surface. The inside of the tread and/or of the sidewalls has foam with E-modulus less than 5 x 10 power 5 N/sq. m (measured dynamically) at -20 deg. + 80 deg. C, density at least 35 kg/cu. cm, air resistance of 50-300 Rayl/cm (5 x 10 power 5 - 3 x 10 power 4 Ns/m4), and at least 15 mm thick. The chemical compsn. of the foam is not critical; a suitable material is polyurethane, it can be applied separately to the inner tyre surface or foamed in situ. The system is effective with tubeless or inner tubed tyres. Construction reduces noise of movement and hence total vehicle noise without being expensive or heavy or affecting tyre properties, is esp. effective in the physiologically important frequency range of 500-2,500 Hz.

Description

Great efforts are made in the automotive industry.

taken to further the noise emission from moving vehicles to lower, which is a big one especially for the residents of busy streets This is a problem that is not only caused by road construction measures (choice of suitable Road surfaces, erection of noise barriers and fences).

The previous attempts at noise abatement on motor vehicles were largely limited to reducing drive noise. The driving noise of a motor vehicle is only predominant in very few operating states determined by the drive noises. The essential and usually predominant The noise component is the rolling noise of the vehicle; by this one understands that Sound of a vehicle rolling with the engine switched off. Illustrate this the following measured values for the respective proportions taken from the specialist literature of the rolling and driving noise at the peak level of a car in three different ways Operating states. The measurement was carried out at a distance of 7.5 m from the center of the vehicle and at a height of 1.7 m above street level: Drive operating status Rolling driving state of car level in dB (A) loo km / h, 4th gear on concrete 75.8 80.1 81.5 50 km / h, city traffic on asphalt 66.9 67.8 70.4 It follows that the reduction of rolling noise is of particular importance, with a reduction of around 5 dB (A) would already lead to a very considerable reduction in the burden on the environment. This Value is therefore used as an objective by the automotive and tire industries used as a basis in the development work.

There is some recent scientific research on it the causes of the rolling noises caused by the vehicle tires, cf. E.g. D. Denker in Automobil-Industrie "3/78, 17-23. It follows that for the noise causes are currently Mainly two hypotheses are discussed: 1. "Air pumping "through the tread and 2. tire vibrations emitting airborne sound, whereby far more importance was attached to the first hypothesis, but this was due to the more recent findings may be inaccurate. The practical ones also speak in favor of this Experience with changes to the tire treads, which only lead to very slight reductions in the noise level have led, although considerable efforts have been made in this area up to the most recent times have been undertaken (see DE-OS 29 o3 670, 29 o3 671, 29 o3 846 and 29 o5 o51).

From DE-OS 20 40 898 it is known, the inner surface of pneumatic vehicle tires or to equip air hoses in whole or in part with a sound-absorbing covering, where it is an (open-cell) foam or textile fiber covering.

The drawing shows that this coating is about 5 mm thick. He should serve to counteract the balloon reverberation effect inside the tire, that the sound-reflecting inner walls are sound-absorbing through the covering. Research has shown, however, that this way there is no noticeable reduction the tire rolling noise can be achieved, which is probably due to it is that Balion reverb effects do not play an essential role.

In DE-AS lo lo 398 there is a proposal to dampen noise to work in these thin plates or strips in tires, which are made of rubber or plastic with a high plasticizer content of up to 300%. Because of hers low modulus of elasticity, their low thickness, only a few millimeters, and the lack of air permeability of the possibly porous, but due to the production method in any case closed-cell deposits is the noise-reducing However, the effect is small. According to DE-PS 15 o5 877 should be a vehicle pneumatic tire a vibration-damping intermediate layer between the tread and the carcass be built into a homogeneous or cellular material. It arises from it an extremely complicated tire production without the desired vibration damping at the same time leads to a corresponding noise reduction.

In contrast, the invention is based on the object of providing suitable means to find effective structure-borne noise damping of pneumatic vehicle tires in order to address them Way the rolling noise and thus the overall noise level of moving vehicles to lower.

The measures must not be too costly and do not cause any impairment the other running and driving properties of the tires. With that in mind came it is above all a matter of finding means that effectively dampen structure-borne noise in the physiologically particularly important frequency range of around 300 to 5000, in particular allow 500 to 2500 Hz without those important for driving behavior To influence vibrations at lower frequencies noticeably. Finally was it is essential to avoid a noticeable increase in the weight of the vehicle tires, because in the automotive industry the general trend is to save weight in order to improve economy in terms of fuel consumption.

The invention relates to a pneumatic vehicle tire in which on the inside of the tread and / or the inside of the sidewalls of the tire an open-cell foam material, which is in the temperature range of -20 up to + 8o0C an elastic modulus of less than 5 105 N / m2 (measured dynamically on the foam), 3 a density of at least 35 kg / m and an air flow resistance of 50 to 300 Rayl / cm (5-104 to 3 105 Ns / m4), in a layer thickness of at least 15 mm is applied.

Preferably, the airflow resistance of the foam material lies between 80 and 150 Rayl / cm (8.104 to 4 1.5-105 Ns / m, measured according to DIN 52 213. The layer thickness of the foam material is preferably between about 15 and 50 mm and in particular about 20 to 30 mm.

The density of the foam is preferably between 3 approximately 35 and 300 kg / m, in particular 50 to 150, for example 100 kg / m³. That the density desired in each case can be adjusted in a known manner by adding inorganic Fillers such as carbon black, chalk, slate powder, kaolin, barium sulfate and others can be set.

The modulus of elasticity of the foam (measured dynamically in accordance with DIN 53 426 on the foamed material) should not exceed 5-10 N / m2 and preferably at about 1o5 to 5'10 N / m2.

The chemical composition of the foam material is not critical, as long as the parameters specified above are adhered to and in particular it is ensured that the modulus of elasticity is within the temperature range that occurs in practice from approx. -2o0C (with frost in winter) to approx. + 8o0C (warming of the tires with high Driving speed) is within the required values. A particularly suitable one The material is cross-linked polyurethane foam. There are also foams the end Natural rubber, chloroprem, acrylonitrile / butadiene / styrene or styrene / acrylonitrile rubber or similar elastomers or made of foamed polyvinyl chloride are useful.

The foam material can subsequently be applied to the inside of the finished Pneumatic vehicle tires are applied. It is essential for the effect that the foam is firmly glued to the inner surfaces, since a loosely inserted one Foam material does not provide the desired structure-borne sound insulation.

On the other hand, it is also possible during the tire manufacture an integrated foam layer by foaming up on the inside of the tire to produce which has the required material properties. This can then cut to the desired dimensions and at the same time from the Outer skin can be freed in order to achieve the required permeability.

It is known that one has to look for effective structure-borne noise damping coatings made of viscoelastic materials are required.

However, such materials are for the present purpose because of the strong temperature influence on their stability unsuitable. It is totally surprising and due to the current state of knowledge also not fully explainable, that with the help of a non-viscoelastic foam material in pneumatic vehicle tires an effective structure-borne sound attenuation can be achieved, as the measured values of the following Examples show. That it was actually the observed effect around structure-borne sound absorption, but not absorption of the air-borne sound inside the tire acts, proves, among other things, the fact that a loosely inserted, but foam material lying on the inner surfaces only has a minor effect shows and that a firm connection of the foam with the inner surfaces of the tire (e.g. by gluing) is essential for success.

The invention is particularly suitable for tubeless tires, however hoses can possibly also be inserted without the effect being lost The following example is intended to provide a more detailed explanation of the invention Results are shown graphically in the accompanying figures.

Example Flexible foam sheets of different thicknesses were made of crosslinked Polyurethane was used, which had the following characteristics: Volume weight in kg / m3 air flow resistance modulus in N / m2 stood in Rayl / cm A 300 115 4 105 B 50 11o 2.105 C 50 930 1o6 D 20 23 10 Experiment 1 In Figure 1 are the Loss factors depending on the frequency for the foam sheets A, B, C and D at 2o0C and a layer thickness of 30 mm each. It is clear, that with the materials A and B to be used according to the invention in the primarily interesting Frequency range above 500 Hz a significantly higher loss factor is achieved is considered to be with materials C (with too high a modulus of elasticity and air flow resistance) and D (with too low a density and too low an air flow resistance).

Experiment 2 The measured values shown in Figure 2 for the with the Foam material B glued tires show what is essential in practice extremely low temperature dependence of the damping; the measured values at 20 and 8o0C are almost identical.

Experiment 3 The foam material B was in layer thicknesses of 20, 30 and 40 mm used. The measured values shown in FIG. 3 show at increasing layer thickness a certain shift towards lower frequencies, but it is clear that a layer thickness of about 30 mm is sufficient to be particularly significant frequency range above 500 Hz to achieve considerable damping. In contrast, with a layer thickness of 4 mm, there is no loss factor at any frequency reached over o, ol, as a comparison measurement showed.

Experiment 4 It was the sound attenuation achieved on tires on a Acoustic test bench measured at room temperature on a steel roller at 100 km / h. A commercially available untreated tubeless tire (size 155 SR 13 on 5 inches Rims) had a noise level of 99.6 dB (A). A sticker on the inside the treads with a 40 mm thick foam sheet B led to a subsidence the level to 95.8 dB (A), with a complete covering with a 30 mm thick Foil of material B a further reduction to 93.6 dB (A) was achieved.

The measurement was carried out at a height of 420 mm at a distance of 560 mm from the tire.

Claims (4)

Pneumatic vehicle tires Patent claims Pneumatic vehicle tires, their inner surfaces completely or partially with a noise-reducing covering made of open-cell foam are provided, characterized in that on the inside of the tread and / or the insides of the sidewalls of the tire an open cell foam material, which in the temperature range between -20 and + 80 ° C has a modulus of elasticity of less than 5-105 N / m2 (measured dynamically ar foam), a density of at least 35 kg / m3 and an air flow resistance of 50 to 300 Rayl / cm (5-104 to 3,105 Ns / m), is applied in a layer thickness of at least 15 mm. 2. Pneumatic vehicle tire according to claim 1, characterized in that the foam material has a layer thickness of 15 to 50, in particular about 20 to 30 mm. 3. Pneumatic vehicle tire according to one of claims 1 or 2, characterized in that that the foam material subsequently applied to the inside of the tire is firmly connected to the inner surfaces, preferably glued. 4. Pneumatic vehicle tire according to claims 1 or 2, characterized in that that the tire inner surfaces with an integrated, produced in the tire manufacture Foam layer are provided.