WO2016046615A1

WO2016046615A1 - Tyre comprising a tread having a stiffness gradient

Info

Publication number: WO2016046615A1
Application number: PCT/IB2015/001659
Authority: WO
Inventors: José Merino Lopez
Original assignee: Compagnie Générale Des Établissements Michelin; Michelin Recherche Et Technique S.A.
Priority date: 2014-09-22
Filing date: 2015-09-21
Publication date: 2016-03-31
Also published as: FR3026055B1; FR3026055A1

Abstract

The invention relates to a tyre (1) comprising two sidewalls (2), a crown (3) provided radially externally with a tread (4), a carcass-type reinforcing structure (5), and at least one crown ply (6), the tread comprising an acoustic energy absorption layer (10) extending from one shoulder to the other and made from materials having stiffness characteristics that vary from the centre to the shoulders, with a reduction in stiffness from the centre towards the shoulders.

Description

TIRE WITH BEARING BAND HAS A GRADIENT OF RIGIDITY

TECHNICAL FIELD OF THE INVENTION

The invention relates to a tire having two sidewalls, a crown provided radially outwardly of a tread, a carcass-type reinforcement structure, at least one crown reinforcement, and means for reducing rolling noise. .

STATE OF THE PRIOR ART

[0002] Tires provided with devices or means for reducing rolling noise are known. Most of the time, noise attenuators are foam with many porosities and are arranged either against the inner wall of the tread or against the rim. These inserts, because of their large volume, have a substantially large mass. They also constitute an additional component at the wheel. [0003] EP 2554617 discloses a tire provided with a layer of anti-noise foam glued inside the tire, under the tread. A silicone adhesive is applied to the receiving surface prior to application of the foam layer. The two-stage application process, the step of applying the foam layer involves tedious handling of a difficult to handle layer, is complex, expensive and subject to hazards.

The application WO2012161314 describes a tire comprising a pair of rods, a toroidal carcass layer and extends between the pair of rods and a tread portion which has a surface contact with the road. The tread portion includes a central section that does not include a foam rubber layer, and an outer section that includes the foam rubber layer. Compressibility levels between the center and

CONFIRMATION C0PY the shoulder differs but the center, being devoid of foam, is also devoid of the absorption properties of the latter.

There is therefore a need for a tire with rolling noise attenuation characteristics that do not have the drawbacks of current solutions. There is also a need for a tire provided with means to reduce the impact of rolling noise without affecting the mass of the wheel.

To overcome these disadvantages, the invention provides different technical means.

SUMMARY OF THE INVENTION

First, a first object of the invention is to provide a tire having a reduced noise level.

Another object of the invention is to provide a tire with a reduced noise level, without significant deterioration of the rolling resistance characteristics.

Yet another object of the invention is to provide a tire having a reduced noise level, without significant deterioration of the characteristics related to wear. Another object of the invention to provide a tire having a reduced noise level without significant increase in mass.

To do this, the invention firstly provides a tire having two sidewalls, a crown provided radially outwardly of a tread, said tread having a shoulder at each axial end, a reinforcing structure of carcass type, at least one crown reinforcement, the tread comprising an acoustic energy absorption layer extending from one shoulder to the other, said layer being made of materials of which the rigidity characteristics vary from the center towards the shoulders with, from the center towards the shoulders, a decrease in rigidity, said acoustic energy absorption layer comprising a material arranged according to two zones of levels of rigidity and hardness different, the difference between the hardness levels of the different zones being at least 10 Shore A units between each zone.

The presence of the anti-noise layer allows a reduction of the internal noise level (often referred to as the "Road Noise") perceived by the end user. At the same time, there is a reduction or suppression of cavity noise.

According to an advantageous embodiment, the difference between the hardness levels of the different zones is greater than 15 Shore A units between each of the zones.

In an advantageous variant, the hardness level is included for the central zone between 60 and 70 Shore A and preferably 65 Shore A, and for the shoulder zone between 40 and 60 Shore A, and preferably 50 Shore. AT.

According to yet another advantageous embodiment, the acoustic energy absorbing layer is composed of a usual mixture in the tire comprising an elastomer (such as NR, SBR, PB, etc.), a charge (such as black carbon or silica), plasticizers (such as resins or oils), vulcanizing additives or other materials such as thermoplastics, or one or more of the following: polyurethane, polyethylene, polypropylene, polyimide, polychloroprene, EPDM rubber, ethylene vinyl coacetate and mixtures thereof.

The absorption layer of the acoustic energy preferably extends continuously from one shoulder to the other of the tire. In an advantageous embodiment, the area of lower stiffness extends continuously from one shoulder to the other passing radially inwardly with respect to the higher stiffness layer.

According to another advantageous embodiment, the thickness of the area of lower rigidity is less than that of the zone of higher rigidity.

DESCRIPTION OF THE FIGURES

All the details of embodiment are given in the description which follows, supplemented by FIGS. 1 and 2, presented solely for purposes of non-limiting examples, and in which:

- Figure 1 is a schematic representation of a cross section of a first example of a tire according to the invention;

FIG. 2 is a schematic representation of a cross section of an alternative embodiment of the example of FIG. 1.

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DETAILED DESCRIPTION OF THE INVENTION

DEFINITIONS

In the present document, the term "cavity mode" means a vibratory mode according to which the rolling of a tire on a surface having macro roughness causes an excitation of the tire structure, but also an excitation of the tire. air located inside the tire cavity. The air column present inside the cavity of the tire vibrates according to its natural excitation mode or modes. The first natural mode, referred to as the "first cavity mode", is generally between 200 Hz and 250 Hz for a motor vehicle tire, depending on the size of the tire. During the resonance, there is creation of an acoustic pressure on the mounted assembly comprising a wheel and a tire that can cause the vibration of this mounted assembly. These vibrations are then transmitted to the center of the wheel, then to the cabin, by means of a propagation by the structure of the wheel. vehicle. Since this is a structural sound vibration, the vehicle structure can have a significant influence on overall performance.

Figure 1 is a schematic representation of an embodiment of a tire 1 according to the invention, shown in cross section. The two sides 2 are surmounted by a vertex 4. A carcass-type reinforcement structure 5 maintains the assembly, while one or more crown reinforcement 6 are provided to reinforce this area of the tire. The portion of the radially outer tread, that is to say the one in contact with the running surface during running, comprises a layer 10 (or an arrangement) for absorbing the acoustic energy. This layer extends continuously from one shoulder to the other, through the center of the tread. Such continuity ensures maximum efficiency, avoiding that the energy can pass through a possible discontinuity.

According to the invention, the acoustic energy absorbing layer 10 is made of materials whose stiffness characteristics vary from the center to the shoulders with, from the center to the shoulders, a decrease in rigidity. This provides a good compromise to achieve a good level of absorption of acoustic energy while ensuring good rigidity of the central area to minimize wear and rolling resistance.

In the example of Figure 1, the material of the acoustic energy absorbing layer 10 is arranged in two areas 1 1 and 12 each having a distinct level of rigidity, a shoulder zone 11 surrounding a central zone 12 on either side. The level of rigidity is lower in the shoulder zone 11 in comparison with that of the central zone 12. In the example of FIG. 1, the hardness of the material of the shoulder zone is substantially 50 shore A and the the central zone is approximately 65 shore A. This type of architecture offers the double advantage of well containing the level of acoustic vibrations while minimizing the deterioration of rolling resistance and wear performance. 2 illustrates an alternative embodiment of the example of Figure 1 wherein the shoulder zone has a radially inner portion to the central zone extending from one shoulder to the other passing radially inwardly to the central area. The hardness levels of the materials are similar to those mentioned above. This variant is an advantageous compromise with regard to the desired characteristics of low rolling resistance and low level of wear.

According to various embodiments, different materials may be used to form the areas. Advantageously used is one or more mixtures typically used for the implementation of tires, comprising an elastomer (such as NR, SBR, PB, etc.), a filler (such as carbon black or silica), plasticizers (such as resins or oils), vulcanizing additives or other materials such as thermoplastics, or one or more of the following: polyurethane, polyethylene, polypropylene,

Polyimide, melamine, polychloroprene, EPDM rubber, ethylene vinyl acetate, and mixtures thereof. Each zone may consist of one or more materials. Areas of several types and / or shapes and / or profiles and / or dimensions can be applied to the same tire. The figures and their descriptions made above illustrate the invention rather than limiting it. In particular, the invention and its various variants have just been described in connection with a particular example comprising an arrangement at the tread of the tire.

Nevertheless, it is obvious to a person skilled in the art that the invention may be extended to other embodiments in which, in variants, different distributions of the respective zones are provided, with more or less wide zones and / or thick, etc., depending on the characteristics sought.

The reference signs in the claims are not limiting in nature. The verbs "understand" and "include" do not exclude the presence of elements other than those listed in the claims.

Claims

1. A tire (1) comprising two sidewalls (2), a crown (3) provided radially on the outside with a tread (4), said tread

A bearing having a shoulder at each axial end, a carcass-type reinforcement structure (5), at least one crown reinforcement (6), the tread comprising an acoustic energy absorption layer (10); extending from one shoulder to the other, said layer being made of materials whose stiffness characteristics vary from center to shoulders with a decrease in rigidity in the center to the shoulders, said layer ( 10) of acoustic energy absorption comprising a material arranged in two zones (11, 12) of different levels of stiffness and hardness, characterized in that the difference between the hardness levels of the different zones is at least 10 Shore A units between each zone.

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2. A tire according to claim 1, wherein the difference between the hardness levels of the different zones is greater than 15 Shore A units between each zone. 0

Tire according to one of claims 1 or 2, wherein the hardness level is included for the central zone (12) between 60 and 70 Shore A and preferably 65 Shore A, and for the shoulder zone (1 ) between 40 and 60 Shore A, and preferably 50 Shore A.

The tire according to one of the preceding claims, wherein the acoustic energy absorbing layer is composed of a usual mixture in the tire comprising an elastomer, a filler, plasticizers, vulcanizing additives or other materials such as thermoplastics, or one or more of the following materials: polyurethane, polyethylene, polypropylene, polyimide, polychloroprene, EPDM rubber, ethylene vinyl acetate, and mixtures thereof.

5. A tire according to one of the preceding claims, wherein the layer (10) for absorbing acoustic energy extending continuously from one shoulder to the other of the tire.

6. A tire according to one of claims 1 to 5, wherein the zone (11) of lower stiffness extends continuously from one shoulder to the other passing radially inwardly with respect to the layer (2). of higher rigidity.

7. A tire according to one of claims 1 to 5, wherein the thickness of the zone (11) of lower stiffness is lower than that of the zone (12) of higher rigidity.