WO2016046616A1

WO2016046616A1 - Tyre comprising a tread having a compressibility gradient

Info

Publication number: WO2016046616A1
Application number: PCT/IB2015/001660
Authority: WO
Inventors: José Merino Lopez
Original assignee: Compagnie Generale Des Etablissements 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: FR3026056A1; FR3026056B1

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 compressibility characteristics that vary from the centre to the shoulders, with an increase in compressibility from the centre towards the shoulders.

Description

TIRE HAVING A TREAD BAND COMPRISING A

GRADIENT OF COMPRESSIBILITY

TECHNICAL FIELD OF THE INVENTION [0001] The invention relates to a tire comprising two flanks, a crown provided radially outwardly of a tread, a carcass-type reinforcement structure, at least one crown reinforcement, and means enabling to reduce 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.

[0004] WO2012 / 161314 discloses a tire having a pair of rods, a toroidal carcass layer and extends between the pair of rods and a tread portion which has a road contacting surface. The document discloses a tire whose tread comprises a layer of foam material, this layer being present on the sides of the tread, but not in the central portion of the latter. Thus, the tread described has a discontinuity in the central zone which does not comprise foam material. DE3703480 describes a tire whose tread comprises a layer of foam material whose volume is greater than at least 10% of the volume of the entire tread. The elastomeric foam material consists of an elastomeric composition containing elastomeric components each having a glass transition threshold of not greater than -60 ° C. The document does not disclose compressibility characteristics that vary from center to shoulder with, from the center to the shoulders, an increase in compressibility.

WO2012146868 discloses a tire comprising a tread having a rolling layer consisting of a cellular material having a thickness E and an expansion ratio greater than or equal to 50%. The rolling layer has hollow carving elements. At least 95% of the hollow carving elements satisfy both of the following conditions: a) and b): a) a carving element is separated from at least one other hollow carving element by a distance of less than or equal to DP = 7 mm and b) the carving element has a depth of at least 80% of the thickness E of the rolling layer. The various embodiments presented comprise a foam layer whose composition is uniform over the entire running surface. 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 having a reduced sound level without significant deterioration of the rolling resistance characteristics.

[0010] Yet another object of the invention is to provide a tire with a reduced sound level, without significant deterioration of the wear characteristics.

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 comprising two sidewalls, a top provided radially externally with a strip of

15, said tread having a shoulder at each axial end, a carcass-type reinforcing structure, at least one crown reinforcement, the tread having an acoustic energy absorption layer extending from one shoulder to another and said layer being made of materials whose compressibility characteristics vary from center to shoulders, with an increase in compressibility from the center to the shoulders.

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 elimination of cavity noises.

According to an advantageous embodiment, the acoustic energy absorption layer comprises an absorbent material arranged in two zones of different levels of expansion. Advantageously, the two zones of different levels of expansion consist of a shoulder zone and a central zone, with a more expanded foam material in the shoulder zone than in the central zone of the tread area. . In an advantageous variant, the acoustic energy absorption layer also comprises a zone with a very high rate of expansion, provided radially internally to the shoulder zone and whose expansion rate is greater than that of the shoulder zone. of the shoulder area and the central area.

According to one embodiment, the area with a very high rate of expansion is arranged only at the shoulders, radially inwardly to the shoulder area.

According to another embodiment, the zone with a very high rate of expansion is distributed over the entire width of the tread, radially inwardly to the shoulder zone and the central zone. Advantageously, the shoulder zone comprises an inner axial extension radially interior to the central zone.

[0020] Also advantageously, the difference between the expansion rates of the different zones is at least 10% and more preferably greater than 20%.

Advantageously, the expansion rates are included, for the central zone between 30% and 40%, for the shoulder zone between 60% and 80%, and for the zone with a very high rate of expansion. between 80% and 100%, and preferably between 95% and 100%.

According to another advantageous embodiment, the absorption layer of the acoustic energy is composed of a usual mixture in the tire comprising an elastomer (such as NR, SBR, PB, etc.), a charge (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 materials: polyurethane, polyethylene, polypropylene, polyimide, polychloroprene, EPDM rubber, ethylene vinyl acetate, and mixtures thereof.

Advantageously, the acoustic energy absorption layer extends continuously from one shoulder to the other of the tire.

DESCRIPTION OF THE FIGURES

All the details of embodiment are given in the description which follows, supplemented by FIGS. 1 to 4, 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;

- Figure 3 is a schematic representation of a cross section of another embodiment of the tire according to the invention;

FIG. 4 is a schematic representation of a cross-section of an alternative embodiment of the example of FIG. 3.

DETAILED DESCRIPTION OF THE INVENTION

DEFINITIONS:

In this document, the term "foam" or "foam material", an elastomeric material comprising cells or bubbles more or less expanded, depending on the areas where they are arranged. Highly expanded cells have a higher acoustic damping potential than less expanded cells. By cons, the desired characteristics of low rolling resistance and wear, vary in the opposite direction. It is therefore advantageous to dispose the elastomer foams in a way that optimizes the noise reduction characteristics, while minimizing the losses of other characteristics also useful for the durability of the product and the qualities of behavior of the latter. Such a material can be manufactured for example as described in the application FR2974539, using a pore-forming agent comprising ρ, ρ'-oxybis ("benzene sulfonyl") hydrazide.

The term "cavity mode" means a vibratory mode in 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 air located at the 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, designated by the term "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 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. As illustrated in FIGS. 1 to 4, the acoustic energy absorption layer consists of materials whose compressibility characteristics vary from the center towards the shoulders with, from the center towards the shoulders, an increase compressibility. The layer 10 is made of foamed foam material. The level of expansion of the foam depends on the area of the layer.

In the example of Figure 1, the material of the acoustic energy absorbing layer 10 is arranged in two zones 11 and 12 each having a distinct level of expansion, that is to say a shoulder zone 11 surrounding a central zone 12 o 'on both sides. The foam material is more expanded in the shoulder zone 11 than in the central zone 12. In the example of FIG. 1, the expansion level of the foam material of the shoulder zone is substantially 70% and that the central area is approximately 35%. This type of architecture offers the double advantage of well containing the level of acoustic vibrations while

15 minimizing deterioration in rolling resistance and wear performance.

FIG. 2 illustrates an alternative embodiment of the example of FIG. 1 in which the shoulder zone comprises a portion radially inner to the central zone extending from one shoulder to the other while radially passing internally. at the central area. Expansion rates 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.

[0031] FIGS. 3 and 4 illustrate an alternative embodiment in which the foam material of the acoustic energy absorption layer 10 comprises a third zone 13, occupied by a high expansion foam material, provided radially internally to the shoulder zone 11. In the embodiment of Figure 3, this zone 13 of high expansion foam material extends axially only at the shoulders. In the variant illustrated in FIG. 4, this zone 13 of high expansion material is extended by one shoulder to the other, passing through the center. It is surmounted radially outwardly in the center by the central zone 12 of low expansion foam material, and at the shoulders by the shoulder zone 11 with an intermediate expansion foam material. According to various embodiments, different materials may be used to form the sound energy absorption zones. Advantageously 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 materials: polyurethane, polyethylene, polypropylene, polyimide, melamine, polychloroprene, EPDM rubber, ethylene vinyl coacetate 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 limit 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 variants are provided for different distributions of the respective zones, with more or less wide zones and / or 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 outwardly of a tread (4), said tread having a shoulder at each axial end, a reinforcing structure (5) of the carcass type, at least one crown reinforcement (6), characterized in that the tread comprises an acoustic energy absorption layer (10) extending from one shoulder to the other and in this respect that said layer consists of materials whose compressibility characteristics vary from center to shoulders with, from the center to the shoulders, an increase in compressibility.

2. A tire according to claim 1, wherein the layer (10) for absorbing acoustic energy comprises an absorbent material arranged in two zones (1 1, 12) of different levels of expansion.

A tire according to claim 2, wherein the two zones of different expansion levels consist of a shoulder zone (1) and a central zone (12), with a more expanded foam material in the shoulder zone ( ) than in the central area (12) of the tread.

4. A tire according to one of the preceding claims, wherein the acoustic energy absorbing layer (10) further comprises a zone (13) with a very high expansion rate, provided radially inwardly to the shoulder zone. (11) and whose expansion rate is greater than that of the shoulder zone (1) and the central zone (12).

5. The tire of claim 4, wherein the zone (13) with a very high expansion ratio is arranged only radially inwardly to the shoulder zone (1 1).

The tire according to claim 4, wherein the zone (13) with a very high expansion ratio is distributed over the entire width of the tread (10), radially inwardly of the shoulder zone (1 1) and at the central area (12).

7. The tire according to one of the preceding claims, wherein the shoulder zone (11) comprises an inner axial extension radially interior to the central zone (12).

8. A tire according to one of claims 1 to 7, wherein the difference between the expansion rates of the different zones (11, 12, 13) is at least 10% and more preferably greater than 20%.

9. A tire according to one of claims 1 to 8, wherein the expansion rates are comprised, for the central zone (12) between 30% and 40%, for the shoulder zone (11) between 60% and 80%, and for the zone with a very high expansion rate (13) between 80% and 100%, and preferably between 95% and 100%.

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, vulcanization 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.

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