WO2016156745A1

WO2016156745A1 - Tyre including a tread

Info

Publication number: WO2016156745A1
Application number: PCT/FR2016/050730
Authority: WO
Inventors: Marie-Hélène VANTAL; Quentin BONNETON; Serge TIBERIO; Michel Montarras; Kazutaka YOKOKAWA
Original assignee: Compagnie Generale Des Etablissements Michelin; Michelin Recherche Et Technique S.A.
Priority date: 2015-04-01
Filing date: 2016-03-31
Publication date: 2016-10-06
Also published as: FR3034356B1; FR3034356A1

Abstract

The invention relates to a tyre including a tread (1) comprising a plurality of blocks (3) separated by grooves (5), each block (3) including a contact surface (7) intended for engaging with the ground and at least one complex incision (9) with a depth P and a length L defined by two rubber walls facing one another. Every wall of at least one complex incision (9) comprises an alternation of bumps (11) and recesses (13) extending from the contact surface of the block to a depth Pa lower than the depth P. The alternations of bumps and recesses of the two walls defining the complex incision are complementary so that the space between same is constant overall in said alternation area. The complex incision widens from the depth Pa to form a recess (15) with width W extending in the length L.

Description

PNEUMATIC COMPRISING A TREAD

FIELD OF THE INVENTION [01] The present invention relates to a tire comprising a tread for a pneumatic tire of the snow tire type. More particularly, the invention relates to a tire comprising a plurality of complex incisions.

STATE OF THE ART [02] A tire for winter driving, called a snow tire, comprises in a manner known per se a tread provided with a plurality of incisions. This addition of incisions in the tread of a tire has, in particular, been disclosed in the document FR759592 and its addition FR43383.

[03] The incisions delimit on the tread rubber blades having ridges able to scratch the snow during a taxi on a snow-covered road, which improves the grip on this road. The action of the ridges on the road is all the more important when the tread is in new condition. Indeed, in this state, the rubber blades have a large slenderness, that is to say a great height for a small width relative to this height. Thus, when the blades penetrate the footprint of the contact with the roadway, they fall over. The pressures exerted by the edges of the blades on the road are then increased. Such a phenomenon is particularly illustrated in FIG. 3 of document FR2418719.

[04] With the wear of the tread, the height of the blades decreases and the deformation of these blades, when they penetrate the contact footprint, also decreases. As a result, the scraping effect of the edges decreases with the wear of the tread. [05] There is therefore a need to improve the grip of snow tires, especially at the end of life, while maintaining or even improving their overall mechanical strength.

DEFINITIONS

[06] "Pneumatic" means all types of elastic bandages subjected to internal pressure or not.

[07] "Tread" of a tire means a quantity of rubber material delimited by lateral surfaces and by two main surfaces, one of which is intended to come into contact with a roadway when the tire is rolling.

[08] "Incision" means a cut-out generating opposite material walls. The distance between the material walls of the incision is appropriate to allow the at least partial contact of these walls during the passage in the footprint of contact with the ground.

[09] By "complex incision" is meant a cut-out comprising at a certain depth an enlargement intended to form a groove.

[10] "Simple incision" means a cutout having a constant thickness throughout its depth. [11] "Groove" means a cutout generating opposite material walls. The distance between the material walls of the groove is such that these walls can not come into contact with one another under normal rolling conditions.

[12] By "block" is meant a raised element delimited by grooves and comprising side walls and a contact surface, the latter being intended to come into contact with a ground while driving. SUMMARY OF THE INVENTION

[13] The invention relates to a tire having a tread. The tread comprises a plurality of blocks separated by grooves, each block having a contact surface intended to come into contact with a ground and at least one complex incision of depth P and length L, each complex incision being delimited by two rubber walls opposite. For at least one complex incision of length L, each wall delimiting this complex incision comprises an alternation of bumps and depressions in the length L of this complex incision. The alternation of bumps and depressions extends from the contact surface of the block to a depth Pa less than the depth P of the complex incision. The alternations of bumps and depressions of the two walls defining the complex incision are complementary so that the space between these walls is generally constant in this zone of alternation. The complex incision widens from the depth Pa to form a depression. This depression extends into the length L of the complex incision so that the complex incision has a width W in this area of depression.

[14] The enlargements in the complex incisions make it possible to generate grooves on the surface of the tread when this tread reaches a certain level of wear. These grooves are reservoirs able to evacuate water on a wet pavement or to store snow on a snow-covered road. This makes it possible to guarantee the adhesion of the tire on a wet pavement or a snow-covered road, even in a state of advanced wear of the tread. However, the presence of an enlargement in the complex incision makes the gum block less rigid in the area of rubber present around this complex incision, especially when the tire is in new condition. This block is then more sensitive to major deformations that can cause cracks in the bottom of the incision. By the use of humps and recesses present in a complementary manner on the walls of the incision, more particularly on the upper part of this incision, the relative movements of the walls of the incision are limited relative to one another. other. In this way, the rigidity of the block is increased by attenuating the shear phenomena that apply to this block, especially when turning. In addition, the fact that enlargement starts from the depth Pa, that is to say at the end of alternations of bumps and depressions maximizes the useful parts of the incision, that is to say the area of alternations of bumps and hollows, as well as the enlargement area. There is therefore not at the level of the incision, of intermediate part between the zone of alternations and the zone of widening. [15] The total depth P of the complex incision is, in general, about 8mm. The depth Pa represents 20 to 80% of the total depth P of the complex incision, preferably less than 50%.

[16] In a preferred embodiment, the bumps and depressions gradually attenuate near the depth Pa. The attenuation is such that the connection zone between the corrugated zone and the driving zone is rectilinear.

[17] In this way, it is ensured that the transition between the alternating zone of the complex incision and the driving zone of this complex incision is progressive. This provides a more regular form of wear.

[18] In an alternative embodiment, the tire comprises a plurality of studs extending from the recesses, in the alternating zone, said pads locally decreasing the distance between the two walls of the complex incision.

[19] The presence of pads in the complex incision decreases the closing time of the complex incision when it enters the area of contact with the ground. In this way, optimal block stiffness is reached more quickly in the contact area. In an alternative embodiment, the bumps and the recesses of the complex incision form a first corrugated trace of amplitude A on the contact surface of the block. This amplitude A is less than or equal to the width W of the complex incision measured in the depression zone. This optimizes the operation of the complex incision, especially in case of high shear on the block. An amplitude A greater than the width W would have the disadvantage of locally generating a non-regular form of wear.

[21] In an alternative embodiment, the block comprises at least one simple incision adjacent to the complex incision, said single incision extending in the depth of the block beyond the depth Pa and at most up to the level where the complex incision has maximum enlargement. In this way, the rate of notching of the blocks is increased in the new state, which improves the snow adhesion performance of the tire. At the end of life, the notching is brought by the widening of the complex incision which is then at its maximum. The use of simple incisions at this level of wear is no longer necessary because the evacuation of snow or water is provided by the complex incision. In addition, by limiting the depth of the simple incisions in the depth of the tread, it maintains a certain rigidity of the block.

[23] In an alternative embodiment, the single incision forms a second corrugated trace on the contact surface of the block, the first corrugated trace of the complex incision and the second corrugated trace of the single incision having an identical shape.

[24] In this way, an aesthetic continuity of the corrugated traces on the surface of the tread is ensured.

[25] In an alternative embodiment, the first corrugated trace of the complex incision and the second corrugated trace of the single incision are in phases. [26] This facilitates the release of the tire from the mold.

[27] In an alternative embodiment, the first corrugated trace of the complex incision and the second corrugated trace of the single incision are out of phase.

[28] Each incision complex or simple, is molded from a lamella housed in a mold. By providing out-of-phase corrugated traces, expanded spaces are created between these corrugated traces but also between the lamellae housed in the mold able to mold these corrugated traces. These enlargements allow to insert between the slats venting systems, ensuring better evacuation of air out of the mold during molding.

BRIEF DESCRIPTION OF THE DRAWINGS

[29] Other features and advantages of the invention will become apparent from the following description, given by way of example, without limitation, with reference to the accompanying drawings, in which: FIG. 1 represents a partial view of the tread surface of a tread of a tire according to the invention; FIG. 2 diagrammatically represents a complex incision of the tire of FIG. 1, according to a first sectional view, made in the length of the complex incision; FIG. 3 diagrammatically represents the complex incision of the tire of FIG. 1, according to a second sectional view; FIG. 4 represents a complex incision of the tire of FIG. 1, according to a second variant embodiment; FIG. 5 represents a third variant embodiment of the invention; FIG. 6 represents a fourth variant embodiment of the invention; FIG. 7 represents a fifth variant embodiment of the invention.

[30] In the following description, substantially identical or similar elements will be designated by identical references. [31] The tread 1 illustrated in Figure 1, comprises several blocks 3. Each block 3 is separated by grooves 5, comprises a contact surface 7 and at least one complex incision 9. The complex incisions 9 comprise two walls 10 facing each other which are corrugated on the side of the surface with an alternation of recesses 13 and bumps 11. The recesses 13 and the bumps 11 are preferably symmetrical with each other, that is to say say that with respect to a plane of symmetry of the complex incision 9, the recesses 13 and the bumps 11 have identical dimensions.

[32] We see in Figure 2, one of the walls 10 of the complex incision 9 with depressions 13 and bumps 11. The recesses 13 and the bumps 11 are reduced to a depth Pa to which the wall 10 becomes straight. Below the depth Pa, the complex incision 9 widens to define a depression or enlargement also called "drop of water". Here, it is constituted by a first inclined portion 150, a second vertical portion 151 or perpendicular to the running surface and a horizontal portion 152 or parallel to the running surface. The rectilinear part of the wall 10 constitutes a connection zone between the corrugated part and the depression 15 [33] The recesses 13 and the bumps 11 of the complex incision 9 define a ripple of amplitude A. The sides of the recesses 13 and bumps 11 may be rounded to facilitate demolding.

[34] The depression 15 has a width W at the bottom according to the horizontal portion 152 (see Figure 3). This width W is preferably greater than or equal to the amplitude A of the corrugated portion of the complex incision 9, which facilitates the demolding of the tire.

[35] In the variant shown in Figure 4, the recesses 13 have studs 19 embossed, here circular, but any other shape is possible (oval, rectangular, square, triangular ...). These pads 19 will locally reduce the space between the two walls 10 of the complex incision 9 and thus reduce its closing time and improve its rigidity.

[36] In Figure 5, a single incision 21 is made next to the complex incision 9. This simple incision 21 is rectilinear, has a depth Ps and has parallel walls with respect to each other. Its depth Ps is preferably greater than the depth Pa, but deep down stops at the beginning of the vertical portion 151 of the depression 15. The notching of the blocks 3 in the new state is thus maximum, and end of life it is the complex incision 9 which is maximum without requiring additional notching. The single incision 21 is placed outside the area of the depression 15 so as not to create a rupture zone between the two incisions.

[37] Figure 6, the complex incision 9 and the single incision 21 are corrugated, of the same amplitude A and in phase. The corrugations of the single incision 21 are made to be outside the area of the recess 15. [38] In FIG. 7, the complex incision 9 (here in the center) and the simple incisions 21 are corrugated. , of the same amplitude A and in opposition of phase. The corrugations of the single incision 21 are outside the area of the depression 15.

[39] The invention is not limited to the examples described and shown and various modifications can be made without departing from its scope. [40] In a particular embodiment, the shape of the single incision

21 varies in the depth of the tread. A corrugated trace on the tread surface, the single incision 21 can become linear at its base.

[41] In another embodiment, the tread comprises a plurality of studs in the single incision, these pads locally decreasing the distance between the two walls of the single incision.

[42] Figure 1 shows complex incisions 9 crossing through their respective block. Alternatively, it is possible that the complex incisions 9 only open onto a single block side wall. One of the ends of the complex incisions is then bridged.

Claims

A tire having a tread (1), said tread (1) comprising a plurality of blocks (3) separated by grooves (5), each block (3) having a contact surface (7) for contacting a floor and at least one complex incision (9) of depth P and length L, each complex incision (9) being delimited by two rubber walls facing each other, characterized in that for at least a complex incision (9), each wall delimiting this complex incision comprises an alternation of bumps (11) and recesses (13) in the length L of this complex incision (9), said alternation extending from the contact surface ( 7) of the block to a depth Pa less than the depth P of the complex incision, the alternations of bumps and depressions of the two walls delimiting the complex incision being complementary so that the space between these walls is generally constant in this zone of alternations and in that the complex incision expands from the depth Pa to form a depression (15), said depression (15) extending in the length L of the complex incision (9) so that the complex incision (9) has a width W in this depression area.

2. A tire according to claim 1, characterized in that the bumps (11) and the depressions (13) gradually attenuate near the depth Pa.

3. A tire according to one of claims 1 to 2, characterized in that the tire comprises a plurality of studs (19) extending from the recesses (13) in the zone of alternations, said pads locally decreasing the distance between the two walls of the complex incision.

4. A tire according to any one of claims 1 to 3, characterized in that the bumps (11) and recesses (13) of the complex incision (9) form a first corrugated trace of amplitude A on the surface of contact (7) of the block, said amplitude A being less than or equal to the width W of the complex incision measured in the area depressing (15).

Pneumatic tire according to one of claims 1 to 4, characterized in that the block (3) comprises at least one simple incision (21) adjacent to the complex incision (9), said single incision (21) extending in the depth of the block beyond the depth Pa and at most up to the level where the widening of the complex incision (9) has a maximum widening.

Pneumatic tire according to claim 5, characterized in that the single incision (21) forms a second corrugated trace on the contact surface of the block, the first corrugated trace of the complex incision (9) and the second corrugated trace of the single incision (21) having an identical shape.

7. A tire according to claim 6, characterized in that the first corrugated trace of the complex incision (9) and the second corrugated trace of the single incision (21) are in phase.

8. A tire according to claim 6, characterized in that the first corrugated trace of the complex incision (9) and the second corrugated trace of the single incision (21) are out of phase.