FR3083161A1 - TIRE COMPRISING A TREAD - Google Patents

Abstract

The invention relates to a rubber material tire comprising a tread (1), said tread comprising at least two ribs (10A, 10B) separated by a circumferential groove (20). Each rib (10A, 10B) comprises a plurality of blocks of generally identical shape with at least two blocks (10A, 10B) of said plurality of blocks of different circumferential lengths (LA, LA '; LB, LB'). Each rib (10A, 10B) has a plurality of cutouts (13, 14, 15, 16) opening into said circumferential groove (20). The cutouts (13, 14) of the first rib (10A) open into the circumferential groove (20) at the same level as the cutouts (15, 16) of the second rib (10B). The cutouts (15, 16) of the second rib (10B) open into the circumferential groove (20) at the same level as the cutouts (13, 14) of the first rib (10A).

Description

TIRE COMPRISING A TREAD

TECHNICAL FIELD OF THE INVENTION

The present invention relates to a tire for a motor vehicle comprising a tread with at least one circumferential groove. TECHNICAL BACKGROUND OF THE INVENTION

A tire is known comprising a tread with at least two ribs separated by a circumferential groove. Each rib comprises a plurality of blocks of identical shape and of variable circumferential length. Each block generates noise when it passes through Taire de contact. The variation in block length in the ribs allows mixing of the noise generated by the blocks and avoids the emergence of a main harmonic. However, the presence of blocks of variable length in the ribs can degrade the overall aesthetics of the tire due to the non-alignment of said blocks between the two adjacent ribs.

There is therefore a need to propose a tire which is not very noisy when running while having an improved visual quality at the level of the tread.

SUMMARY OF THE INVENTION

The present invention aims to remedy this drawback.

The invention relates to a tire made of rubber material comprising a tread. The tread has at least two ribs separated by a circumferential groove. Each rib comprises a plurality of blocks of identical shape and of variable circumferential length L. Each rib has a plurality of cutouts opening onto said circumferential groove. According to a general characteristic, the cutouts of the first rib open into the circumferential groove at the same level as cutouts of the second rib and the cutouts of the second rib open into the circumferential groove at the same level as cutouts of the first rib .

By "pneumatic" is meant all types of elastic tires subjected to internal pressure or not.

By “rubber material” is meant a diene elastomer, that is to say in known manner an elastomer derived at least in part (that is to say homopolymer or a copolymer) from diene monomers (monomers carrying two carbon-carbon double bonds, conjugated or not).

By “tread” of a tire is meant an amount of rubber material delimited by lateral surfaces and by two main surfaces, one of which, called the tread surface, is intended to come into contact with a roadway when the tire rolled. The tread includes a plurality of cutouts which define the tread pattern of the tire. In the following description, it is agreed that the tread extends to the ends of the cutouts, on the border with the sidewall of the tire.

By "cutting" means an element which recesses in the tread. A cutout designates either a groove or an incision and corresponds to the space delimited by walls of material facing each other and distant from each other by a non-zero distance. What differentiates an incision from a groove is the value taken by this distance; in the case of an incision, this distance is less than or equal to 2 millimeters (mm). In the case of a groove, the distance between the walls is greater than 2 mm. Thus, the walls of this groove cannot come into contact with one another under the usual driving conditions.

By "circumferential" groove is meant a groove whose main direction of development is substantially in a circumferential direction. By definition, the circumferential direction is the direction which is tangent to any circle centered on the axis of rotation of the tire. This direction is perpendicular to both an axial direction and a radial direction. The radial direction is the direction which is perpendicular to the axis of rotation of the tire (this direction corresponds to the direction of the thickness of the tread). The axial direction is the direction parallel to the axis of rotation of the tire.

By a cutout opening into the circumferential groove "at the same level" as another cutout, it is meant that the cutouts are substantially aligned with each other at the circumferential groove. In other words, a straight line connecting the cutouts to each other in the circumferential groove is substantially parallel with the axial direction. There may be an offset between the outputs of the cutouts in the circumferential groove, but this offset is less than or equal to 1 mm, in said circumferential direction.

By "block" means an element in relief delimited by deep cutouts and comprising side walls and a contact face, the latter being intended to come into contact with a roadway during driving.

By “circumferential length” of a block is meant a measurement in the circumferential direction between two side walls of a block, these side walls being opposite each other side walls belonging to other blocks of the same rib. The circumferential length is measured at the center of the block.

By "rib" is meant a set of blocks which follow one another over the entire circumference of the tire.

According to other optional features for carrying out the invention:

- part of the cutouts of at least one of the ribs are shallow incisions. By "shallow depth" incision is meant an incision whose depth is less than or equal to 1 mm. For a shallow incision, the walls of said incision do not come into contact with each other under the usual driving conditions. Conversely, for a deep incision with a depth greater than 1 mm, the walls of said deep incision come into contact with one another under the usual driving conditions;

- the shallow incisions emerge in the circumferential groove at the same level as deep cutouts. By "deep" cut is meant a cut (groove or incision) whose depth is greater than 1 mm;

- the deep incisions widen on the contact surface of the tread;

- the shallow incisions open into the circumferential groove at the same level as the grooves;

- one of the ribs forms an edge of the tread.

BRIEF DESCRIPTION OF THE DRAWINGS

Other particularities and advantages will emerge clearly from the description which is given below, for information and in no way limitative, with reference to the appended drawings, in which:

FIG. 1 is a partial view of a tread of a tire according to the invention.

DETAILED DESCRIPTION OF AT LEAST ONE EMBODIMENT OF THE INVENTION

In Figure 1, identical or similar elements have the same references. The description of their structure and their function is therefore not systematically repeated.

In what follows, the orientations are the usual orientations of a tire. In particular, the "radial direction (Z)" is a direction which is perpendicular to the axis of rotation of the tire. In other words, this radial direction (Z) corresponds to the direction of the thickness of the tread. "Axial direction (Y)" is a direction parallel to the axis of rotation of the tire. "Circumferential direction (X)" is a direction that is tangent to any circle centered on the axis of rotation. This circumferential direction is perpendicular to both the axial direction and the radial direction.

FIG. 1 illustrates a part of a tread Id’ of a tire according to an embodiment of the invention. The tread includes:

- at least two ribs 10A, 10B;

- at least one circumferential groove 20.

Each rib 10A, 10B of the at least two ribs of the tread comprises a plurality of blocks 11 A, 11 A ’; 11B, 11B 'which follow one another on the circumference of the tread. The blocks are separated by deep cutouts, that is to say cutouts (grooves, incisions) whose depth is greater than 1 mm. For the same rib 10A, 10B, the blocks have an identical general shape. In other words, the blocks are the repetition of the same basic element with, for certain blocks, differences concerning one or more dimensions. For example in FIG. 1, for the same rib 10A, 10B, at least two blocks 11 A,

11A ’; 11B, 11B ’have circumferential lengths LA, LA’; LB, LB ’different. Each circumferential length LA, LA ’; LB, LB ’of a block is measured between two side walls of said block and in the center of said block. In this particular embodiment, the first rib 10A is one of the ribs most offset from the center of the tread. This rib 10A forms one of the edges 12 of the tread, at the border with the sidewall 17 of the tire. In more detail, the rib 10A comprises a succession of blocks 11A, 11A ’. These blocks 11A, 11A 'are here separated by cutouts 13 which have a depth greater than 1 mm and a width greater than 2 mm. These cutouts are then called grooves. The rib 10A also includes shallow incisions 14, that is to say cutouts of width less than or equal to 2 mm and of depth less than or equal to 1mm. The shallow incisions 14 are here generally parallel to the side walls of the blocks 11 A, 11 A ’. As already mentioned, the tread 1 also includes a second rib 10B adjacent to the first rib 10A. The second rib 10B comprises a succession of blocks 11B, 11B ’. These blocks 11B, 11B 'are here separated by cutouts 15 which have a depth greater than 1 mm and a width less than or equal to 2mm. These cutouts 15 are then called deep incisions. The deep incisions make it possible to reduce the overall rigidity of the rib and they improve the flattening of the tread 1. The cutouts 15 have here a curved shape on the surface of the tread. The second rib 10B also includes shallow incisions 16. The shallow incisions improve the overall appearance of the tread. These shallow incisions 16 also have a curved shape on the surface of the tread. In the nonlimiting embodiment illustrated in FIG. 1, each shallow incision 16 extends in the direction of a deep incision 15.

The ribs 10A and 10B are here separated by a circumferential groove 20. This circumferential groove 20 facilitates the evacuation of water out of the tread when driving on a wet roadway. The grooves 13, the shallow incisions 14 of the rib 10A as well as the deep incisions 15 and the shallow incisions 16 of the second rib 10B open into the circumferential groove 20. In addition, the grooves 13 of the rib 10A open in said circumferential groove 20 at the same level as the shallow incisions 16. In other words, the grooves 13 and the shallow incisions 16 face each other at the level of the circumferential groove 20. More particularly, the shallow incisions 16 are at the same level as the neutral fibers of the grooves 13 in the circumferential groove 20. By “neutral fiber” is meant a straight line which separates the groove 13 in its length, into two identical half-grooves. In addition, the shallow incisions 14 of the first rib 10A open into the circumferential groove 20 at the same level as the deep incisions 15 of the second rib 10B.

The cutouts 13, 14 of the first rib 10A thus open into the circumferential groove 20 at the same level as the cutouts 15, 16 of the second rib 10B and the cutouts 15, 16 of the second rib 10B open into the circumferential groove 20 to the same level as the cutouts 13, 14 of the first rib 10A. In other words, all the cutouts 13, 14 of the first rib 10A which open into the circumferential groove 20 are opposite with cutouts 15, 16 of the second rib 10B and all the cutouts 15, 16 of the second rib 10B which open into the circumferential groove 20 are vis-à-vis with cutouts 13, 14 of the first rib 10A.

In the nonlimiting embodiment illustrated in FIG. 1, the deep incisions 15 of the second rib 10B are widened near the contact surface of the tread. There is thus formed a chamfered zone comprising inclined walls.

The invention is not limited to the embodiment and variant presented and other embodiments and variants will become apparent to those skilled in the art.

Thus, in a nonlimiting embodiment, the ribs can include blocks which can take three different circumferential lengths.

Claims (6)

1. A tire made of rubber material comprising a tread (1), said tread comprising at least two ribs (10A, 10B) separated by a circumferential groove (20), each rib (10A, 10B) comprising a plurality of blocks of generally identical shape with for at least two blocks (10A, 10B) of said plurality of blocks of different circumferential lengths (LA, LA; LB, LB '), each rib (10A, 10B) comprising a plurality of cutouts (13, 14, 15, 16) opening into said circumferential groove (20) characterized in that the cutouts (13, 14) of a first rib (10A) of the at least two ribs (10A, 10B) open into the circumferential groove (20 ) at the same level as cutouts (15, 16) of the second rib (10B) and in that the cutouts (15, 16) of a second rib (10B) of the at least two ribs (10A, 10B) open out in the circumferential groove (20) at the same level as cutouts (13, 14) of the first rib (10A). 2. A tire according to claim 1, characterized in that a part of the cutouts (14, 16) of at least one of the ribs (10A, 10B) are shallow incisions. 3. A tire according to claim 2, characterized in that the shallow incisions (14, 16) open into the circumferential groove at the same level as deep cutouts (13, 15). 4. A tire according to claim 3, characterized in that deep incisions (15) widen on the contact surface of the tread (1). 5. A tire according to any one of claims 2 to 4, characterized in that shallow incisions (16) open into the circumferential groove (20) at the same level as grooves (13). 6. A tire according to any one of claims 2 to 5, characterized in that one of the ribs (10A) forms an edge (12) of the tread (1).