DEVICE FOR ATTENUATING ROLLING NOISE FOR A TIRE

Abstract

The subject of the disclosure is a tread for a tire, this tread having a tread surface intended to come into contact with a roadway and comprising at least one groove of width W and depth P delimited by two facing lateral walls, these lateral walls being connected together by a groove bottom. At least one groove has a plurality of closing devices for reducing the running resonance noise generated by this groove, each closing device comprising at least two flexible blades, a first flexible blade secured to the bottom of the groove and intended to flex around a first axis, and a second flexible blade secured to a lateral wall delimiting the groove and intended to flex around a second axis, the first flexible blade connected to the bottom having a maximum height H.

Claims

1. A tread for a tire, comprising: a tread surface including at least one groove of depth P delimited by two facing lateral walls, the two facing lateral walls being connected together by a groove bottom, at least one groove with a plurality of closing devices for reducing the running resonance noise generated by the at least one groove, each closing device comprising at least two flexible blades, a first flexible blade secured to the bottom of the groove and able to flex around a first axis, and a second flexible blade secured to a lateral wall delimiting the groove and intended to flex around a second axis, the first flexible blade connected to the bottom having a maximum height H, wherein the flexible blades are configured such that they have geometries to cooperate with one another to close at least 70% of the cross section of the groove, and the thickness of the first flexible blade is carried by the groove bottom is less than the thickness of each second flexible blade carried by a lateral wall. The tread according to claim 1, wherein the maximum height H of the flexible blade fixed to the bottom is at most equal to 80% of the depth P of the groove.

3. The tread according to claim 1, wherein the first flexion axis of the first flexible blade is perpendicular to the second axis of the second flexible blades.

4. The tread according to claim 1, wherein the flexible blades have an edge that makes a non-zero average angle with a direction tangential to the tread surface in the new state.

5. The tread according to claim 4, wherein the average angle of the internal edge of the second flexible blades is at least equal to 20° to a transverse direction.

6. The tread according to claim 1, wherein the flexible blades of the device cooperate to close the cross section of the groove over at least 90% of this cross section.

7. The tread according to claim 1, wherein the noise reducing device formed in a groove comprises a first flexible blade of triangular geometry connected to the bottom of the groove and at least one second flexible blade which is carried on a lateral wall and the geometry of which is complementary to that of the first blade.

8. The tread according to claim 1, wherein the noise reducing device formed in a groove comprises a first flexible blade of triangular geometry connected to the bottom of the groove, this first blade itself being formed of at least two blades, and at least one second flexible blade which is carried on a lateral wall and the shape of which is complementary to that of the first blade.

9. The tread according to claim 1, wherein the noise reducing device formed in a groove comprises a first flexible blade of triangular geometry connected to the bottom of the groove and at least one second flexible blade which is carried on a lateral wall and the shape of which is complementary to that of the first blade, these first and second flexible blades being offset from one another in the main direction of the groove so as to be able to create a slight overlap between said blades and thus to obtain a larger degree of closure of the cross section of the groove.

10. The tread according to claim 1, wherein the thickness of each first flexible blade (500) connected to the bottom is at most equal to 0.4 mm and even more preferably at most equal to 0.3 mm.

Description

BRIEF DESCRIPTION OF THE FIGURES

[0042] FIG. 1 shows a surface view of a tread according to the disclosure in the new state;

[0043] FIG. 2 shows a device according to the disclosure in a position closing a groove;

[0044] FIG. 3 shows the device from FIG. 2 in an open position under the action of a flow of liquid in the groove;

[0045] FIG. 4 shows a variant of the disclosure in a position closing a groove;

[0046] FIG. 5 shows a variant of the disclosure in a position closing a groove;

[0047] FIG. 6 shows another variant of the disclosure in a position closing a groove;

[0048] FIG. 7 shows a surface view of the variant shown in FIG. 6.

DETAILED DESCRIPTION

[0049] For the figures accompanying this description, identical reference signs can be used to denote variants of the disclosure where these reference signs refer to elements of the same kind, whether structurally or functionally.

[0050] FIG. 1 shows a partial view of the surface of a tire tread, this tread comprising three grooves 2 of circumferential orientation. In order to reduce the noise associated with the resonance of air in each groove on passing through the contact with the road, a plurality of noise reducing devices according to the disclosure are formed in each groove, each device being formed of several flexible blades.

[0051] In FIG. 2, one of these devices 5 is shown in the closed state, that is to say in a position such that the cross section of the groove 2 is completely closed—in this case the cross section of the groove is closed over 90% of its area—by this device 5 in order to reduce the length of the air-filled pipe that can start to resonate during contact with a road, specifically in order to prevent the air from circulating.

[0052] In this FIG. 2, a groove 2 of generally circumferential orientation formed on the tread 1 can be seen. This groove 2 is delimited by lateral walls 21, 22 of raised elements, these facing lateral walls being connected by a groove bottom 20. This groove 2 has a total depth P in the new state, that is to say before any rolling and thus before any wear. The tread has a tread surface 10 intended to come into contact with the roadway during rolling. With wear, this tread surface changes and approaches the bottom of the grooves. In order to retain a sufficient drainage capacity with regard to safety, provision is made to dispose indicators of the wear limit not to be exceeded in the grooves. This wear limit is generally set by national legislatures (a dashed line is indicated in FIG. 2 and is located at a depth P′ less than the depth P of the groove).

[0053] A plurality of devices 5 for reducing noise generated by resonance have been formed in this groove 2, each device 5 being formed, in this first variant of the disclosure, by a first flexible blade 500 and two second flexible blades 51, 52, all of these flexible blades being made of rubber material of the same kind as the material of which the tread is made. The first flexible blade 500 is fixed to the bottom 20 of the groove, that is to say to the part connecting the lateral walls 21, 22, specifically to height equal to the wear limit fixed by the regulations. This first flexible blade 500 is secured to the bottom of the groove and has two free edges 501, 502 for forming an isosceles triangle geometry, these free edges meeting at an apex S, this apex S being located at a distance H from the bottom of the groove that is substantially equal to 15% of the total depth P of the groove. This first flexible blade 500 has a thickness equal to 0.4 mm.

[0054] Each second flexible blade 51, 52 is secured to one of the lateral walls 21, 22, respectively, and extends widthwise in the groove over about 50% of this width. Each second flexible blade 51, 52 has an upper edge 510, 520, respectively, these edges being intended to come into wearing contact with the road during rolling, and a lower edge 511, 521, respectively, these lower edges being intended to face an edge 501, 502 of the first blade 500 in order to ensure complementarity and thus to close the cross section of the groove. The two second flexible blades 51, 52 are positioned so as to face one another in order to ensure, with the first blade, that the groove is closed over at least 70% of the cross section of this groove.

[0055] In the present case, the first blade 500 fixed to the bottom 20 of the groove is intended to flex around an axis joining the points of intersection of the end wall of this first blade with the bottom of the groove (this axis is parallel to the direction indicated by the dashed line in FIG. 2).

[0056] In this variant, the flexible blades are suitable for flexing under the action of a force generated by a flow of liquid notably when driving over a roadway covered with water, as shown in FIG. 3, which shows the device 5 from FIG. 2 in an open position. The arrow F indicates the direction of a flow of liquid flowing inside the groove. It is under the action of this flow that the flexible blades forming the device 5 flex around an axis parallel to the direction of the connection between the flexible blade and the wall carrying said blade.

[0057] In this variant, the second flexible blades 51, 52 have a thickness equal to 1 mm, while the first flexible blade fixed to the bottom of the groove has a thickness equal to 0.6 mm. The choice of a smaller thickness for the first blade is very favorable since it makes it possible to reduce the force needed to flex this blade, regardless of the level of wear to the tread.

[0058] In a variant shown in FIG. 4, a noise reducing device 5 according to the disclosure comprises a first blade 500 and a second blade 50. The first flexible blade 500 connected to the bottom 20 of a groove has a trapezoidal geometry, one of its sides following the profile of a lateral wall 21 delimiting the groove over a height H corresponding to the maximum height of this first blade measured with respect to the innermost point of the bottom 20 of the groove. Furthermore, the second blade 50 connected to a lateral wall has a geometry complementary to that of the first blade and extends over the entire width of the groove 2 in order to close the cross section of the groove virtually completely.

[0059] In another variant, shown in FIG. 5, a device 5 according to the disclosure comprises a first blade 500 and two second blades 51, 52. The first flexible blade 500 connected to the bottom of a groove is composed of two flexible blades 503, 504 that are separated from one another along a cut oriented in the direction of the depth of the groove. This first blade 500 has an edge which follows a semicircular geometry, the radius of this semicircle in this case being equal to half the width of the groove. The device also comprises two second blades 51, 52 complementary to the first blade in order to close the cross section of the groove over at least 70% of this cross section.

[0060] The first and second flexible blades of the variants described by way of the variants shown in FIGS. 1 to 5 are disposed in the same plane.

[0061] In another variant, shown in FIG. 6, a noise reducing device according to the disclosure is similar to the one shown in FIG. 5, except that the first and second flexible blades are not all positioned in the same plane. Specifically, an offset has been created between the blades so as to be able to create a slight overlap between the blades and thus to ensure a better degree of closure of the cross section of the groove. The space between the blades is as small as possible while satisfying the manufacturing constraints.

[0062] In FIG. 7, which shows the tread surface of the tread in the new state, it can be seen in the groove 2 that the first flexible blade 500 and second flexible blades 51, 52 are disposed with a slight offset with respect to one another in the main direction of the groove so as to allow a slight overlap therebetween and thus to increase the degree of closure and therefore increase the effectiveness of the device.

[0063] While the disclosure has been described in general terms and using a number of variants, it should be understood that this disclosure is not limited just to these variants shown and described. Notably, when the lateral walls delimiting a groove make an angle other than 90 degrees with the tread surface in the new state, it is easy for a person skilled in the art to adapt the geometries of each blade to allow the cross section of the groove to be opened when driving over a roadway covered with water. Furthermore, the variants described here can be combined with one another by a person skilled in the art depending on the objective being pursued, without departing from the scope of the disclosure as defined by the claims.