FR3060455A1 - PNEUMATIC REINFORCED FLANKS - Google Patents

Abstract

The invention relates to a tire for a wheel assembly comprising a rim and a tire, said tire comprising at least one carcass reinforcement (2) surmounted radially on the outside of a crown reinforcement (3), itself radially the interior of a tread (4) having two axially outermost ends, said crown reinforcement (3) consisting of at least one layer of reinforcing elements, said tread (4) being connected with two beads (5) via two sidewalls (6), said beads (5) being intended to come into contact with a rim (7) having rim hook tops (7a), each bead (5) having at least one circumferential reinforcing element, said sidewalls (6) having, on their outer surface, a series of alternating protuberances (8) with recesses (9), the protuberances (8) being arranged on the surface of the sidewall (6). ) regularly or irregularly, each protuberance (8) having a substantially longitudinal shape with two side walls extending over a continuous or discontinuous neutral fiber length (Fn), wherein each side wall comprises an undercut portion extending from a point V of said side wall at a point U of said side wall such that a straight line passing through the points V and U forms with a straight line (Pn) perpendicular to the neutral fiber extending in a plane tangent to the neutral fiber since said side wall towards the recess (9) adjacent to said side wall a non-zero angle β strictly less than 90 °, said undercut portion extending over a surface representing at least 20% of the surface of the side wall.

Description

Holder (s): COMPAGNIE GENERALE DES ETABLISSEMENTS MICHELIN Limited partnership with shares, MICHELIN RECHERCHE ET TECHNIQUE S.A. Limited company.

Extension request (s)

Agent (s): REGIMBEAU.

TIRE WITH REINFORCED SIDES.

FR 3 060 455 - A1 (ü /) The invention relates to a tire for a rolling assembly comprising a rim and a tire, said tire comprising at least one carcass reinforcement (2) surmounted radially outside a reinforcement of crown (3), itself radially inside a tread (4) having two axially outermost ends, said crown reinforcement (3) consisting of at least one layer of reinforcing elements , said tread (4) being connected to two beads (5) via two sidewalls (6), said beads (5) being intended to come into contact with a rim (7) having hook tops rim (7a), each bead (5) comprising at least one circumferential reinforcement element, said sidewalls (6) comprising, on their external surface, a series of protrusions (8) alternated with recesses (9), the protuberances (8 ) being arranged on the surface of the sidewall (6) of in a regular or irregular manner, each protuberance (8) having a substantially longitudinal shape with two side walls extending over a length of continuous or discontinuous neutral fiber (Fn), in which each side wall comprises an undercut portion extending from a point V of said side wall to a point U of said side wall such that a straight line passing through points V and U forms with a straight line (Pn) perpendicular to the neutral fiber extending in a plane tangent to the neutral fiber from said side wall towards the hollow (9) adjacent to said side wall a non-zero angle β strictly less than 90 °, said undercut portion extending over a surface representing at least 20% of the surface of the side wall.

Reinforced sidewall tire

FIELD OF THE INVENTION

The invention relates to tires with a radial carcass or with a crossed carcass.

STATE OF THE ART

Radial carcass tires have gradually established themselves on various markets, and in particular the market for passenger car tires. This success is due in particular to the endurance, comfort and low rolling resistance qualities of the radial technology.

The main parts of a tire are the tread, the sidewalls and the beads. The beads are intended to come into contact with the rim. In a tire of radial technology, each of the main parts constituting the tire, namely the tread, the sidewalls and the beads, has functions which are well separated from each other, and therefore has a well-known specific constitution.

The radial tire is essentially reinforced by a carcass reinforcement comprising at least one carcass ply having an angle substantially equal to 90 ° relative to the circumferential direction of the tire. This carcass reinforcement is surmounted radially on the outside, and under the tread, by reinforcing plies forming a belt.

The cross-ply tire is distinguished from a radial technology tire by the presence of at least two crossed ply plies whose angle is different from 90 ° relative to the circumferential direction of the tire. The tablecloths are said to be "crossed" because the angles are of opposite signs from one tablecloth to another.

It will be recalled that, according to the invention, the circumferential direction of the tire is the direction included in a plane perpendicular to the axis of rotation of the tire and tangent to the reinforcement of the tire belt.

Following the appearance of a radial carcass tire, certain cross-carcass tires have also been provided with a belt reinforcement under the tread.

In these two types of tire, the tread, in direct contact with the ground, has the particular function of ensuring contact with the road and must adapt to the shape of the ground. The sides, on the other hand, absorb the irregularities of the ground while transmitting the mechanical forces necessary to carry the load of the vehicle and ensure its movement.

The belt reinforcement is a reinforcement which must, on the one hand, be sufficiently rigid with respect to the deformations on the edge so that the tire develops the thrust drifts necessary for its guidance, and transmit the engine or braking torque, and on the other hand, to be very flexible in bending, that is to say to allow variations in the curvature of its plane to ensure a sufficient contact surface of the tire on the ground.

Consequently, the belt reinforcement generally has a composite structure, allowing it to have the rigidity required for a relatively low weight. The belt reinforcement generally consists of at least two plies having different angles, comprising reinforcements, in the form of a cable, coated with rubber. The reinforcing elements are crossed from one ply to another with respect to the circumferential direction and are symmetrical or not with respect to this direction.

When impacting with a sidewalk or a pothole, the tire can be damaged, in particular by wedging it between the rim and the obstacle. As a result of the impact, the reinforcement elements of the sidewall of the tire can be damaged or broken. The tire can deform locally and / or lose its inflation pressure.

To overcome this drawback, several different solutions have been proposed. For example, it has been proposed to increase the breaking force of the cables of the carcass ply, or even to increase the number of reinforcing layers, typically with bi-ply solutions. Another solution is to have a set of protrusions and recesses on the sidewall of the tire which limit the stress on the cables during impacts. International applications WO 2014/207093 and WO 2014/207094 published on December 31, 2014 describe exemplary embodiments of tires incorporating alternating protrusions and hollows on the sidewalls to increase the resistance of these tires to lateral impacts.

The solutions proposed in these documents are effective with regard to protection against lateral impacts but can sometimes increase the rolling resistance of the tire, in particular since the flattening of the tire is less easy.

There is a need for a robust tire, particularly on the sidewall, which is resistant to physical attack such as side impact, and which has improved rolling resistance compared to existing solutions.

Another object of the present invention is to provide a tire having increased resistance against impacts at the sidewalls and which has increased marking functionalities on the sidewalls of said tire.

STATEMENT OF THE INVENTION

To this end, there is provided a tire for a rolling assembly comprising a rim and a tire, said tire comprising at least one carcass reinforcement surmounted radially outside a crown reinforcement, itself radially inside a tread having two axially outermost ends, said crown reinforcement consisting of at least one layer of reinforcing elements, said tread being connected to two beads by means of two sides, said beads being intended to come into contact with a rim having rim hook tops, each bead comprising at least one circumferential reinforcement element, said flanks comprising, on their external surface, a series of protuberances alternating with recesses, the protuberances being arranged at the flank surface in a regular or irregular manner, each protuberance having a sensibleme shape nt longitudinal with two side walls extending over a length of continuous or discontinuous neutral fiber (Fn), in which each side wall comprises an undercut portion extending from a point V of said side wall to a point U of said side wall such that a straight line passing through points V and U forms with a straight line (Pn) perpendicular to the neutral fiber extending in a plane tangent to the neutral fiber from said side wall towards the hollow adjacent to said wall lateral a non-zero angle β strictly less than 90 °, said undercut portion extending over a surface representing at least 20% of the surface of the lateral wall.

Preferred but non-limiting aspects of this tire, taken alone or in combination, are the following:

the angle β of the undercut portion is strictly less than 85 °, preferably strictly less than 80 °, and more preferably between 30 ° and 75 °.

the undercut portion extends over an area representing at least 50% of the surface of the side wall.

the undercut portion extends over an area representing at least 75% of the surface of the side wall.

the undercut portion extends over a surface representing the entire surface of the side wall.

the area of said flank where the protrusions alternate with the hollows, the full surface area rate is greater than 60%, preferably between 70% and 95%. the undercut portion of the side wall is straight or curved.

each protrusion has a cross section having a trapezoidal, pentagonal or hexagonal shape.

each recess has a cross section having a first rectangular or trapezoidal portion positioned towards the outside of the tire, and a second circular portion extending towards the inside of the tire, each side wall of the protuberance comprises a clearance portion which complements of the undercut portion, the undercut portion being located radially innermost with respect to the undercut portion.

each protrusion extends over a length of at least 10 mm.

the protrusions have variable heights, the maximum height being between 3 mm and 10 mm, and preferably between 4 mm and 8 mm. EQ designates the most axially outer point of the flank, Req being the radius at the point EQ, each protuberance having a height at the point EQ less than the height of said protuberance at the points EQ + and EQ- located respectively at distances Req + 20mm and Req - 20 mm from the axis of rotation of the tire.

the tread comprises at at least one axially outermost end a circumferential groove, where at least one protuberance partially or totally interrupts or does not interrupt said circumferential groove, said circumferential groove having side walls also having a counter portion skin in a shape identical to that of the protrusions, at least two protrusions have a length different from each other, two adjacent protrusions are substantially parallel to each other.

the neutral fiber of each protuberance passes through a radially innermost end and through a radially outermost end, and has an angle relative to the radial direction ZZ 'of between -60 ° and + 60 °. said protrusions are arranged continuously, between a point A and a point E, o said point A being disposed at the intersection of the radially outer surface of the tread and the sidewall, and of a distant radial axis ZZ ' of the equatorial plane AA 'of a length LA between ¹ Z * (L60mm) and ¹ Z * (L-10mm), L being the nominal flange size, and o said point E being arranged in a radius such that R2 <Re <Ra-25mm, R2 being the radius of the top of the rim hook and Ra being the radius of point A.

each protuberance has an average height greater than 80% of the maximum height over at least 80% of the distance between points A and E. the protrusions cover at least 40% of the total circumferential surface of the flank between points A and E .

DESCRIPTION OF THE FIGURES

Other characteristics and advantages of the invention will emerge from the description which follows, which is purely illustrative and not limiting and should be read with reference to the appended drawings, in which:

Figure 1 schematically shows the section of a tire along a radial plane;

FIG. 2 schematically represents an enlarged portion of a sidewall of a tire comprising a series of protrusions and recesses;

3 shows a sectional view of several adjacent protrusions of a tire according to the prior art, along the axis A-A of Figure 2;

4 shows a sectional view of several adjacent protrusions of a tire according to a first embodiment of the invention, along the axis A-A of Figure 2;

5 shows a sectional view of several adjacent protrusions of a tire according to a second embodiment of the invention, along the axis A-A of Figure 2;

6 shows a sectional view of several adjacent protrusions of a tire according to a third embodiment of the invention, along the axis A-A of Figure 2;

FIG. 7 represents a sectional view of several adjacent protuberances of a tire according to a fourth embodiment of the invention, along the axis A-A of FIG. 2.

DETAILED DESCRIPTION OF THE INVENTION

In this document, “rolling surface” means all the points of the tread of a tire which are liable to come into contact with the ground when the tire is rolling.

In the use of the term "radial" it is necessary to distinguish several different uses of the word by the person skilled in the art.

First, the expression refers to a radius of the tire. A "radial direction" is a direction intersecting the axis of rotation of the tire and perpendicular to it. It is in this sense that we say of a point P1 that it is "radially inside" to a point P2 (or "radially inside" of the point P2) if it is closer to the axis of rotation of the tire as point P2. Conversely, a point P3 is said to be "radially outside" a point P4 (or "radially outside" of the point P4) if it is further from the axis of rotation of the tire than point P4. You will say that you are advancing "radially inward (or outward)" when advancing towards smaller (or larger) spokes. When it comes to radial distances, this sense of the term also applies. Furthermore, the radial distance between the axis of rotation of said tire and the point X is called the radius Rx of a point X of the tire.

On the other hand, a wire or a reinforcement is said to be "radial" when the wire or the reinforcing elements of the reinforcement make with the circumferential direction an angle greater than or equal to 80 ° and less than or equal to 90 °. Clarification that in this document, the term "thread" should be understood in a very general sense and includes threads in the form of monofilaments, multifilaments, a cable, a twist or a equivalent assembly, and this, whatever the material constituting the wire or the surface treatment to promote its bond with the rubber.

Finally, by “radial section” or “radial section” here is meant a section or section along a plane which contains the axis of rotation of the tire. A “radial or meridian plane” is a plane which contains the axis of rotation of the tire.

The "median or equatorial plane" of the tire is the plane which is perpendicular to the axis of rotation of the tire and which is equidistant from the annular reinforcing structures of each bead. This plane divides the tire into two substantially equal halves, that is to say which passes through the middle of the tread.

An "axial" direction is a direction parallel to the axis of rotation of the tire. A point P5 is said to be "axially inside" at a point P6 (or "axially inside" of the point P6) if it is closer to the median plane of the tire than point P6. Conversely, a point P7 is said to be "axially outside of" a point P8 (or "axially outside" of the point P8) if it is further from the median plane of the tire than point P8.

A "circumferential direction" or "longitudinal direction" is a direction which is perpendicular both to a radius of the tire and to the axial direction. This corresponds to the rolling direction of the tire.

A "circumferential section" or "circumferential section" is respectively a section or a section along a plane perpendicular to the axis of rotation of the tire. A "circumferential plane" is a plane perpendicular to the axis of rotation of the tire.

In Figure 1 is shown the section of a tire 1 along a radial plane.

Conventionally, the tire 1 comprises at least one carcass reinforcement 2 surmounted radially outside a crown reinforcement 3, itself radially inside a tread 4 having two axially most outside.

The crown reinforcement 3 consists of at least one layer of reinforcing elements, and generally of several reinforcing layers.

The tread 4 is connected to two beads 5 by means of two sides 6.

The beads 5 are intended to come into contact with a rim 7 having rim hook tops 7a. Each bead 5 preferably comprises at least one circumferential reinforcement element.

In order to reinforce the tire 1 and in particular to prevent the sidewall reinforcing elements from being damaged or broken by lateral impacts, the sidewalls 6 have, on their outer surface, a series of protrusions 8 alternating with recesses 9, the protrusions 8 being arranged on the surface of the sidewall 6 in a regular or irregular manner.

Each protrusion 8 has a substantially longitudinal shape and extends along a length of neutral fiber (Fn), continuously or discontinuously. By neutral fiber is meant a neutral axis which passes substantially at the center of the volume of each protuberance 8, and which undergoes neither shortening nor elongation when it is subjected to compression and / or depression.

In Figure 1 we can see a protrusion 8, in section, extending continuously along the neutral fiber. The protrusions 8 may however also be arranged, on the surface of the sidewall 6, discontinuously along the neutral fiber (Fn).

In the example illustrated in FIG. 1, each protuberance 8 extends continuously between a point A and a point E, where:

point A is arranged at the intersection of the radially outer surface of the tread 4 and the sidewall 6, and of a radial axis ZZ 'distant from the equatorial plane AA' with a length LA of between ¹ Z * ( L-60mm) and ¹ Z * (L-10mm), L being the nominal flange size, and point E being arranged in a radius Re such that R2 <Re <Ra-25mm, R2 being the radius of the top of the hook rim and Ra being the radius of point A.

In Figures 2 and 3 are shown protrusions as they exist in the prior art. As seen in particular in Figure 3, such protrusions 8 have a profile with side walls in relief, that is to say that the side walls are inclined so as to facilitate the release of the mold used to form the protrusions 8 on the flank 6.

The draft angle noted a is represented in FIG. 3. In the prior art, a draft angle is chosen a allowing the tire to be demolded after curing without deformation of the final structure of the protuberances, this draft angle a possibly being for example of the order of 6 ° to 8 °.

According to the invention and contrary to the teachings of the prior art, it is proposed to form protuberances which have at least one portion in undercut.

By undercut portion is meant a portion which - unlike an undercut shape - comes to oppose the withdrawal movement of the mold once the structure has been formed.

An undercut portion is generally caused by problematic forms such as cavities and retentions or specific inclinations of walls, these types of form can generate an additional force during demolding after cooking.

It being understood that a protuberance 8 has a longitudinal shape with two side walls extending over a length of neutral fiber (Fn), it is proposed to form protuberances where each side wall comprises an undercut portion.

The undercut portion extends from a point V of said side wall to a point U of said side wall such that a straight line passing through points V and U forms with a straight line (Pn) perpendicular to the neutral fiber (Fn) extending in a plane tangent to the neutral fiber in the direction of the hollow (9) adjacent to said side wall a non-zero angle β strictly less than 90 °. More precisely, the angle β is the angle formed between the vector Pn and the vector VU, the vector Pn being oriented along the straight line (Pn) so as to go from the material of the protuberance towards the hollow comprised between two adjacent protuberances .

The point V corresponds to the point of the lateral wall of the protuberance 8 most axially inward relative to the cross section of said protuberance 8.

The point U is a point on the side wall of the protuberance 8 being axially more outside relative to the point V. Preferably, the point U corresponds to the point of the side wall of the protuberance 8 most axially to the outside with respect to the cross section of said protuberance 8.

The point V is radially more inside than the point U. It can also be said that the point V is closer to the base of the protuberance 8, that is to say closer to the hollow 9 adjacent to the protuberance 8, that point U.

Preferably, the angle β of the undercut portion is strictly less than 85 °, or even strictly less than 80 °.

According to a preferred embodiment, the angle β of the undercut portion is between 30 ° and 75 °.

The undercut portion extends over an area representing at least 20% of the surface of the side wall. Thus, at least 20% of the total lateral surface of all the protrusions is undercut.

Preferably the undercut portion extends over a surface representing at least 30% of the surface of the side wall, more preferably at least 50% of the surface of the side wall, or even at least 75% of the surface. of the side wall.

According to a more preferred embodiment, the undercut portion extends over a surface representing the entire surface of the side wall.

The fact of having an undercut portion at the walls of the protuberance 8 makes it possible to have protuberances having more flexibility. This makes it possible to reduce the overall rigidity of the protrusions with iso-volume of material. Thus, the rolling resistance is reduced since the flattening of the tire is easier.

Another advantage of this particular shape of the protrusions with an undercut makes it possible to increase the marking surface on the sidewall 6. In fact, the undercut portions make it possible to maintain an extended upper surface of the protrusions 8, which even covers a most of the free space in the pits 9.

In the area of said sidewall 6 where the protrusions 8 alternate with the hollows 9, the surface area ratio is greater than 60%, preferably between 70% and 95%.

Finally, this particular shape also enhances the protrusions 8 relative to the hollows which are darker.

In Figure 4 is illustrated an embodiment in which the protrusions 8 have a trapezoidal cross section, the small base corresponding to the base of the protrusion 8, that is to say the connection with the surface of the sidewall 6, while that the large base corresponds to the external surface of the protuberance 8. According to this example, the side wall of the undercut portions is straight.

According to the example of FIG. 4, the two side walls of the protuberance 8 have identical undercut portions, that is to say that the side walls form with the bottom Pn of the hollow 9 the same angle β. According to this example, the cross section of the protuberance is an isosceles trapezoid. These angles could however be different, thus forming two undercut portions with different inclinations.

In FIG. 5 is precisely presented an embodiment of protuberances, in which each of the two side walls (8a, 8b) of the protuberance 8 has undercut portions different from each other. Such a design will, for example, facilitate the demolding of the mold during the formation of the protrusions.

In particular, the angles of inclination β and β ’of the lateral walls with respect to the bottom Pn and Pn’ of the recesses 9 adjacent to the protuberance 8 are different.

According to the example of Figure 5, the protrusion has a pentagonal cross section. According to this example, the side wall of the undercut portions is straight.

Indeed, the wall 8a of the side walls (8a, 8b) of the protuberance 8 has not only an undercut portion extending from point U to for V, but also a portion undercut.

The wall 8b of the side walls (8a, 8b) of the protuberance 8 has for its part only an undercut portion which extends from a point U 'located at the base of the wall 8b to point V' located at the level of the upper surface of the protuberance 8.

One embodiment could be envisaged (not shown) where the protuberance has a cross section of hexagonal shape, that is to say where each of the two side walls comprises an undercut portion and a undercut portion.

Figures 6 and 7 illustrate examples where the protrusions have undercut portions formed by curved walls. The undercut portion of the side wall is therefore curved.

The protrusions 8 according to the examples of FIGS. 6 and 7 have walls both having an undercut portion and a clearance portion, the undercut portion being positioned radially inward relative to the portion bare.

The shape of the protrusions 8 can be defined from the shapes of the recesses 9 separating two adjacent protrusions.

Thus, according to these examples, each recess 9 has a cross section having a first rectangular or trapezoidal portion 9a positioned towards the outside of the tire, and a second circular portion 9b extending from the first portion 9a.

The first portion 9a defines the clearance portion of the protuberance 8, while the circular portion 9b defines the curved undercut portion of the protuberance 8.

In FIG. 6 is illustrated an example of protuberance with a large undercut portion relative to the undercut portion, both in terms of relative heights and of radius of curvature of the undercut portion.

In FIG. 7, the protuberance has an undercut portion having a height substantially greater than the height of the undercut portion.

In the examples of FIG. 6 and of FIG. 7, the circular portion 9b has dimensions optimized to prevent cracking at the bottom of the trough. Thus the diameter of the circular portion 9b is chosen as a function of the curvature of the sidewall.

In addition to the particular forms of the protrusions as presented above, with in particular the presence of an undercut portion, these protuberances can be characterized by their general dimensions.

Thus, each protuberance 8 preferably extends over a length of at least mm.

Each protuberance 8 preferably has an average width of between 4 mm and 12 mm.

Each protuberance has for example an average height of between 3 mm and 10 mm, preferably between 5 mm and 8 mm.

The protrusions can have variable heights, the maximum height being between 3 mm and 10 mm, and preferably between 4 mm and 8 mm.

By designating by EO the most axially outer point of the flank 6 and Req being the radius at the point EO, and if the protuberance has a variable height along its length, then said protuberance 8 preferably has a height at the point EO less than the height of said protuberance 8 at the points EO + and EO- located respectively at distances Req + 20mm and Req - 20 mm from the axis of rotation of the tire 1.

The protrusions 8 of the same flank 6 can have different lengths.

Preferably, two adjacent protuberances 8 are substantially parallel to one another.

The neutral fiber of each protuberance 8 passes through a radially innermost end and through a radially outermost end, and has an angle relative to the radial direction ZZ ’between -60 ° and + 60 °.

In one possible embodiment, the tread 4 comprises at at least one axially outermost end a circumferential groove, where at least one protuberance 8 partially or totally interrupts or does not interrupt said circumferential groove.

In this case, it is advantageous for the circumferential groove to include side walls also having an undercut portion in a shape identical to that of the protrusions 8.

BIBLIOGRAPHICAL REFERENCES

- WO 2014/207093

- WO 2014/207094

Claims (20)

1. A tire for a rolling assembly comprising a rim and a tire, said tire comprising at least one carcass reinforcement (2) surmounted radially outside a crown reinforcement (3), itself radially inside d 'a tread (4) having two axially outermost ends, said crown reinforcement (3) consisting of at least one layer of reinforcing elements, said tread (4) being connected to two beads ( 5) by means of two sidewalls (6), said beads (5) being intended to come into contact with a rim (7) having rim hook tops (7a), each bead (5) comprising at least one circumferential reinforcement element, said flanks (6) comprising, on their outer surface, a series of protrusions (8) alternated with recesses (9), the protrusions (8) being arranged on the surface of the flank (6) in a regular manner or irregular, each protuberance (8) having a substantially longitudinal shape with two side walls extending over a length of continuous or discontinuous neutral fiber (Fn), characterized in that each side wall comprises an undercut portion extending from a point V of said side wall at a point U of said side wall such that a straight line passing through points V and U forms with a straight line (Pn) perpendicular to the neutral fiber extending in a plane tangent to the neutral fiber from said side wall towards the hollow (9) adjacent to said side wall a non-zero angle β strictly less than 90 °, said undercut portion extending over a surface representing at least 20% of the surface of the side wall. 2. A tire according to claim 1, in which the angle β of the undercut portion is strictly less than 85 °, preferably strictly less than 80 °, and more preferably between 30 ° and 75 °. 3. A tire according to any one of claims 1 or 2, wherein the undercut portion extends over an area representing at least 50% of the surface of the side wall. 4. A tire according to any one of claims 1 or 2, wherein the undercut portion extends over an area representing at least 75% of the surface of the side wall. 5. A tire according to any one of claims 1 or 2, wherein the undercut portion extends over a surface representing the entire surface of the side wall. 6. A tire according to any one of claims 1 to 5, in which in the region of said sidewall (6) where the protrusions (8) alternate with the recesses (9), the rate of full surface is greater than 60%, preferably between 70% and 95%. 7. A tire according to any one of claims 1 to 6, in which the undercut portion of the side wall is straight or curved. 8. A tire according to any one of claims 1 to 7, wherein each protuberance (8) has a cross section having a trapezoidal, pentagonal or hexagonal shape. 9. Tire according to any one of claims 1 to 7, in which each recess (9) has a cross section having a first rectangular or trapezoidal portion positioned towards the outside of the tire, and a second circular portion extending towards the inside the tire. 10. A tire according to any one of claims 1 to 9, in which each side wall of the protuberance (8) comprises an undercut portion complementing the undercut portion, the undercut portion being located radially the innermost with respect to the clearance portion. 11. A tire according to any one of claims 1 to 10, in which each protuberance (8) extends over a length of at least 10 mm. 12. A tire according to any one of claims 1 to 11, in which the protrusions (8) have variable heights, the maximum height being between 3 mm and 10 mm, and preferably between 4 mm and 8 mm. 13. A tire according to any one of claims 1 to 12, in which EQ designates the most axially outer point of the sidewall (6), Req being the radius at the point EQ, each protuberance (8) having a height at the point EQ less than the height of said protuberance (8) at the points EQ + and EQ- located respectively at distances Req + 20mm and Req - 20 mm from the axis of rotation of the tire. 14. Tire according to any one of claims 1 to 13, in which the tread (4) comprises at at least one axially outermost end a circumferential groove, where at least one protuberance (8) interrupts partially or totally or does not interrupt said circumferential groove, said circumferential groove having side walls also having an undercut portion in a shape identical to that of the protrusions (8). 15. A tire according to any one of claims 1 to 14, in which at least two protrusions (8) have a length different from one another. 16. A tire according to any one of claims 1 to 15, in which two adjacent protuberances (8) are substantially parallel to one another. 17. A tire according to any one of claims 1 to 16, in which the neutral fiber of each protuberance (8) passes through a radially innermost end and through a radially outermost end, and has an angle relative to the radial direction ZZ 'between -60 ° and + 60 °. 5 18. A tire according to any one of claims 1 to 17, in which said protuberances (8) are arranged continuously, between a point A and a point E, said point A being disposed at the intersection of the radially outer surface of the tread (4) and of the sidewall (6), and of a radial axis ZZ 'distant from the equatorial plane AA' of a length LA between ¹ A * (L-60mm) and ¹ A * (L -10mm), L 10 being the nominal flange size, and said point E being disposed within a radius such that R2 <Re <Ra-25mm, R2 being the radius of the top of the rim hook and Ra being the radius of point A. 19. A tire according to claim 18, in which each protuberance (8) has an average height greater than 80% of the maximum height over at least 80% of the 15 distance between points A and E. 20. Tire according to any one of claims 18 or 19, in which the protrusions (8) cover at least 40% of the total circumferential surface of the sidewall between points A and E.