EP3227126A2

EP3227126A2 - Extended-mobility cross-ply or radial tyre

Info

Publication number: EP3227126A2
Application number: EP15802123.8A
Authority: EP
Inventors: Jacky Pineau; Hervé FERIGO; José Merino Lopez
Original assignee: Compagnie Generale des Etablissements Michelin SCA
Current assignee: Compagnie Generale des Etablissements Michelin SCA
Priority date: 2014-12-03
Filing date: 2015-12-01
Publication date: 2017-10-11
Also published as: FR3029461B1; WO2016087437A2; CN107000505A; FR3029461A1; WO2016087437A3; US10682891B2; US20170355232A1; CN107000505B

Abstract

The invention relates to a tyre for a rolling assembly comprising a rim and a tyre, said tyre having at least one carcass reinforcement (2) comprising an inner wall (2a) surmounted radially on the outside by a crown reinforcement (3), which is itself radially on the inside of a tread (4) having two axially outermost ends, said crown reinforcement (3) being made up of at least one layer of reinforcing elements, said tread (4) being connected to two beads (5) by way of two sidewalls (6), said beads (5) being intended to come into contact with a rim (7) having rim flange tops (7b), each bead (5) having at least one circumferential reinforcing element, said sidewalls (6) having, on their outer surfaces, a series of protuberances (8) alternating with recesses (9), said tread (4) comprising, at at least one axially outermost end (4a), a circumferential furrow (10), characterized in that each protuberance (8) is disposed at the surface of a sidewall, the different protuberances being disposed in a regular or irregular manner, and in a continuous or discontinuous manner, between a point A and a point E, and in that the inner wall (2a) of the carcass ply (2) of the tyre is partially or entirely covered with at least one layer of a self-sealing composition (2b).

Description

TIRE WITH RADIAL OR CROSS CARCASS

A EXTENDED MOBILITY

The invention relates to tires with radial carcass or cross-carcass with extended mobility.

[0002] Radial-carcass tires have gradually imposed themselves on various markets, and in particular the tire market for passenger vehicles. This success is due in particular to the endurance, comfort and low rolling resistance qualities of 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 well separated from each other, and therefore has a specific constitution well known.

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

The cross-carcass tire is distinguished from a tire of radial technology by the presence of at least two crossed carcass plies whose angle is different from 90 ° with respect to the circumferential direction of the tire. Tablecloths are said to be "crossed" because the angles are of opposite signs from one tablecloth to another. It is recalled that, according to the invention, the circumferential direction of the tire is the direction in a plane perpendicular to the axis of rotation of the tire and tangent to the belt reinforcement of the tire,

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

In both types of tire, the tread, in contact directly with the ground, has a particular function to ensure contact with the road and must adapt to the shape of the ground. The flanks, meanwhile, 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 an armature which must, on the one hand, be sufficiently rigid vis-à-vis the edge deformations so that the tire develops the drift thrusts necessary for its guidance, and transmit the engine torque or braking, and secondly, be very flexible in bending, that is to say allow variations in curvature of its plane to ensure a contact surface of the tire on the ground sufficient.

Therefore, the belt reinforcement generally has a composite structure, allowing it to have the required rigidity for a relatively low weight. The belt reinforcement generally consists of at least two plies with different angles, including reinforcements, cable-shaped, coated with rubber. The reinforcing elements are crossed from one sheet to the other with respect to the circumferential direction and are symmetrical or not with respect to this direction.

[0011] Hereinafter denoted by: - "longitudinal or circumferential direction": rolling direction of the tire,

- "radial direction": direction intersecting the axis of rotation of the tire and perpendicular to it,

- "axial direction": direction parallel to the axis of rotation of the tire,

- "radially inner to" means closer to the axis of rotation,

- "radially outside" means more distant from the axis of rotation,

- "equatorial plane or median plane": plane perpendicular to the axis of rotation of the tire and which divides the tire into two substantially equal halves,

- "transverse direction of the tire": direction parallel to the axis of rotation,

- "radial or meridian plane" means a plane which contains the axis of rotation of the tire.

During a perforation of the wall of a tire by a perforating object such as a screw or a nail, or "puncture", the air inflation of the tire can escape through the perforation and the loss consecutive pressure will cause the tire to lay flat and the vehicle to stop.

To solve this problem of punctures which dates from the very beginning of the use of tires with inflated tires, the usual solution is to stop and replace the wheel concerned by a spare wheel.

Other solutions have been imagined and are available on the market to avoid having to use a spare wheel.

US 5,916,921 discloses an aerosol container comprising an aqueous latex emulsion mixed with various products including fibrous products and a propellant gas. In the case of a flat tire, this container is intended to be fixed to the tire valve and to send into the internal cavity of the tire the propellant gas and the sealing / repair emulsion. The tire is then re-inflated at least partially, the emulsion closes the perforation and can be rolled again, at a reduced speed first to distribute the emulsion well over the entire internal surface of the tire and then normally.

There are also repair kits, offered by some car manufacturers instead of a spare wheel. This has the advantage of reducing the weight of the car, so its fuel consumption and free space under the floor of the trunk.

Tire repair kits and aerosol cans are only temporary repairs. It should not exceed a given speed of about 80 km / h and have his tire checked or changed quickly.

Tire manufacturers have also proposed tires provided on their inner wall or in their structure with a layer of elastic products, viscous or pasty, called "self-sealing products", allowing closure of the perforations.

But the application of these self-sealing products can only strengthen the crown area of the tire against punctures. Indeed, the application of these self-sealing products does not take place on the inner surface of the sidewalls, since during rolling, the centrifugal force exerted on the tire would not allow the initial maintenance in place self-sealing product.

Another anti puncture solution would be to increase the thickness of the sidewalls. But this would cause an increase in mass and penalize the rolling resistance of the tire. Also, there remains the need to stiffen the sidewalls of a pneumatic coated with a self-sealing composition to thereby reduce the bending movements of the sidewalls, and consequently to prevent the flanks come into contact with the radial interior of the crown zone which is then coated with the self-sealing product whose stickiness is particularly important.

The invention therefore relates to a tire for a wheel assembly comprising a rim and a tire, said tire comprising at least one carcass reinforcement comprising an inner wall and radially surmounted on the outside of a crown reinforcement, it -even 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 the intermediate of two flanks, said beads being intended to come into contact with a rim having rim hook heights, each bead having at least one circumferential reinforcing element, said flanks comprising, on their outer surface, a series of alternating protuberances with depressions, the inner wall of the carcass ply of the tire being covered partially or totally at least one layer of a self-sealing composition.

The tire is characterized in that each protuberance is disposed on the surface of a sidewall, the various protuberances being 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 and the sidewall, and of a radial axis ZZ 'distant from a plane AA' of a length L _A between ½ (L -60mm) and ½ (L-10mm), L being the nominal coil size, said plane AA 'being parallel to the equatorial plane and tangential to the sidewall, and said point E being disposed, optionally, in a radius such that R ₂ <E <(R _A -15mm), R ₂ being the radius of the top of the rim hook and R _A the radius of the point A, and in this respect the inner wall of the carcass ply of the tire is partially or completely covered with at least one layer of a self-sealing composition.

[0024] Preferably, the tread comprises at least one axially outermost end a circumferential groove.

Preferably, at least one protrusion interrupts partially or totally or does not interrupt said circumferential groove.

By the terms "does not interrupt" is meant that the radially upper end of a protuberance is either adjacent to the circumferential groove, or distant a distance "d" substantially disposed in a radial direction and between 2 and 10mm.

By the terms "partially interrupts" is meant that the radially upper end of a protuberance partially intersects the circumferential groove.

By the terms "totally interrupts" is meant that the radially upper end of a protuberance reaches the axially outer end of the tread which is closest thereto.

When the protuberance partially interrupts the groove, this interruption is performed between 2 and 97% of the total axial distance of said groove, preferably between 20 and 80%, and more preferably between 30 and 50%.

The groove is an area of a given width located around the point A, and having a longitudinal void ratio greater than 70%>. By the term "regular", it is defined that the protuberances arranged between the points A and E are arranged next to each other in a radial direction, with possible symmetry, and uniformly.

By the term "irregular", it is defined that the protuberances disposed between the points A and E are arranged in an offset manner in two parallel radial directions without symmetry and non-uniformly.

The radius R _A is a function of the length L _A , itself a function of the length L.

R 1 can be in the range between (0.8R ₂ + 0.2R _A ) and (0.2R ₂ + 0.8R _A ).

The nominal flange size L is defined by the flange size of a tire mounted on the rim and inflated; the flange size being, according to the invention, the distance between the outside of the flanks of an inflated tire, by incorporating the surface relief of the flanks. Ri corresponds to the radius of the point on the outer surface of the flank furthest from the median plane.

The tire according to the invention has the advantage of being quick and easy to produce, and to make it possible to easily stiffen the sidewalls.

The tire according to the invention has the advantage of having overall performance, such as rolling resistance, wear, endurance similar to that of conventional tires.

Another object of the invention is a mounted assembly comprising a rim and the tire as described above. Preferably, the self-sealing composition has a Shore 00 hardness less than or equal to 10, preferably less than or equal to 5, and more preferably equal to zero.

Preferably, the self-sealing composition is chosen from a composition based on a thermoplastic styrene elastomer (TPS), or from a composition comprising at least one unsaturated diene elastomer, or from terpene resins and polybutenes as the main component. or from silicone based, urethane based, styrene based or ethylene based compounds, or from a butyl elastomer composition.

Preferably, the composition based on a thermoplastic styrene elastomer (TPS) comprises more than 200 phr of an extension oil of said elastomer.

Preferably, the composition comprising at least one unsaturated diene elastomer comprises between 30 and 90 phr of a hydrocarbon resin, a liquid plasticizer whose vitreous temperature (Tg) is below -20 ° C. at a weight content of between 0.degree. and 60pce and from 0 to 120pc of a charge.

The composition based on a butyl elastomer may comprise a non-halogenated butyl elastomer.

[0044] Preferably, the composition based on a butyl elastomer comprises between 5 and 40 phr of an extender oil, such as polyisobutylene, between 5 and 55 phr of a tackifying resin, and a non-reinforcing filler. The polyisobutylene preferably has a molecular weight less than or equal to 10,000, and preferably less than or equal to 5,000. The non-reinforcing filler is preferably selected from chalk or kaolin.

Preferably, at least one protuberance has a height and a length, said height being minimal to the coil size and progressively increasing in size. on both sides of said flange size with a minimum height at a distance of between 0.9Ri and 1.1 Ri

Preferably, at least two protuberances have a length different from each other.

Preferably, each protuberance has a mean height between

3 and 10mm.

Preferably, each protuberance has an average width between

4 and 12mm.

The average height of each protuberance, may be between 5 and 8mm. The protuberances may have an average height greater than 80% of the maximum height over at least 80% of the distance between the points A and E. The average height is defined as being the average of the height between the ends of a protuberance .

The protuberances preferably have a rake angle of less than or equal to 20 °, and preferably between 5 and 8 °.

Two adjacent protuberances may be spaced from each other by an average distance less than or equal to 2 times the average width of a protuberance, and may be substantially parallel to each other.

The protuberances preferably cover at least 40% of the total circumferential surface of the flank between points A and E.

Each protuberance, of defined geometric shape or any one, may comprise a neutral fiber, passing through a radially innermost end and a radially outermost end, and having an angle β, with respect to the radial direction ZZ ' between -60 ° and + 60 °. The outer side of the tire side (that is to say outside when mounted on the vehicle) and the inner side of the tire side (that is to say inside when mounted on the tire). vehicle) may comprise each of the protuberances in any combination of possible inclinations.

Similarly, the four tires of a vehicle may have variable inclinations depending on each axle and / or on the same axle.

Preferably, the hollow between two adjacent protuberances extends axially in the extension of the hollow of a circumferential groove of the tread, passing through the point A, said groove being disposed on at least one axial end of the tread. tread.

Preferably, the hollow between two adjacent protuberances has an angle, with the circumferential direction between -15 ° and + 15 ° in a zone of the sidewall close to the point A, that is to say between 3 and 8 mm.

Preferably, according to a defined radial plane, and whatever said plane lies between the points A and E, the sum of the widths, which may be variable, of each protuberance, in the circumferential direction, is greater than or equal to 60.degree. % of the total circumferential length, said length being measured at the location of the protuberances.

The tire according to the invention may have a ratio [sum of the total widths of each protuberance] / 2 R greater than or equal to 30%>, and more preferably equal to 60%>, the widths of each protuberance being defined at 50% of the total height of said protrusion, the radius R being a mean radius.

The protrusion may be present over the entire circumferential length of the tire sidewall. The protuberances present on the sidewalls according to the invention consist of a material identical to that of the sidewalls.

The invention will now be described with the aid of the examples and drawings which follow and which are given solely by way of illustration, and in which:

FIG. 1 represents, schematically, the section of a tire of the invention in a radial plane comprising a continuous protuberance,

[0064] FIGS. 2A and 2B show schematically and in three dimensions a portion of a sidewall and the corresponding tread of a tire according to the invention,

FIG. 3 schematically represents an enlarged portion of a sidewall comprising continuous protuberances of a tire according to the invention,

FIG. 4 represents a sectional view, of two adjacent protuberances of a tire according to the invention, along the axis AA of FIG. 3,

FIGS. 5A and 5B show, in a first variant, a portion of a radially outer portion of a sidewall and the corresponding three-dimensional tread of a tire according to the invention,

[0068] FIG. 6A represents, according to a second variant, a portion of a radially outer portion of a sidewall and the corresponding three-dimensional tread of which certain protuberance completely interrupts a circumferential groove of a tire according to FIG. 'invention,

[0069] FIG. 6B shows, according to another variant, a portion of a radially outer portion of a sidewall and the corresponding tread in three parts. dimensions of which certain protuberance partially interrupts a circumferential groove of a tire according to the invention,

[0070] FIG. 7A represents a partial view in radial section of a part of a sidewall and a part of the corresponding tread according to another variant,

[0071] FIG. 7B represents a partial view in radial section of a portion of a sidewall and a part of the corresponding tread according to another variant of a tire according to the invention,

FIG. 8 schematically represents, in three dimensions, a portion of a sidewall and the corresponding bead of a tire according to the invention,

FIG. 9 schematically represents the section of a tire of the invention in a radial plane comprising a discontinuous protuberance,

- Figures 10 and 11 show, schematically and in three dimensions, an enlarged portion of a sidewall and the corresponding tread of a tire according to the invention and comprising a discontinuous protuberance.

In the different figures, identical or similar technical elements bear the same reference. Their description is not repeated so as not to weigh down the text.

As shown in Figure 1, the tire for passenger vehicle general reference 1 comprises a carcass reinforcement 2, comprising an inner wall 2a, covered with a layer of self-sealing composition 2b, radially inner to a reinforcement of general reference belt 3, said reinforcement of belt 3 being radially inside a tread 4 itself connected to two beads 5 via two sides 6. The beads 5 are intended to come into contact with a rim 7 (partially shown). Each bead comprises at least one circumferential reinforcing element 7a. The flanks comprise, on their surface, a series of protuberances 8 regularly alternating with recesses 9 (shown in FIG. 2).

In Figure 1 we can see a protrusion 8, in section, having a continuous neutral fiber. It is recalled here that a neutral fiber is called a neutral axis which passes substantially in the center of the volume of each protuberance, and which undergoes neither shortening nor elongation when it is subjected to compression and / or depression.

As shown in Figure 1, the protuberances 8 are disposed on the surface of the sidewall, on a continuous neutral fiber length which extends from a point A to a point E.

The point E is disposed at a radius less than (0.75Ri + 0.25R ₂ ). Ri is the radius of the nominal flange size L, and R _A is the radius of the point A.

The point E is disposed at a radius of 232mm for a reference tire 205/55 R 16 mounted on the rim 6.5 J 16 for which RA is equal to 298mm, R ₂ is equal to 220mm and Ri is equal to 261mm.

The definition according to the invention of the coil size is adaptable to any type of envelope combined with any type of rim.

The point A is disposed at the intersection of the radially outer surface of the tread and the sidewall, and an axis ZZ 'distant from the equatorial plane AA' of a length L _A equal to ½ (L - 45mm). For a 205/55 reference tire R 16, R _A is equal to 298mm. The plane AA 'is parallel to the equatorial plane and tangential to the flank surface.

The protuberances are not inserted rubber elements, added in the flank rubber, but are obtained by molding during the firing step. They are obtained in a manner similar to that of the sculptures made on the tread.

FIG. 2A represents an alternation of protuberances 8 and recesses 9, shown enlarged in FIGS. 3 and 4. FIG. 2B represents a variant of FIG. 2A in which the protuberances are arranged at an angle to the axial direction. According to this embodiment, the longest continuous protuberances 8 have a neutral fiber length of about 75 mm for a tire of dimension 205/55 R 16. They are arranged radially (FIG. 2) substantially parallel to one another others, are spaced about 4.50mm, have a height of about 6mm, and a width of about 8.6mm in their axially innermost part.

The clearance angle α is about 8 °. Such a clearance angle value allows a release of the tire after firing without deterioration of the final structure.

According to this embodiment, the protuberances have a ratio [sum of the widths of each protuberance] / 2 R equal to 30%, halfway and have no angle relative to the radial plane.

FIG. 5A shows a three-dimensional representation of the radially outer portion 8a of the protuberances 8 and its enlargement in FIG. 5B of FIG. 5A. In these FIGS. 5A and 5B, the portion 8a of each protuberance 8 as well as the recesses 9 are adjacent to a groove 10 arranged, circumferentially, on the surface of the tread 4 at its axially outermost end 4a. The groove 10 is not interrupted in its length.

According to this particular embodiment, the groove 10 has an axial width "1" along the axis YY'may be between 2 and 10mm, and a radial height "h" along the axis ZZ'comprise between 3 and 8mm.

FIG. 6A also shows a three-dimensional representation of the radially outer portion 8a of the protuberances 8. Unlike FIGS. 5A and 5B, the groove 10 is interrupted. Indeed, the end 8a of the protuberances 8 and adjacent recesses 9 completely cut the groove 10 in the circumferential direction of the tire.

FIG. 6B shows another variant of a three-dimensional representation of said radially outer portion 8a of the protuberances 8. In this figure, the protuberance 8 partially cuts the groove 10 in the circumferential direction of the tire.

FIGS. 7A and 7B show that the radially inner portion 8b (shown in dotted lines) of the protuberance 8 is spaced a thickness "d" from the radially inner portion 10b of the recess 10. This thickness "d" is smaller than at 2mm, and preferably less than 1mm.

FIG. 8 shows that the radially upper end of the protuberances 8b and 8c is adjacent to the circumferential groove 10, and that the radially upper end of the protuberance 8d completely interrupts the groove 10 to join the elastomer gum rolls of the tread 4. This figure thus shows an embodiment of a tire according to the invention wherein each protuberance 8b, 8c is alternated with a hollow 9. Each of the protuberances 8b, 8c extend from point A to point E. In Figure 9 we can see a protrusion 8, in section, having a discontinuous neutral fiber length.

It is recalled here that a neutral fiber is called a neutral axis which passes substantially in the center of the volume of each protuberance, and which undergoes neither shortening nor elongation.

The protuberances 8 are arranged on the surface of the sidewall on a discontinuous neutral fiber length which extends from a point A to B and a point C to D.

The point A is disposed at the intersection of the radially outer surface of the tread and the sidewall, and an axis ZZ 'distant from the equatorial plane with a length equal to 90 mm.

The point B is located in a radius equal to 266mm the point C in a radius equal to 258mm, and the point D in a radius equal to 238mm for a 205/5 R16 reference tire mounted on a 6.5 J rim 16 .

The protuberances are not inserted rubber elements, added in the rubber flanks, but are obtained by molding during the firing step. They are obtained in a manner similar to that of the sculptures made on the tread. The inner wall 2a comprises a layer of self-sealing composition 2b.

Figures 10 and 11 show an alternation of protuberances 8 and recesses 9. Figure 11 shows a variant of Figure 10 where the protuberances are arranged at an angle relative to the axial direction. According to this embodiment, the protuberances 8 are discontinuous, and have a discontinuous neutral fiber length of approximately 45 mm for the PI part (between C and D) and 40 m for the P2 part (between A and B) for a tire of dimension 205/55 R 16. They are arranged substantially parallel to one another, are spaced apart about 4.50mm, have a height of about 6mm, and a width of about 8.6mm in their axially innermost part.

The tire according to the invention is obtained after baking and molding in a baking mold in a conventional manner.

[00101] Example 1: Sidewalk shock test

This test was carried out with a reference tire 205/55 RI 6 comprising different representations of protuberances, at the same control tire without protuberances.

The tires PI to P4 are different tires according to the invention.

The protuberances of the tires PI and P4 have no angle of inclination with respect to the radial direction.

The protuberances of the tires P2 and P3 have an angle of inclination with respect to the radial direction.

The "Angle" column corresponds to the angle that each protuberance makes with the radial direction of the tire.

The draft angle α is the angle that each end of a protuberance, as shown in Figure 4, to facilitate the demolding.

The pitch of a protuberance is the distance extending from the center of a first hollow to the center of a second hollow adjacent to the first.

H (mm) is the average height of the protuberances, 1 (mm) is the average width of the protuberances.

[00110] Ri is the radius of the nominal coil size, R ₂ is the radius of the hook top, RE is the radius corresponding to the point E, and R _{A is} the radius of the point A. The flange size with the reliefs includes the nominal flange size and the height of the protuberances on the surface of the flanks.

Table I below summarizes the measurable technical characteristics of the various tires according to the invention.

Pneumatic Witness PI P2 P3 P4

Angle (degree) none 0 +60 -60 0

Draft angle of - 8 8 6 6

protuberance (degree)

Protrusion height - 8 8 6 5

H (mm)

Protrusion width - 10 10 5 7

1 (mm)

Fiber length 53 75 75 55

neutral of the

protuberance (mm)

Ri (mm) 260 261 261 261 261

R ₂ (mm) 220 220 220 220 220

R _E (mm) - 224.1 224.1 224.1 228

R _A (mm) - 298 298 298 298 Bulk size with 212 223 223 220 223

reliefs (mm)

Step (mm) 0 15 15 7 14

Table I

This test was carried out under the following operating conditions.

The tire, mounted on a 6.5 J 16 rim and inflated to the pressure of 1.9 bar, is disposed on the front right axle of a vehicle, and supports a load of 350kg.

The test is to perform, at different speeds, a shock called "sidewalk shock" of the tire on a metal block of height 90mm, at an angle of 30 ° with the block, relative to the direction of travel of the tire. .

This test is performed with a control tire (without protuberance) and different tires according to the invention which comprise protrusions having or not an angle with the radial axis of the tire.

The results in Table II below show the gain obtained in speed, between a control tire (result equal to 100) and the various tires according to the invention, mentioned above, before the tire puncture.

Pneumatic Gain in speed (%)

Witness 100

PI 120 P3 135

P4 120

Table II

The results of Table II show that the tire according to the invention, whatever the embodiment, allows a sharp increase in the attack speed of the sidewalk before its puncture. Example 2: Sidewalk shock test

This test was carried out with a 245/40 RI 8 reference tire comprising different representations of protuberances, at the same control tire without protuberances.

The tires PI to P4 are different tires according to the invention. The various technical characteristics mentioned for example 1 are reproduced in example 2.

Table III below summarizes the measurable technical characteristics of the various tires according to a variant of the invention.

Pneumatic Witness PI P2

Angle (degree) none 0 +30

Draft angle of - 8 8

protuberance (degree)

Protrusion height H (mm) - 6 6 Protrusion width 1 (mm) - 6 6

Neutral fiber length of the - 45 52

protuberance (mm)

Ri (mm) 277 277 277

R ₂ (mm) 248 248 248

R _E (mm) - 272,272

R _A (mm) - 313 313

Size boudin with reliefs 249 249 249

(Mm)

Step (mm) 0 12 12

Table III

This test was carried out under the same operating conditions as those explained in Example 1 with a rim 8.5 J 18 and a tire inflated to the pressure of 2.3 bars, all mounted on a right front axle. a vehicle, and supporting a load of 580kg.

The results of Table IV below show the gain obtained in speed, between a control tire (result equal to 100) and the various tires according to the invention, cited above, before the tire puncture. Pneumatic Gain in speed (%)

Witness 100

PI 128

P2 130

Table IV

The results of Table IV show that the tire according to the invention, whatever the embodiment, allows a sharp increase in the attack speed of the sidewalk before its puncture.

Claims

A tire for a wheel assembly comprising a rim and a tire, said tire comprising at least one carcass reinforcement (2) comprising an inner wall (2a) and radially surmounted outside a crown reinforcement (3), -even 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 rim hook tops (7b), each bead (5) comprising at least one circumferential reinforcing element, said sidewalls (6) having, on their outer surface, a series of alternating protuberances (8) with recesses (9), the inner wall (2a) of the carcass ply (2) of the tire being re partially or totally covered with at least one layer of a self-sealing composition (2b), characterized in that each protuberance (8) is disposed on the surface of the sidewall (6), said protuberances (8) being arranged continuous between a point A and a point E, said point A being disposed at the intersection of the radially outer surface of the tread and the sidewall, and a radial axis ZZ 'distant from a plane AA' of a length L _A of between ½ (L-60mm) and ½ (L-10mm), L being the nominal coil size, said plane AA 'being parallel to the equatorial plane and tangential to the sidewall (6), and said point E being disposed optionally in a radius such that P ₂ <E <(R _A - 15mm), where R ₂ is the radius of the top of the rim hook and R _{A is} the radius of the point A.

2. A tire according to claim 1, characterized in that at least one protuberance (8) has a height and a length, said height being minimal to the coil size and gradually increasing on either side of said coil size with a minimum height at a distance between 0.9Ri and 1.1 Ri.

3. A tire according to claim 1, characterized in that at least two protuberances (8) have a length different from each other.

4. A tire according to claim 1, characterized in that each protuberance (8) has an average height of between 3 and 10mm.

5. A tire according to claim 1, characterized in that each protuberance (8) has an average width of between 4 and 12mm.

6. A tire according to claim 4, characterized in that the average height of each protuberance (8) is preferably between 5 and 8mm.

7. A tire according to one of claims 1, 4 or 6, characterized in that each protuberance (8) has an average height greater than 80% of the maximum height over at least 80% of the distance between the points A and E.

8. A tire according to claim 1, characterized in that each protuberance (8) has a draft angle of less than or equal to 20 °, and preferably between 5 and 8 °.

9. A tire according to claim 1, characterized in that two adjacent protuberances (8) are spaced from each other by an average distance less than or equal to 2 times the average width of a protuberance.

10. A tire according to claim 1, characterized in that two adjacent protuberances (8) are substantially parallel to one another.

11. A tire according to claim 1, characterized in that the protuberances (8) cover at least 40% of the total circumferential surface of the sidewall between points A and E.

12. A tire according to claim 1, characterized in that each protuberance (8), of definite geometric shape or any, comprises a neutral fiber, passing through a radially innermost end and a radially outermost end, and having a angle β, with respect to the radial direction ZZ ', between -60 ° and + 60 °.

13. A tire according to claim 1, characterized in that the recess (9) between two adjacent protuberances (8) extends axially in the extension of the hollow of a circumferential groove of the tread passing through the point A, said groove being disposed on at least one axial end of the tread.

14. A tire according to claim 1 or 13, characterized in that two adjacent projections (8) form a recess between them, the wall of a protuberance (8) forming an angle α, with the circumferential direction between -15 ° and + 15 ° in a zone of the flank close to point A.

Tire according to claim 1, characterized in that the sum of the width of the protuberances in the circumferential direction is greater than or equal to 60% of the total circumferential length.

16. A tire according to claim 1, characterized in that it has a ratio [sum of the total widths of each protuberance] / 2 R greater than or equal to 30%, and more preferably greater than or equal to 60%> and less than or equal to at 70%), the widths of each protrusion (8) being defined at 50%> of the total height of said protrusion (8) and the radius R of the tire being a mean radius.