WO2019086785A1

WO2019086785A1 - Tyre with optimised self-supporting sidewalls

Info

Publication number: WO2019086785A1
Application number: PCT/FR2018/052656
Authority: WO
Inventors: Gérald HABERT; Jean-Marc Viller; Serge Lefebvre
Original assignee: Compagnie Generale Des Etablissements Michelin
Priority date: 2017-10-31
Filing date: 2018-10-26
Publication date: 2019-05-09

Abstract

An extended mobility tyre having a mounting direction, the sidewalls (25,26) being reinforced by sidewall inserts (ie, ii), such that the maximum axial width (Le) of the insert (ie) external to the vehicle is at least equal to the maximum axial width (Li) of the internal insert (ii) increased by 2 mm and at most equal to the maximum axial width (Li) of the internal insert (ii) increased by 6 mm, and such that the rubber compositions constituting said inserts (ie, ii) have a complex dynamic shear modulus G, measured at 23°C, at least equal to 1.0 and at most equal to 5.0 MPa, having a dynamic loss tan5, measured at a temperature of 23°C and under a stress of 0.7 MPa at 10 Hz, at most equal to 0.15.

Description

Self-supporting sidewall tire optimized

FIELD OF THE INVENTION

The present invention relates to an asymmetrical self-supporting sidewall type extended mobility tire.

A tire having a geometry of revolution with respect to an axis of rotation, the tire geometry is generally described in a meridian plane containing the axis of rotation of the tire. For a given meridian plane, the radial, axial and circumferential directions respectively designate the directions perpendicular to the axis of rotation of the tire, parallel to the axis of rotation of the tire and perpendicular to the meridian plane. The median circumferential plane said equatorial plane divides the tire into two substantially symmetrical half-tores, the tire may have tread asymmetries, architecture, related to the accuracy of manufacture or sizing.

In what follows, the expressions "radially inner to" and "radially outside to" respectively mean "closer to the axis of rotation of the tire, in the radial direction, that" and "further from the axis of rotation of the tire, in the radial direction, that ». The expressions "axially inner to" and "axially outside to" respectively mean "closer to the equator plane, in the axial direction, than" and "further from the equator plane, in the axial direction, than". A "radial distance" is a distance from the axis of rotation of the tire, and an "axial distance" is a distance from the equator plane of the tire. A "radial thickness" is measured in the radial direction, and an "axial width" is measured in the axial direction.

A crown comprising at least one crown reinforcement, a tread intended to come into contact with the ground via a running surface. A tire also comprises two beads intended to come into contact with a rim and two flanks connecting the top to the beads. In addition, a tire comprises a carcass reinforcement comprising at least one carcass layer, radially inner to the top and connecting the two beads. A tire also includes a radially innermost sealing layer of the tire.

The crown reinforcement comprises at least one working reinforcement comprising at least two working layers, radially external to the carcass reinforcement and radially inner to the tread. These working layers are superimposed and formed of reinforcements or parallel cables in each layer and crossed from one layer to the next. The crown reinforcement may also comprise a hooping layer whose reinforcing elements are at an angle to the circumferential direction at most equal to 10 °.

The tire manufacturers are making particularly important efforts to develop original solutions to a problem dating back to the very beginning of the use of tires with inflated type tires, namely how to allow the vehicle to continue its journey despite a significant or total loss of pressure of one or more tires. For decades, the spare wheel was considered the unique and universal solution. Then, more recently, the considerable benefits of its eventual removal have emerged. The concept of "extended mobility" has developed. The associated techniques make it possible to ride with the same tire, according to certain limits to be respected, after a puncture or a pressure drop. This allows for example to get to a breakdown point without having to stop, in often hazardous circumstances, to install the spare wheel. [0007] A self-supporting flank-type extended-mobility tire comprises flank inserts included between the most axially inner reinforcing elements of the at least one carcass layer and the most radially inner sealing layer of the tire. In case of loss of pressure, these inserts give structural stiffness to the tire and support the top, allowing extended mobility. BACKGROUND

[0008] A tire is characterized by a speed index. This speed index is assigned if the tire satisfies endurance tests known as instantaneous speed limits. During these tests, the tire performs on a rolling machine well known to those skilled in the art running at higher speeds at defined load and pressure conditions. These tests are regulated. They take place without camber of the tire. For example, at an ambient temperature of 25 ° C, a limit speed test consists of rolling on a metal wheel of 8.5 m circumference, the pressure depending on the nominal pressure of the tire and a regulated load dependent the nominal load of the tire. The tire rolls in increasing speed increments, lasting 20 minutes each, the increment in speed is 10 km / h. The tires are classified according to the maximum speed reached and the driving time during the last speed step reached.

Vehicle manufacturers usually put a negative camber or camber to improve the road holding of the vehicle cornering. This camber influences the mechanical and thermal stresses of the tire and some manufacturers of so-called sports vehicles have special requirements in terms of endurance tests and in particular instantaneous speed limit. These specific tests add a camber condition which penalizes the mechanical and thermal resistance of the tire and influences the speed level reached during the test. SUMMARY OF THE INVENTION

[001 1] One of the objectives of the present invention is therefore to improve the performance on speed limit endurance tests including negative camber, while maintaining a running mode extended compatible with the requirements of manufacturers.

This objective is achieved by a tire adapted for running with extended mobility, intended to be mounted on a mounting rim of a wheel of a vehicle and having a mounting direction on the predetermined vehicle,

Comprising a tread extending between an outer axial edge and an inner axial edge, the inner axial edge being the edge intended to be mounted on the side of the vehicle body when the tire is mounted on the vehicle in said direction of travel; predetermined assembly, the tread comprising grooves,

At least one carcass-type reinforcing structure joining on each side of said tire a bead whose base is intended to be mounted on a seat of the rim, the carcass-type reinforcing structure comprising at least one carcass layer comprising elements reinforcement substantially parallel to each other and forming with the radial direction an angle at most equal to 15 °,

Each of said beads extending substantially radially outwards in the form of flanks, ie an inner flank intended to be positioned on the inside of the vehicle, and an outer flank intended to be positioned on the outside of the vehicle,

The carcass-type reinforcing structure extending circumferentially from the bead towards said flank, and radially inner to a crown reinforcement,

• the inner and outer flanks joining radially outwardly the tread,

Each of said flanks being reinforced by a flank insert, an inner insert in the inner side, and an outer insert in the outer side, axially inner to the most axially inner reinforcing elements of the at least one carcass layer,

Said inserts consisting of rubber compositions allowing the sidewalls to bear a load corresponding to a part of the weight of the vehicle during a situation in which the inflation pressure is substantially reduced or zero,

The maximum axial width of the outer insert measured perpendicularly to the carcass reinforcements is at least equal to the maximum axial width of the inner insert increased by 2 mm and at most equal to the maximum axial width of the inner insert increased by 6; mm

The rubber compositions constituting said inserts have a complex dynamic shear modulus G *, measured at 23 ° C. according to ASTM D 5992-96, at least equal to 1.0 and at most equal to 5.0 MPa,

The rubber compositions constituting said inserts having a dynamic loss tanδ, measured according to the same standard ASTM D 5992 - 96 at a temperature of 23 ° C. and under a stress of 0.7 MPa at 10 Hz, at most equal to 0 , 15, preferably at most equal to 0.12.

In a preferred embodiment, the inner insert in the inner side, and the outer insert in the outer side are between the most axially inner reinforcing elements of the at least one carcass layer and a layer. most radially inner seal of the tire. Nevertheless, the sealing properties of the inner and outer flanks inserts as well as their axial widths may make it possible not to use a sealing rubber axially internally to said inserts, a sealing rubber being disposed radially internally to the top layers and axially internally to the beads.

In the speed limit tests comprising negative camber failure of the tire mainly occurs by a tip failure overloaded by the camber against the side of the tire on the vehicle interior side. In front of this solicitation dissymet, it is advisable to opt for a design dissymmetry. More specifically, the objective is achieved by a tire intended to be mounted on a mounting rim of a wheel of a vehicle and having a mounting direction on the predetermined vehicle, comprising a tread extending between an edge. external axial and an inner axial edge, the inner axial edge being the edge intended to be mounted on the side of the vehicle body when the tire is mounted on the vehicle according to said predetermined mounting direction,

The invention consists in differentiating the architecture of the tire between the flank of the side of the inner axial edge (said inner sidewall) and the flank of the side of the outer axial edge (said outer sidewall) of the tire. A natural solution would be to strengthen the top on the side of the inner axial edge while avoiding modifying the sidewall insert that guarantees extended mobility performance.

Surprisingly, the invention consists in precisely reducing the thickness of the insert of the vehicle interior while it is the most mechanically stressed while controlling a level of rigidity and hysteresis of the materials of the inserts to optimize their mechanical and thermal operation not only in running at zero pressure but also on speed limit tests including camber. Indeed the decrease in the thickness and therefore the mass of the vehicle-side insert makes it possible to reduce the centrifugal force under test at the limit speed and thus to reduce the mechanical stresses during the limit speed test while the control of the hysteresis of the material of the insert makes it possible to reduce the thermal stresses in the zone. On the other hand, it is necessary to control the reduction of rigidity brought about by the reduction of the thickness of the insert of the inner side to maintain or even improve the running performance at low pressure or zero pressure, by an adequate rigidity of the rubber composition (s). constituting the inserts. This rigidity of these rubber compositions is the complex dynamic shear modulus G ^* , measured at 23 ° C. according to ASTM D 5992-96 at least equal to 1.0 and at most equal to 5.0 MPa. In addition, this reduction in mass is accompanied by a reduction in cost and rolling resistance. For materials in which the complex dynamic shear modulus G * is less than 1.0 MPa, the tire no longer attains the performance in load capacity during zero-pressure rolling, and for materials whose complex dynamic shear modulus G * is above 5.0 MPa, comfort performance is degraded.

The properties of the rubber compositions are measured on glued specimens extracted from the tire. Specimens such as those described in ASTM D 5992-96 (version published September 2006, initially approved in 1996) in Figure X2.1 (circular embodiment) are used. The diameter "d" of the test piece is 10 mm [0 to + 0.04 mm], the thickness "L" of each of the rubber composition portions is 2 mm [1.85-2.20].

These properties are measured on a viscoanalyzer of Metravib VA4000 type on vulcanized specimens. The terms complex, elastic and viscous modules denote dynamic properties well known to those skilled in the art. The "complex modulus" G * is defined by the following relation: G * = (G ' ² + G " ² ) in which G' represents the elastic modulus and G" represents the viscous modulus. The phase angle δ between the force and the displacement translates into a dynamic loss tanô is equal to the ratio G'VG '

The response of a sample of vulcanized rubber composition subjected to a sinusoidal stress in alternating simple shear at the frequency of 10 Hz at imposed stress is recorded symmetrically about its equilibrium position. An accommodation of the specimen is carried out prior to the temperature scanning measurement. The specimen is therefore subjected to sinusoidal shear at 10 Hz at 100% peak-to-peak deformation at 23 ° C.

The scanning temperature measurement is performed during a ramp of increasing temperature of 1.5 ° C per minute, since a temperature Tmin less than the glass transition temperature Tg of the material, up to a temperature Tmax which can correspond to the rubbery plate of the material. Before starting the sweep, the sample is stabilized at the Tmin temperature for 20 minutes to obtain a homogeneous temperature within the sample. The results exploited at the chosen temperature and stress are generally the complex dynamic shear modulus G *, comprising an elastic part G ', a viscous part G "and the phase angle δ between the force and the displacement translated into a loss factor The glass transition temperature Tg is the temperature at which the tanδ dynamic loss reaches a maximum during the temperature sweep.

These tests relate more specifically to tires for so-called sports vehicles whose nominal width is at least 205 mm and the flank height, preferably at least equal to 235 mm, measured on a meridian plane between the most radially point. tire outside and the most radially inner point of the tire, is at most equal to 120 mm.

According to a first advantageous embodiment, the rubber compositions constituting said inserts have a dynamic loss tanδ, measured according to the same standard ASTM D 5992 - 96 at a temperature of 23 ° C and under a constraint of 0.7 MPa at 10 Hz, at least 0.01, preferably at least 0.02. The low hysteresis materials are indeed sensitive to cracking and are not suitable for constituting inserts for the flanks of tires with extended mobility.

According to an advantageous embodiment, the rubber compositions constituting said inserts have a complex dynamic shear modulus G *, measured at 23 ° C. according to ASTM D 5992-96, at least equal to 1, 9 and at most equal to 3.3 MPa allowing an optimum between the performance in load capacity during zero pressure rollings and the comfort in running under service pressure.

It is advantageous that the crown reinforcement comprises at least one hybrid shrouding layer aramid and nylon overflowing layers of work so that the top does not deform excessively when driving to zero pressure postponing over-stressing on the flank inserts degrading this performance or to limit the centrifugation of the summit during the speed limit tests. By overlying fretted layer is meant a shrink layer whose axially outermost point is axially external to the most axially outer point of the working layers, on both inner and outer sides of the crown of the tire.

Preferably, the tire is bidirectional, namely that no preferential direction of rolling is etched on the sidewalls of the tire and the design of the tread is such that the performance of the tread is of the same order as the tire is used in one or the other of the two possible driving directions for the tire. Indeed the use of bidirectional tires allows a simplification of the production. For the same axle, a single bidirectional tire model according to the invention is usable. If the tire is directional, it is necessary to have tires according to the invention differentiated according to whether they equip the left side or the right side of the vehicle, which multiplies the costs of molds, inventory and management.

According to another advantageous embodiment, when the tread of the tire according to the invention comprises non-circumferential grooves, these non-circumferential grooves located in the shoulders form an angle with the transverse axis of the tire at most equal to 30 ° to guarantee the bidirectional character of the tire. The tread is divided into three thirds in its axial width of equal widths. A central third and two thirds axially outside on either side of the central third commonly referred to as the shoulder.

For the same reason, it is preferred that the grooves of the tread are asymmetrical with respect to the median circumferential plane.

The use of this solution is particularly suitable for vehicles having, on at least one axle, a static counter camber between 0.5 ° and 5 °, preferably between 1 ° and 3 ° and more particularly of which the dimensions of the tires are different between the front axle and the rear axle of the vehicle. Indeed, the tires according to the invention are essentially intended for so-called sporting vehicles for which tire mounts are differentiated between the front and rear axles to optimize the performance of said vehicle. This solution is particularly interesting for tires mounted on the rear axles of vehicles whose characteristics are more commonly in the mentioned ranges in order to optimize the behavior of the vehicle. The wheels on which the tires according to the invention are mounted, are of types H2, EH2 and EH2 +. It is advantageous to make the tire by laying two identical sections of the minimum thickness of the inner sidewall insert and add a second outer side edge profile to obtain the desired asymmetry. One or both inserts can therefore be composed of several different rubber compositions in that the rigidity and the hysteresis of the insert respect the necessary mechanical and hysteretic characteristics of the invention.

It is particularly advantageous that the bead of the tire is designed so that the tire is undetachable even at zero pressure for example by the use of rigid rods in rotation. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 shows a tire according to the invention.

[0034] Figure 2 illustrates the terms 'inner edge' and 'outer edge' of a tread.

Figures 3A and 3B illustrate the method for determining the tread width of a tire.

DETAILED DESCRIPTION OF THE DRAWINGS

The expression "rubber composition" denotes a material comprising at least one elastomer and at least one filler. Figure 1 schematically shows a tire according to the invention. The tire comprises a crown comprising a crown reinforcement (50) surmounted by a tread 10, two sidewalls (25, 26), an inner side (26) intended to be positioned on the inside of the vehicle, and a sidewall outside (25), intended to be positioned on the outer side of the vehicle, said sidewalls extending the crown radially inward, and two radially inner flanges to the sidewalls (25, 26). The apex extending between an outer axial edge (45) and an inner axial edge (46), the inner axial edge being the edge intended to be mounted on the side of the vehicle body when the tire is mounted on the vehicle according to said predetermined mounting direction, the tread (10) including grooves.

FIG. 1 represents the carcass-type reinforcement structure comprising at least one carcass layer (31) comprising reinforcement elements that are substantially parallel to one another and form, with the radial direction, an angle at most equal to 15 °. This reinforcing structure can be composed of one, two or more reinforcing layers.

Said flanks (25, 26) are reinforced by a flank insert, an inner insert (ii) in the inner side, and an outer insert (ie) in the outer side, between the most reinforcing elements. axially inner portions of the at least one carcass layer (31) and a radially innermost sealing layer (32) of the tire, and such that the maximum axial width (Le) of the outer insert (ie) is at least equal to the maximum axial width (Li) of the inner insert (ii) increased by 2 mm and at most equal to the maximum axial width (Li) of the inner insert increased by 6 mm. It is possible that the flank inserts (ii and ie) comprise one or more materials complying with the rigidity and hysteresis conditions mentioned.

FIG. 1 shows a layer of radially outermost reinforcing elements protruding with respect to the radially inner crown layers. Figure 2 shows schematically the top of a tire to be mounted on a mounting rim of a wheel of a vehicle and having a mounting direction on the vehicle, predetermined. It comprises a tread extending between an outer axial edge 45 and an inner axial edge 46, the inner axial edge 46 being the edge intended to be mounted on the side of the vehicle body when the tire is mounted on the vehicle according to said predetermined mounting direction, as suggested in Figure 2 which schematically shows a vehicle 200.

Figures 3A and 3B, is determined on a meridian plane axial boundaries 7 of the tread surface that measure the tread width on this meridian plane. In FIG. 3A, where the rolling surface 21 is intersecting with the external axial surface of the tire 8, the axial boundary 7 is trivially determined by those skilled in the art. In FIG. 3B, where the rolling surface 21 is continuous with the external axial surface of the tire 8, the tangent to the rolling surface at any point of the rolling surface in the zone of the tire is drawn on a meridional section of the tire. transition to the flank. The first axial boundary 7 passes through the point for which the angle β (beta) between said tangent and an axial direction YY 'is equal to 30 °. When there exist on a meridian plane, several points for which the angle β between said tangent and an axial direction YY 'is equal to 30 °, one retains the point radially the outermost. The same procedure shall be used to determine the second axial boundary of the running surface. The width of the tread at the meridian plane is the axial distance between the two points of the meridian plane of the two axial boundaries of the tread surface. The width of the tread of the tire is the maximum value of the widths of the tread on all the meridians. This width is used to determine the positioning of the shoulders of the tire.

This invention was performed on a tire size 275 / 35R19 100Y. The tire A whose flank inserts are symmetrical and an axial width I of 9 mm, made of the same material having a complex dynamic shear modulus G ^* equal to 3.15 MPa and whose dynamic loss tanô , measured at a temperature of 23 ° C and under a stress of 0.7 MPa at 10 Hz, equal to 0.09. The tire comprises a shrink layer: hybrid aramid and nylon whose axial width is greater than the axial width of the working layers of 12 mm and overflowing.

The tire B according to the invention, the sidewall inserts are asymmetrical. The inner insert has an axial width of 6 mm and the outer insert has an axial width of 9 mm. They consist of the same material having a complex dynamic shear modulus G ^* , equal to 3.15 MPa and whose dynamic loss tanδ, measured at a temperature of 23 ° C and under a stress of 0.7 MPa at 10 Hz , equal to 0.09.

The tire B improves the speed limit endurance performance by at least 1 step of 10 km / h for 10 minutes compared to the tire A and from 20 to 100% the mileage achieved on the vehicle in extended mobility The gain in mass is 300g (AB), the RRt is lowered by 0.1 kg / T for a tire A which weighs 13.7 kg.

Claims

1. Pneumatic tire adapted for traveling with extended mobility, intended to be mounted on a mounting rim of a wheel of a vehicle and having a direction of mounting on the predetermined vehicle, comprising a tread (10) extending between an outer axial edge (45) and an inner axial edge (46), the inner axial edge being the edge intended to be mounted on the side of the vehicle body when the tire is mounted on the vehicle in said predetermined mounting direction, the tread (10) comprising grooves,

At least one carcass-type reinforcing structure joining on each side of said tire a bead (20) whose base is intended to be mounted on a seat of the rim, the carcass-type reinforcement structure comprising at least one carcass layer (31) comprising reinforcing elements substantially parallel to each other and forming with the radial direction an angle at most equal to 15 °,

Each of said beads (20) extending substantially radially externally in the form of flanks, an inner flank (26) intended to be positioned on the inside of the vehicle, and an outer flank (25) intended to be positioned on the inside of the vehicle; outside of the vehicle,

· The carcass-type reinforcement structure extending radially from the bead towards said sidewall, and radially inner to a crown reinforcement,

• the inner and outer flanks joining radially outwardly the tread,

Each of said flanks being reinforced by a flank insert, an inner insert (ii) in the inner side, and an outer insert (ie) in the outer side, axially inner to the most axially inner reinforcing elements of the at least one a carcass layer (31), Said inserts (ii, ie) consisting of rubber compositions allowing the sidewalls to support a load corresponding to a portion of the weight of the vehicle during a situation in which the inflation pressure is substantially reduced or zero,

Characterized in that the maximum axial width (Le) of the outer insert (ie) measured perpendicularly to the carcass reinforcements is at least equal to the maximum axial width (Li) of the inner insert (ii) increased by 2 mm and at most equal to the maximum axial width (Li) of the inner insert increased by 6 mm,

In that the rubber compositions constituting said inserts (ie, ii) have a complex dynamic shear modulus G *, measured at 23 ° C. according to ASTM D 5992-96, at least equal to 1, 0 and more equal to 5.0 MPa.

In that the rubber compositions constituting said inserts (ii, ie) have a dynamic loss tanδ, measured according to the same standard ASTM D

5992 - 96, at a temperature of 23 ° C. and under a stress of 0.7 MPa at 10 Hz, at most equal to 0.15, preferably at most equal to 0.12.

2. A tire according to claim 1, wherein the rubber compositions constituting said inserts (ii, ie) have a dynamic loss tanδ, measured at a temperature of 23 ° C and a stress of 0.7 MPa at 10 Hz, at least equal to 0.01, preferably at least 0.02.

3. A tire according to any one of claims 1 or 2, the rubber compositions constituting said inserts (ii, ie) have a complex dynamic shear modulus G *, measured at 23 ° C according to ASTM D 5992 - 96 , at least equal to 1, 9 and at most equal to 3.3 MPa.

4. A tire according to any one of claims 1 to 3, wherein the tire is bidirectional.

A tire whose tread comprises non-circumferential grooves according to any one of claims 1 to 4, wherein the non-circumferential grooves in the shoulders of the tread form an angle with the transverse axis of the tire at more equal to 30 °.

A tire whose tread comprises non-circumferential grooves according to any one of claims 4 or 5, wherein the grooves of the tread are asymmetrical with respect to the medial circumferential plane.

7. Use of a tire according to any one of claims 1 to

6 on a car having, on at least one axle, a static camber against between 0.5 ° and 5 °, preferably between 1 ° and 3 °.

8. Use of the tires according to any one of claims 1 to

7 on a car having, on at least one axle, a static camber between 0.5 ° and 5 °, preferably between 1 ° and 3 ° and whose tire dimensions are different between the front and rear axle of the car.