EP3532313A1

EP3532313A1 - Aircraft tyre crown reinforcement

Info

Publication number: EP3532313A1
Application number: EP17797403.7A
Authority: EP
Inventors: Marc ROMERO DE LA OSA; Didier MALIN
Original assignee: Compagnie Generale des Etablissements Michelin SCA
Current assignee: Compagnie Generale des Etablissements Michelin SCA
Priority date: 2016-10-26
Filing date: 2017-10-24
Publication date: 2019-09-04
Also published as: FR3057809A1; WO2018078268A1; CN109843605A; US20190263182A1

Abstract

The subject of the present invention is an aircraft tyre crown reinforcement and the object of the present invention is to increase the mechanical strength thereof so as to increase the bursting pressure of the tyre during a pressure test in accordance with prescribed standards. An aircraft tyre comprises a working reinforcement consisting of a strip (5) wound continuously in a zigzag from a starting end (51) to a finishing end (52) in a circumferential direction (XX') of the tyre, according to a periodic curve (7) that, with the circumferential direction (XX') of the tyre and in an equatorial plane (XZ) of the tyre, makes a non-zero angle A. According to the invention, the respective starting end (51) and finishing end (52) of the strip (5) are positioned, axially from an axial end (E1, E2) of the working reinforcement, at a distance (DI, DF) at most equal to 0.25 times the axial width W_T of the working reinforcement.

Description

PNEUMATIC SUMMIT FRAME FOR AIRCRAFT

The present invention relates to an aircraft tire and its object, in particular, a tire crown reinforcement for aircraft. In what follows, and by convention, the circumferential, axial and radial directions respectively designate a direction tangent to the running surface of the tire in the direction of rotation of the tire, a direction parallel to the axis of rotation of the tire. and a direction perpendicular to the axis of rotation of the tire. By "radially inner, respectively radially outer" is meant "closer or more distant from the axis of rotation of the tire". By "axially inner, respectively axially outer" is meant "closer or more distant from the equatorial plane of the tire", the equatorial plane of the tire being the plane passing through the middle of the running surface of the tire and perpendicular to the tire. rotation axis of the tire. In general, a tire comprises a tread intended to come into contact with a ground via a rolling surface, the tread being connected by two sidewalls to two beads, the two beads. being intended to provide a mechanical connection of the tire with a rim on which the tire is mounted. [0004] A radial tire for aircraft more particularly comprises a radial carcass reinforcement and a crown reinforcement, as described, for example, in document EP 1381525.

The radial carcass reinforcement is the reinforcing structure of the tire connecting the two beads of the tire. The radial carcass reinforcement of an aircraft tire generally comprises at least one carcass layer, each carcass layer consisting of reinforcements, most often textile, coated with a polymeric material of elastomer type, obtained by mixing its constituents, or elastomeric mixture, said reinforcements being parallel to each other and forming, with the circumferential direction, an angle of between 80 ° and 100 °. The crown reinforcement is the reinforcing structure of the tire radially inner to the tread and generally radially external to the radial carcass reinforcement. The crown reinforcement generally comprises at least one crown layer, each crown layer consisting of reinforcements parallel to each other and coated with an elastomeric mixture. Among the top layers, the working layers, constituting the reinforcement and usually comprising textile reinforcements, and the protective layers constituting the protective reinforcement and comprising metal or textile reinforcements, are usually distinguished. protective armature being arranged radially outside the working armature. The working frame conditions the overall mechanical behavior of the crown reinforcement, while the protective armature essentially protects the working layers from aggressions that can propagate through the tread radially inwardly of the tire.

In the technical field of aircraft tires, the textile reinforcements of the carcass layers and crown layers are most often made of filament yarns preferably of aliphatic polyamide or aromatic polyamide. The metal reinforcements, potentially used as a protective layer, are cables made of metal wires.

During the manufacture of an aircraft tire, and more specifically during the step of setting up the reinforcement, a working layer is most often obtained by a continuous circumferential winding zigzag d a strip, on a cylindrical laying surface having for axis of revolution the axis of rotation of the tire. The strip is generally made of at least one continuous textile reinforcement coated in an elastomeric mixture and, most often, a juxtaposition of textile reinforcements parallel to each other. The working layer is then constituted by the juxtaposition of strip portions.

By circumferential winding in a zigzag strip is meant a winding of the strip, in the circumferential direction, and in a periodic curve, that is to say a curve formed of periodic corrugations oscillating between extrema . Wrapping a strip according to a periodic curve means that the average line of the strip, equidistant from the edges of the strip, coincides with the curve periodic. In a zigzag circumferential roll of a strip, the working layers are laid in pairs, each pair of working layers constituting a working bin. Thus a working bin is constituted, in the current zone, that is to say axially inside its axial ends, by two radially superimposed working layers. At its axial ends, a working bin generally comprises more than two radially superimposed working layers. Axial end allowance is the axial end portion of a working bin comprising more than two radially superimposed working layers. This axial end allowance is generated by the crosses of the strip at the end of working bin at each winding turn zigzag. Such a working frame comprising working pairs obtained by a zigzag circumferential winding of a strip has been described in the documents EP 0540303, EP 0850787, EP 1163120 and EP 1518666.

Generally, the zigzag circumferential winding of the strip begins and ends at the equatorial plane of the tire, circumferential plane passing through the middle of the armature and perpendicular to the axis of rotation of the tire. Consequently, the strips of reinforcing ends are positioned in the center of the work armature and therefore axially inside the axial ends of the working armature, a highly mechanically stressed zone in which the reinforcing ends, not carrying load, would be likely to create weak points in the structure and reduce the burst pressure potential of the frame of work.

The inventors, however, found that the median positioning of the ends of tape reinforcements was a weak point vis-à-vis the mechanical strength of the reinforcement work during burst pressure tests with water tire in accordance with TSO C62-e. The reinforcement is indeed the fuse of the tire during burst pressure tests.

To increase the strength of the work frame, it is known to increase the number of working layers and / or choose reinforcements of working layers having a higher breaking strength. The inventors have set themselves the objective of increasing the mechanical strength of the working frame of a tire for an airplane, and therefore of increasing the pressure of the tire burst, during a normative pressure test, without modifying the design of the reinforcement, in terms of the number of working layers and / or the choice of reinforcing layers of work and / or angles of the reinforcements of working layers.

This object has been achieved, according to the invention, by an aircraft tire, comprising:

a working frame radially inner to a tread and radially external to a carcass reinforcement,

the working armature being limited axially by two axial ends, distant from an axial width W _T , and comprising at least two radially superposed working layers,

each working layer consisting of a juxtaposition of portions of a strip of width W,

the strip being continuously wound in a zigzag manner, starting from a starting end to an end end, in a circumferential direction of the tire, on a cylindrical surface, having as axis of revolution the axis of rotation of the tire; and according to a periodic curve forming, with the circumferential direction of the tire and in an equatorial plane of the tire, a non-zero angle A,

the respective starting and end ends of the strip being positioned axially from an axial end of the working reinforcement at a distance at most equal to 0.25 times the axial width W _T of the working reinforcement.

The working frame of a pneumatic tire for the state of the art generally comprises at least two radially superposed working layers constituting a working bin. More specifically, a working bin comprises two working layers in the current zone, axially inside the axial end thickenings, and more than two working layers at the axial end thickenings.

A working binappe is generally constituted by a continuous circumferential winding in a zigzag of a strip of width W, from a starting end to an end end. This winding is carried out in a circumferential direction of the tire, on a cylindrical surface, also called a radius-laying surface R, having as axis of revolution the axis of rotation of the tire. In in addition, the winding is made according to a periodic curve, corresponding to the average line of the strip, forming, with the circumferential direction of the tire, a non-zero angle A. More specifically, the working bin is constituted by the winding of a number N of circumferential length periods P of the periodic curve over a number T of winding turns, that is to say a number T of circumferences 2I1R of the cylindrical surface laying radius R, which results in the relationship N * P = T * 2I1R.

Each working layer is thus constituted by a juxtaposition of portions of a strip of width W, in the circumferential direction of the tire. Two portions of consecutive strip are juxtaposed, in the circumferential direction, that is to say in contact with each other. In other words, two consecutive strip portions are neither disjoint nor partially overlapping. Their respective mean lines are borne by the periodic curve, which is wound on the strip, and therefore have extrema, which correspond to the axial ends of the working layer.

The reinforcement is a radial superposition of working layers that do not necessarily have the same axial width, the axial ends of the working reinforcement are called the axial ends of the working layer having the greatest axial width. . Consequently, the axial width W _T of the working reinforcement is equal to the maximum axial width of the working layer.

According to the invention, the respective start and end ends of the strip are positioned axially from an axial end of the reinforcement at a distance not greater than 0.25 times the axial width W _T of the strip. frame of work. In other words, each end end or end strip is positioned axially inside one of the two side portions of the work frame having an axial width equal to one quarter of the axial width W _T of the working armature, that is to say axially outside of a median portion of the armature having an axial width equal to half the axial width W _T of the armature of job. This positioning of the ends of the start and end of the strip allows to leave the area of maximum tensile stress, under the action of the inflation pressure, which increases the mechanical strength of the armature of work and, correspondingly, the bursting pressure of the tire. Advantageously, the respective start and end ends of the strip are positioned axially from an axial end of the reinforcement at a distance at most equal to 0.1 times the axial width W _T of the reinforcement. job.

This positioning is a compromise that makes it possible to be as close as possible to an axial end of the working reinforcement, that is to say the furthest possible from the medial portion of the working reinforcement, while avoiding the axial end thickening generated by the crosses of the strip at the end of the working bin at each winding turn zigzag, this excess thickness being a mechanically stressed area.

Preferably, the respective start and end ends of the strip are positioned axially from an axial end of the reinforcement at a distance at least equal to 0.05 times the axial width W _T of the reinforcement. job.

This positioning at a minimum axial distance from an axial end of the working frame makes it possible to avoid the axial end allowance generated by the crossings of the strip, at the end of the work bin, at each turn of rotation. winding in zigzag, this extra thickness being a mechanically stressed area. Thus the ends of the start and end respectively of the strip, privileged points for the initiation of cracks, are positioned axially outside the areas of strong mechanical stress generated by the crushing of the tire on the ground, which improves the holding of endurance of the crown frame. According to a first embodiment of the invention, the respectively starting and end ends of the strip are positioned axially from the same axial end of the reinforcement, that is to say that the two ends of the strip are positioned on the same side with respect to the equatorial plane. This first embodiment makes it possible to optimize the length of strip laid and to avoid a local extra thickness resulting from a superposition of strip portions in the rectilinear portions of the trajectory of the strip.

According to a second variant embodiment of the invention, the respective start and end ends of the strip are positioned axially from two different axial ends of reinforcement, that is to say that the two ends of the strip are positioned on opposite sides with respect to the equatorial plane.

This second embodiment allows a greater tolerance of axial positioning of the respectively starting and end ends of the strip in manufacture and thus facilitate the manufacture of the frame, particularly for small size tires, for example intended to be mounted on a rim of nominal diameter at most equal to 15 inches.

According to a preferred embodiment of the invention, the ends of the start and end respectively of the strip are positioned axially at an identical distance.

This preferred embodiment ensures a constant thickness of the reinforcement of work in the rectilinear portions of the trajectory of the strip, locally avoiding oversizes or holes. The angle A formed by the periodic curve, with the circumferential direction of the tire and in the equatorial plane of the tire, is still advantageously at least equal to 5 °. An angle A of at least 5 ° guarantees a minimum drift rigidity for the tire.

The angle A formed by the periodic curve, with the circumferential direction of the tire and in the equatorial plane of the tire, is also advantageously at most equal to 20 °. Beyond an angle A equal to 20 °, the drift rigidity of the aircraft tire becomes too great for the desired performance.

The width W of the strip is preferably at least 2 mm, preferably at least 6 mm. A minimum value of strip width is necessary for both the technological feasibility of the strip and the productivity of laying the strip.

The width W of the strip is still advantageously at most equal to 20 mm, preferably at most equal to 14 mm. A maximum value of strip width makes it possible to reduce the number of zigzag laying turns of the strip, necessary for the production of the working bin, which results in a reduction in the time required to produce the working bin and thus a gain of productivity.

The strip consisting of reinforcements coated in an elastomeric mixture, the strip comprises, according to a first embodiment of reinforcements, reinforcements made of a textile material, preferably an aliphatic polyamide. Indeed, the textile reinforcements, in particular of aliphatic polyamide such as nylon, have a relatively low mass compared to metal reinforcements, which allows a significant gain on the mass of the tire and therefore on the payload of the aircraft .

The strip consisting of reinforcements embedded in an elastomeric mixture, the strip comprises, according to a second embodiment of the reinforcements, reinforcements consisting of an aromatic polyamide. The reinforcements made of aromatic polyamide, such as aramid, make it possible to obtain a good compromise between high mechanical strength and low mass.

The strip consisting of reinforcements embedded in an elastomeric mixture, the strip comprises, according to a third embodiment of reinforcements, hybrid reinforcements consisting of a combination of an aliphatic polyamide and an aromatic polyamide. Such reinforcements are usually called hybrid reinforcements and have the technical advantages of nylon and aramid: high mechanical strength, high tensile deformability and low mass. The invention also relates to a method of manufacturing a tire for an airplane, comprising a step of manufacturing the reinforcement, in which the strip is wound continuously zigzag, from a starting end. to an end end, in the circumferential direction of the tire, on a cylindrical surface, having the axis of rotation of the axis of rotation of the tire, and in a periodic curve forming with the circumferential direction of the tire and in the plane equatorial tire, a non-zero angle A, so that the ends respectively starting and end of the strip are positioned axially from an axial end of working armature at a distance at most equal to 0.25 times the axial width W _T of the working armature.

The characteristics and other advantages of the invention will be better understood with the aid of the following figures 1 to 5, not shown on the scale:

-Figure 1: half-sectional view of an aircraft tire according to the invention, in a meridian or radial plane (YZ) passing through the axis of rotation (ΥΥ ') of the tire.

FIG. 2 is a perspective view of a strip wound circumferentially in a zigzag pattern, in a periodic curve, on a cylindrical surface.

-Figure 3: developed view of a circumferentially zigzag rolled strip, with positioning respectively ends of the start and end of the strip in the equatorial plane of the tire, according to the state of the art.

FIG. 4 is a developed view of a strip wound circumferentially in a zig-zag configuration, with positioning of the respectively starting and end ends of the strip on the same side of the equatorial plane of the tire, according to a first embodiment of the invention.

FIG. 5 is a developed view of a strip circumferentially wound in a zig-zag fashion, with positioning of the ends respectively of the start and the end of the strip on either side of the equatorial plane of the tire, according to a second variant embodiment of the invention.

FIG. 1 represents a half-view in section, in a radial plane (YZ), of a tire 1 for aircraft of the state of the art, comprising a working frame 2 radially inner to a tread. 3 and radially external to a carcass reinforcement 4. In the example shown, the working armature 2 comprises a working bin, consisting of two radially superposed working layers (21, 22), obtained by the circumferential winding. in zigzag (see FIG. 2) of a strip of width W, on a cylindrical laying surface 6 of radius R, having for axis of revolution the axis of rotation (ΥΥ ') of the tire. The axial end thickenings of the working bin 21 are not shown, for the sake of simplicity. In a radial plane, each working layer (21, 22) consists of an axial juxtaposition of strip portions 5 of width W / cosA, where W is the width of the strip 5, measured perpendicular to its mean line, and A is the angle (see Figure 3) formed by the average line of the strip 5, with the circumferential direction (XX '), in the equatorial plane (XZ). The width of the working armature being equal to W _T , its half-width W _T / 2 is represented in FIG. 1. FIG. 2 is a perspective view of a strip 5 constituting a working armature of a pneumatic tire of the state of the art wound circumferentially in a zig-zag manner, according to a periodic curve 7, on a cylindrical laying surface 6, of revolution about the axis of rotation (ΥΥ ') of the tire, having a radius R. In Figure 2 are shown only 3 winding turns of the strip 5, that is to say a working layer in progress.

FIG. 3 is a developed view showing the beginning and the end of a zigzag winding of a strip 5 having a width W and whose mean line 7 forms, with the circumferential direction XX 'and in the equatorial plane. XZ, an angle A, the intermediate portion of the winding is not shown here. The amplitude of the zigzag defines the axial width W _T of the working reinforcement, that is to say the axial distance between the two axial ends El and E2 of the working reinforcement. The winding of the state of the art, represented in FIG. 3, is characterized by a positioning of the start and end ends of the strip in the equatorial plane XZ, which can be more generally in the vicinity of the equatorial plane XZ. . Figure 4 is a developed view showing the beginning and the end of a zigzag winding of a strip 5, according to a first embodiment of the invention. In this case, respectively the starting ends 51 and end ends 52 of the strip 5 are positioned axially, from the same axial end E2 of reinforcement, at respective distances DI and DF at most equal to 0.25 times the axial width W _T of the reinforcement.

Figure 5 is a developed view showing the beginning and the end of a zigzag winding of a strip 5, according to a second embodiment of the invention. In this case, the starting end 51 is positioned axially, starting from the axial end E2 of reinforcement, at a distance DI at most equal to 0.25 times the axial width W _T of the working reinforcement, and the end end 52 is positioned axially, from the axial end E1 of opposite working reinforcement, at a distance DF at most equal to 0.25 times the axial width W _T of the working reinforcement.

The inventors have made a pneumatic tire 50x20R22 dimension, respectively according to the state of the art and according to the second embodiment of the invention. The tire according to the second embodiment of the invention is characterized by an axial positioning of the respectively starting and end ends of the strip, on either side of the equatorial plane of the tire, and at axial distances with respect to the axial ends of the armature identical and equal to DI = DF = 0.1W _T.

These tires were subjected to a water pressure test according to TSO C62-e. Both tires burst as a result of a break in their working frame. The burst pressure measured for the tire of the invention is greater than 0.2Pn than that measured for the tire of the state of the art, Pn being the nominal inflation pressure of the tire.

Claims

CLAIMS 1 - Pneumatic (1) for aircraft comprising:

a working armature (2) radially inner to a tread (3) and radially external to a carcass reinforcement (4),

the working armature (2) being axially limited by two axial ends (E1, E2), distant from an axial width W _T , and comprising at least two radially superposed working layers (21, 22),

each working layer (21, 22) consisting of a juxtaposition of portions of a strip (5) of width W,

the strip (5) being continuously wound in zigzag, from a starting end (51) to an end end (52), in a circumferential direction (XX ') of the tire, on a cylindrical surface ( 6), having for axis of revolution the axis of rotation (ΥΥ ') of the tire, and according to a periodic curve (7) forming with the circumferential direction (XX') of the tire and in an equatorial plane (XZ) of the tire , a non-zero angle A,

characterized in that the respectively starting end (51) and end (52) ends of the strip (5) are axially positioned from an axial end (E1, E2) of reinforcement (2) at a distance (DI, DF) at most equal to 0.25 times the axial width W _T of the working reinforcement (2). 2 - tire (1) for an aircraft according to claim 1, wherein respectively the ends of departure (51) and end (52) of the strip (5) are positioned axially from an axial end (E1, E2) of working reinforcement (2) at a distance (DI, DF) at most equal to 0.1 times the axial width W _T of the working reinforcement (2).

3 - pneumatic tire (1) for aircraft according to one of claims 1 or 2, wherein the respectively starting ends (51) and end (52) of the strip (5) are positioned axially from an axial end (E1, E2) of working reinforcement (2) at a distance (DI, DF) at least equal to 0.05 times the axial width W _T of the working reinforcement (2).

4 - pneumatic tire (1) for aircraft according to any one of claims 1 to 3, wherein the respectively starting ends (51) and end (52) of the strip (5) are positioned axially from the same axial end (E1, E2) of reinforcement (2).

5 - pneumatic tire (1) for aircraft according to any one of claims 1 to 3, wherein the ends respectively start (51) and end (52) of the strip (5) are positioned axially from two axial ends (E1, E2) different reinforcement (2).

6 - tire (1) for an aircraft according to any one of claims 1 to 5, wherein respectively the ends of departure (51) and end (52) of the strip (5) are positioned axially at a distance (DI, DF) identical. 7 - tire (1) for aircraft according to any one of claims 1 to 6, wherein the angle A formed by the periodic curve (7), with the circumferential direction (XX ') of the tire and in the equatorial plane ( XZ) of the tire, is at least equal to 5 °.

8 - tire (1) for aircraft according to any one of claims 1 to 7, wherein the angle A formed by the periodic curve (7), with the circumferential direction

(XX ') of the tire and in the equatorial plane (XZ) of the tire, is at most equal to 20 °.

9 - pneumatic tire (1) for aircraft according to any one of claims 1 to 8, wherein the width W of the strip (5) is at least 2 mm, preferably at least 6 mm.

10 - tire (1) for aircraft according to any one of claims 1 to 9, wherein the width W of the strip (5) is at most equal to 20 mm, preferably at most equal to 14 mm.

11 - tire (1) for aircraft according to any one of claims 1 to 10, the strip (5) consisting of reinforcements embedded in an elastomeric mixture, wherein the strip (5) comprises reinforcements made of a textile material preferably an aliphatic polyamide.

12 - tire (1) for aircraft according to any one of claims 1 to 10, the strip (5) consisting of reinforcements embedded in an elastomeric mixture, wherein the strip (5) comprises reinforcements consisting of an aromatic polyamide . 13 - tire (1) for aircraft according to any one of claims 1 to 10, the strip (5) consisting of reinforcements embedded in an elastomeric mixture, wherein the strip (5) comprises hybrid reinforcements consisting of a combination an aliphatic polyamide and an aromatic polyamide. 14 - A method of manufacturing an aircraft tire (1) according to any one of claims 1 to 13, comprising a step of manufacturing the work frame (2), wherein the strip (5) is wound continuously zigzagging from a starting end (51) to an end end (52) in the circumferential direction (XX ') of the tire on a cylindrical laying surface (6) of radius R having for an axis of revolution, the axis of rotation (ΥΥ ') of the tire, and according to a periodic curve (7) corresponding to the mean line of the strip (5) and forming, with the circumferential direction (XX') of the tire and in the equatorial plane (XZ) of the tire, a non-zero angle A, so that the respectively starting ends (51) and end (52) of the strip (5) are positioned axially from an axial end (E1, E2) working reinforcement (2) at a distance (DI, DF) at most equal to 0.25 times the axial width W _T of the working armature (2).