Tyre for a heavy-duty vehicle for off-road use comprising sidewalls protected against attack

Abstract

The present invention relates to a tyre (1) for a heavy-duty vehicle for off-road use and is aimed at protecting the sidewalls (2) thereof against mechanical attack. A sidewall (2) comprises, on a sidewall outer face (21), a plurality of circumferentially distributed protrusions (6). Every protrusion (6) has a mean thickness (E), a mean circumferential length (A) and a mean radial height (C), and is separated from the adjacent protrusions by a mean circumferential pitch (P). According to the invention, the mean circumferential length (A) is at least equal to 20% of the mean circumferential pitch (P), the mean circumferential pitch (P) is at most equal to 20% of the free outside diameter (De), the mean thickness (E) is at least equal to 0.2% of the free outside diameter (De), the radial distance (D) is at most equal to 50% of the section height (H) and the mean radial height (C) is at least equal to 2% of the section height (H).

Description

Tire for a heavy vehicle for off-road use including sidewalls protected against attacks

[0001] The present invention relates to a tire for a heavy vehicle for off-road use, intended to run on uneven and stony ground, such as, for example, a civil engineering vehicle or a vehicle for military use. This invention relates more particularly to the sidewalls of such a tire.

[0002] By definition, the circumferential or longitudinal direction is the direction of rotation of the tire, the axial or transverse direction is the direction parallel to the axis of rotation of the tire and the radial direction is a direction perpendicular to the axis of rotation of the tire.

[0003] Generally speaking, a tire consists of two sidewalls, which are two lateral portions connecting a tread to two beads. The tread is positioned around the circumference of the tire and is intended to be worn down as the tire rolls. The beads are intended to ensure the tire is mounted on a rim.

[0004] More precisely, a sidewall usually comprises, axially from the outside to the inside of the tire, at least one outer layer of rubber material, in contact with the atmospheric air and generally comprising, on an outer face, a set of hollow or raised markings, a carcass reinforcement comprising at least one layer of metal reinforcements coated in a rubber material, and at least one inner layer of rubber material, intended to be in contact with the inflation gas when the tire is mounted and inflated on its rim.

[0005] A recurring problem with tires for heavy vehicles for off-road use is the occurrence of mechanical damage, when driving on uneven and unpaved ground, by stones or other blunt objects present on said ground, for example metal bodies. These mechanical damages mainly concern the tread and the sidewalls of the tire. With regard to the sidewalls in particular, these mechanical damages are likely to initiate cracks, which can propagate into the sidewall of the tire and cause damage to the carcass of the tire. tire likely to cause the tire to rupture and therefore be removed from the vehicle.

[0006] To combat the initiation and propagation of cracks in the flank, the installation of protrusions distributed circumferentially on the outer face of the flanks has been proposed, for example, in documents JP 4202168 B2 and EP 3523141 Bl.

[0007] The inventors set themselves the objective of reducing the sensitivity to mechanical damage of the sidewalls of a tire intended to equip a heavy vehicle for off-road use, by choosing an optimized circumferential distribution of sidewall protrusions.

[0008] This objective was achieved by a tire for a heavy vehicle for off-road use, comprising two sidewalls connecting a tread, intended to come into contact with the ground, respectively to two beads, intended to come into contact with a rim, -the tire having an axis of revolution, a free external diameter, measured on the tire not mounted on its rim and not inflated, and a section height within the meaning of the standard of the “European Tire and Rim Technical Organization”, -at least one sidewall comprising, on an outer sidewall face in contact with atmospheric air, a plurality of protuberances in relief relative to the outer sidewall face and distributed circumferentially in a circumferential direction of the tire, - any protuberance having an average thickness, measured perpendicular to the outer side of the flank, an average circumferential length, measured at mid-thickness of the protuberance in an axial plane, parallel to the axis of revolution, and an average radial height, measured at mid-thickness of the protuberance in a circumferential plane, perpendicular to the axis of revolution, - any protrusion being radially positioned relative to a tread end at a radial distance, measured at mid-thickness of the protrusion at the point corresponding to the maximum thickness of the protrusion, -two consecutive protuberances being circumferentially separated by an average circumferential distance, measured at mid-thickness of said protuberances in a plane axial, - the average circumferential pitch between two consecutive protuberances being the sum of the average circumferential length of a protuberance and the average circumferential distance between said two consecutive protuberances, - the average circumferential length being at least equal to 20% of the average circumferential pitch, - the average circumferential pitch being at most equal to 20% of the free external diameter, - the average thickness being at least equal to 0.2% of the free external diameter, - the radial distance being at most equal to 50% of the section height, -and the average radial height being at least equal to 2% of the section height.

[0009] The invention essentially consists of protecting, against mechanical attacks, a tire sidewall, intended to be driven off-road, by a circumferential distribution of protuberances, optimized in terms of average dimensions of the protuberances, average circumferential pitch of the distribution and radial positioning of the protuberances relative to the tread. The objective is to have a total volume of protuberances sufficient to guarantee effective protection, but not too high to minimize the quantity of material.

[0010] Geometrically, any protuberance has an average thickness, measured perpendicular to the outer flank face, an average circumferential length, measured at mid-thickness of the protuberance in an axial plane, parallel to the axis of revolution, and an average radial height, measured at mid-thickness of the protuberance in a circumferential plane, perpendicular to the axis of revolution. A protuberance is not, generally, strictly parallelepipedal, but can have a more or less complex shape, hence the interest in characterizing it geometrically by average dimensions, measured at mid-thickness of the protuberance. The average dimensions previously described are most often, but not necessarily, identical for all protuberances.

[0011] The radial distance of a protrusion from a tread end characterizes its position on the sidewall. The radial distance is most often, but not necessarily, the same for all protrusions.

[0012] The average circumferential pitch between two consecutive protrusions, defined as the sum of the average circumferential length of a protrusion and the average circumferential distance between said two consecutive protrusions, characterizes the density of material in relief at the wheel revolution. The circumferential pitch is generally, but not necessarily, constant.

[0013] According to the invention, the average circumferential length is at least equal to 20% of the average circumferential pitch. In other words, the volume ratio of protrusions, defined as the ratio between the average circumferential length of the protrusion and the average circumferential pitch between two consecutive protrusions, is at least equal to 20%, which guarantees a sufficient quantity of rubber material to protect the sidewall.

[0014] Also according to the invention, the average circumferential pitch is at most equal to 20% of the free external diameter, which guarantees a homogeneous and sufficiently dense distribution of the protuberances and, consequently, effective protection over the entire circumference.

[0015] Still according to the invention, the average thickness is at least equal to 0.2% of the free external diameter. This characteristic guarantees a thickness of rubber material sufficient to possibly repel obstacles and limit attacks by said obstacles.

[0016] According to another essential characteristic of the invention, the radial distance is at most equal to 50% of the section height. This condition makes it possible to position the protuberances, and therefore the associated protection, radially in a flank zone relatively close to the ground on which foreign bodies are present which are likely to attack it.

[0017] According to another essential characteristic of the invention, the average radial height is at least equal to 2% of the section height. This condition makes it possible to have a protuberance resistant to possible tearing resulting from attacks.

[0018] Advantageously, the average circumferential length is at least equal to 25% of the average circumferential pitch. This minimum volumetric material rate guarantees even more effective protection.

[0019] Also advantageously the average circumferential pitch is at most equal to 18% of the free outside diameter. A reduced average circumferential pitch, i.e. an increased density of protuberances, further improves the effectiveness of the protection over the entire circumference.

[0020] Advantageously, the average thickness is at least equal to 0.25% of the free outside diameter. The higher the average thickness, the better the protection.

[0021] Advantageously, the radial distance is at most equal to 30% of the section height. The closer the protrusions are to the ground, the higher the probability of acting effectively against attacks.

[0022] Also advantageously the average radial height is at least equal to 4% of the section height. The higher the average radial height, the higher the tear resistance of the protuberance.

[0023] Always advantageously the average radial height is at most equal to 25% of the section height, preferably at most equal to 20% of the section height. This limitation of the radial height of the protuberance makes it possible to limit the volume of rubber material to the strict minimum and the rise in temperature in the sidewall, which could cause deterioration thereof.

[0024] The characteristics of the invention are illustrated by the following figures 1 to 4, schematic and not shown to scale: -Figure 1: Side view of a portion of tire according to the invention, -Figure 2: Top view of a portion of tire according to the invention, -Figure 3: Overall side view of a tire according to the invention, -Figure 4: Half meridian section of a tire according to the invention inflated and crushed.

[0025] Figure 1 is a side view of a portion of a tire according to the invention. The tire 1 for a heavy vehicle for off-road use comprises two sidewalls 2 connecting a tread 3, intended to come into contact with a ground, respectively to two beads 4, intended to come into contact with a rim 5. Figure 1 is represented in a cylindrical reference frame, in which the circumferential or longitudinal direction XX' is the direction of rotation of the tire, the axial or transverse direction YY' is the direction parallel to the axis of rotation of the tire and the radial direction ZZ' is a direction perpendicular to the axis of rotation of the tire The tire 1 has an axis of revolution YY', a free outside diameter De, measured on the tire 1 not mounted on its rim 5 and not inflated, and a section height H within the meaning of the standard of the "European Tire and Rim Technical Organization". The sidewall 2 of Figure 1 comprises, on an outer sidewall face 21 in contact with the atmospheric air, a plurality of protuberances 6 in relief relative to the outer sidewall face 21 and distributed circumferentially in a circumferential direction XX' of the tire.Each protuberance 6 has an average thickness E (not shown in FIG. 1), measured perpendicular to the outer sidewall face 21, an average circumferential length A, measured at mid-thickness of the protuberance in an axial plane XY, parallel to axis of revolution YY', and an average radial height C, measured at mid-thickness of the protuberance in a circumferential plane XZ, perpendicular to axis of revolution YY'. Each protuberance 6 is radially positioned relative to a tread end at a radial distance D, measured at mid-thickness of the protuberance at the point corresponding to the maximum thickness of the protuberance. Two consecutive protuberances 6 are circumferentially separated by an average circumferential distance B, measured at mid-thickness of said protuberances in an axial plane XY.The average circumferential pitch P between two consecutive protuberances 6 is the sum of the average circumferential length A of a protuberance 6 and the average circumferential distance B between said two consecutive protuberances 6. According to the invention, the average circumferential length A is at least equal to 20% of the average circumferential pitch P, the average circumferential pitch P is at most equal to 20% of the free outside diameter De, the average thickness E is at least equal to 0.2% of the free outside diameter De, the radial distance D is at most equal to 50% of the section height H, and the average radial height C is at least equal to 2% of the section height H.

[0026] Figure 2 is a top view of a portion of tire according to the invention. This figure illustrates more particularly the raised positioning of the protuberances 6 relative to the outer face 21 of the sidewall 2 and radially inside the tread 3. It also represents the average thickness E of a protuberance 6, measured perpendicular to the outer face of the sidewall 21, the circumferential length average A of a protuberance 6, as well as the average circumferential distance B and the average circumferential pitch P, sum of the average circumferential length A and the average circumferential distance B, the characteristics A, B and P all being measured in an axial plane XY, at mid-thickness of said protuberances 6, that is to say at an axial distance E / 2 from the outer flank face 21. In the embodiment shown, the section of a protuberance 6, in an axial plane XY, has a substantially trapezoidal shape, particularly effective in terms of protection. The sides of the trapezoid, connecting its bases, have an inclination, relative to the direction perpendicular to the outer face of the flank, adapted, and are connected to the flank by fillets having an optimized radius.

[0027] Figure 3 is an overall side view of a tire according to the invention. This figure illustrates more particularly a circumferential distribution with constant pitch of protuberances 6, arranged in a radially outer part of the sidewall 2 of the tire 1, radially inside a tread 3.

[0028] Figure 4 is a half-meridian section of a tire according to the invention inflated and crushed. This figure illustrates in particular the protective function of the sidewall 2, extending between the tread 3 and the bead 4, by the protuberance 6 in relief relative to the outer sidewall face 21, with respect to an obstacle 7, when the tire 1, mounted and inflated on its rim 5, is crushed. The outer profile of the protuberance 6 before the tire is crushed is shown in dotted lines.

[0029] Table 1 below shows an example of characteristics according to the invention, for a tire of dimension 59 / 80 R 63 intended to equip a heavy civil engineering vehicle, of the dumper type: [Table 1]

Claims

Claims Tire (1) for a heavy vehicle for off-road use comprising two sidewalls (2) connecting a tread (3), intended to come into contact with a ground, respectively to two beads (4), intended to come into contact with a rim (5), -the tire (1) having an axis of revolution (YY'), a free outside diameter (De), measured on the tire (1) not mounted on its rim (5) and not inflated, and a section height (H) within the meaning of the standard of the "European Tire and Rim Technical Organization", -at least one sidewall (2) comprising, on an outer sidewall face (21) in contact with atmospheric air, a plurality of protuberances (6) in relief relative to the outer sidewall face (21) and distributed circumferentially in a circumferential direction (XX') of the tire, - any protuberance (6) having an average thickness (E), measured perpendicular to the outer flank face (21), an average circumferential length (A), measured at mid-thickness of the protuberance in an axial plane (XY), parallel to the axis of revolution (YY'), and an average radial height (C), measured at mid-thickness of the protuberance in a circumferential plane (XZ), perpendicular to the axis of revolution (YY'), - any protuberance (6) being radially positioned relative to a tread end at a radial distance (D), measured at mid-thickness of the protuberance at the point corresponding to the maximum thickness of the protuberance, -two consecutive protuberances (6) being circumferentially separated by an average circumferential distance (B), measured at mid-thickness of said protuberances in an axial plane (XY), -the average circumferential pitch (P) between two consecutive protuberances (6) being the sum of the average circumferential length (A) of a protuberance (6) and the average circumferential distance (B) between said two consecutive protuberances (6), characterized in that the average circumferential length (A) is at least equal to 20% of the average circumferential pitch (P), in that the average circumferential pitch (P) is at most equal to 20% of the free outside diameter (De), in that the average thickness (E) is at least equal to 0.2% of the free outside diameter (De), in that the radial distance (D) is at most equal to 50% of the section height (H) and in that the average radial height (C) is at least equal to 2% of the section height (H). Tire (1) according to claim 1, in which the average circumferential length (A) is at least equal to 25% of the average circumferential pitch (P). Tire (1) according to one of claims 1 or 2, in which the average circumferential pitch (P) is at most equal to 18% of the free outside diameter (De). Tire (1) according to any one of claims 1 to 3, in which the average thickness (E) is at least equal to 0.25% of the free outside diameter (De).Tire (1) according to any one of claims 1 to 4, wherein the radial distance (D) is at most equal to 30% of the section height (H). Tire (1) according to any one of claims 1 to 5, wherein the average radial height (C) is at least equal to 4% of the section height (H). Tire (1) according to any one of claims 1 to 6, wherein the average radial height (C) is at most equal to 25% of the section height (H), preferably at most equal to 20% of the section height (H).

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