Tire having reinforced sidewalls

Abstract

A tire having a radial carcass reinforcement, made up of a single layer of reinforcing elements anchored in each of the beads by being turned up around a bead wire, reinforced by a stiffener. In the sidewall of the tire, the profile of the outer surface of the tire is at a constant distance from the carcass reinforcement layer between the points F and A, and meets the outer surface of the bead at the point C, forming two successive circular arcs.

Claims

1. A tire configured to be mounted on a hollow rim of the 15° drop center type, comprising: a radial carcass reinforcement made up of a single carcass reinforcement layer formed of reinforcing elements, a crown reinforcement, itself capped radially by a tread, said tread being joined to two beads via two sidewalls, the layer of reinforcing elements of the carcass reinforcement being anchored in each of the beads by being turned up around a bead wire to form a main part of the carcass reinforcement layer extending from one bead wire to the other and a turn-up of the carcass reinforcement layer in each of the beads, said turn-up of the carcass reinforcement being reinforced by at least one layer of reinforcing elements or stiffener, wherein in a meridian cross section of said tire, wherein in an uninflated state the centers of mass of the bead wires form an axially oriented straight line, said centers of mass being at a distance from each other by a distance equal to the width of the rim increased by 20 mm and decreased by twice a distance measured axially between a center of mass of a bead wire and a point on the outer surface of the tire; any point of the profile of an outer surface (S) of the tire, between a first point (F), itself defined by an intersection of an axially oriented straight line, passing through an axially outermost point (E) of the main part of the carcass reinforcement layer and the outer surface (S) of the tire, and a point (A), is at a constant distance (T) from the main part of the carcass reinforcement layer, said distance being measured at any point in a direction normal to the main part of the carcass reinforcement layer, the point (A) is radially on the outside of a first circle (C1) of radius R1 that is centered on the end of the turn-up of the carcass reinforcement layer, R1 being between 8 and 13 mm, radially on the inside of the point (A), the outer surface (S) of the tire is continued by a circular arc of radius R2, the center of which is axially on the outside of the surface (S) of the tire, and the radius R2 of which is between 50% and 125% of the distance between the point (F) and the center of gravity of the bead wire, the circular arc of radius R2 is tangent at its radially innermost end (B) to a circular arc of radius R3, the center of which is axially on the inside of the surface (S) of the tire, and continues the outer surface (S) of the tire radially inwards as far as the point (C), said point (C) being a point of contact between the circular arc of radius R3 and the circle (C2) of radius R1 centered on the radially outermost end of the stiffener, said point (C) being radially on the inside of the axially outermost point (D) of the circle (C2), the radius R3 being between 50% and 125% of the distance between the point (F) and the center of gravity of the bead wire, and the radius R2 is between 1.5 times the radius R1 and 8 times the radius R1.

2. The tire according to claim 1, wherein the reinforcing elements of the carcass reinforcement layer are cords having at least two layers, at least one internal layer being sheathed with a layer made of a rubber composition that is not crosslinkable, is crosslinkable or is crosslinked, preferably based on at least one diene elastomer.

3. The tire according to claim 1, wherein, in any meridian plane, in each bead, the tire (1) has a retention reinforcement surrounding the bead wire and a volume of rubber compound in direct contact with the bead wire.

4. The tire according to claim 1, wherein a radially innermost end of the stiffener is radially on the outside of a radially innermost point of the bead wire.

5. The tire according to claim 1, wherein the axially outermost point (E) of the main part of the carcass reinforcement layer is determined on a mounted tire inflated under nominal conditions.

6. The tire according to claim 1, wherein the radial distance between the point (F) and the point (A) is greater than 70% of the radial distance between the point (F) and the radially outermost point (G) of the outer surface (S) of the tire, for which the distance, measured in a direction normal to the main part of the carcass reinforcement layer, between said main part of the carcass reinforcement layer and the surface (S), is equal to (T), said distance between any point, on the outer surface (S) of the tire, radially between the points (F) and (G) and the main part of the carcass reinforcement layer being constant.

7. The tire according to claim 6, wherein the reinforcing elements of the carcass reinforcement layer are cords having at least two layers, at least one internal layer being sheathed with a layer made of a rubber composition that is not crosslinkable, is crosslinkable or is crosslinked, preferably based on at least one diene elastomer.

8. The tire according to claim 1, wherein the radially outermost end of the stiffener is radially on the outside of the end of the turn-up of the carcass reinforcement layer.

9. The tire according to claim 8, wherein the reinforcing elements of the carcass reinforcement layer are cords having at least two layers, at least one internal layer being sheathed with a layer made of a rubber composition that is not crosslinkable, is crosslinkable or is crosslinked, preferably based on at least one diene elastomer.

10. The tire according to claim 8, wherein, in any meridian plane, in each bead, the tire has a retention reinforcement surrounding the bead wire and a volume of rubber compound in direct contact with the bead wire.

11. The tire according to claim 1, wherein distance (T), measured in a direction normal to the main part of the carcass reinforcement layer, is greater than 3 mm and preferably less than 7 mm.

12. The tire according to claim 11, wherein the radial distance between the point (F) and the point (A) is greater than 70% of the radial distance between the point (F) and the radially outermost point (G) of the outer surface (S) of the tire, for which the distance, measured in a direction normal to the main part of the carcass reinforcement layer, between said main part of the carcass reinforcement layer and the surface (S), is equal to (T), said distance between any point, on the outer surface (S) of the tire, radially between the points (F) and (G) and the main part of the carcass reinforcement layer being constant.

13. The tire according to claim 11, wherein the radially outermost end of the stiffener is radially on the outside of the end of the turn-up of the carcass reinforcement layer.

14. The tire according to claim 11, wherein, in any meridian plane, in each bead, the tire has a retention reinforcement surrounding the bead wire and a volume of rubber compound in direct contact with the bead wire.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Further details and advantageous features of the invention will become apparent in the following text from the description of exemplary embodiments of the invention, in particular with reference to FIGS. 1 to 3, in which:

(2) FIG. 1 shows a schematic meridian view of a tire according to the invention,

(3) FIG. 2 shows an enlarged schematic depiction of the outer surface of the tire between the bead region and the point F,

(4) FIG. 3 shows an enlarged schematic depiction of the region of a bead of a reference tire.

(5) In order to make them easier to understand, the figures are not shown to scale.

(6) FIGS. 1 and 3 show only a half-view of a tire, which extends symmetrically with respect to the axis XX′, which represents the circumferential median plane, or equatorial plane, of the tire.

DETAILED DESCRIPTION OF THE PRESENTLY PREFERRED EMBODIMENTS

(7) In FIG. 1, the tire 1 is of size 315/70 R 22.5. Said tire 1 comprises a radial carcass reinforcement 2 anchored in two beads 3. The carcass reinforcement 2 is hooped at the crown of the tire by a crown reinforcement 5, itself capped by a tread 6.

(8) The carcass reinforcement 2, formed by a single layer of metal cords, is wound, in each of the beads 3, around a bead wire 4 and forms, in each of the beads 3, a turn-up 7 of the carcass reinforcement layer having an end 8.

(9) Located axially on the outside of the turn-up 7 is a stiffener 9, the radially outermost end 10 of which is radially on the outside of the end 8 of the turn-up 7 of the carcass reinforcement layer.

(10) The radially innermost end 11 of the stiffener 9 is radially on the outside of the radially innermost point of the bead wire 4.

(11) FIG. 2 schematically illustrates the outer surface S of the tire between the point F and the region of the bead 3 in a meridian cross section of the tire, which is defined such that the centers of mass of the bead wires 4 form an axially oriented straight line, said centers of mass being at a distance from each other by a distance equal to the width of the nominal rim increased by 20 mm and decreased by twice the distance measured axially between a center of mass of a bead wire 4 and a point on the outer surface of the tire.

(12) The axially outermost point E of the carcass is, for example, determined by tomography, the tire being mounted/inflated under nominal conditions.

(13) The point F is then determined by axial projection of the point E onto the outer surface S of the tire.

(14) The outer surface S of the tire describes a first portion, from the point F to the point A, the latter being radially on the outside of the circle C1 of radius R1 centered on the end 8 of the turn-up of the carcass reinforcement layer.

(15) The distance T measured between any point on the outer surface S of the tire and the main part of the carcass reinforcement layer, said distance being measured at any point in a direction normal to the main part of the carcass reinforcement layer, is equal to 4.7 mm and is substantially constant over this portion between the points F and A.

(16) The radius R1 of the circle 1 is equal to 8.3 mm.

(17) The outer surface S of the tire then continues radially inwards through a circular arc 12 of radius R2, which is itself tangent at B to a circular arc of radius R3, said circular arc continuing the outer surface S of the tire as far as the point C.

(18) The point C is the point of contact between the circular arc 13 and the circle C2 centred on the radially outermost end of the stiffener.

(19) The point C is radially on the inside of the axially outermost point D of the circle C2.

(20) The radius R2 is equal to 90 mm.

(21) The radius R3 is equal to 121 mm.

(22) The distance between the point F and the center of gravity of the bead wire is equal to 119 mm.

(23) The radii R2 and R3 are thus clearly between 50% and 125% of this distance between the point F and the center of gravity of the bead wire.

(24) The radial distance between the point F and the point A is equal to 37 mm.

(25) The point G, which is visible in FIG. 1, is the point, radially on the outside of the point F, from which the distance between a point on the outer surface S of the tire and the main part of the carcass reinforcement layer, measured at any point in a direction normal to the main part of the carcass reinforcement layer, is greater than the distance T.

(26) The radial distance between the point F and the point G is equal to 38 mm.

(27) The radial distance between the point F and the point A is thus clearly greater than 70% of the radial distance between the point F and the point G.

(28) Endurance tests were carried out by running two shaved tires one on the other with a regulated pressure of 5.5 bar and a load of 4571 daN at a speed of 50 km/h and at an ambient temperature of 15° C. for 20 000 km.

(29) The tires according to the invention were compared with reference tires, of which the profile of the outer surface is more conventional. Such a tire profile is shown in FIG. 3.

(30) In this FIG. 3, which shows a tire 31 of the same size, it appears that the region of the bead 33 is similar to that of the tire according to the invention and that the structure of the carcass reinforcement layer 32 is identical, the latter being turned-up around a bead wire 34 in order to form a turn-up 37 reinforced by a stiffener 39. By contrast, the profile of the outer surface of the tire 31 is different from that of the tire according to the invention.

(31) The tests were carried out for the tires according to the invention under conditions identical to those applied to the reference tires.

(32) The tires according to the invention yielded results substantially identical to those of the reference tires.

(33) Further tests were carried out to test the performance levels in terms of resistance to impacts with and/or rubbing against kerbs.

(34) In order to carry out these tests, the tires were also provided with radial striations on their sidewalls.

(35) These tests were carried out on a footway having a 15 cm high kerb. The tire was mounted on a vehicle, the path of which drove the tire at a speed of 20 km/h with an angle of incidence of 10° with respect to the kerb.

(36) The operation was repeated 6 times and then the sidewall was analyzed to detect any tears.

(37) The reference tire had two tears, as did the tire according to the invention.

(38) As far as the surface that struck the kerb is concerned, it is 10% weaker on the tire according to the invention compared with the reference tire.

(39) The scope of protection of the invention is not limited to the examples given hereinabove. The invention is embodied in each novel characteristic and each combination of characteristics, which includes every combination of any features which are stated in the claims, even if this feature or combination of features is not explicitly stated in the examples.