Tire carcass reinforcement for two-wheeled vehicles

Abstract

A tire having a crown reinforcement (5), comprising at least one crown layer (51), and a carcass reinforcement (6), comprising at least one turned-up carcass layer (61), the turned-up carcass layer (61) comprising mutually parallel reinforcers turned up, within each bead, from the inside towards the outside of the tire around a bead wire (7), to form a turn-up (8) comprising a free end (E). The turned-up carcass layer (61) comprises a crown portion (611) and a lateral portion (612), the crown portion (611) extending axially between a first and a second end (E.sub.1, E′.sub.1) which is symmetric about the equatorial plane (P), the lateral portion (612) extending radially inwards, from a first end (E.sub.2) as far as a second end (E3). The reinforcers of the lateral portion (612) and the reinforcers of the turn-up (8) form, with the circumferential direction (X), specified angles.

Claims

1. A tire for a motorized two-wheeled vehicle of the motorbike type, comprising: a tread connected by two sidewalls to two beads; a crown reinforcement, radially on the inside of the tread, comprising at least one crown layer; a carcass reinforcement, radially on the inside of the crown reinforcement, comprising at least one turned-up carcass layer; the turned-up carcass layer comprising mutually parallel reinforcers turned up, within each bead, from the inside towards the outside of the tire around a bead wire, to form a turn-up comprising a free end; the turned-up carcass layer comprising a crown portion and a lateral portion; the crown portion extending axially between a first and a second end which is symmetric about the equatorial plane of the tire, wherein the crown portion has an axial width at least equal to 0.3 times and at most equal to 0.9 times the width of the tread; the lateral portion extending radially inwards, from a radially outermost first end, radially on the inside of the free end of the turn-up, as far as a radially innermost second end, radially on the inside of the radially innermost point of the bead wire, the free end arranged between a respective end of the crown portion and the radially outermost first end of the lateral portion; wherein the reinforcers of the crown portion form, with the circumferential direction, a substantially constant angle at least equal to 65°, wherein the reinforcers of the lateral portion form, with the circumferential direction, an angle that increases, from the radially outermost first end to the radially innermost second end from an angle at least 5° smaller than the substantially constant angle formed by the reinforcers of the crown portion, and wherein the reinforcers of the turn-up form, with the circumferential direction, an angle which is equal in terms of absolute value to, but of opposite sign from, the angle formed by the reinforcers of the lateral portion.

2. The tire according to claim 1, wherein the substantially constant angle formed, with the circumferential direction, by the reinforcers of the crown portion, is at least equal to 80°.

3. The tire according to claim 1, wherein the angle formed, with the circumferential direction, by the reinforcers of the lateral portion, increases from a minimum angle of between 45° and 80°, to a maximum angle of between 55° and 85°.

4. The tire according to claim 1, wherein the lateral portion has a radial height at least equal to 0.5 times and at most equal to 0.9 times the design section height of the meridian section of the tire.

5. The tire according to claim 1, wherein the reinforcers of a carcass layer are made of textile.

6. The tire according to claim 1, wherein the crown reinforcement comprises a circumferential crown layer comprising circumferential reinforcers forming, with the circumferential direction, an angle at most equal to 5°.

7. The tire according to claim 1, wherein the crown reinforcement comprises two working crown layers, comprising circumferential reinforcers forming, with the circumferential direction, an angle of between 15° and 35° and which are crossed from one layer to the next.

8. The tire according to claim 1, wherein the reinforcers of a crown layer are made of textile, or are made of metal.

9. The tire according to claim 1, wherein the reinforcers of a carcass layer are made of polyester or of nylon.

10. The tire according to claim 1, wherein the reinforcers of a crown layer are made of polyester or of nylon.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Other advantageous features and details of the invention will become apparent hereinafter from the description of the invention with reference to FIGS. 1 and 2 which depict:

(2) FIG. 1, a meridian section of a tire,

(3) FIG. 2, the graph representing the range of change of the angle formed, with the circumferential direction, by the reinforcers of the carcass layer with a turn-up along its curved abscissa comprised between the equatorial plane and the end of the turn-up.

(4) In order to make them easier to understand, FIGS. 1 and 2 are not drawn to scale.

DETAILED DESCRIPTION OF THE DRAWINGS

(5) FIG. 1 depicts a tire 1 comprising a tread 2 connected by two sidewalls 3 to two beads 4, a crown reinforcement 5, radially on the inside of the tread 2, comprising at least one crown layer 51, a carcass reinforcement 6, radially on the inside of the crown reinforcement 5, comprising at least one carcass layer with turn-up 61. The carcass layer with turn-up 61 comprises reinforcers with are mutually parallel and turned up, within each bead 4, from the inside towards the outside of the tire, around a bead wire 7 to form a turn-up 8.

(6) The crown portion 611 of the carcass layer with a turn-up 61 extends axially between a first and a second end E.sub.1 and E′.sub.1 which are symmetric about the equatorial plane P, over an axial width L.sub.1 comprised between 0.3 times and 0.9 times the axial width L of the tread as defined between the two axial ends of the tread surface. The crown portion 611 is thus centred with respect to the equatorial plane P of the tire, defined by the respectively circumferential X and radial Z directions.

(7) The transition portion marking the transition between the crown portion and the lateral portion is delimited by the points E.sub.1 and E.sub.2.

(8) The lateral portion 612 of the carcass layer with a turn-up 61 extends, in the sidewall 3, radially toward the inside, from a radially outermost first end E.sub.2, radially on the inside of the free end of the turn-up E, to a radially innermost second end E.sub.3 radially on the inside of the radially innermost point I of the bead wire 7. It also extends axially on the inside of the turn-up 8. The radial height H.sub.2 between the first and second ends E.sub.2 and E.sub.3 is comprised between 0.5 times and 0.9 times the design section height H, measured between the point, on the tread surface, that is positioned in the equatorial plane, and the radially innermost point of the bead 4.

(9) The turn-up 8 extends radially outwards from the radially innermost end E.sub.3 of the lateral portion 612 as far as the free end E of the turn-up 8.

(10) FIG. 2 shows the range of change of the angle A formed, with the circumferential direction X, by the reinforcers of the carcass layer with a turn-up, as a function of the curved abscissa value s, comprised between the point M of the equatorial plane and the end E of the turn-up. The curve C.sub.max is the envelope curve of maximum angle. The curve C.sub.min is the envelope curve of minimal angle. The curve C is a standard example of how the angle changes, as a function of the curve abscissa value along the carcass layer with a turn-up. Positive values for the angle correspond to the changes in the angle respectively along the crown portion, the transition portion and the lateral portion. Negative values for the angle correspond to changes in the angle along the turn-up.

(11) The first portion of the range of change corresponds to that part of the crown portion 611 that is comprised between the points M and E.sub.1, for which the reinforcers form, with the circumferential direction X, a substantially constant angle A.sub.1 comprised between 65° and 90°.

(12) The second portion of the range of change corresponds to the transition portion comprised between the end E.sub.1 of the crown portion and the radially outermost end E.sub.2 of the lateral portion 612, for which portion the reinforcers form, with the circumferential direction X, a decreasing angle A.sub.2.

(13) The third portion of the range of change corresponds to the lateral portion 612 comprised between the ends E.sub.2 and E.sub.3 which are respectively the radially outermost and the radially innermost ends, for which portion the reinforcers form, with the circumferential direction X, an angle A.sub.3 that increases, from the radially outermost first end E.sub.2 to the radially innermost second end E.sub.3, from an angle at least 5° smaller than the substantially constant angle A.sub.1 formed, with the circumferential direction, by the reinforcers of the crown portion 611.

(14) The fourth portion of the range of change corresponds to the turn-up 8 in which the reinforcers form, with the circumferential direction X, an angle A.sub.4, the opposite of the angle A.sub.3, formed by the reinforcers of the lateral portion 612. This angle A.sub.4, of opposite sign to the angle A.sub.3, decreases, in terms of absolute value, from a maximum angle of between 55° and 85° at the radially innermost end E.sub.3 of the lateral portion 612 until it reaches a minimum angle of between 45° and 80° at the end E of the turn-up.

(15) The invention has been studied more specifically for the 190/55 ZR 17 size. In that particular case, the substantially constant angle A.sub.1 of the reinforcers of the crown portion which extends axially over a width L.sub.1 equal to 138 mm, namely 0.71 times the width of the tread which is equal to 194 mm, is equal to 80°. The angle A.sub.3 of the reinforcers in the lateral portion, which extends radially over a height H.sub.2 equal to 0.65 times the design section height H equal to 104.5 mm, increases from 62° at the point E.sub.2 to 70° at the point E.sub.3.

(16) For this size studied, the reinforcers of the carcass layer with turn-up are made of nylon, while the reinforcers of the circumferential crown layer are made of aramid.

(17) The cornering stiffness of this size was compared against the respective cornering stiffnesses of a first reference size R.sub.1 and of a second reference size R.sub.2. The first reference size R.sub.1 comprises a carcass reinforcement made up of a single carcass layer at 90° and a crown reinforcement made up of a single circumferential crown layer. Reference R.sub.1 is the reference with straight-line stability. The second reference size R.sub.2 comprises a carcass reinforcement made up of two carcass layers at 65° which are crossed, and a crown reinforcement made up of a single circumferential crown layer. The reference R.sub.2 is the reference for cornering stability.

(18) The results obtained are set out in Table 1 below:

(19) TABLE-US-00001 TABLE 1 Reference R.sub.1 Reference R.sub.2 Invention Cornering rigidity 100 110 100 for zero camber angle Cornering rigidity 100 120 120 for a camber angle of 30°

(20) The dimension under study exhibits cornering rigidity levels that are at least equivalent to the best-performing reference, whether they are in a straight line with zero camber angles or in a curve with a high camber angle. It displays a cornering stiffness that is somewhat low in a straight line and somewhat high under cornering.

(21) The invention must not be interpreted as being limited to the description of the examples above and notably extends to cover tires that may comprise carcass reinforcements in which no carcass layer has a turn-up. The lateral portion of carcass without a turn-up is then axially on the inside not of a turn-up but of a independent carcass layer portion anchored in the bead.