Carcass Reinforcement For Motor Bike Tire

Abstract

Tire (1) for a motorized two-wheeled vehicle of the motorbike type. A good compromise between the stability of the motorbike in a straight line at high speed and the stability of the motorbike in a curved path with a high camber angle is achieved with reinforcers of a first carcass layer (61) that form, with the circumferential direction (XX′), an angle (A.sub.1) at most equal to 75°, the reinforcers of a second carcass layer (62) form, with the circumferential direction, an angle (A.sub.2) at least equal to 80° and at most equal to 90°, the difference between the angles (A1, A2) of the respective reinforcers of the first and second carcass layers (61, 62) is at least equal to 10° and at most equal to 20° and the angles (A1, A2) of the respective reinforcers of the first and second carcass layers (61, 62) are oriented in the same direction.

Claims

1. Tire for a motorized two-wheel vehicle of the motorbike type, comprising: a tread connected by two sidewalls to two beads, each said bead comprising a metal circumferential reinforcing element or bead wire; a crown reinforcement extending radially inside the tread and comprising at least one crown layer, the at least one crown layer comprising mutually parallel reinforcers forming, with a circumferential direction of the tire, an angle at most equal to 5°; a carcass reinforcement extending radially on the inside of the crown reinforcement as far as into the beads and comprising at least two carcass layers, each of the at least two carcass layers comprising mutually parallel reinforcers forming, with the circumferential direction of the tire, an angle at least equal to 65°, wherein the reinforcers of a first of said carcass layers forms, with the circumferential direction, an angle at most equal to 75°, wherein the reinforcers of a second of said second carcass layers forms, with the circumferential direction, an angle at least equal to 80° and at most equal to 90°, wherein the difference between the angles of the respective reinforcers of the first and second carcass layers is at least equal to 10° and at most equal to 20° and wherein the angles of the respective reinforcers of the first and second carcass layers are oriented in the same direction.

2. The tire according to claim 1, wherein the carcass reinforcement is made up of two carcass layers.

3. The tire according to claim 1, wherein the first carcass layer is a carcass layer turned up around the bead wire of each said bead.

4. The tire according to claim 1, wherein the first carcass layer is radially on the inside of the second carcass layer.

5. The tire according to claim 1, each said bead comprising a metallic circumferential reinforcing element or bead wire, wherein the second carcass layer is a carcass layer not turned up around the bead wire of each said bead.

6. The tire according to claim 1, wherein the respective reinforcers of the first and second carcass layers are made of textile material.

7. The tire according to claim 1, wherein the respective reinforcers of the first and second carcass layers are made of the same textile material.

8. The tire according to claim 1, wherein the respective reinforcers of the first and second carcass layers are made of polyester.

9. The tire according to claim 1, wherein the crown reinforcement is made of one single crown layer.

10. The tire according to claim 1, wherein the reinforcers of the at least one crown layer are made of textile material.

11. The tire according to claim 1, each of the at least two carcass layers having a crown portion extending symmetrically on each side of an equatorial plane passing through the middle of the tread and perpendicular to an axis of rotation of the tire, wherein the mean radial distance respectively between the respective reinforcers of two consecutive said carcass layers, in their crown portions, on the one hand, and between the respective reinforcers of the radially said outermost carcass layer, in its crown portion, and of the radially said innermost crown layer, on the other hand, is at most equal to 0.3 mm.

12. The tire according to claim 11, wherein the mean radial distance is at most equal to 0.1 mm.

13. The tire according to claim 10, wherein the textile material is aromatic polyamide.

Description

[0037] Further details and advantageous features of the invention will become apparent hereinafter from the description of the invention given with reference to FIGS. 1 and 2 which depict:

[0038] FIG. 1: a meridian half section of a reference tire of the prior art,

[0039] FIG. 2: a view from above of the crown of a tire according to a preferred embodiment of the invention.

[0040] In order to make them easier to understand, FIGS. 1 and 2 have not been drawn to scale.

[0041] FIG. 1 depicts, in a meridian plane YZ defined by the respectively axial YY′ and radial ZZ′ directions, a meridian half section of a tire 1 for a motorized two-wheeled vehicle of the motorbike type, comprising a tread 2 connected by two sidewalls 3 to two beads 4, each bead 4 comprising a metal circumferential reinforcing element or bead wire 7. The tire 1 comprises a crown reinforcement 5 extending radially on the inside of the tread 2 and comprising a single crown layer 51, the crown layer 51 comprising mutually parallel reinforcers forming, with a circumferential direction XX′ of the tire, an angle B at most equal to 5°. Furthermore, the tire 1 comprises a carcass reinforcement 6 extending radially on the inside of the crown reinforcement 5 as far as into the beads 4 and made up of two carcass layers (61, 62), each of the two carcass layers (61, 62) comprising mutually parallel reinforcers forming, with the circumferential direction XX′ of the tire, an angle (A1, A2) at least equal to 65°. The radially inner layer 61 is a carcass layer turned up around the bead wire 7, whereas the radially outer layer of 62 is a carcass layer that is not turned up or wrapped round. A free end portion of the carcass that is not turned up 62 is axially on the inside of and in contact with the turnup of the turned-up carcass layer 61.

[0042] FIG. 2 depicts a view from above of a crown portion of a tire according to the invention. More specifically, this is a view in cross section illustrating the respective angles of the layers radially superposed from the inside to the outside: a radially inside first carcass layer 61, a radially outside second carcass layer 62 and the crown layer 51. According to the invention, the reinforcers of the first carcass layer 61 form, with the circumferential direction XX′, an angle A.sub.1 at most equal to 75°. The reinforcers of the second carcass layer 62 form, with the circumferential direction XX′, an angle A.sub.2 at least equal to 80° and at most equal to 90°. The difference between the angles (A1, A2) of the respective reinforcers of the first and second carcass layers (61, 62) is at least equal to 10° and at most equal to 20°. The angles (A1, A2) of the respective reinforcers of the first and second carcass layers (61, 62) are oriented in the same direction. The crown layer 51 comprises mutually parallel reinforcers forming, with the circumferential direction XX′, an angle B at most equal to 5°.

[0043] The invention has been studied more particularly in the 200/55 ZR 17 size. In this particular case, the angle A1 of the reinforcers of the radially inside turned-up first carcass layer is equal to 75°, the angle A2 of the reinforcers of the radially outside second carcass layer that has no turnup is equal to 90° and the angle B of the reinforcers of the single crown layer is equal to 0°. This architecture was compared against that of a tire of the state of the art comprising a radially inside turned-up first carcass layer of which the reinforcers form an angle A1 equal to −80°, a radially outside second carcass layer without a turnup, the reinforcers of which form an angle A2 equal to +80°, which are therefore criss-crossed with those of the first carcass layer, and a crown layer the reinforcers of which are circumferential.

[0044] In this study, the reinforcers of the two carcass layers are made of polyester whereas the reinforcers of the crown layer are made of aramid. In addition, the mean radial distance respectively between the respective reinforcers of two consecutive carcass layers, in their crown portions, on the one hand, and between the respective reinforcers of the radially outermost carcass layer, in its crown portion, and of the crown layer, on the other hand, is equal to 0.1 mm for the tire according to the invention and to 0.3 mm for the reference tire of the prior art.

[0045] The two tires were tested on a motorbike in subjective tests of stability in a straight line and in a curve. The results obtained are given in table 1 below:

TABLE-US-00001 TABLE 1 Reference Invention Stability in a straight line 100 120 Stability in a curve 100 140

[0046] The invention should not be interpreted as being limited to the description of the examples above and notably extends to tires that may comprise carcass reinforcements comprising more than two carcass layers and a crown reinforcement comprising more than one crown layer. Moreover, all the combinations of carcass layers with and/or without turnups are conceivable. Finally, the crown layer reinforcers are not limited to textile materials, but may be made of metal.