Vehicle tire comprising a layer of circumferential reinforcing elements

Abstract

A tire with radial carcass reinforcement comprises a crown reinforcement including a layer of circumferential reinforcing elements distributed axially at a variable pitch. The layer of circumferential reinforcing elements is radially crowned by a tread strip, which is connected to two beads by two sidewalls. The layer of circumferential reinforcing elements comprises five parts, including a central part, two intermediate parts and two axially outer parts. The value of the pitch in the two intermediate parts is less than a value of the pitch in the two axially outer parts. Each axially outer part is axially separated from the central part by a corresponding intermediate part. The value of the pitch in each intermediate part is less than a value of the pitch in the central part, and the value of the pitch in each axially outer part is less than the value of the pitch in the central part.

Claims

1. A tire with a radial carcass reinforcement comprising: a crown reinforcement comprising at least one layer of circumferential reinforcing elements distributed axially at a variable pitch, wherein said at least one layer of circumferential reinforcing elements is radially crowned by a tread strip, wherein said tread strip is connected to two beads by two sidewalls, wherein said at least one layer of circumferential reinforcing elements comprises five axially contiguous parts, including a central part, two intermediate parts and two axially outer parts, wherein an axial width of each of said two axially outer parts of said at least one layer of circumferential reinforcing elements is between 7% and 15% of an axial width of said at least one layer of circumferential reinforcing elements, wherein each pitch value in each of said two intermediate parts is less than each pitch value in each of said two axially outer parts, wherein each of said two axially outer parts is axially separated from said central part by a corresponding one of said two intermediate parts, wherein each pitch value in said each intermediate part is less than each pitch value in said central part, and wherein each pitch value in each of said two axially outer parts is less than each pitch value in said central part said central part being between 0.5 and 0.95.

2. The tire according to claim 1, wherein a ratio of each value of the pitch in said two intermediate parts to each value of the pitch in said central part is between 0.4 and 0.7.

3. The tire according to claim 1, wherein an axial width of said central part of said at least one layer of circumferential reinforcing elements is between 10 and 50% of an axial width of said at least one layer of circumferential reinforcing elements.

4. The tire according to claim 1, wherein an axial width of each of said two intermediate parts of said at least one layer of circumferential reinforcing elements is between 10 and 38% of an axial width of said at least one layer of circumferential reinforcing elements.

5. The tire according to claim 1, wherein a distribution of values of said variable pitch of said at least one layer of circumferential reinforcing elements is symmetric with respect to an equatorial plane of the tire.

6. The tire according to claim 1, wherein said crown reinforcement comprises at least two working crown layers of inextensible reinforcing elements, and wherein the inextensible reinforcing elements of each of said at least two working crown layers are crossed with the inextensible reinforcing elements of its neighbouring working crown layers at an angle between 10 and 45 with the circumferential direction.

7. The tire according to claim 1, wherein said crown reinforcement further comprises at least two layers of reinforcing elements, and wherein the reinforcing elements of each of said at least two layers are crossed with the reinforcing elements of its neighbouring layers at an angle between 20 and 160 with one another.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Further details and advantageous features of the invention will emerge hereinafter from the description of the exemplary embodiments of the invention, given with reference to FIGS. 1 to 3 which depict:

(2) FIG. 1 is a meridian view of a tire layout according to a first embodiment of the invention.

(3) FIG. 2 is a meridian view of a tire layout according to a second embodiment of the invention; and

(4) FIG. 3 is a meridian view of a tire layout according to a third embodiment of the invention.

(5) For ease of understanding, FIGS. 1 to 3 are not drawn to scale.

DETAILED DESCRIPTION OF THE PRESENTLY PREFERRED EMBODIMENTS

(6) FIG. 1 depicts a tire 1 of 190/50 ZR 17 type intended to be fitted to the rear of a motorcycle. This tire 1 comprises a carcass reinforcement consisting of a layer 2 comprising reinforcing elements of the textile type. The layer 2 consists of reinforcing elements arranged radially. The radial positioning of the reinforcing elements is defined by the angle at which the reinforcing elements are laid; a radial arrangement corresponds to the elements being laid at an angle comprised between 65 and 90 with respect to the longitudinal direction.

(7) The layer 2 is anchored on each side of the tire 1 in a bead 3 the base of which is intended to be mounted on a rim seat. Each bead 3 is extended radially outwards by a sidewall 4, the sidewall 4 radially towards the outside meeting the tread strip 5. The tire 1 thus constructed has a curvature value in excess of 0.15 and preferably in excess of 0.3. The curvature value is defined by the Ht/Wt ratio, namely the ratio of the height of the tread strip to the maximum width of the tread strip of the tire. The curvature value will advantageously be between 0.25 and 0.5 for a tire intended to be fitted at the front of a motorcycle and will be advantageously comprised between 0.2 and 0.5 for a tire intended to be fitted at the rear.

(8) The tire 1 further comprises a crown reinforcement 6 consisting of two layers 7 and 8 of reinforcing elements making angles with the circumferential direction, the reinforcing elements being crossed from one layer to the next and making angles of 50 between them in the region of the equatorial plane, the reinforcing elements of each of the layers 7 and 8 making an angle of 25 to the circumferential direction.

(9) The reinforcing elements of the two layers 7 and 8 are made of a textile material and, more specifically, of aramid.

(10) The crown reinforcement 6 according to the invention comprises a layer of circumferential reinforcing elements 10 radially on the outside of the layers 7, 8. The layer of circumferential reinforcing elements 10 is thus the radially outermost part of the crown reinforcement 6 and the two working layers 7, 8 are interposed between the carcass layer 2 and the layer of circumferential reinforcing elements 10. The layer of circumferential reinforcing elements 10 advantageously consists of a single thread which has been wound to make an angle substantially equal to 0 with the longitudinal direction. The layer of circumferential reinforcing elements 10 may alternatively be produced by the simultaneous winding of several bare or rubberized threads or threads in the form of strips when they are embedded in rubber.

(11) The circumferential reinforcing elements 10 are wound in such a way that the pitch between two circumferential reinforcing elements varies in the axial direction.

(12) This variation in the laying pitch leads to a variation in the density of the circumferential reinforcing elements that is such that the density is greater in the intermediate parts 11a and 11b. The circumferential reinforcing element densities will therefore decrease, firstly from these intermediate parts 11a and 11b with a density of 100 threads/dm (pitch of 1 mm) towards the central part 12 of the layer of circumferential reinforcing elements 10, the central part 12 being axially contiguous with the intermediate parts 11a and 11b, with a density of 75 threads/dm (pitch of 1.33 mm), and secondly, from these intermediate parts 11a and 11b towards the lateral parts 13a and 13b of the layer of circumferential reinforcing elements 10 the lateral parts 13a and 13b being axially contiguous with the respective intermediate parts 11a and 11b, with a density of 70 threads/dm (pitch of 1.43 mm).

(13) The ratio of the value of the pitch in the axially outer parts 13a, 13b to the value of the pitch in the central part 12 is equal to 1.07 and therefore falls between 1.05 and 4.

(14) The ratio of the value of the pitch in the intermediate parts 11a, 11b to the value of the pitch in the central part 12 is equal to 0.75, and therefore falls between 0.5 and 0.95.

(15) The width of the layer of circumferential reinforcing elements 10 is equal to 170 mm.

(16) The parts 11a and 11b each have an axial width of 62 mm. The axial width of each of the intermediate parts 11a and 11b of the layer of circumferential reinforcing elements is equal to 36% of the axial width of the layer of circumferential reinforcing elements, which falls between 10 and 38% of the width.

(17) The central part 12 has an axial width of 20 mm. The axial width of the central part of the layer of circumferential reinforcing elements is equal to 12% of the axial width of the layer of circumferential reinforcing elements and therefore falls between 10 and 50% of the width.

(18) The parts 13a and 13b each have an axial width of 13 mm. The axial, width of each of the axially outer parts 13a and 13b of the layer of circumferential reinforcing elements is equal to 8% of the axial width of the layer of circumferential reinforcing elements and therefore falls between 7 and 15% of the width.

(19) According to the invention, in the case of a tire intended to be fitted at the rear of a motorcycle, the value of the pitch in an axially outer part is greater than the value of the pitch in the central part. The stiffness in the circumferential direction of the axially outer part of the layer of circumferential reinforcing elements is therefore lower than the stiffness of the central part in the circumferential direction.

(20) The presence of the layer of circumferential reinforcing elements in the tire contributes firstly to improving performance in terms of endurance and secondly the distribution at a variable pitch allows the circumferential stiffnesses of the crown reinforcement of the tire to be modulated in order to optimize the compromises between flattening, wear and high-speed performance of the tire.

(21) The layer of circumferential reinforcing elements 10 consists of textile reinforcements of the metal 6*23 type.

(22) FIG. 2 depicts a tire 21 similar to that of FIG. 1 and which differs therefrom in the radial position of the layer of circumferential reinforcing elements 201. In this second depiction according to the invention, the layer of circumferential reinforcing elements 210 has been positioned radially on the inside of the carcass reinforcement 2 and therefore radially on the inside of the two working layers 27, 28. This radial position of the layer of circumferential reinforcing elements 210 allows in particular a further improvement in the grip and traction properties of the tire.

(23) FIG. 3 depicts a tire 31 of 120/70 ZR 17 type intended to be fitted at the front of a motorcycle.

(24) The crown reinforcement 36 of the tire 31 is similar to that of the tire 1 illustrated in FIG. 1. The only difference is in the layer of circumferential reinforcing elements 310 and, more specifically, the variation in the pitch at which the reinforcing elements are laid.

(25) As in the case of FIG. 1 and according to the invention, the variation in laying pitch leads to a variation in the density of circumferential reinforcing elements which is such that the density is greater in the intermediate parts 311a and 311b. The circumferential reinforcing element densities therefore decrease, firstly, from these intermediate parts 311a and 311b at which the density is 90 threads/dm (pitch of 1.11 mm) towards the central part 312 of the tire at which the density is 60 threads/dm (pitch of 1.67 mm), and, secondly, from these intermediate parts 311a and 311b towards the lateral parts 313a, 313b of the layer of circumferential reinforcing elements 310 where the density is 70 threads/dm (pitch of 1.43 mm).

(26) Unlike the situation in FIG. 1, and according to the invention for a tire intended to be fitted at the front of a motorcycle, the value of the pitch in an axially outer part 313a, 313b is lower than the value of the pitch in the central part. The stiffness, in the circumferential direction, of the axially outer part of the layer of circumferential reinforcing elements is therefore greater than the stiffness, in the circumferential direction, of the central part.

(27) The ratio of the value of the pitch in the axially outer parts 313a, 313b to the value of the pitch in the central part 312 is equal to 0.86 and therefore falls between 0.5 and 0.95.

(28) The ratio of the value of the pitch in the intermediate parts 11a, 11b to the value of the pitch in the central part 12 is equal to 0.67 and therefore falls between 0.4 and 0.7.

(29) The width of the layer of circumferential reinforcing elements 10 is 106 mm.

(30) The parts 311a and 311b each have an axial width equal to 20 mm. The axial width of each of the intermediate parts 311a and 311b of the layer of circumferential reinforcing elements is equal to 19% of the axial width of the layer of circumferential reinforcing elements which falls between 10 and 38% of the width.

(31) The central part 312 has an axial width of 40 mm. The axial width of the central part 312 of the layer of circumferential reinforcing elements is equal to 38% of the axial width of the layer of circumferential reinforcing elements and therefore falls between 10 and 50% of the width.

(32) The parts 313a and 313b each have an axial width of 13 mm. The axial width of each of the axially outer parts 313a and 313b of the layer of circumferential reinforcing elements is equal to 12% of the axial width of the layer of circumferential reinforcing elements and therefore falls between 7 and 15% of the width.

(33) The layer of circumferential reinforcing elements 10 consists of textile reinforcements of the metal 4*23 type.

(34) The invention should not be interpreted as being restricted to the description of the examples above. The invention notably encompasses tires that may have more complex crown reinforcements, for example comprising 3 or more working layers of reinforcing elements making an angle with the circumferential direction.

(35) The invention also applies to the various types of crown reinforcement listed hereinabove and notably those described in patent applications WO 2004/018236, WO 2004/018237, WO 2005/070704, WO 2005/070706, notably exhibiting the various radial positions of the layers that make up the crown reinforcement relative to one another, and their radial position with respect to the carcass structure, plus also the makeup of a layer formed of a thread constituting portions connected by loops or even varied angles formed by the portions with the axial direction.