Abstract
A tire (1) has improved handling and comprises a stiffening structure (7) comprising two stiffening elements (8), each extending continuously in the toroidal interior cavity (6) from a crown interface (81) connected to a radially inner face of the crown (23) to a bead interface (82) connected to an axially inner face of the bead (41). The stiffening structure (7) is distributed circumferentially around the entire circumference of the tire. The crown interface (81) is positioned, with respect to the equatorial plane (XZ), at an axial distance A at most equal to 0.45 times the axial width S and the bead interface (82) is positioned, with respect to a radially innermost point (I) of the axially inner face of the bead (41), at a radial distance B at least equal to 0.10 times the radial height H and at most equal to 0.5 times the radial height H.
Claims
1.-15. (canceled)
16. A vehicle tire, which is intended to be mounted on a nominal rim and inflated to a nominal pressure P, has an axial width S and a radial height H in the mounted and inflated state, and comprises: a crown having a radially outer tread surface, intended to come into contact with ground, and two axial ends, each extended radially toward an inside by a sidewall and then by a bead intended to come into contact with the rim, the crown, the sidewalls, and the beads delimiting a toroidal interior cavity, and the vehicle tire having an equatorial plane XZ passing through a middle of a tread surface and perpendicular to an axis of rotation YY′, wherein the tire comprises a stiffening structure comprising two stiffening elements, each extending continuously in the toroidal interior cavity from a crown interface connected to a radially inner face of the crown to a bead interface connected to an axially inner face of the bead, wherein the stiffening structure is distributed circumferentially around an entire circumference of the vehicle tire, wherein the crown interface is positioned, with respect to the equatorial plane XZ, at an axial distance A at most equal to 0.45 times the axial width S, and wherein the bead interface is positioned, with respect to a radially innermost point I of the axially inner face of the bead, at a radial distance B at least equal to 0.10 times the radial height H and at most equal to 0.5 times the radial height H.
17. The vehicle tire according to claim 16, wherein the two stiffening elements are positioned symmetrically on either side of the equatorial plane XZ.
18. The vehicle tire according to claim 16, wherein the crown interface is positioned, with respect to the equatorial plane XZ, at an axial distance A at least equal to 0.05 times and at most equal to 0.15 times the axial width S.
19. The vehicle tire according to claim 16, wherein the bead interface is positioned, with respect to a radially innermost point I of the axially inner face of the bead, at a radial distance B at most equal to 0.35 times the radial height H.
20. The vehicle tire according to claim 16, wherein the crown interface is distributed across a width A1 at least equal to 0.1 times the axial width.
21. The vehicle tire according to claim 16, wherein the crown interface comprises a cushion made of elastomer compound positioned at least partially between the stiffening element and the radially inner face of the crown.
22. The vehicle tire according to claim 16, wherein the crown interface is distributed across a width A1, and wherein the bead interface is distributed across a width B1 at least equal to the width A1.
23. The vehicle tire according to claim 16, wherein the bead interface comprises a cushion made of elastomer compound at least partially in contact with the stiffening element and the axially inner face of the bead.
24. The vehicle tire according to claim 23, wherein the cushion made of elastomer compound of the bead interface is at least partially in contact with a reinforcing layer such that the cushion is delimited by the stiffening element, the axially inner face of the bead, and the reinforcing layer.
25. The vehicle tire according to claim 16, wherein each stiffening element comprises a material selected from the group consisting of an aliphatic polyamide polymeric material, an aromatic polyamide polymeric material, a polyester polymeric material, a metal material, a glass-type material, a carbon-type material and combinations thereof.
26. The vehicle tire according to claim 16, wherein the stiffening element is not sealed.
27. The vehicle tire according to claim 16, wherein each stiffening element comprises filamentary reinforcing elements that are coated, at least in a vicinity of the crown interface and bead interface, respectively, with an elastomer compound, such that the stiffening element is not sealed.
28. The vehicle tire according to claim 27, wherein each stiffening element is made up of a family of filamentary reinforcing elements that are mutually parallel and form, with a circumferential direction XX′, an angle C1 at least equal to 85° and at most equal to 95°.
29. The vehicle tire according to claim 27, wherein each stiffening element is made up of a first family of filamentary reinforcing elements that are mutually parallel and form, with a circumferential direction XX′, an angle C1 at least equal to 45° and at most equal to 75°, the first family being crossed with respect to a second family of filamentary reinforcing elements that are mutually parallel and form, with a circumferential direction XX′, an angle C2 at least equal to 45° and at most equal to 75°.
30. The vehicle tire according to claim 29, wherein the angles C1 and C2 are equal in terms of absolute value and opposite.
Description
[0044] The invention is illustrated in the figures referenced below, which are not to scale and are described in the following text:
[0045] FIG. 1: Meridian section through a tyre according to the invention.
[0046] FIG. 2: Meridian section through a tyre according to a preferred embodiment of the invention, with elastomer cushions at the crown interface and bead interface.
[0047] FIG. 3: Perspective view of a preferred embodiment of the invention, with stiffening elements comprising filamentary reinforcing elements.
[0048] FIG. 4: Stiffening element comprising filamentary reinforcing elements coated, in the vicinity of the crown interface and bead interface, with an elastomer compound.
[0049] FIG. 5: Stiffening element comprising filamentary reinforcing elements coated with an elastomer compound having holes.
[0050] FIG. 6: Stiffening element comprising a family of substantially radial filamentary reinforcing elements.
[0051] FIG. 7: Stiffening element comprising two families of filamentary reinforcing elements that are inclined with respect to the circumferential direction and crossed from one family to the other.
[0052] FIG. 8: Comparison of radial stiffnesses K.sub.ZZ between a tyre according to the invention and a reference tyre of the prior art.
[0053] FIG. 9: Comparison of transverse or axial stiffnesses K.sub.YY between a tyre according to the invention and a reference tyre of the prior art.
[0054] FIG. 1 shows a meridian section through a tyre according to the invention. The tyre 1 is intended to be mounted on a nominal rim 5 and inflated to a nominal pressure P, and has an axial width S and a radial height H in the mounted and inflated state. The tyre 1 comprises a crown 2 having a radially outer tread surface 21, intended to come into contact with the ground, and two axial ends 22, each extended radially towards the inside by a sidewall 3 and then by a bead 4 intended to come into contact with the rim 5. The crown 2, the sidewalls 3 and the beads 4 delimit a toroidal interior cavity 6. The tyre 1 has an equatorial plane XZ passing through the middle of its tread surface 21 and perpendicular to an axis of rotation YY′. According to the invention, the tyre 1 comprises a stiffening structure 7 comprising two stiffening elements 8 that extend continuously in the toroidal interior cavity 6 from a crown interface 81 connected to a radially inner face of the crown 23 to a bead interface 82 connected to an axially inner face of the bead 41. The stiffening structure 7 is distributed circumferentially around the entire circumference of the tyre. The two stiffening elements 8 that make up the stiffening structure 7 are not connected to one another inside the toroidal interior cavity 6, extend continuously in the toroidal interior cavity 6 without intersecting the equatorial plane XZ and are symmetric with respect to the equatorial plane XZ. The crown interface 81 of the stiffening element 8 is positioned, with respect to the equatorial plane XZ, at an axial distance A at most equal to 0.45 times the axial width S. The bead interface 82 of the stiffening element 8 is positioned, with respect to a radially innermost point I of the axially inner face of the bead 41, at a radial distance B at least equal to 0.10 times the radial height H and at most equal to 0.5 times the radial height H.
[0055] FIG. 2 shows a meridian section through a tyre according to a preferred embodiment of the invention, with elastomer cushions at the crown interface and bead interface. The additional elements with respect to FIG. 1 are described below. The crown interface 81 is distributed across a width A1 at least equal to 0.1 times the axial width S and comprises a cushion 811 made of elastomer compound positioned at least partially between the stiffening element 8 and the radially inner face of the crown 23. The bead interface 82 is distributed across a width B1 at least equal to the width A1 and comprises a cushion 821 made of elastomer compound at least partially in contact with the stiffening element 8 and the axially inner face of the bead 41. Lastly, the cushion 821 made of elastomer compound of the bead interface 82 is at least partially in contact with a reinforcing layer 822 such that the cushion 821 is delimited by the stiffening element 8, the axially inner face of the bead 41 and the reinforcing layer 822.
[0056] FIG. 3 shows a perspective view of a preferred embodiment of the invention, with stiffening elements comprising filamentary reinforcing elements. The stiffening structure 7 is made up of two stiffening elements 8 comprising filamentary reinforcing elements 83 that extend continuously in the toroidal interior cavity from a crown interface 81 connected to a radially inner face of the crown 23 to a bead interface 82 connected to an axially inner face of the bead 41. The stiffening element 8 is not sealed. In this instance, the filamentary reinforcing elements 83 are coated, at least in the vicinity of the crown interface 81 and bead interface 82, respectively, with an elastomer compound 84, such that the stiffening element 8 is not sealed.
[0057] FIG. 4 shows a stiffening element comprising filamentary reinforcing elements coated, in the vicinity of the crown interface and bead interface, with an elastomer compound. The stiffening element 8 comprises filamentary reinforcing elements 83 that are coated, in the vicinity of the crown interface 81 and bead interface 82, respectively, with an elastomer compound 84, such that the stiffening element 8 is not sealed. As a result, the pressure of the inflation gas is identical on both sides of the stiffening element 8, which therefore does not delimit a secondary cavity with a pressure different from that of the main cavity.
[0058] FIG. 5 shows a stiffening element comprising filamentary reinforcing elements coated with an elastomer compound having holes. The stiffening element 8 comprises filamentary reinforcing elements 83 that are coated along their entire length between the crown interface 81 and bead interface 82, respectively, with an elastomer compound 84 comprising holes, such that the stiffening element 8 is not sealed. This is another embodiment of a stiffening element that is not sealed.
[0059] FIG. 6 shows a stiffening element comprising a family of substantially radial filamentary reinforcing elements. The stiffening element 8 is made up of a family of filamentary reinforcing elements 83 that are mutually parallel and form, with a circumferential direction XX′, an angle C1 at least equal to 85° and at most equal to 95°. The filamentary reinforcing elements 83 are all coated, in the vicinity of the crown interface 81 and bead interface 82, respectively, with an elastomer compound 84, such that the stiffening element 8 is not sealed.
[0060] FIG. 7 shows a stiffening element comprising two families of filamentary reinforcing elements that are inclined with respect to the circumferential direction and crossed from one family to the other. The stiffening element 8 is made up of a first family of filamentary reinforcing elements 83 that are mutually parallel and form, with a circumferential direction XX′, an angle C1 at least equal to 45° and at most equal to 75°, said first family being crossed with respect to a second family of filamentary reinforcing elements 83 that are mutually parallel and form, with a circumferential direction XX′, an angle C2 at least equal to 45° and at most equal to 75°. In the case shown, the angles C1 and C2 are equal in terms of absolute value and opposite, that is to say symmetric with respect to the circumferential direction XX′. The filamentary reinforcing elements 83 are all coated, in the vicinity of the crown interface 81 and bead interface 82, respectively, with an elastomer compound 84, such that the stiffening element 8 is not sealed.
[0061] FIG. 8 is a graph showing a comparison of the radial stiffnesses K.sub.ZZ between a tyre according to the invention and a reference tyre of the prior art. For a given inflation pressure P and a given radial distortion f, the radial force Z generated by the tyre according to the invention is higher than that generated by the reference tyre. The gradient of the curve of radial force Z as a function of radial distortion f of the tyre, that is to say the radial displacement of the crown of the tyre, represents the radial stiffness K.sub.ZZ of the tyre. Therefore, the radial stiffness K.sub.ZZ of the tyre according to the invention is higher than that of the reference tyre.
[0062] FIG. 9 is a graph showing a comparison of the transverse or axial stiffnesses K.sub.YY between a tyre according to the invention and a reference tyre of the prior art. For a given inflation pressure P, a given radial distortion f, and a given transverse offset d, the transverse force Y generated by the tyre according to the invention is higher than that generated by the reference tyre. The gradient of the substantially linear portion of the curve of transverse force Y as a function of transverse offset d of the tyre, that is to say the transverse displacement thereof, represents the transverse stiffness K.sub.YY of the tyre. The substantially linear portion of the curve of transverse force Y corresponds, in the case shown, to a transverse offset at most equal to around 20 mm. Therefore, the transverse stiffness K.sub.YY of the tyre according to the invention is higher than that of the reference tyre. Above 20 mm of transverse offset, the transverse force Y reaches a plateau on account of the slipping of the tread surface of the tyre across the ground. In the case of the invention, this stabilizing of the transverse force Y occurs at a higher level, above 25 mm, on account of a higher transverse stiffness K.sub.YY making it possible to maintain a more uniform distribution of pressure in the contact patch, under transverse force Y.
[0063] The invention was studied more particularly in the case of a passenger vehicle tyre of size 255/35R19. A reference tyre R was thus compared with a first example of a tyre I1 according to the invention, with a crown interface and bead interface in accordance with FIG. 2, and comprising two stiffening elements made up of a family of filamentary reinforcing elements of the cord type that are mutually parallel and form, with the circumferential direction, an angle C1 substantially equal to 90° in accordance with FIG. 4. It was also compared with a second example of a tyre 12 according to the invention, with a crown interface and bead interface in accordance with FIG. 2, and comprising two stiffening elements made up of a first family of filamentary reinforcing elements of the cord type that are mutually parallel and form, with a circumferential direction, an angle C1 equal to 60°, said first family being crossed with respect to a second family of filamentary reinforcing elements of the cord type that are mutually parallel and form, with the circumferential direction, an angle C2 equal to the angle C1 in terms of absolute value but opposite thereto in accordance with FIG. 7.
[0064] The reference tyre R, tyre according to the invention I1 and tyre according to the invention I2, respectively, are mounted on a nominal 9J19 rim and inflated to a nominal pressure P of 2.5 bar. Their axial widths S and their radial heights H, in the mounted and inflated state, are equal to 255 mm and 89 mm, respectively.
[0065] The first example I1 is characterized by a stiffening structure, as shown in FIG. 2, with two stiffening elements that are symmetric with respect to the equatorial plane of the tyre. Each stiffening element is composed of a juxtaposition of filamentary reinforcing elements of the cord type that have a cross-sectional area equal to 0.8 mm.sup.2, are mutually parallel and are distributed at a spacing equal to 1.25 mm. The constituent material of the stiffening elements is a fabric made up of textile reinforcers made of polyester (or PET) that are coated in the vicinity of the crown interface and bead interface with an elastomer compound. The textile reinforcers are positioned in substantially meridian planes of the tyre. The crown interface and bead interface are distributed across axial widths A1, of between 0.1 and 0.15 times the axial width S of the tyre, and B1, of between 0.25 and 0.3 times the radial height H of the tyre, respectively. Moreover, they respectively comprise elastomer cushions that are positioned between the stiffening element and the attachment wall. Furthermore, the crown interface and bead interface are produced by hot vulcanization.
[0066] The second example I2 differs from the first example I1 in the makeup of the two stiffening elements, which are each made up of two families of filamentary reinforcing elements of the cord type that are crossed with respect to one another, forming, with the circumferential direction, two angles C1 and C2 that are equal to 60° in terms of absolute value and opposite.
[0067] Table 1 below summarizes the differences in performance obtained between the first example of a tyre I1 and the reference tyre R, and between the second example of a tyre I12 and the reference tyre, respectively:
TABLE-US-00001 TABLE 1 Difference in Difference in performance between performance between Performance the tire I1 and the the tire I2 and the characteristics tire R tire R Radial stiffness K.sub.ZZ No difference +20% Transverse stiffness K.sub.YY +70% +85% Rolling resistance −0.8 kg/t Not determined (calculated) Noise inside vehicle No difference Not determined
[0068] The results of Table 1 show an improved compromise in performance between the rolling resistance and the handling for the invention. It should be noted that this compromise is variable. Specifically, the prestress applied to the stiffening elements during the inflation of the tyre can be varied, resulting in a variation in stiffnesses, and in particular in the transverse stiffness K.sub.YY, depending on the level of prestress.
