Abstract
A tire with improved handling having a stiffening structure with a stiffening element 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. The stiffening structure is distributed circumferentially over the circumference of the tire, the axially outermost stiffening element 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 the radially outermost stiffening element 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 0.5 times the radial height H.
Claims
1. A vehicle tire, intended to be mounted on a nominal rim and inflated to a nominal pressure P, having an axial width S and a radial height H in the mounted and inflated state, and comprising a crown having a radially outer tread surface, intended to come into contact with the ground, and two axial ends, each extended radially towards the 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, the tire having an equatorial plane (XZ) passing through the middle of its tread surface and perpendicular to an axis of rotation, wherein the tire comprises a stiffening structure, comprising at least one stiffening element 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, in that the stiffening structure is distributed circumferentially over the entire circumference of the tire, in that the axially outermost stiffening element 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 in that the radially outermost stiffening element 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 0.5 times the radial height H.
2. The tire according to claim 1, wherein the stiffening structure comprises several stiffening elements not joined to one another in the toroidal interior cavity.
3. The tire according to claim 1 the at least one stiffening element of the stiffening structure extends continuously in the toroidal interior cavity without intersecting the equatorial plane (XZ).
4. The tire according to claim 3, wherein the stiffening structure is symmetric with respect to the equatorial plane (XZ).
5. The tire according to claim 1, wherein the axially outermost stiffening element crown interface is positioned, with respect to the equatorial plane (XZ), at an axial distance A at most equal to 0.15 times and at least equal to 0.05 times the axial width S.
6. The tire according to claim 1, wherein the radially outermost stiffening element 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 0.10 times, the radial height H.
7. The tire according to claim 2, wherein the stiffening structure is made up of mutually identical stiffening elements.
8. The tire according to claim 1, wherein any stiffening element comprises a polymeric material, a metal material, or a glass- or carbon-type material or any combination thereof.
9. The tire according to claim 1, wherein any stiffening element is a two-dimensional element.
10. The tire according to claim 9, wherein any two-dimensional stiffening element is made up of a reinforcing fabric comprising reinforcing elements coated in an elastomer compound.
11. The tire according to claim 1, wherein any stiffening element is a one-dimensional element of filament or cord type.
Description
[0043] The invention is illustrated in the figures referenced hereinbelow, which are not to scale and are described below:
[0044] FIG. 1A: A meridian cross section through a tire according to a first embodiment of the invention.
[0045] FIG. 1B: A meridian cross section through a tire according to a second embodiment of the invention.
[0046] FIG. 1C: A meridian cross section through a tire according to a third embodiment of the invention.
[0047] FIG. 2: A perspective view of a first example of a tire according to the invention, with two-dimensional stiffening elements of film type.
[0048] FIG. 3: A perspective view of a second example of a tire according to the invention, with one-dimensional stiffening elements of cord type.
[0049] FIG. 4: Comparison of radial stiffnesses K.sub.ZZ between a tire according to the invention and a reference tire of the prior art.
[0050] FIG. 5: Comparison of transverse or axial stiffnesses K.sub.YY between a tire according to the invention and a reference tire of the prior art.
[0051] FIG. 1A depicts a meridian cross section through a tire according to a first embodiment of the invention. The tire 1 depicted, which is for a passenger vehicle, 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 tire 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 delimiting a toroidal interior cavity 6. The tire 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 this first embodiment of the invention, the tire 1 comprises a stiffening structure 7, comprising two stiffening elements 8 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 over the entire circumference of the tire. 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 stiffening element 8 crown interface 81, necessarily the axially outermost one in this instance, given the presence of a single stiffening element 8 on each side of the equatorial plane XZ, is positioned, with respect to the equatorial plane letter XZ, at an axial distance A at most equal to 0.45 times the axial width S. The stiffening element 8 bead interface 82, necessarily the radially outermost one in this instance, 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 most equal to 0.5 times the radial height H. it should be noted that, in instances in which each stiffening element 8, as depicted in FIG. 1A, is of the one-dimensional or filamentary type, this element is not necessarily contained in a meridian plane YZ, but may potentially be inclined with respect to the meridian plane YZ.
[0052] FIG. 1B depicts a meridian section of a tire according to a second embodiment of the invention, in which the stiffening structure 7 comprises, on each side of the equatorial plane XZ, three stiffening elements 8 as previously described. The maximum characteristics regarding the respectively axial positioning, with axial distance A, and radial positioning, with radial distance B, relate to the axially outermost stiffening element on each side of the equatorial plane XZ.
[0053] FIG. 1C depicts a meridian section of a tire according to a third embodiment of the invention, in which the stiffening structure 7 comprises, a single stiffening element 8 passing across the toric cavity 6, intersecting the equatorial plane 7. This single stiffening element 8 conforms to the maximum characteristics regarding the respectively axial positioning, with axial distance A, and radial positioning, with radial distance B.
[0054] FIG. 2 depicts a partial perspective view of a first example of a tire according to the invention, comprising a stiffening structure 7 with two two-dimensional stiffening elements 8 of film type extending 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. These two two-dimensional stiffening elements 8 of the film type are symmetric about the equatorial plane of the tire. Since the crown interface 81 of each stiffening element 8 is positioned at an axial distance A away from the equatorial plane of the tire, the axial distance separating the two respective crown interfaces 81 is 2A. Each stiffening element 8, which exhibits symmetry of revolution about the axis of rotation of the tire, extends circumferentially and uniformly around the entire circumference of the tire.
[0055] FIG. 3 depicts a partial perspective view of a second example of a tire according to the invention, comprising a stiffening structure 7 with one-dimensional stiffening elements 8 of cord type extending 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. These one-dimensional stiffening elements 8 of the cord type are divided between two groups that are symmetric about the equatorial plane of the tire. The stiffening elements of each group are distributed circumferentially and uniformly over the entire circumference of the tire and are therefore spaced apart, one from its pair, by a constant spacing. Since, as in the embodiment of FIG. 2, the crown interface 81 of each stiffening element 8 being positioned at an axial distance A away from the equatorial plane of the tire, the axial distance separating the two respective crown interfaces 81 of two symmetric stiffening elements 8 is 2A.
[0056] FIG. 4 is a graph showing a comparison of radial stiffnesses K.sub.ZZ between a tire according to the invention and a reference tire of the prior art. For a given inflation pressure P and a given radial distortion f, the radial force Z generated by the tire according to the invention is higher than that generated by the reference tire. The gradient of the curve of radial force Z as a function of the radial distortion f of the tire, namely the radial displacement of the crown of the tire, represents the radial stiffness K.sub.ZZ of the tire. Therefore, the radial stiffness K.sub.ZZ of the tire according to the invention is higher than that of the reference tire.
[0057] FIG. 5 is a graph showing a comparison of transverse stiffnesses K.sub.YY between a tire according to the invention and a reference tire 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 tire according to the invention is higher than that generated by the reference tire. The gradient of the substantially linear portion of the curve of transverse force Y as a function of the transverse offset d of the tire, namely the transverse displacement thereof, represents the transverse stiffness K.sub.YY of the tire. The substantially linear portion of the curve of transverse force Y corresponds, in the instance depicted, to a transverse offset at most equal to around 30 mm. Therefore, the transverse stiffness K.sub.YY of the tire according to the invention is higher than that of the reference tire. Upwards of 30 mm of transverse offset, the transverse force Y reaches a plateau because of the slipping of the tread surface of the tire across the ground. In the case of the invention, this is stabilizing of the transverse force Y occurs at a higher level, because of the 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.
[0058] The invention has been studied more particularly in the case of a passenger vehicle tire of size 205/55R16. Thus, a reference tire R was compared against a first example of a tire I1 according to the invention, with two-dimensional stiffening elements of the film type, shown in FIG. 2, and with a second example of a tire I2 according to the invention, with one-dimensional stiffening elements of the cord type, shown in FIG. 3.
[0059] The respective tires, R reference, I1 according to the invention, and I2 according to the invention are intended to be mounted on a nominal 6.5J16 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 respectively equal to 209 mm and 104 mm.
[0060] The first example I1 is characterized by a stiffening structure, as depicted in FIG. 2, with two two-dimensional stiffening elements of film type which are symmetric with respect to the equatorial plane of the tire. Each two-dimensional stiffening element is made up of a juxtaposition of strips, each strip having a width of 6 cm, with a tolerance of 1 cm. The material of the strips is a fabric made up of textile reinforcers made of polyester coated with an elastomer compound, the said textile reinforcers having a unit section equal to 0.42 mm.sup.2 and being distributed at a constant spacing equal to 0.96 mm. The textile reinforcers are positioned radially, namely in meridian planes of the tire. In order to make up the crown interface, the radially outer end of each strip is secured to the radially inner face of the crown by hot vulcanizing. In order to make up the bead interface, the radially inner end of each strip is clamped between the bead and the rim. Furthermore, the axial distance A is comprised between 0.05 times and 0.15 times the axial width S of the tire, and the radial distance B is at most equal to 0.05 times the radial height H of the tire.
[0061] The second example I2 is characterized by a stiffening structure, as depicted in FIG. 3, with one-dimensional stiffening elements of cord type which are distributed in two groups which are symmetric with respect to the equatorial plane of the tire. Each one-dimensional stiffening element is a textile reinforcer made up of a combination of an aromatic polyamide of the aramid type, and an aliphatic polyamide of the nylon type, with a unit section equal to 1 mm.sup.2. The stiffening elements in each group are distributed circumferentially and uniformly over the entire circumference of the tire and are spaced each from its pair by a constant spacing equal to 30 mm and are inclined, with respect to a meridian plane, by an angle substantially equal to 10°. The respective crown and bead interfaces of each one-dimensional stiffening element are created by connecting the corresponding ends to attachments positioned respectively on the axially inner face of the crown and on the axially inner face of the bead before the tire is cured.
[0062] Table 1 below summarizes the differences in performance obtained respectively between the first example of a tire I1 and the reference tire R, and between the second example of a tire I2 and the reference tire:
TABLE-US-00001 TABLE 1 Difference in Difference in performance performance between the between the Performance tire I1 and the tire I2 and characteristics tire R the tire R Radial stiffness K.sub.ZZ +20% 0% Transverse stiffness K.sub.YY +50% +30% Cornering stiffness D.sub.Z +5% (Z = 480daN) Not determined +20% (Z = 800daN) Rolling resistance −0.2 kg/t Not determined (calculated)
[0063] 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: a first example I1, characterized by a high density of textile reinforcers, offers a greater shift in performance than the second example I2, which itself represents a shift with respect to the reference tire R.
