Extended-Mobility Cross-Ply Or Radial Tire

Abstract

Tire with sidewalls (6) having, on their outer surfaces, a set of protuberances (8) that alternate with voids (9). The tread (4) comprises a circumferential groove (10) at at least one axially outermost end (4a). Each protuberance (8) is disposed at the surface of a sidewall, the different protuberances being disposed regularly or irregularly and continuously or discontinuously between a point A and a point E. The inner wall (2a) of the carcass ply (2) of the tire is partially or entirely covered with at least one layer of a self-sealing composition (2b).

Claims

1. A tire for a rolling assembly comprising a rim and a tire, said tire having at least one carcass reinforcement that comprises an inner wall and is surmounted radially on the outside by a crown reinforcement, itself radially on the inside of a tread having two axially outermost ends, said crown reinforcement comprising at least one layer of reinforcing elements, said tread being connected to two beads by way of two sidewalls, said beads being configured to come into contact with a rim having rim flange tops, each bead having at least one circumferential reinforcing element, said sidewalls having, on their outer surfaces, a set of protuberances that alternate with voids, the inner wall of the carcass ply of the tire being partially or entirely covered with at least one layer of a self-sealing composition, wherein each said protuberance is disposed at the surface of the sidewall, said protuberances being disposed continuously between a point A and a point E, said point A being disposed at the intersection of the radially outer surface of the tread and of the sidewall, with a radial axis ZZ′ at a distance from a plane AA′ by a length L.sub.A of between ½(L−60 mm) and ½(L−10 mm), L being the nominal section width, said plane AA′ being parallel to the equatorial plane and tangential to the sidewall, and said point E being disposed, as desired, in a radius such that R.sub.2<E<(R.sub.A−15 mm), R.sub.2 being the radius at the rim flange top and R.sub.A being the radius at the point A.

2. The tire according to claim 1, wherein at least one protuberance has a height and a length, said height being at a minimum at the section width and increasing progressively on either side of said section width with a minimum height at a distance of between 0.9R.sub.1 and 1.1R.sub.1.

3. The tire according to claim 1, wherein at least two protuberances have different lengths from one another.

4. The tire according to claim 1, wherein each said protuberance has an average height of between 3 and 10 mm.

5. The tire according to claim 1, wherein each said protuberance has an average width of between 4 and 12 mm.

6. The tire according to claim 4, wherein the average height of each said protuberance is between 5 and 8mm.

7. The tire according to claim 1, wherein each said protuberance has an average height greater than 80% of the maximum height over at least 80% of the distance between the points A and E.

8. The tire according to claim 1, wherein each said protuberance has a relief angle α less than or equal to 20°.

9. The tire according to claim 1, wherein two adjacent said protuberances are spaced apart from one another by an average distance less than or equal to 2 times the average width of a protuberance.

10. The tire according to claim 1, wherein two adjacent said protuberances are substantially parallel to one another.

11. The tire according to claim 1, wherein said protuberances cover at least 40% of the overall circumferential surface of the sidewall between the points A and E.

12. The according to claim 1, wherein each said protuberance, of defined or arbitrary geometric shape, comprises a neutral fibre that passes through a radially innermost end and through a radially outermost end and is set at an angle β, with respect to the radial direction ZZ′, of between −60° and +60°.

13. The tire according to claim 1, wherein the void between two adjacent said protuberances extends axially in the continuation of the void of a circumferential groove of the tread, passing through the point A, said groove being disposed at at least one axial end of the tread.

14. The tire according to claim 1, wherein two adjacent said protuberances form a void between one another, the wall of one said protuberance making an angle α with the circumferential direction of between −15° and +15° in a sidewall region close to the point A.

15. The tire according to claim 1, wherein the sum of the widths of the protuberances in the circumferential direction is greater than or equal to 60% of the total circumferential length.

16. The tire according to claim 1, wherein the tire has a [sum of the total widths of each protuberance]/2πR ratio greater than or equal to 30%, the widths of each said protuberance being defined at 50% of the total height of said protuberance and the radius R of the tire being an average radius.

17. The tire according to claim 1, wherein each said protuberance has a relief angle α between 5 and 8°.

18. The tire according to claim 1, wherein the tire has a [sum of the total widths of each protuberance]/2πR ratio greater than or equal to 60% and less than or equal to 70%, the widths of each said protuberance being defined at 50% of the total height of said protuberance and the radius R of the tire being an average radius.

Description

[0072] The invention will now be described with the aid of examples and drawings which follow and which are given purely by way of illustration, and in which:

[0073] FIG. 1 schematically shows the cross section of a tire according to the invention in a radial plane comprising a continuous protuberance,

[0074] FIGS. 2A and 2B are three-dimensional schematic depictions of a portion of a sidewall and of the corresponding tread of a tire according to the invention,

[0075] FIG. 3 schematically shows an enlarged portion of a sidewall comprising continuous protuberances of a tire according to the invention,

[0076] FIG. 4 shows a view in section on the line AA in FIG. 3 of two adjacent protuberances of a tire according to the invention,

[0077] FIGS. 5A and 5B show, in a first variant, a portion of a radially outer part of a sidewall and the corresponding tread in three dimensions of a tire according to the invention,

[0078] FIG. 6A shows, in a second variant, a portion of a radially outer part of a sidewall and of the corresponding tread in three dimensions, of which a certain protuberance completely interrupts a circumferential groove in a tire according to the invention,

[0079] FIG. 6B shows, in another variant, a portion of a radially outer part of a sidewall and of the corresponding tread in three dimensions, of which a certain protuberance partially interrupts a circumferential groove in a tire according to the invention,

[0080] FIG. 7A shows a partial view in radial section of a part of a sidewall and of a part of the corresponding tread according to another variant,

[0081] FIG. 7B shows a partial view in radial section of a part of a sidewall and of a part of the corresponding tread according to another variant of a tire according to the invention,

[0082] FIG. 8 is a three-dimensional schematic depiction of a portion of a sidewall and of the corresponding bead of a tire according to the invention,

[0083] FIG. 9 schematically shows the cross section of a tire according to the invention in a radial plane comprising a discontinuous protuberance,

[0084] FIGS. 10 and 11 are three-dimensional schematic depictions of an enlarged portion of a sidewall and of the corresponding tread of a tire according to the invention and comprising a discontinuous protuberance.

[0085] In the various figures, identical or similar technical elements have been given the same reference numbers. In order not to overburden the text, their descriptions are not repeated.

[0086] As FIG. 1 shows, the passenger-vehicle tire of general reference 1 comprises a carcass reinforcement 2, comprising an inner wall 2a, covered with a layer of self-sealing composition 2b, radially on the inside of a belt reinforcement of overall reference 3, said belt reinforcement 3 being radially on the inside of a tread 4 itself connected to two beads 5 by way of two sidewalls 6. The beads 5 are intended to come into contact with a rim 7 (shown in part). Each bead comprises at least one circumferential reinforcing element 7a. On their surfaces, the sidewalls have a series of protuberances 8 that regularly alternate with voids 9 (shown in FIG. 2).

[0087] FIG. 1 shows a protuberance 8 in cross section, having a continuous neutral fibre. It will be recalled here that a neutral fibre is the name given to a neutral axis that passes substantially through the centre of the volume of each protuberance and which neither shortens nor lengthens when it is subjected to compression and/or depression.

[0088] As FIG. 1 shows, the protuberances 8 are disposed, at the surface of the sidewall, along a continuous length of neutral fibre that extends from a point A to a point E.

[0089] The point E is disposed at a radius less than (0.75R.sub.1+0.25R.sub.2). R.sub.1 is the radius at the nominal section width L, and R.sub.A is the radius at the point A.

[0090] The point E is disposed at a radius of 232 mm for a tire of reference 205/55 R 16 mounted on a 6.5 J 16 rim for which R.sub.A is equal to 298 mm, R.sub.2 is equal to 220 mm and R.sub.1 is equal to 261 mm.

[0091] The definition of section width according to the invention is suitable for any type of casing combined with any type of rim.

[0092] The point A is disposed at the intersection of the radially outer surface of the tread and of the sidewall, with an axis ZZ′ at a distance from the equatorial plane AA′ by a length L.sub.A equal to ½(L−45 mm). For a tire of reference 205/55 R 16, R.sub.A is equal to 298 mm The plane AA′ is parallel to the equatorial plane and tangential to the surface of the sidewall.

[0093] The protuberances are not inserted rubber elements added into the rubber of the sidewalls but are moulded in during the curing stage. They are obtained in a similar way to the tread patterns produced on the tread.

[0094] FIG. 2A shows an alternation of protuberances 8 and of voids 9, represented in enlarged manner in FIGS. 3 and 4. FIG. 2B shows a variant of FIG. 2A in which the protuberances are set at an angle with respect to the axial direction. In this embodiment, the longest continuous protuberances 8 have a neutral-fibre length of around 75 mm for a tire of size 205/55 R 16. They are disposed radially (FIG. 2) in a manner substantially parallel and next to one another and are spaced apart by around 4.50 mm, have a height of around 6 mm and a width of around 8.6 mm in their axially innermost part.

[0095] The relief angle α is around 8°. Such a relief angle value allows the tire to be demoulded after curing without damage to the final structure.

[0096] According to this embodiment, the protuberances have a [sum of the widths of each protuberance]/2πR ratio equal to 30%, at mid-height and are set at no angle with respect to the radial plane.

[0097] FIG. 5A shows a three-dimensional depiction of the radially outer part 8a of the protuberances 8 and FIG. 5B an enlargement thereof from FIG. 5A. In these FIGS. 5A and 5B, the part 8a of each protuberance 8 and the voids 9 are adjacent to a groove 10 disposed circumferentially on the surface of the tread 4 at the axially outermost end 4a thereof. The groove 10 is not interrupted in its length.

[0098] In this particular embodiment, the groove 10 has an axial width “l” along the axis YY′ that may be between 2 and 10 mm and a radial height “h” along the axis ZZ′ of between 3 and 8 mm.

[0099] FIG. 6A also shows a three-dimensional depiction of the radially outer part 8a of the protuberances 8. Unlike in FIGS. 5A and 5B, the groove 10 is interrupted. Specifically, the end 8a of the protuberances 8 and the adjacent voids 9 completely intersect the groove 10 in the circumferential direction of the tire.

[0100] FIG. 6B shows another variant of a three-dimensional depiction of said radially outer part 8a of the protuberances 8. In this figure, the protuberance 8 partially intersects the groove 10 in the circumferential direction of the tire.

[0101] FIGS. 7A and 7B show that the radially inner portion 8b (shown by way of a dotted line) of the protuberance 8 is at a distance from the radially inner part 10b of the void 10 by a thickness “d”. This thickness “d” is less than 2 mm and preferably less than 1 mm.

[0102] FIG. 8 shows that the radially upper end of the protuberances 8b and 8c is adjacent to the circumferential groove 10 and that the radially upper end of the protuberance 8d entirely interrupts the groove 10 to meet the blocks of elastomeric rubber of the tread 4. This figure thus shows an embodiment of a tire according to the invention in which each protuberance 8b, 8c alternates with a void 9. Each of the protuberances 8b, 8c extends from the point A to the point E.

[0103] FIG. 9 shows a protuberance 8 in cross section, having a discontinuous neutral fibre length.

[0104] It will be recalled here that a neutral fibre is the name given to a neutral axis that passes substantially through the centre of the volume of each protuberance and which neither shortens nor lengthens.

[0105] The protuberances 8 are disposed, at the surface of the sidewall, along a discontinuous length of neutral fibre that extends from a point A to B and from a point C to D.

[0106] The point A is disposed at the intersection of the radially outer surface of the tread and of the sidewall, with an axis ZZ′ at a distance from the equatorial plane by a length equal to 90 mm

[0107] The point B is situated in a radius equal to 266 mm, the point C in a radius equal to 258 mm, and the point D in a radius equal to 238 mm for a tire of reference 205/5 R 16 mounted on a 6.5 J 16 rim.

[0108] The protuberances are not inserted rubber elements added into the rubber of the sidewalls but are moulded in during the curing stage. They are obtained in a similar way to the tread patterns produced on the tread. The inner wall 2a comprises a layer of self-sealing composition 2b.

[0109] FIGS. 10 and 11 show an alternation of protuberances 8 and voids 9. FIG. 11 shows a variant of FIG. 10 in which the protuberances are set at an angle with respect to the axial direction. According to this embodiment, the protuberances 8 are discontinuous and have a discontinuous neutral fibre length of around 45 mm for the part P1 (between C and D) and of 40 mm for the part P2 (between A and B) for a tire of size 205/55 R 16. They are disposed in a manner substantially parallel and next to one another and are spaced apart by around 4.50 mm, have a height of around 6 mm and a width of around 8.6 mm in their axially innermost part.

[0110] The tire according to the invention is obtained after curing and moulding in a curing mould in the conventional way.

EXAMPLE 1

Kerbing Test

[0111] This test was carried out with a tire of reference 205/55 R16 comprising various styles of protuberance, against the same control tire without protuberances.

[0112] The tires P1 to P4 are various tires according to the invention.

[0113] The protuberances of tires P1 and P4 are set at no angle of inclination with respect to the radial direction.

[0114] The protuberances of tires P2 and P3 are set at an angle of inclination with respect to the radial direction.

[0115] The “Angle” column corresponds to the angle that each protuberance makes with the radial direction of the tire.

[0116] The relief angle α is the angle that each end of a protuberance makes, as shown in FIG. 4, intended to make same easier to demould.

[0117] The spacing of a protuberance is the distance between the centre of a first void and the centre of a second void adjacent to the first.

[0118] H (mm) is the average height of the protuberances, 1 (mm) is the average width of the protuberances.

[0119] R.sub.1 is the radius at the nominal section width, R.sub.2 is the radius at the top of the rim flange, R.sub.E is the radius corresponding to the point E and R.sub.A the radius at the point A.

[0120] The section width with the reliefs comprises the nominal section width and the height of the protuberances present on the surface of the sidewalls.

[0121] Table I below collates the measurable technical features of the various tires according to the invention.

TABLE-US-00001 TABLE I Tire Control P1 P2 P3 P4 Angle (degrees) None 0 +60 −60 0 Protuberance relief angle — 8 8 6 6 (degrees) Protuberance height H (mm) — 8 8 6 5 Protuberance width l (mm) — 10 10 5 7 Protuberance neutral fibre — 53 75 75 55 length (mm) R.sub.1 (mm) 260 261 261 261 261 R.sub.2 (mm) 220 220 220 220 220 R.sub.E (mm) — 224.1 224.1 224.1 228 R.sub.A (mm) — 298 298 298 298 Section width with reliefs (mm) 212 223 223 220 223 Spacing (mm)  0 15 15 7 14

[0122] This test was carried out under the following operating conditions.

[0123] The tire, mounted on a 6.5 J 16 rim and inflated to a pressure of 1.9 bar is fitted to the front right axle of a vehicle and supports a load of 350 kg.

[0124] The test consists in carrying out, at various speeds, a knock against a kerb referred to as a “kerbing” of the tire against a metal block 90 mm tall, at an angle of 30° to the block with respect to the direction of running of the tire.

[0125] This test is carried out with a control tire (without protuberances) and with various tires according to the invention that comprise protuberances that may or may not be set at an angle to the radial axis of the tire.

The results in table II below show the gain obtained in terms of speed between a control tire (result equal to 100) and the various tires according to the invention, mentioned above, before the tire is punctured.

TABLE-US-00002 TABLE II Tire Gain in speed (%) Control 100 P1 120 P2 125 P3 135 P4 120

[0126] The results in table II clearly show that the tire according to the invention, whatever the embodiment, provides a marked increase in the speed with which the kerb can be hit before the tire is punctured.

EXAMPLE 2

Kerbing Test

[0127] This test was carried out with a tire of reference 245/40 R18 comprising various styles of protuberance, against the same control tire without protuberances.

[0128] The tires P1 to P4 are various tires according to the invention.

[0129] The various technical features mentioned for Example 1 are reproduced in Example 2.

[0130] Table III below collates the measurable technical features of the various tires according to a variant of the invention.

TABLE-US-00003 Tire Control P1 P2 Angle (degrees) None 0 +30 Protuberance relief angle — 8 8 (degrees) Protuberance height H (mm) — 6 6 Protuberance width l (mm) — 6 6 Protuberance neutral fibre — 45 52 length (mm) R.sub.1 (mm) 277 277 277 R.sub.2 (mm) 248 248 248 R.sub.E (mm) — 272 272 R.sub.A (mm) — 313 313 Section width with reliefs (mm) 249 249 249 Spacing (mm)  0 12 12

[0131] This test was carried out under the same operating conditions as those explained in Example 1 with an 8.5 J 18 rim and a tire inflated to a pressure of 2.3 bar, all mounted on the front right axle of a vehicle and supporting a load of 580 kg.

[0132] The results in table IV below show the gain obtained in terms of speed between a control tire (result equal to 100) and the various tires according to the invention, mentioned above, before the tire is punctured.

TABLE-US-00004 TABLE IV Tire Gain in speed (%) Control 100 P1 128 P2 130

[0133] The results in table IV clearly show that the tire according to the invention, whatever the embodiment, provides a marked increase in the speed with which the kerb can be hit before the tire is punctured.