LOW-NOISE TIRE

Abstract

The tire (10) for a passenger vehicle has an axially central portion and axially lateral portions. The axially central portion and each axially lateral portion satisfies just one of conditions I, II, III: I—the portion comprises no transverse cut (90, 90′), II—the portion comprises N transverse cuts (90, 90′) arranged in such a way that π×OD/N≥40 mm, III—the portion comprises N transverse cuts (90, 90′) arranged in such a way that π×OD/N≤24 mm, condition I or II being satisfied by the axially central portion or by an axially lateral portion, and condition III being satisfied by the axially central portion or by an axially lateral portion.

Claims

1.-15. (canceled)

16. A tire (10) for a passenger vehicle having an outside diameter OD and comprising a tread (14) intended to come into contact with a ground, when the tire (10) is running, via a tread surface (38) axially delimited by first and second axial edges (41, 42) of the tread surface (38), the tread (14) comprising: an axially central portion (P0) comprising main circumferential grooves (52, 54, 56, 58) having a depth (Hr) greater than or equal to 50% of a tread pattern height (Hs) comprising at least first and second main circumferential grooves (52, 54) which are arranged axially one on each side of a median plane (M) of the tire (10), the first and second main circumferential grooves (52, 54) being the main circumferential grooves axially furthest toward the outside of the tread (14), the axially central portion (P0) extending axially from an axially outside edge (521) of the first main circumferential groove (52) as far as an axially outside edge (541) of the second main circumferential groove (54), the axially central portion (P0) comprising at least one central rib (62, 64, 66), the or each central rib (62, 64, 66) being axially delimited by two main circumferential grooves (52, 54, 56, 58) having a depth (Hr) greater than or equal to 50% of the tread pattern height (Hs); first and second axially lateral portions (P1, P2) arranged axially on an outside of the axially central portion (P0) axially one on each side of the axially central portion (P0) with respect to the median plane (M) of the tire (10) and arranged in such a way that: the first axially lateral portion (P1) extends axially from a first axial edge (41) of the tread surface (38) as far as the axially outside edge (521) of the first main circumferential groove (52), the second axially lateral portion (P2) extends axially from a second axial edge (42) of the tread surface (38) as far as the axially outside edge (541) of the second main circumferential groove (54), the or each central rib (62, 64, 66) and each first and second axially lateral portion (P1, P2) comprises at least one axial portion (P62, P64, P66, P11, P21, P641, P642, P643, P644, P622, P662) that satisfies only one of the following conditions I, II, III, an axial width of a whole of the axial portion or portions of the or each central rib (62, 64, 66) and of each first and second axially lateral portion (P1, P2) each satisfying only one of conditions I, II, III being greater than or equal to 70% of an axial width (Ln2, Ln4, Ln6, L1, L2) of the or each central rib (62, 64, 66) and of each first and second axially lateral portion (P1, P2): (I) the axial portion (P62, P64, P66, P642, P643, P622, P662) comprises no transverse cut (90, 90′) having a depth (Ht) greater than or equal to 20% of the tread pattern height (Hs) and an axial length (La, Lb, Lc) greater than or equal to 20% of the axial width (Ln2, Ln4, Ln6, L1, L2) of the central rib (62, 64, 66) or of the axially lateral portion (P1, P2), the axial portion possibly comprising at least one circumferential cut (72, 74, 76, 82, 84) having a depth (Hc2, Hc4, Hc6, Hl2, Hl4) strictly less than 50% of the tread pattern height (Hs), (II) the axial portion (P644) comprises transverse cuts (90, 90′) having a depth (Ht) greater than or equal to 20% of the tread pattern height (Hs) and an axial length (La, Lb, Lc) greater than or equal to 20% of the axial width of the central rib (62, 64, 66) or of the axially lateral portion (P1, P2), a collection of the N transverse cuts (90, 90′) of the axial portion having a depth (Ht) greater than or equal to 20% of the tread pattern height (Hs) and an axial length (La, Lb, Lc) greater than or equal to 20% of the axial width (Ln2, Ln4, Ln6, L1, L2) of the central rib (62, 64, 66) or of the axially lateral portion (P1, P2) being arranged in such a way that π×OD/N≥40 mm, the axial portion possibly comprising at least one circumferential cut (72, 74, 76, 82, 84) having a depth (Hc2, Hc4, Hc6, Hl2, Hl4) strictly less than 50% of the tread pattern height (Hs), (III) the axial portion (P11, P21, P621, P641, P661, P643) comprises transverse cuts (90, 90′) having a depth (Ht) greater than or equal to 20% of the tread pattern height (Hs) and an axial length (La, Lb, Lc) greater than or equal to 20% of the axial width (Ln2, Ln4, Ln6, L1, L2) of the central rib (62, 64, 66) or of the axially lateral portion (P1, P2), a whole of the N transverse cuts (90, 90′) of the central rib (62, 64, 66) or of the axial portion having a depth (Ht) greater than or equal to 20% of the tread pattern height (Hs) and an axial length (La, Lb, Lc) greater than or equal to 20% of the axial width (Ln2, Ln4, Ln6, L1, L2) of the central rib (62, 64, 66) or of the axially lateral portion (P1, P2) being arranged in such a way that π×OD/N≤24 mm, the axial portion possibly comprising at least one circumferential cut (72, 74, 76, 82, 84) having a depth (Hc2, Hc4, Hc6, Hl2, Hl4) strictly less than 50% of the tread pattern height (Hs), condition I or II being satisfied at least by one of the axial portions of the or each of the central ribs (62, 64, 66) or by one of the axial portions of the first axially lateral portion (P1) or by one of the axial portions of the second axially lateral portion (P2), and condition III being satisfied at least by one of the axial portions of the or each of the central ribs (62, 64, 66) or by one of the axial portions of the first axially lateral portion (P1) or by one of the axial portions of the second axially lateral portion (P2).

17. The tire (10) according to claim 16, wherein at least one of the axial portions of the or each central rib (62, 64, 66) satisfies condition I or II, and at least one of the axial portions of each first and second axially lateral portion (P0, P1) satisfies condition III.

18. The tire (10) according to claim 16, wherein the whole of the N transverse cuts (90, 90′) of the or each central rib (62, 64, 66) or of the or each axially lateral portion (P0, P1) having a depth greater than or equal to 20% of the tread pattern height (Hs) and an axial length (La, Lb, Lc) greater than or equal to 20% of the axial width (L1, L2, Ln1, Ln4, Ln6) of the or of each central rib (62, 64, 66) or of the or each axially lateral portion (P1, P2), and satisfying condition III is arranged in such a way that π×OD/N≥10 mm.

19. The tire (10) according to claim 16, wherein the axial width of the whole of the axial portion or portions of the or each central rib (62, 64, 66) and of each first and second axially lateral portion (P1, P2) each satisfying only one of conditions I, II, III is greater than or equal to 80% of the axial width (Ln2, Ln4, Ln6, L1, L2) of the or each central rib (62, 64, 66) and of each first and second axially lateral portion (P1, P2).

20. The tire (10) according to claim 16, wherein, with the or each central rib (62, 64, 66) or the first axially lateral portion (P1) or the second axially lateral portion (P2) comprising several axial portions each satisfying only one of conditions I, II, III, the whole of the axial portions of the or each central rib (62, 64, 66) or of the first axially lateral portion (P1) or of the second axially lateral portion (P2) satisfies only one of conditions I, II, III.

21. The tire (10) according to claim 16, wherein the or each central rib (62, 64, 66) and each first and second axially lateral portion (P1, P2) comprises an axial portion satisfying only one of conditions I, II, III and having an axial width greater than or equal to 70% of the axial width of the or each central rib (62, 64, 66) and of each first and second axially lateral portion (P1, P2).

22. The tire (10) according to claim 16, wherein a ratio of the axial width (L0) of the central portion (P0) to the axial width (L1, L2) of each first and second axially lateral portion (P1, P2) is greater than or equal to 3.0.

23. The tire (10) according to claim 16, wherein, with each first and second axially lateral portion (P1, P2) comprising transverse cuts (90, 90′) extending axially from an axially outside end (E1) as far as an axially inside end (E2), at least 50% of each of the transverse cuts (90, 90′) of each first and second axially lateral portion (P1, P2) is at least partially blocked off by a connecting bridge (100) connecting a leading face (Ft1) and trailing face (Ft2) forming the axially inside end (E2) of the transverse cut (90, 90′).

24. The tire (10) according to claim 16, wherein a surface-area void ratio of each first and second axially lateral portion (P1, P2) ranges from 20% to 30%.

25. The tire (10) according to claim 16, wherein a volume void ratio of each first and second axially lateral portion (P1, P2) ranges from 5% to 10%.

26. The tire (10) according to claim 16, wherein a surface-area void ratio of the or each central rib (62, 64, 66) ranges from 5% to 10%.

27. The tire (10) according to claim 16, wherein a volume void ratio of the or each central rib (62, 64, 66) ranges from 0.5% to 5%.

28. The tire (10) according to claim 16, wherein the axially central portion (P0) comprises at least a third main circumferential groove (56) and at least first and second central ribs (62, 64, 66) arranged in such a way that: the first central rib (62) is comprised axially between the first main circumferential groove (52) and the third main circumferential groove (56); and the second central rib (64) is comprised axially between the second main circumferential groove (54) and the third main circumferential groove (56).

29. The tire (10) according to claim 16, wherein the axially central portion (P0) comprises third and fourth main circumferential grooves (56, 58) and at least first, second and third central ribs (62, 64, 66) arranged in such a way that: the first central rib (62) is comprised axially between the first main circumferential groove (52) and the third main circumferential groove (56); the second central rib (64) is comprised axially between the third main circumferential groove (56) and the fourth main circumferential groove (58); and the third central rib (66) is comprised axially between the fourth main circumferential groove (58) and the second main circumferential groove (54).

30. The tire (10) according to claim 16, wherein at least one of the or each central rib (62, 64, 66) comprises at least one additional circumferential cut (72, 74, 76), the or each additional circumferential cut (72, 74, 76): being arranged axially between the two circumferential grooves (52, 54, 56, 58) between which the or each central rib (62, 64, 66) is comprised; and having a depth (Hc) strictly less than 50% of the tread pattern height (Hs).

Description

[0145] The invention will be understood better on reading the following description, which is given purely by way of non-limiting example and with reference to the drawings, in which:

[0146] FIG. 1 is a view, in a meridian plane of section parallel to the axis of rotation of the tyre, of a tyre according to a first embodiment of the invention,

[0147] FIG. 2 is a cutaway view of the tyre of FIG. 1, illustrating the arrangement of the filamentary reinforcing elements in and under the crown,

[0148] FIG. 3 is a perspective view of the tread of the tyre of FIG. 1,

[0149] FIG. 4 is a view, in a meridian plane of section parallel to the axis of rotation of the tyre, of the tread of FIG. 3,

[0150] FIG. 5 is a detail view of the region V of FIG. 4,

[0151] FIG. 6 is a detail view of the region VI of FIG. 3,

[0152] FIG. 7 is a detail view of the region VII of FIG. 6,

[0153] FIG. 8 is a detail view of the region VIII of FIG. 6,

[0154] FIG. 9 is a schematic view of the tyre of FIG. 1, and

[0155] FIGS. 10 to 13 are views similar to that of FIG. 9 of tyres respectively according to second, third, fourth and fifth embodiments of the invention.

[0156] A frame of reference X, Y, Z corresponding to the usual axial (Y), radial (Z) and circumferential (X) directions, respectively, of a tyre is shown in the figures relating to the tyre.

[0157] In the description that follows, the measurements taken are, with the exception of the measurements of the volume void ratio and of the surface-area void ratio, taken on an unladen and non-inflated tyre.

[0158] FIG. 1 shows a tyre according to the invention and denoted by the general reference 10. The tyre 10 has a substantially toric shape about an axis of revolution substantially parallel to the axial direction Y. The tyre 10 is intended for a passenger vehicle and has the size 245/45 R18. In the various figures, the tyre 10 is depicted as new, which is to say when it has not yet been run. The outside diameter OD of the tyre 10 is equal to 678 mm.

[0159] The tyre 10 comprises a crown 12 comprising a tread 14 intended to come into contact with the ground when it is running and a crown reinforcement 16 extending in the crown 12 in the circumferential direction X. The tyre 10 also comprises an airtight layer 18 that is airtight with respect to an inflation gas intended to delimit an internal cavity closed with a mounting support for the tyre 10 once the tyre 10 has been mounted on the mounting support, for example a rim.

[0160] The crown reinforcement 16 comprises a working reinforcement 20 and a hoop reinforcement 22. The working reinforcement 16 comprises at least one working layer and in this case comprises two working layers 24, 26. In this particular instance, the working reinforcement 16 is made up of the two working layers 24, 26. The radially inner working reinforcement 24 is arranged radially on the inside of the radially outer working layer 26.

[0161] The hoop reinforcement 22 comprises at least one hooping layer and in this case comprises one hooping layer 28. The hoop reinforcement 22 is in this case made up of the hooping layer 28.

[0162] The crown reinforcement 16 is surmounted radially by the tread 14. In this case, the hoop reinforcement 22, in this case the hooping layer 28, is arranged radially on the outside of the working reinforcement 20 and is therefore interposed radially between the working reinforcement 20 and the tread 14. Preferably, it may be conceivable for the hoop reinforcement 22 to have an axial width at least as large as the axial width of the working reinforcement 20 and, in this particular instance, in the embodiment illustrated in FIG. 1, the hoop reinforcement 22 has an axial width greater than the axial width of the working reinforcement 20.

[0163] The tyre 10 comprises two sidewalls 30 extending the crown 12 radially inwards. The tyre 10 also has two beads 32 radially on the inside of the sidewalls 30. Each sidewall 30 connects each bead 32 to the crown 12.

[0164] The tyre 10 comprises a carcass reinforcement 34, anchored in each bead 32 and, in this instance, wrapped around a bead wire 33. The carcass reinforcement 34 extends in each sidewall 30 and radially on the inside of the crown 12. The crown reinforcement 16 is arranged radially between the tread 14 and the carcass reinforcement 34. The carcass reinforcement 34 comprises at least one carcass layer and in this case comprises a single carcass layer 36. In this particular instance, the carcass reinforcement 34 is made up of the single carcass layer 36.

[0165] Each working layer 24, 26, hooping layer 28 and carcass layer 36 comprises an elastomer matrix in which one or more filamentary reinforcing elements of the corresponding layer are embedded. These layers will now be described with reference to FIG. 2.

[0166] The hoop reinforcement 22, in this case the hooping layer 28, is delimited axially by two axial edges 28A, 28B of the hoop reinforcement 22. The hoop reinforcement 22 comprises one or more hooping filamentary reinforcing elements 280 wound circumferentially in a helix so as to extend axially from the axial edge 28A to the other axial edge 28B of the hooping layer 28 in a main direction D0 of each hooping filamentary reinforcing element 280. The main direction D0 forms an angle AF, in terms of absolute value, less than or equal to 10°, preferably less than or equal to 7° and more preferably less than or equal to 5° with the circumferential direction X of the tyre 10. In this case, AF=−5°. The hooping layer 28 comprises a density of 98 hooping filamentary reinforcing elements per decimetre, this density being measured perpendicular to the direction D0.

[0167] The radially inner working layer 24 is delimited axially by two axial edges 24A, 24B. The radially inner working layer 24 comprises working filamentary reinforcing elements 240 extending axially from the axial edge 24A to the other axial edge 24B in a manner substantially parallel to one another along a main direction D1. Similarly, the radially outer working layer 26 is delimited axially by two axial edges 26A, 26B. The radially outer working layer 26 comprises working filamentary reinforcing elements 260 extending axially from the axial edge 26A to the other axial edge 26B in a manner substantially parallel to one another along a main direction D2. The main direction D1 along which each working filamentary reinforcing element 240 of the radially inner working layer 24 extends and the main direction D2 along which each working filamentary reinforcing element 260 of the other of the radially outer working layer 26 extends form angles AT1 and AT2, respectively, of opposite orientations with the circumferential direction X of the tyre 10. Each main direction D1, D2 forms an angle AT1, AT2, respectively, in terms of absolute value, strictly greater than 10°, preferably ranging from 15° to 50° and more preferably ranging from 15° to 30°, with the circumferential direction X of the tyre 10. In this case, AT1=−26° and AT2=+26°.

[0168] The carcass layer 36 is delimited axially by two axial edges 36A, 36B. The carcass layer 36 comprises carcass filamentary reinforcing elements 360 extending axially from the axial edge 36A to the other axial edge 36B of the carcass layer 36 along a main direction D3 forming an angle AC, in terms of absolute value, greater than or equal to 60°, preferably ranging from 80° to 90° and in this case AC=+90°, with the circumferential direction X of the tyre 10.

[0169] Each hooping filamentary reinforcing element 280 conventionally comprises two multifilament strands, each multifilament strand being made up of a spun yarn of aliphatic polyamide, in this instance nylon, monofilaments, with a thread count equal to 140 tex, these two multifilament strands being twisted in a helix individually at 250 turns per metre in one direction and then twisted together in a helix at 250 turns per metre in the opposite direction. These two multifilament strands are wound in a helix around one another. As an alternative, use could be made of a hooping filamentary reinforcing element 280 comprising one multifilament strand being made up of a spun yarn of aliphatic polyamide, in this case nylon, monofilaments with a thread count equal to 140 tex, and one multifilament strand being made up of a spun yarn of aromatic polyamide, in this case aramid, monofilaments with a thread count equal to 167 tex, these two multifilament strands being twisted in a helix individually at 290 turns per metre in one direction and then twisted together in a helix at 290 turns per metre in the opposite direction. These two multifilament strands are wound in a helix around one another. This variant will give AT1=−29° and AT2=+29°.

[0170] Each working filamentary reinforcing element 180 is an assembly of two steel monofilaments wound in a helix at a pitch of 14 mm, each steel monofilament having a diameter equal to 0.30 mm. As an alternative, use could also be made of an assembly of six steel monofilaments having a diameter equal to 0.23 mm and comprising an internal layer of two monofilaments wound together in a helix at a pitch of 12.5 mm in a first direction, for example the Z direction, and an external layer of four monofilaments wound together in a helix around the internal layer at a pitch of 12.5 mm in a second direction the opposite of the first direction, for example the S direction. In another variant, each working filamentary reinforcing element 180 is made up of a steel monofilament having a diameter equal to 0.30 mm. More generally, the steel monofilaments have diameters ranging from 0.25 mm to 0.32 mm.

[0171] Each carcass filamentary reinforcing element 340 conventionally comprises two multifilament strands, each multifilament strand made up of a spun yarn of polyesters, in this case of PET, monofilaments these two multifilament strands being twisted in a helix individually at 240 turns per metre in one direction and then twisted together in a helix at 240 turns per metre in the opposite direction. Each of these multifilament strands has a thread count equal to 220 tex. In other variants, use could be made of thread counts equal to 144 tex and twists equal to 420 twists per metre or thread counts equal to 334 tex and twists equal to 270 twists per metre.

[0172] With reference to FIGS. 1, 3 and 4, the tread 14 comprises a tread surface 38 by means of which the tread 14 comes into contact with the ground. The tread surface 38 is intended to come into contact with the ground when the tyre 10 is running along the ground and is delimited axially by first and second axial edges 41, 42 passing through each point N arranged on each side of the median plane M and for which the angle between the tangent T to the tread surface 38 and a straight line R parallel to the axial direction Y passing through this point is equal to 30°.

[0173] With reference to FIGS. 1 and 3 to 5, the tread 14 comprises an axially central portion P0 and first and second axially lateral portions P1, P2 arranged axially on the outside of the axially central portion P0 axially one on each side of the axially central portion P0 with respect to the median plane M of the tyre 10.

[0174] The axially central portion P0 has an axial width L0 greater than or equal to 50%, preferably greater than or equal to 60%, and less than or equal to 80%, preferably less than or equal to 70% of the axial width L of the tread surface 38 of the tyre 10 when new.

[0175] Each first and second axially lateral portion P1, P2 has an axial width L1, L2 less than or equal to 25%, preferably less than or equal to 20% and greater than or equal to 5%, preferably greater than or equal to 10% of the axial width L of the tread surface 38 of the tyre 10 when new.

[0176] The ratio of the axial width L0 of the central portion P0 to the axial width L1, L2 of each first and second axially lateral portion P1, P2 is greater than or equal to 3.0, preferably ranges from 3.0 to 5.0 and more preferably ranges from 4.0 to 4.5.

[0177] In this case, L0=140 mm, L1=L2=33 mm and L=206 mm.

[0178] The axially central portion comprises main circumferential grooves comprising first, second, third and fourth main circumferential grooves denoted by the references 52, 54, 56, 58 respectively. First and second grooves 52, 54 are arranged axially one on each side of the median plane M of the tyre 10 and are the main circumferential grooves axially furthest towards the outside of the tread 14.

[0179] With reference to FIGS. 3 to 5, each first, second, third and fourth main circumferential groove 52, 54, 56, 58 is, at a radial dimension equal to the radial dimension of the tread surface 38, delimited axially by an axially outside edge respectively denoted by the reference 521, 541, 561, 581 and by an axially inside edge respectively denoted by the reference 522, 542, 562, 582.

[0180] With reference to FIGS. 4 and 5, each main circumferential groove 52, 54, 56, 58 is, at a radial dimension on the inside of the radial dimension of the tread surface 38, delimited axially by an axially inside lateral face Fr1 and an axially outside lateral face Fr2 axially delimiting each main circumferential groove 52, 54, 56, 58. Each main circumferential groove 52, 54, 56, 58 is delimited radially towards the inside by a bottom face Frd.

[0181] Each main circumferential groove 52, 54, 56, 58 is chamfered, which is to say that each main circumferential groove 52, 54, 56, 58 is arranged in such a way that at least one, and in this instance each, of the axially inside faces Fr1 and outside faces Fr2 is connected by a chamfer Cf to each of the axially inside edges 522, 542, 562, 582 and axially outside edges 521, 541, 561, 581 of said main circumferential groove 52, 54, 56, 58.

[0182] Each main circumferential groove 52, 54, 56, 58 has a depth respectively denoted by the reference Hr2, Hr4, Hr6, Hr8 and ranging from 4.0 mm to the tread pattern height Hs, preferably ranging from 5.0 mm to the tread pattern height Hs, and more preferably still, ranging from 5.5 mm to the tread pattern height Hs. Each depth Hr2, Hr4, Hr6, Hr8 is greater than or equal to 50% of the tread pattern height Hs. In this case, Hs=Hr6=Hr8=6.5 mm and Hr2=Hr4=6.0 mm.

[0183] Each main circumferential groove 52, 54, 56, 58 has a width respectively denoted by the reference Lr2, Lr4, Lr6, Lr8 and greater than or equal to 1.0 mm, preferably greater than or equal to 5.0 mm and more preferably greater than or equal to 8.0 mm and more preferably still, ranging from 8.0 mm to 15.0 mm. In this case Lr2=Lr4=10.0 mm and Lr6=Lr8=12.5 mm.

[0184] The axially central portion P0 extends axially from the axially outside edge 521 of the first main circumferential groove 52 as far as the axially outside edge 541 of the second main circumferential groove 54.

[0185] The axially central portion P0 comprises first, second and third central ribs respectively denoted by the references 62, 64, 66. Each central rib 62, 64, 66 is delimited axially by two main circumferential grooves, in this case by two of the first, second, third and fourth main circumferential grooves 52, 54, 56, 58.

[0186] The first central rib 62 is arranged in such a way that it is comprised axially between the first main circumferential groove 52 and the third main circumferential groove 56. In this case, the first central rib 62 extends axially from the axially inside edge 522 of the first main circumferential groove 52 to an axially outside edge 561 of the third main circumferential groove 56.

[0187] The second central rib 64 is arranged in such a way that it is comprised axially between the third main circumferential groove 56 and the fourth main circumferential groove 58. In this case, the second central rib 64 extends axially from an axially inside edge 562 of the third main circumferential groove 56 to an axially inside edge 582 of the fourth main circumferential groove 58.

[0188] The third central rib 66 is arranged in such a way that it is comprised axially between the fourth main circumferential groove 58 and the second main circumferential groove 54. In this case, the third central rib 66 extends axially from an axially outside edge 581 of the fourth circumferential groove to an axially inside edge 542 of the second main circumferential groove 54.

[0189] Each central rib 62, 64, 66 has an axial width respectively denoted by the reference Ln2, Ln4, Ln6 that is less than or equal to 30%, preferably less than or equal to 25% and greater than or equal to 10%, preferably greater than or equal to 15% of the axial width LO of the axially central portion P1. Each axial width Ln2, Ln4, Ln6 ranges from 20 mm to 40 mm, preferably from 25 mm to 35 mm. In this case, Ln2=Ln4=Ln6=29.5 mm.

[0190] The axially central portion PO comprises at least one additional circumferential cut formed in one of the central ribs 62, 64, 66. In this case, each central rib 62, 64, 66 respectively comprises an additional circumferential cut 72, 74, 76. Each additional circumferential cut 72, 74, 76 is arranged axially respectively between the two circumferential grooves 52 and 56, 56 and 58, 58 and 54 between which each central rib 62, 64, 66 is comprised.

[0191] Each additional circumferential cut 72, 74, 76 has a depth strictly less than 50% of the tread pattern height Hs, preferably less than or equal to 30% of the tread pattern height Hs and more preferably ranging from 10% to 30% of the tread pattern height Hs. Each additional circumferential cut 72, 74, 76 respectively has an axial width Lc2, Lc4, Lc6 ranging from 4% to 15%, preferably from 4% to 10% respectively of each axial width Ln2, Ln4, Ln6. Each axial width Lc2, Lc4, Lc6 ranges from 1.0 mm to 4.0 mm and in this case Lc2=Lc4=Lc6=2.0 mm. Each additional circumferential cut 72, 74, 76 respectively has a depth Hc2, Hc4, Hc6 less than or equal to 3.0 mm, preferably ranging from 1.0 mm to 3.0 mm and in this case Hc2=Hc4=Hc6=1.0 mm.

[0192] With reference to FIG. 9, each central rib 62, 64, 66 comprises an axial portion respectively P62, P64, P66 and in this case consists of each axial portion P62, P64, P66. Each axial portion P62, P64, P66 has an axial width equal to each axial width Ln2, Ln4 and Ln6. Each axial portion P62, P64, P66 comprises no transverse cut having a depth greater than or equal to 20% of the tread pattern height Hs and an axial length greater than or equal to 20% of the axial width Ln2, Ln4 and Ln6 of each central rib 62, 64, 66, such that each of these axial portions P62, P64, P66 satisfies just one of conditions I, II, III, in this case condition I. The axial width of the whole of the axial portions P62, P64, P66, in this case the axial width of each axial portion P62, P64, P66 of each central rib 62, 64, 66 is greater than or equal to 70%, preferably 80%, and more preferably 90%, of the axial width of each central rib 62, 64, 66 and in this case equal to 100% of each axial width Ln2, Ln4, Ln6.

[0193] With reference to FIG. 3, the first axially lateral portion P1 is arranged in such a way that it extends axially from the first axial edge 41 of the tread surface 38 as far as the axially outside edge 521 of the first main circumferential groove 52.

[0194] The second axially lateral portion P2 is arranged in such a way that it extends axially from the second axial edge 42 of the tread surface 38 as far as the axially outside edge 541 of the second main circumferential groove 54.

[0195] With reference to FIGS. 4 to 6, each first and second axially lateral portion P1, P2 comprises an additional circumferential cut 82, 84 formed in each first and second axially lateral portion P1, P2. The additional circumferential cut 82 is arranged axially between the first circumferential groove 52 and the first axial edge 41 of the tread surface 38. The additional circumferential cut 84 is arranged axially between the second circumferential groove 54 and the second axial edge 42 of the tread surface 38.

[0196] Each additional circumferential cut 82, 84 has a depth strictly less than 50% of the tread pattern height Hs, preferably less than or equal to 30% of the tread pattern height Hs and more preferably ranging from 10% to 30% of the tread pattern height Hs. Each additional circumferential cut 82, 84 respectively has an axial width Ll2, Ll4 ranging from 3% to 15%, preferably from 3% to 10% respectively of each axial width L1, L2. Each axial width Ll2, Ll4 ranges from 1.0 mm to 4.0 mm and in this case Ll2=Ll4=2.0 mm. Each additional circumferential cut 82, 84 respectively has a depth Hl2, Hl4 less than or equal to 3.0 mm, preferably ranging from 1.0 mm to 3.0 mm and in this case Hl2=Hl4=1.0 mm.

[0197] With reference to FIG. 6, each axially lateral portion P1, P2 respectively comprises transverse cuts 90, 90′ having a depth greater than or equal to 20% of the tread pattern height Hs. In this particular instance, all the transverse cuts 90, 90′ of each axially lateral portion P1, P2 have a depth Ht greater than or equal to 20%, preferably 30%, and more preferably, 40%, of the tread pattern height Hs. Each transverse cut 90, 90′ has a depth Ht ranging from 2.0 mm to the tread pattern height Hs, preferably ranging from 4.0 mm to the tread pattern height Hs, and more preferably still, ranging from 5.0 mm to the tread pattern height Hs, and here Ht=6.0 mm.

[0198] With reference to FIGS. 7 and 8, each transverse cut 90, 90′ is, at a radial dimension equal to the radial dimension of the tread surface 38, delimited circumferentially by a leading edge 901 and by a trailing edge 902. Each transverse cut 90, 90′ is, at a dimension radially on the inside of the radial dimension of the tread surface 38, delimited circumferentially by a leading face Ft1 and a trailing face Ft2. Each transverse cut 90, 90′ is delimited radially towards the inside by a bottom face Ftd. Each transverse cut 90, 90′ is chamfered, which is to say that each transverse cut 90, 90′ is arranged in such a way that each of the leading faces Ft1 and trailing faces Ft2 is connected by a chamfer Cf respectively to each of the leading edges 901 and trailing edges 902 of each transverse cut 90, 90′. Each transverse cut 90, 90′ extends axially from an axially outside end E1 as far as an axially inside end E2 defining a total curvilinear length Tl of each transverse cut 90, 90′ as well as an axial length La, La′ of each transverse cut 90, 90′.

[0199] Amongst the transverse cuts 90, 90′ having a depth greater than or equal to 20% of the tread pattern height Hs, a distinction is made between four families of transverse cuts 90 comprising transverse cuts 92, 94, 96, 98 formed in the first axially lateral portion P1, and three families of transverse cuts 90′ comprising transverse cuts 92′, 94′, 96′ formed in the second axially lateral portion P2. These cuts have different widths and are arranged circumferentially irregularly so as to avoid whining noises and also so as to maintain the uniformity of the tyre. Each width of each transverse cut 90, 90′ is less than or equal to 2.0 mm, and preferably ranges from 0.5 mm to 2.0 mm. Thus, each transverse cut 92, 94, 96, 98, 92′, 94′, 96′ has a width Lt2, Lt4, Lt6, Lt8, Lt2′, Lt4′, Lt6′ such that Lt2=Lt2′=1.2 mm, Lt4=Lt4′=Lt8=1.5 mm and Lt6=Lt6′=0.8 mm.

[0200] With reference to FIGS. 3, 7 and 8, the first axially lateral portion P1 comprises transverse cuts 92, 94, 96, 98 each comprising a main portion respectively denoted by the reference 921, 941, 961, 981 and a complementary portion respectively denoted by the reference 922, 942, 962, 982, the main and complementary portions being separated from one another by a discontinuity 923, 943, 963, 983 in the curvature of each leading face Ft1 and trailing face Ft2. Each complementary portion 922, 942, 962, 982 is arranged axially on the outside of each main portion 921, 941, 961, 981 and has a width Ls2, Ls4, Ls6, Ls8 greater than the width Lp2, Lp4, Lp6, Lp8 of each main portion 921, 941, 961, 981 which here is equal to each width Lt2, Lt4, Lt6, Lt8. Each main portion 921, 941, 961, 981 extends over a main curvilinear length Tp strictly greater than 50% of the total curvilinear length Tl of each transverse cut 92, 94, 96, 98. Each complementary portion 922, 942, 962, 982 extends over a complementary curvilinear length Tc strictly less than 50% of the total curvilinear length Tl of each transverse cut 92, 94, 96, 98.

[0201] Each transverse cut 92, 94, 96, 98 has an axial length La greater than or equal to 20%, preferably 30%, more preferably 50%, and more preferably still, 75%, of the axial width L1 of the first axially lateral portion P1. In this case, La=42 mm.

[0202] The transverse cuts 90, which here consist of the transverse cuts 92, 94, 96, 98, having a depth greater than or equal to 20% of the tread pattern height Hs and an axial length La greater than or equal to 20% of the axial width of the first axially lateral portion P1, are N=125 in number over the whole of the circumference of the tyre 10. In a variant of the first embodiment, N=98.

[0203] As is visible in FIG. 3, the second axially lateral portion P2 comprises transverse cuts 92′, 94′, 96′, each consisting of a main portion of which the curvilinear length is equal to the curvilinear length of the cut.

[0204] Each transverse cut 92′, 94′, 96′ has an axial length La′ greater than or equal to 20%, preferably 30%, more preferably 50%, and more preferably still, 75%, of the axial width L2 of the second axially lateral portion P2. In this case, La2′=42 mm.

[0205] The transverse cuts 90′, which here consist of the transverse cuts 92′, 94′, 96′, having a depth greater than or equal to 20% of the tread pattern height Hs and an axial length La′ greater than or equal to 20% of the axial width of the second axially lateral portion P2, are N′=125 in number over the whole of the circumference of the tyre 10. In the variant described above, N′=98.

[0206] Each transverse cut 90, 90′ of each first and second axially lateral portion P1, P2 is at least partially closed off by a connecting bridge 100 connecting the leading face Ft1 and trailing face Ft2, this connecting bridge 100 forming the axially inside end E2 of each transverse cut 90, 90′. Each connecting bridge 100 is arranged here in such a way as to completely block off communication between each transverse cut 90, 90′ and each first and second main circumferential groove 52, 54 when the transverse cut enters the contact patch in which the tyre is in contact with the ground on which it is running.

[0207] Thus, with reference to FIG. 9, each first and second axially lateral portion P1, P2 comprises first axial portions respectively P11, P21 comprising the N, N′ transverse cuts 90, 90′ and second axial portions respectively P12, P22 consisting of the connecting bridges 100. Each second axial portion P12, P22 is arranged axially on the inside of each first axial portion P11, P21.

[0208] Each axial portion P11, P21 has an axial width greater than or equal to 70%, preferably 80%, more preferably 90%, and here equal to 91%, of the axial width of each axially lateral portion P1, P2. Here, each first axial portion P11, P21 has an axial width equal to 30 mm. To complement that, each second axial portion P12, P22 has an axial width equal to 3 mm. Each axial portion P11, P21 satisfies only condition III because π×OD/N≤24 mm. Furthermore, π×OD/N≥10 mm. In this particular instance π×OD/N=17 mm. In the variant described hereinabove with N=98, π×OD/N≤24 mm and π×OD/N≥10 mm and more specifically π×OD/N=22 mm.

[0209] It will be noted that, in the first embodiment, in order to limit the transition zones, each central rib 62, 64, 66 and each first and second axially lateral portion P1, P2 comprises an axial portion respectively P62, P64, P66, P11, P21, satisfying just one of conditions I, II, III and having an axial width greater than or equal to 70%, preferably 80%, and more preferably 90%, of the axial width of each central rib 62, 64, 66 and of each first and second axially lateral portion P1, P2.

[0210] The surface-area void ratio of the tread 14 ranges from 27% to 45%, preferably from 30% to 40% and is here equal to 36%. The volume void ratio of the tread 14 ranges from 17% to 35%, preferably from 20% to 30% and is here equal to 24%.

[0211] The surface-area void ratio of each first and second axially lateral portion P1, P2 ranges from 20% to 30% and is here equal to 25%. The volume void ratio of each first and second axially lateral portion P1, P2 ranges from 5% to 10% and is here equal to 8%.

[0212] The surface-area void ratio of the axially central portion P0 ranges from 35% to 45% and is here equal to 41%. The volume void ratio of the axially central portion P0 ranges from 25% to 35% and is here equal to 30%.

[0213] The surface-area void ratio of each central rib 62, 64, 66 ranges from 5% to 10% and is here equal to 7%. The volume void ratio of each central rib 62, 64, 66 ranges from 0.5% to 5%, preferably from 0.5% to 2% and is here equal to 1%.

[0214] The ratio of the surface-area void ratio of each central rib 62, 64, 66 to the surface-area void ratio of each first and second axially lateral portion P1, P2 is less than or equal to 0.35, preferably less than or equal to 0.30 and more preferably ranges from 0.10 to 0.30, and is here equal to 0.28. The ratio of the volume void ratio of each central rib 62, 64, 66 to the void ratio of each first and second axially lateral portion P1, P2 is less than or equal to 0.20, preferably less than or equal to 0.15 and more preferably ranges from 0.10 to 0.15, and is here equal to 0.13.

[0215] A tyre according to a second embodiment of the invention will now be described with reference to FIG. 10. Elements similar to those of the first embodiment are denoted by identical references.

[0216] Unlike in the first embodiment, the central rib 64 does not have a circumferential cut having a depth strictly less than 50% of the tread pattern height. In this case, the central rib does not comprise the additional circumferential cut 74.

[0217] Furthermore, the central rib 64 comprises several axial portions each satisfying just one of conditions I, II, III. In this particular instance, the central rib 64 comprises, on the one hand, a first axial portion P641 of axial width equal to 50% of the axial width Ln4 of the central rib 64 and satisfying only condition III and, on the other hand, a second axial portion P642 of an axial width equal to 50% of the axial width Ln4 of the central rib 64 and satisfying only condition I. Thus, the axial width of the whole of the first and second axial portions P641 and P642 of the central rib 64 each satisfying just one of conditions I, II, III, is greater than or equal to 70%, preferably 80%, and more preferably 90%, of the axial width of the central rib 64 and here equal to 100% of the axial width Ln4.

[0218] More specifically, the axial portion P641 comprises transverse cuts 91 having a depth Ht greater than or equal to 20% of the tread pattern height Hs and an axial length Lb greater than or equal to 20%, here equal to 50%, of the axial width of the central rib 64. The cuts 91 are N=125 in number over the whole of the circumference of the tyre. The whole of the N transverse cuts 91 is arranged in such a way that π×OD/N≤24 mm so as to satisfy only condition III. In a variant of this second embodiment, N=98 and likewise π×OD/N≤24 mm.

[0219] It will be noted that, unlike in the first embodiment, the central rib 64 comprises a transition zone between the first and second axial portions P641 and P642 and first and second axial portions P641 and P642 of which the axial widths are such that the central rib 64 does not comprise any axial portion satisfying just one of conditions I, II, III and having an axial width greater than or equal to 70% of the axial width of the central rib 64.

[0220] A tyre according to a third embodiment of the invention will now be described with reference to FIG. 11. Elements similar to the previous embodiments are denoted by identical references.

[0221] Unlike in the first embodiment, each central rib 62, 64, 66 does not have any circumferential cut having a depth strictly less than 50% of the tread pattern height. In this case, each central rib 62, 64, 66 does not comprise each additional circumferential cut 72, 74, 76.

[0222] Furthermore, just as in the second embodiment, each central rib 62, 64, 66 comprises several axial portions each satisfying just one of conditions I, II, III. In this particular instance, each central rib 62, 64, 66 comprises, on the one hand, a first axial portion P621, P641, P661 of axial width equal to 50% of each axial width Ln2, Ln4, Ln6 of each central rib 62, 64, 66 and satisfying only condition III and, on the other hand, a second axial portion P622, P642, P662 of an axial width equal to 50% of each axial width Ln2, Ln4, Ln6 of each central rib 62, 64, 66 and satisfying only condition I. Thus, the axial width of the whole of the first and second axial portions P621 and P622, P641 and P642, P661 and P662 of each central rib 62, 64, 66 each satisfying just one of conditions I, II, III, is greater than or equal to 70%, preferably 80%, and more preferably 90%, of the axial width of the central rib 64 and here equal to 100% of each axial width Ln2, Ln4, Ln6.

[0223] A tyre according to a fourth embodiment of the invention will now be described with reference to FIG. 12. Elements similar to the previous embodiments are denoted by identical references.

[0224] Unlike in the first embodiment, the central rib 64 does not have a circumferential cut having a depth strictly less than 50% of the tread pattern height. In this case, the central rib does not comprise the additional circumferential cut 74.

[0225] Furthermore, the central rib 64 comprises several axial portions P641, P643 each satisfying just one of conditions I, II, III and a central portion P642 not satisfying any of conditions I, II, III.

[0226] In this particular instance, on the one hand, the axial portion P641 has an axial width equal to 50% of the axial width Ln4 of the central rib 64 and satisfies only condition III and, on the other hand, the axial portion P643 has an axial width equal to 25% of the axial width Ln4 of the central rib 64 and satisfies only condition III, such that the axial width of the whole of the axial portions P641 and P643 each satisfying just one of conditions I, II, III, in this case condition III, is greater than or equal to 70%, of the axial width of the central rib 64 and here equal to 75% of the axial width Ln4.

[0227] Furthermore, unlike in the second and third embodiments, even though the central rib 64 comprises several axial portions P641, P643 each satisfying just one of conditions I, II, III, the whole of the axial portions P641, P643 of the fourth embodiment satisfies just one of conditions I, II, III, in this case only condition III.

[0228] It will also be noted that, unlike in the first embodiment, the central rib 64 comprises two transition zones between the various axial portions P641, P642 and P643 and axial portions P641, P642 and P643 of which the axial widths are such that the central rib 64 does not comprise any axial portion satisfying just one of conditions I, II, III and having an axial width greater than or equal to 70% of the axial width of the central rib 64.

[0229] More specifically, each axial portion P641, P643 respectively comprises transverse cuts 91, 93 having a depth Ht greater than or equal to 20% of the tread pattern height Hs and an axial length Lb, Lc greater than or equal to 20%, here respectively equal to 50% and 25%, of the axial width of the central rib 64. The cuts 91, 93 are respectively N1=N3=125 in number over the whole of the circumference of the tyre. The whole of the N1 transverse cuts 91 and the whole of the N3 transverse cuts 93 are arranged in such a way that π×OD/N1≤24 mm and π×OD/N3≤24 mm so as to satisfy only condition III. A variant of this fourth embodiment will give N1=N3=98 so this likewise will give π×OD/N1≤24 mm and π×OD/N3≤24 mm so as to satisfy only condition III.

[0230] The axial portion P642 does not satisfy any one of conditions I, II, III. Specifically, although the axial portion P642 comprises N2 transverse cuts 95 over the whole of the circumference of the tyre in FIG. 12, these N2=65 transverse cuts 95 having a depth Ht greater than or equal to 20% of the tread pattern height Hs and an axial length greater than or equal to 20%, here equal to 25%, of the axial width Ln4 of the central rib 64, the whole of the N transverse cuts 95 is arranged in such a way that 24 mm<π×OD/N2<40 mm.

[0231] A tyre according to a fifth embodiment of the invention will now be described with reference to FIG. 13. Elements similar to the previous embodiments are denoted by identical references.

[0232] Unlike in the fourth embodiment, the central rib 64 comprises several axial portions P641, P643, P644 each satisfying just one of conditions I, II, III as well as a central portion P642 not satisfying any of conditions I, II, III.

[0233] In this particular instance, on the one hand, the axial portion P641 has an axial width equal to 25% of the axial width Ln4 of the central rib 64 and satisfies only condition III, on the other hand, the axial portion P643 has an axial width equal to 25% of the axial width Ln4 of the central rib 64 and satisfies only condition I, and finally the axial portion P644 has an axial width equal to 25% of the axial width Ln4 of the central rib 64 and satisfies only condition II such that the axial width of the whole of the axial portions P641, P643 and P644 each satisfying just one of conditions I, II, III, in this case conditions I, II and III, is greater than or equal to 70%, of the axial width of the central rib 64 and here equal to 75% of the axial width Ln4.

[0234] More specifically, the axial portion P641 comprises transverse cuts 91 having a depth Ht greater than or equal to 20% of the tread pattern height Hs and of axial length Lc greater than or equal to 20%, here equal to 25%, of the axial width of the central rib 64. The cuts 91 are N1=125 in number over the whole of the circumference of the tyre. The whole of the N1 transverse cuts 91 is arranged in such a way that π×OD/N1≤24 mm so as to satisfy only condition III. A variant of this fifth embodiment will give N1=98 so that π×OD/N1≤24 mm so as to satisfy only condition III.

[0235] Just as in the fourth embodiment, the axial portion P642 does not satisfy any of conditions I, II, III.

[0236] The axial portion P644 comprises transverse cuts 97 having a depth Ht greater than or equal to 20% of the tread pattern height Hs and an axial length Lc greater than or equal to 20%, here equal to 25%, of the axial width of the central rib 64. These cuts 97 are N4=25 in number over the whole of the circumference of the tyre. The whole of the N4 transverse cuts 97 of the axial portion P644 is arranged in such a way that π×OD/N4≥40 mm, preferably in such a way that π×OD/N4≥60 mm and more preferably still, in such a way that π×OD/N4≥80 mm.

[0237] It will be noted that, unlike in the first embodiment, the central rib 64 comprises three transition zones between the various axial portions P641, P642, P643 and P644 and axial portions P641, P642, P643 and P644 of which the axial widths are such that the central rib 64 does not comprise any axial portion satisfying just one of conditions I, II, III and having an axial width greater than or equal to 70% of the axial width of the central rib 64.

Comparative Tests

[0238] Tests were conducted on the tyre 10 according to the first embodiment of the invention, together with a control tyre W not in accordance with the invention and in which, unlike the tyre 10 according to the first embodiment, each axial portion P62, P64, P66 comprises transverse cuts having a depth greater than or equal to 20% of the tread pattern height Hs and an axial width greater than or equal to 20% of the axial width Ln2, Ln4 and Ln6 of each central rib 62, 64, 66 such that each of these axial portions P62, P64, P66 satisfies condition III.

[0239] During these tests, a vehicle was fitted with four identical tyres 10 or W inflated to 2.5 bar and subjected to a load equal to 470 daN, and the noise generated by the tyres tested in accordance with UNECE Regulation 51-03 was measured.

[0240] A first test measured the external noise generated by the tyres tested at constant speed, which is to say with zero acceleration. A second test measured the external noise generated by the tyres tested in an acceleration phase with an acceleration equal to 3 m.Math.s.sup.−2. The results are collated in Table 1 below. In this table, the noise generated by the tyres W at constant speed is denoted R and that generated in the acceleration phase is denoted R′.

TABLE-US-00001 TABLE 1 Tyre tested Constant speed Acceleration phase W R R′ 10 R-0.4 dB R′-3.5 dB

[0241] It will be noted that the tyre 10 according to the invention allows a significant reduction in the external noise generated by the tyre whether at constant speed or in an acceleration phase.

[0242] The invention is not limited to the embodiment described above.

[0243] Specifically, it is possible, without departing from the scope of the invention, to contemplate an axially central portion comprising first, second and third main circumferential grooves and first and second central ribs arranged such that: [0244] the first central rib is comprised axially between the first main circumferential groove and the third main circumferential groove, [0245] the second central rib is comprised axially between the second main circumferential groove and the third main circumferential groove.