Tyre for vehicle wheels

Abstract

Tyre for vehicle wheels, the tyre comprising, in a central annular portion (A) of its tread band (110): a central circumferential groove (115) extending on an axially opposite portion with respect to an equatorial plane (E) of the tyre; a circumferential row of first blocks (125) having a respective axial inner side (126) delimited by a central circumferential groove (115) and a respective axial outer side (127) delimited by a respective first circumferential groove (120); and a circumferential row of second blocks (155) having a respective axial inner side (156) delimited by a central circumferential groove (115) and a respective axial outer side (157) delimited by a respective second circumferential groove (160) arranged on a portion axially opposite the respective first circumferential groove (120) with respect to the central circumferential groove (115). The axial inner side (126; 126 ') of each of the first block (125) and the second block (155). 156) comprises, in the circumferential direction, respective opposite free ends (126a, 126b; 156a, 156b) and a corresponding central portion (126c; 156c) in the housing. The first blocks (125) are circumferentially offset relative to the second blocks (155) such that opposite free ends (126a, 126b) of each of the first blocks (125) are arranged at central portions (156c) of two circumferentially successive second blocks (155) and opposite free ends (156a, 156b) of each of the second blocks (155) are arranged at central portions (126c) of two circumferentially successive first blocks (125).

Description

Technical Field

[0001] The invention relates to a tyre for vehicle wheels.

[0002] The tyre of the invention is preferably a tyre intended for use on low-grip road surfaces, in particular icy and possibly snow-covered road surfaces, for example as an alternative to studded tyres when or where the use of studded tyres is not permitted.

[0003] Preferably, the tire of the invention is intended for use in high performance and ultra high performance vehicles, which are generally defined as "HP" or "UHP" tires. Such tires are especially those allowing speeds exceeding 190 km / h, up to a maximum of more than 300 km / h.

[0004] According to the ETRTO standard (European Tire and Rim Technical Organization), examples of "HP" or "UHP" tires are tires with speed codes "T", "U", "H", "V", "Z", "W", "Y". Typically, such tires have a radial section width greater than or equal to 185 mm, preferably between 195 mm and 385 mm, more preferably between 195 mm and 355 mm, and are mounted on a rim with a mounting diameter greater than or equal to 13 inches, preferably not greater than 24 inches, more preferably between 16 inches and 23 inches.

[0005] Throughout this specification and in the claims that follow, when referring to certain values ​​of certain angles, these values ​​are to be regarded as absolute values, ie both positive and negative values ​​relative to a reference plane or direction, unless otherwise specified.

[0006] In addition, when any numerical range between a minimum value and a maximum value is mentioned, the aforementioned minimum value and maximum value are deemed to be included in the aforementioned range unless explicitly stated otherwise.

[0007] Furthermore, all ranges include any combination of the recited minimum and maximum values ​​and include any intermediate ranges, even if not specifically recited.

[0008] Even if not expressly stated, any numerical value is deemed to be preceded by the term "about" to also indicate any value that differs slightly from the stated value, for example taking into account dimensional tolerances that are typical for the art in question.

[0009] Hereinafter, the following definitions apply.

[0010] The term “equatorial plane” of the tire is used to denote the central plane perpendicular to the axis of rotation of the tire.

[0011] The terms "radial" and "axial" and the expressions "radially inner / outer" and "axially inner / outer" are used with reference to a direction substantially parallel to the equatorial plane of the tire and a direction substantially perpendicular to the equatorial plane of the tire, respectively, i.e. with reference to a direction substantially perpendicular to the axis of rotation of the tire and a direction substantially parallel to the axis of rotation of the tire, respectively.

[0012] The expressions "axially outer" and "axially inner" denote respectively positions which are further away and closer to the equatorial plane. Correspondingly, the expressions "axially outermost" and "axially innermost" denote respectively positions which are farthest away and closest to the equatorial plane relative to a reference element. Thus, for example, if a first portion of the tread band is situated at a greater axial distance from the equatorial plane than a second portion of the tread band is situated at the axially outermost position relative to the second portion of the tread band. Similarly, if a first portion of the tread band is situated at a less axial distance from the equatorial plane than a second portion of the tread band is situated at the axially innermost position relative to the second portion of the tread band.

[0013] The term "parallel" is not only used to indicate a completely parallel state, but may also indicate a state slightly deviating from completely parallel, for example, the angle of deviation is not greater than 5°.

[0014] The term “perpendicular” is used to indicate not only a completely perpendicular or orthogonal state but also a state slightly deviated from the completely perpendicular or orthogonal state, for example, the angle of deviation is not greater than 5°.

[0015] The term "circumferential extension" of a tyre, a tread band or parts thereof is intended to denote the extension of the radially outermost surface of the tyre, the tread band or parts thereof, on a plane tangential to the tyre.

[0016] The term "radial section" of the tire is intended to denote a section taken on a plane normal to the equatorial plane and containing the axis of rotation of the tire.

[0017] The term "circumferential dimension" is used to refer to a dimension measured along a direction lying on or parallel to the equatorial plane.

[0018] The term "groove" is used to denote a recess formed in the tread band, the width of which is greater than or equal to 2 mm. More preferably, the depth of the groove is greater than or equal to 3 mm.

[0019] The term "circumferential groove" is used to denote a groove extending in one or more directions oriented at an angle of not more than 45° relative to the equatorial plane. In the case where the circumferential groove is formed by segments of various orientations, the term "circumferential segment" is used to denote a groove segment extending in a direction oriented at an angle of not more than 45° relative to the equatorial plane.

[0020] The terms "transverse groove" or "transverse segment" of a groove are used to denote a groove or a groove segment extending in a direction oriented at an angle of not more than 45° relative to a plane orthogonal to the equatorial plane.

[0021] The term "sipe" is used to denote a hollow formed in the tread band and having a width less than 2 mm.

[0022] The term "width" of a groove or sipe is used to denote the dimension measured at a certain point of the groove or sipe along a direction orthogonal to the direction in which the groove or sipe extends at that point. For example, the width of a circumferential groove parallel to the equatorial plane is measured along a direction orthogonal to the circumferential direction, while the width of a transverse groove parallel to the axis of rotation of the tire is measured along a direction orthogonal to the axial direction.

[0023] The term "block" is used to denote a portion of the tread band delimited by grooves other than sipes. In case a block is positioned at the axially outermost portion of the tread band, the block is delimited in axial direction partly by the axially outermost portion of the tread band and partly by the grooves.

[0024] The term "free end" of a block or of one side of a block in a predetermined direction is used to denote a point of the block or of one side of a block in this direction and which is arranged at the tread band area where two grooves delimiting the block meet.

[0025] The term "substantially concave profile" of a side of the block relative to the equatorial plane is used to denote a profile of a side having opposite free ends and a central portion in a circumferential direction, wherein at least one of the opposite free ends is close to the equatorial plane and the central portion is remote from the equatorial plane.

[0026] The equatorial plane is considered to be "completely contained" in the central circumferential groove (or the central circumferential groove is considered to "completely contain" the equatorial plane) when the equatorial plane is arranged relative to the blocks adjacent to it so that none of these blocks has a block portion extending from one side of the equatorial plane and from the other side of the equatorial plane, or in other words, when none of the above blocks traverses the equatorial plane from one side to the other.

[0027] The "depth" of a tread band or a groove or a sipe is measured at the groove or sipe in a direction substantially perpendicular to the bottom of the groove or sipe.

[0028] The term "tread pattern" is used to denote the whole of blocks and grooves provided on the tread band.

[0029] The term “void / solid ratio” is used to indicate the ratio between the total surface of the grooves (excluding sipes) of a certain annular portion, possibly the entire tread band of the tyre and the surface of said portion, possibly the entire tread band.

[0030] The term "footprint" of a tyre is used to denote the portion of the tyre which is in contact with the ground or road surface when the tyre is mounted on a wheel rim and a predetermined vertical load is applied to the tyre. If the tread band of the tyre is provided with grooves, the footprint also includes such grooves.

[0031] The term "pitch" in relation to the tread band is used to denote a portion of the tread band which is repeated a number of times substantially identically along the entire circumferential extension of the tyre. Pitches of different circumferential dimensions may be provided in the tyre.

[0032] The term "axial extension" of a zig-zag track is used to denote the width, in the axial direction, of the tread band portion comprising such a track.

[0033] The expression "mirror-image shape" in relation to two blocks is used to indicate that the two blocks have substantially the same shape but are arranged relative to each other so that a first of the two blocks can be substantially superimposed on the other block only after the first block is rotated 180° relative to its center of gravity axis. If the two blocks are offset relative to each other in the circumferential direction, the two blocks can be substantially superimposed on each other after a certain relative displacement in the circumferential direction so as to eliminate this offset. Background Art

[0034] Tires for icy and / or snow-covered roads are described, for example, in JP 2019137090A, JP 2020100191A, US 20200298627 A1, WO 201901789 A1, WO 201901790 A1, JP 2020199841A, US 5591280A, JP 2017088021A, EP 3421264 B1. Such tires have a tread band comprising a plurality of circumferential grooves and transverse grooves defining a plurality of blocks provided with sipes in the tread band. Summary of the invention

[0035] The Applicant has focused its attention on tires intended to equip high-performance and ultra-high-performance vehicles and for use on road surfaces in conditions of low grip due to the presence of ice and possible snow.

[0036] This type of tire needs to have a high ability to adhere to icy and possibly snow-covered roads in order to be able to effectively discharge the high drive torques to which they are subjected to to the ground, thereby achieving effective traction and braking.

[0037] The Applicant has observed that in order to give the aforementioned tyre the desired grip on icy / snow-covered roads, it is advisable both to provide a sufficiently large footprint of the mutual contact surface between the tread band and the road surface, so as to increase the effective transmission of the driving torque to the surface on which the ground lies during running, and to distribute the contact pressure inside the footprint as evenly as possible, so as to tend towards an optimal running condition in which the same contact pressure acts on all the areas of contact between the tread band and the road surface. For this reason, the tread band of the aforementioned tyre typically has a plurality of blocks delimited by circumferential grooves and transverse grooves.

[0038] The Applicant has considered how to enlarge the mutual contact surface between the road surface and the tread band at its central annular portion and thus tend towards a desired uniform distribution of the contact pressure within the footprint of the tyre.

[0039] The Applicant believes that, in order to achieve this objective, it is necessary to reduce the void / solid ratio at least in the central annular portion of the tread band.

[0040] With particular reference to a tyre provided with a central circumferential groove arranged at the equatorial plane and with a plurality of rows of blocks arranged on opposite portions with respect to the equatorial plane, the Applicant considers that such a reduction in the void / solid ratio can be achieved by reducing the size of the void inevitably provided between a first row of blocks arranged on a portion of the equatorial plane and a second row of blocks arranged on the opposite portion of the equatorial plane.

[0041] The applicant has realized that the size of the aforementioned gap can be reduced by providing the axial inner sides of the aforementioned first and second blocks with a basically concave profile along the circumferential direction relative to the equatorial plane, and circumferentially offsetting the aforementioned first block relative to the aforementioned second block so that the relative free ends of the axial inner sides of each of the first blocks are arranged at the central parts of the axial inner sides of two circumferentially consecutive second blocks and the relative free ends of the axial inner sides of each of the second blocks are arranged at the central parts of the axial inner sides of two circumferentially consecutive first blocks.

[0042] The Applicant has therefore found that, in the central annular portion of the tread band, at least two circumferential rows of blocks are provided, arranged on axially opposite portions with respect to the equatorial plane, and each circumferential row of blocks having:

[0043] an axially inner side having a central portion remote from the equatorial plane and opposite free ends, at least one of which is close to the equatorial plane, the axially inner side being delimited by a central circumferential groove extending over an axially opposite portion with respect to the equatorial plane,

[0044] - an axially outer side, which is delimited by a corresponding circumferential groove, and

[0045] - opposite sides in the circumferential direction delimited by respective transverse grooves extending from the portion of the tread band arranged at the central circumferential groove until close to the sidewalls,

[0046] Furthermore, the two rows of blocks are arranged offset in the circumferential direction, so that the opposite free ends of the blocks in one row are arranged at the central parts of two circumferentially consecutive blocks in the other row, and vice versa.

[0047] This makes it possible to reduce the size of the aforementioned voids close to the equatorial plane and, therefore, to increase the surface of the blocks at the central annular portion of the tread band. This provides the central annular portion with the ability to fully deform both in the axial direction and in the circumferential direction at the footprint of the tyre during running, thus maintaining a large mutual contact area between the road surface and the tread band in the central zone, in order to favour grip on icy and possibly snow-covered roads.

[0048] The invention relates to a tyre for vehicle wheels, said tyre comprising a tread band extending between opposite sidewalls.

[0049] Preferably, the tread band comprises a central annular portion and opposing shoulder annular portions.

[0050] Preferably, each shoulder annular portion is adjacent a respective one of said opposing sidewalls.

[0051] Preferably, said central annular portion comprises a central circumferential groove.

[0052] Preferably, said central circumferential groove extends on axially opposite portions with respect to the equatorial plane.

[0053] Preferably, said central annular portion comprises a circumferential row of first blocks.

[0054] Preferably, said first blocks have a respective axial inner side delimited by said central circumferential groove.

[0055] Preferably, said first blocks have respective axial outer sides delimited by respective first circumferential grooves.

[0056] Preferably, each of said first blocks is delimited in the circumferential direction by respective segments of opposing first transverse grooves.

[0057] Preferably, said first transverse groove extends from a portion of said tread band arranged at said central circumferential groove as far as a first shoulder annular portion.

[0058] Preferably, said first transverse groove extends up to the axially outer end of said first shoulder annular portion.

[0059] Preferably, said central annular portion comprises a circumferential row of second blocks.

[0060] Preferably, said second blocks have a respective axial inner side delimited by said central circumferential groove.

[0061] Preferably, said second blocks have respective axial outer sides delimited by respective second circumferential grooves which are arranged on portions axially opposite to said first circumferential grooves with respect to the central circumferential groove.

[0062] Preferably, each of said second blocks is delimited in the circumferential direction by a respective segment of an opposing second transverse groove.

[0063] Preferably, said second transverse groove extends from the portion of said tread band arranged at said central circumferential groove up to a second shoulder annular portion arranged on the side axially opposite to said first shoulder annular portion with respect to the central circumferential groove.

[0064] Preferably, said first transverse groove extends up to the axially outer end of said second shoulder annular portion.

[0065] Preferably, the axial inner side of each of the first blocks comprises corresponding opposite free ends in the circumferential direction, and at least one of the opposite free ends is close to the equatorial plane.

[0066] Preferably, the axial inner side of each of the second blocks comprises corresponding opposite free ends in the circumferential direction, and at least one of the opposite free ends is close to the equatorial plane.

[0067] Preferably, the axial inner side of each of the first blocks includes a respective central portion in the circumferential direction away from the equatorial plane.

[0068] Preferably, the axial inner side of each of the second blocks includes a respective central portion in the circumferential direction away from the equatorial plane.

[0069] Preferably, the first block is circumferentially offset relative to the second block.

[0070] Preferably, the offset is such that the opposite free end of each of the first blocks is arranged at a central portion of two circumferentially consecutive second blocks.

[0071] Preferably, the offset is such that the opposite free end of each of the second blocks is arranged at a central portion of two circumferentially consecutive first blocks.

[0072] The Applicant believes that a tread band made according to the above has a central annular portion capable of being fully deformed at the footprint during running of the tire, both in the axial direction and in the circumferential direction. This makes it possible to achieve the desired increase in the contact area with the road surface at the footprint and the desired uniform distribution of the contact pressure inside the footprint, thus providing the tire with a high ability to adhere to low-grip roads.

[0073] The present invention may have at least one of the preferred features described below.

[0074] Preferably, the other free end of the axially inner opposite free ends of each of the first blocks is away from the equatorial plane.

[0075] Preferably, the other free end of the axially inner opposite free ends of each of the second blocks is away from the equatorial plane.

[0076] In this way, the width of the central circumferential groove varies gradually in the circumferential direction from the axially inner free end of the first block towards the aforementioned axially inner central part of the first block (and therefore gradually from the axially inner central part of the second block towards the aforementioned axially inner free end of the second block) and from the axially inner central part of the first block towards the aforementioned axially inner other free end of the first block (and therefore from the axially inner free end of another block circumferentially successive to the previous second block towards the axially inner central part of this other second block). This width variation actually leads to a reduction in the void / solid ratio at the equatorial plane of the tyre, thereby increasing the mutual contact surface between the road surface and the tread band at the central annular part of the tread band, so as to favour the behaviour of the tyre on low-grip road surfaces.

[0077] In various embodiments, the other free end of the axially inner opposite free ends of each of the first blocks is close to the equatorial plane.

[0078] In various embodiments, the other free end of the axially inner opposite free ends of each of the second blocks is close to the equatorial plane.

[0079] Preferably, the first block has a generally quadrilateral shape.

[0080] Preferably, the second block has a generally quadrilateral shape.

[0081] Preferably, the first block has a shape that is a mirror image of the shape of the second block.

[0082] Thanks to the above provisions, the first and second blocks provide the tread band with the ability to deform substantially uniformly in two orthogonal directions, thereby facilitating grip on icy and possibly snow-covered roads. A favourable distribution of the blocks in the circumferential and transverse directions is also obtained, which also brings benefits in terms of the noise caused by the rolling of the tyre.

[0083] Preferably, each transverse groove extends from the equatorial plane up to the corresponding sidewall of the tire. In this way, when the tire is driven on a wet road, water is helped to drain from the tread.

[0084] More preferably, each transverse groove has a first inclination relative to a direction orthogonal to the equatorial plane at the central annular portion, and has an inclination at opposite shoulder annular portions which is smaller than the first inclination and gradually decreases as it approaches the corresponding sidewall.

[0085] Preferably, close to the equatorial plane, each transverse groove is inclined at an angle greater than 20° with respect to a direction normal to the equatorial plane.

[0086] Preferably, the angle is smaller than 45°.

[0087] In a preferred embodiment, the aforementioned angle is between 20° and 45°, for example equal to 37°.

[0088] Preferably, each transverse groove is substantially perpendicular to the equatorial plane, close to the respective side wall.

[0089] Preferably, said central circumferential groove extends along a first zigzag trajectory.

[0090] Preferably, the first zigzag trajectory is defined by a plurality of first circumferential segments which are inclined relative to the equatorial plane over a portion and a plurality of second circumferential segments which are inclined relative to the first circumferential segments, more preferably substantially parallel to the equatorial plane.

[0091] Preferably, each of said second circumferential segments connects two consecutive first circumferential segments.

[0092] The zigzag shape of the central circumferential groove increases the ability of the tread band to deform in different directions.

[0093] Preferably, said central circumferential groove has a non-constant width along said first circumferential segment.

[0094] Preferably, said central circumferential groove has a non-constant width along said second circumferential segment.

[0095] As described above, such a width variation is obtained by providing the end portions of the aforementioned first and second blocks close to the equatorial plane and the central portions of the aforementioned first and second blocks far from the equatorial plane.

[0096] Preferably, a circumferential dimension of the first circumferential segment is substantially equal to a circumferential dimension of the second circumferential segment.

[0097] Preferably, said first circumferential segments are substantially parallel to each other.

[0098] Preferably, said second circumferential segments are substantially parallel to each other.

[0099] Preferably, the first circumferential segment delimits both an axially inner first portion of the respective first block and an axially inner first portion of the respective second block.

[0100] Preferably, the second circumferential segment delimits both the remainder of the axially inner side of the first block and the remainder of the axially inner side of the second block.

[0101] Preferably, the first portion on the axially inner side of the first block extends from one of the opposite free ends of the corresponding first block to the central portion of the corresponding first block.

[0102] Preferably, the remaining portion of the axially inner side of the first block extends from the other of the opposite free ends of the corresponding first block to the central portion of the corresponding first block.

[0103] Preferably, the first portion on the axially inner side of the second block extends from one of the opposite free ends of the corresponding second block to the central portion of the corresponding second block.

[0104] Preferably, the remaining portion of the axially inner side of the second block extends from the other of the opposite free ends of the corresponding second block to the central portion of the corresponding second block.

[0105] Preferably, the first portion on the axially inner side of the first block is substantially parallel to the equatorial plane.

[0106] Preferably, the remaining portion of the axially inner side of the first block is inclined at a first angle greater than 5° relative to the equatorial plane.

[0107] Preferably, the remaining portion of the axially inner side of the first block is inclined at a first angle less than 15° relative to the equatorial plane.

[0108] In a preferred embodiment, the first angle is between 5° and 15°.

[0109] Preferably, the remaining portion of the axially inner side of the second block is substantially parallel to the equatorial plane.

[0110] Preferably, the first portion on the axially inner side of the second block is inclined at a second angle greater than 5° relative to the equatorial plane.

[0111] Preferably, the first portion on the axially inner side of the second block is inclined at a second angle smaller than 15° relative to the equatorial plane.

[0112] In a preferred embodiment, the second angle is between 5° and 15°.

[0113] In a particularly preferred embodiment, the second angle is substantially equal to the first angle.

[0114] Preferably, each of said first transverse grooves comprises a respective first transverse section arranged between two respective first circumferential grooves.

[0115] Preferably, the first circumferential grooves and the first transverse segments follow each other in an alternating manner along the second zigzag trajectory.

[0116] Preferably, the axial extension of the second zigzag trajectory is greater than the axial extension of the first zigzag trajectory.

[0117] Preferably, said first circumferential grooves are substantially parallel to each other.

[0118] Preferably, said first transverse sections are substantially parallel to each other.

[0119] Preferably, the first circumferential groove is inclined with respect to the equatorial plane on the same portion as the first circumferential groove.

[0120] Preferably, each first block of said circumferential row of first blocks comprises a respective axial outer side delimited only by a respective first circumferential groove.

[0121] Preferably, the axially outer side is inclined at a third angle greater than 5° relative to the equatorial plane.

[0122] Preferably, the axially outer side is inclined at a third angle less than 25° relative to the equatorial plane.

[0123] In a preferred embodiment, the third angle is between 5° and 25°.

[0124] Preferably, the first transverse section is inclined at a fourth angle greater than 20° relative to the equatorial plane.

[0125] Preferably, the first transverse section is inclined at a fourth angle smaller than 45° relative to the equatorial plane.

[0126] In a preferred embodiment, the fourth angle is between 20° and 45°.

[0127] Preferably, each of said second transverse grooves comprises a respective second transverse section arranged between two respective second circumferential grooves.

[0128] Preferably, the second circumferential grooves and the second transverse segments follow each other in an alternating manner along the third zigzag trajectory.

[0129] Preferably, the axial extension of the third zigzag trajectory is greater than the axial extension of the first zigzag trajectory.

[0130] Preferably, the axial extension of said third zigzag trajectory is substantially equal to the axial extension of said second zigzag trajectory.

[0131] Preferably, said second circumferential grooves are substantially parallel to each other.

[0132] Preferably, said second transverse sections are substantially parallel to each other.

[0133] Preferably, the second circumferential groove is inclined with respect to the equatorial plane at a portion opposite to the first circumferential groove.

[0134] Preferably, the second transverse section is inclined relative to the equatorial plane at a portion opposite to the first transverse section.

[0135] Preferably, each second block of said circumferential row of second blocks comprises a respective axial outer side delimited only by a respective second circumferential groove.

[0136] Preferably, the axially outer side is inclined at a fifth angle greater than 5° relative to the equatorial plane.

[0137] Preferably, the axially outer side is inclined at a fifth angle less than 15° relative to the equatorial plane.

[0138] In a preferred embodiment, the fifth angle is between 5° and 15°.

[0139] In a particularly preferred embodiment, the fifth angle is substantially equal to the third angle.

[0140] Preferably, the second transverse section is inclined at a sixth angle greater than 20° relative to the equatorial plane.

[0141] Preferably, the second transverse section is inclined at a sixth angle less than 45° relative to the equatorial plane.

[0142] In a preferred embodiment, the sixth angle is between 20° and 45°.

[0143] In a particularly preferred embodiment, the sixth angle is substantially equal to the fourth angle.

[0144] Preferably, the axially outer side of each of the second blocks is inclined with respect to the equatorial plane at an opposite portion with respect to the axially outer side of each of the first blocks.

[0145] Preferably, said central annular portion comprises a circumferential row of third blocks arranged between said first circumferential groove and a third circumferential groove arranged in an axially outer position with respect to said first circumferential groove.

[0146] Preferably, said central annular portion comprises a circumferential row of fourth blocks arranged between said second circumferential groove and a fourth circumferential groove, said fourth circumferential groove being arranged in an axially outer position with respect to said second circumferential groove.

[0147] Blocks are also provided at the axially outermost annular portion of the central annular portion of the tread band, providing said central annular portion with a distribution of blocks in the circumferential and transverse directions, with the resulting advantages not only as to the uniformity and constancy of the performance of the tyre during running on icy and possibly snow-covered roads, but also as to the noise caused by the rolling of the tyre.

[0148] Preferably, the third block is circumferentially offset relative to the first block.

[0149] Preferably, said third block is substantially axially aligned with said second block.

[0150] Preferably, the fourth block is circumferentially offset relative to the second block.

[0151] Preferably, the fourth block is substantially axially aligned with the first block.

[0152] Preferably, the third block has a generally quadrilateral shape.

[0153] Preferably, the fourth block has a generally quadrilateral shape.

[0154] Preferably, the third block has a shape that is a mirror image of the shape of the fourth block.

[0155] Preferably, each of said first transverse grooves comprises a respective third transverse section arranged between two respective third circumferential grooves.

[0156] Preferably, the third circumferential grooves and the third transverse segments follow each other in an alternating manner along the fourth zigzag trajectory.

[0157] Preferably, the axial extension of the fourth zigzag trajectory is greater than the axial extension of the first zigzag trajectory.

[0158] Preferably, the axial extension of said fourth zigzag trajectory is substantially equal to the axial extension of said second zigzag trajectory.

[0159] Preferably, each third block of said circumferential row of third blocks comprises a respective axial inner side delimited only by a respective first circumferential groove.

[0160] Preferably, said third circumferential grooves are substantially parallel to each other.

[0161] Preferably, said third circumferential groove is substantially parallel to said first circumferential groove.

[0162] Preferably, said third transverse sections are substantially parallel to each other.

[0163] Preferably, the third transverse segment is inclined at the fourth angle relative to the equatorial plane.

[0164] Preferably, each third block of said circumferential row of third blocks comprises a respective axial outer side delimited only by a respective third circumferential groove.

[0165] Preferably, an axially outer side of each of the third blocks is substantially parallel to an axially outer side of each of the first blocks.

[0166] Preferably, each of said second transverse grooves comprises a respective fourth transverse section arranged between two respective fourth circumferential grooves.

[0167] Preferably, the fourth circumferential grooves and the fourth transverse segments follow each other in an alternating manner along the fifth zigzag trajectory.

[0168] Preferably, the axial extension of the fifth zigzag trajectory is greater than the axial extension of the first zigzag trajectory.

[0169] Preferably, the axial extension of said fifth zigzag trajectory is substantially equal to the axial extension of said third zigzag trajectory.

[0170] Preferably, each fourth block of said circumferential row of fourth blocks comprises a respective axial inner side delimited only by a respective second circumferential groove.

[0171] Preferably, said fourth circumferential grooves are substantially parallel to each other.

[0172] Preferably, said fourth circumferential groove is substantially parallel to said second circumferential groove.

[0173] Preferably, said fourth transverse sections are substantially parallel to each other.

[0174] Preferably, the fourth transverse segment is inclined at the sixth angle relative to the equatorial plane.

[0175] Preferably, each fourth block of said circumferential row of fourth blocks comprises a respective axial outer side delimited only by a respective fourth circumferential groove.

[0176] Preferably, an axially outer side of each of the fourth blocks is substantially parallel to an axially outer side of each of the second blocks.

[0177] Preferably, each of said shoulder annular portions comprises a plurality of respective blocks.

[0178] Preferably, the equatorial plane of the tyre is completely contained within the central circumferential groove.

[0179] According to the applicant, such an arrangement increases the deformability of the first and second blocks in the circumferential direction. In fact, in this way, possible interference between the first and second blocks on their respective axial inner sides when the first block is deformed in the circumferential direction is avoided. Such interference would hinder the free deformation of the blocks in the circumferential direction.

[0180] Preferably, the void / solid ratio of the tread band is less than or equal to 0.30. The Applicant has found that such an arrangement makes it possible to maximize the contact area between the tread band and the road surface at the footprint, thus facilitating grip on icy roads.

[0181] Preferably, the void / solid ratio is greater than or equal to 0.24.

[0182] Preferably, the void / solid ratio is between 0.24 and 0.30.

[0183] Preferably, the tread band has a tread pattern having a number of pitches greater than or equal to 54, more preferably greater than or equal to 56. The Applicant has found that such an arrangement makes it possible to improve traction and braking on snow-covered roads.

[0184] Preferably, the tread band has a tread pattern comprising a plurality of first pitches having a first circumferential dimension.

[0185] Preferably, the tread pattern comprises a plurality of second pitches having a second circumferential dimension different from the first circumferential dimension.

[0186] Preferably, the tread pattern comprises a plurality of third pitches having a third circumferential dimension different from the first circumferential dimension.

[0187] Preferably, the third circumferential dimension is different from the second circumferential dimension.

[0188] According to the applicant, providing at least two types of pitches with different sizes produces a beneficial effect on the rolling induced noise. This beneficial effect is even greater by providing three types of pitches with different sizes. In fact, in this way, it is possible to appropriately alternate the various pitches along the circumferential extension of the tire (for example, by suitable frequency optimization software) and increase the size difference between the shorter pitch and the longer pitch, so as to avoid the generation of undesirable frequency repetitions that would lead to an increase in the rolling induced noise.

[0189] Preferably, at least some of said first blocks, more preferably all of said first blocks, comprise a plurality of respective sipes.

[0190] This is also for excellent performance on snow, especially in terms of traction and braking.

[0191] Furthermore, the provision of sipes in the blocks, combined with the provision of a tread pattern with at least two pitches of different sizes, allows a better distribution of the sipes in the circumferential direction over the tread band, further improving the performance on snow.

[0192] Preferably, at least some of said second blocks, more preferably all of said second blocks, comprise a plurality of respective sipes.

[0193] Preferably, the sipes of the first block are identical to the sipes of the second block.

[0194] Preferably, the sipes extend along a non-straight trajectory on the radially outer surface of the respective first block.

[0195] Preferably, the sipes extend along a non-straight trajectory on the radially outer surface of the respective second block.

[0196] Preferably, the sipes extend in a radial direction along the non-planar surface.

[0197] The sipe thus has a substantially three-dimensional shape. This shape ensures that an interlock is created between the two block portions separated by the first sipe, avoiding excessive deformation of the blocks.

[0198] Preferably, at least some of the third and / or fourth blocks, more preferably the third and / or fourth blocks, comprise a plurality of sipes.

[0199] Preferably, at least some of said first blocks, more preferably all of said first blocks, comprise a first tapered portion at said central circumferential groove.

[0200] Preferably, at least some of said first blocks, more preferably all of said first blocks, comprise a second tapered portion at adjacent transverse grooves.

[0201] The applicant has demonstrated that providing the aforementioned tapered portion in the first block allows the edges of the circumferentially adjacent blocks and the edges of the axially adjacent blocks to grip the snow-covered road surface (which would otherwise be "hidden" by the aforementioned first block), thereby increasing the grip on the snow in both the circumferential and lateral directions without weakening the first block.

[0202] Preferably, at least some of said second blocks, more preferably all of said second blocks, comprise a first tapered portion at said central circumferential groove.

[0203] Preferably, at least some, more preferably all, of said second blocks comprise second tapered portions at adjacent transverse grooves.

[0204] Preferably, the size of the block portion where the first tapered portion is located is larger than the size of the block portion where the second tapered portion is located.

[0205] Preferably, at least some of said third blocks, more preferably all of said third blocks, comprise at least one first tapered portion at said first circumferential groove.

[0206] Preferably, at least some of said fourth blocks, more preferably all of said fourth blocks, comprise at least one first tapered portion at said second circumferential groove.

[0207] Preferably, at least some of said third blocks, more preferably all of said third blocks, comprise at least one second tapered portion at adjacent transverse grooves.

[0208] Preferably, at least some of said fourth blocks, more preferably all of said fourth blocks, comprise at least one second tapered portion at adjacent transverse grooves.

[0209] Preferably, the depth of the tread band near the opposite shoulder annular portions is less than the depth at the central annular portion. Such an arrangement helps to reduce the noise caused by rolling. BRIEF DESCRIPTION OF THE DRAWINGS

[0210] Further features and advantages of the present invention will become more apparent through the following description of the preferred embodiments of the present invention in conjunction with the accompanying drawings. In such drawings:

[0211] - Figure 1 is a schematic perspective view of a tire according to the present invention;

[0212] - Figure 2 yes Figure 1 a view of an enlarged portion of a tire;

[0213] - Figure 3a and Figure 3b yes Figure 1 an enlarged view of a portion of a central portion of a central annular portion of a tread band of a tire;

[0214] - Figure 4a and Figure 4b yes Figure 1 an enlarged view of portions of opposite side portions of a central annular portion of a tread band of a tire;

[0215] - Figure 5 yes Figure 1 Another view of an enlarged portion of the tread band of the tire;

[0216] - Figure 6 Schematically shows Figure 1 The tread of the tire. DETAILED DESCRIPTION

[0217] exist Figure 1 In the drawing, a tyre according to the invention is indicated by 100. The tyre 100 is in particular an HP or UHP tyre for sports and / or high performance or ultra high performance vehicles and is intended for use on low grip surfaces, in particular icy and possibly snow covered surfaces.

[0218] The tyre 1 comprises a carcass structure 103, a belt structure (not visible) arranged in a radially outer position with respect to the carcass structure 103, and a tread band 110 made of elastomeric material and arranged in a radially outer position with respect to the belt structure.

[0219] The tread band 110 is provided on the opposite sidewall 105 ( Figure 1 only one of which is visible).

[0220] Each sidewall 105 is applied on a respective lateral surface of the carcass structure 103 , in an axially external position relative to the carcass structure 103 itself, and extends from this lateral surface as far as the tread band 110 .

[0221] like Figure 2 As shown, the tread band 110 comprises a central annular portion A extending from an axially opposite portion with respect to the equatorial plane E of the tyre 100 and two shoulder annular portions S1 , S2 arranged on axially opposite portions with respect to the axially central annular portion A.

[0222] Each shoulder annular portion S1 , S2 is adjacent to a corresponding sidewall 105 .

[0223] The tread band 110 has a greater depth at the central annular portion A than at the shoulder annular portions S1 , S2. The depth preferably decreases gradually from the central annular portion A towards the opposite shoulder annular portions S1 , S2.

[0224] In a preferred embodiment, the tread band 110 has a depth equal to 8.5 mm in the central annular portion A and a depth equal to 7.5 mm in the shoulder annular portions S1 , S2 .

[0225] Reference Figure 2 The central annular portion A includes: a central circumferential groove 115, which extends on an axially opposite portion with respect to the equatorial plane E; a plurality of first circumferential grooves 120, which are arranged on a portion with respect to the central circumferential groove 115; and a plurality of second circumferential grooves 160, which are arranged on a portion axially opposite to the plurality of first circumferential grooves 120 with respect to the central circumferential groove 115.

[0226] The central annular portion A further includes a plurality of third circumferential grooves 140 arranged in an axially outer position relative to the plurality of first circumferential grooves 120 and a plurality of fourth circumferential grooves 180 arranged in an axially outer position relative to the plurality of second circumferential grooves 160 .

[0227] The first circumferential grooves 120 are substantially parallel to each other.

[0228] The second circumferential grooves 160 are substantially parallel to each other and are inclined with respect to the equatorial plane E at a portion opposite to the first circumferential grooves 120 .

[0229] The third circumferential grooves 140 are substantially parallel to each other and are inclined with respect to the equatorial plane E on the same portion as the first circumferential grooves 120 . Preferably, the third circumferential grooves 140 are substantially parallel to the first circumferential grooves 120 .

[0230] The fourth circumferential grooves 180 are substantially parallel to each other and are inclined on a portion opposite to the first circumferential grooves 120 with respect to the equatorial plane E. Preferably, the fourth circumferential grooves 180 are substantially parallel to the second circumferential grooves 160.

[0231] The inclination angle of the first circumferential groove 120 relative to the equatorial plane E is preferably between 5° and 25°, for example equal to 15°.

[0232] In one embodiment, the equatorial plane E is completely contained in the central circumferential groove 115 .

[0233] The tread band 110 comprises a plurality of first transverse grooves 210 on one side ( Figure 2 The tread band 110 extends from an axially central portion of the tread band 110, close to the central circumferential groove 115, to the axially outer end of the shoulder annular portion S1.

[0234] The first transverse grooves 210 are substantially parallel to each other.

[0235] The tread band 110 further comprises a plurality of second transverse grooves 220, which are provided on the other side with respect to the equatorial plane E ( Figure 2 The tread band 110 extends from an axially central portion of the tread band 110, close to the central circumferential groove 115, to the axially outer end of the shoulder annular portion S2.

[0236] The second transverse grooves 220 are substantially parallel to each other.

[0237] In the embodiment shown in the drawings, each first transverse groove 210 extends from the central circumferential groove 115 on one side of the equatorial plane E to the corresponding side wall 105 , and each second transverse groove 220 extends from the central circumferential groove 115 on the other side of the equatorial plane E to the opposite side wall 105 .

[0238] The transverse groove 210 is circumferentially offset relative to the transverse groove 220 .

[0239] The first lateral groove 210 is connected to the first circumferential groove 120 and to the third circumferential groove 140 .

[0240] The second lateral groove 220 is connected to the second circumferential groove 160 and to the fourth circumferential groove 180 .

[0241] At the central annular portion A, each transverse groove 210 , 220 is inclined relative to a direction orthogonal to the equatorial plane E by an angle comprised between 20° and 45°, for example equal to 37°.

[0242] This inclination angle decreases at the respective shoulder annular portion S1 , S2 and then gradually becomes substantially equal to zero towards the respective sidewall 105 , so that each transverse groove 210 , 220 is substantially perpendicular to the equatorial plane E close to the respective sidewall 105 .

[0243] The aforementioned grooves 115, 120, 140, 160, 180, 210, 220 define a plurality of blocks, as described below.

[0244] The central circumferential groove 115 and the first circumferential groove 120 delimit, on axially opposite portions, a circumferential row of first blocks 125 having a substantially quadrilateral shape. The first blocks 125 are delimited, on circumferentially opposite portions, by respective segments of two circumferentially consecutive transverse grooves 210 .

[0245] The central circumferential groove 115 and the second circumferential groove 160 delimit on axially opposite portions a circumferential row of second blocks 155 having a generally quadrilateral shape and mirroring the shape of the first blocks 125. The second blocks 155 are delimited on circumferentially opposite portions by respective segments of two circumferentially consecutive transverse grooves 220.

[0246] The second block 155 is circumferentially offset relative to the first block 125 .

[0247] The first circumferential groove 120 and the third circumferential groove 140 delimit on axially opposite portions a circumferential row of third blocks 135 having a substantially quadrilateral shape. The third blocks 135 are delimited on circumferentially opposite portions by respective segments of two aforementioned circumferentially consecutive transverse grooves 210.

[0248] In the embodiment shown in the drawings, the third block 135 is offset relative to the first block 125 in the circumferential direction and is substantially aligned with the second block 155 in the axial direction.

[0249] The second circumferential grooves 160 and the fourth circumferential grooves 180 delimit, on axially opposite portions, a circumferential row of fourth blocks 175 having a generally quadrilateral shape and substantially mirroring the shape of the third blocks 135. The fourth blocks 175 are delimited, on circumferentially opposite portions, by respective segments of the two aforementioned circumferentially consecutive transverse grooves 220.

[0250] The fourth block 175 is circumferentially offset relative to the third block 135 .

[0251] In the embodiment shown in the drawings, the fourth block 175 is offset relative to the second block 155 in the circumferential direction and is substantially aligned with the first block 125 in the axial direction.

[0252] As described below, further blocks 190, 195 are provided at the shoulder annular portions S1, S2.

[0253] The row of further blocks 190 is delimited on an axially opposite portion by a third circumferential groove 140 and by one of the two side walls 105. The further blocks 190 are delimited on a circumferentially opposite portion by respective segments of two circumferentially consecutive transverse grooves 210.

[0254] A row of further blocks 195 is delimited on axially opposite portions by a fourth circumferential groove 180 and by the other of the two side walls 105. This further block 195 has a shape substantially mirroring that of the block 190 and is delimited on circumferentially opposite portions by respective segments of two circumferentially consecutive transverse grooves 220.

[0255] Block 195 is circumferentially offset relative to block 190 .

[0256] Reference Figure 3a and Figure 3b Each of the first blocks 125 includes a respective axial inner side 126 defined by the central circumferential groove 115 and a respective axial outer side 127 defined by the first circumferential groove 120 .

[0257] Similarly, each of the second blocks 155 comprises a respective axially inner side 156 defined by the central circumferential groove 115 and a respective axially outer side 157 defined by the second circumferential groove 160 .

[0258] The axial inner side 126 of the block 125 includes a free end 126 a close to the equatorial plane E, an opposite free end 126 b away from the equatorial plane E, and a central portion 126 c away from the equatorial plane E in the circumferential direction.

[0259] Similarly, the axial inner side 156 of the block 155 includes a free end 156 a close to the equatorial plane E, an opposite free end 156 b away from the equatorial plane E, and a central portion 156 c away from the equatorial plane E in the circumferential direction.

[0260] The circumferential offset of the first blocks 125 relative to the second blocks 155 causes the relative free ends 126a, 126b of each of the first blocks 125 to be arranged at the central portions 156c of two circumferentially consecutive second blocks 155, and the free ends 156a, 156b of each of the second blocks 155 to be arranged at the central portions 126c of two circumferentially consecutive first blocks 125.

[0261] Reference Figure 4a Each of the third blocks 135 comprises a respective axial inner side 136 defined by the first circumferential groove 120 and a respective axial outer side 137 defined by the third circumferential groove 140. The third axial grooves also define an axial inner side 191 of the further block 190.

[0262] Similarly, refer to Figure 4b Each of the fourth blocks 175 comprises a respective axial inner side 176 defined by the second circumferential groove 160 and a respective axial outer side 177 defined by the fourth circumferential groove 180. The fourth axial groove also defines an axial inner side 196 of the further block 195.

[0263] In the embodiment shown in the drawings, the axial outer side 127 of the first block 125 and the axial inner side 136 of the third block are substantially parallel and inclined relative to the equatorial plane E at an angle equal to the inclination angle of the first circumferential groove 120 ( Figure 3b ). Preferably, each circumferential groove 120 defines the entire axial outer side 127 of the corresponding first block 125 and the entire axial inner side 136 of the corresponding third block 135 .

[0264] In the embodiment shown in the drawings, the axial outer side 157 of the second block 155 and the axial inner side 176 of the fourth block 175 are substantially parallel and inclined with respect to the equatorial plane E at an angle equal to the inclination angle of the second circumferential groove 160 ( Figure 3b). Preferably, each circumferential groove 160 defines the entire axial outer side 157 of the corresponding second block 155 and the entire axial inner side 176 of the corresponding fourth block 175 .

[0265] In the embodiment shown in the drawings, the axial outer side 137 of the third block 135 and the axial inner side 191 of the block 190 are substantially parallel and are inclined relative to the equatorial plane E at an angle equal to the inclination angle of the third circumferential groove 140 ( Figure 4a ). Preferably, each circumferential groove 140 defines the entire axial outer side 137 of the corresponding third block 135 and the entire axial inner side 191 of the corresponding block 190 .

[0266] In the embodiment shown in the drawings, the axial outer side 177 of the fourth block 175 is substantially parallel to the axial inner side 196 of the block 195 and is inclined relative to the equatorial plane E at an angle equal to the inclination angle of the fourth circumferential groove 180 ( Figure 4b ). Preferably, each circumferential groove 180 defines the entire axial outer side 177 of the corresponding fourth block 175 and the entire axial inner side 196 of the corresponding block 195 .

[0267] On the other hand, the axial outer sides of the blocks 190 and 195 are defined by the corresponding side walls 105 .

[0268] Reference Figure 3a and Figure 3b , the central circumferential groove 115 extends along a first zigzag trajectory defined by a plurality of first circumferential segments 115a substantially parallel to one another and inclined over a portion relative to the equatorial plane E, and a plurality of second circumferential segments 115b substantially parallel to one another and inclined relative to the first circumferential segments 115a, in particular substantially parallel to the equatorial plane E. Each of the second circumferential segments 115b connects two consecutive first circumferential segments 115a and vice versa.

[0269] The first circumferential segment 115 a is inclined relative to the equatorial plane E on the same portion as the first circumferential groove 120 .

[0270] The second circumferential segment 115 b is inclined relative to the equatorial plane E on the same portion as the second circumferential groove 160 .

[0271] The inclination angle of the first circumferential segment 115a relative to the equatorial plane E is preferably smaller than the inclination angle of the first circumferential groove 120, more preferably between 5° and 15°, for example equal to 9°.

[0272] The inclination angle of the second circumferential segment 115b relative to the equatorial plane E is preferably smaller than the inclination angle of the second circumferential groove 160, more preferably between 5° and 15°, for example equal to 9°.

[0273] The first circumferential segment 115a defines both the portion of the axial inner side 126 of the first block 125 extending from the corresponding free end 126a to the corresponding central portion 126c of the first block 125 and the portion of the axial inner side 156 of the second block 155 extending from the corresponding free end 156b to the corresponding central portion 156c of the second block 155.

[0274] The second circumferential segment 115b defines both the portion of the axial inner side 126 of the first block 125 extending from the corresponding free end 126b to the corresponding central portion 126c of the first block 125 and the portion of the axial inner side 156 of the second block 155 extending from the corresponding free end 156b to the corresponding central portion 156c of the second block 155.

[0275] The portion of the axial inner side 126 of each of the first blocks 125 extending from the free end 126a to the central portion 126c is inclined relative to the equatorial plane E at an angle equal to the angle at which the first circumferential segment 115a of the central circumferential groove 115 is inclined relative to the equatorial plane E.

[0276] The portion of the axial inner side 156 of each second block 155 extending from the free end 156a to the central portion 156c is inclined relative to the equatorial plane E at an angle equal to and opposite to the angle of inclination of the first circumferential segment 115a. The second circumferential segment 115b of the central circumferential groove 115 is substantially parallel to the equatorial plane E.

[0277] The portion of the axial inner side 126 of each of the first blocks 125 extending from the free end 126b to the central portion 126c and the portion of the axial inner side 156 of each of the second blocks 155 extending from the free end 156b to the central portion 156c are substantially parallel to the equatorial plane E.

[0278] Due to the geometry of the axial inner sides 126 of the first block 125 and 156 of the second block 155 as described above, the central circumferential groove 115 has a non-constant width in the circumferential direction both along the first circumferential segment 115a and along the second circumferential segment 115b.

[0279] Reference Figure 4a , each of the first transverse grooves 210 includes a first transverse section 210 a arranged between two corresponding first circumferential grooves 120 .

[0280] The first transverse segments 210 a and the first circumferential grooves 120 follow each other in an alternating manner along a second zigzag trajectory, the axial extension of which is greater than that of the first zigzag trajectory.

[0281] Reference Figure 4bEach second transverse groove 220 includes a second transverse segment 220a, which is arranged between two corresponding second circumferential grooves 160 and is inclined relative to the equatorial plane E at a portion opposite to the first transverse segment 210a.

[0282] The second transverse segments 220a and the second circumferential grooves 160 follow each other in an alternating manner along a third zigzag trajectory, the axial extension of which is greater than that of the first zigzag trajectory, preferably equal to that of the second zigzag trajectory.

[0283] The inclination angle of the circumferential groove 160 is preferably equal to the inclination angle of the circumferential groove 120 .

[0284] Reference Figure 4a , each first transverse groove 210 further includes a third transverse segment 210b which is arranged between two corresponding third circumferential grooves 140 and which is inclined relative to the equatorial plane E on the same portion as the first transverse segment 210a.

[0285] The third transverse segments 210 b and the third circumferential grooves 140 follow each other in an alternating manner along a fourth zigzag trajectory, the axial extension of which is greater than that of the first zigzag trajectory, preferably equal to that of the second zigzag trajectory.

[0286] Reference Figure 4b Each second transverse groove 220 further includes a fourth transverse segment 220b which is arranged between two corresponding fourth circumferential grooves 180 and is inclined relative to the equatorial plane E at a portion opposite to the first transverse segment 210a.

[0287] The fourth transverse segments 220b and the fourth circumferential grooves 180 follow each other in an alternating manner along a fifth zigzag trajectory, the axial extension of which is greater than that of the first zigzag trajectory, preferably equal to that of the third zigzag trajectory.

[0288] like Figure 2 As shown, in its embodiment, the tire 100 has a plurality of corresponding sipes L1 in each of the above-mentioned blocks 125 , 135 , 155 , 175 , 190 , 195 .

[0289] Preferably, the sipes L1 have a three-dimensional shape, ie they extend along a non-rectilinear trajectory on the radially outer surface of the blocks 125 , 135 , 155 , 175 , 190 , 195 and along a non-planar surface in the radial direction.

[0290] The sipes L1 of the block 125 are preferably identical to the sipes L1 of the block 155 , but oriented with respect to the equatorial plane E on a portion opposite to the latter.

[0291] The sipes L1 of the block 125 are preferably identical to the sipes L1 of the block 175 , but oriented with respect to the equatorial plane E on a portion opposite to the latter.

[0292] The sipes L1 of the block 190 are preferably identical to the sipes L1 of the block 195 , but oriented with respect to the equatorial plane E on a portion opposite to the latter.

[0293] The sipes L1 of the blocks 125 extend along an at least partially zigzag path, with a trajectory substantially parallel to the trajectory of the corresponding segment 210 a of the transverse groove 210 .

[0294] Similarly, the sipes L1 of the blocks 155 extend along an at least partially zigzag path with a trajectory substantially parallel to the trajectory of the corresponding segment 220 a of the transverse groove 220 .

[0295] The sipes L1 of the blocks 190 extend along an at least partially zigzag path with a trajectory substantially parallel to the trajectory of the corresponding end segments of the transverse grooves 210 .

[0296] Similarly, the sipes L1 of the blocks 195 extend along an at least partially zigzag path with a trajectory substantially parallel to the trajectory of the corresponding end segment of the transverse groove 220 .

[0297] The sipes L1 of the blocks 135 extend along an at least partially zigzag path, on opposite portions relative to the corresponding segments 210 b of the transverse grooves 210 , with a trajectory inclined relative to a plane orthogonal to the equatorial plane E.

[0298] The sipes L1 of the blocks 175 extend along an at least partially zigzag path with a trajectory inclined relative to a plane orthogonal to the equatorial plane E, on the opposite portion relative to the corresponding segment 220 b of the transverse groove 220 .

[0299] Reference Figure 5 , each of the blocks 125, 135, 155, 175, 190, 195 includes a respective first tapered portion 126', 136', 156', 176', 191', 196' on the respective axial inner side 126, 136, 156, 176, 191, 196 and a respective second tapered portion 125', 135', 155', 175', 190', 195' at a side of the block adjacent to the respective transverse groove 210, 220 (the side located below with reference to the orientation of the tire 100 shown in the drawings).

[0300] The first tapered portion 126', 136', 156', 176', 191', 196' is arranged in a portion of the corresponding block 125, 135, 155, 190, 195, the size of which is larger than the size of the block portion where the second tapered portion 125', 135', 155', 175', 190', 195' is arranged. In particular, the size of the first tapered portion 126', 136', 156', 176', 191', 196' is larger than the size of the second tapered portion 125', 135', 155', 175', 190', 195'. More specifically, the size of the first tapered portions 126', 136', 156', 176', 191', 196' is larger than half the size of the corresponding blocks 125, 135, 155, 190, 195, while the size of the second tapered portions 125', 135', 155', 175', 190', 195' is smaller than half the size of the corresponding blocks 125, 135, 155, 190, 195.

[0301] Each of the aforementioned first tapered portions 126', 136', 156', 176', 191', 196' and second tapered portions 125', 135', 155', 175', 190', 195' has a generally triangular shape, the vertex of the triangle corresponds to the highest point of the slope, on the radial outer surface of the corresponding block 125, 135, 155, 190, 195, and gradually widens as it moves away from the vertex parallel to the adjacent groove. The inclination angle of the aforementioned first tapered portions 126', 136', 156', 176', 191', 196' and second tapered portions 125', 135', 155', 175', 190', 195' relative to the radial outer surface of the corresponding block 125, 135, 155, 190, 195 is preferably between 20° and 50°, for example equal to 30°.

[0302] Thanks to the provision of all the blocks described above, the tread band 110 has a void / solid ratio less than or equal to 0.30, preferably comprised between 0.24 and 0.30.

[0303] The arrangement of the above-mentioned blocks and of the above-mentioned grooves is such that the tread pattern comprises a number of pitches greater than or equal to 54, for example equal to 68.

[0304] In particular, if Figure 2 As schematically shown, three different types of pitches P1 , P2 , P3 are provided, which differ from one another in that they have different circumferential dimensions.

[0305] The pitches P1 , P2 and P3 are suitably alternated in the tread pattern according to a predetermined sequence obtained, for example, by suitable software. Figure 2Only a portion of the possible sequences are shown as examples.

[0306] Comparison test

[0307] The applicant has manufactured some tires of size 205 / 55R16 according to the present invention. These tires are hereinafter indicated as INV.

[0308] These tyres have the same structure and dimensions as those of the applicant which are valued by customers for their excellent behaviour on low-grip road surfaces, in particular on icy and possibly snow-covered road surfaces. This tyre is denoted below by Ref.

[0309] Therefore, the tire INV differs from the tire Ref. only in the tread pattern.

[0310] An outdoor comparative test was conducted on the tire INV and the tire Ref.

[0311] The test was performed by mounting the above tires (inflated with the same inflation pressure for the same wheels) on wheels of the same vehicle under substantially the same weather conditions.

[0312] The performance of the tires INV and Ref. was evaluated and the drivers' opinions were asked. In particular, the items listed in the following Table 1 were evaluated, and the qualitative opinions given by the drivers were also provided.

[0313] In Table 1, "=" indicates that the tire Ref. obtained a positive evaluation, and "+" indicates an improvement over the tire Ref.

[0314] Table 1

[0315] Ref. INV. Braking on snow ＝ ＝ Traction on snow ＝ + Braking on ice ＝ + Traction on ice ＝ +

[0316] Table 1 shows that the tire INV provides improved performance relative to the tire Ref., particularly in terms of traction and braking on icy roads and in terms of traction on snow-covered roads, and in terms of braking on snow-covered roads, its performance is substantially the same as that of the tire Ref. Thus, the applicant has determined that the specific tread pattern employed in the tire of the present invention is effective in obtaining the desired improvement in performance on low-grip roads.

[0317] The excellent performance of the tire of the present invention on low-grip roads is also achieved by Figure 6 The shape of its footprint shown is confirmed. Such a footprint is obtained in particular by subjecting the tire INV to a vertical load of 450 kg.

[0318] It can be seen that the footprint has a generally oval shape with a very regular perimeter. This confirms that the contact surface with the road surface has been maximized, which is what is expected of a tire intended for use on low-grip surfaces. The general consistency of the gray color throughout the footprint also indicates that the distribution of contact pressure inside the footprint is regular and uniform, a feature that is also expected for a tire intended for use on low-grip surfaces.

[0319] Of course, those skilled in the art may make further modifications and variations to the tire of the invention described above in order to meet specific and situation-dependent application requirements, these variations and modifications being in any case within the scope of protection of the invention as defined by the following claims.

Claims

1. A tyre (100) for a vehicle wheel, said tyre comprising a tread band (110) extending between opposite sidewalls (105), wherein: The tread band (110) comprises a central annular portion (A) and opposite shoulder annular portions (S1, S2), each shoulder annular portion (S1, S2) being adjacent to a respective sidewall (105), wherein the central annular portion (A) comprises: - a central circumferential groove (115) extending on axially opposite portions with respect to the equatorial plane (E); - a circumferential row of first blocks (125) having a respective axially inner side (126) defined by said central circumferential groove (115) and a respective axially outer side (127) defined by a respective first circumferential groove (120), wherein each of said first blocks (125) is delimited in circumferential direction by a respective segment of an opposite first transverse groove (210) extending from a portion of said tread band (110) arranged at said central circumferential groove (115) up to an axially outer end of a first shoulder annular portion (S1); - a circumferential row of second blocks (155) having a respective axially inner side (156) defined by said central circumferential groove (115) and a respective axially outer side (157) defined by a respective second circumferential groove (160) arranged on a portion axially opposite to said first circumferential groove (120) with respect to said central circumferential groove (115), wherein each of said second blocks (155) is delimited in circumferential direction by a respective segment of an opposite second transverse groove (220) extending from a portion of said tread band (110) arranged at said central circumferential groove (115) up to an axially outer end of a second shoulder annular portion (S2) arranged on a portion axially opposite to said first shoulder annular portion (S1) with respect to said central circumferential groove (115); The axial inner side (126) of each of the first blocks (125) comprises, in the circumferential direction: corresponding relative free ends (126a, 126b), at least one of the relative free ends being close to the equatorial plane (E); and a corresponding central portion (126c), the central portion being far away from the equatorial plane (E); The axial inner side (156) of each of the second blocks (155) comprises, in the circumferential direction: corresponding relative free ends (156a, 156b), at least one of the relative free ends being close to the proximal side of the equatorial plane (E); and a corresponding central portion (156c), the central portion being far away from the equatorial plane (E); Wherein, the first block (125) is offset circumferentially relative to the second block (155), so that the relative free ends (126a, 126b) of each of the first blocks (125) are arranged at the central parts (156c) of two circumferentially consecutive second blocks (155), and the relative free ends (156a, 156b) of each of the second blocks (155) are arranged at the central parts (126c) of two circumferentially consecutive first blocks (125).

2. The tire (100) according to claim 1, wherein: The central circumferential groove (115) extends along a first zigzag trajectory, which is defined by a plurality of first circumferential segments (115a) and a plurality of second circumferential segments (115b), wherein the first circumferential segments are inclined relative to the equatorial plane (E) on a portion and the second circumferential segments are inclined relative to the first circumferential segments (115a), wherein each of the second circumferential segments (115b) connects two consecutive first circumferential segments (115a).

3. The tire (100) according to claim 1 or 2, wherein: Each of the first transverse grooves (210) comprises a respective first transverse segment (210a) arranged between two respective first circumferential grooves (120), and wherein the first circumferential grooves (120) and the first transverse segments (210a) follow each other in an alternating manner along a second zigzag trajectory.

4. The tire (100) according to claim 3 when dependent on claim 2, wherein: The axial extension of the second zigzag-shaped trajectory is greater than the axial extension of the first zigzag-shaped trajectory.

5. Tyre (100) according to any one of the preceding claims, wherein: Each of the second transverse grooves (220) comprises a respective second transverse segment (220a) arranged between two respective second circumferential grooves (160), and wherein the second circumferential grooves (160) and the second transverse segments (220a) follow each other in an alternating manner along a third zigzag trajectory.

6. The tyre (100) according to claim 5 when appended to claim 2, wherein: The axial extension of the third zigzag trajectory is greater than the axial extension of the first zigzag trajectory.

7. Tyre (100) according to any one of the preceding claims, wherein: The central annular portion (A) comprises: - a circumferential row of third blocks (135) arranged between said first circumferential groove (120) and a third circumferential groove (140), said third circumferential groove being arranged in an axially outer position relative to said first circumferential groove (120); - a circumferential row of fourth blocks (175) arranged between said second circumferential groove (160) and a fourth circumferential groove (180), said fourth circumferential groove being arranged in an axially outer position relative to said second circumferential groove (160).

8. The tire (100) according to claim 7, wherein: Each of the first transverse grooves (210) comprises a respective third transverse segment (210b) arranged between two respective third circumferential grooves (140), and wherein the third circumferential grooves (140) and the third transverse segments (210b) follow each other in an alternating manner along a fourth zigzag trajectory.

9. The tyre (100) according to claim 8 when appended to claim 2, wherein: The axial extension of the fourth zigzag trajectory is greater than the axial extension of the first zigzag trajectory.

10. The tyre (100) according to any one of claims 7 to 9, wherein: Each of the second transverse grooves (220) comprises a respective fourth transverse segment (220b) arranged between two respective fourth circumferential grooves (180), and wherein the fourth circumferential grooves (180) and the fourth transverse segments (220b) follow each other in an alternating manner along a fifth zigzag trajectory.

11. The tyre (100) according to claim 10 when dependent on claim 2, wherein: The axial extension of the fifth zigzag trajectory is greater than the axial extension of the first zigzag trajectory.

12. Tyre (100) according to any one of the preceding claims, wherein: The equatorial plane (E) is completely contained in the central circumferential groove (115).

13. Tyre (100) according to any one of the preceding claims, wherein: The tread band (110) has a void / solid ratio less than or equal to 0.

30.

14. Tyre (100) according to any one of the preceding claims, wherein: The tread band (110) has a tread pattern comprising a number of pitches (P1, P2, P3) greater than or equal to 54.

15. The tire (100) according to claim 13, wherein: The tread band (110) has a tread pattern, the tread pattern comprising a plurality of first pitches (P1) having a first circumferential dimension, a plurality of second pitches (P2) having a second circumferential dimension different from the first circumferential dimension, and a plurality of third pitches (P3) having a third circumferential dimension different from the first circumferential dimension and the second circumferential dimension.

16. Tyre (100) according to any one of the preceding claims, wherein: Each of the first block (125) and the second block (155) includes a plurality of sipes (L1).

17. The tire (100) according to claim 16, wherein: The sipes (L1) extend along a non-linear trajectory on the radially outer surfaces of the respective first block (125) and the second block (155) and extend along a non-planar surface in the radial direction.

18. Tyre (100) according to any one of the preceding claims, wherein: Each of the first block (125) and the second block (155) includes a first tapered portion (126'; 156') located at the central circumferential groove (115).

19. Tyre (100) according to any one of the preceding claims, wherein: Each of the first block (125) and the second block (155) includes a second tapered portion (125'; 155') at adjacent transverse grooves (210; 220).

20. Tyre (100) according to any one of the preceding claims, wherein: The tread band (110) has a depth near the opposite shoulder annular portions (S1, S2) that is less than the depth at the central annular portion (A).

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