Tires for vehicle wheels

Abstract

A tire for a vehicle wheel includes a tread band (2) having a plurality of first pairs of main grooves formed by first main grooves (10) and second main grooves (20) extending from first shoulder regions (4) and second shoulder regions (5) toward a central region (6); and a plurality of second main grooves formed by third main grooves (30) and fourth main grooves (40) extending from the first shoulder regions (4) and second shoulder regions (5) toward the central region (6). and a plurality of second pairs of main grooves (50, 60) extending between two consecutive first main grooves (10) and two consecutive second main grooves (20), respectively, and formed by fifth and sixth main grooves (50) and (60) having a smaller inclination than the first and second main grooves (10, 20) but in the same direction as the first and second main grooves (10, 20). Each pair of consecutive first main grooves (10) circumferentially bounds a first group of shoulder blocks (110) and a second group of shoulder blocks (120) separated from each other by a third main groove (30), and a first group of central blocks (100) separated from the first group of shoulder blocks (110) and the second group of shoulder blocks (120) by a fifth main groove (50).

Description

[Technical Field]

[0001] The present invention relates to tires for vehicle wheels, in particular winter tires. [Background technology]

[0002] A tire generally comprises a carcass structure formed toroidally about an axis of rotation and including at least one carcass ply having end flaps engaged with respective annular anchoring structures called bead cores.

[0003] In the case of automobile tires, a belt structure is provided at a radially outer position relative to the carcass structure, comprising at least two radially superimposed rubberized fabric strips, the strips comprising reinforcing cords, usually of metal, which are parallel to each other in each strip but cross the cords of adjacent strips, and are preferably arranged symmetrically relative to the equatorial plane of the tire.

[0004] Preferably, the belt structure also comprises a third layer of textile or metal cords arranged circumferentially (at 0 degrees) at the radially outer position, at least at the ends of the underlying belt pieces. In tubeless type tires, there is also a radially inner layer with impermeable properties called a "liner" to make the tire itself airtight.

[0005] A tread band made of elastomeric material is applied at a radially outer position relative to the belt structure and defines a tread surface intended to come into contact with the road surface.

[0006] The tire also has a tread band provided with grooves of various configurations and shapes to obtain sufficient road grip even on wet surfaces, said grooves delimiting the parts of the tread band intended to come into contact with the ground, called blocks.

[0007] The main function of the grooves is to drain any water present between the tire surface and the road surface upon contact with the latter, so that the hydrostatic pressure resulting from the water impinging on the advancing tire can prevent the tire from even partially lifting off the road surface and resulting in loss of control of the vehicle.

[0008] In winter tires, the blocks of the tread band are generally formed with small notches called "sipes" that extend from the tread surface of the tire towards the inside of the blocks, the function of which is to provide an additional grip element when driving on snowy roads and to improve grip on the road surface by retaining a certain amount of snow.

[0009] Furthermore, the blocks of the tread band can be provided with studs, some of which protrude beyond the tread band, thereby improving grip characteristics on icy roads.

[0010] The overall shape of the tread band defined by the combination of grooves and blocks forms the tread pattern.

[0011] WO 2020012277 of the same applicant describes a winter tire in which the tread pattern is formed by a plurality of shoulder blocks and central blocks arranged successively along the circumferential development of the tread band.

[0012] The term "circumferential" direction means a direction substantially parallel to the direction of rotation of the tire or at most slightly inclined (at most about 5°) to the direction of rotation of the tire.

[0013] The term "axial" direction means a direction substantially parallel to the axis of rotation of the tire or at most slightly inclined (at most about 5°) to this axis of rotation of the tire. The axial direction is generally perpendicular to the circumferential direction.

[0014] The term "equatorial plane" of a tire means the center plane perpendicular to the tire's axis of rotation.

[0015] The term "central region" of a tread band means that portion of the tread band extending circumferentially around the equatorial plane of the tire over at least 30% of the width of the tread band, and preferably over 40% to 60% of this width.

[0016] The central region may or may not extend symmetrically with respect to the equatorial plane.

[0017] The term "shoulder regions" of a tread band means those portions of the tread band extending circumferentially on either side of the central region at axially outer locations of the tread band to the axial ends of the tread band.

[0018] Preferably, each shoulder region extends over a width equal to at least 10% of the width of the tread band.

[0019] The term "groove" means a recess formed in a tread band portion and having a width of 1.5 mm or more.

[0020] A groove is said to be "circumferential" when it extends in the circumferential direction or is inclined at an angle of less than 5° to the circumferential direction.

[0021] A groove is said to be "transverse" when it extends in a direction inclined at an acute angle of at least 10° relative to the circumferential direction.

[0022] The term "sipe" means a recess formed in a tread band portion and having a width of less than 1.5 mm, preferably 1 mm or less.

[0023] The width of sipes and grooves is intended to be measured at a depth of 1 mm or more, preferably 1.5 mm or more.

[0024] If the width of a groove or sipe varies along its longitudinal development, an average width is considered, the value of which is obtained as the average of the various width values, appropriately weighted as a function of their relative longitudinal length. For example, if a groove has a width of 5 mm over 80% of its longitudinal length and a width of 3 mm over the remaining 20%, the average width considered is 5 x 0.8 + 3 x 0.2 = 4.6 mm.

[0025] Likewise, if the width of a groove, in particular the width of a transverse groove, varies along the tread band as a function of the length of the pitch to which it belongs, the average value is taken into account.

[0026] A groove is defined as a "major" groove when it is at least 5 mm deep. Preferably, the major groove has a width of at least 3 mm.

[0027] A groove is defined as a "minor" groove when it is less than 5 mm deep. Preferably, a minor groove has a width of less than 4 mm.

[0028] The inclination of a groove relative to the circumferential direction specified in the tread band is determined by the acute angle formed by the groove with the circumferential direction: in the special case, a groove extending parallel to the axis of the tire will have an inclination of 90° relative to the circumferential direction.

[0029] The two (or more) transverse grooves are inclined in a "concordant manner" when considered in orthogonal planes disposed (tangentially) on the tread band, with longitudinal axes parallel to the circumferential direction and transverse axes parallel to the axis of the tire, such that the progression thereof increases or decreases for both, either positive or negative.

[0030] Thus, two transverse grooves are "oppositely" inclined when, when considered in this orthogonal plane, one groove has a positive inclination and the other groove has a negative inclination.

[0031] Two grooves are "substantially aligned" when the offset of their longitudinal axes, at least in the region where their respective ends meet, is less than the width of the largest groove.

[0032] Two grooves are "contiguous" when one groove continues into the other on the tread surface, taking into account rotation in either of the two directions of tire rotation. In particular, two grooves of the same shape are contiguous when there is no other groove of the same shape between them.

[0033] In particular, a plurality of grooves may be arranged in a "regular succession" on the tread surface along the circumferential development of the tread band when the grooves are arranged successively according to a predetermined pattern of circumferential distance.

[0034] The term "block" means a tread band portion bounded by at least one groove, preferably at least two different grooves, the radially outer surface of which defines the tread band portion intended to come into contact with the road surface.

[0035] A block is therefore considered to be both a tread band portion having a closed contour, bounded by three or more grooves, and a circumferential rib bounded by a pair of grooves extending circumferentially around the tread band.

[0036] The blocks formed in the central region of the tread band are defined as "central blocks," while the blocks formed in the shoulder regions of the tread band are defined as "shoulder blocks."

[0037] The area of ​​the radially outer surface of the blocks is calculated without taking into account surfaces with potential internal grooves for the blocks.

[0038] The term "tread pattern" means the overall shape of the tread band as defined by the combination of grooves and the blocks bounded by the grooves.

[0039] A tread pattern is of the "directional" type when it is configured to be mounted on a vehicle so as to roll in the preferred direction of travel.

[0040] A "module" of a tread pattern is defined by the smallest portion of the tread band extending between its axial ends, the shape of which is repeated successively along the circumferential development of the tread band to form said tread band.

[0041] Furthermore, the modules may have slightly different circumferential dimensions (called "pitch") relative to each other while maintaining the same basic shape; for example, a tread band may use modules with two, three, or four different pitches, interlaced in various ways.

[0042] The modules may be formed by two or more elementary portions (or sub-modules) extending between the two axial ends of the tread band and arranged in the same sequential configuration within each module.

[0043] In this case, each basic portion may have the same basic shape in different modules, but may have a slightly different "pitch" from one another so that each module is formed by basic portions having different circumferential dimensions (i.e., "pitch").

[0044] Two or more directions, or two or more elements extending in each direction, such as, for example, two or more grooves, are "substantially parallel" when they are inclined at an angle of less than 10°, preferably less than 5°, relative to each other.

[0045] Two or more elements have "substantially equal" lengths when their respective lengths differ from one another by no more than 10% of the maximum length.

[0046] Two or more elements or groups of elements are considered "substantially symmetric" with respect to a plane of symmetry even when they are slightly offset relative to one another in a direction parallel to the plane of symmetry. For example, two grooves, two blocks, or two groups of blocks are symmetric with respect to the equatorial plane even when they are circumferentially spaced apart by a distance shorter than the pitch of the tread pattern. Here, the pitch can correspond, for example, to the circumferential distance between two consecutive main grooves. In absolute terms, the circumferential distance between two substantially symmetric elements is less than 50 mm, preferably less than 40 mm.

[0047] Two elements, for example two blocks or two grooves, are "axially offset" or "axially offset" when they are spaced apart from one another in the circumferential direction of the tread band. Summary of the Invention [Problem to be solved by the invention]

[0048] The applicant has preliminarily observed that the performance level of a tire on snowy roads is related to the amount and extent of sipes formed in the blocks. In particular, the applicant has noticed that, for the same tread pattern, blocks with more sipes formed therein provide better behavior on snow.

[0049] However, the applicant has further observed that the presence of sipes weakens the structure of the block, reducing its rigidity and therefore its ability to withstand external stresses, particularly tangential stresses.

[0050] This weakening can result in relative deformation of the blocks when braking, accelerating or cornering, causing the blocks to partially lift off the road surface, reducing the contact area between the blocks and the road surface and, consequently, the overall frictional force exerted by the tire on the road surface.

[0051] Applicant has further observed that low block stiffness can also adversely affect the performance level of a studded tire.

[0052] In fact, the Applicant has found that studs fixed to highly deformable blocks are not only less effective in terms of grip on icy roads, but are also more likely to slip out of their seats, thereby causing the studs to become dislodged from the tread band and, in some cases, resulting in an irreversible reduction in efficiency when driving on icy roads.

[0053] Indeed, the applicant has determined that the ability of the tire to retain the studs within their properly provided seats in the tread band is a critical parameter for obtaining an adequate performance level during the life of the studded tire.

[0054] The Applicant has further observed that this requirement is generally met by shaping and dimensioning the seat for receiving the stud and the portion of the stud intended to be received in the seat so as to provide a large interference with the possible movement of the stud as it leaves the seat.

[0055] However, applicant has determined that these arrangements have limitations and may be insufficient as a result of the need to insert the studs into their respective seats during the tire manufacturing process.

[0056] The Applicant has therefore recognised that in order to improve the effectiveness of the gripping action of the studs and the ability to retain them within their seats, it may be advantageous to configure the tread pattern so as to limit as much as possible excessive local deformation of the tread band, particularly for individual blocks.

[0057] To achieve this objective, the Applicant has realized that the tread pattern must be configured not only to have as high as possible stiffness characteristics, but also to have as uniform as possible stiffness characteristics in the different regions of the tread band so that any tangential stresses that may arise are distributed as uniformly as possible.

[0058] To meet both requirements and thereby not impair the ability to evacuate water from the tread band, the Applicant considered that it might be possible to use deeper grooves to define relatively large macro regions in the tread band, and shallower grooves to define two or more blocks within the macro region.

[0059] This allows the Applicant greater freedom in designing the tread pattern, allowing for macro-regions formed by multiple blocks having uniform properties relative to one another, e.g., similar surface areas, even though the blocks may be substantially different from one another when viewed individually.

[0060] Finally, the Applicant has discovered that by appropriately defining in the tread band a plurality of main grooves extending from the shoulder regions toward the equatorial plane and connected to one another so as to define first and second groups of shoulder blocks arranged alternately in the circumferential direction relative to one another, and a first group of central blocks axially inward of and adjacent to the two groups of shoulder blocks, a tread pattern is obtained that is suitable for uniformly bearing tangential stresses, preventing excessive localized deformation of the blocks, and therefore improving the ability to retain the studs in their respective seats. [Means for solving the problem]

[0061] In particular, in a first aspect, the invention relates to a tyre for a vehicle wheel comprising a tread band.

[0062] Preferably, the tread band defines first and second axially opposed shoulder regions and a central region sandwiched between said first and second shoulder regions.

[0063] Preferably, the tread band defines a plurality of first pairs of main grooves arranged regularly and successively along the circumferential development of said tread band.

[0064] Preferably, each first pair is formed by a first main groove extending from the first shoulder region toward the central region and a second main groove extending from the second shoulder region toward the central region.

[0065] Preferably, the first main groove has an inclination with respect to the circumferential direction that decreases from the first shoulder region toward the central region.

[0066] Preferably, the second main groove has an inclination with respect to the circumferential direction that decreases from the second shoulder region toward the central region.

[0067] Preferably, the first main groove has an axially inner end connected to the second main groove.

[0068] Preferably, the second main groove is axially inward and has an end extending between the first main groove and a further first main groove of the first pair of subsequent main grooves.

[0069] Preferably, the tread band defines a plurality of second pairs of main grooves arranged regularly and successively along the circumferential development of said tread band.

[0070] Preferably, said second pair of main grooves are arranged in the tread band in alternating positions relative to said first pair of main grooves.

[0071] Preferably, each second pair of main grooves is formed by a third main groove extending from the first shoulder region toward the central region and a fourth main groove extending from the second shoulder region toward the central region.

[0072] Preferably, the third main groove has an inclination with respect to the circumferential direction that decreases from the first shoulder region toward the central region.

[0073] Preferably, the fourth main groove has an inclination with respect to the circumferential direction that decreases from the second shoulder region toward the central region.

[0074] Preferably, the tread band defines a plurality of third pairs of main grooves regularly and successively arranged along the circumferential development of said tread band.

[0075] Preferably, each third pair of major grooves is formed by a fifth major groove and a sixth major groove.

[0076] Preferably, said fifth major groove extends between two first major grooves of said first pair of adjacent major grooves.

[0077] Preferably, the fifth main groove is connected to the axially inner end of the third main groove.

[0078] Preferably, the fifth main groove has a smaller inclination with respect to the circumferential direction than the first main groove.

[0079] Preferably, the fifth main groove has a slope in the same direction as the first main groove.

[0080] Preferably, said sixth major groove extends between two second major grooves of said first pair of adjacent major grooves.

[0081] Preferably, the sixth main groove is connected to the axially inner end of the fourth main groove.

[0082] Preferably, the sixth main groove has a smaller inclination with respect to the circumferential direction than the second main groove.

[0083] Preferably, the sixth main groove has an inclination in the same direction as the second main groove.

[0084] Preferably, each first pair of consecutive main grooves circumferentially bounds a first group of shoulder blocks and a second group of shoulder blocks.

[0085] Preferably, the first and second shoulder block groups extend from the first shoulder region toward the central region.

[0086] Preferably, the first group of shoulder blocks and the second group of shoulder blocks are separated from each other by the third main groove.

[0087] Preferably, each first pair of consecutive main grooves circumferentially bounds a first group of central blocks separated from said fifth main groove by said first group of shoulder blocks and said second group of shoulder blocks.

[0088] Applicant believes that a tire constructed in accordance with the above aspects of the invention may advantageously provide substantially uniform behavior in various regions of the tread band when subjected to both axial and circumferential tangential stresses.

[0089] As a result, the tire, when provided with sipes and studs in the tread band, has an optimum behavior on different road surfaces, both dry and wet, as well as snowy or icy roads.

[0090] More specifically, the applicant believes that the provision of main grooves allows water to be rapidly evacuated from the central region toward the shoulder regions on both sides. This is achieved in particular by the first pair of main grooves connected to each other and to the first pair of consecutive transverse grooves in the region of the axially inner ends of the main grooves. In this way, a network of channels is formed that can collect water and rapidly transport it toward the shoulder regions.

[0091] Additionally, the first pair of main grooves are separated by a second pair of unconnected main grooves, also intended to evacuate water towards the shoulder areas, thereby preventing a weakened central area.

[0092] Finally, the substantially uniform behavior of the tread band with respect to tangential stresses allows the tread pattern of the tire of the present invention to be advantageously used as the basis for a studded tire.

[0093] In the above-described aspects, the present invention can have at least one of the following additional preferred features.

[0094] In some embodiments, each second pair of consecutive main grooves circumferentially bounds a third group of shoulder blocks and a fourth group of shoulder blocks.

[0095] Preferably, the third and fourth shoulder block groups extend from the second shoulder region toward the central region.

[0096] Preferably, the third and fourth shoulder block groups are separated from each other by the fourth main groove.

[0097] Preferably, each second pair of consecutive main grooves circumferentially bounds a second group of central blocks.

[0098] Preferably, the second group of center blocks is separated from the third group of shoulder blocks and the fourth group of shoulder blocks by the sixth main groove.

[0099] This allows the above-mentioned technical advantages to be obtained over the entire tread surface.

[0100] Preferably, the first group of shoulder blocks, the second group of shoulder blocks and the first group of central blocks, taken as a whole, extend from the axial ends of the tread band to or very near the equatorial plane.

[0101] In some embodiments, the first group of shoulder blocks is substantially symmetrical about the equatorial plane relative to the third group of shoulder blocks.

[0102] In some embodiments, the second group of shoulder blocks is substantially symmetrical with respect to the equatorial plane relative to the fourth group of shoulder blocks.

[0103] In some embodiments, the first group of central blocks is substantially symmetrical about the equatorial plane relative to the second group of central blocks.

[0104] In this way, the arrangement of the first shoulder blocks, the second shoulder blocks and the first central blocks is set in a substantially symmetrical manner on both halves of the tread band, which results in a particularly balanced behavior of the tread band.

[0105] In some embodiments, the first group of shoulder blocks is formed by a first pair of shoulder blocks.

[0106] Preferably, the blocks of the first group of shoulder blocks are separated by a first minor groove extending between the first major groove and the third major groove.

[0107] In this way, the blocks forming the first shoulder block group are separated from one another by grooves of shallow depth less than 5 mm, so that they are relatively connected to one another and therefore generally less susceptible to deformation.

[0108] In some embodiments, the first minor groove is parallel to the fifth major groove.

[0109] In some embodiments, the second group of shoulder blocks is formed by a second pair of shoulder blocks.

[0110] Preferably, the blocks of the second shoulder block group are separated by second minor grooves, which extend between the third major groove and the further first major groove that follows the first major groove.

[0111] In this way, the blocks forming the second shoulder block group are separated from one another by grooves of shallow depth less than 5 mm, so that they are relatively connected to one another and therefore generally less susceptible to deformation.

[0112] In some embodiments, the second minor groove is parallel to the fifth major groove.

[0113] In some embodiments, the second minor groove is aligned with the first minor groove.

[0114] This provides a single outflow direction for water from the first and second shoulder block groups towards the first and third main grooves, facilitating rapid evacuation therefrom when driving on wet roads.

[0115] In some embodiments, the first group of central blocks is formed by a first pair of central blocks.

[0116] Preferably, the blocks of the first central group are separated by a third minor groove.

[0117] In this way, the blocks forming the first central group of blocks are separated from one another by grooves of shallow depth, less than 5 mm, so that they are relatively connected to one another and therefore generally less susceptible to deformation.

[0118] Preferably, the third minor groove extends between the first major groove and the fifth major groove.

[0119] Preferably, the third minor groove is inclined in the opposite direction to the fifth major groove.

[0120] Preferably, said third minor groove is aligned with an end of a further second major groove.

[0121] In some embodiments, the first pair of central blocks is formed by a first central block that is axially inward and a second central block that is axially outward relative to the first central block.

[0122] Preferably, the first central block has a V-shape with an apex directed toward the first shoulder region and a pair of branches extending in respective directions toward the second shoulder region at opposite inclinations relative to the circumferential direction.

[0123] Preferably, said second central block has a substantially triangular shape.

[0124] In some embodiments, each third major groove is substantially parallel to said first major groove.

[0125] In some embodiments, each fourth major groove is substantially parallel to said second major groove.

[0126] In some embodiments, the third group of shoulder blocks is formed by a third pair of shoulder blocks.

[0127] Preferably, the blocks of the third group of shoulder blocks are separated by a fourth minor groove, the fourth minor groove extending between the second major groove and the fourth major groove.

[0128] In this way, the blocks forming the third shoulder block group are separated from each other by grooves of shallow depth less than 5 mm, so that they are relatively connected to each other and therefore generally less susceptible to deformation.

[0129] In some embodiments, the fourth minor groove is parallel to the sixth major groove.

[0130] In some embodiments, the fourth group of shoulder blocks is formed by a fourth pair of shoulder blocks.

[0131] Preferably, the blocks of the fourth shoulder block group are separated by a fifth minor groove, which extends between the fourth main groove and the further second main groove that follows the second main groove.

[0132] In this way, the blocks forming the fourth shoulder block group are separated from one another by grooves of shallow depth less than 5 mm, so that they are relatively connected to one another and therefore generally less susceptible to deformation.

[0133] In some embodiments, the fifth minor groove is parallel to the sixth major groove.

[0134] In some embodiments, the fifth minor groove is aligned with the fourth minor groove.

[0135] This provides a single outflow direction for water from the third and fourth shoulder block groups towards the second and fourth main grooves, facilitating rapid evacuation therefrom when driving on wet roads.

[0136] In some embodiments, the second group of central blocks is formed by a second pair of central blocks.

[0137] Preferably, the blocks of the second central block group are separated by a sixth minor groove.

[0138] In this way, the blocks forming the second central group of blocks are separated from one another by grooves of shallow depth, less than 5 mm, so that they are relatively connected to one another and therefore generally less susceptible to deformation.

[0139] Preferably, the sixth minor groove extends between the second major groove and the sixth major groove.

[0140] Preferably, the sixth minor groove is inclined in the opposite direction to the sixth major groove.

[0141] In some embodiments, the second pair of central blocks is formed by a third central block that is axially inward and a fourth central block that is axially outward relative to the third central block.

[0142] Preferably, the third central block has a V-shape with an apex directed toward the second shoulder region and a pair of branches extending in respective directions toward the first shoulder region at opposite inclinations relative to the circumferential direction.

[0143] In this way, the third central block is axially offset relative to the first central block, but in a substantially mirror-like shape.

[0144] Preferably, one branch of each first central block is partially received in a recess in the third central block.

[0145] Preferably, one branch of each third central block is partially received in a recess in the first central block.

[0146] In this way, the first central block and the third central block are partially embedded in each other and assist each other in withstanding tangential stresses.

[0147] Preferably, the apexes of said first central block are circumferentially aligned.

[0148] Preferably, the apexes of said third central blocks are substantially circumferentially aligned.

[0149] Preferably, said fourth central block has a substantially triangular shape.

[0150] Preferably, each of the first main grooves has a first portion in the form of a curve extending from the first shoulder region towards the equatorial plane of the tread band, the first portion in the form of a curve having an inclination relative to the circumferential direction that generally decreases from the first shoulder region towards the central region.

[0151] Preferably, each of the second main grooves comprises a first portion in the form of a curve extending from the second shoulder region towards the equatorial plane of the tread band, the first portion in the form of a curve having a generally decreasing inclination with respect to the circumferential direction from the second shoulder region towards the central region.

[0152] Preferably, the first portion of the first main groove and the first portion of the second main groove are inclined in opposite directions with respect to the circumferential direction.

[0153] In this way, when the tire is rotated in a predetermined direction corresponding to the preferred direction of travel, the evacuation of water from the central region towards the respective shoulder regions is particularly encouraged.

[0154] Preferably, the first portion of each of the first main groove and the second main groove has a curved shape with no inflection points.

[0155] Preferably, the inclination of the first portion of each of the first main groove in the first shoulder region and / or the second main groove in the second shoulder region with respect to the circumferential direction is determined by an angle of 70° to 90°.

[0156] Preferably, the inclination of the first portion of each of the first main groove and / or the second main groove in the central region with respect to the circumferential direction is determined by an angle of 20° to 40°.

[0157] In this way, this promotes rapid evacuation of water from the central region towards the shoulder regions while at the same time maintaining a high level of resistance of the shoulder regions to transverse tangential stresses.

[0158] Preferably, each of the first main grooves has a width that decreases from the first shoulder region toward the equatorial plane.

[0159] Preferably, each of the second main grooves has a width that decreases from the second shoulder region toward the equatorial plane.

[0160] In this way, on the one hand, the outflow of water from the central region towards the respective shoulder regions is promoted, and on the other hand, the rigidity of the first and second central block groups, respectively, is increased.

[0161] Preferably, each of the first main groove, and / or the second main groove, and / or the third main groove, and / or the fourth main groove, and / or the fifth main groove, and / or the sixth main groove has a variable width of 3 mm to 10 mm.

[0162] Preferably, each of the first main groove, and / or the second main groove, and / or the third main groove, and / or the fourth main groove, and / or the fifth main groove, and / or the sixth main groove has a depth of 6 mm to 12 mm, more preferably a depth of 7 mm to 10 mm.

[0163] Preferably, each of the first minor groove, and / or the second minor groove, and / or the third minor groove, and / or the fourth minor groove, and / or the fifth minor groove, and / or the sixth minor groove has a variable width of 2 mm to 5 mm.

[0164] Preferably, each of the first minor groove, and / or the second minor groove, and / or the third minor groove, and / or the fourth minor groove, and / or the fifth minor groove, and / or the sixth minor groove has a depth of 2.5 mm to 4.5 mm.

[0165] Preferably, in each first pair of main grooves, the first main groove and the second main groove are axially offset.

[0166] Preferably, in each second pair of main grooves, the third main groove and the fourth main groove are axially offset.

[0167] This advantageously reduces the noise generated by the tire rolling over the road surface, as the impact of each groove edge with the ground is offset relative to one another, reducing the overall intensity of the generated noise.

[0168] Preferably, the third main groove and the fourth main groove have shapes that are substantially symmetrical with respect to the circumferential direction.

[0169] In some embodiments, the ends of the second main grooves extend across the equatorial plane of the tread band, preferably in a zigzag manner.

[0170] Preferably, the end of the second main groove comprises a first portion extending from the first main groove toward the first shoulder region.

[0171] Preferably, the end of the second main groove includes a second portion extending continuously from the first portion, and more preferably, a second portion extending toward the second shoulder region.

[0172] Preferably, the end of the second main groove comprises a third portion extending subsequent to the second portion, more preferably a third portion extending towards the first shoulder region to the further first main groove.

[0173] Preferably, the first and third portions of the end are substantially parallel.

[0174] In some embodiments, the minor groove has a depth that is less than 50% of the depth of the major groove.

[0175] In some embodiments, the fifth main groove is inclined at an angle of 5° to 25°, preferably about 15°, relative to the circumferential direction.

[0176] In some embodiments, the first minor groove, and / or the second minor groove, and / or the fourth minor groove, and / or the fifth minor groove are inclined at an angle of 5° to 25°, preferably about 15°, relative to the circumferential direction.

[0177] In some embodiments, the third minor groove and / or the sixth minor groove is inclined at an angle of 25° to 45°, preferably about 35°, relative to the circumferential direction.

[0178] In some embodiments, the first group of shoulder blocks, the second group of shoulder blocks, and the first group of central blocks define respective radially outer surfaces, each of the radially outer surfaces having a respective area that differs from an average value of the areas of the radially outer surfaces by less than 30% of the average value, preferably less than 25% of the average value.

[0179] In some embodiments, each block of the shoulder blocks, the second shoulder blocks, and the first central blocks defines a respective radially outer surface, each of the radially outer surfaces of the blocks having a respective area that differs from the average value of the areas of the radially outer surfaces of the blocks by less than 30%, preferably less than 25% of the average value.

[0180] In some embodiments, said tread band defines a tread pattern formed by the totality of all grooves and all blocks, and modules formed by the smallest portions of the tread band extending between the axial ends of the tread band, the configuration being repeated continuously along the circumferential development of the tread band to form said tread pattern.

[0181] Preferably, said module is formed by a tread band portion between two of said first pairs of mutually adjacent main grooves.

[0182] Preferably, the module is formed by a first basic portion extending from the first pair of main grooves to the second pair of main grooves and a second basic portion extending from the second pair of main grooves to the first consecutive pair of main grooves.

[0183] In some embodiments, each of the plurality of sipes is formed in at least some of the blocks defined in said tread band, and more preferably in all of the blocks defined in said tread band.

[0184] In some embodiments, the blocks are provided on at least some of the blocks defined in said tread band.

[0185] The features and advantages of the present invention will be better understood from the detailed description of some preferred exemplary embodiments of the invention, illustrated by way of non-limiting examples with reference to the accompanying drawings, in which: [Brief explanation of the drawings]

[0186] [Figure 1] 1 is a front view of a tire for a vehicle wheel constructed in accordance with the present invention; [Figure 2] FIG. 2 is a partial front view of a first modified configuration example of the tire of FIG. 1. [Figure 3] 2 is a schematic diagram showing an enlarged plan view of a significant portion of the tread band of the tire of FIG. 1; FIG. [Figure 4] 2 is an enlarged schematic view of a portion of the tread band of the tire of FIG. 1 showing the modules of the tread band. FIG. DETAILED DESCRIPTION OF THE INVENTION

[0187] With reference to the accompanying drawings, a tire for a vehicle wheel constructed in accordance with the present invention is shown at 1.

[0188] The tire 1 comprises a conventional tire structure (not shown in the accompanying drawings) and a tread band 2 defining a tread surface 3 located radially outward relative to the tread band 2 and intended to come into contact with the road surface.

[0189] The tire 1 has a conventional toroidal shape extending about an axis of rotation, which defines, in a tread surface 3, an axial direction Y parallel to the axis of rotation, which is passed by an equatorial plane X perpendicular to the axis of rotation, which defines, in the tread surface 3, a circumferential direction parallel to the equatorial plane X.

[0190] The tread band 2 has a width L specified as the maximum width of the tread band intended to come into contact with the ground in normal conditions of use.

[0191] The tire 1 is a directional type tire, which has a preferred rolling direction, indicated by arrow F in the figure.

[0192] The tread band 2 further defines a first shoulder region 4 bounded axially outwardly by a first lateral edge 4a of the tread band 2, a second shoulder region 5 axially opposite the first shoulder region 4 and bounded axially outwardly by a second lateral edge 5a of the tread band 2, and a central region 6 sandwiched between the first shoulder region 4 and the second shoulder region 5 and extending astride the equatorial plane X.

[0193] The tread band 2 defines a plurality of first pairs of main grooves that are arranged continuously and regularly along the circumferential development of the tread band 2 and extend transversely from the shoulder regions 4, 5 on both sides towards the equatorial plane X.

[0194] In particular, each first pair of main grooves is formed by a first main groove 10 extending transversely from the first shoulder region 4 towards the central region 6 and a second main groove 20 extending transversely from the second shoulder region 5 towards the central region 6.

[0195] Each first main groove 10 has a first portion 11 extending from an axially outer end 10a opening at the first side edge 4a of the first shoulder region 4 to an axially inner end 10b opening at the second main groove 20.

[0196] In particular, the first main groove 10 merges with the second main groove 20 immediately after crossing the equatorial plane X. The first portion 11 has the shape of a curve without inflection points, with an inclination relative to the circumferential direction that generally decreases from the first shoulder region 4 toward the central region 6, starting from an inclination of approximately 80° in the region of the axially inner end 10a to an inclination of approximately 30° in the region of the axially inner end 10b.

[0197] Each second main groove 20 has a first portion 21 extending from an axially outer end 20a opening at the second side edge 5a of the second shoulder region 5 to a junction with the axially inner end 10b of the first main groove 10.

[0198] Similar to the first portion 11 of the first main groove 10, the first portion 21 of the second main groove 20 also has a curved shape with no inflection points, with the inclination relative to the circumferential direction decreasing generally from an inclination of approximately 80° in the region of the axially inner end 20 a to an inclination of approximately 30° in the region of the junction with the axially inner end 10 b of the first main groove 10, from the second shoulder region 5 toward the central region 6.

[0199] Each second main groove 20 further has an axially inner end 22 which extends continuously from the first portion 21, following the first main groove 10 which forms a first pair of main grooves together with the second main groove 20, until it opens into the additional first main groove 10 at the axially inner end 20b of the second main groove 20.

[0200] The end 22 of each second main groove 20 has a broken line shape and includes a first portion 23 extending continuously from the first portion 21 toward the first shoulder region 4, a second portion 24 extending continuously from the first portion 23 toward the second shoulder region 5, and a third portion 26 extending continuously from the second portion 24 toward the first shoulder region 4 to the axially inner end 20b. In particular, the third portion 26 merges with the additional first main groove 10 immediately after crossing the equatorial plane X.

[0201] This leaves the first portion 11 of the additional first main groove 10, and therefore the first portion 11 of each first main groove 10, with an inner end region 15 defined therein, bounded by the end 20a of the second main groove 20 and the axially inner end 10b of the first main groove 10.

[0202] The first portion 23, the second portion 24, and the third portion 26 are substantially straight, more specifically, curved with a radius of curvature of 120 mm to 150 mm, extend across the equatorial plane X of the tread band 2, and are alternately inclined in opposite directions relative to the circumferential direction. In particular, the first portion 23 and the third portion 26 are substantially parallel to each other, and the second portion 24 and the inner end region 15 of the first main groove 10 are also substantially parallel.

[0203] Therefore, in this manner, the fold line is formed in a zigzag shape and is defined by the inner end region 15 of the first main groove 10, the first portion 23 of the end 22, the second portion 24 of the end 22, and the third portion 26 of the end 22.

[0204] This polygonal line extends continuously around the entire circumference of the equatorial plane X, and intersects the equatorial plane X at each successive portion of the polygonal line.

[0205] Thus, the first main groove 10 and second main groove 20 of each first pair of main grooves will be of generally similar shape, with the associated portions of the respective first portions 11 and 21 having recesses that are substantially symmetrical about the equatorial plane X and facing the same side of the tread band 2.

[0206] However, the second main grooves 20 are offset axially with respect to the first transverse grooves 10. In fact, their respective axially outer ends 10a and 20a are offset by a value between 5 mm and 20 mm, preferably between 10 mm and 20 mm, measured circumferentially.

[0207] Furthermore, the tread band 2 defines a plurality of second pairs of main grooves arranged consecutively and regularly along the circumferential development of the tread band 2 in alternating positions relative to the first pairs of main grooves 10 and 20.

[0208] Each second pair is formed by a third main groove 30 extending from the first shoulder region 4 toward the central region 6 and a fourth main groove 40 extending from the second shoulder region 5 toward the central region 6.

[0209] In particular, each third main groove 30 extends between an axially outer end 30 a that opens into the first shoulder region 4 and an axially inner end 30 b.

[0210] Similarly, each fourth main groove 40 extends between an axially outer end 40 a that opens into the second shoulder region 5 and an axially inner end 40 a.

[0211] The third and fourth main grooves 30 and 40 are curved shapes that are substantially parallel to the first main groove 10 and the second main groove 20, respectively.

[0212] Furthermore, the third main groove 30 and the fourth main groove 40 are axially offset with respect to one another but are substantially symmetrical with respect to one another about the equatorial plane X. In particular, their respective ends 30a and 40a are offset by a value between 5mm and 20mm, preferably between 10mm and 20mm, measured circumferentially.

[0213] Advantageously, the second portion 24 of the end portion 22 is located on a theoretical extension of the third main groove 30 even if there is no contact point between them.

[0214] Similarly, the third portion 26 of the end portion 22 is also located on a theoretical extension of the fourth main groove 40 .

[0215] The tread band 2 further defines a plurality of third pairs of main grooves arranged continuously and regularly along the circumferential development of the tread band 2 .

[0216] Each third pair is formed by a fifth main groove 50 and a sixth main groove 60, which are axially offset but substantially symmetrical to one another about the equatorial plane X.

[0217] In particular, each fifth main groove 50 extends between two adjacent first main grooves 10 and is connected to the axially inner end 30 b of the third main groove 30 in the central region of the fifth main groove 50 .

[0218] Each fifth main groove 50 is oriented in the same direction as the first main grooves 10 relative to the circumferential direction X, but is inclined at a smaller angle than the first main grooves 10, for example, about 15°.

[0219] Similarly, each sixth main groove 60 extends between two adjacent second main grooves 20 and is connected to the axially inner end 40 b of the fourth main groove 40 in the central region of the sixth main groove 60 .

[0220] Each sixth main groove 60 is inclined in the same direction as the second main grooves 20 relative to the circumferential direction X, but at a smaller angle than the second main grooves 20, for example, about 15°.

[0221] The first main groove 10, second main groove 20, third main groove 30, fourth main groove 40, fifth main groove 50, and sixth main groove 60 all have a depth of approximately 8.5 mm. Furthermore, the first main groove 10, second main groove 20, third main groove 30, and fourth main groove 40 have variable widths that decrease from their respective axially outer ends toward their respective axially inner ends. Specifically, the widths of these main grooves vary from approximately 7 mm to 10 mm in their respective shoulder regions to approximately 3.5 mm to 5 mm in the center region 6.

[0222] The fifth main groove 50 and the sixth main groove 60 have variable widths ranging from 2.5 mm to 4 mm.

[0223] The shape of the main grooves described above defines a number of blocks in the tread band 2, which will be explained in more detail below.

[0224] Each pair of first consecutive main grooves 10 circumferentially bounds a first group of shoulder blocks 110, a second group of shoulder blocks 120 separated from the first group of shoulder blocks 110 by a third main groove 30, and a first group of central blocks 100 separated from the first and second groups of shoulder blocks 110, 120 by a fifth main groove 50.

[0225] Similarly, each pair of second consecutive main grooves 20 circumferentially bounds a third group of shoulder blocks 130, a fourth group of shoulder blocks 140 separated from the third group of shoulder blocks 130 by a fourth main groove 40, and a second group of central blocks 150 separated from the third and fourth groups of shoulder blocks 130, 140 by a sixth main groove 60.

[0226] As a result of the main grooves that define them being substantially symmetrical about the equatorial plane, the third shoulder block group 130, the fourth shoulder block group 140, and the second central block group 150 are substantially symmetrical with respect to the first shoulder block group 110, the second shoulder block group 120, and the first central block group 100, respectively.

[0227] The first central block group 100 and the second central block group 150 are separated from each other by the end 22 of the second main groove 20 .

[0228] It can be noticed that all the blocks are bounded by the major groove and separated from each other, and therefore lie in a relatively deep groove.

[0229] The first shoulder block group 110 is formed by a first pair of shoulder blocks 111 , 112 separated from each other by a first minor groove 16 extending between the first main groove 10 and the third main groove 30 .

[0230] Similarly, the second shoulder block group 120 is formed by a second pair of shoulder blocks 121, 122 separated from each other by a second minor groove 25 extending between the third main groove 30 and an additional first main groove 10 following the first main groove 10.

[0231] The first minor groove 16 and the second minor groove 25 are substantially aligned with one another and are substantially parallel to the fifth major groove 50 .

[0232] The third shoulder block group 130 is formed by a third pair of shoulder blocks 131 , 132 separated from each other by a fourth minor groove 45 extending between the second main groove 20 and the fourth main groove 40 .

[0233] Similarly, the fourth shoulder block group 140 is formed by a fourth pair of shoulder blocks 141, 142 separated from each other by a fifth minor groove 55 extending between the fourth main groove 40 and an additional second main groove 20 following the second main groove 20.

[0234] The fourth minor groove 45 and the fifth minor groove 55 are substantially aligned with each other and are substantially parallel to the sixth major groove 60 .

[0235] The first central block group 100 is also formed by a pair of blocks, in particular a first central block 101 that is axially inner and a second central block 102 that is axially outer relative to the first central block 101 and separated from the first central block 101 by a third minor groove 35.

[0236] The third minor groove 35 extends between the first major groove 10 and the fifth major groove 50 and is inclined in the opposite direction to the fifth major groove 50 at an angle of approximately 35°.

[0237] The first central block 101 has a V-shape with an apex directed toward the first shoulder region 4 and a pair of branches extending in each direction at opposite inclinations relative to the circumferential direction toward the second shoulder region 5.

[0238] The second central block 102 has a substantially triangular shape with its longest side facing the axially inner blocks 112 and 122 of the first and second shoulder block groups 110 and 120, respectively.

[0239] Similarly, the second central block group 150 is formed by a third central block 151 that is axially inner and a fourth central block 152 that is axially outer relative to the third central block 151 and separated from the third central block 151 by a sixth minor groove 65.

[0240] The sixth minor groove 65 extends between the second major groove 20 and the sixth major groove 60 and is inclined in the opposite direction to the sixth major groove 60 at an angle of approximately 35°.

[0241] The third central block 151 has a V-shape with an apex directed toward the second shoulder region 5 and a pair of branches extending in each direction toward the first shoulder region 4 at opposite inclinations relative to the circumferential direction.

[0242] The fourth central block 152 has a substantially triangular formation with its largest side facing the axially inward blocks 132, 142 of the third and fourth shoulder block groups 130, 140, respectively.

[0243] The fourth minor groove 45, the fifth minor groove 55, and the sixth minor groove 65 are substantially symmetrical to the first minor groove 16, the second minor groove 25, and the third minor groove 35, respectively, about the equatorial plane X, but are axially offset relative to one another.

[0244] In this way, each block is substantially symmetrical about the equatorial plane relative to the other blocks of the tread band 2.

[0245] In particular, each third central block 151 is axially offset relative to the first central block 101 but has a substantially mirror-like shape.

[0246] Each third central block 151 and each first central block 101 have respective recesses directed towards each other and are further partially aligned not only in the axial direction Y but also in the circumferential direction X. In other words, the respective circumferential protrusions of the first central block 101 and the third central block 151 partially overlap. In particular, the branch portions of each first central block 101 are partially received in the recesses of the third central block 151, and conversely, the branch portions of each third central block 151 are partially received in the recesses of the first central block 101.

[0247] The first minor groove 16, the second minor groove 25, the third minor groove 35, the fourth minor groove 45, the fifth minor groove 55, and the sixth minor groove 65 all have a depth of about 4 mm and a variable width between about 2.5 mm and 4 mm.

[0248] The above-identified blocks and grooves generally define the tread pattern of tire 1.

[0249] The tread pattern is formed by the continuous, uninterrupted repetition of a single module M formed by the tread band portion between the first successive pairs of two main grooves 10 and 20.

[0250] Each module M is formed by a first basic portion extending from a first pair of main grooves 10 and 20 to a second pair of main grooves 30 and 40, and a second basic portion extending from the second pair of main grooves 30 and 40 to a consecutive first pair of main grooves 10 and 20.

[0251] Each first elementary portion and each second elementary portion may have a circumferential dimension corresponding to the major pitch or a value corresponding to a minor pitch that is shorter than the major pitch.

[0252] In particular, the long pitch is about 30% longer than the short pitch.

[0253] Each module M can be formed by first and second basic portions having a short or long pitch combined with each other in various ways so as to provide in the tread pattern a module in which the first and second basic portions both have a long pitch, a module in which the first and second basic portions both have a short pitch, a module in which the first basic portion has a short pitch and the second basic portion has a long pitch, or a module in which the first basic portion has a long pitch and the second basic portion has a short pitch.

[0254] All of the blocks listed above have sipes formed in them that increase the tire's performance level in snowy road conditions.

[0255] In particular, the blocks of the first block group 100 and the second block group 150 are formed with sipes that extend substantially in the axial direction Y, while the axially inner blocks of the shoulder block groups 110, 120, 130, and 140 are formed with sipes that extend transversely to the main direction of block extension (defined by the direction of extension of the first or second main groove), and the axially outer blocks of the shoulder block groups 110, 120, 130, and 140 are formed with sipes that extend substantially parallel to the main direction of block extension (defined by the direction of extension of the first or second main groove).

[0256] The tread band 2 of the tire 1 may further be provided with a plurality of studs 200 at suitable positions in different blocks, as can be seen in the different structure of the tire 1 shown in Figure 2, in order to make it particularly suitable for driving on icy roads.

[0257] Each shoulder block group and each central block group remains defined with a respective radially outer surface that actually constitutes part of the tread surface 3 .

[0258] As a result of the above groove and block configuration, each of the radially outer surfaces of the first shoulder block group 110, the second shoulder block group 120, and the first central block group 100 differs from the average value of the radially outer surfaces by less than 25%.

[0259] Not only this, but the individual blocks forming the different shoulder groups also have respective radially outer surfaces that differ by less than 25% from the average value of the radially outer surfaces of those blocks.

[0260] Obviously, as a result of the above symmetrical relationship, the same relationship between the radially outer surfaces also applies to the third and fourth shoulder block groups 130, 140, as well as the second central block group 150.

[0261] In this way, the tread band 2 is subdivided by the main grooves into contact areas (blocks) with the road surface, each having a substantially uniform area.

[0262] This allows the tread band to react substantially uniformly to tangential stresses, preventing excessive localized deformations that could impair the roadholding of the tire 1 and, in the case of studded tires, reducing the likelihood of the studs coming out of their seats. [Example]

[0263] A tire of size 205 / 55R16 was constructed in accordance with the above-described embodiment of the invention.

[0264] Table 1 below shows the radially outer surface dimensions of the first shoulder block group 110, the second shoulder block group 120, and the first central block group 100, as well as the percentage difference in surface dimensions of each block group relative to the average surface dimensions.

[0265] For the specific tire used here, this average value is approximately 1185 mm 2 is.

[0266] [Table 1]

[0267] It will be noted that the radially outer surfaces of the individual blocks vary from the average value of the surface by a percentage value of less than 25% of the average value, so that each block moves in contact with the road surface with a surface having substantially the same size, thereby providing substantially uniform resistance to tangential stresses.

[0268] Table 2 below shows the size of each of the radially outer surfaces of the individual blocks forming the first shoulder block group 110, the second shoulder block group 120, and the first central block group 100, as well as the percentage difference of each block size from the average block size.

[0269] In this particular case, this average value is approximately 593 mm 2 is.

[0270] [Table 2]

[0271] Again, it can be noted that the radially outer surfaces of the individual blocks in each group of blocks differ from the average surface value by a percentage value of less than 25% of the average value, so that each block comes into contact with the road surface at a surface substantially equal to that of the other blocks, thereby providing a substantially uniform resistance to tangential stresses.

[0272] Table 3 below shows the stiffness values ​​calculated by finite element simulation of the first shoulder block group 110, the second shoulder block group 120, and the first central block group 100, as well as the percentage difference of each block group's stiffness value from the average stiffness value. Stiffness value is defined as the ratio of the reaction force a block exerts on the road surface to the movement of the block itself.

[0273] [Table 3]

[0274] It can therefore be observed that the blocks have roughly similar stiffness values ​​both when the tangential stresses they are subjected to are axial and when these tangential stresses are circumferential.

[0275] This uniformity of stiffness values ​​between the different block groups is reflected in a uniform behavior of the tread band and gives the tire several important advantages, including better roadholding regardless of the road surface, better results in terms of tire wear, and (in the case of studded tires) greater support for the studs, which manifests itself as a greater holding capacity of the studs and a greater grip efficiency on icy roads.

Claims

1. A tire for a vehicle wheel comprising a tread band (2), said tread band (2) comprising: - a first shoulder region (4) and a second shoulder region (5) axially opposite each other; a central region (6) sandwiched between said first shoulder region (4) and said second shoulder region (5); a plurality of first pairs of main grooves regularly and successively arranged along the circumferential development of said tread band, each first pair comprising: i. a first main groove (10) extending from the first shoulder region (4) towards the central region (6), the inclination of which with respect to the circumferential direction decreases from the first shoulder region (4) towards the central region (6); ii. a second main groove (20) extending from the second shoulder region (5) toward the central region (6), the inclination of which with respect to the circumferential direction decreases from the second shoulder region (5) toward the central region (6); is formed by a plurality of first pairs of main grooves, each of which has an axially inner end (10b) connected to the second main groove (20), and each of which has an end (22) that is axially inner and extends between the first main groove (10) and a further first main groove belonging to a subsequent first pair of main grooves; a plurality of second pairs of main grooves arranged regularly and successively along the circumferential development of said tread band in alternating positions with respect to said first pairs of main grooves (10, 20), each second pair comprising: i. a third main groove (30) extending from the first shoulder region (4) towards the central region (6), the inclination of which with respect to the circumferential direction decreases from the first shoulder region (4) towards the central region (6); ii. a fourth main groove (40) extending from the second shoulder region (5) towards the central region (6), the inclination of which with respect to the circumferential direction decreases from the second shoulder region (5) towards the central region (6); a plurality of second pairs of major grooves formed by a plurality of third pairs of main grooves regularly and successively arranged along the circumferential development of said tread band, each third pair of main grooves having: i. a fifth main groove (50) extending between two first main grooves (10) of the first pair of main grooves that are continuous with each other, connected to the axially inner end (30b) of the third main groove (30), and having an inclination with respect to the circumferential direction that is smaller than that of the first main groove (10) and that is in the same direction as that of the first main groove (10); ii. a sixth main groove (60) extending between two second main grooves (20) of the first pair of main grooves that are continuous with each other, connected to the axially inner end (40b) of the fourth main groove (40), and having an inclination with respect to the circumferential direction that is smaller than that of the second main groove (20) and that is oriented in the same direction as that of the second main groove (20); is formed by a plurality of third pairs of main grooves, each pair of consecutive first main grooves (10) circumferentially delimiting a first group of shoulder blocks (110) and a second group of shoulder blocks (120) both extending from the first shoulder region (4) toward the central region (6) and separated from one another by the third main groove (30), and a first group of central blocks (100) separated from the first group of shoulder blocks (110) and the second group of shoulder blocks (120) by the fifth main groove (50); is defined, the tire.

2. 2. The tire of claim 1, wherein each pair of consecutive second main grooves (20) circumferentially bounds a third group of shoulder blocks (130) and a fourth group of shoulder blocks (140) extending from the second shoulder region (5) toward the central region (6) and separated from one another by the fourth main groove (40), and a second group of central blocks (150) separated from the third group of shoulder blocks (130) and the fourth group of shoulder blocks (140) by the sixth main groove (60).

3. 3. The tire of claim 2, wherein the first shoulder block group (110), the second shoulder block group (120), and the first central block group (100) are substantially symmetrical about the equatorial plane relative to the third shoulder block group (130), the fourth shoulder block group (140), and the second central block group (150), respectively.

4. 2. The tire of claim 1, wherein the first shoulder block group (110) is formed by a first pair of shoulder blocks (111, 112) separated by a first minor groove (16) extending between the first main groove (10) and the third main groove (30).

5. A tire according to claim 4, wherein said first minor groove (16) is parallel to said fifth major groove (50).

6. 2. A tire according to claim 1, wherein the second shoulder block group (120) is formed by a second pair of shoulder blocks (121, 122) separated by a second minor groove (25) extending between the third main groove (30) and the further first main groove following the first main groove (10).

7. A tire according to claim 6, wherein said second minor groove (25) is parallel to said fifth major groove (50).

8. A tyre according to claim 6 or 7, wherein said second minor groove (25) is aligned with said first minor groove (16).

9. 2. A tire according to claim 1, wherein said first group of central blocks (100) is formed by a first pair of central blocks (101, 102) separated by a third minor groove (35).

10. 10. Tyre according to claim 9, wherein said third minor groove (35) extends between said first main groove (10) and said fifth main groove (50).

11. A tire according to claim 9 or 10, wherein said third minor groove (35) is inclined inversely relative to said fifth major groove (50).

12. 10. Tyre according to claim 9, wherein said third minor groove (35) is aligned with said end of a further second major groove.

13. 2. A tire according to claim 1, wherein each third main groove (30) is substantially parallel to said first main groove (10).

14. 2. The tire of claim 1, wherein each fourth main groove (40) is substantially parallel to said second main groove (20).

15. 2. A tire according to claim 1, wherein the ends (22) of the second main grooves (20) extend in a zigzag manner across the equatorial plane (X) of the tread band (2).

16. 2. A tire according to claim 1, wherein the end (22) of the second main groove (20) comprises a first portion (23) extending from the first main groove (10) towards the first shoulder region (4), a second portion (24) extending contiguously with the first portion (23) towards the second shoulder region (5), and a third portion (26) extending contiguously with the second portion (24) towards the first shoulder region (4) to the further first main groove.

17. 17. A tire according to claim 16, wherein said first portion (23) and said third portion (26) of said end (22) are substantially parallel.

18. 5. The tire of claim 4, wherein each of said minor grooves has a depth that is less than 50% of the depth of each of said major grooves.

19. 2. The tire according to claim 1, wherein said fifth main groove (50) is inclined at an angle of 5° to 25° with respect to said circumferential direction.

20. 2. The tire according to claim 1, wherein the third minor groove (35) is inclined at an angle of 25° to 45° with respect to the circumferential direction.

21. 2. The tire of claim 1, wherein the first group of shoulder blocks (110), the second group of shoulder blocks (120), and the first group of central blocks (100) define respective radially outer surfaces, each of the radially outer surfaces having a respective area that differs from an average value of the areas of the radially outer surfaces by less than 30% of the average value.

22. 2. The tire of claim 1, wherein each block of the shoulder block group (110), the second shoulder block group (120), and the first central block group (100) defines a respective radially outer surface, and each of the radially outer surfaces of the blocks has a respective area that differs from an average value of the areas of the radially outer surfaces of the blocks by less than 30% of the average value.

23. 2. The tire of claim 1, wherein each main groove has a depth of from 6 mm to 12 mm.

24. 5. The tire of claim 4, wherein each minor groove has a depth of from 2.5 mm to 4.5 mm.

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