Tyre for vehicle wheels

Abstract

The present application relates to a tyre for a vehicle wheel, the tyre comprising a tread band (2) on which are defined: a plurality of first sets of shoulder blocks (110) extending from a first shoulder region (4) of the tread band (2) towards a central region (6); a plurality of second set of shoulder blocks (120) extending from the first shoulder region (4) towards the central region (6) and alternating with the first set of shoulder blocks (110); and a plurality of first set of central blocks (100) adjacent to and axially inward of the respective first set of shoulder blocks (110) and the respective second set of shoulder blocks (120), and a plurality of first set of central blocks (100) adjacent to and axially inward of the respective first set of shoulder blocks (110) and the respective second set of shoulder blocks (120). The groups of blocks (110, 120, 100) are separated from each other by at least one main groove (10, 30, 50), while the blocks (111, 112; 121, 122; 101, 102) are separated by at least one secondary trench (16, 25, 35). The area of the respective radially outer surfaces of each group of block bodies differs from an average value of the areas of these radially outer surfaces by a value less than 30% of the average value.

Description

Technical Field

[0001] The present invention relates to a tire for a vehicle wheel, in particular to a winter tire. Background Art

[0002] A tyre generally comprises a carcass structure shaped annularly about an axis of rotation and comprising at least one carcass ply having end flaps engaged in respective annular anchoring structures, called bead cores.

[0003] In a radially external position with respect to the carcass structure, a belt structure is provided which, in the case of a car tyre, comprises at least two radially superposed strips of rubberised fabric provided with reinforcing cords (generally made of metal) arranged parallel to one another in each strip but in a crossed manner with respect to the reinforcing cords of adjacent strips, preferably symmetrically with respect to the equatorial plane of the tyre.

[0004] In a radially external position, the belt structure preferably also comprises a third layer of textile or metal cords arranged circumferentially (0 degrees) at least below the ends of the belt strips. In tubeless type tires, there is also a radially internal layer called a liner, which has impermeable properties to ensure the airtightness of the tire itself.

[0005] In a radially outer position with respect to the belt structure, there is applied a tread band made of elastomeric material and defining thereon a tread surface intended to come into contact with the road surface.

[0006] In order to ensure sufficient road grip even on wet road surfaces, the tread band of the tyre is provided with grooves of various shapes and geometries, which grooves delimit portions of the tread band intended to come into contact with the ground, said portions being called blocks.

[0007] The main function of the grooves is to allow the drainage of water present between the tire surface and the road surface during their mutual contact, thereby preventing the hydrostatic pressure generated by the impact of water on the advancing tire from causing the tire to be lifted off the road surface or even partially and resulting in loss of control of the vehicle.

[0008] In the case of winter tires, small indentations called "sipes" are generally formed on the blocks of the tread band, extending from the tread surface of the tire towards the interior of the blocks. The function of the sipes is to provide additional grip elements in the case of driving on snow-covered roads and to retain a certain amount of snow, thereby improving grip on the road surface.

[0009] Furthermore, the blocks of the tread band may be provided with studs which improve the grip properties on icy roads due to a portion of the stud protruding from the tread.

[0010] The overall configuration of the tread band defined by all of the grooves and blocks constitutes the tread pattern.

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

[0012] The term "circumferential" direction is understood to mean a direction substantially parallel to the direction of rotation of the tyre or a direction at most slightly inclined (at most about 5°) relative to the direction of rotation of the tyre.

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

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

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

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

[0017] The term "shoulder regions" of the tread band refers to those tread band portions which extend circumferentially in axially outer positions of the tread band, at opposite sides of the central region, up 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" refers to a recess formed in the tread band portion and having a width greater than or equal to 1.5 mm.

[0020] A groove is called a “circumferential” groove when it extends in the circumferential direction or is at most inclined at an angle of less than 5° relative to the circumferential direction.

[0021] A groove is called a "transverse" groove when it extends in a direction inclined at an acute angle of at least greater than 10° with respect to the circumferential direction.

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

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

[0024] If the width of a groove or sipe varies along its longitudinal extent, the average width is taken into account, the value of which is obtained as the average of the different width values ​​appropriately weighted according to the relative longitudinal extent. For example, if a groove has a width of 5 mm over 80% of its longitudinal extent and a width of 3 mm over the remaining 20%, the average value of the width to be taken into account would be equal to 5×0.8+3×0.2=4.6 mm.

[0025] Similarly, if the width of the grooves, in particular the transverse grooves, varies along the tread band according to the length of the pitch to which they belong, the average value is taken into account.

[0026] A groove is defined as a "main" groove when its depth is at least 5 mm. Preferably, the width of the main groove is at least 3 mm.

[0027] When the groove depth is less than 5 mm, the groove is defined as a "secondary" groove. Preferably, the width of the secondary groove is less than 4 mm.

[0028] The inclination of the grooves relative to the circumferential direction defined on the tread band is defined by the acute angle that the grooves make with the circumferential direction. As a special case, the inclination of the grooves extending parallel to the tire axis relative to the circumferential direction is 90°.

[0029] Two (or more) transverse grooves are inclined "in a uniform manner" if, when considered in a Cartesian plane (with the ordinate axis parallel to the circumferential direction and the transverse axis parallel to the axis of the tire) positioned on (tangent to) the tread band, they have a direction that is either increasing or decreasing.

[0030] Therefore, when considered in this Cartesian plane, the two transverse grooves are inclined in an “uneven manner” when their course is increasing for one groove and decreasing for the other groove.

[0031] Two grooves are “substantially aligned” when the longitudinal axes of the two grooves are offset by less than the maximum groove width, at least in the region of their mutually facing ends.

[0032] Two grooves are "consecutive" when they are arranged one after the other on the tread surface, taking into account rotation of the tire in either of its two directions of rotation. In particular, two grooves of the same configuration are consecutive when no other groove of the same configuration is arranged between them.

[0033] In particular, a plurality of grooves may be arranged on the tread band in a "regular succession" manner along the circumferential extension of the tread band when the grooves are arranged one after the other according to a predetermined pattern of circumferential distances.

[0034] The term "block" is intended to be understood as a tread band portion delimited by at least one groove, preferably by at least two distinct grooves, wherein on the radially outer surface is defined the tread band portion intended for contact with the road surface.

[0035] Thus, a block is considered to be a portion of the tread band having a closed outline defined by three or more grooves and a circumferential rib defined 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", whereas 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 a set of blocks is calculated without taking into account the surface affected by possible internal grooves relative to the set of blocks.

[0038] The term "tread pattern" is intended to mean the overall configuration of the tread band defined by the combination of grooves and blocks, the blocks being delimited by the grooves.

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

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

[0041] Furthermore, while maintaining the same basic configuration, the modules may have slightly different circumferential dimensions (called "pitch") from each other, for example modules with two, three or four different pitches may be used on the tread band, these modules being combined with each other in various ways.

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

[0043] In this case, provision is made for each basic portion to have the same basic configuration in different modules, but with circumferential dimensions (that is to say "pitch") that differ slightly from one another, so that each module can be formed from basic portions having a different pitch.

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

[0045] The lengths of two or more elements are "substantially equal" when the respective lengths of the two or more elements differ from each other by a range equal to at most 10% of the maximum length.

[0046] Two or more elements or groups of elements are considered "substantially symmetrical" with respect to a plane of symmetry even if they are slightly offset relative to one another in a direction parallel to the plane of symmetry. For example, two grooves or two blocks or two groups of blocks are symmetrical with respect to the equatorial plane even if the circumferential spacing between them is less than the pitch of the tread pattern, where the pitch may correspond, for example, to the circumferential distance between two consecutive main grooves. In absolute terms, the circumferential distance between two substantially symmetrical elements is less than 50 mm, preferably less than 40 mm.

[0047] Two elements, such as for example two blocks or two grooves, are "axially offset" or "offset relative to the axial direction" when they are spaced from each other in the circumferential direction of the tread band. Summary of the Invention

[0048] The Applicant has initially observed that the performance level of a tire on snow-covered roads depends in a corresponding manner on the number and extent of the sipes formed on the blocks. In particular, the Applicant has noted that, for the same tread pattern, blocks with more sipes offer better behavior on snow.

[0049] However, the Applicant has also observed that the presence of the sipes weakens the structure of the block, making it less rigid and therefore reducing its ability to withstand external stresses, in particular tangential stresses.

[0050] Due to this weakening, the block may deform to a corresponding extent under braking, acceleration or cornering, thereby causing the block to be partially lifted from the road surface, resulting in a reduction in the contact area between the block and the road surface, and thus reducing the total friction exerted by the tire on the road surface.

[0051] Furthermore, the Applicant has observed that the lower stiffness of the blocks may also have a negative impact on the performance level of the studded tyre.

[0052] In fact, the Applicant has demonstrated that studs fixed to highly deformable blocks not only provide less effective grip on icy roads, but are also more likely to be pulled out of their seats more easily, causing the stud to become detached from the tread band and therefore leading to an irreversible loss of efficiency when driving on icy roads.

[0053] In fact, the Applicant has demonstrated that the ability of the tyre to retain the studs in seats properly positioned in the tread band is a key parameter for the studded tyre to obtain an adequate level of performance during its service life.

[0054] The Applicant has also observed that responding to this requirement is usually achieved by shaping and dimensioning the receiving seat of the cleat and the portion of the cleat intended to be received in this seat so as to interfere with a large degree of movement that may occur when the cleat leaves the seat.

[0055] However, the Applicant has verified that these arrangements have limitations and may not be sufficient due to the need to insert the studs into the respective seats during the tyre production steps.

[0056] The Applicant has therefore considered that, in order to improve the efficiency of the gripping behavior of the stud and its ability to remain in the seat, the tread pattern may advantageously be configured so as to limit as much as possible excessive local deformations of the tread band, and in particular of the individual blocks.

[0057] To achieve this, the Applicant believes that the tread pattern must be configured not only to have the highest possible stiffness properties, but also to make the stiffness as uniform as possible in the different areas of the tread band, thereby distributing possible tangential stresses in the most uniform way possible.

[0058] In order to meet these two requirements without compromising the ability to drain water from the tread band, the Applicant has considered that it would be possible to use grooves of greater depth defining a relatively wide area on the tread band and within said large area grooves of lesser depth defining two or more blocks.

[0059] The Applicant has thus gained greater freedom in designing the tread pattern, being able to configure large areas formed by blocks having mutually homogeneous properties (e.g. similar surface extent), even in the presence of blocks that individually may differ greatly from each other.

[0060] Finally, the Applicant has found that by defining on the tread band a first group of shoulder blocks and a second group of shoulder blocks alternating circumferentially relative to each other and a first group of central blocks situated axially inside and adjacent to the two groups of shoulder blocks, all said blocks being separated from each other by one or more main grooves, that is to say, having a large depth, and the individual blocks situated within each group of blocks being separated from each other by one or more secondary grooves, that is to say, having a reduced depth, a tread pattern is obtained which is suitable for withstanding tangential stresses in a uniform manner, thereby preventing excessive local deformation of the blocks and thereby increasing the ability to retain the studs in the respective receiving seats.

[0061] In particular, the present invention relates, in one of its aspects, to a tyre for vehicle wheels comprising a tread band.

[0062] Preferably, the tread band has defined thereon first and second shoulder regions axially opposite to each other and a central region interposed between the first and second shoulder regions.

[0063] Preferably, a first plurality of shoulder blocks are defined on the tread band.

[0064] Preferably, each first set of shoulder blocks extends from said first shoulder region towards said central region of said tread band.

[0065] Preferably, a second plurality of shoulder blocks are defined on the tread band.

[0066] Preferably, each second set of shoulder blocks extends from said first shoulder region towards said central region of said tread band.

[0067] Preferably, each shoulder block of the first group and each shoulder block of the second group are arranged alternately one after the other along the circumferential development of said tread band.

[0068] Preferably, a first plurality of central blocks is defined on the tread band, said first plurality of central blocks being arranged successively along the circumferential extension of said tread band.

[0069] Preferably, each center block of the first group is adjacent to and located in an axially inner position relative to a respective first group of shoulder blocks and a respective second group of shoulder blocks.

[0070] Preferably, the blocks of each first set of shoulder blocks are separated from each other by at least one secondary groove.

[0071] Preferably, the blocks of each second set of shoulder blocks are separated by at least one secondary groove.

[0072] Preferably, the blocks of each first group of central blocks are separated from each other by at least one secondary groove.

[0073] Preferably, each of the second group of shoulder blocks is separated from the two adjacent groups of the first group of shoulder blocks by at least one main groove.

[0074] Preferably, each of the first group of center blocks and the adjacent first and second groups of shoulder blocks are separated by at least one main groove.

[0075] Preferably, respective radially outer surfaces are defined on the first set of shoulder blocks, the second set of shoulder blocks and the first set of center blocks, 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.

[0076] The Applicant believes that a tyre constructed according to the above-described aspect of the invention advantageously allows obtaining a substantially uniform behaviour in the different zones of the tread band when subjected to tangential stresses, whether axial or circumferential.

[0077] The tyre thus has an optimal behaviour on mutually different road surfaces (on wet roads and on dry roads, as well as on snow-covered roads or on icy roads) in which the tread band is provided with sipes and studs.

[0078] Furthermore, the substantial uniformity of the tread band's behavior with respect to tangential stresses allows the advantageous use of the tread pattern of the tire of the invention as an effective basis for a studded tire. Indeed, by avoiding the presence of localized areas of high deformability, each block has a uniform stiffness, thereby increasing the ability to retain the stud in the corresponding seat by preventing the loss of the stud.

[0079] In the above aspects, the present invention may have at least one of the additional preferred features noted below.

[0080] In some embodiments, each of the areas of the radially outer surface differs from the average by less than 25% of the average.

[0081] In some embodiments, a third plurality of shoulder blocks are further defined on said tread band, said third plurality of shoulder blocks being arranged successively along the circumferential extension of said tread band.

[0082] Preferably, each third set of shoulder blocks extends from said second shoulder region towards said central region.

[0083] In some embodiments, a fourth plurality of shoulder blocks are further defined on said tread band, said fourth plurality of shoulder blocks being arranged successively along the circumferential extension of said tread band.

[0084] Preferably, each fourth group of shoulder blocks extends from said second shoulder region towards said central region.

[0085] Preferably, each shoulder block of the fourth group is arranged along the circumferential development of said tread band in a position alternating with one of the shoulder blocks of said third group.

[0086] In some embodiments, a second plurality of central blocks is further defined on said tread band, said second plurality of central blocks being arranged successively along the circumferential extension of said tread band.

[0087] Preferably, each center block of the second group is adjacent to and located in an axially inner position relative to a respective third group of shoulder blocks and a respective fourth group of shoulder blocks.

[0088] Preferably, the blocks of each third group of shoulder blocks are separated from each other by at least one secondary groove.

[0089] Preferably, the blocks of each fourth group of shoulder blocks are separated from each other by at least one secondary groove.

[0090] Preferably, the blocks of each second group of central blocks are separated from each other by at least one secondary groove.

[0091] Preferably, each of the fourth group of shoulder blocks is separated from the two adjacent groups of the third group of shoulder blocks by at least one main groove.

[0092] Preferably, each of the second group of center blocks is separated from the third group of shoulder blocks and the fourth group of shoulder blocks adjacent thereto by at least one main groove.

[0093] Preferably, respective radially outer surfaces are defined on the third set of shoulder blocks, the fourth set of shoulder blocks and the second set of centre blocks.

[0094] Preferably, each of said radially outer surfaces has a respective area that differs from an average value of the areas of said radially outer surfaces by less than 30% of said average value.

[0095] In some embodiments, each of the third set of shoulder blocks is substantially symmetrical with respect to the first set of shoulder blocks, except for the axial offset.

[0096] In some embodiments, each of the fourth group of shoulder blocks is substantially symmetrical relative to the second group of shoulder blocks, except for the axial offset.

[0097] In some embodiments, each of the second set of central blocks is substantially symmetrical relative to the first set of central blocks, except for the axial offset.

[0098] In this way, the configuration of the first set of shoulder blocks, the second set of shoulder blocks and the first set of central blocks are arranged in a substantially symmetrical manner on the two halves of the tread band, thereby obtaining a particularly balanced behaviour of the tread band.

[0099] In some embodiments, a plurality of first pairs of main grooves are defined on said tread band, said plurality of first pairs of main grooves extending from said first and second shoulder regions towards said central region and arranged in a regular, successive manner along the circumferential extension of said tread band.

[0100] Preferably, a plurality of second pairs of main grooves are defined on said tread band, said plurality of second pairs of main grooves extending from said first and second shoulder regions towards said central region and arranged in a regular successive manner along the circumferential development of said tread band.

[0101] Preferably, the second pair of main grooves are arranged in alternating positions relative to the first pair of main grooves.

[0102] In some embodiments, the plurality of first pairs of main grooves and the plurality of second pairs of main grooves separate the plurality of first groups of shoulder blocks from the plurality of second groups of shoulder blocks.

[0103] In some embodiments, the plurality of first pairs of main grooves and the plurality of second pairs of main grooves separate the plurality of third groups of shoulder blocks from the plurality of fourth groups of shoulder blocks.

[0104] Preferably, each first pair of main grooves 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.

[0105] More preferably, the first main groove includes an axially inner end portion connected to the second main groove.

[0106] In some embodiments, the second main groove includes an end portion that is axially inward and extends between the first main groove and another first main groove belonging to a subsequent first pair of main grooves.

[0107] Preferably, the end portion separates the first group of central blocks from the second group of central blocks.

[0108] In some embodiments, 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.

[0109] In some embodiments, each third main trench is substantially parallel to the first main trench.

[0110] In some embodiments, each fourth main trench is substantially parallel to the second main trench.

[0111] In some embodiments, a plurality of third pairs of main grooves are defined on said tread band, said plurality of third pairs of main grooves being arranged in a regular, successive manner along the circumferential extension of said tread band.

[0112] Preferably, each third pair of main grooves is formed by a fifth main groove and a sixth main groove.

[0113] Preferably, the fifth main groove separates the first group of center blocks from the first group of shoulder blocks and from the second group of shoulder blocks.

[0114] Preferably, the sixth main groove separates the second group of center blocks from the third group of shoulder blocks and from the fourth group of shoulder blocks.

[0115] Preferably, the fifth main groove extends between two first main grooves of the first pair of main grooves that are consecutive to each other.

[0116] Preferably, the fifth main groove is connected to an axially inner end portion of the third main groove.

[0117] Preferably, the fifth main groove has an inclination with respect to the circumferential direction that is smaller than that of the first main groove. Preferably, the fifth main groove has an inclination that is consistent with that of the first main groove.

[0118] Preferably, the sixth main groove extends between two second main grooves of the first pair of main grooves that are consecutive to each other.

[0119] Preferably, the sixth main groove is connected to an axially inner end portion of the fourth main groove.

[0120] Preferably, the sixth main groove has an inclination with respect to the circumferential direction that is smaller than that of the second main groove.

[0121] Preferably, the sixth main groove has an inclination consistent with that of the second main groove.

[0122] Preferably, the first main groove and the third main groove extend from the first shoulder region toward the center region and have an inclination decreasing from the first shoulder region toward the center region with respect to the circumferential direction.

[0123] Preferably, the second main groove and the fourth main groove extend from the second shoulder region toward the center region and have an inclination that decreases from the second shoulder region toward the center region with respect to the circumferential direction.

[0124] In some embodiments, each first group of shoulder blocks is formed by a first pair of shoulder blocks separated by a first sub-groove.

[0125] In this way, the blocks forming the first group of shoulder blocks are separated from each other by grooves of small depth (less than 5 mm) to be relatively connected to each other and thus the overall deformation is small.

[0126] Preferably, the first sub-groove extends between the first main groove and the third main groove.

[0127] Preferably, the first primary groove is parallel to the fifth main groove.

[0128] In some embodiments, each second group of shoulder blocks is formed by a second pair of shoulder blocks separated by a secondary groove.

[0129] In this way, the blocks forming the second group of shoulder blocks are separated from each other by grooves of small depth (less than 5 mm) to be relatively connected to each other and thus the overall deformation is small.

[0130] Preferably, the secondary secondary groove extends between the third main groove and the further first main groove subsequent to the first main groove.

[0131] Preferably, the secondary groove is parallel to the fifth main groove.

[0132] Preferably, the secondary grooves are aligned with the primary grooves.

[0133] In this way, a single outflow direction of water from the first and second groups of shoulder blocks toward the first and third main grooves is defined, thereby promoting rapid drainage of water in the event of running on a wet road surface.

[0134] In some embodiments, the first set of center blocks is formed by a first pair of center blocks separated by a third trench.

[0135] In this way, the blocks forming the first group of central blocks are separated from each other by grooves of small depth (less than 5 mm) to be relatively connected to each other and thus the overall deformation is small.

[0136] Preferably, the third tertiary groove extends between the first main groove and the fifth main groove.

[0137] Preferably, the third tertiary groove is inclined in a non-uniform manner relative to the fifth main groove.

[0138] In some embodiments, the first pair of central blocks is formed by a first central block located axially on the inner side and a second central block located axially on the outer side relative to the first central block.

[0139] Preferably, the first center block has a V-shaped configuration and comprises: an apex directed toward the first shoulder region; and a pair of branches extending toward the second shoulder region in respective directions oppositely inclined relative to the circumferential direction.

[0140] Preferably, the second central block has a generally triangular shape.

[0141] In some embodiments, a corresponding radially outer surface is defined on each block of the first group of shoulder blocks, the second group of shoulder blocks and the first group of center blocks, and each of the radially outer surfaces of the blocks has a corresponding area that differs from the average value of the areas of the radially outer surfaces of the blocks by less than 30% of the average value, preferably less than 25% of the average value.

[0142] Preferably, the first set of shoulder blocks, the second set of shoulder blocks and the first set of centre blocks, when considered as a whole, extend from one axial end of the tread band up to or in close proximity to the equatorial plane.

[0143] In some embodiments, the third group of shoulder blocks is formed by a third pair of shoulder blocks.

[0144] Preferably, the blocks of said third set of shoulder blocks are separated by fourth secondary grooves extending between said second main groove and said fourth main groove.

[0145] In this way, the blocks forming the third group of shoulder blocks are separated from each other by grooves of small depth (less than 5 mm) to be relatively connected to each other and thus the overall deformation is small.

[0146] In some embodiments, the fourth sub-groove is parallel to the sixth main groove.

[0147] In some embodiments, the fourth group of shoulder blocks is formed by a fourth pair of shoulder blocks.

[0148] Preferably, the blocks of said fourth group of shoulder blocks are separated by a fifth secondary groove extending between said fourth main groove and said further second main groove subsequent to said second main groove.

[0149] In this way, the blocks forming the fourth group of shoulder blocks are separated from each other by grooves of small depth (less than 5 mm) to be relatively connected to each other and thus the overall deformation is small.

[0150] In some embodiments, the fifth sub-groove is parallel to the sixth main groove.

[0151] In some embodiments, the fifth sub-groove is aligned with the fourth sub-groove.

[0152] In this way, a single outflow direction of water from the third and fourth groups of shoulder blocks toward the second and fourth main grooves is defined, thereby promoting rapid drainage of water in the event of running on a wet road surface.

[0153] In some embodiments, the second set of central blocks is formed by a second pair of central blocks.

[0154] Preferably, the blocks of the second set of central blocks are separated by sixth secondary grooves.

[0155] In this way, the blocks forming the second group of central blocks are separated from each other by grooves of small depth (less than 5 mm) to be relatively connected to each other and thus the overall deformation is small.

[0156] Preferably, the sixth sub-groove extends between the second main groove and the sixth main groove.

[0157] Preferably, the sixth sub-groove is inclined in a non-uniform manner relative to the sixth main groove.

[0158] In some embodiments, the second pair of central blocks is formed by a third central block located axially on the inside and a fourth central block located axially on the outside relative to the third central block.

[0159] Preferably, the third center block has a V-shaped configuration and includes: an apex directed toward the second shoulder region; and a pair of branches extending toward the first shoulder region in respective directions oppositely inclined with respect to the circumferential direction.

[0160] In this way, the third central block is essentially a mirror image with respect to the first central block, although offset with respect to the axial direction.

[0161] Preferably, one branch of each first central block is partially received in the concave shape of the third central block.

[0162] Preferably, one branch of each third central block is partially received in the concave shape of the first central block.

[0163] In this way, the first central block and the third central block are partially embedded in each other, assisting each other in bearing tangential stresses.

[0164] Preferably, the vertices of the first central block are aligned in a circumferential direction.

[0165] Preferably, the vertices of the third central block are substantially aligned in the circumferential direction.

[0166] Preferably, the fourth central block has a substantially triangular shape.

[0167] Preferably, each of said first main grooves comprises a first segment having a curvilinear course extending from said first shoulder region of said tread band towards the equatorial plane and with an inclination with respect to said circumferential direction decreasing substantially from said first shoulder region towards said central region.

[0168] Preferably, each of said second main grooves comprises a first section having a curvilinear course extending from said second shoulder region of said tread band towards the equatorial plane and with an inclination with respect to said circumferential direction decreasing substantially from said second shoulder region towards said central region.

[0169] Preferably, the first section of the first main groove and the first section of the second main groove are inclined in a non-uniform manner with respect to the circumferential direction.

[0170] In this way, when the tyre rotates in a predetermined direction corresponding to the preferred direction of advancement, drainage of water from the central region towards the respective shoulder regions is particularly promoted.

[0171] Preferably, the first section of each of the first main groove and the second main groove has a curved course without any inflection point.

[0172] Preferably, the inclination of the first segment of each of the first main grooves with respect to the circumferential direction in the region of the first shoulder region is defined by an angle between 70° and 90°, and / or the inclination of the first segment of each of the second main grooves with respect to the circumferential direction in the region of the second shoulder region is defined by an angle between 70° and 90°.

[0173] Preferably, the inclination of the first section of each of the first main groove and / or the second main groove relative to the circumferential direction in the region of the central region is defined by an angle between 20° and 40°.

[0174] In this way, a rapid drainage of water from the central region towards the shoulder regions is promoted, while maintaining a high level of resistance of the shoulder regions to transverse tangential stresses.

[0175] Preferably, each of the first main grooves has a width that decreases from the first shoulder region toward the equatorial plane.

[0176] Preferably, each of the second main grooves has a width that decreases from the second shoulder region toward the equatorial plane.

[0177] In this way, on the one hand, the outflow of water from the central area towards the corresponding shoulder areas is promoted and, on the other hand, the stiffness of the first and second sets of central blocks, respectively, is increased.

[0178] 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 between 3 mm and 10 mm.

[0179] 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 between 6 mm and 12 mm, more preferably between 7 mm and 10 mm.

[0180] Preferably, each of the first and / or second and / or third and / or fourth and / or fifth and / or sixth grooves has a variable width between 2 mm and 5 mm.

[0181] Preferably, each of the first and / or second and / or third and / or fourth and / or fifth and / or sixth grooves has a depth between 2.5 mm and 4.5 mm.

[0182] Preferably, in each first pair of main grooves, the first main groove and the second main groove are axially staggered.

[0183] Preferably, in each second pair of main grooves, the third main groove and the fourth main groove are axially staggered.

[0184] In this way, since the edges of the corresponding grooves hit the ground at different angles, the noise generated by the tire rolling on the road surface is advantageously reduced, thereby reducing the intensity of the noise generated overall.

[0185] Preferably, the third main groove and the fourth main groove have substantially symmetrical orientations relative to the circumferential direction.

[0186] In some embodiments, said end portion of said second main groove extends so as to straddle the equatorial plane of said tread band, preferably in a zigzag manner.

[0187] Preferably, the end portion of the second main groove includes a first portion extending from the first main groove toward the first shoulder region.

[0188] Preferably, the end portion of the second main groove includes a second portion extending continuously from the first portion, and more preferably, the second portion extends toward the second shoulder region.

[0189] Preferably, the end portion of the second main groove includes a third portion extending continuously from the second portion. More preferably, the third portion extends toward the first shoulder region up to the other first main groove.

[0190] Preferably, the first and third portions of the end portion are substantially parallel.

[0191] In some embodiments, the depth of the secondary trench is less than 50% of the depth of the primary trench.

[0192] In some embodiments, the fifth main groove is inclined at an angle between 5° and 25° relative to the circumferential direction, preferably about 15°.

[0193] In some embodiments, the first secondary groove and / or the second secondary groove and / or the fourth secondary groove and / or the fifth secondary groove are inclined relative to the circumferential direction at an angle between 5° and 25°, preferably about 15°.

[0194] In some embodiments, the tertiary groove and / or the sixth secondary groove are inclined relative to the circumferential direction at an angle between 25° and 45°, preferably about 35°.

[0195] In some embodiments, a tread pattern and modules are defined on the tread band, the tread pattern being formed by the integrity of all the grooves and all the blocks, the modules being formed by the smallest tread band portion extending between the axial ends of the tread band, the configuration of the modules being successively repeated along the circumferential extension of the tread band to form the tread pattern.

[0196] Preferably, said module is formed by a portion of the tread band situated between two mutually successive main grooves of said first pair.

[0197] Preferably, the module is formed by a first substantial portion extending from the first pair of main grooves as far as the second pair of main grooves and a second substantial portion extending from the second pair of main grooves as far as the first consecutive pair of main grooves.

[0198] In some embodiments, at least some of the blocks defined on said tread band have a corresponding plurality of sipes formed thereon, and more preferably, all of the blocks defined on said tread band have a corresponding plurality of sipes formed thereon.

[0199] In some embodiments, at least some of the blocks defined on said tread band are provided with studs. BRIEF DESCRIPTION OF THE DRAWINGS

[0200] The characteristics and advantages of the invention will be better understood from the detailed description of a number of preferred embodiments thereof, illustrated by way of non-limiting examples, with reference to the accompanying drawings, in which:

[0201] - Figure 1 is a front view of a tire for a vehicle wheel constructed in accordance with the present invention;

[0202] - Figure 2 yes Figure 1 A partial front view of a first structural variant of a tire;

[0203] - Figure 3 yes Figure 1 a schematic diagram of a substantial portion of a tread band of a tire drawn to an enlarged scale and developed in a plane;

[0204] - Figure 4 It shows Figure 1 Schematic drawing on an enlarged scale of a tread band portion of a module of a tread band of a tire. DETAILED DESCRIPTION

[0205] With reference to the accompanying drawings, reference numeral 1 designates as a whole a tyre for vehicle wheels constructed in accordance with the present invention.

[0206] The tyre 1 comprises a tyre structure conventional per se (not shown in the drawings) and a tread band 2 on which is defined a tread surface 3 arranged in a radially outer position relative to the tread band 2 and intended for contact with the road surface.

[0207] The tire 1 has a generally annular shape extending around an axis of rotation, defining on the tread surface 3 an axial direction Y parallel to the axis of rotation and passed through by an equatorial plane X perpendicular to the axis of rotation and defining on the tread surface 3 a circumferential direction parallel thereto.

[0208] The tread band 2 has a width L defined as the maximum width of the tread band intended to come into contact with the ground under standard conditions of use.

[0209] The tire 1 is of the directional type, wherein a preferred rolling direction of the tire is defined, which is indicated by arrow F in the Figures.

[0210] The tread band 2 also defines: a first shoulder region 4, which is delimited on the axially outer side by a first lateral edge 4a of the tread band 2; a second shoulder region 5, which is axially opposite the first shoulder region 4 and is delimited on the axially outer side by a second lateral edge 5a of the tread band 2; and a central region 6, which is interposed between the first shoulder region 4 and the second shoulder region 5 and extends to straddle the equatorial plane X.

[0211] The tread band 2 defines a plurality of first pairs of main grooves arranged successively and regularly along the circumferential development of the tread band 2 and extending transversely towards the equatorial plane X from opposite shoulder regions 4 and 5 .

[0212] 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 .

[0213] Each first main groove 10 comprises a first section 11 extending from an axially outer end 10 a open at the first lateral edge 4 a of the first shoulder region 4 to an axially inner end 10 b open at the second main groove 20 .

[0214] In particular, the first main groove 10 joins the second main groove 20 shortly after crossing the equatorial plane X. The first section 11 has a curved course without any inflection points, and the inclination relative to the circumferential direction 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 outer end 10 a to an inclination of approximately 30° in the region of the axially inner end 10 b.

[0215] Each second main groove 20 comprises a first section 21 extending from an axially outer end 20a open at the second lateral edge 5a of the second shoulder region 5 to a junction with the axially inner end 10b of the first main groove 10 .

[0216] Similar to the first section 11 of the first main groove 10, the first section 21 of the second main groove 20 also has a curved course without any inflection point, and the inclination relative to the circumferential direction generally decreases from the second shoulder area 5 toward the center area 6, starting from an inclination of approximately 80° in the area of ​​the axially outer end 20a to an inclination of approximately 30° in the area adjacent to the axially inner end 10b of the first main groove 10.

[0217] Each second main groove 20 further includes an end portion 22, which is located axially inside and extends continuously from the first section 21 until its axially inner end 20b opens in another first main groove 10 subsequent to the first main groove 10, and the first main groove 10 and the second main groove 20 together form a first pair of main grooves.

[0218] The end portion 22 of each second main groove 20 has a broken line configuration and includes: a first portion 23, which extends from the first segment 21 toward the first shoulder region 4; a second portion 24, which extends from the first portion 23 toward the second shoulder region 5; and a third portion 26, which extends from the second portion 24 toward the first shoulder region 4 to the axially inner end 20b. In particular, the third portion 26 joins another first main groove 10 shortly after crossing the equatorial plane X.

[0219] Thus, an inner end region 15 is still defined on the first section 11 of the other first main groove 10 and therefore on the first section 11 of each first main groove 10, which is bounded by the axial inner end 20b of the second main groove 20 and the axial inner end 10b of the first main groove 10.

[0220] The first portion 23, the second portion 24 and the third portion 26 are substantially rectilinear, more specifically, they are curved with a radius of curvature between 120 mm and 150 mm and extend so as to straddle the equatorial plane X of the tread band 2 and are inclined alternately in a non-uniform manner relative to the circumferential direction. In particular, the first portion 23 and the third portion 26 are substantially parallel to one another, and the second portion 24 and the inner end region 15 of the first main groove 10 are also substantially parallel.

[0221] Thus, in this way, a fold line is formed in a zigzag manner and is defined by the inner end region 15 of the first main groove 10 , the first portion 23 of the end portion 22 , the second portion 24 of the end portion 22 , and the third portion 26 of the end portion 22 .

[0222] This broken line extends continuously along the entire circumference of the equatorial plane X and crosses said equatorial plane in each of its successive portions.

[0223] Thus, the first main groove 10 and the second main groove 20 of each first pair of main grooves have a substantially similar course, with the relevant parts of the respective first segments 11 and 21 being substantially symmetrical with respect to the equatorial plane X and having a concavity directed towards the same side of the tread band 2 .

[0224] However, the second main groove 20 is axially offset relative to the first main groove 10. In fact, the respective axially outer ends 10a and 20a are offset by a value between 5 and 20 mm, preferably between 10 and 20 mm, measured in the circumferential direction.

[0225] The tread band 2 also defines a plurality of second pairs of main grooves arranged successively and regularly along the circumferential extension of the tread band 2 , their positions alternating with respect to the first pairs of main grooves 10 and 20 .

[0226] Each second pair of main grooves 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 .

[0227] In particular, each third main groove 30 extends between an axially outer end 30 a and an axially inner end 30 b , the axially outer end 30 a opening in the first shoulder region 4 .

[0228] Similarly, each fourth main groove 40 extends between an axially outer end portion 40 a and an axially inner end portion 40 b , the axially outer end portion 40 a opening in the second shoulder region 5 .

[0229] The third main trench 30 and the fourth main trench 40 have similar curved directions, and the third main trench and the fourth main trench are substantially parallel to the first main trench 10 and the second main trench 20 , respectively.

[0230] Furthermore, although the third main groove 30 and the fourth main groove 40 are axially offset from each other, they are substantially symmetrical with respect to the equatorial plane X. In particular, the offset of the respective axially outer ends 30 a and 40 a is between 5 mm and 20 mm, preferably between 10 mm and 20 mm, as measured in the circumferential direction.

[0231] Advantageously, the second portion 24 of the end portion 22 is situated on the theoretical extension of the third main groove 30 even though there is no point of contact between these grooves.

[0232] Similarly, the third portion 26 of the end portion 22 is also located on the theoretical extension of the fourth main groove 40 .

[0233] The tread band 2 also defines a plurality of third pairs of main grooves thereon, said third pairs of main grooves being arranged successively and regularly along the circumferential extension of the tread band 2 .

[0234] Each third pair of main grooves is formed by a fifth main groove 50 and a sixth main groove 60 , which are substantially symmetrical to each other about the equatorial plane X although they are axially offset.

[0235] In particular, each fifth main groove 50 extends between two mutually consecutive first main grooves 10 and is connected to the axially inner end portion 30 b of the third main groove 30 in a central region thereof.

[0236] Each fifth main groove 50 is inclined with respect to the circumferential direction X in a manner consistent with the first main grooves 10 , but at an angle smaller than that of the first main grooves 10 , for example, approximately 15°.

[0237] Similarly, each sixth main groove 60 extends between two mutually consecutive second main grooves 20 and is connected to the axially inner end portion 40 b of the fourth main groove 40 in a central region thereof.

[0238] Each sixth main groove 60 is inclined with respect to the circumferential direction X in a manner consistent with the second main grooves 20 , but at an angle smaller than that of the second main grooves 20 , for example, approximately 15°.

[0239] The depth of all first main grooves 10, second main grooves 20, third main grooves 30, fourth main grooves 40, fifth main grooves 50, and sixth main grooves 60 is approximately 8.5 mm. Furthermore, first main grooves 10, second main grooves 20, third main grooves 30, and fourth main grooves 40 have a variable width that decreases from their respective axially outer ends toward their axially inner ends. Specifically, the width of these main grooves varies from approximately 7 to 10 mm in the respective shoulder regions to values ​​of approximately 3.5 to 5 mm in the center region 6.

[0240] The fifth main groove 50 and the sixth main groove 60 have a variable width between 2.5 mm and 4 mm.

[0241] The configuration of main grooves listed above defines on the tread band 2 several groups of blocks which will be described in more detail below.

[0242] Each pair of consecutive first main grooves 10 circumferentially defines a first group of shoulder blocks 110 , a second group of shoulder blocks 120 separated from the first group of shoulder blocks 110 by third main grooves 30 , and a first group of center blocks 100 separated from the first group of shoulder blocks 110 and the second group of shoulder blocks 120 by fifth main grooves 50 .

[0243] Similarly, each pair of consecutive second main grooves 20 circumferentially defines 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 center blocks 150 separated from the third group of shoulder blocks 130 and the fourth group of shoulder blocks 140 by a sixth main groove 60.

[0244] Since the main grooves defining the multiple groups of blocks are substantially symmetrical relative to the equatorial plane, the third group of shoulder blocks 130, the fourth group of shoulder blocks 140 and the second group of center blocks 150 are substantially symmetrical relative to the first group of shoulder blocks 110, the second group of shoulder blocks 120 and the first group of center blocks 100 respectively.

[0245] The first group of central blocks 100 is separated from the second group of central blocks 150 by the end portion 22 of the second main groove 20 .

[0246] It can be noted that all the blocks are bounded by the main grooves and separated from each other by the main grooves, and therefore have a relatively large depth.

[0247] The first group of shoulder blocks 110 is formed by a first pair of shoulder blocks 111 , 112 separated from each other by a first primary groove 16 extending between the first main groove 10 and the third main groove 30 .

[0248] Similarly, the second group of shoulder blocks 120 is formed by a second pair of shoulder blocks 121 , 122 separated from each other by a secondary groove 25 extending between the third main groove 30 and a further first main groove 10 subsequent to the first main groove 10 .

[0249] The first sub-grooves 16 and the second sub-grooves 25 are substantially aligned with each other and substantially parallel to the fifth main grooves 50 .

[0250] The third group of shoulder blocks 130 is formed by a third pair of shoulder blocks 131 , 132 separated from each other by a fourth secondary groove 45 extending between the second main groove 20 and the fourth main groove 40 .

[0251] Similarly, the fourth group of shoulder blocks 140 is formed by a fourth pair of shoulder blocks 141 , 142 separated from each other by a fifth secondary groove 55 extending between the fourth main groove 40 and a further second main groove 20 subsequent to the second main groove 20 .

[0252] The fourth sub-groove 45 and the fifth sub-groove 55 are substantially aligned with each other and substantially parallel to the sixth main groove 60 .

[0253] The first group of central blocks 100 is also formed by a pair of blocks, in particular, it is formed by an axially inner first central block 101 and an axially outer second central block 102 relative to the first central block 101, and the second central block 102 is separated from the first central block 101 by a third groove 35.

[0254] The tertiary groove 35 extends between the first main groove 10 and the fifth main groove 50 , and is inclined in a non-uniform manner with respect to the fifth main groove 50 , with an inclination angle of about 35°.

[0255] The first center block 101 has a V-shaped configuration and includes an apex directed toward the first shoulder region 4 and a pair of branches extending toward the second shoulder region 5 in respective directions oppositely inclined with respect to the circumferential direction.

[0256] The second central block 102 has a generally triangular shape, the largest side of which faces the axially inner blocks 112 of the first set of shoulder blocks 110 and the axially inner blocks 122 of the second set of shoulder blocks 120 .

[0257] Similarly, the second group of central blocks 150 is formed by a third central block 151 located axially inside and a fourth central block 152 located axially outside the third central block 151 , and the fourth central block is separated from the third central block 151 by the sixth secondary groove 65 .

[0258] The sixth sub-groove 65 extends between the second main groove 20 and the sixth main groove 60 , and is inclined in a non-uniform manner with respect to the sixth main groove 60 , with an inclination angle of about 35°.

[0259] The third center block 151 has a V-shaped configuration and includes an apex directed toward the second shoulder region 5 and a pair of branches extending toward the first shoulder region 4 in respective directions oppositely inclined with respect to the circumferential direction.

[0260] The fourth central block 152 has a generally triangular shape, the largest side of which faces the axially inner blocks 132 of the third set of shoulder blocks 130 and the axially inner blocks 142 of the fourth set of shoulder blocks 140 .

[0261] The fourth, fifth and sixth secondary grooves 45, 55 and 65 are substantially symmetrical with the first, second and third secondary grooves 16, 25 and 35, respectively, with respect to the equatorial plane X, although they are axially offset with respect to each other.

[0262] In this way, each block is substantially symmetrical with respect to the equatorial plane with respect to another block of the tread band 2 .

[0263] In particular, each third central block 151 is substantially a mirror image of the first central block 101 , although offset with respect to the axial direction.

[0264] Each third central block 151 and each first central block 101 have respective concave shapes directed toward each other and are partially aligned not only in the axial direction Y but also in the circumferential direction X. In other words, the respective projections of the first central block 101 and the third central block 151 in the circumferential direction partially overlap. In particular, the branches of each first central block 101 are partially received in the concave shape of the third central block 151, and vice versa, the branches of each third central block 151 are partially received in the concave shape of the first central block 101.

[0265] All of the first, second, third, fourth, fifth, and sixth secondary grooves 16, 25, 35, 45, 55, and 65 have a depth of approximately 4 mm and a variable width between approximately 2.5 mm and 4 mm.

[0266] The blocks and grooves identified above generally define the tread pattern of tire 1 .

[0267] The tread pattern is formed by the repetition in successive and continuous manner of a single module M formed by the portion of the tread band situated between two consecutive first pairs of main grooves 10 and 20 .

[0268] Each module M is in turn formed by a first basic portion extending from the first pair of main grooves 10 and 20 to the 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 the successive first pair of main grooves 10 and 20.

[0269] Each of the first basic portions and each of the second basic portions may have a circumferential dimension corresponding to the long pitch or a value corresponding to a short pitch smaller than the long pitch.

[0270] In particular, the long pitch is approximately 30% longer than the short pitch.

[0271] Each module M can be formed by a first basic part and a second basic part, which have a short pitch or a long pitch combined with each other in various ways, so that a module having a first basic part and a second basic part both having a long pitch is provided on the tread pattern, or a module having a first basic part and a second basic part both having a short pitch, or a module having a first basic part with a short pitch and a second basic part with a long pitch, or finally a module having a first basic part with a long pitch and a second basic part with a short pitch.

[0272] Sipes are formed on all of the above blocks, and the sipes improve the performance level of the tire on snow-covered road conditions.

[0273] In particular, sipe patterns extending basically along the axial direction Y are formed on the blocks of the first group of blocks 100 and the second group of blocks 150, and sipe patterns extending along the transverse direction relative to the main extension direction of the blocks (defined by the extension direction of the first main groove or the second main groove) are formed on the axially inner blocks of each group of shoulder blocks 110, 120, 130 and 140, and sipe patterns extending basically parallel to the main extension direction of the blocks (also defined by the direction of the first main groove or the second main groove) are formed on the axially outer blocks of each group of shoulder blocks 110, 120, 130 and 140.

[0274] A plurality of anti-slip studs 200 may also be provided at appropriate positions on the tread band 2 of the tire 1 on different blocks, such as Figure 2 A variant of the construction of the tire 1 shown is visible, making it particularly suitable for driving on icy roads.

[0275] Each group of shoulder blocks and each group of central blocks define a corresponding radially outer surface, which in fact constitutes a part of the tread surface 3 .

[0276] Due to the configuration of the grooves and blocks described above, each of the radially outer surfaces of the first set of shoulder blocks 110 , the second set of shoulder blocks 120 and the first set of central blocks 100 differs from an average value of the radially outer surfaces by less than 25%.

[0277] Furthermore, the 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 these blocks.

[0278] Obviously, due to the above-mentioned symmetrical relationship, the same relationship between the radially outer surfaces also applies to the third group 130 and the fourth group 140 of shoulder blocks and the second group 150 of center blocks.

[0279] In this way, the tread band 2 is subdivided by the main grooves into regions (groups of blocks) in contact with the road surface and having a substantially uniform area.

[0280] This enables the tread band to react to tangential stresses in a substantially uniform manner, thereby preventing excessive local deformations that could impair the road grip of the tyre 1 and, in the case of studded tyres, allowing the likelihood of the studs being pulled out from the respective seats to be reduced.

[0281] Example

[0282] A tire measuring 205 / 55R16 has been constructed in accordance with the embodiments of the invention described above.

[0283] Table 1 below lists the respective extents of the radially outer surfaces of the first group of shoulder blocks 110 , the second group of shoulder blocks 120 and the first group of center blocks 100 and the percentage difference of the surface extent of each group of blocks relative to the average of these surface extents.

[0284] In the specific example of the tire used here, this average is approximately 1185 mm 2 .

[0285] Block Group <![CDATA[Surface (mm 2 )]]> Percent difference from the mean The first set of shoulder blocks 1104 -6.8％ Second set of shoulder blocks 1313 +21.6％ The first set of central blocks 1138 -7.9％

[0286] Table 1

[0287] It will be noted that the radially outer surface of each group of blocks differs from the surface average by a percentage value less than 25% of the average value, so that each group of blocks enters contact with the road surface with a surface of substantially the same extent, thereby providing a substantially uniform resistance to tangential stresses.

[0288] Table 2 below lists the respective extents of the radially outer surfaces of the blocks forming the first group of shoulder blocks 110 , the second group of shoulder blocks 120 and the first group of center blocks 100 and the percentage difference of each block's extent relative to the average of the block's extents.

[0289] In this particular case, the average is about 593 mm. 2 .

[0290]

[0291]

[0292] Table 2

[0293] In this case, it can also be noted that the percentage difference between the radial outer surface of each block in each group of blocks and the surface average value is less than 25% of the average value, so that the surface of each block in contact with the road surface is basically the same as that of other blocks, thereby providing basically uniform resistance to tangential stress.

[0294] Table 3 below lists the stiffness values ​​calculated by finite element simulation for the first group of shoulder blocks 110, the second group of shoulder blocks 120, and the first group of center blocks 100, as well as the percentage difference between the stiffness values ​​of each group of blocks and the average of these stiffness values. The stiffness value is defined as the ratio between the reaction force exerted by the block on the road and the motion applied to the block itself.

[0295]

[0296] Table 3

[0297] It can therefore be observed that the stiffness values ​​of the various groups of blocks are substantially similar when the tangential stresses to which they are subjected have an axial direction and when these tangential stresses have a circumferential direction.

[0298] The uniformity of the stiffness values ​​between the different blocks is reflected in the consistency of the tread band behaviour, giving the tyre many important advantages, including: better road grip (regardless of the road surface), better results in terms of tyre wear, greater support for the studs (in the case of studded tyres), which makes manifest a greater ability to hold the studs and a higher grip efficiency on icy roads.

Claims

1. A tyre for a vehicle wheel, said tyre comprising a tread band (2) on which are defined: - a first shoulder region (4) and a second shoulder region (5) axially opposite each other; - a central region (6) interposed between said first shoulder region (4) and said second shoulder region (5); - a plurality of first group shoulder blocks (110) arranged successively along the circumferential development of the tread band (2), each first group shoulder block (110) extending from the first shoulder region (4) towards the central region (6); a plurality of shoulder blocks (120) of a second group arranged successively along the circumferential extension of the tread band (2), each shoulder block (120) of the second group extending from the first shoulder region (4) towards the central region (6) and arranged along the circumferential extension of the tread band in an alternating position alternating with one of the shoulder blocks (110) of the first group; - a plurality of first group central blocks (100) arranged successively along said circumferential extension of said tread band (2), each first group central block (100) being adjacent to a respective first group of shoulder blocks (110) and a respective second group of shoulder blocks (120) and being situated in an axially inner position relative thereto, in: - the blocks (111, 112) of each first set of shoulder blocks (110) are separated from one another by at least one secondary groove (16), - the blocks (121, 122) of each second set of shoulder blocks (120) are separated from one another by at least one secondary groove (25), - the blocks (101, 102) of each first set of central blocks (100) are separated from one another by at least one secondary groove (35), - each shoulder block (120) of the second group is separated from two adjacent shoulder blocks (110) of the first group by at least one main groove (10, 30), - each first group of center blocks (100) and the adjacent first group of shoulder blocks (110) and the second group of shoulder blocks (120) are separated by at least one main groove (50), and - Respective radially outer surfaces are defined on the first set of shoulder blocks (110), the second set of shoulder blocks (120) and the first set of center blocks (100), 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.

2. The tire according to claim 1, wherein Each of the areas of the radially outer surface differs from the average by less than 25% of the average.

3. The tire according to claim 1 or 2, wherein: The tread band (2) is further defined as follows: - a plurality of shoulder blocks (130) of a third group arranged successively along said circumferential extension of said tread band (2), each shoulder block (130) of a third group extending from said second shoulder region (5) towards said central region (6); a plurality of shoulder blocks (140) of a fourth group arranged successively along the circumferential extension of the tread band (2), each shoulder block (140) of the fourth group extending from the second shoulder region (5) towards the central region (6) and arranged along the circumferential extension of the tread band (2) in a position alternating with one of the shoulder blocks (130) of the third group; - a plurality of central blocks (150) of a second group, said plurality of central blocks of the second group being arranged successively along said circumferential extension of said tread band (2), each central block (150) of the second group being adjacent to a respective shoulder block (130) of the third group and a respective shoulder block (140) of the fourth group and being situated in an axially inner position relative thereto, in: - the blocks (131, 132) of each third group of shoulder blocks (130) are separated from one another by at least one secondary groove (45), - the blocks (141, 142) of the fourth set of shoulder blocks (140) are separated from each other by at least one secondary groove (55), - the blocks (151, 152) of said second set of central blocks (150) are separated from one another by at least one secondary groove (65), - Each fourth group of shoulder blocks (140) is separated from two adjacent third group of shoulder blocks (130) by at least one main groove (20, 40), - Each second group of center blocks (150) is separated from the third group of shoulder blocks (130) and the fourth group of shoulder blocks (140) adjacent thereto by at least one main groove (60), and - Respective radially outer surfaces are defined on the third group of shoulder blocks (130), the fourth group of shoulder blocks (140) and the second group of center blocks (150), 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.

4. The tire according to claim 3, wherein: Each of the third set of shoulder blocks (130) is substantially symmetrical relative to the first set of shoulder blocks (110), except for the axial offset.

5. The tire according to claim 3 or 4, wherein: Each of the fourth set of shoulder blocks (140) is substantially symmetrical relative to the second set of shoulder blocks (120), except for the axial offset.

6. The tire according to any one of claims 3 to 5, wherein: Each of the second set of central blocks (150) is substantially symmetrical relative to the first set of central blocks (100), except for the axial offset.

7. The tire according to any one of claims 3 to 6, wherein: Defined on the tread band (2) are: a plurality of first pairs of main grooves (10, 20) extending from said first shoulder region (4) and said second shoulder region (5) towards said central region (6) and arranged in a regular successive manner along the circumferential development of said tread band (2); and a plurality of second pairs of main grooves (30, 40) extending from said first shoulder region (4) and said second shoulder region (5) towards said central region (6) and arranged in a regular, successive manner along the circumferential development of said tread band (2) in alternating positions relative to said first pair of main grooves (10, 20), wherein the plurality of first pairs of main grooves (10, 20) and the plurality of second pairs of main grooves (30, 40) separate the plurality of first groups of shoulder blocks (110) from the plurality of second groups of shoulder blocks (120), and separate the plurality of third groups of shoulder blocks (130) from the plurality of fourth groups of shoulder blocks (140).

8. The tire according to claim 7, wherein: Each first pair of main grooves is formed by: - a first main groove (10) extending from the first shoulder region (4) towards the central region (6); and - a second main groove (20) extending from the second shoulder region (5) towards the central region (6); The first main groove (10) includes an axially inner end portion (10b) connected to the second main groove (20).

9. The tire according to claim 7 or 8, wherein: The second main groove (20) includes an end portion (22) located axially inward and extending between the first main groove (10) and another first main groove belonging to the subsequent first pair of main grooves, the end portion (22) separating the first group of central blocks (100) from the second group of central blocks (150).

10. The tire according to any one of claims 7 to 9, wherein Each second pair of main grooves 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).

11. The tire according to any one of claims 3 to 10, wherein: A plurality of third pairs of main grooves (50, 60) are defined on the tread band (2), the plurality of third pairs of main grooves being arranged in a regular, successive manner along the circumferential extension of the tread band, each third pair of main grooves being formed by: - a fifth main groove (50) separating the first group of central blocks (100) from the first group of shoulder blocks (110) and separating the first group of central blocks from the second group of shoulder blocks (120); and - a sixth main groove (60) separating the second group of central blocks (150) from the third group of shoulder blocks (130) and separating the second group of central blocks from the fourth group of shoulder blocks (140).

12. The tire according to claim 11, wherein The fifth main groove (50) extends between two first main grooves (10) in a first pair of main grooves that are consecutive to each other and is connected to an axially inner end portion (30b) of the third main groove (30).

13. The tire according to claim 11 or 12, wherein: The fifth main groove (50) has an inclination smaller than that of the first main groove (10) relative to the circumferential direction, and the inclination direction of the fifth main groove is consistent with the inclination direction of the first main groove (10).

14. The tire according to any one of claims 11 to 13, wherein: The sixth main groove (60) extends between two second main grooves (20) in the first pair of main grooves that are consecutive to each other and is connected to an axially inner end portion of the fourth main groove (40).

15. The tire according to any one of claims 11 to 14, wherein The sixth main groove (60) has an inclination smaller than that of the second main groove (20) relative to the circumferential direction, and the inclination direction of the sixth main groove is consistent with the inclination direction of the second main groove (20).

16. The tire according to any one of claims 10 to 15, wherein The first main groove (10) and the third main groove (30) extend from the first shoulder region (4) toward the center region (6) with an inclination decreasing from the first shoulder region (4) toward the center region (6) relative to the circumferential direction.

17. The tire according to any one of claims 10 to 16, wherein: The second main groove (20) and the fourth main groove (40) extend from the second shoulder region (5) toward the center region (6) with an inclination decreasing from the second shoulder region (5) toward the center region (6) relative to the circumferential direction.

18. Tire according to any one of the preceding claims, wherein Each first group of shoulder blocks (110) is formed by a first pair of shoulder blocks (111, 112) separated by a first sub-groove (16).

19. The tire according to claim 18, wherein The first sub-groove (16) extends between the first main groove (10) and the third main groove (30).

20. The tire according to claim 18 or 19, wherein: The first primary groove (16) is parallel to the fifth main groove (50).

21. Tire according to any one of the preceding claims, wherein Each second group of shoulder blocks (120) is formed by a second pair of shoulder blocks (121, 122) separated by a secondary groove (25).

22. The tire according to claim 21, wherein The secondary secondary groove (25) extends between the third main groove (30) and the other first main groove subsequent to the first main groove (10).

23. The tire according to claim 21 or 22, wherein: The secondary groove (25) is parallel to the fifth main groove (50).

24. The tire according to claim 21, 22 or 23, wherein: The secondary groove (25) is aligned with the primary groove (16).

25. Tire according to any one of the preceding claims, wherein The first set of central blocks (100) is formed by a first pair of central blocks (101, 102) separated by a third groove (35).

26. The tire according to claim 25, wherein The third tertiary groove (35) extends between the first main groove (10) and the fifth main groove (50).

27. The tire according to claim 25 or 26, wherein: The third tertiary groove (35) is inclined in a non-uniform manner relative to the fifth main groove (50).

28. Tire according to any one of the preceding claims, wherein A corresponding radially outer surface is defined on each of the first group of shoulder blocks (110), the second group of shoulder blocks (120) and the first group of center blocks (100), and each of the radially outer surfaces of the blocks has an 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.

29. Tire according to any one of the preceding claims, wherein The depth of each main groove is between 6 mm and 12 mm.

30. Tire according to any one of the preceding claims, wherein The depth of each secondary groove is between 2.5 mm and 4.5 mm.

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