Tyre for vehicle wheels

Abstract

A tyre (1) for vehicle wheels comprises a first block (60), a second block (70) and a third block (80), which are at least partially delimited laterally by a first main groove (10) and said second main groove (20) and are separated from each other by a first secondary groove (30) and a second secondary groove (40). Each edge (61; 71) of the first block (60), the second block (70) and the third block (80) facing the first secondary groove (30) or the second secondary groove (40) comprises at least a first edge portion (61a, 71a; 77a, 81a), defined by an angular edge, and at least a second edge portion (61b, 71b; 77b, 81b), adjacent to the first edge portion (61a, 71a; 77a, 81a) and defined by a chamfer, connected to each other by at least a first connecting angular edge (63, 73; 78, 83) extending over said tread surface portion. The first edge portion (61a, 71a; 77a, 81a) and the first connecting angular edge (63, 73; 78, 83) define a first angle (A, A'; A1, A1') on the portion of tread surface (3) whose bisector (R, R'; R1, R1') is inclined with respect to a circumferential direction defined on the tread band by an angle of less than 15°.

Description

[0001] TYRE FOR VEHICLE WHEELS

[0002] DESCRIPTION

[0003] The present invention concerns a tyre for vehicle wheels, in particular a winter tyre. A tyre generally comprises a carcass structure shaped toroidally around a rotation axis and including at least one carcass ply having end flaps which are engaged in respective annular anchoring structures, called bead cores.

[0004] In a position radially external to the carcass structure, a belt structure is provided comprising, in the case of car tyres, at least two radially superimposed strips of rubberised fabric provided with reinforcing cords, usually metallic, arranged in each strip parallel to each other but crossed with respect to the cords of the adjacent strip, preferably symmetrically with respect to the equatorial plane of the tyre.

[0005] Preferably, the belt structure further comprises in a radially external position, at least on the ends of the underlying belt strips, also a third layer of textile or metallic cords, arranged circumferentially (at 0 degrees). In tubeless type tyres, there is also a radially internal layer, called "liner", which has waterproofing characteristics to allow air sealing to the tyre itself.

[0006] In a position radially external to the belt structure, a tread band, made of elastomeric material, is applied on which a tread surface intended for contact with the road surface is defined.

[0007] The tyres, in order to obtain adequate grip even on a wet road surface, have a tread band provided with grooves of various shapes and geometry whose main function is to allow the evacuation of the water present between the surface of the tyre and the road surface at the time of mutual contact, preventing the hydrostatic pressure deriving from the impact of the water against the forward travelling tyre from causing the tyre to lift even partially from the road surface and the consequent loss of control of the vehicle (a phenomenon known as "aquaplaning'").

[0008] The grooves formed in the circumferential direction also affect the directionality and travel stability characteristics of the tyre in relation to the ability of the tyre to bear the tangential stresses parallel to the rotation axis of the tyre.

[0009] The grooves formed in the transverse direction, in turn, affect the traction characteristics of the tyre, i.e. the ability to transmit the tangential stresses parallel to the travel direction to the road surface, in particular during the acceleration and braking of the vehicle.

[0010] The grooves, overall, define on the tread band a plurality of blocks, each of which comprises a radially external surface intended for contact with the road surface, and which, therefore, forms a portion of the tread surface of the tyre. Each block is furthermore delimited, at least partially, by one or more walls of the grooves that surround it.

[0011] In the case of winter tyres, small notches, known as "sipes", are generally made in the tread blocks of the tread belt, extending from the tread surface of the tyre towards the inside of the block, their function is to provide additional grip when driving on snowy surfaces and to retain a certain amount of snow, thus improving grip with the road surface.

[0012] With "circumferential" direction is intended to mean a direction generally oriented according to the rotation direction of the tyre, or, in any case, slightly inclined (at most at about 10°) with respect to the rotation direction of the tyre.

[0013] The term "axial" and the expressions "axially internal / external" are used with reference to the axial direction of the tyre, i.e. to a direction parallel to the rotation axis of the same or at most inclined at 5° with respect to it. The axial direction is generally perpendicular to the circumferential direction.

[0014] The terms "transverse" and "transversely" indicate a direction inclined with respect to the circumferential direction by an acute angle greater than at least 10°.

[0015] The term "equatorial plane" of the tyre is intended to mean an axial centre line plane perpendicular to the rotation axis of the tyre.

[0016] With "shoulder regions" of the tread band, is intended to mean the portions of tread band that extend circumferentially in a position axially external to the tread band itself.

[0017] Preferably, each shoulder region extends over a width equal to at least 10% of the width of the tread band, more preferably equal to at least 20% of the width of the tread band.

[0018] Preferably, each shoulder region extends over a width less than 30% of the width of the tread band, more preferably less than 25% of the width of the tread band.

[0019] With "equatorial region" of the tread band is intended to mean the portion of tread band extending circumferentially in a symmetrical manner around the equatorial plane and delimited on its axially opposed sides by said shoulder regions.

[0020] The term "groove" is intended to mean a cavity formed in a portion of tread band, having a width greater than or equal to 1.5 mm, and preferably a depth greater than 3 mm.

[0021] The term "sipe" is intended to mean a cavity formed in a portion of tread band, having a width less than 1.5 mm, preferably less than or equal to 1 mm. With "block" is intended to mean a portion of tread surface that is delimited by at least one groove, preferably by at least two distinct grooves, on which there is defined, on the radially external surface thereof, a portion of tread surface intended for contact with the road surface.

[0022] The "wall" of a groove refers to the area generally extending towards the tread surface from a groove bottom.

[0023] The "edge" of a block is defined as the region of the block that joins a wall of a groove delimiting the block with the portion of the block's tread surface. The edge as defined above is to be understood as separate from the wall, i.e. the edge is not part of the wall.

[0024] The edge, or a portion of it, may be formed by an angular edge, where the wall of the groove directly intersects the portion of tread surface, or it may be formed by a connecting surface that connects the wall with the portion of tread surface.

[0025] The "chamfer" of a block is understood to be this connecting surface.

[0026] Preferably the chamfer is formed by a flat surface, but it can also take on a rounded shape.

[0027] If the chamfer is formed by a flat surface, the chamfer is inclined with respect to both the tread surface and the groove wall.

[0028] The "width" of a chamfer is defined as the measurement of the width of an orthogonal projection thereof on the tread surface calculated in a direction perpendicular to the longitudinal direction of the edge on which the chamfer is formed.

[0029] Two edge portions of respective blocks separated by a groove are "facing" each other when the orthogonal projections of the two edge portions on a plane parallel to the longitudinal direction of the groove overlap by at least 80%, and preferably at least 90%, of the smaller projection.

[0030] In other words, two edge portions of two blocks persisting on the same groove are said to be "facing" when they are substantially positioned opposite each other.

[0031] A groove is said to be a "main groove" when it extends transversely from a shoulder region to an equatorial region of the tread band. Preferably, a main groove extends on the tread band so as to cover at least 30% of the width of the tread band, more preferably at least 40% of the width of the tread band.

[0032] Preferably, a main groove is open at an axial end of the tread band.

[0033] Preferably a main groove has a decreasing inclination with respect to an equatorial plane of the tread band from the shoulder region towards the equatorial region. Preferably, a main groove has a depth of at least 5 mm. Preferably, a main groove has a width of at least 3 mm, more preferably of at least 5 mm.

[0034] A groove is said to be a "secondary groove" when it extends between a pair of main grooves.

[0035] WO 2016 / 189418, on behalf of the same Applicant, describes a winter tyre comprising a plurality of main grooves extending transversely from opposing shoulder regions to the equatorial plane, which are connected two by two by secondary grooves.

[0036] WO 2023 / 238027, on behalf of the same Applicant, describes a winter tyre in which, in some blocks, the edges comprise portions defined by angular edges alternating with portions defined by chamfers.

[0037] The Applicant noted that the particular edge conformation described in WO 2023 / 238027 leads to the creation of new gripping angular edges on those edges. In fact, due to the lower height of the chamfered edge portion with respect to the angular edge portion, a protrusion remains defined at the end of the angular edge portion facing the chamfered edge portion, which, like a sort of "tooth", allows the snowy ground to be cut more effectively, improving the tyre's road grip.

[0038] The Applicant, moreover, verified that the effectiveness of these new grip edges in cutting the snowy ground is also a function of the orientation of these angular edges on the tread band, so that, in particular, the presence of a projection having an angular edge facing in the circumferential direction allows the snowy ground to be cut more effectively during acceleration or braking, depending on the direction of orientation of the angular edge.

[0039] The Applicant then realised that a tread pattern configured in such a way as to define on the blocks of the tread band a plurality of projections suitably oriented and arranged in a "regular" manner along the axial extension of the tread band would increase, at least on snowy surfaces, the performance of the tyre during acceleration and / or braking.

[0040] The Applicant finally found that a tread band having at least three blocks aligned in a transverse direction between the shoulder region and the equatorial region and separated by respective grooves, wherein the edges of the blocks facing the respective grooves are shaped with alternating chamfered and angular portions defining one or more circumferentially directed projections distributed along the axial direction of the tread band, provides effective and uniform grip on snowy surfaces under acceleration and braking. In particular, in a first aspect thereof, the invention relates to a vehicle wheel tyre comprising a tread band on which a first main groove and a second main groove are defined, both extending transversely from a first shoulder region to an equatorial region of said tread band.

[0041] Preferably, a first secondary groove and a second secondary groove are defined on said tread band.

[0042] Preferably, said first secondary groove and said second secondary groove extend between said first main groove and said second main groove.

[0043] Preferably, a first block, a second block and a third block are defined on said tread band.

[0044] Preferably, said first block, said second block and said third block are at least partially delimited on a pair of opposing sides by said first main groove and, respectively, by said second main groove.

[0045] Preferably, said first block and second block are separated from each other by said first secondary groove.

[0046] Preferably, said second block and said third block are separated from each other by said second secondary groove.

[0047] Preferably, each edge of said first block and of said second block facing said first secondary groove comprises at least a first edge portion defined by an angular edge formed between a wall of said first secondary groove and a portion of tread surface. Preferably, each edge of said first block and of said second block facing said first secondary groove comprises at least a second edge portion, adjacent to said first edge portion and defined by a chamfer extending between said wall of said first secondary groove and said portion of tread surface.

[0048] Preferably, each edge of said first block and of said second block facing said first secondary groove comprises at least one first connecting angular edge extending over said portion of tread surface between said first edge portion and said second edge portion.

[0049] Preferably, each edge of said second block and of said third block facing said second secondary groove comprises at least a first edge portion defined by an angular edge formed between a wall of said second secondary groove and a portion of tread surface.

[0050] Preferably, each edge of said second block and of said third block facing said second secondary groove comprises at least a second edge portion, adjacent to said first edge portion and defined by a chamfer extending between said wall of said second secondary groove and said portion of tread surface.

[0051] Preferably, each edge of said second block and of said third block facing said second secondary groove comprises at least one first connecting angular edge extending over said portion of tread surface between said first edge portion and said second edge portion.

[0052] Preferably, said at least a first edge portion and said at least a first connecting angular edge define a first angle on said portion of tread surface.

[0053] Preferably, the bisector of said first angle is inclined with respect to a circumferential direction defined on said tread band by an angle of less than 15°.

[0054] Due to these tyre characteristics, the Applicant believes that the tyre is able to impact a snow-covered road surface more effectively and is particularly efficient when accelerating and braking.

[0055] The Applicant notes that this configuration defines additional angular edges on both sides of the respective groove so that they face in opposite directions. Thus, additional angular edges defined on one side of a groove can effectively contribute to tyre grip during acceleration while additional angular edges defined on the other side of the groove can effectively contribute to tyre grip during braking.

[0056] The Applicant also considers that the provision of additional angular edges as described above in at least two secondary grooves extending between main grooves extending from a shoulder region to an equatorial region of the tread band, allows for appropriate distribution of the additional angular edges along the axial direction of the tread band, so as to achieve more homogeneous tyre road behaviour.

[0057] The present invention, in the aforesaid aspect, may have at least one of the further preferred features set out below.

[0058] In some embodiments, said bisector of said first angle formed on the portion of tread surface by said at least one first edge portion and said at least one first connecting angular edge is inclined with respect to said circumferential direction by an angle of less than 10°, more preferably less than 5°.

[0059] In some embodiments, a first edge of said first block and a first edge of said second block face each other on said first secondary groove.

[0060] Preferably, in at least one of said first edge of said first block and said first edge of said second block, said first edge portion is interposed between said second edge portion and a further second edge portion.

[0061] In this way, an additional gripping angular edge is defined on the edge of the first block and / or the second block facing the first secondary groove. Preferably, said at least one of said first edge of said first block and said first edge of said second block comprises a second connecting angular edge extending over said portion of tread surface between said first edge portion and said further second edge portion, wherein said first edge portion and said second connecting angular edge define a second angle on said portion of tread surface.

[0062] Preferably, the bisector of said second angle is inclined with respect to an axial direction defined on said tread band by an angle of less than 15°, more preferably less than 10°, even more preferably less than 5°.

[0063] In this way, the additional gripping angular edge defined on the edge of the first and / or second block facing the first secondary groove is oriented along the axial direction, so that the tyre has better road grip on bends.

[0064] In some embodiments, in at least one of said first edge of said first block and said first edge of said second block, said second edge portion is interposed between said first edge portion and a further first edge portion.

[0065] In this way, an additional gripping angular edge is defined on the edge of the first block and / or the second block facing the first secondary groove.

[0066] Preferably, said at least one of said first edge of said first block and said first edge of said second block comprises a second connecting angular edge extending over said portion of tread surface between said further first edge portion and said second edge portion, wherein said further first edge portion and said second connecting angular edge define a second angle on said portion of tread surface.

[0067] Preferably, the bisector of said second angle is inclined with respect to an axial direction defined on said tread band by an angle of less than 15°, more preferably less than 10°, even more preferably less than 5°.

[0068] In this way, the additional gripping angular edge defined on the edge of the first and / or second block facing the first secondary groove is oriented along the axial direction, so that the tyre has better road grip on bends.

[0069] In some embodiments, each first edge portion of said first edge of said first block is facing a second edge portion of said first edge of said second block.

[0070] In some embodiments, each second edge portion of said first edge of said first block is facing a first edge portion of said first edge of said second block.

[0071] In this way, the chamfered edge portions of one block are positioned opposite a corresponding angular edge portion of the other block and vice versa. This particular configuration promotes the retention of snow within the first secondary groove, increasing the tyre's grip on snowy surfaces. In some embodiments, said first edge portions and said second edge portions facing each other at said first secondary groove have a substantially equal length.

[0072] In this way, the action exerted on the snow in the first secondary groove by the respective pairs of first and second edge portions facing each other is homogeneous, increasing the snow-holding capacity within the first secondary groove.

[0073] In certain embodiments, in said first edge of said first block and / or in said first edge of said second block, said at least one first edge portion and said at least one second edge portion have a substantially constant length. Preferably, all the first edge portions and second edge portions have substantially the same length, more preferably comprised between 4 and 6 mm, e.g. around 5 mm.

[0074] In other words, the first edge of the first block and / or the first edge of the second block are equally divided into one or more first edge portions and one or more second edge portions, and preferably such first edge portions and second edge portions are alternating with each other.

[0075] In some embodiments, on said first block and on said second block, a plurality of sipes is formed, open on said first edge of said first block and on said first edge of said second block, respectively.

[0076] Preferably, said plurality of sipes separates, on the first edge of said first block and of said second block, respectively, said at least one first edge portion from said at least one second edge portion.

[0077] In this way, the "natural" subdivision of the edge of the block into adjacent portions defined by the provision of the sipes on the block is exploited.

[0078] In some embodiments, said plurality of sipes of said first block and / or said second block extends parallel to an alignment direction of said first block and said second block defined by said first main groove and said second main groove.

[0079] In other embodiments, said plurality of sipes of said first block and / or of said second block extends transversely to said alignment direction, except for an end region, open at the respective edge facing the first secondary groove, substantially parallel to said alignment direction.

[0080] In some embodiments, a second edge of said second block and a first edge of said third block face each other on said second secondary groove.

[0081] Preferably, in at least one of said second edge of said second block and said first edge of said third block, said first edge portion is interposed between said second edge portion and a further second edge portion.

[0082] In this way, an additional gripping angular edge is defined on the edge of the second block and / or the third block facing the second secondary groove.

[0083] Preferably, said at least one of said second edge of said second block and said first edge of said third block comprises a second connecting angular edge extending over said portion of tread surface between said first edge portion and said further second edge portion, wherein said first edge portion and said second connecting angular edge define a second angle on said portion of tread surface.

[0084] Preferably, the bisector of said second angle is inclined with respect to an axial direction defined on said tread band by an angle of less than 15°, more preferably less than 10°, even more preferably less than 5°.

[0085] In this way, the additional gripping angular edge defined on the edge of the second and / or third block facing the second secondary groove is oriented along the axial direction, so that the tyre has better road grip on bends.

[0086] In some embodiments, in at least one of said second edge of said second block and said first edge of said third block, said second edge portion is interposed between said first edge portion and a further first edge portion.

[0087] In this way, an additional gripping angular edge is defined on the edge of the first block and / or the second block facing the second secondary groove.

[0088] Preferably, said at least one of said second edge of said second block and said first edge of said third block comprises a second connecting angular edge extending over said portion of tread surface between said further first edge portion and said second edge portion, wherein said further first edge portion and said second connecting angular edge define a second angle on said portion of tread surface.

[0089] Preferably, the bisector of said second angle is inclined with respect to an axial direction defined on said tread band by an angle of less than 15°, more preferably less than 10°, even more preferably less than 5°.

[0090] In this way, the additional gripping angular edge defined on the edge of the second and / or third block facing the second secondary groove is oriented along the axial direction, so that the tyre has better road grip on bends.

[0091] In some embodiments, each first edge portion of said second edge of said second block is facing a second edge portion of said first edge of said third block.

[0092] In some embodiments, each second edge portion of said second edge of said second block is facing a first edge portion of said first edge of said third block.

[0093] In this way, the chamfered edge portions of one block are positioned opposite a corresponding angular edge portion of the other block and vice versa. This particular configuration promotes the retention of snow within the second secondary groove, increasing the tyre's grip on snowy surfaces.

[0094] In some embodiments, said first edge portions and said second edge portions facing each other at said second secondary groove have a substantially equal length.

[0095] In this way, the action exerted on the snow in the second secondary groove by the respective pairs of first and second edge portions facing each other is homogeneous, increasing the snow-holding capacity within the second secondary groove.

[0096] In certain embodiments, in said second edge of said second block and / or in said first edge of said third block, said at least one first edge portion and said at least one second edge portion have a substantially constant length. Preferably, all the first edge portions and second edge portions have substantially the same length, more preferably comprised between 4 and 6 mm, e.g. around 5 mm.

[0097] In other words, the second edge of the second block and / or the first edge of the third block are equally divided into one or more first edge portions and one or more second edge portions, and preferably such first edge portions and second edge portions are alternating with each other.

[0098] In some embodiments, on said second block and on said third block, a plurality of sipes is formed, open on said second edge of said second block and on said first edge of said third block, respectively.

[0099] Preferably, said plurality of sipes separates, on the second edge of said second block and on the first edge of said third block, respectively, said at least one first edge portion from said at least one second edge portion.

[0100] In some embodiments, said plurality of sipes of said second block and / or said third block extends parallel to an alignment direction of said second block and said third block defined by said first main groove and said second main groove.

[0101] In other embodiments, said plurality of sipes of said second block and / or of said third block extends transversely to said alignment direction, except for an end region, open at the respective edge facing the second secondary groove, substantially parallel to said alignment direction.

[0102] In some embodiments, a third secondary groove separating said third block from a fourth block extends between said first main groove and said second main groove. Preferably, said third block comprises a second edge facing said third secondary groove and said fourth block comprises a first edge facing said third secondary groove.

[0103] Preferably, said second edge of said third block and said first edge of said fourth block each comprise at least a first edge portion, defined by an angular edge formed between a wall of said third secondary groove and a portion of tread surface.

[0104] Preferably, said second edge of said third block and said first edge of said fourth block each comprise at least a second edge portion, adjacent to the first edge portion and defined by a chamfer extending between said wall of said third secondary groove and said portion of tread surface.

[0105] Preferably, said second edge of said third block and said first edge of said fourth block each comprise at least a first connecting angular edge extending over said portion of tread surface between said first edge portion and said second edge portion.

[0106] Preferably, said first edge portion and said first connecting angular edge define a first angle on said portion of tread surface and the bisector of said first angle is inclined with respect to a circumferential direction defined on said tread band by an angle of less than 15°, more preferably less than 10°, even more preferably less than 5°.

[0107] In this way, additional gripping edges are obtained that are oriented substantially along the circumferential direction and axially distanced from the gripping angular edges defined on the first secondary groove and the second secondary groove, further improving the tyre's road grip on snowy surfaces under acceleration and braking.

[0108] In some embodiments, in at least one of said second edge of said third block and said first edge of said fourth block, said first edge portion is interposed between said second edge portion and a further second edge portion.

[0109] In this way, an additional gripping angular edge is defined on the edge of the third block and / or the fourth block facing the third secondary groove.

[0110] Preferably, said at least one of said second edge of said third block and said first edge of said fourth block comprises a second connecting angular edge extending over said portion of tread surface between said first edge portion and said further second edge portion, wherein said first edge portion and said second connecting angular edge define a second angle on said portion of tread surface.

[0111] Preferably, the bisector of said second angle is inclined with respect to an axial direction defined on said tread band by an angle of less than 15°, more preferably less than 10°, even more preferably less than 5°.

[0112] In this way, the additional gripping angular edge defined on the edge of the third and / or fourth block facing the third secondary groove is oriented along the axial direction, so that the tyre has better road grip on bends.

[0113] In some embodiments, in at least one of said second edge of said third block and said first edge of said fourth block, said second edge portion is interposed between said first edge portion and a further first edge portion.

[0114] Preferably, said at least one of said second edge of said third block and said first edge of said fourth block comprises a second connecting angular edge extending over said portion of tread surface between said second edge portion and said further first edge portion, wherein said further first edge portion and said second connecting angular edge define a second angle on said portion of tread surface.

[0115] Preferably, the bisector of said second angle is inclined with respect to an axial direction defined on said tread band by an angle of less than 15°, more preferably less than 10°, even more preferably less than 5°.

[0116] In this way, the additional gripping angular edge defined on the edge of the third and / or fourth block facing the third secondary groove is oriented along the axial direction, so that the tyre has better road grip on bends.

[0117] In some embodiments, each first edge portion of said second edge of said third block is facing a second edge portion of said first edge of said fourth block.

[0118] In some embodiments, each second edge portion of said second edge of said third block is facing a first edge portion of said first edge of said fourth block.

[0119] In this way, the chamfered edge portions of one block are positioned opposite a corresponding angular edge portion of the other block and vice versa. This particular configuration promotes the retention of snow within the third secondary groove, increasing the tyre's grip on snowy surfaces.

[0120] In some embodiments, said first edge portions and said second edge portions facing each other at said third secondary groove have a substantially equal length.

[0121] In this way, the action exerted on the snow in the third secondary groove by the respective pairs of first and second edge portions facing each other is homogeneous, increasing the snow-holding capacity within the third secondary groove.

[0122] In certain embodiments, in said second edge of said third block and / or in said first edge of said fourth block, said at least one first edge portion and said at least one second edge portion have a substantially constant length. Preferably, all the first edge portions and second edge portions have substantially the same length, more preferably comprised between 4 and 6 mm, e.g. around 5 mm.

[0123] In other words, the second edge of the third block and / or the first edge of the fourth block are equally divided into one or more first edge portions and one or more second edge portions, and preferably such first edge portions and second edge portions are alternating with each other.

[0124] In some embodiments, on said third block and on said fourth block, a plurality of sipes is formed, open on said second edge of said third block and on said first edge of said fourth block, respectively.

[0125] Preferably, said plurality of sipes separates, on the second edge of said third block and on the first edge of said fourth block, respectively, said at least one first edge portion from said at least one second edge portion.

[0126] In some embodiments, said plurality of sipes of said third block and / or said fourth block extends parallel to an alignment direction of said third block and said fourth block defined by said first main groove and said second main groove.

[0127] In other embodiments, said plurality of sipes of said third block and / or of said fourth block extends transversely to said alignment direction, except for an end region, open at the respective edge facing the third secondary groove, substantially parallel to said alignment direction.

[0128] In some embodiments, in one or more of the edges of said first block, of said second block, of said third block and / or of said fourth block, said first angle defined on said portion of tread surface between said first edge portion and said first connecting angular edge portion is comprised between 60° and 120°, preferably between 80° and 100°, more preferably it is about 90°.

[0129] In some embodiments, in one or more of the edges of said first block, said second block, said third block and / or said fourth block, said second angle defined on said portion of tread surface between said first edge portion and said second connecting angular edge is comprised between 60° and 120°, preferably between 80° and 100°, more preferably it is about 90°.

[0130] Preferably, said first main groove extends to an equatorial plane of the tread band. In some embodiments, said first main groove and said second main groove have sections with different inclination with respect to an equatorial plane. Preferably the difference in inclination between each section of said first main groove and a corresponding section of said second main groove is less than 20°, more preferably less than 10°, even more preferably less than 5°.

[0131] In some embodiments, said first main groove and said second main groove have a width between 3 mm and 11 mm.

[0132] Preferably, said first main groove and said second main groove have a width which decreases from a first end thereof which is defined in said shoulder region to a second end thereof which is defined in said equatorial region.

[0133] In some embodiments, said first main groove and said second main groove are formed in alternating succession along the entire circumferential development of said tread band.

[0134] In some embodiments, said first main groove and said second main groove have a depth greater than 5 mm, preferably greater than 7 mm, more preferably of about 9 mm.

[0135] In some embodiments, said first main groove and said second main groove have a greater depth than a depth of said first secondary groove and said second secondary groove.

[0136] In some embodiments, said first secondary groove and said second secondary groove have a depth greater than 3 mm.

[0137] In some embodiments, said first secondary groove and said second secondary groove have a depth of less than 8 mm.

[0138] In some embodiments, said first secondary groove has a width greater than a width of said second secondary groove.

[0139] In some embodiments, said first secondary groove and said second secondary groove have a width greater than 2 mm.

[0140] In some embodiments, said first secondary groove and said second secondary groove have a width of less than 4 mm.

[0141] In some embodiments, said first secondary groove has a width greater than the width of said second secondary groove.

[0142] In some embodiments, said third secondary groove has a width substantially equal to the width of said second secondary groove.

[0143] In some embodiments, said third secondary groove has a depth substantially equal to the depth of said second secondary groove.

[0144] In some embodiments, the distance between said first secondary groove and said second secondary groove measured along the axial direction is comprised between 10% and 30% of the width of said tread band.

[0145] In some embodiments, the distance between said second secondary groove and said third secondary groove measured along the axial direction is comprised between 10% and 30% of the width of said tread band.

[0146] In some embodiments, said first secondary groove and said second secondary groove are axially spaced by a measurement greater than 10 mm.

[0147] In some embodiments, said first secondary groove and said second secondary groove are axially spaced by a measurement less than 30 mm.

[0148] In some embodiments, said first secondary groove is in an axially inner position with respect to said second secondary groove. In some embodiments, said second secondary groove is in an axially inner position with respect to said third secondary groove.

[0149] In some embodiments, said first block is in an axially inner position with respect to said second block.

[0150] Preferably, said first block is crossed by an equatorial plane of said tread band or is less than 10 mm from said equatorial plane.

[0151] In some embodiments, said second block is in an axially inner position with respect to said third block.

[0152] In some embodiments, said third block is in an axially inner position with respect to said fourth block.

[0153] Preferably, said fourth block is crossed by an axial end of said tread band.

[0154] In some embodiments, in one or more of the edges of said first block, second block, third block and fourth block, said first edge portion comprises a surface inclined with respect to the tread surface by an angle comprised between 30° and 60°, preferably about 45°.

[0155] In some embodiments, in one or more of the edges of said first block, second block, third block and fourth block, said first edge portion has a width comprised between 0.5 mm and 3 mm, preferably about 1 mm.

[0156] In some embodiments, all the edges of the blocks facing said first secondary groove, said second secondary groove and said third secondary groove have the same total number of first and second edge portions, preferably two or three or four.

[0157] In some embodiments, the edges of the blocks facing said first secondary groove have a total number of first and second edge portions less than the total number of first and second edge portions of the edges of the blocks facing said third secondary groove.

[0158] The characteristics and advantages of the invention will become clearer from the detailed description of an embodiment shown, by way of non-limiting example, with reference to the appended drawings wherein:

[0159] - Figure 1 is a schematic front view of a significant portion of tread band, extended on a plane, of a tyre for vehicle wheels made in accordance with the present invention,

[0160] - Figure 2 is a schematic view on an enlarged scale of a portion of the tread band of the tyre in Figure 1,

[0161] - Figure 2a is a further enlarged scale schematic view of a portion of Figure 2,

[0162] - Figure 3 is a perspective view of part of the portion of tread band in Figure 2, and - Figures 4 and 5 are schematic views, on a further enlarged scale, of respective details of the portion of tread band in Figure 3.

[0163] With reference to the attached figures, 1 globally denotes a tyre for vehicle wheels made in accordance with the present invention.

[0164] The tyre 1 has a conventional generally toroidal shape extended around a rotation axis, defining an axial direction Y of the tyre, and crossed by an equatorial plane X, perpendicular to the rotation axis.

[0165] The tyre 1 comprises a tread band 2 on which a tread surface 3 is defined which is arranged in a position that is radially external to the tread band 2 and intended for contact with a road surface.

[0166] The tread band 2 has a width L and extends axially between a first axial end 2a and an opposite second axial end 2b.

[0167] The tyre 1 has, for example, a nominal section width of about 225 mm with a shoulder diameter of 17 inches.

[0168] An equatorial region 4, which extends circumferentially and symmetrically around the equatorial plane X, as well as a first shoulder region 5 and a second shoulder region 6, which extend respectively at the axially opposite sides of the equatorial region 4, in a position axially external to the same tread band 2 up to the respective axial ends 2a, 2b of the tread band 2, remain defined on the tread band 2.

[0169] Each shoulder region 5 and 6 is delimited on the axially inner side by respective secondary grooves, in particular the axially outer secondary grooves formed in the tread band, as further detailed below.

[0170] The equatorial region 4 is approximately 56% of the width of the tread band 2, so that, consequently, each shoulder region 5 and 6 is approximately 22% of the width of the tread band 2.

[0171] A plurality of grooves of various sizes and configurations delimiting a plurality of blocks is formed on the tread strip 2, so as to define, as a whole, the tread pattern of the tyre 1 which, in the preferred example described herein, is configured to roll in a preferential direction of travel F.

[0172] In particular, the tread pattern has a modular configuration in which some pitches M are defined, repeated in succession along the circumferential extension of the tread band 2 according to an appropriate sequence.

[0173] The different pitches M all have the same general configuration of grooves and blocks but may differ slightly in terms of circumferential dimensions.

[0174] An example of a pitch M, represented in enlarged scale in Figure 2, comprises a first main groove 10 and a second main groove 20, which both extend from the first axial end 2a of the tread band 2 up to the equatorial region 4, crossing the first shoulder region 5.

[0175] In particular, the first main groove 10 extends between a first, axially external end 11, which open at the first axial end 2a of the tread band 2, and a second, axially internal end 12, which closes an end section 13 of the first main groove 10 that extends in a zig-zag manner along the equatorial plane X.

[0176] The second main groove 20 extends between a first, axially external end 21, which opens at the first axial end 2a of the tread band 2, and a second, axially internal end 22, which converges into the end section 13 of the first main groove 10.

[0177] Corresponding main grooves 10a and 20a extend from the second axial end 2b of the tread band 2 up to the equatorial region 4, crossing the second shoulder region 6.

[0178] The course of the main grooves 10a, 20a is substantially similar to that of the first and second main groove 10, 20, so the following detailed description of the main grooves 10 and 20 may also refer, mutatis mutandis, to the main grooves 10a, 20a. The two pairs of main grooves 10, 20 and 10a, 20a, are in fact substantially symmetrical with respect to the equatorial plane X, apart from a slight circumferential offset and apart from the end section 13 of the first main groove 10, on which the main grooves 10a and 20a also converge.

[0179] The first main groove 10 and the second main groove 20 have a slightly curvilinear course, with an inclination with respect to the equatorial plane X that decreases from the first shoulder region 5 up to the equatorial region 4.

[0180] The first main groove 10 and the second main groove 20 have a depth varying from about 7 mm in the first shoulder region 5 to about 8.8 mm in the equatorial region 4, and they have a width which decreases from a first end 11, 21 thereof, where it is between 7 mm and 11 mm, up to the end section 13 (and to the second end 12) and, respectively, to the second end 22, where it is between 3.5 mm and 5.5 mm.

[0181] A first secondary groove 30, a second secondary groove 40 and a third secondary groove 50 further extend between the first main groove 10 and the second main groove 20, as well as between the second main groove 20 and the first main groove 10 of the next pitch M.

[0182] Specifically, the first secondary groove 30 is defined in an axially internal position, the third secondary groove 50 is defined in an axially external position, delimiting the first shoulder region 5 from the equatorial region 4, and the second secondary groove 40 is defined in an intermediate position between the other two secondary grooves 30 and 50.

[0183] The first secondary groove 30 extends in a substantially rectilinear manner between a first and a second end, which are open on the first main groove 10 and the second main groove 20, respectively.

[0184] The first secondary groove 30 has a constant width, e.g. about 3.5 mm, and a substantially constant depth, e.g. about 7 mm at one of its central regions, while its opposing end regions are chamfered towards the bottom of the respective main grooves 10 and 20.

[0185] The first secondary groove 30 comprises a bottom 31 from which a pair of walls 32 rises towards the tread surface 3, with a substantially constant inclination, slightly divergent with respect to the radial direction of the tyre, with which it forms an angle comprised between about 2° and about 10°.

[0186] The second secondary groove 40 extends in a substantially rectilinear manner, substantially parallel to the first secondary groove 30, between a first and a second end, which are open on the first main groove 10 and the second main groove 20, respectively.

[0187] The second secondary groove 40 has a width and depth less than the width and depth of the first secondary groove 30.

[0188] In particular, the second secondary groove 40 has a substantially constant width of, e.g., approximately 2.5 mm and a substantially constant depth of, e.g., approximately 4 mm at one of its central regions, while its opposing end regions are chamfered towards the respective main grooves 10 and 20.

[0189] The second secondary groove 40 comprises a bottom 41 from which a pair of walls 42 rises towards the tread surface 3, with a substantially constant inclination, slightly divergent with respect to the radial direction of the tyre, with which it forms an angle comprised between about 2° and about 10°.

[0190] The third secondary groove 50 extends along a curvilinear direction between a first and second end open on the first main groove 10 and the second main groove 20, respectively.

[0191] The third secondary groove 50 has a substantially constant depth and width, for example equal to about 4 mm and about 3.5 mm, respectively.

[0192] The third secondary groove 50 comprises a bottom 51 from which a pair of walls 52 rises towards the tread surface 3, with a substantially constant inclination, slightly divergent with respect to the radial direction of the tyre, with which it forms an angle comprised between about 2° and about 10°.

[0193] The third secondary groove 50, moreover, is crossed by a sipe 53, blind, which is formed longitudinally on its bottom.

[0194] Between each main groove 10a and the main groove 20a, as well as between the main groove 20a and the main groove 10a of the next pitch M, there are formed corresponding secondary grooves 30a, 40a and 50a which are entirely similar to the first secondary groove 30, to the second secondary groove 40 and to the third secondary groove 50, respectively.

[0195] The first main groove 10 and the second main groove 20 delimit laterally, from the equatorial plane X to the axial end 2a, a first block 60, a second block 70, a third block 80 and a fourth block 90, aligned along an alignment direction Z, defined by the longitudinal extension of the main grooves 10, 20, and separated from each other by the secondary grooves 30, 40 and 50.

[0196] Naturally, the main grooves 10a and 20a and the secondary grooves 30a, 40a and 50a delimit the corresponding blocks 60a, 70a, 80a and 90a, which are entirely analogous to the blocks 60, 70, 80 and 90 described in detail below.

[0197] The first block 60, axially inner with respect to the other blocks delimited by the first and second main grooves 10 and 20 and crossed by the equatorial plane X of the tread band 2, comprises a first edge 61, facing the first secondary groove 30.

[0198] The first edge 61 is subdivided into three edge portions, adjacent to each other and having substantially the same length, e.g. approximately 5 mm, formed by two first edge portions 61a, both defined by an angular edge, interspersed with a second edge portion 61b in turn defined by a chamfer.

[0199] The two first edge portions 61a are substantially identical to each other, with the edge formed by the intersection of the wall 32 of the first secondary groove 30 with the portion of tread surface 3 of the first block 60. The chamfer of the second edge portion 61b is formed by a substantially flat surface, about 1 mm wide, and inclined at about 45°, extending between the portion of tread surface 3 of the first block 60 and the wall 32 of the first groove 30.

[0200] On the first block 60 there is a pair of sipes 62, extending longitudinally and open on the first edge 61 to separate the first edge portion 61a from the second edge portion 61b.

[0201] The first edge 61 further comprises a first connecting angular edge 63 and a second connecting angular edge 64 extending over the portion of tread surface 3 between the two first edge portions 61a and the second edge portion 61b interposed between them.

[0202] As can best be seen in Figure 4, the second edge portion 61b is connected to the two first edge portion adjacent to it by a pair of side walls 65, generically triangular in shape, extending to the opposing sides of the second edge portion 61b.

[0203] The intersections of the two side walls 65 with the tread surface portion 3 form the first connecting angular edge 63 and the second connecting angular edge 64, respectively, while the intersections of the two side walls 65 with the wall 32 of the first secondary groove 30 form two additional angular edges 66a and 66b, extending from the tread surface portion 3 towards the bottom 31 of the first secondary groove 30.

[0204] The first connecting angular edge 63 forms on the portion of tread surface 3 with the first edge portion 61a to which it is connected, a first angle A of approximately 90°, whose bisector R. extends substantially along the circumferential direction.

[0205] In turn, the second connecting angular edge 64 forms on the portion of tread surface 3 with the first edge portion 61a to which it is connected, a second angle B of approximately 90°, whose bisector S extends substantially along the axial direction. The second block 70, axially external to the first block 60, comprises a first edge 71, facing the first secondary groove 30 on the opposite side of the first edge 61 of the first block 60.

[0206] The first edge 71 of the second block 70 is subdivided into three edge portions, adjacent to each other and having substantially the same length, e.g. equal to about 5 mm, formed by two second edge portions 71b, both defined by a chamfer extending to connect the wall 32 with the tread surface portion 3, interspersed with a first edge portion 71a, in turn defined by an angular edge resulting from the intersection of the wall 32 with the tread surface portion 3.

[0207] The first edge portions 61a and 71a of the first block 60 and the second block 70 are substantially identical to each other, as are the second edge portions 61b and 71b of the first block 60 and the second block 70.

[0208] The two second edge portions 71b of the second block 70 are facing a respective first edge portion 61a of the first block 60, while the first edge portion 71a of the second block 70 is facing the second edge portion 61b of the first block 60.

[0209] Similarly to the first block 60, a pair of sipes 72, extending longitudinally and open on the first edge 71 to separate the second edge portion 71b from the first edge portion 71a, is also formed on the second block 70.

[0210] The first edge 71 further comprises a first connecting angular edge 73 and a second connecting angular edge 74, extending over the portion of tread surface 3 of the second block 70 between the two second edge portions 71b and the first edge portion 71a interposed between them.

[0211] As can best be seen in Figure 5, the first edge portion 71a is connected to the two second edge portions 71b adjacent to it by a pair of side walls 75, generically triangular in shape, extending to the opposing sides of the first edge portion 71a. The intersections of the two side walls 75 with the tread surface portion 3 of the second block 70 form the first connecting angular edge 73 and the second connecting angular edge 74, respectively, while the intersections of the two side walls 75 with the wall 32 of the first secondary groove 30 form two additional angular edges 76a and 76b, extending from the tread surface portion 3 of the second block 70 towards the bottom 31 of the first secondary groove 30.

[0212] The first connecting angular edge 73 forms on the portion of tread surface 3 with the first edge portion 71a to which it is connected, a first angle A' of approximately 90°, whose bisector R. extends substantially along the circumferential direction.

[0213] In turn, the second connecting angular edge 74 forms on the portion of tread surface 3 with the first edge portion 71a to which it is connected, a second angle B' of approximately 90°, whose bisector S' extends substantially along the axial direction. It will be noted that the additional angular edges 76a and 76b defined in the first edge 71 of the second block 70 are directed in the opposite direction to the additional angular edges 66a and 66b defined in the first edge 61 of the first block 60.

[0214] In particular, while the additional angular edge 66a of the first block 60 faces circumferentially in the direction opposite to the direction of travel F, the additional angular edge 76a of the second block 70 faces circumferentially in the same direction as the direction of travel F, and, similarly, while the additional angular edge 66b of the first block 60 faces axially away from the equatorial plane X, the additional angular edge 76b of the second block 70 faces axially towards the equatorial plane X.

[0215] A second edge 77 of the second block 70, longitudinally opposing the first edge 71, and a first edge 81 of the third block 80, face the secondary groove 40.

[0216] The configuration of the second edge 77 of the second block 70 and the first edge 81 of the third block 80 is entirely analogous to that of the first edge 61 of the first block 60 and the second edge 71 of the second block 70 facing the first secondary groove 30, described in detail in the preceding paragraphs with reference to Figures 4 and 5. Thus, the second edge 77 of the second block 70 comprises two first edge portions 77a interspersed with a second edge portion 77b, for example, all of which are approximately 5 mm in length, adjacent to each other and separated from each other by the sipes 72.

[0217] The first two edge portions 77a are defined by an edge resulting from the intersection of the wall 42 with the portion of tread surface 3 of the second block 70, while the second edge portion 77b, in turn, is defined by a chamfer extending to connect the wall 42 of the second secondary groove 40 and the portion of tread surface 3 of the second block 70.

[0218] The second edge portion 77b is connected to the two first edge portions 77a adjacent to it by a first connecting angular edge 78 and a second connecting angular edge 79. The latter form on the portion of tread surface 3 with the respective first edge portions 77a a first angle Al, of approximately 90°, whose bisector R.1 extends substantially along the circumferential direction, and a second angle Bl, of approximately 90°, whose bisector SI extends substantially along the axial direction. Similarly to the first edge 71 of the second block 70, the first edge 81 of the third block 80 comprises two second edge portions 81b, defined by a chamfer extending between the wall 42 of the second secondary groove 40 and the tread surface portion 3 of the third block 80, interspersed with a first edge portion 81a, defined by an angular edge resulting from the intersection of the wall 42 with the tread surface portion 3. All the first and second edge portions have a length of e.g. approximately 5 mm and are separated from each other by a pair of sipes 82 formed longitudinally on the third block 80.

[0219] The first edge portion 81a is connected to the two second edge portions 81b adjacent to it by a first connecting angular edge 83 and a second connecting angular edge 84. The latter form on the portion of tread surface 3 of the third block 80 with the respective first edge portions 81a a first angle Al', of about 90°, whose bisector R.1' extends substantially along the circumferential direction, and a second angle Bl', of about 90°, whose bisector SI' extends substantially along the axial direction.

[0220] The configuration of the second edge 77 of the second block 70 and the first edge 81 of the third block 80 thus defines the same plurality of additional angular edges as previously identified in the edges facing the first secondary groove 30, but offset axially by an amount equal to the axial dimension of the second block 70.

[0221] A second edge 87 of the third block 80, longitudinally opposed to the first edge 81, and a first edge 91 of the fourth block 90 face the third secondary groove 50. With the exception of the curvilinear profile of the median edge portion, the configuration of the second edge 87 of the third block 80 and the first edge 91 of the fourth block 90 is entirely analogous to that of the first edge 61 of the first block 60 and the second edge 71 of the second block 70 facing the first secondary groove 30, described in detail in the preceding paragraphs with reference to Figures 4 and 5.

[0222] Thus, the second edge 87 of the third block 80 comprises two first edge portions 87a interspersed with a second edge portion 87b adjacent to each other and separated from each other by the sipes 82.

[0223] The first two edge portions 87a are defined by an edge resulting from the intersection of the wall 52 with the portion of tread surface 3 of the third block 80, while the second edge portion 87b, in turn, is defined by a chamfer extending to connect the wall 52 of the third secondary groove 50 and the portion of tread surface 3 of the third block 80.

[0224] The second edge portion 87b is connected to the two first edge portions 87a adjacent to it by a first connecting angular edge 88 and a second connecting angular edge 89. The first connecting angular edge 88 forms on the portion of tread surface 3 with the first edge portion 87a, a first angle A2 of approximately 120°, whose bisector R.2 extends substantially along the circumferential direction.

[0225] Similarly to the first edge 71 of the second block 70, the first edge 91 of the fourth block 90 comprises two second edge portions 91b, defined by a chamfer extending between the wall 52 of the third secondary groove 50 and the tread surface portion 3 of the fourth block 90, interspersed with a first edge portion 91a, defined by an angular edge resulting from the intersection of the wall 52 with the tread surface portion 3. The first and second edge portions are separated from each other by a pair of sipes 92 formed longitudinally on the fourth block 90.

[0226] The first edge portion 91a is connected to the two second edge portions 91b adjacent to it by a first connecting angular edge 93 and a second connecting angular edge 94. The first connecting angular edge 93 forms on the portion of tread surface 3 of the fourth block 90 with the first edge portion 91a to which it is connected, a first angle A2' of approximately 120°, whose bisector R.2' extends substantially along the circumferential direction.

[0227] The configuration of the second edge 87 of the third block 80 and the first edge 91 of the fourth block 90 thus defines a further plurality of additional circumferentially directed angular edges, appropriately offset from those defined on the second secondary groove 40 along the axial direction by an amount equal to the axial dimension of the third block 80.

[0228] As can also be seen in the portion of tread band shown in Figure 1, the different circumferential dimension between the pitches M can lead to variations in the number of edge portions into which each edge of the blocks facing a secondary groove is divided, so that this number can be different from three, for example four or two.

[0229] In particular, it is possible that in some pitches M, the edges 87 and 91 of the blocks 80 and 90 facing the third secondary groove 50 are subdivided into four first and second edge portions and the edges 61 and 71 of the blocks 60 and 70 facing the first secondary groove 30 are divided into three first and second edge portions.

[0230] Or, in other pitches M, it is possible that the edges 87 and 91 of the blocks 80 and 90 facing the third secondary groove 50 are subdivided into three first and second edge portions and that the edges 61 and 71 of the blocks 60 and 70 facing the first secondary groove 30 are subdivided into two first and second edge portions.

[0231] Tests conducted by the Applicant on a tyre made according to the preferred example described above showed good behaviour on snow-covered roads.

[0232] In fact, as mentioned above, due to the above-mentioned characteristics, the tread band has a plurality of additional gripping edges at the secondary grooves facing in the circumferential direction and along the axial direction, which are generally evenly distributed along the axial dimension of the tread band.

[0233] Naturally, those skilled in the art may make further modifications and variants to the above-described invention with the purpose of meeting specific and contingent application needs, variants and modifications in any case falling within the scope of protection as defined by the successive claims.

Claims

CLAIMS1. Tyre (1) for vehicles wheels comprising a tread band (2), on which there are defined:- a first main groove (10) and a second main groove (20) which both extend transversely from a first shoulder region (5) to an equatorial region (4) of said tread band (2),- a first secondary groove (30) and a second secondary groove (40) which both extend between said first main groove (10) and said second main groove (20),- a first block (60), a second block (70) and a third block (80), each of which is at least partially delimited at a pair of opposite sides by said first main groove (10) and by said second main groove (20), respectively, wherein said first block (60) and said second block (70) are separated from each other by said first secondary groove (30) and said second block (70) and said third block (80) are separated from each other by said second secondary groove (40), wherein each edge (61; 71) of said first block (60) and said second block (70) which faces said first secondary groove (30) and each edge (77; 81) of said second block (70) and said third block (80) which faces said second secondary groove (40) comprises:- at least one first edge portion (61a, 71a; 77a, 81a) which is defined by an angular edge which is formed between a wall (32; 42) of said first secondary groove (30) or said second secondary groove (40) and a portion of tread surface (3),- at least one second edge portion (61b, 71b; 77b, 81b) which is adjacent to the first edge portion (61a, 71a; 77a, 81a) and which is defined by a chamfer which extends between said wall (32; 42) of said first secondary groove (30) or said second secondary groove (40) and said portion of tread surface (3),- at least one first connection angular edge (63, 73; 78, 83) which extends on said portion of tread surface (3) between said first edge portion (61a, 71a; 77a, 81a) and said second edge portion (61b, 71b; 77b, 81b), wherein said at least one first edge portion (61a, 71a; 77a, 81a) and said at least one first connection angular edge (63, 73; 78, 83) define a first angle (A, A'; Al, Al') at said portion of tread surface (3) and the bisector (R, R'; Rl, Rl') of said first angle (A, A'; Al, Al') is inclined with respect to a circumferential direction which is defined on said tread band at an angle less than 15°.

2. Tyre according to claim 1, wherein a first edge (61) of said first block (60) and afirst edge (71) of said second block (70) face said first secondary groove (30) and, in at least one of said first edge (61) of said first block (60) and said first edge (71) of said second block (70), said first edge portion (71a) is interposed between said second edge portion (71b) and an additional second edge portion (71b).

3. Tyre according to claim 2, wherein said at least one of said first edge (61) of said first block (60) and said first edge (71) of said second block (70) comprises a second connection angular edge (74) which extends on said portion of tread surface (3) between said first edge portion (71a) and said additional second edge portion (71b), wherein said first edge portion (71a) and said second connection angular edge (74) define a second angle (B') on said portion of tread surface (3) and the bisector (S') of said second angle (B') is inclined with respect to an axial direction (Y) which is defined on said tread band (2) at an angle less than 15°.

4. Tyre according to any one of claims 1 to 3, wherein a first edge (61) of said first block (60) and a first edge (71) of said second block (70) face said first secondary groove (30) and, in at least one of said first edge (61) of said first block (60) and said first edge (71) of said second block (70), said second edge portion (61b) is interposed between said first edge portion (61a) and an additional first edge portion (61a).

5. Tyre according to claim 4, wherein said at least one of said first edge (61) of said first block (60) and said first edge (71) of said second block (70) comprises a second connection angular edge (64) which extends on said portion of tread surface (3) between said additional first edge portion (61a) and said second edge portion (61b), wherein said additional first edge portion (61a) and said second connection angular edge (64) define a second angle (B) on said portion of tread surface (3) and the bisector (S) of said second angle (B) is inclined with respect to an axial direction (Y) which is defined on said tread band (2) at an angle less than 15°.

6. Tyre according to any one of claims 2 to 5, wherein each first edge portion (61a) of said first edge (61) of said first block (60) faces a second edge portion (71b) of said first edge (71) of said second block (70).

7. Tyre according to any one of claims 2 to 6, wherein each second edge portion (61b) of said first edge (61) of said first block (60) faces a first edge portion (71a) of said first edge (71) of said second block (70).

8. Tyre according to any one of the preceding claims, wherein a second edge (77) ofsaid second block (70) and a first edge (81) of said third block (80) face said second secondary groove (40), and wherein, in at least one of said second edge (77) of said second block (70) and said first edge (81) of said third block (80), said first edge portion (81a) is interposed between said second edge portion (81b) and an additional second edge portion (81b).

9. Tyre according to claim 8, wherein said at least one of said second edge (77) of said second block (70) and said first edge (81) of said third block (80) comprises a second connection angular edge (84) which extends on said portion of tread surface (3) between said first edge portion (81a) and said additional second edge portion (81b), wherein said first edge portion (81a) and said second connection angular edge (84) define a second angle (Bl') on said portion of tread surface (3) and the bisector (SI') of said second angle (Bl') is inclined with respect to an axial direction (Y) which is defined on said tread band (2) at an angle less than 15°.

10. Tyre according to any one of the preceding claims, wherein a second edge (77) of said second block (70) and a first edge (81) of said third block (80) face said second secondary groove (40), and wherein, in at least one of said second edge (77) of said second block (70) and said first edge (81) of said third block (80), said second edge portion (77b) is interposed between said first edge portion (77a) and an additional first edge portion (77a).

11. Tyre according to claim 10, wherein said at least one of said second edge (77) of said second block (70) and said first edge (81) of said third block (80) comprises a second connection angular edge (79) which extends on said portion of tread surface (3) between said additional first edge portion (77a) and said second edge portion (77b), wherein said additional first edge portion (77a) and said second connection angular edge (79) define a second angle (Bl') on said portion of tread surface (3) and the bisector of said second angle (Bl') is inclined with respect to an axial direction which is defined on said tread band (2) at an angle less than 15°.

12. Tyre according to any one of claims 8 to 11, wherein each first edge portion (77a) of said second edge (77) of said second block (70) faces a second edge portion (81b) of said first edge (81) of said third block (80).

13. Tyre according to any one of claims 8 to 12, wherein each second edge portion (77b) of said second edge (77) of said second block (70) faces a first edge portion (81a) of said first edge (81) of said third block (80).

14. Tyre according to any one of the preceding claims, wherein between said first main groove (10) and said second main groove (20) a third secondary groove (50) extends, separating said third block (80) from a fourth block (90),Tyre according to any one of the preceding claims, wherein a third secondary groove (50) which separates said third block (80) from a fourth block (90) extends between said first main groove (10) and said second main groove (20), wherein said second edge (87) of said third block (80) and said first edge (91) of said fourth block (90) each comprise:- at least one first edge portion (87a, 91a) which is defined by an angular edge which is formed between a wall (52) of said third secondary groove (50) and a portion of tread surface (3),- at least one second edge portion (87b, 91b) which is adjacent to the first edge portion (87a, 91a) and which is defined by a chamfer which extends between said wall (52) of said third secondary groove (50) and said portion of tread surface (3),- at least one first connection angular edge (88, 93) which extends on said portion of tread surface (3) between said first edge portion (87a, 91a) and said second edge portion (87b, 91b), wherein said first edge portion (77a, 91a) and said first connection angular edge (88, 93) define a first angle (A2, A2') on said portion of tread surface (3) and the bisector of said angle (R.2, R.2') is inclined with respect to a circumferential direction which is defined on said tread band (2) by an angle less than 15°.

15. Tyre according to claim 14, wherein, in at least one of said second edge (87) of said third block (80) and said first edge (91) of said fourth block (90), said first edge portion (91a) is interposed between said second edge portion (91b) and an additional second edge portion (91b).

16. Tyre according to claim 14 or 15, wherein, in at least one of said second edge (87) of said third block (80) and said first edge (91) of said fourth block (90), said second edge portion (87b) is interposed between said first edge portion (87a) and an additional first edge portion (87a).

17. Tyre according to any one of claims 14 to 16, wherein each first edge portion (87a) of said second edge (87) of said third block (80) faces a second edge portion (91b) of said first edge (91) of said fourth block (90).

18. Tyre according to any one of claims 14 to 17, wherein each second edge portion (87b) of said second edge (87) of said third block (80) faces a first edge portion(91a) of said first edge (91) of said fourth block (90).

19. Tyre according to any one of the preceding claims, wherein, in one or more of the edges of said first block (60), said second block (70) and said third block (80), said first angle (A, A'; Al, Al'; A2) which is defined on said portion of tread surface (3) between said first edge portion (61a, 71a; 77a, 81a; 87a) and said first connection angular edge (63, 73; 78, 83; 88) is between 60° and 120°.

20. Tyre according to any one of claims 14 to 19, wherein, in said fourth block (90), said first angle (A2') which is defined on said portion of tread surface between said first edge portion (91a) and said first connection angular edge (93) is between 60° and 120°.

21. Tyre according to any one of claims 11 to 20, wherein, in one or more of the edges of said first block (60), said second block (70) and said third block (80), said second angle (B, B'; Bl, Bl') which is defined on said portion of tread surface (3) between said first edge portion (61a, 71a; 77a, 81a; 87a) and said second connection angular edge (64, 74; 79, 84) is between 60° and 120°.

22. Tyre according to any one of the preceding claims, wherein the distance between said first secondary groove (30) and said second secondary groove (40) measured in the axial direction (Y) is between 10% and 30% of the width (L) of said tread band (2).

23. Tyre according to any one of claims 14 to 22, wherein the distance between said second secondary groove (40) and said third secondary groove (50) measured in the axial direction (Y) is between 10% and 30% of the width (L) of said tread band (2).

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