Tyre

Abstract

A Tyre comprising a tread band (2) comprising: - a plurality of grooves (4), - a plurality of blocks (5) which are delimited by said plurality of grooves (4); - at least a first sipe (10) which extends on at least one block (5) of said plurality of blocks from a radially external surface (3) of said tread band to a radially inner surface of said tread band, wherein said first sipe (10) comprises - a middle portion (140) having a first depth (P1), and - a first lateral portion which extends between said middle portion (140) and a first end (11) of the first sipe (10) and which is open in a groove of said plurality of grooves (4), wherein said first lateral portion (110) comprises - a first section (111) which is adjacent to said middle portion (140), which has a second depth (P2) which is less than said first depth (P1), and - at least a second section (112) which is arranged between said first section (111) and said first end of the first sipe (10), which has a third depth (P3) which is less than said second depth (P2).

Description

[0001] TYRE

[0002] The present invention concerns a pneumatic tyre for vehicle wheels.

[0003] In more detail, the invention concerns a tyre with improved performance, in particular on snowy road surfaces.

[0004] A tyre generally comprises a carcass structure, toroidally shaped about a rotation axis on which there are applied a belt structure, in a radially outer position, and, further overlapped, a tread band, made of elastomeric material, on which a tread surface intended for contact with the road surface is defined.

[0005] On the tread band, there is typically defined a plurality of grooves of various shape and geometry, with a circumferential and / or transverse course, which delimit a plurality of blocks. The overall configuration of the tread band defined by the grooves and blocks represents the tread pattern.

[0006] The characteristics of the tread pattern, and in particular the amount and configuration of the grooves and blocks provided on the tread surface, primarily determine the performance of the tyre in terms of its road behaviour, particularly in relation to the possible different conditions of the road surface itself.

[0007] In addition, in order to improve the performance of a tyre on a snowy surface, small notches, called "sipes", are generally made on the blocks of the tread band, which extend from the tread surface of the tyre towards the inside of the block. The function of the sipes is generally to offer additional grip elements in the case of driving on a snowy surface and to retain a certain amount of snow, thereby improving grip with the road surface. It is known, in fact, that snow-snow friction (i.e. between the snow retained inside the sipes and the snow-covered road surface) is greater than tyre-snow friction (i.e. between the tread band and the snow-covered road surface).

[0008] Different types of winter tyres with blocks comprising sipes are known.

[0009] An example is present in the international document W02023119019A1, which describes a winter tyre whose blocks are provided with sipes.

[0010] Further examples of tyres whose blocks are provided with sipes are described in patent documents US12054008B2 and US11801715B2.

[0011] In this description and in the following claims, the following definitions shall apply. The term "radial" and the expressions "radially inner / outer" are used with reference to the axis of rotation of the tyre, while the terms "circumferential" and "circumferentially" are used with reference to the direction of the annulardevelopment of the tyre, i.e. the rolling direction of the tyre, which corresponds to a direction lying on a plane coincident with or parallel to the equatorial plane of the tyre.

[0012] In particular:

[0013] the term "radial direction" is used to indicate a direction substantially perpendicular to the axis of rotation of the tyre, or in any case lying on a plane containing the axis of rotation of the tyre and away from it;

[0014] the term "circumferential direction" is used to indicate a direction substantially parallel to the rolling direction of the tyre, i.e. inclined with respect to the rolling direction by an angle of less than 45°.

[0015] The term "groove" is intended to mean a notch made on a portion of the tread band, having at least one portion having a width of at least 1.5 mm, and preferably said groove has a minimum depth of about 3 mm.

[0016] A groove is defined "circumferential" when it extends along a circumferential direction or, at most, is inclined at an angle of less than 10° with respect to the circumferential direction.

[0017] A groove is defined "transverse" when it extends along a direction that is inclined with respect to the circumferential direction by an acute angle of at least 10°. The term "sipe" is intended to mean a notch formed in a portion of the tread band having a maximum width between about 0.1 mm and 1.5 mm. This sipe, depending on the performance required of the tyre, extends along a trajectory defined by a straight line or a curved line or a broken line, wherein the term "broken line" is used to indicate a line composed of two or more consecutive straight and / or curvilinear lines that are inclined with respect to each other (e.g. zig-zag).

[0018] By "depth" of a section or of a portion of a sipe, it is intended to indicate the distance between the radially external surface of the tread portion and the radially inner surface of the tread band, measured in a radial direction of the tyre at said section or portion.

[0019] In the event that the depth of the section or portion varies along its longitudinal development, the average depth is considered, the value of which is obtained as an average of the different depth values suitably weighed as a function of the relative longitudinal extensions.

[0020] By "longitudinal development direction" referred to a sipe, it is intended to indicatethe path or direction along which the sipe extends between its two opposite ends. Two sipes are "adjacent" when they are arranged on the tread surface one after the other, considering the rotation of the tyre in any of the two directions of rotation.

[0021] Each sipe separates the block on which it is formed into two block portions having respective mutually facing surfaces.

[0022] These surfaces extend along a respective "reference plane" incident to the tread surface and coincident with the surface net of any protrusions and recesses.

[0023] A sipe is of the "three-dimensional" type when at least one of the mutually facing surfaces of the block portions has at least one protrusion, while the other of these surfaces has a corresponding recess, adapted to at least partially receive this protrusion.

[0024] In other words, the respective projections of the two block portions separated by the sipe, along any direction lying on each reference plane placed at the corresponding projection and recess, are at least partly overlapped.

[0025] In this way, a relative displacement of the two block portions along a direction lying on the reference plane is hindered by interference between the two block portions at the protrusion and recess.

[0026] The Applicant has observed that the mutual positioning of grooves and sipes on the tread band affects the directionality and running stability characteristics of the tyre. In particular, the performance of a tyre on a snowy surface depends on the shape and distribution of the sipes identified on the blocks of the tread band. However, the Applicant has observed that the presence of sipes, while improving the behaviour of the block for example on the snowy surface, in particular, in some areas of the same that are more subject to localised stresses, makes the structure thereof weaker and, therefore, a reduction in the resistance capacity to external stresses (e.g. shear) may occur.

[0027] Due to this weakening, for example during braking, acceleration or travel on bends, the block undergoes significant deformations that lead to a relative early deterioration.

[0028] In particular, the Applicant has observed that the block portions identified by the confluence of a sipe in a groove are areas that are particularly subject to localised stresses.

[0029] The Applicant has therefore felt the need to create a sipe configured to make theaction of contrasting the deformation of the block portions mentioned above more effective.

[0030] The Applicant has further foreseen that the strength of the block can be improved by creating a structure of the sipe that allows a stiffening of the block, at least in the specific area of confluence of the sipe in the groove.

[0031] The Applicant finally found that a sipe having a structure having portions which extend from the radially external surface of the tread band to a radially inner surface of said tread band according to differentiated depths, wherein a deeper sipe portion is gradually connected to the surface of the tread band, so as to keep it away from an area of confluence of the sipe with a groove, allows to achieve an adequate stiffness of the block, while maintaining the mobility characteristics of the block portion in which it is formed, so as to improve the behaviour of the tyre, in particular on a snowy surface.

[0032] In particular, in a first aspect thereof, the invention relates to a tyre comprising a tread band comprising a plurality of grooves and a plurality of blocks which are delimited by said plurality of grooves.

[0033] Preferably, said tread band comprises at least a first sipe which extends on at least one block of said plurality of blocks from a radially external surface of said tread band to a radially inner surface of said tread band.

[0034] Preferably, said first sipe comprises a middle portion having a first depth.

[0035] Preferably, said first sipe comprises a first lateral portion which extends between said middle portion and a first end of the first sipe, and which is open in a groove of said plurality of grooves.

[0036] Preferably, said first lateral portion comprises a first section, which is adjacent to said middle portion and which has a second depth which is less than said first depth.

[0037] Preferably, said first lateral portion comprises at least a second section which is arranged between said first section and said first end of the first sipe, which has a third depth which is less than said second depth.

[0038] Providing on the block a sipe having the above characteristics advantageously allows to increase the stiffness of the block in or near the area of confluence of a sipe with a groove, without limiting its mechanical properties or snow retention performance.

[0039] The Applicant has verified, in particular, that a configuration of this type will reducethe deterioration of the block in the areas subject to localised stresses, and consequently the possible formation of tears and / or cracks.

[0040] The present invention, in the aforesaid aspect, may have at least one of the preferred features indicated below, considered individually or in combination with each other.

[0041] Preferably, said first sipe comprises a second lateral portion, which extends between said middle portion and a second end of the first sipe, opposite said first end.

[0042] Preferably, said second lateral portion comprises at least a third section which has a fourth depth which is less than said first depth.

[0043] Preferably, said second lateral portion extends over a length between 5% and 25% of the extension of the first sipe along said first longitudinal development direction. In this way, the sipe has a structure having a further portion adapted to stiffen the block, at the second end of the sipe itself.

[0044] Preferably, the value of the second depth of the first section of the first lateral portion is in a range between 40% and 80% of the value of the first depth of said middle portion.

[0045] Preferably, the value of the third depth of the second section of the first lateral portion is in a range between 10% and 50% of the value of the first depth of said middle portion.

[0046] Preferably, the value of the fourth depth of the third section of the second lateral portion is in a range between 10% and 50% of the value of the first depth of said middle portion.

[0047] Preferably, said first sipe is open on said radially external surface of said tread band, so as to define a first longitudinal development direction.

[0048] Preferably, said plurality of grooves comprises at least one transverse groove comprising at least one section which extends in a second longitudinal direction. Preferably, said first longitudinal direction of the sipe forms an angle between 10° and 70° with the second longitudinal direction of said transverse groove.

[0049] Preferably, said first longitudinal direction of the sipe forms an angle of 45° with the second longitudinal direction of said transverse groove.

[0050] Preferably, the second section of said first lateral portion has a length greater than or equal to 1.5 mm.

[0051] In this way, the stiffening effect of the block at the first end of the sipe, on whichthe lateral portion ends, is particularly effective.

[0052] Preferably, there is defined in said first sipe a bottom part which extends between said first end and said second end.

[0053] Preferably, said bottom part comprises a first surface portion at said middle portion.

[0054] Preferably, said bottom part comprises a second surface portion at said first section of the first lateral portion.

[0055] Preferably, said bottom part comprises a third surface portion at said second section of the first lateral portion.

[0056] Preferably, said first surface portion is connected to said second surface portion by means of a first connection surface which comprises a substantially planar first portion.

[0057] Preferably, said first substantially planar portion is inclined with respect to a radial direction of said tyre by an angle between 45° and 90°.

[0058] Preferably, said second surface portion is connected to said third surface portion by means of a second connection surface comprising a substantially planar second portion.

[0059] Preferably, said second substantially planar portion is inclined with respect to_a radial direction of said tyre by an angle between 45° and 90°.

[0060] Preferably, said first connection surface is connected to said first surface portion by means of a first curvilinear section with concavity which is directed towards the exterior of the block.

[0061] Preferably, said first curvilinear section is provided with a radius of curvature. Preferably, said radius of curvature of said first curvilinear section is between 1 and 3 mm.

[0062] Preferably, said first connection surface is connected to said second surface portion by means of a second curvilinear section with concavity which is directed towards the inner of the block.

[0063] Preferably, said second curvilinear section is provided with a radius of curvature. Preferably, said radius of curvature of said second curvilinear section is between 1 and 3 mm.

[0064] Preferably, said second connection surface is connected to said second surface portion by means of a third curvilinear section with concavity which is directed towards the exterior of the block.Preferably, said third curvilinear section is provided with a radius of curvature. Preferably, said radius of curvature of said third curvilinear section is between 1 and 3 mm.

[0065] Preferably, said second connection surface is connected to said third surface portion by means of a fourth curvilinear section with concavity which is directed towards the inner of the block.

[0066] Preferably, said fourth curvilinear section is provided with a radius of curvature. Preferably, said radius of curvature of said fourth curvilinear section is between 1 and 3 mm.

[0067] According to this configuration, a more progressive variation in the depth of the sipe is achieved, starting from the middle area up to the first end of the sipe, so as to obtain a stiffening of the block and at the same time optimising the deformability of the block, so as to make it more suitable for use on snowy surfaces.

[0068] Furthermore, the provision of connecting the surfaces of the first lateral portion placed at different depths, by means of the radii of curvature described above, allows to further reduce the risk of crack formation.

[0069] In some embodiments, there is formed a plurality of second sipes on said at least one block which are arranged along directions substantially mutually parallel. Preferably, said second sipes are arranged along directions parallel to the first longitudinal direction of said first sipe.

[0070] Preferably, a sipe of said plurality of second sipes, which is adjacent to said at least one first sipe, has a distance from said first sipe, in circumferential direction, less than or equal to 7 mm.

[0071] In some embodiments, the second end of the first sipe is open in a groove of said plurality of grooves, preferably on a circumferential groove.

[0072] Preferably, said fourth depth of said second lateral portion is substantially equal to the third depth of the second section of said first lateral portion.

[0073] In this way, the first lateral portion and the second lateral portion exert their stiffening action on both sides of the block, so as to obtain an adequate homogeneity of behaviour.

[0074] Preferably, said first lateral portion comprises a complementary section which is arranged between said second section and the first end of said first sipe.

[0075] Preferably, said complementary section has a length greater than or equal to 1.5mm.

[0076] According to such a configuration, the consolidation action in the area adjacent to the first end of the sipe is effectively achieved.

[0077] Preferably, said complementary section has a fifth depth less than said third depth. In this way, an even more gradual connection area is created between the middle portion of the sipe and the radially external surface of the tread.

[0078] Preferably, said middle portion, said first lateral portion and said second lateral portion are substantially aligned along said first longitudinal development direction of said first sipe.

[0079] Preferably, said middle portion has a length between 6 mm and 10 mm Preferably, said first lateral portion has a length between 4 mm and 8 mm.

[0080] Preferably, said first sipe is a three-dimensional sipe.

[0081] Preferably, said first depth is between 6 mm and 10 mm.

[0082] Preferably, said first depth is substantially constant along the entire extension of said middle portion.

[0083] Preferably, the middle portion extends over a length between 50% and 80% of the extension of the first sipe along said first longitudinal development direction. Preferably, said second depth is between 3 mm and 6 mm.

[0084] Preferably, said second depth is substantially constant along the entire extension of said first section.

[0085] Preferably, said third depth is between 1 mm and 3 mm.

[0086] Preferably, said third depth is substantially constant along the entire extension of said second section.

[0087] Preferably, said fourth depth is between 1 mm and 4 mm.

[0088] Preferably, said fourth depth is substantially constant along the entire extension of said second lateral portion.

[0089] Preferably, on all the blocks of said plurality of blocks, there are formed first and second sipes.

[0090] The characteristics and advantages of the invention will become clearer from the detailed description of a preferred embodiment thereof, shown by way of nonlimiting example, with reference to the appended drawings wherein:

[0091] Figure 1 schematically shows a view of a group of blocks comprising sipes according to the present invention; and

[0092] Figure 2 is a schematic view of a front view of a sipe according to the presentinvention.

[0093] With initial reference to the attached figures, 1 globally denotes a tyre for vehicle wheels (not fully illustrated) made in accordance with the present invention.

[0094] The tyre 1 has a conventional generally toroidal shape, not depicted in the attached figures, developed around an axis of rotation defining an axial direction Y of the tyre, and crossed by an equatorial plane X, perpendicular to the axis of rotation. The tyre 1 comprises a tread band 2 on which a tread surface is defined which is arranged in a position radially external to the tread band 2 and intended for contact with a road surface.

[0095] On the tread band 2 there is formed a plurality of grooves, all identified with the reference numeral 4, which delimit a respective plurality of blocks 5.

[0096] By way of example, a group of blocks 5 is schematically depicted in Figure 1, wherein a first sipe 10 is defined on at least one block 5. It is understood that the characteristics of said block 5 also apply in a similar way to all the other blocks formed in the tread band 2.

[0097] The first sipe 10 extends on said block 5 from a radially external surface 3 of said tread band 2, to a radially inner surface of the tread band.

[0098] More in detail, as shown in Figures 1 and 2, the first sipe 10 is open on said tread surface and extends, according to a first longitudinal development direction A, between a first end 11 and a second end 12 which are axially opposite.

[0099] The first sipe 10 comprises a middle portion 140, having a first depth Pi and a first lateral portion 110 which extends between said middle portion 140 and said first end 11.

[0100] Advantageously, said first end 11 is open in a groove 4 of said plurality of grooves. The lateral portion 110 comprises a first section 111, which is adjacent to said middle portion 140, and a second section 112, which is arranged between said first section 111 and said first end 11 of the first sipe 10.

[0101] The first section 111 has a second depth P2 and the second section 112 has a third depth P3.

[0102] The first sipe is conformed so that the depths of said middle portion 140 and of the respective sections of the first lateral portion 110 are differentiated; advantageously, in fact, the second depth Pzof the first section 111 is less than the first depth Pi of the middle portion 140, and the third depth P3 of the second section 112 is less than the second depth P2 of the first section 111.Advantageously, the value of the second depth P2 of said first section 111 is in a range between 40% and 80% of the value of the first depth Pi of said middle portion 140. Preferably said value of the second depth P2 is 55% of the value of the first depth Pi.

[0103] Advantageously, the value of the third depth P3 of the second section 112 of the first lateral portion 110 is in a range between 10% and 50% of the value of the first depth Pi of said middle portion 140. Preferably said value of the third depth P3 is 15% of the value of the first depth Pi.

[0104] Advantageously, the first depth Pi of the middle portion 140 is between 6 mm and 10 mm, preferably it is equal to 7 mm. Preferably, said first depth Pi is substantially constant along the entire extension of said middle portion.

[0105] Advantageously, the second depth P20f the first section 111 is between 3 mm and 6 mm, preferably it is equal to 4 mm. Preferably, said second depth P2 is substantially constant along the entire extension of said first section 111.

[0106] Advantageously, the third depth P3 of the second section 112 is between 1 mm and 3 mm, preferably it is equal to 2 mm. Preferably, said third depth P3 is substantially constant along the entire extension of said second section 112. By way of example, the first sipe 10 extends between its first end 11 and its second end 12 over a length between 15 mm and 40 mm.

[0107] Advantageously, the middle portion 140 extends over a length between 50% and 80% of the extension of the first sipe 10 along said first longitudinal development direction.

[0108] Exemplarily, the second section 112 of said first lateral portion has a length greater than or equal to 1.5 mm.

[0109] In the embodiment described herein, the first sipe 10 further comprises a second lateral portion 120, which extends between said middle portion 140 and the second end 12 of the first sipe 10.

[0110] Preferably, said second lateral portion 120 extends over a length between 5% and 25% of the extension of the first sipe 10 along said first longitudinal development direction.

[0111] The second lateral portion 120 comprises at least a third section 113 which has a fourth depth P4, preferably less than the first depth Pi of said middle portion 140. Advantageously, the value of the fourth depth P4 of said third section 113 is in a range between 10% and 50% of the value of the first depth Pi of said middleportion 140. Preferably said value of the second depth P4 is 15% of the value of the first depth Pi.

[0112] Advantageously, said fourth depth P40f the third section 113 is between 1 mm and 4 mm. Preferably, said fourth depth P4 is substantially constant along the entire extension of said third section 113 of said second lateral portion 120.

[0113] Preferably, said fourth depth P4 is substantially equal to the third depth P3 of the second section 112 of said first lateral portion 110.

[0114] Advantageously, the second end 12 of the first sipe 10 is open in a groove of said plurality of grooves, preferably on a circumferential groove 4.

[0115] According to the preferred embodiment described herein, the middle portion 140, the first lateral portion 110 and the second lateral portion 120, are substantially aligned along said first longitudinal development direction A of said first sipe. In an alternative embodiment (not shown in the figures), said first lateral portion comprises a complementary section which is arranged between said second section 112 and the first end 11 of said first sipe 10, which has a fifth depth less than said third depth P3.

[0116] With reference to Figure 2, on the first sipe 10 there is a bottom part which extends between said first end 11 and said second end 12.

[0117] Advantageously, said bottom part comprises a first surface portion 51 at said middle portion 140; preferably, said first surface portion lies in a plane parallel to the radially external surface 3 of the tread band, identified at the block 5 on which the first sipe 10 is formed.

[0118] Said bottom part further comprises a second surface portion 52 at said first section 112 of the first lateral portion 110 and a third surface portion 53 at said second section 112 of the first lateral portion 120.

[0119] In the preferred embodiment, as shown in Figure 2, said first surface portion 51 is connected to said second surface portion 52 by means of a first connection surface which comprises a first substantially planar portion 61 and two curvilinear sections 610, 620, which are placed at the junction area between said first substantially planar portion 61 and respectively said first and second surface portions 51, 52. More in detail, said first substantially planar portion 61 is inclined with respect to a radial direction of the tyre by an angle between 45° and 90° and is connected to said first surface portion 51 by means of a first curvilinear section 610, having concavity which is directed towards the exterior of the block and to said secondsurface portion 52 by means of a second curvilinear section 620, having concavity directed towards the inner of the block.

[0120] Advantageously, said first curvilinear section 610 has a radius of curvature between 1 and 3 mm.

[0121] Advantageously, said second curvilinear section 620 has a radius of curvature between 1 and 3 mm.

[0122] Furthermore, the second surface portion 52 identified on the bottom part of said first sipe 10 is connected to said third surface portion 53 by means of a second connection surface comprising a second substantially planar portion 62, and two curvilinear sections 630, 640, placed at the junction area between said second substantially planar portion 62 and respectively said second and third surface portions 52, 53.

[0123] More in detail, said second substantially planar portion 62 is inclined with respect to a radial direction of the tyre by an angle between 45° and 90° and is connected to said second surface portion 52 by means of a third curvilinear section 630, having concavity which is directed towards the exterior of the block and to said third surface portion 53 by means of a fourth curvilinear section 640, having concavity directed towards the inner of the block.

[0124] Advantageously, said third curvilinear section 630 has a radius of curvature between 1 and 3 mm.

[0125] Advantageously, said fourth curvilinear section 640 has a radius of curvature between 1 and 3 mm.

[0126] According to a preferred embodiment, as shown in Figure 2, said bottom part comprises a fourth surface portion 54 at said third section 113 of the second lateral portion 120.

[0127] Said fourth surface portion 54 is connected to the first surface portion 51 by means of a fourth connection surface which comprises a third substantially planar portion 63 and two curvilinear sections 640, 650, placed at the junction area between said third substantially planar portion 63 and respectively said first and fourth surface portions 51, 54.

[0128] More in detail, said third substantially planar portion 63 is inclined with respect to a radial direction of the tyre by an angle between 45° and 90° and is connected to said first surface portion 51 by means of a fifth curvilinear section 650, having concavity which is directed towards the exterior of the block and to said fourthsurface portion 54 by means of a sixth curvilinear section 660, having concavity which is directed towards the inner of the block.

[0129] Advantageously, said fifth curvilinear section 650 has a radius of curvature between 1 and 3 mm.

[0130] Advantageously, said sixth curvilinear section 660 has a radius of curvature between 1 and 3 mm.

[0131] Advantageously, as can be seen by way of example in Figure 1, a transverse groove 4 of said plurality of grooves comprises a section which extends along a second longitudinal direction B.

[0132] Advantageously, the first longitudinal direction A, identified by said first sipe 10, forms an angle between 10° and 70° with the second longitudinal direction B of said transverse groove. Preferably, the angle between the first longitudinal direction A and the second longitudinal direction B is 45°.

[0133] Advantageously, on one or more blocks 5 of said plurality, there is further formed a plurality of second sipes 20 which are arranged along third longitudinal directions C substantially mutually parallel. Said third longitudinal directions C are preferably parallel to the first longitudinal direction A of said first sipe 10.

[0134] Advantageously, in the embodiment described above, each of said second sipes 20 of said plurality of second sipes, if arranged in a position adjacent to said first sipe 10, has a distance from said first sipe 10 in the circumferential direction of less than or equal to 7 mm.

Claims

Claims1. Tyre comprising a tread band (2) comprising:- a plurality of grooves (4),- a plurality of blocks (5) which are delimited by said plurality of grooves (4), - at least a first sipe (10) which extends on at least one block (5) of said plurality of blocks from a radially external surface (3) of said tread band to a radially inner surface of said tread band,wherein said first sipe (10) comprises- a middle portion (140) having a first depth (Pi), and- a first lateral portion which extends between said middle portion (140) and a first end (11) of the first sipe (10) and which is open in a groove of said plurality of grooves (4),wherein said first lateral portion (110) comprises- a first section (111) which is adjacent to said middle portion (140) and which has a second depth (P2) which is less than said first depth (Pi), and- at least one second section (112) which is arranged between said first section (111) and said first end of the first sipe (10) which has a third depth (P3) which is less than said second depth (P2).

2. Tyre (1) according to claim 1, wherein said first sipe (10) comprises a second lateral portion (120) which extends between said middle portion (140) and a second end (12) of the first sipe (10), opposite said first end (11), said second lateral portion (120) comprising at least one third section (113) which has a fourth depth (P4) which is less than said first depth (Pi).

3. Tyre (1) according to claim 1 or 2, wherein the value of the second depth (P2) of the first section (111) of the first lateral portion (110) is between 40% and 80% of the value of the first depth (Pi) of said middle portion (140).

4. Tyre (1) according to any one of the preceding claims, wherein the value of the third depth (P3) of the second section (112) of the first lateral portion (110) is between 10% and 50% of the value of the first depth (Pi) of said middle portion (140).

5. Tyre (1) according to any one of the preceding claims, wherein said first sipe (10) is open on said radially external surface (3) of said tread band so as to define a first longitudinal development direction (A), and said plurality of grooves (4)comprises at least one transverse groove (4) comprising at least one section which extends in a second longitudinal direction (B), forming an angle between 10° and 70° with the first longitudinal direction of said first sipe (10).

6. Tyre (1) according to any one of the preceding claims, wherein there is defined in said first sipe (10) a bottom part which extends between said first end (11) and said second end (12), said bottom part comprising:- a first surface portion (51) at said middle portion (140),- a second surface portion (52) at said first section (111) of said first lateral portion (110), and- a third surface portion (53) at said second section (112) of the first lateral portion (HO).

7. Tyre according to claim 6, wherein said first surface portion (51) is connected to said second surface portion (52) by means of a first connection surface which comprises a first substantially planar portion (61) which is inclined with respect to a radial direction of said tyre (1) by an angle between 45° and 90°.

8. Tyre according to claim 6 or 7, wherein said second surface portion (52) is connected to said third surface portion (53) by means of a second connection surface comprising a second substantially planar portion (62) which is inclined with respect to a radial direction of said tyre by an angle between 45° and 90°.

9. Tyre according to any one of claims 6 to 8, wherein said first connection surface is connected to said first surface portion (51) by means of a first curvilinear section (610) which has concavity directed towards the exterior of the block (5) and which is provided with a radius of curvature, and connected to said second surface portion (52) by means of a second curvilinear section (620) which has concavity directed towards the inner of the block and which is provided with a radius of curvature.

10. Tyre according to any one of claims 6 to 9, wherein said second connection surface is connected to said second surface portion (52) by means of a third curvilinear section (630) with concavity which is directed towards the exterior of the block (5) and which is provided with a radius of curvature, and connected to said third surface portion (53) by means of a fourth curvilinear section (640) with concavity which is directed towards the inner of the block (5) and which is provided with a radius of curvature.

11. Tyre (1) according to any one of the preceding claims, wherein there are formed in said at least one block a plurality of second sipes (20) which are arranged along directions substantially parallel to each other and to the first longitudinal direction (A) of said first sipe (10).

12. Tyre (1) according to claim 11, wherein a sipe of said plurality of second sipes (20), which is adjacent to said at least one first sipe (10), has a distance from said first sipe (10) in the circumferential direction less than or equal to 7 mm.

13. Tyre (1) according to any one of the preceding claims, wherein said fourth depth (P4) of said second lateral portion (120) is substantially equal to the third depth (P3) of the second section (112) of said first lateral portion (110).

14. Tyre (1) according to any one of claims 2 to 13, wherein said first lateral portion (110) comprises a complementary section which is arranged between said second section (112) and the first end (11) of said first sipe (10), which has a fifth depth less than said third depth (P3).

15. Tyre (1) according to any one of claims 5 to 14, wherein said middle portion (140), said first lateral portion (110) and said second lateral portion (120) are substantially in alignment in said first longitudinal development direction of said first sipe (10).

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