Tyre
The tyre design addresses uneven deformation and snow trapping issues by using decoupling elements and varying sipe configurations on shoulder regions, enhancing traction and braking on snowy surfaces.
Patent Information
- Authority / Receiving Office
- WO · WO
- Patent Type
- Applications
- Current Assignee / Owner
- PIRELLI TYRE SPA
- Filing Date
- 2025-12-12
- Publication Date
- 2026-07-02
AI Technical Summary
The mutual positioning of grooves and sipes on the tread band affects the directionality and travel stability characteristics of tyres, particularly on snowy surfaces, leading to uneven deformation of block portions and reduced snow trapping capacity.
The tyre design incorporates decoupling elements between adjacent block portions in the circumferential direction, featuring sipes with varying widths and orientations on shoulder regions to enhance uniform snow retention and deformation capacity.
This design improves traction and braking performance on snowy surfaces by balancing block deformation and increasing snow trapping capacity without compromising stiffness.
Smart Images
Figure IB2025062801_02072026_PF_FP_ABST
Abstract
Description
[0001] TYRE
[0002] The present invention concerns a tyre for vehicle wheels, in particular a winter tyre.
[0003] In more detail, the invention concerns a winter tyre with improved performance, in particular on snowy road surfaces.
[0004] A tyre generally comprises a toroidally conformed carcass structure around an axis of rotation 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 winter tyres provided with sipes are described in Patent Applications US2023234401A1 and US2020122514A1.
[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 annular development 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 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 expression "axial direction" or "transverse direction" is intended to indicate a direction parallel to the axis of rotation of the tyre, i.e. inclined with respect to this direction by an angle less than or equal to 45°.
[0016] The term "groove" is intended to mean a notch formed in a portion of the tread band having, for a prevalent part of its longitudinal extension of development, a width of at least 1.5 mm. Preferably said groove has a minimum depth of about 3 mm.
[0017] The term "sipe" is intended to mean a notch formed in a portion of the tread band having, for a prevalent part of its longitudinal extension of development, a 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 "prevalent part" of a notch (groove or sipe) it is intended to mean a portion of the notch greater than or equal to half of the longitudinal extension of its development.
[0019] By "width" of a notch (groove or sipe), or a portion thereof, it is intended to mean the dimension parallel to the tread surface and perpendicular to the longitudinal extension of development of the notch or a portion thereof.
[0020] By "longitudinal development direction" of a notch (sipe or groove) it is intended to indicate the path or direction along which the notch extends between its two opposite ends.The term "effective width" referred to the tread band is intended to mean the width of the radially outermost portion of the tread band (from edge to edge) intended for contact with the ground.
[0021] By "central region" of the tread band, it is intended to mean a portion of the tread band which extends circumferentially astride an equatorial plane of said tyre for a width equal to at least 30% of the effective width of the tread band, preferably for a width between 40% and 75% of said effective width.
[0022] The central region may extend symmetrically or asymmetrically with respect to the equatorial plane.
[0023] In particular, when circumferential or almost circumferential grooves are provided on the tread band, the central region can be delimited on one or both sides, by one of said circumferential grooves.
[0024] By "shoulder regions" of the tread band, it is intended to mean the portions of the tread band which extend circumferentially to the opposite sides of the central region, in an axially outer position of the tread band.
[0025] Preferably, each shoulder region extends over a width equal to at least 10% of the effective width of the tread band.
[0026] A shoulder region is called "inner" when it is intended to be directed towards the vehicle when the tyre is mounted on the vehicle, and, similarly, it is called "outer" when it is intended to be directed towards the exterior of the vehicle when the tyre is mounted on the vehicle.
[0027] A tyre is called "asymmetrical" when its tread pattern is not symmetrical with respect to the equatorial plane. An asymmetrical tyre comprises an inner shoulder region and an outer shoulder region, as defined above.
[0028] A "module" of the tread pattern is defined by the minimum portion of tread band whose configuration is repeated in succession along the circumferential development of the tread band to form said tread pattern.
[0029] A module typically extends between the axial ends of the tread band. Furthermore, while maintaining an identical base configuration, the modules may have a circumferential dimension (called "pitch") that is slightly different from one another, for example, modules having two, three or four different pitches, variously combined with one another, may be used on a tread band.
[0030] The Applicant has observed that the mutual positioning of the grooves and sipes on the tread band affects the directionality and travel stability characteristics ofthe tyre. In particular, the performance of a tyre on a snowy surface depends on the shape of the sipes as well as their arrangement on the blocks in which they are made.
[0031] The Applicant has further observed that in some portions of the tread band, such as the shoulder regions, the blocks may have a predominant dimension in the axial direction with respect to the dimension in the circumferential direction.
[0032] The Applicant has also verified that, by providing on these blocks so conformed a plurality of sipes having a substantially axial development direction, makes it possible to obtain the mobility properties suitable to allow adequate grip, traction and / or braking performance of the tyre on a snowy road surface.
[0033] However, the Applicant has observed that, during the rolling of the tyre, the block portions which meet the road surface in succession deform unevenly; the deformation of the block portions, which are adjacent and separated by sipes, in fact progressively decreases as does the snow trapping capacity.
[0034] The Applicant has, therefore, realized that, by introducing decoupling elements between adjacent block portions in the circumferential direction, it is possible to change the mode of deformation of the block in response to tangential stresses, improving the efficiency in traction and / or braking of the tyre, in particular on snowy surface.
[0035] Finally, the Applicant has found that by providing on a shoulder region of the tyre at least a first block and a second block which are arranged in succession along the circumferential development, wherein there is formed on the first block a sipe having a width, measured at the tread surface, which grows between an axially inner region and an axially outer region of the tread band and wherein there is formed on the second block a sipe having a width, measured at the tread surface, which decreases between an axially inner region and an axially outer region of the tread band, each block is given a more uniform snow retention capacity, when the tyre is subjected to the typical driving stresses, without penalizing its stiffness properties.
[0036] In particular, in a first aspect thereof, the invention relates to a tyre for vehicle wheels comprising a tread band in which there is defined a pair of axially opposite shoulder regions and a central region which is interposed between said shoulder regions.
[0037] Preferably, there is defined on at least a first shoulder region of said pair a pluralityof transverse grooves, and a plurality of blocks which are delimited by at least a pair of said plurality of transverse grooves.
[0038] Preferably, said plurality of blocks comprises at least one first block and at least one second block.
[0039] Preferably, said at least one first block and said at least one second block are arranged in succession along the circumferential development of said first shoulder region.
[0040] Preferably, there is defined on said at least one first block a first main sipe which extends along a first longitudinal development direction.
[0041] Preferably, said first main sipe comprises first lateral walls which extend from a radially inner surface of said tread band towards a radially outer surface of said tread band.
[0042] Preferably, said first lateral walls have respective first upper edges which meet the radially outer surface of the tread band along respective first contact lines.
[0043] Preferably, said first main sipe comprises a first section which extends along said first longitudinal development direction between a first axially inner end and a first intermediate portion of said first main sipe.
[0044] Preferably, in said first section said first contact lines are parallel to each other and arranged at a first distance DI.
[0045] Preferably, said first main sipe comprises a second section which extends along the first longitudinal development direction from said first intermediate portion towards said first axially external end of said main sipe.
[0046] Preferably, in said second section said first contact lines diverge, until being arranged at a maximum distance D2, one from the other.
[0047] Preferably, there is defined on said at least one second block a second main sipe which extends along a respective second longitudinal development direction. Preferably, said second main sipe comprises second lateral walls which extend from a radially inner surface of said tread band towards a radially outer surface of said tread band.
[0048] Preferably, said second lateral walls have respective second upper edges which meet the radially outer surface of the tread band along respective second contact lines.
[0049] Preferably, said second main sipe comprises a first section which extends along said second longitudinal development direction, between a second axially innerend and a second intermediate portion of said second main sipe.
[0050] Preferably, said second contact lines are arranged at a third maximum distance D3, more preferably at said second axially inner end.
[0051] Preferably, in said first section said second contact lines converge towards said second intermediate portion, at which they are arranged at a fourth distance D4. Preferably, said second main sipe comprises a second section which extends along said second longitudinal development direction, between said second intermediate portion and a second axially external end of said second main sipe.
[0052] Preferably, in said second section of the second main sipe, said second contact lines are parallel to each other and arranged at said fourth distance D4.
[0053] Thanks to these characteristics, the efficiency of the tyre is improved, in particular on snowy road surfaces, as the deformation capacity of the shoulder blocks in response to tangential stresses is more balanced.
[0054] The provision of the decoupling elements of adjacent block portions, in fact, allows to create greater mobility of these portions, increasing the snow trapping capacity. The present invention, in the aforesaid aspect, may have at least one of the further preferred features set out below.
[0055] Preferably, said second distance D2 is greater than said first distance DI.
[0056] Preferably, said third D3 is greater than said fourth distance D4.
[0057] Preferably, said first distance DI is greater than or equal to 0.3 mm.
[0058] Preferably, said first distance DI is less than or equal to 1.2 mm.
[0059] Preferably, said second distance D2 is greater than or equal to 1.5 mm.
[0060] Preferably, said second distance D2 is less than or equal to 4 mm.
[0061] Preferably, said third distance D3 is greater than or equal to 1.5 mm.
[0062] Preferably, said third distance D3 is less than or equal to 4 mm.
[0063] Preferably, said fourth distance D4 is greater than or equal to 0.3 mm.
[0064] Preferably, said fourth distance D4 is less than or equal to 1.2 mm.
[0065] Preferably, said second distance D2 is substantially equal to said third distance D3. Preferably, said first distance DI is substantially equal to said fourth distance D4. In some embodiments, in the first section of said first main sipe, said first lateral walls extend parallel with each other from said radially inner surface towards the radially outer surface of the tread band, according to a radial direction.
[0066] Preferably, in the second section of said first main sipe, said first lateral wallsextend parallel with each other, according to a radial direction, between said radially inner surface of the tread band and a first connection line, and then diverge according to a first inclination with respect to said radial direction, between said first connection line and the radially outer surface of the tread band.
[0067] In some embodiments, said first inclination with respect to the radial direction of the tyre is between 75° and 90°.
[0068] In one example, said first inclination with respect to the radial direction of the tyre is 88°.
[0069] Preferably, in said second section of said second main sipe, said second lateral walls extend parallel with each other between said radially inner surface and said radially outer surface of the tread band, according to said radial direction.
[0070] Preferably, in said first section of said second main sipe, said second lateral walls extend parallel with each other, according to a radial direction, between said radially inner surface of the tread band and a respective second connection line, and then diverge according to a second inclination, between said second connection line and the radially outer surface of the tread band.
[0071] In this way, a flaring is also made at a radially inner area of the tyre shoulder, which improves the snow trapping capacity as it offers a useful volume in which the snow can be collected.
[0072] Preferably, said second inclination with respect to the radial direction of the tyre is between 45° and 80°.
[0073] In one example, said second inclination with respect to the radial direction of the tyre is 70°.
[0074] In some embodiments, said first axially inner end of said first main sipe is open on a circumferential groove which delimit said first shoulder region.
[0075] In some embodiments, said second axially inner end of said second main sipe is open on a circumferential groove which delimit said first shoulder region.
[0076] Preferably, said first axially external end of said first main sipe is open on a first lateral edge of said tread band.
[0077] Preferably, said second axially external end of said second main sipe is open on a first lateral edge of said tread band.
[0078] In some embodiments, on at least said first shoulder region is defined a plurality of secondary sipes.
[0079] Preferably, said plurality of secondary sipes extend on said plurality of blocksaccording to a third longitudinal development direction.
[0080] Preferably, said plurality of secondary sipes arranged along longitudinal development directions substantially parallel to each other.
[0081] Preferably, said first main sipe and said second main sipe have a minimum width greater than the maximum width of the secondary sipes of said plurality.
[0082] Preferably, the width of said first main sipe and said second main sipe is substantially twice the width of said second sipes.
[0083] This configuration further improves the deformation capacity of the blocks, increasing their performance.
[0084] Preferably, said first main sipe comprises a third section which extends along said first longitudinal development direction between said second section and said first radially external end of said first main sipe.
[0085] Preferably, in said third section said first contact lines converge at a vertex at the first axially external end of said first main sipe.
[0086] Preferably, in the third section said first lateral walls extend parallel with each other, according to a radial direction, between said radially inner surface of the tread band and a third connection line contiguous with said first connection line. In some embodiments, said vertex of said first main sipe is arranged on a first lateral edge of said tread band.
[0087] In this way, at the aforesaid vertex, a snow-binding area is made at the first lateral edge of the tread band, which can be particularly advantageous, for example, in cases where fresh snow is present on the road surface: in such conditions, the snow, due to its consistency, tends to make the tyre sink into it and the points of attachment of the snow on the lateral edge can further improve traction and / or braking.
[0088] In some embodiments, the first lateral walls of said first main sipe extend between said first connection line and the radially outer surface of the tread band with a substantially planar shape.
[0089] In some embodiments, the second lateral walls of said second main sipe extend between said second connection line and the radially outer surface of the tread band in mutually divergent directions, with a substantially planar shape.
[0090] Preferably, the longitudinal development directions of said first and second main sipe are inclined, respectively, with respect to said circumferential direction by an angle between 40° and 90°.Preferably, said first shoulder region is an inner shoulder region of said tread band. On said tread band there are defined a tread pattern formed by the configuration of grooves and blocks formed on said tread band and a module of said tread pattern.
[0091] Preferably, in said module, at said first shoulder region, said first block and said second block are arranged consecutively with respect to each other in said circumferential direction.
[0092] 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:
[0093] - Figure 1 schematically shows a view of a group of blocks comprising sipes according to the present invention;
[0094] - Figure 1A shows a detail of the group of blocks of Figure 1;
[0095] - Figure 2 is a perspective schematic view of a first main sipe according to the present invention;
[0096] - Figure 3 is a side schematic view of the sipe of Figure 2;
[0097] - Figure 4 is a top schematic view of the sipe of Figure 2;
[0098] - Figure 5 is a schematic view of a second main sipe according to the present invention;
[0099] - Figure 6 is a side schematic view of the sipe of Figure 5;
[0100] - Figure 7 is a front schematic view of the sipe of Figure 5;
[0101] - Figure 8 is a top schematic view of the sipe of Figure 5;
[0102] - Figures 9A and 9B are schematic radial sectional views of a portion of a block comprising respectively only three-dimensional sipes and sipes according to the present invention; and
[0103] - Figure 10 is a three-dimensional perspective view of a first main sipe according to the present invention.
[0104] With initial reference to the attached figures, 1 globally designates a tyre for vehicle wheels (not fully illustrated) made in accordance with the present invention.
[0105] 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 of the tyre, and crossed by an equatorial plane, perpendicular to the axis of rotation.
[0106] The tyre 1 comprises a tread band on which a tread surface is defined which isarranged in a position radially external to the tread band and intended for contact with a road surface.
[0107] On the tread band there is defined a central region 6, which extends circumferentially around an equatorial plane of said tyre, as well as a pair of shoulder regions 4, 5 which extend circumferentially on opposite sides of said central region 6, in an axially outer position of the tread band.
[0108] On the tread band there is also formed a plurality of grooves 7, 8, which delimit a respective plurality of blocks 50, 51, 52.
[0109] In the embodiment described herein, said pair of shoulder regions comprises a first shoulder region 4, which extends between a first lateral edge 11 of the tread band and said central region 6. Preferably, said first shoulder region 4 extends between said first lateral edge 11 of the tread band and a circumferential groove 8, which delimits the central region 6, separating it from said first shoulder region 4. Preferably, the tyre 1 is a tyre of the asymmetrical type. Preferably the first shoulder region 4 is an inner shoulder region of the tyre 1, i.e. the shoulder region intended to be directed toward the vehicle when the tyre 1 is mounted on the vehicle.
[0110] By way of example, in Figure 1, a group of blocks is schematically depicted, on which a plurality of sipes 20, 40, 90 is provided.
[0111] Preferably, the blocks of said plurality of blocks which are arranged on said first shoulder region 4, are delimited by at least one pair of transverse grooves 7, of said plurality of grooves, and comprise a first block 51 and a second block 52. Preferably, said first block 51 and said second block 52 are arranged in succession along the circumferential development of the first shoulder region 4, more preferably consecutive to one another in circumferential direction.
[0112] In particular, on the first block 51 there is defined at least one first main sipe 20, which extends along a first longitudinal development direction A. Said first main sipe 20 comprises a pair of first lateral walls 21 and 22, which extend from a radially inner surface of the tread band towards the radially outer surface 3 of the tread band.
[0113] Preferably, the first lateral walls 21, 22 of said first main sipe 20 have upper edges 210, 220, which meet the radially outer surface 3 of the tread band along respective first contact lines 31, 32.
[0114] The first main sipe 20 is also advantageously configured so as to comprise a firstsection 20a and a second section 20b, which differ from each other due to the mutual position of said first lateral walls 21 and 22, and consequently due to the profile of said first contact lines 31 and 32 identified on the radially outer surface of the tread band.
[0115] In detail, the first section 20a preferably extends along said first longitudinal development direction A, between a first axially inner end 23 and a first intermediate portion 24 of said first main sipe 20.
[0116] The second section 20b extends along the first longitudinal development direction A between said first intermediate portion 24 towards a first axially external end 25. Preferably, at said first section 20a, said first contact lines 31, 32 are parallel to each other and are arranged at a first distance DI.
[0117] By way of example only, in the case in the figure this distance DI is equal to 0.8 mm.
[0118] In some embodiments, in the first section of said first main sipe, said first lateral walls extend from said radially inner surface towards the radially outer surface of the tread band parallel to each other, according to a radial direction.
[0119] Preferably, at said second section 20b, said first contact lines 31, 32 diverge, starting from said first intermediate portion 24 towards a first radially external end 25 of said first main sipe 20, at which they are arranged at a maximum distance D2, one from the other.
[0120] By way of example only, in the case in the figure, this distance D2 is equal to 2 mm.
[0121] Preferably said first main sipe 20 comprises a third section 20c which extends along said first longitudinal development direction A between said second section 20a and said first radially external end 25, wherein the first contact lines 31, 32 converge at a vertex 26, at said first axially external end 25. In some embodiments, said vertex 26 of said first main sipe 20 is arranged on a first lateral edge 11 of said tread band.
[0122] Preferably, the extension of said first section 20a is greater than the extension of said second section 20b.
[0123] Preferably, the extension of said third section 20c is less than the extension of said first section 20a and the extension of said second section 20b.
[0124] On the second block 52 there is defined at least one second main sipe 40 which extends along a respective second longitudinal development direction B.Preferably, the second main sipe 40 comprises second lateral walls 41, 42, which extend from the radially inner surface of the tread band towards the radially outer surface 3 of the tread band.
[0125] Preferably, said second lateral walls 41, 42 of said second main sipe 40 have upper edges 410, 420, which meet the radially outer surface 3 of the tread band along respective second contact lines 33, 34.
[0126] The second main sipe 40 is also advantageously configured so as to comprise a first section 40a and a second section 40b, which differ from each other due to the mutual position of said second lateral walls 41 and 42, and consequently due to the profile of said second contact lines 41 and 42 identified on the radially outer surface of the tread band.
[0127] In detail, the first section 40a extends along said second longitudinal development direction B preferably between a second axially inner end 43 and a second intermediate portion 44 of said second main sipe 40. The second section 40b instead extends along said second longitudinal development direction B between said second intermediate portion 44 and a first axially outer end 45. Preferably, in said first section 40a, said second contact lines 33, 34 are arranged at a third distance D3, at said second axially inner end 43, and converge from said second axially inner end 43 towards said second intermediate portion 44, at which they are arranged at a fourth distance D4.
[0128] Preferably, the extension of said second section 40b is greater than the extension of said first section 40a.
[0129] By way of example only, in the case in the figure, said third distance D3 is equal to 2 mm.
[0130] By way of example only, in the case in the Figure, said fourth distance D4 is equal to 0.8 mm.
[0131] Preferably, at said second section 40b, said second contact lines 33, 34 are parallel to each other and arranged at said fourth distance D4.
[0132] Preferably, in said second section of said second main sipe, said second lateral walls extend parallel with each other between said radially inner surface and said radially outer surface of the tread band, according to said radial direction.
[0133] Advantageously, said second distance D2 is substantially equal to said third distance D3. Advantageously, said first distance DI is substantially equal to said fourth distance D4.Advantageously, as shown in Figures 2 and 4, in the second section 20b of said first main sipe 20, said first lateral walls 21, 22 extend parallel with each other between said inner surface of the tread band and a respective first connection line 61, and then diverge according to a first inclination with respect to said radial direction, between said first connection line 61 and the radially outer surface 3 of the tread band.
[0134] Advantageously, said first inclination with respect to the radial direction of the tyre is between 75° and 90°. In the example shown in the figure, said first inclination is about 88°.
[0135] Advantageously, in the third section 20c of said first main sipe 20, said first lateral walls 21, 22 extend parallel with each other, according to a radial direction, between said radially inner surface of the tread band and a third connection line 63 contiguous with said first connection line 61, and up to said vertex 26.
[0136] Advantageously, as shown in Figures 5 and 6, in said first section 40a of said second main sipe 40, said second lateral walls 41, 42 extend parallel with each other, according to a radial direction, between said radially inner surface of the tread band and respective second connection lines 62, and then diverge according to a second inclination, between said second connection line 62 and the radially outer surface 3 of the tread band.
[0137] Advantageously, said second inclination is between 45° and 80°. In the example shown in Figure 5, said second inclination is 70°.
[0138] Advantageously, said first axially inner end 23 of said first main sipe 20 is open on a circumferential groove 8, which delimits said first shoulder region 4, preferably separating it from said central region 6.
[0139] Advantageously, the first axially outer end 25 of the first main sipe 20 is open on a lateral edge 11 of said tread band.
[0140] Advantageously, said second axially inner end 43 of said second main sipe 40 is open on a circumferential groove 8, which delimits said first shoulder region 4, preferably separating it from said central region 6.
[0141] Advantageously, the second axially external end 45 of said second main sipe 40 is open on a lateral edge 11 of said tread band.
[0142] By way of example, the first block 51 and the second block 52 have, respectively, a dimension in a circumferential direction between 15 mm and 35 mm and a dimension in an axial direction between 24 mm and 52 mm.In a preferred embodiment, on at least said first shoulder region 4 there is defined a plurality of secondary sipes 90 which extend on said plurality of blocks 50, 51, 52, according to a third longitudinal development direction C.
[0143] Preferably, said secondary sipes 90 are arranged along directions substantially parallel to each other.
[0144] Advantageously, said first main sipe 20 and said second main sipe 40 have a width, greater than the width of said plurality of secondary sipes 90.
[0145] Preferably, the width of said first main sipe 20 and said second main sipe 40 is substantially twice the width of said secondary sipes 90.
[0146] Preferably, the first lateral walls 21, 22 of said first main sipe 20 extend between said first connection line 31 and the radially outer surface 3 of the tread band with a substantially planar shape.
[0147] Preferably, the second lateral walls 41, 42 of said second main sipe 40 extend between said second connection line 62 and the radially outer surface 3 of the tread band in mutually divergent directions, with a substantially planar shape. Preferably, the longitudinal development directions of said first and second main sipe 20, 40 are inclined with respect to said circumferential direction by an angle between 40° and 90°.
[0148] In a further embodiment of the first main sipe, shown by way of example in Figure 10, the second divergent section has an increasing depth towards the first axially external end. In further embodiments not shown, the second divergent section of the first main sipe or the first convergent section of the second main sipe may diverge or converge with portions of contact lines according to different angles with respect to the respective longitudinal development lines.
[0149] Figure 9A depicts a portion of block comprising a plurality of secondary sipes 90, while Figure 9B depicts a block made according to an embodiment of the first block 51 or the second block 52, wherein a plurality of secondary sipes 90 is interspersed with a main sipe 20, 40, made in accordance with the invention.
[0150] When the block is subjected to a tangential stress F, the deformation of the block portions separated by the sipes of the same type decreases starting from the portion of block that first comes into contact with the ground, progressively decreasing in the block portions that follow each other in the circumferential direction.
[0151] The introduction of a main sipe, creating an area of discontinuity between theportions of the block which are with respect to it facing each other, allows to improve the degree of deformation of the block portions that come into contact with the ground subsequently.
[0152] This feature is particularly advantageous on a snowy surface, as it allows to further increase the snow trapping capacity, both at the main sipe and at the remaining sipes on the block, thus improving the performance of the tyre on a snowy surface.
Claims
Claims1. Tyre (1) comprising a tread band, in which there is defined a pair of axially opposite shoulder regions (4, 5) and a central region (6) which is interposed between said shoulder regions (4, 5), wherein there is defined on at least one first shoulder region (4) of said pair:- a plurality of transverse grooves (7),- a plurality of blocks (50, 51, 52) which are delimited by at least one pair of said plurality of transverse grooves (7),said plurality of blocks comprising at least one first block (51) and at least one second block (52) which are arranged in succession along the circumferential development of said first shoulder region (4), whereinthere is defined on said at least one first block (51) a first main sipe (20) which extends along a first longitudinal development direction (A), said first main sipe (20) comprising:- first lateral walls (21, 22) which extend from a radially inner surface of said tread band towards a radially outer surface (3) of said tread band;- a first section (20a) which extends along said first longitudinal development direction (A) between a first axially inner end (23) and a first intermediate portion (24) of said first main sipe (20), wherein said first lateral walls (21, 22) have respective first upper edges (210, 220) which meet the radially outer surface (3) of the tread band along respective first contact lines (31, 32) which are parallel to each other and which are arranged at a first distance DI;- a second section (20b) which extends along said first longitudinal development direction (A) from said first intermediate portion (24) towards said first axially external end (25), wherein said first contact lines (31, 32) diverge, until being arranged at a maximum distance D2, one from the other;and wherein there is defined on said at least one second block (52) a second main sipe (40) which extends along a respective second longitudinal development direction (B), said second main sipe (40) comprising:- second lateral walls (41, 22) which extend from a radially inner surface of said tread band towards a radially outer surface (3) of said tread band;- a first section (40a) which extends along said second longitudinal development direction (B) between a second axially internal end (43) and a second intermediateportion (44) of said second main sipe (40), wherein said second lateral walls (41, 42) have respective second upper edges (410, 420) which meet the radially outer surface (3) of the tread band along respective second contact lines (33, 34) which are arranged at a third maximum distance D3, and which converge towards said second intermediate portion (44), at which they are arranged at a fourth distance D4; and- a second section (40b) which extends in said second longitudinal development direction (B) between said second intermediate portion (44) and a second axially external end (45) of said second main sipe, wherein said second contact lines (33, 34) are parallel to each other and arranged at said fourth distance D4.
2. Tyre (1) according to claim 1, wherein said second distance D2 is substantially equal to said third distance D3 and / or said first distance DI is substantially equal to said fourth distance D4.
3. Tyre (1) according to claim 1 or 2, wherein, in the second section (20b) of said first main sipe (20), said first lateral walls (21, 22) extend parallel with each other in a radial direction, between said inner surface of the tread band and a respective first connection line (61), and then diverge according to a first inclination with respect to said radial direction, between said first connection line (61) and the radially outer surface (3) of the tread band.
4. Tyre (1) according to any one of the preceding claims, wherein in said first section (40a) of said second main sipe (40) said second lateral walls (41, 42) extend parallel with each other in a radial direction, between said radially inner surface of the tread band and a respective second connection line (62), and then diverge according to a second inclination, between said second connection line (62) and the radially outer surface (3) of the tread band.
5. Tyre (1) according to any one of the preceding claims, wherein said first axially internal end (23) of said first main sipe (20) and / or said second axially internal end (43) of said second main sipe (40) are open on a circumferential groove (8) which delimit said first shoulder region (4).
6. Tyre (1) according to any one of the preceding claims, wherein said first main sipe (20) comprises a third section (20c) which extends along said first longitudinal development direction (A), between said second section (20b) and said first axially external end (25) of said first main sipe (20), wherein said first contact lines (31, 32) converge in a vertex (26) at the first axially external end (25) of said first main sipe (20).
7. Tyre (1) according to any one of the preceding claims, wherein said first axially external end (25) of said first main sipe (20) and / or said second axially external end (45) of said second main sipe (40) are open on a first lateral edge (11) of said tread band.
8. Tyre (1) according to any one of the preceding claims, wherein on at least said first shoulder region is defined a plurality of secondary sipes (90) which are arranged along longitudinal development directions (C) substantially parallel to each other.
9. Tyre (1) according to claim 8, wherein said first main sipe (20) and said second main sipe (40) have a minimum width greater than a maximum width of said secondary sipes (90).
10. Tyre (1) according to any one of claims 3 to 9, wherein the first lateral walls (21, 22) of said first main sipe (20) extend between said first connection line (31) and the radially outer surface (3) of the tread band with a substantially planar shape.
11. Tyre (1) according to any one of claims 3 to 10, wherein said first inclination with respect to the radial direction of the tyre is between 75° and 90°.
12. Tyre (1) according to any one of claims 4 to 11, wherein the second lateral walls (41, 42) of said second main sipe (40) extend between said second connection line (62) and the radially outer surface (3) of the tread band in mutually divergent directions, with a substantially planar shape.
13. Tyre (1) according to any one of claims 4 to 12, wherein said second inclination with respect to the radial direction of the tyre is between 45° and 80°.
14. Tyre (1) according to any one of the preceding claims, wherein the longitudinal development directions (A, B) of said first and second main sipes (20, 40) are inclined with respect to said circumferential direction by an angle between 40° and 90°.
15. Tyre (1) according to any one of the preceding claims, wherein said first shoulder region (4) is an internal shoulder region of said tread band.
16. Tyre (1) according to any one of the preceding claims, wherein there are defined on said tread band (2):- a tread pattern which is formed by the configuration of grooves (7, 8) and blocks (50, 51, 52) which are formed on said tread band (2) and- a module (M) of said tread pattern,and wherein said module (M), at said first shoulder region (4), comprises said first block (51) and said second block (52) which are arranged consecutively with each other in said circumferential direction.