Tyre comprising flexible tread

Abstract

The invention relates to a tyre (10) comprising first, second and third circumferential grooves (62, 64, 66), transverse grooves (72), first, second and third circumferential columns (22, 24, 28) of blocks (20), and additional circumferential columns (30, 32) of blocks (20), the transverse grooves (72) are substantially parallel to each other and intersect each of the first, second and third circumferential grooves (62, 64, 66). The angle (D1, D2, D3) formed by the leading edge edge (202) of each block of each of the first, second and third circumferential columns (22, 24, 28) with the circumferential direction (X) is strictly greater than the angle (A1, A2) formed by the average direction of the leading edge edges (202) of each block of the additional circumferential columns (30, 32).

Description

Technical Field

[0001] The present invention relates to a tyre. A tyre is understood to be a casing intended to form, by interaction with a supporting element, such as a rim, a cavity capable of being pressurized to a pressure greater than atmospheric pressure. The tyre according to the invention has a generally annular structure with rotational symmetry about the main axis of the tyre. Background Art

[0002] The prior art discloses racing tires intended for use in rally events during which vehicles equipped with such tires are driven on rocky terrain. The known tire is the MICHELIN LATITUDE tire.

[0003] For many years, rallies (also called special stages) have been relatively long. In order for the tire to show sufficient durability in each special stage, it is preferred to consider tires with relatively hard treads. Recently, special stages have been shortened, so relatively high tread stiffness is not necessarily required. Summary of the invention

[0004] The purpose of the present invention is to make the tire have better performance on special stages where lower tread stiffness is required.

[0005] To this end, the invention relates to a tire having an inner side and an outer side defined when the tire is mounted on a vehicle, the tire comprising a tread comprising a first axial edge and a second axial edge arranged on the inner side and on the outer side, respectively, the tread comprising a plurality of blocks and a plurality of grooves, the plurality of blocks and the plurality of grooves comprising:

[0006] - at least a first circumferential groove, a second circumferential groove and a third circumferential groove, the first circumferential groove, the second circumferential groove and the third circumferential groove being arranged so that there is at least a first substantially circumferential line, a second substantially circumferential line and a third substantially circumferential line respectively passing through the first circumferential groove, the second circumferential groove and the third circumferential groove and extending continuously around the circumference of the tire without intersecting any of the plurality of blocks, the first substantially circumferential line, the second substantially circumferential line and the third substantially circumferential line each having an axial width greater than or equal to 2 mm, the first circumferential groove, the second circumferential groove and the third circumferential groove each being arranged in an axial portion having an axial width equal to at most 75% of the axial width of the tread and extending from a first axial edge,

[0007] - at least a first circumferential row, a second circumferential row and a third circumferential row of block portions of a plurality of block portions,

[0008] - transverse grooves extending continuously from a first axial edge to a second axial edge of the tread and being substantially parallel to one another, each transverse groove intersecting the first circumferential groove, the second circumferential groove and the third circumferential groove, respectively,

[0009] at least one additional circumferential row of blocks of the plurality of blocks, the additional circumferential row or each additional circumferential row being the first, second and third circumferential rows of blocks and the circumferential row of the additional circumferential rows axially closest to the second axial edge,

[0010] Each block of the plurality of blocks comprises a leading edge corner, and an angle formed by an average direction of the leading edge corners of each block of at least each first circumferential row, second circumferential row and third circumferential row of blocks and the circumferential direction of the tire is strictly greater than an angle formed by an average direction of the leading edge corners of each block of the additional circumferential row or each additional circumferential row of blocks and the circumferential direction of the tire.

[0011] The combination of the presence of the first, second and third circumferential grooves in an axial portion extending from the first axial edge and having an axial width equal to at most 75% of the axial width of the tread and a transverse groove extending from the first axial edge to the second axial edge while intersecting the first, second and third circumferential grooves can ensure a relatively high flexibility of the tread in this axial portion (which is the portion that is most often in contact with the ground due to the camber angle of the motor vehicle). In particular, these first, second and third circumferential grooves act as hinges that are oriented in the circumferential direction and axially bend the tread to better match the contour of the ground on which the tire travels. This improved adaptability of the tread can improve the performance of the tire. The transverse grooves can provide circumferential bending over the entire width of the tread and thus better match the contour of the ground. As an example, a test conducted on rocky ground between a vehicle equipped with the above-mentioned tire of the prior art and the same vehicle equipped with a tire according to the present invention achieved a gain of one second per kilometer. This time gain is considerable.

[0012] A substantially circumferential line is a line which, at any point of the line, forms an angle with the circumferential direction of the tyre that is less than or equal to 5°.

[0013] The presence of the first, second and third circumferential rows of blocks makes it possible to effectively transmit forces in the circumferential direction due to the orientation of the leading edge corners of each block in these circumferential rows. When running in a straight line, for example during acceleration or braking, these blocks are substantially loaded due to the negative camber angles usually encountered by motor vehicles, in particular motor racing vehicles, which results in greater loads being experienced by the portion of the tread situated inside the vehicle.

[0014] In addition, the orientation of the leading edge corners of each block of the additional circumferential row can effectively transmit drift force. This drift force is often encountered when turning in rallies on rocky ground. Specifically, when turning, the transmission of loads related to the kinematics of the running device of the vehicle will cause the part of the tread located on the outside of the vehicle (therefore the block of the additional circumferential row) to be subjected to a greater load. The circumferential row of blocks is understood to mean a row in which a translational movement along the circumferential direction causes a transfer from one block of the row to another identical block of the row. In the same circumferential row of blocks, a single type of block can be provided, i.e., two circumferentially continuous blocks of the row are identical. It is also possible to have multiple different types of blocks, i.e., at least two identical blocks of the first type of the row are circumferentially separated by at least one block of the second type (which is different from the first type). Type is understood to mean the geometry of the block, such as its external geometry or any sipes that may be formed therein.

[0015] The tire according to the invention is a tire having an inner side and an outer side which are defined when mounted on a vehicle. This means that the tire is designed so that one side thereof is arranged on the inner side and the other side is arranged on the outer side. The expression "outer side" means the side of the tire which is fully visible from the outside of the vehicle when the tire is mounted on the vehicle. The expression "inner side" means the side of the tire which faces the wheel arch of the vehicle on which the tire is mounted. Usually, the tire has markings indicating the inner side and the outer side.

[0016] The block usually has a plurality of corners which define the contour of the block. These corners may be straight or curved. A distinction is made between leading, trailing and side corners. The leading corner is the corner which first comes into contact with the ground when the tyre rotates in its forward direction of rotation. The trailing corner is the corner which last comes into contact with the ground when the tyre rotates in its forward direction of rotation. The side corner is the corner which connects the leading and trailing corners.

[0017] The angle between two directions is the angle of smaller absolute value of the two angles defined between a reference direction of the tire (most often the circumferential direction) and another direction.

[0018] The average direction formed by the corner is the direction of a straight line connecting both ends of the corner.

[0019] In the case of racing tires, the axial width of the tread is determined on an unmounted and uninflated tire by measuring the axial distance between the corners of first and second axial edges forming the tread, these axial edges forming the limit between the tread and the sidewalls of the tire. In the case of racing tires, each of these first and second axial edges comprises a side corner of the axially outermost blocks of the tread.

[0020] In the case of tires not intended for racing, the tread surface area may be determined on a tire mounted on a measuring rim and inflated to its nominal pressure (250 kPa or 290 kPa, depending on whether it is a standard tire or a reinforced tire), said tread surface area being, within the meaning of the ETRTO (“European Tyre and Rim Technical Organization”) Manual of Standards (2021), the surface area in contact with the ground when the tire is loaded to 80% of its load capacity within the meaning of the ETRTO Manual of Standards (2021), this load being representative of the conditions of use normally encountered. Another method may consist in determining, on an unloaded tire mounted on a measuring rim and inflated to its nominal pressure within the meaning of the ETRTO Manual of Standards (2021) (250 kPa or 290 kPa, depending on whether it is a standard tire or a reinforced tire), the axial limits of the tread surface, for example by considering at each axial limit of the tread surface the point at which the angle between a tangent through the tread surface and a straight line parallel to the axial direction and passing through that point is equal to 30°. When there are a plurality of points at which the absolute value of the angle is equal to 30° in the meridian cross-sectional plane, the radially outermost point is used.

[0021] The invention relates in particular to racing tyres for motor vehicles.Racing is understood to mean officially timed events, as opposed to free running (sometimes called "track days" or "HDPE" (High Driving Performance Events)) which covers events that are not officially timed.

[0022] Very particularly and very preferably, the invention relates to a tyre for rallying, more preferably to a tyre for rallying at least on rocky and / or gravel and / or muddy ground, very preferably to a tyre for rallying on rocky ground.

[0023] The tyre according to the invention has a generally annular shape around an axis of rotation (substantially coinciding with the axis of rotation of the tyre). This axis of rotation defines three directions commonly used by those skilled in the art: axial, circumferential and radial.

[0024] The tread surface of a tire is the surface of the tread that comes into contact with the ground when the tire is running on the ground.

[0025] An axial direction is understood to mean a direction substantially parallel to the axis of rotation of the tyre, ie the axis of rotation of the tyre.

[0026] By circumferential direction is understood a direction which is substantially perpendicular simultaneously to the axial direction and to the radius of the tire (in other words tangential to a circle centred on the axis of rotation of the tire).

[0027] A radial direction is understood to be a direction along a radius of the tire, ie any direction intersecting the axis of rotation of the tire and being substantially perpendicular to this axis.

[0028] The median plane of the tire, denoted M, is understood to be the plane perpendicular to the axis of rotation of the tire and situated axially midway between the two beads and passing through the axial middle of the crown reinforcement.

[0029] The equatorial circumferential surface of the tire is understood to be the surface which passes through the equator of the tire in a meridian section plane and is perpendicular to the median plane and to the radial direction. The equator of the tire is the axis which is parallel to the axis of rotation of the tire in a meridian section plane (a plane perpendicular to the circumferential direction and parallel to the radial and axial directions) and is equidistant between the radially outermost point of the tread intended to come into contact with the ground and the radially innermost point of the tire intended to come into contact with a support, such as a rim.

[0030] A meridian plane is understood to be a plane parallel to and containing the axis of rotation of the tyre and perpendicular to the circumferential direction.

[0031] “Radially inside” and “radially outside” mean “closer to the tire’s axis of rotation” and “further away from the tire’s axis of rotation”, respectively. “Axially inside” and “axially outside” mean “closer to the tire’s median plane” and “further away from the tire’s median plane”, respectively.

[0032] Bead is understood to be the radial portion of the tire intended to attach the tire to a mounting support, such as a wheel comprising a rim. Thus, each bead is particularly intended to come into contact with a flange of the rim so that it can be attached.

[0033] Any numerical interval represented by the expression "between a and b" means a numerical range from greater than a to less than b (i.e., excluding the limits a and b), while any numerical interval represented by the expression "from a to b" means a numerical range from a to b (i.e., including the strict limits a and b).

[0034] The cuts represent grooves or sipes and form spaces that open into the tread surface.

[0035] The sipe or groove has two main characteristic dimensions on the tread surface: width and curve length, satisfying that the curve length is at least equal to twice the width. The sipe or groove is thus delimited by at least two main side surfaces that determine its curve length and are connected by a bottom surface, the two main side surfaces being spaced apart from each other by a non-zero distance (called the width of the cut).

[0036] On a new tyre, the width of the incision is the maximum distance between the two main lateral surfaces measured at the radial dimension coinciding with the tread surface when the incision does not have a chamfer, and the width of the incision is the maximum distance between the two main lateral surfaces measured at the radially outermost radial dimension of the incision and the radially innermost dimension of the chamfer when the incision has a chamfer. The width is measured substantially perpendicular to the main lateral surfaces.

[0037] The sipes are such that the distance between the main lateral surfaces is adapted to allow the main lateral surfaces delimiting said sipes to come into at least partial contact when passing through the contact patch, in particular when the tyre is brand new.

[0038] The grooves are such that the distance between the main lateral surfaces is such that these main lateral surfaces cannot touch each other, in particular when the tyre is new.

[0039] The cuts may be transverse or circumferential.

[0040] The transverse incision satisfies that the incision extends along an average direction forming an angle strictly greater than 30°, preferably greater than or equal to 45°, with the circumferential direction of the tire. The average direction is the shortest curve connecting the two ends of the incision and parallel to the tread surface. The transverse incision can be continuous, that is, not interrupted by a block or another incision, so that the two main side surfaces that determine its length are uninterrupted along the length of the transverse incision. The transverse incision can also be discontinuous, that is, interrupted by one or more blocks and / or one or more incisions, so that the two main side surfaces that determine its length are interrupted by one or more blocks and / or one or more incisions.

[0041] The circumferential incision is such that the incision extends along an average direction forming an angle less than or equal to 30°, preferably less than or equal to 10°, with the circumferential direction of the tire. The average direction is the shortest curve connecting the two ends of the incision and parallel to the tread surface. In the case of a continuous circumferential incision, the two ends coincide with each other and are connected by a curve forming a complete circumference around the tire. The circumferential incision can be continuous, i.e. not interrupted by a block or another incision, so that the two main side surfaces that determine its length are uninterrupted around the complete circumference of the tire. The circumferential incision can also be discontinuous, i.e. interrupted by one or more blocks and / or one or more incisions, so that the two main side surfaces that determine its length are interrupted by one or more blocks and / or one or more incisions around the complete circumference of the tire.

[0042] In some embodiments, the circumferential cut or each circumferential cut has a chamfer. The chamfer of the circumferential cut can be a straight chamfer or a round chamfer. The straight chamfer is formed by a plane inclined relative to the axial inner surface and the axial outer surface, and the plane continues the axial inner surface and the axial outer surface until the axial inner edge or the axial outer edge of the circumferential cut is axially defined. The round chamfer is formed by a curved surface tangent to the axial inner surface or the axial outer surface, and the curved surface continues the axial inner surface or the axial outer surface. The chamfer of the circumferential cut is characterized in that the height and width are respectively equal to the radial distance and axial distance between the common point shared by the axial inner surface or the axial outer surface continued by the chamfer and the axial inner edge or the axial outer edge of the circumferential cut axially defined.

[0043] In some embodiments, the transverse cut or each transverse cut has a chamfer. In other words, each transverse cut is radially delimited by surfaces that delimit the transverse cut circumferentially and are connected to each other by a bottom surface that delimits the transverse cut radially inwardly. The chamfer of the transverse cut can be a straight chamfer or a rounded chamfer. The straight chamfer is formed by a plane inclined relative to the face, which continues the face until the edge that delimits the transverse cut circumferentially. The rounded chamfer is formed by a curved surface that merges tangentially with the face, which continues the face. The chamfer of the transverse cut is characterized in that the height and width are respectively equal to the radial distance and the axial distance in a direction perpendicular to the face between the common point shared by the face continued by the chamfer and the edge that delimits the transverse cut circumferentially.

[0044] On a new tire, the depth of the cut is the maximum radial distance between the bottom of the cut and its projection on the ground when the tire is running. The maximum depth of the cut is called the tread height.

[0045] In a preferred embodiment, the axial width of each of the first substantially circumferential line, the second substantially circumferential line and the third substantially circumferential line is greater than or equal to 5 mm, more preferably greater than or equal to 7 mm. This promotes the hinge effect of the first circumferential groove, the second circumferential groove and the third circumferential groove.

[0046] In a preferred embodiment of utilizing the optimal positions of the first circumferential groove, the second circumferential groove and the third circumferential groove to improve the adaptability of the tire tread (especially when running in a straight line), the first circumferential groove, the second circumferential groove and the third circumferential groove are each arranged in an axial portion having an axial width equal to at most 70% of the axial width of the tread and extending from the first axial edge.

[0047] In an advantageous but optional embodiment, the average direction of the leading edge angles of each block of at least each first, second and third circumferential row of blocks forms an angle greater than or equal to 50°, preferably 60° with the circumferential direction of the tire.

[0048] Therefore, by changing the angle formed by the leading edge corners of each block portion of the first circumferential row, the second circumferential row and the third circumferential row with the circumferential direction (increasing the angle in this case), the position of the leading edge corners can be optimized to position them as perpendicularly as possible relative to the overall direction of the force when driving in a straight line, thereby improving the transmission of force and thereby increasing traction.

[0049] In an advantageous but optional embodiment, the average direction of the leading edge angles of each block of the or each additional circumferential row of blocks forms an angle less than or equal to 60°, preferably 50°, with the circumferential direction of the tyre.

[0050] Therefore, by changing the angle formed by the leading edge corners of each block-like portion of the or each additional circumferential row with the circumferential direction (in this case reducing the angle), the position of the leading edge corners can be optimized to position them as perpendicularly as possible relative to the overall direction of the cornering force, thereby improving the transmission of force and thereby increasing traction.

[0051] Advantageously, the first circumferential groove is the circumferential groove axially closest to the first axial edge among the first circumferential groove, the second circumferential groove and the third circumferential groove, the third circumferential groove is the circumferential groove axially closest to the second axial edge among the first circumferential groove, the second circumferential groove and the third circumferential groove, and the second circumferential groove is axially located between the first circumferential groove and the third circumferential groove.

[0052] In a preferred embodiment utilizing the optimal positions of the first circumferential groove, the second circumferential groove and the third circumferential groove to improve the conformability of the tire tread:

[0053] - the first circumferential groove is axially arranged in a first axial portion extending axially from the first axial edge between axial limits at 3% and 25%, preferably 5% and 20%, of the axial width of the tread, and / or

[0054] - the second circumferential groove is axially arranged in a second axial portion extending axially from the first axial edge between axial limits at 19% and 42%, preferably 23% and 39%, of the axial width of the tread, and / or

[0055] - The third circumferential groove is axially arranged in a third axial portion extending axially from the first axial edge between axial limits at 42% and 70%, preferably 46% and 66%, of the axial width of the tread.

[0056] Advantageously, the first circumferential row of block portions is the row of block portions axially closest to the first axial edge among the first circumferential row, the second circumferential row and the third circumferential row of block portions, the third circumferential row of block portions is the row of block portions axially closest to the second axial edge among the first circumferential row, the second circumferential row and the third circumferential row of block portions, and the second circumferential row of block portions is axially located between the first circumferential row and the third circumferential row.

[0057] In some embodiments:

[0058] - each block of a first circumferential row is axially delimited by a first circumferential groove and a first axial edge,

[0059] - each block of the second circumferential row is delimited axially by a first circumferential groove and a second circumferential groove,

[0060] Each block of the third circumferential row is at least partially delimited in the axial direction by a third circumferential groove.

[0061] In an advantageous but optional embodiment in which each transverse groove extends axially in an axially variable main direction, the angle formed by the main direction of each transverse groove and the circumferential direction of the tire is:

[0062] - exhibits a non-zero monotonic variation between a first axial edge and a second axial edge of the tread, or

[0063] is constant over at least one axial portion between a first axial edge and a second axial edge of the tread and exhibits a non-zero monotonic variation over at least one additional axial portion between the first axial edge and the second axial edge of the tread.

[0064] The expression "variable in axial direction" is understood to mean that the main direction of each transverse groove is variable in axial direction along each transverse groove.

[0065] The additional portion satisfies that, when considered together, the additional portion extends integrally from a first axial edge to a second axial edge of the tread.

[0066] A constant angle corresponds to zero change in angle.

[0067] The expression “non-zero monotonic variation” is understood to mean that the angle only increases or only decreases between a first axial edge and a second axial edge of the tread.

[0068] Thus, since each transverse groove defines the leading edge angle of the blocks of each block row, a non-zero monotonic variation enables traction to vary with the rotation angle of the tire about the running device axis and thus enables continuous traction between straight running and cornering.

[0069] More preferably, the angle formed by the main direction of each transverse groove and the circumferential direction of the tire at the first axial edge is greater than the angle formed by the main direction of each transverse groove and the circumferential direction of the tire at the second axial edge. Thus, in the case of a non-zero monotonic variation, the angle decreases only from the first axial edge to the second axial edge of the tread, or only over the corresponding portion between the first and second axial edges of the tread.

[0070] In a preferred embodiment, the angle formed by the average direction of the leading edge angle of each block of at least one given circumferential row of blocks with the circumferential direction is strictly greater than the angle formed by the average direction of the leading edge angle of each block of the circumferential row of blocks adjacent thereto in the axial direction, the axially adjacent row being closer to the second axial edge than the given circumferential row of blocks. More preferably, for at least 50% of the pairs of circumferential rows of blocks adjacent to each other in the axial direction, even more preferably for at least 75% of the pairs of circumferential rows of blocks adjacent to each other in the axial direction, and in this case for each pair of circumferential rows of blocks adjacent to each other in the axial direction, the angle formed by the average direction of the leading edge angle of each block of the first circumferential row of the circumferential rows of blocks of the pair with the circumferential direction is strictly greater than the angle formed by the average direction of the leading edge angle of each block of the second circumferential row of blocks of the pair with the circumferential direction, the second circumferential row of blocks of each pair being the row closest to the second axial edge in the first and second circumferential rows of blocks of the pair.

[0071] In a preferred embodiment, the angle formed by the main direction of each transverse groove and the circumferential direction of the tire at the first axial edge ranges from 70° to 90°, and the angle formed by the main direction of each transverse groove and the circumferential direction of the tire at the second axial edge ranges from 30° to 60°.

[0072] In a preferred embodiment, the angle formed by the average direction of the leading edge angle of each block portion in the first circumferential row and the circumferential direction is greater than or equal to the angle formed by the average direction of the leading edge angle of each block portion in the second circumferential row and the circumferential direction (which is strictly greater than the angle formed by the average direction of the leading edge angle of each block portion in the third circumferential row and the circumferential direction).

[0073] Therefore, since each transverse groove defines the leading edge corner of the block of each block row, excellent traction is provided when running straight due to the relatively large angle between the leading edge corner of the block near the first edge (which corresponds to the inner side subjected to load when running straight) and the circumferential direction, and excellent traction is also provided when turning due to the relatively small angle between the leading edge corner of the block near the second edge (which corresponds to the outer side subjected to load when turning) and the circumferential direction.

[0074] Preferably, the average direction of the leading edge angles of each block of each first and second circumferential row forms an angle with the circumferential direction in the range of 70° to 90°. Preferably, the average direction of the leading edge angles of each block of the third circumferential row forms an angle with the circumferential direction in the range of 50° to 70°. Preferably, the average direction of the leading edge angles of each block of the or each additional circumferential row forms an angle with the circumferential direction in the range of 30° to 60°.

[0075] In an advantageous but optional embodiment, the tread comprises a fourth circumferential row of blocks of a plurality of blocks, said fourth circumferential row being axially located between the second circumferential row and the third circumferential row of blocks, the angle formed by the average direction of the leading edge angle of each block of the fourth circumferential row of blocks being strictly greater than the angle formed by the average direction of the leading edge angle of each block of the or each additional circumferential row of blocks.

[0076] In an advantageous but optional embodiment, the average direction of the leading edge angles of each block of the fourth circumferential row forms an angle with the circumferential direction strictly greater than the angle formed by the average direction of the leading edge angles of each block of the third circumferential row.

[0077] Preferably, the average direction of the leading edge angles of each block-shaped portion of the fourth circumferential row forms an angle with the circumferential direction in the range of 65° to 85°.

[0078] Preferably, each block of the fourth circumferential row is delimited in the axial direction by a second circumferential groove and a third circumferential groove.

[0079] In other embodiments, it would be possible to envisage a tread comprising a fifth or even a sixth circumferential row of blocks of a plurality of blocks, said fifth or even the sixth circumferential row being axially located between the second and the third circumferential rows of blocks, the angle formed by the average direction of the leading edge angles of the blocks of this fifth row or of these fifth and sixth rows of blocks being strictly greater than the angle formed by the average direction of the leading edge angles of each block of the additional circumferential row of blocks or of each additional circumferential row.

[0080] In an advantageous but optional embodiment, the or each block of the additional circumferential row of blocks is delimited by at least one inclined groove intersecting at least two circumferentially continuous transverse grooves and arranged so that no circumferential line extends continuously around the circumference of the tire and passes through the or each inclined groove delimiting each block of the or each additional circumferential row of blocks without intersecting a block of the said additional circumferential row of blocks.

[0081] Thus, compared to the first, second and third circumferential grooves, each inclined groove does not form a hinge.

[0082] Two circumferentially consecutive transverse grooves satisfy that no other transverse grooves are circumferentially between the two circumferentially consecutive transverse grooves.

[0083] Optionally, the tread comprises a first additional circumferential row and a second additional circumferential row of blocks of the plurality of blocks, the first additional circumferential row and the second additional circumferential row each being axially closer to the second axial edge than the first, second and third circumferential rows of blocks,

[0084] The angle formed by the average direction of the leading edge angle of each block portion in at least the first circumferential row, the second circumferential row and the third circumferential row of block portions is strictly greater than the angle formed by the average direction of the leading edge angle of each block portion in the first additional circumferential row and the second additional circumferential row of block portions,

[0085] Each block of the first additional circumferential row of blocks is delimited in the axial direction by two inclined grooves intersecting two circumferentially continuous transverse grooves,

[0086] each block of the second additional circumferential row of blocks is delimited axially by an inclined groove intersecting two circumferentially continuous transverse grooves and a second axial edge,

[0087] Each block of each of the first additional circumferential row of blocks and the second additional circumferential row of blocks is arranged so that no circumferential line extends continuously around the circumference of the tire and passes through the inclined groove or each inclined groove defining each block of each of the first additional circumferential row of blocks and the second additional circumferential row of blocks without intersecting with the blocks of each of the first additional circumferential row of blocks and the second additional circumferential row of blocks, respectively.

[0088] In a favorable but optional embodiment (the second additional circumferential row is arranged axially outside the first additional circumferential row), the angle formed by the average direction of the leading edge angle of each block portion of the first additional circumferential row and the circumferential direction is strictly greater than the angle formed by the average direction of the leading edge angle of each block portion of the second additional circumferential row and the circumferential direction.

[0089] In an advantageous but optional embodiment, the average direction of the leading edge angles of each block of each of the first and second additional circumferential rows of blocks forms an angle less than or equal to 60°, preferably 50°, with the circumferential direction of the tyre.

[0090] As previously indicated, by changing (in this case reducing) the angle formed by the leading edge angle with the circumferential direction, the transfer of force and thus traction is improved.

[0091] In an advantageous but optional embodiment, the first and second circumferential rows of blocks each comprise a single block between two circumferentially consecutive transverse grooves.

[0092] The presence of a single block between two circumferentially continuous transverse grooves enables the blocks of each of the first and second circumferential rows of blocks to have a relatively large length in the circumferential direction and therefore limits any chipping of these blocks (which are subjected to higher loads when running in a straight line, especially during the acceleration and braking phases).

[0093] In an advantageous but optional embodiment, the third circumferential row of blocks comprises at least two blocks, preferably only two blocks, between two circumferentially consecutive transverse grooves.

[0094] Since the blocks of the third circumferential row of blocks are further to the inside than the blocks of the first and second circumferential rows of blocks, the blocks of the third circumferential row of blocks are subjected to smaller loads than the blocks of the first and second circumferential rows of blocks and are therefore less sensitive to possible chipping. Therefore, it is possible to reduce its length in the circumferential direction and thus maximize the number of leading edge corners in contact with the ground by increasing the number of leading edge corners between two circumferentially consecutive transverse grooves.

[0095] Preferably, at least a portion of the block portions in the third circumferential row of block portions, preferably at least 50% of the block portions in the third circumferential row of block portions, and more preferably at least 75% of the block portions in the third circumferential row of block portions, have a curve length of the leading edge corners that is strictly greater than the curve length of each side corner of the block portion.

[0096] The greater the curve length of the leading edge corner, the better the traction and braking performance.

[0097] In an embodiment in which the tread comprises a fourth circumferential row of blocks axially between the second and third circumferential rows of blocks, the fourth circumferential row of blocks comprises at least two blocks, preferably only two blocks, between two circumferentially consecutive transverse grooves.

[0098] Preferably, the curve length of the leading edge corner of at least a portion of the block portions in the fourth circumferential row of block portions, preferably at least 50% of the block portions in the fourth circumferential row of block portions, and more preferably at least 75% of the block portions in the fourth circumferential row of block portions is strictly greater than the curve length of each side corner of the block portion.

[0099] Here too, the multiplication of the blocks between two circumferentially consecutive transverse grooves and the maximization of the curve length of the leading edge corners of the blocks provide good traction and braking performance.

[0100] Preferably, the additional circumferential row of blocks comprises a single block between two circumferentially consecutive transverse grooves.

[0101] If the tread comprises a first and a second additional circumferential row of blocks, the first and second additional circumferential row of blocks each comprise a single block between two circumferentially consecutive transverse grooves.

[0102] Similar to the first and second circumferential rows of block portions, the presence of a single block portion between two circumferentially continuous transverse grooves enables the block portions of the first additional circumferential row and the second additional circumferential row of block portions to have a relatively large length in the circumferential direction, thereby limiting any chipping of these block portions (which are subjected to higher loads when turning).

[0103] In an embodiment particularly suitable for racing tires, in particular tires for rally racing, the width of each circumferential groove is greater than or equal to 2 mm, preferably ranging from 5 mm to 15 mm, more preferably ranging from 7 mm to 12 mm.

[0104] Still in an embodiment particularly suitable for racing tires, in particular tires for rally racing, the width of each oblique groove is greater than or equal to 2 mm, preferably ranging from 5 mm to 15 mm, more preferably ranging from 7 mm to 12 mm.

[0105] Still in an embodiment particularly suitable for racing tires, in particular tires for rallying, the width of each transverse groove is greater than or equal to 2 mm, preferably ranging from 5 mm to 15 mm, more preferably ranging from 7 mm to 12 mm.

[0106] Still in an embodiment particularly suitable for racing tires, in particular tires for rallying, the tread pattern height is greater than or equal to 7 mm, preferably ranging from 9 mm to 16 mm.

[0107] Still in an embodiment particularly suitable for racing tires, in particular for rally tires, the tread has an area void ratio associated with grooves having a width greater than or equal to 2 mm, preferably 4 mm, ranging from 35% to 55%, preferably from 40% to 50%.

[0108] Still in an embodiment particularly suitable for racing tires, in particular for rally tires, the volume void ratio of the tread associated with grooves having a width greater than or equal to 2 mm, preferably 4 mm, ranges from 30% to 45%, preferably from 35% to 45%.

[0109] The area-to-void ratio associated with the trench is the ratio of:

[0110] - the difference between the imaginary total area AT of the tread without the grooves and the contact area AC of the block portion of the tread, and

[0111] - the imaginary total area AT of the contact patch of the tread without said grooves.

[0112] The contact patch of the blocks is measured on a brand new tire. For example, the individual surfaces of the blocks can be measured manually. It is also possible to run a brand new, unmounted and uninflated tire on a smooth surface (e.g. a piece of glass) and optically measure the individual surfaces of each block and infer the contact patch therefrom.

[0113] The volume void ratio associated with a groove is the ratio of the total volume of said grooves of a brand new, unmounted and uninflated tire to the total volume of a brand new tread not including any of said grooves. To measure this volume void ratio, one of the methods described in WO2021 / 089958 can in particular be used.

[0114] The above characteristics characterize the tire when new.

[0115] The invention also relates to a pair of first and second tires, each as defined above, in which the tread of the first tire is symmetrical to the tread of the second tire relative to a symmetry plane substantially perpendicular to an axis of rotation common to the first and second tires.

[0116] The invention also relates to a tyre having an inner side and an outer side which are defined when the tyre is mounted on a vehicle, or a pair of first and second tyres as defined above, for use in a competition, preferably in a rally, more preferably in a rally on at least rocky and / or gravelly and / or muddy ground, very preferably in a rally on rocky ground, said tyre comprising a tread comprising a first axial edge and a second axial edge arranged on the inner side and on the outer side, respectively, said tread comprising a plurality of blocks and a plurality of grooves, said plurality of blocks and a plurality of grooves comprising:

[0117] - at least a first circumferential groove, a second circumferential groove and a third circumferential groove, the first circumferential groove, the second circumferential groove and the third circumferential groove being arranged so that there is at least a first substantially circumferential line, a second substantially circumferential line and a third substantially circumferential line respectively passing through the first circumferential groove, the second circumferential groove and the third circumferential groove and extending continuously around the circumference of the tire without intersecting any of the plurality of blocks, the first substantially circumferential line, the second substantially circumferential line and the third substantially circumferential line each having an axial width greater than or equal to 2 mm, the first circumferential groove, the second circumferential groove and the third circumferential groove each being arranged in an axial portion having an axial width equal to at most 75% of the axial width of the tread and extending from a first axial edge,

[0118] - at least a first circumferential row, a second circumferential row and a third circumferential row of block portions of a plurality of block portions,

[0119] - transverse grooves extending continuously from a first axial edge to a second axial edge of the tread and being substantially parallel to one another, each transverse groove intersecting the first circumferential groove, the second circumferential groove and the third circumferential groove, respectively,

[0120] at least one additional circumferential row of blocks of the plurality of blocks, the additional circumferential row or each additional circumferential row being the first, second and third circumferential rows of blocks and the circumferential row of the additional circumferential rows axially closest to the second axial edge,

[0121] , each of the plurality of blocks comprises a leading edge corner, and an angle formed by an average direction of the leading edge corners of each block of at least the first circumferential row, the second circumferential row and the third circumferential row of blocks and the circumferential direction of the tire is strictly greater than an angle formed by an average direction of the leading edge corners of each block of the additional circumferential row or each additional circumferential row of blocks and the circumferential direction of the tire. BRIEF DESCRIPTION OF THE DRAWINGS

[0122] The invention will be better understood by reading the following description given by way of non-limiting example only and with reference to the accompanying drawings, in which:

[0123] - Figure 1 is a prior art tire MICHELIN LATITUDE A schematic top view of the tread of

[0124] - Figure 2 is a top view of a tire according to the present invention,

[0125] - Figure 3 is a top view of a pair of first and second tires according to the present invention,

[0126] - Figures 4 to 8 for Figure 2 a detail of the same block of the tread of the tire, and

[0127] - Figures 9 to 12 Detailed views of blocks according to various embodiments. DETAILED DESCRIPTION

[0128] In the drawings reference frames X, Y, Z are shown which correspond respectively to the general axial direction (Y), radial direction (Z) and circumferential direction (X) of the tyre.

[0129] Figure 2A tyre according to the invention is shown, indicated by the general reference numeral 10. The tyre 10 has a generally annular shape about an axis of rotation R substantially parallel to the axial direction Y. The tyre 10 has a size 17 / 65R15 and is intended for competition, in this case for rallying, more preferably for rallying at least on rocky and / or gravelly and / or muddy ground, very preferably for rallying on rocky ground. The value "17" relates to the theoretical width of the tread, which in this case is 17 cm, the value 65 relates to the theoretical diameter of the tyre, which in this case is 65 cm, and the value "R15" characterizes a radial tyre designed to be mounted on a 15-inch rim. In the various figures, the tyre 10 is shown brand new, i.e. when it has not yet been driven.

[0130] The tire 10 comprises a crown 12 comprising a tread 14 intended to come into contact with the ground through a tread surface 16 when the tire is running. The tread 14 comprises and is delimited by first and second axial edges 16A and 16B, which define an axial width L of the tread surface 16. In this case, L=178 mm. The tire 10 has an inner side INT and an outer side EXT defined when the tire 10 is mounted on a vehicle. The first axial edge 16A is arranged at the inner side INT and the second axial edge 16B is arranged at the outer side EXT.

[0131] The tire 10 comprises two sidewalls 18 extending radially inwardly the crown 12. The tire 10 also comprises two beads (not shown) radially inside the sidewalls 18 and intended to attach the tire 10 to a mounting support, such as a rim. Each sidewall 18 connects each bead to the crown 12.

[0132] The tread 14 includes a plurality of blocks 20 and a plurality of cutouts 50 defining the plurality of blocks 20. The plurality of cutouts 50 include a plurality of grooves 60 and a plurality of sipes 80.

[0133] The plurality of grooves 60 include first, second and third circumferential grooves 62, 64, 66 arranged so that there are at least first, second and third substantially circumferential lines 63, 65, 67 that pass through the first, second and third circumferential grooves 62, 64, 66, respectively, and extend continuously around the circumference of the tire without intersecting any of the plurality of blocks 20. The axial width Lc of each of the first, second and third substantially circumferential lines 63, 65, 67 is greater than or equal to 2 mm, preferably greater than or equal to 5 mm, and in this case greater than or equal to 7 mm.

[0134] The first circumferential groove 62 is the circumferential groove axially closest to the first axial edge 16A among the first circumferential grooves, the second circumferential grooves, and the third circumferential grooves 62, 64, 66. The third circumferential groove 66 is the circumferential groove axially closest to the second axial edge 16B among the first circumferential grooves, the second circumferential grooves, and the third circumferential grooves 62, 64, 66. The second circumferential groove 64 is axially located between the first circumferential groove 62 and the third circumferential groove 66.

[0135] The first, second and third circumferential grooves 62 , 64 , 66 are each arranged in an axial portion having an axial width P equal to at most 75%, preferably at most 70%, of the axial width L of the tread 14 and extending from the first axial edge 16A.

[0136] More specifically, the first circumferential groove 62 is axially arranged in a first axial portion P1 extending axially from the first axial edge 16A between axial limits at 3% and 25%, preferably 5% and 20%, of the axial width L of the tread 14. The second circumferential groove 64 is axially arranged in a second axial portion P2 extending axially from the first axial edge 16A between axial limits at 19% and 42%, preferably 23% and 39%, of the axial width L of the tread 14. The third circumferential groove 66 is axially arranged in a third axial portion P3 extending axially from the first axial edge 16A between axial limits at 42% and 70%, preferably 46% and 66%, of the axial width L of the tread 14.

[0137] The plurality of grooves 60 further include transverse grooves 72 extending continuously from the first axial edge 16A to the second axial edge 16B of the tread 14. The transverse grooves 72 extend substantially parallel to each other. Each transverse groove 72 extends axially in an axially variable main direction. Each transverse groove 72 intersects the first circumferential groove, the second circumferential groove, and the third circumferential groove 62, 64, 66, respectively.

[0138] The angle formed by the main direction of each transverse groove 72 and the circumferential direction X is constant over the axial portion extending axially from the first axial edge 16A and the first circumferential line 63, and exhibits a non-zero monotonic variation (strictly decreasing in this case) over an additional axial portion extending axially from the first circumferential line 63 and the second axial edge 16B. Furthermore, the angle DA formed by the main direction DR of each transverse groove 72 and the circumferential direction X of the tire at the first axial edge 16A is greater than the angle DB formed by the main direction DR of each transverse groove 72 and the circumferential direction X at the second axial edge 16B. The angle DA ranges between 70° and 90°, being substantially equal to 90° in this case. The angle DB ranges between 30° and 60°, being substantially equal to 50° in this case.

[0139] The plurality of blocks 20 include a first circumferential row, a second circumferential row, a third circumferential row, and a fourth circumferential row of blocks 20 (represented by reference numerals 22, 24, 28, 26, respectively) of the plurality of blocks 20 and a first additional circumferential row and a second additional circumferential row 30, 32 of the blocks 20 of the plurality of blocks 20. The first additional circumferential row and the second additional circumferential row 30, 32 of the blocks 20 are separated from the first circumferential row, the second circumferential row, the third circumferential row, and the fourth circumferential row 22, 24, 28, 26 of the blocks 20. The additional circumferential row 30, 32 is axially closer to the second axial edge than the first circumferential row, the second circumferential row, and the third circumferential row 22, 24, 28, 26, respectively. The first circumferential row 22 of the blocks 20 is a row of blocks axially closest to the first axial edge 16A among the first circumferential row, the second circumferential row, and the third circumferential row 22, 24, 26 of the blocks. The third circumferential row 28 is the row of blocks axially closest to the second axial edge 16B among the first, second, third and fourth circumferential rows 22, 24, 28 and 26 of blocks. The second circumferential row 24 is axially located between the first circumferential row 22 and the third circumferential row 28. The fourth circumferential row 26 is axially located between the second circumferential row 24 and the third circumferential row 28.

[0140] Each block 20 of the first circumferential row 22 is axially bounded by the first circumferential groove 62 and the first axial edge 16A. Each block 20 of the second circumferential row 24 is axially bounded by the first and second circumferential grooves 62, 64. Each block 20 of the third circumferential row 28 is axially bounded at least in part by the third circumferential row 66. Each block 20 of the fourth circumferential row 26 is axially bounded by the second and third circumferential grooves 64, 66.

[0141] The first and second circumferential rows 22, 24 each include a single block 20 between two circumferentially consecutive transverse grooves 72. The third and fourth circumferential rows 28, 26 each include at least two blocks 20, preferably only two blocks 20, between two circumferentially consecutive transverse grooves 72.

[0142] The first and second additional circumferential rows 30, 32 of blocks 20 are each axially outward of the third circumferential row 28. The second additional circumferential row 32 is axially outward of the first additional circumferential row 30.

[0143] Each block 20 of the first additional circumferential row 30 is axially delimited by two inclined grooves 68, 70 intersecting two circumferentially continuous transverse grooves 72. Each block 20 of the second additional circumferential row 32 is axially delimited by an inclined groove 70 intersecting two circumferentially continuous transverse grooves 72 and a second axial edge 16B.

[0144] Figure 2 Two circumferential lines 69, 71 are shown that pass through the oblique grooves 68, 70, respectively. Each of these circumferential lines 69, 71 must intersect with a block 20 of the first and second additional circumferential rows, 30, 32, respectively. Thus, more generally, each block 20 of the first and second additional circumferential rows, 30, 32, respectively, is arranged so that no substantially circumferential line extends continuously around the circumference of the tire and passes through each oblique groove 68, 70 that delimits each block of the first and second additional circumferential rows, 30, 32, respectively, without intersecting with a block 20 of the first and second additional circumferential rows, 30, 32, respectively.

[0145] The first and second additional circumferential rows 30 , 32 each comprise a single block 20 between two circumferentially consecutive transverse grooves 72 .

[0146] Each of the plurality of blocks 20 includes a plurality of corners, in this case defining a substantially polygonal profile. Each of the first, second, third and fourth circumferential rows 22, 24, 28, 26 and each of the first and second additional circumferential rows 30, 32 includes a leading edge corner 202, a trailing edge corner 204 and side corners 206, 208.

[0147] The angles D1, D2, D3, D4 formed by the average direction of the leading edge angle 202 of each block portion 20 of the first circumferential column, the second circumferential column, the third circumferential column and the fourth circumferential column 22, 24, 28, 26 and the circumferential direction X are strictly greater than the angles A1, A2 formed by the average direction of the leading edge angle 202 of each block portion 20 of the first additional circumferential column and the second additional circumferential column 30, 32 and the circumferential direction X.

[0148] An angle D1, D2, D4, D3, A1, A2 formed by the average direction of the leading edge angle 202 of each block portion 20 of each circumferential row 22, 24, 26, 28, 30, 32 and the circumferential direction X is strictly greater than the angle D2, D4, D3, A1, A2 formed by the average direction of the leading edge angle 202 of each block portion 20 of the circumferential row 24, 26, 28, 30, 32 adjacent to it in the axial direction and the circumferential direction X, and each row 24, 26, 28, 30, 32 adjacent to a given circumferential row 22, 24, 26, 28, 30, 32 in the axial direction is closer to the outer side EXT than each corresponding given circumferential row 22, 24, 26, 28, 30, 32.

[0149] The curve length of the leading edge corners 202 of 100% of the blocks 20 in the third and fourth circumferential rows 28 , 26 is strictly greater than the curve length of each side corner 206 , 208 of the block 20 .

[0150] Each angle D1, D2, D3, D4 is greater than or equal to 50°, preferably greater than or equal to 60°. Angle D1 is greater than or equal to angle D2. Angle D2 is strictly greater than angle D3. Angle D4 is strictly greater than angle D3. In this particular case, each angle D1, D2 ranges from 70° to 90°, angle D3 ranges from 50° to 70°, and angle D4 ranges from 65° to 85°. D1 = 90°, D2 = 85°, D3 = 60° and D4 = 75°.

[0151] Each angle A1 , A2 is less than or equal to 60°, preferably less than or equal to 50°. Angle A1 is strictly greater than angle A2. In this particular case, each angle A1 , A2 ranges from 30° to 60°. A1 = 45° and A2 = 40°.

[0152] The width of each of the first, second and third circumferential grooves 62, 64, 66 is greater than or equal to 2 mm, preferably ranging from 5 mm to 15 mm, more preferably ranging from 7 mm to 12 mm, in this case equal to 9.7 mm, 8.7 mm and 9.7 mm, respectively. The width of each transverse groove 72 is greater than or equal to 2 mm, preferably ranging from 5 mm to 15 mm, more preferably ranging from 7 mm to 12 mm, in this case equal to 9.6 mm. The width of each oblique groove 68, 70 is greater than or equal to 2 mm, preferably ranging from 5 mm to 15 mm, more preferably ranging from 7 mm to 12 mm, in this case equal to 10 mm.

[0153] The area void ratio of the tread 14 associated with grooves having a width greater than or equal to 2 mm, preferably 4 mm (in this case associated with the circumferential grooves 62, 64, 66, the transverse grooves 72 and the oblique grooves 68, 70) ranges from 35% to 55%, preferably from 40% to 50%, in this case equal to 44%. The volume void ratio of the tread associated with grooves having a width greater than or equal to 2 mm, preferably 4 mm (in this case associated with the circumferential grooves 62, 64, 66, the transverse grooves 72 and the oblique grooves 68, 70) ranges from 30% to 45%, preferably from 35% to 45%, in this case equal to 39%.

[0154] The tread pattern height is greater than or equal to 7 mm, preferably ranging from 9 mm to 16 mm, and in this case equal to 12 mm.

[0155] refer to Figure 3 , shows a pair 100 of first and second tires 10, 10', both in accordance with the present invention. The tread 14 of the first tire 10 is symmetrical to the tread 14' of the second tire 10' relative to a symmetry plane S substantially perpendicular to the common rotation axis R of the first and second tires 10, 10'. Figure 3 In the example, the first tire 10 is intended to be mounted on the right side of the vehicle, while the second tire 10' is intended to be mounted on the left side of the vehicle, so that the inner sides INT of the first and second tires 10, 10' respectively face the wheel arches of the vehicle and so that when the tires are mounted on the vehicle, the sides EXT of the first and second tires 10, 10' respectively are completely visible from the outside of the vehicle.

[0156] refer to Figure 2 , each block 20 of the tread 14 comprises a single sipe 80. Each block 20 of each of the first and second circumferential rows 22, 24 and the additional circumferential row 30 comprises a sipe 82 referred to as an extended sipe, in this case a single extended sipe 82.

[0157] Now refer to Figure 4 and Figure 5The blocks 20 of the second circumferential row 24 of blocks and the elongated sipes 82 formed therein are described in detail.

[0158] refer to Figure 4 , each block 20 of the second circumferential row 24 is longer in the circumferential direction X. Specifically, each block 20 of the second circumferential row 24 is inscribed in a rectangle RE, two sides of which are parallel to the axial direction Y, and the other two sides are parallel to the circumferential direction X. Since the two sides parallel to the axial direction Y are smaller than the two sides parallel to the circumferential direction X, each block 20 of the second circumferential row 24 is longer in the circumferential direction X. The line LE of the slenderness of each block 20 of the second circumferential row 24 is a curve connecting two corners (the leading edge corner 202 and the trailing edge corner 204), and is equidistant from the side corners 206, 208 connecting the leading edge corner 202 and the trailing edge corner 204. The average direction Ep of the slenderness is a straight line passing through the intersection between the curve of the slenderness and the two corners (the leading edge corner 202 and the trailing edge corner 204) intersecting therewith.

[0159] The circumferential length of each block 20 of the second circumferential row 24 (i.e., the length of the two sides of the rectangle RE parallel to the circumferential direction X in this case) is equal to 40 mm. The width of each block 20 of the second circumferential row 24 (i.e., the length of the two sides of the rectangle RE parallel to the axial direction Y in this case) is equal to 22 mm.

[0160] The depth of each extended sipe 82 is greater than or equal to 9 mm, preferably ranging from 10 mm to 14 mm, in this case equal to 12 mm. This depth is greater than or equal to 50%, preferably 70%, more preferably 90% of the height of the block 20 forming said extended sipe 82. In this case, the height of each block 20 of the second circumferential row 24 is substantially equal to 12 mm. The width of each extended sipe 82 is less than or equal to 2.0 mm, preferably ranging from 0.5 mm to 2.0 mm, in this case equal to 1.0 mm.

[0161] Each extended slit 82 includes a central portion 84 and first and second extended portions 86, 88, each of which is in communication with the central portion 84. Each extended slit 82 also includes first and second blind end portions 90, 92 and first and second dimension points 94, 96, which are arranged to define the central portion 84 disposed between the first and second dimension points 94, 96 on one side, and to define each first and second extended portion 86, 88 disposed between each first and second dimension points 94, 96 and each first and second blind end portion 90, 92, respectively, on the other side. Each first and second dimension point 94, 96 is separated from each first and second blind end portion 90, 92, respectively.

[0162] The curve length of each of the first and second extensions 86, 88 (i.e. the curve length between each first and second dimension point 94, 96 and each first and second blind end 90, 92, respectively) is equal to 8 mm in this case. The central portion 84 (i.e. the curve length between each first and second dimension point 94, 96) is equal to 30 mm in this case. Therefore, the ratio between the curve length of each first and second extension 86, 88 and the curve length of the central portion 84 is strictly less than 1.0, preferably less than or equal to 0.7, preferably 0.5 and greater than or equal to 0.1, preferably 0.2, more preferably in the range of 0.2 to 0.5, in this case equal to 0.27.

[0163] refer to Figure 5 , the first and second dimension points 94, 96 define the slenderness direction Ei of the extended sipe 82, the maximum dimension Lmax of the extended sipe 82 in the slenderness direction Ei of the extended sipe 82, and the maximum dimension Imax of the extended sipe 82 in the direction Epi perpendicular to the slenderness direction Ei. Generally, it should be noted that the slenderness direction Ei of the extended sipe 82 coincides with the slenderness direction of the central portion 84. The first and second extended portions 86, 88 extend in the extension directions Ea1, Ea2, respectively. In this case, Lmax=31 mm, lmax=10 mm, so that the slenderness ratio of the extended sipe 82 is greater than or equal to 1.5, preferably 1.7, more preferably 2.0, and in this case is equal to 3.1.

[0164] The angle formed by the extension directions Ea1 and Ea2 of the first and second extension parts 86 and 88 respectively and the slenderness direction Ei of the extended sipe 82 is less than or equal to 80°, preferably in the range of 30° to 70°, more preferably in the range of 30° to 50°, which is equal to 37° in this case.

[0165] refer to Figure 6 The angle formed by the average slenderness direction Ep of the block portion 20 and the slenderness direction Ei of the extended sipe 82 is less than or equal to 45°, preferably 30°, more preferably 15°, and even more preferably 5°.

[0166] refer to Figure 7The distance Li between the first and second dimension points 94, 96 for determining the dimension of the extended sipe 82 in the average slenderness direction Ep of the block 20 is equal to 31 mm in this case, and the distance Lp between the first and second dimension points 98, 100 for determining the dimension of the block 20 in the average slenderness direction Ep of the block 20 is equal to 41 mm in this case. The ratio between Li and Lp is greater than or equal to 0.5, preferably 0.7, and in this case is equal to 0.76.

[0167] refer to Figure 8 , the extended slit 82 has a first dimension point and a second dimension point for determining the size of the extended slit 82 in a direction Epp perpendicular to the average slenderness direction Ep of the block 20. In this case, each first dimension point and second dimension point for determining the size of the extended slit 82 in the direction Epp coincides with each first and second blind end 90, 92, respectively. The distance li between the first and second dimension points 90, 92 for determining the size of the extended slit 82 in the direction Epp is equal to 11 mm. The block 20 has a first and second dimension point 102, 104 for determining the size of the block 20 in the direction Epp. The distance lp between the first and second dimension points 102, 104 for determining the size of the block 20 in the direction Epp is equal to 22 mm. The ratio between li and lp is greater than or equal to 0.3, preferably 0.5, and in this case is equal to 0.5.

[0168] refer to Figure 5 The central portion 84 and each of the first and second extension portions 86, 88 are arranged so that along the extended knife groove 82 from each of the first and second extension portions 86, 88 to the central portion 84, there is a change in direction relative to the slenderness direction Ei of the extended knife groove 82 that passes through each first dimension point 94, 96 for determining the size of the extended knife groove 82.

[0169] The central portion 84 is arranged such that along the extended sipe 82 in the central portion 84 from the first dimension point 94 to the second dimension point 96 there is no change in direction relative to the elongation direction Ei of the extended sipe 82 .

[0170] The first extension portion 86 is arranged such that there is no change in direction relative to the slenderness direction Ei along the extension sipe 82 in the first extension portion 86 from the first dimension point 94 to the first blind end portion 90. Similarly, the second extension portion 88 is arranged such that there is no change in direction relative to the slenderness direction Ei along the extension sipe 82 in the second extension portion 88 from the second dimension point 96 defining the slenderness direction Ei to the second blind end portion 92.

[0171] Return to Figure 2 , it is noted that at least 20%, preferably at least 30%, in this case 50%, by number of the blocks of the tread comprise extended sipes 82, in this particular case the blocks 20 of the circumferential rows 22, 24 and 30. At least 50%, preferably 75%, by number of the blocks have a circumferential slenderness, i.e. in this case at least 50%, preferably 75% by number of the blocks 20 of the circumferential rows 22, 24, 30 and 32 comprise extended sipes 82.

[0172] Figures 9 to 12 Blocks including extended sipes 82 are shown according to other embodiments.

[0173] Compared with the extended sipe 82 described with reference to the previous figures, Fig. 9 and Fig.10 The extended sipe 82 satisfies the central portion 84 is not a straight line. However, similar to the extended sipe 82 described with reference to the previous figures, along the extended sipe 82 in the central portion 84 from the first dimension point 94 to the second dimension point 96 defining the slenderness direction Ei, there is no change in direction relative to the slenderness direction Ei.

[0174] Compared to the extended sipe 82 described with reference to the previous figures, the first and second extended portions 86 , 88 are bent in the same direction.

[0175] Compared with the extended sipe 82 described with reference to the previous figures, Fig.12 The extended knife groove 82 in FIG. 8 includes a single extended portion 86 .

[0176] The present invention is not limited to the above-described embodiments.

Claims

1. A tire (10), the tire (10) having an inner side (INT) and an outer side (EXT) defined when the tire is mounted on a vehicle, the tire comprising a tread (14), the tread (14) comprising a first axial edge and a second axial edge (16A, 16B) arranged on the inner side and the outer side, respectively, the tread (14) comprising a plurality of blocks (20) and a plurality of grooves (62, 64, 66, 68, 70, 72), the plurality of blocks (20) and the plurality of grooves (62, 64, 66, 68, 70, 72) comprising: - at least first, second and third circumferential grooves (62, 64, 66) arranged so that there are at least first, second and third substantially circumferential lines (63, 65, 67) passing through the first, second and third circumferential grooves (62, 64, 66) respectively and extending continuously around the circumference of the tire without intersecting the first, second and third substantially circumferential lines (63, 65, 67) respectively Any of the plurality of blocks (20) intersects, the first substantially circumferential line, the second substantially circumferential line and the third substantially circumferential line (63, 65, 67) each have an axial width (Lc) greater than or equal to 2 mm, the first circumferential groove, the second circumferential groove and the third circumferential groove (62, 64, 66) are each arranged in an axial portion having an axial width (P) equal to at most 75% of the axial width (L) of the tread (14) and extending from the first axial edge (16A), - at least a first circumferential row, a second circumferential row and a third circumferential row (22, 24, 28) of block-shaped parts (20) of a plurality of block-shaped parts (20), - transverse grooves (72) extending continuously from a first axial edge (16A) to a second axial edge (16B) of the tread (14) and being substantially parallel to one another, each transverse groove (72) intersecting the first, second and third circumferential grooves (62, 64, 66), respectively, - at least one additional circumferential row (30, 32) of a block portion (20) of the plurality of blocks (20), the additional circumferential row (30, 32) or each additional circumferential row (30, 32) being the first, second and third circumferential rows (22, 24, 28) of the blocks and the circumferential row of the additional circumferential rows (30, 32) axially closest to the second axial edge (16B), Each block (20) of the plurality of blocks (20) comprises a leading edge angle (202), wherein an angle (D1, D2, D3) formed by an average direction of the leading edge angle (202) of each block of at least a first circumferential row, a second circumferential row and a third circumferential row (22, 24, 28) of the blocks and a circumferential direction (X) of the tire is strictly greater than an angle (A1, A2) formed by an average direction of the leading edge angle (202) of each block of an additional circumferential row (30, 32) of the blocks or each additional circumferential row (30, 32) of the blocks and the circumferential direction (X) of the tire.

2. Tyre (10) according to the preceding claim, each transverse groove extending axially in an axially variable main direction, the angle formed by the main direction of each transverse groove and the circumferential direction of the tyre being: - exhibits a non-zero monotonic variation between a first axial edge and a second axial edge of the tread, or is constant over at least one axial portion between a first axial edge and a second axial edge of the tread and exhibits a non-zero monotonic variation over at least one additional axial portion between the first axial edge and the second axial edge of the tread.

3. Tyre (10) according to any of the preceding claims, the tyre (10) being intended for rallying, more preferably intended for rallying at least on rocky and / or gravel and / or muddy ground, very preferably intended for rallying on rocky ground.

4. Tyre (10) according to any one of the preceding claims, wherein: The first circumferential groove (62) is the circumferential groove closest to the first axial edge (16A) in the axial direction among the first circumferential groove, the second circumferential groove and the third circumferential groove (62, 64, 66), the third circumferential groove (66) is the circumferential groove closest to the second axial edge (16B) in the axial direction among the first circumferential groove, the second circumferential groove and the third circumferential groove (62, 64, 66), and the second circumferential groove (64) is axially located between the first circumferential groove (62) and the third circumferential groove (66).

5. Tyre (10) according to any one of the preceding claims, wherein: The first circumferential row (22) of block parts is the row of block parts axially closest to the first axial edge (16A) among the first circumferential row, the second circumferential row and the third circumferential row (22, 24, 28) of block parts, the third circumferential row (28) of block parts is the row of block parts axially closest to the second axial edge (16B) among the first circumferential row, the second circumferential row and the third circumferential row (22, 24, 28) of block parts, and the second circumferential row (24) of block parts is axially located between the first circumferential row (22) and the third circumferential row (28).

6. Tyre (10) according to any one of the preceding claims, wherein: - each block (20) of the first circumferential row (22) is delimited axially by a first circumferential groove (62) and a first axial edge (16A), - each block (20) of the second circumferential row (24) is delimited axially by a first circumferential groove and a second circumferential groove (62, 64), Each block (20) of the third circumferential row (28) is at least partially delimited in the axial direction by a third circumferential groove (66).

7. Tyre (10) according to any one of the preceding claims, wherein: The tread (14) comprises a fourth circumferential row (26) of blocks (20) of a plurality of blocks (20), the fourth circumferential row (26) being axially located between the second circumferential row and the third circumferential row (24, 28) of blocks, the angle (D4) formed by the average direction of the leading edge angle (202) of each block of the fourth circumferential row (26) of blocks being strictly greater than the angle (A1, A2) formed by the average direction of the leading edge angle (202) of each block of the additional circumferential row (30, 32) of blocks or each additional circumferential row (30, 32).

8. Tyre (10) according to the preceding claim, wherein: Each block (20) of the fourth circumferential row (26) is axially bounded by second and third circumferential grooves (64, 66).

9. Tyre (10) according to any one of the preceding claims, wherein: The additional circumferential row (30, 32) of blocks, or each block (20) of each additional circumferential row (30, 32), is delimited by at least one inclined groove (68, 70) intersecting at least two circumferentially continuous transverse grooves (72) and arranged so that no circumferential line extends continuously around the circumference of the tire and passes through the inclined groove (68, 70) of each block (20) of the additional circumferential row (30, 32) of blocks, or each inclined groove (68, 70) of the additional circumferential row (30, 32) of blocks without intersecting a block of the additional circumferential row (30, 32) of blocks.

10. Tyre (10) according to any one of the preceding claims, wherein: The tread (14) includes a first additional circumferential row and a second additional circumferential row (30, 32) of blocks of the plurality of blocks, the first additional circumferential row and the second additional circumferential row (30, 32) each being axially closer to the second axial edge (16B) than the first, second and third circumferential rows (22, 24, 28) of blocks, The angle (D1, D2, D3) formed by the average direction of the leading edge angle (202) of each block portion of at least the first circumferential row, the second circumferential row and the third circumferential row (22, 24, 28) of the block portions is strictly greater than the angle (A1, A2) formed by the average direction of the leading edge angle (202) of each block portion of the first additional circumferential row and the second additional circumferential row (30, 32) of the block portions, Each block (20) of the first additional circumferential row (30) of blocks is delimited axially by two inclined grooves (68, 70) intersecting two circumferentially continuous transverse grooves (72), Each block (20) of the second additional circumferential row (32) of blocks is axially delimited by an inclined groove (70) intersecting two circumferentially continuous transverse grooves (72) and a second axial edge (16B), Each block (20) of each of the first and second additional circumferential rows (30, 32) of blocks is arranged so that no circumferential line extends continuously around the circumference of the tire and passes through the inclined groove (68, 70) or each inclined groove (68, 70) defining each of the first and second additional circumferential rows (30, 32) of blocks without intersecting the blocks of the first and second additional circumferential rows (30, 32) of blocks, respectively.

11. Tyre (10) according to any one of the preceding claims, wherein: The first and second circumferential rows (22, 24) of blocks each include a single block (20) between two circumferentially consecutive transverse grooves (72).

12. Tyre (10) according to any one of the preceding claims, wherein: The third circumferential row (28) of blocks comprises at least two blocks (20), preferably only two blocks (20), between two circumferentially consecutive transverse grooves (72).

13. Tyre (10) according to any one of the preceding claims, wherein: The curve length of the leading edge corner (202) of at least a portion of the blocks of the third circumferential row (28) of blocks is strictly greater than the curve length of each side corner (206, 208) of the blocks.

14. A pair of first and second tires (10, 10'), each according to any one of the preceding claims, in which the tread (14) of the first tire (10) is symmetrical with the tread (14') of the second tire (10') relative to a symmetry plane (S) substantially perpendicular to the common rotation axis (R) of the first and second tires (10, 10').

15. A tyre (10) having an inner side (INT) and an outer side (EXT) defined when the tyre is mounted on a vehicle, or a pair of first and second tyres (10, 10') according to the preceding claim, for use in a competition, preferably in a rally, more preferably in a rally on at least rocky and / or gravelly and / or muddy ground, very preferably in a rally on rocky ground, the tyre comprising a tread (14), the tread (14) comprising a first axial edge and a second axial edge (16A, 16B) arranged on the inner side and the outer side, respectively, the tread (14) comprising a plurality of blocks (20) and a plurality of grooves (62, 64, 66, 68, 70, 72), the plurality of blocks (20) and the plurality of grooves (62, 64, 66, 68, 70, 72) comprising: - at least first, second and third circumferential grooves (62, 64, 66) arranged so that there are at least first, second and third substantially circumferential lines (63, 65, 67) passing through the first, second and third circumferential grooves (62, 64, 66) respectively and extending continuously around the circumference of the tire without intersecting the first, second and third substantially circumferential lines (63, 65, 67) respectively Any of the plurality of blocks (20) intersects, the first substantially circumferential line, the second substantially circumferential line and the third substantially circumferential line (63, 65, 67) each have an axial width (Lc) greater than or equal to 2 mm, the first circumferential groove, the second circumferential groove and the third circumferential groove (62, 64, 66) are each arranged in an axial portion having an axial width (P) equal to at most 75% of the axial width (L) of the tread (14) and extending from the first axial edge (16A), - at least a first circumferential row, a second circumferential row and a third circumferential row (22, 24, 28) of block-shaped parts (20) of a plurality of block-shaped parts (20), - transverse grooves (72) extending continuously from a first axial edge (16A) to a second axial edge (16B) of the tread (14) and being substantially parallel to one another, each transverse groove (72) intersecting the first, second and third circumferential grooves (62, 64, 66), respectively, - at least one additional circumferential row (30, 32) of a block portion (20) of the plurality of blocks (20), the additional circumferential row (30, 32) or each additional circumferential row (30, 32) being the first, second and third circumferential rows (22, 24, 28) of the blocks and the circumferential row of the additional circumferential rows (30, 32) axially closest to the second axial edge (16B), Each block (20) of the plurality of blocks (20) comprises a leading edge angle (202), and an angle (D1, D2, D3) formed by an average direction of the leading edge angle (202) of each block in at least the first circumferential row, the second circumferential row and the third circumferential row (22, 24, 28) of the block and a circumferential direction (X) of the tire is strictly greater than an angle (A1, A2) formed by an average direction of the leading edge angle (202) of each block in the additional circumferential row (30, 32) of the block or each additional circumferential row (30, 32) of the block and the circumferential direction (X) of the tire.

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