Vehicle Wheel Tire

Abstract

The tire (1) includes a plurality of blocks (5, 6) defined in a tread band (2) and at least one first sipe (10; 20) formed in each block. The first sipe (10; 20) extends in a first longitudinal direction (A) and includes a first straight portion (11) that extends substantially along the first longitudinal direction (A), a single wave portion (12) that extends following the first straight portion (11), and a second straight portion (13) that extends following the single wave portion (12). The single wave portion (12) is inclined and includes a first segment (14) that extends from the first straight portion (11) to a first peak (15), a second segment (16) that is inclined and extends from the first peak (15) to a second peak (17) on the opposite side, and a third segment (18) that is inclined and extends from the second peak (17) to the second straight portion (13). The second segment (16) of the single wave portion (12) is inclined at an angle greater than that of the first segment (14) and the third segment (18) with respect to the first longitudinal direction (A).

Description

Technical Field

[0001] The present invention relates to a tire for a vehicle wheel, and more particularly to a winter tire.

Background Art

[0002] Generally, a tire has a carcass structure that takes a toroidal shape around a rotational axis and includes at least one carcass ply having an edge that engages with a respective annular anchoring structure called a bead core.

[0003] A belt structure is provided at a position radially outward of the carcass structure. In the case of a tire for an automobile, the belt structure includes at least two strips of rubberized fabric that overlap in the radial direction, and the rubberized fabric is provided with reinforcing cords. The reinforcing cords are usually made of metal, are parallel to each other, but cross with respect to the cords of adjacent strips, and are preferably arranged symmetrically with respect to the equatorial plane of the tire, on each strip.

[0004] Preferably, the belt structure further includes a third layer of fibers or metal cords arranged circumferentially (at 0°) at a radially outer position of at least the end of the underlying belt strip. In a tubeless tire, there is further a radially inner layer known as a "liner" that has an impermeable property to obtain the airtightness of the tire itself.

[0005] A tread band made of an elastomeric material and defining a tread surface intended to contact the road surface is attached at a position radially outward of the belt structure.

Summary of the Invention

[0006] In order to further obtain sufficient road grip on wet road surfaces, the tire has a tread band provided with grooves having various shapes and geometries, the main purpose of which is to enable the drainage of water present between the surface of the tire and the road surface during mutual contact.

[0007] Generally, the grooves define a plurality of blocks on the tread band, each of which has a radially outer surface intended to contact the road surface and thus forms a part of the tread surface of the tire. Each block is further at least partially bounded by one or more walls defined by the grooves surrounding the block.

[0008] In some cases, the wall of the block or a part thereof is connected to the tread surface of the block by a chamfer, which is typically formed by a plane suitably inclined with respect to the wall and the tread surface and defines the edge of the block.

[0009] In the case of winter tires, generally small recesses called "sipes" are formed on the blocks of the tread band, which extend from the tread surface of the tire towards the interior of the block. The function of the sipes is to provide additional grip elements when driving on snow surfaces and to hold a certain amount of snow, thereby improving the grip on the road surface. The sipes can have extremely diverse and different configurations, for example, the sipes can have a linear shape, a curved shape, or a shape with an undulating progression.

[0010] The term "circumferential direction" means a direction generally oriented in the rotational direction of the tire or, in any case, slightly (up to approximately 5°) inclined with respect to the rotational direction of the tire.

[0011] The term "axial direction" means a direction that is substantially parallel to the rotational axis of the tire or, at most, is inclined slightly (up to about 5°) with respect to this rotational axis of the tire. The axial direction is generally perpendicular to the circumferential direction.

[0012] The term "radial direction" means a direction that intersects perpendicularly to the rotational axis of the tire or, at most, is inclined slightly (e.g., up to about 5°) with respect to the direction perpendicular to the rotational axis of the tire.

[0013] The term "equatorial plane" of the tire means the axial direction centerline plane perpendicular to the rotational axis of the tire.

[0014] The term "groove" means a recess formed in the tread band portion, extending in the main longitudinal direction, and having a width of 1.5 mm or more. Preferably, the groove has a depth of at least 3 mm.

[0015] The term "sipe" means a recess formed in the tread band portion, extending in the main longitudinal direction, and having a width of less than 1.5 mm.

[0016] The "longitudinal development direction" of the sipe is defined by the linear progression of the sipe in the region of the radially outer surface of the block.

[0017] The term "block" means a tread band portion that is intended to contact the road surface and is delimited over its entire peripheral edge by one or more grooves and, where applicable, by the axial ends of the tread band.

[0018] Accordingly, a block is considered to be both a tread band portion having a closed contour delimited by three or more grooves and a circumferential rib delimited by a pair of grooves that extend circumferentially around the tread band.

[0019] The "central block" is defined as a block that is not bounded by the axial ends of the tread band, while a block that is partially bounded by one of the axial ends of the tread band is defined as a "shoulder block".

[0020] The term "wall" of a block means a surface that extends generally from the bottom of the groove bounding the block towards the tread surface portion of the block.

[0021] The term "edge" of a block means the block region where the wall of the block joins the tread surface portion of the block.

[0022] The edge may be formed by a corner if the wall intersects the tread surface portion directly, or may be formed by a connecting surface connecting the wall and the tread surface portion defined as a "chamfer".

[0023] Two or more straight-line distances, such as two or more distances between sipes or between sipe elements, have "substantially equal" lengths if their respective lengths differ from each other by at most an amount equal to 10% of the maximum length.

[0024] Two or more directions or two or more elements extending in their respective directions, such as two or more sipes or portions thereof, are "substantially parallel" if they are inclined with respect to each other at an angle of less than 10°, preferably less than 5°.

[0025] The inclination of a first direction with respect to a second direction, for example, the direction of a sipe portion with respect to the longitudinal development direction of the sipe, is defined by the acute angle formed by the first direction with respect to the second direction. As a specific example, when the first direction is perpendicular to the second direction, the inclination is 90°.

[0026] For example, two or more directions or two or more elements extending in respective directions, such as two or more cycles or portions thereof, are inclined “in a concordant manner” with respect to a further direction when considered on a Cartesian plane that includes the two or more directions and has an axis of abscissa parallel to another direction. For example, two different portions of a cycle extending in the longitudinal development direction of the cycle are inclined concordantly with respect to the longitudinal development direction of the cycle when considered on a Cartesian plane having an axis of abscissa parallel to the longitudinal development direction of the cycle and both of the said portions of the cycle extend in respective directions in which both rise or both fall.

[0027] Consequently, two or more directions or two or more elements extending in respective directions, such as two or more cycles or portions thereof, are inclined “discordantly” when considered on this Cartesian plane and their trends rise for one or more of the said directions and fall for one or more of the other directions of the said directions.

[0028] The term “peak” defined in a cycle or a portion of a cycle means an interval taking a maximum value or an interval taking a minimum value defined in a linear region of the cycle or the portion of the cycle when considered on a Cartesian plane in which an axis of abscissa is positioned in the longitudinal development direction of the cycle.

[0029] Two cycle portions spaced apart from each other are such that in at least the regions of their respective ends facing each other, their longitudinal directions are - aligned, or - inclined at an angle of less than 10°, preferably less than 5°, when their respective longitudinal directions are incident with respect to each other, or - When the longitudinal directions are parallel to each other, they are "substantially aligned" when the longitudinal direction is shifted by a value less than 1.5 mm.

[0030] Two sipes are "continuous" when they are arranged one after the other on the tread surface of the block, considering a direction perpendicular to at least one of the longitudinal unfolding directions of the two sipes.

[0031] The term "single wave portion" of a sipe means a section of the linear trend of the sipe on the radially outer surface of the block that is continuous and has a first peak and a second peak on the side opposite to the longitudinal unfolding direction of the sipe itself.

[0032] The sipe formed in the block separates this block into two block portions each having a surface facing each other.

[0033] A sipe is defined as "composite" when at least one of the surfaces facing each other of the block portions has at least one protrusion, while the other of these surfaces has a corresponding recess that can receive this protrusion at least partially. In other words, each protrusion in a plane perpendicular to the radial direction of the two block portions separated by the sipe overlaps at least partially in the region of the protrusion and the corresponding recess.

[0034] In this way, the relative movement of the two block portions in the radial direction is prevented by the interference between the two block portions in the region of the protrusion and the recess.

[0035] A composite sipe is also known in the art as a "three-dimensional" sipe.

[0036] A sipe is defined as "simple" when there are no protrusions and / or recesses that interfere with each other during the relative movement of the two block portions in the radial direction on the surfaces facing each other of the block portions.

[0037] Examples of sipes configured in various patterns are described, for example, in EP3375639, U.S. Patent No. 5198047, U.S. Patent Application Publication No. 2021 / 0107319, EP3867081A1, Japanese Patent No. 6946658, JP 2018020689, U.S. Patent No. 3799231, U.S. Patent Application Publication No. 20030029537, U.S. Patent Application Publication No. 2005 / 0150581, EP0598300, U.S. Patent No. 5327953, and U.S. Patent No. 5591280.

[0038] The applicant recognized that the performance level of the tire on the icy and snowy road surface depends, within an appropriate range, on the amount and spread of the sipes formed in the block. Therefore, for the same tread pattern, blocks with multiple sipes formed therein can provide better behavior on snow.

[0039] However, the applicant further recognized that the presence of the sipes weakens the structure of the block, reduces the rigidity of its structure, and thus reduces the ability of the block to withstand external stresses, specifically tangential stresses.

[0040] As a result of this weakening, when braking, accelerating, or driving in the curved portion, the block is deformed accordingly, resulting in a partial lifting of the block from the road surface, and consequently reducing the contact area between the block and the road surface, thereby possibly reducing the overall frictional force applied to the road surface by the tire.

[0041] The applicant has demonstrated that the cause of this weakening of the block is related to the fact that the sipes divide the block into two parts that can slide relative to each other in the region of the sipes.

[0042] Specifically, the applicant has recognized that this sliding occurs in a direction parallel to the separating surface of those two parts, and can thus always be regarded as the composition of movements in two main directions defined on the separating surface, which two main directions are the direction extending perpendicularly from the bottom of the sipe to the tread surface (generally corresponding to the radial direction of the tread band), and a second direction parallel to the longitudinal development direction of the sipe.

[0043] The applicant has demonstrated that the resistance of the blocks in the area of the sipe can be improved by interfering with or limiting to the greatest possible extent the possibility of mutual sliding in these two main directions.

[0044] The applicant has recognized that a composite sipe having a profile provided with protrusions and corresponding recesses can resist the mutual sliding of the block parts, specifically the movement in the first direction identified above. However, even with this type of profile, it is not always sufficient to effectively resist the sliding action in the second direction (parallel to the longitudinal development direction of the sipe), especially in the area of the tread surface.

[0045] Therefore, the applicant has recognized that it is generally known to configure a sipe with an undulating linear progression, such as a zigzag, to resist this type of sliding.

[0046] The applicant has further recognized that in order to obtain a sufficiently effective counteraction, this undulating linear progression needs to extend over most of the longitudinal development of the sipe and provide a plurality of waves having a generally symmetrical form.

[0047] However, the applicant has demonstrated that the counteraction provided by this configuration against the tangential sliding of the block parts is not always effective.

[0048] Therefore, the applicant of the present application has recognized the need to provide a sipe that is particularly configured to more effectively counter the sliding of the block portion in the longitudinal development direction of the sipe without necessarily using a fluctuating trend with a large number of waves. To meet this requirement, the applicant has understood that by giving a specific configuration to the sipe, particularly in the wave region, the above-mentioned counteraction can be made more effective.

[0049] Finally, the applicant provides a sipe comprising a first straight portion and a second straight portion that are straight or slightly curved and have a single wave portion interposed therebetween, the single wave portion being - a first segment inclined with respect to the longitudinal direction of the sipe from the first straight portion to the first peak; - a second segment inclined with respect to the longitudinal direction of the sipe and extending from the first peak to the second peak; - a third segment inclined with respect to the longitudinal direction and extending from the second peak to the second straight portion, and has found that when the second segment is inclined more greatly with respect to the longitudinal direction than the first segment and the third segment, the sipe provides an effective counteraction against the longitudinal sliding of the block portion separated by the sipe even with a small number of waves.

[0050] Specifically, in a first aspect of the present invention, the present invention relates to a tire comprising a tread band and a tread surface that is radially outward of the tread band.

[0051] Preferably, a plurality of blocks are defined in the tread band.

[0052] Preferably, at least one first sipe opening on the tread surface is formed in each of the plurality of blocks.

[0053] Preferably, the first sipe is open on the tread surface so as to define a first longitudinal unfolding direction of the first sipe.

[0054] Preferably, the first sipe comprises a first straight portion that extends substantially along the first longitudinal direction.

[0055] Preferably, the first straight portion is in a straight line shape or a curved shape having a minimum curvature radius of 20 mm or more.

[0056] Preferably, the first sipe comprises a single wave portion that extends following the first straight portion.

[0057] Preferably, the first sipe comprises a second straight portion that extends following the single wave portion.

[0058] Preferably, the second straight portion is in a straight line shape or a curved shape having a minimum curvature radius of 20 mm or more.

[0059] Preferably, the single wave portion comprises a first segment that is inclined with respect to the first longitudinal direction.

[0060] Preferably, the first segment extends from the first straight portion to the first peak of the single wave portion.

[0061] Preferably, the single wave portion comprises a second segment that is inclined with respect to the longitudinal direction.

[0062] Preferably, the second segment extends from the first peak to the second peak of the single wave portion.

[0063] Preferably, the second peak is defined on the opposite side of the first peak with respect to the first longitudinal direction.

[0064] Preferably, the single-wave portion includes a third segment that is inclined with respect to the first longitudinal direction.

[0065] Preferably, the third segment extends from the second peak to the second straight portion.

[0066] Preferably, the second segment is inclined at an angle greater than that of the first segment and the third segment with respect to the first longitudinal direction.

[0067] As a result of this specific configuration, the applicant believes that it is possible to effectively resist the sliding action of the block portions separated by the cycles, even if the number of waves is extremely small, for example, one or two over the entire cycle, and to obtain a block that is more rigid and provides better behavior on dry and even frozen road surfaces under the same other conditions.

[0068] In the above-described aspect, the present invention may have at least one of the following additional preferred features.

[0069] In some embodiments, the first segment of the single-wave portion is inclined at an angle between 20° and 45°, more preferably about 24°, with respect to the first longitudinal direction.

[0070] In some embodiments, the third segment of the single-wave portion is inclined at an angle between 20° and 45°, more preferably about 24°, with respect to the first longitudinal direction.

[0071] Preferably, the first segment and the third segment of the single-wave portion are inclined in a consistent manner with respect to each other.

[0072] Preferably, the second segment of the single-wave portion is inclined in a non-consistent manner with respect to the first segment and the third segment of the single-wave portion.

[0073] In some embodiments, the first segment and the third segment of the single-wave portion are substantially parallel to each other.

[0074] In some embodiments, the second segment of the single-wave portion is inclined at an angle between 60° and 90°, more preferably about 80°, with respect to the first longitudinal direction.

[0075] In some embodiments, the first segment of the single-wave portion has substantially the same length as the third segment of the single-wave portion.

[0076] Preferably, the first segment and the third segment have a length between 1.5 mm and 3 mm, more preferably about 2 mm.

[0077] In some embodiments, the distance of the first peak from the first longitudinal direction is substantially the same as the distance of the second peak from the first longitudinal direction. Preferably, the distance is between 0.5 mm and 1.5 mm, more preferably about 1 mm.

[0078] In some embodiments, the second straight portion has a length that is at least 50%, preferably at least 100%, more preferably at least 200% greater than that of the first straight portion.

[0079] In this way, the single-wave portion of the first size is highly eccentric with respect to the first portion and the second portion, enabling the positioning of the single-wave portion near the edge of the block, where the function of the single-wave portion to stiffen the block can be more effectively achieved.

[0080] In some embodiments, the first longitudinal deployment direction of the first size intersects the first edge and the second edge of the block.

[0081] Preferably, the first straight portion extends toward the first edge.

[0082] Preferably, the second straight portion extends toward the second edge.

[0083] Preferably, the distance of the single-wave portion from the first edge measured along the first longitudinal direction is between 5% and 40%, more preferably between 25% and 35%, of the distance between the first edge and the second edge measured along the first longitudinal direction.

[0084] In this way, the single-wave portion of the cusp is positioned near the edge of the block so that the single-wave portion can more effectively fulfill its function of reinforcing the block.

[0085] Preferably, the distance of the single-wave portion from the second edge measured along the first longitudinal direction is at least twice the distance of the single-wave portion from the first edge measured along the first longitudinal direction.

[0086] It should be noted that the distances of the single-wave portion from the first edge or the second edge are each measured from the center point of the single-wave portion at the first edge and the second edge respectively.

[0087] In some embodiments, the first straight portion opens at the first edge of the block.

[0088] Preferably, the first straight portion has a length between 2 mm and 5 mm.

[0089] Preferably, the first cusp has a depth less than the depth of the first cusp in the region of the single-wave portion in the region of the first straight portion.

[0090] In this way, the reinforcing effect of the block in the region of the first straight portion is advantageously increased.

[0091] In some embodiments, the second straight portion opens at the second edge of the block.

[0092] Preferably, the second straight portion has a length between 4 mm and 25 mm.

[0093] Preferably, the second straight portion is substantially aligned with the first straight portion along the first longitudinal direction.

[0094] In some embodiments, the first side comprises only one single-wave portion.

[0095] In some embodiments, the block further has a plurality of sides formed in the same configuration as at least one first side.

[0096] In some specific embodiments, the block further has a second side extending in a second longitudinal direction.

[0097] Preferably, the second side is continuous with the first side.

[0098] Preferably, the second side is similar to the first side.

[0099] It should be noted that in the second side, if the same main elements, i.e., the single-wave portion intervening between the first straight portion and the second straight portion, can be identified, the second side is considered similar to the first side even if they have different dimensions.

[0100] Specifically, the second side preferably - has a first straight portion extending substantially along the second longitudinal direction, - has a single-wave portion extending following the first straight portion, - and has a second straight portion extending following the single-wave portion.

[0101] Preferably, the first straight portion and the second straight portion of the second side are in a straight line shape or a curved shape having a minimum curvature radius of 20 mm or more.

[0102] Furthermore, the single-wave portion of the second side is preferably - a first segment that is inclined with respect to the second longitudinal direction and extends from the first straight portion to the first peak of the second side, - a second segment that is inclined with respect to the second longitudinal direction and extends from the first peak of the second side to a second peak defined on the opposite side of the first peak with respect to the second longitudinal direction, - a third segment that is inclined with respect to the second longitudinal direction and extends from the second peak of the second side to the second straight portion of the second side.

[0103] Preferably, the second segment of the second side is inclined at an angle larger than that of the first segment and the third segment of the second side with respect to the second longitudinal direction.

[0104] Preferably, the second side has only one single-wave portion.

[0105] In some embodiments, the first longitudinal direction of the first side and the second longitudinal direction of the second side intersect the first edge and the second edge of the block.

[0106] Preferably, the first straight portion of the first side opens at the first edge of the block.

[0107] Preferably, the single-wave portion of the first profile is between 5% and 40%, more preferably between 25% and 35%, of the distance between the first edge and the second edge measured along the first longitudinal direction of the first profile, and has a distance from the first edge measured along the first longitudinal direction of the first profile.

[0108] Preferably, the first straight portion of the second profile is open at the second edge of the block.

[0109] Preferably, the single-wave portion of the second profile is between 5% and 40%, more preferably between 25% and 35%, of the distance between the second edge and the first edge measured along the second longitudinal direction of the second profile, and has a distance from the second edge measured along the second longitudinal direction of the second profile.

[0110] In this way, the single-wave portion of the first profile and the single-wave portion of the second profile are positioned near the opposite edges of the block, and provide a reinforcing effect of the single-wave portion on both sides of the block so as to obtain sufficient uniformity of behavior.

[0111] Preferably, the first longitudinal direction of the first profile and the second longitudinal direction of the second profile are substantially parallel to each other.

[0112] Preferably, the first peak closer to the first edge of the first profile and the first peak closer to the second edge of the second profile are laterally offset on the same side with respect to the first longitudinal direction of the first profile and the second longitudinal direction of the second profile, respectively.

[0113] In other words, the first segment, the second segment, and the third segment of the first profile are inclined with respect to the first longitudinal direction or the second longitudinal direction in a non-matching manner with respect to the first segment, the second segment, and the third segment of the second profile, respectively.

[0114] In this way, each of the first and second segments of the first and second sipes, which are intended to provide the greatest counteracting action against longitudinal sliding of the block portion, is inclined non-uniformly with respect to each other so as to substantially equalize the rigidity of the block when the block receives tangential stresses parallel to the first longitudinal direction and the second longitudinal direction, which are oriented in opposite directions.

[0115] In some embodiments, at least three mutually continuous sipes are formed in the block, and the at least three sipes are formed by alternating one of the first sipes and one of the second sipes.

[0116] In some embodiments, a central block is formed in the tread band, and the central block is delimited by only one or more grooves.

[0117] In some embodiments, each central block of the tread band comprises at least one of the first sipes.

[0118] Preferably, all sipes formed in the central block of the tread band having a length greater than a predetermined minimum value are one of the first sipes or one of the second sipes, and more preferably have only one single-wave portion.

[0119] Preferably, the predetermined minimum value is between 5 mm and 15 mm, for example about 10 mm.

[0120] In this way, the sipes can have a configuration with a single-wave portion interposed between two straight portions and extend sufficiently apart with suitable dimensions.

[0121] In some embodiments, two single-wave portions separated from each other by the second straight portion are defined on the first side.

[0122] In some embodiments, the tread band is formed with shoulder blocks that are partially delimited by the axial ends of the tread band.

[0123] Preferably, the first side on which the two single-wave portions are defined is formed on the shoulder block.

[0124] More preferably, each side formed on the shoulder block is one of the first sides having two single-wave portions separated from each other by the second straight portion.

[0125] In some embodiments, the at least one side is of a composite type.

[0126] The features and advantages of the present invention will be better understood from the following detailed description of a plurality of preferred embodiments of the present invention shown as non-limiting examples with reference to the accompanying drawings.

Brief Description of the Drawings

[0127]

Figure 1

Figure 2

Modes for Carrying Out the Invention

[0128] Referring to the accompanying drawings, a tire for a vehicle wheel (not fully shown) produced according to the present invention is designated as 1 as a whole.

[0129] The tire 1 has a conventional general toroidal shape that unfolds around a rotation axis, defines the axial direction Y of the tire, and is passed through by an equatorial plane X perpendicular to the rotation axis.

[0130] The tire 1 includes a tread band 2, and on the tread band 2, a tread surface 3 is defined which is arranged at a radially outer position with respect to the tread band 2 and is intended to contact the road surface.

[0131] The tire 1 has, for example, a nominal cross-sectional width of about 205 mm with a rim diameter of 16 inches (40.64 cm).

[0132] On the tread band 2, a central region that extends circumferentially and symmetrically around the equatorial plane X and a pair of shoulder regions that extend axially on both sides of the central region to the respective axial ends of the tread band 2 are defined and remain.

[0133] On the tread band 2, a plurality of grooves that divide the respective plurality of central blocks 5, all designated as 4 and formed in the central region of the tread band 2, and a plurality of shoulder blocks 6 that are formed in the shoulder region of the tread band 2 and are delimited in the axially outer region by the axial end 2a of the tread band 2 are formed.

[0134] In the embodiments described herein, the grooves 4 have a depth between 3 mm and 9 mm and a width between 2.5 mm and 9.5 mm.

[0135] As an example, FIG. 1 schematically shows the central blocks 5 and the shoulder blocks 6, and it is understood that the same concept applies equally to all other central blocks and other shoulder blocks 6 formed on the tread band 2.

[0136] The central block 5 is defined on its radially outer surface and is intended to contact the road surface, with a tread surface portion 3, and a first edge 8 that joins the tread surface portion 3 of the central block 5 to the wall of each groove 4, and a second edge 9 on the opposite side of the first edge 8, are defined.

[0137] Both the first edge 8 and the second edge 9 delimit the tread surface portion 3 of the central block 5 and may be chamfered either completely or partially.

[0138] A plurality of first sipes 10 and a plurality of second sipes 10a are formed on each central block 5, alternating with each other.

[0139] The first sipes 10 extend in their respective first longitudinal directions A, while the second sipes 10a extend in their respective second longitudinal directions B. All of the first longitudinal direction A and the second longitudinal direction B are substantially parallel to each other.

[0140] In the embodiment of the central block 5 shown in the figure, the first longitudinal direction A and the second longitudinal direction B are inclined at about 60° with respect to the equatorial plane X, but these directions can have different inclinations and can be parallel to the axial direction Y.

[0141] The first blocks 10 and the second blocks 10a are formed alternately with each other in the central block 5 and are preferably equidistant, for example, in the range of about 5 mm to about 6 mm.

[0142] The first sipes 10 and the second sipes 10a are staggered and continuous with each other and have similar forms, as will be described in more detail below.

[0143] As can be better seen in Figure 2, each first sipe 10 extends in the first longitudinal direction A so as to pass over the central block 5 and open at the first edge 8 and the second edge 9.

[0144] Each first side 10 includes a first linear portion 11 that opens at the first edge 8, a single-wave portion 12 that extends following the first linear portion 11, and a second linear portion 13 that extends following the single-wave portion 12 and opens at the second edge 9.

[0145] Both the first linear portion 11 and the second linear portion 13 are substantially linear in shape and are aligned in the first longitudinal direction A.

[0146] The second linear portion 13 may have a length greater than that of the first linear portion 11. Preferably, the second linear portion 13 is at least 50%, more preferably at least 100%, and even more preferably at least 200% greater than the first linear portion 11.

[0147] The first linear portion 11 has a length between 2 mm and 5 mm, while the second linear portion 13 has a length between 4 mm and 25 mm.

[0148] The single-wave portion 12 - a first substantially linear segment 14 that extends from the first linear portion 11 to the first peak 15 and is inclined with respect to the first longitudinal direction A; - a second substantially linear segment 16 that extends from the first peak 15 to the second peak 17 defined on the opposite side of the first peak 15 with respect to the first longitudinal direction A; - a third substantially linear segment 18 that extends from the second peak 17 to the second linear portion 13 and is inclined with respect to the first longitudinal direction A.

[0149] The first segment 14 and the third segment 18 are substantially parallel to each other and are inclined at about 30° with respect to the first longitudinal direction A. Further, the first segment 14 and the third segment 18 have a substantially equal length of about 2 mm.

[0150] The second segment 16 is inclined at approximately 80° with respect to the first longitudinal direction A, non-uniformly with respect to the first segment 14 and the third segment 18 with respect to the first longitudinal direction A.

[0151] The distances of the first peak 15 and the second peak 17 from the first longitudinal direction A are each substantially the same and equal to approximately 1 mm.

[0152] Therefore, the single-wave portion 12 is substantially symmetric with respect to the point where the second segment 16 intersects the first longitudinal direction A defined by the first straight portion 11 and the second straight portion 13.

[0153] Each first groove 10 has a width of approximately 0.5 mm and has a variable depth between its end regions, specifically from 3 mm in the first straight portion 11 to approximately 7 mm in the single-wave portion 12 and the central region of the first groove 10.

[0154] Each first groove 10 is more preferably of a composite type, and the composite type has one or more protrusions and corresponding recesses along its radial profile that inhibit the radial free sliding of each part of the central block 5 separated by the same first groove 10.

[0155] As described above, the second groove 10a is similar to the first groove 10. In fact, in each second groove 10a, the first straight portion 11, the subsequent single-wave portion 12, and thus the subsequent second straight portion 13, which is longer than the first straight portion 11, can be identified.

[0156] In the second groove 10a, each second groove 10a is different from any first groove 10 in that the first straight portion 11 opens at the second edge 9 (and the first edge 8), and the second straight portion 13 opens at the first edge 8 (and the second edge 9).

[0157] As a result of the first cogs 10 being alternately arranged with the second cogs 10a, the single-wave portions 12 of the first cogs 10 and the second cogs 10a are alternately positioned near the first edge 8 and near the second edge 9 so as to substantially uniformly reinforce both edges of the central block 5.

[0158] Furthermore, the first peaks 15 of each of the first cogs 10 and the first peaks 15 of each of the second cogs 10a are laterally offset on the same side with respect to their respective longitudinal directions A and B.

[0159] This configuration is obtained by configuring the cogs 10 and the cogs 10a such that the first segment 14, the second segment 16, and the third segment 18 of the first cogs 10 are inclined with respect to the first longitudinal direction A in a non-matching manner with respect to the first segment 14, the second segment 16, and the third segment 18 of the second cogs 10a.

[0160] Preferably, all the cogs formed in the central block 5 are the first cogs 10 or the second cogs 10a, provided that their total length is greater than a minimum value of about 10 mm.

[0161] In the case of the corner regions shown in FIG. 1, when the central block 5 is provided with cogs of a smaller size, these cogs are designated 19 in FIG. 1, and the cogs may have different configurations, for example, be linear or have a single peak with undulations.

[0162] In the shoulder block 6, a plurality of third cogs 20 are formed that extend parallel to each other in respective third longitudinal deployment directions A' that are generally different from the first longitudinal direction A and the second longitudinal direction B.

[0163] The third sip 20 is similar to the first sip 10 and the second sip 10a formed in the central block 5, but unlike the first sip 10 and the second sip 10a which each have only one single-wave portion 12, the third sip 20 has two single-wave portions. In fact, each third sip 20 may be regarded as a first sip 10 having two single-wave portions.

[0164] Accordingly, each third sip 20 includes a first straight portion 21 that opens at the first edge 7 of the shoulder block 6, a first single-wave portion 22 that extends following the first straight portion 21, a second straight portion 23 that extends following the first single-wave portion 22, a second single-wave portion 24 that extends following the second straight portion 23, and a third straight portion 25 that extends from the second single-wave portion 24 to the axial end 2a of the tread band 2.

[0165] It should be noted that the third straight portion 25 may be regarded as the first straight portion of the second single-wave portion 24, and the second straight portion 23 is common to both the single-wave portion 22 and the single-wave portion 24.

[0166] The single-wave portions 22 and 24 of the sip 20 are exactly similar to the single-wave portion 12 described in detail above with reference to the first sip 10 and the second sip 10a.

[0167] The applicant has demonstrated that the central block 5 and the shoulder block 6 provided with a plurality of sips as described above have optimal resistance to tangential stress directed in the longitudinal unfolding direction and improve the performance levels on frozen roads and dry roads.

[0168] Of course, in order to comply with specific and uncertain application requirements, those skilled in the art may also apply additional modified and deformed forms that are still included within the protection scope defined by the appended claims to the present invention described above.

[0169] For example, the number of the first type and / or the second type existing in the central block may be different from the number described above, and the central block may also have a type having a different configuration, such as the third type described in this specification in the shoulder block, or a type having a plurality of single-wave portions.

Claims

1. A tire (1) comprising a tread band (2), a tread surface (3) radially outward of the tread band, a plurality of blocks (5, 6) defined in the tread band (2), and at least one first sipe (10; 20) formed in each block of the plurality of blocks (5, 6), wherein the first sipe (10; 20) opens in the tread surface (3) so as to define a first longitudinal development direction (A) of the first sipe (15), and the first sipe is - a first straight portion (11) extending substantially along the first longitudinal direction (A); - a single-wave portion (12) extending following the first straight portion (11); - a second straight portion (13) extending following the single-wave portion (12), wherein the first straight portion (11) and the second straight portion (13) are in a straight line shape or a curved shape having a minimum curvature radius of 20 mm or more, and the single-wave portion (12) is - a first segment (14) inclined with respect to the first longitudinal direction (A) and extending from the first straight portion (11) to a first peak (15); - a second segment (16) inclined with respect to the first longitudinal direction (A) and extending from the first peak (15) to a second peak (17) defined on the opposite side of the first peak (15) with respect to the first longitudinal direction (A); - a third segment (18) inclined with respect to the first longitudinal direction (A) and extending from the second peak (17) to the second straight portion (13), wherein the second segment (16) is inclined at an angle greater than that of the first segment (14) and the third segment (18) with respect to the first longitudinal direction (A). A tire (1).

2. The tire (1) according to claim 1, wherein the first segment (14) and the third segment (18) of the single-wave portion (12) are inclined at an angle between 20° and 45° with respect to the first longitudinal direction (A).

3. The tire (1) according to claim 1 or 2, wherein the second segment (16) of the single-wave portion (12) is inclined at an angle between 60° and 90° with respect to the first longitudinal direction (A).

4. The tire (1) according to any one of claims 1 to 3, wherein the first segment (14) and the third segment (18) of the single-wave portion (12) are substantially parallel.

5. The tire (1) according to any one of claims 1 to 4, wherein the first segment (14) of the single-wave portion (12) has substantially the same length as the third segment (18) of the single-wave portion (12).

6. The tire (1) according to any one of claims 1 to 5, wherein the distance from the first longitudinal direction (A) to the first peak (15) is substantially the same as the distance from the first longitudinal direction (A) to the second peak (17).

7. The tire (1) according to any one of claims 1 to 6, wherein the second straight portion (13) has a length at least 50% greater than that of the first straight portion (11).

8. The tire (1) according to claim 7, wherein the second straight portion (13) has a length at least 100% greater than that of the first straight portion (11).

9. The tire (1) according to claim 8, wherein the second straight portion (13) has a length at least 200% greater than that of the first straight portion (11).

10. The first longitudinal development direction (A) of the first sipe (10) intersects the first edge (8) and the second edge (9) of the block, the first straight portion (11) extends toward the first edge (8), the second straight portion (13) extends toward the second edge (9), and the distance of the single-wave portion (12) from the first edge (8) measured along the first longitudinal direction (A) is between 5% and 40% of the distance between the first edge (8) and the second edge (9) measured along the first longitudinal direction (A). The tire (1) according to any one of claims 1 to 9.

11. The tire (1) according to claim 10, wherein the distance of the single-wave portion (12) from the second edge (9) measured along the first longitudinal direction (A) is at least twice the distance of the single-wave portion (12) from the first edge (8) measured along the first longitudinal direction (A).

12. The tire (1) according to claim 10 or 11, wherein the first straight portion (11) opens at the first edge (8) of the block (5).

13. The tire (1) according to any one of claims 1 to 12, wherein the first straight portion (11) has a length between 2 mm and 5 mm.

14. The tire (1) according to any one of claims 1 to 13, wherein the first sipe (10) has a depth less than the depth of the first sipe (10) in the region of the single wave portion (12) in the region of the first straight portion (11).

15. The tire (1) according to any one of claims 10 to 14, wherein the second straight portion (13) opens at the second edge (9) of the block (5).

16. The tire (1) according to any one of claims 1 to 15, wherein the second straight portion (13) has a length between 4 mm and 25 mm.

17. The tire (1) according to any one of claims 1 to 16, wherein the second straight portion (13) is substantially aligned with the first straight portion (11) along the first longitudinal direction (A).

18. The tire (1) according to any one of claims 1 to 17, wherein the first sipe (10) comprises only one single wave portion (12).

19. The block (5) is further formed with a second sipe (10a) extending in a second longitudinal direction (B), and the second sipe is continuous with the first sipe (10), and - a first straight portion (11) substantially extending along the second longitudinal direction (B), - a single wave portion (12) extending following the first straight portion (11), - a second straight portion (13) extending following the single wave portion (12), and The tire (1) according to any one of claims 1 to 18, wherein the first straight portion (11) and the second straight portion (13) are in a straight shape or a curved shape having a minimum curvature radius of 20 mm or more.

20. The tire (1) according to claim 19, wherein the first sipe and the second sipe each have only one single wave portion (12).

21. The first longitudinal direction (A) of the first sipe (10) and the second longitudinal direction (B) of the second sipe (10a) intersect the first edge (8) and the second edge (9) of the block (5), - the first straight portion (11) of the first sipe (10) opens at the first edge (8) of the block. - The single-wave portion (12) of the first rib (10) has a distance from the first edge (8) measured along the first longitudinal direction (A) of the first rib (10) that is between 5% and 40% of the distance between the first edge (8) and the second edge (9) measured along the first longitudinal direction of the first rib (10), - The first straight portion (11) of the second rib (10a) opens at the second edge (9) of the block (5), - The single-wave portion (12) of the second rib (10a) has a distance from the second edge (9) measured along the second longitudinal direction (B) of the second rib (10a) that is between 5% and 40% of the distance between the second edge (9) and the first edge (8) measured along the second longitudinal direction (B) of the second rib (10a), the tire (1) according to claim 20.

22. The tire (1) according to claim 21, wherein the first longitudinal direction (A) of the first rib (10a) and the second longitudinal direction (B) of the second rib (10a) are substantially parallel to each other.

23. The first peak (15) of the first rib (10) closer to the first edge (8), and the first peak (15) of the second rib (10a) closer to the second edge (9) are each laterally offset on the same side with respect to the first longitudinal direction (A) of the first rib and the second longitudinal direction (B) of the second rib (10a), the tire (1) according to any one of claims 19 to 22.

24. At least three mutually continuous ribs are formed in the block (5), and the at least three ribs are formed by alternately continuing one of the first ribs (10) and one of the second ribs (10a), the tire (1) according to any one of claims 19 to 23.

25. A central block (5) is formed in the tread band (2), the central block (5) is delimited only by one or more grooves (4), and each central block (5) comprises at least one of the first ribs (10), the tire (1) according to any one of claims 1 to 24.

26. All sipes formed in the central block (5) of the tread band (2) having a length greater than a predetermined minimum value are one of the first sipes (10) or one of the second sipes (10a), and the tire (1) according to claim 25 having only a single wave portion (12).

27. The tread band (2) is formed with shoulder blocks (6) partially delimited by the axial ends (2a) of the tread band, and each sipe (20) formed in the shoulder block (6) is one of the first sipes having two single wave portions (22, 24) spaced apart from each other by the second straight portion (23). The tire (1) according to any one of claims 1 to 26.

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