Vehicle wheel tyre

Abstract

A vehicle wheel tyre (1) comprises a tread band (2), a tread surface (3), a plurality of blocks (5, 6) defined on the tread band (2), and at least one sipe (15) formed on at least one of the blocks (5). And at least one sipe (15) open on the tread surface portion (7) and at least on one first edge (11) of the block (5) so as to define at least one first edge portion (20) and at least one second edge portion (21) adjacent to each other and at least partially delimited by the sipe (15), the first edge portion (20) is defined by a chamfer (22) extending between the tread surface portion (7) and the wall (8) of the block (5), and the second edge portion (21) is defined by a corner (23) resulting from the intersection of the tread surface portion (7) and the wall (8).

Description

Technical Field

[0001] The present invention relates to a vehicle wheel tyre, in particular to a winter tyre. Background Art

[0002] The tyre generally comprises a carcass structure shaped annularly about an axis of rotation and comprising at least one carcass ply, the end flaps of which are engaged in respective anchoring annular structures, called bead cores.

[0003] In a radially external position of the carcass structure there is arranged a belt structure which, in the case of a car tyre, comprises at least two radially superposed rubberised textile strips provided with reinforcing cords, generally metal cords, arranged parallel to one another in each strip but crossed with respect to the cords of adjacent strips, preferably symmetrically with respect to the equatorial plane of the tyre.

[0004] Preferably, the belt structure also comprises a third layer of textile or metal cords arranged circumferentially (0 degrees) in a radially external position at least on the ends of the underlying belt strips. In tubeless tyres there is also a radially internal layer called "liner" which has waterproof properties to ensure the airtightness of the tyre itself.

[0005] Radially applied to the outside of the belt structure is a tread band made of elastomeric material, on which is defined a tread surface intended to contact the road surface.

[0006] In order to ensure adequate grip even on wet roads, the tread band of the tyre is provided with grooves of various shapes and geometries, the main function of which is to drain water from between the tyre surface and the road surface when the two come into contact with each other, thereby preventing the hydrostatic pressure generated by the impact of water on the tyre as the tyre moves forward from causing the tyre to even partially lift off the road surface and thereby cause the vehicle to lose control (a phenomenon known as "hydroplaning").

[0007] Grooves formed in the circumferential direction also affect the directional characteristics and driving stability of the tire, which is related to the tire's ability to withstand tangential stresses parallel to the tire's axis of rotation.

[0008] Grooves formed in the transverse direction affect the tire's traction characteristics, that is, the tire's ability to transfer tangential stresses parallel to the direction of travel to the road surface, especially during vehicle acceleration and braking.

[0009] These grooves as a whole define a plurality of blocks on the tread band, each block comprising a radially outer surface intended to contact the road surface and thus forming part of the tread surface of the tyre. Each block is also at least partially delimited by one or more walls defined by the grooves around it.

[0010] In some cases, the wall of the block or a portion thereof is connected to the tread surface of the block by a chamfer, typically formed by a plane appropriately inclined relative to the wall and the tread surface, thereby defining an edge of the block.

[0011] In the case of winter tires, small grooves are usually formed in the tread band blocks, which are called "sipes", extending from the tread surface of the tire towards the inside of the block. The function of the sipes is to provide additional grip elements when driving on snowy surfaces and to retain a certain amount of snow, thereby improving the grip with the road surface.

[0012] WO 2019111089 in the name of the same applicant discloses a tire without sipes, in which some edges of the blocks or ribs are chamfered.

[0013] WO 2019030664 in the name of the same applicant shows an example of a winter tire in which the blocks are provided with a corresponding plurality of sipes opening at the longitudinal ends on the opposite block walls. Summary of the invention

[0014] A “circumferential” direction is understood to mean a direction pointing substantially in the direction of rotation of the tyre or in any case a direction slightly inclined (at most about 5°) relative to the direction of rotation of the tyre.

[0015] An "axial" direction is a direction substantially parallel to the axis of rotation of the tyre or at most slightly inclined (at most about 5°) relative to the axis of rotation of the tyre. The axial direction is generally perpendicular to the circumferential direction.

[0016] The term "equatorial plane" of the tire means the axial centerline plane perpendicular to the tire's axis of rotation.

[0017] By "shoulder region" of the tread band is meant that portion of the tread band extending circumferentially in a position axially external to the tread band itself.

[0018] Preferably, each shoulder region extends over a width of at least 10% of the width of the tread band.

[0019] The term "groove" means a depression formed in a portion of the tread band, having a width greater than or equal to 1.5 mm and preferably a depth greater than 3 mm.

[0020] The term "sipe" means a depression formed in a portion of the tread band, the width of which is less than 1.5 mm, preferably less than or equal to 1 mm.

[0021] A "block" is defined as a portion of the tread surface delimited by at least one groove, preferably at least two separate grooves, on which the portion of the tread surface intended to contact the road surface is defined on its radially outer surface.

[0022] Thus, a portion of a tread band having a closed profile delimited by three or more grooves or a circumferential rib delimited by a pair of grooves extending circumferentially around the tread band is considered to be a block.

[0023] A "central block" is defined as a block not bounded by the axial ends of the tread band, whereas a block partially bounded by one of the axial ends of the tread band is defined as a "shoulder block".

[0024] A "wall" of a block refers to a surface that extends generally from the bottom of a groove that delimits the block toward the tread surface portion of the block.

[0025] The "edge" of a block refers to the area of ​​the block where the wall of the block joins the tread surface portion of the block. The edge as defined above should be considered distinct from the wall (ie, the edge is not part of the wall).

[0026] When the block is completely bounded by the groove, the edge defines the peripheral contour of the tread surface portion of the block.

[0027] The portion of the edge to which the first end of the sipe formed on the block opens may be identified as the “first edge.” If a plurality of sipes are formed on the block, wherein the first end opens on the edge, the “first edge” may be identified as the portion of the edge of the block to which the respective first ends of the plurality of sipes open.

[0028] Similarly, when one or more sipes open to a different portion of the edge with their respective second end (opposite the first end), the different portion of the edge may be identified as a "second edge."

[0029] Therefore, it should be noted that the definition of a "first edge" or a "second edge" cannot be attributed solely to the geometrical design of the block, but is closely related to the presence and design of the sipe or sipes on the block.

[0030] The edge or part thereof may be formed by a corner where the wall directly intersects the tread surface portion, or may be formed by a connecting surface connecting the wall and the tread surface portion.

[0031] The "chamfer" of a block refers to such a connection surface.

[0032] Preferably, the chamfer is formed by a planar surface, but it may also take a rounded shape.

[0033] If the chamfer is formed by a planar surface, the chamfer is inclined relative to the tread surface and the wall of the block.

[0034] The “width” of a chamfer is understood to mean the measurement of the orthogonal projection of this surface on the tread surface, calculated in a direction substantially perpendicular to the longitudinal direction of the edge forming said chamfer.

[0035] One or more edge portions have "substantially equal" lengths when the respective lengths of the two or more edge portions differ from each other by at most 10% of the larger length.

[0036] Two or more directions or two or more elements (eg two or more sipes) extending in respective directions are "substantially parallel" when they are inclined to each other at an angle of less than 10°, preferably less than 5°.

[0037] The Applicant has observed that the performance of the tire on snowy roads depends largely on the number and size of the sipes on the block, so that, for the same tread pattern, the more sipes are formed on the block, the better the behavior it can provide on snow.

[0038] However, the Applicant has also noted that the presence of the sipes weakens the structure of the block, making it less rigid and thus less capable of withstanding external stresses, in particular tangential stresses.

[0039] Due to this weakening, the tire blocks deform significantly during braking, acceleration or cornering, causing the blocks to be locally lifted off the road surface, thereby reducing the contact area between the blocks and the road surface and thus reducing the overall friction force exerted by the tire on the road surface.

[0040] In other words, the Applicant has observed that providing a large number of sipes on a block, while on the one hand improving the block's behaviour on snowy roads, impedes its grip both on dry and wet roads.

[0041] The Applicant therefore believes that there is a need to provide a winter tire that, despite a relatively low number of sipes on its blocks, still offers excellent performance on snowy roads.

[0042] In order to meet this requirement, the applicant considered the possibility of introducing chamfers at the edges of the blocks in order to increase the grip angle. However, providing continuous chamfers on the edges of the blocks may result in a reduction in the tread surface of the blocks, thereby reducing the tire surface in contact with the road surface, while also weakening the rigidity of the blocks.

[0043] However, the applicant has noted that a chamfer formed on a block edge portion adjacent to a portion of a "sharp corner" edge (i.e. defined by the intersection of the wall of the block with the tread surface of the block) defines an additional gripping corner precisely at the end of the sharp corner edge portion facing the chamfered edge portion.

[0044] The Applicant further notes that providing sipes on a block "naturally" subdivides the block into a plurality of adjacent parts, each part being delimited by a pair of sipes and, if these sipes open on the wall of the block, the corresponding edge is also subdivided by the sipes into a plurality of consecutive parts.

[0045] The Applicant has therefore realised that this edge subdivision can be advantageously exploited to introduce chamfers in some of these edge portions, while leaving other edge portions as sharp corners (ie without chamfers), in order to create new grip corners without thereby excessively reducing the tread surface of the block.

[0046] Finally, the applicant has discovered that a block on which at least one sipe is formed, opening on the tread surface and on at least one first edge of the block so as to define at least one first edge portion and at least one second edge portion adjacent to each other and bounded by the at least one sipe, provides a tread having excellent behavior both on snow-covered roads and on dry or wet roads.

[0047] In particular, the present invention relates in a first aspect thereof to a tyre for vehicle wheels comprising a tread band and a tread surface radially external to said tread band.

[0048] Preferably, a plurality of blocks are defined on said tread band.

[0049] Preferably, at least one sipe is formed on at least one block among the plurality of blocks.

[0050] Preferably, said at least one sipe is open on a tread surface portion of said block.

[0051] Preferably, said at least one incision opens on at least a first edge of said block.

[0052] Preferably, said at least one incision defines at least one first edge portion and at least one second edge portion.

[0053] Preferably, said at least one second edge portion is adjacent to said at least one first edge portion.

[0054] Preferably, said at least one first edge portion and said at least one second edge portion are at least partially delimited by said at least one incision.

[0055] Preferably, said at least one first edge portion is defined by a chamfer extending between said tread surface portion and a wall of said block.

[0056] Preferably, said at least one second edge portion is defined by a corner created by the intersection of said tyre belt portion with said wall.

[0057] The Applicant believes that, thanks to these features, the blocks have a large number of grip angles useful for improving the behavior of the tire on snow-covered roads, but without losing too much tread surface area and without significantly affecting the rigidity of the blocks.

[0058] The present invention in the above aspects may have at least one of the other preferred features listed below.

[0059] In some embodiments, the at least one sipe opens on the first edge at a straight section or a curved section of the first edge.

[0060] In some embodiments, the at least one sipe opens on the first edge at a location having a continuous tangent line.

[0061] In other words, said at least one incision preferably opens at a position on the first edge that does not correspond to a vertex on the peripheral profile of the block.

[0062] Preferably, a plurality of the sipes are formed on the at least one block among the plurality of blocks.

[0063] In some embodiments, at least two of the first edge portions are defined by the plurality of sipes on the first edge to be arranged alternately with second edge portions.

[0064] In some embodiments, at least two of the second edge portions are defined by the plurality of sipes on the first edge and are arranged alternately with first edge portions.

[0065] In some embodiments, at least two of the second edge portions and at least two of the second edges are defined by the plurality of sipes on the first edge and are arranged alternately with each other.

[0066] In this way, the number of grip corners formed by arranging the first edge portion adjacent to the second edge portion is advantageously maximized.

[0067] In some embodiments, the chamfer comprises a surface inclined at an angle of between 30° and 60°, preferably about 45°, relative to the tread surface.

[0068] Preferably, the inclined surface is a planar surface.

[0069] In some embodiments, the chamfer has a width between 0.5 mm and 3 mm.

[0070] In some embodiments, a plurality of first edge portions are defined by the plurality of sipes on the first edge.

[0071] Preferably, all first edge portions defined on said first edge have substantially equal length.

[0072] In some embodiments, the at least one first edge portion and the at least one second edge portion have a length between 4 mm and 8 mm.

[0073] In some embodiments, a plurality of said second edge portions are defined by said plurality of said sipes on said first edge.

[0074] Preferably, all second edge portions defined on said first edge have substantially equal lengths.

[0075] In some embodiments, the at least one first edge portion and the at least one second edge portion have substantially equal lengths.

[0076] In some embodiments, the sipes are substantially parallel to each other.

[0077] In some embodiments, the at least one sipe also opens on the second edge of the block.

[0078] In some embodiments, the at least one sipe opens on the second edge at a straight section or a curved section of the second edge.

[0079] In some embodiments, the at least one sipe opens on the second edge at a location having a continuous tangent line.

[0080] In other words, at least one sipe preferably opens at a position on the second edge that does not correspond to a vertex on the peripheral contour of the block.

[0081] Preferably, the second edge is different from the first edge.

[0082] In some embodiments, the at least one sipe further partially defines at least one of the first edge portions and at least one of the second edge portions on the second edge.

[0083] Preferably, on the second edge, said at least one of the second edge portions is adjacent to said at least one of the first edge portions.

[0084] In this way, the creation of additional grip corners is advantageously extended to more edges of the blocks, thereby improving overall tire performance.

[0085] In some embodiments, at least one area of ​​the block is defined by the at least one sipe.

[0086] Preferably, the region is bounded by one of the first edge portions and one of the second edge portions at opposite ends of the region.

[0087] In some embodiments, the at least one region of the block is defined by a pair of the sipes.

[0088] In some embodiments, each region of the block bounded by a pair of the sipes is bounded at opposite ends of the region by one of the first edge portions and one of the second edge portions.

[0089] Thereby, the structure of the block and its stiffness properties are balanced in such a way as to favour a uniform behaviour of the block when subjected to tangential stresses.

[0090] In some embodiments, the block of the plurality of blocks is a central block.

[0091] In other words, said blocks are all the blocks of the tread band, except for the blocks partially delimited by the axial ends of the tread band. BRIEF DESCRIPTION OF THE DRAWINGS

[0092] The characteristics and advantages of the present invention will become more apparent from the following detailed description of some preferred embodiments thereof shown by way of non-limiting examples, with reference to the accompanying drawings, in which:

[0093] - Figure 1 is a schematic front view of a tread band portion of a vehicle wheel tire manufactured in accordance with the present invention;

[0094] - Figure 2 yes Figure 1 a schematic perspective view, on an enlarged scale, of a block of a tread band of a tyre;

[0095] - Figure 3 yes Figure 1 Cross-sectional view of a block of the tread band of the tyre along line III-III. DETAILED DESCRIPTION

[0096] With reference to the accompanying drawings, 1 generally indicates a vehicle wheel tyre made in accordance with the present invention.

[0097] The tyre 1 has a generally toroidal shape extending around an axis of rotation defining an axial direction Y of the tyre and intersecting an equatorial plane X, which is perpendicular to the axis of rotation.

[0098] The tyre 1 comprises a tread band 2 on which is defined a tread surface 3 arranged radially externally of the tread band 2 and intended to come into contact with a road surface.

[0099] For example, the nominal section width of the tire 1 is about 205 mm and the rim diameter is 16 inches.

[0100] On the tread band 2, a central region extending circumferentially and symmetrically around the equatorial plane X and a pair of shoulder regions are defined, in axially outer positions of the tread band 2 up to respective axial ends of the tread band 2, the pair of shoulder regions extending respectively to axially opposite sides of the central region.

[0101] Formed on the tread band 2 are a plurality of grooves, all referenced 4, which delimit a respective plurality of blocks 5 formed on the tread band 2 and in particular in a central region thereof. Since the blocks 5 are completely delimited by the grooves 4, they are central blocks.

[0102] The grooves 4 also partially define shoulder blocks 6 formed on the shoulder regions and delimited on their axial sides by the axial ends of the tread band 2 .

[0103] In the embodiment described here, the grooves 4 have a depth between 3 mm and 9 mm and a width between 2.5 mm and 9.5 mm.

[0104] For example, in Figure 2 In FIG. 4 , blocks 5 are schematically shown on a central region of the tread band 2 , it being understood that the same considerations apply analogously to all other central blocks of the tread band except for the shoulder blocks 6 .

[0105] The block 5 comprises a tread surface portion 7 defined on its radially outer surface and intended to contact the road surface, and a plurality of walls 8 extending towards the tread surface portion 7 through respective bottoms 9 of the grooves 4 delimiting the block 5 .

[0106] Each wall 8 extends from the bottom of the groove 4 toward the tread surface portion 7 at a substantially constant inclination which is slightly deviated from the radial direction of the tire, each wall forming an angle between about 2° and about 20° with the radial direction of the tire, for example, about 5°, about 10° or about 15°.

[0107] Walls 8 are joined to the tread surface portion 7 to define the edges of the blocks 5 .

[0108] exist Figure 2 In the example shown of a block 5 having a generally rhombus-shaped design, a first edge 11 formed by a pair of adjacent sides of the rhombus and a second edge 12 formed by another pair of adjacent sides of the rhombus can be identified.

[0109] At least one sipe 15 is formed on the block 5 , opening on the tread surface portion 7 and extending along a main longitudinal direction referenced A in the figures.

[0110] The at least one sipe 15 has a width of about 0.5 mm and a depth comprised between 3 mm and 7 mm.

[0111] In the example of the block 5 shown in the figures, a plurality of sipes 15 are preferably formed, all of which extend parallel to the longitudinal direction A.

[0112] The longitudinal direction A is inclined at approximately 60° relative to the equatorial plane X, however, it is provided that the longitudinal direction may have a different inclination and may be parallel to the axial direction Y.

[0113] Each sipe 15 extends along the longitudinal direction A through the block 5 so that it also opens on the wall 8 and therefore on the edge of the block 5. In particular, Figure 2 In the block 5 shown, the sipe 15 extends between the first edge 11 and the second edge 12 .

[0114] Each sipe 15 may have a straight design, as in the example of the block 5 shown in the figures, however, provision is made that each sipe 15 may adopt another design, such as a curved or folded line or even a zigzag design.

[0115] When the number of sipes 15 is three or more, the sipes are also equally spaced from each other, preferably spaced by a distance between about 4 mm and about 8 mm, and more preferably spaced by a distance between about 5 mm and about 6 mm.

[0116] In the example shown in Fig. 5, the sipes 15 subdivide the block 5 into adjacent block regions 16a, 16b, 16c, 16d, 16e. Each block region 16a, 16b, 16c, 16d, 16e is defined by a pair of sipes 15 and is defined at its longitudinally opposite ends by a portion of the first edge 11 and a portion of the second edge 12, respectively. Therefore, the first edge 11 and the second edge 12 are also divided into adjacent and different portions by the sipes 15.

[0117] In particular, the first edge 11 is subdivided into a plurality of first edge portions 20 and a plurality of second edge portions 21 alternating with each other, wherein each first edge portion 20 is defined by a chamfer 22 extending between the tread surface portion 7 and the wall 8 of the block 5, and each second edge portion 21 is defined by a corner 23 generated by the intersection of the tread surface portion 7 with the wall 8 of the block 5.

[0118] In other words, the first edge 11 is formed by alternating chamfers 22 and corners 23 , all of which have substantially the same length.

[0119] Each chamfer 22 consists of a planar surface inclined at an angle of about 45° relative to the tread surface portion 7 and has a length of about 5 to 6 mm and a width of about 2 mm. The chamfer 22 is also inclined at a non-zero angle relative to the wall 8 and is a function of the inclination of the wall relative to the radial direction, as described above.

[0120] It should be noted that the provision of chamfers 22 defines, at their longitudinal ends, in the block region adjacent thereto, a step structure 24 in which the second edge portion 21 is defined. It should also be noted that each step structure 24 is delimited by a corner which facilitates the grip of the block 5 on a snow-covered surface.

[0121] Similar to the first edge 11 , the second edge 12 is also subdivided by the sipe 15 into a plurality of first edge portions 20 (defined by chamfers 22 ) and a plurality of second edge portions 21 (defined by corners 23 ) that alternate with each other.

[0122] Thus, the second edge 12 is also formed by alternating chamfers 22 and corners 23 , all of which have substantially the same length.

[0123] However, it is contemplated that the alternating arrangement of chamfers 22 and corners 23 in the first edge 11 will deviate from the alternating arrangement of chamfers 22 and corners 23 in the second edge 12. Thus, moving along the longitudinal direction A, each first edge portion 20 defined on the first edge 11 corresponds to a second edge portion 21 defined on the second edge 12, and vice versa.

[0124] Thus, each region 16a, 16b, 16c, 16d, 16e of the block 5 is delimited at opposite longitudinal ends by a first edge portion 20 (defined by the chamfer 22) and a second edge portion 21 (defined by the corner 23).

Claims

1. A vehicle wheel tyre (1) comprising a tread band (2), a tread surface (3) located radially outside of said tread band (2), a plurality of blocks (5, 6) defined on said tread band (2) and at least one sipe (15) formed on at least one block (5) of said plurality of blocks (5, 6), said at least one sipe (15) opening on a tread surface portion (7) of said block and at least on a first edge (11) of said at least one block (5) so as to define at least one first edge portion (20) and at least one second edge portion (21) adjacent to said at least one first edge portion (20), said at least one first edge portion (20) and said at least one second edge portion (21) being at least partially delimited by said at least one sipe (15), wherein: - said at least one first edge portion (20) is defined by a chamfer (22) extending between said tread surface portion (7) and a wall (8) of said at least one block (5), and - said at least one second edge portion (21) is defined by a corner (23) resulting from the intersection of said tread surface portion (7) with said wall (8).

2. The vehicle wheel tire according to claim 1, wherein: A plurality of the sipes (15) are formed on at least one block (5) among the plurality of blocks (5, 6).

3. The vehicle wheel tire according to claim 2, wherein: On the first edge (11), at least two of the first edge portions (20) are defined by the plurality of sipes and are arranged alternately with second edge portions (21).

4. The vehicle wheel tire according to claim 2, wherein: On the first edge (11), at least two of the second edge portions (21) are defined by the plurality of sipes and are arranged alternately with the first edge portions (20).

5. The vehicle wheel tire according to claim 2, wherein: On the first edge (11), at least two of the first edge portions (20) and at least two of the second edge portions (21) are defined by the plurality of sipes and are arranged alternately with each other.

6. A tyre for vehicle wheels according to any one of the preceding claims, wherein: The chamfer (22) comprises a surface inclined at an angle between 30° and 60° relative to the tread surface.

7. The vehicle wheel tire according to claim 6, wherein: The width of the chamfer (22) is between 0.5 mm and 3 mm.

8. A vehicle wheel tyre according to any one of claims 2 to 7, wherein: On the first edge (11), a plurality of first edge portions (20) are defined by the plurality of sipes, and all the first edge portions (20) defined on the first edge (11) have substantially equal lengths.

9. A vehicle wheel tyre according to any one of claims 2 to 8, wherein: A plurality of second edge portions (21) are defined on the first edge (11) by the plurality of sipes, and all of the second edge portions (21) defined on the first edge (11) have substantially the same length.

10. A tyre for vehicle wheels according to any one of the preceding claims, wherein: The at least one first edge portion (20) and the at least one second edge portion (21) have substantially equal lengths.

11. A vehicle wheel tyre according to any one of claims 2 to 10, wherein: The sipes (15) are substantially parallel to each other.

12. A tyre for vehicle wheels according to any one of the preceding claims, wherein: The at least one sipe (15) opens on the second edge (12) of the at least one block (5) and also at least partially defines at least one of the first edge portions (20) and at least one of the second edge portions (21) on the second edge (12).

13. The vehicle wheel tyre according to claim 12, wherein: At least one area (16a, 16b, 16c, 16d, 16e) of at least one block (5) is delimited by at least one sipe (15) and, at opposite ends of the area, by one of the first edge portions (20) and one of the second edge portions (21).

14. The vehicle wheel tyre according to claim 13, wherein: Said at least one region (16a, 16b, 16c, 16d, 16e) of said at least one block (5) is delimited by a pair of said sipes (15).

15. The vehicle wheel tyre according to claim 14, wherein: Each area (16a, 16b, 16c, 16d, 16e) of said at least one block (5) delimited by a pair of said sipes (15) is delimited at opposite ends of said area by one of said first edge portions (20) and one of said second edge portions (21).

16. A tyre for vehicle wheels according to any one of the preceding claims, wherein: The block of the plurality of blocks is a central block.

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