Tire of a vehicle wheel
By incorporating chamfered edges and sharp corners in the tire blocks, the tire achieves improved traction on snow and ice while maintaining frictional force on dry and wet surfaces, addressing the trade-off between sipe density and block rigidity.
Patent Information
- Application Number
- JP2024563532
- Authority / Receiving Office
- JP · JP
- Patent Type
- Applications
- Current Assignee / Owner
- Priority Date
- 2022-06-10
- Filing Date
- 2023-06-06
- Publication Date
- 2025-06-26
AI Technical Summary
Winter tires with a large number of sipes provide better traction on ice and snow but weaken the block structure, leading to reduced rigidity and increased deformation during braking, acceleration, or cornering, which affects frictional force on dry and wet road surfaces.
Introducing chamfered portions at the edges of blocks to increase gripping angles without significantly reducing the tread surface area or hindering block rigidity, by alternating chamfered edges with sharp corners, thereby creating additional gripping corners without compromising tread contact or block stiffness.
The solution enhances the tire's performance on both icy and snowy surfaces while maintaining effective load-holding capabilities on dry and wet road surfaces, by optimizing the number of gripping corners without sacrificing tread area or block rigidity.
Smart Images
Figure 2025519327000001_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to tires for vehicle wheels, particularly winter tires.
Background Art
[0002] A tire is generally formed in a toroidal shape around a rotation axis and has a carcass structure including at least one carcass ply, and the carcass ply has an end flap engaged with a respective fixed annular structure called a bead core.
[0003] At a position radially outside the carcass structure, in the case of an automobile tire, a belt structure is provided with at least two rubberized textile strips stacked radially, and the textile strips usually have reinforcing cords made of metal. The reinforcing cords are parallel to each other in each textile strip, but are arranged in a crossed manner with respect to the cords of adjacent textile strips, preferably symmetrically with respect to the equatorial plane of the tire.
[0004] Preferably, the belt structure also includes, at a radially outer position, at least at the end of the lower belt strip, a third layer of textile or metal cords arranged circumferentially (at 0 degrees). In tubeless type tires, there is also a radially inner layer known as a "liner" having a waterproof characteristic to ensure the airtightness of the tire itself.
[0005] A tread band made of an elastomer material is applied radially outside the belt structure, and thereon, a tread surface intended to contact the road surface is defined.
[0006] The tire has a tread band with grooves of various shapes and geometries in order to ensure appropriate road-holding performance even on wet road surfaces. The main function of these grooves is to drain the water present between the tire's surface and the road surface when they come into contact with each other, and to prevent the tire from partially lifting off the road surface due to the hydrostatic pressure generated by the impact of water on the tire as the tire moves forward, which would otherwise result in the loss of vehicle control (a phenomenon known as "hydroplaning").
[0007] Circumferential grooves also affect the directional characteristics and running stability of the tire in relation to the tire's ability to withstand tangential stresses parallel to the tire rotation axis.
[0008] Transverse grooves affect the traction characteristics of the tire, i.e., the ability to transmit a tangential stress parallel to the running direction to the road surface, especially during vehicle acceleration and braking.
[0009] The grooves as a whole define a plurality of blocks in the tread band. Each block 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 also bounded, at least in part, by one or more walls defined by the grooves surrounding the block.
[0010] In some cases, the wall or a part of the wall of the block is connected to the tread surface of the block by a chamfer formed by a plane appropriately inclined with respect to the wall and the tread surface, defining the edge of the block.
[0011] In the case of winter tires, small grooves known as "sipes" are usually present in the blocks of the tread band and extend 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 ice and snow surfaces and to hold a specific amount of snow, thereby improving the grip with the road surface.
[0012] International Publication No. 2019 / 111089 granted to the same applicant discloses a tire without siping in which some edges of the blocks or ribs are chamfered.
[0013] International Publication No. 2019 / 030664 granted to the same applicant shows an example of a winter tire in which the blocks are provided with a plurality of sipings that open at the longitudinal ends of the walls of the opposing blocks.
[0014] The "circumferential direction" generally refers to the direction of rotation of the tire, or in any case, a direction slightly inclined (at most about 5°) with respect to the direction of rotation of the tire.
[0015] The "axial direction" refers to a direction substantially parallel to the axis of rotation of the tire, or at most, a direction slightly inclined (at most about 5°) with respect to the axis of rotation of the tire. The axial direction is generally perpendicular to the circumferential direction.
[0016] The term "equatorial plane" of the tire refers to the plane of the axial center line perpendicular to the axis of rotation of the tire.
[0017] The "shoulder region" of the tread band refers to the portion of the tread band that extends circumferentially at an axially outer position of 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" refers to a recess in a portion of the tread band having a width of 1.5 mm or more and preferably a depth deeper than 3 mm.
[0020] The term "siping" refers to a recess in a portion of the tread band having a width narrower than 1.5 mm, preferably a width of 1 mm or less.
[0021] A "block" is defined as a portion of the tread surface bounded by at least one groove, preferably at least two separate grooves, and the block defines a portion of the tread surface intended to contact the road surface at the radially outer surface.
[0022] Accordingly, any portion of the tread band having a closed contour separated by three or more grooves, or any circumferential rib separated by a pair of grooves extending circumferentially around the tread band, is considered a block.
[0023] A "central block" is defined as a block not bounded by the axial ends of the tread band, while a block partially bounded by one of the axial ends of the tread band is defined as a "shoulder block".
[0024] The "wall" of a block generally refers to a surface that extends generally from the bottom of the groove defining the boundary of the block towards the tread surface portion of the block.
[0025] The "edge" of a block refers to the block region that joins the wall of the block to the tread surface portion of the block. The edge defined above should be considered distinct from the wall (i.e., the edge is not part of the wall).
[0026] When a block is completely bounded by grooves, the edge defines the contour around the tread surface portion of the block.
[0027] The portion of the edge where the first end of a sipe in the block opens can be identified as the "first edge". If there are multiple sipes in the block and the first ends open to the edge, the "first edge" may be identified by the edge portion of the block where the first ends of each of the multiple sipes open.
[0028] Similarly, when the side or sides open at different portions of the edge at respective second ends opposite the first end, such different portions of the edge may be specified as "second edges".
[0029] Note that the definition of "first edge" or "second edge" does not solely result from the geometric design of the block. Instead, it is closely related to the presence and design of one or more sides of the block.
[0030] An edge or a part thereof may be formed by a corner where the wall intersects the tread surface portion directly, or may be formed by a connecting surface connecting the wall to the tread surface portion.
[0031] The "chamfer" of the block refers to such a connecting surface.
[0032] Preferably, the chamfer is formed by a plane, but it can also have a rounded shape.
[0033] When the chamfer is formed by a plane, the chamfer is inclined with respect to both the tread surface and the wall of the block.
[0034] The "width" of the chamfer refers to the dimension calculated by projecting the chamfer surface onto the tread surface in a direction substantially perpendicular to the longitudinal direction of an edge of the chamfer.
[0035] When the lengths of each of two or more edge portions differ from each other by at most 10% of the larger length, these edge portions have "substantially equal" lengths.
[0036] Two or more elements extending along respective directions, such as two or more sides, are "substantially parallel" when they are inclined with respect to each other at an angle less than 10°, preferably less than 5°.
[0037] The applicant has observed that the performance of a tire on an ice and snow surface depends greatly on the number and size of the sipes in the block, and as a result, for the same tread pattern, a block with more sipes can provide better behavior on snow.
[0038] However, the applicant has also noticed that the presence of sipes weakens the structure of the block, thereby reducing its rigidity and, consequently, its ability to withstand external stresses, especially tangential stresses.
[0039] As a result of this weakening of the block structure, during braking, acceleration, or cornering, the blocks of the tire may be greatly deformed, causing the blocks to partially lift off the road surface. As a result, the contact area between the blocks and the road surface decreases, and consequently, the overall frictional force exerted by the tire on the road surface decreases.
[0040] In other words, the applicant has observed that while providing a large number of sipes in the block improves the behavior of the block on ice and snow surfaces, it can interfere with the performance of the block regarding load holding on both dry and wet road surfaces.
SUMMARY OF THE INVENTION
PROBLEM TO BE SOLVED BY THE INVENTION
[0041] Therefore, the applicant felt the need to provide a winter tire that can provide excellent performance on ice and snow roads despite having a small number of sipes in the blocks.
MEANS FOR SOLVING THE PROBLEM
[0042] To meet this requirement, the applicant considered the possibility of introducing chamfered portions at the edges of the blocks to increase the gripping angle. However, providing a continuous chamfered portion at the edge of the block may cause a reduction in the tread surface of the block, decreasing the tire surface in contact with the road surface and possibly weakening the rigidity of the block.
[0043] However, the applicant has noticed that for the edge portion of the "sharp corner" (i.e., the portion defined by the wall of the block that intersects the tread surface of the block), the chamfered portion at the edge of the adjacent block exactly defines an additional gripping corner at the end of the edge portion of the sharp corner facing the chamfered edge portion.
[0044] The applicant has further noticed that when a sipe is provided in the block, the block is "naturally" subdivided into adjacent portions, each portion being bounded by a pair of sip es, and when these sip es open into the wall of the block, the corresponding edges are also subdivided into continuous portions by the sip es.
[0045] Therefore, the applicant has recognized that by taking advantage of this edge subdivision, chamfered portions can be introduced into some of these edge portions, while leaving other edge portions as sharp corners (i.e., without chamfering), thereby generating new gripping corners without overly reducing the tread surface of the block. The applicant has finally found that in a block having at least one sipe, when the sipe opens into the tread surface and at least one first edge of the block, as a result, at least one first edge portion and at least one second edge portion that are adjacent to each other and bounded by the at least one sipe are defined, the first edge portion is defined by a chamfered portion, and the second edge portion is defined by a sharp corner, i.e., an edge resulting from the intersection of the tread surface with the wall of the block, the block provides excellent behavior on both icy and snowy road surfaces and dry or wet road surfaces to the tread.
[0046] In particular, in its first aspect, the present invention relates to a tire for a vehicle wheel comprising a tread band and a tread surface radially outside the tread band.
[0047] Preferably, a plurality of blocks are defined in the tread band.
[0048] Preferably, at least one siped is in at least one of the plurality of blocks.
[0049] Preferably, the at least one siped opens to a tread surface portion of the block.
[0050] Preferably, the at least one siped opens to at least a first edge of the block.
[0051] Preferably, the at least one siped defines at least a first edge portion and at least a second edge portion.
[0052] Preferably, the at least one second edge portion is adjacent to the at least one first edge portion.
[0053] Preferably, the at least one first edge portion and the at least one second edge portion are at least partially bounded by the at least one siped.
[0054] Preferably, the at least one first edge portion is defined by a chamfer portion extending between the tread surface portion and the wall of the block.
[0055] Preferably, the at least one second edge portion is defined by an angle resulting from the tire band portion intersecting the wall.
[0056] The applicant believes that due to these characteristics, the block has a number of useful gripping corners, which is useful for improving the behavior of the tire on a snow-covered road without significantly sacrificing the tread area and without significantly hindering the rigidity of the block.
[0057] In the above aspect, the present invention can have at least one of the further preferred features listed below.
[0058] In some embodiments, the at least one cusp opens into the first edge at a straight or curved portion of the first edge.
[0059] In some embodiments, the at least one cusp opens into the first edge at a location having a continuous tangent.
[0060] In other words, the at least one cusp preferably opens at a location on the first edge that does not correspond to a vertex on the contour around the block.
[0061] Preferably, a plurality of the cusps are in at least one of the plurality of blocks.
[0062] In some embodiments, at least two of the first edge portions, which are alternately arranged with the second edge portions by the plurality of the cusps, are defined on the first edge.
[0063] In some embodiments, at least two of the second edge portions, which are alternately arranged with the first edge portions by the plurality of the cusps, are defined on the first edge.
[0064] In some embodiments, at least two of the second edge portions, which are alternately arranged with each other by the plurality of the cusps, and at least two of the second edge portions are defined on the first edge.
[0065] In this way, the number of gripping corners formed by arranging the first edge portion adjacent to the second edge portion is advantageously maximized.
[0066] In some embodiments, the chamfered portion includes a surface inclined at an angle of 30° to 60°, preferably about 45°, with respect to the tread surface.
[0067] Preferably, the inclined surface is a flat surface.
[0068] In some embodiments, the chamfer portion has a width of 0.5 mm to 3 mm.
[0069] In some embodiments, on the first edge, a plurality of the first edge portions are defined by the plurality of the saw teeth.
[0070] Preferably, all the first edge portions defined on the first edge have substantially equal lengths.
[0071] In some embodiments, the at least one first edge portion and the at least one second edge portion have a length of 4 mm to 8 mm.
[0072] In some embodiments, on the first edge, a plurality of the second edge portions are defined by the plurality of the saw teeth.
[0073] Preferably, all the second edge portions defined on the first edge have substantially equal lengths.
[0074] In some embodiments, the at least one first edge portion and the at least one second edge portion have substantially equal lengths.
[0075] In some embodiments, the saw teeth are substantially parallel to each other.
[0076] In some embodiments, the at least one saw tooth also opens to a second edge of the block.
[0077] In some embodiments, the at least one saw tooth opens to the second edge at a straight or curved portion of the second edge.
[0078] In some embodiments, the at least one saw tooth opens to the second edge at a location having continuous tangents.
[0079] In other words, at least one sieve preferably opens at a location of a second edge that does not correspond to a vertex on the contour around the block.
[0080] Preferably, the second edge is different from the first edge.
[0081] In some embodiments, the at least one sieve also at least partially defines at least one of the first edge portions and at least one of the second edge portions on the second edge.
[0082] Preferably, on the second edge, the at least one of the second edge portions is adjacent to the at least one of the first edge portions.
[0083] In this way, the formation of additional gripping corners is advantageously extended to more edges of the block, improving the performance of the entire tire.
[0084] In some embodiments, at least one region of the block is bounded by the at least one sieve.
[0085] Preferably, the region is bounded at both ends of the region by one of the first edge portions and one of the second edge portions.
[0086] In some embodiments, the at least one region of the block is bounded by a pair of the sieves.
[0087] In some embodiments, each region of the block bounded by a pair of the sieves is bounded at both ends of the region by one of the first edge portions and one of the second edge portions.
[0088] Thereby, the structure of the block, and thus its stiffness characteristics, are balanced to provide uniform behavior of the block when subjected to tangential stress.
[0089] In some embodiments, the block of the plurality of blocks is a central block.
[0090] In other words, the block is all the blocks of the tread band except for the blocks partially bounded by the axial ends of the tread band.
[0091] The features and advantages of the present invention will become apparent from a detailed description of some preferred embodiments shown by way of non-limiting example with reference to the accompanying drawings.
Brief Description of the Drawings
[0092]
Figure 1
Figure 2
Figure 3
Modes for Carrying Out the Invention
[0093] Referring to the accompanying drawings, 1 generally shows a tire of a vehicle wheel made according to the present invention.
[0094] The tire 1 has a normal toroidal shape developed around a rotational axis defining the axial direction Y of the tire and traversed by an equatorial plane X perpendicular to the rotational axis.
[0095] The tire 1 includes a tread band 2, and a tread surface 3 is defined on the tread band 2 and is disposed radially outside the tread band 2 and is intended to contact the road surface.
[0096] The tire 1 has, for example, a nominal cross-sectional width of about 205 mm with a rim diameter of 16 inches.
[0097] The tread band 2 is defined with a central region that extends symmetrically circumferentially around the equatorial plane X, and a pair of shoulder regions that extend respectively on both axial sides of the central region at axially outer positions of the tread band 2 up to respective axial ends of the tread band 2.
[0098] The tread band 2 has a plurality of grooves, all of which are shown as 4 and separate the respective plurality of blocks 5 formed in the tread band 2, particularly in its central region. Since the blocks 5 are completely separated by the grooves 4, they are, therefore, central blocks.
[0099] The groove 4 also partially defines a shoulder block 6, which is formed in the shoulder region and is axially bounded by the axial ends of the tread band 2.
[0100] In the embodiments described herein, the groove 4 has a depth of 3 mm to 9 mm and a width of 2.5 mm to 9.5 mm.
[0101] In FIG. 2, as an example, the block 5 is schematically represented in the central region of the tread band 2, and it will be understood that the same considerations apply equally to all other central blocks of the tread band except the shoulder block 6.
[0102] The block 5 includes a tread surface portion 7 defined on the radially outer surface of the block 5 and intended to contact the road surface, and a plurality of walls 8 extending from the respective bottoms 9 of the grooves 4 that separate the block 5 towards the tread surface portion 7.
[0103] Each wall 8 extends from the bottom of the groove 4 towards the tread surface portion 7 with a substantially constant inclination forming an angle of about 2° to about 20°, for example about 5°, about 10°, or about 15°, which is slightly flared from the radial direction of the tire.
[0104] The wall 8 is joined to the tread surface portion 7 to define the edge of the block 5.
[0105] In the example of block 5 shown in FIG. 2 having a general diamond design, a first edge 11 formed by a pair of adjacent sides of the diamond and a second edge 12 formed by the other pair of adjacent sides of the diamond can be identified.
[0106] Block 5 has at least one sipe 15 that opens into the tread surface portion 7 and extends along the major longitudinal direction shown as A in the figure.
[0107] The at least one sipe 15 has a width of about 0.5 mm and a depth in the range of 3 mm to 7 mm.
[0108] In the example of block 5 shown in the figure, there are preferably a plurality of sipess 15, all extending parallel to the longitudinal direction A.
[0109] The longitudinal direction A is inclined at about 60° with respect to the equatorial plane X, but this longitudinal direction can have different inclinations and is defined to be parallel to the axial direction Y.
[0110] Each sipe 15 extends through block 5 along the longitudinal direction A, and as a result, each sipe 15 also opens into the wall 8 and thus into the edge of block 5. In particular, in block 5 shown in FIG. 2, the sipe 15 extends between the first edge 11 and the second edge 12.
[0111] Each sipe 15 can have a linear design as in the example of block 5 shown in the figure, but each sipe 15 is defined to be able to take other designs, such as a curved or dashed or zigzag design.
[0112] When there are three or more sipess 15, they are preferably spaced equidistantly from each other by about 4 mm to about 8 mm, more preferably about 5 mm to about 6 mm.
[0113] In the example shown in FIG. 5, the sipe 15 divides the block 5 into adjacent block regions 16a, 16b, 16c, 16d, 16e. Each block region 16a, 16b, 16c, 16d, 16e is bounded by a pair of sip es 15, and at both ends in their longitudinal directions, the boundaries are defined by a part of the first edge 11 and a part of the second edge 12, respectively. As a result, the first edge 11 and the second edge 12 are also divided into separate parts adjacent to each other by the sipe 15.
[0114] In particular, the first edge 11 is subdivided into a plurality of first edge portions 20 and a plurality of second edge portions 21 arranged alternately. Each first edge portion 20 is defined by a chamfer portion 22 extending between the tread surface portion 7 and the wall 8 of the block 5, while each second edge portion 21 is defined by a corner 23 formed by the intersection of the tread surface portion 7 and the wall 8 of the block 5.
[0115] In other words, the first edge 11 is formed by alternately arranging the chamfer portions 22 and the corners 23, all having substantially the same length.
[0116] Each chamfer portion 22 consists of a plane inclined at an angle of about 45° with respect to the tread surface portion 7, having a length of about 5 - 6 mm and a width of about 2 mm. The chamfer portion 22 is also inclined at a non-zero angle with respect to the wall 8 and is correlated with the inclination of the wall with respect to the radial direction as shown above.
[0117] It should be noted that by providing the chamfer portion 22, a step structure 24 is defined in the adjacent block regions where the second edge portion 21 is defined at the longitudinal ends thereof. It should also be noted that each step structure 24 is bounded by an angle that is advantageous for gripping the block 5 on a snow-covered road surface.
[0118] 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 the chamfer portions 22 and a plurality of second edge portions 21 defined by the corners 23, which are arranged alternately.
[0119] Therefore, the second edge 12 is also formed by alternately arranging chamfered portions 22 and corners 23, all having substantially the same length.
[0120] However, it is expected that the alternate arrangement of the chamfered portions 22 and the corners 23 on the first edge 11 is offset from the alternate arrangement of the chamfered portions 22 and the corners 23 on the second edge 12. Accordingly, each first edge portion 20 defined on the first edge 11 corresponds to the second edge portion 21 defined on the second edge 12 when moving along the longitudinal direction A, and vice versa.
[0121] Therefore, each region 16a, 16b, 16c, 16d, 16e of the block 5 is bounded at both longitudinal ends by a first edge portion 20 (defined by the chamfered portion 22) and a second edge portion 21 (defined by the corner 23).
Claims
1. A tire (1) for a vehicle wheel, comprising a tread band (2), a tread surface (3) radially outside the tread band (2), a plurality of blocks (5, 6) defined in the tread band (2), and at least one sipe (15) formed in at least one block (5) of the plurality of blocks (5, 6), wherein the at least one sipe (15) opens to a tread surface portion (7) of the block and at least a first edge (11) of the block (5), resulting in defining at least one first edge portion (20) and at least one second edge portion (21) adjacent to the at least one first edge portion (20), and the at least one first edge portion (20) and the at least one second edge portion (21) are at least partially bounded by the at least one sipe (15), - the at least one first edge portion (20) is defined by a chamfer portion (22) extending between the tread surface portion (7) and a wall (8) of the block (5), - the at least one second edge portion (21) is defined by an angle (23) resulting from the tread surface portion (7) intersecting the wall (8).
2. The tire according to claim 1, wherein a plurality of the sip es (15) are formed in the at least one block (5) of the plurality of blocks (5, 6).
3. The tire according to claim 2, wherein at least two of the first edge portions (20) arranged alternately with the second edge portions (21) are defined on the first edge (11) by the plurality of the sip es.
4. The tire according to claim 2, wherein at least two of the second edge portions (21) arranged alternately with the first edge portions (20) are defined on the first edge (11) by the plurality of the sip es.
5. The tire according to claim 2, wherein at least two of the first edge portions (20) and at least two of the second edge portions (21) arranged alternately with each other are defined on the first edge (11) by the plurality of the sip es.
6. The tire according to any one of claims 1 to 5, wherein the chamfer portion (22) has a surface inclined at an angle of 30° to 60° with respect to the tread surface.
7. The tire according to claim 6, wherein the chamfered portion (22) has a width of 0.5 mm to 3 mm.
8. On the first edge (11), a plurality of the first edge portions (20) are defined by the plurality of the sipes, and all of the first edge portions (20) defined on the first edge (11) have substantially equal lengths. The tire according to any one of claims 2 to 7.
9. On the first edge (11), a plurality of the second edge portions (21) are defined by the plurality of the sipes, and all of the second edge portions (21) defined on the first edge (11) have substantially equal lengths. The tire according to any one of claims 2 to 8.
10. The tire according to any one of claims 1 to 9, wherein the at least one first edge portion (20) and the at least one second edge portion (21) have substantially equal lengths.
11. The tire according to any one of claims 2 to 10, wherein the sipes (15) are substantially parallel to each other.
12. The at least one sipe (15) opens to the second edge (12) of the block (5), and at least one of the at least one first edge portion (20) and at least one of the second edge portions (21) are at least partially defined on the second edge (12). The tire according to any one of claims 1 to 11.
13. At least one region (16a, 16b, 16c, 16d, 16e) of the block (5) is bounded by the at least one sipe (15), and at both ends of the region, one of the first edge portions (20) and one of the second edge portions (21) define a boundary. The tire according to claim 12.
14. The tire according to claim 13, wherein the at least one region (16a, 16b, 16c, 16d, 16e) of the block (5) is bounded by a pair of the sipes (15).
15. Each region (16a, 16b, 16c, 16d, 16e) of the block (5) bounded by a pair of the sipes (15) is bounded at both ends of the region by one of the first edge portions (20) and one of the second edge portions (21). The tire according to claim 14.
16. The tire according to any one of claims 1 to 15, wherein the block of the plurality of blocks is a central block.