tire

Abstract

To suppress deterioration of noise performance while improving drainability.SOLUTION: At least one of main grooves 2 is a meandering main groove 21, and each of first and second groove walls 2a and 2b thereof has upper and lower groove wall parts. The upper groove wall part is connected to a groove bottom 2c with the lower groove wall part between. In the first groove wall 2a, a lower groove wall upper end edge 2ale extends in a wave shape in a tire circumferential direction such that minimum and maximum groove wall angle parts alternately appear in the tire circumferential direction at a prescribed repetitive period, In the second groove wall 2b, a lower groove wall upper end edge 2ble extends in a wave shape in the tire circumferential direction. In the first groove wall 2a, the minimum groove wall angle part is at a same position as that of a wide groove part, and the maximum groove wall angle part is at a same position as that of a narrow groove part in the tire circumferential direction. The upper groove wall upper end edge 2aue of the first groove wall 2a extends in a linear, wave, or zigzag shape in which amplitude is smaller than that of the lower groove wall upper end edge 2ale of the first groove wall 2a.SELECTED DRAWING: Figure 3

Description

Technical Field

[0001] The present invention relates to a tire.

Background Art

[0002] Conventionally, many proposals have been made to suppress the hydroplaning phenomenon and improve the drainage performance of tires. For example, Patent Document 1 proposes a tire in which both groove walls of the main groove are meandered along the tire circumferential direction in a tread surface view. According to the tire described in Patent Document 1, the drainage performance of the tire can be improved.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, in the tire described in the above Patent Document 1, compared with a tire in which the groove wall of the main groove extends linearly along the tire circumferential direction, the compression rigidity of the land portion forming the main groove varies greatly along the tire circumferential direction, so there is a problem that the noise performance is likely to deteriorate.

[0005] Therefore, an object of the present invention is to provide a tire that can improve the drainage performance while suppressing the deterioration of the noise performance.

Means for Solving the Problems

[0006] The means for achieving the above object are as follows.

[0007] (1) The tire of the present invention is a tire having at least one main groove extending in the tire circumferential direction on a tread surface, At least one of the main grooves is a meandering main groove in which, when viewed from the tread surface, at least a portion of the groove surface extends in a wavy manner along the circumferential direction of the tire. In the meandering main groove, the first groove wall, which is the groove wall on one side in the tire width direction, and the second groove wall, which is the groove wall on the other side in the tire width direction, each have, in a cross-sectional view in the tire width direction, an upper groove wall portion that extends linearly or in an arc shape with a constant curvature having the center of curvature on the groove side, from the tread surface, and a lower groove wall portion that extends in an arc shape connected to the upper groove wall portion with a constant curvature having the center of curvature on the groove side, which is larger than the upper groove wall portion, and the upper groove wall portion is connected to the groove bottom via the lower groove wall portion. In a cross-sectional view in the width direction of the tire, the angle of the upper groove wall portion on the tread surface with respect to the normal line drawn on the tread surface is called the upper groove wall angle, and in a cross-sectional view in the width direction of the tire, the upper end of the upper groove wall portion and the boundary between the upper groove wall portion and the lower groove wall portion, which are connected in the circumferential direction of the tire, are called the upper groove wall upper edge and the lower groove wall upper edge, respectively, and furthermore, the distance in the width direction of the tire between the upper groove wall edges of the lower groove walls on both groove walls of the meandering main groove is called the groove wall spacing, The first groove wall of the meandering main groove has a minimum groove wall angle portion where the upper groove wall angle is smallest, and a maximum groove wall angle portion where the upper groove wall angle is largest, which alternate along the tire circumferential direction at a predetermined repeating period, such that the upper edge of the lower groove wall extends in a wavy shape along the tire circumferential direction when viewed from the tread surface. The second groove wall of the meandering main groove has an upper edge of the lower groove wall that extends in a wavy shape along the tire circumferential direction when viewed from the tread surface. The portion of the first groove wall of the meandering main groove with the minimum groove wall angle is at the same position in the tire circumferential direction as the wide groove portion where the groove wall spacing of the meandering main groove is maximum, and the portion of the first groove wall of the meandering main groove with the maximum groove wall angle is at the same position in the tire circumferential direction as the narrow groove portion where the groove wall spacing of the meandering main groove is minimum. The upper edge of the upper groove wall of the first groove wall of the meandering main groove extends in a linear, wavy, or zigzag pattern along the tire circumferential direction when viewed from the tread surface, with an amplitude in the tire width direction smaller than the amplitude in the tire width direction of the upper edge of the lower groove wall. According to the tire of the present invention, it is possible to improve drainage performance while suppressing deterioration of noise performance.

[0008] (2) In the tire described in (1) above, Preferably, the upper edge of the upper groove wall of the first groove wall of the meandering main groove extends in a straight line along the tire circumferential direction when viewed from the tread surface. In this case, the deterioration of noise performance can be suppressed more effectively.

[0009] (3) In the tire described in (1) above, The upper groove wall angle of the maximum groove wall angle portion of the first groove wall of the meandering main groove is preferably 25° or less. In this case, drainage can be improved more effectively. Furthermore, it is also preferable that the tire described in (2) above has the configuration described in (3) above.

[0010] (4) In any of the tires described in (1) to (3) above, Preferably, the upper edge of the upper groove wall of the second groove wall of the meandering main groove extends in a wavy manner along the tire circumferential direction. In this case, drainage can be improved more effectively. Furthermore, it is also preferable that the tire (3) having the configuration of (2) also has the configuration of (4).

[0011] (5) In any of the tires described in (1) to (3) above, It is preferable that the amplitude in the tire width direction of the upper edge of the lower groove wall of the first groove wall of the meandering main groove is smaller than the amplitude in the tire width direction of the upper edge of the lower groove wall of the second groove wall of the meandering main groove. In this case, drainage can be improved more effectively. Furthermore, it is also preferable that the tire (3) having the configuration of (2) above, and the tire (4) having the configurations of (2) and (3) above, also have the configuration of (5) above.

[0012] (6) In the tire of (1) above, the tire has a plurality of the main grooves, the meandering main groove is preferably the outermost main groove in the tire width direction on the inner side of the vehicle mounting among the plurality of the main grooves. In this case, the drainage performance can be improved more effectively. In addition, in a tire having at least one configuration of (1) to (5) above, it is also preferable to have the configuration of (6) above.

Advantages of the Invention

[0013] According to the present invention, it is possible to provide a tire that can improve drainage performance while suppressing deterioration of noise performance.

Brief Description of the Drawings

[0014] [Figure 1] It is a front view of the tire according to the first embodiment of the present invention. [Figure 2] It is a developed view obtained by developing the tread surface of part A in FIG. 1 into a plane. [Figure 3] It is an enlarged view of part B in FIG. 2. [Figure 4] (a) is a cross-sectional view taken along line X1-X1 in FIG. 3, and (b) is a cross-sectional view taken along line X2-X2 in FIG. 3. [Figure 5] It is a cross-sectional view taken along line Y1-Y1 in FIG. 3. [Figure 6] It is an enlarged developed view similar to FIG. 3, showing a part of the tread surface of the tire according to the second embodiment of the present invention in an enlarged manner. [Figure 7] (a) is a cross-sectional view taken along line X3-X3 in FIG. 6, and (b) is a cross-sectional view taken along line X4-X4 in FIG. 6.

Modes for Carrying Out the Invention

[0015] The tire according to the present invention can be suitably used for any type of tire, for example, it can be suitably used for pneumatic tires for passenger cars, pneumatic tires for trucks and buses, etc.

[0016] Hereinafter, embodiments of the tire according to the present invention will be described with reference to the drawings. In each figure, common components and parts are denoted by the same reference numeral. In some figures, the tire width direction is indicated by the reference numeral "WD", the tire circumference direction by the reference numeral "CD", the inside of the vehicle mounting (the side that is on the inside of the vehicle in the tire width direction when the tire is mounted on the vehicle) is indicated by "IN", and the outside of the vehicle mounting (the side that is on the outside of the vehicle in the tire width direction when the tire is mounted on the vehicle) is indicated by "OUT".

[0017] Although a detailed explanation will be omitted, the tire of the embodiment described below can be a general tire structure in which, for example, a carcass has carcass plies made of, for example, organic fiber cords or steel cords that extend from one bead portion through the tread portion to the other bead portion, and a belt having a belt layer made of, for example, steel cords, is disposed between the carcass and the tread rubber of the tread portion.

[0018] Unless otherwise specified, the positional relationships and dimensions of each element shall be measured under standard conditions, with the tire mounted on the applicable rim, filled to the specified internal pressure, and unloaded. Furthermore, in this specification, "tread surface" refers to the outer circumference of the tire that comes into contact with the road surface when the tire is mounted on the applicable rim, filled to the specified internal pressure, and under maximum load. The width of the tread surface in the tire width direction shall be called "tread width (TW)," and the end of the tread surface in the tire width direction shall be called "tread end (TE)." Here, the dimensions of each element such as grooves on the tread surface shall be measured in tread surface view. Here, in this specification, "tread surface view" refers to viewing the tread surface in plan view with the tread surface laid out on a plane.

[0019] In this specification, "applicable rim" refers to the standard rim (Measuring Rim in the ETRTO STANDARDS MANUAL, Design Rim in the TRA YEAR BOOK) for the applicable size, which is listed or will be listed in the industrial standards valid in the region where the tire is produced and used, such as the JATMA YEAR BOOK of JATMA (Japan Automobile Tire Manufacturers Association) in Japan, the STANDARDS MANUAL of ETRTO (The European Tyre and Rim Technical Organisation) in Europe, and the YEAR BOOK of TRA (The Tire and Rim Association, Inc.) in the United States. However, for sizes not listed in these industrial standards, it refers to a rim with a width corresponding to the bead width of a pneumatic tire. "Applicable rim" includes not only current sizes but also sizes that will be listed in the aforementioned industrial standards in the future. An example of "sizes that will be listed in the future" is the size listed as "FUTURE DEVELOPMENTS" in the ETRTO 2013 edition.

[0020] In this specification, "specified internal pressure" refers to the air pressure (maximum air pressure) corresponding to the maximum load capacity of a single wheel in the applicable size and ply rating as described in the aforementioned industrial standards such as the JATMA YEAR BOOK. For sizes not listed in the aforementioned industrial standards, it refers to the air pressure (maximum air pressure) corresponding to the maximum load capacity specified for each vehicle on which the tire is mounted. Furthermore, in this specification, "maximum load" refers to the load corresponding to the maximum load capacity of a tire of the applicable size as described in the aforementioned industrial standards, or, for sizes not listed in the aforementioned industrial standards, the load corresponding to the maximum load capacity specified for each vehicle on which the tire is mounted.

[0021] (First Embodiment) Figures 1 to 5 are diagrams illustrating a tire 10 according to the first embodiment of the present invention. Figure 1 is a front view of the tire according to the first embodiment of the present invention. Figure 2 is an unfolded view of the tread surface of part A in Figure 1 laid out on a plane. Figure 3 is an enlarged view of part B in Figure 2. Figure 4(a) is a cross-sectional view along the line X1-X1 in Figure 3, Figure 4(b) is a cross-sectional view along the line X2-X2 in Figure 3, and Figure 5 is a cross-sectional view along the line Y1-Y1 in Figure 3. Here, in Figures 2 and 3, for ease of understanding, only the meandering main groove 21, which will be described later, is depicted not only at the groove opening but also in detail inside it (the part inside the groove depth direction from the groove opening). In Figure 3, for ease of understanding, only the outlines of the serpentine main groove 21, which will be described later, and the raised portion 5 that rises from the tread surface 1 and the groove bottom 2c are drawn with slightly thicker lines. The slightly thinner lines between them in Figure 3 (and by extension, Figure 2) are edges (lines) that connect points in the tire circumferential direction where the curvature (and therefore the radius of curvature) changes in a cross-sectional view in the tire width direction. The tire 10 in this embodiment may be configured as any type of tire. However, the tire 10 in this embodiment is configured as a tire whose mounting direction to the vehicle is specified by markings on the tire or by the instruction manual.

[0022] As shown in Figures 1 and 2, the tire 10 of this embodiment has at least one (four in the illustrated example) main grooves 2 (21, 22, 23, and 24) extending in the circumferential direction of the tire on the tread surface 1. Each main groove 2 extends continuously along the entire circumferential direction of the tire. Furthermore, each main groove 2, more specifically, both opening edges of each main groove 2 to the tread surface 1, may extend linearly along the circumferential direction of the tire, as shown in Figure 2, or they may extend in a wavy or zigzag pattern, unless otherwise specified. Hereinafter, "extending in a wavy pattern" means extending while repeatedly bending at rounded bends, "extending in a smooth wavy pattern" means extending while repeatedly bending at rounded bends and without having any straight sections, and "extending in a zigzag pattern" means extending while repeatedly bending at angular bends. Furthermore, in this specification, "extending in a wave-like manner (or extending)" is also referred to as "meaning," and "extending in a smooth wave-like manner (or extending)" is also referred to as "meaning smoothly." In this embodiment, the tire 10 has four main grooves 2 on the tread surface 1, but it is sufficient for at least one main groove 2 to be formed on the tread surface 1, for example, there may be 1 to 3 or 5 or more. However, from the viewpoint of ensuring sufficient drainage, it is preferable to have multiple main grooves 2 (2 or more), and from the viewpoint of achieving a good balance between drainage and handling stability, it is even more preferable to have about 3 to 5 grooves.

[0023] In this embodiment, at least one of the main grooves 2 described above (one in the illustrated example) is a meandering main groove, in which at least a portion of the groove surface extends in a wave-like manner along the tire circumferential direction when viewed from the tread surface. More specifically in this embodiment, as shown in Figures 1 and 2, among the multiple main grooves 2 (four in the illustrated example), the outermost main groove in the tire width direction on the vehicle mounting side (the first main groove counting from the innermost part of the vehicle mounting; hereinafter also referred to as the "first main groove") 21 is a meandering main groove. Hereinafter, the first main groove 21, which is a meandering main groove, will also be simply referred to as the meandering main groove 21. The meandering main groove 21 will be described in detail later.

[0024] In this embodiment, more specifically, as shown in Figures 1 and 2, of the main grooves 2, the outermost main groove in the tire width direction on the vehicle mounting side (first main groove) 21 is a meandering main groove as described above, the second main groove from the outside in the tire width direction on the vehicle mounting side (the second main groove counting from the innermost part of the vehicle mounting; hereinafter also referred to as the "second main groove") 22, the second main groove from the outside in the tire width direction on the vehicle mounting side (the third main groove counting from the innermost part of the vehicle mounting; hereinafter also referred to as the "third main groove") 23, and the outermost main groove in the tire width direction on the vehicle mounting side (the fourth main groove counting from the innermost part of the vehicle mounting; hereinafter also referred to as the "fourth main groove") 24 are non-meandering main grooves, that is, in tread view, at least a portion of the groove surface does not extend in a wave-like manner along the tire circumferential direction. However, in this embodiment, it is sufficient that at least one of the main grooves 2 is a meandering main groove. For example, at least one of the second main groove 22, third main groove 23, and fourth main groove 24 may be a meandering main groove instead of or in addition to the first main groove 21. However, from the viewpoint of improving drainage, it is preferable that at least the first main groove 21 is a meandering main groove, and from the viewpoint of achieving both improved drainage and suppression of deterioration of noise performance, it is more preferable that only the first main groove 21 is a meandering main groove, as in this embodiment. In this embodiment, as shown in Figures 1 and 2, the second main groove 22, the third main groove 23, and the fourth main groove 24, which are non-swerving main grooves, are all straight main grooves in which both opening edges to the tread surface 1 extend in a straight line along the tire circumferential direction.

[0025] The width of the opening of each main groove 2 into the tread surface 1 in the tire width direction (hereinafter also referred to as the "groove opening width") Wo (the maximum value if the groove opening width Wo varies in the tire circumferential direction) is not particularly limited, but can be, for example, 4 to 15 mm. Similarly, the groove depth D (hereinafter also referred to as "groove depth") of each main groove 2, measured in a direction perpendicular to the tread surface 1 (if the groove depth D fluctuates, the maximum value thereof), is not particularly limited, but can be, for example, 6 to 20 mm.

[0026] As shown in Figures 1 and 2, the tire 10 of this embodiment has at least two (five in the illustrated example) land portions 3 (31, 32, 33, 34, and 35) on the tread surface 1, and each of the main grooves 2 described above is formed between adjacent land portions 3 in the tire width direction. In this embodiment, the land portion 3 includes the outermost land portion in the tire width direction on the vehicle mounting side (the first land portion counting from the innermost land portion on the vehicle mounting side; hereinafter also referred to as the "first land portion") 31, the second land portion from the outermost land portion in the tire width direction on the vehicle mounting side (the second land portion counting from the innermost land portion on the vehicle mounting side; hereinafter also referred to as the "second land portion") 32, and the outermost land portion in the tire width direction on the vehicle mounting side (the fifth land portion counting from the innermost land portion on the vehicle mounting side; hereinafter also referred to as the "fifth land portion") 3 5 is a rib-shaped land area where the land area is continuous in the circumferential direction of the tire. The land area including the tire equatorial plane CL (the third land area counting from the innermost part mounted on the vehicle; hereinafter also referred to as the "third land area") 33 and the second land area from the outermost part in the tire width direction on the outer side of the vehicle (the fourth land area counting from the innermost part mounted on the vehicle; hereinafter also referred to as the "fourth land area") 34 are block-shaped land areas where the land area is divided in the circumferential direction of the tire by the lateral grooves 4 (more specifically, lateral grooves 43 or 44) described later. However, each land area 3 may be either a rib-shaped land area or a block-shaped land area.

[0027] As shown in the examples in Figures 1 and 2, each land portion 3 may have a plurality of lateral grooves 4 extending in a direction intersecting the tire circumferential direction. More specifically, in this embodiment, as shown in Figures 1 and 2, the first land portion 31 has a plurality of lateral grooves 41 extending from one end of the first land portion 31 in the tire width direction (the end on the vehicle mounting side) and terminating within the first land portion 31. The second land portion 32 has a plurality of lateral grooves 42 extending from the other end of the second land portion 32 in the tire width direction (the end on the vehicle mounting side) and terminating within the second land portion 32. The third land portion 33 has a plurality of lateral grooves 43 extending from one end of the third land portion 33 in the tire width direction across the third land portion 33 to the other end of the third land portion 33 in the tire width direction. The fourth tread section 34 has multiple lateral grooves 44 extending from one end of the fourth tread section 34 in the tire width direction across the fourth tread section 34 to the other end of the fourth tread section 34 in the tire width direction, and multiple lateral grooves 45 extending from the other end of the fourth tread section 34 in the tire width direction (the end on the outside of the vehicle mounting) and terminating inside the fourth tread section 34, alternating in the tire circumferential direction. The fifth tread section 35 has multiple lateral grooves 46 extending from one end of the fifth tread section 35 in the tire width direction (the end on the inside of the vehicle mounting) and terminating inside the fifth tread section 35, and multiple lateral grooves 47 extending from the other end of the fifth tread section 35 in the tire width direction (the end on the outside of the vehicle mounting) and terminating inside the fifth tread section 35, alternating in the tire circumferential direction. The configuration of these lateral grooves 4 (41-47) makes it possible to equalize the stiffness distribution in the tire circumferential direction for the entire tread surface, and consequently contribute to improving noise performance, etc.

[0028] In particular, in this embodiment, as shown in Figures 1 and 2, the lateral groove 42 within the second land section 32, that is, the lateral groove 42 communicating with the main groove 22 adjacent to the meandering main groove 21 (more specifically, in the illustrated example, on the inner side in the tire width direction of the meandering main groove 21), extends within the second land section 32 (more specifically, in the illustrated example, outward in the tire width direction within the second land section 32) toward the vicinity of the narrow groove section Pwn of the meandering main groove 21, which will be described later. In particular, this makes it possible to equalize the stiffness distribution in the circumferential direction of the tire, and consequently contributes to improving noise performance, etc. Furthermore, in this embodiment, as shown in Figures 1 and 2, the lateral grooves 42 within the second land section 32 terminate within the second land section 32, as described above. This makes it possible to more uniformize the stiffness distribution in the circumferential direction of the tire, and consequently contribute to improving noise performance and other factors. However, the configuration of the horizontal groove 4 is arbitrary, and at least some or all of the multiple land sections 3 do not need to have the horizontal groove 4.

[0029] Next, with reference to Figures 3 to 5, the first main groove 21 (serpentine main groove 21), which is defined as a serpentine main groove in this embodiment, will be described in detail. In the tread surface view, at least a portion of the groove surface of the meandering main groove 21 extends in a wave-like manner along the tire circumferential direction. More specifically, in this embodiment, as shown in Figure 3, at least a portion of the groove surface of the meandering main groove 21, excluding the upper edge 2aue of the upper groove wall of the first groove wall 2a (described later), of the first groove wall 2a, the second groove wall 2b, and the groove bottom 2c (in the illustrated example, for example, the lower upper edge 2ale of the first groove wall 2a, the boundary edge between the first groove wall 2a and the groove bottom 2c, the boundary edge between the second groove wall 2b and the groove bottom 2c, the lower upper edge 2ble of the second groove wall 2b, and the upper upper edge 2bue of the upper groove wall of the second groove wall 2b, etc., described later), extends in a wave-like manner along the tire circumferential direction, i.e., meanders. In this embodiment, as shown in Figures 3 and 4(a) and (b), the meandering main groove 21 is formed asymmetrically on the first groove wall 2a side and the second groove wall 2b side. That is, the meandering main groove 21 does not have a symmetric axis extending in the circumferential direction of the tire.

[0030] In this embodiment, as shown in Figures 3 and 4(a) and (b), the first groove wall 2a, which is the groove wall on one side in the tire width direction (outer side in the tire width direction in the illustrated example), and the second groove wall 2b, which is the groove wall on the other side in the tire width direction (inner side in the tire width direction in the illustrated example), each have a constant curvature (radius of curvature) with their center of curvature in a straight line or on the groove side (more specifically, on the main groove 2(21) side, not on the land portion 3(31 or 32) side) in a cross-sectional view in the tire width direction. The tread has upper groove wall portions 2au and 2bu that extend from the tread surface 1 in an arc shape with the reciprocal of the curve, and lower groove wall portions 2al and 2bl that extend in an arc shape connected to the upper groove wall portions 2au and 2bu with a constant curvature, having the center of curvature on the larger groove side (more specifically, the main groove 2(21) side rather than the land portion 3(31 or 32) side), and the upper groove wall portions 2au and 2bu are connected to the groove bottom 2c via the lower groove wall portions 2al and 2bl. In the examples shown in Figures 4(a) and 4(b), in a cross-sectional view in the tire width direction, the upper groove wall portions 2au and 2bu extend linearly from the tread surface 1 (i.e., with a curvature of 0 and a radius of curvature of ∞). However, in a cross-sectional view in the tire width direction, the upper groove wall portions 2au and 2bu may extend from the tread surface 1 in an arc shape with a constant curvature, having the center of curvature on the groove side (in the illustrated example, the side of the meandering main groove 21) (i.e., convex toward the land side (in the illustrated example, the side of the first land portion 31 or the second land portion 32)). Furthermore, in the examples shown in Figures 4(a) and (b), as described above, in a cross-sectional view in the tire width direction, the lower groove wall portion 2al of the first groove wall 2a extends in conjunction with the upper groove wall portion 2au and is an arc shape with a constant curvature having its center of curvature on the groove side (i.e., convex toward the land side (first land portion 31 side in the illustrated example)), and this constant curvature is greater than the curvature of the upper groove wall portion 2au (0 in the illustrated example). Similarly, in the examples shown in Figures 4(a) and (b), in a cross-sectional view in the tire width direction, the lower groove wall portion 2bl of the second groove wall 2b extends in conjunction with the upper groove wall portion 2bu and is an arc shape with a constant curvature having its center of curvature on the groove side (i.e., convex toward the land side (second land portion 32 side in the illustrated example)), and this constant curvature is greater than the curvature of the upper groove wall portion 2bu (0 in the illustrated example). In this embodiment, in a cross-sectional view in the tire width direction, the upper groove wall portion 2au and the lower groove wall portion 2al of the first groove wall 2a have different curvatures (and therefore different radii of curvature), but are smoothly connected at their boundary edge (the upper edge 2ale of the lower groove wall, described later) (that is, they have a common tangent at their boundary edge (in the illustrated example, the straight upper groove wall portion 2au is the tangent to the lower groove wall portion 2al at the upper edge 2ale of the lower groove wall)). As a result, the upper groove wall portion 2au and the lower groove wall portion 2al are smoothly connected. The same applies to the upper groove wall portion 2bu and the lower groove wall portion 2bl of the second groove wall 2b.

[0031] In this embodiment, as described above, as shown in Figures 4(a) and (b), the upper groove wall portions 2au and 2bu of the first groove wall 2a and the second groove wall 2b are connected to the groove bottom 2c via the lower groove wall portions 2al and 2bl, respectively. That is, the upper groove wall portions 2au and 2bu are connected to the groove bottom 2c smoothly, so to speak, via the lower groove wall portions 2al and 2bl, which extend in an arc shape with a constant curvature having the center of curvature on the groove side. In this embodiment, as shown in the figure, in a cross-sectional view in the tire width direction, the groove bottom 2c extends in connection with the lower groove wall portions 2al and 2bl. However, the upper groove wall portions 2au and 2bu may each be connected to the groove bottom 2c via, for example, a groove wall portion having a larger curvature than the lower groove wall portions 2al and 2bl, which extends further downward in the groove depth direction of the lower groove wall portions 2al and 2bl, and has a similar configuration to the lower groove wall portions 2al and 2bl. However, from the viewpoint of simplifying the configuration of the meandering main groove 2, it is preferable that the upper groove wall portions 2au and 2bu are connected to the groove bottom 2c only via the lower groove wall portions 2al and 2bl, as shown in the illustrated example. In this embodiment, in a cross-sectional view in the tire width direction, the upper groove wall portion 2au and the groove bottom portion 2c of the first groove wall 2a are smoothly connected at their boundary edge (that is, they have a common tangent at their boundary edge (in the illustrated example, the straight groove bottom portion 2c is tangent to the lower groove wall portion 2al at the boundary edge)). As a result, the lower groove wall portion 2al and the groove bottom portion 2c are smoothly connected. The same applies to the lower groove wall portion 2bl and the groove bottom portion 2c of the second groove wall 2b. Herein, in this specification, "groove bottom (2c)" refers to the portion of the groove surface where the groove depth is maximum. The groove bottom 2c may have a width in the tire width direction (≠0) at each position in the tire circumferential direction, or it may not have a width in the tire width direction (i.e., the width in the tire width direction may be 0). That is, the groove bottom 2c may not have a width in the tire width direction, and for example, the deepest part in the groove depth direction of the lower groove wall portions 2al, 2bl may be the groove bottom 2c. In this embodiment, as shown in Figures 3 and 4(a) and (b), the groove bottom 2c has a width in the tire width direction (≠0) at each position in the tire circumferential direction. When the groove bottom 2c has a width in the tire width direction (≠0), in a cross-sectional view in the tire width direction, the groove bottom 2c is linear (i.e., curvature 0, radius of curvature ∞).

[0032] In this embodiment, as described above, in a cross-sectional view in the tire width direction, the upper groove wall portion 2au and the lower groove wall portion 2al of the first groove wall 2a are smoothly connected at their boundary edge (the upper edge 2ale of the lower groove wall, described later). Therefore, the height from the groove bottom 2c of the upper edge 2ale of the lower groove wall in the minimum groove wall angle portion Pamin (see Figure 4(b)) of the first groove wall 2a, described later, is higher than the height from the groove bottom 2c of the upper edge 2ale of the lower groove wall in the maximum groove wall angle portion Pamax (see Figure 4(a)) of the first groove wall 2a, described later. On the other hand, in this embodiment, the height of the upper edge 2ble of the lower groove wall of the second groove wall 2b (see Figures 4(a) and 4(b)) from the groove bottom 2c is constant along the tire circumferential direction. In this embodiment, the height of the upper edge 2ble of the lower groove wall of the second groove wall 2b from the groove bottom 2c is lower than the height of the upper edge 2ale of the lower groove wall in the minimum groove wall angle portion Pamin of the first groove wall 2a from the groove bottom 2c, and higher than the height of the upper edge 2ale of the lower groove wall in the maximum groove wall angle portion Pamax of the first groove wall 2a from the groove bottom 2c.

[0033] Next, referring to Figures 3 and 4(a) and (b), in the present invention, in a cross-sectional view in the tire width direction, the groove wall angle of the upper groove wall portion (2au, 2bu) on the tread tread 1 (in other words, at the upper edge 2aue, 2bue of the upper groove wall described later) with respect to the normal line drawn on the tread tread 1 is called the "upper groove wall angle (θ2a, θ2b)", and the upper end of the upper groove wall portion (2au, 2bu) in a cross-sectional view in the tire width direction (i.e., both groove opening ends to the tread tread) Furthermore, the edges (lines) that connect the boundaries between the upper groove wall portions (2au, 2bu) and the lower groove wall portions (2al, 2bl) in the tire circumferential direction are called the "upper groove wall upper edge (2aue, 2bue)" (i.e., the edges of the groove openings on both sides of the tread surface) and the "lower groove wall upper edge (2ale, 2ble)", respectively. In addition, the distance in the tire width direction between the lower groove wall upper edges (2ale, 2ble) on both groove walls (2a, 2b) of the meandering main groove 21 is called the "groove wall spacing (Ww)". Here, the upper groove wall angles θ2a and θ2b are defined as follows: a positive angle is defined when the upper groove wall portion 2au or 2bu slopes toward the groove side (in the illustrated examples, the meandering main groove 21 side) as it moves from the upper edge 2aue or 2bue of the upper groove wall toward the groove bottom 2c, as shown in the examples in Figures 4(a) and (b); a negative angle is defined when it slopes toward the land side (in the illustrated examples, the first land portion 31 or the second land portion 32 side); and when determining the relative magnitudes of the upper groove wall portions 2au or 2bu at each position in the circumferential direction of the tire, the positive and negative angles are taken into consideration when determining the relative magnitudes.

[0034] In this embodiment, as shown in Figures 3 and 4(a) and (b), the first groove wall 2a of the meandering main groove 21 has a minimum groove wall angle portion Pamin where the upper groove wall angle θ2a is smallest, and a maximum groove wall angle portion Pamax where the upper groove wall angle θ2a is largest, which alternately appear along the tire circumferential direction at a predetermined repeating period (length in the tire circumferential direction). The upper edge 2ale of the lower groove wall extends in a wavy pattern along the tire circumferential direction (i.e., repeatedly bending at rounded bends) when viewed from the tread surface, i.e., it meanders along the tire circumferential direction. Here, in this specification, "minimum groove wall angle portion (Pamin, Pbmin)" refers to the position in the tire circumferential direction of the meandering main groove where the upper groove wall angle (θ2a, θ2b) is smallest, and "maximum groove wall angle portion (Pamax, Pbmax)" refers to the position in the tire circumferential direction of the meandering main groove where the upper groove wall angle (θ2a, θ2b) is largest. Figures 4(a) and (b) show cross-sections of the meandering main groove 21 in the tire width direction at the maximum groove wall angle portion Pamax and the minimum groove wall angle portion Pamin of the first groove wall 2a, respectively. In this embodiment, the upper groove wall angle θ2a changes smoothly along the tire circumferential direction between the minimum groove wall angle portion Pamin and the maximum groove wall angle portion Pamax.

[0035] In this embodiment, the "predetermined repetition period" is constant in the tire circumferential direction. However, the "predetermined repetition period" may vary in the tire circumferential direction. However, from the viewpoint of rigidity balance in the tire circumferential direction, it is preferable that the "predetermined repetition period" is constant in the tire circumferential direction. Also, in this embodiment, as shown in Figure 3, the upper edge 2ale of the lower groove wall extends in a smooth wave-like manner along the tire circumferential direction when viewed from the tread surface (i.e., it repeatedly bends at rounded bends and does not have straight sections), that is, it smoothly meanders along the tire circumferential direction. However, the upper edge 2ale of the lower groove wall only needs to extend in a wave-like manner and does not need to extend in a smooth wave-like manner. However, from the viewpoint of improving drainage performance through more effective flow straightening, it is preferable that the upper edge 2ale of the lower groove wall extends in a smooth wave-like manner. In this embodiment, as shown in Figure 3, the upper edge 2ale of the lower groove wall of the first groove wall 2a and the boundary edge between the lower groove wall portion 2al and the groove bottom portion 2c extend in a wave-like manner (meander) along the tire circumferential direction, such that they are furthest from the second groove wall 2b side at the minimum groove wall angle portion Pamin and closest to the second groove wall 2b side at the maximum groove wall angle portion Pamax. In other words, in this embodiment, the upper edge 2ale of the lower groove wall of the first groove wall 2a and the boundary edge between the lower groove wall portion 2al and the groove bottom portion 2c extend along the tire circumferential direction with the same repeating period.

[0036] In this embodiment, the upper groove wall angle θ2a (see Figure 4(a)) at the maximum groove wall angle portion Pamax of the first groove wall 2a of the meandering main groove 21 is preferably 25° or less, and more preferably 20° or less. Furthermore, the upper groove wall angle θ2a is preferably 10° or more, and more preferably 15° or more. By having the upper groove wall angle θ2a at the maximum groove wall angle portion Pamax be 25° or less, the groove cross-sectional area does not become unnecessarily small, and thus sufficient drainage can be ensured, and by having it be 10° or more, the rigidity of the adjacent land area can be ensured. In the example shown in Figure 4(a), the upper groove wall angle θ2a is set to approximately 17°. Furthermore, in this embodiment, the upper groove wall angle θ2a (see Figure 4(b)) at the minimum groove wall angle portion Pamin of the first groove wall 2a of the meandering main groove 21 is preferably 15° or less, and more preferably 10° or less. Also, the upper groove wall angle θ2a is preferably 0° or more, and more preferably 5° or more. By having the upper groove wall angle θ2a at the minimum groove wall angle portion Pamin be 15° or less, the groove cross-sectional area does not become unnecessarily small, and thus sufficient drainage can be ensured, and by being 0° or more, the rigidity of the adjacent land area can be ensured. In the example shown in Figure 4(b), the upper groove wall angle θ2a is set to approximately 7°.

[0037] In this embodiment, as shown in Figures 3 and 4(a) and (b), the second groove wall 2b of the meandering main groove 21, like the first groove wall 2a described above, has a lower groove wall upper edge 2ble that extends in a wavy pattern along the tire circumferential direction when viewed from the tread surface (i.e., repeatedly bending at rounded bends). However, in this embodiment, unlike the first groove wall 2a described above, the upper groove wall angle θ2b of the second groove wall 2b does not change in the tire circumferential direction and remains constant. However, as in the second embodiment described later with reference to Figures 6 and 7, the upper groove wall angle θ2b of the second groove wall 2b may change in the tire circumferential direction. In this embodiment, as shown in Figure 3, similar to the first groove wall 2a, the upper edge 2ble of the lower groove wall of the second groove wall 2b and the boundary edge between the lower groove wall portion 2bl and the groove bottom portion 2c extend in a wave-like manner (meander) along the tire circumferential direction, such that they are furthest from the first groove wall 2a side at the minimum groove wall angle portion Pamin of the first groove wall 2a and closest to the first groove wall 2a side at the maximum groove wall angle portion Pamax of the first groove wall 2a. In other words, in this embodiment, the upper edge 2ble of the lower groove wall of the second groove wall 2b and the boundary edge between the lower groove wall portion 2bl and the groove bottom portion 2c extend along the tire circumferential direction with the same repeating period. In this embodiment, the upper edge 2ble of the lower groove wall 2b of the second groove wall extends in a wavy manner along the tire circumferential direction when viewed from the tread surface. Other aspects of this extension are the same as those described above for the upper edge 2ale of the lower groove wall 2a of the first groove wall 2a, except for the amplitude in the tire width direction which will be described later, so a detailed explanation is omitted.

[0038] In this embodiment, the upper groove wall angle θ2b (constant) of the second groove wall 2b of the meandering main groove 21 can be, for example, 10° to 20°, or more specifically, 13° to 17°, etc.

[0039] In this embodiment, the first groove wall 2a, except for the upper end edge of the first groove wall 2a (i.e., the opening edge on one side of the meandering main groove 21 to the tread surface 1) 2aue, has a line drawn in the tire width direction connecting points on the first groove wall 2a at any height from the groove bottom 2c, which extends (meanders) along the tire circumferential direction when viewed from the tread surface. This line extends (meanders) with an amplitude greater than the amplitude of the upper end edge 2aue in the tire width direction if the upper end edge 2aue extends in a wave-like or zigzag pattern. For example, a line drawn in the tire width direction connecting points on the first groove wall 2a at a height of 10% of the groove depth (maximum depth) D from the groove bottom 2c extends (meanders) along the tire circumferential direction when viewed from the tread surface. In other words, the first groove wall 2a, except for the upper edge 2aue of the upper groove wall, extends (meanders) in a wavy pattern along the tire circumferential direction when viewed from the tread surface (if the upper edge 2aue of the upper groove wall extends in a wavy or zigzag pattern, it extends in a wavy pattern with an amplitude greater than the amplitude of the upper edge 2aue of the upper groove wall in the tire width direction). Furthermore, in this embodiment, the line drawn in the tire width direction from points on the second groove wall 2b at any height from the groove bottom 2c extends in a wavy (serpentine) manner along the tire circumferential direction when viewed from the tread surface. For example, the line drawn in the tire circumferential direction from points on the second groove wall 2b at a height of 10% of the groove depth (maximum depth) D from the groove bottom 2c extends in a wavy (serpentine) manner along the tire circumferential direction when viewed from the tread surface. In other words, the entire second groove wall 2b, so to speak, extends in a wavy (serpentine) manner along the tire circumferential direction when viewed from the tread surface. In this embodiment, the above configuration makes it possible to more reliably improve drainage performance.

[0040] In this embodiment, the amplitude in the tire width direction of the upper edge 2ale of the lower groove wall of the first groove wall 2a of the meandering main groove 21 is smaller than the amplitude in the tire width direction of the upper edge 2ble of the lower groove wall of the second groove wall 2b of the meandering main groove 21. Here, in this specification, "amplitude in the tire width direction" of the upper groove wall upper edge or lower groove wall upper edge, etc., refers to the distance in the tire width direction between the position in the tire width direction when the edge, etc., extending in the circumferential direction of the tire is furthest towards the land and the position in the tire width direction when it is furthest towards the groove, as viewed from the tread surface (see reference numeral "Wa" in Figure 3 as an example).

[0041] In this embodiment, as shown in Figure 3, the minimum groove wall angle portion Pamin of the first groove wall 2a of the meandering main groove 21 is at the same circumferential position as the wide groove portion Pwb where the groove wall spacing Ww (the distance in the tire width direction between the upper edge 2ale of the lower groove wall of the first groove wall 2a and the upper edge 2ble of the lower groove wall of the second groove wall 2b) of the meandering main groove 21 is at its maximum, and the maximum groove wall angle portion Pamax of the first groove wall 2a of the meandering main groove 21 is at the same circumferential position as the narrow groove portion Pwn where the groove wall spacing Ww of the meandering main groove 21 is at its minimum. Here, "wide groove portion Pwb" refers to the position in the tire circumferential direction of the meandering main groove 21 where the groove wall spacing Ww takes its maximum value Wwmax, and "narrow groove portion Pwn" refers to the position in the tire circumferential direction of the meandering main groove 21 where the groove wall spacing Ww takes its minimum value Wwmin. As described above, in this embodiment, the minimum groove wall angle portion Pamin of the first groove wall 2a of the meandering main groove 21 is at the same position in the tire circumferential direction as the wide groove portion Pwb, and the maximum groove wall angle portion Pamax of the first groove wall 2a of the meandering main groove 21 is at the same position in the tire circumferential direction as the narrow groove portion Pwn. In other words, in this embodiment, as shown in Figure 3, the lower upper edge 2ale of the first groove wall 2a and the lower upper edge 2ble of the second groove wall 2b extend in a wave-like manner (meander) along the tire circumferential direction, with the same repetition period and a phase difference of 180°. Furthermore, the above-mentioned "same tire circumferential position" means that it is sufficient if it is substantially the same. For example, a circumferential deviation of approximately 5% or less of the repetition period (tire circumferential length) of the upper groove wall angle θ2a is acceptable.

[0042] In this embodiment, as shown in Figure 3, the upper end edge of the upper groove wall of the first groove wall 2a of the meandering main groove 21 (i.e., the opening edge on one of the two opening edges of the meandering main groove 21 to the tread surface 1 (in the illustrated example, the outer side in the tire width direction)) 2aue extends in a linear, wavy, or zigzag shape along the tire circumferential direction when viewed from the tread surface, with an amplitude in the tire width direction smaller than the amplitude Wa of the lower end edge 2ale of the first groove wall 2a in the tire width direction. More specifically, in this embodiment, as shown in Figure 3, the upper edge 2aue of the upper groove wall of the first groove wall 2a of the meandering main groove 21 extends linearly along the tire circumferential direction (i.e., with an amplitude of 0 in the tire width direction) when viewed from the tread surface. However, the upper edge 2aue of the upper groove wall of the first groove wall 2a may extend in a wavy or zigzag shape along the tire circumferential direction, as long as the amplitude in the tire width direction is smaller than the amplitude Wa of the lower groove wall upper edge 2ale in the tire width direction. However, from the viewpoint of more effectively suppressing deterioration of noise performance, it is preferable that the upper edge 2aue of the upper groove wall of the first groove wall 2a extends linearly along the tire circumferential direction.

[0043] Furthermore, in this embodiment, as shown in Figure 3, the upper end edge of the upper groove wall of the second groove wall 2b of the meandering main groove 21 (i.e., the opening edge on the other side of the two opening edges of the meandering main groove 21 to the tread surface 1 (in the illustrated example, the inner side in the tire width direction)) 2bue extends in a wavy shape (more specifically, in a smooth wavy shape) along the tire circumferential direction when viewed from the tread surface. However, as in the second embodiment described later with reference to Figures 6 to 7, the upper end edge 2bue of the upper groove wall of the second groove wall 2b may extend in a straight line, for example, along the tire circumferential direction. However, from the viewpoint of more effectively improving drainage performance, it is preferable that the upper end edge 2bue of the upper groove wall of the second groove wall 2b extends in a wavy shape along the tire circumferential direction.

[0044] In this embodiment, as described above, as shown in Figure 3, in a view of the tread surface, the upper edge of the upper groove wall of the first groove wall 2a of the meandering main groove 21 (i.e., the outer opening edge of the meandering main groove 21 to the tread surface 1 in the tire width direction) 2aue extends linearly along the tire circumferential direction, while the upper edge of the upper groove wall of the second groove wall 2b of the meandering main groove 21 (i.e., the inner opening edge of the meandering main groove 21 to the tread surface 1 in the tire width direction) 2bue extends in a wavy shape along the tire circumferential direction. In other words, in this embodiment, only the outer opening edge (2aue) of the meandering main groove 21 to the tread surface 1 is linear, while the inner opening edge (2bue) is wavy. In this case, when the circumferential rigidity of the tire on land fluctuates, by making only the opening edge adjacent to the land on the outer side in the tire width direction (i.e., the shoulder side of the tire), which is more prone to uneven wear than the inner side in the tire width direction, a straight shape where the circumferential rigidity of the adjacent land area is less likely to fluctuate, it is possible to improve drainage performance while effectively suppressing not only the deterioration of noise performance but also the deterioration of resistance to uneven wear.

[0045] Furthermore, in this embodiment, as shown in Figure 3, the upper end edge of the second groove wall 2b of the meandering main groove 21 (i.e., the opening edge on the other side of the two opening edges of the meandering main groove 21 to the tread surface 1 (in the illustrated example, the inner side in the tire width direction)) 2bue extends in a wave-like manner (meanders) along the tire circumferential direction, such that it is furthest from the first groove wall 2a side at the minimum groove wall angle portion Pamin of the first groove wall 2a, and closest to the first groove wall 2a side at the maximum groove wall angle portion Pamax of the first groove wall 2a. In other words, in this embodiment, the upper groove edge 2bue of the second groove wall 2b extends along the tire circumferential direction with the upper groove edge 2ale of the lower groove wall of the first groove wall 2a, the boundary edge between the lower groove wall portion 2al of the first groove wall 2a and the groove bottom portion 2c, the upper groove edge 2ble of the lower groove wall of the second groove wall 2b, and the boundary edge between the lower groove wall portion 2bl of the second groove wall 2b and the groove bottom portion 2c, with the same repeating period.

[0046] Furthermore, in this embodiment, as shown in Figure 3, the tire circumferential position where the groove opening width Wo of the meandering main groove 21 is maximum is the wide groove section Pwb (and consequently, the section with the minimum groove wall angle Pamin), and the tire circumferential position where the groove opening width Wo of the meandering main groove 21 is minimum is the narrow groove section Pwn (and consequently, the section with the maximum groove wall angle Pamax). Also, the tire circumferential position where the groove bottom width Wb of the meandering main groove 21 is maximum is the wide groove section Pwb (and consequently, the section with the minimum groove wall angle Pamin), and the tire circumferential position where the groove bottom width Wb of the meandering main groove 21 is minimum is the narrow groove section Pwn (and consequently, the section with the maximum groove wall angle Pamax). In this embodiment, the ratio Womax / Womin, which is the ratio of the maximum value Womax to the minimum value Womin of the groove opening width Wo of the meandering main groove 21, is preferably 1.25 to 1.50, and more preferably 1.30 to 1.45, from the viewpoint of more effectively achieving both improved drainage and securing the rigidity of the land area. In the example shown in Figures 3 to 4, Womax / Womin is set to approximately 1.38.

[0047] Furthermore, in this embodiment, as shown in Figure 3, the meandering main groove 21 has a groove opening width Wo greater than the groove wall spacing Ww at all positions in the tire circumferential direction. Similarly, the meandering main groove 21 has a groove opening width Wo greater than the groove bottom width Wb at all positions in the tire circumferential direction. These configurations ensure sufficient rigidity of the land portion 3 adjacent to the meandering main groove 21.

[0048] In this embodiment, as shown in Figures 3, 4(a), (b), and 5, the meandering main groove 21 has a raised portion 5 formed at the groove bottom 2c that rises outward in the radial direction of the tire. In this embodiment, the raised portion 5 is formed in a region that includes the wide groove portion Pwb in the circumferential direction of the tire. Thus, in this embodiment, the raised portion 5 is formed on the groove bottom 2c of the region of the meandering main groove 21 that includes the wide groove portion Pwb, so that it rises outward in the radial direction of the tire. As a result, water flowing near the wide groove portion Pwb in the meandering main groove 21 can flow more easily along the first groove wall 2a and the second groove wall 2b due to the raised portion 5, thereby effectively improving drainage. However, the meandering main groove 21 does not necessarily have to have the raised portion 5. However, from the viewpoint of effectively improving drainage, it is preferable that the meandering main groove 21 has the raised portion 5, as in this embodiment.

[0049] In this embodiment, as shown in Figure 3, in a view of the tread surface, the side edge of the raised portion 5 on the first groove wall 2a side extends in a curved shape so as to be substantially parallel to the first groove wall 2a (more specifically, the upper end edge 2ale of the lower groove wall of the first groove wall 2a and the boundary edge between the lower groove wall portion 2al of the first groove wall 2a and the groove bottom portion 2c, etc.), and the side edge of the raised portion 5 on the second groove wall 2b side also extends in a curved shape so as to be substantially parallel to the second groove wall 2b (more specifically, the upper end edge 2ble of the lower groove wall of the second groove wall 2b and the boundary edge between the lower groove wall portion 2bl of the second groove wall 2b and the groove bottom portion 2c, etc.). With the above configuration of the raised section 5, water flowing near the wide groove section Pwb within the meandering main groove 21 can flow more easily along the first groove wall 2a and the second groove wall 2b, thereby further improving drainage.

[0050] In this embodiment, as shown in Figure 3, the raised portion 5 is formed in a shape that is elongated along the tire circumferential direction, with its length (maximum length) Lr (see Figure 5) in the tire circumferential direction being longer than its width (maximum width) Wr (see Figure 4(b)) in the tire width direction, as viewed from the tread surface. More specifically, the raised portion 5 is formed in a shape that is elongated along the tire width direction, with its width gradually narrowing towards both ends of the raised portion 5 in the tire circumferential direction, as viewed from the tread surface. Furthermore, in this embodiment, as shown in Figure 4(b), the raised portion 5 is formed in a roughly triangular shape, with its height from the groove bottom 2c decreasing towards both ends of the raised portion 5 in the tire width direction, as viewed from the tire width direction in cross-section. Due to the respective configurations of the raised section 5, the water flowing near the wide groove section Pwb within the meandering main groove 21 is not abruptly altered by the raised section 5, and flows more easily along the first groove wall 2a and the second groove wall 2b, thereby further improving drainage.

[0051] The height (maximum height) Hr of the raised portion 5 from the bottom of the groove 2c (see Figure 4(b)) is not particularly limited, but it is preferable that it be less than 1 / 5 of the groove depth (maximum depth) D (see Figure 4(b)) of the meandering main groove 21. In this case, the cross-sectional area of ​​the meandering main groove 21 will not become unnecessarily small due to the presence of the raised portion 5, and consequently, sufficient drainage can be ensured. Furthermore, the width (maximum width) Wr of the raised portion 5 in the tire width direction (see Figure 4(b)) is not particularly limited, but it is preferable that it be less than half the groove opening width (maximum width) Wo of the meandering main groove 21. In this case, the cross-sectional area of ​​the meandering main groove 21 will not become unnecessarily small due to the presence of the raised portion 5, and consequently, sufficient drainage can be ensured.

[0052] Next, the main effects of the first embodiment of the present invention described above will be summarized and explained again below as necessary. First, in this embodiment, at least one of the main grooves 2 is a meandering main groove in which, when viewed from the tread surface, at least a portion of the groove surface extends in a wave-like manner along the circumferential direction of the tire. Therefore, turbulence of water flowing within the main groove can be suppressed and straightened more easily, thereby suppressing hydroplaning and improving drainage. Furthermore, in this embodiment, the first groove wall 2a and the second groove wall 2b in the meandering main groove 21 each have, in a cross-sectional view in the tire width direction, an upper groove wall portion 2au that extends linearly or in an arc shape with a constant curvature having the center of curvature on the groove side, from the tread surface, and a lower groove wall portion 2al that extends in an arc shape connected to the upper groove wall portion 2au with a constant curvature having the center of curvature on the groove side, which is larger than the upper groove wall portion 2au. The upper groove wall portion 2au is connected to the groove bottom portion 2c via the lower groove wall portion 2al. Therefore, since the upper groove wall portion 2au is smoothly connected to the groove bottom portion 2c via the lower groove wall portion 2al, it becomes easier to straighten the water flowing in the meandering main groove 21, and groove bottom cracks that tend to occur particularly near both ends in the tire width direction of the groove bottom portion 2c can be effectively suppressed. Furthermore, in this embodiment, the upper edge 2ale of the lower groove wall of the first groove wall 2a of the meandering main groove 21 extends in a wavy pattern along the tire circumferential direction when viewed from the tread surface, such that the minimum groove wall angle portion Pamin and the maximum groove wall angle portion Pamax alternate along the tire circumferential direction at a predetermined repeating period. The upper edge 2ble of the lower groove wall of the second groove wall 2b of the meandering main groove 21 extends in a wavy pattern along the tire circumferential direction when viewed from the tread surface. In addition, the minimum groove wall angle portion Pamin of the first groove wall 2a of the meandering main groove 21 is at the same position in the tire circumferential direction as the wide groove portion Pwb of the meandering main groove, and the maximum groove wall angle portion Pamax of the first groove wall 2a of the meandering main groove 21 is at the same position in the tire circumferential direction as the narrow groove portion Pwn of the meandering main groove 21. These configurations make it easier to more effectively straighten the water flowing within the meandering main groove 21. Furthermore, in this embodiment, the upper edge 2aue of the upper groove wall 2a of the meandering main groove 21 extends in a linear, wavy, or zigzag pattern along the tire circumferential direction when viewed from the tread surface, such that the amplitude in the tire width direction is smaller than the amplitude in the tire width direction of the upper edge 2ale of the lower groove wall 2a of the meandering main groove 21. This makes it possible to suppress fluctuations in the compressive stiffness in the tire circumferential direction of the first land portion 31 (and by extension, the entire land portion constituting the tread surface 1) that forms the first groove wall 2a of the meandering main groove 21, and consequently, to suppress deterioration of the noise performance of the tire 10 caused by making at least one of the main grooves 2 a meandering main groove. As described above, this embodiment makes it possible to improve drainage performance while suppressing deterioration of noise performance.

[0053] In this embodiment, the upper edge 2aue of the upper groove wall 2a of the meandering main groove 21 extends linearly along the tire circumferential direction when viewed from the tread surface. In this case, fluctuations in the compressive stiffness in the tire circumferential direction of the first land portion 31 (and by extension, the entire land portion constituting the tread surface 1) that forms the first groove wall 2a of the meandering main groove 21 can be more effectively suppressed, and consequently, deterioration of noise performance can be more effectively suppressed. In addition, in this case, the rubber flow during tire manufacturing (especially vulcanization molding) becomes more uniform, leading to the suppression of bare rubber and improvement of uniformity.

[0054] In this embodiment, as described above, the upper groove wall angle θ2a (see Figure 4(a)) at the maximum groove wall angle portion Pamax of the first groove wall 2a of the meandering main groove 21 may be 25° or less. In this case, the groove cross-sectional area of ​​the meandering main groove 21 does not become unnecessarily small, and consequently, sufficient drainage can be ensured, thereby improving drainage more effectively.

[0055] In this embodiment, the upper edge 2bue of the upper groove wall 2b of the meandering main groove 21 extends in a wavy manner along the tire circumferential direction when viewed from the tread surface. In this case, the water flowing through the meandering main groove 21 becomes easier to straighten, and consequently, the drainage performance can be improved more effectively.

[0056] In this embodiment, the amplitude in the tire width direction of the upper edge 2ale of the lower groove wall 2a of the first groove wall 2a of the meandering main groove 21 is smaller than the amplitude in the tire width direction of the upper edge 2ble of the lower groove wall 2b of the meandering main groove 21. In this case, the groove cross-sectional area of ​​the meandering main groove 21 does not become unnecessarily small, and consequently, sufficient drainage can be ensured, thereby improving drainage more effectively.

[0057] In this embodiment, the tire 10 has a plurality of main grooves 2, and the meandering main groove is the outermost main groove 21 in the tire width direction on the vehicle mounting side of the plurality of main grooves 2. Since tires are typically mounted on vehicles with negative camber, the contact pressure on the inner side of the tire is often higher than that on the outer side. Therefore, as mentioned above, by placing the meandering main groove on the outermost part of the tire in the width direction on the inner side of the tire, hydroplaning can be suppressed more effectively, and consequently, drainage can be improved more effectively.

[0058] Other effects of this embodiment are as described above.

[0059] (Second Embodiment) Next, a tire 20 according to a second embodiment of the present invention will be described with reference to Figures 6 and 7. Figure 6 is an enlarged unfolded view similar to Figure 3, showing an enlarged portion of the tread surface of the tire according to the second embodiment of the present invention. Figure 7(a) is a cross-sectional view along the line X3-X3 in Figure 6, and Figure 7(b) is a cross-sectional view along the line X4-X4 in Figure 6. Here, in Figure 6, for ease of understanding, the outlines of the opening edges and raised portions 5 of the main groove 2 (hereinafter simply referred to as "serpentine main groove 2") which is a meandering main groove, are drawn with slightly thicker lines, and the slightly thinner lines between them in Figure 6 are edges (lines) that connect points in the tire circumferential direction where the curvature (and thus the radius of curvature) changes in a cross-sectional view in the tire width direction. In Figure 6, the lateral groove 4 is also drawn with slightly thicker lines. Regarding Figures 6 and 7, components and parts similar to those in Figures 1 to 5 are given the same reference numerals as in Figures 1 to 5, and their descriptions are omitted. The tire 20 according to the second embodiment of the present invention differs from the tire 10 of the first embodiment mainly in that the configuration of the meandering main groove 2 differs from the configuration of the meandering main groove 21 of the tire 10 of the first embodiment of the present invention shown in Figures 2 to 5, and is otherwise substantially the same as the tire 10 of the first embodiment. The following section will describe the second embodiment, focusing on the differences from the first embodiment.

[0060] The number of main grooves 2 extending in the circumferential direction of the tire 20 in the second embodiment is the same as in the first embodiment, and the tire 20 only needs to have at least one main groove. Furthermore, although not shown in the illustrations, in this embodiment, the position of the serpentine main groove 2 shown in Figure 6 on the tread surface may be arbitrary. That is, for example, as in the first embodiment (see Figure 2, etc.), the outermost main groove in the tire width direction on the vehicle mounting side of a plurality of main grooves (for example, four) may be the serpentine main groove 2 shown in Figure 6, or, instead of or in addition to this, at least one of the remaining main grooves may be the serpentine main groove 2 shown in Figure 6. Furthermore, in this embodiment, as in the first embodiment, the configuration and presence or absence of the transverse grooves 4 are arbitrary. In the example shown in Figure 6, each of the land portions 3 on both sides that form the meandering main groove 2 has transverse grooves 4 that communicate with the meandering main groove 2.

[0061] In this embodiment, as shown in Figures 6 and 7(a) and 7(b), the meandering main groove 2 is formed symmetrically with respect to the groove centerline, unlike the meandering main groove 21 of the first embodiment in which the first groove wall 2a side and the second groove wall 2b side are formed asymmetrically with respect to each other. More specifically, in this embodiment, similar to the first embodiment (see Figures 3 and 4(a) and (b)), the first groove wall 2a of the meandering main groove 2 is configured such that a minimum groove wall angle portion Pamin, where the upper groove wall angle θ2a is smallest, and a maximum groove wall angle portion Pamax, where the upper groove wall angle θ2a is largest, alternate along the tire circumferential direction at a predetermined repetition period. On the other hand, unlike the first embodiment, the second groove wall 2b of the meandering main groove 2 is also configured such that a minimum groove wall angle portion Pbmin, where the upper groove wall angle θ2b is smallest, and a maximum groove wall angle portion Pbmax, where the upper groove wall angle θ2b is largest, alternate along the tire circumferential direction at a predetermined repetition period. In this embodiment, as shown in Figure 6, the repetition period for which the upper groove wall angle θ2a of the first groove wall 2a and the upper groove wall angle θ2b of the second groove wall 2b change is the same for both. Consequently, in the meandering main groove 2, the minimum groove wall angle portion Pamin of the first groove wall 2a, the minimum groove wall angle portion Pbmin of the second groove wall 2b, and the wide groove portion Pwb are all at the same position in the tire circumferential direction. Furthermore, in the meandering main groove 2, the maximum groove wall angle portion Pamax of the first groove wall 2a, the maximum groove wall angle portion Pbmax of the second groove wall 2b, and the narrow groove portion Pwn are all at the same position in the tire circumferential direction. Figure 7(a) shows the cross-section of the meandering main groove 2 in the tire width direction at the maximum groove wall angle portion Pamax of the first groove wall 2a and consequently at the maximum groove wall angle portion Pbmax of the second groove wall 2b, and Figure 7(b) shows the cross-section of the meandering main groove 2 in the tire width direction at the minimum groove wall angle portion Pamin of the first groove wall 2a and consequently at the minimum groove wall angle portion Pbmin of the second groove wall 2b.

[0062] In this embodiment, as shown in Figure 6, unlike the first embodiment (see Figure 3), the amplitude of the upper edge 2ale of the lower groove wall of the first groove wall 2a in the tire width direction is the same as the amplitude of the upper edge 2ble of the lower groove wall of the second groove wall 2b in the tire width direction.

[0063] Furthermore, in this embodiment, as shown in Figure 6, similar to the first embodiment (see Figure 3), the upper edge 2aue of the upper groove wall 2a of the meandering main groove 2 extends linearly along the tire circumferential direction when viewed from the tread surface. However, unlike the first embodiment, the upper edge 2bue of the upper groove wall 2b of the meandering main groove 2 also extends linearly along the tire circumferential direction when viewed from the tread surface. In this embodiment, the upper groove wall upper edge 2aue of the first groove wall 2a and the upper groove wall upper edge 2bue of the second groove wall 2b of the meandering main groove 2 may, in a view of the tread surface, extend in a wavy or zigzag pattern along the tire circumferential direction, similar to the upper groove wall upper edge 2aue of the first groove wall 2a of the meandering main groove 21 in the first embodiment, such that the amplitude in the tire width direction is smaller than the amplitude in the tire width direction of the lower groove wall upper edge 2ale of the first groove wall 2a or the lower groove wall upper edge 2ble of the second groove wall 2b.

[0064] In this embodiment, as shown in Figures 6 and 7(a) and 7(b), the meandering main groove 2 has a raised portion 5 formed at the groove bottom 2c that rises outward in the radial direction of the tire, similar to the first embodiment. The raised portion 5 is formed in the region including the wide groove portion Pwb in the circumferential direction of the tire, similar to the first embodiment. The raised portion 5 is formed in an elongated vertical shape in the circumferential direction of the tire, similar to the first embodiment, when viewed from the tread surface. However, in this embodiment, as shown in Figures 7(a) and 7(b), the cross-sectional shape of the raised portion 5 in the tire width direction is different from the first embodiment, being formed in a rectangular shape. In this embodiment, the dimensions of the raised portion 5 may be the same as those of the raised portion 5 in the first embodiment.

[0065] The tire 20 according to the second embodiment of the present invention, configured as described above, can also improve drainage performance while suppressing deterioration of noise performance, similar to the tire 10 of the first embodiment described above. Comparing the tire 10 of the first embodiment with the tire 20 of the second embodiment, in the tire 10 of the first embodiment shown above, the entire second groove wall 2b, including the upper edge 2bue of the upper groove wall of the second groove wall 2b, extends in a wavy shape along the tire circumferential direction when viewed from the tread surface. This makes it easier for water that enters the meandering main groove 21 to be straightened, and consequently, it has superior drainage performance. Furthermore, in the tire 20 of the second embodiment shown above, the upper edge 2bue of the upper groove wall of the second groove wall 2b extends linearly along the tire circumferential direction when viewed from the tread surface, similar to the upper edge 2aue of the upper groove wall of the first groove wall 2a. This reduces fluctuations in the compressive stiffness in the tire circumferential direction, and consequently, it is easier to suppress deterioration of noise performance. Furthermore, the raised portion 5 formed on the tire 20 of the second embodiment also facilitates the flow of water that has entered the meandering main groove 2 along the first groove wall 2a and the second groove wall 2b, thereby effectively improving drainage. The other configurations and effects of the tire 20 of this embodiment are the same as those of the tire 10 of the first embodiment described above.

[0066] The above describes exemplary embodiments of the present invention, and various modifications can be made without departing from the scope of the claims. For example, the tire 10 in the first embodiment described above is a tire whose mounting direction on the vehicle is specified by markings on the tire or by an instruction manual, but the tire of the present invention may be a tire in which the mounting direction on the vehicle is not specified. Furthermore, for example, in the tire 10 of the first embodiment described above, the first groove wall 2a, whose upper groove wall angle changes, is positioned on the vehicle-mounted side and on the outside in the tire width direction relative to the second groove wall 2b. However, the tire width direction positions of the first groove wall 2a and the second groove wall 2b may be reversed, so that the first groove wall 2a is positioned on the vehicle-mounted side and on the inside in the tire width direction relative to the second groove wall 2b. [Industrial applicability]

[0067] The tire according to the present invention can be suitably used for any type of pneumatic tire, for example, pneumatic tires for passenger cars, pneumatic tires for trucks and buses, etc. [Explanation of symbols]

[0068] 10, 20: Tires, 1: Tread surface, 2, 21, 22, 23, 24: Main groove, 2a: 1st groove wall, 2b: 2nd groove wall, 2c: groove bottom, 2au, 2bu: Upper groove wall portion, 2aue, 2bue: Upper edge of the upper groove wall, 2al, 2bl: Lower groove wall portion, 2ale, 2ble: Upper edge of the lower groove wall, 3, 31, 32, 33, 34, 35: Rikube, 4, 41, 42, 43, 44, 45, 46, 47: Yokomizo, 5: Protuberance, CD: Circumferential direction of the tire, CL: Equatorial direction of the tire, D: Groove depth, IN: Inner side of the vehicle mounting surface. Lr: Length of the raised part, Hr: Height of the raised part, OUT: Outer side when mounted on the vehicle. Pamin, Pbmin: minimum groove wall angle part, Pamax, Pbmax: Maximum groove wall angle portion, Pwb: Wide groove section, Pwn: Narrow groove section, TE: Tread edge, WD: Tire width direction, Wa: Amplitude, Wb: Groove bottom width, Wr: Width of raised section, Wo: Groove opening width Ww: Groove wall spacing, Wwmin: Minimum groove wall spacing, Wwmax: Maximum groove wall spacing, θ2a, θ2b: Upper groove wall angle

Claims

1. A tire having at least one main groove extending in the circumferential direction of the tire on the tread surface, At least one of the main grooves is a meandering main groove in which, when viewed from the tread surface, at least a portion of the groove surface extends in a wavy manner along the circumferential direction of the tire. In the meandering main groove, the first groove wall, which is the groove wall on one side in the tire width direction, and the second groove wall, which is the groove wall on the other side in the tire width direction, each have, in a cross-sectional view in the tire width direction, an upper groove wall portion that extends linearly or in an arc shape with a constant curvature having the center of curvature on the groove side from the tread surface, and a lower groove wall portion that extends in an arc shape with a constant curvature having the center of curvature on the groove side, connected to the upper groove wall portion, and the upper groove wall portion is connected to the groove bottom via the lower groove wall portion. In a cross-sectional view in the width direction of the tire, the angle of the upper groove wall portion on the tread surface with respect to the normal line drawn on the tread surface is called the upper groove wall angle, and in a cross-sectional view in the width direction of the tire, the upper end of the upper groove wall portion and the boundary between the upper groove wall portion and the lower groove wall portion, which are connected in the circumferential direction of the tire, are called the upper groove wall upper edge and the lower groove wall upper edge, respectively, and furthermore, the distance in the width direction of the tire between the upper groove wall edges of the lower groove walls on both groove walls of the meandering main groove is called the groove wall spacing, The first groove wall of the meandering main groove has a minimum groove wall angle portion where the upper groove wall angle is smallest, and a maximum groove wall angle portion where the upper groove wall angle is largest, which alternate along the tire circumferential direction at a predetermined repeating period, such that the upper edge of the lower groove wall extends in a wavy shape along the tire circumferential direction when viewed from the tread surface. The second groove wall of the meandering main groove has an upper edge of the lower groove wall that extends in a wavy shape along the tire circumferential direction when viewed from the tread surface. The portion of the first groove wall of the meandering main groove with the minimum groove wall angle is at the same position in the tire circumferential direction as the wide groove portion where the groove wall spacing of the meandering main groove is maximum, and the portion of the first groove wall of the meandering main groove with the maximum groove wall angle is at the same position in the tire circumferential direction as the narrow groove portion where the groove wall spacing of the meandering main groove is minimum. The upper edge of the upper groove wall of the first groove wall of the meandering main groove extends in a linear, wavy, or zigzag pattern along the tire circumferential direction when viewed from the tread surface, such that the amplitude in the tire width direction is smaller than the amplitude in the tire width direction of the upper edge of the lower groove wall of the first groove wall. A tire in which the amplitude in the tire width direction of the upper edge of the lower groove wall of the first groove wall of the meandering main groove is smaller than the amplitude in the tire width direction of the upper edge of the lower groove wall of the second groove wall of the meandering main groove.

2. The tire according to claim 1, wherein the upper edge of the upper groove wall of the first groove wall of the meandering main groove extends linearly along the tire circumferential direction when viewed from the tread surface.

3. The tire according to claim 1, wherein the upper groove wall angle of the portion of the first groove wall of the meandering main groove that has the maximum groove wall angle is 25° or less.

4. The tire according to any one of claims 1 to 3, wherein the upper edge of the upper groove wall of the second groove wall of the meandering main groove extends in a wavy manner along the tire circumferential direction when viewed from the tread surface.

5. The aforementioned tire has a plurality of main grooves, The tire according to claim 1, wherein the meandering main groove is the outermost main groove in the tire width direction on the vehicle mounting side of the plurality of main grooves.

Images