pneumatic tires

Abstract

Pneumatic tires (10), including: a pair of first main grooves (11, 11a) extending in the circumferential direction (C) of the tire, which are formed in a tire width direction on opposite outer sides of a first rib section (21) which includes an equatorial plane (E) of the tire; a pair of second main grooves (12, 12a) extending in the circumferential direction (C) of the tire, which are arranged further outwards in the width direction of the tire than the first main grooves (11, 11a); and Auxiliary grooves (31) are arranged in second web sections (22) located between the first main grooves (11, 11a) and the second main grooves (12, 12a), which open towards the corresponding first main groove (11, 11a) or the corresponding second main groove (12, 12a) and end in the corresponding second web section (22); wherein each of the auxiliary grooves (31) bends at a curved section (S2) and includes a first auxiliary groove (31A) extending from the opening (S1) to the curved section (S2) and a second auxiliary groove (31B) extending from the curved section (S2) to a blind-ending section (S3); a length a of the first auxiliary groove (31A) and a length b of the second auxiliary groove (31B) are in a ratio of 0.3a < b < 0.8a to each other; an angle θ formed by the first auxiliary groove (31A) and the second auxiliary groove (31B) on the curved section (S2) lies in a range of 0° < θ < 90°; the groove width of the first auxiliary groove (31A) gradually decreases as the first auxiliary groove (31A) extends from the opening (S1) towards the curved section (S2); an angle φ is defined as an angle of a tangent (S6) of a center line (S4) at the opening (S1) of the first auxiliary groove (31A) with respect to the tire circumferential direction (C), the angle φ lies between 30° and 70°; the pneumatic tire (10) has second narrow grooves (41) arranged in the second rib sections (22), wherein the second narrow grooves (41) form an angle α with the tire circumferential direction (C) of 30° to 70°; the first auxiliary grooves (31A) cut the second narrow grooves (41); and The angle φ and the angle α are in a plus / minus opposite relationship to each other.

Description

Technical area

[0001] The present invention relates to a pneumatic tire. State of the art

[0002] The goal for pneumatic tires is to improve quietness, i.e., reduce driving noise. However, improvements in quietness tend to reduce performance in other areas. Through further developments in tire structure and surface patterns, the performance of pneumatic tires is continually being improved in various areas. For all-season pneumatic tires designed for wet and snow performance, patterns that improve wet and snow performance tend to reduce quietness.

[0003] A pneumatic tire that reduces driving noise is known, which includes a plurality of arcuate lug grooves arranged in a land portion of a tread portion. The lug grooves promote the dissipation of air column resonance in the main grooves (see, for example, Patent Document 1 and Patent Document 2).

[0004] Furthermore, a pneumatic tire is known that is designed to provide improved steering stability on wet road surfaces while ensuring adequate performance on snow. This is achieved by a configuration including sub-grooves that terminate in a land portion and are bent in the opposite direction (see, for example, Patent Document 3). List of citationsPatent literature Patent Document 1: Unexamined Japanese Patent Application, Publication No. JP 2012 - 171 479 A Patent Document 2: Unexamined Japanese Patent Application, Publication No. JP 2007 - 237 816 A Patent Document 3: Unexamined Japanese Patent Application, Publication No. JP 2010-47134 A

[0005] EP 2 193 937 A1 discloses a pneumatic tire having a sound absorption effect through lateral grooves. The tire tread has circumferential grooves continuously formed in the circumferential direction and lateral grooves extending from a circumferential groove. One end of each lateral groove is connected to the circumferential groove, and the other end is a closed end. Each of the lateral grooves includes a one-way groove extending in one direction from the circumferential groove to a side edge of the tire, and an opposite-way groove extending in another direction from the circumferential groove to the side edge of the tire. A root portion of the one-way groove located near the circumferential groove and a root portion of the opposite-way groove located near the circumferential groove are formed by a common groove.A leading part of the groove running in one direction and a leading part of the groove running in the other direction branch off from each other from a leading end of the common groove.

[0006] JP 2010-47134 A discloses a pneumatic tire in which a pair of first main grooves and a pair of second main grooves are formed on both sides of a tire equator line of a tread surface, each extending in the tire circumferential direction, and five land portions are formed on the tread surface. The centers of these main grooves are set at predetermined positions. In second land portions separated by the first main grooves and the second main grooves located on either side thereof, a plurality of sub-grooves are formed. The sub-grooves extend obliquely in the tire width direction from the second main grooves toward the first main grooves, are curved in the opposite direction on the side of the first main grooves, and then terminate in the land portions. The length of a center line of each of these sub-grooves is 1.25 to 1.75 times the pitch length of the sub-groove.

[0007] JP 2005 161 921 A discloses a pneumatic tire having central land portions and lateral land portions defined by an arrangement of central main grooves and lateral main grooves on the half regions of a tread portion divided by a centerline of a pattern. Lateral land portions are formed as a block row consisting essentially of blocks formed by the arrangement of intersecting grooves. In the central land portions, blocks are formed by arranging first slant grooves opening toward the lateral main grooves and extending toward the central main grooves and terminating at the position forward of the central main grooves, peripheral grooves extending from the end portions of the first slant grooves, and second slant grooves extending from the end portions of the peripheral grooves and opening into the lateral main grooves. Summary of the inventionTechnical problem

[0008] The pneumatic tires described in Patent Documents 1 to 3 have improved wet performance and snow performance, but there is still room for improvement in terms of quietness.

[0009] It is an object of the present invention to provide a pneumatic tire with improved wet performance, snow performance, and low noise. Summary of the invention

[0010] In order to achieve the above-described object, a pneumatic tire according to the invention comprises: a pair of first tire circumferentially extending main grooves formed in a tire width direction on opposite outer sides of a first land portion including an equatorial plane of the tire, are trained; a pair of second main grooves extending in the tire circumferential direction and arranged further outward in the tire width direction than the first main grooves; and auxiliary grooves arranged in second web sections lying between the first main grooves and the second main grooves, which auxiliary grooves open towards the corresponding first main groove or the corresponding second main groove and end in the corresponding second web section; wherein each of the auxiliary grooves bends at a bent portion and includes a first auxiliary groove extending from the opening to the bent portion and a second auxiliary groove extending from the bent portion to a blind-ended portion; a length a of the first auxiliary groove and a length b of the second auxiliary groove are in a ratio of 0.3a < b < 0.8a to each other; and an angle θ formed by the first auxiliary groove and the second auxiliary groove at the bent portion is in a range of 0° < θ < 90°.

[0011] The pneumatic tire according to the invention preferably further comprises third land portions arranged further outward in the tire width direction than the second auxiliary grooves, and third auxiliary grooves arranged in the third land portions and extending outward in the tire width direction; wherein the end portions of the third auxiliary grooves end near the second main grooves in the third land portions.

[0012] The pneumatic tire according to the invention further comprises first narrow grooves arranged in the first land portions.

[0013] The pneumatic tire according to the invention preferably has a configuration in which the first narrow grooves end in the first land portions.

[0014] The pneumatic tire according to the invention preferably has a configuration in which the first narrow grooves have a width of 1.2 mm or less.

[0015] The pneumatic tire according to the invention preferably has a configuration in which the second land portions have a point-symmetric configuration with respect to an equatorial plane of the tire.

[0016] The pneumatic tire according to the invention preferably has a configuration in which a groove width of the first auxiliary groove at the bent portion is 10% to 50% smaller than a groove width at the opening portion.

[0017] The pneumatic tire according to the invention has a configuration in which the first auxiliary groove forms an angle with the tire circumferential direction of 30° to 70°.

[0018] The pneumatic tire according to the invention further comprises second narrow grooves arranged in the second land portion, wherein the second narrow grooves form an angle with the tire circumferential direction of 30° to 70°.

[0019] The pneumatic tire according to the invention has a configuration in which the first auxiliary grooves intersect the second narrow grooves.

[0020] The pneumatic tire according to the invention preferably has a configuration in which the second narrow grooves have a width of 1.2 mm or less.

[0021] The pneumatic tire according to the invention preferably has a configuration in which the first auxiliary grooves open towards the second main grooves.

[0022] The pneumatic tire according to the invention preferably further comprises third narrow grooves arranged in the third land portions, the third narrow grooves extending in a shoulder direction.

[0023] The pneumatic tire according to the invention preferably has a configuration in which the third narrow grooves do not open toward the second cup grooves.

[0024] The pneumatic tire according to the invention preferably has a configuration in which the third narrow grooves have a width of 1.2 mm or less.

[0025] The pneumatic tire according to the invention preferably has a configuration in which sidewalls extend in the tire width direction of the first main grooves and the second main grooves have a zigzag shape in which a position of the sidewalls in the tire circumferential direction changes regularly. Advantageous effects of the invention

[0026] According to the pneumatic tire of the present invention, snow performance and quietness can be improved while maintaining wet performance, and thus a high degree of wet performance, snow performance and quietness can be achieved. Brief description of the drawings Fig. 1 is a meridian cross-sectional view illustrating a pneumatic tire according to an embodiment of the present invention. Fig. 2 is a development view illustrating a tread pattern of the pneumatic tire according to the embodiment of the present invention. Fig. Figure 3 is a plan view looking toward a second land portion of the tread pattern of Fig. 2 is focused. Fig. Figure 4 is a plan view of the second land portion of the tread pattern of Fig. 2 is focused. Fig. 5 is a development view illustrating another example of a tread pattern of a pneumatic tire according to the embodiment of the present invention. Description of the embodiment

[0027] Embodiments of the pneumatic tire according to the invention will be described below with reference to the drawings. However, the present invention is not limited to these embodiments. Furthermore, the components of the embodiments include components that are interchangeable without affecting the consistency of the invention, as well as obviously interchangeable components. Furthermore, modified examples described in the embodiments can be combined as desired within the scope obvious to one skilled in the art.

[0028] Fig.1 is a meridian cross-sectional view illustrating a pneumatic tire according to one embodiment of the present invention. Fig. 2 is a development view illustrating a tread pattern of the pneumatic tire according to the embodiment of the present invention. Fig. Figure 3 is a plan view looking toward a second land portion of the tread pattern of Fig. 2 is focused. Fig. Figure 4 is a plan view of the second land portion of the tread pattern of Fig. 2 is focused.

[0029] In the following description, "tire radial direction" refers to the direction perpendicular to the rotation axis (not shown) of a pneumatic tire 10. "Tire radial inward" refers to the direction facing the rotation axis in the tire radial direction, and "tire radial outward" refers to the direction away from the rotation axis in the tire radial direction. The "tire circumferential direction" refers to the circumferential direction with the rotation axis as the center axis. Furthermore, "tire width direction" refers to the direction parallel to the rotation axis. "Tire width inward" refers to the direction facing an equatorial plane of the tire E in the tire width direction, and "tire width outward" refers to the direction away from the equatorial plane of the tire E in the tire width direction."Equatorial plane of the tire E" refers to a plane orthogonal to the rotation axis of the pneumatic tire 10 and passing through the center of the pneumatic tire 10 in the tire width direction. "Tire width" is a width in the tire width direction between components located outward in the tire width direction, or in other words, the distance between the components farthest outward in the tire width direction from the equatorial plane of the tire E. "Tire equator line" refers to a line along the tire circumferential direction of the pneumatic tire 10 that lies on the equatorial plane of the tire E.

[0030] As in Fig.1, the pneumatic tire 10 of the present embodiment is provided with a tread portion 1 extending in the tire circumferential direction to form an annular shape, a pair of sidewall portions 2, 2 arranged on both sides of the tread portion 1, and a pair of bead portions 3, 3 arranged on the inner side of the sidewall portions 2 in the tire radial direction.

[0031] A carcass layer 4 is disposed between the pair of bead portions 3, 3. The carcass layer 4 includes a plurality of reinforcing cords extending in the tire radial direction and folded back from a tire inner side to a tire outer side around a bead core 5 disposed in each of the bead portions 3. A bead filler 6 having a triangular cross-sectional shape and formed from a rubber composition is disposed on a periphery of the bead cores 5.

[0032] A plurality of belt layers 7 are embedded on an outer circumferential side of the carcass layer 4 in the tread portion 1. These belt layers 7 include a plurality of reinforcing cords inclined with respect to the tire circumferential direction, with the reinforcing cords of different layers arranged to intersect each other. In the belt layers 7, the inclination angle of the reinforcing cords with respect to the tire circumferential direction is set in a range of, for example, 10° to 40°. Steel cords are preferably used as the reinforcing cords of the belt layers 7. To improve high-speed durability, at least one belt cover layer 8 is arranged on the outer circumferential side of the belt layers 7, in which the reinforcing cords are oriented at an angle of, for example, 5° or less to the tire circumferential direction.Organic fiber cord made of nylon, aramid or the like is preferably used as reinforcing steel cords of the belt cover layer 8.

[0033] It should be noted that the tire inner structure described above is an embodiment of a pneumatic tire, but is not limited thereto.

[0034] As in Fig.As illustrated in Fig. 2, a pair of first main grooves 11 and a pair of second main grooves 12 are formed in the tread portion 1. The first main grooves 11 are located on opposite sides of the equatorial plane of the tire E and extend in the tire circumferential direction C. The second main grooves 12 are located on opposite sides of the equatorial plane of the tire E, farther outward in the tire width direction than the first main grooves 11, and extend in the tire circumferential direction. The first main grooves 11 and the second main grooves 12 have, for example, a groove width of 5.0 (mm) to 15.0 (mm) and a groove depth of 5.0 (mm) to 15.0 (mm) measured in the tire width direction. It should be noted that the groove width and groove depth of the first main grooves 11 and the second main grooves 12 are not limited to the ranges described above.

[0035] The first main grooves 11 and second main grooves 12 formed in the tread portion 1 define a plurality of land portions. More specifically, the tread portion 1 includes a land portion located between the pair of first main grooves 11 that intersect the equatorial plane of the tire E and extend in the tire circumferential direction. This land portion is referred to as a first land portion 21. The tread portion 1 includes land portions between the first main grooves 11 and the second main grooves 12 that extend in the tire circumferential direction. These land portions are referred to as second land portions 22. In addition, the tread portion 1 includes land portions located outward in the tire width direction of the second main grooves 12. These land portions are referred to as third land portions 23.

[0036] In the first land portion 21 of the tread portion 1, a plurality of first narrow grooves 32 are formed at equal intervals in the tire circumferential direction C. The plurality of first narrow grooves 32 are formed in such an orientation that they extend in the tire width direction. Each first narrow groove 32 terminates at both end portions in the first land portion 21. More specifically, each first narrow groove 32 terminates before the equatorial plane of the tire E without crossing the equatorial plane of the tire E and also terminates in the first land portion 21 without opening to the corresponding first main groove 11. The first narrow grooves 32 are, for example, sipes. The same applies to other narrow grooves described below. Note that the width of the first narrow grooves 32 is 1.2 (mm) or less.

[0037] The second land portions 22 are arranged on opposite sides of the equatorial plane of the tire E. The second land portions 22 on opposite sides of the equatorial plane of the tire E have the same shape when rotated 180°. Accordingly, the second land portions 22 are arranged point-symmetrically across the equatorial plane of the tire E.

[0038] In the land portions 22 arranged between the first main grooves 11 and the second main grooves 12, a plurality of auxiliary grooves 31 are formed at equal intervals in the tire circumferential direction C. The auxiliary grooves 31 have a curved shape of a bent fish hook. As shown in Fig. 3 and Fig.4, each auxiliary groove 31 opens at one end portion toward the second main groove 12 and terminates at the second end portion, a blind-ended end portion S3, in the second land portion 22. Each auxiliary groove 31 is composed of a first auxiliary groove 31A and a second auxiliary groove 31B. The first auxiliary groove 31A extends from an opening portion to the second main groove 12, which is an open end S1, to a curvature point S2. The second auxiliary groove 31B extends from the curvature point S2 to the blind-ended end portion S3. The positions of the open end S1, the curvature point S2, and the blind-ended end portion S3 are determined using center lines passing through the center in the tire width direction of the first auxiliary groove 31A and the second auxiliary groove 31B. In other words, the curvature point S2 is an intersection point between the center line of the first auxiliary groove 31A and the center line of the second auxiliary groove 31b.Each auxiliary groove 31 has a shape in which the second auxiliary groove 31B is bent from the curvature point S2 toward the end S1 open to the second main groove 12, and the blind-ended end portion S3 is located near the first auxiliary groove 31A.

[0039] The first auxiliary groove 31A of the present embodiment is formed with the open end S1 on the side with the second main groove 12. However, in other embodiments, the open end S1 may be located on the side of the first main groove 11.

[0040] The open end S1 of the auxiliary groove 31 has a width larger than the width of other portions. The groove width of the first auxiliary groove 31A of the auxiliary groove 31 decreases smoothly as the first auxiliary groove 31A narrows from the open end S1, which is the opening portion, toward the bending point S2, which is a bent portion. In the present embodiment, a groove width H2 of the first auxiliary groove 31A at the bent portion is from 10% to 50% narrower than the groove width H1 at the opening portion. In other words, the groove width H2 at the bent portion is from 50% to 90% of the groove width H1 at the open end S1. The groove width of the first auxiliary groove 31A at the bent portion is the width of the groove wall surface of the second auxiliary groove 31B when the groove wall is stretched out.In this way, the groove width of the first auxiliary groove 31A gradually decreases as the first auxiliary groove 31A extends from the open end S1 toward the bending point S2, and the second auxiliary groove 31B is angled from the bending point S2 and ends at the blind-ended end portion S3.

[0041] The first auxiliary groove 31A and the second auxiliary groove 31B, which constitute the auxiliary groove 31, have a length a and a length b, respectively. The ratio between the length a and the length b is: 0.3a <b<0,8a. In other words, the length b of the second auxiliary groove 31B is more than 30% and less than 80% of the length a of the first auxiliary groove 31A. The length of the first auxiliary groove 31A, as shown in Fig.3, is the length of a center line S4 extending from the open end S1 to the curvature point S2 and passing through the centers in the width direction of the first auxiliary groove 31A. The length b of the second auxiliary groove 31B, as shown in Fig. 3, is the length of a center line S5 extending from the blind-ended end portion S3 to the curvature point S2 and passing through the center points in the width direction of the second auxiliary groove 31B. Note that the wall surface constituting the first auxiliary groove 31A has a length a', and the wall surface constituting the second auxiliary groove 31B has a length b'. The relationship between the length a' and the length b' is preferably similar to that described above, namely: 0.3a′ <b′<0,8a′.

[0042] In addition, an angle θ formed by the first auxiliary groove 31A and the second auxiliary groove 31B is preferably an acute angle in the following range: 0°<θ<90°. In embodiments in which the wall surface of the first auxiliary groove 31A or the second auxiliary groove 31B is curved, the angle θ of the tangent at each point of the curved line of the curved surface in a plan view is preferably in the following range: 0°<θ<90°.

[0043] A plurality of second narrow grooves 41, which are inclined with respect to the tire circumferential direction C, are formed at equal intervals in the second land portion 22 in the tire circumferential direction C. The second narrow grooves 41 are inclined with respect to the tire circumferential direction. The second narrow grooves 41 are formed to span the second land portion 22 and intersect the auxiliary grooves 31. An inclination angle α of the second narrow grooves 41 with respect to the tire circumferential direction C is preferably from 30° to 70°.

[0044] Furthermore, as in Fig.As illustrated in Figure 3, in the pneumatic tire 10, an angle φ and the inclination angle α of the second narrow grooves 41 with respect to the tire circumferential direction C are in a plus / minus opposite relationship to each other. The angle φ is the angle of a tangent S6 of the center line S4 at the open end S1 of the first auxiliary groove 31A with respect to the tire circumferential direction C. Consequently, the first auxiliary groove 31A and the second narrow grooves 41 intersect.

[0045] A plurality of lug grooves extending outward in the tire width direction are arranged at equal intervals in the tire circumferential direction C in each of the third land portions 23 located in shoulder regions of the tread portion 1. These lug grooves are referred to as third auxiliary grooves 33. Each third auxiliary groove 33 terminates at the end portion near the second main groove 12 in the third land portion 23.

[0046] In addition, third narrow grooves 43 are arranged in the third land sections 23. The third narrow grooves 43 are preferably straight or curved. Inner sections of the third narrow grooves 43 are preferably curved, or in other words, the third narrow grooves 43 are preferably 3D sipes. The third narrow grooves 43 preferably have a shape that represents only a line even after wear. The third narrow grooves 43 do not open toward the second main grooves 12.

[0047] In addition, a narrow longitudinal groove 53 extending in the tire radial direction is formed in each of the third land portions 23. There are no particular restrictions on the groove width of the narrow longitudinal grooves 53, but they may, for example, be in a range of 1 (mm) to 25 (mm).

[0048] The above-described pneumatic tire of the present embodiment includes: a pair of first main grooves 11 extending in the tire circumferential direction C, which are formed on opposite outer sides in a tire width direction of a first land portion 21 including an equatorial plane of the tire E; a pair of second main grooves 12 extending in the tire circumferential direction C, which are arranged further outward in the tire width direction than the first main grooves 11; in at least one of the second land sections 22 arranged between the first main grooves 11 and the second main grooves 12, auxiliary grooves 31 which open towards the corresponding first main groove (11) or the corresponding second main groove (12) and end in the corresponding second land section 22.

[0049] Each of the auxiliary grooves 31 bends at a bent portion and includes a first auxiliary groove 31A extending from the opening to the bent portion and a second auxiliary groove 31B extending from the bent portion to a blind-ended portion. The length a of the first auxiliary groove 31A and the length b of the second auxiliary groove 31B are in a relationship of 0.3a < b < 0.8a. The angle θ formed by the first auxiliary groove 31A and the second auxiliary groove 31B at the bent portion is in a range of 0° < θ < 90°. According to this pneumatic tire, snow performance and quietness can be improved while maintaining wet performance, and thus, high levels of wet performance, snow performance, and quietness can be achieved.

[0050] In addition, the tread portion of the present embodiment further includes the third land portions 23 arranged outward in the tire width direction of the second main grooves 12. Each third land portion 23 includes third auxiliary grooves 33, which are lug grooves extending outward in the tire width direction. The end portions of each auxiliary groove 33 near the second main groove 12 terminate in the third land portion 23. By eliminating the groove opening toward the second main groove 12, noise can be suppressed.

[0051] Furthermore, the first land portion 21 is arranged between the first main grooves 11 and intersects the equatorial plane of the tire E. In the first land portion 21, which is a central portion of the tire, the first narrow grooves 32 are arranged instead of the auxiliary grooves. By using narrow grooves instead of auxiliary grooves, the ground contact area can be ensured in the central portion of the tire, which increases traction, especially during driving.

[0052] In addition, the first narrow grooves 32 in the first land portion 21 do not open toward the first main grooves 11 and end in the first land portion 21. By having the first narrow grooves 32 in a shape that does not open toward the first main grooves 11, the air column resonance of the first main grooves 11 can be suppressed.

[0053] The second land portions 22 are arranged on opposite sides of the equatorial plane of the tire E. The second land portions 22 on opposite sides of the equatorial plane of the tire E have the same shape when rotated 180°. Accordingly, the second land portions 22 are arranged point-symmetrically across the equatorial plane of the tire E. By equally arranging the second land portions 22 on the inner side in the vehicle width direction and the outer side in the vehicle width direction, water drainage properties can be ensured when driving straight on wet roads.

[0054] In the present embodiment, the open end S1 of the auxiliary groove 31 is located near the second main groove 12. By making the auxiliary groove 31 wider at the open end S1 located on the outer side in the tire width direction than at other portions, snow performance can be improved.

[0055] In the present embodiment, the groove width H2 of the first auxiliary groove 31A at the bent portion is 10% to 50% smaller than the groove width H1 at the opening portion. In other words, the groove width H2 at the bent portion is 50% to 90% of the groove width H1 at the opening portion. Consequently, the drainage of snow and water through the grooves improves, enabling the improvement of on-snow performance and wet performance. It should be noted that in the auxiliary groove 31, if the difference in groove depth from the opening portion to the blind-ended portion is too large, the quietness is adversely affected and other problems related to wear and so on occur. According to the present embodiment, such problems do not exist.

[0056] The plurality of third auxiliary grooves 43, which are lug grooves extending in the tire width direction, are arranged at equal intervals in the tire circumferential direction C in each of the third land portions 23 located in shoulder regions of the tread portion 1. By arranging the third narrow grooves 43 in the shoulder regions of the tread portion 1, snow performance can be improved.

[0057] The third narrow grooves 43 do not open toward the second main grooves 12. Because the third narrow grooves 43 do not open toward the second main grooves 12, driving noise caused by air column resonance from the second main grooves 12 can be suppressed, thus further improving the low noise level.

[0058] The pneumatic tire described above includes a plurality of second main grooves 31B having a curved shape arranged in the second land portions 22 located between the first auxiliary grooves 11 and the second auxiliary grooves 12, wherein the land portions 22 are not divided into a plurality of blocks. As a result, an increase in tread noise can be prevented. Furthermore, since the plurality of auxiliary grooves 31B having a curved shape opens toward the second main grooves 12, the air column resonance from the second main grooves 12 can be dampened by the noise-damping effect of the auxiliary grooves 31.

[0059] Furthermore, by having the auxiliary grooves 31 in a shape in which the second auxiliary groove 31B curves toward the first auxiliary groove 31A at the curvature point S2, the wet performance and the snow performance can be improved through the action of the edges of the first auxiliary grooves 31A and the second auxiliary grooves 31B. Specifically, the auxiliary groove 31 has a structure in which the groove width of the first auxiliary groove 31A gradually decreases as the first auxiliary groove 31A extends from the open end S1 toward the curvature point S2, thus assisting in the discharge of snow accumulated in the auxiliary groove 31. As a result, deterioration in the snow performance caused by snow accumulation can be prevented.Furthermore, in embodiments in which the groove width of the first auxiliary groove 31A gradually decreases as the auxiliary groove 31A extends from the open end S1 to the bending point S2, the drainage of water in the auxiliary grooves 31 is improved, whereby an improvement in wet performance can be achieved.

[0060] In the pneumatic tire described above, the first main grooves 11 are arranged farther outward in the tire width direction than the equatorial plane of the tire, and the second main grooves 12 are arranged farther outward in the tire width direction than the first main grooves 11. An end portion of the first auxiliary grooves 31A opens toward the second main groove 12, thus, the auxiliary groove 31 opens outward at an end portion in the tire width direction. As a result, excellent snow performance can be exhibited.

[0061] Furthermore, in the pneumatic tire described above, the first land portion 21 is arranged on the equatorial plane of the tire E, and the second land portions 22 including the plurality of auxiliary grooves 31 are arranged on opposite sides of the first land portion 21. As a result, the braking performance on snow is improved, and thus excellent snow performance is enabled.

[0062] As in Fig.As illustrated in Figure 3, the bending angle θ between the first auxiliary groove 31A and the second auxiliary groove 31B of the auxiliary groove 31 is less than 90°. As a result, the performance of the edges of the auxiliary grooves 31 can be sufficiently ensured, and thus, the snow performance can be improved. The first auxiliary groove 31A and the second auxiliary groove 31B can be formed in a straight line or a curved line. In either case, the bending angle θ is the angle at the curvature point S2 formed by the first auxiliary groove 31A and the second auxiliary groove 31B. Note that when the bending angle θ is 90° or larger, the pitch between the auxiliary grooves 31 must be increased, and therefore the performance of the edges becomes insufficient.

[0063] As described above, the plurality of second narrow grooves 41 inclined with respect to the tire circumferential direction C are arranged in every second land portion 22 at equal intervals in the tire circumferential direction C. By setting the inclination angle α of the second narrow grooves 41 with respect to the tire circumferential direction C in the range of 30° to 70°, the snow performance and the wet performance can be improved by the action of the edges of the second narrow grooves 41.

[0064] In addition, as described above and in Fig.As illustrated in Fig. 3, the angle φ of the tangent S6 of the center line S4 at the open end S1 of the first auxiliary groove 31A with respect to the tire circumferential direction C and the inclination angle α of the second narrow grooves 41 with respect to the tire circumferential direction C are in a plus / minus relationship with each other, and the first auxiliary grooves 31A and the narrow grooves 41 intersect. By intersecting the second narrow grooves 41 and the first auxiliary grooves 31A, uneven collapse of the second land portions 22 caused by the first auxiliary grooves 31A can be prevented. When the inclination angle α of the second narrow grooves 41 with respect to the tire circumferential direction C is outside the above-described range, the improvement in snow performance and the improvement in wet performance will be lower.

[0065] Fig.5 is a development view illustrating another example of a tread pattern of a pneumatic tire according to the embodiment of the present invention. As shown in Fig.As illustrated in Fig. 5, a pair of first main grooves 11a (first main grooves) and a pair of second main grooves 12a (second main grooves) are formed in the tread portion 1a. The first main grooves 11a are arranged on opposite sides of the equatorial plane of the tire E in the tire circumferential direction. The second main grooves 12a are arranged on opposite sides of the equatorial plane of the tire E, farther outward in the tire width direction than the first main grooves 11, and extend in the tire circumferential direction. Both the main grooves 11a and the main grooves 12a have a zigzag shape. The zigzag shape of the main grooves 11a and the main grooves 12a may meander at angles in the tire circumferential direction, or may meander in a smooth curve in the tire circumferential direction.In other words, the zigzag shape of the present embodiment [may] have a shape in which the position in the tire width direction of the sidewalls of the main grooves 11a and the main grooves 12a extending in the tire circumferential direction changes regularly. The main grooves 11a and the main grooves 12a include two sidewalls extending in the tire circumferential direction. Both sidewalls have a zigzag shape. The main grooves 11a and the main grooves 12a need only have a zigzag shape in the road contact surface that comes into contact with the road during driving. The sidewalls of the main grooves 11a and the main grooves 12a may have a zigzag shape from the road contact surface to the groove bottom, or they may have a zigzag shape formed by chamfering the sidewalls on the side near the road contact surface.Furthermore, the main grooves 11a and the main grooves 12a are preferably provided in the tire circumferential direction, with at least one zigzag pattern repeating between lug grooves of the same shape. Furthermore, the zigzag shape has the same wave-like pattern throughout the tire circumferential direction, but different wave-like shapes may be formed throughout the tire circumferential direction. The dimensions of the main grooves 11a and the main grooves 12a are not particularly limited. For example, the groove width, as measured in the tire width direction, may be from 5.0 (mm) to 15.0 (mm), and the groove depth may be from 5.0 (mm) to 15.0 (mm).

[0066] By forming the main grooves 11a and the main grooves 12a of the tread portion 1a in a zigzag shape, air column resonance of the main grooves 11a and the main grooves 12a can be suppressed. Furthermore, by forming the main grooves 11a and the main grooves 12a of the tread portion 1a in a zigzag shape, wet performance and snow performance can be improved by the action of the edges of the edge portions of the zigzag shape.

[0067] Furthermore, by having the auxiliary grooves 31 of the tread portion 1a in a shape in which the second auxiliary groove 31B curves toward the first auxiliary groove 31A at the curvature point P2, wet performance and snow performance can be improved through the action of the edges of the first auxiliary grooves 31A and the second auxiliary grooves 31B. Specifically, the auxiliary groove 31 has a structure in which the groove width of the first auxiliary groove 31A gradually decreases as the first auxiliary groove 31A extends from the open end S1 toward the curvature point S2, thus assisting in the discharge of snow accumulated in the auxiliary groove 31. As a result, deterioration in snow performance caused by snow accumulation can be prevented.Furthermore, in embodiments in which the groove width of the first auxiliary groove 31A gradually decreases as the auxiliary groove 31A extends from the open end S1 to the bending point S2, the drainage of water in the auxiliary grooves 31 is improved, whereby an improvement in wet performance can be achieved.

[0068] As a result, the synergistic effect of the tread portion 1a having the main grooves 11a and the main grooves 12a in zigzag shape and the plurality of auxiliary grooves 31 having a curved shape can improve the quietness, the snow performance, and the wet performance. Embodiment 1

[0069] Tables 1 to 3 show the performance test results of pneumatic tires according to the present invention. For the performance test, evaluations of wet performance, snow performance, and low noise levels of various pneumatic tires were conducted. In these performance tests, pneumatic tires with a tire size of 205 / 55 R16 91V were mounted on a rim with a rim size of 16x6.5JJ and inflated to an air pressure of 200 kPa. Furthermore, a front-engine, front-wheel-drive passenger car with a displacement of 1.6 l was used as the test vehicle.

[0070] In the wet performance test, the vehicle was driven on a test track with a wet road surface, and at a driving speed of 100 km / h, braking was performed using an anti-lock braking system (ABS) to stop the vehicle. The braking distance was measured. For evaluation, the reciprocals of the measured values ​​were taken and expressed as index values, using the values ​​of the tire of the prior art example as the reference value (100). Larger values ​​represent a shorter braking distance and thus desirable superior wet performance.

[0071] In the snow performance test, the test vehicle was driven on a test track with compacted snow. While driving at an initial speed of 40 km / h, braking was performed using an anti-lock braking system (ABS). The distance traveled until the vehicle came to a stop was measured and evaluated. For evaluation, the results were expressed as index values, using the values ​​of the tire of the prior art example as the reference value (100). Higher values ​​are preferred.

[0072] During the low-noise performance test, the test vehicle was driven on a test track with a dry road surface. The test driver performed a sensory evaluation of the vehicle's interior noise while idling at a speed of 100 km / h to 20 km / h. For the evaluation, the results were expressed as index values, using the values ​​of the prior art tire as the reference value (100). Higher values ​​are preferred.

[0073] It should be noted that in these performance tests, pneumatic tires with a score of 104 or higher are considered superior and pneumatic tires with a score in a range of 100 to 103 are considered equivalent.

[0074] The pneumatic tires of the embodiments 1, 6 to 9 and 11 to 30 and the comparative examples 2 to 5 and 10 each include: a pair of first tire circumferentially extending main grooves formed on opposite outer sides in a tire width direction of a first land portion including an equatorial plane of the tire E; a pair of second main grooves extending in the tire circumferential direction and arranged further outward in the tire width direction than the first main grooves; auxiliary grooves arranged in at least one of second land sections lying between the first main grooves and the second main grooves, which auxiliary grooves open towards the corresponding first main groove or the corresponding second main groove and end in the corresponding second land section.

[0075] Each of the auxiliary grooves bends at the bent portion and includes a first auxiliary groove extending from the opening to the bent portion and a second auxiliary groove extending from the bent portion to the blind-ended portion. The angle θ formed by the first auxiliary groove and the second auxiliary groove at the bent portion is in a range of 0° < θ < 90° (in other words, an acute angle).

[0076] The tires of Working Examples 1, 6 to 9, and 11 to 30, as well as Comparative Examples 2 to 5 and 10, were determined as shown in Tables 1 to 3. In other words, the tires were prepared with variations of the following specifications: Number of main grooves: two, four; the ratio between the length a of the first auxiliary groove 31A and the length b of the second auxiliary groove 31B, which together constitute the auxiliary groove 31 bent like a fishhook: 0.2a = b (20%), 0.3a = b (30%), 0.5a = b (50%), 0.8a = b (80%), 0.9a = b (90%); the bending angle θ formed by the first auxiliary groove 31A and the second auxiliary groove 31B at the bent portion at the bending point S2: 70°, 80°, 85°, 90°; the inclination angle α of the first main grooves 31A with respect to the tire circumferential direction C: 20°, 30°, 70°, 80°; the third auxiliary grooves 33, which are lug grooves in the third land section 23, which open or not towards the second main groove 12 (end in the third land section 23); the first narrow grooves 32, which are arranged or not in the first web portion 21; the first narrow grooves 32 in the first web section 21 open towards the first main groove 11 or not (end in the first web section 21); the shape of the second web sections 22 is point-symmetric or asymmetric with respect to the equatorial plane of the tire E; the groove width at curvature point S2, which is the angled portion, with respect to the open end S1, which is the opening portion of the first auxiliary groove 31A in the second land portion 22: the same, 10% smaller, 50% smaller, or 60% smaller; the inclination angle α of the second narrow grooves 41 with respect to the tire circumferential direction C: 30°, 70°, 90°; the first auxiliary groove 31A opens inward in the tire width direction (opens toward the first main groove 11) or opens outward (opens toward the second main groove 12); the third narrow grooves 43 are arranged in the third web sections 23 or not; the third narrow grooves 43 in the third web sections 23 open towards the second main groove 12 or not (end in the third web sections 23); The width of the first narrow grooves 32, the second narrow grooves 41, and the third narrow grooves 43: 1.0 (mm), 1.2 (mm), 1.5 (mm). Furthermore, in the second land portion 22, the first auxiliary groove 31A opens toward the second main groove 12, and the second auxiliary groove 31B terminates in the second land portion 22.

[0077] For comparison, the tire of the prior art example includes auxiliary grooves with a straight shape (no curvature) that open to both sides in the tire width direction (inward and outward) and are point-symmetric with respect to the equatorial plane of the tire E. Furthermore, the tire of the prior art example 1 includes auxiliary grooves with a straight shape (no curvature) that open to both sides (inward and outward) and are not point-symmetric with respect to the equatorial plane of the tire E.

[0078] These test tires were evaluated for wet performance, snow performance, and noise according to the evaluation procedures described above. The results are presented in Tables 1 and 3.

[0079] As shown in Tables 1 to 3, tires having four main grooves and a ratio between the length a of the first auxiliary groove 31A and the length b of the second auxiliary groove 31B in a range of 0.3a < b < 0.8a exhibited better wet performance, snow performance, and quietness than that of the prior art example 1.

[0080] In addition, tires with the following specifications demonstrated excellent wet performance, snow performance, and low noise: the bending angle θ formed by the first auxiliary groove 31A and the second auxiliary groove 31B is: 80°; the inclination angle α of the first narrow groove 31A with respect to the tire circumferential direction C is from 30° to 70°; the first auxiliary grooves 31A in the second land sections 22 do not open towards the second main groove 12 (end in the second land sections 22); the lug grooves (the third auxiliary grooves 33) are arranged in the third land portion 23; the first narrow grooves 32 in the first land section 21 do not open towards the first main groove 11 (end in the first land section 21); the shape of the second web sections 22 is point-symmetrical with respect to the equatorial plane of the tire E; the groove width at the open end S1 of the first auxiliary groove 31A in the second land portion 22 is from 10% to 50% less than the groove width at the curvature point S2; the inclination angle α of the second narrow grooves 41 with respect to the tire circumferential direction C is from 30° to 70°; the first auxiliary groove 31A opens to the outside in the tire width direction (opens to the second main groove 12); the third narrow grooves 43 are arranged in the third web sections 23; the third narrow grooves 43 in the third land section 23 do not open towards the second main groove 12 (end in the third land section 23); the width of the first narrow grooves 32, the second narrow grooves 41, and the third narrow groove 43 is 1.2 (mm).

[0081] According to one embodiment, a pneumatic tire has: a pair of first tire circumferentially extending main grooves formed on opposite outer sides in a tire width direction of a first land portion including an equatorial plane of the tire; a pair of second main grooves extending in the tire circumferential direction and arranged further outward in the tire width direction than the first main grooves; and auxiliary grooves arranged in second web sections lying between the first main grooves and the second main grooves, which auxiliary grooves open towards the corresponding first main groove or the corresponding second main groove and end in the corresponding second web section; wherein each of the auxiliary grooves bends at a bent portion and includes a first auxiliary groove extending from the opening to the bent portion and a second auxiliary groove extending from the bent portion to a blind-ended portion; a length a of the first auxiliary groove and a length b of the second auxiliary groove are in a ratio of 0.3a < b < 0.8a to each other; and an angle 8 formed by the first auxiliary groove and the second auxiliary groove at the bent portion is in a range of 0° < θ < 90°.

[0082] According to one embodiment, the pneumatic tire further comprises: third land portions arranged further outward in the tire width direction than the second auxiliary grooves, and third auxiliary grooves arranged in the third land portions and extending outward in the tire width direction; wherein the end portions of the third auxiliary grooves end near the second main grooves in the third land portions.

[0083] According to one embodiment, the pneumatic tire further has first narrow grooves arranged in the first land portion.

[0084] According to one embodiment, the first narrow grooves end in the first web section.

[0085] According to one embodiment, the first narrow grooves have a width of 1.2 mm or less.

[0086] According to one embodiment, the second web portions have a point-symmetric configuration with respect to the equatorial plane of the tire.

[0087] According to one embodiment, a groove width of the first auxiliary groove at the bent portion is 10% to 50% smaller than the groove width at the opening portion.

[0088] According to one embodiment, the first auxiliary groove forms an angle with the tire circumferential direction of 30° to 70°.

[0089] According to one embodiment, the pneumatic tire further has second narrow grooves arranged in the second land portions, wherein the second narrow grooves form an angle with the tire circumferential direction of 30° to 70°.

[0090] According to one embodiment, the first auxiliary grooves intersect the second narrow grooves.

[0091] According to one embodiment, the second narrow grooves have a width of 1.2 mm or less.

[0092] According to one embodiment, the first auxiliary grooves open towards the second main grooves.

[0093] According to one embodiment, the pneumatic tire has third narrow grooves arranged in the second land portions, the third narrow grooves extending in a shoulder direction.

[0094] According to one embodiment, the third narrow grooves do not open towards the second main grooves.

[0095] According to one embodiment, the third narrow grooves have a width of 1.2 mm or less.

[0096] According to one embodiment, sidewalls extending in the tire circumferential direction of the first main grooves and the second main grooves have a zigzag shape in which a position of the sidewalls changes regularly in the tire width direction. [Table 1-I] Example state of the art Comparison example 1 Example 1 Comparison example 2 Comparison example 3 Comparison example 4 Number of main grooves 2 4 2 4 4 4 Shape of the auxiliary grooves in the second web section Opens Opens Ends Ends Ends Ends Shape of the auxiliary groove No curvature No curvature Fishhook shape Fishhook shape Fishhook shape Fishhook shape Length ratio of the auxiliary grooves Same Same 50 % 20 % 20 % 20 % Bending angle of the first auxiliary groove None 100° 80° 80° 90° 85° Inclination angle of the first auxiliary groove None 70° 70° 70° 70° Shape of the auxiliary grooves in the third web section Opens Opens Opens Ends Ends Ends Narrow grooves in the first web section Unavailable Unavailable Unavailable Unavailable Unavailable Unavailable Shape of the auxiliary grooves in the first web section Opens Opens Opens Opens Opens Opens Shape of the second web section Point-symmetric Asymmetrical Asymmetrical Asymmetrical Asymmetrical Asymmetrical Groove width of the first auxiliary groove Same Same Same Same Same Same Inclination angle of the narrow grooves in the first web section None None 90° 90° 90° 90° Side to which the first auxiliary groove opens Both Both inside inside inside inside Narrow grooves in the third web section Available Available Unavailable Unavailable Unavailable Unavailable Shape of the narrow grooves in the third web section Opens Opens Opens Opens Opens Opens Width of the narrow groove 1.0 mm 1.0 mm 1.0 mm 1.0 mm 1.0 mm 1.0 mm Performance in wet conditions 100 100 103 103 104 104 Performance on snow 100 103 103 103 103 104 Low noise 100 103 101 103 104 104 [Table 1-II] Comparison example 5 Example 6 Example 7 Example 8 Example 9 Comparison example 10 Number of main grooves 4 4 4 4 4 4 Shape of the auxiliary grooves in the second web section Ends Ends Ends Ends Ends Ends Shape of the auxiliary groove Fishhook shape Fishhook shape Fishhook shape Fishhook shape Fishhook shape Fishhook shape Length ratio of the auxiliary grooves 20 % 30 % 80 % 90 % 50 % 50 % Bending angle of the first auxiliary groove 70° 80° 80° 80° 80° 80° Inclination angle of the first auxiliary groove 70° 70° 70° 70° 70° 20° Shape of the auxiliary grooves in the third web section Ends Ends Ends Ends Ends Ends Narrow grooves in the first web section Unavailable Unavailable Unavailable Unavailable Unavailable Available Shape of the auxiliary grooves in the first web section Opens Opens Opens Opens Opens Opens Shape of the second web section Asymmetrical Asymmetrical Asymmetrical Asymmetrical Asymmetrical Asymmetrical Groove width of the first auxiliary groove Same Same Same Same Same Same Inclination angle of the narrow grooves in the first web section 90° 90° 90° 90° 90° 90° Side to which the first auxiliary groove opens inside inside inside inside inside inside Narrow grooves in the third web section Unavailable Unavailable Unavailable Unavailable Unavailable Unavailable Shape of the narrow grooves in the third web section Opens Opens Opens Opens Opens Opens Width of the narrow groove 1.0 mm 1.0 mm 1.0 mm 1.0 mm 1.0 mm 1.0 mm Performance in wet conditions 105 105 106 106 107 108 Performance on snow 104 105 106 109 109 110 Low noise 106 106 106 105 105 105 [Table 2-I] Example 11 Example 12 Example 13 Example 14 Example 15 Number of main grooves 4 4 4 4 4 Shape of the auxiliary grooves in the second web section Ends Ends Ends Ends Ends Shape of the auxiliary groove Fishhook shape Fishhook shape Fishhook shape Fishhook shape Fishhook shape Length ratio of the auxiliary grooves 50 % 50 % 50 % 50 % 50 % Bending angle of the first auxiliary groove 80° 80° 80° 80° 80° Inclination angle of the first auxiliary groove 30° 70° 80° 70° 80° Shape of the auxiliary grooves in the third web section Ends Ends Ends Ends Ends Narrow grooves in the first web section Available Available Available Available Available Shape of the auxiliary grooves in the first web section Opens Opens Opens Ends Ends Shape of the second web section Asymmetrical Asymmetrical Asymmetrical Point-symmetric Point-symmetric Groove width of the first auxiliary groove Same Same Same Same Same Inclination angle of the narrow grooves in the first web section 90° 90° 90° 90° 90° Side to which the first auxiliary groove opens inside inside inside inside inside Narrow grooves in the third web section Unavailable Unavailable Unavailable Unavailable Unavailable Shape of the narrow grooves in the third web section Opens Opens Opens Opens Opens Width of the narrow groove 1.0 mm 1.0 mm 1.0 mm 1.0 mm 1.0 mm Performance in wet conditions 108 109 109 110 110 Performance on snow 110 109 110 112 112 Low noise 106 106 107 107 108 [Table 2-II] Example 16 Example 17 Example 18 Example 19 Example 20 Number of main grooves 4 4 4 4 4 Shape of the auxiliary grooves in the second web section Ends Ends Ends Ends Ends Shape of the auxiliary groove Fishhook shape Fishhook shape Fishhook shape Fishhook shape Fishhook shape Length ratio of the auxiliary grooves 50 % 50 % 50 % 50 % 50 % Bending angle of the first auxiliary groove 80° 80° 80° 80° 80° Inclination angle of the first auxiliary groove 70° 70° 70° 70° 70° Shape of the auxiliary grooves in the third web section Ends Ends Ends Ends Ends Narrow grooves in the first web section Available Available Available Available Available Shape of the auxiliary grooves in the first web section Ends Ends Ends Ends Ends Shape of the second web section Point-symmetric Point-symmetric Point-symmetric Point-symmetric Point-symmetric Groove width of the first auxiliary groove 10% less 50% less 60% less 10% less 50% less Inclination angle of the narrow grooves in the first web section 90° 90° 90° 30° 30° Side to which the first auxiliary groove opens inside inside inside inside inside Narrow grooves in the third web section Unavailable Unavailable Unavailable Unavailable Unavailable Shape of the narrow grooves in the third web section Opens Opens Opens Opens Opens Width of the narrow groove 1.0 mm 1.0 mm 1.0 mm 1.0 mm 1.0 mm Performance in wet conditions 111 112 113 114 115 Performance on snow 111 113 114 115 116 Low noise 109 110 111 111 112 [Table 3-I] Example 21 Example 22 Example 23 Example 24 Example 25 Number of main grooves 4 4 4 4 4 Shape of the auxiliary grooves in the second web section Ends Ends Ends Ends Ends Shape of the auxiliary groove Fishhook shape Fishhook shape Fishhook shape Fishhook shape Fishhook shape Length ratio of the auxiliary grooves 50 % 50 % 50 % 50 % 50 % Bending angle of the first auxiliary groove 80° 80° 80° 80° 80° Inclination angle of the first auxiliary groove 70° 70° 70° 70° 70° Shape of the auxiliary grooves in the third web section Ends Ends Ends Ends Ends Narrow grooves in the first web section Available Available Available Available Available Shape of the auxiliary grooves in the first web section Ends Ends Ends Ends Ends Shape of the second web section Point-symmetric Point-symmetric Point-symmetric Point-symmetric Point-symmetric Groove width of the first auxiliary groove 10% less 50% less 10% less 50% less 10% less Inclination angle of the narrow grooves in the first web section 30° 30° 70° 70° 70° Side to which the first auxiliary groove opens outside outside outside outside outside Narrow grooves in the third web section Unavailable Unavailable Unavailable Unavailable Available Shape of the narrow grooves in the third web section Opens Opens Opens Opens Ends Width of the narrow groove 1.0 mm 1.0 mm 1.0 mm 1.0 mm 1.0 mm Performance in wet conditions 115 116 116 116 117 Performance on snow 116 117 118 119 119 Low noise 113 113 113 113 114 [Table 3-II] Example 26 Example 27 Example 28 Example 29 Example 30 Number of main grooves 4 4 4 4 4 Shape of the auxiliary grooves in the second web section Ends Ends Ends Ends Ends Shape of the auxiliary groove Fishhook shape Fishhook shape Fishhook shape Fishhook shape Fishhook shape Length ratio of the auxiliary grooves 50 % 50 % 50 % 50 % 50 % Bending angle of the first auxiliary groove 80° 80° 80° 80° 80° Inclination angle of the first auxiliary groove 70° 70° 70° 70° 70° Shape of the auxiliary grooves in the third web section Ends Ends Ends Ends Ends Narrow grooves in the first web section Available Available Available Available Available Shape of the auxiliary grooves in the first web section Ends Ends Ends Ends Ends Shape of the second web section Point-symmetric Point-symmetric Point-symmetric Point-symmetric Point-symmetric Groove width of the first auxiliary groove 50% less 10% less 50% less 10% less 50% less Inclination angle of the narrow grooves in the first web section 70° 70° 70° 70° 70° Side to which the first auxiliary groove opens outside outside outside outside outside Narrow grooves in the third web section Available Available Available Available Available Shape of the narrow grooves in the third web section Ends Ends Ends Ends Ends Width of the narrow groove 1.0 mm 1.5 mm 1.5 mm 1.2 mm 1.2 mm Performance in wet conditions 118 118 119 119 120 Performance on snow 120 120 120 120 120 Low noise 114 115 116 117 118 List of reference symbols 1 tread section 2 side wall section 3 bead section 4 carcass layers 5 tire bead core 6 Tire bead filler 7 belt layer 8 Belt cover layer 10 pneumatic tires 11, 11a First main groove 12, 12a Second main groove 21 First bridge section 22 Second bridge section 23 Third bridge section 31 auxiliary groove 31A First auxiliary groove 31B Second auxiliary groove 32 First narrow groove 33 Third auxiliary groove 41 Second narrow groove 43 Third narrow groove 53 Narrow longitudinal groove C Tire circumferential direction E Tire equator plane

Claims

[1] Pneumatic tire (10), comprising: a pair of first main grooves (11, 11a) extending in the tire circumferential direction (C) formed on opposite outer sides in a tire width direction of a first land portion (21) including an equatorial plane (E) of the tire; a pair of second main grooves (12, 12a) extending in the tire circumferential direction (C) and arranged further outward in the tire width direction than the first main grooves (11, 11a); and auxiliary grooves (31) arranged in second web sections (22) lying between the first main grooves (11, 11a) and the second main grooves (12, 12a), which open towards the corresponding first main groove (11, 11a) or the corresponding second main groove (12, 12a) and end in the corresponding second web section (22); wherein each of the auxiliary grooves (31) bends at a bent portion (S2) and includes a first auxiliary groove (31A) extending from the opening (S1) to the bent portion (S2) and a second auxiliary groove (31B) extending from the bent portion (S2) to a blind-ended portion (S3); a length a of the first auxiliary groove (31A) and a length b of the second auxiliary groove (31B) are in a ratio of 0.3a < b < 0.8a to each other; an angle θ formed by the first auxiliary groove (31A) and the second auxiliary groove (31B) at the bent portion (S2) is in a range of 0° < θ < 90°; a groove width of the first auxiliary groove (31A) gradually decreases as the first auxiliary groove (31A) extends from the opening (S1) toward the bent portion (S2); an angle φ is defined as an angle of a tangent (S6) of a center line (S4) at the opening (S1) of the first auxiliary groove (31A) with respect to the tire circumferential direction (C), the angle φ is between 30° and 70°; the pneumatic tire (10) has second narrow grooves (41) arranged in the second web portions (22), wherein the second narrow grooves (41) form an angle α with the tire circumferential direction (C) of 30° to 70°; the first auxiliary grooves (31A) intersect the second narrow grooves (41); and the angle φ and the angle α are in a plus / minus opposite relationship to each other. [2] A pneumatic tire (10) according to claim 1, further comprising third land portions (23) arranged further outward in the tire width direction than the second auxiliary grooves (31B), and third auxiliary grooves (33) arranged in the third land portions (23) and extending outward in the tire width direction; wherein the end portions of the third auxiliary grooves (33) end near the second main grooves (12, 12a) in the third land portions (23). [3] A pneumatic tire (10) according to claim 1 or 2, further comprising first narrow grooves (32) arranged in the first land portion (21). [4] A pneumatic tire (10) according to claim 3, wherein the first narrow grooves (32) terminate in the first land portion (21). [5] A pneumatic tire (10) according to claim 3 or 4, wherein the first narrow grooves (32) have a width of 1.2 mm or less. [6] A pneumatic tire (10) according to any one of claims 1 to 5, wherein the second land portions (22) have a point-symmetric configuration with respect to the equatorial plane (E) of the tire. [7] A pneumatic tire (10) according to any one of claims 1 to 6, wherein a groove width (H2) of the first auxiliary groove (31A) at the bent portion (S2) is 10% to 50% smaller than a groove width (H1) of the first auxiliary groove (31A) at the opening (S1). [8] A pneumatic tire (10) according to any one of claims 1 to 7, wherein the second narrow grooves (41) have a width of 1.2 mm or less. [9] A pneumatic tire (10) according to any one of claims 1 to 8, wherein the first auxiliary grooves (31A) open toward the second main grooves (12, 12a). [10] A pneumatic tire (10) according to any one of claims 1 to 9, further comprising third land portions (23) arranged further outward in the tire width direction than the second auxiliary grooves (31B); and third narrow grooves (43) arranged in the third web sections (23), wherein the third narrow grooves (43) extend in a shoulder direction. [11] A pneumatic tire (10) according to claim 10, wherein the third narrow grooves (43) do not open toward the second main grooves (12, 12a). [12] A pneumatic tire (10) according to claim 10 or 11, wherein the third narrow grooves (43) have a width of 1.2 mm or less. [13] A pneumatic tire (10) according to any one of claims 1 to 12, wherein sidewalls extending in the tire circumferential direction (C) of the first main grooves (11, 11a) and the second main grooves (12, 12a) have a zigzag shape in which a position of the sidewalls changes regularly in the tire width direction.

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