Tire

Abstract

Provided is a tire capable of improving snow performance without impairing wear resistance. A pair of bent main grooves (11) disposed on both sides of a tire equator (CL) and extending in a zigzag shape in the tire circumferential direction, a plurality of bent inclined grooves (12) extending from the bent main grooves (11) in the direction of the tire equator (CL), and inclined narrow grooves (13) connecting the bent inclined grooves (12) on both sides of the tire equator (CL) are provided as grooves for partitioning blocks (B) in a tread section (1). The bent inclined groove (12) is configured from: a first inclined groove section (12a) which extends obliquely with respect to the tire circumferential direction from the bent main groove (11) in the direction of the tire equator (CL) and which has at least one bending point; and a second inclined groove section (12b) which terminates in the same direction as the first inclined groove section (12a) and which is inclined further toward the tire circumferential direction than the first inclined groove section (12a) and does not exceed the tire equator (CL). At least one sipe (S) is formed in each block (B) by inclining the inclined narrow groove (13) in the opposite direction to the bent inclined groove (12) and connecting the midway portion of the second inclined groove portion (12b).

Description

Technical Field

[0001] The present invention relates to a tire intended for traveling on unpaved roads and the like, and more particularly to a tire capable of improving snow performance without impairing wear resistance. Background Art

[0002] Tires that are intended to travel on unpaved roads (uneven ground, muddy ground, sandy ground, rocky ground, etc.) in addition to paved roads (for example, high-travel tires (All-Terrain Tire), all-terrain tires, etc.) are required to have excellent off-road performance. In addition, in order to achieve stable driving even when snowing, excellent snow performance is also required. In recent years, among these performances, snow performance has been given particular attention, and sufficient performance is required even on snowy roads in extremely harsh cold regions. As such tires, there is a tendency to adopt tread patterns that are mainly composed of transverse grooves and blocks with a large edge component and a large groove area (for example, refer to Patent Document 1). On the other hand, tread patterns with a large groove area tend to have a tendency to reduce the rigidity of the blocks, and measures are also required to maintain sufficient wear resistance. Based on the above, it is required to highly balance snow performance and wear resistance.

[0003] Prior art literature

[0004] Patent Literature

[0005] Patent Document 1: Japanese Patent Application Publication No. 2019-137218 Summary of the Invention

[0006] Problems to be solved by the invention

[0007] An object of the present invention is to provide a tire capable of improving snow performance without impairing wear resistance.

[0008] Means for solving problems

[0009] A tire according to the present invention, for achieving the above-mentioned object, includes a tread portion having an annular shape extending in the tire circumferential direction, characterized in that the tread portion includes a plurality of blocks demarcated by a plurality of grooves, the plurality of grooves including: a pair of curved main grooves arranged on either side of the tire equator and extending in a zigzag pattern along the tire circumferential direction; a plurality of curved oblique grooves extending from each of the pair of curved main grooves toward the tire equator; and an inclined narrow groove connecting the curved oblique grooves on one side of the tire equator with the curved oblique grooves on the other side of the tire equator. Each of the curved oblique grooves is composed of a first inclined groove portion extending from the pair of curved main grooves toward the tire equator with respect to the tire circumferential direction, and a second inclined groove portion extending in the same direction as the first inclined groove portion and inclined further toward the tire circumferential side than the first inclined groove portion. The first inclined groove portion has at least one bending point, and the second inclined groove portion terminates without exceeding the tire equator. The inclined narrow groove is inclined in a direction opposite to the curved oblique groove and connects the intermediate portions of the second inclined groove portions. At least one sipe is formed in each of the plurality of blocks.

[0010] Effects of the Invention

[0011] The tire of the present invention, because the blocks formed between a pair of curved main grooves and each groove have the aforementioned structure, can improve snow performance without compromising wear resistance. In particular, since the main grooves (curved main grooves) extending along the tire circumference are a pair (two), block rigidity is ensured in the central region between the main grooves, maintaining excellent wear resistance. Furthermore, since the main grooves (curved main grooves) are curved, even a pair (two) can still achieve excellent snow performance. Furthermore, the inclusion of curved inclined grooves can also improve snow performance. However, since the curved inclined grooves (second inclined groove portions) terminate within the tire equator, block rigidity is ensured while maintaining excellent wear resistance. Furthermore, by slanting the inclined fine grooves in the opposite direction to the curved inclined grooves and connecting the mid-portions of the second inclined groove portions, the inclined grooves can be arranged in various directions, thereby improving snow performance. Furthermore, by forming at least one sipe in each block, the edge effect achieved by the sipes can be ensured, further improving snow performance. Through their collaboration, a high degree of balance between wear resistance and snow performance can be achieved.

[0012] In the present invention, it is preferred that the first inclined groove portion have an inclination angle θ1 relative to the tire circumferential direction of 50° to 85°, the second inclined groove portion have an inclination angle θ2 relative to the tire circumferential direction of 5° to 40°, and the difference θ1-θ2 between the inclination angles θ1 and θ2 is 30° to 80°. By setting the inclination angles of each portion in this manner, the curved inclined groove has a better shape, which contributes to improved snow performance.

[0013] In the present invention, preferably, the groove depth of the bent inclined groove is 50% to 100% of the groove depth of the main bent groove, and the groove depth of the inclined fine groove is 60% to 100% of the groove depth of the bent inclined groove. By setting the groove depths of the respective grooves in this way, it is beneficial to improve the snow performance while ensuring the block rigidity.

[0014] In the present invention, preferably, the length L1 of the first inclined groove portion and the length L2 of the second inclined groove portion satisfy the relationship of L2 / L1≥1.7. Thereby, the balance between the circumferential groove component and the widthwise groove component ensured by the bent inclined groove becomes good, which is beneficial to improving the snow performance.

[0015] In the present invention, preferably, the plurality of grooves include sub-inclined grooves that communicate with the main bent groove and the second inclined groove portion and incline in the same direction as the first inclined groove portion. By including the sub-inclined grooves in this way, the groove component is added, and thus it is beneficial to improve the snow performance.

[0016] In the present invention, preferably, the plurality of grooves include shoulder cross grooves that extend from the main bent groove toward the outer side in the tire width direction. When the number of bending points of the first inclined groove portion is set as N1, the number of bending points of the second inclined groove portion is set as N2, the number of bending points of the inclined fine groove is set as N3, and the number of bending points of the shoulder cross groove is set as Ns, the numbers of these bending points satisfy the relationship of Ns≤N2<N1≤N3. By setting it as such a configuration, the bending shape of each groove becomes good, and in addition to ensuring the block rigidity (maintaining the abrasion resistance) and improving the edge effect (improving the snow performance), an improvement in the snow performance achieved by the improvement of the snow removal performance can also be expected.

[0017] In the present invention, preferably, the plurality of grooves include a cross-connecting groove that connects the second inclined groove portion on one side of the tire equator and the second inclined groove portion on the other side of the tire equator at a position closer to the terminal side of the second inclined groove portion than the inclined fine groove. By including the cross-connecting groove in this way, the edge effect achieved by this groove can be ensured, which is beneficial to improving the snow performance.

[0018] In the present invention, preferably, the plurality of grooves include a circumferential connecting groove that connects the second inclined groove portions adjacent to each other in the tire circumferential direction on one side of the tire equator. By including the circumferential connecting groove in this way, the edge effect achieved by this groove can be ensured, which is beneficial to improving the snow performance.

[0019] In the present invention, preferably, a convex portion that bulges from the groove bottom is provided at the intersection of at least one of the pair of main bent grooves and the bent inclined groove. By providing the convex portion in this way, the snow performance can be improved without affecting the abrasion resistance.

[0020] The tire of the present invention is preferably a pneumatic tire, but may also be a non-pneumatic tire. In the case of a pneumatic tire, an inert gas such as air, nitrogen, or other gas can be filled inside the tire. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 This is a meridian cross-sectional view of a tire according to an embodiment of the present invention.

[0022] Figure 2 This is a front view showing the tread surface of a tire according to the embodiment of the present invention.

[0023] Figure 3 It will Figure 2 An explanatory diagram showing an extracted portion of the image. DETAILED DESCRIPTION

[0024] Hereinafter, the configuration of the present invention will be described in detail with reference to the accompanying drawings.

[0025] The tire of the present invention is Figure 1 In the case of the pneumatic tire shown in FIG. 1 , the tire includes a tread portion 1 that contacts the road surface, a pair of sidewall portions 2 disposed on both sides of the tread portion 1, and a pair of bead portions 3 disposed radially inward of the sidewall portions 2. Figure 1 In FIG, the reference symbol CL represents the tire equator. Figure 1 Since this is a meridian cross-sectional view, it is not described, but the tread portion 1, the sidewall portion 2, and the bead portion 3 extend in the tire circumferential direction and form a ring shape, thereby forming the basic ring-shaped structure of the pneumatic tire. Figure 1 The description is basically based on the meridian cross-sectional shape shown in the figure, but each tire component is a ring-shaped member extending in the tire circumferential direction.

[0026] A carcass layer 4 is provided between a pair of left and right bead portions 3. The carcass layer 4 includes a plurality of reinforcing cords extending in the radial direction of the tire and folded back from the inner side to the outer side in the tire width direction around the bead core 5 provided at each bead portion 3. In addition, a bead filler 6 is provided on the outer periphery of the bead core 5, and the bead filler 6 is wrapped by the main body and the folded back portion of the carcass layer 4. On the other hand, a plurality of layers (in the outer periphery of the carcass layer 4 at the tread portion 1) are embedded. Figure 1 The belt layer 7 is composed of two layers. Each belt layer 7 includes a plurality of reinforcing cords inclined relative to the tire circumferential direction, and is arranged in a manner that the reinforcing cords intersect each other between layers. In these belt layers 7, the inclination angle of the reinforcing cords relative to the tire circumferential direction is set in the range of 10° to 40°, for example. In addition, at least one layer (in the outer peripheral side of the belt layer 7) is provided. Figure 1The belt reinforcement layer 8 includes two layers (two layers in the tire). The belt reinforcement layer 8 includes organic fiber cords oriented in the tire circumferential direction. In the belt reinforcement layer 8, the angle of the organic fiber cords relative to the tire circumferential direction is set to, for example, 0° to 5°.

[0027] Since the present invention relates to a tread pattern formed on the surface of the tire tread portion 1 as described below, the basic structure (cross-sectional structure) of the tire is not limited to the general structure described above. In addition, as long as a surface that contacts the road surface (a portion of a pneumatic tire corresponding to the surface of the tread portion 1) is provided, the tire can be applied to various tires, including non-pneumatic tires.

[0028] The surface of the tread portion 1 in the tire of the present invention is as follows Figure 2 As shown, a plurality of blocks B are provided, each divided by a plurality of grooves. The plurality of grooves dividing the plurality of blocks B must include three types of grooves, described later: the bent main grooves 11, the bent oblique grooves 12, and the oblique fine grooves 13. Furthermore, at least one sipe S must be formed in each of the plurality of blocks B.

[0029] The bending main groove 11 is a groove extending in a zigzag shape along the circumferential direction of the tire, and a pair (2) of them are arranged on both sides of the tire equator. The zigzag shape is a shape obtained by alternatingly connecting a straight line portion inclined in one direction relative to the circumferential direction of the tire with a straight line portion inclined in another direction in the circumferential direction of the tire. The point where the straight line portion inclined in one direction relative to the circumferential direction of the tire and the straight line portion inclined in another direction in the bending main groove 11 are connected is called a bending point. In the following description, there is a case where the area between a pair of bending main grooves 11 is called a central area, and the area outside each bending main groove 11 in the tire width direction is called a shoulder area. The bending main groove 11 is the groove with the largest groove width and groove depth among the three types of grooves mentioned above. Specifically, the groove width of the bending main groove 11 is preferably 3mm to 13mm, and more preferably 5mm to 11mm. The groove depth of the bending main groove 11 is preferably 8mm to 16mm, and more preferably 10mm to 15mm.

[0030] The curved inclined groove 12 is a groove extending from each of the pair of curved main grooves 11 toward the tire equator CL. Multiple curved inclined grooves 12 are provided at intervals along the tire circumferential direction. In the illustrated example, the curved inclined groove 12 extends from the inward bending point of each curved main groove 11 in the tire width direction. The curved inclined groove 12 consists of a first inclined groove portion 12a extending from the curved main groove 11 toward the tire equator CL, obliquely relative to the tire circumferential direction, and a second inclined groove portion 12b extending in the same direction as the first inclined groove portion 12a but tilted further toward the tire circumferential side than the first inclined groove portion 12a. By connecting these first inclined groove portion 12a and second inclined groove portion 12b, the curved inclined groove 12 as a whole has one bending point. However, the first inclined groove portion 12a has at least one additional bending point. One end of the second inclined groove portion 12b is connected to the first inclined groove portion 12a, and the other end terminates without exceeding the tire equator CL. Specifically, the other end of the second inclined groove portion 12b has a tapered shape with its width converging toward the terminal end. It has an acute-angled tip (the apex of the acute angle) at the terminal end. However, this tip (apex) is located on one side of the tire equator CL (the side on which the curved inclined groove 12 to which the second inclined groove portion 12b belongs is located), and the second inclined groove portion 12b does not intersect the tire equator CL. The curved inclined groove 12 (the first inclined groove portion 12a and the second inclined groove portion 12b) has a groove width and groove depth that are equal to or less than that of the curved main groove. The groove width of the curved inclined groove 12 is preferably 80% to 97% of the groove width of the curved main groove 11, more preferably 85% to 95%. The groove depth of the curved inclined groove 12 is preferably 50% to 100% of the groove depth of the curved main groove 11, more preferably 70% to 100%.

[0031] The inclined groove 13 connects the curved inclined groove 12 on one side of the tire equator CL with the curved inclined groove 12 on the other side of the tire equator CL. Therefore, the inclined groove 13 must intersect the tire equator CL. The inclined groove 13 is inclined in the opposite direction to the curved inclined groove 12 and connects the midway portions of the second inclined groove portions 12b. The inclined groove 13 can also be bent. In the illustrated example, the inclined groove 13 is bent in a Z-shape and has two bending points. The curved groove 13 has a groove width and groove depth that are smaller than the groove width and groove depth of the curved inclined groove 12. The groove width of the curved groove 13 is preferably 35% to 75% of the groove width of the curved inclined groove 12, and more preferably 45% to 65%. The groove depth of the curved groove 13 is preferably 50% to 100% of the groove depth of the curved inclined groove 12, and more preferably 70% to 100%.

[0032] As described above, at least one sipe S is provided in each block B. In the illustrated example, each block B is provided with two sipes S extending in a zigzag pattern. The shape of the sipe S is not particularly limited; in addition to the zigzag shape illustrated, various other shapes, such as straight lines, can be employed. The number of sipes S provided in each block B can be appropriately set depending on the size of the block, but is preferably 1 to 4, and more preferably 2 to 3. The sipes S are fine grooves having a width of, for example, 0.5 mm to 2.0 mm and a depth of, for example, 2 mm to 15 mm.

[0033] By providing various grooves as described above, the tire of the present invention can improve snow performance without compromising wear resistance. That is, since the main grooves (bent main grooves 11) extending along the circumference of the tire are a pair (two), the block rigidity between the main grooves (central area) can be ensured and good wear resistance can be maintained. On the other hand, since the main grooves (bent main grooves 11) are bent, even if there are only two of them (a pair), good snow performance can be achieved. In addition, by providing the bent inclined grooves 12, snow performance can also be improved. However, since the bent inclined grooves 12 (second inclined groove portions 12b) terminate without exceeding the tire equator CL, block rigidity can be ensured and good wear resistance can be maintained. Moreover, by inclining the inclined fine grooves 13 in the opposite direction to the bent inclined grooves 12 and connecting the mid-portions of the second inclined groove portions 12b to each other, grooves inclined in various directions are arranged, thereby improving snow performance. In addition, by forming at least one sipe S in each block B, the edge effect achieved by the sipe S can be ensured, thereby improving snow performance. By cooperating with each other, a high degree of balance between wear resistance and snow performance can be achieved.

[0034] Without any of the three aforementioned groove types, or even if grooves are provided in the same position but their bend shape, tilt direction, and other characteristics do not meet the aforementioned conditions, the aforementioned effects achieved by each groove are insufficient, making it difficult to achieve a well-balanced balance between wear resistance and snow performance. Furthermore, if the groove width or groove depth of each groove is smaller than the aforementioned ranges, sufficient groove volume cannot be ensured, failing to improve snow performance. Conversely, if the groove width or groove depth of each groove is larger than the aforementioned ranges, the groove volume increases, making it impossible to ensure block rigidity, making it difficult to maintain sufficient wear resistance.

[0035] In the present invention, the plurality of grooves defining the blocks B preferably include, in addition to the three types of grooves described above, additional secondary inclined grooves 14, transverse connecting grooves 15, and circumferential connecting grooves 16, described below. The inclusion of these grooves provides additional groove components extending in various directions, thereby ensuring the edge effect achieved by each groove, contributing to improved snow performance. Furthermore, since the inclination direction, groove width, and groove depth of each groove are set as described below, sufficient block rigidity can be maintained, and good wear resistance can be maintained even with the addition of these grooves.

[0036] The secondary inclined groove 14 is a groove that connects to the curved main groove 11 and the second inclined groove portion 12b and is inclined in the same direction as the first inclined groove portion 12a. In the illustrated example, the secondary inclined groove 14 extends from a bend point on the inner side of each curved main groove 11 in the tire width direction that is not connected to the curved inclined groove 12 (first inclined groove portion 12a). The secondary inclined groove 14 preferably has the same curved shape as the first inclined groove portion 12a. The secondary inclined groove 14 preferably connects to a position within 10% of the length of the second inclined groove portion 12b from the center to both sides in the tire circumferential direction. The secondary inclined groove 14 preferably has a groove width and groove depth that are equal to or less than those of the curved inclined groove 12. Specifically, the groove width of the secondary inclined groove 14 is preferably 50% to 100% of the groove width of the curved inclined groove 12, and more preferably 65% ​​to 85%. The groove depth of the auxiliary inclined groove 14 is preferably 50% to 100% of the groove depth of the bent inclined groove 12 , and more preferably 70% to 100%.

[0037] The transverse connecting groove 15 connects the second inclined groove portion 12b on one side of the tire equator C1 with the second inclined groove portion 12b on the other side of the tire equator, closer to the terminal end of the second inclined groove portion 12b than the inclined narrow groove 13. However, the transverse connecting groove 15 is connected to a position offset from the top end (apex) of the second inclined groove portion 12b, and a top end (apex) must exist at the terminal end of the second inclined groove portion 12b. The transverse connecting groove 15 preferably inclines in the opposite direction to the inclined narrow groove 13. The transverse connecting groove 15 has a groove depth that is equal to or less than that of the curved inclined groove 12 (second inclined groove portion 12b). Specifically, the groove depth of the transverse connecting groove 15 is preferably 70% to 100% of the groove depth of the curved inclined groove 12, and more preferably 75% to 100%. On the other hand, the transverse connecting groove 15 has a groove width that is sufficiently smaller than that of the curved inclined groove 12 (second inclined groove portion 12b). Specifically, the width of the transverse connecting groove 15 is preferably 20% to 60% of the width of the curved inclined groove 12b, and more preferably 30% to 50%. Because the width of the transverse connecting groove 15 is intentionally smaller than the width of the curved inclined groove 12 (second inclined groove portion 12b), even if the transverse connecting groove 15 is connected to the terminal end (near the top end) of the second inclined groove portion 12b, the curved inclined groove 12 (second inclined groove portion 12b) is considered to form the terminal end.

[0038] The circumferential connecting groove 16 connects adjacent second inclined groove portions 12b in the tire circumferential direction on one side of the tire equator CL. In the illustrated example, the circumferential connecting groove 16 connects the end of one second inclined groove portion 12b on the first inclined groove portion 12a side to the terminal end (near the top end) of the second inclined groove portion 12b adjacent to the second inclined groove portion 12b. The circumferential connecting groove 16 preferably inclines in the opposite direction to the second inclined groove portion 12b. Furthermore, the circumferential connecting groove 16 connects to a position offset from the top end (apex) of the second inclined groove portion 12b, ensuring that the terminal end of the second inclined groove portion 12b has a top end (apex). The circumferential connecting groove 16 has a groove depth that is equal to or less than that of the curved inclined groove 12 (second inclined groove portion 12b). Specifically, the groove depth of the circumferential connecting groove 16 is preferably 80% to 100% of the groove depth of the curved inclined groove 12, and more preferably 90% to 100%. On the other hand, the circumferential connecting groove 16 has a sufficiently smaller groove width than that of the curved inclined groove 12 (second inclined groove portion 12b). Specifically, the groove width of the circumferential connecting groove 16 is preferably 40% to 90% of the groove width of the curved inclined groove 12, and more preferably 55% to 75%. Because the groove width of the circumferential connecting groove 16 is intentionally smaller than the groove width of the curved inclined groove 12 (second inclined groove portion 12b), even if the circumferential connecting groove 16 is connected to the terminal end (near the tip) of the second inclined groove portion 12b, the curved inclined groove 12 (second inclined groove portion 12b) can be considered to form a terminal end.

[0039] In addition, the structure of the shoulder region is not particularly limited, but it is preferable to provide shoulder cross grooves 17 extending outward in the tire width direction from the bent main groove 11. It is advisable to provide a plurality of shoulder cross grooves 17 at intervals in the tire circumferential direction. In the illustrated example, the shoulder cross grooves 17 are connected to the bending points on the outer side in the tire width direction of each bent main groove 11. The groove width of the shoulder cross grooves 17 is preferably 70% to 98% of the groove width of the bent main groove 11, more preferably 80% to 95%. The groove depth of the shoulder cross grooves 17 is preferably 75% to 100% of the groove depth of the bent main groove 11, more preferably 80% to 98%.

[0040] As described above, in the present invention, the plurality of grooves partitioning the plurality of blocks B must include the bent inclined grooves 12 (the first inclined groove portion 12a and the second inclined groove portion 12b) and the inclined fine grooves 13. And, at least the first inclined groove portion 12a and the inclined fine grooves 13 among these grooves (groove portions) must be bent, and the second inclined groove portion 12b can also be bent arbitrarily. At this time, when the number of bending points of the first inclined groove portion 12a is set to N1, the number of bending points of the second inclined groove portion 12b is set to N2, and the number of bending points of the inclined fine grooves 13 is set to N3, the number of these bending points preferably satisfies the relationship of N2 < N1 ≤ N3. For example, in the illustrated example, the number of bending points N1 of the first inclined groove portion 12a is 2, the number of bending points N2 of the second inclined groove portion 12b is 0, and the number of bending points N3 of the inclined fine grooves 13 is 2. Therefore, the above size relationship is satisfied. By adopting such a configuration, the bending shape of each groove becomes good, and in addition to ensuring the block rigidity (maintaining the wear resistance) and improving the edge effect (improving the snow performance), an improvement in the snow performance achieved by improving the snow removal performance can also be expected. In addition, in the case where the shoulder cross grooves 17 are provided, when the number of bending points of the shoulder cross grooves 17 is set to Ns, the number of bending points preferably satisfies the relationship of Ns ≤ N2 < N1 ≤ N3. The specific number of bending points of each groove is not particularly limited, but the number of bending points N1 of the first inclined groove portion 12a = 2 to 3, the number of bending points N2 of the second inclined groove portion 12b = 0 to 2, the number of bending points N3 of the inclined fine grooves 13 = 2 to 4, and the number of bending points Ns of the shoulder cross grooves 17 = 0 to 1 are advisable.

[0041] The various grooves described above are all inclined with respect to the tire circumferential direction, but their inclination angles with respect to the tire circumferential direction are preferably set as described below. In addition, the inclination angle of each groove is Figure 3 measured based on the center line of each groove as shown. In addition, in the case where the groove is bent, the angle formed by the straight line connecting the groove width centers at the ends of the groove with respect to the tire circumferential direction is set as the inclination angle. Figure 3 is to Figure 2The figure is a part of the tire that is extracted and shown, and omits the sipe pattern S, the notch, and the convex portion 18 described later, and extracts and shows the main grooves (the bending main groove 11, the bending inclined groove 12, the inclined fine groove 13, the secondary inclined groove 14, the transverse connecting groove 15, the circumferential connecting groove 16, and the shoulder lug groove 17).

[0042] The inclination angle θ1 of the first inclined groove portion 12a relative to the tire circumferential direction is preferably 50° to 85°, more preferably 60° to 80°. This ensures a groove component extending in the tire width direction, thereby improving traction on snowy roads. If the inclination angle θ1 is less than 50°, the edge effect is reduced. If the inclination angle θ1 exceeds 85°, steering stability on snowy roads is reduced. The inclination angle θ2 of the second inclined groove portion 12b relative to the tire circumferential direction is preferably 5° to 40°, more preferably 8° to 30°. This ensures a groove component extending in the tire circumferential direction, thereby improving steering stability on snowy roads. If the inclination angle θ2 is less than 5°, the edge effect is reduced. If the inclination angle θ2 exceeds 40°, steering stability on snowy roads is reduced. The difference θ1-θ2 between these inclination angles θ1 and θ2 is preferably 30° to 80°, more preferably 40° to 70°. By setting the difference in inclination angles in this manner, the overall curved shape of the curved inclination groove 12 is improved, thereby improving the balance between traction and handling stability on snowy roads, effectively enhancing snow performance. If the difference in inclination angles θ1-θ2 is less than 30°, the edge effect is reduced. If the difference in inclination angles θ1-θ2 exceeds 80°, the edge effect is also reduced.

[0043] The inclination angle θ3 of the inclined fine groove 13 relative to the tire circumferential direction is preferably 90° to 135°, more preferably 110° to 130°. This is conducive to improving the snow performance and wear resistance (block rigidity) in a well-balanced manner. If the inclination angle θ3 exceeds 135°, the edge effect decreases. If the inclination angle θ3 is less than 90°, the wear resistance (block rigidity) decreases. The inclination angles of other grooves are not particularly limited. The inclination angle θ4 of the secondary inclined groove 14 relative to the tire circumferential direction can be set to, for example, 60° to 80°, the inclination angle θ5 of the transverse connecting groove 15 relative to the tire circumferential direction can be set to, for example, 50° to 75°, and the inclination angle θ6 of the circumferential connecting groove 16 relative to the tire circumferential direction can be set to, for example, 110° to 130°. In addition, when the shoulder lug groove 17 is provided, its inclination angle θs relative to the tire circumferential direction can be set to, for example, 90° to 120°.

[0044] As described above, the curved main groove 11 has a shape in which linear portions inclined in one direction relative to the tire circumferential direction alternate with linear portions inclined in the other direction. Specifically, the curved main groove 11 is composed of a linear portion inclined in the same direction as the curved inclined groove 12 (hereinafter referred to as the first linear portion 11a) and a linear portion inclined in the opposite direction relative to the curved inclined groove 12 (hereinafter referred to as the second linear portion 11b). If the inclination angle of the first linear portion 11a relative to the tire circumferential direction is α1 and the inclination angle of the second linear portion 11b relative to the tire circumferential direction is α2, the inclination angle α1 can be set, for example, to 10° to 60°, and the inclination angle α2 can be set, for example, to 85° to 145°.

[0045] When the bending inclined groove 12 is composed of the first inclined groove portion 12a and the second inclined groove portion 12b, by making the length of the second inclined groove portion 12b sufficiently large relative to the first inclined groove portion 12a, it is possible to ensure the groove component extending in the circumferential direction of the tire, which is beneficial to improving the handling stability on snowy roads. In particular, it is preferred that: the length L1 of the first inclined groove portion 12a and the length L2 of the second inclined groove portion 12b preferably satisfy the relationship of L2 / L1≥1.7, and more preferably satisfy the relationship of 2.0≤L2 / L1≤3.0. If the relationship is L2 / L1<1.7, the length of the second inclined groove portion 12b cannot be fully ensured, and the effect of improving the handling stability on snowy roads cannot be fully expected. In addition, if Figure 3 As shown, the length L1 is the length measured along the tire width direction, and the length L2 is the length measured along the tire circumferential direction.

[0046] Alternatively, a protrusion 18, which rises from the groove bottom, may be provided at the intersection of at least one of the pair of curved main grooves 11 and the curved inclined groove 12. The provision of such a protrusion 18 enhances the snow-edge effect and improves snow performance without compromising wear resistance. The protrusion 18's height from the groove bottom is preferably 2% to 20% of the groove depth of the curved main groove 11, more preferably 5% to 15%. Furthermore, the protrusion 18 preferably extends over a portion of the groove bottom of the curved main groove 11, rather than the entire width. In particular, the width of the protrusion 18 is preferably 10% to 50% of the groove width of the curved main groove 11, more preferably 10% to 30%. Furthermore, when providing the protrusion 18, it is preferably positioned offset from the point where the shoulder lug groove 17 connects to the curved main groove 11, so as not to impede the snow removal effect from the curved main groove 11 toward the shoulder lug groove 17.

[0047] Hereinafter, the present invention will be further described with reference to Examples, but the scope of the present invention is not limited to these Examples.

[0048] Example

[0049] Manufactured 13 pneumatic tires with a tire size of LT265 / 70R17 121 / 118S and having Figure 1 the exemplified basic structure (cross-sectional structure) and based on Figure 2 the tread pattern, the shape of the main groove, the presence or absence of the bent inclined groove, the number of bent points of the first inclined groove portion, the terminal position of the second inclined groove portion, the inclination direction of the inclined fine groove, the presence or absence of the sipes, the inclination angle θ1 of the first inclined groove portion with respect to the tire circumferential direction, the inclination angle θ2 of the second inclined groove portion with respect to the tire circumferential direction, the difference θ1 - θ2 between these inclination angles, the groove depth of the bent inclined groove, the groove depth of the inclined fine groove, the length ratio L2 / L1 of the first inclined groove portion to the second inclined groove portion, the relationship between the number of bending times N1 to N3 and Ns, and the presence or absence of convex portions were set as shown in Tables 1 to 2 for the conventional Example 1, Comparative Examples 1 to 2, and Examples 1 to 15.

[0050] In Table 1, for the column of "Shape of the main groove", the case where the main groove extends linearly is indicated as "Straight", and the case where it extends in a zigzag shape is indicated as "Bent". For the column of "Terminal position of the second inclined groove portion", the case where the second inclined groove portion forms a terminal without reaching the tire equator is indicated as "Not reaching the equator", and the cases where it reaches the tire equator and extends beyond the tire equator are indicated as "Reaching the equator". For the column of "Inclination direction of the inclined fine groove", the case where the inclined fine groove inclines in the same direction as the bent inclined groove is indicated as "Same direction", and the case where it inclines in the opposite direction is indicated as "Opposite direction". For the column of "Groove depth of the bent inclined groove", the value of the ratio [unit: %] of the groove depth of the bent inclined groove to the groove depth of the bent main groove is shown. For the column of "Groove depth of the inclined fine groove", the value of the ratio [unit: %] of the groove depth of the inclined fine groove to the groove depth of the bent inclined groove is shown. For the column of "Relationship of the number of bending times", the case where the number of bent points N1 of the first inclined groove portion, the number of bent points N2 of the second inclined groove portion, the number of bent points N3 of the inclined fine groove, and the number of bent points Ns of the shoulder transverse groove satisfy the relationship Ns ≤ N2 < N1 ≤ N3 is indicated as "Suitable", and the case where it does not satisfy is indicated as "No".

[0051] Regarding these pneumatic tires, the snow performance and abrasion resistance were evaluated by the following evaluation methods, and the results are shown together in Tables 1 to 2.

[0052] Snow performance

[0053] Each test tire was assembled onto a wheel with a rim size of 17×8J. The front tires were inflated to 450 kPa, and the rear tires were inflated to 550 kPa. The tires were then installed on a test vehicle (traction test vehicle). A test driver conducted a sensory evaluation of traction (starting performance) on a snowy test course. The evaluation results were expressed as an index, with the value of Conventional Example 1 set to 100. A higher index value indicates better snow performance.

[0054] Wear resistance

[0055] Each test tire was assembled onto a wheel with a 17×8J rim size. The front tires were inflated to 450 kPa, and the rear tires were inflated to 550 kPa. The tires were then installed on a test vehicle (a four-wheel-drive SUV). A test driver drove the tires along a test route. The estimated wear life was calculated based on the wear after 8,000 km of driving. The evaluation results were expressed as an index, with the value of Conventional Example 1 set to 100. A larger index value indicates a longer distance traveled until complete wear, indicating superior wear resistance.

[0056] [Table 1]

[0057] Table 1

[0058]

[0059] [Table 2]

[0060] Table 2

[0061]

[0062] As can be seen from Tables 1 and 2, the pneumatic tires of Examples 1 to 15 exhibit improved snow performance and wear resistance compared to Conventional Example 1, achieving a well-balanced balance between these properties. On the other hand, in Comparative Example 1, since the second inclined groove portion extends beyond the equator, wear resistance is reduced and sufficient snow performance is not achieved. In Comparative Example 2, since the inclined narrow grooves are inclined in the same direction as the curved inclined grooves, the edge effect is reduced and sufficient snow performance is not achieved.

[0063] Description of Reference Numerals

[0064] 1. Tread

[0065] 2 Sidewall

[0066] 3 Bead

[0067] 4 carcass layers

[0068] 5 Bead core

[0069] 6 Bead filler

[0070] 7 Belt

[0071] 8 belt reinforcement layer

[0072] 11 Bending main groove

[0073] 12 Bending inclined slots

[0074] 12a First inclined groove portion

[0075] 12b Second inclined groove portion

[0076] 13 Inclined slots

[0077] 14 auxiliary inclined slots

[0078] 15 Cross-connection groove

[0079] 16 Circumferential connecting grooves

[0080] 17 shoulder grooves

[0081] 18 convex part

[0082] CL Tire Equator

[0083] Block B

[0084] S sipe

Claims

1. A tire having a tread surface that extends in a circumferential direction of the tire and is annular, characterized in that the tread surface has a plurality of blocks delimited by a plurality of grooves, the plurality of grooves include: a pair of bent main grooves disposed on both sides of the tire equator and extending in a zigzag shape along the circumferential direction of the tire; a plurality of bent inclined grooves extending from each of the pair of bent main grooves toward the tire equator; and a thin inclined groove connecting the bent inclined grooves on one side of the tire equator to the bent inclined grooves on the other side of the tire equator, each of the bent inclined grooves is composed of a first inclined groove portion extending obliquely with respect to the circumferential direction of the tire from the pair of bent main grooves toward the tire equator, and a second inclined groove portion extending in the same direction as the first inclined groove portion and more obliquely toward the circumferential side of the tire than the first inclined groove portion. The first inclined groove portion has at least one bending point, and the second inclined groove portion forms a terminal not exceeding the tire equator, the thin inclined groove is inclined in a direction opposite to that of the bent inclined groove and connects the middle portions of the second inclined groove portions to each other, at least one siped is formed in each of the plurality of blocks.

2. The tire according to claim 1, characterized in that the inclination angle θ1 of the first inclined groove portion with respect to the circumferential direction of the tire is 50° to 85°, the inclination angle θ2 of the second inclined groove portion with respect to the circumferential direction of the tire is 5° to 40°, and the difference θ1 - θ2 between the inclination angles θ1 and θ2 is 30° or more and 80° or less. [[ID=并向与所述第一倾斜槽部相同方向且比所述第一倾斜槽部更向轮胎周向侧倾斜的第二倾斜槽部构成,所述第一倾斜槽部具有至少1处弯折点,所述第二倾斜槽部不超过轮胎赤道地形成终端,8]]3. The tire according to claim 1 or 2, characterized in that the groove depth of the bent inclined groove is 50% to 100% of the groove depth of the bent main groove, and the groove depth of the thin inclined groove is 60% to 100% of the groove depth of the bent inclined groove.

4. The tire according to any one of claims 1 to 3, characterized in that the length L1 of the first inclined groove portion and the length L2 of the second inclined groove portion satisfy the relationship L2 / L1 ≥ 1.

7.

5. The tire according to any one of claims 1 to 4, characterized in that the plurality of grooves include auxiliary inclined grooves that communicate with the bent main groove and the second inclined groove portion and are inclined in the same direction as the first inclined groove portion.

6. The tire according to any one of claims 1 to 5, characterized in that the plurality of grooves include shoulder cross grooves extending from the bent main groove toward the outer side in the tire width direction, when the number of bending points of the first inclined groove portion is set as N₁, the number of bending points of the second inclined groove portion is set as N₂, the number of bending points of the thin inclined groove is set as N₃, and the number of bending points of the shoulder cross groove is set as Ns, the number of these bending points satisfies the relationship Ns ≤ N₂ < N₁ ≤ N₃.

7. The tire according to any one of claims 1 to 6, characterized in that the plurality of grooves include a transverse connecting groove that connects the second inclined groove portions on one side of the tire equator to the second inclined groove portions on the other side of the tire equator at a side closer to the terminal of the second inclined groove portion than the thin inclined groove.

8. The tire according to any one of claims 1 to 7, characterized in that The plurality of grooves includes a circumferential connecting groove that connects the second inclined groove portions adjacent to each other in the tire circumferential direction on one side of the tire equator.

9. The tire according to any one of claims 1 to 8, characterized in that A convex portion protruding from a groove bottom is provided at an intersection of at least one of the pair of bending main grooves and the bending inclined groove.

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