tire

Abstract

To provide a tire capable of improving snow performance without deteriorating abrasion resistance.SOLUTION: There are provided a pair of bent main grooves 11 which are arranged on both sides of a tire equator CL and extend in a zigzag shape in the tire circumferential direction, a plurality of bent inclined grooves 12 extending in the tire equator CL direction from the bent main grooves 11 and inclined narrow grooves 13 for connecting the bent inclined grooves 12 on both sides of the tire equator CL as grooves for dividing a block C in a tread part 1, wherein the bent inclined grooves 12 are constituted by first inclined groove parts 12a which incline and extend in the tire circumferential direction toward the tire equator CL direction from bent main grooves 11 and have at least one bent point and second inclined groove parts 12b which incline in the same direction as the first inclined groove parts 12a and in the tire circumferential direction side from the first inclined groove parts 12a and terminate without exceeding the tire equator CL and inclined narrow grooves 13 are inclined in the opposite direction to the bent inclined grooves 12 to connect the middle part of the second inclined groove part 12b and at least one sipe S is formed in each block B.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a tire intended for running on unpaved roads and the like, and more particularly to a tire which enables improved snow performance without impairing wear resistance. [Background technology]

[0002] In addition to paved road surfaces, tires (e.g., all-terrain tires, all-terrain type tires, etc.) that are intended to run on unpaved roads (rough ground, muddy ground, sandy ground, rocky areas, etc.) are required to have excellent off-road performance. They are also required to have excellent snow performance to enable stable running even during snowfall. In particular, in recent years, snow performance has been emphasized among these performances, and tires are required to have sufficient performance even on snowy road surfaces in extremely cold regions. For such tires, there is a tendency to adopt a tread pattern that is mainly composed of lug grooves and blocks with many edge components and has a large groove area (see, for example, 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 to maintain sufficient wear resistance are also required. For the above reasons, there is a demand for a high degree of compatibility between snow performance and wear resistance. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2019-137218 A Summary of the Invention [Problem to be solved by the invention]

[0004] An object of the present invention is to provide a tire which enables improved snow performance without impairing wear resistance. [Means for solving the problem]

[0005] A tire according to the present invention for achieving the above object is a tire having a tread portion extending in a circumferential direction of the tire to form an annular shape, the tread portion having a plurality of blocks partitioned by a plurality of grooves, the plurality of grooves including a pair of bent main grooves disposed on both sides of the tire equator and extending in a zigzag pattern along the tire circumferential direction, a plurality of bent oblique grooves extending from each of the pair of bent main grooves toward the tire equator, and an oblique narrow groove connecting the bent oblique groove on one side of the tire equator and the bent oblique groove on the other side of the tire equator, Each of the plurality of blocks is composed of a first inclined groove portion extending from the pair of bent main grooves toward the tire equator at an incline with respect to the tire circumferential direction, and a second inclined groove portion inclined in the same direction as the first inclined groove portion and toward the tire circumferential side of the first inclined groove portion, the first inclined groove portion has at least one bending point, the second inclined groove portion terminates without passing the tire equator, the inclined narrow groove is inclined in the opposite direction to the bent inclined groove and connects the middle portions of the second inclined groove portions, and at least one sipe is formed in each of the plurality of blocks. Effect of the Invention

[0006] In the tire of the present invention, since the blocks and each groove formed between the pair of bent main grooves have the above-mentioned structure, the snow performance can be improved without impairing the wear resistance. In particular, since there are a pair (two) of main grooves (bent main grooves) extending along the tire circumferential direction, the block rigidity between the main grooves (center region) can be secured and the wear resistance can be maintained well. On the other hand, since the main grooves (bent main grooves) are bent, even a pair (two) of them can exhibit good snow performance. In addition, the provision of bent inclined grooves can also improve snow performance. However, since the bent inclined grooves (second inclined groove portions) end without crossing the tire equator, the block rigidity can be secured and the wear resistance can be maintained well. Furthermore, the inclined narrow grooves are inclined in the opposite direction to the bent inclined grooves to connect the middle parts of the second inclined groove portions, so that the inclined grooves are arranged in various directions, and the snow performance can be improved. In addition, at least one sipe is formed in each block, so that the edge effect of the sipes can be secured and the snow performance can be improved. These cooperations can achieve a high degree of both wear resistance and snow performance.

[0007] In the present invention, it is preferable that the inclination angle θ1 of the first inclined groove portion with respect to the tire circumferential direction is 50° to 85°, the inclination angle θ2 of the second inclined groove portion with respect to the tire circumferential direction is 5° to 40°, and the difference θ1-θ2 between the inclination angles θ1 and θ2 is 30° to 80°. Setting the inclination angles of each portion in this manner improves the shape of the bent inclined grooves, which is advantageous for improving snow performance.

[0008] In the present invention, it is preferable that the groove depth of the bent oblique groove is 50% to 100% of the groove depth of the bent main groove, and the groove depth of the oblique narrow groove is 60% to 100% of the groove depth of the bent oblique groove. Setting the groove depth of each groove in this manner is advantageous for improving snow performance while ensuring block rigidity.

[0009] In the present invention, it is preferable 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. Thereby, the balance between the circumferential groove component and the widthwise groove component ensured by the bent inclined groove becomes good, which is advantageous for improving the snow performance.

[0010] In the present invention, it is preferable that the plurality of grooves include sub-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. By including the sub-inclined grooves in this way, groove components are added, which is advantageous for improving the snow performance.

[0011] In the present invention, the plurality of grooves include shoulder lug grooves extending outward in the tire width direction from the bent main groove. When the number of bending points of the first inclined groove portion is N1, the number of bending points of the second inclined groove portion is N2, the number of bending points of the inclined fine groove is N3, and the number of bending points of the shoulder lug groove is Ns, it is preferable that these numbers of bending points satisfy the relationship Ns ≤ N2 < N1 ≤ N3. 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), it is possible to expect an improvement in the snow performance due to the improvement of the snow removal performance.

[0012] In the present invention, it is preferable that the plurality of grooves include a transverse connection 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 on the end side of the second inclined groove portion rather than the inclined fine groove. By including the transverse connection groove in this way, the edge effect by this groove can be ensured, which is advantageous for improving the snow performance.

[0013] In the present invention, it is preferable that the plurality of grooves include a circumferential connection 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 connection groove in this way, the edge effect by this groove can be ensured, which is advantageous for improving the snow performance.

[0014] In the present invention, it is preferable that at least one of the pair of bent main grooves has a protrusion protruding from the groove bottom at the intersection with the bent oblique groove. By providing such a protrusion, it is possible to improve snow performance without affecting wear resistance.

[0015] 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, the interior thereof can be filled with air, an inert gas such as nitrogen, or other gases. [Brief description of the drawings]

[0016] [Figure 1] 1 is a meridian cross-sectional view of a tire according to an embodiment of the present invention. [Diagram 2] 1 is a front view showing a tread surface of a tire according to an embodiment of the present invention. [Diagram 3] FIG. 3 is an explanatory diagram showing a part of FIG. 2. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0017] The configuration of the present invention will be described in detail below with reference to the accompanying drawings.

[0018] When the tire of the present invention is a pneumatic tire as shown in Fig. 1, it includes a tread portion 1 that contacts the road surface, a pair of sidewall portions 2 arranged on both sides of the tread portion 1, and a pair of bead portions 3 arranged on the tire radial inner side of the sidewall portions 2. In Fig. 1, the symbol CL indicates the tire equator. Although not depicted in Fig. 1 because it is a meridian cross section, the tread portion 1, the sidewall portions 2, and the bead portions 3 each extend in the tire circumferential direction to form an annular shape, thereby forming a basic toroidal structure of a pneumatic tire. The following explanation using Fig. 1 is basically based on the meridian cross section shown in the figure, but each tire component extends in the tire circumferential direction to form an annular shape.

[0019] A carcass layer 4 is installed between a pair of left and right bead portions 3. The carcass layer 4 includes a plurality of reinforcing cords extending in the tire radial direction, and is folded back from the vehicle inner side to the vehicle outer side around the bead cores 5 arranged in each bead portion 3. A bead filler 6 is arranged on the outer periphery of the bead cores 5, and the bead filler 6 is wrapped by the main body and the folded back portion of the carcass layer 4. Meanwhile, a plurality of belt layers 7 (two layers in FIG. 1) are embedded on the outer periphery side of the carcass layer 4 in the tread portion 1. Each belt layer 7 includes a plurality of reinforcing cords inclined with respect to the tire circumferential direction, and the reinforcing cords are arranged so as to cross each other between the layers. In these belt layers 7, the inclination angle of the reinforcing cords with respect to the tire circumferential direction is set to, for example, a range of 10° to 40°. Furthermore, at least one belt reinforcing layer 8 (two layers in FIG. 1) is provided on the outer periphery side of the belt layer 7. The belt reinforcing layer 8 includes organic fiber cords oriented in the tire circumferential direction. In the belt reinforcing layer 8, the organic fiber cords are set at an angle of, for example, 0° to 5° with respect to the tire circumferential direction.

[0020] As described below, the present invention relates to a tread pattern formed on the surface of the tire tread portion 1, and therefore the basic structure (cross-sectional structure) of the tire is not limited to the general structure described above. In addition, the present invention can be applied to various tires, including non-pneumatic tires, as long as they have a surface that comes into contact with the road surface (a portion corresponding to the surface of the tread portion 1 in a pneumatic tire).

[0021] A plurality of blocks B defined by a plurality of grooves are provided on the surface of the tread portion 1 of the tire of the present invention, as shown in Fig. 2. The grooves defining the plurality of blocks B necessarily include three types of grooves, namely, a curved main groove 11, a curved oblique groove 12, and an oblique narrow groove 13, which will be described later. Also, at least one sipe S is necessarily formed in each of the plurality of blocks B.

[0022] The bend main groove 11 is a groove extending in a zigzag shape along the tire circumferential direction, and a pair (two grooves) are arranged on both sides of the tire equator. The zigzag shape is a shape in which linear portions inclined in one direction with respect to the tire circumferential direction and linear portions inclined in the other direction are alternately connected in the tire circumferential direction. In the bend main groove 11, a point where a linear portion inclined in one direction with respect to the tire circumferential direction connects with a linear portion inclined in the other direction is called a bend point. In the following description, the region between a pair of bend main grooves 11 may be called a center region, and the region on the outer side of each bend main groove 11 in the tire width direction may be called a shoulder region. The bend main groove 11 is a groove with the largest groove width and groove depth among the above-mentioned three types of grooves. Specifically, the groove width of the bend main groove 11 is preferably 3 mm to 13 mm, more preferably 5 mm to 11 mm. The groove depth of the bend main groove 11 is preferably 8 mm to 16 mm, more preferably 10 mm to 15 mm.

[0023] The bent inclined groove 12 is a groove extending from each of the pair of bent main grooves 11 toward the tire equator CL. A plurality of bent inclined grooves 12 are provided at intervals in the tire circumferential direction. In the illustrated example, the bent inclined groove 12 extends from a bent point on the inner side of each bent main groove 11 in the tire width direction. The bent inclined groove 12 is composed of a first inclined groove portion 12a extending from the bent main groove 11 toward the tire equator CL at an incline with respect to the tire circumferential direction, and a second inclined groove portion 12b inclined in the same direction as the first inclined groove portion 12a and toward the tire circumferential side more than the first inclined groove portion 12a. The first inclined groove portion 12a and the second inclined groove portion 12b are connected to each other, so that the bent inclined groove 12 has one bend point as a whole, and in addition, the first inclined groove portion 12a has at least one bend 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. More specifically, the other end of the second inclined groove portion 12b has a tapered shape in which the groove width converges toward the end, and has an acute-angled tip (acute apex) at the end position, but this tip (apex) is located on one side of the tire equator CL (the side where the bent inclined groove 12 to which the second inclined groove portion 12b belongs is provided), and the second inclined groove portion 12b does not intersect with the tire equator CL. The bent inclined groove 12 (the first inclined groove portion 12a and the second inclined groove portion 12b) is a groove whose groove width and groove depth are equal to or less than those of the bent main groove. The groove width of the bent inclined groove 12 is preferably 80% to 97%, more preferably 85% to 95%, of the groove width of the bent main groove 11. The groove depth of the bent inclined groove 12 is preferably 50% to 100%, more preferably 70% to 100% of the groove depth of the bent main groove 11.

[0024] The inclined narrow groove 13 is a groove that connects the bent inclined groove 12 on one side of the tire equator CL and the bent inclined groove 12 on the other side of the tire equator CL. Therefore, the inclined narrow groove 13 necessarily intersects with the tire equator CL. The inclined narrow groove 13 is inclined in the opposite direction to the bent inclined groove 12, and connects the middle parts of the second inclined groove parts 12b. The inclined narrow groove 13 may be bent. In the illustrated example, the inclined narrow groove 13 is bent in a Z-shape and has two bending points. The bent narrow groove 13 is a groove whose groove width and groove depth are smaller than those of the bent inclined groove 12. The groove width of the bent narrow groove 13 is preferably 35% to 75%, more preferably 45% to 65%, of the groove width of the bent inclined groove 12. The groove depth of the bent narrow groove 13 is preferably 50% to 100%, more preferably 70% to 100%, of the groove depth of the bent inclined groove 12.

[0025] As described above, at least one sipe S is provided in each block B. In the illustrated example, two sipes S extending in a zigzag pattern are provided in each block B. The shape of the sipes S is not particularly limited, and various shapes such as a straight line can be adopted in addition to the zigzag shape shown in the figure. The number of sipes S provided in each block B can be appropriately set according to the size of the block, but is preferably 1 to 4, and more preferably 2 to 3. The sipes S are fine grooves with a groove width of, for example, 0.5 mm to 2.0 mm and a groove depth of, for example, 2 mm to 15 mm.

[0026] By providing various grooves as described above, the tire of the present invention can improve snow performance without impairing wear resistance. That is, since there are a pair (two) of main grooves (bent main grooves 11) extending along the tire circumferential direction, the block rigidity between the main grooves (center region) can be secured and the wear resistance can be maintained well. On the other hand, since the main grooves (bent main grooves 11) are bent, good snow performance can be achieved even if there are only two (a pair) of them. In addition, the provision of the bent inclined groove 12 can also improve snow performance. However, since the bent inclined groove 12 (second inclined groove portion 12b) terminates without exceeding the tire equator CL, the block rigidity can be secured and the wear resistance can be maintained well. Furthermore, the inclined narrow groove 13 is inclined in the opposite direction to the bent inclined groove 12 and connects the middle parts of the second inclined groove portions 12b, so that grooves inclined in various directions are arranged, and the snow performance can be improved. In addition, by forming at least one sipe S in each block B, the edge effect of the sipe S can be secured and the snow performance can be improved. This combination of features enables a high level of both wear resistance and snow performance to be achieved.

[0027] If the tire does not include any of the three types of grooves described above, or if the grooves are provided in the same positions but the curved shape or inclination direction does not satisfy the above conditions, the above effects of each groove will be insufficient, making it difficult to achieve a good balance between wear resistance and snow performance. Also, if the groove width or groove depth of each groove is smaller than the above range, the groove volume will not be sufficient and snow performance will not be improved. Conversely, if the groove width or groove depth of each groove is larger than the above range, the groove volume will be large and block rigidity will not be ensured, making it difficult to maintain sufficient wear resistance.

[0028] In the present invention, the grooves dividing the blocks B preferably include, in addition to the three types of grooves described above, the sub-inclined grooves 14, the transverse connecting grooves 15, and the circumferential connecting grooves 16 described below. By including these grooves, groove components extending in various directions are added, so that the edge effect of each groove can be secured, which is advantageous for improving snow performance. In addition, since the inclination direction, groove width, and groove depth of each groove are set as described below, even if each groove is added, the block rigidity can be sufficiently secured and the wear resistance can be maintained well.

[0029] The sub-inclined groove 14 is a groove that communicates with the bent 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 sub-inclined groove 14 extends from a bending point on the inner side in the tire width direction of each bent main groove 11 that is not connected to the bent inclined groove 12 (first inclined groove portion 12a). The sub-inclined groove 14 may have a bending shape similar to that of the first inclined groove portion 12a. The sub-inclined groove 14 may be connected to a position within 10% of the length of the second inclined groove portion 12b on both sides in the tire circumferential direction from the center of the second inclined groove portion 12b. The sub-inclined groove 14 may have a groove width and groove depth equal to or less than those of the bent inclined groove 12. Specifically, the groove width of the sub-inclined groove 14 may be preferably 50% to 100% of the groove width of the bent inclined groove 12, more preferably 65% ​​to 85%. The groove depth of the sub inclined groove 14 is preferably 50% to 100% of the groove depth of the bent inclined groove 12, and more preferably 70% to 100%.

[0030] The transverse connecting groove 15 is a groove that connects the second inclined groove portion 12b on one side of the tire equator Cl and the second inclined groove portion 12b on the other side of the tire equator at the end side of the second inclined groove portion 12b beyond the inclined narrow groove 13. However, the transverse connecting groove 15 is connected at a position that is off the tip (apex) of the second inclined groove portion 12b, and the end of the second inclined groove portion 12b always has a tip (apex). The transverse connecting groove 15 is preferably inclined in the opposite direction to the inclined narrow groove 13. The transverse connecting groove 15 has a groove depth equal to or less than that of the bent inclined groove 12 (second inclined groove portion 12b). Specifically, the groove depth of the transverse connecting groove 15 is preferably 70% to 100%, more preferably 75% to 100%, of the groove depth of the bent inclined groove 12. On the other hand, the transverse connecting groove 15 has a groove width that is sufficiently smaller than that of the bent inclined groove 12 (second inclined groove portion 12b). Specifically, the groove width of the transverse connecting groove 15 is preferably 20% to 60%, more preferably 30% to 50%, of the groove width of the bent inclined groove 12b. Since the groove width of the transverse connecting groove 15 is significantly smaller than the groove width of the bent inclined groove 12 (second inclined groove portion 12b), even if the transverse connecting groove 15 is connected to the terminal side (near the tip) of the second inclined groove portion 12b, the bent inclined groove 12 (second inclined groove portion 12b) is considered to be terminated.

[0031] The circumferential connecting groove 16 is a groove that connects the second inclined groove portions 12b adjacent to each other 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 side (near the tip) of the second inclined groove portion 12b adjacent to the second inclined groove portion 12b. The circumferential connecting groove 16 is preferably inclined in the opposite direction to the second inclined groove portion 12b. The circumferential connecting groove 16 is connected to a position that is off the tip (apex) of the second inclined groove portion 12b, and the tip (apex) is always present at the terminal of the second inclined groove portion 12b. The circumferential connecting groove 16 has a groove depth equal to or less than that of the bent inclined groove 12 (second inclined groove portion 12b). Specifically, the groove depth of the circumferential connecting groove 16 is preferably 80% to 100%, more preferably 90% to 100%, of the groove depth of the bent inclined groove 12. On the other hand, the circumferential connecting groove 16 has a groove width sufficiently smaller than that of the bent inclined groove 12 (second inclined groove portion 12b). Specifically, the groove width of the circumferential connecting groove 16 is preferably 40% to 90%, more preferably 55% to 75% of the groove width of the bent inclined groove 12. Since the groove width of the circumferential connecting groove 16 is significantly smaller than that of the bent inclined groove 12 (second inclined groove portion 12b) in this way, even if the circumferential connecting groove 16 is connected to the terminal side (near the tip) of the second inclined groove portion 12b, the bent inclined groove 12 (second inclined groove portion 12b) is considered to be terminated.

[0032] The structure of the shoulder region is not particularly limited, but it is preferable to provide shoulder lug grooves 17 extending from the flexion main grooves 11 toward the outside in the tire width direction. A plurality of shoulder lug grooves 17 may be provided at intervals in the tire circumferential direction. In the illustrated example, the shoulder lug grooves 17 are connected to the flexion points of the flexion main grooves 11 on the outside in the tire width direction. The groove width of the shoulder lug grooves 17 is preferably 70% to 98%, more preferably 80% to 95%, of the groove width of the flexion main grooves 11. The groove depth of the shoulder lug grooves 17 is preferably 75% to 100%, more preferably 80% to 98% of the groove depth of the flexion main grooves.

[0033] As described above, in the present invention, the plurality of grooves partitioning the plurality of blocks B necessarily 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. Among these grooves (groove portions), at least the first inclined groove portion 12a and the inclined fine grooves 13 necessarily bend, and the second inclined groove portion 12b can also bend optionally. At this time, if the number of bending points of the first inclined groove portion 12a is N1, the number of bending points of the second inclined groove portion 12b is N2, and the number of bending points of the inclined fine grooves 13 is N3, it is preferable that the number of these bending points satisfies the relationship of N2 < N1 ≤ N3. For example, in the illustrated example, since 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, the above-mentioned magnitude 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), it is possible to expect an improvement in the snow performance by improving the snow removal performance. In addition, when the shoulder lug groove 17 is provided, if the number of bending points of the shoulder lug groove 17 is Ns, it is preferable that the number of bending points 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 lug groove 17 = 0 to 1 are preferable.

[0034] Each of the above-mentioned various grooves is inclined with respect to the tire circumferential direction, but the inclination angle with respect to each tire circumferential direction is preferably set as described below. In addition, as shown in FIG. 3, the inclination angle of each groove is measured based on the center line of each groove. Further, when 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 defined as the inclination angle. FIG. 3 shows an extraction of a part of FIG. 2, omitting the sipes S, notches, and the convex portion 18 described later, and extracting and showing the main grooves (the bent main groove 11, the bent inclined groove 12, the inclined fine groove 13, the sub-inclined groove 14, the transverse connecting groove 15, the circumferential connecting groove 16, the shoulder lug groove 17).

[0035] The inclination angle θ1 of the first inclined groove portion 12a with respect to the tire circumferential direction is preferably 50° to 85°, more preferably 60° to 80°. This allows groove components extending in the tire width direction to be secured, which is advantageous for improving traction performance on snowy road surfaces. If the inclination angle θ1 is less than 50°, the edge effect is reduced. If the inclination angle θ1 exceeds 85°, the steering stability on snowy road surfaces is reduced. The inclination angle θ2 of the second inclined groove portion 12b with respect to the tire circumferential direction is preferably 5° to 40°, more preferably 8° to 30°. This allows groove components extending in the tire circumferential direction to be secured, which is advantageous for improving steering stability on snowy road surfaces. If the inclination angle θ2 is less than 5°, the edge effect is reduced. If the inclination angle θ2 exceeds 40°, the steering stability on snowy road surfaces 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 the inclination angles in this way, the overall bent shape of the bent inclined groove 12 is improved, and the balance between the traction and steering stability on snowy road surfaces is improved, effectively improving snow performance. If the difference in the inclination angles θ1-θ2 is less than 30°, the edge effect is reduced. If the difference in the inclination angles θ1-θ2 is more than 80°, the edge effect is reduced.

[0036] The inclination angle θ3 of the inclined narrow groove 13 with respect to the tire circumferential direction is preferably 90° to 135°, more preferably 110° to 130°. This is advantageous for improving 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 the other grooves are not particularly limited, but the inclination angle θ4 of the sub-inclined groove 14 with respect to the tire circumferential direction can be set to, for example, 60° to 80°, the inclination angle θ5 of the transverse connecting groove 15 with respect 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 with respect to the tire circumferential direction can be set to, for example, 110° to 130°. In addition, when the shoulder lug groove 17 is provided, the inclination angle θs with respect to the tire circumferential direction can be set to, for example, 90° to 120°.

[0037] As described above, the bent main groove 11 has a shape in which linear portions inclined in one direction with respect to the tire circumferential direction and linear portions inclined in the other direction are alternately connected in the tire circumferential direction. That is, the bent main groove 11 is composed of a linear portion (hereinafter referred to as a first linear portion 11a) inclined in the same direction as the bent oblique groove 12, and a linear portion (hereinafter referred to as a second linear portion 11b) inclined in the opposite direction to the bent oblique groove 12. When the inclination angle of the first linear portion 11a with respect to the tire circumferential direction is α1 and the inclination angle of the second linear portion 11b with respect to the tire circumferential direction is α2, the inclination angle α1 can be set to, for example, 10° to 60°, and the inclination angle θ2 can be set to, for example, 85° to 145°.

[0038] When the bent inclined groove 12 is formed by the first inclined groove portion 12a and the second inclined groove portion 12b, the length of the second inclined groove portion 12b is made sufficiently larger than that of the first inclined groove portion 12a to ensure a groove component extending in the tire circumferential direction, which is advantageous for improving the steering stability on snowy road surfaces. In particular, it is preferable that the length L1 of the first inclined groove portion 12a and the length L2 of the second inclined groove portion 12b satisfy the relationship L2 / L1≧1.7, more preferably 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 sufficiently ensured, and the effect of improving the steering stability on snowy road surfaces cannot be sufficiently expected. As shown in FIG. 3, the length L1 is measured along the tire width direction, and the length L2 is measured along the tire circumferential direction.

[0039] A protrusion 18 protruding from the groove bottom can be provided at the intersection of the pair of bend main grooves 11 with at least one of the bend oblique grooves 12. Providing the protrusion 18 in this manner can enhance the edge effect on snow without affecting the wear resistance, and improve snow performance. The protrusion height from the groove bottom of the protrusion 18 is preferably 2% to 20%, more preferably 5% to 15% of the groove depth of the bend main groove 11. The protrusion 18 is preferably not protruding over the entire width of the groove bottom of the bend main groove 11, but is preferably a shape in which only a part of it is protruding. In particular, the width of the protrusion 18 is preferably 10% to 50%, more preferably 10% to 30% of the groove width of the bend main groove 11. When the protrusion 18 is provided, it is preferable to provide the protrusion 18 at a position away from the point where the shoulder lug groove 17 connects to the bend main groove 11 so as not to impede the snow removal effect from the bend main groove 11 to the shoulder lug groove 17.

[0040] The present invention will be further described below with reference to examples, but the scope of the present invention is not limited to these examples. EXAMPLES

[0041] Thirteen types of pneumatic tires (Conventional Example 1, Comparative Examples 1-2, and Examples 1-15) were produced, with a tire size of LT265 / 70R17 121 / 118S and a basic structure (cross-sectional structure) as exemplified in FIG. 1, based on the tread pattern of FIG. 2, in which the shape of the main groove, the presence or absence of bent inclined grooves, the number of bend points of the first inclined grooves, the end position of the second inclined groove portion, the inclination direction of the inclined narrow grooves, the presence or absence of sipes, the inclination angle θ1 of the first inclined groove portion with respect to the circumferential direction of the tire, the inclination angle θ2 of the second inclined groove portion with respect to the circumferential direction of the tire, the difference between these inclination angles θ1-θ2, the groove depth of the bent inclined grooves, the groove depth of the inclined narrow grooves, the length ratio L2 / L1 of the first inclined groove portion to the second inclined groove portion, the relationship between the number of bends N1-N3 and Ns, and the presence or absence of convex portions were set as shown in Table 1.

[0042] In Table 1, for the column of "Shape of Main Groove", when the main groove extends linearly, it is indicated as "Straight", and when it extends in a zigzag shape, it is indicated as "Bent". For the column of "Terminal Position of Second Inclined Groove Portion", when the second inclined groove portion terminates without reaching the tire equator, it is indicated as "Not Reached the Equator", and when it reaches the tire equator or extends beyond the tire equator, it is indicated as "Reached the Equator". For the column of "Inclination Direction of Inclined Fine Groove", when the inclined fine groove inclines in the same direction as the bent inclined groove, it is indicated as "Same Direction", and when it inclines in the opposite direction, it is indicated as "Opposite Direction". For the column of "Groove Depth of 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 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 Number of Bends", when the number of bending points N1 of the first inclined groove portion, the number of bending points N2 of the second inclined groove portion, the number of bending points N3 of the inclined fine groove, and the number of bending points Ns of the shoulder lug groove satisfy the relationship Ns ≦ N2 < N1 ≦ N3, it is indicated as "Conform", and when not satisfied, it is indicated as "No".

[0043] For these pneumatic tires, the snow performance and wear resistance were evaluated by the following evaluation methods, and the results are shown together in Table 1.

[0044] Snow Performance Each test tire was assembled on a wheel with a rim size of 17×8J, and mounted on a test vehicle (traction test vehicle) with the air pressure of the front tire being 450 kPa and the air pressure of the rear tire being 550 kPa. A sensory evaluation by a test driver was conducted on the tractability (starting performance) on a test course consisting of a snow-covered road surface. The evaluation results were shown in an index with the value of Conventional Example 1 being 100. The larger this index value is, the better the snow performance. Incidentally, if this index value is less than "110", it means that sufficient snow performance could not be obtained.

[0045] Wear Resistance Each test tire was mounted on a wheel with a rim size of 17x8J, and the front tire air pressure was set to 450kPa and the rear tire air pressure was set to 550kPa. The test vehicle (four-wheel drive SUV) was then fitted with the tire and a test driver performed a test run on a test course. The estimated wear life was calculated from the amount of wear after 8000km of driving. The evaluation results were expressed as an index, with the value of Conventional Example 1 being set at 100. The higher the index value, the longer the driving distance until complete wear and the better the wear resistance.

[0046] [Table 1]

[0047] As is clear from Table 1, the pneumatic tires of Examples 1 to 15 had improved snow performance and wear resistance compared to Conventional Example 1, and these performances were well balanced. On the other hand, in Comparative Example 1, the second inclined groove portion extended beyond the equator, so the wear resistance was reduced and sufficient snow performance was not obtained. In Comparative Example 2, the inclined narrow groove was inclined in the same direction as the bent inclined groove, so the edge effect was reduced and sufficient snow performance was not obtained.

[0048] The present disclosure includes the following inventions. Invention [1] A tire having a tread portion extending in a circumferential direction of the tire and forming an annular shape, The tread portion includes a plurality of blocks defined 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 pattern along the tire circumferential direction, a plurality of bent oblique grooves extending from each of the pair of bent main grooves toward the tire equator, and an oblique narrow groove connecting the bent oblique groove on one side of the tire equator and the bent oblique groove on the other side of the tire equator, Each of the bent inclined grooves includes a first inclined groove portion that extends inclined with respect to the tire circumferential direction from the pair of main bent grooves toward the tire equator direction, and a second inclined groove portion that is inclined in the same direction as the first inclined groove portion and is inclined more toward the tire circumferential direction side than the first inclined groove portion. The first inclined groove portion has at least one bent point, and the second inclined groove portion terminates without crossing the tire equator. The inclined fine grooves are inclined in a direction opposite to that of the bent inclined grooves and connect intermediate portions of the second inclined groove portions. A tire, wherein at least one sipe is formed in each of the plurality of blocks. Invention [2] The tire according to invention [1], wherein an inclination angle θ1 of the first inclined groove portion with respect to the tire circumferential direction is 50° to 85°, an inclination angle θ2 of the second inclined groove portion with respect to the tire circumferential direction is 5° to 40°, and a difference θ1 - θ2 between the inclination angles θ1 and θ2 is 30° or more and 80° or less. Invention [3] The tire according to invention [1] or [2], wherein a groove depth of the bent inclined groove is 50% to 100% of a groove depth of the main bent groove, and a groove depth of the inclined fine groove is 60% to 100% of the groove depth of the bent inclined groove. Invention [4] The tire according to any one of inventions [1] to [3], wherein a length L1 of the first inclined groove portion and a length L2 of the second inclined groove portion satisfy a relationship of L2 / L1 ≧ 1.7. Invention [5] The tire according to any one of inventions [1] to [4], wherein the plurality of grooves includes auxiliary inclined grooves that communicate with the main bent groove and the second inclined groove portion and are inclined in the same direction as the first inclined groove portion. Invention [6] The plurality of grooves includes shoulder lug grooves that extend outward in the tire width direction from the main bent groove. When the number of bent points of the first inclined groove portion is N1, the number of bent points of the second inclined groove portion is N2, the number of bent points of the inclined fine groove is N3, and the number of bent points of the shoulder lug groove is Ns, the number of these bent points satisfies a relationship of Ns ≦ N2 < N1 ≦ N3. The tire according to any one of inventions [1] to [5]. Invention [7] A tire according to any one of inventions [1] to [6], characterized in that the plurality of grooves include a transverse 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, on the terminal side of the second inclined groove portion relative to the inclined narrow groove. Invention [8] A tire as described in any one of inventions [1] to [7], characterized in that the plurality of grooves include a circumferential connecting groove that connects adjacent second inclined groove portions in the tire circumferential direction on one side of the tire equator. Invention [9] The tire according to any one of inventions [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 bend main grooves with the bend oblique groove. [Explanation of symbols]

[0049] 1 Tread section 2 Sidewall 3 Bead section 4 Carcass layer 5 Bead Core 6 Bead Filler 7 Belt layer 8 Belt reinforcement layer 11 Bent main groove 12 Bend inclined groove 12a First inclined groove part 12b Second inclined groove part 13 Slanted narrow groove 14 Minor inclined groove 15 Transverse connecting groove 16 Circumferential connection groove 17 Shoulder lug groove 18 Convex CL Tire Equator Block B S Sipe

Claims

1. A tire having a tread portion extending in a circumferential direction of the tire and forming an annular shape, The tread portion includes a plurality of blocks defined 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 pattern along the tire circumferential direction, a plurality of bent oblique grooves extending from each of the pair of bent main grooves toward the tire equator direction, an oblique narrow groove connecting the bent oblique groove on one side of the tire equator and the bent oblique groove on the other side of the tire equator, and a shoulder lug groove extending from the bent main groove toward the outside in the tire width direction, Each of the bent inclined grooves is composed of a first inclined groove portion extending from the pair of bent main grooves toward the tire equator at an incline with respect to the tire circumferential direction, and a second inclined groove portion inclined in the same direction as the first inclined groove portion and toward the tire circumferential side of the first inclined groove portion, the first inclined groove portion has at least one bending point, the second inclined groove portion has an acute-angled tip end at a terminal position to which no other grooves are connected, and the acute-angled tip end is disposed at a position not exceeding the tire equator, The inclined narrow groove is inclined in a direction opposite to the bent inclined groove and connects the middle portions of the second inclined groove portions, At least one sipe is formed in each of the plurality of blocks, When the number of bending points of the first inclined groove portion is N1, the number of bending points of the second inclined groove portion is N2, the number of bending points of the inclined narrow groove is N3, and the number of bending points of the shoulder lug groove is Ns, the numbers of these bending points satisfy the relationship Ns≦N2<N1≦N3.

2. A tire having a tread portion extending in a circumferential direction of the tire and forming an annular shape, The tread portion includes a plurality of blocks defined 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 pattern along the tire circumferential direction, a plurality of bent oblique grooves extending from each of the pair of bent main grooves toward the tire equator, and an oblique narrow groove connecting the bent oblique groove on one side of the tire equator and the bent oblique groove on the other side of the tire equator, Each of the bent inclined grooves is composed of a first inclined groove portion extending from the pair of bent main grooves toward the tire equator at an incline with respect to the tire circumferential direction, and a second inclined groove portion inclined in the same direction as the first inclined groove portion and toward the tire circumferential side of the first inclined groove portion, the first inclined groove portion has at least one bending point, the second inclined groove portion has an acute-angled tip end at a terminal position to which no other grooves are connected, and the acute-angled tip end is disposed at a position not exceeding the tire equator, the inclination angle θ1 of the first inclined groove portion with respect to the tire circumferential direction is 50° to 85°, the inclination angle θ2 of the second inclined groove portion with respect to the tire circumferential direction is 5° to 40°, and the difference θ1-θ2 between the inclination angles θ1 and θ2 is 30° or more and 80° or less; The inclined narrow groove is inclined in a direction opposite to the bent inclined groove and connects the middle portions of the second inclined groove portions, At least one sipe is formed in each of the plurality of blocks.

3. A tire having a tread portion extending in a circumferential direction of the tire and forming an annular shape, The tread portion includes a plurality of blocks defined 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 pattern along the tire circumferential direction, a plurality of bent oblique grooves extending from each of the pair of bent main grooves toward the tire equator, and an oblique narrow groove connecting the bent oblique groove on one side of the tire equator and the bent oblique groove on the other side of the tire equator, Each of the bent inclined grooves is composed of a first inclined groove portion extending from the pair of bent main grooves toward the tire equator at an incline with respect to the tire circumferential direction, and a second inclined groove portion inclined in the same direction as the first inclined groove portion and toward the tire circumferential side of the first inclined groove portion, the first inclined groove portion has at least one bending point, the second inclined groove portion has an acute-angled tip end at a terminal position to which no other grooves are connected, and the acute-angled tip end is disposed at a position not exceeding the tire equator, a length L1 of the first inclined groove portion and a length L2 of the second inclined groove portion satisfy a relationship of L2 / L1≧1.7, The inclined narrow groove is inclined in a direction opposite to the bent inclined groove and connects the middle portions of the second inclined groove portions, At least one sipe is formed in each of the plurality of blocks.

4. The tire according to any one of claims 1 to 3, characterized in that the groove depth of the bent oblique groove is 50% to 100% of the groove depth of the bent main groove, and the groove depth of the oblique narrow groove is 60% to 100% of the groove depth of the bent oblique groove.

5. The tire according to any one of claims 1 to 3, characterized in that the plurality of grooves include a sub-inclined groove that is connected to the bent main groove and the second inclined groove portion and is inclined in the same direction as the first inclined groove portion.

6. The tire according to any one of claims 1 to 3, characterized in that the plurality of grooves include a transverse 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 terminal side of the second inclined groove portion relative to the inclined narrow groove.

7. The tire according to any one of claims 1 to 3, characterized in that the plurality of grooves include a circumferential connecting groove that connects adjacent second inclined groove portions in the tire circumferential direction on one side of the tire equator.

8. The tire according to any one of claims 1 to 3, characterized in that a protrusion protruding from a groove bottom is provided at an intersection of at least one of the pair of bent main grooves with the bent oblique groove.

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