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 have a bent shape in which circumferential direction groove parts 11a and width direction groove parts 11b are alternately connected in the tire circumferential direction, a plurality of bent inclined grooves 12 comprising first inclined groove parts 12a extending from each of the bent main grooves 11 toward the tire equator CL direction and second inclined groove parts 12b which incline and extend in the same direction as the first inclined groove parts 12a and in the tire circumferential direction side and terminate without exceeding the tire equator CL, a plurality of shoulder lug grooves 13 extending toward the outside of the tire width direction along the extension direction of the width direction groove parts 11b from the end of the width direction groove parts 11b and crossing grooves 14 which are inclined in the opposite direction to the bent inclined grooves 12 and connect a pair of bent main grooves 11 as a plurality of grooves for dividing a plurality blocks B in a tread part 1, wherein at least one sipe S is formed in each of the plurality of blocks 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 flexion main grooves disposed on both sides of the tire equator and extending along the tire circumferential direction, a plurality of flexion oblique grooves extending from each of the pair of flexion main grooves toward the tire equator direction, a plurality of shoulder lug grooves extending from each of the pair of flexion main grooves toward the outside in the tire width direction, and a transverse groove connecting the flexion main groove on one side of the tire equator and the flexion main groove on the other side of the tire equator, and the flexion main groove is a flexion groove in which circumferential groove portions extending along the tire circumferential direction and widthwise groove portions extending along the tire width direction are alternately connected in the tire circumferential direction. the cross groove has a shape such that each of the bent inclined grooves is composed of a first inclined groove portion extending from a middle portion of the circumferential groove portion toward the tire equator at an incline with respect to the tire circumferential direction, and a second inclined groove portion extending from an end portion of the first inclined groove portion at an incline in the same direction as the first inclined groove portion and toward the tire circumferential side of the first inclined groove portion, the second inclined groove portion terminates without crossing the tire equator, each of the shoulder lug grooves extends from an end portion of the widthwise groove portion on the outer side in the tire width direction along an extension direction of the widthwise groove portion, the transverse groove is inclined in the opposite direction to the bent inclined groove, both ends are connected to the middle portion of the circumferential groove portion and intersects with the bent inclined groove on both one side and the other side of the tire equator, 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 groove (bent main groove) is made of a circumferential groove portion and a width direction groove portion and is bent, even a pair (two) of main grooves can exhibit good snow performance. In addition, since the width direction groove portion and the shoulder lug groove extend continuously, the snow removal performance of discharging snow in the groove when not in contact with the ground can be improved, and from this point of view, the snow performance can be improved. Furthermore, by providing the bent inclined groove and the transverse groove, the snow performance (especially the steering stability on a snowy road surface) can be improved. However, since the bent inclined groove (second inclined groove portion) ends without crossing the tire equator, the block rigidity can be secured and the wear resistance can be maintained well. In addition, by forming at least one sipe in each block, the edge effect of the sipe 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.

[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 length L1 of the first inclined groove portion and the length L2 of the second inclined groove portion satisfy the relationship L2 / L1 ≥ 1.5, which provides a good balance between the circumferential groove component and the widthwise groove component ensured by the bent inclined grooves, and is advantageous for improving snow performance.

[0009] In the present invention, it is preferable that the plurality of grooves includes a circumferential connecting groove that connects adjacent second inclined groove portions in the tire circumferential direction on one side of the tire equator. By including such a circumferential connecting groove, an edge effect of the groove can be ensured, which is advantageous for improving snow performance.

[0010] In the present invention, it is preferable that the transverse groove intersects with the second inclined groove portion on both one side and the other side of the tire equator, which improves the block shape defined by the transverse groove and the second inclined groove portion and is advantageous for maintaining good wear resistance.

[0011] In the present invention, it is preferable that the bottom of any one of the plurality of grooves is provided with a protrusion protruding from the bottom of the groove. By providing such a protrusion, an edge effect can be added by the protrusion, which is advantageous for improving snow performance without affecting wear resistance.

[0012] In the present invention, it is preferable that one end of the sipe opens into one of the plurality of grooves and the other end terminates within the block, which makes it possible to suppress a decrease in block rigidity caused by the provision of the sipe, and is advantageous in maintaining good abrasion resistance.

[0013] 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 inside of the tire can be filled with air, an inert gas such as nitrogen, or other gases. [Brief description of the drawings]

[0014] [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

[0015] The configuration of the present invention will be described in detail below with reference to the accompanying drawings.

[0016] 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.

[0017] 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.

[0018] As described below, the present invention relates to a tread pattern formed on the surface of the tread portion 1 of a tire, and therefore the basic structure (cross-sectional structure) of the tire is not limited to the general structure described above. In addition, the following description will be based on the pneumatic tire shown in Fig. 1 etc., but 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).

[0019] 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 four types of grooves, namely, a bent main groove 11, a bent oblique groove 12, a shoulder lug groove 13, and a transverse groove 14, which will be described later. At least one sipe S is necessarily formed in each of the plurality of blocks B.

[0020] The bent main groove 11 is a groove having a bent shape in which circumferential groove portions 11a extending along the tire circumferential direction and widthwise groove portions 11b extending along the tire width direction are alternately connected in the tire circumferential direction, and a pair (two grooves) is arranged on both sides of the tire equator. A point where the circumferential groove portion 11a and the widthwise groove portion 11b are connected in the bent main groove 11 is called a bending point. In particular, in the illustrated example, the bent main groove 11 includes two types of circumferential groove portions 11a with different positions in the tire width direction and two types of widthwise groove portions 11b with different inclination directions. Specifically, the first width direction groove portion 11b is inclined in approximately the same direction as the shoulder lug groove 13 on an extension line of the shoulder lug groove 13 described later, the first circumferential groove portion 11a of the two types of circumferential groove portions 11a is located on the inner side in the tire width direction (the tire equator CL side) and one end is connected to the inner end of the first width direction groove portion 11b in the tire width direction, the second width direction groove portion 11b is inclined in the opposite direction to the first width direction groove portion 11b, and the second circumferential groove portion 11a of the two types of circumferential groove portions 11a is located on the outer side in the tire width direction and one end is connected to the outer end of the second width direction groove portion 11b in the tire width direction and the other end is connected to the outer end of the first width direction groove portion 11b in the tire width direction. These are connected repeatedly in order in the tire circumferential direction, so that the curved main groove 11 is curved in an approximately rectangular wave shape. In the following description, the region between the pair of flexion main grooves 11 may be referred to as the center region, and the region on the outer side of each flexion main groove 11 in the tire width direction may be referred to as the shoulder region. The flexion main groove 11 is the groove with the deepest groove depth among the above-mentioned three types of grooves. Specifically, the groove depth of the flexion main groove 11 is preferably 7 mm to 17 mm, more preferably 9 mm to 15 mm. The groove width of the flexion main groove 11 may be set to preferably 4 mm to 16 mm, more preferably 6 mm to 15 mm.

[0021] 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 the circumferential groove portion 11a of each bent main groove 11 (particularly the circumferential groove portion 11a located on the tire equator side). 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 have the same inclination direction but different inclination angles, so that when they are connected, the connection point between them becomes a bending point, and the bent inclined groove 12 is bent as a whole. One end of the second inclined groove portion 12b is connected to the first inclined groove portion 12a, and the other end terminates without passing the tire equator CL. In detail, 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) has a groove depth equal to or less than that of the bent main groove. Specifically, the groove depth of the bent inclined groove 12 is preferably 50% to 100% of the groove depth of the bent main groove 11, and more preferably 65% ​​to 85%. The groove width of the bent oblique groove 12 is not particularly limited, but can be set to preferably 50% to 150%, more preferably 70% to 130% of the groove width of the bent main groove 11.

[0022] The shoulder lug grooves 13 are grooves extending from each of the pair of bend main grooves 11 toward the outside in the tire width direction. A plurality of shoulder lug grooves 13 are provided at intervals in the tire circumferential direction. The shoulder lug grooves 13 extend from the end of the width direction groove portion 11b of the bend main groove 11 on the outside in the tire width direction along the extension direction of the width direction groove portion 11b. That is, the width direction groove portion 11b and the shoulder lug groove 13 extend linearly to form a continuous groove. The shoulder lug grooves 13 are grooves having a groove depth equal to or less than that of the bend main grooves. Specifically, the groove depth of the shoulder lug grooves 13 is preferably 50% to 100%, more preferably 60% to 90%, of the groove depth of the bend main grooves 11. The groove width of the shoulder lug grooves 13 is not particularly limited, but can be set to preferably 60% to 140%, more preferably 80% to 120% of the groove width of the bend main grooves 11.

[0023] The transverse groove 14 is a groove that connects the bent main groove 11 on one side of the tire equator CL and the bent main groove 11 on the other side of the tire equator CL. In particular, both ends of the transverse groove 14 connect to the middle of the circumferential groove portion 11a of the bent main groove 11 (particularly the circumferential groove portion 11a located on the tire equator side). The transverse groove 14 is inclined in the opposite direction to the bent inclined groove and extends substantially along the tire width direction. A plurality of transverse grooves 14 are provided at intervals in the tire circumferential direction. The transverse groove 14 is not only connected to the bent main groove 11, but also may intersect the bent inclined groove 12 (particularly the second inclined groove portion 12b) on both sides of the tire equator CL as shown in the figure (in FIG. 2, the portion where the transverse groove 14 intersects and overlaps with the second inclined groove portion 12b is shown by a broken line). The transverse groove 14 may be bent, and may be bent in a zigzag shape in the region sandwiched between the bent inclined grooves 12 on both sides of the tire equator CL as shown in the figure, for example. The positions where both ends of the transverse groove 14 connect to the circumferential groove portion 11a are not particularly limited, but when the circumferential groove portion 11a is bent as in the illustrated example, it is preferable that the ends of the transverse groove 14 connect to the bent points. The transverse groove 14 has a groove depth equal to or less than that of the bent main groove. Specifically, the groove depth of the transverse groove 14 is preferably 50% to 100%, more preferably 60% to 80%, of the groove depth of the bent main groove 11. The groove width of the transverse groove 14 is not particularly limited, but can be set to preferably 70% to 130%, more preferably 70% to 100%, of the groove width of the bent main groove 11.

[0024] As described above, at least one sipe S is provided in each block B. The shape of the sipe S is not particularly limited, and in addition to the zigzag shape shown in the figure, various shapes adopted in tires, such as a straight shape, can be used. However, from the viewpoint of ensuring block rigidity, it is preferable that the sipe has a shape in which one end opens into one of the multiple grooves and the other end terminates within the block. The number of sipes S provided in each block B can be appropriately set according to the size of the block. For example, in the example shown in the figure, six sipes are provided in each block B on the tire equator, two sipes are provided in each block located outside the curved main groove 11 in the tire width direction, and three sipes are provided in each of the other blocks. The sipe S is a fine groove with a groove width of, for example, 0.5 mm to 2.0 mm. The depth of the sipe S is not particularly limited, but from the viewpoint of improving snow performance by ensuring an edge effect while suppressing a decrease in block rigidity due to the provision of sipes, it can be set to preferably 50% to 100%, more preferably 60% to 90% of the groove depth of the curved main groove 11.

[0025] 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 bent main grooves 11 extending along the tire circumferential direction, the block rigidity of the center region can be secured and wear resistance can be maintained well. On the other hand, since the bent main grooves 11 are composed of the circumferential groove portion 11a and the width direction groove portion 11b and are bent, even a pair (two) of them can exhibit good snow performance. In addition, since the width direction groove portion 11b and the shoulder lug groove 13 extend continuously, the snow removal performance of discharging snow in the groove when the tire is not in contact with the ground can be improved, and this point can also improve the snow performance. Furthermore, by providing the bent inclined groove 12 and the transverse groove 14, the snow performance (especially the steering stability on a snowy road surface) can be improved. However, since the bent inclined groove 12 (the second inclined groove portion 12b) ends without exceeding the tire equator CL, the block rigidity can be secured and wear resistance can be maintained well. In addition, by forming at least one sipe S in each block B, the edge effect of the sipe S is ensured, and snow performance can be improved. These cooperations make it possible to achieve a high level of both wear resistance and snow performance.

[0026] If the tire does not include any of the four types of grooves described above, or if the grooves are provided in the same positions but the bending shape, connection position, inclination direction, etc. do 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.

[0027] As described above, the bent inclined groove 12 (first inclined groove portion 12a) is connected to the circumferential groove portion 11a of the bent main groove 11. If the connection position coincides with the bending point of the bent main groove 11 on the inner side in the tire width direction, the first inclined groove portion 12a, the width direction groove portion 11b, and the shoulder lug groove 13 will extend continuously. In this embodiment, snow pushed out from the tire equator side CL of the first inclined groove portion 12a is not compacted inside the bent main groove 11 (circumferential groove portion 11a), and snow column shear force at the time of contact with the ground cannot be secured. Therefore, it is preferable that the first inclined groove portion 12a is connected to a position away from the bending point on the inner side in the tire width direction of the bent main groove 11. In particular, it is preferable that the first inclined groove portion 12a is connected to the circumferential groove portion 11a side by 50% or more of the groove width of the width direction groove portion 11b from the bending point on the inner side in the tire width direction of the bent main groove 11.

[0028] As described above, it is preferable that both ends of the transverse groove 14 are always connected to the bent main groove 11, and further intersect with the second inclined groove portion 12b of the bent inclined groove 12 on both sides of the tire equator CL. When the transverse groove 14 intersects with the second inclined groove portion 12b, the intersection point is preferably 40% to 60%, more preferably 45% to 55%, of the length L2 of the second inclined groove portion 12b from the tip of the second inclined groove portion 12b. This improves the shape of the block B defined by the bent main groove 11, the bent inclined groove 12, and the transverse groove 14, and the block shape is not distorted or excessively small, which is advantageous for maintaining good wear resistance.

[0029] In the present invention, the plurality of grooves that divide the plurality of blocks B preferably include, in addition to the above-mentioned four types of grooves, a circumferential connecting groove 15 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. By including such a circumferential connecting groove 15, a groove component extending in a direction different from the above-mentioned four types of grooves is added, so that the edge effect of each groove can be secured, which is advantageous for improving snow performance. In the illustrated example, the circumferential connecting groove 15 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 15 is preferably inclined in the opposite direction to the second inclined groove portion 12b. Note that the circumferential connecting groove 15 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 end of the second inclined groove portion 12b. The circumferential 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 circumferential connecting groove 15 is preferably 50% to 90%, more preferably 70% to 80%, of the groove depth of the bent inclined groove 12. On the other hand, the circumferential connecting groove 15 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 15 is preferably 40% to 90%, more preferably 60% to 80% of the groove width of the bent inclined groove 12. In this way, since the groove width of the circumferential connecting groove 15 is significantly smaller than the groove width of the bent inclined groove 12 (second inclined groove portion 12b), even if the circumferential 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.

[0030] When the circumferential connecting groove 15 is provided as described above, the circumferential connecting groove 15 is connected to a position that is preferably 2% to 25%, more preferably 5% to 15%, of the length L2 of the second inclined groove portion 12b from the tip of the second inclined groove portion 12b. In this case, a block B is defined by the bent main groove 11, the bent inclined groove 12, the transverse groove 14, and the circumferential connecting groove 15, and if the connecting position of the circumferential connecting groove 15 is within the above-mentioned range, the area of ​​this block B can be secured to be appropriately large, and the block rigidity can be maintained favorably.

[0031] The above-mentioned grooves (or groove portions) are all inclined relative to the tire circumferential direction or tire width direction, and each inclination angle is preferably set as described below. The inclination angle of each groove is measured based on the center line of each groove, as shown in FIG. 3. In addition, when a groove is bent, the inclination angle is the angle that a straight line connecting the groove width centers at the ends of the groove forms with the tire circumferential direction or tire width direction. FIG. 3 shows an extracted portion of FIG. 2, omitting sipes S and convex portions 16 described below, and showing main grooves (bent main groove 11, bent oblique groove 12, shoulder lug groove 13, transverse groove 14, circumferential connecting groove 15).

[0032] The inclination angle α of the circumferential groove portion 11a of the bent main groove 11 with respect to the tire circumferential direction is preferably 9° to 13°, more preferably 10° to 11°. 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 α is less than 9°, braking and driving performance on snow will decrease. If the inclination angle α exceeds 13°, steering stability on snow will decrease. The inclination angle β of the widthwise groove portion 11b of the bent main groove 11 with respect to the tire circumferential direction is preferably 61° to 80°, more preferably 65° to 75°. This allows groove components extending in the tire width direction to be secured, which is advantageous for improving braking and driving performance on snowy road surfaces. If the inclination angle β is less than 61°, braking and driving performance on snow will decrease. If the inclination angle β exceeds 80°, steering stability on snow will decrease. The difference β-α between these inclination angles α and β is preferably 30° to 60°, more preferably 40° to 50°. By setting the difference in the inclination angles in this way, the overall bend shape of the bent main groove 11 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 β-α is less than 30°, the balance of steering stability is reduced. If the difference in the inclination angles β-α is more than 60°, the balance of steering stability is reduced.

[0033] 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 65° to 75°. 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 steering stability on snow will decrease. If the inclination angle θ1 exceeds 85°, the braking and driving performance on snow will decrease. 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 15° 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 braking and driving performance on snow will decrease. If the inclination angle θ2 exceeds 40°, the steering stability on snow will decrease. The difference θ1-θ2 between these inclination angles θ1 and θ2 is preferably 30° to 80°, more preferably 40° to 60°. By setting the difference in the inclination angles in this way, the overall curved shape of the curved inclined groove 12 is improved, and the balance between the traction and steering stability on snowy road surfaces is improved, and snow performance can be effectively improved. If the difference in the inclination angles θ1-θ2 is less than 30°, the overall performance on snow decreases. If the difference in the inclination angles θ1-θ2 is more than 80°, the overall performance on snow decreases.

[0034] The inclination angle θ3 of the shoulder lug groove 13 with respect to the tire circumferential direction is preferably 61° to 90°, more preferably 80° to 90°. This ensures groove components extending in the tire width direction, which is advantageous for improving traction performance on snowy road surfaces. If the inclination angle θ3 is less than 61°, braking and driving performance on snow will decrease. If the inclination angle θ3 exceeds 90°, steering stability performance on snow will decrease. In particular, the angle difference between the inclination angle θ3 and the inclination angle β of the widthwise groove portion 11b of the bent main groove 11 with respect to the tire circumferential direction is preferably within ±30°, more preferably 0° (the widthwise groove portion 11b and the shoulder lug groove 13 have the same angle). This improves the flow of snow discharged from the widthwise groove portion 11b toward the shoulder lug groove 13, which is advantageous for improving snow removal when the tire is not in contact with the ground.

[0035] The inclination angle θ4 of the transverse groove 14 with respect to the tire circumferential direction is preferably 60° to 90°, more preferably 70° 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. Furthermore, since the transverse groove 14 extends approximately along the tire width direction, the corners of the blocks B defined by the grooves extending along the circumferential direction (the circumferential groove portion 11a of the curved main groove 11 and the second inclined groove portion 12b of the curved inclined groove 12) and the transverse groove 14 do not become extremely acute angles, which is advantageous for securing block rigidity and maintaining wear resistance. If the inclination angle θ4 is less than 60°, braking and driving performance on snow is reduced. If the inclination angle θ4 exceeds 90°, steering stability on snow is reduced.

[0036] The inclination angle θ5 of the circumferential connecting groove 15 with respect to the tire circumferential direction is preferably 10° to 60°, and more preferably 20° to 40°. This ensures groove components extending in the tire circumferential direction, which is advantageous for improving traction performance on snowy roads. If the inclination angle θ5 is less than 10°, braking and driving performance on snow will decrease. If the inclination angle θ5 is more than 60°, steering stability on snow will decrease.

[0037] 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, so that the groove components extending in the tire circumferential direction are secured, which is advantageous for improving the driving 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≧1.5, more preferably 2.0≦L2 / L1≦5.0. If the relationship is L2 / L1<1.5, the length of the second inclined groove portion 12b cannot be secured sufficiently, and the effect of improving the driving stability on snowy road surfaces cannot be expected sufficiently. 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.

[0038] A convex portion 16 protruding from the groove bottom of any of the grooves that divide the block B may be provided. For example, in the illustrated example, the convex portion 16 is provided in each of the circumferential groove portion 11a of the bent main groove 11 and the shoulder lug groove 13. By providing the convex portion 16 in this manner, it is possible to enhance the edge effect on snow without affecting the wear resistance, and improve the snow performance. The protrusion height of the convex portion 16 from the groove bottom is preferably 2% to 20%, more preferably 2% to 10%, of the groove depth of the groove in which the convex portion 16 is provided. In addition, the convex portion 16 is preferably a shape in which the entire width of the groove bottom of the groove in which the convex portion 16 is provided is not protruding, but a part of it is protruding. In particular, the width of the convex portion 16 is preferably 10% to 80%, more preferably 30% to 60% of the groove width of the groove in which the convex portion 16 is provided.

[0039] 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

[0040] Fourteen types of pneumatic tires, namely Conventional Example 1, Comparative Example 1, and Examples 1 to 12, were manufactured having a tire size of LT265 / 70R17 121 / 118S and a basic structure (cross-sectional structure) as illustrated in FIG. 1 , with the main groove shape, the presence or absence of bent inclined grooves, the terminal position of the second inclined groove portion, the arrangement of shoulder lug grooves, the presence or absence of transverse grooves, the intersection position of the transverse groove and the bent inclined groove, the presence or absence of circumferential connecting grooves, the sipe shape, the presence or absence of convex portions, the inclination angle θ1 of the first inclined groove portion, the inclination angle θ2 of the second inclined groove portion, the difference between these inclination angles θ1-θ2, the inclination angle θ4 of the transverse groove, and the length ratio L2 / L1 of the first inclined groove portion to the second inclined groove portion being set as shown in Table 1.

[0041] In Table 1, in the column of "shape of main groove", the case where the main groove extends in a straight line along the main direction is indicated as "straight line", and the case where the main groove extends in a bent manner as shown in Figure 2 is indicated as "bent". In the column of "termination position of second inclined groove portion", the case where the second inclined groove portion terminates without reaching the tire equator is indicated as "not reaching the equator", and the case where the second inclined groove portion reaches the tire equator or extends beyond the tire equator is indicated as "reaching the equator". In the column of "arrangement of shoulder lug groove", the case where the shoulder lug groove extends continuously with the width direction groove portion of the bent main groove is indicated as "continuous", and the case where the shoulder lug groove and the width direction groove portion of the bent main groove are misaligned is indicated as "discontinuous". In the column of "sipe shape", the case where both ends of the sipe open into either groove is indicated as "open on both sides", and the case where one end opens into the groove and the other end terminates within the block is indicated as "termination on one side".

[0042] The snow performance and wear resistance of these pneumatic tires were evaluated by the following evaluation methods, and the results are shown in Table 1.

[0043] Snow Performance Each test tire was mounted on a wheel with a rim size of 17x8J, and the front tire was set at an air pressure of 450kPa and the rear tire at an air pressure of 550kPa. The test vehicle (four-wheel drive SUV) was then fitted with the tire, and a sensory evaluation of the steering stability was carried out by a test driver on a test course consisting of a snowy road surface. The evaluation results were expressed as an index, with the value of Conventional Example 1 being 100. The higher the index value, the better the snow performance.

[0044] Abrasion 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 to measure the distance traveled (unit: km) until complete wear. The evaluation results were expressed as an index with the value of Conventional Example 1 being 100. The higher the index value, the longer the distance traveled until complete wear and the better the wear resistance.

[0045] [Table 1]

[0046] As is clear from Table 1, the pneumatic tires of Examples 1 to 12 had improved snow performance and wear resistance, and achieved a good balance between these performances, compared to Conventional Example 1. On the other hand, in Comparative Example 1, the second inclined groove portion extended beyond the equator, and the shoulder lug groove did not extend continuously with the width direction groove portion of the bend main groove, so that the wear resistance was reduced.

[0047] 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 flexion main grooves disposed on both sides of the tire equator and extending along the tire circumferential direction, a plurality of flexion oblique grooves extending from each of the pair of flexion main grooves toward the tire equator direction, a plurality of shoulder lug grooves extending from each of the pair of flexion main grooves toward the outside in the tire width direction, and a transverse groove connecting the flexion main groove on one side of the tire equator and the flexion main groove on the other side of the tire equator, The bent main groove has a bent shape in which circumferential groove portions extending along the tire circumferential direction and widthwise groove portions extending along the tire width direction are alternately connected in the tire circumferential direction, Each of the bent inclined grooves is composed of a first inclined groove portion extending from a middle portion of the circumferential groove portion toward the tire equator at an incline with respect to the tire circumferential direction, and a second inclined groove portion extending from an end portion of the first inclined groove portion at an incline in the same direction as the first inclined groove portion and toward the tire circumferential side of the first inclined groove portion, the second inclined groove portion terminating without passing the tire equator, Each of the shoulder lug grooves extends from an outer end of the widthwise groove portion in the tire width direction along an extension direction of the widthwise groove portion, The transverse groove is inclined in the opposite direction to the bent inclined groove, and both ends are connected to the middle part of the circumferential groove portion. The second inclined groove portion Intersect with The second inclined groove portion terminates at a position beyond the transverse groove, A tire characterized in that at least one sipe is formed in each of the plurality of blocks. Invention [2] The tire according to invention [1], characterized in 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° or more and 80° or less. Invention [3] The tire according to invention [1] or [2], wherein the length L1 of the first inclined groove portion and the length L2 of the second inclined groove portion satisfy the relationship L2 / L1 ≧ 1.5. Invention[4] 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 flexion main grooves disposed on both sides of the tire equator and extending along the tire circumferential direction, a plurality of flexion oblique grooves extending from each of the pair of flexion main grooves toward the tire equator direction, a plurality of shoulder lug grooves extending from each of the pair of flexion main grooves toward the outside in the tire width direction, and a transverse groove connecting the flexion main groove on one side of the tire equator and the flexion main groove on the other side of the tire equator, The bent main groove has a bent shape in which circumferential groove portions extending along the tire circumferential direction and widthwise groove portions extending along the tire width direction are alternately connected in the tire circumferential direction, Each of the bent inclined grooves is composed of a first inclined groove portion extending from a middle portion of the circumferential groove portion toward the tire equator at an incline with respect to the tire circumferential direction, and a second inclined groove portion extending from an end portion of the first inclined groove portion at an incline in the same direction as the first inclined groove portion and toward the tire circumferential side of the first inclined groove portion, the second inclined groove portion terminating without passing the tire equator, Each of the shoulder lug grooves extends from an outer end of the widthwise groove portion in the tire width direction along an extension direction of the widthwise groove portion, the transverse groove is inclined in a direction opposite to that of the bent inclined groove, both ends of the transverse groove are connected to the middle part of the circumferential groove portion, and the transverse groove intersects with the bent inclined groove on both one side and the other side of the tire equator, 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. fruit, At least one sipe is formed in each of the plurality of blocks. It is characterized by Ruta No. Invention [5] The tire according to any one of inventions [1] to [4], characterized in that the transverse groove intersects with the second inclined groove portion on both one side and the other side of the tire equator. Invention [6] The tire according to any one of inventions [1] to [5], characterized in that a groove bottom of any one of the plurality of grooves has a convex portion protruding from the groove bottom. Inventions[7] 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 flexion main grooves disposed on both sides of the tire equator and extending along the tire circumferential direction, a plurality of flexion oblique grooves extending from each of the pair of flexion main grooves toward the tire equator direction, a plurality of shoulder lug grooves extending from each of the pair of flexion main grooves toward the outside in the tire width direction, and a transverse groove connecting the flexion main groove on one side of the tire equator and the flexion main groove on the other side of the tire equator, The bent main groove has a bent shape in which circumferential groove portions extending along the tire circumferential direction and widthwise groove portions extending along the tire width direction are alternately connected in the tire circumferential direction, Each of the bent inclined grooves is composed of a first inclined groove portion extending from a middle portion of the circumferential groove portion toward the tire equator at an incline with respect to the tire circumferential direction, and a second inclined groove portion extending from an end portion of the first inclined groove portion at an incline in the same direction as the first inclined groove portion and toward the tire circumferential side of the first inclined groove portion, the second inclined groove portion terminating without passing the tire equator, Each of the shoulder lug grooves extends from an outer end of the widthwise groove portion in the tire width direction along an extension direction of the widthwise groove portion, the transverse groove is inclined in a direction opposite to that of the bent inclined groove, both ends of the transverse groove are connected to the middle part of the circumferential groove portion, and the transverse groove intersects with the bent inclined groove on both one side and the other side of the tire equator, At least one sipe is formed in each of the plurality of blocks,The sipe has one end that opens into any one of the grooves and the other end that terminates within the block. Ruta No. [Explanation of symbols]

[0048] 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 11a Circumferential groove 11b Width direction groove 12 Bend inclined groove 12a First inclined groove part 12b Second inclined groove part 13 Shoulder lug groove 14 Crossing Ditch 15 Circumferential connection groove 16 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 flexion main grooves disposed on both sides of the tire equator and extending along the tire circumferential direction, a plurality of flexion oblique grooves extending from each of the pair of flexion main grooves toward the tire equator direction, a plurality of shoulder lug grooves extending from each of the pair of flexion main grooves toward the outside in the tire width direction, and a transverse groove connecting the flexion main groove on one side of the tire equator and the flexion main groove on the other side of the tire equator, The bent main groove has a bent shape in which circumferential groove portions extending along the tire circumferential direction and widthwise groove portions extending along the tire width direction are alternately connected in the tire circumferential direction, Each of the bent inclined grooves is composed of a first inclined groove portion extending from a middle portion of the circumferential groove portion toward the tire equator at an incline with respect to the tire circumferential direction, and a second inclined groove portion extending from an end portion of the first inclined groove portion at an incline in the same direction as the first inclined groove portion and toward the tire circumferential side of the first inclined groove portion, the second inclined groove portion terminating without passing the tire equator, Each of the shoulder lug grooves extends from an outer end of the widthwise groove portion in the tire width direction along an extension direction of the widthwise groove portion, the transverse groove is inclined in a direction opposite to that of the bent inclined groove, both ends of the transverse groove are connected to the middle portions of the circumferential groove portion, and the transverse groove intersects with the second inclined groove portion of the bent inclined groove on both one side and the other side of the tire equator, and the second inclined groove portion terminates at a position beyond the transverse groove, At least one sipe is formed in each of the plurality of blocks.

2. The tire according to claim 1, characterized in that 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.

3. The tire according to claim 1 or 2, 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.

5.

4. A tire having a tread portion extending in a circumferential direction of the tire to form 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 flexion main grooves disposed on both sides of the tire equator and extending along the tire circumferential direction, a plurality of flexion oblique grooves extending from each of the pair of flexion main grooves toward the tire equator direction, a plurality of shoulder lug grooves extending from each of the pair of flexion main grooves toward the outside in the tire width direction, and a transverse groove connecting the flexion main groove on one side of the tire equator and the flexion main groove on the other side of the tire equator, The bent main groove has a bent shape in which circumferential groove portions extending along the tire circumferential direction and widthwise groove portions extending along the tire width direction are alternately connected in the tire circumferential direction, Each of the bent inclined grooves is composed of a first inclined groove portion extending from a middle portion of the circumferential groove portion toward the tire equator at an incline with respect to the tire circumferential direction, and a second inclined groove portion extending from an end portion of the first inclined groove portion at an incline in the same direction as the first inclined groove portion and toward the tire circumferential side of the first inclined groove portion, the second inclined groove portion terminating without passing the tire equator, Each of the shoulder lug grooves extends from an outer end of the widthwise groove portion in the tire width direction along an extension direction of the widthwise groove portion, the transverse groove is inclined in a direction opposite to that of the bent inclined groove, both ends of the transverse groove are connected to the middle part of the circumferential groove portion, and the transverse groove intersects with the bent inclined groove on both one side and the other side of the tire equator, 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, At least one sipe is formed in each of the plurality of blocks.

5. 3. The tire according to claim 1, wherein the transverse groove intersects with the second inclined groove portion on both one side and the other side of the tire equator.

6. 3. The tire according to claim 1, wherein a groove bottom of any one of the plurality of grooves is provided with a protrusion protruding from the groove bottom.

7. A tire having a tread portion extending in a circumferential direction of the tire to form 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 flexion main grooves disposed on both sides of the tire equator and extending along the tire circumferential direction, a plurality of flexion oblique grooves extending from each of the pair of flexion main grooves toward the tire equator direction, a plurality of shoulder lug grooves extending from each of the pair of flexion main grooves toward the outside in the tire width direction, and a transverse groove connecting the flexion main groove on one side of the tire equator and the flexion main groove on the other side of the tire equator, The bent main groove has a bent shape in which circumferential groove portions extending along the tire circumferential direction and widthwise groove portions extending along the tire width direction are alternately connected in the tire circumferential direction, Each of the bent inclined grooves is composed of a first inclined groove portion extending from a middle portion of the circumferential groove portion toward the tire equator at an incline with respect to the tire circumferential direction, and a second inclined groove portion extending from an end portion of the first inclined groove portion at an incline in the same direction as the first inclined groove portion and toward the tire circumferential side of the first inclined groove portion, the second inclined groove portion terminating without passing the tire equator, Each of the shoulder lug grooves extends from an outer end of the widthwise groove portion in the tire width direction along an extension direction of the widthwise groove portion, the transverse groove is inclined in a direction opposite to that of the bent inclined groove, both ends of the transverse groove are connected to the middle part of the circumferential groove portion, and the transverse groove intersects with the bent inclined groove on both one side and the other side of the tire equator, At least one sipe is formed in each of the plurality of blocks, one end of the sipe opening into any one of the plurality of grooves and the other end terminating within the block.

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