JP7610140B2 - tire - Google Patents

Description

The present invention relates to tires intended for driving on unpaved roads, and more specifically, to tires that enable improved snow performance without compromising wear resistance.

Tires (e.g., all-terrain tires, all-terrain tires, etc.) that are intended to run on unpaved roads (rough ground, muddy ground, sandy ground, rocky areas, etc.) in addition to paved road surfaces 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. Such tires tend to adopt tread patterns that are mainly made up of lug grooves and blocks with a large edge component and have 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 level of both snow performance and wear resistance.

JP 2019-137218 A

The objective of the present invention is to provide a tire that improves snow performance without compromising wear resistance.

The tire of 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 arranged on both sides of the tire equator and extending along the tire circumferential direction, a plurality of flexion inclined 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 flexion main groove being 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. Each of the bent inclined grooves is composed of a first inclined groove portion extending from the middle 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 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 the end of the widthwise groove portion on the outer side in the tire width direction along the 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 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 multiple blocks.

In the tire of the present invention, the blocks formed between the pair of bent main grooves and each groove have the above-mentioned structure, so that 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 that discharges snow in the groove when not in contact with the ground can be improved, and from this point of view, the snow performance can also 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) terminates without exceeding 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 sipes is ensured, improving snow performance. These combined effects allow for a high level of both wear resistance and snow performance.

In the present invention, it is preferable that the inclination angle θ1 of the first inclined groove portion relative to the tire circumferential direction is 50° to 85°, the inclination angle θ2 of the second inclined groove portion relative 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. Setting the inclination angles of each portion in this way improves the shape of the bent inclined grooves, which is advantageous for improving snow performance.

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. This provides a good balance between the circumferential groove components and the widthwise groove components secured by the bent inclined grooves, which is advantageous for improving snow performance.

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 the circumferential connecting groove in this way, the edge effect of this groove can be secured, which is advantageous for improving snow performance.

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. This improves the block shape defined by the transverse groove and the second inclined groove portion, which is advantageous for maintaining good wear resistance.

In the present invention, it is preferable that the bottom of any one of the multiple grooves is provided with a protrusion that protrudes from the bottom of the groove. By providing a protrusion in this way, an edge effect can be added by the protrusion, which is advantageous for improving snow performance without affecting wear resistance.

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

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.

1 is a meridian cross-sectional view of a tire according to an embodiment of the present invention. 1 is a front view showing a tread surface of a tire according to an embodiment of the present invention. FIG. 3 is an explanatory diagram showing a part of FIG. 2 .

The configuration of the present invention will be described in detail below with reference to the attached drawings.

When the tire of the present invention is a pneumatic tire as shown in FIG. 1, it has 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 inside of the sidewall portions 2. In FIG. 1, the symbol CL indicates the tire equator. Although not depicted because FIG. 1 is a meridian cross section, the tread portion 1, sidewall portions 2, and bead portions 3 each extend in the tire circumferential direction to form an annular shape, which constitutes the 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.

A carcass layer 4 is mounted 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 inside to the outside of the vehicle 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 this bead filler 6 is wrapped by the main body and folded back portions of the carcass layer 4. On the other hand, a plurality of belt layers 7 (two layers in FIG. 1) are embedded on the outer periphery 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 that they 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 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.

The present invention relates to a tread pattern formed on the surface of the tread portion 1 of a tire, as described below, so the basic structure (cross-sectional structure) of the tire is not limited to the general structure described above. In addition, the following explanation will be based on the pneumatic tire shown in Figure 1, etc., but the present invention can be applied to various tires, including non-pneumatic tires, as long as they have a surface that contacts the road surface (a portion corresponding to the surface of the tread portion 1 in a pneumatic tire).

As shown in FIG. 2, the surface of the tread portion 1 of the tire of the present invention is provided with a plurality of blocks B divided by a plurality of grooves. The grooves dividing the plurality of blocks B necessarily include four types of grooves, namely, the bent main groove 11, the bent oblique groove 12, the shoulder lug groove 13, and the transverse groove 14, which will be described later. In addition, at least one sipe S is necessarily formed in each of the plurality of blocks B.

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 arranged in the tire circumferential direction, and a pair (two grooves) is arranged on both sides of the tire equator. The point where the circumferential groove portion 11a and the widthwise groove portion 11b connect in the bent main groove 11 is called a bending point. In particular, in the illustrated example, it 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, a first width direction groove portion 11b which is inclined in substantially the same direction as the shoulder lug groove 13 on an extension line of the shoulder lug groove 13 described below; a first circumferential groove portion 11a of the two types of circumferential groove portions 11a which is located on the inner side in the tire width direction (the tire equator CL side) and has one end connected to the inner end of the first width direction groove portion 11b in the tire width direction; a second width direction groove portion 11b which has an inner end in the tire width direction connected to the other end of the first circumferential groove portion 11a and is inclined in the opposite direction to the first width direction groove portion 11b; and a second circumferential groove portion 11a of the two types of circumferential groove portions 11a which is located on the outer side in the tire width direction and has one end connected to the outer end of the second width direction groove portion 11b in the tire width direction and the other end connected to the outer end of the first width direction groove portion 11b in the tire width direction. These are repeatedly connected in sequence in the tire circumferential direction, so that the curved main groove 11 is curved in a substantially 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 of the three types of grooves mentioned above. 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.

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 direction 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 than the first inclined groove portion 12a. Although the first inclined groove portion 12a and the second inclined groove portion 12b have the same inclination direction, they have 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. The second inclined groove portion 12b has one end connected to the first inclined groove portion 12a, and the other end terminates without exceeding 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 disposed 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%, more preferably 65% to 85%, of the groove depth of the bent main groove 11. The groove width of the bent inclined groove 12 is not particularly limited, but can be set to preferably 50% to 150% of the groove width of the bent main groove 11, and more preferably 70% to 130%.

The shoulder lug grooves 13 are grooves that extend 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 outer end of the width direction groove portion 11b of the bend main groove 11 in the tire width direction along the extension direction of the width direction groove portion 11b. In other words, the width direction groove portion 11b and the shoulder lug groove 13 extend linearly to form a continuous groove. The shoulder lug groove 13 is a groove whose groove depth is equal to or less than that of the bend main groove. Specifically, the groove depth of the shoulder lug groove 13 is preferably 50% to 100%, more preferably 60% to 90%, of the groove depth of the bend main groove 11. The groove width of the shoulder lug groove 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 groove 11.

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 approximately 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 intersects with 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 dashed line). The transverse groove 14 may be bent, and may be bent in a zigzag shape in the area sandwiched between the bent inclined grooves 12 on both sides of the tire equator CL as shown in the figure. The positions at which 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 bend point. 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.

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 sipes S are fine grooves with a groove width of, for example, 0.5 mm to 2.0 mm. The depth of the sipes S is not particularly limited, but from the viewpoint of improving snow performance by ensuring the edge effect while suppressing the decrease in block rigidity caused by 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.

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 groove 11 is composed of a circumferential groove portion 11a and a widthwise groove portion 11b and is bent, even a pair (two) of grooves can exhibit good snow performance. In addition, since the widthwise groove portion 11b and the shoulder lug groove 13 extend continuously, the snow removal performance that discharges snow in the groove when not in contact with the ground can be improved, and this also improves snow performance. Furthermore, by providing the bent inclined groove 12 and the transverse groove 14, snow performance (especially steering stability on snowy road surfaces) can be improved. 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 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, improving snow performance. These cooperations allow for a high level of both wear resistance and snow performance.

If the tire does not contain any of the four types of grooves mentioned above, or if grooves are provided in similar positions but the bending shape, connection position, tilt direction, etc. do not satisfy the above-mentioned conditions, the above-mentioned effects of each groove will be insufficient, making it difficult to achieve a good balance between wear resistance and snow performance. Furthermore, if the groove width or groove depth of each groove is smaller than the above-mentioned ranges, 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-mentioned ranges, the groove volume will be large and block rigidity will not be ensured, making it difficult to maintain sufficient wear resistance.

As described above, the bent inclined groove 12 (first inclined groove portion 12a) connects to the circumferential groove portion 11a of the bent main groove 11, but if the connection position coincides with the bending point on the inner side of the bent main groove 11 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, so it is preferable that the first inclined groove portion 12a connects to a position away from the bending point on the inner side of the bent main groove 11 in the tire width direction. In particular, it is preferable that the first inclined groove portion 12a connects 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 of the bent main groove 11 in the tire width direction.

As described above, both ends of the transverse groove 14 are always connected to the bent main groove 11, and it is preferable that the transverse groove 14 intersects 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 does not become distorted or excessively small, which is advantageous for maintaining good wear resistance.

In the present invention, the multiple grooves that divide the multiple blocks B preferably include, in addition to the four types of grooves described above, 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 four types of grooves described above 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 that second inclined groove portion 12b. The circumferential connecting groove 15 is preferably inclined in the opposite direction to the second inclined groove portion 12b. In addition, 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.

When the circumferential connecting groove 15 is provided as described above, the circumferential connecting groove 15 is preferably connected at a position from the tip of the second inclined groove portion 12b to 2% to 25%, more preferably 5% to 15%, of the length L2 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 connection 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 good block rigidity can be maintained.

The various grooves (or groove portions) described above are all inclined relative to the tire circumferential direction or tire width direction, and it is preferable to set the inclination angle of each groove as described below. The inclination angle of each groove is measured based on the center line of each groove, as shown in Figure 3. In addition, if the groove is curved, the inclination angle is the angle that a straight line connecting the groove width centers at the ends of the groove makes with the tire circumferential direction or tire width direction. Figure 3 shows an extracted portion of Figure 2, omitting sipes S and protrusions 16 described below, and showing the main grooves (curved main groove 11, curved inclined groove 12, shoulder lug groove 13, transverse groove 14, circumferential connecting groove 15).

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 performance 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 performance 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 inclination angle in this way, the overall bend shape of the bend main groove 11 is improved, and the balance between traction and handling stability on snowy road surfaces is improved, as described above, effectively improving snow performance. If the difference in inclination angle β-α is less than 30°, the balance of handling stability is reduced. If the difference in inclination angle β-α is more than 60°, the balance of handling stability is reduced.

The inclination angle θ1 of the first inclined groove portion 12a relative 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 relative 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°. Setting the difference in inclination angles in this way improves the overall curved shape of the curved inclined groove 12, improving the balance between traction and steering stability on snowy roads as mentioned above, and effectively improving snow performance. If the difference in inclination angles θ1-θ2 is less than 30°, overall performance on snow will decrease. If the difference in inclination angles θ1-θ2 exceeds 80°, overall performance on snow will decrease.

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 that the groove components extend 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 not on the ground.

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 ensures that the groove components extend in the tire width direction, 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 block 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 ensuring block rigidity and maintaining wear resistance. If the inclination angle θ4 is less than 60°, braking and driving performance on snow will decrease. If the inclination angle θ4 exceeds 90°, steering stability on snow will decrease.

The inclination angle θ5 of the circumferential connecting groove 15 relative to the tire circumferential direction is preferably 10° to 60°, and more preferably 20° to 40°. This ensures groove components that extend 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 exceeds 60°, steering stability on snow will decrease.

When forming the bent inclined groove 12 by the first inclined groove portion 12a and the second inclined groove portion 12b, by making the length of the second inclined groove portion 12b sufficiently larger than that of the first inclined groove portion 12a, a groove component extending in the tire circumferential direction is secured, which is advantageous for improving 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≧1.5, 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 steering stability on snowy road surfaces cannot be expected sufficiently. As shown in FIG. 3, the length L1 is the length measured along the tire width direction, and the length L2 is the length measured along the tire circumferential direction.

A convex portion 16 protruding from the groove bottom of any of the grooves that divide the block B can 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 and improve snow performance without affecting the wear resistance. 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 only a part of the groove bottom is protruding, rather than the entire width of the groove in which the convex portion 16 is provided. 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.

The present invention will be further explained below with reference to examples, but the scope of the present invention is not limited to these examples.

Fourteen types of pneumatic tires, Conventional Example 1, Comparative Example 1, and Examples 1 to 12, were manufactured with tire sizes of LT265/70R17 121/118S and the basic structure (cross-sectional structure) illustrated in FIG. 1, with the main groove shape, the presence or absence of bent inclined grooves, the end 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 grooves and the bent inclined grooves, 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 set as shown in Table 1.

In Table 1, in the column "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 "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 "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 arranged with a misalignment is indicated as "discontinuous". In the column "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 "terminating on one side".

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

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 450 kPa and the rear tire at an air pressure of 550 kPa. The test vehicle (four-wheel drive SUV) was then fitted with each test 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.

Wear resistance 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 450 kPa and the rear tire at an air pressure of 550 kPa. The test tire was then mounted on a test vehicle (four-wheel drive SUV), 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 larger the index value, the longer the distance traveled until complete wear, which means that the tire has excellent wear resistance.

As is clear from Table 1, the pneumatic tires of Examples 1 to 12 have improved snow performance and wear resistance compared to Conventional Example 1, achieving a good balance between these performances. On the other hand, Comparative Example 1 has reduced wear resistance because the second inclined groove portion extends beyond the equator and the shoulder lug groove does not extend continuously with the width direction groove portion of the bent main groove.

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 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.
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 a middle portion 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 .
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 protrusion protruding from the groove bottom.
Invention [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 a middle portion 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.

Reference Signs List 1 tread portion 2 sidewall portion 3 bead portion 4 carcass layer 5 bead core 6 bead filler 7 belt layer 8 belt reinforcing layer 11 bend main groove 11a circumferential groove portion 11b widthwise groove portion 12 bend oblique groove 12a first oblique groove portion 12b second oblique groove portion 13 shoulder lug groove 14 transverse groove 15 circumferential connecting groove 16 convex portion CL tire equator B block S sipe

Claims (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 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. The tire described in claim 1, characterized in that the inclination angle θ1 of the first inclined groove portion relative to the tire circumferential direction is 50° to 85°, the inclination angle θ2 of the second inclined groove portion relative 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 tire according to claim 1 or 2, characterized in that the length L1 of the first inclined groove portion and the length L2 of the second inclined groove portion satisfy the relationship L2/L1 ≧ 1.5. 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,
At least one sipe is formed in each of the plurality of blocks . The tire according to claim 1 or 2, 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. The tire according to claim 1 or 2, characterized in that the bottom of any one of the plurality of grooves has a protrusion protruding from the bottom of the groove. 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, 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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