JP7553842B2 - tire - Google Patents

Description

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

In addition to paved road surfaces, 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.) 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 sufficient performance is required even on snowy road surfaces in extremely cold regions. For such tires, there is a tendency to adopt tread patterns that are mainly made up of lug grooves and blocks with many edge components and have a large groove area (see, for example, Patent Document 1). In addition, multiple sipes and notched grooves are provided on the tread surfaces of blocks and ribs (see, for example, Patent Document 2). On the other hand, tread patterns with a large groove area and tread patterns with a large number of sipes and notched grooves tend 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.

JP 2019-137218 A JP 2019-043307 A

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

In order to achieve the above object, the tire of the present invention has a tread portion extending in a circumferential direction of the tire to form an annular shape, the tread portion has at least four flexion main grooves extending in a zigzag pattern along the tire circumferential direction, at least three rows of land portions defined between the flexion main grooves are defined into a plurality of blocks by a plurality of lug grooves arranged at intervals in the tire circumferential direction, the at least three rows of land portions include a center land portion provided on the tire equator, and the tread surface of each of the plurality of blocks has a pair of sipes and a pair of notches. The tire has grooves, the pair of sipes extending in the same direction with an angular difference of 10° or less, one end of each of the pair of sipes opening into the bend main groove and the other end terminating within the block, the pair of notch grooves extending in the same direction with an angular difference of 10° or less, one end of each of the pair of notch grooves opening into the bend main groove and the other end terminating within the block , and in a center block that defines the center land portion among the multiple blocks, the inclination direction of the pair of sipes and the inclination direction of the pair of notch grooves are opposite to each other .

The tire of the present invention has sipes and notch grooves arranged as described above in a pattern divided into a plurality of blocks, and therefore can improve snow performance without compromising wear resistance. In particular, by providing a pair of sipes and notch grooves, it is possible to efficiently improve snow performance while suppressing the total number of sipes and notch grooves. On the other hand, since the sipes and notch grooves each terminate within a block, it is possible to maintain good wear resistance. Furthermore, since a pair of sipes extends approximately parallel (in the same direction with an angle difference of 10° or less) and a pair of notch grooves extends approximately parallel (in the same direction with an angle difference of 10° or less), an edge effect is exerted in the same direction, and traction performance on snowy road surfaces is efficiently improved, and snow performance can be effectively exerted. In addition, the aforementioned roughly parallel arrangement makes the spacing between the sipes and notched grooves roughly uniform, suppressing differences in stiffness due to differences in spacing (for example, partial reductions in block stiffness in areas with narrow spacing), and better maintains block stiffness and wear resistance than when the orientation of the sipes and notched grooves is random. These cooperations allow for a high degree of both wear resistance and snow performance.

In the present invention, it is preferable that each of the pair of sipes extends in the same direction with an angle difference of 10° or less with respect to the groove wall of one of the pair of lug grooves adjacent to the block in which the pair of sipes is provided. With such an arrangement, the edge effect of the groove wall (block wall) of the lug groove and the edge effect of the sipes are aligned, and the synergistic effect of these effects can provide excellent snow performance. In addition, since the sipes and the lug groove walls are approximately parallel, the spacing between them becomes approximately uniform, which can suppress stiffness differences due to differences in spacing (for example, partial reduction in block stiffness in areas with narrow spacing) and maintain good wear resistance.

In the present invention, the land portion partitioned on the outer side in the tire width direction of the bend main groove arranged at the outermost side in the tire width direction is partitioned into a plurality of shoulder blocks by a plurality of shoulder lug grooves arranged at intervals in the tire circumferential direction, and a pair of shoulder sipes and one shoulder notch groove are provided on the tread surface of each of the plurality of shoulder blocks, one end of each of the pair of shoulder sipes opens into the bend main groove and the other end terminates in the shoulder block, and one shoulder notch groove is arranged in an area closer to the bend main groove than the tire width center of the shoulder block and closer to the shoulder lug groove on one side in the tire circumferential direction than the tire circumferential center of the shoulder block, and it is preferable that one end of this shoulder notch groove opens into the bend main groove and the other end terminates in the shoulder block. By providing shoulder blocks in this way and providing shoulder sipes and shoulder notch grooves there, the edge effect and snow column shear force can be improved even in the shoulder blocks, which is advantageous for improving snow performance. Furthermore, by setting the number and arrangement of the shoulder sipes and shoulder notch grooves as described above, the block rigidity of the shoulder blocks can be maintained, and good wear resistance can be maintained.

In this case, it is preferable that the groove depth of the notched groove is 25% to 95% of the groove depth of the bent main groove, and that the groove depth of the shoulder notched groove is greater than the groove depth of the notched groove. By making the groove depth of the notched groove greater on the shoulder side in this way, it is possible to achieve a good balance between the edge effect and block rigidity depending on the widthwise position of the block, which is advantageous for achieving both snow performance and wear resistance.

It is also preferable that the length of the sipes is 35% to 75% of the maximum length of the shoulder sipes. By making the sipe length longer on the shoulder side in this way, it is possible to achieve a good balance between the edge effect and block rigidity depending on the widthwise position of the block, which is advantageous in achieving both snow performance and abrasion resistance.

In the present invention, it is preferable that the length of the notched groove is 30% to 100% of the maximum length of the sipes provided in the same block. This provides a good balance between the lengths of the sipes and notched grooves provided in one block, which is advantageous for achieving a good balance between snow performance and wear resistance.

In the present invention, it is preferable that the pair of sipes and the pair of notched grooves are arranged in a staggered pattern within the block. This arrangement prevents the sipes and notched grooves from being arranged biased to one side within the block, making it possible to achieve a good balance between edge effect and block rigidity, which is advantageous in achieving both snow performance and wear 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, and the symbol E indicates the ground contact edge. Although not depicted because FIG. 1 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, 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 (particularly the structure and arrangement of sipes 40 and notched grooves 50 described below) formed on the surface of the tread portion 1 of the 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 the tire has 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 at least three (four in the figure) flexion main grooves 10 extending in a zigzag pattern along the tire circumferential direction. The zigzag shape is a shape in which straight portions inclined in one direction with respect to the tire circumferential direction and straight portions inclined in the other direction are alternately connected in the tire circumferential direction. In the illustrated example, the flexion main grooves 10 include a pair of inner flexion main grooves 11 arranged on both sides of the tire equator CL, and a pair of outer flexion main grooves 12 arranged on the outer side in the tire width direction. Of these four flexion main grooves, a pair of outer flexion main grooves 12 are arranged on the outermost sides in the tire width direction. In the following description, the region on the inner side in the tire width direction of the outer flexion main grooves 12 (the tire equator CL side) of the outer flexion main grooves 12 may be referred to as the center region, and the region on the outer side in the tire width direction of the outer flexion main grooves 12 may be referred to as the shoulder region.

The shape of the bend main groove 10 is not particularly limited as long as it is the zigzag shape described above, but it is preferable that the inner bend main groove 11 and the outer bend main groove 12 each have the shape shown in the figure. That is, the outer bend main groove 12 has a shape in which a straight portion (first outer straight portion 12a) inclined in one direction with respect to the tire circumferential direction and a straight portion (second outer straight portion 12b) inclined in the other direction are alternately connected in the tire circumferential direction, and it is preferable that these first outer straight portion 12a and second outer straight portion 12b have the same groove width. In addition, it is preferable that the tire circumferential length of the first outer straight portion 12a is preferably 50% to 70% of the tire circumferential length of the second outer straight portion 12b. On the other hand, the inner bend main groove 11 has a shape in which a straight portion (first inner straight portion 11a) inclined in one direction with respect to the tire circumferential direction and a straight portion (second inner straight portion 11b) inclined in the other direction are alternately connected in the tire circumferential direction, and it is preferable that the groove width of the second inner straight portion 11b is smaller than that of the first inner straight portion 11a. Specifically, the groove width of the second inner straight portion 11b is preferably 55% to 75% of the groove width of the first inner straight portion 11a. Also, the circumferential length of the second inner straight portion 11b is preferably 15% to 35% of the circumferential length of the first outer straight portion 11a.

At least two rows (three rows in the figure) of land portions 20 are defined between the bend main grooves 10, and a plurality of lug grooves 30 extending along the tire width direction are provided at intervals in the tire circumferential direction. Both ends of these lug grooves 30 are connected to the bend main grooves, thereby dividing the land portion 20 into a plurality of blocks 20B. In the example shown in the figure, the land portion 20 includes one row of land portions (center land portion 21) defined between a pair of inner bend main grooves 11, and two rows of land portions (middle land portion 22) defined between the inner bend main grooves 11 and the outer bend main grooves 12. In the following description, the lug groove 30 provided in the center land portion 21 may be referred to as the center lug groove 31, and the block 20B defined by the center lug groove 31 may be referred to as the center block 21B. Similarly, the lug groove 30 provided in the middle land portion 22 may be referred to as the middle lug groove 32, and the block 20B defined by the middle lug groove 32 may be referred to as the middle block 22B.

In particular, in the illustrated example, the center lug groove 31 includes a first center lug groove 31a that is inclined in one direction and a second center lug groove 31b that is inclined in the opposite direction to the first center lug groove 31a, and these first center lug grooves 31a and second center lug grooves 31b are arranged alternately in the tire circumferential direction. In addition, the first center lug groove 31a is curved, but the second center lug groove 31b extends in a straight line. Both ends of the first center lug groove 31a communicate with the first inner straight portion 11a on both sides in the tire width direction, and the second center lug groove 31b communicates with the bending points in the inner bending main grooves 11 on both sides in the tire width direction. The intermediate lug grooves 32 include a first intermediate lug groove 32a that communicates with the bending point of the outer flex main groove 12 and the bending point of the inner flex main groove 11, and a second intermediate lug groove 32b that communicates with the bending point of the outer flex main groove 12 and the first inner straight portion 11a, and these first intermediate lug grooves 32a and second intermediate lug grooves 32b are arranged alternately in the tire circumferential direction. The first intermediate lug grooves 32a and the second intermediate lug grooves 32b are preferably inclined in the same direction and have the same bending shape.

A pair of sipes 40 and a pair of notch grooves 50 are provided on the tread surface of each of the blocks B partitioned by the above-mentioned bent main grooves 10 and lug grooves 30. In other words, only two sipes 40 and only two notch grooves 50 are provided in each block B. In the following description, the sipes 40 and notch grooves 50 provided in the center block 21B may be referred to as center sipes 41 and notch grooves 51. Similarly, the sipes 40 and notch grooves 50 provided in the intermediate block 22B may be referred to as intermediate sipes 42 and intermediate notch grooves 52. The sipes 40 are fine grooves with a groove width of, for example, 0.5 mm to 2.0 mm and a groove depth of, for example, 2 mm to 15 mm. The shape of the sipes 40 is not particularly limited, and various shapes generally used in tires, such as a straight shape or a zigzag shape as shown in the figure, may be adopted. The notched groove 50 is a groove that has a short length of 50% or less of the block width, terminates within the block B, and has a tapered shape in which the groove width narrows toward the end (for example, the end has a triangular or trapezoidal shape).

The pair of sipes 40 provided in each block B extend in the same direction with an angular difference of 10° or less, preferably in the range of 0° to 5°. In other words, the pair of sipes 40 extend approximately parallel to each other. Furthermore, one end of each of the pair of sipes 40 opens into the flex main groove 10 and the other end terminates within the block B. Similarly, the pair of notched grooves 50 provided in each block B extend in the same direction with an angular difference of 10° or less, preferably in the range of 0° to 5°. In other words, the pair of notched grooves 50 also extend approximately parallel to each other. Furthermore, one end of each of the pair of notched grooves 50 opens into the flex main groove 10 and the other end terminates within the block B.

In this way, a pair of sipes 40 and a pair of notched grooves 52 are provided in each block B, so that snow performance can be improved without compromising wear resistance. That is, by providing a pair of sipes 40 and a pair of notched grooves 50, snow performance can be efficiently improved while suppressing the total number of sipes 40 and notched grooves 50. On the other hand, since the sipes 40 and the notched grooves 50 each terminate within the block B, wear resistance can be maintained well. Furthermore, since the sipes 40 extend approximately parallel to each other and the notched grooves 50 extend approximately parallel to each other, an edge effect is exerted in the same direction, and the traction performance on snowy road surfaces can be efficiently improved and snow performance can be effectively exerted. In addition, the aforementioned approximately parallel arrangement makes the spacing between the sipes 40 and notched grooves 50 approximately uniform, suppressing differences in stiffness due to differences in spacing (for example, partial reductions in block stiffness in areas with narrow spacing), and better maintains block stiffness and wear resistance than when the orientation of the sipes 40 and notched grooves 50 is random. These cooperations allow for a high level of both wear resistance and snow performance.

If the number of sipes 40 or notch grooves 50 provided in each block B is more than one pair, the block rigidity cannot be sufficiently maintained and the wear resistance is reduced. If the sipes 40 or notch grooves 50 do not terminate within the block B, the block rigidity cannot be sufficiently maintained and the wear resistance is reduced. If the angle difference between the sipes 40 or notch grooves 50 exceeds 10° and they are no longer approximately parallel, the spacing between the sipes 40 or notch grooves 50 will no longer be uniform, and the block rigidity will partially decrease in the narrower spacing, resulting in poor wear resistance. In addition, as described above, the approximately parallel arrangement will not be able to provide an edge effect in the same direction and will not be able to improve traction performance on snowy roads. As a result, the balance between the edge effect and block rigidity will be poor, and the effect of achieving both snow performance and wear resistance will not be fully achieved.

When a pair of sipes 40 and a pair of notched grooves 50 are provided in one block B, they are preferably arranged in a staggered manner. That is, in the present invention, four groove elements consisting of a pair of sipes 40 and a pair of notched grooves 50 are provided in one block B, but it is preferable that adjacent groove elements in the tire circumferential direction in one block B are different types (combinations of sipes 40 and notched grooves 50) and adjacent groove elements in the tire width direction are different types (combinations of sipes 40 and notched grooves 50). Furthermore, it is preferable that adjacent groove elements sandwiching the lug groove 30 are also different types (combinations of sipes 40 and notched grooves 50). By arranging in this way, the sipes 40 and notched grooves 50 are not arranged biased to one side in the block B, so that the balance between the edge effect and the block rigidity can be improved, which is advantageous for achieving both snow performance and wear resistance.

The pair of sipes 40 are not only approximately parallel to each other, but also approximately parallel to the groove walls of one of the pair of lug grooves 30 adjacent to the block B in which the pair of sipes 40 are provided, that is, the angle difference is preferably within 10°, more preferably in the range of 0° to 8°, and extends in the same direction. For example, in the illustrated example, the intermediate sipe 42 provided in the intermediate block 22B extends approximately parallel to the intermediate lug groove 32. Also, the center sipe 41 provided in the center block 21B extends approximately parallel to the first center lug groove 31a. By arranging in this way, the edge effect due to the groove wall (block wall) of the lug groove 30 and the edge effect due to the sipes are aligned, so that excellent snow performance can be achieved by the synergistic effect of these. In addition, since the sipes and the lug groove walls are approximately parallel, the intervals between them become approximately uniform, and the rigidity difference due to the difference in the intervals (for example, partial decrease in block rigidity in a narrow space) can be suppressed, and the wear resistance can be maintained well. If the angle difference between the sipes 40 and the groove walls of the lug grooves 30 exceeds 10 degrees and they are no longer approximately parallel, the aforementioned effect of improving snow performance cannot be fully expected. In addition, because the sipes and the lug groove walls are not approximately parallel, the distance between them is no longer uniform, and there is concern that the block rigidity may be partially reduced in areas where the distance is narrow.

The pair of notch grooves 50 are not only substantially parallel to each other, but also substantially parallel to the groove walls of one of the pair of lug grooves 30 adjacent to the block B in which the pair of notch grooves 50 are provided, that is, the angle difference is preferably within 10°, more preferably in the range of 0° to 8°, and extends in the same direction. For example, in the illustrated example, the intermediate notch groove 52 provided in the intermediate block 22B extends substantially parallel to the intermediate lug groove 32. Also, the center notch groove 51 provided in the center block 21B extends substantially parallel to the second center lug groove 31b. By arranging in this way, the edge effect due to the groove wall (block wall) of the lug groove 30 and the edge effect due to the notch groove are aligned, so that excellent snow performance can be achieved by the synergistic effect of these. In addition, since the notch groove and the lug groove wall are substantially parallel, the interval between them becomes substantially uniform, and the rigidity difference due to the difference in the interval (for example, partial decrease in block rigidity at a place where the interval is narrow) can be suppressed, and the wear resistance can be maintained well. If the angle difference between the notch groove 50 and the groove wall of the lug groove 30 exceeds 10 degrees and they are no longer approximately parallel, the effect of improving snow performance described above cannot be fully expected. In addition, if the notch groove and the lug groove wall are not approximately parallel, the distance between them will no longer be uniform, and there is a concern that the block rigidity will be partially reduced in areas where the distance is narrow.

In particular, in the illustrated example of center block 21B, the inclination direction of the pair of center sipes 41 oriented approximately parallel to each other is opposite to the inclination direction of the pair of center notched grooves 51 oriented approximately parallel to each other, and these inclination directions intersect. Therefore, the center sipes 41 and center notched grooves 51 each extend so as to converge toward the center of center block 21B. By arranging the pair of sipes 40 and the pair of notched grooves 50 in block B on the tire equator CL in this way, the edge effect can be more effectively enhanced.

In each block B (center block 21B and intermediate block 22B), the length of the notch groove 50 is preferably 30% to 100%, more preferably 30% to 90%, of the maximum length of the sipes 40 provided in the same block B. This provides a good balance between the lengths of the sipes 40 and the notch grooves 50 provided in one block B, which is advantageous for achieving a good balance between snow performance and wear resistance. If the length of the notch groove 50 is less than 30% of the maximum length of the sipes 40, the notch groove 50 is too short and the edge effect of providing the notch groove 50 cannot be fully expected. If the length of the notch groove 50 exceeds 100% of the maximum length of the sipes 40, it becomes difficult to maintain good block rigidity.

The structure of the shoulder region is not particularly limited, but as shown in the example, the land portion 20 (shoulder land portion 23) partitioned on the outer side in the tire width direction of the bend main groove 10 (outer bend main groove 12) arranged at the outermost side in the tire width direction may be partitioned into multiple shoulder blocks 23B by multiple shoulder lug grooves 33 arranged at intervals in the tire circumferential direction. Furthermore, a pair of shoulder sipes 43 and one shoulder notch groove 53 may be provided on the tread surface of each of the multiple shoulder blocks 23B. By providing shoulder blocks 23B in this way and providing shoulder sipes 43 and shoulder notch groove 53 there, the edge effect and snow column shear force can be improved in the shoulder blocks 23B as well, which is advantageous for improving snow performance.

At this time, the pair of shoulder sipes 23B preferably extend in the same direction with an angle difference of 10° or less, more preferably in the range of 0° to 8°. In other words, the pair of shoulder sipes 43 preferably extend approximately parallel to each other. Each of the pair of shoulder sipes 43 preferably has one end opening into the bent main groove and the other end terminating within the shoulder block 23B. In addition, the pair of shoulder sipes 43 are not only approximately parallel to each other, but also approximately parallel to one of the groove walls of the pair of shoulder lug grooves 33 adjacent to the shoulder block 23B in which the pair of shoulder sipes 43 are provided, that is, the pair of shoulder sipes 43 preferably extend in the same direction with an angle difference of 10° or less, more preferably in the range of 0° to 8°. By providing the shoulder sipes 43 in this way, it is possible to improve snow performance while maintaining the block rigidity of the shoulder block 23B, which is advantageous for achieving a good balance between snow performance and wear resistance.

One end of each shoulder notch groove 53 may open into the bend main groove 10 (outer bend main groove 12) and the other end may terminate within the shoulder block 23B. Furthermore, the shoulder notch groove 53 may be disposed in an area closer to the bend main groove 10 than the tire width center of the shoulder block 23B and closer to the shoulder lug groove 33 on one side of the tire circumferential center of the shoulder block 23B in the tire circumferential direction. Specifically, as shown in Fig. 3, a rectangular area is assumed to be surrounded by a line passing through the innermost point of the shoulder block 23B in the tire width direction and extending in the tire circumferential direction, the ground contact edge E, a line passing through one end point of the shoulder block 23B in the tire circumferential direction and extending in the tire width direction, and a line passing through the other end point of the shoulder block 23B in the tire circumferential direction and extending in the tire width direction. Of the four sections obtained by dividing this area in half in the tire width direction, the shoulder notch groove 53 is preferably positioned in the section on the inner side in the tire width direction and on one side in the tire circumferential direction (the shaded area in the figure). Providing the shoulder notch groove 53 in such a position is advantageous for improving snow performance while maintaining good block rigidity of the shoulder block 23B.

The ground contact edge E is the end in the tire width direction of the ground contact area formed when the tire is mounted on a standard rim, inflated to the standard internal pressure, placed vertically on a flat surface, and subjected to a standard load. A "standard rim" is a rim that is determined for each tire by the standard system that includes the standard on which the tire is based, for example, the standard rim for JATMA, the "Design Rim" for TRA, or the "Measuring Rim" for ETRTO. The term "normal internal pressure" refers to the air pressure determined for each tire by the respective standards, including the standards on which the tire is based. In the case of JATMA, this is the maximum air pressure, in the case of TRA, this is the maximum value described in the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES", and in the case of ETRTO, this is the "INFLATION PRESSURE", but in the case of a tire for a passenger car, this is 180 kPa. "Normal load" is the load determined for each tire by each standard, including the standard on which the tire is based. For JATMA, it is the maximum load capacity. For TRA, it is the maximum value listed in the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES." For ETRTO, it is the "LOAD CAPACITY." However, if the tire is for passenger cars, it is a load equivalent to 88% of the above load.

When the shoulder sipes 43 and the shoulder notch grooves 53 are provided as described above, it is preferable to make the groove depth of the shoulder notch grooves 53 greater than the groove depth of the notch grooves 50 in the center region. In addition, when the center region includes three or more rows of land portions, it is preferable that the groove depth of the notch grooves 50 provided in the land portions closer to the tire equator CL is smaller. In the illustrated example, the center region includes three rows of land portions consisting of one row of center land portion 21 and two rows of intermediate land portions 22, and it is preferable that the groove depth of the intermediate notch grooves 52 provided in the intermediate blocks 22B defined in the intermediate land portion 22 is greater than the center notch grooves 51 provided in the center blocks 21B defined in the center land portion 21. In this way, by making the groove depth of the notch grooves 50 greater toward the outer side in the tire width direction, it is possible to achieve a good balance between the edge effect and the block rigidity depending on the widthwise position of the block, which is advantageous for achieving both snow performance and wear resistance.

The groove depth of the notch grooves 50 (center notch groove 51, middle notch groove 52) and shoulder notch groove 53 is preferably 25% to 95%, more preferably 30% to 95%, of the groove depth of the flexion main groove 10, regardless of the position of the block B to be provided. By setting the groove depth in this manner, it is possible to achieve a good balance between the edge effect and block rigidity of the notch grooves 50 and shoulder notch grooves 53. If the groove depth of the notch grooves 50 and shoulder notch grooves 53 is less than 25% of the groove depth of the flexion main groove 10, the notch grooves 50 and shoulder notch grooves 53 are too shallow and the edge effect cannot be expected to be sufficient. If the groove depth of the notch grooves 50 and shoulder notch grooves 53 exceeds 95% of the groove depth of the flexion main groove 10, it becomes difficult to maintain good block rigidity.

When the groove depth of the notched grooves 50 is increased toward the outer side in the tire width direction as described above, the groove depth of the notched grooves 50 (center notched groove 51, intermediate notched groove 52) in the center region is preferably 25% to 40%, more preferably 30% to 40%, of the groove depth of the curved main groove 10. In particular, when the center land portion 21 and the intermediate land portion 22 are formed in the center region as shown in the figure and the groove depth of the notched grooves 50 (center notched groove 51, intermediate notched groove 52) is differentiated between these land portions, the groove depth of the center notched groove 51 is preferably 25% to 35%, more preferably 30% to 35%, of the groove depth of the curved main groove 10, and the groove depth of the intermediate notched groove 52 is preferably 30% to 40%, more preferably 35% to 40%, of the groove depth of the curved main groove 10. On the other hand, the groove depth of the shoulder notch groove 53 is preferably 80% to 90% of the groove depth of the bend main groove 10, and more preferably 85% to 90%.

When the shoulder sipes 43 are provided as described above, the length of the sipes 40 (center sipes 41, intermediate sipes 42) provided in the center region is preferably 35% to 75% of the maximum length of the shoulder sipes 43, more preferably 40% to 70%. By setting such a length relationship, it is possible to achieve a good balance between the edge effect and the block rigidity according to the position in the tire width direction, which is advantageous for achieving both snow performance and wear resistance. If the length of the sipes 40 provided in the center region is less than 35% of the maximum length of the shoulder sipes 43, the edge effect of the sipes 40 will be limited because the length of the sipes 40 is too short. If the length of the sipes 40 provided in the center region exceeds 75% of the maximum length of the shoulder sipes 43, it becomes difficult to maintain sufficient block rigidity in the center region. The lengths of the sipes 40 (center sipes 41, intermediate sipes 42) and the shoulder sipes 43 are lengths measured along the extension direction of the sipes 40 or the shoulder sipes 43. When these sipes have a zigzag shape, the length of the straight line connecting the ends of the sipes (in the illustrated example, the opening end and the terminal end) is the sipe length.

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.

The tire size was LT265/70R17 121/118S, and the basic structure (cross-sectional structure) was shown in FIG. 1. Based on the tread pattern shown in FIG. 2, the shape of the main groove, the number of sipes in the block in the center region, the ends of the sipes, the inclination direction between the sipes, the inclination direction of the sipes relative to the groove wall of the lug groove, the number of notched grooves, the ends of the notched grooves, the inclination direction between the notched grooves, the arrangement of the sipes and the notched grooves, the ratio of the notched groove length to the sipe length (unit: %), the number of sipes in the block in the shoulder region, the end positions of the sipes, the inclination direction between the sipes, the number of notched grooves, the arrangement of the notched grooves, the relationship of the groove depth of the notched grooves between the shoulder region and the center region, and the relationship of the sipe length between the shoulder region and the center region were set as shown in Table 1. Ten types of pneumatic tires, namely Conventional Example 1, Comparative Examples 1-2, and Examples 1-7, were manufactured.

In addition, Conventional Example 1 has a structure in which all the bent main grooves in the tread pattern in Figure 2 are replaced with main grooves that extend linearly in the tire circumferential direction, and is an example in which no sipes or notches are provided as shown in the table. Comparative Example 1 is an example in which each block has one sipe or one notch groove, and has a structure in which one of the two sipes or two notch grooves in Figure 2 has been deleted.

In Table 1, the columns for "end of sipe" and "end of notched groove" indicate "opening" when both ends are connected to the main groove, and "termination" when the end not connected to the main groove terminates within the block. The columns for "inclination direction between sipes" and "inclination direction of notched groove" indicate "approximately parallel" when sipes or notched grooves extend in the same direction with an angular difference of 10° or less, and "non-parallel" when the angular difference exceeds 10°. For "inclination direction of sipe relative to groove wall of lug groove", "approximately parallel" when the angular difference is within 10°, and "non-parallel" when the angular difference exceeds 10°. In the column "Arrangement of sipes and notch grooves", the case where a pair of sipes and a pair of notch grooves are arranged in a staggered manner in a block as shown in the example is indicated as "staggered arrangement", and the case where both of the pair of sipes are arranged only on one side in the tire width direction and both of the pair of notch grooves are arranged only on the other side in the tire width direction is indicated as "one-sided arrangement". In the column "Arrangement of notch grooves", the case where the notch grooves are arranged biasedly in the shaded section shown in Figure 3 is indicated as "inside section", and the case where the notch grooves are arranged at the circumferential center position of the block (on the dotted line that divides the rectangular area in the tire circumferential direction in Figure 3) is indicated as "center". In the column "Relationship of groove depth of notch grooves between Sh region/Ce region", the case where the groove depth of the notch grooves is the same in the shoulder region and the center region is indicated as "Sh = Ce", and the case where the groove depth of the notch grooves is larger on the shoulder region side is indicated as "Sh > Ce". In the "Relationship of sipe length between Sh region and Ce region" column, when the sipe length is the same in the shoulder region and center region, it is shown as "Sh = Ce", and when the sipe length is longer in the shoulder region, it is shown as "Sh > Ce".

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 (traction test vehicle) was then fitted with the tire and subjected to a sensory evaluation of traction (starting performance) on a test course consisting of a snowy road surface by a test driver. 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. An index value of "105" or less means that sufficient snow performance was not obtained.

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 was set at an air pressure of 550 kPa. The test vehicle (four-wheel drive SUV) was then fitted with the tire. A test driver performed a test run on a test course, and the estimated wear life was calculated from the amount of wear after 8000 km of running. 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 running distance until complete wear and the better the wear resistance. Note that an index value of "102" or less means that sufficient wear resistance was not obtained.

As is clear from Table 1, the pneumatic tires of Examples 1 to 7 had 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 had a small number of sipes and notched grooves, but both ends of the sipes were open, resulting in poor wear resistance. Comparative Example 2 was unable to sufficiently improve snow performance and wear resistance because the sipes or notched grooves in the center region were not parallel to each other.

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 at least four curved main grooves extending in a zigzag pattern along the tire circumferential direction,
At least three rows of land portions defined between the bending main grooves are defined into a plurality of blocks by a plurality of lug grooves arranged at intervals in the tire circumferential direction, and the at least three rows of land portions include a center land portion provided on the tire equator,
A pair of sipes and a pair of notched grooves are provided on the tread surface of each of the plurality of blocks, the pair of sipes extending in the same direction with an angular difference of 10° or less, each of the pair of sipes having one end opening into the bend main groove and the other end terminating within the block, the pair of notched grooves extending in the same direction with an angular difference of 10° or less, each of the pair of notched grooves having one end opening into the bend main groove and the other end terminating within the block ,
A tire characterized in that , in a center block that defines the center land portion among the plurality of blocks, the inclination direction of the pair of sipes and the inclination direction of the pair of notched grooves are opposite to each other .
Invention [2] The tire according to invention [1], characterized in that each of the pair of sipes extends in the same direction with respect to either groove wall of a pair of lug grooves adjacent to the block in which the pair of sipes is provided, with an angular difference of within 10°.
Invention [3] A land portion partitioned on the outer side in the tire width direction of the bent main groove arranged on the outermost side in the tire width direction is partitioned into a plurality of shoulder blocks by a plurality of shoulder lug grooves arranged at intervals in the tire circumferential direction,
A pair of shoulder sipes and one shoulder notch groove are provided on the tread surface of each of the plurality of shoulder blocks, and each of the pair of shoulder sipes has one end opening into the bent main groove and the other end terminating within the shoulder block,
The tire according to invention [1] or [2] , characterized in that the one shoulder notch groove is disposed within a region closer to the flexion main groove than the tire width direction center of the shoulder block and closer to the shoulder lug groove on one side of the tire circumferential center of the shoulder block, and one end of the shoulder notch groove opens into the flexion main groove and the other end terminates within the shoulder block.
Invention [4] The tire according to invention [3], characterized in that the groove depth of the notched groove is 25% to 95% of the groove depth of the flexion main groove, and the groove depth of the shoulder notched groove is greater than the groove depth of the notched groove.
Invention [5] The tire according to invention [3] or [4], characterized in that the length of the sipes is 35% to 75% of the maximum length of the shoulder sipes.
Invention [6] A tire according to any one of inventions [1] to [5], characterized in that the length of the notch groove is 30% to 100% of the maximum length of the sipes provided in the same block.
Invention [7] The tire according to any one of inventions [1] to [6], characterized in that the pair of sipes and the pair of notched grooves are arranged in a staggered pattern within the block.

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 10 Bend main groove 11 Inner bend main groove 11a First inner straight portion 11b Second inner straight portion 12 Outer bend main groove 12a First outer straight portion 12b Second outer straight portion 20 Land portion 20B Block 21 Center land portion 21B Center block 22 Intermediate land portion 22B Intermediate block 23 Shoulder land portion 23B Shoulder block 30 Lug groove 31 Center lug groove 31a First center lug groove 31b Second center lug groove 32 Intermediate lug groove 32a First intermediate lug groove 32b Second intermediate lug groove 33 Shoulder lug groove 40 Sipe 41 Center sipe 42 Intermediate sipe 43 Shoulder sipe 50 Notch groove 51 Center notch groove 52 Intermediate notch groove 53 Shoulder notch groove CL Tire equator E Ground contact edge

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 at least four curved main grooves extending in a zigzag pattern along the tire circumferential direction,
At least three rows of land portions defined between the bending main grooves are defined into a plurality of blocks by a plurality of lug grooves arranged at intervals in the tire circumferential direction, and the at least three rows of land portions include a center land portion provided on the tire equator,
A pair of sipes and a pair of notched grooves are provided on the tread surface of each of the plurality of blocks, the pair of sipes extending in the same direction with an angular difference of 10° or less, each of the pair of sipes having one end opening into the bend main groove and the other end terminating within the block, the pair of notched grooves extending in the same direction with an angular difference of 10° or less, each of the pair of notched grooves having one end opening into the bend main groove and the other end terminating within the block ,
A tire characterized in that , in a center block that defines the center land portion among the plurality of blocks, the inclination direction of the pair of sipes and the inclination direction of the pair of notched grooves are opposite to each other . The tire according to claim 1, characterized in that each of the pair of sipes extends in the same direction with an angle difference of 10° or less with respect to the groove wall of one of the pair of lug grooves adjacent to the block in which the pair of sipes is provided. A land portion partitioned on the outer side in the tire width direction of the bent main groove arranged at the outermost side in the tire width direction is partitioned into a plurality of shoulder blocks by a plurality of shoulder lug grooves arranged at intervals in the tire circumferential direction,
A pair of shoulder sipes and one shoulder notch groove are provided on the tread surface of each of the plurality of shoulder blocks, and each of the pair of shoulder sipes has one end opening into the bent main groove and the other end terminating within the shoulder block,
3. The tire according to claim 1 , wherein the shoulder notch groove is disposed within a region closer to the flexion main groove than the tire width direction center of the shoulder block and closer to the shoulder lug groove on one side of the tire circumferential center of the shoulder block, and one end of the shoulder notch groove opens into the flexion main groove and the other end terminates within the shoulder block. The tire described in claim 3, characterized in that the groove depth of the notched groove is 25% to 95% of the groove depth of the bend main groove, and the groove depth of the shoulder notched groove is greater than the groove depth of the notched groove. The tire described in claim 3, characterized in that the length of the sipes is 35% to 75% of the maximum length of the shoulder sipes. The tire described in claim 1 or 2, characterized in that the length of the notch groove is 30% to 100% of the maximum length of the sipes provided in the same block. The tire according to claim 1 or 2, characterized in that the pair of sipes and the pair of notched grooves are arranged in a staggered pattern within the block.

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