JP7255361B2 - tire - Google Patents

Description

TECHNICAL FIELD The present invention relates to a tire, and more particularly to a tire having a tread portion composed of four land portions.

Patent Literature 1 listed below proposes a tire having a tread portion with a specified mounting direction to a vehicle. The tread portion is formed with an outboard middle land portion, an outboard shoulder land portion, an inboard middle land portion, and an inboard shoulder land portion. JP-A-2003-100001 expects to improve on-snow performance while suppressing a decrease in rigidity of the outer middle land portion by specifying grooves arranged in the outer middle land portion.

JP 2015-120380 A

The tire of Patent Literature 1 tends to lack lateral rigidity in the outer middle land portion, and improvement in steering stability on dry road surfaces has been demanded.

The present invention has been devised in view of the problems described above, and aims to provide a tire having a tread composed of four land portions and exhibiting excellent performance on snow and steering stability on dry road surfaces. This is the main issue.

The present invention provides a tire having a tread portion with a specified mounting direction to a vehicle, wherein the tread portion includes a first tread end positioned outside the vehicle when mounted on the vehicle and a first tread end positioned inside the vehicle when mounted on the vehicle. a second tread edge and three main grooves extending continuously in the tire circumferential direction between the first tread edge and the second tread edge; The main groove includes a first shoulder main groove arranged closest to the first tread edge among the three main grooves, and the first shoulder main groove of the first shoulder main groove. and a crown main groove adjacent to a second tread end side, the land portion including a first middle land portion partitioned between the first shoulder main groove and the crown main groove, the first middle land portion. The land portion has the largest width in the tire axial direction among the four land portions, and the first middle land portion has a plurality of first inclined grooves inclined in the first direction with respect to the tire axial direction. and a plurality of second slanted grooves slanted in the first direction, and a plurality of third slanted grooves slanted in a second direction opposite to the first direction, wherein the first slanted grooves are completely crossing the first middle land portion, the second inclined groove extending from the crown main groove and discontinuing within the first middle land portion, the angle of the first inclined groove with respect to the tire circumferential direction and the second inclination; The angles of the grooves with respect to the tire circumferential direction gradually increase from the crown main groove toward the first tread end side, and at least one of the third inclined grooves is the first inclined groove and the second inclined groove. communicates with

In the tire of the present invention, it is desirable that the first inclined groove and the third inclined groove intersect.

In the tire of the present invention, it is preferable that each of the first inclined groove and the second inclined groove is curved, and the radius of curvature of the second inclined groove is smaller than the radius of curvature of the first inclined groove. .

In the tire of the present invention, it is preferable that the third inclined groove is curved, and the radius of curvature of the third inclined groove is larger than the radius of curvature of the first inclined groove.

In the tire of the present invention, it is preferable that the width of the first inclined groove is reduced from the first shoulder main groove toward the crown main groove.

In the tire of the present invention, it is preferable that the width of the second inclined groove is reduced from the crown main groove toward the first shoulder main groove.

In the tire of the present invention, it is desirable that the groove width of the third inclined groove is constant.

In the tire of the present invention, it is preferable that the angle between the first shoulder main groove and the third inclined groove is larger than the angle between the crown main groove and the first inclined groove.

In the tire of the present invention, the crown main groove is preferably arranged between the tire equator C and the second tread edge.

The present invention is a tire having a tread portion with a specified mounting direction on a vehicle, wherein the tread portion is composed of four land portions divided by three main grooves. The land portion includes a first middle land portion partitioned between the first shoulder main groove and the crown main groove. As in the present invention, the tread portion composed of four land portions exerts a large ground contact pressure on the first middle land portion during straight running and turning. It has the widest width in the tire axial direction among the four land parts and has high rigidity. Therefore, the first middle land portion of the present invention helps improve steering stability on dry road surfaces.

In the first middle land portion, a plurality of first inclined grooves inclined in a first direction with respect to the axial direction of the tire, a plurality of second inclined grooves inclined in the first direction, and the first direction A plurality of third slanted grooves slanted in the opposite second direction are provided. Since a large ground pressure acts on the first middle land portion, each inclined groove provided in this land portion provides a large snow column shearing force during running on the snow.

The first inclined groove completely crosses the first middle land portion. Therefore, the first inclined groove can form a laterally elongated snow column when traveling on snow, and can enhance traction on snow.

The second inclined groove extends from the crown main groove and discontinues within the first middle land portion. Such a second inclined groove maintains the rigidity of the first middle land portion, and can improve performance on snow while maintaining steering stability on a dry road surface.

The angle of the first inclined groove with respect to the tire circumferential direction and the angle of the second inclined groove with respect to the tire circumferential direction are each gradually increased from the crown main groove toward the first tread end side. As a result, the lateral rigidity of the first middle land portion is increased toward the first shoulder main groove, and the steering stability on dry road surfaces is enhanced.

At least one of the third inclined grooves communicates with the first inclined groove and the second inclined groove. Such a third inclined groove can strongly press and harden the snow at the portion communicating with the first inclined groove and the second inclined groove when traveling on snow, thereby further enhancing performance on snow.

1 is a developed view of a tread portion of a tire according to one embodiment of the present invention; FIG. FIG. 2 is an enlarged view of a first middle land portion of FIG. 1; FIG. 3 is a cross-sectional view taken along line AA of FIG. 2; FIG. 3 is a cross-sectional view taken along line BB of FIG. 2; FIG. 2 is an enlarged view of a second middle land portion of FIG. 1; FIG. 2 is an enlarged view of a first shoulder land portion of FIG. 1; FIG. 3 is a developed view of a tread portion of a tire of a comparative example;

An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a developed view of a tread portion 2 of a tire 1 showing one embodiment of the present invention. The tire 1 of the present embodiment is suitably used as, for example, a pneumatic tire for passenger cars. However, the present invention is not limited to such an aspect, and may be used for heavy-duty pneumatic tires and non-pneumatic tires in which the interior of the tire is not filled with pressurized air.

As shown in FIG. 1, a tire 1 of the present invention has a tread portion 2 with a specified mounting direction on a vehicle. The tread portion 2 has a first tread end Te1 positioned on the vehicle outer side when the tire 1 is mounted on the vehicle, and a second tread end Te2 positioned on the vehicle inner side when the tire 1 is mounted on the vehicle. The mounting direction to the vehicle is indicated, for example, by characters or symbols on the sidewall portion (not shown).

In the case of a pneumatic tire, the first tread end Te1 and the second tread end Te2 are the outermost ground contact positions in the tire axial direction when the tire 1 in a normal state is applied with a normal load and is grounded on a flat surface with a camber angle of 0°. be. A normal state is a state in which the tire is mounted on a normal rim, is inflated to a normal internal pressure, and has no load. In this specification, unless otherwise specified, the dimensions of each part of the tire are the values measured in the normal condition.

A "regular rim" is a rim defined for each tire in a standard system including the standard on which the tire is based. If there is, it is "Measuring Rim".

"Regular internal pressure" is the air pressure specified for each tire by each standard in the standard system including the standards on which tires are based. Maximum value described in VARIOUS COLD INFLATION PRESSURES", or "INFLATION PRESSURE" for ETRTO.

"Normal load" is the load defined for each tire by each standard in the standard system including the standard on which the tire is based. AT VARIOUS COLD INFLATION PRESSURES", and for ETRTO, it is "LOAD CAPACITY".

The tread portion 2 includes three main grooves 3 continuously extending in the tire circumferential direction between a first tread end Te1 and a second tread end Te2, and four land areas divided by the three main grooves 3. It consists of part 4.

The main grooves 3 include first shoulder main grooves 5 arranged between the first tread edge Te1 and the tire equator C, and second shoulder main grooves arranged between the second tread edge Te2 and the tire equator C. 6 and a crown main groove 7 disposed between the first shoulder main groove 5 and the second shoulder main groove 6 . The first shoulder main groove 5 is located closest to the first tread edge Te1 among the three main grooves 3 . The crown main groove 7 is adjacent to the first shoulder main groove 5 on the second tread end Te2 side.

The axial distance La from the tire equator C to the groove centerline of the first shoulder main groove 5 or the second shoulder main groove 6 is preferably, for example, 0.20 to 0.35 times the tread width TW. . The axial distance Lb from the tire equator C to the groove centerline of the crown main groove 7 is preferably, for example, 0.15 times or less the tread width TW. The tread width TW is the axial distance of the tire from the first tread end Te1 to the second tread end Te2 in the normal state.

The crown main groove 7 of this embodiment is provided, for example, between the tire equator C and the second tread edge Te2. However, the position of the crown main groove 7 is not limited to such a mode.

Each main groove 3 of the present embodiment extends linearly parallel to the tire circumferential direction, for example. Each main groove 3 may, for example, extend in a wavy shape.

A groove width Wa of each main groove 3 is at least 3.0 mm or more, and preferably, for example, 4.0% to 7.0% of the tread width TW. In this specification, vertical narrow grooves having a groove width of less than 3.0 mm are distinguished from the main grooves 3 . Further, the groove width is the distance between the groove edges in the direction perpendicular to the groove center line. The depth of each main groove 3 is desirably 5 to 10 mm, for example, in the case of pneumatic tires for passenger cars.

The land portion 4 is composed of a first middle land portion 11 , a second middle land portion 12 , a first shoulder land portion 13 and a second shoulder land portion 14 . The first middle land portion 11 is divided between the first shoulder main groove 5 and the crown main groove 7 . The second middle land portion 12 is divided between the second shoulder main groove 6 and the crown main groove 7 . The first shoulder land portion 13 is divided between the first shoulder main groove 5 and the first tread edge Te1. The second shoulder land portion 14 is divided between the second shoulder main groove 6 and the second tread edge Te2.

FIG. 2 shows an enlarged view of the first middle land portion 11. As shown in FIG. As shown in FIG. 2 , the first middle land portion 11 has the largest axial width W1 of the four land portions 4 . As in the present invention, the tread portion 2 composed of four land portions exerts a large ground pressure on the first middle land portion 11 during straight running and turning. has the largest width in the tire axial direction among the four land portions and has high rigidity. Therefore, the first middle land portion 11 of the present invention helps improve steering stability on dry road surfaces. The width W1 of the first middle land portion 11 is preferably, for example, 0.25 to 0.35 times the tread width TW (shown in FIG. 1 and the same applies hereinafter).

The first middle land portion 11 has a plurality of first inclined grooves 16 inclined in a first direction (downward to the right in FIG. 2) with respect to the axial direction of the tire, and a plurality of first inclined grooves 16 inclined in the first direction. Two inclined grooves 17 and a plurality of third inclined grooves 18 inclined in a second direction opposite to the first direction (upward to the right in FIG. 2) are provided. Since a large ground pressure acts on the first middle land portion 11, each inclined groove provided in this land portion provides a large snow column shearing force during running on snow. As a desirable aspect, each of the first inclined groove 16, the second inclined groove 17 and the third inclined groove 18 of this embodiment is curved.

The first inclined groove 16 completely crosses the first middle land portion 11 . Therefore, the first inclined groove 16 can form a laterally long snow column when traveling on snow, and can enhance traction on snow.

The second inclined groove 17 extends from the crown main groove 7 and discontinues within the first middle land portion 11 . Such second inclined grooves 17 can maintain the rigidity of the first middle land portion 11 and improve the on-snow performance while maintaining steering stability on dry road surfaces.

Each of the first slanted groove 16 and the second slanted groove 17 extends from the crown main groove 7 toward the first tread end Te1 while gradually increasing the angle with respect to the tire circumferential direction. As a result, the lateral rigidity of the first middle land portion 11 is increased toward the first shoulder main groove 5 side, and thus the steering stability on dry road surfaces is enhanced.

At least one of the third inclined grooves 18 communicates with the first inclined groove 16 and the second inclined groove 17 . As a desirable aspect, in this embodiment, each third inclined groove 18 communicates with the first inclined groove 16 and the second inclined groove 17 . Such third inclined grooves 18 can strongly compact the snow at the portions communicating with the first inclined grooves 16 and the second inclined grooves 17 when traveling on snow, thereby further enhancing the on-snow performance. In this specification, one groove communicates with another groove means that these two grooves intersect to form a four-way intersection, and two grooves form a three-way intersection. including.

The first inclined groove 16 is curved, for example, in a convex direction toward one side (upper side in FIG. 2) in the tire circumferential direction from a straight line connecting both ends of the groove center line. The radius of curvature of the first inclined groove 16 is, for example, 90-110 mm. In addition, in this specification, the curvature radius of the inclined groove shall be measured at the groove center line. In addition, when the slanted groove is not an exact circular arc, the radius of curvature of the slanted groove means the radius of curvature of an imaginary arc passing through three points, ie, both ends of the groove and the center in the longitudinal direction of the groove.

It is desirable that the angle of the first inclined groove 16 with respect to the tire circumferential direction is, for example, 45 to 55 degrees. Such first inclined grooves 16 can exert snow column shear forces in multiple directions.

The width of the first inclined groove 16 is reduced from the first shoulder main groove 5 toward the crown main groove 7 side. That is, the groove width of the end portion of the first inclined groove 16 on the first shoulder main groove 5 side is larger than the groove width of the end portion of the first inclined groove 16 on the crown main groove 7 side. The groove width of the end of the first inclined groove 16 on the side of the first shoulder main groove 5 is, for example, 6.0 to 8.0 mm. The groove width of the end of the first inclined groove 16 on the crown main groove 7 side is, for example, 5.0 to 7.0 mm.

FIG. 3 shows a cross-sectional view of the first inclined groove 16 taken along line AA. As shown in FIG. 3, it includes an outer portion 16a communicating with the first shoulder main groove 5 side and an inner portion 16b communicating with the crown main groove 7 side. The inner portion 16b has a smaller depth than the outer portion 16a. The depth d2 of the inner portion 16b is, for example, 0.40 to 0.70 times the depth d1 of the outer portion 16a. Further, the inner portion 16b is formed closer to the crown main groove 7 than the center position of the first middle land portion 11 in the tire axial direction. Such an inner portion 16b helps improve steering stability on dry road surfaces.

As shown in FIG. 2, the second inclined groove 17 preferably crosses, for example, the center position 11c of the first middle land portion 11 in the tire axial direction. Further, it is desirable that the length L1 of the second inclined groove 17 in the axial direction of the tire is, for example, 0.70 to 0.85 times the width W1 of the first middle land portion 11 in the axial direction of the tire. Such second inclined grooves 17 serve to improve performance on snow and steering stability on dry road surfaces in a well-balanced manner.

The second inclined grooves 17 are curved in the same direction as the first inclined grooves 16, for example. The radius of curvature of the second inclined grooves 17 is preferably smaller than the radius of curvature of the first inclined grooves 16 . The difference in radius of curvature between the second inclined groove 17 and the first inclined groove 16 is, for example, 10 to 50 mm. Specifically, the radius of curvature of the second inclined groove 17 is, for example, 50-200 mm, and more preferably 80-110 mm.

It is desirable that the angle of the second inclined groove 17 with respect to the tire circumferential direction is, for example, 45 to 55 degrees.

The width of the second inclined groove 17 is desirably reduced from the crown main groove 7 toward the first shoulder main groove 5 side. That is, the groove width of the end portion of the second inclined groove 17 on the crown main groove 7 side is larger than the groove width of the end portion of the second inclined groove 17 in the first middle land portion 11 . The groove width of the end of the second inclined groove 17 on the crown main groove 7 side is, for example, 10.0 to 12.0 mm. The groove width of the end portion of the second inclined groove 17 within the first middle land portion 11 is, for example, 1.0 to 3.0 mm. In addition, the groove width of the end portion in the first middle land portion 11 is measured at the portion excluding the arc-shaped edge at the end of the groove. Such second inclined grooves 17 maintain the rigidity of the first middle land portion 11 together with the above-described first inclined grooves 16 and provide a large shearing force of the snow column.

As a more desirable aspect, the groove width of the second inclined groove 17 of this embodiment gradually decreases from the crown main groove 7 to the end portion within the first middle land portion 11 . Such second inclined grooves 17 can further suppress a decrease in rigidity of the first middle land portion 11 .

FIG. 4 shows a cross-sectional view of the second inclined groove 17 taken along line BB. As shown in FIG. 4, it is desirable that the depth of the second inclined groove 17, for example, gradually decrease from the crown main groove 7 toward the first shoulder main groove 5 side. Such second inclined grooves 17, together with the above-described first inclined grooves 16, enhance performance on snow and steering stability on dry road surfaces in a well-balanced manner.

The second inclined groove 17 of this embodiment includes, for example, a first constant depth portion 17a, a second constant depth portion 17b, and a variable depth portion 17c therebetween. The first constant depth portion 17a communicates with the crown main groove 7 and extends at a constant depth. The first constant depth portion 17a preferably has the same depth as the outer portion 16a of the first inclined groove 16, for example.

The second constant-depth portion 17b is arranged, for example, closer to the first shoulder main groove 5 than the first constant-depth portion 17a. The second constant depth portion 17b has a depth smaller than that of the first constant depth portion 17a and extends at a constant depth. The second constant depth portion 17b preferably has the same depth as the inner portion 16b of the first inclined groove 16, for example. The depth d4 of the second constant depth portion 17b is 0.40 to 0.70 times the depth d3 of the first constant depth portion 17a.

The variable-depth portion 17c has a bottom surface that is inclined with respect to the tire axial direction, and the depth gradually decreases from the first constant-depth portion 17a toward the second constant-depth portion 17b.

As shown in FIG. 2, the third inclined groove 18 extends, for example, from the first shoulder main groove 5 toward the crown main groove 7 side. The third oblique groove 18 preferably crosses the center position 11c. The first inclined groove 16 and the third inclined groove 18 intersect with each other on the crown main groove 7 side of the center position 11c. The angle θ1 between the first slanted groove 16 and the third slanted groove 18 is preferably 40-55°, for example. The third inclined groove 18 communicates with the second inclined groove 17 on the crown main groove 7 side of the center position 11c. The third inclined groove 18 does not intersect with the second inclined groove 17 and forms a three-forked path near the end of the second inclined groove 17 on the crown main groove 7 side.

The third inclined groove 18 is curved, for example, in a convex direction toward the other side (lower side in FIG. 2) in the tire circumferential direction with respect to a straight line connecting both ends of the groove center line. The radius of curvature of the third slanted grooves 18 is preferably larger than the radius of curvature of the first slanted grooves 16 . The difference in radius of curvature between the third inclined groove 18 and the first inclined groove 16 is, for example, 50-200 mm. It is desirable that the radius of curvature of the third inclined groove 18 is, for example, 150-450 mm.

It is desirable that the angle of the third inclined groove 18 with respect to the tire circumferential direction gradually decreases toward the crown main groove 7 side. The angle of the third inclined groove 18 with respect to the tire circumferential direction is, for example, 60 to 80°.

The angle between the first shoulder main groove 5 and the third slant groove 18 is preferably greater than the angle between the crown main groove 7 and the first slant groove 16 . As a result, the rigidity of the first middle land portion 11 on the side of the first shoulder main groove 5 is relatively high, which in turn stabilizes the behavior of the vehicle when a large steering angle is applied to the tires during running on a dry road surface. .

The groove width of the third inclined groove 18 is desirably constant in its longitudinal direction. The groove width of the third inclined groove 18 is, for example, 2.0 to 3.0 mm. Moreover, it is desirable that the depth of the third inclined groove 18 is constant in its longitudinal direction. The depth of the third inclined groove 18 of the present embodiment is smaller than, for example, the depth of the outer portion 16a of the first inclined groove 16 and the depth of the first constant depth portion 17a of the second inclined groove 17 . In a more desirable aspect, the depth of the inner portion 16b of the first inclined groove 16, the depth of the second constant depth portion 17b of the second inclined groove 17, and the depth of the third inclined groove 18 are the same.

The third inclined groove 18 may be provided with a groove bottom sipe that opens at the bottom and extends along the length direction of the third inclined groove 18 (not shown). As used herein, a sipe means an incision with a width of 1.5 mm or less. The third inclined groove 18 having such a groove bottom sipe improves steering stability on dry road surfaces while maintaining performance on snow.

A plurality of fourth inclined grooves 19 and a plurality of fifth inclined grooves 20 are provided in the first middle land portion 11 of the present embodiment.

The fourth inclined groove 19 preferably communicates with the first inclined groove 16 on the side of the first shoulder main groove 5 rather than the end of the second inclined groove 17 on the first shoulder main groove 5 side, for example. The fourth inclined groove 19 of this embodiment communicates with the outer portion 16a (shown in FIG. 3) of the first inclined groove 16. As shown in FIG. From the groove edge of the first shoulder main groove 5, the communication portion between the fourth inclined groove 19 and the first inclined groove 16 (the groove center line of the fourth inclined groove 19 and the imaginary extension line of the groove edge of the first inclined groove 16 The length L2 of the spaced portion 21 to the intersection point of ) is preferably, for example, 0.05 to 0.20 times the width W1 of the first middle land portion 11 in the axial direction of the tire. As a result, performance on snow and steering stability on dry road surfaces are improved in a well-balanced manner.

The fourth oblique groove 19 extends obliquely in the second direction, for example, from near the end of the first oblique groove 16 on the side of the first shoulder main groove 5 . The fourth oblique groove 19 crosses the central position 11c. The fourth inclined groove 19 intersects with the second inclined groove 17 and is discontinued within the first middle land portion 11 in a region closer to the crown main groove 7 than the center position 11c. The fourth inclined groove 19 of the present embodiment communicates with, for example, the first constant depth portion 17a (shown in FIG. 4) of the second inclined groove 17. As shown in FIG. As a result, the fourth slanted groove 19 communicates with the deeper portions of the first slanted groove 16 and the second slanted groove 17 to form a solid snow column at the intersection of the grooves. Further, the axial length of the fourth inclined groove 19 is smaller than the axial length of the third inclined groove 18 . Such a fourth inclined groove 19 maintains the rigidity of the first middle land portion 11 and enhances on-snow performance.

It is desirable that the fourth inclined groove 19 is convex and curved in the same direction as the third inclined groove 18, for example. It is desirable that the radius of curvature of the fourth inclined groove 19 is, for example, 150-450 mm. In this embodiment, the radius of curvature of the fourth inclined groove 19 is the same as the radius of curvature of the third inclined groove 18 . Such fourth inclined grooves 19 can further maintain the rigidity of the first middle land portion 11 .

The angle between the first shoulder main groove 5 and the fourth inclined groove 19 is preferably 60-80°, for example. The angle θ2 between the first slanted groove 16 and the fourth slanted groove 19 is preferably 45-55°, for example.

The groove width of the fourth inclined groove 19 is desirably constant in its longitudinal direction. It is desirable that the groove width of the fourth inclined groove 19 is, for example, larger than the groove width of the third inclined groove 18 and smaller than the maximum groove width of the first inclined groove 16 . Moreover, it is desirable that the maximum depth of the fourth inclined groove 19 is greater than the maximum depth of the third inclined groove 18 . Such fourth inclined grooves 19 can enhance performance on snow and steering stability on dry road surfaces in a well-balanced manner.

The fifth inclined groove 20 communicates with the first inclined groove 16 and the second inclined groove 17 without passing through the first inclined groove 16 and the second inclined groove 17, for example. Thus, both ends of the fifth inclined groove 20 form a three-forked path with the first inclined groove 16 or the second inclined groove 17 . However, the fifth inclined groove 20 may intersect the first inclined groove 16 or the second inclined groove 17 without being limited to such an aspect. The fifth inclined groove 20 communicates with the first inclined groove 16 on the crown main groove 7 side of the center position 11c, and communicates with the second inclined groove 17 on the first shoulder main groove 5 side of the center position 11c. ing. Thereby, the fifth inclined groove 20 crosses the center position 11c. Specifically, the fifth inclined groove 20 communicates with the inner portion 16b (shown in FIG. 3) of the first inclined groove 16, and the second constant depth portion 17b (shown in FIG. 4) of the second inclined groove 17. shown). The fifth inclined groove 20 can maintain the rigidity of the land portion by communicating with the shallow portions of the first inclined groove 16 and the second inclined groove 17 .

The axial length of the fifth inclined groove 20 is preferably smaller than the length of the fourth inclined groove 19 . The fifth inclined groove 20 is inclined in the second direction, for example. The fifth inclined groove 20 extends parallel to the fourth inclined groove 19, for example. The angle θ3 between the second inclined groove 17 and the fifth inclined groove 20 is preferably 45-55°.

The groove width of the fifth inclined groove 20 is desirably constant in its longitudinal direction. The groove width of the fifth inclined groove 20 is preferably larger than the groove width of the fourth inclined groove 19 and smaller than the maximum groove width of the first inclined groove 16, for example. Also, the maximum depth of the fifth inclined groove 20 is preferably smaller than the maximum depth of the fourth inclined groove 19 .

A plurality of sipes 25 are preferably provided in the first middle land portion 11 of the present embodiment. Desirably, the width of the sipe is, for example, 0.4 to 1.0 mm. Each sipe 25 helps enhance on-snow performance.

The sipe 25 provided in the first middle land portion 11 is desirably inclined in the second direction, for example. Moreover, it is desirable that the sipe 25 is convexly curved in the same direction as the third inclined groove 18 . Such a sipe 25 maintains the rigidity of the first middle land portion 11 and provides a frictional force by its edge.

The first middle land portion 11 of the present embodiment includes, for example, a first sipe 26 and a second sipe 27 extending from the first shoulder main groove 5 to the second inclined groove 17 , and a groove extending from the crown main groove 7 to the first inclined groove 16 . and a fourth sipe 29 extending from the first inclined groove 16 to the fourth inclined groove 19 are provided.

The first sipe 26 is arranged, for example, between the third inclined groove 18 and the fourth inclined groove 19 . The first sipe 26 traverses the first slanted groove 16, for example. The first sipe 26 of this embodiment communicates with the second inclined groove 17 on the crown main groove 7 side of the center position 11c. In a preferred embodiment, first sipe 26 extends parallel to third angled groove 18 .

The second sipe 27 is arranged, for example, between the third inclined groove 18 and the fourth inclined groove 19 . The second sipe 27 preferably communicates with the second inclined groove 17 on the first shoulder main groove 5 side of the center position 11c, for example. In a preferred embodiment, the second sipe 27 intersects a region extending the fifth inclined groove 20 toward the first shoulder main groove 5 side. Also, the second sipe 27 preferably extends parallel to the fourth inclined groove 19 .

The third sipe 28 is arranged, for example, between the first inclined groove 16 and the second inclined groove 17 . The third sipe 28 is arranged, for example, closer to the crown main groove 7 than the center position 11c. The third sipe 28 intersects, for example, a region obtained by extending the fifth inclined groove 20 toward the crown main groove 7 side. Also, the third sipe 28 preferably extends parallel to the third inclined groove 18 .

The fourth sipe 29 is arranged closer to the crown main groove 7 than the center position 11 c and extends from the first inclined groove 16 to the end of the fourth inclined groove 19 . The fourth sipe 29 desirably extends parallel to the fifth inclined groove 20 .

FIG. 5 shows an enlarged view of the second middle land portion 12. As shown in FIG. As shown in FIG. 5, it is desirable that the axial width W2 of the second middle land portion 12 is, for example, 0.10 to 0.20 times the tread width TW.

The second middle land portion 12 is provided with, for example, a plurality of middle lateral grooves 30 . The middle lateral groove 30 , for example, extends from the crown main groove 7 and discontinues within the second middle land portion 12 .

The middle lateral groove 30 includes, for example, a first portion 31 extending obliquely in the first direction from the crown main groove 7 and a second portion 32 connected to the first portion 31 and extending along the tire circumferential direction. Such a middle lateral groove 30 provides a snow column shearing force in the tire circumferential direction and the tire axial direction during running on snow.

A plurality of first middle sipes 33 and a plurality of second middle sipes 34 are provided on the second middle land portion 12 . The first middle sipe 33 , for example, extends from the crown main groove 7 and discontinues within the second middle land portion 12 . The second middle sipe 34 , for example, extends from the second shoulder main groove 6 and communicates with the middle lateral groove 30 .

The second middle land portion 12 of the present embodiment is provided with cut elements 35 in which a plurality of fine cuts extend between two sipe pieces 36 . The two sipe pieces 36 extend, for example, from the first middle sipe 33 to the first portion 31 of the middle lateral groove 30 while reducing the distance between them. Such cut elements 35 serve to improve the grip performance at the start of use of the tire.

FIG. 6 shows an enlarged view of the first shoulder land portion 13. As shown in FIG. As shown in FIG. 6, the axial width W3 of the first shoulder land portion 13 is preferably larger than the axial width W2 of the second middle land portion 12 . The axial width W3 of the first shoulder land portion 13 is preferably 0.15 to 0.25 times the tread width TW, for example.

A plurality of shoulder lateral grooves 40 and a plurality of shoulder sipes 41 extending in the tire axial direction are provided in the first shoulder land portion 13 . Such shoulder lateral grooves 40 and shoulder sipes 41 serve to improve on-snow performance.

As shown in FIG. 1 , the second shoulder land portion 14 is provided with shoulder lateral grooves 40 and shoulder sipes 41 similar to those of the first shoulder land portion 13 .

In a preferred embodiment, the second shoulder land portion 14 has a chamfered portion 42 between its tread surface and the side surface on the second shoulder main groove 6 side. In a further preferred embodiment, the outer surface of the chamfered portion 42 is formed with a plurality of fine grooves extending from the tread surface to the side surface. Thereby, the second shoulder main groove 6 can provide a large snow column shear force.

Although the tire of one embodiment of the present invention has been described in detail above, the present invention is not limited to the specific embodiment described above, and can be implemented in various ways.

A trial tire of size 215/60R16 having the basic pattern of FIG. 1 was produced. As a comparative example, a tire having a first middle land portion a shown in FIG. 7 was produced. In the tire of the comparative example, the first middle land portion a is provided with an inclined groove b that completely crosses the land portion and an inclined groove c that communicates with only one inclined groove b. It does not have grooves corresponding to the inclined grooves and the third inclined grooves. It should be noted that the tire of the comparative example has substantially the same pattern as that shown in FIG. 1, except for the above items. Each test tire was tested for snow performance and steering stability on dry roads. Common specifications and test methods for each test tire are as follows.
Mounting rim: 16 x 6.5
Tire internal pressure: 240kPa
Test vehicle: 2500cc displacement, front-wheel drive Tire mounting position: All wheels

<Snow Performance>
Performance when the test vehicle was driven on a snowy road was evaluated by the senses of the driver. The results are scored with the comparative example being 100, and the larger the number, the better the on-snow performance.

<Driving stability on dry road surface>
The steering stability of the test vehicle was evaluated by the driver's sensory perception when the test vehicle was driven on a dry road surface. The results are scored with the comparative example being 100, and the larger the number, the better the steering stability on a dry road surface.
Test results are shown in Table 1.

As a result of the test, it was confirmed that the tires of Examples exhibit excellent performance on snow and steering stability on dry road surfaces.

2 tread portion 3 main groove 4 land portion 5 first shoulder main groove 7 crown main groove 11 first middle land portion 16 first inclined groove 17 second inclined groove 18 third inclined groove Te1 first tread edge Te2 second tread edge

Claims (9)

A tire having a tread portion with a specified orientation for mounting on a vehicle,
The tread portion is
Having a first tread end positioned on the vehicle outer side when mounted on the vehicle and a second tread end positioned on the vehicle inner side when mounted on the vehicle,
and three main grooves continuously extending in the tire circumferential direction between the first tread end and the second tread end; and four land portions divided by the three main grooves. ,
The main grooves include a first shoulder main groove arranged closest to the first tread end side among the three main grooves, and a crown main groove adjacent to the second tread end side of the first shoulder main groove. a groove;
the land portion includes a first middle land portion divided between the first shoulder main groove and the crown main groove;
The first middle land portion has the largest axial width of the four land portions,
In the first middle land portion, a plurality of first inclined grooves inclined in a first direction with respect to the axial direction of the tire, a plurality of second inclined grooves inclined in the first direction, and the first direction a plurality of third inclined grooves inclined in the opposite second direction,
the first inclined groove completely crosses the first middle land portion;
the second inclined groove extends from the crown main groove and discontinues within the first middle land portion;
The angle of the first slanted groove with respect to the tire circumferential direction and the angle of the second slanted groove with respect to the tire circumferential direction gradually increase from the crown main groove toward the first tread end side,
At least one of the third slanted grooves communicates with the first slanted groove and the second slanted groove,
tire. The tire according to claim 1, wherein the first slanted groove and the third slanted groove intersect. Each of the first inclined groove and the second inclined groove is curved,
The tire according to claim 1 or 2, wherein the radius of curvature of said second inclined groove is smaller than the radius of curvature of said first inclined groove. The third inclined groove is curved,
The tire according to claim 3, wherein the radius of curvature of the third slanted groove is larger than the radius of curvature of the first slanted groove. 5. The tire according to any one of claims 1 to 4, wherein the first inclined groove has a groove width that decreases from the first shoulder main groove toward the crown main groove. The tire according to any one of claims 1 to 5, wherein the second inclined groove has a groove width that decreases from the crown main groove toward the first shoulder main groove. The tire according to any one of claims 1 to 6, wherein the third inclined groove has a constant groove width. The tire according to any one of claims 1 to 7, wherein an angle between said first shoulder main groove and said third inclined groove is larger than an angle between said crown main groove and said first inclined groove. . 9. Tire according to any one of the preceding claims, wherein the crown main groove is arranged between the tire equator C and the second tread edge.

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