JP2020196279A - tire - Google Patents

Abstract

To exhibit, in a tire the tread portion of which is composed of four land portions, excellent on-snow performance and steering stability on a dry road surface.SOLUTION: A tire has a tread portion 2 specified in terms of the direction in which the tire is attached to a vehicle. A first middle land portion 11 has a width, in a tire axial direction, greatest among four land portion 4. The first middle land portion 11 is provided with a plurality of first inclination grooves 16 and a plurality of second inclination grooves 17, and a plurality of third inclination grooves 18. The first inclination grooves 16 completely cross the first middle land portion 11. The second inclination grooves 17 extend from a crown main groove 7 and discontinue in the first middle land portion 11. The angle of each of the first inclination grooves with respect to a tire circumferential direction and the angle of each of the second inclination grooves with respect to the tire circumferential direction gradually increase toward a first tread end from the crown main groove. At least one of the third inclination grooves 18 communicates with the first inclination grooves 16 and the second inclination grooves 17.SELECTED DRAWING: Figure 1

Description

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

The following Patent Document 1 proposes a tire having a tread portion in which the direction of mounting on a vehicle is specified. The tread portion is formed with an outer middle land portion, an outer shoulder land portion, an inner middle land portion, and an inner shoulder land portion. Patent Document 1 is expected to improve the performance on snow while suppressing the decrease in rigidity of the outer middle land portion by specifying the groove arranged in the outer middle land portion.

JP-A-2015-120380

The tire of Patent Document 1 tends to lack the lateral rigidity of the outer middle land portion, and improvement in steering stability on a dry road surface has been required.

The present invention has been devised in view of the above problems, and is to exhibit excellent on-snow performance and steering stability on a dry road surface in a tire having a tread portion composed of four land portions. It is the main issue.

The present invention is a tire having a tread portion whose mounting direction on a vehicle is specified, and the tread portion is located on a first tread end located on the outside of the vehicle when mounted on the vehicle and on the inside of the vehicle when mounted on the vehicle. It is divided into three main grooves having a second tread end and continuously extending in the tire circumferential direction between the first tread end and the second tread end, and the three main grooves. The main groove is composed of four land portions, the first shoulder main groove arranged on the end side of the first tread among the three main grooves, and the first shoulder main groove. The land portion includes a crown main groove adjacent to the end side of the second tread, and the land portion includes a first middle land portion divided between the first shoulder main groove and the crown main groove, and the first middle 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. A plurality of second inclined grooves inclined in the first direction and a plurality of third inclined grooves inclined in the second direction opposite to the first direction are provided, and the first inclined groove is formed. Completely crossing the first tread, the second tread extends from the crown main groove and is interrupted within the first tread, the angle of the first tread with respect to the tire circumferential direction and the second tread. 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. It communicates with.

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

In the tire of the present invention, each of the first inclined groove and the second inclined groove is curved, and it is desirable that 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, the third inclined groove is curved, and it is desirable that 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 desirable that the groove width of the first inclined groove is reduced from the first shoulder main groove toward the crown main groove side.

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

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 desirable 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, it is desirable that the crown main groove is arranged between the tire equator C and the second tread end.

The present invention is a tire having a tread portion whose mounting direction on a vehicle is specified, and the tread portion is composed of four land portions divided by three main grooves. The land portion includes a first middle land portion divided between the first shoulder main groove and the crown main groove. As in the present invention, in the tread portion composed of four land portions, a large contact pressure acts on the first middle land portion when traveling straight and turning, but in the present invention, the first middle land portion is said to be the same. It has the largest tire axial width of the four treads and has high rigidity. Therefore, the first middle land portion of the present invention helps to improve steering stability on a dry road surface.

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

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

The second inclined groove extends from the crown main groove and is interrupted in the first middle land portion. Such a second inclined groove can maintain the rigidity of the first middle land portion, maintain steering stability on a dry road surface, and enhance performance on snow.

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 gradually increase from the crown main groove toward the first tread end side, respectively. As a result, the lateral rigidity of the first middle land portion is increased toward the first shoulder main groove side, and the steering stability on a dry road surface is improved.

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 compact the snow at a portion communicating with the first inclined groove and the second inclined groove when traveling on snow, and can further improve the performance on snow.

It is a development view of the tread part of the tire of one Embodiment of this invention. It is an enlarged view of the 1st middle land part of FIG. FIG. 2 is a cross-sectional view taken along the line AA of FIG. FIG. 2 is a cross-sectional view taken along the line BB of FIG. It is an enlarged view of the 2nd middle land part of FIG. It is an enlarged view of the 1st shoulder land part of FIG. It is a development view of the tread part of the tire of the comparative example.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a developed view of a tread portion 2 of a tire 1 showing an embodiment of the present invention. The tire 1 of the present embodiment is suitably used as, for example, a pneumatic tire for a passenger car. However, the present invention is not limited to such an aspect, and may be used for a pneumatic tire for a heavy load or a non-pneumatic tire in which the inside of the tire is not filled with pressurized air.

As shown in FIG. 1, the tire 1 of the present invention has a tread portion 2 whose mounting direction on a vehicle is specified. The tread portion 2 has a first tread end Te1 located on the outside of the vehicle when the tire 1 is mounted on the vehicle, and a second tread end Te2 located on the inside of the vehicle when the tire 1 is mounted on the vehicle. The orientation of mounting on the vehicle is indicated by characters or symbols on the sidewall (not shown), for example.

In the case of a pneumatic tire, the first tread end Te1 and the second tread end Te2 are at the most outer contact positions in the tire axial direction when a normal load is applied to the tire 1 in the normal state and the tire 1 touches the plane at a camber angle of 0 °. is there. The normal state is a state in which the tire is rim-assembled on the normal rim, the normal internal pressure is applied, and there is no load. In the present specification, unless otherwise specified, the dimensions and the like of each part of the tire are values measured in the normal state.

A "regular rim" is a rim defined for each tire in the standard system including the standard on which the tire is based. For example, "standard rim" for JATMA, "Design Rim" for TRA, and ETRTO. If there is, it is "Measuring Rim".

"Regular internal pressure" is the air pressure defined for each tire in the standard system including the standard on which the tire is based. For JATTA, "maximum air pressure", for TRA, the table "TIRE LOAD LIMITS AT" The maximum value described in "VARIOUS COLD INFLATION PRESSURES", or "INFLATION PRESSURE" for ETRTO.

"Regular load" is the load defined for each tire in the standard system including the standard on which the tire is based. For JATMA, "maximum load capacity", for TRA, the table "TIRE LOAD LIMITS" The maximum value described in "AT VARIOUS COLD INFLATION PRESSURES", or "LOAD CAPACITY" for ETRTO.

The tread portion 2 has three main grooves 3 extending continuously in the tire circumferential direction between the first tread end Te1 and the second tread end Te2, and four lands divided into these three main grooves 3. It is composed of a part 4.

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

The distance La in the tire axial direction from the tire equator C to the groove center line 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. .. It is desirable that the distance Lb in the tire axial direction from the tire equator C to the groove center line of the crown main groove 7 is, for example, 0.15 times or less of the tread width TW. The tread width TW is the distance in the tire axial direction from the first tread end Te1 to the second tread end Te2 in the normal state.

The crown main groove 7 of the present embodiment is provided, for example, between the tire equator C and the second tread end Te2. However, the position of the crown main groove 7 is not limited to such an aspect.

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

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

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 end Te1. The second shoulder land portion 14 is divided between the second shoulder main groove 6 and the second tread end Te2.

FIG. 2 shows an enlarged view of the first middle land portion 11. As shown in FIG. 2, the first middle land portion 11 has the largest width W1 in the tire axial direction among the four land portions 4. As in the present invention, in the tread portion 2 composed of four land portions, a large contact pressure acts on the first middle land portion 11 when going straight and turning, but in the present invention, the first middle land portion 11 Has the largest tire axial width of the four treads and has high rigidity. Therefore, the first middle land portion 11 of the present invention is useful for improving steering stability on a dry road surface. It is desirable that the width W1 of the first middle land portion 11 is, for example, 0.25 to 0.35 times the tread width TW (shown in FIG. 1 and the same applies hereinafter).

In the first middle land portion 11, a plurality of first inclined grooves 16 inclined in the first direction (downward to the right in FIG. 2) with respect to the tire axial direction, and a plurality of first inclined grooves 16 inclined in the first direction. The two inclined grooves 17 and a plurality of third inclined grooves 18 inclined in the second direction (upward to the right in FIG. 2) opposite to the first direction are provided. Since a large ground pressure acts on the first middle land portion 11, each inclined groove provided in the land portion provides a large snow column shearing force when traveling on snow. As a desirable embodiment, each of the first inclined groove 16, the second inclined groove 17, and the third inclined groove 18 of the present 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 horizontally long snow pillar when traveling on snow, and can enhance traction on snow.

The second inclined groove 17 extends from the crown main groove 7 and is interrupted in the first middle land portion 11. Such a second inclined groove 17 can maintain the rigidity of the first middle land portion 11 and improve the performance on snow while maintaining the steering stability on a dry road surface.

Each of the first inclined groove 16 and the second inclined groove 17 extends from the crown main groove 7 toward the first tread end Te1 side by 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 the steering stability on a dry road surface is improved.

At least one of the third inclined grooves 18 communicates with the first inclined groove 16 and the second inclined groove 17. As a preferred embodiment, in the present embodiment, each third inclined groove 18 communicates with the first inclined groove 16 and the second inclined groove 17. Such a third inclined groove 18 can strongly compact the snow at the portion communicating with the first inclined groove 16 and the second inclined groove 17 when traveling on snow, and can further improve the performance on snow. In the present specification, the fact that one groove communicates with another means both a mode in which these two grooves intersect to form a four-way junction and a mode in which the two grooves form a three-way junction. including.

The first inclined groove 16 is curved in a direction that is convex toward one side (upper side in FIG. 2) in the tire circumferential direction with respect to the straight line connecting both ends of the groove center line, for example. The radius of curvature of the first inclined groove 16 is, for example, 90 to 110 mm. In the present specification, the radius of curvature of the inclined groove shall be measured at the groove center line. When the inclined groove is not in an accurate arc shape, the radius of curvature of the inclined groove means the radius of curvature of the virtual arc passing through three points at both ends of the groove and the center in the length direction of the groove.

The angle of the first inclined groove 16 with respect to the tire circumferential direction is preferably 45 to 55 °, for example. Such a first inclined groove 16 can exert a snow column shearing force 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. 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 first shoulder main groove 5 side 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 sectional view taken along line AA of the first inclined groove 16. As shown in FIG. 3, the outer portion 16a communicating with the first shoulder main groove 5 side and the inner portion 16b communicating with the crown main groove 7 side are included. The inner portion 16b has a depth smaller than that of 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 configured on the crown main groove 7 side of the center position of the first middle land portion 11 in the tire axial direction. Such an inner portion 16b helps to improve steering stability on a dry road surface.

As shown in FIG. 2, it is desirable that the second inclined groove 17 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 tire axial direction is, for example, 0.70 to 0.85 times the width W1 of the first middle land portion 11 in the tire axial direction. Such a second inclined groove 17 is useful for improving the performance on snow and the steering stability on a dry road surface in a well-balanced manner.

The second inclined groove 17 is curved in the same direction as the first inclined groove 16, for example. It is desirable that the radius of curvature of the second inclined groove 17 is smaller than the radius of curvature of the first inclined groove 16. The difference in the 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 to 200 mm, and more preferably 80 to 110 mm.

The angle of the second inclined groove 17 with respect to the tire circumferential direction is preferably 45 to 55 °, for example.

It is desirable that the width of the second inclined groove 17 decreases 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 in the first middle land portion 11 is, for example, 1.0 to 3.0 mm. The groove width at the end of the first middle land portion 11 is measured at a portion excluding the arcuate edge at the end of the groove. Such a second inclined groove 17, together with the above-mentioned first inclined groove 16, provides a large snow column shearing force while maintaining the rigidity of the first middle land portion 11.

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

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

The second inclined groove 17 of the present embodiment includes, for example, a first constant depth portion 17a, a second constant depth portion 17b, and a variable depth portion 17c between them. The first constant depth portion 17a communicates with the crown main groove 7 and extends at a constant depth. It is desirable that the first constant depth portion 17a has, for example, the same depth as the outer portion 16a of the first inclined groove 16.

The second constant depth portion 17b is arranged, for example, on the side of the first shoulder main groove 5 with respect to 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. It is desirable that the second constant depth portion 17b has, for example, the same depth as the inner portion 16b of the first inclined groove 16. 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 inclined with respect to the tire axial direction, and the depth gradually decreases from the first constant depth portion 17a to the second constant depth portion 17b.

As shown in FIG. 2, the third inclined groove 18 extends from the first shoulder main groove 5 to the crown main groove 7 side, for example. It is desirable that the third inclined groove 18 crosses the center position 11c. Further, 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 inclined groove 16 and the third inclined groove 18 is preferably, for example, 40 to 55 °. Further, 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-way junction near the end of the second inclined groove 17 on the crown main groove 7 side.

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

It is desirable that the angle between the first shoulder main groove 5 and the third inclined groove 18 is larger than the angle between the crown main groove 7 and the first inclined groove 16. As a result, the rigidity of the first shoulder main groove 5 side of the first middle land portion 11 becomes relatively high, and as a result, the behavior of the vehicle when a large steering angle is given to the tires during running on a dry road surface is stabilized. ..

It is desirable that the groove width of the third inclined groove 18 is constant in the length direction thereof. The groove width of the third inclined groove 18 is, for example, 2.0 to 3.0 mm. Further, it is desirable that the depth of the third inclined groove 18 is constant in the length direction thereof. 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 embodiment, 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 made the same.

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

The first middle land portion 11 of the present embodiment is provided with a plurality of fourth inclined grooves 19 and a plurality of fifth inclined grooves 20.

It is desirable that the fourth inclined groove 19 communicates with the first inclined groove 16 on the first shoulder main groove 5 side rather than the end portion of the second inclined groove 17 on the first shoulder main groove 5 side. The fourth inclined groove 19 of the present embodiment communicates with the outer side portion 16a (shown in FIG. 3) of the first inclined groove 16. 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 virtual extension line of the groove edge of the first inclined groove 16). It is desirable that the length L2 of the separation portion 21 up to the intersection) is, for example, 0.05 to 0.20 times the width W1 of the first middle land portion 11 in the tire axial direction. As a result, the performance on snow and the steering stability on a dry road surface are improved in a well-balanced manner.

The fourth inclined groove 19 extends in a second direction from the vicinity of the end of the first inclined groove 16 on the first shoulder main groove 5 side, for example. The fourth inclined groove 19 crosses the center position 11c. Further, the fourth inclined groove 19 intersects with the second inclined groove 17 in the region 7 side of the crown main groove 7 from the central position 11c, and is interrupted in the first middle land portion 11. 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 a result, the fourth inclined groove 19 can communicate with the deep portion of the first inclined groove 16 and the second inclined groove 17, and a hard snow pillar can be formed at the intersection of the grooves. Further, the length of the fourth inclined groove 19 in the tire axial direction is smaller than the length of the third inclined groove 18 in the tire axial direction. Such a fourth inclined groove 19 enhances the performance on snow while maintaining the rigidity of the first middle land portion 11.

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. The radius of curvature of the fourth inclined groove 19 is preferably, for example, 150 to 450 mm. In the present 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 a fourth inclined groove 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, for example, 60 to 80 °. The angle θ2 between the first inclined groove 16 and the fourth inclined groove 19 is preferably 45 to 55 °, for example.

It is desirable that the groove width of the fourth inclined groove 19 is constant in the length direction thereof. It is desirable that the groove width of the fourth inclined groove 19 is larger than, for example, the groove width of the third inclined groove 18 and smaller than the maximum groove width of the first inclined groove 16. Further, it is desirable that the maximum depth of the fourth inclined groove 19 is larger than the maximum depth of the third inclined groove 18. Such a fourth inclined groove 19 can improve the performance on snow and the steering stability on a dry road surface in a well-balanced manner.

The fifth inclined groove 20 communicates with the first inclined groove 16 and the second inclined groove 17 without penetrating the first inclined groove 16 and the second inclined groove 17, for example. As a result, a three-way junction is formed with the first inclined groove 16 or the second inclined groove 17 at both ends of the fifth inclined groove 20. However, the present invention is not limited to such an aspect, and the fifth inclined groove 20 may intersect the first inclined groove 16 or the second inclined groove 17. 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. As a result, 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 of the second inclined groove 17 (in FIG. 4). (Show). The fifth inclined groove 20 can maintain the rigidity of the land portion by communicating with the portion where the depth of the first inclined groove 16 and the second inclined groove 17 is small.

It is desirable that the length of the fifth inclined groove 20 in the tire axial direction is 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 in parallel with, for example, the fourth inclined groove 19. The angle θ3 between the second inclined groove 17 and the fifth inclined groove 20 is preferably 45 to 55 °.

It is desirable that the groove width of the fifth inclined groove 20 is constant in the length direction thereof. It is desirable that the groove width of the fifth inclined groove 20 is larger than, for example, the groove width of the fourth inclined groove 19 and smaller than the maximum groove width of the first inclined groove 16. Further, it is desirable that the maximum depth of the fifth inclined groove 20 is smaller than the maximum depth of the fourth inclined groove 19.

It is desirable that a plurality of sipes 25 are provided on the first middle land portion 11 of the present embodiment. The width of the sipe is preferably, for example, 0.4 to 1.0 mm. Each sipe 25 helps to improve performance on snow.

It is desirable that the sipe 25 provided on the first middle land portion 11 is inclined in the second direction, for example. Further, it is desirable that the sipe 25 is convexly curved in the same direction as the third inclined groove 18. Such a sipe 25 provides frictional force by its edge while maintaining the rigidity of the first middle land portion 11.

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 crown main groove 7 to the first inclined groove 16. A third sipe 28 extending to 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 crosses, for example, the first inclined groove 16. The first sipe 26 of the present embodiment communicates with the second inclined groove 17 on the crown main groove 7 side of the center position 11c. In a preferred embodiment, the first sipe 26 extends parallel to the third inclined groove 18.

The second sipe 27 is arranged, for example, between the third inclined groove 18 and the fourth inclined groove 19. It is desirable that the second sipe 27 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. Further, it is desirable that the second sipe 27 extends in parallel with 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, on the crown main groove 7 side of the center position 11c. The third sipe 28 intersects, for example, a region extending the fifth inclined groove 20 toward the crown main groove 7 side. Further, it is desirable that the third sipe 28 extends in parallel with the third inclined groove 18.

The fourth sipe 29 is arranged closer to the crown main groove 7 than the central position 11c, and extends from the first inclined groove 16 to the end of the fourth inclined groove 19. It is desirable that the fourth sipe 29 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. 5, it is desirable that the width W2 of the second middle land portion 12 in the tire axial direction 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 extends from the crown main groove 7 and is interrupted in the second middle land portion 12, for example.

The middle lateral groove 30 includes, for example, a first portion 31 extending inclined 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 when traveling on snow.

A plurality of first middle sipe 33 and a plurality of second middle sipe 34 are provided in the second middle land portion 12. The first middle sipe 33 extends from, for example, the crown main groove 7 and is interrupted in the second middle land portion 12. The second middle sipe 34 extends from, for example, 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 a notch element 35 in which a plurality of minute notches extend between the two sipe pieces 36. The two sipe pieces 36 extend from the first middle sipe 33 to the first portion 31 of the middle lateral groove 30 while reducing the distance from each other, for example. Such a notch element 35 helps to improve the grip performance at the start of using the tire.

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

The first shoulder land portion 13 is provided with a plurality of shoulder lateral grooves 40 extending in the tire axial direction and a plurality of shoulder sipes 41. Such a shoulder lateral groove 40 and a shoulder sipe 41 are useful for enhancing the performance on snow.

As shown in FIG. 1, the second shoulder land portion 14 is provided with a shoulder lateral groove 40 and a shoulder sipe 41 similar to the first shoulder land portion 13.

In a preferred embodiment, the second shoulder land portion 14 has a chamfered portion 42 between its tread and the side surface on the second shoulder main groove 6 side. In a more desirable embodiment, a plurality of fine grooves extending from the tread to the side surface are formed on the outer surface of the chamfered portion 42. As a result, the second shoulder main groove 6 can provide a large snow column shearing 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 modified to various embodiments.

A size 215 / 60R16 tire having the basic pattern shown in FIG. 1 was prototyped. As a comparative example, a tire having the first middle land portion a shown in FIG. 7 was prototyped. The tire of the comparative example 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 in the first middle land portion a, and is the second aspect of the present invention. It does not have a groove corresponding to the inclined groove and the third inclined groove. The tire of the comparative example has substantially the same pattern as that shown in FIG. 1 except for the above items. The snow performance of each test tire and the steering stability on dry roads were tested. The common specifications and test methods for each test tire are as follows.
Mounting rim: 16 x 6.5
Tire internal pressure: 240kPa
Test vehicle: Displacement 2500cc, front-wheel drive vehicle Tire mounting position: All wheels

<Snow performance>
The performance of the test vehicle when traveling on a snowy road was evaluated by the driver's sensuality. The result is a score with a comparative example of 100, and the larger the value, the better the performance on snow.

<Maneuvering stability on dry roads>
The steering stability of the test vehicle when traveling on a dry road surface was evaluated by the driver's sensuality. The result is a score of 100 in the comparative example, and the larger the value, the better the steering stability on the dry road surface.
The test results are shown in Table 1.

As a result of the test, it was confirmed that the tire of the example exhibited excellent performance on snow and steering stability on a dry road surface.

2 Tread part 3 Main groove 4 Land part 5 1st shoulder main groove 7 Crown main groove 11 1st middle land part 16 1st inclined groove 17 2nd inclined groove 18 3rd inclined groove Te1 1st tread end Te2 2nd tread end

Claims (9)

A tire that has a tread that is oriented to be mounted on a vehicle.
The tread portion is
It has a first tread end located on the outside of the vehicle when mounted on the vehicle and a second tread end located on the inside of the vehicle when mounted on the vehicle.
Further, it is composed of three main grooves extending continuously 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 groove is the first shoulder main groove arranged on the first tread end side of the three main grooves, and the crown main groove adjacent to the second tread end side of the first shoulder main groove. Including grooves
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 width in the tire axial direction among the four land portions.
In the first middle land portion, a plurality of first inclined grooves inclined in the first direction with respect to the tire axial direction, a plurality of second inclined grooves inclined in the first direction, and the first direction are A plurality of third inclined grooves inclined in the second direction in the opposite direction are provided, and a plurality of third inclined grooves are provided.
The first inclined groove completely crosses the first middle land portion.
The second inclined groove extends from the crown main groove and is interrupted in the first middle land portion.
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 gradually increase from the crown main groove toward the first tread end side, respectively.
At least one of the third inclined grooves communicates with the first inclined groove and the second inclined groove.
tire. The tire according to claim 1, wherein the first inclined groove and the third inclined groove intersect with each other. 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 the second inclined groove is smaller than the radius of curvature of the first inclined groove. The third inclined groove is curved and
The tire according to claim 3, wherein the radius of curvature of the third inclined groove is larger than the radius of curvature of the first inclined groove. The tire according to any one of claims 1 to 4, wherein the first inclined groove has a groove width reduced from the first shoulder main groove toward the crown main groove side. The tire according to any one of claims 1 to 5, wherein the second inclined groove has a groove width reduced from the crown main groove toward the first shoulder main groove side. The tire according to any one of claims 1 to 6, wherein the groove width of the third inclined groove is constant. The tire according to any one of claims 1 to 7, wherein 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. .. The tire according to any one of claims 1 to 8, wherein the crown main groove is arranged between the tire equator C and the second tread end.

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