JP2020168943A - tire - Google Patents

Abstract

To exhibit excellent steering stability and ride comfort of a tire of which a tread part is partitioned into four land parts.SOLUTION: A tire includes a tread part 2. The tread part 2 is structured of three main grooves 3 and four land parts 4. The main groove 3 is structured of a first shoulder main groove 5, a second shoulder main groove 6, and a crown main groove 7. The land part 4 includes a first middle land part 11 between the first shoulder main groove 5 and the crown main groove 7, and a second middle land part 12 between the second shoulder main groove 6 and the crown main groove 7. The first middle land part 11 is arranged so that a tire equator is positioned on a ground contact surface. Each of the first middle land part 11 and the second middle land part 12 has a plurality of fine grooves 15.SELECTED DRAWING: Figure 1

Description

The present invention relates to a tire, and more particularly to a tire in which a tread portion is divided into four land portions by a main groove.

Patent Document 1 below proposes a tire in which the tread portion is divided into four land portions by three vertical main grooves. The tire of Patent Document 1 is configured as a rib in which each land portion extends continuously in the tire circumferential direction.

Japanese Unexamined Patent Publication No. 2009-040156

Generally, when the land portion of the tread portion has high rigidity, the steering stability tends to be improved, but the ride comfort tends to be deteriorated. In particular, when the tread portion is composed of four land portions as in the tire of Patent Document 1, the above tendency is remarkable because the width of each land portion in the tire axial direction is large and the rigidity in the width direction is high. Easy to appear.

The present invention has been devised in view of the above problems, and the main object of the present invention is to exhibit excellent steering stability and ride comfort in a tire in which the tread portion is divided into four land portions. There is.

The present invention is a tire including a tread portion, the tread portion includes a first tread end and a second tread end, and a tire circumferential direction is provided between the first tread end and the second tread end. It is composed of three main grooves extending continuously and four land portions divided into the main grooves, and the main grooves are the first arranged between the tire equatorial line and the first tread end. One shoulder main groove, a second shoulder main groove arranged between the tire equatorial line and the second tread end, and one arranged between the first shoulder main groove and the second shoulder main groove. The land portion is composed of a crown main groove, and the land portion is between a first middle land portion between the first shoulder main groove and the crown main groove, and between the second shoulder main groove and the crown main groove. The first middle land portion includes the second middle land portion, and the first middle land portion is arranged so that the tire equatorial line is located on the ground surface thereof, and each of the first middle land portion and the second middle land portion has A plurality of treads are provided.

In the tire of the present invention, at least one of the first middle land portion and the second middle land portion has a transverse groove that crosses the land portion and a transverse groove that extends from the crown main groove and crosses the land portion. It is desirable to include non-transverse grooves and not.

In the tire of the present invention, both the first middle land portion and the second middle land portion are provided with a plurality of the transverse grooves and a plurality of non-cross grooves, and each of the non-cross grooves is provided. It is desirable that the tire communicates with the transverse groove adjacent to the tire in the circumferential direction.

In the tire of the present invention, the non-transverse groove preferably includes a first portion extending along the transverse groove and a second portion that bends from the first portion and extends to the transverse groove.

In the tire of the present invention, it is desirable that the maximum depth of the second portion is smaller than the maximum depth of the first portion.

In the tire of the present invention, in the first middle land portion, the non-transverse groove communicates with the transverse groove adjacent to the first tire circumferential direction, and in the second middle land portion, the non-cross groove Is preferably communicated with the transverse groove adjacent to the second tire circumferential direction opposite to the first tire circumferential direction.

In the tire of the present invention, the non-transverse groove arranged in the first middle land portion is smoothly continuous with the transverse groove arranged in the second middle land portion via the crown main groove. It is desirable to have.

In the tire of the present invention, the non-transverse groove arranged in the second middle land portion is smoothly continuous with the transverse groove arranged in the first middle land portion via the crown main groove. It is desirable to have.

In the tire of the present invention, it is desirable that the depth of both ends of the transverse groove in the tire axial direction is larger than the depth of the central portion in the tire axial direction.

In the tire of the present invention, the first middle land portion is arranged so that the tire equator is located on the ground contact surface thereof. As a result, excessive deformation of the tread portion is suppressed, and excellent steering stability is exhibited.

In the tire of the present invention, a plurality of narrow grooves are provided in each of the first middle land portion and the second middle land portion. As a result, the rigidity of the first middle land portion and the second middle land portion is relaxed, and excellent riding comfort can be obtained.

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 and the 2nd 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. FIG. 2 is a cross-sectional view taken along the line CC of FIG. FIG. 2 is a cross-sectional view taken along the line DD of FIG. FIG. 2 is a cross-sectional view taken along the line EE of FIG. FIG. 2 is a sectional view taken along line FF of FIG. It is an enlarged view of the 1st shoulder land part of FIG. 9 is a cross-sectional view taken along the line GG of FIG. It is an enlarged view of the 2nd shoulder land part of FIG. FIG. 11 is a cross-sectional view taken along the line HH 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 embodiment has a tread portion 2 whose mounting direction on a vehicle is specified. However, the tire of the present invention is not limited to such an aspect. 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 direction 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 a normal state and the tire 1 touches a 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 is composed of 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 land portions 4 divided into the main grooves 3. It is configured.

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. It is composed of 6 and a single crown main groove 7 arranged between the first shoulder main groove 5 and the second shoulder main groove 6.

The distance L1 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 0.15 to 0.35 times 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, on the second tread end Te2 side of the tire equator C. The distance L2 in the tire axial direction from the tire equator C to the groove center line of the crown main groove 7 is preferably, for example, 0.05 to 0.10 times the tread width TW.

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 W1 of each main groove 3 is preferably, for example, 4.0% to 7.0% of the tread width TW. 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 includes 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 and the second middle land portion 12. As shown in FIG. 2, the width W2 of the first middle land portion 11 in the tire axial direction and the width W3 of the second middle land portion 12 in the tire axial direction are, for example, 0.10 of the tread width TW. It is desirable that it is ~ 0.25 times. In the present embodiment, the width W2 of the first middle land portion 11 and the width W3 of the second middle land portion 12 are substantially the same.

The first middle land portion 11 is arranged so that the tire equator is located on the ground contact surface thereof. As a result, excessive deformation of the tread portion 2 is suppressed, and excellent steering stability is exhibited. In the present embodiment, the tire equator C is arranged on the second tread end Te2 side of the center position 11c of the first middle land portion 11 in the tire axial direction. It is desirable that the distance L3 in the tire axial direction between the tire equator C and the center position 11c is, for example, 0.20 to 0.40 times the width W2 of the first middle land portion.

A plurality of narrow grooves 15 are provided in each of the first middle land portion 11 and the second middle land portion 12. As a result, the rigidity of the first middle land portion 11 and the second middle land portion 12 is relaxed, and excellent riding comfort can be obtained. In this specification, the narrow groove 15 means a groove having a groove width of 3.0 mm or less on the ground contact surface of the land portion, and includes a notch called a so-called sipe.

The groove 15 of the present embodiment includes a plurality of transverse grooves 16 that cross the land portion 4 and a plurality of non-crossing grooves 17 that extend from the crown main groove 7 and do not cross the land portion 4. Further, the transverse groove 16 includes a transverse groove 16A arranged in the first middle land portion 11 and a transverse groove 16B arranged in the second middle land portion 12. Further, the non-crossing groove 17 includes a non-crossing groove 17A arranged in the first middle land portion 11 and a non-crossing groove 17B arranged in the second middle land portion 12.

The transverse groove 16A provided in the first middle land portion 11 is inclined in the first direction (downward to the right in FIG. 2) with respect to the tire axial direction, for example. The angle of the transverse groove 16A with respect to the tire axial direction is, for example, 5 to 10 °. Further, it is desirable that the transverse groove 16A of the present embodiment is slightly curved so that the angle with respect to the tire axial direction gradually increases toward the second tread end Te2 side.

The transverse groove 16A provided in the first middle land portion 11 includes, for example, the first transverse groove 21 and the second transverse groove 22. The first transverse groove 21 and the second transverse groove 22 are provided alternately in the tire circumferential direction, for example.

FIG. 3 shows a sectional view taken along line AA of the first transverse groove 21 of FIG. As shown in FIG. 3, the first transverse groove 21 is arranged in a narrow portion 25 having a width W4 of 1.5 mm or less and a narrow portion 25 outside in the tire radial direction in its cross section, and is narrow. It includes an opening 26 having a width larger than that of the portion 25 and opening to the ground plane of the land portion. The width W5 of the opening 26 of the first transverse groove 21 at the ground contact surface is preferably, for example, 1.8 to 2.5 mm. The depth of the opening 26 is, for example, 1.0 to 2.0 mm. Such a first transverse groove 21 makes it easier for the ground contact surface to follow the road surface, which helps to improve the initial response during steering.

FIG. 4 shows a sectional view taken along line BB of the first transverse groove 21 of FIG. As shown in FIG. 4, the first transverse groove 21 has, for example, a first deep bottom portion 21a and a second deep bottom portion 21b arranged on both sides in the tire axial direction, and a first deep bottom portion 21a and a second depth. It includes a first deep bottom portion 21a arranged between the bottom portion 21b and a first shallow bottom portion 21c having a depth smaller than that of the second deep bottom portion 21b. That is, in the first transverse groove 21, the depth of both ends in the tire axial direction is larger than the depth of the central portion in the tire axial direction. Such a first transverse groove 21 is useful for improving steering stability and riding comfort in a well-balanced manner.

The maximum depth d3 of the transverse groove 16 (in the present embodiment, corresponds to the depth of the first deep bottom portion 21a or the second deep bottom portion 21b of the first transverse groove 21) is, for example, the crown main groove 7. It is 0.60 to 1.00 times the depth d1 of the above, and more preferably 0.65 to 0.75 times. It is desirable that the depth d2 of the first shallow bottom portion 21c is, for example, 0.30 to 0.50 times the depth d1 of the crown main groove 7.

The length L4 of the first shallow bottom portion 21c in the tire axial direction is, for example, 0.25 to 0 of the width W2 of the first middle land portion 11 in the tire axial direction (shown in FIG. 2 and hereinafter the same). .50 times. It is desirable that the length L4 of the first shallow bottom portion 21c in the tire axial direction is larger than, for example, the length of the first deep bottom portion 21a in the tire axial direction and the length of the second deep bottom portion 21b in the tire axial direction. Such a first shallow bottom portion 21c exhibits excellent riding comfort and also improves wear resistance.

As shown in FIG. 2, the second transverse groove 22 extends, for example, along the first transverse groove 21 and, in a preferred embodiment, parallel to the first transverse groove 21.

For example, it is desirable that the entire second transverse groove 22 has a width of 1.5 mm or less, and in the present embodiment, the entire second transverse groove 22 has a width of 0.5 to 1.0 mm.

FIG. 5 shows a sectional view taken along line CC of the second transverse groove 22 of FIG. As shown in FIG. 5, the second transverse groove 22 has a second shallow bottom portion 22a and a third shallow bottom portion 22b arranged on both sides in the tire axial direction, and a second shallow bottom portion 22a and a third shallow bottom portion 22b. It includes a second shallow bottom portion 22a and a third deep bottom portion 22c which is arranged between the two and has a depth larger than that of the third shallow bottom portion 22b. The third deep bottom portion 22c is arranged at a position including the central portion of the second transverse groove 22 in the tire axial direction. In this embodiment, the second shallow bottom portion 22a is arranged on the first tread end Te1 side of the third deep bottom portion 22c. Further, the third shallow bottom portion 22b is arranged on the second tread end Te2 side of the third deep bottom portion 22c. Such a second transverse groove 22 cooperates with the first transverse groove 21 described above to improve steering stability and wear resistance in a well-balanced manner.

It is desirable that the depth d4 of the third deep bottom portion 22c is, for example, 0.60 to 1.00 times the depth d1 of the crown main groove 7. In the present embodiment, the depth d4 of the third deep bottom portion 22c is the same as the depth of the first deep bottom portion 21a and the second deep bottom portion 21b (shown in FIG. 4).

The depth d5 of the second shallow bottom portion 22a is, for example, 0.15 to 0.50 times the depth d1 of the crown main groove 7. In a more preferred embodiment, the depth d5 of the second shallow bottom 22a is 0.40 to 0.85 times the depth d4 of the third deep bottom 22c. It is desirable that the depth d6 of the third shallow bottom portion 22b is smaller than that of the second shallow bottom portion 22a. In the present embodiment, the depth d6 of the third shallow bottom portion 22b is the same as the depth of the opening 26 (shown in FIG. 3) of the first transverse groove 21. Such a second transverse groove 22 maintains the rigidity of the first middle land portion 11 on the tire equator C side, and improves steering stability and wear resistance.

The length L5 of the third deep bottom portion 22c in the tire axial direction is, for example, 0.45 to 0.65 times the width W2 of the first middle land portion 11 in the tire axial direction. It is desirable that the length L5 of the third deep bottom portion 22c of the present embodiment in the tire axial direction is larger than, for example, the length L4 of the first shallow bottom portion 21c of the first transverse groove 21 in the tire axial direction.

The length L6 of the second shallow bottom portion 22a in the tire axial direction includes the length L5 of the third deep bottom portion 22c in the tire axial direction, the length L7 of the third shallow bottom portion 22b in the tire axial direction, and the first transverse groove. It is smaller than the length L4 of the first shallow bottom portion 21c of 21 in the tire axial direction. Specifically, the length L6 of the second shallow bottom portion 22a is 0.05 to 0.20 times the width W2 of the first middle land portion 11 in the tire axial direction. Such a second shallow bottom portion 22a makes it easy to open the first tread end Te1 side of the second transverse narrow groove 22, and can improve the wet performance.

The length L7 of the third shallow bottom portion 22b in the tire axial direction is smaller than, for example, the length L5 of the third deep bottom portion 22c in the tire axial direction, and in a more desirable embodiment, the length of the first shallow bottom portion 21c in the tire axial direction. It is smaller than L4. The length L7 of the third shallow bottom portion 22b is, for example, 0.30 to 0.40 times the width W2 of the first middle land portion 11.

As shown in FIG. 2, it is desirable that each of the non-crossing grooves 17 communicates with the crossing grooves 16 adjacent to each other in the tire circumferential direction. Each of the non-crossing grooves 17A provided in the first middle land portion 11 communicates with the first crossing groove 21 adjacent to the first tire circumferential direction (upward in FIG. 2). Further, in the first middle land portion 11, the non-transverse groove 17A is provided between the first cross groove 21 and the second cross groove 22.

For example, the non-transverse groove 17 is preferably formed with a width of 1.5 mm or less as a whole, and in the present embodiment, the whole is made of a width of 0.5 to 1.0 mm.

The non-transverse groove 17 includes a first portion 31 that is inclined in the first direction with respect to the tire axial direction, and a second portion 32 that bends from the first portion 31 and extends to the transverse groove 16. It is desirable that the first portion 31 extends along, for example, the transverse groove 16. The second portion 32 bends in an arc shape from the first portion 31 and communicates with the transverse groove 16. Further, the non-crossing groove 17 crosses the center position 11c of the first middle land portion 11 in the tire axial direction, and the second portion 32 is located closer to the first tread end Te1 side than the center position 11c. 1 It communicates with the transverse groove 21. Such a non-crossing groove 17 improves wet performance while maintaining steering stability and wear resistance. However, the non-transverse groove 17 is not limited to such an aspect.

FIG. 6 shows a sectional view taken along line DD of the first portion 31 of FIG. As shown in FIG. 6, the maximum depth d8 of the non-transverse groove 17 (corresponding to the maximum depth of the first portion 31 in this embodiment) is the maximum depth d3 of the transverse groove 16. It is 0.40 to 1.50 times (shown in FIG. 4), and more preferably 0.99 to 1.10 times. Further, it is desirable that the first portion 31 has, for example, a shallow bottom portion 31a in which the end portion on the crown main groove 7 side is raised. The shallow bottom portion 31a of the first portion 31 has substantially the same shape as the second shallow bottom portion 22a of the second transverse groove 22, for example, and has the above-mentioned configuration of the second shallow bottom portion 22a as the shallow bottom portion 31 of the first portion 31. It can be applied to the bottom 31a.

The maximum depth of the second portion 32 is, for example, smaller than the maximum depth of the first portion 31. It is desirable that the maximum depth of the second portion 32 is smaller than the depth of the shallow bottom portion 31a of the first portion 31. In the present embodiment, the depth of the second portion 32 is the same as the depth of the opening 26 of the first transverse groove 21.

As shown in FIG. 2, the transverse groove 16B and the non-crossing groove 17B provided in the second middle land portion 12 are inclined in the first direction with respect to the tire axial direction, for example. The transverse groove 16B provided in the second middle land portion 12 is inclined at a larger angle with respect to the tire axial direction than the transverse groove 16A provided in the first middle land portion 11. The angle of the transverse groove 16B provided in the second middle land portion 12 with respect to the tire axial direction is, for example, 20 to 30 °. Further, it is desirable that the transverse groove 16B of the present embodiment is slightly curved so that the angle with respect to the tire axial direction gradually increases toward the second tread end Te2 side.

The transverse groove 16B provided in the second middle land portion 12 includes a third transverse groove 23 and a fourth transverse groove 24. The third transverse groove 23 has a cross-sectional shape similar to that of the first transverse groove 21 shown in FIG. 3 in at least a part of the cross section thereof, and the narrow portion 25 having a width of 1.5 mm or less. And an opening 26 having a width larger than that of the narrow portion and opening to the ground plane of the land portion. Further, it is desirable that the fourth transverse groove 24 has a width of 1.5 mm or less as a whole like the second transverse groove 22, and in the present embodiment, the whole is 0.5 to 1.0 mm. It is composed of the width of.

FIG. 7 shows a sectional view taken along line EE of the third transverse groove 23 of FIG. As shown in FIG. 7, the third transverse groove 23 includes, for example, a first groove portion 23a communicating with the crown main groove 7, a second groove portion 23b communicating with the second shoulder main groove 6, and a first groove portion 23a. A third groove portion 23c between the second groove portion 23b and the second groove portion 23b is included. The first groove portion 23a and the second groove portion 23b include the narrow portion 25 and the opening 26. Further, the third groove portion 23c has a depth smaller than that of the first groove portion 23a and the second groove portion 23b, and in the present embodiment, the third groove portion 23c is composed of only the opening portion 26. Such a third transverse groove 23 maintains the rigidity of the second middle land portion 12 and helps to exhibit excellent steering stability and wear resistance.

The third groove portion 23c crosses the center position in the tire axial direction of the second middle land portion 12, for example. The length L8 of the third groove portion 23c in the tire axial direction is, for example, 0.35 to the width W3 of the second middle land portion 12 in the tire axial direction (shown in FIG. 2 and hereinafter the same). It is desirable that it is 0.50 times.

FIG. 8 shows a sectional view taken along line FF of the fourth transverse groove 24 of FIG. As shown in FIG. 8, the bottom surface of the fourth transverse groove 24 is raised at least in the region including the end portion on the crown main groove 7 side. The fourth transverse groove 24 of the present embodiment includes, for example, a fourth shallow bottom portion 24a and a fifth shallow bottom portion 24b arranged on both sides in the tire axial direction, a fourth shallow bottom portion 24a, and the fifth shallow bottom portion 24b. It includes a fourth deep bottom portion 24a arranged in between and a fourth deep bottom portion 24c having a depth larger than that of the fourth shallow bottom portion 24a and the fifth shallow bottom portion 24b. The fourth shallow bottom portion 24a is provided on the first tread end Te1 side of the fourth deep bottom portion 24c, and the fifth shallow bottom portion 24b is provided on the second tread end Te2 side of the fourth deep bottom portion 24c.

The fourth shallow bottom portion 24a is configured to have the same depth as the above-mentioned opening 26, for example. It is desirable that the length L9 of the fourth shallow bottom portion 24a in the tire axial direction is larger than the length L8 of the third groove portion 23c of the third transverse groove 23 in the tire axial direction (shown in FIG. 7). The length L9 of the fourth shallow bottom portion 24a is 0.40 to 0.55 times the width W3 of the second middle land portion 12 in the tire axial direction. Such a fourth shallow bottom portion 24a is useful for maintaining the rigidity of the second middle land portion 12 on the tire equator C side.

It is desirable that the depth of the fifth shallow bottom portion 24b is larger than the depth of the fourth shallow bottom portion 24a, for example. The fifth shallow bottom portion 24b has substantially the same shape as the second shallow bottom portion 22a of the second transverse groove 22 shown in FIG. 5, and the configuration of the second shallow bottom portion 22a described above is applied. Can be done.

The depth d7 of the fourth deep bottom portion 24c is, for example, 0.60 to 1.00 times the depth d1 of the crown main groove 7. The fourth deep bottom portion 24c crosses, for example, the center position of the second middle land portion 12 in the tire axial direction. The length L10 of the fourth deep bottom portion 24c in the tire axial direction is larger than, for example, the length of the first groove portion 23a or the second groove portion 23b of the third transverse groove 23 in the tire axial direction. Specifically, the length L10 of the fourth deep bottom portion 24c is 0.30 to 0.50 times the width W3 of the second middle land portion 12 in the tire axial direction.

As shown in FIG. 2, the non-crossing groove 17B provided in the second middle land portion 12 communicates with the crossing groove 16 adjacent to the tire circumferential direction. It is desirable that the non-transverse groove 17B communicates with the cross groove 16 adjacent to the second tire circumferential direction (downward in FIG. 2) opposite to the first tire circumferential direction, for example. Each of the non-crossing grooves 17B of the present embodiment communicates with the third crossing groove 23. Such an arrangement of the non-transverse groove 17 is useful for suppressing uneven wear of each land portion.

The non-transverse groove 17B provided in the second middle land portion 12 has substantially the same configuration as the non-crossing groove 17A provided in the first middle land portion 11 except for the above configuration. Therefore, the above-mentioned configuration of the non-crossing groove 17A can be applied to the non-crossing groove 17B provided in the second middle land portion 12.

The non-transverse groove 17A arranged in the first middle land portion 11 is smoothly continuous with any of the transverse grooves 16B arranged in the second middle land portion 12 via the crown main groove 7. Further, the non-crossing groove 17B arranged in the second middle land portion 12 is smoothly continuous with any of the crossing narrow grooves 16A arranged in the first middle land portion 11 via the crown main groove 7. Such a groove arrangement helps to enhance wet performance and ride comfort. The fact that the two fine grooves 15 are smoothly continuous through the crown main groove 7 means that the first virtual groove portion in which one fine groove is extended in the length direction thereof and the other fine groove have the length thereof. This includes an aspect in which the distance between the second virtual groove portion extended in the longitudinal direction and the tire circumferential direction is 2 mm or less in the crown main groove 7. In a more desirable embodiment, the first virtual groove portion and the second virtual groove portion overlap in the crown main groove 7.

Specifically, it is desirable that the non-transverse groove 17A provided in the first middle land portion 11 is smoothly continuous with the fourth cross groove 24 via the crown main groove 7. It is desirable that the non-crossing narrow groove 17B provided in the second middle land portion 12 is smoothly continuous with the second crossing narrow groove 22 via the crown main groove 7. As a more desirable embodiment, in the present embodiment, the first transverse groove 21 is smoothly continuous with the third transverse groove 23 via the crown main groove 7.

In the first middle land portion 11, the total number N1 of the crossing narrow grooves 16A is larger than the total number N2 of the non-crossing fine grooves 17A. Further, also in the second middle land portion 12, the total number N1 of the crossing narrow grooves 16B is larger than the total number N2 of the non-crossing narrow grooves 17B. The total number N1 is, for example, 1.5 to 2.5 times the total number N2. Such an arrangement of the fine grooves can ensure wet performance while exhibiting the above-mentioned effects.

The first middle land portion 11 and the second middle land portion 12 of the present embodiment are provided with only the above-mentioned fine groove 15 having a groove width of 3.0 mm or less, and the groove width is larger than 3.0 mm. Is not provided. With such a groove arrangement, excellent steering stability and wear resistance can be obtained.

FIG. 9 shows an enlarged view of the first shoulder land portion 13. As shown in FIG. 9, the first shoulder land portion 13 has the largest width of the ground contact surface in the tire axial direction among the four land portions. It is desirable that the width W6 of the first shoulder land portion 13 in the tire axial direction is, for example, 0.25 to 0.35 times the tread width TW. Such a first shoulder land portion 13 can make the steering response at the time of turning linear, and thus can improve the steering stability.

The first shoulder land portion 13 includes a plurality of first shoulder lateral grooves 35 having a groove width on the ground contact surface of more than 3.0 mm, and a plurality of first shoulder grooves having a groove width on the ground contact surface of 3.0 mm or less. A shoulder narrow groove 36 is provided.

The first shoulder lateral groove 35 extends from, for example, the first tread end Te1 and is interrupted in the first shoulder land portion 13. The first shoulder lateral groove 35 crosses, for example, the center position of the first shoulder land portion 13 in the tire axial direction. The length L11 of the first shoulder lateral groove 35 in the tire axial direction is, for example, 0.75 to 0.90 times the width W6 of the first shoulder land portion 13 in the tire axial direction. Such a first shoulder lateral groove 35 is useful for improving steering stability and riding comfort in a well-balanced manner.

For example, it is desirable that the first shoulder groove 36 has a width of 1.5 mm or less as a whole, and in the present embodiment, the first shoulder groove 36 has a width of 0.5 to 1.0 mm as a whole. The first shoulder narrow groove 36 extends from the first shoulder main groove 5 and is interrupted in the first shoulder land portion 13, for example. The first shoulder narrow groove 36 is interrupted on the first shoulder main groove 5 side of the center position of the first shoulder land portion 13 in the tire axial direction, for example. Further, the first shoulder narrow groove 36 is interrupted on the first tread end Te1 side of the inner end inside the tire axial direction of the first shoulder lateral groove 35. The length L12 of the first shoulder groove 36 in the tire axial direction is, for example, 0.35 to 0.45 times the width W6 of the first shoulder land portion 13 in the tire axial direction.

FIG. 10 shows a sectional view taken along line GG of the first shoulder narrow groove 36 of FIG. As shown in FIG. 10, it is desirable that the first shoulder groove 36 includes a shallow bottom portion 36a having a raised bottom surface in a region including an end portion on the inner side in the tire axial direction. Since such a first shoulder narrow groove 36 does not open excessively when touched down, steering stability and wear resistance are improved.

As shown in FIG. 9, it is desirable that each of the first shoulder lateral groove 35 and the first shoulder narrow groove 36 is inclined in the second direction opposite to the first direction with respect to the tire axial direction. .. Further, it is desirable that each of the first shoulder lateral groove 35 and the first shoulder narrow groove 36 has an angle of 5 to 20 ° with respect to the tire axial direction.

FIG. 11 shows an enlarged view of the second shoulder land portion 14. As shown in FIG. 11, the second shoulder land portion 14 has the smallest width of the ground contact surface in the tire axial direction among the four land portions. The width W7 of the second shoulder land portion 14 in the tire axial direction is 0.10 times or more the tread width TW, and preferably 0.12 to 0.25 times the tread width TW. Such a second shoulder land portion 14 can further enhance the riding comfort.

The second shoulder land portion 14 has a plurality of second shoulder lateral grooves 37 having a groove width larger than 3.0 mm on the ground contact surface, and a plurality of second shoulder groove widths 37 having a groove width on the ground contact surface of 3.0 mm or less. A shoulder narrow groove 38 is provided.

The second shoulder lateral groove 37 extends from, for example, the second tread end Te2 and is interrupted within the second shoulder land portion 14. The length L13 of the second shoulder lateral groove 37 in the tire axial direction is, for example, 0.50 times or more the width W7 of the second shoulder land portion 14 in the tire axial direction, and more preferably 0.60 to 0.60 to the tread width TW. It is 0.80 times. Such a second shoulder lateral groove 37 can improve ride comfort and wet performance while maintaining steering stability.

The second shoulder lateral groove 37 includes a tip detail 37a whose groove width gradually decreases toward the inner end 37i on the inner side in the tire axial direction. The depth of the detail 37a gradually decreases toward the inner end 37i. Such a second shoulder lateral groove 37 can suppress uneven wear at the tip detail 37a.

The second shoulder groove 38 has, for example, a narrow portion 25 having a width of 1.5 mm or less and a width larger than the narrow portion 25, similar to the cross-sectional shape of the first transverse groove 21 shown in FIG. Includes an opening 26 that opens to the ground plane of the portion. It is desirable that the length of the second shoulder narrow groove 38 in the tire axial direction is larger than the length of the second shoulder lateral groove 37 in the tire axial direction. The second shoulder narrow groove 38 of the present embodiment extends from, for example, the second shoulder main groove 6 to the second tread end Te2.

FIG. 12 shows a cross-sectional view taken along the line HH of the second shoulder groove 38 of FIG. As shown in FIG. 12, it is desirable that the second shoulder groove 38 includes a shallow bottom portion 38a having a raised bottom surface in a region including an end portion on the inner side in the tire axial direction. Such a second shoulder narrow groove 38 is useful for improving steering stability and riding comfort in a well-balanced manner.

As shown in FIG. 11, it is desirable that each of the second shoulder lateral groove 37 and the second shoulder narrow groove 38 is inclined in the second direction with respect to the tire axial direction. Further, it is desirable that each of the second shoulder lateral groove 37 and the second shoulder narrow groove 38 has an angle of 5 to 20 ° with respect to the tire axial direction.

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 may be modified to various embodiments.

A size 235 / 50R18 tire having the basic pattern shown in FIG. 1 was prototyped. As a comparative example, a tire having the basic pattern shown in FIG. 13 was prototyped. In the tire of the comparative example, the tire equator C is arranged in the crown main groove a, and only the lateral groove d having a groove width larger than 3 mm is arranged in the first middle land portion b and the second middle land portion c. There is. The steering stability and ride comfort of each test tire were tested. The common specifications and test methods for each test tire are as follows.
Mounting rim: 18 x 7.5J
Tire internal pressure: front wheels 240kPa, rear wheels 240kPa
Test vehicle: Displacement 3000cc, four-wheel drive vehicle Tire mounting position: All wheels

<Maneuvering stability>
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 with a comparative example of 100, and the larger the value, the better the steering stability.

<Ride comfort>
The ride comfort when the test vehicle traveled 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 riding comfort.
The test results are shown in Table 1.

As a result of the test, it was confirmed that the tires of the examples exhibited excellent steering stability and ride comfort.

2 Tread part 3 Main groove 4 Land part 5 1st shoulder main groove 6 2nd shoulder main groove 7 Crown main groove 11 1st middle land part 12 2nd middle land part 15 Fine groove Te1 1st tread end Te2 2nd tread end

Claims (9)

A tire that includes a tread
The tread portion includes a first tread end and a second tread end, and has three main grooves continuously extending in the tire circumferential direction between the first tread end and the second tread end, and said. It consists of four treads divided into main ditches.
The main groove includes a first shoulder main groove arranged between the tire equator and the first tread end, a second shoulder main groove arranged between the tire equator and the second tread end, and the above. It is composed of one crown main groove arranged between the first shoulder main groove and the second shoulder main groove.
The land portion includes a first middle land portion between the first shoulder main groove and the crown main groove, and a second middle land portion between the second shoulder main groove and the crown main groove. ,
The first middle land portion is arranged so that the tire equator is located on the ground contact surface.
A plurality of fine grooves are provided in each of the first middle land portion and the second middle land portion.
tire. At least one of the first middle land portion and the second middle land portion has a transverse trench that crosses the land portion and a non-cross groove that extends from the crown main groove and does not cross the land portion. The tire according to claim 1. A plurality of the transverse grooves and a plurality of non-crossing grooves are provided in both the first middle land portion and the second middle land portion.
The tire according to claim 2, wherein each of the non-transverse grooves communicates with the cross groove adjacent to the tire in the circumferential direction. The tire according to claim 3, wherein the non-transverse groove includes a first portion extending along the transverse groove and a second portion that bends from the first portion and extends to the transverse groove. The tire according to claim 4, wherein the maximum depth of the second portion is smaller than the maximum depth of the first portion. In the first middle land portion, the non-transverse groove communicates with the cross groove adjacent to the first tire circumferential direction.
According to claims 3 to 5, in the second middle land portion, the non-transverse groove communicates with the transverse groove adjacent to the second tire circumferential direction opposite to the first tire circumferential direction. Tires listed in either. The non-transverse groove arranged in the first middle land portion is smoothly continuous with the transverse groove arranged in the second middle land portion via the crown main groove, claim 3 to 3. The tire according to any one of 6. 3. The non-transverse groove arranged in the second middle land portion is smoothly continuous with the transverse groove arranged in the first middle land portion via the crown main groove. The tire according to any one of 7. The tire according to any one of claims 2 to 8, wherein the transverse groove has a depth at both ends in the tire axial direction larger than a depth at the central portion in the tire axial direction.

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