JP7103001B2 - tire - Google Patents

Description

The present invention relates to a tire, and more particularly to a tire in which a land portion is divided between two main grooves.

Patent Document 1 below proposes a pneumatic tire in which a center land portion is divided between two center main grooves. A center sipe that communicates a pair of center main grooves is provided in the center land portion of Patent Document 1.

Japanese Unexamined Patent Publication No. 2015-024797

The pneumatic tire of Patent Document 1 is required to have further improvement in steering stability. In particular, the pneumatic tire of Patent Document 1 has a problem that the initial response at the time of turning is poor.

The present invention has been devised in view of the above circumstances, and a main object of the present invention is to provide a tire capable of exhibiting excellent steering stability.

The present invention is a tire having a tread portion, wherein the tread portion includes a first crown main groove and a second crown main groove continuously extending in the tire circumferential direction across the tire equatorial line, and the first crown main groove. It has a crown land portion divided between the crown main groove and the second crown main groove, and the center of the crown land portion in the tire axial direction is located on the side of the second crown main groove with respect to the tire equatorial line. The land portion of the crown includes a first crown sipe that communicates the first crown main groove and the second crown main groove, and a second crown sipe that extends from the first crown main groove and is interrupted in the land portion of the crown. A third crown sipe that extends from the second crown main groove and is interrupted within the land portion of the crown is provided.

In the tire of the present invention, the first crown sipe has a wide width that is arranged outside the main body portion in the tire radial direction and has a width larger than that of the main body portion in a cross section orthogonal to the length direction thereof. It is desirable to include the part.

On the outer surface of the tread portion of the tire of the present invention, it is desirable that the opening width of the first crown sipe is larger than the opening width of the second crown sipe and the opening width of the third crown sipe.

In the tire of the present invention, each of the second crown sipe and the third crown sipe has an inner end that is interrupted in the land portion of the crown, and the inner end of the third crown sipe is the second crown sipe. It is desirable that it is located closer to the first crown main groove side than the inner end.

In the tire of the present invention, it is desirable that the maximum depth of the second crown sipe and the maximum depth of the third crown sipe are smaller than the maximum depth of the first crown sipe, respectively.

In the tire of the present invention, it is desirable that the maximum depth of the second crown sipe is larger than the maximum depth of the third crown sipe.

In the tire of the present invention, the first crown sipe has a shallow bottom portion having a depth smaller than the maximum depth thereof, and the maximum depth of the third crown sipe is the shallow depth of the first crown sipe. It is desirable that it is larger than the depth of the bottom.

In the tire of the present invention, the tread portion has an inner tread end located inside the vehicle when mounted on the vehicle by designating the mounting direction on the vehicle, and the second crown main groove is the tire equator. It is desirable that it is arranged between the inner tread end and the inner tread end.

The tread portion of the tire of the present invention is located between the first crown main groove and the second crown main groove extending continuously in the tire circumferential direction across the equator of the tire, and between the first crown main groove and the second crown main groove. It has a separate crown land area. The center of the land portion of the crown in the tire axial direction is located on the second crown main groove side of the tire equator. Further, in the land part of the crown, a first crown sipe that connects the first crown main groove and the second crown main groove, a second crown sipe that extends from the first crown main groove and is interrupted in the land part of the crown, and a second crown sipe. A third crown sipe that extends from the main groove of the crown and is interrupted within the land of the crown is provided.

In the second crown sipe and the third crown sipe that are interrupted in the land portion of the crown, the outer end side that communicates with the main groove of the crown is relatively easy to open, and the inner end side that is interrupted in the land portion of the crown is relatively difficult to open. Therefore, the land portion of the crown provided with the second crown sipe and the third crown sipe is likely to be twisted and deformed on the ground contact surface. In particular, in the present invention, since the center of the land portion of the crown in the tire axial direction is located closer to the second crown main groove side than the equator of the tire, the contact patch of the land portion of the crown is further twisted and deformed due to the change in the contact pressure. easy. Therefore, in the tire of the present invention, when a slip angle is given, the ground contact surface of the crown land portion follows the road surface and rapidly twists and deforms, and thus a cornering force is generated without delay. Therefore, the tire of the present invention has a high initial response when turning and exhibits excellent steering stability.

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 crown land part of FIG. (A) is a cross-sectional view taken along the line AA of FIG. 2, and FIG. 2B is a cross-sectional view taken along the line BB of FIG. (A) is a sectional view taken along line CC of FIG. 2, and (B) is a sectional view taken along line DD of FIG. It is an enlarged view of the outer shoulder land part of FIG. FIG. 5 is a cross-sectional view taken along the line EE of FIG. FIG. 5 is a cross-sectional view taken along the line FF of FIG. It is an enlarged view of the land part of the inner shoulder of FIG. FIG. 8 is a cross-sectional view taken along the line GG of FIG. It is an enlarged view of the crown land part of the tire of another embodiment of this invention. It is an enlarged view of the crown land part of the tire of another embodiment of this invention. It is an enlarged view of the crown land part of the tire of another embodiment of this invention. It is an enlarged view of the crown land part of a comparative example.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 shows a development view of the tread portion 2 of the tire 1 of the present embodiment. As shown in FIG. 1, the tire 1 of the present embodiment is configured as, for example, a pneumatic tire for a passenger car. However, the present invention is not limited to such an aspect.

For example, the tire 1 of the present embodiment is designated to be mounted on a vehicle. The direction of mounting on the vehicle is indicated by characters or figures on the sidewall portion (not shown) of the tire 1, for example. When the tire 1 is mounted on the vehicle, the right side of FIG. 1 corresponds to the inside of the vehicle, and the left side of FIG. 1 corresponds to the outside of the vehicle.

By designating the mounting direction on the vehicle, the tread portion 2 is defined as an outer tread end T1 located on the outside of the vehicle when mounted on the vehicle and an inner tread end T2 located on the inside of the vehicle when mounted on the vehicle. There is. As a result, the tread portion 2 includes an outer tread portion 2A between the tire equator C and the outer tread end T1, and an inner tread portion 2B between the tire equator C and the inner tread end T2.

In the case of a pneumatic tire, the outer tread end T1 and the inner tread end T2 are the outermost 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 flat surface at a camber angle of 0 °. 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 a 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 JATMA, "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 includes a main groove 3 that extends continuously in the tire circumferential direction. The main groove 3 extends continuously in the tire circumferential direction with a relatively large width and depth in order to discharge water on the road surface to the rear of the tire. In a preferred embodiment, each main groove 3 has a groove width and depth of 5 mm or more, more preferably 6 mm or more. The groove width W1 of the main groove 3 is, for example, 5.0% to 9.0% of the tread width TW. The depth of the main groove 3 is, for example, 5 to 12 mm. Each main groove of the present embodiment extends straight along the tire circumferential direction, for example. In another aspect, each main groove may be non-linear, such as zigzag or wavy. The tread width TW is the distance in the tire axial direction from the outer tread end T1 to the inner tread end T2 in the normal state.

The main groove 3 includes a first crown main groove 4 and a second crown main groove 5 arranged so as to sandwich the tire equator C. The first crown main groove 4 is provided between the tire equator C and the outer tread end T1. The second crown main groove 5 is provided between the tire equator C and the inner tread end T2.

The distance L1 in the tire axial direction from the tire equator C to the groove center line of the first crown main groove 4 and the distance L2 in the tire axial direction from the tire equator C to the second crown main groove 5 are, for example, the tread width TW. It is desirable that the value is 0.08 to 0.20 times. Further, in the present embodiment, the distance L1 is smaller than the distance L2.

The tread portion 2 has a crown land portion 6, an outer shoulder land portion 7, and an inner shoulder land portion 8 due to the main groove 3 described above. The crown land portion 6 is divided between the first crown main groove 4 and the second crown main groove 5. The outer shoulder land portion 7 is divided between the first crown main groove 4 and the outer tread end T1. The inner shoulder land portion 8 is divided between the second crown main groove 5 and the inner tread end T2.

FIG. 2 shows an enlarged view of the land portion 6 of the crown. As shown in FIG. 2, the width W2 of the crown land portion 6 is preferably, for example, 0.15 to 0.25 times the tread width TW (shown in FIG. 1 and the same applies hereinafter). .. Further, the center of the crown land portion 6 in the tire axial direction is located on the second crown main groove 5 side of the tire equator C. As a result, in the present embodiment, the width of the crown land portion 6 included in the inner tread portion 2B is increased, and excellent steering stability is exhibited.

It is desirable that the misalignment amount Lc of the center of the crown land portion is, for example, 0.05 to 0.10 times the width W2 of the crown land portion 6 in the tire axial direction. The misalignment amount Lc is the distance in the tire axial direction from the tire equator C to the center 6c of the crown land portion 6 in the tire axial direction.

A plurality of crown sipes 10 are provided on the crown land portion 6. In addition, in this specification, "sipe" is defined as a narrow notch in which the width of the main body is less than 2.0 mm. The width of the main body of the sipe is preferably less than 1.5 mm, more preferably 0.4 to 1.0 mm. The sipe may have an opening width of 1.5 to 2.5 mm on the tread surface, for example. Note that sipes are distinguished from shallow grooves with a width and depth of less than 1.5 mm.

The crown sipe 10 includes a first crown sipe 11, a second crown sipe 12, and a third crown sipe 13. The first crown sipe 11 communicates the first crown main groove 4 and the second crown main groove 5. The second crown sipe 12 extends from the first crown main groove 4 and is interrupted in the crown land portion 6. The third crown sipe 13 extends from the second crown main groove 5 and is interrupted in the crown land portion 6. A shallow groove having a width and a depth of less than 1.5 mm may be connected to the second crown sipe 12 and the third crown sipe 13.

Each such crown sipe 10 can appropriately relax the rigidity of the crown land portion 6 and improve the riding comfort while maintaining the steering stability. In addition, each crown sipe 10 also helps to equalize the rigidity distribution of the crown land portion 6 and suppress uneven wear of the crown land portion 6.

In the second crown sipe 12 and the third crown sipe 13 that are interrupted in the crown land portion 6, the outer end side that communicates with the crown main groove is relatively easy to open, and the inner end side that is interrupted in the crown land portion 6 is relatively difficult to open. .. Therefore, the land portion 6 of the crown provided with the second crown sipe 12 and the third crown sipe 13 is likely to be twisted and deformed on the ground contact surface. In particular, in the present invention, since the center of the crown land portion 6 in the tire axial direction is located closer to the second crown main groove 5 than the tire equator, the contact patch of the crown land portion 6 is twisted and deformed due to a change in the contact pressure. Is even more likely to occur. Therefore, in the tire of the present invention, when a slip angle is given, the ground contact surface of the crown land portion 6 follows the road surface and rapidly twists and deforms, and eventually a cornering force is generated without delay. Therefore, the tire of the present invention has a high initial response when turning and exhibits excellent steering stability.

It is desirable that the first crown sipe 11 is curved in a direction that is convex to one side in the tire circumferential direction, for example. The radius of curvature of the first crown sipe 11 is, for example, 45 to 65 mm. Further, in the first crown sipe 11 of the present embodiment, the angle with respect to the tire axial direction gradually increases from the first crown main groove 4 side toward the second crown main groove 5. The angle of the first crown sipe 11 with respect to the tire axial direction is preferably, for example, 5 to 30 °. Such a first crown sipe 11 can provide frictional forces in multiple directions due to its edges.

FIG. 3A shows a sectional view taken along line AA of the first crown sipe 11 of FIG. FIG. 3A is a cross section orthogonal to the length direction of the first crown sipe 11. As shown in FIG. 3A, the first crown sipe 11 includes a main body portion 11a and a wide portion 11b arranged outside the main body portion 11a in the radial direction of the tire and having a width larger than that of the main body portion 11a. .. The width W3 of the main body 11a is preferably 0.4 to 0.8 mm, for example. The width W4 of the wide portion 11b is preferably 1.0 to 2.0 mm, for example. It is more desirable that the width W4 of the wide portion 11b is 1.5 to 4.0 times the width W3 of the main body portion 11a. Such a first crown sipe 11 can sufficiently relax the rigidity of the crown land portion 6 and exhibit excellent riding comfort.

FIG. 3B shows a sectional view taken along line BB of the first crown sipe 11 of FIG. As shown in FIG. 3B, the first crown sipe 11 has a shallow bottom portion 11c having a depth smaller than its maximum depth. The first crown sipe 11 of the present embodiment has, for example, shallow bottom portions 11c at both ends in the tire axial direction. Such a first crown sipe 11 can prevent excessive opening when a contact pressure acts on the land portion 6 of the crown, and can exhibit excellent steering stability and uneven wear resistance.

The maximum depth d1 of the first crown sipe 11 is, for example, 0.60 to 1.00 times the depth of the main groove 3. The depth d2 of the shallow bottom portion 11c of the first crown sipe 11 is, for example, 0.40 to 0.85 times the maximum depth d1.

As shown in FIG. 2, the second crown sipe 12 and the third crown sipe 13 are provided between two adjacent first crown sipe 11 in the tire circumferential direction. The length L3 of the second crown sipe 12 in the tire axial direction and the length L4 of the third crown sipe 13 in the tire axial direction are, for example, 0.50 to 0.80 times the width W2 of the crown land portion 6. be.

Each of the second crown sipe 12 and the third crown sipe 13 has an inner end that is interrupted within the land portion 6 of the crown. In the present embodiment, the inner end 13i of the third crown sipe 13 is located closer to the first crown main groove 4 than the inner end 12i of the second crown sipe 12. The sipe overlap length L5, which is the distance in the tire axial direction from the inner end 12i of the second crown sipe 12 to the inner end 13i of the third crown sipe 13, is, for example, preferably 0.25 of the width W2 of the crown land portion 6. It is more than twice, more preferably 0.30 times or more, preferably 0.45 times or less, and more preferably 0.40 times or less. Such an arrangement of the second crown sipe 12 and the second crown sipe 12 facilitates twisting deformation of the crown land portion 6 and helps to enhance the initial responsiveness.

Each of the second crown sipe 12 and the third crown sipe 13 is curved in the same direction as the first crown sipe 11 so as to be convex. As a result, the angles of the second crown sipe 12 and the third crown sipe 13 with respect to the tire axial direction gradually increase from the first crown main groove 4 side to the second crown main groove 5 side. It is desirable that the angles and the radius of curvature of the second crown sipe 12 and the third crown sipe 13 with respect to the tire axial direction be in the same range as that of the first crown sipe 11.

It is desirable that the second crown sipe 12 and the third crown sipe 13 extend from the tread on the land to the bottom with a width of 0.4 to 0.8 mm, for example. As a result, on the outer surface of the tread portion 2, the opening width of the first crown sipe 11 is larger than the opening width of the second crown sipe 12 and the opening width of the third crown sipe 13. As a result, the uneven wear resistance in the vicinity of the second crown sipe 12 and the third crown sipe 13 is enhanced.

FIG. 4 (A) shows a sectional view taken along line CC of the second crown sipe 12, and FIG. 4 (B) shows a sectional view taken along line DD of the third crown sipe 13. There is. As shown in FIGS. 4A and 4B, the maximum depth d3 of the second crown sipe 12 and the maximum depth d5 of the third crown sipe 13 are the maximum depths of the first crown sipe 11, respectively. It is preferably smaller than the depth d1, and specifically, it is 0.40 to 0.90 times the depth d1. Such a second crown sipe 12 and a third crown sipe 13 are useful for suppressing an excessive decrease in rigidity of the crown land portion 6 and improving steering stability.

It is desirable that the maximum depth d3 of the second crown sipe 12 is larger than the maximum depth d5 of the third crown sipe 13.

In order to further enhance the initial responsiveness, it is desirable that the maximum depth d5 of the third crown sipe 13 is larger than the depth d2 of the shallow bottom portion 11c of the first crown sipe 11.

It is desirable that each of the second crown sipes 12 has a shallow bottom portion 12c having a depth smaller than its maximum depth. Similarly, the third crown sipe 13 preferably has a shallow bottom 13c with a depth smaller than its maximum depth. In the present embodiment, the shallow bottom portions 12c and 13c are provided at the ends on the main groove 3 side. Such shallow bottom portions 12c and 13c help prevent the sipes from opening excessively and improve steering stability.

The depth d4 of the shallow bottom portion 12c of the second crown sipe 12 and the depth d6 of the shallow bottom portion 13c of the third crown sipe 13 are, for example, 0.15 to 0.30 times the depth of the main groove. In a preferred embodiment, the depth d4 of the shallow bottom 12c of the second crown sipe 12 and the depth d6 of the shallow bottom 13c of the third crown sipe 13 are each greater than the depth d2 of the shallow bottom 11c of the first crown sipe 11. small. As a result, the rigidity in the vicinity of the second crown sipe 12 and the third crown sipe 13 is increased, and the uneven wear resistance is improved.

FIG. 5 shows an enlarged view of the outer shoulder land portion 7. As shown in FIG. 5, the outer shoulder land portion 7 has a wider tire axial width than the crown land portion 6 and the inner shoulder land portion 8. Such an outer shoulder land portion 7 has high rigidity and can enhance steering stability while exhibiting excellent uneven wear resistance. It is desirable that the width W5 of the outer shoulder land portion 7 in the tire axial direction is, for example, 0.30 to 0.45 times the tread width TW.

The outer shoulder land portion 7 is provided with an outer shoulder lateral groove 20 and an outer shoulder sipe 21. The outer shoulder lateral groove 20 extends from the outer tread end T1 and is interrupted within the outer shoulder land portion 7. The outer shoulder sipe 21 extends from the first crown main groove 4 and is interrupted within the outer shoulder land portion 7.

The outer shoulder land portion 7 provided with the outer shoulder lateral groove 20 and the outer shoulder sipe 21 is liable to be twisted and deformed on the ground contact surface, and as a result, the initial responsiveness at the time of turning can be enhanced.

Each of the outer shoulder lateral groove 20 and the outer shoulder sipe 21 has a break in the outer shoulder land portion 7. The break end 21i of the outer shoulder sipe 21 of the present embodiment is located outside the break end 20i of the outer shoulder lateral groove 20 in the tire axial direction. As a result, the outer shoulder land portion 7 is likely to be twisted and deformed, and the initial responsiveness can be further improved.

The distance L11 in the tire axial direction from the break end 20i of the outer shoulder lateral groove 20 to the break end 21i of the outer shoulder sipe 21 is, for example, 0.20 to 0.35 times the width W5 of the outer shoulder land portion 7 in the tire axial direction. Is. As a result, excellent initial responsiveness is exhibited while maintaining ride quality.

The outer shoulder lateral groove 20 is, for example, smoothly curved. It is desirable that the angle of the outer shoulder lateral groove 20 with respect to the tire axial direction gradually increases from the outer tread end T1 toward the first crown main groove 4 side. The angle of the outer shoulder lateral groove 20 with respect to the tire axial direction is preferably 0 to 20 °, for example.

It is desirable that the length L6 of the outer shoulder lateral groove 20 in the tire axial direction is, for example, 0.70 to 0.92 times the width W5 of the outer shoulder land portion 7 in the tire axial direction. Further, it is desirable that the groove width W6 of the outer shoulder lateral groove 20 is 0.25 to 0.45 times the groove width W1 of the main groove 3.

FIG. 6 shows a sectional view taken along line EE of the outer shoulder lateral groove 20 of FIG. As shown in FIG. 6, the outer shoulder lateral groove 20 includes an inner portion 23 on the first crown main groove 4 side with respect to the interrupted end 21i (shown in FIG. 5) of the outer shoulder sipe 21. It is desirable that the inner portion 23 gradually decreases in depth toward the inner side in the tire axial direction, for example. The outer shoulder lateral groove 20 having such an inner portion 23 can improve riding comfort and steering stability in a well-balanced manner.

As shown in FIG. 5, the outer shoulder sipe 21 is curved in the same direction as the outer shoulder lateral groove 20 so as to be convex, for example. It is desirable that the angle of the outer shoulder sipe 21 with respect to the tire axial direction is in the same range as the outer shoulder lateral groove 20. The radius of curvature of the outer shoulder sipe 21 is preferably, for example, 100 to 150 mm. In a preferred embodiment, the radius of curvature of the outer shoulder sipe 21 is greater than the radius of curvature of the first crown sipe 11.

It is desirable that the length L7 of the outer shoulder sipe 21 in the tire axial direction is, for example, 0.30 to 0.70 times the width W6 of the outer shoulder land portion 7 in the tire axial direction.

It is desirable that the outer shoulder sipe 21 has a cross-sectional shape similar to that of the first crown sipe 11 in a cross section orthogonal to the length direction thereof. That is, the outer shoulder sipe 21 includes a main body portion and a wide portion arranged outside the main body portion in the radial direction of the tire and having a width larger than that of the main body portion (not shown). Such an outer shoulder sipe 21 helps to enhance ride comfort.

FIG. 7 shows a sectional view taken along line FF of the outer shoulder sipe 21 of FIG. As shown in FIG. 7, the outer shoulder sipe 21 has a shallow bottom portion 21c having a depth smaller than its maximum depth. The outer shoulder sipe 21 of the present embodiment has, for example, a shallow bottom portion 21c at an end portion on the inner side in the tire axial direction. The shallow bottom 21c helps prevent excessive opening of the sipe and enhances steering stability.

The depth d8 of the shallow bottom portion 21c is preferably 0.15 to 0.50 times the depth of the main groove 3. Further, it is desirable that the depth d8 of the shallow bottom portion 21c is, for example, 0.60 to 0.75 times the maximum depth d7 of the outer shoulder sipe 21.

The length L9 of the shallow bottom portion 21c in the tire axial direction is larger than, for example, the distance L8 in the tire axial direction (shown in FIG. 5) from the groove edge of the first crown main groove 4 to the break end 20i of the outer shoulder lateral groove 20. Is desirable. Such a shallow bottom portion 21c can sufficiently suppress the opening of the outer shoulder sipe 21, and can improve steering stability and uneven wear resistance.

FIG. 8 shows an enlarged view of the inner shoulder land portion 8. As shown in FIG. 8, it is desirable that the width W7 of the inner shoulder land portion 8 in the tire axial direction is, for example, 0.25 to 0.35 times the tread width TW.

The vertical narrow groove 25 is provided in the inner shoulder land portion 8. The vertical narrow groove 25 has a groove width and a groove depth of less than 5 mm, and is distinguished from the above-mentioned main groove. The groove width W8 of the vertical narrow groove 25 of the present embodiment is, for example, 0.20 to 0.30 times the groove width W1 of the main groove 3. The inner shoulder land portion 8 is a first portion 26 divided between the second crown main groove 5 and the vertical narrow groove 25, and a second portion divided between the vertical narrow groove 25 and the inner tread end T2. 27 and is included.

It is desirable that the width W9 of the first portion 26 in the tire axial direction is, for example, 0.55 to 0.65 times the width W7 of the inner shoulder land portion 8. It is desirable that the width W10 of the second portion 27 in the tire axial direction is, for example, 0.30 to 0.40 times the width W7 of the inner shoulder land portion 8.

The inner shoulder land portion 8 is provided with an inner shoulder lateral groove 28 and an inner shoulder sipe 29. The inner shoulder lateral groove 28 extends from the inner tread end T2 and is interrupted within the inner shoulder land portion 8. The inner shoulder sipe 29 extends from the second crown main groove 5 to the inner tread end T2.

The inner shoulder lateral groove 28 crosses the vertical narrow groove 25 and is interrupted in the first portion 26 of the inner shoulder land portion 8. It is desirable that the length L10 of the inner shoulder lateral groove 28 in the tire axial direction is, for example, 0.80 to 0.90 times the width W7 of the inner shoulder land portion 8 in the tire axial direction.

It is desirable that the depth of the inner shoulder lateral groove 28 gradually decreases toward the inside in the tire axial direction, for example, between the vertical narrow groove 25 and the second crown main groove 5. Such an inner shoulder lateral groove 28 is useful for improving ride comfort and steering stability in a well-balanced manner.

The inner shoulder sipe 29 is curved in a direction that is convex to one side in the tire circumferential direction, for example. It is desirable that the radius of curvature of the inner shoulder sipe 29 is larger than, for example, the radius of curvature of the first crown sipe 11. Specifically, the radius of curvature of the inner shoulder sipe 29 is 120 to 150 mm.

It is desirable that the inner shoulder sipe 29 has a cross-sectional shape similar to that of the first crown sipe 11 in a cross section orthogonal to the length direction thereof. That is, the inner shoulder sipe 29 includes a main body portion and a wide portion arranged outside the main body portion in the radial direction of the tire and having a width larger than that of the main body portion (not shown). Such an inner shoulder sipe 29 helps to enhance ride comfort.

FIG. 9 shows a sectional view taken along line GG of the inner shoulder sipe 29. As shown in FIG. 9, the inner shoulder sipe 29 has a shallow bottom 29c having a depth smaller than its maximum depth. The inner shoulder sipe 29 of the present embodiment has, for example, a shallow bottom portion 29c at an end portion on the inner side in the tire axial direction. The shallow bottom 29c prevents the inner shoulder sipe 29 from opening excessively, which helps to improve steering stability and uneven wear resistance.

In the present embodiment, the width of the shallow bottom portion 29c arranged on the inner shoulder sipe 29 in the tire axial direction is larger than the width of the shallow bottom portion of each crown sipe 10 in the tire axial direction. Such an inner shoulder sipe 29 helps to suppress uneven wear of the inner shoulder land portion 8.

As shown in FIG. 1, it is desirable that the land ratio of the outer tread portion 2A is larger than the land ratio of the inner tread portion 2B. As a result, the outer tread portion 2A exerts a large cornering force, and excellent steering stability can be exhibited. In the present specification, the “land ratio” is the ratio Sb / Sa of the actual total ground contact area Sb to the total area Sa of the virtual ground contact patch in which each groove and sipe are completely filled.

10 to 12 show enlarged views of the land portion of the crown according to another embodiment of the present invention. In FIGS. 10 to 12, the elements common to the above-described embodiments are designated by the same reference numerals, and the description thereof is omitted here.

In the embodiment of FIGS. 10 to 12, a shallow groove 50 having a width and a depth of less than 1.5 mm is provided. For easy understanding, the shallow groove 50 is colored in FIGS. 10 to 12. The shallow groove 50 is useful for appropriately increasing the grip force at the start of using the tire. The shallow groove 50 also helps to shorten the break-in distance until the new tire exerts its original grip force.

In the embodiment shown in FIG. 10, the shallow groove 50 extends linearly from the inner end 12i of the second crown sipe 12 to the inner end 13i of the third crown sipe 13. Further, the angle of the shallow groove 50 of this embodiment with respect to the tire axial direction is larger than the angle of each sipe provided on the crown land portion 6 with respect to the tire axial direction. Such a shallow groove 50 is useful for increasing the frictional force in the tire axial direction.

In the embodiment shown in FIG. 11, the shallow groove 50 is, for example, a first shallow groove 50a extending from the inner end 12i of the second crown sipe 12 to the first crown sipe 11, and the inner end of the third crown sipe 13. It includes a second shallow groove 50b extending from 13i to the first crown sipe 11. The first shallow groove 50a and the second shallow groove 50b are connected to, for example, the second crown sipe 12 or the third crown sipe 13 so as to form an acute angle.

It is desirable that the first shallow groove 50a is continuous with the second shallow groove 50b communicating with the same first crown sipe 11 via the first crown sipe 11. It should be noted that this aspect includes a mode in which at least a part of the region extending the first shallow groove 50a intersects with the end portion of the second shallow groove 50b. Such a shallow groove 50 can prevent the rubber from being chipped near the edge of the first crown sipe 11.

In the embodiment shown in FIG. 12, a first shallow groove 50a extending from the second crown sipe 12 to the first crown sipe 11 and a second shallow groove 50b extending from the third crown sipe 13 to the first crown sipe 11 are provided. , It is curved in the direction of convexity in the tire axis direction.

In a more desirable embodiment of this embodiment, the first shallow groove 50a and the second shallow groove 50b are convexly curved in opposite directions to each other. Such a shallow groove 50 can effectively suppress uneven wear at the start of tire use near the edge of each crown sipe 10.

Although the tire of the 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 into various embodiments.

A size 195 / 65R15 pneumatic tire with the basic tread pattern of FIG. 1 was prototyped based on the specifications in Table 1. As a comparative example, as shown in FIG. 10, the center of the crown land portion a in the tire axial direction is located on the tire equator C, and the first sipe b and the second sipe c completely cross the crown land portion a. A pneumatic tire with a tire was prototyped. The first sipe b has a wide portion, and the second sipe c does not have a wide portion. The tire pattern of the comparative example is the same as that shown in FIG. 1 except for the above configuration. The steering stability, ride quality and uneven wear resistance of each test tire were tested. The common specifications and test methods for each test tire are as follows.
Rim: 15 x 6.0
Tire internal pressure: 200kPa
Test vehicle: Displacement 2000cc, front-wheel drive vehicle Tire mounting position: All wheels

<Maneuvering stability>
The steering stability (including the initial responsiveness when turning) when the test vehicle traveled on a dry paved 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 steering stability.

<Ride quality>
The ride quality of the test vehicle when traveling on a dry paved road 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.

<Uneven wear resistance>
A wear energy measuring device was used to measure the wear energy of the land part of the crown. The result is an index with the wear energy of the comparative example as 100, and the smaller the value, the smaller the wear energy and the better the uneven wear resistance performance.
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 steering stability. In addition, it was confirmed that the tires of the examples had improved ride quality and uneven wear resistance.

2 Tread part 4 1st crown main groove 5 2nd crown main groove 6 Crown land part 11 1st crown sipe 12 2nd crown sipe 13 3rd crown sipe C tire equator

Claims (8)

A tire with a tread
The tread portion is divided into a first crown main groove and a second crown main groove that continuously extend in the tire circumferential direction across the equator of the tire, and the first crown main groove and the second crown main groove. Has a crown land area
The center of the land portion of the crown in the tire axial direction is located on the side of the second crown main groove with respect to the equator of the tire.
In the land part of the crown,
A first crown sipe that communicates the first crown main groove and the second crown main groove,
A second crown sipe that extends from the first crown main groove and is interrupted within the land portion of the crown.
A third crown sipe that extends from the second crown main groove and is interrupted in the land portion of the crown is provided .
The angle of the first crown sipe with respect to the tire axial direction gradually increases from the first crown main groove toward the second crown main groove.
tire. A tire with a tread
The tread portion is divided into a first crown main groove and a second crown main groove extending continuously in the tire circumferential direction across the tire equator, and the first crown main groove and the second crown main groove. Has a crown land area
The center of the land portion of the crown in the tire axial direction is located on the side of the main groove of the second crown with respect to the equator of the tire.
In the land part of the crown,
A first crown sipe that communicates the first crown main groove and the second crown main groove,
A second crown sipe that extends from the first crown main groove and is interrupted within the land portion of the crown.
A third crown sipe that extends from the second crown main groove and is interrupted in the land portion of the crown is provided.
The maximum depth of the second crown sipe is greater than the maximum depth of the third crown sipe.
tire. A tire with a tread
The tread portion is divided into a first crown main groove and a second crown main groove extending continuously in the tire circumferential direction across the tire equator, and the first crown main groove and the second crown main groove. Has a crown land area
The center of the land portion of the crown in the tire axial direction is located on the side of the main groove of the second crown with respect to the equator of the tire.
In the land part of the crown,
A first crown sipe that communicates the first crown main groove and the second crown main groove,
A second crown sipe that extends from the first crown main groove and is interrupted within the land portion of the crown.
A third crown sipe that extends from the second crown main groove and is interrupted in the land portion of the crown is provided.
The maximum depth of the second crown sipe and the maximum depth of the third crown sipe are each smaller than the maximum depth of the first crown sipe.
tire. The first crown sipe includes a main body portion and a wide portion arranged outside the main body portion in the tire radial direction and having a width larger than that of the main body portion in a cross section orthogonal to the length direction thereof. Item 2. The tire according to any one of Items 1 to 3. A tire with a tread
The tread portion is divided into a first crown main groove and a second crown main groove extending continuously in the tire circumferential direction across the tire equator, and the first crown main groove and the second crown main groove. Has a crown land area
The center of the land portion of the crown in the tire axial direction is located on the side of the second crown main groove with respect to the equator of the tire.
In the land part of the crown,
A first crown sipe that communicates the first crown main groove and the second crown main groove,
A second crown sipe that extends from the first crown main groove and is interrupted within the land portion of the crown.
A third crown sipe that extends from the second crown main groove and is interrupted in the land portion of the crown is provided.
The first crown sipe includes a main body portion and a wide portion arranged outside the main body portion in the tire radial direction and having a width larger than that of the main body portion in a cross section orthogonal to the length direction thereof.
The first crown sipe has a shallow bottom portion having a depth smaller than the maximum depth of the first crown sipe due to a raised bottom portion in the main body portion.
The maximum depth of the third crown sipe is greater than the depth of the shallow bottom of the first crown sipe.
tire. The tire according to claim 5, wherein on the outer surface of the tread portion, the opening width of the first crown sipe is larger than the opening width of the second crown sipe and the opening width of the third crown sipe. Each of the second crown sipe and the third crown sipe has an inner end that is interrupted within the land portion of the crown.
The tire according to any one of claims 1 to 6, wherein the inner end of the third crown sipe is located closer to the first crown main groove side than the inner end of the second crown sipe. The tread portion has an inner tread end located inside the vehicle when mounted on the vehicle by designating the direction of mounting on the vehicle.
The tire according to any one of claims 1 to 7, wherein the second crown main groove is arranged between the equator of the tire and the inner tread end.

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