JP2021075109A - tire - Google Patents

Abstract

To provide a tire capable of maintaining uneven wear resistance and furthermore capable of exhibiting excellent wet performance.SOLUTION: A tire has a tread portion 2. The tread portion 2 includes a peripheral direction groove 3 and a middle land portion 7. The middle land portion 7 includes a plurality of middle lateral sipes 10 and a plurality of middle vertical grooves 11. The middle lateral sipes 10 and the middle vertical grooves 11 are arranged alternately in a tire circumferential direction. Each of the middle vertical grooves 11 extends in a wave shape. Each of the middle vertical grooves 11 includes a first end communicating with one of the lateral sipes 10 on one side in the tire circumferential direction and a second end communicating with one of lateral sipes on the other side in a tire circumferential direction. The second end of the middle vertical grooves 11 is provided at a position different from the first end of the middle vertical grooves 11 in a tire axial direction.SELECTED DRAWING: Figure 1

Description

The present invention relates to a tire.

Patent Document 1 below proposes a tire having improved wet performance and wear resistance by improving the arrangement of grooves.

Japanese Unexamined Patent Publication No. 2016-210226

The above tire has a small amount of edge components extending in the tire circumferential direction, and tends to have insufficient frictional force in the tire axial direction on a wet road surface. On the other hand, if the land portion of the tire is provided with a groove that extends continuously in the tire circumferential direction, the rigidity of the land portion is lowered, which may cause uneven wear.

The present invention has been devised in view of the above problems, and its main object is to provide a tire capable of exhibiting excellent wet performance while maintaining uneven wear resistance.

The present invention is a tire having a tread portion, and the tread portion includes a circumferential groove continuously extending in the tire circumferential direction and a middle land portion divided into the circumferential groove, and the middle land portion. Includes a plurality of middle lateral sipe crossing the middle land portion and a plurality of middle vertical grooves extending in the tire circumferential direction, and the middle lateral sipe and the middle vertical groove are arranged alternately in the tire circumferential direction. Each of the middle flutes extends in a wavy shape, and each of the middle flutes has a first end communicating with one of the middle lateral sipes on one side in the tire circumferential direction and a tire circumference. The second end of the middle flute is different from the first end of the middle flute in the tire axial direction, including a second end communicating with one of the middle lateral sipes on the other side of the direction. It is provided at the position.

In the tire of the present invention, the tread portion includes a crown land portion adjacent to the middle land portion, and the crown land portion is continuous with a plurality of crown lateral sipes crossing the crown land portion in the tire circumferential direction. It is desirable to include a crown flute extending in a wavy shape.

In the tire of the present invention, the ratio Lm / Wm of the distance Lm in the tire axial direction from the first end to the second end of the middle vertical groove with respect to the width Wm of the middle land portion in the tire axial direction is the crown land. It is desirable that the ratio of the peak-to-peak amplitude amount Ac of the crown vertical groove to the width Wc in the tire axial direction of the portion is larger than Ac / Wc.

In the tire of the present invention, the ratio Lm / Wm is preferably 1.5 to 6.0 times the ratio Ac / Wc.

In the tire of the present invention, the ratio Lm / Wm is preferably 0.3 to 0.6.

In the tire of the present invention, the ratio Ac / Wc is preferably 0.1 to 0.2.

In the tire of the present invention, it is desirable that the groove center line of the crown vertical groove crosses the center position of the crown land portion in the tire axial direction a plurality of times.

In the tire of the present invention, the maximum depth of the middle flutes is preferably 5% to 30% of the maximum depth of the circumferential grooves.

In the tire of the present invention, it is desirable that the middle flutes cross the center position of the middle land portion in the tire axial direction.

In the tire of the present invention, each of the middle flutes extends with a first arc portion extending on the first end side and is curved with a convex shape extending on the second end side and in the opposite direction to the first arc portion. It is desirable to include the second arc portion.

In the tire of the present invention, the first end is located outside the center position in the tire axial direction of the middle land portion, and the second end is located outside the center position of the middle land portion in the tire axial direction. It is desirable that the first arc portion is located on the inner side in the axial direction and is convexly curved toward the outer side in the tire axial direction.

In the tire of the present invention, it is desirable that the middle lateral sipe includes a first convex portion that is convex on one side in the tire circumferential direction and a second convex portion that is convex on the other side in the tire circumferential direction.

In the tire of the present invention, the middle lateral sipe includes a first convex portion convex on one side in the tire circumferential direction and a second convex portion convex on the other side in the tire circumferential direction, and the first end thereof. Is preferably communicated with the second convex portion.

In the tire of the present invention, the middle lateral sipe includes a first convex portion that is convex on one side in the tire circumferential direction and a second convex portion that is convex on the other side in the tire circumferential direction, and the second end. Is preferably communicated with the first convex portion.

It is desirable that the tire of the present invention is for a heavy-duty vehicle.

The middle land portion of the tire of the present invention includes a plurality of middle lateral sipes that cross the middle land portion and a plurality of middle flutes that extend in the tire circumferential direction. The middle horizontal sipe and the middle vertical groove are alternately arranged in the tire circumferential direction. During wet running, the tire of the present invention exerts a frictional force in the tire circumferential direction due to the edge of the middle lateral sipe, and exerts a frictional force in the tire axial direction due to the middle vertical groove. In particular, since each of the middle flutes extends in a wavy shape, a sufficient length is secured, and the turning performance on a wet road surface is effectively enhanced.

Each of the middle flutes has a first end communicating with one of the middle lateral sipes on one side in the tire circumferential direction and a second end communicating with one of the middle lateral sipes on the other side in the tire circumferential direction. And include. As a result, during wet running, the water in the middle vertical groove is easily discharged to the circumferential groove side via the middle horizontal sipe, so that excellent wet performance is exhibited.

Further, in the tire of the present invention, since the second end of the middle flute is provided at a position different from the first end of the middle flute in the tire axial direction, the first end or the said. Uneven wear near the second end can be effectively suppressed.

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 middle land part of FIG. It is an enlarged view of the crown land part of FIG. It is an enlarged view of the shoulder circumferential groove 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 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 suitably used as, for example, a pneumatic tire for a heavy-duty vehicle. However, the tire of the present invention is not limited to such an aspect.

As shown in FIG. 1, the tread portion 2 of the tire 1 is provided with a plurality of circumferential grooves 3 that extend continuously in the tire circumferential direction. The circumferential groove 3 includes a shoulder circumferential groove 4 arranged on the Te side of the tread end, and a crown circumferential groove 5 arranged on the tire equator C side of the shoulder circumferential groove 4.

The "tread end Te" is a flat tire 1 with a normal load applied to a tire 1 in a normal state, which is assembled on a regular rim (not shown), is filled with a regular internal pressure, and has no load, and has a camber angle of 0 °. This is the most outer contact position in the tire axial direction when the tire is grounded.

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 JATTA and "Design Rim" for TRA. If it is ETRTO, 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.

In the tread portion 2 of the present embodiment, two shoulder circumferential grooves 4 arranged on the tread end Te side and two crown circumferential grooves 5 arranged on both sides of the tire equator C are arranged. There is.

It is desirable that the distance L1 in the tire axial direction from the tire equator C to the groove center line of the shoulder circumferential groove 4 is, for example, 0.15 to 0.25 times the tread width TW. The distance L2 in the tire axial direction from the tire equator C to the groove center line of the crown circumferential groove 5 is preferably, for example, 0.05 to 0.15 times the tread width TW. The tread width TW is the distance in the tire axial direction between the tread ends Te and Te of the tire 1 in the normal state.

The circumferential groove 3 of the present embodiment extends linearly, for example. However, the present invention is not limited to such an aspect, and the circumferential groove 3 may extend in a wavy shape, for example.

The groove width W1 of the circumferential groove 3 is at least 2 mm or more, preferably 3 mm or more, and more preferably 4 mm or more. Further, in the case of a pneumatic tire for a heavy-duty vehicle, the groove width W1 of the circumferential groove 3 is 4.0% to 7.0% of the tread width TW in order to ensure sufficient drainage. desirable. From the same viewpoint, the groove depth of the shoulder circumferential groove 4 is preferably 10 to 25 mm.

The tread portion 2 of the present embodiment is divided into one crown land portion 6, two middle land portions 7, and two shoulder land portions 8 by the above-mentioned circumferential groove 3. The crown land portion 6 is divided between the two crown circumferential grooves 5. The middle land portion 7 is divided between the crown circumferential groove 5 and the shoulder circumferential groove 4, and is adjacent to the crown land portion 6. The shoulder land portion 8 is divided into the outer side of the shoulder circumferential groove 4 in the tire axial direction, and is adjacent to the middle land portion 7.

FIG. 2 shows an enlarged view of the middle land portion 7. As shown in FIG. 2, the middle land portion 7 includes a plurality of middle lateral sipes 10 that cross the middle land portion 7 and a plurality of middle vertical grooves 11 that extend in the tire circumferential direction. The middle horizontal sipe 10 and the middle vertical groove 11 are alternately arranged in the tire circumferential direction. In addition, in this specification, a "sipe" means a notch having a width of 1.5 mm or less.

The tire of the present invention exerts a frictional force in the tire circumferential direction by the edge of the middle lateral sipe 10 and exerts a frictional force in the tire axial direction by the middle vertical groove 11 during wet running. In particular, since each of the middle flutes 11 extends in a wavy shape, a sufficient length is secured, and the turning performance on a wet road surface is effectively enhanced. The fact that the middle flute 11 extends in a wavy shape means a mode in which at least one portion is curved in a certain direction and the portion is curved in the opposite direction. The middle flute 11 may have various embodiments such as a sinusoidal shape, a rectangular wavy shape, a circular wavy shape, and a zigzag shape.

Each of the middle flutes 11 has a first end 11a communicating with one of the middle lateral sipes 10 on one side in the tire circumferential direction (upper side in FIG. 2) and the other side in the tire circumferential direction (in FIG. 2). Includes a second end 11b that communicates with one of the middle lateral sipes 10 at the lower side.). As a result, during wet running, the water in the middle vertical groove 11 is easily discharged to the circumferential groove 3 (shown in FIG. 1 and the same applies hereinafter) via the middle lateral sipe 10, which is excellent. Wet performance is demonstrated.

Further, in the tire of the present invention, since the second end 11b of the middle vertical groove 11 is provided at a position different from the first end 11a of the middle vertical groove 11 in the tire axial direction, the first end 11a or the first Uneven wear near the two ends 11b can be effectively suppressed.

The middle land portion 7 of the present embodiment has recesses 13 arranged on the side walls 7w on both sides thereof. The end of the middle lateral sipe 10 in the tire axial direction communicates with the recess 13. This improves wet performance.

The middle lateral sipe 10 extends in a zigzag shape, for example. The middle lateral sipe 10 of the present embodiment is arranged between two sipe pieces 10a inclined in the first direction (upward to the right in FIG. 2) with respect to the tire axial direction and these two sipe pieces 10a. It is composed of one sipe piece 10b that is inclined in a second direction (downward to the right in FIG. 2) that is opposite to the first direction with respect to the tire axial direction. As a result, the middle lateral sipe 10 includes a first convex portion 16 that is convex on one side in the tire circumferential direction and a second convex portion 17 that is convex on the other side in the tire circumferential direction. The middle lateral sipe 10 of the present embodiment is composed of one first convex portion 16 and one second convex portion 17. Further, the apex 16t of the first convex portion 16 is closer to the crown circumferential groove 5 side than the center position in the tire axial direction of the middle land portion 7, and the apex 17t of the second convex portion 17 is the tire of the middle land portion 7. It is on the shoulder circumferential groove 4 side from the center position in the axial direction. Such a middle lateral sipe 10 is useful for suppressing uneven wear of the middle land portion 7.

The first convex portion 16 and the second convex portion 17 are each bent at an obtuse angle. The bending angle θ1 of the first convex portion 16 and the bending angle θ2 of the second convex portion 17 of the present embodiment are, for example, 130 to 150 °. In a more desirable embodiment, the angle θ1 and the angle θ2 are the same. The middle lateral sipe 10 having such a first convex portion 16 and a second convex portion 17 suppresses uneven wear near the edge thereof, and reduces the rigidity of the middle land portion 7 when the sipe walls facing each other come into contact with each other. It can be increased moderately. Thereby, the uneven wear resistance performance can be further improved.

The one-pitch length P1 of the middle lateral sipe 10 in the tire circumferential direction is, for example, 90% to 120% of the width Wm of the middle land portion 7 in the tire axial direction. Such a middle lateral sipe 10 is useful for improving wet performance and uneven wear resistance in a well-balanced manner.

From the same viewpoint, it is desirable that the maximum depth of the middle lateral sipe 10 is 40% to 80% of the maximum depth of the circumferential groove 3.

The middle flute 11 crosses, for example, the center position of the middle land portion 7 in the tire axial direction. The middle flute 11 of the present embodiment crosses the center position at only one place. However, the middle flute 11 is not limited to such an aspect.

The first end 11a of the middle vertical groove 11 is located outside the center position in the tire axial direction of the middle land portion 7 in the tire axial direction. The second end 11b of the middle vertical groove 11 is located inside the center position of the middle land portion 7 in the tire axial direction.

The first end 11a of the middle vertical groove 11 communicates with, for example, the second convex portion 17 of the middle horizontal sipe 10. In a preferred embodiment, the first end 11a of the middle flute 11 communicates with the apex 17t of the second convex portion 17 of the middle lateral sipe 10 in the tire circumferential direction. Similarly, the second end 11b of the middle vertical groove 11 communicates with, for example, the first convex portion 16 of the middle horizontal sipe 10. In a preferred embodiment, the second end 11b of the middle flute 11 communicates with the apex 16t of the first convex portion 16 of the middle lateral sipe 10 in the tire circumferential direction. As a result, water is likely to move between the middle vertical groove 11 and the middle horizontal sipe 10, and the wet performance is further improved.

Each of the middle flutes 11 has a first arc portion 18 extending on the first end 11a side and a second arc portion 18 extending on the second end 11b side and being curved in a convex shape opposite to the first arc portion 18. Includes the arc portion 19. The middle vertical groove 11 of the present embodiment is composed of one first arc portion 18 and one second arc portion 19. The first arc portion 18 is convex and curved outward in the tire axial direction (in other words, the shoulder circumferential groove 4 side). The second arc portion 19 is convex and curved inward in the tire axial direction (in other words, on the crown circumferential direction groove 5 side).

In order to improve the uneven wear resistance and the wet performance in a well-balanced manner, the peak-to-peak amplitude Am of the middle vertical groove 11 is, for example, 10% to 25% of the width Wm of the middle land portion 7 in the tire axial direction. Is desirable.

From the same viewpoint, the ratio Lm / Wm of the distance Lm in the tire axial direction from the first end 11a to the second end 11b of the middle vertical groove 11 to the width Wm in the tire axial direction of the middle land portion 7 is, for example, 0. It is 3 to 0.6.

The middle vertical groove 11 has, for example, a groove width and a groove depth smaller than those of the circumferential groove 3. The maximum groove width W2 of the middle vertical groove 11 is preferably 2.5 mm or less, for example. The maximum groove depth of the middle vertical groove 11 is preferably 5% to 30% of the maximum depth of the circumferential groove 3.

The area of the cross section perpendicular to the length direction of the middle vertical groove 11 is, for example, 0.25 mm2 or more, preferably 2.0 to 4.0 mm2. As a result, uneven wear of the middle land portion 7 is suppressed while ensuring the drainage property of the middle vertical groove 11.

FIG. 3 shows an enlarged view of the land portion 6 of the crown. As shown in FIG. 3, the crown land portion 6 includes a plurality of crown lateral sipes 20 that cross the crown land portion 6 and a crown longitudinal groove 21 that extends continuously in the tire circumferential direction.

The crown land portion 6 of the present embodiment has recesses 23 arranged on the side walls 6w on both sides thereof. The end of the crown lateral sipe 20 in the tire axial direction communicates with the recess 23. Such an arrangement of the crown lateral sipes 20 is useful for enhancing wet performance.

The crown lateral sipe 20 extends in a zigzag shape, for example. The crown lateral sipe 20 of the present embodiment is composed of, for example, two first sipe pieces 20a inclined in the first direction with respect to the tire axial direction, and a second sipe piece 20b between them. The second sipe piece 20b is inclined in the first direction and is inclined at an angle larger than that of the first sipe piece 20a with respect to the tire axial direction. As a result, the entire crown lateral sipe 20 is inclined in the same direction (first direction) with respect to the tire axial direction.

The angle θ3 of the first sipe piece 20a with respect to the tire axial direction is, for example, 10 to 20 °. It is desirable that the angle θ3 of the first sipe piece 20a is smaller than the angle of the sipe piece of the middle lateral sipe 10 with respect to the tire axial direction. The angle θ4 of the second sipe piece 20b with respect to the tire axial direction is, for example, 40 to 50 °. The bending angle θ5 between the first sipe piece 20a and the second sipe piece 20b is, for example, 140 to 160 °. It is desirable that the bending angle θ5 is larger than the bending angle θ1 of the first convex portion 16 of the middle lateral sipe 10 or the bending angle θ2 of the second convex portion 17. As a result, the progress of wear of the crown land portion 6 and the middle land portion 7 can be easily made uniform.

The length L3 of the second sipe piece 20b in the tire axial direction is smaller than, for example, the distance Lm (shown in FIG. 2) in the tire axial direction from the first end 11a to the second end 11b of the middle vertical groove 11. The length L3 of the second sipe piece 20b is, for example, 10% to 25% of the width Wc of the crown land portion 6 in the tire axial direction.

The one-pitch length P2 of the crown lateral sipe 20 in the tire circumferential direction is, for example, 90% to 120% of the width Wm of the crown land portion 6 in the tire axial direction. In the present embodiment, the one-pitch length P2 of the crown lateral sipe 20 is the same as the one-pitch length P1 of the middle lateral sipe 10. As a result, the uneven wear resistance performance of the crown land portion 6 and the middle land portion 7 is further improved.

The maximum depth of the crown lateral sipe 20 is preferably 40% to 80% of the maximum depth of the circumferential groove 3.

The crown flute 21 extends, for example, in a wavy shape. In the crown vertical groove 21 of the present embodiment, one cycle of waves is formed between the two crown horizontal sipes 20. The crown flute 21 of the present embodiment extends in a sinusoidal shape, but is not limited to such a mode, and various modes such as a rectangular wavy shape, a circular wavy shape, or a zigzag shape can be adopted.

The crown flutes 21 extend in the tire circumferential direction at the center of the crown land portion 6 in the tire axial direction. In a preferred embodiment, the groove centerline of the crown vertical groove 21 crosses the center position of the crown land portion 6 in the tire axial direction a plurality of times.

The crown flute 21 communicates with, for example, the central portion of the crown lateral sipe 20 in the tire axial direction. Specifically, the crown vertical groove 21 communicates with the second sipe piece 20b of the crown horizontal sipe 20. Such a crown flute 21 is useful for improving wet performance and uneven wear resistance in a well-balanced manner.

The ratio Ac / Wc of the peak-to-peak amplitude amount Ac of the crown vertical groove 21 to the width Wc of the crown land portion 6 in the tire axial direction is, for example, 0.1 to 0.2. The amplitude amount Ac of the crown vertical groove 21 is 80% to 120% of the peak-to-peak amplitude amount Am of the middle vertical groove 11 (shown in FIG. 2 and the same applies hereinafter). As a result, the uneven wear resistance performance of the crown land portion 6 and the middle land portion 7 is further improved.

As a preferred embodiment, in the present embodiment, the ratio Lm / Wm of the distance Lm in the tire axial direction from the first end 11a to the second end 11b of the middle vertical groove 11 with respect to the width Wm in the tire axial direction of the middle land portion 7 is determined. It is larger than the ratio Ac / Wc of the peak-to-peak amplitude amount Ac of the crown vertical groove 21 to the width Wc of the crown land portion 6 in the tire axial direction. Specifically, the ratio Lm / Wm is 1.5 to 6.0 times the ratio Ac / Wc. As a result, uneven wear of the crown land portion 6 on which a large ground pressure acts is suppressed, and excellent wet performance is exhibited in the middle vertical groove 11.

The above-mentioned configuration of the middle vertical groove 11 can be applied to the groove width, depth and cross-sectional area of the crown vertical groove 21.

As shown in FIG. 1, the tread surface of the shoulder land portion 8 is not provided with a groove having a width of at least 1.5 mm. As a preferred embodiment, the shoulder land portion 8 of the present embodiment is a smooth rib in which the groove and the sipe having a width of 1.5 mm or less are not provided on the entire tread surface. Such a shoulder land portion 8 has high rigidity and is useful for enhancing uneven wear resistance and steering stability.

FIG. 4 shows an enlarged view of the shoulder circumferential groove 4. In FIG. 4, the groove wall 4w of the shoulder circumferential groove 4 is colored. As shown in FIG. 4, it is desirable that the groove bottom portion 4d of the shoulder circumferential groove 4 of the present embodiment oscillates in the tire axial direction. Such a shoulder circumferential groove 4 can exhibit excellent drainage for a long period of time.

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 pneumatic tire for a heavy-duty vehicle of size 11R22.5 having the basic tread pattern of FIG. 1 was prototyped based on the specifications in Table 1. As a comparative example, a tire having a tread pattern shown in FIG. 5 was prototyped. As shown in FIG. 5, the middle land portion a of the tire of the comparative example is provided with a plurality of lateral sipes b that cross the middle land portion a and a vertical groove c that continuously extends in a wavy shape in the tire circumferential direction. Has been done. The tread pattern of the comparative example is substantially the same as that shown in FIG. 1, except for the above configuration. The wet performance and uneven wear resistance of each test tire were tested. The common specifications and test methods for each test tire are as follows.
Mounting rim: 22.5 x 7.50
Tire internal pressure: 720kPa
Test vehicle: 10t truck, 50% of the standard load capacity is loaded in the center of the loading platform Test tire mounting position: All wheels

<Wet performance>
In the above test vehicle, the time when orbiting a circuit having a radius of 120 m composed of an asphalt road surface having a water film having a thickness of 2 mm was measured. The result is the reciprocal of the time, and is shown by an exponent with a comparative example of 100. The larger the value, the better the wet performance.

<Uneven wear resistance>
After traveling a certain distance with the above test vehicle, the degree of uneven wear in the middle land area was visually evaluated. The result is a score with a comparative example of 100, and the larger the value, 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 wet performance while maintaining uneven wear resistance.

2 Tread part 3 Circumferential groove 7 Middle land part 10 Middle horizontal sipe 11 Middle vertical groove 11a 1st end 11b 2nd end

Claims (15)

A tire with a tread
The tread portion includes a circumferential groove that extends continuously in the tire circumferential direction and a middle land portion that is divided into the circumferential grooves.
The middle land portion includes a plurality of middle lateral sipes that cross the middle land portion and a plurality of middle flutes that extend in the tire circumferential direction.
The middle horizontal sipe and the middle vertical groove are alternately arranged in the tire circumferential direction.
Each of the middle flutes extends in a wavy shape.
Each of the middle flutes has a first end communicating with one of the middle lateral sipes on one side in the tire circumferential direction and a second end communicating with one of the middle lateral sipes on the other side in the tire circumferential direction. Including and
The second end of the middle flute is provided at a position different from the first end of the middle flute in the tire axial direction.
tire. The tread portion includes a crown land portion adjacent to the middle land portion.
The tire according to claim 1, wherein the crown land portion includes a plurality of crown lateral sipes that cross the crown land portion and a crown longitudinal groove that extends continuously in a wavy shape in the tire circumferential direction. The ratio Lm / Wm of the distance Lm in the tire axial direction from the first end to the second end of the middle vertical groove with respect to the width Wm in the tire axial direction of the middle land portion is the ratio Lm / Wm of the tire axial direction of the crown land portion. The tire according to claim 2, wherein the ratio of the peak-to-peak amplitude amount Ac of the crown flute to the width Wc is larger than Ac / Wc. The tire according to claim 3, wherein the ratio Lm / Wm is 1.5 to 6.0 times the ratio Ac / Wc. The tire according to claim 3 or 4, wherein the ratio Lm / Wm is 0.3 to 0.6. The tire according to any one of claims 3 to 5, wherein the ratio Ac / Wc is 0.1 to 0.2. The tire according to any one of claims 2 to 6, wherein the groove center line of the crown vertical groove crosses the center position of the crown land portion in the tire axial direction a plurality of times. The tire according to any one of claims 1 to 7, wherein the maximum depth of the middle flutes is 5% to 30% of the maximum depth of the circumferential grooves. The tire according to any one of claims 1 to 8, wherein the middle flute crosses the center position of the middle land portion in the tire axial direction. Each of the middle flutes has a first arc portion extending on the first end side and a second arc portion extending on the second end side and curved in a convex direction opposite to the first arc portion. The tire according to any one of claims 1 to 9, which includes a part. The first end is located outside the tire axial direction from the center position of the middle land portion in the tire axial direction.
The second end is located inside the tire axial direction from the center position of the middle land portion.
The tire according to claim 10, wherein the first arc portion is curved convexly toward the outside in the tire axial direction. One of claims 1 to 11, wherein the middle lateral sipe includes a first convex portion that is convex on one side in the tire circumferential direction and a second convex portion that is convex on the other side in the tire circumferential direction. Tires listed in. The middle lateral sipe includes a first convex portion that is convex on one side in the tire circumferential direction and a second convex portion that is convex on the other side in the tire circumferential direction.
The tire according to any one of claims 1 to 12, wherein the first end communicates with the second convex portion. The middle lateral sipe includes a first convex portion that is convex on one side in the tire circumferential direction and a second convex portion that is convex on the other side in the tire circumferential direction.
The tire according to any one of claims 1 to 13, wherein the second end communicates with the first convex portion. The tire according to any one of claims 1 to 14, wherein the tire is for a heavy-duty vehicle.

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