JPH08337102A - Pneumatic tire with low inclination groove having directionality - Google Patents

Abstract

PURPOSE: To lower a tire noise by improving riding comfort against a vibration, regarding a pneumatic tire with a tread pattern to form a V-shaped center block out of an low inclination groove of directionality. CONSTITUTION: This pneumatic tire has the tread pattern where many low inclination grooves 1 having directionality extended like a V-shape at a relatively small angle with a peripheral direction are arranged at intervals along a tire peripheral direction right and left via a pattern center, and a V-shaped center block is formed out of the grooves 1. Also, a groove side wall angle θ1 at a tread end is larger than a side wall angle θ2 at the pattern center, regarding side wall angles with a tread normal line N in cross section along a direction orthogonal with the extension of the grooves 1 at a tread outer zone over an area from a position approximately 50% of a distance from the pattern center to both tread ends.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pneumatic tire, and particularly to a left and right side of a pattern center with a relatively small inclination angle of 5 to 30 degrees, preferably 10 to 20 degrees with respect to the circumferential direction. Pneumatic with a tread pattern in which a large number of directional low-tilt grooves extending in a V shape are arranged at intervals in the tire circumferential direction, and a V-shaped center block is formed by the directional low-tilt grooves. It concerns tires.

In the present specification, a "directionally inclined groove" is a groove extending obliquely with respect to the circumferential direction, and a portion of the groove extending obliquely near the equatorial plane of the tire is grounded first. , A groove in which a so-called directional tread pattern is formed, in which the direction of rotation (normal direction) of the tire when it is mounted on a vehicle is specified so that the side farther from the equatorial plane will come into contact with the ground later, The "outer region" is the pattern
It refers to the area from about 50% of the distance from the center to both ends of the tread to both ends of the tread, and the "tread inner area" means about 50% of the distance from the pattern center to both ends of the tread to the inside of the tread. Refers to the region, the "groove sidewall angle" refers to the angle of the groove sidewall with respect to the tread normal in the cross section perpendicular to the direction in which the groove extends, and "the stepping side of the block" refers to one of the blocks of the tire. Refers to the side to be grounded first during normal rotation,
The “block kick-out side” refers to the side of one block that comes into contact with the ground later when the tire rotates normally.

[0003]

2. Description of the Related Art A pneumatic tire to which the present invention is applied, that is, a tire having a large number of directional low-inclination grooves extending in a V shape at a relatively small inclination angle with respect to the circumferential direction on both sides of a pattern center. A pneumatic tire having a tread pattern, which is arranged at intervals in the circumferential direction and has a V-shaped center block formed by the directional low-inclination groove, has a circumferential groove extending parallel to the circumferential direction. The noise generated from the tire during traveling is larger than that of a pneumatic tire equipped with, and there is a strong demand to reduce the noise.

A pneumatic tire to which the present invention is directed, that is, a large number of directional low-inclination grooves extending in a V shape at a relatively small inclination angle with respect to the circumferential direction on both sides of the pattern center are provided in the tire circumferential direction. In a region closer to the pattern center of a pneumatic tire having a tread pattern in which the V-shaped center blocks are formed by the directional low-angled grooves, the V-shaped center blocks are provided. The taper tip has a large negative ratio, and the V-shaped center block has a small negative ratio in the thick part. As a result, the flow of the tread / rubber during vulcanization becomes non-uniform and the thickness of the block increases at the tapered tip. To make it easier to understand, if you express it a little too much, the inner surface of the tire is wavy in the circumferential direction in the mold at the end of vulcanization, and the inner surface of the tire at the tapered tip of the V-shaped center block is It is convex inside, and it is almost the same inside before the tire is filled with internal pressure, but when the tire is assembled on the rim and filled with internal pressure, the tapered tip of the V-shaped center block is tapered. The surface of the block tends to be convex toward the outside of the tire when approaching the parts.

[0005]

As a method of reducing the noise of tires, pitch variation has been known and has been put to practical use. This is a method for reducing tire noise based on the theory of frequency modulation, in which the circumferential length (pitch) of the minimum unit pattern that constitutes the pattern is set to two or more types, and This is a technique for reducing tire noise, in which the noise generated from the tire is dispersed into many sidebands having a low sound pressure level by appropriately arranging the tires. Strictly speaking, however, this pitch variation method is a method of widely dispersing the frequency of tire noise to make it difficult to hear the tire noise, and does not reduce the noise energy itself.

A large number of directional low-inclination grooves extending in a V shape at a relatively small inclination angle with respect to the circumferential direction sandwiching the pattern center are arranged at intervals in the tire circumferential direction. As described above, the pneumatic tire having the tread pattern in which the V-shaped center block is formed by the inclined groove has the surface of the block on the outside of the tire near the tapered tip of the V-shaped center block. It tends to be convex, the radial runout (dimensional non-uniformity in the radial direction) becomes large, the radial force variation (fluctuation of the force in the radial direction) becomes large, and the tire uniformity level increases. It easily deteriorates, and the tire ride comfort performance deteriorates.

The object of the present invention is to eliminate the above-mentioned problems of the prior art, and to sandwich the pattern center on the left and right,
A large number of directional low-inclination grooves extending in a V shape at a relatively small inclination angle with respect to the circumferential direction are arranged at intervals in the tire circumferential direction, and the directional low-inclination grooves form a V-shaped center block. It is to reduce the energy of noise generated from a pneumatic tire having a known tread pattern to reduce the tire noise in the original sense.

Another object of the present invention is to solve the above-mentioned problems of the prior art and to extend a large number of V-shapes on both sides of the pattern center at a relatively small inclination angle with respect to the circumferential direction. Uniformity level in a pneumatic tire having a tread pattern in which directional low-tilt grooves are arranged at intervals in the tire circumferential direction, and V-shaped center blocks are formed by the directional low-tilt grooves. To prevent the deterioration of tire vibration and ride comfort performance.

[0009]

In order to achieve the above object, the pneumatic tire of the present invention has a pattern center between which is 5 to 30 degrees, preferably 10 to 20 degrees in the circumferential direction. A tread in which a large number of directional low-inclination grooves extending in a V shape are arranged at relatively small inclination angles at intervals in the tire circumferential direction, and a V-shaped center block is formed by the directional low-inclination grooves. -In a pneumatic tire provided with a pattern, at least in the tread outer area from the position of about 50% of the distance from the pattern center to both ends of the tread to the tread outer ends
Among the groove side wall angles of the directional low-inclination groove with respect to the tread normal in a cross section perpendicular to the groove extending direction, the tread end side groove side wall angle is larger than the pattern center side groove side wall angle. Pneumatic tire characterized by.

In the pneumatic tire of the present invention, it is preferable that the groove side wall angle on the tread end side of the directional low inclination groove is larger than the groove side wall angle on the pattern center side in the entire tread area. .

In the pneumatic tire of the present invention, in the tread inner region inside about 50% of the distance from the pattern center to both ends of the tread, the groove sidewall of the directional low inclination groove on the tread end side is formed. The angle is smaller than the groove side wall angle on the pattern center side, and in the connection region between the tread outer region and the tread inner region, the groove side wall angle on the tread end side of the directional low inclination groove and the pattern. -It is preferable that the side walls of the groove on the center side have the same angle.

The pneumatic tire of the present invention has a pattern center and is sandwiched between 45 and 90 degrees with respect to the circumferential direction.
V with a relatively large inclination angle of preferably 60 to 80 degrees
A large number of directional high-inclination grooves extending in a letter shape are arranged at intervals in the tire circumferential direction, and at least about 50% of the distance from the pattern center to both ends of the tread to the outside of the tread from both ends of the tread. In the area,
Of the groove sidewall angles with respect to the tread normal in the cross section in the direction perpendicular to the direction in which the groove extends, the angle of the groove sidewall that contacts the ground later when the tire rotates normally is greater than the angle of the sidewall that contacts the ground first. Is preferred.

In the pneumatic tire of the present invention, in the entire tread region, the groove side wall angle of the directional high-inclination groove that comes into contact later when the tire is normally rotated is larger than the groove side wall angle that comes into contact first. It is preferable.

In the pneumatic tire of the present invention, in the inner region of the tread, which is inside about 50% of the distance from the pattern center to both ends of the tread, the directional high-inclination groove is grounded after the tire is normally rotated. The groove side wall angle is smaller than the groove side wall angle to be grounded first, and in the connection area between the tread outer area and the tread inner area, the directional high-inclination groove is grounded later when the tire is normally rotated. It is preferable that the groove side wall angle to be formed is the same as the groove side wall angle to be grounded first.

[0015]

[Function] Noise generated while the tire is running includes "groove air pumping noise", "block or lug vibration noise" and "other noise (ground friction noise, tire vibration due to road surface irregularities). Sound, or air-pumping noise in recesses on the road surface, etc.) ”, but it is the former two that cause patterns such as lugs, ribs or blocks formed on the tread surface of tires by grooves. . Further, in a tire provided with a block pattern or a lug pattern, the "block or lug vibration sound" tends to be loud. For pneumatic tires with a block or lug pattern, when the tire rolls, the block or lug collides with the road surface when the discontinuity on the tread rubber surface that is the boundary between the block and the lug and lug touches the ground. Then, the impact force causes the block or lug to vibrate and emit a sound (block or lug excitation sound). Sound emission acts as a speaker, so to speak, with the side walls of the tire and the tread surface acting as a diaphragm.

In a pneumatic tire provided with an inclined groove extending in a direction inclined with respect to the circumferential direction, among the side walls of the inclined groove, the side wall which comes into contact with the ground later when the tire rolls collides with the road surface when it is just stepping on the ground. The impact force causes the block or lug to vibrate and emit the loudest sound.
In other words, the V-shaped center /
In a pneumatic tire having a tread pattern in which blocks are formed, of the sidewalls of the inclined groove, the groove sidewall on the inner side of the tire rotation axis collides with the road surface when the vehicle is just stepping on the ground, and the impact force causes blockage. Vibrates and emits the loudest sound.

In the pneumatic tire of the present invention, as described above, a large number of directional low-inclination grooves extending in a V shape are formed on the left and right sides of the pattern center with a relatively small inclination angle with respect to the circumferential direction. In a pneumatic tire having a tread pattern that is spaced in the direction and has a V-shaped center block formed by the directional low-inclination grooves, at least in the tread outer region, the directional low-inclination grooves are provided. Since the groove side wall angle on the tread end side of is larger than the groove side wall angle on the pattern center side, the rigidity of the side wall of the inclined groove that emits the largest sound, that is, the groove side wall on the pattern center side is weakened. ing. As a result, the input level to the block when the vehicle collides with the road surface when stepping on the ground is reduced, and the level of radiated sound is also reduced. In the pneumatic tire of the present invention, in the case of only aiming to reduce noise, the groove side wall angle on the tread end side of the directional low inclination groove is larger than the groove side wall angle on the pattern center side in the entire tread area. Preferably there is.

The basic construction of the pneumatic tire of the present invention is such that a large number of directional low-inclination grooves extending in a V shape at a relatively small inclination angle with respect to the circumferential direction sandwiching the pattern center are provided in the tire circumferential direction. A pneumatic tire with a tread pattern that is spaced apart and has a V-shaped center block formed by directional low-sloping grooves, which is an inevitable consequence of such a tread pattern configuration. In the area near the pattern center, the negative ratio of the tapered tip of the V-shaped center block is large,
The negative ratio of the wide portion of the V-shaped center block becomes small, and the negative ratio tends to be uneven in the circumferential direction of the tire. However, the pneumatic tire of the present invention, in the tread outer region, of the directional low inclination groove,
The groove side wall angle on the tread end side is larger than the groove side wall angle on the pattern center side, and in the tread inner region, the groove side wall angle on the tread end side of the directional low inclination groove is the groove side wall on the pattern center side. The angle is smaller than the angle, and in the connection area between the tread outer area and the tread inner area, the groove side wall angle on the tread end side and the groove side wall angle on the pattern center side of the directional low inclination groove are the same. , In the inner area of the tread where the negative ratio becomes large, increase the groove side wall angle on the pattern center side,
In the outer region of the tread where the block volume is increased and the negative ratio is reduced, the groove side wall angle on the pattern center side is reduced to reduce the block volume, so that the negative ratio in the tire circumferential direction is not uniform. Will be alleviated. As a result, the ground reaction force is made uniform when the tires are rolling, suppressing radial runout and eventually uniformity level, especially radial force variation, and suppressing noise (striking noise) and improving vibration ride comfort. can do.

In the pneumatic tire of the present invention, the inclination angle of the directional low inclination groove is preferably 5 to 30 degrees,
More preferably, it is 10 to 20 degrees. If this angle is too small, the block formed between the directional low-inclination grooves becomes small, the block rigidity becomes insufficient, and the steering stability on a dry road surface deteriorates. Therefore, in order to increase the size of the block in order to increase the block rigidity, the pitch must be set to a large value, and the number of pitches must be reduced. It stands out. If this angle is too large, the drainage performance on the wet road surface due to the directional low inclination groove is deteriorated, and the function of preventing or suppressing the hydroplaning phenomenon is reduced. Further, the angle of intersection between the low-directional directional groove and the high-directional directional groove becomes small, the block rigidity becomes insufficient, the steering stability on the dry road surface deteriorates, and uneven wear easily occurs.

In the pneumatic tire of the present invention, in addition to the directional low inclination groove, the directional high inclination groove having an inclination angle of 45 to 90 degrees, preferably 60 to 80 degrees with respect to the circumferential direction is provided. Are preferable for improving drainage performance on a wet road surface. In other words, the directional low-tilt groove mainly has the action of enhancing the drainage performance of the tire by pushing the water forward when stepping on the ground, but in addition to the directional low-tilt groove, the directional low-tilt groove is provided. As a result, the action of draining water laterally from the tread edge is strengthened, and the drainage performance of the tire can be efficiently improved as a whole. In addition, increasing the groove volume in the ground contact surface is an effective means to improve the drainage performance of the tire, but if you try to secure the required groove volume only with directional low-inclination grooves, block rigidity on the tread will increase. Therefore, it is preferable to secure a necessary groove volume for the directional low-inclination groove and the directional high-inclination groove, because such a non-uniformity causes a problem such as deterioration of tire noise.
If the inclination angle of the high inclination groove with respect to the circumferential direction is too smaller than the above angle, the intersection angle between the directional low inclination groove and the directional high inclination groove becomes small, resulting in insufficient block rigidity and steering stability on dry road surfaces. And the uneven wear is likely to occur. Further, the block formed between the low-directional directional groove and the high-directional directional groove becomes small, resulting in insufficient block rigidity and reduced steering stability on a dry road surface. If the inclination angle of the high-inclination groove with respect to the circumferential direction is larger than the above angle, the tread-shaped stepped end portion of the tread coincides with the stepped corner portion of the directional high-inclination groove, and noise increases.

As described above, in the basic structure of the pneumatic tire of the present invention, it is preferable to provide the directional high inclination groove in addition to the directional low inclination groove. In this case, the directional high inclination groove is formed. Blocks tend to have more heel and toe wear, especially in the outer tread area. The directional low-inclination groove, which is in a sloping relationship with the circumferential direction, inclines from the pattern center to the outer area of the tread to divide the incoming directional high-inclination groove. The rigidity of the block in the outer region of the tread that is formed tends to be uneven on the circumference of the tire, and the heel and toe wear described above is more likely to occur. However, in the pneumatic tire of the present invention, at least in the tread outer region, among the groove side wall angles with respect to the tread normal in the cross section in the direction perpendicular to the direction in which the groove extends, the groove side wall angle that comes into contact with the tire at the time of forward rotation first comes first. Focusing on the block formed by the directional high-inclination groove, which is larger than the side wall angle of the groove to be grounded, in other words, the groove side wall angle located on the stepping side f of the block is located on the kicking side k of the same block. The angle is larger than the groove side wall angle, and therefore the rigidity on the step-in side f of the block is high and the rigidity on the kick-out side k is weak, so that "escape" to the kick-out side k of the block during load rolling of the tire. The above behavior is possible to prevent or suppress heel and toe wear. If attention is paid only to the prevention or suppression of heel-and-toe wear, the pneumatic tire of the present invention has a kicked side wall angle on the stepping side of the directional high-inclination groove not only in the tread outer region but also in the entire tread region. The angle is preferably larger than the groove side wall angle on the projecting side.

A tread pattern in which a large number of directional high-inclination grooves extending in a V shape at a relatively large inclination angle with respect to the circumferential direction sandwiching the pattern center are arranged at intervals in the tire circumferential direction. In a pneumatic tire provided with, not only prevention or suppression of heel-and-toe wear but also reduction of tire noise due to highly directional directional grooves may be required. In a pneumatic tire that has a high-slope groove that extends in a direction that is inclined at a relatively large angle with respect to the circumferential direction, of the sidewalls of the high-slope groove, the side wall that will come into contact with the ground later when the tire rolls is the road surface when the ground is just stepped on. The block or lug vibrates due to the impact force and radiates the loudest sound. In other words, paying attention to the block formed by the directional high-inclination groove, in other words, the corner on the stepping side of the block (the corner that comes in contact with the ground first when the tire rolls) collides with the road surface just when stepping on the ground, Generates noise. The tire noise is generated more in the tread inner area than in the tread outer area. As described above, in the pneumatic tire of the present invention, in the tread inner region inside about 50% of the distance from the pattern center to both ends of the tread, the directional high inclination groove is perpendicular to the extending direction of the groove. Among the angles of the groove side walls with respect to the tread normal in the direction cross section, the angle of the groove side wall that comes into contact later when the tire rotates normally is smaller than the angle of the groove side wall that comes in contact with the tire first, so The rigidity is weakened, the impact force when the vehicle collides with the road surface is mitigated, and tire noise is suppressed.

[0023]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment according to the present invention will be described with reference to the drawings. FIG. 1 is a partially enlarged front view of a tread pattern of a pneumatic tire for passenger cars according to the embodiment of the present invention. 225 / 50R16. The tread pattern of the tire according to the embodiment of the present invention shown in FIG. 1 is V with a relatively small inclination angle of about 18 degrees with respect to the circumferential direction on both sides of the equatorial line (E) of the tire which is the pattern center. A large number of directional low-inclination grooves (1) extending in a letter shape are arranged at intervals in the tire circumferential direction, and the directional low-inclination grooves (1) form a V-shaped center block. In addition to the directional low inclination groove (1), a large number of directional high inclination grooves (2) extending in a V shape at a relatively large inclination angle of about 65 degrees with respect to the circumferential direction are spaced in the tire circumferential direction. Are arranged. In the tire of Example 1 according to the present invention shown in FIG. 1, the side of the portion of the directional low-inclination groove (1) extending obliquely that is closer to the tire equatorial plane is grounded first, and the side farther from the tire equatorial plane is grounded later. As described above, the so-called directional tread pattern in which the rotation direction (R) of the tire when it is mounted on the vehicle is designated is provided. As shown in the AA cross-sectional view, in the tread outer area (S) from the position of 50% of the distance from the pattern center to both ends of the tread to the both ends of the tread, the groove of the directional low inclination groove (1) extends. Of the groove side wall angle with respect to the tread normal (N) in the cross section perpendicular to the direction, the groove side wall angle (θ1) on the tread end side is 30 degrees, and the groove side wall angle (θ2) on the pattern center side is 10 degrees. is there. As shown in the B-B cross-sectional view, in the inner tread area (C) from the position of 50% of the distance from the pattern center to both ends of the tread, in the direction in which the directional low inclination groove (1) extends. Among the groove side wall angles with respect to the tread normal (N) in the cross section in the perpendicular direction, the groove side wall angle (θ3) on the tread end side is 10 degrees, and the groove side wall angle (θ4) on the pattern center side is 30.
It is degree. In the connection region between the tread outer region (S) and the tread inner region (C), the groove sidewall angle on the tread end side and the groove sidewall angle on the pattern center side of the directional low inclination groove (1) are the same. is there. The groove width (W) of the directional low inclination groove (1) is 13 mm, and the groove depth (D) is 8 mm.
The directional high-inclination groove (2) has a groove side wall angle of 15 degrees on the side to be grounded first and the side to be grounded at the time of forward rotation, the groove width (W) is 5.5 mm, and the groove depth (D) is It is 6 mm. Example 1
The tires of (1) are mainly aimed at meeting the demands of improving the uniformity level and improving the vibration riding comfort performance of the tires.

The tire of Example 2 has a cross section of the directional low-inclination groove (1) in a direction perpendicular to the groove extending direction in the entire tread area including the tread outer area (S) and the tread inner area (C). Among the groove side wall angles with respect to the tread normal (N) in the above, the groove side wall angle (θ1) on the tread end side is 30.
Degree, the groove side wall angle (θ2) on the pattern center side is 1
It is the same as the tire of Example 1 except that it is 0 degree. The tire of Example 2 is a tire whose main purpose is to meet the demand for reducing noise of the tire.

The tire of Example 3 has a groove side wall angle (θ1) on the tread end side of 30 degrees and a groove side wall angle (θ2) of the pattern center side in the tread outer region (S) as in the case of the tire of Example 1. Is 10 degrees, but as shown in FIG. 2, in the inner region (C) of the tread, the directional low inclination groove (1) is formed.
The groove side wall angle on the pattern center side of
The groove side wall angle (θ5) on the tread surface side is 5 degrees, the groove side wall angle (θ6) on the groove bottom side is 30 degrees, and the groove side wall angle (θ7) on the tread end side is 20 degrees. The tire of Example 3 is the same as the tire of Example 1 except for this.
The tire of Example 3 has improved uniformity level and improved vibration ride comfort performance of the tire.
It is a tire whose design goal is to meet the demand to reduce the noise of the tire. As a modified design example of the tire of Example 3, as shown in FIG. 3, in the tread inner region (C), the cross section of the groove side wall on the pattern center side of the directional low inclination groove (1) is formed in a curved line. Even if the groove cross-sectional shape is such that the groove side wall angle with respect to the tread normal (N) in the cross section perpendicular to the direction in which the groove extends is 0 ° on the tread surface and gradually increases toward the groove bottom. Good.

In the pneumatic tire of the conventional example, the left and right groove sidewall angles with respect to the tread normal (N) are the same at any position of the directional low-inclination groove (1) in a cross section perpendicular to the direction in which the groove extends. And the groove side wall angle (β) outside the tire rotation axis
Is the same as the pneumatic tire of Example 1 except that the groove side wall angle (α) inside the tire rotation axis is also 20 degrees.

Regarding the pneumatic tire of Example 1 according to the present invention and the pneumatic tire of the conventional example described above, the tire was pressed against a rotating drum to apply a load, and a uniform axial distance was provided between the tire and the drum. As a result, the pneumatic tire of Example 1 was about 30% in radial runout and about 25% in radial force variation (fluctuation in radial direction) as compared with the pneumatic tire of the conventional example. It turned out to be improved. An indoor evaluation test of tire noise was carried out on the pneumatic tire of Example 2 according to the present invention and the pneumatic tire of the conventional example described above based on the automobile standard tire noise test method JASO C606. The test conditions are a rim of 8 J × 16, a tire internal pressure of 3.1 kgf / cm ² , a load of 500 kgf, and a speed of 60 km / h. as a result,
The pneumatic tire of Example 2 is 1.2 dB in noise (sound pressure level) in all frequency bands as compared with the pneumatic tire of the conventional example.
(A) It was reduced. Similarly, the pneumatic tire of Example 3 is improved by about 20% in radial force variation (fluctuation of force in the radial direction) as compared with the pneumatic tire of the conventional example, and noise (sound in all frequency bands is improved. It was found that the pressure level was reduced by 1.0 dB (A).

[0028]

From the above evaluation results, it can be seen that the pneumatic tires of the examples according to the present invention are superior in vibration ride comfort and tire noise as compared with the conventional pneumatic tires.

[Brief description of drawings]

1 is a partially enlarged front view and groove sectional view of a tread pattern of a pneumatic tire according to the present invention.

FIG. 2 is a groove cross-sectional view of the pneumatic tire according to the present invention.

FIG. 3 is a groove sectional view of the pneumatic tire according to the present invention.

[Explanation of Codes] 1 Directional low inclination groove 2 Directional high inclination groove E Tire equator line (pattern center) D Tire rotation direction N Tread normal

Claims (9)

[Claims] 1. A V which has a relatively small inclination angle of 5 to 30 degrees with respect to the circumferential direction on both sides of the pattern center with respect to the V direction.
A pneumatic tire having a tread pattern in which a large number of directional low-inclination grooves extending in a V shape are arranged at intervals in the tire circumferential direction, and a V-shaped center block is formed by the directional low-inclination grooves. At least about 5 of the distance from the pattern center to both ends of the tread
In the tread outer region from the position of about 0% to both ends of the tread, among the side wall angles of the directional low-inclination groove with respect to the tread normal line in a cross section in a direction perpendicular to the direction in which the groove extends, the side wall angle on the tread end side. Is larger than the groove side wall angle on the pattern center side. 2. The tread edge side groove angle of the directional low-angle groove is larger than the groove side wall angle of the pattern center side in the entire tread area. Pneumatic tire. 3. A tread normal line in a cross section of the directional low-inclination groove in a cross section perpendicular to a direction in which the groove extends in a tread inner region inside about 50% of a distance from the pattern center to both ends of the tread. Of the groove side wall angle on the tread end side is smaller than the groove side wall angle on the pattern center side, and in the connection region between the tread outer region and the tread inner region, the directional low inclination groove is formed. 2. The pneumatic tire according to claim 1, wherein the groove side wall angle on the tread end side and the groove side wall angle on the pattern center side are the same. 4. The tilt angle of the directional low tilt groove with respect to the circumferential direction is 10 to 20 degrees.
The pneumatic tires according to 1 to 3. 5. A relatively large inclination angle of 45 to 90 degrees with respect to the circumferential direction on the left and right sides of the pattern center,
2. A plurality of directional highly inclined grooves extending in a V shape are arranged at intervals in the tire circumferential direction.
The pneumatic tire according to any one of 4 to 4. 6. The tilt angle of the directional high tilt groove with respect to the circumferential direction is 60 to 80 degrees.
Pneumatic tire described. 7. A cross section of the directional high-inclination groove at a right angle to a direction in which the groove extends, at least in a tread outer region from a position of about 50% of a distance from the pattern center to both ends of the tread to both ends of the tread. 7. The pneumatic tire according to claim 5, wherein among the groove side wall angles with respect to the tread normal line, the groove side wall angle that comes into contact later with the tire during normal rotation is larger than the groove side wall angle that comes into contact with the tire first. . 8. The angle of the side wall of the directional high-inclination groove, which comes into contact with the ground later when the tire is normally rotated, is larger than the angle of the groove side wall that comes into contact with the ground first, in the entire tread region. Item 7. The pneumatic tire according to item 7. 9. In a tread inner area inside about 50% of the distance from the pattern center to both ends of the tread, the directional high-inclination groove has a groove side wall angle which comes into contact with the ground later when the tire is normally rotated. The angle is smaller than the groove side wall angle to be grounded first, and in the connection region between the tread outer region and the tread inner region, the directional high-inclination groove has a groove side wall angle to be grounded later when the tire rotates in the normal direction. The pneumatic tire according to claim 7, wherein the side walls of the groove that come into contact with the ground first have the same angle.