JPH1142910A - Pneumatic tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a pneumatic tire low in tire noise without lowering the steering stability of the tire. SOLUTION: A tire is structured so that it is provided with directional tread patterns including a center peripheral rib 1 provided at a pattern center, a plurality of slant grooves 2 provided at intervals in circumferential direction, and a plurality of blocks 3 held between the slanted grooves 2 and located at intervals in circumferential direction. Also the slant grooves 2 extend, in V-shape, from the center peripheral ribs in right and left sides at an angle of approximately 15 to 45 deg. relative to the peripheral direction, change a slant angle at both ends of the tread, and open to both ends of the tread. In addition, in these grooves 2, the rotating direction of the tire is specified so that the portion of the groove extending aslant nearer a tire equatorial plane is first brought in contact with the ground so as to form a directional V-shaped slant grooves. Then a plural of small sipes which are 5 mm or below in surface peripheral length and 40 to 90% of the depths of the slant grooves 2 in depth are arranged approximately uniform on the blocks.

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 more particularly to a pneumatic tire including a central circumferential rib provided on a pattern center and a plurality of circumferentially spaced directional inclined grooves. The present invention relates to a pneumatic tire having a directional tread pattern and having excellent hydroplaning resistance when running on a wet road surface.

[0002] In the present specification, a "directionally inclined groove" is a groove that extends obliquely with respect to the circumferential direction, and the side of the obliquely extending portion of the groove that is closer to the tire equatorial plane is grounded first. The direction of rotation (forward rotation) of the tire when the tire is mounted on a vehicle such that the side farther from the equatorial plane comes into contact with the ground later is designated, that is, a groove in which a so-called directional tread pattern is formed.

[0003]

2. Description of the Related Art As a pneumatic tire having excellent hydroplaning resistance when traveling on a wet road surface, a pneumatic tire having a so-called directional tread pattern formed by directional inclined grooves has been proposed and put into practical use. Has been

[0004]

A pneumatic tire provided with a directional inclined groove is excellent in hydroplaning resistance when running on a wet road surface, but has a disadvantage that tire noise (pattern noise) is large. If the width of the directional inclined groove is increased to improve drainage performance when traveling on a wet road surface, tire noise (pattern noise) will be further increased, and the tire noise will be reduced. When the width of the directional inclined groove is reduced, the drainage performance is reduced.

It is an object of the present invention to provide a pneumatic tire which solves the above-mentioned disadvantages of the prior art and has low tire noise (pattern noise) without deteriorating the steering stability of the tire.

[0006]

In order to achieve the above object, a pneumatic tire according to the present invention comprises a central circumferential rib provided at a pattern center and a plurality of circumferentially spaced ribs. A pneumatic tire provided with a directional tread pattern including a sloping groove and a plurality of blocks circumferentially spaced between the sloping grooves. From the direction ribs, it is inclined at an angle of about 15 to 45 degrees to the circumferential direction and extends right and left in a V-shape. The direction of rotation (normal rotation) of the tire when it is mounted on a vehicle is specified so that the side near the equatorial plane of the tire that opens at What is called directionality A directional V-shaped inclined groove on which a red pattern is formed. (2) A small sipe having a surface peripheral length of 5 mm or less and a depth of 40 to 90% of the depth of the inclined groove on the block. Are substantially uniformly arranged in a large number.

In order to achieve the above object, the pneumatic tire of the present invention has a sipe arrangement density defined by a sipe surface perimeter (mm) per unit area (cm ² ) of a block surface of 5 to 30 mm /. cm ² is preferred.

In order to achieve the above object, in the pneumatic tire of the present invention, the sipe is a columnar sipe having a quadrangular surface, or the sipe is a needle-shaped sipe having a circular or elliptical surface. Preferably, there is.

The pneumatic tire according to the present invention has the above-described structure. In particular, the inclined groove is inclined from the central circumferential rib at an angle of approximately 15 to 45 degrees with respect to the circumferential direction to form a V-shaped right and left. It extends at 75 to 105 degrees to the circumferential direction by changing the inclination angle at both sides of the tread and opens at both ends of the tread, and the side of the groove that extends obliquely near the tire equatorial plane contacts the ground first. A directional V-shaped inclined groove in which a so-called directional tread pattern is formed, in which the direction of rotation (forward rotation) of the tire when the tire is mounted on a vehicle such that the side farther from the equatorial plane comes into contact with the ground later is specified. . When the inclined groove is inclined from the central circumferential rib at an angle smaller than 15 degrees with respect to the circumferential direction and extends right and left in a V-shape, the block rigidity is reduced and the steering stability performance of the tire is reduced. , 45 °, the drainage performance deteriorates. When the inclined groove extends at an angle smaller than 75 degrees to the circumferential direction at both sides of the tread and changes at an angle of less than 75 degrees and opens at both ends of the tread, the traction performance of the tire is insufficient, while when it exceeds 105 degrees, uneven wear occurs Easier to do.

[0010] A directional tread pattern is provided which includes a large number of circumferentially-spaced inclined grooves and a large number of circumferentially-spaced blocks sandwiched between the inclined grooves. In the pneumatic tire of the present invention as described above, in the initial stage of the vulcanization step of the tire manufacturing process,
When an unvulcanized green tire is pressed against the inner surface of the vulcanization mold, it is molded while being pressed by the bone of the mold corresponding to the groove of the tire. The belt is waving. As a result, a large number of blocks provided at intervals in the circumferential direction sandwiched between the inclined grooves are warped in the circumferential direction, so that the surface pressure at the edge portions of the blocks is increased and tire noise (pattern noise) is increased. That is. This tendency of the tire noise to worsen becomes more pronounced as the groove width of the inclined groove increases.

The pneumatic tire of the present invention has the above-described structure, and particularly has a surface peripheral length of 5 mm or less on a large number of blocks provided in the circumferential direction and interposed between the inclined grooves. A large number of small sipes having a depth of 40 to 90% of the depth of the inclined groove are arranged almost uniformly, and are defined by the peripheral length (mm) of the sipe surface per unit area (cm ² ) of the block surface. Sipe arrangement density is 5-30mm
/ Cm ² , which effectively prevents or suppresses the belt from waving in the tire vulcanizing step.
That is, at the initial stage of the vulcanization step of the tire manufacturing process, when the tread portion of the unvulcanized green tire is pressed against the inner surface of the vulcanization mold, the tread portion of the unvulcanized green tire is pressed into the bone of the mold corresponding to the groove of the tire. The tread portion is molded while being pushed, but in the pneumatic tire of the present invention, since a large number of sipes are arranged on the block almost uniformly, the presence of a blade for forming the sipe causes the unvulcanized green and green. A reaction force is generated by the frictional resistance between the tread and the blade surface, and the difference in the reaction force from the mold received by the tread portion between the groove portion and the block portion is reduced, thereby suppressing the belt waving phenomenon.

The pneumatic tire of the present invention has the above-described configuration. In particular, when the peripheral length of the sipe is more than 5 mm, the block rigidity is reduced and the steering stability of the tire is reduced. In the pneumatic tire of the present invention, the sipe arrangement density is 5 to 30 mm as described above.
/ Cm ² a but, if this value is less than 5 mm / cm ^2, smaller frictional resistance unvulcanized green tread and the blade surface, the smaller the belt wavy suppression effect, whereas, 30 mm / If it is larger than cm ^{2, the} rigidity of the block is reduced and the steering stability of the tire is reduced. Further, in the pneumatic tire of the present invention, the sipe depth is 40 to 90% of the depth of the inclined groove as described above. If this value is smaller than 40%, the timing at which the green tread contacts the blade is reduced. Later, the effect of suppressing the belt waving phenomenon decreases, while if it exceeds 90%, the block rigidity decreases and the steering stability of the tire decreases.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments according to the present invention and conventional examples will be described below with reference to the drawings. In each case, the size of the tire is 255 / 45ZR18. FIG. 1 is a schematic view showing a pattern provided on a tread of a tire according to an embodiment of the present invention, and FIG. 2 is a perspective view of a columnar sipe and a needle sipe according to the present invention.

As shown in FIG. 1, a pneumatic tire according to a first embodiment of the present invention includes a central circumferential rib 1 provided at a pattern center located on a tire equatorial plane EL;
A directional tread pattern including a large number of inclined grooves 2 provided at intervals in the circumferential direction and a large number of blocks 3 provided at intervals in the circumferential direction sandwiched between the inclined grooves 2 is provided. . The inclined groove 2 is inclined from the central circumferential rib 1 at an angle of about 30 degrees with respect to the circumferential direction and extends right and left in a V-shape.
Degree, it opens at both ends TE of the tread, and the side near the tire equatorial plane EL of the part of the groove that extends inclining is grounded first,
A directional V-shaped inclined groove in which a so-called directional tread pattern is formed, in which a rotation (forward rotation) direction RD of a tire when the tire is mounted on a vehicle such that a side farther from the equatorial plane EL comes into contact with the ground later is specified. is there. On the block 3, a large number of sipe 4 whose surface peripheral length is 3 mm and whose depth is 70% of the depth of the inclined groove 2 are almost uniformly arranged. Sipe surface perimeter (m) per unit area (cm ² ) of block surface
The sipe arrangement density defined by m) is 10 mm / cm ² .

The pneumatic tire according to the second embodiment of the present invention has substantially the same configuration as the pneumatic tire according to the first embodiment except that the arrangement density of the sipes 4 is 30 mm / cm ² .

The conventional pneumatic tire has substantially the same configuration as the pneumatic tire of the first embodiment except that the pneumatic tire is not provided with the sipes 4.

The pneumatic tire of Comparative Example 1 has substantially the same configuration as the pneumatic tire of Example 1 except that the arrangement density of the sipes 4 is 3 mm / cm ² .

The pneumatic tire of Comparative Example 2 has substantially the same configuration as the pneumatic tire of Example 1 except that the depth of the sipe 4 is 30% of the depth of the inclined groove 2.

The pneumatic tire of Comparative Example 3 was the same as the pneumatic tire except that the depth of the sipe 4 was 100% of the depth of the inclined groove 2.
The configuration is almost the same as that of the pneumatic tire of the first embodiment.

The pneumatic tire of Comparative Example 4 has substantially the same configuration as the pneumatic tire of Example 1 except that the arrangement density of the sipes 4 is 50 mm / cm ² .

The pneumatic tire of Comparative Example 5 has substantially the same configuration as the pneumatic tire of Example 1 except that the peripheral length of the surface of the sipe 4 is 6 mm.

The pneumatic tires of Examples 1 and 2 according to the present invention, the pneumatic tires of the prior art, and the pneumatic tires of Comparative Examples 1 to 5 were run on a test course to determine the noise performance and the tire performance. A comparative test of steering stability performance was performed. In the comparative test of tire noise performance, a microphone was installed at the position of the ear of the test driver, and the noise was measured when traveling on a straight road at a speed of 60 km / h. In the comparative test of steering stability performance, evaluation was made based on a test driver's feeling when driving in a dry circuit having a radius of 50 m in various driving modes. Table 1 shows the evaluation results of the comparative test, with the test result of the pneumatic tire of the conventional example being 100.
The larger the number, the better the tire performance.

[0023]

[Table 1]

[0024]

From the above evaluation results, it can be seen that the pneumatic tire of the embodiment based on the present invention has improved tire noise performance without lowering the steering stability performance as compared with the conventional pneumatic tire. I understand.

[Brief description of the drawings]

FIG. 1 is a schematic view of a tread pattern of a pneumatic tire according to the present invention.

FIG. 2 is a perspective view of a columnar sipe and a needle sipe according to the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Central circumferential rib 2 Slant groove 3 Block 4 Sipe

Claims (4)

[Claims] 1. A central circumferential rib provided at a pattern center, a number of inclined grooves provided at intervals in the circumferential direction, and a plurality of inclined grooves provided at intervals in the circumferential direction between the inclined grooves. (1) The inclined groove is inclined from the central circumferential rib at an angle of approximately 15 to 45 degrees with respect to the circumferential direction from the central circumferential rib to the left and right. V-shaped, extending at 75 to 105 degrees with respect to the circumferential direction at both sides of the tread, changing the inclination angle, opening at both ends of the tread, and the side of the groove that extends obliquely near the tire equatorial plane first A directional V-shaped slope in which a so-called directional tread pattern is formed, in which the direction of rotation (forward rotation) of the tire is specified when the tire is mounted on a vehicle so that the side farther from the equatorial plane comes into contact with the ground later. (2) the blower On click, pneumatic tire characterized by sipes surface perimeter there is a small 40 to 90% of the depth of the inclined groove depth 5mm or less is substantially uniformly mass deployment. 2. The sipe arrangement density defined by the sipe surface perimeter (mm) per unit area (cm ² ) of the block surface is 5 to 30 mm / cm ² . Pneumatic tire. 3. The pneumatic tire according to claim 1, wherein the sipe is a column-shaped sipe having a quadrangular surface. 4. The pneumatic tire according to claim 1, wherein the sipe is a needle-shaped sipe having a circular or elliptical surface.