JPH06199109A - Pneumatic tire - Google Patents

Abstract

PURPOSE:To improve noise property and drainage property on a wet road surface of a pneumatic tire having good driving stability on a dry road surface. CONSTITUTION:A pneumatic tire partitions its tread 1 into a central area 4 and a pair of side areas 5 on both sides of the central area 4 by a pair of main circumferential grooves 3 separated at least a quarter of the tread width extending in parallel beyond a central circumference 4 and also has a directiveness tread pattern which is the tread partitioned along its circumference by diagonal grooves 6 which cross the main circumferential grooves 3, extend to the central area 4 from each side area 5 diagonally and facing each other, and respectively end at the central area 4. The pneumatic tire also has groove strips of the diagonal grooves 6 increasing their curvature from the side areas 5 toward the central area 4 and having a maximum groove width enlarged near their 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 having good pattern noise and good drainage on a wet road surface without deteriorating driving stability on a dry road surface.

[0002]

2. Description of the Related Art It has been known that in order to improve the drainage performance of a pneumatic tire, it is necessary to increase the negative ratio of the tread (ratio of the groove area to the entire tread). Since the rigidity is reduced, driving / braking performance is deteriorated. Therefore, studies are underway to improve drainage without increasing the negative rate.

For example, a pneumatic groove having a so-called directional pattern in which a circumferential groove extending linearly along the circumference of the tread and an oblique groove that sequentially enters the contact area from the central area to the lateral area are provided. There are tires (Fig. 5).

A pneumatic tire having a directional pattern is generally excellent in drainage to the front side of the tire when running at high speed on a wet road surface, but the circumferential length of the ground contact surface is in the central area compared to the both areas. In a tire having a long tread and a wide tread having a flat cross section, it is difficult to remove water in the central area of the tread in the ground contact plane, which easily causes a hydroplaning phenomenon during high speed running. Therefore, in this pneumatic tire, it is common to arrange the circumferential groove in the central region of the tread.

[0005]

However, in the pneumatic tire having the above-mentioned directional pattern, it is generally sufficient that the oblique grooves are arranged diagonally extending from each side area to the central area, and the problem of noise is taken into consideration. The optimization of the arrangement angle and groove width of the oblique groove has not been sufficiently studied. This pneumatic tire had circumferential grooves arranged in the central region, but this increases the negative ratio in the central region, so
This is advantageous for drainage, but on the other hand, it reduces the rigidity of the land part and deteriorates the steering stability on a dry road surface. As a result of intensive studies to achieve both of these performances, it was found that by disposing diagonal grooves in an appropriate shape, drainage performance can be ensured even if the number of circumferential grooves located in the central region is reduced. It was also found that pattern noise can be reduced by changing the groove width of the oblique groove.

Therefore, the object of the present invention is to optimize the arrangement shape of the oblique groove and its groove width, thereby maintaining good steering stability without lowering the rigidity of the land portion in the central region of the tread. It is an object of the present invention to provide a pneumatic tire having low noise characteristics and high drainage characteristics.

[0007]

One example of the pneumatic tire of the present invention is shown in FIG. 1, in which 1 is a tread, 2 is a central circumferential line, 3 is a main circumferential groove, 4 is a central region, and 5 is a side. Area 6, is an oblique groove. According to the present invention, a tread 1 is provided with a central region 4 and a pair of side regions 5 sandwiching the tread 1 with a pair of main circumferential grooves 3 that extend in parallel with each other so that at least a quarter width of the tread width of the tire is separated from the central circumferential line 2 of the tread 1. And the main circumferential groove 3
Pneumatic with a directional tread pattern in which the tread 1 is divided along its circumference by oblique grooves 6 that intersect with each other from each side area 5 and obliquely extend to the central area 4 and terminate at each of the central areas 4. In the tire, a diagonal tire 6 has a groove line whose curvature increases from the side region 5 toward the central region 4 and has a maximum groove width enlarged near the end thereof. is there.

The slanted groove 6 has groove lines that face each other from each side area 5 toward the central area 4 and have a convexly increasing curvature,
The intersection angle between the tangent line of the oblique groove 6 and the line parallel to the central circumferential line 2 is
The side region 5 preferably has a range of 45 to 80 °, and the central region 4 preferably has a range of 25 to 45 °. If the cross angle in the side area 5 is too small, drainage performance to the side of the tire is lowered, and if it is too large, pattern noise is deteriorated because it approximately matches the tire ground contact shape. This is also because if the intersection angle in the central region 5 is too small, sufficient land rigidity cannot be obtained, and if it is too large, drainage performance deteriorates.

Further, the oblique groove 6 has an enlarged maximum groove width near the end thereof, and the ratio of the maximum groove width near the end to the groove width at the tread end position is 1.1 to 2.0. It is preferably in the range of. This is because if this ratio is less than 1.1, a sufficient negative ratio in the central region 4 cannot be obtained, and if it exceeds 2.0, the land portion rigidity of the central region 4 is reduced. Further, it is preferable that the oblique groove 6 has a groove width that gradually increases from the side area of the tread toward the central area 4 in order to reduce pattern noise. The groove width is measured in the direction orthogonal to the tangent line of the groove.

In order for a pneumatic tire to obtain good drainage, it is common to set the negative ratio of the tread (total groove area / (total groove area + total land area) × 100) to 30% or more. However, in the present invention, in order to achieve both drainage and pattern noise, it is preferable to suppress the negative ratio of the oblique groove to about 15%. Therefore, considering that the remaining negative ratio of about 15% is secured by disposing the main circumferential groove 3 and the land portion rigidity of the central region 4 is also maintained, the main circumferential groove 3 is provided in the tread width of the tire. At least a quarter of the width was placed in parallel and spaced from the central circumference 2 of the tread 1.

Further, in order to improve the ground contacting property of the tire, it intersects with a plurality of diagonal grooves 6 in the opposite direction, and extends diagonally from each side area 5 to the central area 4 at intervals along the circumference of the tread. Sipe or notch 7 may be placed (Fig. 2).

When higher drainage is required, one central groove 8 (FIG. 1) or two central grooves 8 (FIG. 2) may be provided in the central region 4, but the central region 4 may be provided in the central region 4. When the tangent of the diagonal groove 6 located and the plane including the central circumferential line 2 are very small, the need for the central main groove 8 is scarce. When the central main groove 8 is provided, from the viewpoint of securing the rigidity of the land portion in the central region 4, the diagonal groove 6 is arranged so that the end of the diagonal groove 6 is kept within the land portion without intersecting the central main groove 8. To do.

Further, in the central region 4, in order to secure the negative ratio of the main groove of the tire having the conventional directional pattern and to suppress the decrease in land rigidity to the minimum, as shown in FIG. A branch groove 9 extending from the end of the groove 6 toward the rear contact area of the tire with a small inclination with respect to the plane including the tread circumference and extending toward the main circumferential groove 3 and terminating in the land portion may be arranged. Further, in order to enhance drainage to the side of the tire, auxiliary diagonal grooves 10 may be provided between the diagonal grooves 6 adjacent to each other along the circumference of the tread. This auxiliary diagonal groove 10
May communicate with the branch groove 9 (FIG. 4), but need not (FIG. 3). The auxiliary branch groove 11 (FIG. 4) and the auxiliary circumferential groove 12 (FIG. 3) may be provided to compensate for the lack of the negative ratio.

[0014]

In the pneumatic tire of the present invention, the oblique groove 6 is provided in the side area 5.
From the central region 4 of the tread 1 to the drainage can be secured without lowering the rigidity of the land portion by using the groove stripes whose curvature increases from the center region 4 to the central region 4. , The drainage is further improved by increasing the maximum groove width. Further, the pattern noise can be reduced by making the groove width substantially narrow from the central region 4 to the side regions 5. Further, by providing the main circumferential groove 3 with a width of at least a quarter of the tread width from the central circumferential line 2, higher drainage performance can be expected.

[0015]

【Example】

Example 1 A test was conducted on an invention tire having a tread 1A shown in FIG. 1 having a tire size of PSR 205 / 60R15 and a tread width W of 160 mm. In the tire of the present invention, a pair of linear main circumferential grooves 3 (groove width: 6 mm) intersect the diagonal grooves 6 near the tread ends, and are arranged parallel to a plane including the tread circumference. Further, in order to obtain a high drainage property, a single linear central groove 8 (groove width: 9 mm) parallel to the above-mentioned plane is arranged at the central circumferential position. Diagonal groove 6
Are arranged so as to extend obliquely from each side region 5 toward the central region 4 and end opposite to each other while gradually decreasing the inclination angle of the tangent line of the oblique groove 6 to the plane in that direction. The arrangement angle of the oblique groove 6 was 65 ° at the tread end position, 50 ° at the main circumferential groove position, and 20 ° at the groove end position with respect to the plane including the tread circumference. The diagonal grooves facing each other with the central circumferential line 2 sandwiched therebetween were arranged so as to be displaced in the circumferential direction by a half pitch (15 mm) of the pitch of the adjacent diagonal grooves 6 along the tread circumference. Groove width is 4.0 at the tread edge position
mm and 4.5 mm at the end position of the groove. In the present invention, conventional products were used for structures other than the tread.

Example 2 An invention tire having a tread 1B shown in FIG. 2 was tested. In the tire of the present invention, two central grooves 8 (groove width: 7 mm) are arranged so as to sandwich the central circumferential line 2, and a main circumferential groove 3 is formed.
The groove width is 5 mm, the oblique groove 6 is disposed at an angle of 65 ° at the tread end position, 55 ° at the main circumferential groove position, and 20 ° at the groove end position with respect to the plane including the tread circumference. The groove width is 3.0 mm at the tread end position and 4. at the groove end position.
The tire has the same structure as that of the invention tire used in Example 1 except that the sipe is arranged at a distance of 5 mm along the circumference of the tread in a direction opposite to the direction in which the oblique groove 6 is arranged.

Example 3 A test was conducted on an invention tire having the tread 1C shown in FIG. The tire size of this invention tire is PSR
225 / 50R16 with a tread width W of 200 mm was used, and one central main groove 8 (groove width:
10 mm) in the central circumferential position, and the width of the main circumferential groove is 8 m
m. The oblique groove 6 has an enlarged maximum groove width (7 mm) near the end thereof, and the oblique groove 6 is disposed at an angle of 70 ° at the tread end position with respect to a plane including the tread circumference. It was set to 60 ° near the position. In addition, a branch groove 9 extending from the end of the oblique groove 6 toward the rear contact area of the tire and extending asymptotically to the main circumferential groove 3 while having a curvature with respect to a plane including the tread circumference and forming a dead end in the land portion is arranged. The groove width of the branch groove 9 was set to 7 mm at the end position with the oblique groove 6 and 3 mm at the end of the branch groove 9. In addition, an auxiliary oblique groove 10 substantially parallel to the oblique groove 6 is provided in the side area 5 at a half pitch position of the pitch of the adjacent oblique grooves 6 along the circumference of the tread, and in the center of the lateral area 5. The auxiliary circumferential groove 12 is arranged along the circumference of the tread. Structures other than the above are the same as those of the invention tire used in Example 1.

Example 4 A test was conducted on an invention tire having a tread 1D shown in FIG. The tire size of this invention tire is PSR
225 / 50R16 with a tread width W of 200 mm is used, and one tread 1 has a central groove 8 (groove width: 4
mm) at the central circumferential position, and the groove width of the main circumferential groove 3 is 6 mm.
And The oblique groove 6 has an enlarged maximum groove width (8 mm) near the end thereof, and the oblique groove 6 is disposed at an angle of 70 ° at the tread end position with respect to a plane including the tread circumference. It was set to 55 ° near the position. Further, there is a branch groove 9 that linearly and taperly extends from the end of the oblique groove 6 in the direction of the rear contact area of the tire. The branch groove 9 is arranged at an angle with respect to the plane including the tread circumference. 14 ° near the circumference and 11 ° near the main circumferential groove, and the groove width is 8 at the end position of the oblique groove 6.
mm and 5 mm at the end of the branch groove 9. In addition, an auxiliary diagonal groove 10 that extends substantially parallel to the diagonal groove 6 and communicates with the branch groove 9 from the side area 5 at a half pitch position of the pitch of the adjacent diagonal grooves 6 along the circumference of the tread, Further, there is provided an auxiliary branch groove 11 which branches from the auxiliary oblique groove 10 located in the side region 5 and extends in the trailing ground contact direction of the tire, intersects with the oblique groove 6 and ends in the land portion. Structures other than the above are the same as those of the invention tire used in Example 1.

Conventional Example A conventional tire having the tread 11 shown in FIG. 4,
The other structures are the same as those of the invention tire used in Example 1. The tire size is PSR 205 / 65R
Two types, 15 and PSR 225 / 50R16, were used.

Test method For the pneumatic tire having the tread shown in FIGS. 1 to 5 described above, a wet road surface was obtained under the conditions that the tire internal pressure was 2.0 kgf / cm 2 and the tire load was equivalent to two real vehicles. Tests were conducted on the drainage performance on the road, the steering stability on a dry road surface, and the putter noise. The drainage property was evaluated by measuring the remaining area of the tire contact surface when running on a wet road surface having a water depth of 6 mm. The steering stability was evaluated by the feeling evaluation of the test driver when running sports on the dry circuit course in various driving modes. Pattern noise is 100 km / h on a straight smooth road.
It was performed by the feeling evaluation of the in-vehicle sound when coasting at / h.

Test results Tables 1 and 2 show the test results. The numerical values in the table are expressed by index comparison with the conventional example being 100 in all tests, and the larger the value, the better.

[0022]

[Table 1]

[0023]

[Table 2]

From these test results, the inventive tire is superior to the conventional tire in drainage performance on a wet road surface and pattern noise performance, and the steering stability on a dry road surface is almost the same or more than that. Is.

[0025]

According to the present invention, the angle of disposition of the oblique groove is made smaller in the central area of the tread with respect to the plane including the tread circumference, and the groove width is made larger, whereby the pattern in that area is formed. Sufficient drainage is obtained without deteriorating noise,
Further, by increasing the angle of disposition of the oblique groove with respect to the plane in both areas of the tread and reducing the groove width of the oblique groove, the drainage performance in the area is not deteriorated and the pattern noise is greatly reduced. Can be reduced. From the above, the present invention, without reducing the driving stability on a dry road surface,
This made it possible to provide a pneumatic tire with low pattern noise and high drainage performance on wet road surfaces.

[Brief description of drawings]

FIG. 1 shows a tread 1A of the pneumatic tire of the present invention used in Example 1.

FIG. 2 shows a tread 1B of the pneumatic tire of the present invention used in Example 2.

FIG. 3 shows a tread 1C of the pneumatic tire of the present invention used in Example 3.

FIG. 4 shows a tread 1D of the pneumatic tire of the present invention used in Example 4.

FIG. 5 shows a tread 1E of a conventional tire used in a conventional example.

[Explanation of symbols]

 1A, 1B, 1C, 1D, 1E Tread 2 Central circumferential line 3 Main circumferential groove 4 Central area 5 Side area 6 Diagonal groove 7 Sipes 8 Central groove 9 Branch groove 10 Auxiliary oblique groove 11 Auxiliary branch groove 12 Auxiliary circumferential groove 13 circumference Groove W tread width

Claims (2)

[Claims] 1. A tread is divided into a central region and a pair of side regions sandwiching the tread by a pair of main circumferential grooves that extend in parallel at least a quarter width of the tread width of a tire from a central circumferential line of the tread. A pneumatic tire having a directional tread pattern in which the tread is divided along the circumference by diagonal grooves that intersect the main circumferential groove, face each other from each side area, and obliquely extend to the central area and end in the central area. In the pneumatic tire, the oblique groove has a groove line whose curvature increases from the side region to the central region, and has a maximum groove width enlarged near the end of the groove. 2. The pneumatic tire according to claim 1, wherein the oblique groove has a groove width that gradually increases from a side area of the tread toward a central area.