JPH0717216A - Pneumatic tire - Google Patents

Abstract

PURPOSE:To provide a pneumatic tire which has plural lateral grooves at its tread portion and can restrain the occurrence of partial wear and the generation of noise due to vibration of tread portion and secure the drainage property at the last stage of tire wear. CONSTITUTION:A pneumatic tire 1 is equipped with a belt of at least two layers which becomes the crossing arrangement of a comparatively small angle in regard to a plane, and a tread portion 5 strengthened with the belt, at the outer part of a carcass which consists of at least one ply of cords that become substantially directly-angled crossing arrangement in regard to the plane including a tire circumference 2 and forms a toroid shape, and the tire 1 has at its tread portion 5 plural lateral grooves 7 that cross the plane and run along the tire circumference 2 and are arranged at intervals, and as for each lateral groove 7, plural buttresses are equipped at least one of two inside corners formed with a groove bottom 8 and both groove walls 9, 10 and at intervals along a lateral groove 7, and a buttress extends from a top portion that is located on a tire radial inner side than a tread 15 to the lowest portion 16 that coincides substantially with the groove bottom 8 of a lateral groove 7.

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 a plurality of lateral grooves, and more specifically, to a tread by reducing the rate of decrease in bending rigidity along the circumference of the tread due to the arrangement of the lateral grooves. The present invention relates to a pneumatic tire that suppresses noise due to part vibration and that also secures drainage, particularly drainage at the end of tire wear.

[0002]

2. Description of the Related Art In order to secure drainage and the like, a pneumatic tire has a circumferential main groove extending parallel to a plane including the tire circumference, and a lateral groove extending across the circumferential main groove. It is common to have a so-called tread pattern in which tread grooves are arranged, but especially in the case of a block pattern in which the tread land portion is divided by a circumferential main groove and a lateral groove, it follows the tire circumference of the block land portion. The flexural rigidity decreases due to the disposition of the lateral grooves, and the flexural rigidity decreases as the disposition angle of the lateral grooves increases with respect to the plane including the tire circumference.
When it is at least 0 °, the flexural rigidity is remarkably reduced, and when a tire having this tread pattern is subjected to load rolling, the movement of the land edge forming the groove wall of the lateral groove along the tire circumference becomes particularly large. The movement of the land edge causes uneven wear due to dragging and causes noise due to vibration of the tread portion. Therefore, in order to suppress the decrease in the bending rigidity, it is useful to provide a shallow bottom portion having a constant height between the groove bottom of the lateral groove and both groove walls over the entire length of each lateral groove or partially.

[0003]

However, in the pneumatic tire having the shallow groove as described above, which is provided in the entire length of the lateral groove or in a part thereof, at the end of the tire wear, the groove volume of the lateral groove cannot be sufficiently secured and the drainage property is deteriorated. Was supposed to be significantly worse.

Therefore, in the present invention, when the tread portion has a plurality of lateral grooves, a decrease in bending rigidity along the tire circumference of the tread land portion is suppressed as much as possible and the groove volume of the lateral groove at the end of tire wear is secured. Thus, it is an object of the present invention to complete a pneumatic tire capable of suppressing uneven wear and noise due to vibration of a tread portion and ensuring drainage at the end of tire wear.

[0005]

DISCLOSURE OF THE INVENTION The present invention is directed to the outside of a toroidal carcass consisting of at least one ply of cords that are arranged substantially orthogonal to the plane containing the tire circumference, compared to said plane. At least two layers of belts that are arranged in a crossing arrangement with a relatively small angle, and a tread portion reinforced by the belt, and a plurality of lateral grooves that are arranged at intervals along the circumference of the tire intersecting with the plane in the tread portion. ,
Each lateral groove is provided with a plurality of buttresses at intervals along the lateral groove in at least one of the two corners formed by the groove bottom and both groove walls, and this buttress is located on the inner side in the tire radial direction from the tread. The pneumatic tire is characterized in that it extends over the lowest portion that substantially coincides with the groove bottom of the lateral groove.
The buttress referred to here means a protrusion extending outward in the tire radial direction, which is arranged at the corner of the lateral groove, and that the lowest part of the buttress is substantially the same as the groove bottom of the lateral groove from the tread. It means that the ratio of the depth to the lowest position of the buttress to the groove depth of the lateral groove is 0.9 or more.

FIG. 1 shows a part of a tread pattern in which a tread portion is developed of a typical pneumatic tire according to the present invention, and FIG. 2 shows an enlarged oblique view of the lateral groove shown in FIG. A cross section in the width direction is shown in FIG. 3, and reference numeral 1 in FIGS.
Is a pneumatic tire, 2 is a tire circumference, 3 is a carcass, 4
Is a belt, 5 is a tread portion, 6 is a circumferential main groove, 7 is a lateral groove,
8 is the groove bottom, 9 and 10 are groove walls, 11 and 12 are entry corners, 1
3 is a buttress, 14 is a top part, 15 is a tread, and 16 is a lowest part. The pneumatic tire 1 shown in FIGS. 1 to 3 has a toroidal carcass 3 formed of two plies of cords that are arranged substantially orthogonal to a plane including the tire circumference 2. The two-layer belt 4 and the tread portion 5 reinforced by the belt 4 are arranged in an intersecting arrangement with a relatively small angle, and the tread portion 5 has four circumferential main grooves 6
And a plurality of lateral grooves 7 which are arranged so as to intersect with the plane and are arranged at intervals along the tire circumference 2. Note that FIG.
In order to increase tire rigidity, a cap layer 17 that covers the entire surface of the belt and a narrow layer layer 18 that covers both ends of the cap layer 17 are provided.

Each lateral groove 7 is provided with a plurality of buttresses 13 at two entrance corners 11 and 12 formed by the groove bottom 8 and the groove walls 9 and 10 at intervals along the lateral groove 7, and the buttresses 13 are treads 15. 1 located inward in the tire radial direction
4 to the lowest portion 16 which coincides with the groove bottom 8 of the lateral groove 7. In FIG. 5, the inner corners 11 and 1 on both sides of each lateral groove 7 are shown.
The buttresses 13 are arranged in a staggered manner along the line 2, but as long as the lowest portion 16 of the buttresses 13 is at a position substantially corresponding to the groove bottom 8 of the lateral groove 7, as shown in FIG.
1 and the buttresses 13 arranged along the inner corner 12 may be aligned in the same tire width direction cross section, or along the tire circumference 2 reduced by the arrangement of the lateral grooves 7. It may be arranged in only one of the inner corners 11 and 12 as long as the bending rigidity can be reinforced. Besides this,
As shown in FIG. 4d, the buttress 13 may be arranged between the groove bottom 8 and both groove walls 9 and 10, but in this case, the groove depth g from the tread 15 to the lowest portion 16 of the buttress 13 is the lateral groove. It is preferable that the ratio to the groove bottom depth D be 0.9 or more in order to secure drainage at the end of tire wear. In order to secure the groove volume of the lateral groove 7 by providing the buttress 13, particularly the groove volume at the end of tire wear, FIG.
Also, as shown in b), the groove wall position facing the buttress 13 can be recessed. Buttress 13
The cross-sectional shape is preferably rectangular, triangular, trapezoidal, circular, etc., as shown in FIGS. 4a and 4c, but is not particularly limited. As described above, an example of the disposition form of the buttress in the typical tire of the present invention has been shown, but the disposition form of the buttress can be changed under other predetermined conditions.

[0008]

According to the present invention, each lateral groove 7 has a groove bottom 8 and both groove walls 9, 1.
By providing a plurality of buttresses 13 at least at one of the two corners 11 and 12 formed with 0 at intervals along the lateral groove 7, the bending rigidity along the tire circumference 2 of the tread land portion can be reinforced. In addition, the top 14 of the buttress 13
Is located on the inner side in the tire radial direction with respect to the tread 15, so that the tread portion 5 is worn and the buttress top portion 14 is worn.
A sufficient groove volume can be secured until the position is reached. Further, since the lowest portion 16 of the buttress 13 is located at a position that substantially coincides with the groove bottom 8 of the lateral groove 7, a groove volume sufficient to secure drainage is obtained even at the end of tire wear.

[0009]

EXAMPLES Specific examples of the pneumatic tire according to the present invention will be described. The example is based on an invention tire having the tread portion 5 shown in FIGS. 1 to 3, and the tire 1 has a size of 255 / 40R17 and is arranged substantially orthogonal to a plane including the tire circumference 2. Code of 2
On the outside of the toroidal carcass 3 made of ply,
A two-layer belt 4 and a cap layer 17 covering the entire surface of the belt, which are arranged in a 25 ° crossing arrangement with respect to the plane;
A narrow layer layer 18 covering both ends of the cap layer 17,
These belt 4, cap layer 17 and layer layer 18
Equipped with a tread portion 5 reinforced by
It has a land portion row divided by 6 circumferential main grooves 6, and each land portion row is divided by 60 lateral grooves 7a, 7b, 7c arranged at intervals along the tire circumference 2. It consists of a block land area. The lateral grooves 7a, 7b, 7c arranged in each land portion row are arranged at an angle of 75 ° for the lateral groove 7a, 50 ° for the lateral groove 7b, and 90 ° for the lateral groove 7c with respect to the plane. 7a is 6 mm, 6 mm, 7
b was 7 mm, 6 mm, and 7c was 7 mm, 6 mm. In each of the lateral grooves 7a, 7b, 7c, a plurality of buttresses 13 are arranged in a zigzag pattern at two entrance corners 11, 12 formed by the groove bottom 8 and the both groove walls 9, 10 at intervals (7 mm) along the lateral grooves. The buttresses 1 arranged in the entry corners 11 and 12
In relation to each other, the distance a measured along the lateral groove is 10m.
m, the distance b measured in the direction orthogonal to the lateral groove was 1 mm. The top 14 of the buttress 13 is on the inner side of the tread 15 in the tire radial direction, and the height H of the buttress 13 is 4
mm, the width c of the buttress 13 was 2.5 mm, and the thickness d of the buttress 13 was 3 mm.

The conventional example is a conventional tire having a block pattern having no buttress in the lateral groove 7.

The tests were conducted for tire noise, uneven tread wear, and drainage. As the tire noise, the noise when coasting and rolling on the drum was measured. The uneven wear of the tread was evaluated by measuring the level difference between the edges of the tread land portion which constitutes both groove walls of the lateral groove after traveling 5000 km. The drainage property was evaluated by running a turning course having a water depth of 5 mm and a radius of 100 m on a vehicle with each tire in a new state and a final wear state, and measuring the cornering hydroplaning generation rate at this time.

[0012]

[Table 1]

From the test results, the tire noise amount of the embodiment was smaller than that of the conventional example, the uneven wear amount of the tread was small, and the drainage property was the same from the new state of the tire to the end-of-wear state.

[0014]

According to the present invention, in each lateral groove 7, a plurality of buttresses 13 are provided at least along one of the two corners 11 and 12 formed by the groove bottom 8 and the groove walls 9 and 10 at intervals along the lateral groove 7. Since the flexural rigidity of the tread land portion along the tire circumference 2 can be reinforced by including the above, it is possible to suppress uneven wear and noise due to vibration of the tread portion. Further, since the top portion 14 of the buttress 13 is located inside the tread 15 in the tire radial direction, the tread portion 5
A sufficient groove volume can be secured until the buttress 13 reaches the position of the buttress top portion 14 due to wear, and the lowest portion 16 of the buttress 13 is at a position that substantially coincides with the groove bottom 8 of the lateral groove 7, so that at the end of tire wear. Since the groove volume of the lateral groove 7 can be secured, good drainage can be obtained from a new tire state to a final tire wear state.

[Brief description of drawings]

FIG. 1 is a plan view of a tread pattern when a part of a typical pneumatic tire according to the present invention used in an example is developed.

FIG. 2 is a view of a cross-section of a lateral groove obtained by cutting the tread pattern shown in FIG.

FIG. 3 is a cross-sectional view in the width direction of the pneumatic tire shown in FIGS. 1 and 2.

FIG. 4 is a widthwise cross-sectional view of a lateral groove according to the present invention,
It has a buttress shape in which a and b are rectangular, c is triangular, and d is an approximate trapezoid.

FIG. 5a is a plan view of an arrangement shape of a lateral groove according to the present invention as seen from above the tread, and b is a line B- shown in a.
It is a width direction sectional view of a lateral groove cut along a line B.

[Explanation of symbols]

 1 Pneumatic tire 2 Tire circumference 3 Carcass 4 Belt 5 Tread portion 6 Circumferential main groove 7 Lateral grooves 7a, 7b, 7c Lateral groove 8 Groove bottom 9, 10 Groove wall 11, 12 Inlet corner 13 Buttress 14 Top portion 15 Tread 16 Minimum part 17 Cap layer 18 Layer layer

Claims (1)

[Claims] 1. A carcass having at least one ply of cords arranged substantially orthogonally to a plane including a tire circumference, and arranged outside a toroidal carcass at a relatively small angle with respect to the plane. At least two layers of belts,
And a tread portion reinforced with a belt, and the tread portion has a plurality of lateral grooves that are arranged at intervals along the circumference of the tire so as to intersect the plane, and each lateral groove is formed by the groove bottom and both groove walls. At least one of the two corners is provided with a plurality of buttresses at intervals along the lateral groove, the buttress extending from a top located radially inward of the tire to a tire radial direction to a lowest portion substantially matching the groove bottom of the lateral groove. Pneumatic tire characterized by.