JPS6355443B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a radial tire with improved uneven wear resistance and wet grip.

Generally, in order to improve the braking force and turning performance of a tire on a wet road surface, it is necessary to effectively eliminate the water that exists between the tread surface and the road surface, so rib and lug types have been traditionally used in the tread pattern. By increasing the groove width or groove depth of the zigzag main groove that extends in the circumferential direction, and by arranging wide lateral grooves that extend from the zigzag main groove to the tread end, water can be effectively directed to the rear and sides of the tire. Excluded. However, when such a tread pattern is applied to a steel radial tire, uneven wear occurs at the rear end of the block in the running direction, so-called heel-and-toe wear, and shoulder wear occurs where the tread shoulder area wears more rapidly than the tread center area. There is a drawback that phenomena such as falling wear occur. That is, in FIG. 1, which shows a partial cross-sectional view of the tire, and FIG. 2, which shows a partial plan view of the tread portion of the tire, a highly rigid steel cord is used for the belt layer 2 of the radial tire, and the tread section is Since the rudder portion is located at the end of the belt layer, the rigidity of the tread is rapidly reduced. Therefore, in FIG. 2, when the tire runs in the direction P, that is, the contact area with the road surface moves from the rear edge E of the block 3a of the tread shoulder section defined by the lateral groove 2 to the front edge F of the block 3b. At this time, since the rear end region of the block 3a is blocked by the lateral groove, wear due to sliding progresses preferentially in this region, resulting in so-called heel-and-toe wear. Therefore, the inventor conducted various studies regarding the problem of uneven wear on radial tires with a rib/lug pattern, and found that the above uneven wear can be effectively prevented by making a predetermined cut in the tread shoulder part. This was discovered and the present invention was achieved. In other words, conventional rib-type treads have a configuration in which the side walls of the zigzag grooves extending in the circumferential direction are partially incised in the lateral direction of the ribs, thereby increasing the number of edges in the circumferential direction of the tire and improving wet grip performance based on the wipe-pink effect. There are known ways to improve this. However, when this is applied to the rib or block part of a rib-lug type tire, it significantly reduces the tread stiffness in the notched area, promotes uneven wear in the tread shoulder part, and impairs steering stability. This is undesirable because it interferes with the environment. Therefore, in the present invention, the above-mentioned problem has been solved by making the cuts made in the tread shoulder part extend from the shoulder main groove to the tread end. Further optimization was achieved by specifying the relationship with the shape and arrangement of the lug type. Therefore, the present invention provides a rebrake type tire with excellent braking power on wet road surfaces.
That is, the object of the present invention is to provide a radial tire that effectively prevents uneven wear of the tread shoulder portion while maintaining wet grip performance.

Embodiments of the radial tire of the present invention will be described below with reference to the drawings. FIG. 3 shows a partial plan view of the tread portion of the radial tire of the present invention, and FIG. 4 shows a partial cross-sectional view. In the figure, the radial tire of the present invention has a pair of zigzag shoulder main grooves 4 continuous in the circumferential direction, and divides the tread surface into a tread center portion 5 and a pair of left and right tread shoulder portions 6. A carcass 7 consisting of a tread part 1 in which the shoulder part is divided into blocks by a sub groove 2 which opens from the shoulder main groove 4 to the tread end, and cords arranged at an angle of 80 to 90 degrees with respect to the tire equatorial plane c. and a belt layer 8 made of steel cord disposed between the carcass 7 and the tread portion 1, and at least the tread shoulder portion 6 of the tread portion has a shoulder main layer 8 at an angle intersecting the tire equatorial plane c. From groove 4 to tread end
It is characterized in that a plurality of notches 9 extending to TE are provided in the circumferential direction.

In the present invention, the notch 9 is a thin cut made by cutting the tread of a vulcanized tire with a knife, and has substantially no groove width. The incisions 9 are preferably substantially straight and equally spaced in the circumferential direction. Therefore, since the notches 9 impart flexibility to the area of the rear end 10, the uneven wear caused by slipping during running is greatly alleviated. Moreover, since the notch 9 has virtually no groove width, the amount of deformation in the direction away from the sub-groove 2 is approximately the same as when there is no notch, so the rigidity of the tread is not unduly reduced and the steering is stable. It does not interfere with various characteristics such as sex. The depth d of the notch 9 should be substantially the same as or less than the groove depth D of the shoulder main groove 4, but in order to fully exhibit the effect of preventing uneven wear, the shoulder main groove 4 should be It is desirable that the groove depth is 20% or more of the groove depth D.
Furthermore, 1 to 3 notches 9 are provided on one block, and the angle α between the notches and the tire circumferential surface is
is preferably set in the range of 45° to 90°. If an unreasonably large number of the above-mentioned notches are provided, the rigidity of the tread block will be reduced, resulting in a significant loss of handling stability and wear resistance.If the angle α is too small, the effect of preventing uneven wear will be reduced and the wet grip performance will be reduced. No improvement was observed.

In the present invention, in order to further improve the effect of the notches 9, it is desirable to adopt the following specific rib/lug type tread. In FIG. 3, the groove width W of the sub-groove 2 is 1 mm or more and 10 mm or less. When the groove width W is less than 1 mm, the heel-and-toe wear phenomenon is hardly observed, and therefore the effect of the notches 9 solely contributes to wet grip performance. Moreover, if it exceeds 10 mm, the effect of improving uneven wear by the cut 9 tends to decrease. Furthermore, the minor groove 2 is 60~
It is preferable that the block be formed at an angle of 120 degrees and be located at the protruding corner 12 of the shoulder main groove, thereby making the corners of the blocks 3a and 3b of the tread shoulder section partitioned by the sub groove 2 obtuse. , effectively preventing local wear and damage to the corners.

Furthermore, in the present invention, one or two central main grooves in the circumferential direction having approximately the same groove width as the shoulder main groove are arranged in the tread center portion 5, thereby further enhancing the drainage effect on the tread surface. Can be done. Furthermore, the notches 9 can be provided not only in the tread shoulder portion 6 but also in the central portion of the tread, in which case the notches 9 in the central portion 5 of the tread exclusively contribute to wet grip properties.

Therefore, in the radial tire of the present invention, when specific notches are made in the tread shoulder portion of the rib-lug type tread, uneven wear in this area can be effectively prevented without reducing the rigidity of the block, and wet grip can be applied. This can further improve performance.

[Brief explanation of the drawing]

FIG. 1 is a partial sectional view of a radial tire, FIG. 2 is a partial plan view of the radial tire, FIG. 3 is a partial plan view of the radial tire of the present invention, and FIG. 4 is a partial sectional view thereof. show.

Claims (1)

[Claims] 1. On the surface of the tread portion of a tire comprising a carcass made of cords arranged at an angle of 80 to 90 degrees with respect to the tire equatorial plane, and a belt layer made of steel cords arranged between the carcass and the tread portion,
A pair of zigzag-shaped shoulder main grooves that are continuous in the circumferential direction are arranged, and the tread surface is divided into a tread center part and a pair of left and right tread shoulder parts, and at least one circumferentially continuous main groove is provided in the tread center part. In the tire, the shoulder portion is provided with a plurality of longitudinal blocks divided into longitudinal blocks in the circumferential direction by a sub-groove that opens from the shoulder main groove to the tread end. Using a thin knife, make a cut in the shoulder section that has virtually no groove width and extends from the shoulder main groove to the tread edge at an angle that intersects the tire's equatorial plane.
A radial tire characterized by having a plurality of treads spaced apart in the circumferential direction by cutting the treads.