JPH04183609A - Radial tire for heavy load use - Google Patents

Abstract

PURPOSE:To prevent the biting of pebbles into narrow grooves while maintaining track wandering resistance by alternately arranging stairlike projections in the circumferential direction of a tire on both sides of the narrow groove provided to the end part of each shoulder of the tire along its circumferential direction. CONSTITUTION:On the tread surface, a plurality of main grooves 5 are provided in the circumferential direction of a tire, so that ribs 6 are formed. On the end parts of both shoulders, narrow grooves 1 are provided along the circumferential direction of the tire respectively, thereby flixibility is given to produce a high track wandering resistance. Further, on the inside walls of the narrow groove 1, a large number of kerfs 7 are provided at regular pitches along the circumferential direction of the tire, so that track wandering resistance can be further enhanced. In the above structure, on the both side walls 2a, 2b of the narrow groove 1, stairlike projections 3 are alternately provided. When pebbles or the like are intruded into the narrow groove through the opening 1a of the longitudinal groove 1, further intrusion is prevented by the upper surfaces 3a of the projections 3, and they are pushed out through the opening 1a.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a heavy-duty radial tire that prevents the narrow grooves in the tire shoulder portion from becoming stoney while maintaining rut-wandering resistance.

[Conventional technology]

BACKGROUND ART Conventionally, in order to improve the rut wandering resistance of radial tires for heavy loads such as buses and trunks, there are tires in which narrow grooves are provided in the shoulder portion of the tire along the tire circumferential direction.

However, when this tire is run on a gravel road or the like, there is a problem in that the narrow grooves become stony, and localized stress is applied to the bottom of the grooves, causing cracks.

Therefore, as a countermeasure to this problem, a proposal has been made in which a large number of protrusions are provided at a predetermined pitch along the circumferential direction of the tire on one side wall surface of the narrow groove.

However, in this proposal, the protrusion is provided only on one wall surface, so when a stone gets stuck, the resistance on the opposite wall surface becomes weaker, making it easier for stones to get stuck. Therefore, stones and the like that once entered the narrow grooves were not pushed out from the openings and entered the bottom of the grooves, which did not provide an essential solution.

Furthermore, as a measure to prevent stones from getting stuck in the grooves as described above, it is conceivable to make the groove width of the narrow groove extremely narrow to the extent that stones do not get caught. However, if this is done, the effect of making the shoulder portion flexible and improving the rut wandering resistance will be diminished.

[Problem to be solved by the invention]

The present invention has been made in view of the above-mentioned circumstances, and an object of the present invention is to provide a heavy-duty radial tire that prevents the narrow grooves of the tire shoulder portion from becoming stoney while maintaining rut wandering resistance.

[Means to solve the problem]

The present invention is a pneumatic tire in which a narrow groove is arranged along one circumference in the tire circumferential direction at the shoulder end of the tire tread,
The tire is characterized in that step-shaped protrusions are alternately arranged on both side wall surfaces of the narrow groove in the tire circumferential direction.

In this way, in the present invention, since the step-like protrusions are provided alternately in the tire circumferential direction on both side wall surfaces of the narrow groove, the protrusion on the side wall on the other side corresponds between the two protrusions on the wall surface on one side. The thrift in plan view has a zigzag shape. Therefore, even if a stone or the like enters the opening of this narrow groove, at least one of the protrusions provided on both side wall surfaces will obstruct the stone or the like and push the stone or the like directly into the opening. In this way, the probability of cracking the groove bottom surface is reliably reduced, and the rut wandering resistance is not reduced.

Hereinafter, the above means will be explained in detail with reference to the drawings.

FIG. 4 illustrates a tread pattern provided on the heavy-duty radial tire of the present invention.

A plurality of main grooves 5 are provided in the tire circumferential direction on the tread surface, and ribs 6 are formed separated by these main grooves 5. A narrow groove 1 is formed along the circumferential direction of the tire at both shoulder ends, and the narrow groove 1 gives the shoulder end flexibility and exhibits a high degree of rut wandering resistance. ing. Further, on the inner wall side of the narrow groove 1, a large number of kerfs 7 are provided with a constant width along the circumferential direction of the tire, thereby further improving the rut wandering resistance.

1 to 3 are enlarged views of the narrow groove 1 provided at the shoulder end as described above.

In these figures, both side walls 2a of the narrow groove l.

2b is provided with step-shaped protrusions 3 alternately so that two protrusions 3 provided on one side wall 2a face each other. Therefore, even if a stone or the like enters through the opening 1a of the vertical groove 1, the upper surface 3a of at least one of the protrusions 3 blocks further entry and is pushed out from the opening 1a. The shape and arrangement of the protrusion 3 are not particularly limited, but preferably the first
As shown in the drawings and FIG. 3, it is desirable to form the grooves in the following manner in relation to the narrow grooves 1.

When the width of the vertical groove 1 is W and the length of the protrusion 3 in the protruding direction is W, W=1.5 to 5.0 mm.

w/W=0.4 to 0.6, where the depth of the vertical groove 1 is D and the height of the protrusion 3 is d, d/D=0.2 to 0.5, as shown in Figure 1. As such, the length h of the protrusion 3 in the tire circumferential direction is h = 3 to 6 ma + The radius of curvature R between the lower part of the protrusion 3 and its opposing side wall surface on the groove bottom surface 1b is R = 1 .0~2.5ga
m The inclination angle θ of the outer surface of the protrusion 3 with respect to the plane orthogonal to the tire rotation axis should be set to θ≧−20°, assuming that the inclination in the direction of increasing the groove width toward the groove bottom is negative (−). .

〔Effect of the invention〕

As explained above, according to the present invention, step-like protrusions are arranged alternately in the tire circumferential direction on both side walls of a narrow groove provided along the tire circumferential direction at the shoulder end of the tire as a rut wandering prevention measure. As a result, even if a stone or the like enters the opening of this narrow groove, the protrusions provided on both side wall surfaces will obstruct it, and the stone or the like will be pushed back into the opening. Moreover, since the narrow grooves are not made extremely narrow, the rut wandering resistance can be maintained.

[Brief explanation of the drawing]

FIG. 1 is an explanatory plan view showing a part of the present invention, and FIG.
The drawing is a perspective view of the protrusion 3 in Fig. 1, Fig. 3 is an explanatory cross-sectional view taken along line A-A in Fig. 1, and Fig. 4 is a plan view showing an example of the trend pattern of the heavy-duty radial tire of the present invention. It is. DESCRIPTION OF SYMBOLS 1... Vertical groove, 1a... Opening part, 2b... Groove bottom, 2a, 2b... Side wall surface, 3... Protrusion part. Figure 1, Figure 3, Figure 4

Claims (1)

[Claims] A pneumatic tire with narrow grooves arranged circumferentially around the shoulder end of the tire tread, the heavy-load radial tire having stepped protrusions arranged alternately in the tire circumferential direction on both side walls of the narrow grooves. tire.