JPH064365B2 - Pneumatic tires for heavy vehicles - Google Patents

Description

TECHNICAL FIELD The present invention relates to a pneumatic tire for a heavy vehicle, and particularly to a pneumatic tire for a heavy vehicle that can be suitably used for a heavy vehicle such as a truck or a bus with reduced stone entrainment. .

[Conventional technology]

Recently, as a pneumatic tire for a heavy vehicle, a radial tire in which metal cords are arranged at a relatively shallow angle in the tire circumferential direction above a crown portion of a carcass in which metal cords are arranged in the tire radial direction is widely used. This radial tire has a tread portion reinforced, so wear resistance,
While excellent in puncture resistance etc., in this type of tire,
A so-called rib type in which vertical grooves extending in the tire circumferential direction are arranged to reduce heat generation is adopted as a tread pattern.

As a result, when tires of this kind enter a construction site where unpaved roads, crushed stones, etc. are scattered, stone chips are likely to occur in the vertical grooves. In particular, since the tread portion of the radial tire is reinforced by the belt layer of the metal cord, the movement of the tread portion is suppressed, and therefore, once stone entrapment occurs, the binding is strong and the stone is difficult to be released. As a result, the groove bottom of the vertical groove is damaged due to the deformation during tire rotation, and further, the inside of the tire is broken. It should be noted that this kind of adverse effect is small to the tire with the bias structure,
The same happens.

Therefore, conventionally, a method of forming the vertical groove in two stages, a method of forming a protrusion continuous in the circumferential direction in the vertical groove, and the like have been proposed.

[Problems to be solved by the invention]

However, although these methods are effective from the viewpoint of protecting the bottom of the trench, they were not necessarily sufficient in terms of releasing the bite stone.

It is an object of the present invention to provide a pneumatic tire for a heavy vehicle, which can solve the problem of stone entrapment in a tire having a radial structure or a bias structure having a rib type tread pattern.

[Means for solving problems]

The present invention comprises a plurality of zigzag or straight flutes extending in the tire circumferential direction in the tread portion, at least one of the flutes having a groove width gradually decreasing in the depth direction, and The slanted side wall part where the rate of gradual decrease decreases from the middle and the slanted / vertical side wall part with a constant groove width are alternately repeated in the middle in the circumferential direction. The pneumatic tire for a heavy vehicle is characterized in that a protrusion spaced apart from the wall by a predetermined distance is provided, and the inclined / vertical wall portion has a two-step groove shape that forms a step in the middle of both side walls.

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a partial plan view of a tire tread portion of the present invention, FIG.
The drawing is an enlarged view of the vertical groove G2, FIG. 3 is a sectional view taken along the line I-I of the vertical groove G2, and FIG. 4 is a sectional view taken along the line II-II of the vertical groove G2.

In the figure, a pneumatic tire for a heavy vehicle (hereinafter referred to as a tire) has, for example, three main grooves G1, G2, G3 extending in the tire circumferential direction in a tread portion T, and the tread portion T has longitudinal grooves on both sides. The grooves G1 and G3 have a zigzag shape, while the vertical groove G2 arranged in the center of the tire is linearly formed. Further, the vertical groove G2 has an inclined side wall portion B having a cross-sectional shape with a constant inclination in the depth direction and a small inclination from the middle, and an inclined vertical side wall portion C having a constant groove width from the middle alternately in the circumferential direction. Is formed in. Therefore, in the inclined side wall portion B, the side wall has a bent groove shape that is bent in the middle, and the inclination angle α1 of the upper side wall portion above the bending point of the side wall is 5 ° to 5 °.
25 °, the inclination angle β1 of the lower side wall below the bending point is 3 ° ~
Set in the range of 8 °. A projection R projects from the groove bottom on the inclined side wall portion B, and the width S1 of the projection R is the vertical groove G.
1 is in the range of 25 to 40% of the upper opening width X1, and the height Y2 of the protrusion R is in the range of 20 to 60% with respect to the groove depth Y1. Next, for the protrusion R, the width S1 at the top is set to the width X at the base.
A rectangular parallelepiped shape equivalent to that of No. 3 or a cross-sectional shape of a tossle that is formed to be smaller than that and has a wide spread. That is, S1 ≦ X3
Is. The width X3 of the base of the protrusion R is set to be 3 to 6 mm narrower than the groove bottom width X2. Also, the circumferential length L1 of the protrusion R, the circumferential length L2 of the portion having no protrusion on the groove bottom, and the pitch length L = L
When 1 + L2, the ratio of L1 to L is 30 to 80
%, And the pitch L is preferably 0.3 to 2% of the outer circumference of the tire when the tire is mounted on the regular rim and the specified internal pressure is filled. The protrusion R is located at the center of the inclined side wall portion B, and therefore the length ratio to the inclined vertical side wall portion C is also determined according to the pitch length.

On the other hand, the upper side wall portion above the side wall of the inclined vertical type side wall portion C is inclined so that the groove width becomes narrow in the depth direction as described above, and is inclined with respect to the normal line passing through the ridge line of the rib. The angle α2 is in the range of 5 ° to 25 ° similarly to the inclination angle α1, and at a position of a height Y3 of 20 to 60% of the groove depth Y1, in this example, it is horizontally or obliquely downward toward the groove center. It has an inclined step, that is, a two-step groove shape in which the placket home P is provided on both side walls, and the lower side wall is a vertical wall that is horizontal to the normal line and has a constant groove width.

By configuring the vertical groove G2 located in the central portion of the tread with the most stones in the groove of the tread in this way, the vertical groove G
2 is in the bottom position, which prevents stones trampled during running from intruding into the groove, and the projection R and the bracket home P are vertically compressed at the portions that come into contact with the stones taken into the groove when touching down. When the repulsive force to the outside of the groove accumulates, and when the tire moves to the jumping-out area from the ground contact step due to rolling, it is taken into the groove due to the above-mentioned repulsive force as the groove width of the vertical groove G2 is restored. Stones will be released to the outside. Experiments have shown that such a function can be most effectively exhibited by constructing the groove portion B having the projection R and the two-step groove portion C as described above, and does not impair other performances of the tire.

〔Example〕

Tire size 10 with tread pattern shown in Figs.
A tire of 00R20 was prototyped according to the specifications shown in Table 1 to evaluate the stone carburizing property. As comparative examples, those without protrusions and placket homes (Comparative Example 1) and those without plaquette homes (Comparative Example 2) were used.

〔The invention's effect〕

As described above, the present invention is based on forming a protruding plaquette platform intermittently in the circumferential direction on the groove bottom of the longitudinal groove extending in the tire circumferential direction, and a stone trapped in the groove at the most ground contact point of the tire movement is The projection does not reach the bottom of the groove due to the placket home, and the projection that comes into contact with the stone and the top surface of the placket home are compressed in the vertical direction, so the main groove is repulsive when moving from the stepping area to the kicking area at the time of touchdown. It will be released to the outside of, and stone chew will be effectively mitigated.

[Brief description of drawings]

FIG. 1 is a partial plan view of a tire tread portion showing an embodiment of the present invention, FIG. 2 is an enlarged plan view of a longitudinal groove G2 thereof, FIG. 3 is its I-I cross-sectional view, and FIG. 4 is its II. -II cross section, 5th
The figure is a III-III sectional view thereof. T ... tread portion, G1, G2, G3 ... vertical groove, R ... protrusion,
P ... Plaquette home.

Claims (1)

[Claims] 1. A tread portion is provided with a plurality of zigzag-shaped or linear flutes extending in the tire circumferential direction, and at least one of the flutes has a groove width gradually decreasing in the depth direction,
In addition, the sloped side wall portion where the rate of gradual decrease decreases from the middle and the sloped / vertical side wall portion with a constant groove width are alternately repeated in the circumferential direction, and the groove bottom of the sloped side wall portion is A pneumatic tire for a heavy vehicle, characterized in that a protrusion is formed at a constant distance from both sidewalls, and the inclined / vertical wall portion has a two-step groove shape that forms a step in the middle of both side walls.