JPS62194908A - Heavy duty pneumatic tire - Google Patents

Abstract

PURPOSE:To prevent stones from wedging into a heavy duty tire for busses or the like, by forming a plurality of main grooves in the tread section so that the narrow width of the grooves gradually decreases in the depthwise direction, and by forming a platform on the bottom of each main groove. CONSTITUTION:Zigzagged main grooves G1-G3 are formed in the tread section T of a pneumatic tire. Among these grooves, the main groove G2 is defined by side surfaces (g, g) inclined at an angle alpha of 3-15 deg. so that the width of the groove gradually decreases in the depthwise direction, and a platform P is formed in the bottom of the groove. This platform P is composed of wide width parts PB formed in corner sections and narrow width parts PA formed in the straight sections, the heights Y2, Y3 of the sections PA<PB of the platform P being set to be about 20-60% of the depth Y1 of the groove. Further, the widths S1, S2 of tops of the sections PA, PB are set to be less than the base widths X3, X4 thereof. With this arrangement it is possible to prevent stones from wedging into the tire.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a pneumatic tire for heavy vehicles, and particularly to a pneumatic passenger tire for trucks and buses with reduced stone build-up.

[Conventional technology]

BACKGROUND ART Recently, so-called radial tires, in which metal cords are arranged at a relatively shallow angle in the circumferential direction of the tire, have been frequently used as pneumatic tires for heavy vehicles. This radial tire has excellent wear resistance and puncture resistance because the I and red parts are reinforced, but in order to reduce heat generation, which is always a problem with this type of tire, the tread part is further strengthened. The pattern used is a so-called rib type in which vertical grooves extending in the circumferential direction of the tire are arranged. If this type of tire is driven into a construction site where crushed stones and the like are scattered, stones will form in the vertical grooves.

In particular, since the tread of a radial tire is reinforced by the belt layer of the metal cord, movement of the tread is suppressed, and therefore, once stone buildup occurs, it is tightly bound and difficult to release. As a result, the bottom of the vertical groove is damaged fI4 due to the deformation when the tire is rotated, and this results in damage to the inside of the tire. Note that this type of problem also occurs in tires with a bias structure, although to a lesser extent.

Conventionally, methods to prevent stone build-up have been proposed, such as making vertical grooves two-tiered or forming protrusions that continue in the circumferential direction on the bottom of the vertical groove, but these methods are said to protect the bottom of the groove. Although the effect was recognized from a viewpoint, it was not necessarily sufficient in terms of releasing the trapped stones.

[Problems to be solved]

SUMMARY OF THE INVENTION An object of the present invention is to solve the problem of stone build-up in pneumatic tires for heavy vehicles having a radial structure or a bias structure having a rip-type tread pattern.

[Technical means]

The present invention provides a tread portion with a plurality of zigzag or linear main grooves extending in the circumferential direction of the tire, at least one of the 9M main grooves having a sidewall slope that becomes narrower in the depth direction, A pneumatic tire for a heavy vehicle is characterized in that a platform is disposed on the seabed that is continuous in the circumferential direction or is intermittent in the circumferential direction.

Embodiments of the present invention will be described in detail below with reference to the drawings. FIG. 1 is a partial plan view of the tire tread portion of the present invention;
Figure 2 is an enlarged view of main/RG2, Figure 3 is A- of main groove G2.
A sectional view and FIG. 4 are BB sectional views of the main groove G2. In the figure, the trend portion T has three zigzag-shaped main grooves Gl, G2. G3. A platform P that extends continuously in the circumferential direction is arranged at the bottom of the main groove G2 arranged in the center of the tire.

The platform P is composed of a wide part PB disposed at the interval between the zigzag grooves and a narrow part PA disposed at the straight part 6) of the zigzag groove. Here, the height Y2 of the wide part PB and the narrow part PA of the platform P. Y3 is groove depth Y
It is in the range of 20% to 60% with respect to l. Next, the width St and S2 at the top of the platform P are the width X3 at the base. X4
Each has a smaller cross-sectional shape with a wider base.

That is, X3>Sl and X4>S2. Also wide part PB
The circumferential length L of the narrow portion PA with respect to the circumferential length Ll of
The ratio of 2 is in the range of 30% to 80%.・φAlso L1+
The appropriate length of L2 is 0.3% to 0.8% of the tire's outer circumference when the tire is mounted on a regular rim and filled with the specified internal pressure. Furthermore, each inclination α of the main groove 02 is in the range of 3° to 15°, and by forming the above-mentioned platform P at the groove bottom of the main groove 02, the main groove G2 becomes a raised bottom state, and the grooves of stones stepped on when driving are formed. Not only does it function to prevent stones from entering the groove, but when the platform P touches the ground, it is compressed vertically at the part where it comes into contact with the stones trapped inside the groove, so a repulsive force outwards from the groove is accumulated, When moving from the ground-contact area to the launch area due to transfer, the stones trapped inside the groove are ejected outside due to the repulsive force as the groove width of the main groove 02 is restored. This function can be most effectively exhibited by configuring the wide portion PB and narrow portion PA of Plan I/Home P as described above.

Other embodiments of the present invention are shown in FIGS. 5-8. Figures 5 and 6 show platforms P2 that are continuous in the circumferential direction within the main groove, while Figures 7 and 8 show platforms P3 that are disposed intermittently in the circumferential direction within the main groove. It is.

Example Tire size 10 with tread pattern shown in Figures 1 to 4
．． A 00R20 tire was manufactured as a trial tire according to the specifications shown in Table 1, and its rock-biting properties were evaluated. As comparative examples, one without a platform and one with a changed platform shape were used. .

〔Effect of the invention〕

As described above, the present invention has a platform that is continuous or discontinuous in the circumferential direction at the bottom of the zigzag-shaped main groove extending in the circumferential direction of the tire, so that stones that are taken into the main groove at the contact area during tire movement are removed by the platform. Since it does not reach the bottom and the J-plane of the platform in contact with the stone is compressed in the vertical direction, it is ejected outward from the main groove due to repulsive force when transitioning from the landing area to the launching area. As a result, the stone problem will be effectively reduced.

[Brief explanation of drawings]

FIG. 1 is a partial view of the tie-1/1-red portion of the embodiment of the present invention, and FIG. 2 is an enlarged view of the main groove 02 thereof. Fig. 3 is a cross-sectional view of the main groove G2 along line A, Fig. 4 is a cross-sectional view of main groove G2 along line B-8, Fig. qS5 is an enlarged view of the main groove of another embodiment, and Fig. 6 is its c- CWFR plane view, FIG. 7 is an enlarged view of the main groove of another embodiment, and FIG. 8 is a DD cross-sectional view thereof. T...Tread portion, Gl 02. G3--Main groove, P...-Platform.

Claims (2)

[Claims] (1) The tread portion is provided with a plurality of zigzag or linear main grooves extending in the tire circumferential direction, and at least one of the main grooves has a sidewall slope that becomes narrower in the depth direction;
A pneumatic tire for a heavy vehicle, characterized in that a platform that is continuous in the circumferential direction or discontinuous in the circumferential direction is disposed at the groove bottom. (2) A pneumatic tire for a heavy vehicle according to claim 1, wherein the platform is composed of a wide part and a narrow part.