JPS6325107A - Pneumatic tire for heavy car - Google Patents

Abstract

PURPOSE:To lessen the possibility of stone snapping of a tire by forming a straight groove provided on the tread section of the captioned tire for a bus or the like in such a way that slant type side sections having projections at the bottom of the groove and slant.perpendicular type side wall sections forming step sections at the middle are arranged alternately. CONSTITUTION:Londitudinal grooves G1-G3 formed on a tread T are such that the grooves G1 and G2 are zigzag and the central groove G2 is straight. And the groove G2 is formed in such a way that a slant type side wall B slanting at a fixed slant rate and then at a gradually lessening slant rate from the middle section, and a slant.perpendicular type side wall C whose groove width becomes a fixed width from the middle are arranged alternately. And the inclination degrees alpha and beta of the upper and lower side wall sections of the the slant type side wall section B are set at a degree of about 5-25 deg. and about 3-8 deg. respectively, and projections R whose width S1 is about 25-40% of groove depth X1 and whose height Y2 is about 20-60% of groove depth Y1 are also formed at the bottom of the groove. And on the slant.perpendicular side wall section C, a step P is formed at the position of Y3 whose height is about 20-60% of the groove depth Y1. This constitution will lessen the possibility of stone snapping of a tire.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a pneumatic tire for heavy vehicles, and particularly to a pneumatic tire for heavy vehicles that has reduced stone build-up and can be suitably used for heavy vehicles such as trucks and buses. .

[Conventional technology]

Recently, radial tires have been widely used as pneumatic tires for heavy vehicles, in which metal cords are arranged at a relatively shallow angle in the circumferential direction of the tire on the upper side of the crown of a carcass in which metal cords are arranged in the radial direction of the tire. This radial tire has a reinforced tread, so it has excellent wear resistance and
While this type of tire has excellent puncture resistance,
In order to reduce heat generation, a so-called rib type tread pattern in which vertical grooves extending in the circumferential direction of the tire are arranged is used as the tread pattern.

As a result, when this type of tire is driven onto an unpaved road or a construction site where crushed stones are scattered, stones are likely to form in the longitudinal grooves. In particular, since the tread portion of a radial tire is reinforced by the metal cord bell (75), movement of the tread portion is suppressed, and therefore, once stone encroachment occurs, the binding is strong and it is difficult for the stone to be ejected. the result,
As the tire is deformed during rotation, the bottom of the vertical groove may be damaged, and furthermore, the inside of the tire may be destroyed. Although this kind of problem is to a lesser extent in tires with a bias structure, it also occurs in the same way. A method of forming continuous protrusions has been proposed.

[Problem that the invention seeks to solve]

However, although these methods were effective from the perspective of protecting the trench bottom, they were not necessarily sufficient in terms of releasing embedded stones.

An object of the present invention is to provide a pneumatic tire for a heavy vehicle that can solve the problem of stone buildup in a tire having a radial or bias structure having a lip type trend pattern.

[Means for solving problems]

The present invention includes a plurality of zigzag grooves or four linear grooves extending in the circumferential direction of the tire, and at least one of the longitudinal grooves has a groove width in the depth direction of ifi.
A sloped sidewall portion in which the groove width gradually decreases and the rate of gradual decrease decreases from the middle, and a sloped/superposed sidewall portion whose groove width becomes constant from the middle are repeated in the circumferential direction in an intersecting direction IL, and furthermore, the sloped sidewall portion The bottom of the groove is provided with a protrusion spaced apart from both side walls by a certain distance, and the inclined/vertical wall portions are groove-shaped on both sides (2Y! forming a step in the middle of the 1!J wall). This is a pneumatic tire for heavy vehicles.

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, and FIG.
The figure 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 cross-sectional view of the vertical groove G2.

In the figure, a pneumatic tire for a heavy vehicle (hereinafter referred to as a tire) has a tread portion T, for example, three main iG1, G2, and G3 extending in the tire circumferential direction, and vertical grooves on both sides of the tread portion T. G1 and G3 are formed in a zigzag pattern, while the vertical groove G2 arranged in the center of the tire is formed in a straight line. Further, the vertical groove G2 has an inclined side wall portion B having a cross-sectional shape that has a constant slope in the depth direction and whose slope becomes smaller from the middle, and an inclined vertical side wall portion C which has a constant groove width from the middle, alternating in the circumferential direction. is formed. Therefore, the 4g4 diagonal side wall portion B
The side wall has a bent groove shape that is bent in the middle,
The inclination angle α1 of the upper side wall above the bending point of the side wall is 5°.
~25°, the inclination angle ρl of the lower wall below the bending point is 3°
Set in the range of ~8°. In addition, the inclined side wall part B has a projection R.
protrudes from the bottom 8, and the width S1 of this protrusion R is in the range of 25 to 40% of the upper opening X1 of the vertical groove G1, and the height Y2 of the protrusion R is 20 to 40% of the groove depth Yl. It is in the range of 60%. Next, the protrusion R has a rectangular parallelepiped shape with the width 81 at the top equal to the width X3 at the base, or has a wider cross-sectional shape with a wider base. That is, S1≦X
It is 3. Also, the middle x3 at the base of the projection R is set 3 to 6 times narrower than the groove bottom middle x2. Also, the circumferential length Ll of the protrusion R
, when the circumferential length of the part without protrusions on the groove bottom is L2, and the pitch length L=L1+L2, the ratio of Ll to ■ is 3.
It is in the range of 0 to 80%, and in a pinch, it is 0.3 of the tire's outer circumference when the tire is mounted on a regular rim and filled to the specified internal pressure.
~2% is appropriate. The protrusion R is located at the center of the inclined side wall B, and is therefore at the same length as the inclined vertical side wall C. kh is also determined according to the length of the bit.

On the other hand, as described above, the upper side wall part of the side wall of the inclined vertical type side wall part C is inclined so that the groove width becomes narrower in the depth direction, and the inclination with respect to the normal line passing through the ridgeline of the rib is The angle α2 is in the range of 5° to 25°, similar to the inclination angle α1, and is at a height Y3 of 20 to 60% of the groove depth Yl, in this example horizontally or diagonally downward toward the center of the groove. It has a two-step groove shape with inclined steps, that is, platforms P, provided on both side walls, and the lower wall portion is a vertical wall parallel to the normal line, and has a groove width of -.

By configuring groove G2 in this way, which is located in the center of the trend where there are the most stones, the vertical groove G2 becomes raised and the stones stepped on while driving are prevented from penetrating into the groove. At the same time, the protrusion R/platform P is vertically compressed at the part where it contacts the stone that has been taken into the groove at the time of ground contact, so a repulsive force is accumulated toward the outside of the groove, and as the tire is transferred, there is a jump from the contact area. When moving to the protrusion area, as the groove width of the vertical groove 62 is restored, the stone trapped inside the groove is released by the repulsive force.
As a result of experiments, it has been found that configuring the stepped groove portion C as described above can provide the most effective performance and does not impair other performances of the tire.

〔Example〕

Tire circumferential direction 10 of the tread pattern shown in Figures 1 to 4
．． 0 OR20 tires were prototyped according to the specifications shown in Table 1, and their stone catching properties were evaluated. As comparative examples, one without a protrusion or a platform (Comparative Example 1) and one without a platform (Comparative Example 2) were used.

〔Effect of the invention〕

As described above, the present invention is based on forming protrusions and plant platforms that are discontinuous in the circumferential direction on the bottom of the vertical groove extending in the circumferential direction of the tire, and the stone that is taken into the groove at the closest point of tire movement. The stone does not reach the groove bottom due to the protrusion and the platform platform, and the top surface of the protrusion and platform that contact the stone is compressed in the vertical direction, so when it transitions from the stepping area to the kicking area at the time of touchdown, it is stuck in the repulsive force. Since the stone is discharged to the outside of the main groove, the stone build-up is effectively reduced.

[Brief explanation 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 its klG2, Fig. 3 is its I-1 sectional view, and Fig. 4 is its n-Tl A cross-sectional view, FIG. 5 is a cross-sectional view of II[-I[[. 1゛・-Tread part, G1, G2, G3--Vertical groove, R・-Protrusion, P・-Platform.

Claims (1)

[Claims] (1) The tread portion is provided with a plurality of zigzag or linear vertical grooves extending in the circumferential direction of the tire, and at least one of the vertical grooves has a groove width that gradually decreases in the depth direction, and The sloped sidewalls have a smaller rate of gradual decrease, and the sloped/vertical sidewalls have a constant groove width from the middle, which are alternately repeated in the circumferential direction. In addition to providing protrusions that are more regularly spaced,
A pneumatic tire for a heavy vehicle, wherein the inclined/vertical wall portions have a two-step groove shape with a step formed in the middle of both side walls.