JP2004098914A - Heavy load tire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a tread pattern capable of maintaining such tread pattern performance as in a new product when wear proceeds on a tread surface. <P>SOLUTION: The heavy load tire comprises three lines of blocks defined on the tread surface by two peripheral grooves extending in zigzag along a tire equator and a number of transverse grooves connecting the peripheral grooves together and the peripheral grooves to tread ends. Side transverse grooves connecting the peripheral grooves to the tread ends have groove widths which get gradually greater from the peripheral grooves to the tread ends, and center transverse grooves connecting the two peripheral grooves together have bent portions at the centers. <P>COPYRIGHT: (C)2004,JPO

Description

【００３２】
かくして得られた試作タイヤを、２２．５×７．５０のリムに組み９００ｋＰａの内圧に調整したのち、２ＤＤダンプカーの車両に装着して、ウェット路での旋回試験に供した。すなわち、半径３０ｍのコンクリート路面周回路に水深２ｍｍで水を撒いて、該周回路の一周毎のラップタイムを１０回測定し、その平均値を算出した。この試験を、タイヤ新品時、タイヤの磨耗末期、そしてその中間の磨耗中期に、それぞれ行った。かくして得られた測定値について、比較例の新品時の測定値を１００としたときの指数にて、表２に表示した。この指数が大きいほど、ラップタイムが短いことを示している。
【００３３】
【表２】

【００３４】
【発明の効果】
この発明によれば、トレッド表面の磨耗が進行した際にも新品時におけるトレッドパターン性能、とりわけウェット性能が維持される、タイヤの提供が可能になる。
【図面の簡単な説明】
【図１】従来のトレッドパターンを示す図である。
【図２】この発明のトレッドパターンを示す図である。
【図３】比較のトレッドパターンを示す図である。
【符号の説明】
１ａ　周方向溝
１ｂ　周方向溝
２　センター横溝
３ａ　サイド横溝
３ｂ　サイド横溝
４　ブロック列
５　ブロック列
６　ブロック列
７　細溝[0001]
[Industrial applications]
The present invention relates to a heavy-duty tire, and more particularly to a heavy-duty radial tire to be used for running on rough roads, and to achieve both traction performance and wet performance.
[0002]
[Prior art]
Frequently used on rough roads, and also used on paved roads, for example, a tire for a dump truck combines a circumferential groove extending along the equator of the tire and a lateral groove extending across the tire. A so-called rib lug pattern is often used. That is, the tread pattern is intended to have both excellent ruggedness in the lug pattern and excellent high-speed running and wet performance in the rib pattern.
[0003]
For example, Patent Literature 1 describes a rib lug pattern that mainly considers running on a rough road. That is, as shown in FIG. 1, two circumferential grooves 10a and 10b extending in a zigzag shape along the equator O of the tire, and between the circumferential grooves 10a and 10b, as well as the circumferential grooves 10a and 10b and the tread end T A large number of lateral grooves 11a to 11c connecting the spaces define three block rows 12 to 14 in a row.
[0004]
This tread pattern secures skid resistance particularly on a wet road surface by extending the circumferential grooves in a zigzag shape, while a large number of circumferential tread patterns are connected between the circumferential grooves and between the circumferential grooves and the tread end T, respectively. Due to the horizontal groove, it is difficult to clog mud into the groove and easy to discharge the mud clogged in the groove, especially on bad roads, so-called mud repellency, difficult to clog stone in the groove, and clogged in the groove The stones are easy to discharge, so-called stone bite.
[0005]
[Patent Document 1]
JP-A-8-72509
[Problems to be solved by the invention]
However, since the contact pressure of the tread contact surface is higher in the central region in the width direction than in the other regions, after the middle stage of wear that progresses with the use of the tire, the edge effect in the central region is reduced, and the wetness is reduced. The problem is that the performance, especially the skid resistance on wet road surfaces, is degraded.
[0007]
SUMMARY OF THE INVENTION The present invention has been made to solve the above problems of the prior art, and its object is to maintain the performance of a new tread pattern even when the tread surface wears. It is to propose a tread pattern.
[0008]
[Means for Solving the Problems]
The gist configuration of the present invention is as follows.
(1) On the tread surface of the tire, two circumferential grooves extending in a zigzag manner along the equator of the tire, and a large number of lateral grooves connecting between the circumferential grooves and between the circumferential groove and the end of the tread, respectively. A heavy load tire in which three block rows are sectioned,
The center lateral groove connecting the two circumferential grooves has a bent portion at the center thereof, while the side lateral groove connecting the circumferential groove and the tread end has a groove width gradually increasing from the circumferential groove toward the tread end. A heavy-duty tire characterized in that:
[0009]
(2) The heavy duty tire according to the above (1), wherein the depth of the circumferential groove is 80 to 100% of the depth of the lateral groove.
[0010]
(3) The heavy duty tire according to the above (1) or (2), wherein the circumferential groove is arranged in an area of 25 to 65% of a half width of the tread centered on the equator of the tire.
[0011]
(4) The heavy load tire according to any one of (1) to (3), wherein the length of the side lateral groove is 50% or more of the half width of the tread.
[0012]
(5) The heavy duty tire according to any one of (1) to (4), wherein the width of the center lateral groove is 30 to 50% of the width of the side lateral groove.
[0013]
(6) The center lateral groove and the side lateral groove extend obliquely with respect to the equator of the tire, and the orientation of the tire with respect to the equator is opposite between the center lateral groove and the side lateral groove. The heavy-duty tire according to any one of the above items.
[0014]
(7) The heavy load tire according to the above (6), wherein the inclination angle of the center lateral groove and the side lateral groove with respect to the equator of the tire is 40 to 90 °.
[0015]
(8) The heavy load tire according to any one of (1) to (7), wherein each block of the block row sandwiched between the circumferential grooves has a narrow groove having a narrow opening width.
[0016]
BEST MODE FOR CARRYING OUT THE INVENTION
Now, the tread pattern of the present invention will be described in detail with reference to FIG.
That is, the illustrated tread pattern includes two circumferential grooves 1a and 1b extending in a zigzag shape along the equator O of the tire, a large number of center lateral grooves 2 connecting between the circumferential grooves 1a and 1b, and a circumferential direction. Three block rows 4 to 6 are formed by partitioning the grooves 1a and 1b and the number of side lateral grooves 3a and 3b connecting the tread ends T respectively.
[0017]
Here, it is important that the center transverse groove 2 connecting the two circumferential grooves 1a and 1b has a bent portion 20 at the center thereof in order to improve the circumferential edge component and prevent the occurrence of side slip. . Thus, when the bent portion 20 is provided at the center of the center horizontal groove 2, it is possible to increase an edge component due to bending, particularly a circumferential edge component, as compared with a normal linear horizontal groove having no bent portion. , A tread pattern that is strong against skidding can be realized.
[0018]
The bent portion 20 preferably has a refraction angle α shown in FIG. That is, when the refraction angle α is less than 70 °, the tip of the bent portion 20 is easily chipped, and when it exceeds 120 °, the water film destruction effect on a wet road and the hooking effect on a road surface on a bad road are reduced. There is a risk.
[0019]
On the other hand, providing the bent portion 20 at the center of the center lateral groove 2 may lead to a decrease in the above-described mud-peeling property. Therefore, the side lateral grooves 3a and 3b connecting the circumferential grooves 1a and 1b and the tread end T are provided. It is important that the groove has a groove width that gradually increases from the circumferential grooves 1a and 1b toward the tread end T in order to improve the mud repelling property and the stone biting property. That is, since the tread in the contact area has a higher contact pressure in the central area than in the width direction side area, mud and stones receive a force to be pushed outward from the tread central area through the lateral grooves. Therefore, by gradually increasing the groove width of the side lateral grooves 3a and 3b toward the tread end T, mud and stone can be pushed out smoothly from the tread central region to the outside.
[0020]
In particular, it is preferable that the groove widths of the side lateral grooves 3a and 3b gradually increase as shown in FIG. 2 so that the ratio Wmax / Wmin of the maximum width Wmax and the minimum width Wmin becomes 1.2 to 2.5. . Because, when the ratio Wmax / Wmin is less than 1.2, the effect of pushing out the above-mentioned mud or stone from the tread central region to the outside is poor, and when the ratio exceeds 2.5, the width of the lateral groove in the tread side region is wide. As a result, the block area in the same area is reduced, and as a result, the block rigidity is reduced, and uneven wear, particularly heel and toe wear, may occur.
[0021]
Further, it is advantageous that the depth of the circumferential grooves 1a and 1b is 80 to 100% of the depth of the lateral grooves 2 and 3a and 3b, particularly in order to improve the skid resistance in the latter half of tread wear. That is, by setting the depth of the circumferential grooves 1a and 1b within the above range, an edge component can be secured until the end of wear, so that the occurrence of side slip can be suppressed even at the end of wear.
[0022]
The circumferential grooves 1a and 1b are preferably arranged in an area of 25 to 65% of a half tread half width TW / 2, which is a half of the tread width, which is an interval between the tread ends T about the equator O of the tire. . This is because, by arranging the circumferential grooves 1a and 1b in the above-described range, an edge component when the vehicle is empty, which will be described later, can be secured.
[0023]
Next, the length of the side transverse grooves 3a and 3b, that is, the axial length of the groove passing through the center of the width of the side transverse groove, is defined as the axial length of the groove extending from the tread end T to the center of the circumferential width of the circumferential grooves 1a and 1b. It is preferable that the distance L is 50% or more of the tread half width TW / 2 in order to continuously secure a sufficient edge component. Specifically, it is preferable that the distance L is about 30 to 80 mm.
[0024]
Further, the width of the center lateral groove 2 is preferably 30 to 50% of the width of the side lateral grooves 3a and 3b, that is, the average groove width of the side lateral grooves 3a and 3b. If the width of the center lateral groove 2 is less than 30% of the average groove width of the side lateral grooves, the mud repelling property is deteriorated. On the other hand, if the width exceeds 50%, the edge component of the ground contact surface may be reduced.
[0025]
Further, the center lateral groove 2 and the side lateral grooves 3a and 3b extend obliquely with respect to the equator O of the tire, and the orientation of the tire with respect to the equator O is opposite between the center lateral groove 2 and the side lateral grooves 3a, 3b. This is advantageous for preventing vehicle flow. That is, by inverting the inclination of the tire with respect to the equator O between the center lateral groove 2 and the side lateral grooves 3a, 3b, forces canceling each other out of each block are generated mutually, effectively acting to suppress the flow of the vehicle. I do.
[0026]
Here, as shown in FIG. 2, the inclination angle of each lateral groove with respect to the equator O of the tire is β, and the inclination angle of the lateral lateral grooves 3a and 3b with respect to the equator O of the tire is γ. β and γ are preferably from 40 to 90 ° in order to ensure excellent traction.
[0027]
Further, it is effective to provide a narrow groove 7 having a narrow opening width in each block of the block rows 4 to 6 sandwiched between the circumferential grooves 3a and 3b in order to strengthen an edge component when the vehicle is empty. In other words, when the vehicle is empty, that is, when the load applied to the tires is small, the contact area is about half of that when the vehicle is loaded. The edge component at the time will be enhanced.
[0028]
Preferably, the opening width of the narrow groove is about 2 to 10 mm and the depth is about 10 to 75% of the depth of the circumferential grooves 3a and 3b. If the width and depth of the narrow groove exceed the upper limits, the rigidity of the block is reduced and the stone biting property is deteriorated. On the other hand, if the width is less than the lower limit, the water film breaking effect may be reduced.
[0029]
In addition, as shown in the figure, it is preferable that the shape of the narrow groove be provided with a bent portion so as to further increase the edge component.
[0030]
【Example】
A tire having the specifications shown in Table 1 based on the tread pattern of FIG. 2 and having a size of 11R22.5 was prototyped. Further, as a conventional example, a tire having the tread pattern shown in FIG. 1 and a tire having the tread pattern shown in FIG. The tread pattern shown in FIG. 3 is different from the tread pattern of FIG. 2 in that a zigzag circumferential groove 1c is further provided at the center of the tread width, and the circumferential grooves 1a to 1c are connected by lateral grooves 3c and 3d, respectively. In particular, the width of the side lateral grooves 3a and 3b is constant.
[0031]
[Table 1]

[0032]
The prototype tire thus obtained was assembled on a rim of 22.5 × 7.50, adjusted to an internal pressure of 900 kPa, mounted on a 2DD dump truck, and subjected to a turning test on a wet road. That is, water was sprinkled at a depth of 2 mm on a concrete road peripheral circuit having a radius of 30 m, and the lap time for each round of the peripheral circuit was measured ten times, and the average value was calculated. This test was performed at the time of a new tire, at the end of tire wear, and at an intermediate period of wear. The measured values thus obtained are shown in Table 2 by using an index when the measured value of the comparative example when the product is new is 100. The larger the index, the shorter the lap time.
[0033]
[Table 2]

[0034]
【The invention's effect】
ADVANTAGE OF THE INVENTION According to this invention, even if the wear of a tread surface progresses, tread pattern performance at the time of a new article, especially the wet performance can be provided, and a tire can be provided.
[Brief description of the drawings]
FIG. 1 is a diagram showing a conventional tread pattern.
FIG. 2 is a diagram showing a tread pattern according to the present invention.
FIG. 3 shows a comparative tread pattern.
[Explanation of symbols]
1a Circumferential groove 1b Circumferential groove 2 Center lateral groove 3a Side lateral groove 3b Side lateral groove 4 Block row 5 Block row 6 Block row 7 Narrow groove

Claims (8)

Three rows of two circumferential grooves extending in a zigzag shape along the equator of the tire on the tread surface of the tire, and a large number of lateral grooves respectively connecting between the circumferential grooves and between the circumferential groove and the end of the tread. A heavy load tire in which a block row of sections is formed,
The center lateral groove connecting the two circumferential grooves has a bent portion at the center thereof, while the side lateral groove connecting the circumferential groove and the tread end has a groove width gradually increasing from the circumferential groove toward the tread end. A heavy-duty tire characterized in that: The heavy load tire according to claim 1, wherein the depth of the circumferential groove is 80 to 100% of the depth of the lateral groove. The heavy load tire according to claim 1 or 2, wherein the circumferential groove is arranged in an area of 25 to 65% of a half width of the tread centered on the equator of the tire. The heavy load tire according to any one of claims 1 to 3, wherein the length of the side lateral groove is 50% or more of the half width of the tread. The heavy load tire according to any one of claims 1 to 4, wherein the width of the center lateral groove is 30 to 50% of the width of the side lateral groove. The center lateral groove and the side lateral groove extend obliquely with respect to the equator of the tire, and the orientation of the tire with respect to the equator is opposite between the center lateral groove and the side lateral groove. Heavy duty tires. The heavy load tire according to claim 6, wherein the inclination angle of the center lateral groove and the side lateral groove with respect to the equator of the tire is 40 to 90 °. The heavy load tire according to any one of claims 1 to 7, wherein each block of the block row sandwiched between the circumferential grooves has a narrow groove having a narrow opening width.

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