JPS5963206A - Pneumatic tire for heavy load - Google Patents

Abstract

PURPOSE:To improve wear resistance of a block pattern, by a method wherein the entire surface area of a second block file is made larger than that of a shoulder block file and both blocks are arranged in a crossing state so that center lines of lateral grooves of both blocks do not coincide with each other. CONSTITUTION:A tread area of a land part of a second block file 4 is made larger than that of a shoulder block file 3 by making an opening area in a tread of a lateral groove 5 of the shoulder block file 3 larger than that of the second block file 4. Both the blocks are arranged in an uneven state so that the lateral grooves 5 and 6 of both the blocks 3 and 4 do not become in a line with each other. With this construction, effective expansion of an effective tread area and alleviation of concentration of the tread in a block edge of an edge part of the lateral grooves 5 and 6 are contrived as a whole and an improvement in wear resistance is realized.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a pneumatic tire for heavy loads, and particularly aims to propose an improvement in the tread pattern thereof.

The so-called block pattern of conventional tires of this type has the advantage of superior grip performance on wet roads, but its structure reduces the actual contact area with the road surface within the contact patch (
(hereinafter referred to as "effective ground contact area") 1 [It had the disadvantage of inferior wear performance compared to the rib pattern, that is, the wear life was shortened.

Conventional measures aimed at improving the wear life of block tires include increasing the groove depth and reducing the groove area, but these all increase the tread weight. However, there were disadvantages associated with cost disadvantages.

The object of this invention is to improve the wear performance of a block pattern without increasing tread weight.

In general, the block pattern of pneumatic tires for heavy loads such as trucks and buses has eight or more circumferential grooves extending along the circumference of the tread, and these grooves form at least the outermost shoulder block row of the tread and the adjacent inner side thereof. Each block in the same block row has substantially the same width through both block rows, and the surface of these blocks is 7001111.
Hereinafter, it is customary to form the above-mentioned tread with a crown radius of 300 or more.

The concept of the present invention, which is an improvement on such a block pattern, is shown in FIG. 1(a) and compared with FIG. 1(b), which shows the basics of the conventional block pattern. In the figure, 1 is the tread, 2 is the circumferential groove, 8 is the shoulder block row, 4 is the second block row, 8'14' is each block in both book rows, and 5°6 indicates both block rows. 7 is the equator of the tire.

Now, the crown radius mentioned above should meet the requirements of suppressing uneven wear before complete tread wear and preventing separation at the end of the belt or breaker.
It is determined based on empirical rules, but as a result, under normal use conditions, under the action of the load applied to the tire and the internal pressure filled in the tire to counter this, the tread is parallel to the equator 7. The contact length of the tread in the second block row is longer than that in the shoulder block row 8. Therefore, the opening area in the ground contact surface of the horizontal groove 5 of the shoulder block row 8 is made larger than that of the horizontal groove 6 of the second block row 4.
By making it larger than that of , the effective ground contact area can be advantageously expanded as a whole, which can contribute to improving wear resistance performance.

On the other hand, in the arrangement in which the lateral grooves 5 and 6 are aligned in the lateral direction of the tread as shown in Fig. 1(b), both block rows 8゜4 face the block Bl toward the contact area, and the stepping and kicking of blocks 41 from the contact area. At the time of ejecting, the wear life deteriorates due to uneven wear called heel-and-toe wear.However, as shown in FIG.
6 in a staggered arrangement in which their center lines do not coincide, adjacent blocks are always located on the extension of both lateral grooves 5-6, so that the ground pressure is concentrated at the block edge at the edge of the lateral grooves 15.6. This effectively alleviates the ground pressure, and therefore, the ground pressure is evenly distributed over the entire block surface, which effectively helps prevent uneven wear.

In the illustrated example of FIG. 1(a), the total number of blocks in the second block row is 1/2 of that in the shoulder block row.
However, it is also the best embodiment in terms of uniformity of ground pressure distribution, and is more advantageous for the purpose of the present invention.

On the other hand, in the case of FIG. 1, etc., the entire ridge area of the tread 1 is the same as the example of FIG. 1(a), but the effective ground contact area is much smaller.

Therefore, by improving the block pattern according to the present invention shown in FIG. 1(a), compared to the conventional pattern shown in FIG. 1(b), advantageous improvement in wear resistance can be achieved without increasing the tread weight. This can be achieved by preventing.

Roughly speaking, in this invention, each block has the same surface shape within the same block row, the angle of the center line of the lateral groove 5.6 with respect to the tire equator 7 is 80 to 90 degrees, and each block has the same surface shape. The length on the tread circumference corresponds to 60 to 984 of the arrangement pitch, and the width of the lateral groove 6 in the second block row 4 is 1/3 or less of the length on the tread circumference (of the block 8' in the shoulder block row 8). It is also preferable that the block arrangement pitch in the shoulder block row 3 be 10 to 60 times the width of one tread, from the viewpoint of making the ground pressure distribution uniform and maintaining and improving wet resistance performance.

Regarding the tire of the embodiment shown in Fig. 1(a).

The center line of the lateral groove 6 in the second block row 4 passes through the longitudinal center of the block 3' of the adjacent shoulder block row 3, and the width of the lateral groove 5 in the shoulder block row 3 is equal to the width of the lateral groove 6 in the second block row 4. (Of course, the groove width must not be such that the total surface area of the blocks in the second block row 4 is equal to or less than the total surface area of the blocks in the shoulder block row 8.)
I like it a lot.

In Section 2 II (a) and (b), a more practical block pattern improvement A according to the present invention was compared with the conventional block pattern B.

Each pattern was applied to a test tire of size 1000R20, and an actual driving test was conducted, and the improvement effect of the block pattern according to the present invention was shown in the table below, with the result of the conventional pattern set as 100.〇Note-Index The uneven wear index in the table is approximately 50,000 km after driving with the drive shaft installed.
The reciprocal of the amount of step difference occurring between the leading ground contact part and the trailing ground contact part within one block at a time point is converted into an index.

Furthermore, the wear resistance index is an index of the reciprocal of the amount of wear under the same conditions as the uneven wear index.

As described above, according to the present invention, the ridge area in the shoulder block row can be reduced without increasing the tread weight accompanying conventional measures such as deepening the tread grooves or narrowing the groove area. By making it larger in the second block row, the effective tread contact area is expanded and wear resistance performance is advantageously improved.The staggered arrangement of blocks in each row effectively prevents uneven wear. As a result, the wear life of heavy-duty tires can be significantly increased without deteriorating the grip performance on wet roads due to the block pattern.□

[Brief explanation of the drawing]

Figures 1 (a) and (b) are pattern comparison diagrams comparing the improvement of the block type tread pattern by this invention with a conventional example, and Figures 2 (a) and (b) are diagrams for confirming the effects of this invention. FIG. 3 is a diagram showing each part of the test tires used. 1... Tread, 2... Circumferential groove, 3... Shoulder block row %3'... Shoulder block, 4... Second block row, 4'... Second block, 5.6
...Horizontal groove O Fig. 1 (a) (b) Fig. 2 (a) (b)

Claims (1)

[Scope of Claims] L: Eight or more circumferential grooves extending along the circumference of the tread are provided, and these grooves partition at least the outermost shoulder block row of the tread and the second block row adjacent to the inner side of the shoulder block row. Each block in the same block row shall have substantially the same width throughout both block rows, and the above-mentioned tread with a crown back length of 700 squares or less is formed by the surfaces of these four wheels. - The total block surface area of the second block row is larger than that of the shoulder block row, and the extension of each center line is the same as that of the horizontal groove extending between the shoulder block row knob blocks and that of the second block row. do not. A heavy-duty pneumatic tire characterized by a tread pattern that is interlocking. 2. The tire according to 1, wherein each block in the shoulder block row and the second block row exhibits the same surface shape as each other within each block row & lateral grooves extending between the blocks in the shoulder block row and the second block row, respectively. 3. The tire according to 1 or 2, wherein the center line of the tire has an angle of 80 to 90 degrees with respect to the equator of the tire. 4. The tire according to 1, 2 or 3, in which each block in the shoulder block row and the second block row spans a length on the tread circumference corresponding to 60 to 98 degrees of the respective arrangement pitch. 5. The tire according to any one of 1 to 4, wherein the width of the lateral groove extending between the blocks in the second block row is 1/3 or less of the length on the tread circumference of the blocks in the shoulder block row. The block arrangement pitch in the shoulder block row is 10 to 60' of the tread width! The tire according to any one of 1 to 5. 7. The total number of blocks in the second block row is less than the total number of blocks in the shoulder block row (1 to 6) (tires listed in any one of q. & The total number of blocks in the shoulder block row is an even number and 1
7. The tire according to 7, wherein the total number of blocks in the secondary block row is 1/2 of that number. 9. The tire according to 7 or 8, wherein the center line of the lateral groove extending between the blocks in the second block row passes through the longitudinal center of the blocks in the adjacent shoulder block row. 1α Is the width of the horizontal groove separating the blocks in the shoulder block row the same or less than that in the second block row? Or the tire according to 8.