JPH04274906A - Tire for heavy load - Google Patents

Abstract

PURPOSE:To prevent wet traction lowering at the latter half of the wear of a tread portion. CONSTITUTION:A tread portion 2 is equipped with a main groove 4 extending in a tire 1 peripheral direction and protrusions 11 separated from groove walls 10 are provided at the groove bottom 9 of the main groove 4 at intervals in the tire peripheral direction, and a recessed groove 12 extending in the peripheral direction is provided at the head top surface 11A of the projection 11.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to heavy-duty tires used for trucks, buses, etc.

0002

[Prior Art] Conventionally, a tread part has a plurality of main grooves extending in the circumferential direction of the tire, and protrusions that are spaced apart from the groove wall at the bottom of the main grooves are provided at intervals in the circumferential direction of the tire. Heavy-duty tires are known (for example, Japanese Patent Application Laid-Open No. 56-79
(See Publication No. 006). This tire can prevent stones from building up in the main groove and protect the groove bottom.

0003

[Problems to be Solved by the Invention] However, in the above-mentioned prior art, the main focus is on preventing stone bite, and no consideration is given to the effect on wet traction when the amount of wear on the tread exceeds a predetermined value. Therefore, when the protrusion on the groove bottom becomes flush with the tread contact surface in the latter half of wear, the groove area is significantly reduced and wet traction is reduced.

The present invention has been made in view of the above-mentioned circumstances, and an object thereof is to provide a heavy-duty tire that can prevent a decrease in wet traction in the latter half of tread wear. .

[0005]

[Means for Solving the Problems] In order to achieve the above object, the present invention takes the following technical measures. That is, the present invention provides a heavy-duty tire having a tread portion with a main groove extending in the circumferential direction of the tire, and a groove bottom of the main groove having protrusions spaced apart from the groove wall at intervals in the tire circumferential direction. The above-mentioned projection is characterized in that a concave groove extending in the circumferential direction is provided on the top surface of the projection.

[0006]

[Operation] According to the present invention, in the latter half of the tire tread wear, the top surface of the protrusion provided at the groove bottom is in contact with the road surface, that is, it is flush with the tread surface, and the main groove groove Even if the area decreases, the groove area reduction rate is reduced by the grooves provided on the top surface of the protrusion, and a decrease in wet traction is prevented. Further, the prevention of stones from entering the main groove and the protection of the groove bottom are not hindered by the concave groove provided in the protrusion.

[0007]

Embodiments Hereinafter, embodiments of the present invention will be explained based on the drawings. In the drawings, reference numeral 1 indicates an automobile tire, which is a pneumatic radial tire used for general roads, snowy and icy roads, heavy loads, etc. The tire 1 has a wide main groove 4 in the circumferential direction from the tread part 2 to the shoulder part 3;
A large number of ribs (blocks) 6 are formed by narrow sub-grooves 5 in the axial direction (width direction), and the carcass 7
and a breaker layer 8 are buried therein.

[0008] The main groove 4 is provided in a zigzag shape in the circumferential direction of the tire 1, and protrusions 11, which are spaced apart from the groove wall 10, are provided on the groove bottom 9 and project at intervals in the tire circumferential direction. The groove wall 10 of the main groove 4 is the tread contact surface 2A.
A part of the side is widened toward the ground plane 2A to prevent stones from forming. The protrusion 11 is provided with a groove 12 extending in the circumferential direction of the tire on the top surface 11A. As shown in FIG. 4, the projection 11 has a projection height H, a projection width A, a groove width B, and a groove depth C in relation to the main groove depth D and the main groove bottom width W.
It is preferable that each dimensional ratio is within the following range. In other words, the ratio of protrusion height H/main groove depth D is preferably 0.2 to 0.4; if it is less than 0.2, the effect of preventing stone bite is insufficient, and if it exceeds 0.4, it may cause a decrease in wet traction. Become. Protrusion width A/main groove bottom width W is 0.3 to 0
．． 5 is desirable; if it is less than 0.3, no stone trapping prevention effect can be expected, and if it exceeds 0.5, it will cause a decrease in wet traction in the latter half of wear. Also, the groove depth C
/Protrusion height H is preferably 0.3 to 0.5; if it is less than 0.3, it is difficult to ensure wet traction, and if it exceeds 0.5, the effect of preventing groove bottom cracking will be reduced. Note that the protrusion height H - groove depth C is set to 1.6 mm, which is the same as the slip sign height. Furthermore, it is desirable that the groove width B/protrusion width A be 0.3 to 0.5; if it is less than 0.3, it will be difficult to ensure wet traction, and if it exceeds 0.5, the effect of preventing groove bottom cracking will be reduced. I can't wait.

[0009] Therefore, a TB of size 10,000R20
Using a radial tire, we conducted tests on three examples with three straight main grooves and the bottom of the center groove set to each of the above dimension ratios, as well as a conventional example and three comparative examples. It was as shown in Tables 1 to 4. In Tables 1 to 4, the circumferential length of the projections 11 is 26 mm, the circumferential interval is 3 mm, and the main groove bottom width W is 7.5 mm.

0010

[Table 1]

[0011]

[Table 2]

0012

[Table 3]

[0013]

[Table 4]

[0014] Furthermore, the wet traction (friction coefficient) in Tables 1 to 4 is expressed as an index based on the conventional example.
After driving on a road surface covered with pebbles of approximately
It represents the number of stones embedded inside. Regarding wet traction, in Table 1, tests were performed on new tires, and in Tables 2 to 4, tests were performed on tires worn to the point where the top surface 11A of the protrusion 11 was in contact with the ground. Furthermore, the number of cracks in the bottom of the groove is calculated by counting the number of cracks in the bottom of the main groove 4 provided with the protrusion 11 after the vehicle is actually running.

As is clear from Tables 1 to 4, Example 1
- 3 are good in terms of the number of stone bites, the number of groove bottoms, and the overall effect of reducing wet traction, and grooves 12
The effect of preventing a decrease in wet traction is remarkable. The present invention is not limited to the above embodiments, and can be applied to tires with various tread patterns.

[0016]

Effects of the Invention As described above, the present invention includes a main groove extending in the circumferential direction of the tire in the tread portion, and protrusions spaced apart from the groove wall at the groove bottom of the main groove at intervals in the tire circumferential direction. This heavy-duty tire is characterized by having a concave groove extending in the circumferential direction on the top surface of the protrusion, which prevents stones from entering the main groove and prevents cracks in the bottom of the main groove. Not only can protection be achieved by prevention, but also a reduction in wet traction in the latter half of wear of the tire tread portion can be achieved.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of a main part of an embodiment of the present invention.

FIG. 2 is a plan view of FIG. 1;

FIG. 3 is a sectional view taken along line III-III in FIG. 1;

FIG. 4 is an enlarged sectional view of the main groove.

[Explanation of symbols]

1 Tires 2 Tread part 4 Main groove 9 Groove bottom 10 Groove wall 11 Protrusion 11A Parietal surface 12 Concave groove

Claims (1)

[Claims] 1. A heavy-duty tire comprising a main groove extending in the circumferential direction of the tire in the tread portion, and protrusions spaced apart from the groove wall at the groove bottom of the main groove at intervals in the tire circumferential direction. A heavy-duty tire, characterized in that a concave groove extending in the circumferential direction is provided on the top surface of the protrusion.