JPH10151914A - Pneumatic radial tire for heavy load - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve early abrasion of a center part while showing stone bite prevention effect in a pneumatic radial tire for heavy load. SOLUTION: This radial tire has three peripheral direction grooves 2 extending to tire peripheral direction T on a tread surface 1 and one of the peripheral direction grooves 2 is arranged in a center part and other two are arranged at both sides of the center part and a land part 3 divided by the three peripheral direction grooves 2 is formed and a stone bite preventing projected part 5 is disposed in a groove bottom 2a of the peripheral direction groove 2A arranged in the center part. In this case, a projected shaped part 6 is disposed along the tire peripheral direction T in the groove bottom 2b of the two peripheral direction groove 2B at both sides and also height of the projected shaped part 6 and that of the stone bite preventing projected part 5 are changed so that the height of the stone bite preventing projected part 5 is lower.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heavy-duty pneumatic radial tire, and more particularly, to a heavy-duty pneumatic radial tire designed to improve the early wear of the center portion while ensuring the effect of preventing stone bite. About.

[0002]

2. Description of the Related Art Conventionally, for example, there has been proposed a pneumatic radial tire for heavy loads as shown in FIG. Tread surface 1
1, three circumferential grooves 12 extending in the tire circumferential direction T are provided, and ribs 13 are separately formed by these three circumferential grooves 12. The ribs 13 located on the shoulder portion on the outer side of the tire with respect to the circumferential grooves 12 on both sides have the tire circumferential direction T
The lug grooves 14 are formed at a predetermined pitch along the line.

The circumferential grooves 12 are both formed as straight grooves in order to reduce noise and improve drainage. In the heavy-duty pneumatic tire having such a configuration, there is a problem that the stone is easily bitten particularly in the circumferential groove 12a arranged in the tread center portion. Therefore, as a solution to the above, as shown in FIG. 6, there is a proposal of a tire in which a stone biting prevention projection 15 is provided along the tire circumferential direction T at a groove bottom of a circumferential groove 12a arranged in a center portion. . However, when the projections 15 for preventing stone bite are provided in this manner, the contact pressure on the tread surface near the circumferential groove 12a in the center portion where the projections 15 are provided suddenly increases, so that the center portion of the trend surface 11 is formed. However, there is a problem in that the steel is worn out early.

[0004]

SUMMARY OF THE INVENTION An object of the present invention is to provide a pneumatic radial tire for heavy loads capable of improving the early wear of the center portion while exhibiting the effect of preventing stone bite.

[0005]

According to the present invention for achieving the above object, three circumferential grooves extending in the tire circumferential direction are provided on a tread surface, and one of the circumferential grooves is provided at a center portion and the other two circumferential grooves are provided.
The book was arranged on both sides thereof to form a land portion divided by these three circumferential grooves, and a stone biting prevention projection was provided at the bottom of the circumferential groove arranged at the center portion. In the pneumatic radial tire for heavy load, a convex portion is provided along the tire circumferential direction at the groove bottom of the two circumferential grooves on both sides, and the height of the convex portion and the height of the stone biting prevention protrusion are determined. Are different so that the height of the projection is reduced.

The inventor of the present invention has conducted intensive studies on the early wear of the center portion of the tread surface caused by the stone biting prevention projection. As a result, when the stone biting prevention projection is provided at the groove bottom of the circumferential groove, the projection is formed. It has been found that the spacing between the reinforcing cords of the belt layer facing the portion is expanded at the time of the vulcanization molding, and becomes rougher than other portions. As a result, at the time of filling the internal pressure, the restraining force is low at a rough portion of the reinforcing cord, and the tire expands and protrudes toward the outer diameter side of the tire more than other portions, so that the contact pressure increases. Further study of this protrusion,
It has been found that the higher the height of the protrusion, the coarser the spacing between the reinforcing cords of the belt layer.

Therefore, in the present invention, in addition to the stone biting prevention protrusion provided at the groove bottom of the circumferential groove disposed at the center portion,
In the circumferential grooves on both sides, convex portions similar to the stone biting preventing protrusions are arranged on the bottoms of the grooves, and their heights are made different as described above. This makes it possible to disperse the ground pressure, which tends to concentrate near the circumferential groove arranged at the center of the tread surface, near the circumferential groove arranged on both sides. Therefore, it is possible to prevent early wear of the center portion due to concentration of the ground pressure. In addition, at the same time, the tread surface can be uniformly worn, so that the wear life can be extended.

Further, in a heavy-duty pneumatic tire,
In particular, since the protrusion for preventing stone biting is provided on the groove bottom of the circumferential groove disposed at the center portion where stone biting is likely to occur, the effect of preventing stone biting can be exhibited.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The configuration of the present invention will be described below in detail with reference to the accompanying drawings. FIG. 1 shows an example of a tread pattern of a pneumatic radial tire for heavy loads according to the present invention. Reference numeral 1 denotes a tread surface, and the tread surface 1 is provided with three circumferential grooves 2 extending along the tire circumferential direction T. One of the circumferential grooves is arranged at the center of the tread surface 1 and the other two are on both sides thereof. A land portion 3 including a plurality of ribs is formed separately by the circumferential grooves 3.

Each of the three circumferential grooves 2 is formed as a straight groove, and has a circumferential groove 12A arranged at the center.
Are arranged on the tire equator line CL, and the two circumferential grooves 12B on both sides are arranged symmetrically with respect to the tire equator line CL. All three circumferential grooves 2 have the same groove depth. Note that the straight groove here is a so-called see-through groove that allows the end of the groove to be seen through the tread surface when the tread surface is developed. Therefore, even if the groove is slightly zigzag, if it can be seen through the end of the groove on the tread surface, it belongs to the straight groove.

A lug groove 4 is formed in both shoulder portions 1B on the outer side of the tire by the circumferential grooves 2B on both sides in the tire circumferential direction T.
Are provided at a predetermined pitch. On the groove bottom 2a of the circumferential groove 2A, a stone biting prevention protrusion 5 is provided along the tire circumferential direction T. The projections 5 are provided so as to be separated from both wall surfaces of the circumferential groove 2A,
It is composed of a large number of small block-shaped protrusions 5a arranged along the tire circumferential direction T.

According to the present invention, in the pneumatic radial tire for heavy load having the above-mentioned structure, the stone bottoms 2b of the two circumferential grooves 2B disposed on both sides are provided along the tire circumferential direction T for preventing stone biting. A projection 6 similar to the projection 5 is provided. As shown in FIG. 2, the height H of the convex portion 6 and the height h of the projection 5 for preventing stone bite, as shown in FIG.
Are different from each other. Convex part 6
Is formed so as to be spaced apart from both wall surfaces of the circumferential groove 2 </ b> B in the same manner as the stone biting prevention protrusion 5, and includes a number of small block-shaped protrusions 6 a arranged along the tire circumferential direction T. Have been.

The inventor of the present invention has conducted intensive studies on the premature wear of the center portion of the trend surface caused by the stone bite preventing projections and found the following. That is, as shown in FIG. 3, when a protrusion 7 for preventing stone biting or the like is formed at the groove bottom of the circumferential groove 2, the space between the reinforcing cords 8a of the belt layer 8 facing the protrusion 7 is vulcanized. It was found that it was sometimes pushed out and became rougher than other parts. Therefore, when the internal pressure is charged, the rough portion of the reinforcing cord 8a is weakly restrained, and the portion is inflated and protruded to the outer diameter side of the tire to increase the contact pressure. It was found that the higher the value, the coarser the arrangement interval of the reinforcing cords 8a was.

Therefore, in the present invention, in order to exhibit the effect of preventing stone bite, while the protrusion 5 for stone bite prevention is provided on the groove bottom 2a of the circumferential groove 2A disposed in the center portion as in the conventional case,
Stone biting prevention projections 5 are also provided on groove bottoms 2B of both circumferential grooves 2B.
The convex portions 6 similar to those described above are arranged so that the height of the stone bite preventing projections 5 arranged at the center portion where the ground pressure is high is lower.

In general, the tread surface has a tire meridian cross section formed in an arc shape that is convex toward the tire outer diameter side. Therefore, the contact length becomes longer and the contact pressure becomes higher toward the tire equator (FIG. 4). (A)). If the stone biting prevention projection is arranged as shown in FIG. 6, the contact length on the tire equator line side is further increased as shown in FIG. 4B, and the contact pressure is further increased. In the present invention, the convex portions 6 are also provided on the groove bottoms 2b of the circumferential grooves 2B on both sides as described above, so that the spacing between the reinforcing cords of the belt layer there is made coarse and the ground pressure is increased.
Moreover, by forming the projecting portion 5 for preventing stone bite lower than the protruding portion 6, the interval between the reinforcing cords of the belt layer in the vicinity of the circumferential groove 2A is made denser than in the case of the protruding portion 6, and the grounding thereof is achieved. The pressure is made lower than the vicinity of the circumferential groove 2B.

Therefore, the grounding shape of the tread surface 1 is as shown in FIG. 4 (c), and the grounding pressure distribution from the vicinity of the circumferential grooves 2B on both sides to the circumferential grooves 2A of the center portion 1A is smoothed. And a circumferential groove 2A at the center
The contact pressure, which tends to be concentrated in the vicinity, is reduced by the circumferential grooves 2B on both sides.
Can be dispersed in the vicinity. As a result, the circumferential groove 2
The center portion 1A near A does not wear out early.
Further, since the land portions 3 formed on the tread surface 1 can be uniformly worn, the wear life can be extended.

Further, in the present invention, in the pneumatic radial tire for heavy load, the stone biting prevention projection 5 is provided on the groove bottom 2a of the circumferential groove 2A at the center portion where the stone biting is particularly likely to occur. It does not impair the bite prevention effect. The height H of the convex portion 6 may be in a relationship of 0.1D ≦ H ≦ 0.2D with respect to the depth D of the circumferential groove 2B provided with the convex portion. Also, the height h of the stone biting prevention protrusion 5
Is 0.1 in relation to the height H of the convex portion 6.
H ≦ h ≦ 0.5H can be set.

If the height H of the projection 6 is less than 0.1 D, the height h of the projection 5 becomes too low, and it is difficult to exhibit the stone bite prevention effect. Conversely, if it exceeds 0.2D, the stiffness of the projections will be lost and the convex portions will be torn off due to stone biting and friction with the road surface. The height h of the projection 5 is preferably set to 0.3H ≦ h ≦ 0.5H. In the present invention, in the above-described embodiment, an example in which straight grooves are used as the three circumferential grooves 2 has been described. However, the present invention is not limited thereto, and a heavy-load pneumatic radial in which three circumferential grooves are arranged. Any tire can be suitably used as long as it causes early center wear when a stone biting prevention projection is provided at the groove bottom of the circumferential groove arranged at the center.

[0019]

[Example] The tire size is made common to 11R22.5,
The stone groove prevention protrusion is provided in the circumferential groove arranged on the tire equator line in the center part, and the protrusions are provided in the circumferential grooves on both sides, and the height of the stone bite prevention protrusion is lower than the protrusion. The tire of the present invention having the configuration shown in FIG. 1 and a comparative tire having the same height of the protrusion for preventing stone bite and the convex portion in the tire of the present invention, and the conventional tire 1 having the configuration shown in FIG. The conventional tire 2 having the configuration shown in FIG. 6 in which the stone biting prevention projections were provided only in the circumferential grooves arranged on the tire equator line was manufactured.

In each of the test tires, the depth D of the circumferential groove is 1
The height H of the convex portion in the tire of the present invention is 0.2D, and the height h of the protrusion for preventing stone bite is 0.5H. The height H of the convex portion in the comparative tire is 0.2 D, and the height of the stone biting prevention portion of the conventional tire 2 is 3 mm (0.2 D).

Each of these test tires was rim size 22.5
It was mounted on a rim of × 7.50, the air pressure was set to 700 kPa, and the vehicle was mounted on a 10-ton vehicle. Under the following measurement conditions, an evaluation test of stone bite and early wear of the center was performed. I got

Stone Crushing Property and Premature Wear of Center Part After traveling 50,000 km on a general road, the wear amount of the rib edge part facing the circumferential groove of the center part and the number of bitten stones were measured. Was evaluated with an index value of 100. The larger the value is, the more the early wear of the center portion and the stone bite are improved.

[0023]

[Table 1] As is clear from Table 1, it can be seen that the tire of the present invention can improve the early wear of the center portion while exhibiting the stone bite prevention effect.

[0024]

As described above, the present invention relates to a heavy-duty pneumatic radial tire in which three circumferential grooves are provided and a stone biting prevention projection is provided at the bottom of the circumferential groove disposed at the center. A convex portion is provided at the groove bottom of the two circumferential grooves arranged on both sides, and the height of the convex portion and the height of the stone biting prevention protrusion are adjusted so that the height of the protrusion is reduced. Because of the difference, it is possible to improve the early wear of the center portion without impairing the stone bite prevention effect.

[Brief description of the drawings]

FIG. 1 is a development view of a main portion of a tread surface showing an example of a pneumatic radial tire for heavy loads according to the present invention.

FIG. 2A is a cross-sectional view showing an example of a stone biting prevention protrusion provided on a groove bottom of a circumferential groove, and FIG. 2B is an example of a convex portion provided on the groove bottom of a circumferential groove on both sides. FIG.

FIG. 3 is an explanatory cross-sectional view showing a state in which the arrangement intervals of the reinforcing cords of the belt layer are disturbed and roughened when a protrusion is provided at the groove bottom of the circumferential groove.

FIG. 4 (a) is an explanatory view showing a ground contact shape of a tire tread surface of a conventional heavy-load pneumatic radial tire having the configuration shown in FIG. 5;
(B) is an explanatory view showing the ground contact shape of the tire tread of the heavy-load pneumatic radial tire having the configuration of FIG. 6, and (c) is the ground contact shape of the tire tread of the heavy-load pneumatic radial tire having the configuration of FIG. 1. FIG.

FIG. 5 is a development view of a main part of a tread surface showing an example of a conventional pneumatic radial tire for heavy load.

FIG. 6 is a development view of a main portion of a tread surface showing another example of a conventional pneumatic radial tire for heavy load.

[Explanation of symbols]

1 Tread surface 2, 2A, 2B
Circumferential grooves 2a, 2b Groove bottom 3 Land portion 5 Stone bite prevention protrusion 5a Small block-shaped protrusion 6 Convex portion 6a Small block-shaped protrusion T Tire circumferential direction

Claims (4)

[Claims] 1. A tread surface is provided with three circumferential grooves extending in a tire circumferential direction, and one of the circumferential grooves is provided at a center portion,
The remaining two are arranged on both sides thereof to form a land portion divided by the three circumferential grooves, and a stone biting prevention projection is formed on the groove bottom of the circumferential groove arranged in the center portion. In a heavy-duty pneumatic radial tire provided with a protrusion, a convex portion is provided along the tire circumferential direction at the bottom of two circumferential grooves on both sides, and the height of the convex portion and the protrusion for preventing stone biting are provided. And the height of the protruding portion is reduced so that the pneumatic radial tire for heavy load. 2. The height H of the convex portion is 0.1D ≦ H ≦ 0.2D with respect to the depth D of a circumferential groove in which the convex portion is provided, and the height h of the stone biting prevention protrusion is set to With respect to the height H of the convex portion, 0.
The pneumatic radial tire for heavy loads according to claim 1, wherein 1H≤h≤0.5H. 3. The pneumatic radial tire for heavy loads according to claim 1, wherein the circumferential groove is a straight groove. 4. The pneumatic radial tire for heavy loads according to claim 1, wherein said projecting portion for preventing stone biting and said projecting portion are constituted by small block-shaped projecting portions arranged in the tire circumferential direction.