JP3357721B2 - Pneumatic radial tire for heavy loads - Google Patents

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 for preventing uneven wear of a shoulder of a heavy-duty pneumatic radial tire. Related to radial tires.

[0002]

2. Description of the Related Art Heavy-load pneumatic radial tires used for trucks, buses and the like have a problem of uneven shoulder wear in that the shoulder ends are worn earlier than the center area of the tread due to the high rigidity of the tread. are doing.
Conventionally, as a countermeasure for suppressing the uneven wear of the shoulder, there is a technique in which a rigid groove at the end of the shoulder is reduced by providing a narrow groove extending in the tire circumferential direction at the end of the tread.

However, when a narrow groove is provided at the end of the tread as described above, a difference in rigidity occurs between the ribs on both sides of the narrow groove, so that cracks are easily generated at the groove bottom, and the narrow groove bottom crack grows. Thus, there is a problem that the thin outer thin shoulder ribs having small rigidity are broken.

[0004]

SUMMARY OF THE INVENTION An object of the present invention is to provide a heavy duty pneumatic radial tire provided with a narrow groove extending in the tire circumferential direction at the shoulder end to prevent uneven shoulder wear. It is an object of the present invention to provide a pneumatic radial tire for heavy loads, the generation of which is reduced.

[0005]

According to the present invention, there is provided a tire for heavy load having a main groove extending in a tire circumferential direction on a tread surface and a narrow groove extending in a tire circumferential direction at a shoulder end. In the pneumatic radial tire, at least one incision extending in the tire circumferential direction is provided on the inner wall of the narrow groove on the inner side of the tire, and the area S _I of the inner wall on the inner side of the tire is calculated from the area S _O of the inner wall on the outer side of the tire. Is also made larger.

As described above, at least one incision extending in the tire circumferential direction is provided on the inner wall of the narrow groove near the tire inner side,
The area S _I of the inner wall of the tire inner side, to be greater than the area S _O of the tire outer Distance <br/> Rino inner wall, to equalize the stress of both the inner wall, reducing the shearing force generated narrow groove bottom By doing so, the occurrence of cracks at the bottom of the narrow groove can be reduced.

Hereinafter, the present invention will be described in detail with reference to the drawings. FIG. 1 is an example of a tread pattern provided on the heavy-duty pneumatic radial tire of the present invention, and FIG. 2 is a sectional view taken along line AA of FIG. In FIG. 1, 3 is a main groove extending in the tire circumferential direction, and 1 is a narrow groove provided at a shoulder end. As shown in FIG. 2, a cut groove 2 extending in the tire circumferential direction is provided on the inner wall of the narrow groove 1 near the tire inside. By providing the kerf 2, the area S _I of the inner wall between AB and near the tire inside is larger than the area S _{O of} A′B near the tire outside. With the configuration having such a cut groove, it is possible to greatly reduce the occurrence of cracks at the bottom of the narrow groove. The reason will be described below with reference to FIG.

As shown in FIG. 5, the contact pressure distribution of a heavy duty pneumatic radial tire having a narrow groove 1 at a shoulder end portion sharply increases around the narrow groove 1. When the incision 2 is not provided, the contact pressure distribution between the rib on the outside of the tire and the rib on the inside of the tire from the narrow groove 1 shows that the rib on the inside of the tire having higher rigidity is larger and thinner as shown by the broken line. The peak is at the edge portion in contact with the groove 1. Accordingly, the shear stress a along the inner wall of the narrow groove 1 along the tire is larger than the shear stress b along the inner wall of the tire outside (a> b). For this reason, a crack is generated at the groove bottom of the narrow groove 1 due to the difference in the shearing force.

On the other hand, when the kerf 2 is provided, a ≒
Since b is obtained, the occurrence of cracks at the groove bottom of the narrow groove 1 is suppressed. However, when the kerf 2 is provided on the inner wall of the narrow groove 1 inside the tire as in the present invention and the area S _I of the inner wall is larger than the area S _{O of} the outer wall, the shear stress a generated on the inner wall becomes And becomes approximately a ≒ b. Therefore, the occurrence of cracks at the groove bottom of the narrow groove 1 is reduced.

In the present invention, the inner wall area S _I of the narrow groove 1 on the inner side of the tire must be larger than the inner wall area S _O of the outer side (S _I > S _O ). Further, in order to obtain the effect of the present invention described above, the number of cut grooves is not limited to one, and may be plural as shown in FIG. Further, the narrow groove is not necessarily required to be perpendicular to the tread surface, and the groove bottom side of the narrow groove 1 may be inclined toward the shoulder side surface as shown in FIG. By inclining the narrow groove in this way, it is possible to prevent chipping and uneven wear of the rib edge from the narrow groove 1 to the inside of the tire.

In the present invention, when the number of the cut grooves 2 provided on the inner wall of the narrow groove 1 on the inner side of the tire is only one,
The depth d and width w of the kerf 2 are set to the narrow groove 1 and the main groove 3 respectively.
, And the groove depth D of the narrow groove 1 is 0.
It is desirable that the values be in the range of 1 ≦ d / W ≦ 0.3 and 0.05 ≦ w / D ≦ 0.1. If the d / W of the kerf 2 is less than 0.1 or the w / D is less than 0.05, the shear stress on the inner wall near the tire inner side cannot be sufficiently reduced. If w / D is less than 0.05, processing is substantially impossible. When d / W is larger than 0.3 or w / D is larger than 0.1, the shear stress a of the inner wall on the inner side of the tire is excessively reduced, and the balance with the shear stress b of the inner wall on the outer side. Collapses and conversely cracks occur.

[0012]

EXAMPLE The tire size was 1000R20, and the tread pattern was such that a narrow groove was provided at the shoulder end as shown in FIG. 1, and the number of cut grooves provided on the inner wall of the narrow groove near the tire inner side was 0. Tires of the present invention made into one, two, and three tires, respectively.
, A total of four types of heavy duty pneumatic radial tires were manufactured.

However, the groove width of the narrow groove: 2 mm, the groove depth D:
The groove width was 14 mm, the groove width w was 1 mm, and the groove depth d was 5 mm. Each of the above four types of tires is rim 20 × 7.
Assembled on a rim at 00T, filled with air pressure of 7.25 kg / cm ² , mounted on a 10-ton load truck,
After traveling m, the number of cracks at the bottom of the narrow groove was visually observed, and the number of cracks having a length of 7 mm or more was counted.
It was shown to. The number of cracks is one less than the number of cracks in the conventional tire.
It was indicated by an index of 00. The lower the index, the smaller the number of cracks generated.

[0014] As is clear from Table 1, the number of occurrences of cracks in each of the tires 1, 2, and 3 of the present invention is significantly reduced as compared with the conventional tire.

[0015]

As described above, the pneumatic radial tire for heavy loads according to the present invention has a notch extending in the tire circumferential direction on the inner wall near the tire inner side of the narrow groove provided at the shoulder end along the tire circumferential direction. Since the area S _I of the inner wall on the inner side of the tire is made larger than the area S _O of the inner wall on the outer side of the tire, the shear stress generated on both the left and right inner walls of the narrow groove is balanced and generated at the bottom of the narrow groove. Cracks can be reduced.

[Brief description of the drawings]

FIG. 1 is a plan view showing an example of a tread pattern provided on a pneumatic radial tire for heavy loads according to the present invention.

FIG. 2 is a sectional view taken along line AA of FIG.

FIG. 3 is a sectional view of a shoulder end portion of a tire according to another embodiment of the present invention.

FIG. 4 is a sectional view of a shoulder end of a tire according to still another embodiment of the present invention.

FIG. 5 is an explanatory diagram showing a pressure distribution near a narrow groove.

[Explanation of symbols]

 1 Narrow groove 2 Cut groove 3 Main groove

Continuation of front page (58) Field surveyed (Int.Cl. ⁷ , DB name) B60C 11/01-11/13

Claims (2)

(57) [Claims] 1. A heavy-duty pneumatic radial tire in which a main groove extending in a tire circumferential direction is provided on a tread surface and a narrow groove extending in a tire circumferential direction is provided at a shoulder end portion, wherein the inner wall of the narrow groove near the tire inner side is provided. A pneumatic radial tire for heavy load, wherein at least one groove is provided in the tire circumferential direction, and the area S _I of the inner wall near the tire inner side is larger than the area S _O of the inner wall near the tire outer side. 2. One of the kerfs is provided, and the depth d and the width w of the kerfs are determined with respect to the groove depth D of the narrow groove and the distance W between the narrow groove and a main groove adjacent thereto. , Each 0.1 ≦ d /
2. The method according to claim 1, wherein W ≦ 0.3 and 0.05 ≦ w / D ≦ 0.1.
The pneumatic radial tire for heavy loads according to 1.