JPH0752613A - Pneumatic radial tire for heavy load - Google Patents

Abstract

PURPOSE:To reduce occurrence of stone biting and edge crack without impairing braking drive performance of closed siping itself. CONSTITUTION:In a pneumatic radial tire for heavy load which has a rib pattern or a block pattern and in which a closed siping 5 in which a bent siping section 5e which extends in the peripheral direction of tire is formed at both ends of a central siping section 5c which extends in the cross direction of tire is provided on the rib or block, width (t) of the central siping section 5c is 0.4-0.6mm, and width T of the bend siping 5e is more than twice the width (t) of the central siping section 5c.

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 in which damage such as edge cracks of closed sipes provided on ribs or blocks is reduced.

[0002]

2. Description of the Related Art A rib pattern or a block pattern is often used for a tread pattern of a heavy-duty pneumatic radial tire (hereinafter referred to as a heavy-load radial tire), but the pattern is constructed to improve its braking drive performance. There are ribs and blocks that have closed sipe so that both edges stop inside.

However, the closed sipes described above
Generally, the width is about 0.8 mm or more, so it is easy to bite stones,
There is a drawback that cracks are likely to occur on both edges of the closed sipe due to the stone being caught. Moreover, there is a problem that the cracks once generated easily grow and eventually cause tread chipping. As a measure to solve this problem, narrow the width of closed sipes,
There have been proposals such as a method of bending the central portion to form a “V” shape, or making the central portion shallow (raising the bottom). However, none of these measures has the drawback that the effect of preventing stone trapping or the effect of suppressing the generation of cracks on both edges is insufficient, or that the effect of the sipe's original braking and driving performance is reduced, It wasn't satisfactory.

[0004]

SUMMARY OF THE INVENTION The object of the present invention is to prevent the original closed-sipe braking and driving performance from being impaired.
An object of the present invention is to provide a heavy-duty radial tire that can reduce the occurrence of stone trapping and edge cracking.

[0005]

The present invention for achieving the above object has a rib pattern or a block pattern, and the rib or block extends in the tire circumferential direction at both ends of a central sipe portion extending in the tire width direction. In a heavy-duty pneumatic radial tire provided with a closed sipe forming a bent sipe portion, the width t of the central sipe portion is 0.4 to 0.6 mm, and the width T of the bent sipe is the width of the central sipe portion. It is characterized in that it is twice or more than t.

As described above, the width of the central sipe portion of the closed sipe is set to 0.4 to 10 which is narrower than the conventional sipe width of 0.8 mm.
By making it 0.6 mm, it becomes difficult to open and it is hard to cause stone trapping, and at the both ends of this central sipe portion, by providing a bent sipe portion that is at least twice its width,
The stress applied to the edge can be dispersed to suppress the occurrence of cracks and tread chipping.

The present invention will be described in detail below with reference to the drawings. 2 and 3 show examples of a rib pattern and a block pattern provided in the heavy duty radial tire of the present invention, respectively. In the former rib pattern, a plurality of main grooves 1 extending in the tire circumferential direction form a plurality of ribs 3, and the ribs 3 are provided with closed sipes 5. In the latter block pattern, the main groove 1 and the lateral groove 2 are provided to form a plurality of blocks 4, and the blocks 4 are provided with the closed sipes 5.

FIG. 1 shows an example of a closed sipe 5 formed on the rib or block described above. The closed sipe 5 includes a central sipe portion 5c having a width t that is inclined at an angle α with respect to a tire radial direction FF ′, and a tire circumferential direction E− that is bent from both ends of the central sipe portion 5c.
Bend sipe portion 5e having a width T inclined at an angle β with respect to E ′
It consists of

In the present invention, the width t of the central sipe portion 5c is
Is narrower in the range of 0.4 to 0.6 mm, and the width T of the bent sipe portion 5e is twice or more the width t of the central sipe portion 5c. If the width t of the central sipe portion 5c is larger than 0.6 mm, the central sipe portion 5c is easily opened and the effect of suppressing stone trapping is deteriorated. On the other hand, if it is less than 0.4 mm, the sipe forming property is deteriorated and the tire productivity is lowered. On the other hand, bent sipes 5
If the width T of e is less than twice the width t of the central sipe portion 5c, the stress dispersion effect at the edge of the bent sipe portion 5e becomes small, and the edge crack cannot be reduced.

When the width T of the bent sipe portion is set to be twice or more the width t of the central sipe portion, a large radius of curvature R can be easily attached to the edge. Can be further dispersed. The upper limit of the width T of the bent sipe portion is not particularly limited, but if it is set too large,
Since the bent sipe portion easily causes stone trapping, it is preferable to set the upper limit to about 4 times the width t of the central sipe portion.

In the closed sipe formed in the rib or block in the present invention, the angle α of the central sipe portion with respect to the tire radial direction FF ′ is set in the range of −30 ° to + 30 °, and the tire circumference of the bent sipe portion is set. It is desirable that the angle β with respect to the direction EE ′ be in the range of −15 ° to + 15 °. Also, the depth of the closed sipes should be the same along the length direction so that the edge effect can be exhibited until the end of wear.

[0012]

EXAMPLES Tires 1 and 2 of the present invention and tires 1 to 3 of the present invention in which the tire size, the tread pattern, and the number of sipes in the tire are common as shown below, and the shapes and dimensions of the sipes are different as shown in Table 1 are as follows. And a comparative tire was manufactured.
(Note that the angle α of the central sipe portion and the angle β of the bent sipe portion of the closed sipes of FIGS. 4 and 6 were each 0 °, and the length of the bent sipe was 3 mm.) Tire size: 11R22.5 14PR tread pattern: Fig. 2 (rib pattern) Number of sipes in tire: about 400 Length of sipes: 15 mm These 6 types of tires were subjected to a road test by the following method, and the results are shown in Table 1.

Cracking test : 7.0 on the test tire
It is filled with air pressure of 0 kg / cm ² and mounted on the front wheels of vehicle 2D-4, and the tread at the time when 30,000 km of the paved road 99% and bad road 1% is completed by applying the regular load specified by JATMA. The appearance of cracks in the sipe was visually inspected.

[0014] From Table 1, the tires 1 and 2 of the present invention are both conventional tires 1
It can be seen that the occurrence of cracks is significantly reduced as compared with, and the length of cracks is also short.

On the other hand, as in the case of the conventional tire 2, the sipe width of the conventional tire 1 is made smaller, as in the case of the conventional tire 3, the width of the bent sipe is the same as that of the central sipe portion, As described above, even if the both ends of the conventional tire 2 are made spherical, unlike the tire of the present invention, the occurrence of cracks cannot be significantly reduced and the length cannot be reduced.

[0016]

According to the present invention, the width of the central sipe portion of the closed sipe is set to 0.4 to 0.6 mm, which is narrower than the width of 0.8 mm of the conventional sipe so that it is difficult to open and stone trapping occurs. Moreover, by providing bent sipe portions having a width twice or more the width at both ends of the central sipe portion, it is possible to disperse the stress applied to the edge and suppress the occurrence of cracks.

[Brief description of drawings]

FIG. 1 is a plan view showing an example of a closed sipe provided in a heavy duty radial tire of the present invention.

FIG. 2 is a plan view showing an example of a rib pattern provided on the heavy duty radial tire of the present invention.

FIG. 3 is a plan view showing an example of a block pattern provided in the heavy duty radial tire of the present invention.

FIG. 4 is a plan view showing another example of closed sipes.

FIG. 5 is a plan view showing another example of closed sipes.

FIG. 6 is a plan view showing another example of closed sipes.

FIG. 7 is a plan view showing still another example of closed sipes.

[Explanation of symbols]

3 ribs 4 blocks 5 closed sipes 5c central sipes 5e bent sipes

Claims (1)

[Claims] 1. A heavy load having a rib pattern or a block pattern, wherein the rib or block is provided with a closed sipe formed with bent sipe portions extending in the tire circumferential direction at both ends of a central sipe portion extending in the tire width direction. A heavy-duty pneumatic radial tire in which the width t of the central sipe portion is 0.4 to 0.6 mm and the width T of the bent sipe is twice or more the width t of the central sipe portion. .