JPH06191234A - Pneumatic radial tire for heavy load - Google Patents

Abstract

PURPOSE:To provide a pneumatic radial tire suppressing heel and toe wear and preventing the bite of a stone into a sipe and the generation of a sipe edge crack by providing a block with closed sipes. CONSTITUTION:In a pneumatic radial tire for heavy load having an openlug type pattern with plural blocks 4 provided at the tread, the block 4 is provided with one set or more of sipe cluster part with two or more closed sipes 5, extended in the tire width direction, as one set. The positions of the closed sipes 5 in each set are mutually shifted in both width direction and circumferential direction of the tire. The circumferential offset quantity M is to be 3-10mm, and the width direction offset quantity N is to be within + or -3mm.

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 having a block pattern. More specifically, it suppresses heel and toe wear and prevents stone trapping and sipe edge cracks in the sipe. The present invention relates to a heavy-duty pneumatic radial tire capable of performing.

[0002]

2. Description of the Related Art As a tread pattern provided on a heavy duty pneumatic radial tire, an open lug type block pattern is preferably used because of its advantage of exhibiting excellent traction performance until the end of wear. However, this open lug type block pattern has a drawback that heel and toe wear and groove cracks are likely to occur. The width of the lug groove can be increased to prevent the occurrence of groove cracks, but in this case, the block must be increased due to the relationship of the groove contact area required for heavy-duty tires. And toe wear is more likely to occur.

Therefore, the present inventor studied groove cracks and heel-and-toe wear, which are in a trade-off relationship, and as a result, prevented the occurrence of groove cracks by enlarging the blocks and providing closed sipes extending in the tire width direction. However, we have found that it is possible to suppress heel and toe wear. However, when the block is provided with the closed sipe as described above, although heel and toe wear is less likely to occur, there is a new problem that stone trapping inside the sipe and sipe edge cracks occur. In addition, in order to suppress heel and toe wear, it is effective to increase the number of closed sipes in the block or increase the tire width direction length of the closed sipes, but as shown in FIG. As the number of sipes in the block is increased and the ratio of the sipe length to the block width is increased as shown in FIG. 9, the number of stones trapped in the sipe and the sipe edge crack length are more and more increased. understood.

[0004]

SUMMARY OF THE INVENTION An object of the present invention is to prevent heel-and-toe wear by providing a closed sipe on a block in an open lug type block pattern, and to prevent stones from being caught in the sipe and sipe edge cracks. It is intended to provide a heavy-duty pneumatic radial tire capable of preventing the occurrence of

[0005]

A heavy duty pneumatic radial tire of the present invention for achieving the above object is a heavy duty pneumatic radial tire having an open lug type block pattern in which a plurality of blocks are provided on a tread. The block is provided with at least one set of sipe collecting parts each including two or more closed sipes extending in the tire width direction, and the mutual positions of the closed sipes in each set are offset from each other in the tire width direction and the circumferential direction, and the circumferential direction is set. The offset amount of 3 to 10 mm and the offset amount in the width direction are within ± 3 mm.

By thus providing the block with a plurality of closed sipes extending in the tire width direction, it is possible to suppress heel and toe wear of a heavy duty pneumatic radial tire having an open lug type block pattern, and Two or more closed sipes in each block are set as one set, and the mutual positions of the closed sipes in each set are offset from each other in the tire width direction and the circumferential direction, and the circumferential offset amount is set to 3 to 10 mm, and the width direction By setting the offset amount within ± 3 mm, it is possible to prevent stone trapping inside the sipe and the occurrence of sipe edge cracks.

In the present invention, the offset amount is a relative offset amount measured with reference to a state in which a pair of closed sipes are arranged side by side in the width direction, and between the end portions of the pair of closed sipes. This is for specifying the distance in the circumferential direction and the width direction. Hereinafter, the configuration of the present invention will be described in detail with reference to the accompanying drawings.

FIG. 1 shows a tread pattern of a heavy duty pneumatic radial tire. In the figure, on a tread surface 1, a plurality of main grooves 2 extending in the tire circumferential direction,
A plurality of open lug type lug grooves 3 extending in the tire width direction and passing through to the shoulder end portion are provided, whereby a plurality of blocks 4 are divided and formed. Each block 4 is provided with a plurality of closed sipes 5 extending in the tire width direction. This closed sipe 5
It is provided in the block 4 so as not to be connected to the main groove 2 and the lug groove 3. The depth of the closed sipe 5 is generally shallower than the depth of the main groove 2 and the lug groove 3, but it is not always necessary to make the depth uniform, and for example, the bottom may be raised at the center. .

Closed sipes 5 in each block 4
Are arranged such that two or more adjacent ones form one set, and the mutual positions of the closed sipes 5 in each set are displaced from each other in the tire width direction and the circumferential direction. As shown in FIG.
One set of closed sipes 5 has a circumferential offset amount M.
Is 3 to 10 mm, and the offset amount N in the width direction is set to be within ± 3 mm. However, the offset amount N
Indicates that the amount of overlap between the pair of closed sipes 5 in the tire width direction is positive, and the amount of separation is negative. Further, in the figure, the case where two closed sipes 5 form one set is shown, but when three or more closed sipes 5 form one set, one pair that is in a close relationship to each other is used. Closed sipe 5 of the above M
= 3 to 10 mm and N = ± 3 mm are satisfied.

By providing the block 4 with the plurality of closed sipes 5 extending in the tire width direction as described above,
It is possible to suppress the heel and toe wear specific to the block pattern. Moreover, two or more closed sipes 5 in each block 4 are set as one set, and the positions of the closed sipes 5 in each set are offset from each other in the tire width direction and the circumferential direction, and the offset amount M is 3 to 10 mm and the offset amount N is N.
By setting the distance within ± 3 mm, the size of each sipe can be reduced, so that the occurrence of stone trapping in the sipe can be prevented, and the movement of the block can be suppressed as compared with a large sipe. Therefore, it is possible to prevent the occurrence of sipe edge cracks. Offset amount M is 3
If it is less than mm, a pair of closed sipes 5 that are close to each other in the set are connected to each other by running and are substantially 1
As it is a large sipe, it is easy for stones to get caught in the sipe and sipe edge cracks.
If it exceeds m, the effect of suppressing heel-and-toe wear due to formation of the set is reduced. Further, when the offset amount N is less than -3 mm, the closed sipe 5 becomes short, so that the effect of suppressing heel and toe wear is reduced. On the contrary, when the offset amount N exceeds 3 mm, the closed sipe 5 becomes long, and stones are trapped in the sipe and Sipe edge cracks are more likely to occur.

In the present invention, the total length (W ₂ + W ₃ ) of the pair of closed sipes 5 is the width W of the block 4.
It is preferably 30 to 60% of ₁ . By setting the total length of the closed sipes 5 as described above, it is possible to more reliably prevent the occurrence of stone trapping and sipe edge cracks in the sipes. Further, it is preferable that the closed sipes 5 extending in the tire width direction are bent in the tire circumferential direction at both ends thereof, and such a shape can effectively prevent the occurrence of sipe edge cracks. In particular, as shown in FIG. 1, when the closed sipes 5 are Z-shaped and the adjacent ends are bent in a direction away from each other, the closed sipes 5 are less likely to be connected in the set. Further, the shape of the closed sipe 5 is not particularly limited, and can be U-shaped as shown in FIG. 10 or zigzag-shaped as shown in FIG. 11.

[0012]

EXAMPLE A tire size of 11R22.5 14PR, a block pattern having a developed width of 220 mm (block width: 40 mm, length: 45 mm, pitch: 60 mm), and only the closed sipes provided on the block are various as shown below. We manufactured different pneumatic radial tires for heavy loads. Comparative Tire 1 As shown in FIG. 3, the block had no closed sipes. Comparative tire 2 As shown in Fig. 4, each block was provided with one closed sipe, and the sipe length was 40% of the block width. Comparative tire 3 As shown in Fig. 5, each block was provided with two closed sipes, and the length of the sipes was set to 20% of the block width. Comparative tire 4 As shown in FIG. 5, each block was provided with two closed sipes, and the length of the sipes was set to 40% of the block width. Comparative tire 5 As shown in FIG. 5, each block was provided with two closed sipes, and the length of the sipes was 60% of the block width. Comparative tire 6 As shown in FIG. 6, each block was provided with three closed sipes, and the length of the sipes was 40% of the block width. Comparative tire 7 As shown in FIG. 7, two sets of closed sipes, one set for each block, are provided in each block, and the total length of the closed sipes of each set is set to 50% of the block width. The offset amount M in the circumferential direction was set to 0 mm, and the offset amount N in the width direction was set to -4 mm. Tire 1 of the present invention As shown in FIG. 1, each block is provided with two sets of closed sipes, and the total length of the closed sipes of each set is 50% of the block width. The offset amount M in the circumferential direction was set to 5 mm, and the offset amount N in the width direction was set to 0 mm. Inventive Tire 2 In the inventive tire 1, only the offset amount M of the closed sipe was changed to 3 mm. Inventive Tire 3 In the inventive tire 1, only the offset amount M of the closed sipe was changed to 10 mm. Inventive tire 4 In the inventive tire 1, only the offset amount N of the closed sipe was changed to -3 mm. Inventive Tire 5 In the inventive tire 1, only the offset amount N of the closed sipe was changed to +3 mm.

The above-mentioned comparative tires 1 to 7 and the tires 1 to 5 of the present invention were mounted on a large-sized vehicle (two front wheels, four rear wheels) with an air pressure of 7.0 kg / cm ² , and the paved surface was 99%.
After running 10,000 km on a general road consisting of gravel surface and 1% of gravel surface, uneven wear amount due to heel and toe wear, crack length of sipe edge and number of stones trapped in sipe were measured, and the results are shown in Table 1. It was In Table 1, the uneven wear amount is a measure of uneven wear amount due to heel-and-toe wear occurring in the block, and is an average value for six tires. The crack length is a measurement of the total crack length generated at the sipe edge in one block.
It is an average value in 10 blocks of each of the tires. The number of stones bitten is the number of stones bitten in the block 5 pitch sipe, and is an average value for 6 tires.

[0014] As can be seen from Table 1, in all of the tires 1 to 5 of the present invention, the heel and toe wear is suppressed by providing the block with the closed sipe, and moreover, stone trapping inside the sipe and sipe edge cracks are almost generated. Didn't. On the other hand, in the comparative tires 1 to 7, it was not possible to simultaneously suppress heel and toe wear and prevent stone trapping in the sipe and sipe edge cracks.

[0015]

As described above, according to the present invention, in a heavy duty pneumatic radial tire having a block pattern of an open lug type in which a plurality of blocks are provided on a tread, the blocks extend in the tire width direction.
Providing one or more sets of sipe collecting parts each having one or more closed sipes as one set, the mutual positions of the closed sipes in each set are offset from each other in the tire width direction and the circumferential direction, and the offset amount in the circumferential direction is set to 3 to 10 mm. By setting the offset amount in the width direction within ± 3 mm, heel-and-toe wear specific to the block pattern can be suppressed, and further, stone trapping inside the sipe and occurrence of sipe edge cracks can be prevented.

[Brief description of drawings]

FIG. 1 is a development view showing a tread pattern of a heavy duty pneumatic radial tire according to an embodiment of the present invention.

FIG. 2 is an enlarged view of a block in FIG.

FIG. 3 is a development view showing a tread pattern of a comparative tire (without sipes).

FIG. 4 is a development view showing a tread pattern of a comparative tire (one sipe).

FIG. 5 is a development view showing a tread pattern of a comparative tire (two sipes).

FIG. 6 is a development view showing a tread pattern of a comparative tire (three sipes).

FIG. 7 is a development view showing a tread pattern of a comparative tire (2 sipes × 2 sets).

FIG. 8 is a diagram showing the relationship among the number of sipes in one block, the amount of heel and toe wear, the length of sipe edge cracks, and the number of stones trapped in the sipes.

FIG. 9 is a diagram showing the relationship between the ratio of the sipe length to the block width, the heel and toe wear amount, the sipe edge crack length, and the number of stones trapped in the sipe.

FIG. 10 is a development view showing a tread pattern of a heavy duty pneumatic radial tire according to another embodiment of the present invention.

FIG. 11 is a development view showing a tread pattern of a heavy duty pneumatic radial tire according to still another embodiment of the present invention.

[Explanation of symbols]

 1 Tread surface 4 Block 5 Closed sipe M Offset amount N Offset amount

Claims (1)

[Claims] 1. A pneumatic radial tire for heavy load having a block pattern of an open lug type in which a plurality of blocks are provided on a tread, and a sipe assembly including a set of two or more closed sipes extending in the tire width direction in the block. One or more sets of parts are provided, and the mutual positions of the closed sipes in each set are offset from each other in the tire width direction and the circumferential direction so that the circumferential offset amount is 3 to 10 mm and the width offset amount is within ± 3 mm. Pneumatic radial tire for heavy loads.