JPH08216626A - Pneumatic tire for running on icy snow road - Google Patents

Abstract

PURPOSE: To provide a pneumatic tire for running on icy snow road capable of maintaining good contact property between a tread and an icy road even after the intermediate period of wear as a result of preventing step wear per calf (calf cupping). CONSTITUTION: In the case of a pneumatic tire for running on icy snow road having many blocks 3 on a tread 2, more than 3 pieces of calves 4, 4a, 4b in the tire width direction are provided on the blocks and also one-side ends of these calves are placed in alternate connection to grooves 5 in the tire peripheral direction adjacent to both sides of the blocks. Furthermore, in the case of 2 sheets of calves positioned in both outermost ends in the tire peripheral direction, depth C of a connection part 6 onnected to the grooves in the tire peripheral direction is made shallower than the depth of block width central area and also set to 30 to 40% of the width D of the groove in the tire peripheral direction and the width A of the connection part shall be set to 5 to 15% of a lateral width B of the blocks.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pneumatic tire for icy and snowy roads, and more particularly to a studless tire applied to running on icy and / or snowy roads.

[0002]

2. Description of the Related Art Generally, a studless tire is provided with a block pattern on a tread, and a plurality of kerfs in the tire width direction are provided on each block, and the edge effect of these kerfs and adhesion by a rubber having a low hardness used for the tread are provided. The performance on ice is obtained by the friction force.

However, among the above-mentioned effects, the edge effect of the kerf is sufficiently effective when it is new, but as the wear progresses during running, uneven wear such as cupping occurs, so that the effect is reduced. That is, in the case of a studless tire in which a kerf in the tire width direction is provided in a block so that one end thereof is alternately opened in a circumferential groove in the tire circumferential direction, as shown in FIGS. 8 (a) and 8 (b), a sub block (Land portion between kerfs) The step wear (calf cupping) that occurs every 7 is significant, and if the degree of this step wear is large,
Since the ground contact between the tread and the icy road is lower than that of a new product, the performance on ice will be degraded. However, FIG. 8 (a)
Shows 10% to 15% wear, and FIG. 8 (b) shows 20% to 30% wear.

[0004]

SUMMARY OF THE INVENTION An object of the present invention is to prevent step wear (calf cupping) of each calf, and
An object of the present invention is to provide a pneumatic tire for ice and snow roads that can maintain good ground contact between the tread and the ice road even after the middle period of wear.

[0005]

That is, a pneumatic tire for ice and snow roads according to the present invention is a pneumatic tire for ice and snow roads having a large number of blocks on a tread, and the blocks are provided with three or more kerfs in the tire width direction. At the same time, one ends of these kerfs are alternately communicated with the grooves in the tire circumferential direction that are adjacent to both sides of the block, and the two kerfs located at both outermost ends in the tire circumferential direction are the grooves in the tire circumferential direction. The depth C of the connecting portion connecting with the groove is made shallower than the depth of the central region of the block width, and the groove depth D of the groove in the tire circumferential direction is set.
And the width A of the connecting portion is set to 5 to 15% of the lateral width B of the block.

[0006]

As described above, the block is provided with three or more kerfs in the tire width direction, one end of the kerf is alternately communicated with the groove in the tire circumferential direction, and the kerfs are located at both outermost ends in the tire circumferential direction. The depth C of the connecting portion where the two kerfs connect the groove in the tire circumferential direction is set to 30 to 40% of the groove depth D of the groove in the tire circumferential direction, and the width A of the connecting portion is set. By setting the width B of the block to 5 to 15%,
After the middle stage of wear, both ends of the kerf located at the outermost end are in a state of being closed with respect to the groove in the tire circumferential direction, the block rigidity is increased, and uneven wear can be prevented.

The pneumatic tire for ice and snow roads according to the present invention will be described below with reference to the drawings. 1 and 2 show a main part of a pneumatic retired tire for ice and snow roads, which has a large number of blocks 3 on a tread 2, and each block 3 has a width of 4 in the tire width direction.
Book kerfs 4 (4a, 4b, 4b, 4a) are provided. At least three or more kerfs 4 are provided for each block.

As shown in FIG. 1, each of these kerfs 4 has its one end alternately connected to a groove 5 in the tire circumferential direction (hereinafter referred to as a circumferential groove) adjacent to both sides of the block 3. ing. Then, with respect to the tire circumferential direction F, the two kerfs 4a located at both outermost ends of the block 3 have the depth C of the connecting portion 6 connected to the circumferential groove 5 as shown in FIG. It is shallower than the depth of the area, and the groove depth D of the circumferential groove 5 is
Of 30 to 40%. Furthermore, this connecting portion 6
The width A of the block 3 is set to 5 to 15% of the width B of the block 3.

When the depth C of the connecting portion 6 is less than 30%, the kerf 4a is less opened and a sufficient edge effect cannot be obtained in an ice road. However, if it exceeds 40%, the occurrence of calf cupping tends to be remarkable. On the other hand, when the width A of the connecting portion 6 is less than 5%, the rigidity of the connecting portion 6 becomes insufficient and kerf cracks are likely to occur. Further, when it exceeds 15%, the edge amount of the kerf decreases and the kerf 4a opens less, so that the performance on ice is deteriorated.

As for the depth of the kerf 4, the depth E of the kerf 4a located at the outermost end of the block 3 in the tire circumferential direction and the depth E of the kerf 4b located inside thereof are equal to the depth E of the block width central region. 'Is set to the same depth. The kerf depths E and E ′ are preferably 60 to 90% of the depth D of the circumferential groove 5. If it is less than 60%, it is not possible to obtain a sufficient edge effect as a kerf at 50% wear, which is the limit of use as a studless tire. If it exceeds 90%, kerf cracks are likely to occur at the bottom of the kerf.

When the pneumatic tire for ice and snow roads according to the present invention described above is worn by 25 to 30%, as shown in FIGS. 5 and 6, the kerfs 4a located at both outermost ends of the block 3 in the tire circumferential direction are provided. Since the peripheral grooves 5 on both sides are closed, the block rigidity is increased. As a result, as shown in FIG.
As shown in (b), uneven wear does not occur in each sub-block, and the grounding property can be improved.

[0012]

EXAMPLE A tire size is 185 / 70R13, a plan view is FIG. 1, and kerfs at both outer ends in the tire circumferential direction are shown in FIG.
The tires 1 to 5 of the present invention and the comparative tires 1 to 8 having a block pattern composed of blocks having inner kerfs configured as shown in FIG. A conventional tire having a block pattern made up of a large number of blocks as shown in FIG. 4 was produced, and these 14 types of tires were assembled on a rim 13 × 5J and mounted on a 1500 cc FF vehicle, The following test methods evaluated braking property on ice, uneven wear resistance, and kerf crack resistance, and the results are shown in Table 1. The air pressure was set to 1.9 kgf / cm ² .

-Breaking property on ice Evaluation was carried out by measuring the braking distance when lock-braking from a speed of 40 km / h at an air temperature of -5 to -8 ° C and a temperature of -3 to -8 ° C. did. The evaluation results are shown by reciprocal numbers, and the results are shown by an index with the conventional tire being 100. The larger this index, the better the braking performance on ice.

Uneven wear resistance A large amount of step wear of the sub-block (land portion between the kerfs) on the tread surface after running a pattern run in which a dry road surface is run at a predetermined speed and running for 10,000 km. Figure 7
As shown in, the step (height difference) H on the ground side of the sub-block 7
It was evaluated by measuring (mm). The results are shown as an index with the conventional tire being 100. The larger this index is,
Excellent resistance to uneven wear.

· Calf crack resistance Under the above conditions, after running through an urban area for 30,000 km, the occurrence of a fault from the kerf was visually confirmed.

[0016]

[Table 1]

[0017]

As described above, according to the present invention, the block is provided with three or more kerfs in the tire width direction, and one end of each kerf is alternately communicated with the groove in the tire circumferential direction. The two kerfs located at both outermost ends set the depth C of the connecting portion that is connected to the groove in the tire circumferential direction to 30 to 40% of the groove depth D of the groove in the tire circumferential direction, and The width A of the connecting portion is 5 to 15% of the width B of the block.
Since the kerf located at the outermost end is closed with respect to the tire circumferential groove at the middle of wear, since the rigidity of the sub block does not decrease, kerf cupping is suppressed and the tire touches the ground. The sex is not lost. As a result, it is possible to suppress a decrease in adhesion frictional force and prevent a decrease in performance on ice.

[Brief description of drawings]

FIG. 1 is a plan view showing a main part of a pneumatic tire for ice and snow roads according to the present invention.

FIG. 2 is a sectional view taken along line II-II of FIG.

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

4 is a sectional view taken along line IV-IV in FIG.

FIG. 5 shows a pneumatic tire for ice and snow roads according to the present invention.
It is a top view which shows the principal part at the time of 30% wear.

6 is a cross-sectional view taken along the line VI-VI of FIG.

FIG. 7 is an explanatory diagram showing a method of measuring step wear.

FIG. 8 (a) is a side view when a conventional tire is worn by 10 to 15%. (B) It is a side view at the time of 25-30% wear of the conventional tire.

[Explanation of symbols]

2 tread 3 block 4, 4a, 4b calf 5 groove in tire circumferential direction 6 connecting portion

Claims (2)

[Claims] 1. A pneumatic tire for ice and snow roads having a large number of blocks on a tread, wherein the blocks are provided with three or more kerfs in the tire width direction, and one end of these kerfs is adjacent to both sides of the block in the tire circumferential direction. The two kerfs located at both outermost ends in the tire circumferential direction are connected to the grooves of the tire alternately, and the depth C of the connecting portion that is connected to the grooves in the tire circumferential direction is set to the depth of the central area of the block width. And the groove depth D of the groove in the tire circumferential direction is 30 to
A pneumatic tire for ice and snow roads, in which the width A of the connecting portion is set to 5% to 15% of the lateral width B of the block. 2. The depth E of the kerfs located at the outermost ends of both blocks in the tire circumferential direction and the depth E'of the kerfs located inside the outer ends of the blocks are set to the same depth, and The pneumatic tire for ice and snow roads according to claim 1, wherein the groove depth D of the groove in the tire circumferential direction is 60 to 90%.