JP3191128B2 - Pneumatic tires for icy and snowy roads - Google Patents

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, which has improved braking / driving performance as well as skid resistance.

[0002]

2. Description of the Related Art A pneumatic tire for icy and snowy roads has a block pattern formed on its tread surface, and a large number of kerfs in the width direction of the tire are formed on the block. I try to improve. However, simply increasing the number of kerfs formed on the block has a disadvantage in that the rigidity of the block is reduced and traction performance is rather deteriorated.

Further, in the conventional tire, a kerf is provided in the width direction of the tire mainly in consideration of braking performance and drivability in a traveling direction. There was a problem that sufficient performance could not be exhibited.

[0004]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a pneumatic tire for snowy roads in which a kerf is formed on a block and which has improved braking / driving performance and anti-skid performance as well. Is to do.

[0005]

The tire according to the present invention which achieves the above object is defined on the tread surface by a plurality of main grooves in the tire circumferential direction and a plurality of sub-grooves intersecting the main grooves. In a pneumatic tire for icy and snowy roads in which a large number of blocks are formed and a plurality of kerfs extending in the tire width direction are provided in these blocks, the depth of the kerfs provided in the blocks is lower at the center in the tire width direction. The present invention is characterized in that kerfs that change convexly and kerfs that change upwardly convex are alternately arranged in the tire circumferential direction.

As described above, by alternately providing the kerf whose depth changes convexly downward at the center in the tire width direction and the kerf changing upwardly convex, each of the small kerfs is divided into small kerfs. The contact pressure distribution of the blocks changes in the tire width direction, and small blocks having the largest contact pressure at the center in the tire width direction and small blocks having the largest contact pressure at both ends in the tire width direction are alternately arranged. . Therefore, the portion where the contact pressure becomes maximum is distributed in a plurality of points in the block in a dot-like manner.
It is possible to improve the driving performance and reduce the side slip on the snowy road.

Hereinafter, the present invention will be specifically described with reference to embodiments shown in the drawings. In the tread pattern shown in FIG. 1, a plurality of main grooves 1 extending in the tire circumferential direction LL 'and a sub-groove 2 intersecting with the main groove 1 are provided on the tread surface. A number of blocks 3 divided by 2 are arranged in the tire circumferential direction. Each block 3 has a plurality of calfs 4 in the tire width direction (3 in the figure).
Book) and small blocks 3a, 3b, 3c, 3d are formed.

[0008] Of the three kerfs 4 provided in each block 3, kerfs 4a located at both ends in the tire circumferential direction have lower depths at the center in the tire width direction as shown in FIG. As shown in FIG. 4, the calf 4b having a convex arc shape and located at the center in the tire circumferential direction has a convex arc shape upward at the center in the tire width direction. As described above, the blocks 3 are divided into small blocks 3a, 3b, 3c by the kerfs 4a, 4b, 4c whose depth changes in the tire width direction.
c, 3d, the small blocks 3a, 3b, 3b against the bending action when the tire rotates on the ground.
The rigidity of the kerfs 4a. The portions adjacent to the shallow portions 4b and 4c exhibit high rigidity, and the deep portions exhibit low rigidity.

Therefore, when the tire rotates in the direction of arrow R, each of the small blocks 3a, 3b, 3c and 3d bends differently at the center and both ends in the tire width direction, and EE 'in FIG. 5 is deformed as shown in FIG. 5 at the cross-sectional position (the center part in the tire width direction), and deformed as shown in FIG. 6 at the cross-sectional positions (both ends in the tire width direction) of DD ′ and FF ′ in FIG. I do. Therefore, the ground pressure distribution of each of the small blocks 3a and 3c is as shown in FIG. 7, and the ground pressure distribution of each of the small blocks 3b and 3d is as shown in FIG. Are distributed.

That is, the tire exhibits a contact pressure similar to that of a stud tire, so that not only the braking / driving performance can be improved but also the side slip can be suppressed. In order to further enhance such an effect, it is desirable to provide kerfs whose depth is convex downward on both ends in the tire circumferential direction. The calf provided in the present invention is:
The ratio d / D of the minimum depth d to the maximum depth D is 0.4
It is desirable to set it to 0.9. This ratio d / D is 0.4
As described above, the function and effect of the present invention can be made remarkable. If it is larger than 0.9, there is no difference from the conventional calf, and the effect of the present invention cannot be sufficiently exhibited.

[0011]

EXAMPLE A tire size of 31 × 10.5R15, a tread pattern of FIG. 1, a kerf width of 0.7 mm [a maximum depth D of the kerf of 10 mm, and a minimum depth of 5 mm (d / D =
0.5)], and the tires of the present invention and the comparative tires in which the depths and arrangements of the kerfs are different as described below (having a convex arc-shaped bottom on the upper side and the lower side) as follows: 1, 2 and conventional tires were manufactured, respectively.

Tire of the present invention : Maximum depth D = 10 mm, minimum depth d = 5 mm (d / D =
0.5) at both ends, the maximum depth D = 10 mm and the minimum depth d = 5 mm (d / D = 0.5)
Comparative tire 1 in which the kerf of FIG. 3 is alternately arranged at the center: maximum depth D = 10 mm, minimum depth d = 5
mm (d / D = 0.5), only the kerf in FIG. 3 is arranged. Comparative tire 2 : Maximum depth D = 10 mm, minimum depth d = 5
mm (d / D = 0.5) only the kerf of FIG. 4 is arranged Conventional tire : Only the kerf of uniform depth 7.5 mm is arranged These four tires are braked on an icy road by the following test method. And the skid resistance on a snowy road were measured, and the results are shown in Table 1.

[0013] On- ice braking performance : A test tire was mounted on a small passenger car, the vehicle was running on an icy road , braking was started at an initial speed of 40 km / h, and the distance from when the vehicle was locked to stop was repeatedly measured five times. I asked. The evaluation was performed using the reciprocal, and the index was expressed using the reciprocal of the value of the conventional tire as a reference (100). The larger this index is, the better the on-ice road braking performance is.

Snow skiing resistance : The skid resistance when the test tire is mounted on a small passenger car and runs on a snow-covered road,
The feeling was evaluated by five specialized panelists, and the evaluation was made based on the average value. Based on the average value of conventional tires (10
0). The larger this index is, the more excellent the skid resistance on a snow-covered road is.

[0015] From Table 1, it can be seen that the tires of the present invention have improved both the braking performance on ice and the skid resistance against snowy roads compared to the conventional tires, while the comparative tires 1 and 2 have the braking performance on ice and skid resistance against snowy roads. It can be seen that even if one of them is equal or improved, the performance of the other decreases.

[0016]

According to the present invention, as a plurality of kerfs provided on a block, a kerf that is convex upward and a kerf that is convex downward are provided alternately at a central portion in the width direction of the tire. Since the maximum portion of the contact pressure in the block plane is locally generated in a point-like manner, it is possible to improve both the braking / driving performance in the tire circumferential direction and the anti-lateral skid property in the tire width direction.

[Brief description of the drawings]

FIG. 1 is a plan view showing an example of a block pattern provided in a pneumatic tire for icy and snowy roads according to the present invention.

FIG. 2 is an enlarged plan view showing one block of FIG. 1;

FIG. 3 is a sectional view taken along the line III-III in FIG. 2;

FIG. 4 is a sectional view taken along the line IV-IV in FIG. 2;

FIG. 5 is a side view showing a deformed state of a center portion of the block in the tire width direction.

FIG. 6 is a side view showing a deformed state of both side portions in the tire width direction of the block.

FIG. 7 is a ground pressure distribution diagram of the small blocks 3a and 3c.

FIG. 8 is a ground pressure distribution diagram of the small blocks 3b and 3d.

[Explanation of symbols]

3 blocks 3a, 3b, 3c, 3d
Small block 4,4a, 4b, 4c calf

Continuation of the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) B60C 11/12 B60C 11/11 B60C 11/03

Claims (1)

(57) [Claims] 1. A plurality of blocks formed on a tread surface by a plurality of main grooves in a tire circumferential direction and a plurality of sub-grooves crossing the main grooves, and a plurality of blocks extending in the tire width direction are formed on these blocks. In a pneumatic tire for snowy and snowy roads provided with a book kerf, the kerf provided in the block is provided with a kerf whose depth changes convexly downward at the center in the tire width direction and a kerf whose convexity changes upward. Pneumatic tires for ice and snow roads arranged alternately in the circumferential direction.