JPH06320917A - Pneumatic tier for icy and snowy road - Google Patents

Abstract

PURPOSE:To improve turning performance without injuring braking performance during straight advance on a pressed snowy road and an icy road. CONSTITUTION:In a tire having a block pattern composed of a plurality of block lines B-1 to 5 divided by at least three main grooves 1 extending in the peripheral direction of the tire, the block lines B-1, B-5 located at both right and left shoulder ends of a tread face are composed of blocks 3 provided with sip 4 inclining in the same direction at an angle theta1 of 55 to 70 to the periphery of the tire. The block lines B-2, B-4 severally adjacent to the inside of the block lines at both the shoulder ends are composed of the blocks 3 provided with a siping 4 inclining in the same direction at an angle theta2 of 100 to 110 to the periphery of the tire, and the block lines are positioned so as to be about symmetrical to the center of the tire.

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 ice and snow roads, which has improved turning performance on a snow and snow road.

[0002]

2. Description of the Related Art Generally, a pneumatic tire for ice and snow roads has a block pattern composed of a plurality of main grooves extending in the tire circumferential direction and a plurality of sub-grooves intersecting with the main grooves on the tread surface. There is. Sipes are formed on the blocks forming this block pattern, and the edge effect thereof improves the braking performance when going straight on a snow-covered road or an ice road.

However, in conventional pneumatic tires for ice and snow roads, since the sipes provided on the block are substantially perpendicular to the tire circumferential direction, although the braking performance is excellent when going straight, skidding is likely to occur when turning. There was a drawback.

[0004]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a pneumatic tire for ice and snow roads, which has improved turning performance without impairing braking performance when traveling straight on a snowy road or an icy road.

[0005]

An object of the present invention is to provide at least three main grooves extending in the tire circumferential direction on a tread surface and a plurality of sub-grooves intersecting with the main grooves, In a tire having a block pattern composed of a plurality of block rows divided by grooves, the block rows located at the left and right shoulder ends of the tread surface are respectively formed in the same direction at an angle of 55 to 70 ° with respect to the tire circumferential direction. A block row provided with a sipe that inclines to each other, and the block rows adjacent to the inner side of the block rows at the shoulder end portions are respectively 100 to 100 in the tire circumferential direction.
This can be achieved by comprising a block provided with sipes inclined in the same direction at an angle of 110 ° and arranging the block row substantially symmetrically with respect to the tire center.

As described above, when the sipe having an angle of 55 to 70 ° with respect to the tire circumferential direction is formed in the blocks forming the row of blocks at both shoulder ends, when turning through a snowy road or an icy road, The sipe becomes almost orthogonal to the lateral direction of the vehicle, and a large cornering force is generated due to its high edge effect. Moreover,
The sipes formed in the blocks of the block row arranged inside the block row are 100 to 110 in the tire circumferential direction.
By setting the angle to °, the water film generated between the ice and snow road surface and the tire during braking on the ice and snow road can be effectively discharged into the main groove.
Braking performance is not impaired. Further, since each of these block rows is symmetrical with respect to the tire center line, the edge effect is sufficiently exerted when going straight, and high braking performance can be secured.

The present invention will be described in detail below with reference to the drawings. FIG. 1 shows a block pattern of a pneumatic tire for ice and snow roads according to the present invention. As shown in the figure, four tread-side main grooves 1 in the tire circumferential direction and sub-grooves 2 intersecting with the main grooves 1 are shown.
And a block row B-1 of five rows extending in the tire circumferential direction composed of a large number of blocks 3 divided by the ground contact end E,
B-2, B-3, B-4 and B-5 are formed. Of these, the shoulder end block rows B-1 and B-
A plurality of sipes 4, which are inclined in the same direction at an angle θ ₁ of 55 to 70 ° with respect to the tire circumferential direction, are formed in the block 3 constituting the tire 5 at substantially equal intervals. Here, if the angle θ ₁ is less than 55 °, braking performance on ice deteriorates, and if it exceeds 70 °, the circle turning performance on ice decreases. Further, the block rows B-2, B-2 adjacent to the inside of these block rows B-1, B-5,
In the block 3 constituting B-4, a plurality of sipes 4 inclined in the same direction at an angle θ ₂ of 100 to 110 ° with respect to the tire circumferential direction are formed at substantially equal intervals. When the angle θ ₂ is less than 100 ° or more than 110 °,
The braking performance on ice is reduced. Also, the block rows B-2, B
The blocks 3 that form the central block row B-3 sandwiched by -4 are formed with sipes 4 at substantially equal intervals at an angle of 90 ° with respect to the tire circumferential direction. In the above configuration,
The left and right two block rows are symmetrical with respect to the tire center line.

In the present invention, the number of the main groove and the sub groove, the groove width, the size of the block, the number of sipes, and the like have a value of the snow attraction index (STI) of 180 to 250.
It is configured to be set in the range of. ST here
I is an index indicating the on-snow performance level calculated by the tire cross-section direction (tire width direction) component of the groove and sipe length on the surface of the tread pattern described in SAE Paper 82345 and the groove depth. Represented by

STI = −6.8 + 2202ρ ₁ + 672ρ ₂ + 7.6Dg In the above equation, ρ _{1 is} the sum of the projected lengths of the grooves in the tire cross-sectional direction (1 / mm) in the total contact surface area of the tread portion, and ρ _{2 is the} surface contact of the tread surface. The sum of the projected lengths of the sipes in the tire cross-sectional direction (1 / mm) in the entire area of the part (1 / mm) Dg: Average groove depth (mm).

In the present invention, the number of sipes formed in the block is 190 to 2 within the above STI setting range.
It is preferably in the range of 40. When there are a plurality of sipes, it is desirable to form them so that their relative intervals are substantially the same. The shape of the sipes may be straight, zigzag or meandering and may not be in communication with the main groove for optimum block rigidity.

[0011]

EXAMPLE A tread pattern is shown in FIG. 1, an STI is 230,
As shown in Table 1, seven types of tires having different sipe angles were manufactured with the same tire size of 185 / 70R13. For these tires, the following braking performance on ice and circle turning performance on ice were evaluated. The results are shown in Table 1.

Braking performance on ice: The braking distance when the vehicle is running (locked) on an ice test road having an ice temperature of -7 ° C to -9 ° C and an air temperature of -6 ° C to -10 ° C at a speed of 40 km / h. It was evaluated by measuring. The evaluation results are shown as the reciprocal of the braking distance, and are shown as an index with the reciprocal of the braking distance of the conventional tire in which all sipes are 90 ° with respect to the circumferential direction as a reference (100). The larger this index, the better the braking performance on ice.

Circle turning performance on ice: Evaluation was made by measuring the time required to run a certain section during a steady turning run on a circle having a radius of 30 m on the same test road as on the ice as in the method of measuring the braking performance on ice. The evaluation result is shown by the reciprocal of the measurement time, and the reciprocal of the measurement time of the conventional tire is used as a reference (1
00). The larger this index, the better the circle turning performance on ice.

[0014]

[Table 1] From Table 1, all of the tires 1 to 4 of the present invention are excellent in the circle turning performance on ice as compared with the conventional tires, and the braking performance on ice is substantially equal to or higher than that of the conventional tires. Although the circle turning performance on ice is improved, the braking performance on ice is reduced. Further, it is understood that the comparative tires 3 and 4 do not have sufficient circular turning performance on ice, and the comparative tires 5 to 8 have deteriorated braking performance on ice.

[0015]

According to the present invention, since the blocks forming the row of blocks at both shoulder end portions are formed with sipes having an angle of 55 to 70 ° with respect to the tire circumferential direction, when turning on a snowy road or an icy road. Has a high edge effect and produces a large cornering force because the sipe is in a state of being substantially perpendicular to the lateral direction of the vehicle. In addition, the sipes formed on the blocks of the block row inside the shoulder end block row are attached to
Since the angle is set to 00 to 110 °, the water film on the road surface can be discharged toward the main groove at the time of braking on the ice and snow road, and the braking performance can be secured. Further, since the block rows are symmetrical with respect to the tire center line, the edge effect can be sufficiently exerted when going straight, and high braking performance can be secured.

[Brief description of drawings]

FIG. 1 is a plan view showing an example of a tread pattern of a tire of the present invention.

[Explanation of symbols]

3 Blocks 4 Sipe B-1, B-5 Left and right shoulder end block row B-2, B-4 Shoulder end block inner block row θ ₁ Left and right shoulder end block row block sipe angle sipe angle of the block of theta ₂ shoulder end block row inner block row

Claims (1)

[Claims] 1. A block pattern comprising at least three main grooves extending in the tire circumferential direction on a tread surface and a plurality of sub-grooves intersecting with the main grooves, and a plurality of block rows divided by the main grooves. In the tire having, the block rows located at both left and right shoulder end portions of the tread surface are configured from blocks provided with sipes inclined in the same direction at an angle of 55 to 70 ° with respect to the tire circumferential direction, respectively. The block rows adjacent to the inner side of the block rows at both shoulder end portions are constituted by blocks provided with sipes inclined in the same direction at an angle of 100 to 110 ° with respect to the tire circumferential direction, and the block rows are formed. Pneumatic tires for ice and snow roads that are approximately symmetrical with respect to the tire center.