JPH01317809A - Pneumatic radial tire - Google Patents

Abstract

PURPOSE:To improve the braking efficiency on the road surface covered with snow or frozen and wear resistance on the dry road surface by setting respective widths of a main groove, auxiliary groove and thin groove and the aspect ratio of the block formed by main grooves and auxiliary grooves such as to satisfy the specific relational expression. CONSTITUTION:On the tread pattern of a tire, straight or transparent zigzag main grooves arrayed parallel along the tire circumference, auxiliary grooves 2 arrayed parallel along the radial of the tire orthogonally to the main grooves 1, and thin grooves 4 arrayed parallel to the auxiliary grooves 2 with the width smaller than that of auxiliary grooves 2 are respectively provided, and these form a large number of blocks 3. The aspect ratio a/b of the block 3 formed by the respective widths e, c, d of respective grooves 1, 2, 4, respective main grooves 1 and the auxiliary grooves 2 is set to satisfy the following expression: c=e(0.6 to 1.1), d<=0.5c, a/b=0.9 to 1.4.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a pneumatic radial tire, particularly a studless tire for small trucks, which has both performance on ice and snow, wear resistance, and uneven wear resistance.

[Conventional technology]

Conventionally, tires with high ground pressure, such as radial tires for light trucks, have not been able to fully satisfy the performance requirements of tires, especially in terms of performance on snow and ice (hereinafter referred to as snow performance) and durability. Currently, it has not been developed as a studless tire because it is technically difficult to achieve both wear resistance and uneven wear resistance.

[Problem to be solved by the invention]

The object of the present invention is to exhibit sufficient braking and driving performance not only on snowy roads, especially on soft snow-covered roads, but also on hard, compacted snowy roads, and even on icy roads, and to provide wear resistance and uneven wear resistance on dry roads, etc. To provide a light truck tire, especially a studless radial tire, having an excellent tread pattern.

[Means to solve the problem]

The object of the present invention is to provide at least three straight and/or see-through zigzag main grooves parallel to the tire circumferential direction, a straight minor groove orthogonal to the main grooves and parallel to the tire radial direction, and parallel to the major groove and the minor groove dividing the block formed by the minor groove;
a narrow groove having a groove width smaller than the width of the sub-groove, and is formed by the main groove width e, the sub-groove width c, the narrow groove width d, and the main groove and the sub-groove. Aspect ratio a/
Each of b can be achieved by a pneumatic radial tire provided with a trend pattern that satisfies the following relationship.

c = e (0.6~1.1”) d≦0.50 a / b = 0.9 to 1.4 Hereinafter, the present invention will be described in detail with reference to the drawings.

Figures 1 (a), (b) and (c) respectively show pneumatic radial tires of the present invention (hereinafter simply referred to as tires).
FIG. 3 is a plan view showing an example of a tread pattern.

As shown in the figure, the tread pattern of the tire of the present invention is
Straight main groove 1 and see-through zigzag shape (offset shape) provided parallel to the tire circumferential direction
A main groove 1, a sub groove 2 arranged in parallel along the tire radial direction orthogonal to these main grooves l, and a sub groove 2 that divides a block 3 constituted by the main groove 1 and the sub groove 2. It consists of narrow grooves 4 which are parallel to each other and have a groove width smaller than that of the sub-grooves 2. The snow removal function of the tire of the present invention is achieved through straight and see-through zigzag (offset) main grooves 1 arranged in parallel along the tire circumferential direction and a plurality of sub grooves 2 orthogonal to these main grooves 1. As shown in the figure, the main groove 1 is preferably composed of a straight groove and a see-through zigzag (offset) groove.

Further, the present invention divides the block 3 by a narrow groove 4 having a groove width smaller than the sub-groove 2 and a shallow groove depth (wider than a sipe to be described later), preferably two closely symmetrical grooves. It is unique in that it is divided into shapes and improves the snow performance of the tire.

In the tire of the present invention having such a tread pattern, the groove width e of the main groove 1, the groove width c of the minor groove 2, and the narrow groove 4.
It is necessary that the groove width d and the aspect ratio a/b of the block 3 formed by the main groove 1 and the sub-groove 2 satisfy the following relationship.

c = e (0,6 to 1.1) d≦0.5c a / b = 0.9 to 1.4.

FIG. 2 shows the groove width e of the main groove 1, the groove width c of the sub-groove 2, the groove width d of the narrow groove 4, and the aspect ratio a/b of the block 3 formed by the main groove 1 and the sub-groove 2. FIG. 2 is a plan view of blocks for explaining the relationship between the two blocks, and corresponds to the blocks constituting the tread pattern of FIG. 1(A).

In the tire of the present invention, if the groove width C of the minor groove 2 is smaller than 0.6 times the groove width e of the main groove 1, the snow performance of the tire will be insufficient, and if it is larger than 1.1 times, the tire will have insufficient snow performance. If the groove width d of the narrow groove 4 is larger than 0.5 times the groove width C of the sub-groove 2, the wear resistance or uneven wear resistance will decrease. For the same reason, the depth of the narrow groove 4 is preferably lower than the depth of the sub-groove 2.

Furthermore, if the aspect ratio a/b of the block 3 is smaller than 0.9, the wear resistance will be insufficient, which is undesirable.
If it exceeds 1.4, snow performance deteriorates, which is not preferable.

Further, block 3 constituting the tread pattern of the present invention
As shown in Figure 1 (a), (b) and (c),
It is preferable that at least one sipe 5 is provided parallel to the sub-groove 2.

The sipes 5 produce two edge effects, the sipes and the blocks 3, which improve the ground contact of the tire tread surface. The effect of improving ground contact by the sipes 5 provided on such blocks is not only effective on the above-mentioned compacted snow roads and icy roads, but also on
The same goes for dry roads, reducing heel and toe wear on tires.

The sipe is provided in a straight, curved or zigzag shape, preferably straight, in a direction across the main groove or the tire circumferential direction, and one end of the sipe is as shown in FIG. may reach the end of the block, or both ends of the sipe may reach the end of the block as shown in FIG. 1(b). Furthermore, as shown in FIG. 1(c), the end of the sipe may be sealed inside the pro-7. Further, the depth of the sipe is preferably at least 60% or more of the depth of the main groove in order to make the effect on icy and snowy roads up to the snow wear limit indication (50χ of the main groove depth).

〔Example〕

EXAMPLES Hereinafter, the present invention and its effects will be explained in more detail with reference to Examples.

The evaluation method for wear resistance and performance on ice and snow is as follows.

Wear resistance performance: Test tires were attached to all wheels of a test truck, and the vehicle was driven for 50,000 m.

Heel-and-toe wear was investigated based on the amount of step difference between the blocks in the circumferential direction of the tire after driving on an actual vehicle, and shoulder drop wear was investigated based on the amount of step difference between the block rows in the crown center area and the block rows in the shoulder area. The larger these relative index values are, the better the uneven wear resistance performance is.

In addition, the estimated lifespan was evaluated from the amount of wear of the grooves as uneven wear resistance. The larger this value (relative index value) is, the longer the estimated lifespan is.

On ice and snow: M' basis value: Braking was started from a vehicle speed of 30 km on a snow-compacted road and a water road, and the braking distance until the vehicle came to a stop was measured. The larger the relative index value, the better these performances. - Evaluation results are shown in Table 1 as relative index values with the measured value of conventional tire A set as 100.

Example 1, Comparative Examples 1 to 4, Conventional Examples A and B As tread patterns, Example Tire 1 of the present invention and Comparative Example Tires 1, 2, 3 and 4 are shown in Fig. 1 (A) and Fig. 2. For conventional tires A and H, the patterns shown in FIGS. 3(a) and 3(b) were adopted, respectively, and seven types of tires (tire size 6. 50R1610PR) prepared,
These snow performance, abrasion resistance, and heel and toe abrasion resistance were evaluated.

In the table, the a/b ratio, presence/absence of narrow grooves, d/c, and presence/absence of sipes are shown in Figures 2 and 3, respectively (
These are the values measured at the locations shown in (b), where Example 1 tire of the present invention and Comparative Example tire 1.2.3.
As shown in FIG. 1(a), the narrow grooves of No. 4 are also provided in the central block, but in the conventional tires A and B, the narrow grooves are provided only in some of the blocks at the shoulders.

〔Effect of the invention〕

According to the present invention, for the first time, a pneumatic radial tire, particularly a studless radial tire for small trunks, that satisfies both snow performance, wear resistance, and uneven wear resistance is provided for the first time, and its technical significance is extremely high. It's large.

[Brief explanation of the drawing]

FIGS. 1(A), 1(B), and 1(C) are a plan view showing one example of the tread pattern of the tire of the present invention, and FIG.
The figure is an enlarged plan view of the blocks that make up the trend pattern in Figure 1 (a), and Figures 3 (a) and (b) are respectively a plan view and a plan view of the tread pattern of a conventional small truck tire for use on icy and snowy roads. FIG. 3 is an enlarged plan view of the block. 1... Main groove, 2... Minor groove, 3... Block, 4
...Narrow groove, 5...Sipe. Agent Patent Attorney Nobuo Ogawa −

Claims (1)

[Claims] At least three straight and/or see-through zigzag main grooves parallel to the tire circumferential direction, a straight sub-groove orthogonal to the main grooves and parallel to the tire radial direction, and the main groove The sub-groove is parallel to the sub-groove and has a groove width smaller than that of the sub-groove, dividing the block formed by the sub-groove. Groove width c
, a groove width d of the narrow grooves, and an aspect ratio a/b of the block formed by the main groove and the sub-groove each satisfy the following relationship. c=e(0.6~1.1) d≦0.5c a/b=0.9~1.4