JP2973028B2 - Pneumatic tires for icy and snowy roads - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement of a pneumatic tire for use on icy and snowy roads, and more particularly, to prevent skidding during cornering without impairing traction performance and braking performance on icy and snowy roads. The present invention relates to a pneumatic tire for ice and snow roads that can be used.

[Conventional technology]

In recent years, regulations on spike pollution such as dust and noise have become stricter, and as the regulated area has expanded, pneumatic tires for snowy and snowy roads without spikes called studless tires have been developed.

The mainstream of these studless tires is to form a block pattern on the tread surface and improve running performance on icy and snowy roads by the edge effect of these blocks.

That is, in the conventional studless tire, as shown in FIG. 4, a plurality of main grooves 1 extending in the circumferential direction of the tire on the tread surface T are provided, and a plurality of transverse grooves 2 intersecting the main grooves 1 are provided. Is formed by arranging a plurality of sipes 4 in each block 3 in a lateral direction of the tire, that is, a direction perpendicular to the circumferential direction of the tire.

The groove area ratio of this studless tire is 20-50
%, Snow Traction Index (STI) 170-25
It is often set in the range of 0.

However, the conventional studless tire has a problem that when the steering wheel is turned to the right or left while traveling on an icy road, a side slip occurs.

That is, the conventional studless tire has a block 3
Traction performance and braking performance on ice and snowy roads are improved by the edge effect of the sipe 4
Are arranged in the lateral direction of the tire, so that at the time of cornering, the edge effect of the sipe 4 is not sufficiently exhibited, and there is a problem that the turning performance is temporarily reduced to cause the tire to slide. .

[Problems to be solved by the invention]

The present invention has been made in order to solve the above-mentioned problems in the conventional studless tire, and has been made on an ice snow road air in which side slip during cornering is eliminated without impairing traction performance and braking performance on an ice snow road. It is intended to provide a tire with a tire.

[Means for solving the problem]

That is, the pneumatic tire for icy and snowy roads of the present invention forms a plurality of blocks by providing a plurality of main grooves extending in the tire circumferential direction on the tread surface and providing transverse grooves intersecting the main grooves. A pneumatic tire for snowy and snowy roads having a groove area ratio of 20 to 50% and a snow traction index (STI) of 170 to 250 represented by the following formula (I). A sipe arranged in a block existing within a range of 1/3 of the contact width W is formed so that a ratio c / l of a lateral direction component 1 and a circum direction component c of the tire becomes 0.7 to 1.0. The sipe of the block in the remaining central region is formed substantially in the lateral direction.

STI = −6.8 + 2202ρg + 672ρs + 7.6Dg (I) where ρg: (total groove length projected in the lateral direction) / (contact width × perimeter) (1 / mm) ρs: (total sipe projected in the lateral direction) Length) / (contact width × perimeter) (1 / mm) Dg: average groove depth (mm) Here, the groove area ratio of the tire refers to the total contact area (contact width × perimeter) of the tread surface. It refers to the ratio of the groove area. If the groove area ratio is less than 20%, the on-snow performance of the tire decreases, and if it exceeds 50%, the on-ice performance of the tire decreases, which is not preferable.

The snow traction index (STI) refers to the performance level on snow calculated by the lateral direction (tire width direction) component of the groove and sipe length on the tread pattern surface and the groove depth described in SAE Paper 820345. And is represented by the above formula (I). This ST
If I is smaller than 170, good running performance on ice and snow roads is not exhibited, and if it is larger than 250, the rigidity of the tire is reduced, and the running performance on dry roads is undesirably hindered.

Further, the ratio c / l of the lateral direction component 1 to the circum direction component c of the sipe provided in the block existing within the range of 1/3 of the ground width W from the ground end is 0.7 to 1.0, particularly 0.8 to 1.0.
It is important that the ratio c / l is less than 0.7, so that the side slip at the time of cornering cannot be eliminated. Also, 1.
Exceeding 0 is not preferable because traction performance and braking performance decrease.

Further, the sipe provided in the remaining tread center area in the above range needs to be substantially in the lateral direction as in the conventional tire.

In this way, after the sipe provided in the block in the tread center area is made substantially in the lateral direction, the sipe provided in the block within a range of 1/3 of the contact width W from the contact end is moved in the lateral direction of the tire. By forming the ratio c / l of the component 1 to the circum direction component c to be 0.7 to 0.1, the traction and braking performances are maintained at the same level as those of conventional tires, and the circumferential The edge effect by the directional component c is sufficiently exhibited, and the side slip at the time of cornering can be eliminated.

The pneumatic tire for icy and snowy roads of the present invention will be described below with reference to the drawings.

FIG. 1 is a development view of a tread pattern of a pneumatic tire for icy and snowy roads according to the present invention. In a tread surface T, a plurality of (three in the figure) main grooves 1 extending in the circumferential direction of the tire are provided.
0, 11, and 12 are provided. In addition, these main grooves 10, 11, 12
The main grooves 10, 11, 12 and the horizontal grooves 20 form a large number of blocks 30. In addition, the groove area ratio is specified in the range of 20 to 50%, and the snow traction index (STI) is specified in the range of 170 to 250.

Among the blocks 30, most of the blocks 30b except for the block 30a existing within the range of 1/3 of the grounding end W from the left and right grounding ends e have a sipe 40 directly in the tire lateral direction. Are arranged side by side.

On the other hand, the block 30a existing within the range of 1/3 of the ground width W from the ground end e has a mountain-shaped and step-shaped sipe having a convex shape from the ground end e toward the center line C. 42 are arranged in a triple manner, and a plurality of linear sipes 41 are juxtaposed in a portion facing the center line C side in the lateral direction of the tire. Moreover, the sipe 41, 42 disposed in the block 30a has a ratio c / l of the component l in the lateral direction of the tire to the component c in the circum direction of 0.7 to 0.7.
It is formed to be 1.0.

〔Example〕

The caramel block pattern shown in Fig. 1 is formed on the tread surface with a tire size of 185 / 70R13, and the groove area ratio is 30%, the STI is 220, and the block is within 1 / 3W from the ground end e. The tire I of the present invention in which the ratio c / l of the lateral component l to the circum component c of the sipe provided is 0.85.
Was made.

Further, the caramel block pattern shown in FIG. 2 was formed on the tread surface, and the same as the above-described tire I of the present invention except that the ratio c / l between the lateral direction component 1 and the circum direction component c of the tire was 1.0. A tire II of the present invention having a structure was manufactured.

On the other hand, for comparison, the caramel block pattern shown in FIG. 3 was formed on the tread surface, and the ratio of the lateral direction component 1 to the circum direction component c was 1.5, except that the ratio c / l was 1.5. A comparative tire having the same structure was manufactured.

Further, a conventional tire was manufactured in which the caramel block pattern shown in FIG. 4 was formed on the tread surface, and a sipe in the lateral direction was provided on all blocks.

The following Table shows the results of measuring the braking performance on ice for the four types of tires by the braking test on ice under the following conditions.
Similarly, the results of the measurement of the on-ice turning performance by the on-ice turning test are shown in the same table.

The following table shows the index when the reciprocal of the measured value of the conventional tire is set to 100, and the larger the index, the better the result.

Braking performance on ice Braking was started at a speed of 40 km / h, and the braking distance until the vehicle stopped was measured.

Turning performance on ice When turning on a snow-covered ice surface with a radius of 30m, the time required for one round was measured.

From the above results, it is clear that the tires I and II of the present invention have improved turning performance on ice without impairing braking performance on ice.

〔The invention's effect〕

As described above, according to the present invention, the sipe of the block in the tread center region is substantially in the lateral direction, while the sipe provided in the block within the range of 1/3 of the contact width W from the contact end is used for the tire. Since the ratio c / l of the lateral direction component l and the circum direction component c was formed to be 0.7 to 1.0, the circum direction component of the sipe described above at the time of cornering without impairing the traction performance and braking performance when traveling straight. The edge effect due to c was exhibited, and the side slip at the time of cornering could be eliminated.

[Brief description of the drawings]

1 and 2 are tread pattern development views of a pneumatic tire for icy and snowy roads according to the present invention, FIG. 3 is a tread pattern development view of a comparative tire, and FIG. 4 is a tread pattern development view of a conventional studless tire. is there. 1,10,11,12 …… Main groove, 2,20 …… Horizontal groove, 3,30,30a, 30b ……
Block, 4,40,41,42 ... Sipe, T ... Tread surface.

Claims (1)

(57) [Claims] 1. A plurality of blocks are formed by providing a plurality of main grooves extending in the circumferential direction of a tread surface tire, and forming a number of blocks by providing transverse grooves intersecting the main grooves. Is 20 to 50%, and the snow traction index (STI) represented by the following formula (I) is 170 to 50%.
In the pneumatic tire for snowy and snowy roads, which is 250, a sipe disposed in a block existing within a range of 1/3 of the contact width W from the contact end of the block is a lateral component 1 and a circum direction component of the tire. A pneumatic tire for snowy and snowy roads, wherein the ratio c / l to c is 0.7 to 1.0 and the sipe of the block in the remaining central region is formed substantially in the lateral direction. STI = −6.8 + 2202ρg + 672ρs + 7.6Dg (1) where ρg: (length of all grooves projected in the lateral direction) / (contact width ×
Perimeter) (1 / mm) ρs: (total sipe length projected in the lateral direction) / (contact width x perimeter) (1 / mm) Dg: average groove depth (mm)