JPH0485107A - Pneumatic tire for snowy/icy road - Google Patents

Abstract

PURPOSE:To improve performance on ice by providing a tread face with circumferential ribs, and the ribs with numerous thin slits in the tire width direction, and specifying a ratio between the sum of the projected length to the tire width direction face of the thin slit and the surface area of the rib. CONSTITUTION:On both sides of a tread center line CL, there are provided two ribs 5 formed by three circumferential main grooves l, and the ribs 5 are provided with numerous thin slits 4 formed parallel at equal spaces apart. When the density of the thin slits is obtained by the ratio B/A between the sum B of the projected length to the face, orthogonal to the tire peripheral direction, of this thin slit 4 and the surface area A of the rib 5, it is so set that this density B/A becomes 0.15/mm.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an expert tire for snow and ice roads with improved performance on ice.

[Conventional technology]

Conventionally, pneumatic tires with improved on-ice performance have used rubber compounds with low modulus at low temperatures and excellent adhesion and friction as the cap tread rubber, and have changed the tread pattern in the circumferential direction of the tire, as shown in Figure 3. A block pattern consisting of blocks 3 defined by a main groove l extending in the direction of the main groove l and a sub groove 2 intersecting the main groove l,
Furthermore, it was common to form a thin cut 4 such as a kerf or sipe on the surface of the block 3 with at least one end connected to the main groove.

However, tires with this block pattern,
In particular, in tires where the aforementioned low modulus rubber compound is used for the cap tread rubber, increasing the density of the thin cuts in the block may reduce the rigidity of the tread, causing the block to buckle, or the angle at which the block collapses. There was a problem in that the edge effect could not be fully exerted because it became too large.

[Problem to be solved by the invention]

The purpose of the present invention is to
By increasing the density of thin cuts as much as possible,
The objective is to provide a pneumatic tire with improved on-ice performance.

[Means to solve the problem]

The object of the present invention is to provide a tread surface with at least one rib extending in the circumferential direction of the tire, and to provide a large number of thin cuts in the width direction of the tire on the rib. This can be achieved by a pneumatic tire in which the density of the thin cuts defined by the ratio B/A of the projected total length B of the thin cuts and the surface area A of the rib is 0.15/-1 or more. .

In the present invention, the density of the thin cuts is determined relative to the surface area A (■m'') of the rib 5, which is expressed as the product of the circumferential length a of the tire and the length b in the direction perpendicular to this, as shown in FIG. The ratio of the sum B of the length J (s■) of the thin cut 4 (generally equivalent to the total circumferential length of the tire) projected onto a plane perpendicular to the tire circumferential direction E-E' (axis m) B/
A (unit: 1/-1).

In this way, based on the fact that the tread surface is provided with ribs extending in the circumferential direction of the tire that are not blocked by sub-grooves, by forming thin cuts in these ribs, without substantially reducing rigidity, It becomes possible to increase the edge effect and improve on-ice performance.

Hereinafter, the present invention will be specifically described with reference to the drawings.

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

As shown in the figure, two ribs 5 separated by three main grooves l extending in the circumferential direction of the tire are provided on both sides of the tread center line CL at the center of the tire tread during contact with the ground. A large number of thin cuts 4 perpendicular to the tire circumferential direction are formed parallel to each other and at equal intervals.

In addition, blocks 3 separated by a plurality of sub-grooves 2 intersecting the tire circumferential direction are provided on both outer shoulders of these ribs 5 .

FIG. 2 is a plan view showing an example of another tread pattern of the tire of the present invention. In this example, blocks 3 separated by three main grooves 1 extending in the tire circumferential direction and sub-grooves 2 intersecting these are arranged along the tire circumferential direction on both sides of the tread center line CL, and are arranged in two rows. They form a row of blocks.

Ribs 5 extending in the circumferential direction of the tire are arranged at parts of both shoulders on the outside of these block rows.

A large number of thin cuts 4 are formed in this rib 5 in parallel with each other and at equal intervals, perpendicular to the tire circumferential direction. Each of these thin cuts 4 is connected to the main groove 1 at one end, but does not penetrate the rib 5 at the other end.

The ribs constituting the tread pattern of the tire of the present invention include:
The thin cut has a density of 0.15 according to the above definition.
/mm or more to enhance the edge effect of these thin cuts and improve on-ice performance. The density of these thin cuts is more desirably 0.20/mm or more.

Even with such a high density of thin cuts, the ribs are not divided by sub-grooves like blocks, so they are difficult to buckle even when vertical loads are applied, and extreme collapse occurs due to braking and driving forces. Therefore, the edge effect of the thin cuts becomes even greater, improving on-ice performance. Furthermore, since the rigidity of the tread portion is not reduced in this way, it is possible to use a low modulus rubber compound as the cap rubber compound, making it possible to further improve on-ice performance.

Also, the width of this rib is 2 W when the tire tread is in contact with the ground.
It is desirable to set it to be 0χ to 35χ. 2
By making it occupy a width of 0% or more, the above-mentioned improvement in on-ice performance can be ensured. Also, 35
% or less, the tire performance such as snow removal performance and drainage performance can be improved.

The placement position of the rib is not particularly limited, and it may be placed either on a part of the tread center or a part of the shoulder, or it may be placed on both at the same time. , it is desirable to use it in conjunction with a block column,
In this case, thin cuts can be formed in the block within a range that does not reduce its rigidity.

In order to improve on-ice performance, it is desirable that at least one end of the thin cuts formed in the ribs and blocks communicate with the main groove. Preferably, both ends communicate with the main groove.

The direction of this thin cut is not particularly limited, and can be formed, for example, in a direction perpendicular to the tire circumferential direction, in the same direction as the sub-groove, or in a direction having a certain angle to the tire circumferential direction. Further, the shape can be a straight line, a curved line, a broken line, or the like. Furthermore, the depth of the thin cuts can be all constant or can be changed for each rib. Furthermore, the plurality of thin cuts formed in the same rib can have different depths.

〔Example〕

Tires 1 and 2 of the present invention having the tread pattern shown in FIG. 1 and having the thin cut density (density of sipes) changed as shown in the table, and Comparative Tire 1, having the block pattern shown in FIG. A total of six types of tires were manufactured, Comparative Tires 2 to 4, whose densities were changed as shown in the table.

All of these tire sizes are the same 185/70R.
It was set at 13.

The on-ice braking performance of these tires was evaluated using the following evaluation method, and the results shown in the table were obtained.

゛ Top: Each tire was installed on an actual vehicle, and the stopping distance from an initial speed of 40 kph to 7 o'clock was measured on an icy road with an ice temperature of -7°C to -9°C.
I found its reciprocal. The measured value of Comparative Tire 3 was set as 100 and expressed as an index. The larger this number is, the better the braking performance on ice is.

(Main text below, margins) From the table above, it can be seen that Tires 1 and 2 of the present invention both have excellent braking performance on ice because the sipe density of the ribs is set to 0.15/mm or more. On the other hand, as in Comparative Tire 1, when the sipe density of the ribs is less than 0°157-, the effect of improving on-ice braking performance is small; By doing so, the braking performance on ice improves, but in Comparative Tire 4 with a sipe density of 0.20/Kakuen, the rigidity of the block decreases significantly, making the block easily chipped due to buckling or falling down, and the durability decreases. could not be said to be satisfactory.

〔Effect of the invention〕

According to the present invention, thin notches are formed in the ribs with a density of 0.15/mm or more using the rib as a base, so that thin cuts can be made without substantially reducing the rigidity of the tread portion. The edge effect due to the notch can be increased. Furthermore, by maintaining the rigidity of the tread portion, it is possible to use a low modulus rubber compound as the cap tread rubber, thereby further improving on-ice performance.

[Brief explanation of drawings]

1 and 2 are plan views showing an example of the tread pattern of the tire of the present invention, FIG. 3 is a plan view showing an example of a conventional block pattern, and FIG. 4 is a plan view showing an example of a conventional block pattern. FIG. 3 is a partial plan view for explaining the density of FIG. 1... Main groove, 2... Minor groove, 3... Block, 4...
...Thin cuts, 5...ribs. Diagram Diagram Procedure Auxiliary Device August 27, 1990

Claims (1)

[Claims] The tread surface is provided with at least one rib extending in the tire circumferential direction, and the rib is provided with a large number of thin cuts in the tire width direction, and the length of the thin cuts projected on a plane perpendicular to the tire circumferential direction is A pneumatic tire for snowy and icy roads, wherein the density of thin cuts defined by the ratio B/A of the total sum B and the surface area A of the ribs is 0.15/mm or more.