JPH03186407A - Pneumatic tire - Google Patents

Abstract

PURPOSE:To improve draining performance and an edge effect against lateral force without deteriorating block rigidity by arranging peripheral direction sipes in a small block in a branching manner from tire width direction sipes of the block formed in tread surfaces of a tire. CONSTITUTION:The block pattern of a tire is formed of many blocks 3 partitioned by a plurality of main grooves 1 in a tire peripheral direction and a plurality of subgrooves 2 traversing these main grooves 1. Here width direction spies 4, extending in a tire width direction, is arranged to form small blocks 6. Also short peripheral direction sipes 8, extending in the tire peripheral direction, are arranged so as to traverse the width direction sipes 4. At least one end part of the width direction sipe 4 is connected to the main groove 1. On the other hand, one end part of the peripheral direction sipe 8 is connected to width direction sipe 4 while the other end part thereof is terminated inside each small block 6.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a pneumatic tire, and more particularly, to a pneumatic tire that has improved braking performance on ice, traction performance, and maneuverability. It is something.

[Conventional technology]

Pneumatic tires used for driving on icy and snowy roads generally have a block pattern on the tread surface, and the block surface is further provided with sipes that extend in the tire width direction (radial direction) to divide the block into small blocks to improve drainage. Efforts have been made to improve driving performance on icy and snowy roads by improving the stability and edge effect. However, this configuration in which the block is divided into small blocks is mainly aimed at improving braking performance and traction performance when driving straight, but there is a problem in that the performance is not fully demonstrated when driving when cornering.

[Problems to be Solved by the Invention] An object of the present invention is to provide a pneumatic tire having a block pattern that not only improves braking performance and traction performance on icy and snowy roads but also improves steering stability. There is a particular thing.

(Means for Solving the Problems) In order to achieve the above object, the pneumatic tire of the present invention has a tread surface mainly formed by a block pattern, and the blocks constituting the block pattern have at least one end. A widthwise sipe that communicates with the outside of the block and extends in the tire width direction, and a circumferential sipe that communicates with the widthwise sipe at one end and extends in the tire circumferential direction, and the other end of the circumferential sipe is connected to the widthwise sipe. It is formed so that it ends within a small block divided into .

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

FIG. 1 shows an example of a block pattern of a pneumatic tire according to the present invention, and arrow T indicates the circumferential direction of the tire. The block pattern shown in the figure has a plurality of upper grooves 1 in the circumferential direction of the tire and a number of sub-grooves 2 extending across them, and constitutes a large number of blocks 3 partitioned by the upper grooves 1 and the sub-grooves 2. There is.

Each block 3 is provided with a widthwise sipe 4 in the tire radius direction, and a small block 6 is formed. Further, short circumferential sipes 8 in the tire circumferential direction are provided so as to cross these width direction sipes 4. The groove width of these sipes 4, 8 is generally about 0.5 to 1.5 mm.

The width direction sipe 4 is provided in at least one of the blocks so as to communicate with the main groove l. That is, in the block 3 at the center, both ends of the width direction sipe 4 are communicated with the main groove 1, but in the block 3 at the shoulder part, only one end of the width direction sipe 4 is communicated.

Further, the circumferential sipe 8 is formed such that one end communicates with the widthwise sipe 4 and the other end ends within the small block 6. The above-mentioned width direction sipes 4 and circumferential direction sipes 8 improve drainage performance due to capillary phenomenon, so under such conditions of high drainage performance, braking performance due to the edge effect of the width direction sipes 4,
The separation situation will further improve. Furthermore, the circumferential sipes 8 improve the edge effect particularly against external forces in the axial direction of the tire, thereby improving steering stability during cornering.

Next, the width direction sipe 4 and the circumferential direction sipe 8 will be further explained with reference to FIGS. 2 and 3.

The longer the length l of the circumferential sipe 8 that protrudes from the widthwise sipe 4, the more the edge effect against lateral force increases and the steering stability is improved, but if it is too long, the block rigidity decreases and the general Driving stability on the road decreases. Therefore, for the length L of the small block 6 in the tire circumferential direction, 1
/L≦1/3. However, even if it is too short, the steering stability effect of the circumferential sipe 10 will be reduced, so it is usually preferable to set f/L to 1/10 or more.

Further, the depth d of the circumferential sipe is preferably d≧2 and d/D≦1.0 with respect to the circumferential sipe length l and the widthwise sipe depth D. If we set this to d<ffi,
The effectiveness of the circumferential sipes 10 quickly deteriorates due to tread wear. Moreover, when d/D>1.0, the block rigidity decreases, which is not preferable.

The arrangement of the width direction sipes and the circumferential direction sipes may be arranged in various ways other than that shown in FIG. 2, as illustrated in FIGS. 4 to 8. That is, in FIG. 4, the circumferential sipes 8 are provided only on one side of the widthwise sipes 4. In FIG. 5, the circumferential sipes 8 are made into a straight zigzag shape, and the characteristics of the widthwise sipes are added to the circumferential sipes 8. On the contrary, in FIG. 6, the characteristics of the circumferential sipes 8 are added to the widthwise sipes 4 by making the widthwise sipes 4 into a zigzag shape.

In FIG. 7, the width direction sipes 4 are tilted with respect to the tire axial direction A to take into account the characteristics of the circumferential direction sipes, and in FIG. 8, the circumferential direction sipes 8 are also tilted with respect to the tire circumferential direction T. ,
In each case, characteristics in the circumferential direction are taken into account in the width direction, and characteristics in the width direction are taken into account in the circumferential direction.

〔Example〕

The tires of the present invention have the same block pattern as shown in FIG. 1 except that the sipes provided on each block are different, and the sipes provided on the blocks are as shown in FIG. 2, FIGS. 9 and 10 Comparative tire I (No. 9
A comparative tire (Fig. 1) and a comparative tire (Fig. 10) were prepared.The tire size was the same, 185R14, and the other dimensions were set to the following values.

Tread development width: 140 mm Top groove width: 8.0 open, main groove depth: 12.5 aem Pitch number = 56 Small block tire circumferential length L near, 0 + m Sipe width = 0.8 Open width direction sipe depth D : 8.4mm Circumferential sipe depth d: 8.0m+w (inventive tire and comparative tire ■) Length f of circumferential sipe protruding from widthwise sipe: 1.
7mm (tire of the present invention) The above three types of tires were sequentially installed on the same test vehicle, and the dry road handling stability, ice and snow road handling stability, ice and snow road braking performance, and ice and snow road traction performance were actually measured using the test method described below. The results are shown in the table.

Dry road steering stability test: Five test drivers evaluated the feeling when cornering on a dry test course using a 5-point method, and the average value of the five test drivers was expressed as an index with the comparison tire ■ as 100. Ta.

Icy and snowy road handling stability test: Five test drivers evaluated the feeling when cornering on an icy and snowy road using a 5-point method, and compared the average value of the five test drivers.
It is expressed as an index of 00.

Icy road braking performance test: Initial speed 40km+/h on frozen road surface
The braking distance from to stopping was measured. The reciprocal of the result was expressed as an index with Comparative Tire I as 100.

Ice and snow road handling ability test: Start climbing on a slope made of compacted snow at an initial speed of 30 km/11, measure the time required to climb the slope, and compare the reciprocal of the measured value Tire I 1
It is expressed as an index of 00.

(Margin) 4゜As shown in the table, the tire of the present invention has the same dry road handling stability as the conventional tire of Comparative Tire I, and also has improved braking performance and traction performance in ice and snow performance, as well as improved handling stability. It's improving. On the other hand, the comparison tire (3) had a marked decrease in dry road handling stability due to a significant decrease in block rigidity.

〔Effect of the invention〕

As explained above, in the pneumatic tire of the present invention, circumferential sipes are provided in the small blocks branching from the tire width direction sipes of the block formed on the tread surface, so drainage can be carried out without reducing block rigidity. The edge effect on the lateral force in the width direction of the tire can be increased. Therefore, braking performance and traction performance on icy and snowy roads can be improved without sacrificing steering stability on dry road surfaces, and driving stability on icy and snowy roads can be improved.

[BRIEF DESCRIPTION OF THE DRAWINGS] Fig. 1 is a partially exploded view showing an example of the trend pattern of the pneumatic tire of the present invention, Fig. 2 is an enlarged view of the block surface shown in Fig. 1, and Fig. 3 is Fig. 2. A cross-sectional view taken along the line ■-■,
4 to 8 are block surface views showing an example of an embodiment of the present invention, FIG. 9 is a block surface view of comparative tire I, and FIG. 1O is a block surface view of comparative tire H. l...Main groove, 2...Minor groove, 3...Block, 4...
... Width direction sipe, 6... Small block, 8... Circumferential direction sipe, T... Tire circumferential direction.

Claims (1)

[Claims] The tread surface is mainly formed by a block pattern,
The blocks constituting this block pattern include a widthwise sipe whose at least one end communicates with the outside of the block and extends in the tire width direction, and a circumferential sipe whose one end communicates with the widthwise sipe and extends in the tire circumferential direction. , and the other end of the circumferential sipe is formed to end within a small block divided into the widthwise sipes.