JPH08244418A - Pneumatic tire applicable to icy road running - Google Patents

Abstract

PURPOSE: To improve edge effect and water eliminating effect by sipes by providing additive sipes to lateral sipes to a center zone and a middle zone in a tread pattern for parting the pattern into plural micro-blocks, and setting the number of the micro-blocks to be low in the middle zone compared to the middle zone. CONSTITUTION: In a tread pattern, a center block 21 is parted by vertical grooves 11, 11 and a lateral groove 14, a middle block 23 is parted by circumferential grooves 12, 12 and a lateral groove 15, and a shoulder block 25 is parted by the circumferential groove 12, a tread end 18, and a lateral groove 16. Lateral sipes 3 in zigzag forms are then provided substantially in parallel in each block 21, 23, 25, so they are parted into plural micro-blocks 8 of which number is low in a middle zone compared to a center zone. Additive sipes 5 are provided to cross folding points of the zigzag forms of the lateral sipes 3 in the center zone and the middle zone.

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 running on ice and snow roads, and more particularly to a pneumatic tire having excellent running performance on ice.

[0002]

2. Description of the Related Art A typical example of a conventional tread pattern applied to a pneumatic tire for traveling on ice and snowy roads is shown in FIG.

As shown in FIG. 3, in a typical conventional pneumatic tire for traveling on ice and snow roads, zigzag grooves 71 and straight grooves 73 extending continuously in the tire circumferential direction are alternately arranged in the tire axial direction. , A plurality of lateral grooves 76 are arranged at intervals in the circumferential direction so as to connect these circumferential grooves, and a plurality of block rows 77 are formed by the circumferential grooves 71, 73 and the lateral grooves 76. A plurality of sipes 79 are arranged substantially in parallel with each other, and the negative ratio is 35 to 4
Equipped with a 5% tread pattern, it exhibits excellent performance for ice and snow running.

However, since the coefficient of friction of the frozen road surface is lowered due to the warm winter in recent years, the emergence of a tire capable of exhibiting excellent on-ice performance, that is, turning performance and braking performance as compared with the conventional tire is strongly desired.

In order to improve the performance on ice, the frictional force is increased by increasing the ground contact surface area (positive), and the digging effect is obtained by increasing the number of sipes (density) and increasing the edge component (hereinafter Measures such as enhancing the edge effect) can be taken. Furthermore, it has been found that it is important to remove the water film that springs up to the ground contact surface, especially on ice near 0 ° C. For this purpose, it is effective to raise the sipe density, but if it is raised too much, the rigidity of the block will decrease too much and uneven wear will occur, and at the same time, the bending deformation of the block will reduce the ground contact area,
Rather, the performance on ice may decrease.

Foamed rubber as disclosed in Japanese Unexamined Patent Publication No. 62-283001 is often used for a tread of a tire running on a snowy road, but it is softer than a general tread rubber, and therefore a foamed rubber is adopted. When using sipes with high density in the tread, it is important to secure the block rigidity.

[0007]

DISCLOSURE OF THE INVENTION An object of the present invention is to focus on the arrangement of sipes in a block, to improve the edge effect and water removal effect by the sipes, and to secure the rigidity of the block on snow, especially on ice. It is to provide a novel tret pattern having excellent performance. Another object of the present invention is to provide a pneumatic tire having a pattern for traveling on ice and snowy roads, which is suitable for a tread made of a relatively soft rubber such as the foamed rubber.

[0008]

SUMMARY OF THE INVENTION The present invention as set forth in claim 1 is a tread pattern having a number of blocks having a plurality of lateral sipes extending substantially axially, the blocks being axial. When viewed in the direction, it is composed of a central area, both end areas and a central area between the central area and both end areas.In the central area and the middle area, additional sipes are connected to the lateral sipes and the central area and the middle area are divided into a plurality of micro blocks. The pneumatic tire is subdivided and has a tread pattern which is characterized in that the number of microblocks is smaller in the middle area than in the central area, and is suitable for ice and snow running.

The present invention according to claim 2 is the pneumatic tire according to claim 1, wherein the lateral sipe has a zigzag shape.

The present invention according to claim 3 is the pneumatic tire according to any one of claims 1 and 2, wherein the microblock defined by the lateral sipe and the additional sipe has a polygonal shape. Is characterized by.

The present invention according to claim 4 is the pneumatic tire according to any one of claims 1 to 3, wherein the front and rear ends of the block in the circumferential direction are substantially continuous along the end. It is characterized by having sex.

[0012]

According to the pneumatic tire of the present invention as set forth in claim 1, a plurality of lateral sipes extending substantially in the axial direction are arranged in the block, and the central region is connected to the lateral sipes by additional sipes. By subdividing into microblocks and providing an intermediate area having a relatively small number of microblocks between the both end areas, the block rigidity is gradually changed from the center toward both ends. Improves drainage of the water film on ice while improving ground contact and maintaining uneven wear resistance.

The lateral sipes have a water removing effect of cutting the water film sprung on the road surface in addition to the edge effect of the edges provided by the sipes. When one independent block touches the ice surface, the water film inside the block is drained to the outside of the block ground plane by the open sipe that opens in the adjacent main groove, but the central area of the block away from the main groove is drained. It tends to be difficult to be done. It is advantageous for drainage to increase the sipe density in the central area of the block.

If the sipe of the entire surface of the block is densely applied, the edge effect and the drainage effect are improved, but if the block is left as it is, the rigidity of the block is lowered and the effective ground contact area is reduced due to the deformation of the block, resulting in deterioration of the braking performance and the like. Therefore, the central and intermediate areas of the block are subdivided into microblocks, an intermediate area is provided between the central area and both end areas, and this intermediate area is provided with a smaller number of microblocks than the central area and both end areas are arranged. By changing the block rigidity from the center to both end areas in a stepwise manner by connecting it to the block, the block rigidity in the central area will be reduced, but the surrounding block rigidity will be sufficiently secured in stages and the grounding property will be improved as a whole. Also, in the central area where drainage is poor, sipes communicate with each other and allow water to pass through, thus improving the water removal effect.

In the pneumatic tire of the second aspect of the present invention, since the lateral sipe has a zigzag shape, the sipe length can be shortened and the edge effect can be enhanced.

In the pneumatic tire of the present invention as set forth in claim 3, since the microblocks have a polygonal shape, a circumferential component is imparted to the sipes in the central area of the block so that the circumferential direction of the tire is increased. It becomes easy to secure the rigidity in the front-back direction.

In the pneumatic tire of the present invention as set forth in claim 4, since the front and rear ends of the block in the circumferential direction are substantially continuous along the end,
It is possible to secure the rigidity of the block and avoid a reduction in the ground contact area due to large deformation.

[0018]

Embodiments of the present invention will now be described in detail with reference to the drawings. 1 and 2 show a first embodiment and a second embodiment, each having a tire size of 185/7.
At 0R14, the tread width TW is about 148 mm, and the negative rate is 29%. The width of the sipes applied is 0.5 mm.

As shown in FIG. 1, the tread pattern of the first embodiment has a circumferential groove 11, 12 and a lateral groove 1.
A large number of blocks 21, 2 formed by 4, 15, 16
It is equipped with 3 and 25. The central groove 21 is defined by the circumferential grooves 11, 11 and the lateral groove 14, and the circumferential groove 1
1, 12 and the lateral groove 15 define an intermediate block 23, and the circumferential groove 12, the tread end 18 and the lateral groove 16 define a shoulder block 25. Here, the width of each of the circumferential grooves 11 and 12 is 5
mm and 6 mm, and the groove widths of the lateral grooves 14, 15 and 16 are all 6 mm. These lateral grooves 14, 15,
Reference numeral 16 denotes narrow groove portions 14A, 15A, 16 having a narrow groove width (2 mm in this example) such that both side walls of the groove are in close contact when grounded.
A is provided. These narrow groove portions 14A, 15A, 16
A brings continuity to the front and rear blocks at the time of grounding, and secures the rigidity of each block 21, 23, 25 as a block row in the circumferential direction.

In a pneumatic tire for running on ice and snowy roads, in order to increase the friction coefficient, a foam rubber having a low hardness is often used for a tread, and a block is provided with a large number of sipes. As a result, a phenomenon may occur in which the tire tread rigidity is insufficient and the tread rubber (block) buckles directly under a load. In order to prevent this, it is necessary to secure the rigidity in the tread center region where the ground contact pressure is high. In the present embodiment, the narrow groove portion 1
The continuity provided by 4A, 15A, 16A ensures circumferential tread stiffness.

In the central block 21, the intermediate block 23 and the shoulder block 25, a plurality of zigzag-shaped lateral sipes 3 are arranged substantially in parallel. As shown in the drawing, the lateral sipe 3 can be slightly inclined with respect to the tire axial direction, and extends in the axial direction as a whole. Further, the lateral sipes 3 are arranged so as to be substantially parallel to the lateral grooves 14 so that the edge effect can be efficiently obtained.

Reference numeral 5 denotes an additional sipe, which is connected to the lateral sipe 3. As shown in the figure, each block is divided into a central area 21A, 23A, 25A, both end areas 21C, 23C, 25C, and an intermediate area 21B, 23B, 25B between the central area and both end areas, as shown in the figure, depending on how the sipes are applied. .

The additional sipe 5, together with the lateral sipe 3, subdivides the block excluding both end regions into microblocks. Whereas the lateral sipes extend substantially in the tire axial direction, the additional sipes 5 extend substantially in the tire circumferential direction, and in this example, the zigzag of the lateral sipes 3 in the central area and the intermediate area. The central areas 21A, 23A, 25A and the intermediate areas 21B, 2 are arranged so as to intersect the bending points.
3B and 25B are assumed to have polygonal microblocks 8. The number of micro blocks is the central block 21
5 in the central area 21A, 2 in the intermediate area 21B, 8 in the intermediate area 23A of the intermediate block 23, and 2 in the intermediate area 23B. The number of microblocks in the middle area is smaller than that in the central area, and the central areas are connected in steps toward both end areas. In this example, the two mini-blocks in the middle section are arranged circumferentially adjacent to each other.

Although the lateral sipe 3 has a zigzag shape in this example, the lateral sipe 3 is not limited to this and may be a bent sipe including a wavy shape or the like. Further, the microblock 8 to be subdivided can have any shape such as various polygonal shapes and substantially circular shapes.

A ₁ , a ₂ and a ₃ are axial widths of central areas of the central block 21, the intermediate block 23 and the shoulder block 25, b ₁ , b ₂ and b, respectively.
Similarly, ₃ indicates the axial width of the intermediate areas 21B, 23B and 25B of each block, and c ₁ , c ₂ and c ₃ indicate the axial width of the end areas 21C, 23C and 25C of each block, respectively. In the first embodiment, a ₁ , a ₂ and a ₃ are 4 mm, 8 mm and 4 mm, and b ₁ , b ₂ and b ₃
Is 4 mm, and c ₁ , c ₂ and c ₃ are all 6
mm.

The front and rear ends 21 ', 23', 25 'of the blocks 21, 23, 25 in the circumferential direction are continuously arranged along the ends without substantially being provided with sipes. Have sex.

As shown in FIG. 2, the tread pattern of the second embodiment is similar to the first embodiment in that the block 21,
23 and 25 are defined and siping is performed. In this second embodiment, the intermediate areas 21B and 23B of each block are
2 and 25B are different from the first embodiment in that two microblocks 25B and 25B are arranged apart from each other, and the other parts are the same.

[Test Example] The above-described first embodiment and FIG.
With respect to the pneumatic tire for a passenger car of the conventional example shown in, the evaluation test of the cornering performance on ice, the braking performance on ice, and the traction performance on ice was carried out. Table 1 shows the evaluation results.

The tire of the conventional example (FIG. 3) has the same size as that of the example, has a negative ratio of 35%, a zigzag circumferential groove 71 has a groove width of 5 to 7 mm, and a linear circumferential groove 73.
The width of the groove was 4 mm, the width of the lateral groove 76 was 6 mm, and the width of the sipe was 0.7 mm.

The test conditions are: tire internal pressure of 2.0 kg / cm ² ,
The cornering performance on ice is the time required to make a circular turn with a radius of 20 m on the ice board, and the braking performance on ice is 20 km / on the ice board.
The braking distance and traction performance on ice when the vehicle is running at a speed of h for full braking is an evaluation result of the time required for a full acceleration of 100 m from a state of running at a speed of 20 km / h on an ice plate.

The evaluation results are shown in index form with the result of the pneumatic tire of the conventional example as 100, and the larger the number, the better the performance.

[0032]

[Table 1]

From the results shown in Table 1, it was found that the pneumatic tire for passenger cars according to the first embodiment of the present invention has far better ice performance than the pneumatic tire for passenger cars according to the conventional example. It was

[0034]

According to the pneumatic tire of claim 1, the block is divided into a central portion, both ends and an intermediate region therebetween.
The area excluding both end areas is subdivided into mini-blocks, and the number of steps for forming mini-blocks is stepwise, so it has a high drainage effect and improves the grounding property and uneven wear resistance of the block. It has an excellent effect that it is suitable for running on ice and snow, especially on ice.

In the pneumatic tire of the second aspect of the present invention, since the sipes arranged in the both side areas have a zigzag shape, a high edge effect is obtained.

According to the pneumatic tire of the third aspect of the present invention, the mini block has a polygonal shape, and has a high edge effect and a circumferential rigidity.

In the pneumatic tire of the present invention as defined in claim 4, since the front and rear ends of the block in the circumferential direction are substantially continuous along the end, the rigidity of the block is improved. Has the effect of ensuring.

[Brief description of drawings]

FIG. 1 is a plan view of a first embodiment of the present invention.

FIG. 2 is a plan view of a second embodiment of the present invention.

FIG. 3 is a plan view showing a conventional example.

[Explanation of symbols]

11, 12 Circumferential groove 14, 15, 16 Horizontal groove 21 Central block 23 Intermediate block 25 Shoulder block 21A, 23A, 25A Central area of each block 21B, 23B, 25B Intermediate area of each block 21C, 23C, 25C Each block End areas a ₁ , a ₂ , a ₃ axial widths of central areas b ₁ , b ₂ , b ₃ axial widths of intermediate areas c ₁ , c ₂ , c ₃ axial widths of both end areas 3 lateral sipe 5 Additional Sipe 8 Micro Block

Claims (4)

[Claims] 1. A tread pattern having a number of blocks having a plurality of lateral sipes extending substantially in an axial direction of a tire, wherein the blocks have a central section, both end sections and a central section and both ends in the axial direction. It consists of an intermediate area between the areas, and in the central area and the intermediate area, additional sipes are connected in a lateral sipe and the central area and the intermediate area are subdivided into a plurality of microblocks. Pneumatic tire suitable for ice and snow running with a tread pattern characterized by less than 2. The pneumatic tire according to claim 1, wherein the lateral sipe has a zigzag shape. 3. The pneumatic tire according to claim 1, wherein the microblock defined by the lateral sipe and the additional sipe has a polygonal shape. 4. The pneumatic tire according to claim 1, wherein the front and rear ends of the block with respect to the circumferential direction are substantially continuous along the end.