JP2002192917A - Pneumatic tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a pneumatic tire capable of realizing the superior braking performance on ice and reducing the partial abrasion by effectively preventing the falling-down, in particular, near a center of a block even when the density of sipings is increased. SOLUTION: In this pneumatic tire with a tread pattern having plural blocks 1 with plural sipings, closing ends 10a of plural sipings 10 extended from one side in the tire width direction are located near a boundary line BL dividing the block 1 into two near the center in the tire width direction or three at both sides of the center, the sipings 11 are extended from the other side in the tire width direction toward the approximately center between the closing ends 10a, and their losing ends 11a are located near the boundary line BL.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a pneumatic tire provided with a tread pattern having a plurality of blocks forming a plurality of sipes, and is particularly useful as a studless tire.

[0002]

2. Description of the Related Art Conventionally, there has been known a tire pattern in which a plurality of sipes are arranged at respective portions (a center portion, a mediate portion, and a shoulder portion) for the purpose of improving ice performance of a studless tire. As a shape of such a sipe, a sipe having a straight or corrugated cross section is generally used. By forming such a sipe in a block, an edge effect, a water removal effect, and an adhesion effect are improved, and the number of sipes tends to increase in recent years.

However, if the sipe density is increased by increasing the number of sipes, the number of edges is increased, but the rigidity of the entire block is reduced and the sipe is excessively collapsed, so that the ground contact area is reduced. There is a problem that ice braking performance is reduced. Also, if the sipe falls excessively, the contact pressure becomes uneven on the surface of each block divided by the sipe, and the difference in the amount of wear between the blocks on both sides with the sipe as a boundary tends to occur.

On the other hand, sipes formed in blocks have
There are two-sided open sipes (both sides open sipes) that open on both sides on the side wall of the block, closed sipes (closed sipes) that do not open on both sides, and one-side open sipes (one-side open sipes) that only open on one side. It is known that closed sipes are most difficult to reduce the rigidity of the block.

Japanese Unexamined Patent Publication (Kokai) No. 6-219108 proposes an ice-snow road tire in which a closed sipe and a one-side open sipe are combined and arranged in a block in order to simultaneously improve uneven wear resistance and ice braking performance. Have been.

[0006]

However, in this tire for icy and snowy roads, the closed end of the closed sipe and the closed end of the one-sided open sipe are arranged near the side wall of the block, and the sipe separates the block except at the end of the block. I'm doing
In the vicinity of the center of the block where the amount of falling of the block is largest, the effect of suppressing the falling is small. For this reason, the sipe density could not be sufficiently increased, and there was a limit to the improvement in uneven wear resistance or ice braking performance.

[0007] Some pneumatic tires are discontinuous in that the sipes extending from the side walls on both sides of the block are cut off in the middle, but in order to maintain durability, the distance between the closed ends of the cut off portions must be reduced to some extent. Because of the need to increase the size, there was a limit in increasing the sipe density.

Accordingly, an object of the present invention is to provide a good ice braking performance even when the sipe density is increased, particularly by effectively suppressing the fall near the center of the block.
Moreover, it is an object of the present invention to provide a pneumatic tire in which uneven wear hardly occurs.

[0009]

The above object can be achieved by the present invention as described below. That is, in the pneumatic tire of the present invention, in a pneumatic tire provided with a tread pattern having a plurality of blocks forming a plurality of sipes, the block is divided into two near the center in the tire width direction or three at both sides of the center. In the vicinity of the boundary line, the closed ends of a plurality of sipes extending from one side in the tire width direction are arranged, and the sipe is extended from the other side in the tire width direction toward substantially the center between the closed ends, and the closed end is formed as described above. It is characterized by being arranged near the boundary line.

In the above, the closed ends of a plurality of single-sided openings sipe extending from the side walls on both sides of the block are respectively arranged near two boundary lines dividing the block into three parts on both sides at the center in the tire width direction. It is preferable that a plurality of closed sipes are provided extending from the center in the tire width direction to both sides toward a substantially center between the closed ends, and the closed ends on both sides are preferably disposed near the two boundary lines. .

It is preferable that a closed end of the one-side opening sipe and a closed end of the closed sipe are arranged within a region of 5 mm or less in a tire width direction along the boundary line.

Further, it is preferable that at least one of the closed sipe and the one-sided open sipe has a wavy or zigzag cross-sectional shape.

According to the present invention, the block is divided into two near the center in the tire width direction or three at both sides of the center.
In a region along the boundary line to be divided, a continuous portion of the block that suppresses the block from falling is formed, so that the falling near the center of the block can be particularly effectively suppressed. That is, the closed ends of a plurality of sipes extending from one side in the tire width direction are arranged near the boundary line, and the sipe is extended from the other in the tire width direction toward substantially the center between the closed ends, and the closed end is defined as a boundary. Because it is located near the line, the blocks are continuous in the area along the boundary line, and the overlap of the sipe ends extending from both sides at the continuous portion is small (or no), and the closed ends do not extremely approach each other Therefore, the continuous portion has a reinforcing effect of suppressing the block from falling down. Since this reinforcing effect is obtained in the vicinity of the center of the block or on both sides of the center, it is possible to effectively suppress the block from falling near the center, thereby improving the sipe density. Ice braking performance can be exhibited, and uneven wear can be suppressed.

As described above, the block is divided into three parts, the closed ends of a plurality of one-sided openings sipe extending from the side walls on both sides are arranged near the boundary line, and the center of the sipe in the width direction of the tire is directed substantially toward the center between the closed ends. When a plurality of closed sipes extending from both sides from the center side are provided, and the closed ends on both sides are arranged near the two boundary lines, the side wall side of the block of the one-sided open sipe has an appropriate amount of leaning. In addition, the ice braking performance can be obtained without excess or deficiency, and the reinforcing effect as described above is provided near the closed end of the one-sided open sipe, whereby the entire block is appropriately suppressed from falling down, and the ice braking performance and uneven wear resistance are improved. At the same time, it can be significantly improved.

When the closed end of the one-sided opening sipe and the closed end of the closed-side sipe are arranged within a region of 5 mm or less in the tire width direction along the boundary line, both sides of the continuous portion of the block as described above are used. The overlap of the ends of the sipe extending from the squeeze becomes smaller, and the effect of suppressing the falling of the block by the continuous portion is further increased.

When at least one of the closed sipe and the one-sided open sipe has a wavy or zigzag cross-sectional shape, an edge component with respect to a lateral force increases.
Where uneven wear is likely to occur, it is possible to suppress uneven wear while exhibiting good ice braking performance by the above-described effects.

[0017]

Embodiments of the present invention will be described below with reference to the drawings. As shown in FIG. 1, the pneumatic tire of the present invention includes a tread pattern T having a plurality of blocks 1 in which a plurality of sipes 10 and 11 are formed. In the present embodiment, an example is shown in which a block 1 divided by a circumferential groove 2 and a lateral groove 3 is formed, and five rows of blocks 1 are arranged in the tire width direction.

In the present invention, the block 1 is divided into two near the center in the tire width direction by the boundary line or three at both sides of the center.
In this embodiment, as shown in FIG. 2, the block 1 is divided into two boundary lines B on both sides at the center in the tire width direction.
An example is shown in which an opening sipe 10 is provided on both sides of a boundary line BL and a closing sipe 11 is provided at the center thereof while being divided into three by L.

A plurality of one-side open sipes 10 are formed extending from the side walls 1a and 1b on both sides of the block 1 toward the center, respectively, and the closed ends 10a are arranged near two boundary lines BL.

The cross-sectional shape of the one-sided opening sipe 10 may be a straight line or a shape close to a straight line, but for the above-mentioned reason, a wave shape or a zigzag shape is preferable. This is the same for the closed sipes 11. The shape of the wave or zigzag is not limited to a shape close to a sine wave, and may be any shape such as a shape close to a wavy line in which straight lines and curves are alternately combined or a shape close to a rectangular wave. In addition, the one-sided opening sipe 10 may have a straight portion in which the cross-sectional shape is partially straight. When a straight portion is provided, it is preferably provided at the end of the non-linear portion. By making the end portion straight, it is possible to prevent the end portion from opening at an acute angle to the groove, so that the acute angle portion is easily damaged.

The period of the unevenness (for example, the distance between the convex and the convex top) of the cross-sectional shape of the one-sided opening sipe 10 is preferably 1.5 to 5 mm in order to suitably exhibit the characteristics of a so-called corrugated sipe. The sum of the heights of the top portions on both sides is preferably 1.5 to 5 mm.

On the other hand, the closed sipes 11 extend to both sides from the center in the width direction of the tire toward substantially the center between the closed ends 10a of the one-sided open sipes 10, and the closed ends 11a on both sides are formed near two boundary lines BL. It is located in.

That is, the closed ends of a plurality of sipes extending from one side in the tire width direction are arranged near the boundary line, and the sipes are extended from the other side in the tire width direction toward substantially the center between the closed ends to close the sipes. An edge is located near the boundary. This forms a continuous portion of the block that suppresses the falling of the block, so that the falling of the block can be effectively suppressed.

In the present invention, assuming that the position of the boundary line BL is a position where the distance from the closed end 10a is equal to the distance from the closed end 11a, the position of the divided boundary line BL is divided into the center of the block. 20 to 7 of block width centered on
It is preferable to arrange in the 0% area. Further, it is preferable that the position of the boundary line BL divided into two is arranged in an area within 30% of the block width centered on the block center.

In the present invention, for example, the closed end 10a of the one-side opening sipe 10 and the closed end 11a of the closed sipe 11
Is preferably arranged in an area of 5 mm or less in the tire width direction along the boundary line BL, and more preferably in an area of 3 mm or less in the tire width direction.
In the area exceeding 5 mm in the tire width direction along the boundary line,
When the closed end 10a and the closed end 11a are arranged, the overlap between the sipes 10, 11 extending from both sides becomes large, and the reinforcing effect for suppressing the falling of the block at that portion tends to be small. Or sipe 1 extending from both sides
When 0 and 11 are too far apart, the sipe density tends to decrease and the edge effect tends to be insufficient.

The groove width of the one-side opening sipe 10 and the closing sipe 11 is preferably 0.2 to 0.7 mm. Further, the groove depth of the one-side opening sipe 10 and the closing sipe 11 is preferably 30 to 80% of the main groove depth. The sipes 10 and 11 are generally formed so as to be perpendicular to the block surface, but the sipes may be slightly inclined (for example, 15 ° or less) with respect to a normal to the block surface. .

In the present invention, the number of edges is increased by increasing the number of auxiliary sipes 11 while suppressing the falling of the block 1, thereby increasing the number of edges to further enhance the edge effect. From such a viewpoint, the present invention provides:
A sipe density of 0.1 to 0.3 mm / mm ² is preferred,
0.15 to 0.25 mm / mm ² is more preferable.

The pneumatic tire of the present invention is the same as a normal pneumatic tire except that it has the tread pattern T as described above, and any conventionally known materials, shapes, structures, manufacturing methods, etc. are employed in the present invention. it can.

The pneumatic tire of the present invention has the above-mentioned effects and is excellent in ice performance, and is particularly useful as a studless tire.

[Other Embodiments] Hereinafter, other embodiments of the present invention will be described.

(1) In the above-described embodiment, the block is divided into three by two boundary lines on both sides of the center in the tire width direction, and a one-sided opening sipe is provided on both sides of the boundary line, and the center is closed at the center. The example in which the sipes are provided so that their closed ends are located substantially on the boundary line is shown. However, assuming that the sipes extending from both sides have a larger overlapping amount or that the sipes are divided into two near the center in the tire width direction. 3 (a) and 3 (b).

FIG. 3 (a) shows an example in which the ends of the sipes 10, 11 extending from both sides have a larger overlapping amount as compared with FIG. In the overlapping portion near the boundary line BL, the ends of the sipe 10 and the sipe 11 have substantially the same shape and are arranged at positions shifted in the tire circumferential direction. In the present invention, the overlap amount can be reduced, and the closed end 10a and the closed end 11a can be arranged on a straight line.
1a may be arranged away from the boundary line BL.
However, it is preferable to dispose it in a region having a certain width or less along the boundary line BL as described above. At this time, the overlapping amount of the sipe may change depending on the site.

In FIG. 3B, closed ends 13a and 14a of sipes 13 and 14 extending from both sides are arranged near a boundary line BL that is divided into two near the center in the tire width direction. Further, the sipes 13 and 14 are provided with their reference lines slightly inclined from the tire width direction. Thus, the sipe in the present invention does not need to be parallel to the tire width direction, but the angle between the direction of the reference line and the tire width direction is preferably 0 to 45 °.

(2) In the above-described embodiment, an example of the block pattern as shown in FIG. 1 has been described. However, the present invention is not limited to the block having this shape, but may be a parallelogram, V-shaped, pentagon, or curved tone. It may be a block. Further, a block with a groove or a part of a land portion may be continuous in the circumferential direction near the center or near the end. An example of another preferable pattern according to the present invention is as follows.

In this example, as shown in FIG. 4, a block 1 divided by a circumferential groove 2, lateral grooves 3, 5 and an oblique groove 4 is used.
Are formed, and six rows of blocks 1 are arranged in the tire width direction. Further, the block 1 has a different shape depending on the position in the tire width direction, and in any of the shapes, the periphery thereof has a zigzag shape. In such a tread pattern T, the one-side opening sipe 10 and the closing sipe 11 have a shape and an arrangement as shown in FIG.
Are formed.

(3) In the above-described embodiment, an example is shown in which the sipes extending from the side wall of the block are all open in the groove adjacent to the block, but may be closed ends that do not open in the side wall of the block. It can be properly used depending on the pattern configuration.

[0037]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments and the like specifically showing the configuration and effects of the present invention will be described below. In addition, each performance evaluation of the tire was performed as follows. The sipe density was adjusted by changing the sipe interval.

(1) Ice braking performance Using actual tires (domestic 2000cc class FF sedan)
The vehicle was run on a frozen road surface under the load condition of a single rider, and the braking distance when the vehicle was fully locked by applying a braking force at a speed of 40 km / h was evaluated by an index. In addition, evaluation is shown by the index display when the conventional product (Comparative Example 1) is set to 100,
Higher values indicate better results.

(2) Abrasion Resistance The amount of step wear (step on both side blocks of the sipe due to abrasion) when traveling 8,000 km on a pavement was measured and evaluated by an index. In addition, the evaluation was 10 for the conventional product (Comparative Example 1).
The result is indicated by an index when it is set to 0, and a larger value indicates a better result. Example 1 In the tread pattern as shown in FIG. 1, a sipe having the shape shown in FIG.
A 70R14 radial tire was manufactured. Table 1 shows the results of the performance evaluations described above using this tire.
7mm sipe depth, 0.3mm groove width, 1.5m amplitude
m, period 4.0 mm, sipe density 0.20 mm / mm
^2. The width of the overlapping region at the end of the sipe was 0.6 mm.

Embodiment 2 In a tread pattern as shown in FIG.
A sipe having the shape of (a) was formed in the following size to manufacture a radial tire of size 185 / 70R14. Table 1 shows the results of the performance evaluations described above using this tire. Sipe depth 7mm, groove width 0.3mm, amplitude 1.5mm, cycle 4.0mm, sipe density 0.23m
m / mm ² , and the width of the overlapping region at the sipe end was 2.3 mm.

Comparative Example 1 (Conventional Product) In Example 1, a waveform sipe as shown in FIG. 5 was formed at a sipe density of 0.18 mm / mm ² (conventional wave type sipe). Similarly, size 18
5 / 70R14 radial tires were manufactured and the above-described performance evaluations were performed. Table 1 shows the results.

Comparative Example 2 In Comparative Example 1, only the sipe density was increased to 0.2
Except having made it 1 mm / mm < ² >, it carried out similarly to the comparative example 1, and
Manufacture radial tires of size 185 / 70R14,
Each performance evaluation described above was performed. Table 1 shows the results.

[0043]

[Table 1] As shown in the results of Table 1, in the example, the ice braking performance was better than the conventional product due to the effect of suppressing the block from falling down. On the other hand, in Comparative Example 2 in which only the density of the conventional wavy sipe was increased, the ice braking performance was slightly improved, but the wear resistance performance was reduced.

[Brief description of the drawings]

FIG. 1 is a plan view showing a tread surface of an example of a pneumatic tire of the present invention.

FIG. 2 is an enlarged view of a main part showing an example of a block according to the present invention.

FIG. 3 is an enlarged view of a main part showing another example of a block according to the present invention.

FIG. 4 is a plan view showing a tread surface of another example of the pneumatic tire of the present invention.

FIG. 5 is an enlarged view of a main part showing an example of a block adopted in a comparative example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 block 10 One-sided opening sipe 10a Closed end 11 Closed sipe 11a Closed end 13-14 Sipe 13a-14a Closed end T Tread pattern BL boundary

Claims (4)

[Claims] 1. A pneumatic tire having a tread pattern having a plurality of blocks formed with a plurality of sipes, wherein the block is divided into two near the center in the tire width direction or three near both sides of the center in the vicinity of a boundary line. Along with disposing the closed ends of a plurality of sipes extending from one in the tire width direction, extending the sipes from the other in the tire width direction toward substantially the center between the closed ends, and disposing the closed ends near the boundary line A pneumatic tire characterized in that: 2. A plurality of one-sided open sipes extending from side walls on both sides of the block are respectively disposed near two boundary lines dividing the block into three parts at both sides in the center in the tire width direction, and 2. A plurality of closed sipes extending to both sides from the center in the tire width direction toward substantially the center between the closed ends, and the closed ends on both sides are arranged near the two boundary lines. Pneumatic tires. 3. The pneumatic tire according to claim 2, wherein a closed end of the one-side opening sipe and a closed end of the closed sipe are arranged within a region of 5 mm or less in a tire width direction along the boundary line. 4. The pneumatic tire according to claim 2, wherein at least one of the closed sipe and the one-side open sipe has a wavy or zigzag cross-sectional shape.