JP2003072324A - Pneumatic tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a pneumatic tire having large edge components in the lateral direction and longitudinal direction and an improving effect of both ice braking performance and ice turning performance. SOLUTION: This pneumatic tire is provided with a tread pattern having a plurality of blocks 1 having a sipe 10 including a wave-like part 11 or a zigzag-like part. The wave-like part 11 or the zigzag-like part of the sipe 10 includes a first part 11a of which tangent has an angle of -20 to 20 deg. with respect to tire width direction WD at 20 to 70% in length in one cycle and a second part 11b of which tangent has an angle of -20 to 20 deg.C with respect to tire circumferential direction PD at 20 to 70% in length in one cycle.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pneumatic tire having a tread pattern having a plurality of blocks forming sipes each including a wavy portion or a zigzag portion,
It is particularly useful as a studless tire.

[0002]

2. Description of the Related Art Heretofore, an example has been known in which a large number of sipes are arranged in each part (center part, mediate part, shoulder part) of a tire pattern for the purpose of improving the ice performance of a studless tire. For the purpose of improving ice braking performance, many sipes extending in the tire width direction have been arranged to improve the edge effect in the front-rear direction. Further, for the purpose of improving the ice turning performance, the sipe component having an angle approaching the tire circumferential direction has been increased to improve the lateral edge effect.

As a method for improving both the ice braking performance and the ice turning performance, it is general practice to form a wavy or zigzag sipe in the tire width direction instead of the straight sipe in the tire width direction. Came. In such a corrugated sipe, in addition to a portion having an angle close to the tire width direction, there is a portion having an angle close to about 45 ° from the tire width direction. Therefore, the ice turning performance should be improved as compared with the straight sipe. You can

However, in the above corrugated sipes, the reduction of the component in the tire width direction cannot be avoided, and the component in the tire circumferential direction is not sufficient at an angle of about 45 °. Both the turning performance and the improvement effect were insufficient.

[0005]

On the other hand, Japanese Patent Laid-Open No. 2000-
In Japanese Patent No. 94909, the ratio of short side to long side (short side / long side) of a zigzag sipe extending in the tire width direction is 0.25.
.About.0.75, the long side has an inclination angle of 65 to 90.degree. With respect to the tire circumferential direction, the long side and the short side have an intersection angle of 90 to 130.degree., And the lateral groove and the long side have an inclination. Pneumatic tires with opposite directions have been proposed. And
It is disclosed that such sipe formation improves ice braking performance, ice running stability, and edge wear resistance.

However, since the sipe described above extends in the tire width direction, the length of the short side is small, and its angle also allows a large deviation from the tire circumferential direction. It seems that there is almost no effect of improving sex. Further, in the above-mentioned publication, the effect of improving the ice running stability is positioned as the effect of making the inclination direction of the lateral groove and the inclination direction of the long side of the sipe opposite to each other.

SUMMARY OF THE INVENTION An object of the present invention is to provide a pneumatic tire having a large edge component in the lateral and longitudinal directions and a great effect of improving both ice braking performance and ice turning performance.

[0008]

The above object can be achieved by the present invention as described below. That is, the present invention, in a pneumatic tire having a tread pattern having a plurality of blocks forming a sipe including a wavy portion or zigzag portion, the wavy portion or zigzag portion of the sipe,
The tangent line includes a first portion having an angle of −20 to 20 ° with respect to the tire width direction in a period of 20 to 70%, and the tangent line has an angle of −20 to 20 ° with respect to the tire circumferential direction. Second
It is characterized in that a portion is included in one cycle with a length of 20 to 70%.

In the above, the ratio of the lengths of the first part and the second part (first part / second part) is 0.8-1.
It is preferably 2.

The sipe extends from at least one end of the wavy portion or the zigzag portion to the side wall of the block or the vicinity thereof, and the direction thereof is -20 with respect to the tire width direction.
It is preferable to include a substantially straight portion with an angle of -20 °.

[Operation and Effect] According to the present invention, since the tangent includes the first portion having an angle of −20 to 20 ° with respect to the tire width direction within a period of 20 to 70% within one cycle of the sipe, The number of edge components in the direction is increased, and the front-rear performance such as ice braking property is improved. In addition, the tangent to the tire circumferential direction −
The second part with an angle of 20 to 20 is 2 in one cycle of sipes.
Since it is contained in the length of 0 to 70%, the edge component in the horizontal direction is increased, and the ice swirling property is improved. Then, the ratio of the lengths of the two parts (first part / second part) is also within a certain range, so that both the ice braking performance and the ice turning performance can be improved in good balance. In addition, since the sipe component of about 45 ° with respect to the tire width direction is reduced, the block pieces are less likely to open when longitudinal force or lateral force is generated, and the block pieces do not fall down easily. It is possible to prevent step wear from occurring.

Further, when the ratio of the lengths of the first portion and the second portion (first portion / second portion) is 0.8 to 1.2, the ice braking performance and the ice turning performance are more well balanced. Both can be improved.

The sipe extends from at least one end of the wavy portion or the zigzag portion to the side wall of the block or the vicinity thereof, and the direction thereof is -20 to 20 with respect to the tire width direction.
If the block includes a substantially straight line portion, the angle of the block with respect to the side wall is unlikely to be small, and thus damage to the block piece in the vicinity of the sipe end can be prevented.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a plan view showing a tread surface of an example of a pneumatic tire of the present invention.
Further, FIG. 2A is an enlarged view of an essential part showing a block on the tread surface of FIG. 1, and FIG. 2B is an enlarged view of an essential part of the sipe.

As shown in FIG. 1, the pneumatic tire of the present invention has a tread pattern T having a plurality of blocks 1 each having a sipe 10 including a wavy portion or a zigzag portion.
Equipped with. In the present embodiment, an example is shown in which a rectangular block 1 is formed by being divided by the circumferential groove 2 and the lateral groove 3, and five rows of blocks 1 are arranged for the tire center CL. In this example, sipe 1 in each block 1
Although the direction of 0 is arranged so as to be opposite in each block, they may be arranged in the same direction.

The sipe 10 according to the present invention is shown in FIG.
As shown in (b), the tangent line of the wavy portion 11 or the zigzag portion of the sipe 10 is − with respect to the tire width direction WD.
The first portion 11a having an angle of 20 to 20 ° is set to 20 within one cycle.
It is characterized in that it includes the second portion 11b having a length of ˜70% and a tangent line having an angle of −20 to 20 ° with respect to the tire circumferential direction PD and having a length of 20 to 70% within one cycle. . Figure 2
(B) shows the sipe 10 contained in one cycle corresponding to the pitch PI with the length of the first portion 11a being 42% and the length of the second portion 11b being 42%. In addition, sipe 1
The tangent line of 0 is determined based on the sipe center line.

According to the present invention, the length of the first portion 11a within one cycle is 40 to 6 in order to improve the balance between the ice braking performance and the ice turning performance while maintaining both performances above a certain level.
0%, the length of one cycle of the second portion 11b is 40 to 60%
Is preferred.

The length ratio of the first portion 11a and the second portion 11b (first portion / second portion) is preferably 0.8 to 1.2, more preferably 0.9 to 1. .1. Most preferably, the first portion 11a and the second portion 11
By making the length ratio of b substantially the same and repeating this in the same cycle, the wavy portion 11 of the sipe 10 is formed.

In the present invention, the wavy portion 1 as shown in FIG.
Although a zigzag portion may be provided instead of providing 1, the bent portion 11c of the sipe 10 preferably has a circular arc portion as shown in FIG. 2 in order to improve the wear resistance of the bent portion. . Further, the bent portion does not have to be formed only by an arc, and may be an elliptic arc or a part of a parabola.

On the other hand, the sipe 10 in this embodiment is
As shown in FIG. 2A, at least one end of the wavy portion 11 extends to the side wall of the block or the vicinity thereof, and includes a substantially straight portion 12 whose direction is an angle of −20 to 20 ° with respect to the tire width direction WD. There is.

Further, the plurality of sipes 10 are closed on one side, and the closed sides are alternately arranged on the left and right so that the open side and the closed side of the sipe 10 alternate on the block side wall. As a result, the block rigidity near the side wall of the block is maintained, and uneven wear at that portion is effectively prevented.

In the example shown in FIG. 2, eight sipes 10 are arranged for each block 1, but in the present invention, it is preferable to arrange a plurality of sipes 10 for each block 1. By increasing the number of sipes 10 in this way,
The sipe density can be increased, but the sipe density is 0.
It is preferably 1 mm / mm ² or more.

The plurality of sipes 10 are preferably arranged so that the wavy portions 11 or the zigzag portions thereof have their reference directions substantially parallel to each other. Furthermore, it is preferable to synchronize the cycles of the adjacent sipes 10.

The depth of the sipes is preferably about 1 to 8 mm, and the groove width of the sipes is preferably about 0.1 to 0.5 mm.

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 material, shape, structure, manufacturing method and the like are adopted in the present invention. it can.

The pneumatic tire of the present invention can be applied to so-called summer tires, but is particularly useful as a studless tire because it has the above-described operational effects.

[Other Embodiments] Other embodiments of the present invention will be described below.

(1) In the above-described embodiment, an example in which the sipe 10 shown in FIGS. 1 and 2 is formed is shown, but the sipe in the present invention is shown, for example, in FIGS. 3 (a) to 3 (c). It may be something like this.

In the sipe 10 shown in FIG. 3 (a), the sipe 10 is formed only by the wavy portion 11 without providing a substantially straight portion extending from the wavy portion 11 at an angle of −20 to 20 ° with respect to the tire width direction. It is an example. Even in this case, it is preferable that the end of the wavy portion 11 be at an angle of −20 to 20 ° with respect to the block side wall, and in order to achieve this, the periodicity of the end of the wavy portion 11 is slightly increased. You may change it.

The sipe 10 shown in FIG.
The whole is slightly inclined with respect to the one shown in (a), and the angle is slightly changed. As a result, the wavy portion 11
Alternatively, the direction of the substantially straight line portion 12 extending from at least one end of the zigzag portion to the side wall of the block or the vicinity thereof is substantially 0 ° with respect to the tire width direction.

The sipe 10 shown in FIG. 3 (c) is a sipe having a corrugated portion 11 or a zigzag portion similar to a square wave. Even with the sipe 10 having such a shape,
The tangent line includes a first portion having an angle of −20 to 20 ° with respect to the tire width direction in a period of 20 to 70%, and the tangent line has an angle of −20 to 20 ° with respect to the tire circumferential direction. Second
It is possible to include a portion with a length of 20 to 70% in one cycle.

(2) Although the sipe shape does not change in the depth direction in the above-described embodiment, a concave portion and a convex portion which engage with each other may be formed on the inner surface of the sipe which faces each other. In that case, the shape of the concave portion and the convex portion, hemispherical,
Examples thereof include conical or pyramidal irregularities.

(3) In the above-mentioned embodiment, an example is shown in which the reference plane of the sipe is formed so as to be perpendicular to the block surface, but the reference plane of the sipe is slightly different from the normal line of the block surface. It may be inclined (for example, 15 ° or less).

(4) In the above-described embodiment, an example of the block pattern as shown in FIG. 1 is shown, but not limited to a rectangular block, a parallelogram, a V-shape, a pentagon, or a curve-based block. But it's okay. In addition, a block having a groove up to the vicinity of the center or the vicinity of the edge or a part of the land may be continuous in the circumferential direction.

[0035]

EXAMPLES Examples and the like specifically showing the constitution and effects of the present invention will be described below. In addition, each performance evaluation of the tire was performed as follows.

(1) Ice braking performance tires are used as actual vehicles (domestic 2000cc class FF sedan)
The vehicle was mounted on a vehicle and the vehicle was run on a frozen road surface under a load condition of one passenger, and braking force was applied at a speed of 40 km / h to fully lock the vehicle. In addition, the evaluation is shown by the index display when the conventional product (Comparative Example 1) is 100,
The larger the value, the better the result.

(2) Ice turning performance tires are mounted on the same actual vehicle as above, and the same road surface is selected on the same road surface under the load condition of one passenger riding (8-shaped curve: R = 2).
(5m yen), and evaluated the lap time with an index. The evaluation is indicated by an index when the conventional product (Comparative Example 1) is 100, and the larger the value, the better the result.

(3) Abrasion resistance performance The amount of step wear (step difference between the block pieces on both sides of the sipe due to wear) when traveling 8000 km on a paved road was measured and evaluated by an index. The conventional product (Comparative Example 1) was evaluated as 10
It is indicated by an index when 0 is set, and the larger the value, the better the result.

Examples 1 to 3 In the tread pattern shown in FIG. 1, under the conditions shown in Table 1, a sipe having a depth of 7 mm, a width of 0.3 mm, a wavy portion period of 2.5 mm, and an amplitude of 2.25 mm was formed. Then, a radial tire of size 185 / 70R14 was manufactured, and the above performance evaluations were performed. The results are shown in Table 1. In addition,
The sipe of Example 3 corresponds to FIG.

Comparative Example 1 (Conventional Product) In a tread pattern as shown in FIG. 1, a conventional corrugated sipe extending in the tire width direction (mainly an inclined portion of about 45 ° with respect to the tire width direction) was formed. Size 185 /
A 70R14 radial tire was manufactured and the above performance evaluations were performed. The results are shown in Table 1.

Comparative Example 2 A radial tire of size 185 / 70R14 was manufactured in the same manner as in Example 1 except that the length of the second portion of the sipes was changed as shown in Table 1. The above performance evaluations were performed. The results are shown in Table 1.

[0042]

[Table 1] As shown in the results of Table 1, in the examples, the edge components in the lateral direction and the front-back direction are large, so that the ice braking performance, the ice turning performance and the wear resistance performance are significantly improved as compared with the conventional product. On the other hand, in Comparative Example 2 in which the length of the second portion of the sipe was small, there was almost no effect of improving the ice turning performance.

[Brief description of 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 an essential part showing a block on the tread surface of FIG.

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

[Explanation of symbols]

1 block 10 sipes 11 Wavy part of sipe 11a First part 11b Second part 12 approximately straight line PI pitch WD tire width direction PD tire circumferential direction

Claims (3)

[Claims] 1. A pneumatic tire provided with a tread pattern having a plurality of blocks forming a sipe including a wavy portion or a zigzag portion, wherein the wavy portion or the zigzag portion of the sipe has a tangent to the tire width direction. 20-70% of the length of the first part within one cycle, and the tangent to the tire circumferential direction is the second part at an angle of -20 to 20 °.
A pneumatic tire characterized by being included in a cycle with a length of 20 to 70%. 2. The pneumatic tire according to claim 1, wherein the length ratio of the first portion and the second portion (first portion / second portion) is 0.8 to 1.2. 3. The sipe extends from at least one end of the wavy portion or the zigzag portion to the side wall of the block or the vicinity thereof, and the direction is −20 to 2 with respect to the tire width direction.
The pneumatic tire according to claim 1 or 2, which includes a substantially straight line portion having an angle of 0 °.