JP2002046426A - Pneumatic tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a pneumatic tire capable of providing large edge components in the lateral and longitudinal directions, making it hard for the bent part of sipes to be worn, and capable of suitably disposing the sipes. SOLUTION: This pneumatic tire comprises a tread pattern having a plurality of blocks 1 with sipes 10 formed therein. The sipes 10 comprise a plurality of districts having the reference lines B divided by two or more curved points 11. Each district further comprises a first district L1 having the reference line B with an angle α1 of -45 to 45 deg. relative to a tire circumferential direction CL and a second district L2 having the reference line B with an angle α2 of -30 to 30 deg., relative to a tire lateral direction WA. The curved angle θ between the reference lines B is 80 deg. or more.

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 having a sipe bent at two or more locations, and is particularly useful as a studless tire.

[0002]

2. Description of the Related Art Heretofore, there has been known an example in which a large number of sipes are arranged at respective portions (center portion, mediate portion, shoulder portion) of a tire pattern for the purpose of improving ice performance of a studless tire. In particular, as means for improving the ice turning performance, one or two circumferential sipes were added to the shoulder portion that greatly contributes to the ice turning performance, or an angle of 5 ° or more was formed with respect to the tire width direction. Diagonal sipes have been provided to improve the lateral edge effect.

However, in the circumferential sipe, the number of the sipe is small, so that the edge effect in the horizontal direction is not sufficient, and since the sipe is often arranged so as to intersect with the sipe in the width direction,
The sipe density is too high and the block rigidity is reduced, which tends to lead to a reduction in the overall ice performance. In the case of an oblique sipe with an angle, the edge component in the horizontal direction is small, and the effect is reduced.

Japanese Patent Laid-Open Publication No. Hei 10-44718 proposes a pneumatic tire having a block 1 provided with a substantially Z-shaped sipe 10 as shown in FIG. .

[0005]

However, in the above-described substantially Z-shaped sipe 10, although the edge components in the lateral direction and the front-back direction are large, the angle θ of the bent portion of the sipe 10 is small (16 to 70 °). However, since the bent portion has an acute angle, it is likely to be deformed at that portion to cause step wear. Further, there is a problem that the edge effect is reduced due to abrasion, and it becomes difficult to obtain desired ice performance. Further, when a plurality of such sipes are formed, the angle of the bent portion is small, so that the restriction on the arrangement is large. Therefore, it is difficult to arrange the sipes with a suitable sipe density in a well-balanced manner.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a pneumatic tire which has a large edge component in the lateral and front-rear directions, hardly causes abrasion at a bent portion of the sipe, and enables a suitable arrangement of the sipe.

[0007]

The above object can be achieved by the present invention as described below. That is, the present invention is a pneumatic tire having a tread pattern having a plurality of blocks forming a sipe, wherein the sipe has a plurality of sections whose reference line is divided by two or more bending points, Each section is -45 to 45 degrees with respect to the tire circumferential direction.
A first section having a reference line having an angle of? And a second section having a reference line having an angle of -30 to 30 with respect to the tire width direction, and the bending angle between the reference lines is not less than 80 °. There is a feature. Here, the sections corresponding to the first section may have the same angle or different angles, and the same applies to the second section.

In the above, it is preferable that the bent portion of the sipe corresponding to the bent point of the reference line has an arc portion having a curvature radius of 0.5 mm or more.

Preferably, a plurality of the sipes are arranged for each block, and the sipe density is 0.1 mm / mm ² or more.

At this time, the first sections and the second sections of the plurality of sipes are arranged substantially parallel to each other, and the distance between the first sections and the distance between the second sections of adjacent sipes are reduced. Are preferably substantially the same.

According to the present invention, the sipe is
Since the first section having the reference line at an angle of −45 ° to 45 ° with respect to the tire circumferential direction is provided, the edge component in the lateral direction increases, and the ice turning performance is improved. In addition, since the second section having the reference line at an angle of -30 to 30 ° with respect to the tire width direction is provided, the edge component in the front-rear direction increases, and the front-rear performance such as braking performance and acceleration performance is improved. Furthermore, since the bending angle between these reference lines is 80 ° or more, the block rigidity of the bent portion is easily secured, and the wear resistance is improved.
Further, since the reference line has three or more sections, the angle of the sipe can be adjusted to an angle of 60 to 90 ° with respect to the edge of the block, and the wear resistance near the edge can be increased. .

When the bending portion of the sipe corresponding to the bending point of the reference line has an arc portion having a curvature radius of 0.5 mm or more, the bending angle of the bending portion is 80 ° or more. The wear resistance can be further improved.

It is preferable that a plurality of the sipes are arranged for each block, and the sipe density is 0.1 mm / mm ² or more. The edge effect as described above can be more suitably exerted by a plurality of sipes having an appropriate density.

The first sections of the plurality of sipes and the second sections are arranged substantially in parallel, and the distance between the first sections and the distance between the second sections of adjacent sipes are substantially the same. In this case, it is possible to avoid a partial decrease in the sipe edge effect due to the local narrowing of the sipe interval.

[0015]

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 each having a sipe 10 formed thereon. In the present embodiment, an example is shown in which a rectangular block 1 is formed by being divided by a circumferential groove 2 and a lateral groove 3, and five rows of blocks 1 are arranged for the tire center CL.

As shown in FIG. 2, the sipe 10 of the present invention has a plurality of sections in which the reference line B is divided by two or more bending points 11, and each section is in the tire circumferential direction ( CL), a first section L1 having a reference line B at an angle α1 of −45 to 45 ° and a second section L having a reference line B at an angle α2 of −30 to 30 ° with respect to the tire width direction (WA).
Section L2, and the bending angle θ between the reference lines B is 8
It is characterized by being at least 0 °.

In order to suitably develop the edge component in the horizontal direction as described above, the preferable range of the angle α1 is 10 to 4
0 °. Further, in order to appropriately express the edge component in the front-rear direction, the preferable range of the angle α2 is 10 to 30 °.
It is. The angle α1 and the angle α2 in the present specification are values in which the angle formed in the clockwise direction is represented as a negative angle. Accordingly, in the illustrated example, the angle α1 is + 27 ° and the angle α2 is + 27 °, and as a result, the bending angle θ is 90 °.
It becomes.

The bending angle θ between the reference lines B of each section is preferably 85 ° or more from the viewpoint of the abrasion resistance of the bent portion. In order to improve the wear resistance of the bent portion, it is preferable that the bent portion of the sipe corresponding to the bent point 11 of the reference line B has an arc portion as shown in FIG. The radius R is preferably 0.5 mm or more, and more preferably 0.8 mm or more. The bent portion does not need to be formed only by a circular arc, but may be an elliptical arc or a part of a parabola.

In the illustrated example, three sipes 10 are arranged for each block 1 (one is omitted in FIG. 2), but in the present invention, the sipes 10 are arranged for each block 1.
Are preferably arranged in plural. The sipe density can be increased by increasing the number of sipes 10 in this manner, but the sipe density is preferably 0.1 mm / mm ² or more, more preferably 0.15 mm / mm ² or more.

The plurality of sipes 11 are preferably arranged such that the first sections L1 and the second sections L2 are substantially parallel to each other. Further, it is preferable that the distance D1 between the first sections L1 of the adjacent sipes 10 and the distance D2 between the second sections L2 are substantially the same. Also, the first section L of the plurality of sipes 11
1, it is preferable that the distance between the first section L1 closest to the edge 1a in the width direction of the block 1 and the edge 1a is 3 mm or more. The sipe depth is preferably about 1 to 8 mm, and the sipe groove width is preferably about 0.1 to 0.5 mm.

On the other hand, the angle of the sipe 10 with respect to the end sides 1a and 1b of the block 1 becomes 60 to 90 °,
It is preferable from the point of abrasion resistance near the edge. In the illustrated example, the reference line B has three sections, and the first section L
The second section L2 disposed on both sides of the first section 1 intersects the end side 1a, so that the angle between them is 50 to 90 °. In this way, the first section L1 and the second section L2 are alternately and repeatedly arranged, and the second section L1
Preferably, the sections L2 intersect. Further, although the sipe 10 does not intersect the end side 1b, the virtual line L3
As described above, a sipe may be further provided, which includes a portion corresponding to the first section and the second section, and a portion corresponding to the second section intersects the end 1b in the circumferential direction.

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 of conventionally known materials, shapes, structures, manufacturing methods and the like are employed in the present invention. it can.

The pneumatic tire of the present invention exhibits the above-described effects and is therefore particularly useful as a studless tire.

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

(1) In the above-described embodiment, an example is shown in which the sipe 10 shown in FIGS. 1 and 2 is formed. However, the sipe in the present invention is, for example, shown in FIGS. 3 (a) to 3 (d) and FIG. 3 (a ') to 3 (d'). 3 (a) to 3 (d) show a type in which the sipe and the reference line coincide with each other, and FIGS. 3 (a ') to 3 (d') have the same reference line as the sipe and the sipe. The reference line does not match. In each case, only one sipe is shown, but a plurality of sipe may be formed.

FIG. 3A shows an example of a sipe (angle α2 = 0 °) in which the second section L2 coincides with the width direction. FIG. 3 (a ′) shows a sipe 10 having a waveform (lamellan) formed entirely on the reference line shown in FIG. 3 (a).

FIG. 3B shows an example of a sipe (angle α1 = 0 °) in which the first section L1 coincides with the circumferential direction. In FIG. 3B ′, a sipe 10 having a waveform (lamellan) is formed only in the second section L2 using the reference line shown in FIG. 3B as a reference line.

FIG. 3C shows an example in which the second section L2 has different angles (α1 = 0 ° and −27 °). In FIG. 3 (c ′), the sipe 10 which is partially interrupted is formed with the one shown in FIG. 3 (c) as a reference line. The sipe 10 of the present invention is preferably a continuous integrated sipe, but may have a seam (interruption) of less than about 0.5 mm for convenience in manufacturing. Further, the sipe 10 does not have to cross the end of the block 1.

FIG. 3D shows an example in which the bending angle θ between the reference lines of the first section L1 and the second section L2 is an acute angle. FIG. 3D ′ is an example of a sipe 10 in which a bent portion is formed by a straight line connecting the reference lines with the reference line shown in FIG. 3D.

(2) In the above-described embodiment, the first sections and the second sections of the plurality of sipes are arranged substantially in parallel,
In addition, the example in which the distance between the first sections and the distance between the second sections of the adjacent sipes are set to be substantially the same is shown in FIGS.
A sipe as shown in FIG.

FIG. 4A shows a plurality of sipes 1.
0, the first sections L1 and the second sections L2 are arranged substantially in parallel, and the distance D1 between the first sections L1 of the adjacent sipes 10 and the distance D2 between the second sections L2 are different. It is. FIG. 4B shows an example in which the plurality of sipes 10a to 10c are all formed at different angles, and the plurality of sipes 10a to 10c are not parallel.

(3) In the above embodiment, the sipe is the first
Although an example (a total of three sections) constituted by the section and the second sections on both sides of the section is shown, the section may be constituted by more sections as shown in FIGS.

FIG. 4C shows an example in which the first section L1 and the second section L2 are alternately repeated (a total of 7 sections). FIG. 4D shows an example in which the first section L1 and the second section L2 are alternately repeated in two sections (a total of seven sections).

(4) 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 a rectangular block, but may be a parallelogram, V-shaped, pentagon, or curve-based block. May be. In addition, 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.

[0035]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments and the like that specifically show the structure 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 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) Ice Acceleration Performance The tires were mounted on the same actual vehicle as described above, the vehicle traveled on the same road surface under the load condition of one passenger, and the running time from the stop to 30 m was evaluated by an index. The evaluation is indicated by an index when the conventional product (Comparative Example 1) is set to 100, and the larger the numerical value, the better the result.

(3) Ice turning performance A tire is mounted on the same actual vehicle as described above, and the same road surface is subjected to a lemniscate curve (eight-shaped curve: R = 2) under the load conditions of one passenger.
(5m yen) and the lap time was evaluated by an index. The evaluation is indicated by an index when the conventional product (Comparative Example 1) is set to 100, and the larger the numerical value, the better the result.

(4) Abrasion resistance The amount of step wear (step between sipe and sipe due to abrasion) when traveling 8,000 km on a pavement was measured and evaluated by an index. The evaluation is indicated by an index when the conventional product (Comparative Example 1) is set to 100, and the larger the numerical value, the better the result.

Examples 1 to 3 In the tread pattern shown in FIG. 1, a sipe is formed under the conditions shown in Table 1 (the radius of curvature of the bent portion is 0.8 mm), and a radial tire of size 185 / 70R14 is formed. Was manufactured, and each performance evaluation described above was performed. Table 1 shows the results.

Example 4 In Example 2, instead of forming a straight sipe,
The size is 185 / 70R14 in the same manner except that a wavy sipe (sine wave, cycle 2 mm, amplitude 2 mm) is formed.
Was manufactured, and the above-described performance evaluations were performed. Table 1 shows the results.

[0042]

[Table 1] Comparative Example 1 (Conventional product) In a tread pattern as shown in FIG.
5 / 70R14 radial tires were manufactured and the above-described performance evaluations were performed. Table 2 shows the results.

Comparative Examples 2 to 6 In the tread pattern shown in FIG. 1, a sipe is formed under the conditions shown in Table 2 (the radius of curvature of the bent portion is 0.8 mm), and a radial tire of size 185 / 70R14 is formed. Was manufactured, and each performance evaluation described above was performed. Table 2 shows the results.

[0044]

[Table 2] As shown in the results of Tables 1 and 2, in the examples, the edge components in the lateral direction and the front-back direction are large, and wear is less likely to occur at the bent portion of the sipe. Therefore, ice braking performance, ice acceleration performance, ice turning performance and Abrasion resistance performance was equal to or higher than conventional products. On the other hand, in Comparative Examples 2 to 5 in which either the angle α1 or the angle α2 was out of the range of the present invention, the ice braking performance and the ice acceleration performance or the ice turning performance were inferior to the conventional products. In Comparative Example 6, in which only the refraction angle was out of the range of the present invention, the abrasion resistance performance was insufficient.

[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 a block on a tread surface in FIG. 1;

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

FIG. 4 is an enlarged view of a main part showing another example of a sipe according to the present invention.

FIG. 5 is an enlarged view of a main part showing an example of a conventional sipe.

[Explanation of symbols]

 1 Block 10 Sipe 11 Bending point B Reference line CL Tire circumferential direction WA Tire width direction α1 First section angle α2 Second section angle θ Bending angle

Claims (4)

[Claims] 1. A pneumatic tire provided with a tread pattern having a plurality of blocks forming a sipe, wherein the sipe has a plurality of sections whose reference lines are divided by two or more bending points. Each section has a first reference line having an angle of −45 to 45 ° with respect to the tire circumferential direction.
A pneumatic tire comprising a section and a second section having a reference line at an angle of -30 to 30 with respect to the tire width direction, wherein a bending angle between the reference lines is 80 ° or more. 2. The pneumatic tire according to claim 1, wherein the bent portion of the sipe corresponding to the bent point of the reference line has an arc portion having a curvature radius of 0.5 mm or more. 3. The pneumatic tire according to claim 1, wherein a plurality of the sipes are arranged for each block, and a sipe density is 0.1 mm / mm ² or more. 4. A method according to claim 1, wherein the first sections and the second sections of the plurality of sipes are arranged substantially in parallel, and a distance between the first sections and a distance between the second sections of adjacent sipes are determined. The pneumatic tire according to claim 3, which is substantially the same.