JP2000211320A - Pneumatic tire and siping blade - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a pneumatic tire and a siping blade that enhance wet performance while ensuring dry steering stability. SOLUTION: A narrow portion 24 with a width X1 and a wide portion 26 with a width X2 are formed in a block 18. Since little of the wide portion 26 is exposed in the beginnings of wear, the area of contact with a road surface is large for greater steering stability. At the same time, a siping 22 is opened as the surface makes contact with the road surface thanks to a low block stiffness, which contributes to a greater performance of dispersing water. In the middle and later stages of wear, the ratio of the exposed areas in the wide portion 26 increases to ensure good performance of dispersing water, though the siping 22 tends to become hard to open due to an increased block stiffness. Further, a good steering stability is ensured thanks to the increased block stiffness despite a decreased area of the surface in contact with the road surface. The blade can be manufactured at low cost by placing two plates together.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pneumatic tire with improved wet performance while ensuring steering stability, and a sipe blade used for manufacturing the tire.

[0002]

2. Description of the Related Art Conventionally, pneumatic tires have been improved in tread pattern in order to improve wet performance. That is, the drainage property has been improved by improving the arrangement of the tire circumferential groove or the tire width direction groove on the tread surface. Generally, drainage depends on the volume of the ditch. Therefore, in order to improve drainage, the volume of the groove may be increased.

[0003] However, when the width of the groove is increased, the contact area of the tire is reduced, and there is a possibility that the dry steering stability is reduced.

[0004]

Further, in order to prevent a decrease in the contact area of the tire, a method of supplementing drainage by using a sipe instead of increasing the volume (width) of the groove has been attempted. Since the sipe is sufficiently narrow, it is possible to suppress a decrease in the contact area of the tire. However, in order to ensure sufficient drainage, a large number of sipe must be provided on the block-shaped land portion.
As a result, there is a problem that the rigidity of the block-shaped land portion is reduced, leading to a reduction in steering stability.

The present invention has been made to solve the above problems, and an object of the present invention is to provide a pneumatic tire and a sipe blade that improve wet performance while ensuring steering stability.

[0006]

According to a first aspect of the present invention, there is provided a tread surface comprising a plurality of block-like land portions defined by a plurality of mutually intersecting grooves on a tread surface. A pneumatic tire provided with a sipe in a land portion, wherein the sipe has a narrow portion formed with a predetermined width in a sipe width direction and a wide portion formed with a width wider than the predetermined width. The wide portion increases from the tread surface to the sipe bottom and from the center to the bottom in the sipe longitudinal direction.

The operation of the first aspect of the present invention will be described.

In the pneumatic tire according to the present invention, since the rigidity of the block-shaped land portion is low at the beginning of wear, when the block-shaped land portion comes into contact with the ground, the sipe opens well to enhance drainage. After the middle period of wear, the rigidity of the block-shaped land portion increases, and the sipe becomes difficult to open. However, since the proportion of the wide portion increases in the sipe exposed on the tread, drainage can be ensured. In other words, when the rigidity of the block-shaped land portion is low (the sipe opens), a large contact area is secured, and when the rigidity of the block-shaped land portion is large (the sipe does not open), the contact area is reduced to reduce drainage. Is secured. This makes it possible to achieve both drainage and steering stability.

The rigidity of the block-shaped land portion is lower at the end than at the center. However, since the wide portion increases from the tread to the bottom of the sipe and from the center to the bottom in the longitudinal direction of the sipe, the rigidity of the block-shaped land portion is more uniformly secured and drainage is improved. improves.

According to a second aspect of the present invention, in the first aspect of the present invention, the sipe has a ratio of the widest width of the wide portion to the width of the narrow width portion of 1.2 to 4.0. And

The operation of the second aspect of the present invention will be described.

Since the ratio of the widest portion of the sipe to the widest portion of the sipe is in the range of 1.2 to 4.0, both rigidity and drainage are reliably achieved. That is, the ratio is 1.2
If it is less than this, the drainage by the wide part is not sufficient,
If it is 4.0 or more, the steering stability is affected by a decrease in rigidity of the block-shaped land portion and a decrease in the contact area.

According to a third aspect of the present invention, there is provided the sipe according to the first or second aspect, wherein the sipe has at least one cross section intersecting the sipe depth direction in the sipe length direction. A wide portion and a narrow portion are provided alternately.

The operation of the third aspect of the present invention will be described.

In the pneumatic tire according to the present invention, at least in one cross section intersecting in the sipe depth direction, the sipe is provided with the wide portions and the narrow portions alternately in the longitudinal direction, that is, the wide portion is formed in the sipe longitudinal direction. Due to the dispersion in the direction, the rigidity of the block-shaped land portion is equalized. Therefore, steering stability is further ensured.

According to a fourth aspect of the present invention, in order to achieve the above object, in the first aspect of the present invention, the sipe is formed of only a wide portion at the bottom of the sipe. It is characterized by.

The operation of the invention according to claim 4 will be described.

By making the sipe bottom all wide in the sipe longitudinal direction, a substantial drainage channel is secured at the sipe bottom, and drainage is further improved.

According to a fifth aspect of the present invention, in order to achieve the above object, the sipe according to any one of the first to fourth aspects is characterized in that the sipe bottom is formed of an R-curved surface. And

The operation of the invention will be described.

In the block-shaped land portion, stress is concentrated most at the bottom of the sipe. Therefore, by forming the sipe bottom with an R-curved surface, stress concentration is prevented, and cracks at the bottom are prevented.

According to a sixth aspect of the present invention, in order to achieve the above object, a first plate having irregularities formed in a thickness direction of a sipe in press forming and a second plate closing at least the concave portion are overlapped. It is characterized by being formed by this.

The operation of the invention according to claim 6 will be described.

The blade according to the present invention uses a blade formed by superposing a first plate on which irregularities are formed in the sipe thickness direction by press molding, and a second plate for closing a concave portion of the first plate. Therefore, it is not necessary to manufacture blades having partially different thicknesses by a high-pressure press, and the blades can be manufactured at low cost.

In order to achieve the above object, the present invention according to claim 7 is characterized in that, in the invention according to claim 6, a portion where the sipe thickness increases toward the blade end forming the sipe bottom. And

The operation of the seventh aspect of the present invention will be described.

By using this blade, the pneumatic tire according to claims 1 to 4 can be easily manufactured.

[0028]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A pneumatic tire and a sipe blade according to one embodiment of the present invention will be described in detail. Hereinafter, the present embodiment will be described with reference to FIGS.

As shown in FIG. 1, a pneumatic tire 10
Is provided with a cylindrical tread 12 straddling a pair of left and right sidewalls (not shown). On tread 12,
A plurality of main grooves 14 formed along the tire circumferential direction (arrow P direction) and a plurality of lug grooves 16 formed along the tire width direction (arrow W direction) are formed. A plurality of blocks 18 are defined by the main groove 14 and the lug groove 16. The blocks 18 are formed with sipes 22 extending along the tire width direction.

As shown in FIG. 2, the sipe 22 is a double-sided sipe having both ends opened at the block end surfaces. The sipe 22 has a shape obtained by stacking a triangular plate having a thickness of X2 on a rectangular plate having a thickness of X1 and attaching a columnar body to a lower portion thereof. That is, the sipe 22 includes a narrow portion 24 having a width X1, a wide portion 26 having a width X2, and a bottom portion 30 having a circular cross section. Therefore, in side view from the tire width direction,
The sipe 22 has a flask shape. The wide portion 26 has a triangular shape with one point on the tread surface 28 side as a vertex and the bottom 30 side of the sipe 22 as a bottom side (FIG. 3).
(A)).

That is, the sipe 22 is configured such that the proportion of the wide portion 26 in the longitudinal direction (the direction of arrow A) increases from the center toward both ends as going from the tread surface 28 to the bottom portion 30.

The pneumatic tire 10 manufactured as described above
The operation of will be described.

When the pneumatic tire 10 having the block 18 in which the sipe 22 is formed is mounted on an automobile and travels, the following effects can be obtained.

In the initial stage of wear, the sipe 22 is exposed on the tread side of the block 18 by the narrow portion 24.
Only (or only the wide portion 26 is slightly exposed), the exposed area of the sipe 22 is sufficiently small, and the contact area of the pneumatic tire 10 is sufficiently ensured. On the other hand, in the initial stage of wear, the block rigidity of the block 18 is low, and the sipe 22 is opened by contact with the ground, so that the water that has entered inside is discharged well.

In the middle period of wear, since the height of the block 18 is reduced, the rigidity of the block is increased, and the sipe 22 becomes difficult to open due to grounding. However, the ratio of the wide portion 26 increases in the portion exposed on the tread surface 28 of the sipe 22. That is, about half of the exposed sipe 22 becomes the wide portion 26. As a result, the exposed area of the sipe 22 is increased, and the decrease in drainage due to an increase in block rigidity is compensated for. Further, since the wide portion 26 is located closer to the center than the end in the sipe length direction, the block 18
Is made uniform in rigidity.

At the end of wear, the tread 2 of the sipe 22
All of the portions exposed to 8 become wide portions 26. As a result, the exposed area of the sipe 22 increases, and drainage is ensured. That is, the decrease in drainage due to the decrease in the depth of the main groove 14 and the lug groove 16 is compensated for, and the pneumatic tire 10
To suppress the deterioration of wet performance. Moreover, Sipe 22
Despite the increase in the exposed area, the height of the block 18 is reduced, so that the rigidity is high and the steering stability is not impaired.

The ratio of the width X1 to the width X2 (X2 / X1)
Is not particularly limited, but is preferably from 1.2 to 4.0. That is, if the ratio is less than 1.2, the wide portion 26
Drainage due to water becomes insufficient. On the other hand, when the ratio exceeds 4.0, the block rigidity of the block 18 and the installation area are remarkably reduced, which greatly affects the steering stability.

Next, a method of manufacturing the blade 40 used in manufacturing the sipe 22 described above will be described with reference to FIG.
This will be described with reference to FIG.

As shown in FIG. 4, the blade 40 is composed of rectangular plates 42 and 44 having a thickness of XA and a substantially cylindrical body 46. The plate 44 has a triangular projection 48 formed by press molding. By overlapping the plate 42 and the plate 44, the concave portion formed on the back side of the convex portion 48 is closed from the outside. The blade 40 is manufactured by inserting the superposed plates 42 and 44 into the grooves 50 of the cylindrical body 46.

The outer edge of the convex portion 48 of the plate 44 and the portion where the outer edge contacts the plate 42 are denoted by R.
By forming the shape, cracks in the formed sipe can be suppressed.

Thus, the blades 40 having different thicknesses can be easily manufactured. Therefore, the blade 40 does not need to be manufactured by a high-pressure press, and can be manufactured at low cost.

Next, the pneumatic tire 10 having a different shape of the sipe 22 will be described with reference to FIGS.
5 to 7 show the shapes of the sipe 22 and the blade 40 as in FIG.

FIG. 5 shows a sipe 22 having two wide portions 26. This is because the apex of the tread surface 28 is one place, and the narrow portions 24 and the wide portions 26 are alternately arranged in the middle of wear in the longitudinal direction of the sipe.
Block rigidity in the longitudinal direction of the sipe is made uniform, and steering stability is reliably ensured.

FIG. 6 shows the sipe 22 provided with two wide portions 26 having different vertices on the tread surface 28. In this case, even in the early stage of wear, the wide portion 26 is formed.
And the narrow portions 24 are alternately arranged, so that the block rigidity is made more uniform. Also, as shown in FIG.
6 can be provided at three places.

As described above, the wide portion 2 extends in the longitudinal direction of the sipe.
It is possible to adjust the block rigidity as appropriate by arranging a plurality of 6. [Test Example] A steering performance test and a hydroplaning test were performed to confirm the operation and effect of the pneumatic tire of the present embodiment thus formed.

The conventional example 1 and the example 1 tire have a sipe extending in the tire width direction formed on a block of the tread pattern shown in FIG. In the tires of Conventional Example 2 and Example 2, the sipe extending in the tire circumferential direction is formed on the block of the tread pattern shown in FIG. In the sipe shapes of Conventional Examples 1 and 2, the portions corresponding to the wide portion and the narrow portion of the embodiment are formed with a width X1 (the width of the narrow portion). Examples 1 and 2 are diagrams of the embodiment. 7 is a sipe having the same shape as that shown in FIG. The tire sizes are 205 / 55R16, respectively.

The dry operation test and the wet operation test were carried out on a circuit having a circumference of 4 km (dry road surface and wet road surface) at a speed of 80 km / h to 140 kph.
The straightness and lane change performance were tested at speeds up to m / h, and the cornering performance was tested on an S-shaped or other handling road installed in the course. This was determined by feeling evaluation of a skilled driver. Table 1 shows the test results. In addition, the index of the conventional example 1 is expressed as an index with 100 being set (the index is large is good).

[0048]

[Table 1]

The hydroplaning test was conducted at a water depth of 20
The vehicle accelerated on a wet road surface of mm, and the speed at which the hydroplaning phenomenon occurred was measured. Table 2 shows the test results. It should be noted that the index is displayed with the generation speed of Conventional Example 1 set to 100 (the index is large).

[0050]

[Table 2]

From all the tests, it was confirmed that the example exhibited excellent wet performance, and that the dry operation performance exhibited the same performance as the conventional example.

Next, how the dry operation performance and the wet operation performance change depending on the ratio (X2 / X1) of the width X1 of the narrow portion 24 and the width X2 of the wide portion 26 in the sipe 22 will be described. Examined. The pneumatic tire subjected to the test is the same as that in Example 1 in the above test.
Here, Examples A to J correspond to the narrow portions 2 of the sipe 22 respectively.
4 is kept constant and the width of the wide portion 26 is changed. Therefore, in Example A (ratio 1.0), the width of the sipe 22 is constant. Dry operation performance and wet operation performance test conditions and evaluation methods are the same as those in the above test. Table 3 shows the test results. Example A
Is indicated by an index with the evaluation of 100 as the index (large index is good).

[0053]

[Table 3]

When the dry operation performance is 98 or more, it is determined that the dry operation performance is sufficiently ensured.
When the wet steering performance was 105 or more, it was determined that the superiority was sufficiently secured with respect to the tire having a constant sipe width (Example A). Thereby, the narrow portion 2
4 is 1.2 to 4.0 (Example C)
To H) were confirmed to be suitable.

[0055]

The pneumatic tire according to the present invention has excellent wet performance (drainage,
Wet operation performance).

[Brief description of the drawings]

FIG. 1 is a tread plan view of a pneumatic tire according to an embodiment.

FIG. 2 is a perspective view of a block in which a sipe according to the embodiment is formed.

FIG. 3A is an explanatory diagram of a sipe, and FIG. 3B is an explanatory diagram of a blade.

FIG. 4 is an exploded perspective view of the blade according to the embodiment.

FIG. 5A is an explanatory diagram of a sipe according to another embodiment, and FIG. 5B is an explanatory diagram of a blade.

FIG. 6A is an explanatory diagram of a sipe according to another embodiment, and FIG. 6B is an explanatory diagram of a blade.

FIG. 7A is an explanatory diagram of a sipe according to another embodiment, and FIG. 7B is an explanatory diagram of a blade.

FIG. 8 is a tread plan view of a pneumatic tire used in Example 2 and Conventional Example 2.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Pneumatic tire 18 Block (block-shaped land part) 22 Sipe 24 Narrow part 26 Wide part 28 Tread surface 30 Bottom part

Claims (7)

[Claims] 1. A pneumatic tire comprising a plurality of block-shaped land portions defined on a tread surface by a plurality of grooves intersecting with each other, and a sipe is provided in the block-shaped land portion. A narrow portion formed with a predetermined width in the sipe width direction and a wide portion formed with a width wider than the predetermined width, from the tread surface toward the sipe bottom, and an end in the sipe longitudinal direction. A pneumatic tire characterized in that the wide portion increases from the center to the skirt. 2. The pneumatic tire according to claim 1, wherein a ratio of a width of the wide portion to a width of the narrow portion is 1.2 to 4.0. 3. The sipe according to claim 1, wherein wide portions and narrow portions are alternately provided in a sipe length direction at least in a cross section intersecting in a sipe depth direction. Pneumatic tires. 4. The sipe according to claim 1, wherein the sipe is formed of only a wide portion at the bottom of the sipe.
The pneumatic tire according to any one of claims 1 to 4. 5. The pneumatic tire according to claim 1, wherein the sipe has a sipe bottom formed with an R-curved surface. 6. A sipe blade formed by laminating a first plate having irregularities formed in a sipe thickness direction in press forming and a second plate closing at least the concave portion. 7. The sipe blade according to claim 6, wherein the thickened portion of the sipe increases toward the blade end forming the sipe bottom.