JPH10236111A - Pneumatic tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve an excellent drainage characteristic on a wet road surface and stability in steering even when large transverse force is exerted on a block land part particularly at the time of travelling on a circuit. SOLUTION: A tread part 1 is provided with at least two main circumferential grooves 3 extending along the circumference of a tire and a plurality of main inclined grooves 5 extending and opened to the main circumferential grooves 3 so as to converge from both tread ends 4a and 4b. The main circumferential grooves 3 and the main inclined grooves 5 opened thereto form the acute parts 7 of block land parts 6. The acute part 7 is provided with a first chamfered part 9 in which the height of a land is gradually reduced toward its top 8. A groove wall 3a in the side of the acute part 7 facing the main circumferential groove 3 is provided with a second chamfered part 11 in which the height of the land is gradually reduced from a block land tread 10 to the bottom of the main circumferential groove 3.

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 excellent drainage and handling stability on a wet road surface, and more particularly to a high-performance tire suitable for running on a circuit.

[0002]

2. Description of the Related Art A high-performance tire has a circumferential groove extending along the circumference of a tire and a slope extending from both ends of the tread toward the circumferential groove in order to achieve both drainability and steering stability. It is common to form a so-called directional pattern in which inclined grooves are provided which extend.

[0003] In the above-mentioned tire, it is preferable in terms of drainage if the arrangement angle of the inclined groove with respect to the tire equatorial plane is small, but it is not preferable in terms of steering stability because the rigidity of the block land portion is small. Increasing the arrangement angle is preferable in terms of steering stability, but is not preferable in terms of drainage. In addition, the groove volume (mainly the groove area) is preferably large from the viewpoint of drainage, but is preferably small from the viewpoint of steering stability. Therefore, in general, drainage performance and steering stability are in conflict with each other.

[0004] As means for achieving both drainage and steering stability, the slope groove is steeply inclined in the central region of the tread (that is, the arrangement angle is made small) so as to penetrate the central region of the tread. The drained water is quickly discharged to improve drainage, and the inclined groove is gently inclined in the tread side region (that is, the arrangement angle is increased) to increase the land portion rigidity in the region. It is useful to improve steering stability.

[0005] In the case of a tire having such an inclined groove,
The quality of drainage depends largely on whether or not the water that has entered the central region of the tread can smoothly branch from the circumferential groove to the inclined groove, join and discharge toward the ground contact end.

[0006]

However, in the conventional tire described above, an acute angle portion of the block land portion exists due to the circumferential main groove and the inclined main groove.
At the time of branching and merging, the sharp angle portion is used as an obstacle and collides with this, and the water flow tends to be largely turbulent, and it becomes difficult for the water to flow smoothly in the groove, and there is a tendency for bubbles to be generated in the water flow. Therefore, the groove volume cannot be used effectively, and as a result,
Drainage was worsened.

Further, in the above-mentioned conventional tire, when a large lateral force acts on the block land portion, such as during circuit running, the edge portion of the block land portion tends to crash, and the edge portion tends to crash. Crushing resulted in a decrease in the contact pressure and worsened steering stability.

An object of the present invention is to provide a tire having the above-described directional pattern, which faces an acute angle portion of a block land portion divided by a circumferential main groove and an inclined main groove opening to the circumferential main groove. By forming the groove portion on the acute angle side with an appropriate shape, excellent drainage on a wet road surface, and sufficient maneuvering even when a large lateral force acts on the block land portion, such as during circuit running, is sufficient. An object of the present invention is to provide a pneumatic tire having stability.

[0009]

In order to achieve the above object, a pneumatic tire according to the present invention has at least two circumferential main grooves extending along the tire circumference in a tread portion, and converges from both tread ends. A plurality of inclined main grooves extending to an opening in the circumferential main groove in the direction in which the inclined main groove is formed. In the tire, the acute angle portion is provided with a first chamfered portion whose land portion height gradually decreases toward the vertex, and the groove wall on the acute angle portion side facing the circumferential main groove, from the block land portion tread surface. A second chamfer is provided in which the land height gradually decreases toward the groove bottom of the circumferential main groove. Note that the angle of the acute angle portion of the block land portion is specifically in the range of 10 to 60 °.

It is preferable that the first chamfered portion has a curved surface convex outward in the tire radial direction. The second chamfered portion preferably has a curved surface convex outward in the tire radial direction, and more preferably, the convex curved surface of the second chamfered portion has a radius of curvature of 1 to 5 mm.
It is preferable that the curvature of the convex curved surface of the second chamfer is smaller than the curvature of the convex curved surface of the first chamfer.

[0011] Further, when the steering stability is particularly important, the inclined main groove is located at a position immediately before opening to the circumferential main groove.
In addition to being bent in a direction in which the arrangement angle with respect to the tire equatorial plane increases, in addition to the first chamfered portion, the extension length of the side wall facing the inclined main groove faces the circumferential main groove. More preferably, it is longer than the extension length of the side wall.

Further, on the groove wall opposite to the groove wall on the first chamfered portion facing the inclined main groove, the land portion height gradually decreases from the block land portion tread surface to the groove bottom of the inclined main groove. It is preferable to provide a third chamfer, more preferably the third chamfer has a curved surface convex outward in the tire radial direction, furthermore, the curvature of the convex curved surface of the third chamfer is:
It is preferable that the curvature is smaller than the curvature of the convex curved surface of the first chamfer.

[0013]

FIG. 1 shows a part of a typical tread pattern of a pneumatic tire according to the present invention, wherein 1 is a tread portion, 2 is a tire circumference, 3 is a circumferential main groove, and 4a. 4b is the tread edge, 5 is the inclined main groove, 6 is the block land,
7 is an acute angle portion of the block land portion, 9 is a first chamfered portion, and 11 is a second chamfered portion.

The tire having the tread pattern shown in FIG. 1 has at least two circumferential main grooves 3 extending along the tire circumference (or tire equatorial plane 2) in the tread portion 1.
It has a plurality of inclined main grooves 5 extending from both tread ends 4a, 4b in a direction converging to open in the circumferential main groove 3, and is blocked by the circumferential main groove 3 and the inclined main grooves 5 opening therethrough. An acute angle portion 7 of the land portion 6 is defined.

In FIG. 1, the tread edges 4a and 4b extend from the tread ends 4a and 4b to the tire equatorial plane 2 in order to improve the front-rear edge component effective for traction and braking, drainage to the contact end, and contact improvement in the tread. Although a plurality of gentle inclined grooves 12 extending toward the circumferential main groove 3 at a large arrangement angle and communicating with the inclined main groove 5 or both the inclined main groove 5 and the circumferential main groove 3 are provided,
The mildly inclined groove 12 can be provided as needed.

The main feature of the present invention is that the acute angle portion 7 has a land height h toward the apex 8 thereof.
A first chamfered portion 9 is provided, and a block land tread 10 is formed on the groove wall 3a on the side of the acute angle portion 7 facing the circumferential main groove 3.
The second chamfered portion 11 in which the land height h gradually decreases from the bottom to the groove bottom of the circumferential main groove 3.

That is, providing the first chamfered portion 9,
Preferably, by providing the first chamfered portion 9 having a curved surface projecting toward the tire radial direction, the water flow at the time of branching and merging from the circumferential main groove 3 to the inclined main groove 5 becomes the acute angle which becomes an obstacle. Because there is no large disturbance at the position of the part 7,
Almost no bubbles are generated in the water flow, and the circumferential main groove 3
The water in the groove (especially in the groove located at the center of the tread) flows smoothly toward the ground contact end, thereby effectively draining water. Can be improved.

Further, a second chamfer 11 is provided, preferably a curved surface (preferably having a radius of curvature of 1 to 5 mm) convex in the tire radial direction. In this way, it is possible to prevent the block edge from collapsing against a large lateral force acting on the block land portion particularly during circuit running, thereby suppressing a decrease in the contact pressure, thereby improving the steering stability. still,
The disposition of the second chamfered portion 11 can further stabilize the water flow in the groove by a synergistic effect with the first chamfered portion 9.

The angle θ of the acute angle portion 7 of the block land portion 6 is specifically set in the range of 10 to 60 °. Angle θ of the acute angle portion 7
The smaller the better, to get a smooth water flow,
In addition, since it is more preferable to increase the rigidity of the block land portion, it is preferable to set the angle within the above-mentioned angle range in consideration of the balance between the two according to the application.

If the angle θ is less than 10 °, the rigidity of the land tends to be insufficient. If the angle θ exceeds 60 °, the water flowing in the groove collides with the acute angle portion 7 so that the water flow is reduced. This is because the water is easily disturbed and the drainage property is deteriorated.

In addition, depending on the pattern configuration, in addition to providing the first and second chamfers 9 and 11, the groove wall 5 a on the side of the first chamfer 9 facing the inclined main groove 5 is further opposite. When the third chamfered portion 13 in which the land height h gradually decreases from the block land portion tread surface 10 to the groove bottom of the inclined main groove 5 is provided on the side groove wall 5b, a large lateral force acting on the block land portion is obtained. On the other hand, the fall of the block edge can be prevented by preventing the block edge from falling down, so that the steering stability can be further improved. In addition, the arrangement of the third chamfered portion 13 can further stabilize the water flow in the groove by a synergistic effect with the first and second chamfered portions 9,11.

Preferably, the third chamfered portion 13 has a curved surface convex outward in the tire radial direction.
More preferably, the radius of curvature of these convex surfaces is 1 to 5 mm.

The arrangement of the second and third chamfers 11, 13 has the effect of making the water in the grooves even smoother.
Since the main purpose of the arrangement is to prevent the block land from being crushed by the lateral force, in the case of the present invention, the curvatures of the second and third chamfers 11, 13 are as follows. It is preferable that the curvature is smaller than the curvature of the first chamfered portion 9. If the curvatures of the second and third chamfers 11 and 13 are larger than the curvature of the first chamfer 9, the contact area is impaired and steering stability deteriorates.

As another embodiment, when drainage is important, it is preferable to open the inclined main groove at an angle as small as possible with respect to the circumferential main groove. When it is necessary to increase the rigidity of the portion, especially the block land portion located in the central region of the tread, as shown in FIG. It is preferable to bend in a direction in which the arrangement angle with respect to the tire equatorial plane 2 increases.

In this case, the first chamfered portion 9 has an extension length b of the side wall portion 9a facing the inclined main groove 5 and an extension length of the side wall portion 9b facing the circumferential main groove 3. If the length a is the same, the rigidity of the edge portion of the block land portion facing the circumferential main groove 3 is insufficient, and the contact pressure tends to decrease. The extension length b of the side wall 9a facing
It is preferable that the length is set to be longer than the extension length a of the side wall portion 9b facing the circumferential main groove 3, thereby securing the rigidity of the edge portion of the block land portion 6 facing the circumferential main groove 3. be able to.

In FIGS. 1 and 2, for convenience of explanation, only one chamfered portion 9, 11, 13 is hatched, but these chamfered portions 9, 11, 13 are entirely formed. It may be provided or partially provided, and may be provided as needed. What has been described above is merely an example of the embodiment of the present invention, and various changes can be made within the scope of the claims.

[0027]

EXAMPLES Next, a pneumatic tire according to the present invention was prototyped and its performance was evaluated. Example 1 This tire is a pneumatic radial tire for racing having the tread pattern shown in FIG. 1 and having a tire size of 22.5 × 9.5-13 (tread width: 240 mm).
Table 1 shows the dimensions and the like of the inclined main groove 5 and the first to third chamfers 9, 11, and 13. The height h of the block land portion 6 was 6 mm. Further, the present invention is characterized by a tread pattern, and other tire structures such as a carcass, a belt, and the like are usually used.

[0028]

[Table 1]

Example 2 This tire has a tread pattern shown in FIG. 2, and has a circumferential main groove 3, an inclined main groove 5, and first and second treads shown in Table 2.
Example 1 except that the dimensions of the chamfers 9 and 11 were different.
Has a structure substantially similar to that of the tire.

[0030]

[Table 2]

Conventional Example This tire has the tread pattern shown in FIG. 4, and has the dimensions of the circumferential main groove 101, the inclined main groove 102, and the inclined auxiliary groove 103 shown in Table 3.

[0032]

[Table 3]

(Test Method) The test tires were assembled on a rim, and the tire wheels with an air pressure of 1.0 kgf / cm ² were mounted on a vehicle, and the vehicle was driven on a wet road surface. The steering stability was evaluated. Drainability is 5mm deep
The vehicle traveled on a wet road surface, and the speed at which hydroplaning occurred was measured and evaluated. Driving stability was evaluated based on the test driver's feeling when sports running on a circuit course in a just wet state in various running modes. Table 4 shows the evaluation results.
Shown in The numerical values in Table 4 are all shown as index ratios with the conventional example being 100, and the larger the value, the better.

[0034]

[Table 4]

From the evaluation results shown in Table 4, Examples 1 and 2 show that
Both were superior in drainability and steering stability on a wet road surface as compared with the conventional example.

[0036]

According to the present invention, it has become possible to provide a pneumatic tire excellent in drainage and handling stability on a wet road surface, particularly a high-performance tire suitable for running on a circuit.

[Brief description of the drawings]

FIG. 1 is a diagram showing a part of a typical tread pattern of a pneumatic tire according to the present invention.

FIG. 2 is a diagram showing another embodiment.

3A is a sectional view taken along line AA of FIG. 1, and FIG. 3B is a sectional view of FIG.
FIG. (c) is a sectional view taken along line CC of FIG. 1.

FIG. 4 is a diagram showing a part of a tread pattern of a tire used in a conventional example.

[Explanation of symbols]

 1 Tread part 2 Tire equatorial plane 3 Circular main groove 4a, 4b Tread end 5 Inclined main groove 6 Block land part 7 Block land part 6 acute angle part 8 Sharp corner part 7 vertex 9 First chamfer part 10 Block land part tread 11 Second chamfered part 12 Slightly inclined groove 13 Third chamfered part 14 Bend position of inclined main groove 5 15 Bent part of inclined main groove 5

Claims (8)

[Claims] 1. A tread portion having at least two circumferential main grooves extending along the circumference of a tire, and a plurality of inclined main grooves extending from both tread ends to the circumferential main grooves until they are opened. In a pneumatic tire having a block main part formed by a circumferential main groove and an inclined main groove that opens into the pneumatic tire, the land part height gradually decreases toward the apex of the sharp part. A second chamfered portion is provided, and a land portion height is gradually reduced from a block land portion tread surface to a groove bottom of the circumferential main groove on the groove wall on the acute angle side facing the circumferential main groove. A pneumatic tire having a chamfer. 2. The pneumatic tire according to claim 1, wherein the first chamfered portion has a curved surface convex outward in the tire radial direction. 3. The pneumatic tire according to claim 1, wherein the second chamfered portion has a curved surface convex outward in the tire radial direction. 4. The curvature radius of the convex curved surface of the second chamfered portion is 1 to
The pneumatic tire according to claim 3, which is in a range of 5 mm. 5. The inclined main groove according to claim 1, wherein the inclined main groove is bent at a position immediately before opening to the circumferential main groove in a direction in which an arrangement angle with respect to the tire equatorial plane increases. Pneumatic tire. 6. The air according to claim 5, wherein, in the first chamfered portion, the extension length of the side wall facing the inclined main groove is longer than the extension length of the side wall facing the circumferential main groove. Containing tires. 7. A land portion having a land portion height gradually decreasing from a block land portion tread surface to a groove bottom of the inclined main groove on a groove wall opposite to the groove wall on the first chamfered portion facing the inclined main groove. The pneumatic tire according to any one of claims 1 to 6, further comprising a three-chamfered portion. 8. The pneumatic tire according to claim 7, wherein the third chamfer has a curved surface convex outward in the tire radial direction.