JP3011967B2 - Pneumatic radial tire - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a high-performance pneumatic radial tire having a so-called directional pattern, and to wet drainage without sacrificing steering stability on a dry road surface. It brings the improvement of the nature.

(Prior art) High-performance pneumatic radial tires require high handling stability on dry roads and excellent wet drainage. Therefore, the inclined grooves are formed from the tread central area to the tread from the front of the tire when viewed from the front. A directional pattern that extends obliquely upward toward the end and gradually changes the angle of each inclined groove with respect to the tire equatorial plane from its tread side end portion to the tread center area has been widely used conventionally. I have.

(Problems to be solved by the invention) However, in such conventional tires,
When the average angle with respect to the tire equatorial plane is increased, the wet drainage property is reduced. Conversely, when the average angle with respect to the tire equatorial plane is reduced, the block defined by the inclined groove is reduced due to its rigidity decrease. There is a problem that steering stability on a dry road surface is deteriorated due to susceptibility to damage, and it has been difficult to achieve both of these performances having a trade-off characteristic at a high level.

The present invention advantageously solves such a problem of the prior art, and by arranging the inclined grooves in consideration of the degree of contribution to the steering stability and wet drainage of the tread width direction position on a dry road surface. Another object of the present invention is to provide a pneumatic radial tire capable of sufficiently satisfying both steering stability on a dry road surface and wet drainage.

(Means for Solving the Problems) The pneumatic radial tire of the present invention is particularly suitable for a tire having a directional pattern, in which first and second inclined grooves are alternately arranged in the tire circumferential direction. The first inclined groove is inclined at an angle within the range of 50 to 85 ° at the tread side end portion with respect to the circumferential straight groove, and intersects with the circumferential straight groove, and the tread side end of the second inclined groove is inclined. The portion extends approximately parallel to the same portion of the first sloping groove, and the second sloping groove extends 30-60% of the tread half width.
If the angle of inclination of the second inclined groove portion closer to the center of the tread than the curved portion with respect to the circumferential straight groove is smaller than the angle of the corresponding portion of the first inclined groove, In short, the small inclined portion intersects the first inclined groove.

Here, preferably, the tread side end portion of the second inclined groove is set at 50 ° to 85 ° with respect to the circumferential linear groove, and particularly at 60 ° to
It is inclined within a range of 70 °, and the small inclined portion thereof is inclined within a range of 3 ° to 20 °, particularly 5 ° to 15 ° with respect to the circumferential linear groove.

Here, the second inclined groove can be terminated without opening the lower end of the small inclined portion to the circumferential linear groove, and the second inclined groove can be made to cross the circumferential linear groove. It can also be extended.

By the way, when the second inclined groove is extended so as to intersect the circumferential linear groove, the radius of curvature of the intersection is 10 mm.
On the other hand, it is preferable that the radius of curvature be equal to or less than the radius of curvature of the same portion of the first inclined groove.

(Operation) In this pneumatic radial tire, by arranging the first and second inclined grooves having different shapes from each other, the first inclined grooves mainly serve to improve the steering stability. The partitioning of the rigid land portion is performed, and the second inclined groove mainly provides an improvement in drainage.

Further, the first inclined groove is inclined at an angle within a range of 50 to 85 ° at the tread side end portion with respect to the circumferential linear groove, and the tread side end portion of the second inclined groove is moved from the tread end. For example, by extending approximately 40% of the tread half-width approximately parallel to the corresponding portion of the first inclined groove, the block rigidity in the area that has the greatest influence on steering stability on a dry road surface is sufficiently provided. As well as draining to the tread edge can be done very quickly. This means that the tread-side end portion of the second inclined groove is also inclined at an angle in the range of 50 ° to 85 °, preferably 60 ° to 70 ° with respect to the circumferential linear groove. It is particularly effective.

Further, in the portion of the second inclined groove, which is largely curved in a region within the range of 30 to 60% of the half width of the tread, and is closer to the central region of the tread than the curved portion, the inclination angle with respect to the circumferential straight groove is set to the first inclination. By making the angle smaller than the angle of the corresponding part of the groove, the drainage effect is greatly improved at the small slope part that does not significantly affect the steering stability on dry road surface and realizes excellent wet drainage This improvement in drainage is more effective when the small inclined portion is inclined at an angle of 3 ° to 20 °, particularly 5 ° to 15 ° with respect to the circumferential linear groove. . That is, if it exceeds 20 °, it is impossible to bring about the same drainage action as the circumferential straight groove. If it is less than 3 °, the circumferential straight groove at the tread side end portion of the second inclined groove is not provided. In the required range.

Here, when the above-mentioned curved region is less than 30% of the half width of the tread, uneven wear of the corner of the land portion sharply changes due to a sudden change in angle of the corner of the land portion defined thereby.
By the way, if the curved area exceeds 60%, the inclined groove area having a large angle with respect to the circumferential linear groove at the tread side end portion is narrowed, which impairs stability and makes it difficult to provide a circumferential auxiliary groove. .

In addition, the first inclined groove intersecting with the circumferential straight groove and the second inclined groove intersecting with the small inclined portion are alternately arranged in the circumferential direction.
Drainage can be drawn into the first inclined groove from the circumferential straight groove, and the drainage can be further efficiently drained through the small inclined portion of the second inclined groove. Further, here, by extending the small inclined portion having excellent drainage action so as to intersect the first inclined groove, the total length of the small inclined portion can be increased, and the drainage effect can be further enhanced.

In the above description, the lower end of the small inclined portion of the second inclined groove may be terminated without opening to the circumferential linear groove. In this case, based on not opening the small inclined portion to the circumferential linear groove, in addition to being able to advantageously reduce the pattern noise, the case where the small inclined portion is directly extended and opened to the circumferential linear groove, The occurrence of sharp land corners narrowed by the small inclined portion and the circumferential straight groove can be prevented, and the uneven wear resistance and, consequently, the steering stability can be improved.

In addition, the second inclined groove can further improve drainage performance by intersecting it with the circumferential linear groove, and in this case, the radius of curvature of the intersection is set to 10 mm or more. At the same time, by making the radius of curvature not more than the radius of curvature of the same portion of the first inclined groove, uneven wear of the land portion narrowed by the circumferential straight groove and the second inclined groove is effectively prevented. In addition, it is preferable to ensure smooth drainage by the second inclined groove. Here, if the radius of curvature of the second inclined groove is set to be larger than that of the first inclined groove, the angle change of the second inclined groove with respect to the circumferential straight groove becomes too large, thereby smoothly conducting drainage. It becomes difficult to jump.

Thus, with this pneumatic tire, sufficient rigidity is imparted to the land portion particularly partitioned at the tread side end portion,
By ensuring excellent drainage properties mainly by the small inclined portions of the second inclined grooves, high wet drainage properties can be realized without impairing steering stability on dry road surfaces.

Embodiment An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 shows a tread pattern showing an embodiment of the present invention. The internal reinforcing structure of this tire is the same as that of a conventional general radial or semi-radial tire, and therefore, is not shown here.

In the figure, reference numeral 1 denotes a tread portion. In this example, a single circumferential straight groove 2 extending in the tire circumferential direction is provided in a central area of the tread portion 1, and also at a side end portion thereof, A single circumferential auxiliary groove 3 extending linearly in the tire circumferential direction is provided, and the tread portion 1 extends obliquely upward from the tread central area toward the tread end when viewed from the front of the tire. Then, the first and second inclined grooves 4, 5 opening at the tread end are alternately arranged at predetermined intervals in the tire circumferential direction.

Here, the first inclined groove 4 extends obliquely at an angle within the range of 50 to 85 ° at the tread side end portion with respect to the circumferential straight groove 2 and intersects with the circumferential straight groove 2. From one tread edge to the other tread edge.

The second inclined groove 5 extends from the end of the tread to the first inclined groove 4 over a range of, for example, 40% of the tread half width.
Has a tread-side end portion 5a extending substantially parallel to the tread-side end portion, and the tread-side end portion 5a is preferably 50 ° to 85 ° with respect to the circumferential linear groove 2, particularly 60 °. Incline in the range of ~ 70 ゜.

The second inclined groove 5 also has a curved portion 5b which is greatly curved over a length in a range of 30 to 60% of a half width of the tread, at a portion closer to the center of the tread than the tread side end portion 5a, Further, at a portion closer to the center of the tread than the curved portion 5b, the angle of inclination with respect to the circumferential linear groove 2 is smaller than the angle of the corresponding portion of the first inclined groove 4, and extends crossing the first inclined groove 4. There is a small inclined groove portion 5c that exists. The preferred inclination angle of the small inclined groove portion 5c with respect to the circumferential linear groove 2 is in the range of 3 ° to 20 °, especially 5 ° to 15 °.

The second inclined groove 5 having the respective parts as described above
In this example, for the purpose of reducing the pattern noise, and at the same time, preventing the sharp land corners adjacent to the circumferential linear groove 2 from being generated, without opening the circumferential linear groove 2 Terminate. Thus, here, the second inclined groove 5 is located symmetrically on each side of the circumferential linear groove 2.

The tire configured as described above has a high performance without sacrificing steering stability on a dry road surface, as described above, based on the actions of the first and second inclined grooves 4 and 5, in particular. It can exhibit wet drainage.

FIG. 2 is a tread pattern showing another embodiment of the present invention, in which the second inclined groove 5 intersects the circumferential straight groove 2 for the purpose of further improving drainage. Thus, one second inclined groove 5 extends symmetrically with respect to the circumferential straight groove 2 from one tread end to the other tread end.

In the case of this example, the radius of curvature at the intersection between the second inclined groove 5 and the circumferential linear groove 2 is reduced by uneven wear of the land portion narrowed by the inclined groove 5 and the circumferential linear groove 2. To prevent
Preferably, the radius of curvature is set to 15 mm or more, and in order to cause the drainage to flow smoothly by the second inclined groove 5, the radius of curvature thereof is set at the intersection of the first inclined groove 4 and the circumferential straight groove 2. Preferably, the radius of curvature is smaller than the radius of curvature.

The tires of this example also have respective inclined grooves 4,
Under the operation of 5, the same operation and effect as those shown in FIG. 1 can be achieved.

(Comparative example)

Hereinafter, a comparative test between the inventive tire and the conventional tire on steering stability on a dry road surface, wet drainage performance, wet brake performance, and pattern noise will be described.

◎ Test tire size is 205/60 R15, tread width is 164mm, negative rate is 35%. ・ Invention tire I A tire having a tread pattern shown in FIG. The circumferential auxiliary groove width is 7 mm, the first and second inclined groove widths are gradually changed within a range of 4 to 7 mm, and the angle of the tread side end portion of the second inclined groove with respect to the circumferential straight groove is changed. 70mm, groove width 7mm,
The groove width of the curved part is 5-6mm,
The angle with respect to the circumferential linear groove is 10 °, the groove width is 4 mm, and the first inclined groove at the intersection with the circumferential linear groove,
The tire having the tread pattern shown in FIG. 2 which is basically the same as that shown in FIG.
Crosses the circumferential linear groove with a groove width of 5 mm and a radius of curvature of 30 mm, and the second inclined groove crosses the circumferential linear groove with a groove width of 5 mm and a radius of curvature of 20 mm. The angle of the intersection with the circumferential straight groove is 60 ° ・ Conventional tire Tire with tread pattern shown in Fig. 3 ◎ Test method In actual vehicle running under normal load and normal internal pressure based on JIS standard Driving stability on dry road surfaces was evaluated based on the feeling of a test test run by a test driver on a dry circuit course.
Evaluated by measuring the remaining area of the ground contact surface when driving on a wet road surface with a depth of 5 mm, the wet brake performance is
On a just wet road surface at a water depth of 0 to 2 mm,
The braking distance during running at ~ 60km / h was measured and evaluated. As for the pattern noise, the passenger compartment noise during traveling at 40 to 100 km / h was evaluated by feeling.

◎ Test results The results of each of these performance tests are indicated by indices in the table below. The larger the index value, the better the result.

According to this table, it is clear that the inventive tire can effectively improve wet drainage without impairing the steering stability on a dry road surface.

(Effect of the Invention) Thus, according to the present invention, it is possible to improve wet drainage without sacrificing steering stability on a dry road surface.

BRIEF DESCRIPTION OF THE DRAWINGS FIGS. 1 and 2 each show a tread pattern showing an embodiment of the present invention, and FIG. 3 shows a tread pattern showing a conventional example. DESCRIPTION OF SYMBOLS 1 ... Tread part 2, ... Circumferential linear groove 3 ... Circumferential auxiliary groove 4, ... First inclined groove 5 ... Second inclined groove, 5a ... Tread side end part 5b ... Curved part , 5c …… Small slope

Claims (4)

(57) [Claims] At least one circumferential straight groove extending in the circumferential direction of the tire in a central region of the tread, and a tread extending obliquely upward from the central region of the tread toward an end of the tread in a front view of the tire. A tire comprising a first and a second inclined groove opening at an end, wherein the first and the second inclined grooves are alternately arranged in the tire circumferential direction, and the first inclined groove is formed. With respect to the circumferential straight groove, the tread side end portion is inclined at an angle within the range of 50 to 85 °, and intersects with the circumferential straight groove, and the tread side end portion of the second inclined groove is set to the first tread side end portion. The inclined groove extends substantially parallel to the same portion, and the second inclined groove is formed with a tread half width.
It is largely bent in the range of 30 to 60%, and the inclination angle of the second inclined groove portion closer to the center of the tread than the curved portion with respect to the circumferential straight groove is determined by the corresponding portion of the first inclined groove. A pneumatic tire having an angle smaller than the angle, and the small inclined portion intersecting the first inclined groove. 2. The tread-side end portion of a second inclined groove,
The small inclined portion is inclined at an angle within a range of 3 ° to 20 ° with respect to the circumferential straight groove while being inclined at an angle within a range of 50 ° to 85 ° with respect to the circumferential straight groove. The pneumatic radial tire according to claim 1. 3. The pneumatic radial tire according to claim 1, wherein the second inclined groove is terminated without opening the lower end of the small inclined portion to the circumferential linear groove. 4. The pneumatic radial tire according to claim 1, wherein the second inclined groove crosses the circumferential linear groove.