JP3323630B2 - Pneumatic tire - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pneumatic tire.

[0002]

2. Description of the Related Art Pneumatic tires are required to have various performances such as durability, handling stability, and low noise. Although the conventional development has reached a certain level, the required level has been further increased. Accordingly, tires that meet the required performance are becoming composites having more complicated structures.

[0003]

SUMMARY OF THE INVENTION The present inventors have studied the noise of tires, which has recently become a problem, especially the noise generated by grooves arranged in the tread, that is, the so-called pattern noise. The present invention has been made to achieve a reduction in pattern noise. In order to reduce the pattern noise, it is only necessary to reduce the cross-sectional area of the groove to suppress air column resonance. However, as the cross-sectional area of the groove is reduced, the wandering property is deteriorated and the drainage property is deteriorated, which is contrary to the pattern noise reduction.

Accordingly, an object of the present invention is to reduce pattern noise while maintaining wandering and drainage.

[0005]

According to the present invention, a land portion is formed by arranging a plurality of grooves in a cylindrical tread portion, and a cross-sectional shape of the groove located on the outer side in the width direction of the tread portion is as follows.
An opening expanding on the surface of the tread portion and a pair of side walls extending radially inward from the opening form a convex curve and have a portion extending inward in the tire radial direction while reducing the groove width. The pneumatic tire is characterized in that a groove bottom portion extending radially inward turns and widens.

[0006]

First, in the present invention, the groove depth is the same as the conventional one. For example, in the case of a radial tire for a light truck, the groove depth is set in the range of 8 to 12 mm. Generally, the wandering property is deteriorated by a lateral force generated by a rut on a road surface. Therefore, it is preferable to reduce the lateral force, and it is preferable to increase the camber thrust. In the present invention, the groove depth is conventionally equal, and the camber thrust is to be maintained at the same level as the conventional one. I will not let you.

In the present invention, the opening width of the groove is conventionally the same. For example, in the case of a radial tire for a light truck, the opening width is set in the range of 9 to 14% of the tread width. The reason why the opening width is made equal to the conventional one is based on a design consideration that gives a sense of security to the consumer by making it seem that the groove width is sufficient. The cross-sectional shape of the groove is such that the opening and a pair of side walls extending inward in the tire radial direction from the opening form a convex curve and have a portion extending toward the tire radial direction while reducing the groove width, thereby cutting off the groove. By reducing the area, columnar resonance can be suppressed, and pattern noise can be reduced.

[0008] Further, the bottom of the groove connected to the inner side in the tire radial direction of the side wall is wider than that between the side walls.
A drainage channel can be secured, and the drainage performance can be made equal to the conventional one.

[0009] The reason that the groove having the above-mentioned cross-sectional shape is provided in the groove located on the outer side in the width direction of the tread portion is as follows.
This is because the groove is the largest sound source for pattern noise. Therefore, it means that at least the outer groove in the width direction should have the above-described cross-sectional shape, and all the grooves may have the above-mentioned cross-sectional shape.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to the drawings. FIG. 1 is a development view of a tread pattern applied to a tire having a size of 205 / 85R16, and FIG. 2 shows a groove cross-sectional shape according to the present invention in the tire of FIG. FIG.
In the tread portion 1, four grooves 2 extending zigzag in the tire circumferential direction are arranged, and five ribs 3 are formed.
Further, among the five ribs 3, an S-shaped sipe 4 which is open in the groove on both sides in the width direction sandwiching the rib is arranged on the second rib 3-2, and the second rib 3-2 faces the groove located on the outside in the width direction. A short notch 5 is also formed at the convex part of the second rib 3-2 and the shoulder rib 3-3, and a shoulder sipe extending from the shoulder rib 3-3 to the buttress 7 near the tread width end 6.
8 are located.

In FIG. 2, reference numeral 20 denotes an opening which expands on the surface of the tread portion, reference numeral 22 denotes a pair of side walls extending radially inward from the opening, and reference numeral 24 denotes a groove bottom which extends radially inward from the side wall in the tire radial direction. In the case of this tire, the width W of the opening 20 is 6 m, which is about 10% of the tread width as in the conventional case.
m and the groove depth D are 5.3 mm as in the prior art.
2, the opening 20 and the side wall 22 form a convex curve having a radius of curvature R of 2.1 mm, and extend inward in the tire radial direction while narrowing the groove width. Is the opening width of 4.
2.4 mm, which corresponds to 0%. The width of the narrowest portion 26 is preferably 30 to 50% of the opening width, and the narrowest portion 26 extends from the tread surface to the groove bottom by 3 times the groove depth D.
It may be set so that it is located at a position of 0 to 70%. Here, the narrowest portion 26 is located from the tread surface to the groove bottom over a range of 40 to 60% of the groove depth, but the narrowest portion 26 maintains the width in the tire radial direction. The shape does not need to be continuous. Further, the groove bottom 24 connected to the inner side in the tire radial direction is wider than the narrowest portion 26, and the cross-sectional shape of the groove is a so-called flask shape. The maximum width of the groove bottom 24 is 36 mm.

Although FIG. 1 shows the case where the groove 2 extends in the circumferential direction of the tire, the present invention is not limited to this and can be applied to any groove. For example, when the groove 2 extends obliquely with respect to the tire circumferential direction, only a portion of the groove located outside in the width direction may have a solid shape in the present invention, that is, a region outside the width direction of the tread portion. It is sufficient that the cross-sectional shape of the groove located at the shape of the present invention is the shape of the present invention.

Test Example An inventive tire having the tread pattern of FIG. 1 and the cross-sectional shape of the groove of FIG. 2 in all grooves was prototyped. For further comparison, the tread pattern is the same as that of the inventive tire shown in FIG.
A conventional tire having the shape shown in FIG. In FIG. 3, the opening width W and the groove depth D are the same as those of the inventive tire, but the cross-sectional shape of the groove is such that the angle θ between the shape from the opening 20 to the side wall 22 and the normal n set on the tread surface is formed. Since the groove is a substantially straight line at 15 ° and the groove bottom 28 is also a straight line substantially parallel to the tread surface, the cross-sectional shape of the groove is substantially trapezoidal.

Further, as a comparative tire, the tread pattern shown in FIG. 1 has a substantially trapezoidal groove cross-sectional shape like the conventional tire, but only the groove depth is smaller than that of the conventional tire.
A prototype of a 2.6 mm tire was manufactured. The groove bottom 30 of the groove cross section of the comparative tire is shown by a dotted line in FIG. Here, assuming that the groove cross-sectional shape of the conventional tire is 100 (expressed as an index), the groove cross-sectional area of the inventive tire was 50, and the groove cross-sectional area of the comparative tire was 40.

The test tires were tested for passing noise, wandering, and drainage as described below. None of the test, after teamed tire on a rim, inner pressure 4.25kgf / cm ² in a tire to be mounted on the front, the tire to be mounted to the rear filled with inner pressure 5.25kgf / cm ^2, vehicle mounted I went. First, for the passing noise test, the speed 6
The test was performed by coasting at 0 km / h and measuring the sound pressure level of passing noise with an instrument. In the wandering test, a test course on which a rutted road was formed was run at a speed of 60 km / h, and feeling was evaluated by a test driver. Then, in the drainage test, on a water channel with a water depth of 10 mm, the vehicle first penetrated at a speed of 60 km / h and then accelerated, and the speed at which a hydroplaning phenomenon occurred was measured. The results of the above tests are shown in Table 1 in the index notation with the conventional tire being 100. In addition, in the index display of Table 1, the larger the passing noise, wandering, and drainage, the better.

[0016]

[Table 1]

As is clear from this table, the comparative tire was able to reduce the passing noise, that is, the pattern noise, but the wandering and drainage were worse than the conventional tire because the groove depth was simply reduced. . On the other hand, the inventive tire was able to reduce the pattern noise, and at the same time, had the same wandering and drainage properties as the conventional tire.

[0018]

According to the present invention, pattern noise can be reduced while maintaining wandering and drainage.

[Brief description of the drawings]

FIG. 1 is a development view of a tread pattern of a tire.

FIG. 2 is a sectional view of a groove of an inventive tire.

FIG. 3 is a groove sectional view of a conventional tire and a comparative tire.

[Explanation of symbols]

 1 Tread 2 Groove 3 Rib 3-2 Second rib 3-3 Shoulder rib 4 Sipe 5 Cut 6 Tread end 7 Buttress 8 Shoulder sipes 20 Opening 22 Side wall 24 Groove bottom 26 Narrowest part 28 Groove bottom (conventional tire) 30 groove Bottom (Comparative tire) W Opening width D Groove depth n Normal line on tread surface

Claims (1)

(57) [Claims] 1. An opening in which a plurality of grooves are arranged on a tread portion extending in a cylindrical shape to form a land portion, and a cross-sectional shape of the groove located on the outer side in the width direction of the tread portion expands on the surface of the tread portion. And a pair of side walls extending inward in the tire radial direction from the opening have a portion extending in the tire radial direction while forming a convex curve and reducing the groove width, while a groove bottom continuous inward in the tire radial direction of the side wall has A pneumatic tire characterized by turning over and widening.