JP3009050B2 - Pneumatic radial tire - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial application field) The present invention relates to an improvement of a pneumatic radial tire, and more specifically, uneven wear during cornering without sacrificing drainage performance and tread durability. The present invention relates to a pneumatic radial tire having improved performance and reduced pattern noise.

(Prior Art) Generally, a tread pattern of a combination of various groove shapes and blocks is formed on a tread portion of a high performance tire typified by a flat radial tire, thereby providing drainage and high-speed durability. Improvements such as have been planned.

And especially with the complete road network in recent years,
With the development of vehicles that can run at high speeds of 200 to 300 km / h, tires are expected to have even higher performance improvements.

Among the pneumatic radial tires used for high-speed running, those having the tread pattern shown in FIG. 3 are mainly used as tires having improved drainage performance in rainy weather, which is one of the performances particularly required. Occupy.

In FIG. 3 (a), the tread portion T of the tire includes:
A plurality of, for example, four circumferential main grooves 1 are provided on both sides of the central circumferential line (equatorial line) O linearly and endlessly in parallel with the circumferential direction of the tire. And a plurality of lug grooves 2 arranged at predetermined intervals to form a directional pattern in which land portions (blocks) B are arranged on the circumference of the tire.

The circumferential main groove 1 is formed to have a relatively wide groove width in order to enhance drainage, and has a U or V-shaped cross section as shown in FIG. 3 (b). The inclination angle α of the groove wall is formed so that the tread end side e of the tire and the center peripheral line O side are both equal.

(Problems to be Solved by the Invention) However, in the above-described conventional pneumatic radial tires, although the drainage performance is excellent, particularly in the case of high-speed turning, the block is not provided in the tire tread area facing the outside of the vehicle. There is a problem that side wall wear is remarkable.

That is, when a large input is applied from the outside of the vehicle during turning, for example, in FIG. 3A, the side wall 1C of the circumferential main groove facing the land portion B defined by the tread end e and the circumferential main groove 1 Due to the above input, the tire is largely deformed into the circumferential main groove 1, and as a result, the side wall 1D on the tire center side of the circumferential main groove 1 receives a large input, and comes close to the side wall of the land portion following the side wall 1D. The area was significantly worn against the area adjacent to the side wall of the land following the side wall 1C, and there was a tendency for a step or uneven wear to occur on both sides of the main groove 1.

The uneven wear described above becomes milder toward the center of the tire. However, if uneven wear grows at the portion of the tread edge e, the contact characteristics are deteriorated, and drainage, steering stability and noise are reduced. Therefore, it is extremely inconvenient for high-speed driving.

Therefore, an object of the present invention is to solve the problems of the conventional pneumatic radial tire described above.

Accordingly, it is an object of the present invention to provide a pneumatic radial tire that can improve uneven wear during turning and reduce pattern noise without sacrificing drainage performance and tread durability.

[Configuration of the Invention] (Means for Solving the Problems) That is, in the pneumatic radial tire of the present invention, a pair of sidewalls and a cylindrical tread straddling both sidewalls are connected in a toroidal shape, and the tread is a central circumferential line. And at least one linear circumferential main groove extending in the circumferential direction between the tread end and a plurality of circumferentially inclined main grooves extending from the tread end with respect to the circumferential main groove and arranged at predetermined intervals in the circumferential direction. In a tire including a lug groove and a land portion divided by the groove group and the tread end, the circumferential main groove has an inclination angle formed by an extension of the groove wall and a vertical line standing on the land contact surface, The tread end side has a deformed U or V-shaped cross section larger than the central circumferential side, and the circumferential main groove wall on the side where the inclination angle is large has a circumferential length of a single land portion.
It is characterized in that it has a cross-sectional enlarged portion that is notched in the groove bottom direction over a length of 20 to 70%.

(Operation) The pneumatic radial tire of the present invention can prevent the tread end side circumferential main groove wall from falling down toward the center of the tire particularly at the time of high-speed turning by the above configuration, and as a result, it is possible to effectively prevent the occurrence of uneven wear. In addition to the above, it is possible to advantageously reduce the pattern noise generated due to the air column sound of the straight groove.

(Example) Hereinafter, an example of the pneumatic radial tire of the present invention will be described in detail with reference to the drawings.

In this embodiment, the tread portion T of the pneumatic radial tire of the present invention shown in FIG. 1 has four circumferential portions between the center circumferential line (equatorial line) O of the tire and both tread ends e and e '. The direction main grooves 10, 11, 12, and 13 are linearly and endlessly arranged at predetermined intervals in the width direction.

The number of circumferential main grooves is four in the drawing, but generally two to seven, usually three to six.

Also, the tread T has its tread ends e and e '
A plurality of lug grooves 20 obliquely crossing the circumferential main grooves 12 and 13 are arranged at predetermined intervals in the circumferential direction.

Although the lug groove 20 is terminated in the drawing without opening in the circumferential main grooves 10 and 11 in the center area of the tire, the lug groove 20 can also open in these circumferential main grooves 10 and 11.

The land portion 31, the land portion 31 and the lug groove 20 are formed by the four circumferential main grooves 10, 11, 12, and 13, the tread ends e, e ', and the lug groove 20.
32 ... are classified.

Here, the circumferential width of the main grooves 10 to 13 is usually 7 to 14 m.
m and depth are usually set in the range of 7 to 9 mm.

The lateral width and the depth of the lateral groove 20 are set to be equal to or less than the circumferential main groove.

In FIG. 1, D indicates the outside of the tire on the vehicle, but in this embodiment, the outside and the inside of the vehicle are symmetrical and have the same configuration.

In FIG. 1, the tread end e and the circumferential main groove 12 are shown.
Is divided into complete blocks, but the land portion 32 between the circumferential main groove 10 and the circumferential main groove 12 is not a complete block.

Here, the most important requirement in the pneumatic radial tire of the present invention is a condition relating to a groove wall inclination angle of the circumferential main groove 12 which partitions the land portion 31 on the tread end side.

That is, as shown in FIGS. 1 (b) and 1 (c), the circumferential main groove 12 is formed on the tread end side groove wall (that is, the land portion 31).
Side wall) 12A, groove wall on the tire center circumference side (ie land part 3)
The groove walls 12A and 12B have different inclination angles as described below.

First, the cross section taken along the line AA in FIG.
As shown in FIG. 9A, the inclination angle α between the vertical line l standing on the land contact surface, the tread end-side groove wall 12A, and the center circumferential line-side groove wall 12B is α> β. And preferably have an angle difference of α-β = 25-40 °.

As described above, by changing the groove wall inclination angle facing the circumferential main groove 12 to make the groove shape a modified U or V-shaped cross section, the volume of the land portion 31 can be increased, and The cross-sectional area of the directional main groove 12 is reduced, and the rigidity between the land portions in particular can be improved. During high-speed turning, the tread end e-side groove wall 12A of the circumferential main groove 12 falls down to the tire center side, and the center side groove wall 12B is biased. Not only can a bad tendency to cause wear be eliminated, but also pattern noise can be reduced.

However, when the tread end side groove wall 12A having such a large groove wall inclination angle forms, for example, the entire circumferential direction of the single land portion 31, it is effective for improving the rigidity of the land portion, but the circumferential main groove is not provided. As the cross-sectional area of 12 decreases, drainage performance decreases.

Accordingly, the tread end-side groove wall 12A having a large groove wall inclination angle is, for example, only the portions of the single land portion 31 in the circumferential both-side regions T1 and T2, and the other portion of the single land portion 31 (the circumferential center region T1). ) Has the following cross-sectional enlarged portion 12D to maintain drainage.

That is, the cross section taken along the line BB in FIG. 1 (a) is as shown in FIG. 2 (b), and the tread end side groove wall 12A of the circumferential main groove 12 crosses the circumferential center area. The groove is provided with a groove wall 12A 'whose surface is notched in the direction of the groove bottom 12C, whereby the circumferential main groove 12 has a cross-sectional enlarged portion 12D, and drainage is maintained by compensating the cross-sectional area in this way. -ing

Here, for example, the circumferential length of the single land portion 31 (T1 + T + T
The ratio of the circumferential length (T) of the cross-sectional enlarged portion 12D to 2) is in the range of 20 to 70%, and if it is less than 20%, drainage and heat generation deteriorate, and if it is more than 70%, uneven wear and pattern noise are caused. Is likely to occur, which is not preferable.

Further, as shown in FIGS. 2 (a) and 2 (b), the inclination angle γ of the groove wall 12A ′ in the enlarged cross section 12D with respect to the vertical line l standing on the land contact surface is determined by the inclination of the groove wall 12A. In relation to the angle α, α-γ = 5 to 20 °, and the facing groove wall 12B
Is approximately equal to the inclination angle β.

In the above, the example of the best mode in which the cross-sectional enlarged portion 12D of the circumferential main groove 12 is provided on the side wall of the circumferential central area T of the single land portion 31 has been described. It is a matter of course that the same effect can be expected by providing one side or both sides in the circumferential direction of the side wall.

In the above-described configuration, for example, the connecting portion between the circumferential central region T of the land portion 31 and both side regions T1 and T2 may be continuous with a step or may be continuous with a smooth curve.

The connection between the groove wall 12A and the notched groove wall 12A 'at the groove bottom 12C of the circumferential main groove 12 may be smoothly continuous or may be continuous with an inflection point.

Furthermore, in the pneumatic radial tire of the present invention,
The cross-sectional enlarged portion 12D of the circumferential main groove 12 is provided in principle on all land portions on the circumference on the tread end side, but there is a land portion without the cross-sectional enlarged portion 12D unless the purpose is impaired. It is permissible to do so.

The enlarged transverse cross section 12D of the circumferential main groove 12 can be provided by appropriate means at the time of molding or after molding the green tire.

Next, the configuration and effects of the pneumatic radial tire of the present invention will be described in more detail with reference to test examples.

(Test example) Tire size 255 / 40ZR17 (H / S = 0.4), rim used: 9J
-17, air pressure: 2.6 kg / cm ² , the block pattern shown in FIG. 1 and FIG. 2 was formed on the tread portion of a radial tire for a passenger car having a load of 500 kg, and the tire was evaluated. .

In addition, since other structures and manufacturing conditions such as a radial carcass and a belt layer of the tire were the same as those of a conventional tire,
Details are omitted.

That is, in FIG. 1 and FIG.
10-13 depth: 8mm, groove width: 12mm, depth of each lug groove 20: 6.5m
m, groove width: 4.5 mm, circumferential length of land 31: 36 mm, radial length: 30 mm, and circumferential main grooves 12, 13; length of circumferential central section T: 24 mm, each groove wall Inclination angle α: 35 °, β: 10
{, Γ: 10} to obtain the tire of the present invention.

On the other hand, for the sake of comparison, as shown in FIG. 3, the same applies except that the transverse main groove 12 was not provided with an enlarged cross-sectional portion and the circumferential main grooves 12, 13 were each set to have a groove wall inclination angle of 10 °. Thus, a conventional tire was obtained.

An actual vehicle test was performed on these two types of tires under the following conditions to evaluate uneven wear, drainage, and pattern noise.

(Evaluation method) Uneven wear After running the vehicle on a dry road and repeating high-speed turns the same number of times, the amount of land wear on the tire tread end side was evaluated by index.

Drainage The lateral acceleration measurement value when a WET road surface was subjected to actual vehicle cornering and hydroplaning tests was evaluated by index.

Pattern noise Measures in-vehicle sound (sound pressure) when driving an actual vehicle and evaluates the index.

 The results are shown in the following table.

All the evaluation results are index evaluations when the conventional tire is set to 100, and the larger the index, the better.

As is apparent from the above results, the tire of the present invention has improved uneven wear during turning and reduced pattern noise as compared with the conventional tire without sacrificing drainage.

[Effects of the Invention] As described above in detail, the pneumatic radial tire of the present invention has a structure in which the structure of the circumferential main groove is formed by the extension of the groove wall and the perpendicular formed on the land contact surface. The angle has a deformed U or V-shaped cross section on the tread end side larger than the central circumferential line side, and the circumferential main groove groove wall on the side where the inclination angle is large is the circumferential length of the single land portion. Is formed so as to have a cross-sectional enlarged portion notched in the groove bottom direction over a length of 20 to 70% of the length of the groove, for example, the relationship between a single land portion on the tread end side and a circumferential main groove corresponding to the land portion In this, the circumferential land volume of the single land portion can be partially increased, and the groove cross-sectional area of the corresponding circumferential main groove can be partially reduced, and the rigidity of these portions is improved. In particular, when the tread edge side circumferential main groove wall is tilted toward the tire center during high-speed turning Write can be prevented. As a result, not only the problem of uneven wear can be effectively eliminated, but also pattern noise can be reduced.

Furthermore, by providing the above-mentioned cross-section enlarged part,
Since the circumferential land volume of the single land portion can be partially reduced, and the groove cross-sectional area of the corresponding circumferential main groove can be partially increased, drainage is compensated, and block heat due to heat generation is also effective. Can be prevented.

Therefore, according to the pneumatic radial tire of the present invention, uneven wear during turning can be improved without sacrificing drainage performance and tread durability, and pattern noise can be reduced. Excellent running feeling can be realized.

[Brief description of the drawings]

FIG. 1 (a) is a development view of a tread portion showing one embodiment of a pneumatic radial tire of the present invention, FIG. 1 (b) is an enlarged explanatory view of an S portion in FIG. 1 (a), and FIG. (C) is a perspective explanatory view of the same, and FIG. 2 (a) is AA in FIG. 1 (a).
FIG. 2 (b) is a sectional view taken along the line BB in FIG. FIG. 3 (a) is a development view of a tread portion of a conventional pneumatic radial tire, and FIG. 3 (b) is an explanatory sectional view taken along line AA in FIG. 3 (a). T: Tread portion 10: Main circumferential groove 11: 〃 12: 〃 13: 〃 12A: Groove wall 12B: 〃 12C: Groove bottom 12D: Cross-sectional enlarged portion 20: Lug groove 31 …… Land part 32 …… 〃

Claims (1)

(57) [Claims] 1. A pair of sidewalls and a cylindrical tread spanning both sidewalls are connected in a toroidal shape, and the tread has at least one linear circumferential main portion extending circumferentially between a central circumferential line and an end of the tread. A tire including a groove, a large number of lug grooves crossed from the tread end with respect to the circumferential groove at a predetermined interval in the circumferential direction, and a land portion divided by the groove group and the tread end. In the above, the circumferential main groove has a deformed U-shaped or V-shaped cross-section in which an inclination angle between an extension of the groove wall and a vertical line formed on the land contact surface is larger on the tread end side than on the central circumferential side. And the circumferential main groove wall on the side where the inclination angle is large has a cross-sectional enlarged portion cut out in the groove bottom direction over a length of 20 to 70% of the circumferential length of the single land portion. Features pneumatic radial tires.