JP2816863B2 - Pneumatic radial tires for passenger cars - Google Patents

Description

Description: BACKGROUND OF THE INVENTION The present invention relates to a pneumatic radial tire for a passenger car, in particular, in which pattern noise of high-frequency sounds around 800 to 1000 Hz is reduced.

[Conventional technology]

Sound generated during running of the tire due to the tread pattern is generally called pattern noise.

In recent years, with the improvement of the performance of commercial vehicles, demands for the reduction of the pattern noise have been increasing more and more, and among them, the reduction of high-frequency sounds particularly around 800 to 1000 Hz has been strongly demanded. However, so far 10
At present, no consideration has been given to reducing the sound pressure level near 00 Hz.

In the case of a tire having a plurality of main grooves in the tire circumferential direction in the tread and a sub-groove crossing the main groove at least in the shoulder contact area, and forming a block pattern, the air volume ( Air column resonance). Therefore, the sound pressure level of the high-frequency sound can be reduced by reducing the groove volume. However, when the groove volume in the shoulder contact area is reduced as described above, there is a problem that the wet performance is reduced and uneven friction occurs due to imbalance in rigidity between the shoulder portion and the center portion.

[Problems to be solved by the invention]

The present invention minimizes the decrease in the wet performance,
It is another object of the present invention to provide a pneumatic radial tire for a passenger car in which the high-frequency noise is reduced without generating partial friction.

[Means for solving the problem]

The object of the present invention is to provide a tread pattern in which at least two inner and outer block rows are formed by providing a plurality of main grooves extending in a tire circumferential direction on a tread and providing a sub-groove intersecting the main groove in a shoulder contact area. The sub-grooves that respectively traverse the two inner and outer block rows are arranged so as to directly communicate with each other, the groove width y of the sub-groove of the inner block row is 1.0 to 2.5 mm mm, and the inner groove is The ratio A / B of the groove cross-sectional area A of the sub-groove of the block row to the groove cross-sectional area B of the sub-groove of the outer block row is 0.6 or less, and the length l of the sub-groove of the inner block row and this sub-groove Can be achieved by setting the ratio l / D of the distance D of the length of the sub-groove from the inner end to the ground contact end of the tread to 0.5 or less.

 Hereinafter, this will be described in detail with reference to the drawings.

In FIG. 1, the tread is provided with a plurality of main grooves 1 extending in the tire circumferential direction and having a relatively large groove width, and a sub-groove 2 intersecting with the main groove 1. A number of blocks 3 partitioned by are formed. These blocks 3 form a plurality of block rows along the tire circumferential direction. Of these block rows, the shoulder contact region of the tread block row 3 ₁ and block row 3 ₂
Bets are placed on the inner and outer two rows, the outer block row 3 ₁ Shoulder ground end E is adapted to position. The sub-grooves 2 ₁ and block row 3 ₂ minor groove 2 ₂ of these block rows 3 ₁ is provided at a position directly communicate with each other, an inner block row 3 ₂ minor groove
2 ₂ has a small groove width y than minor groove 2 ₁ outer block row 3 _1, and the groove cross-sectional area is smaller. CL is the center line.

In the present invention, as shown in FIG. 2, groove width y of the sub-grooves 2 ₂ of the inner block row 3 ₂ 1.0 to 2.5 mm, more preferably set to 1.0 to 2.0 mm, and the inner the ratio a / B of the groove cross-sectional area B of the sub-grooves 2 ₁ a block row 3 of the _second sub-grooves 2 ₂ groove cross-sectional area a and an outer block row 3 ₁ 0.6, sub of the inner block row 3 ₂ the ratio l / D and the distance D of the minor groove length from the inner end of the minor groove 2 ₂ grooves 2 _second length l Toko to the ground terminal E of the tread 0.5
It is set as follows.

Here, when the shape of the sub-groove is curved, the distance D of the length of the sub-groove and the length 1 of the sub-groove are referred to as “D and l”, respectively, with “the arc length of the groove”.

It is desirable that the groove width of the main groove 1 be at least 5 mm.

Thus, among the block row of the shoulder ground area, to reduce the groove cross-sectional area A and the groove width y of the sub-grooves 2 ₂ inner block row 3 ₂ to 2.5mm or less, by reducing the air volume In addition, it is possible to suppress the flow of air and reduce the high-frequency sound pressure level due to the air column resonance generated near the ground contact end of the tire.

Thus the minor groove 2 ₂ groove width y is small in the block row of the shoulder ground area, and the groove cross-sectional area A becomes smaller, generally decreased as described above, drainage, also the block rigidity is increased. However, in the tire of the present invention,
The block row of the shoulder ground area and two rows, the minor groove 2 ₁ block row 3 ₁ outside inner block row 3 ₂ of the sub-grooves 2 ₂
In place in a position to communicate with each other, and suppresses short length l of the sub-grooves 2 ₂ l / D ≦ 0.5, the outer block row 3 ₁
By the minor groove 2 ₁ of groove cross-sectional area B larger than groove cross-sectional area A of the inner block row 3 ₂ minor groove 2 _2, possible to improve the drainage of the shoulder ground end E from the tread center portion Can be.

On the other hand, if y is less than 1 mm, the rigidity of the block is increased, so that uneven wear occurs and the drainage property on a wet road surface is unpreferably reduced.

In addition, since the relationship between the groove cross-sectional areas A and B is set to A / B ≦ 0.6, the increase in block rigidity in the entire shoulder contact region is reduced. As a result, the imbalance of the difference with the rigidity of the center region is eliminated, and the occurrence of partial friction can be prevented.

Incidentally, the groove width y of the sub-grooves 2 ₂ of the inner block row 3 ₂ 2.5m
By shallow grooves of even a minor groove 2 ₂ beyond m, although it is possible to reduce the groove cross-sectional area A, in this case, livability increases block rigidity of the block row 3 ₂ (ride sex) or decreased, during running, minor groove 2 ₂ tread pattern changes with wear, thus varying the tire performance.

〔Example〕

The third has a tread pattern shown in FIG, second view of the inner rows of blocks 2 ₂ minor groove 2 ₂ groove width y, the length l and the sub-grooves 2 ₂ and sub-grooves 2 ₁ groove cross-sectional area ratio A / B changed as shown in Table 1 5
Inventive tires I and II and comparative tires I, II and III were prepared. For comparison, has a tread pattern shown in FIG. 4, the sub-grooves 2 ₂ groove width y, the length l and groove cross-sectional area ratio A / B was prepared a conventional tire I as shown in Table 1 .

The size of each of these tires is 205 / 65R15.

The following wet performance and high-frequency sound feeling performance were evaluated for these six types of tires. The results are shown in Table 1.

Wet performance: In a steady circular turning with a radius of 100 m, the speed was increased while partially passing through a wet road surface having a depth of 5 mm, and the critical lateral G when passing through the wet road surface was measured. Limit the speed of conventional tires to 10
The index was set to 0.

High-frequency sound feeling performance: The high-frequency sound generated when traveling on a general road surface at a speed of 40 km / hr, 60 km / hr, 80 km / hr and meandering to 100 km / hr was evaluated by feeling. The index is shown as an index where the evaluation point of the conventional tire I is 100.

As is clear from Table 1, the comparative tire I, which satisfies the groove width y of the sub-groove specified in the present invention but does not satisfy the groove cross-sectional area ratio A / B and the groove length l, and the groove width y and the groove breakage The comparative tires II satisfying the area ratio A / B but not satisfying the groove length 1 have a high frequency noise reduction effect as compared with the conventional tire I, but the wet performance is significantly reduced. . The comparative tire III, which satisfies the groove cross-sectional area ratio A / B and the groove length l but does not satisfy the groove width y, did not show the effect of reducing the high-frequency sound.

On the other hand, the groove width y and the groove cross-sectional area ratio defined in the present invention are
A tire provided with a sub-groove satisfying A / B and its length 1 in the shoulder portion can reduce high-frequency sound while substantially maintaining wet performance.

Then, having a tread pattern shown in FIG. 3, the sub-grooves 2 ₂
Groove width y of the present invention tire III which are as shown in Table 2, each length l and the groove cross-sectional area ratio A / B, has a tread pattern shown in FIG. 4, the sub-grooves 2 ₂ Groove width y, length l
A conventional tire II having a groove cross-sectional area ratio A / B as shown in Table 2 was produced. The size of each of these tires is 205 / 65R15.

The following indoor unit noise test was performed on these tires. The results are shown in Table 5.

Indoor noise test: air pressure 2.10Kg / cm ² , load 4000K
g, using a rim of 15 × 6.5 JJ, the sound pressure level (1000 Hz) in the room when the vehicle ran at a speed of 20 to 120 km / hr was measured.

From FIG. 5, it can be seen that the tire II of the present invention has a lower sound pressure level in the entire speed range than the conventional tire II,
It can be seen that the generation of high frequency sound is small.

[Effects of the Invention] As described above, according to the present invention, in a tire having a tread pattern in which at least two inner and outer block rows are formed in a shoulder contact area of a tread, a sub-crossing the two inner and outer block rows is performed. The grooves are arranged so as to directly communicate with each other, and the ratio A of the groove width y of the sub-grooves of the inner block row and the groove cross-sectional area A of the sub-grooves of the inner block row to the groove cross-sectional area B of the sub-groove of the outer block row is shown. / B and the ratio l / D of the length l of the sub-groove of the inner block row to the distance D of the length of the sub-groove from the inner end of this sub-groove to the tread contact edge reduces the air volume. To reduce the flow of air,
In addition to reducing the high-frequency sound pressure level due to air column resonance generated near the tire ground contact end, maintaining good drainage from the center region of the tread to the shoulder region, ensuring wet performance, and securing the tread center and the shoulder. The occurrence of uneven friction can be prevented by balancing the rigidity of the two regions.

[Brief description of the drawings]

FIG. 1 shows one of the tread patterns of the radial tire of the present invention.
FIG. 2 is a partial cross-sectional view showing an example, FIG. 2 is a perspective view for explaining the dimensional relationship of sub-grooves in the shoulder contact area of the radial tire of the present invention, FIG. 3 is a tread pattern showing one embodiment of the tire of the present invention, FIG. FIG. 5 is a tread pattern of a conventional tire, and FIG. 5 is a graph showing a relationship between a running speed and a high-frequency sound pressure level. 1 ... main groove, 2 ₁ , 2 ₂ ... sub groove, 3 ₁ , 3 ₂ ... block, A, B
... groove cross-sectional area, y ... groove width of sub-groove, l ... length of sub-groove.

Continuation of front page (56) References JP-A-63-279903 (JP, A) JP-A-1-36505 (JP, A) JP-A-1-28009 (JP, A) JP-A-61-287803 (JP) JP-A-62-157810 (JP, A) JP-A-63-61608 (JP, A) JP-A-63-78805 (JP, A) JP-A-1-85803 (JP, A) 1-36508 (JP, A) JP-A-1-178006 (JP, A) JP-A-64-25907 (JP, U) Patent 2644499 (JP, B2) (58) Fields investigated (Int. Cl. ⁶ , (DB name) B60C 11/00 B60C 11/04 B60C 11/06 B60C 11/11

Claims (1)

(57) [Claims] 1. A tread pattern having a plurality of main grooves extending in the circumferential direction of a tire on a tread, and a sub-groove intersecting the main groove in a shoulder contact area, forming at least two inner and outer block rows. The sub-grooves respectively traversing the two inner and outer block rows are arranged so as to directly communicate with each other, the width of the sub-grooves of the inner block row is set to 1.0 to 2.5 mm, and the inner block row is formed. Groove cross-sectional area A of the sub-groove and groove cross-sectional area B of the sub-groove of the outer block row
Ratio A / B of 0.6 or less, and the ratio l / D of the length l of the sub-groove of the inner block row and the distance D of the length of the sub-groove from the inner end of the sub-groove to the ground contact end of the tread. Pneumatic radial tires for passenger cars with 0.5 or less.