JPH0328006A - Pneumatic radial tire for car - Google Patents

Abstract

PURPOSE:To prevent partial wear to restrain noise by directly connecting sub- grooves intersecting plural block-lines formed by a peripheral groove and the sub-grooves on the ground-contact area of the shoulder part, and specifying the width of the sub-groove of the inside block, the ratio of sectional areas of the inside and outside blocks, and the ratio of the length of the sub-groove of the inside block to the length of the sub--groove to the ground contact end. CONSTITUTION:Two inside and outside block lines 31, 32 of plural block-lines formed by a main groove and sub-grooves on the tread part are formed on the ground contact area of a shoulder, and the sub-grooves 21, 22 intersecting the block-lines are directly connected to each other. The groove-width y of the inside sub-groove 22 ranges from 1.0 to 2.5mm, and the ratio A/B of the groove-sectional area A of the inside sub-groove to the groove-sectional area B of the outside sub-groove 21 is set at 0.6 or less. Further, the ratio l/D of the length l of the inside sub-groove to the length D of the sub-groove from the inside end to the ground contact end is set at 0.5 or lees. In this constitution, partial wear can be prevented to reduce high frequency noise.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a pneumatic radial tire for passenger cars that reduces pattern noise of high frequency sounds, particularly around 800 to 1000 Hz. [Prior Art] The sound generated while a tire is running due to its tread pattern is generally called pattern noise.

In recent years, as the performance of commercially available cars has improved, there has been an increasing demand for reducing pattern noise, and in particular, there has been a strong demand for reducing high frequency sounds around 800 to 1000 Hz. However, the current situation is that no study has been made to reduce the sound pressure level around 1000 Hz.

In the case of a tire that has a plurality of circumferential main grooves in the tread and a block pattern formed by providing a sub-groove that crosses the main groove in at least the shoulder contact area, the air volume in the sub-groove ( air column resonance). Therefore, by reducing the groove volume, the sound pressure level of high-frequency sound can be reduced.

However, reducing the groove volume in the shoulder ground contact area in this manner poses problems such as a decrease in wet performance and occurrence of uneven wear due to an imbalance in rigidity between a portion of the shoulder and a portion of the center.

[Problem to be solved by the invention]

SUMMARY OF THE INVENTION An object of the present invention is to provide a pneumatic radial tire for a passenger car that minimizes the deterioration of the webbing performance and reduces the high frequency sound without causing uneven wear.

[Means to solve the problem]

The above object of the present invention is to provide a tread pattern in which a plurality of main grooves extending in the circumferential direction of the tire are provided in the tread, and sub-grooves intersecting with the main grooves are provided in the shoulder contact area to form at least two inner and outer block rows. The minor grooves that cross the two inner and outer bronch rows are arranged so as to directly communicate with each other, and the groove width y of the minor groove of the inner bronch row is 1.0 to 2.5 mm. ? The ratio A/B of the groove cross-sectional area A of the minor groove of the inner block row to the groove cross-sectional area B of the minor groove of the outer block row is 0.6 or less, and the length of the minor groove of the inner block row is The ratio between e and the distance D of the length of the minor groove from the inner end of this minor groove to the grounding end of the tresode is 7! /
This can be achieved by setting D to 065 or less.

A detailed description will be given below with reference to the drawings.

In FIG. 1, the tread is provided with a plurality of relatively wide main grooves 1 extending in the circumferential direction of the tire and a sub-groove 2 that intersects with the main groove a1. A large number of partitioned blocks 3 are formed. These blocks 3 form a plurality of block rows along the tire circumferential direction. Among these block rows, in the shoulder ground contact area of the top and lid, the block row 3 and the front and back row 3 are arranged in two rows, inside and outside, so that the shoulder ground contact end E is located in the outer block row 31. It has become. The minor groove 2l of these block rows 3 and the minor groove 2 of block row 3
■ Are they directly related to each other? The minor groove 2■ of the inner block row 3■ is provided at a position where the minor groove 2■ of the outer block row 3 is
The groove radius y is smaller than l, and the groove cross-sectional area is smaller. Note that CL is the center line.

In the present invention, as shown in FIG.
+, more preferably set to 1.0 to 2.0+am, and the groove cross-sectional area A of the minor groove 2■ of the inner block row 3■ and the groove cross-sectional area of the minor groove 2 of the outer block row 3. B
The ratio A/B is 0.6 or less, the inner block row 32
The ratio 6/D of the length l of the minor groove 2■ to the distance D of the minor groove length from the inner end of the minor groove 2t to the ground contact edge E of the tread is 0.
It is set to 5 or less.

Here, when the shape of the sub-groove is curved, the distance D of the sub-groove length and the length l of the sub-groove are defined as the "arc length of the groove", respectively.

Further, the width of the main groove 1 is preferably small (5 mm in total).

? As shown in the above, among the block rows in the shoulder grounding area, the groove width y of the minor groove 2■ of the inner block row 3■ is set to 2.5.
By making the groove cross-sectional area A smaller than mm and reducing the air volume, it is possible to suppress the air flow and reduce the high-frequency sound pressure level due to air column resonance that occurs near the contact edge of the tire. .

As described above, when the groove width y of the sub-groove 2 and the groove cross-sectional area 8 in the block row in the shoulder ground contact area become small, the drainage performance generally decreases and the block rigidity increases, as described above. However, in the tire of the present invention,
There are two rows of blocks in the shoulder grounding area, and the minor grooves 2 of the outer bronc row 3 are placed in a position where they communicate with the minor grooves 2t of the inner block row 3■, and While keeping the length 2 short to l/D≦0.5,
By making the groove cross-sectional area B of the sub-groove 2I of the outer block row 3I larger than the groove cross-sectional area A of the sub-groove 2■ of the inner block row 3I, the shoulder ground contact edge E is removed from a part of the tread center.
Good drainage? can do.

On the other hand, if y is less than 1 mn+, the rigidity of the block will increase, resulting in uneven wear, and the drainage performance on wet road surfaces will be significantly reduced, which is not preferable.

Further, 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 area is alleviated. As a result, the imbalance between the rigidity of the center region and the center region is eliminated, and uneven wear can be prevented from occurring.

Note that the groove width y of the sub groove 2■ of the inner block row 3■ is 2
．． Even if it exceeds 5 mm, the groove cross-sectional area A can be made smaller by making the sub-groove 2t shallower, but in this case, block row 3! The block rigidity of the 2. This causes the tresode pattern to change and tire performance to fluctuate.

〔Example〕

It has the tread pattern shown in FIG. The groove width y and length e of the minor groove 2■ of the inner block row 2■ and the groove cross-sectional area ratio A/B of the minor groove 2■ and the minor groove 2 were changed as shown in Table 1. Inventive tire I, ■, Comparative tire I,
If, III was created.

For comparison, a conventional tire I was prepared which had the tread pattern shown in FIG. 4 and whose groove width y, length e and groove cross-sectional area ratio A/B of the sub-groove 2 were as shown in Table 1. .

The size of these tires is 205/65R1.
It is 5.

These six types of tires were evaluated for the following wet performance and high frequency sound feeling performance. Results first
Shown in the table.

Erection work: During a steady circular turn with a radius of 100+n, the speed was increased while partially passing through a wet road surface with a water depth of 5 wml, and the critical lateral G when passing through the wet road surface was measured.

It is expressed as an index with the limit speed of conventional tires as 100.

RO'3 FU 1 NG scolding: 40km/hr, 60km/hr on general roads.
High-frequency sounds generated when traveling at 80 Km/hr and meandering to 100 Km/hr were evaluated by feeling. It is expressed as an index with the evaluation score of the conventional tire (■) as 100.

As is clear from Table 1, the comparison tire I, which satisfies the groove width y of the minor 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 cross-section Comparative tire ■ that satisfies the area ratio A/B but does not satisfy the groove length l is superior in reducing high-frequency sound compared to conventional tire I, but its wet performance is significantly reduced. . In addition, although the groove cross-sectional area ratio A/B and the groove length l are satisfied, the groove width y
For the comparison tire (■) that did not satisfy the above criteria, no high-frequency sound reduction effect was observed.

On the other hand, the groove width y and the groove cross-sectional area ratio A defined in the present invention
A tire in which a minor groove that satisfies /B and the length E is provided in a part of the shoulder can reduce high-frequency sound while substantially maintaining wet performance.

Table I? It has a tread pattern shown in FIG. 3, with minor grooves 2,
The tire (2) of the present invention has the groove width y, the length l, and the groove cross-sectional area ratio A/B as shown in Table 2, and the tire (2) has the tread pattern shown in FIG. Groove width y2
A conventional tire (2) having a length l and a groove cross-sectional area ratio A/B as shown in Table 2 was prepared. The size of these tires is 205/65R15. We conducted the following indoor unit noise test on these tires. 5th result
Shown in the figure.

Indoor unit noise test: Air pressure 2.10Kg/cm"
Load: 400Kg. The test was conducted by measuring the sound pressure level (1000 Hz) in the room when running at a speed of 20 to 120 κ/hr under the conditions of the rim used: 15 x 6.5 JJ.

From FIG. 5, it can be seen that the tire (2) of the present invention has a lower sound pressure level in the entire speed range than the conventional tire (2), and generates less high-frequency sound. Table 2 (Effects of the Invention) As explained above, according to the present invention, in a tire having a tread pattern in which at least two rows of inner and outer block rows are formed in the shoulder contact area of the tread, the two rows of inner and outer block rows are provided.・The sub-grooves that cross the rows of grooves are arranged so as to communicate directly with each other, and the groove width y of the sub-grooves of the inner block row is
, the ratio A/B of the groove cross-sectional area A of the minor groove in the inner block row and the groove cross-sectional area B of the minor groove in the outer block row, the length E of the minor groove in the inner block row, and the distance from the inner end of this minor groove to the tread. By specifying the ratio 1/D of the sub-groove length to the distance HD to the tire contact edge, the air volume can be reduced to suppress the air flow, and high-frequency sound pressure due to air column resonance generated near the tire contact edge can be reduced. In addition to maintaining good drainage from the center area of the tread to the shoulder areas, wet performance is ensured, and the rigidity of both the center and shoulder areas of the tread is balanced to prevent uneven wear. It can be prevented.

[Brief explanation of drawings]

Figure 1 shows the tread pattern of the radial tire of the present invention. Part 1
FIG. 2 is a perspective view illustrating the dimensional relationship of the minor 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. 4 is a partial sectional view showing an example; is a conventional tire tread pattern, No. 5
The figure shows a club showing the relationship between running speed and high-frequency sound pressure level. 1...Main groove, 2■21...Minor groove, 3I, 31...Bronk, A. B...groove cross-sectional area, y...groove width of the minor groove, E
... Length of minor groove. Figure 1

Claims (1)

[Claims] The tread has a tread pattern in which a plurality of main grooves extending in the circumferential direction of the tire are provided, and sub-grooves intersecting with the main grooves are provided in the shoulder ground contact area to form at least two rows of blocks, the inner and outer blocks. The sub-grooves that cross the block rows in each row are arranged so as to directly communicate with each other, and the groove width y of the sub-grooves in the inner block row is set to 1.0.
~2.5 mm, and the ratio A/B of the groove cross-sectional area A of the minor groove of the inner block row to the groove cross-sectional area B of the minor groove of the outer block row is 0.6 or less, and the inner block row A pneumatic radial tire for a passenger car in which the ratio l/D of the length l of the sub-groove to the distance D of the sub-groove length from the inner end of the sub-groove to the ground contact end of the tread is 0.5 or less.