JP3520944B2 - Pneumatic radial tires for passenger cars - 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 radial tire for a passenger vehicle, which is designed to reduce tire noise (particularly passage noise) caused by a block provided on a tread.

[0002]

2. Description of the Related Art Pneumatic radial tires for passenger cars are
In order to improve the wet performance, there is a block row 14 arranged on the shoulder portion of the tread pattern as shown in FIG. Further, the tread profile 15 in the tire meridian cross section is generally formed of a single or a plurality of continuous arcs as shown in FIG. 5, and the ground contact shape is a substantially circular compound arc shape. Therefore, when the block row 14 of the shoulder portion comes into contact with the tire when rolling, the block 13 vibrates, and as a result, slipping occurs between the block 13 and the road surface, which increases tire noise, particularly passing noise. there were. In particular, this tendency becomes more remarkable as the tire having a lower flatness ratio has a higher ground contact pressure at the shoulder portion, and has been a problem particularly in a tire having 60% or less.

[0003]

SUMMARY OF THE INVENTION It is an object of the present invention to have a pneumatic tire for passenger cars which has a tread pattern for arranging a block row on the shoulder portion and which can reduce tire noise when the flatness ratio is 60% or less. To provide radial tires.

[0004]

In order to achieve the above object, the present invention provides a pneumatic radial tire for a passenger vehicle, which has a tread pattern in which a block row is arranged in a shoulder portion and has a flatness of 60% or less, In the shoulder portion of the tread profile in the meridian section of the tire,
An inflection point is formed in which a bulging portion that protrudes outward in the radial direction is formed from a virtual extension line of a circular arc that forms the tread profile central region, and the circular arc of the bulging portion intersects the circular arc that forms the tread profile central region. Is provided in the block row.

The arc forming the central region of the tread profile is not limited to a single arc, but includes a plurality of inscribed arcs. By providing the bulging portion on the shoulder portion in the tread profile as described above, by positioning the inflection point where the arc of the bulging portion and the arc of the tread profile central region intersect within the block row of the shoulder portion,
An inflection point is also formed on the grounding edge in the grounding shape of the shoulder block row.

On the other hand, since the vibration of the block is generated in the direction orthogonal to the tangent line of the ground edge, by forming the inflection point at the ground edge of the block as described above, the vibration of the blocks on both sides from this inflection point is generated. The directions can cancel each other out. As a result, the amount of vibration is suppressed, and tire noise due to vibration or slippage can be reduced.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be specifically described below based on the embodiments shown in the drawings. FIG. 1 illustrates a half width of a tread pattern 1 of a pneumatic radial tire for passenger cars according to the present invention. In this tread pattern 1, lug grooves 3a are provided on the shoulder portion at a predetermined pitch to form a block row 4 composed of a plurality of blocks 3 in the tire circumferential direction. As shown in FIGS. 2 and 3, the tread profile 5 in the meridian section of the tire has an arc 5a forming a central region of the tread profile in the shoulder portion.
Arc 5b projecting radially outward from the virtual extension line 5c
To form a bulge 9. The arc 5b of the bulging portion 9 and the arc 5a forming the central region of the tread profile are
An inflection point 8 is formed by intersecting within the area of the block row 4 arranged in the shoulder portion. When the tire having the tread profile 5 comes into contact with the road surface, the contact shape 2 of the tire forms an inflection point 2a in the shoulder area as shown in FIG. 1, and the inflection point 2a is the inflection point 8 described above.
Similarly to the above, the block row 4 is located in the area. That is, the inflection point 2a in the ground contact shape of the tire
And the inflection point 8 in the tread profile have a relationship corresponding to each other.

In the pneumatic radial tire for passenger cars described above, the vibration direction when the block 3 is deformed by the ground contact is a direction orthogonal to the outer tangent line of the ground contact shape 2.
Therefore, as the inflection point 2a is located within the area of the block row 4 as described above, the vibration direction of the block component inside the tire and the vibration direction of the block component outside the tire interfere with each other with respect to the inflection point 2a. It will fit.

That is, since the vibrations of both block components cancel each other out, the overall amount of vibration is reduced and the noise caused by the vibration of the block is reduced. In the tire of the present invention described above, the distance a from the inner end 6 of the block row 4 to the inflection point 8 is the same as the inner end 6 of the block row 4.
To the width-direction grounding end 7 to the distance d, the ratio a / d is
0.2 to 0.8 is preferable, and 0.3 is more preferable.
It is good to be set to 0.7. If a / d is less than 0.2 or more than 0.8, the vibration amount of one of the block components bounded by the inflection point 2a becomes too small. It becomes difficult to cancel each other out, and the tire noise cannot be reduced. Also, the radius of curvature R of the arc 5b forming the bulge 9
₂ forms the tread profile central area ,
The radius of curvature R ₁ of the arc 5a extending the virtual extension line 5c
And the ratio R ₂ / R ₁ is 0.05 <R ₂ / R ₁ <
It is preferable that the range is 0.15. If it is less than 0.05, the radius R ₂ becomes too small, and uneven wear is likely to occur in the shoulder portion. If it is 0.15 or more, the amount of protrusion of the bulging portion 9 cannot be sufficiently secured, and it is difficult to expect a tire noise reducing effect.

The maximum protruding height of the bulging portion 9 from the inflection point 8 in the radial direction of the tire is preferably within 1/2 of the height h from the inflection point 8 to the tire outer diameter. The bulge 9 is separated by a distance h
If it is projected in the radial direction of the tire to exceed 1/2, it will cause uneven wear. According to the present invention having the above-described configuration, the flatness rate of 60% is particularly high, which increases the ground contact pressure of the shoulder portion.
In the following tires, the noise reduction effect as described above can be made remarkable.

[0011]

EXAMPLE A tire size is 225 / 50R16 (oblateness 50%), a tread pattern is shown in FIG. 1, a tread profile in a meridional section is shown in FIG. 2, and a bulge portion is formed in a shoulder portion, and R ₁ = 700 mm. , R ₂
The tires 1 to 4 of the present invention were manufactured by changing the value of a / d for determining the position of the inflection point 8 as shown in Table 1 with the same configuration of = 65 mm.

Further, for comparison, a conventional tire having the same tire size and the same tread pattern as the tire of the present invention, different in that a tread profile of R ₁ = 350 mm was used without forming a bulge portion on the shoulder portion was manufactured. did.
For each of these five types of tires, the passing noise was measured by the following test method and the tire ground contact shape was observed, and the results shown in Table 1 were obtained. From the results in Table 1,
It can be seen that in each of the tires 1 to 4 of the present invention, the tire ground contact shape forms an inflection point in the block row, and the passing noise is reduced as compared with the conventional tire. Especially, a / d is 0.2
It can be seen that the effects of the tires 2 and 3 of the present invention in the range of 0.8 are remarkable.

(Measuring method of passing noise) JA was used as a test tire.
Attached to the TMA standard rim, set the air pressure to 200 kPa,
It was attached to a 2000 cc passenger car and the sound intensity (energy) was measured by the test method of JASO C606. The evaluation is represented by an index with the measured value of the conventional tire being 100, and the smaller the index value, the lower the noise.

[0014]

[0015]

As described above, according to the present invention, in the pneumatic radial tire for passenger cars having the tread pattern in which the row of blocks is arranged in the shoulder portion and the flatness ratio is 60% or less, the shoulder portion in the tread profile is formed. Since the bulging part is provided and the inflection point where the arc of this bulging part and the arc forming the central region of the tread profile intersect is located in the block row of the shoulder part, the ground contact shape when the tire touches the road surface Also, by forming an inflection point in the shoulder block row and canceling out the vibrations of the block components on both sides from the inflection point, the amount of vibration is reduced, and as a result, the tire noise due to block vibration and slippage Can be reduced.

[Brief description of drawings]

FIG. 1 is a plan view showing a half width of a tread pattern of a pneumatic radial tire for passenger cars according to the present invention together with a ground contact shape.

FIG. 2 is a sectional view showing a tread profile in a meridional section of the tire shown in FIG.

FIG. 3 is an enlarged view showing a main part of the tread profile shown in FIG.

FIG. 4 is a plan view showing a half width of a tread pattern of a conventional pneumatic radial tire for passenger cars together with a ground contact shape.

5 is a cross-sectional view showing a tread profile in a meridional section of the tire shown in FIG.

[Explanation of symbols]

1 tread pattern 2 Tire ground contact shape 2a, 8 inflection point 4 block row 5 tread profile 5a Arc in the central area of the tread profile 5b Arc of bulge 5c Virtual extension of arc in the central area of the tread profile 6 block row inner end 7 width direction ground end 9 Bulging part

─────────────────────────────────────────────────── ─── Continuation of the front page (56) Reference JP-A-7-164823 (JP, A) JP-A-54-70501 (JP, A) JP-A-62-295702 (JP, A) JP-A-5- 77608 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) B60C 11 / 00,11 / 01,11 / 11

Claims (4)

(57) [Claims] 1. A pneumatic radial tire for a passenger vehicle, which has a tread pattern in which a row of blocks is arranged in the shoulder portion, and has an aspect ratio of 60% or less, in the shoulder portion of the tread profile in the meridional section of the tire,
An inflection point is formed that forms a bulge projecting outward in the radial direction from a virtual extension line of an arc forming the tread profile central region, and the arc of the bulge and the arc forming the tread profile central region intersect. A pneumatic radial tire for a passenger vehicle, in which the block row is provided. 2. The ratio a / d of the distance a from the inside of the block row to the inflection point to the distance d from the inside of the block row to the width direction grounding end is 0.2 to 0.8. 1. A pneumatic radial tire for passenger cars according to 1. 3. A radius of curvature R of an arc forming the bulging portion
Co when forming the tread profile central region of ₂
And the ratio R ₂ / R ₁ to the radius of curvature R ₁ of the arc extending the virtual extension line is 0.05 <R ₂ / R ₁ <0.15.
The pneumatic radial tire for passenger cars according to claim 1 or 2. 4. The maximum protruding height of the bulging portion from the inflection point in the tire radial direction is within 1/2 of the height h from the inflection point to the tire outer diameter. One of
A pneumatic radial tire for a passenger car according to the item.