JP2804218B2 - 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 capable of reducing passing noise without deteriorating hydroplaning resistance.

[0002]

2. Description of the Related Art With the recent development of automobile technology, the speed of vehicles has been increased, and the noise of automobiles has been increased.

The contribution rate of tire noise to vehicle noise (the ratio of tire noise energy to the noise energy of the entire vehicle) has been steadily increased due to the progress of vehicle noise measures (quiet drive system, exhaust system, intake system, etc.). Sometimes 60-70
%, And even during accelerated driving, the value is increasing to 10-30% in recent years. Especially during accelerated driving, the noise energy of the whole vehicle is large.

A plurality of vertical grooves having a groove width of about 10 to 20 mm are arranged on the tread of the tire so as to eliminate water between the tread surface and the road surface during running in rainy weather. Maintains wet grip performance.
However, these flutes cause tire noise while improving drainage.

[0005] One of the noises generated by the flutes is caused by air column resonance. In the air column resonance, the air in the air column formed between the vertical groove and the road surface is resonated by the excitation force by the tire pattern during the rolling of the tire and the input from the road surface on the tire contact surface, and is specified. A sound having a wavelength, that is, a wavelength of about twice the length of the air column is generated.

[0006] This phenomenon is called air column resonance, and in the case of tires for passenger cars, it is the main source of unpleasant 800 Hz to 1 kHz noise. The wavelength of the columnar resonance sound becomes a substantially constant frequency irrespective of the speed of the tire, and increases the inside sound and outside sound.

As means for preventing the air column resonance, it is known to reduce the number and volume of the vertical grooves and to provide a partition wall in the grooves. The performance of preventing the hydroplaning phenomenon that occurs when traveling at high speed is reduced.

[0008]

On the other hand, in order to improve the wet grip performance, on the other hand, it is necessary to increase the number and the volume of the vertical grooves. However, as described above, this may cause an increase in tire noise. Was thought. It has been considered that such an increase causes a decrease in dry grip performance due to a decrease in the contact area and a decrease in steering stability performance due to a decrease in rigidity of the tread pattern.

Therefore, conventionally, such conflicting performance has been adjusted according to the performance required for the tire.

In order to improve the wet grip performance, Japanese Patent Application Laid-Open No. 63-34204 proposes a technique in which a depression is formed in the center of the tread, and the tread surface on both sides is formed by a small radius arc. ing. This is 2
Two small radius arcs drain water on both sides to improve wet grip performance.However, since the tread area of the entire tread is reduced, dry grip performance and steering stability performance are likely to be reduced,
Also, noise cannot be reduced much.

The present inventors inspired the fact that it is generally effective to attach a conducting resonator to the pipe in order to attenuate or mute the sound propagating in the pipe. As a result of repeated research to apply to the tread surface, an auxiliary groove corresponding to the resonator was provided in the vertical main groove generating noise, and the auxiliary groove and the vertical main groove were connected with a connecting groove, and It has been found that by restricting the dimensions of the auxiliary groove and the connecting groove to predetermined ranges, it is possible to effectively reduce the passing noise without impairing the hydroplaning resistance.

An object of the present invention is to provide a pneumatic tire capable of reducing passing noise without deteriorating hydroplaning resistance.

[0013]

SUMMARY OF THE INVENTION The present invention relates to a pneumatic tire having one or more vertical main grooves circumferentially continuous on a tread surface and having a groove width of 5 mm or more. one, whereupon conduction a plurality of auxiliary grooves provided intermittently for resonances extending circumferentially along the said longitudinal main groove, and said main grooves, the connecting groove between each auxiliary groove
In both cases, the auxiliary groove has a volume V of 200
300 mm ³ or less and 10 or more for one of the longitudinal main groove Hythe
And the connecting groove is cut in a direction perpendicular to the groove center line.
An area 10 mm ² or less, 10 mm or less groove length l, the main grooves
The number n of the connection grooves provided between one auxiliary groove is 1
0 or less, and expressed by (V × l) / (n × S)
A pneumatic tire characterized in that the groove coefficient K is set to 2,000 or more and 40,000 or less .

[0014]

In the case where a plurality of vertical main grooves are provided, it is not necessary to provide an auxiliary groove up to the vertical main groove located at a position off the ground plane.

[0016]

Since the auxiliary groove and the connecting groove having the above configuration are provided in the vertical main groove, noise generated by the air column formed by the road surface and the vertical main groove when the tire is running is absorbed by the auxiliary groove, and the passing noise is reduced. Reduction can be achieved. Moreover, no sound-insulating wall is provided in the vertical main groove, so that the drainage performance is not impaired and the hydroplaning resistance can be maintained.

[0017]

An embodiment of the present invention will be described below with reference to the drawings. 1 to 3, a pneumatic tire 1 includes a tread portion 12 forming a tread surface 2 and a pair of sidewall portions 13, 13 extending radially inward from both sides thereof.
And a bead portion 14 extending inward of the sidewall portion 13
And

The pneumatic tire 1 has a tread 12
A carcass 16 having a folded portion 16b that turns around the bead core 15 from the inside in the tire axial direction to the outside in the body portion 16a extending from the side to the sidewall portion 13 to the bead portion 14, and a tread outside the carcass 16 And a belt layer 17 disposed inside the section.

In this embodiment, a bead apex 18 made of hard rubber having a triangular cross section is raised outwardly of the bead core 15 in the radial direction and between the main body portion 16a and the folded portion 16b of the carcass 16. .

In the present embodiment, the carcass 16 is composed of two carcass plies 16A and 16B, and each carcass ply 16A and 16B is a tire having a carcass cord made of an organic fiber such as nylon, polyester, rayon or aromatic polyamide. It is formed as a radial or semi-radial arrangement juxtaposed at an angle of 75 to 90 ° with respect to the equator C, and the carcass cords are arranged between the carcass plies 16A and 16B so as to cross each other. In the present example, the height of the tip of the folded portion 16b from the bead base line is formed as a high turn-up that is greater than the height of the tip of the bead apex 18.

In this embodiment, the belt layer 17 is composed of two belt plies. Each belt ply is made of an organic fiber such as nylon, rayon, or aromatic polyamide, or a belt cord made of a steel cord. 1
It consists of cut plies arranged at an angle of 0 to 70 °. Note that the belt cords are arranged in a direction crossing each other between the belt plies.

The tread surface 2 is provided with one or a plurality of, in this example, four vertical main grooves 3 continuous in the circumferential direction.
Each of these vertical main grooves 3 is formed as a straight groove and has a groove width WG of 5 mm or more and 0.16 times or less of the tread width WT.

If the groove width WG is less than 5 mm, drainage becomes insufficient during running on a wet road surface, and hydroplaning is apt to occur. If the groove width is larger than 0.16 times the tread width WT, the contact pressure of the tread surface 2 is increased. It becomes excessive, in addition to poor abrasion resistance, Ru Oh because uneven wear is likely to occur in the groove edge.

In this embodiment, in the normal state where the tire is assembled on the rim and a normal internal pressure and a normal load are applied, the four vertical main grooves 3. Of the two vertical main grooves 3A, 3A located at the central portion.

Each of the vertical main grooves 3A, 3A is provided with a plurality of intermittent auxiliary grooves 4 extending along the vertical main groove 3A, respectively. Each auxiliary groove 4
Are electrically connected to each other by the connection groove 5.

The auxiliary grooves 4 are arranged substantially in parallel with the inner vertical main groove 3A and alternately on both sides of the groove at an interval from the inner main vertical groove 3A. In this embodiment, the auxiliary grooves 4 are rectangular grooves having a rectangular vertical section. Is formed as The auxiliary groove 4 has a volume V per unit of 20,000.
mm ³ is disposed below and more than 10 to the longitudinal main groove 3A of the one. By arranging ten or more, one or two of the auxiliary grooves 4 are always present on the ground plane L at the time of grounding.

The connecting groove 5 has a smaller groove sectional area than the auxiliary groove 4 and has a sectional area S of 10 mm ^{2 in} a direction perpendicular to the groove center line of one connecting groove 5. Hereinafter, the groove length l is set to 10 mm or less,
Moreover, it is preferable that the number of connecting grooves 5 provided between the inner vertical main groove 3A and one auxiliary groove 4 is 10 or less.

The dimensional restriction between the auxiliary groove 4 and the connecting groove 5 is based on the following reason.

In general, in order to suppress the air column resonance caused by the fluid flowing through the pipe, a noise reduction effect is produced by forming a cavity Do in the middle of the pipe Po, as schematically shown in FIG. The transmission loss TL is TL = 10 log | 1 + [{(Vo · So / lo) / (2So)} / (f / fp-fp / f)] ² | dB where fp is a resonance frequency, It can be obtained from the following equation. fp = (C / 2π) × {(n · So) / (Vo / lo)} Vo: Volume of resonator Do So: Cross-sectional area of connecting hole To lo: Length of connecting hole To C: Sound speed n: Number of connection holes To

An experiment was conducted to apply this theory to the reduction of the noise of the tire. As a result, the resonance frequency ft was 500 Hz.
Hz1500 Hz, and it was confirmed that the condition of 2 × 10 ³ ≤ {(V × 1) / (n × S)} ≦ 4 × 10 ⁴ ... I got it. Where: V: volume of auxiliary groove 4 (mm3) S: sectional area of connecting groove 5 (mm2) l: groove length of connecting groove 5 (mm) n: number of connecting grooves 5

When V, l, and S are large, air pumping sound or impact sound is likely to be generated. Therefore, it is appropriate that V ≦ 20,000 mm ³ or less, 1 ≦ 10 mm S ≦ 10 mm ² . The value of n is preferably 10 or less because increasing the value of n leads to a decrease in the rigidity of the partition formed between the vertical main groove 3A and the auxiliary groove 4.

FIG . 5 shows one vertical main groove 3B on the tire equator .
Is shown, and another mode in which the auxiliary groove 4 is provided along the vertical main groove 3B is shown.

The auxiliary groove may be limited to only one side of the vertical main groove, and a vertical groove intersecting with the vertical main groove may be interposed on the tread surface. It can be transformed into something.

[0034]

[Specific Example] A tire ( example ) having a tire size of 205/55 R15 and having the configuration shown in FIG. 1 was prototyped and its performance was tested. For comparison, a test was also performed on a tire having a conventional configuration (conventional example) and a tire having no configuration (comparative example) to compare the performance.

1) Passing noise The running noise was carried out by an actual vehicle coasting test specified in JASO C606. A vehicle equipped with test tires was allowed to coast on a straight test course at a passing speed of 60 km / H and a distance of 50 m. Passing noise was measured by a fixed microphone installed at a position at a height of 1.2 m from the test road surface at a distance of 7.5 m laterally from the running center line at the middle point of the course.

2) Hydroplaning performance A test tire was mounted on an actual vehicle, and a straight line distance of 5 mm in water depth was 10
The speed at which the vehicle entered at 0 km / H and the front tires were locked and the frictional force was recovered was measured. The higher the value, the better. Table 1 shows the test results.

[0037]

[Table 1]

[0038] Results Example tests pass-by noise is reduced as compared with the conventional example and the comparative example, and hydroplaning performance was confirmed to have been retained.

[0039]

[0040]

As described above, the pneumatic tire of the present invention has the following features.
Since at least one of the vertical main grooves is provided with an auxiliary groove for resonance extending in the circumferential direction and the connection between the vertical main groove and the auxiliary groove is conducted by the connecting groove, the hydroplaning resistance is reduced. And the passing noise can be reduced.

[Brief description of the drawings]

FIG. 1 is a sectional view showing an embodiment of the present invention.

FIG. 2 is a plan view showing a tread pattern on the ground plane.

FIG. 3 is a perspective view illustrating an essential part thereof.

FIG. 4 is a cross-sectional view schematically showing a noise canceling action of a resonance sound.

FIG. 5 is a plan view showing another example of the pattern of the ground plane.
You.

FIG. 6 is a plan view showing a pattern of a ground plane according to a conventional example.
You.

FIG. 7 is a plan view showing a ground plane pattern of a comparative example.

[Explanation of symbols]

 2 Tread surface 3, 3A, 3B Vertical main groove 4 Auxiliary groove 5 Connecting groove l Groove length of connecting groove S Cross-sectional area of connecting groove V Volume of auxiliary groove WG Groove width

Claims (1)

(57) [Claims] 1. A pneumatic tire comprising one or more vertical main grooves circumferentially continuous on a tread surface and having a groove width of 5 mm or more, wherein at least one of the vertical main grooves is provided with the vertical main grooves. a plurality of auxiliary grooves intermittently for resonances extending circumferentially along the provided, or
The connection between the vertical main groove and each of the auxiliary grooves is provided by a connecting groove , and the auxiliary groove has a volume V of 20,000 mm ³ per piece.
Below and 10 or more per vertical main groove
The connection groove has a cross-sectional area S in a direction perpendicular to the groove center line.
10mm ² or less, 10mm and groove length l, main grooves and one
The number n of the connection grooves provided between the auxiliary groove and the auxiliary groove is 10 or more.
And a groove member represented by (V × l) / (n × S)
A pneumatic tire, wherein the number K is 2,000 or more and 40,000 or less .