JP3365653B2 - 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 lowering hydroplaning resistance.

[0002]

2. Description of the Related Art As the speed of vehicles increases with the development of automobile technology in recent years, vehicle noise also increases and it is desired to reduce it.

The contribution rate of tire noise to vehicle noise (the ratio of tire noise energy to the noise energy of the entire vehicle) is determined by the progress of vehicle noise countermeasures (quiet system, exhaust system, intake system, etc.) to make steady running. 60 to 70 by the hour
%, The value has been increasing in recent years to 10 to 30% even during accelerating traveling, and particularly during accelerating traveling, the noise energy of the entire vehicle is large, so that it is necessary to reduce the noise of tires.

A plurality of vertical grooves which are continuous in the tire circumferential direction and have a groove width of about 6 to 20 mm are arranged on the tread of the tire to eliminate water between the tread surface and the road surface when running in the rain. Maintains the wet grip performance.
However, the vertical grooves cause tire noise while improving drainage.

One of the noises generated by the vertical groove is air column resonance. In this air column resonance, the air in the air column formed between the vertical groove and the road surface on the tire contact surface resonates due to the excitation force by the tire pattern during tire rolling and the input from the road surface, A sound having a wavelength, that is, a wavelength about twice the length of the air column is generated.

This phenomenon is called air column resonance, and in the case of tires for passenger cars, it becomes a main sound source of noise of 800 Hz to 1 kHz which is offensive to the ears. The wavelength of the air column resonance sound has a substantially constant frequency regardless of the speed of the tire, increasing the vehicle interior sound and the vehicle exterior sound.

As a means for preventing this air column resonance, it is known to reduce the number and volume of vertical grooves, and further to provide partition walls in the grooves. This is to improve wet grip performance, particularly wet road surface. This leads to a reduction in the performance of preventing the hydroplaning phenomenon that occurs when traveling at high speed.

[0008]

On the other hand, in order to improve the wet grip performance, conversely, the number of vertical grooves and the volume may be increased. However, as described above, this causes an increase in tire noise. Was being considered. It has also been considered that the increase of these causes a decrease in dry grip performance due to a decrease in the ground contact area and a decrease in steering stability performance due to a decrease in rigidity of the tread pattern.

Therefore, conventionally, such contradictory performances have been adjusted according to the performance required for the tire.

In order to improve the wet grip performance, JP-A-63-34204 proposes a technique of forming a depression in the center of the tread and forming the tread surface on both sides of the depression with an arc having a small radius. ing. This is 2
With two small radius arcs, water is discharged to both sides to improve wet grip performance, but since the ground contact area of the entire tread is reduced, it is easy to cause deterioration of dry grip performance and steering stability performance,
In addition, the noise cannot be reduced significantly.

The inventors have found that it is generally effective to provide a cavity in a part of the pipe in order to attenuate or mute the sound propagating in the pipe. As a result of repeated research to apply it to the tread surface, a wide groove portion for noise reduction is interposed in the vertical main groove that generates noise, and the hydroplaning resistance is impaired by regulating each dimension of this wide groove portion within a predetermined range. It has been found that the passing noise can be effectively reduced without the need.

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

[0013]

The present invention relates to a pneumatic tire having a single or a plurality of longitudinal main grooves continuous in the circumferential direction on a tread surface, wherein the vertical main groove is 8 mm.
At least 10 wide sound absorbing grooves are provided in the main groove having the above groove width, and the wide groove has a circumferential length Lm of 45 mm or more and 90 mm or less and a normal internal pressure applied to the tire. And a normal load are added, the cross-sectional area Sm in the direction perpendicular to the groove center line at the midpoint in the circumferential direction of the wide groove portion is smaller than the length in the circumferential direction of the grounding surface in the normal state. 2 times or more and 4 times or less of the cross-sectional area Sg of the main groove portion in the direction perpendicular to the groove center line , and
The main groove portion has a peripheral wall of the main groove portion that is a circumferential end of the wide groove portion.
Open the end of the protrusion that protrudes into the wide groove at the edge position.
It is a pneumatic tire characterized by having .

The wide groove portion is formed in front of the opening end of the main groove portion.
The protrusion that is the circumferential length to the circumferential edge of the wide groove portion
It is preferable that the insertion length Ls of the portion is larger than 0 and not more than 0.25 times the circumferential length Lm of the wide groove portion.

[0015] Also, the wide groove, the cross sectional area of the circumferential end edge of the wide groove, preferably smaller than the cross-sectional area Sm of the intermediate point.

When a plurality of vertical main grooves are provided, it is not necessary to provide a wide groove portion in the vertical main groove arranged at a position off the ground contact surface.

[0017]

With the wide groove portion having the above-described structure provided in the vertical main groove, the noise generated by the air column formed by the road surface and the main groove portion of the vertical main groove is suppressed by the wide groove portion while the tire is running, and the passing noise is reduced. It can be planned. Moreover, since it is not necessary to provide a sound insulating wall in the vertical main groove, the drainage performance is not impaired and the hydroplaning resistance can be maintained.

[0018]

DESCRIPTION OF THE PREFERRED EMBODIMENTS 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 and 13 extending inward in the tire radial direction from both sides thereof.
And a bead portion 14 extending inward of the sidewall portion 13
Have and.

Further, the pneumatic tire 1 has a tread portion 12
A carcass 16 having a body 16a extending from the side wall 13 to the bead 14 and folding back around the bead core 15 from the inner side in the tire axial direction to the outer side; Part 12
And a belt layer 17 disposed on the inner side of the belt.

In the present embodiment, a bead apex 18 made of hard rubber is formed on the outer side of the bead core 15 in the radial direction and between the main body portion 16a of the carcass 16 and the folded portion 16b. .

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

The belt layer 17 is composed of two belt plies in this embodiment, and each belt ply has a belt cord made of an organic fiber such as nylon, rayon, aromatic polyamide, or a steel cord with respect to the tire equator C. 2
It consists of cut plies arranged at an angle of 0 to 70 °. The belt cords are arranged so as to intersect with each other between the belt plies.

The tread surface 2 is provided with one or a plurality of circumferentially continuous vertical main grooves 3 in this example. The vertical main groove 3 has a groove width WG of 8 mm or more and a tread width W.
At least 10 wide groove portions 5 ... Are interposed in the main groove portion 4 which is 0.16 times or less than T and extends linearly in the circumferential direction.

When the groove width WG of the main groove portion 4 is less than 8 mm, drainage becomes insufficient during running on a wet road surface, hydroplaning is likely to occur, and if the tread width WT becomes wider than 0.16 times, the tread width becomes wider. This is because the ground pressure on the surface 2 becomes excessively large, the wear resistance is poor, and uneven wear is likely to occur at the groove edges. The groove depth of the main groove portion 4 is preferably in the range of 0.01 to 0.10 times the tread width WT.

Further, in the present embodiment, in the normal state in which the tire is assembled on the rim and the normal internal pressure and the normal load are applied, the four vertical main grooves 3 ... Are all located on the ground plane L.

The wide groove portion 5 is interposed between the main groove portions 4 and 4, and in the present embodiment, has a long hexagonal shape that is long in the circumferential direction. Also above
In the main groove portion 4, the peripheral wall 21 of the main groove portion 4 surrounds the wide groove portion 5.
At the position of the end edge F in the direction,
And has an open end E at its tip. In other words,
The wide groove portion 5 extends along the protruding portion 21 beyond the opening end E.
Extends to both sides in the circumferential direction up to the edge F in the circumferential direction, and the protrusion
In the portion 7, the peripheral wall 21 of the main groove portion 4 projects toward the wide groove portion 5.
Around the open end E of the main groove portion 4 and the wide groove portion 5
It is formed between the facing edge F.

The circumferential length Lm of the wide groove, which is the circumferential length F between the circumferential edges F of the wide groove 5, is 45 mm or more and 90 mm or less, and a normal internal pressure and a normal load are applied to this tire. It is smaller than the ground plane length L which is the circumferential length of the ground plane S (shown by the one-dot chain line in FIG. 2) in the normal state.

The wide groove portion 5 has a spindle shape or a shape similar thereto, and the cross-sectional area Sm of the main groove portion 4 at a right angle to the groove center l2 at the circumferential middle point M is a cross-sectional area Sg of the main groove portion 4 at a right angle. 2 times or more and 4 times or less. Thus the wide groove 5 is sectional area in the circumferential direction edge F is smaller than the cross-sectional area Sm of the midpoint m, there may be a case where sectional area of MataShu direction edge F is substantially zero.

Further, the wide groove portion 5 has the length of the protruding portion 7, that is,
The insertion length Ls, which is the circumferential distance between the opening end E of the main groove portion 4 and the circumferential end edge F of the wide groove portion 5, is greater than 0 and is 0.25 times the circumferential length Lm of the wide groove portion 5. It is as follows.

10 or more wide groove portions 5 having the above-mentioned structure are provided for one vertical main groove 3. The size regulation of the wide groove portion 5 is based on the following reason. Generally, as one of the methods for reducing the noise propagating in the pipe, there is a cavity silencer in which a cavity v is provided in the middle of the pipe p as schematically shown in FIG. The transmission loss TL representing the sound deadening effect in such a cavity silencer is as follows: Sg: sectional area of the tube p Sm: sectional area of the cavity v m = sm / sg lm: length of the cavity v k = 2πf / c where c Is the sound velocity, TL = 10log [1+ (1/4) (m−1 / m) ² sin ² (k × lm)] (1)

In the formula (1), the maximum silencing effect is obtained when 2πf / c × lm = k × lm = π / 2. On the other hand, the air column resonance to be silenced is 1000 Hz, which is the most offensive noise among the noise, and when these numerical values are substituted into the equation (1) to obtain the cavity length lm, lm = 90 mm is obtained. On the other hand, in the tire, the wide groove portion 5 forming the cavity is moved by rotation of the tire and is repeatedly grounded and ungrounded.
The reason for this is that the same phenomenon occurs as when the groove width of the vertical main groove is extremely widened and the noise level is rather increased.

The wide groove portion 5 with respect to the cross-sectional area Sg of the main groove portion 4
As for the ratio m of the cross-sectional area Sm of the above, if the value of m is increased, the transmission loss TL is increased and the sound deadening effect is enhanced, but in the grounded state in which the wide groove portion opens at the edge of the grounded portion S Causes the groove width of the vertical main groove 3 to become large as a result, which becomes a factor of increasing the noise level. Further, the rigidity variation of the tread portion becomes large, and as a result, the noise level is further deteriorated. For this reason, the cross-sectional area ratio Sm / Sg is set to 2 or more and 4 or less.

Further, one wide main groove 3 has one wide groove portion 4
By arranging 0 or more, one or two wide groove portions 5 always exist on the ground plane.

The projecting portion 7 of the main groove portion 4 has a circumferential length, that is, an insertion length Ls with which the main groove portion 4 is inserted into the wide groove portion 5.
Is greater than 0 and is 0.2 of the circumferential length Lm of the wide groove portion.
It is 5 times or less. By providing such a protruding portion 7, the ground contact rigidity can be secured. If the insertion length Ls exceeds 0.25 times the circumferential length Lm of the wide groove portion 5 and becomes large, the groove portion area on the ground contact surface L becomes too large, and the ground contact rigidity is lowered, and uneven wear is likely to occur.

As shown in FIG. 5, the wide groove portion 5 may be formed in a barrel shape having a middle bulge, and its peripheral wall 21 needs to be streamlined so as to reduce air resistance.

[0036]

SPECIFIC EXAMPLES Tires (Examples 1 to 4) each having a tire size of 205/55 R15 and having the structure shown in FIG. 1 were prototyped and their performances were tested. For comparison, a tire having a conventional configuration (conventional example) was also tested and the performance was compared.

1) Passing noise Carried out by an actual vehicle coasting test stipulated in JASO C606, a vehicle equipped with test tires was passed over a straight test course at a passing speed of 60 km / H and a distance of 50 m while coasting. The passing noise was measured at a midpoint of the course by a stationary microphone placed laterally 7.5 m from the running center line and 1.2 m in height from the test road surface.

2) Hydroplaning performance A test tire was mounted on an actual vehicle, and a linear distance of 5 mm in water depth was set to 10
The speed at which the vehicle entered at 0 km / H and only the front tire was locked and the frictional force was recovered was measured and displayed as an index with 100 as the conventional example. The larger the value, the better. The test results are shown in Table 1.

[0039]

[Table 1]

As a result of the test, it was confirmed that the noises of Examples 1 to 4 were lower than those of the conventional example and the hydroplaning performance was maintained.

[0041]

As described above, the pneumatic tire of the present invention is
The gist of the present invention is to interpose 10 or more wide wide grooves for silencing in the main groove portion of the longitudinal main groove that is continuous in the circumferential direction, and the passing noise can be reduced without lowering the hydroplaning resistance.

[Brief description of drawings]

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

FIG. 2 is a plan view showing the tread pattern.

FIG. 3 is a perspective view illustrating an example of a main part thereof.

FIG. 4 is a cross-sectional view schematically showing a silencing effect of resonance sound.

FIG. 5 is a plan view showing another example of the tread pattern.

FIG. 6 is a plan view showing a conventional tread pattern.

[Explanation of symbols]

2 tread surface 3 vertical main groove 4 main groove 5 Wide groove E Main groove opening end F Circumferential edge of wide groove L contact surface length Lm Wide groove circumferential length Ls insertion length M midpoint S ground plane Sg Cross-sectional area of main groove Sm Wide groove cross-sectional area WG groove width

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Claims (3)

(57) [Claims] 1. A pneumatic tire having a single or a plurality of longitudinal main grooves continuous in the circumferential direction on a tread surface, wherein the vertical main groove has at least a main groove portion having a groove width of 8 mm or more. 10 wide grooves for noise reduction are interposed, and the wide grooves have a circumferential length Lm of 45 mm or more and 90 mm or less, and the contact in a normal state in which a normal internal pressure and a normal load are applied to the tire. The cross-sectional area Sm in the direction perpendicular to the groove center line at the circumferential midpoint of the wide groove is perpendicular to the groove center line of the main groove, while being smaller than the ground contact surface length that is the circumferential length of the ground. 2 times or more and 4 times or less of the cross-sectional area Sg of the main groove portion and the peripheral wall of the main groove portion is the circumferential direction of the wide groove portion
Open at the tip of the protrusion that protrudes into the wide groove at the position of the facing edge
A pneumatic tire having an end . 2. The wide groove portion is provided in front of the opening end of the main groove portion.
The protrusion that is the circumferential length to the circumferential edge of the wide groove portion
The pneumatic tire according to claim 1, wherein the insertion length Ls of the portion is greater than 0 and not more than 0.25 times the circumferential length Lm of the wide groove portion. Wherein the wide groove, the wide a cross sectional area at the circumferential end edge of the groove, according to claim 1 or 2, wherein the pneumatic characterized by being smaller than the cross-sectional area Sm of the intermediate point tire.