JPH05116510A - Pneumatic tire - Google Patents

Abstract

PURPOSE:To eliminate uncomfortability and fatigue from the driver by reducing noise, in particular, having a frequency higher than 250Hz during running while holding a hydroplaning function. CONSTITUTION:A plurality of longitudinal grooves including those extending circumferentially at positions symmetric with respect to the equator of a tire are formed on the tread surface of the tire, the symmetric longitudinal grooves G1, G2 are formed with a plurality of transition parts having longitudinal grooves which are laterally shifted in the tire-axial direction, and also having a circumferential length L which is 0.3 to 0.9 times as long as the ground contact length in a direction passing through the tire equator at the ground contact surface S of the tire in such a condition that the tire is inflated by a normal internal pressure and is applied with a normal load, and a lateral shift value I which is 0.4 to 0.8 times as large as the width WG of the longitudinal grooves. Further, the transition parts 3 are arranged circumferentially so that they are present at least their circumferential one end part on the rolling ground contact surface.

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 high frequency noise generated from a circumferential groove at the time of contact with a ground and reducing a driver's tiredness.

[0002]

2. Description of the Related Art With the recent increase in speed of vehicles, it is required to improve the high-speed running property of tires. On the other hand, when traveling at high speed on a wet road surface, the so-called handloplaning phenomenon, in which the tire floats completely above the water surface and glides, tends to occur, and once hydroplaning occurs, the vehicle becomes uncontrollable. Become.

Therefore, in a conventional tire considering hydroplaning, as shown in FIG. 5, the longitudinal grooves a extending in the circumferential direction have a large cross section to efficiently collect rainwater accumulated on the tread surface b. In addition, it is formed so that it can be reliably discharged.

[0004]

However, when the transverse cross section of the vertical groove is increased, a tunnel-shaped air column space with openings at both ends formed by the groove portion between the tread surface and the road surface is formed during traveling, and therefore, during high speed traveling. At this time, the air column resonates to generate high-frequency noise of 800 to 1200 Hz, which produces a shearing sound or a shoeing sound. Particularly in recent years when high-speed driving is increasing, the driver feels tired, and thus there is a demand for reduction of the noise.

The frequency of such high frequency noise is related to the circumferential direction of the vertical groove on the ground plane, and its primary resonance frequency can be obtained by the following equation. Resonance frequency (Hz) = (1 / 2L) V where V: sound velocity L: circumferential length of vertical groove on ground plane

On the other hand, in the conventional tire, a vertical groove having a large groove width is continuous in the tire circumferential direction as shown in FIG. 4 for the purpose of preventing the occurrence of hydroplane.
Generation of high frequency noise is inevitable.

In order to eliminate this high frequency noise, it is sufficient to divide the vertical groove. However, by dividing the vertical groove, the drainage property is lowered and thus hydroplane is likely to occur.

As a result of repeated research by the inventor to achieve both reduction of high frequency noise and prevention of hydroplaning, dislocations formed by partially shifting the flutes laterally in the tire direction. It has been found that both the reduction of high frequency noise and the suppression of hydroplaning can be achieved by providing the portions and by setting the circumferential length of the dislocation portion and the lateral shift amount within the regulated ranges.

It is an object of the present invention to provide a pneumatic tire capable of reducing the noise particularly in a high frequency range at the time of high speed running, and further suppressing the occurrence of hydroplaning to achieve safe running.

[0010]

SUMMARY OF THE INVENTION The present invention is a pneumatic tire having a plurality of flutes, which include flutes extending in the circumferential direction at symmetrical positions with respect to the tire equator, on the tread surface. In the symmetrical vertical groove, while providing a plurality of dislocation portions that are laterally displaced in the tire axial direction, the dislocation portion,
The length in the circumferential direction is 0.3 times or more of the circumferential ground contact length passing through the tire equator of the ground contact surface in a normal state in which the tire is mounted on a standard rim and a normal internal pressure and a normal load are applied, and 0 9 times or less, and the lateral shift amount is less than the groove width of the vertical groove.
4 times or more and 0.8 times or less, and further, the dislocation portions are arranged in a circumferential direction in which at least one end portion in the circumferential direction of the dislocation portions is arranged on the rolling contact surface in the circumferential direction. is there.

Further, the tread surface may be provided with a plurality of lateral grooves passing through at least both circumferential ends of the dislocation portion and extending from the tread edge.

[0012]

In the symmetrical longitudinal groove, a plurality of dislocation portions are provided in the tire circumferential direction, which are laterally displaced in the axial direction of the tire. As a result, the flutes are continuously connected in the circumferential direction to maintain drainage and prevent the occurrence of hydroplaning, while separating the air column formed by the flutes and the road surface on the ground contact surface to reduce high frequency noise. I can.

The frequency of the high frequency noise is related to the circumferential length L of the vertical groove in the ground plane, and its primary resonance frequency (Hz) can be obtained by the following formula. Resonance frequency (Hz) = (1 / 2L) V where V: speed of sound

In the driver, 800-1200
Sound in the frequency range of Hz is an unpleasant sound, and receiving this unpleasant sound causes fatigue and hinders long-term driving. Therefore, in order to remove the unpleasant sound, the length of the vertical groove that is the length of the air column in the ground plane is shortened, and the vertical groove is laterally displaced, thereby shifting the resonance frequency to a higher frequency range and making it unpleasant. The sound can be removed, and the majority of the noise is absorbed by the groove wall, so that the emission of the noise to the outside can be significantly reduced.

The length of the dislocation portion in the tire circumferential direction is set to 0.3 times or more and 0.9 times or less of the ground contact length of the ground contact surface. If it is less than 0.3 times, a large number of bent portions are formed on the ground contact surface and the hydroplaning performance is deteriorated.
If it exceeds twice, the air column length is almost the same as that of the conventional straight groove, and the noise reduction effect does not appear.

The amount of lateral deviation is set to 0.4 times or more and 0.8 times or less the groove width of the vertical groove. If it is less than 0.4 times, the effect of reducing noise is small, and if it exceeds 0.8 times, drainage becomes poor and the hydroplaning performance deteriorates.

Moreover, since the dislocation portions are arranged in the circumferential direction so that one end portion of the dislocation portion is interposed between the rolling contact surface and the rolling contact surface, the dislocation portion always has one end portion in the contact surface of the rolling tire. Therefore, the noise during traveling is continuously reduced.

As described above, according to the invention of the present application, the above-mentioned components are organically combined and integrated to separate the air column, which is formed by the vertical groove and reduces the generation of noise, and the flow of air discharged at the time of grounding. Is suppressed, the sound pressure level of noise itself can be lowered, and since the resonance frequency is dispersed, it is possible to significantly reduce the release of high-frequency unpleasant sound to the outside, and it is possible to reduce driver fatigue. Become. In addition, since drainage is ensured, the occurrence of hydroplaning is suppressed and running safety can be maintained.

When the lateral groove is provided, the length of the dislocation portion in the circumferential direction can be accurately set, noise can be more effectively reduced, and drainage can be improved.

[0020]

DETAILED 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 radial tire 1 is provided with a plurality of vertical grooves G, including a pair of vertical grooves G1, G1 extending in the circumferential direction at a symmetrical position around a tire equator C on a tread surface 2. Therefore, in this embodiment, a plurality of lateral grooves g extending from the tread edge E are provided. Also, the symmetrical vertical groove G
1, G1 are provided with a plurality of dislocation portions 3 ... In which the vertical grooves G1, G1 are laterally displaced in the tire axial direction.

Further, the pneumatic tire 1 is located at sidewall portions 13 and 13 extending inward in the tire equatorial direction from both ends of the tread portion 12 forming the tread surface 2 and the radially inner end of the sidewall portion 13. Bead part 14, 14
And a bead core 1 provided on each bead portion 14, 14.
A toroidal carcass 16 passing through the side wall portions 14 and 14 and the tread portion 12 is bridged between the portions 5 and 15, and is located radially outside and in the tread portion 12 as well.
The belt layer 17 is arranged inside the.

The carcass 16 is a so-called radial or semi-radial direction array in which the carcass cords are arranged at an angle of 70 to 90 degrees with respect to the equator C of the tire in this embodiment, and as the carcass cord, organic nylon or polyester. Fiber cords of rayon, aromatic polyamide, etc. are adopted.

In this embodiment, three belt plies are arranged on the belt layer 17 from the carcass 16 side toward the outer side in the radial direction of the tire. Further, the belt layer 17 includes belt cords in which cords of respective belt plies are inclined with respect to the tire equator C and intersect each other. The belt cord is made of steel, nylon similar to carcass 16,
Organic fiber cords such as polyester, rayon and aromatic polyamide are used.

In the present embodiment, the longitudinal grooves G are a central longitudinal groove GO that circulates on the tire equator C, and a pair of symmetrical longitudinal grooves arranged on both sides of the tire equator C and at symmetrical positions. It comprises grooves G1 and G1. Therefore, on the tread surface 2,
A pair of inner ribs 21, 21 interposed between the central vertical groove GO and the symmetrical vertical groove G1 and a pair of outer ribs 22 positioned between the symmetrical vertical groove G1 and the tread edge, 22 and four ribs are formed.

The lateral groove g has an inclination from the one tread edge E to the tire axis and extends to the other end edge E while intersecting each longitudinal groove G. Therefore, the inner rib 21 and the outer rib 22 are provided with inner blocks 21B ... Outer blocks 22B arranged in the circumferential direction, respectively. In this embodiment, the lateral grooves g are formed over the entire circumference at a pitch P that is substantially equal in the tire circumferential direction.

Further, the pneumatic tire 1 has a so-called ground contact surface S which has a certain spread and is in contact with the ground. The ground contact surface S has a ground contact width SW in the tire axial direction in a standard condition in which the tire is mounted on a standard rim J and a normal internal pressure and a normal load are applied. And the circumferential length SL of the ground contact S on the tire equator C is set to a range of 0.6 to 1.0 times the tread width.

The symmetrical vertical grooves G1 and G1 respectively pass through the area of the ground plane S, and in the present embodiment, the area of the ground plane S is also at the intersection A where the lateral groove g intersects the symmetrical vertical groove G1. It is located inside.

The dislocation portion 3 provided in the symmetrical vertical groove G1 is
In this embodiment, the intersection A of the symmetrical vertical groove G1 and the horizontal groove g is set as one end, and the distance 2 from the intersection A is twice the pitch P of the horizontal groove g.
The intersection A1 that separates P in the circumferential direction is used as the other end, and the position is displaced in the tire axial direction in the symmetrical vertical groove G1 between the intersection A and the intersection A1. In the dislocation portion 3, one symmetrical vertical groove G1 (right side in FIG. 1) is displaced to the tire equator C side, and the other symmetrical vertical groove G2 (left side in FIG. 1) is substantially opposed. At the position, it is dislocated to the tread edge E side.

The dislocation portion 3 has a circumferential length L, that is, the distance between the intersection A and the intersection A1 in this example is 0.3 times or more and 0.8 times the circumferential ground length L of the ground plane S. On the other hand, the lateral deviation amount 1 is set to 0.4 times or more and 0.8 times or less of the groove width WG of the symmetrical vertical groove G1.

Such a dislocation portion 3 has a circumferential length L.
A plurality of dislocation parts 3 are arranged in the circumferential direction at substantially equal intervals, and therefore, the dislocation parts 3 are arranged in a circumferential direction in which at least one end part of the dislocation parts in the circumferential direction is interposed in the rolling contact surface. ..

FIG. 5 shows another embodiment. In this example, the lateral groove g
The outer rib 22 between the tread edge E and the symmetrical longitudinal groove G1
The symmetrical vertical groove G1 is formed only on one side and has one end and the other end of the dislocation portion 3 at a position different from the intersection with the horizontal groove g. The dislocation portion 3 is connected to the main body of the vertical groove G1 at one end and the other end thereof by connecting grooves 5 and 5 of small length.

In the pneumatic tire of the present invention, the symmetrical vertical grooves may have a gentle wavy shape extending in the tire circumferential direction and having a small wave height, and a rib rug pattern having lugs instead of the lateral grooves. However, the present invention can be modified into various embodiments.

[0033]

[Examples] A tire (Example) having a tire size of 165 / 70R13 and the structure shown in FIGS. 1 and 2 was prototyped, and the tire was mounted on all wheels of a test vehicle and subjected to a noise test by running on the road. The performance was investigated. For comparison, a tire (comparative example) having the same size as that of the example and having a tread pattern shown in FIG. 5 and having a conventional structure was also tested to test its performance.

The noise was measured in the following manner. JA
It was carried out by the actual vehicle coasting test method specified in SOC 606, and an actual vehicle equipped with test tires was coasted along a linear test course at a constant speed for a distance of 50 m, and at the midpoint of the course, 7 laterally from the running center line. The passing noise was measured by a stationary microphone installed at a height of 1.2 m from the test road surface at a distance of 0.5 m, and the frequency of the noise was analyzed and shown in dB (A). The passing speed was set to 80 km / H during the test.

The test results are shown in the graph of FIG. In the figure, the broken line shows the example, and the solid line shows the comparative example.

As a result of the test, it was confirmed that the noise in the high frequency region of 800 Hz or higher was remarkably reduced in the example, compared with the comparative example.

[0037]

As described above, in the pneumatic tire of the present invention, a plurality of dislocation portions laterally displaced in the tire axial direction are provided in symmetrical vertical grooves arranged on the tread surface, and at the same time, in the circumferential direction of the ground contact surface. The gist is that the ratio of the length in the circumferential direction to the length and the amount of lateral deviation with respect to the groove width of the vertical groove are regulated respectively, so that the drainage performance is maintained and the occurrence of hydroplaning is suppressed while reducing noise during traveling, In particular, high-frequency noise of 800 Hz or higher can be reduced, driver discomfort and fatigue can be eliminated, and the driving environment can be improved.

[Brief description of drawings]

FIG. 1 is a plan view showing a tread pattern according to an embodiment of the present invention.

FIG. 2 is a sectional view of the tire in the axial direction.

FIG. 3 is a graph showing a result of frequency analysis of noise.

FIG. 4 is a plan view showing a tread pattern of another embodiment.

FIG. 5 is a plan view showing a conventional tread pattern.

[Explanation of symbols]

 2 Tread surface 3 Dislocation part C Tire equator E Tread edge G Vertical groove G1 Symmetrical vertical groove g Horizontal groove J Rim L Circumferential length l Horizontal deviation S Grounding surface SL Circumferential grounding length WG Groove width

Claims (2)

[Claims] 1. A pneumatic tire having a plurality of vertical grooves including circumferentially extending vertical grooves on a tread surface at symmetrical positions about the tire equator, wherein the vertical grooves are provided on the symmetrical vertical grooves. While providing a plurality of dislocation portions in which the grooves are laterally displaced in the tire axial direction, the dislocation portions have a circumferential length obtained by mounting the tire on a standard rim and applying a regular internal pressure and a regular load. 0.3 times or more and 0.9 times or less of the circumferential contact length of the contact surface in the normal state passing through the tire equator, and the lateral deviation amount is 0.4 times or more and 0.8 times the groove width of the vertical groove. The pneumatic tire is characterized in that the number of dislocations is equal to or less than twice, and the dislocation parts are arranged in a circumferential direction in which at least one end part in the circumferential direction of the dislocation parts is interposed in the rolling contact surface. 2. The pneumatic tire according to claim 1, wherein the tread surface includes a plurality of lateral grooves that pass through at least both circumferential ends of the dislocation portion and extend from a tread edge.