JP2001239809A - Pneumatic low-noise tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a pneumatic tire for effectively reducing noise caused by columnar resonance and noise caused by vibration of a tread and side walls causing tire noise without impairing wet performance and traveling performance. SOLUTION: In the pneumatic tire, a tread is arranged on the outer side in the radial direction of a crown part of a carcass by taking the carcass extending between a pair of bead cores as a frame, and a circumferential groove extending in the tread circumferential direction is formed on the front surface of the tread. A resonance pipe structure is provided by connecting a cavity provided inside the tread to the circumferential groove by a passage.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pneumatic tire in which noise during running is totally reduced.

[0002]

2. Description of the Related Art A pneumatic tire is provided with a plurality of circumferential grooves extending in the tread circumferential direction at intervals in the tread width direction for guiding drainage on the tread surface in order to ensure wet performance of the tire. , As usual.

When the tire rolls, the air compressed between the tread and the road surface on the tread contact surface rapidly flows out of the tire through the circumferential groove extending in the circumferential direction of the tread, and the air intermittently flows. As a result, the noise spreads outside. In particular, this noise, in the circumferential groove,
Since a so-called air column resonance is generated and a high sound is generated, it occupies a large part of the tire.

[0004] In order to reduce the air column resonance sound through such a circumferential groove, it is known to reduce the number and the volume of the circumferential groove and to provide a partition in the circumferential groove. This method impairs the original function of the circumferential groove, that is, the drainability of the tread, and causes a decrease in wet performance.

On the other hand, Japanese Patent Application Laid-Open Nos.
No. 76203 discloses a technique for suppressing air column resonance by providing a resonance recess in an adjacent area along a circumferential groove. In this method, air column resonance can be reduced without reducing the number and volume of the circumferential grooves.

[0006]

However, as recesses for resonance, a resonance chamber in Japanese Patent Application Laid-Open No. 5-338411 and an auxiliary groove in Japanese Patent Application Laid-Open No. 7-76203 are arranged at equal intervals along a plurality of circumferential grooves. Therefore, there is a disadvantage that noise resulting from the inflow and discharge of compressed air between the tread and the road surface into these recesses, that is, so-called pattern noise is newly generated.

Another type of tire noise includes noise generated when the tread and sidewalls are vibrated by an input from a tread contact surface when the tire rolls on an uneven road surface, and the vibrations are propagated in the air. However, it is preferable that this noise be reduced together with the noise caused by the air column resonance. However, there is no known technology for reducing both noise due to air column resonance and noise due to tread and sidewall vibrations.

Since the noise due to the vibration of the tread and the sidewall depends on the input from the tread tread, it is effective to reduce the impact from the road surface at the tread tread portion. For example, it is conceivable to soften the rubbery material of the tread surface layer, but on the other hand, the driving performance, especially the dry performance such as steering stability, is remarkably reduced.

Therefore, the present invention has effectively reduced noise caused by air column resonance and noise caused by tread and sidewall vibrations, which cause tire noise, without sacrificing wet performance or running performance. The purpose is to propose a pneumatic tire.

[0010]

That is, the gist of the present invention is as follows. (1) A pneumatic tire having a carcass extending across a pair of bead cores as a skeleton, a tread disposed radially outside a crown portion of the carcass, and a circumferential groove extending in a tread circumferential direction on a surface of the tread. Comprising a cavity provided inside the tread and the peripheral groove connected by a passage,
A low-noise pneumatic tire having a resonance tube structure.

(2) The low-noise pneumatic tire according to the above (1), wherein the passage and the cavity have a shape and a size that become a resonance tube for a frequency range of air column resonance in the circumferential groove.

(3) In the above (1) or (2), when the tire is mounted on the standard rim, adjusted to the maximum air pressure, and a load corresponding to the maximum load capacity is applied, the tire is contacted with one circumferential groove. A low-noise pneumatic tire having one resonance tube structure.

(4) In any one of the above (1) and (2), when the tire is mounted on a standard rim, adjusted to the maximum air pressure and a load corresponding to the maximum load capacity is applied,
A low-noise pneumatic tire having a plurality of resonance tube structures for one circumferential groove.

(5) In the above (4), the plurality of resonance tube structures provided for one peripheral groove on the grounding surface are characterized in that one or both of the dimensions of the passage and the cavity are different from each other. Noise pneumatic tire.

(6) In any one of the above (1) to (5), the minimum diameter of the passage in the cross section in the tread width direction is 0.5 mm.
As described above, a low-noise pneumatic tire having a diameter less than the maximum diameter of the cavity.

[0016]

FIG. 1 illustrates a pneumatic radial tire for a passenger car according to the present invention. This tire is 1
A carcass 2 composed of plies radially arranged across a pair of bead cores 1 as a skeleton, and at least two layers of a belt 3 and a tread 4 sequentially arranged radially outside a crown portion of the carcass 2; A plurality of circumferential grooves 5 extending in the circumferential direction are provided on the surface of the tread 4.

Here, it is important that the circumferential groove 5 has a resonance tube structure 8 formed by connecting a cavity 6 provided inside the tread 4 by a passage 7. For example, as shown in FIG. 2, a plurality of resonance pipe structures 8 provided in the respective circumferential grooves 5 at intervals in the circumferential direction are provided for the air column formed by the circumferential groove 5 portion of the tread contact surface and the road surface. It functions as a resonance tube and plays a role in attenuating the resonance sound in the air column.

In order to function as a resonance tube for the air column, it is necessary to provide a closed space having a small opening. Therefore, a structure in which the cavity 6 is embedded in the tread rubber is optimal. Moreover, since the resonance tube structure is not exposed on the tread surface, it does not cause the generation of new pattern noise which is a problem in the above-described conventional technology. On the other hand, since it is not necessary to reduce the number and volume of the circumferential grooves, the wet performance is maintained.

Further, it is advantageous that the cavity 6 and the passage 7 have a shape and a size that become a resonance tube for the frequency range of the air column resonance in the circumferential groove 5. That is, it is preferable to give the cavity 6 and the passage 7 a shape and dimensions that resonate in the frequency range in which the columnar resonance sound is generated in the circumferential groove 5. Specifically, as shown in FIG. 3, when the volume of the cavity 6 is W, the cross-sectional area of the passage 7 is S, and the length of the passage 7 is 1, the resonance tube composed of the cavity 6 and the passage 7 absorbs. air from can be represented by the speed of sound, the frequency f ₀ is: frequency f _0, according to resonator theory of Helmholtz, the following equation _{f 0 = c / 2π · {} S / (l · W)} 1/2 However, c Finding W, S, and l that are the column resonance frequency range, the cavity 6 and the passage 7
Should be designed.

Therefore, as long as the cavity 6 and the passage 7 have a shape and size that resonate in the frequency range of air column resonance, the shape may be free. In particular, the cavity 6 may have a polygonal cross section in addition to a circular cross section. Good. Further, the cavity 6 may be a series of spaces continuous in the circumferential direction of the tread as shown in FIG. 4 in addition to being provided intermittently in the circumferential direction of the tread as shown in FIG. , All achieve similar functions.

On the other hand, the diameter of the passage 7 in the cross section in the tread width direction is preferably 0.5 mm or more and less than the maximum diameter of the cavity 6. If the diameter of the passage 7 is less than 0.5 mm, the passage is collapsed due to the compression in the ground contact surface, and the passage becomes inoperable. Since the compression stiffness becomes small, the passage may become a core of uneven wear and wear may progress.

Changing the shapes and dimensions of the cavity 6 and the passage 7 changes the W, S and l, and also changes the air column resonance sound frequency attenuated by the resonance tube structure. The combination of cavities 6 and passages 7 of different geometries allows attenuation for different frequencies. That is, noise can be reduced over a wide frequency range. Incidentally, since the frequency range in which air column resonance occurs in the circumferential groove is in the range of about 200 to 20000 Hz, various cavities 6 and passages 7 may be designed for this frequency range.

In particular, the resonance tube structure including the cavity 6 and the passage 7 has one circumferential groove on the tread contact surface when the tire is mounted on the standard rim, adjusted to the maximum air pressure, and a load corresponding to the maximum load capacity is applied. Preferably, at least one is provided. In other words, the attenuation of the air column resonance sound is determined by the number of resonance pipe structures attached to the circumferential groove, so that at least one resonance pipe structure is required for each circumferential groove in the ground plane where the air column is formed. is there. Of course, by increasing the number of installed resonance tube structures within a range that does not impair tire performance, it is possible to enhance the ability to attenuate resonance sound. For example, when the frequency range of the attenuated resonance sound is wide, a plurality of resonance tube structures including cavities 6 and passages 7 of various shapes and sizes are provided for each ground contact surface length of each circumferential groove as shown in FIG. It is advantageous to provide.

Further, since the cavity 6 is formed behind the tread surface, the impact applied from the road surface to the tread contact surface is greatly reduced, so that tire noise due to vibration of the tread and sidewalls is suppressed. Is done. That is, by providing the cavity 6 in the surface layer of the tread, the compression rigidity of the tread is reduced, so that the impact can be absorbed in the surface region of the tread, and in the propagation of the vibration from the ground contact surface to the circumferential direction of the tread, the rubber and the cavity are not covered. Since the speeds of the vibrations transmitted through the inside are different, the vibrations interfere with each other and the vibrations are reduced. As a result, noise is suppressed. On the other hand, since the cavity 6 is buried inside the tread and does not affect the shear rigidity of the tread surface, the running performance of the tire is not hindered.

Further, the cavity 6 and the passage 7 function as a new drainage ditch when the tread is worn and the passage 7 and the cavity 6 are worn until the passage 6 and the cavity 6 are exposed. Can be maintained.

Next, means for forming the above-described resonance tube structure will be described. First, the cavity 6 can be formed by (i) a pre-cured tread method and (ii) a tube method. That is, the above method (i) is mainly used for manufacturing a retreaded tire, and when the retreading of the tire is performed using a vulcanized and molded precured tread, a predetermined surface is previously applied to the back surface of the precured tread. This method is to form a groove between the belt and the tread by forming a groove having a shape and a length, and bonding the precured tread to a base tire.

In the above method (ii), as shown in FIG. 6, a bag 11 containing a gas generating substance 10 which is vaporized in a temperature range exceeding room temperature and lower than the rubber internal temperature at the time of vulcanization is unpacked. Vulcanized rubber
After being buried in the vulcanized rubber 12, the unvulcanized rubber 12 is vulcanized, and during the vulcanization, the bag 11 is inflated by the vaporization of the gas generating substance 10, whereby the vulcanized rubber 13 is passed through the bag 11. A cavity 6 can be formed therein. At this time, it is necessary to securely seal the bag 11 so that the gas in the bag 11 does not leak out of the bag due to the vulcanization pressure.

That is, in the manufacture of a tire, after the carcass, bead ring, various reinforcing materials and belt materials are pasted on a forming drum, the above-mentioned gas generation occurs in the tread rubber before the tread rubber is finally pasted. A green tire is manufactured by embedding a bag 12 in which the substance 10 is encapsulated, and thereafter attaching a tread rubber, and the green tire is vulcanized and molded to obtain a desired size and shape in the tread rubber through the above process. Is formed.

The gas generating substance 10 preferably has a saturated vapor pressure at 170 ° C. of 0.7 MPa or more. That is, a bag filled with gas from a gas generating substance
11, to against the pressure exerted to the rubber in the rubber during vulcanization is necessary to maintain the expanded state in the rubber, the saturated vapor pressure P ₁ in the gas generating material enclosing the rubber internal temperature of vulcanization There is at the pressure P ₂ or more applied to the rubber is required during vulcanization. And this requirement is for 170
It is satisfied when the saturated vapor pressure at ℃ is 0.7 MPa or more.

Specifically, as the gas generating substance 10, water,
Alcohol, hydrous inorganic salt, silane coupling agent + silicon
Mixtures and foaming agents can be used. Inside
, Water-containing inorganic salt, silane coupling agent + silica mixture
And foaming agents are powders and are handled in comparison to liquids.
Recommended because it is easy. That is, hydrated inorganic salts
As NiSO_Four ・ 7H_TwoO, CoSO_Four ・ 7H_TwoO, NaSO_Four ・ 10H_Two
O, CaSO_Four ・ 2H_TwoO, CuSO_Four ・ 5H_TwoO, Al_Two(SO_Four)_Three ・ 18H_TwoO
 , FeSO_Four ・ 7H_TwoO, ZnSO_Four・ 7H_TwoO, MgSO_Four ・ 7H_TwoO, Na_TwoS ・
9H_TwoO, Na_ThreePO_Four・ 12H_TwoO, Ni_Three(PO_Four)_Two ・ 8H_TwoO, Mg_Three(PO_Four)_Two 
・ 8H_TwoO, Li_ThreePO_Four・ 5H_TwoO, Na_FourP_TwoO₇ ・ 6H_TwoO, Mn_Four(P_TwoO₇)_Three・
14H_TwoO, CoCO_Three ・ 6H_TwoO, NiCO_Three ・ 6H_TwoO, Na_TwoCO_Three・ 10H_TwoO
 , Nd_Two(CO_Three)_Three ・ 8H_TwoO, Na_TwoSO_Three・ 7H_TwoO, CaCl _Two ・ 6H_TwoO, N
iCl_Two ・ 6H_TwoO, Na_TwoB_FourO₇ ・ 10H_TwoO, FeCl_Three ・ 6H_TwoO, Na_TwoSi
O_Four ・ 9H_TwoO, and the like.

Examples of the foaming agent include dinitrosopentamethylenetetraamine (DPT), azodicarbonamide (ADCA), dinitrosopentastyrenetetramine, benzenesulfonyl hydrazide derivative, oxybisbenzenesulfonyl hydrazide (OBSH) and the like. There is
Among them, ADCA is advantageous in terms of manufacturing processability.

Further, as the bag 12, a thermoplastic resin, for example, polyethylene, polypropylene, nylon, acrylic or the like, or rubber can be used. The rubber may be the same or different from the rubber used for the dread,
It is preferable to use a material that has been subjected to vulcanization or semi-vulcanization before the vaporization reaction of the gas generating substance 10, particularly before encapsulation in a bag.

Next, for example, after one cavity 6 is formed per ground surface length of each peripheral groove 5 by each of the above-described methods, a passage 7 for connecting the cavity 6 to the peripheral groove 5 is formed as follows.
It can be formed by (I) drill forming, (II) hot melt forming, and (III) die forming. That is,
In the method (I), a passage 7 is formed by drilling a hole having a predetermined diameter toward the cavity 6 from the groove wall or the groove bottom of the circumferential groove 5 using an electric drill.

In the above method (II), a passage 7 is formed by drilling a hole of a predetermined diameter from the groove wall or the groove bottom of the circumferential groove 5 toward the cavity 6 using, for example, a heating wire.

According to the method of the above (III), a projection, which becomes a hole extending toward the cavity 6 from the groove wall or the groove bottom of the peripheral groove 5, is formed on the protruding portion for engraving the peripheral groove 5 of the vulcanizing mold. Then, the passage 7 is formed by performing vulcanization molding using the mold.

[0036]

EXAMPLE According to the tire structure shown in FIG. 1, size: 20
In trial production of 5 / 65R15 radial tires for passenger cars, carcass, bead rings, various reinforcing materials and belt materials are first bonded on a forming drum, and then, before the tread rubber is bonded, To
A polyethylene tube filled with sodium pyrophosphate decahydrate as a gas-generating substance, both openings of which are closed with the same unvulcanized rubber as the tread rubber, bag (length: 10 cm, diameter: 5 m)
m) in three rows in the width direction of the tread and in the circumferential direction of the tread with a gap of 5 cm between the bags, and the tread rubber is attached to produce a green tire. Green tires were vulcanized. The bag had a recess formed on the surface opposite to the side on which the circumferential groove was formed during the extrusion molding of the tread rubber, and was disposed in the recess.

Next, it was confirmed from a cross-sectional photograph using X-rays that three rows of cavities arranged in the width direction were intermittently arranged in the circumferential direction on the tread of the tire after vulcanization. Four circumferential grooves (width and depth: 8 mm) were carved and formed at positions along each hollow row. And Invention Example 1
As a result of calculating the cross-sectional area and length of the passage from the above equation so as to resonate with the frequency of 2000 Hz under the obtained cavity volume W, the passage having a diameter of 4 mm and a length of 4 mm was It was formed at intervals of 15 cm in the circumferential direction from the circumferential groove side using a drill. As Example 2, as a result of calculating the cross-sectional area and the length of the passage from the above formula so as to resonate with the frequency of 1000 Hz under the obtained volume W of the cavity, the diameter:
3 mm and length: 8 mm passage with an electric drill
It was formed at intervals of 15 cm in the circumferential direction from the circumferential groove side.

Four tires of each specification thus obtained are prepared, and each tire is assembled to a standard rim, adjusted to the maximum air pressure, mounted on an actual vehicle, and then coasted on a test course (ISO CD13325). , Tire noise was measured, and a wet performance test was conducted in which five pylons were placed at a predetermined interval on a wet road surface having a section of 90 m and a water depth of 5 mm, and evaluated based on a passage time when the section was zigzag-traveled. . The shorter the transit time, the better the wet performance.

For comparison, a tire having the same structure and size was experimentally manufactured except that the resonance tube structure was not provided, and the same evaluation was performed. Further, after the above test was finished, each tire was worn by buffing until the passage was exposed on the tread surface, and then the same wet performance test as described above was performed.

Table 1 shows the evaluation results. In addition,
The wet performance and the wettability after abrasion were indicated by an index when the result of Comparative Example was set to 100. The larger the value, the better the result.

[0041]

[Table 1]

[0042]

According to the present invention, noise caused by air column resonance and noise caused by tread and sidewall vibrations, which occupy a large part of tire noise, can be reduced without sacrificing wet performance or running performance. Can be suppressed.

[Brief description of the drawings]

FIG. 1 is a diagram showing a tire structure of the present invention.

FIG. 2 is a diagram showing the arrangement of cavities and passages.

FIG. 3 is a diagram for explaining a method of calculating a resonance frequency in a resonance tube.

FIG. 4 is a diagram showing the arrangement of cavities and passages.

FIG. 5 is a diagram showing the arrangement of cavities and passages.

FIG. 6 is a diagram illustrating molding of a cavity in rubber.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Bead core 2 Carcass 3 Belt 4 Tread 5 Circumferential groove 6 Cavity 7 Passage 8 Resonance tube structure 10 Gas generating substance 11 Bag 12 Unvulcanized rubber 13 Vulcanized rubber

Claims (6)

[Claims] An air having a carcass extending over a pair of bead cores as a skeleton, a tread disposed radially outside a crown portion of the carcass, and a circumferential groove extending in a tread circumferential direction on a surface of the tread. A low-noise pneumatic tire having a resonance tube structure, comprising a cavity provided inside a tread and the above-mentioned circumferential groove connected by a passage. 2. The method of claim 1, wherein the passage and the cavity are:
A low-noise pneumatic tire having a shape and a size that serves as a resonance tube for a frequency range of air column resonance in a circumferential groove. 3. The tire according to claim 1, wherein the tire is mounted on a standard rim, adjusted to a maximum air pressure, and a load corresponding to the maximum load capacity is applied to a peripheral groove.
A low-noise pneumatic tire having two resonance tube structures. 4. A plurality of resonance tubes according to claim 1, wherein the tire is mounted on a standard rim, adjusted to a maximum air pressure and a load corresponding to a maximum load capacity is applied, and a plurality of resonance pipes are assigned to one circumferential groove on a ground contact surface. A low-noise pneumatic tire having a structure. 5. The low-noise air according to claim 4, wherein one or both of the passage and the cavity have different dimensions and shapes from each other in the plurality of resonance tube structures provided on the grounding surface to one peripheral groove. Containing tires. 6. The method according to claim 1, wherein
A low-noise pneumatic tire, wherein a minimum diameter of a passage in a cross section in a tread width direction is 0.5 mm or more and less than a maximum diameter of a cavity.