JPH10147113A - Low noise pneumatic tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve a vibration characteristic in a side wall part in a pneumatic radial tire for a heavy load in particular as to lower a tire noise by arranging a recess part, which is formed by recessing the surface of the side wall part toward the tire inside, between each of the positions, between which a maximum clearance is provided between the side wall parts, and each of tread ends. SOLUTION: In a pneumatic tire for a heavy load, a tread 6 is arranged on the surface of a cylindrical crown part, and from the both sides of the crown part, a pair of side wall parts 4 are arranged toward the radius directional inside respectively. In this case, between the positions S, between which a maximum interval is provided between the side wall parts 4, and tread ends E, the surfaces of the side wall parts 4 are recessed toward the inside of a tire so as to be formed into recess parts 7, and in each of the recess parts 7, an outline in the tire cross section is formed into a circular arc whose radius of curvature is about 100mm or less. In this way, generation of a vibration in the intensest vibration generating part in the side wall part 4, a tire noise, an ozone crack in a buttress part, or the like can be suppressed, while a coulisse which tends to generate in the buttress part during production can be prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pneumatic tire, particularly to a heavy-duty pneumatic radial tire for trucks and buses, and particularly to a reduction in tire noise.

[0002]

2. Description of the Related Art A running tire is vibrated due to local fluctuations in rigidity due to a tread pattern or unevenness of a road surface, and the vibration propagates in the air to generate noise. Since the tire noise is closely related to the resonance vibration of the tread and the sidewall, it is particularly effective to improve the vibration characteristics of the sidewall to reduce the tire noise.

With respect to the vibration characteristics of the sidewall portion, various measures have been proposed for tires for passenger cars, but for heavy-duty pneumatic radial tires for trucks and buses, measures for improving this kind of tire noise have been proposed. It has not been.

[0004]

SUMMARY OF THE INVENTION Therefore, the present invention
In particular, it is intended to reduce tire noise by improving the vibration characteristics of a sidewall portion of a heavy-duty pneumatic radial tire.

[0005]

The present inventors have observed the vibration behavior of the sidewall portion in detail, and have found that the amplitude at the maximum width position of the tire and its vicinity is remarkably large. Then, as a result of variously examining the shape and thickness of the sidewall portion, it was found that it is advantageous to optimize the thickness of the sidewall portion, and the present invention was completed.

That is, according to the present invention, a tread is disposed on the surface of a cylindrical crown portion, and a pair of sidewall portions and a pair of bead portions are formed from both ends of the crown portion inward in the radial direction, respectively. A series of pneumatic tires, characterized in that a concave portion is provided between the position where the interval between the sidewall portions is maximum and the tread edge, the concave portion having the surface of the sidewall portion depressed inside the tire. Pneumatic tire with low noise.

Here, the concave portion has an arc-shaped contour in the cross section of the tire, has a radius of curvature of 100 mm or less, and has a maximum depth of 1/10 of the thickness of the sidewall portion.
That is, the concave portions are provided continuously on the same circumference, for example, continuously in a wave shape, and the concave portions are provided discontinuously on the same circumference, for example, arranged in a staggered manner. Is advantageous as an embodiment.

Further, in the tire described above, a thickened portion or a weight region made of rubber having a high specific gravity is provided in the sidewall portion on the tire radially inner side of the concave portion, which is effective for further reducing noise. is there.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows a left half section of a pneumatic radial tire according to the present invention. It goes without saying that the right half (not shown) is symmetrical with the left half. In the drawing, 1 is a bead core, 2 is a carcass composed of one ply, extends in a toroidal form between the bead cores 1 along the inner wall of the tire, and is wound from the inside to the outside of the tire by the bead core 1 to form a bead portion 3. Along the side wall part 4
It has a folded portion 2a extending toward the rear. At the crown portion of the carcass 1, at least two layers of a belt 5 and a tread 6 are arranged in order in a radially outward direction of the tire.

In the tire according to the present invention, the surface of the sidewall portion 4 is provided between the position S where the interval between the sidewall portions 4 is maximum (hereinafter, referred to as the maximum width position) and the tread end E. There is a feature in that a concave portion 7 is provided which is depressed inward. By providing the concave portion 7 in a region between the maximum width position S and the tread end E, that is, the portion where the vibration is most intense in the sidewall portion, the vibration here is suppressed, and the tire noise is reduced. is there.

Here, the recess 7 has an arc-shaped contour in a tire cross section, in particular, a radius of curvature of the arc.
It is preferably 100 mm or less. This is because, by making the contour arc-shaped, it is possible to suppress the occurrence of ozone cracks and diagonal cracks in the buttress portion, and it is also effective in preventing crispness in the buttress portion during manufacturing.

Further, the maximum depth a of the concave portion 7 measured starting from the original contour L of the sidewall portion 4 in the concave portion 7 is equal to one of the thickness A of the sidewall portion 4 similarly measured.
/ 10 or more is preferable. This is because if the maximum depth a is too small, the noise reduction effect is also reduced.

The recesses 7 may be provided continuously on the same circumference as shown in FIG. 3 or may be provided discontinuously on the same circumference as shown in FIG. A change in weight or cross-sectional area may be provided between the maximum width portion S and the tread end E.

The recess 7 shown in FIG. 3 (a) has an opening shape that matches the circumference, and the recess 7 shown in FIG. 3 (b) has an opening shape extending in a wavy shape on the same circumference. . FIG.
(a) shows an example in which a large number of recesses 7 are arranged at equal intervals on the same circumference, and FIG. 2 (b) shows an example in which the arrangement of the many recesses 7 is staggered. In each case, the desired effects of the present invention can be obtained.

Further, it is possible to change the depth of the concave portion 7 by forming the contour of the concave portion 7 in a cross section parallel to the tread peripheral surface passing through the center of the opening of the concave portion 7 as shown in FIG. This is effective for suppressing the vibration of the side wall portion which causes noise. That is, although it is not clear, it is considered that there is an effect that the transmission phase from the tread is shifted and the level is reduced.

When the recesses 7 shown in FIG. 4 are provided discontinuously, it is preferable that the boundary between the recesses 7 and the recesses 7 and the surface of the sidewall portion be smoothly continuous. Similarly, it is preferable that the boundary between the concave portion 7 and the side wall surface in the tire radial direction is also smoothly continued. Specifically, it is desirable that the boundary is a curved surface having a radius of curvature of about 10 mm.

Further, in the above-mentioned tire, if a thickened portion or a weight region made of rubber having a high specific gravity is provided in a sidewall portion on the tire radially inner side of the concave portion, noise reduction can be promoted. That is, as shown in FIG. 6, a sidewall portion inside the recess 7 in the tire radial direction is protruded outside the tire, or as shown in FIG. 7, a thickened portion 8 is provided inside the recess 7 in the tire radial direction. . The thickness of the thickened portion 8 should be at least 1.4 times the minimum thickness of the sidewall portion.
This is advantageous for reducing noise.

Also, by providing a weight region made of rubber having a high specific gravity at the position where the thickened portion 8 is provided, instead of increasing the thickness of the sidewall portion, the same effect as the thickened portion can be expected. . Here, the specific gravity of the weight region is preferably at least 1.3 times the specific gravity of the rubber adjacent thereto. Because the transmission rate is suppressed in proportion to the specific gravity of the rubber, the effect is reduced when the ratio is less than 1.3 times.

Here, if a thickened portion or a weight region is provided in the sidewall portion on the tire radial direction inner side of the concave portion, the rubber mass in this region is increased as compared with other portions, so that the tread surface is removed from the road surface. Vibration transmitted through this region can be absorbed in this region, and vibration at the sidewall portion is suppressed, leading to further reduction in tire noise. In order to enjoy the reduction of the tire noise due to the above-described effects, the thickened portion or the weight region must be located inside the concave portion in the tire radial direction, and from the position where the interval between the sidewall portions is maximum, in the tire radial direction. It is preferable to provide the outer side with a distance of 5% or more of the tire section height.

[0020]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Size according to the structure shown in FIGS.
11R22.5 pneumatic radial tires for trucks and buses were prototyped under the specifications shown in Tables 1 and 2, respectively. These tires are mounted on the applicable rim, run at 50 km / h on a drum test machine with a specified load applied after filling the specified internal pressure, and at a position 1.0 m away from the contact surface between the tire and the drum. A microphone was placed, and the sound pressure of the noise from the tire was measured. The measurement results are shown in Tables 1 and 2. In addition, noise was similarly measured for a conventional tire having no recess in the sidewall portion.

[0021]

[Table 1]

[0022]

[Table 2]

Also, the invention tire according to FIG. 1 and the conventional tire are assembled on a rim of 7.5 × 22.5 and filled with an internal pressure of 7.0 kgf / cm ^2. One point at the center was vibrated (input), the output was measured with an accelerometer attached at 1 cm intervals to the sidewall of the tire, and the output at one point at the maximum width of the tire was subjected to FET analysis. Is plotted on the horizontal axis of the frequency, and the magnitude is graphed, as shown in FIG.

Furthermore, the invention tire according to FIG. 6 and the conventional tire were assembled on a 7.5 × 22.5 rim and charged with an internal pressure of 7.0 kgf / cm ^2. FIG. 9 shows the result of vibrating (inputting) one point at the center, measuring the output with an accelerometer attached to the sidewall of the tire at intervals of 1 cm, and calculating the output / input as the transmission rate. . As shown in the figure, it can be seen that the transmissivity in the side wall portion is reduced by 2.9 dB to 3.3 dB.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view in the tread width direction of a tire according to the present invention.

FIG. 2 is a diagram showing a contour of a concave portion in a tire cross section.

FIG. 3 is a diagram showing an opening shape of a concave portion.

FIG. 4 is a diagram showing an opening shape of a concave portion.

FIG. 5 is a diagram showing a contour of a concave portion in a cross section parallel to a tread peripheral surface.

FIG. 6 is a cross-sectional view in the tread width direction of the tire according to the present invention.

FIG. 7 is a cross-sectional view in the tread width direction of a tire according to the present invention.

FIG. 8 is a diagram showing a transmissivity of a sidewall portion.

FIG. 9 is a diagram showing a transmission rate of a sidewall portion.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Bead core 2 Carcass 3 Bead part 4 Side wall 5 Belt 6 Tread 7 Depression 8 Thickened part

Claims (12)

[Claims] 1. A pneumatic system in which a tread is arranged on the surface of a cylindrical crown portion, and a pair of sidewall portions and a pair of bead portions are connected from both ends of the crown portion radially inward. In the tire, between the position where the interval between the sidewall portions is maximum and the tread edge,
A pneumatic tire with low noise, characterized in that a concave portion is provided by recessing the surface of a sidewall portion inside the tire. 2. The concave portion has an arc-shaped contour in a tire cross section and a radius of curvature of 100 mm or less.
A pneumatic tire according to claim 1. 3. The pneumatic tire according to claim 1, wherein the maximum depth of the concave portion is at least 1/10 of the thickness of the sidewall portion. 4. The pneumatic tire according to claim 1, wherein the recess is provided continuously on the same circumference. 5. The pneumatic tire according to claim 4, wherein the concave portions are continuous in a wave shape. 6. The pneumatic tire according to claim 1, wherein the recesses are provided discontinuously on the same circumference. 7. The pneumatic tire according to claim 6, wherein the concave portions are arranged in a staggered manner. 8. The pneumatic tire with low noise according to claim 1, wherein a thickened portion is provided on a sidewall portion inside the recess in the tire radial direction. 9. The tire according to claim 8, wherein the thickened portion is provided at a distance of not less than 5% of a tire cross-sectional height from a position where a distance between sidewall portions is maximum, to a radially outer side of the tire. Pneumatic tire. 10. The pneumatic tire with low noise according to claim 1, wherein a weight region made of rubber having a high specific gravity is provided in a sidewall portion inside the recess in the tire radial direction. 11. The air according to claim 10, wherein the weight region is provided at a distance of 5% or more of the tire cross-sectional height from the position where the interval between the sidewall portions is maximum to the radially outer side of the tire. Containing tires. 12. The rubber according to claim 10, wherein the specific gravity of the rubber in the weight region is at least 1.3 times the specific gravity of the rubber adjacent to the weight region.
2. The pneumatic tire according to 1.