JPH0732819A - Pneumatic tire - Google Patents

Abstract

PURPOSE:To make compatible the wetness characteristic and the low-noise characteristic which are in antinomy relation to each other as far as the tread pattern is concerned, by forming main grooves in the tread of a pneumatic tire that circumferentially extend and by forming fine grooves in the side walls of the main grooves that extend along the main grooves. CONSTITUTION:A plurality of main grooves (straight grooves) 1 are formed in the pneumatic tire in such a manner as to extend circumferentially of a tread T. Further, fine grooves 2 are formed in the side wall of each main groove 1 in such a manner as to extend along the main groove 1. Columnar tube resonance vibrations which during the travel of the pneumatic tire occur due to the vibrations of the tread portion T caused by uneveness of the road surface are suppressed by the fine grooves 2. Further, simultaneously, the vibrations caused at the groove bottom 3 of each main groove 1 are also suppressed. Furthermore, the wetness characteristic (water expellency) as veiwed from each main groove 1 is also improved. As a result of the pattern noise in the pneumatic tire is decreased.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pneumatic tire having a main groove extending substantially in the circumferential direction on a tread designed to reduce noise generated during running, so-called pattern noise.

[0002]

2. Description of the Related Art As one of the main functions of a pattern that has been conventionally applied to a tire tread, it is important to ensure drainage while the tire is running on a wet road surface. Various tread patterns have been developed in consideration of the appearance. A typical example is a recent straight groove, that is, a tread pattern having a groove extending substantially in the circumferential direction on a tread.

[0003]

However, the presence of the grooves extending substantially in the circumferential direction in such a tread improves the drainage property from the tread surface, and as a result, the wettability is remarkably improved, while the ground contact surface is improved. An air column tube formed by the wall surface of the groove extending substantially in the circumferential direction on the road surface and the tread is formed in the surface, and when the tread is vibrated by the road surface irregularities, resonance occurs in this air column tube, which causes tire noise. It becomes a big factor. This air columnar resonance sound is proportional to the volume of the groove extending substantially in the circumferential direction on the tread, and as the volume increases, the air columnar resonance sound level also increases. On the contrary, since the wettability is improved by increasing the volume of the groove, there is a problem how to reduce the noise without reducing the groove volume as much as possible. The present invention was created in order to solve the above problems, and an object thereof is to provide a pneumatic tire having a tread pattern that can achieve both anti-wetting property and low noise property. And

[0004]

To achieve the above object, in the pneumatic tire of the present invention, a main groove extending substantially in the circumferential direction is arranged on the tread, and the main groove is formed on the groove wall of the main groove. An arrangement of substantially continuous slots extending along the same is provided. When the width w and the depth h are the substantially continuous narrow grooves extending along the main groove on the groove wall of the main groove, the narrow groove width is: 0.05 × H ≦ w ≦ 0.5 × H (H: main groove Depth) (1) Fine groove depth: 0.05 × W ≦ h ≦ 0.3 × W (W: rib width) (2) In addition, when a plurality of narrow grooves are placed on one groove side surface, the total value of the narrow groove widths is (1)
It is desirable to be in the range of.

[0005]

In the pneumatic tire, the air columnar resonance noise caused by the main groove extending substantially circumferentially in the tread, that is, the straight groove is remarkably generated in the vicinity of 700 Hz to 1200 Hz. Further, when the tire noise of a tire having such straight grooves is measured on two types of road surfaces having different roughnesses of road surface irregularities, as shown in FIG. 1, the noise level of the rough road surface is higher in the frequency region of the air column resonance noise. Is large. It is considered that the tread vibration was excited by the road surface unevenness input and the air column resonance tube was generated. In addition, when measuring the vibration in the straight groove surface when rolling the tire on this rough road surface, it was found that the vibration was particularly large at the groove bottom surface, and to reduce the air column resonance tube, this groove bottom vibration was reduced. Is effective. Here, when the method for reducing the groove bottom vibration was earnestly studied, it is effective to reduce the compression rigidity in the vicinity of the straight groove, and the groove wall of the main groove extending substantially circumferentially in the tread extends along the main groove. It was confirmed that the vibration of the groove bottom was reduced and the noise level was lowered by adding a substantially continuous narrow groove. This effect is less effective when the fine groove width w is smaller than 0.05 × H (H is the depth of the main groove) or when the fine groove depth h is smaller than 0.05 × w (w is the rib width). Become. It was also found that the durability of the rib portion is significantly impaired when w is larger than 0.50 × H or when h is larger than 0.3 × w.

[0006]

Embodiments will be described below with reference to the drawings. FIG. 1 is a diagram showing a comparison of sound pressure levels due to differences in road surface unevenness with respect to bench tire noise. FIG. 2 is a diagram showing a main part of the first embodiment of the present invention. FIG. 3 is a diagram showing a main part of a second embodiment of the present invention. FIG. 4 is a diagram showing the results of the tire noise spectrum on the bench. FIG. 2 shows Example 1 of a tire having two main grooves (straight grooves) extending in the circumferential direction of the tread T, in which a groove 2 along the main groove 1 is formed on the groove wall of the main groove 1.
The air columnar resonance noise generated by the vibration of the tread portion T being excited by the road surface unevenness input during traveling by the groove 2 is reduced, and the vibration of the groove bottom 3 of the main groove 1 during tire rolling is reduced. Is suppressed. Fine groove depth h in that case
= 4 mm, fine groove depth w = 2 mm, main groove depth H = 9 mm, maximum width B = 12 mm, distance W = 30 mm between main grooves. Example 2 is shown in FIG. 3. Of the two main grooves 1 and 1, one is provided with fine grooves 2 ₁ and 2 ₂ vertically in two steps, and the other is provided with a slightly larger groove 2. The sidewall is provided in the circumferential direction. These grooves 2 may be provided substantially continuously. Next, Example 1 shown in FIG. 2 and a conventional example having no groove 2 on the groove wall were applied to a tire having a tire size of 225 / 50R16 to perform a single bench test, and noise was measured with a bench noise measurement drum. The wettability was evaluated by running straight on a water pool with a water depth of 10 mm by running an actual vehicle and measuring the minimum speed at which hydroplaning occurs. The results are shown below.

[0007] From the above results, as can be seen from FIG. 4, frequency 1000H
It was found that the sound pressure level at z was reduced by 1.0 dB.

[0008]

Since the present invention is configured as described above in detail, the main groove extending substantially in the circumferential direction is arranged on the tread, while the groove wall of the main groove extends substantially continuously along the main groove. By arranging the narrow grooves, drainage from the main groove of the tread during traveling is improved, and air columnar resonance noise generated by the vibration of the tread portion T excited by the road surface unevenness input is reduced, and the tire rolling Since the vibration of the groove bottom 3 of the main groove 1 during the movement is also suppressed, the effect such as contributing to the reduction of the tire pattern noise as a whole is exhibited.

[Brief description of drawings]

FIG. 1 is a diagram showing a comparison in sound pressure level due to a difference in road surface unevenness with respect to bench tire noise.

FIG. 2 is a diagram showing a main part of the first embodiment of the present invention.

FIG. 3 is a diagram showing a main part of a second embodiment of the present invention.

FIG. 4 is a diagram showing a result of a tire noise spectrum on a bench.

[Explanation of symbols]

1 main groove 2 narrow groove 2 ₁ narrow groove 2 ₂ narrow groove 3 groove bottom T tread

Claims (1)

[Claims] 1. A pneumatic tire characterized in that a main groove extending substantially circumferentially is arranged on a tread, and a substantially continuous narrow groove extending along the main groove is arranged on a groove wall of the main groove.