JPH04108004A - Pneumatic tire - Google Patents

Abstract

PURPOSE:To decrease vibration or beat sound caused by periodicity of a pitch arrangement in a harmonic arrangement having a highly resistant ability to partial abrasion by setting an arrangement of land part elements so as to have substantially periodicity of a mirror surface symmetry relating to the equator and/or circumferential grooves of a tire. CONSTITUTION:A tire tread has plural number of circumferential grooves 1a-1d extending along the circumference of the tread and five rows of land parts 2-6 compartmented with both tread edges T, and also the respective land parts consist of a large number of blocks 8a-8e compartmented with the circumferential grooves 1a-1d and lateral grooves 7a-7e connecting together both tread edges E. Assuming that a circumferential length of a block containing one of lateral grooves surrounding two sides of a block is pitch P in the above- mentioned land part, the respective land parts are constituted from the blocks having at least two kinds of pitches P, and also the blocks of the respective land parts are arranged according to a harmonic arrangement. Furthermore, the pitch arrangement of the respective land parts is set so as to have periodicity of a mirror surface symmetry relating to at least a single of the circumferential grooves 1a-1d and/or the equator of the tire.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a pneumatic tire having a tread pattern with low tire noise, especially low pattern noise.

Tire noise is generated by various causes, and among them, so-called pattern noise caused by the tread pattern accounts for a large proportion. This pattern noise is caused by air compressed between the tread contact surface and the road surface that suddenly flows out of the tread contact surface through the tread grooves, and this phenomenon occurs intermittently. Also called pink noise.

(Prior Art) This pattern noise can be reduced by imparting so-called pitch variations to the tread pattern.

For example, Japanese Patent Publication No. 51-41723 discloses introducing pitch variations substantially according to the rules of a sequence of pseudo-random binary signals.

Pattern noise is reduced by the pitch variation of this random arrangement, but in a random arrangement,
For example, the minimum pitch is placed immediately after the maximum pitch, etc.
Since there is a large difference in pitch length between adjacent pitches, this creates a rigidity step on the tread circumference, which is disadvantageous as it becomes the core of uneven wear.

On the other hand, the pitch variation described in JP-A-54-115801 has a pitch arrangement in which the tread is divided into harmonic segments and each segment follows a sine wave.
This is the introduction of a so-called harmonic arrangement.

(Problem to be solved by the invention) This harmonic arrangement reduces the rigidity difference between each pitch, making it possible to avoid uneven wear. However, since the pitch arrangement itself has periodicity, it is possible to avoid this periodicity. Particularly when driving at high speeds, it acts as a uniformity component and causes vibration or beat noise.

In other words, the 22-foti component caused by the harmonic arrangement acts as a source of low-frequency excitation to the vehicle during high-speed driving, similar to uniformity caused by normal manufacturing reasons, and is particularly important for vehicles installed in vehicles that are sensitive to low frequencies. In such cases, it may cause significant vibrations, beat sounds, etc.

Therefore, it is an object of the present invention to propose a pitch variation that can advantageously reduce the vibration or beat sound caused by the periodicity of the pitch arrangement in a harmonic arrangement with high resistance to uneven wear.

(Means for Solving the Problems) The present invention provides a tread that extends between a pair of sidewalls in a toroidal shape, and includes at least one circumferential groove extending along the circumference of the tread, and the circumferential groove and both treads. A pneumatic tire comprising a land section divided at an end, the land section having a plurality of types of land elements having different lengths on the tread circumference arranged harmoniously along the tread circumference, the above land section element. This pneumatic tire is characterized in that the array has periodicity that is substantially mirror-symmetric with respect to the tire's equator and/or the circumferential groove.

Here, the harmonic arrangement refers to land elements arranged so that the lengths of the elements gradually change sinusoidally in the circumferential direction of the land area. The equator of a tire is the circumference passing through the center of the tread in the width direction.

Next, the present invention will be described in detail with reference to the main part of the tread shown in FIG.

The illustrated tread is divided by a plurality of circumferential grooves 1a to 1d extending along the circumference of the tread and both tread ends T.
It has land parts 2 to 6 of the row, and each land part has a circumferential groove Ia-1.
6 and a large number of blocks 8a to 8e partitioned by lateral grooves 7a=7e connecting both tread ends E.

In the above-mentioned land part, if the pitch P is the block circumference including one of the lateral grooves surrounding the two sides of the block as shown in the figure,
Each land section is composed of blocks of at least two types of pitches P, and the blocks in each land section are arranged according to a harmonic arrangement. Let's assume that the land area has three types of pitches: PI, P2. In the case of P3 (pitch length P + < P 2 < P3), for example, the pitches P and P should be arranged in the order of P2 P3 PtPIP2 so that they are not adjacent to each other, that is, the pitch length is gentle. The pitch array changes to follow a sine wave.

Furthermore, it is important that the pitch arrangement in each land portion has mirror-symmetric periodicity with respect to at least one of the circumferential grooves 1a to 1d and/or the equator of the tire.

For example, in order to obtain a pitch arrangement having periodicity that is mirror-symmetric between land portions 2 and 3 that are adjacent to each other with the circumferential groove 1a in between,
Pitch arrangement j of land section 2 or P2P3 P2 described above
If the order is PI P2, the pitch arrangement of the land portion 3 is in the order P2 PI P2 P3 P2.

(Function) By making the pitch arrangement in the land area divided by the circumferential groove and the tread edge of the tread follow a harmonic arrangement, the rigidity difference in the land area that is a problem with irregular pitch is reduced, and uneven wear resistance is improved. You can try to improve it.

When configuring a tread pattern according to this harmonic arrangement, it is customary to make the periodicity of the pitch arrangement in each land part circular, as shown in Figure 2 (a), where the pitch change is approximated to a wave shape. be. Therefore, since the phase of each land area is the same, the periodicity of the harmonic arrangement itself of each land area is emphasized,
The same figure (as shown in b+, pattern noise N in the high frequency range
Low frequency components such as vibrations and beat sounds that appear in a lower frequency range are amplified.

Therefore, as shown in FIG. 3+a+, the present invention provides periodicity of mirror symmetry with respect to at least one of the circumferential grooves and/or the equator of the tire to the pitch arrangement of the land portion.
By canceling the periodicity of the harmonic array described above,
), we achieved a reduction in low frequency components.

(Example) According to the tread pattern shown in FIG. 1, three types of pneumatic radial tires (tires I, ■, and ■) with a tire size of 185/60R14 were manufactured. The circumferential groove of these prototype tires is 8 m wide and 9 mm deep, with a near depth of 4 m.
m lateral grooves were arranged in the circumferential direction of the tread as follows.

The land portions 2 to 6 in the tread pattern of each trial tire were arranged in pitch according to the harmonic arrangement shown below. The numbers in the array indicate the pitch length, each 1:
25.6mm, 2:32.9mm and 3:4
0.2 mm (pitch ratio 7:9:11).

A:2222223332222111112222
2333332222111112222233333
221111111B:2111111122222
2333222211111222223333322
221111122222333332C:22222
2111112222333222221111111
1222233322222111111122333
3 [Tire ■] Land parts 2, 4, 6: Harmonic arrangement A Land parts 3, 5: Harmonic arrangement B [Tire ■] Land parts 2, 4, 6: Harmonic arrangement A Land parts 3, 5: Harmonic arrangement C [ Tire ■] Land Department 2. 3. 4. 5. 6: Harmonic Arrangement A For each of the above tires, an actual vehicle filling test was conducted under the following conditions.

Rim: 5!4 JJX14 Internal pressure: 2. Okgf/cm'' Vehicle: 180Occ Road surface: Good road speed: 80 to 120 km/h The evaluation was based on sensory evaluation, and the score was the average value of the scores of two panelists.

Note: ($1) Not noticeable at all (*2) Not noticeable at all (book 3) Slightly noticeable (effects of the invention) According to this invention, pattern noise is low and uneven wear resistance is achieved. It is possible to reduce the low frequency components in the high harmonic array of the pneumatic tire, and it is possible to provide a pneumatic tire with extremely low tire noise including vibration and beat noise.

[Brief explanation of the drawing]

Fig. 1 is a developed view of the main part of the tread of a pneumatic radial tire according to the present invention, Fig. 2 (al is a schematic diagram showing changes in pitch length,
b) is a graph showing the measurement results of noise in the pitch arrangement of Fig. 3 (a), Fig. 3 ta+ is a schematic diagram showing the change in pitch length, Fig. 3 (
b) is a graph showing the measurement results of noise in the pitch arrangement of FIG. 1a-1d... Circumferential groove 2-6... Land portion 7
a~7e...Horizontal groove 8a~8e...Block E...Tread end P...Pitch P
−−−−Pi, + Fig. 2 Zhou Shij (Sentence (Hz)) Fig. 3 Zhou 7 Reverberation Large (Hz)

Claims (1)

[Scope of Claims] 1. A tread extending in a toroidal shape between a pair of sidewalls, at least one circumferential groove extending along the circumference of the tread, and defined by the circumferential groove and both tread ends. In a pneumatic tire, the land portion has a plurality of types of land elements having different lengths on the tread circumference and arranged harmoniously along the tread circumference. A pneumatic tire characterized by having periodicity that is substantially mirror-symmetrical with respect to the equator and/or the circumferential groove.