JP2000085317A - Pneumatic tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To favorably reduce vibration or a beat noise caused by periodicity of pitch arrangement in harmonic arrangement of high uneven abrasion resistance. SOLUTION: Periodicity of substantial mirror symmetry relating to the equator of a tire and/or a circumferential groove is imparted to arrangement for flat elements, in a pneumatic tire in which at least one circumferential groove 1a-1d extended along a tread circumference, and flat parts 2-6 divided by the circumferential groove and both tread ends are provided in treads arranged successively toroidal-likely astride a pair of side walls and in which the flat parts are constituted by harmonic-arranging plural kinds of flat part elements different in lengths on the tread circumference along the tread circumference.

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 tread pattern with low tire noise, especially low pattern noise.

[0002] Tire noise is generated by various causes,
Above all, the ratio of so-called pattern noise caused by the tread pattern is large. This pattern noise is
The air compressed between the tread contact surface and the road surface suddenly flows out of the tread contact surface through the groove of the tread,
This noise occurs because this phenomenon occurs intermittently, and is also called pumping noise.

[0003]

2. Description of the Related Art This pattern noise can be reduced by giving a so-called pitch variation to a tread pattern. For example, Japanese Patent Publication No. 51-41723 discloses that a pitch variation is introduced substantially according to the rules of a pseudo-random binary signal sequence.

[0004] Although pattern noise is reduced by the pitch variation of the random arrangement, the difference in pitch length between adjacent pitches is large in the random arrangement, for example, the minimum pitch is arranged immediately after the maximum pitch. Therefore, there is a disadvantage that a rigid step is formed on the circumference of the tread, and this becomes a core of uneven wear.

On the other hand, a pitch variation described in Japanese Patent Application Laid-Open No. 54-115801 is one in which a tread is divided into harmonic segments, and a pitch arrangement in which each segment follows a sine wave, a so-called harmonic arrangement, is introduced. .

[0006]

The harmonic arrangement reduces the rigidity step between the pitches and can prevent uneven wear. However, since the pitch arrangement itself has a periodicity, the periodicity is reduced. In particular, it acts as a uniformity component during high-speed running, causing vibration or beat sound.

That is, the uniformity component caused by the harmonic arrangement acts as a low-frequency excitation source for the vehicle during high-speed running, and is mounted on a vehicle particularly sensitive to the low-frequency range, similarly to the uniformity caused by normal manufacturing reasons. If
It may cause significant vibration and beat sound.

Accordingly, an object of the present invention is to propose a pitch variation which can advantageously achieve a reduction in vibration or beat sound due to the periodicity of the pitch arrangement in a harmonic arrangement having high resistance to uneven wear.

[0009]

According to the present invention, at least one circumferential groove extending along the circumference of the tread, the circumferential groove and both treads are provided on a tread continuous in a toroidal manner between a pair of sidewalls. A pneumatic tire in which a plurality of types of land elements having different lengths on the tread circumference are arranged in harmony along the tread circumference. Is a pneumatic tire characterized in that it has a substantially mirror-symmetric periodicity with respect to the equator of the tire and / or the circumferential groove.

Here, the harmonic arrangement refers to an arrangement in which land elements are arranged such that the lengths of the elements gradually change in a sinusoidal manner in the circumferential direction of the land. The equator of the tire is the circumference passing through the center in the width direction of the tread.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, the present invention will be described in detail with reference to the essential parts of the tread shown in FIG. The illustrated tread has a plurality of circumferential grooves 1a to 1d extending along the circumference of the tread and five rows of land portions 2 to 6 defined by both tread ends E. Further, each land portion has a circumferential groove 1a to It comprises a large number of blocks 8a to 8e partitioned by 1d and lateral grooves 7a to 7e connecting both tread ends E.

In the above-mentioned land portion, assuming that the block circumference including one of the lateral grooves surrounding two sides of the block is a pitch P as shown in the figure, each land portion is composed of at least two types of blocks having a pitch P. The blocks on land are arranged according to a harmonic arrangement. If the pitch P ₁ of the three land portions, P _2, P ₃
When configuring a: (pitch length _{P 1 <P 2 <P 3} ) , for example P2 -P3 -P2 -P1 -P2 ── order in such a pitch sequence that does not Tonariawa and the pitch P1 and P3 of That is, the pitch arrangement is such that the pitch length gradually changes so as to follow a sine wave.

[0013] Further, the pitch arrangement in each land portion is based on a circumferential groove.
It is important to have a mirror-symmetric periodicity with respect to at least one of 1a to 1d and / or the equator of the tire. That is, when the pitch change of each land portion is approximated to a waveform as shown in FIG. 3A described later, the waveform according to the pitch arrangement of each land portion has a line-symmetric relationship between adjacent land portions. It is important to add the periodicity to the pitch arrangement of each land part.

For example, as shown in FIG. 3 (a) described later, a pitch arrangement having a mirror-symmetrical periodicity between land portions 2 and 3 adjacent to each other with the circumferential groove 1a interposed therebetween is provided. , The pitch arrangement of the land portion 2 is P2-P3-P2-P1-P2.
, The pitch arrangement of the land 3 is P2-P1-P2
−P3 −P2}.

[0015] By arranging the pitch arrangement in the land section defined by the circumferential groove of the tread and the tread edge in accordance with the harmonic arrangement, the rigidity step in the land section, which is a problem with irregular pitch, is reduced, and the uneven wear resistance is reduced. Can be improved.

When a tread pattern is formed in accordance with this harmonic arrangement, it is customary to make the pitch arrangement periodic in each land portion the same, as shown in FIG. . Accordingly, since the phase of each land portion is the same, the periodicity of the harmonic arrangement itself in each land portion is emphasized, and vibrations appearing in a frequency range lower than the pattern noise N in the high frequency range as shown in FIG. A low frequency component T such as a beat sound is amplified.

Accordingly, the present invention provides a pitch arrangement of land portions with a substantially mirror-symmetric (line-symmetric) periodicity with respect to at least one circumferential groove and / or the equator of the tire, as shown in FIG. 3a. As a result, the phases of the adjacent land portions are shifted from each other to cancel the periodicity of the above-described harmonic arrangement, and the low-frequency component T is reduced as shown in FIG.

[0018]

EXAMPLES Three types of pneumatic radial tires (tires, II and III) having a tire size of 185 / 60R14 were produced according to the tread pattern shown in FIG. The circumferential grooves of these prototype tires had a width of 8 mm and a depth of 9 mm, and lateral grooves having a depth of 7.4 mm were arranged according to the set pitch.

The land portions 2 to 6 in the tread pattern of each prototype tire have a pitch arrangement according to the following harmonic arrangement. Note that the numbers representing the arrangement indicate the pitch length,
They are 1: 25.6 mm, 2: 32.9 mm and 3: 40.2 mm, respectively (pitch ratio 7: 9: 11). A: 22222233322221111122222333332222111112222233333221111111 B: 21111111222222333222211111222223333322221111122222333332 C: 22222211111222233322222111111112222333222221111111223333

[Tire I] Land portions 2, 4, 6: Harmonic array A Land portions 3, 5: Harmonic array B

[Tire II] Land parts 2, 4, 6: Harmonic arrangement A Land parts 3, 5: Harmonic arrangement C

[Tire III] Land portions 2, 3, 4, 5, and 6: Harmonic arrangement A For each of the above tires, an actual vehicle feeling test was performed under the following conditions.

Rim: 5 1 / 2-JJ × 14 Internal pressure: 2.0 kgf / cm ² Vehicle: 1800 cc vehicle Road surface: good road Speed: 80-120 km / h

The evaluation was performed according to a sensory evaluation, and the average score of the two panelists was used. Table 1 shows the evaluation results.

[0025]

[Table 1]

[0026]

According to the present invention, it is possible to reduce low frequency components in a harmonic arrangement having low pattern noise and high uneven wear resistance, and to provide a pneumatic tire having extremely low tire noise including vibration and beat sound. Can be provided.

[Brief description of the drawings]

FIG. 1 is a development view of a main part of a tread of a pneumatic radial tire according to the present invention.

FIG. 2 (a) is a schematic diagram showing a change in pitch length,
FIG. 6B is a graph showing the measurement results of noise in the pitch arrangement of FIG.

FIG. 3A is a schematic diagram showing a change in pitch length,
FIG. 6B is a graph showing the measurement results of noise in the pitch arrangement of FIG.

[Description of Signs] 1a-1d Circumferential groove 2-6 Land part 7a-7e Horizontal groove 8a-8e Block E Tread end P Pitch

Claims (3)

[Claims] 1. A tread continuous in a toroidal shape extending between a pair of sidewalls, at least one circumferential groove extending along the circumference of the tread, and a land portion defined by the circumferential groove and both ends of the tread. In a pneumatic tire in which a plurality of land elements having different lengths on the tread circumference are arranged in harmony along the tread circumference, the arrangement of the land elements is substantially related to the equator of the tire. A pneumatic tire having upper mirror symmetry periodicity. 2. A tread continuous in a toroidal shape extending between a pair of sidewalls, at least one circumferential groove extending along the circumference of the tread, and a land portion defined by the circumferential groove and both ends of the tread. In a pneumatic tire in which a plurality of types of land elements having different lengths on the tread circumference are arranged in harmony along the tread circumference, the land elements are arranged substantially in relation to the circumferential groove. A pneumatic tire having upper mirror symmetry periodicity. 3. A tread continuous in a toroidal shape over a pair of sidewalls, at least one circumferential groove extending along the circumference of the tread, and a land portion defined by the circumferential groove and both tread ends. In a pneumatic tire in which a plurality of land elements having different lengths on the tread circumference are arranged in harmony along the tread circumference, the land elements are arranged at the equator of the tire and the land. A pneumatic tire having substantially periodic mirror symmetry with respect to a circumferential groove.