JPH02234809A - Peumatic tire - Google Patents

Abstract

PURPOSE:To reduce pattern noise by forming tread pattern over one turn of tread surface at many pitches having different lengths circumferentially, and specifying the pitch ratio of the longest pitch length to the shortest. CONSTITUTION:In a pitch as minimum unit to form tread pattern of a tire, one turn of tread surface is formed from at least three sorts of pitches having different length circumferentially. The pitch ratio alpha of the longest pitch length Pmax to the shortest pitch length Pmin shall be set to 1.40-1.52. When the extent from any shortest pitch till one before the first shortest pitch in the next period is assumed as fundamental period, the total number of fundamental period in one turn around the tire shall be set to 6 or more. Further, the period length ratio beta of the largest period length Tmax to the smallest period length Tmin shall be set to 1.1 or less.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a pneumatic tire having a tresode pattern that reduces noise (pattern noise) generated due to tire transfer.

[Conventional technology]

Conventionally, as a method to reduce tire pattern noise, the length of the pitch, which is the smallest unit that makes up a trend pattern, is divided into several different sizes, and these pitches are arranged appropriately on the same side of the trend surface. This is done by dispersing the sound frequencies and dispersing the peaks of the sound pressure level. In other words, a pitch variation method is generally used in which the peak of harmonics (Harmonies) whose primary order is the total number of pitches within one tire circumference is dispersed by frequency modulation and turned into white noise (for example, "Automotive Technology J. Vol.28, k2.
1974, USP 4,474,223, USP
4,327,792).

However, although this pitch variation method is effective for alleviating the first-order peak among harmonics that are an integral multiple of the total number of pitches in one tire rotation,
Pattern noise has not yet been sufficiently reduced. Here, harmonics refers to the number of times vibrations occur per rotation of the tire. For example, if the total number of pitches in one rotation of the tire is 64, vibrations occur 64 times.

[Problem to be solved by the invention]

The present invention has been made in view of the above circumstances, and consists of dispersing the peak of the sound pressure level by appropriately arranging several pitches around the circumference of the tread surface, as in the pitch variation method. Rather than increasing the degree of harmonics, conversely, the peak of the sound pressure level is concentrated in a certain harmonic to reduce the sharpness of the peak, and when viewed over a wide area, the harmonics near the first harmonic and its integer harmonics are The purpose of the present invention is to provide a tread pattern that reduces pattern noise and improves the comfort and comfort of an automobile by devising ways to disperse the peaks of

[Means for Solving the Problems] Therefore, in the pneumatic tire of the present invention, one circumference of the tire tread surface is made up of at least three pitches having different circumferential lengths, and the pitch length P sin of the shortest pitch is Pitch ratio α(P
．． ．． ．． /P,. in) from 1.40 to 1.52,
Starting from the shortest pitch, 1 of the shortest pitch at the beginning of the next period
If the basic period is up to the pitch before tire 1,
The total number of basic periods in the cycle is 6 or more, and the maximum period length T s m with respect to the minimum period length T ah i n
The tread pattern has a period length ratio β (T..X/T.in) of 1.1 or less.

This means will be explained in detail below.

In the present invention, at least three types of pitches having different circumferential lengths constitute one circumference of the tire tread surface. More preferably, it is composed of four to five types of pitches. If there are two or less types of pitches, the effect of pitch variation cannot be sufficiently obtained, and there is a problem that a clear difference from the case where all pitches are the same length cannot be recognized.

In addition, in the present invention, the pitch length P +hi++ of the shortest pitch among the at least three types of pitches described above is compared to the pitch length P +hi++. The pitch length of the longest pitch P. ■ Pisochi ratio α (Pmax/Pmi
n) is set to 1.40 to 1.52.

If the pitch ratio α is smaller than 1.40, the peak of the sound pressure level will concentrate too much on a specific harmonic, as shown in Figure 1 (A), and pattern noise will not be reduced (Figure 1). In (A), the peak of the sound pressure level is concentrated at the harmonics 64). Also, the pitch ratio α is 1.5
If it is larger than 2, the pitch length P,■ and the bisochi length P Bin
If the difference becomes too large, uneven wear on the torso surface is likely to occur.

Furthermore, in the present invention, when the basic period starts from the shortest pitch and ends at the pitch one pitch before the shortest pitch at the beginning of the next cycle, the total number of basic periods in one tire rotation is 6.
In addition to the above, the period length ratio β (T-x/T-i
,,) is 181 or less. Here, the fundamental period is, in other words, when there are multiple shortest pitches lined up, from the first shortest pitch in that group to the pitch one step before the shortest pitch that appears first after passing through that group. This is the pitch group of . In this fundamental period, when the waveform of the frequency generated by each pitch is expanded into a Fourier series, the first-order component becomes dominant.

In the present invention, the total number n of fundamental periods is 6 or more, preferably 7 to 9. When n is smaller than 6, Fig. 1 (
This is because, as shown in B), the peak of the sound pressure level cannot be concentrated on a specific harmonic.

In addition, if the period length ratio β is larger than 1.1, as shown in Fig. 1 (C
), the peak of the sound pressure level cannot be similarly concentrated on a specific harmonic. In this way, in the present invention, one circumference of the tire tread surface is made up of at least three types of pitches having different circumferential lengths, the pitch ratio α is set to 1.40 to 1.52, and the total number of basic periods is set to 6 or more. Furthermore, since the period length ratio β is set to 1.1 or less, the peak of the sound pressure level concentrates on a specific harmonic, as shown in Figure 2 (A), and the sharpness of the peak is reduced (Figure 2 (A)). In (A), the peak of the sound pressure level is concentrated at the harmonics 57). On the other hand, in the conventional tread pattern based on the pitch variation method, as shown in Fig. 2 (B
), the sound pressure level peaks are dispersed over a wide range over various harmonics. Therefore, when frequency analysis is performed on the measurement results of noise generated by the tread pattern of the present invention, as shown in FIG. 3(A), the sharpness of the peak of the frequency component corresponding to the first order is reduced, and In the order components, the peaks are finely dispersed, and the sharpness of the peaks is alleviated as a whole. Therefore, pattern noise is reduced. On the other hand, when frequency analysis is performed on the noise measurement results of a conventional tread pattern using the pitch variation method, as shown in Figure 3 (B), although the first-order component increases to some extent, it does not spread over all orders. The sharpness of the peak is not sufficiently reduced. Furthermore, when frequency analysis is performed on the noise measurement results using a trend pattern in which the pitches are arranged at regular intervals, the sound pressure level peaks are sharp across all orders, as shown in Figure 3 (C). You will have to concentrate.

Examples are shown below.

〔Example〕

The following (Cl evaluation method) was used to evaluate the noise (pattern noise), maneuverability, stability,
Ride comfort was evaluated.

The specifications of the above two types of test tires are size;
Using 95/65 R15, each trend pattern was produced by regrouping straight grooves having a width of 4 mm and a depth of 8 mm perpendicular to the circumferential direction as shown in (a) and (b) below.

(a1 1 period of the present invention trend pattern (248.5 mn+): EDCBABCD bisochi length: A -37.4 mm, B = 35.3 m
m, C=30.8 mm, D=26.8
mm, E = 25.3mh+ (5 types) Full circumference: 1 period x 8 (Number of basic periods: 8) Total number of pitches:
64 Pitch ratio α: 1.48 Period length ratio β: 1.00 (b) Comparison tresode pattern 1 period (372.9 mm): CCCBBBAAAB
BB 2 cycles (621.51): CCCCCBBBBBAAA
AABBBBBB 3 cycles (994.4 mm): CCCCCCCCBB
BBBBBBAAAA AAAABBBBB BB Pitch length: A = 37.4 mm, B = 30.8
mm. ．． C=25.3 mm (3 types) Total circumference = 1 period x 1 + 2 periods x 1 + 3 periods x 1 (Number of basic periods: 3) Total number of pitches: 64 Pitch ratio α: 1.48 Period length ratio β: 994. 4/372.9・2.67(C
)Evaluation Method ■Measurement of Indoor Single Noise According to JIS Z8731, tires were run on a rotating drum in an anechoic chamber, and the generated noise was measured using a microphone.

■Evaluation by actual vehicle sensory test
When installed on a 00 cc class sedan), it improves noise, maneuverability, stability, and ride comfort when driving on smooth general roads.
Evaluated by feeling by several trained evaluators,
By taking the average value.

The measurement results show that for indoor single noise, the speed is 100.
At km/h, the noise of the tire of the present invention is 88.3 dB.
(A), and the noise of the comparison tire is 88.4 dB (A).
Met. In addition, the results of the actual vehicle sensory tests are shown in Table 1 for noise, and Table 2 for maneuverability, stability, and ride comfort.
In the table, the comparison tire is set as 100, and each index is displayed. The larger the number, the better.

(Left space below this page) Table 2 As is clear from these results, according to the present invention, pattern noise can be sufficiently reduced without reducing maneuverability, stability, and ride comfort. .

〔Effect of the invention〕

As explained above, according to the present invention, the pitch type, pitch ratio, number of fundamental periods, and period length ratio constituting the tresodo pattern are defined, and the peak of the sound pressure level is concentrated on a specific harmonic. 4. Since the sharpness of one mark is relaxed, pattern noise can be reduced.

[Brief explanation of drawings]

Figure 1 (A) is a diagram of the relationship between the sound pressure level and harmonics when the pitch ratio α<1.40, and Figure 1 (B) is the number of cycles n.
Figure 1 (C) is a diagram of the relationship between the sound pressure level and harmonics when the period length ratio β is <6. Figure 2 (A) is the diagram of the relationship between the sound pressure level and harmonics when the period length ratio β is 1.1. An explanatory diagram showing how sound pressure level peaks are concentrated at specific harmonics in the tread pattern of the present invention. FIG. Figure 3 (A) is an explanatory diagram showing the frequency analysis of the measurement results of the noise generated by the tread pattern of the present invention, and Figure 3 (B) is the conventional method using the pitch variation method. Figure 3 (C) is an explanatory diagram showing a frequency analysis of noise measurement results with a tread pattern of 2. Figure 3 (C) is a frequency analysis of noise measurement results with a conventional tread pattern with pitches arranged at equal intervals. FIG. Agent Patent Attorney Shinichi Ogawa

Claims (1)

[Claims] At least three types of pitches with different circumferential lengths constitute one circumference of the tire tread surface, and the pitch length of the shortest pitch P_
Pitch length P_m_a_ of the longest pitch for m_i_n
If the pitch ratio α (P_m_a_x/P_m_i_n) of The total number of basic periods in the cycle is 6 or more, and the period length ratio β (T_m_
A pneumatic tire having a tread pattern in which a_x/T_m_i_n) is 1.1 or less.