JP2796241B2 - Pneumatic tire - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a tire noise reduction of 1 / f
The present invention relates to a pneumatic tire that can impart characteristics close to the fluctuation characteristics of the tire and can reduce noise discomfort.

[0002]

2. Description of the Related Art Generally, a tread pattern formed on a tread surface of a tire is formed by continuously repeating a pattern element as a pattern constituent unit in a tire circumferential direction. Therefore, at the time of rolling the tire, the compression / release of the air in the groove and the impact sound with the road surface are periodically generated for each of the pattern elements or for each of the plurality of pattern elements,
Pattern noise is generated by the pulse-like vibration.

Conventionally, in order to reduce the pattern noise, a plurality of types of pattern elements having different pitch lengths in the circumferential direction are used, and a pattern variation method of dispersing the pattern noise itself into a wide frequency band to produce white noise is used. Has been widely adopted.

[0004]

However, in the conventional pitch variation method for producing white noise, although the maximum sound pressure is reduced and the pitch sound is hardly perceived, the sound is heard as an artificial noise. It will cause discomfort.

[0005] Accordingly, the present inventor has studied to reduce this discomfort. As a result, by providing the noise with a fluctuation characteristic in which the sound pressure fluctuates depending on the value of the frequency, the noise can be made closer to a natural sound and the discomfort can be reduced. It has been found that it is preferable to use an intensity close to 1 / f, which is the reciprocal of the frequency f, that is, the amplitude.

That is, an object of the present invention is to provide a pneumatic tire capable of giving a fluctuation characteristic close to 1 / f to the suppression of amplitude by a pattern element and reducing noise discomfort.

[0007]

In order to achieve the above object, a pneumatic tire according to the present invention is a pneumatic tire having a tread pattern in which n pattern elements constituting a pattern constituting unit are arranged on a tread surface in a tire circumferential direction. A row of the pattern elements arranged in the tire circumferential direction, each pattern element being a unit pulse and one pattern element as a starting point, in the order of the arrangement, and the circumferential length of each pattern element. Is replaced by a pulse train separated in the circumferential direction, and this pulse train is expanded into a Fourier series. The following formula (3) can be calculated from the Fourier coefficients of the following formulas (1) and (2). ) Based on a Fourier series of 1 to n / 2
The next [(n is an odd number, 1 to (n-1) / 2]] amplitude A
k is the following equation (4) based on the third-order amplitude A3:
A pneumatic tire that satisfies Expression (5).

[0008]

(Equation 4)

[0009]

(Equation 5)

[0010]

(Equation 6)

Formula (4): A1 / A3 ≦ 0.5, A
2 / A3 ≦ 0.5 Equation (5) When 4 ≦ k 2.5 / k ≦ Ak / A3
≤ 3.5 / k In the equation, C is the tire circumference, k is the order, and xi is the position of the pulse in the pulse train.

[0012]

[Function] "1 / f fluctuation" is, for example, when a heartbeat cycle is quantitatively examined from an electrocardiogram recorded in a resting state, it is observed that each heartbeat cycle fluctuates, albeit minutely. The power spectrum of this fluctuation is substantially proportional to the reciprocal 1 / f of the frequency f, and such a fluctuation is called 1 / f fluctuation. Body is 1 / f in various parts other than heartbeat
It is known that although having fluctuation, a human feels comfort when the body receives a stimulus having 1 / f fluctuation. Therefore, by giving the noise a fluctuation characteristic close to the noise, unpleasant discomfort can be reduced and the sound can be modulated to a comfortable sound.

First, the frequency f (unit Hz) of the pitch sound generated from each pattern element is determined by the peripheral speed V of the tire.
(Unit: mm / sec) and pitch length Li of the pattern element
(Unit: mm), f = V / Li. In order to prevent harsh sound, the intensity of the sound to be generated is determined by a power element having a magnitude corresponding to the reciprocal 1 / f of the frequency,
That is, it is preferable to use the amplitude.

For this purpose, as described above, the sequence of the pattern elements is replaced with a pulse train of a unit pulse, and this pulse train is expanded into a Fourier series. In the amplitude Ak of the equation (3) obtained from the coefficient, the condition of the equation (5) is satisfied at the fourth or higher frequency.

The ratios A1 / A3 and A2 / A3 of the first- and second-order amplitudes A1 and A2 to the third-order amplitude A3 are set to 0.5 or less, and the frequencies are 1 and 2 more than those of the third-order frequencies. The amplitude Ak of the following is set to be small. However, this means that when increasing the amplitude Ak of the primary and secondary frequencies rather than the 1 / f fluctuation effect, the RFV (radial force fluctuation) is increased and the vibration is increased. It becomes easy to be heard, and the fluctuation period of the sound becomes long, so that it can be heard as an unpleasant pulsating sound rather than a fluctuation sound. It is intended to prevent this. Preferably, the ratio A1
/ A3 and A2 / A3 are set to 0.

In the case of fourth or higher order, 2.5 /
Although it is set to be not less than k and not more than 3.5 / k, if it is less than 2.5, the noise of the low-order part becomes too large (large) as compared with the others, so that the low-order part (particularly the third-order, then the fourth-order...) This is because the noise of the part is felt loud. Further, the reason why the ratio is set to 3.5 / k or less is to prevent the degree of noise reduction from becoming too small as the order becomes higher, and to effectively exhibit 1 / f fluctuation.

In general, the sound generated by n pattern elements has a frequency in the vicinity of n × the tire rotation speed (per second), and depends on the pattern element and the speed. Become. According to the present invention, by appropriately selecting the amplitude Ak, a fluctuation or fluctuation corresponding to 1 / f fluctuation can be given to the audible sound, and the unpleasant sound can be reduced.

[0018]

An embodiment of the present invention will be described below with reference to the drawings. In FIG. 1, which shows a part of the tread surface developed, a pneumatic tire 1 is attached to a tread portion 2 in this example.
For example, four vertical grooves 3 extending in the circumferential direction of the tire and a horizontal groove 5 extending in a direction intersecting with the vertical grooves 3 are provided.
The lateral groove 5 forms a tread pattern of a block type, a block rib type, a rib / lug type, or the like.

Further, the tread pattern is formed by arranging n pattern elements Ei constituting the pattern constituent units in the circumferential direction of the tire. In this example, the tread pattern is formed by the rib RA passing on the tire equator and the rib RA on the outside thereof. A block rib type having four block rows RB in which the blocks B are spaced.

In the present embodiment, the pattern element Ei is constituted by a set of blocks B and ribs RA arranged from one tread end e to the other tread end e and adjacent to each other in the tire axial direction.

As the tread pattern, a lug type in which the vertical groove 3 is eliminated and a rib type in which the horizontal groove 5 is eliminated can be employed. In the rib type, the pattern elements are divided by, for example, a zigzag pitch of the vertical groove.

Further, as described above, in the tire of the present invention, as shown in FIG. 2, a row of the pattern elements Ei arranged in the circumferential direction of the tire is formed by using each pattern element Ei as a unit pulse and one pulse. Starting from the pattern element E1, the pitch length Li, which is the circumferential length of each pattern element Ei, is replaced with a pulse train Pi separated in the circumferential direction of the pattern elements Ei, and this pulse train is developed into a Fourier series. The amplitude Ak of the equation (3) calculated from the following equations (1) and (2) is
Equations (4) and (5) are set.

[0023]

(Equation 7)

[0024]

(Equation 8)

In the equation, C is the tire circumference, xi
Is the position of the pulse in the pulse train Pi, and n is the number of pattern elements Ei as described above. Again
Is the order, and is a value from the 1st to n / 2th order (1 to (n-1) / 2nd order when n is an odd number) of the Fourier series.

[0026]

(Equation 9)

As described above, the amplitude Ak of the equation (3)
With reference to the following equation (4) based on the third-order amplitude A3:
(5) is satisfied.

Formula (4) A1 / A3 ≦ 0.5, A
2 / A3 ≦ 0.5 Equation (5) When 4 ≦ k 2.5 / k ≦ Ak / A3
≤ 3.5 / k

As described above, in each pattern element Ei, the amplitude Ak replaced with a pulse train and expanded into a Fourier series is set in such a range. Therefore, as described in the above-mentioned “action”, the sound pressure of the noise is the frequency. And fluctuates close to 1 / f fluctuation depending on the value of, and noise discomfort can be reduced.

In the formulas (1) and (2), f (x) in the general formulas of the formulas (6) and (7) of the Fourier series is replaced by 1 because the unit pulse is replaced in the present invention. Yes, and assuming that a unit pulse exists only in the position of xi in one cycle, the integral can be easily obtained from this general formula by summing the n-pieces. Note that 1 / C in the general formula is omitted because it is canceled later.

[0031]

(Equation 10)

[0032]

[Equation 11]

Further, the coordinates are represented by rectangular coordinates, and
Equation (3) is obtained from (2). FIGS. 3 and 4 show equations (1) when the order k is 1, 2, respectively. In the figure, the sum of the heights yi up to the waveform at each position of the pulse is expressed by equation (1).
Indicates.

Next, a method of selecting a pattern element Ei according to the present invention will be described with reference to FIG. FIG. 5 shows tire size 1
A 95 / 65R15 tire is taken as an example.

[First Step] First, the number n of pattern elements on the entire circumference of the tire in the block row is selected. As a result, the order number k is n / 2 (n is an even number), (n +
1) / 2 (n is an odd number). According to the concept of Fourier series expansion, the amplitude and phase of half the number of pattern elements n are determined. This is a constraint when a Fourier series defined by an infinite number of coordinate points is given by a finite number of coordinate points, and the independent variables before expansion (time and space) and the independent variables after expansion (order and phase) Φ) can be considered to be derived from the point that should match.

In the example of FIG. 5, the number of pattern elements Ei is set to, for example, 60, and therefore, the number of orders k is selected to be 30.

[Second Step] As described above, in the equations (4) and (5), the third-order amplitude A3 is set to 1 and A
1, A2 ... Ak is determined.

In the example of FIG. 5, for example, A1 and A2 are set to 0, and the RFV is reduced. Further, 2.5 / k of the equation (5)
In 3.5-k, for example, 3 is selected from 3 between 2.5 and 3.5. Thereby, as shown in FIG.
A4 = 3/4 = 0.750, A5 = 3/5 = 0.60
0,... A30 = 3/30 = 0.100.

[Step 3] Next, the original waveform of the array of the pattern elements Ei is calculated using the equation (8). It is determined by the formula. In equation (8), i = 1 to n (= 60).

[0040]

(Equation 12)

Here, φk is the phase angle of the wave in each order, which is a random value to prevent monotonization of the original waveform.

Equation (8) is derived from another general equation (abbreviating height drift) of equation (9) of Fourier series.

[0043]

(Equation 13)

In the above equation (9), Ak = √ (ak ² + bk ² ), Φk = tan ⁻¹ ak / b
Equation (8) can be easily obtained by setting k, In addition, in order to obtain Φk, in the example of FIG. 5, a computer generates random numbers from 0 to 1 and calculates 2π (= 360 °).
Is multiplied by

[Step 4] The i-th pitch length Li from the maximum value eM and the minimum value em of ei in the expression (4) and the maximum value LM and the minimum value Lm of the pitch length Li of the pattern element is calculated. It is determined by the following equation (10).

Equation (10) Li = [(LM−Lm) ·
ei / (eM-em)] + C / n

In equation (10), C is the tire circumference, and the ratio LM / L of the maximum and minimum pitch lengths LM and Lm.
m is selected in the range of 1.2 to 2.0.

When LM / Lm is less than 1.2, the difference in pitch length is small, the dispersion of the frequency is poor, and the sound is concentrated in a part of the frequency, so that the sound is noisy. On the other hand, if it exceeds 2.0, the difference in rigidity of the blocks becomes too large, and adverse effects such as uneven wear appear.

Therefore, in the example of FIG. 5, LM / Lm =
1.51, and from the average pitch length Li based on the ratio of the tire circumference C to the number of pattern elements Ei,
LM = 39.63 mm and Lm = 26.30 mm.

FIG. 5 shows the result of obtaining the pitch length Li of each pattern element Ei by the equation (10).

[0051]

[Specific Example] A block-rib type tread pattern shown in FIG. 1 was formed on the tread surface of a tire having a tire size of 195 / 65R15 based on the specifications shown in FIG. In addition, a prototype tire was manufactured together with a comparative example tire, and the noise performance of the prototype tire was compared by an actual vehicle running test.

The noise performance is determined by the tire internal pressure (2.0 ks
c) a five-point evaluation of the noise in the vehicle when traveling under the conditions of a rim (6JJ × 15), a traveling road surface (asphalt), and a traveling vehicle (passenger car: 2000 cc; FF); The higher the score, the better. Table 1 shows the results.

[0053]

[Table 1]

[0054]

Since the pneumatic tire of the present invention is constructed as described above, it can give characteristics close to 1 / f fluctuation in noise sound pressure, and can reduce noise discomfort. .

[Brief description of the drawings]

FIG. 1 is a development view of a tread pattern for explaining an embodiment of the present invention.

FIG. 2 is a diagram illustrating a pulse train.

FIG. 3 is a diagram showing a waveform when k = 1 in equation (1).

FIG. 4 is a diagram showing a waveform when k = 2 in equation (1).

FIG. 5 is an explanatory diagram illustrating a procedure for obtaining a comparative example product used in a specific example.

[Explanation of symbols]

 E, E1, E2,... Ei Pattern element Li Pitch length

Claims (1)

(57) [Claims] 1. A pneumatic tire having a tread pattern in which n pattern elements constituting a pattern constituting unit are arranged on a tread surface in a tire circumferential direction, wherein a row of the pattern elements arranged in a tire circumferential direction. With each pattern element as a unit pulse and starting with one pattern element as a starting point, the pitch length Li, which is the circumferential length of each pattern element, is replaced with a pulse train separated in the circumferential direction. When the pulse train is expanded into a Fourier series, the following equations (1) and (2) can be calculated from the Fourier coefficients of the following equations (1) and (3). 1− (n−1) / 2 order]
However, the following formulas (4) and (5) are satisfied on the basis of the third-order amplitude A3. (Equation 1) (Equation 2) (Equation 3) Formula (4) A1 / A3 ≦ 0.5, A2 / A3 ≦
0.5 Equation (5) When 4 ≦ k 2.5 / k ≦ Ak / A3
≤ 3.5 / k In the equation, C is the tire circumference, k is the order, and xi is the position of the i-th unit pulse in the pulse train.