JP2021092419A - Tire sound radiation evaluation method - Google Patents

Abstract

To evaluate a contribution of oscillation on a tire surface to sound radiation generating from tires in a rolling motion.SOLUTION: An evaluation method of sound radiation from tires includes the steps of: obtaining a relationship between a sound at a sound source location and tire surface oscillation thereat from a signal of the sound at the sound source location when acoustically oscillating a tire surface standing still by the sound from the sound source, and a signal obtained by measuring the tire surface oscillation generating due to the acoustic oscillation at an oscillation measurement location; causing the tire to roll, and measuring the tire surface oscillation in a rolling motion at the oscillation measurement location, and measuring sound radiation from the tire in the rolling motion at the sound source location; obtaining a calculatory signal at a sound source location of the sound arising from the tire surface oscillation in the rolling motion from a signal of the tire surface oscillation in the rolling motion, and the relationship; and obtaining a ratio of the signal of the sound radiation from the tire in the rolling motion measured at the sound source position, and the calculatory signal at the sound source position of the sound arising from the tire surface oscillation in the rolling motion measured at the sound source position.SELECTED DRAWING: Figure 2

Description

The present invention relates to a method for evaluating tire radiation sound.

For example, as described in Patent Document 1, a radiated sound is generated from a tire that rolls on a road surface. Radiated noise is noise inside and outside the vehicle, so it is required to reduce it. Causes of radiation noise include vibration of the tire surface (particularly the sidewall portion), resonance in the groove of the tire tread, contact and friction between the tire and the road surface, and the like.

Japanese Unexamined Patent Publication No. 2010-036850

In order to take effective measures against radiated sound, it is necessary to clarify how much each of the above-mentioned causes contributes to radiated sound. However, the method has not been established until now.

Therefore, an object of the present invention is to provide a method for evaluating the contribution of vibration on the tire surface to the radiated sound generated from a rolling tire.

In the evaluation method of the embodiment, the sound signal at the sound source position when the tire surface stationary at a predetermined position is acoustically vibrated by the sound from the sound source position and the tire surface vibration generated by the acoustic vibration are vibrated. From the signal obtained by measuring at the measurement position, the step of obtaining the relationship between the sound at the sound source position and the tire surface vibration, and the step of rolling the tire at the predetermined position and controlling the tire surface vibration during rolling are described. From the process of measuring at the vibration measurement position and measuring the radiated sound from the rolling tire at the sound source position, and the signal of the rolling tire surface vibration and the above relationship, the rolling tire surface vibration is obtained. The process of obtaining the calculated signal at the sound source position of the resulting sound, the signal of the radiated sound from the rolling tire measured at the sound source position, and the sound caused by the tire surface vibration during rolling. It is a method of evaluating the radiated sound from a tire, which includes a step of obtaining a ratio with a calculated signal at the sound source position.

According to the above evaluation method, it is possible to evaluate the contribution of the vibration of the tire surface to the radiated sound generated from the rolling tire.

The figure which shows the arrangement of a measuring instrument and the like. The flowchart of the evaluation method of an embodiment.

The embodiment will be described with reference to the drawings. It should be noted that the embodiments described below are merely examples, and those which have been appropriately modified without departing from the spirit of the present invention shall be included in the scope of the present invention.
1. 1. Arrangement of measuring instruments, etc. The arrangement of pneumatic tires (hereinafter referred to as “tires”) and equipment, etc. in the present embodiment will be described. As shown in FIG. 1, a sound source position P and a vibration measurement position V are provided at positions in the axial direction of the tire T. A speaker 10 that generates sound is arranged at the sound source position P, and a laser Doppler vibrometer 11 that measures the vibration velocity is arranged at the vibration measurement position V. Further, at the sound source position P, a microphone 12 for measuring sound pressure is also arranged adjacent to the speaker 10. The laser Doppler vibrometer 11 and the microphone 12 are connected to the analyzer 13. Further, the speaker 10 is connected to the control device 14, and starts and stops the generation of sound under the control of the control device 14.

These tires, equipment, etc. are arranged in an anechoic chamber, a semi-anechoic chamber, or outdoors without shielding. Therefore, the method of the present embodiment is performed in an anechoic chamber, a semi-anechoic chamber, or outdoors without shielding.

The sound generating part of the speaker 10 and the detecting part of the laser Doppler vibrometer 11 face the direction of the tire T. Therefore, the speaker 10 generates a sound toward the tire T, and the laser Doppler vibrometer 11 measures the vibration speed of the surface of the tire T (hereinafter referred to as “tire surface”). Note that FIG. 1 shows a state in which the sound generating part of the speaker 10 and the detecting part of the laser Doppler vibrometer 11 are facing the direction of the sidewall part SW. These generating parts and the detecting part are the tire T. It may be facing the direction of another part of.

The sound source position P is closer to the tire T than the vibration measurement position V. As a result, there is no obstacle between the speaker 10 and the tire T, and the sound generated from the speaker 10 reaches the tire T without being affected by the obstacle. Further, since the sound generated from the speaker 10 does not directly enter the detection unit of the laser Doppler vibrometer 11, the detection unit of the laser Doppler vibrometer 11 is less likely to shake and accurate measurement is possible.

The sound source position P is defined by, for example, the so-called JASO point (a position having a height of 25 mm at a point 1 m away from the tire contact center) in the bench test and the international standard (ECE R117-02) concerning the noise regulation of a single tire. This is the position of the microphone when measuring the outside noise.

The tire T is attached to a general testing machine. The testing machine has a rotating road surface R, and the tire T is in contact with the ground on the rotating road surface R. The rotating road surface R starts and stops rotating under the control of the control device 14. When the rotating road surface R rotates, the tire T rolls. However, the tire T rolls in a fixed position even during rolling and does not move back and forth. The rotating road surface R is appropriately selected from a resin road surface, an asphalt road surface, a concrete road surface, and the like, and the surface roughness thereof is also appropriately set.

The tire T is rim-assembled on a predetermined rim, a predetermined internal pressure is applied, and a predetermined load is applied. The conditions of internal pressure and load are not limited.

In the first measurement described later, the rotating road surface R does not rotate, and the tire T is held in a stationary state. When a sound is generated from the speaker 10 in that state, the sound reaches the tire T in a stationary state and the tire surface vibrates. That is, the speaker 10 acoustically vibrates the tire surface. The laser Doppler vibrometer 11 measures the vibration speed. Further, the microphone 12 measures the sound pressure of the sound generated from the speaker 10. The measurement data of the laser Doppler vibrometer 11 and the microphone 12 are sent to the analyzer 13.

Further, in the second measurement described later, the rotating road surface R rotates and the tire T rolls. When the tire T rolls, the tire surface vibrates. In addition to the vibration of the tire surface, resonance in the groove of the tread and contact and friction between the tire T and the rotating road surface R also cause radiation noise from the tire T. The microphone 12 measures the sound pressure of the radiated sound from the tire T, and the laser Doppler vibrating meter 11 measures the vibration speed of the tire surface. The measurement data of the microphone 12 and the laser Doppler vibrometer 11 are sent to the analyzer 13.

The tire T is in the same predetermined position (position on the rotating road surface R) during the first measurement and the second measurement. Further, the positions of the laser Doppler vibrometer 11 and the microphone 12 are also the same between the first measurement and the second measurement.

2. Evaluation Method of Tire Radiation Sound As shown in FIG. 2, the method of the present embodiment includes steps S1 to S5. Step S1 is a first measurement step of acoustically exciting the stationary tire T with the sound from the speaker 10 at the sound source position P to measure the sound at the sound source position P and the tire surface vibration. Step S2 is a second measurement step in which the tire T is rolled, the radiated sound from the tire T is measured at the sound source position P, and the tire surface vibration is measured. Step S3 is a step of obtaining the relationship (transfer function) between the sound at the sound source position P and the tire surface vibration from the sound signal (Fourier spectrum) and the tire surface vibration signal (Fourier spectrum) obtained in the first measurement. Is. In step S4, the sound source position P of the sound caused by the tire surface vibration at the time of the second measurement is based on the signal (auto power spectrum) of the tire surface vibration obtained in the second measurement and the above-mentioned relationship (transfer function). This is the process of obtaining the signal (auto power spectrum) in. In step S5, based on the signal of the radiated sound measured at the time of the second measurement (auto power spectrum) and the signal obtained in step S4 (auto power spectrum), the rotation with respect to the radiated sound generated from the rolling tire T is performed. This is a process for obtaining the contribution rate of sound caused by the vibration of the tire surface during movement. Hereinafter, steps S1 to S5 will be specifically described.

(1) Step S1
In the first measurement step S1, the control device 14 generates a sound from the speaker 10 toward the stationary tire T. The tire surface vibrates due to the sound from the speaker 10. While the sound is generated from the speaker 10 and the tire surface is vibrating, the microphone 12 measures the sound pressure of the sound generated from the speaker 10, and in parallel with this, the laser Doppler vibrometer 11 vibrates the tire surface. To measure. Each measurement data is sent to the analysis device 13.

(2) Step S2
In the second measurement step S2, the control device 14 rotates the rotating road surface R to roll the tire T. When the tire T rolls, radiation noise is generated from the tire T, and the tire surface vibrates. While the tire T is rolling, the microphone 12 measures the sound pressure of the radiated sound from the tire T, and in parallel with this, the laser Doppler vibrometer 11 measures the vibration velocity of the tire surface. Each measurement data is sent to the analysis device 13.

(3) Step S3
In step S3 for obtaining the transfer function, first, the analyzer 13 first measures the Fourier spectrum R (f) of the vibration velocity of the tire surface measured by the laser Doppler vibrometer 11 at the time of the first measurement, and the Fourier of the sound pressure measured by the microphone 12. Find the spectrum Q (f). Note that f is a frequency. Next, the analysis device 13 obtains the two transfer functions H _vQR (f) (v = 1, 2) as follows.

ここで、Ｒ（ｆ）^＊はＲ（ｆ）の複素共役、Ｑ（ｆ）^＊はＱ（ｆ）の複素共役である。また、Ｃ_ＱＱ（ｆ）はマイクロホン１２で測定した音圧のオートパワースペクトル、Ｃ_ＲＲ（ｆ）はレーザードップラー振動計１１で測定したタイヤ表面の振動速度のオートパワースペクトル、Ｃ_ＱＲ（ｆ）は前記振動速度の前記音圧に対するクロスパワースペクトル、Ｃ_ＲＱ（ｆ）は前記音圧の前記振動速度に対するクロスパワースペクトル、である。ただしここでのオートパワースペクトルやクロスパワースペクトルは第１測定時のものである。

Here, R (f) ^* is the complex conjugate of R (f), and Q (f) ^* is the complex conjugate of Q (f). _{Also, C} QQ (f) the sound pressure of the auto power spectrum measured by the microphone _{12, C} RR (f) is the vibration velocity of the tire surface as measured by laser Doppler vibrometer 11 auto power _{spectrum, C} QR (f) is _CRQ (f) is a cross power spectrum of the vibration velocity with respect to the sound pressure, and CRQ (f) is a cross power spectrum of the sound pressure with respect to the vibration velocity. However, the auto power spectrum and the cross power spectrum here are those at the time of the first measurement.

_{As can be seen from the equations (I) and (II), the transfer function H vQR} (f) (v = 1, 2) obtained in this way is the sound pressure measured at the sound source position P and the vibration measurement position V. It shows the relationship with the measured vibration velocity of the tire surface.

(4) Step S4
In the next step S4, the analysis unit 13, an auto power spectrum of the vibration velocity of the measured tire surface during the second measurement _C RR (f), said transfer function _{H vQR (f) (v =} 1,2) _{Therefore, the auto power spectrum C QQ} (f) at the sound source position P of the sound pressure caused by the vibration of the tire surface at the time of the second measurement (during the rolling of the tire T) is obtained. Specifically, the analysis device 13 _{obtains the auto power spectrum C QQ} (f) by the following equation.

ここで、

here,

である。

Is.

Here, it is proved that the equation (III) holds. First, from the characteristics of the Fourier transform, the following equations (V) and (VI) hold.

そして式（I）（II）（V）（VI）から、式（IV）は次のようになる。

Then, from equations (I), (II), (V), and (VI), equation (IV) becomes as follows.

よって式（III）が成立する。

Therefore, equation (III) holds.

Incidentally, obtained in the step S4 auto power spectrum C _{QQ (f),} since the auto power spectrum of the sound resulting from the vibration of the tire surface during rolling of the tire T, usually, the automatic power in process S3 spectrum C _{QQ (f} ) (That is, the autopower spectrum of the sound when the stationary tire T is acoustically vibrated). However, the auto power spectra C _QQ (f) of steps S3 and S4 are the same in that they are auto power spectra of the sound at the sound source position P, which is related to the vibration of the tire surface.

(5) Step S5
_{In the next step S5, first, the analyzer 13 first measures the autopower} spectrum C qq (f) of the sound pressure of the sound radiated from the tire T measured at the sound source position P during the second measurement (during the rolling of the tire T). ). This auto power spectrum C _qq (f) can be obtained as follows using the Fourier spectrum q (f) of the sound pressure measured at the sound source position P at the time of the second measurement and its complex conjugate q (f) ^*. ..

このオートパワースペクトルＣ_ｑｑ（ｆ）は、タイヤ表面の振動に起因する音と、それ以外のことに起因する音とが合わさった音のオートパワースペクトルである。

The auto power spectrum C _qq (f) is an auto power spectrum of a sound obtained by combining a sound caused by vibration of the tire surface and a sound caused by other factors.

Then analyzer 13 includes, for particular frequency i, and Motoma' in step S4 auto power spectrum C _{QQ (f) (i.e.,} the sound computational auto power spectrum C _QQ of pressure arising from the vibration of the tire surface during rolling The ratio of the sound pressure actually measured during the rolling of the tire T to the above-mentioned auto power spectrum C _qq (f) of (f)) is obtained. That is, the analysis device 13 obtains the following σi for a specific frequency i.

解析装置１３は、１又は複数の周波数ｉについて、このようなσｉを求める。このようにして求まったσｉは、転動中のタイヤＴから発生する周波数ｉの放射音における、タイヤ表面振動に起因する周波数ｉの音の寄与率を表している。

The analyzer 13 obtains such σi for one or more frequencies i. The σi obtained in this way represents the contribution ratio of the sound of the frequency i caused by the vibration of the tire surface to the radiated sound of the frequency i generated from the tire T during rolling.

3. 3. Effect of Embodiment As described above, the sound signal (Fourier spectrum) at the sound source position P and the sound when the stationary tire surface is acoustically vibrated by the sound from the sound source position P in the steps S1 and S3. The relationship (transmission function) between the sound at the sound source position P and the tire surface vibration can be obtained based on the signal (Fourier spectrum) obtained by measuring the tire surface vibration generated by the vibration at the vibration measurement position V. it can.

In addition to step S1, step S2 is performed in which the tire surface vibration during rolling is measured at the vibration measurement position V and the radiated sound from the rolling tire T is measured at the sound source position P. Then, in step S4, from the signal (auto power spectrum) of the tire surface vibration during rolling and the above relationship (transfer function), in the calculation at the sound source position P of the sound caused by the tire surface vibration during rolling. Signal (auto power spectrum) can be obtained.

Then, in step S5, the signal (auto power spectrum) of the radiated sound from the rolling tire T measured at the sound source position P and the calculation at the sound source position P of the sound caused by the tire surface vibration during rolling. The ratio with the above signal (auto power spectrum) can be obtained. The ratio is the contribution ratio of the sound caused by the tire surface vibration to the radiated sound generated from the tire T during rolling.

In this way, the contribution of vibration on the tire surface to the radiated sound generated from the rolling tire T can be evaluated. If such an evaluation can be made, effective measures can be taken against the radiated sound generated from the rolling tire T.

4. Modification Examples A plurality of modification examples with respect to the above embodiment will be described. Any one of the plurality of modified examples may be applied to the above embodiment, or any two or more of the plurality of modified examples may be applied in combination. In addition to the following modification examples, various modifications are possible.

(1) Change example 1
The first measurement step S1 may be replaced with a simulation using a computer. That is, a simulation may be performed in which the tire model is vibrated by the sound from the sound source and the acceleration of the vibration is acquired. Using the result, the transfer function can be obtained in the same manner as in step S3.

(2) Change example 2
The means for measuring the vibration of the tire surface is not limited to the laser Doppler vibrometer 11 described above. As a means for measuring the vibration of the tire surface, a contact type or non-contact type displacement meter, speedometer, accelerometer or the like can be used. For example, the vibration of the tire surface may be measured by fixing the accelerometer to the tire surface.

(3) Change example 3
The above-mentioned first measurement and second measurement may be performed with the tire T attached to the vehicle body.

(4) Change example 4
As the measurement of the sound generated from the speaker 10 during the first measurement and the measurement of the radiated sound generated from the tire T during the second measurement, the particle velocity may be measured instead of the sound pressure measurement.

(5) Change example 5
At the time of the first measurement, instead of generating sound from the speaker 10 and measuring the sound pressure of the sound with the microphone 12, a particle velocity meter having a known volume may be arranged in front of the speaker 10 to measure the volume velocity.

(6) Change example 6
A signal different from the Fourier spectrum or the auto power spectrum may be used in the method of evaluating the contribution of the vibration of the tire surface to the radiated sound generated from the tire T during rolling.

Regardless of the type of signal, the sound signal at the sound source position P when the stationary tire surface is acoustically vibrated by the sound from the sound source position P and the tire surface vibration generated by the acoustic vibration are measured at the vibration measurement position V. The relationship between the tire surface vibration and the sound at the sound source position P can be obtained from the signal obtained by measuring in.

On the other hand, the tire T is rolled, the tire surface vibration during rolling is measured at the vibration measurement position V, and the radiated sound from the rolling tire T is measured at the sound source position P. Then, from the above relationship between the tire surface vibration and the sound at the sound source position P and the signal of the tire surface vibration during rolling, the signal at the sound source position P of the sound caused by the tire surface vibration during rolling is obtained. Ask.

Then, by obtaining the ratio of the signal of the radiated sound from the rolling tire T measured at the sound source position P to the above-mentioned signal at the sound source position P of the sound caused by the vibration of the tire surface during rolling. , The contribution of the tire surface vibration to the radiated sound generated from the rolling tire T can be evaluated.

R ... rotating road surface, T ... tire, SW ... sidewall part, P ... sound source position, V ... vibration measurement position, 10 ... speaker, 11 ... laser Doppler vibrometer, 12 ... microphone, 13 ... analyzer, 14 ... control device

Claims (2)

Obtained by measuring the sound signal at the sound source position when the tire surface stationary at a predetermined position is acoustically vibrated by the sound from the sound source position and the tire surface vibration generated by the acoustic vibration at the vibration measurement position. The process of finding the relationship between the tire surface vibration and the sound at the sound source position from the received signal,
A step of rolling the tire at the predetermined position, measuring the tire surface vibration during rolling at the vibration measurement position, and measuring the radiated sound from the rolling tire at the sound source position.
From the signal of the tire surface vibration during rolling and the above relationship, a step of obtaining a calculated signal at the sound source position of the sound caused by the tire surface vibration during rolling, and
A step of obtaining the ratio of the signal of the radiated sound from the rolling tire measured at the sound source position to the calculated signal at the sound source position of the sound caused by the vibration of the tire surface during the rolling.
How to evaluate the radiated sound from the tire, including. The evaluation method according to claim 1, wherein the tire surface is acoustically vibrated by the sound from the speaker arranged at the sound source position, and the tire surface vibration is measured by the device arranged at the vibration measurement position.

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