JP2004233226A - Belt vibration measuring method and belt sound production evaluation method using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a new procedure for specifying a belt slip sound caused by micro-vibration in the pulley radial direction generated by misalignment or the like, and elucidating its sound production mechanism. <P>SOLUTION: Laser light transmitted from an optical Doppler vibration measuring device 3 is reflected by a belt back face vibrating in the pulley radial direction, and receives a Doppler shift. The reflected light is allowed to optically interferes with reference laser light, to be thereby converted into a voltage signal. The FM modulated wave is recorded as a vibration speed signal proportional to the Doppler shift by an optical heterodyne detection demodulation unit. Simultaneously, a noise level signal is recorded as time series data by a microphone 4 provided near the laser light irradiation position. The sound production time is specified from agreement of peaks of a pair of waveforms, and a coherence function is operated from a frequency spectrum of the pair of waveforms, and the sound production frequency is specified by using the coherent value as a determination standard value. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
According to the present invention, a relative vibration (fine vibration) generated between a transmission belt such as a flat belt, a V-belt, and a V-ribbed belt used for friction transmission and a predetermined pulley of a group of pulleys that rotates substantially integrally with the belt is described. More specifically, the present invention relates to a method for identifying and evaluating a sound generated due to this vibration, and more specifically, a method for measuring a vibration speed of a belt which relatively vibrates (finely vibrates) in a pulley radial direction, and is a sound generation evaluation method using the same.
[0002]
[Prior art]
Conventionally, various studies have been made on a method of measuring the vibration of a belt related to a frictional slip generated between a belt and a pulley or a method of evaluating a sound generation property caused by the vibration. There are still many unknowns, and no reliable method has been established.
[0003]
For example, a friction slip phenomenon of a belt on a pulley, a method of measuring the vibration of the belt due to a small slip in the pulley circumferential direction as a vibration component in the pulley circumferential direction is disclosed in the following document by the present applicant. ing.
[0004]
[Patent Document 1]
JP, 2000-131055, A The following documents are indicated as a technique related to a laser Doppler vibration measuring method of an optical heterodyne detection and demodulation method according to the present invention.
[0005]
[Patent Document 2]
The technique disclosed in Japanese Patent No. 2866784 discloses a technique in which the vibration speed of a predetermined pulley and the vibration speed of a belt running on the pulley are simultaneously measured, and a pair of measured waveforms is tabulated. This is a method of specifying the mode of the micro-slip of the friction transmission belt by comparing and comparing the results with each other, and further comparing the result with the noise level waveform to clarify the sounding time or sounding mechanism.
[0006]
That is, as shown in FIG. 5 (a), in a complete frictional transmission state, the vibration speeds of the pulley and the belt match, and no minute slippage occurs. However, if the friction transmission is incomplete due to any cause, such as insufficient belt tension or a decrease in friction coefficient, the belt cannot follow the vibration speed of the driving pulley, as shown in FIG. Let it.
[0007]
The graphs shown in FIGS. 5 (a) and 5 (b) are the results of an experiment performed using an automobile engine accessory drive belt, in which the rotation fluctuation of the engine crankshaft is superimposed on the crank pulley. Thus, the presence / absence and occurrence time of minute slippage of the belt driven by this can be confirmed.
[0008]
The method of measuring the above-mentioned minute slip is disclosed in the above-mentioned Japanese Patent Application Laid-Open No. 2000-131055, and the outline thereof is shown in FIG. 6A and FIG. Irradiates the side of the belt 1 with the laser light of the optical pulley 2 to measure the vibration velocity in the circumferential direction of the pulley 2 and simultaneously irradiates the side of the belt 1 with the laser light of the other optical Doppler type vibration measuring instrument 3. This is a method of measuring the vibration velocity (in the circumferential direction of the pulley) and judging the nature of the minute slip from the pair of waveform data.
[0009]
[Problems to be solved by the invention]
However, in the prior art which attempts to identify the time of occurrence of minute slippage of the transmission belt by comparing the vibration speed of the pulley 2 with the vibration speed of the belt 1 on this pulley, and to clarify the sound generation mechanism. The following issues were found.
[0010]
That is, in the conventional belt vibration velocity measuring method, as shown in FIGS. 6A and 6B, the laser beam transmitted from the optical Doppler vibration measuring device 3 is moved in the left-right direction (the pulley circumferential direction) in the drawing. Irradiating the side surface of the moving belt 1, the FM modulated wave which is Doppler shifted in proportion to the moving speed of the measured object is input to the photoelectric converter and converted into a voltage signal, and the FM modulated wave is converted by the heterodyne detection demodulation unit. This is a method of performing FM demodulation, extracting a beat signal, and detecting a vibration speed proportional to the Doppler shift.
[0011]
Similarly, the vibration speed of the pulley 2 to be compared with the belt vibration speed is measured simultaneously by using another optical Doppler vibration measuring device 3. At this time, in order to record the presence / absence of sound generation due to the belt 1 on the pulley, a microphone 4 is installed in the immediate vicinity of the pulley 2, noise level data is simultaneously recorded, and the audibility measurement result at this time is recorded.
[0012]
The discussion on such a minute slip is as described with reference to FIGS. 5A and 5B, and is an effective method for specifying the occurrence time of the minute slip. However, when trying to associate the relationship between micro-slip and pronunciation, it became clear that the following problems remained.
[0013]
Hereinafter, the problem will be described in detail with reference to FIGS. 7A and 7B. FIG. 7A is a graph in which a belt vibration velocity waveform measured by using the optical Doppler vibration measuring device 3 and a noise level waveform measured simultaneously therewith are graphed in a time series. From this graph, the peak of the noise level can be confirmed, but the peak of the belt vibration speed cannot be confirmed.
[0014]
Therefore, in order to clarify the relationship between the slight slip of the belt 1 and the sound generation, the frequency spectra of the belt vibration velocity waveform data and the noise level waveform data were calculated, and the coherence function of the pair of data was calculated.
[0015]
The results are as shown in FIG. 7 (b). Although a slight correlation (coherent value = 0.71) is observed near the frequency of 2.2 kHz, a peak is observed in the belt vibration speed itself near the frequency of 2.2 kHz. I couldn't.
[0016]
From the above, the above-mentioned conventional method is an effective method as a means for specifying the time of occurrence of a minute slip between the belt 1 and the pulley 2, but as a method for specifying the nature of this sound generation in relation to the noise level. Is not enough.
[0017]
[Means for Solving the Problems]
The invention according to claim 1 is a belt vibration measuring method for measuring a vibration speed of a belt traveling on a pulley, and a main part of the method is that the measured vibration speed is a vibration speed in a pulley radial direction. In addition, the method of measuring the vibration speed is such that the reflected laser light radiated to the back of the belt from the pulley radial direction and subjected to Doppler shift and the reference laser light whose frequency of the irradiated laser light is shifted by a predetermined frequency cause optical interference. The characteristic feature is that the obtained interference laser light is converted into an electric signal, and the resulting signal is subjected to FM demodulation to detect a vibration speed.
[0018]
The invention according to claim 2 is a belt sounding evaluation method for evaluating sound generation characteristics caused by vibration of a belt running on a pulley, wherein the vibration of the belt is a vibration defined by a belt vibration speed in a pulley radial direction. And, the belt vibration speed was obtained by causing light interference between the reflected laser light which was irradiated from the pulley radial direction to the belt back surface and shifted by Doppler shift and the reference laser light which was shifted the frequency of the irradiated laser light by a predetermined frequency. The interference laser light is converted into an electric signal, which is detected by FM demodulation. The belt vibration velocity waveform by the obtained interference laser light, the noise level waveform detected in synchronization with the belt vibration velocity waveform, Is expressed as a time-series waveform, and based on the coincidence of the peak value of the belt vibration velocity waveform and the peak value of the noise level waveform, a belt pronunciation evaluation that specifies a sounding time. It is a method.
[0019]
According to a third aspect of the present invention, each frequency spectrum is calculated from a belt vibration velocity waveform caused by interference laser light and a noise level waveform measured in synchronization with the waveform, and a coherence function is calculated from the pair of frequency spectra. 3. The belt sounding evaluation method according to claim 2, wherein a sounding time and a sounding frequency are specified from the obtained peak value of the coherence function.
[0020]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a block diagram showing a belt vibration measuring method and a sound generation evaluation method according to the embodiment, and FIG. 2 is a flowchart showing a belt vibration measurement method and a sound generation evaluation method according to the embodiment. FIG. 3 is a schematic diagram showing the principle of measuring the vibration of the belt according to the embodiment.
[0021]
4A and 4B are graphs showing a belt vibration measurement result and a sounding evaluation result according to the example. FIGS. 4A and 4B show a time-series belt vibration velocity waveform and a noise level waveform, respectively. (C) shows a frequency spectrum of the belt vibration velocity and the noise level, and a coherence function of the belt vibration velocity and the noise level.
[0022]
FIGS. 8A and 8B are schematic views showing a belt driving device according to the present invention. FIG. 8A shows the entire belt driving device, and FIG. 8B shows a cross section of the belt.
[0023]
First, an example of the belt driving device according to the present invention will be described with reference to FIG. In FIG. 8A, the belt 1 is wound around six pulleys, a rotational force is applied by an engine crank pulley (Crack / P), and each auxiliary pulley (ACG pulley, P / S) is passed through the belt 1. Driving pulleys, W / P pulleys, A / C pulleys, and tensioner pulleys (A / T).
[0024]
As the belt 1 used for serpentine driving as shown in FIG. 8A, a V-ribbed belt having excellent flexibility is usually used. As shown in FIG. 8 (b), this V-ribbed belt is a stretched rubber 1b in which a cord 1c made of a stretched cord, an adhesive rubber 1d for embedding the cord, and a canvas 1a with rubber are laminated on the upper side thereof. On the lower side, a rib is formed with a predetermined number of ribs in the longitudinal direction of the belt.
[0025]
Next, a belt vibration measuring method according to the present invention and a pronunciation evaluation method using the same will be described in detail with reference to FIG. In FIG. 1, a laser beam emitted from an optical Doppler vibration measuring device 3 is split by a first prism (beam splitter) in a direction perpendicular to a straight traveling direction, and a laser beam traveling in the straight traveling direction is irradiated to the back surface of the belt 1 as it is. , Reflected on its back.
[0026]
This reflected light undergoes a Doppler shift due to the belt vibration velocity oscillating in the radial direction of the pulley, re-enters the second prism, and is guided in a right angle direction. This guided reflected light is further guided in a right angle direction via a mirror. On the other hand, the laser beam split in the right angle direction by the first prism is converted into a reference laser beam having undergone a predetermined frequency shift by the optical modulator.
[0027]
The reflected light and the reference laser light interfere with each other via the third prism, and become interference laser light and enter the photoelectric converter. A beat signal is extracted from the FM modulated wave converted by the photoelectric converter into a voltage signal by the optical heterodyne detection and demodulation unit, and a voltage signal proportional to the Doppler shift is output as a vibration velocity.
[0028]
Further, a noise level signal near the laser light irradiation point is measured simultaneously via a microphone 4 installed at a position immediately adjacent to the laser light irradiation point, and the noise level signal is time-series synchronized data together with the vibration velocity waveform. Is input to the FFT analyzer 5.
[0029]
The input time-series waveform is processed in real time, or after being recorded in a storage medium, is subjected to waveform processing as appropriate. In any case, the correlation between the noise level waveform and the belt vibration waveform is appropriately determined, and the processing is effectively performed as a sound generation evaluation method for specifying a sound generation time and a sound generation frequency.
[0030]
Next, the flow of the belt vibration measurement method and the sound generation evaluation method using the same will be described in detail with reference to FIG. In FIG. 2, the procedure for measuring the belt vibration is as follows. First, the belt 1 to be evaluated is prepared in a runnable state, then the microphone 4 for measuring the noise level is installed, and the belt in the radial direction which is a main part of the present invention is provided. An optical Doppler vibrometer 3 for measuring vibration with high accuracy is installed.
[0031]
With the above preparation, the belt 1 is run, and the noise level and the belt vibration velocity are measured simultaneously. This waveform data is temporarily stored in an external storage device, or waveform processing of the noise level and the belt vibration speed is executed in real time. If the peak values of the pair of time-series waveforms match at this stage, it is determined that there is a strong correlation with each other, the sounding time is specified, and the frequency spectra of the belt vibration velocity waveform and the noise level waveform are calculated.
[0032]
A coherence function is calculated from the pair of frequency spectra, and if the peak value of the coherence function is larger than a predetermined determination value α, it is determined that there is a strong causal relationship between the sound generation and the belt vibration speed, and the sound generation frequency is determined. Identify. However, if the peak value is smaller than the determination value α, it is determined that the pronunciation cannot be specified.
[0033]
As described above, the present invention has a remarkable feature in the direction of the belt vibration velocity to be measured, and the conventional method is a method for measuring the component in the belt running direction, that is, the vibration velocity in the pulley circumferential direction. On the other hand, the present invention is characterized in that a belt vibration speed oscillating in a direction perpendicular to this, that is, in a radial direction of the pulley is measured.
[0034]
Next, the difference between the vibration direction according to the conventional method and the vibration direction according to the present invention will be described with reference to FIG. FIG. 3A is a perspective view showing the belt vibration direction, and shows how the belt 1 slightly vibrates in the radial direction of the pulley 2. This fine vibration can be detected by irradiating the back surface of the belt 1 with a laser beam and measuring the optical Doppler shift in the radial direction, so that the vibration speed proportional to the Doppler shift can be detected.
[0035]
More specifically, FIG. 3B shows a cross section of the belt 1 wound around the pulley 2 in the belt width direction, and the belt 1 extends in the pulley radial direction along the groove shape of the pulley 2. You can see how it vibrates. Hereinafter, the operation and effect of the method of the present invention will be described in detail based on examples.
[0036]
【Example】
The belt drive device used in the embodiment is an engine accessory drive belt device used for an in-line four-cylinder 1800 cc engine, and a schematic layout is as shown in FIG. The belt 1 tested in this test was a Mitsuboshi Belt V-ribbed belt 6PK1940 (belt circumference 1940 mm).
[0037]
In order to facilitate the analysis of the test results, a prime mover that drives the belt 1 is separately provided with a prime mover having a rotation fluctuation output function on the output shaft, which is mounted on the crankshaft of the belt unit for driving the engine auxiliary machine. did. At this time, the number of revolutions of the crankshaft was 800 rpm, and the belt tension at this time was 23.5 kgf / 6 rib, which was appropriately applied using an auto tensioner (A / T).
[0038]
The optical Doppler vibration meter 3 uses an Ono Sokki optical Doppler vibration meter (LV-1720), the noise level meter uses an Ono Sokki sound meter (M1-1233), and the A mode Was measured. The FFT analyzer 5 used was DS-2000 manufactured by Ono Sokki.
[0039]
FIG. 4 shows the results obtained based on the above configuration. FIG. 4A is a time-series waveform of the back vibration of the belt 1 measured in the radial direction of the pulley using the optical Doppler vibrometer 3, and FIG. 4B is measured in synchronization with FIG. This is the noise level waveform obtained.
[0040]
From the graphs shown in FIGS. 4A and 4B, it can be determined that a clear peak exists in each of the noise level waveform and the belt vibration velocity waveform. In addition, since the occurrence times of the peaks clearly coincide with each other, it is possible to accurately specify the generation of the sound and the sound generation time.
[0041]
On the other hand, from the vibration data in the circumferential direction of the pulley according to the conventional method, it was not possible to determine the presence of a peak in the belt vibration velocity waveform as shown in the graphs of FIGS. 7 (a) and 7 (b).
[0042]
Next, in order to specify the frequency of the sound, the frequency spectra of the belt vibration velocity waveform and the noise level waveform were calculated, and a coherence function was calculated from the pair of frequency spectra, and the result was displayed in FIG.
[0043]
In other words, it can be seen from the graph of FIG. 4C that the peak of the coherence function exists near the frequency of 6.7 kHz, and the coherent value is extremely large at 0.95.
[0044]
Since this coherent value means that the frequency of the belt vibration velocity waveform and the noise level waveform have an intensity correlation, if this coherent value is registered in advance as the judgment value α of the pronunciation evaluation program, the Time and frequency can be specified accurately.
[0045]
That is, by measuring the belt vibration velocity in the radial direction of the pulley according to the method of the present invention, it becomes possible to measure the fine vibration (high frequency range) which cannot be obtained by the conventional measurement of the vibration velocity in the circumferential direction. The pronunciation can be specified.
[0046]
【The invention's effect】
According to the first aspect of the present invention, it is possible to measure the belt vibration velocity in the pulley radial direction, and to clarify the vibration phenomenon caused by the minute vibration due to misalignment or the like.
[0047]
According to the second aspect of the present invention, it is possible to specify the sound generation time of the sound generated due to the belt minute vibration in the pulley radial direction, and the analysis of the sound generation mechanism is facilitated.
[0048]
According to the third aspect of the present invention, it is possible to specify the sound generation time and the sound generation frequency of the sound caused by the belt micro-vibration in the pulley radial direction, which is effective in elucidating the sound generation mechanism and improving the sound generation performance of the belt. is there.
[Brief description of the drawings]
FIG. 1 is a block diagram illustrating a belt vibration measuring method and a sound generation evaluating method according to an embodiment.
FIG. 2 is a flowchart illustrating a belt vibration measuring method and a sound generation evaluating method according to the embodiment.
FIG. 3 is a schematic diagram illustrating a principle of measuring belt vibration according to the embodiment.
FIGS. 4A and 4B are graphs showing a belt vibration measurement result and a sounding evaluation result according to the embodiment. FIGS. 4A and 4B show a time-series belt vibration velocity waveform and a noise level waveform, respectively. c) shows the frequency spectrum of the belt vibration velocity and the noise level, and the coherence function of the vibration velocity and the noise level.
5A and 5B are graphs showing measurement results of a minute slip of a belt according to a conventional example, where FIG. 5A shows a state without a minute slip and FIG. 5B shows a state with a minute slip.
FIG. 6 is a schematic diagram showing a belt vibration measuring method according to a conventional example.
7A and 7B are graphs showing a belt vibration measurement result and a sounding evaluation result according to a conventional example, wherein FIG. 7A shows a time-series belt vibration velocity waveform and a noise level waveform, and FIG. 2) shows the frequency spectrum of FIG. 2 and the coherence function of the belt vibration velocity and the noise level.
FIGS. 8A and 8B are schematic diagrams showing a belt driving device according to the present invention, wherein FIG. 8A shows the entire belt driving device, and FIG. 8B shows a cross section of the belt.
[Explanation of symbols]
1 Belt 2 Pulley 3 Optical Doppler Vibrometer 4 Microphone 5 FFT Analyzer

Claims (3)

In a belt vibration measuring method for measuring a vibration speed of a belt running on a pulley,
The vibration speed of the belt is a vibration speed in the pulley radial direction, and the vibration speed is the Doppler-shifted reflected laser light irradiated to the back of the belt from the pulley radial direction, and the frequency of the irradiated laser light is shifted by a predetermined frequency. A belt vibration measuring method, wherein light interference occurs between the reference laser light and the obtained interference laser light, the obtained interference laser light is converted into an electric signal, and the signal is detected by FM demodulation. In a belt sounding evaluation method for evaluating sounding characteristics caused by vibration of a belt running on a pulley,
The vibration of the belt is a vibration defined by a belt vibration velocity in a pulley radial direction, and the belt vibration velocity is a reflected laser light irradiated to the back of the belt from the pulley radial direction and subjected to Doppler shift, and an irradiation laser light. Optical interference between the reference laser light whose frequency is shifted by a predetermined frequency, conversion of the obtained interference laser light into an electric signal, which is detected by FM demodulation,
The belt vibration velocity waveform due to the interference laser light and the noise level waveform detected in synchronization with the belt vibration velocity waveform are displayed as a time-series waveform, and the peak value of the belt vibration velocity waveform and the peak value of the noise level waveform are compared. A belt pronunciation evaluation method characterized by specifying a pronunciation time. A belt vibration velocity waveform by the interference laser light and a noise level waveform measured in synchronization with the belt vibration velocity waveform are calculated, and a coherence function is calculated from the pair of frequency spectra. 3. The belt sounding evaluation method according to claim 2, wherein a sounding time and a sounding frequency are specified from the peak value.

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