JP3202584B2 - Vibration analysis method and device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention performs an FFT analysis on a vibration signal forming a noise source of an automobile engine, especially a diesel engine mounted on a truck, a bus, or the like, or a compressor for optimal design and noise reduction. The present invention relates to a vibration analysis method and a vibration analysis method.

[0002]

2. Description of the Related Art In order to reduce vibration noise, it is necessary to grasp the vibration characteristics of the sound source and to understand the phenomena, and then to carry out a required modeling. For this purpose, a vibration test using a real or model is performed, and a frequency response function or a unit impact response is obtained by signal processing by FFT analysis from the measurement results of the excitation force and the response obtained by the vibration test, and the natural vibration number and modal damping are obtained. The mode characteristic represented by the ratio and the eigenmode is identified. On the other hand, a so-called F-model, which performs a modal analysis on a finite element model created by making full use of a theoretical structure analysis such as a finite element method to verify the behavior of the structure.
EM numerical analysis is performed. Conventionally, the signal processing from the vibration test and the measurement result in the actual machine test and the modal analysis used for verifying the FEM numerical analysis have been performed by taking many days (about 5 days) by the acceleration pickup measurement. It was, but recently the laser Doppler shown in FIG. 13
The use of the vibration meter system makes it possible to significantly reduce the measurement time, and the system is frequently used for specifying the vibration of the noise source.

As shown in FIG. 13, the laser Doppler vibrometer system includes a laser unit 101 and a controller unit 102. Laser unit 101
Is composed of a laser photoelectric system and a CCD camera, irradiates a laser beam to the oscillating measurement object 100 by the laser photoelectric system, measures the frequency change due to the Doppler effect of the reflected light, and calculates the vibration speed of the object. A vibration signal is output, and a vibration distribution of the measurement surface is output from the CCD camera as a video signal. On the other hand, the controller unit 102 includes an FFT analyzer that performs signal processing of the vibration signal, and an image processing unit that forms the vibration image by processing the video signal.

When the FFT frequency analysis, which is used and required for the vibration mode analysis, is used for, for example, the vibration analysis of a four-cycle diesel engine, the time corresponding to two revolutions, which is the basic cycle of the four-cycle engine, is set to one. Sampling is performed as a cycle , and collective FFT analysis is performed. For example, when a time waveform composed of four single-degree-of-freedom impulse responses shown in (14-A) of FIG. 14 is subjected to collective Fourier transform over a fundamental period T, a line spectrum shown in (14-B) of FIG. can get. However, (15-
A) and the impulse response x (t) expressed by the equation (1) originally have a distribution spectrum shown in FIG.
It should exhibit a continuous smooth curve X (ω) represented by equation (2).

[0005]

(Equation 1)

(Equation 2) Here, t: time [s] ω: angular frequency [rad / s] ωn: natural angular frequency of the system [rad / s] ：: damping ratio φ: initial phase [rad] Such an impulse response x (t) When four times occur with a shift of ず れ of the sampling time T, they are represented by x (t−τ) and τ = 0, T / 4, 2T / 4, 3T / 4, respectively, and their composite function y ( t) and frequency spectrum Y
(Ω) is represented by Expressions (3) and (4).

[0006]

(Equation 3)

(Equation 4) Here, considering the frequency resolution of the Fourier spectrum, ω = 2πm / T, (order m = 0, 1,...), So that equation (4) is further expanded to obtain equation (5).

[0007]

(Equation 5) In this manner, a line spectrum appears with the number of repetitions of the impulse response (the number of periodic intermittent signals) as the cycle. That is, four impulse response examples “(16-
In (A) ", a spectrum line having one value appears following three zero-amplitude spectrum lines as shown in FIG. 16 (B), and its repetition period appears as four lines.

In the actual engine vibration, the repetition of each impulse response is slightly different for each excitation cylinder.
The interference result of the spectrum does not necessarily cancel each other, and the frequency response exhibits a complicated spectrum shape as shown in FIG. 14 (14-B), and the mode characteristic represented by the natural frequency, the mode attenuation ratio, and the natural mode Identification was difficult.

[0009]

SUMMARY OF THE INVENTION Therefore, the invention according to claim 1 of the present invention is based on a circulating periodic vibration signal incorporated in each of a plurality of time sections forming a fundamental cycle, and the time corresponding to the fundamental cycle is obtained. In a vibration signal forming a waveform,
It is an object of the present invention to provide a vibration analysis method that removes a complex spectrum found in a frequency response function obtained by a conventional method of performing a collective FFT analysis of the vibration signal for each fundamental period and enables accurate mode characteristic identification. Things.
Another object of the present invention is to provide a vibration analysis method incorporating an averaging process for specifying the circulating periodic vibration signal as an intermittent impulse signal and enabling time-division FFT analysis to be obtained in the form of a power spectrum. It is what it was. Further, an invention according to claim 2, wherein, in addition to the purpose of the invention, the circulating periodic vibration signal is constituted by an intermittent impulse signal generated by the ignition of a diesel engine, separator of the time segment, the diesel engine It is an object of the present invention to provide a vibration analysis method in which the ignition timing of each cylinder is set as a delimiter and one vibration is sequentially generated in the time section.

[0010] In addition to the above-mentioned object, the invention according to claim 3 aims at providing a vibration analysis method which can increase the density of measurement information by scan measurement. A fourth aspect of the present invention is to provide a time-division frequency analysis apparatus suitably applied to the first to third aspects of the present invention. According to a fifth aspect of the present invention, in addition to the object of the fourth aspect, a time-division frequency suitably applied to an apparatus having a vibration source in which the circulating periodic vibration signal is constituted by an intermittent impulse signal. An analyzer is provided. The invention described in claim 6 has the object of the invention described in claim 4 ,
It is an object of the present invention to provide a time-division frequency analyzer that can be used for vibration analysis of a diesel engine.

[0011]

According to a first aspect of the present invention, a plurality of vibrations caused by a plurality of vibration sources periodically appear at different timings. In the vibration signal analyzing method, the vibration signal within a desired sampling time is time-divided for each of the plurality of vibrations, and the time waveform of each of the time-divided vibration signals is divided from the start of division to the end of the division. Ma
After performing the FFT transform individually in each section, the respective FFT transform results are summed to enable the frequency analysis within the desired sampling time, and the vibration signal is a plurality of intermittent impulse response signals. The time divisional intermittent impulse response signals are individually FFT-transformed to obtain a time divisional power spectrum. The frequency analysis based on the time-division FFT transform enables a single-point frequency analysis. For example, in the case of a diesel engine, an original resonance peak corresponding to the natural frequency of the engine structure is obtained.

[0012]

[0013]

According to a second aspect of the present invention, there is provided a vibration analysis method for a vibration signal which forms a time waveform corresponding to the basic period by circulating periodic vibrations incorporated in each of a plurality of time segments forming the basic period. In the above, the basic period is time-divided for each of the plurality of time segments, and each time-divided time waveform is defined as a section from the start of division to the end of the division.
After the individual FFT transforms are performed, the sums are subjected to frequency analysis of the entire cycle, and the circulating periodic vibration signal is constituted by an intermittent impulse signal generated by the ignition of the diesel engine. The ignition timing of each cylinder of the diesel engine is set as a delimiter, and the ignition timing is generated one by one in the time section.

According to a third aspect of the present invention, there is provided a method of analyzing a vibration signal of a vibration signal forming a time waveform of the basic period by circulating periodic vibrations built in each of a plurality of time sections forming the basic period. In the above, the basic period is time-divided for each of the plurality of time segments, and each time-divided time waveform is defined as a section from the start of division to the end of the division.
After performing individual FFT transforms, the sum is added to perform frequency analysis of the entire cycle, and furthermore, the vibration points are sequentially scanned and measured by laser light, thereby increasing the density of measurement information. It is.

The above-described scan measurement makes it possible to accurately and easily select a required frequency band. In addition, the vibration mode of the engine surface during combustion of each cylinder of the engine can be individually analyzed. In addition, a non-contact scanning laser Doppler vibrometer can be used in combination with the scanning function instead of the conventional vibration measurement using an acceleration sensor, so that it is possible to increase the density of measurement information (surface information) and speed up measurement. Can be.

According to a fourth aspect of the present invention, there is provided a vibration signal analyzing apparatus configured by periodically generating a plurality of vibrations caused by a plurality of vibration sources. A non-contact vibrometer for detecting, a sampling means for sampling a time waveform of the vibration signal within a desired sampling time, and a method for dividing the desired sampling time into a plurality of time segments to oscillate respective vibrations of the plurality of vibration sources. Time-division means for time-dividing the time waveform so as to have the initial value of the signal at the division start position, and each section from the start of division of the time- divided time waveform to the end of the division
A time-division frequency analysis apparatus characterized by comprising a frequency analysis unit including an FFT conversion unit for individually performing FFT conversion and a controller including a vibration characteristic identification unit, an image processing unit and a display unit.

According to a fifth aspect of the present invention, in the time division frequency analyzer according to the fourth aspect , the vibration signal has a vibration source composed of a plurality of intermittent impulse response signals. FFT for obtaining and averaging time-division power spectrum for each time-division time waveform
It is characterized by comprising a conversion unit and a total calculation unit for calculating the power spectrum of the entire basic period by combining the average value thereof.

According to a sixth aspect of the present invention, there is provided a vibration analyzing apparatus for a four-cycle engine having a circulating periodic vibration built in each of a plurality of time segments forming a fundamental period. A non-contact vibrometer for detecting a time waveform for the basic period to be formed, and a sampling means for sampling the time waveform for the basic period,
Min dividing means when dividing at a time waveform so as to have a division start position initial value of the circulating cyclical oscillation signal by dividing the basic period into a plurality of time segments, the said time division time waveform
Each section from the start of the split to the end of the split is individually F
A frequency analysis unit including an FFT conversion unit for performing FT conversion, and a controller including a vibration characteristic identification unit, an image processing unit, and a display unit, wherein the basic period is configured by two rotations of an engine. It is.

Further, the vibrometer according to claim 6 is characterized in that:
A CCD camera is built-in and can be scanned vertically and horizontally, and the controller is provided with image processing of a video signal from the CCD camera and display means therefor.

According to this invention, a single-point frequency analysis becomes possible because a frequency analysis based on a time-division FFT conversion is used instead of the conventional frequency analysis based on a batch FFT conversion. For example, in the case of a diesel engine, An original resonance peak corresponding to the natural frequency of the engine structure is obtained.

[0022]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be described.
This will be described together with the illustrated example. However, unless otherwise specified, the dimensions, shapes, relative positions, and the like of the components described in this embodiment are not intended to limit the scope of the present invention, but are merely illustrative examples. Absent. FIG.
FIG. 1 shows an outline of a vibration analysis method of the present invention for a six-cylinder four-cycle diesel engine, and FIG. 2 is a schematic diagram showing a schematic configuration of an optical system of a laser Doppler vibrometer of a time division frequency analyzer of the present invention. FIG. 3 is a block diagram showing an electrical configuration of FIG. 2, FIG. 4 is a flowchart showing a process of converting an electric signal converted from an optical signal into a speed signal, and FIG. 5 is a time division frequency of the present invention. FIG. 2 is a block diagram illustrating a schematic configuration of a controller of the analyzer.

The vibration analysis method of the present embodiment employs a plurality of vibration
Multiple timing-dependent oscillations caused by different sources
Analysis of vibration signal composed by appearing in
In the method, the desired sampling time is
According to the conventional frequency analysis method for wave number analysis,
A time-sharing function for time-sharing each of the multiple vibrations
In addition, measurement is performed for each of the time-divided sections so that the transient vibration generated in each of the sections can be accurately grasped, and (1-A) to (1-D) of FIG. The periodic intermittent signal is treated as a time waveform of a vibration signal in a vibration period of two revolutions, which is a basic cycle for a four-stroke engine, with a transient vibration caused by combustion of each cylinder of a six-cylinder four-cycle diesel engine, and a required frequency analysis is performed. Is performed.

The procedure of frequency analysis will be described below with reference to the drawings. That is, two rotations (total vibration data) of the time data (time waveform) of the vibration signal synchronized with the rotation of the engine shown in (1-A) of FIG. 1 are sampled over the basic cycle T, and each cylinder ignition timing is separated. As many as the number of cylinders (6
(Time segments), and transient vibrations generated in the cylinders due to the combustion are stored in each time segment. Next, the time-division vibration data stored in each time section shown in (1-B) of FIG. 1 is extracted. Next, FFT transform is performed for each piece of time-division vibration data to obtain a Fourier spectrum shown in FIG. It is averaged to obtain each time-division power spectrum. Then, as shown in (1-D) of FIG. 1, a Nyquist diagram having the real part of the Fourier spectrum on the abscissa and the imaginary part on the ordinate is drawn, and the average values are summed to obtain the overall value. Get the power spectrum. By adopting the time division method as described above, each impulse response can be individually analyzed, the vibration mode pattern can be properly grasped, and the engine vibration can be efficiently analyzed.

Also, the time division means extracts only an arbitrary vibration component on the time waveform of the vibration signal stored in the specific time section, performs an FFT transform on this, and analyzes the frequency to determine the vibration mode in the specific time zone. Obtainable. The frequency analysis method based on the time division method is effective not only for the above-mentioned vibration but also for the analysis of noise data.

The time-division frequency analyzer of the present invention comprises a laser unit and a controller unit, and the laser unit comprises a CCD camera and a laser Doppler vibrometer and has a scanning function. The above-mentioned laser Doppler vibrometer irradiates a vibrating object to be measured with laser light, measures a frequency change of the reflected light due to the Doppler effect, and calculates a vibration speed of the object. The calculated surface vibration is directly measured, and a built-in CCD camera is used to obtain a video signal of the vibration distribution on the measurement surface. Also,
By the scanning function, the irradiation of the laser beam is scanned up, down, left and right over the vibration surface of the object to be measured, so that the vibration state of the entire vibration surface or a required portion can be measured.

FIG. 2 is a schematic diagram showing a schematic configuration of an optical system of the laser Doppler vibrometer. The He-Ne laser beam 10 emitted from the laser oscillator 10a is divided into a reference beam 11 and an object beam 12 by a beam splitter (hereinafter referred to as BS) BS1. The object light 12 passes through the BS 2 as shown by a solid line arrow, and is condensed on the measurement object 13 vibrating by the lens L. The object light 12 irradiating the measurement object 13 becomes reflected scattered light 14 whose frequency has changed in proportion to the vibration speed of the object due to the Doppler effect, returns along the same optical path along the dotted arrow, is reflected by BS2, and reaches BS3. On the other hand, the reference light 11 is a reference modulated light 16 indicated by a double-dot chain line arrow that is shifted by a certain frequency by the acousto-optic modulator 15 in order to enable the vibration direction of the object to be distinguished.
The reflected scattered light 14 (dotted arrow) and the reference modulated light 16 (2
Double-dashed arrows) indicate photodiodes D1,
D2, the signal is converted into an electric signal.
And output as a speed signal or amplitude signal via the signal processing unit 25a.

FIG. 3 is a block diagram showing the electrical configuration of the laser Doppler vibrometer shown in FIG.
As shown in the figure, an interferometer unit 25a including an amplifier 22, an interferometer 23, and a photoelectric converter 24, a preamplifier tracking filter 26, a signal level setting unit 27, and an R
F signal oscillator 28, FM demodulator 29a, PM demodulator 29
b, and outputs a speed signal or an amplitude signal.

FIG. 4 is a block diagram in which an electric signal output from the photoelectric conversion unit 24 is converted into a speed signal. In the figure, after the electric signal is amplified by an amplifier 61, only a specific frequency component is passed by a band-pass filter 62, amplified by an amplifier 63 and input to a tracking filter 64. The tracking filter 64 extracts the same frequency component as the reference signal by the phase detector 641, passes the specific frequency signal through the voltage-frequency converter 643 via the loop filter 642, and outputs the specific frequency signal together with the signals of the main oscillator 67 and the sub-oscillator 68. The signal is sent to a demodulator 65 and output as a speed signal via a low-pass filter 66.

Since the laser unit is composed of a CCD camera and a laser Doppler vibrometer and has a scanning function, the required frequency band on the vibration surface can be arbitrarily and accurately selected by the control unit shown in FIGS. It can be measured, in other words, output as a speed signal. Further, the engine surface vibration mode during combustion of each cylinder of the engine can be individually analyzed by scan measurement, and the contribution ratio of each cylinder to engine surface vibration (noise) can be obtained.

As shown in the block diagram of FIG. 5, the controller unit includes an A / D converter 30 for A / D converting a speed signal voltage input from a vibrometer, and a time waveform obtained by A / D conversion. A sampling means 31 for synchronizing and sampling the combustion of a cylinder via a CLK 31a over a period T, and a sampling time waveform is time-divided by a selector 32a in accordance with the combustion time of each cylinder by a selector 32a. Time division means 32 for dividing and storing the divided time waveforms in six cylinders, time division FFT conversion sections 34a to 34f for performing time division FFT conversion on the divided and stored time waveforms in the form of a power spectrum and averaging the time waveforms. A frequency analyzing means 35 comprising a sum calculating section 35a for calculating the entire power spectrum by combining, Identification of the vibration characteristics to identify sex and 3
6, an image processing unit 37 and a display unit 38. The image processing section 37 performs required image processing on the video signal from the CCD camera. The scanning mechanism 39 is synchronized with the combustion timing of the cylinder via the CLK 31a. The above block diagram describes a case of a 6-cylinder 4-cycle engine.

Next, the operation of the time-division frequency analyzer of the present invention up to the start of measurement and the operation of displaying the measurement result after the end of the measurement will be described with reference to the flowchart of the measurement setting shown in FIG. 6 and the measurement result display shown in FIG. This will be described with reference to the flowchart of FIG. Before starting the measurement, various measurement elements are set. Step 40
The analysis frequency range and the number of FFT lines are set in step 41, the trigger source and trigger level are set and confirmed in step 41, and then the number of frames, the frame interval and the number of cylinder pulses are set in step 42. The operation up to the start of measurement ends.

As shown in FIG. 7, in the display of the measurement result, in step 51, a point display or a pattern display is selected.
Next, points are displayed in steps 52a to 52c,
At steps 53a to 53c, a pattern is displayed.

[0034]

FIG. 8 shows a time waveform of a vibration speed measured at one point on an engine gear case of a four-cycle four-cylinder diesel engine operating at an engine speed of 2400 rpm and a load of 50% over a basic cycle T. is there. The data length is equivalent to two revolutions of the engine (basic cycle), and is excited by the combustion impact force and piston slap force of each cylinder.
Transient responses.

FIG. 17 shows the result of a 1/3 octave analysis of noise measured at a distance of 50 cm while facing the same engine in operation. In the original, the sounding peak at 2 kHz is the noise level (overall value). Dominant). Here, the entire gear case (made of aluminum) that closes most of the front seats of the engine is sound-insulated with a sound-insulating material, so that the noise level is reduced by 3.3 dB (contribution ratio 53).
%), And the noise was significantly reduced in a high frequency range of 2 kHz or more. That is, the result of suppressing the sound of 2 kHz is shown, which is consistent with the analysis result obtained by the time division of the present invention described below. That is, when this time waveform is subjected to frequency analysis by a conventional batch FFT, a spectrum shape as shown in (9-A) of FIG. When this is time-divided according to the present invention, the time waveform of the vibration for two revolutions of the engine is equally divided into four frames, and the FFT frequency analysis is performed on each frame. As a result, (10-A) to (10-D) in FIG. 4) are obtained as a smooth original spectrum shape. Note that (9-B) in FIG. 9 is the entire power spectrum obtained by summing the four frames, and it is understood that the resonance peak at 1.8 to 2 kHz is dominant.

FIG. 11 shows the result of scanning measurement using the scanning function of the time-division frequency analyzer of the present invention to determine the vibration mode of the gear case.
As shown in FIG. The frequency of interest is a resonance peak of 1.8 to 2 kHz. Measurement points are arranged in a grid on the gear case.
0 points were set. The time required for the measurement was about 40 minutes, which was much more efficient than the measurement that required several days with a conventional acceleration sensor.

(11-A) to (11-D) of FIG. 11 show the vibration modes of each frame obtained by equally dividing the time waveform of the vibration for two revolutions of the engine into four frames, and show the vibration speed. The absolute value of the amplitude is displayed in a wire frame model. Each flame is fired in each cylinder (ignition order 1-3)
-4-2 cylinders).

FIG. 12 shows contour lines of vibration modes on a video image of an object (gear case). The contour lines at the lower portion of the gear case indicate that the amplitude is large in a dense portion. These can also display a color moving image by changing the phase on a computer CRT, and make it possible to visually recognize the image of the vibration mode.

From the above results, there is a large mode between the lower end flange portion of the gear case and the oil seal portion of the crankshaft, which is dominant. In addition, this mode is used when the first and second cylinders burn (first and fourth cylinders). It is understood that the amplitude is large and the contribution rate is high.

[0040]

According to the above configuration, the vibration characteristics of the vibration source can be grasped, the phenomenon can be well understood, and the required modeling can be achieved. In particular, when a basic cycle includes a plurality of periodic intermittent vibrations, such as a diesel engine, each impulse response generated by combustion in each cylinder is individually determined by the time-division FFT frequency analysis method of the present invention. The analysis can be performed accurately, and the required eigen-number, the mode damping ratio, and the mode characteristic represented by the eigen mode can be identified. Further, by using the scanning function and the non-contact laser meter together, the surface vibration mode of the running engine can be measured in a short time and accurately, which has a remarkable effect on noise reduction or optimal design.

[Brief description of the drawings]

FIG. 1 shows an outline of a vibration analysis method according to the present invention for a six-cylinder four-cycle diesel engine.
Is a diagram showing total vibration data, (1-B) is a diagram showing time-division vibration data, (1-C) is a diagram showing a time-division frequency spectrum, and (1-D) is a diagram showing a time-division Nyquist diagram. It is.

FIG. 2 is a schematic diagram showing a schematic configuration of an optical system of a laser drip vibrometer of the time division frequency analyzer according to the present invention.

FIG. 3 is a block diagram showing an electrical configuration of FIG. 2;

FIG. 4 is a flowchart showing a process of converting an electric signal converted from an optical signal into a speed signal.

FIG. 5 is a block diagram showing a schematic configuration of a controller of the time-division frequency analysis device of the present invention.

FIG. 6 is a flowchart of measurement setting of the time-division frequency analysis device of the present invention.

FIG. 7 is a flowchart of a measurement result display of the time-division frequency analysis device of the present invention.

FIG. 8 shows a time waveform of a vibration speed measured at one point on an engine gear case when a 4-cycle 4-cylinder diesel engine is operating at an engine speed of 2400 rpm and a 50% load.

9 shows a result obtained by frequency analysis of the time waveform of FIG. 8, where (9-A) is a diagram showing a frequency response function obtained by conventional batch FFT frequency analysis, and (9-A).
4B is a diagram illustrating a frequency response function obtained by the time-division FFT frequency analysis of the present invention.

10 shows a frequency response function obtained by performing the time-division frequency analysis of the present invention on the time waveform of FIG. 8 for each frame, where (10-A) shows a frequency response function of the first frame; (10-B) shows a frequency response function of the second frame, (10-C) shows a frequency response function of the third frame, and (10-D) shows a frequency response function of the fourth frame. It is.

11 shows the vibration mode of each frame in FIG. 10, (11-A) shows the vibration mode of the first frame, (11-B) shows the vibration mode of the second frame, 11-C) is a diagram showing a vibration mode of the third frame, and (11-D) is a diagram showing a vibration mode of the fourth frame.

FIG. 12 is an image diagram showing vibration mode contours formed on the gear case of FIG. 4 displayed on a video image.

FIG. 13 is a diagram showing an outline of a conventional laser drap vibrometer system.

FIG. 14 shows the results of a conventional batch FFT analysis on the vibration analysis of a 4-cycle diesel engine.
(14-A) is a diagram showing a time waveform of a basic cycle (for two engine revolutions) showing impulse responses of four multi-degree-of-freedom systems;
(14-B) shows the time waveform of FIG.
It is a figure showing the line spectrum (frequency response function) obtained by FT analysis.

FIG. 15 shows a frequency spectrum function to be originally obtained for one impulse, which is (15-A).
Is a time waveform chart showing the impulse response x (t) shown in the equation (1), and (15-B) is the above-mentioned frequency spectrum function X
It is a figure showing (ω).

FIG. 16 is a schematic diagram showing a time waveform and a frequency response function when four impulse response trains are collectively frequency-analyzed in a basic period, where (16-A) is a time waveform diagram and (16-B)
FIG. 3 is a diagram showing a frequency spectrum function.

FIG. 17 is a diagram showing a noise 1 before the engine shown in FIG. 4;
It is a figure which shows a / 3 octave analysis result.

[Explanation of symbols]

 Reference Signs List 10 He-Ne laser light 10a Laser oscillator 11 Reference light 12 Object light 13 Measurement object 14 Reflected scattered light 15 Acousto-optic modulator 16 Reference modulation light 21 Differential preamplifier 24 Photoelectric conversion unit 25a Interferometer unit 25b Signal processing unit 26 Preamplifier tracking filter 29a FM demodulator 30 A / D conversion unit 31 Sampling unit 32 Time division unit 35 Frequency analysis unit 36 Vibration characteristic identification unit 37 Image processing unit 38 Display unit 39 Scanning mechanism

──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Selbach Helmut 2-38-5 Akebonocho, Tachikawa-shi, Tokyo Inside P.I.Polytech Co., Ltd. (56) References JP-A-5-77642 (JP, A) (58) ) Fields investigated (Int. Cl. ⁷ , DB name) G01M 15/00 F02B 77/08 G01H 17/00

Claims (6)

(57) [Claims] 1. A vibration analysis method for a vibration signal, wherein a plurality of vibrations caused by a plurality of vibration sources periodically appear at different timings, wherein the plurality of vibration signals are generated within a desired sampling time. Time-divided for each vibration, and the respective time waveforms of the time-divided vibration signal
After performing FFT transformation individually from the start of division to the end of the division as each section, the respective FFT transformation results are summed to enable frequency analysis within the desired sampling time, and the vibration signal is A vibration analysis method comprising a plurality of intermittent impulse response signals, wherein the time-divided intermittent impulse response signals are individually subjected to FFT to obtain a time-division power spectrum. 2. A vibration analysis method for a vibration signal for forming a time waveform of the basic period by circulating periodic vibrations built in each of a plurality of time sections forming a basic period, , And time-divides each time-divided time waveform from the start of division to the end of the division.
After performing FFT transform individually for each section , the sum is added to perform frequency analysis of the entire cycle, and the circulating periodic vibration signal is constituted by an intermittent impulse signal generated by ignition of a diesel engine. A vibration analysis method in which a time segment is divided one by one in the time segment with the ignition timing of each cylinder of the diesel engine as a segment. 3. A vibration analysis method for a vibration signal forming a time waveform of the basic period by circulating periodic vibrations built in each of a plurality of time segments forming a basic period. , And time-divides each time-divided time waveform from the start of division to the end of the division.
After performing FFT conversion individually for each section , the sum is added to perform frequency analysis of the entire cycle. Furthermore, the scanning points of the vibration points are sequentially scanned and measured with laser light, and the density of the measurement information is increased. A vibration analysis method characterized by the above-mentioned. 4. A vibration analysis apparatus for a vibration signal, wherein a plurality of vibrations caused by a plurality of vibration sources appear periodically, respectively, wherein: a non-contact vibrometer for detecting a time waveform of the vibration signal; Sampling means for sampling a time waveform of the vibration signal within a desired sampling time; dividing the desired sampling time into a plurality of time segments to divide an initial value of each vibration signal of the plurality of vibration sources into a division start position dividing means and, the end of the division from the division start the said time division time waveform when so split at a time waveform having a
A frequency analysis unit including an FFT conversion unit for performing FFT conversion individually for each section up to each section, and a controller including a vibration characteristic identification unit, an image processing unit, and a display unit. 5. The time-division frequency analysis device according to claim 4, wherein the vibration signal has a vibration source composed of a plurality of intermittent impulse response signals. A time-division frequency analysis apparatus characterized by comprising: an FFT conversion section that obtains a time-division power spectrum and performs an averaging process; and a sum calculation section that combines the average value and calculates a power spectrum of the entire basic period. . 6. A vibration analyzing apparatus for a four-cycle engine having a circulating periodic vibration built in each of a plurality of time sections forming a basic cycle, wherein a time corresponding to the basic cycle formed by the circulating periodic vibration signal is provided. A non-contact vibrometer for detecting a waveform, sampling means for sampling a time waveform for a basic cycle, and dividing the basic cycle into a plurality of time segments to have an initial value of a circulating periodic vibration signal at a division start position. Time-dividing means for time-dividing a time waveform into the time-divided time waveform ;
And a controller provided with a vibration characteristic identification unit, an image processing unit, and a display unit. The basic cycle is configured by two revolutions of the engine. A time-division frequency analysis device characterized in that: