JPS6341012B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a device for detecting the operating state of a machine or the like, such as an abnormality or a sign thereof, based on the sound or vibration generated by the machine or the like.

In order to prevent accidents with machinery, etc., or to predict the lifespan of machinery, etc., the operating state of machinery, etc., is measured based on the sound or vibration generated by the operation or operation of machinery, etc. Observations are often made. For example, the noise generated by rotating gears that mesh with each other is
This occurs because the gear itself or its surrounding members are excited by the discontinuous impact force caused by the meshing, and the impact force is mainly caused by errors in the tooth profile. The meshing noise tends to increase as the tooth profile error increases, so by measuring this meshing noise, it is possible to detect gear tooth profile errors or wear and tear during actual operating conditions. .

However, in reality, a large number of gears coexist in a machine, and there are noise components unrelated to the meshing of the gears, so in order to accurately detect the operating state of a gear, it is necessary to detect these unnecessary components. It is necessary to remove the noise and extract only the target gear meshing sound. Therefore, two noise removal techniques are used in conventional state detection devices. Part 1
The first is to limit the passband of the signal using a bandpass filter. As mentioned above, the noise generated by meshing is caused by the natural vibration of the gear itself or its surrounding parts, so by focusing only on the main component and blocking all other components, noise components can be eliminated. Remove. The noise component can be removed by appropriately selecting the passband of the bandpass filter, and the signal obtained from the bandpass filter is considered to be the natural vibration frequency component of the gear. It is extremely difficult to detect abnormalities or signs thereof, such as scratches on gears.

The other method is to remove irregular signals by focusing on the periodicity of the signals that indicate the abnormality.
The goal is to eliminate noise and extract only signals that indicate gear abnormalities or their signs. Gears are normally rotated at a constant rotation speed, and the meshing noise caused by gear abnormalities has periodicity.
Therefore, if the signals for each rotation of the gears are synchronized and superimposed, the above-mentioned meshing noise components will accumulate and increase, but since the irregular noise is thought to have a symmetrical distribution, the positive and negative cancel each other out. Does not increase.
For example, if the superposition is performed m times and then averaged, the variance of the noise becomes 1/m, which is very small. This method is effective for relatively low frequency signals or events that can be precisely synchronized, but
When applied to gear condition detection, the result is that the meshing sound component is also lost as the noise component decreases. This is because in gears and the like, it is difficult to accurately match the phase of signals in each cycle. For example, the natural frequency of a gear with a pitch circle diameter of 125 mm, a module of 5 mm, and a tooth width of about 20 mm is 5 to 10 KHz.
If there is a time difference of 0.1ms between the first and second rotation signals in the 5KHz signal,
This corresponds to a phase difference of 180 degrees, so when these signals are superimposed, they cancel each other out and the meshing sound disappears. It is virtually impossible to synchronize the detection signal from the gear sound detector with the phase signal from the gear rotation phase detector with an accuracy of 0.1 ms or more.

The present invention has been made in view of the above circumstances, and provides a detection device that can eliminate unnecessary noise and accurately extract only desired signals representing the state of a machine, etc. .

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments in which the present invention is applied to gear state detection will be described in detail with reference to the drawings.

A detection signal from a sound or vibration detector 1 placed near the gear is amplified by an amplifier 2 and then sent to a bandpass filter 3. Of the detection signals from the detector 1, only the natural vibration frequency component of the target gear (signal A, see Figure 3) is transmitted to the filter 3.
is selectively extracted, and unnecessary components such as noise are removed. The output signal A of the filter 3 is then sent to an envelope detection circuit 4. Band pass filter 3
If the extracted signal A is averaged as it is, the damaged signal will disappear, but this is because the damaged signal is a high-frequency signal, and the phase of the signal will have to be strictly controlled in the subsequent signal superposition stage. is difficult to match. Therefore, envelope detection is performed as a preprocessing for averaging to remove high frequency components. As shown in FIG. 2, this detection circuit 4 is composed of an absolute value detection circuit 41 or a square circuit 42 that rectifies the signal, and a smoothing circuit 43 that smoothes the outputs of these circuits 41 and 42. The envelope waveform of signal A is detected and an envelope signal B (see FIG. 3) is output. On the other hand, a phase detection signal is output from a phase detector 6 such as a rotary transducer installed on the rotating shaft of a gear or a rotating shaft interlocked with the rotating shaft, and this signal is It is input to the averaging circuit 5 as a synchronizing signal. The averaging circuit 5 superimposes the envelope signal B from the detection circuit 4 multiple times for each rotation of the gear while being synchronized with the phase detection signal. This superimposed final detection signal C is displayed or recorded on an X-Y recorder, cathode ray tube oscilloscope, or other display or recording device 7.

Of the sound or vibration detection signals generated from gears, etc., only the natural vibration frequency component A of the gear to be detected is extracted by the filter 3, so there is no noise component unrelated to the sound caused by gear meshing. has been removed in advance. In FIG. 3, the period of this natural vibration is indicated by t. Then, the envelope waveform B of the natural vibration frequency component signal A is detected by the envelope detection circuit 4, and the information of the gear meshing sound is stored in the form of an envelope. Next, since this envelope signal B is superimposed in synchronization with each rotation of the gear, only the components with the same period as the rotation period T of the gear are accumulated and increased, and other irregular signals The components are averaged and gradually approach a constant value. In other words, the observation signal S' (θ ₁ ) at a certain rotation angle (θ ₁ ) of the gear is determined by dividing the periodic signal by S (θ ₁ ) and the noise by n(θ ₁
)
Then, S′(θ ₁ )=S(θ ₁ )+n(θ ₁ ) ………(1) If we synchronize and average over m times, we get 1/m _n 〓 ^k=1 S′k (θ ₁ )=S(θ ₁ )+1/m _n 〓 ^k=1 nk(θ ₁ )...(2). If the noise n(θ ₁ ) has a normal distribution, the variance will be 1/m and the S/N ratio will be improved. This processing is performed by the averaging circuit 5, and the phase detection signal becomes the synchronization signal at this time. Therefore, in the final detection signal C, periodic signal components representing scratches on the gear or other abnormalities or signs thereof are left in an amplified manner. Period t of natural frequency component A from filter 3
Even if the envelope signal B is very short, the envelope signal B has a relatively long period or time width. For the line signal B, this corresponds to an extremely small phase shift, and the information expressed in the envelope of the meshing sound never cancels out each other.

FIG. 4 shows the waveform obtained when the device according to the present invention was actually applied to a gear with a single flaw. The purpose of this test is to detect scratches on gears. The natural vibration frequency component A has a passband of 500
It has passed through a filter 3 set at Hz to 20KHz. Components D ₁ and D ₂ appearing in the envelope signal B representing the envelope of the signal A indicate flaw signals at the first and second rotations of the gear, respectively. It will be understood that the detection signal C is an average of the eight times the signal B is superimposed, and the noise component disappears and only the flaw signal D clearly appears.

It goes without saying that the condition detection device according to the present invention can be applied not only to gears but also to any device that operates with a predetermined cycle, such as machinery such as bearings and clutches, internal combustion engines, and other devices.

As described above, according to the present invention, the condition of a machine, etc. that operates at a predetermined cycle, such as an abnormality or its sign, can be accurately detected based on the sound or vibration generated from the target machine, etc. during its operation. It becomes possible to detect

[Brief explanation of the drawing]

The drawings show an embodiment of the present invention. FIG. 1 is an overall block diagram, FIG. 2 is a block diagram showing an envelope detection circuit, FIG. 3 is a waveform diagram of signals from each block, and FIG. 4 is an actual diagram. FIG. 2 is a waveform diagram of a signal obtained in a test conducted in 2008. 1...Sound or vibration detector, 3...Band pass filter, 4...Envelope detection circuit, 5...Averaging circuit.

Claims (1)

[Claims] 1 A detector that detects sounds or vibrations from machinery, etc.;
A bandpass filter that selectively extracts the natural vibration frequency component of the target machine, etc. from the detection signal of this detector, an envelope detection circuit that detects the envelope waveform of the output signal of this filter, and a predetermined frequency component of the machine, etc. A state detection device for a machine, etc., comprising an operation cycle detector that detects an operation cycle, and an averaging circuit that superimposes the output of the envelope detection circuit multiple times in synchronization with the detected operation cycle.