JPH0748070B2 - Sliding motion part reliability evaluation system - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial application] The present invention relates to a diagnostic system using an acoustic emission (AE) measurement method, and in particular, a newly developed product having a sliding motion section that performs rotational motion. The present invention relates to a reliability evaluation system of a sliding motion unit suitable for carrying out a reliability test including the life of the device.

[Conventional technology]

A compressor used for a room air conditioner, a refrigerator, etc. has a sliding motion unit that performs a rotary motion. The compressor compresses a refrigerant such as CFC gas, and the sliding motion part is precisely made. In the development of new products, if abnormalities such as poor lubrication of sliding motion parts or deterioration of materials of sliding members occur due to poor design, the sliding motion parts will be damaged and the sliding motion parts will be locked and burned. Leading to. Therefore, in developing a new compressor product, it is necessary to perform a reliability test.

Conventionally, a compressor reliability test is performed for several months (for example, about six months).
During this period, test operation is performed and the compressor is disassembled after the test operation is completed. The test operation may be a continuous operation or an intermittent operation with different operation modes, and further an operation in which a refrigerant called liquid return is changed from gas to liquid during operation.

However, in such a reliability test, the test result cannot be known until after the test operation is completed, and the product development period cannot be avoided.

On the other hand, as a method for diagnosing abnormality during operation of the compressor, for example, as described in JP-A-62-75092, noise or vibration signals generated from the compressor are detected, and the maximum and minimum values of the signals are detected. A method for determining an abnormality from the ratio with a value or a limit value is set for the time characteristic pattern and frequency pattern of the vibration signal generated from the compressor as described in JP-A-58-176545. Methods have been proposed for diagnosing an abnormality that exhibits a pattern exceeding the range. However, the operating state of the compressor is very unstable at the start of rotation and when the liquid returns in the intermittent operation, and noise and vibration generated from the compressor also change greatly. Therefore, there is a practical problem that an abnormality cannot be detected accurately and early.

In order to solve such a problem of the conventional technique, it is considered to perform reliability diagnosis of the compressor by using the AE signal.

[Problems to be Solved by the Invention]

In recent years, inverter noise compressors have been developed, but the revolution speed of the inverter noise compressor changes significantly due to load fluctuations. The reliability test operation is also performed by changing the load. AE during unstable conditions where the compressor speed changes
The amplitude level of the signal changes. For this reason, there is a problem that the compressor, especially the sliding motion part, cannot be accurately diagnosed.

An object of the present invention is to provide a reliability evaluation system for a sliding motion part, which can accurately and early perform reliability diagnosis of the sliding motion part.

[Means for Solving the Problems]

The present invention determines that the compressor is in a stable state as a result of re-determination after activating the compressor and determining that the number of revolutions has reached a stable state, and then determining again by the fluctuation rate of the rotation signal of the compressor. When the judgment is made, the AF signal is taken in to judge the abnormality.

[Action]

When the rotation speed of the compressor is stable, the amplitude level of the AE signal is stable and the background noise is small. Therefore, it becomes possible to accurately and early perform abnormality diagnosis on the AE signal.

〔Example〕

 FIG. 1 shows an embodiment of the present invention.

In FIG. 1, the AE sensor 2 is mounted in the chamber of the compressor 1. The compressor 1 is provided with a rotation detection sensor 3 for detecting the number of rotations. The output of the AE sensor 2 is amplified by the amplifier 4 and then detected by the detector 5, and the detected signal is input to the A / D converter 6. The output (rotation signal) of the rotation detection sensor 3 is also input to the A / D converter 6. The rotation signal of the rotation detection sensor 3 is also input to the signal determination unit 7. The signal determination section 7 is composed of a rising edge detection circuit 7a, a time counter 7b and a stability check circuit 7c.
The rotation rising signal and the rotation stabilizing signal output from the signal determining unit 7 are transmitted to the personal computer 8 via the digital interface DIO. The personal computer 8 judges the stable state again based on the fluctuation rate of the rotation signal of the compressor 1 after the AND condition of the rotation start signal and the rotation stabilization signal is satisfied, and when it is in the stable state, the A / D converter 6 is operated via the interface GPIB.
The detection signal (AE signal) is acquired from and diagnosed. Personal computer 8
The diagnostic result and the AE signal are displayed on the CRT display 9 or printed on the printer 10. Floppy disk 11
Various data such as diagnosis time, AE signal average value, AE signal peak value, and frequency analysis result are stored in.

Next, the operation will be described with reference to the flow chart shown in FIG. 2 and the time chart shown in FIG.

In FIG. 2, the part surrounded by the broken line is the process of the signal determination unit 7, and the part surrounded by the alternate long and short dash line is the process by the personal computer 8.

When the compressor 1 is operated as shown in FIG. 3, the rotation signal of the rotation detection sensor 3 is input to the signal determination unit 7. The rise detection circuit 7a compares the rotation signal with the set rotation speed to detect the rotation rise of the compressor 1 (period I in FIG. 3). When the number of revolutions of the compressor 1 reaches the set number of revolutions and the time set by the time counter 7b (the period II in FIG. 3) elapses, the time counter 7b outputs a rotation rising signal. The time of the time counter 7b is set only for the time until the rotation speed of the compressor 1 stabilizes.
The rotation rising signal is input to the stability check circuit 7c. When the rotation rising signal is input, the stability check circuit 7c checks the stability of the rotation speed output from the rotation detection sensor 3 (period III in FIG. 3). When the stability of the rotation speed is within the set range, the stability check circuit 7c outputs the rotation stabilization signal shown in FIG. The rotation start signal and the rotation stabilization signal are transmitted to the personal computer 8 through the interface DIO. When the AND condition of the rotation start signal and the rotation stabilization signal is satisfied, the personal computer 8 will use the interface GPIB.
Through, the respective outputs of the detector 5 and the rotation detection sensor 3 are made to be taken in by the A / D converter 6, and the processing of taking in the AE signal and the rotation signal is executed (IV period in FIG. 3). The personal computer 8 receives an AE detection signal 50 and a rotation signal 51 as shown in FIG. 4, for example. It should be noted that the rotation start-up signal is reset after a lapse of a prescribed time as shown in FIG. 3 to avoid taking in the AE signal and the rotation signal under the unstable operation state when returning the liquid.

When the personal computer 8 takes in the rotation signal from the A / D converter 6, the personal computer 8 obtains the fluctuation rate of the rotation signal in step 41a. The fluctuation rate of the rotation signal is obtained as follows. The number of words w _i at the zero-cross point of the rotation signal shown in FIG. 6 fetched from the A / D converter 6 is measured, and the average value thereof is calculated by the following equation.

In step 41a, after obtaining the variation rate, it is determined whether or not it is within the range shown by the equation (2). If it is within the range, step 42
The process shifts to a and 42b, and when it is out of the range, step 41b
Then, the processing for fetching the signal from the A / D converter 6 is executed again.

−w _k <w _i <+ w _k (2) Note that expression (2) w _k has no particular effect on the addition and averaging process even if there is a slight change in the number of revolutions, so it is provided to have a little width. It is an allowable value. When it is determined that the equation (2) is not satisfied for the specified number of times (k) or more in step 41b, the process proceeds to step 42g, and the message of the rotational speed instability is output to the outside by the CRT display 9 or the printer 10. The operator can take a measure such as a defective sensor or a defective mounting that causes a fluctuation in the rotation speed, or a replacement of the compressor itself, by seeing the message that the rotation speed is unstable.

On the other hand, if it is determined to be within the range in step 41a, step 42a
The arithmetic mean processing is executed at. The above averaging process is AE
This is performed in order to remove random noise included in the detection signal 50 and effectively extract only the AE signal generated due to the sliding portion damage. At the same time as the averaging process in step 42a, the frequency analysis process of the AE detection signal 50 is performed in step 42b. After step 42a, a waveform calculation is performed in step 42c to detect the number of AE signals generated per revolution of the compressor for the arithmetic mean processing waveform. If abnormalities occur in the sliding parts of the compressor,
As shown in the figure, in addition to the steady AE wave 21 generated from a normal product, the abnormal AE wave 60 is generated from the abnormal sliding portion due to scratches. In step 42c, as shown in FIG. 7, the threshold value V _th is compared with the arithmetic mean processing waveform, and the number N of signals _exceeding the threshold value V _th is calculated. Step number of signals in 42d N and compares the set value k _1, the process proceeds to step 42h is judged to be normal when the k _1> N, the process proceeds to step 42i and determines that the abnormality when Nk _1. In step 42h or 42i, the determination result is output to the outside via the CRT display 9 and the printer 10.

Next, in step 42b, frequency analysis processing is performed,
AE generated from normal products and abnormal wear products shown in Fig. 7
The frequency analysis of the waveform 61 is as shown in FIG. For normal product, the frequency component f _r corresponding to the rotational speed of the compressor becomes a first peak voltage, in the form of its fold harmonic component is attenuated gradually. However, in the case of abnormal wear products,
Only the f _r value is noticeable. When the process of step 42b ends, the process proceeds to step 42e and the frequency ratio calculation process is executed. In step 42e, the calculation shown in the following equation is executed based on the frequency analysis data.

K _r f = Af _r / Af _t (3) Af _{t in the} equation (3) is the total value of the intensities over all frequencies of the frequency analysis result, and Af _r is the frequency component corresponding to the compressor speed. Strength. In step 42f, the frequency ratio K _r f value obtained in step 42e is compared with the set value k ₂ to determine whether it is normal or abnormal. The determination result of step 42f is output to the outside by the CRT display 9 and the printer 10.

In this way, the abnormality of the sliding motion part of the compressor 1 is diagnosed by using the AE signal. However, when the rotation state of the compressor 1 is in a stable state, the AE signal is captured and diagnosed. Can be done accurately. FIG. 5 is a simulation result of the averaging process. As shown in FIG. 5, it can be seen that when there is no fluctuation in the number of revolutions, there is no disturbance in the waveform as compared with when there is fluctuation.

FIG. 9 shows another embodiment of the present invention.

In the embodiment shown in FIG. 9, an uninterruptible power supply 12 is provided as a power source for the personal computer 8 and a plurality of compressors 1a-1n are provided with AE sensors 2a-2n and rotation detection sensors 3a-3n, respectively. Are switched by multiplexers 70a and 70b to be sequentially fetched.

In the embodiment shown in FIG. 9, a large number of compressors can be diagnosed simultaneously with a common diagnostic device.

〔The invention's effect〕

According to the present invention, it is possible to accurately diagnose an abnormality in the sliding motion portion using the AE signal, and also to diagnose the abnormality early during the test operation.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention, FIG. 2 is a flow chart for explaining the operation of the present invention, FIG. 3 is a time chart for explaining the operation of the present invention, and FIGS. Is a waveform diagram for explaining the present invention, and FIG. 9 is a configuration diagram showing another embodiment of the present invention. 1 ... Compressor, 2 ... AE sensor, 3 ... Rotation detection sensor, 5 ... Wave detector, 6 ... A / D converter, 7 ... Signal determination unit, 8 ... Personal computer.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Sosuke Tanaka 800 Tomita, Ohira Town, Shimotsuga-gun, Tochigi Hitachi Co., Ltd. Tochigi Factory (56) Reference JP 62-151621 (JP, A) JP Sho 59-63529 (JP, A) JP 62-19755 (JP, A) JP 63-304128 (JP, A) JP 58-176545 (JP, A) JP 63-304131 (JP, A)

Claims (1)

[Claims] 1. A sliding motion device that performs a rotary motion, a rotation detection sensor that detects the rotation of the sliding motion device, an AE sensor provided in the sliding motion device, and an AE sensor that is detected by the AE sensor. A detector for detecting an AE signal, a state determination device that inputs the rotation signal detected by the rotation detection sensor and determines whether the rotation speed of the sliding motion device is in a stable state, and the state determination device is After determining the stable state, the fluctuation rate of the rotation signal is obtained to re-determine whether the sliding motion device is in the stable state, and when it is determined to be in the stable state by the re-determination, it is detected by the detector. A reliability evaluation system for a sliding motion part, comprising: a diagnostic device for taking an AE signal and determining an abnormality of the sliding motion device.