JP2008139284A - In particular, vibration sensor for rotary machine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve that the factors of limiting a wide use in a monitoring method by a vibration sensor are the price of a sensor assembly or a signal processing device and the need of each machine for such a constitution. <P>SOLUTION: This sensor comprises a first piezo-electric element 5 which has a first resonance frequency under the influence of vibration, and a second piezo-electric element 6 which has a second resonance frequency having the different resonance frequency to the first resonance frequency, and each of elements 5, 6 is connected to each of voltmeters 9, 10, respectively. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  In order to ensure the reliability of the rotating machines, in particular the pumps, the service and repair departments use so-called predictive maintenance methods to schedule the necessary adjustments outside the operating period of the equipment.

  The principle of predictive measurement is to compare the change in the wear parameters of the machine with the “experience” curve.

  A sensor is permanently installed in the pump during its manufacture to track changes in the parameters described above.

  During the initial operation of the pump at the customer site, the measurement allows the state of previously formed initial parameters meaningful for the pump wear to be recorded.

  By observing those parameters that are most meaningful and predictive of component deterioration over the life of similar products, the selection of monitored parameters is determined experimentally.

By monitoring vibration,
Changes in balance and balance of rotating mass It has been found that the behavior of active components can be evaluated.

  A distinct specific frequency, ie a frequency band between 20 Hz and 16000 Hz, is consistent with each monitored event.

  The vibration measurement is not particularly difficult, and a commercially available vibration sensor is easy to use and economical.

  In the currently used technology, vibration sensors are made of piezoelectric crystals and record all vibrations between 20 Hz and 16000 Hz as well as the corresponding amplitude in the form of voltages.

  The related computer extracts each band of the frequency spectrum, and selects the fundamental frequency and their harmonics in the form of an FFT curve by a Fourier series operation.

  Mathematical processing on the collected vibrations is necessary to be able to divide the frequencies by band and observe each amplitude.

US Pat. No. 5,191,796 (column 8, lines 36 to 48) German Patent Application No. 19612013

  Factors that limit its widespread use in this monitoring method are the sensor assembly, the price of the signal processor, and the need for such a configuration for each machine.

  The present invention improves this problem with sensors. In a sensor including a first piezoelectric element having a first resonance frequency under the influence of vibration and a second piezoelectric element having a second resonance frequency different from the first resonance frequency, each element Is connected to its own voltmeter, or its two elements are connected to the same multiplexer connected to a single voltmeter.

  Under the influence of vibration, a wear characteristic of the first part of the rotating machine at a first resonance frequency and a voltage that can be easily measured by a voltmeter are generated at the terminal of the first piezoelectric element.

  At the first resonance frequency, the second piezoelectric element does not resonate. In practice, no voltage is generated at that terminal. At the second resonant frequency, the characteristics of the wear state of the second part of the rotating machine, the opposite is seen.

  Therefore, the computer that is permanently connected to the machine, or the disadvantage of not being continuously monitored for wear, and the inconvenience of having to constantly move and connect to the computer, alternatively to the rotating machine intermittently Can be fully supplied by a computer coupled to the.

  Each piezoelectric element can be connected to its own voltmeter, and according to an advantageous embodiment, the two piezoelectric elements are connected to a common multiplexer connected to a single voltmeter. Therefore, fewer components are needed to form the sensor, especially in the usual case where there are not only two piezoelectric elements, but also a large number of such elements. Thirty piezoelectric elements are preferably used, and the resonance frequency varies continuously from 1Hz to 1/3 of an octave from 20Hz to 16KHz. In other words, the first resonance frequency differs from the second resonance frequency by 1/3 of one octave. Further, the third resonance frequency differs from the second resonance frequency by 1/3 of one octave.

  According to an embodiment that is very easy to install, all the piezoelectric elements are integrated in the same semiconductor branch. Preferably, if there is also a multiplexer, the multiplexer is incorporated into this branch.

  The present invention also relates to a rotating machine, and more particularly to not only a pump but also a turbine, a fan, or another device that has a fixed portion and a piezoelectric element in a sensor according to the present invention is fixed to the fixed portion. .

  Patent Documents 1 and 2 do not separate electrical signals obtained continuously over a period of time, but collect and superimpose signals (for example, US Pat. Reference states that the output level of the sensor is substantially constant).

  FIG. 1 shows a pump comprising a shaft (1) driven by a motor (2) and supported by a bearing (3). The shaft (1) rotates the hydraulic wheel.

  Only two of the 30 piezoelectric elements are shown, ie the first piezoelectric element (5) and the second piezoelectric element (6) are fixed to the bearing (3).

  When exposed to mechanical vibration, the first piezoelectric element (5) has a resonance frequency that is different from the resonance frequency of the second piezoelectric element (6). In order to obtain this frequency difference, the two piezoelectric elements are designed differently, in particular with different dimensions.

  The terminals of the piezoelectric elements (5, 6) are connected to a multiplexer (7) and are also connected to a voltmeter (8).

  The voltmeter continuously displays voltages generated at the terminals of the piezoelectric element (5), the terminals of the piezoelectric element (6), and the terminals of the following 28 other elements over a certain period.

  If the voltage is at the voltmeter (8) at a time corresponding to one of the element (5) or the element (6), the part of the pump corresponding to one resonant frequency of 30 piezoelectric elements The degree of use can be deduced therefrom.

  In FIG. 2, the terminals of the piezoelectric elements (5, 6) are directly connected to the voltmeters (9, 10) without interposing a multiplexer.

  In this case, the piezoelectric elements (5, 6) are in the T branch of the same semiconductor and the voltmeters are independent, whereas in the embodiment of FIG. It remains independent from the T branch, but a multiplexer (7) is also integrated into the T branch.

In the accompanying drawings which are given solely by way of example, FIG. 1 is a diagram showing a preferred embodiment of a rotating machine according to the invention. Another specific example is shown.

Claims (6)

A first piezoelectric element (5) having a first resonance frequency under the influence of vibration, and a second piezoelectric element (6) having a second resonance frequency different from the first resonance frequency; In sensors including
Each element is connected to its own voltmeter (9, 10), or its two elements are connected to the same multiplexer (7) connected to a single voltmeter (8). A sensor characterized by that.   The sensor according to claim 1, wherein the first resonance frequency differs from the second resonance frequency by 1/3 of one octave.   3. A sensor according to claim 2, comprising 30 piezoelectric elements and continuously having a different resonance frequency by 1/3 of an octave.   4. The sensor according to claim 1, wherein all the piezoelectric elements are incorporated in the same semiconductor branch.   5. The sensor according to claim 1, wherein the multiplexer is incorporated in the branch.   6. A rotating machine having a fixed part, wherein the piezoelectric element of the sensor according to claim 1 is fixed to a fixed part.

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