JP2004061347A - Piezo-electric vibration energy sensor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a piezoelectric vibration sensor which operates semipermanently without power supply from outside and records the number of vibration for a long time by using fatigue due to polarization inversion of a ferroelectric thin film. <P>SOLUTION: The piezoelectric vibration sensor comprises: a charge generating piezoelectric material 1 for changing vibration energy into electric energy; a ferroelectric memory 2 for counting energy and the number of vibration by using charge generated; an RF antenna 4 for reading recorded data from outside without contact; and a control circuit 3. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to prediction of fatigue failure due to vibration of a structure such as a building, an automobile, a ship, and an aircraft, extension of life by diagnosis of remaining life, and reduction of maintenance cost.
[0002]
[Prior art]
Until now, it was difficult to diagnose the remaining life of buildings, automobiles, ships, aircraft, and the like. As a conventional technique, there is a means for periodically diagnosing a damaged portion due to internal fatigue using X-ray or ultrasonic diagnosis. In addition, as a technique developed in recent years, there is a means for monitoring by embedding a sensor such as an optical fiber or a strain gauge in a place where damage due to fatigue is likely to occur.
[Problems to be solved by the invention]
The conventional means for diagnosing a damaged portion due to internal fatigue using X-ray or ultrasonic diagnosis is used only for a special structure such as a nuclear power plant or an aircraft due to an increase in maintenance cost. In addition, the means for monitoring embedded sensors such as optical fibers and strain gauges requires an external energy supply for monitoring, and cannot be used by the sensor alone. Required. For this reason, the production cost is increased and it can be used only for special structures.
[0004]
An object of the present invention is to solve the above-mentioned conventional problems, and specifically, has the following problems.
(1) Operate semi-permanently without requiring external power supply.
(2) It is possible to record tens of thousands to millions of vibrations over a long period of several decades.
(3) The structure of the sensor is simplified, the size can be reduced to about the size of a business card or smaller, and the price is lower than the conventional one, and it is used not only for special structures but also for general consumer use. .
[0005]
[Means for Solving the Problems]
In order to solve the above-mentioned problems, the present invention includes a charge-generating piezoelectric material that converts vibrational energy into electric energy, and a ferroelectric memory that repeats polarization inversion by the generated charge, and is characterized by fatigue caused by repetition of the polarization inversion. Thereby reducing the value of remanent polarization and enabling the number of vibrations to be counted.
[0006]
In order to solve the above-mentioned problems, the present invention provides a charge-generating piezoelectric material that converts vibration energy into electric energy, a ferroelectric memory that repeats polarization reversal by the generated charge, an RF antenna, and control of the RF antenna. Circuit, wherein the ferroelectric memory reduces the value of remanent polarization due to fatigue caused by the repetition of the polarization inversion, enables the number of vibrations to be counted, and the RF antenna stores data recorded by the ferroelectric memory. A piezoelectric vibration energy sensor characterized in that the piezoelectric vibration energy sensor reads the data from outside without contact.
[0007]
BEST MODE FOR CARRYING OUT THE INVENTION
Embodiments of a piezoelectric vibration energy sensor according to the present invention will be described based on examples with reference to the drawings. The present invention is a vibration energy sensor which can be driven semi-permanently without supplying energy from the outside and digitize and record a vibration distortion energy signal applied to a structure. It will be explained.
[0008]
(principle)
Normally, a ferroelectric thin film used as a nonvolatile memory records data using polarization inversion that occurs when a voltage is applied. However, when the polarization reversal is repeated, the value of the remanent polarization of the film decreases due to fatigue. The present invention pays attention to this point and utilizes the piezoelectric vibration energy sensor.
[0009]
That is, when vibration is applied to the place where the piezoelectric sensor is attached, the vibration energy is converted into electric energy by the piezoelectric effect, but the electric energy is lost with the passage of time, and is stored as electric energy for a long time. It is difficult. In order to record this electric energy for a long time, in the present invention, the electric energy is converted into fatigue of remanent polarization of the ferroelectric thin film and recorded.
[0010]
(Example)
FIG. 1 is a diagram showing a configuration of a vibration energy sensor according to the present invention. As shown in FIG. 1, the vibration energy sensor includes a charge generation piezoelectric body 1 that converts vibration energy into electric energy, a ferroelectric memory 2 that counts vibration energy and the number of times using generated charges, and records. It comprises an RF antenna 4 for reading data from outside in a non-contact manner and a control circuit 3 for the RF antenna.
[0011]
When using this vibration energy sensor, it is attached to a structure such as a building, an automobile, a ship, or an aircraft by sticking it to a place where fatigue failure due to vibration is likely to occur.
[0012]
When vibration as shown in FIG. 2A is applied to the place where the vibration energy sensor is attached, the vibration energy is converted into electric energy as shown in FIG. 2B by the piezoelectric effect of the piezoelectric body 1 for charge generation. With this electric energy, the ferroelectric memory 2 voltage is applied.
[0013]
When a voltage is applied to the ferroelectric memory 2 by electric energy due to vibration, the number of vibrations is recorded by polarization reversal. However, when the polarization reversal is repeated, the value of the remanent polarization of the film decreases due to fatigue as shown in FIG. The degree of the decrease due to fatigue depends on the number of vibrations, the material characteristics of the ferroelectric thin film, the applied voltage, and the like.
[0014]
Therefore, the vibration energy sensor of the present invention is designed such that the number of vibrations is intentionally manufactured so that the decrease due to fatigue exceeds a predetermined threshold value in the order of tens of thousands to millions of times. By applying, it is possible to grasp the state of fatigue.
[0015]
In particular, by using such ferroelectric thin films having different fatigue characteristics collectively as one cell, the number of times of polarization inversion can be accurately obtained from each fatigue state.
[0016]
In the example of FIG. 2B, data is written in a cell whose polarization is inverted at threshold voltages L1, L2, and L3. In this vibration, polarization reversal occurs once in the cell L1, twice in the cell L2, and three times in the cell L3, and the cell is fatigued. By preparing a large number of cells having different voltages for polarization reversal, it is possible to record the exact magnitude of the vibration energy.
[0017]
After that, energy is temporarily supplied from the outside using an RF antenna or the like to operate the control circuit, and the information is transmitted to the outside as accurate fatigue information compared with the ferroelectric thin film cell for comparison. As a result, it is possible to know the sum of the strain energies applied so far to this structure, and to perform a remaining life diagnosis from the material characteristics of the structure.
[0018]
As described above, the present invention has been described with reference to the embodiments. However, it is needless to say that the present invention is not limited to such embodiments, and there are various embodiments within the scope of technical matters described in the claims.
[0019]
【The invention's effect】
If the present invention having the above-described configuration is used, by attaching this sensor to a structure such as a building, an automobile, a ship, and an aircraft, the magnitude and the number of strains applied to the structure can be counted. This makes it possible to predict the fatigue fracture of the structure, thereby improving the reliability of the structure and reducing the maintenance cost.
[0020]
That is, according to the present invention, the piezoelectric vibration energy sensor can operate semi-permanently without supplying electric power from the outside by utilizing the piezoelectric effect. Further, by utilizing fatigue due to polarization reversal of the ferroelectric thin film as a recording medium, it is possible to record tens of thousands to millions of vibrations over a long period of several decades.
[0021]
The structure of the sensor is simple, the size can be as small as the size of a business card or smaller, and the sensor can be manufactured at a lower price than a conventional system. Therefore, it can be used not only for special structures but also for general consumer use.
[Brief description of the drawings]
FIG. 1 is a diagram illustrating an overall configuration of a vibration energy sensor according to the present invention.
FIG. 2 is a diagram illustrating conversion of vibration energy into electric energy in a vibration energy sensor according to the present invention.
FIG. 3 is a diagram illustrating the fatigue behavior of a ferroelectric thin film capacitor in the vibration energy sensor according to the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Piezoelectric for charge generation 2 Ferroelectric memory 3 Control circuit 4 RF antenna

Claims (2)

A piezoelectric element for generating electric charge that converts vibration energy into electric energy, and a ferroelectric memory that repeats polarization inversion by the generated electric charge. A piezoelectric vibration energy sensor capable of counting the number of times. A charge generation piezoelectric body that converts vibration energy into electric energy, a ferroelectric memory that repeats polarization inversion by the generated charge, an RF antenna, and a control circuit for the RF antenna,
In the ferroelectric memory, the value of the remanent polarization decreases due to fatigue caused by the repetition of the polarization inversion, and the number of vibrations can be counted.
A piezoelectric vibration energy sensor, wherein the RF antenna is configured to read data recorded by the ferroelectric memory from outside without contact.

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