JPH08129071A - Earthquake vibration detector and si value-detecting apparatus - Google Patents

Abstract

PURPOSE: To provide an SI value detector apparatus which is small, inexpensive and accurate with remarkably small noises caused by heat. CONSTITUTION: An SI value-detecting apparatus 1 is provided with an earthquake vibration detector consisting of an acceleration detection means 2 for detecting an earthquake vibration using a piezoelectric element and an amplifier means 3 for amplifying an output of the acceleration detection means 2, and an SI conversion circuit 4 for converting an output of the earthquake vibration detector to an SI value. In the apparatus 1, the amplifier means 3 has a considerably high input impedance of not lower than 2000MΩ and selectively amplifies signals of a frequency band of 0.1-100Hz. The SI value detection circuit 4 selects a larger one of speed response values to two natural frequencies in a speed response spectrum obtained from the output of the acceleration sensor and multiplies the output by 1.75/2.4 thereby to obtain the SI value.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention has an SI value (Spectrum Intensity) in order to minimize damage caused by an earthquake.
Value to determine the earthquake damage value,
Seismic motion detector (acceleration sensor) for SI value measurement system to implement safety measures such as "stop supply of gas in gas pipeline network", "stop supply of chemical raw material in chemical plant", "stop elevator" ) And an SI value detector.

[0002]

2. Description of the Related Art In order to detect seismic vibration, it has been conventionally practiced to detect acceleration by using an accelerometer and indicate the magnitude of seismic motion. The development of a sensor for detecting such acceleration is being rapidly made mainly for automobile airbag sensors. This sensor has only one sensitive axis, and the characteristics at low frequencies deteriorate rapidly. Therefore, when using this sensor for seismic measurement, it is necessary to place the two sensors exactly orthogonal to each other. There are problems such as poor sensitivity at the low frequency required for measurement.

Further, the damage caused to the structure by the earthquake motion is not always related to the maximum acceleration,
It has been confirmed by past seismic observations and vibration experiments that damage to structures may be minor even when the maximum acceleration is large. Therefore, in the event of a major earthquake, the system will be automatically shut down to prevent the spread of damage to equipment and systems such as city gas, water, electricity, transportation, chemical plants, and elevators, and to prevent the occurrence of secondary disasters. In the automatic emergency stop device, when controlling the system using only maximum acceleration detection, it operates to stop these systems even if there is no damage to these structures or facilities or a slight earthquake. Will end up. There is a problem in that a complicated and enormous amount of work and time are required to restore the system that has been stopped, which causes a great loss.

Therefore, instead of detecting the seismic motion due to acceleration, for example, as shown in Japanese Patent Laid-Open No. 62-12884, the system may be controlled by using an SI value that is deeply related to the magnitude of damage due to the seismic motion. it was thought. This S
The I value is a scale defined by the average value of the response speed in the range of 0.1 second to 2.5 seconds of the natural period of the velocity response spectrum of the one-degree-of-freedom vibration system with a damping constant of 20%. It is known that it can be determined in comparison with the correlation of the damage of the object and is well correlated with the damage of the structure.

Gas supply companies such as Tokyo Gas spread the installation of a gas meter having a function of interrupting the supply of gas at a certain acceleration or more as an emergency measure in case of an earthquake, and the vibration energy of a structure caused by an earthquake. We have developed a facility that measures SI value that has a strong correlation with earthquake damage and focuses on, and automatically shuts off the gas supply to the relevant parts of the gas pipeline network when this value exceeds a predetermined value. I have done the installation.

A conductive coil type accelerometer is used as the SI value measuring accelerometer used in this apparatus. However, the accelerometer itself is expensive because the outer shape is large and the buried portion is limited. Therefore, there was a problem that the system became expensive. That is, S
The seismic motion detector for SI value measurement that can measure I value is an expensive product of 1 million yen per unit, and has not been widely spread to local gas companies. Also, a simple SI
As a value detecting accelerometer, a system in which the natural frequency of the pendulum is adjusted to 2 seconds is used. However, this method also has a problem that the external appearance is large and the buried portion is limited.

The acceleration detector for SI value measurement needs to be a sensor capable of detecting biaxial or triaxial acceleration in accordance with the vibration of an earthquake. Moreover, the acceleration detector for SI value measurement needs to be a sensor with high accuracy of an acceleration measurement value. Furthermore, the output of the acceleration detector for SI value measurement must be small in fluctuation due to heat and high in measurement accuracy.

[0008]

SUMMARY OF THE INVENTION An object of the present invention is to provide a small and inexpensive seismic motion detector for SI value measurement and an SI value detector device. A further object of the present invention is to provide an SI motion measuring seismic motion detector and SI value detecting device which are highly accurate and have little noise due to heat.

[0009]

The seismic-motion detector of the present invention comprises an acceleration-detecting means for detecting acceleration of seismic-motion and converting it into an electric signal, and an amplifying means for amplifying a signal output by the sensor element section. Further, the SI value detecting device of the present invention is an acceleration detecting means for detecting an acceleration of seismic motion and converting it into an electric signal, an amplifying means for amplifying a signal output by the sensor element part, and an output of the amplifier for converting into an SI value. It is provided with a SI value conversion means.

Further, the seismic motion detector and SI of the present invention
In the value detecting device, the input impedance of the amplifying means is made extremely high so that sufficient output can be obtained even in the frequency range of 0.1 to 100 Hz corresponding to the seismic frequency.

Further, in the present invention, in order to eliminate fluctuation due to heat of the power source, an amplifier circuit having a reduced number of parts is used to improve measurement accuracy.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The construction of an embodiment of the SI value detecting apparatus according to the present invention will be described below with reference to the drawings. FIG. 1 shows an embodiment of an SI value detecting device using a seismic motion detector according to the present invention.
The SI value detecting device 1 includes an acceleration detecting means 2 for detecting triaxial acceleration, an amplifying means 3 for amplifying and outputting a low frequency component of the output of the acceleration detecting means 2, and an SI output from the amplifying means 3. SI value conversion means 4 for calculating a value. The acceleration detecting means 2 and the amplifying means 3 constitute a seismic motion detector.

As the acceleration detecting means 2, it is possible to use an acceleration sensor which can detect accelerations in three axial directions, which is formed by using a piezoelectric ceramic element which is small, lightweight and inexpensive. FIG. 2 shows the outline of the configuration of this acceleration sensor, and FIG. 3 shows its operation.

FIG. 2A is a plan view of an example of the acceleration detecting means used in the present invention, and FIG. 2B is its AA line.
It is a longitudinal cross-sectional view along the line. The acceleration detecting means 2 includes a flexible disc-shaped strain element 22 having a peripheral portion fixed to a fixed frame 21, a lower electrode 23 provided on the upper surface of the strain element 22, and the electrode. Piezoceramic 2 stacked on top of
5 and the upper electrodes 26 and 27 attached to this surface
And a weight 29 attached to the central portion of the lower surface of the flexure element 22. The flexure element 22 includes a pair of elements 28X for detecting strain in the X-axis direction.
And four pairs of piezoelectric elements, that is, a pair of elements 28Y that detect strain in the Y-axis direction and two pairs of elements 28Z that detect strain in the Z-axis direction.

The operating principle of the acceleration detecting means 2 will be described with reference to FIG. 3A shows the principle of detecting acceleration in the X-axis direction or Y-axis direction, and FIG. 3B shows the principle of detecting acceleration in the Z-axis direction. In (A), when the acceleration in the X-axis direction acts as illustrated, for example, the weight body 2
9 rotates counterclockwise around the portion O attached to the flexure element 22 as a center. Due to this rotation, the strain element 22 also rotates counterclockwise around O, and a strain having a magnitude proportional to the magnitude of acceleration is generated between the strain element 22 and the fixed frame 21. A voltage having the illustrated polarity is generated at each electrode of the piezoelectric element 28X provided in the portion where the strain is generated, and this voltage is proportional to the magnitude of the strain. The magnitude and direction of acceleration can be detected by detecting the magnitude and polarity of this voltage. Y
The detection of the axial acceleration is performed by the same principle. (B)
In, at the Z-axis direction acceleration is applied, the weight 29
Vibrates to the upper limit together with the flexure element 22, and a strain having a magnitude proportional to the magnitude of acceleration is generated between the piezoelectric element 28Z and the fixed frame 21. A voltage having the illustrated polarity is generated at each electrode of the piezoelectric element 28Z provided in the portion where the strain is generated, and this voltage is proportional to the magnitude of the strain. The magnitude and direction of acceleration can be detected by detecting the magnitude and polarity of this voltage.

It is advantageous in terms of characteristics and sensitivity in the low frequency band to increase the area of the acceleration detecting means 2 as much as possible, but the acceleration detecting means 2 has an appropriate size in consideration of the purpose of "miniaturization". . The acceleration detecting means 2 detects the acceleration in the biaxial direction or the triaxial direction and outputs it to the amplifying means 3. The amplifying means 3 has 0.1 to 1 of the signals from the acceleration sensor 2.
The 00 Hz component is amplified and output to the SI value conversion means 4. The SI value conversion means 4 processes the signal from the amplifier to obtain the SI value, and outputs it to the gas safety valve control means or the like.

Generally, a sensor using a piezoelectric ceramic element takes out a change in output due to a change in charge amount by a charge amplifier system shown in FIG. 5 for signal detection. Is not so large, the change in the amount of electric charge of the sensor element is not so large. Therefore, in this circuit system, the capacitor Cf for detecting the change in the amount of electric charge in the sensor has a very small capacitance, and measurement accuracy is required. That makes it unrealistic. Further, in the sensor unit according to the present invention, the wiring length from the acceleration detecting means 2 to the amplifying means 3 is fixed and can be made extremely short. Therefore, the merit that the capacitance of the wiring path, which is an advantage of the charge amplifier system, can be ignored. Is not necessary either.

In the acceleration detection of the present invention, the frequency range that needs to be detected to obtain the SI value is 0.1 to
Since it is 100 Hz, the circuit input impedance is extremely high so as not to reduce the sensitivity in the low range.
An appropriate low-pass filter (LPF) was built in in order to remove an unnecessary vibration signal of a frequency component of 100 Hz or more in obtaining the SI value.

That is, a specific circuit configuration of the SI value detecting device of the present invention is shown in FIG. SI value detecting device 1 of the present invention
Includes an acceleration detecting means 2, an amplifying means 3 including a first-stage amplifying circuit 31, a filter 32 and a latter-stage amplifying circuit 33, and an SI value converting means 4. Each means corresponds to the X axis, the Y axis and the Z axis. And three sets are provided. Only the circuit configuration corresponding to one X-axis will be described below. The other 2
The shaft has the same structure.

The acceleration detecting means 2 comprises the accelerometer 2 shown in FIG. The first stage amplifier 31 of the amplification means 3 is
An extremely high resistance value connected in parallel with the piezoelectric element 28,
For example, an input resistor 311 having a resistance value of 2000 MΩ,
An operational amplifier 312 that receives the voltage of the input resistor 311 as one input, a capacitor 313 and a resistor 314 that are connected in parallel to the output terminal of the operational amplifier, and a sensitivity adjustment resistor that is installed in series with this parallel body. 315 and 316, and the potential at the connection point between the capacitor 313, the resistor 314, and the sensitivity adjusting resistors 315 and 316 is the operational amplifier 31.
The other input of 2. The reference voltage 317 is supplied to the first-stage amplifier 31. The output of the operational amplifier 312 is output to the filter 32 via the capacitors 34 and 35 that cut off the DC component. The filter 32 includes a resistor 321 connected in parallel to the output of the first-stage amplifier circuit 31, a resistor 322 connected in series to the output of the first-stage amplifier circuit 31, and a resistor 321 connected in parallel via the resistor 321 and the resistor 322. It is composed of a capacitor 323, and the input signal is 0.1 to 1
Low-pass filter (LPF) that passes only 00Hz
Is composed. The post-stage amplifier circuit 33 is the filter 3
Operational amplifier 331 having two outputs as one input, capacitor 332 and resistor 333 connected in parallel to this output
And an output resistor 334 connected in series to the output, and the other ends of the capacitor 332 and the resistor 333 are used as the other input of the operational amplifier 331.

The SI value converting means 4 for each axis respectively has an arithmetic circuit 41 for calculating an Sv value having a natural period of 1.5 sec,
Arithmetic circuit 42 for computing the Sv value with a natural period of 2.5 sec
And a selector 43 and a multiplier 44 which receive the outputs of both arithmetic circuits and select and output the larger value. The arithmetic circuit 41 includes multipliers 411, 412, 413.
, Adder 414, and integrators 415 and 416. The acceleration signal (z 〃) from the amplifying means 3 is input to the multiplier 411, multiplied by -1 and used as the first input of the adder 414. The output (x〃) of the adder 414 is integrated by the integrator 415, and the output (x ′) of the integrator 415 is output to the third multiplier 413 and the second integrator 416, and the arithmetic circuit 41 Is output (x). The output (x) of the second integrator 416 is output to the second multiplier 412. The output (−ωx) of the second multiplier 412 and the third
The output (−2ωhx ′) of the multiplier 413 of
Is input to. The arithmetic circuit 42 is similarly configured.

The SI value calculation will be described below. The SI value in the present specification is an amount defined by the following formula (1), and the natural period T0.1 to 2.5 sec of the speed response spectrum Sv having a damping constant h of 20%, that is, 0.4. ~ 1
It means the average amplitude in the section of 0 Hz.

[0023]

[Equation 1]

In order to actually obtain this SI value, it is necessary to calculate the fluctuations of a large number of one-degree-of-freedom systems having different natural frequencies, but this calculation needs to be performed easily in a short time and easily. is there. The circuit shown in the arithmetic circuit 41 of the SI value conversion means 4 in FIG. 4 is an example of a circuit for actually obtaining the speed response required for calculating the SI value in real time. Generally, the equation of motion of the one-degree-of-freedom system can be expressed by the following equation (2).

[0025]

[Equation 2] Here, M is a mass, C is a damping, k is a spring coefficient, x is a displacement of a mass constituting a building with respect to the ground, and z is a displacement of a coordinate axis-shaped ground fixed in space. If this equation is divided by M and standardized using the natural frequency ω and the damping coefficient n, the following equation (3) is obtained.

[0026]

(Equation 3) By further summarizing this equation for d ² x / dt ² , the following equation (4) is obtained.

[0027]

[Equation 4] Therefore, the SI value having a certain natural frequency ω and the damping constant h can be obtained in an analog manner by using the acceleration input d ² z / dt ² and using the second-order integrating circuit. To obtain the SI value shown above using this circuit, for example, if the natural frequency is obtained at intervals of 0.1 sec,
Twenty-five analog calculation circuits are required, which is not very practical.

Then, focusing on the spectrum of the earthquake,
In general, the value rises in a short period and rises in a long period, and a constant value is shown in a long period. Therefore, when the SI value is estimated from the frequency of the velocity response spectrum for a certain two natural periods and compared with the equation (1), a very good agreement is obtained. Show. That is, the natural period 1.
If the larger value of the 5 sec and 2.5 sec spectrum values is taken and the approximate value SIe of the SI value is calculated by the following equation (5), approximation is established.

SIe = 1.75 / 2.4x (x is the larger value of Sv of T = 1.5 or 2.5) (5) Therefore, it is possible to obtain an approximate SI value with two analog computers and one multiplier. .

In the present invention, since it is necessary to measure the vibration with an accuracy of several gals, it is necessary to minimize the noise of the amplifier circuit itself. Even when realizing the input impedance, the circuit configuration is as simple as possible. Similarly, output voltage without vibration (hereinafter referred to as offset voltage)
Also, do not adjust with a variable resistor for adjustment,
The reference voltage generating IC is used to suppress variations in offset voltage as much as possible.

The trimming resistors for increasing the sensitivity accuracy are the primary adjustment resistor 315 and the fine adjustment resistor 316.
The resistance is not adjusted by the resistor 314, and the frequency characteristic of the circuit is not changed by the time constant with the capacitor 313.

[0032]

As described above, according to the present invention, it is possible to accurately detect low frequency acceleration due to biaxial or triaxial seismic motion by using the acceleration detecting means using the piezoelectric element. It is possible to provide a seismic motion detector and an SI value detecting device which are much smaller and cheaper than those of the above sensors.

[Brief description of drawings]

FIG. 1 is a block diagram showing an outline of a seismic motion detector and an SI value detection device according to the present invention.

FIG. 2 is a diagram showing a configuration of acceleration detecting means used in the present invention.

FIG. 3 is a diagram showing an operation of an acceleration detecting means used in the present invention.

FIG. 4 is a circuit configuration diagram showing configurations of a seismic motion detector and an SI value detection device according to the present invention.

FIG. 5 is a diagram showing an operation example of a conventional piezoelectric sensor.

[Explanation of symbols]

 1: SI value detection device 2: Acceleration detection means 3: Amplification means 4: SI value conversion means 31: First stage amplification circuit 32: Filter 33: Rear stage amplification circuit

 ─────────────────────────────────────────────────── ─── Continued Front Page (72) Inventor Hironobu Kanamori 3-3-13 Minami, Takaoka-shi, Toyama Prefecture Microgenics Co., Ltd.

Claims (10)

[Claims] 1. A seismic motion detector comprising an acceleration detecting means for detecting an earthquake motion using a piezoelectric element and an amplifying means for amplifying an output of the acceleration detecting means, wherein the amplifying means has an extremely high input impedance. , 0.
A seismic motion detector characterized by selectively amplifying a signal in a frequency band of 1 to 100 Hz. 2. The amplifier has an input impedance of 2000.
The earthquake motion detector according to claim 1, which has a resistance of MΩ or more. 3. The seismic motion detector according to claim 1, wherein a stable and highly accurate reference voltage source is used for the amplifier, and a noise source such as a voltage adjusting resistor is removed. 4. A piezoelectric element constituting acceleration detecting means,
The seismic motion detector according to any one of claims 1 to 3, which is a triaxial piezoelectric element. 5. A seismic motion detector comprising an acceleration detecting means for detecting seismic motion using a piezoelectric element and an amplifying means for amplifying an output of the acceleration detecting means, and an output of the seismic motion detector is S.
In an SI value detecting device having an SI conversion circuit for converting into an I value, the amplifying means has an extremely high input impedance and selectively amplifies a signal in a frequency band of 0.1 to 100 Hz. Characteristic S
I-value detector. 6. The amplifier has an input impedance of 2000.
The SI value detecting device according to claim 5, which is MΩ or more. 7. The SI value detecting device according to claim 5, wherein a stable reference voltage source with extremely high accuracy is used for the amplifier, and a noise source such as a voltage adjusting resistor is removed. 8. The SI value detection circuit selects a larger value of the speed response values for two natural frequencies of the speed response spectrum obtained from the output of the acceleration sensor, and multiplies this output by 1.75 / 2.4 times. The SI value detecting device according to any one of claims 5 to 7, wherein the SI value detecting circuit is a circuit for obtaining an SI value. 9. The SI value detection circuit selects a larger value of velocity response values for two natural frequencies of the velocity response spectrum obtained from the output of the acceleration sensor, and multiplies this output by 1.75 / 2.4. 9. The SI value detecting device according to claim 6, wherein the SI value detecting circuit is a circuit for obtaining an SI value. 10. The SI value detecting device according to claim 6, wherein the piezoelectric element forming the acceleration detecting means is a triaxial piezoelectric element.