JPH0245137B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an earthquake sensor that detects vibrations caused by earthquakes and the like.

[Problems to be solved by conventional technology and invention]

First, we will explain the frequency of earthquakes.

It is generally said that the main component of seismic waves has a frequency of 1 to 10 Hz, and among these, the 1 to 5 Hz component is particularly prominent. Figure 2 shows 17:00 on June 12, 1978.
As an example, the power spectrum of the seismic waves observed in Ofunato is shown for the Miyagi Prefecture-Oki Earthquake that occurred on the 14th minute. The predominant frequency is 2-3Hz (2.4Hz), 1
-5Hz power is large (although not shown, the Fourier spectrum has almost the same shape and has many 1-5Hz components).

In addition, minute vibrations in the ground and buildings caused by various causes such as trains, dump trucks, construction work, and rotating machinery are different from seismic waves and constitute disturbance vibrations, but these disturbance vibrations are often over 20Hz, but also include vibrations around 10Hz. Therefore, in order to prevent malfunction, the Japan Elevator Association's technical standards for seismic design and construction guidelines state that the frequency characteristics of the sensor are ``a flat characteristic in the range of 1 to 5 Hz for normal grade, and a flat characteristic in the range of 0.1 to 5 Hz for precision grade. The sensitivity should be flat in the range exceeding 5 Hz.''

In response to the above-mentioned characteristics of earthquakes, conventional earthquake sensors are generally of an electrodynamic type, a strain gauge type, a piezoelectric type, or a mechanical weight drop type.

FIG. 3 shows an example of the structure of an electrodynamic earthquake sensor (vertical sensor). In this electrodynamic earthquake sensor, when a coil 3 fixed to a weight 2 moves up and down due to vibration in a magnetic flux 5 generated by a permanent magnet 4, a voltage is generated at both ends of the coil 3. Earthquakes are sensed by utilizing the fact that the size is proportional to the moving speed of the coil 3. In addition, 1
6 is a spring system that supports the weight 2, and 6 is a yoke that forms a magnetic path. The natural frequency of this spring system 1 is normally set to about 4 Hz, but it is difficult to make the frequency characteristics fall above 5 Hz as mentioned above with this method (spring system problem), and it is usually about 10 Hz. The above results in a descending characteristic. Furthermore, since the natural frequency is greatly affected by the precision of the spring system 1 and the weight 2, the weight of the weight, etc. is actually adjusted by hand in the final process. In other words, this electrodynamic seismic sensor has problems in terms of accuracy and the amount of effort required for adjustment.

In addition, in a strain gauge type earthquake sensor, strain gauges are installed in the X and Y directions, and their electrical outputs are vector-combined to obtain acceleration, but the frequency characteristics of the strain gauges themselves are Since it reaches up to KHz, an electric filter can be used to
It is designed to attenuate frequencies above Hz. Therefore, strain gauge type earthquake detectors are greatly affected by the characteristics of this filter, and also include many error factors, such as the need for multipliers to perform vector synthesis, which poses problems in terms of reliability. be. Note that piezoelectric earthquake sensors also use a vector synthesis method and have similar problems.

FIG. 4 shows an example of the structure of a falling weight type earthquake sensor. This is because in a stationary state, a weight 13 (magnetic material such as iron) is attracted to the permanent magnet 11 fixed to the case 10, but when vibrations above a certain level occur, the weight 13 falls. The lever 12 fitted into the weight 13 is the fulcrum 15
By rotating in the direction of the arrow around the center, the actuator 14' of the micro switch 14 is actuated to sense an earthquake. Although this method is simple, the sensing level is affected by the relationship between the attraction force of the magnet and the weight of the weight, and it is difficult to adjust, and at the same time, it has the disadvantage that it is difficult to detect at low frequencies (1 Hz or less). However, there are still problems with accuracy and reliability.

For this reason, the applicant proposed a new type of earthquake sensor in Japanese Patent Application No. 88902/1983. That's the fifth
As shown in FIG. 6 and FIG. 6, a liquid 32 such as mercury or oil is placed in a cylindrical container 31, and a light source 34 such as a light emitting diode is mounted on the lid of the container 31 to receive reflected light from the liquid 32. When the liquid 32 in the container 31 is shaken by seismic waves, the luminance distribution of reflected light that changes due to the change in the shape of the liquid surface is converted into an electrical signal by the light receiving element 35 and output. signal processing unit 21
This is a new type of earthquake sensor that identifies the vibration level according to the magnitude of this output signal 20a.

The operating principle of this earthquake sensor is as follows.

That is, for simplicity, when a small cylindrical container containing a liquid is vibrated in the horizontal direction with a constant vibration acceleration, the wave movement on the surface of the liquid is expressed as A, the magnitude of the vibration acceleration,
The acceleration of gravity is g, the amplitude of the wave is a, and its wavelength is λ
If we take the x-axis along the wave path, then the 8th
As shown in the figure, the main component of the vibration is a 1/2-wavelength sine wave that forms peaks or valleys on the side wall of the small cylindrical container. When the angle of inclination θ of the liquid level is small, it is given by the following equation.

θ=A/g=2πa/λ・cos2πx/λ...In other words, the magnitude A of the vibrational acceleration is proportional to the inclination angle of the liquid surface, so in order to detect the vibrational acceleration, we need to detect the inclination angle of the liquid surface. It will be a good thing.

Waves in a cylindrical container like this require the liquid to move vertically at the side wall, and the wave pattern is large enough to have peaks or troughs at the side wall, resulting in horizontal excitation. The fundamental wave mode is as shown in FIG. 8 at the time, and as shown in FIG. 9 during vertical vibration.

Next, the basic optical system for detecting the angle of inclination of the liquid level is shown in FIG.

That is, the incident light beam on the liquid surface is φ ₁ , the reflected light beam on the stationary liquid surface is φ ₂ , the reflected light beam on the tilted liquid surface is φ ₃ , and the photoelectric conversion element when the liquid surface changes by the tilt angle θ If the amount of change in the luminous flux incident on is φ ₄ , then
As is clear from the figure, when the liquid surface is tilted by an angle of θ, the moving angle of the reflected light flux becomes 2θ, so the amount of change in the light flux incident on the photoelectric conversion element is φ ₄ (the amount of change in the light flux reflected from the liquid surface) ) is proportional to θ.

Now, when we use something like a photodiode as a photoelectric conversion element, its output is proportional to the incident luminous flux (light amount), so when the cylindrical container is accelerated,
The output u at that time can be expressed by the following formula, considering the formula.

u= _K1・θ= _K2・A... However, _K1 and _K2 are constants. In other words, the output of the photoelectric conversion element is proportional to the vibration acceleration.

That is, this earthquake sensor receives a signal 2 proportional to the vibration acceleration output from the light receiving element 35 of the sensing section 20.
0a is amplified by an AC amplifier 22, and multiple levels of earthquakes are detected by comparators 23, 25, etc., but factors that affect this sensing characteristic include the shape of the container, the type and amount of liquid, and the emitted Various miscellaneous factors such as the characteristics of the light-receiving element itself can be considered, and in particular, fluctuations in the amount of light emitted by the light-emitting element and fluctuations in the amount of light received by the light-receiving element due to fluctuations in power supply voltage, changes in ambient temperature, changes over time, etc. voltage 20
This will cause the output level of a to fluctuate greatly,
There is a risk that the sensitivity and accuracy of earthquake detectors will be significantly affected.

The present invention has been made in view of the above points, and it is an object of the present invention to provide an earthquake sensor with sensitivity correction that can withstand long-term use without the risk of being affected by changes in the environment or changes over time. With the goal.

[Means for solving problems]

The present invention includes a container with a sealed structure that blocks light from the outside, the container contains a liquid that reflects light, and above the liquid there is a light source that illuminates the inside of the container, and a light source that reflects the light emitted by the light source. A photoelectric conversion element that receives reflected light from the liquid surface and converts the amount of light into an electrical signal is installed. An earthquake sensor equipped with a signal processing unit that outputs an output when a signal is larger than a predetermined value includes a reference voltage generator that always outputs a constant voltage command, and a filter that extracts a DC component from the output electrical signal of a photoelectric conversion element. A comparison amplifier that compares the voltage command of the reference voltage generator with the DC component of the filter and amplifies and outputs the difference signal, and a current control section that controls the voltage flowing to the light source according to the output signal of the comparison amplifier. It is.

[Effect]

With the above configuration, the brightness of the light source is controlled so that the DC component always has a constant voltage value.

〔Example〕

FIG. 1 is a block diagram showing the configuration of an embodiment of the present invention, in which the same reference numerals as in FIGS. 41 is a DC amplifier, 42 is a reference voltage generator that always outputs a constant voltage command 42a, and 43 is a filter that compares the voltage command 42a of the reference voltage generator 42 and the output signal 41a of the DC amplifier 41, and generates a difference signal. A comparison amplifier 44 amplifies and outputs the output signal 43a, and a current control section 45 composed of, for example, a transistor, which controls the current flowing through the light emitting element 34 in accordance with the output signal 43a of the comparison amplifier 43.
For example, there are four different reference level voltages 4.
5a1, 45a2, 45a3, 45a4 (for example, 45a with reference to the setting values of technical standards for elevators)
1 is 10gal, 45a2 is 80gal, 45a3 is
120gal, 45a4 is a reference voltage generator that outputs the voltage value corresponding to 150gal), 46, 47, 48, 4
9 is the output signal 22'a of the AC amplifier 22' including a bandpass filter, that is, the output signal 2 of the sensing section 20.
Compare the AC signal 0a with each level voltage 45a1, 45a2, 45a3, 45a4 of the reference voltage generator 45, and if the signal 22'a is larger, it is a high level, and if the signal 22'a is smaller, it is a low level. A comparator that outputs a signal; 50 is a counter that counts when the comparator 46 outputs a pulse signal; and when the counted value reaches a predetermined value, outputs a high-level output signal 50a; 51 is a counter that outputs a high-level output once the comparator 46 outputs a high-level signal; Even if a predetermined period of time elapses after outputting the signal, the comparator 47
52 is an automatic reset signal generator that outputs a high level signal if it does not output a high level output signal or if the state in which the comparator 46 outputs a high level signal and the comparator 47 outputs a low level signal continues for a predetermined period of time; 52 is a four RS flip-flop; A storage device consisting of terminals S1, S2,
If a high level signal is input to S3 and S4, terminals 01 and 0 will be reset unless a high level reset signal is input to terminals R1, R2, R3, and R4.
It continues to output high level signals on 2, 03, and 04.

Here, if the container of the earthquake sensor is placed in a stationary state, the liquid inside the container is also in a stationary state,
Therefore, the brightness distribution inside the container is constant and the output signal 20a of the light receiving element 35 is only a constant DC voltage as shown in FIG. The shape of the surface changes, the form of reflection and scattering of light changes, and the brightness distribution inside the container also changes. Correspondingly, based on the above-mentioned principle, the output signal 20a of the light receiving element 35 also changes as shown in FIGS. 7b and c.
Changes as shown in . (FIG. 7b shows the case where the vibration frequency is low, and FIG. 7c shows the case where the vibration frequency is high.) There is a substantially proportional relationship between the acceleration of the vibration and the voltage of the variable current component of the output signal 20a.

By the way, as shown in FIG. 6, the direct current component Va of the output signal 20a of the sensing unit 20 is affected by the effects of the light emitting element due to fluctuations in the power supply voltage, changes in ambient temperature, changes over time, etc. It changes due to fluctuations in the amount of light emitted and the amount of light received by the light receiving element, and depending on the magnitude of this DC component Va, the output width of the AC component will differ even if the vibration is caused by the same acceleration, leading to false detection if left as is. However, in the present invention, the DC component 41 of the light receiving element
The current controller 4 controls the current controller 4 so that a (output after passing through the filter 40 and the DC amplifier 41) always matches the constant voltage command 42a commanded by the reference voltage generator 42.
4 to control the current flowing to the light emitting element 34, as long as the AC amplifier 2 is vibrated with the same acceleration.
The output signal 22'a of 2' is always the same signal, and there is no possibility of erroneous detection in subsequent signal processing.

In other words, two types of vibration waves are mixed in an earthquake: vertical vibration waves (hereinafter referred to as P waves) and horizontal vibration waves (hereinafter referred to as S waves), and P waves are caused by vibration acceleration that occurs in the early stages of an earthquake. The value is relatively small 10gal
~ several tens of gal, and if a P wave occurs due to this earthquake, the output voltage 22'a of the AC amplifier 22'
becomes larger than the reference voltage value 45a1 periodically and the comparator 46 generates a continuous pulse signal, so the counter 50 counts the predetermined number of pulses and then
Emit a high level output signal (P due to noise vibration)
(If the wave is a wave, it will end up as a single pulse signal, so the counting device 50 will not emit a high level output signal).The storage device 52 stores the occurrence of an earthquake and also sends it to an elevator control device (not shown), etc. A stop command 52a1 is output. In addition, the S wave occurs approximately 7 to 30 seconds after the initial tremor P wave occurs (depending on the distance between the epicenter and the observation site, but past earthquake data indicates that it is actually an earthquake that causes damage to elevators, etc.) If the value of the vibration acceleration that occurs after the elapse of time) is greater than a large number + gal, and this main shock S wave occurs and reaches, for example, 80 gal, the output voltage 22'a of the AC amplifier 22' will become the reference voltage value. 45a2, the comparator 47
outputs a high level signal, and the storage device 52 memorizes that the main shock has occurred, and outputs an emergency stop command 52a2 etc. to the elevator control device etc. if the elevator is running. If the earthquake becomes even stronger and reaches 120 gal or 150 gal, the moment the output voltage 22'a of the AC amplifier 22' momentarily becomes larger than the reference voltage value 45a3 or 45a4,
The comparators 48 and 49 output high-level signals, and the storage device 52 stores the fact that a strong earthquake has occurred, and outputs operation prohibition commands 52a3 and 52a4 to the elevator control device, etc., and an inspection is performed by a specialized engineer. Post-manual reset signal 5
The driving prohibition will continue unless it is canceled by inputting 2b. On the other hand, the output signal 52a of the storage device 52
1 and 52a2, the output signal of the comparator 46 is at High level, and the output signal of the comparator 47 is at High level.
Low level state for a specified period of time (at least 30 seconds)
If this continues, the automatic reset signal generator 51 will automatically reset the elevator, so that the elevator can resume operation without waiting for an inspection by a specialist engineer.

〔Effect of the invention〕

As described above, according to the present invention, even if there are fluctuation factors that cannot be avoided when using an earthquake sensor, such as changes in the surrounding environment and aging, the correction circuit is provided that can sufficiently absorb the fluctuations. Therefore, an extremely reliable earthquake sensor can be obtained.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing the configuration of an embodiment of the present invention, FIG. 2 is a diagram showing an example of the power spectrum of seismic waves, FIG. 3 is a diagram showing an example of the structure of an electrodynamic earthquake sensor, and FIG. Figure 4 shows an example of the structure of a falling weight earthquake sensor, Figure 5 is a block diagram showing the configuration of a new type of earthquake sensor, and Figure 6 shows the sensing section of a new type of earthquake sensor. A structural sectional view showing an example,
FIG. 7 is a diagram showing the waveform of the output signal 20a of the sensing section, and FIGS. 8 to 10 are explanatory diagrams showing the basic principle of the new type of earthquake sensor. 20... Sensing unit, 21... Signal processing unit, 22,
22'... AC amplifier, 23, 25, 46, 47,
48, 49... Comparator, 24, 26... Output circuit, 31... Container, 32... Liquid, 34...
Light source, 35... Light receiving element, 40... Filter, 4
2... Reference voltage generator, 43... Comparison amplifier, 44...
...Current control section.

Claims (1)

[Claims] 1. A container having a sealed structure that blocks light from the outside, the container containing a liquid that reflects light,
A light source that illuminates the inside of the container above the liquid;
A photoelectric conversion element is provided that receives reflected light from the liquid surface out of the light emitted by the light source and converts the amount of light into an electrical signal, and changes in the amount of reflected light from the liquid surface are determined based on the inclination of the liquid surface. In an earthquake sensor equipped with a signal processing unit that outputs an output when the output electrical signal of the photoelectric conversion element is larger than a predetermined value, a reference voltage generator that always outputs a constant voltage command;
a filter for extracting a DC component from the output electrical signal of the photoelectric conversion element, and a comparison amplifier for comparing the voltage command of the reference voltage generator with the DC component of the filter and amplifying and outputting a difference signal, the comparison amplifier An earthquake sensor with sensitivity correction, comprising a current control section that controls a current flowing through the light source according to an output signal of the light source.