JPH0512649B2 - - Google Patents

Description

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

[Conventional technology]

First, we will explain the frequency of earthquakes.

Generally, it is said that the frequency of the main component of seismic waves is in the range of 1 to 10 Hz, and among these, the component in the range of 1 to 5 Hz is particularly prominent. In addition, minute vibrations in the ground and buildings caused by various causes such as trains, dump trucks, construction work, and rotating machinery cause disturbances to earthquake detectors, and the frequency of this disturbance vibration is often over 20Hz, but there are cases around 10Hz. In order to prevent malfunctions, 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. Flat characteristics in the 5Hz range,
In the range exceeding 5Hz, the sensitivity shall have a decreasing characteristic.''

However, as conventional earthquake detectors, electrical electrodynamic type, strain gauge type, piezoelectric type, or mechanical weight drop type are generally used.
All of these have drawbacks such as difficulty in obtaining the desired frequency characteristics for the earthquake sensor mentioned above and difficulty in precise adjustment.
61-137024, JP 61-142425, JP 61-164125, JP 61-207931, etc.).

It has a conically shaped bottom 40 in the container 40, as shown for example in FIGS. 2 and 3.
A is a double layer consisting of a liquid 41, such as mercury, which has a high specific gravity, low viscosity, and high surface reflectance, and a liquid 42, such as aircraft hydraulic oil, which has a low specific gravity, high viscosity, and low surface reflectance. liquid 43
and place the double layer liquid 43 on the center line of this container 40.
A light source 44 such as a light emitting diode and a photoelectric conversion element 46 for receiving light are provided above, and when the liquid 43 in the container 40 is shaken by seismic waves, the shape of the liquid surface changes and the container changes. 4
The luminance distribution within 0 is converted into an electric signal by the photoelectric conversion element 46, and the signal processing section 21 (consisting of a preamplifier, a comparator, and an output circuit) adjusts each electric level according to the magnitude of this output signal 10a. This is a new type of earthquake sensor with an identification function.

That is, in this earthquake sensor, a signal 10a corresponding to the luminance distribution inside the container 40 outputted from the photoelectric conversion element 46 of the sensing section 10 is amplified by the preamplifier 22 (AC amplifier), and a plurality of signals are amplified by the comparators 23, 25, etc. It is designed to identify and detect earthquakes of this level.

[Problem to be solved by the invention]

However, subsequent experimental results have revealed that even this new type of earthquake sensor has the following drawbacks.

Unless the liquid in the container becomes a double layer liquid,
It is difficult to obtain the desired frequency characteristics, and if oil is selected as one of the liquids, the viscosity of the oil will change due to the influence of temperature changes, which will cause the output level of the sensor to fluctuate and the frequency characteristics to change as well. Put it away.

As shown in FIG. 4, the sensing section connects a photoelectric conversion element 46 to a cylinder 40 containing a double-layer liquid via a transparent plate 45, a ring 49, and a transparent plate 48.
Since the light sources 44 are stacked one on top of the other, not only manufacturing errors of parts but also assembly errors are added, making it difficult to center the optical axis, and the output level of the sensor is uniform depending on the direction of vibration. Otherwise, there is a risk of malfunction.

Since it is basically a reflective seismic sensor that captures light reflected from liquid, it has the disadvantage of low detection sensitivity.

The present invention was made in view of the above points, and an object of the present invention is to provide an earthquake sensor with high detection sensitivity and stable frequency characteristics.

[Means to solve the problem]

In the present invention, a liquid that hardly transmits light is placed in the bottom of an inverted dome-shaped transparent container, and a light source is provided below the container to irradiate light toward the liquid.
A photoelectric conversion element that receives light from the light source and converts it into an electrical signal is provided above the container, and when the output signal of the photoelectric conversion element is larger than a predetermined value, a signal processing unit generates an output. It is something.

[Effect]

With the configuration as described above, changes in direct light from the light source can be captured, and it is possible to obtain electrical signals with high sensitivity depending on the intensity of the seismic intensity.

〔Example〕

An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a cross-sectional view showing an example of the structure of a sensing unit 50 according to the present invention, and FIG. 5 is an example of a block diagram showing the structure of an earthquake sensor according to the present invention. Container, 52 is a transparent container 51
A liquid with a high specific gravity, low viscosity, and almost no light transmission, such as mercury, contained in
53 is also an inert gas such as nitrogen gas sealed in the transparent container 51, 54 is an upper lid made of a material that transmits the light of the transparent container 51, and 55 is a light-transmitting container in which the transparent container 51 is fitted in the upper part. A hollow cylindrical case made of a material that does not transmit light; 56 is a support member made of a material that does not transmit light; a hollow protrusion 56a is fitted into the lower part of the cylindrical case 55 and is fixed to the cylindrical case 55 with a bolt 56c; A light source 57, such as a light emitting diode, is fitted into the hollow portion 56b of 56a. Reference numeral 58 denotes a case cover made of a material that does not transmit light, which is placed over the upper part of the cylindrical case 55 so as to cover the upper lid 54 of the cylindrical case 55 and the transparent container 51, and has a hole 58a for light passage in the center facing the upper lid 54. A mounting hole 58b is provided around this hole 58a. 59 is a photoelectric conversion element disposed on the upper part of the case cover 58 facing the hole 58a of the case cover 58, and is a photoelectric conversion element such as a photodiode, which receives light from the light source 57 and converts it into an electric signal. Reference numeral 60 denotes a holding member having a hole 60a in the center for passing the electric wire cord 59a of the photoelectric conversion element 59, and a hole 60b for bolt attachment around the hole 60a. Place the bolt 61 on the member 60 and the bolt mounting hole 60b of the member 60 and the hole 5 of the case cover 58.
The case cover 58, the photoelectric conversion element 59, and the holding member 60 are fixed to the cylindrical case 55 by passing through the cylindrical case 8b and inserting them into the tap holes 55a provided in the cylindrical case 55.

Next, in FIG. 5, 71 is a DC amplifier that amplifies the output signal 50a of the photoelectric conversion element 59 of the sensing section 50;
72 is a current control device for the light source 57 that controls the current flowing through the light source 57 based on the DC signal component output from the DC amplifier 71 to automatically adjust the luminance brightness;
73 is an AC amplifier equipped with a low-pass filter that passes only the AC signal component of the output signal 71a of the DC amplifier 71 and attenuates frequency components other than the frequency component of the seismic motion; 73a is the output thereof; [For example, when an output signal with a level of about 10 gal or higher is generated (initial microtremor (hereinafter referred to as P wave))], the comparators 74B, 74C, etc. input the signal 74Aa to the output device 75, and the sensing unit 50
is a predetermined value [for example, the main shock (hereinafter referred to as S wave) 80 gal,
When output signals with a level of about 120 gal or higher are issued sequentially, the corresponding signals 74Ba and 74
a comparator that inputs Ca,... to the output device 75;
The output device 75 includes comparators 74A, 74B, 7
When a signal from 4C, .

Next, the operation and characteristics of the sensing unit 50 according to the present invention will be explained separately for vertical vibration (main component of P wave) and horizontal vibration (main component of S wave).

First, when the sensing part 50 is vibrated in the vertical direction, the liquid 52 in the transparent container 51 is moved by the dashed line (see FIG. b plane diameter d ₁ part) to the broken line (6th
The output _73a of the AC amplifier 73 outputs an AC signal having the same period as the excitation period T as shown in FIG. 7. It was found from experimental results that the acceleration-output characteristics and frequency characteristics (frequency 73a of the AC amplifier 73) with respect to the vertical vibration of the sensing section 50 are as shown in FIGS. 8 and 9. As can be seen from FIG. 8, this sensing section 5
0, an electrical output signal approximately proportional to the acceleration of the excitation force is obtained, and as can be seen from Figure 9, the resonance point (which does not appear as clearly as in the case of horizontal vibration described later) is around 10 Hz. The low-pass filter circuit in the AC amplifier 73 can easily electrically process the characteristics shown by the two-dot chain line in FIG. 9, and the frequency characteristics necessary for the earthquake sensor can be easily obtained.

Furthermore, when the sensing section 50 is vibrated in the horizontal direction,
As shown in FIGS. 10a and 10b, the static state shown by the solid line changes to the state shown by the dashed-dotted line and the broken line, and the output 73a of the AC amplifier 73 has an excitation period T as shown in FIG. Outputs an AC signal with a period of 1/2. According to experimental results, the acceleration-output characteristics and frequency characteristics (output 73a of the AC amplifier 73) with respect to horizontal vibration of the sensing section 50 are as follows:
It was found that the characteristics were as shown in Figures 1 and 13. As can be seen from FIG. 12, this sensing section 50 can obtain an electrical output signal that is approximately proportional to an excitation acceleration of approximately 80 gal or more, and as shown in FIG. 13, the resonance point is higher than that in the case of vertical motion. (The position of the resonance point is determined by the radius of curvature of the bottom surface of the transparent container 51 and the amount of liquid 52, but the same as in the case of vertical motion) is around 10Hz, so the low-pass filter circuit in the AC amplifier 73 is By intervening, the first
By simply electrically processing the characteristics shown by the two-dot chain line in Figure 3, the frequency characteristics necessary for an earthquake sensor can be obtained extremely easily.

FIG. 14 shows the output 73a for the vibration acceleration during vertical vibration and horizontal vibration in this sensing unit 50.
As is clear from the figure, the sensitivity to vertical vibration is high in the low acceleration range, and the sensitivity to horizontal vibration is high in the high acceleration range. With these characteristics, vertical vibrations can be detected with good sensitivity within the range of P wave detection settings (e.g. 2.5 gal to 10 gal) during an earthquake, and S wave detection settings (e.g. 60 gal)
~150 gal), horizontal vibrations can be detected with good sensitivity.

Furthermore, by using a liquid such as mercury whose viscosity does not change due to temperature, the sensitivity of earthquake detection to temperature can be kept almost constant as shown in Figure 15.
It can be seen that stable earthquake detection sensitivity can be obtained even when the ambient temperature changes.

Furthermore, Fig. 16 is a diagram plotting the output 73a of the AC amplifier 73 over 360° when the sensing section 50 is excited in an arbitrary horizontal direction with the same excitation force. As can be seen, the sensing section 50 according to the present invention has substantially the same sensitivity in all directions.

〔Effect of the invention〕

As described above, according to the present invention, ideal frequency characteristics can be obtained using a single type of liquid such as mercury, without using a liquid such as oil whose viscosity changes significantly depending on the ambient temperature. Therefore, it exhibits extremely stable detection performance compared to reflective earthquake detectors.
Furthermore, since the light source and the liquid container are assembled using the cylindrical case as a common reference, there is almost no assembly error and centering of the optical axis is extremely easy, and the detection sensitivity is uniform in all excitation directions, resulting in good sensing. You can get the equipment.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing an example of the structure of a sensing section according to the present invention, FIG. 2 is a sectional view showing the structure of a conventional earthquake sensing section, and FIG. 3 is a block diagram showing the configuration of a conventional earthquake sensor. FIG. 4 is an exploded structural diagram showing the specific structure of a conventional reflection-type earthquake sensing section, FIG. 5 is a block diagram showing an example of the configuration of an earthquake sensor according to the present invention, and FIG. 6 is a diagram showing the present invention during vertical vibration. Figure 6a is a front view and Figure 6b is an explanatory diagram showing the state of the liquid applied to the
is a plan view, FIG. 7 is an output signal waveform diagram of the sensing section according to the present invention during vertical vibration, FIG. 8 is an acceleration-output characteristic diagram of the sensing section according to the present invention during vertical vibration, and FIG. 9 is a vertical diagram. A frequency characteristic diagram of the sensing section according to the present invention during vibration, FIG. 10 is an explanatory diagram showing the state of the liquid according to the present invention during horizontal vibration, FIG. 10a is a front view, FIG. 10b is a plan view, FIG. 11 is an output signal waveform diagram of the sensing section according to the present invention during horizontal vibration, the first
Figure 2 is an acceleration-output characteristic diagram of the sensing unit according to the present invention during horizontal vibration, Figure 13 is a frequency characteristic diagram of the sensing unit according to the present invention during horizontal vibration, and Figure 14 is a diagram of the frequency characteristic of the sensing unit according to the present invention during horizontal vibration. A characteristic diagram showing the relationship between sensitivity to vertical vibration and sensitivity to horizontal vibration, FIG. 15 is a characteristic diagram showing the sensitivity of the sensing section according to the present invention to ambient temperature, and FIG. 16 is a characteristic diagram showing the excitation direction of the sensing section according to the present invention. It is a characteristic diagram showing the sensitivity to. 51... Transparent container, 41, 42, 52... Liquid, 44, 57... Light source, 46, 59... Photoelectric conversion element, 21, 70... Signal processing section.

Claims (1)

[Claims] 1. A light source that irradiates light toward the liquid is provided below a transparent container with an inverted dome-shaped bottom containing a liquid that hardly transmits light, and a light source that irradiates light toward the liquid is provided above the container. An earthquake sensor comprising a photoelectric conversion element that receives light and converts it into an electrical signal, and a signal processing section that outputs an output when the output signal of the photoelectric conversion element is larger than a predetermined value.