JPS60231120A - Earthquake sensor - Google Patents

Abstract

PURPOSE:To accurately detect the seismic intensity of an earthquake, by such a simple apparatus constituted so that a container storing a liquid is irradiated with a light source and the reflected light from the liquid surface is received to be converted to an electric signal which is, in turn, compared with a threshold value. CONSTITUTION:The bottom of a container 31 is sealed with a liquid 32 and a light emitting element 34 is driven by a power source 33 to irradiate the surface of the liquid 32. The change in the reflected light by the shaking of the surface of the liquid generated by an earthquake is photoelectrically converted by a light receiving element 35 to output a signal 20a. The signal 20a is inputted to a plurality of comparators while amplified by the amplifying circuit not shown in the drawing and compared with the different threshold values of the comparators and seismic intensity is judged on the basis of the output from the comparator having a corresponding number. As the liquid to be used, oil, which is flat at 0-5Hz but shows a falling characteristic at 5Hz or more and has a frequency characteristic coincided with that of a seismic wave, is used. By this method, up- and-down movement or horizontal movement can be detected by a simple apparatus.

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 techniques and inventions] 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, but the 1 to 5 Hz component is particularly prominent. Figure 1 shows the power spectrum of seismic waves observed at Ofunato, as an example, for the Miyagi Prefecture-Oki Earthquake that occurred at 17:14 on June 12, 1973. The dominant frequency is 2 to 3 Hz (2,4 Hz), and the power in the 1 to 5 Hz range is large (although not shown, the Fourier spectrum has a similar shape and has many 1 to 5 Hz components).

In addition, micro-vibrations in the ground and buildings caused by trains, dump trucks, construction work, rotating machinery, etc. are different from seismic waves and constitute disturbance vibrations, but these disturbance vibrations are often over 20H2, but can also be 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 flat in the range of 1 to 5 Hz for the normal class, and 01 to 01 for the precision class.
The sensitivity shall have a flat characteristic in the 5Hz range, and a decreasing characteristic in the range exceeding 5Hz.

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.

Figure 2 shows an example of the structure of an electrodynamic seismic 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. Note that 1 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 characteristic with this method fall above 5 Hz as mentioned above (spring system problem), and it is usually set to about 10 Hz. The above results in a descending characteristic. Furthermore, since the natural frequency is greatly affected by the accuracy of the spring system 1 and the weight 2, the weight of the weight, etc. is actually adjusted by hand in the final process. That is, 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 calculate acceleration, but the frequency characteristics of the strain gauges themselves are Since the frequency ranges up to several kHz, an electric filter is used to attenuate frequencies above 5 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. . Note that piezoelectric earthquake sensors also use a vector synthesis method and have similar problems.

FIG. 3 shows an example of the structure of a falling weight type earthquake sensor. This is a weight (magnetic material such as iron) in a stationary state.
13 is fully attracted to the permanent magnet 11 fixed to the case 10, but when vibrations above a certain level occur, this weight 13 falls and is fitted into the weight 13.
2 rotates in the direction of the arrow around the fulcrum 15,
The actuator 14' of the microswitch 14 can be actuated to sense an earthquake.

Although this method is simple, the detection 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 (below IHz). There are still problems with accuracy and reliability.

[Means and effects for solving the problems] The present invention provides a sensing unit including a container containing a liquid, a light source that irradiates the inside of the container, and a photoelectric conversion element that receives the light inside the container; The sensor is characterized by comprising a signal processing section that generates an output when the output of the sensing section is larger than a predetermined value.

The sensing section converts the luminance distribution inside the container, which changes as the liquid inside the container is shaken by seismic waves and changes the shape of the liquid surface, into an electrical signal and outputs it. to identify the vibration level. This provides a highly reliable earthquake sensor with a simple configuration and high accuracy that can detect both horizontal vibration waves (hereinafter referred to as S waves) and vertical vertical vibration waves (hereinafter referred to as P waves). be.

[Embodiment] FIG. 4 is a block diagram showing the configuration of an embodiment of the present invention. In the figure, 20 receives light inside a container containing liquid, and generates a signal according to the luminance distribution inside the container. a sensing unit that outputs 20a, 2;
Reference numeral 1 denotes a signal processing section that outputs an output when the signal 20a exceeds a predetermined value.

In this example, the signal processing unit 21 has two levels of set values, and when the output of the preamplifier (AC amplifier) 22 is larger than the first set value, the first comparator 23 and output circuit 24 output a signal. When the signal 24a is fully output and is still larger than the second set value, the second comparator 25 and the output circuit 26 output a signal 26a. Note that a filter for noise removal may be provided after the preamplifier 22, and the set value is not limited to two stages as described above, but may be set to any number of stages.

FIG. 5 is a sectional view showing the structure of one embodiment of the sensing section 20, in which 31 is a container, 32 is a liquid such as oil or mercury, 33 is a power source,
34 is a light source such as a light emitting diode, and 35 is a photoelectric conversion element that receives light. In FIG. 5, when the container 31 is placed in a stationary state, the liquid 32 is also in a stationary state, so the brightness distribution inside the container 31 is constant, and the output 20a of the photoelectric conversion element 35 is also constant. When the liquid 32 is shaken by such vibrations, the shape of the liquid surface changes, the form of reflection and scattering of light changes, and the brightness distribution inside the container 31 also changes, and the output of the photoelectric conversion element 35 changes accordingly. 20a
Also fluctuates.

FIG. 6 is a diagram showing how the liquid 32 oscillates within the container 31 when horizontal vibration occurs. In the case of a relatively low frequency, the liquid 32 oscillates as shown in (a). In the case of a large movement in the direction of the arrow and a relatively high frequency, as shown in (b), the surface of the liquid 320 shakes little by little, and the liquid does not move.

In this way, the manner in which the liquid oscillates differs depending on the frequency of vibration, resulting in photoelectric detection.

FIG. 7 shows the experimental results for the output 20a of the photoelectric conversion element 35 (output after passing through the preamplifier 22), where (a) shows the case where the frequency is low, and (b) shows the result when the frequency is low. The cases where the vibration frequency is high are shown respectively.

FIG. 8 is a diagram showing the experimental results of the output characteristics of the output voltage shown in FIG. 7 with respect to the vibration frequency when engine oil is used as the liquid. Here, the parameter (
al, a2. a3°a4) is the vibration acceleration, - for example aII=30gal, a2=80ga1. a3=
120 gal.

If a4=150gal, the output voltage at 5Hz is thenFb1-0.45V, b2=1.2V
.

b3=L85V, b4-2.3L, and the ratio of the magnitude of acceleration and the output voltage is almost proportional.

In this way, the relationship between acceleration and output voltage is linear,
Furthermore, as is clear from Figure 8, the frequency characteristics are almost flat between 1 and 5 Hz, and the falling characteristics above 5 Hz match the frequency characteristics of seismic waves, making them ideal characteristics for earthquake detectors (in the case of mercury, shows particularly sharp output characteristics at 3 to 4 Hz).

The above has been described in the case of S waves, but in the case of P waves, the liquid oscillates as shown in Figure 9, and changes in the brightness distribution inside the container, that is, the output voltage of the sensing section, By capturing changes in the P wave, P waves can be sensed in the same way as S waves.

Additionally, mercury or oil with an appropriate viscosity is suitable as the liquid in the container, but oil is more accurate in detecting only seismic waves because it can detect frequencies as low as 0.1 Hz in high places such as skyscrapers. In cases where it is necessary to use mercury,
Each one is slightly better.

[Effects of the Invention] According to the present invention, as mentioned above, the sensing section itself matches the frequency characteristics of seismic waves very well, so malfunctions can be almost eliminated, and installation adjustment requires almost no effort ( Strict leveling is not required), and its configuration is very simple (low price). Furthermore, since the output voltage of the sensing section is linear with respect to the magnitude of acceleration, the set value can be set in any number of stages, and it is possible to detect both P-wave and S-wave seismic waves. It has many excellent features that have not been seen before.

[Brief explanation of the drawing]

Figure 1 shows an example of the power spectrum of seismic waves, Figure 2 shows an example of the structure of an electrodynamic earthquake sensor, and Figure 3 shows an example of the structure of a falling weight earthquake sensor. , FIG. 4 is a block diagram showing the configuration of an embodiment of the present invention, FIG. 5 is a sectional view showing the structure of an embodiment of the sensing section, and FIG. Figure 7 is a diagram showing the experimental results regarding the output of the sensing section, and Figure 8 is a diagram showing the
FIG. 9 is a diagram showing experimental results of output characteristics with respect to vibration frequency for the output voltage shown in FIG. 20,... Sensing section 21. ,,signal processing unit 22, ,preamplifier 23.25. ,, comparator 24.26. , Output circuit 31 , Container 32 , Liquid 34 , Light source 35 , Photoelectric conversion element patent applicant Fushichik Co., Ltd. 1 Figure 2 Figure 3 4 Figure 1 ! Figure 7 (α) (7)) Number of liquids for Figure 8 CHg) Figure 9 CCI)Cb')

Claims (1)

[Claims] A sensing unit comprising a container containing a liquid, a light source that illuminates the inside of the container, a photoelectric conversion element that receives the light inside the container and converts it into an electrical signal, and outputs an output when the output of the sensing unit is larger than a predetermined value. An earthquake detector consisting of a signal processing section that emits signals.