JPS61142425A - Seismic sensor - Google Patents

Abstract

PURPOSE:To enable accurate detection, by providing a temperature control section for holding the liquid temperature of a sensor container to prevent variations in the sensor sensitivity due to changes in the ambient temperature. CONSTITUTION:When the sensing temperature of a temperature sensor 48 reaches a specified temperature T2, a comparator 50 emitts an output signal to close a contact 51a by a controlling section 51 and current is fed to a heater 47 from a power source 52 to heat a liquid 43. On the other hand, when with the action of hysteresis thereof 50, the comparator 50 heats the generation of the output signal to open the contact 51a by the controlling section 51 as the sensing temperature exceeds the temperature T2 to reach a certain temperature. Thereafter, as the sensing temperature of the sensor 48 falls below the temperature T2, current is fed to the heater 47 through the contact 51a. The temperature of the liquid 43 is kept near temperature T2 by repeating the operation to ensure a constant sensitivity of the sensor thereby enabling accurate detection.

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.

[Prior art and problems to be solved by the invention] First, we will explain the frequency of earthquakes.

It is generally said that the frequency of the main component of seismic waves is in the range of 1 to 1OH2, of which the component of 1 to 5 Hz is particularly prominent. Figure 2 shows the power spectrum of the seismic waves observed in Ofunato as an example for the Miyagi Prefecture-oki Earthquake that occurred at 17:14 on June 12, 1973.The dominant frequency was 2 to 3 Hz (2, 4Hz), and the power between 1 and 5 Hz is large.

(Although not shown, the Fourier spectrum has almost the same shape and has many 1 to 5 Hz 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. 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 normal edges, and 0.1 for precision grade.
The sensitivity should be flat in the range of ~5 Hz, and the sensitivity should decrease in the range exceeding 5 Hz.

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

゛ Figure 3 shows an example of the structure of an electrodynamic earthquake sensor (vertical sensor). When the filter 3 moves up and down due to vibration, a voltage is generated at both ends of the filter 30, and the magnitude of this voltage is proportional to the moving speed of the coil 3, which is used to detect an earthquake.

Note that 1 is a spring system that supports the weight 2, and 6 is a yoke that forms a straw 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 with this method fall at 5 Hz or higher as described above (between spring systems!l), and usually It has a falling characteristic at about 10Hz or higher. 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, the electrodynamic seismic sensor has problems in terms of accuracy and adjustment effort.

In addition, a strain gauge type earthquake sensor IT, a strain gauge (strain gauge) is installed in the X and Y directions, and these electrical outputs are combined to determine the acceleration, but the frequency of the strain gauge itself is Since the characteristics extend to several kHz, an electric filter should be used to attenuate frequencies above 5 Hz.

Therefore, the strain gauge type earthquake sensor + 1 is greatly influenced by the characteristics of this filter, and it also includes many error factors such as the need for a multiplier to perform vector synthesis, which poses a problem in terms of reliability. . 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 +1 weight (magnetic material such as iron) 13 is attracted to the permanent magnet 11 fixed to the case 10, but when a vibration of a certain degree or more occurs, this weight 13 falls, is fitted into the weight 13, and rotates in the direction of the arrow around the fulcrum 15, causing the actuator 14' of the microswitch 14 to move.
It is used to sense earthquakes by activating the

Although this method is simple, it has the disadvantage that the sensing level varies depending on the relationship between the attraction force of the magnet and the weight of the weight, making it difficult to adjust, and at the same time, it is difficult to detect at low frequencies (below IHz). 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. 59-98902.

As shown in Figs. 5 and 6, it is a cylindrical container 3.
A liquid 32 such as mercury or oil is placed in a container 31, and a light source 34 such as a light emitting diode is attached to the lid of the container 31. I
When the liquid 32 in the container 31 is shaken by seismic waves, the light receiving element 35 electrically detects the luminance distribution inside the container 31, which changes as the shape of the liquid surface changes. This is a new type of earthquake sensor in which a signal processing unit 21 identifies the vibration level according to the magnitude of the output signal 20a.

That is, in this earthquake sensor, a signal 20a corresponding to the luminance distribution inside the container 31, which has been outputted by the light receiving element 35 of the sensing part 2o, is amplified by the preamplifier 22 (AC amplifier), and then sent to the amplifiers 23, 25, etc. by: This device detects earthquakes at multiple levels, but since the viscosity, which is an important property of the liquid 32 in the container 31, changes due to the influence of ambient temperature, it is possible to detect earthquakes at multiple levels at the same vibration level. Subsequent experimental results revealed that even if the sensor is present, the sensitivity of the sensor changes, causing false positives and making accurate detection difficult.

The present invention has been made in view of the above points, and an object of the present invention is to provide an earthquake sensor in which the sensitivity of the sensor/device does not change even if the ambient temperature changes.

FIG. 1 is a sectional view showing an example of a sensor according to the present invention, in which 40 is a cylindrical container, 41 is a liquid such as mercury, which has a high specific gravity, low viscosity, and high surface reflectance, and 42 is a liquid. The double layer liquid 43 is made of a liquid such as aircraft hydraulic oil, which has a high viscosity with a small specific gravity and little change in viscosity due to temperature compared to 4i, and has a low surface reflectance. 44 is a power source, 45 is a light source such as a light emitting diode, 46 is a photoelectric conversion element that receives light,
47 is a heater for warming the double layer liquid 43; 48 is a temperature sensor such as a thermistor; 49 is an amplifier that amplifies the output signal of the temperature sensor 4B which is proportional to the temperature; That is, double layer liquid 43
a humpator with hysteresis that emits an output signal when the temperature drops below a predetermined temperature (for example, 0°C) and stops generating the output signal when the temperature exceeds a predetermined temperature (for example, 10°C), 51
5 is an operation unit that closes the contact 51m when the comparator 50 issues an output signal, and opens the contact 51m when the output signal disappears;
Reference numeral 2 denotes a power source that supplies current to the heating element 47 through the contact 51a. The signal processing section is exactly the same as in FIG. 5.

In FIG. 1, when the container 40 is placed at rest, the double layer liquid 43 is also at rest and therefore the container 40 is placed at rest.
The brightness distribution within 0 is constant and the output 203 of the photoelectric conversion element 46
is only a constant DC voltage, but when the double layer liquid 43 is shaken due to vibrations such as earthquakes, the shape of the surface of each liquid 41 and 42 that makes up the double layer changes, and the form of light reflection and scattering changes. As a result, the luminance distribution inside the container 40 changes, and correspondingly, the output 20a of the photoelectric conversion element 46 (output after passing through the preamplifier 22, hereinafter referred to as the output voltage of the sensor 20) changes as shown in FIG. (a) shows the case where the vibration frequency is low, and (b) shows the case where the vibration frequency is high).
- If the vibration frequency of the earthquake changes, the behavior of the liquid 43# will also differ depending on whether it is a vertical vertical vibration wave (hereinafter referred to as P wave) or a horizontal vibration wave (hereinafter referred to as S wave). The brightness distribution also changes slightly, and its influence appears on the output voltage.

Incidentally, when this new type of sensor is vibrated with a constant acceleration, the output characteristics of the sensing section 20 with respect to the vibration frequency are as shown in FIG. FIG. 8(a) shows the case of horizontal vibration (hereinafter referred to as horizontal motion), FIG. 8(b) shows the case of vertical vertical vibration (hereinafter referred to as vertical motion), and the parameters TI, T2. TI differs depending on the type of liquid 42, but for example, in the case of aircraft hydraulic fluid, T1 is about 40°C and T2 is 0°C.

T3 is the temperature of the liquid 43 that satisfies the condition of Ts > Tt > Ts such as -10°C, vl is the output voltage of the sensing unit 20 when the liquid temperature Ts is the horizontal vibration frequency l11z, and v2
is the output voltage of the sensing unit 20 when the liquid temperature is T2 and the horizontal vibration frequency is from 112 to 5 Hz, 3 is the output voltage of the sensing unit 20 when the liquid temperature is T3 and the horizontal vibration frequency is IHz, V
4 is the output voltage of the sensing unit 20 when the liquid temperature T1 is the vertical vibration frequency IHz, v5 is the output voltage of the sensing unit 20 when the liquid temperature T2 is the vertical vibration frequency IHz to 5Hz, v6 is the liquid temperature T3, This is the output voltage of the sensing section 20 when the vertical vibration frequency is IHz.

As is clear from Fig. 8, when the liquid temperature is T2, the frequency characteristics are ideal as a flat sensor between 111z and 511z, but when the liquid temperature is T2, the frequency characteristics are ideal as a flat sensor.
If it is 1 or more and T3 or less, the frequency characteristic is IHz to 5H.
The liquid temperature is not flat between z and T! When the liquid temperature T3 is lower than □, the Inx side rises, while when the liquid temperature T1 is higher than the liquid temperature 12, the Inx side rises.
There is a tendency for the x side to decrease, and a tendency opposite to that described above appears near 5 Hz. In other words, the liquid temperature is T1 or higher and T3
In the following cases, even if the sensor 20 is vibrated at a constant acceleration, if the frequency changes, the output voltage of the sensor 20 will change and there is a risk of false detection. The output characteristics of the sensor that are actually obtained when the sensor is vibrated in the horizontal direction with an electric current of 80 gal are as shown in Figure 9, and the output voltage FEVt
-1,2V (Tt-0℃), v1Φ1.14V (Tl
-40℃)+Vs゛*1.26V(Ts*-10
℃), and □ "The technical standard for elevators is that the accuracy of a normal edge sensor is ± (10% of the setting value + 7) gal, and the accuracy of a precision grade sensor is ± (5% of the setting value + 5) 'gal. The room temperature in the elevator machine room is 4G.
Since it is stipulated that a ventilation system must be provided to maintain the temperature below C, experiments have revealed that if the temperature is 12 or higher, it can meet the requirements for a precision sensor.

The reason why the characteristics change with temperature is that as the temperature decreases, the viscosity of the oil increases, and the liquid within the 4° container has the characteristics of an oil-only liquid with a large viscous resistance (as shown in Figure 10 (a)). As the temperature increases, the viscosity of the oil decreases, the viscous resistance becomes less sensitive, and the damping effect decreases, resulting in the characteristics shown in FIG.
This is because the characteristics of silver alone become dominant.

Therefore, in the present invention, for example, when the temperature sensed by the temperature sensor 48 reaches T2, the humpator 50 emits an output signal,
The operation unit 51 closes the contact 51a and supplies current to the heater 47 to warm the liquid 43. When the sensed temperature exceeds T2 and reaches a certain temperature up to T1 due to the hysteresis of the fan plater 50, the fan plater 50 outputs an output signal. The operation section 51 opens the contact 518 after stopping the occurrence of the . After that, when the temperature sensed by the temperature sensor 48 falls below T2 again, current is again supplied to the heater 47 via the contact 51a to raise the temperature of the liquid 43, and by repeating this operation, the temperature of the liquid 43 is maintained near T2. , always IHz ~ 5Hz
This is to maintain a substantially flat frequency characteristic between the two regions, so that there is no problem in using the earthquake sensor, especially in cold regions.

The above explanation describes an example in which liquid No. 42 aircraft hydraulic oil is used.If other liquids are used, the frequency characteristics using the melting temperature as a parameter will be different, but the technical idea of the present invention is It is clear that the method can be easily applied even if the type of material changes.

As described above, according to the present invention, since a temperature control unit is provided that keeps the temperature of the liquid within a predetermined range, ideal characteristics that match the frequency characteristics of seismic waves can always be maintained regardless of the ambient temperature, and malfunctions can occur. The new type of earthquake sensor has the unique effect of eliminating the fear of this, and making full use of the unique feature of the new type of earthquake sensor, which is the ability to provide multiple levels of sensing with a single sensor.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing an example of a sensing section according to the present invention, and FIG.
Figure 3 shows an example of the structure of an electrodynamic seismic sensor; Figure 4 shows an example of the structure of a drop-weight seismic sensor; Figure 5 is a block diagram showing the configuration of a new type of earthquake sensor, Figure 6 is a cross-sectional view of the structure of an example of the sensing section of the new type of earthquake sensor, and Figure 7 is an experimental result of the output of the sensing section. FIGS. 8 and 9 are diagrams showing experimental results of the output characteristics of the ground m sensor with respect to vibration frequency according to the present invention, and FIGS.
The figure is an explanatory diagram illustrating the characteristics of the earthquake sensor of the present invention. 2σ00. Sensing unit 21, , Signal processing unit 22, Preamplifiers 23, 25, , Humperator 24.2B,
,,output circuit 31.40. ,, Container 32.41,42,43. ,,liquid 34.45. ,, light source 35.46. ,,Photoelectric conversion element 47,,,Heater 48,,,Temperature sensor patent applicant Fujichik Co., Ltd. J Figure 62V21 Stock movement? ! (J(x) 3rd helmet 4 [￥l も 5 [21 I To 6 fig. 7 fig. (IIL) (b) ￥iJ
8 Figure (c) Cb) field

Claims (1)

[Scope of Claims] A container containing a liquid, a light source that illuminates the inside of the container, a sensing section that includes a photoelectric conversion element that receives light in the container and converts it into an electrical signal, and an output of the sensing section that has a predetermined value. What is claimed is: 1. An earthquake sensor comprising a signal processing section that emits an output when the temperature is greater than a value, and further comprising a temperature control section for the liquid.