JP2001013160A - Acceleration responding element and acceleration sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a small-size acceleration responding element outputting a sufficiently large output signal, allowing an easy distinction process between earthquake vibration and living vibration. SOLUTION: This acceleration responding element 1 has a nearly cylindrical sealed vessel 2 that is a main electrode, and plural sub electrodes 5A, 5B disposed at even intervals. An electroconductive liquid 4 is enclosed in the sealed vessel 2 by a proper amount. When a slant angle of the sealed vessel 2 changes, a contact amount between the sub electrodes 5A, 5B and the electroconductive liquid 4 changes to cause a change in a resistance between the main electrode 2 and the sub electrodes 5A, 5B. By setting an inner diameter of the sealed vessel 2 to 4-25 mm, a resonance frequency can become higher than a frequency of an earthquake wave. By disposing the respective electrodes 5A, 5B at intervals above at least 1 mm from each other within a moving range of a liquid surface 4A, influence of viscosity of the electroconductive liquid 4 upon movement of the liquid 4 can be reduced to a negligible degree.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention provides an acceleration response element and an acceleration sensor which are small, easy to handle, and output a signal which changes in proportion to the magnitude of the vibration or the inclination angle.

[0002]

2. Description of the Related Art As a conventional acceleration sensor, there is known an acceleration sensor that opens and closes a contact point using a vibrator such as a steel ball.
However, in such an accelerometer, the signal output is only on or off, so it is only possible to know whether the magnitude of the vibration is above or below a certain threshold. In order to obtain a seismic sensor whose display or processing needs to be changed accordingly, it is necessary to use a large number of acceleration sensors having different sensitivities to vibration.

On the other hand, as an acceleration sensor capable of continuously detecting the magnitude of vibration, there are a type using a piezoelectric element and a type detecting a change in capacitance. In the apparatus using a piezoelectric element, a piezoelectric element is arranged on a cantilever or the like that bends according to vibration acceleration to generate a voltage according to the amount of bending. In addition, there is a device that detects the capacitance by detecting the magnitude of the vibration by a change in the capacitance between the tip portion and the wall surface due to the movement due to the vibration of the cantilever.

[0004]

However, in the case of using a piezoelectric element, an amplifier is indispensable because the amount of generated electric charge is small, and since the voltage is generated in accordance with the change in acceleration, the amplifier is in an inclined state. It is not possible to detect a state in which a constant acceleration is maintained by the sensor as in the above. When the capacitance type is miniaturized, the distance between the opposing electrodes must be set with extremely high accuracy and the interval must be small to obtain the required capacitance, which is difficult to miniaturize. Accompanied by

[0005] Furthermore, when these devices are miniaturized, the weight provided at the tip of the cantilever has only a small mass. Therefore, if the cantilever is bent sufficiently to generate a signal, it is necessary to improve the sensitivity. Needs to be suppressed. For this reason, the impact acceleration generated during handling easily exceeds the rigidity described above, and the cantilever is deformed or damaged, so that there is a problem of the load acceleration with respect to the sensitivity of causing a characteristic change or failure.

Accordingly, the present applicant has filed Japanese Patent Application No. 11-12928.
0 and Japanese Patent Application No. 11-143163 have proposed an acceleration sensor and an acceleration response element that use a liquid and change the output by moving the liquid by acceleration. In this acceleration sensor, a conductive liquid is sealed in a cylindrical hermetic container in which a plurality of electrodes are fixed through, and a change in resistance between the electrodes due to acceleration or inclination is detected. This acceleration sensor utilizes the fluctuation of the contact area between the electrode and the conductive liquid caused by the fluctuation of the liquid level due to vibration. In the case of such a structure, the larger the diameter of the container, the greater the fluctuation distance of the liquid level and the greater the signal output of the sensor, but the lower the resonance frequency of the liquid, especially when used in a seismic sensor. There is a possibility that the vibration frequency due to the vibration and the resonance frequency overlap, and the magnitude of the shaking due to the earthquake cannot be measured accurately. In addition, when the container is small, not only the fluctuation distance of the liquid surface is shortened, but also if the distance between the electrodes is narrow, the effects of the viscosity and surface tension of the liquid cannot be ignored, and the operation of the conductive liquid is braked. There is a possibility that the sensor output cannot sufficiently follow the acceleration.

[0007]

SUMMARY OF THE INVENTION Accordingly, an acceleration response element according to the present invention has a substantially cylindrical hermetic container having both ends closed, in which a main electrode and a plurality of sub-electrodes are insulated from each other. The sub-electrodes are arranged at equal intervals with the same distance from the main electrode, and the closed container is filled with a conductive liquid and the amount of the conductive liquid is Is the amount at which at least a part of the sub-electrode is positioned on the liquid surface in the normal posture,
In the acceleration response element in which the amount of contact between the sub-electrode and the conductive liquid is changed by changing the inclination angle and the inclination direction from the closed posture, the resistance value between the main electrode and the sub-electrode changes, Inner diameter of sealed container is 4mm or more and 25
mm or less, and the electrodes are arranged so as to have an interval of at least 1 mm or more within a range in which the liquid surface moves.

According to the present invention, by setting the inner diameter of the closed vessel to 4 mm or more and 25 mm or less, the resonance frequency is made higher than the frequency of the seismic wave, and the electrodes are arranged so as to have a distance of at least 1 mm from each other. Accordingly, the effect of the viscosity of the conductive liquid on the movement of the liquid can be made negligible.

In the acceleration-responsive element according to the present invention, the closed casing of the acceleration-responsive element comprises a cylindrical metal container having one end closed, and a metal disk fixed to an opening of the metal container. The present invention is characterized in that a metal container and a disk are used as a main electrode, and a metal lead terminal as a sub-electrode is fixed through the disk in an electrically insulating manner.

Further, by arranging four lead terminals, it is possible to detect the components of the acceleration in the X and Y directions.

Further, the acceleration sensor according to the present invention is characterized in that each sub-electrode is connected so as to form a Wheatstone bridge circuit by an acceleration response element and a fixed resistor.

Further, an acceleration sensor according to the present invention has two of the above-described acceleration response elements, and the two acceleration response elements are arranged so that the arrangement directions of the lead terminals are in a predetermined positional relationship. The two sensors are connected to each other to form a Wheatstone bridge circuit.

Further, a reference fixed resistor is connected in series with the Wheatstone bridge circuit, and the voltage ratio between both ends of the Wheatstone bridge circuit voltage application and both ends of the reference fixed resistor is measured. Since the acceleration and the change state of the acceleration can be detected while detecting the temperature of the liquid, it is possible to correct a change in characteristics due to a temperature change of the conductive liquid or the like.

In the case where an acceleration response element capable of obtaining a signal as an electrical output by movement of the conductive liquid is used, the power supply for driving the acceleration response element is an AC power supply such as an AC sine wave or an AC rectangular wave. By sampling the output from the acceleration response element in synchronization with the cycle of the power supply voltage, it is possible to prevent a change in characteristics due to electrolysis and polarization of the conductive liquid and to obtain a more accurate acceleration signal even in the case of an AC wave. Can be easily obtained.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to the drawings. FIG. 1 is a longitudinal sectional view of an acceleration response element 1 of the present invention. The acceleration response element 1 includes a cylindrical metal container 2 having one end closed and a metal disk 3 closing an open end of the container. The container 2 and the metal plate 3 are fixed to each other by, for example, ring projection welding, which is a kind of resistance welding, to form a closed container. The metal container 2 and the metal plate 3 are main electrodes of the acceleration response element 1. Becomes A predetermined amount of a conductive liquid 4 selected in consideration of the fact that the material of the container and the lead terminal is not corrosive or the like is sealed inside the closed container. In the present invention, the inner diameter of the metal container 2 is 4 mm or more and 25 mm or less.
By setting the inner diameter of the metal container to this range, the resonance frequency of the acceleration response element is located between 5 and 20 Hz.

A plurality of through holes 3A are formed in the metal plate 3 at equal intervals. In the embodiment, as shown in the perspective view of FIG. 2, four through holes 3A are formed, and metal lead terminals 5A to 5D serving as sub-electrodes move the liquid level of the conductive liquid 4 in each of the through holes. Within the range, they are arranged at regular intervals of at least 1 mm or more, and are fixed by an electrically insulating filler 6 such as glass. Each lead terminal as a sub-electrode also has an interval of at least 1 mm or more with respect to the inner surface of the metal container 2 as a main electrode, and the distance between each lead terminal and the inner surface of the closed container is equal. Although not shown, a plurality of lead terminals may be penetrated and fixed to one through hole having a size in which the four through holes 3A are put together by a filler such as glass. The lead terminals 5A to 5A
D protrudes greatly into the inside of the container, and is arranged so that its tip comes out above the liquid surface 4A of the conductive liquid 4 in the normal posture shown in FIG. This acceleration response element 1
When the acceleration is applied, the conductive liquid moves to change the resistance between the main electrode and the sub-electrode, thereby obtaining a signal as an electrical output.

In this embodiment, the resonance frequency of the acceleration response element is determined by the relationship between the type of the conductive liquid as the movable portion and the size of the closed container. The relationship between the inner diameter of the closed container and the resonance frequency is shown in FIG. Shown in the graph. As is clear from this graph, the smaller the inner diameter of the closed container, the higher the resonance frequency, and conversely, the larger the inner diameter, the lower the resonance frequency.
Since the output from the acceleration response element becomes larger in the vicinity of the resonance frequency than in other frequencies, the influence of the resonance frequency can be reduced by correcting the signal as described later. However, if the inner diameter of the closed vessel is set to a value larger than 25 mm, the resonance frequency will be less than 5 Hz, so that the vibration frequency due to the earthquake and the resonance frequency will overlap, and even if the signal output from the acceleration response element is corrected, the vibration will not be accurate. It becomes difficult to detect a large size.

On the other hand, if the inner diameter is less than 4 mm, in a structure such as the present invention in which a plurality of lead terminals are inserted, it is very difficult to make the distance between the electrodes 1 mm or more. In this case as well, for example, by making the diameter of the lead terminal thinner, it is possible to allow a larger margin in dimension, but in this embodiment, the diameter of the lead terminal is set to 0.5 mm. If the diameter is reduced, the movement of the conductive liquid may cause the lead terminals to bend and the like, so that accurate acceleration detection may not be possible. When the distance between the electrodes is small, the resistance between the electrodes can be adjusted by adjusting the specific resistance of the conductive liquid, but the viscosity or surface tension of the liquid itself within the range in which the liquid surface moves can be adjusted. The effect on the movement of the conductive liquid cannot be ignored. In particular, the effect of viscosity is large, and the movement of the conductive liquid between the electrodes during vibration is disturbed and cannot move quickly, so it does not follow the vibration reliably and the output of the acceleration response element can reproduce the vibration waveform. become unable.

Therefore, in one embodiment of the present invention, by setting the inner diameter of the closed vessel to 4 mm or more and 25 mm or less, the resonance frequency is made higher than the frequency of the seismic wave, and each electrode is moved at least within the range in which the liquid surface moves. 1m
By arranging them so as to have an interval of m or more, the effect of the viscosity and surface tension of the conductive liquid on the movement of the liquid during vibration can be made negligible.

In the embodiment, as the conductive liquid 4, a liquid in which cyclohexanone having no conductivity is used as a solvent and lithium nitrate is dissolved as an electrolyte is used. For example, as the conductive liquid, besides this, a liquid having conductivity itself or a solution in which an electrolyte is dissolved in a solvent having no conductivity itself can be used. Examples include methyl alcohol, ethyl alcohol, isopropyl alcohol, acetone, cyclohexanone, ethyl methyl ketone, diethylene glycol monobutyl ether, etc.
And those in which conductivity is adjusted by adding an additive such as potassium iodide to these. The kinematic viscosities of these liquids are between about 0.4 and 3.5 mm ² / s at room temperature. However, if the kinematic viscosity is low, the liquid tends to bounce, and if the kinematic viscosity is high, the ability to follow vibrations is reduced. .0
It is preferable to be in the range of 2.0 mm ² / s.

The acceleration responsive element 1 detects the resistance value of each of the lead terminals 5A to 5D using the metal container 2 or the metal plate 3 as one terminal, thereby detecting the liquid level 4A of the conductive liquid 4.
Can be known. For example, when acceleration is applied in the direction indicated by arrow A, the liquid level 4A
As shown by the dotted line 4B. At this time, the contact portion of one of the lead terminals 5A with the conductive liquid 4 increases, and the contact portion of the other 5C with the liquid decreases. Also in this case,
Since there is no acceleration component in the direction connecting the lead terminals 5B and 5D, the lead terminals 5B and 5D are located at the center of the inclination of the liquid surface, and there is no substantial change in the contact portion with the liquid. The contact area between the conductive liquid and the closed container does not change in the contacting range. Therefore, by detecting and comparing the resistance value between the container serving as the main electrode and the respective lead terminals serving as the sub-electrodes, the inclination direction and the inclination angle of the liquid surface can be known. You can know the size of.

Next, FIG. 3 shows an example of an equivalent circuit of the acceleration sensor 101 using the acceleration response element 1 for use as a seismic sensor or the like. In this acceleration sensor 101, the container 2 is connected to one end A of a bridge power supply V for a Wheatstone bridge circuit described later, and is connected to lead terminals 5A to 5D via a conductive liquid 4. The bridge power supply V is an AC power supply that generates a sine wave, and applies positive and negative currents to the acceleration response element 1 alternately. Here, the reason why the power supply connected to the acceleration response element 1 is an AC sine wave is to avoid electrolysis of the conductive liquid 4 by DC current and change in resistance value due to polarization of the liquid. It is needless to say that an AC rectangular wave which does not cause electrolysis may be applied.

The container 2 and the respective lead terminals 5A to 5A
D and R5A to R5D
Indicated by The other end of each lead terminal is connected to the other end B of the bridge power supply V via fixed resistors R1 to R4, respectively, so that the acceleration response element 1 and the fixed resistors R1 to R4 are connected.
A set of Wheatstone bridge circuits (hereinafter simply referred to as bridge circuits) is configured. Here, the lead terminal 5 of FIG.
The direction of the imaginary straight line connecting A and 5C (the left-right direction in the drawing) is defined as the X direction with respect to the acceleration response element 1, and the direction (the front-back direction in the drawing) connecting the lead terminals 5B and 5D (not shown) orthogonal to the direction is Y. Direction, the voltage change between the intermediate points X1 and X2 of one bridge circuit is detected to determine the liquid surface tilt angle in the X direction, and similarly, the voltage between the intermediate points Y1 and Y2 of the other bridge circuit. By detecting the change, the liquid surface tilt angle in the Y direction can be known. The actual inclination angle of the liquid surface, that is, the acceleration sensor 101 is obtained by combining the X and Y directions obtained here.
Can be obtained. Here, in practice, the voltage change at the intermediate point of each bridge circuit is output in the form of a superposition of the AC change of the driving power supply applied to the bridge circuit and the change due to vibration, so apply the measured voltage. It is necessary to perform processing in accordance with the change in the applied voltage or to synchronize the timing of measuring the voltage with the drive power supply, which will be described later.

Next, detection of acceleration by the acceleration sensor 101 will be described. Actually acceleration sensor 1
01 is supplied with an AC sine wave or a rectangular wave from the bridge power supply V. For the sake of easy understanding, the bridge power supply V has a DC constant voltage with the A side as a + power supply and the B side as a ground. In the following description, it is assumed that is applied. Acceleration response element 1
In a state where the lead terminals 5A to 5D are in the normal posture and are not subjected to the horizontal acceleration, the lead terminals 5A to 5D are in contact with the conductive liquid 4 in the same manner. R5A to R5D have substantially equivalent resistance values, and by setting the resistance values of the fixed resistors R1 to R4 to be substantially equal, the potentials of the intermediate points X1, X2, Y1 and Y2 of each bridge circuit have the same value. And the potential difference between the intermediate points of each bridge circuit is zero.

Here, for example, when the acceleration response element 1 receives an acceleration in the direction of arrow A in FIG. 1, the liquid surface tilts as 4B, and the contact amount between the lead terminal 5A and the liquid increases, so that the lead terminal 5A The resistance R5A between the power supply and the container 2 decreases, and the potential of the intermediate point X1 with respect to the other end B of the power supply increases substantially in proportion to the amount of contact between the lead terminal and the liquid. On the other hand, since the amount of contact between the lead terminal 5C and the liquid decreases, the resistance value R5C increases, and the potential of the intermediate point X2 with respect to the other end B of the power supply decreases. By detecting the potential difference between the intermediate points X1 and X2 of the bridge circuit, it is detected that the liquid surface of the conductive liquid 4 is inclined with respect to the X direction, and the inclination angle is obtained. Further, from the potential difference between the intermediate points Y1 and Y2, Y
The actual inclination angle of the liquid surface can be obtained by calculating the inclination angle in the direction and combining the inclination angle in the X direction, and the magnitude of the acceleration received by the acceleration detecting device can be obtained from the inclination angle. it can. Further, the direction of the acceleration applied to the acceleration sensor 101 can be known from the magnitudes and directions of both the X direction and the Y direction acceleration.

Since the acceleration sensor 101 detects a change in the electric resistance between the lead terminal and the container due to the inclination of the liquid surface, the acceleration sensor 101 detects the acceleration and deceleration of a moving body such as an automobile, as described above. Detection of relatively low frequency vibrations such as earthquakes, and acceleration sensor 10
It is possible to reliably detect a case where the acceleration does not alternately change, such as a case where 1 is inclined in one direction, or a state where the acceleration does not change while being inclined at a certain angle. In the above description, the initial orientation of the acceleration sensor was described on the assumption that each lead terminal as a sub-electrode was in the normal orientation of being immersed in liquid of the same size. When the processing function is provided, the potential difference in the X direction and the Y direction in the initial posture in which no acceleration occurs can be used as a reference. Normally, the initial allowable inclination angle of the acceleration response element that can be used by this offset processing is 5 to 6 degrees, which is a mounting error with respect to the normal posture, and up to about 10 degrees even if it is a special one. In this case, the fluctuation of the output characteristics due to the inclination of the element can be considered to be within the range of the error. When the offset processing of the output signal based on the initial attitude is performed as described above, it is not necessary to make the mounting attitude of the acceleration response element or the acceleration sensor strict, so that the mounting operation becomes easy.

Here, when the acceleration sensor and the acceleration response element are inclined beyond the allowable inclination range as described above, the output characteristics from the sensor with respect to the vibration acceleration may be significantly different from those in the normal posture. . Thus, even when the acceleration sensor is tilted more than the specified, it is possible to use the acceleration sensor by performing the offset processing of the output signal with respect to the initial posture and the correction processing for the fluctuation of the output characteristic. Requires complicated signal processing, so that the signal processing circuit becomes complicated and expensive. However, in actuality, the inclination beyond the specified value is due to an initial mounting posture defect or an inclination due to an accident or the like. Therefore, both of them should be treated as abnormal, and complicated signal processing is not required.

Further, even if a bridge circuit is not provided, for example, the inclination of the liquid level of the acceleration response element can be detected by directly measuring the resistance value (voltage) of each resistance portion of the acceleration sensor. Acceleration sensor 1 in case
01 is the normal posture and the resistance value of the resistance portion is 500 kΩ, whereas the resistance value changes only about 20 kΩ even if the liquid surface is inclined by 10 degrees. Therefore, in order to sufficiently obtain the analysis capability of the voltage change at both ends of the resistor, a high-performance signal processing circuit having a high resolution with respect to the maximum voltage range is required for the change of several percent. On the other hand, when a bridge circuit is formed, the signal processing circuit only has to look at the potential difference at the output of the acceleration sensor. Circuit design becomes easy.

The acceleration responsive element of the acceleration sensor according to the present invention uses the conductive liquids as described above, but these conductive liquids generally change in their specific resistance to temperature, and are similar to the above-described bridge circuit. When used in combination with a fixed resistor having a small resistance change due to temperature, the potential difference output from the bridge circuit may change due to a change in ambient temperature. In other words, the potential difference that should occur at the midpoint of the bridge circuit when the liquid level is tilted fluctuates with the temperature of the liquid, and the accurate tilt angle of the liquid level is measured,
That is, there is a possibility that the measurement of the acceleration or the inclination angle with respect to the acceleration sensor cannot be performed. To solve this problem, it is necessary to accurately grasp the temperature of the conductive liquid and correct the output from the sensor based on the temperature. However, when detecting the temperature of a conductive liquid with a thermistor or thermocouple, it is difficult for a small sensor to put them in the container of the acceleration response element, and at the same time, it affects the behavior of the conductive liquid. If it is attached to the outside of the container, a temperature difference between the ambient temperature and the conductive liquid may occur, so that accurate temperature may not be grasped.

Therefore, in the present invention, the circuit diagram of FIG.
Connect a fixed reference resistor in series with the bridge circuit as shown.
Then, both ends to which the voltage of the bridge circuit is applied and the fixed resistor
By measuring and processing the ratio of the voltage to both ends of the resistor
The temperature of the conductive liquid of the acceleration response element is detected. Figure
In the case of the third embodiment, the common main power of the two bridge circuits is used.
Reference for temperature detection in electrical series with metal container 2 which is a pole
Fixed resistor R_A(Hereinafter referred to as reference resistance)
You. This reference resistance R_AIs the temperature within the operating temperature range of the sensor.
The change in the resistance value is a normal fixed resistance that can be ignored
Yes, its resistance is sufficiently higher than the resistance of the bridge circuit.
It is set small. For example, in the embodiment, both bridge times
Although the combined resistance of the road is about 250 kΩ at room temperature,
Quasi-resistance R _AIs 10 kΩ.

The reference resistance _RA is a normal fixed resistance, and its resistance value does not substantially change within the operating temperature range, for example, -30 to 80 ° C., whereas the conductivity of the acceleration response element constituting the bridge circuit is changed. Liquid has a large change in specific resistance depending on temperature. Therefore, if the combined resistance value of the bridge circuit is measured, the resistance value of the conductive liquid is substantially measured, and the temperature of the conductive liquid can be known from the resistance value. This resistance value can be measured from a comparison between the voltage at both ends of the bridge circuit to which the voltage is applied and the voltage at both ends of the reference resistor whose resistance value does not substantially change, that is, the ratio of the two voltages.

To explain this point, for example, in this embodiment in which lithium nitrate is dissolved in cyclohexanone as the conductive liquid, the resistance value of the conductive liquid decreases as the temperature increases. Specifically, the resistance value of each of the resistance portions R5A to R5D is about 120 at −30 ° C.
However, at 80 ° C., the resistance drops to about 350 kΩ, and accordingly, the combined resistance value between D and E by the two bridge circuits shown in the circuit of FIG.
In the case of Ω, it is 425 kΩ at −30 ° C., but decreases to about 210 kΩ at 80 ° C. Also in this case, the reference resistance _RA, which is a fixed resistance, is substantially negligible in resistance change in the operating temperature range of the acceleration sensor.
The resistance value between -D can be regarded as constant.

When the acceleration sensor is tilted, D-
Although the combined resistance value between E fluctuates, the variation value is negligible since the change in resistance of the entire bridge circuit of the sensor is slight even if a 10% change in resistance occurs between the resistance portions due to the inclination. Specifically, when the resistance value of the fixed resistance of the bridge circuit is substantially equal to the resistance value of the resistance part in the normal posture, D
The change rate of the combined resistance value between −E and 0.25% is 0.25%. Even when the resistance value of the conductive liquid becomes about 2.5 times the fixed resistance at the lower limit temperature of the operating temperature range, the change rate is 0.1%. It is about 5%.

The resistance between D and E due to temperature change
Due to the change, between C and D when a voltage is applied between C and E
Voltage V_RAnd the voltage V between D and E_SAnd the ratio fluctuates.
Here, the resistance between CD and D is known in advance from this voltage ratio.
Therefore, the resistance value between D and E is known, and furthermore, the bridge circuit
The resistance values of the fixed resistors R1 to R4 used are known.
Can detect a change in resistance of the conductive liquid.
Wear. Thus, the reference resistance R_AAnd bridge circuit voltage
The temperature of the conductive liquid by measuring the ratio of
it can. Further, the voltage value applied between CE and E is V
If it is known in advance, the voltage between CD and D
If measured, the voltage between D and E is automatically determined,
This means that the above-mentioned ratio has been measured,
The temperature can be known virtually. Therefore, in this case,
Quasi-resistance R_AThe voltage V across _RThe conductive liquid itself
The signal indicates the temperature. The voltage V between D and E_SOnly
It is easy to understand that measurement can be handled in the same way.
I can solve it.

For example, by using this temperature information in a later-described correction process of an output signal from the acceleration sensor, appropriate signal processing can be performed in accordance with a change in viscosity or resonance frequency due to the temperature of the conductive liquid. If it can be considered that the temperature of the entire device to which the sensor is attached is also changing, it is possible to control the entire device according to the temperature change by inputting this temperature information to the control part of the device itself. it can.

As shown in FIG. 4, by forming a bridge circuit using two substantially identical acceleration response elements, the resistance of the entire bridge circuit can be similarly changed with temperature change. According to this method, an output change with respect to a resistance change of the bridge circuit can be suppressed, and an output from the bridge circuit can be increased. This example will be described with reference to FIGS. In the circuit of the acceleration sensor 201, two acceleration response elements 1
And 11 are used. Each of these acceleration response elements uses a conductive liquid as described above, and the configuration thereof is the same as that of the above-described example.

In this acceleration sensor 201, the acceleration responsive elements 1 and 11 are arranged in the same direction in which the lead terminals as sub-electrodes are arranged.
Is connected to one terminal A of the bridge power supply V via a reference fixed resistor _RA, and the container 12 of the other acceleration response element 11 is connected to the other terminal B of the bridge power supply V. Further, the respective lead terminals are connected in a predetermined combination to form two bridge circuits. The combination of the connection between the lead terminals is such that the connection on the X-axis and the connection on the Y-axis are performed, and when the resistance is increased, the other is reduced when the inclination is increased. Specifically, FIG.
As shown in the wiring diagram of FIG.
A is connected to the lead terminal 15C of the acceleration response element 11, and the lead terminal 5C is connected to the lead terminal 15A. Although not shown in detail, it is apparent from FIG. 4 that the lead terminal 5B and the lead terminal 15B are also connected to the corresponding lead terminals 15D and 5D. In this example, when acceleration acts in the X-axis direction indicated by arrow A, the liquid 2 is biased toward the lead terminals 5A and 15A, so that the resistances R5A and R15A decrease and the resistances R5C and R15
C increases.

If the acceleration sensor is a circuit as shown in FIG. 4, the intermediate point X1 of the bridge circuit with respect to the other end B of the power supply
Is almost twice as high at the same acceleration as compared with the above-described one using the fixed resistance, and the potential is also reduced about twice as much as the conventional one at the intermediate point X2. Certain potential differences also have twice the amount of change as compared to those described above. Therefore, especially at a small acceleration, the output voltage based on the change in the potential increases, and the detection of the acceleration becomes more reliable. When the acceleration includes a component in the Y-axis direction, the intermediate points Y1 and Y2 also have X1 and X2.
It is easy to understand that a potential change similar to that described above occurs.

Furthermore, since the acceleration sensor circuit uses the same acceleration response element having the same structure, the resistance portion is the same conductive liquid. Therefore, the specific resistance of the conductive liquid changes with the change of the ambient temperature. However, since the portions connected in series, for example, the resistors R5A and R15C similarly cause a resistance change, the potential of the intermediate point X1 is not affected. Even if the resistance changes, R5A and R15A due to the inclination of the liquid surface
Does not change, the potential change at the intermediate point X1 does not change. Resistors R5A to R5 of each bridge circuit
Since D and R15A to R15D all change in this manner, the characteristics of the bridge circuit do not substantially change even if the ambient temperature changes, that is, the influence of the temperature change on the detected value can be compensated. . Note that connects the reference fixed resistor R _A in the same manner as the bridge circuit in series with the previous example in this embodiment, the end portions of the both end portions and the fixed resistor R _A of the voltage of the bridge circuit is applied By measuring and processing the voltage ratio, the temperature of the conductive liquid in the acceleration response element can be detected. By using this temperature information to correct the output signal from the acceleration sensor, the signal from the acceleration sensor can be corrected more accurately, and this temperature information can be input to the control section of the device to which the sensor is attached. By doing so, control according to the temperature change can be performed for the entire device.

Next, a signal processing method when the acceleration sensor using the acceleration response element is used for detecting a seismic wave will be described. In the detection of a seismic wave, a low frequency vibration from 1 to 5 Hz, which is the main vibration frequency of the earthquake, to about 10 Hz as necessary is detected.

By the way, a seismic sensor for detecting a seismic wave is sometimes used by being incorporated in a microcomputer meter of city gas or propane gas. In this case, the operating temperature range is about -30 to + 80 ° C. The conductive liquid of the acceleration sensor used for this is required to have as little change in viscosity as possible due to temperature, and particularly to have relatively low viscosity even at low temperatures. Therefore, as the conductive liquid, a liquid having low viscosity such as methyl alcohol, ethyl alcohol, and acetone, or a liquid in which an additive for adjusting conductivity is dissolved using these as a solvent may be used. In the embodiment, as described above, cyclohexanone having no conductivity is used as a solvent, and an electrolyte in which lithium nitrate is dissolved is used. These liquids have a low freezing point, can maintain the fluidity of the liquid even in the above-mentioned use temperature range, and have a relatively small change in viscosity, so that the acceleration sensor can obtain stable operation characteristics.

As shown in FIG. 1, when an acceleration sensor using a liquid is used for vibration detection, the movement of the conductive liquid increases near a resonance frequency determined by the liquid as the movable portion and the container. However, in the case of a solid-state sensor in which a movable part such as one that opens and closes a contact point using a vibrator such as a steel ball described above as a conventional example or a piezoelectric type or a capacitance type causes resonance, the movable part supports or moves. In the acceleration sensor of the present invention as shown in FIG. 1, since the movable part is a liquid, the resonance movement of the movable part at the resonance frequency is a solid compared to the case where the part in contact with the part is likely to be broken. The impact force is small compared to that of No, and there is no worry about destruction. The resonance frequency is determined by the viscosity of the liquid, the size of the sensor container and the dimensions of the lead terminals.
When the above liquid is used when the thickness is about 0 to 15 mm, the resonance frequency is located in a range of about 7 Hz. Since the movement of the conductive liquid increases in the frequency region near the resonance frequency, the output characteristics of the acceleration sensor with respect to the vibration frequency (hereinafter referred to as frequency characteristics) are such that the output voltage is compared with the output voltage due to vibration at other frequencies. High. As a result, when this acceleration sensor is used for detecting a seismic wave, a large output voltage is output even at a small acceleration near the resonance frequency, so that there is a problem that an erroneous determination occurs in the detection of the seismic wave.

FIG. 6 shows this frequency characteristic. Frequency characteristic of the acceleration sensor as curve L ₁ shown in FIG. 6 (A) when the vibration acceleration of a constant amplitude is applied, the output voltage tends to increase in frequency before and after around a resonant frequency f _R Can be Here, when this acceleration sensor is used as a seismic sensor for detecting an earthquake, the resonance frequency becomes 10
There is a problem that it exists around Hz.

In other words, while the frequency of the seismic wave is mainly 1 to 5 Hz, the vibration wave mainly caused by living vibrations caused by hitting a person or an object, passing of a car, or vibration from a construction site mainly exceeds 10 Hz. However the resonant frequency f _R of 10Hz or less, for example be set to about 7 Hz, raise the sensitivity of the acceleration sensor in particular the lower part of the frequency of the living vibration, more likely to malfunction as a seismic sensor. Also, since the sensitivity of seismic waves increases on the higher frequency component side, if the frequency component of the vibration is high and close to the resonance frequency of the sensor, it is erroneously determined that even a weak earthquake that does not usually cause any problem is a large earthquake. May be lost. For this reason, it is necessary to correct the signal of the acceleration sensor in order to have uniform sensitivity to the entire seismic wave and to prevent malfunction due to living vibration.

Therefore, in the acceleration sensor of this embodiment,
Is the output from the acceleration response element at the specified sampling interval.
Is measured a predetermined number of times, and the average of the values during this period is the acceleration value
It is evaluated as. According to this method,
Get the interval (ie sampling frequency) and one average
To sample the value from the acceleration response element
By determining in advance, any vibration frequency, such as
Virtually eliminates the sensitivity of the detection circuit to the resonance frequency
be able to. This process also allows the acceleration response element to share
Acceleration response for seismic frequency components lower than the vibration frequency
The output from the element is not corrected very much,
It is possible to gradually increase the correction amount as you get closer
It is possible to use an acceleration response element toward the resonance frequency
These increases in output can be offset, and FIG.
Curve L₂As shown by the resonance frequency f _RThe increase in sensitivity at
Corrected. In this way, detection based on the tilt state of the acceleration sensor
Outgoing signal, of course,
In the frequency domain up to the detection signal due to vibration,
The output signal from the accelerometer at speed is almost uniform.
You can make it.

This correction will be described with reference to FIGS. In these examples, a sine wave is used as a vibration waveform for exciting the sensor for easy understanding. An AC rectangular wave is applied as a driving power supply to a bridge circuit formed by the acceleration sensor in order to prevent electrolysis of a liquid. FIG. 7 shows the relationship between the output ratio of the signal before and after the correction and the vibration frequency, and FIG. 8 is a waveform diagram at each vibration frequency for explaining the curve of FIG. FIG. 9 is a block diagram showing an embodiment of a circuit for performing the correction processing, FIG. 10 is a view showing a flow of signal processing from the sensor, and FIG. 11 is a view for explaining how to take in an output from the sensor. FIG.

The circuit shown in FIG. 9 is a sensor 2 similar to those shown as the acceleration sensors 101 and 102 in the above-described example.
1 and a microcomputer (hereinafter referred to as a microcomputer) 22 for processing a signal from the sensor. In this embodiment, the microcomputer 22 includes a power supply unit 41, a recognition unit 42, a correction unit 43,
It has a synthesizing unit 44 and a temperature detecting unit 45 as functions. If necessary, some or all of these functions may be provided independently of the microcomputer. The sensor 21 has the same bridge circuit as the acceleration sensor using the acceleration response element 1 shown in FIG. Microcomputer 2
2 has an output terminal X in the X direction on the sensor 21 side.
A / D converter 23 for converting a potential difference between X1 and X2 from an analog signal to a digital signal, and an A / D converter 23 for converting a potential difference between output terminals Y1 and Y2 in the Y direction into a digital signal.
A D converter 24 is connected, and the other
2 is connected to a D / A converter 25 for converting the output signal from the digital signal 2 into a digital signal into an analog signal.

Next, the operation of this circuit will be described.
First, when the power is turned on, the microcomputer 22, the A / D converter 31, and the D / A converter 2
5. A drive current is supplied to each part of the amplifier 29, and the reference voltage circuit 27 is driven. The reference voltage circuit 27 _{supplies a} reference voltage V _ref 2 to the sensor 21 and A /
The reference voltage V _ref 1 is supplied to the D converters 23, 24 and 31. In the present embodiment, a rectangular wave having a predetermined period for driving the bridge circuit of the sensor 21 is output from the power supply unit 41 of the microcomputer 22 as the driving voltage supplied to the sensor 21. In the embodiment, the power supply unit 41 of the microcomputer 22 driven by 5V outputs a rectangular wave of 0V-5V. The amplitude of this rectangular wave is adjusted to 0V-3V by the waveform adjusting circuit 28, and the rectangular wave is offset to ± 1.5V.
, And is input to the sensor 21 via a reference resistor 30 for temperature detection.

When the current is supplied in this manner, the sensor 21
The signal of the potential difference corresponding to the inclination angle of the liquid surface with respect to the electrode of the conductive liquid in the sensor is output from the intermediate electrode of the bridge circuit to the recognition unit 42 of the microcomputer 22. At this time, the signal output from the sensor 21 is a signal obtained by modulating a rectangular wave for driving the bridge circuit. This will be described with reference to FIG. When a rectangular wave 52 is supplied from the power supply unit 41 for driving the sensor via the waveform adjusting circuit 28, when the acceleration as shown in the waveform 51 is supplied to the sensor 21,
A signal output 53 modulated according to the acceleration is output from the bridge circuit of the sensor. At this stage, the output signal 5
Reference numeral 3 denotes a so-called analog signal.
Or 24 converts it into a digital signal.

The A / D converted signal is supplied to the microcomputer 22
Is sampled and accumulated by the recognition unit 42 of In the present embodiment, the recognizing unit 42 samples the output of the signal output 53 in synchronization with the cycle of the rectangular wave 52 which is the power supply for driving the bridge circuit formed by the sensor. Here, the polarity of the original signal output 53 is changed in synchronization with the rectangular wave 52. Therefore, if the timing at which the recognizing unit 42 samples the signal output 53 is made independent of the period of the rectangular wave, the sampled output data becomes data whose polarity changes depending on both the sensor driving power supply and the vibration waveform. For this reason, it is not clear whether the polarity change is caused by the drive power supply waveform or the vibration waveform. In order to detect the vibration waveform, it is necessary to determine the polarity change by a microcomputer or the like, and data processing is extremely difficult. Become complicated.

Therefore, in this embodiment, the recognition unit 42 is a sensor
A signal is output in synchronization with the cycle of the square wave 52 that is the driving power supply
53 output is sampled. In addition, rectangular wave 5
In the rising part of 2, the voltage overshoots and the rectangular
The waveform and signal output voltage may be unstable
Therefore, in the embodiment, the rise of the voltage of the square wave becomes stable.
The sampling time is set to
Synchronize the mining. Thus, the recognition unit 42 accelerates.
P along a curve 54 similar to the degree waveform 51 ₁,
P₂, P₃... P_n-1, P_nSeries of data
A sequence is obtained. Fig. 11 Acceleration for easy understanding
Cycle of the square wave 52 is too high with respect to the cycle of the degree waveform 51
The interval between each data is wide because it is explained with something that is not
However, the frequency of the square wave 52, that is, the sampling frequency
By increasing the number of samples by increasing the wave number sufficiently,
The data sequence approximates a curve 54 similar to the acceleration waveform 51.
And more accurate waveform information can be obtained.
In this way, the output is synchronized with the period of the sensor drive power supply
If you want to sample the
In addition to AC square waves, AC sine waves can be used.
Wear.

Here, if the sensor 21 is not subjected to vibration and is in the normal posture, no potential difference is generated at the intermediate electrode of the bridge circuit. However, if the sensor 21 is inclined due to a sensor mounting error or the like, it does not receive vibration. Even in the state, since a potential difference is generated due to the inclination, accurate detection of vibration is affected. Therefore, in this embodiment, the microcomputer 2 outputs the output from the sensor 21 for a predetermined time, for example, one second after the power is turned on.
The correction unit 43 of the microcomputer 22 recognizes and stores the offset value such that the output signal is regarded as a normal posture if the sensor inclination amount is within a range allowable as a mounting error in this state. Subsequent offset processing by the correction unit 43 when the sensor is tilted or vibrated is performed based on the stored offset value. Alternatively, the offset value may be reset periodically after installation of the acceleration sensor in consideration of the possibility that the sensor is tilted within an allowable range. For example, the offset value in the initial state is used as the reference value, and the offset value is periodically taken and compared with the reference value, so that the inclination amount of the sensor with respect to the initial state is constantly monitored and more appropriate according to the sensor inclination amount at that time. It is possible to perform accurate output correction with a large offset value.

After the offset value recognition and storage, the correction unit 43 performs a predetermined correction process as well as the above-described offset process on the signal sampled at predetermined time intervals by the recognition unit 42. Here, for convenience of explanation, ,
An example will be described in which the sampling frequency by the recognition unit 42 is 100 Hz and the number of times of sampling for obtaining one data is 10 times. A rectangular wave for driving the sensor is output from the power supply unit 41 of the microcomputer 22. In this example, the frequency of the rectangular wave is used in order to perform sampling in synchronization with the plus output side of the rectangular wave for the reason described above. Is also set to 100 Hz (0.01 second cycle) similarly to the sampling frequency. The potential difference between the output terminals X1 and X2 and the potential difference between Y1 and Y2 of the sensor 21 due to the rectangular wave are converted into digital signals by A / D converters 23 and 24, respectively, and input to the microcomputer 22. In the microcomputer 22, the recognition unit 42 samples the signal input from the sensor in synchronization with the rectangular wave. By accumulating this sampling a predetermined number of times, in this case 10 times, a value from the sensor of substantially 0.1 seconds is obtained.

In the case of the output terminals X1 and X2 in the X direction, for example, when the acceleration frequency applied to the sensor is a sine wave of 1 Hz, the amplitude data of the vibration waveform A1 shown in FIG. The data is input to the microcomputer 22 through the / D converters 23 and 24, and is sampled by the recognition unit 42. Sampling of the data is repeated timing synchronized with the rectangular wave, i.e. every 0.01 seconds, 0.09 seconds up data _d 1 _{to d 1 0,} considering the time until just before taking the next data _{d 11} This is performed for substantially 0.1 second, and data of 1/10 cycle is taken in for 1 second of the cycle of the vibration waveform which is a sine wave. Thus outputs an average value d _X1 to the sampled 10 times the value calculated by the correction unit 43.

Next, the recognizing unit 42 sets the data d after 0.01 seconds.
₁₁ Discard the first sampling data _{d 1} in the previous measurement fetches the data this time _d 2 _{to d 11}
The average value d _{X2 up} to is calculated by the correction unit 43 and is output as a value 0.01 seconds after the previously output average value d _X1 .

In this correction processing method, as shown in FIG. 8A, the corrected data d _X1 for the vibration waveform A1
Is output after d ₁₀ to be input to the end of the data to be averaged, and is outputted at the same timing with regard followed d _X2 subsequent data. Therefore, the corrected data has a delay corresponding to the measurement time when viewed from the time when the measurement is started as shown by the waveform A2. However, in the case of the embodiment, the delay time is about 0.1 second. Considering the measurement time for preventing erroneous determination which is set when used for a seismic sensor or the like, this delay is practically impossible. It doesn't matter.

As described above, although the corrected data actually causes a time delay, the waveform A based on the corrected data has a waveform A.
FIG. 8 (B) shows a plot obtained by re-plotting each correction value at an intermediate position of the sampling time zone and moving up the time axis in order to make it easier to directly compare the waveform A1 with the waveform A1 of the original data. The description will be made assuming that the time axis is advanced as shown in the figure. 8 (C) and 8 (D) shown in the following description also show the time axis raised.

Thus, the A / D converter 25 converts the output repeated from the microcomputer 22 to obtain a corrected waveform A2. Note that the waveform A2 shown here indicates an arbitrary portion of the correction processing that is continuously repeated with respect to the original vibration waveform A1. As an acceleration detecting device, the output waveform A2 may be directly input to a control device or the like. For example, the output waveform A2 may be converted into a smooth waveform by a filter (not shown)
By amplifying to a predetermined voltage by 9, it is possible to obtain an evaluation output of the seismic sensor which is more faithful to the given vibration wave. Further, the D / A converter 25 can be substituted by a ladder resistor or the like. This output waveform can be input to a determination device or the like to determine the magnitude or type of vibration and drive a control device or the like that operates a solenoid valve for city gas or the like. The microcomputer 22 may output a signal to a device to be controlled such as an electromagnetic valve and perform an appropriate process.

The corrected data obtained as described above is used when the ratio of the measurement time width to the vibration cycle is small in the low frequency region of the measurement target as shown in FIG. 8B. There is little correction to the data because the waveform fluctuations within are relatively gentle. Therefore (hereinafter referred to output ratio) Output ratio after correction for the output from the acceleration sensor as shown in curve L ₃ in Fig. 7 increases, waveform A2 after correction as shown in FIG. 8 (B) is the uncorrected It almost coincides with the waveform A1.

On the other hand, the vibration waveform when the acceleration frequency is 5 Hz has a vibration cycle of 0.2 seconds as shown by a waveform B1 in FIG. 8C, and the measurement time width is 0.1 seconds. It is 1/2 of the oscillation period. At this time, the average value is calculated in the same manner as in the case of 1 Hz described above, and becomes about 0.64 times the original waveform, and becomes a waveform like B2. FIG. 8D shows the vibration waveform when the acceleration frequency is 10 Hz.
As shown in C1, the oscillation cycle is 0.1 second, and the measurement time width and one cycle of the oscillation waveform are synchronized. Therefore, the average value C2 of the sampling data is always zero.

In this correction method, when the sampling frequency and the vibration frequency match, only the peak time of the vibration waveform is captured depending on the sampling timing.
Conversely, there is a possibility that only the part that becomes zero will be captured. However, an acceleration sensor using a liquid as a movable portion has a frequency characteristic that the liquid cannot sufficiently follow the vibration of a high frequency due to its viscosity, and the output of the sensor decreases. This frequency characteristic varies slightly depending on the inner diameter of the container and the type of liquid, but is generally 40 to 50H.
When z is exceeded, the output from the sensor becomes almost zero,
This is not a problem in the present invention using such an acceleration sensor. That is, since the actual sampling process is performed at 100 Hz or more in consideration of the resolution and the like, the output from the sensor is zero when the sampling frequency matches the vibration frequency, and the corrected output is also zero. Also, when used for a seismic sensor, such a high frequency vibration is a living vibration and need not be detected.

In the acceleration detecting device according to the embodiment, this average value is actually synthesized with the average value in the Y direction by the synthesizing section 44 of the microcomputer 22 before being output.
This synthesis processing is performed by calculating the average value d _{X in the} X direction and the average value d in the Y direction.
_The square root of the sum of the squares of _Y and the sum is calculated. Thus, the output from the microcomputer 22 is 360 °
It is output as a signal indicating the magnitude of the vibration in all directions and the waveform of the vibration. Of course, if necessary, the XY signals may be output to a control device or the like without being synthesized.

FIG. 7 shows the variation of the output ratio due to the above correction. As described above, the output ratio changes depending on the ratio of the measurement time width to the vibration cycle. However, this can be replaced with the relationship between the output ratio and the vibration frequency when the measurement time width is constant. For example, if the wavelength of one cycle is defined as synchronizing frequency f _a vibration frequency which matches the measured time width, the output ratio in the case vibration frequency as shown by a curve L ₃ is sufficiently lower than the synchronous frequency f _a in FIG. 5 It is high, decreases as the oscillation frequency approaches the synchronous frequency f _a. The output ratio where vibration frequency coincides with the synchronizing frequency f _a once becomes zero. When the vibration frequency further increases, the output ratio increases again. However, since one cycle included in the measurement time is effectively canceled, only the integrated value of a portion less than one cycle is divided by the measurement time. . That to become divided by the whole part of the duration, the maximum value thereof remains in 0.2 strong, yet results in a doubling of a point 2f _a of reduced again as the the vibration frequency increases synchronizing frequency f _a Then it becomes zero again.

[0064] with such output ratio repeatedly increases and decreases while becomes zero where the integral multiple of the vibration frequency synchronizing frequency f _a, the maximum value at the time of increasing the higher the oscillation frequency becomes higher going down. Thus, the signal output after the correction can be reduced for the vibration having a high frequency. By this correction, even when the acceleration sensor has a resonance frequency near the measurement region and the output increases as in the acceleration detection device of the present embodiment, the increase in the output near the resonance frequency can be suppressed. Further, when used as a seismic sensor, the output due to vibration at a higher frequency than the vibration due to the earthquake is suppressed, so that malfunction due to living vibration and the like can be prevented.

For example, as a correction method according to the frequency characteristics of the sensor output, in addition to the above-described method, the frequency characteristics are stored in advance in a correction processing circuit, and the frequency components of the input vibration are analyzed and A method may be used in which correction is performed for each frequency and output.

The resonance frequency can be slightly adjusted by changing the size of the container or the viscosity of the liquid. However, the viscosity of the conductive liquid should be increased to such an extent that the resonance frequency is practically changed for the above-mentioned reason. Can not. Also, when changing the size of the container, if the resonance frequency is set to 1 Hz or less, which is the lower limit of the frequency of the seismic wave, the inner diameter of the container becomes 1
It is not practical when seeking a small acceleration sensor because it needs to be at least 00 mm, and the sensitivity also increases for the frequency components before and after the resonance frequency, so that uniform characteristics cannot be obtained over the entire seismic wave. . Also, when the inner diameter is reduced, if the distance between the container and the lead terminal becomes smaller than necessary, the influence of the surface tension and the like appears, which naturally has a limit. For example, in the case of using a conductive liquid obtained by dissolving lithium nitrate in cyclohexanone as shown in the embodiment, the diameter of the inner surface of the container is set to about 6 mm, and the resonance frequency is set to about 14 Hz.

[0067] Although the description of the correction process by the above-described correction unit described in what 10Hz the relationship between period and sampling frequency of the AC square wave sensors driven for ease of understanding is the synchronous frequency f _a, This synchronization frequency f _a
Is not limited to this and can be set to any frequency. For example, in the acceleration sensor described above resonant frequency is 14Hz, as slightly higher 16Hz than the resonance frequency 14Hz is synchronizing frequency _{f a,} it is set to 128Hz sampling frequency, the number of samples 8. With this setting, the output from the acceleration sensor is not unnecessarily corrected in the low-frequency region where the output is relatively flat, and the output ratio gradually increases toward the resonance frequency at which the sensor output increases. , The fluctuation due to the resonance of the sensor output can be offset, and a substantially flat output characteristic can be obtained for a wide range of vibrations. When the vibration frequency exceeds the resonance frequency, the output after the correction sharply drops, and as described above, the output becomes zero at 16 Hz where the measurement time ratio becomes 1, and the output after the correction does not increase so much even in a higher region. However, there is no problem for a seismic sensor because it is the frequency range of living vibration that does not need to be detected.

In the above description, a simple sine wave was used as the waveform of the vibration applied to the acceleration detection device. However, the actual seismic wave is a combination of vibration waves of different frequencies. In this case, the above correction is performed to eliminate the disturbance of the waveform due to the resonance frequency of the acceleration sensor and to suppress the noise of the high-frequency component included in the signal from the sensor, and to make the output waveform more faithful to the original seismic wave. Can be reproduced. By processing the signal in this manner, the analysis of the vibration frequency by an external control device or the like becomes easy, and the processing method by the control device can be changed according to the magnitude of the vibration acceleration and the vibration frequency.

Further, in the embodiment, the correction method has been described in which the output characteristics become almost flat up to the living vibration in the frequency domain of the seismic wave and higher frequency domain. Needless to say, if detection is not performed, the sampling frequency and the sampling number may be set so that the portion having flat output characteristics is narrowed down to the frequency of the seismic wave and the output becomes zero at 8 to 10 Hz.

Further, in the embodiment, the correction method has been described in which the output characteristic becomes substantially flat up to the life vibration in the frequency domain of the seismic wave and higher frequency domain. In the case where the resonance frequency is around 5 Hz like the ones, the sampling frequency and the sampling number may be set so that the output becomes zero at the resonance frequency so that vibrations of frequencies other than seismic waves are not detected from the beginning. Needless to say.

Further, in this embodiment, a fixed resistor is connected in series with an end of the sensor 21 to which a voltage is applied in order to perform an output correction according to the temperature characteristic. A / D converter 31
Is input to the microcomputer 22 via the CPU 22 and measured by the temperature detecting unit 45. Here, it is the sensor 21 having a conductive liquid that changes the resistance according to the temperature. However, since the voltage applied to the entire circuit in which the reference resistance and the sensor are connected in series is predetermined, the temperature detection unit 45 The voltage change of the sensor 21 can be estimated by measuring the change in the voltage applied to both ends of the reference resistor which is a fixed resistor whose resistance value hardly changes within the operating temperature range of the present sensor. Since the resistance value of the sensor 21, that is, the temperature of the conductive liquid in the sensor can be determined from the voltage value obtained by the temperature detection unit 45 in this manner, by inputting this voltage value to the correction unit 43, the temperature characteristic of the conductive liquid can be obtained. Output correction according to the above. Further, by outputting this voltage value as temperature information to the outside, it is possible to input the voltage value to a control part of a device to which the sensor is attached or a peripheral device thereof, so that these devices are controlled according to a temperature change. .

In the above-described example, a case in which four lead terminals as sub-electrodes as shown in FIGS. 1 and 2 are fixed is used as the acceleration response element. As shown in (A) and (B), a through-hole 63A is formed on the center line of the metal plate 63, and the two lead terminals 65A and 65B are electrically insulative so as to be equidistant from a metal container (not shown). Those sealed and fixed at 66 may be used. If a bridge circuit is formed by using one of the acceleration response elements, an acceleration sensor that detects only a direction component of the inclination or acceleration along the lead terminal can be obtained. Further, by using two acceleration response elements and arranging each lead terminal along the X direction and the Y direction, the acceleration sensor having the circuit shown in FIG. 3 can be obtained. Further, by preparing a plurality of such acceleration response elements, arranging them in different detection directions at, for example, every 60 degrees or 45 degrees, and synthesizing the respective detection values, a more accurate acceleration sensor can be obtained. .

Further, in this embodiment, an example in which a plurality of lead terminals serving as sub-electrodes are fixed through through a metal hermetic container serving as a main electrode as an acceleration response element has been described. For example, as shown in FIG. 13, a metal container or a closed container made of an electrically insulating material such as glass may be provided with a plurality of lead terminals serving as sub-electrodes centered on lead terminals serving as main electrodes. In the acceleration response element 71, a conductive liquid 73 is sealed in a sealed container 72 made of glass. The sealed container 72 is provided with a main electrode 74 at the center thereof and auxiliary electrodes 75A to 75A.
5D are arranged at equal intervals and at the same distance from the main electrode. In this example, the main electrode 74 is set so that its tip is below the liquid level,
Although the contact area does not change, there is no problem because the liquid level hardly changes at the center of the sealed container 72 even if the tip is above the liquid surface.

In the acceleration response element 71, when the liquid surface is inclined by inclination or acceleration, the main electrode 7 located at the center is
Since 4 is in the conductive liquid 73, the contact area with the liquid does not change, and the liquid level with respect to the sub-electrodes 75A to 75D changes with the inclination. By detecting, the inclination angle of the liquid surface can be known. Needless to say, the acceleration response element 71 constitutes a bridge circuit similar to that of the above-described embodiment to form an acceleration sensor, and an acceleration detection device can be obtained using the acceleration sensor.

According to the acceleration response element 71, since the hermetically sealed container is an electrically insulating material, the distance between the sub-electrode and the container can be reduced within a range where the influence of surface tension does not occur. As a result, the sub-electrode is separated from the center. Therefore, the change in the liquid level with respect to the sub-electrode when the liquid level is inclined can be increased, and the output of the acceleration sensor with respect to acceleration and inclination can be increased. Each of the above-described acceleration response elements can be used even if it is installed upside down.

[0076]

According to the acceleration response element of the present invention, the inner diameter of the sealed container is set to 4 mm or more and 25 mm or less, and the electrodes are arranged so as to have a distance of at least 1 mm from each other within a range in which the liquid level moves. In this way, the effect of the resonance frequency of the acceleration response element itself on the detection of seismic waves can be eliminated, and the effect of the viscosity and surface tension of the conductive liquid on the operation of the liquid can be reduced to a negligible level. Can be.

Further, according to the present invention, since the conductive liquid is used, it is possible to provide a small-sized sensor which is strong against impact acceleration and easy to handle, and can obtain a signal proportional to the magnitude of acceleration or inclination. In addition, since the state of inclination due to the mounting error can be removed by the offset processing, the acceleration in all directions can be reliably detected with a simple structure having a small number of parts.

According to the present invention, the movable part responding to the acceleration is a liquid, and the other parts are only the sealed container and the lead terminal. There is no breakage or change in characteristics due to impact acceleration in normal handling.

When two acceleration response elements are used for an acceleration sensor, and each lead terminal is connected so that both sensors constitute a bridge circuit,
The output voltage from the sensor can be doubled, and the influence of the resistance change due to the temperature of the conductive liquid can be eliminated to prevent erroneous determination and malfunction of the acceleration sensor due to a change in the ambient temperature.

Further, by connecting a fixed resistor in series with the bridge circuit of the acceleration sensor and measuring the ratio of the voltage between both ends of the bridge circuit to which the voltage is applied and both ends of the fixed resistor, the conductivity of the acceleration response element is measured. By detecting the temperature of the liquid, it is possible to perform correction or the like according to the temperature characteristics of the conductive liquid or the like of the sensor output.

Further, by sampling the output signal from the acceleration response element in synchronization with the power supply for driving the sensor, the acceleration sensor can be driven by a power supply whose voltage fluctuates like an AC power supply. Can be easily processed even if is modulated.
Further, by applying an AC voltage such as a sine wave or a rectangular wave as a driving power supply, it is possible to avoid a change in resistance value due to electrolysis of the conductive liquid used for the acceleration response element and polarization of the liquid.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view showing one embodiment of an acceleration response element of the present invention.

FIG. 2 is a perspective view showing a positional relationship between lead terminals of the acceleration response element shown in FIG. 1;

FIG. 3 is a circuit diagram showing one embodiment of the acceleration sensor of the present invention.

FIG. 4 shows another embodiment of the acceleration sensor according to the present invention.

FIG. 5 is a schematic diagram illustrating the circuit of FIG. 4;

FIG. 6 is a diagram showing frequency characteristics of an acceleration response element.

FIG. 7 is a diagram showing a relationship between an output ratio of a signal before and after correction and a vibration frequency.

FIG. 8 is a waveform chart at each vibration frequency for explaining the curve of FIG. 7;

FIG. 9 is a block diagram showing an embodiment of a circuit for correcting the output from the acceleration sensor.

FIG. 10 is a block diagram showing a flow of signal processing from a sensor.

FIG. 11 is a waveform chart for explaining how to capture an output from a sensor.

FIG. 12 is a perspective view showing another embodiment of the acceleration response element according to the present invention.

FIG. 13 is a perspective view showing another embodiment of the acceleration response element used in the present invention.

FIG. 14 is a diagram showing the relationship between the inner diameter of the acceleration response element and the resonance frequency.

[Explanation of symbols]

1, 11, 71: acceleration response element 2, 12: container (main electrode) 3: metal plate (main electrode) 4: conductive liquid 5A, 5B, 5C, 5D, 15A, 15B, 15C, 1
5D, 65A, 65B: Lead terminal (sub electrode) 21: Sensor 22: Microcomputer 23, 24: A / D converter 30, _RA : Reference resistor 41: Power supply unit 42: Recognition unit 43: Correction unit 44: Synthesizing unit 45: temperature detection unit 72: sealed container 73: conductive liquid 74: main electrode 75A, 75B, 75C, 75D: sub-electrode

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Satoshi Teranishi 4-30-30 Hoshocho, Minami-ku, Nagoya-shi Co., Ltd. Inside the Shakukata Factory (72) Inventor Takashi Toda 4-30 Hoshocho, Minami-ku, Nagoya-shi Stock Company (72) Inventor Hideki Koseki 4-30, Hoshocho, Minami-ku, Nagoya Co., Ltd.

Claims (11)

[Claims] 1. A closed container having a substantially cylindrical shape with both ends closed, a main electrode and a plurality of sub-electrodes provided in a state insulated from each other, and each of the sub-electrodes is connected to the main electrode. The conductive liquid is sealed in the closed container, and the amount of the conductive liquid is set such that at least a part of the sub-electrode has a liquid surface in a normal posture. The amount of contact between the sub-electrode and the conductive liquid is changed by changing the inclination angle and the inclination direction of the closed container from the normal posture, and the distance between the main electrode and the sub-electrode is changed. In the acceleration response element in which the resistance value changes, the inner diameter of the closed vessel is 4 mm or more and 25 mm
In the following, each electrode is arranged so as to have a distance of at least 1 mm from each other within a range in which the liquid surface moves. 2. An airtight container for an acceleration response element comprises a cylindrical metal container having one end closed and a metal disk fixed to an opening of the metal container. The metal container and the disk are mainly used. 2. The acceleration responsive element according to claim 1, wherein the electrode is an electrode, and a metal lead terminal serving as a sub-electrode is fixed through the disk electrically insulated. 3. The acceleration response device according to claim 1, wherein four sub-electrodes are provided. 4. An acceleration sensor, wherein each sub-electrode is connected to form a Wheatstone bridge circuit by the acceleration response element according to claim 1 and a fixed resistor. 5. An acceleration response element according to claim 1, wherein the two acceleration response elements are arranged such that the arrangement directions of the lead terminals are in a predetermined positional relationship. An acceleration sensor, wherein each of the sub-electrodes is connected so that both acceleration response elements constitute a Wheatstone bridge circuit. 6. A reference fixed resistor is connected in series with the Wheatstone bridge circuit, and the conductivity of the acceleration response element is measured by measuring the ratio of the voltage between both ends of the Wheatstone bridge circuit to which voltage is applied and both ends of the reference fixed resistor. 6. The acceleration sensor according to claim 4, wherein the acceleration and the change state of the acceleration can be detected while detecting the temperature of the ionic liquid. 7. An acceleration responsive element capable of obtaining a signal as an electrical output by movement of the conductive liquid,
An acceleration sensor, wherein an output from the acceleration response element is sampled in synchronization with a cycle of the power supply voltage for driving the acceleration response element. 8. The acceleration sensor according to claim 7, wherein the power supply for driving the acceleration response element is an AC sine wave. 9. The acceleration sensor according to claim 7, wherein the power supply for driving the acceleration response element is an AC rectangular wave. 10. The acceleration sensor according to claim 7, wherein the acceleration sensor and the fixed resistor are connected to form a Wheatstone bridge circuit. 11. An acceleration response element having two acceleration response elements, wherein the two acceleration response elements are arranged so that the arrangement directions of lead terminals are in a predetermined positional relationship, and both acceleration response elements are connected to a Wheatstone bridge circuit. The acceleration sensor according to any one of claims 7 to 9, wherein the acceleration sensor is connected so as to form the following.