JPS6351255B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a vibration sensor using a linear pressure-sensitive element, and particularly to a vibration sensor suitable for vibrations from arbitrary directions such as earthquakes.

Various types of earthquake detectors have been proposed and used. One of these is a type in which a vibration-sensitive ball is placed on a tray with a weir around it, and when the vibration exceeds a certain level, the vibration-sensitive ball passes over the weir and falls. However, with this type of ball, if the weir of the receiver on which the vibration-sensitive ball is placed is not strictly horizontal, even the slightest vibration other than an earthquake will cause it to fall from the low height of the weir, and you will have to reset it each time. There is a practical complication of not having to do this. Not only that, even if the product is designed and manufactured to be able to detect only earthquakes of a certain magnitude or more, for example, earthquakes of 150 gal or more, if it is not installed correctly and horizontally, it will also detect very small earthquakes below the set value. It has the disadvantage of sensing
In addition, in order to install it strictly horizontally, manufacturing precision and handling equivalent to that of a precision machine are strictly required, and there is a drawback that it is not versatile.

Other types are capable of highly sensitive detection of vibrations only in a specific direction, including both transverse and longitudinal waves such as those caused by earthquakes, and must be able to detect transverse waves from any direction. In some cases, one vibration sensor alone is not sufficient, and many vibration sensors must be installed, which increases the cost and is complicated to install on the device. It is impossible to say.

These problems are not limited to earthquake sensing, but are found in vibration sensing in general, and there is a demand for a device that can detect vibrations from any direction, but there are problems in terms of cost and handling. There was nothing that could be put to practical use.

In view of the above-mentioned drawbacks, the present invention has been developed so that a linear piezoelectric material can respond to stress in any direction perpendicular to the axial direction of the linear piezoelectric material.
It was developed with the focus on the fact that piezoelectricity can be equally generated, and the piezoelectricity generated at that time is large enough to be used as a signal for sensing various vibrations including earthquakes. A combination of a weight and a linear pressure-sensitive element, for example,
By comprising a fixed support frame and a weight supported by the fixed support frame through a support at least a part of which is made of a linear pressure-sensitive element, displacement of the weight with respect to the fixed support frame due to vibration can be avoided. The present invention aims to provide a vibration sensor that is practical and capable of detecting vibrations from any direction with high sensitivity without directional dependence by detecting the change in stress on a linear pressure-sensitive element. It is. Furthermore, the purpose is to easily and correctly install the vibration sensor without requiring a high degree of precision in the equipment to which the vibration sensor is to be installed.

According to the present invention, the object is to provide a frame body, a weight suspended from the frame body by a linear body, and a linear body whose one end is connected to the weight body and the other end is connected to the frame body. This is achieved by a vibration sensor consisting of a pressure sensitive element and a detection circuit electrically connected to the linear pressure sensitive element to detect an electrical signal generated in the linear pressure sensitive element.

A vibration sensor for detecting an earthquake according to an embodiment of the present invention will be described below with reference to FIGS. 1 and 2. This vibration sensor has a structure in which a weight 2 is supported from two directions via linear piezoelectric bodies 3a and 3b whose both ends are supported by a support frame 1 as a U-shaped frame fixed to the ground. The linear piezoelectric bodies 3a and 3b as linear pressure-sensitive elements have internal electrodes and surface electrodes inside and outside the tubular piezoelectric body, respectively, and these are connected to an electric signal detection circuit as a detection circuit. has been done.

Here, tension is applied to the linear piezoelectric body 3b above the weight 2 due to the load of the weight 2, but the linear piezoelectric body 3b
Tension may or may not be applied to a.

FIG. 2 shows an enlarged view of the end of the linear piezoelectric body 3,
and one of the attached electrical parts in the electrical signal detection circuit.
An example is shown in a block diagram. 6 is an internal electrode of the linear piezoelectric material, 6a is a surface electrode of the linear piezoelectric material, 7 is a preamplifier, 8 is a bandpass filter,
9 is an amplifier, and 10 is a disaster prevention operation circuit. Here, the bandpass filter 8 passes only signals in this frequency band, taking advantage of the fact that the frequency of earthquakes is limited to 1 to 10 hertz, and most frequencies are 3 to 7 hertz, and thereby allows signals other than earthquakes to pass through. This is to cut noise as much as possible, and the disaster prevention operation circuit 10 closes the main valves of gas pipes and oil pipes, and turns off the power. In this embodiment (FIGS. 1 and 2), a linear piezoelectric body 3b is used as the linear body.

Here, as the linear piezoelectric material, a tubular polyvinylidene fluoride resin described in Japanese Patent Application No. 141754/1989 filed by the applicant of the present application is preferred because it has high piezoelectricity. An example of the manufacturing method is
A polyvinylidene fluoride resin is formed into a tubular shape using a known hollow fiber manufacturing method. Next, an internal electrode made of a conductor having fluidity at a temperature below the melting point of the polymeric material of the tubular body is formed inside the hollow tube of the tubular body. Such conductors include low melting point metal alloys, electrolyte solutions, conductive resins, conductive rubbers, and the like. These can be formed inside a hollow tube by suctioning from one end of the tubular body and injecting it from the other end, by coextruding conductive resin, or by injecting conductive rubber in an uncrosslinked state and then crosslinking it. methods etc. are used. After forming the internal electrodes by such a method, the tubular body may be stretched, or depending on the method of forming the electrodes, stretching may be performed first. Further, electrodes are formed on the surface of the tubular body by vapor deposition or the like, and orientation polarization is performed to obtain a linear piezoelectric body.

Next, to explain the operation of the vibration sensor configured as above, the support frame 1 fixed to the ground vibrates due to the transverse waves of an earthquake, and the weight 2 also vibrates due to this relative displacement. do. As a result, the weight 2
The linear piezoelectric bodies 3a and 3b engaged with each other undergo expansion and contraction due to changes in tension, and this force generates piezoelectricity between the internal electrode and the surface electrode. This piezoelectricity is detected using an electric signal detection circuit, amplified and recorded, and used for disaster prevention operations. Here, the linear piezoelectric bodies are separate linear piezoelectric bodies 3a,
3b, a single linear piezoelectric body 3 may be used and the weight 2 may be placed in the middle thereof.

By using such a vibration sensor, vibrations can be detected in any direction without requiring strict installation conditions.

FIG. 3 is a perspective view of a second embodiment of the sensor of the present invention, in which one of the linear pressure sensitive bodies in the first embodiment is shown.
The other is made up of a metal wire 5 as a linear body. In Fig. 1, the linear piezoelectric body 3b, which is constantly subjected to stress due to the load of the weight 2, may not be able to withstand the load of the weight 3 depending on the configuration of the linear piezoelectric body, and even if it is not so severe, it may not be able to withstand the load of the weight 3 for a long time. It may undergo deformation due to stress loading over a period of time and exceed its elastic limit. In such a case, by replacing the linear piezoelectric bodies 3a and 3b with the metal wire 5 of 3b, the elastic limit due to the load will not be exceeded, and in this case, one linear piezoelectric body 3a connected to the weight 2 can be replaced. Since piezoelectricity is generated between the inner electrode and the surface electrode by the expansion and contraction of the electrode, it is possible to detect not only earthquakes but also vibrations. In addition, although only an example of a metal wire is shown in the figure, it is not limited to a metal wire, and any linear rigid body that can withstand the load of the weight 2, including fibers, may be used. It goes without saying that a structure in which a part of a linear rigid body such as a metal wire is replaced with a linear pressure-sensitive element may also be used.

FIG. 4 is a perspective view of a third embodiment of the sensor of the present invention, in which linear piezoelectric bodies 3c, 3d, 3e, 3f, 3
g and 3h are in a set of 3 and each has 2 weights.
It is divided into upper and lower parts. It should be noted that the vibration of the weight 2 does not have to be strictly in the horizontal direction; if it is in a substantially horizontal direction, the propagation direction of the transverse wave can be detected from the magnitude of the piezoelectricity that is generated without any practical problem. Further, when three or more linear piezoelectric bodies are used in each of the upper and lower directions as shown in FIG. 4, it is possible to detect the propagation direction of this wave. In this embodiment, linear piezoelectric bodies 3c, 3d, and 3e are used as the linear bodies.

FIG. 5 is a perspective view of a fourth embodiment of the vibration sensor of the present invention, in which three linear piezoelectric bodies are fixed to the support frame 1 in different directions approximately horizontally and one in the approximately vertical direction. ing. In this case, arbitrary horizontal vibrations and vertical vibrations can be detected separately.

Note that in this embodiment, a metal wire 5 is used as the linear body.

In the above embodiments, a linear piezoelectric material was used as an example of a linear pressure-sensitive element, but a wide range of pressure-sensitive elements such as pressure-sensitive resistance elements such as pressure-sensitive rubber may also be used. used. That is, in the present invention, stress-electrical transducers such as piezoelectric elements and pressure-sensitive resistance elements are collectively referred to as pressure-sensitive elements.

As is clear from the above description, the vibration sensor of the present invention is versatile, practical, and capable of highly sensitive detection of vibrations from any direction, including earthquakes, without directional dependence. . Furthermore, the equipment to be attached to the vibration sensor does not require the same precision as a precision machine, and can be easily and correctly set.
Industrially useful.

[Brief explanation of drawings]

FIG. 1 is a perspective view showing a first embodiment of the vibration sensor of the present invention, FIG. 2 is an enlarged perspective view of the end of a linear piezoelectric body and a block diagram of the attached electric components, and FIG. FIG. 4 is a perspective view of the second embodiment, FIG. 4 is a perspective view of the third embodiment, and FIG. 5 is a perspective view of the fourth embodiment. DESCRIPTION OF SYMBOLS 1... Support frame, 2... Weight, 3... Linear piezoelectric body, 4... Fixed end, 5... Metal wire, 6, 6a...
Electrode, 9...amplifier.

Claims (1)

[Claims] 1. A frame, a weight suspended from the frame by a linear body, and a linear pressure-sensitive element whose one end is connected to the weight and the other end is connected to the frame. and a detection circuit electrically connected to the linear pressure-sensitive element in order to detect an electrical signal generated in the linear pressure-sensitive element. 2. The vibration sensor according to claim 1, wherein the linear pressure-sensitive element is a linear piezoelectric material. 3. The vibration sensor according to claim 1 or 2, wherein the linear pressure-sensitive element is a linear piezoelectric material made of a polyvinylidene fluoride resin tubular body.