JPH09325067A - Variable cycle type vibration meter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce a characteristic frequency of a vibrator without damaging mechanical strength of a supporting spring of an electrodynamic vibration meter. SOLUTION: Relating to an electrodynamic vibration meter comprising a case 1 of non-magnetic material, a vibrator 2 assigned in the case 1 while movement in Z-Z axis direction is allowed by a supporting spring 3, coils 4a and 4b assigned at the vibrator 2, and magnets 5a and 5b, ferromagnetic bodies 9a and 9b are assigned at both end parts of the vibrator 2, and by utilizing a force generated at the ferromagnetic bodies 9a and 9b by the leakage magnetic flux of the magnets 5a and 5b as a negative restoring force of the supporting spring, the reduction of characteristic frequency of the vibrator 2 becomes possible without damaging mechanical strength of the supporting spring 3.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrodynamic vibrometer (seismometer), and more particularly to a natural frequency of the vibrometer which can be lowered without lowering mechanical strength.
A variable period vibrometer.

[0002]

2. Description of the Related Art In an electrodynamic vibrometer (seismometer) for observing micro earthquakes and microtremors of the ground, it is possible to accurately observe vibrations and earthquakes in a low frequency region by lowering the natural frequency of the vibrator. Is known to be effective for However, lowering the natural frequency of the oscillator to 1 Hz or lower leads to a decrease in the spring constant of the oscillator support spring and lowers the mechanical strength, so it is often used for portable use in the field or in adverse environments. Is accompanied by difficulties. In order to overcome this, various efforts have been made in the past, such as the use of a non-linear spring, the use of an inverted pendulum utilizing the acceleration of gravity,
It has been proposed to use a feedback circuit together.

[0003]

By the way, in the case of using a non-linear spring, it is difficult to machine the spring, and it is practically impossible to significantly lower the natural frequency of the vibrator below 1 Hz. In addition, the inverted pendulum utilizing the acceleration of gravity cannot be used for the vertical movement component, and the one using the feedback circuit requires a complicated electronic circuit. The present invention seeks to solve such problems.

[0004]

[Means for Solving the Problems] In the case of a conventional pendulum type utilizing acceleration of gravity represented by an inverted pendulum, a pendulum
Whereas the acceleration of gravity applied to the (weight) is configured to act as a kind of negative spring that exerts a force in a direction that cancels the restoring force of the mechanical spring supporting the pendulum,
According to the present invention, the force corresponding to the negative restoring force due to the acceleration of gravity is obtained by the force generated in the ferromagnetic body by the leakage flux of the magnet.

That is, according to the present invention, a cylindrical case made of a non-magnetic material and a support spring arranged inside the case concentrically with the central axis of the case are movably supported in the central axis direction. And a vibrator made of a non-magnetic material that is formed in the shape of a rotating body having the central axis as an axis, and a pair of coils that are attached to the vibrator concentrically with the central axis of the case and are connected in series with each other. In an electrodynamic vibrometer having a pair of magnets attached to the case for generating electromotive force in each coil when the vibrator moves, leakage of each magnet at both ends of the vibrator A pair of ferromagnets are attached at the positions where the magnetic flux reaches, and the attachment positions of the ferromagnets are set so that the magnetic force due to the leakage flux of each magnet exerted on the same pair of ferromagnets is set to solve the problem. Is used as a means.

Further, a screw is engraved on the outer circumference of each of the ferromagnetic bodies and screwed into the case, and the ferromagnetic bodies are rotated from the outside of the case to rotate the ferromagnetic bodies and the magnets. It is a means of solving the problem by adjusting the interval between the and.

Further, in the case, each passage portion of each leakage magnetic flux of each magnet is composed of a magnetic body portion made of a magnetic body, and each magnetic body is brought into close contact with each magnet,
A movable magnet is attached to each of the magnetic body portions of the case so as to face each of the ferromagnetic bodies, as means for solving the problem.

Further, a screw is engraved on the outer periphery of each of the movable magnets, is screwed into each of the magnetic members of the case, and each of the movable magnets is rotatably operated from the outside of the case. The distance between the magnet and each of the magnets is adjusted so as to solve the problem.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a vertical sectional view of a variable period vibrometer as the first embodiment, and FIG. 2 is a spring characteristic diagram of its supporting spring. , Fig. 3 is a magnetic force characteristic diagram of the ferromagnetic material, Fig. 4
5 is a synthetic spring characteristic diagram thereof, and FIG. 5 is a vertical sectional view of a variable period vibrometer as a second embodiment thereof. The same reference numerals in FIGS. 1 and 5 indicate almost the same members.

First, a first embodiment will be described with reference to FIGS. Reference numeral 1 denotes a case made of a cylindrical body. The case 1 is made of a non-magnetic material, and a vibrator 2 made of a non-magnetic material is provided inside the center axis Z of the case 1 via a support spring 3.
It is arranged so as to be movable in the -Z direction.

The vibrator 2 is formed in a shape of a rotary body having the central axis Z--Z of the case 1 as its axis, and its cross section has an upper flange portion 2a, a lower flange portion 2b, and a central columnar portion 2c connecting both flange portions. Has a left-right and top-bottom symmetric I-shaped shape, and has an upper flange portion 2a and a lower flange portion 2
It is movably supported by the case 1 by a pair of upper and lower donut-shaped support springs 3 on each outer peripheral surface of b. The support spring 3 is made of a non-magnetic material and is attached to the outer peripheral surface of each of the flange portions 2a and 2b. The vibrator 2 is attached to the case 1 concentrically by the support spring 3.

A pair of ring-shaped upper magnets 5a and ring-shaped lower magnets 5 having the same magnetic force are formed on the inner surface of the case 1.
b is attached, and magnetic members are attached to the upper magnet 5a and the lower magnet 5b, respectively, and the upper magnetic pole 6a and the lower magnetic pole 6b are constituted by these.

Further, a pair of upper and lower yokes 7a and 7b are provided on the inner surface of the case 1 so as to project between the bent tip portions 7a-1 and 7b-1 of the yokes 7a and 7b and the upper magnetic pole 6a and the lower magnetic pole 6b. The coils 4a, 4b in the gap formed in
Are arranged. The coils 4a and 4b are the oscillator 2
Are mounted concentrically with the vibrator 2 on the inner surfaces of the upper flange portion 2a and the lower flange portion 2b facing each other, and the coil 4a and the coil 4b are connected in series. Reference numerals 8a and 8b denote terminals of coils 4a and 4b (hereinafter referred to as "coil 4") connected in series.

Both ends on the central axis of the vibrator 2, that is, the upper flange portion 2a and the lower flange portion 2b of the vibrator 2
Rod-shaped ferromagnetic bodies 9a and 9b are attached to the central portion of. Screws are formed on the outer circumferences of the ferromagnetic bodies 9a and 9b, and the upper flange portion 2a and the lower flange portion 2b are formed.
It is designed to be screwed from the outside into the screw hole formed in. Reference numerals 1a and 1b denote insertion holes of the screwing tool formed in the case 1.

The ferromagnetic bodies 9a and 9b are magnets 5a and 5b.
The magnetic flux due to the leakage flux of the magnets 5a and 5b, which is located on the movable axis (Z-Z line) of the coil and which acts on both the ferromagnetic bodies 9a and 9b, is equalized while the leakage flux of the static magnetic field of b passes. Is installed.

That is, in this embodiment, ferromagnetic materials 9a and 9b having the same material and the same size are mounted on both flange portions 2a and 2b at positions equidistant from the magnets 5a and 5b, respectively. The electrodynamic vibrator including the above-described members is formed symmetrically with respect to the Z-Z axis and also symmetrical with respect to the X-X axis orthogonal to the Z-Z axis.

In the above structure, when the case 1 is fixed to a building or the like and a vibration such as an earthquake occurs in the ZZ axis direction in the structure, the relative movement between the case 1 and the vibrator 2 occurs. Displacement occurs and electromotive force is generated in the coil 4. Vibration is detected and analyzed by measuring the electromotive force.

The oscillator 2 is supported by a support spring 3,
The spring characteristic of this support spring is as shown by the curve A in FIG. 2, and in the conventional one (without the ferromagnetic bodies 9a and 9b), the natural frequency of the vibrometer is determined exclusively by the spring constant of the support spring 3. .

On the other hand, when the vibrator 2 vibrates, the ferromagnetic materials 9a,
9b also vibrates in the ZZ axis direction together with the vibrator. Therefore, the distance between the ferromagnetic bodies 9a and 9b and the magnets 5a and 5b is also
It changes with the vibration of the vibrator 2.

Here, the ferromagnetic bodies 9a, 9b are magnets 5a,
Since the magnetic force received from 5b changes in inverse proportion to the square of the distance between the two, the magnetic force characteristic of the ferromagnetic material (acting force of the magnet on the ferromagnetic material) is shown in FIG. 3 (from the neutral position of the oscillator 2). Displacement: Horizontal axis, force acting on ferromagnet:
The curve B is plotted on the vertical axis.

Since the spring force of the support spring and the magnetic force with respect to the ferromagnetic substance are simultaneously acting on the vibrator 2, the vibrator 2 has a combined spring characteristic (Fig. 4 indicated by the curve C).

As described above, in this embodiment, the ferromagnetic body is attached to the vibrator, and the force generated in the ferromagnetic bodies 9a and 9b by the leakage magnetic flux of the magnets 5a and 5b is applied to the support springs 3 and 3 by the negative restoring force. It is possible to apparently adjust the spring force of the support springs 3 and 3 by using the above-mentioned, and it is possible to reduce the natural frequency of the vibrator 2 without reducing the mechanical strength of the support spring 3. .

The acting force of the magnet on the ferromagnetic body can be adjusted by adjusting the mounting positions of the ferromagnetic bodies 9a and 9b by screwing or loosening the ferromagnetic bodies 9a and 9b with a tool. Yes (the shape of curve B in FIG. 3 can be changed). Therefore, the ferromagnetic materials 9a, 9
By adjusting the position of b from the outside of the case 1, fine adjustment of the natural frequency of the vibrator can be performed from the outside of the case after assembling. Further, by selecting the dimensions (diameter, length) and materials of the ferromagnetic bodies 9a and 9b, it is possible to attach a ferromagnetic body having desired magnetic characteristics to the vibrator.

Next, a second embodiment will be described with reference to FIG. The vibrometer of this embodiment is also arranged so as to be movable in the direction of the central axis ZZ of the case 1 through the case 1 formed of a cylindrical body and the support spring 3 in the case 1, and Z-
The vibrator 2 formed in the shape of a rotating body having the Z axis as an axis, the pair of coils 4a and 4b, the upper magnet 5a and the lower magnet 5b, the upper magnetic pole 6a and the lower magnetic pole 6b, and the yoke 7.
The basic configuration including a and 7b and ferromagnetic bodies 9a and 9b is not different from that of the vibrometer of the first embodiment.

However, the portions of the case 1 which are the paths of the leakage magnetic flux of the magnets 5a and 5b are made of a magnetic material to form the upper magnetic material portion 1A and the lower magnetic material portion 1B, and the magnetic material portions 1A and 1B. Are closely contacted with the upper magnetic pole 6a and the lower magnetic pole 6b, respectively, so that the magnetic body portions 1A and 1B of the case 1 also constitute magnetic poles.

Further, the ferromagnetic material 9 is provided on both ends of the vibrator 2.
a and 9b are fixed, and each ferromagnetic material 9a and 9b
Movable magnets 10a and 10b each having a screw formed on the outer peripheral portion are screwed into the magnetic body portions 1A and 1B so as to be opposed to. The movable magnets 10a and 10b are provided with engaging grooves for tools (for example, a driver) on the outer surfaces thereof.
The attachment positions of a and 10b can be adjusted from the outside.

The ferromagnetic bodies 9a, 9b and the movable magnets 10a, 10b are provided on the movable axis of the oscillator 2, that is, the coil 4 and at the positions where the leakage magnetic fluxes of the static magnetic fields of the magnets 5a, 5b pass. Moreover, the point that the magnetic forces of the leakage magnetic fluxes of the magnets 5a and 5b exerted on the two ferromagnetic bodies 9a and 9b are set to be the same amount is the same as in the case of the first embodiment.

By concentrating the leakage magnetic flux by making the portions of the magnets 5a, 5b of the case 1 which are the passages of the leakage magnetic flux of magnetic material and providing the movable magnets 10a, 10b on the magnetic material portion. , Which allows the ferromagnetic material 9a,
The installation effect of 9b can be improved.

Also in this embodiment, by mounting the movable magnets 10a and 10b and the ferromagnetic bodies 9a and 9b, the spring characteristics acting by the vibrator at the time of vibration are the same as in the case of the first embodiment. Can have a composite spring characteristic (shown by curve C in FIG. 4), and the movable magnet 10
The composite spring characteristic can be adjusted by adjusting the mounting positions of a and 10b. In this way, even in the case of the second embodiment, the natural frequency of the vibrator can be lowered without lowering the mechanical strength of the support spring 3.

The natural frequency can be adjusted from the outside of the case 1 after assembling the vibrometer, as in the first embodiment. In the above description of the first and second embodiments, the moving direction of the vibrator 2 is set to the ZZ axis direction (vertical direction), but the vibrometer may be changed from the posture shown in FIG. 1 or FIG. ° After turning, the moving direction of vibrator 2 is X-
It goes without saying that it is also possible to use it in the X-axis direction (horizontal direction) or the YY axis direction (horizontal direction orthogonal to the XX axis).

[0031]

As described in detail above, according to the variable period vibrometer of the present invention, the following effects and advantages can be obtained. (1) In an electrodynamic vibrator, it is possible to lower the natural frequency of the vibrator, especially the natural frequency to 1 Hz or less, without lowering the mechanical strength of the support spring that supports the vibrator. Becomes (2) The natural frequency of the vibrator can be adjusted from outside the case by a simple operation. (3) By the above (1) and (2), it is possible to accurately observe micro earthquakes and microtremors of the ground in the low frequency region.

[Brief description of drawings]

FIG. 1 is a vertical cross-sectional view of a variable period vibrometer according to a first embodiment of the present invention.

FIG. 2 is a spring characteristic diagram of the support spring.

FIG. 3 is a magnetic force characteristic diagram of the ferromagnetic material.

FIG. 4 is a characteristic diagram of the composite spring.

FIG. 5 is a vertical sectional view of a variable period vibrometer according to the second embodiment.

[Explanation of symbols]

 1 case 1A upper magnetic body portion 1B lower magnetic body portion 2 vibrator 2a upper flange portion 2b lower flange portion 3 support springs 4, 4a, 4b coil 5a upper magnet 5b lower magnet 6a upper magnetic pole 6b lower magnetic pole 7a, 7b yoke 9a, 9b Ferromagnetic material 10a, 10b Movable magnet

Claims (4)

[Claims] 1. In an electrodynamic vibrometer, a cylindrical case made of a non-magnetic material and a support spring arranged inside the case concentrically with the central axis of the case move in the central axis direction. A vibrator made of a non-magnetic material that is rotatably supported and is formed in the shape of a rotating body having the center axis as an axis, and a pair of the vibrator that is concentrically attached to the center axis of the case and connected in series. And a pair of magnets attached to the case to generate an electromotive force in each coil when the vibrator moves, and each leakage magnetic flux of each magnet reaches at both ends of the vibrator. A pair of ferromagnetic bodies are attached to the positions, and the mounting positions of the ferromagnetic bodies are set so that the magnetic forces due to the leakage magnetic flux of the magnets exerting on the same pair of ferromagnetic bodies are equal. A variable period vibrometer. 2. A screw is engraved on the outer periphery of each of the ferromagnetic bodies and screwed into the case, and the ferromagnetic body and the ferromagnetic body are connected to each other by rotating the ferromagnetic body from the outside of the case. The variable period vibrometer according to claim 1, characterized in that a space between each magnet can be adjusted. 3. In the case, each passage portion of each leakage magnetic flux of each magnet is composed of a magnetic body portion made of a magnetic body, and each magnetic body is closely contacted with each magnet, The variable period vibrometer according to claim 1, wherein a movable magnet is attached to each of the magnetic body portions of the case so as to face the magnetic body. 4. A screw is engraved on the outer circumference of each of the movable magnets and screwed into each of the magnetic body portions of the case, and the movable magnets are rotated by an operation of rotating the movable magnets from the outside of the case. The variable period vibrometer according to claim 3, wherein a space between the magnet and each of the magnets can be adjusted.