JP2810481B2 - Acceleration sensor - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an acceleration sensor used in a special measurement field, a seismometer, and the like. In particular, a weight is displaced by acceleration, and a displacement of the weight is measured to measure the acceleration. It relates to an acceleration sensor for detecting.

2. Description of the Related Art In an acceleration sensor, a force F received by a weight having a mass m due to an acceleration α is balanced with a spring having a spring constant K, and the amount of expansion and contraction of the spring from the position of the zero acceleration weight (displacement amount of the weight) at that time. By measuring X, the force F received by the weight is detected by the weight of the mass m, the acceleration α, the spring constant K and X, and it is conventionally obtained from the following equation: α = (K / m) · X More known.

As the acceleration sensor, a sensor using a differential transformer for measuring a displacement, a sensor using a linear potentiometer, and the like are known.

Problems to be Solved by the Invention However, the conventional acceleration sensor uses a differential transformer or a linear potentiometer for measuring the amount of displacement of the weight, which complicates the structure of the device, thus reducing the size and weight of the device. In the case of not being able to do or a differential transformer, it had to be used in combination with other sensors.

Further, in an acceleration sensor using a change in physical properties such as a piezoelectric acceleration sensor, a separate sensor is incorporated in order to compensate for temperature characteristics of physical properties.

In view of the above, it is an object of the present invention to provide an acceleration sensor which has a simple structure, can be easily reduced in size and weight, and can easily perform temperature compensation without using a temperature sensor.

Means for Solving the Problems FIG. 1 is a diagram for explaining the principle of the present invention.

According to the present invention, the weight 1
Is an acceleration sensor that obtains an acceleration by detecting the displacement of the weight 1 by means of a magnetoelastic wave. The fixed excitation means 3 generates a magnetoelastic wave, and the first detection coil 4 and the second detection coil 5 which are the means for detecting the elastic wave detect the arrival of the respective elastic waves and reduce the acceleration to zero. The direction and magnitude of the acceleration applied to the weight 1 are detected from the difference between the propagation time at that time and the propagation time at a certain acceleration, and the propagation velocity of the magnetoelastic wave.

When a magnetic field is applied to a part of the high magnetostrictive magnetic body 2 by the excitation means 3, the change causes a change in magnetization according to the magnetization curve. Magnetostriction is generated by the change in magnetization, and the magnetoelastic wave propagates in the high magnetostriction magnetic body 2 as the elastic wave. Conversely, when a magnetoelastic wave is present in the high magnetostrictive magnetic body 2, the distortion caused by the magnetoelastic wave causes a change in magnetization due to the Villari effect, and the change in magnetization changes the surrounding magnetic field. Magneto-elastic waves can be detected by detecting a change in the magnetic field using a coil or the like.

By using a rod-shaped body as the high magnetostrictive magnetic body 2, the propagation path becomes one-dimensional, so that the distance can be known from the propagation time of the magnetoelastic wave between the first and second detection coils 4 and 5.

The weight 1 is guided by a guide means (not shown) so as to be movable only in one axial direction so as to be movable only in a direction (left / right) indicated by an arrow A. The elastic bodies 6 and 7 extending in the left-right direction make the mechanical displacement of the weight 1 follow the acceleration, and are stretched between the mounts 8 and 9 and the weight 1, respectively. The bar-shaped high magnetostrictive magnetic body 2 is arranged in parallel to the displacement direction of the weight 1 and is fixed to the frames 8 and 9 by means that does not reflect magnetoelastic waves. Excitation means 3, second detection coil
5, The first detection coil 4 fixed to the weight 1 is wound around the high magnetostriction magnetic body 2 in a non-contact state.

Even if the detection coil 4 is displaced, it does not contact the high magnetostriction magnetic body 2. A magnetoelastic wave is generated by the excitation means 3 fixed to the high magnetostriction magnetic body 2, a detection pulse is generated in the second detection coil 5, and a detection pulse is generated in the second detection coil 4. The acceleration is detected from the difference in the detection time of the magnetoelastic wave between the detection coils 4 and 5.

Embodiment FIG. 2 is a sectional view of an embodiment of the acceleration sensor according to the present invention. In the figure, reference numeral 11 denotes a weight corresponding to the above-described weight 1. Similarly, reference numerals 16 and 17 denote elastic bodies and compression springs corresponding to the elastic bodies 6 and 7. Reference numerals 18 and 19 denote stators corresponding to the gantry 4 and 5. Reference numeral 13 denotes a drive coil corresponding to the excitation means 3. 15 corresponds to the second detection coil 5, and 14 corresponds to the first detection coil 4, respectively.

In this embodiment, the acceleration in the direction indicated by arrow A is to be detected. The weight 11 is cylindrical and has a high magnetostrictive magnetic body 16 inserted in the center hole, and the outer periphery is guided by the inner periphery of the cylindrical case 20 so as to be movable in the direction of arrow A.

The high magnetostrictive magnetic body 12 is stretched between stators 18 and 19 fixed to both ends of the case 20, respectively.

The high magnetic material 12 is prepared by spinning in a rotating liquid (JP-A-55-64948).
No.) was created on a fine wire by a manufacturing method called
It consists of an Fe—Si—B-based amorphous magnetic wire.

Compression coil springs 16 and 17 are arranged between the weight 11 and the stators 18 and 19, respectively, to preload the weight 11.

On the stator 19, a cylindrical projection 19a surrounding the high magnetostriction magnetic body 16 is extended from the stator 19, and holds a drive coil 13 and a second detection coil 15 as excitation means on the inner periphery thereof.
The first detection coil 14 is fixed to the weight 11 and has a high magnetostriction magnetic material 12.
Has been inserted.

The electrical connection to the first detection coil 14 is a compression coil spring
Wiring is simplified by using 16, 17 as conductors.

 Next, the operation of this embodiment will be described.

When the pulse current P ₀ shown in FIG. 3A is applied to the drive coil 13, a magnetoelastic wave is generated from the portion where the drive coil 13 is wound, propagates through the high magnetostriction magnetic body 12, Figure 3 in the detection coil 15 of the generates a detection pulse P ₁ of (b), further propagates the high magnetostrictive magnetic 12 medium, third to first detection coil 14
It is detected as a detection pulse P ₂ in FIG. (C).

Detection pulse P ₁ and the detection pulse time t between P _2, and previously measured from the propagation velocity v of the magnetoelastic wave are detected coil 14
The distance h along the high magnetostriction magnetic body 12 between the sensor coil 15 and the detection coil 15 can be calculated from the following equation: h = t · v. The position of the weight 11 is determined by the balance of the force applied to the weight 11 and the compression coil springs 16 and 17 in proportion to the acceleration, so the difference between the propagation time when the acceleration is zero and the propagation time of a certain acceleration indicates the displacement amount of the weight 11. . Since the amount of displacement is proportional to the acceleration, the direction and magnitude of the acceleration can be detected. The processing for calculating the acceleration from the difference in the propagation times is performed by a signal processing circuit (not shown).

By the way, the propagation velocity V of the magnetoelastic wave is high magnetostrictive magnetic material 12.
Since temperature changes with temperature, precise acceleration detection requires temperature compensation, but the distance between the drive coil 13 and the second detection coil 15 along the high magnetostriction magnetic body 12 is measured in advance,
Driving coil 13 and the propagation time between the second detection coil 15, the propagation speed of the detection pulse P ₁ and magnetoelastic wave detection pulse P high magnetostrictive magnetic member 12 by performing a comparison of the time t between ₂ Can be compensated without using a temperature sensor even if the temperature changes with temperature.

The elongation causes the temperature sensor and the like to be used in combination, but this detection method eliminates the need.

Note that the present invention is not limited to the above embodiment, and the following modifications are possible.

The function of the drive coil 13 and the function of the second detection coil 15 can be shared by one coil. The drive coil 13, the second detection coil 15, and the first detection coil 14 are arranged in this order.
Although the magnetoelastic wave arrives first at the second detection coil 15, the arrangement may be changed so that the magnetoelastic wave arrives first at the first detection coil 14. Further, the excitation means may be another means for generating a magnetoelastic wave in the high magnetostriction magnetic material, for example, a piezoelectric element. May also be excited with bursts current is not limited to the pulse current P _0. Further, instead of the compression coil springs 16 and 17, an elastic body such as a tension coil spring or rubber can be used.

To measure the time t between the pulses P ₁ and P ₂ , it is necessary to form a timing circuit such as a quartz oscillator in the circuit,
Instead of measuring the time t, the switching circuit to trigger a detection pulse P ₁ and the detection pulse P ₂ is provided to generate a waveform of FIG. 3 (d), comparing the processing (e.g. integration) and output this Thus, the direction and magnitude of the acceleration applied to the weight 11 can be detected. The high-magnetostriction magnetic material 2 may be a rod, such as a wire, a ribbon, or an elongated plate.

As described above, the present invention measures the propagation time of the magnetoelastic wave generated by the excitation means between the two detection means, detects the displacement of the weight, and obtains the acceleration. If the distance between the excitation means and the second detection coil is measured in advance even if the propagation speed of the magnetoelastic wave of the high magnetostrictive magnetic material changes depending on the temperature,
Temperature compensation can be easily performed without using a temperature sensor.

[Brief description of the drawings]

FIG. 1 is a view for explaining the principle of the present invention, FIG. 2 is a sectional view showing an embodiment of the present invention, and FIG. 3 is a waveform chart for explaining the operation of the embodiment of FIG. 1 ... weight 2 ... high magnetostrictive magnetic material 3 ... excitation means 4
... First detection coil, 5... Second detection coil, 6, 7
…… Elastic body, 8,9 …… Stand.

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Kozo Uga 1-4-1, Fujimi-cho, Gyoda-shi, Saitama Prefecture Jeco Corporation (72) Inventor Sumio Masuda 1-4-1, Fujimi-cho, Gyoda-shi, Saitama Jeco Corporation (56) References JP-A-3-84468 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) G01P 15/11 G01V 1/16

Claims (1)

(57) [Claims] An acceleration sensor for displacing a weight at an equilibrium position only in one axial direction by a restoring force of an elastic body, measuring an amount of displacement of the weight by acceleration, and detecting the axial acceleration. A rod-shaped high magnetostrictive magnetic body disposed in parallel with the magnetic field; an exciting means for generating a magnetoelastic wave in the high magnetostrictive magnetic body; fixed to a weight and displaced relative to the high magnetostrictive magnetic body integrally with the weight. A first detection coil for detecting arrival of a magnetoelastic wave; and a second detection coil fixed in position with respect to the high magnetostriction magnetic body and detecting arrival of the magnetoelastic wave, wherein the first detection coil is provided. An acceleration sensor configured to detect acceleration from a change in a detection time difference of a magnetoelastic wave between the second detection coil and the second detection coil.