JPH11352144A - Acceleration sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an acceleration sensor capable of detecting a direct current component and acceleration of a very low frequency vibration. SOLUTION: This acceleration sensor is equipped with an elastic body 3 fixed in a case 2, a weight 5 fixed on the elastic body 3, and a stress sensor 4 embedded in the elastic body 3 and detecting the change of stress generated in the elastic body 3. Material which has a magnetic impedance effect and whose magnetostriction constant is not zero, namely, an amorphous wire is used as the stress sensor 4.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an acceleration sensor using a magneto-impedance element for detecting stress.

[0002]

2. Description of the Related Art As a conventional acceleration sensor, a servo type, a piezoelectric type, a capacitance type, a piezoresistive type and the like have been proposed. Above all, the piezoelectric acceleration sensor has features of simpler structure, sturdiness, smaller size and lighter weight than other systems, and is widely used as a pickup for vibration analysis. Such a conventional acceleration sensor will be described with reference to a cross-sectional view of FIG. In the figure, 13 is a piezoelectric element, 15 is a weight, 14 and 16 are lead wires, and 12 is a case. These constitute the acceleration sensor 11. Piezoelectric element 1
Numeral 3 is tightly fixed to the bottom of the case 12, and a weight 15 is tightly fixed to the upper surface of the piezoelectric element 13. Lead wires 14, 1 connected to the upper and lower surfaces of the piezoelectric element 3,
6 is drawn out from an appropriate hole provided in the case 12 to the outside. With such a configuration, when no acceleration is applied to the acceleration sensor 11, the weight 15 is stationary, but the vertical acceleration is applied to the acceleration sensor 11 and the weight 15 is displaced. Then, stress is applied to the piezoelectric element 13, and a voltage is generated at both ends of the piezoelectric element 13. Since the magnitude of this voltage corresponds to the applied acceleration, an acceleration signal can be obtained using an appropriate circuit, and the acceleration can be detected.

[0003]

However, the acceleration sensor shown in FIG. 3 has a high output impedance and it is difficult to detect a small displacement at a low frequency. There is a problem that the output is extremely small with respect to an extremely low frequency vibration generated in an object, a ship, or the like, and it is difficult to detect the output. Therefore, the present invention has been made to solve such a problem, and can detect an acceleration including a DC component such as an acceleration of an object moving at a constant acceleration or a gravitational acceleration. It is an object of the present invention to provide an acceleration sensor capable of detecting an acceleration of an extremely low frequency vibration generated in a large building or a ship.

[0004]

In order to solve the above problems, an acceleration sensor according to the present invention comprises an elastic member fixed to a case, a weight fixed to the elastic member, and an elastic member embedded in the elastic member. And a stress sensor for detecting a change in stress applied to the substrate, wherein the stress sensor is made of a material having a magneto-impedance effect and a magnetostriction constant other than 0. Further, it is characterized in that the material is an amorphous wire. Since the amorphous wire is used as described above, the direct current component and the low frequency component of the acceleration can be detected.

[0005]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a sectional view of an acceleration sensor showing an embodiment of the present invention. In the figure, 3 is an elastic body, 5 is a weight, 6 is a lead wire, 2 is a case, 4 is an amorphous wire as a stress sensor, and these constitute the acceleration sensor 1. The elastic body 3 is fixed to the bottom of the case 2 in close contact, and a weight 5 is fixed to the upper surface of the elastic body 3 in close contact. An amorphous wire 4 having a magneto-impedance effect is vertically fitted to the center of the elastic body 3 and reaches the upper and lower surfaces, and is connected to the lead wire 6 on the upper and lower surfaces. The lead wire 16 is drawn out of a suitable hole provided in the case 2 to the outside. Here, the magnetic impedance effect means, for example, that Mori
As described in Vol. 2, No. 3, p. 341 of 1996, when a magnetic field is applied in the line length direction of an amorphous wire having a magnetic domain formed in the circumferential direction, a voltage is applied to both ends of the wire based on a change in magnetic permeability. It is a phenomenon that the voltage that changes. When a material having magnetostriction such as an amorphous wire is used, the permeability changes due to the inverse magnetostriction effect only by applying a stress to the amorphous wire, and the same voltage change as when a magnetic field is applied occurs.

Next, the operation of the acceleration sensor 1 having such a configuration will be described. When no acceleration is applied to the acceleration sensor 1, the weight 5 is stationary, but when an acceleration in the vertical direction is applied to the acceleration sensor 1, the acceleration is applied to the weight 5 and the elastic body 3 moves in the direction of the acceleration. And the stress according to the size. When the elastic body 3 receives a stress, the amorphous wire 4 also receives a longitudinal stress corresponding to the acceleration,
Since the magnetic permeability of the amorphous wire 4 changes due to the inverse magnetostriction effect, the voltage at both ends of the amorphous wire 4 changes. The voltage can be converted into a signal corresponding to the acceleration using, for example, the signal processing circuit shown in FIG. 2, and the acceleration can be detected by obtaining the acceleration signal. As described above, an acceleration detecting device can be formed by combining the signal processing circuit and the acceleration sensor 1.

[0007]

As described above, according to the present invention, when acceleration is applied to the weight, a stress corresponding to the acceleration is generated in the amorphous wire embedded in the elastic body, and the acceleration is calculated from the change in the voltage generated in the amorphous wire. Since it can be detected, the DC component of the acceleration can also be detected. Therefore, acceleration generated by extremely low frequency vibration can be detected with high sensitivity in addition to the acceleration and the gravitational acceleration at the time of the uniform acceleration motion, and there is an effect that a high-performance acceleration sensor can be provided.

[Brief description of the drawings]

FIG. 1 is a sectional view of an acceleration sensor showing an embodiment of the present invention.

FIG. 2 is a circuit configuration diagram used for acceleration detection of the acceleration sensor of the present invention.

FIG. 3 is a sectional view of an acceleration sensor showing a conventional example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1, 11 Acceleration sensor 2, 12 Case 3 Elastic body 4 Amorphous wire 5, 15 Weight 6, 14, 16 Lead wire 13 Piezoelectric element

Claims (2)

[Claims] An acceleration comprising an elastic body fixed to a case, a weight fixed to the elastic body, and a stress sensor embedded in the elastic body and detecting a change in stress applied to the elastic body. In the sensor, the stress sensor uses a material having a magneto-impedance effect and a magnetostriction constant other than 0. 2. The acceleration sensor according to claim 1, wherein the material is an amorphous wire.