JPH07280830A - Acceleration sensor - Google Patents

Abstract

PURPOSE:To provide a high accurate small-sized acceleration sensor which can detect acceleration in biaxial and triaxial directions simultaneously. CONSTITUTION:The acceleration sensor comprises a wire supporting spring 22 made of a soft magnetic material having magnetostrictive constant being set close to zero, a permanent magnet 21 supported by the spring 22 at the upper end thereof, and field sensors 24a, 25a, 26a disposed on a circle, separated by a predetermined distance from the outer periphery of the permanent magnet 21, at a constant interval of 90 deg. with one ends thereof being set at positions separated by a predetermined distance from the permanent magnet 21.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a small and lightweight acceleration sensor capable of detecting accelerations in three-dimensional and two-dimensional directions.

[0002]

2. Description of the Related Art Conventionally, a small and lightweight sensor has been required for detecting a collision of an automobile, and a sensor for detecting a displacement of an object supported by a spring due to an acceleration as a change in capacitance or a piezoelectric element is used. What detects such stress strain as a piezo voltage was used.

All of them detect acceleration in one axis direction, and in order to detect acceleration in three dimensions, it is necessary to use detection elements in combination with three axes. On the other hand, a mechanical gyro that uses a top that rotates at high speed has been generally used for the attitude control of an airplane because it is basically necessary to detect 3-axis acceleration.

When a rotational angular velocity is applied to a vibrating object, Coriolis force Fc = 2 in the direction perpendicular to the vibration.
m × V × ωp However, there is also a piezoelectric gyro that detects the Coriolis force with a piezoelectric element by utilizing the fact that Fc: Coriolis force m: mass V: velocity ωp: angular velocity is generated.

[0005]

However, in the mechanical gyro used for controlling the attitude of the airplane and the like, in order to improve the accuracy, it is inevitable that the mass of the top is increased and the rotation speed is increased, and the size is reduced. It is difficult.

The piezoelectric gyro is used for car navigation, four-wheel steering system, camera shake prevention, etc., but it has been difficult to downsize the vibrator. Further, there is a capacitance change type accelerometer that detects the minute unit due to acceleration as a capacitance change by adding a mass to one of the two electrodes constituting the capacitance and supporting it by a spring. Since the impedance of the sensor portion is high in capacitance, it is weak against external noise, and there is a problem that there are many restrictions, such as the connection distance with the detection circuit being limited.

In view of the problems of the prior art, it is an object of the present invention to provide a small-sized acceleration sensor capable of high-accuracy and simultaneously detecting acceleration in three axial directions.

[0008]

SUMMARY OF THE INVENTION An acceleration sensor according to the present invention comprises a year-like support spring made of a soft magnetic material and having spring properties, a permanent magnet supported by the support spring at the upper end of the support spring, and an outer circumference of the permanent magnet. It has a magnetic field sensor for detecting a magnetic flux change at a position at a predetermined distance from.

Further, the permanent magnet of the acceleration sensor of the present invention has a cylindrical shape or a cylindrical shape having magnetic poles of N pole and S pole at both end surfaces. In the acceleration sensor of the present invention for detecting acceleration in the three-dimensional direction, the supporting member supports the permanent magnet on the upper end, and further supports the lower end by another elastic member.

In the acceleration sensor for detecting two-dimensional acceleration according to the present invention, the supporting member supports the permanent magnet on the upper end and further supports the lower end on the base.

The acceleration sensor of the present invention comprises a magnetic field sensor and
The mounting position of the permanent magnet has a gap indicated by G in FIG. In the acceleration sensor of the present invention, a magnetic shield member is provided on the outer periphery of the acceleration sensor, and the acceleration sensor and the magnetic shield member are fixed by the acceleration sensor support member.

[0012]

In the acceleration sensor for detecting three-dimensional acceleration according to the present invention, the wire-shaped support spring having one end supported by the elastic member and having the spring property has the permanent magnet fixed to the other end, so that the change in acceleration can be prevented. The permanent magnet is displaced in the three axis directions.

The magnitude and direction of acceleration are detected by a magnetic field sensor. That is, the two-dimensional movement can be detected by comparing the output differences of the magnetic field sensors facing each other. Further, with respect to the vertical movement of the support spring in the vertical direction, the outputs of the four magnetic field sensors increase / decrease in the same manner, and therefore, the detection is performed by comparing their in-phase components.

On the other hand, in the acceleration sensor for detecting the two-dimensional direction of the present invention, one end is fixed by the base, and the wire-like support spring having spring property has the permanent magnet fixed at the other end. Since the permanent magnet is displaced only in the biaxial direction with respect to the change, only the two-dimensional movement is detected by the magnetic field sensor.

The present invention is structurally simple and can easily realize a high-performance acceleration sensor, and since external electromagnetic noise is absorbed by the magnetic shield member, it is not affected by the external electromagnetic noise.

[0016]

【Example】

(1) First Embodiment A first embodiment of the present invention will be described with reference to the drawings. Figure 1
FIG. 2 is a plan view illustrating the entire structure of the acceleration sensor of the present invention, and FIG. 2 is a sectional view of the acceleration sensor of the present invention.

In FIG. 2, the permanent magnet 21 is a columnar magnet having a central hole 32 as shown in FIG. Further, it has magnetic poles of N pole and S pole in the direction of both end faces of the column.
The support spring 22 fixes the permanent magnet 21 at its upper end and fixes it to the support spring base 29 at its lower end. The material of the support spring 22 is a soft magnetic material whose magnetostriction constant is set near zero, and is, for example, a NiFe alloy or a CoZr-based amorphous material.

The support spring base 29 is engaged with and supported by the base 23 and can move in the vertical direction. Support spring stand 2
9. The material of the base 23 is also a material having excellent magnetic characteristics, for example, a soft magnetic material. Further, springs 210 and 211 are arranged above and below the support spring base 29. Spring 211
Are held and fixed by spring retainers 212.

The magnetic pole rods 24a and 24b are provided with a detection coil 2
5a, 25b and drive coils 26a, 26b are wound, and both ends are fixedly supported by the base 23 and the pole bar support ring 28. The material of the pole bar is also a soft magnetic material. The material of the pole bar support ring 28 is a non-magnetic material.

As shown in FIG. 1, the magnetic pole rods have their inner ends facing the same circle in a plane with the permanent magnet 11 as the center,
14a, 14b, 14c and 14d are arranged so as to be orthogonal to each other. The acceleration sensor of the first embodiment,
The magnetic pole rods 14a, 14b, 14c, 14d shown in FIG. 1, and the base 23, the support spring base 29, and the support spring 2 shown in FIG.
2. The permanent magnet 21 and the air gap form a magnetic circuit.

The magnetic flux generated from the permanent magnet 21 is generated by the magnetic pole rods 24a, 24b (in FIG. 1, 14a, 14b, 14c,
14d), the base 23, the support spring 29, the support spring 2
It flows through a magnetic circuit composed of two. The magnetic pole rods 14a, 14b, 14c and 14d shown in FIG. 1 include drive coils 16a, 16b, 16c and 16d and a detection coil 15a.
15b, 15c and 15d are wound. An alternating current is applied to the drive coils 16a to 16d.

Next, the operation of the acceleration sensor of the present invention will be described. When the permanent magnet 11 is displaced due to the change in acceleration,
Each magnetic pole bar 14a, 14b, 14c, 14d and the permanent magnet 1
The distance from 1 changes and the magnetic flux flowing through each pole bar changes. Since the magnetic pole rods 14a to 14d are excited by alternating current, the change in magnetic flux changes the magnetic operating point of the magnetic pole rods 14a to 14d. As a result, the output of the detection coils 15a, 15b, 15c, 15d wound around the magnetic pole rods 14a to 14d shows the second harmonic component of the frequency of the drive current that does not occur unless the magnetic flux changes.

FIG. 4 is a diagram for explaining the magnetic operation of each magnetic pole rod in this embodiment. FIG. 4A is a graph showing the magnetization curve of the pole bar, in which the horizontal axis represents the applied magnetic field and the vertical axis represents the amount of magnetic flux. FIG. 4B shows the output magnetic flux that changes with time of the magnetic pole rod. Since the voltage output to the detection coil is the time change of the magnetic flux, this time differential waveform appears.

FIG. 4 (c) shows the temporal change of the magnetic field applied to the pole bar. The waveform shown by the solid line is the magnetic field generated by an external sinusoidal current in the drive coil. The dotted line indicates the magnetic field when an external magnetic field, which is the measurement target, is applied. At this time, in FIG. 4A, the operating point of the magnetic pole rod moves to the point (d), and the output waveform of FIG. 4B becomes like a dotted line. That is, due to the magnetic saturation of the magnetic pole rod, the symmetry is broken, and the output waveform includes harmonics. If even-order harmonics are extracted from this harmonic and the magnitude and phase thereof are checked, an output indicating the magnitude and direction of the external magnetic field proportional to the external magnetic field can be obtained, so that the magnetic field sensor has high sensitivity.

The detection of such a magnetic field change is based on the same principle as the fluxgate type magnetic field sensor. FIG. 5 shows a functional block diagram of the flux gate type magnetic field sensor. The flux gate type magnetic field sensor includes an oscillator 51, an amplifier 52, a high permeability magnetic core 53, a drive coil 54, a detection coil 55, a bandpass filter 56, a phase detector 57, and a phase converter 5.
8 and a frequency multiplier 59.

Using the principle of this flux gate type magnetic field sensor and comparing the second harmonic components of each axis in the plane,
The movement of the permanent magnet 11 and its direction can be detected. That is, the two-dimensional movements are arranged at right angles to each other,
It can be obtained by comparing the output differences of the detection coils wound around the pairs 14a and 14b and 14c and 14d of the magnetic pole rods. For example, in FIG. 1, the permanent magnet 11 has the magnetic pole bar 14a.
Detection coil 15 of the pole bar 14a when it moves in the direction of
The output of a increases and the output of the detection coil 15b of the pole bar 14b decreases. Detection coil 1 for the pole bars 14c, 14d
The outputs of 5c and 15d do not change.

For the vertical movement of the support spring 12 in the vertical direction, the four magnetic pole rods 14a, 14b, 14c,
Since the output of 14d similarly increases and decreases, the displacement can be detected by comparing those in-phase components. G shown in FIG. 2 is a gap between the center of the cross section of the magnetic pole bar and the center of the permanent magnet 21 in the thickness direction. For the upward movement of the permanent magnet, the detection coils of the magnetic pole bars 14a to 14d are shown. 15a
The output of the detection coils 15a to 15d decreases with respect to the downward movement. Therefore, by providing the gap G, the directivity in the vertical direction can also be detected.

Next, a method of manufacturing the magnetic field sensor of this embodiment will be described with reference to FIG. The magnetic pole rod 61 of FIG. 6 has a wire diameter of φ15.
It is an amorphous material of 0 μm or less, and the surface of the magnetic pole bar 61 made of an amorphous material is coated with a coating material 62 having excellent electrical insulation characteristics. The material of the coating material is, for example, a baking coating of polyurethane material. Further, parallel wires 63 are wound around the outer circumference of the magnetic pole rod 61 coated with the coating material 62. The parallel wire 61 is made of two ultrafine wires, which are made of polyurethane material and are insulated from each other.
The book is bound in parallel. Then, the magnetic field sensor is formed by solidifying the parallel wire 61 with the bonding material 54 so as not to unwind after the winding. With such a structure, the manufacture of the magnetic field sensor becomes extremely easy.

As another embodiment of the magnetic field sensor, in the embodiment of the magnetic field sensor, the parallel wire 61 is
Two ultrafine wires are bundled in parallel with each other in a state where their insulation is secured by a self-bonding bond-met material. A feature of the self-bonding bond-met material is that the bond-met material is softened when heat is applied and fused to each other. By winding the parallel wire around the pole bar 61 and then heating the wires, the wires after the winding are fused to each other, so that the bonding material 64 becomes unnecessary.

In FIG. 6, one side of the winding start of the parallel wire 63 is the driving coil winding start 65, and the one that is electrically connected to the driving coil winding start 65 of the winding end of the parallel wire 63 is the driving coil winding end 66. . Similarly, one side of the winding start of the parallel wire 63 becomes the detection coil winding start 67, and the side of which the driving coil winding start 65 at the winding end of the parallel wire 63 is electrically connected becomes the detection coil winding end 68.

(2) Second Embodiment Next, a second embodiment of the acceleration sensor of the present invention will be described with reference to FIG. In FIG. 7, the spring 710 is a support spring 72.
Is fixed to the lower end of the support spring fastening portion 712,
The spring 710 includes a spring support base 713 and a spring support base fastening portion 7.
Fix at 11. The spring support base 713 is fixed to the base 73.

When the support spring 72 moves in the vertical direction, that is, in the vertical direction, the side surface of the support spring 72 and the base 7 are moved.
The center hole of 3 slides. In the first embodiment, the spring 2
In order to avoid fastening 10 and 211 to the related members, the movement of the support spring was braked by two springs, but it can be realized by one spring in the second embodiment.

(3) Third Embodiment A third embodiment of the acceleration sensor of the present invention will be described with reference to FIG. In FIG. 8, the lower end 82 of the support spring is inserted and fixed in a support spring fixing hole 87 provided in the base 83. As a result, the permanent magnet 81 fixed to the support spring 82 does not move in the vertical direction of the support spring 82, that is, in the vertical direction. By limiting the movement of the permanent magnet 81 to a two-dimensional movement, a two-dimensional acceleration sensor is obtained, but the structure of the detection circuit can be simplified, and the behavior due to the acceleration change of the permanent magnet 81 is stable, so that it is stable. It is possible to obtain the measured value.

As shown in FIG. 1, the magnetic pole rods have their inner ends facing the same circle in a plane with the permanent magnet 11 as the center,
14a, 14b, 14c and 14d are arranged so as to be orthogonal to each other.

(4) Fourth Embodiment FIG. 9 shows a plan view of a fourth embodiment of the acceleration sensor of the present invention, and FIG. 10 shows a sectional view of the fourth embodiment. As shown in FIG. 9, the magnetic pole rods are arranged so that their inner ends face each other with the permanent magnet 91 as the center, and they are orthogonal to each other like 94a and 94b.

In FIG. 10, the permanent magnet 101 is shown in FIG.
It is a cylindrical magnet shown in. Further, it has magnetic poles of N pole and S pole in the direction of both end faces of the column. The support spring 102 fixes the permanent magnet 101 at the upper end and the support spring fixing hole 1 at the lower end.
It is driven into 09 and fixed to the base 103.

The acceleration sensor of the fourth embodiment is composed of the magnetic pole rods 94a and 94b shown in FIG. 9 and the base 103 shown in FIG.
The support spring 102, the permanent magnet 101, and the gap form a magnetic circuit. In the fourth embodiment, since the permanent magnet 91 is composed of two magnetic pole rods 94a and 94b so as to be orthogonal to each other with their inner ends facing each other, the first and second embodiments are arranged. As in the third embodiment, the method of detecting the acceleration and its direction by comparing the output differences of the detection coils wound on the magnetic pole rods facing each other cannot be adopted, so the measurement accuracy is poor, but 94a, 94a
Only the signals detected by the two detection coils mounted on the two pole bars of b need be processed.

Further, since the support spring 102 is fixed to the base 103, it has a structure capable of measuring only two-dimensional acceleration. However, the advantage of the fourth embodiment is that the configuration of the detection circuit can be greatly simplified by using two magnetic pole bars and by limiting the movement of the permanent magnet to two-dimensional movement. A two-dimensional acceleration sensor can be realized at low cost.

(5) Fifth Embodiment FIG. 11 shows a fifth embodiment of the acceleration sensor of the present invention. As shown in FIG. 11, the pole bar has the permanent magnet 111 as the center,
114a, 114b, 114 with their inner ends facing
As shown in c, they are arranged on the same plane at an angle of 120 °. Other configurations on the magnetic circuit may be either the first embodiment or the fourth embodiment.

By arranging such a magnetic field sensor, it is possible to detect the two-dimensional acceleration and its direction by comparing the output differences of the detection coils wound on the respective magnetic pole rods, and In contrast to the first embodiment, only three pole bars are required. (6) Sixth Embodiment FIG. 12 shows a sixth embodiment of the acceleration sensor of the present invention.

In FIG. 12, the acceleration sensor 121 is
The acceleration sensor described in the first embodiment, the second embodiment, the third embodiment, the fourth embodiment, or the fifth embodiment. The acceleration sensor 121 and the magnetic shield member 123 are connected and fixed to each other by an acceleration sensor support member 122.
The acceleration sensor support member 122 is made of a non-magnetic material. The magnetic shield member 123 is made of a magnetic material. Ideally, the magnetic shield member 123 is made of a material having a high saturation magnetic flux density, and a material having a high magnetic permeability. Specifically, the magnetic shield member 123 can be implemented by a permalloy material, electromagnetic pure iron, a silicon steel plate, a carbon steel plate, or the like.

With such a structure, the magnetic shield member 123 completely prevents the measurement error due to the influence of external magnetic noise or geomagnetism on the acceleration sensor 121, and serves as a protective case for the acceleration sensor 121. And also improves the practicality of the acceleration sensor.

[0043]

By adopting the structure of the present invention, the supporting spring structure for simultaneously detecting the accelerations in the three-axis direction and the two-axis direction becomes simple, and the highly accurate acceleration sensor can be easily manufactured. . Also, the influence of external magnetic noise is eliminated when measuring acceleration.

[Brief description of drawings]

FIG. 1 is a plan view of a first embodiment of an acceleration sensor according to the present invention.

FIG. 2 is a sectional view of a first embodiment of the acceleration sensor of the present invention.

FIG. 3 is a permanent magnet of the acceleration sensor of the present invention.

FIG. 4 is a diagram illustrating the magnetic operation of each magnetic pole rod according to the embodiment.

FIG. 5 is a functional block diagram of a flux gate type magnetic field sensor.

FIG. 6 is a magnetic field sensor of the present invention.

FIG. 7 is a sectional view of a second embodiment of the acceleration sensor of the present invention.

FIG. 8 is a sectional view of a third embodiment of the acceleration sensor of the present invention.

FIG. 9 is a plan view of a fourth embodiment of the acceleration sensor of the present invention.

FIG. 10 is a sectional view of a fourth embodiment of the acceleration sensor according to the present invention.

FIG. 11 is a plan view of a fifth embodiment of the acceleration sensor of the present invention.

FIG. 12 is a sectional view of a sixth embodiment of the acceleration sensor of the invention.

[Explanation of symbols]

11, 21, 31, 71, 81, 91, 101, 111
Permanent magnets 12, 22, 72, 82, 92, 102, 112 Support springs 13, 23, 73, 83, 93, 103, 113 Bases 14a, 14b, 14c, 14d, 24a, 24b, 6
1, 74a, 74b, 84a, 84b, 94a, 94
b, 104a, 104b, 114a, 114b, 114
c Magnetic pole bars 15a, 15b, 15c, 15d, 25a, 25b, 5
5, 75a, 75b, 85a, 85b, 95a, 95
b, 105a, 105b, 115a, 115b, 115
c Detection coils 16a, 16b, 16c, 16d, 26a, 26b, 5
4, 76a, 76b, 86a, 86b, 96a, 96
b, 106a, 116a, 116b, 116c Drive coil 17, 27, 97, 107, 117 Center recess 18, 28, 78, 88, 98, 108, 118 Magnetic pole rod support ring 29 Support spring base 32 Center hole 51 Transmitter 52 Amplifier 53 High-permeability magnetic core 56 Bandpass filter 57 Phase detector 58 Phase converter 59 Frequency multiplier 62 Coating material 63 Parallel wire 64 Bonding material 65 Drive coil winding start 66 Drive coil winding end 67 Detection coil winding 68 Detection coil winding End 87, 109 Support spring fixing hole 121 Acceleration sensor 122 Acceleration sensor support member 123 Magnetic shield member 210, 211, 710 Spring 212 Spring retainer 711 Spring support base fastening part 712 Support spring fastening part 713 Spring support base

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yasuhiro Koshimoto 1-1-6 Uchisaiwaicho, Chiyoda-ku, Tokyo Nihon Telegraph and Telephone Corporation (72) Inventor Tadamichi Kawada 1-1-6 Uchiyuki-cho, Chiyoda-ku, Tokyo No. Nihon Telegraph and Telephone Corporation (72) Inventor Kiyo Itao 6-6-8 Jomyoji, Kamakura City, Kanagawa Prefecture (72) Inventor Tetsuo Uchiyama 3-6-1, Surugadai, Chiyoda-ku, Tokyo ETI Co., Ltd. Within

Claims (16)

[Claims] 1. A wire-shaped support spring (22) having a spring property of a soft magnetic material whose magnetostriction constant is set to near zero, and a permanent magnet (21) supported at one end of the support spring (22).
A permanent magnet (21) supported by a support spring (22), one end of each of which is arranged on the same circumference, and the permanent magnets (21) are arranged at substantially equal intervals with an angle of about 90 °, and An acceleration sensor comprising: a magnetic field sensor (24a, 25a, 26a) arranged at a predetermined distance from the outer circumference of the magnet (21). 2. The acceleration sensor according to claim 1, wherein
An acceleration sensor in which both end surfaces of the permanent magnet (21) have magnetic poles of N pole and S pole, and the shape thereof is a cylindrical shape. 3. The acceleration sensor according to claim 1, wherein
Magnetic field sensor (24a, 25a, 26a) and permanent magnet (2
An acceleration sensor in which the mounting position of 1) is away from the central axis of the magnetic pole bar (24a) and the central cross section of the permanent magnet (21) in the thickness direction by a predetermined distance. 4. The acceleration sensor according to claim 1, wherein
One end of the wire-shaped support spring (22) is connected to the elastic member (21
0, 211) supported acceleration sensor. 5. The acceleration sensor according to claim 4,
In order to be able to change the longitudinal distance of the support spring (22) between the wire-shaped support spring (22) and the pole bar (24a), pressure is applied in the first longitudinal direction of the support spring (22). An acceleration sensor having a first spring (210) and a second spring (211) that pressurizes in a second direction opposite to the first direction. 6. The acceleration sensor according to claim 4,
One end is fixed to the support spring (22) and the other end is fixed to the spring so that the length of the support spring (22) between the wire support spring (22) and the pole bar (24a) can be changed. An acceleration sensor having a spring (710) fixed to a support (713). 7. The acceleration sensor according to claim 1, wherein
Magnetic pole bar (24a, 25a, 26a) of magnetic field sensor (24a, 25a, 26a)
An acceleration sensor having a driving coil (26a) and a detection coil (25a) formed by coating a coating material on the outer periphery of a) and winding parallel wires on the outer periphery thereof. 8. The acceleration sensor according to claim 1, wherein
A magnetic shield member (1
23) is provided, and the acceleration sensor (121) and the magnetic shield member (123) are connected and fixed by a non-magnetic member (122). 9. The acceleration sensor according to claim 5,
The magnetic shield member (123) is the same as the acceleration sensor (12
An acceleration sensor forming a part of the protective case of 1). 10. The acceleration sensor according to claim 1, wherein a support spring base (29) having a support spring (22) fixed thereto is movably supported in the longitudinal direction of the support spring (22), and the spring (210, 211) is held on the support spring base (29) so that a predetermined pressure is applied, and the pole bar (24
An acceleration sensor having a base (23) supporting a). 11. A magnet supporting means (22) having a spring property of a soft magnetic material, whose magnetostriction constant is set to near zero, a permanent magnet (21) fixed to the magnet supporting means (22), and substantially 90 ° to each other. The four magnetism detecting means (24a, 25a, 26) are arranged at substantially equal intervals with an angle of, and are arranged at a predetermined distance from the outer circumference of the permanent magnet (21).
a) An acceleration sensor comprising: 12. Four magnetic detection means (24a, 25)
12. The acceleration sensor according to claim 11, wherein a, 26a) are arranged on substantially the same plane, and this plane and one magnetic pole end surface of the permanent magnet (21) are arranged substantially parallel to each other with a predetermined distance. 13. A magnet support means (22) and an elastic support means (210, 211) for applying an elastic force in a direction of changing the distance between the permanent magnet (21) and the four magnetic detection means (24a, 25a, 26a). ) The acceleration sensor according to claim 11. 14. Four magnetic detection means (24a, 25)
14. The acceleration sensor according to claim 13, further comprising sensor support means for supporting a, 26a), operably supporting magnet supporting means (22) and elastic supporting means (210, 211). 15. A wire-shaped support spring (102) having a spring property of a soft magnetic material whose magnetostriction constant is set to near zero.
And a permanent magnet (101) supported at one end of the support spring (102) and a first magnetic field arranged at an angle of 90 ° to each other and arranged at a predetermined distance from the outer circumference of the permanent magnet (91). Sensors (94b, 95b, 96b),
An acceleration sensor comprising a base (103) in which one end of a wire-shaped support spring (102) is fixed by a support spring fixing hole (109). 16. A wire-shaped support spring (112) having a spring property of a soft magnetic material whose magnetostriction constant is set near zero.
And a permanent magnet (11) supported at one end of the support spring (112).
1) and a permanent magnet (111) supported by a support spring (112)
And one end of each of which is arranged on the same circumference, and is arranged at an equal angle with each other at an angle of about 120 °, and is arranged at a predetermined distance from the outer circumference of the permanent magnet (111). Magnetic field sensors (114a, 115a, 1
16a) and the second magnetic field sensor (114b, 115b,
116b) and the third magnetic field sensor (114c, 115).
c, 116c).