JPH09196686A - Angular velocity sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an angular velocity sensor whose configuration is simple and whose sensitivity and accuracy are enhanced. SOLUTION: When an AC current is applied to a winding 15 at a detection part 10, ferromagnetic parts 12, 13 are excited, and the respective ferromagnetic parts 12, 13 are vibrated (expanded and contracted) in the length direction due to a magnetostrictive effect. When the ferromagnetic parts 12, 13 being vibrated are turned at an angular velocity ω, Coriolis' force Fc acts on the ferromagnetic parts 12, 13, a support member 11 is bent, and a stress acts on the ferromagnetic parts 12, 13 in such a way that the other out of the ferromagnetic parts 12, 13 is contracted when one out of them is expanded. Thereby, a difference is generated in the impedance of the ferromagnetic parts 12, 13 due to a reverse magnetostrictive effect. Consequently, a high-frequency voltage Vs is applied across the ferromagnetic parts 12, 13 by a high-frequency power supply 21, and the difference in a current flowing to the ferromagnetic parts 12, 13 is amplified by a differential amplifier 22. Thereby, the angular velocity ωcan be found on the basis of the output of the differential amplifier 22.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an angular velocity sensor utilizing the magnetostrictive effect and inverse magnetostrictive effect of a ferromagnetic material.

[0002]

2. Description of the Related Art Conventionally, various types of angular velocity sensors using a piezoelectric ceramic element (hereinafter simply referred to as a piezoelectric element) such as a piezo gyro have been proposed. For example, in a piezo gyro, a driving piezoelectric element and a detecting piezoelectric element are attached to a vibrating body, the vibrating body is vibrated by the driving piezoelectric element, and the Coriolis force acting on the vibrating body depending on the angular velocity is used by the detecting piezoelectric element. It is designed to detect.

[0003]

However, in the conventional angular velocity sensor as described above, the output of the detecting piezoelectric element is small, and the sensitivity is inferior because, for example, an amplifier for amplifying the output by about 30 times is required. There was a point. Also,
There are problems that the structure is complicated, the number of assembling steps is large, and the cost is high. Further, there is a problem that the drift and the offset are large and the accuracy is poor.

The present invention has been made in view of the above problems, and an object thereof is to provide an angular velocity sensor having a simple structure and high sensitivity and accuracy.

[0005]

The angular velocity sensor of the present invention comprises an elongated support member having two parallel surfaces, and two elongated ferromagnetism having a magnetostrictive effect and an inverse magnetostrictive effect respectively provided on the two surfaces of the support member. A body part, a winding wound around the ferromagnetic part, and a coil for vibrating the ferromagnetic part in the longitudinal direction due to the magnetostrictive effect when an alternating current is applied, and a Coriolis force acting on the ferromagnetic part by the angular velocity. And a detection unit for detecting a signal corresponding to the difference in impedance between the two ferromagnetic material portions caused by the inverse magnetostriction effect in accordance with the bending of the supporting member caused by.

In this angular velocity sensor, when an alternating current is applied to the winding wound around the ferromagnetic material portion, the ferromagnetic material portion vibrates in the longitudinal direction due to the magnetostrictive effect. A Coriolis force corresponding to the angular velocity acts on the vibrating ferromagnetic body portion, and the Coriolis force causes the supporting member to bend. This causes a difference in impedance between the two ferromagnetic body portions due to the inverse magnetostrictive effect. Therefore, the angular velocity can be obtained by detecting the signal according to the difference in impedance between the two ferromagnetic parts by the detecting means.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

FIG. 1 is an explanatory view showing the constitution of an angular velocity sensor according to a first embodiment of the present invention, and FIG. 2 is a plan view of a detecting portion in FIG. As shown in these drawings, the angular velocity sensor according to the present embodiment includes the detection unit 10 attached to the measurement target. The detection unit 10 is formed of a non-magnetic material having an appropriate elastic modulus, and has an elongated plate-like support member 11 having two parallel surfaces, and a magnetostrictive effect provided on each of the two parallel surfaces of the support member 11. Two elongated plate-shaped ferromagnetic parts 12, 13 having an inverse magnetostrictive effect
An electrode portion 14 provided at both ends of each of the ferromagnetic material portions 12 and 13, a support member 11 and a ferromagnetic material portion 1
The detection unit 10 is provided around the windings 2 and 13 and has a winding 15 for vibrating (expanding and contracting) the ferromagnetic material portions 12 and 13 in the longitudinal direction by the magnetostrictive effect when an alternating current is applied.

The ferromagnetic portions 12 and 13 are made of a Ni--Fe system,
Co-Fe based alloys (eg Permalloy (trade name))
It is formed of a ferromagnetic material having a magnetostrictive effect and an inverse magnetostrictive effect such as amorphous and amorphous. The magnetostriction constant of the ferromagnetic material is set to a value larger than 1 × 10 ⁻⁶ , for example. As an example of the composition of such a ferromagnetic material, Co65%, Fe10%, Ca1
5% and B10% are included. The ferromagnetic material parts 12 and 13 have, for example, a length of 15 mm, a width of 0.1 mm, and a thickness of 25 mm.
μm. The ferromagnetic parts 12, 13 are preferably attached to the support member 11 so as to be slidable in the longitudinal direction so that they can vibrate (expand and contract) in the longitudinal direction. Electrode part 14
Is formed by, for example, depositing a silver paste (a mixture of silver powder and an organic curable resin) on both ends of the ferromagnetic parts 12, 13. An excitation signal V _r having a frequency higher than 100 Hz, for example, is applied to the winding 15 by the AC power supply 20. As shown in FIG. 1, the detection unit 10 is fixed to the measurement position with two fulcrums 16 near both ends of the support member 11.

The angular velocity sensor according to the present embodiment further includes two ferromagnetic bodies produced by the inverse magnetostrictive effect in accordance with the bending of the support member 11 caused by the Coriolis force acting on the ferromagnetic bodies 12 and 13 due to the angular velocity. As a detection means for detecting a signal corresponding to the difference in impedance between the parts 12 and 13, a high frequency power source 21 for applying a high frequency voltage V _s to each ferromagnetic part 12 and 13, and each ferromagnetic material by this high frequency voltage V _s . The differential amplifier 22 amplifies the difference between the currents flowing in the parts 12 and 13.

Here, the relationship between the stress acting on the ferromagnetic material portions 12 and 13 of the detection portion 10 and the impedance will be described with reference to FIG. Here, as shown in FIG. 3, let us consider an element 30 in which a ferromagnetic layer 32 is bonded to one surface of an elongated plate-shaped substrate 31 having an appropriate elastic modulus. The ferromagnetic layer 32 has a magnetostrictive effect and an inverse magnetostrictive effect, like the ferromagnetic parts 12 and 13. This element 30 is
Two points near both ends of the base 31 on the side opposite to the surface to which the ferromagnetic layer 32 is joined are fixed to the measurement point as fulcrums 34, 34.

An alloy film or an amorphous film of a ferromagnetic material such as Ni-Fe system or Co-Fe system has a magnetostriction effect, and the magnetostriction constant (λ) is about ± 50 × 10 ^-6 , but the stress It has been clarified that it also has an inverse magnetostriction effect in which magnetic properties such as coercive force, inductance, and magnetic permeability change accordingly.

Here, the relationship between stress and magnetic permeability in a ferromagnetic material having an inverse magnetostrictive effect will be considered. In the case of isotropic magnetostriction, assuming that the stress is σ, the magnetoelastic energy (uniaxial anisotropy energy) E generated inside the ferromagnetic material is expressed by the following equation (1) (K. (See page 130 of "Magnetism" (published by Zenkabo, 1936)).

[0014]

[Equation 1] E = (− 3/2) · λ · σ (1)

The magnetoelastic energy E affects the magnetic permeability μ of the ferromagnetic material and has the relationship of the following equation (2) (see the above-mentioned “ferromagnetism”, page 187).

[0016]

[Equation 2] μ∝1 / E (2)

Here, in a range where the absolute value of the stress σ is small, that is, in the range where the absolute value of the magnetoelastic energy E is small, the variation Δμ of the magnetic permeability μ is approximately expressed by the following equation (3). You can

[0018]

[Equation 3] Δμ∝E (3)

On the other hand, the element 30 having the structure shown in FIG.
Then, when the external force F acts on the base 31, the base 31 bends, and stress acts on the ferromagnetic layer 32. The relationship between the external force F and the stress σ acting on the ferromagnetic layer 32 is expressed by the following equation (4). However, k is a coefficient.

[0020]

[Equation 4] σ∝k · F (4)

From equations (1), (3) and (4),
The following equation (5) is derived.

[0022]

[Equation 5] Δμ∝E∝λ ・ σ∝λ ・ F (5)

Since the variation ΔL of the inductance L of the ferromagnetic layer 32 is proportional to Δμ, the following equation (6) is derived.

[0024]

[Equation 6] ΔL∝F (6)

Here, when the measurement angular frequency is ω, the impedance Z of the ferromagnetic layer 32 is expressed by the following equation (7). However, R is a resistance.

[0026]

[Equation 7] Z = R + j · ω · L (7)

From the equations (6) and (7), it can be seen that the inductance L and the impedance Z of the ferromagnetic layer 32 change according to the external force F.

FIG. 4 shows that 13M is provided between both ends of the ferromagnetic layer 32.
13 MHz is applied to the ferromagnetic layer 32 by applying a high frequency voltage of Hz.
It is an example of the result of measuring the relationship between the stress acting on the element 30 (proportional to the external force F) and the reactance (ω · L) of the ferromagnetic layer 32 when a high frequency current of z is applied. In addition, here, the one on the left side of the two scales on the vertical axis of FIG. 4 is used. From this figure, it can be seen that in the range where the stress (external force) is small, the reactance (ω · L) that determines the impedance Z of the ferromagnetic body portion 12 changes substantially linearly according to the stress (external force).

Further, as shown in FIG. 3, a winding 35 formed by winding a conductor wire, for example, 200 times is provided around the base 31 and the ferromagnetic layer 32, and a high frequency current of 1 MHz is supplied to the winding 35. FIG. 4 also shows the result of measuring the relationship between the stress acting on the element 30 and the reactance (ω · L) of the coil including the ferromagnetic layer 32 and the winding 35 when current is applied to the element 30.
As described above, the relationship between the stress acting on the element 30 and the reactance (ω · L) of the ferromagnetic layer 32 is similar. Note that the right one of the two vertical scales in FIG. 4 is used here. Therefore, in the range where the stress (external force) is small, the reactance (ω ·) that determines the impedance Z of the coil including the ferromagnetic layer 32 and the winding 35.
It can be seen that L) changes substantially linearly according to the stress (external force).

Thus, when the stress is applied to the ferromagnetic layer 32, the impedance of the ferromagnetic layer 32 and the impedance of the coil including the ferromagnetic layer 32 and the winding 35 change. The same applies to the detection unit 10 in FIG. 1, and when stress acts on the ferromagnetic material portions 12 and 13, the impedance of the ferromagnetic material portions 12 and 13 changes.

Next, the operation of the angular velocity sensor according to this embodiment will be described.

An AC power supply 20 is provided on the winding 15 of the detection unit 10.
Thus, an excitation signal V _r having a frequency higher than 100 Hz, for example, is applied, and an alternating current is passed through the winding 15. As a result, the ferromagnetic portions 12 and 13 are excited,
The ferromagnetic portions 12 and 13 vibrate (expand and contract) in the longitudinal direction due to the magnetostrictive effect. Ferromagnetic material part 1 vibrating in this way
When 2 and 13 rotate at the angular velocity ω as shown in FIG. 1, the Coriolis force F _c acts on the ferromagnetic parts 12 and 13. If the speed of vibration of the ferromagnetic parts 12 and 13 is v,
The Coriolis force F _c has a magnitude proportional to ωv, and the direction is 90 ° in the direction of the velocity v in the direction opposite to the direction of the angular velocity ω.
It is the direction of rotation. When the ferromagnetic members 12 and 13 receive the Coriolis force F _c , the supporting member 11 bends, and when one of the ferromagnetic members 12 and 13 expands, the other contracts, so that stress is applied to the ferromagnetic members 12 and 13. To work. As a result, the impedances of the ferromagnetic material portions 12 and 13 change due to the inverse magnetostrictive effect, and the amount of change in the impedance of the ferromagnetic material portions 12 and 13 differs.
13 causes a difference in impedance. Therefore, the angular velocity ω can be obtained by detecting a signal corresponding to the difference in impedance between the ferromagnetic material portions 12 and 13. In the present embodiment, in order to detect a signal according to the impedance difference between the ferromagnetic material portions 12 and 13, a high frequency power supply 21 applies a high frequency voltage V _s to each ferromagnetic material portion 12 and 13, The difference between the currents flowing through the ferromagnetic parts 12, 13 is amplified by the differential amplifier 22, and the angular velocity ω can be obtained from the output of the differential amplifier 22.

As described above, the angular velocity sensor according to the present embodiment has a simple structure, so that the cost can be reduced. In addition, the configuration is simple,
Since the signal corresponding to the difference in impedance between the similar ferromagnetic material portions 12 and 13 is detected, the drift and the offset are small (the offset can be almost zero) and the accuracy is improved. Further, in the angular velocity sensor according to the present embodiment, a large output of, for example, 10 times or more can be obtained as compared with the conventional angular velocity sensor using the piezoelectric element, so that the sensitivity is improved.

FIG. 5 is an explanatory view showing the structure of the angular velocity sensor according to the second embodiment of the present invention. The angular velocity sensor according to the present embodiment includes a detection unit 40 attached to the measurement target. The detection unit 40 has a support member 41 formed of a non-magnetic material having an appropriate elastic modulus.
The support member 41 has two elongated plate-shaped portions 41a and 41b arranged in parallel at a predetermined interval, and these plate-shaped portions 41a and 41b.
It is formed in a shape in which both ends of b are connected. The detector 40 further includes two elongated plate-shaped ferromagnetic bodies 4 having a magnetostrictive effect and an inverse magnetostrictive effect, which are provided on two parallel outer surfaces of the plate-shaped portions 41a and 41b of the support member 41, respectively.
2, 43, and the plate-shaped portion 41a and the ferromagnetic material portion 42 are wound around, and the ferromagnetic material portion 42 vibrates (expands and contracts) in the longitudinal direction by the magnetostrictive effect when a high-frequency current is applied, and at the same time, the ferromagnetic material portion 42. 45a for detecting a change in impedance of the ferromagnetic material portion 4a, and is wound around the plate-like portion 41b and the ferromagnetic material portion 43.
3 has a winding 45b for vibrating (expanding and contracting) in the longitudinal direction by the magnetostrictive effect and for detecting a change in impedance of the ferromagnetic body portion 43. Ferromagnetic material parts 42, 4
3 is the ferromagnetic material parts 12, 13 in the first embodiment.
The method of attaching to the plate-shaped portions 41a and 41b is also the same as that of the first embodiment. Detection unit 4
0 is fixed to the measurement point with two points near both ends of the support member 41 as fulcrums 46.

The angular velocity sensor according to the present embodiment further includes two magneto-strictive effects produced by the inverse magnetostrictive effect according to the bending of the plate-like portions 41a and 41b caused by the Coriolis force acting on the ferromagnetic portions 42 and 43 due to the angular velocity. Ferromagnetic part 4
The high frequency voltage V is applied to each of the windings 45a and 45b as a detecting means for detecting a signal corresponding to the difference in impedance between the coils 2 and 43.
A high frequency power supply 51 for applying _s and a differential amplifier 52 for amplifying the difference between the currents flowing through the windings 45a and 45b by the high frequency voltage V _s are provided.

Next, the operation of the angular velocity sensor according to this embodiment will be described.

Each of the windings 45a and 45b of the detecting section 40 includes:
The high frequency power supply 51 applies a high frequency voltage of 1 MHz, for example. This high frequency voltage is applied to each of the ferromagnetic material parts 42,
Excitation signal for vibrating 43 and each ferromagnetic material portion 42,
It also serves as a high-frequency voltage for detecting a change in the impedance of 43. By applying this high-frequency voltage, the ferromagnetic portions 42 and 43 vibrate (expand and contract) in the longitudinal direction due to the magnetostrictive effect. When the vibrating ferromagnetic parts 42 and 43 rotate at the angular velocity ω as shown in FIG. 5, the Coriolis force F _c acts on the ferromagnetic parts 42 and 43. If the speed of vibration of the ferromagnetic parts 42 and 43 is v,
The Coriolis force F _c has a magnitude proportional to ωv, and the direction is 90 ° in the direction of the velocity v in the direction opposite to the direction of the angular velocity ω.
It is the direction of rotation. The ferromagnetic members 42 and 43 receive the Coriolis force F _c , so that the plate-like portion 41 of the support member 41.
Stress acts on the ferromagnetic material portions 42 and 43 such that the a and 41b bend and one of the ferromagnetic material portions 42 and 43 contracts when the other extends. As a result, the impedances of the ferromagnetic portions 42 and 43 change due to the inverse magnetostrictive effect, and the impedance change amounts of the ferromagnetic portions 42 and 43 differ, resulting in a difference in the impedances of the ferromagnetic portions 42 and 43. . Therefore, the angular velocity ω can be obtained by detecting the signal corresponding to the difference in impedance between the ferromagnetic material portions 42 and 43. In the present embodiment, the high frequency power source 51
Each of the windings 45a, 45b by applying a high frequency voltage by
The difference between the currents flowing in the differential amplifier 52 is amplified by the differential amplifier 52, and the angular velocity ω is obtained from the output of the differential amplifier 52.

Other configurations, operations and effects of the angular velocity sensor according to this embodiment are the same as those in the first embodiment.

The present invention is not limited to the above embodiments, and the conditions such as the shapes and materials of the ferromagnetic material portions 12, 13, 42, 43 can be set appropriately according to the application. it can. Further, the configuration of the detecting means is not limited to that shown in each of the embodiments, and for example, the phase difference between the currents flowing through the ferromagnetic material portions 12 and 13 in the first embodiment and the second embodiment. It is also possible to detect the phase difference between the currents flowing in the windings 45a and 45b in the above, and obtain the angular velocity from this phase difference. Also, for example, the ferromagnetic material parts 12, 1
3, ferromagnetic material part 42 and winding 45a, ferromagnetic material part 43
Alternatively, the winding 45b and the winding 45b may be respectively configured to have L (inductance) of an LC (inductance / capacitor) oscillator, and the angular velocity may be obtained from a change in the oscillation frequency of each LC oscillator.

[0040]

As described above, according to the angular velocity sensor of the present invention, the ferromagnetic body portion is vibrated in the longitudinal direction by the magnetostrictive effect, and the inverse of the bending force of the support member caused by the Coriolis force depending on the angular velocity is reversed. Since the angular velocity is detected by detecting the signal according to the impedance difference between the two ferromagnetic parts generated by the magnetostrictive effect, the configuration is simple, and the angular velocity sensor using the conventional piezoelectric element is used. As compared with the above, a large output can be obtained, so that the sensitivity is improved, and the drift and the offset are reduced, so that the accuracy is improved.

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing a configuration of an angular velocity sensor according to a first embodiment of the present invention.

FIG. 2 is a plan view of a detection unit in FIG.

FIG. 3 is a perspective view for explaining the relationship between stress and impedance that acts on the ferromagnetic body portion of the detection unit in FIG.

FIG. 4 is a characteristic diagram showing an example of a result of measuring a relationship between stress acting on the element shown in FIG. 3 and reactance.

FIG. 5 is an explanatory diagram showing a configuration of an angular velocity sensor according to a second embodiment of the present invention.

[Explanation of symbols]

10 ... Detection part, 11 ... Support member, 12, 13 ... Ferromagnetic material part, 15 ... Winding 20 ... AC power supply, 21 ... High frequency power supply, 22 ... Differential amplifier

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Toshio Aizawa 6-735 Kitashinagawa, Shinagawa-ku, Tokyo Sony Corporation

Claims (1)

[Claims] 1. An elongated supporting member having two parallel surfaces, two elongated ferromagnetic members having a magnetostrictive effect and an inverse magnetostrictive effect, which are provided on the two surfaces of the supporting member, respectively, and the ferromagnetic member. Of a coil for winding the ferromagnetic material portion in the longitudinal direction by magnetostriction effect by energizing with an alternating current, and of the supporting member generated by Coriolis force acting on the ferromagnetic material portion due to angular velocity. An angular velocity sensor, comprising: a detection unit that detects a signal corresponding to a difference between impedances of two ferromagnetic bodies caused by an inverse magnetostriction effect in accordance with bending.