JPH09222328A - Angular velocity sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To miniaturize an angular velocity sensor by simplifying configuration and at the same time improve accuracy. SOLUTION: A magnetic field generation part 10 forms a DC bias magnetic field between two magnetic cores 11 and 12. A vibrator 30 vibrates a support member 20 up and down within the bias magnetic field. When the support member 20 being vibrated rotates at an angular velocity of ω, coriolis force is applied to the support member 20 and the support member 20 is displaced so that it is inclined. When the support member 20 is displaced, an angle formed by variable inductance elements 21 and 22 and the bias magnetic field changes and the inductance of the variable inductance elements 21 and 22 changes. Therefore, the angular velocity (1) can be obtained by detecting a signal corresponding to the inductance of the variable inductance elements 21 and 22.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to an angular velocity sensor for detecting an angular velocity by utilizing Coriolis force.

[0002]

2. Description of the Related Art Conventionally, various types of angular velocity sensors using 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 angular velocity sensor using the piezoelectric element, the structure is complicated and the size is increased, and the drift (for example, the sensitivity is 1 [de
g / sec] 800 μV in the case of 24 mV per unit) and temperature characteristics (for example, 15 of full scale at -20 to 50 ° C)
%) Is large and the accuracy is inferior.

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

[0005]

An angular velocity sensor according to the present invention comprises a magnetic field generating means for generating a predetermined magnetic field, and a support which is arranged in a magnetic field generated by the magnetic field generating means and is displaceable by receiving a Coriolis force. A member, a vibrating means for vibrating the support member in a certain direction so that the Coriolis force acts on the support member due to the angular velocity, and a vibrating means attached to the support member and generated by the magnetic field generation means in response to the displacement of the support member by the Coriolis force It is provided with one or more variable impedance elements whose impedance changes with the angle formed with the magnetic field, and detection means for detecting a signal corresponding to the impedance of the variable impedance element.

In the angular velocity sensor of the present invention, the magnetic field generating means generates a predetermined magnetic field, and the vibrating means vibrates the support member in a fixed direction in the magnetic field. When there is an angular velocity, the Coriolis force acts on the support member, and the Coriolis force displaces the support member. When the support member is displaced, the angle formed by the variable impedance element and the magnetic field changes, and the impedance of the variable impedance element changes. Therefore, the angular velocity can be obtained by detecting the signal corresponding to the impedance of the variable impedance element by the detection 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 a perspective view showing a structure of an angular velocity sensor according to an embodiment of the present invention, and FIG. 2 is a side view showing a main part of the angular velocity sensor shown in FIG. As shown in these drawings, the angular velocity sensor according to the present embodiment has a magnetic field generation unit 10 as a magnetic field generation unit that generates a predetermined bias magnetic field, and a bias magnetic field generated by the magnetic field generation unit 10. A support member 20 that is arranged and is displaceable by receiving a Coriolis force, a vibrator 30 as a vibrating unit that vibrates the support member 20 in a certain direction so that the Coriolis force acts on the support member 20 due to an angular velocity, and a support member. Two
The two variable inductance elements 21 are attached to No. 0, the angle formed with the bias magnetic field changes according to the displacement of the support member 20 due to the Coriolis force, and the inductance that determines the impedance changes according to the change in the angle formed with the bias magnetic field. , 22 and a shield case 31 surrounding each of these components.

The magnetic field generator 10 has a rectangular column shape whose lower ends are bent inward, and has two magnetic cores 11 and 12 arranged facing each other with a predetermined gap, and one end of the magnetic core 11. It has a bias magnet 13 joined to the lower end and the other end joined to the lower end of the magnetic core 12. The magnetic cores 11 and 12 are made of, for example, ferrite, the bias magnet 13 is made of, for example, barium ferrite, and are magnetized so that one of both ends has an N pole and the other has an S pole. With such a configuration, a DC bias magnetic field that is substantially parallel to the line connecting the magnetic cores 11 and 12 is formed between the two magnetic cores 11 and 12 as indicated by reference numeral 51 in FIG.

The support member 20 is formed of a rigid body such as ceramics or Ni alloy. The support member 20 is formed in a triangular prism shape whose cross section is an isosceles triangle, and a surface 20 a corresponding to the base of the isosceles triangle is joined to the bias magnet 13 via the vibrator 30. 2 of isosceles triangle
Two faces 20b, 2 of the support member 20 corresponding to one hypotenuse
0c includes variable inductance elements 21 and 22 respectively.
Are joined.

The variable inductance elements 21 and 22 respectively include elongated plate-shaped ferromagnetic portions 21a and 22a and windings 21 wound around the ferromagnetic portions 21a and 22a.
b and 22b. Ferromagnetic material parts 21a, 22a
Is formed of, for example, a ferromagnetic material such as Co—Fe based amorphous. As an example of the composition of such a ferromagnetic material, Co71.2%, Fe4.8%, Si1
5% and B9% are included. Ferromagnetic material parts 21a, 22a
Has a length of 3 mm, a width of 0.2 mm, and a thickness of 50, for example.
μm. The windings 21b and 22b are formed by winding a conductive wire 200 times, for example. The variable inductance elements 21 and 22 are joined to the surfaces 20b and 20c of the support member 20 by, for example, bonding so that the longitudinal direction thereof is parallel to the directions of the oblique sides of the isosceles triangle forming the cross-sectional shape of the support member 20. There is. The magnetic permeability of the ferromagnetic parts 21a and 22a formed of a ferromagnetic material changes according to an external magnetic field. Windings 21 are formed around the ferromagnetic portions 21a and 22a.
Variable inductance element 2 formed by winding b and 22b
The inductances of 1 and 22 are the same as the ferromagnetic material portions 21a and 22.
Since it is proportional to the magnetic permeability of a, it changes according to the external magnetic field.

The vibrator 30 is formed of a piezoelectric element such as PZT (lead zirconate titanate) or a magnetostrictive vibrator, and the support member 20 is vertically moved, that is, in a direction orthogonal to the direction of the bias magnetic field, for example, 20 kHz. It is designed to vibrate at the frequency.

The shield case 31 shields the magnetic field in order to prevent the influence of the earth's magnetism. For example, Fe and Ni are used.
It is made of alloy.

As shown in FIG. 4, the angular velocity sensor according to the present embodiment further detects, as a detection means, a signal corresponding to the difference in inductance (difference in impedance) between the two variable inductance elements 21 and 22. For this purpose, the windings 21b and 22 of the variable inductance elements 21 and 22 are
A high frequency power source 41 for applying a high frequency voltage to b and a differential amplifier 42 for amplifying the difference between the currents flowing through the windings 21b and 22b by the high frequency voltage are provided.

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

In the angular velocity sensor according to the present embodiment, the magnetic field generator 10 causes the magnetic core 1 to be interposed between the two magnetic cores 11 and 12, as indicated by reference numeral 51 in FIG.
A DC bias magnetic field that is substantially parallel to the line connecting 1 and 12 is formed. In this bias magnetic field, the support member 20 is vertically vibrated by the vibrator 30. When there is no angular velocity, the variable inductance elements 21 and 22 make the same angle with the bias magnetic field, and the variable inductance elements 21 and 22 have the same inductance and impedance. On the other hand, when the vibrating support member 20 rotates at the angular velocity ω, the Coriolis force F _c acts on the support member 20. If the vibration speed of the support member 20 is V _f , the Coriolis force F _c
Is expressed by the following equation (1). Note that m is the mass of the support member 20.

[0017]

## EQU1 ## F _c = 2mωV _f (1)

As shown in FIG. 2, the direction of the Coriolis force F _c is a direction obtained by rotating the direction of the velocity V _f by 90 ° in the direction opposite to the direction of the angular velocity ω. The Coriolis force F _c causes the support member 20 to be displaced so as to be inclined. Support member 20
Is displaced, the angle formed by the variable inductance elements 21 and 22 with the bias magnetic field changes, and the inductance and impedance of the variable inductance elements 21 and 22 change. Therefore, the variable inductance elements 21, 22
The angular velocity ω can be obtained by detecting a signal corresponding to the inductance or impedance of the.

FIG. 3 shows variable inductance elements 21 and 2.
3 is a characteristic diagram showing the relationship between the angles θ ₁ and θ ₂ formed by 2 with the bias magnetic field and the inductances L ₁ and L ₂ of the variable inductance elements 21 and 22. FIG. As shown in this figure, the inductance L _1, L ₂ is the angle theta _1, continuously changes in accordance with the theta _2, the angle theta _1, theta ₂ is 0 ° i.e. variable inductance elements 21 and 22 are bias field Takes a minimum value when it is horizontal, and takes a maximum value when the angles θ ₁ and θ ₂ are 90 °, that is, when the variable inductance elements 21 and 22 are perpendicular to the bias magnetic field, and when the angles θ ₁ and θ ₂ are 45 °. Takes an intermediate value L ₀ . When the Coriolis force F _c increases and the inclination of the support member 20 increases, one of the angles θ ₁ and θ ₂ increases and the other decreases, so the variable inductance element 2
The inductance of one of the variable inductance elements 21 and 22 increases and the inductance of the other decreases, so that the difference in the inductance and the difference in the impedance of the variable inductance elements 21 and 22 increase. For example, now in FIG. 3, the angle θ
Assuming that ₁ and θ ₂ are θ ₁₀ and θ ₂₀ , respectively, and that the inductances L ₁ and L ₂ are L ₁₀ and L ₂₀ , respectively, and the inclination of the support member 20 increases, θ ₁ , L ₁ , θ ₂ and L ₂ increase.
₂ is the angle θ ₁ , as indicated by reference numerals 51 and 52, respectively.
The difference between θ _{2 and} the difference between the inductances L ₁ and L ₂ change in the expanding direction.

Therefore, the variable inductance elements 21 and 2 are
Assuming that the inductance difference of 2 is ΔL, approximately,
As in the following formula (2), ΔL is proportional to the Coriolis force F _c .

[0021]

[Equation 2] ΔL∝F _c (2)

Therefore, the following equation (3) is derived from the equations (1) and (2).

[0023]

[Formula 3] ΔL∝2mωV _f (3)

From the equation (3), the angular velocity ω is obtained by the following equation (4). Note that k is a proportional constant.

[0025]

Ω = kΔL / mV _f (4)

Therefore, the variable inductance elements 21 and 2 are
The angular velocity ω can be obtained by detecting a signal corresponding to the inductance difference ΔL of 2. In the present embodiment, in order to detect a signal according to the difference ΔL between the inductances of the variable inductance elements 21 and 22, the variable inductance elements 21 and 2 are driven by the high frequency power supply 41.
A high frequency voltage is applied to each of the windings 21b and 22b of the differential amplifier 2 and the difference between the currents flowing in the windings 21b and 22b is measured by the differential amplifier 42.
The angular velocity ω can be obtained from the output of the differential amplifier 42.

As described above, the angular velocity sensor according to the present embodiment has a simple structure and can be downsized as compared with the conventional angular velocity sensor using a piezoelectric element, and also has a large sensitivity and a large drift. Since the temperature characteristic is small, the accuracy is improved.

The present invention is not limited to the above-described embodiment. For example, a coil (electromagnet) is provided instead of the bias magnet 13 and a direct current or an alternating current is passed through this coil to generate a direct current or an alternating current. A bias magnetic field may be generated. The shape of the support member 20 is not limited to the triangular prism shape, but may be a square prism shape, a columnar shape, or the like. Further, the conditions such as the shapes and materials of the ferromagnetic material parts 21a and 22a can be appropriately set according to the application. The configuration of the detecting means is not limited to that shown in FIG. 4, and for example, the phase difference between the currents flowing in the windings 21b and 22b may be detected and the angular velocity may be obtained from this phase difference. In addition, each variable inductance element 21, 22 is
Each may be configured to have an 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.

The angular velocity can also be detected by one variable inductance element arranged so that the angle formed with the bias magnetic field changes according to the displacement of the supporting member 20 due to the Coriolis force. In the state where there is no angular velocity, the variable inductance elements 21 and 22 have the same inductance (impedance), and the difference in the impedance (impedance) of the variable inductance elements 21 and 22 depends on the displacement of the support member 20 due to the Coriolis force. By arranging the variable inductance elements 21 and 22 so as to expand, the angular velocity can be detected more accurately.

[0030]

As described above, according to the angular velocity sensor of the present invention, the vibrating means supports the Coriolis force so that the Coriolis force acts on the supporting member by the angular velocity in the predetermined magnetic field generated by the magnetic field generating means. Oscillates in a certain direction, and the angle formed by the magnetic field of the variable impedance element attached to the support member changes according to the displacement of the support member due to the Coriolis force, so that the impedance of the variable impedance element changes. Since the angular velocity is detected by detecting the signal corresponding to the impedance of the element, the structure is simple and downsizing is possible, and the sensitivity is large and the drift and temperature characteristics are small, so that the accuracy is improved. .

[Brief description of drawings]

FIG. 1 is a perspective view showing a configuration of an angular velocity sensor according to an embodiment of the present invention.

FIG. 2 is a side view showing a main part of the angular velocity sensor shown in FIG.

FIG. 3 is a characteristic diagram showing the relationship between the angle formed by the variable inductance element and the bias magnetic field in the angular velocity sensor shown in FIG. 1 and the inductance of the variable inductance element.

FIG. 4 is a circuit diagram showing a circuit for obtaining an angular velocity in the angular velocity sensor according to the embodiment of the present invention.

[Explanation of symbols]

10 ... Magnetic field generation part, 11, 12 ... Magnetic core, 13 ... Bias magnet, 20 ... Support member 21,22 ... Variable inductance element, 30 ... Vibrator, 31 ... Shield case

Claims (2)

[Claims] 1. A magnetic field generation means for generating a predetermined magnetic field, a support member arranged in a magnetic field generated by the magnetic field generation means and displaceable by receiving a Coriolis force, and Coriolis on the support member by an angular velocity. A vibrating means for vibrating the supporting member in a certain direction so that a force acts thereon, and an angle formed by the magnetic field generating means attached to the supporting member and generated by the magnetic field generating means in response to the displacement of the supporting member by the Coriolis force. An angular velocity sensor comprising: one or more variable impedance elements that change in impedance to change; and a detection unit that detects a signal corresponding to the impedance of the variable impedance element. 2. The two variable impedance elements are provided, and each of the variable impedance elements is arranged so that a difference in impedance between the two variable impedance elements expands in accordance with a displacement of the supporting member due to Coriolis force, and the detection is performed. The angular velocity sensor according to claim 1, wherein the means detects a signal corresponding to a difference in impedance between the two variable impedance elements.