JPH09318360A - Elastic surface wave gyroscope - Google Patents

Abstract

PROBLEM TO BE SOLVED: To achieve a high detection level of a Coriolis force. SOLUTION: IDTs(interdigital transducers) 23 and 24 for generating elastic surface waves and reflectors 25, 25'-27 and 27' are arrayed on the surface of a piezo-electric substrate 21 in one row sandwiching an IDT 22 for detecting a Coriolis force. High frequencies (f0 +Δf) and (f0 -Δf) are applied respectively to the IDTs 23 and 24 from a high frequency oscillator to generate two kinds of elastic surface waves. Both the elastic surface waves are reflected by the reflectors 25 and 25' and the reflectors 26 and 26' to make a standing wave and an interfering wave (f0 ) is generated between the IDTs 23 and 24. Under such a condition, when the piezo-electric substrate 21 makes a rotating motion, an elastic surface wave attributed to the Coriolis force with the phase thereof shifted is generated by 90 deg. by interaction with the interfering wave. This elastic surface wave is reflected by reflectors 27 and 27' to make a standing wave. This standing wave is converted to an electrical signal by a piezo-electric effect and detected by the IDT 22.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an elastic device for converting a Coriolis force generated on a substrate surface by an interaction between surface vibration of a piezoelectric substrate due to a surface acoustic wave and a rotational motion of the piezoelectric substrate into a voltage by a piezoelectric effect and detecting the voltage. It relates to a surface wave gyroscope.

[0002]

2. Description of the Related Art Conventionally, a gyroscope using a surface acoustic wave has been proposed as disclosed in, for example, Japanese Patent Laid-Open No. 6-281465.

In the above publication, one interdigital transducer (hereinafter referred to as an IDT for detection (Inter-Digital Transd) for detecting Coriolis force is formed on one surface of a piezoelectric substrate.
ucer). ), A pair of IDTs (hereinafter referred to as driving IDTs) that generate surface acoustic waves of the same frequency, and a pair of reflectors that reflect the surface acoustic waves to the detection IDT side outside the driving IDTs. A surface acoustic wave gyroscope having a configuration in which they are formed in a predetermined positional relationship with each other is shown.

FIG. 19 is a view showing a detection IDT, a pair of driving IDTs and a pair of reflectors formed on the surface of the piezoelectric substrate of the surface acoustic wave gyroscope.

The distances d1 and d2 between the comb-shaped electrodes D1 and D2 of the detection IDT 101 and the driving IDTs 102 and 103 formed on the surface of the piezoelectric substrate 100 have the same pitch (1/2 of the wavelength λ of the surface acoustic wave). Have The reflectors 104 and 105 are grating radiators in which 100 linear electrodes D3 are arranged at a predetermined pitch (pitch of approximately λ / 2).

The piezoelectric substrate 100 includes the driving IDT 10
2, 103 generate surface acoustic waves traveling outward from both sides, and the surface acoustic waves are reflected by the reflectors 104,
By reflecting the light toward the detection IDT 101 side by 105, a standing wave of a surface acoustic wave is generated between the reflectors 104 and 105. The detection IDT 101 is formed at a predetermined position where each of the comb-shaped electrodes D1 and D2 is a node of the surface acoustic wave (standing wave).

In the surface acoustic wave gyroscope described above, when the piezoelectric substrate 100 makes a rotational motion in the state where a standing wave of the surface acoustic wave is generated on the surface of the piezoelectric substrate 100, the surface acoustic wave oscillates in the direction of vibration by the surface acoustic wave. In the vertical direction, a surface acoustic wave (standing wave) is generated due to the Coriolis force that is 90 ° out of phase with this surface acoustic wave, so that it corresponds to the vibration of this surface acoustic wave converted by the piezoelectric effect from the detection IDT 101. The voltage is detected.

[0008]

The conventional surface acoustic wave gyroscope described above drives the surface acoustic waves of the same frequency generated by the driving IDTs 102 and 103 by the reflectors 104 and 105 to the detection IDT 101 side for driving. IDT
A standing wave of a surface acoustic wave is generated between 102 and 103. The Coriolis force generated by the interaction between the surface acoustic wave and the rotational movement of the piezoelectric substrate 100 is 90
Since the phases are out of phase, it is difficult to arrange the reflectors 104 and 105 at positions having sufficient reflection characteristics for both the surface acoustic wave and the surface acoustic wave caused by the Coriolis force.

The reflector 10 is placed at a suitable reflection position for the surface acoustic waves generated by the driving IDTs 102 and 103.
By disposing 4, 105, surface acoustic waves caused by Coriolis force are sufficiently detected by the reflectors 104, 105.
The IDT for detection may not be reflected to the first side and may be absorbed or reflected to weaken the incident wave in some cases.
In 101, it is difficult to obtain a sufficient Coriolis force (standing wave) detection voltage.

The present invention has been made in view of the above problems, and provides a surface acoustic wave gyroscope having a high detection sensitivity for generating a standing wave of a surface acoustic wave caused by Coriolis force. Is.

[0011]

According to the present invention, a Coriolis force detecting portion, which is formed by arranging a plurality of electrodes on a surface of a piezoelectric substrate, is provided, and the detecting portion is caused to vibrate by a surface acoustic wave. A surface acoustic wave gyroscope for detecting a Coriolis force generated by an interaction between vibration and a rotational movement of a piezoelectric substrate by converting it into a voltage by a piezoelectric effect, wherein the detection unit generates a first surface acoustic wave. Therefore, the first drive electrode to which the first high frequency is applied, and the second high frequency to which the second high frequency is applied to generate the second surface acoustic wave having a frequency different from that of the first surface acoustic wave. The first surface acoustic wave is formed on both outer sides of the driving electrode and the first and second driving electrodes so as to generate a standing wave of the first surface acoustic wave. A pair of first reflector electrodes that reflect to the electrode side And the second surface acoustic wave is formed on both outer sides of the first and second driving electrodes so as to generate a standing wave of the second surface acoustic wave, and the second surface acoustic wave is directed to the second driving electrode side. A pair of second reflector electrodes for reflection, and a third elasticity based on the Coriolis force generated by the interaction between the interference wave of the first surface acoustic wave and the second surface acoustic wave and the rotational movement of the piezoelectric substrate. A pair of first surface acoustic waves are formed on both outer sides of the first and second driving electrodes to make the surface waves a standing wave and reflect the third surface acoustic wave to the first and second driving electrode sides. No. 3 reflector electrode, and a detection electrode formed between the first and second driving electrodes for detecting an electric signal generated according to the strain caused by the Coriolis force due to the piezoelectric effect. (Claim 1).

According to the above structure, the first driving electrode is
For example, when a first high frequency wave having a frequency f _H (= f ₀ + Δf) is applied, a first surface acoustic wave vibrating at a frequency f _H is generated on the surface of the substrate due to an inverse piezoelectric effect, and this first surface acoustic wave is generated. It propagates to both outer sides of the first driving electrode.

When a second high frequency wave having a frequency f _L (= f ₀ −Δf) is applied to the second driving electrode, the second elasticity vibrates at the frequency f _{L on the} substrate surface due to the inverse piezoelectric effect. A surface wave is generated, and this second surface acoustic wave propagates to both outsides of the second driving electrode.

The first surface acoustic wave propagates to the pair of first reflector electrodes without being reflected by the detection electrode, the second driving electrode, and the second and third reflector electrodes. First
Is reflected by the reflector electrode toward the first driving electrode to generate a standing wave of the first surface acoustic wave between the pair of first reflector electrodes.

Similarly, the second surface acoustic wave propagates to the pair of second reflector electrodes without being reflected by the detection electrode, the first driving electrode, and the first and third reflector electrodes. Then, the second reflector electrode is reflected toward the second driving electrode side to generate a second surface acoustic wave standing wave between the pair of second reflector electrodes.

Then, a surface acoustic wave having a frequency f ₀ is generated between the first driving electrode and the second driving electrode due to the interference of the first and second surface acoustic waves, and the surface acoustic wave causes the substrate. When the piezoelectric substrate makes a rotational motion while the surface is vibrating, the third surface of the frequency f ₀ based on the Coriolis force 90 ° out of phase with the surface acoustic wave is generated in the plane orthogonal to the surface of the surface acoustic wave. Surface acoustic waves are generated.

The third surface acoustic wave is propagated to the pair of third reflector electrodes without being reflected by the first and second driving electrodes, and the third reflector electrode detects the detection electrode side. The third surface acoustic wave standing wave is generated between the pair of third reflector electrodes.

The detection electrode is provided at a predetermined relational position with respect to the standing wave of the third surface acoustic wave, and an electric signal generated by the piezoelectric effect according to the strain caused by the third surface acoustic wave. Is detected from the detection electrode.

Further, according to the present invention, two Coriolis force detecting portions, each of which is formed by arranging a plurality of electrodes in a direction orthogonal to each other on the surface of the piezoelectric substrate, are provided, and each detecting portion is oscillated by a surface acoustic wave. A surface acoustic wave gyroscope that generates and converts the Coriolis force generated by the interaction between the vibration and the rotational movement of the piezoelectric substrate into a voltage by a piezoelectric effect, and detects the voltage. A first driving electrode to which a first high frequency is applied to generate a surface acoustic wave, and a second high frequency to generate a second surface acoustic wave having a frequency different from that of the first surface acoustic wave are generated. The first surface acoustic wave is formed on both outer sides of the applied second drive electrode and the first and second drive electrodes so as to generate a standing wave of the first surface acoustic wave. Is reflected to the first driving electrode side A pair of first reflector electrodes is formed on both outer sides of the first and second driving electrodes to generate a standing wave of the second surface acoustic wave. It is generated by the interaction between the pair of second reflector electrodes reflecting to the second driving electrode side, the interference wave of the first surface acoustic wave and the second surface acoustic wave, and the rotational movement of the piezoelectric substrate. The third surface acoustic wave based on the Coriolis force is formed on both outer sides of the first and second driving electrodes so as to make it a standing wave, and the third surface acoustic wave is used for the first and second driving electrodes. A pair of third reflector electrodes reflecting on the electrode side;
And a detection electrode which is formed between the second driving electrode and which detects an electric signal generated according to the strain caused by the Coriolis force due to the piezoelectric effect (claim 2).

According to the above structure, in one of the detection portions formed on the surface of the piezoelectric substrate, the detection electrode, the first and second driving electrodes, and the third radiator electrode which form the detection portion are formed. The first surface acoustic wave (frequency (f1 + Δ
f)), an interference wave (frequency f1) of the second surface acoustic wave (frequency (f1−Δf)) is generated, and the first based on the Coriolis force generated by the interaction between this interference wave and the rotational movement of the piezoelectric substrate. The surface acoustic wave No. 3 is reflected by the third reflector electrode to form a standing wave, and an electric signal generated according to the distortion of the substrate surface due to the standing wave is detected by the detection electrode by the piezoelectric effect.

Similarly, in the other detecting section, the fourth surface acoustic wave (in the direction of arrangement of the detecting electrode, the first and second driving electrodes, and the third radiator electrode forming the detecting section) An interference wave (frequency f2) of the frequency (f2 + Δf)) and the fifth surface acoustic wave (frequency (f2-Δf)) is generated,
The sixth surface acoustic wave based on the Coriolis force generated by the interaction between the interference wave and the rotational movement of the piezoelectric substrate is reflected by the third reflector electrode to form a standing wave, and the standing wave is generated by the piezoelectric effect. An electric signal generated according to the distortion of the substrate surface is detected from the detection electrode.

Since the constituent electrodes of both detectors are arranged in directions orthogonal to each other, the mutually orthogonal components of the Coriolis force are detected from the detection electrodes of each detector.

In the surface acoustic wave gyroscope, the pair of third reflector electrodes may be formed adjacent to the first and second drive electrodes, respectively (claim 3).

According to the above structure, the first and second reflector electrodes are arranged outside the third reflector electrode, and the electrode coating portion between the pair of third reflector electrodes is reduced as much as possible. Therefore, the attenuation of the third surface acoustic wave due to the transmission loss in the metal coating portion is reduced. Thereby, the detection level of the detection electrode can be increased.

[0025]

1 is a block diagram of a surface acoustic wave gyroscope according to the present invention. Further, FIG. 2 is a diagram showing an electrode structure formed on the piezoelectric substrate.

The gyroscope 1 is provided with a detection element 2 for detecting the Coriolis force and high frequency oscillators 3 and 4 which are drive sources of surface acoustic waves.

The detection element 2 has a rectangular piezoelectric substrate 21, and a transducer 22 for detecting the Coriolis force and a frequency f _H (= f ₀ + Δf [H
z]) surface acoustic wave generating transducer 2
3. Transducer 24 for generating a surface acoustic wave of frequency f _L (= f ₀ −Δf [Hz]) and each pair of reflectors 2.
5, 25 '(shown by "A" in FIG. 1), reflectors 26, 2
6 '(shown by "B" in FIG. 1) and reflectors 27, 27'.
(Indicated by "C" in FIG. 1), a Coriolis force detecting portion is formed.

Transducers 22-24 and reflector 2
5, 25 'to 27, 27' are arranged in a line in the longitudinal direction of the piezoelectric substrate 21. The transducer 22 for detecting the Coriolis force is arranged substantially at the center of the piezoelectric substrate 21, and a surface acoustic wave having a frequency f _H is located on the left side of the transducer 22 so as to sandwich the transducer 22 (hereinafter referred to as a first surface acoustic wave).
A transducer 23 for generating is arranged, and a transducer 24 for generating a surface acoustic wave having a frequency f _L (hereinafter referred to as a second surface acoustic wave) is arranged on the right side of the transducer 22.
Is arranged. Further, reflectors 27 ', 26' and 25 'are arranged in this order from the center side on the outside of the transducer 24, and reflectors 27', 26 'and 25' are arranged on the outside of the transducer 23.
Similarly, 25 and 26 are arranged in this order from the center side.

The high frequency oscillator 3 is an oscillator for generating a high frequency of a frequency f _H , and the high frequency oscillator 4 is a frequency f _L.
It is an oscillator that generates high frequency. High frequency oscillator 3,4
Is a surface acoustic wave oscillator using a surface acoustic wave resonator formed on a piezoelectric substrate made of the same material as the piezoelectric substrate 21, and the output terminal bb 'of the high frequency oscillator 3 is connected to a transducer 23. 4 output terminal c-
c ′ is connected to the transducer 24.

The high frequency oscillators 3 and 4 are, for example, in the BE pierce oscillator circuit shown in FIG. 3 or the CB pierce oscillator circuit shown in FIG. 4, and the resonance element θ is constituted by the surface acoustic wave resonator shown in FIG. It can be realized by The surface acoustic wave resonator shown in FIG. 5 is a grating reflector (open type grating) in which a large number of linear electrodes D are arranged on both sides of an interdigital transducer (hereinafter referred to as IDT) 28 on a piezoelectric substrate 21 '. Reflector)
29 and 30 are arranged. The resonance frequency of the surface acoustic wave resonator of the high frequency oscillator 3 is set to (f ₀ + Δf), and the resonance frequency of the surface acoustic wave resonator of the high frequency oscillator 3 is set to (f ₀ −Δf).

The high-frequency oscillation paths 3 and 4 may be those using a crystal oscillator or other oscillator having a high Q. However, if stabilization of the temperature characteristics of the gyroscope 1 is considered, the same piezoelectric member as the piezoelectric substrate 21 is used. It is preferable that the surface acoustic wave resonator is composed of an oscillator.

For example, when LiNbO ₃ is used as the material of the piezoelectric substrate 21 having a large electromechanical coupling coefficient k ² , its temperature characteristic is about 70 ppm and the reflectors 25, 25 '.
When the resonance band of .about.27,27 'is 5 MHz, for example, the resonance characteristics of the reflectors 25,25' to 27,27 'are predetermined in the temperature range of -20.degree. It may go out of the resonance band. For example, the reflectors 25 and 25 'reflect the first surface acoustic wave and generate a standing wave, but the reflector 2
If the resonance characteristics of 5, 25 'drift and sufficient reflection characteristics cannot be obtained, it becomes impossible to obtain a stable level of the standing wave of the first surface acoustic wave. This also applies to the reflectors 26 and 26 'and the reflectors 27 and 27'.

The surface acoustic wave gyroscope detects the Coriolis force generated by the interaction between the surface vibration and the rotational movement when the piezoelectric substrate rotates while the surface of the piezoelectric substrate is vibrated. The stability of the surface vibration frequency (that is, the frequency of the surface acoustic wave) is also important, but the amplitude of the surface vibration of the piezoelectric substrate is more important in terms of the detection sensitivity of the Coriolis force.

Therefore, in the present embodiment, the oscillating elements of the high frequency oscillating paths 3 and 4 are constituted by the surface acoustic wave resonator made of the same piezoelectric member as the gyroscope 1, and the reflector 25,
The standing waves of the first and second surface acoustic waves are stabilized by drifting the oscillation characteristics of the high frequency oscillation paths 3 and 4 according to the drift of the resonance characteristics of 25 ', 26, 26'. .

In the present embodiment, the resonance frequency of the surface acoustic wave resonator θ of the high frequency oscillator 3 is (f ₀ +
When Δf) drifts to (f ₀ + Δf + Δf _t ) and the oscillation frequency fluctuates, the resonance frequency (that is, the reflection frequency) of the reflectors 25 and 25 ′ also changes from (f ₀ + Δf) to (f ₀ +
Since drift Δf + Δf _t), the first surface acoustic wave even when the frequency of the first surface acoustic wave generated on the substrate surface of the piezoelectric substrate 21 is varied is preferably reflected by the reflector 25, 25 ', the 1 The surface acoustic wave (standing wave) amplitude is stabilized against temperature changes. Similarly, the resonance frequency of the surface acoustic wave resonator θ of the high-frequency oscillator 4 changes by (f
₀ drift -.DELTA.f) from the (f ₀ -Δf + Δf _t), if you change the oscillation frequency, because drifts resonant frequency from (f ₀ -.DELTA.f) to (f ₀ -Δf + Δf _t) of the reflector 26, 26 ' Even when the frequency of the second surface acoustic wave generated on the substrate surface of the piezoelectric substrate 21 fluctuates, the second surface acoustic wave is preferably reflected by the reflectors 26 and 26 ', and the second surface acoustic wave (standing wave The amplitude of the wave) is stabilized against temperature changes.

Therefore, the frequency of the interference wave of the first and second surface acoustic waves fluctuates to (f ₀ + Δf _t ) with respect to the temperature change, but the amplitude fluctuation is reduced, and the interference wave and the piezoelectric substrate 21 are reduced. It is possible to improve the temperature characteristic of the detection level of the Coriolis force generated by the interaction with the rotational movement of the.

The high-frequency oscillators 3 and 4 are composed of the detection element 2
However, it is preferable that the surface acoustic wave resonator θ is formed on the substrate of the piezoelectric substrate 21 and is formed on this substrate. By doing this, gyroscope 1
Can be configured compactly.

The piezoelectric substrate 21 is, for example, lead zirconate titanate (PbTiO ₃ , PbZrO ₃ ), LiNbO ₃ , L.
It is made of a member having a piezoelectric effect such as iTaO ₃ . Each of the transducers 22 to 24 is an interdigital transducer (IDT) formed by forming thin films of comb-shaped electrodes D1 and D2 that intersect each other on the surface of the piezoelectric substrate 21.

The frequency of the surface acoustic wave depends on the transducer 2.
It is determined by the pitch d of the comb electrodes D1 and D2 of 3,24. An appropriate frequency can be selected as the frequency of the surface acoustic wave as the vibration source of the piezoelectric substrate 21, and a high frequency is preferable in consideration of miniaturization. It is possible to use a high frequency up to several GHz in terms of the processing technology of the comb electrodes D1 and D2, but due to other factors such as the manufacturing cost, there is a certain limitation in increasing the frequency, and usually 10 to 100 MHz is used. Frequency is used.

In the transducer 23 for generating the first surface acoustic wave (hereinafter referred to as the driving IDT 23), the inter-electrode pitch d of the comb-shaped electrodes D1 and D2 is the wavelength λ _H (= v ₀ / of the first surface acoustic wave). f _H , v ₀ ; the propagation velocity on the free surface) and the transducer 2 for generating the second surface acoustic wave.
4 (hereinafter referred to as the driving IDT 24), the inter-electrode pitch d of the comb-shaped electrodes D1 and D2 is the wavelength λ of the second surface acoustic wave.
It is set to _L (= v ₀ / f _L ). Driving IDT2
3, 24 are driving IDTs 23, 2 as shown in FIG.
Four wave numbers of frequency Δf are formed between the four positions (N is a natural number).

Transducer 22 for detecting Coriolis force
(Hereinafter, referred to as detection IDT 22) is a comb-shaped electrode D.
A wavelength λ ₀ (= v ₀ / f) of a surface acoustic wave (hereinafter referred to as an interference wave) having a frequency f ₀ generated by the interference between the first surface acoustic wave and the second surface acoustic wave with the inter-electrode pitch d of 1 and D2. It is set to ₀ ). Further, in the detection IDT 22, the comb-shaped electrodes D1 and D2 of the detection IDT 22 are positioned at the nodes of the standing wave of the interference wave generated between the driving IDT 23 and the driving IDT 24 as described later. It is arranged.

Reflectors 25, 25 'and reflectors 26, 26'
The reflectors 27 and 27 'are open grating reflectors in which a large number of linear electrodes D3 are arranged at a predetermined pitch.

The reflectors 25 and 25 'reflect the first surface acoustic wave toward the driving IDT 23 and generate a standing wave of the first surface acoustic wave between the reflectors 25 and 25'. The inter-electrode pitch P1 of the reflectors 25 and 25 'is 1/2 of the wavelength λ _H of the first surface acoustic wave so that the center frequency is the frequency f _H (= f ₀ + Δf) of the first surface acoustic wave. Is set to
The number of linear electrodes D3 (100 in the present embodiment) is set so that the bandwidth is less than 2Δf. Since the reflection band of the reflector 25 is f _H ± Δf (f _{0 to} f ₀ + 2Δf), the second surface acoustic wave (frequency f _L = f ₀ −Δf) from the driving IDT 24 is reflected by the reflector 25. Without passing through, the light propagates to the reflector 26.

The reflectors 25 and 25 'are formed in a predetermined relational position with respect to the driving IDT 23 so that the first surface acoustic wave can be efficiently reflected.

As shown in FIG. 7, the distance between the reflector and the driving IDT is set to the center of the linear electrode D _ref located closest to the driving IDT side of the reflector and to the most reflector side of the driving IDT. _Assuming that the distance L between the centers of the comb-shaped electrodes D _drv is equal to, the distance L of the reflector is generally L =
It is formed at a relational position satisfying (k + 1/4) · λ / 2 (k = 1, 2, 3, ...). Note that the above equation is for the case where the surface acoustic wave propagation medium is uniform. If there is a different propagation medium portion on the propagation path, the wavelength (or propagation velocity) at this portion changes, so It is necessary to correct the distance of the part.

In the present embodiment, for example, the driving IDT 2
In the case of the position of the reflector 25 with respect to 3, the driving IDT 23
Since the reflector 27 is formed between the reflector 25 and the reflector 25, it is necessary to correct the distance in the section of the reflector 27.
No. 5 is arranged at a position that satisfies the conditional expression of the interval L'described below with respect to the driving IDT 23.

The conditional expression for the distance L is determined based on the wavelength λ of the surface acoustic wave on the free surface on which the metal coating is not formed. As shown in FIG. 8, the surface acoustic wave W
In the portion where the metal coating D such as a reflector is formed on the surface of the substrate 21, the propagation speed becomes slower than that of the free surface,
Apparently, the wavelength λ'at the metal film forming portion becomes shorter than the wavelength λ at the free surface.

Now, assuming that the wavelength shortening rate is K, the distance q · λ for q wavelengths on the free surface is K · q on the metal film forming surface.
・ Reduced to λ. Interval L assuming that the reflector 27 is not formed between the reflector 25 and the driving IDT 23
As described above, the conditional expression of 1 is L1 = (k + 1/4) ·
λ _H / 2, k = 1, 2, 3, ..., λ _H = v ₀ / f _H.
Assuming that the r wavelength portion of the distance L1 is composed of the reflector 27, the distance L2 of the reflector 27 portion is K ·
r · λ ₀ , which is (1-K) ・ compared to the case of a free surface.
It will be shortened by r · λ ₀ .

Therefore, the conditional expression of the satisfying distance L'between the driving IDT 23 and the reflector 25 when the reflector 27 is present is L '= L1- (1-K) .r.λ _0. .
Now, let m be the number of linear electrodes D3 of the reflector 27,
Let v _{m be} the propagation velocity of the surface acoustic wave in the part of
2r, K = λ _m / λ ₀ = v _m / v ₀ , so (1-K)
_{· R · λ 0 = (1} -v m / v 0) · (m / 2) · (v 0 / f
₀ ) = m (v ₀ −v _m ) / (2f ₀ ), and L ′ is given by the following equation.

[0050]

[Equation 1]

For example, as the piezoelectric material, LiNbO ₃ 128 is used.
In the case of using XY, the velocity v _{0 of the} surface acoustic wave on the free surface is 3960 m / s, and the velocity v _{m of the} surface acoustic wave on the metal film forming portion is about 3920 _m / s.
f ₀ = 60 MHz, Δf = 5 MHz, k = 113, m =
Assuming 100, the distance L ′ between the driving IDT 23 and the reflector 25 is 3424.05 μm (= 113.5 × 3960 / 130-100).
× 40/120).

The reflector 25 'can also be used as the reflector 25'.
Similarly, the driving IDT 23 is designed to satisfy the conditional expression of the interval L ″ between the driving IDT 23 and the reflector 25 ′ in consideration of the wavelength shortening in the detection IDT 22, the driving IDT 24, and the reflectors 27 ′ and 26 ′. Is formed in a predetermined position with respect to.

The reflectors 26 and 26 'reflect the second surface acoustic wave toward the driving IDT 24 and generate a standing wave of the second surface acoustic wave between the reflectors 26 and 26'. The inter-electrode pitch P2 of the reflectors 26 and 26 'is 1 / the wavelength λ _L of the second surface acoustic wave so that the center frequency is the frequency f _L (= f ₀ -Δf) of the second surface acoustic wave. Set to 2,
The number of linear electrodes D3 (100 in the present embodiment) is set so that the bandwidth is less than 2Δf. The reflection band of the reflector 26 'is f _L ± Δf (f ₀ -2Δf to f ₀ ).
Therefore, the first surface acoustic wave (frequency f _H = f ₀ + Δf) from the driving IDT 24 is transmitted without being reflected by the reflector 26 ′ and propagates to the reflector 25 ′.

The reflector 26 includes the detection IDT 22,
The reflector 26 'is formed at a predetermined position with respect to the driving IDT 24 so as to satisfy a predetermined conditional expression of the distance between the driving IDT 24 and the reflector 26 in consideration of wavelength shortening in the driving IDT 23 and the reflectors 27 and 25. Is the reflector 2
In order to satisfy the predetermined conditional expression of the distance between the driving IDT 24 and the reflector 26 'in consideration of the wavelength shortening in 7',
It is formed at a predetermined position with respect to the driving IDT 24.

The reflectors 27, 27 'reflect the third surface acoustic wave to the IDT 22 side for detection and generate a standing wave of the second surface acoustic wave between the reflectors 27, 27'. The inter-electrode pitch P3 of the reflectors 27, 27 'is set to ½ of the wavelength λ ₀ of the third surface acoustic wave so that the center frequency becomes the frequency f ₀ of the third surface acoustic wave, and the bandwidth of the reflectors 27, 27' is reduced. Is 2Δf
The number of the linear electrodes D3 (100 in the present embodiment) is set so as to be less than 100.

The reflection band of the reflectors 27 and 27 'is f ₀ ± Δ
because it is _{f (f 0 -Δf~f 0 + Δf} ), driving IDT
23 from the first surface acoustic wave (frequency f _H = f ₀ + Δf) and the second surface acoustic wave from the driving IDT 24 (frequency f _H
= F ₀ −Δf) is transmitted without being reflected by the reflectors 27 and 27 ′, and is reflected by the reflectors 25, 25 ′, 26 and 2 respectively.
Propagate to the 6'side.

The reflector 27 includes the driving IDT 22 and the reflector 2 in consideration of the wavelength shortening in the driving IDT 23.
In order to satisfy the predetermined conditional expression of the interval between 7
The reflector 27 'is formed at a predetermined position with respect to the DT 22.
Is formed at a predetermined position with respect to the driving IDT 22 so as to satisfy a predetermined conditional expression of the distance between the driving IDT 22 and the reflector 27 'in consideration of the wavelength shortening in the driving IDT 24.

In the above structure, the driving IDTs 23, 2
When high frequencies of frequencies f _H and f _L are applied to 4, the substrate surface is displaced by the inverse piezoelectric effect of the piezoelectric substrate 21, and the first surface acoustic wave and the second surface acoustic wave are generated. For example, in the case of a Rayleigh wave, this wave has displacement components in the direction perpendicular to the substrate surface and the traveling direction, and each particle on the surface of the piezoelectric substrate 21 rotates in the opposite direction to the traveling direction as shown in FIG. It is displaced by drawing an elliptical orbit. The size of this elliptical orbit is small in the depth direction of the piezoelectric substrate 21, and most of the energy of the Rayleigh wave is concentrated within one wavelength in the depth direction, so the Rayleigh wave becomes a surface wave. And proceed.

The first elastic surface generated by the driving IDT 23 is propagated in the longitudinal direction of the piezoelectric substrate 21 from both sides of the driving IDT 23.

In FIG. 1, the first surface acoustic wave propagating rightward from the driving IDT 23 is the detecting IDT 22,
The IDT 2 for detection propagates on the surface of the substrate on which the driving IDT 24 and the reflectors 27 ', 26', 25 'are formed.
2. The driving IDT 24 and the reflectors 27 'and 26' are the first
Since the reflector 25 'has a reflection band in a frequency band different from the frequency band of the surface acoustic wave, and the reflector 25' has a reflection band in the frequency band of the first surface acoustic wave, these IDTs 22 and 23 are provided.
Also, the reflectors 27 'and 26' propagate to the reflector 25 'side without being reflected to the driving IDT 23 side, and are reflected to the driving IDT 23 side by this reflector 25'.

The first surface acoustic wave propagating leftward from the driving IDT 23 propagates on the surface of the substrate on which the reflectors 27 and 25 are formed, and the reflector 27 produces the frequency of the first surface acoustic wave. Has a reflection band in a frequency band different from the band,
Since the reflector 25 has a reflection band in the frequency band of the first surface acoustic wave, the reflector 27 propagates to the reflector 25 without being reflected by the driving IDT 23 side, and this reflector 2
5 is reflected to the driving IDT 23 side.

Since the distance between the reflectors 25 and 25 'is set to a predetermined distance which is an integral multiple of the wavelength λ _H of the first surface acoustic wave, as shown in FIG.
The traveling wave of the first surface acoustic wave from 23 and the reflectors 25, 2
A standing wave of frequency f _H (= f ₀ + Δf) is generated between the reflectors 25 and 25 ′ due to the interference with the reflected wave of the first surface acoustic wave reflected at 5 ′.

The second generated by the driving IDT 24
The elastic surface is also propagated in the longitudinal direction of the piezoelectric substrate 21 from both sides of the driving IDT 24.

In FIG. 1, the second surface acoustic wave propagating rightward from the driving IDT 24 is reflected by the reflectors 27 'and 2'.
6'is propagated on the surface of the substrate on which the reflector 2
7'has a reflection band in a frequency band different from the frequency band of the second surface acoustic wave, and the reflector 26 'has a reflection band in the frequency band of the second surface acoustic wave. Therefore, the reflector 27' has a driving IDT 24. It propagates to the reflector 26 'without being reflected to the side, and is reflected to the driving IDT 24 side by this reflector 26'.

The first surface acoustic wave propagating to the left from the driving IDT 24 is the detection IDT 22 and the driving IT 22.
The DT23 and the reflectors 27, 25, 26 propagate on the surface of the substrate on which the detection IDT22 and the driving IDT2 are transmitted.
3 and the reflectors 27 and 25 have a reflection band in a frequency band different from the frequency band of the second surface acoustic wave, and the reflector 26 has a reflection band in the frequency band of the second surface acoustic wave. 23 and the reflectors 27 and 25 propagate to the reflector 26 without being reflected to the driving IDT 24 side, and are reflected to the driving IDT 24 side by the reflector 26.

Since the distance between the reflectors 26 and 26 'is set to a predetermined distance which is an integral multiple of the wavelength λ _L of the second surface acoustic wave, as shown in FIG.
2nd surface acoustic wave traveling wave from 24 and reflectors 26, 2
A standing wave having a frequency f _L (= f ₀ −Δf) is generated between the reflectors 26 and 26 ′ due to interference with the reflected wave of the second surface acoustic wave reflected at 6 ′.

Further, the frequency f ₀ (= (f _L + f _H ) / 2) is generated between the reflector 25 and the reflector 26 ′ due to the interference between the standing wave of the frequency f _{H and} the standing wave of the frequency f _L. Interference wave is generated.

When the piezoelectric substrate 21 rotates while the surface of the piezoelectric substrate 21 is vibrated by the interference wave, a Coriolis force acts on the interference wave. The Coriolis force f _C is related to the particle density ρ of the piezoelectric substrate 21, the vibration velocity V of the particles performing the elliptic motion, and the rotational angular velocity Ω of the piezoelectric substrate 21, and is expressed by the following vector formula. In addition,
In the formula, the Gothic type symbol indicates that it is a vector.

[0069]

[Equation 1]

Now, when the xy plane is on the surface of the piezoelectric substrate 21, an orthogonal coordinate system of xyz is set in which the z axis is the normal direction of the surface of the piezoelectric substrate 21 and the x axis is the traveling direction of the interference wave W (see FIG. 13), and the vibration velocity V of the particle that makes an elliptic motion in the xz plane is the component V _{x in the x-} axis direction and the component V _{z in the} z-axis direction.
And can be separated into

The piezoelectric substrate 21 rotates about the z-axis at an angular velocity Ω.
_{When the} rotational motion is performed at _z , the direction of the vibration velocity component V _{z and} the direction of the rotation axis (z axis) are parallel to each other, so that only the vibration velocity component V _{x of the} particle, as shown in FIG. Coriolis force f _Cy (= -2ρ ·) parallel to the xy plane orthogonal to the x-axis
V _x · Ω _z ) acts. This Coriolis force f _Cy is generated with a 90 ° phase shift with respect to the interference wave W due to the interaction between the elliptical motion of the particle based on the interference wave W and the rotational motion of the piezoelectric substrate 21, and as shown in FIG. As the interference wave W propagates, it becomes a surface acoustic wave that propagates in synchronization with this.

However, a surface acoustic wave based on the Coriolis force f _Cy is generated between the reflectors 27 and 27 ′ (a surface acoustic wave having the same frequency f _{0 as the} interference wave W and a phase shifted by 90 ° (hereinafter referred to as the third surface acoustic wave). Is set to a predetermined interval that is an integral multiple of the wavelength λ ₀ of the reflector 2 as shown in FIG.
A standing wave of the third surface acoustic wave C based on the Coriolis force f _Cy is generated between 7, 27 '.

It should be noted that the Coriolis force f when the piezoelectric substrate 21 rotates about the y-axis at the rotational angular velocity Ω _y and when it rotates about the x-axis at the rotational angular velocity Ω _x
C becomes as follows.

That is, when the piezoelectric substrate 21 rotates about the y-axis at the rotation angular velocity Ω _y , the rotation axis (y
Axial) direction both vibration velocity components V _x, so is orthogonal to the V _z, both vibration velocity components V _x, respectively Coriolis force f _Cz against V _z and _{(= 2ρ · V x · Ω} y) f Cx (= -2ρ ・ V _z・
Ω _y ) and the piezoelectric substrate 21 rotates about the x axis at a rotational angular velocity Ω _x , the rotation axis (x axis)
Since the direction is parallel to the direction of the vibration velocity component V _x, the Coriolis force f _Cy (= 2) is applied only to the vibration velocity component V _{z of the} particle.
ρ · V _x · Ω _z ) acts.

[0075] Thus, x-axis, a unit vector in each axis direction of the y-axis and z-axis is denoted by i _x, i _y, i _z, to represent the vector expression shown by the formula in each direction component, the following formula become that way. In the formula, the Gothic type symbol indicates that it is a vector.

[0076]

[Equation 2]

From the above equation, the Coriolis force f _C is calculated as follows:
Although it is a combined force of the y-axis and z-axis components in each axial direction, each component of the Coriolis force f _C has a predetermined relationship with the polarization direction of the piezoelectric substrate 21, the detection electrode 23, and the surface acoustic wave W. It can be separated and detected by setting the relationship.

Therefore, in the present embodiment, for convenience of description, the following description will be made by taking the case where the piezoelectric substrate 21 makes a rotational motion around the z axis at the rotational angular velocity Ω _z as an example.

FIG. 13 is a diagram showing the relationship between the interference wave W and the third surface acoustic wave C displaced in the y-axis direction generated by the Coriolis force f _Cy .

The phase of the third surface acoustic wave C displaced in the y-axis direction generated by the Coriolis force f _Cy with respect to the interference wave W displaced in the z-axis direction is shifted by 90 °, and the reflectors 27, 27 '.
It is a standing wave between. In the detection IDT 22, the comb-shaped electrodes D1 and D2 serve as nodes of the interference wave W (that is,
Since it is formed at a position which is the antinode of the third surface acoustic wave C, the comb-shaped electrode D1 and the comb-shaped electrode D2 are displaced in opposite directions due to the distortion in the y-axis direction caused by the third surface acoustic wave C (( (Refer to the arrow direction in FIG. 13), the piezoelectric effect of the piezoelectric substrate 21 generates a voltage E _DET between the comb electrodes D1 and D2 according to the amount of displacement, and this voltage E _DET is the Coriolis force f _Cy.
Is detected as

As described above, the frequency f _H (= f) higher than the detection frequency f ₀ of the Coriolis force f _Cy is detected on the surface of the piezoelectric substrate 21.
₀ + Δf) of the first surface acoustic wave and a second surface acoustic wave of frequency f _L (= f ₀ −Δf) lower than the detection frequency f ₀ are generated, and the detection frequency f is generated by the interference of both surface acoustic waves. ₀ with make interference wave W of a Coriolis force f _Cy a dedicated reflector 27, 27 'to the Coriolis force f _Cy generated by the interaction of the rotational movement of the interference wave W and the piezoelectric substrate 21 Since the standing wave of the third surface acoustic wave C caused by is generated, the Coriolis force f _Cy which is voltage-converted by the piezoelectric effect without being affected by the first and second surface acoustic waves and the interference wave is generated. The detection can be performed at a level as high as possible, and thus the detection sensitivity can be improved.

In the above-described embodiment, as shown in FIG. 1, the reflector 25 'for the first surface acoustic wave is arranged on the outermost side on the right side of the detection IDT 22 to detect the detection IDT 2.
Although the reflector 26 for the second surface acoustic wave is arranged on the outermost side on the left side of 2, the driving IDT 23 and the driving ID are
If a third surface acoustic wave which is an interference wave of the first surface acoustic wave and the second surface acoustic wave can be generated between T24 and the reflectors 25, 25 ', the reflectors 26, 26' and the reflectors Bowl 2
The arrangement of 7, 27 'is not limited to the related positions shown in FIG.

For example, as shown in FIG. 14, the positions of the reflector 25 'and the reflector 26' in FIG. 1 may be replaced with each other, so that the relational position may be changed. As shown in FIG. And the reflector 26 may be replaced with each other. Further, as shown in FIG. 16, for example, the positions of the reflectors 25 'and 27' in FIG. 14 may be interchanged, but the reflection of the third surface acoustic wave caused by the Coriolis force f _Cy may be performed. Considering the transmission loss in the reflectors 25, 25 ', the reflectors 27, 27' are preferably arranged at the innermost side.

FIG. 17 is a configuration diagram showing a second embodiment of a surface acoustic wave gyroscope according to the present invention.

In the second embodiment, the accuracy of the formation position of the detection IDT 22 is reduced. In FIG. 1, the detection circuit 31 is connected to the output terminals a and a'of the detection IDT 22. Is.

Since the interference wave of the first surface acoustic wave and the second surface acoustic wave and the third surface acoustic wave based on the Coriolis force have the same frequency and a phase difference of 90 °, the detection IDT 22 has the above-described third surface acoustic wave. If the surface acoustic wave is not accurately formed at a predetermined position with respect to the standing wave, the detection signal of the detection IDT 22 includes a component of a signal obtained by piezoelectrically converting the interference wave. The detection circuit 31 removes the signal component based on the interference wave from the detection signal from the detection IDT 22 and extracts only the signal component based on the Coriolis force.

The detection circuit 31 is composed of a high frequency oscillator 32 for generating a high frequency of frequency f ₀ , a phase shifter 33 and a differential amplifier 34. The high frequency oscillator 32 is configured by an oscillator using a surface acoustic wave resonator θ having a resonance frequency f ₀ , like the high frequency oscillators 3 and 4.

The phase shifter 33 has a high frequency detecting IDT 22 and a driving IDT 2 output from the high frequency oscillator 32.
It is intended to correct the phase shift based on the difference in distance from 3, 24. The phase shifter 33 includes, for example, a phase-advancing all-pass active filter, and can adjust the phase of the high frequency from the high frequency oscillator 31 to an arbitrary phase by the variable resistor R1.

The differential amplifier 34 is the operation amplifier 3
4a is used, and this operation amplifier 34a
The phase-adjusted high frequency is input to the-input terminal of the input via the input resistors R1 and R3, and the detection signal of the detection IDT 22 is input to the + input terminal via the resistor R4. In addition,
The resistors R3 and R5 are variable resistors for adjusting the input level and the gain, respectively.

The differential amplifier 34 has a level E _{DET of} the Coriolis force (a signal converted to a high frequency of frequency f ₀ by the piezoelectric effect) detected by the detection IDT 22 and the high frequency oscillator 3.
The level difference ΔE (= E _DET −E from the level E _r of the reference high frequency of the frequency f ₀ input from 1 through the phase shifter 33.
_r ) is amplified and output.

The detection circuit 31 uses the frequency and phase shifter 33 of the high frequency oscillator 31 so that the output from the differential amplifier 34 becomes "0" under the driving condition in which the piezoelectric substrate 21 is not rotating in advance. The phase amount of has been adjusted.

In the above structure, when the piezoelectric substrate 21 makes a rotational movement, the detection IDT 22 detects a high frequency of frequency f ₀ obtained by piezoelectrically converting the Coriolis force, and the differential amplifier 34 detects this high frequency detection level E. Reference high frequency level E _{r of} frequency f ₀ input from _DET and high frequency oscillator 31
And the level difference ΔE between and is amplified and output.

However, the detection circuit 31 detects the difference amplifier 3 in a state where no Coriolis force is generated, that is, only the signal component based on the interference wave is detected from the detection IDT 22.
Since it is adjusted in advance so that the output from 4 becomes “0” (the signal component based on the interference wave is canceled), even if the detection signal of the detection IDT 22 includes the signal component based on the interference wave, Only the signal component corresponding to the Coriolis force is output from the detection circuit 31 and is not affected by the interference wave.

Therefore, by adopting this detection method, the Coriolis force can be accurately detected even when the position accuracy of the detection IDT 22 is not sufficient.

FIG. 18 is a block diagram of the third embodiment of the surface acoustic wave gyroscope according to the present invention.

In the third embodiment, in FIG. 1, the detection IDT 22 on the surface of the piezoelectric substrate 21 and the driving IDT 2 are shown.
3, driving IDT 24, reflectors 25, 25 ', reflector 2
6, 26 'and reflectors 27, 27' in the direction (y direction) orthogonal to the array direction, the detection IDT 22, the driving IDT 23, the driving IDT 24, the reflectors 25, 25 ',
A detection IDT 35, a driving IDT 36, a driving IDT 37, reflectors 38, 38 ', and reflectors 39, 39' having the same structure as the reflectors 26, 26 'and the reflectors 27, 27'.
And the reflectors 40, 40 'are arranged, and the output terminals bb', cc 'of the high-frequency oscillator 3 and the high-frequency oscillator 4 are arranged.
Are connected to the driving IDT 36 and the driving IDT 37, respectively.

In the first embodiment, since the surface acoustic wave propagating in the x direction is used, only the y direction component of the Coriolis force f _C can be detected, but in the second embodiment, y
Since the surface acoustic wave propagating in the direction is also used, the x-direction component of the Coriolis force f _C can be detected from the output terminal d-d ′ of the detection IDT 35. The same effect can be obtained by using two gyroscopes 1 according to the first embodiment that are arranged so as to be orthogonal to each other, but according to the third embodiment, two gyroscopes 1 are provided on the same piezoelectric substrate 21. Since each gyroscope 1 is configured, the gyroscope can be downsized and made compact.

[0098]

As described above, according to the present invention, the Coriolis force detecting portion, which is formed by arranging a plurality of electrodes on the surface of the piezoelectric substrate, is provided, and the detecting portion oscillates due to the surface acoustic wave. A surface acoustic wave gyroscope that detects the Coriolis force generated by the interaction between this vibration and the rotational movement of the piezoelectric substrate by converting it into a voltage by the piezoelectric effect. No. 3, a first driving electrode for generating a first surface acoustic wave, which is arranged with a detection electrode for detecting the surface acoustic wave, and a second surface acoustic wave having a frequency different from that of the first surface acoustic wave. From the second drive electrode and the first to third reflector electrodes having a paired structure that respectively reflect the first to third surface acoustic waves on both outer sides of the first and second drive electrodes. Between the first and second drive electrodes First and second surface acoustic wave (standing wave)
Generating an interference wave and resonating with the Coriolis force (standing wave of the third surface acoustic wave) generated by the interaction between the interference wave and the rotational movement of the piezoelectric substrate, the voltage-converted electric signal is detected. Since the detection is performed in step S1, the standing wave of the third surface acoustic wave based on the Coriolis force can be generated at a high level, and the detection sensitivity of the Coriolis force is improved.

Further, according to the present invention, the detection electrode, the two drive electrodes for generating two kinds of surface acoustic waves having different frequencies are provided in two directions orthogonal to each other on the surface of the piezoelectric substrate, and the three electrodes of the pair structure are provided. Two detectors composed of reflector electrodes are formed, and an interference wave of a surface acoustic wave (standing wave) is generated between two driving electrodes in each direction, and this interference wave and the rotational movement of the piezoelectric substrate Since the Coriolis force (standing wave of the third surface acoustic wave) generated by the interaction of the two is detected by the detection electrodes, the gyroscope that can detect the Coriolis force in two orthogonal directions is compactly configured. can do.

Further, the reflector electrodes for reflecting the surface acoustic waves caused by the Coriolis force are arranged adjacent to the drive electrodes, respectively, and the area of the metal coating portion between the reflector electrodes is reduced as much as possible. Therefore, it is possible to reduce the attenuation of the surface acoustic wave due to the Coriolis force due to the transmission loss in the metal coating portion, and it is possible to increase the detection level of the detection electrode.

[Brief description of drawings]

FIG. 1 is a configuration diagram of a surface acoustic wave gyroscope according to the present invention.

FIG. 2 is a diagram showing an electrode structure formed on a piezoelectric substrate.

FIG. 3 is a diagram showing a basic circuit configuration of a high-frequency oscillator using a surface acoustic wave resonator.

FIG. 4 is a diagram showing another example of a basic circuit configuration of a high-frequency oscillator using a surface acoustic wave resonator.

FIG. 5 is a plan view showing the structure of a surface acoustic wave resonator.

FIG. 6 is a diagram showing a mutual relationship position of a pair of driving IDTs with respect to a surface acoustic wave.

FIG. 7 is a diagram showing a definition of a distance between a driving IDT and a reflector.

FIG. 8 is a diagram for explaining the shortening of the wavelength of a surface acoustic wave on the surface of a metal coating.

FIG. 9 is a diagram showing displacement of particles on a substrate surface in Rayleigh waves.

FIG. 10 is a diagram showing frequencies of standing waves generated between the reflectors.

FIG. 11 is a diagram showing a generation direction of a Coriolis force with respect to an elliptic motion of particles due to surface acoustic waves.

FIG. 12 is a diagram showing propagation of surface acoustic waves based on surface acoustic waves and Coriolis force.

FIG. 13 is a diagram showing a relationship between an interference wave and a third surface acoustic wave which is generated by a Coriolis force f _Cy and which is displaced in the y-axis direction.

FIG. 14 is a diagram showing a second embodiment of arrangement positions of reflectors formed on a piezoelectric substrate.

FIG. 15 is a configuration diagram of a third embodiment of arrangement positions of reflectors formed on a piezoelectric substrate.

FIG. 16 is a configuration diagram of a fourth embodiment of arrangement positions of reflectors formed on a piezoelectric substrate.

FIG. 17 is a configuration diagram of a second embodiment of a surface acoustic wave gyroscope according to the present invention.

FIG. 18 is a configuration diagram of a third embodiment of a surface acoustic wave gyroscope according to the present invention.

FIG. 19 is a view showing a detection IDT, a driving IDT and a reflector formed on a piezoelectric substrate of a conventional surface acoustic wave gyroscope.

[Explanation of symbols]

1 Gyroscope 2 Detection element 3,4 High frequency oscillator 21 Piezoelectric substrate 22,35 Detection IDT (detection electrode) 23,36 Drive IDT (first drive electrode) 24,37 Drive IDT (second drive) Electrode 25), 25 ', 38, 38' reflector (first reflector electrode) 26, 26 ', 39, 39' reflector (second reflector electrode) 27, 27 ', 40, 40' Reflector (third reflector electrode) 28 IDT 29, 30 Reflector 31 Detection circuit 32 High frequency oscillator 33 Phase shifter 34 Differential amplifier 34a Operation amplifier

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Shoshin Fukuda 3-8-3, new work in Takatsu-ku, Kawasaki City, Kanagawa Prefecture (72) Inventor Toshiro Higuchi, 3-26-3, Edahigashi, Tsuzuki-ku, Yokohama City, Kanagawa Prefecture (72) ) Inventor Minoru Kurosawa 1-6-11 Susukino, Midori Ward, Yokohama City, Kanagawa Prefecture

Claims (3)

[Claims] 1. A piezoelectric substrate is provided with a Coriolis force detecting portion formed by arraying a plurality of electrodes on the surface thereof, and the detecting portion is caused to vibrate by a surface acoustic wave. Is a surface acoustic wave gyroscope that detects the Coriolis force generated by the interaction of the above by converting it into a voltage by a piezoelectric effect, and a first high frequency is applied to the detection unit to generate a first surface acoustic wave. A first drive electrode, a second drive electrode to which a second high frequency is applied to generate a second surface acoustic wave having a frequency different from that of the first surface acoustic wave, and the first drive electrode A pair of first surface acoustic waves that are formed on both outer sides of the first and second driving electrodes to generate a standing wave of the surface acoustic wave and that reflect the first surface acoustic wave to the first driving electrode side. No. 1 reflector electrode and the second surface acoustic wave To generate the standing wave of
And a pair of second surface acoustic waves that are formed on both outer sides of the second drive electrode and that reflect the second surface acoustic wave to the second drive electrode side.
The third surface acoustic wave based on the Coriolis force generated by the interaction between the interfering wave of the first surface acoustic wave and the second surface acoustic wave and the rotational movement of the piezoelectric substrate and the standing wave A pair of third reflector electrodes that are formed on both outer sides of the first and second driving electrodes to reflect the third surface acoustic wave to the first and second driving electrode sides. And a detection electrode that is formed between the first and second driving electrodes and that detects an electrical signal generated according to the strain caused by the Coriolis force due to a piezoelectric effect. Surface acoustic wave gyroscope. 2. A piezoelectric substrate is provided with two Coriolis force detection units each having a plurality of electrodes arranged in a direction orthogonal to each other on the surface of the piezoelectric substrate, and each detection unit generates a vibration due to a surface acoustic wave. A surface acoustic wave gyroscope that detects a Coriolis force generated by an interaction between vibration and a rotary motion of a piezoelectric substrate by converting it into a voltage by a piezoelectric effect, wherein each of the detection units detects a first surface acoustic wave. A first drive electrode to which a first high frequency is applied to generate, and a second high frequency to apply a second surface acoustic wave having a frequency different from that of the first surface acoustic wave. Two driving electrodes and the first and second driving electrodes are formed on both outer sides of the first and second driving electrodes to generate a standing wave of the first surface acoustic wave. A pair of first antireflections that are reflected to the drive electrode side It is formed on both outer sides of the emitter electrode and the first and second driving electrodes to generate a standing wave of the second surface acoustic wave, and the second surface acoustic wave is used for the second driving. A pair of second reflector electrodes that reflect to the electrode side, and a first electrode based on the Coriolis force generated by the interaction between the interference wave of the first surface acoustic wave and the second surface acoustic wave and the rotational movement of the piezoelectric substrate. The third surface acoustic wave is formed on both outer sides of the first and second driving electrodes so as to make the third surface acoustic wave a standing wave, and reflects the third surface acoustic wave to the first and second driving electrode sides. From a pair of third reflector electrodes and a detection electrode that is formed between the first and second driving electrodes and that detects an electric signal generated according to the strain caused by the Coriolis force due to the piezoelectric effect. A surface acoustic wave gyroscope characterized by being configured. 3. The surface acoustic wave gyroscope according to claim 1, wherein the pair of third reflector electrodes are formed adjacent to the first and second driving electrodes, respectively. Surface acoustic wave gyroscope featuring.