JP4668441B2 - Vibrating gyro - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a vibrating gyroscope that detects angular velocity.
[0002]
[Prior art]
Conventionally, a mechanical rotary gyroscope has been used as an inertial navigation device for airplanes and ships, but the device is large and expensive, so it is difficult to incorporate it into a small electronic device or a small transport machine.
[0003]
In recent years, however, research on miniaturization of gyroscopes has progressed, and a vibrating body is excited by a piezoelectric element, and a voltage generated by vibration caused by Coriolis force that the vibrating body receives by rotation is detected by another piezoelectric element provided on the vibrating body. Vibrating gyros have been put into practical use and are used in automobile navigation systems and video camera shake detection devices.
[0004]
In particular, a vibrating gyroscope using a piezoelectric single crystal has a simple structure, is easy to adjust, and has excellent temperature characteristics, and is considered promising. As an example using a piezoelectric single crystal, the structure of a tuning fork type vibration gyro using quartz will be described below with reference to the drawings. FIG. 5 is a perspective view showing a tuning fork type vibration gyro.
[0005]
In FIG. 5, the tuning fork J10 has a structure in which a drive detection electrode is vapor-deposited on an integrally processed quartz. That is, the tuning fork J10 has a structure in which the first foot J11 and the second foot J12 arranged in parallel are coupled to the base portion J15. Drive electrodes J3 and J4 are vapor-deposited on the first leg J11, and detection electrodes J6, J7 and J8 are vapor-deposited on the second leg J12. The bottom surface of the base J15 is used for support. Here, the extending direction of the foot is defined as the Y ′ direction, the direction in which the two feet are aligned is defined as the X direction, and the direction orthogonal to the X and Y ′ directions is defined as the Z ′ direction.
[0006]
The operation will be described. FIG. 6 is a schematic view of a cross section and a drive detection circuit for explaining a drive detection method of a conventional tuning fork type crystal gyro. In FIG. 6, the cross section of the drive electrodes J1, J2, J3 and J4 is arranged on the cross section of the first leg J11 shown on the left side, and the detection electrodes J5, J6 and J6 are shown on the cross section of the second leg J12 shown on the right side. Cross sections of J7 and J8 are arranged.
[0007]
First, when the first leg J11 is bent in the X direction, for example, toward the second leg J12, the vicinity of the electrode J2 extends in the Y ′ direction and the vicinity of the electrode J4 contracts in the Y ′ direction. Due to the effect, an electric field is generated in the X direction in the vicinity of the electrode J2, and in the -X direction in the vicinity of the electrode J4. At this time, considering the direction of the electric field, the electrodes J2 and J4 have the same potential, for example, a higher potential than the center of the foot. When viewed in the X direction, the electrodes J1 and J3 disposed in the vicinity of the center of the foot have a relatively lower potential than the electrodes J2 and J4, and therefore there is a potential difference between the electrodes J2 and J4 and the electrodes J1 and J3. Occurs. Since the piezoelectric effect is reversible, if a potential difference is applied between the electrodes J2 and J4 and the electrodes J1 and J3, an electric field corresponding to this is generated inside the crystal, and the first foot J11 bends in the X direction. It will be. From these things, for example, the potential of the electrodes J1 and J3 is used as a reference to amplify with the amplifier JG at an amplification factor exceeding the oscillation condition, and adjusted to a phase satisfying the oscillation condition by the phase shift circuit JP and returned to the electrodes J2 and J4. As a result, energy exchange occurs between the mechanical return force and the electric force accompanying the bending of the first foot J11, and the first foot J11 can oscillate in the X direction.
[0008]
Looking at the tuning fork J10 as a whole, when the first foot J11 moves in the X direction to balance the momentum of the first foot J11 and the second foot J12, the second foot J12 moves in the -X direction, When the first foot J11 moves in the -X direction, the second foot J12 moves in the X direction. This is because it is ideal that a normal tuning fork vibrates in one plane. Although referred to as in-plane bending vibration, the vibration generated by the first foot J11, the amplifier JG and the phase shift circuit JP is the same operation as the in-plane bending vibration, and the frequency thereof is the resonance frequency of the in-plane bending vibration of the tuning fork J10. Almost matches.
[0009]
When the entire tuning fork J10 is rotated around the Y ′ axis at an angular velocity Ω in this state, the Coriolis force FC acts on the two legs of the tuning fork J10 in the Z ′ direction orthogonal to the in-plane bending vibration. The Coriolis force FC can be expressed by the following equation.
FC = 2MΩV (1)
Here, M is the mass of the first foot J11 or the second foot J12, and V is the velocity of the first foot J11 or the second foot J12. This Coriolis force FC excites bending vibration displaced in the Z ′ direction perpendicular to the X direction, which is the operation direction of in-plane bending vibration, on the first foot J11 and the second foot J12. Hereinafter, this is referred to as out-of-plane bending vibration. Further, since the Coriolis force is not a displacement but a force proportional to the velocity, the out-of-plane bending vibration generated by the Coriolis force is generated with a phase delay of 90 degrees from the in-plane bending vibration.
[0010]
By this out-of-plane bending vibration, for example, the vicinity of the electrodes J5 and J8 of the second foot J12 expands and contracts in the Y ′ direction, and the vicinity of the electrodes J6 and J7 expands and contracts in a phase opposite to that of the vicinity of the electrodes J5 and J8. For example, when the vicinity of the electrodes J5 and J8 extends in the Y ′ direction, an electric field is generated in the X direction in the vicinity of the electrodes J5 and J8 inside the second foot J12. At this time, in the vicinity of the electrodes J6 and J7 Is contracted in the Y ′ direction, an electric field is generated in the −X direction in the vicinity of the electrodes J6 and J7 inside the second leg 12. That is, when the potential of the electrode J5 is higher than the potential of the electrode J8, the potential of the electrode J7 is higher than the potential of the electrode J6. When the vicinity of the electrodes J5 and J8 is contracted in the Y ′ direction, an electric field is generated in the −X direction in the vicinity of the electrodes J5 and J8 inside the second foot J12. At this time, the electrodes J6 and J7 Since the vicinity extends in the Y ′ direction, an electric field is generated in the X direction in the vicinity of the electrodes J6 and J7 inside the second leg 12. That is, when the potential of the electrode J5 is lower than the potential of the electrode J8, the potential of the electrode J7 is lower than the potential of the electrode J6.
[0011]
The potential difference between the electrodes J5 and J8 and the electrodes J6 and J7 generated by the out-of-plane bending vibration changes according to the direction of the second foot J12 that swings in the Z ′ direction. In other words, for example, when the electrode J5 is at a high potential, the electrode J7 is also at a high potential. At this time, the electrodes J6 and J8 are at a low potential, and when the electrode J5 is at a low potential, the electrode J7 is also at a low potential. The hour electrode J6 and the electrode J8 are at a high potential. The Coriolis force appears as a potential difference between the electrode J5 or the electrode J7 and the electrode J6 or the electrode J8.
[0012]
The detection signal of the Coriolis output is guided to the multiplication circuit JM through the differential buffer JD with the electrodes J5 and J7 as one input signal and the electrodes J6 and J8 as the other input signal, and the in-plane bending vibration is detected. The output of the amplifier JG is shifted by 90 degrees by the phase shift circuit JP2 and multiplied by the reference signal binarized by the comparator JC for the purpose of correcting the generation of the Coriolis force delayed by 90 degrees. The result detected by multiplication is further smoothed by the integrating circuit JS and can be detected as an accurate DC output. Since this DC output is proportional to the Coriolis force FC, and the Coriolis force FC is proportional to the angular velocity Ω, the angular velocity Ω can be known from this DC output.
[0013]
[Problems to be solved by the invention]
However, the tuning fork type vibration gyro using the conventional piezoelectric single crystal has the following problems. In general, the performance of a vibrating gyroscope is measured by S / N. However, when a piezoelectric single crystal is used, it is difficult to improve the S / N because a resonance type having a large output S cannot be obtained. This situation will be described in detail.
[0014]
The magnitude S of the output of the vibration gyro can be well explained when viewed as forced excitation of the detection vibration system by Coriolis force. Hereinafter, T.W. IEEE Japan, Vol. 118-E, no. 7/8, '98 “Design Guidelines for Vibrating Micro Gyro”
[0015]
It has already been described that the directions of the drive vibration and the detection vibration are orthogonal, and the Coriolis force distributes the force in the detection force direction orthogonal to the drive vibration. Here, when the time displacement of the detection foot in the driving direction is expressed by a sine wave of amplitude D, it can be written as DSIN (ωt). Here, ω represents the resonance frequency of the drive vibration. Since the speed V is obtained by time differentiation, V = DωCOS (ωt). Substituting this into the definition of the Coriolis force in the equation (1), FC = 2MΩV = 2MΩDωCOS (ωt) (2)
It becomes. Here, the vibration direction is changed to the detection direction. Here, for example, an equation of motion of forced vibration due to Coriolis force is established for the detected vibration of the second foot J12.
(D ^ 2 / dt ^ 2 + (ωZ / QZ) d / dt + ωZ ^ 2) ξ (t)
= 2DΩωCOS (ωt) (3)
Here, ωZ is the resonance frequency of the detected vibration, QZ is the Q value of the detected vibration, and ξ (t) is a function representing the temporal displacement of the center of gravity of the second foot J12 in the Z ′ direction. The solution of this equation solved under appropriate initial conditions when QZ 'is large is as follows.
ξ (t) = (ωZ / ωd) Aexp (−ωZt / 2QZ) COS (ωd−φ)
+ ACOS (ωt−Ψ) (4)
Since the phase shift of vibration is not discussed, it is simply written as φ and Ψ. Here, the amplitude A is expressed as follows.
A = 2DΩ (1 / ωZ) Δω ((1-Δω ^ 2) ^ 2
+ (Δω / QZ) ^ 2) ^ (-1/2) (5)
Further, the frequency ωd related to the Q value QZ is expressed as follows.
ωd = (1- (1 / 2QZ) ^ 2) ^ (1/2) (6)
Here, the ratio ω / ωZ of the resonance frequency ωZ of the drive vibration and the resonance frequency ωZ of the detection vibration is the frequency ratio Δω.
[0016]
Equation (5) indicates that the amplitude A is Δω = 1, in other words, the resonance type is maximized when ω = ωZ, and the generally used detuning degree | ω−ωZ | / ω is smaller. The empirical fact that the output of the gyro is large is well expressed. According to the literature, the first term on the right side of equation (4) is a transient solution that expresses the Coriolis force, the second term is a steady solution that expresses the Coriolis force, and the amplitude A shown in equation (5) is the magnitude thereof. It is supposed to show. If a transient solution exists, the output of the vibrating gyroscope does not become proportional only to the angular velocity, so the transient solution must be removed. According to the literature, the transient solution can be removed by phase detection that blocks | ω−ωd |, which is approximately equal to the frequency difference | ω−ωZ |, if the Q value QZ is large, but this is greater than the frequency difference between driving and detection. This indicates that the gyro cannot expect the frequency response.
[0017]
However, a vibration gyro called a general resonance type obtains practical responsiveness while utilizing a very small degree of detuning in order to obtain performance. This is due to the following reason. Focusing on the exponential function of the transient solution, this term shows that it rapidly decreases when the frequency ωZ is large or the Q value QZ is small. Except for piezoelectric single crystals, the vibration factor such as PZT generally used for gyros has a Q value of 1000 or less. If the Q value is 300, the transient solution is exponential at a general frequency of use of about 10 kHz. Since it attenuates to 5% or less in about 0.1 seconds depending on the function term, it is not necessary to worry about the degree of detuning. On the other hand, in many piezoelectric single crystals, the Q value is well over 5000. In this case, the decay of the transient term due to the exponential term can no longer be expected. In a gyro using a piezoelectric single crystal having a high Q value, the output once emitted does not stop, and in order to exclude this, there is no choice but to rely on phase detection with a large degree of detuning. In order to obtain a response of 10 Hz with a vibration gyro of 10 kHz, a detuning of at least twice as much as 1000 PPM is required. In other words, in consideration of responsiveness, in a vibrating gyroscope using a piezoelectric single crystal, it is not practical to improve the performance by reducing Δω and increasing the output, as shown in Equation (5). Therefore, a large output S cannot be expected.
[0018]
[Object of invention]
An object of the present invention is to solve the above-mentioned problems, and to provide a vibrating gyroscope having a high S / N and good detection accuracy.
[0019]
[Means for Solving the Problems]
In order to solve the above object, the vibration gyro of the present invention employs the following configuration.
[0020]
A first vibrating body made of crystal and having a driving foot is combined with a second vibrating body made of a non-piezoelectric material, having a detection foot and having a lower Q value than the first vibrating body. It is characterized by comprising: a composite vibrator; an oscillating means for driving and vibrating the drive leg; and a detecting means for detecting a detection vibration generated on the detection leg by a Coriolis force generated by the rotation of the composite vibrator .
[0021]
[Action]
The vibration gyro according to the present invention is composed of a vibrator made of a material having a high Q value and a vibrator having a low Q value, and uses a driving vibration having an extremely high Q value and little vibration leakage to the outside. By using a detector that reduces N and does not vibrate due to drive vibration, noise N is further reduced, a vibrator having a low Q value is used for detection, and only the detected vibration has a low Q value. By constructing the vibrator for generating the driving vibration not to be deformed in the detection direction during the generation, a resonance type with a small detuning degree is realized without sacrificing responsiveness, and a large output S is obtained. High S / N is realized.
[0022]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an embodiment according to the best mode for carrying out a vibrating gyroscope of the present invention will be described with reference to the drawings. 1 to 4 show a vibrating gyroscope according to an embodiment of the present invention. FIG. 1 is a perspective view showing an appearance of an H-type vibrating gyro, which will be referred to as a composite tuning fork 10 hereinafter, and coordinates used for the following description. 2 is a plan view, circuit block, and wiring schematic diagram of the composite tuning fork 10, FIG. 3 is an operation explanatory view of the cross section of the drive foot showing the drive vibration of the composite tuning fork 10, and FIG. It is operation | movement explanatory drawing of the cross section of the detection leg | foot which shows a vibration.
[0023]
[Structural description of vibrating gyroscope: FIGS. 1 and 2]
In the present embodiment, a crystal having a particularly high Q value is used among the piezoelectric single crystals for generating the drive vibration. More specifically, a 206 type crystal resonator having an oscillation frequency of 32.768 kHz used for a clock oscillator with stable quality is used. Hereinafter, this crystal resonator is referred to as a 206 type resonator 11. In order to generate the detection vibration, a plate of Erinba with good temperature characteristics formed by press working and PZT with good piezoelectric efficiency is pasted. These are combined to form a composite tuning fork 10.
[0024]
FIG. 1 is a view of the composite tuning fork 10 as viewed from an oblique direction. As shown in FIG. 1, the composite tuning fork 10 is composed of an Erinba plate to which a 206-type vibrator 11 and PZT are attached. The composite tuning fork 10 has a planar shape as a whole. For convenience of the following description, the Y axis is taken in the direction in which the legs are extended, the X axis is taken in the direction in which the legs are lined up, and the Z axis is provided in the thickness direction. The 206 type vibrator is made of quartz having elasticity and piezoelectricity, and has a tuning fork shape in which the ends of two legs 1 and 2 arranged in parallel to each other are joined to a rectangular base from the same direction. The end of three parallel legs are joined to the rectangular base from the same direction, and in the future the shape resembles the shape of a Chinese character called a mountain. There are PZT plates 6 and 7 with metal films deposited on both sides except for the center foot 5 and deposited in a direction perpendicular to the surface, and are electrically conductive to the elimba. It is stuck and pasted. The 206-type vibrator 11 and the mountain-shaped vibrator 12 are arranged with their legs extending in opposite directions, and the bottom surfaces of the bases are joined to each other.
[0025]
FIG. 2 shows a plan view, a circuit block, and a schematic wiring diagram of the composite tuning fork 10, and shows the connection relationship between the electrodes and the drive detection circuit. The drive circuit is composed of a self-excited oscillation circuit that returns a signal from one of the two drive electrodes 8 and 9 of the 206-type vibrator 11 to the other electrode using the amplifier G and the phase shift circuit P. Are a differential buffer D for detecting signals from the metal films on the upper surfaces of the two piezoelectric elements 6 and 7 attached to the mountain-shaped vibrator 12, a phase shift circuit P2 for changing the phase of the output of the amplifier G, and a phase. It comprises a comparator C that binarizes the signal of the detection circuit, a multiplication circuit M that multiplies the output of the differential buffer D by the output of the phase shift circuit P2, and an integration circuit S that integrates the multiplication result into a direct current.
When configuring a three-power-supply circuit, the elimber is grounded.
[0026]
[Description of operation and action of vibrating gyroscope: FIGS. 2, 3 and 4]
Hereinafter, the driving and detection vibration of the composite tuning fork 10 will be described with reference to FIGS. 3 and 4, and the composite tuning fork 10 will be electrically driven using FIG. 2 and the result of the rotation of the composite tuning fork 10 in the Y-axis direction will be described. A method for determining the angular velocity from a certain voltage output will be described.
[0027]
The ideal in a vibration gyro is to obtain a stable vibration gyro that does not depend on the external environment by using only a self-contained vibration mode in the vibration body and supporting the vibration node in this vibration mode. As an example, such a vibrating body can be realized by supporting between the legs of a pair of two-leg tuning forks, an H-shaped tuning fork having a shape in which two pairs of two-leg tuning forks are arranged to face each other. The two-leg tuning fork is one of the most excellent vibrating bodies in the so-called in-plane vibration in which the primary bending vibration occurs while balancing the two legs in the opposite directions in the plane determined by the two legs. The pair of legs of the H-shaped tuning fork constitutes a two-leg tuning fork, which can be realized as an excellent vibrator. Further, the four legs of the H-type tuning fork are excellent vibrators even in the so-called out-of-plane vibration in the direction orthogonal to the in-plane vibration. Such an H-shaped vibrator has already been proposed in US Pat. No. 3,515,914 in 1970. In this embodiment, a vibrating body as shown in US Pat. No. 3,515,914 is used for drive detection vibration of a vibrating gyroscope.
[0028]
Moreover, in the vibration gyro, the detection unit does not generate an output irrelevant to the Coriolis force while the drive vibration is occurring, which suppresses high S / N and troublesome output drift at the time of no rotation. It is valid. This is because there is no drift if there is no output during no rotation. If the orthogonality between the drive and detection vibrations is incomplete, the output irrelevant to the Coriolis force will cause the drive vibration to mechanically generate the detection vibration in the vibrating detector, and the symmetry of the electrodes of the drive vibrator will be If it is incomplete, the detection output that vibrates will generate the detection output electrically, so the vibrating body manufactured with finite machining accuracy will be driven when driving vibration occurs when there is no rotation. A structure in which the detection unit is stationary regardless of vibration and the detection unit vibrates greatly as a part of the vibration body of the detection vibration when detection vibration is generated by rotation is desirable. In the present embodiment, the 206-type vibrator 11 for an oscillator and the mountain-shaped vibrating body 12 are combined to form the H-shaped vibrating body as a whole, and the tip of the foot at the center of the mountain-shaped vibrating body 12 is formed. By supporting, a vibrating body that satisfies all of the above-mentioned desirable matters is provided.
[0029]
The drive vibration of the composite tuning fork 10 will be described with reference to FIG. FIG. 3 is a cross-sectional view of the driving feet 1 and 2 of the 206-type vibrator 11, and the direction and magnitude of the foot bending at a certain moment are represented by arrows. The driving feet 1 and 2 are opposed to each other in the X direction.
[0030]
The detected vibration of the composite tuning fork 10 will be described with reference to FIG. FIG. 4 is a cross-sectional view of the detection legs 3 and 4 of the mountain-shaped vibrator 12 and the center leg 5 used for support, and the direction and magnitude of the leg bending at a certain moment are represented by arrows. In addition, the vibration shown in FIG. 4 includes two legs on both sides in the thickness direction, which are used as detection vibrations in the present embodiment among several vibration modes of an H-shaped vibrating body such as the composite tuning fork 10. This is a natural vibration mode in which bending vibration is performed oppositely. In this embodiment, the frequency of this vibration mode is adjusted to 32.768 kHz and used as detected vibration. When this detected vibration occurs, the composite tuning fork 10 receives the rotational force in the Y-axis foot direction, that is, the ZX plane as a whole.
[0031]
In the detection vibration of the composite tuning fork 10, the length of the detection feet 3 and 4 and the length of the base are changed to adjust the rotation moment of the entire composite tuning fork 10 and the moment that the bending of the detection feet 3 and 4 gives to the composite tuning fork 10. By doing so, it is possible to prevent the rotational moment of the entire composite tuning fork 10 from being transmitted to the support portion by moving the bending vibration node of the detection foot in the Y direction to the vicinity of the base of the central foot used for support. By such a device, the entire center foot 5 of the mountain-shaped vibrator 12 used as the support portion can be used as a vibration node, and the detected vibration can be an excellent vibration body that does not cause vibration leakage to the outside. Further, by adjusting the width and thickness of the detection legs 3 and 4, the detection legs 3 and 4 can be adjusted so as not to bend and deform in the X direction when a drive vibration occurs.
[0032]
Next, the state of the driving feet 1 and 2 of the composite tuning fork 10 during detection vibration generation will be described. Since the 206 vibrator 11 used in the composite tuning fork 10 has a thickness of 230 μm and a foot width of 380 μm, when attention is paid only to the foot portion, the resonance frequency of the bending vibration in the driving direction and the resonance frequency in the direction orthogonal thereto Are separated by nearly 60%, and the driving foot is hardly deformed in the Z direction at the driving frequency.
[0033]
Next, the relationship between drive vibration and detection vibration and Coriolis force will be described. In the composite tuning fork 10 that performs drive vibration, when the composite tuning fork 10 is rotated at an angular velocity Ω in the foot Y-axis direction at this time, the Coriolis force FC acts in the direction orthogonal to the drive vibration on the drive foot 1 that moves at the speed VX. A Coriolis force -FC acts on the driving foot 2 moving at a speed -VX in a direction orthogonal to the driving vibration. That is, the Coriolis forces FC and -FC act on the driving feet 1 and 2 of the composite tuning fork 10 in the direction orthogonal to the driving vibration at the frequency of the driving vibration. However, as described above, at this frequency, the driving feet 1 and 2 hardly bend and displace in the Z-axis direction. Therefore, the Coriolis force gives rotational vibration to the base through the roots of the driving feet 1 and 2, and rotates the composite tuning fork 10 as a whole. Vibration is excited. If the resonance frequency of the detection foot is adjusted to be closest to 32.768 kHz, a large detection vibration is generated by the Coriolis force on the feet 3 and 4 on both sides of the mountain- shaped tuning fork that is stationary when there is no rotation.
[0034]
Next, an electrical drive detection method using an actual drive detection circuit will be described. FIG. 2 shows a plan view, a circuit block, and a wiring schematic diagram of the composite tuning fork 10, and shows the connection relationship between the electrodes and the drive detection circuit. First, the voltage from one drive electrode 9 of the 206-type vibrator 11 is input to the amplifier G, the output of the amplifier G is phase-shifted by the phase shift circuit P, and applied to the other drive electrode 8. Make the vibration self-oscillate.
[0035]
When the entire composite tuning fork 10 is rotated in the Y-axis direction at an angular velocity Ω in this state, the movement of the driving feet 1 and 2 of the composite tuning fork 10 is caused to rotate to the composite tuning fork 10 via the Coriolis force as described above. Occurs, and out-of-plane vibration is generated in the detection legs 3 and 4 of the mountain- shaped vibrator 12 that is stationary when there is no rotation. The case where the foot 3 vibrates by detection will be described. When the foot 3 bends in the detection direction, for example, the piezoelectric element 6 contracts. At this time, due to the piezoelectric effect, for example, a positive voltage is generated in the piezoelectric element 6 depending on the polarization direction. At this time, the other piezoelectric element 7 extends. Due to the piezoelectric effect, this piezoelectric element 7 generates a negative voltage. Since the piezoelectric elements 6 and 7 are attached to the elember with conductivity, the detection vibration can be detected as voltages in opposite directions generated in the metal films of the two piezoelectric elements with reference to the potential of the elember. Of course, you may measure the voltage between electrodes directly, without using an erimba.
[0036]
The detection signal of the Coriolis force is obtained by connecting the elimber to the ground to generate a reference voltage, inputting the voltages of the metal films of the two piezoelectric elements 6 and 7 to the differential buffer D, and passing through the differential buffer D to the multiplication circuit M. The reference of the output of the amplifier G is shifted 90 degrees by the phase shift circuit P2 and binarized by the comparator C for the purpose of correcting the oscillation output of the driving vibration to be delayed by 90 degrees. The result of multiplication by the signal and detection by multiplication can be further smoothed by the integration circuit S and detected as an accurate DC output. Since this DC output is proportional to the Coriolis force, and the Coriolis force is proportional to the angular velocity Ω, the angular velocity Ω can be known from this DC output. Here, the reason why the differential detection is used for the detection is to improve the symmetry of the circuit and reduce the drift of the circuit system.
[0037]
The detection vibrations of the detection feet 3 and 4 of the composite tuning fork 10 shown in FIG. 4 are excited by the Coriolis force as a medium from the drive vibration that is the opposing operation of the drive feet 1 and 2 shown in FIG. At this time, paying attention to the operation of the driving feet 1 and 2, in the detected vibration, the driving feet 1 and 2 cannot bend so much in the direction orthogonal to the driving vibration, and are hardly deformed. This means that the vibration generated by the Coriolis force bends and deforms only the portion of the vibrating body having a low Q value, while hardly bending the portion of the vibrating body having a high Q value. In other words, the vibration caused by the Coriolis force attenuates very quickly. Therefore, the composite tuning fork 10 according to the present embodiment is also used in a resonance type design that guarantees a high output by driving a vibration body having a low Q and a high Q value while matching the frequencies of the drive vibration and the detection vibration. A vibration gyro with practical response can be realized.
【The invention's effect】
As apparent from the above description, the vibration gyro according to the present invention is composed of a vibrator made of a material having a high Q value and a vibrator having a low Q value, and has a very high Q value and vibration to the outside. Noise N is reduced by using drive vibration with less leakage, noise N is further reduced by using a detection unit that does not vibrate due to drive vibration, and only the detected vibration is low by using a vibrator having a low Q value for detection. By realizing a Q value and further preventing the vibration for driving vibration from being deformed in the detection direction during detection vibration generation, a resonance type with low detuning can be realized without sacrificing responsiveness. A large output S is obtained, and as a result, a high S / N is realized.
[Brief description of the drawings]
FIG. 1 is a perspective view showing an appearance of an H-type vibrating gyroscope according to an embodiment of the present invention and showing coordinates used for the following description.
FIG. 2 is a schematic diagram showing a front side of a composite tuning fork according to an embodiment of the present invention, and showing circuit blocks and wiring.
FIG. 3 is an operation explanatory diagram showing drive vibration of the H-type vibrating body according to the embodiment of the present invention.
FIG. 4 is an operation explanatory view showing detected vibration of the H-shaped vibrating body according to the embodiment of the present invention.
FIG. 5 is a perspective view showing the appearance of a conventional tuning-fork type crystal gyro, showing coordinates, showing a part of an electrode, and showing the rotation direction of an anisotropic crystal.
FIG. 6 is a schematic diagram of a cross section of a foot and a wiring of a drive detection circuit of a conventional tuning fork type crystal gyro.
[Explanation of symbols]
1-5 feet 6,7 PZT
8, 9 Electrode 10 H-type vibration gyro 11 Tuning fork type vibrator 12 Mountain type vibrator C Comparator D Differential buffer G Amplifier M Multiplying circuit P, P2 Phase shift circuit S Integration circuit FC, -FC Coriolis force VX, -VX Speed J1 to J8 Electrode J10 Tuning fork type vibrator J11 First leg J12 Second leg J15 Base JC Comparator JD Differential buffer JG Amplifier JM Multiplication circuit JP, JP2 Phase shift circuit JS Integration circuit

Claims (7)

A first vibrating body made of crystal and having a driving foot is combined with a second vibrating body made of a non-piezoelectric material, having a detection foot and having a lower Q value than the first vibrating body. A composite oscillator,
Oscillating means for driving and vibrating the driving foot;
A vibration gyro comprising: detection means for detecting a detection vibration generated in the detection foot by a Coriolis force generated by the rotation of the composite vibrator . The first vibrating body generates the detected vibration by separating the resonance frequency of the bending vibration in the driving direction and the resonance frequency in a direction orthogonal to the bending frequency in the driving direction by making the thickness and width of the driving foot different. 2. The vibrating gyroscope according to claim 1, wherein bending in the detection direction at the time is suppressed. The said 2nd vibrating body suppressed the bending to the drive direction at the time of the generation | occurrence | production of the said drive vibration by making the thickness and width | variety of the said detection leg | foot differ. Vibration gyro. The first vibrating body has two driving feet,
The second vibrating body has two detection legs,
4. The vibration gyro according to claim 1, wherein the composite vibrator is formed by coupling bases of the first vibration body and the second vibration body . Before Stories second vibrator is disposed between the two detection leg includes a long central legs than the detection leg, according to claim 4, characterized in that for supporting the distal end of said central leg Vibration gyro. The vibrating gyroscope according to claim 1, wherein the driving foot and the detection foot have different thicknesses. The vibrating gyroscope according to any one of claims 1 to 6, wherein the second vibrating body is formed of an erinba having a surface provided with PZT .

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