JP2001194148A - Vibrating gyro - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a vibrating gyro having high accuracy and mass- producibility. SOLUTION: A peanut-shaped vibrator is used to achieve a high Q value of vibration caused by drive. A detecting part which is not displaced by the vibration caused by drive is also used. The peanut-shaped vibrator is used to provide a structure such that vibrations for both drive and detection are carried out within the same plane.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vibrating gyroscope for detecting an angular velocity.

[0002]

2. Description of the Related Art Conventionally, mechanical rotary gyroscopes have been used as inertial navigation devices for airplanes and ships. However, the devices are large and expensive, so that they can be incorporated into small electronic devices and small transport machines. It is difficult.

In recent years, however, research into miniaturization of gyroscopes has been advanced, and a vibrator is excited by a piezoelectric element, and another piezoelectric element provided on the vibrator generates a voltage generated by vibration caused by Coriolis force applied to the vibrator by rotation. The vibrating gyroscope for detecting the vibration has been put into practical use, and is used for a car navigation system, a camera shake detecting device of a video camera, and the like.

In particular, a vibrating gyroscope using a piezoelectric single crystal is promising because of its simple structure, easy adjustment, and excellent temperature characteristics. As an example using a piezoelectric single crystal, a structure of a tuning fork type vibration gyro using quartz will be described with reference to the drawings. FIG. 5 is a perspective view showing a tuning fork type vibration gyro.

In FIG. 5, a 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 connected by the base J15. The drive electrodes J3 and J4 are deposited on the first foot J11, and the detection electrodes J6, J7 and J8 are deposited on the second foot J12. The bottom surface of the base J15 is used for support. Here, the direction in which the feet extend is the Y 'direction, the direction in which the two feet are arranged is the X direction,
And a direction orthogonal to the Y ′ direction is defined as a Z ′ direction.

The operation will be described. FIG. 6 is a schematic diagram of a cross section of a foot and a drive detection circuit for describing a conventional drive detection method of a tuning fork type crystal gyro. In FIG.
The drive electrode J1,
Sections of J2, J3 and J4 are arranged, and the second
The detection electrodes J5, J6, J7 and J
Eight sections are arranged. First, when the first foot J11 bends in the X direction toward, for example, the second foot J12, the vicinity of the electrode J2 extends in the Y ′ direction, and the vicinity of the electrode J4 contracts in the Y ′ direction. Effect of electrode J2
An electric field is generated in the X direction in the vicinity and in the -X direction in the vicinity of the electrode J4. At this time, considering the direction of the electric field, the electrode J2
And J4 have the same potential, for example, a potential higher than the center of the foot. When viewed in the X direction, the electrode J located near the center of the foot
Since 1 and J3 have a relatively lower potential than the electrodes J2 and J4, a potential difference occurs between the electrodes J2 and J4 and the electrodes J1 and J3. Because 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 quartz crystal,
The first foot J11 bends in the X direction. From these facts, for example, with reference to the potentials of the electrodes J1 and J3, amplification is performed using the amplifier JG with an amplification factor exceeding the oscillation condition, the phase is adjusted to a phase satisfying the oscillation condition by the phase shift circuit JP, and the phase is 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 self-oscillate in the X direction. Looking at the entire tuning fork J10, 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, and when the first foot J11 moves in the -X direction, the second foot J12 moves in the X direction. This is performed by a normal tuning fork vibrating in one plane. Is called an in-plane flexural vibration from the customary practice of making the first leg J11,
The vibration generated by the amplifier JG and the phase shift circuit JP is the same operation as the in-plane bending vibration, and its frequency substantially matches the resonance frequency of the in-plane bending vibration of the tuning fork J10. In this state, when the entire tuning fork J10 is rotated around the Y ′ axis at an angular velocity ω, a Coriolis force Fc acts on the two feet 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 = 2 · M · ω · V Here, M is the mass of the first foot J11 or the second foot J12, and V is the speed of the first foot J11 or the second foot J12. The Coriolis force FC excites the first foot J11 and the second foot J12 with bending vibration that is displaced in the Z ′ direction orthogonal to the X direction, which is the operation direction of the in-plane bending vibration.
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 speed, the out-of-plane bending vibration generated by the Coriolis force is delayed by 90 degrees from the in-plane bending vibration. Due to 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 closes the electrodes J5 and J8.
Expands and contracts in a phase opposite to that of. For example, electrodes J5 and J
8 extends in the Y ′ direction, an electric field is generated in the X direction near the electrodes J5 and J8 inside the second foot J12. An electric field is generated in the −X direction near the electrodes J6 and J7 inside the second foot 12 because of contraction. 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. In addition, electrodes J5 and J
8 is contracted in the Y ′ direction, an electric field is generated in the −X direction near the electrodes J5 and J8 inside the second foot J12. At this time, the vicinity of the electrodes J6 and J7 is in the Y ′ direction. Therefore, an electric field is generated in the X direction near the electrodes J6 and J7 inside the second foot 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. These electrodes J5 and J8 generated by out-of-plane bending vibration and electrodes J6 and J7
Varies in accordance with the direction of the second foot J12 swinging in the Z ′ direction. From another point of view, for example, the electrode J5
Is high potential, the electrode J7 is also high potential.
The electrode J8 is at a low potential, and when the electrode J5 is at a low potential, the electrode J7 is also at a low potential. At this time, the electrodes J6 and J8 are at a high potential. Coriolis force can be measured at electrode J5 or electrode J7
And the potential difference between the electrode J6 and the electrode J8.

The detection signal of the Coriolis output includes the electrodes J5 and J7 as one input signal and the electrodes J6 and J8.
Is input to the multiplication circuit JM via the differential buffer JD, which is the other input signal, and the output of the oscillation system of the in-plane bending vibration is corrected in order to correct the occurrence of the Coriolis force delayed by 90 degrees.
The output of the amplifier JG is phase-shifted by 90 degrees by the phase shift circuit JP2, multiplied by the reference signal binarized by the comparator JC, and the result of the multiplication detected is further smoothed by the integration circuit JS to obtain an accurate DC signal. Can be detected as 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 the DC output.

[0008]

However, the tuning fork type vibration gyro using the conventional piezoelectric single crystal has the following problems. In a tuning fork type vibrating gyroscope, a rod-shaped vibrating body handles bending vibrations in two directions perpendicular to the direction in which the rods extend, but if the resonance frequencies of these two directions of bending vibrations are adjusted to a difference within several percent, The cross section of a rod-shaped object is
It becomes a square, regular polygon, or circle. On the other hand, as a processing method of the piezoelectric single crystal, if the shape is a plane type, the etching process is superior to the mechanical processing such as grinding in terms of the degree of freedom of the shape and particularly the precision. Etching is preferable in a vibrating gyroscope in which the processing accuracy affects performance, but in the etching, if the thickness is large, the processing accuracy is not improved. Therefore, a vertical vibrating gyroscope having a square cross section cannot be processed with high precision even by etching, and the performance cannot be improved.

In the two-leg tuning fork type vibrating gyroscope, the rod-shaped vibrating body does not drive and detect.
The detector is vibrating. Theoretically, the drive direction is orthogonal to the detection direction, so the influence of the drive vibration does not affect the detection vibration.However, in actual machining accuracy, this orthogonality is not sufficient, and the detection direction is determined in advance by the drive. The detection electrode is vibrating, and the detection electrode detects the drive vibration due to the capacitance of the electrode. This means that the output is output despite the absence of the Coriolis force, and the S / N is reduced.

[Object of the Invention] An object of the present invention is to solve the above-mentioned problems, and to provide a vibrating gyroscope capable of high-accuracy processing, high in mass productivity, and high in detection accuracy.

[0011]

In order to solve the above-mentioned object, a vibration gyro according to the present invention employs the following configuration.

A vibrating gyroscope according to the present invention includes a vibrator having an electrode for oscillation, a detecting section having an electrode for detecting angular velocity, a connecting section for connecting a node of the vibrator vibration to the detecting section, and a detecting section. In a vibrating gyroscope consisting of supporting parts,
The transducer, the joint, the detector, and the support have a planar structure with a substantially constant thickness, the transducer has a point-symmetric shape with respect to the center point, and the transducer has an even number of It is constituted by a curve having an inflection point, and the driving vibration and the detected vibration are in the same plane.

[0013] It is characterized in that all the constituent elements are integrally formed of a piezoelectric single crystal.

The vibrator is characterized in that it has a structure in which only arcs are connected.

It is characterized in that there are two detection units.

The detection is characterized by differential detection of signals from the two detection units.

The difference between the resonance frequencies of excitation and detection is 1000
It is characterized by being at least 0 PPM.

[Operation] The vibrating gyroscope according to the present invention employs a peanut shape and supports a node of vibration, thereby using a driving vibration having a very high Q value and little noise, and a detecting section which does not vibrate due to the driving vibration. By using
Achieve high S / N. In addition, by adopting a planar structure capable of realizing driving and detection vibration in the same plane, a very thin planar structure can be realized. As a result, high-precision processing by the etching method can be performed, performance degradation due to processing errors can be reduced, and a high-precision vibration gyro can be mass-produced.

[0019]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view of a vibrating gyroscope according to a preferred embodiment of the present invention. FIGS. 1 to 4 and FIGS. 7 and 8 show a vibrating gyroscope according to an embodiment of the present invention. FIG. 1 shows the appearance of a peanut type vibrating gyroscope, hereinafter referred to as a peanut 10, and the coordinates used in the following description will be described. FIG. 2 is a top view showing a part of the electrode, and FIG. 2 is a bottom view showing the appearance of a peanut-shaped vibrating gyroscope, showing coordinates, and showing a part of the electrode.
FIG. 3 is a schematic view of a cross section, a circuit block and wiring of the peanut 10, FIG. 4 is a perspective view of a coordinate system showing a rotation direction of a cutting direction of the anisotropic crystal, and FIG. FIG. 8 is an operation explanatory diagram showing the detection vibration of the peanut type vibrator.

[Structural Description of Vibrating Gyroscope: FIGS. 1, 2 and 4] In the present embodiment, a quartz crystal having particularly excellent temperature characteristics is used among piezoelectric single crystals. The crystal is S
i02 is a single crystal belonging to a trigonal system having four crystal axes at room temperature. One of the crystal axes is called a c-axis, which is a crystal axis passing through a vertex of the crystal, and the other three are called a-axes, and crystal axes which form an angle of 120 degrees with each other in a plane perpendicular to the c-axis. It is. Here, one of the three a-axes is set as the X-axis, the c-axis is set as the Z-axis, and the Y-axis is set in a direction orthogonal to the X-axis and the Z-axis.

As shown in FIG. 4, the coordinate system used in the present embodiment is such that the X, Y, and Z axes move from the X axis to the Z axis around the X axis.
Coordinate axis Y 'axis, Z' rotated by θ degrees from axis to Y axis direction
The axis and the X axis are used. At this time, the rotation angle θ is set to 0 to 10 degrees. As the rotation angle shown here, an optimum rotation angle is selected based on the temperature characteristics and the stability of vibration. Peanuts 10
Is a two-dimensional shape having a certain thickness, and this thickness direction is cut out in the Z′-axis direction. The peanut shape of the peanut 10 thus cut out is expressed in a two-dimensional shape in the XY ′ plane. Here, in the following description, Z ′
The axial direction is the front and back direction.

FIG. 1 is a view of the peanut 10 as viewed from the front. As shown in FIG. 1, the peanut 10 is composed of a vibrator 1, detecting sections 2-3, joining sections 4-7, and a supporting section 9. Is done. The vibrator 1 is made of quartz having elasticity and piezoelectricity, has a peanut shape, and has electrodes made of a metal deposition film provided on the upper, lower, and side surfaces. The peanut shape is a shape of an arc-shaped fragment obtained by dividing a ring shape having a thickness t in an XY ′ plane into four parts in a plane parallel to the radial direction of the ring and the Z ′ axis direction in a rotation direction around the Z ′ axis. Are rotated and translated in the same plane, and each cut surface is viewed as a contour in the plane, so that a closed curve having four inflection points is formed. It is obtained by joining to. At this time, each arc-shaped fragment at the time of joining has its cut surfaces joined so that the adjacent arc-shaped fragments at two locations have the same rectangular outline as the cut surfaces. In the present embodiment, eight arc-shaped pieces are used for simplification of the shape. However, any shape that is point-symmetric in a plane and has a plurality of inflection points can be considered. Can be The base 9 is made of elastic quartz and is a rectangle having a thickness t in the XY ′ plane. The detectors 2 and 3 have a thickness t in the XY ′ plane.
Is a rectangle. The detectors 2 and 3 are arranged so as to form a shape symmetrical about the center with the base 9 interposed therebetween. The detectors 2 and 3 and the base 9 are arranged inside the vibrator 1 configured in a peanut shape symmetrical with respect to the center. The four vibration nodes are connected to the detection units 2 and 3 using the joints 4 to 7 having the thickness t. All of the above parts are of unitary construction.

FIGS. 1 and 2 show an example in which an electrode made of a metal deposition film is formed on a peanut 10 as an example of the electrode. FIG. 2 shows the peanut 10 viewed from behind. Hereinafter, the surface illustrated in FIG. 1 is referred to as a front surface, and the surface illustrated in FIG. 2 is referred to as a back surface. The shape of the electrode is formed by preparing a mask in which the shape is formed in advance by etching, bringing the mask into close contact with the surface of the peanut 10 on which the electrode is to be formed, and performing vacuum deposition. The drive electrodes DLU1, DLU2, DLU3, DRU1, and DRU are provided on two confined portions on the surface of the vibrating body 1.
2 and DRU3 are deposited, and the two
Driving electrodes DLD1, DLD2, DLD3, DRD1, D
RD2 and DRD3 are deposited. Further, detection electrodes S1 and S2 and a ground GND are deposited on the surface of the detection unit 2, detection electrodes S3 and S4 and a ground GND are deposited on the surface of the detection unit 3, and terminals are disposed on the surface of the support unit 9. TS1,
TS2, TS3, TS4 and TG are deposited, and terminals TD + and TD− are deposited on the back surface. The terminals TD + and TD− also have a function of fixing the peanuts 10 to the outside by soldering or the like. The detection electrode S1 is connected to the terminal TS1,
The detection electrode S2 is connected to the terminal TS2,
3 is connected to terminal TS3, and detection electrode S4 is connected to terminal T3.
S4, and the ground GND is connected to the terminal TG. The drive electrodes DLU1, DLU3, and DRU2 are connected by a conductive wire WU1 deposited on the upper surface of the vibrator, and the drive electrodes DLD2, DRD1, and DRD3 are connected by a conductive wire WD1 deposited on the lower surface of the vibrator, and the conductive wires WU1 and WD1 are connected.
Are connected by a conducting wire WB1 turning around the side surface, and the conducting wire WD1 is connected to a terminal TD + formed on the lower surface. Therefore, the drive electrodes DLU1, DLU3, DRU2, DLD2, DRD
1 and DRD3 are electrically connected to terminal TD +.
The drive electrodes DLU2, DRU1, and DRU3 are connected by a conductive wire WU2 deposited on the surface of the vibrator, and the drive electrodes DLD
1, DLD3, DRD2 are connected by a conductive wire WD2 deposited on the back surface of the vibrating body, the conductive wires WU2 and WD2 are connected by a conductive wire WB2 running around the side surface, and the conductive wire WD2 is connected to a terminal TD- formed on the back surface. Therefore, the driving electrode DLU
2, DRU1, DRU3, DLD1, DLD3 and DR
D2 is electrically connected to terminal TD-.

FIG. 3 shows driving electrodes DLU1, DLU2, DLU3, DL of the same vibrating body 1 as shown in FIGS.
D1, DLD2, DLD3, DRU1, DRU2, DR
U3, DRD1, DRD2, DRD3 and the detection electrodes S1, S2, the ground GND, and the conducting wire WD1 of the detection unit 2 show the cross sections SEC1 to SEC3 at the position A in the Y 'direction perpendicular to the Y' axis direction and detected. Detection electrode S of part 3
3, SEC4, a section SEC4 at a position B in the Y 'direction perpendicular to the Y' axis direction, including the ground GND and the conductor WD2.
Shows a connection relation of each electrode and a drive detection circuit. The drive detection circuit includes a self-excited oscillation circuit that returns a signal from the drive electrode to the drive electrode using an amplifier G and a phase shift circuit P. The detection circuit includes a differential buffer amplifier that detects a signal from the detection electrode. D, a phase shift circuit P2 for changing the phase of the output of the amplifier G, a comparator C for binarizing the signal of the phase detection circuit, and a phase shift circuit P2 for outputting the output of the differential buffer amplifier D.
, And an integrating circuit S that integrates the multiplication result and converts the result to a direct current.

[Description of operation and action of vibrating gyroscope: FIGS.
FIGS. 3, 7, and 8] Hereinafter, the driving vibration of the peanut-type vibrator will be described with reference to FIG. 7, and the detection vibration of the peanut-type vibrator will be described with reference to FIG. FIG.
A method for electrically driving the peanut 10 and finding the angular velocity from the voltage output resulting from the rotation of the peanut 10 will be described with reference to FIG.

The peanut-type vibrator has a number of natural vibration modes. Among them, the vibration completed in a plane perpendicular to the thickness direction of the peanut shape, that is, in the XY 'plane, is generated in the ten planes of the peanut. It is called vibration. The natural vibration mode used in the present embodiment is a low-order vibration mode in the in-plane vibration of the peanut 10. When the peanut-shaped vibrator is made of an isotropic elastic body, the in-plane vibration mode is completed within the plane, and there is no displacement in the thickness direction.

On the other hand, the quartz used in the present embodiment is an anisotropic single crystal, and has a different elastic modulus depending on the direction. In this case, there is a slight displacement in the thickness direction. This vibration displacement in the thickness direction causes deterioration of the support characteristics,
The thickness direction is not defined as the Z-axis direction.
Coordinate axes Y 'axis, Z' axis and X rotated by θ degrees in the direction of the axis
By using a shaft and setting the thickness direction to the Z′-axis direction, vibration displacement in the thickness direction can be reduced, and the support characteristics can be improved. At this time, the rotation also changes the temperature characteristics of the resonance frequency of the driving vibration due to this rotation. Therefore, the rotation angle θ is determined in consideration of the support characteristics and the temperature characteristics. The rotation angle θ is optimally 0 to 10 degrees.

The driving vibration mode of the peanut 10 will be described with reference to FIG. Among the low-order vibration modes of the peanuts 10, there is a vibration mode in which the vibrating body 1 repeatedly expands and contracts in the X direction due to bending. FIG. 7 shows a state in which the vibrating body 1 expands in the X direction in this vibration mode by a solid line, but shows a shape at rest by a broken line so as to be compared with this. The vibrating body 1 has a shape symmetrical in the X direction, and the left and right portions on the paper surface have a momentum balance while elastically deforming each portion to form a curved portion.
A bending vibration is performed in which the expanded state shown in FIG. 7 and the concave state corresponding to the expanded state are repeated. This is called the first bending vibration of the vibrating body 1. The bending deformation occurs in all portions of the vibrating body 1, but slightly large deformation occurs in the constricted portions on the left and right. In the vibrator 1, the shape has a symmetry axis also in the Y 'direction,
From the center of the arc-shaped portion of the vibrating body 1, in the XY ′ plane, in the direction opposite to the constriction, in the direction making 25 ° with the Y ′ direction, the vicinity of the intersection of the arc and the half line is the vibrating body 1. It is a node of the vibration, and the vicinity of the intersection of the straight line and the arc drawn from the center of the arc-shaped portion of the vibrating body 1 in the direction opposite to the constriction in the Y 'direction and -25 degrees is also the vibration of the vibrating body 1. Is a clause. Vibrator 1
Since there are two arc-shaped portions in the Y ′ direction, that is, on the top and bottom on the paper surface, the vibration nodes of the first bending vibration of the vibrating body 1 have a total of 4
Exists. The nodes of the vibration of the first bending vibration of the vibrating body 1 hardly perform parallel movement during bending, but slightly rotate in the XY ′ plane. In the peanut 10, the rectangular detection units 2 and 3 and the first vibrating body 1
The first bending vibration can be smoothly performed by joining the four vibration nodes of the bending vibration at the shortest distance with good symmetry using the joints 4 to 7.

In the actual trial evaluation, the first bending vibration of the peanut 10 has an ideal vibration characteristic which is hardly influenced by the supporting method of the supporting portion. As a vibrating body that generally performs bending vibration for some time, it has been considered that an in-plane vibration of a two-leg tuning fork has the most excellent vibration characteristics. In a two-legged tuning fork, a high Q value can be realized without being substantially affected by the method of supporting the supporting portion, but the first bending vibration of the peanut 10 is 2
It can be seen as one of the few vibrations comparable to the in-plane vibration of a leg tuning fork. In addition, the vibrating part of the two-leg tuning fork has a cantilever structure, and its oscillation frequency is easily affected by the gravitational acceleration due to the posture, and similarly, it is easily affected by the acceleration disturbance due to the translational movement of the whole vibrating gyroscope. As a characteristic of the beam, the bending displacement of the vibrating part is extremely concentrated near the supporting part. For example, if the amplitude is increased to obtain stable vibration, the displacement of the part where the displacement is concentrated becomes extremely large, and this part The transition to non-linear vibration occurs, and the frequency fluctuation accompanying the vibration is likely to occur. On the other hand, the first bending vibration of the peanut 10 is doubly supported and supported by the center of gravity. Since the deformation is not concentrated on a part like a cantilever, even if the amplitude is increased, the degree to which the frequency changes due to the transition to the nonlinear vibration is small.

The detection vibration mode of the peanut 10 will be described with reference to FIG. The detected vibration mode is not the natural vibration of the vibrating body 1. The main displacement parts in the detection mode are the detection units 2 and 3. One side of the rectangular detectors 2 and 3 is joined to the support, and the other side is joined to the vibrating body 1 by joints 4 to 7. The support portion is fixed to the outside by soldering or the like, and the vibrating body 1 can move freely. Therefore, the detection portions 2 and 3 behave as cantilever beams with one support and the other weight. However, since the detection units 2 and 3 are symmetrical in the Y ′ direction with the support unit interposed therebetween and are coupled to the vibrator 1, the vibrator 1 is allowed to be bent in the XY ′ plane. Accordingly, the detection units 2 and 3 vibrate in directions opposite to each other when viewed in the X direction. In FIG. 8, the vibrating body 1 rotates clockwise as viewed from the front, and the detecting unit 2 bends in the X direction with this.
The moment when the detection unit 3 is bent in the −X direction is indicated by a solid line, and the state in which the vibrating body 1 is not rotating is indicated by a broken line to make the deformation easy to understand. The corresponding vibration that repeats between the deformation in which the vibrating body 1 turns to the left is called the second bending vibration.

The second bending vibration is not a self-contained vibration. In the second bending vibration, the peanuts 10 form a vibrating body integrally with the external housing joined to the support.
To stabilize the vibration, at least 10 of peanuts 10
It is desirable to join to a housing having twice or more mass. In addition, the second bending vibration largely depends on the state of support. That is, it is desirable that the joining method between the support portion 9 and the housing should be physically stable. In the present embodiment, the peanut 10 and the metal casing are joined by soldering or the like, so that Q
Sufficient vibration characteristics of about 1000 are obtained. In the vibration gyro, the Q value of the drive vibration that needs to give a large amplitude is desirably as high as possible in consideration of drift and the like, whereas the Q value of the detected vibration is 300
A degree is sufficient. The reason is that the sensitivity of the vibration gyro increases as the Q value on the detection side increases while the Q value on the detection side is low, but the sensitivity rises to a plateau in a region where Q exceeds 300. If the Q value on the detection side is too high, the output will not rapidly attenuate when the resonance frequencies of the driving vibration and the detection vibration are made closer, and the resonance frequency will not be made closer, thus limiting the sensitivity.

Next, the relationship between the first bending vibration and the second bending vibration and the Coriolis force will be described. As shown in FIG. 7, in the peanut 10 performing the first bending vibration, the center of gravity of the left half on the paper of the vibrating body 1 divided into two by the symmetry axis viewed in the X-axis direction is defined as GL. When the GL performs displacement in the -X direction, the center of gravity GL has a velocity -VX in the -X direction. The right half center of gravity is GR. When the GR performs displacement in the X direction, the center of gravity GR has a velocity VX in the X direction. At this time, when the peanut 10 is rotated around Z ′ at an angular velocity ω, the center of gravity G
A Coriolis force FC acts on L in a direction orthogonal to the speed -VX, and a Coriolis force -FC acts on the center of gravity GR in a direction orthogonal to the speed VX. Coriolis force FC acts in Y 'direction,
Since the Coriolis force -FC acts in the -Y 'direction, the peanut 10 rotates clockwise as a whole as viewed from the Z' axis direction, as shown in FIG. Therefore, when the peanut 10 in which the first bending vibration is generated is rotated around the Z ′ axis at an angular velocity ω, the second bending vibration is generated by the Coriolis force. However, since the Coriolis force is a force proportional to the velocity, the displacement phase of the second bending vibration caused by the first bending vibration must be delayed by 90 degrees with respect to the displacement phase of the first bending vibration. No.

The thickness t of the peanuts 10 will be described. The natural frequencies of the first bending vibration and the second bending vibration described so far are the X-rays of the vibrator 1 and the detectors 2 and 3.
It is related to the width in the Y ′ plane. On the other hand, the vibration of the peanut 10 includes an out-of-plane vibration of the peanut 10, which is a vibration in a direction orthogonal to the XY ′ in-plane vibration of the peanut 10.
The frequency of the out-of-plane vibration of the peanut 10 is
Depends on the thickness t. When the thickness t of the peanut 10 is as large as the width of the vibrating body 1 and the widths of the detection units 2 and 3, not only does the accuracy of the etching process not increase, but also the resonance of the first bending vibration or the second bending vibration. There is a risk that the natural frequency of the out-of-plane vibration of the peanut 10 that is not used in the peanut 10 near the frequency may occur as spurious.

The peanuts 10 are manufactured by an etching method. The etching method has a characteristic that the smaller the thickness is, the higher the relative accuracy is, as compared with the extent of expansion in a plane. Therefore, the first bending vibration and the second bending vibration used as the vibrating gyroscope are both vibrations in the XY ′ plane, and in the peanut 10 whose frequency is not related to the thickness, the thickness is reduced by reducing the thickness. The processing accuracy can be improved without limit, and the performance can be improved. This is one of the advantages that the peanut 10 has as a vibrating gyroscope over a conventional tuning fork vibrating gyroscope. In a conventional tuning-fork type vibrating gyroscope, the beam thickness must be about the same as the beam width in order to make the resonance frequency of the in-plane vibration of the vibrating part used for driving and the resonance frequency of the out-of-plane vibration of the vibrating part used for detection nearly match. In other words, a thick planar shape was inevitable, and high precision could not be achieved even by using etching, and high performance could not be achieved. However, when the thickness of the peanut 10 is reduced, a large number of natural frequencies of higher-order out-of-plane vibrations are generated as spurious, so that spurious is generated near the resonance frequency of the first bending vibration or the second bending vibration. It should be noted that choosing a thickness that does not.

Next, an actual driving detection method will be described. FIG. 3 shows two Z′-X cross sections of the peanut 10. One is a section where the vibrating body 1 near the center of the peanut 10 shown by the broken line A in FIGS. 1 and 2 is constricted, and is a cross section including the driving unit and the detecting unit 2 of the vibrating body 1.
The other is a peanut 10 indicated by a broken line B in FIGS.
3 is a cross section including the detection unit 3 near the central part of FIG. The top of the paper,
The cross section S of the vibrating body 1 at the position of the broken line A from the left of the paper surface
EC1 and drive electrodes DLU1, DLU2, DLU3, D
Sections of LD1, DLD2, DLD3, section SEC2 of detection section 2, detection electrodes S1, S2, and ground GN
D, section of the conductor WD1, and section SEC3 of the vibrating body 1
And drive electrodes DRU1, DRU2, DRU3, DRD
1, a cross section of DRD2, DRD3 is shown, and below that, a cross section of the section SEC4 of the detection section 3, the detection electrodes S3, S4, the ground GND, and the conductor WD2 at the position of the broken line B is shown.

First, when the left half of the vibrating body 1 expands, for example, in the −X direction, the constricted portion of the vibrating body 1 extends in the Y ′ direction on the left side and contracts in the Y ′ direction on the right side. Then, an electric field is generated in the X direction near the electrodes DLU1 and DLD1 and in the −X direction near the electrodes DLU3 and DLD3 due to the piezoelectric effect. At this time, considering the direction of the electric field, the electrodes DLU1, DLD1, DLU3, and DLD3 have, for example, a higher potential than the electrodes DLU2 and DLD2 at the center when viewed in the X direction, and the vibrator 1 left section SEC1 when viewed in the X direction.
DLU1, DLD1, DLU3 and D
A potential difference is generated between LD3 and the electrodes DLU2 and DLD2 near the center of the vibrator 1 left section SEC1.

A phenomenon occurs in the right half of the vibrating body 1 symmetrically with the left half. For example, when the right half expands in the X direction, the constricted portion extends on the right side in the Y 'direction and on the left side in the Y' direction. At this time, the electrode D
In the vicinity of RU1 and DRD1, in the -X direction, and the electrode DR
An electric field is generated in the X direction near U3 and DRD3. At this time, considering the direction of the electric field, the electrodes DRU1, DRD1,
The electrodes DRU3 and DRD3 have, for example, a lower potential than the electrodes DRU2 and DRD2 located at the center in the X direction, and the electrodes DR located outside the right section SEC3 of the vibrating body 1 as viewed in the X direction.
U1, DRD1, DRU3 and DRD3, and electrodes DRU2 and DRD near the center of the vibrating body 1 right section SEC3
2 generates a potential difference.

On the other hand, since the piezoelectric effect is reversible, the electrode electrodes DLU1, DLD1, DLU3 or DLD3 are
When the potential is set higher than LU2 or DLD2, an electric field corresponding to this is generated inside the crystal, and the left half of the vibrating body 1 is X
The left half of the vibrating body 1 expands in the −X direction. In the right half of the vibrating body 1, a phenomenon symmetrical to the left half occurs, and the electrode electrodes DRU1 and DRD
1, DRU3 or DRD3, electrode DRU2 or DRD
When the potential is set lower than 2, an electric field corresponding to this is generated inside the crystal, the right half of the vibrating body 1 bends in the X direction, and the right half of the vibrating body 1 expands in the X direction.

From these facts, for example, the electrodes DLU2,
DLD2, DRU1, DRD1, DRU3 and DRD3
Are amplified using an amplifier JG with an amplification factor exceeding the oscillation condition with reference to the potential of the terminal TD + to which the electrode DRU is electrically coupled, and adjusted to a phase satisfying the oscillation condition by the phase shift circuit JP.
2, DRD2, DLU1, DLD1, DLU3 and DL
By returning D3 to the electrically coupled terminal TD-,
Energy exchange occurs between a mechanical return force and an electric force accompanying the bending of the vibrating body 1, and the vibrating body 1 can oscillate the first bending vibration by self-excitation.

In this state, when the entire peanut 10 is rotated around the Z ′ axis at an angular velocity ω, the second bending vibration is generated in the vibrating body 1 of the peanut 10 as described above.
Due to this second bending vibration, the electrodes S1 of the detection units 2 and 3
And the vicinity of S4 expands and contracts in the Y 'direction, and the vicinity of the electrodes S2 and S2 and S3 expands and contracts in the opposite phase to the vicinity of the electrodes S1 and S4.

For example, the vicinity of the electrode S1 of the detecting section 2 is Y '.
When the electrode S1 extends in the direction, an electric field is generated in the X direction near the electrode S1, so that the electrode S1 has a higher potential than the electrode GND of the detection unit 2. At this time, since the vicinity of the electrode S2 contracts in the Y ′ direction, an electric field is generated in the −X direction near the electrode S2, so that the electrode S2 has a higher potential than the electrode GND of the detection unit 2. On the other hand, when the vicinity of the electrode S4 of the detection unit 3 extends in the Y ′ direction, an electric field is generated in the X direction near the electrode S4, and thus the electrode S4 has a lower potential than the electrode GND of the detection unit 2. At this time, since the vicinity of the electrode S3 shrinks in the Y ′ direction, an electric field is generated in the −X direction near the electrode S3.
S3 has a lower potential than the electrode GND of the detection unit 3. Therefore, the Coriolis force appears as a symmetrical potential difference between the electric connection of the electrodes S1 and S2 and the electric connection of the electrodes S3 and S4 with the electric potential of the ground electrode GND interposed therebetween.

The signal for detecting the Coriolis force is obtained by electrically connecting the terminal TS1 of the electrode S1 and the terminal TS2 of the electrode S2 to one input signal, and electrically connecting the terminal TS3 of the electrode S3 and the terminal TS4 of the electrode S4. The resulting signal is used as the other input signal and is led to the multiplication circuit M via a differential buffer D that operates symmetrically with respect to the potential of the ground electrode GND,
In order to correct the output of the oscillation system of the in-plane bending vibration, the occurrence of the Coriolis force delayed by 90 degrees, the output of the amplifier G is
The phase shifted by 90 degrees by the phase shift circuit P2, multiplied by the reference signal binarized by the comparator C, and the result detected by the multiplication is further smoothed by the integration circuit S, and can be 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 the DC output.

Here, it is very important that the detection of the Coriolis force is a differential detection of two outputs from the detector 2 and the detector 3 arranged symmetrically from the center of the support. have. In general, many vibrating gyros have a configuration in which translational acceleration and angular velocity cannot be distinguished from each other, as described as being weak to vibration. In the peanut 10, when the second bending vibration is generated due to the Coriolis force, the displacement of the detection unit 2 and the detection unit 3 in the X direction is opposite, and the outputs of the terminals TS1 and TS2 and the outputs of the terminals TS3 and TS4. And the opposite output occurs. On the other hand, when translational acceleration acts on the peanut 10 and the mass of the vibrator 1 deforms the detection units 2 and 3, the displacement of the detection unit 2 and the detection unit 3 in the X direction is the same, and the terminals TS1 and TS2 The same output occurs between the output and the outputs of TS3 and TS4. In the configuration of the present embodiment, by taking the difference between these two outputs, the effect of the translational acceleration is negated, so that the effect of the translational acceleration and vibration is less.

Next, the resonance between the first bending vibration and the second bending vibration of the peanut 10 will be described using specific numerical values. Peanuts 10 manufactured with high precision by etching
Is that the Q value of the first bending vibration in the drive mode is 100,000 or more, and the Q value of the second bending vibration in the detection mode is about 1000. When the resonance frequency is designed at 10 kHz, the Q value on the detection side is sufficiently high. Therefore, when the resonance type of the first bending vibration and the second bending vibration is designed to have the same resonance frequency, the second bending generated by the Coriolis force is performed. , The temporal decay of the bending vibration becomes moderate, and the time response of the detection output to the change in the angular velocity ω becomes extremely poor, which is not practical.
In contrast, in a design in which the resonance frequencies of the first bending vibration and the second bending vibration are separated from each other, the time response is exponentially improved with respect to the difference between the two resonance frequencies. By setting the difference between the resonance frequencies of the first bending vibration and the second bending vibration to about 10,000 PPM, 100
Hz.

[0045]

As is apparent from the above description, the vibrating gyroscope according to the present invention uses a piezoelectric single crystal having a high Q value,
By adopting a peanut-type configuration and supporting the nodes of the vibration of the vibrating body 1, by using a driving vibration having a very high Q value and a low noise of the vibrating body 1, by using a detection unit that does not vibrate depending on the driving vibration, Achieve high S / N. Also,
As a feature of the peanut type structure, since the driving and the detection vibration can be realized in the same plane, a very thin planar structure can be realized. As a result, high-precision processing by the etching method can be performed, performance degradation due to processing errors can be reduced, and a high-precision vibration gyro can be mass-produced.

[Brief description of the drawings]

FIG. 1 shows the appearance of a peanut-shaped vibrating gyroscope according to an embodiment of the present invention, and shows coordinates used in the following description,
It is a front view which shows a part of electrode.

FIG. 2 shows the appearance of a peanut-shaped vibrating gyroscope according to an embodiment of the present invention, and shows coordinates used in the following description;
It is a rear view which shows a part of electrode.

FIG. 3 is a schematic diagram showing a cross section of a peanut according to an embodiment of the present invention, showing circuit blocks and wiring.

FIG. 4 is a perspective view of a coordinate system showing a rotation direction of the anisotropic crystal of the present invention.

FIG. 5 is a perspective view showing an appearance of a conventional tuning-fork type crystal gyro, showing coordinates, showing a part of an electrode, and showing a rotation direction of an anisotropic crystal.

FIG. 6 is a schematic sectional view of a foot and wiring of a drive detection circuit of a conventional tuning fork type crystal gyro.

FIG. 7 is an operation explanatory diagram showing driving vibration of the peanut-type vibrating body according to the embodiment of the present invention.

FIG. 8 is an operation explanatory diagram showing driving vibration of the peanut-type vibrating body according to the embodiment of the present invention.

[Explanation of symbols]

 DLU1, DLU2, DLU3 electrode DRU1, DRU2, DRU3 electrode DLD1, DLD2, DLD3 electrode DRD1, DRD2, DRD3 electrode TD +, TD− terminal S1 to S4 electrode TS1 to TS4 terminal GND electrode and terminal GL, GR center of gravity 1 vibrator 2, Reference Signs List 3 Detection unit 4-7 Connection unit 9 Support unit 10 Peanut-shaped vibrating gyroscope A, B Cross-sectional position C Comparator D Differential buffer G Amplifier M Multiplying circuit P, P2 Phase shift circuit S Integrating circuit FC Coriolis force -FC Coriolis force VX speed-VX speed WU1, WU2 Conductor WD1, WD2 Conductor WB1, WB2 Conductor SEC1-SEC4 Cross-section J1-J8 Electrode J10 Tuning fork type vibrator J11 First leg J12 Second leg J15 Base JC Comparator JD Differential buffer JM multiplication circuit JP, JP2 Phase shifter JS Integrator

Claims (6)

[Claims] An oscillator having an electrode for oscillation, a detector having an electrode for detecting angular velocity, a joint for connecting a node of vibration of the oscillator to the detector, and a support for supporting the detector. In the vibrating gyroscope provided with, the vibrator, the joint portion, the detecting portion, and the supporting portion have a planar structure having a substantially constant thickness, and the vibrator has a point-symmetric shape with respect to a center point, and The vibrating gyroscope is characterized in that the vibrator is constituted by a curve having an even number of inflection points in a plane, and the drive vibration and the detected vibration are in the same plane. 2. The vibrating gyroscope according to claim 1, wherein all the components are integrally formed of a piezoelectric single crystal. 3. The vibrating gyroscope according to claim 1, wherein the vibrator has a structure in which only arcs are connected. 4. The vibrating gyroscope according to claim 1, wherein the number of detecting units is two. 5. The vibrating gyroscope according to claim 4, wherein the detection is a differential detection of signals from two detection units. 6. The vibrating gyroscope according to claim 2, wherein a difference between a resonance frequency of the vibration and a resonance frequency of the vibration is 10000 PPM.
A vibrating gyroscope characterized by the above.