JP3409476B2 - Driving method of vibrating gyroscope - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for driving a vibration gyro which is small in size, lightweight, simple in structure and manufacturing method, and sufficiently accurate.

[0002]

2. Description of the Related Art As an example of a conventional vibrating gyro, K. Maenaka and T. Shiozawa, “Si Ray Rate Sensor Using Anisotropic Etching Technology” by K. Maenaka and T. Shiozawa.
licon rate sensor using anisotropic etching techno
logy ”), the Digest of Technical Pay Paz, Transducers 93 (Dig. of Tech. Pape
rs, Transducers 93), 1993, pp. 642-645, as shown in FIGS. 8 (a), (b) and (c). 8A is a perspective view, FIG. 8B is a cross-sectional view,
FIG. 8C is a schematic circuit diagram when used. In FIG.
Reference numeral 1 denotes a support portion, and this portion is vibrated in the x-axis direction of (b) by the lower piezoelectric element 3 together with the glass pedestal 2 in FIGS. 8 (a) and 8 (b). It supports the beam 6. An attempt is made to rotate a plane including the vibration direction of the vibrating beam 6 (orthogonal to the paper surface) about an axis in the plane and orthogonal to the vibration direction (orthogonal to the paper surface), that is, the z-axis direction of (b). Then, in response thereto, Coriolis force is generated in a direction perpendicular to the vibration direction of the vibrating beam 6, that is, in the y-axis direction of (b). The movement of the vibrating beam 6 due to this Coriolis force is detected via the detection electrode 5. Reference numeral 4 denotes a vibration monitoring electrode, which monitors the vibration amplitude of the vibrating beam 6. The support 1, the detection electrode 5, and the vibrating beam 6 are all structures formed from a (110) silicon substrate by an anisotropic etching technique.
In FIG. 8C, 7 is a drive power source for driving the piezoelectric element 3, 8 is a buffer, 9 is an amplifier, and 10 is a demodulator. The displacement of the vibrating beam 6 in the x-axis direction (driving direction) by the piezoelectric element and the displacement in the y-axis direction (detection direction of the vibrating surface rotation) due to the Coriolis force are as shown in FIG. 8C. 6 is grounded, and measurement is performed by a change in electric capacitance between the vibration monitoring electrode 4 and the detection electrode 5. The magnitude of the Coriolis force Fc (t) generated when the angular velocity Ω is input is represented by the following equation (1).

Fc (t) ≈2 · m · Vm (t) · Ω (1) where m is the mass of the vibrating beam 6 and Vm (t) is the piezoelectric element 7.
Is the speed of the vibrating beam 6 driven by. The maximum Coriolis force is when the drive vibration is in resonance (drive amplitude and Vm
(T) is maximum), the resonance state is as shown in FIG.
Ref. Shown in (c). It can be realized by adjusting the drive frequency of the drive power supply 7 so that the signal becomes maximum.
Further, from the equation (1), the vibration in the detection direction of the vibrating beam 6 due to the Coriolis force Fc (t) has the same frequency as the drive frequency and the vibration amplitude in the detection direction proportional to the vibration amplitude in the drive direction. Therefore, as shown in FIG.
From Ref. By demodulating the signal from the detection electrode 5 by the demodulator 10 using the signal, the displacement due to the Coriolis force of the vibrating beam 6 corrected by the drive amplitude can be measured, and the change in the drive amplitude due to the disturbance acceleration input or the like is corrected. be able to.

[0004]

However, the above-mentioned conventional vibrating gyro requires a vibration monitoring electrode for monitoring the driving vibration state of the vibrating beam 6, which is the vibrating mass, and the structure and the processing steps during manufacturing are required. However, there have been problems such as the complexity of the product and the difficulty in reducing the size and cost.

The present invention solves the above-mentioned problems of the conventional vibration gyro driving method, has a simple structure, a simple manufacturing process, and a sufficiently high precision vibration gyro driving method. The challenge is to provide.

[0006]

In order to solve the above problems, the present invention is constructed as described in the claims. That is, in the invention according to claim 1, when a plane including the vibration direction of the vibrating body vibrating in a certain direction is rotated around an axis existing on the plane and orthogonal to the vibration direction, the vibration is generated. In a driving method of a vibrating gyroscope, which detects the Coriolis force acting on the body and measures the angular velocity of the rotation, an electrode pair disposed opposite to the vibrating body on each side of the vibrating body is provided. Then, a driving voltage is alternately applied to the electrode pair at a specific frequency, and electrostatic attraction in the opposite direction is alternately applied to the vibrating body to drive and excite the vibrating body. The vibration state of the vibrating body is also monitored so that the vibration state of the vibrating body is controlled to be always constant.

Specifically, in order to drive and vibrate the vibrating body by electrostatic attraction, a driving voltage is alternately applied at a specific frequency between the vibrating body and the electrode pair, and the electrode pair is also applied. The first time zone where no voltage is applied to any of
A voltage for reading the driving vibration amplitude of the vibrating body during the first time period is applied to the electrode pair at the same time or applied to the vibrating body, and the vibration is caused by a change in the electric capacitance between the read electrode pair and the vibrating body. The excitation vibration amplitude of the body is read out.

Further, in the invention as set forth in claim 2 , in order to drive and excite the vibrating body by electrostatic attraction, the vibrating body is provided between the vibrating body and a pair of electrodes arranged on opposite sides thereof. , A first time zone in which a drive voltage is alternately applied at a specific first frequency and a voltage is not applied to any of the electrode pairs, and the vibrating body and the electrode pair are respectively provided in the first time zone. A carrier voltage for reading the electric capacitance between the vibrating body is applied to the vibrating body, and the vibration state of the vibrating body is monitored by the read electric capacity between the vibrating body and each of the electrode pairs. . In the invention according to claim 3 , the first frequency of the driving voltage alternately applied between the vibrating body and the electrode pair arranged on the opposite side of the vibrating body coincides with the resonance frequency of the vibrating body. It is configured to allow.

[0009]

The two electrodes, which are arranged on the opposite sides of the vibrating body so as to alternately apply the electrostatic attraction in the opposite direction to the vibrating body, are used for driving and exciting the vibrating body. Since the electrodes are also used to monitor the vibration state of the vibrating body, we decided to control so that the vibrating state of the vibrating body is always constant, so the structure is simpler and mass production is easier than in the case of the conventional technology, and the size is small. It can be formed at low cost.

[0010]

【Example】

First Embodiment: FIG. 3 (a) (plan view), FIG. 3 (b) (cross-sectional view), and FIG. 1 (a) (block diagram of drive and detection circuit), FIG. b) and FIG. 1C (time chart of voltage application). In this embodiment, the vibration system is a silicon substrate 1a on which an oxide film 20 is formed.
Is configured on. The vibration system is composed of a vibrating mass 13 and a support 30. The vibrating mass and the support are composed of crystalline silicon (or polysilicon) or metal deposited by the plating method. The support 30 is fixed to the silicon substrate by the fixing portion 14. Further, the vibrating mass and an electrical connection portion to the support body are configured in the fixed portion 14 (electric wiring is not shown for simplification of the drawing). Comb-shaped electrodes 18 for driving the oscillating mass (in the horizontal direction in the drawing) by electrostatic attraction are formed on the side surfaces of the oscillating mass. An electrode 16 for detecting a displacement of the vibrating mass in the y-axis direction as a change in electrostatic capacitance is formed immediately below the vibrating mass (FIG. 6B).

In FIG. 1A showing the block diagram of the drive and detection circuit of the vibrating gyroscope in this embodiment, the portion surrounded by the dotted line corresponds to the vibrating mass, which is connected to the common potential VL. Cd1 and Cd2 are electric capacities between the driving electrode facing the vibrating mass and the vibrating mass, and are connected to the driving power source 21 via the reference capacitance Cr2 and a driving voltage is applied thereto. Since the impedance of the electric capacitance is expressed by the following equation (2), Zc = 1 / jωC (2), driving by setting Cr2 to be sufficiently larger than the electric capacitances Cd1 and Cd2 between both drive electrodes and the oscillating mass The loss of voltage Cr2 is almost negligible. Actually, since the values of Cd1 and Cd2 are about pF, it is easy to realize Cr2 even on the same substrate. The potentials Vd1 and Vd2 at the connection points between Cd1 and Cd2 and the reference capacitor Cr2 are input to the demodulator 24 via the buffer 25 and demodulated using the output of the driving power supply 21. The demodulated signal is amplified to a predetermined value by an amplifier and becomes a feedback signal for controlling the output amplitude of the driving power supply 21.

The driving voltage is applied as shown in the time charts of FIGS. 1 (b) and 1 (c). The driving voltage is composed of a voltage vd for generating a driving force and a read voltage vc for detecting the vibration mass displacement. vd and vc are applied alternately in different periods. In the figure, a time interval of 0V application is provided between vd and vc application, but the essential function is the same even if this time interval is not provided. The driving voltage is in opposite phases to the electric capacitances Cd1 and Cd2 between the driving electrode and the oscillating mass that generate driving forces in mutually opposite directions, and the read voltage vc is the time interval τ when vd is not applied to both driving electrodes. Within
It is applied to both drive electrodes simultaneously. Even if the read voltage vc is a unipolar pulse with respect to VL as shown in FIG. 1 (b),
Alternatively, as shown in FIG. 1C, a bipolar pulse may be applied to VL.

With respect to the potential Vm (= VL) of the oscillating mass 13, the oscillating mass 13 supported by the support 30 by alternately applying the driving voltage to the drive electrode ends Vd1 and Vd2 (FIG. 3A). , (B) are oscillated in the x-axis direction (left and right). The resonance frequency fxr of the vibrating mass in the x-axis direction is determined by the mass of the vibrating mass and the spring constant of the support in the x-axis direction. Therefore,
The resonance state can be easily realized by electrically adjusting the applied frequency of the driving power source 21 (FIG. 1A).

Cs1 and Cs2 are electric capacities between the detection electrodes facing the vibrating mass and the vibrating mass, and are connected to the detection power source 22 (FIG. 1A) via the reference capacity Cr1 to read the displacement of the vibrating mass. The broth voltage C is applied. In the figure, the read voltage C is the same signal synchronized with the driving voltage vc, but there is essentially no problem even if it is a different signal. Cs1,
The potentials Vs1 and Vs2 at the connection point between Cs2 and the reference capacitor Cr1 are input to the demodulator 24 via the buffer 25 and the detection power source 22 is supplied.
Is demodulated using the output of. The demodulated signal is amplified to a predetermined value by an amplifier and output.

In order to measure the Coriolis force with high accuracy, it is necessary to drive the vibrating mass at a constant frequency and a constant amplitude. Since the vibration frequency matches the drive frequency, OSC1
It suffices to keep the frequency of 1 constant. At the time of applying the drive voltages D and D through the reference capacitance Cr2, the drive electrode terminals Vd1 and Vd are applied.
If the potential of d2 is read out via the buffer 25 and the differential is detected by the demodulator 24 in synchronization with the drive frequency of the drive power supply OSC1, information regarding the vibration amplitude of the vibrating mass can be obtained. Further, in the case of the present embodiment, the displacement detection voltage C of the vibrating mass is
May be used for demodulation. Therefore, by applying negative feedback to the driving power supply OSC1 so that the obtained amplitude information has a predetermined value and adjusting the amplitude of vd of the driving voltage, it is possible to drive the vibrating mass at a constant amplitude.
Further, as in the present embodiment, a voltage is applied to the comb-teeth electrode to drive the vibrating mass by electrostatic attraction, and the vibration amplitude reading voltage v
When c is simultaneously applied to the drive electrodes for the oscillating mass connected to the common potential VL, the electrostatic attractive forces generated by vc on both drive electrodes cancel each other out and do not affect the oscillating state.

Detection of a change in capacitance between the detection electrode pair and the oscillating mass due to the Coriolis force acting on the oscillating mass is
A reference electric capacity Cr1 that is substantially equal to Cs1 and Cs2 is connected in series to each detection electrode terminal Vs1 and Vs2, and a detection voltage C is applied using the detection power supply 22 via the reference electric capacity Cr1 to detect each detection electrode terminal. The potentials Vs1 and Vs2 are read out via the buffer 25, and the differential is detected by the demodulator 24 in synchronization with the drive frequency of the detection power supply OSC3. Since the Coriolis force and OSC3 have the same frequency, a DC signal corresponding to the amount of displacement in the y-axis direction can be obtained.

The following effects can be obtained in the first embodiment.
Since the vibration monitoring electrode for monitoring the driving vibration state of the vibrating mass 13 is also used as the driving electrode, the structure and the manufacturing process are simplified, and the size and cost can be reduced. When a voltage is applied to the comb-teeth electrode to drive the vibrating mass by electrostatic attraction, and a vibration amplitude reading voltage vc is simultaneously applied to the drive electrode for the grounded vibrating mass, both drive electrodes generate vc. Since the electrostatic attraction forces cancel out each other, the vibration amplitude of the vibrating mass can be accurately detected by sufficiently increasing the amplitude of vc without affecting the vibration state. Since the control means for measuring the drive amplitude of the oscillating mass 13 and keeping it constant is provided,
It is possible to eliminate the influence of the drive amplitude variation due to the disturbance acceleration that affects the generated Coriolis force. Since we have realized an angular velocity sensor using a semiconductor manufacturing process, we have made it smaller and
It is possible to reduce the weight and cost and mass-produce sensors with uniform characteristics. By using electrostatic attraction drive and electrostatic capacitance detection, the vibrating mass and each support can be made to have the same potential, and electrical wiring is easy. Since the vibrating mass is directly driven, the vibration amplitude of the vibrating mass can be controlled with higher accuracy. It is possible to perform constant control of the vibration amplitude without using an electrode for monitoring the vibration amplitude. By forming the detection unit, the drive circuit of the detection unit, and the signal processing circuit on the same substrate, it is possible to greatly reduce the influence of external noise mixed during inputting a minute generated signal to the processing circuit. Also,
The pairing of the reference capacitances Cr1 and Cr2 can be improved, and the driving force and the output signal offset can be reduced. The driving comb-teeth electrode 18 is oscillated mass 1
Since it is formed on the side surface of No. 3, the opposing area of the drive electrode can be effectively secured, and the vibrational mass can be efficiently vibrated.

Second Embodiment: FIG. 3A shows the second embodiment.
(Plan view), FIG. 3 (b) (cross-sectional view), and FIG. 2 (a)
(Block diagram of drive and detection circuit), FIG. 2 (b), FIG. 2 (c) (time chart of voltage application). In this embodiment, a carrier voltage for reading the electric capacitance between the vibrating body and the two driving electrodes is applied to the vibrating body (instead of being simultaneously applied to the two driving electrodes) in the first time zone. Different from the first embodiment. FIG. 2A is a block diagram of the drive and detection circuit of the vibration gyroscope in this embodiment.
Shown in. In the figure, the part surrounded by the dotted line corresponds to the vibrating mass,
This is connected to the detection power source 22 (OSC3). C
d1 and Cd2 are electric capacities between the driving electrode facing the vibrating mass and the vibrating mass, and the driving power source 21 is connected via the reference capacity Cr2.
And the driving voltage is applied. Since the impedance of the electric capacitance is expressed by the following formula (2) Zc = 1 / jωC (2), if Cr2 is made sufficiently larger than the electric capacitances Cd1 and Cd2 between both drive electrodes and the oscillating mass, the drive voltage The loss in Cr2 is almost negligible. In fact, Cd1,
The value of Cd2 is about pF, so Cd2 is C on the same substrate.
r2 is easy to implement. The potentials Vd1 and Vd2 at the connection points between Cd1 and Cd2 and the reference capacitor Cr2 are input to the demodulator 24 via the buffer 25 and demodulated using the output of the driving power supply 21. The demodulated signal is amplified to a predetermined value by an amplifier and becomes a feedback signal for controlling the output amplitude of the driving power supply.

The driving voltage is as shown in FIG. 2 (b) or FIG. 2 (c).
Apply as shown in the time chart of. The driving voltage is composed of the voltage vd for generating the driving force. The driving voltage has opposite phases to the electric capacitances Cd1 and Cd2 between the driving electrodes and the vibrating body that generate driving forces in opposite directions, and there is a time interval τ in which vd is not applied to both driving electrodes. Is applied. The reading voltage vc of the electric capacity is shown in FIG.
It may be a unipolar pulse for VL as shown in (b) or a bipolar pulse for VL as in FIG. 2 (c). In the figure, the read voltage vc is applied with the pulse width τ during the time interval τ, but the essential function is the same even if the pulse width is τ or less.

The vibrating mass 13 supported by the support 30 is vibrated in the x-axis direction by alternately applying a driving voltage to the driving electrode ends Vd1 and Vd2 with respect to the potential Vm of the vibrating mass 13. Resonance frequency fxr of the vibrating mass in the x-axis direction
Is determined by the mass of the oscillating mass and the spring constant of the support in the x-axis direction. Therefore, the resonance state can be easily realized by electrically adjusting the applied frequency of the driving power source 21.

Cs1 and Cs2 are electric capacities between the detection electrode facing the vibrating mass and the vibrating mass, and are connected to the common potential VL via the reference capacity Cr1. Cs1, Cs2 and reference capacity Cr1
The potentials Vs1 and Vs2 at the connection point between and are input to the demodulator 24 via the buffer 25 and demodulated using the output of the detection power supply 22 (OSC3). The demodulated signal is amplified to a predetermined value by the amplifier and output.

In order to accurately measure the Coriolis force, it is necessary to drive the vibrating mass at a constant frequency and a constant amplitude. Since the vibration frequency matches the drive frequency, the OSC
The frequency of 1 may be kept constant. Power supply for detection 22
When the voltage vc for reading the electric capacity by (OSC3) is applied, the potentials of the drive electrode terminals Vd1 and Vd2 are read out through the buffer 25, and the differential is detected by the demodulator 24 as the detection power source O.
If the detection is performed in synchronization with the frequency of SC3, information on the vibration amplitude of the vibrating mass can be obtained. Therefore, by applying negative feedback to the drive power supply OSC1 so that the obtained amplitude information has a predetermined value and adjusting the amplitude of the drive voltage vd, it is possible to drive the vibration mass with a constant amplitude. Further, as in the present embodiment, a voltage is applied to the comb-teeth electrode to drive the vibrating mass by electrostatic attraction, and a vibration amplitude read voltage vc
Is applied to the vibrating mass (vibrating body) during the time period when the electric potentials of both drive electrodes are VL, the electrostatic attractive forces generated by vc in both drive electrodes cancel each other out, and thus do not affect the vibration state.

The change in the capacitance of the detection electrode pair due to the Coriolis force is detected by detecting Cs1 and Cs2 at both detection electrode ends Vs1 and Vs2.
A reference electric capacitance Cr1 which is almost equal to is connected in series and grounded, a detection voltage C is applied to the oscillating mass 13 using a detection power source 22, and the potentials of both detection electrode ends Vs1 and Vs2 are passed through a buffer 25. The differential is detected by the demodulator 24 in synchronization with the drive frequency of the detection power supply OSC3. Since the change in capacitance corresponds to the displacement of the oscillating mass, a DC signal corresponding to the amount of displacement in the y-axis direction can be obtained.

The effects of the second embodiment differ from those of the first embodiment in the following points. The read voltage vc is the detection power supply 22 within the time interval τ when vd is not applied to both drive electrodes.
By virtue of this (as opposed to applying a read voltage to both drive electrodes simultaneously in the first embodiment), the vibration mass 13 is applied.
Therefore, between the vibrating mass and both drive electrodes, the read voltage vc
Since the electrostatic attractive forces generated by the above cancel each other, the vibration amplitude of the vibrating mass can be accurately detected by sufficiently increasing the amplitude of vc without affecting the vibration state.

Third Embodiment: A third embodiment will be described with reference to FIGS. 4, 5 and 1. In this embodiment, when the displacement due to the Coriolis force is measured as a change in the electric capacity in the first time zone, a dedicated electrode pair provided separately from the vibrating body driving electrode pair for detecting the Coriolis force is used. The voltage is detected and the voltage is simultaneously applied to the detection electrode pair as in the case of the first embodiment.

The structure of the vibrating gyroscope of this embodiment is shown in FIG. 4 (plan view) and FIG. 5 (cross-sectional view). Reference numeral 13 (a portion where the shaded color is light) is an oscillating mass made of polysilicon, and is supported by the first supporting portion 12 (thin beam-shaped portion) also made of polysilicon. The first support portion 12 is connected to a connection portion 17 (a substantially square frame-shaped portion with a light shaded color) reinforced by a truss structure, and is in the x-axis direction (up and down direction in the figure).
Is displaceable and has sufficient rigidity in the y-axis direction (left and right). Reference numeral 28 denotes a high-concentration diffusion layer (a shaded portion having a dark shade), which is located behind a shaded portion in a direction perpendicular to the paper surface. A comb-teeth electrode 18 is formed on the side of the vibrating mass 13, and the vibrating mass is moved to x by electrostatic attraction.
Drive vibration in the axis (vertical) direction. A comb-teeth-shaped electrode is formed on the outer side of the connection portion 17, and the capacitance between the comb-teeth-shaped counter electrode connected to the fixed portion 14 and the vibrating mass 1 is generated.
A pair of detection electrodes 16a for detecting the displacement in the y-axis (left-right) direction of 3 is configured. The distance between the comb-teeth electrodes of the detection electrodes 16a is not uniform and the arrangement thereof is as shown in FIG.
As shown in FIG. 11, d1 << d2 is set so that each pair of opposing comb-teeth electrodes does not electrically interfere with each other. In each fixed part, each support part and the comb-shaped electrode are shown in FIG. 5 (b) or FIG. 5 (c).
As shown in FIG. 3, the metal wiring 26 is electrically connected via the high-concentration diffusion layer 28 or the polysilicon wiring 27.
Reference numeral 28 denotes an electrode formed of a high-concentration diffusion layer for stabilizing the potentials of the oscillating mass 13 and the first and second supporting portions, and is electrically connected to the metal wiring 26 similarly to the fixed portion 14. The metal wiring 26 is connected to a signal input / output pad or a peripheral circuit for driving or signal processing formed on the same substrate (the metal wiring, the pad and the peripheral processing circuit are omitted for simplification of the drawing). did). The respective members are electrically connected as shown by the solid line in FIG. The potential of each member is shown as Vm, Vd1, Vd2, Vs1, Vs2, Vs. Usually, the electrode 2 formed of a high-concentration diffusion layer for stabilizing the potential Vm of the oscillating mass 13 and the first and second supporting portions.
The potential Vs of 8 is the same as Vm.

FIG. 1 shows a block diagram of a vibrating gyro drive and Coriolis force detection circuit in this embodiment. In the figure, the portion surrounded by the dotted line corresponds to the oscillating mass, which is connected to the common potential VL. Cd1 and Cd2 are electric capacities between the driving electrode facing the vibrating mass and the vibrating mass, and are connected to the driving power source 21 via the reference capacitance Cr2 and a driving voltage is applied thereto. Since the impedance of the electric capacitance is expressed by the following formula (2) Zc = 1 / jωC (2), if Cr2 is made sufficiently larger than the electric capacitances Cd1 and Cd2 between both drive electrodes and the oscillating mass, the drive voltage The loss in Cr2 is almost negligible. Practically Cd
Since the values of 1 and Cd2 are about pF, it is easy to realize Cr2 even on the same substrate. Cd1, Cd2 and reference capacity Cr2
The potentials Vd1 and Vd2 at the connection point with are input to the demodulator 24 via the buffer 25 and demodulated using the output of the driving power supply 21. The demodulated signal is amplified to a predetermined value by an amplifier and becomes a feedback signal for controlling the output amplitude of the driving power supply.

When the influence of the stray capacitance on Vd1 and Vd2 cannot be ignored, the structure shown in FIG. 7 may be used. Reference numeral 29 is a guard electrode, for example, as shown in FIG.
Is electrically connected via the polysilicon film 27,
It can be realized by forming a high-concentration diffusion layer immediately below it.

The driving voltage is applied as shown in the time charts of FIGS. 1 (b) and 1 (c). The driving voltage is composed of a voltage vd for generating a driving force and a reading voltage vc for detecting displacement of the vibrating mass. vd and vc are applied alternately. In the drawing, a time interval of 0V application is provided between vd and vc application, but the essential function is the same even if this time interval is not provided. The driving voltage is the electric capacitances Cd1 and Cd2 between the driving electrode and the oscillating mass that generate driving forces in opposite directions.
Further, the read voltage vc is applied to both drive electrodes at the same time in opposite phases during a time interval τ when vd is not applied to both drive electrodes. The read voltage vc is shown in Fig. 1 (b).
The pulse may be a unipolar pulse with respect to VL, or a bipolar pulse with respect to VL, as shown in FIG.

With respect to the potential Vm of the vibrating mass 13, the vibrating mass 13 supported by the first supporting portion 12 is moved in the x-axis (vertical) direction by alternately applying the driving voltage to the drive electrode ends Vd1 and Vd2. Vibration drive. The resonance frequency fxr of the oscillating mass in the x-axis direction is determined by the mass of the oscillating mass and the spring constant of the first supporting part in the x-axis direction because the second support 15 has sufficient rigidity in the x-axis direction. Therefore, the resonance state can be easily realized by electrically adjusting the applied frequency of the driving power source 21.

Cs1 and Cs2 are electric capacities between the detection electrodes facing the vibrating mass and the vibrating mass, which are connected to the detection power source 22 (OSC3) via the reference capacity Cr1 and the displacement reading voltage C of the vibrating mass is obtained. Is being applied. In the figure, the read voltage C is the same signal synchronized with the driving voltage vc,
There is essentially no problem with different signals. Cs1, Cs2
The potentials Vs1 and Vs2 at the connection point between the reference capacitor Cr1 and the reference capacitor Cr1 are input to the demodulator 24 via the buffer 25 and demodulated using the output of the detection power supply 22. The demodulated signal is amplified to a predetermined value by an amplifier and output.

When the influence of the stray capacitance on Vs1 and Vs2 cannot be ignored, the configuration shown in FIG. 7 may be used. In the figure, reference numeral 29 denotes a guard electrode, which can be realized, for example, by electrically connecting from the fixing portion 14 through the polysilicon film 27 as shown in FIG. 5C, and forming a high-concentration diffusion layer immediately below it. Is.

In the third embodiment, the following effects can be obtained in addition to the effects obtained in the first embodiment. As shown in FIG. 5C, the electrical connection from the fixing portion 14 is changed to the polysilicon film 27.
By forming the high-concentration diffusion layer 29 in the substrate portion immediately below the polysilicon film 27 and setting it as the guard potential, it is possible to reduce the capacitive coupling between the signal extraction wiring and the substrate. It is possible to reduce mixing of external noise due to routing of the signal extraction wiring.

Fourth Embodiment: A fourth embodiment will be described with reference to FIGS. 4, 5 and 2. In this embodiment, when reading the displacement of the vibrating mass, a voltage is applied to the vibrating body. Also in this embodiment, a Coriolis force detecting electrode pair is provided separately from the vibrating mass driving electrode pair. A block diagram of the drive and detection circuit of the vibration gyroscope in this embodiment is shown in FIG. In the figure, the portion surrounded by the dotted line corresponds to the oscillating mass, which is connected to the detection power source 22 (OSC3). Cd1,
Cd2 is an electric capacitance between the driving electrode facing the oscillating mass and the oscillating mass, and the driving power source 21 (O
It is connected to SC1) and a driving voltage is applied. Since the impedance of the electric capacitance is expressed by the following formula (2) Zc = 1 / jωC (2), if Cr2 is made sufficiently larger than the electric capacitances Cd1 and Cd2 between both drive electrodes and the oscillating mass, the drive voltage The loss in Cr2 is almost negligible. Practically Cd
Since the values of 1 and Cd2 are about pF, it is easy to realize Cr2 even on the same substrate. Cd1, Cd2 and reference capacity Cr2
The potentials Vd1 and Vd2 at the connection point with are input to the demodulator 24 via the buffer 25 and demodulated using the output of the driving power supply 21. The demodulated signal is amplified to a predetermined value by an amplifier and becomes a feedback signal for controlling the output amplitude of the driving power supply.

When the influence of the stray capacitance on Vd1 and Vd2 cannot be ignored, the configuration shown in FIG. 7 may be used. 29
Is a guard electrode, for example, as shown in FIG.
This can be realized by making electrical connection from 4 through the polysilicon film 27 and forming a high-concentration diffusion layer directly thereunder.

The driving voltage is applied as shown in the time charts of FIGS. 2 (b) and 2 (c). The driving voltage is composed of the voltage vd for generating the driving force. The driving voltage has opposite phases to the driving electrodes that generate driving forces in opposite directions and the electric capacitances Cd1 and Cd2 between the oscillating masses, and there is a time interval τ in which the voltage vd is not applied to both driving electrodes. Is applied so that The read voltage vc is the time interval τ
It is applied to the oscillating mass 13 from the power source 22 for detection. The read voltage vc may be a unipolar pulse with respect to VL as shown in FIG. 2B or a bipolar pulse with respect to VL as shown in FIG. 2C. In the figure, the read voltage vc is applied with the pulse width τ during the time interval τ, but the essential function is the same even if the pulse width is τ or less.

With respect to the potential Vm of the vibrating mass 13, the driving voltage is alternately applied to the driving electrode ends Vd1 and Vd2 to vibrate and drive the vibrating mass 13 supported by the first support portion 12 in the x-axis direction. . Resonance frequency fx of the vibrating mass in the x-axis direction
r is determined by the mass of the oscillating mass and the spring constant of the first support portion in the x-axis direction, because the second support portion has sufficient rigidity in the x-axis direction. Therefore, the resonance state can be easily realized by electrically adjusting the applied frequency of the driving power source 21.

Cs1 and Cs2 are electric capacities between the detection electrode facing the vibrating mass and the vibrating mass, and are connected to the common potential VL via the reference capacity Cr1. The potentials Vs1 and Vs2 at the connection point between Cs1 and Cs2 and the reference capacitor Cr1 are input to the demodulator 24 via the buffer 25 and demodulated using the output of the detection power supply 22 (OSC3). The demodulated signal is amplified to a predetermined value by an amplifier and output.

When the influence of the stray capacitance on Vs1 and Vs2 cannot be ignored, the configuration shown in FIG. 7 may be used. 29
Is a guard electrode, for example, as shown in FIG.
This can be realized by making electrical connection from 4 through the polysilicon film 27 and forming a high-concentration diffusion layer directly thereunder.

The effects of the fourth embodiment differ from those of the third embodiment in the following points. A voltage is applied to the comb electrodes to drive the oscillating mass by electrostatic attraction, and Coriolis force detection and read voltage vc is oscillated by the detection power supply 22 within a time interval τ when vd is not applied to both drive electrodes. Applied to mass 13. Therefore, the electrostatic attractive forces generated by vc in both drive electrodes of the vibrating mass 13 cancel each other out, so that the vibration amplitude of the vibrating mass can be accurately measured by sufficiently increasing the amplitude of vc without affecting the vibration state. Can be detected.

[0041]

As described above, according to the present invention, a silicon substrate is processed by an anisotropic etching technique, and other LSI techniques are applied to form a vibrating body and electrodes, and a vibrating body is formed. An electrode pair for driving and exciting and an electrode pair for monitoring the vibration state of the vibrating body (further, an electrode pair for detecting Coriolis force)
Since the same electrode pair is used for and, and a special electrode pair specially designed for Coriolis force detection is used, a sufficiently large voltage can be applied, so it is small, lightweight, easy to mass-produce, and highly accurate. A vibrating gyro was obtained.

[Brief description of drawings]

FIG. 1 is a schematic circuit diagram for explaining first and third embodiments of the present invention.

FIG. 2 is a schematic circuit diagram for explaining second and fourth embodiments of the present invention.

FIG. 3 is a diagram for explaining the structures of the first and second embodiments of the present invention.

FIG. 4 is a plan view for explaining the structures of the third and fourth embodiments of the present invention.

FIG. 5 is a cross-sectional view for explaining the structures of the third and fourth embodiments of the present invention.

FIG. 6 is a diagram for explaining a detection electrode unit according to third and fourth embodiments of the present invention.

FIG. 7 is a diagram for explaining means for preventing the influence of stray capacitance in the third and fourth embodiments of the present invention.

FIG. 8 is a diagram for explaining an example of a conventional vibrating gyro.

[Explanation of symbols]

1, 1a ... Silicon substrate 2 ... Glass pedestal 3 ... Piezoelectric element 4 ... Vibration monitoring electrode 5 ... Detection electrode 6 ... Vibrating beam 7 ... Driving power supply 8 ... Buffer 9 ... Amplifier 10 ... Demodulator 11 ... High-concentration diffusion layer 12 ... 1st support part 13 ... Oscillating mass 14 ... Fixed part 15 ... 2nd support part 16, 16a ... Detection electrode 17 ... Connection part 18 ... Comb-shaped electrode 19 ... Passivation film 20 ... Oxide film 21 ... Driving power supply OSC1 22 ... Detection Power supply OSC3 23 ... Amplifier 24 ... Demodulator 25 ... Buffer 26 ... Metal wiring 27 ... Polysilicon wiring 28 ... Electrode 29 formed of high-concentration diffusion layer ... High-concentration diffusion layer 30 for guard potential ... Support

Claims (3)

(57) [Claims] Claim: What is claimed is: 1. When a plane including the vibration direction of a vibrating body vibrating in a constant direction is rotated around an axis existing on the plane and orthogonal to the vibrating direction, Coriolis force acting on the vibrating body is generated. A method for driving a vibrating gyroscope, which detects and measures the angular velocity of the rotation, includes an electrode pair arranged on each side of the vibrating body opposite to the vibrating body, and the vibrating body is electrostatically charged. Drive vibration by attractive force
Alternating between the vibrating body and the electrode pair for movement.
Drive voltage at a specific frequency to the electrode pair, and
The first time zone where no voltage is applied to any of the
For reading the driving vibration amplitude of the vibrating body in one hour
Voltage is applied to the electrode pair at the same time or applied to the vibrating body.
Change in electrical capacitance between the electrode pair and the vibrating body read out
To read out the excitation vibration amplitude of the vibrating body by
A method for driving a vibrating gyro , wherein the electrode pair is also used for monitoring the excitation state of the vibrating body and is controlled so that the excitation state of the vibrating body is always constant. 2. A vibration direction of a vibrating body vibrating in a fixed direction.
Exists on this plane and is orthogonal to the vibration direction
Coriolis acting on the vibrating body when rotating around the axis
The force of the rotation is detected and the angular velocity of the rotation is measured.
In a method of driving a vibrating gyroscope, the vibrating gyroscopes are arranged on opposite sides of the vibrating body so as to face the vibrating body.
And a pair of electrode pairs arranged on the opposite side of the vibrating body to alternately excite the vibrating body by electrostatic attraction. A first time zone in which a driving voltage is applied at one frequency and a voltage is not applied to any of the electrode pairs is provided, and an electric capacitance between the vibrating body and each of the electrode pairs is provided in the first time zone. A carrier voltage for reading is applied to the vibrating body, and the vibration state of the vibrating body is monitored by the electric capacitance between the read vibrating body and each of the electrode pairs .
Also, the above-mentioned electrode pair is also used for monitoring the excitation state of the vibrating body.
Control so that the excitation state of the vibrating body is always constant
A method for driving a vibrating gyro, which is characterized in that 3. The first frequency of the drive voltage alternately applied between the vibrating body and the electrode pair arranged on the opposite side of the vibrating body is the same as the resonance frequency of the vibrating body. The method for driving a vibration gyro according to claim 2 .