JP2000292172A - Driving and detecting device for piezoelectric vibrator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide the driving and detecting device for piezoelectric vibrator which enables the piezoelectric vibrator to output an output current with a constant amplitude without using an automatic gain control means. SOLUTION: When a driver resistance RD is interposed between a drive means 27 and a piezoelectric vibrator 11, a driving voltage VC can be determined by the division ratio of the drive resistance RD and the internal resistance Z of the piezoelectric vibrator 11. When the output current I1 tends to decrease at high temperature, the internal resistance Z increases and the drive voltage VC can be set large, so that the mechanical amplitude of the piezoelectric vibrator 11 increases. The decrease of the output current I1 due to the increase in the internal loss of the piezoelectric vibrator 11 is therefore compensated. At low temperature, the internal resistance Z becomes small and the drive voltage VC drops to the contrary, so the mechanical amplitude can be made small. The increase of the output current I1 of the piezoelectric vibrator 11 can be compensated. Namely, no AGC circuit is needed, so the trouble of an AGC circuit can be eliminated.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a driving and detecting device for a piezoelectric vibrator used in a gyroscope or the like, and more particularly to a driving and detecting device for a piezoelectric vibrator capable of operating in a stable state against a temperature change. It relates to a detection device.

[0002]

2. Description of the Related Art FIG. 8 is a block diagram showing a circuit configuration of a conventional gyroscope. FIG. 9 shows an input voltage signal of an oscillating means (output voltage of an automatic gain adjusting means). 10 shows the output of the gyroscope corresponding to FIGS. 9A and 9B when a disturbance occurs, FIG. 11A shows the case where there is no disturbance, B shows the case where a disturbance occurs, and FIG. 11 shows the resistance of the internal impedance of the piezoelectric vibrator. FIG. 12 shows a temperature characteristic of a component (internal resistance), and FIG. 12 shows a temperature characteristic of an output current of the piezoelectric vibrator.

As shown in FIG. 8, the circuit configuration of the gyroscope detects an angular velocity from a driving system that applies a predetermined driving vibration to the piezoelectric vibrator 1 to vibrate the piezoelectric vibrator 1 and a Coriolis force generated in the piezoelectric vibrator 1. And a detection system.

The control system comprises I / V (current / voltage) conversion means 2A and 2B, binarization means 3A and 3B, and phase difference detection means 4. The phase difference detecting means 4 includes a phase comparator 4a, 4b, a low-pass filter 4,
c, 4d, differential amplifier 4e and low-pass filter 4f
It is composed of

On the other hand, the driving system comprises an AGC circuit (automatic gain adjusting means) 5, a PLL (phase locked loop) 6, a low-pass filter 7, and a driving means 8, and the AGC circuit 5 comprises an amplitude detector. The PLL 6 includes a low-pass filter 6a, a VCO (voltage controlled oscillator) 6b, and a frequency divider 6c. The PLL 6 includes an amplitude reference voltage generator 5b, a differential amplifier 5c, and an amplitude adjuster 5.

The piezoelectric vibrator 1 is, for example, a tripod tuning fork type vibrator. When a predetermined AC drive signal (drive signal) S is supplied from the drive means 8 to the drive electrode, each vibrator is driven to vibrate. The output currents I1 and I
2 is output. When the piezoelectric vibrator 1 is placed in a rotating system, a Coriolis force acts on the piezoelectric vibrator 1 and a phase difference occurs between the output currents I1 and I2.

The output currents I1 and I2 are equal to I /
The output voltages V1 and V2 are output from the V conversion means 2A and 2B.
The output voltages V1 and V2 are output to the binarization means 3A and 3B and the AGC circuit 5, respectively.
In the binarization means 3A and 3B, based on a predetermined reference voltage,
The output voltages V1 and V2 are converted into digital signals D1 and D2 having pulse widths proportional to their own pulse widths, and these digital signals D1 and D2 are output to the phase difference detecting means 4.

In the phase difference detecting means 4, the phase comparators 4a, 4a
At 4b, a signal is generated by comparing the reference signal ref output from the frequency divider 6c of the PLL 6 with each of the digital signals D1 and D2, and these compared signals are added (added signal) and input to the PLL 6. . In PLL6,
Based on this addition signal, the reference signal ref is shifted by a predetermined phase (for example, π) from the midpoint of the phase difference between the digital signals D1 and D2.
The VCO 6b is oscillated so as to be delayed by (/ 2).

In the AGC circuit 5, the piezoelectric vibrator 1
The control signal S0 is adjusted so that the output currents I1 and I2, which are the outputs of the above, always have a constant amplitude. That is,
The first stage amplitude detector 5a of the AGC circuit performs amplitude detection on the signal obtained by adding the output voltages V1 and V2. The differential amplifier 5c obtains a difference signal between the signal after the detection and the reference signal generated by the reference voltage generating means 5b, amplifies the difference signal, and outputs the amplified signal to the amplitude adjuster 5d.
The amplitude adjuster 5d generates a control signal S0 in which the amplitude of the reference signal ref output from the PLL 6 is adjusted based on the difference signal. The control signal S0 has a low-pass filter 7 from which excess high-frequency components are removed, and the drive means 8 generates a final drive signal S for driving the piezoelectric vibrator 1 based on the control signal S0.

When the gyroscope constructed as described above is placed in a certain rotation, the Coriolis force F is applied to the piezoelectric vibrator 1.
Occurs. This Coriolis force F is expressed as F = 2 · m (v ×
ω). Here, m is the mass of the piezoelectric vibrator 1 and v
Is a vibration speed (vector value) of the piezoelectric vibrator 1 in the vibration direction, ω is an angular velocity (vector value), and X is a vector product. The Coriolis force F causes the output current I
1 and I2, a phase difference λ occurs.

In the detection system of the gyroscope, a phase difference detecting means 4 detects a phase difference λ between the digital signals D1 and D2, and detects this phase difference as a DC voltage output V.
Output as out. This DC voltage output Vout is an output proportional to the angular velocity ω generated in the rotating system. Then, this angular velocity ω (DC voltage output Vout) is time-integrated in, for example, a navigation body equipped with a gyroscope, and the angle θ is obtained.

[0012]

In order to drive the piezoelectric vibrator 1 efficiently, it is ideal that the piezoelectric vibrator 1 is driven near a mechanical resonance point where the internal impedance of the piezoelectric vibrator 1 becomes minimum. However, the resistance component (internal resistance) Z of the internal impedance of the piezoelectric vibrator 1 has the characteristic that it changes depending on the temperature as shown in FIG. In a general piezoelectric vibrator, there is a tendency that the higher the temperature, the higher the internal impedance Z, and the lower the temperature, the lower the internal impedance Z. Therefore, in this case, the internal loss of the piezoelectric vibrator 1 becomes higher at higher temperatures, and lower at lower temperatures.

On the other hand, as shown in FIG. 12, the output currents I1 and I2 of the piezoelectric vibrator 1 have such characteristics that they become smaller at high temperatures and larger at low temperatures. For this reason, the amplitudes of the output voltages V1 and V2 after the voltage conversion are output smaller at higher temperatures and larger at lower temperatures.

Therefore, in the circuit configuration of the conventional gyroscope, even when the temperature changes, the output voltage V1
The amplitude of the AC drive signal S is adjusted using the AGC automatic gain adjustment means 5 so that the amplitudes of V and V2 are stabilized.

However, as shown in FIG. 9A, for example, when an impulse disturbance N composed of a high frequency component is applied to the output voltage of the automatic gain adjusting means 6, the output of the automatic gain adjusting means 6 becomes as shown in FIG. 9B. Behavior. That is, the disturbance N is removed from the output voltages V1 and V2 by the noise removing means 3, but the automatic gain adjusting means 6 causes the sine wave output to temporarily become non-output state (time t).

Therefore, as shown in FIG. 10B, the output Vout of the gyroscope is not directly affected by the high-frequency disturbance, but is affected by the no-signal generated by the automatic gain adjusting means 6 on the output Vout. The adverse effect of appearing occurs.

If the automatic gain adjusting means 6 itself is removed in order to prevent such an adverse effect of the automatic gain adjusting means 6, the amplitudes of the output voltages V1 and V2 fluctuate with a change in temperature. There is a problem that the output Vout tends to be unstable.

If the internal impedance Z of the piezoelectric vibrator 1 has a temperature change, the relationship between the temperature and the internal impedance is determined in advance, and this relationship is stored as temperature correction data. Is detected by a temperature sensor such as a thermistor, the correction data is read for each detected temperature, and the oscillating means 2 is controlled based on the data. However, in general, a temperature sensor cannot be directly attached to a piezoelectric vibrator, so that only a temperature near the temperature sensor can be detected. Therefore, the temperature of the place where the temperature sensor is installed is different from the actual temperature of the piezoelectric vibrator 1, and it is difficult to accurately control the amplitude of the output current of the piezoelectric vibrator 1.

An object of the present invention is to solve the above-mentioned conventional problems, and to drive and detect a piezoelectric vibrator capable of outputting a constant amplitude output current without using an automatic gain adjusting means. It is intended to provide a device.

The present invention also provides a piezoelectric vibrator driving and detecting apparatus for driving a piezoelectric vibrator capable of always outputting an output current having a constant amplitude even when the internal impedance of the piezoelectric vibrator changes in temperature. It is intended to provide.

[0021]

According to the present invention, there is provided a piezoelectric vibrator having a temperature characteristic in which an internal impedance and an output current change according to a rise in temperature, and a drive means for supplying an AC drive signal to the piezoelectric vibrator. And an I / V conversion means for converting an output current of the piezoelectric vibrator into an output voltage. A driving and detecting device for a piezoelectric vibrator, wherein a temperature is increased between the piezoelectric vibrator and the driving means. Sometimes, the drive voltage applied to the piezoelectric vibrator is increased to prevent a decrease in the output current of the piezoelectric vibrator, and when the temperature drops, the drive voltage of the piezoelectric vibrator is reduced to reduce the output of the piezoelectric vibrator. A drive resistor for preventing an increase in current and keeping the amplitude of the output current constant is inserted.

According to the present invention, there is provided a piezoelectric vibrator having a positive temperature characteristic in which the internal impedance increases as the temperature rises and a negative temperature characteristic in which the output current decreases as the temperature rises. And a drive unit for supplying an AC drive signal to the piezoelectric vibrator and an I / V conversion unit for converting an output current of the piezoelectric vibrator into an output voltage. Between the means, the drive voltage applied to the piezoelectric vibrator when the temperature rises is increased to prevent a decrease in the output current of the piezoelectric vibrator, and the drive voltage for the piezoelectric vibrator when the temperature falls And a drive resistor for preventing the output current of the piezoelectric vibrator from increasing and keeping the amplitude of the output current constant is inserted.

According to the present invention, the positive temperature characteristic and the negative temperature characteristic of the piezoelectric vibrator, that is, the positive temperature characteristic of the piezoelectric vibrator that the internal impedance rises when the temperature rises and falls when the temperature falls. Characteristics and
Focusing on the negative temperature characteristic of the piezoelectric vibrator that the output current decreases when the internal impedance is large and increases when the internal impedance is small, and compensates for the negative temperature characteristic with the positive temperature characteristic. Even when a change occurs, it is possible to prevent the output current from changing.

In general, when the drive voltage directly applied to the piezoelectric vibrator is increased, the output current increases because the mechanical amplitude of the piezoelectric vibrator increases. When a drive resistor is inserted between the piezoelectric vibrator and the drive means, the internal impedance (internal resistance) Z of the piezoelectric vibrator and the drive resistance R _D
And the division ratio Z / (R _D + Z) is established. Since the internal impedance (internal resistance) Z of the piezoelectric vibrator has a positive temperature characteristic, when the temperature rises, the division ratio Z /
(R _D + Z) can be increased, and when the temperature decreases, the division ratio Z / (R _D + Z) can be reduced. Therefore, for example, when the input voltage (drive signal voltage) between the internal impedance Z of the piezoelectric vibrator and the drive resistance _RD is constant, the internal impedance of the piezoelectric vibrator itself changes with temperature. It is possible to self-adjust the drive voltage directly applied to the motor. That is, when the temperature is high, the driving voltage increases, so that the mechanical amplitude of the piezoelectric vibrator increases, thereby making it possible to compensate for the decrease in the output current. Conversely, when the temperature decreases, the drive voltage also decreases, so the mechanical amplitude of the piezoelectric vibrator decreases,
The output current can be prevented from increasing.

For example, the division ratio between the drive resistance R _D and the resistance component Z of the internal impedance is Z / (R _D + Z)
When the resistance component Z changes with a positive temperature characteristic, the drive resistance R _D becomes equal to the division ratio Z / (R _D + Z).
Is preferably set in the range of 1/15 to 1/2.

If the drive resistance R _D is set in such a range, if the voltage value V _{S of the} general drive signal _S (peak voltage 2 to 15 volts) is used, the piezoelectric vibrator The drive voltage can be adjusted by the internal impedance Z of the piezoelectric vibrator 11 changed by the temperature, and the output current can be kept constant.

[0027]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing a drive system and a detection system of the piezoelectric gyroscope, FIG. 2 is a perspective view showing a piezoelectric vibrator used in the piezoelectric gyroscope, and FIG.
FIG. 3 is a front view of the piezoelectric vibrator viewed from a direction III.

The block diagram shown in FIG. 1 has a piezoelectric vibrator (piezoelectric tuning fork) 11 as a center, and a drive system for driving the piezoelectric vibrator 11 and an output current output from the piezoelectric vibrator 11 are detected. And a feedback control system in which a part of the detection system returns to the drive system.

As shown in FIG. 2, for example, the piezoelectric vibrator 11 is made of a plate made of a constant elastic material such as an elinvar with a piezoelectric material laminated on both front and back surfaces, or a plate made of a piezoelectric material such as PZT or quartz. The vibrating legs 11u, 11v, and 11w are formed at the tip of the piezoelectric vibrator 11 in a branched manner.

As shown in FIG. 2 and FIG.
On one surface (+ Y side) of 1u, 11v and 11w,
Drive electrodes 11a, 11b, 11c, 11d, 11e, 1
1f are printed. On the other surface (−Y side), output electrodes 1 corresponding to the respective drive electrodes are provided.
1a ', 11b', 11c ', 11d', 11e ', 1
1f 'are printed. The drive electrodes 11a, 11b, 1
When a sinusoidal AC drive signal (drive signal) S is given to 1c, 11d, 11e and 11f, the vibration leg 11
u, 11v, and 11w are driven to vibrate in the X direction (+ X and -X directions) in which the vibrating legs are arranged by the piezoelectric effect.

Each of the vibrating legs 11u, 11v and 11w is
Bending deformation vibration is generated in the X direction in the first or several modes. The vibrating legs 11u and 11w on both sides are driven in the same phase, and the center vibrating leg 11v is
And 11w are driven so as to have a phase difference of π (180 degrees). That is, when the direction of the amplitude of the vibrating legs 11u and 11w on both sides at a certain point is the + X direction, the amplitude direction of the central vibrating leg 1v is the -X direction.

When the piezoelectric vibrator 11 is placed in a rotation system around the Z axis in the state of being driven as described above, Coriolis in a direction perpendicular to the direction of vibration is applied to each of the vibrating legs 11u, 11v and 11w. A force is applied to each of the vibrating legs 11u, 1
1v and 11w vibrate in the Y direction. Vibration components due to this Coriolis force also have opposite phases between the vibrating legs 11u and 11w on both sides and the central vibrating leg 11v. When the vibrating legs 11u and 11w on both sides have an amplitude component in the + Y direction due to Coriolis force at a certain point in time, the center vibrating leg 11v has an amplitude component in the −Y direction.

As shown in FIG. 1, a detection system is provided downstream of the piezoelectric vibrator 11. The detection system includes I / V (current / voltage) conversion means 12 and 12 'for converting the sine-wave output currents I1 and I2 into sine-wave output voltages V1 and V2, and converts the sine-wave output voltages V1 and V2 into digital signals. D1, D
Binarization means 13 and 13 'for converting to 2;
The circuit comprises phase comparators 14 and 14 'comprising EXor1 and EXor2 gate circuits and the like, low-pass filters 15 and 15', differential amplifier 16 and low-pass filter 17, and the like.

On the other hand, a drive system is configured in front of the piezoelectric vibrator 11. The drive system is a low-pass filter 22, V
It comprises a CO (voltage controlled oscillator) 23, a frequency dividing means 24, an amplitude stabilizing means 25, a secondary low-pass filter 26 and a driving means 27. And dividing means 2
4 is used as a reference signal ref.
4, 14 '. Note that the low-pass filter 22, the VCO (voltage controlled oscillator) 23 and the frequency dividing means 2
4 constitutes a PLL (Phase Lock Loop). In this PLL, the divided reference signal re
The VCO 23 oscillates so that f is delayed by π / 2 from the center of the phase difference between the outputs of the phase comparison means 14 and 14 '.

FIG. 4 is a circuit diagram of a piezoelectric gyroscope driving device showing an embodiment of the present invention, FIG. 5 is an equivalent circuit diagram of the piezoelectric gyroscope driving device of FIG. 4, and FIG. 6 is driving of a piezoelectric vibrator. FIG. 7 is a diagram illustrating a temperature characteristic of a driving voltage applied directly to an electrode, and FIG. 7 is a diagram illustrating a temperature characteristic of an output current of a piezoelectric vibrator.

FIG. 4 is a block diagram of FIG. 1 in which the piezoelectric vibrator 11 and the drive means 27 provided at the preceding stage and the two I / V converting means 12 and 12 provided at the subsequent stage of the piezoelectric vibrator 11 are shown. 'Is shown more specifically. The I / V conversion means 12 and the I / V conversion means 12 '
Since the functions are the same, the following mainly describes the I / V conversion means 1
2 will be described.

As shown in FIG. 4, the drive means 27
For example, it comprises an inverting amplifier circuit mainly composed of an operational amplifier 27A such as an operational amplifier. The output terminal 27c of the drive unit 27 is connected to each of the vibrating legs 11u of the piezoelectric vibrator 11,
11v and 11w drive electrodes 11a, 11b, 11
c, 11d, 11e and 11f are connected via a drive resistor _RD .

On the other hand, the I / V converters 12 and 12 'are composed of operational amplifiers 12A and 12B such as operational amplifiers. In the I / V conversion means 12, 12 ', inverting input terminals (-terminals) 12a, 12a of the operational amplifiers 12A, 12B.
a 'and the output electrode 11c', 1 of the center vibrating leg 11v.
1d 'are connected to each other. The inverting input terminals 12a, 12a 'and the output terminals 12c, 12c' are connected via predetermined resistors Rf, Rf, respectively.
The non-inverting input terminals 12b and 12b 'are connected to the reference potential V0.
(For example, 0 volt). In addition, I / V
The input impedance of the conversion means 12, 12 'is almost zero. The output current I1 output from the output electrode 11c 'of the vibrating leg 11v is output from the output voltage V
The output voltage V1 is V1 = −Rf ·
I1. Similarly, a relationship of V2 = −Rf · I2 is established between the output current I2 and the output voltage V2.

The other vibrating legs 1 of the piezoelectric vibrator 11
1u and 11w output electrodes 11a ', 11b', 11
e 'and 11f' are connected to the reference potential V0.

The operation of the driving device for a piezoelectric gyroscope will be described below. As shown in FIG.
The signal oscillated by 23 is frequency-divided by frequency dividing means 24 so as to have a predetermined driving frequency, and input to amplitude stabilizing means 25. The amplitude stabilizing means 25 adjusts the amplitude of the drive signal S to be constant regardless of the power supply voltage fluctuation.
The frequency-divided signal whose amplitude has been adjusted in this way is converted into a sine wave by removing the high frequency by the low-pass filter 26, and the inverted terminal (− terminal) 27 a of the drive unit 27 is provided.
Is input as a control signal S0.

In the drive means 27, a drive signal S is generated by amplifying the control signal S0, and this drive signal S is applied to each drive electrode 11a, 11b, 11c, 11d of the piezoelectric vibrator 11 via a drive resistor _RD. , 11e and 11f.

When the drive signal S is supplied, each of the vibrating legs 11u, 11v and 11w of the piezoelectric vibrator 11 starts vibrating as described above. Then, output currents I1 and I2 are detected from output electrodes 11c 'and 11d' of vibrating leg 11v. When a gyroscope having such a piezoelectric vibrator 11 is placed in a rotating system, each vibrating leg 1
Because 1u, 11v and 11w have Coriolis forces,
A phase difference corresponding to the angular velocity occurs between the output currents I1 and I2.

As shown in FIG. 5, the internal impedance (internal resistance) Z of the piezoelectric vibrator 11, the voltage V _S of the drive signal S, and the drive voltage V _C applied directly to the piezoelectric vibrator 11
Between, represented by _{V C = V S · Z /} (R D + Z). However, the reference potential V0 is set to 0 volt. At this time, the output current of output electrode 11c 'is changed to I1 and I / V
The converted output voltage is assumed to be V1.

As described above, when the temperature of the piezoelectric vibrator 11 increases, the internal loss in the piezoelectric vibrator 11 increases (see FIG. 11), so that the internal impedance Z also increases. As a result, the amplitude of the output current I1 flowing out of the output electrode 11c 'of the piezoelectric vibrator 11 (flowing into the I / V conversion means 12) decreases, so that the output voltage V after the I / V conversion is reduced.
1 also decreases. Conversely, when the temperature of the piezoelectric vibrator 11 decreases, the internal loss in the piezoelectric vibrator 11 decreases, so that the internal impedance Z also decreases. Therefore, I
Since the amplitude of the output current I1 flowing into the / V conversion means 12 increases, the amplitude of the output voltage V1 after the I / V conversion also increases. That is, in this gyroscope detection system,
The output voltage V1 has a negative temperature characteristic in which the amplitude is small at high temperatures and large at low temperatures.

On the other hand, as shown in FIG. 6, in the drive system of the gyroscope, when the temperature of the piezoelectric vibrator 11 increases,
Since the division ratio Z / (R _D + Z) comprising the internal impedance Z of the piezoelectric vibrator 11 and the drive resistance _RD increases, the drive voltage V _C applied to the drive electrode of the piezoelectric vibrator 11 increases. Therefore, the mechanical amplitude of the piezoelectric vibrator 11 increases. When the temperature of the piezoelectric vibrator 11 decreases, the internal impedance Z of the piezoelectric vibrator 11 decreases, and the division ratio Z /
(R _D + Z) also decreases. Therefore, in this case, the drive voltage V _C is also reduced, and the mechanical amplitude of the piezoelectric vibrator 11 is reduced.

That is, in this gyroscope drive system, the drive voltage V _C applied to the drive electrode of the piezoelectric vibrator 11
However, it has a positive temperature characteristic that it is large at high temperatures and small at low temperatures.

In the above detection system, when the output current I1 tends to decrease at a high temperature due to the negative temperature characteristic of the detection system and the positive temperature characteristic of the drive system, the piezoelectric vibrator 11 is large in the drive system. It is possible to compensate for a decrease in the output current I1 due to an increase in the internal loss of the piezoelectric vibrator 11 because the operation is performed with an appropriate amplitude. When the output current I1 tends to increase at a low temperature, the piezoelectric vibrator 11 can be operated with a small mechanical amplitude in the drive system. It is possible to make up for it.

That is, by inserting the drive resistor _RD , in the drive system of the gyroscope, the drive voltage V _C applied to the drive electrode of the piezoelectric vibrator 11 is set high at high temperature, and the mechanical Since the amplitude can be increased, the output current I1 which tends to decrease in the detection system
Can be increased to secure a constant amplitude. At a low temperature, the drive voltage V _C of the piezoelectric vibrator 11 is set low in the drive system, and the mechanical amplitude of the piezoelectric vibrator 11 can be reduced. Therefore, the output current I1, which tends to increase in the detection system, is reduced to be constant. Can be secured.

For example, the peak voltage of the drive signal S of the drive means 27 is 4 [V], and the drive resistance is 47 [K].
Ω], the internal resistance Z of the internal impedance of the piezoelectric vibrator at −20 ° C. shown in FIG.
Ω], the division ratio is Z / (R _D + Z) = 4
× 10 ³ / (4 + 47) × 10 ³ ≒ 0.08. Therefore, as shown in FIG. 6, the driving voltage V _C is V _C = 0.08 × 4
= 0.32 [V]. And, as shown in FIG.
At this time, the output current I1 is about I1 = 8 [μA].

Further, since the internal resistance Z of the piezoelectric vibrator 11 at 80 ° C. shown in FIG. 11 is about Z = 19 [KΩ], the division ratio is Z / (R _D + Z) = 19 × 10 ³ / (19+
47) × 10 ³ ≒ 0.29. Therefore, as shown in FIG. 6, the driving voltage V _C is V _C = 0.29 × 4 = 0.16
[V]. The output current I1 at this time shown in FIG. 7 is about I1 = 6.1 [μA]. From these facts, the output current I1 can be set to a substantially constant value without largely changing.

In this example, the division ratio Z / (R _D + Z) is
It is 0.08 at low temperature (−20 ° C.) and at high temperature (80 ° C.).
° C), which is 0.29, so that the drive resistance is selected with some margin, if the division ratio Z / (R _D + Z) is selected to be set at about 1/15 to 1/2. It turns out to be good. However, this division ratio is determined by the drive means 27
When the voltage V _{S of the} drive signal supplied from the controller changes, the drive voltage V _C directly applied to the piezoelectric vibrator 11 also changes, but the range of the general input power supply voltage (for example, 2 [v] to 15 [V])
[V]), the above-mentioned division ratio Z / (R _D +
It can be said that the setting range 1/15 to 1/2 of Z) is almost appropriate.

As described above, when the drive resistor _RD is inserted between the drive means 27 and the piezoelectric vibrator 11, FIG.
The output currents I1 and I1 over a wide temperature range as shown in FIG.
2 can be set to a constant amplitude.
The output voltages V1 and V2 after V conversion can be set to a constant amplitude.

As described above, the output voltages V1 and V2 always output as a constant amplitude without being affected by the temperature change.
Are converted into digital signals D1 and D2 having pulse widths proportional to the pulse widths of the output voltages V1 and V2 by the binarizing means 13 and 13 '. Then, the phase comparison means 14 and 14 'provide the reference signal ref and the digital signal D
1 and the exclusive OR output of the reference signal ref and the digital signal D2, and their inverted outputs, and by adding the output signals to each other, the output current I1 and I2 And outputs a pulse signal corresponding to the phase difference. The low-pass filters 15 and 15 'convert the pulse output corresponding to the phase difference into a DC voltage signal by integrating and smoothing the pulse output. The differential amplifying means 16 obtains the differential amplified output of the DC voltage signals of the low-pass filters 15 and 15 ', thereby obtaining the output currents I1 and I1.
The DC voltage output Vout is proportional to the phase difference between the two, that is, the angular velocity ω.

In the above embodiment, the phase control is performed by using the PLL circuit. However, the present invention is not limited to this. For example, a CR sine wave oscillation circuit mainly including an operational amplifier may be used. May be used.

[0055]

According to the present invention described in detail above, a drive resistor is inserted between the drive means and each drive electrode of the piezoelectric vibrator without using an automatic gain adjustment means such as an AGC circuit as in the prior art. Since the amplitude of the output current can be kept constant by simply performing the operation, the circuit configuration can be simplified.

Further, since the automatic gain adjusting means (AGC circuit) need not be used, no adverse effect is caused by the automatic gain adjusting means itself when a disturbance is input.

Further, even when the internal impedance of the piezoelectric vibrator changes in temperature, the amplitude of the output voltage of the I / V conversion means can be kept constant. Therefore, a highly accurate angular velocity can be detected from the output voltage.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a circuit configuration of a piezoelectric gyroscope.

FIG. 2 is a perspective view showing a piezoelectric vibrator used for a piezoelectric gyroscope;

FIG. 3 is a front view of the piezoelectric vibrator of FIG. 2 as viewed from a direction III.

FIG. 4 is a circuit diagram of a driving and detecting device for a piezoelectric vibrator according to an embodiment of the present invention;

5 is an equivalent circuit diagram of the driving and detecting device of the piezoelectric vibrator of FIG. 4,

FIG. 6 is a diagram showing a temperature characteristic of a driving voltage.

FIG. 7 is a diagram showing a temperature characteristic of an output current of the piezoelectric vibrator;

FIG. 8 is a block diagram showing a conventional driving device for a piezoelectric vibrator for a gyroscope.

FIG. 9 shows an input voltage signal of the oscillation means (output voltage signal of the automatic gain adjustment means), where A is when there is no disturbance, B is when there is disturbance,

10A and 10B show outputs of the gyroscope corresponding to FIGS. 9A and 9B, where A is when there is no disturbance, B is when there is disturbance,

FIG. 11 is a diagram showing a temperature characteristic of a resistance component of an internal impedance of the piezoelectric vibrator;

FIG. 12 is a diagram showing a temperature characteristic of an output current of the piezoelectric vibrator;

[Explanation of symbols]

11 Piezoelectric vibrator 12, 12 'I / V (current / voltage) conversion means 13, 13' Binarization means 14, 14 'Phase comparison means 27 Drive means _RD Drive resistance I1, I2 Output current V1, V2 Output voltage V _S drive signal voltage V _C drive voltage S drive signal Z resistance component of the internal impedance of the piezoelectric vibrator (internal resistance)

Claims (3)

[Claims] 1. A piezoelectric vibrator having a temperature characteristic in which an internal impedance and an output current change in accordance with a rise in temperature, a drive means for applying an AC drive signal to the piezoelectric vibrator, and an output current of the piezoelectric vibrator. And an I / V conversion means for converting a voltage into an output voltage. A driving and detecting device for the piezoelectric vibrator, wherein a voltage is applied between the piezoelectric vibrator and the driving means when the temperature rises. The drive voltage of the piezoelectric vibrator is increased to prevent the output current of the piezoelectric vibrator from decreasing, and when the temperature decreases, the drive voltage of the piezoelectric vibrator is reduced to prevent the output current of the piezoelectric vibrator from increasing, thereby reducing the output current. A drive and detection device for a piezoelectric vibrator, wherein a drive resistor for maintaining a constant output current amplitude is inserted. 2. A piezoelectric vibrator having a positive temperature characteristic in which the internal impedance increases as the temperature rises and a negative temperature characteristic in which the output current decreases as the temperature rises. Drive means for providing a drive signal;
I / V for converting an output current of the piezoelectric vibrator into an output voltage
A driving and detecting device for a piezoelectric vibrator comprising: a converting means, wherein a driving voltage applied to the piezoelectric vibrator when the temperature rises is increased by increasing a driving voltage between the piezoelectric vibrator and the driving means. The output voltage of the piezoelectric vibrator is prevented from decreasing, and the drive voltage of the piezoelectric vibrator is reduced when the temperature drops, thereby preventing the output current of the piezoelectric vibrator from increasing and keeping the amplitude of the output current constant. A drive and detection device for a piezoelectric vibrator in which a drive resistor is inserted. 3. A division ratio between the drive resistance _RD and the internal resistance Z of the internal impedance is Z / ( _RD + Z).
When the internal resistance Z changes with a positive temperature characteristic, said drive resistor R _D is the value of the division ratio Z / (R _D + Z) 1
The piezoelectric vibrator driving and detecting device according to claim 1 or 2, wherein the driving frequency is set in a range of / 15 to 1/2.