JPH07239232A - Drive detection circuit for piezoelectric vibration gyroscope - Google Patents

Abstract

PURPOSE:To obtain constant detection sensitivity regardless of temperature by connecting a temperature compensation circuit containing a thermistor to the detection terminal of a piezoelectric vibrator and compensating the fluctuation of the output voltage from the vibrator. CONSTITUTION:In a high temperature state of 80 deg.C, for example, the resistances of thermistor 13 and 14 become small and therefore, due to the voltage dividing effect with a voltage dividing circuit with a parallel circuit of a resistor 15 in a temperature compensation circuit and a thermistor 13 and a resistor 17 and a voltage dividing circuit with a parallel circuit of a resistor 16 and a thermistor 14 and a resistor 18, the input voltage of a differential amplifier circuit 19 and an additional amplifier circuit 20 become relatively large. And the decrease of the output voltage from the piezoelectric vibrator is to be corrected. It is reversed in low temperature state below 0 deg.C. Thus, stable detection sensitivity not affected by the environmental temperature change can be obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a so-called piezoelectric vibrating gyroscope using ultrasonic vibration of a piezoelectric vibrator, and more particularly to a so-called piezoelectric vibrating gyroscope, which is used in a gyroscope used for a camera-integrated VTR to prevent camera shake and a navigation system of an automobile. The present invention relates to a drive detection circuit for self-exciting drive of a piezoelectric vibrator and obtaining a detection signal of a rotational angular velocity.

[0002]

2. Description of the Related Art A piezoelectric vibrating gyro is a gyroscope that utilizes a mechanical phenomenon in which a Coriolis force is generated in a direction perpendicular to the vibrating direction when a rotating angular velocity is applied to a vibrating object. When one of the vibrations is excited and the vibrator is rotated, the Coriolis force causes a force to act in a direction perpendicular to the vibration, and the other vibration is excited. The magnitude of this vibration is proportional to the magnitude of the vibration on the input side and the rotational angular velocity, so with the input voltage kept constant,
The magnitude of the rotational angular velocity can be obtained from the magnitude of the output voltage proportional to the magnitude of this vibration.

FIG. 3 is a schematic structural view of a piezoelectric vibrator used in a piezoelectric vibrating gyro. In FIG. 3, six strip-shaped electrodes 2 to 7 (5 and 6 not shown) are formed parallel to the length direction at positions where the circumference is divided into six equal parts on the outer peripheral surface of the piezoelectric ceramic cylinder 1. There is. The six strip-shaped electrodes 2 to 7 are connected to the connection electrodes 8a to 8b at both ends thereof every other one along the circumference. These strip electrodes 2 to 7 are directly formed around the piezoelectric ceramic cylinder 1 by screen printing, or after an electrode film is formed on the entire surface by plating or the like,
It is easily manufactured by removing unnecessary portions other than the electrodes by photoetching.

FIG. 4 is a cross-sectional view of the piezoelectric vibrator. Of the six strip-shaped electrodes 2 to 7, every other earth terminal 2, 4 and 6 is provided along the circumference, and one strip-shaped electrode 3 is a driving terminal and the remaining two strip-shaped electrodes 5, 5. 7 is a detection terminal. In the following description, they will be referred to as ground terminals 2, 4, 6, drive terminal 3, and detection terminals 5, 7.

FIG. 5 is a circuit example of a drive detection circuit used in a conventional piezoelectric amplitude gyro.
9, an addition amplification circuit 20, a synchronous detection circuit 21, and a phase shift circuit 22. In FIG. 5, the detection terminal 5
And 7 are connected to the input terminal of the summing amplifier circuit 20, and the output voltage of the summing amplifier circuit 20 is applied to the drive terminal 3 via the phase shift circuit 22 to oscillate at the resonance frequency of the bending vibration of the piezoelectric ceramic cylinder 1. It constitutes an excitation oscillation drive circuit.

On the other hand, the detection terminals 5 and 7 are simultaneously connected to the input terminal of the differential amplifier circuit 19, and an AC voltage having an amplitude proportional to the rotational angular velocity is obtained at the output terminal of the differential amplifier circuit 19. By inputting the output voltage of the differential amplifier circuit 19 and the output voltage of the addition amplifier circuit 20 to the synchronous detection circuit 21, it is possible to obtain a DC voltage having a polarity according to the rotation direction and proportional to the rotational angular velocity. That is, the differential amplifier circuit 19 and the synchronous detection circuit 21 act as a detection circuit.

[0007]

By the way, when the conventional drive detection circuit shown in FIG. 5 is used, the mechanical sharpness Q of the piezoelectric vibrator changes with the ambient temperature, so that the drive terminal 3 is driven. Even if the drive voltage is constant, the output of the piezoelectric vibrator changes, and as a result, the detection sensitivity of the piezoelectric vibrating gyro is also affected by temperature.

An object of the present invention is to eliminate the above-mentioned drawbacks of the conventional piezoelectric vibration gyro drive detection circuit, and to provide a drive detection circuit in which the detection sensitivity of the piezoelectric vibration gyro is always constant and does not depend on temperature. To do.

[0009]

The present invention includes a drive terminal and a drive terminal.
A detection circuit including a differential amplifier circuit for inputting output voltages of the two detection terminals of the piezoelectric vibrator including one detection terminal;
In a piezoelectric vibrating gyro drive detection circuit having an oscillating circuit including a summing amplifier circuit for synthesizing the two output voltages and a phase shift circuit to give a drive signal to the drive terminal, a temperature is detected at a detection terminal of the piezoelectric vibrator It is characterized in that a compensation circuit is connected to compensate the fluctuation of the output voltage due to the temperature change of the piezoelectric vibration gyro.

[0010]

In the piezoelectric vibrating gyro, as the mechanical sharpness Q of the piezoelectric vibrator changes depending on the ambient temperature, the output voltage of the piezoelectric vibrator changes even if the drive voltage is constant. When using the piezoelectric vibration gyro drive detection circuit of the present invention,
By appropriately selecting the constants of the two resistors and the thermistor connected to each of the two detection terminals, the resistance value of the temperature compensation circuit changes with temperature, and even when the output voltage of the piezoelectric vibrator changes with temperature. The resistance value can be changed so as to compensate for the change. Therefore, the piezoelectric vibration gyro using the piezoelectric vibration gyro drive detection circuit of the present invention can always obtain a constant detection sensitivity without being affected by the temperature change.

[0011]

Embodiments of the present invention will be described below with reference to the drawings. 1 and 2 show two examples of a piezoelectric vibration gyro drive detection circuit using the temperature compensation circuit of the present invention. In FIG. 1, the output of the phase shift circuit 22 is connected to the drive terminal 3 of the piezoelectric vibrator. Figure 3 for a piezoelectric vibrator
The same piezoelectric vibrator as shown in is used.

The mechanical sharpness Q of the piezoelectric vibrator depends on the ambient temperature, and the temperature characteristic of the mechanical sharpness Q affects the output voltage (output voltage of the detection terminals 5 and 7) of the piezoelectric vibrator. For example, even if the driving voltage (input voltage of the driving terminal 3) is constant, the mechanical sharpness Q becomes small in a high temperature state of about 70 to 80 ° C., and the output voltage of the piezoelectric vibrator also becomes small accordingly. . As a result, the detection sensitivity of the piezoelectric vibration gyro decreases. On the other hand, the opposite is true in the low temperature state of 0 ° C. or lower. Further, when a load resistor is connected to the detection terminal of the piezoelectric vibrator, the detection sensitivity increases as the load resistance value increases, and conversely, the detection sensitivity decreases as the load resistance value decreases, when the drive voltage is constant.

Therefore, as shown in FIG. 1, a resistor 15 is inserted and connected to the output line of the detection terminal 5 of the piezoelectric vibrator, and the thermistor 1 having a negative temperature coefficient is connected in parallel to the resistor 15.
3, the resistor 16 is inserted and connected to the output line of the detection terminal 7, and the thermistor 14 having a negative temperature coefficient is connected in parallel to the resistor 16. Further, a resistor 17 is connected between one end of the resistor 15 on the side opposite to the detection terminal 5 and a reference voltage source (not shown), and similarly, a resistor 18 is also provided between the resistor 16 and the reference voltage source. Connected.

In order to make these circuits act as a temperature compensating circuit, when the output voltage of the piezoelectric vibrator changes with temperature, the resistance value of the temperature compensating circuit is changed so as to correct the change in the output voltage. It is necessary to let
Here, the thermistors 13, 14 and resistors 15, 16, 1
By properly selecting the constants 7 and 18, the resistance value of the temperature compensation circuit can have an arbitrary temperature characteristic corresponding to the temperature change of the output voltage.

For example, in a high temperature state of about 80 ° C., the output voltage of the piezoelectric vibrator in the conventional drive detection circuit, that is, the input voltage of the differential amplification circuit 19 and the addition amplification circuit 20 becomes small. On the other hand, when the piezoelectric vibration gyro drive detection circuit of the present invention is used, the thermistor 13,
Since the resistance value of 14 becomes small, the voltage compensating circuit of the temperature compensating circuit comprises a parallel circuit of the resistor 15 and the thermistor 13 and the voltage dividing circuit of the resistor 17, and a voltage dividing circuit of the parallel circuit of the resistor 16 and the thermistor 14 and the voltage dividing circuit of the resistor 18. Due to the pressure effect, the input voltage of the differential amplifier circuit 19 and the addition amplifier circuit 20 becomes relatively large, and the output voltage of the piezoelectric vibrator becomes small. The opposite is true in low temperature conditions such as 0 ° C. or lower.

In FIG. 2, a temperature compensation circuit using thermistors 23 and 24 having a positive temperature coefficient is connected between each of the detection terminals 5 and 7 and a reference voltage source (not shown). That is, between the detection terminal 5 and the reference voltage source,
Connect a series circuit of resistors 25 and 26, and
A thermistor 23 is connected in parallel with the resistor 27, a series circuit of resistors 27 and 28 is connected between the detection terminal 7 and the reference voltage source, and a thermistor 24 is connected in parallel with the resistor 27.
Also in this example, as in the case of FIG.
By appropriately selecting the constants of 3, 24 and each resistance, the resistance value of the temperature compensation circuit can have an arbitrary temperature characteristic corresponding to the temperature change of the output voltage. For example, when the temperature is high, the thermistors 23 and 24 have a positive temperature coefficient, so that the resistance value becomes large. That is, the resistance value of the temperature compensation circuit increases. As a result, the detection terminals 5,
The voltage at the connection point between the output line of 7 and the temperature compensation circuit rises, the input voltage of the differential amplification circuit 19 and the summing amplification circuit 20 increases, and the output voltage of the piezoelectric vibrator decreases. be able to. The reverse is true at low temperatures.

As described above, as a result of using the piezoelectric vibration gyro drive detection circuit using the temperature compensation circuit according to the present invention, stable detection sensitivity that is not affected by changes in ambient temperature can be obtained. Such a piezoelectric vibration gyro drive detection circuit according to the present invention is suitable for use in the range of approximately -20 ° C to 100 ° C.

[0018]

As described above, according to the present invention, a drive detection circuit for a piezoelectric vibration gyro that can always obtain a constant detection sensitivity without being affected by ambient temperature changes can be obtained, and a highly accurate piezoelectric vibration can be obtained. A gyro can be provided.

[Brief description of drawings]

FIG. 1 is a diagram showing a first example of a piezoelectric vibration gyro drive detection circuit of the present invention.

FIG. 2 is a diagram showing a second example of the piezoelectric vibration gyro drive detection circuit of the present invention.

FIG. 3 is a structural schematic diagram of a piezoelectric vibrator used in the present invention.

FIG. 4 is a cross-sectional view of the piezoelectric vibrator shown in FIG.

FIG. 5 is a diagram showing a conventional drive detection circuit for a piezoelectric vibration gyro.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Piezoelectric ceramics cylinder 2, 4, 6 Ground terminal (belt electrode) 3 Driving terminal (belt electrode) 5, 7 Detection terminal (belt electrode) 8a, 8b Connection electrode 19 Differential amplification circuit 20 Summing amplification circuit 21 Synchronous detection circuit 22 Phase shift circuit 13,14 Thermistor with negative temperature coefficient 23,24 Thermistor with positive temperature coefficient

Claims (3)

[Claims] 1. A detection circuit including a differential amplification circuit for inputting output voltages of the two detection terminals of a piezoelectric vibrator including a drive terminal and two detection terminals, and an addition amplification for combining the two output voltages. In a drive detection circuit for a piezoelectric vibration gyro having an oscillation circuit that includes a circuit and a phase shift circuit and supplies a drive signal to the drive terminal, a temperature compensation circuit is connected to the detection terminal of the piezoelectric vibrator, and a piezoelectric vibration gyro A drive detection circuit for a piezoelectric vibrating gyro, which is characterized by compensating for a change in the output voltage caused by a temperature change. 2. The piezoelectric vibrating gyro drive detection circuit according to claim 1, wherein the temperature compensation circuit is inserted and connected to output lines of the two detection terminals, respectively.
And a thermistor having negative temperature characteristics connected in parallel to these first and second resistors, respectively, and
A drive detection circuit for a piezoelectric vibration gyro, which includes a third resistance and a fourth resistance connected between each of the ends of the second resistor on the side opposite to the detection terminal and a reference voltage source. 3. The piezoelectric vibration gyro drive detection circuit according to claim 1, wherein the temperature compensation circuit is connected between each of the output lines of the two detection terminals and a reference voltage source. The temperature compensating section is composed of first and second resistors connected in series and a thermistor having a positive temperature characteristic connected in parallel to the first resistor. Drive detection circuit for piezoelectric vibration gyro.