JP3232638B2 - DC amplification circuit of piezoelectric 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 technique for correcting the temperature dependency of sensitivity in a piezoelectric vibrating gyroscope.

[0002]

2. Description of the Related Art As a conventional piezoelectric vibrating gyroscope, for example, there is one shown in FIG. Generally, when an angular velocity is applied to a vibrating object, a Coriolis force is generated in a direction perpendicular to the vibration direction. The vibrating gyroscope utilizes the above phenomenon. The vibrating gyroscope includes piezoelectric elements 12A and 12B for driving the vibrator bonded to the vibrator 11, and a voltage is applied from the oscillation circuit 14 to the piezoelectric elements 12A and 12B to vibrate the vibrator 11. Let it. When an angular velocity is applied in this state, the generated piezoelectric elements 13L and 13R are distorted by the generated Coriolis force, and electric charges are generated on the surfaces thereof. Since the directions of increase and decrease of the detection voltages of the piezoelectric elements 13L and 13R are in opposite phases, the outputs thereof are differentially amplified by the differential amplifier circuit 15, and the synchronous detection circuit 1
After the synchronous detection in step 6, the DC speed is amplified by the DC amplifier circuit 17 to detect the angular velocity. FIG. 11 is a diagram showing an output signal waveform of each block in FIG. Further, as shown in FIG. 12, a type in which the vibrator has a triangular prism is also known. In FIG. 12, 21 is a vibrator, 2
2 is a piezoelectric element, 23L and 23R are detection piezoelectric elements, 24
Is an oscillation circuit, 25 is a differential amplifier circuit, 26 is a synchronous detection circuit, 27 is a DC amplifier circuit, and the operation principle is the same as that of FIG.

[0003]

In the conventional piezoelectric vibrating gyroscope as described above, the piezoelectric element has a piezoelectric constant d _31.
, The detection sensitivity changes as the temperature changes. As means for correcting the temperature characteristic of the detection sensitivity, for example, as shown in FIG. 3, there is a circuit for performing temperature correction using a series circuit of a fixed resistor 44 and a thermistor 43 as a feedback resistor of a DC amplifier circuit. However, in such a circuit, as shown by the one-dot chain line 6 in FIG. 7, the increase in the amplification factor due to the increase in the resistance of the thermistor becomes large in the low temperature region, and therefore, as shown by the one-dot chain line 6 in FIG. There is a problem that the sensitivity becomes extremely large and the temperature characteristic as a whole deteriorates. Further, as shown in FIG. 4, a circuit in which a fixed resistor 71 is connected in parallel with the thermistor 43 is conceivable in order to suppress the above-mentioned increase in resistance in a low-temperature region. In this case, the circuit is indicated by a broken line 7 in FIG. like,
There is a problem in that the correction effect in the normal temperature range becomes small, and the fluctuation in sensitivity cannot be suppressed to a small value. The details of FIGS. 3 to 7 will be described in detail in the section of Examples.

SUMMARY OF THE INVENTION The present invention has been made to solve the problems of the prior art as described above, and includes a low temperature range, a normal temperature range,
It is an object of the present invention to provide a DC amplification circuit of a piezoelectric vibrating gyroscope that can reduce the temperature change width of sensitivity in the entire high temperature range.

[0005]

Means for Solving the Problems In order to achieve the above object, the present invention is configured as described in the claims. That is, in the present invention, a series circuit of a fixed resistor and a first temperature correction thermistor is inserted into a feedback loop of a DC amplifier circuit, and a second circuit is provided between a reference potential Vs and an input terminal of an operational amplifier. A temperature correction thermistor is inserted. And the present invention
The resistance change rate of each thermistor with respect to temperature
Linear approximation and use temperature range of low temperature range, normal temperature range, high temperature
When separated from the temperature range, the slope of the straight line
The logarithmic value is higher than the second temperature correction thermistor by the first temperature.
Make the compensation thermistor larger and
Asymptote of linear approximation in the temperature region and asymptotic line approximation in the low temperature region
The temperature at which the lines intersect is higher than that of the second temperature compensation thermistor.
Make sure that the first temperature compensation thermistor is higher.
That is, the temperature at which the temperature change rate of the resistance value significantly changes is the first temperature.
Temperature compensation thermistor
I have.

[0006]

Normally, a fixed resistor (for example, 61 in FIG. 3) is connected between the reference potential Vs and the input terminal of the operational amplifier. In the present invention, a second thermistor is used instead of the fixed resistor. Is used. Therefore, in the low temperature range,
When the resistance value of the first thermistor inserted in the feedback loop increases, the resistance value of the second thermistor also increases, so that a large increase in the amplification factor of the operational amplifier in a low temperature range can be suppressed. . Therefore, in the normal temperature range and the high temperature range, the sensitivity change due to temperature is suppressed by the first thermistor, and in the low temperature range, the excessive correction by the first thermistor is suppressed by the second thermistor as described above. The change in sensitivity can be reduced.

[0007]

FIG. 1 is a circuit diagram of an embodiment of the present invention. For example, a DC amplifier circuit corresponding to the DC amplifier circuit 17 in FIG. 10 is shown. In FIG. 1, one input terminal (+ terminal) of the operational amplifier 41 is connected to a DC signal (for example, FIG. 10) obtained from the output of the piezoelectric vibrating gyroscope.
Output of the synchronous detection circuit 16). The other input terminal (− terminal) of the operational amplifier 41 and the output terminal 46
Between them, an integration capacitor 42 and a series circuit of a fixed resistor 44 for signal amplification and a thermistor 43 for temperature correction are connected in parallel as a feedback loop. A thermistor 45 is inserted between the predetermined reference potential Vs and the other input terminal of the operational amplifier 41. The thermistor 45 has an action of suppressing an increase in the amplification factor in a low temperature range. The reference potential Vs determines an output potential when the angular velocity is zero.

FIGS. 2 to 4 are circuit diagrams for explaining the operation of FIG. 1. FIG. 2 is a circuit without temperature correction. FIG. 3 is a diagram showing a thermistor 43 for temperature correction in a feedback loop. FIG. 4 shows a circuit in which a fixed resistor 71 is connected in parallel to the thermistor 43 of FIG. FIG.
9 are temperature characteristic diagrams of the respective circuits of FIGS. 1 to 4, FIG. 5 and FIG. 6 are temperature characteristic diagrams of the overall sensitivity of the piezoelectric element of the vibrating gyroscope and the DC amplifier circuit, and FIG. 7 and FIG. FIG. 9 is a temperature characteristic diagram of the resistance value of the thermistor in the amplification circuit.

The operation of the circuit of FIG. 1 will be described below with reference to FIGS. First, the temperature characteristic of the overall sensitivity when the DC amplifier circuit without temperature correction shown in FIG. 2 is used is as shown by a solid line 5 in FIG. In this case, the amplification factor of the DC amplifier circuit is such that the resistance value of the resistor 51 is R ₅₁ ,
When 2 of the resistance value is R _52, as shown in the following equation (1) below. (R ₅₁ + R ₅₂ ) / R ₅₂ (Equation 1) In this case, the overall sensitivity becomes a straight line as shown by the solid line 5 in FIG. 5, and changes in proportion to the temperature change.

Next, the temperature characteristic of the sensitivity when the temperature characteristic is corrected by adding the thermistor 43 to the feedback loop as shown in the circuit shown in FIG. 3 is shown by the one-dot chain line 6 in FIG. In this case, the amplification factor of the DC amplifier circuit is expressed by the following (Equation 2). (R ₄₃ + R ₄₄ + R ₆₁ ) / R ₆₁ (Equation 2) In the equation (Equation 2), the resistance R ₄₃ of the thermistor 43 is obtained.
9 changes as shown by the solid line in FIG. 9, so that the amplification factor represented by the equation (2) becomes smaller as the temperature becomes higher in the normal temperature range and the high temperature range as shown by the one-dot chain line 6 in FIG. Therefore, the temperature characteristics of the piezoelectric element can be corrected.
However, as can be seen from the characteristics of FIG. 9, the resistance value of the thermistor 43 becomes extremely large in the low temperature range, so that the amplification factor also becomes extremely large in the low temperature range as shown in FIG. Therefore, the overall sensitivity including the temperature characteristics of the piezoelectric element becomes a characteristic that sharply increases in a low temperature region as shown by a dashed line 6 in FIG.
When the entire low-temperature range, normal-temperature range, and high-temperature range are considered, the change width of the sensitivity does not decrease much as compared with before the correction.

Next, as shown in FIG. 4, in a circuit in which a fixed resistor 71 is connected in parallel to the thermistor 43 of FIG. 3 to suppress the resistance increase of the thermistor 43 in a low temperature range,
The amplification factor is as shown in the following (Equation 3).

[0012]

(Equation 3)

The characteristic of the above equation (3) is as shown by a broken line 7 in FIG. That is, in this case, the rapid increase in the low temperature range is suppressed, but the rate of change in the normal temperature range and the high temperature range is also suppressed.
As shown by the broken line 7 in FIG. In other words, the characteristics in the low temperature range are better than when only the thermistor 43 is used, but the characteristics in the normal temperature range and the high temperature range are worse than when only the thermistor 43 is used.

Next, in the circuit of the present invention shown in FIG. 1, the sensitivity change rate in the normal temperature range and the high temperature range is suppressed to be equal to that of the thermistor 43 alone, and a sharp increase in the sensitivity in the low temperature range is suppressed. Therefore, a thermistor 45 is inserted instead of a fixed resistor between the reference potential Vs and the input terminal (-terminal) of the operational amplifier 41. The amplification factor in this case is represented by the following (Equation 4), assuming that the resistance of the thermistor 45 is R ₄₅ . (R ₄₃ + R ₄₄ + R ₄₅ ) / R ₄₅ (Equation 4) If the temperature characteristic of the resistance of the thermistor 45 is as shown by the broken line in FIG. 9, the characteristic of the equation (4) becomes the broken line in FIG. 4
Therefore, the overall sensitivity is as shown by the broken line 4 in FIG. As can be seen from FIG. 8, in the circuit of FIG. 1, a sharp increase in the sensitivity in the low-temperature region is suppressed as compared with the characteristic of the circuit in FIG. Can be suppressed to be equivalent to the circuit of FIG. Therefore, the change width of the sensitivity can be reduced over the entire range.

A good result can be obtained by setting the characteristics of the thermistors 43 and 45 as follows.
That is, as shown in the characteristic of FIG. 9, when the resistance change rate of the thermistor with respect to the temperature is linearly approximated, the thermistor 43 has a larger absolute value of the inclination of the straight line in the normal temperature region and the high temperature region than the thermistor 45. So that the temperature at which the asymptote of the linear approximation in the high temperature region and the asymptote of the linear approximation in the low temperature region intersect becomes higher in the thermistor 43 than in the thermistor 45, that is, the temperature change of the resistance value. The temperature at which the rate changes significantly is set to be higher in the thermistor 43.

[0016]

As described above, according to the present invention, the first thermistor is inserted into the feedback loop of the operational amplifier for temperature compensation of the sensitivity, and the resistance of the thermistor in the low temperature region is reduced. A second thermistor is connected between the reference potential Vs and the input terminal of the operational amplifier in order to suppress a sharp increase in sensitivity due to an increase in the sensitivity temperature in the normal temperature range and the high temperature range. The rate of change can be suppressed as small as the correction method using a single thermistor, and the temperature change width of sensitivity in a low temperature range can be greatly reduced. Therefore, the change width of sensitivity over a wide temperature range should be small. Can be obtained.

[Brief description of the drawings]

FIG. 1 is a circuit diagram of an embodiment of a DC amplifier circuit according to the present invention.

FIG. 2 is a circuit diagram of an example of a DC amplifier circuit without a temperature correction function.

FIG. 3 is a circuit diagram of a DC amplification circuit using a thermistor in a feedback loop.

FIG. 4 is a circuit diagram of a DC amplifier circuit in which a fixed resistor is connected in parallel to a thermistor.

FIG. 5 is a temperature characteristic diagram of the overall sensitivity when the DC amplifier circuits of FIGS. 2 to 4 are used;

FIG. 6 is a temperature characteristic diagram of the overall sensitivity when the DC amplifier circuits of FIGS. 1 and 3 are used.

FIG. 7 is a temperature characteristic diagram of an amplification factor in the DC amplifier circuits of FIGS. 3 and 4;

FIG. 8 is a temperature characteristic diagram of an amplification factor in the DC amplifier circuits of FIGS. 1 and 3;

FIG. 9 is a temperature characteristic diagram of the resistance value of the thermistor.

FIG. 10 is a circuit diagram of an example showing an entire configuration of a conventional piezoelectric vibrating gyroscope.

11 is a signal waveform diagram in FIG.

FIG. 12 is a circuit diagram of another example showing the entire configuration of a conventional piezoelectric vibrating gyroscope.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 11 ... Transducer 12A, 12B ... Piezoelectric element 13L, 13R ... Detection piezoelectric element 14 ... Oscillation circuit 15 ... Differential amplifier circuit 16 ... Synchronous detection circuit 17 ... DC amplifier circuit 21 ... Vibrator 22 ... Piezoelectric element 23L, 23R ... Piezoelectric element for detection 24 Oscillation circuit 25 Differential amplification circuit 26 Synchronous detection circuit 27 DC amplification circuit 41 Operational amplifier 42 Capacitor 43 Thermistor 44 Resistor 45 Thermistor 46 Output terminals 51, 52, 61, 71 ... resistance

Continuation of the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) G01C 19/56 G01P 9/04 H03F 1/30

Claims (1)

(57) [Claims] 1. A direct current obtained from an output of a piezoelectric vibrating gyroscope.
Current signal to one input terminal of the operational amplifier,
A reference potential is applied to the input terminal, and the other input terminal
DC with feedback loop connected between output terminal
In the amplifying circuit, a fixed resistance and a first temperature correction are added to the feedback loop.
Insert a series circuit with the thermistor for
Between the input terminal and the other input terminal.
Insert MisterAnd Linear approximation of the rate of change of resistance with respect to temperature for each of the above thermistors
The temperature range to be used is divided into low temperature range, normal temperature range, and high temperature range.
The absolute value of the slope of the straight line in the normal temperature range and high temperature range
The first temperature compensation thermistor is more than the second temperature compensation thermistor.
-Ensure that the mister is larger and
Asymptote of linear approximation intersects asymptote of linear approximation in low temperature region
The first temperature is higher than that of the second temperature compensating thermistor.
So that the temperature correction thermistor is higher,
The temperature at which the temperature change rate of the resistance value changes significantly is the first temperature compensation.
The thermistor is set to be higher Specially
DC amplification circuit of piezoelectric vibrating gyroscope.