JP2002372420A - Vibration gyroscope drive detection circuit - Google Patents

Abstract

(57) [Problem] To provide a drive detection circuit for a vibration gyro in which the sensitivity of the vibration gyro is optimized and the size thereof is reduced. SOLUTION: A self-excited oscillation circuit 105 is connected to a load resistor 104.
And the driving efficiency of the piezoelectric vibrator defined based on a signal applied to the internal resistance of the piezoelectric vibrator 101, and the capacitance between the drive detection electrode 102 and the common electrode 103 of the piezoelectric vibrator. The drive detection efficiency obtained by multiplying the detection efficiency of the piezoelectric vibrator defined based on the signal detected by the internal resistance of the piezoelectric vibrator and the parallel resistance of the load resistance has a resistance value close to the drive detection efficiency. Then, the resistance value of the load resistance is selected.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a drive detection circuit for a vibration gyroscope for detecting a camera shake of a video camera or a digital still camera, for controlling an attitude of a vehicle, calculating a heading direction, and the like.

[0002]

2. Description of the Related Art Various gyroscopes (hereinafter abbreviated as gyroscopes) have been developed as sensors for detecting angular velocity. The types are roughly classified into mechanical type gyroscopes, fluid type gas rate gyroscopes, vibrating gyroscopes using vibrating sound bars and tuning forks, optical fiber gyroscopes, and ring laser gyroscopes. The optical gyro detects the Sagnac effect, and the others detect the angular velocity using the Coriolis force, which is a manifestation of the law of conservation of angular momentum of the rotating body. Sensor is selected.

A vibration gyro-type angular velocity sensor is disclosed in, for example, Japanese Patent No. 2780643. This patent publication relates to a vibrating gyroscope of a quadrangular prism sound piece type. The vibrator is a quadrangular prism sound piece having a bimetal structure using a piezoelectric substrate, and has electrodes formed on the main surface of the piezoelectric body. One electrode is used as a common electrode, and the other electrode is divided and used as a drive detection electrode serving both for driving and for detecting. In driving, a drive voltage from an oscillation circuit is applied to a drive detection electrode via a load resistor to excite drive vibration. On the other hand, the Coriolis force Fc is expressed as Fc = 2mv × Ω, where m is the mass, v is the vibration speed, and Ω is the rotational angular velocity. In this case, if the rotation axis is taken in the longitudinal direction of the prism, the Coriolis force is The force Fc is generated in a direction perpendicular to the driving vibration and parallel to the prism cross section. At this time, the Coriolis force is calculated by amplifying the difference between the charges generated in the divided electrodes. Another example is a triangular prism sound piece gyro disclosed in Japanese Patent Application Laid-Open No. H10-325727. In this publication, the vibrator is formed of a constant elastic metal such as an elinvar, and a piezoelectric body is adhered to the vibrator to excite driving vibration via a load resistor. The method of detecting the Coriolis force and using the load resistance is the same as in the case of Japanese Patent No. 2780643.

[0004]

SUMMARY OF THE INVENTION In a vibrating gyroscope mounted on a small home appliance, there is a strong demand for miniaturization. Therefore, various ingenuity is made even in the vibration gyro,
For example, a load resistance for exciting a driving vibration to a vibrator and detecting a charge generated by a Coriolis force is also used to reduce the number of circuit components and to use electrodes efficiently.

However, since the load resistance is also used, the sensitivity dependence on the drive side / detection side cannot be set optimally, and the sensitivity is dependent on the load resistance. .

The present invention has been made in view of such a problem, and an object of the present invention is to provide a drive detection circuit for a vibrating gyroscope in which the sensitivity of the vibrating gyroscope is optimized and the size is reduced.

[0007]

In order to achieve the above object, a drive detecting circuit for a first vibrating gyroscope according to the present invention comprises: a piezoelectric vibrator that bends and vibrates in at least a columnar or tuning fork shape; A drive detection electrode formed on one main surface and serving both as a function of exciting the piezoelectric vibrator and a function of detecting generated charges, a common electrode formed on the other main surface of the piezoelectric vibrator, and connected to the drive detection electrode A drive detection circuit for a vibrating gyroscope having a load resistance and a driving efficiency of the piezoelectric vibrator defined based on a signal applied to an internal resistance of the piezoelectric vibrator via the load resistance; Via the capacitance between the drive detection electrode and the common electrode of the vibrator, the detection efficiency of the piezoelectric vibrator defined based on the signal detected by the parallel resistance of the internal resistance and the load resistance of the piezoelectric vibrator and Drive detection efficiency To have a resistance value in the vicinity of the, wherein the resistance value of the load resistor is selected.

In order to achieve the above object, a drive detecting circuit for a second vibrating gyroscope according to the present invention includes a vibrator that bends and vibrates at least in a columnar or tuning fork shape, and is formed on the vibrator to excite the vibrator. A driving detection circuit of a vibrating gyroscope having a piezoelectric body also having a function of detecting generated electric charges and a load resistance connected to a surface electrode of the piezoelectric body. Based on the driving efficiency of the vibrator defined based on the applied signal and the signal detected by the parallel resistance of the internal resistance of the piezoelectric body and the load resistance via the capacitance between the surface electrodes of the piezoelectric body The resistance value of the load resistor is selected so as to have a resistance value near the maximum driving detection efficiency multiplied by the specified detection efficiency of the piezoelectric body.

According to the drive detecting circuit of the first or second vibrating gyroscope having the above configuration, the driving circuit is controlled under a constant driving voltage in consideration of an equivalent circuit including resonance of the piezoelectric vibrator or the piezoelectric body. The drive-side drive efficiency and the detection-side generated charge detection efficiency are obtained, and the overall drive-detection efficiency is determined by multiplying the two. The load resistance is determined so as to have a resistance value of the maximum value (-3 dB). This makes it possible to optimize the drive efficiency and the detection efficiency under the condition that the drive voltage is constant, and to reduce the size of the circuit.

In order to achieve the above object, a drive detecting circuit for a third vibrating gyroscope according to the present invention includes a piezoelectric vibrator that bends and vibrates at least in a columnar or tuning fork shape, and is formed on the piezoelectric vibrator and includes a piezoelectric vibrator. A drive detection circuit for a vibrating gyroscope having a drive detection electrode that combines the function of exciting the vibrator and detecting generated charges, and a load resistance connected to the drive detection electrode. Is determined by the ratio of the magnitude of the internal resistance of the piezoelectric vibrator to the magnitude of the load resistance, and the voltage applied to the piezoelectric vibrator is determined from the drive amplitude. The resistance value of the load resistor is selected so as to have a corresponding resistance value.

In order to achieve the above object, a fourth drive detecting circuit for a vibrating gyroscope according to the present invention comprises a vibrator that bends and vibrates at least in a columnar or tuning fork shape, and is formed on the vibrator to excite the vibrator. A drive detection circuit for a vibrating gyroscope having a piezoelectric body also having a function of detecting generated charges and a load resistance connected to a surface electrode of the piezoelectric body, wherein a ratio of a voltage applied to the piezoelectric body to a load resistance is Has a resistance value corresponding to a voltage near the maximum voltage that can be applied to the piezoelectric body, as determined by the ratio of the magnitudes of the internal resistance and the load resistance of the piezoelectric body, and the voltage applied to the piezoelectric body is determined from the drive amplitude. Thus, the resistance value of the load resistance is selected.

According to the drive detecting circuit of the third or fourth vibrating gyroscope having the above configuration, the voltage should be applied to the piezoelectric vibrator or the piezoelectric body based on the driving amplitude required for the piezoelectric vibrator or the vibrator. The voltage value is determined in advance, and the load resistance and the applied voltage to the piezoelectric vibrator or the piezoelectric element are proportional to the value of the load resistance and the internal resistance. Is determined, and the value of the load resistance is determined accordingly. For this reason, it is possible to detect the generated charge of the piezoelectric vibrator or the piezoelectric body with the load resistance showing the maximum efficiency under the condition where the drive amplitude is constant.

In order to attain the above object, a fifth aspect of the present invention provides a drive detecting circuit for a vibrating gyroscope, which comprises a piezoelectric vibrator that bends at least in a columnar or tuning fork shape, and a piezoelectric vibrator formed on the piezoelectric vibrator. A drive detection circuit for a vibrating gyroscope having a drive detection electrode serving both as a function of exciting the element and detecting a generated charge, and a load resistance connected to the drive detection electrode, wherein the load resistance, the internal resistance of the piezoelectric vibrator, And compare
If the value of the load resistance is large, the Coriolis force is detected based on the potential difference between both ends of the piezoelectric vibrator. If the value of the load resistance is small, the Coriolis force is detected based on the potential difference between both ends of the load resistance. It is characterized by the following.

In order to achieve the above object, a sixth aspect of the present invention provides a vibrating gyroscope drive detecting circuit which is formed at least in a columnar or tuning fork shape and vibrates, and which is formed on the vibrator to excite the vibrator. A driving detection circuit for a vibrating gyroscope having a piezoelectric body also having a function of detecting generated charges and a load resistance connected to a surface electrode of the piezoelectric body, and compares the load resistance with the internal resistance of the piezoelectric body. If the value of the load resistance is large, the Coriolis force is detected based on the potential difference between both ends of the piezoelectric body. If the value of the load resistance is small, the Coriolis force is detected based on the potential difference between both ends of the load resistance. It is characterized by the following.

According to the fifth or sixth driving detection circuit for the vibrating gyroscope having the above configuration, the leakage voltage from the driving side to the detection side at a desired load resistance is considered in consideration of the amount of leakage of the driving voltage to the output stage. Determine the installation position of the load resistance that reduces the load. For this reason, although the sensitivity on the detection side does not change, it is possible to improve the S / N ratio.

In order to achieve the above object, a drive detecting circuit for a seventh vibrating gyroscope according to the present invention includes a piezoelectric vibrator that bends and vibrates at least in a columnar or tuning fork shape, and is formed on the piezoelectric vibrator and includes a piezoelectric vibrator. At least two drive detection electrodes that also function to excite the element and detect generated charges, a load resistor connected to each of the drive detection electrodes, and a differential amplifier circuit connected to the drive detection electrode and the load resistor. And a drive detection circuit of a vibration gyro comprising: a drive detection electrode, each of the drive detection electrodes, the resistance value of each of the load resistance is selected so that the phase of the leakage signal of the drive voltage for excitation of the piezoelectric vibrator, Further, the differential amplifier circuit is characterized in that the leak signal is amplified at a ratio inversely proportional to the amplitude of each of the leak signals and the common signal is removed.

According to an eighth aspect of the present invention, there is provided a drive detection circuit for a vibrating gyroscope according to the present invention, wherein the vibrator vibrates at least in a columnar or tuning fork shape, and is formed on the vibrator to excite the vibrator. And at least two piezoelectric bodies that also have a function of detecting generated charges, a load resistance connected to each surface electrode of the piezoelectric body, and a differential connected to each surface electrode and the load resistance of each piezoelectric body. A driving detection circuit of a vibration gyro having an amplification circuit, wherein the resistance value of each load resistance is adjusted so that the phase of the leakage signal of the driving voltage for excitation of the vibrator matches at each surface electrode of the piezoelectric body. The differential amplifying circuit selects and amplifies the leakage signal at a ratio inversely proportional to the amplitude of each of the leakage signals and removes the same in phase.

According to the drive detecting circuit of the seventh or eighth vibrating gyroscope having the above configuration, the phase of the leakage signal of the drive voltage for vibrator excitation at the drive detecting electrode or the surface electrode of the piezoelectric body is matched. The value of each load resistance is adjusted. Therefore, by combining with a differential amplifier circuit having an amplification factor that is inversely proportional to the amplitude of each leakage signal, it is possible to remove in-phase the leakage signal of the driving voltage that is orders of magnitude larger than the detection signal corresponding to the Coriolis force. , S / N ratio can be greatly improved.

[0019]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below with reference to the drawings.

(First Embodiment) FIG. 1 is a schematic configuration diagram of a drive detection circuit for a vibrating gyroscope according to a first embodiment of the present invention.

In FIG. 1, reference numeral 101 denotes a quadrangular prism sound piece type piezoelectric vibrator, which is composed of a quadrangular prism (shown in cross section) in which a piezoelectric substrate whose polarization axis is directed in the opposite direction is bonded. 102 is
A drive detection electrode 103 formed on one main surface of the piezoelectric vibrator 101 and having both functions of exciting the piezoelectric vibrator 101 and detecting generated charges, and a drive detection electrode 103 is formed on the other main surface of the piezoelectric vibrator 101. Common electrode. Reference numeral 105 denotes a self-excited oscillation circuit of the piezoelectric vibrator 101, which applies an AC voltage between the drive detection electrode 102 and the common electrode 103 via a load resistor 104 to drive the piezoelectric vibrator 101. 1
Reference numeral 06 denotes a differential amplifier circuit, which is a divided drive detection electrode 1
The potential difference generated between 02 is detected.

In a vibration gyro, vibration is usually excited in a desired direction using resonance. In the present embodiment, vibration is excited in a direction perpendicular to the main surface of the piezoelectric vibrator 101 by applying an AC voltage between the drive detection electrode 102 and the common electrode 103. In this case, the detection axis of the angular velocity is along the longitudinal direction of the piezoelectric vibrator 101 (the direction perpendicular to the plane of FIG. 1), and the Coriolis force appears as vibration in a direction parallel to the main surface of the piezoelectric vibrator 101. The angular velocity is detected by calculating the vibration caused by the Coriolis force based on the potential difference between the divided drive detection electrodes 102. FIG. 1 is characterized in that the load resistor 104 is used for both driving and detecting.

In the present embodiment, the efficiency on the drive side and on the detection side when the piezoelectric vibrator 101 is driven in resonance under the condition that the drive voltage is constant is considered. FIG. 2 shows the piezoelectric vibrator 10.
1 is an equivalent circuit diagram of FIG. In FIG. 2, the left side shows the electrical characteristics, that is, the capacitance between the drive detection electrode 102 and the common electrode 103 (hereinafter, referred to as a parallel capacitance Cp). The right side shows the mechanical characteristics, which is an RLC series resonance circuit. Here, the resonance frequency of the piezoelectric vibrator 101 is determined by the L component and the C component, and the sharpness (Q factor) of the resonance is determined by the resistance component (hereinafter, referred to as the internal resistance rd).

FIG. 3 is a drive-side equivalent circuit diagram in which the equivalent circuit of the piezoelectric vibrator 101 of FIG. 2 is introduced into FIG. In FIG. 3, the output voltage from self-excited oscillation circuit 105 in FIG.
d, Assuming that the voltage applied to the piezoelectric vibrator 101 is V1, the voltage applied to the piezoelectric vibrator 101 during the resonance driving is represented by a circuit composed of a simple resistor and a capacitor as shown in FIG. Here, reference numeral 301 denotes a parallel resistance of the two load resistors 104 (hereinafter, referred to as a parallel load resistance, and the resistance value is RL /
2), 302 is the internal resistance rd of the piezoelectric vibrator, 30
3 is a parallel capacitance Cp.

In the driving-side equivalent circuit, the frequency characteristic of the voltage V1 with respect to the voltage Vd is a low-pass filter (hereinafter, referred to as a low-pass filter).
The LPF cutoff frequency (the frequency at which the amplitude becomes -3 dB) is determined by the drive frequency of the piezoelectric vibrator 101 and the equivalent circuit constant. Unaffected until MΩ order. Therefore, the voltage V1 applied to the piezoelectric vibrator 101 may be considered only by the resistance division of the parallel load resistance (RL / 2) and the internal resistance rd. On the other hand, since the Q factor of the driving vibration mode of the piezoelectric vibrator 101 is considered to be substantially constant unless the driving voltage becomes excessive, the driving amplitude Ad is considered to be proportional to the voltage V1 applied to the piezoelectric vibrator 101. Therefore, the driving efficiency KD is equal to the parallel load resistance 301.
(Resistance value: RL / 2) and a resistance division of the internal resistance rd, and as shown in FIG. 4, the load resistance (RL)
, The drive efficiency KD changes. Considering only the driving side, the condition that the resistance value RL of the load resistor 104 is sufficiently smaller than the internal resistance rd is a condition for increasing the driving efficiency KD.

Next, consider the generated charge detection efficiency KS on the detection side. If a Coriolis force is generated in the configuration of FIG. 1, a potential difference is generated between the divided drive detection electrodes 102 in the opposite phase. At this time, the generated charge is considered to appear in the branch representing the electrical characteristics in FIG. 2, so that the voltage V2 detected by the differential amplifier circuit 106 of the Coriolis force during resonance driving is equivalent to the equivalent circuit shown in FIG. Can be calculated from In FIG. 5, 50
1 is a generated potential difference source, 502 is a parallel capacitance Cp, 503 is a parallel load resistance (resistance value: RL / 2), and 504 is an internal resistance r.
d. That is, the equivalent circuit on the detection side is the load resistance R
When L is the horizontal axis, a high-pass filter (hereinafter referred to as HPF) determined by a parallel resistance of RL / 2 and rd and a parallel capacitance Cp.
). This HPF characteristic represents the detection efficiency KS and is shown in FIG.

Therefore, the overall drive detection efficiency KDS of the drive detection circuit is obtained as a product of the drive efficiency KD and the detection efficiency KS, and as shown in FIG. In FIG. 7, if the resistance value RL of the load resistance that maximizes the drive detection efficiency KDS is selected, the Coriolis force can be detected most efficiently. Actually, the dependency of the Coriolis force detection sensitivity on the load resistance under the condition that the drive voltage is constant also shows the same tendency as in FIG.

As described above, according to the first embodiment, the Coriolis force can be detected with the maximum efficiency under the condition that the drive voltage is fixed, so that the effect is great. The calculation of the equivalent circuit constant of the piezoelectric vibrator 101 includes a certain error. Therefore, for example, if the appropriate load resistance range RA is defined within the efficiency range of −3 dB from the maximum efficiency of FIG. 7 and the resistance value RL of the load resistance is selected within that range, the drive detection efficiency K
DS can be kept at a high level.

In the present embodiment, the drive detection electrode 1
02, only two electrodes are assumed. However, if one or three or more electrodes determine the optimum load resistance based on the same concept, the maximum load under the condition that the drive voltage is constant is the same as in the present embodiment. The Coriolis force can be detected by the load resistance indicating the efficiency.

In this embodiment, the piezoelectric vibrator 10
Although it is assumed that a prism-type resonating unit is used as 1, the shape of the resonating unit is a cylindrical resonating unit as long as the equivalent circuit of the vibrator can be represented as shown in FIG. There is no problem even if it has a tuning fork shape.

(Second Embodiment) FIG. 8 is a schematic configuration diagram of a drive detection circuit for a vibrating gyroscope according to a second embodiment of the present invention.

In FIG. 8, reference numeral 801 denotes a triangular prism sound piece type vibrator made of a constant elastic metal such as an elinvar. Reference numeral 802 denotes a detection piezoelectric body, which detects charges via a load resistor connected to an electrode (surface electrode) formed on the surface thereof. Reference numeral 803 denotes a driving piezoelectric body, 804 denotes a load resistor that also serves as drive detection, 805 denotes a self-excited oscillation circuit, and 806 denotes a differential circuit.

In the present embodiment, by applying an AC voltage to the surface electrode of the driving piezoelectric body 803, the driving piezoelectric body 8
Excitation is excited in the direction perpendicular to 03. In this case, the detection axis of the angular velocity is along the longitudinal direction of the vibrator 801 (the direction perpendicular to the plane of FIG. 8), and the Coriolis force appears as vibration in the direction parallel to the driving piezoelectric body 803. By calculating the vibration due to this Coriolis force from the potential difference between the two detection piezoelectric members 802, the angular velocity can be obtained.

FIGS. 8 and 1 are different from each other in the structure of the vibrator. However, when examining the electrical characteristics of the vibrator, the vibrator of FIG. 8 is also represented by the equivalent circuit of FIG. 2 as in FIG. It is possible to select the resistance value of the load resistance that shows the maximum efficiency under the conditions described above.

As described above, even if the structure of the vibrator is different, it is possible to select a load resistor exhibiting the optimum efficiency under the condition that the driving voltage is constant, as long as it is represented by an electrically similar equivalent circuit. Becomes

This concept can be applied to a case where the detection circuit is not of a differential configuration. In this case, the resistance value of the load resistor may be handled as RL instead of RL / 2.

In this embodiment, the vibrator is assumed to be of the prism type resonating type, but the equivalent circuit of the vibrator is shown in FIG.
As long as it can be expressed as, and also serves as a load resistor for driving and detecting, and uses a piezoelectric material for driving and detecting the vibrator, the shape may be a cylindrical sound piece or a tuning fork shape. No problem.

(Third Embodiment) Next, a third embodiment of the present invention will be described.
The drive detection circuit of the vibrating gyroscope according to the embodiment will be described. The schematic configuration of the drive detection circuit according to the present embodiment may be the configuration shown in FIG. 1 or the configuration shown in FIG. 8, and there is no change in the basic configuration of the vibrating gyroscope. However, in the present embodiment, the efficiency on the drive side and the efficiency on the detection side when the vibrator is resonantly driven under the condition that the drive amplitude is constant will be described.

In general, the sharpness (Q factor) of resonance of a vibrator is determined to be substantially constant by the material and structure.
If the drive amplitude Ad for obtaining the desired sensitivity of the vibrating gyroscope is determined, the necessary drive voltage is uniquely determined. On the other hand, when a drive voltage is applied to the vibrator via the load resistance, the load resistance and the voltage applied to the vibrator are determined by the ratio between the load resistance and the internal resistance rd of the piezoelectric vibrator or the piezoelectric body. Therefore, in order to maintain the desired drive amplitude as the resistance value RL of the load resistor increases, the output voltage Vd of the self-excited oscillation circuit increases according to the value of the resistance ratio. If there is enough, what kind of resistance value RL is the load resistance
Does not change the efficiency.

On the other hand, the generated charge detection efficiency KS on the detection side is:
Since it is similar to the first and second embodiments, as shown in FIG. 6, a parallel resistance of a parallel load resistance (RL / 2) and an internal resistance rd with respect to a resistance value RL of the load resistance, and a parallel capacitance It has an HPF characteristic determined by Cp.

Therefore, the overall drive detection efficiency KDS of the drive detection circuit is basically determined by the characteristics shown in FIG. 6, and the load resistance is set to a value equal to or higher than the cutoff resistance value of the HPF characteristics. If so, the overall efficiency will be maximum. However, the output of the self-excited oscillation circuit has an upper limit value, which determines the upper limit resistance value of the load resistance for obtaining a required drive amplitude. Therefore, the output resistance Vd of the self-excited oscillation circuit is determined by the output upper limit value of the self-excited oscillation circuit and the ratio of the load resistance to the internal resistance rd of the piezoelectric vibrator or the piezoelectric body. By setting the resistance value RL of the load resistance, it becomes possible to detect the Coriolis force with the maximum efficiency under the condition that the drive amplitude is constant.

Note that this concept can be applied to a case where the detection circuit does not have a differential configuration. In this case, the resistance value of the load resistor may be handled as RL instead of RL / 2.

Further, in this embodiment, a prism type resonator is assumed as the vibrator, but the equivalent circuit of the vibrator is shown in FIG.
As long as it can be expressed as, and also serves as a load resistor for driving and detecting, and uses a piezoelectric material for driving and detecting the vibrator, the shape may be a cylindrical sound piece or a tuning fork shape. No problem.

(Fourth Embodiment) Next, a fourth embodiment of the present invention will be described.
The drive detection circuit of the vibrating gyroscope according to the embodiment will be described. The schematic configuration of the drive detection circuit according to the present embodiment is shown in FIG. 1 or FIG. That is,
FIGS. 1 and 9 have substantially the same general configuration, but differ in that the location where the Coriolis force detection voltage is obtained is a load resistor or a (piezoelectric) vibrator. In the present embodiment, a configuration will be described in which the Coriolis force can be detected with a high S / N ratio when the resistance value of the load resistance is determined.

When the configuration shown in FIG. 1 for calculating the Coriolis force based on the difference between the potential differences between both ends of the piezoelectric vibrator 101 is used, as described in the first embodiment,
1 is determined by the resistance division of the load resistance 104 and the internal resistance rd.
It is determined by the F characteristic. At this time, one load resistance 104
The characteristics of the amount of leakage KR of the drive voltage to the detection side as seen in FIG.
It is represented by a downward-sloping characteristic shown by a curve 1001 of 0.
In FIG. 1, this leakage component is removed by using the differential amplifier circuit 106. However, since there is always a deviation in the balance, the characteristic of the final leakage amount also becomes a characteristic shown by a curve 1001. .

On the other hand, when the configuration shown in FIG. 9 is used in which the Coriolis force is calculated based on the difference between the potential differences between both ends of the load resistor 104, the driving efficiency of the piezoelectric vibrator 101 and the detection efficiency of the generated charges are both as shown in FIG. Is exactly the same as However, the amount of leakage K to the detection side of the drive voltage as seen by one load resistor 104
The characteristic of R is represented by a characteristic that rises to the right as shown by a curve 1002 in FIG. In FIG. 9 as well, this leakage component is removed by using the differential amplifier circuit 106. However, since there is always a deviation in the balance, the characteristic of the final leakage amount also becomes a characteristic shown by a curve 1002. .

Therefore, when the resistance value RL of a certain load resistance is selected, by changing the location for detecting the Coriolis force,
It is possible to change the amount of leakage voltage that causes noise without changing the sensitivity characteristics. For example, curve 10 in FIG.
When a load resistor having a resistance value RL larger than the resistance value RP corresponding to the intersection P of the curve 1002 with the curve 01 is selected, the configuration shown in FIG. When a load resistor having a resistance value RL smaller than the value RP is selected, the configuration in FIG. 9 may be adopted.

As described above, in this embodiment, when the load resistance is selected, the load resistance and the internal resistance rd of the vibrator are determined.
In comparison with the above, it is possible to reduce the amount of leakage of the drive voltage to the output stage by changing the detection location without changing the sensitivity characteristics at all.

In the present embodiment, the parallel capacitance Cp of the piezoelectric vibrator 101 is neglected when examining the characteristics on the driving side. However, depending on the equivalent circuit constant, the LPF characteristics described in the first embodiment may be different. It cannot be ignored. Therefore, in such a case, there is no problem if the leakage voltage characteristic of FIG. 10 is also considered in consideration of the LPF characteristic, and the option that the phase rotation is small is added.

(Fifth Embodiment) Finally, a drive detection circuit for a vibrating gyroscope according to a fifth embodiment of the present invention will be described. The schematic configuration of the drive detection circuit according to the present embodiment is shown in FIG. 1, FIG. 8, FIG. 9, and the like. In the present embodiment, a method of adjusting each resistance value of a plurality of load resistors will be described.

In the present embodiment, as described above, there are two detection systems, and the detected charges due to the Coriolis force are generated in the opposite phases between the divided drive detection electrodes 102, so that the differential detection is performed. The Coriolis force is detected most efficiently by calculating the difference between the two outputs by the amplifier circuit 106 and the like.

By the way, even if the size of each drive detection electrode 102 is set to be the same, actually, each drive detection electrode 102 and the shared electrode 103 may The formed parallel capacitance Cp, the internal resistance rd of the piezoelectric vibrator or the piezoelectric body, and the values of L and C connected in series vary between the drive detection electrodes 102. That is, although the equivalent circuit of FIG. 3 is approximately established for each drive system, the parallel capacitance Cp,
Due to the fluctuation of the internal resistance rd, etc., the resonance frequency also differs,
The phase and amplitude of the leakage signal V1 of the drive voltage Vd are slightly different for each drive detection electrode. Therefore, in order to remove a leakage signal of a driving voltage which is overwhelmingly larger than the generated charges corresponding to the Coriolis force and secure a sufficient S / N ratio, it is necessary to adjust both the phase and the amplitude for each driving detection electrode. There is.

By changing the resistance value of the load resistance, it is possible to independently adjust the phase and amplitude of each drive detection electrode. However, it is virtually impossible to match at the same time. The differential amplifier circuit at the subsequent stage is usually composed of an operational amplifier or the like, and can easily make a difference between amplification factors between inputs. However, for adjusting a phase, a capacitive element (C) or an inductive element (L ) Must be added. Therefore, the phase of the leak signal at each drive detection electrode 102 is
By fixing one load resistance 104 of one system, adjusting the load resistance 104 of the other system so as to match, and setting the amplification factor of the differential amplifier circuit 106 to a ratio inversely proportional to the amplitude of the leakage signal, Without complicating the circuit configuration, it is possible to sufficiently suppress the leakage signal of the driving voltage and secure a sufficient S / N ratio.

In the present embodiment, the drive detection electrode 1
Although only two electrodes are assumed as 02, if three or more electrodes determine the optimum load resistance based on the same concept, it is possible to detect the charge corresponding to the Coriolis force without loss as in the present embodiment. become.

Further, in this embodiment, a prism-type sound piece type is assumed as the vibrator, but the equivalent circuit of the vibrator is shown in FIG.
As long as it can be expressed as follows and the load resistance for both driving and detection is used, there is no problem even if the shape is a cylindrical sound piece or a tuning fork shape.

Further, in the present embodiment, the prism type resonating piece is assumed as the vibrator, but the equivalent circuit of the vibrator can be represented as shown in FIG. 2, and the load resistance for driving and for detecting is shared. However, as long as the piezoelectric body is used for driving and detecting the vibrator, there is no problem whether the shape is a cylindrical sound piece or a tuning fork shape.

[0057]

As described above, according to the present invention,
When the load resistance of the drive side and the detection side is shared by the vibrating gyroscope, the load resistance can be set to the maximum sensitivity value in consideration of the electrical characteristics of the vibrator and piezoelectric body. It is possible to reduce the number of load resistors and reduce the size of the circuit while maintaining the optimum condition. Therefore, the practical effect is great.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of a drive detection circuit of a vibration gyro according to a first embodiment of the present invention.

FIG. 2 is an equivalent circuit diagram of the piezoelectric vibrator 101 of FIG.

FIG. 3 is an equivalent circuit diagram on the drive side of the drive detection circuit of FIG. 1;

FIG. 4 is a diagram showing characteristics of drive efficiency KD with respect to a resistance value RL of a load resistor based on the equivalent circuit of FIG. 3;

FIG. 5 is an equivalent circuit diagram on the detection side of the drive detection circuit of FIG. 1;

6 is a diagram showing characteristics of detection efficiency KS with respect to resistance value RL of a load resistor based on the equivalent circuit of FIG.

7 is a diagram showing characteristics of a drive detection efficiency KDS obtained by multiplying the drive efficiency KD of FIG. 4 and the detection efficiency KS of FIG. 6;

FIG. 8 is a schematic configuration diagram of a drive detection circuit of a vibration gyro according to a second embodiment of the present invention.

FIG. 9 is a schematic configuration diagram of a drive detection circuit of a vibration gyro according to a fourth embodiment of the present invention.

FIG. 10 is a diagram showing characteristics of a leakage amount KR of a drive voltage to a detection side in the case where charge detection points are in FIG. 1 and FIG. 9 in the fourth embodiment of the present invention.

[Explanation of symbols]

101 Piezoelectric vibrator 102 Drive detection electrode 103 Common electrode 104, 804 Load resistance 105, 805 Self-excited oscillation circuit 106, 806 Differential amplification circuit 301, 503 Parallel load resistance 302, 504 Internal resistance rd 303, 502 Parallel capacitance Cp 501 Potential difference source 801 Oscillator 802 Detecting piezoelectric body 803 Driving piezoelectric body 1001 Leakage voltage curve from driving side to detecting side when detecting location is shown in FIG. 1 1002 From driving side to detecting side when detecting location is shown in FIG. 9 Leakage voltage curve

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Takafumi Koike 1006 Kazuma Kadoma, Kadoma, Osaka Prefecture F-term (reference) 2F105 AA01 AA08 BB02 CC01 CC05 CC06 CC07 CC08 CD02 CD06 CD11

Claims (8)

[Claims] 1. A piezoelectric vibrator that bends and vibrates at least in a columnar or tuning fork shape, and drive detection formed on one main surface of the piezoelectric vibrator and having both functions of exciting the piezoelectric vibrator and detecting generated charges. An electrode, a common electrode formed on the other main surface of the piezoelectric vibrator, and a drive detection circuit of a vibration gyro including a load resistor connected to the drive detection electrode, The driving efficiency of the piezoelectric vibrator defined based on a signal applied to the internal resistance of the piezoelectric vibrator, and the capacitance between the drive detection electrode and the common electrode of the piezoelectric vibrator. A resistance value in the vicinity where the drive detection efficiency obtained by multiplying the internal resistance of the piezoelectric vibrator and the detection efficiency of the piezoelectric vibrator defined based on the signal detected by the parallel resistance of the load resistance is maximized To have Vibrating gyroscope drive detection circuit, wherein a resistance value of the load resistor is selected. 2. A vibrator that bends and vibrates at least in a columnar or tuning fork shape; a piezoelectric body formed on the vibrator and having a function of exciting the vibrator and detecting generated charges; and a surface electrode of the piezoelectric body A driving resistance circuit for a vibrating gyroscope having a load resistance connected to the vibrator, and a driving efficiency of the vibrator defined based on a signal applied to an internal resistance of the piezoelectric body via the load resistance. Multiplying the detection efficiency of the piezoelectric body defined based on a signal detected by a parallel resistance of the internal resistance of the piezoelectric body and the load resistance via a capacitance between surface electrodes of the piezoelectric body. The drive detection circuit for a vibration gyro, wherein the resistance value of the load resistor is selected so as to have a resistance value near the maximum drive detection efficiency. 3. A piezoelectric vibrator that bends and vibrates at least in a columnar or tuning fork shape; a drive detection electrode formed on the piezoelectric vibrator and having a function of exciting the piezoelectric vibrator and detecting a generated charge; A drive detection circuit for a vibration gyro including a load resistor connected to a detection electrode, wherein a ratio of an applied voltage to the piezoelectric vibrator and the load resistance is equal to an internal resistance of the piezoelectric vibrator and the load resistance. The load resistance is determined by a magnitude ratio, and assuming that the applied voltage to the piezoelectric vibrator is determined from the drive amplitude, the load resistance has a resistance value corresponding to a voltage near the maximum that can be applied to the piezoelectric vibrator. A drive detection circuit for a vibrating gyroscope, wherein a resistance value is selected. 4. A vibrator that bends and vibrates at least in a columnar or tuning fork shape; a piezoelectric body formed on the vibrator, which functions to excite the vibrator and detect generated charges; and a surface electrode of the piezoelectric body A drive detection circuit for a vibrating gyroscope having a load resistor connected to the piezoelectric device, wherein a ratio of an applied voltage to the piezoelectric body and the load resistance is a ratio of an internal resistance of the piezoelectric body to a magnitude of the load resistance. The resistance value of the load resistor is selected so as to have a resistance value corresponding to a voltage near the maximum that can be applied to the piezoelectric body, assuming that the voltage applied to the piezoelectric body is determined from the drive amplitude. A drive detection circuit for a vibrating gyroscope. 5. A piezoelectric vibrator that bends and vibrates at least in a columnar or tuning fork shape, a drive detection electrode formed on the piezoelectric vibrator, and has a function of exciting the piezoelectric vibrator and detecting generated electric charges; A drive detection circuit for a vibration gyro having a load resistance connected to a detection electrode, wherein the load resistance is compared with an internal resistance of the piezoelectric vibrator,
When the value of the load resistance is large, the Coriolis force is detected based on the potential difference between both ends of the piezoelectric vibrator. When the value of the load resistance is small, the Coriolis force is detected based on the potential difference between both ends of the load resistance. A drive detection circuit for a vibrating gyroscope that detects a force. 6. A vibrator that bends and vibrates at least in a columnar or tuning fork shape; a piezoelectric body formed on the vibrator and having a function of exciting the vibrator and detecting generated charges; and a surface electrode of the piezoelectric body A drive detection circuit for a vibrating gyroscope having a load resistance connected to the piezoelectric gyroscope, wherein the load resistance is compared with an internal resistance of the piezoelectric body. A drive detection circuit for a vibration gyro, wherein a Coriolis force is detected based on a potential difference between both ends, and when the value of the load resistance is small, a Coriolis force is detected based on a potential difference between both ends of the load resistance. 7. A piezoelectric vibrator that bends and vibrates at least in a columnar or tuning fork shape, and at least two drive detection electrodes formed on the piezoelectric vibrator and serving both to excite the piezoelectric vibrator and to detect generated charges. A drive resistance circuit connected to each of the drive detection electrodes; and a drive detection circuit of a vibration gyro, comprising: a drive amplifier and a differential amplifier circuit connected to the load resistance. In each of the detection electrodes, the resistance value of each of the load resistors is selected so that the phase of the leakage signal of the drive voltage for excitation of the piezoelectric vibrator matches, and in the differential amplifier circuit, each of the leakage signals is selected. A drive detecting circuit for a vibrating gyroscope, wherein the leakage signal is amplified at a ratio inversely proportional to the amplitude and the common signal is removed. 8. A vibrator that bends and vibrates in at least a columnar or tuning fork shape, at least two piezoelectric bodies formed on the vibrator and having both functions of exciting the vibrator and detecting generated charges, and the piezoelectric body A load resistance connected to each of the surface electrodes, and a drive detection circuit for a vibrating gyroscope including a differential amplifier circuit connected to each of the surface electrodes of the piezoelectric body and the load resistance, In each surface electrode of the piezoelectric body, each resistance value of the load resistor is selected so that the phase of the leakage signal of the drive voltage for excitation of the vibrator matches, and the differential amplifier circuit selects the leakage signal. Wherein the leakage signal is amplified at a ratio inversely proportional to the amplitude of each of the signals and the common signal is removed.