JP2010071909A - Piezoelectric vibration gyro - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a piezoelectric vibration gyro having a small output drift and a low noise, capable of acquiring stable output. <P>SOLUTION: The gyro has a constitution wherein output from a current detection circuit 8 is used as the first injection signal, and the first injection signal is connected to an inverting terminal or a non-inverting terminal of addition/subtraction amplifying circuits 2, 3 through the first amplitude adjustment circuit, and the second injection signal acquired by allowing the output from the current detection circuit 8 to pass a 90-degree phase shift circuit 13 is connected to the non-inverting terminal or the inverting terminal of the addition/subtraction amplifying circuits 2, 3 through the second amplitude adjustment circuit, to thereby reduce and adjust an output amplitude of the addition/subtraction amplifying circuits 2, 3. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a vibration gyro used as an angular velocity sensor, and more particularly to a vibration gyro suitable for a gyroscope used in a navigation system, an attitude control device, a camera-integrated VTR, a camera shake prevention device for a digital camera, etc. .

  A vibrating gyroscope is an angular velocity sensor that utilizes a dynamic phenomenon in which when a rotational angular velocity is applied to an object having a velocity, a Coriolis force is generated in the object itself in a direction perpendicular to the velocity direction. The vibration gyro can excite mechanical vibration (hereinafter referred to as “driving mode”) by applying an electrical signal, and mechanical vibration in a direction orthogonal to the driving vibration (hereinafter referred to as “driving mode”). , Referred to as “detection mode”) in a state where the magnitude of the detection mode) can be electrically detected and the drive mode is excited in advance, the line of intersection between the vibration surface in the drive mode and the vibration surface in the detection mode When a rotational angular velocity about an axis parallel to the axis is given, a detection mode is generated by the action of the Coriolis force described above, and can be detected as an output voltage. Since the detected output voltage is proportional to the magnitude of the drive mode and the rotational angular velocity, the magnitude of the rotational angular velocity can be obtained from the magnitude of the output voltage when the magnitude of the drive mode is constant.

  In recent years, as with other electronic components, vibration gyros have been rapidly reduced in size and price. For example, an anti-shake device or the like generally requires detection of a biaxial rotational angular velocity, and conventionally, in most cases, two products capable of detecting a single axial rotational angular velocity are used. Recently, however, vibratory gyros that enable detection of the rotational angular velocity of two axes with one product have been commercialized. Compared to producing single-axis products separately, it is possible to share common parts such as circuit parts and packages such as ICs, and the size and price can be reduced.

  FIG. 6 is a top view showing the vibrator for piezoelectric vibration gyro. The piezoelectric vibration gyro vibrator in FIG. 6 is a piezoelectric vibration gyro vibrator capable of detecting a biaxial rotational angular velocity. The additional mass portions 104a to 104d are connected to the frame body 102 by beams 103a to 103h to form the vibrator 101. Beams 103a to 103d are connected to the additional mass portions 104a to 104d, respectively. Further, the detection electrode 106a and reference voltage electrodes 107c and 107d are provided on the surface of the beam 103a, the detection electrode 106b and reference voltage electrodes 107f and 107g are provided on the surface of the beam 103b, and the detection electrode 106c and reference voltage are provided on the surface of the beam 103c. The electrodes 107f and 107h, the detection electrode 106d and the reference voltage electrodes 107c and 107e on the surface of the beam 103d, the drive electrode 105a and the reference voltage electrode 107a on the surface of the beam 103e, and the drive electrode 105b and the surface of the beam 103f, A reference voltage electrode 107b is formed.

  FIG. 7 is a top view showing a vibration mode of the vibrator for piezoelectric vibration gyro of FIG. 7A shows the X mode, FIG. 7B shows the Y mode, and FIG. 7C shows the Z mode. In the X mode shown in FIG. 7 (a), referring to FIG. 6 at the same time, the two in-phase additional mass portions 104a and 104c and the two in-phase additional mass portions 104b and 104d are in opposite phases, and The additional mass part is vibrated in the X-axis direction. When an angular velocity about an axis parallel to the Y axis is applied in the state where the X mode is excited, a Coriolis force acts on the additional mass unit, and the additional mass units 104a and 104c and the additional mass units 104b and 104d are in opposite phases. Vibrates in the Z-axis direction.

  That is, by exciting the X mode, the additional mass portions 104a and 104c have a velocity in the + X direction, and the additional mass portions 104b and 104d have a velocity in the -X direction, the angular velocity about the axis parallel to the Y axis. When the Coriolis force is generated, the additional mass portions 104a and 104c receive a force in the -Z direction, and the additional mass portions 104b and 104d receive a force in the + Z direction. The Z mode can be used to detect this vibration.

  Similarly, when an angular velocity about an axis parallel to the Z-axis is applied, Coriolis force acts on the additional mass unit, and the additional mass units 104a and 104c and the additional mass units 104b and 104d are in opposite phases with respect to the Y-axis direction. Receive. However, the beams 103a to 103d are connected to the additional mass portions 104a to 104d, respectively, and displacement in the Y-axis direction is limited. Therefore, each additional mass part rotates and vibrates in the Z-axis direction.

  That is, by exciting the X mode, the additional mass portions 104a and 104c have a velocity in the + X direction, and the additional mass portions 104b and 104d have a velocity in the -X direction, the angular velocity about the axis parallel to the Z axis. When the Coriolis force is generated, the additional mass portions 104a and 104c receive a force in the + Y direction, and the additional mass portions 104b and 104d receive a force in the -Y direction. However, in order to limit the displacement in the Y-axis direction due to the presence of the beams 103a to 103d, each additional mass portion tries to rotate around the connection portion with the beam. As a result, the additional mass portions 104a and 104d are displaced in the + Z direction, and the additional mass portions 104b and 104c are displaced in the −Z direction. Therefore, the additional mass portions 104a and 104d and the additional mass portions 104b and 104c vibrate in the Z-axis direction in opposite phases. The Y mode can be used to detect this vibration.

  An X-mode resonance signal is input to drive electrodes 105a and 105b formed on the beams 103e and 103f of the vibrator 101 to excite the X mode, and the detection electrodes 106a to 106d formed on the beams 103a to 103d are excited. By detecting the generated charges, vibrations in the Y mode and the Z mode can be detected, and the angular velocities around the axes parallel to the Z axis and the Y axis can be detected.

  FIG. 8 is a block diagram showing a drive detection circuit of a conventional piezoelectric vibration gyro. FIG. 9 is a diagram illustrating an example of a circuit configuration of an input amplifier unit of a conventional piezoelectric vibration gyro. FIG. 9A shows a current detection circuit, and FIG. 9B shows a charge amplifier circuit. A drive circuit having a current detection circuit 8, a phase adjustment circuit 9, and an automatic gain control circuit (hereinafter referred to as AGC circuit) 10 as drive means for causing the vibrator 101 of FIG. 6 to self-oscillate at a resonance frequency, and input amplifiers 1a to 1a as detection means. 1d, addition / subtraction amplification circuits 2 and 3, phase adjustment circuit 11, synchronous detection circuits 4 and 5, and low-pass filter circuits 6 and 7, and a reference voltage circuit 12 that generates an operation reference voltage for each circuit. As shown in FIG. 9A, the input amplifiers 1a to 1d include a current detection circuit in which a fixed resistor 1f is connected between the inverting terminal and the output terminal of the operational amplifier 1e, and the non-inverting terminal is grounded to the reference voltage. A charge amplifier circuit or the like in which a fixed resistor 1g and a capacitor 1h are connected between the inverting terminal and the output terminal of the operational amplifier 1e as shown in 9 (b) and the non-inverting terminal is grounded to the reference voltage is used.

  In order to drive the drive electrodes 105a and 105b at the frequency of the X mode, the output of the AGC circuit 10 for keeping the drive state constant is connected to the drive electrodes 105a and 105b, and the input of the current detection circuit 8 is connected to the reference voltage electrode 107a and Connect to 107b. Due to the virtual ground effect of the current detection circuit, the potentials of the reference voltage electrodes 107a and 107b are fixed to the reference voltage, and the drive voltage can be applied between the drive electrodes 105a and 105b and the reference voltage electrodes 107a and 107b.

  The drive current flowing through the drive electrodes 105a and 105b flows through the current detection resistor 8a of the current detection circuit 8, is converted into a voltage and detected, and the phase adjustment circuit 9 adjusts the phase of self-excited oscillation, and the AGC circuit 10 The amplitude is adjusted and applied again to the drive electrodes 105a and 105b. This closed loop enables self-excited oscillation at the X-mode resonance frequency. At the same time, the output of the current detection circuit 8 passes through the phase adjustment circuit 11 and is input to the synchronous detection circuits 4 and 5 as a reference signal.

  As described above, when an angular velocity is applied around the Z axis in a state where the X mode is self-excited, charges in opposite phases are generated in the detection electrodes 106a and 106d and the detection electrodes 106b and 106c due to the vibration of the Y mode. . Input electrodes 1a to 1d are connected to the detection electrodes 106a to 106d, respectively, and generated charges are converted into voltages. Input amplifiers 1a and 1d are connected to the inverting terminal side of the addition / subtraction amplifier circuit 2 via fixed resistors 2a and 2d, and input amplifiers 1b and 1c are connected to the non-inverting terminal side via fixed resistors 2b and 2c. By adding the signals of the in-phase components and subtracting the signals of the anti-phase components, a signal proportional to the angular velocity around the Z axis is amplified and taken out as a DC signal by the synchronous detection circuit 4 and the low-pass filter circuit 6. Can do. Fixed resistors 2e and 2f are used as resistors used in the addition / subtraction amplifier circuit 2.

  Similarly, when an angular velocity is applied around the Y axis, charges in opposite phases are generated in the detection electrodes 106a and 106c and the detection electrodes 106b and 106d by the vibration of the Z mode. Input amplifiers 1a and 1c are connected through fixed resistors 3a and 3c to the inverting terminal side of addition / subtraction amplifier circuit 3, and input amplifiers 1b and 1d are connected through fixed resistors 3b and 3d to the non-inverting terminal side. By adding the signals of the in-phase components and subtracting the signals of the opposite-phase components, a signal proportional to the angular velocity around the Y axis is amplified and taken out as a DC signal by the synchronous detection circuit 5 and the low-pass filter circuit 7. Can do. Fixed resistors 3e and 3f are used as resistors used in the addition / subtraction amplification circuit 3.

  Further, the charge generated by the Y mode is canceled by the addition / subtraction amplification circuit 3, and the charge generated by the Z mode is canceled by the addition / subtraction amplification circuit 2. Accordingly, the output of the low-pass filter circuit 6 is an output proportional to the angular velocity only around the Z axis, and the output of the low-pass filter circuit 7 is an output proportional to the angular velocity only around the Y axis. Such a vibration gyro is disclosed in Patent Document 1.

JP 2008-145325 A

  Since the X mode, the Y mode, and the Z mode of the vibrator 101 shown in FIGS. 7A to 7C are independent, the vibrator 101 is self-oscillated in the X mode and is rotated around the Z axis. When an angular velocity is not applied around the Y axis, that is, in a state where the Y mode and the Z mode are not excited by the Coriolis force, ideally no signal is detected at the output terminals of the input amplifiers 1a to 1d.

  However, in reality, due to variations in the processing dimensional accuracy of the vibrator, variations in the dimensions of the electrodes formed on the vibrator surface, etc., the X-mode vibration direction of the vibrator is not parallel to the X axis, but becomes oblique vibration, In some cases, the vibration direction is not a straight line but an elliptical vibration. In this case, unnecessary charges are generated in the detection electrode even if the angular velocity is not applied. In addition, there is a considerable amount of stray capacitance between the electrodes formed on the surface of the vibrator, and errors due to coupling of the capacitance are amplified by the input amplifiers 1a to 1d and output as unnecessary error signals to the output terminals. It will be done.

  Hereinafter, the case where the input amplifiers 1a to 1d are the current detection circuit of FIG. 9A will be described. When the input amplifier uses the charge amplifier shown in FIG. 9B, the phase of the input signal and the output signal of the charge amplifier are shifted by 90 degrees. It will shift.

  FIG. 10 is a schematic diagram of a waveform of an error signal in a drive detection circuit of a conventional piezoelectric vibration gyro. 10A shows the current detection circuit output waveform of the drive circuit, FIG. 10B shows the error signal waveform output from the input amplifier 1a, and FIG. 10C shows the four input amplifiers 1a to 1d. FIG. 10D shows the error signal waveform output from the addition / subtraction amplification circuit. An example of the operation will be described with reference to the waveform schematic diagram of FIG. Of the error signals, the first error signal generated by oblique vibration or the like is a signal having the same phase (or opposite phase) as the drive current detected by self-oscillation of the vibrator. That is, it becomes the same phase (or opposite phase) as the output of the current detection circuit 8.

  On the other hand, the second error signal due to elliptical vibration or stray capacitance component is a signal component that is shifted by 90 degrees from the phase of the drive current. In other words, the signal is 90 degrees shifted from the output of the current detection circuit 8. Accordingly, the resultant error signal is a composite signal of the first error signal having the same phase (or opposite phase) as the drive current and the second error signal that is 90 degrees out of phase with the drive current.

  That is, if the output waveform 51 shown in FIG. 10A is the output waveform of the current detection circuit 8, the error signal waveform 54 shown in FIG. 10B is applied to the detection electrode 106a in a state where no angular velocity is applied. It is the output waveform of the connected input amplifier 1a. The error signal waveform 54 output from the input amplifier 1a is a first error signal component 52 of the error signal output from the input amplifier 1a in phase with the output waveform 51 of the current detection circuit 8 shown in FIG. And the second error signal component 53 of the error signal output from the input amplifier 1a that is 90 degrees out of phase.

  Similarly, error signal waveforms 56 to 58 output from the input amplifiers 1b to 1d connected to the detection electrodes 106b to 106d are as shown in FIG. 10C, for example, and are signal waveforms having different amplitudes and phases. Then, the respective signals are added and subtracted, and the output of the next addition / subtraction amplification circuit 2 becomes an error signal waveform 61 output from the addition / subtraction amplification circuit of FIG. As a matter of course, the error signal waveform 61 output from the addition / subtraction amplification circuit in FIG. 10D is also the first error signal of the error signal output from the addition / subtraction amplification circuit having the same phase as the output waveform 51 of the current detection circuit 8. This is a waveform obtained by synthesizing the component 59 and the second error signal component 60 of the error signal output from the addition / subtraction amplification circuit 90 degrees out of phase. However, since the error signal is generated due to processing accuracy, electrode accuracy, stray capacitance, etc. as described above, the error signals output from the input amplifiers 1a to 1d do not have the same waveform.

  In general, these unnecessary error signals can be reduced by grinding an arbitrary portion of the vibrator itself or removing the electrode itself formed on the vibrator surface. Laser trimming, sandblasting, or the like is used for adjusting these vibrators.

  However, since these vibrator adjustments are performed in the middle of the assembly process of the piezoelectric vibration gyroscope, the characteristics of the vibrators are affected by thermal stress such as heating or external mechanical stress due to the casing in the assembly process after adjustment. It may change. Therefore, the degree of adjustment of the vibrator is shifted, and as a result, when combined with the drive detection circuit, an error signal is output to the input amplifiers 1a to 1d.

  Accordingly, an object of the present invention is to make use of the fact that the error signal output from the adder / subtracter amplifier circuit is a composite signal of a component that is in phase (or opposite phase) to the drive current and a component that is shifted by 90 degrees. An error signal that could not be adjusted in the process or an error signal generated by the change in state after adjustment is canceled and reduced by the addition / subtraction amplification circuit, so that a stable output can be obtained, low output drift, and low noise It is to provide a piezoelectric vibration gyro.

  The present invention makes use of the fact that the error signal is a composite signal of a component that is in phase (or opposite phase) to the drive current and a component that is shifted by 90 degrees. This is a piezoelectric vibration gyro configured to cancel and reduce an error signal generated due to a state change after adjustment by an addition / subtraction amplification circuit.

  According to the present invention, a piezoelectric vibrator having at least two drive electrodes for vibrating at a resonance frequency and at least two detection electrodes for detecting a signal generated as an angular velocity is applied, and the piezoelectric vibrator A detection circuit comprising an input amplifier unit, an addition / subtraction amplification circuit, a synchronous detection circuit, a low-pass filter circuit that amplifies a minute signal output proportional to the angular velocity detected by the detection electrode and outputs it as a DC voltage, and a resonance frequency of the piezoelectric vibrator. A piezoelectric vibration gyro comprising a drive circuit comprising a current detection circuit for providing a signal for self-excited oscillation to the drive electrode, a phase adjustment circuit, and an automatic gain control circuit, the output of the current detection circuit being As the first injection signal, the first injection signal is connected to the inverting terminal or the non-inverting terminal of the addition / subtraction amplifier circuit through the first amplitude adjustment circuit. Further, the addition / subtraction amplification is performed by connecting the output of the current detection circuit to the non-inverting terminal or the inverting terminal of the addition / subtraction amplification circuit through the second amplitude adjustment circuit through the second injection signal that has passed through the 90-degree phase shift circuit. A piezoelectric vibration gyro characterized by reducing and adjusting the output amplitude of the circuit is obtained.

  According to the present invention, in the piezoelectric gyro, the first and second amplitude adjustment circuits are configured by variable resistors, and the signal amplitude input to the addition / subtraction amplification circuit is adjusted by changing the resistance value of the variable resistors. A piezoelectric vibration gyro characterized by the above can be obtained.

  According to the present invention, in the piezoelectric gyro, each of the first and second amplitude adjustment circuits includes an operational amplifier circuit capable of varying an amplifier gain and a fixed resistor connected to the next stage, and the operational amplifier circuit A piezoelectric vibration gyro characterized by adjusting the amplitude of the signal input to the adder / subtractor amplifier circuit by changing the amplifier gain is obtained.

  According to the present invention, in the piezoelectric gyro, an input terminal of the addition / subtraction amplifier circuit for inputting the first and second injection signals is provided by a changeover switch provided at a stage subsequent to the first and second amplitude adjustment circuits. A piezoelectric vibration gyro characterized by having a structure capable of switching between an inverting terminal and a non-inverting terminal is obtained.

  According to the present invention, a piezoelectric vibrator having at least two drive electrodes for vibrating at a resonance frequency and at least two detection electrodes for detecting a signal generated as an angular velocity is applied, and the piezoelectric vibrator A detection circuit comprising an input amplifier unit, an addition / subtraction amplification circuit, a synchronous detection circuit, a low-pass filter circuit that amplifies a minute signal output proportional to the angular velocity detected by the detection electrode and outputs it as a DC voltage, and a resonance frequency of the piezoelectric vibrator. A piezoelectric vibration gyro comprising a drive circuit comprising a current detection circuit for providing a signal for self-excited oscillation to the drive electrode, a phase adjustment circuit, and an automatic gain control circuit, the output of the current detection circuit being One is directly connected to one of the selector switches provided in the next stage, and the other is connected to the output of the current detection circuit via an inverting amplifier circuit. Connected to the other of the switch, the polarity is switched by the changeover switch, and connected to either the inverting terminal or the non-inverting terminal of the addition / subtraction amplification circuit through the first amplitude adjustment circuit in the subsequent stage, and the current detection circuit Is connected to one of the selector switches provided in the next stage, and the other is connected to the output of the current detection circuit via an inverting amplifier circuit. The piezoelectric vibration gyro is connected to the other, the polarity is switched by the changeover switch, and connected to either the inverting terminal or the non-inverting terminal of the addition / subtraction amplification circuit through the second amplitude adjustment circuit at the subsequent stage. Is obtained.

  According to the present invention, the error signal is a combined signal of a component that is in-phase (or anti-phase) with the driving current and a component that is shifted by 90 degrees. The error signal generated by the state change after adjustment is canceled and reduced by the addition / subtraction amplification circuit, so that a stable output can be obtained, and a low-noise piezoelectric vibration gyro with low output drift can be provided.

  The piezoelectric vibration gyro of the present invention cannot be adjusted in the vibrator adjustment process by utilizing that the error signal is a composite signal of a component that is in phase (or opposite phase) to the drive current and a component that is shifted by 90 degrees. The error signal or the error signal generated by the change in state after adjustment is canceled and reduced by the addition / subtraction amplification circuit.

  Embodiments of the present invention will be described below with reference to the drawings.

(Embodiment 1)
FIG. 1 is a block diagram showing a drive detection circuit of a piezoelectric vibration gyro according to Embodiment 1 of the present invention. As in the conventional example shown in FIG. 8, a drive circuit having a current detection circuit 8, a phase adjustment circuit 9, and an AGC circuit 10, and input amplifier units 1a to 1d as detection means, addition / subtraction amplification circuits 2 and 3, a phase adjustment circuit 11 , A detection circuit having synchronous detection circuits 4 and 5, low-pass filter circuits 6 and 7, and a reference voltage circuit 12 for generating an operation reference voltage for each circuit. Since the connection between the vibrator 101 and the drive detection circuit is the same as that in FIG. 8, the description thereof is omitted here, and different portions from the conventional example will be described below.

  The output (first injection signal) of the current detection circuit 8 is connected to the inverting terminal of the addition / subtraction amplification circuit 2 via the variable resistor 14a and the changeover switch 16a, and to the non-inverting terminal via the variable resistor 14b and the changeover switch 16b. . Further, the output (second injection signal) obtained by passing the output of the current detection circuit 8 through the 90-degree phase shift circuit 13 is connected to the inverting terminal of the addition / subtraction amplification circuit 2 via the variable resistor 15a and the changeover switch 17a, and the non-inverting terminal. Are connected to each other via a variable resistor 15b and a changeover switch 17b.

  Similarly, the output (first injection signal) of the current detection circuit 8 is supplied to the inverting terminal of the addition / subtraction amplification circuit 3 via the variable resistor 14c and the changeover switch 16c, and to the non-inverting terminal via the variable resistance 14d and the changeover switch 16d. Connecting. Further, the output (second injection signal) obtained by passing the output of the current detection circuit 8 through the 90-degree phase shift circuit 13 is connected to the inverting terminal of the adder / subtractor amplifier circuit 3 via the variable resistor 15c and the changeover switch 17c. Are connected to each other via a variable resistor 15d and a changeover switch 17d.

  The first injection signal is adjusted to an arbitrary amplitude by adjusting the resistance value of the variable resistor 14a or 14b, respectively, and one of the switches 16a or 16b is turned on to invert the addition / subtraction amplifier circuit 2. The polarity of the signal to be injected can be switched by selecting a terminal or a non-inverting terminal.

  Similarly, the first injection signal is adjusted to an arbitrary amplitude by adjusting the resistance value of the variable resistor 14c or 14d, and one of the switches 16c or 16d is turned on to invert the addition / subtraction amplification circuit 3. The polarity of the signal to be injected can be switched by selecting a terminal or a non-inverting terminal.

  Also, the second injection signal is adjusted to an arbitrary amplitude by adjusting the resistance value of the variable resistor 15a or 15b, and either one of the changeover switches 17a or 17b is turned on to turn on the addition / subtraction amplification circuit 2. The polarity of a signal to be injected can be switched by selecting a non-inverting terminal or an inverting terminal. Similarly, the second injection signal is adjusted to an arbitrary amplitude by adjusting the resistance value of the variable resistor 15c or 15d, and either the changeover switch 17c or 17d is turned on to turn off the addition / subtraction amplification circuit 3. The polarity of the signal to be injected can be switched by selecting the inverting terminal or the inverting terminal.

  FIG. 2 is a schematic waveform diagram illustrating an example of an error signal reduction operation in the piezoelectric vibration gyro drive detection circuit according to the first embodiment of the present invention. 2A shows a current detection circuit output waveform of the drive circuit (a waveform obtained by voltage conversion of the drive current), FIG. 2B shows an error signal waveform output from the addition / subtraction amplification circuit, and FIG. Shows the first and second injection signal waveforms applied to the addition / subtraction amplification circuit, and FIG. 2 (d) shows the output waveform of the addition / subtraction amplification circuit after the addition of the first and second injection signals.

  An example of the operation will be described with reference to the waveform schematic diagram of FIG. FIG. 2A shows an output waveform 31 of the current detection circuit 8 configured in the drive circuit, and corresponds to a drive current that flows through the drive electrodes 105 a and 105 b due to self-oscillation of the vibrator 101. FIG. 2B shows an error signal waveform 34 output to the addition / subtraction amplification circuit when no angular velocity is applied, which is the same as FIG. 10D. The error signal waveform 34 output to the addition / subtraction amplification circuit is a component that is 90 degrees out of phase with the first error signal component 32 of the error signal output to the addition / subtraction amplification circuit having the same phase component as the output waveform 31 of the current detection circuit 8. This is a waveform obtained by synthesizing the second error signal component 33 of the error signal output to the addition / subtraction amplification circuit. FIG. 2C shows a signal waveform that is output to the addition / subtraction amplification circuit and is to be injected into the addition / subtraction amplification circuit 2 in order to cancel the error signal waveform 34, and an addition / subtraction amplification circuit having the same phase component as the output waveform 31 of the current detection circuit 8. The first injection signal waveform 35 to be added to the addition / subtraction amplification circuit of the component 90 degrees out of phase with the first injection signal waveform 35 to be added to FIG. However, the two waveforms shown here are waveforms when viewed as the output of the addition / subtraction amplification circuit 2.

  First, since the first error signal component 32 of the error signal output to the addition / subtraction amplification circuit and the first injection signal waveform 35 applied to the addition / subtraction amplification circuit have the same phase, the first injection signal applied to the addition / subtraction amplification circuit. The change-over switch 16a connected to the inverting terminal of the addition / subtraction amplification circuit 2 is adjusted with the variable resistor 14a so that the waveform 35 has the same amplitude as the first error signal component 32 of the error signal output to the addition / subtraction amplification circuit. Is turned on (the changeover switch 16b is turned off) to subtract the two waveforms, thereby canceling the first error signal component 32 of the error signal output to the addition / subtraction amplification circuit.

  Further, since the second error signal component 33 of the error signal output to the addition / subtraction amplification circuit and the second injection signal waveform 36 applied to the addition / subtraction amplification circuit are in opposite phases, the second injection signal applied to the addition / subtraction amplification circuit. The amplitude of the waveform 36 is adjusted by the variable resistor 15b so as to have the same amplitude as that of the second error signal component 33 of the error signal output to the addition / subtraction amplification circuit, and the switching connected to the non-inverting terminal of the addition / subtraction amplification circuit 2 The second error signal component 33 of the error signal output to the addition / subtraction amplification circuit is canceled by switching the switch 17b on (the changeover switch 17a is off) and adding the two waveforms. Therefore, by injecting the first injection signal waveform 35 applied to the addition / subtraction amplification circuit and the second injection signal waveform 36 applied to the addition / subtraction amplification circuit, the error signal output to the addition / subtraction amplification circuit output to the addition / subtraction amplification circuit 2 is obtained. The waveform 34 is similar to the output signal waveform 37 of the addition / subtraction amplification circuit after adding the first and second injection signals, and unnecessary error signals can be eliminated. The same operation is performed on the addition / subtraction amplification circuit 3 side.

  FIG. 3 is a schematic waveform diagram illustrating an example of a reduction operation of an error signal at the time of self-excited oscillation modulation in the drive detection circuit of the piezoelectric vibration gyro according to the first embodiment of the present invention. 3A shows a current detection circuit output waveform of the drive circuit (a waveform obtained by voltage conversion of the drive current), FIG. 3B shows an error signal waveform output from the addition / subtraction amplification circuit, and FIG. Shows the first and second injection signal waveforms applied to the addition / subtraction amplification circuit, and FIG. 3 (d) shows the output waveform of the addition / subtraction amplification circuit after the addition of the first and second injection signals.

  Next, reduction of output noise according to the present invention will be described. The self-excited oscillation of the vibrator may cause an unstable state for some reason. In such a state, it is observed that the output waveform (during modulation) 38 of the current detection circuit 8 is modulated as shown in FIG. If the self-excited oscillation becomes unstable, the detected waveform of the vibrator becomes unstable as a matter of course. That is, the outputs of the input amplifiers 1a to 1d are also modulated, and as a result, the error signal waveform (during modulation) 39 output to the addition / subtraction amplifier circuit is also modulated as shown in FIG. When the error signal waveform (during modulation) 39 output to the addition / subtraction amplifier circuit is modulated, the modulation component is also superimposed on the DC signal output through the subsequent synchronous detection circuit 4 and low-pass filter circuit 6, which This will result in noise in the output signal.

  Here, if the output waveform 38 of the current detection circuit 8 is modulated, the first injection signal waveform (during modulation) 40 applied to the addition / subtraction amplification circuit and the addition / subtraction amplification circuit as shown in FIG. Since the second injection signal waveform (during modulation) 41 is similarly modulated, the modulation of the error signal waveform (during modulation) 39 output to the addition / subtraction amplification circuit is performed after adjusting the output amplitude of the addition / subtraction amplification circuit of the present invention. The components are canceled and the output of the addition / subtraction amplification circuit 2 is an unnecessary error such as the output signal waveform (during modulation) 42 of the addition / subtraction amplification circuit after adding the first and second injection signals of FIG. The modulation component can be canceled together with the signal. Therefore, according to the present invention, it is possible to reduce a noise component caused by modulation of self-excited oscillation among causes of noise generated in the output signal. The same operation is performed on the addition / subtraction amplification circuit 3 side.

(Embodiment 2)
FIG. 4 is a block diagram showing a drive detection circuit of the piezoelectric vibration gyro according to the second embodiment of the present invention. It is another embodiment of the present invention. The output (first injection signal) of the current detection circuit 8 is supplied to the inverting terminal of the addition / subtraction amplification circuit 2 via the amplitude adjustment amplifier 18a, the fixed resistor 20a, and the changeover switch 16a, and to the non-inverting terminal, the amplitude adjustment amplifier 18a and the fixed resistance 20b. And are connected via the changeover switch 16b. Further, the output (first injection signal) of the current detection circuit 8 is fixed to the inverting terminal of the addition / subtraction amplification circuit 3 via the amplitude adjustment amplifier 18b, the fixed resistor 20c, and the changeover switch 16c, and the amplitude adjustment amplifier 18b is fixed to the non-inverting terminal. The resistor 20d and the changeover switch 16d are connected to each other.

  On the other hand, the output (second injection signal) obtained by passing the output of the current detection circuit 8 through the 90-degree phase shift circuit 13 is connected to the inverting terminal of the addition / subtraction amplification circuit 2 via the amplitude adjustment amplifier 19a, the fixed resistor 21a, and the changeover switch 17a. The non-inverting terminal is connected to each other through the amplitude adjusting amplifier 19a, the fixed resistor 21b, and the changeover switch 17b. The output (second injection signal) obtained by passing the output of the current detection circuit 8 through the 90-degree phase shift circuit 13 is connected to the inverting terminal of the addition / subtraction amplification circuit 3 via the amplitude adjustment amplifier 19b, the fixed resistor 21c, and the changeover switch 17c. The non-inverting terminal is connected to each other through the amplitude adjusting amplifier 19b, the fixed resistor 21d, and the changeover switch 17d.

  In the first embodiment shown in FIG. 1, the amplitude of the injection signal is adjusted by changing the resistance values of the variable resistors 14a to 14d and 15a to 15d, but in the embodiment shown in FIG. 4, the amplitude adjusting amplifiers 18a and 18b are adjusted. , 19a and 19b are adjusted by changing the gain. As in the case of FIG. 1, the polarity of the first injection signal is the selector switch 16a or 16b and 16c or 16d, and the polarity of the second injection signal is the selector switch 17a or 17b and the switch 17c or 17d. Is turned on to switch between the inverting terminal and the non-inverting terminal of the addition / subtraction amplification circuits 2 and 3 for injection.

(Embodiment 3)
FIG. 5 is a block diagram showing a drive detection circuit of a piezoelectric vibration gyro according to Embodiment 3 of the present invention. It is another embodiment of this invention. One of the outputs (first injection signal) of the current detection circuit 8 is connected to the changeover switch terminal 24a of the changeover switch 24, and the other is connected to the changeover switch terminal 24b of the changeover switch 24 via the inverting amplification circuit 22 having a gain of 1. Connect to. The changeover switch terminal 24c of the changeover switch 24 is connected to either the inverting terminal or the non-inverting terminal of the addition / subtraction amplification circuit 2 and the addition / subtraction amplification circuit 3 via the variable resistor 26a and the variable resistor 26b. FIG. 5 shows an example of connection to the inverting terminal.

  Similarly, the output (second injection signal) obtained by passing the output of the current detection circuit 8 through the 90-degree phase shift circuit 13 is connected to the changeover switch terminal 25a of the changeover switch 25, and the other is inverted and amplified by 1 time. The switch 23 is connected to the changeover switch terminal 25 b of the changeover switch 25 through the circuit 23. The changeover switch terminal 25c of the changeover switch 25 is connected to either the inverting terminal or the non-inverting terminal of the addition / subtraction amplification circuit 2 and the addition / subtraction amplification circuit 3 via the variable resistor 27a and variable resistor 27b. FIG. 5 shows an example of connection to the inverting terminal.

  In the first embodiment shown in FIG. 1, the first injection signal selects either the inversion terminal or the non-inversion terminal of the addition / subtraction amplification circuit 2 by turning on either the changeover switch 16a or 16b, and the changeover switch 16c or By turning on one of the switches 16d, the inverting terminal or the non-inverting terminal of the addition / subtraction amplification circuit 3 can be selected, and the polarity of the signal to be injected can be switched. The second injection signal selects either the inversion terminal or the non-inversion terminal of the addition / subtraction amplification circuit 2 by turning on either the changeover switch 17a or 17b, and turns on either the changeover switch 17c or 17d. By turning ON, the inverting terminal or non-inverting terminal of the addition / subtraction amplification circuit 3 can be selected, and the polarity of the injected signal can be switched.

  However, in the third embodiment of FIG. 5, the changeover switch terminal 24a, the changeover switch terminal 24b, the changeover switch terminal 25a, and the changeover switch terminal 25b are signals of opposite phases, so the polarity of the first injection signal is the changeover switch. The polarity of the second injection signal can be selected by switching between the terminal 25a and the terminal 25b by switching between the terminal 24a and the changeover switch terminal 24b. Therefore, there is an advantage that the number of changeover switches can be reduced from 8 to 2 and the number of variable resistors can be reduced from 8 to 4 compared with the embodiment of FIG.

  In the present invention, the first and second injection signals are added so as to cancel the error signal output to the addition / subtraction amplifier circuit. However, the error signal output to the original input amplifiers 1a to 1d by the same method. The first and second injection signals may be added so as to cancel each other, and as a result, the output of the addition / subtraction amplification circuit may be adjusted to be reduced.

  As in the above-described embodiment, according to the present invention, the vibrator is adjusted by utilizing the fact that the error signal is a combined signal of the component in phase (or opposite phase) to the drive current and the component shifted by 90 degrees. An error signal that could not be adjusted in the process or an error signal generated by the change in state after adjustment is canceled and reduced by the addition / subtraction amplification circuit, so that a stable output can be obtained, low output drift, and low noise A piezoelectric vibration gyro can be provided.

  The present invention has been described above using the embodiments. However, the present invention is not limited to these embodiments, and the present invention can be applied to design changes that do not depart from the gist of the present invention. included. That is, various modifications and corrections that can naturally be made by those skilled in the art are also included in the present invention.

  By using the piezoelectric vibration gyro of the present invention, a stable output can be obtained in various angular velocity sensors represented by a gyroscope, and a low noise system with a small output drift can be constructed.

1 is a block diagram showing a drive detection circuit for a piezoelectric vibration gyro according to a first embodiment of the present invention. FIG. 6 is a schematic waveform diagram illustrating an example of an error signal reduction operation in the piezoelectric vibration gyro drive detection circuit according to the first embodiment of the present invention. FIG. 2A shows a current detection circuit output waveform of the drive circuit (a waveform obtained by converting the drive current voltage). FIG. 2B shows an error signal waveform output from the addition / subtraction amplification circuit. FIG. 2C shows first and second injection signal waveforms applied to the addition / subtraction amplifier circuit. FIG. 2D shows an output waveform of the addition / subtraction amplification circuit after adding the first and second injection signals. FIG. 3 is a schematic waveform diagram illustrating an example of a reduction operation of an error signal at the time of self-oscillation modulation in the piezoelectric vibration gyro drive detection circuit according to Embodiment 1 of the present invention. FIG. 3A shows a current detection circuit output waveform of the drive circuit (a waveform obtained by converting the drive current voltage). FIG. 3B shows an error signal waveform output from the addition / subtraction amplification circuit. FIG. 3C shows first and second injection signal waveforms applied to the addition / subtraction amplification circuit. FIG. 3D shows an output waveform of the addition / subtraction amplification circuit after adding the first and second injection signals. The block diagram which shows the drive detection circuit of the piezoelectric vibration gyroscope in Embodiment 2 of this invention. The block diagram which shows the drive detection circuit of the piezoelectric vibration gyro in Embodiment 3 of this invention. The top view which shows the vibrator | oscillator for piezoelectric vibration gyroscopes. The top view which shows the vibration mode of the vibrator | oscillator for piezoelectric vibration gyros of FIG. 7A is a diagram showing the X mode, FIG. 7B is a diagram showing the Y mode, and FIG. 7C is a diagram showing the Z mode. The block diagram which shows the drive detection circuit of the conventional piezoelectric vibration gyro. The figure which shows an example of the circuit structure of the input amplifier part of the conventional piezoelectric vibration gyro. FIG. 9A shows a current detection circuit. FIG. 9B shows a charge amplifier circuit. The schematic diagram of the waveform of the error signal in the drive detection circuit of the conventional piezoelectric vibration gyroscope. FIG. 10A shows the output waveform of the current detection circuit of the drive circuit. FIG. 10B shows an error signal waveform output from the input amplifier. FIG. 10C shows error signal waveforms output from four input amplifiers. FIG. 10D shows an error signal waveform output from the addition / subtraction amplification circuit.

Explanation of symbols

1a to 1d Input amplifier 1h Capacitor 1e Operational amplifiers 1f, 1g, 2a to 2f, 3a to 3f, 20a to 20d, 21a to 21d Fixed resistor 2, 3 Addition / subtraction amplifier circuit 4, 5 Synchronous detection circuit 6, 7 Low pass filter circuit 8 Current detection circuit 8a Current detection resistors 9, 11 Phase adjustment circuit 10 Automatic gain control circuit (AGC circuit)
12 Reference voltage circuit 13 90 degree phase shift circuit 14a-14d, 15a-15d, 26a, 26b, 27a, 27b Variable resistor 16a-16d, 17a-17d Changeover switch 18a, 18b, 19a, 19b Amplitude adjustment amplifier 22, 23 Gain 1 × inverting amplifier circuit 24, 25 changeover switch 24a-24c, 25a-25c changeover switch terminal 31 output waveform 32 of current detection circuit first error signal component 33 of error signal output to addition / subtraction amplification circuit to addition / subtraction amplification circuit Second error signal component 34 of output error signal Error signal waveform 35 output to addition / subtraction amplification circuit First injection signal waveform 36 applied to addition / subtraction amplification circuit Second injection signal waveform 37 applied to addition / subtraction amplification circuit First Output signal waveform 38 of the addition / subtraction amplifier circuit after adding the second injection signal and the output signal of the current detection circuit Shape (during modulation)
39 Error signal waveform output to addition / subtraction amplification circuit (during modulation)
40 First injection signal waveform applied to addition / subtraction amplification circuit (during modulation)
41 Second injection signal waveform to be added to addition / subtraction amplification circuit (during modulation)
42 Output signal waveform of addition / subtraction amplification circuit after adding first and second injection signals (during modulation)
51 Output waveform 52 of current detection circuit 52 First error signal component 53 of error signal output from input amplifier Second error signal component 54 of error signal output from input amplifier Error signal waveform 56 output from input amplifier 57, 58 Error signal waveform output from input amplifier 59 First error signal component 60 of error signal output from addition / subtraction amplification circuit Second error signal component 61 of error signal output from addition / subtraction amplification circuit 61 Addition / subtraction amplification Error signal waveform output from circuit 101 Vibrator 102 Frames 103a to 103h Beams 104a to 104d Additional mass portions 105a and 105b Drive electrodes 106a to 106d Detection electrodes 107a to 107h Reference voltage electrodes

Claims (5)

Detected by a piezoelectric vibrator having at least two drive electrodes for oscillating at a resonance frequency, at least two detection electrodes for detecting a signal generated as an angular velocity is applied, and the detection electrodes of the piezoelectric vibrator In order to amplify a minute signal output proportional to the angular velocity and output it as a DC voltage, a detection circuit comprising an addition / subtraction amplification circuit, a synchronous detection circuit, a low-pass filter circuit, and a self-oscillation of the piezoelectric vibrator at a resonance frequency A piezoelectric vibration gyro comprising a drive circuit comprising a current detection circuit, a phase adjustment circuit, and an automatic gain control circuit for providing the drive electrode with a signal of
The output of the current detection circuit is a first injection signal, the first injection signal is connected to the inverting terminal or the non-inverting terminal of the addition / subtraction amplification circuit through a first amplitude adjustment circuit, and the current detection circuit The output amplitude of the addition / subtraction amplification circuit is reduced and adjusted by connecting the second injection signal whose output has passed through the 90-degree phase shift circuit to the non-inverting terminal or the inverting terminal of the addition / subtraction amplification circuit through the second amplitude adjustment circuit. A piezoelectric vibration gyro characterized by that.   2. The piezoelectric gyro according to claim 1, wherein the first and second amplitude adjustment circuits are configured by variable resistors, and a signal amplitude input to the addition / subtraction amplification circuit is adjusted by changing a resistance value of the variable resistors. A piezoelectric vibration gyro characterized by that.   2. The piezoelectric gyro according to claim 1, wherein the first and second amplitude adjustment circuits include an operational amplifier circuit capable of varying an amplifier gain and a fixed resistor connected to a subsequent stage thereof, and the operational amplifier circuit is provided. The piezoelectric vibration gyro is characterized in that the amplitude of the signal input to the addition / subtraction amplification circuit is adjusted by changing the amplifier gain.   4. The piezoelectric vibration gyro according to claim 1, wherein an input terminal of the addition / subtraction amplification circuit for inputting the first and second injection signals is connected to the first and second amplitude adjustments. 5. A piezoelectric vibration gyro characterized by having a structure that can be switched between an inversion terminal and a non-inversion terminal by a change-over switch provided at the next stage of the circuit. Detected by a piezoelectric vibrator having at least two drive electrodes for oscillating at a resonance frequency, at least two detection electrodes for detecting a signal generated as an angular velocity is applied, and the detection electrodes of the piezoelectric vibrator In order to amplify a minute signal output proportional to the angular velocity and output it as a DC voltage, a detection circuit comprising an addition / subtraction amplification circuit, a synchronous detection circuit, a low-pass filter circuit, and a self-oscillation of the piezoelectric vibrator at a resonance frequency A piezoelectric vibration gyro comprising a drive circuit comprising a current detection circuit, a phase adjustment circuit, and an automatic gain control circuit for providing the drive electrode with a signal of
One of the outputs of the current detection circuit is directly connected to one of the changeover switches provided in the next stage, and the other is connected to the other of the changeover switches via the inverting amplifier circuit, and the other is connected to the other of the changeover switches. The polarity is switched by a changeover switch, connected to either the inverting terminal or the non-inverting terminal of the addition / subtraction amplifier circuit through the first amplitude adjustment circuit at the subsequent stage, and the output of the current detection circuit is a 90-degree phase shift circuit One of them is connected to one of the changeover switches provided in the next stage as it is, and the other is connected to the other of the changeover switches via the inverting amplifier circuit, and the other is connected to the other of the changeover switches. The piezoelectric vibration jar is switched in polarity and connected to either the inverting terminal or the non-inverting terminal of the adder / subtractor amplifier circuit through the second amplitude adjusting circuit in the subsequent stage. B.

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