JP2008151630A - Acceleration detector - Google Patents

Abstract

An acceleration detection device that operates stably even when subjected to an impact other than acceleration is provided.
A VCXO2 having a tuning fork type crystal resonator element 20 as a resonator, a VCO3, a phase comparison circuit 4 for comparing the phases of an output signal of the VCXO2 and an output signal of the VCO3, and an output signal of the phase comparison circuit 4 A DCF LP5, a high gain amplifier circuit 6 that amplifies the output of the LPF5, and a DC servo circuit 8 that outputs a control voltage corresponding to the DC component of the output signal output from the high gain amplifier circuit 6. The oscillation frequency of the VCXO 2 is controlled using a part of the output signal output from the gain amplifier circuit 6 as a control voltage, and the oscillation frequency of the VCO 3 is controlled using the signal output from the DC servo circuit 8 as a control voltage.
[Selection] Figure 1

Description

  The present invention relates to an acceleration detection device that detects acceleration using a piezoelectric vibration element.

In recent years, acceleration sensors that detect acceleration have been researched and developed for a wide range of applications such as next-generation automobiles, robots, and the space industry. As an acceleration sensor developed for consumer equipment, a MEMS (Micro Electro Mechanical Systems) sensor in which an acceleration detection mechanism is manufactured by a semiconductor process is well known.
On the other hand, for example, pressure sensors for measuring pressures of gases and liquids have been developed using tuning fork vibrators in addition to MEMS sensors.

FIG. 8 is a diagram showing a configuration of a conventional vibration sensor circuit disclosed in Patent Document 1. In FIG. A conventional sensor circuit 100 shown in FIG. 8 includes a sensor unit 101 and a drive circuit 102. The sensor unit 101 includes a vibrator 101a which is a sensor element, an amplifier 101b, and a rectifier circuit 101c. The vibrator 101a is, for example, a vibrator assembled with lead zirconium titanate (PZT).
The drive circuit 102 includes a voltage controlled oscillator 102a, an amplifier 102b, and a phase comparator 102c. In the sensor circuit 100 configured as described above, the vibrator 101 a of the sensor unit 101 is driven by the voltage controlled oscillator 102 a of the drive circuit unit 102.
Here, when the vibrator 101a receives physical stress (pressure), the resonance frequency of the vibrator 101a changes. When the resonance frequency of the vibrator 101a changes, the phase of the output signal output from the phase comparator 102c of the drive circuit 102 changes. Thus, the output signal of the voltage controlled oscillator 102a is controlled to coincide with the resonance frequency of the vibrator 101a, and the vibrator 101a vibrates at the resonance frequency corresponding to the stress. Therefore, the stress value received by the vibrator 101a can be detected by taking the output of the line 104 or 103 as a detection signal.
Japanese Utility Model Publication No. 62-155336

By the way, when the vibration sensor circuit 100 as described above is mounted on a moving object or the like as an acceleration sensor, if the resonance frequency of the vibrator 101a suddenly fluctuates due to an impact other than acceleration received when the moving object moves, the phase comparator 102c. The output signal of the signal fluctuates rapidly. However, since the vibration type sensor circuit 100 shown in FIG. 8 has a PLL control configuration that feeds back a phase comparison result based on the output of the vibrator 101a to the voltage controlled oscillator 102a, the output signal of the phase comparator 102c fluctuates rapidly. In this case, the voltage controlled oscillator 102a cannot follow the PLL control. As a result, the voltage controlled oscillator 102a may stop oscillating. For this reason, an acceleration detection device cannot be configured using the conventional vibration sensor circuit 100.
The present invention has been made in view of the above points, and an object of the present invention is to provide an acceleration detection device that operates stably even when subjected to an impact other than acceleration.

In order to achieve the above object, an acceleration detection device of the present invention includes a voltage-controlled piezoelectric oscillation circuit including a stress-sensitive element made of a piezoelectric material as a resonator, a voltage-controlled oscillation circuit, and an output of the voltage-controlled piezoelectric oscillation circuit. A phase comparison circuit that compares the phase of the signal and the output signal of the voltage controlled oscillation circuit, a low-pass filter that converts the phase difference signal output from the phase comparison circuit into a direct current, and an output signal that is output from the low-pass filter And a DC servo circuit that includes a time constant circuit and outputs a control voltage according to the output signal of the amplifier circuit, and outputs the output signal output from the amplifier circuit as an acceleration detection signal, and the amplifier circuit Part of the output signal output from the control circuit is fed back as a control voltage to control the oscillation frequency of the voltage-controlled piezoelectric oscillation circuit. By feeding back the output signal to be force as a control voltage and controls the oscillation frequency of the voltage controlled oscillator circuit.
According to the present invention, the oscillation frequency of the voltage control type oscillation circuit is controlled by the time constant of the DC servo circuit with a delay from the oscillation frequency of the voltage control type piezoelectric oscillation circuit. It is possible to obtain a phase difference output by acceleration detected by the stress sensitive element of the voltage control type piezoelectric oscillation circuit.
Even when a strong impact other than acceleration is applied momentarily and the frequency of the stress sensitive element fluctuates greatly, the voltage controlled oscillator circuit does not follow the voltage change caused by the instantaneous frequency fluctuation due to the time constant of the DC servo circuit. Thus, it is possible to prevent a problem that the frequency control is disabled in the voltage controlled oscillation circuit and the oscillation is stopped.

The acceleration detecting device of the present invention includes a buffer amplifier circuit that buffers an output signal output from the amplifier circuit, and outputs the output of the buffer amplifier circuit as a control voltage to a voltage-controlled piezoelectric oscillation circuit or / and a DC servo circuit. It is characterized by that.
According to the present invention, correction can be made in consideration of drift of the buffer amplifier circuit.

In the acceleration detecting device of the present invention, the stress sensitive element is a tuning fork type vibration element having two vibration arms arranged in parallel and a coupling portion coupling one end in the extension direction of the two vibration arms. The part was fixed and arranged so that the extending direction of the two vibrating arms coincided with the acceleration detection direction.
According to the present invention, a tuning fork type vibration element can be used as a stress sensitive element for detecting acceleration.

In the acceleration detecting device of the present invention, the stress sensitive element is a double tuning fork type vibrating element having two vibrating arms arranged in parallel and a coupling portion in which both ends in the extending direction of the two vibrating arms are coupled. Yes, either one of the coupling portions is a fixed end and the other is a free end, and the extending direction of the two vibrating arms is arranged to coincide with the acceleration detection direction.
According to the present invention as described above, a double tuning fork type vibration element can be used as a stress sensitive element for detecting acceleration, so that the stress sensitivity can be increased as compared with the case where a tuning fork type vibration element is used.

  The acceleration detection device of the present invention includes at least a voltage control type piezoelectric oscillation circuit or a rectangular circuit that rectangularizes an output signal waveform output from the voltage control oscillation circuit. With this configuration, even when the output signal waveform output from the voltage-controlled piezoelectric oscillation circuit and the voltage-controlled oscillation circuit is a sinusoidal waveform, at least one of the voltage-controlled piezoelectric oscillation circuit and the voltage-controlled oscillation circuit is used. Since the waveform of the output signal output to the phase comparison circuit can be made rectangular, the phase comparison circuit can reliably perform the phase comparison.

Embodiments of the present invention will be described below with reference to the drawings.
FIG. 1 is a block diagram showing the configuration of the acceleration detection device according to the first embodiment of the present invention.
1 includes a voltage controlled crystal oscillation circuit (hereinafter referred to as a VCXO (voltage controlled crystal oscillator)) 2, a voltage controlled oscillation circuit (hereinafter referred to as a VCO (voltage controlled oscillator)) 3. , A phase comparison circuit 4, a low-pass filter (hereinafter referred to as LPF) 5, a high gain amplifier circuit 6, a buffer amplifier circuit (hereinafter referred to as buffer amplifier) 7, and a DC servo circuit (hereinafter referred to as DC servo circuit) 8. Is done.
The VCXO 2 includes a tuning fork type crystal vibrating element 20 as a tuning fork type vibrating element. The tuning fork type crystal vibrating element 20 functions as a resonator of the oscillation circuit and also functions as an acceleration detecting element that detects acceleration. In the VCXO2, the output signal of the high gain amplifier circuit 6 is applied as a control voltage Vcont1 to a variable capacitance diode (not shown in the figure) of the VCXO2, thereby changing the load capacity of the oscillation loop, and the oscillation frequency of the output signal is constant. It is controlled to become.

The VCO 3 includes a resonance circuit such as a capacitor and a resistor, for example. By applying the control voltage Vcont2 from the DC servo circuit 8 to a variable capacitance diode (not shown), the load capacitance of the oscillation loop is changed to oscillate the output signal. The frequency is controlled to be constant.
The phase comparison circuit 4 compares the phase of the output signal output from the VCXO 2 with the phase of the output signal output from the VCO 3 and outputs the comparison result.
The low-pass filter 5 converts the phase difference signal output from the phase comparison circuit 4 into a direct current and outputs it. The high gain amplifier 6 amplifies and outputs the output signal from the LPF 5. The signal amplified by the high gain amplifier 6 is output as the acceleration detection signal Sα via the buffer amplifier 7. A part of the signal amplified by the high gain amplifier 6 is fed back to the VCXO 2 as a control voltage Vcont 1 and output to the DC servo circuit 8.
The DC servo circuit 8 is composed of, for example, a time constant circuit including a resistor R and a capacitor C and an operational amplifier OP, and delays the signal amplified by the high gain amplifier 6 and feeds it back to the VCO 3 as a control voltage Vcont2. .

FIG. 2 is a diagram showing an example of the circuit configuration of the VCXO 2 described above.
The VCXO 2 shown in FIG. 2 includes a phase inverting amplifier (hereinafter referred to as a MOS inverter) IC1 as an oscillation circuit. Between the input and output of the MOS inverter IC1, a series circuit in which a feedback resistor R1 for self-bias and a capacitor C1 and a tuning fork type crystal resonator element 20 are connected in series is connected in parallel. Further, a capacitor C2 is connected between the connection point between the output terminal of the MOS inverter IC1 and the tuning fork type crystal resonator element 20 and the ground (GND), and the connection point between the capacitor C1 and the tuning fork type crystal resonator element 20 and the ground (GND). A variable capacitance diode D1 is connected between them. The variable capacitance diode D1 has an anode connected to the ground side and a cathode connected to the tuning fork type crystal vibrating element 20.
In the VCXO 2 configured as described above, an oscillation loop is configured by the tuning fork type crystal resonator element 20, the capacitors C1 and C2, and the variable capacitance diode D1. Accordingly, by applying the control voltage Vcont1 to the cathode of the variable capacitance diode D1 constituting the oscillation loop via the resistor R2 to vary the capacitance of the variable capacitance diode D1, the load capacitance of the oscillation loop is changed to change the oscillation frequency. Is configured to be controllable so as to have a predetermined oscillation frequency. Further, the VCXO2 using such a MOS inverter IC1 has a rectangular output signal waveform.

FIG. 3 is a diagram schematically showing the configuration of the tuning fork type crystal vibrating element 20 provided in the VCXO 2. The tuning-fork type crystal vibrating element 20 shown in FIG. 3 includes two vibrating arms 21a and 21b arranged in parallel and a coupling portion 22 that couples one end in the extension direction of the two vibrating arms 21a and 21b. . The coupling portion 22 of the tuning fork type crystal resonator element 20 is fixed to a substrate (not shown) on which the tuning fork type crystal resonator element 20 is mounted. At this time, as shown in FIG. 3, the extending directions of the vibrating arms 21a and 21b of the tuning-fork type crystal vibrating element 20 are made to coincide with the acceleration detection axis direction.
In the tuning fork type crystal resonator element 20 configured as described above, when an AC voltage is applied to a driving electrode (not shown), the two vibrating arms 21a and 21b arranged in parallel vibrate symmetrically as shown by broken lines. Then, for example, when the acceleration α in the direction of the arrow shown in FIG. 3 is applied in the state of bending vibration, an inertial force in the direction opposite to the direction of the acceleration α is apparently generated in the tuning fork type crystal resonator element 20. Due to this influence, the vibrating arms 21a and 21b of the tuning-fork type crystal vibrating element 20 receive a tensile stress that is pulled in a direction opposite to the acceleration α. In this case, the frequency of the tuning fork type crystal resonator element 20 is increased under the influence of tensile stress. On the other hand, when an acceleration in the direction opposite to the direction of the arrow shown in FIG. 3 is applied, an inertial force that appears in the direction opposite to the direction of the acceleration is apparently generated in the tuning fork type crystal vibrating element 20. The arms 21 a and 21 b receive a compressive stress that compresses in the direction of the coupling portion 22. In this case, the frequency of the tuning fork type crystal resonator element 20 is affected by the compressive stress and is lower than that in the case of the acceleration α. Therefore, in the present embodiment, the acceleration detection signal Sα is obtained based on a frequency change that occurs when acceleration is applied to the tuning fork type crystal resonator element 20.
Such a tuning-fork type crystal vibrating element 20 has a wide dynamic range (for example, ± 3 g to ± 400 g) and a high linearity (for example, 0.05% FS) as compared with a conventional MEMS acceleration sensor. There is an advantage that sensitivity stability is good.
In FIG. 3, the concept of bending vibration of the tuning-fork type crystal vibrating element 20 is shown by a broken line for easy understanding, but in reality, the shape of the tuning-fork type crystal vibrating element 20 is hardly displaced.

Hereinafter, the operation of the acceleration detection device 1 of the present embodiment will be described based on the characteristics of the tuning fork type crystal resonator element described above.
In the acceleration detection device 1 shown in FIG. 1, the oscillation frequency of the VCXO 2 and the VCO 3 is constant in a constant speed motion state in which no acceleration is applied in the acceleration detection axis direction of the tuning fork type crystal vibrating element 20 provided in the VCXO 2. The phase difference between the VCXO2 output signal detected by the phase comparison circuit 4 and the VCO3 output signal becomes zero.
On the other hand, when acceleration is applied in the acceleration detection axis direction of the tuning fork type crystal vibrating element 20 provided in the VCXO 2 and the oscillation frequency of the tuning fork type crystal vibrating element 20 changes, the output signal between the VCXO 2 and the output signal of the VCO 3 changes. A phase shift occurs. Then, a phase difference signal corresponding to the phase difference is output from the phase comparison circuit 4, thereby changing the output voltage of the LPF 5.
Therefore, in this embodiment, the output of the LPF 5 is amplified by the high gain amplifier 6 and then output as the acceleration detection signal Sα via the buffer amplifier 7.

Further, in the acceleration detection apparatus 1 of the present embodiment, a part of the output signal of the high gain amplifier 6 is fed back as the control voltage Vcont1 so as to perform PLL control on the VCXO2, and also supplied to the DC servo circuit 8, so that the DC servo circuit 8 is fed back to the VCO 3 as a control voltage Vcont2. In such a configuration, the control voltage Vcont2 applied to the VCO 3 is compared with the control voltage Vcont1 applied to the VCXO 2 by a time constant circuit provided in the DC servo circuit 8 against a sudden level fluctuation of the output signal of the LPF 5. Do not follow. Therefore, with this configuration, the phase comparison circuit 4 can output the phase difference due to the acceleration detected by the tuning fork type crystal resonator element 20 of the VCXO2. That is, for example, for a sudden acceleration change that repeatedly accelerates and decelerates, the phase difference varies between the output signal of VCXO2 and the output signal of VCO3 as the frequency of the tuning fork type crystal vibrating element 20 of VCXO2 varies. Occurs. This phase difference fluctuation is detected by the phase comparison circuit 4. Based on the detection result, the VCXO 2 is PLL-controlled by applying the control voltage Vcont1 so that the oscillation frequency becomes a desired value (value before fluctuation). Therefore, the control voltage Vcont1 can be output as the acceleration detection signal Sα via the buffer amplifier 7 or the like.
On the other hand, the output voltage of the LPF 5 accompanying the sudden acceleration change described above fluctuates in a high frequency manner. Since the DC servo circuit 8 does not output an output signal that follows the supply of such a high frequency output voltage, the control voltage Vcont2 is maintained at a substantially constant value regardless of the change in acceleration, and the oscillation of the VCO3. Does not fluctuate frequency.
Therefore, the acceleration detection apparatus 1 can output the acceleration detection signal Sα based on the detection result of the tuning fork crystal resonator 20 with respect to the acceleration change.

Further, in the acceleration detecting device 1 of the present embodiment, even when a strong impact other than acceleration is momentarily applied and the oscillation frequency of the tuning fork type crystal vibrating element 20 of the VCXO 2 greatly fluctuates, the VCO 3 is the time constant of the DC servo circuit 8. Therefore, the voltage change accompanying the instantaneous frequency fluctuation is not followed, so that the frequency control of the VCO 3 becomes impossible and the oscillation does not stop. Therefore, for example, even if an impact at the time of traveling of an automobile or the like is applied to the acceleration detection device 1, no malfunction occurs. That is, it is possible to prevent problems such as when a conventional sensor circuit is mounted as an acceleration sensor.
On the other hand, in the constant acceleration state, for example, when the value of the control voltage Vcont1 drifts (the output signal of the high gain amplifier circuit 6 drifts) due to the influence of the temperature characteristics of the electrical characteristics of the high gain amplifier circuit 6, Based on this, the value of the acceleration detection signal Sα also tries to drift.
However, in this case, since the above-mentioned drift tends to change relatively slowly with respect to the acceleration change, the DC servo circuit 8 follows the drift to control the control voltage Vcont2 and change the oscillation frequency of the VCO3. Can do.
Therefore, even if the oscillation frequency of VCXO2 fluctuates so as to increase due to the influence of drift, the oscillation frequency of VCO3 fluctuates so as to follow this, so the phase difference between the oscillation frequencies of both oscillators. The fluctuation can be suppressed, and the drift of the value of the acceleration detection signal Sα can be suppressed.

For example, in the conventional sensor circuit 100 shown in FIG. 8, it is conceivable to use the DC output (control voltage) of the phase comparator 102c of the drive circuit unit 102 as a stress value signal (acceleration signal). However, normally, an LC resonator or a CR resonator is used as the voltage controlled oscillator 102a, and the voltage controlled oscillator 102a having such a resonator has a large amount of frequency change with respect to the control voltage Vcont as shown in FIG. That is, the frequency sensitivity characteristic is high. Therefore, when the control voltage Vcont of the phase comparator 102c is used as the detection result of the stress value signal (acceleration signal) without using the resonance frequency as the detection result in the conventional sensor circuit 100, the control voltage Vcont with respect to the frequency change amount. It is not possible to realize a sensor with a small change amount and high detection sensitivity.
On the other hand, in the acceleration detection device 1 of the present embodiment, the control voltage of the VCXO 2 is used as an acceleration signal. Since VCXO has a narrow frequency variable range for the control voltage compared to the VCO (frequency control sensitivity is low), a change in the output voltage (control voltage) of the LPF to a large current (high potential) with respect to the frequency change accompanying the acceleration operation. ). A highly sensitive sensor can be realized with respect to acceleration changes.

Next, an acceleration detection apparatus according to the second embodiment of the present invention will be described.
FIG. 5 is a block diagram showing a configuration of an acceleration detection apparatus according to the second embodiment of the present invention. The same blocks as those in the acceleration detection apparatus 1 shown in FIG.
In the acceleration detection device 30 shown in FIG. 5, a part of the signal amplified by the high gain amplifier 6 is fed back to the VCXO 2 as the control voltage Vcont 1 and a part of the acceleration detection signal Sα output through the buffer amplifier 7 is fed back. The acceleration signal Sα output from the buffer amplifier 7 is delayed and fed back to the VCO 3 as the control voltage Vcont2. In the case of such a configuration, in addition to the above function, even if a frequency drift due to the influence of electrical characteristics of the high gain amplifier circuit 6 and the buffer amplifier 7 occurs, it can be corrected.

Next, an acceleration detection apparatus according to the third embodiment of the present invention will be described.
The same blocks as those in the acceleration detection apparatus 1 shown in FIG. The acceleration detection device 31 shown in FIG. 6 is characterized in that it includes first and second rectangularization circuits (waveform shaping circuits) 32 and 33 that rectangularize the waveforms of output signals output from the VCXO 2 and the VCO 3. . This is because the phase comparison circuit 4 provided in the acceleration detection device of the present embodiment may not be able to accurately perform phase comparison unless at least one of the two signal waveforms to be compared is a rectangular wave. If the levels of the two signals input to the comparison circuit 4 do not match, the detection result will include a value based on the difference in signal level in addition to the phase difference between the two input signals, so accurate acceleration detection I can't get results.

Therefore, in the acceleration detection device 31 shown in FIG. 6, a comparator or the like is used to make the output signal waveforms of VCXO2 and VCO3 rectangular between VCXO2 and the phase comparison circuit 4 and between VCO3 and the phase comparison circuit 4, respectively. First and second rectangularization circuits 32 and 33 are provided.
With this configuration, the phase comparison circuit 4 can reliably perform phase comparison. In the third embodiment, the first and second rectangularization circuits 32 and 33 are provided between the VCXO 2 and the phase comparison circuit 4 and between the VCO 3 and the phase comparison circuit 4, respectively. 4 can reliably perform phase comparison if the waveform of the output signal output from either VCXO2 or VCO3 is rectangular, so at least one of the output signal waveforms output from VCXO2 or VCO3. It is only necessary to provide one of the first rectangular circuit 32 and the second rectangular circuit 33 so as to make the rectangle rectangular.

Further, in the present embodiment, the tuning fork type crystal vibrating element 20 has been described as an example of the stress sensitive element. However, this is merely an example, and as the stress sensitive element, for example, a double tuning fork type crystal vibrating element as shown in FIG. It is also possible to use.
The double tuning fork type crystal vibrating element 23 shown in FIG. 7 includes two vibrating arms 21a and 21b arranged in parallel and a coupling portion 22a in which both ends in the extending direction of the two vibrating arms 21a and 21b are coupled. 22b. In this case, for example, only one of the coupling portions 22a and 22b is fixed to a substrate (not shown) on which the double tuning fork type crystal vibrating element 23 is mounted, and the other is set as a free end. do it.
When the acceleration detecting device of the present embodiment is configured using the double tuning fork type crystal vibrating element 23, the coupling portion 22b on the free end side functions as a weight, so that the acceleration sensitivity is higher than that of the tuning fork type crystal vibrating element 20 described above. be able to.
In the present embodiment, a tuning fork type vibration element has been described as an example of the stress sensitive element. However, this is only an example, and so-called AT-cut crystal vibration is used as long as the resonance frequency changes according to acceleration. Various piezoelectric vibration elements such as a child and a resonator can be applied as a stress sensitive element.

It is the figure which showed the structure of the acceleration detection apparatus which concerns on the 1st Embodiment of this invention. It is the figure which showed an example of the circuit structure of VCXO. It is the figure which showed the structure of the tuning fork type crystal vibrating element. It is the figure which showed the frequency sensitivity characteristic of VCXO and VCO. It is the figure which showed the structure of the acceleration detection apparatus which concerns on 2nd Embodiment. It is the figure which showed the structure of the acceleration detection apparatus which concerns on 3rd Embodiment. It is the figure which showed the structure of the double tuning fork type crystal vibrating element. It is the figure which showed the structure of the conventional vibration type sensor circuit.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1, 30, 31 ... Acceleration detection apparatus, 2 ... VCXO, 3 ... VCO, 4 ... Phase comparator, 5 ... LPF, 6 ... High gain amplifier, 7 ... Buffer amplifier, 8 ... DC servo circuit, 20 ... Tuning fork type crystal Vibration element, 21a, 21b ... vibrating arm, 22, 22a, 22b ... coupling part, 23 ... double tuning fork type crystal vibration element, 32, 33 ... rectangularization circuit

Claims (5)

A voltage controlled piezoelectric oscillation circuit including a stress sensitive element made of a piezoelectric material as a resonator;
A voltage controlled oscillator circuit;
A phase comparison circuit for comparing the phase of the output signal of the voltage controlled piezoelectric oscillation circuit and the output signal of the voltage controlled oscillation circuit;
A low-pass filter for converting the phase difference signal output from the phase comparison circuit into a direct current,
An amplifier circuit for amplifying an output signal output from the low-pass filter;
A DC servo circuit that includes a time constant circuit and outputs a control voltage according to the output signal of the amplifier circuit;
The output signal output from the amplifier circuit is output as an acceleration detection signal, and a part of the output signal output from the amplifier circuit is fed back as a control voltage to control the oscillation frequency of the voltage-controlled piezoelectric oscillation circuit. Further, the acceleration detection apparatus is characterized in that an output signal output from the DC servo circuit is fed back as a control voltage to control an oscillation frequency of the voltage controlled oscillation circuit.   A buffer amplifier circuit for buffering an output signal output from the amplifier circuit is provided, and the output of the buffer amplifier circuit is output as a control voltage to a voltage control type piezoelectric oscillation circuit and / or the DC servo circuit. The acceleration detection apparatus according to claim 1.   The stress sensitive element is a tuning fork type vibration element having two vibrating arms arranged in parallel and a coupling portion that couples one end in the extension direction of the two vibrating arms, and fixes the coupling portion. The acceleration detection device according to claim 1, wherein an extension direction of the two vibrating arms is arranged to coincide with an acceleration detection direction.   The stress-sensitive element is a double tuning fork type vibration element having two vibrating arms arranged in parallel and a coupling portion that couples both ends in the extension direction of the two vibrating arms. 3. The acceleration detection device according to claim 1, wherein either one of the two is a fixed end and the other is a free end, and the extension directions of the two vibrating arms are arranged to coincide with the acceleration detection direction.   5. A rectangular circuit for rectangularizing at least one of the voltage-controlled piezoelectric oscillation circuit and an output signal waveform output from the voltage-controlled oscillation circuit. The acceleration detection device according to item.

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