JP2008064657A - Angular velocity detection method, angular velocity sensor element piece, and angular velocity detection circuit - Google Patents

Abstract

An object of the present invention is to enable driving (excitation) and detection of angular velocity with two terminals.
An angular velocity sensor element piece is formed from a crystal plate to a tuning fork type vibration piece. The quartz plate 18 has θ = 0 °, 90 °, 180 °, 270 when the rotation angle around the Y axis with respect to the XY plane is θ, where the crystal axes of the quartz crystal are X, Y, Z. It has a cut angle that is in the range excluding °. In the tuning fork type angular velocity sensor element piece 10, when the vibrating arms 14 and 16 are excited, the vibration component of the bending vibration in the direction along the main surface and the vibration component of the bending vibration in the direction orthogonal to the main surface are synthesized. Perform circular vibration.
[Selection] Figure 2

Description

  The present invention relates to a method for detecting an angular velocity, and more particularly to a method for detecting an angular velocity by a vibration method, an angular velocity sensor element piece, and an angular velocity detection circuit.

  There are various methods for detecting the angular velocity, such as a mechanical method using a rotating piece, an optical method such as an optical fiber gyro, a fluid method using a gas flow, and a vibration method using vibration of a vibrating body. In particular, a so-called vibration gyro of a vibration type that detects a change in vibration due to the action of a Coriolis force generated by rotation of a vibrating body that is vibrated to obtain the magnitude of the angular velocity can be manufactured in a small size and at low cost. For this reason, in recent years, vibration gyros have been widely used for correcting camera shake of digital cameras.

As an angular velocity sensor element piece of a vibrating gyroscope, a tuning fork type vibrating piece is known as described in Patent Document 1. The angular velocity sensor element piece described in Patent Document 1 forcibly causes bending vibration in the X-axis direction of a crystal crystal using one of a pair of arms of a tuning fork type vibrating piece made of a crystal as a driving arm. The other of the pair of arms is used as a detection arm, and charges generated when the detection arm is bent can be detected by the Coriolis force accompanying the angular velocity acting on the vibration piece.
JP-A-2005-241606

  However, the angular velocity sensor element piece described in Patent Document 1 uses one of a pair of arms as a drive arm and the other arm as a detection arm. For this reason, the angular velocity sensor element piece described in Patent Document 1 includes a pair of drive terminals for applying a drive voltage to the drive arm, and a pair of detection terminals for detecting the charge generated in the detection arm. 4 terminals are required. Therefore, the angular velocity sensor element piece described in Patent Document 1 has the same shape as a tuning fork type piezoelectric vibrating piece (ordinary resonator) having only two driving terminals (a pair), but the number of terminals. Therefore, it cannot be manufactured in the same manufacturing process as the tuning fork type piezoelectric vibrating piece, and the number of terminals is large, so that the manufacturing process becomes complicated as compared with the manufacturing process of the tuning fork type piezoelectric vibrating piece.

  In addition, since the angular velocity sensor element piece described in Patent Document 1 is driven (excited) by only one of the pair of arms, the CI value becomes large and is difficult to drive. And if such a resonator element is further reduced in size, which has become increasingly demanding, the CI value becomes larger and side effects such as requiring a large drive power will occur. If you do not like the side effects, you will not be able to reduce the size sufficiently. In the angular velocity sensor element piece described in Patent Document 1, the state of vibration due to the Coriolis force acting on the drive arm is transmitted to the detection arm through the base, and the detection arm is bent as a reaction force. For this reason, the amount of deflection of the detection arm is small, and in order to detect charges based on the amount of deflection, a large gain is required, and a special voltage such as a lock-in amplifier is required to obtain a signal voltage corresponding to the amount of charge from noise. And a detection circuit becomes expensive. Further, the angular velocity sensor element piece described in Patent Document 1 requires an analog detection circuit for detecting charges generated in the detection arm, and the integrated circuit (IC) constituting the detection circuit is increased in size.

The present invention has been made to solve the above-described drawbacks of the prior art, and has an object to enable driving (excitation) and detection of angular velocity with two terminals.
Another object of the present invention is to be able to manufacture the same tuning fork type piezoelectric vibrating piece in the same process.

Another object of the present invention is to reduce current consumption.
Another object of the present invention is to make it possible to reduce the size of an IC without requiring a special circuit for detecting angular velocity.

  In order to achieve the above object, an angular velocity detection method according to the present invention causes a vibrating piece to vibrate in a circle and detects a change in the circular vibration to detect in a plane perpendicular to the axis of the circular vibration of the vibrating piece. It is characterized by obtaining the angular velocity at.

  In the present invention as described above, the vibration piece is intentionally caused to circularly vibrate. When such a circularly vibrating piece is rotated in a plane perpendicular to the axis of the circular vibration (angular velocity acts), the frequency of the circular vibration increases or decreases depending on the direction of the acting angular velocity. To do. Therefore, by detecting the vibration frequency of the circular vibration of the resonator element, the direction and speed of the angular velocity acting in the plane perpendicular to the axis of the circular vibration of the resonator element can be obtained.

  If the vibrating arm is a tuning-fork-type vibrating piece (resonator) that has previously vibrated circularly, a slight change in the frequency of the circular vibration of the driving arm caused by the rotational motion acting on the vibrating piece is caused at the driving terminal Can be detected. That is, it is not necessary to provide a detection terminal in particular, and an angular velocity sensor element can be realized even with two terminals like a normal tuning fork type piezoelectric vibrating piece. For this reason, it can manufacture in the same manufacturing process as a normal tuning fork type piezoelectric vibrating piece, can utilize a conventional installation as it is, and can reduce cost. Since the two arms of the tuning fork type vibrating piece are driven (excited), the CI value of the vibrating piece can be reduced, the power consumption can be reduced, and the sensor element piece can be made smaller. be able to. In the present invention, the circular vibration includes elliptical vibration.

  The change in the circular vibration may be a change in the frequency or period of the circular vibration. A change in circular vibration can be obtained as a change in amplitude. However, if it is detected as a change in frequency (resonance frequency), the difference between the resonance excitation when the angular velocity is acting and the resonance excitation when it is not acting. Can be easily obtained. Therefore, it is possible to easily detect a change in circular vibration. The same applies when obtaining a change in the period of circular vibration. As described above, when the change in the circular vibration is obtained as the change in the frequency or the period, a special circuit such as a lock-in amplifier is not required for the detection circuit, and the detection circuit can be manufactured at low cost. In particular, when a change in circular vibration is detected as a change in frequency, the detection circuit can be easily digitized, and an A / D converter is not required, so that the size of the IC can be reduced.

  The angular velocity sensor element piece for carrying out the angular velocity detection method described above is a range excluding θ = 0 °, 90 °, 180 °, and 270 °, where θ is the rotation angle of the crystal around the Y axis with respect to the Z plate. It is a tuning fork type vibration piece made of a quartz plate having a main surface.

  A tuning fork type resonator element comprising a quartz plate having cut angles other than θ = 0 °, 90 °, 180 °, and 270 °, where θ is the rotation angle around the Y axis of the crystal with respect to the XY plane of the crystal, is a tuning fork. When the arm (vibrating arm) is excited, it vibrates circularly. That is, when the vibrating arm is excited (driven), the vibrating arm combines a normal bending vibration in the plane of the tuning-fork type vibrating piece and a bending vibration in a direction perpendicular to the main surface of the vibrating piece called a walking mode. Vibrate. Therefore, the driving arm of the tuning fork type vibrating piece made of the quartz plate having the cut angle can be caused to vibrate only by being normally excited. Since both of the pair of vibrating arms can be driven, the CI value can be reduced, power consumption can be reduced, and further downsizing can be achieved.

  An angular velocity detection circuit according to the present invention includes a first voltage-controlled oscillator including a resonator element having a vibrating arm that vibrates circularly as a resonator, a second voltage-controlled oscillator, an output signal of the first voltage-controlled oscillator, and the A phase comparator for phase comparison of the output signal of the second voltage controlled oscillator, a low pass filter for converting the output signal of the phase comparator to DC, and an output signal of the low pass filter for the second voltage controlled oscillator And a configuration in which the output signal of the low-pass filter is applied to the first voltage controlled oscillator, and the output signal of the low-pass filter is used as angular velocity information. It is characterized by that. Thereby, said effect can be acquired.

  The vibrating piece may be a tuning fork type vibrating piece. The vibrating piece is a tuning fork type vibrating piece made of a quartz plate. When the crystal axis of the crystal is X, Y, Z and the rotation angle about the Y axis with respect to the XY plane is θ, θ = 0 °, It is good to form from the quartz plate which has a main surface which is a range except 90 degrees, 180 degrees, and 270 degrees.

Preferred embodiments of an angular velocity detection method, an angular velocity sensor element piece, and an angular velocity detection circuit according to the present invention will be described in detail with reference to the accompanying drawings.
FIG. 1 is a perspective view schematically showing an angular velocity sensor element piece according to the present invention. In FIG. 1, the angular velocity sensor element piece 10 is formed into a tuning fork-shaped vibrating piece by a piezoelectric substrate. That is, the angular velocity sensor element piece 10 includes a base portion 12 formed in a substantially rectangular shape and a pair of vibrating arms 14 and 16 which are a pair of vibration portions projecting in parallel in the same direction from one side of the base portion 12.

  In the case of the embodiment, the angular velocity sensor element piece 10 is composed of a quartz crystal plate 18 having a cut angle shown in FIG. The three orthogonal X, Y, and Z axes shown in FIG. 2 are crystal axes of the crystal, where the X axis is the electrical axis, the Y axis is the mechanical axis, and the Z axis is the optical axis. The quartz plate 18 has a cut angle obtained by rotating the angle θ around the Y axis with respect to the XY plane serving as the quartz Z plate 20. The surface of the crystal plate 18 is the main surface of the angular velocity sensor element piece 10.

  In the embodiment, the rotation angle θ around the Y axis is in the range of θ ≠ 0 °, 90 °, 180 °, 270 °. In the case of θ = 0 ° and 180 °, when the vibrating arms 14 and 16 are excited, only bending vibration is performed in the plane of the tuning fork-type vibrating piece (X-axis direction), and the direction orthogonal to the surface of the vibrating piece (Z-axis direction) In the case of θ = 90 ° and 270 °, when the vibrating arms 14 and 16 are excited, only bending vibration in the direction (Z-axis direction) perpendicular to the surface of the tuning-fork type vibrating piece is performed. It does not include a vibration component in the plane of the vibrating piece (X-axis direction), and circular vibration described later cannot be performed. On the other hand, the quartz plate 18 having a cut angle (main surface) excluding θ = 0 °, 90 °, 180 °, and 270 ° forms a tuning fork type vibration piece and drives (excites) the vibrating arm. The vibration component of the bending vibration as a tuning fork in which the two vibrating arms swing symmetrically in the direction along the main surface and the two vibrating arms in a direction opposite to each other in the direction orthogonal to the main surface of the quartz plate 18 A circular vibration in which a vibration component of a bending vibration called a so-called walking mode is synthesized is synthesized.

  In the angular velocity sensor element piece 10, a pair of vibrating arms 14 and 16 are formed in a substantially prismatic shape, and excitation electrodes are provided on the vibrating arms 14 and 16, respectively. The excitation electrodes include main surface electrodes 22 and 24 (the back surface is not shown) formed on the front and back main surfaces of the vibrating arms 14 and 16, and side electrodes 26 and 28 (on the both side surfaces orthogonal to the main surface). The left side surface of FIG. 1 consists of (not shown). The left and right side electrodes of the vibrating arms 14 and 16 are connected to each other via tip connecting electrode portions 30 and 32 formed at the tip ends of the main surfaces of the vibrating arms 14 and 16, respectively. Further, the main surface electrode 22 formed on the main surface of one vibration arm 14 is connected to the side electrodes 28 formed on both side surfaces of the other vibration arm 16 via the conductive pattern 34 provided on the base 12. . The main surface electrode 22 and the side surface electrode 28 are formed integrally with the extraction electrode 36 provided on the base 12. Similarly, the main surface electrode 24 of the other vibrating arm 16 is connected to the side electrode 26 of one vibrating arm 14 via a conductive pattern 38. The main surface electrode 24 and the side surface electrode 26 are formed integrally with the extraction electrode 40 provided on the base 12.

  These lead electrodes 36 and 40 are driving terminals for driving (exciting) the vibrating arms 14 and 16 and are also detecting terminals for detecting changes in the circular vibration of the vibrating arms 14 and 16. Therefore, like a normal tuning fork type piezoelectric vibrating piece, it can have two terminals, and can be manufactured by a manufacturing process of a normal tuning fork type piezoelectric vibrating piece. For this reason, the manufacturing cost of the angular velocity sensor element piece 10 can be reduced. In addition, each extraction electrode 36 and 40 is extended also to the back surface side through the side surface of the base 12. FIG. And the electrode is formed in the back surface of the angular velocity sensor element piece 10 symmetrically with the surface.

  In the angular velocity sensor element piece 10 thus configured, the extraction electrodes 36 and 40 provided on the base 12 are joined to a joining electrode provided on a package (not shown) via a conductive adhesive or the like, and vacuum or It is hermetically sealed in an inert gas atmosphere. Then, the angular velocity sensor element piece 10 formed of a tuning fork type vibrating piece has a center line 42 of the tuning fork type vibrating piece as a detection axis (sensitive axis), and detects an angular velocity ω around the center line 42.

  An angular velocity sensor element piece 10 formed from a crystal plate 18 having a cut angle rotated by θ in a range other than θ = 0 °, 90 ° 180 °, and 270 ° with respect to the XY plane drives the vibrating arms 14 and 16. When (excitation) occurs, the vibrating arms 14 and 16 perform circular vibration around the axis of the vibrating arms. That is, when a voltage of a predetermined frequency is applied between the angular velocity sensor element piece 10 and the extraction electrodes 36 and 40, the vibration components of the flexural vibration in the direction along the main surface and the vibration arms 14 and 16 are applied to the main surface. A clockwise vibration or a counterclockwise circular vibration in which the vibration components (walking mode) of the bending vibration in the orthogonal direction are combined is performed. The direction of rotation of this circular vibration is uniquely determined by the value of θ. In the case of the embodiment, the period of the bending vibration in the direction along the main surfaces of the vibrating arms 14 and 16 and the period of the bending vibration in the direction orthogonal to the main surfaces are substantially matched. The coincidence of both periods can be performed by adjusting the width b and thickness d of the vibrating arms 14 and 16.

  When the vibrating arms 14 and 16 are performing circular vibration, an equivalent circuit of the angular velocity sensor element piece 10 can be expressed as shown in FIG. That is, the angular velocity sensor element piece 10 that is circularly vibrating has an equivalent component 46 of the bending vibration of the tuning fork in the direction along the main surface and the main surface when viewed from the electrical terminals (extracting electrodes 36 and 40) 44 and 44. It can be considered that the equivalent circuit 48 of the bending vibration in the so-called walking mode in the direction orthogonal to the direction is electrically coupled by the coupling circuit 50. For example, when the circular vibration changes, such as when the frequency of the circular vibration changes, it can be considered that the coupling coefficient of the coupling circuit 50 has changed.

  For example, the angular velocity sensor element piece 10 is assumed to vibrate counterclockwise as shown in FIG. 4 when the vibrating arms 14 and 16 are excited. At this time, it is assumed that the angular velocity sensor element piece 10 receives clockwise rotation in a plane orthogonal to the axis of the circular vibration of the vibrating arms 14 and 16 that are the vibrating portions. That is, it is assumed that the angular velocity sensor element piece 10 is subjected to a counterclockwise angular velocity ω in a plane orthogonal to the center line 42. At this time, the vibrating arms 14 and 16 receive a force that can prevent circular vibration due to the angular velocity ω, and the amplitude of the circular vibration decreases and the frequency of the circular vibration decreases. On the other hand, as shown in FIG. 4, when the vibrating arms 14 and 16 vibrate counterclockwise, when subjected to the action of the clockwise angular acceleration, the circular vibration is promoted and the amplitude of the circular vibration is increased. As the frequency increases.

  Such a change in circular vibration (change in frequency) is detected by a circuit as shown in FIG. 5, and is converted into a signal corresponding to the direction and magnitude of the angular velocity by a conversion circuit (angular velocity calculation circuit) (not shown). Is done. The circuit shown in FIG. 5 is an example of a frequency detection circuit. The angular velocity sensor element piece 10 formed as a tuning fork type vibrating piece is connected to a voltage controlled oscillation circuit 52 as a resonator, and forms a voltage controlled crystal oscillator (VCXO) 54 as a first voltage controlled oscillator together with the voltage controlled oscillation circuit 52. To do. The output signal of the voltage controlled crystal oscillator 54 is input to the phase comparator 56. Further, the output signal of the second voltage controlled oscillator (VCO) 58 is input to the phase comparator 56.

  A low-pass filter 60 is provided on the output side of the phase comparator 56. On the output side of the low-pass filter 60, an amplifier 62 and an amplifier 64 are connected in parallel. The amplifier 62 inputs an output signal as a frequency control voltage to the voltage control type variable capacitance element in the voltage control oscillation circuit 52. The output signal of the amplifier 62 is output as frequency information of circular vibration through the amplifier 66. On the other hand, the output signal of the amplifier 64 is input as a frequency control signal to the voltage controlled oscillator 58 via the delay circuit 68. In the embodiment, the delay circuit 68 includes an integrating circuit in which a resistor R and a capacitor C are connected in series. The delay circuit 68 gives the output signal of the low-pass filter amplified by being delayed by a time constant determined by R and C as a frequency control voltage to the voltage control type variable capacitance element of the voltage control oscillator 58.

  In the detection circuit configured as described above, the resonance frequency of the voltage controlled crystal oscillator (VCXO) 54 when the angular velocity sensor element piece 10 is not acting is matched with the resonance frequency of the voltage controlled oscillator 58. In addition, the phase adjustment circuit (not shown) synchronizes the initial phase (the phase when the switch is turned on) of the output signal of the voltage controlled crystal oscillator 54 and the output signal of the voltage controlled oscillator 58 input to the phase comparator 56. is there. Therefore, when the in-plane angular velocity ω orthogonal to the center line 42 of the angular velocity sensor element piece 10 is not acting, the output signals of the voltage controlled crystal oscillator 54 and the voltage controlled oscillator 58 input to the phase comparator 56 are Are the same and have the same phase. For this reason, the output signal of the phase comparator 56 is zero.

  When the angular velocity ω having an in-plane component orthogonal to the center line 42 acts on the angular velocity sensor element piece 10, the frequency of circular vibration (the rotational speed of the vibrating arms 14 and 16) changes as described above. For this reason, a phase shift occurs between the output signal of the voltage controlled crystal oscillator 54 input to the phase comparator 56 and the output signal of the voltage controlled oscillator 58. The phase comparator 56 outputs a phase difference signal (voltage) corresponding to this phase difference. A high-frequency component is removed from the output signal of the phase comparator 56 by the low-pass filter 60 to obtain a DC signal (DC voltage). This DC voltage is amplified by the amplifier 62 and applied to the voltage controlled oscillation circuit 52 of the voltage controlled crystal oscillator 54 as a frequency control voltage. The voltage controlled crystal oscillator 54 oscillates at a frequency corresponding to the frequency control voltage input to the voltage controlled oscillation circuit 52.

  On the other hand, the output signal (voltage) of the low-pass filter 60 amplified by the amplifier 64 via the delay circuit 68 is input to the voltage controlled oscillator 58 as a frequency control signal. That is, the voltage-controlled oscillator 58 changes its oscillation frequency following the control voltage output from the low-pass filter with a delay of a time constant determined by R and C of the delay circuit 68. Therefore, the voltage signal extracted from the output side of the amplifier 62 is a signal corresponding to a phase difference due to a change in oscillation frequency based on the magnitude of the angular velocity received by the angular velocity sensor element piece 10 at that time. Therefore, the output signal of the amplifier 62 is amplified by the amplifier 66 (this amplifier 66 can be omitted when the output of the amplifier 62 is sufficiently large), and is output to a converter (angular velocity calculator) (not shown). As a result, the direction and magnitude of the angular velocity acting on the angular velocity sensor element piece 10 can be obtained.

  Thus, since the angular velocity sensor element piece 10 of the embodiment excites the pair of vibrating arms 14 and 16, the CI value can be reduced. Accordingly, the angular velocity sensor element piece 10 has a small CI value, and thus can reduce power consumption. Further, since a change in circular vibration is detected as a change in frequency, a special circuit such as a lock-in amplifier is not required, and the detection circuit can be configured at low cost. Furthermore, since the angular velocity can be obtained by detecting the frequency, an analog circuit is not required, and the detection circuit can be downsized and easily digitized.

  The above embodiment is an aspect of the present invention, and is not limited to the embodiment. For example, in the above-described embodiment, the case where the vibrating body is formed in a tuning fork shape has been described. However, the vibrating body only needs to be capable of causing a circular vibration such as a simple bar shape. In the above embodiment, the case where the change in the circular vibration is detected as the change in the frequency has been described. However, the change in the circular vibration may be detected as a change in the period or a change in the amplitude.

Further, the circular vibration of the vibrating arms 14 and 16 in the above embodiment includes elliptical vibration and perfect circular vibration.
In particular, since the balance of the rotational motion is better as the vibrating arms 14 and 16 are moved in a perfect circular motion or a circular motion close thereto, an angular velocity sensor element having high sensitivity characteristics can be obtained.

  In the detection circuit, the oscillator that compares the phase with the voltage-controlled crystal oscillator 54 is not described as the resonator of the voltage-controlled oscillator 58, but other CL resonance circuits including a coil and a capacitor are used as the resonator. In addition, when a voltage controlled crystal oscillator using an AT crystal unit or the like is applied, a high frequency temperature characteristic can be obtained, so that a high performance can be obtained with respect to the starting characteristic of the angular velocity detection circuit.

  That is, in the case of a CL resonance circuit with relatively poor frequency temperature characteristics, the temperature may deviate significantly from the desired frequency when the angular velocity detection circuit is started up. Therefore, the feedback control (phase) is not repeated until the desired operating state is reached. Comparison and frequency control) are required, or feedback control becomes impossible.

  On the other hand, when an AT crystal unit having excellent frequency temperature characteristics is used, it does not deviate significantly from the desired frequency depending on the temperature. Therefore, the number of feedback control until reaching the desired operating state is sufficient. .

It is a perspective view of the angular velocity sensor element piece which concerns on embodiment. It is explanatory drawing of the cut angle of the crystal plate which forms the angular velocity sensor element piece which concerns on embodiment. It is an equivalent circuit diagram of the angular velocity sensor element piece according to the embodiment. It is explanatory drawing of an effect | action of the angular velocity sensor element piece which concerns on embodiment. It is a figure which shows an example of the circuit which detects the frequency change by the angular velocity of the angular velocity sensor element piece which concerns on embodiment.

Explanation of symbols

  10 ......... Angular velocity sensor element piece (vibrating piece), 12 ......... Base, 14, 16 ......... Vibrating arm, 22, 24 ......... Main surface electrode, 26, 28 ......... Side electrode, 36, 40 ……… Extraction electrode (terminal).

Claims (6)

  A method for detecting an angular velocity, comprising: vibrating a vibrating piece in a circle; and detecting a change in the circular vibration to obtain an angular velocity in a plane perpendicular to the axis of the circular vibration of the vibrating piece. The angular velocity detection method according to claim 1,
The change in circular vibration is a change in frequency or period of the circular vibration.   When the crystal axes of the quartz are X, Y, and Z, the main surface is in a range excluding θ = 0 °, 90 °, 180 °, and 270 °, where θ is the rotation angle around the Y axis with respect to the XY plane. An angular velocity sensor element piece, which is a tuning fork type vibration piece made of a quartz plate having   A first voltage-controlled oscillator including a resonator element whose resonator arm vibrates circularly as a resonator, a second voltage-controlled oscillator, an output signal of the first voltage-controlled oscillator, and an output signal of the second voltage-controlled oscillator Phase comparator, a low-pass filter that converts the output signal of the phase comparator into a direct current, and an output signal of the low-pass filter that is applied to the second voltage-controlled oscillator via a delay circuit And an arrangement for applying the output signal of the low-pass filter to the first voltage-controlled oscillator, and an arrangement using the output signal of the low-pass filter as angular velocity information. The angular velocity detection circuit according to claim 4,
An angular velocity detection circuit, wherein the vibrating piece is a tuning fork type vibrating piece. The angular velocity detection circuit according to claim 4,
The vibrating piece is a tuning fork type vibrating piece made of a quartz plate, and the tuning fork type vibrating piece is θ when the crystal axis of the crystal is X, Y, Z and the rotation angle about the Y axis with respect to the XY plane is θ. = An angular velocity detection circuit comprising a quartz plate having a main surface in a range excluding 0 °, 90 °, 180 °, and 270 °.

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