JPH10170271A - Angular velocity detector - Google Patents

Abstract

(57) Abstract: A vibrator-type angular velocity detection device capable of obtaining a detection signal from which a leakage vibration component is completely removed is provided. An oscillator, an exciting unit for exciting the oscillator, and a detecting unit for detecting an amplitude of vibration based on Coriolis force generated by rotation of the oscillator excited by the exciting unit. And an angular velocity calculating device for calculating an angular velocity of rotation from the magnitude of the amplitude detected by the detecting means, wherein the vibrator has two excitation vibrating reeds connected at one end, This excitation vibrating reed is a quadrangular prism, at least one of the side surfaces bent by the excitation is inclined with respect to the excitation direction, and the two excitation vibrating reeds are arranged plane-symmetrically. It is characterized by being.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an angular velocity detecting device used for an automobile navigation system and attitude control, and more particularly to a vibration type angular velocity detecting device.

[0002]

2. Description of the Related Art Conventionally, there has been known a vibration type angular velocity detecting apparatus utilizing the fact that when a vibrating body is rotated, a new vibration corresponding to the rotational angular velocity is generated by Coriolis force. As an example of such an angular velocity detecting device, for example, there is a vibrating gyroscope described in Japanese Patent Application Laid-Open No. 2-38917. The vibrating gyroscope includes a vibrator integrally provided with a detecting diaphragm having a thickness direction perpendicular to the thickness direction of the driving diaphragm at a tip of the driving diaphragm, and a support shaft penetrating through the center of gravity of the vibrator. Accordingly, the influence of the drive side on the piezoelectric element for detection provided on the diaphragm for detection, that is, the leakage vibration is reduced.

[0003]

However, in this conventional vibrating gyroscope, the driving vibration is hardly transmitted to the detecting diaphragm by making the thickness directions of the driving diaphragm and the detecting diaphragm orthogonal to each other, so that the leakage vibration is reduced. However, the structure was not designed to positively eliminate the leakage vibration, so that the leakage vibration could not always be sufficiently suppressed.

[0004]

SUMMARY OF THE INVENTION The present invention has been made to solve such a problem, and has a vibrator, an exciting means for exciting the vibrator, and a vibration excited by the exciting means. Detecting means for detecting the amplitude of the vibration based on the Coriolis force generated as the child rotates, and angular velocity calculating means for calculating the angular velocity of rotation from the magnitude of the amplitude detected by the detecting means. In the angular velocity detecting device, the vibrator has two excitation vibrating reeds connected at one end, and the excitable vibrating reed is a quadrangular prism, and at least one of the side surfaces bent by the excitation has an excitation direction. , And the two excitation vibrating reeds are arranged in plane symmetry.

[0005] Since the vibrating piece for excitation is a quadrangular prism and at least one of the side surfaces bent by the excitation is inclined with respect to the excitation direction, the leakage vibration in the direction perpendicular to the excitation direction, that is, the detection vibration direction. Are always constant, and the two excitation vibrating pieces are arranged in plane symmetry. Therefore, when the two excitation vibrating pieces are excited in opposite phases to each other, the two excitation vibrating pieces are excited. Since the respective leakage vibration components of the pieces are in phase, they can be canceled out by subtraction. When the two excitation vibration pieces are excited in the same phase, the leakage vibration components of the respective excitation vibration pieces are opposite. Since they are in phase, they can be canceled by adding.

[0006]

FIG. 1 is a perspective view showing a vibrator used in an embodiment of an angular velocity detecting device according to the present invention, and FIG. 2 is a block diagram showing an entire structure including the vibrator. In FIG. 1, a vibrator 10 is placed on an XY plane in an XYZ three-dimensional orthogonal coordinate space, and has a vibrator base 11 extending in the X-axis direction and an excitation base extending from the vibrator base 11 in the + Y direction. First vibrating reeds 12 and 13 and second vibrating reeds 14 and 1 extending from transducer base 11 coaxially with first vibrating reeds 12 and 13 in the −Y direction, respectively.
5, a support bar 16 extending in the -Y direction from the vibrator base 11 between the second vibrating bars 14 and 15, and a support bar 1
The fixing plate 17 provided at the end of the sixth unit 6 is integrally formed of a metal such as stainless steel. And the first
The vibrating bars 12 and 13 are quadrangular prisms, and their outer side surfaces are inclined at substantially the same angle with respect to the YZ plane in plane symmetry with each other.

[0007] Piezoelectric elements 21 and 22 are attached to the outer side surfaces of the first vibrating bars 12 and 13, respectively. Each of the piezoelectric elements 21 and 22 has a structure in which a strip-shaped plate made of a piezoelectric material such as PZT (lead zirconate titanate) is sandwiched between two metal electrodes. Its polarity and PZT due to the piezoelectric effect
In the direction of electrostriction. Piezoelectric elements 21 and 22
One electrode is attached to the outer side surface of the first vibrating reeds 12 and 13 with a conductive adhesive, and when a positive or negative voltage is applied to the other electrode while the vibrator 10 is grounded, the Y-axis direction Expand and contract.

In this embodiment, as will be described later, the piezoelectric element 22 is used for excitation driving, and the piezoelectric element 21 is used for detecting excitation vibration. The piezoelectric element 22 expands and contracts when an AC voltage is applied, whereby the first resonator element 12 vibrates in the X direction. This vibration energy is transmitted to the other first vibrating reed 13 via the vibrator base 11, and the first vibrating reed 13 vibrates in the X direction with an opposite phase to the first vibrating reed 12.

The detection of the vibration by the piezoelectric element 21 utilizes the piezoelectric effect of the piezoelectric element. When the first vibrating reed 12 vibrates in the X direction, the piezoelectric element 21 expands and contracts in the Y direction. If the vibrator 10 is grounded, a positive or negative voltage is generated in the electrode that is not in contact with the first vibrating reed in accordance with expansion and contraction. By detecting this, vibration can be detected.

The detecting piezoelectric elements 23 and 24 attached to the upper surfaces of the second vibrating reeds 14 and 15 for detection also include
The piezoelectric element 21 has the same structure as the piezoelectric elements 21 and 22, and vibrates the second vibrating reeds 14 and 15 in the Y direction.
The detection is performed based on the same principle as described above.

When the vibrator 10 rotates at an angular velocity ω about an axis parallel to the Y axis (including the Y axis) in a state where the first vibrating bars 12 and 13 are excited in the X direction in mutually opposite phases. A Coriolis force F represented by F = 2 mV · ω is generated in the Z direction in each of the resonator elements 12 and 13. Here, m is the mass of the resonator element, and V is the vibration speed. Due to the generation of the Coriolis force F, the first vibrating bars 12 and 13 vibrate in the Z direction with a 90 ° phase shift with respect to the vibration in the X direction. That is, the first vibrating reeds 12 and 13 also vibrate in the Z direction in opposite phases at the excitation frequency. Since this frequency is adjusted so as to substantially coincide with the coupled natural frequency of the first and second vibrating bars in the Z direction, the frequency is efficiently transmitted to the second vibrating bars 14 and 15. Therefore, if the Z-direction vibration of the second vibrating reeds 14, 15 is detected by the piezoelectric elements 23, 24, the angular velocity ω
Can be calculated.

Next, the overall configuration of the angular velocity detecting device of the present embodiment shown in FIG. 2 will be described.

The excitation circuit 50 includes a current-voltage conversion circuit 51, an automatic gain control circuit 52, and a drive circuit 53.
The detection circuit 60 includes current-voltage conversion circuits 61 and 62, a differential amplifier circuit 63, and a synchronous detection circuit 64.

The driving circuit 53 outputs a pulse wave having an amplitude corresponding to the output voltage value of the automatic gain control circuit 52 and having a predetermined repetition frequency as an excitation signal, and detects a signal having a phase shifted from the output signal by 90 degrees. The output terminal is connected to a surface-side electrode of the piezoelectric element 22 on the side surface of the first vibrating reed 13, which is a circuit for outputting as a detection signal of the synchronous detection circuit 64 in the circuit 60. Upon receiving the excitation signal, the piezoelectric element 22 expands and contracts in the Y direction, and vibrates the first vibrating reeds 12 and 13 in the X direction in opposite phases as described above.

The vibration information of the first vibrating bars 12 and 13 in the X direction is supplied to a current-voltage conversion circuit 51 and an automatic gain control circuit 52.
Is fed back via Current-voltage conversion circuit 51
Is a circuit for converting the amount of change in electric charge generated at the electrodes of the piezoelectric element 21 by the piezoelectric effect caused by the bending of the first vibrating bars 12 and 13 into a voltage value.

The automatic gain control circuit 52 receives the voltage signal output from the current-voltage conversion circuit 51, and decreases the output voltage value when the input voltage value increases, and increases the output voltage value when the input voltage value decreases. It works to be.
Therefore, when the vibration amplitude of the first vibrating reeds 12 and 13 increases, the charge generated at the electrodes of the piezoelectric element 21 also increases, and the output voltage of the current-voltage conversion circuit 51 also increases. As a result, the output voltage value of the automatic gain control circuit 52 decreases, and the amplitude of the output pulse of the drive circuit 53 decreases. Thus, the amplitude of the pulse signal output from the drive circuit 53 is feedback-controlled, and the first vibrating reed 12
And 13 are always stable.

The detection circuit 60 detects the amount of change in the electric charge at the electrodes of the piezoelectric elements 23 and 24 of the second vibrating reeds 14 and 15, and outputs a signal corresponding to the vibration amplitude of the second vibrating reed in the Z direction. . The vibrations of the second vibrating bars 14 and 15 in the Z direction
This is a composite vibration of vibrations of the vibrating bars 12 and 13 leaked in the X direction as Z direction vibrations and vibrations generated based on Coriolis force generated when the vibrator 10 rotates.
In the present embodiment, since the first vibrating bars 12 and 13 are excited in the X direction in mutually opposite phases, the Z-direction vibrations generated based on the Coriolis force vibrate in mutually opposite phases. on the other hand,
The leakage vibrations vibrate in phase with each other due to the shape of the first vibrating reeds 12 and 13. This mechanism will be described later in detail.

The current-voltage conversion circuit 61 is a circuit for amplifying the amount of change in electric charge at the electrode of the piezoelectric element 24 and converting it into a voltage value. Is a circuit that amplifies the voltage and converts it to a voltage value.
The differential amplifying circuit 63 is a circuit that receives the output signals of the current-voltage conversion circuits 61 and 62 and amplifies the potential difference between the two signals.
4 and 15 are proportional to the vibration amplitude change. Since the vibration components based on the Coriolis force are in opposite phases to each other, they are added by differential amplification, and the leakage vibration components are in phase with each other and therefore cancel each other.

The synchronous detection circuit 64 performs synchronous detection using the AC voltage signal output from the differential amplifier circuit 63 as a detection signal using a pulse signal having a 90 ° phase shift with respect to the excitation signal from the drive circuit 53. After that, integration processing is performed, and this is a circuit in which an integration circuit is added to a normal synchronous detection circuit. The vibration in the Z direction due to the Coriolis force is 90 degrees out of phase with respect to the excitation, and thus becomes an integrated value of full-wave rectification by synchronous detection and integration. That is, the synchronous detection circuit 6
The output signal voltage 4 indicates the vibration amplitude in the Z direction due to the Coriolis force of the second vibrating bars 14 and 15.

The angular velocity calculation circuit 70 calculates the rotational angular velocity about the axis parallel to the Y axis of the vibrator 10 based on the output signal of the detection circuit 60 indicating the vibration amplitude of the second vibrating bars 14 and 15. Relational equation between angular velocity and Coriolis force F =
This is a circuit for calculating based on 2 mV · ω.

Next, the leakage vibration in the Z direction of the excitation vibration will be described with reference to FIG. FIG. 3 is a sectional view taken along the line III-I of FIG.
It is II sectional drawing. When the excitation circuit 50 operates, the piezoelectric element 22 expands and contracts in the Y direction as described above, and the first vibrating reeds 12 and 13 vibrate in opposite directions in the X direction as indicated by arrows 31 and 32. However, since the respective outer side surfaces of the first vibrating bars 12 and 13 are inclined, the vibrations are inclined as shown by arrows 37 and 38.
That is, the excitation vibration is represented by Z as shown by arrows 35 and 36.
Directional leakage vibrations. The leakage vibrations 35 and 36 are vibrations that swing downward or in the direction of -Z when the first vibrating bars 12 and 13 are both bent inward. That is, the leakage vibration is caused by the first vibrating reed 12
When and 13 oscillate in the X direction in opposite phases, they oscillate in the Z direction in phase. Then, the first vibrating bars 12 and 13
Vibrating pieces 14 and 15 vibrating in conjunction with
Since the leakage vibrations detected by the piezoelectric elements 23 and 24 have the same phase, the leakage vibration components are canceled and eliminated by subtracting the detection results of the piezoelectric elements 23 and 24 from each other.

Note that arrows 39 and 40 in FIG.
Indicates vibration in the Z direction based on the Coriolis force,
If the excitation vibration is in the opposite phase, the vibration based on the Coriolis force is also in the opposite phase. Therefore, if the difference between the detection results of the piezoelectric elements 23 and 24 is taken, the leakage vibration is canceled out, but the vibration based on the Coriolis force becomes twice the value.

In a conventional general H-type vibrator, the direction of the leakage vibration in the Z direction is not stable because the surface on which the excitation piezoelectric element is attached is perpendicular to the excitation direction. for that reason,
Even if the two vibrating resonating pieces are excited in the X direction in mutually opposite phases, the leakage vibration in the Z direction does not always have the same phase in the two vibrating pieces as in the present embodiment. Therefore, even if a difference in vibration in the Z direction is taken, the difference may not be offset. However, in this embodiment, since the outer side surfaces of the first vibrating reeds 12 and 13 are inclined, the leak vibrations in the Z direction always have the same phase.

If the inclination angles 33 and 34 of the outer side surfaces of the first vibrating reeds 12 and 13 are in the range of 45 to 89 degrees, the X of the two vibrating reeds is set in the same direction as that of the leakage vibration in the Z direction. Excitation in the direction is possible, but actually
It is desirable to be within the range of 85 degrees. If the inclination angle is too small beyond this desirable range, the leakage amplitude increases, and when the leakage vibrations cancel each other out,
It may happen that the vibration cannot be canceled sufficiently due to the variation of the left and right resonator elements. Further, when the inclination angle becomes too close to 90 degrees, it becomes difficult to secure the stability of the direction of the leakage vibration.

In this embodiment, the first vibrating bars 12 and 1
3 are excited in opposite phases, but when excited in the left and right in-phase as shown by arrows 41 and 42 in FIG. 4, the actual vibrations are as shown by arrows 47 and 48, and the leakage vibration component is As shown at 45 and 46, the phases are opposite to each other. In this case, if the detection results of the piezoelectric elements 23 and 24 are added to each other, they are cancelled. Since the vibrations 49 and 50 based on the Coriolis force at this time have the same phase, the addition of the detection results of the piezoelectric elements 23 and 24 results in 2
The value is doubled.

FIGS. 5 and 6 show an example in which the vibrator is the same H-type vibrator as in the above embodiment, but the excitation direction is desired to be in the Z direction instead of the X direction. FIG. 5 is a sectional view at a position similar to FIG. 4. This vibrator 100
Are provided with piezoelectric elements 21 and 22 for excitation on the upper side surfaces of the first vibrating reeds 112 and 113 for excitation, respectively, and the second piezoelectric element for detection provided coaxially with the first vibrating reeds 112 and 113. Piezoelectric elements 23 and 24 for detection are provided on the outer side surface of the resonator element.

FIG. 5 shows a case in which the first vibrating bars 113 and 114 are excited in the Z direction as shown by arrows 131 and 132 in opposite phases, and the upper surface of the vibrating bar, that is, the surface bent by the excitation is an XY plane. , The directions of the excitation vibrations are indicated by arrows 137 and 1
38 and the in-phase leakage vibrations 135 and 136
Occurs. On the other hand, the vibration based on the Coriolis force is indicated by arrow 1
Since the phases are opposite to each other as indicated by 39 and 140, if the vibrations in the X direction detected by the piezoelectric elements 23 and 24 are subtracted from each other, the leakage vibration is canceled out and the vibration based on the Coriolis force is doubled. Appear.

FIG. 6 shows a case where the first vibrating bars 113 and 114 are excited in the same direction in the Z direction as indicated by arrows 141 and 142. Since the upper surface of the vibrating bar is inclined, the first vibrating bars 113 and 114 are excited. The directions are as indicated by arrows 147 and 148, and leakage vibrations 145 and 146 having opposite phases are generated. On the other hand, the vibrations based on the Coriolis force are in phase with each other as shown by arrows 149 and 150.
If the vibrations in the X direction detected at (24) and (24) are added to each other, the leakage vibration is canceled out, and the vibration based on the Coriolis force appears twice.

In each of the above embodiments, an H-shaped vibrator is used. However, a simple tuning fork type vibrator in which an exciting vibrating piece and a detecting vibrating piece are integrated is also referred to as "bending by excitation." At least one of the side surfaces is inclined with respect to the excitation direction, and the two excitation vibrating pieces are arranged in plane symmetry. " Can cancel the leakage vibration.

Although the vibrator of the above embodiment is a metal vibrator, the present invention is not limited to this, and the vibrator itself is made of a piezoelectric material (for example, quartz, LiTaO ₃ (lithium tantalate)). It can also be applied to those composed of

Further, in the above embodiment, only one side surface bent by excitation is inclined with respect to the excitation direction, and the cross-sectional shape of the resonator element is trapezoidal. May be similarly inclined.

Although the present invention specifies the direction of the leakage vibration of the two vibrating bars and attempts to cancel them out easily, there is an advantage that the adjustment of the leakage vibration is also facilitated. In other words, it is clear theoretically and experimentally that grinding the sharp corners of the cross section of the vibrating piece reduces the leakage vibration component. Balance can be easily adjusted.

[0033]

As described above, according to the angular velocity detecting device of the present invention, the vibrating piece for excitation is a quadrangular prism, and at least one of the side faces bent by the excitation is inclined with respect to the excitation direction. Therefore, the direction of the leakage vibration in the direction perpendicular to the excitation direction, that is, in the detection vibration direction, is always constant, and the two excitation vibration pieces are arranged in plane symmetry. When the pieces are excited in opposite phases, the respective leakage vibration components of the two excitation pieces have the same phase, and therefore can be canceled out by subtraction, so that the two excitation pieces have the same phase. When excited, the leakage vibration components of the respective excitation vibrating pieces have opposite phases, and thus can be canceled by adding.

Therefore, the vibration based on the Coriolis force can be accurately extracted, and the angular velocity detecting device has high detection sensitivity.

[Brief description of the drawings]

FIG. 1 is a perspective view showing a vibrator used in an embodiment of the present invention.

FIG. 2 is an overall configuration diagram of an angular velocity detecting device according to an embodiment of the present invention.

FIG. 3 is a sectional view taken along the line III-III in FIG. 1;

FIG. 4 is a sectional view taken along the line III-III in FIG. 1;

FIG. 5 is a cross-sectional view of a vibrator used in another embodiment of the present invention.

FIG. 6 is a sectional view of a vibrator used in another embodiment of the present invention.

[Explanation of symbols]

10 vibrator, 11 vibrator base, 12, 13 first vibrating reed, 14, 15 second vibrating reed, 21, 22, 23, 2
4 Piezoelectric element, 50 Excitation circuit, 60 Detection circuit, 70
... Angular velocity calculation circuit.

Claims (1)

[Claims] A vibrator; an exciting unit for exciting the vibrator; and a detection unit for detecting an amplitude of vibration based on Coriolis force generated by rotation of the vibrator excited by the exciting unit. And an angular velocity calculating means for calculating the angular velocity of the rotation from the magnitude of the amplitude detected by the detecting means, wherein the vibrator has two excitation vibrating pieces connected at one end. The excitation vibrating reed is a quadrangular prism, at least one of the side surfaces bent by the excitation is inclined with respect to the excitation direction, and the two excitation vibrating reeds are An angular velocity detection device characterized by being symmetrically arranged.