JP3136545B2 - Piezoelectric vibration gyro - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ultrasonic vibration of a piezoelectric vibrator, particularly a gyroscope used for attitude control of a moving vehicle such as a ship or a car and the equipment mounted thereon, and a navigation system of a car. The present invention relates to a so-called piezoelectric vibrating gyroscope using a piezoelectric vibrator, and more particularly to a method of driving and detecting a vibrator of a piezoelectric vibrating gyroscope using a vibrator formed of a piezoelectric ceramic cylinder.

[0002]

2. Description of the Related Art A piezoelectric vibrating gyroscope is a gyroscope utilizing a mechanical phenomenon that when a rotating angular velocity is given to a vibrating object, a Coriolis force is generated in a direction perpendicular to the direction of the vibration. When the vibrator is rotated in a state where one vibration is excited, a force acts in a direction perpendicular to the vibration by the action of the aforementioned Coriolis force, and the other vibration is excited. Since the magnitude of this vibration is proportional to the magnitude of the vibration on the input side and the rotational angular velocity, with the input voltage kept constant,
The magnitude of the rotational angular velocity can be determined from the magnitude of the output voltage proportional to the magnitude of the vibration.

FIG. 6 is a schematic diagram showing one configuration of a conventional piezoelectric vibrating gyroscope. In FIG. 6, piezoelectric ceramic thin plates 58, 59 polarized in the thickness direction are respectively joined to adjacent surfaces of a metal prism 57 having a square cross section. The metal prism 57 can bend and vibrate at substantially the same resonance frequency in two directions (X, Y) perpendicular to each other in a direction intersecting the center axis. When a voltage is applied, the piezoelectric ceramic thin plate 58 is bent and vibrated in a direction in which the surface to which the piezoelectric ceramic thin plate 58 is joined becomes uneven. In this state, when the metal prism 57 is rotated about the length direction as the axis (Z), the metal prism 57 bends and vibrates in a direction in which the surface to which the piezoelectric ceramic thin plate 59 is bonded becomes uneven due to the action of Coriolis force.
, A voltage proportional to the rotational angular velocity is generated.

[0004]

However, according to the conventional excitation and detection method shown in FIG. 6, at the inflection point of the vibration, the speed of the vibrator is zero, and the Coriolis force due to the rotation speed does not occur. There is a problem that detection sensitivity and response are poor. In addition, since the vibrator is excited in one direction by using a part (one or more) of the electrodes provided on the vibrator, there is a problem that the displacement, that is, the speed of the vibration is small and the detection sensitivity is low. Therefore, a technical problem of the present invention is to provide a piezoelectric vibrating gyroscope that has a high response speed and a high detection sensitivity in the method of exciting and detecting the piezoelectric vibrating gyroscope, and therefore has high accuracy.

[0005]

According to the present invention, there is provided a piezoelectric ceramic having a cylindrical outer peripheral surface, and a plurality of strip electrodes formed on the outer peripheral surface, wherein the piezoelectric ceramic is bent by a piezoelectric transverse effect. In a piezoelectric vibrator that vibrates, the plurality of strip electrodes are formed along the length direction on the outer peripheral surface, and the plurality of strip electrodes are a grounded reference electrode and all other than the reference electrode. And a detection electrode consisting of all or a part of the drive electrodes, and a vibrator for a piezoelectric vibratory gyroscope is obtained. According to the present invention, there is provided a method of driving the vibrator for a piezoelectric vibrating gyroscope, wherein at least two of the driving electrodes have at least two kinds of resonance frequencies substantially equal to a resonance frequency of a bending vibration of the vibrator and having different phases. A driving method of a piezoelectric vibrating gyroscope is characterized in that an elliptical vibration including a circle is excited in the vibrator by applying an AC voltage. According to the invention, there is provided a method for detecting vibration by the vibrator for a piezoelectric vibrating gyroscope, wherein a rotational angular velocity applied around the longitudinal axis of the vibrator is perpendicular to a tangent of the circular vibration. Thus, a method of detecting the rotational angular velocity is obtained, in which the change in the turning angle is detected as a change in the turning angle due to the Coriolis force applied in various directions, and the change in the turning angle is detected as a change in the potential of the drive electrode.

[0006]

In the present invention, if the mass of a point of interest of a vibrator that excites a circular or elliptical vibration is m and the magnitude of the velocity expressed in the tangential direction of the circular motion is v, the length of the vibrator When a rotational angular velocity ω is applied with the direction as an axis, a Coriolis force represented by F = 2 × m × v × ω is generated in a direction perpendicular to the tangent line of the excited circular motion. Due to this Coriolis force, an electromotive force corresponding to the Coriolis force is generated in each detection electrode by a piezoelectric effect, and the potential of the detection electrode changes. By detecting this potential change, the rotational angular velocity applied to the vibrator can be detected. In addition, by exciting the circular or elliptical vibration from all the electrodes as described above,
Compared with the conventional driving method that excites a single vibration in one direction from one or a plurality of electrodes (except for all), the displacement of vibration is large, that is, the speed at a certain point of interest of the vibrator is high,
Therefore, a pressure vibration gyro having high detection sensitivity can be obtained.

[0007]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a perspective view showing an example of a piezoelectric ceramic cylinder used in the piezoelectric vibrating gyroscope of the present invention.
On the outer peripheral surface of a piezoelectric vibrator (hereinafter referred to as a piezoelectric vibrator) 10 composed of a piezoelectric ceramic cylinder 1, 2n parallel to the length direction is provided.
A plurality (n is 2 or more) of strip electrodes 2 (here, n = 8) are formed. The strip electrode 2 can be easily obtained by directly forming the screen electrode by curved screen printing, or by removing unnecessary portions of the electrode formed on the entire surface by plating or the like by photoetching. This vibrator is fixed in a cylinder by attaching a ring or the like to a node of vibration at a resonance frequency.

In order to simplify the description, the value of n is 4
The case of (8 divisions) will be described. FIG. 2 is a sectional view showing the polarization direction of the piezoelectric ceramic column 1 shown in FIG. In FIG. 1, eight strip electrodes 21, 22, 23, 24, 25, 2 are arranged on a piezoelectric ceramic column 1 at equal intervals.
6, 27 and 28 are formed. These electrodes are connected to every other strip electrode 21, 23, 25, 27 and 2
When the electrodes 2, 24, 26, and 28 are electrically connected and subjected to polarization processing as two terminals, the direction of polarization in the cross-sectional direction of the piezoelectric ceramic cylinder becomes the direction indicated by the broken arrow. G1, G2, G3, G
4, G5, G6, G7 and G8. Now, the gap G1
When an AC voltage is applied to the electrode, an elongation strain occurs in the gap G1 when the direction of the applied electric field is equal to the direction of the polarization, and a contraction strain occurs in the gap G1 when the direction of the applied electric field is opposite to the direction of the polarization. appear. Therefore, when an AC voltage for excitation having a period substantially equal to the resonance frequency of the bending vibration mode of the piezoelectric ceramic cylinder 1 is applied to the gap G1, the piezoelectric ceramic cylinder 1 is moved by the transverse piezoelectric effect to the center of the gap G1 and the center of the cylinder. Flexurally vibrates in the direction of arrow 29 connecting.

FIG. 3 is a sectional view for explaining a connection and driving method of the piezoelectric vibrating gyroscope in the embodiment of the present invention. The drive sources 31, 32, and 34 are connected to the strip electrodes 21, 23, 25, and 27 via coupling resistors 41, 42, 43, and 44, respectively.
33 and 34 are connected. Drive sources 31, 32, 3
AC voltages COSθ, SINθ, −3 which are almost equal to the resonance frequency of the bending vibration mode of the piezoelectric ceramic cylinder 1 and whose phases are delayed by 90 ° with respect to the adjacent driving sources.
When COSθ,-SINθ is applied, the piezoelectric ceramic cylinder 2
A circular vibration is excited in the cross-sectional direction 0 as shown by a broken line 36 in FIG. Here, when a rotational motion is applied about the longitudinal direction of the piezoelectric ceramic cylinder 20 as an axis, the speed and rotation in the tangential direction of the circular vibration in a direction 37 perpendicular to the tangent of the circular vibration shown by the broken line in FIG. Coriolis force acts in proportion to the angular velocity of the motion, and accordingly, a force is generated in a direction to decrease or increase the turning angle 35 (shown in FIG. 4B) of the circular vibration according to the rotation direction.

Further, a detailed description will be given with reference to waveform diagrams of respective parts shown in FIG. FIG. 5A shows a drive voltage waveform of the drive electrode 21, and FIG. 5B shows a drive voltage waveform of the drive electrode 23. FIG.
(C) is the position of the point of interest 20 of the vibrator at time t1, t2, t3, and t4, the velocity 12 represented by the tangential direction, the trajectory 11 of the rotational motion, the Coriolis force 13, and the rotational angular velocity applied to the vibrator. It is sectional drawing which shows the direction 13 of FIG. The drive voltages of the drive electrodes 25 and 27 are the opposite phases of the drive electrodes 21 and 23, and thus description thereof is omitted. When an AC voltage is applied as shown in FIGS.
A circular motion is made as shown by the broken line in (C). When a rotational angular velocity 14 is applied to the vibrator in a circular motion about the longitudinal direction of the vibrator as an axis, the velocity is perpendicular to the velocity (12 in FIG. 5C) represented by the tangential direction of the point of interest 20 of the vibrator. Coriolis force 13 is applied in a desired direction. The direction of Coriolis force 13 is time t1 → t
Arrow 1 of C1, C2, C3, C4 in FIG. 5C depends on the position of the point of interest 20 of the vibrator by turning from 2 to t3 to t4.
It changes as shown in FIG. Due to this Coriolis force, an electromotive force is generated in the drive electrode as shown by a chain line in FIGS. 5A and 5B, respectively. By combining the driving voltage and the electromotive force generated by the Coriolis force, the potential of the driving electrode becomes as shown in FIG.
And (B) as shown by the broken line. By detecting the change in the potential, the rotational angular velocity of the vibrating gyroscope can be detected. This change in potential occurs in all of the strip electrodes 21, 23, 25, and 27 used as drive electrodes, and is detected from some or all of the electrodes.

In the above description, a piezoelectric vibrating gyroscope composed of a piezoelectric ceramic cylinder has been described. However, it is apparent that a similar effect can be expected with a piezoelectric ceramic pipe or a piezoelectric vibrating gyroscope composed of a metal column and a piezoelectric element. is there.

[0012]

As described above, according to the method for driving and detecting a vibrating gyroscope according to the present invention, the displacement of the driven vibration, that is, the speed, is larger than the conventional method for driving and detecting a vibrating gyroscope. , The detection sensitivity of the rotational angular velocity is improved. In addition, since the excitation is performed uniformly in all directions and the excited vibration has no inflection point, Coriolis force always acts on the rotational angular velocity, and the deviation of the vibration direction due to the processing accuracy of the vibrator and the anisotropy of the material, The influence of the aging of the vibrating body and the support for supporting the vibrating body is small, and the rotational angular velocity can be stably detected. As described above, it is possible to provide a vibrating gyro having high detection sensitivity and stable over time, and has a great industrial value.

[Brief description of the drawings]

FIG. 1 is a perspective view showing a structure of a piezoelectric vibrator used in a piezoelectric vibrating gyroscope according to an embodiment of the present invention.

FIG. 2 is a cross-sectional view illustrating a polarization state and a basic principle of a vibrator of a piezoelectric vibrating gyroscope according to an embodiment of the present invention.

FIG. 3 is a cross-sectional view for explaining a connection and driving method of the piezoelectric vibrating gyroscope according to the embodiment of the present invention.

FIG. 4A is a cross-sectional view showing a state of vibration of a piezoelectric vibrating gyroscope and a direction of a Coriolis force when a vibrator rotates in an embodiment of the present invention. (B) is a diagram for explaining the turning angle of the circular vibration driven by the piezoelectric vibrating gyroscope in the embodiment of the present invention.

FIG. 5 is a diagram for explaining an electromotive force generated by a driving voltage and a Coriolis force applied to a driving electrode, a composite waveform of the driving voltage and an electromotive force by a Coriolis force, and a state of a vibrator at that time.

FIG. 6 is a perspective view showing a structural example of a conventional piezoelectric vibrating gyroscope.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Piezoelectric ceramic cylinder 2 Strip electrode 10 Piezoelectric gyro vibrator 11 Dashed line representing the trajectory of circular motion excited by the vibrator 12 Arrow for expressing the tangential velocity at a point of interest 20 of the vibrator at time t 13 Arrow indicating the direction of the Coriolis force 14 Rotational angular velocity applied to the axis in the longitudinal direction of the transducer 20 Point of interest of the transducer 21 Strip electrode 22 Strip electrode 23 Strip electrode 24 Strip electrode 25 Strip electrode 26 Strip electrode 27 Strip electrode REFERENCE SIGNS LIST 31 drive source 32 drive source 33 drive source 34 drive source 35 turning angle of circular vibration driven by piezoelectric ceramic cylinder 41 coupling resistance 42 coupling resistance 43 coupling resistance 44 coupling resistance 57 metal prism 58 piezoelectric ceramic thin plate 59 piezoelectric ceramic thin plate

Continuation of front page (58) Field surveyed (Int.Cl. ⁷ , DB name) G01C 19/56 G01P 9/04

Claims (3)

(57) [Claims] A piezoelectric ceramic having a cylindrical outer peripheral surface; and a plurality of strip electrodes formed on the outer peripheral surface.
In a piezoelectric vibrator that performs bending vibration by the piezoelectric transverse effect of the piezoelectric ceramic, the plurality of strip electrodes are formed along the length direction on the outer peripheral surface, and the plurality of strip electrodes are connected to a ground reference. A vibrator for a piezoelectric vibrating gyroscope, comprising: an electrode; and a detection electrode having a drive electrode formed of all band-shaped electrodes other than the reference electrode and having all or a part of the drive electrode. 2. The method of driving a vibrator for a piezoelectric vibrating gyroscope according to claim 1, wherein at least two of said driving electrodes have at least two different phases substantially equal to a resonance frequency of bending vibration of said vibrator. A driving method for a piezoelectric vibratory gyroscope, wherein an elliptical vibration including a circle is excited in the vibrator by applying a kind of AC voltage. 3. The method for detecting vibrations by a vibrator for a piezoelectric vibrating gyroscope according to claim 1, wherein the rotational angular velocity applied around the longitudinal direction of the vibrator is taken as a tangent to the circular vibration. A rotation angle caused by a Coriolis force applied in a direction perpendicular to the rotation angle, and detecting the change in the rotation angle as a potential change of a drive electrode.