JP3291664B2 - 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 a gyroscope used for preventing camera shake of a camera-integrated VTR and for a navigation system of an automobile, and more particularly to a piezoelectric vibrating gyroscope using ultrasonic vibration of a piezoelectric vibrator made 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. In a vibration system configured to enable excitation and detection in two directions orthogonal to each other, in a state where one vibration is excited, the vibrator itself is centered on an axis parallel to a line where the two vibration surfaces intersect. When rotated, a force acts in a direction perpendicular to this 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, when the input voltage is constant, the magnitude of the rotational angular velocity can be obtained from the magnitude of the output voltage.

FIG. 7 is a schematic view of the structure of a piezoelectric vibrator used in a conventional piezoelectric vibrating gyroscope. The piezoelectric vibrator is located at a position on the outer peripheral surface of the piezoelectric ceramic cylinder 10 which divides the circumference into six equal parts and is parallel to the length direction. Six strip electrodes 1, 2, 3, 4, 5, and 6 are formed. After alternately connecting these band-shaped electrodes to each other to perform a polarization process as two terminals, after the polarization process, connect the other band-shaped electrodes 2, 4, and 6 to each other to form a common ground electrode. Of these, a piezoelectric vibrating gyroscope can be configured using the strip electrode 1 as a drive electrode and the strip electrodes 3 and 5 as detection electrodes.

FIG. 8 shows an example of frequency characteristics of impedance of the piezoelectric vibrator shown in FIG. 7 as viewed from the driving strip electrode 1 and the detecting strip electrodes 3 and 5. When a piezoelectric vibrating gyroscope is configured, it is desirable that these impedance characteristics match as much as possible, and in particular, it is necessary to match their resonance frequencies (frequency at which the impedance becomes minimum).

In the bending vibration of a cylinder, there are vibration modes fx and fy orthogonal to each other, and the vibration modes fx and fy
Are completely coincident (degenerate), and when the cylinder is completely symmetrical in terms of shape and elasticity, these vibration directions can be fixed in any direction of interest. But,
In reality, the vibration modes fx and fy are different due to slight asymmetry, and the vibration direction is limited to a specific direction.

FIG. 9 is a model showing the relationship between these two vibration modes and the driving and detecting strip electrodes. FIG.
9A shows the case where the vibration direction of the vibration mode fx coincides with the center of the driving strip electrode. FIG. 9B shows the case where the vibration direction of the vibration mode fx is at an angle from the center of the driving strip electrode. This shows a case where the position is shifted by δ.

FIG. 8 shows an example in which the vibration modes fx and fy
Are respectively 30.267 KHz and 30.242 KHz,
That is, this corresponds to impedance characteristics when the resonance frequency is different by 25 Hz and the angle δ is shifted by approximately 10 degrees.

When the vibrator is rotated while the piezoelectric vibrating gyroscope is excited in the vibration direction of the vibration mode fx as described above, the vibration of the vibration mode fy is excited, and the magnitude of the vibration of the fy Is detected by a band electrode for detection, and the following basic conditions are required.

The first basic condition is that two band electrodes for detection are arranged symmetrically with respect to the vibration of the vibration mode fx,
The amplitude and phase of the voltage generated when not rotating are the same, and the second basic condition is that the vibration mode f
That is, y matches fx as much as possible.

[0010] Of these two basic conditions, the first condition is more important, and the condition is that the output voltage (null voltage) when the motor does not rotate is as close to zero as possible. The second condition is a condition relating to the sensitivity of the piezoelectric vibrating gyroscope, and the sensitivity increases as the vibration modes fx and fy match.

[0011]

In a conventional piezoelectric vibrating gyroscope using a piezoelectric ceramic cylinder, it is particularly difficult to control the vibration direction, and the vibration direction is effectively controlled by a method that matches the resonance frequencies as viewed from each terminal as much as possible. Is adjusted to the driving electrode. Therefore, it takes time to adjust the resonance frequency from the viewpoint of the three terminals, and the workability is poor.

The main object of the present invention is to deliberately break the symmetry of the piezoelectric ceramic cylinder by appropriately arranging the positions of the strip-shaped electrodes formed on the outer peripheral surface of the piezoelectric ceramic cylinder, thereby reducing the difference between the vibration modes fx and fy. An object of the present invention is to enable the vibration direction to be fixed in a certain direction while being within a predetermined range.

Another object of the present invention is to reduce changes in electrical characteristics when a groove parallel to the longitudinal direction is formed on the outer peripheral surface of a piezoelectric ceramic cylinder to fix the vibration direction.

[0014]

According to the present invention, a piezoelectric ceramic cylinder and first to seventh piezoelectric ceramic cylinders are formed on the outer peripheral surface of the cylindrical cylinder in parallel with the longitudinal direction and at intervals in the circumferential direction.
, And the second and seventh band-shaped electrodes and the third band-shaped electrode are respectively symmetrical with respect to a plane including a center line of the first band-shaped electrode and a center axis of the piezoelectric ceramic cylinder.
And a sixth strip-shaped electrode, the fourth and fifth strip-shaped electrodes are formed, and the first, third and sixth strip-shaped electrodes are commonly connected, and the second, fourth, fifth and seventh strip-shaped electrodes are connected. Are connected in common, and the piezoelectric ceramic cylinder is polarized using these two sets of common connection electrodes as two terminals, and then the second, fourth, fifth, and seventh strip electrodes are connected to a common ground. electrode,
A piezoelectric vibrating gyroscope is obtained, wherein the first band-shaped electrode is a drive electrode, and the third and sixth band-shaped electrodes are each a detection electrode.

[0015]

According to the present invention, there is further provided a piezoelectric ceramic column, and first to sixth strip-shaped electrodes formed on the outer peripheral surface of the column in parallel with the longitudinal direction and spaced apart in the circumferential direction. After polarization using these strip electrodes,
The first, third and fifth strip electrodes are electrically connected to form a common ground electrode, and the fourth strip electrode is a driving electrode,
In the piezoelectric vibrating gyroscope in which the second and sixth strip electrodes are used as detection electrodes, the fourth strip electrode is formed at a position symmetrical to the first strip electrode with respect to the center of the piezoelectric ceramic column. A second surface that is symmetrical with respect to a first plane including the center line of the band-shaped electrode and the center axis of the piezoelectric ceramic cylinder, includes the center axis of the piezoelectric ceramic cylinder, and is orthogonal to the first plane. A piezoelectric vibrating gyroscope is obtained in which the second and sixth strip electrodes and the third and fifth strip electrodes are formed at asymmetric positions, respectively.

[0017]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a perspective view showing an embodiment of a piezoelectric vibrating gyroscope according to the present invention, in which first to seventh strip-shaped electrodes are arranged on the outer peripheral surface of a piezoelectric ceramic column 20 at intervals in the circumferential direction and circumferentially. 11, 12, 13, 14, 15, 16, 1
7 are formed. These positional relationships are determined by the band-shaped electrode 1.
1 and the strip electrodes 12, 17, and 1 are respectively symmetrical with respect to a plane including the center axis of the piezoelectric ceramic cylinder 20.
3 and 16 and 14 and 15 are formed. Moreover, the strip electrodes 11, 13, 16 and the strip electrodes 12, 14, 15, 17
Are electrically connected to each other to perform polarization processing as two terminals, and then the strip electrodes 12, 14, 15, and 17 are used as a common ground electrode, the strip electrodes 11 are used as driving electrodes, and the strip electrodes 13 and 16 are used as detection electrodes. Electrodes.

In the conventional vibrator for a piezoelectric vibrating gyroscope shown in FIG. 7, when the strip electrode 1 is a driving electrode, the vibration direction is the center line of the strip electrode 1 and the center of the piezoelectric ceramic cylinder 10 as described above. It does not always match the direction of the plane containing the line. However, in the case of FIG. 1, all the strip electrodes including the connection electrodes are formed symmetrically with respect to a plane including the center line of the drive strip electrode 11 and the center line of the piezoelectric ceramic cylinder 20. In addition, there is no symmetric surface other than this surface including the center line of the piezoelectric ceramic cylinder 20.

Therefore, as shown in FIG.
The vibration direction of x ′ is fixed in the direction of the plane including the central axis of the piezoelectric ceramic cylinder 20, and the bending vibration f in the direction perpendicular to this direction
The resonance frequency of y 'is shifted. Further, in the vibrator used for the piezoelectric vibrating gyroscope according to the present invention, a thin groove (not shown) is formed in a portion between the strip electrodes 14 and 15 along the length direction of the piezoelectric ceramic cylinder 20 to drive the vibrator. The resonance frequency in the electrode direction can be reduced, and the direction of vibration can be further fixed. However, since the strip electrodes 14 and 15 are both connected to the common ground electrode, the electrical characteristics hardly change even if the groove is formed. On the other hand, since the detection strip electrodes 13 and 16 are arranged at positions symmetrical with respect to the vibration direction of fx ', the above-described first basic condition is satisfied, and satisfactory adjustment can be achieved with almost no adjustment or only slight adjustment. Gyro characteristics can be obtained.

Table 1 shows specific examples of the strip electrodes of the piezoelectric vibrator used in the piezoelectric vibrating gyroscope of the present invention. Table 2 shows examples of transducer characteristics. Table 2 also shows an example of a conventional vibrator in which seven strip-shaped electrodes are formed at equal intervals for comparison. As can be seen from Table 2, according to the present invention, there is a difference of about 50 Hz between the resonance frequency when driven from the drive terminal and the resonance frequency when driven from the detection terminal. Frequency difference is almost 1
Hz or less, indicating that the direction of vibration is substantially symmetric with respect to the detection electrode.

[0021]

[Table 1]

[0022]

[Table 2]

FIG. 3 is a perspective view showing a reference example of the piezoelectric vibrating gyroscope . Components corresponding to those in FIG. First to sixth strip-shaped electrodes 11, 12, 13, 14, 15, 16 are formed on the outer peripheral surface of the piezoelectric ceramic column 20 at intervals in the circumferential direction parallel to the length direction. The band-shaped electrodes 14 are formed at positions symmetrical with respect to the center axis of the band-shaped electrode 11 and the piezoelectric ceramic cylinder 20, and are respectively formed at positions symmetrical with respect to a plane including the center line of the band-shaped electrode 11 and the center axis of the piezoelectric ceramic column 20. 12,1
6 and 13 and 15 are formed.

Further, the center line of the band-shaped electrode 11 and the center line of the piezoelectric ceramic cylinder 20 are symmetrically arranged on the node line of the vibration of the piezoelectric ceramic column 20 at the time of the bending vibration resonance, and include the center line, respectively. External lead connection terminals 22 and 26 are formed at a position at an angle of about 30 ° from the surface, and are connected to the detection strip electrodes 12 and 16 by connection electrodes, respectively.

In FIG. 3, an external lead connection terminal 22 is shown.
And 26 are separated from the center axis of the piezoelectric ceramic column 20 by only 60 °, so that the ground strip electrode 14 sandwiched between them is short, and the drive and detection electrode and the ground electrode are formed. Is kept at a predetermined interval.

In the conventional vibrator for a piezoelectric vibrating gyroscope shown in FIG. 7, when the strip electrode 4 is a driving electrode, the vibration direction is the center line of the strip electrode 4 and the center line of the piezoelectric ceramic cylinder 20 as described above. It does not always coincide with the direction of the included plane. However, in the case of FIG. 3, all the strip electrodes including the external lead connection terminals are formed symmetrically with respect to a plane including the center line of the drive strip electrode 14 and the center line of the piezoelectric ceramic cylinder 20. And a piezoelectric ceramic cylinder 2
There is no plane other than this plane that is symmetric with respect to the plane including the center line of zero.

Therefore, as shown in FIG.
Is fixed in the direction of the plane including the central axis of the piezoelectric ceramic cylinder 20, and the bending vibration fy 'in the direction perpendicular to this direction is fixed.
Are shifted (fx ′> fy ′). However, since the detection electrodes 12 and 16 are arranged at positions symmetrical with respect to the vibration direction of fx ', the first basic condition is satisfied, and good gyro characteristics can be obtained with almost no adjustment or only fine adjustment. Obtainable.

Table 3 shows specific examples of the strip-shaped electrodes of the piezoelectric vibrator used in the piezoelectric vibrating gyroscope of FIG . Table 4 shows examples of transducer characteristics. Table 4 also shows an example of a conventional vibrator in which six strip electrodes are formed at equal intervals for comparison.
As can be seen from Table 4, in the piezoelectric vibrating gyroscope of FIG.
The resonance frequency when driven from the drive terminal and the resonance frequency when driven from the detection terminal are 20 to 30H.
Although there is a difference of about z, the difference in resonance frequency between the detection terminals is almost 1 Hz or less, which indicates that the direction of vibration is substantially symmetric with respect to the detection electrode.

[0029]

[Table 3]

[0030]

[Table 4]

FIG. 5 shows a vibrator for a piezoelectric vibrating gyroscope according to the present invention.
FIG. 10 is a perspective view showing another embodiment of the present invention, in which components corresponding to those in FIG. On the outer peripheral surface of the piezoelectric ceramic column 20, the first to sixth strip-shaped electrodes 11, 12, 13,.
14, 15, 16 are formed. The band-shaped electrodes 14 are formed at positions symmetrical with respect to the center axis of the band-shaped electrode 11 and the piezoelectric ceramic column 20, and are formed at positions symmetrical with respect to a plane including the center line of the band-shaped electrode 11 and the center axis of the piezoelectric ceramic column 20. 12, 16, and 13, 15 are formed. At this time, the strip electrodes 12, 13 and 15, 1
6 each include the center line of the piezoelectric ceramic cylinder 20;
It is formed asymmetrically with respect to a plane orthogonal to the plane of symmetry.

In the conventional vibrator for a piezoelectric vibrating gyroscope shown in FIG. 7, when the belt-shaped electrode 4 is a driving electrode as described above, the vibration direction is as described above with respect to the center line of the belt-shaped electrode 4 and the piezoelectric vibrator. It does not always coincide with the direction of the plane including the center line of the ceramic cylinder 10. However, in the case of FIG. 5, all the strip electrodes including the connection electrodes are formed symmetrically with respect to a plane including the center line of the drive strip electrode 14 and the center line of the piezoelectric ceramic cylinder 20, and In addition, there is no symmetric surface other than the symmetric surface in the plane including the center line of the piezoelectric ceramic cylinder 20.

Therefore, as shown in FIG. 6, the bending vibration fx '
Is fixed in the direction of the plane including the central axis of the piezoelectric ceramic cylinder 20, and the bending vibration fy 'in the direction perpendicular to this direction is fixed.
Are shifted. However, the detection electrodes 12 and 1
6 is arranged at a position symmetrical with respect to the vibration direction of fx ', so that the first basic condition is satisfied, and good gyro characteristics can be obtained with almost no adjustment or only fine adjustment.

Table 5 shows specific examples of the strip electrodes of the piezoelectric vibrator used in the piezoelectric vibrating gyroscope of the present invention. Table 6 shows examples of transducer characteristics. Table 6 also shows an example of a conventional vibrator in which six strip electrodes are formed at equal intervals for comparison. As can be seen from Table 6, according to the present invention, there is a difference of about 20 to 30 Hz between the resonance frequency when driven from the drive terminal and the resonance frequency when driven from the detection terminal. Is almost 1 Hz or less, indicating that the direction of vibration is substantially symmetric with respect to the detection electrode.

[0035]

[Table 5]

[0036]

[Table 6]

[0037]

As described above, according to the present invention,
Since the electrodes for detection are formed at positions symmetrical to the vibration direction, the amplitude and phase of the voltage generated at the electrodes for detection are almost the same, making it easy to adjust the final resonance frequency and to achieve piezoelectric vibration. Variations in gyro characteristics are also reduced.

According to the present invention, when a groove is formed in the piezoelectric ceramic cylinder and fine adjustment of the resonance frequency is performed, the groove is formed in a portion sandwiched between the two earth electrodes. Thus, a vibrator having little change in the electrical characteristics of the vibrator due to the above is obtained.

Further, according to the present invention, since the detection electrodes are formed at positions symmetrical to the vibration direction, the amplitudes and phases of the voltages generated at the detection electrodes are substantially the same.
The final adjustment of the resonance frequency is facilitated, and the variation in the characteristics of the piezoelectric vibrating gyroscope is reduced.

[Brief description of the drawings]

FIG. 1 is a schematic perspective view showing one embodiment of a vibrator for a piezoelectric vibrating gyroscope according to the present invention.

FIG. 2 is a cross-sectional view of the piezoelectric vibrator showing a relationship between two vibration modes of the piezoelectric vibrator shown in FIG. 1 and belt electrodes for driving and detection.

FIG. 3 is a schematic perspective view showing a reference example of a piezoelectric vibrating gyroscope .

FIG. 4 is a cross-sectional view of the piezoelectric vibrator showing a relationship between two vibration modes of the piezoelectric vibrator shown in FIG. 3 and band electrodes for driving and detection.

FIG. 5 is a schematic perspective view showing another embodiment of the piezoelectric vibrating gyroscope of the present invention.

6 is a cross-sectional view of the piezoelectric vibrator showing a relationship between two vibration modes of the piezoelectric vibrator shown in FIG. 5 and driving and detecting strip electrodes.

FIG. 7 is a schematic perspective view showing the structure of a piezoelectric vibrator used in a conventional piezoelectric vibrating gyroscope.

8 is a frequency characteristic diagram of impedance as viewed from a driving band electrode and a detecting band electrode of the piezoelectric vibrator shown in FIG. 7;

9 is a cross-sectional view of the piezoelectric vibrator showing a relationship between two vibration modes of the piezoelectric vibrator shown in FIG. 7 and a strip electrode for driving and detection.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 11 1st strip electrode 12 2nd strip electrode 13 3rd strip electrode 14 4th strip electrode 15 5th strip electrode 16 6th strip electrode 17 7th strip electrode 20 Piezoelectric ceramic cylinder 22 1st External lead terminal 26 Second external lead terminal

────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yasunori Otsuki 21-1, Taishido, Taishiro-ku, Sendai-shi, Miyagi Prefecture Tokin Co., Ltd. (56) References JP-A-5-79844 (JP, A) JP-A Sho62 -185117 (JP, A) (58) Field surveyed (Int. Cl. ⁷ , DB name) G01C 19/56 G01P 9/04

Claims (2)

(57) [Claims] 1. A piezoelectric device comprising: a piezoelectric ceramic column; and first to seventh band-shaped electrodes formed on an outer peripheral surface of the column in parallel with a longitudinal direction of the column and spaced in a circumferential direction. The second and seventh positions are symmetrical with respect to a plane including the center line of the electrode and the center axis of the piezoelectric ceramic cylinder, respectively.
, The third and sixth strip electrodes, the fourth and fifth strip electrodes are formed, and the first, third and sixth strip electrodes are commonly connected, and the second and third strip electrodes are connected. After the fourth, fifth, and seventh strip-shaped electrodes are connected in common, and these two sets of common connection electrodes are used as two terminals, the piezoelectric ceramic cylinder is subjected to a polarization treatment, and then the second, fourth, fifth, and fifth electrodes are connected. 7 is a common ground electrode, the first strip electrode is a drive electrode,
A piezoelectric vibrating gyroscope, wherein the third and sixth strip electrodes are each a detection electrode. 2. A piezoelectric ceramic cylinder and an outer peripheral surface of the cylinder.
In parallel with the longitudinal direction and at intervals in the circumferential direction.
And first to sixth strip-shaped electrodes thus formed.
After the polarization using the electrode, the first, third and
5 are electrically connected to form a common ground electrode,
The fourth strip electrode is a drive electrode, and the second and sixth strips are
In the piezoelectric vibrating gyroscope using the electrode like a detection electrode,
The fourth strip electrode is located at the center of the piezoelectric ceramic column.
With respect to the first strip electrode,
The center line of the first strip-shaped electrode and the piezoelectric ceramic
The piezoelectric ceramic is symmetrical with respect to a first plane including a central axis.
A second axis including a central axis of a check cylinder and orthogonal to the first surface.
The second and sixth belt-shaped electrodes at positions asymmetrical to the plane
And the third and fifth strip electrodes are formed.
Piezoelectric vibratory gyroscope.