JPH074973A - Piezoelectric vibrating gyro - Google Patents

Abstract

PURPOSE:To fix a vibration direction in a constant direction in a state wherein difference in vibration modes is within a predetermined range by making belt electrodes formed on the outer peripheral face of a piezoelectric ceramic cylinder appropriate to destory symmetry of the piezoelectric ceramic cylinder. CONSTITUTION:Belt electrodes 12, 13, 15, 17 are made to be common ground electrodes, a belt electrode 11 is made to be a driving electrode, and belt electrodes 13, 16 are made to be detection electrodes. All of the belt electrodes including a connection electrode are formed symmetrical with respect to a plane including a center line of the driving electrode 11 and a center line of a piezoelectric ceramic cylinder 20, and no other symmetric plane including the center line of the cylinder 20 exists. Therefore, a vibration direction of bending vibration fx' is fixed in a direction of the plane including the center of the cylinder 20, while resonance frequency of bending vibration fy' perpendicular thereto is shifted. Since the detection electrodes 13, 16 are located symmetrically in the vibration direction of fx', good gyro characteristics can be obtained approximately without adjustment or only with slight fine adjustment.

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 a camera-integrated VTR to prevent camera shake and a navigation system for automobiles, and more particularly to a piezoelectric vibrating gyro using ultrasonic vibration of a piezoelectric vibrator made of a piezoelectric ceramic cylinder. .

[0002]

2. Description of the Related Art A piezoelectric vibrating gyro is a gyroscope which utilizes a mechanical phenomenon in which a Coriolis force is generated in a direction perpendicular to the vibrating direction when a rotating angular velocity is applied to a vibrating object. In a vibration system configured to enable excitation and detection in two directions that are orthogonal to each other, with one vibration being excited, the vibrator itself is centered on an axis parallel to the line where the two vibrating planes intersect. When rotated, a force acts in the direction perpendicular to this vibration due to the action of the Coriolis force described above, 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 rotation angular velocity, the magnitude of the rotation angular velocity can be obtained from the magnitude of the output voltage when the input voltage is constant.

FIG. 7 is a schematic view of the structure of a piezoelectric vibrator used in a conventional piezoelectric vibrating gyro. It is parallel to the length direction at a position on the outer peripheral surface of the piezoelectric ceramic cylinder 10 that divides the circumference into six equal parts. Six strip electrodes 1, 2, 3, 4, 5, 6 are formed. These strip electrodes are connected to each other and polarized as two terminals. After polarization, every other strip electrodes 2, 4 and 6 are connected to form a common ground electrode and the remaining strip electrodes are A piezoelectric vibrating gyro can be constructed by 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 viewed from the driving strip electrode 1 and the detection strip electrodes 3 and 5 in the piezoelectric vibrator shown in FIG. When constructing a piezoelectric vibration gyro, it is desirable that these impedance characteristics match as much as possible, and it is particularly necessary to match their resonance frequencies (frequency at which the impedance becomes minimum).

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

FIG. 9 is a model showing the relationship between these two vibration modes and the strip electrodes for driving and detecting. Figure 9
FIG. 9A shows the case where the vibration direction of the vibration mode fx and the center of the driving strip electrode coincide with each other, and FIG. 9B shows the vibration direction of the vibration mode fx at an angle from the center of the driving strip electrode. The case where it is shifted by δ is shown.

In the example shown in FIG. 8, the vibration modes fx and fy
Are 30.267 KHz and 30.242 KHz,
That is, it corresponds to the impedance characteristic when the resonance frequencies are different by 25 Hz and the angle δ is shifted by about 10 degrees.

When the vibrator is rotated while the piezoelectric vibration gyro 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 this fy is increased. Is detected by a strip-shaped electrode for detection, and the following basic conditions are required.

The first basic condition is that two detecting strip electrodes are symmetrically arranged 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 the vibration mode f.
That is, y matches fx as much as possible.

Of these two basic conditions, the first condition is more important and is a condition for making the output voltage (null voltage) when not rotating as close to zero as possible. The second condition is a condition relating to the sensitivity of the piezoelectric vibrating gyro, and the sensitivity increases as the vibration modes fx and fy match.

[0011]

In a conventional piezoelectric vibrating gyro using a piezoelectric ceramic cylinder, it is particularly difficult to control the vibrating direction, and the vibrating direction can be effectively determined by a method of matching the resonance frequencies seen from the terminals as much as possible. Is adjusted to the driving electrode. Therefore, it takes time to adjust the resonance frequency viewed from the three terminals, and the workability is poor.

The main object of the present invention is to intentionally break the symmetry of the piezoelectric ceramic cylinder by appropriately arranging the positions of the strip electrodes formed on the outer peripheral surface of the piezoelectric ceramic cylinder, and to reduce the difference between the vibration modes fx and fy. It is to be able to fix the vibration direction in a fixed direction in a state where the vibration is within a predetermined range.

A further 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 column and first to seventh columns formed in order on the outer peripheral surface of the column in parallel with the longitudinal direction thereof and at intervals in the circumferential direction.
Strip electrodes, and the second and seventh strip electrodes and the third strip electrode at positions symmetrical with respect to a plane including the center line of the first strip electrode and the central axis of the piezoelectric ceramic cylinder, respectively.
And a sixth strip electrode, the fourth and fifth strip electrodes are formed, and the first, third and sixth strip electrodes are commonly connected, and the second, fourth, fifth and seventh strip electrodes are formed. After connecting the strip electrodes in common and using the two sets of common connection electrodes as two terminals to perform polarization treatment on the piezoelectric ceramic cylinder, the second, fourth, fifth, and seventh strip electrodes are connected to a common ground. electrode,
A piezoelectric vibrating gyro is obtained in which the first strip electrodes are drive electrodes and the third and sixth strip electrodes are detection electrodes.

According to the present invention, there is also provided a piezoelectric ceramic column and first to sixth strip electrodes formed on the outer peripheral surface of the column in parallel with the longitudinal direction thereof and at intervals 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 drive electrode,
In the piezoelectric vibrating gyro using the second and sixth strip electrodes 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 cylinder, The second and sixth strip-shaped electrodes and the third and fifth strip-shaped electrodes are arranged at symmetrical positions with respect to a plane including the center line of the strip-shaped electrode of 1 and the center line of the piezoelectric ceramic cylinder, respectively.
Band-shaped electrodes of the piezoelectric ceramic cylinder are formed, and the piezoelectric ceramic cylinder is arranged at a position symmetrical with respect to a plane including the center line of the first belt-shaped electrode and the center axis of the piezoelectric ceramic cylinder on the nodal line of vibration at the time of bending vibration resonance. First and second external lead connection terminals are formed, and these first and second external lead connection terminals are connected to the second and sixth strip electrodes for detection, respectively. A piezoelectric vibration gyro is obtained.

According to the present invention, it further has a piezoelectric ceramic column and first to sixth strip electrodes formed on the outer peripheral surface of the column in order in parallel with the longitudinal direction thereof and at intervals 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 drive electrode,
In the piezoelectric vibrating gyro using the second and sixth strip electrodes 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 cylinder, A second surface which is symmetrical with respect to a first plane including the center line of the one strip electrode and the central axis of the piezoelectric ceramic cylinder and which includes the central axis of the piezoelectric ceramic cylinder and is orthogonal to the first surface. A piezoelectric vibrating gyro is obtained in which the second and sixth strip electrodes and the third and fifth strip electrodes are formed at asymmetrical 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. The first to seventh strip electrodes are arranged on the outer peripheral surface of the piezoelectric ceramic cylinder 20 in parallel with the length direction and at intervals in the peripheral direction. 11, 12, 13, 14, 15, 16, 1
7 are formed. The positional relationship between them is that the strip electrode 1
1 and the strip electrodes 12 and 17 at positions symmetrical with respect to a plane including the center axis of the piezoelectric ceramic cylinder 20 and the center axis of the piezoelectric ceramic column 20, respectively.
3 and 16 and 14 and 15 are formed. Moreover, the strip electrodes 11, 13, 16 and the strip electrodes 12, 14, 15, 17
After being electrically connected to each other and subjected to polarization treatment as two terminals, the strip electrodes 12, 14, 15, 17 are used as a common ground electrode, the strip electrode 11 is used as a driving electrode, and the strip electrodes 13 and 16 are respectively used for detection. It is used as an electrode.

In the conventional piezoelectric vibrating gyro oscillator shown in FIG. 7, when the strip electrode 1 is used as the driving electrode, the vibrating direction is the center line of the strip electrode 1 and the center of the piezoelectric ceramic column 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 connecting electrodes, are formed symmetrically with respect to the plane including the center line of the driving strip electrode 11 and the center line of the piezoelectric ceramic cylinder 20. Moreover, there is no other plane other than this plane that is symmetrical with respect to the plane including the center line of the piezoelectric ceramic cylinder 20.

Therefore, as shown in FIG. 2, the bending vibration f
The vibration direction of x'is fixed in the direction of the surface including the central axis of the piezoelectric ceramic cylinder 20, and the bending vibration f is in the direction perpendicular to this.
The resonant frequency of y'shifts. Further, in the vibrator used in the piezoelectric vibrating gyroscope of the present invention, by forming a thin groove (not shown) along the length direction of the piezoelectric ceramic column 20 in the portion between the strip electrodes 14 and 15, The resonance frequency in the electrode direction can be lowered, and at the same time, the vibration direction can be more 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 strip-shaped electrodes 13 and 16 for detection are arranged at positions symmetrical with respect to the vibration direction of fx ′, the first basic condition described above is satisfied, and almost no adjustment or only fine adjustment is sufficient. Gyro characteristics can be obtained.

Table 1 shows specific examples of the strip electrodes of the piezoelectric vibrator used in the piezoelectric vibration gyro of the present invention. In addition, Table 2 shows examples of oscillator characteristics. For comparison, Table 2 also shows an example of a conventional vibrator in which seven strip electrodes are formed at equal intervals. 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, but the resonance between the detection terminal and The frequency difference is almost 1
It is below Hz, indicating that the direction of vibration is substantially symmetrical with respect to the detection electrode.

[0021]

[Table 1]

[0022]

[Table 2]

FIG. 3 is a perspective view showing another embodiment of the piezoelectric vibrating gyroscope according to the present invention. The same reference numerals are given to the components corresponding to those in FIG. Piezoelectric ceramic cylinder 20
On the outer peripheral surface of the first to sixth strip-shaped electrodes 11, 12, 13, 14, 15, parallel to the length direction and at intervals in the circumferential direction,
16 are formed. The strip electrode 14 is formed at a position symmetrical with respect to the center axis of the strip electrode 11 and the piezoelectric ceramic column 20, and the center line of the strip electrode 11 and the piezoelectric ceramic column 2 are formed.
The strip electrodes 12, 16 and 13, 15 are formed at positions symmetrical with respect to a plane including the central axis of 0, respectively.

Furthermore, on the nodal line of the vibration of the piezoelectric ceramic cylinder 20 during flexural vibration resonance, the center line of the strip electrode 11 and the plane including the center line of the piezoelectric ceramic cylinder 20 are symmetrical with respect to each other. External lead connection terminals 22 and 26 are formed at positions 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, the external lead connection terminal 22 is provided.
Since 26 and 26 are separated from the central axis of the piezoelectric ceramic cylinder 20 by only 60 °, the strip electrode 14 for grounding sandwiched between them is made short, and the electrodes for driving and detecting and the electrode for grounding are formed. The distance between and is kept at a predetermined distance.

In the conventional piezoelectric vibrating gyroscope vibrator shown in FIG. 7, when the strip electrode 4 is used as the driving electrode, the vibrating 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 necessarily match the direction of the containing surface. However, in the case of FIG. 3, all the strip electrodes including the external lead connecting terminals are formed symmetrically with respect to the plane including the center line of the driving strip electrode 14 and the center line of the piezoelectric ceramic cylinder 20. And the piezoelectric ceramic cylinder 2
No plane other than this plane is symmetric with respect to the plane including the center line of 0.

Therefore, as shown in FIG. 4, 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 is fixed.
The resonance frequency of (shift '>fy'). However, since the detection electrodes 12 and 16 are arranged symmetrically with respect to the vibration direction of fx ′, the first basic condition is satisfied, and good gyro characteristics can be obtained by almost no adjustment or only fine adjustment. Obtainable.

Table 3 shows specific examples of the strip electrodes of the piezoelectric vibrator used in the piezoelectric vibration gyro of the present invention. In addition, Table 4 shows an example of oscillator 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, 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. The difference in the resonance frequency of 1 is almost 1 Hz or less, which indicates that the vibration direction is substantially symmetrical with respect to the detection electrode.

[0029]

[Table 3]

[0030]

[Table 4]

FIG. 5 is a perspective view showing still another embodiment of the piezoelectric vibrating gyroscope according to the present invention. The components corresponding to those of FIG. 1 are designated by the same reference numerals. First to sixth strip-shaped electrodes 11, 12, 1 are arranged on the outer peripheral surface of the piezoelectric ceramic column 20 in parallel with the length direction and at intervals in the circumferential direction.
3, 14, 15, and 16 are formed. Strip electrode 14
Are formed at positions symmetrical with respect to the central axes of the strip electrode 11 and the piezoelectric ceramic cylinder 20, and the strip electrodes 12 and 16 are provided at symmetrical positions with respect to a plane including the center line of the strip electrode 11 and the central axis of the piezoelectric ceramic column 20, respectively. And 13, 15 are formed. At this time, the strip electrodes 12, 13 and 1
Reference numerals 5 and 16 each include the center line of the piezoelectric ceramic cylinder 20, and are formed asymmetrically with respect to the plane orthogonal to the plane of symmetry.

In the conventional piezoelectric vibrating gyroscope oscillator shown in FIG. 7, when the strip electrode 4 is used as a driving electrode, as described above, the direction of oscillation is the center line of the strip electrode 4 and the piezoelectric element. It does not necessarily coincide with the direction of the plane including the center line of the ceramic column 10. However, in the case of FIG. 5, all the strip electrodes including the connecting electrodes are formed symmetrically with respect to the plane including the center line of the driving strip electrode 14 and the center line of the piezoelectric ceramic cylinder 20. Moreover, the plane including the center line of the piezoelectric ceramic cylinder 20 and symmetrical with respect to the piezoelectric ceramic column 20 does not exist other than the symmetrical plane.

Therefore, as shown in FIG. 6, 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 is fixed.
The resonance frequency of is deviated. However, the electrodes 12 and 1 for detection
Since No. 6 is arranged at a position symmetrical with respect to the vibration direction of fx ′, the first basic condition is satisfied, and good gyro characteristics can be obtained by 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 gyro of the present invention. In addition, Table 6 shows examples of oscillator characteristics. For comparison, Table 6 also shows an example of a conventional vibrator in which six strip electrodes are formed at equal intervals. 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. The difference in the resonance frequency of 1 is almost 1 Hz or less, which indicates that the vibration direction is substantially symmetrical with respect to the detection electrode.

[0035]

[Table 5]

[0036]

[Table 6]

[0037]

As described above, according to the present invention,
Since the detection electrode is formed at a position symmetrical to the vibration direction, the amplitude and phase of the voltage generated at the detection electrode are almost the same, which makes it easier to adjust the final resonance frequency and also causes piezoelectric vibration. Variations in gyro characteristics are also reduced.

Further, according to the present invention, when the groove is formed in the piezoelectric ceramic cylinder to finely adjust the resonance frequency, the groove is formed in the portion sandwiched between the two electrodes for grounding. It is possible to obtain a vibrator in which the change in the electrical characteristics of the vibrator due to

Further, according to the present invention, since the detection electrode is formed at a position symmetrical to the vibration direction, the amplitude and phase of the voltage generated at the detection electrode are substantially the same,
The final adjustment of the resonance frequency becomes easy, and the variation in the characteristics of the piezoelectric vibration gyro becomes small.

[Brief description of drawings]

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

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

FIG. 3 is a schematic perspective view showing another embodiment of the piezoelectric vibration gyro of the present invention.

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

FIG. 5 is a schematic perspective view showing still another embodiment of the piezoelectric vibration gyro of the present invention.

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

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

8 is a frequency characteristic diagram of impedance as seen from the driving strip electrode and the detecting strip electrode of the piezoelectric vibrator shown in FIG.

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

[Explanation 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 column 22 1st External lead terminal 26 Second external lead terminal

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yasunori Otsuki 21-1 Taishi-dō, Taichiro-ku, Sendai City, Miyagi Prefecture Tokin Co., Ltd.

Claims (3)

[Claims] 1. A piezoelectric ceramic column, and first to seventh band-shaped electrodes formed on the outer peripheral surface of the column in parallel with the longitudinal direction thereof and at intervals in the circumferential direction, and the first band-shaped electrode. The second and seventh electrodes are arranged at symmetrical positions with respect to a plane including the center line of the electrode and the central axis of the piezoelectric ceramic cylinder.
The strip electrodes, 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, After the fourth, fifth, and seventh strip electrodes are commonly connected and the two sets of common connection electrodes are used as two terminals to perform polarization processing on the piezoelectric ceramic cylinder, the second, fourth, fifth, and 7, the strip-shaped electrode is a common ground electrode, the first strip-shaped electrode is a drive electrode,
A piezoelectric vibrating gyro, wherein each of the third and sixth strip electrodes is a detection electrode. 2. A piezoelectric ceramic column, and first to sixth band-shaped electrodes which are sequentially formed on the outer peripheral surface of the column in parallel with the longitudinal direction thereof and at intervals in the circumferential direction, and these band-shaped electrodes are provided. Polarization treatment is performed, and then the first, third and fifth strip electrodes are electrically connected to form a common ground electrode,
In a piezoelectric vibrating gyro using the fourth strip electrode as a drive electrode and the second and sixth strip electrodes 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 cylinder, and with respect to a plane including the center line of the first strip electrode and the center line of the piezoelectric ceramic cylinder. The second and sixth strip electrodes and the third and fifth strip electrodes are respectively formed at symmetrical positions, and the first strip electrodes on the nodal line of vibration at the time of bending vibration resonance of the piezoelectric ceramic column The first and second external lead connecting terminals are formed at positions symmetrical with respect to a plane including the center line and the central axis of the piezoelectric ceramic cylinder, and the first and second external lead connecting terminals are formed. A piezoelectric vibrating gyro, which is connected to the second and sixth strip electrodes for detection, respectively. 3. A piezoelectric ceramic column, and first to sixth band-shaped electrodes formed on the outer peripheral surface of the column in parallel with the longitudinal direction thereof and at intervals in the circumferential direction, and these band-shaped electrodes are provided. Polarization treatment is performed, and then the first, third and fifth strip electrodes are electrically connected to form a common ground electrode,
In a piezoelectric vibrating gyro using the fourth strip electrode as a drive electrode and the second and sixth strip electrodes as detection electrodes,
The fourth strip-shaped electrode is formed at a position symmetrical to the first strip-shaped electrode with respect to the center of the piezoelectric ceramic cylinder, and includes a first axis of the first strip-shaped electrode and a center axis of the piezoelectric ceramic column. A second plane that is symmetric with respect to a plane and includes a central axis of the piezoelectric ceramic cylinder and that is orthogonal to the first plane
A piezoelectric vibrating gyro, wherein the second and sixth strip electrodes and the third and fifth strip electrodes are formed at asymmetrical positions on the surface.