JP2007071692A - Oscillator for piezoelectric oscillation gyro - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an oscillator for a piezoelectric oscillation gyro capable of reducing a change of an output voltage by a temperature. <P>SOLUTION: The output voltage is corrected using a temperature characteristic of ▵f; that is a difference between a resonance frequency of an X-directional vibration and a resonance frequency of a Y-directional vibration, by providing an area different in a Young's modulus in an inside of a columnar piezoelectric ceramic 1. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a piezoelectric vibrator for a piezoelectric vibration gyro using columnar flexural vibration, and more particularly to a gyroscope or a gyro sensor used for camera shake prevention of a camera or a camera-integrated VTR (video tape recorder), an automobile navigation system, or the like. The present invention relates to a suitable piezoelectric vibrator.

  Piezoelectric vibratory gyros belong to a gyroscope that utilizes a dynamic phenomenon in which, when an angular velocity of rotation is given to a vibrating object, a Coriolis force is generated in a direction perpendicular to the vibration direction. In a vibration system in which vibration can be detected with one side as the excitation side and output voltage can be detected with the other as the output side in two directions orthogonal to each other, the line where the two vibration surfaces intersect with the excitation side vibrated When the vibrator itself is rotated with the axis parallel to the center axis as a central axis, a force acts in a direction perpendicular to the vibration direction on the excitation side by the action of the Coriolis force described above, and vibration is excited on the output side. Since the magnitude of the vibration excited on the output side is proportional to the rotational angular velocity, the magnitude of the rotational angular velocity can be obtained from the magnitude of the output voltage generated by the piezoelectric phenomenon on the output side.

  FIG. 1 is a perspective view showing a conventional piezoelectric vibration gyro vibrator, and FIG. 2 is a cross-sectional view of a central portion perpendicular to the central axis of the conventional piezoelectric vibration gyro vibrator. A conventional piezoelectric vibration gyro vibrator will be described with reference to FIGS. The structure of the conventional vibrator for piezoelectric vibration gyro has a belt-like drive electrode 3 parallel to the central axis 9 of the cylinder and a belt-like detection at a position that divides the circumference of the outer peripheral surface 2 of the cylindrical piezoelectric ceramic 1 into six equal parts. Electrodes 5 and 7 and strip-shaped ground electrodes 4, 6 and 8 are formed. Furthermore, both ends in the longitudinal direction of the ground electrodes 4, 6 and 8 are electrically connected by annular electrodes 10 and 11 that make one round on the circumference of the outer peripheral surface of the cylindrical piezoelectric ceramic 1. In FIG. 1, the detection electrode 7 and the ground electrode 8 are not shown because they are hidden behind the cylindrical piezoelectric ceramic 1. Polarization is performed by applying a DC voltage to each of the drive electrode 3, the detection electrode 5, and the detection electrode 7 with the annular electrode 10 or 11 having the ground electrodes 4, 6, and 8 in common as a common ground. By performing the processing, a piezoelectric vibration gyro vibrator is formed.

  When a drive signal is input to the drive electrode 3, vibration is excited in the X direction shown in FIG. In this state, when a rotational force is applied with the central axis 9 as the axis of rotation, the Coriolis force is generated, and vibration is excited in the Y direction shown in FIG. The magnitude of the rotational angular velocity applied to the cylindrical piezoelectric ceramic 1 can be known by taking out and detecting the voltage generated by the vibration in the Y direction from the detection electrode 5 and the detection electrode 7.

  The performance required for the vibrator for a piezoelectric vibration gyro includes detection sensitivity and accuracy of the rotational angular velocity, stability to the environment, and the like. For example, as a method for increasing the detection sensitivity, the length of the detection electrode is made shorter than that of the drive electrode, and the relationship between the electromechanical coupling coefficient kx of the drive unit and the electromechanical coupling coefficient ky of the detection unit is set to kx> ky. Proposals to make it possible have been made. Such a vibrator for a piezoelectric vibration gyro is disclosed in Patent Document 1.

  In addition, as a method of improving the temperature characteristics of sensitivity, there are proposals for correcting the temperature characteristics of the sensitivity of the piezoelectric vibration gyro vibrator with a detection circuit, and circuit configurations that cancel the temperature characteristics of the detection circuit. Proposals have been made to improve temperature characteristics. Such a vibration gyro is disclosed in Patent Document 2.

Japanese Patent Laid-Open No. 9-304080 JP 2000-171258 A

  A conventional vibrator for a piezoelectric vibration gyro has a problem that the output voltage fluctuates due to an influence of a change in ambient temperature. For this reason, as described above, the voltage output from the piezoelectric vibration gyro vibrator is corrected or adjusted by a circuit, and the effect due to this temperature change is apparently reduced, and thus is put into practical use. In recent years, with the miniaturization of mounted cameras and electronic devices, gyro sensors are also required to be miniaturized. However, the downsizing of a vibrator for a piezoelectric vibration gyro has problems such as a decrease in sensitivity and accuracy. Therefore, the change in the output voltage with respect to the temperature must be reduced more than before. It is a big problem.

  Therefore, an object of the present invention is to solve the above-mentioned problems of the prior art. Specifically, an object of the present invention is to provide a piezoelectric vibration gyro vibrator that is small in size and has little change in output voltage due to temperature.

  The present invention employs the following means in order to solve the above problems. That is, according to the present invention, the structure of the vibrator for a piezoelectric vibration gyro is configured such that portions having different Young's moduli exist in the same piezoelectric ceramic. Further, the gist of the invention is that the change in the output voltage due to the temperature is reduced when the piezoelectric vibration gyro is configured by using the temperature characteristic of the dynamic characteristic obtained therefrom.

  According to the present invention, at least one strip-shaped drive electrode, at least two strip-shaped detection electrodes, and at least three strip-shaped ground electrodes are provided on the outer peripheral surface of the columnar piezoelectric ceramic. A vibrator for a piezoelectric vibration gyro in which the ground electrodes are arranged not to be adjacent to each other, wherein a Young's modulus inside the columnar piezoelectric ceramic is partially biased. It is done.

  Strictly speaking, the Young's modulus inside a conventional piezoelectric vibration gyro vibrator is extremely different between a portion where an electrode is present and a portion where no electrode is present. Since the electrodes are arranged on the surface, there is no bias when viewed as a whole. In the present invention, the Young's modulus inside the columnar piezoelectric ceramic is preliminarily provided with a partial bias in advance in the manufacturing stage of the columnar piezoelectric ceramic or in a subsequent process.

  According to the present invention, the piezoelectric vibration characterized in that the resonance frequency of the bending vibration generated between the drive electrode and the ground electrode is different from the resonance frequency of the bending vibration generated between the detection electrode and the ground electrode. A vibrator for gyro is obtained.

  Due to the deviation of the Young's modulus inside the columnar piezoelectric ceramic, a difference occurs in the vibration state between the X direction and the Y direction in the conventional piezoelectric vibration gyro vibrator shown in FIG. That is, as a result of the difference between the stiffness in the X direction and the stiffness in the Y direction, the resonance frequency of the X direction vibration and the resonance frequency of the Y direction vibration show different frequencies. If the difference between the resonance frequency of the X-direction vibration and the resonance frequency of the Y-direction vibration is Δf, Δf inevitably has a temperature characteristic. By using the temperature characteristic of Δf, the output is more than conventional. It is possible to provide a vibrator for a piezoelectric vibration gyro with little change in voltage due to temperature.

  In addition, according to the present invention, it is possible to obtain a vibrator for a piezoelectric vibration gyro characterized in that at least one of the ground electrodes has a shorter dimension in the longitudinal direction than the other ground electrodes. In this configuration, the portion where there is no electrode of the earth electrode whose longitudinal dimension is shorter than the other earth electrodes is not subjected to the polarization treatment because the polarization voltage is not applied in the polarization treatment process. Therefore, the Young's modulus of the part not subjected to the polarization treatment and the Young's modulus of the part subjected to the polarization treatment are different, and the Young's modulus is biased inside the columnar piezoelectric ceramic.

  Furthermore, according to the present invention, there is obtained a vibrator for a piezoelectric vibration gyro characterized in that the earth electrode facing the drive electrode has a shorter dimension in the longitudinal direction than other earth electrodes. By shortening the ground electrode facing the drive electrode and providing a portion that is not subjected to the polarization treatment, it is possible to easily form a Young's modulus bias in the columnar piezoelectric ceramic. The reason why the ground electrode is shortened is that the driving force or the detection sensitivity is not decreased by shortening the driving electrode or the detection electrode.

  In addition, according to the present invention, there is obtained a piezoelectric vibration gyro characterized by using the piezoelectric vibration gyro vibrator described above.

  According to the present invention, the difference between the resonance frequency of the bending vibration generated between the drive electrode and the ground electrode and the resonance frequency of the bending vibration generated between the detection electrode and the ground electrode is detected, and the output voltage is determined. A piezoelectric vibration gyro characterized by correction is obtained. By using the piezoelectric vibration gyro vibrator, a change in the Δf due to the temperature can be detected and the output voltage can be corrected, so that the piezoelectric vibration gyro can reduce the change in the output voltage due to the temperature.

  As described above, according to the present invention, in the piezoelectric vibration gyro vibrator, the temperature characteristic of Δf which is the difference between the resonance frequency in the X direction and the resonance frequency in the Y direction can be used, and the piezoelectric vibration gyro according to the present invention is used. By using the vibrator for a device, it is possible to provide a piezoelectric vibration gyro with little fluctuation in output voltage due to temperature.

  Next, a vibrator for a piezoelectric vibration gyro according to the present invention will be specifically described with reference to the drawings.

  FIG. 3 is a diagram showing a piezoelectric vibration gyro vibrator according to the present invention. 3A is a side view, and FIG. 3B is a cross-sectional view taken along line A1-A2 in FIG. In the position which divides the circumference of the outer peripheral surface 2 of the cylindrical piezoelectric ceramic 1 into six equal parts, the belt-like drive electrode 3 parallel to the central axis 9 of the cylinder, the belt-like detection electrodes 5 and 7, and the belt-like earth electrode 4, 6 and 8 are formed. Furthermore, both ends in the longitudinal direction of the ground electrodes 4, 6 and 8 are electrically connected by annular electrodes 10 and 11 that make one round on the circumference of the outer peripheral surface of the cylindrical piezoelectric ceramic 1. In FIG. 3A, the detection electrode 5 and the ground electrode 4 are not shown because they are hidden behind the cylindrical piezoelectric ceramic 1.

  Regions 12 in FIGS. 3A and 3B show portions having different Young's moduli inside the cylindrical piezoelectric ceramic 1. This region 12 can be formed in advance by changing the density in the manufacture of the cylindrical piezoelectric ceramic 1. Alternatively, after the earth electrode 6 is separated from the annular electrode 10 and further divided at the center in the longitudinal direction, the annular electrode 11 is used as a common earth, and each of the drive electrode 3, the detection electrode 5, and the detection electrode 7 is connected to a direct current. The region 12 can also be formed by applying the polarization voltage and applying the polarization process. This occurs as a result that the portion indicated by the region 12 is not polarized because the ground electrode 6 is separated as described above. In the above case, the disconnected ground electrode 6 may be connected again, but in some cases, the state may be maintained as it is.

  The presence of the regions 12 having different Young's moduli causes a difference in the vibration state between the X direction and the Y direction shown in FIG. That is, as a result of the difference between the stiffness in the X direction and the stiffness in the Y direction, the resonance frequency of the X direction vibration and the resonance frequency of the Y direction vibration show different frequencies. If the difference between the resonance frequency of the X direction vibration and the resonance frequency of the Y direction vibration is Δf, Δf necessarily has temperature characteristics. By utilizing this temperature characteristic of Δf, it is possible to provide a vibrator for a piezoelectric vibration gyro with less change in output voltage due to temperature than in the past.

  Although FIG. 3 shows a cylindrical piezoelectric ceramic, the same effect can be obtained with a polygonal column other than a column as long as it has a columnar bending vibration structure. Moreover, the shape of each electrode shown in FIG. 3 shows a basic shape, and is not limited. For example, FIG. 4 is a diagram showing an example of an electrode pattern of a conventional piezoelectric vibration gyro vibrator. FIG. 4 shows a developed view of the electrode pattern printed on the curved surface of the cylindrical piezoelectric ceramic. The drive electrode 13, the detection electrodes 15 and 17, and the ground electrodes 14, 16 and 18 are arranged in parallel at equal intervals. The ground electrodes 14, 16 and 18 are connected to the common electrode 19 and are common. This electrode is printed on a curved surface of a cylindrical piezoelectric ceramic, the drive electrode 13 and the ground electrode 16 face each other, the detection electrode 15 and the ground electrode 18 face each other, and the detection electrode 17 and the ground electrode 14 face each other. Become. In the present invention, the same effect as described above can be obtained even with such an electrode structure.

  Hereinafter, the piezoelectric vibrator gyro vibrator according to the present invention will be described in more detail with specific examples.

  FIG. 5 is a perspective view illustrating the piezoelectric vibration gyro vibrator according to the first embodiment. The cylindrical piezoelectric ceramic 1 is obtained by sintering a press-molded lead zirconate titanate-based piezoelectric ceramic material and then processing it into a cylindrical shape. The shape was 1 mm in diameter and 10 mm in length. Electrode patterns such as the detection electrodes 25 and 27 and the ground electrode 26 were printed on the outer peripheral surface 2 of the cylindrical piezoelectric ceramic 1 and subjected to polarization treatment to obtain a vibrator for a piezoelectric vibration gyro.

  FIG. 6 is a developed plan view of an electrode pattern of the piezoelectric vibration gyro vibrator according to the first embodiment. The electrodes printed on the outer peripheral surface 2 of the cylindrical piezoelectric ceramic 1 are arranged so that the drive electrode 23, the detection electrodes 25 and 27, and the ground electrodes 24, 26, and 28 are parallel to each other, and the ground electrodes 24, 26, and 28 is a common electrode 29 and is electrically common. Further, the length of the ground electrode 26 is halved compared to the other ground electrode 24 or 28.

  The polarization treatment was performed by setting the common electrode 29 to 0 V potential and applying a high voltage to the drive electrode 23 and the detection electrodes 25 and 27, respectively. At this time, no voltage is applied to the portion 30 without the ground electrode indicated by a dotted line in FIG. 5 or FIG. Therefore, a portion having a Young's modulus is smaller than that of the portion subjected to polarization treatment, and a partial deviation of Young's modulus is generated inside the cylindrical piezoelectric ceramic 1.

  In this state, the resonance frequency of vibration generated between the drive electrode 23 and the ground electrode 26 (or common electrode 29) and the resonance frequency of vibration generated at the detection electrodes 25 and 27 and the ground electrodes 24 and 28 (or common electrode 29) are set. Makes a difference. If this difference is Δf, Δf necessarily has temperature characteristics.

  FIG. 7 is a graph showing the temperature characteristic of Δf. The horizontal axis indicates the temperature, and the vertical axis indicates the amount of change in Δf at each temperature with reference to Δf at 25 ° C. For comparison, the temperature characteristics of Δf of the conventional piezoelectric vibration gyro vibrator having the electrode pattern shown in FIG. 4 and having no partial bias of Young's modulus are also shown. As can be seen from the graph of FIG. 7, the amount of change in Δf due to temperature in Example 1 is much larger than that of the conventional product. Although this result seems to be a contradictory result at first glance to the solution of the problem in the present invention, in fact, this large amount of change is sensitive to temperature, that is, temperature. This shows that the sensitivity is high. Therefore, by using this change to correct the output, the piezoelectric vibration gyro is sensitive to a temperature change and has a very small output change.

  FIG. 8 is a perspective view illustrating the piezoelectric vibration gyro vibrator according to the second embodiment. The cylindrical piezoelectric ceramic 1 is obtained by sintering a press-molded lead zirconate titanate-based piezoelectric ceramic material and then processing it into a cylindrical shape. The shape was 1 mm in diameter and 10 mm in length. Electrodes such as the detection electrodes 35 and 37 and the ground electrode 36 were printed on the outer peripheral surface 2 of the cylindrical piezoelectric ceramic 1 and subjected to polarization treatment to obtain a vibrator for a piezoelectric vibration gyro.

  FIG. 9 is a development view of the electrode pattern of the vibrator for piezoelectric vibration gyro according to the second embodiment. When the electrode printed on the outer peripheral surface 2 of the cylindrical piezoelectric ceramic 1 is developed on a plane, the drive electrode 33, the detection electrodes 35 and 37, and the ground electrodes 34, 36, and 38 become parallel as shown in FIG. The ground electrodes 34, 36 and 38 are electrically shared by the common electrode 39. Further, the length of the ground electrode 36 is 3/4 compared to the other ground electrode 34 or 38.

  The polarization process was performed by setting the common electrode 39 to 0 V potential and applying a high voltage to the drive electrode 33 and the detection electrodes 35 and 37, respectively. At this time, no voltage is applied to the portion 40 without the ground electrode indicated by a dotted line in FIG. 8 or FIG. Therefore, a portion having a Young's modulus is smaller than that of the portion subjected to polarization treatment, and a partial deviation of Young's modulus is generated inside the cylindrical piezoelectric ceramic 1.

  In this state, the resonance frequency of vibration generated between the drive electrode 33 and the ground electrode 36 (or common electrode 39) and the resonance frequency of vibration generated between the detection electrodes 35 and 37 and the ground electrodes 34 and 38 (or common electrode 39). There is a difference between If this difference is Δf, Δf necessarily has temperature characteristics.

  FIG. 10 is a graph showing the temperature characteristic of Δf. The horizontal axis indicates the temperature, and the vertical axis indicates the amount of change in Δf at each temperature with reference to Δf at 25 ° C. For comparison, the temperature characteristic of Δf of a conventional piezoelectric vibration gyro vibrator is also shown. As can be seen from the graph in FIG. 10, the amount of change in Δf due to temperature in Example 2 is very large compared to the conventional product. As described above, this result seems to be contradictory to the solution of the problem in the present invention. However, the large amount of change means that the reaction is sensitive to temperature. , Indicating high sensitivity to temperature. Therefore, by using this change to correct the output, the piezoelectric vibration gyro is sensitive to a temperature change and has a very small output change.

  Further, comparing the amount of change of Δf according to the temperature of Example 1 with the amount of change of Δf of Example 2 due to the temperature, it can be seen that the amount of change of Example 1 is large. From this result, the temperature characteristic of Δf, which is the difference between the resonance frequency of the vibration generated in the drive electrode and the resonance frequency of the vibration generated in the output electrode, depends on the length of the earth electrode and changes the length of the earth electrode. It turns out that it can be controlled. This is an effect by changing the state of bias of Young's modulus inside the cylindrical piezoelectric ceramic 1 depending on the length of the ground electrode.

  FIG. 11 is a block diagram illustrating the configuration of the piezoelectric vibration gyro according to the third embodiment. In Example 3, a piezoelectric vibration gyro provided with the piezoelectric vibration gyro vibrator 41, the drive circuit 42, the temperature compensation circuit 43, and the detection circuit 44 according to Example 1 was prototyped and evaluated.

  The drive circuit 42 includes a self-excited oscillation circuit, and supplies a drive signal to the drive electrode 23 of the piezoelectric vibration gyro vibrator 41 according to the first embodiment to excite the piezoelectric vibration gyro vibrator 41. The detection circuit 44 includes a differential amplifier circuit, detects and amplifies voltages output from the detection electrode 25 and the detection electrode 27 of the piezoelectric vibration gyro vibrator 41 according to the first embodiment, and outputs an output voltage V. Circuit. The temperature compensation circuit 43 detects Δf, which is the difference between the resonance frequency of the vibration obtained from the drive circuit 42 and the resonance frequency of the vibration obtained from the detection electrode 25 and the detection electrode 27 of the piezoelectric vibration gyro vibrator 41 according to the first embodiment. This is a circuit that supplies the detection circuit 44 with a correction signal for the output voltage due to temperature by detecting the difference from Δf at the reference temperature. The ground electrodes 24, 26, and 28 of the piezoelectric vibration gyro vibrator 41 are connected to the circuit ground.

  FIG. 12 is a graph showing the change rate of the output voltage according to the third embodiment. In this graph, the horizontal axis indicates the temperature, and the vertical axis indicates the rate of change of the output voltage V with respect to each temperature when 25 ° C. is used as a reference. For comparison, the graph of FIG. 12 shows a comparison between a conventional product using a vibrator for a piezoelectric vibrating gyroscope having no bias of Young's modulus inside the cylindrical piezoelectric ceramic 1 according to the electrode pattern shown in FIG. The change rate of the output voltage of the piezoelectric vibration gyro when the piezoelectric vibration gyro vibrator 2 is used is also shown.

  As can be seen from the graph, the temperature change of the output of the piezoelectric vibrating gyroscope according to the third embodiment is less changed than the conventional product and greatly improved. Further, the temperature change of the output of the piezoelectric vibration gyro using the piezoelectric vibration gyro vibrator according to the second embodiment is also improved as compared with the conventional product.

  As described above, the piezoelectric vibration gyro vibrator according to the present invention is provided with a bias of Young's modulus inside the cylindrical piezoelectric ceramic. Therefore, there is a difference in Δf between the resonance frequency of the X direction vibration and the resonance frequency of the Y direction vibration. it can. Since the value of Δf changes sensitively with respect to temperature, it is possible to remarkably reduce a change in the output voltage of the piezoelectric vibrating gyroscope due to temperature by performing temperature correction using the property.

  The piezoelectric vibration gyro vibrator and the piezoelectric vibration gyro according to the present invention can be widely used for a camera, a camera-integrated VTR camera shake prevention device, a rotational angular acceleration detection device, a car navigation system sensor, or the like.

FIG. 5 is a perspective view showing a conventional piezoelectric vibration gyro vibrator. Sectional drawing of the center part perpendicular | vertical with respect to the central axis of the vibrator | oscillator for conventional piezoelectric vibration gyroscopes. It is a figure which shows the vibrator | oscillator for piezoelectric vibration gyroscopes by this invention. 3A is a side view, and FIG. 3B is a cross-sectional view taken along line A1-A2 in FIG. The figure which shows an example of the electrode pattern of the vibrator | oscillator for conventional piezoelectric vibration gyroscopes. FIG. 3 is a perspective view illustrating a piezoelectric vibration gyro vibrator according to the first embodiment. FIG. 3 is a plan development view of an electrode pattern of the piezoelectric vibration gyro vibrator according to the first embodiment. 6 is a graph showing temperature characteristics of Δf according to Example 1. FIG. 6 is a perspective view showing a piezoelectric vibration gyro vibrator according to a second embodiment. FIG. 5 is a development view of an electrode pattern of a vibrator for a piezoelectric vibration gyro according to a second embodiment. 6 is a graph showing temperature characteristics of Δf according to Example 2. FIG. 6 is a block diagram illustrating a configuration of a piezoelectric vibration gyro according to a third embodiment. 10 is a graph showing the rate of change of output voltage according to Example 3.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Cylindrical piezoelectric ceramic 2 Outer peripheral surface 3, 13, 23, 33 Drive electrode 4, 6, 8, 14, 16, 18, 24, 26, 28, 34, 36, 38 Ground electrode 5, 7, 15, 17, 25, 27, 35, 37 Detection electrode 9 Center axis 10, 11 Annular electrode 12 Region 19, 29, 39 Common electrode 30, 40 Portion without ground electrode 41 Piezoelectric vibration gyro vibrator 42 according to the present invention Drive circuit 43 Temperature compensation Circuit 44 Detection circuit V Output voltage

Claims (6)

  At least one strip-shaped drive electrode, at least two strip-shaped detection electrodes, and at least three strip-shaped ground electrodes are provided on the outer peripheral surface of the columnar piezoelectric ceramic, and the ground electrodes are adjacent to each other. A vibrator for a piezoelectric vibration gyro, wherein the Young's modulus inside the columnar piezoelectric ceramic is partially biased.   2. The piezoelectric vibration gyro according to claim 1, wherein a resonance frequency of bending vibration generated between the drive electrode and the ground electrode is different from a resonance frequency of bending vibration generated between the detection electrode and the ground electrode. Vibrator.   3. The vibrator for a piezoelectric vibration gyro according to claim 1, wherein at least one of the ground electrodes has a shorter longitudinal dimension than the other ground electrodes.   4. The vibrator for a piezoelectric vibration gyro according to claim 1, wherein the earth electrode facing the drive electrode has a shorter longitudinal dimension than the other earth electrodes. 5.   5. A piezoelectric vibration gyro using the piezoelectric vibration gyro vibrator according to claim 1.   The output voltage is corrected by detecting a difference between a resonance frequency of bending vibration generated between the drive electrode and the ground electrode and a resonance frequency of bending vibration generated between the detection electrode and the ground electrode. Item 6. The piezoelectric vibration gyro according to Item 5.

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