JP3547736B2 - Tuning fork type piezoelectric vibration gyro - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a sensitive and accurate tuning fork type piezoelectric vibratory gyro which is suitable for mass production. SOLUTION: In the turning fork type piezoelectric vibratory gyro having first and second arms and a base for supporting them, a drive electrode for driving tuning fork vibration merely on two specific surfaces of each of the first and second arms, a detection electrode for detecting a rotary angular speed, and a grounded electrode that is set to reference potential are provided. The first and second arms and the base for supporting them are formed in one piece by a piezoelectric single crystal, thus providing the tuning fork type piezoelectric vibratory gyro that can maintain required sensitivity, has a simple electrode configuration, and is suited for mass production.

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a gyro for detecting a rotational angular velocity, and more particularly, to a tuning fork type piezoelectric vibration gyro using a piezoelectric body.
[0002]
In recent years, gyros used for in-vehicle navigation, camera shake prevention, and the like have been required to have higher precision and higher sensitivity. For this reason, technical development related to the piezoelectric vibrating gyroscope has been activated.
[0003]
[Prior art]
The piezoelectric vibrating gyroscope utilizes the fact that when a rotational angular velocity is applied during predetermined vibration, Coriolis force is generated in a direction perpendicular to the vibration. Various types of such a piezoelectric vibrating gyroscope have been proposed. Among them, the tuning-fork type piezoelectric vibration has attracted attention because of its relatively high cost performance. Particularly recently, research and development of a tuning fork type piezoelectric vibrating gyroscope using a piezoelectric single crystal has been actively conducted.
[0004]
A tuning fork type piezoelectric vibrating gyroscope using such a piezoelectric single crystal is disclosed in, for example, US Pat. No. 5,329,816. As shown in FIG. 33, the tuning-fork type piezoelectric vibration gyro (also referred to as a gyro element) has two arms 10 and 12 and a base 14 that supports them, and these are integrally formed of a piezoelectric single crystal. I have. Further, a drive electrode 18 for driving the tuning fork vibration is provided on one arm, and a detection electrode 16 for detecting the rotational angular velocity is provided on the other arm. For convenience, the surface shown in the figure is the surface of the gyro, and the surface facing this surface is the back surface. Two drive electrodes 18 are provided on the surface.
[0005]
FIG. 34 shows a conventional tuning-fork type piezoelectric vibrating gyroscope having a different electrode configuration, which is disclosed in, for example, US Pat. No. 5,251,483. In this electrode configuration, a detection electrode 16 and a drive electrode 18 are provided on each of the arms 10 and 12. FIG. 34 shows a configuration in which the detection electrode 16 is provided on the distal end side of each of the arms 10 and 12, and the drive electrode 18 is provided on the base 14 side. FIG. 35 shows a configuration in which the detection electrode 16 is provided on the base 14 side of each of the arms 10 and 12, and the drive electrode 18 is provided on the distal end side.
[0006]
FIGS. 33, 34 and 35 show examples of respective capacitance ratios.
[Problems to be solved by the invention]
However, the conventional tuning-fork type piezoelectric vibration gyro shown in FIGS. 33 to 35 has the following problems.
[0007]
In the configuration shown in FIG. 33, since the electrodes are provided substantially symmetrically, there is a problem that although the capacitance ratio of drive and detection is well balanced, unnecessary vibration such as bending vibration is output.
[0008]
This problem will be described with reference to FIG. 36 (a) is a perspective view of the gyro shown in FIG. 16, showing unnecessary vibration, FIG. 36 (b) is a side view, FIG. 36 (c) is a diagram showing unnecessary vibration shown in FIG. 36 (a), and FIG. It is a figure showing an electric field inside an arm by vibration. Note that the electrodes are omitted in FIGS. In FIG. 4D, the electrodes in the white portions have the same potential, and the electrodes in the hatched portions have the same potential. In the configuration shown in FIG. 33, unnecessary vibration having the same phase as shown in FIG. 36 occurs. Since the detection electrode is provided on one of the two arms, the potential difference due to the electric field shown in FIG. 36D is detected. This potential difference becomes noise and degrades detection accuracy. Unwanted vibrations include torsional vibrations that cause temperature drift. In addition, there is leakage output due to mechanical coupling or electrostatic coupling between the driving arm and the detection arm.
[0009]
The configuration shown in FIG. 34 has a small driving-side capacitance ratio, so that a low driving voltage can be achieved. In addition, since the detection electrodes 16 are provided on both the arms 10 and 12, unnecessary vibrations can be canceled and the leakage output is small. However, since the capacitance ratio of the resonators at the distal ends of the arms 10 and 12 is about 20 times larger than the resonator at the root thereof, there is a problem that the detection sensitivity is low. Further, since the detection electrodes 16 and the drive electrodes 18 are provided on each of the arms 10 and 12, the wiring becomes complicated and mass productivity is difficult.
[0010]
Since the configuration shown in FIG. 35 has a small detection-side capacitance ratio, high sensitivity can be achieved. However, there is a problem that a high drive voltage is required because the drive-side capacitance ratio is large. Further, since the detection electrodes 16 and the drive electrodes 18 are provided on each of the arms 10 and 12, the wiring becomes complicated, and mass productivity is difficult.
[0011]
SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to solve the above-mentioned problems of the prior art, and to provide a tuning fork type piezoelectric vibration gyro having high sensitivity, high accuracy, and suitable for mass production.
[0012]
[Means for Solving the Problems]
According to a first aspect of the present invention, in a tuning fork type piezoelectric vibrating gyroscope having a first arm, a second arm, and a base for supporting the first arm and the second arm, only two predetermined surfaces of the first and second arms are provided. A drive electrode for driving the tuning fork vibration, a detection electrode for detecting a rotational angular velocity, and a ground electrode set to a reference potential are provided, and the drive electrode, the detection electrode, and the ground electrode are used for driving vibration of the tuning fork type piezoelectric vibration gyro. Two predetermined surfaces of each of the first and second arms which are arranged symmetrically with respect to a center plane; Each aspect of Only the two types of electrodes among the drive electrode, the detection electrode, and the ground electrode are disposed, and the first arm, the second arm, and the base supporting these are integrally formed of a piezoelectric single crystal. It is characterized by having. As a result, a required sensitivity can be maintained, and a tuning fork type piezoelectric vibration gyro suitable for mass production can be provided with a simple electrode configuration.
[0013]
According to a second aspect of the present invention, in the first aspect, the drive electrode is provided on a first surface of each of a first arm and a second arm, and the detection electrode is provided on a first surface facing the first surface. And a voltage corresponding to the angular velocity provided on the second surface of each of the second arms is obtained as a potential difference between detection electrodes provided on the second surfaces of the first and second arms, respectively. This is a tuning fork type piezoelectric vibrating gyroscope.
[0014]
According to a third aspect of the present invention, in the first aspect, the drive electrode is provided on a first surface of each of the first and second arms, and the detection electrode is provided on each of the first and second arms. A tuning fork type piezoelectric vibrating gyroscope provided on a first surface, wherein a voltage corresponding to an angular velocity is obtained as a potential difference between detection electrodes provided on the first surface of the first and second arms, respectively. It is.
[0015]
According to a fourth aspect of the present invention, in the first aspect, the drive electrode is provided on a first surface of each of the first and second arms, and the detection electrode is provided on each of the first and second arms. A first surface, and a second surface of each of the first and second arms opposed to the first surface, wherein a voltage corresponding to the angular velocity is applied to the first and second arms of the first arm. A tuning fork type piezoelectric vibrating gyroscope obtained as a potential difference between a detection electrode provided on a surface and detection electrodes provided on first and second surfaces of a second arm.
[0019]
Claim 5 The invention according to claim 1, wherein the piezoelectric single crystal is LiTaO ₃ A tuning fork type piezoelectric vibration gyro characterized by a 340 ° ± 20 ° rotating Z-plate.
[0020]
Claim 6 The invention according to claim 1, wherein the piezoelectric single crystal is LiTaO ₃ A tuning fork type piezoelectric vibrating gyroscope, which is a 350 ° ± 20 ° rotating Z plate.
[0021]
BEST MODE FOR CARRYING OUT THE INVENTION
First, the present invention Reference example Will be described with reference to FIG. Of the present invention Reference example As shown in FIG. 1A, the tuning-fork type piezoelectric vibrating gyroscope has arms 20, 22 and a base 24 made of a piezoelectric single crystal. As the piezoelectric single crystal, those having a large coupling coefficient of the piezoelectric transverse effect are preferable. For example, LiTaO ₃ 140 ° ± 20 ° rotating Y plate (LiTaO ₃ 40 ° ± 20 ° rotating Z plate), LiNbO ₃ 130 ° ± 20 ° rotating Y plate (LiNbO ₃ A 50 ° ± 20 ° rotating Z plate), a quartz X-cut plate, or the like can be used. The crystal orientation of the piezoelectric single crystal is in the thickness direction.
[0022]
In the configuration shown in FIG. 1, the drive electrodes 28a and 28b are provided on the front surface and the back surface of the base 24 (the surface facing the gyro in the thickness direction). The positions of the drive electrodes 28a and 28b are areas near the bases of the arms 20 and 22 (near the fulcrum). When a drive power supply OSC is connected to the drive electrodes 28a and 28b as shown in FIG. 1B, the arms 20 and 22 generate tuning fork vibrations as shown in FIGS. 1A and 1C. The gyro in this state is called a drive mode. This driving vibration causes the upper surface of the base 24 (the surface on which the arms 20 and 22 are provided) to vibrate as indicated by the arrow A due to the piezoelectric lateral effect. Thus, the arms 20 and 22 vibrate as shown by the broken lines in FIG. When a rotational motion is applied to the vibration axis in such a vibration mode, a Coriolis force is generated in a direction perpendicular to the vibration direction represented by the following equation of motion.
Zx ηx ≒ Fx + 2my Ω0 ηy
Zy ηy ≒ Fy -2mx Ω0 ηx
Here, Zx and Zy are mechanical impedances in the x-axis direction and the y-axis direction (see FIG. (E): the x-axis direction corresponds to the gyro width direction, and the y-axis direction corresponds to the gyro thickness direction). ηx, ηy are velocities in the x-axis and y-axis directions, Fx, Fy are Coriolis forces in the x-axis and y-axis directions, mx, my are masses in the x-axis and y-axis directions, respectively, and Ω0 is an angular velocity.
[0023]
Therefore, an electrode that detects (or excites) the above-described tuning-fork vibration (also referred to as fx mode vibration) in the vertical direction (also referred to as fy mode vibration) should be formed on the arms 20 and 22. Electrical output can be obtained from the bent arm. Here, if one arm is used for driving and the other arm is used for detection as shown in FIG. 16, since even bending vibration other than that caused by Coriolis force is detected, a detection error occurs and a temperature drift occurs. Unnecessary vibration components, such as torsional vibration, which cause the vibration, are also detected.
[0024]
In consideration of this point, as shown in FIG. Reference example By providing the detection electrodes on both the arms 20 and 22, only the mode (FIG. 1 (e)) that vibrates in the opposite direction to each other without detecting the output due to the vibration in the in-phase direction (FIG. 2 (a)). To detect. That is, the two arms 20 and 22 are provided with the detection electrodes so that the phases are inverted. As shown in FIG. 2B, the detection output due to the in-phase vibration is positive in the arms 20 and 22 and has the same voltage value. The outputs of the arms 20 and 22 are differentially amplified to cancel each other. Can be.
[0025]
FIG. 3A shows the vibrations (opposite-phase vibrations) of the arms 20 and 22 when an angular velocity is applied in the drive mode, and FIG. 3B shows the internal electric field resulting therefrom. Electrodes other than the connected electrodes shown in FIG. 2B are set to ground (reference potential). That is, the arms 20 and 22 are provided with detection electrodes so that they output the same phase signal. As a result, the voltage due to the angular velocity becomes positive with respect to the ground potential in one arm and negative in the other arm (ie, differential amplification). In this case, as described with reference to FIG. 2, the detection output due to the in-phase vibration is canceled and does not appear at the output terminal.
[0026]
Further, even with the electrode configuration shown in FIG. 4, it is possible to detect only the output due to the opposite-phase vibration caused by the angular velocity. A differential output can be obtained with the electrode configuration shown in FIG. 4B with respect to the reverse phase vibration shown in FIG. The voltage due to the in-phase vibration cancels the plus component and the minus component by the connection in FIG. 4B and does not appear at the output terminal.
[0027]
As described above, the present invention Reference example In Japanese Patent Application Laid-Open No. H11-207, the drive vibration is generated by utilizing the piezoelectric transverse effect of the piezoelectric single crystal, and the detection of the angular velocity employs an electrode configuration that detects only the reverse-phase vibration caused by the angular velocity.
[0028]
The electrode configuration combining the drive electrodes and the detection electrodes described above is Reference example FIG. FIG. 5A is a front view of the tuning fork type piezoelectric vibrating gyroscope, and FIG. 5B is a plan view. The drive electrodes 28a and 28b are provided on the front and back surfaces of the base 24, respectively, and are located close to the roots of the arms 20 and 22. In other words, it can be said that the drive electrodes 28a and 28b are provided in a region including the fulcrum of the arms 20 and 22. On four surfaces of the arm 20, detection electrodes 26a, 26b, 26c and 26d are provided, and on four surfaces of the arm 22, detection electrodes 27a, 27b, 27c and 27d are provided. These detection electrodes are connected, for example, as shown in FIG. 3B or 4B. As will be described later, it is not necessary to use the eight detection electrodes shown in FIG. 5 in order to detect only in-phase vibration without detecting in-phase vibration.
[0029]
The areas of the drive electrodes 28a and 28b are appropriately selected according to the element characteristics of the gyro. The capacitance ratio is, for example, 478 on the drive electrode side and 221 on the detection electrode side, so that the capacitance ratio does not become large on the drive side and on the detection side unlike the conventional configuration.
[0030]
Here, based on the electrode structure shown in FIG. 5, a modified example of the detection electrode configuration will be described with reference to FIGS. 6 and 7. FIG. FIGS. 6 (a) to 6 (l) utilize the above-described detection electrode configuration of FIG. 3 (b) and divide the detection electrodes into two groups, and FIGS. 7 (a) to 7 (h) show the aforementioned FIG. The detection electrodes are divided into three groups using the detection electrode configuration of (b). For ease of illustration, reference numerals for the electrodes provided on the arms 20 and 22 have been omitted.
[0031]
The electrode configuration shown in FIG. 6A is as follows. Of the detection electrodes provided on the arms 20 and 22, the electrodes drawn from both sides in the thickness direction of one arm and the electrodes drawn from both sides in the thickness direction of the other arm are connected to the reference potential, and the output is the detection electrode. The potential difference between an electrode (● in the drawing) drawn from the front and back surfaces in the width direction of one arm and an electrode (○) drawn from the front and back surfaces in the width direction of the other arm is detected.
[0032]
The electrode configuration shown in FIG. 6B is as follows. Of the detection electrodes provided on the arms 20 and 22, the electrodes drawn from the front and back surfaces in the width direction of one arm are connected to the electrodes drawn from the front and back surfaces in the width direction of the other arm and the reference potential, and the output is detected. The potential difference between an electrode (○) drawn from both sides in the thickness direction of one of the electrodes and an electrode (（) drawn from both sides in the thickness direction of the other arm is detected.
[0033]
The electrode configuration shown in FIG. 6C is as follows. Of the detection electrodes provided on the arms 20 and 22, one electrode drawn from the front and back surfaces in the thickness direction of one arm is connected to the electrode drawn from the front and back surfaces in the thickness direction of the other arm and a reference potential, and the output is detected. The potential difference between an electrode (O) drawn from the widthwise outer surface of one arm of the electrodes and an electrode (●) drawn from the widthwise outer surface of the other arm is detected. The electrode configuration shown in FIG. 6D is as follows. Of the detection electrodes provided on the arms 20 and 22, one electrode drawn from the front and back surfaces in the thickness direction of one arm is connected to the electrode drawn from the front and back surfaces in the thickness direction of the other arm and a reference potential, and the output is detected. A potential difference between an electrode (O) drawn from the widthwise inner surface of one arm of the electrodes and an electrode (●) drawn from the widthwise inner surface of the other arm is detected. The electrode configuration shown in FIG. 6E is as follows. Of the detection electrodes provided on the arms 20 and 22, the electrode drawn from the widthwise outer surface of one arm is connected to the electrode drawn from the thickness direction outer surface of the other arm and the reference potential, and the output is detected. The potential difference between an electrode (●) drawn from the front and back surfaces in the thickness direction of one arm of the electrodes and an electrode (○) drawn from the front and back surfaces in the thickness direction of the other arm is detected.
[0034]
The electrode configuration shown in FIG. 6 (f) is as follows. Of the detection electrodes provided on the arms 20 and 22, the electrodes drawn from the widthwise outer surface and the thickness direction front and back of one arm are the electrodes drawn from the widthwise outer surface and the thickness direction front and back of the other arm. The output is connected to the reference potential, and the output is the potential difference between the electrode (O) drawn from the widthwise outer surface of one arm of the detection electrodes and the electrode (●) drawn from the widthwise outer surface of the other arm. Is detected.
[0035]
The electrode configuration shown in FIG. 6 (g) is as follows. Of the detection electrodes provided on the arms 20 and 22, the electrode pulled out from the width direction inner surface and the thickness direction front and back of one arm is the electrode drawn out from the width direction inner surface and the thickness direction front and back of the other arm. Connected to the reference potential, the output is the potential difference between the electrode (●) drawn from the widthwise inner surface of one arm of the detection electrodes and the electrode drawn from the widthwise inner surface (○) of the other arm. Is detected.
[0036]
The electrode configuration shown in FIG. 6H is as follows. Of the detection electrodes provided on the arms 20 and 22, the electrodes drawn out from the widthwise inner surface of one arm and the widthwise inner surface of the other arm are connected to the reference potential, and the output is outside the width direction of one arm. The potential difference between the electrode (○) drawn from the side surface and the front and back surfaces in the thickness direction and the electrode (●) drawn from the outer surface in the width direction and the front and back surface in the thickness direction of the other arm are detected.
[0037]
The electrode configuration shown in FIG. 6 (i) is as follows. Of the detection electrodes provided on the arms 20 and 22, the electrodes drawn from the widthwise outer surface of one arm and the widthwise outer surface of the other arm are connected to the reference potential, and the output is within the width direction of one arm. The potential difference between the electrode (○) drawn from the side surface and the front and back surfaces in the thickness direction and the electrode (●) drawn from the inner surface in the width direction and the front and back surface in the thickness direction of the other arm are detected.
[0038]
The electrode configuration shown in FIG. 6 (j) is as follows. Of the detection electrodes provided on the arms 20 and 22, electrodes drawn out from both sides in the width direction of one arm, the back side in the thickness direction, the both sides in the width direction of the other arm and the front side in the thickness direction are connected to the reference potential, and the output is one side. The potential difference between the electrode (O) drawn from the thickness direction surface of one arm and the electrode (●) drawn from the thickness direction back surface of the other arm is detected.
[0039]
The electrode configuration shown in FIG. 6 (k) is as follows. Of the detection electrodes provided on the arms 20 and 22, the electrodes drawn from the thickness direction surface of one arm and the thickness direction surface of the other arm are connected to the reference potential, and both the width direction surfaces and the thickness direction back surface of one arm. The potential difference between the electrode (•) drawn from the electrode and the electrode (O) drawn from both sides in the width direction and the back surface in the thickness direction of the other arm is detected.
[0040]
The electrode configuration shown in FIG. 6 (l) is as follows. Of the detection electrodes provided on the arms 20 and 22, the electrodes drawn out from the inner side in the width direction of one arm and the inner side in the width direction of the other arm are connected to the reference potential. The potential difference between the electrode (○) drawn out from the electrode and the electrode (（) drawn from the front and back surfaces in the thickness direction of the other arm is detected.
[0041]
Next, an electrode configuration using the detection electrode configuration of FIG. 4B will be described with reference to FIGS.
[0042]
The electrode configuration shown in FIG. 7A is as follows. Of the detection electrodes provided on the arms 20 and 22, an electrode drawn from the front and back surfaces in the thickness direction of one arm and electrodes drawn from both surfaces in the width direction of the other arm are connected to form a first detection electrode (in FIG. ), An electrode drawn from both sides in the width direction of one arm is connected to an electrode drawn from the front and back surfaces in the thickness direction of the other arm to form a second detection electrode (● in the figure), And a potential difference between the second detection electrodes.
[0043]
The electrode configuration shown in FIG. 7B is as follows. Among the detection electrodes provided on the arms 20 and 22, the first electrode connected to the electrode drawn from the front and back surfaces in the thickness direction of one arm and the electrode drawn from the outer surface in the width direction of the other arm (ア ー ム). The second detection electrode (●) is formed by connecting an electrode drawn from the widthwise outer surface of one arm and an electrode drawn from the front and back surfaces in the thickness direction of the other arm to form a first and a second detection electrode (●). The potential difference between the two detection electrodes is detected.
[0044]
The electrode configuration shown in FIG. 7C is as follows. Of the detection electrodes provided on the arms 20 and 22, the first electrode connected to the electrode drawn from the front and back surfaces in the thickness direction of one arm and the electrode drawn from the inner surface in the width direction of the other arm is connected to the first detection electrode (O). And the second detection electrode (●) is formed by connecting an electrode drawn out from the inner surface in the width direction of one arm and an electrode drawn out from the front and back surfaces in the thickness direction of the other arm to form a first detection electrode (●). The potential difference between the two detection electrodes is detected.
[0045]
The electrode configuration shown in FIG. 7D is as follows. Of the detection electrodes provided on the arms 20 and 22, one electrode is drawn from the back surface in the thickness direction of one arm and the electrode drawn from both surfaces in the width direction of the other arm is connected to form a first detection electrode (O). A second detection electrode (●) is formed by connecting an electrode drawn from both surfaces in the width direction of one arm and an electrode drawn from the front surface in the thickness direction of the other arm to form a first and a second detection electrode. The potential difference between the detection electrodes is detected.
[0046]
The electrode configuration shown in FIG. 7E is as follows. Of the detection electrodes provided on the arms 20 and 22, the first electrode connected to the electrode drawn from the inner surface in the width direction of one arm and the electrode drawn from the outer surface in the width direction of the other arm and the front and back surfaces in the thickness direction are connected to the first electrode. The second detection is performed by connecting an electrode drawn from the outer surface in the width direction of one arm and the front and back surfaces in the thickness direction and an electrode drawn from the inner surface in the width direction of the other arm. An electrode (●) is configured to detect a potential difference between the first and second detection electrodes.
[0047]
The electrode configuration shown in FIG. 7 (f) is as follows. Of the detection electrodes provided on the arms 20 and 22, the first electrode is connected to the electrode drawn from both sides in the thickness direction and the inner surface in the width direction of one arm and the electrode drawn from the outer surface in the width direction of the other arm. And the electrodes drawn out from the outer surface in the width direction of one arm and the front and back surfaces in the thickness direction of the other arm are connected to the electrodes drawn out from the inner surface in the width direction of the other arm. To form a second detection electrode (●), and detect a potential difference between the first and second detection electrodes.
[0048]
The electrode configuration shown in FIG. 7 (g) is as follows. Of the detection electrodes provided on the arms 20 and 22, the first electrode is connected by connecting the electrode extracted from both sides in the thickness direction and the outer surface in the width direction of one arm and the electrode extracted from the outer surface in the width direction of the other arm. And the second detection electrode (●) is formed by connecting the electrodes drawn out from the inner surface in the width direction of one arm, the front and back surfaces in the thickness direction of the other electrode, and the inner surface in the width direction of the other arm. And detects the potential difference between the first and second detection electrodes.
[0049]
As described above, by providing the detection electrodes on the four or three surfaces of each arm and using the above-described wiring, it is possible to accurately detect the rotational angular velocity with a simple configuration.
[0050]
FIG. 8 is a diagram showing a configuration of a tuning fork type piezoelectric vibration gyro having the electrode configuration shown in FIG. 7 (g). In order to make the configuration of the electrodes easy to understand, the thickness of the electrodes and the like are emphasized. 8A is a front view, FIG. 8B is a right side view, FIG. 8C is a rear view, and FIG. 8D is a plan view.
[0051]
The detection electrodes 26a, 26b, and 26d are integrally formed and connected to a terminal 33 for external connection provided on the surface of the base 24 via a lead 31. Similarly, the detection electrodes 27a, 27b, and 27d are integrally formed, and are connected to an external connection terminal 34 provided on the surface of the base 24 via a lead electrode line 32. The detection electrode 26c is connected to a terminal 37 for external connection via a lead electrode line 35. Similarly, the detection electrode 27c is connected to a terminal 38 for external connection via a lead electrode line 36. The drive electrode 28a is connected to a terminal 39 for external connection via a lead electrode line 40. The driving electrode 28b formed on the back surface of the base 24 is connected to an external connection provided on the front surface of the base 24 through a through hole 43 provided on the base 24 and a lead electrode wire 42 passing through the front and back surfaces of the base 24. Connected to terminal 41.
[0052]
Next, an electrode configuration different from the above-described electrode configuration will be described.
[0053]
In the above-described electrode configuration, the drive electrodes 28a and 28b are provided on the front and back surfaces of the base 24 and near the bases of the arms 20 and 22. The electrode configuration described below is characterized in that a drive electrode is provided inside each of the front and back surfaces of each of the arms 20 and 22, and drive vibration is generated by using a lateral piezoelectric effect of a piezoelectric single crystal.
[0054]
FIG. 9 is a diagram showing this electrode configuration. FIG. 9A is a front view of the gyro, and FIG. 9B is a plan view of the gyro. Drive electrodes 48a and 48b having a substantially U-shaped pattern are provided on the front and back surfaces of the gyro as illustrated. The drive electrode 48 a is provided near an inner portion on the surface of the arms 20 and 22 and near the root on the surface of the base 24. Similarly, the drive electrode 48b is provided near an inner portion on the back surface of the arms 20 and 22 and a base on the back surface of the base 24.
[0055]
When a drive signal is applied to the drive electrodes 48a and 48b having such a configuration by the drive power supply OSC, an internal electric field is generated as shown by a linear arrow in FIG. 9B, and as shown in FIG. Elongation vibration (tuning fork vibration) occurs. When the rotational angular velocity is applied in this state (the state in the vibration mode), an internal electric field is generated as shown by a curved arrow due to the displacement shown in FIG. 9B. Therefore, the rotational angular velocity can be detected by detecting the voltage due to the internal electric field. Detection electrodes for detecting this voltage can be provided on the outer portions of each of the front and back surfaces of the arms 20 and 22.
[0056]
FIG. 10 shows such an electrode configuration. 10A is a front view of a tuning fork type piezoelectric vibrating gyroscope having the above-described electrode configuration, FIG. 10B is a right side view, and FIG. 10C is a plan view. The drive electrodes 48a and 48b are provided as described above. In the illustrated electrode configuration, three detection electrodes are provided for each arm. The detection electrodes 46a, 46b, and 46c are provided on the front and back surfaces in the thickness direction and the outer surface in the width direction of the arm 20, respectively. Similarly, detection electrodes 47a, 47b, and 47c are provided on the front and back surfaces in the thickness direction and the outer surface in the width direction of the arm 22, respectively. The detection electrodes 46a and 46b are arranged on the outer portions of the front and back surfaces of the arm 20, respectively. Thus, these electrodes are provided side by side so that the drive electrodes are located inside and the detection electrodes are located outside on the front and back surfaces of the arm 20, respectively. The same applies to the arm 22. Note that, in FIG. 10, the extraction electrode lines, external connection terminals, and the like are omitted for convenience.
[0057]
In the configuration shown in FIG. 10, the capacitance ratio is, for example, 136 on the drive electrode side and 278 on the detection electrode side, such that the capacitance ratio between the drive side and the detection side is large as in the conventional configuration. Never.
[0058]
FIG. 11 is a diagram showing an electrode configuration in the electrode arrangement shown in FIG. FIG. 11A shows a configuration in which the rotational angular velocity is detected by a potential difference between two detection electrodes. FIGS. 11B and 11C show a configuration in which the rotational angular velocity is determined by the potential difference (differential amplification) between the two electrodes with respect to a reference electrode. This is a configuration for detecting.
[0059]
The electrode configuration shown in FIG. 11A is as follows. Among the detection electrodes provided on the arms 20 and 22, a first detection electrode (O) connecting an electrode drawn from the front and back surfaces in the thickness direction of one arm and an electrode drawn from the widthwise outer surface of the other arm. A potential difference between a second detection electrode (●) connected to an electrode drawn from the outer surface in the width direction of one arm and an electrode drawn from the front and back surfaces in the thickness direction of the other arm is detected. The electrode configuration shown in FIG. 11B is as follows. Of the detection electrodes provided on the arms 20 and 22, the electrode drawn from the front and back surfaces in the thickness direction of one arm and the electrode drawn from the front and back surfaces in the thickness direction of the other arm are connected to a reference potential, and the width of one arm is set. The potential difference between the electrode (○) drawn from the outer surface in the direction and the electrode (●) drawn from the outer surface in the width direction of the other arm is detected.
[0060]
The electrode configuration shown in FIG. 11C is as follows. Of the detection electrodes provided on the arms 20 and 22, the electrode drawn from the widthwise outside surface of one arm and the electrode drawn from the widthwise outside electrode of the other arm are connected to a reference potential, and the thickness of one arm is changed. A potential difference between an electrode (●) drawn from the front and back surfaces in the direction and an electrode (○) drawn from the front and back surfaces in the thickness direction of the other arm is detected.
[0061]
12A and 12B show a modification of the tuning-fork type piezoelectric vibrating gyroscope shown in FIG. 10, wherein FIG. 12A is a front view, FIG. 12B is a right side view, and FIG. 12C is a plan view. The drive electrodes 58a and 58b are provided on the surface and the back surface in the thickness direction of the gyro, respectively, and have portions provided inside each arm. The portions 58a 'and 58b' provided on the front and back surfaces of the base 24 of the drive electrodes 58a and 58b are similar to the drive electrodes shown in FIG. That is, the drive electrodes 58a and 58b drive the tuning fork vibration by the piezoelectric lateral effect acting inside the base 24 and the arms 20,22. The drive electrode 58a is connected to an external connection terminal 60 via a lead electrode line 61. The drive electrode 58b is connected to an external connection terminal 67 provided on the surface of the base 24 via a lead electrode line 68 and a through hole 66 provided in the base 24.
[0062]
Each of the arms 20 and 22 is provided with three detection electrodes. Detection electrodes 56a, 56b and 56c are provided on the front and back surfaces in the thickness direction and the outer surface in the width direction of the arm 20, respectively. Similarly, detection electrodes 57a, 57b, and 57c are provided on the front and back surfaces in the thickness direction and the outer surface in the width direction of the arm 22, respectively. These detection electrodes are connected as shown in FIG. The detection electrode 56a is connected to the external connection terminal 62 via the extraction electrode line 63, and the detection electrode 56b is connected to the extraction electrode line 63 via the extraction electrode line 70 and the through hole 69. The detection electrode 56c is connected to an external connection terminal 73 via a lead electrode line 74. Similarly, the detection electrode 57a is connected to the external connection terminal 64 via the extraction electrode line 65, and the detection electrode 57b is connected to the extraction electrode line 65 via the extraction electrode line 72 and the through hole 71. The detection electrode 57c is connected to an external connection terminal 75 via a lead electrode line 76.
Even if the drive electrodes are provided not on the inside of the front and back surfaces of the arms 20 and 22 but on the outside, they can drive the tuning fork vibration by the piezoelectric transverse effect.
[0063]
FIGS. 13A and 13B are diagrams showing a tuning-fork type piezoelectric vibrating gyroscope having this electrode configuration, wherein FIG. 13A is a front view and FIG. 13B is a plan view. Drive electrodes 78a and 78b are provided integrally on the outside of the front and back surfaces of the arms 20, 22 and on the front and back surfaces of the base 24, respectively. When a drive power supply OSC is connected to the drive electrodes 78a and 78b as shown in FIG. 13B, an internal electric field indicated by a straight arrow in FIG. Are bent as shown in FIG. 13A, and tuning fork vibration occurs. When the rotational angular velocity is applied to the gyro in this state (drive mode), an internal electric field is generated as shown by the curved arrow in FIG. By detecting the voltage due to the internal electric field, the rotational angular velocity can be detected.
[0064]
The detection electrodes 76a and 76b are provided on the front and back surfaces in the thickness direction of the arm 20, respectively, and the detection electrode 76c is provided on the inner surface in the width direction. Similarly, detection electrodes 77a and 77b are provided on the front and back surfaces in the thickness direction of the arm 22, respectively, and a detection electrode 77c is provided on the inner surface in the width direction.
[0065]
FIG. 14 is a diagram showing the connection of the detection electrodes. FIG. 14A shows a configuration in which the rotational angular velocity is detected by a potential difference between two detection electrodes. FIGS. 14B and 14C show a configuration in which the rotational angular velocity is determined by a potential difference (differential amplification) between the two electrodes with respect to a reference electrode. This is a configuration for detecting.
[0066]
The electrode configuration shown in FIG. 14A is as follows. Among the detection electrodes provided on the arms 20 and 22, a first detection electrode (O) connecting an electrode drawn from the front and back surfaces in the thickness direction of one arm and an electrode drawn from the inner surface in the width direction of the other arm. The potential difference between a second detection electrode (●) connected to an electrode drawn from the inner surface in the width direction of one arm and an electrode drawn from the front and back surfaces in the thickness direction of the other arm is detected. The electrode configuration shown in FIG. 14B is as follows. Of the detection electrodes provided on the arms 20 and 22, the electrode drawn from the front and back surfaces in the thickness direction of one arm and the electrode drawn from the front and back surfaces in the thickness direction of the other arm are connected to a reference potential, and the width of one arm is set. The potential difference between the electrode (○) drawn from the inner surface in the direction and the electrode (●) drawn from the inner surface in the width direction of the other arm is detected.
[0067]
The electrode configuration shown in FIG. 14C is as follows. Of the detection electrodes provided on the arms 20 and 22, the electrode drawn from the widthwise inner surface of one arm and the electrode drawn from the widthwise inner electrode of the other arm are connected to a reference potential, and the thickness of one arm is changed. A potential difference between an electrode (●) drawn from the front and back surfaces in the direction and an electrode (○) drawn from the front and back surfaces in the thickness direction of the other arm is detected.
[0068]
15A and 15B are diagrams showing a tuning-fork type piezoelectric vibrating gyroscope having the electrode configuration shown in FIG. 14B, wherein FIG. 15A is a front view and FIG. 15B is a plan view. The drive electrodes 88a and 88b are provided on the front and back surfaces of the gyro, respectively, as illustrated. The drive electrode 88b is connected to a terminal 96 for external connection via an extraction electrode line 95 passing through a through hole 94 provided in the base 24. The detection electrodes provided on the surfaces of the arms 20 and 22 are the detection electrodes 86a integrally formed via connection portions provided on the surface of the base 24. Similarly, the detection electrodes provided on the back surfaces of the arms 20 and 22 are the detection electrodes 86b integrally formed via connection portions provided on the back surface of the base 24. The detection electrode 86b is connected to an external connection terminal 92 via a lead electrode line 91 passing through the through hole 90. The detection electrode 86a is connected to an external connection terminal 92 via a lead electrode line 93.
[0069]
FIG. Reference example It is a figure for explaining composition and operation of a detection circuit which detects an output voltage of a tuning fork type piezoelectric vibrating gyroscope. In FIG. 16, reference numeral 100 is the tuning fork type piezoelectric vibration gyro of the present invention described above. The detection circuit has operational amplifiers OP1, OP2, OP3, resistors R1 to R10, and capacitors C1 to C3. Outputs out1 and out2 of the gyro 100 are supplied to non-inverting input terminals of operational amplifiers OP1 and OP2 via resistors R2 and R3, respectively. The output terminal of the operational amplifier OP3 forms the output terminal of the detection circuit.
[0070]
When a rectangular wave is given to the gyro 100 by the oscillator OSC, the output voltage waveform includes a leak output component due to electrostatic coupling or the like. The operational amplifiers OP1 and OP2 amplify the outputs out1 and out2 of the gyro 100, respectively, and the operational amplifier OP3 differentially amplifies the outputs of the operational amplifiers OP1 and OP2. As can be seen from the output waveform of the operational amplifier OP3, leakage such as electrostatic coupling can be removed (cancelled) by differential amplification.
[0071]
As described above, the present invention Reference example Was explained. the above Reference example As can be seen from the above, the rotation angular velocity can be detected with high accuracy and with a simpler configuration than in the prior art without detecting unnecessary vibration. The wiring is simple and suitable for mass production.
[0072]
By the way, Reference example In this case, it is necessary to provide detection electrodes on four or three surfaces of each arm. However, the present inventor has provided drive electrodes and detection electrodes only on two surfaces of each arm, can maintain the required sensitivity, and has a simple electrode configuration. The configuration of a tuning fork type piezoelectric vibrating gyroscope suitable for mass production was studied. This study focuses on the difference in electric field distribution between the drive mode and the detection mode shown in FIG. 18 based on the items shown in FIG. The following description includes portions that partially overlap with the items already described, but this is to make the description easier to understand.
[0073]
First, FIGS. 17A and 17C are perspective views showing the same tuning-fork type piezoelectric vibration gyro. It should be noted that only an element portion made of a piezoelectric material such as a piezoelectric single crystal is shown, and electrodes are not shown. The tuning fork type piezoelectric vibrating gyroscope 100 has two arms 112 and 114 and a base 116 formed integrally therewith.
[0074]
As shown in FIG. 17B, electrodes 131, 132, 137 and 138 are provided on the outer surfaces of the front and back surfaces of the arms 112 and 114 shown in FIG. When a driving voltage is applied between the first and second electrodes 138 and 138, an electric field is generated as shown by the arrows in the arms 112 and 114 in FIG. 17B, and as shown by the arrows in FIGS. Due to the lateral effect, the outer portions of the arms 112 and 114 move in and out. Due to the expansion and contraction movement, tuning fork vibration (also referred to as in-plane vibration or fx mode vibration) can be excited in the arms 112 and 114.
[0075]
When a rotational motion is applied to the vibration axis of the tuning fork vibration, a Coriolis force is generated in a direction perpendicular to the vibration direction as in the following equation of motion.
Zx ηx ≒ Fx + 2my Ω0 ηy
Zy ηy ≒ Fy -2mx Ω0 ηx
Here, Zx, Zy are the mechanical impedances in the X-axis and Y-axis directions shown in FIG. 19, ηx, ηy are the velocities in the x-axis and y-axis directions, respectively, and Fx, Fy are the Coriolis in the X-axis and Y-axis directions, respectively. Force, mx, and my are the masses in the x-axis and y-axis directions, respectively, and Ω0 is the angular velocity. The tuning fork shown in FIG. 18 is made of a piezoelectric single crystal, and has a rotation axis as an X axis. ₃ 40 ° ± 20 ° rotating Z plate and LiNbO ₃ A trigonal crystal such as a 50 ° ± 20 ° rotating Z plate can be used. The crystal orientation of the piezoelectric single crystal is in the thickness direction.
[0076]
Therefore, as shown in FIG. 17D, electrodes 133, 134, 135, and 136 for detecting vibration in a direction perpendicular to the tuning fork vibration (also referred to as plane perpendicular vibration or fy mode vibration) are applied to the two arms 112 and 114. With this configuration, an electric output (a voltage proportional to the angular velocity) can be obtained from the arms that are bent in opposite directions under Coriolis force.
[0077]
In this case, the present inventor pays attention to the difference in the charge distribution between the drive mode and the detection mode shown in FIG. Instead, it was found that the detection mode could be received only on two surfaces of each arm.
[0078]
FIG. 18A shows the fx mode electric field distribution, and FIG. 18B shows the fy mode electric field distribution. In FIGS. 18A and 18B, symbols A to H indicate the charge distributions (and their potentials) generated in the arms 112 and 114, respectively, and “+” and “−” indicate the polarities of the charges, respectively. . Arrows indicate electric fields.
[0079]
FIG. 18A shows a case where the tuning fork vibration is driven by the electrode configuration shown in FIG. 17B. FIG. 18B shows a charge distribution when a Coriolis force due to angular velocity is generated in the state shown in FIG. It was found that the location, polarity and amount of charge generated due to the anisotropy are as shown in the figure. In the present invention, in the charge distribution shown in FIG. 18B, electrodes are provided at a position where the charge is maximum or relatively large and a position where the charge is minimum or relatively small, and an angular velocity is detected by outputting a potential difference generated here. For example, the electrodes are arranged so as to detect a potential difference between the charge distributions A and E in FIG. More specifically, electrodes are provided inside the upper surfaces of the arms 112 and 114 (in FIG. 18B, the electric field distributions A and E have upper surfaces and the electric field distributions C and G have lower surfaces). This electrode configuration corresponds to the electrodes 133 and 135 shown in FIG. In principle, the potential difference generated by the Coriolis force can be detected only by the electrodes 133 and 135. However, the electrodes 134 and 136 shown in FIG. 17D are provided to detect the potential difference between the electric field distributions C and G. Thereby, the sensitivity is improved.
[0080]
Note that in FIG. 18A, when A to H are potentials (potentials), the magnitude relation between them is as follows.
[0081]
A = -D = -E = H> -B = C = F = -G
In FIG. 18B, the magnitude relation between the potentials A to H is as follows.
[0082]
A = -E> -B = -D = F = H> C = G
Note that the electric charge distribution shown in FIG. 18 is not necessarily limited to detecting the potential difference due to the Coriolis force from the inner electrode as shown in FIG. It can be seen that the potential difference may be detected using the electrodes on the outer part. For example, when the potential difference between the charge distributions A and E is detected using the electrodes in the outer portion as the detection electrodes, the detection sensitivity is lower because the spread of the charge distributions A and E is smaller in the outer portion than in the inner portion. Although falling, the potential difference between the charge distributions A and E can be detected.
[0083]
As described above, by providing the detection electrode and the drive electrode only on two surfaces of each arm without providing the detection electrodes on four or three surfaces, the potential difference (voltage proportional to the angular velocity) due to the Coriolis force can be detected. Can be.
[0084]
FIG. 20 is a perspective view of the tuning-fork type piezoelectric vibration gyro of the present invention having the electrodes 131 to 138. In FIG. 20, similar electrodes provided on the back surface opposite to the surfaces of the arms 112 and 114 provided with the electrodes 131 to 138 are not visible, but are provided in the same manner as the electrodes 131 to 138. Reference numerals 141 to 144 denote extraction electrodes of the electrodes 132, 134, 136, and 138, respectively, and reference numerals 145 to 148 denote external connection terminals connected to the extraction electrodes 141 to 144, respectively.
[0085]
Hereinafter, first to ninth electrode configuration examples based on FIG. 18 will be described.
[0086]
FIG. 21 is a diagram illustrating a first electrode configuration example. In the figure, the electrodes 134 and 136 located inside the centers of the arms 112 and 114 function as detection electrodes, and the electrodes 131 and 137 located outside function as drive electrodes. The detection electrodes 134 and 136 and the drive electrodes 131 and 137 are provided on different sides of the arms 112 and 114. Other electrodes function as ground electrodes using the ground potential as a reference potential. Dashed arrows indicate electric fields. When a drive voltage is applied to the drive electrodes 131 and 137, an electric field indicated by an arrow is generated and the arms 112 and 114 vibrate. When the Coriolis force is detected in this state, a potential difference is generated between the electrodes 134 and 136 in proportion to the angular velocity due to the Coriolis force. In addition, since the electrodes 133 and 135 are grounded, the electrical coupling between the arms 112 and 114 can be reduced.
[0087]
FIG. 22 is a diagram illustrating a second electrode configuration example. In the figure, the electrodes 132 and 138 located outside the centers of the arms 112 and 114 function as detection electrodes, and the electrodes 133 and 135 located inside function as drive electrodes. The detection electrodes 132 and 138 and the drive electrodes 133 and 135 are provided on different surfaces of the arms 112 and 114. Other electrodes function as ground electrodes. As shown in FIG. 22, even if the detection electrodes 132 and 138 are provided outside the arms 112 and 114, a potential difference is generated between these electrodes in proportion to the angular velocity due to the Coriolis force.
[0088]
FIG. 23 is a diagram illustrating a third electrode configuration example. As shown in FIG. 23, electrodes 133 and 134 are connected to each other, and electrodes 135 and 136 are connected to each other to form a detection electrode. The electrodes 131 and 137 function as drive electrodes. The electrodes 132 and 138 function as ground electrodes. The charges of the electrode distributions A and C in FIG. 18B are added by connecting the detection electrodes 133 and 134, and the charges of the electrode distributions E and G in FIG. 18B are connected by connecting the detection electrodes 135 and 136. Is added. Therefore, the electrode configuration of FIG. 23 has higher detection sensitivity than the electrode configurations of FIGS. 21 and 22.
[0089]
FIG. Reference example of electrode configuration FIG. The configuration shown in FIG. 24 is different from the configurations shown in FIGS. 21 and 22 in that the detection electrode and the drive electrode are provided on the same surface side of the arms 112 and 114, and furthermore, the detection electrodes and the drive electrodes are substantially on the opposite sides of the arms 112 and 114, respectively. An electrode 132A and an electrode 138A are provided on the surface. The electrodes 131 and 137 are used as drive electrodes, and the electrodes 133 and 135 are used as detection electrodes. Further, the electrodes 132A and 138A (hereinafter also referred to as "full-surface electrodes") are used as ground electrodes. An electric field is generated from the arm 112 in the direction of the arm 114, and a potential difference between the electrodes 133 and 135 proportional to the angular velocity can be detected.
[0090]
FIG. Reference example of electrode configuration FIG. Shown in FIG. The configuration is characterized in that the electrodes 133 and 135 also serve as a drive electrode and a detection electrode. Hereinafter, such an electrode is also referred to as a common electrode. One end of a driving source 151 that generates a rectangular wave is grounded, and the other end is connected to non-inverting input terminals of operational amplifiers (hereinafter, referred to as operational amplifiers) 152 and 153. The inverting input terminals of the operational amplifiers 152 and 153 are connected to the electrodes 133 and 135, respectively. The electrodes 131, 132A, 137 and 138 are grounded.
[0091]
FIG. 26 is a diagram showing a differential amplifier circuit including the operational amplifier 153 shown in FIG. 25 and its peripheral circuit elements (omitted in FIG. 25). The output voltage of the operational amplifier 153 is divided by the resistors R1 and R2, and the divided voltage is supplied to the inverting input terminal. The peripheral circuit of the operational amplifier 152 is also configured as shown in FIG. Since the non-inverting input terminals and the inverting input terminals of the operational amplifiers 152 and 153 are in an imaginary short state, the rectangular wave driving voltage output from the driving source 151 is applied to the electrodes 133 and 135 through the operational amplifiers 152 and 153. When Coriolis force acts in this state, electric charges having different signs are accumulated in the electrodes of the arms 112 and 114. The two horizontal arrows in FIG. 25 indicate the electric field due to the accumulated charges. By comparing this with the rectangular wave by the operational amplifiers 152 and 153, a voltage corresponding to the potential difference between the electrodes 133 and 135, that is, a voltage AB proportional to the angular velocity is obtained.
[0092]
FIG. Reference example of electrode configuration FIG. The configuration shown in FIG. 27 detects a potential difference caused by the amount of charge stored in the arms 112 and 114 from both surfaces of the arms 112 and 114. For this purpose, operational amplifiers 154 and 155 are newly provided in addition to the operational amplifiers 152 and 153 described above. The non-inverting input terminals of the operational amplifiers 154 and 155 are grounded together with the non-inverting input terminals of the operational amplifiers 152 and 153, and the inverting input terminals are connected to the electrodes 132A and 138A, respectively. The driving voltage is applied to the electrodes 131 and 137. The amount of electric charge generated in the arm 112 due to the Coriolis force corresponds to the sum (A + C) of the outputs of the operational amplifiers 152 and 154, and the amount of electric charge generated in the arm 114 corresponds to the sum (B + D) of the outputs of the operational amplifiers 153 and 155. I do. Therefore, the detection output proportional to the angular velocity is (A + C)-(B + D). The configuration shown in FIG. 27 is slightly more complicated than the configuration shown in FIG. 25, but the detection sensitivity is improved.
[0093]
FIG. Reference example of electrode configuration FIG. This electrode configuration corresponds to a simplified version of the electrode configuration shown in FIG. That is, the operational amplifiers 152 and 153 are removed, and the detection voltage AB is obtained from only one side of the arms 112 and 114. Compared to the configuration shown in FIG. 27, the configuration shown in FIG. 28 is simplified, but the detection sensitivity is slightly degraded. In addition, since the terminals 133 and 135 are grounded, the electrical coupling between the arms 112 and 114 can be suppressed small.
[0094]
FIG. Reference example of electrode configuration FIG. In this configuration, electrodes on both surfaces of the arms 112 and 114 are used as common electrodes, and a drive voltage is applied through the common electrodes to detect a detection voltage. The inverting input terminal of the operational amplifier 152 is connected to the electrodes 133 and 132, and the inverting input terminal of the operational amplifier 153 is connected to the electrodes 135 and 138. The inverting input terminal of the operational amplifier 154 is connected to the electrodes 134 and 131, and the inverting input terminal of the operational amplifier 155 is connected to the electrodes 136 and 137. Since the driving voltage is applied from both sides of each of the arms 112 and 114, an electric field is generated in both directions in each arm. The difference between the electric charges generated in each of the arms 112 and 114 due to the Coriolis force is obtained as a detection output (A + C)-(B + D) via the operational amplifiers 152 to 155. Although the configuration shown in FIG. 29 has good detection sensitivity, the circuit is somewhat complicated.
[0095]
FIG. Reference example of electrode configuration FIG. This configuration corresponds to a simplified version of the eighth electrode configuration example shown in FIG. Specifically, the driving voltage is applied only from one of the arms 112 and 114. The drive voltage is applied to the electrodes 133 and 135 via the operational amplifiers 152 and 153. On the surfaces of the arms 112 and 114 opposed to the electrodes 133 and 135, full-surface electrodes 132A and 138A are provided. The entire surface electrode 132A is connected to the inverting input terminal of the operational amplifier 154 and the electrode 131. Further, the entire surface electrode 138A is connected to the inverting input terminal of the operational amplifier 155 and the electrode 137. The detection output proportional to the angular velocity is (A + C)-(B + D). The configuration shown in FIG. 30 is simpler than the configuration shown in FIG.
[0096]
In the above embodiment, the electrodes 131 to 138 are the same size electrode patterns, and the electrodes 132A and 138A are also the same size electrode patterns. It may be.
[0097]
FIG. 31 is a diagram showing the relationship between the electrode size and the three parameters. More specifically, FIG. 31A shows the relationship between the electrode size and the resonance resistance (kΩ), FIG. 31B shows the relationship between the electrode size and the capacitance ratio (γ), and FIG. It is a graph which shows the relationship with Q value. The electrode size is such that the electrodes are provided on the entire two opposing surfaces of the two arms, and the electrodes of the two arms are trimmed by the same amount with laser light to gradually reduce the area. Is the total area. An area that maximizes the Q value and minimizes the capacitance ratio (γ) is preferable. Now the electrode size is 2mm ² When the width of each arm is 1.0 mm and the length of the arm is 7.5 mm, the electrodes provided on each of the two opposing surfaces of each arm have a size less than half the arm width of 1.0 mm. (For example, 0.3 mm). Therefore, it can be seen that even when the total width of the drive electrodes on each surface is smaller than the arm width, the fx mode vibration is favorably generated.
[0098]
FIG. 32 is a diagram showing the relationship between the detection electrode size and the above three parameters. More specifically, FIG. 32A shows the relationship between the detection electrode size and the resonance resistance (kΩ), FIG. 31B shows the relationship between the detection electrode size and the capacitance ratio (γ), and FIG. 5 is a graph showing a relationship between an electrode size and a Q value. The detection electrode size is such that electrodes are provided on the entire two opposing surfaces of the two arms, and the electrodes of the two arms are trimmed by the same amount with laser light to gradually reduce the area of each arm. It is the total area for each. An area that maximizes the Q value and minimizes the capacitance ratio (γ) is preferable. From FIG. 32, the larger the detection electrode is, the more the above condition is satisfied.
[0099]
As described above, from FIGS. 31 and 32, if the drive electrode is relatively small and the detection electrode is relatively large, the capacitance ratio of the detection electrode can be reduced, that is, the sensitivity can be increased.
[0100]
The embodiments of the present invention have been described above. As can be seen from the above description, in the present invention, since the electrodes are provided only on two surfaces of each arm, the required sensitivity can be maintained, and a simpler electrode configuration is more suitable for mass production.
[0101]
【The invention's effect】
As described above, according to the present invention, the following effects can be obtained.
[0102]
According to the first aspect of the present invention, in a tuning fork type piezoelectric vibrating gyroscope having a first arm, a second arm and a base for supporting the first arm and the second arm, predetermined two surfaces of each of the first and second arms are provided. A driving electrode for driving the tuning fork vibration only, a detection electrode for detecting the rotational angular velocity, and a ground electrode set to a reference potential, wherein the driving electrode, the detection electrode, and the ground electrode drive the tuning fork type piezoelectric vibration gyro. The first arm and the second arm are arranged symmetrically with respect to a center plane of vibration. Each of the two specified surfaces Is provided with only two types of electrodes out of the drive electrode, the detection electrode, and the ground electrode, so that a required sensitivity can be maintained, and a tuning fork type piezoelectric vibration gyro suitable for mass production with a simple electrode configuration is provided. be able to.
[0103]
According to the invention described in claim 2, the drive electrode is provided on the first surface of each of the first and second arms, and the detection electrode is provided on the first and second arms facing the first surface. Are provided on the second surface of each of the first and second arms, and the voltage corresponding to the angular velocity is determined as a potential difference between the detection electrodes provided on the second surface of the first and second arms. And a tuning fork type piezoelectric vibration gyro suitable for mass production with a simple electrode configuration can be provided.
[0104]
According to the invention described in claim 3, the drive electrode is provided on the first surface of each of the first and second arms, and the detection electrode is provided on the first surface of each of the first and second arms. Since the voltage provided on the surface and according to the angular velocity is obtained as a potential difference between the detection electrodes provided on the first surface of the first and second arms respectively, the required sensitivity can be maintained and a simple operation can be achieved. A tuning fork type piezoelectric vibrating gyroscope suitable for mass production can be provided with an electrode configuration.
[0105]
According to the invention described in claim 4, the drive electrode is provided on the first surface of each of the first and second arms, and the detection electrode is provided on the first surface of each of the first and second arms. A surface, and a second surface of each of the first and second arms opposed to the first surface, and a voltage corresponding to the angular velocity is provided on the first and second surfaces of the first arm. Potential difference between the detection electrode provided and the detection electrodes provided on the first and second surfaces of the second arm, so that the tuning fork-type piezoelectric element is more sensitive, has a simple electrode configuration, and is suitable for mass production. A vibrating gyro can be provided.
[0109]
Claim 5 or 6 According to the invention described above, it is possible to provide a tuning-fork type piezoelectric vibration gyro suitable for mass production with a simple electrode configuration while maintaining necessary sensitivity by using a commonly available general piezoelectric material.
[Brief description of the drawings]
FIG. 1 is a diagram for explaining a reference example of the present invention.
FIG. 2 is a diagram illustrating a principle in which unnecessary vibration is not detected according to a reference example of the present invention.
FIG. 3 is a diagram showing an electrode configuration for detecting a rotational angular velocity according to a reference example of the present invention.
FIG. 4 is a diagram showing another electrode configuration for detecting a rotational angular velocity according to a reference example of the present invention.
FIG. 5 is a diagram showing a reference example of the present invention.
FIG. 6 is a diagram illustrating a configuration and a wiring example of a detection electrode illustrated in FIG. 5;
FIG. 7 is a diagram showing another configuration and a wiring example of the detection electrode shown in FIG.
8 is a diagram showing a configuration of a tuning fork type piezoelectric vibration gyro having the electrode configuration shown in FIG. 7 (g).
FIG. 9 is a diagram showing the principle of another configuration example of the drive electrode for driving the tuning fork vibration.
FIG. 10 is a diagram showing a configuration of a tuning fork type piezoelectric vibration gyro based on the configuration shown in FIG. 9;
11 is a diagram showing a configuration and an example of wiring of a detection electrode shown in FIG.
FIG. 12 is a diagram showing a modification of the configuration shown in FIG. 10;
FIG. 13 is a diagram showing the principle of still another configuration example of the drive electrode for driving the tuning fork vibration.
FIG. 14 is a diagram illustrating a configuration and a wiring example of a detection electrode illustrated in FIG. 13;
15 is a diagram showing a configuration of a tuning-fork type piezoelectric vibration gyro based on the configuration shown in FIG.
FIG. 16 is a diagram for explaining the configuration and operation of a detection circuit for detecting the output voltage of the tuning-fork type piezoelectric vibrating gyroscope according to the reference example of the present invention.
FIG. 17 is a diagram for explaining the operation principle of the two-sided electrode configuration of the tuning fork type piezoelectric vibrating gyroscope.
FIG. 18 is a diagram showing a charge distribution in a vibration mode of a tuning-fork type piezoelectric vibration gyro.
FIG. 19 is a diagram showing a crystal orientation of a piezoelectric single crystal.
FIG. 20 is a perspective view showing one embodiment of a two-surface electrode configuration of the present invention.
FIG. 21 is a diagram showing a first electrode configuration example according to the present invention.
FIG. 22 is a diagram showing a second electrode configuration example according to the present invention.
FIG. 23 is a diagram showing a third electrode configuration example according to the present invention.
FIG. 24 according to the invention Reference example of electrode configuration FIG.
FIG. 25 according to the invention Reference example of electrode configuration FIG.
FIG. 26 is a diagram showing a differential amplifier circuit used in the configuration shown in FIG. 9;
FIG. 27 according to the invention Reference example of electrode configuration FIG.
FIG. 28 according to the invention Reference example of electrode configuration FIG.
FIG. 29 according to the invention Reference example of electrode configuration FIG.
FIG. 30 according to the invention Reference example of electrode configuration FIG.
FIG. 31 is a diagram showing a relationship between an electrode size and each parameter.
FIG. 32 is a diagram showing a relationship between a detection electrode size and each parameter.
FIG. 33 is a diagram showing a configuration example of a conventional tuning-fork type piezoelectric vibration gyro.
FIG. 34 is a diagram showing another configuration example of a conventional tuning-fork type piezoelectric vibration gyro.
FIG. 35 is a view showing still another configuration example of a conventional tuning-fork type piezoelectric vibration gyro.
FIG. 36 is a diagram showing a problem of the related art.
[Explanation of symbols]
20 arms
22 arm
24 base
26a-26d detection electrode
27a-27b Detection electrode
28a, 28b drive electrode
46a-46c detection electrode
47a-47c detection electrode
48a, 48b drive electrode
56a-56c detection electrode
57a-57c detection electrode
58a, 58b drive electrode
86a-86c detection electrode
87a-87c detection electrode
88a, 88b Drive electrode
100 The tuning fork type piezoelectric vibration gyro of the present invention
110 tuning fork type piezoelectric vibrating gyroscope
112 arm
114 arm
116 base
131-138 electrode
132A, 138A Full surface electrode
141-144 extraction electrode
145 to 148 terminals
151 drive source
152-155 Operational Amplifier (Op Amp)
R1, R2 resistance

Claims (6)

In a tuning fork type piezoelectric vibrating gyroscope having a first arm, a second arm, and a base for supporting the first arm and the second arm,
A drive electrode for driving the tuning fork vibration only on predetermined two surfaces of the first and second arms, a detection electrode for detecting a rotational angular velocity, and a ground electrode set to a reference potential, wherein the drive electrode , The detection electrode and the ground electrode are arranged symmetrically with respect to the center plane of the driving vibration of the tuning-fork type piezoelectric vibrating gyroscope, and each of the predetermined two surfaces of the first and second arms has Only two types of electrodes among the drive electrode, the detection electrode, and the ground electrode are arranged,
The tuning fork type piezoelectric vibration gyro, wherein the first arm, the second arm, and a base supporting the first arm and the second arm are integrally formed of a piezoelectric single crystal. The drive electrode is provided on a first surface of each of the first and second arms,
The detection electrode is provided on a second surface of each of the first and second arms facing the first surface,
2. The tuning fork type piezoelectric vibration gyro according to claim 1, wherein the voltage corresponding to the angular velocity is obtained as a potential difference between detection electrodes provided on the second surface of the first and second arms, respectively. The drive electrode is provided on a first surface of each of the first and second arms,
The detection electrode is provided on a first surface of each of the first and second arms,
2. The tuning-fork type piezoelectric vibration gyro according to claim 1, wherein the voltage corresponding to the angular velocity is obtained as a potential difference between detection electrodes provided on the first surface of the first and second arms. The drive electrode is provided on a first surface of each of the first and second arms,
The detection electrode is provided on a first surface of each of the first and second arms, and on a second surface of each of the first and second arms opposed to the first surface,
The voltage corresponding to the angular velocity is a potential difference between the detection electrodes provided on the first and second surfaces of the first arm and the detection electrodes provided on the first and second surfaces of the second arm. The tuning-fork type piezoelectric vibration gyro according to claim 1, wherein the gyro is obtained as: The piezoelectric single crystal LiTaO 3 ₄₀ ° ± 20 ° rotation Z plate tuning fork type piezoelectric vibrating gyro according to claim 1, characterized in that. 2. The tuning fork type piezoelectric vibrating gyroscope according to claim 1, wherein the piezoelectric single crystal is a LiNbO ₃ 50 ° ± 20 ° rotating Z plate.

Images