JP2002267455A - Tuning fork type oscillation gyro - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a tuning fork type oscillation gyro having a high S/N ratio. SOLUTION: The symmetric tuning fork type oscillation gyro has a driving electrode (31, etc.), and a detection electrode (41, etc.), provided on one arm 2 and a driving electrode (33, etc.), and detection electrodes (44, 46, etc.), provided on another arm 3. These driving electrodes and detection electrodes are longer than the arms 3, 4 and extend to a part of a base 4 so as to meet 0<h/W<2, where W is the width of the arms 3, 4 and h is the length of the driving electrodes and the detection electrodes extending along the base 4.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. 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 vibration gyro using a piezoelectric material.

[0002]

2. Description of the Related Art Gyroscopes have been used as means for confirming the position of moving objects such as aircraft, large ships, and space satellites. It is also used for detecting camera shake of devices.

Among such gyroscopes, a vibrating gyroscope using a piezoelectric material has been put to practical use. The piezoelectric vibrating gyroscope uses a principle that when a rotational angular velocity is applied to a vibrating object, Coriolis force is generated in a direction perpendicular to the vibration. Various types of piezoelectric vibrating gyros have been proposed, but recently, in particular,
Research and development of a tuning fork type vibrating gyroscope using a piezoelectric single crystal such as LiTaO ₃ or LiNbO ₃ has been actively conducted.

A tuning fork type vibration gyro has two arms and a base supporting both arms integrally formed of a piezoelectric single crystal, and has a drive electrode for driving a tuning fork vibration and a detection for detecting a rotational angular velocity. An electrode and an arm are provided on the arm. The tuning fork type vibrating gyroscope is classified into the following two types according to the installation pattern of the drive electrode and the detection electrode. One type is a type in which a drive electrode is provided on one arm and a detection electrode is provided on the other arm (hereinafter, this type is referred to as an asymmetric type). Another type is a type in which a drive electrode and a detection electrode are provided in each arm, and the electrode installation in both arms is symmetric (hereinafter, this type is referred to as a symmetric type).

[0005]

This tuning-fork type vibration gyro is advantageous in that it is smaller, lighter and lower in cost than other gyros such as a coma gyro and an optical gyro, but the measurement accuracy is high. Inferior to other gyros. Therefore,
Improvement of measurement accuracy in tuning fork type vibration gyro, that is,
It is desired to improve the S / N ratio.

In the above-mentioned asymmetric type tuning fork type vibrating gyroscope, since the drive electrode and the detection electrode are provided on separate arms, irregular vibration is generated and a potential difference as noise caused by the vibration is detected. Further, unnecessary output (leakage output) due to mechanical coupling and electrostatic coupling between the arm provided with the drive electrode and the arm provided with the detection electrode is also a problem.
On the other hand, in the above-mentioned symmetric type tuning fork type vibration gyro,
Such irregular vibrations can be offset and the leakage output is small,
There is a problem that the capacitance ratio is high and the detection sensitivity is low.

The present invention has been made in view of such circumstances, and has as its object to provide a tuning fork type vibration gyro capable of improving the S / N ratio as compared with the conventional example.

[0008]

According to a first aspect of the present invention, there is provided a tuning fork type vibration gyro having a first arm, a second arm, and a base for supporting the first and second arms. A base is made of a piezoelectric crystal, and a drive electrode for generating a tuning fork vibration and a detection electrode for detecting an electromotive force generated by Coriolis force are provided on the first arm and the second arm. , Wherein the drive electrode extends to the base.

According to a second aspect of the present invention, in the tuning fork type vibration gyro according to the first aspect, the width of the first and second arms is W, and the length of the drive electrode extending over the base is h. And 0 <h / W <2.

According to a third aspect of the present invention, a tuning fork type vibrating gyroscope includes a first arm, a second arm, and a base for supporting the first and second arms, and the first and second arms and the base are made of a piezoelectric crystal. The drive electrode for generating the tuning fork vibration and the detection electrode for detecting the electromotive force generated by the Coriolis force,
In the tuning fork type vibrating gyroscope provided on the first arm and the second arm, the detection electrode extends to the base.

According to a fourth aspect of the present invention, in the tuning fork type vibrating gyroscope according to the third aspect, the width of the first and second arms is W, and the length of the detection electrode extending over the base is h. And 0 <h / W <2.

According to a fifth aspect of the present invention, in the tuning fork type vibrating gyroscope according to the first or second aspect, the drive electrode is provided so as not to exceed a center line in the width direction of the first arm and the second arm. It is characterized by the following.

According to a sixth aspect of the present invention, there is provided a tuning fork type vibrating gyroscope according to the first, second or fifth aspect, wherein the width of the first and second arms is W, and the width of the first and second arms is equal to that of the base. When the length of the drive electrode from the boundary position is m, m / W> 2 is satisfied.

According to a seventh aspect of the present invention, in the tuning fork type vibrating gyroscope according to the third or fourth aspect, the width of the detection electrode is at least 1/4 times the width of the first and second arms. I do.

According to an eighth aspect of the present invention, in the tuning fork type vibrating gyroscope according to the third, fourth or seventh aspect, the width of the first and second arms is W, and the width of the first and second arms and the base is different. When the length of the detection electrode from the boundary position is r, r / W> 2 is satisfied.

In the symmetric tuning-fork type vibrating gyroscope of the present invention, since the noise signal (N component) is originally small, by extending the drive electrode and / or the detection electrode to the base side,
The drive efficiency of the drive electrode and / or the detection efficiency of the detection electrode are increased to increase the detection signal (S component).

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be specifically described below with reference to the drawings showing the embodiments.

[Asymmetric Tuning Fork Vibratory Gyroscope] First, a general configuration and detection principle of an asymmetric type tuning fork vibratory gyroscope will be described with reference to FIGS. FIG. 1 is a diagram showing the vibration of the tuning fork type vibrator, FIGS. 2 and 3 are diagrams showing the electrode configuration, and FIG. 4 is a diagram showing a specific electrode pattern.

The tuning-fork type vibrating body 1 has two rectangular parallelepiped arms 2 and 3 having a square bottom surface, and a rectangular parallelepiped base 4 supporting both arms 2 and 3. These arms 2 and 3 and base 4 are integrally formed of a piezoelectric single crystal. As shown in FIGS. 1A and 1B, the tuning-fork type vibrator 1 has two types of vibrations: fy mode vibration (vertical surface vibration) and fx mode vibration (in-plane vibration). In an asymmetric type tuning fork type vibration gyro, the tuning fork type vibrating body 1 is driven by fx mode vibration (driving vibration mode), and detection is performed by fy mode vibration (detection vibration mode) to detect an output by Coriolis force. And

FIG. 2 is a diagram for explaining electrodes for driving fx mode vibration (FIG. 2A). The fx mode vibration is based on flexural vibration. As shown in FIG. 2B, one arm 2 is vertically divided into two in a direction orthogonal to the fx mode vibration direction, and when one is extended, a voltage is applied to the arm 2 so that the other is contracted. The electrode configuration in this case is as shown in FIG.
12, 13, and 14 are provided. The two arrows in the figure indicate the direction of the electric field generated by applying a drive voltage to the corresponding electrode.

FIG. 3 is a diagram for explaining electrodes for detecting fy mode vibration (FIG. 3A). The fy mode vibration is based on flexural vibration similarly to the fx mode vibration.
As shown in FIG. 3B, when the other arm 3 is vertically divided into two in a direction orthogonal to the fy mode vibration direction, when one is extended, the other is contracted. Therefore, this arm 3
In contrast, as shown in FIG. 3 (c), the drive electrodes 21, 22, 23,
By providing 24, the voltage for the fy mode vibration can be detected.

Based on the above principle, a general configuration of an asymmetric tuning fork type vibrating gyroscope is as shown in FIG. Tuning fork vibrator 1 which is the tuning fork vibrating gyroscope of the present invention
Has both arms 2 and 3 and a base 4 integrally formed of LiTaO ₃ . Two sets of inner and outer drive electrodes 11, 1 for driving the fx mode vibration are provided on the front and back surfaces of one arm 2, respectively.
2, 13 and 14 (drive electrodes 11 and 12 constitute an inner set of electrodes, and drive electrodes 13 and 14 constitute an outer set of electrodes). Further, detection electrodes 21, 22, 23, and 24 for detecting the fy mode vibration are provided on the front surface, the back surface, the inner side surface, and the outer side surface of the other arm 3. Detection electrode 21,
22 is electrically short-circuited, and the detection electrodes 23 and 24 are electrically short-circuited (see FIG. 3C).

FIG. 5 is a graph showing a result of analyzing a charge component generated by driving vibration of the tuning fork type vibrator 1 having a crystal orientation as shown in FIG. 6A by a finite element method. As shown in FIG. 6A, the tuning fork type vibrator 1
Is a LiTaO ₃ single crystal 40 ° rotation Z plate (130 ° rotation Y plate) having the X axis as the rotation axis, and the arms 2 and 3 are Y ′
The element extends in the direction. Note that the LiTaO ₃ single crystal is not limited to a 40 ° rotating Z plate, and a 40 ° ± 20 ° rotating Z plate may be used. The front surface of the arms 2 and 3 refers to a surface in which the polarization axis direction is in the + direction, and the back surface refers to a surface in which the polarization axis direction is in the-direction.

As shown in FIG. 6B, the width of the arms 2 and 3 is W (about 1 mm), and the length of the arms 2 and 3 is L (about 7 mm). FIG. 5 shows the electric charge distribution at each of the driving electrodes 11, 12, 13, and 14 during the driving vibration. The horizontal axis represents the distance based on the boundary position between the arms 2, 3 and the base 4, and the vertical axis represents the distance. Indicates charge (relative value).

From the results shown in FIG. 5, it can be seen that in the configuration in which the drive electrode is provided only on one arm 2, the charge components generated inside and outside the arm 2 and between the front surface and the back surface are different. Therefore, in such a case, if the detection electrodes having the same shape are provided on the four surfaces of the other arm 3, the charge component of the drive vibration will be detected, and the error will be increased. Therefore, unnecessary charge components can be canceled out by making the detection electrode asymmetrical between the inside and the outside.
Such an example will be described in the following first embodiment.

(First Embodiment) FIG. 7 is a perspective view showing a first embodiment. Only the detection electrode 24 provided on the outer side surface of the arm 3 is shorter by x on the base 4 side than the other three detection electrodes. FIG. 8 is a graph showing a change in leakage voltage when the length of the outer detection electrode 24 is changed. The horizontal axis indicates the shortened length (the arm 3 and the base 4).
Represents the ratio x / W of the missing length x of the detection electrode 24 to the width W of the arm 3 from the boundary position, and the vertical axis represents the leakage voltage (V) generated during driving. By changing the length of the detection electrode 24 (0 <x / W <2), the level of the leakage voltage changes, and when the detection electrode 24 is shortened by x such that x / W = 0.5, the leakage voltage is minimized. Become. Therefore, the length of the detection electrode 24 provided on the outer side surface of the arm 3 as described above is
Detection electrode 23 provided on the inner side surface (not shown in FIG. 7)
By making the length shorter, it becomes possible to suppress the leakage voltage.

(Second Embodiment) Next, the detection electrodes 23 and 24 provided on the inner side surface and the outer side surface of the arm 3 are fixed, and the formation patterns of the detection electrodes 21 and 22 provided on the front and back surfaces of the arm 3 are fixed. An example in which the leakage voltage is reduced will be described as a second embodiment. In such a case, arm 3
In order to avoid the influence of the extra charges outside the sensor, the detection electrodes 21 and 22 formed on the front surface and the back surface are weighted in the width direction to reduce the leakage voltage component.

FIG. 9 shows an example of the second embodiment. In the example of FIG. 9A, the detection electrodes 21 and 22 formed on the front surface and the back surface of the arm 3 are offset (when the distance from the inner side surface is y and the distance from the outer side surface is z, y
<Offset to z). In the example of FIG. 9B, the detection electrodes 21 and 22 formed on the front surface and the rear surface of the arm 3 are shaped so as to be inclined from the outside to the inside.

Next, the shapes of the four drive electrodes provided on the inside and outside of the front and back surfaces of the arm 2 are formed asymmetrically.
Specifically, an example in which the size of the inner drive electrode is made smaller than the size of the outer drive electrode so as to suppress illegal vibration is described in the following third and fourth embodiments. explain.

(Third Embodiment) FIG. 10 is a plan view showing a third embodiment. The width of the drive electrode provided inside the arm 2 is made smaller than the width of the drive electrode provided outside the arm 2, so that the illegal vibration component is reduced. Specifically, arm 2
The width of the drive electrode 11 provided on the inside of the back surface is b, the width of the drive electrode 13 provided on the outside of the front surface is c, and the width of the drive electrode 14 provided on the outside of the back surface is a. Is d, a <c and b <d.

FIG. 11 is a graph showing a change in irregular vibration with respect to a change in asymmetry between the inner drive electrode and the outer drive electrode. represents the ratio of the difference from c ((ac) / W), and the vertical axis represents the illegal vibration coupling value (= perpendicular vibration transmission characteristic).
Is represented. Also, in FIG. 11, the widths a and b of the drive electrodes 11 and 12 provided inside the front and back surfaces of the arm 2
It shows the characteristic change regarding the magnitude relation of the species. As can be seen from the results of FIG. 11, by making the widths of the drive electrodes 11 and 12 inside the front surface and the back surface of the arm 2 different, it is possible to further reduce the illegal vibration component.

(Fourth Embodiment) FIG. 12 is a perspective view showing a fourth embodiment. The length of the drive electrode provided inside the arm 2 is made shorter than the length of the drive electrode provided outside the arm 2, thereby reducing the illegal vibration component. More specifically, the outer drive electrodes 13 and 14 are formed over the entire length of the arm 2, while the inner drive electrodes 11 and 12 extend from the boundary position between the arm 2 and the base 4 to the middle of the arm 2 (length e). ) Only formed.

FIG. 13 is a graph showing a change in the irregular vibration with respect to a change in the length of the inner drive electrode. The horizontal axis indicates the length of the inner drive electrode with respect to the width W of the arm 2. The vertical axis represents the illegal vibration coupling value (= surface vertical vibration transmission characteristic). The widths of the inner and outer drive electrodes are assumed to be the same. It can be seen from FIG. 13 that the irregular vibration component can be suppressed by shortening the length of the inner drive electrode.

(Fifth Embodiment) FIG. 14 is a structural diagram of an asymmetric tuning fork type vibrating gyroscope in consideration of the first and fourth embodiments (asymmetric drive electrode structure and detection electrode structure) as described above. It is. The drive electrodes 11 and 12 provided inside the front surface and the back surface of the arm 2 are formed smaller than the drive electrodes 13 and 14 provided outside the front surface and the back surface, and the detection electrode 24 provided on the outer side surface of the arm 3 is x /. X so that W becomes 0.5
Only short. By employing such an electrode configuration, it is possible to reduce the influence of improper coupling between the drive vibration mode system and the detected vibration mode system.

By the way, as shown in FIG. 5, the charge components are concentrated on the boundary between the arms 2, 3 and the base 4. Therefore, if an electrode is formed in this portion, the tuning fork type vibrator 1 having high efficiency, that is, a small capacitance ratio can be formed. As such an example, the sixth embodiment, the seventh embodiment
Embodiments will be described below.

(Sixth Embodiment) FIG. 15 is a perspective view showing a sixth embodiment. The drive electrode is longer than the arm and extends to a part of the base so that the drive efficiency of the drive electrode is high, that is, the capacitance ratio is small. Specifically, four drive electrodes 11, 12, 13, 14 provided on the arm 2 are provided.
From the entire length of the arm 2 to a part of the base 4 (length f extended to the base 4).

FIG. 16 is a graph showing a change in the capacitance ratio with respect to a change in the extension length of the drive electrodes 11, 12, 13, and 14 from the boundary position between the arm 2 and the base 4. The horizontal axis indicates the boundary. The length of the drive electrodes 11, 12, 13, 14 from the position is represented by the ratio of the extended length f to the width W of the arm 2 (f / W), and the vertical axis represents the capacitance ratio of the drive electrodes (Cp / Cs). When the value of f / W is in the range of 0 to 2, the capacitance ratio is low. When the value of f / W is about 0.5, the smallest capacitance ratio is obtained.

(Seventh Embodiment) FIG. 17 is a perspective view showing a seventh embodiment. The detection electrode is longer than the arm and extends to a part of the base so that the detection efficiency of the detection electrode is high, that is, the capacitance ratio is small. Specifically, two detection electrodes 2 provided on the front and back surfaces of the arm 3
1, 22 are formed from the entire length of the arm 3 to a part of the base 4 (length g extended to the base 4). The four drive electrodes 11, 12, 13, and 14 also extend from the entire length of the arm 2 to the base 4 by f, as in the sixth embodiment.

FIG. 18 is a graph showing a change in the capacitance ratio with respect to a change in the extension length of the detection electrodes 21 and 22 from the boundary position between the arm 3 and the base 4, and the horizontal axis represents the detection from the boundary position. The distance between the electrodes is represented by the ratio of the extended length g to the width W of the arm 3 (g / W), and the vertical axis represents the capacitance ratio of the detection electrode (Cp / Cs). g / W is 0 to
2, the capacity ratio is low, and g / W
When the value of is about 0.5, the smallest capacity ratio is obtained.

(Eighth Embodiment) FIG. 19 shows an asymmetric type tuning fork in consideration of the first, second, sixth and seventh embodiments (asymmetric drive electrode structure and detection electrode structure) described above. It is a lineblock diagram of a type vibration gyro. The drive electrodes 11 and 12 provided inside the arm 2 are formed smaller than the outer drive electrodes 13 and 14, and the detection electrode 24 provided on the outer side surface of the arm 3 is x /
The drive electrodes 11, 12, 13, 14 provided on the arm 2 are extended toward the base 4 by a distance f so that f / W becomes 0.5. The detection electrodes 21 and 22 provided on the front surface and the back surface are extended toward the base 4 by a distance g so that g / W becomes 0.5. By doing so, it is possible to reduce the influence of improper coupling between the driving vibration mode system and the detected vibration mode system.

[Symmetric Tuning Fork Vibratory Gyroscope] Next, a general configuration and detection principle of a symmetrical tuning fork vibratory gyroscope will be described with reference to FIGS. 20 and 21 are diagrams showing an electrode configuration, and FIG. 22 is a diagram showing a specific electrode pattern.

Similarly to the asymmetric type, the symmetric type tuning fork type vibrating body 1 also has two rectangular parallelepiped arms 2 and 3 having a square bottom surface, and a rectangular parallelepiped base supporting both arms 2 and 3. And 4. These arms 2 and 3 and base 4 are integrally formed of a piezoelectric single crystal,
The tuning fork type vibrating body 1 is driven by the fx mode vibration, and the detection is performed by the fy mode vibration to detect the output due to the Coriolis force. However, the arrangement patterns of the drive electrodes and the detection electrodes are different from those of the asymmetric type.

FIG. 20 is a diagram for explaining an electrode for driving the fx mode vibration. The arm 2 shown in FIG.
As shown in FIG. 20 (b), drive electrodes 31, 32, 33, and 34 are provided on the inside of the front and back surfaces of 3 and when a voltage is applied between the drive electrodes 31 and 32 and between the drive electrodes 33 and 34, , FIG. 20 (b)
20A, an electric field is generated, and the outer portions of the arms 2 and 3 expand and contract by the piezoelectric effect as indicated by the arrow in FIG. The fx mode vibration can be excited in the arms 2 and 3 by the expansion and contraction movement.

When a rotational motion occurs on the vibration axis of the fx mode vibration, a Coriolis force is generated in a direction perpendicular to the vibration direction. Therefore, as shown in FIG. 21 (b), detection electrodes 41, 42, 43 are provided on the outer side surface and the outer side surface of the front and back surfaces of the arm 2.
And detection electrodes 44, 45 and 46 are provided on the outer and outer side surfaces of the front and back surfaces of the arm 3, and the fy mode as shown by an arrow in FIG. 21A in a direction perpendicular to the fx mode vibration. By detecting the vibration, it is possible to obtain an electrical output proportional to the angular velocity from the arms 2 and 3 bent in opposite directions by receiving Coriolis force.

Based on the above principle, a general configuration of a symmetrical tuning fork type vibrating gyroscope is as shown in FIG. Tuning fork vibrator 1 which is the tuning fork vibrating gyroscope of the present invention
Are both arms 2 and ₃ integrally formed of LiTaO ₃
(Width W, length L) and a base 4. The fx mode vibration driving 1 is provided inside the front and back surfaces of one arm 2.
A pair of drive electrodes 31 and 32 are provided, and detection electrodes 41, 42 and 43 for detecting the fy mode vibration are provided on the outside of the front and back surfaces and on the outside side surface. Also, the other arm 3
A set of drive electrodes 33 and 34 for driving the fx mode vibration is provided inside the front and back surfaces of the sensor.
44, 45, and 46 are provided. As described above, in the symmetric tuning fork type vibration gyro,
The drive electrode and the detection electrode are provided symmetrically.

In the tuning-fork type vibration gyro of the symmetrical type, since the drive electrodes and the detection electrodes are provided symmetrically on both arms 2 and 3, illegal vibrations can be canceled out and the leakage output is small. Therefore, in order to increase the detection accuracy, that is, the S / N ratio, it is not necessary to consider suppressing the noise signal (N component), and it is necessary to increase the detection signal (S component). Therefore, the following ninth to thirteenth embodiments will be described with respect to an example in which the shape of the drive electrode and the detection electrode is devised to reduce the capacitance ratio of the drive electrode and the detection electrode to improve the detection sensitivity. This will be described in the form of FIG.

(Ninth Embodiment) Even in a symmetric tuning-fork type vibrating gyroscope, charge components are concentrated on the boundary between the arms 2 and 3 and the base 4. Therefore, if an electrode is formed in this portion, the tuning fork type vibrator 1 having high efficiency, that is, a small capacitance ratio can be obtained. FIG. 23 is a perspective view showing the ninth embodiment. The drive electrode and the detection electrode are made longer than the arm and extend to a part of the base so that the drive efficiency of the drive electrode and the detection efficiency of the detection electrode are high, that is, their capacitance ratio is small. Specifically, 4
Drive electrodes 31, 32, 33, 34 and six detection electrodes 41, 4
2, 43, 44, 45, and 46 are formed from the entire length (L) of the arms 2 and 3 to a part of the base 4 (the length h extended to the base 4).

FIG. 24 is a graph showing a change in the capacitance ratio with respect to a change in the extension length of the drive electrode and the detection electrode from the boundary position between the arms 2 and 3 and the base 4, and the horizontal axis represents the drive electrode and the detection electrode. The length of the electrode from the base arm boundary position is represented by the ratio of the extended length h to the width W of the arms 2 and 3 (h / W), and the vertical axis represents the capacitance ratio of the drive electrode and the detection electrode ( Cp / Cs). In the case of the drive electrode,
The capacity ratio is low when the value of h / W is in the range of 0 to 2, and the smallest capacity ratio is obtained when the value of h / W is 0.5. Further, also in the case of the detection electrode, a low capacitance ratio is obtained when the value of h / W is in the range of 0 to 2;
The smallest capacitance ratio is obtained when the value of / W is 0.5.

(Tenth Embodiment) The relationship between the width (formation position) of the drive electrodes 31, 32, 33, 34 provided inside the front and back surfaces of the arms 2, 3 and the capacitance ratio will be described. As shown in FIG. 25, when the widths of the drive electrodes 31, 32, 33, and 34 are i, j, k, and l, respectively, the widths are changed while maintaining the condition of i = j = k = 1. FIG. 26 shows the result of examining the change in the capacitance ratio.

In the graph of FIG. 26, the horizontal axis represents the amount of deviation of the tip of the drive electrode from the center line of the arm, and the vertical axis represents the capacitance ratio (Cp / Cs) of the drive electrode. 0 on the horizontal axis indicates that the width of the drive electrode is only half the width W of the arm, that is,
Indicates that the tip of the drive electrode extending from the inner edge of the arm has reached the center line of the arm, and how much the tip of the drive electrode is displaced from the center line of the arm. The scale on the horizontal axis is taken in the negative direction. For example, in the case of 1 / 4W, the tip of the drive electrode reaches only 1 / 4W before the center line, and its width is 1 / 4W.
In the case of -W, -ＷW is such that the tip of the drive electrode extends beyond the center line to further 1 / 4W, and its width is 3 / 4W.
Is the case.

From the results shown in FIG. 26, it can be seen that when the drive electrode exceeds the center line of the arm, the capacitance ratio increases and the characteristics deteriorate. Therefore, the drive electrodes 31, 32, 33, 34 are connected to the arms 2,
3 must be formed not to exceed the center line.

(Eleventh Embodiment) FIG. 27 is a perspective view showing an eleventh embodiment. The length of the drive electrodes provided inside the front and back surfaces of the arm is reduced. Specifically, each of the detection electrodes 41, 42, 43, 44, 45, 46 is formed over the entire length of the arm 2, 3, while each of the drive electrodes 31, 32, 33, 34 is connected to the arm 2, 3 by the base. Only a portion (length m) is formed from the boundary position with the arm 4 to the middle of the arms 2 and 3 (length m). The driving electrodes 31, 32, 33, 34 and the detecting electrodes 41, 42, 4
3, 44, 45 and 46 extend from the boundary between the arms 2 and 3 and the base 4 to the base 4 by a length h (h / W = 0.5). Further, the widths of the drive electrodes 31, 32, 33, 34 are the same.

FIG. 28 is a graph showing the change in the capacitance ratio with respect to the change in the length of the drive electrode. The horizontal axis indicates the length of the drive electrode from the boundary position with respect to the width W of the arms 2 and 3. The vertical axis represents the capacitance ratio (Cp / Cs) of the drive electrode. From the result of FIG. 28, m
It can be seen that by setting the value of / W to be larger than 2, it is possible to set a small capacity ratio and improve the driving efficiency.

(Twelfth Embodiment) The relationship between the width (formation position) of the detection electrodes 41, 42, 44, 45 provided outside the front and back surfaces of the arms 2, 3 and the capacitance ratio will be described. As shown in FIG. 29, when the widths of the detection electrodes 41, 42, 44, and 45 are n, o, p, and q, respectively, the width is changed while maintaining the condition of n = o = p = q. FIG. 30 shows the result of examining the change in the capacitance ratio.

In the graph of FIG. 30, the horizontal axis represents the amount of deviation of the tip of the detection electrode from the center line of the arm, and the vertical axis represents the capacitance ratio of the detection electrode (Cp / Cs). 0 on the horizontal axis indicates that the width of the detection electrode is only half of the width W of the arm, that is,
Indicates that the tip of the detection electrode extending from the outer edge of the arm has reached the center line of the arm, and how much the tip of the detection electrode is deviated from the center line of the arm. The scale on the horizontal axis is taken in the negative direction. For example, in the case of 1/4 W, the tip of the detection electrode extends beyond the center line to another 1/4 W, and its width is 3/4 W.
In the case of −−１W, the tip of the detection electrode reaches only １ ／ W before the center line, and the width thereof is １ ／ W.
Is the case.

From the results shown in FIG. 30, it is not so important whether the position of the detection electrode exceeds the center line of the arm, unlike the above-described drive electrode.
The width of 4, 45 is 1/4 or more of the width of arms 2 and 3, that is,
It can be seen that by setting it to 1/4 W or more, the detection electrode can be set to a small capacitance ratio, and the detection efficiency can be improved.

(Thirteenth Embodiment) FIG. 31 is a perspective view showing a thirteenth embodiment. The length of the detection electrodes provided outside the front and back surfaces of the arm is shortened. Specifically, the detection electrodes 43 and 46 provided on the outer side surfaces of the arms 2 and 3 and the drive electrodes 31 and 46 provided on the inner surfaces of the front and back surfaces of the arms 2 and 3 are described.
32, 33, and 34 are formed over the entire length of the arms 2 and 3, but the detection electrodes 41, 42, 44, and 45 provided outside the front and back surfaces of the arms 2 and 3 (Length r from the boundary position between the arms 2 and 3 and the base 4). The driving electrodes 31, 32, 33,
34 and the detection electrodes 41, 42, 43, 44, 45, 46 extend by a length h (h / W = 0.5) from the boundary position between the arms 2, 3 and the base 4 to the base 4. Further, the width of each detection electrode 41, 42, 44, 45 is the same.

FIG. 32 is a graph showing the change in the capacitance ratio with respect to the change in the length of the detection electrode. The horizontal axis indicates the length of the detection electrode from the boundary position with respect to the width W of the arms 2 and 3. The vertical axis represents the capacitance ratio of the detection electrode (Cp / Cs). From the result of FIG.
It can be seen that by setting the value of / W to be larger than 2, a small capacitance ratio can be set, and the detection efficiency can be improved.

In the above-described embodiment, LITaO ₃ is used as the piezoelectric single crystal, but LINbO ₃ (Y ′
= 50 ° Y), or other materials such as a piezoelectric single crystal.

[0060]

As described above, in the tuning fork type vibration gyro of the present invention, the drive electrode and / or the detection electrode are formed asymmetrically on the inside and outside of the arm and on the front and back surfaces of the arm. In comparison with the above, the irregular vibration and the leak output can be reduced. Further, since the drive electrode and / or the detection electrode are formed concentrated near the boundary between the arm and the base, the capacitance ratio of the drive electrode and / or the detection electrode is reduced as compared with the conventional example. Drive efficiency and / or
Alternatively, the detection efficiency can be improved.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram of tuning fork vibration.

FIG. 2 is an explanatory diagram of an electrode configuration for causing in-plane vibration (drive vibration).

FIG. 3 is an explanatory diagram of an electrode configuration for causing a plane vertical vibration (detection vibration).

FIG. 4 is a configuration diagram of an asymmetric tuning fork type vibration gyro.

FIG. 5 is a graph showing a charge distribution during driving vibration.

FIG. 6 is a view showing a crystal orientation of a piezoelectric single crystal and dimensions of a tuning fork type vibrating gyroscope.

FIG. 7 is a perspective view of the first embodiment.

FIG. 8 is a graph showing a relationship between a shortened length of a detection electrode and a leakage voltage.

FIG. 9 is a perspective view of the second embodiment.

FIG. 10 is a plan view of a third embodiment.

FIG. 11 is a graph showing a relationship between asymmetry of drive electrodes and irregular vibration.

FIG. 12 is a perspective view of a fourth embodiment.

FIG. 13 is a graph showing a relationship between the length of a drive electrode and irregular vibration.

FIG. 14 is a perspective view of a fifth embodiment.

FIG. 15 is a perspective view of a sixth embodiment.

FIG. 16 is a graph showing the relationship between the extension length of the drive electrode and the capacitance ratio.

FIG. 17 is a perspective view of the seventh embodiment.

FIG. 18 is a graph showing a relationship between an extension length of a detection electrode and a capacitance ratio.

FIG. 19 is a perspective view of the eighth embodiment.

FIG. 20 is an explanatory diagram of an electrode configuration for causing in-plane vibration (drive vibration).

FIG. 21 is an explanatory diagram of an electrode configuration for causing a plane vertical vibration (detection vibration).

FIG. 22 is a configuration diagram of a symmetrical tuning fork type vibration gyro.

FIG. 23 is a perspective view of a ninth embodiment.

FIG. 24 is a graph showing the relationship between the extension length of the drive electrode and the detection electrode and the capacitance ratio.

FIG. 25 is a plan view of the tenth embodiment.

FIG. 26 is a graph showing a relationship between a width of a driving electrode and a capacitance ratio.

FIG. 27 is a perspective view of the eleventh embodiment.

FIG. 28 is a graph showing a relationship between a drive electrode length and a capacitance ratio.

FIG. 29 is a plan view of the twelfth embodiment.

FIG. 30 is a graph showing the relationship between the width of the detection electrode and the capacitance ratio.

FIG. 31 is a perspective view of a thirteenth embodiment.

FIG. 32 is a graph showing the relationship between the length of the detection electrode and the capacitance ratio.

[Description of Signs] 1 Tuning fork type vibrator 2, 3 arm 4 Base 11, 12, 13, 14, 31, 32, 33, 34 Drive electrode 21, 22, 23, 24, 41, 42, 43, 44, 45 , 46 Detection electrode

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Hiroshi Ishikawa 4-1-1, Kamiodanaka, Nakahara-ku, Kawasaki-shi, Kanagawa Prefecture Inside Fujitsu Limited (72) Yoshio Sato 4-1-1, Kamiodanaka, Nakahara-ku, Kawasaki-shi, Kanagawa No. 1 Inside Fujitsu Limited (72) Inventor Ichikazu Kikuchi 3-18-3 Shin-Yokohama, Kohoku-ku, Yokohama, Kanagawa Prefecture F-term within Fujitsu Towa Electron Limited 2F105 AA02 AA03 AA08 BB03 CC01 CD02 CD06

Claims (8)

[Claims] 1. A drive electrode for generating a tuning fork vibration, comprising: a first arm and a second arm; and a base for supporting the first and second arms, wherein the first and second arms and the base are made of a piezoelectric crystal. And a detection electrode for detecting an electromotive force generated by Coriolis force, wherein the drive electrode extends to the base in a tuning-fork type vibration gyro provided on the first arm and the second arm. A tuning fork type vibration gyro characterized by the following. 2. When the width of the first and second arms is W and the length of the drive electrode extending over the base is h, 0 <h / W <2 is satisfied. The tuning fork type vibration gyro described. 3. A drive electrode having a first arm and a second arm, and a base for supporting the first and second arms, wherein the first and second arms and the base are made of a piezoelectric crystal and generate a tuning fork vibration. And a detecting electrode for detecting an electromotive force generated by Coriolis force, wherein the detecting electrode extends to the base in a tuning fork type vibrating gyroscope provided on the first arm and the second arm. A tuning fork type vibration gyro characterized by the following. 4. When the width of the first and second arms is W and the length of the detection electrode extending over the base is h, 0 <h / W <2 is satisfied. The tuning fork type vibration gyro described. 5. The tuning fork type vibrating gyroscope according to claim 1, wherein the drive electrode is provided so as not to exceed a center line in a width direction of the first arm and the second arm. 6. When the width of the first and second arms is W and the length of the drive electrode from the boundary between the first and second arms and the base is m, m / W
The tuning fork-type vibrating gyroscope according to claim 1, 2, or 5, which satisfies> 2. 7. The width of the detection electrode is equal to the first and second widths.
The tuning fork-type vibrating gyroscope according to claim 3 or 4, wherein the width is at least 1/4 times the width of the arm. 8. When the width of the first and second arms is W, and the length of the detection electrode from the boundary position between the first and second arms and the base is r, r / W
The tuning-fork type vibration gyro according to claim 3, 4 or 7, which satisfies> 2.