JPH08313265A - Tuning fork-shaped vibration gyro, sensor system using the gyro and adjusting method for the tuning fork-shaped vibration gyro - Google Patents

Abstract

PURPOSE: To improve an output and to enhance the sensitivity by a constitution wherein a groove is provided to a corner section of an arm in a lengthwise direction for eliminating a mechanical connection which occurs when a resonance frequency of a driving side of a gyro and an anti-resonance frequency of a detection side are equal to or roughly equal to each other. CONSTITUTION: A vibrator is driven by an fx mode via an arm 14 and the fx mode is detected through an arm 12. An electrode 22 and an opposing electrode are attached to the arm 14 and further, an electrode 30 is attached to an end of the same side face. The electrode 30 acts as a grounding electrode and a driving voltage is applied across the electrode 22 and opposing electrode. Detection side electrode set consists of electrodes 26, 28 and the electrode 28 is attached to a side face of the arm 12 as a grounding electrode and the electrode 26 is attached to the other side face. A groove is provided to the arm 14 of the driving side or additionally to the arm 12 of the detection side so that a mechanical connection which may occur when a resonance frequency and anti-resonance frequency are equal to each other is eliminated.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a tuning fork type vibration gyro, and more particularly to a tuning fork type vibration gyro using a piezoelectric material, a sensor system having the same, and a tuning fork type vibration gyro adjusting method.

Gyroscopes have been used for position confirmation in aviation aircraft, large ships, space satellites and the like. Recently, it has been used as a consumer field for car navigation, detection of camera shake of VTRs and still cameras, and the like. The conventional top and bottom gyro detects rotation angular velocity based on the principle that once the top (disk) is rotated, it continues to rotate without changing its posture while maintaining the direction of its center axis even if the device is tilted. There is. Recently, optical gyros and piezoelectric gyros have been developed and are being put into practical use. The principle of the piezoelectric gyro goes back to research around 1950. Tuning forks, cylinders and hemispheres have been developed. Recently, a vibration gyro using a piezoelectric body has been put into practical use. Although the measurement sensitivity and accuracy are inferior to those of coma gyro and optical gyro, they are different from other gyros in that they are small, lightweight and inexpensive.

[0003]

2. Description of the Related Art A piezoelectric vibrating gyro utilizes the fact that when an angular velocity is applied to a vibrating object, a Coriolis force is generated in a direction perpendicular to the vibrating object. The principle of such a piezoelectric vibrating gyro is analyzed by a mechanical model (for example, “Elastic Wave Device Handbook”, Ohmsha, 49).
1-497)). Various piezoelectric vibration gyros have been proposed. For example, the above document describes a Sperry tuning fork gyro, a Watson tuning fork gyro, a tuning piece gyro, a cylindrical vibrating gyro, and the like.

Further, a piezoelectric gyro using a sound piece (vibrating body) made of a LiTaO ₃ single crystal has been proposed (eg, Chino et al., “Basic Experiment of Angular Velocity Sensor Using LiTaO ₃ ”, 1986). Annual Conference of IEICE General Conference, p1-79). Furthermore, JP-A-61-2943
In 11, a tuning fork type gyro made of piezoelectric ceramic is proposed. According to this proposal, the polarizations of the two arms of the vibrating body are changed to form the drive side arm and the detection side arm, respectively.

In such a piezoelectric vibrating gyro, a leakage output (leakage voltage) is generated due to the processing accuracy of the vibrator. The leak voltage is caused by mechanical coupling that may occur when the anti-resonance frequency of the detection side arm and the resonance frequency of the driving side arm are made to match or substantially match in order to efficiently extract the detection voltage. That is, mechanical coupling occurs due to variations in the processing accuracy of the vibrator and the bonding position of the piezoelectric material, and this becomes a leakage voltage. When the leak voltage is generated, the generated Coriolis force is hidden by the leak voltage, and the detection output (voltage) and the detection sensitivity are reduced. The leak output of the piezoelectric vibrating gyroscope is detailed in the following literature: Sugawara et al., "Equivalent Circuit Consideration of Leak Output of Piezoelectric Vibrating Gyroscope", IEICE Transactions, A Vol-J
76-A, No. 3. March 1993, p263-27
2.

[0006] Conventionally, attempts have been made to reduce the leakage voltage. For example, Nakamura, “Piezoelectric vibrating gyro using a regular triangular prism vibrator, aiming for familiar applications at small size, low price,” NIKKEI ELECTRONICS, 19
90.11.26, No. 514, p183-191
(Hereinafter, referred to as Document 1) has proposed a method of performing signal processing on the leak voltage to apparently remove it.

In addition, Konno et al., "Leakage output of vibration gyroscope and its reduction", Proc. Of Acoustical Society of Japan, 1
995.3, p919-920 (hereinafter referred to as Reference 2)
Proposes to reduce the leakage power by cutting the corners of the arm.

Further, Nakamura et al., "On the structure of the sound gyro", 1986 IEICE General Conference, 1
In 986.3, p1-78 (hereinafter referred to as Reference 3),
By inserting a slight cut at the base of the arm, the diagonal mode is transferred to the in-plane and plane vertical mode (vibration),
Stabilization is described.

[0009]

DISCLOSURE OF THE INVENTION Problem to be Solved by the Invention
The method described in (1) is not an essential solution because it does not remove the leakage output itself output from the oscillator. In addition, a special circuit for signal processing the leak output is required.

Further, although Documents 2 and 3 show the possibility of reducing the leakage output, quantitative and concrete explanation is poor, and in particular, what kind of cutting is formed in which arm and in which range. There is no description of what kind of effect can be obtained. Further, the vibrator used in the experiment has a structure in which a piezoelectric ceramic is adhered to an elinvar material, and there is no mention of other materials and configurations.

Therefore, the present invention solves the above-mentioned problems of the prior art, and provides an effect of mechanical coupling that may occur when the resonance frequency of the gyro drive side vibration and the anti-resonance frequency of the detection side vibration are equal or nearly equal. It is an object of the present invention to provide a tuning fork type vibration gyro with high output and high sensitivity, a sensor system using the same, and a tuning fork type vibration gyro adjusting method.

[0012]

According to a first aspect of the present invention, there is provided a tuning fork type vibration gyro having a tuning fork including first and second arms, wherein a resonance frequency and a detection side of a driving side vibration of the gyro. A groove for eliminating mechanical coupling that may occur when the anti-resonance frequency of vibration coincides with or is substantially equal to the vibration is provided at least at a corner portion within a predetermined range in the longitudinal direction of the first arm.

According to a second aspect of the present invention, the groove of the first aspect of the invention is located within the range from the root of the first arm to the central portion in the longitudinal direction. According to a third aspect of the invention, in the first aspect of the invention, the first arm is provided with a first groove located in a portion close to a root of the first arm,
A second groove is provided closer to the tip end side of the first arm than the first groove, and rough adjustment for removing the mechanical coupling is performed by the first groove, and fine adjustment is performed by the first groove. It does in the groove of 2.

According to a fourth aspect of the present invention, in the first aspect of the present invention, the groove of the first arm is provided at a corner portion facing each other in a diagonal direction of a cross section thereof. According to a fifth aspect of the present invention, in the second aspect of the present invention, the second arm has a resonance frequency of drive-side vibration of the gyro and an anti-resonance frequency of detection-side vibration that are equal to or substantially equal to each other. Grooves are provided at the corners to eliminate mechanical coupling that may occur in equal cases.

According to a sixth aspect of the invention, in the invention of the fifth aspect, the groove provided in the second arm is
It is located within the range from the root to the central portion in the longitudinal direction. According to a seventh aspect of the invention, in the fifth or sixth aspect of the invention, the groove of the second arm is provided in a corner portion facing each other in a cross-sectional diagonal direction.

According to an eighth aspect of the invention, in the invention of the first to seventh aspects, the tuning fork type vibration gyro is
It has a supporting substrate attached to the bottom of the tuning fork. According to a ninth aspect of the invention, in the first to eighth aspects of the invention, the tuning fork includes a piezoelectric body.

According to a tenth aspect of the invention, in the invention of the first to ninth aspects, the tuning fork contains a single crystal of LiTaO ₃ or LiNbO ₃ . The invention according to claim 11 has the tuning fork type vibration gyro, an oscillation circuit that oscillates at a resonance frequency of the drive side vibration, and a detection circuit that detects an electric signal corresponding to the detection side vibration. 11. A sensor system using the tuning fork type vibration gyro according to any one of items 1 to 10.

The invention described in claim 12 is the first and second aspects.
A tuning fork type vibration gyro having a tuning fork including the arm of the gyro, wherein mechanical coupling that may occur when the resonance frequency of the driving side vibration of the gyro and the anti-resonance frequency of the detection side vibration are equal or substantially equal to each other is eliminated. For this purpose, a tuning fork type vibration gyro is provided by providing a groove at least at a corner portion within a predetermined range in the longitudinal direction of the first arm.

According to a thirteenth aspect of the invention, in the invention of the twelfth aspect, the tuning fork is LiTaO ₃ or Li.
It includes a single crystal of NbO ₃ .

[0020]

The invention described in claims 1, 11 and 12 is
And a tuning fork type vibration gyro having a tuning fork including a second arm, wherein mechanical coupling can occur when the resonance frequency of the drive side vibration of the gyro and the anti-resonance frequency of the detection side vibration are equal or substantially equal. Groove to remove the
By providing at least a corner portion within a predetermined range in the longitudinal direction of the first arm, this groove has an effect of effectively removing mechanical coupling.

When the groove is located within the range from the root of the first arm to the central portion in the longitudinal direction as described in claim 2, it is possible to effectively remove the mechanical coupling. By providing the first groove and the second groove as described in claim 3, rough adjustment and fine adjustment for removal of mechanical coupling can be performed.

As described in claim 4, the groove of the first arm may be provided at the corner portions facing each other in the diagonal direction of the cross section, whereby the mechanical coupling may be effectively removed. As described in claim 5, in order to eliminate mechanical coupling that may occur when the resonance frequency of the drive side vibration of the gyro and the anti-resonance frequency of the detection side vibration are equal or substantially equal, By providing a groove in the corner portion of the arm as well, even if the groove provided in the first arm cannot effectively remove the mechanical coupling, the groove can be removed.

As described in claim 6, the groove provided in the second arm is provided so as to be located within the range of the central portion in the longitudinal direction from the root of the groove, thereby effectively removing the mechanical coupling. Can be done As described in claim 7, the second
In some cases, the groove of the arm is provided at a corner portion facing in the diagonal direction of the cross section, whereby effective removal of the mechanical coupling may be possible.

According to the eighth aspect of the support substrate, the tuning fork resonates for vibration on the driving side, and the tuning fork and the support substrate resonate integrally on the sensing side for vibration on the driving side.
Since the vibration on the drive side resonates only with the tuning fork, the tuning fork can be efficiently driven, and the vibration on the detection side vibrates integrally with the tuning fork and the supporting substrate, so the desired frequency characteristics can be set depending on the shape of the supporting substrate. The output due to the Coriolis force can be detected with high sensitivity.

[0025]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Before explaining the principle of the present invention, a tuning fork type vibrator will be explained first in order to help understanding of the explanation.
FIG. 1 is a diagram showing vibration of a tuning fork type vibrating body. The tuning fork type vibration body (hereinafter simply referred to as tuning fork) 10 has two arms 12,
It has 14 and the bottom part 16 which supports these. Arm 1
2, 14 and the bottom portion 16 are integrally formed by processing a piezoelectric body. As shown in FIGS. 1 (A) and 1 (B), the tuning fork type vibration body has two kinds of vibrations, fy mode vibration (plane vertical vibration) and fx mode vibration (in-plane vibration). In a normal crystal resonator tuning fork or the like, most of the fx mode vibrations shown in FIG. Vibration modes are different between fx mode vibration and fy mode vibration. As shown in FIG. 1 (A),
Since the fy mode vibration includes torsional vibration (dotted arrow), the fixed point is limited to one point on the bottom surface of the bottom portion 16 as indicated by the symbol "x". Therefore, it is difficult to support the vibrating body. On the other hand, as shown in FIG. 1B, the fixed point of the fx mode vibration is the center line on the bottom surface of the bottom portion 16. Therefore, by appropriately adjusting the length L of the bottom portion 16, for example, the movement of the bottom surface can be suppressed to substantially zero.

In the present invention, the fx mode vibration is driven and f
An output due to the Coriolis force is obtained by detecting the y-mode vibration. An electrode for driving fx mode vibration and an electrode for detecting fy mode vibration will be described with reference to FIGS. 2 and 3. FIG. 2 is a diagram for explaining electrodes that drive fx mode vibration (FIG. 2A). The fx mode vibration is basically flexural vibration. As shown in FIG. 2B, the arm is vertically divided into two in a direction orthogonal to the fx mode vibration direction, and when one extends, a voltage is applied to the arm so that the other contracts. The electrode structure in this case is shown in FIG.
The two sets of electrodes are arranged as shown. The two arrows in the figure indicate the direction of the electric field generated by applying the drive voltage to the corresponding electrodes.

FIG. 3 is a diagram for explaining electrodes for detecting fy mode vibration (FIG. 3A). Like the fx mode vibration, the fy mode vibration is basically flexural vibration.
As shown in FIG. 3B, when the arm is vertically divided into two in a direction orthogonal to the fy-mode vibration, when one is extended, the other is contracted. For this arm, see Fig. 3 (C).
The voltage corresponding to the fy-mode vibration can be detected by providing the electrode shown in FIG.

In order to efficiently take out the detection output (voltage), it is preferable that the resonance frequency of the fx mode vibration on the drive side is matched with the anti-resonance frequency of the fy mode vibration on the detection side. FIG. 4A shows the change (impedance characteristic) of the impedance | z | of fx mode vibration with respect to the frequency f, and FIG. 4B shows the impedance characteristic of fy mode vibration. The detected output voltage can be maximized by matching the resonance frequency of fx mode vibration (frequency with minimum impedance) with the anti-resonance frequency of fy mode vibration (frequency with maximum impedance). A method of matching the resonance frequency of fx mode vibration with the anti-resonance frequency of fy mode vibration will be described later.

As described above, when the resonance frequency of the fx-mode vibration is equal to or almost equal to the anti-resonance frequency of the fy-mode vibration, if the leakage output due to the mechanical coupling occurs, the leakage output is reduced. In order to reduce effectively, the present invention processes the tuning fork 10 described above as follows.

FIG. 5 is a top view of the tuning fork 10. Now
The arm 12 is the detection side and the arm 14 is the driving side.
The present inventor has conducted various experiments and the like to find that the arm 14 on the drive side
Cutting at least one of the two corner portions A on the diagonal line or two corner portions A ′ and two corner portions B ′ on the diagonal side of the arm 12 on the detection side (corner trimming). And a tuning fork capable of reducing or eliminating static coupling, and at least one of two diagonal corners B of the driving side arm 14 or at least four corners A ′, B ′ of the detection side arm 12 in addition to this. We have found that there is a tuning fork that can reduce or eliminate the mechanical coupling by cutting one. In this experiment, 1
A 30 ° rotated Y plate LiTaO ₃ single crystal was used. FIG. 6 shows the relationship between the corner trimming position and efficiency, more specifically,
It is a figure which shows the Q value change of the tuning fork of the type which can reduce or eliminate mechanical coupling by cutting one of the two corner parts A shown in FIG. The leakage voltage increased by making the resonance frequency of the fx mode vibration of the arm 14 equal to or substantially equal to the anti-resonance frequency of the fy mode vibration of the arm 12 becomes a level indicated by * 1 by cutting the corner portion A, It can be seen that it is reduced (substantially eliminated). When the corner B is cut instead of the corner A, the leakage voltage increases as indicated by * 3.

Further, when the arm balance between the two arms 12 and 14 is poor, the mechanical coupling may not be sufficiently reduced even if the corner portion A is cut. In such a case, by cutting at least one of the corners A ′ or B ′ of the arm 12 on the detection side, the mechanical coupling is substantially removed as shown by * 2 in FIG. The voltage can be almost zero.

FIG. 7 shows that in the longitudinal direction of the arm 14,
0% at the tip (free end) and 100% at the base of the arm 14
It is a figure which shows the relationship between a cutting position and a leak voltage at the time of. In this measurement, a 130 ° rotated Y plate LiTaO ₃
A single crystal was used. In addition, the bottom part 1 of the tuning fork used in this experiment
Although 6 is slightly wider than the length connecting the outer surfaces of the arms 12 and 14, the same can be said for the one shown in FIG. The cutting is performed by irradiating the arm 14 of the tuning fork 10 with laser light. The width of the groove formed by this is almost equal to the diameter of the laser beam. Further, the laser light is applied so that the two side surfaces forming the apexes of the corners are cut by the same length. From FIG. 7, 70 from the tip of the arm 14
It can be seen that the leakage output can be significantly reduced by forming the groove between 100% and 100% (about -45 dB at 80%). In addition, 50 from the tip of the arm 14.
Forming a groove between% and 70% can also reduce the leakage power by at least 5 dB. Therefore,
Coarse adjustment from the tip of arm 14 to 70% to 100%
It is also possible to make an adjustment method in which the fine adjustment is performed between 50% and 70% from the tip of the arm 14. In the range of 50% from the tip of the arm 14, even if the groove is provided, the improvement can be less than 5 dB, which is not a substantial improvement.

In addition to the arm 14, substantially the same can be said for the groove provided in the detection side arm 12. Also, L
The same thing can be said for a single crystal of iNbO ₃ .
The same applies to a thin plate provided with a piezoelectric body. FIG. 8 is a perspective view of a tuning fork type vibration gyro according to an embodiment of the present invention. The tuning fork 10 is supported by a support substrate 18 substantially parallel to a base substrate 32 corresponding to a printed wiring board, a case, or the like. The tuning fork 10 is attached to the support substrate 18 so that the support substrate 18 is elastically coupled to the bottom of the tuning fork 10. This will be described in detail below.

As described above, in the tuning fork type vibration gyro of the present invention, the drive vibration mode is set to the fx mode vibration,
The detection vibration mode is set to fy mode vibration. The drive vibration mode is required to constantly maintain a constant vibration. Further, since the detection sensitivity is proportional to the magnitude of the driving vibration, the driving vibration mode is desired to have a high mechanical Q. Therefore, the fx mode vibration on the driving side is caused by the support substrate
The vibrating body 12, 14 vibrates (resonates) fx mode independently of the vibrating body 8, and the fy mode vibration (resonance) on the detection side is generated by the tuning fork 10 and the support substrate 18 integrally.
Are supported by the support substrate 18. With the above configuration, the mechanical Q of the drive vibration mode is set high to cause a large fx mode vibration, while the mechanical Q of the detection vibration mode can be set to a value smaller than the Q value of the drive vibration mode. A gyro that can easily support the body and has high detection sensitivity can be configured. In particular, in the fy mode vibration on the detection side, the vibrating body and the support substrate 18 vibrate together, so that the resonance frequency and the mechanical Q can be changed by the shape and material of the support substrate 18 as described later. The desired frequency band of detection-side vibration can be set. That is, as shown in FIG. 9, the tuning fork-shaped piezoelectric gyro generates vibration in which the driving-side vibration of the sine wave is modulated at the rotational angular velocity on the assumption that it is a sine wave. In order to detect such a modulated vibration, a frequency band including side bands on both sides of its center frequency is necessary. If the mechanical Q value on the detection side is large, a frequency band including this sideband cannot be obtained, but the above-mentioned support structure makes it possible to easily set a mechanical Q that provides a desired frequency band.

The electrodes provided on the tuning fork 10 shown in FIG.
The electrodes are slightly different from those shown in FIGS. 2 and 3. 2 and 3
When the electrode shown in 1 is used, it may not be possible to completely suppress the electrical coupling between the electrode that drives the fx mode vibration and the electrode that detects the fy mode vibration. When electrically coupled, unwanted modes of vibration occur, causing fx
It may be elastically coupled to the modal vibration or the fy mode vibration to deteriorate the detection accuracy of the gyro.

The electrode of the tuning fork 10 shown in FIG. 8 takes this point into consideration, and its configuration is shown in FIG. Drives fx mode vibration via arm 14 and fy via arm 12.
Detects modal vibration. Arms 14 have electrodes 22 and 2
4 are attached to the side edges of the arm 14 so as to face each other,
Further, an electrode 30 is attached so as to cover the end on the same side surface and the side surface connecting them. Although two sets of electrodes are used in FIG. 2C, one set of driving electrodes is used in FIG. 10, but it is possible to cause fx mode vibration even with this configuration. The electrode 30 functions as a ground electrode, and is electrically connected to the electrode 28 of the detection-side electrodes on the arm 12 side described next. The electrodes 22 and 2
A drive voltage is applied to 4 via terminals T1 and T2.

The detection side electrode has an electrode 26 and an electrode 28. The electrode 28 functions as a ground electrode, and
It is provided on one side. On the other side, the electrode 26
Is provided. The structure of the detection side electrode of FIG. 6 is as shown in FIG.
This corresponds to the configuration in which the electrode * is omitted in (C). A drive voltage is applied to the electrodes 26 and 28 via terminals T3 and T4.

Since the electrode 30 is set to the ground potential via the electrode 28 and the electrode 28 covers the three side surfaces of the arm 12, a shield effect for the electrodes 22 and 24 is obtained. Further, the electrode 24 can be floated from the ground and used, which is advantageous in terms of circuit design. Further, it is easy to form the electrode 28 that covers the three side surfaces of the arm, and the ratio of coupling with the drive mode due to the displacement of the electrode is also reduced. The electrodes having the configurations shown in FIGS. 2 and 3 may be used.

The tuning fork 10 can be composed of a bulk of a piezoelectric material such as a piezoelectric single crystal, or a piezoelectric material provided on a thin plate. As the piezoelectric single crystal, the above-mentioned 130-degree rotated y-plate of lithium tantalate (LiTaO ₃ ) can be used. The single crystal has less internal loss than ceramics, has no hysteresis, and can realize a tuning fork oscillator having a high mechanical Q. After processing a cut as a tuning fork with a dicing saw or a wire saw on a rectangular y-plate of 130 degrees rotation of lithium tantalate (LiTaO ₃ ), a thin film (for example, NiCr / Au) is formed on the entire surface including the side surface by sputtering or the like. After the formation, the electrodes and wirings on the front and back surfaces and the side surfaces are processed by a light exposure method (three-dimensional electrodes use oblique exposure). The electrodes provided on the tuning fork 10 shown in FIG. 8 are those shown in FIG. The wiring 34 connects the electrode 22 of the arm 14 to the terminal T1, and the wiring 36 connects the electrode 24 of the arm 14 (not shown in FIG. 8) to the terminal T2. The wiring 38 connects the electrode 26 of the arm 12 and the terminal T3, and has a wide wiring 40.
Connects the electrode 28 of the arm 12, the electrode 30 and the terminal T4. In order to reduce the influence on resonance as much as possible, it is preferable that the pattern and wiring formed on the tuning fork 10 be formed as symmetrical as possible.
Furthermore, in order to reduce the influence on resonance, the supporting substrate 1
It is preferable that the pattern formed on 8 be as symmetrical as possible. In the example of FIG. 8, the terminals T11 to T14 and the external connection terminals T21 to T2 are provided on the support substrate 18.
4 and wiring for connecting them. The shape of the support substrate is not limited to the rectangular shape, and other shapes may be used. A piezoelectric single crystal such as LiNbO ₃ can also be used.

The support substrate 18 has a rectangular shape, and its thickness is substantially equal to the thickness of the tuning fork 10. This is because the support substrate 18 resonates together with the tuning fork 10 by fy mode vibration.
Further, if the thickness is the same, it becomes easy to bring the surface of the bottom portion 16 of the tuning fork 10 and the predetermined side surface of the support substrate 18 into contact with each other so that the respective electrodes face each other.

FIG. 11 shows a method of connecting the tuning fork 10 and the supporting substrate 18. The bottom portion 16 of the tuning fork 10 and a predetermined side surface of the support substrate 18 are butted against each other, and an adhesive layer 40 is interposed therebetween to fix them. Further, the terminal of the tuning fork 10 (terminal T11 in FIG. 8) and the terminal of the supporting substrate 18 (terminal T21 in FIG. 8) facing the terminal are connected to each other by soldering or a conductive adhesive 4
By cross-linking with 2 etc., it can be easily electrically connected.

As shown in FIGS. 11 and 12, the pin 44 attached to the support substrate 18 is attached to the base substrate 32 to support the tuning-fork vibrating gyro. Regarding the fy-mode vibration, since the support substrate 18 constitutes a part of the vibration system, the base substrate 3 is used as it is.
When connected to 2 or a case, it is affected by vibration. Therefore, as shown in FIG. 12, a hole 46 is provided substantially in the center of the support substrate 18, and a thin pin (for example, a needle-shaped wire such as a metal wire) 44 is inserted into the hole 46. Supported by an elastic member 48 such as a rubber
8 is fixed to the base substrate 32. With this configuration, fy
It is possible to prevent the mode vibration from leaking and prevent the vibration from the base substrate 32 from entering the tuning fork 10.

Electrode terminals T21 to T24 on the support substrate 18
And a corresponding terminal on the base substrate 32 can be electrically connected by wire bonding with a soft wire such as copper. Examples of the material of the support substrate 18 include an alumina substrate, an epoxy printed board, a liquid crystal polymer board and the like.

FIG. 13 is a diagram showing a difference in influence depending on the type of the support substrate depending on the vibration mode. Resonance frequency and Q
The values are shown separately for the resonance mode of the fx mode vibration and the fy mode vibration mode. From FIG. 13, the following can be understood. The value of the fx mode vibration does not change significantly before and after the support substrate 18 is connected, whereas the resonance frequency and the Q value of the fy mode vibration greatly change depending on the material of the support substrate 18 to be connected. That is, it can be said that the fy-mode vibration constitutes the resonance system including the support substrate 18.
As a piezoelectric vibration gyro, Q of fy mode vibration on the detection side
It can be seen that the value greatly depends on the material of the support substrate 18. In other words, there is a suitable material for the desired Q value. In summary, if the loss of the supporting substrate 18 is large, the mechanical Q value of the fy-mode vibration including the tuning fork 10 is lowered. Generally, an inorganic substrate such as an alumina substrate has a small loss, and an epoxy resin or the like has a large loss. As described above, it is necessary to set various parameters relating to the supporting substrate 18 and to have elasticity so that the tuning fork 10 and the tuning fork 10 integrally perform fy mode vibration.

Next, the resonance frequency of fx mode vibration and fy
Frequency adjustment for matching the anti-resonance frequency of modal vibration will be described. This work consists of the arm 12 of the tuning fork 10,
This can be done by changing the width of 14 and the width of the groove between them. However, it is difficult to perform this adjustment work in the assembled state as shown in FIG. So fy
Considering that the mode vibration resonates integrally with the tuning fork 10 and the support substrate 18, the anti-resonance frequency of the fy mode vibration is changed with respect to the support substrate 18 by the method described later to match the resonance frequency of the fx mode vibration. . By this method,
The output impedance of the detection side electrode (vibrator) for fy-mode vibration is the highest, and if a circuit with high impedance such as a cathode follower is used as the detection circuit, a high voltage can be obtained at the output.

FIG. 14 is a diagram showing a first method of adjusting the anti-resonance frequency of fy mode vibration. As shown in FIG. 14A, the support substrate 1 to which the tuning fork 10 is attached
The mass of the support substrate 18 is reduced by shaving the end portion opposite to the end portion 8. The part to be cut is indicated by d1 in FIG. The support substrate 18 is preferably ground symmetrically so as not to adversely affect the vibration. When the support substrate 18 is shaved and the mass is reduced, the anti-resonance frequency of the fy-mode vibration is increased as shown in FIG. The support substrate 18 is evenly ground until the anti-resonance frequency becomes equal to the resonance frequency of the fx mode vibration.

FIG. 15B shows the relationship between the resonance frequency of fx mode vibration and the antiresonance frequency of fy mode vibration with respect to the length d of the supporting substrate 18 shown in FIG. 15A. fx
Since the resonance frequency of modal vibration independently vibrates independently of the vibration of the support substrate 18, the resonance frequency is substantially constant even if the length d of the support substrate 18 changes. On the other hand, f
Since the y-mode vibration resonates with the support substrate 18, the mass decreases as the length d decreases, and the resonance frequency decreases. Note that, as an example of the experimental results, when the width is 4.7 mm and the length d is changed from 6 mm to 12 mm, the resonance frequency of the fy mode vibration is shown in the graph of FIG. Varied between about 15 kHz and about 17 kHz.

FIG. 16 is a graph showing changes in the resonance resistance Ro with respect to the length d of the support substrate 18. Support substrate 18
When the length d becomes shorter, the resonance resistance Ro decreases. This raises the resonance frequency. As an example of the experimental results, the width is 4.7 mm and the length d is 6 mm to 12 m.
When changed between m, the resonance resistance Ro was changed between about 1.0 MΩ and about 1.5 MΩ along the graph of FIG.

In FIG. 14 (A), the method of uniformly scraping the edge of the support substrate 18 is used, but as shown in FIG. 17 (A),
The grooves 50 may be provided symmetrically with respect to the center line of the support substrate 18. The groove 50 adjusts the stiffness of the support substrate 18. The groove 50 may penetrate the support substrate 18, or may be provided only on the surface portion. FIG. 17B is a graph showing the relationship between the depth of the groove 50 (direction toward the tuning fork 10) and the resonance frequency of fx mode vibration and the resonance frequency of fy mode vibration. The resonance frequency of the fx mode vibration is almost constant regardless of the groove depth d2, whereas the resonance frequency of the fy mode vibration decreases as the groove depth d2 increases. As an example of the experimental results, the supporting substrate 1 having a width of 4.7 mm and a length of 12.4 mm
8, the groove depth d2 with a width of 0.3 mm is changed from 0 mm to 2
When changed to mm, the resonance frequency of the fy-mode vibration changed from about 18 kHz to about 17 kHz according to the graph of FIG. 17 (B).

FIG. 18 shows that the support substrate 18 has a mass of 5 such as rubber.
A method of adjusting the resonance frequency of fy-mode vibration by adding 2 will be described. The addition of mass 52 lowers the resonant frequency. In order not to affect fy mode vibration,
The mass 52 is preferably provided symmetrically with respect to the center line of the support substrate 18.

When mechanical coupling occurs due to the resonance frequency and the anti-resonance frequency being matched as described above, the drive arm 14 or the arm 14 on the drive side can be processed by the method described with reference to FIG. In addition to this, a groove is provided on the detection side arm 12. In the structure shown in FIG. 8, a groove 52 for this purpose is provided. To form the groove, the supporting substrate 18 with the tuning fork 10 attached
Measure the leakage voltage before attaching to the base substrate 32,
Laser light is emitted according to the measurement result. The groove can be formed even after mounting. For example, when it is necessary to form a groove at the corner on the base substrate 32 side, the arm 14 is irradiated with laser light through a through hole provided in the base substrate 32.

FIG. 19 is a graph showing the results of an experiment in which the effect of the groove 52 was investigated with the tuning fork 10 made of a LiTaO ₃ single crystal attached to the support substrate 18. The arms 12 and 14 of the tuning fork 10 are rectangular parallelepipeds (arm length 7 mm, arm width 1 mm, arm thickness 1 mm, inter-arm width 0.3 mm).
At a position corresponding to the corner portion A of the drive side arm 14 in FIG. 5, a position 6 mm from the tip (86% from the tip
9 is a graph showing an experimental result when a groove 52 (FIG. 8) is formed by irradiating a laser beam to the position (1). NEC laser YAG laser SL-114B was used for the laser beam. The leakage voltage was measured with a gain phase measuring device. The leakage voltage when the groove was not formed was about -20 dB,
As the groove was formed, it could be improved to -46.3 dB.

The sensitivity of this tuning fork type vibration gyro was measured by the measuring system shown in FIG. The synthesizer 110 drives the fx mode vibration of the tuning fork type vibration gyro (indicated by reference numeral 100 in FIG. 20), and the stage 130 is driven.
Under the control of the controller 150, the tuning fork type vibration gyro 100 attached to is rotated in the direction of the arrow by the servo motor 140, and the detection side vibration (fy mode vibration) due to the Coriolis force at this time is detected by the oscilloscope 120.

FIG. 21 is a graph showing the results of measuring the values before mechanical coupling removal (before leakage output removal) and after mechanical output removal (after leakage output removal) in the measurement system shown in FIG. Is. As shown in FIG. 21, a clear difference in sensitivity was observed before and after removal of the mechanical bond. Drive voltage 200mV _PP ,
At a rotation speed of 1 deg / sec, before mechanical bond removal is 0.
The sensitivity was as high as 0.55 mV (deg / sec) after removal of the mechanical bond with respect to 12 mV / (deg / sec).

When a sensor system is constructed using the tuning fork type vibration gyro described above, the drive circuit shown in FIG. 22 and the detection circuit shown in FIG. 23 are used. Hereinafter, these circuits will be described in detail. 22 is a circuit diagram showing a configuration example of a self-excited oscillation circuit of a sensor system using the tuning fork type vibration gyro shown in FIG. In FIG. 22, the portion that vibrates in the fx mode is indicated by the piezoelectric vibrator CRY1.
The self-excited oscillation circuit shown in FIG.
And a phase shift circuit including capacitors C1 to C3 and resistors R1 and R2, and an amplifier circuit including transistors Tr1 to Tr5 and resistors R3 to R7. A piezoelectric vibrator CRY1 is connected between the input and output of the amplifier circuit, and the phase is adjusted by the phase shift circuit so that positive feedback is provided to cause self-excited oscillation. The capacitors C4 and C5 form a power supply filter, filter the power supply voltage Vcc, and output the filtered voltage as the power supply voltage of the self-excited oscillation circuit. Note that T21 and T22 in FIG. 22 correspond to the terminals T21 and T22 provided on the support substrate 18 shown in FIG.
FIG. 23 is a circuit diagram showing a configuration example of a detection circuit of the sensor system connected to the tuning fork type vibration gyro shown in FIG. In FIG. 22, the portion that vibrates in the fy mode is indicated by the piezoelectric vibrator CRY2. The detection circuit shown in FIG.
The piezoelectric vibrator CRY2, an amplifier circuit having a transistor Tr6, a low-pass filter having a capacitor C7 and a resistor R11, a detection circuit having diodes D1 and D2 and transistors Tr7 and Tr8, and a low-pass filter having a capacitor C8 and a resistor R15. And drive transistors Tr9 and Tr10. In addition, the detection circuit includes resistors R8 to R10, R12 to R14,
It has R16 to R20 and a capacitor C6. The output of the transistor Tr6 is taken out from the emitter and given to the base Tr7 of the transistor through the coupling capacitor C6, the diode D1 and the low pass filter. The signal given to the base of the transistor Tr7 serves as a reference signal for synchronous detection. The output of the transistor Tr7 is output to the output terminal OUT via the collector and the transistor Tr9. Further, the collector current of the transistor Tr9 is given to the base of the transistor Tr8 via the low pass filter and the diode D2.

The base of the transistor Tr10 functions as a standby mode terminal, and when the enable signal / ENB (corresponding to the bar in FIG. 22) at this terminal becomes low level (bias level at which the base current flows), the detection circuit. Becomes active. Note that T23 and T24 in FIG. 22 are terminals T23 and T24 provided on the support substrate 18 shown in FIG.

The embodiment of the present invention has been described above. INDUSTRIAL APPLICABILITY The present invention can be applied to various fields such as an automobile navigation device, a suspension control device, and a VTR image stabilization device. Depending on the application, a plurality of tuning fork type vibration gyros of the present invention can be used to detect rotational angular velocities in a plurality of directions.

[0058]

The present invention has the following effects. The invention described in claims 1, 11 and 12 is a tuning fork type vibration gyro having a tuning fork including first and second arms, wherein a resonance frequency of vibration on a driving side of the gyro and an anti-resonance of the vibration on a detecting side. By providing a groove for removing a mechanical coupling that may occur when the frequencies match or almost equal to each other, at least at a corner portion within a predetermined longitudinal range of the first arm, the groove is effectively machined. Can be removed.

According to the second aspect of the invention, when the groove is located within the range from the root of the first arm to the central portion in the longitudinal direction, it is possible to effectively remove the mechanical coupling. According to claim 3, by providing the first groove and the second groove,
Coarse and fine adjustments of mechanical coupling removal are possible.

In the invention according to claim 4, the groove of the first arm may be provided in a corner portion facing each other in a diagonal direction of the cross section, whereby mechanical coupling may be effectively removed. According to a fifth aspect of the present invention, in order to eliminate mechanical coupling that may occur when the resonance frequency of the drive side vibration of the gyro and the anti-resonance frequency of the detection side vibration are equal or substantially equal, By providing a groove in the corner portion of the arm as well, even if the groove provided in the first arm cannot effectively remove the mechanical coupling, the groove can be removed.

In the invention according to claim 6, the groove provided in the second arm is provided so as to be located within the range of the central portion in the longitudinal direction from the root of the groove, thereby effectively removing the mechanical coupling. Can be done In the invention according to claim 7, the groove of the second arm may be provided at a corner portion facing each other in a diagonal direction of the cross section, whereby effective removal of mechanical coupling may be possible.

In the invention described in claim 8, the supporting substrate is
Considering the mounting, vibration on the drive side causes the tuning fork to resonate,
On the detection side, the tuning fork and the supporting substrate resonate together. Since the vibration on the drive side resonates only with the tuning fork, the tuning fork can be efficiently driven, and the vibration on the detection side vibrates as a unit with the tuning fork, so the desired frequency characteristics can be set depending on the shape of the supporting substrate. The output due to the Coriolis force can be detected with high sensitivity.

[Brief description of drawings]

FIG. 1 is a diagram for explaining vibration of a tuning fork.

FIG. 2 is a diagram for explaining an electrode configuration for causing fx mode vibration in a tuning fork.

FIG. 3 is a diagram illustrating an electrode configuration for detecting fy-mode vibration generated in a tuning fork.

FIG. 4 is a diagram for explaining frequency adjustment for matching the resonance frequency of fx mode vibration and the anti-resonance frequency of fy mode vibration.

FIG. 5 is a diagram for explaining the principle of the present invention.

FIG. 6 is a diagram showing a change in mechanical coupling due to corner trimming of the present invention.

FIG. 7 is a diagram showing a trimming position and efficiency of the present invention.

FIG. 8 is a perspective view of a tuning fork type vibration gyro according to an embodiment of the present invention.

FIG. 9 is a waveform diagram showing vibration of a tuning fork.

FIG. 10 is a diagram showing an electrode configuration used in an example of the present invention.

FIG. 11 is a view showing a joint portion between a tuning fork and a support substrate.

12 is a side view of the gyro shown in FIG.

FIG. 13 is a diagram illustrating a case where a vibration mode affects a type of a support substrate.

FIG. 14 is a diagram showing a first method of adjusting the anti-resonance frequency of fy-mode vibration.

FIG. 15 is a graph showing a relationship between a support substrate length and a resonance frequency.

FIG. 16 is a graph showing the relationship between the support substrate length and the resonance resistance.

FIG. 17 is a diagram showing a second method of adjusting the anti-resonance frequency of fy-mode vibration.

FIG. 18 is a diagram showing a third method of adjusting the anti-resonance frequency of fy-mode vibration.

FIG. 19 is a graph showing the effect of forming a groove in one example of the present invention.

20 is a block diagram showing a measurement system for measuring the characteristics of the gyro shown in FIG.

21 is a diagram showing measurement results measured by the measurement system shown in FIG.

22 is a circuit diagram showing a detection circuit of a sensor system using the gyro shown in FIG.

23 is a diagram showing a measurement system for measuring the characteristics of the gyro shown in FIG.

[Explanation of symbols]

 10 Tuning Fork 12 Arm 14 Arm 16 Bottom 18 Support Substrate 52 Groove

 ─────────────────────────────────────────────────── ─── Continued Front Page (72) Inventor Noboru Wakatsuki 1015 Kamiodanaka, Nakahara-ku, Kawasaki City, Kanagawa Prefecture, Fujitsu Limited (72) Inventor Masaaki Ono 1015, Kamedotachu, Nakahara-ku, Kawasaki City, Kanagawa Prefecture, Fujitsu Limited (72) Inventor Yoshitaka Takahashi 2-44 Muromachi, Hadano-shi, Kanagawa Towa Electron Co., Ltd. (72) Inventor Koji Kikuchi 2-44, Muromachi, Hadano-shi, Kanagawa Towa Electron Co., Ltd. (72) Inventor Moto Yamauchi Towa Electron Co., Ltd. 2-444 Muromachi Hadano City, Kanagawa Prefecture

Claims (13)

[Claims] 1. A tuning fork type vibration gyro having a tuning fork including a first arm and a second arm, wherein a resonance frequency of vibration on a driving side of the gyro and an anti-resonance frequency of vibration on a detecting side are equal to or substantially equal to each other. A tuning-fork vibrating gyro, characterized in that a groove for removing a mechanical coupling that may occur is provided at least at a corner portion within a predetermined range in the longitudinal direction of the first arm. 2. The tuning fork type vibration gyro according to claim 1, wherein the groove is located within a range from a root of the first arm to a central portion in the longitudinal direction. 3. The first arm has a first groove located in a portion close to a root thereof, and a second groove located closer to a tip side of the first arm than the first groove. And rough adjustment of removal of the mechanical coupling is performed in the first groove,
The fine adjustment is performed in the second groove.
The tuning fork type vibration gyro described. 4. The tuning-fork type vibration gyro according to claim 1, wherein the groove of the first arm is provided in a corner portion facing each other in a diagonal direction of a cross section thereof. 5. The second arm removes a mechanical coupling that may occur when the resonance frequency of the drive side vibration of the gyro and the anti-resonance frequency of the detection side vibration are equal or substantially equal to each other, 5. The tuning fork type vibration gyro according to claim 1, wherein a groove is provided at a corner portion. 6. The tuning fork type vibration gyro according to claim 5, wherein the groove provided in the second arm is located within the range from the root to the central portion in the longitudinal direction. 7. The tuning fork type vibration gyro according to claim 5, wherein the groove of the second arm is provided in a corner portion facing each other in a diagonal direction of a cross section thereof. 8. The tuning fork type vibration gyro according to claim 1, wherein the tuning fork type vibration gyro includes a support substrate attached to a bottom portion of the tuning fork. 9. The tuning fork type vibration gyro according to claim 1, wherein the tuning fork includes a piezoelectric body. 10. The tuning fork is LiTaO ₃ or LiNb.
10. A single crystal of O ₃ is included, which is characterized in that
A tuning fork type vibration gyro according to any one of the items. 11. A tuning fork type vibration gyro, an oscillation circuit that oscillates at a resonance frequency of the driving-side vibration, and a detection circuit that detects an electrical signal corresponding to the detection-side vibration. A sensor system using the tuning fork type vibration gyro according to any one of 1 to 10. 12. A tuning fork type vibration gyro having a tuning fork including a first arm and a second arm, wherein a resonance frequency of a driving side vibration of the gyro and an anti-resonance frequency of the detection side vibration are equal to or substantially equal to each other. A tuning fork type vibrating gyro adjusting method, wherein a groove is provided at least at a corner portion within a predetermined range in the longitudinal direction of the first arm in order to remove a mechanical coupling that may occur in the first arm. 13. The tuning fork is LiTaO ₃ or LiNb.
13. The tuning fork type vibration gyro adjusting method according to claim 12, comprising a single crystal of O ₃ .