JP2002213963A - Vibration gyroscope - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a miniaturized, highly practical vibration gyroscope with a single vibration body capable of multi-axial detection by improving the electrode location of a three-legged tuning fork and its driving method so that signal leakage between respective directions can be reduced and relatively high sensitivity can be obtained. SOLUTION: This vibration gyroscope has the three-legged tuning fork made of a crystalline material, etc. The tuning fork has, as possible vibration modes, an HS mode wherein its two outer legs are simultaneously opened/closed in X direction, a V mode wherein the two outer legs are alike displaced in Z direction and its middle leg is displaced in the opposite direction, and an HA mode wherein the two outer legs are alike displaced in the X direction and its middle leg is displaced in the opposite direction. It is excited to develop the HS mode by being driven so that the two outer legs are opened/closed in the X direction with the HS and V modes coupled to each other by being given natural vibration frequencies sufficiently close to each other. By synchronously detecting two lines made by giving a 90 deg. phase difference to a voltage induced by the motion of the middle leg in the X direction, the respective components of a Coriolis force developed by rotational movement of the vibrating body around Y and Z axes are separately detected.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a vibratory gyroscope. More specifically, the present invention relates to a multi-axis vibratory gyroscope using a tripod type tuning fork.

[0002]

2. Description of the Related Art Using a tripod type tuning fork, two axes or three axes are used.
A multi-axis vibratory gyroscope for detecting an angular velocity in the rotation direction of a shaft has already been proposed. The tripod tuning fork is substantially common to the present invention and the prior art, and has a shape as shown in the plan view of FIG. (However, the shape of the electrode curtain 6 is different.) In the figure, reference numeral 1 denotes a tripod tuning fork, which is cut out of a flat plate material such as quartz or piezoelectric porcelain. Reference numeral 2 denotes a base on which three parallel vibrating legs are formed. 3, 4
Each of the outer legs has a protruding portion (a protruding portion whose mass is eccentric from the axis) at the distal end as shown in the drawing. Further, in order to define the direction with respect to the tuning fork, orthogonal coordinate axes of X, Y, and Z are set as shown in FIG. Z
The axis is perpendicular to the plate surface, and the Y axis is in the axial direction of each parallel leg.

FIG. 3 defines a fundamental (lowest order) vibration mode that can occur in a tripod tuning fork. (A) is a V mode in which both outer legs 3 and 4 are displaced in the same direction in the Z direction and the middle leg 5 is displaced in the opposite direction.
HS mode that opens and closes simultaneously in the directions, (c) shows both outer legs 3,
4 is an HA mode in which the center leg 5 is displaced in the same direction in the X direction and the middle leg 5 is displaced in the opposite direction, and FIG. 4D is a T mode in which the outer legs 3 and 4 are displaced in the Z direction in opposite directions. Note that the HS mode, the V mode, and the HA mode are particularly related to the present invention. In the figure, U3, U4, and U5 indicate velocity components at a certain point in time in each mode of each leg (in a state of shifting to a displacement as shown).

The principle of operation of the vibrating gyroscope will be described with reference to FIG. (A) is a drive (excitation) mode commonly used in the present invention and the prior art, and is called a V + HS mode. This is a vibration mode in which the two modes are combined. When the natural frequency in the X direction and the natural frequency in the Z direction are brought close to each other by changing the size and the like of each leg and the natural frequency in the X direction is extremely close, both modes are generated at the same time.
Perform elliptical motion (including circular motion) that is plane-symmetric in the plane. At this time, it is not necessary to apply a driving force to both the outer legs in the X and Z directions. If a driving force is applied to only one direction, both combined modes can be excited simultaneously. Adjusting the difference between the natural frequencies of the respective vibration modes changes the phase difference between the two modes.
Processing is performed so that the phase difference is extremely close to 90 °, and the long and short axes of the elliptical trajectories drawn by (the distal ends of) the outer legs are orthogonally oriented in the X and Z directions. This is important for noise-free detection of the mixed signal.

[0005] Other figures (b), (c) and (d) of FIG. 4 show the relationship between the drive mode and the detection mode. The right side of (b) shows the V mode component of the drive, and the right side shows the vibration speed and the angular velocity Ω by the drive when the vibrating body is rotated around the X axis.
This shows a state in which a Coriolis force Fcx proportional to the vector product of x has occurred. Coriolis force Fcx acting on projections of both outer legs
Makes the deflection of both outer legs different from that at the time of non-rotation, and a new HS mode is generated. If the additional deflection is obtained by a circuit processing, Ωx can be detected as a result. Although the Coriolis force Fcx is also generated on the middle leg, it is hard to generate new vibration in the axial direction and does not contribute to detection.

FIG. 4 (c) shows a V-mode component of the drive shown on the left side of the figure, when a rotational angular velocity Ωy about the Y-axis is applied, and additional Coriolis force Fcy is generated in both outer legs in the X direction. The state in which the HA mode is generated is shown on the right side. Since the Coriolis force Fcy acting on the middle leg oscillates the middle leg in the X direction, if the movement of the middle leg is detected piezoelectrically, Ωy
Is obtained. In (d), the left HS
The rotational angular velocity Ωz about the Z axis depends on the driving component of the mode.
Shows a state where an additional HA mode is generated by the Coriolis force Fcz generated in the Y direction on the projections of both outer legs when. Since the middle leg vibrates in the X direction to cancel the asymmetry of the movement of both outer legs in the HA mode, an output proportional to Ωz can be obtained by piezoelectrically detecting the movement of the middle leg.
In both cases (c) and (d), the center leg vibrates in the X direction. However, since the Coriolis force, which is the exciting force, has a phase difference of 90 °, the outputs are separated by performing synchronous detection at different phases. it can.

FIG. 5 is a sectional view showing the arrangement of electrodes on the side surface of the leg of a tripod tuning fork according to the prior art.
-A section. The material is assumed to be quartz, and the azimuths of the X, Y, and Z axes described above are basically made to coincide with the crystal axes of the quartz material. (Predetermined rotation may be performed to improve the characteristics.) Reference numeral 6 denotes an electrode film provided on the surface and side surface of each leg (shown floating above the leg surface), and E denotes an electric field generated inside the leg. Lead lines from each electrode film are connected as shown in the figure. GND is a ground terminal for applying a reference potential. Drv
Is a drive terminal, which is supplied with a sine wave of a constant voltage and drives both outer legs 3, 4 in the V mode. (The vibration of the HS mode is automatically generated by the coupling.)

[0008]

In this conventional example, the main dimensions of the tripod tuning fork are a plate thickness of 0.3 mm and a width of each leg of 0.3 mm.
mm, the middle leg length was 4.5 mm, the outer leg length was 4.2 mm, and the distance from the inside of the outer leg to the tip of the protruding portion was 0.8 mm. As a result of evaluating the results, it was found that, when Ωx and Ωz were measured, there was a signal leakage of about 3% at each output, and it was desirable to improve the use efficiency of the piezoelectric characteristics of the legs and improve the sensitivity. Was. Also, since the narrow leg width is divided into two and the narrower electrode film is juxtaposed, there is a concern about manufacturing problems. SUMMARY OF THE INVENTION An object of the present invention is to improve the electrode arrangement and driving method of a tripod tuning fork so that signal leakage in each direction is small and high sensitivity is obtained, and a small and advanced triangular tuning fork capable of multi-axis detection with one vibrator. An object of the present invention is to provide a vibrating gyroscope having practical utility.

[0009]

In order to achieve the above object, a vibration gyroscope according to the present invention has the following features. (1) The outline of a tripod type tuning fork is formed, and both outer legs each have a projection at the tip, and the Z axis is perpendicular to the tripod surface.
When the Y axis is taken in the direction parallel to the tuning fork axis and the X axis is taken in the direction perpendicular to the Z axis and the Y axis, both outer legs open and close simultaneously in the X direction. In the V mode where the middle leg is displaced in the opposite direction and the middle leg is displaced in the opposite direction,
Has the HA mode in which the center leg is displaced in the same direction and the middle leg is displaced in the opposite direction, and the HS mode and the V mode are given natural frequencies sufficiently close so that coupling occurs with each other. A vibrating body made of a piezoelectric material which is generated when the outer legs are driven so as to open and close in the X direction, the modes are simultaneously generated, and the outer legs are excited to perform an elliptical motion in the XZ plane. By performing synchronous detection of two systems in which a phase difference of 90 ° is given to an induced voltage based on the movement of the middle leg in the X direction detected by an electrode film provided around the middle leg. And separately detecting the components of the Coriolis force appearing due to the rotational movement of the vibrating body around the Y axis and the Z axis.

[0010] The vibration gyroscope of the present invention may further include at least one of the following features. (2) When the HS mode is excited, by detecting a change in the amount of bending of both outer legs, X of the vibrating body is detected.
Further detecting a component of the Coriolis force in the Y direction acting on the projection by the rotation about the axis. (3) The piezoelectric material of the vibrator is quartz.

[0011]

FIG. 1 shows a first embodiment of a vibrating body for a vibrating gyroscope according to the present invention, and FIG. 1 (b) is a plan view showing its shape (already described in connection with the prior art). FIGS. 3A and 3A are AA sectional views showing the arrangement of electrodes around the legs. In (a), the electrode film is provided on all four surfaces of each leg using the full width of the leg. The drive terminal Drv1 has a sine wave with a constant amplitude, and the drive terminal Drv2 has a sine wave with the same amplitude.
Since sine waves having phases different from each other by 80 ° are given, the outer legs 3 and 4 are driven in the X direction and the −X direction, and the HS mode is first excited, and the V mode vibration coupled thereto (the natural mode of both modes) The difference in frequency is adjusted in advance) and 90
Excited simultaneously with a phase difference of °.

The detection terminals Det1 and Det2 are connected to the X
Detects directional movement. Detection terminals Det3 and Det
Reference numeral 4 individually detects the movement of the outer legs 3 and 4 in the X direction, and can also serve as a terminal for extracting a feedback signal for a drive circuit (oscillation circuit). This electrode arrangement is close to the electrode arrangement of a general-purpose quartz tuning fork (two legs), and the electric field E inside the legs is also the same. Therefore, the electrode area is larger than that of the conventional example shown in FIG. 5 (it is not necessary to arrange a narrow electrode film on the same surface of the leg), it can be arranged on all surfaces around the leg, and the utilization efficiency is high (the internal electric field E is also strong). Probably, each leg is almost the same shape, and the manufacture is relatively easy because the conventional method can be used.

FIG. 2 is a block diagram showing an embodiment of a drive detection circuit for a vibration gyroscope according to the present invention. The drive circuit 24 includes detection terminals Det3 and Det4
(Not shown, but the charge amount is converted to a voltage through an IV converter. The same can be applied to other detection terminals. If necessary, an amplifier or the like is added to a key point). In response to the feedback signal obtained by the difference by the adder 28 (or one of which may be inverted before passing through the adder), a drive signal of a constant voltage whose timing is regulated is output and supplied to the drive terminal Drv1. The phase of this signal is inverted by an inverting amplifier circuit 25 and supplied to a drive terminal Drv2 to drive the tripod tuning fork in a mixed mode of V + HS.

The reference signal generation circuit 20 is supplied with a drive output, generates a reference signal (rectangular wave) having a predetermined phase for determining a period for performing synchronous detection, and adjusts circuits 21 and 22.
After finely adjusting the phase, the signals are supplied to the synchronous detection circuits 12 and 13. The reference signal whose phase has been converted by 90 ° by the 90 ° phase shift circuit 23 is supplied to the synchronous detection circuit 11. Detection terminal D
The sum signal (Ωy) of the adder 27 of et1 and Det2 by the adder 27
And information on Ωz) are input to the detection circuit 11, and the detection output from which only the Ωz information is extracted is LPF1.
4. The voltage is smoothed through the integration circuit 17 and output to the Zout terminal as a voltage proportional to Ωz. The added signal of the detection terminals Det1 and Det2 is also applied to the synchronous detection circuit 12, and the detection output (Ωy information) is converted to the LPF 15 and the integration circuit 18
And output to the Yout terminal as a voltage proportional to Ωy.

The difference signal between the detection terminals Det3 and Det4 includes the drive voltage and the Ωx information shown in FIG. This is synchronized with the synchronous detection circuit 13, the LPF 16, the integration circuit 1
9, the output of the driving circuit 24 is converted to DC and smoothed, and the output of the correction voltage generation circuit 26 is subtracted from the subtractor 2
9, only the component proportional to Ωx remains and is output to the Xout terminal. (Instead of detecting and converting the detection signal containing Ωx information to DC as in this example, and subtracting and correcting the drive component, the AC drive component whose phase and amplitude have been adjusted is subtracted from the signal before synchronous detection to obtain only the Ωx component. After that, synchronous detection may be performed.) In this manner, rotation angular velocity information of up to three axes can be obtained from a single vibrator. Of course, any two or one axis can be selected and output,
It is also possible to configure a two-axis gyroscope or a single-axis gyroscope.

FIG. 7 shows the output signal characteristics obtained by the first embodiment of the present invention and those of the conventional example combined in Tables 1 to 5 for easy comparison. . When Table 1 and Table 2 are compared, in the conventional example (Table 1), X
About 3% of Ωz and Ωx signals, which are not measurement targets, were mixed in out and Zout. About 1% of Ωz signal in Yout
Was mixed in. However, in Table 2 (the present invention), it can be seen that other signals are insignificantly mixed into any of the outputs (less than 1/10000), and that there is no problem at all. When the output sensitivities of the respective signals are compared according to Table 3 (conventional example) and Table 4 (the present invention), the present invention is significantly higher (22 to 60 times) in all of Ωx, Ωy, and Ωz. You can see that. Also, in Table 5 comparing the vibration amplitudes (one-sided amplitudes) of the tip of the outer leg in each direction of the elliptical motion, it can be seen that both the maximum displacement in the X direction and the maximum displacement in the Z direction of the present invention are greater than those of the conventional example. It can be seen that a much larger amplitude can be obtained, which is thought to be the reason for the significant improvement in sensitivity.

FIG. 6 is a sectional view showing a second embodiment of the electrode arrangement of a tripod tuning fork for a vibrating gyroscope according to the present invention. In the present embodiment, one electrode of one of the outer legs is replaced so that single-phase driving can be performed. That is, the drive terminal Drv1,
It is not necessary to provide the drive signal of the opposite phase to Drv2, and it is sufficient to provide a single sine wave. Therefore, the inverting amplifier circuit 25 in FIG. 2 becomes unnecessary. Also, detection terminals Det3, Det
An inverting circuit (not shown) for inverting and adding one of the signals to obtain the difference between the four signals is not required, and the circuit configuration can be simplified.

The embodiment of the present invention is not limited to the above-described example. Needless to say, there is room for various changes in the shape and dimensions of the tripod tuning fork, the material of the vibrating body, the structures of the electrode films and the lead wires, and the configurations of the drive circuit and the detection circuit.

[0019]

According to the present invention, since the outer legs are driven in the X direction to excite the coupling mode, the area of the electrodes can be increased and effectively used, and the structure of each leg can be similarly simplified. Manufacturing has become easier. The sensitivity has been dramatically improved, and mutual signal leakage during angular velocity detection has been extremely reduced. Therefore, there is obtained an effect that it is possible to provide a highly practical two-axis or three-axis multifunctional vibration gyroscope that can detect angular velocities of a plurality of axes using a single vibrator that is small and easily supported. .

[Brief description of the drawings]

FIG. 1 shows a first example of a vibrating body of a vibrating gyroscope according to the present invention.
(B) is a plan view showing a shape,
(A) is AA sectional drawing which shows the electrode arrangement | positioning of a leg.

FIG. 2 is a block diagram illustrating an embodiment of a drive detection circuit of the vibration gyroscope according to the present invention.

FIG. 3 is a schematic diagram for explaining four types of vibration modes of a tripod tuning fork.

FIG. 4A shows a driving mode of a vibration gyroscope,
(B), (c), (d) is a schematic diagram for explaining the relationship between the vibration modes used for driving and detection in each axis direction.

FIG. 5 is a sectional view showing an electrode arrangement of a conventional tripod tuning fork for a vibrating gyroscope.

FIG. 6 is a sectional view showing an electrode arrangement of a tripod tuning fork for a vibrating gyroscope according to a second embodiment of the present invention.

FIG. 7 is a table listing signal characteristics obtained by the present invention in comparison with those of a conventional example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Tripod tuning fork 2 Base 3, 4 Outer leg 5 Middle leg 6 Electrode film 11, 12, 13 Synchronous detection circuit 14, 15, 16 LPF 17, 18, 19 Integration circuit 20 Reference voltage generation circuit 21, 22, Adjustment circuit 23 90 ° Phase shift circuit 24 Drive circuit 25 Inverting amplifier circuit 26 Correction voltage generation circuit 27 Adder 28, 29 Subtractor Drv, Drv1, Drv2 Drive terminal Det1, Det2, Det3, Det4 Detection terminal GND Ground terminal E Electric field Fcx, Fcy, Fcz Coriolis Force U3, U4, U5 Leg velocity component X, Y, Z coordinate axes

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Norihiko Shiratori 1173 Kusakoshi, Oaza, Miyoda-cho, Kitasaku-gun, Nagano Prefecture Inside 1394 Micro Stone Co., Ltd. 1394 Micro Stone Co., Ltd. F term (reference) 2F105 BB02 BB03 BB13 BB15 CC01 CC06 CD02 CD06 CD11 CD13

Claims (3)

[Claims] 1. An outline of a tripod type tuning fork, both outer legs each having a projection at a tip end thereof, having a Z axis in a direction perpendicular to the tripod surface and a Y axis in a direction parallel to the tuning fork axis. When the X-axis is taken in a direction perpendicular to the Z-axis and the Y-axis, the HS mode in which both outer legs open and close simultaneously in the X-direction, and the two legs are displaced in the same direction in the Z-direction and the middle leg is opposite The vibration modes include a V mode in which the outer legs are displaced in the same direction and an HA mode in which both outer legs are displaced in the same direction in the X direction and the middle leg is displaced in the opposite direction.
The S mode and the V mode are given natural frequencies sufficiently close so that coupling occurs with each other, and when the outer legs are driven to open and close in the X direction, the two modes are simultaneously generated and the two modes are simultaneously generated. Both outer legs have a vibrating body made of a piezoelectric material that is excited so as to perform an elliptical motion in the XZ plane, and the outer leg has a movement in the X direction of the middle leg detected by an electrode film provided around the middle leg. By performing synchronous detection of two systems in which a phase difference of 90 ° is given to an induced voltage based on the induced voltage, components of Coriolis force appearing due to rotational motion of the vibrating body around the Y axis and the Z axis are separately detected. A vibratory gyroscope characterized by: 2. When the HS mode is excited,
2. A component of a Coriolis force in the Y direction acting on the protrusion due to a rotational movement of the vibrating body around the X axis by detecting a change in the amount of deflection of both outer legs. Vibratory gyroscope. 3. The vibrating gyroscope according to claim 1, wherein the piezoelectric material of the vibrating body is quartz.