JPH0748047B2 - Vibrating gyro - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a vibration gyro that detects Coriolis force for the purpose of detecting angular velocity.

[Conventional technology]

A conventional vibration gyro of this type is shown in FIG. 8, for example.

This is two arm members that extend parallel to each other in the Z-axis direction of the three-dimensional coordinate system and are positioned at a predetermined interval in the Y-axis direction.
A drive vibrator 7 formed by integrally connecting the lower end portions of 4,5 with a base portion 6 is fixed to a base 9 via a support rod 8 and is attached to the base portion 6 of the drive vibrator 7. , And is provided with a detecting means 10 projecting in the X-axis direction.

In such a vibrating gyro, for example, an AC voltage is applied to the driving means 11 and 12 to cause the arm members 4 and 5 to vibrate symmetrically in the Y-axis direction by a piezoelectric method, an electromagnetic method, or the like, while driving the driving vibrator 7. When it is rotated around the Z-axis at an angular velocity ω, each arm member 4 and 5 moving at a velocity V at a certain moment X,
Axial and mutually opposite Coriolis forces Fc are generated.

Here, since the speed V of the arm members 4 and 5 changes alternately,
The Coriolis force Fc is generated in a form modulated by the frequencies of the arm members 4 and 5, and the drive vibrator 7 is torsionally vibrated around the Z axis with respect to the base 9, and the torsion angle is , Coriolis force Fc and, in turn, proportional to angular velocity ω.

Therefore, in this conventional device, the magnitude of the torsional vibration is
The detection means 10 protruding in the X-axis direction is used for detection by a piezoelectric method, an electromagnetic method, or the like. For example, in a piezoelectric method using a bimorph element or the like, torsional vibration is converted into bending vibration of the detection means 10. However, the charge generated by the bimorph element is extracted as a voltage and detected according to the amount of bending.

[Problems to be Solved by the Invention]

However, in such a conventional technique, the vibration of the arm members 4 and 5 in the Y-axis direction of the base member 6 is caused by the unbalance of the mass and the length of the arm members 4 and 5. Detection means due to causing unwanted vibration
Since 10 will output a signal generated by the unnecessary vibration, even if the angular velocity ω is zero, a state as if the Coriolis force is detected, that is, an offset is generated, There is a problem in that the S / N ratio and, eventually, the detection sensitivity are lowered.

In order to reduce such an offset, a method is generally adopted in which the output of the detection means 10 is subjected to synchronous detection, rectification and converted into a direct current, and the remaining direct current component is added / subtracted to / from a separately provided reference voltage to make it zero. ing. However, with this method, the sensitivity of the detection means 10 changes subtly with changes in the ambient temperature, so it was practically impossible to sufficiently and effectively reduce the offset.

Moreover, in this conventional technique, the detection means 10 projects in the X-axis direction, which complicates the structure, increases the size of the device, and increases the cost of the device.

The present invention advantageously solves the problems of the prior art, and provides a vibration gyro having a simple structure, a small size, and a low cost, and a high sensitivity with an excellent S / N ratio.

[Means for Solving the Problems]

The vibrating gyroscope according to the present invention is particularly provided with a detecting means projecting in the Z-axis direction on the base portion of the drive vibrator including the two arm members and the base portion, and the detecting means is polarized in the two-axis directions. An electrode is provided on each of the opposing surfaces of the piezoelectric material parallel to the Z axis, and at least one of the electrodes is positioned so as to be offset to either side in the direction orthogonal to the Z axis. It is a thing.

[Action]

Now, as shown in FIG. 9, considering a case where a rectangular parallelepiped-shaped columnar member 14 projecting from the base 13 in the Z-axis direction is twisted by receiving a couple Mt, the cross section of the columnar member 14 is considered. The dimensions are
When 2b × 2h, the shear stress τw in the U direction and the shear stress τu in the W direction at an arbitrary point P (u, w) in the cross section as shown in FIG. Given in.

Here, when the electric displacement D generated when a stress T and an electric field E are applied to the piezoelectric material is expressed by an equation, If lead zirconate titanate is used as an example of the piezoelectric material, the electric displacement when only the stress T is applied is It is represented by. Here, the applied stresses T _{1 to} T ₆ are
It is assumed that the piezoelectric material is acting in the directions shown in FIGS. 11 and 12, and the piezoelectric material is polarized in the third axis direction as shown by the white arrow.

From this, for example, when electrodes are provided on the respective surfaces orthogonal to the first axis, the electrical displacement D _{1 in} the first axis direction is D ₁ = d ₁₅ T ₅ (5) Function as a detection means that generates electric charge in the electrode only by the shear stress T ₅ around the second axis and is insensitive to other stresses T ₁ , T ₂ , T ₃ , T ₄ , T ₆ . become.

Therefore, when the columnar member 14 shown in FIG. 9 is polarized in the Z-axis direction using a piezoelectric material, the electric displacement Dw in the U direction and the electric displacement Du in the W direction at the point P (u, w) are expressed by the formula (1), From equations (2) and (5), Given in.

By the way, as is clear from the equations (1), (2) and (6), (7), in the UW coordinate system in FIG.
Since the quadrant 17, the second quadrant 16 and the fourth quadrant 18 have different shear stresses τw, τu, and hence the respective electric displacements Dw, Du, from each other, the U direction in FIG. If electrodes are formed on the entire surfaces u ₁ and u ₂ orthogonal to
The electric displacement Dw becomes zero as a whole, and no charge is generated at the electrodes. Similarly, the respective surfaces w ₁ and w ₂ orthogonal to the W direction
Just forming the electrode on the whole of the
No charge based on Du is generated.

Therefore, in the present invention, when the detecting means is configured like the columnar member 14 shown in FIG. 9, in other words, like the support rod 8 shown in FIG. At least one of the electrodes provided on each of the opposite surfaces is arranged so as to be biased to one side orthogonal to the Z axis. For example, in order to generate electric charges by the electric displacement Du, the surfaces w ₁ , w _At least one of the electrodes provided in ₂ ,
It is placed so that it is biased toward the plane u ₁ or u ₂ .

Here, in order to effectively output the electric displacement Du, it is preferable to provide an electrode at a half of the center of the surface w ₁ or w ₂ as a boundary.

Thus, according to the present invention, it is possible to provide a small-sized and inexpensive vibration gyro with a simple structure, and
The detection sensitivity can be greatly improved by advantageously removing the influence of unbalance such as the mass and length of the arm member.

〔Example〕

 Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a perspective view showing an embodiment of the present invention, in which the same parts as those described in the prior art are designated by the same reference numerals.

That is, reference numerals 4 and 5 denote arm members that extend in parallel to each other in the Z-axis direction and are positioned at a predetermined interval in the Y-axis direction, and 6 indicates those arm members 4 and 5. Indicates a base portion integrally connected at the lower end portion, and 7 indicates a drive vibrator including the arm members 4 and 5 and the base portion 6.

Here, the detection means 21 is provided so as to project downward from the base portion 6 of the drive vibrator 7, and the base 9 is fixed to the lower end portion of the detection means 21 to form a vibration gyro.

Therefore, this vibrating gyro can be manufactured only by disposing the detecting means 21 in place of the supporting rod 8 described in the prior art, and therefore the structure of the device is simplified and the device itself. Will be sufficiently small and inexpensive.

Moreover, in this vibration gyro, the detection means 21 functions to detect the torsion moment Mt acting on the Coriolis force Fc caused by the generation of the Coriolis force Fc.
5 depends on its mass, length, and other imbalances,
Even if unnecessary vibration occurs in the Y-axis direction, it is possible to effectively prevent the influence of the vibration from leaking into the detection signal without using a special signal processing unit, and greatly improve the detection sensitivity. it can.

By the way, the detection means 21 which is applied in this way to detect the torsion moment Mt polarizes the piezoelectric material 1 having a rectangular parallelepiped shape in the Z-axis direction, as shown in the UWZ coordinate system in FIG. 2, for example. Together with the surface w ₁ , which is orthogonal to the W direction,
Both of the electrodes 19 and 20 provided on w ₂ may be arranged so as to be deviated to either side of the planes u ₁ and u ₂ orthogonal to the U direction, that is, the plane u ₁ direction in the figure. Therefore, the detection means 21 can detect the electric displacement Du in the region sandwiched by the electrodes 19 and 20 against the action of the torsion moment Mt.

In this example, it is possible to position both electrodes 19 and 20 so as to deviate to the surface u ₂ side, and one of the electrodes is
It is also possible to form over the entire surface of w ₁ or w ₂ .

FIG. 3 shows that, on the surfaces w ₁ and w ₂ of the piezoelectric material 1, electrodes 22 and 24, which are located deviated to the surface u ₁ side, and electrodes 23 and 25, which are located deviated to the surface u ₂ side, respectively, are shown. The detection means 21 is configured by arranging the electrodes. In this example, the electrodes 22 and 25 and the electrodes 23 and 24 generate electric charges having opposite polarities with respect to the torsion moment Mt.

Here, the respective electrodes shown in FIG. 2 and FIG.
It can be formed by applying a conductive film by vacuum vapor deposition, plating or the like and then performing photoetching, or can be formed by a lift-off method or another method.

Further, the detecting means 21 shown in FIG. 4 is formed by forming a groove extending in parallel with the Z axis at an appropriate depth in the approximate center of the surfaces w ₁ and w ₂ by a precision cutting machine or the like. , Surface w ₁ , w ₂
The electrodes formed in the above are divided into respective electrodes 26, 27, 28, 29, and in this example, the electric charges of opposite polarities are generated between the electrodes 26, 29 and the electrodes 27, 28 with respect to the torsion moment Mt. To do.

In this detection means 21, the electrode division processing can be mechanically performed in addition to the cutting processing of the piezoelectric material 1.
21 productivity can be greatly improved.

Further, FIG. 5 shows a detection means 21 which is a combination of two piezoelectric materials 1, which has a predetermined spacing in the U direction between the piezoelectric materials 1 whose polarization directions are opposite to each other. Placed on the surface of each piezoelectric material 1
The electrodes 30 and 31 are provided on w ₁ , and the electrodes 32 and 33 are provided on the surface w ₂ .

According to this, with respect to the torsion moment Mt, the electrodes 30 and 31 on the surface w ₁ side have the same polarity, and the electrodes 32 and 33 on the surface w ₂ side generate charges having the opposite polarity, respectively. , It becomes easy to connect the lead wires during assembly.

The detection means for detecting the electric displacement Du has been described above, but when detecting the electric displacement Dw, the surfaces u ₁ and u ₂ are
The detection means can be constructed by forming electrodes in the same manner as described above.

The detection means 21 is applied to the vibration gyro shown in FIG. 1 in the Z-axis direction of the drive vibrator 7 and the Z-direction of the detection means 21.
This can be done by attaching the detection means 21 to the drive vibrator 7 so as to match the axial direction, and in this case,
The X and Y axis directions of the XYZ coordinate system and the U and W directions of the UWZ coordinate system do not necessarily have to match.

In such a vibration gyro, as described in the prior art,
When an AC voltage is applied to the drive means 11 and 12 to cause the arm members 4 and 5 to vibrate symmetrically in the Y axis direction, the drive vibrator 7 is rotated around the Z axis at an angular velocity ω. , Coriolis forces Fc in opposite directions in the X-axis direction are generated on the respective arm members 4 and 5, and the drive oscillator 7 rotates around the Z-axis with respect to the base 9 by the Coriolis force Fc. It will twist and vibrate.

Therefore, here, based on the torsional vibration, the detection means
By detecting the torsion moment Mt acting on 21 by itself, the Coriolis force Fc can be obtained.

Here, when there is an imbalance between both arm members 4 and 5, the bending vibration as illustrated in FIG. 6 is likely to occur in the detecting means 21, but as described above, the detecting means 21
Since, in principle, it has no sensitivity to the stress caused by flexural deformation, it is possible to widen the tolerance range of the unbalance of the arm members 4 and 5, and greatly improve the production efficiency in mass production. You can By the way, when the detecting means 21 shown in FIG. 4 and a normal bimorph element are attached to a vibration gyro and the offset amounts are compared, the detecting means 21 can reduce the offset amount by about 30 dB. .

Moreover, in this vibrating gyro, since it is not necessary to project the detecting means 21 from the base portion 6 in the X-axis direction, the occupied space in the X-axis direction can be made sufficiently small, and the device can be downsized. It is possible to reduce the man-hours for assembling work effectively by making it simple.

FIG. 7 is a perspective view showing another embodiment of the present invention, in which the drive vibrator 7 is set in a posture opposite to that of the above-described embodiment for the purpose of reducing the occupied space in the Z-axis direction. The detection means 21 and the base 9 are provided between the respective arm members 4 and 5.

Also in this example, the detection means 21 can bring about the same effect as that of the above-mentioned embodiment.

〔The invention's effect〕

Thus, according to the present invention, the offset amount due to the imbalance of the respective arm members can be significantly reduced, so that the sensitivity of the device can be greatly improved and the allowable range of the imbalance can be expanded to increase the production efficiency. Can be effectively improved.

In addition, according to the present invention, by projecting the detecting means in the Z-axis direction, the occupied space in the X-axis direction can be reduced and the apparatus can be downsized, and the assembly work can be facilitated to sufficiently reduce the apparatus cost. Can be made.

[Brief description of drawings]

FIG. 1 is a perspective view showing an embodiment of the present invention, FIGS. 2 to 5 are perspective views each illustrating a detecting means, and FIG. 6 is a front view showing an influence of imbalance of each arm member. FIG. 7 is a perspective view showing another embodiment of the present invention, FIG. 8 is a perspective view showing a conventional example, and FIGS. 9 to 12 are views for explaining the operation principle of the present invention. . 1 ... Piezoelectric material, 4,5 ... Arm member, 6 ... Base portion, 7
...... Drive vibrator, 9 …… base, 19,20,23〜23 …… electrodes,
21 …… Detection means.

Claims (1)

[Claims] 1. Two arm members extending parallel to each other in the Z-axis direction of a three-dimensional coordinate system and positioned at a predetermined interval in the Y-axis direction, and one end portion of each of these arm members. A drive vibrator is configured with a base portion that is integrally connected, and the base portion of the drive vibrator is provided with detection means that projects in the Z-axis direction as the base portion support means. A pair of electrodes is provided on each of the opposing surfaces that are parallel to the Z axis of the piezoelectric material that is polarized in the direction, and at least one of the electrodes is provided in either of the directions orthogonal to the Z axis. A vibration gyro that is constructed by locating it so that it is biased to the side.