JP2000310534A - Angular velocity sensor - Google Patents

Abstract

(57) [Summary] [Object] An object of the present invention is to provide an angular velocity sensor which is reduced in size without lowering the angular velocity detection sensitivity. To achieve the object, when an AC voltage is applied to an excitation electrode, the first branch vibrates torsionally, and this vibration causes a pair of branches connected to the first branch to move in the ZX plane. Move repeatedly in parallel. In this state, when a rotational angular velocity acts around the X-axis, Coriolis force acts in the Y-axis direction, and as a result, a pair of branches vibrate with a component in the Y-axis direction. And
It is possible to configure an angular velocity sensor capable of detecting the magnitude of the rotational angular velocity acting around the X axis based on the amount of the extracted electric charge. By isolating the excitation electrode and the detection electrode (not arranging them on the same branch), it is possible to efficiently take out the angular velocity detection sensitivity even if the size is reduced, thereby solving the problem.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION Exciting motion of torsional vibration around a Y-axis by a vibrator using a quartz crystal is described by Z-axis in rectangular coordinates.
Angular velocity is detected by converting into bending vibration of the branch of the vibrator vibrating parallel to the X plane and detecting the XY plane direction component induced by the Coriolis force generated by rotation about the X axis. The present invention relates to an angular velocity sensor that operates.

[0002]

2. Description of the Related Art A vibrator vibrating along a predetermined direction,
For example, when a vibrator that is parallel to the orthogonal coordinate axis plane (ZX plane) and vibrates symmetrically with respect to the X axis rotates around the X axis, Coriolis force is generated in the Y axis direction of the vibrator. Since this Coriolis force is determined in proportion to the magnitude of the angular velocity, if the Coriolis force is directly measured as the amount of deflection displacement of the vibrator, directly by the piezoelectric effect of the piezoelectric element, capacitance change, etc. The magnitude of the rotational angular velocity acting around the X axis of the child can be obtained. It is also possible to detect the angular velocity when rotating around the Z axis, but this is not preferable because the vibration mode becomes the in-phase mode.

For this reason, a vibrating vibrator is mounted on a vehicle, an aircraft, or the like as an angular velocity detecting element, and its running or flight trajectory is recorded, and yaw rate generated at the time of turning is detected. Further, the angular velocity detecting element is mounted on a robot, and is applied to attitude control and the like.

FIG. 6 is a front view showing a main part of a conventional angular velocity sensor. As shown in FIG. 6, a conventional angular velocity sensor has:
When a vibrator branch vibrates in a predetermined direction and the angular velocity sensor is rotated around the Y axis, the Coriolis force generated in the direction perpendicular to the predetermined direction is generally obtained when the vibrator branch vibrates in a predetermined direction. Is detected, the magnitude of the rotational angular velocity acting around the Y-axis of the angular velocity sensor can be obtained.

[0005]

However, when considering the miniaturization of the sensor element, in the conventional method, the excitation electrode and the detection electrode, or the excitation electrode and the detection electrode, or the respective electrodes are separately formed in the branch portion on the same branch in the conventional method. However, when the surface area (branch surface) is small, it is difficult in terms of manufacturing technology,
In particular, the detection electrode area is inevitably reduced, and the angular velocity detection sensitivity is reduced.

[0006]

In order to solve this problem, the parts of the excitation electrode and the detection electrode are separated to ensure that at least the position of the detection electrode is at the effective portion where the vibration distortion induced by Coriolis force is the largest. It is possible to prevent a decrease in sensitivity, and to reduce noise due to signal crosstalk by remoteting the distance between two electrodes (excitation electrode and detection electrode).

In short, a first branch extending in the Y-axis direction, a second branch extending in the + X-axis direction at an angle of 60 degrees from the + X plane of the first branch, and the second branch X on the branch
The first vibrating element is provided with an AC voltage applied by a quartz resonator element having a third pair of branches arranged axially symmetrically and an excitation electrode formed on a branch surface of the first branch. Branch of Y
The second and third branches are vibrated with an amplitude parallel to the ZX plane by the excited vibration motion, and the roots of the second and third branches are excited. When the second branch and the third branch are repeatedly vibrated in parallel with the ZX plane by the detection electrode formed on the branch surface having the inclination of 60 degrees, When the element rotates around the X axis, the charge generated by the bending vibration due to the vibration component in the direction perpendicular to the ZX plane generated by the Coriolis force acting on the second branch and the third branch is extracted. An angular velocity sensor comprising a detection electrode.

In short, according to the present invention, when an AC voltage is applied to the excitation electrode, the first branch vibrates torsionally, and the vibration causes the second and third branches connected to the first branch to be Z-vibrated. -Reciprocate parallel to the X plane. In this state, when a rotational angular velocity acts around the X axis, Coriolis force acts in the Y axis direction orthogonal to the X axis, and as a result, the second branch portion and the third
Vibrates with a component in the Y-axis direction, charges generated by the vibration are extracted from the detection electrode, and the magnitude of the rotational angular velocity acting around the X-axis is detected based on the amount of the extracted charges.

According to a second aspect of the present invention, the second and third pair of branches forming the detection electrode are connected to the fourth branch on the opposite side of the first branch. By forming a pair of branch portions of the first portion and the fifth branch portion, the electrode area (the number of electrodes) of the detection electrodes is increased, thereby increasing the amount of electric charge generated by the vibration component in the Y-axis direction due to the Coriolis force. Thus, the detection sensitivity of the angular velocity sensor itself can be improved. The pair of branches of the second branch and the third branch, or the pair of the fourth branch and the fifth branch, are connected to a fulcrum (the first branch) in the torsional vibration of the first branch. (The position of the center of gravity of the branch portion: the node portion) is at an equal distance from each other and has a positional relationship in the opposite direction.

[0010]

Embodiments of the present invention will be described below with reference to the accompanying drawings. In each drawing, the same reference numeral indicates the same object. FIG. 1 is a perspective view of the present invention. In FIG. 1, A is a crystal resonator element, and a crystal resonator element A is a first branch A1, a second branch A2, and a third branch A.
3 A first branch A1 and a second branch A2 extending in the + X-axis direction with the base of the first branch having an inclination of 60 degrees and a first symmetrical positional relationship line-symmetric to the X-axis; The third branch portion A3 extending in the + X-axis direction at an angle of 60 degrees at the base of the branch portion is integrally formed by an etching process using a photolithography method.

In the crystal resonator element A, the direction parallel to the longitudinal direction of the first branch A1 is the Y-axis direction, and the direction parallel to the longitudinal direction of the second branch A2 and the third branch A3 is the same. The direction parallel to the + X-axis direction and the direction orthogonal to the XY plane is defined as the Z-axis direction. In addition, as shown in FIG. 2, a pair of branches arranged in the −X-axis direction of the branch A1 with respect to the (a pair of) second branch A2 and the third branch A3 extending in parallel in the + X-axis direction. When the fourth branch A4 and the fifth branch A5 are formed as the parts, and the detection electrodes are respectively disposed, the performance of detecting the Coriolis force can be further improved.

As shown in FIG. 4, the above is the case of the pair of branches (the second branch A2 and the third branch A3, or the fourth branch A4 and the fifth branch A5). 1 branch A1
Needless to say, the same detection effect can be obtained even with a combination in which the opening of 60 degrees from the root is set inside / outside.
The distance (a2) from the fulcrum O (the position of the center of gravity of the first limb: the node) in the torsional vibration of the first limb to the root of the limb A2, and from the fulcrum O to the root of the limb A3 Is the relationship of a2 = a3. Similarly, the distance (a4) from the fulcrum O to the root of the branch A4 and the distance (a5) from the fulcrum O to the root of the branch A5 are also a4 = a
There is a relationship of 5. However, here, it is not always necessary that a1 = a4.

The distance (a2) from the fulcrum O (the position of the center of gravity of the first limb: the node) to the root of the limb A2 in the torsional vibration of the first limb, and the limb from the fulcrum O to the limb A
It should be added that the distance (a3) to the root of No. 3 has a relationship of a2 = a3 in the sensor structure of the present embodiment shown in FIG.

As shown in the plan view of FIG. 3A, focusing on the first branch portion A1, the crystal unit element A thus configured is opposed to the branch portion A1 in the Z-axis direction. Branch surface A1
Excitation electrodes E1 are formed on the branch surfaces A13 and A14, which oppose the branch portions A1 and A12 in the X-axis direction. Also,
As shown in the plan view of FIG. 3B focusing on the second branch A2 (the position of the third branch A3 is axisymmetric to the branch A2), the vicinity of the base of the second branch A2 is shown. Detection electrodes E are provided on the branch surfaces A21, A22, A23, and A24 of the portion inclined at 60 degrees.
Form 2

Then, an AC voltage (excitation vibration signal) is applied to the excitation electrode E1 formed on the first branch A1, and the first branch A1 is torsionally vibrated. Due to the excited vibration, the second branch A2 and the third branch A3 move repeatedly while bending and vibrating with an amplitude parallel to the ZX plane. Although the excitation electrode E1 is disposed on the branch surfaces A11 and A12 of the branch portion A1 facing the Z-axis direction and the branch surfaces A13 and A14 of the branch portion A1 facing the X-axis direction, the excitation effect is larger, although FIG. As shown in (1), the first branch A1 can also be torsional vibrated even if the first branch A1 is arranged on the branch surfaces A11 and A12 facing the Z-axis direction of the branch A1.

Here, when the crystal oscillator element A rotates around the X axis, the Y element is applied to the crystal oscillator element A by Coriolis force.
An axial vibration component is generated, and the second branch A2 and the third branch A3 flex and vibrate with the Y-axis component. This Y
Due to the bending vibration caused by the axial component, electric charges are generated in the second branch portion A2 and the third branch portion A3 in a magnitude proportional to the rotational angular velocity and in a form in which the phase varies depending on the rotation direction. A voltage signal corresponding to the Coriolis force is obtained from E2. From the magnitude of the voltage signal, the magnitude of the rotational angular velocity acting around the X axis can be known.
Further, by comparing the phase of the waveform of the voltage signal with the phase of the waveform of the excitation vibration signal, it is possible to know the direction of the rotational angular velocity based on the lead / lag of the phase.

A first branch extending in the Y-axis direction of the piezoelectric body, which is a feature of the present invention, and a pair of the first branch A1 extending in the X-axis direction at an angle of 60 degrees at the base. A branch (a second branch extending in the + X-axis direction with the base of the first branch having a tilt of 60 degrees, and + X from the first branch in line symmetry with the second branch and the X axis) The “tilt of 60 degrees at the base” in the crystal resonator element A having the third branch portion extending with an inclination of 60 degrees in the axial direction means that the crystal as the sensor element material is a trigonal crystal. , From a crystallographic perspective,
When a plane perpendicular to the Z axis of the quartz crystal (Z plane: this coincides with the Z plane in shape) is viewed from above, three X axes at 120 degrees (X plane)
1, X2, X3), and the longitudinal direction of the portion inclined at 60 degrees coincides with the respective Y-axis (Y1, Y2, Y3) directions.

Therefore, the detection electrode is attached to this part,
When a rotation is given around the X axis as viewed from the top, the generated Coriolis force acts in the X axis direction when viewed from the crystallographic axis. Indeed, it is possible to efficiently trap the charge generated on the crystallographic X plane (perpendicular to the X axis) due to refraction vibration caused by expansion and contraction in the crystallographic Y axis direction.

When the second branch A2 and the third branch A3 are paired symmetrically with respect to the X axis, or the fourth branch A
When the fourth and fifth branch portions A5 are paired in line symmetry with respect to the X axis, the paired branch portions must be equidistant from the fulcrum O in the torsional vibration in opposite directions. And

[0020]

According to the present invention, when an AC voltage is applied to the excitation electrode, the first branch vibrates in a torsional manner, and this vibration causes a pair of branches connected to the first branch to form a ZX plane. Move repeatedly in parallel to. In this state, when a rotational angular velocity acts around the X-axis, Coriolis force acts in the Y-axis direction, and as a result, a pair of branches vibrate with a component in the Y-axis direction. Thus, it is possible to configure an angular velocity sensor that can detect the magnitude of the rotational angular velocity acting around the X axis based on the amount of the extracted electric charge. In addition, by separating the excitation electrode and the detection electrode (not arranged on the same branch), it is possible to efficiently extract the angular velocity detection sensitivity even if the size is reduced.

[Brief description of the drawings]

FIG. 1 is a perspective view of an angular velocity sensor according to the present invention.

FIG. 2 is a perspective view showing another embodiment of the present invention.

FIG. 3 is a plan view illustrating a main part branch of the present invention.

FIG. 4 is a perspective view showing another embodiment of the present invention.

FIG. 5 is a partial sectional view of a first branch showing a position where an excitation electrode of the present invention is formed.

FIG. 6 is a perspective view of a conventional angular velocity sensor.

[Explanation of symbols]

 A Quartz Crystal Resonator Element A1 First Branch A2 Second Branch A3 Third Branch E1 Excitation Electrode E2 Detection Electrode O Supporting Point of First Branch

Claims (3)

[Claims] A first branch extending in the Y-axis direction; a second branch extending in the + X-axis direction at an angle of 60 degrees from a + X plane of the first branch; An AC voltage is applied by a quartz resonator element having a third pair of branches arranged symmetrically in the X-axis on the branches, and an excitation electrode formed on a branch surface of the first branches. The first branch portion is excited torsionally vibrating around the Y axis, and the excited vibrational motion causes the second and third branch portions to vibrate with an amplitude parallel to the ZX plane. The second branch and the third branch are repeatedly vibrated in parallel with the ZX plane by the detection electrode formed on the branch surface having a 60 ° inclination at the root of the third branch. When the crystal resonator element rotates around the X axis,
And a detection structure for extracting a charge generated by bending vibration caused by a vibration component in a direction perpendicular to the ZX plane generated by Coriolis force acting on the third branch. Angular velocity sensor. 2. The second branch portion, wherein the second branch portion is parallel to the X-axis which is a longitudinal direction of the second branch portion and the third branch portion, and the first branch portion is interposed between the second branch portion and the third branch portion. -X which is in the opposite direction to the branch 3
An angular velocity sensor comprising two pairs of a fourth branch in the axial direction and a fifth branch arranged symmetrically with the X-axis on the fourth branch. 3. The pair of branches of the second branch and the third branch according to claim 1, or the pair of branches of the fourth branch and the fifth branch according to claim 2, respectively. An angular velocity sensor equidistant about a fulcrum of torsional vibration of the first branch portion and in a positional relationship in an opposite direction.