JPH10185582A - Angular velocity sensor and its vibration method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To-detect an angular velocity around two axes with a single angular velocity sensor without providing a vibrating device. SOLUTION: A vibration-type angular velocity sensor 30 is constituted of a diaphragm part 20, a support part 21, and a weight part 22. The diaphragm part 20 is vibrated by sound waves or vibration given externally. When an angular velocity around an X axis is applied to the vibration-type angular velocity sensor while the diaphragm part 20 is subjected to resonance vibration in Z direction, a force in Y direction that is proportional to the angular velocity is generated at the weight part 22, thus vibrating in Y direction in synchronization with the resonance vibration in Z direction. Similarly, when an angular velocity around Y axis is applied, a force in X direction that is proportional to the angular velocity is generated at the weight part 22, thus vibrating in X direction in synchronization with the resonance vibration in Z direction. A distortion generated due to the vibration in X direction or Y direction is detected by a distortion detection element 13 at the diaphragm part 20, and the direction and the size of the angular velocity around X axis and Y axis are detected based on the output.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to an angular velocity sensor and a method of exciting the same.

[0002]

2. Description of the Related Art FIG. 8 is a perspective view showing a conventional vibration type angular velocity sensor device.

The vibrator 50 includes a fixed portion 51 extending in one direction and a beam portion 52 extending in a direction perpendicular to the fixed portion 51 and connected to the fixed portion 51. The fixing portion 51 and the beam portion 52 are integrally formed of, for example, silicon. The fixing part 51 supporting the beam part 52 is fixed to the glass substrate 53. A concave portion is formed in a portion of the glass substrate 53 facing the beam portion 52. A fixed electrode 54 is provided on the entire bottom surface of the concave portion formed in the glass substrate 53.
Since the beam 52 is made of silicon, it has conductivity and forms a movable electrode. There is a gap between the lower surface of the beam 52 and the fixed electrode 54, and a capacitor is formed by the lower surface of the beam 52 and the fixed electrode 54.

On the glass substrate 53, a fixed electrode for vibration is also provided.
58A and 58B are provided on both sides of the beam portion 52 along the longitudinal direction of the beam portion 52, respectively. Beam 52,
A gap is also provided between the excitation fixed electrodes 58A and 58B. One side of beam 52 and fixed electrode for vibration
58A, the other side surface of the beam portion 52, and the fixed electrode for vibration 58B also constitute capacitors.

[0005] The glass substrate 53 is also provided with a vibration device 57. The above-mentioned glass substrate 53, vibrator 50, fixed electrode
The angular velocity sensor 60 is constituted by the vibration fixed electrodes 58A, 58B and the vibration device 57.

The longitudinal direction of the beam 52 is defined as the X direction,
The longitudinal direction of 51 is the Y direction. A direction perpendicular to both the X direction and the Y direction is defined as a Z direction. Beam 52 is in Y direction and Z
Vibrates in the direction.

A vibration device provided on the side surface of the glass substrate 53
Due to 57, vibration in the Y direction having a frequency equal to the resonance frequency of the beam portion 52 is applied to the vibrator 50. This causes the beam 52 to resonate and vibrate in the Y direction. Since the beam portion 52 forms a movable electrode, the capacitance between the beam portion 52 and the vibrating electrodes 58A and 58B on both sides of the beam portion 52 changes due to the vibration of the beam portion 52 in the Y direction. The vibration frequency of the beam 52 is detected based on the change in the capacitance between these electrodes. The detected vibration frequency is used to control the vibration frequency of the vibration device 57 so that the beam vibrates at the resonance frequency, and is used as a parameter for calculating the angular velocity.

When the entire vibration type angular velocity sensor 60 is rotated around the X axis while the beam portion 52 of the vibrator 50 is vibrated by the vibration device 57, the beam portion 52 also vibrates in the Z direction. This vibration in the Z direction is due to Coriolis force.
Due to the vibration of the beam 52 in the Z direction, the capacitance between the beam (movable electrode) 52 and the fixed electrode 54 changes. Based on this change in capacitance and the vibration frequency of the beam,
The direction and magnitude of the angular velocity about the X axis are detected.

In order to obtain an angular velocity using such a conventional vibration type angular velocity sensor, it is necessary to vibrate the vibrator to cause the vibrator to vibrate (generally resonate).
Therefore, a vibration device for vibrating the vibrator was indispensable for the angular velocity detecting device including the conventional vibration type angular velocity sensor. For this reason, the overall size of the angular velocity detecting device becomes large, and it is difficult to reduce the size.

Further, a conventional single vibration type angular velocity sensor has one of three directions of X, Y and Z orthogonal to each other.
Is to detect only the angular velocity of rotation about the direction of. For this reason, two angular velocity sensors are required to determine an angular velocity in a two-dimensional direction (angular velocity of rotation about two orthogonal axes), and three angular velocity are required to determine an angular velocity in a three-dimensional direction.
An angular velocity sensor is required, and the angular velocity detecting device is further increased in size.

[0011]

DISCLOSURE OF THE INVENTION It is an object of the present invention to provide an angular velocity sensor which does not require a vibrating device and is therefore miniaturized.

Another object of the present invention is to detect angular velocities around two different axes orthogonal to the normal line of the diaphragm by one angular velocity sensor.

According to a method of exciting an angular velocity sensor according to the present invention, the angular velocity sensor is provided on a diaphragm, a support for supporting the entire periphery of the diaphragm, a weight provided on the diaphragm, and a diaphragm. The angular velocity sensor is constituted by a strain / stress detecting element, and this angular velocity sensor is arranged at a place where a sound wave for exciting the diaphragm propagates or on a vibrating body.

Since a thin diaphragm whose periphery is supported is used, and the diaphragm is provided with a weight portion, the diaphragm can be used regardless of minute vibration such as air vibration, mechanical vibration, or the like. Can be excited. Since no vibrating device is required, the size of the sensor device using the vibration type angular velocity sensor can be reduced, and the production cost of the device can be reduced.

An angular velocity sensor according to the present invention comprises a diaphragm, a support for supporting the entire periphery of the diaphragm, a weight provided on the diaphragm, and a strain / stress detecting element provided on the diaphragm. The above-mentioned strain / stress detecting element is arranged so as to detect vibration components parallel to two different axes orthogonal to the normal line of the diaphragm portion and parallel to the plane of the diaphragm portion.

In one embodiment, the weight is provided at the center of the diaphragm, and the shape of the diaphragm is line-symmetric with respect to the two different axes.

The diaphragm is vibrated by sound waves or vibrations given from the outside as described above. Given a rotation about an axis perpendicular to this direction of vibration and orthogonal to one of the two axes, a vibration component on either of the two axes and parallel to the plane of the diaphragm Occurs. This vibration component is detected by the strain / stress detection element, and the given angular velocity of rotation is obtained based on the detection signal.

Thus, according to the present invention, the direction and magnitude of each of the angular velocities around the two axes can be detected. The direction and magnitude of angular velocity around two axes can be detected by a single angular velocity sensor without using a plurality of angular velocity sensors. Therefore, the size of the sensor device can be reduced. It goes without saying that the angular velocity around one axis can be detected.

Preferably, the thin film portion is circular. Since the circular thin film portion has high responsiveness of deformation to the applied angular velocity, the sensitivity of detecting the angular velocity can be improved.

In one embodiment, the strain / stress detecting element is a piezo element or a piezoelectric element.

[0021]

FIG. 1 is a perspective view showing a vibration type angular velocity sensor. FIG. 2 is a sectional view taken along the line II-II of FIG. In FIG. 2, the thickness of the nitride film constituting the diaphragm and the members constituting each of the strain detection sections are emphasized to be thicker for the convenience of drawing and for easy understanding. This is the same in the cross-sectional views of the sensor in FIGS. 5 and 6 described later.

The vibration type angular velocity sensor 30 includes a square diaphragm portion 20, a support portion 21 for supporting the diaphragm portion 20 over the entire circumference thereof, and a weight portion 22 which is located at the center of the diaphragm portion 20 and is joined to the lower surface thereof. It is composed of The support 21 is a square frame. Support part 21 and weight part 22
Is formed of, for example, silicon. Support 21
The nitride film 11 (e.g.,
A portion of the nitride film 11 existing inside the support portion 21 constitutes the diaphragm portion 20. The nitride film 11 is formed by depositing SiN on a silicon substrate as described later or by nitriding the surface of the silicon substrate.

The support 21 is generally fixed and accommodated in a stem (package), or fixed on a circuit board. At this time, the weight 22 is separated from the bottom surface of the stem. The stem containing the vibration type angular velocity sensor 30 is
Arms, video cameras, automobiles, other machine tools,
It is fixed to the object whose angular velocity is to be detected, such as equipment.

On the surface of the vibration type angular velocity sensor 30, strain detecting sections 40a, 40b, 40c and 40d are provided at the center of each side. Strain detectors 40a, 40b, 40
c and 40d each include a strain detection element 13. The strain detecting element 13 is provided on the periphery of the diaphragm section 20 and on the center of each side. The strain detecting element 13 extends from the periphery of the diaphragm 20 toward the center,
The shape is bent at a right angle and returns to the periphery of the diaphragm portion 20 again. The strain detecting element 13 is, for example, a piezoresistive element. In this case, the resistance of the strain detecting element 13 changes due to the deformation of the diaphragm 12. Both ends of the strain detecting element 13 are connected to bonding pads 15 formed on the support 21 through a wiring pattern 14, respectively.
Further, it is connected to an angular velocity detection circuit (not shown) through a wire bonded to the bonding pad 15. The wiring pattern 14 is covered with a protective film 16 (for example, aluminum oxide).

As the strain detecting element 13, a piezoelectric element may be used. PZ for the material of the piezoelectric element (for example, piezoelectric thin film layer)
T (lead zirconate titanate), BaTiO ₃ (barium titanate) and the like are used. A voltage is induced in the piezoelectric element by the deformation of the diaphragm 12.

FIG. 3 schematically shows the vibration state of the diaphragm of the vibration type angular velocity sensor.

There are various methods for exciting the diaphragm of the angular velocity sensor. One is by sound waves. Noise from a machine tool, a vehicle engine, or the like propagates in the air and vibrates the diaphragm section 20 (see FIG. 3A). Since the diaphragm section 20 of the vibration type angular velocity sensor 30 is formed of the nitride film 11 having a thin elasticity, vibration is generated by propagation of minute vibration such as air vibration. The other is vibration by vibration. In this case, the angular velocity sensor 30 is fixed directly on a vibration source (motor of a machine tool, engine of a vehicle) or on a member to which vibration by the vibration source propagates (FIG. 3B). reference).

Since the weight of the diaphragm portion 20 is provided at the center of the lower surface thereof, the diaphragm portion 20 vibrates in a direction substantially perpendicular to the diaphragm surface when vibration is applied from the outside. When the inherent frequency (resonance frequency) of the diaphragm section 20 matches the frequency (frequency) of air vibration or mechanical vibration transmitted to the diaphragm section 20, the diaphragm section 20 resonates.

The resonance frequency of the diaphragm portion 20 is determined by the size of the surface of the diaphragm portion 20, the thickness of the nitride film used for the diaphragm portion 20, or its tension (the degree of film adhesion).
And the like can be adjusted. The diaphragm section 20 is designed so as to have a resonance frequency corresponding to a frequency band of sound waves from a motor or an engine or vibrations caused by the sound waves.

The direction connecting the strain detectors 40a and 40b is defined as the X direction. The direction connecting the strain detectors 40c and 40d is defined as the Y direction. A direction orthogonal to the X direction and the Y direction is defined as a Z direction.

FIG. 4 schematically shows a state in which an angular velocity around the X axis is applied to the vibration type angular velocity sensor.

In a state where the diaphragm section 20 is vibrated in the Z-direction by resonance, the vibration-type angular velocity sensor 30 is set with the X-direction as an axis (X
When an angular velocity (around the axis) is applied, a force in the Y direction (Coriolis force) proportional to the applied angular velocity is generated in the weight portion 22.

Since the diaphragm portion 20 has elasticity, the weight portion 22 vibrates in the Y direction, and this vibration is synchronized with the resonance vibration in the Z direction. Strain occurs in the diaphragm portion 22 in accordance with the vibration of the weight portion 22.

The Coriolis force acting on the weight 22 in the Y direction is mainly detected by the strain detecting sections 40c and 40d formed along the Y direction of the diaphragm section 20. Based on the detected direction and magnitude of the Coriolis force, the direction and magnitude of the angular velocity of the vibration type angular velocity sensor 30 around the X axis can be calculated.

Similarly, when an angular velocity around the Y direction (around the Y axis) is applied to the vibration type angular velocity sensor 30 in a state where the diaphragm section 20 is resonated and vibrated in the Z direction, the weight section 22 is proportional to the angular velocity. X-direction force (Coriolis force) is generated, and vibrates in the X direction in synchronization with the resonance vibration in the Z direction.

The Coriolis force acting on the weight portion 22 in the X direction is mainly detected by the strain detecting portions 40a and 40b formed along the X direction of the diaphragm portion 20. Based on the direction and magnitude of the detected Coriolis force, the direction and magnitude of the angular velocity of the vibration type angular velocity sensor 30 around the Y axis can be calculated.

In this manner, the vibration type angular velocity sensor 30 can detect the direction and magnitude of the angular velocity around the X axis and the direction and magnitude of the angular velocity around the Y axis by one angular velocity sensor.

According to the angular velocity around the X-axis, the strain detectors 40a and 4a formed along the X-axis
The electrical signal extracted from 0b may change slightly, but this can be ignored or the simulation can be performed by giving various angular velocities in advance, and the final Can be calculated. The influence on the strain detectors 40c and 40d due to the angular velocity around the Y axis can be dealt with in the same manner.

FIGS. 5 and 6 show the steps of manufacturing the vibration type angular velocity sensor shown in FIGS. 1 and 2. FIG.

A silicon substrate 10 is prepared.
A nitride film (SiN film) 11 is deposited on the upper and lower surfaces of 10 (FIG. 5A), or the surface of the silicon substrate 10 is nitrided. The nitride film 11 deposited on the upper surface of the silicon substrate 10 constitutes the diaphragm section 20 of the vibration type angular velocity sensor. On the other hand, the nitride film 11 deposited on the lower surface
It becomes a mask for etching.

On the upper surface of the silicon substrate 10 on which the nitride film 11 is deposited, four strain detecting elements 13 are provided at positions corresponding to the periphery of the portion where the diaphragm portion 20 is to be formed (FIG. 5B). .

A wiring pattern 14 and a bonding pad 15 are formed so as to partially overlap each of the ends of these four strain detecting elements 13 and extend in the direction of the part to be the support part 21 (FIG. 5 ( C)).

Except for the central part of the bonding pad 15, a protective layer 16 is deposited on a part of the strain detecting element 13, the wiring pattern 14, and the part extending from the bonding pad 15 to the end of the nitride film (FIG. 5). (D)). For example, aluminum oxide is used for the protection layer 16 to prevent the wiring pattern 14 from breaking. When mounting the vibration type acceleration sensor, a wire is bonded to the central portion of the bonding pad 15 where the protective layer 16 is not deposited. Through this wire, the strain detecting element 13 and an angular velocity detecting circuit (not shown) are electrically connected.

A silicon substrate is used as an etching mask
Further, a nitride film 11a is deposited on the upper surface of FIG. 10 (FIG. 6 (A)
).

Nitride film deposited on lower surface of silicon substrate 10
Of the portion 11, the nitride film 11 in the portion where the weight portion 22 is to be formed is removed, and isotropic etching is performed. As a result, the nitride film 11
The portion of the silicon substrate 10 from which is removed is vertically cut off halfway (FIG. 6B).

The nitride film 11 is deposited again in the recess formed by the isotropic etching (the portion where the weight 22 is formed). Thereafter, the nitride film 11 in a region where the diaphragm section 20 is to be formed is removed, and anisotropic etching is performed. As a result, the silicon substrate 10 is shaved from the lower surface in a mesa shape, and a diaphragm portion 20 is formed by the nitride film 11 (FIG. 6C).

Finally, the nitride film 11a deposited on the upper surface of the silicon substrate is removed (FIG. 6D).

In the manufacturing process of the vibration type angular velocity sensor 30 shown in FIGS. 5 (A) to 5 (D) and FIGS. 6 (A) to 6 (D), a large number of the same vibration type The angular velocity sensors can be formed by regularly arranging them. When this wafer is divided by dicing, individual vibration type angular velocity sensors 30 are completed.

FIG. 7 is a perspective view showing another example of the vibration type angular velocity sensor. The same components as those shown in FIG. 1 are denoted by the same reference numerals, and redundant description will be avoided.

The vibration type angular velocity sensor 30A differs from the vibration type acceleration sensor 30 shown in FIG. 1 in that the diaphragm formed by a nitride film has a circular shape. The direction connecting the strain detectors 40a and 40b and the direction connecting the strain detectors 40c and 40d pass through the center of the weight 22, but need not necessarily be orthogonal. It is also possible to detect angular velocities around two axes that intersect at an angle other than a right angle.

Since the entire periphery of the circular diaphragm portion 20A is uniformly supported by the support portion 21A, both the vibration in the X direction and the vibration in the Y direction have a high response to the applied angular velocity and a large amplitude. For this reason, the sensitivity to the applied angular velocity is good, and a minute change in the angular velocity can be detected.

[Brief description of the drawings]

FIG. 1 is a perspective view of a vibration type angular velocity sensor.

FIG. 2 is a sectional view taken along the line II-II shown in FIG.

FIGS. 3A and 3B are schematic diagrams showing a state in which a vibration type angular velocity sensor is excited.

FIG. 4 schematically illustrates a vibration-type angular velocity sensor that rotates around an X direction.

5 (A), (B), (C) and (D) show manufacturing steps of a vibration type angular velocity sensor.

6 (A), (B), (C) and (D) show manufacturing steps of a vibration type angular velocity sensor.

FIG. 7 is a perspective view showing another embodiment of the vibration type angular velocity sensor.

FIG. 8 is a perspective view of a conventional vibration type angular velocity sensor.

[Explanation of symbols]

 13 Strain detecting element 14 Wiring pattern 15 Bonding pad 16 Protective layer 20, 20A Diaphragm 21 Support 22 Weight 30, 30A Vibration type angular velocity sensor 40a, 40b, 40c, 40d Strain detector

Claims (3)

[Claims] A diaphragm portion, a support portion for supporting the entire periphery of the diaphragm portion, a weight portion provided on the diaphragm portion, and a strain / stress detecting element provided on the diaphragm portion. An angular velocity sensor wherein the stress detecting element is arranged to detect vibration components parallel to two different axes orthogonal to the normal of the diaphragm and parallel to the plane of the diaphragm. 2. The angular velocity sensor according to claim 1, wherein the weight portion is provided at the center of the diaphragm portion, and the shape of the diaphragm is line-symmetric with respect to the two different axes. 3. An angular velocity sensor comprising a diaphragm, a support for supporting the entire periphery of the diaphragm, a weight provided on the diaphragm, and a strain / stress detecting element provided on the diaphragm. A method of exciting an angular velocity sensor, wherein the angular velocity sensor is arranged on a place or on a vibrating body where a sound wave for exciting the diaphragm propagates.