JPH11304495A - Rotary angular velocity sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a rotary angular velocity sensor which has good measuring accuracy because of a structure which is strong against vibrations although being simple and which stably supports a vibrating body. SOLUTION: The support part of a rotary angular velocity sensor which supports a vibrating body 11 comprises a first support beam 20 whereby the vibrating body 11 is supported in such a way as to be capable of vibrating in the transverse direction, a beam support part 21 supporting the first support beam 20, and a second support beam 22 supporting the beam supporting part 21 and enabling the vibrating body 11 to vibrate in a direction perpendicular to the transverse direction, and is thus formed into a less curved simple shape.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an angular velocity sensor used for detecting the angular velocity of a rotating body, and more particularly, to a rotational angular velocity sensor used for an apparatus which detects the angular velocity and controls the movement and attitude of the rotating body. It is about.

[0002]

2. Description of the Related Art A rotational angular velocity sensor (for example, a gyroscope or a yaw rate sensor) is in great demand as a sensor necessary for a vehicle stability control system of an automobile, a navigation system, a camera shake prevention of a small video camera, and the like.

A wide variety of sensors have been developed so far, such as a mechanical gyro having a rotating sphere or a top, and a fiber gyro using an optical fiber.

[0004] Mechanical gyros and optical fiber gyros have high accuracy but tend to be large in size.

[0005] On the other hand, a piezoelectric gyro in which a piezoelectric element is attached to a triangular prism or cylindrical material to reduce its size has been commercialized. However, it is necessary to combine small parts that require precision processing, which makes it difficult to manufacture the piezoelectric gyro. Therefore, there is a problem that it is difficult to make a circuit-integrated type since it is made up of individual components. In order to address this problem, research and development of a small gyroscope using micromachining technology using a conventional silicon semiconductor process technology have been actively performed. With this technology, it is expected that sensors can be mass-produced inexpensively and that the sensor unit and the peripheral circuit unit can be integrated.

The basic operation principle of an angular velocity sensor using such micromachining technology will be described with reference to the example disclosed in US Pat. No. 5,349,855.
This will be described below.

Generally, the principle of the angular velocity sensor is that an angular velocity around a second axial direction perpendicular to the first axial direction is given to a rotating or inertial body (vibrating body) which is constantly vibrated in the first axial direction. At this time, the angular velocity is detected by detecting a Coriolis force generated in a third axis direction orthogonal to the first axis and the second axis.

[0008] The Coriolis force can be known by measuring the displacement of the inertial body. The angular velocity sensor of the above example includes a vibrating body, a supporting structure supporting the vibrating body, a driving unit of the vibrating body, and a displacement detecting unit based on Coriolis force.

The vibrating body is separated from the substrate by a support beam having an appropriate shape, and is electrostatically driven using a comb-like electrode. The vibration direction is a direction parallel to the substrate. In this state, when a rotation is applied to the vibrator about an axis which is also parallel to the substrate and perpendicular to the vibration direction, the vibrator is displaced in a direction perpendicular to the substrate by Coriolis force.

[0010] This displacement is detected as a change in capacitance using an electrode arranged on the substrate below the vibrating body, and the Coriolis force is measured.

Another example is an angular velocity sensor manufactured using micromachining technology, in which a drive electrode and a displacement detection electrode are provided in a plane parallel to a substrate, and the vibrating body is movable only in this plane. , JP-A-09-11994
No. 2 discloses this.

[0012]

However, as described in the above-mentioned U.S. Pat. No. 5,349,855, the angular velocity sensor in which the displacement of the vibrating body due to the Coriolis force is in a direction perpendicular to the substrate works well in a vacuum, When used in the atmosphere on the premise of an inexpensive package, the vibrating body is affected by viscous resistance due to air when it is displaced in the direction perpendicular to the substrate, making the vibration direction of the vibrating body unstable and lowering sensitivity. The problem of doing it fit.

The angular velocity sensor described in Japanese Patent Application Laid-Open No. 09-119942 has a sensor structure capable of increasing the mass of the vibrating body. There is a problem that the shape of the support portion as a means for temporarily supporting becomes complicated, stress tends to be concentrated on the support beam when the vibrating body vibrates, and as a result, the support portion is easily broken.

SUMMARY OF THE INVENTION An object of the present invention is to propose a structure which has a simple structure, is strong in vibration, and stably supports a vibrating body. As a result, a rotational angular velocity sensor having high measurement accuracy is provided. Is to provide.

[0015]

Means for Solving the Problems In order to achieve the above object, a feature of the rotational angular velocity sensor according to the present invention is that two supporting beams for independently vibrating the vibrating body of the rotational angular velocity sensor in two axial directions are provided. And a beam support portion that supports one support beam and is supported by the other support beam.

Specifically, the present invention provides the following angular velocity sensor.

According to the present invention, a voltage is applied between a vibrating body provided with a comb-shaped movable electrode, a supporting portion for oscillating the vibrating body, and the comb-shaped movable electrode. A rotational angular velocity sensor having a driving fixed electrode for driving a vibrating body, and a displacement detecting fixed electrode for detecting a displacement of the vibrating body generated in a direction different from a direction in which the vibrating body is driven by the driving fixed electrode. In the said support part,
A first support beam that supports the vibrating body so as to be capable of vibrating in a lateral direction, a beam supporting portion that supports the first supporting beam, and a beam supporting portion that supports the beam supporting portion and moves the vibrating body in the lateral direction. And a second support beam that enables vertical vibration.

Further, according to the present invention, a voltage is applied between a vibrating body provided with a comb-shaped movable electrode, a supporting portion for oscillating the vibrating body, and the comb-shaped movable electrode. A driving fixed electrode for driving the vibrating body, and a displacement detecting fixed electrode for detecting a displacement of the vibrating body generated in a direction different from the direction in which the vibrating body is driven by the driving fixed electrode. In the angular velocity sensor, the support portion may include a first plate-shaped support beam that supports the vibrating body from a direction perpendicular to the lateral direction so that the vibrating body can vibrate in the lateral direction; A beam support for supporting the beam,
A rotational angular velocity sensor, comprising: a strip-shaped second support beam that supports the beam support portion from a lateral direction so that the vibrator can vibrate in a direction perpendicular to the lateral direction.

Preferably, the width of the beam support is larger than the width of the first support beam and the second support beam.

Preferably, an excessive vibration preventing portion for preventing the comb-shaped movable electrode from contacting the driving fixed electrode or the displacement detecting fixed electrode is brought close to both ends of the vibrating body on the support portion side. Provided.

Preferably, the vibrator, the driving fixed electrode, the displacement detecting fixed electrode, the support,
The excessive vibration preventing portion is formed of polysilicon or single crystal silicon on a substrate, and each is provided on the same plane on the substrate and has the same thickness.

[0022]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A rotation angular velocity sensor according to an embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 shows a configuration of a rotational angular velocity sensor according to a first embodiment of the present invention. The rotational angular velocity sensor includes a vibrating body 11, a support portion 23, and a fixed driving electrode 31.
And a fixed electrode 32 for displacement detection.

The vibrating body 11 has a structure in which comb-shaped movable electrodes 30 are provided on both sides of the vibrating mass 10.
Are a first support beam 20 and a beam support portion 21 of the first support beam.
And the second support beam 22. Further, the vibrating body 11 is elastically supported by the first support beam 20 at a substantially constant distance from a substrate (omitted in the drawing), and can vibrate in the x-axis direction. I have.

FIG. 1 shows a case where two beams are used as the first support beams, but the number of beams is not necessarily limited to two. Here, the first supporting beam 20 is a beam supporting portion 21 provided at a substantially constant distance from the substrate.
Supported by

The beam supporting portion 21 is supported by a second supporting beam 22, and can be displaced in the y-axis direction by the second supporting beam 22. The second support beam is fixed to the substrate via the anchor part 41.

By configuring the support section 23 as described above, it is possible to vibrate the vibrating body 11 independently in two x- and y-axis directions. Because the beam support 21 is
Is provided between the support beam 20 and the second support beam 22, the displacement of the x-axis and the displacement of the y-axis hardly affect each other, and the coupling of the vibration modes in the x-axis and y-axis directions can be reduced. It is.

The width of the beam support 21 may be sufficiently larger than the width of the first support beam 20 and the second support beam 22, and may be set to a length that can support all the first support beams 20.

An actual driving and detecting method of the rotational angular velocity sensor according to this embodiment will be described with reference to FIG.

To drive the vibrating body 11, a voltage V is applied between the fixed driving electrode 31 and the comb-shaped movable electrode 30,
The vibrating body 11 is pulled in the x-axis direction by the electrostatic force. By forming both the fixed electrode 31 for driving and the movable electrode 30 in a comb shape, the facing area between the electrodes can be increased,
A large electrostatic force can be obtained. In this state, when the voltage V is vibrated with time, the vibrating body 11
It can be vibrated in the axial direction.

Here, by detecting the capacitance between the driving fixed electrode 31 and the comb-shaped movable electrode 30, the displacement of the vibrating body 11 can be determined. When the voltage V is feedback controlled, the vibrating body 1
1 makes it possible to make the amplitude of the vibration in the x-axis direction constant.

As described above, when the vibrating body 11 is excited in the x-axis direction and the angular velocity Ω about the z-axis, that is, the axis perpendicular to the substrate, is applied to the vibrating body 11, Has the Coriolis force Fc given by the following equation (Equation 1)
Working in the y-axis direction, the vibrating body 11 slightly vibrates in the y-axis direction.

Fc = 2mvΩ (Equation 1) In Equation 1, m is the mass of the vibrating body 11, and v is the velocity of the vibrating body 11 excited in the x-axis direction. The displacement of the vibrating body 11 in the y-axis direction due to the Coriolis force Fc can be measured as a change in capacitance between the vibrating mass 10 and the displacement detection fixed electrode 32, and the magnitude of the angular velocity Ω added from the measured value You can know that.

The present embodiment has a first linear support beam 20 and a beam support portion 21 for supporting the first linear support beam 20, and furthermore, the vibrator 11 is independently driven in two axial directions. In order to vibrate, the beam supporting portion 21 is also configured to be movable using the second supporting beam 22, so that the supporting portion 23 for supporting the vibrating body 11 has a simple structure as compared with the conventional one. I have.

Therefore, the number of bent portions is reduced,
This has the effect that stress concentration can be avoided. If the connection between the beam support 21 and the first support beam 20 and the connection between the beam support 21 and the second support beam 22 are appropriately rounded, the concentration of stress can be further reduced. This leads to an improvement in the reliability of the sensor.

Further, by making the width of the beam supporting portion 21 sufficiently larger than the width of the first supporting beam 20 and the second supporting beam 22, the vibration mode of the vibrating body 11 in the x-axis and y-axis directions can be obtained. The coupling can be reduced, which reduces the offset of the sensor output, that is, the drive vibration in the x-axis direction is reduced in the y-axis direction, which is the detection axis, even though the sensor is not rotated (Ω = 0). Leakage leads to a reduction in output from the sensor.

FIG. 2 is a sectional view taken along a line AB in FIG.
Shows a CD section of FIG. As shown in FIG. 2, the beam support 21 and the second support beam 22 are held at equal intervals from the substrate 50, and have the same thickness. Further, as shown in FIG. 3, the beam support 21 and the first support beam 2
0 and the vibrating mass 10 are also held at equal intervals from the substrate 50, and have the same thickness.

FIG. 4 shows the configuration of a rotational angular velocity sensor according to a second embodiment of the present invention. In the present embodiment, the displacement detection fixed electrode 32 provided inside the vibrating mass 10 shown in FIG. 1 of the first embodiment is arranged outside the vibrating mass 10.

The oscillating mass 10 is used for driving,
The comb-shaped movable electrode 30 used for detection is also provided, and the fixed electrode 32 for displacement detection is also made comb-shaped, so that the facing area between the electrodes is increased.

Further, by disposing the displacement detecting fixed electrode 32 outside the vibrating mass 10, the mass of the vibrating mass 10 can be increased, and the sensitivity of the sensor output can be improved.

It is possible to add the supporting structure 23 of the present invention to the rotational angular velocity sensor having the electrode configuration as in the present embodiment, and as a result, the mass of the vibrating mass 10 is increased and the sensitivity is improved. At the same time, the reliability of the sensor can be improved, the coupling of the vibration modes in the x-axis and y-axis directions can be reduced, and the offset of the sensor output can be reduced.

FIG. 5 shows a configuration of a rotational angular velocity sensor according to a third embodiment of the present invention. In the present embodiment, two fixed electrodes for driving 31 and fixed electrodes for displacement detection 32 are collectively arranged between the comb-shaped movable electrodes 30 of the vibrating mass 10.

With such an electrode structure, there is a danger that the movable comb-shaped electrode 30 of the vibrating mass 10 collides with the displacement detection fixed electrode 32 due to the driving in the x-axis direction as in the second embodiment. Therefore, the driving force can be increased, and as a result, large-amplitude driving can be achieved, and a significant improvement in the sensitivity of the sensor output can be expected.

As described above, since the support portion 23 has a simple structure and has few bent portions, the concentration of stress can be reduced. Because of this, it is hard to break,
From the standpoint of reliability, it is particularly advantageous to employ the support of the present invention for a rotational angular velocity sensor that requires a large amplitude drive to increase sensitivity.

Further, there is an effect that the coupling of the vibration mode in the x and y axis directions can be reduced and the offset of the sensor output can be reduced.

In the above embodiment, the vibrating body 11
As the vibrating means, a comb-shaped movable electrode 30 is provided on the vibrating body 11 and an electrostatic force is used. However, the present invention is not limited to this. For example, the vibrating body may be formed by using a piezoelectric material, an electromagnetic force, or the like. You may make it vibrate.

In the above embodiment, the detection means for measuring a change in capacitance has been described. However, the present invention is not limited to this. For example, a piezoresistive element may be used or an induction in a magnetic field may be used. It is also possible to combine with a detection structure such as measuring an electromotive force.

FIG. 6 shows details of the excessive vibration preventing section provided in the rotational angular velocity sensor according to the first and third embodiments of the present invention. In order to prevent the vibrating body 11 from excessively vibrating in the y-axis direction and the comb-shaped movable electrode 30 of the vibrating body 11 coming into contact with the driving fixed electrode 31 or the displacement detecting fixed electrode 32, an excessive vibration preventing unit 40 is provided. Is provided.

[0049] Excess vibration prevention unit 40, the spacing D ₁ of the vibrator 11 with the excess vibration prevention unit 40, vibrator driving fixed electrode 31 and the distance D ₂ of the comb-tooth shaped movable electrode 30, and the displacement detection fixed It is arranged so as to be smaller than the distance D ₃ between the electrode 32 and the vibrating mass 10.

Next, an example of a manufacturing process of the rotational angular velocity sensor according to the first embodiment of the present invention will be described with reference to FIGS. It will be described using FIG.

In order to separate various structures of the rotational angular velocity sensor from the substrate, a layer (sacrificial layer) which disappears in a later step is formed on the substrate in advance, and a layer serving as a structure is stacked thereon. A process of etching the sacrificial layer at the final stage of the process is required.

First, in the step shown in FIG. 7, an insulating thin film such as silicon oxide or silicon nitride is formed as an insulating film 51 on the surface of a substrate 50 made of single crystal silicon by an insulating film forming step.

Next, in a step shown in FIG. 8, a first polysilicon film 52 is formed on the insulating film 51, patterning is performed by dry etching, and an anchor contacting the silicon substrate 50 via the insulating film 51 is formed. The lower part of the part 41 is formed.

Then, in the step shown in FIG. 9, a sacrificial layer 53 of, for example, PSG is formed on the surface of the structure of FIG. 8, and patterning is performed by dry etching. A second polysilicon film 54 is formed thereon and patterned by dry etching to form the first and second support beams 2.
0, 22 and the upper part of the anchor part 41 are completed. Thereafter, heat treatment is performed to thermally diffuse phosphorus in the sacrificial layer 53 such as PSG into the polysilicon, so that the polysilicon films 52 and 54 have conductivity.

Finally, in the step shown in FIG. 10, the sacrificial layer 53 is removed by wet etching, and the first support beam 20, the second support beam 22, the beam support portion 21, and the comb-shaped movable electrode 30 are removed. The vibrating body 11, the fixed electrode 31 for driving, the fixed electrode 32 for displacement detection, and the like, are separated from the substrate 50. In order to facilitate the etching of the sacrificial layer 53, for example, a hole for etching may be provided in the vibrating mass 10 and the beam support 21.

In the above steps, the vibrating body 11 including the anchor portion 41, the first support beam 20, the second support beam 22, the beam support portion 21, the comb-shaped movable electrode 30, the drive fixed electrode 31, the displacement detection The fixed electrodes 32 and the like are formed of polysilicon, and these structures are formed by SOI (Silicon on Insulator).
(ulator) It is also possible to make single crystal silicon using a substrate.

According to the above-described embodiment, the beam support has the first linear support beam 20 and the beam support portion 21, and furthermore, the vibrator 11 is vibrated in two axial directions. Since the portion 21 is also movable by using the second support beam 22, the support portion 23 for supporting the vibrating body 11 is structurally simpler than the conventional one, and the number of bent portions is reduced. Destruction can be avoided and quality can be improved.

Further, by making the width of the beam supporting portion 21 larger than the width of the first supporting beam 20 and the second supporting beam 22, coupling of vibration modes of the vibrating body 11 in the x-axis and y-axis directions can be achieved. And the vibrating body 11 can be independently vibrated in the two axial directions. Therefore, for example, the offset of the sensor output due to the coupling of the vibration modes can be reduced, and the measurement accuracy can be improved.

Further, by providing the excessive vibration preventing section 40, the vibrating body 11 is excessively vibrated in the y-axis direction and
It is possible to avoid that one comb electrode is in contact with the fixed electrode portion.

[0060]

According to the present invention, the accuracy of measurement is improved and the reliability is improved by adopting a structure that is strong in vibration and has a stable structure to support the vibrating body while having a simple structure. Can be done.

[Brief description of the drawings]

FIG. 1 is a plan view showing a configuration of a rotational angular velocity sensor according to a first embodiment of the present invention.

FIG. 2 is a sectional view taken along a line AB in FIG.

FIG. 3 is a sectional view taken along line CD of FIG. 1;

FIG. 4 is a plan view showing a configuration of a rotational angular velocity sensor according to a second embodiment of the present invention.

FIG. 5 is a plan view showing a configuration of a rotational angular velocity sensor according to a third embodiment of the present invention.

FIG. 6 is a plan view showing details of an excessive vibration prevention unit provided in the rotational angular velocity sensor according to the first to third embodiments of the present invention.

FIG. 7 is a sectional view related to an example of a manufacturing process of the rotational angular velocity sensor according to the first embodiment of the present invention.

FIG. 8 is a cross-sectional view in which a first polysilicon film is formed on the substrate of FIG. 7;

9 is a cross-sectional view in which a sacrifice layer and a second polysilicon film 54 are further formed on the substrate of FIG.

FIG. 10 is a cross-sectional view showing a state in which a rotational angular velocity sensor according to the first embodiment of the present invention is formed on a substrate at a distance.

[Explanation of symbols]

10: vibrating mass, 11: vibrating body, 20: first supporting beam,
21 ... beam support part, 22 ... second support beam, 23 ... support part,
30 ... comb-shaped movable electrode, 31 ... fixed electrode for driving, 32 ...
Fixed electrode for displacement detection, 40: excessive vibration preventing portion, 41: anchor portion, 50: substrate, 51: insulating film, 52: first polysilicon film, 53: sacrificial layer, 54: second polysilicon film

 ──────────────────────────────────────────────────の Continued on the front page (72) Inventor Kiyomitsu Suzuki 7-1-1, Omika-cho, Hitachi City, Ibaraki Prefecture Within Hitachi Research Laboratory, Hitachi, Ltd.

Claims (5)

[Claims] 1. A vibrating body provided with a comb-shaped movable electrode, a supporting portion for oscillating the vibrating body, and a voltage applied between the comb-shaped movable electrode and the vibrating body. A fixed electrode for driving to drive, and a rotational angular velocity sensor having a fixed electrode for displacement detection for detecting a displacement of the vibrating body generated in a direction different from the direction in which the vibrating body is driven by the fixed electrode for driving, The support portion includes a first support beam that supports the vibrating body so as to be capable of vibrating in a lateral direction, a beam support portion that supports the first support beam, and a support member that supports the beam support portion and supports the vibrator. A second support beam that enables vibration in a direction perpendicular to the lateral direction. 2. A vibrating body provided with a comb-shaped movable electrode, a supporting portion for oscillatingly supporting the vibrating body, and a voltage applied between the comb-shaped movable electrode and the vibrating body. A fixed electrode for driving to drive, and a rotational angular velocity sensor having a fixed electrode for displacement detection for detecting a displacement of the vibrating body generated in a direction different from the direction in which the vibrating body is driven by the fixed electrode for driving, The support portion supports a first strip-shaped support beam that supports the vibrator in a direction perpendicular to the lateral direction so that the vibrator can vibrate in the lateral direction, and the first support beam. A rotational angular velocity comprising: a beam support portion; and a strip-shaped second support beam that supports the beam support portion from a lateral direction so that the vibrator can vibrate in a direction perpendicular to the lateral direction. Sensor. 3. The rotational angular velocity sensor according to claim 1, wherein a width of the beam supporting portion is larger than a width of the first supporting beam and a width of the second supporting beam. 4. An excessive vibration preventing unit according to claim 1, wherein said comb-shaped movable electrode is prevented from contacting said driving fixed electrode or said displacement detecting fixed electrode.
A rotational angular velocity sensor provided near both ends of the vibrating body on the support portion side. 5. The substrate according to claim 1, wherein the vibrating body, the first supporting beam, the beam supporting portion, and the second supporting beam are substantially fixed on the substrate. A rotational angular velocity sensor which is formed integrally with polysilicon or single crystal silicon with a gap.