JPH10170275A - Vibratory angular velocity sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To sense the angular velocity with good accuracy using a simple configuration without using adhesives, etc. SOLUTION: Beam vibrators 51 and 52 whose ends 55 are excited at a certain frequency are furnished laterally in the Y-direction of a mass part 10 to be excited in the X-direction. These vibrators 51 and 52 are coupled with the mass part 10 by the second beam 32 extending in the Y-direction from the mass part 10. If the mass part 10 is vibrated (displaced) by Corioli's force in the Y-direction in case an angular velocity is generated round the Z-axis, the displacement of the mass part 10 in the Y-direction is transmitted by the second beam 32 to the beam vibrators 51 and 52, and the gap between beams (shape rigidity) varies in accordance with the amount of displacement of the mass part 10 in the Y-direction. This variation of the beam gap results in a change of the resonance frequency in the vibrational mode to excite the ends of the vibrators 51 and 52, so that the angular velocity round the Z-axis can be sensed on the basis of the change in resonance frequency of the beam vibrators.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to an angular velocity sensor for detecting an angular velocity acting on a vehicle such as an automobile or an aircraft and electronic equipment. More specifically, the mass section, which is the inertial mass, is excited, and the angular velocity is determined based on the displacement of the mass section due to the Coriolis force generated in a direction orthogonal to both the excitation direction of the mass section and the rotation axis direction of the angular velocity sensor. The present invention relates to a vibration type angular velocity sensor that detects

[0002]

2. Description of the Related Art Generally, an angular velocity sensor is used for the purpose of detecting the amount of rotation of an object by measuring the angular velocity acting on the object, or controlling the rotational movement of the object by detecting the amount of rotation. The sensor is also called a gyro or rate sensor.

The principle of the angular velocity sensor is roughly classified into an optical gyro utilizing a Sagnac effect (optical path difference) of laser light, an atomic gyro utilizing nuclear magnetism, a rotary gyro utilizing Coriolis force, and a vibration gyro. .

[0004] In these angular velocity sensors, in particular, a vibrating gyro that uses a vibrator and detects a vibration displacement caused by a Coriolis force generated in the vibrator has a simpler structure than other gyros. Relatively easy to produce,
Because it does not require special maintenance, it has attracted attention as a low-cost gyro suitable for mass production for vehicles such as automobiles, and it is currently the mainstream of development targets.

Hereinafter, the configuration of the vibration type gyro will be described. FIG. 12 shows the structure and principle of a conventional vibration type gyro 500, and FIG. 13 shows a cross section of a vibrator 501 of the vibration type gyro 500.

In FIG. 12, a prism 501 having a prism shape is shown.
Has a cantilever structure in which one end face 501a1 is fixed to the wall surface 600a of the anchor portion 600 and the other end face 501a2 is not restricted. Further, as shown in FIG. 13, the side face 50 near the end face 501a1 of the vibrator 501 is provided.
A pair of driving piezoelectric elements 801b1 and 801b2 are respectively attached to 1b1 and 501b2 using an adhesive, and a pair of detecting piezoelectric elements 801c1 are attached to the remaining side surfaces 501c1 and 501c2.
And 801c2 are attached using an adhesive. The vibrator 501 is made of a constant elastic metal material (for example, an Elinvar material) because high elastic characteristics and durability as a vibrator are required.

The vibrator 501 has a side surface 5 facing in the X direction.
The side surfaces 501b1 and 501b2 are based on the inverse piezoelectric effect caused by the application of an AC voltage to the driving piezoelectric elements 801b1 and 801b2 attached as a pair to 01b1 and 501b2.
Due to the tensile or compressive force generated between
It is excited in the direction at a resonance frequency of about 1.8 kHz.

In such a state, when an angular velocity Ω is applied around the long axis direction (= Z direction) of the vibrator 501, Coriolis force is generated in the vibrator 501 in the Y direction, and
1 starts vibrating at the drive resonance frequency also in the Y direction. Therefore, the Y-direction vibration displacement of the vibrator 501 is measured as a voltage (or current) change using the piezoelectric effect of the detecting piezoelectric elements 801c1 and 801c2 attached as a pair to the side surfaces 501c1 and 501c2 opposed in the Y direction. , The magnitude of the applied angular velocity Ω is detected.

The vibration type angular velocity sensor 500 shown in FIG.
In the above, the vibration displacement in the Y direction due to the Coriolis force generated by the applied angular velocity Ω is detected using a piezoelectric element, but instead, the effect of resistance change of a semiconductor strain gauge or the like is used. As a result, the vibration displacement in the Y direction is detected as a stress change.

[0010]

However, as described above, the conventional angular velocity sensor uses a vibrator made of a metal material and applies a very small amount of vibration displacement corresponding to the angular velocity to the piezoelectric element via an adhesive. Detection is performed using the piezoelectric effect and the change in resistance of the strain gauge. Therefore, the following (i) to
There were problems such as (iii).

(I) In a conventional angular velocity sensor, a vibrator is manufactured by machining, and the attachment of a piezoelectric element or a strain gauge, which is a means for exciting and detecting vibration, is left to an adhesive method. As a result, asymmetry of the vibrator shape and slight displacement of the bonding position exist, which adversely affect the vibration characteristics of the driving vibration and the detection vibration of the vibrator, and the resonance frequency fluctuates as well as the vibration change. Mechanical Q closely related to size
(Quality Factor) value, which greatly reduced the sensitivity and detection resolution of the sensor. The adhesive is a material that is very unstable mechanically or electrically. Therefore, for example, the mechanical or electrical characteristics of the adhesive change with changes in environmental temperature or humidity, thereby changing the transmission efficiency when exciting the vibrator and detecting its vibration displacement, and changing the output signal. This was a major error source.

(Ii) In the conventional angular velocity sensor, a minute vibration displacement when an angular velocity acts is converted and detected as an analog quantity by a piezoelectric effect of a piezoelectric element bonded to the vibrator or a resistance change of a strain gauge. ing. For this reason, such a detection means has a problem that the resolution for detecting a minute amount of vibration displacement is poor due to variations in the shape of the vibrator, the presence of an adhesive, and the like, and higher sensor sensitivity is required. . Further, from the viewpoint of facilitation of processing such as angular velocity calculation processing, a configuration that is direct and has higher efficiency and is capable of detecting a vibration change as a digital amount is also desired.

(Iii) Machining for manufacturing the vibrator 501 as shown in FIGS. 12 and 13 or bonding of a piezoelectric element or the like is not a manufacturing method suitable for mass production, and the manufacturing cost of the angular velocity sensor is reduced. This has been a major obstacle in increasing and increasing the application and development of transportation means. Therefore, for example, it is expected that a batch process typified by a semiconductor silicon wafer process is applied to the manufacture of such an angular velocity sensor to greatly reduce the manufacturing cost of the sensor.

SUMMARY OF THE INVENTION An object of the present invention is to provide a vibration type angular velocity sensor which solves the above-mentioned problems and has higher performance and lower cost, and which can easily detect the angular velocity digitally.

[0015]

A vibration type angular velocity sensor according to the present invention excites a mass portion serving as an inertial mass, and a direction orthogonal to both an excitation direction X of the mass portion and a rotation axis direction Z of the angular velocity sensor. A vibration type angular velocity sensor for detecting an angular velocity based on displacement of a mass portion due to a Coriolis force generated in Y, wherein a mass portion exciting means for exciting the mass portion, and capable of vibrating independently of the mass portion. A beam vibrating body disposed on a side of the mass portion in the Y direction, wherein a plurality of beam bodies are connected to each other at least in a part at predetermined intervals in the Y direction; A beam vibrating body exciting means for vibrating the body in a predetermined direction, the mass section and the beam vibrating body being connected to each other, and transmitting the displacement of the mass section in the Y direction to the beam vibrating body to form the beam; A connection beam for changing a distance between the bodies, and a beam vibrating body change detecting means for detecting a change in vibration of the beam vibrating body, wherein an angular velocity in a rotation axis direction Z is determined by a distance between the beam vibrating bodies. The detection is performed based on a vibration change of the beam vibrator caused by the change.

As described above, in the vibration type angular velocity sensor of the present invention, the beam vibrator whose part vibrates at a predetermined frequency is provided on the side of the mass part excited in the X direction in the Y direction. The mass portion is changed to Y by the angular velocity applied around the Z direction.
When the vibration (displacement) occurs in the direction, the vibration of the mass portion in the Y direction is transmitted to the beam vibrator by the connection beam, and the gap (shape rigidity) between the beam members of the beam vibrator is changed to the Y of the mass portion.
It changes according to the amount of vibration change in the direction. Therefore, in the present invention, the angular velocity given around the Z direction is detected as a change in the resonance frequency of the beam vibrator based on the change in the interval of the beam vibrator.

[Outline of the Invention] The outline of the vibration type angular velocity sensor of the present invention will be described below together with the operation principle, operation and effect of the sensor.

In the vibration type angular velocity sensor according to the present invention, the mass portion is always excited in the X direction. On the other hand, the beam vibrating body is also excited by the beam exciting means by a predetermined resonance independently of the excitation of the mass portion. It is always excited at the frequency.

Here, when an angular velocity around the Z direction acts on the angular velocity sensor of the present invention, a mass vibrating in the X direction orthogonal to the Z direction is applied to the Y section orthogonal to the Z direction and the X direction.
A Coriolis force acting in the direction is generated, and the mass portion starts to vibrate in the Y direction at the driving resonance frequency. In addition, X
The driving frequency in the direction and the detection frequency in the Y direction can be designed to be substantially the same, which makes it easy to maximize the vibration displacement in the Y direction of the mass portion caused by the Coriolis force. Become.

When the inertial force accompanying the vibration of the mass portion in the Y direction is transmitted to the beam vibrating body via the connecting beam, as a result, the distance between the beam bodies forming the beam vibrating body whose both ends are excited changes. Then, the resonance frequency of the beam oscillator changes.
Further, when the beam vibrators are disposed on both sides of the mass portion in the Y direction, the mass portion is displaced in the Y direction, so that the resonance frequency of one beam vibrator increases and the other beam vibrator increases. The body's resonant frequency decreases.

If the increasing or decreasing resonance frequency of the beam vibrator is measured using a frequency counter or the like, the angular velocity can be detected as a digital signal. Regarding the measurement of the vibration frequency, even if the increase / decrease of the resonance frequency of one beam vibrator is determined by measurement, the angular velocity can be measured accurately, but the two beam vibrators are simultaneously excited and are based on the differential. If the detection is performed, the angular velocity can be detected with higher performance.

As described above, the vibration type angular velocity sensor according to the present invention is configured to detect the angular velocity based on the change of the resonance frequency of the beam vibrator, and to displace the beam vibrator by the displacement of the mass portion in the Y direction by Coriolis force. Since the change (sensitivity) of the resonance frequency is very large, the angular velocity can be detected with high resolution. Moreover, if the frequency measurement using a frequency counter or the like is used, it is easy to measure the change in the resonance frequency as a digital quantity, and the angular velocity can be accurately detected with a simple configuration.

(Another Embodiment 1 of the Present Invention) The vibration type angular velocity sensor of the present invention can further take the following embodiments.

First, two of the vibration type angular velocity sensors are set to 1
As a set, the two sensors are arranged symmetrically with respect to the X axis, and the two angular velocity sensors are arranged in parallel in the Y direction. Then, the respective mass portions of the set of angular velocity sensors are excited in opposite directions in the X direction. That is, the vibration of each mass is 1
An excitation force is applied to each of the two mass portions so as to have a phase difference of 80 degrees. With such a configuration,
Among the beam vibrators provided on the sides in the Y direction of each mass portion of each angular velocity sensor, for example, the beam vibrators located outside the two mass portions (or the beam vibrators inside the mass portions) By differentially detecting each resonance frequency, it is possible to easily cancel the influence of the acceleration in the Y direction upon detecting the angular velocity.

In the case of a single vibration type angular velocity sensor, when acceleration in the Y direction acts on the mass of the sensor, the resonance frequency of the beam vibrator in the Y direction of the mass is as if the angular velocity was applied. Increase or decrease as in the case. In this case, circuit means for removing a resonance frequency change due to acceleration by frequency separation is used.

As described above, using one set of vibration type angular velocity sensors, the two mass portions are X-phased with a phase difference of 180 degrees.
When the angular velocity is applied, the Coriolis force generated in each of the two mass portions becomes Y when the angular velocity is applied.
The mass portions are displaced in opposite directions in the Y direction. Therefore, the resonance frequency change of the beam vibrator of each sensor is also symmetrical, that is, the positive and negative directions are opposite. Further, when the beam vibrators are provided as a pair on both sides in the Y direction of each mass portion, the change in the resonance frequency of the beam vibrators located in the + Y direction or the −Y direction of each mass portion is reversed. Further, the absolute value of the amount of change in the resonance frequency of the beam vibrator of each sensor is the same for each angular velocity sensor corresponding to the given angular velocity.

On the other hand, in such a configuration, when acceleration is generated in the Y direction, both mass parts are displaced in the same direction in the Y direction. That is, for example, the directions of changes in the resonance frequencies of the beam vibrators disposed on the sides in the + Y direction of the respective mass portions are the same (the beam vibrators provided on the sides in the −Y direction are also in the same direction). The resonance frequency changes). Therefore, if the change in the resonance frequency of each of the beam vibrators provided at least one corresponding to at least the angular velocity sensor is differentially detected and excluded, the effect of the acceleration in the Y direction can be easily canceled, and the reliability is further improved. Is guaranteed.

(Another aspect 2 of the present invention) In the angular velocity sensor of the present invention, the main parts such as the mass portion and the beam vibrating body are floating supported by the anchor portion and the beam in the X direction and the Y direction from both sides thereof. This makes it possible to increase the rigidity in the Z direction of the beam supporting the mass portion and the like. That is, the displacement of the mass portion in the Z direction (thickness direction of the mass portion) can be reduced, and with such a configuration, the influence of crosstalk due to the acceleration action in the Z direction can be reduced.

Further, if the resonance frequency of the beam vibrator is monitored by the beam vibrator monitoring means or the like, it is easy to control the beam vibrator to always vibrate at a constant resonance frequency without being affected by mass vibration. Becomes

Further, in the vibration type angular velocity sensor of the present invention, parts of each sensor such as a mass portion, mass portion exciting means, beam vibrating body, beam exciting means, etc.
on insulator) The substrate, or a polycrystalline silicon layer and a metal film formed on the substrate can be processed and formed integrally. Each part of these sensors is
The substrate can be processed and formed integrally.
Alternatively, all parts constituting the vibration type angular velocity sensor can be integrally formed by processing a polycrystalline silicon layer formed on a substrate.

As described above, according to the vibration type angular velocity sensor of the present invention, the sensor part such as the mass portion and the beam vibrator constituting the vibration type angular velocity sensor is formed by using a SOI substrate or a wafer made of a polycrystalline silicon layer formed on the substrate. When used, it can be etched from the surface and cut into a floating structure to form an integral structure. When manufacturing the sensor, the main parts, such as the mass section and the beam vibrator,
In order to increase rigidity in the Z direction, it is easy to adopt a configuration in which both ends are supported in the X direction and the Y direction by an anchor and a connection beam portion connected to the anchor.

Therefore, the vibration type angular velocity sensor of the present invention
The size can be extremely reduced to about 1 mm square (thickness is about 0.01 mm). In this production process,
As in the well-known silicon wafer process, a mass production technique by batch processing can be applied. As a result, the sensor manufacturing cost is significantly reduced, and development to transportation means such as automobiles is expected. In addition, since the same manufacturing means as that of the silicon wafer process described above is employed, the asymmetry of the shape as in conventional machining is reduced, and since there is essentially no adverse effect due to the misalignment of the adhesive, the applied angular velocity is reduced. Detection can be performed with higher performance.

Further, the vibration type angular velocity sensor according to the present invention can excite the mass portion and the beam vibrating body by using the electrostatic attraction, and when detecting the vibration of the mass portion and the beam vibrating body, the electrostatic force is generated. Changes in capacity can be used. If the important parts of the sensor are electrically controlled and the displacement is detected electrically, the excitation force can be applied to the vibrating body via an adhesive like the piezoelectric element or strain gauge used in conventional angular velocity sensors. Or an output signal corresponding to the angular velocity can be accurately detected with high reliability without being adversely affected by the application of the vibration or the detection of the vibration change via the adhesive.

[0034]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention (hereinafter, referred to as embodiments) will be described below in detail with reference to the accompanying drawings.

[First Embodiment] FIG. 1 shows a vibration type angular velocity sensor 100 (hereinafter simply referred to as an angular velocity sensor 100) according to a first embodiment.

(Configuration of Angular Velocity Sensor 100) "Configuration of Mass Portion and Mass Portion Exciting Mechanism" The angular velocity sensor 100 according to the first embodiment first has a mass portion supported in a floating manner from a substrate of silicon or the like as described later. 10
It has. The mass portion 10 has a function as an inertial mass. For example, the substantial thickness direction is defined as the Z direction, and one side has a plate-like shape of about 400 μm square. In the direction, plates 21 and 22 for exciting the mass unit 10 in the X direction are arranged.

Each of the plates 21 and 22 is floatingly supported from the substrate similarly to the mass section 10, and these plates 21 and 22 have comb teeth sections 201a and 201, respectively.
1b is formed. In the first embodiment,
The plates 21 and 22 are, for example, floatingly supported at a size of about 20 μm in the X direction and about 400 μm in the Y direction.

Further, the comb teeth 2 of each of the plates 21 and 22
01a and 201b in the X direction,
A mass part excitation electrode 411 of the mass part excitation means 41 and a mass part vibration monitoring electrode 421 of the mass part vibration monitoring means 42 are arranged. And these electrodes 41
Comb portions 401 and 402 are formed on 1 and 421 on the side facing the plates 21 and 22, respectively, so as to mesh with the comb portions 201a and 201b.

The plates 21 and 22 are connected to the mass section 10 by first beams 31 (31a, 31b, 31c, 31d), respectively. Each of the plates 21 and 22 has an anchor portion 90 (90) fixed on the substrate via the third beam 33 (33a, 33b, 33c, 33d) from both sides in the Y direction.
a, 90b, 90e, 90f). The third beam 33 is applied to the plates 21 and 22 by Y
These plates are supported so as to allow the excitation motion of the plates 21 and 22 in the X direction while fixing their positions in the directions.

Here, when a periodic voltage is applied between the mass excitation electrode 411 and the plate 21 from an AC power supply (not shown), an electrostatic attraction (excitation force) is induced between the electrodes and the plate 21. An excitation force (electrostatic attraction) in the X direction is applied to 21. Further, the excitation force is 2 μm in beam width, X
The first beam 31 (31
a, 31b), and the mass portion 10 vibrates in the X direction. The frequency and displacement of the mass section 10 in the X direction are monitored by the monitor electrode 421 of the mass section vibration monitoring means 42 that faces the plate section 22 via the plate 22.

When an angular velocity is applied around the Z axis, the mass section 10 excited in the X direction receives Coriolis force, and the direction in which the Coriolis force is generated (in the first embodiment, the excitation direction X and the rotation axis direction). (Ie, in a direction perpendicular to both Z directions, ie, in the Y direction in FIG. 1). The plates 21 and 2
2 is a third beam 33 (33) extending from the anchor portion 90.
a, 33b, 33c, 33d) in the Y direction, and the first beams 31 (31a, 31b, 31c, 31) extending from the plates 21 and 22 in the X direction.
d) supports the mass portion 10 so as to allow displacement in the direction in which the Coriolis force is generated.

[Structure of Beam Vibration Body and Its Excitation / Detection Mechanism] A pair of beam vibration bodies 51 and 52 are arranged in the Y direction with the mass section 10 interposed therebetween as a beam vibration body characteristic of the present invention. Have been. In the first embodiment, the beam vibrators 51 and 52 include a plurality of (here, two) beam members 501 and 502 (see FIG. 2) extending in the X direction, and the both end portions 55 (see FIG. 2) in the X direction. 55
a, 55b, 55c, and 55d) are connected so as to have a constant interval H in the Y direction.

The beam vibrators 51 and 52 and the mass section 10 are connected by a second beam 32 (32a, 32b). Vibration displacement of the mass section 10 in the Y direction is caused by the second beam 32. The beam is transmitted to the vibrators 51 and 52, and the interval H between the central portions of the beam vibrators 51 and 52 changes according to the vibration displacement.

The beam vibrators 51 and 52 are connected to the fourth beams 34 extending from the anchor portions 90c and 90d fixed to the substrate toward the beam vibrators 51 and 52, respectively.
(34a, 34b) floating support on the substrate.

Here, the second beams 32 (32a, 32b) forming the connection beams are respectively transmitted to the beam oscillators 5
The fourth beams 34 (34a, 34b) extending from the anchor portions 90c and 90d are also connected to substantially the center of the beam vibrators 51 and 52 in the X direction. Have been.

In the first embodiment, for example, the second beam 32 (32a, 32b) has a beam width of about 2 μm.
m (however, the vicinity of the connection portion with the beam body 501 on the mass portion 10 side is 4 μm in width), and the beam length in the Y direction is about 150 μm. The fourth beam 34
(34a, 34b) has a beam width of about 4 μm, and the beam length extending from the anchor portions 90c, 90d to the beam vibrators 51 and 52 is about 10 μm.

Each end 55 (55a, 55b, 55c, 55d) of the beam vibrators 51 and 52 in the X direction is provided with a beam excitation electrode 6 for exciting the end 55 in the Y direction.
1, 63, 65 and 67 are provided correspondingly. Further, with each end 55 of the beam vibrators 51 and 52 interposed therebetween,
The beam vibration monitoring electrodes 62, 64, 66, 6 are opposed to the beam excitation electrodes 61, 63, 65, 67.
8 are provided.

Next, taking the beam oscillator 51 as an example, FIG.
The configuration near the end 55 of the beam vibrator will be described with reference to FIG. 2 and FIG. FIG. 2 shows the beam oscillator 51 shown in FIG.
It is an enlarged view of an end 55b region of FIG.

The beam vibrators 51 and 52 have a beam width in the Y direction of about 1.5 μm and a length in the X direction of 400 μm.
The two beam members 501 and 502 are provided, and the beam members 501 and 502 have their ends 55 (55 in FIG. 2).
b), and are configured so as to be parallel with a spacing H of about 20 μm in the Y direction. However, the beam oscillator 51
And 52 are not limited to those in which two beam members are necessarily arranged in parallel at a fixed interval (here, interval H), and the beam is deformed by the displacement of the mass unit 10 in the Y direction. What is necessary is just a structure which changes the shape rigidity.

As shown in an enlarged manner in FIG. 2, the end 55b of the beam vibrator 51 (except for the other ends 55a, 55a)
c, 55d), the comb tooth base 56 extends in the X direction, and the comb tooth parts 57a, 57b extend from the comb tooth base 56 in the Y direction, respectively. Furthermore, this comb tooth 5
The comb-shaped beam excitation electrodes 61 (63, 65, 67) and the beam vibration monitoring electrodes 62 (64, 66, 68) are opposed to the comb-tooth bases 56a and 57b, respectively.
Are arranged in between.

The comb-shaped beam excitation electrode 61 is arranged such that its comb teeth 61a mesh with the comb teeth 57a of the beam vibrator 51, and the beam oscillation is performed by the excitation force applied by the beam excitation electrode 61. End portion 55b of body 51
Are excited in the Y direction. That is, when a periodic electrostatic attraction is induced by the AC power supply 110 between the beam excitation electrode 61 and the comb teeth 57a provided at the end 55b of the beam vibrator 51, the beam vibrator 51 ( And 52)
Oscillates in a bending mode in the Y direction with its central portion as a node of vibration (non-vibration point). However, the beam vibrator 5
In oscillating 1 and 52 in the Y direction, the present invention is not limited to the configuration in which the end portion 55 serving as the maximum displacement portion is excited in this manner. For example, a predetermined position located on the anchor portion 90c, 90d side from the end portion 55 is excited. It is good also as a structure to make it.
However, as shown in FIGS. 1 and 2, if the end 55 is configured to be excited, the end 55 of the beam vibrators 51 and 52 becomes a maximum displacement portion of the vibration during the excitation, and the vibration is efficiently performed. It is easy to know the displacement and frequency of vibration.

Also, a comb-shaped beam vibration monitoring electrode 6
2 indicates that the comb teeth 62 a are the comb teeth 57 of the beam vibrating body 51.
b, and are arranged so as to
The beam excitation electrode 61 sandwiching the comb tooth base 56 of (52)
(63, 65, 66).
The beam vibration monitor electrodes 62 (64, 6)
6, 68) are provided for monitoring and detecting the change in amplitude and the frequency at the end 55.

A constant voltage is applied between the beam vibrating body 51 (52) and the beam vibration monitoring electrodes 62 (64, 66, 68) from the constant voltage source 120 via the resistor 130. When the end portion 55 of the beam vibrator 51 (52) is vibrated in the Y direction by the beam excitation electrode 61, the amount of electric charge (current) generated in a region between the end portion 55 and the beam vibration monitor electrode 62 changes, and the resistance 130 The voltage at both ends changes. Therefore, in the first embodiment, the resistance 130
Is detected by the voltage detector 140 so that a change in the frequency (resonance frequency) of the beam vibrating body 51 (52) can be monitored and measured as a cycle of voltage change.

The beam vibrator 51 in the resonance state
The vibration of the beam vibration monitor electrode 62
Based on the detection results in (64, 66, 68), the excitation frequency at which the amplitude is always maximum is selected, or the amplitude of the beam vibrators 51 and 52 and the driving force for driving them (the applied electrostatic force) This is realized by selecting the excitation frequencies such that the phase with the attractive force is shifted from each other by 90 degrees.

(Operation of angular velocity sensor 100) FIG. 3 shows the angular velocity sensor 100 when the mass section 10 is excited in the X direction.
FIG. 4 schematically shows the state of each part of the angular velocity sensor 100 when the Coriolis force is generated.

In the state where the angular velocity is not acting, the pair of beam vibrators 51 and 52 have, for example, a frequency of about 5
Both ends 55 are excited in the Y direction at 9 kHz. Further, the mass section 10 has an X at a frequency of about 15 kHz.
About 5μm in the direction (maximum vibration velocity 4.7 × 10 ⁵ μm
/ S). FIG. 3 shows the mass portion 1
0 is about 15 kHz in the X direction, and beam oscillators 51 and 5
2 simultaneously expresses a state of vibrating at about 59 kHz in the Y direction.

When an angular velocity Ω about the Z axis is applied when the mass 10 and the beam vibrators 51 and 52 are vibrating, Coriolis force is applied to the mass vibrating in the X direction in the Y direction. Act on. Thereby, the mass portion 10 is displaced in the Y direction by Coriolis force as shown in FIG.
The mass 10 starts to vibrate also in the Y direction at a resonance frequency of 15 kHz. When the mass portion 10 is displaced in the Y direction, the mass portions 10 are displaced via the second beams 32a and 32b.
The gap H at the center of the beam vibrators 51 and 52 changes according to the amount of displacement of the mass 10 in the Y direction. In FIG. 4, the Y of the mass section 10 due to the generation of the Coriolis force
The vibration in the direction and the vibration and deformation of the beam vibrators 51 and 52 are simultaneously expressed (however, the vibration in the X direction of the mass unit 10 is omitted).

The Coriolis force Fc generated in the mass section 10 is
It is represented by the following equation (1) and changes according to the applied angular velocity Ω. Although the Coriolis force itself is a very small amount of dynamics, the excitation force acting on the mass portion 10 that resonates and oscillates in the Y direction is obtained by packaging the angular velocity sensor 100 in a vacuum as described later. (Estimated about 10,000).

[0059]

Fc = 2 × m × V × Ω (1) Fc: Coriolis force m: Mass of mass V: Vibration speed of mass portion in Y direction Ω: Angular speed In addition, beam vibrator whose end is excited Resonance frequency f
Is represented by the following equation (2).

[0060]

(Equation 2) From the equation (2), it can be seen that the resonance frequency f changes according to the magnitude of the shape rigidity I of the beam vibrators 51 and 52.

In the angular velocity sensor 100 of the present embodiment, the exciting force (vibration displacement) caused by the mass portion 10 vibrating in the Y direction is transmitted to the pair of beam vibrators via the second beam 32. , Parallel beam spacing H
Changes. The shape rigidity I changes depending on the shape change of the beam vibrator, that is, the beam interval H.
Therefore, the shape rigidity I is proportional to the angular velocity Ω, and the mass 10
Will change in accordance with the dynamics transmitted via the.

For example, as shown in FIG. 4, when a Coriolis force acts on the mass portion 10 and the mass portion 10 is displaced rightward in the drawing, one of the pair of beam vibrators is used. At 51, the interval H is widened, and at the other beam oscillator 52, the interval H is narrowed. As described above, since the beam intervals of the pair of beam vibrators 51 and 52 change in the opposite direction, the shape rigidity I shown in the equation (2) changes, and as a result, each resonance frequency becomes equal to the beam interval H. It changes according to the increase or decrease.

Therefore, the beam vibrators 51 and 52 are used.
The change of the resonance frequency in the beam vibration monitor electrode 6
2 (64, 66, 68), the applied angular velocity Ω can be detected.

FIG. 5 is a characteristic diagram of the angular velocity sensor 100 shown in FIG. From the figure, for example, when an angular velocity of 50 deg / s is given, one of the beam vibrators 51 (or 52)
It can be seen that the resonance frequency of each of them significantly changes to about 5% (about 3 kHz). The magnitude of the change in the resonance frequency can be adjusted by changing the shape of the beam vibrator and the shape of the mass. As described above, the angular velocity sensor 100 according to the first embodiment can detect an angular velocity with extremely high accuracy as compared with a conventional displacement detection type angular velocity sensor as shown in FIG. 12 for frequency detection.

By the way, the beam vibration monitor electrode 62
The measurement of the resonance frequency using (64, 66, 68)
The change in resonance frequency of only one of the pair of beam vibrators 51 and 52 may be measured. In this case, both end portions 55 (55a, 55a, 55a,
5b) may be excited to detect a change in the resonance frequency at only one end 55 of both ends.

Further, a pair of beam vibrators 51 and 52
May be detected as a differential output, and the angular velocity can be detected with higher accuracy by detecting the differential between the pair of beam vibrators 51 and 52 in this manner. Becomes

The end portions 5 of the beam vibrators 51 and 52
Regarding the excitation drive of No. 5, in the first embodiment, both ends 55 of both vibrators are vibrated in the Y direction at the same frequency and the same phase. However, the present invention is not limited to this, and the end portions 55a and 55b of the beam vibrating body 51 and the beam vibrating body 52
And 55c and 55d may be oscillated at different phases from each other.

(Circuit Configuration for Detecting Angular Velocity) FIG.
3 shows an example of a circuit configuration in a case where a change in the resonance frequency of the pair of beam vibrators 51 and 52 of the angular velocity sensor 100 shown in FIG. 1 is calculated and displayed as a differential output.

In FIG. 6, the mass section excitation electrode and the mass section drive side excitation circuit 410 constitute the mass section excitation means 41, and the voltage supplied from the mass section drive side excitation circuit 410 is applied to the mass section excitation electrode 411. Is applied to the plate 21 to apply an electrostatic attraction to the plate 21.
Are excited in the X direction.

The mass vibration monitoring electrode 421 and the capacitance detection circuit 420 on the mass driving side constitute mass vibration monitoring means 42, and the vibration of the mass 10 is applied to the mass vibration monitoring electrode 421 via the plate 22. It is transmitted as a change in capacitance. The capacitance detection circuit 420 connected to the monitor electrode 421 detects the amount of change in the capacitance, and supplies a predetermined feedback control signal to the excitation circuit 410 on the mass drive side based on the amount of change. Therefore, by such feedback control, the mass unit 10 is stably excited in the X direction at a constant resonance frequency.

The voltage supplied from the AC power supply 110 of the beam excitation circuits 430 and 431 is applied to the pair of beam oscillators 51 and 52 by the beam excitation electrodes 61 (63, 6).
5, 67), the two ends 55
Vibrates in the Y direction. The vibrations of the beam vibrators 51 and 52 are generated by the constant voltage source 120 and the resistor 1 shown in FIG.
Capacity detection circuit 4 including voltage detector 30 and voltage detector 140
40 and 441 are monitored to vibrate at a constant resonance frequency.

Here, when an angular velocity around the Z axis is applied to the angular velocity sensor 100, the resonance frequencies of the pair of beam vibrators 51 and 52 increase or decrease, respectively, as described with reference to FIG. . Thus, the frequency difference detection circuit 450 detects a difference between the resonance frequencies of the two beam vibrators 51 and 52 as a count number, for example, using a frequency counter or the like. The calculation unit 460 calculates the amount of change in the resonance frequency based on the obtained resonance frequency difference (differential output) to calculate the angular velocity, and outputs the calculation result to the display unit 470. A desired display is performed.

Note that the present invention is not necessarily limited to a circuit configuration for calculating a frequency change amount as a digital amount. For example, the frequency difference detection circuit 450 may detect a resonance frequency difference as an analog signal. It may be an arithmetic unit or a digital signal arithmetic unit.

(Manufacturing Method) FIG.
0 shows an example of the manufacturing method. Angular velocity sensor 100
Can be manufactured by etching the SOI substrate 5, and the unit area size of the sensor can be extremely small, about 1 mm square.

FIG. 7A shows a wafer on which a plurality of angular velocity sensors 100 are formed, and FIG. 7B shows a schematic plan structure of the angular velocity sensor 100.
FIG. 7C shows a cross section along the line AA ′ in FIG. 7B.

The SOI substrate 5 has, for example, a thickness of about 500 μm.
m silicon substrate 3 and 1 μm thick silicon oxide (Si
O ₂ ) A three-layer structure of a bonding layer 2 and a silicon layer 1 having a thickness of 10 μm. Further, the SOI substrate 5 is etched from the surface thereof using the pattern portions of the respective components of the angular velocity sensor 100 as a mask, and the silicon oxide bonding layer 2 portion of the substrate 5 is cut out.

The mass portion 10 and the beam vibrators 51 and 52 which are the vibrating portions, and the first to fourth beams 31, 32, 33 and 34 supporting the mass portion 10 and the beam vibrators 51 and 52 are mainly made of silicon. The silicon oxide bonding layer 2 under the silicon layer 1 is selectively removed in these formation regions.

On the other hand, in the region where the anchor portion 90 is formed, the silicon oxide bonding layer 2 is not removed.
It is fixed to a silicon substrate 3 via a silicon oxide bonding layer 2. Further, the mass section exciting means 41, the mass section vibration monitoring means 42, and the beam exciting electrodes 61 (63, 65, 6)
7), beam vibration monitor electrodes 62 (64, 66, 6)
8) is also fixed on the silicon substrate 3 in the same manner as the anchor part 90 except for the comb teeth part, for example.

After processing the SOI substrate 5 and forming a plurality of angular velocity sensors on the same wafer as shown in FIG. 7A, the wafer is diced and separated. Thereafter, by packaging the separated sensor unit in a vacuum sealing atmosphere, the final angular velocity sensor 100 is obtained.

As described above, the angular velocity sensor 100 is configured such that the vibrating portion (mass portion 10, beam vibrators 51 and 52) is supported by the anchor portion 90 in a floating manner from the silicon substrate 3. The vibrating portion, the electrode for exciting the vibrating portion, the electrode for detecting the vibration, and the like are S
It is formed integrally with the OI substrate 5.

The angular velocity sensor 100 has a structure in which the mass 10 is supported from both sides by beams in the Y direction and the X direction, respectively, so that the mechanical rigidity of the angular velocity sensor 100 in the Z direction is increased. Therefore, the structure is hardly affected by crosstalk in the Z direction.

The angular velocity sensor 100 has a 1 mm square area based on the SOI substrate 5 as described above.
It can be manufactured in large quantities by a well-known silicon wafer process. Therefore, the manufacturing cost can be significantly reduced. In addition, by applying such a process, the adverse effect on the vibration characteristics due to the asymmetry of the shape as in the conventional machining can be improved, and the sensitivity and resolution as an angular velocity sensor can be greatly improved. Becomes possible.

By the way, the hole 11 provided inside the mass portion 10 and the hole 25 provided inside the plates 21 and 22 shown in FIG. 1 are formed by etching the silicon oxide bonding layer 2 of the SOI substrate 5. Silicon layer 1 with main part formed
Is provided for etching when floating supported from the silicon substrate 3. The holes 11 and 25 improve the workability and reliability when the silicon oxide bonding layer 2 is removed by etching. However, the shape and size of the holes 11 and 25 are not limited to those illustrated, and can be selected depending on the etching conditions of the silicon oxide bonding layer 2 and the like.

Note that the present angular velocity sensor 100 is not necessarily limited to the one manufactured based on the SOI substrate, and the same effect can be expected by etching a polycrystalline silicon layer formed on the substrate. In addition, even if a metal film formed by a method such as plating is used, a low-cost sensor can be similarly manufactured.

As described above, in the first embodiment, the electrostatic attraction is used as the excitation means of the mass portion, and the vibration displacement of the mass portion due to the application of the angular velocity is used to determine the change in the capacitance. The angular velocity sensor is configured to perform detection. At the same time, the entire sensor is vacuum-sealed and packaged. Therefore, the angular velocity sensor 100 can be manufactured by a simple manufacturing process,
Further, it is possible to detect angular velocity with very high accuracy.

Therefore, as in the conventional angular velocity sensor, the vibrator is excited using a piezoelectric element fixed with an adhesive, and the vibration displacement is detected by another piezoelectric element. There is essentially no adverse effect on the resulting characteristics, and a more durable and reliable angular velocity sensor can be obtained.

[Embodiment 2] Hereinafter, a vibration type angular velocity sensor 200 of Embodiment 2 will be described.

The present angular velocity sensor 100 according to the first embodiment
Has a structure that is hardly affected by acceleration in the Z direction because the mass portion is supported at both ends. However, since the mass portion is used by vibrating in the X and Y directions, the rigidity in these directions is small. In particular, when a large acceleration acts in the Y direction, the change in the resonance frequency of the beam vibrator causes the angular velocity effect. There is a concern that this may occur as in the case of the above.

Therefore, in the second embodiment, the vibration type angular velocity sensor 200 is configured as described below in consideration of the influence of the acceleration crosstalk. FIG. 8 shows a planar structure of the vibration type angular velocity sensor 200 (hereinafter simply referred to as angular velocity sensor 200).

As shown, the angular velocity sensor 200
Uses one set of the angular velocity sensor 100 (the angular velocity sensor elements 210 and 220) of the first embodiment and arranges them in parallel (X
(Arranged symmetrically with respect to the axis) and have a common anchor portion 90d.

In FIG. 8, the plate 211 of the left angular velocity sensor element 210 and the plate 221 of the right angular velocity sensor element 220 are respectively provided by mass excitation means (not shown) (corresponding to the excitation means 41 in FIG. 1). 1
An electrostatic attractive force is applied so that the mass portion vibrates with a phase difference of 80 degrees. Therefore, the mass 230 and the mass 240
Are excited in opposite directions (+ X direction and -X direction).

On the other hand, the angular velocity sensor elements 210 and 220
Have beam oscillators 251 and 25 as a pair, respectively.
2, and the beam vibrators 253 and 254 resonate in a bending mode in the Y direction, similarly to the angular velocity sensor 100 described in the first embodiment.

Here, when the angular velocity Ω around the Z axis is applied, as shown in FIG.
0, Coriolis forces are generated in directions opposite to each other in the Y direction. As a result, the beam vibrators 251 and 253 (or the beam vibrators 25) positioned outside (or inside) each other.
2 and 254), the beam spacing H changes by the same amount, and the resonance frequency decreases (or increases) corresponding to the angular velocity.

Accordingly, the resonance frequency change of at least one of the two sets of beam vibrators is measured by the same circuit configuration as in the first embodiment via the beam vibration monitoring means (not shown). By doing so, the angular velocity applied to the sensor can be detected with high accuracy.

Further, the angular velocity sensor 20 of the second embodiment
A value of 0 has a characteristic that the influence of the crosstalk can be canceled even when the acceleration in the Y direction acts. FIG. 10 shows an angular velocity sensor 20 in a state where no angular velocity is given.
0 indicates a change in the shape of each beam vibrator when an acceleration in the + Y direction is applied.

As shown in FIG. 10, when acceleration in the Y direction is applied to the present angular velocity sensor 200, the left beam vibrators 251 and 254 of the pair of angular velocity sensor elements 210 and 220 both emit the beam. Interval H
Increases, and the resonance frequency correspondingly increases. On the other hand, in the beam oscillators 252 and 253 on the right side, the beam interval H decreases, and the resonance frequency also decreases correspondingly.

As described above, when the acceleration in the Y direction is applied, unlike the case where the angular velocity around the Z axis to be detected is applied as shown in FIG. 9, the beam oscillators 251 and 253 on the outer side are different from each other. (Or the inner side beam oscillator 25)
2 and 254) exhibit diametrically opposite changes.
Therefore, the change in resonance frequency between the outsides (or between the insides) of the two sets of beam vibrators of one set of angular velocity sensors is calculated as a differential output, and this is subtracted from the output due to the action of the angular velocity to obtain the acceleration in the Y direction. The effects of can be offset.

Therefore, the angular velocity sensor 200 according to the second embodiment can not only more reliably detect the angular velocity applied with acceleration with higher accuracy even when mounted on a transportation means (vehicle). Since a signal separated from the acceleration component can be obtained, both the angular velocity signal and the acceleration signal can be detected.

[Embodiment 3] In the angular velocity sensors 100 and 200 described above, the first beams 31 (31a, 31b) for transmitting the excitation force to the mass section are formed by two beams connected to the mass section 10. It is configured. However, the present invention is not limited to this configuration, and the first beam 31 reliably transmits the exciting force to the mass portion, and supports the vibration displacement in the Y direction in opposition to the inertial force accompanying the Y direction vibration of the mass portion. The cross-sectional shape and the number thereof are not particularly limited as long as the role is satisfied.

FIG. 11 shows an angular velocity sensor 300 having one first beam on one side. Specifically, the plate 2 disposed opposite to the electrode of the mass section exciting means 41
The excitation of the plate 21 is applied between the mass section 1 and the mass section 10.
It is connected by one first beam 331a for transmitting to zero. Further, the mass section 10 and the plate 22 are connected by one first beam 331b for transmitting the excitation of the mass section 10 in the X direction to the plate 22. Other configurations are the same as in the first embodiment.

The angular velocity sensor 300 can also detect the applied angular velocity with high accuracy, as in the angular velocity sensor 100 of the first embodiment. If the angular velocity sensor 200 as shown in FIG. 8 is configured by using one set of the angular velocity sensors 300, the angular velocity and the acceleration can be distinguished and detected as in the second embodiment.

As described above, in Embodiments 1 to 3,
Although a case where a DC bias is applied as an AC voltage source serving as an excitation source has been described as an example, an AC voltage source to which no DC bias is applied may be used for each of excitation of the mass section and excitation of the beam vibrator. By doing so, the frequency of the applied voltage is の of the induced frequency of the electrostatic attraction,
The burden on the generation frequency band of the AC voltage source used can be reduced.

[Brief description of the drawings]

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

FIG. 2 is an enlarged view showing an end 55b of a beam vibrator of the vibration type angular velocity sensor 100 of FIG.

FIG. 3 is an explanatory diagram illustrating an operation principle of the vibration type angular velocity sensor according to the first embodiment.

FIG. 4 is an explanatory diagram illustrating an operation principle of the vibration angular velocity sensor according to the first embodiment.

FIG. 5 is a diagram showing detection characteristics of the vibration type angular velocity sensor according to the first embodiment.

FIG. 6 is a circuit block diagram of the vibration type angular velocity sensor according to the first embodiment.

FIG. 7 is a diagram illustrating a method for manufacturing the vibration-type angular velocity sensor according to the first embodiment.

FIG. 8 is a plan view showing a vibration type angular velocity sensor according to Embodiment 2 of the present invention.

FIG. 9 is a plan view showing the operation of the vibration type angular velocity sensor 200 of FIG.

FIG. 10 is a plan view showing the operation of the vibration type angular velocity sensor 200 of FIG.

FIG. 11 is a plan view showing a vibration type angular velocity sensor according to Embodiment 3 of the present invention.

FIG. 12 is a perspective view showing a configuration of a conventional angular velocity sensor.

13 is a diagram showing a configuration of a vibrator 501 in FIG.

[Explanation of symbols]

Reference Signs List 1 silicon layer, 2 silicon oxide bonding layer, 3 silicon substrate, 5 SOI substrate, 10, 230, 240 mass part, 21, 22, 211, 221 plate, 31, 3
31 first beam, 32 second beam, 33 third beam, 34 fourth beam, 41 mass section excitation means, 42
Mass part vibration monitoring means, 51, 52, 251, 25
2,253,254 Beam vibrator, 61,63,6
5,67 beam excitation electrodes, 62,64,66,68
Beam vibration monitor electrode, 100, 200, 300 Vibration type angular velocity sensor.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Hiroshi Nonomura 41-Cho, Yokomichi, Nagakute-cho, Aichi-gun, Aichi Prefecture Inside Toyota Central R & D Laboratories Co., Ltd. 41, Yokomichi, Toyota Central Research Institute, Inc.

Claims (1)

[Claims] 1. A mass portion serving as an inertial mass is excited, and a mass portion is displaced by Coriolis force generated in a direction Y orthogonal to both an exciting direction X of the mass portion and a rotation axis direction Z of the angular velocity sensor. A vibrating angular velocity sensor that detects angular velocity by using a mass section exciting unit that excites the mass section; and A beam vibrating body configured to be connected to each other at least partially in the Y direction so as to be spaced apart from each other by a predetermined distance; a beam vibrating body exciting unit for vibrating the beam vibrating body; A connecting beam for connecting a portion and the beam vibrating body to transmit a displacement of the mass portion in the Y direction to the beam vibrating body to change an interval between the beam bodies; A beam vibrating body change detecting means for detecting a change in vibration of the beam vibrating body, and detecting an angular velocity in the rotation axis direction Z based on a vibration change of the beam vibrating body caused by a change in an interval between the beam vibrating bodies. A vibration type angular velocity sensor characterized by the following.