JP2991033B2 - Angular velocity sensor - Google Patents

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, for example, controlling the attitude of a vehicle and calculating a traveling direction.

[0002]

2. Description of the Related Art A conventional example is disclosed in, for example, JP-A-61-7.
There is an angular velocity sensor disclosed in Japanese Patent No. 7712.

FIG. 10 is a diagram showing the basic principle of this conventional vibration type angular velocity sensor. Reference numerals 101 and 102 denote detection elements, and 103 and 104 denote excitation elements.

Each element is composed of a piezoelectric bimorph, and a pair of an excitation element and a detection element forms a tuning fork. In practice, an AC voltage is applied to an excitation element near the base of the tuning fork to vibrate the detection element, and the angular velocity is obtained by detecting a Coriolis force applied perpendicular to the surface of the detection element.

Conventionally, various gyroscopes (hereinafter abbreviated as gyroscopes) have been used as sensors for detecting angular velocity.
Is being developed. The types are roughly classified into a mechanical top gyro, a fluid type gas rate gyro, a vibration gyro using vibration of a sound piece / tuning fork, an optical fiber gyro, and a ring laser gyro.

The optical gyro detects the Sagnac effect, and the others detect the angular velocity using the Coriolis force, which is a manifestation of the law of conservation of the angular momentum of the rotating body. The accuracy, price, size, etc. depend on the intended use. The sensor to be used is selected in consideration.

In an automobile application, it is used for control of a chassis system and calculation of an azimuth of a navigation system, etc., but is detected particularly in a yaw direction (vertical line) in three kinds of rotational movements of a vehicle body such as yaw, roll, and pitch. It is often the angular velocity (i.e., the yaw rate) of the center ground (rotation in a plane horizontal to the ground).

The purpose of detection is to improve the attitude control performance by feeding back the yaw rate to the control system as one of the attitude information of the vehicle in the case of chassis control such as four-wheel steering (4WS). In the case of a navigation system, the turning angle of the vehicle is calculated by time-integrating the yaw rate.

[0009] The angular velocity sensors usually used in vehicles are a piezoelectric vibrating gyroscope and an optical fiber gyroscope. I have.

[0010]

Focusing on the vibrating gyroscope, the excitation of the vibrating body and the detection of the angular velocity usually utilize the piezoelectric effect of the piezoelectric body.

However, in the case of an automotive application where the use environment of the sensor is particularly severe, the temperature environment is from a high temperature exceeding 80 ° C. to −40 ° C.
Although it changes widely over the following low temperatures, it has been a problem that it is very difficult to maintain stable output characteristics over a wide temperature range due to the effects of the pyroelectric effect and the like with piezoelectric materials.

[0012] In addition, for automotive applications, it is necessary to reduce the size of electronic components. However, a piezoelectric vibratory gyro is not sufficiently small as compared with other components, and there is a problem that the angular velocity sensor is further reduced in size. Was.

An object of the present invention is to provide a small vibration type angular velocity sensor having stable output characteristics in consideration of the above-mentioned problems.

[0014]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention is directed to a substrate, which is movable in a first axial direction included in the surface of the substrate and is supported by the substrate and perpendicular to the surface of the substrate. A vibrating body having a first surface group parallel to the first axis,
A drive electrode including a second surface group parallel to and paired with the first surface group of the vibrating body, wherein static electricity between the first surface group of the vibrator and the second surface group of the drive electrode is provided. The vibrating body is driven in the first axial direction by a force, and includes a detection electrode having a third surface group perpendicular to the substrate surface and parallel to the first axis, and the vibrating body is parallel to the first surface group. And a fourth surface group paired with the third surface group of the detection electrode, and the angular velocity of the vibrating body about a second axis perpendicular to the first axis and included in the substrate plane. An angular velocity sensor characterized by detecting a change in capacitance between a fourth surface group and a third surface group of the detection electrode.

[0015]

According to the present invention, the vibrating body is excited by the electrostatic force between the first surface group of the parallel vibrating body and the second surface group of the driving electrode, so that it is not necessary to use a piezoelectric body for driving. . Therefore, it is possible to configure an angular velocity sensor having stable output characteristics over a wide temperature range.

[0016]

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

Reference Example First, in describing an embodiment of the present invention, the reference and
A reference example will be described with reference to the drawings. Fig. 1
It is a perspective view of the principal part which shows the schematic structure of the angular velocity sensor which becomes a reference example of light . FIG. 2 is a top view of a main part showing a schematic configuration of the reference example shown in FIG.
Likewise each of the reference example A-A ', B-B ', C-
The side view in C 'and DD' cross section is shown.

FIGS. 1 and 2 show only the outline of the silicon plate constituting the central portion of the angular velocity sensor. For convenience of explanation, AA ′ shown in FIGS.
A vector v direction parallel to the cross section and included in the substrate plane is the first axis. A vector ω direction perpendicular to the first axis and parallel to the CC ′ cross section included in the substrate plane is the second axis. A vector Fc direction perpendicular to the plane is defined as a third axis.

In FIG. 1 and FIG. 2, reference numeral 11 denotes an upper surface and a lower surface (a surface perpendicular to the vector Fc) in the thickness direction.
This is a substrate made of a silicon plate which is the 0) plane. Reference numeral 12 denotes a vibrating body, and four beams 15a, 15b, and 15 having flexibility.
It is supported by the substrate 11 by c and 15d, and can vibrate in the first axial direction.

At both ends of the vibrating body 12, a plurality of projections each having a wall surface having a plane orientation (111) perpendicular to the substrate surface and parallel to the AA 'section are provided. The part has a comb shape. The upper and lower surfaces of the vibrating body 12 are formed parallel to the substrate 11.

Reference numerals 13 and 14 denote drive electrodes, which are separated from the substrate 11 and the vibrating body 12, and are respectively installed opposite to both ends of the vibrating body 12.

The ends of the drive electrodes 13 and 14 on the side of the vibrating body 12 are perpendicular to the substrate surface as in the case of the end of the vibrating body 12.
A plurality of protrusions each having a wall surface having a plane orientation (111) parallel to the A ′ cross section are provided in a manner opposite to the protrusions of the vibrating body, and both ends of the cross section parallel to the substrate 11 have a comb shape.

Also, in the side views of FIGS.
a, 61b, 61c, 61d, and 61e correspond to the drive electrode 13 shown in FIGS. 1 and 2 and 62a, 62b, 62c,
62d corresponds to the vibrating body 12.

In FIG. 3, reference numerals 31 and 32 denote insulating substrates made of glass. As shown in FIG.
The angular velocity sensor of the present embodiment is formed so as to sandwich the silicon plate shown in FIG.

Reference numerals 33 and 34 denote insulating substrates 31 and 32, respectively.
The detection electrodes formed on the upper side are formed in parallel with the upper and lower surfaces of the vibrating body 12 (that is, in parallel with the substrate surface).

As shown in FIG. 1 and FIG.
Four beams (15a, 15b, 15c, 15
In d), the thickness in the first axial direction is reduced in order to have flexibility in the first axial direction, and the first beam 15 is formed in the third axial direction so as to be able to vibrate in the third axial direction. The thickness in the third axial direction is also smaller than the thickness of the vibrating body 12.

[0027] The angular velocity sensor of the present embodiment configured as described above will be briefly described a method of manufacturing below.

In this embodiment , a sensor is prepared by using a technique generally called bulk micromachining.

If the exposed portion of the silicon plate in the (110) plane direction is etched using, for example, a 40% KOH aqueous solution at 60 ° C., the exposed surface is gradually anisotropically etched.

The feature of performing anisotropic etching using a (110) plane silicon plate as compared with the (100) plane is that the shape of the etching hole is not rectangular but (111)
The wall surface of the etching hole formed by the surface and the surface of the substrate are formed while maintaining the orthogonal relationship with high precision. Therefore, it is suitable for forming a thin and deep groove in the silicon plate.

In this embodiment , wet etching including the above-described anisotropic etching and dry etching such as RIE (reactive ion etching) are used together with the etching hole while defining the shape of the etching hole using the photolithography technique. A shape as shown in FIG. 2 is formed from a single crystal silicon plate having a (110) plane orientation.

On the other hand, insulating substrates 31 and 32 made of glass
The portions corresponding to the upper and lower surfaces of the vibrating body 12
After the concave portions are formed in parallel with the upper and lower surfaces of the
3, 34 are formed by a technique such as sputtering.

The angular velocity sensor of the present embodiment is formed by anodic bonding a silicon plate and two insulating substrates while precisely positioning them.

Since the drive electrodes 13 and 14 are separated from the substrate 11 and cannot be easily joined to the insulating substrate as it is, for example, in the etching stage, the drive electrodes 13 and 14 are connected to the substrate 11 and joined to the insulating substrate as they are. And finally YA
It may be formed by using a means such as cutting off with a G laser.

[0035] Next, the operation of the angular velocity sensor of the present embodiment. The excitation of the vibrating body 12 uses an electrostatic force between the vibrating body 12 and the drive electrodes 13 and 14.

Both ends of the vibrating body 12 and the driving electrodes 13 and 14
Is composed of comb-shaped protrusions with reversed concavities and convexities, and the interval between the parallel (111) planes forming the wall surfaces of the respective protrusions is extremely small at several μm.

Therefore, a large electrostatic force can be generated by applying a relatively low potential difference to both. However, since the vibrating body 12 has flexibility only in the first axial direction in the plane of the substrate due to the configuration of the beam 15, the vibrating body 12 moves to the side of the drive electrode to which a potential difference has been applied.

Therefore, the vibrating body 12 can be excited in the first axial direction by alternately applying a potential difference to the drive electrodes 13 and 14.

At this time, when the angular velocity ω about the second axis is applied to the sensor, the Coriolis force Fc becomes

[0040]

(Equation 1)

Occurs in the third axial direction according to the formula (where m represents the mass of the vibrating body 12).

Therefore, in proportion to the displacement velocity v of the vibrating body 12 in the first axial direction and the value of the input angular velocity ω, the vibrating body 12
Is displaced in the third axial direction in synchronization with the displacement speed v.

This is connected to the upper and lower surfaces of the vibrating body 12 and the detecting electrode 3.
The input angular velocity can be detected by detecting the change in capacitance between the terminals 3 and 34 (electrical wiring and an electric circuit are not shown for simplicity of description).

As described above, in this embodiment , a vibrating member having a relatively large mass can be formed by using anisotropic etching of the silicon (110) plane.

Although an electrostatic force is used to drive the vibrating body, a wall composed of the (111) plane perpendicular to the upper and lower surfaces can be used as an electrode for driving, and the (111) plane is arranged in parallel in a comb shape. As a result, the equivalent driving electrode area can be made sufficiently large, so that a small-sized but relatively large-mass vibrator can be driven with a relatively low potential difference.

Therefore, the Coriolis force proportional to the mass of the vibrator can be increased, and the angular velocity detection sensitivity can be improved.

The drive surface and the detection surface are made of silicon (11
0) Since it is formed by anisotropic etching of the surface, it can be formed while maintaining the orthogonality of the surface with high accuracy.
Not only the sensitivity to other axes can be reduced, but also a stable angular velocity output can be obtained in a wide temperature range because a piezoelectric body is not used for driving and detection.

In this embodiment , silicon (110)
Although the drive electrode of the vibrator of the angular velocity sensor is configured by using the anisotropic etching characteristics of the surface, it may be formed by using reactive ion etching (RIE).

In the present embodiment , the sensor is formed by anodic bonding of silicon and glass. However, the sensor may be formed by bonding silicon and silicon by appropriately using an insulating film.

Further, in this embodiment , a minute gap is formed between the vibrator and the glass by forming a minute flat recess on the glass side. This is achieved by reducing the thickness of the vibrator made of silicon. It may be formed or is not limited to that method.

( Example ) Next, an example of the present invention will be described with reference to the drawings.

FIG. 7 is a top view of a main part showing a schematic configuration of the angular velocity sensor of this embodiment. FIG. 7 shows only the outline of the silicon plate constituting the central part of the angular velocity sensor of the present embodiment as in FIG.

FIG. 8 and FIG. 9 show E-
It is a side view in E 'and FF' cross section. Also, for reference
As in the example , the first, second, and third axial directions are determined.

As is clear from the comparison between FIGS. 1 to 6 and FIGS. 7 to 9, in this embodiment, the reference electrode and the detection electrode 7 are essentially used.
Only the configurations 1 and 72 are different.

Also in this embodiment, the bulk of the sensor is formed by anisotropically etching the single crystal silicon plate having the plane orientation (110) using the bulk micromachining technique, but the detection electrodes 71 and 72 are driven. Electrodes 13, 14
In the same manner as described above, since it is separated from the substrate 11 and the vibrating body 12, for example , a method as in the reference example is used for the formation.

The detection electrodes 71 and 72 are partially anodically bonded to the insulating substrates 31 and 32 made of glass, and the surface facing the side surface of the vibrating body 12 is parallel to the first axis and is parallel to the substrate 1.
It is formed with a (111) plane perpendicular to 1.

The surface of the vibrating body 12 facing the detection electrodes 71 and 72 is also formed of a (111) plane which is parallel to the first axis and perpendicular to the substrate 11.

Hereinafter, the operation of the angular velocity sensor according to the present embodiment will be described. The driving of the vibrating body 12 is the same as in the reference example . When the angular velocity around the second axis is input, the Coriolis force becomes
This occurs so as to displace the vibrating body 12 in the third axial direction.

At this time, as apparent from FIG.
The overlapping area of the side surface 2 and the detection electrodes 71 and 72 changes. That is, the input angular velocity is detected not as a change in the gap between the capacitor formed by the vibrator and the detection electrode but as a change in capacitance due to a change in area.

As described above, in this embodiment, since the piezoelectric body is not used for driving and detection, not only can a stable angular velocity output be obtained over a wide temperature range, but also a vibrating body having a relatively large mass can be used as a small angular velocity sensor. Drive and angular velocity detection can be performed only on the plane parallel to the substrate,
Accuracy can be relatively easily secured as an angular velocity sensor.

In this embodiment, silicon (110)
Although the drive electrode of the angular velocity sensor vibrator is configured using the anisotropic etching characteristics of the surface, it may be configured using reactive ion etching (RIE).

In this embodiment, the sensor is formed by anodic bonding of silicon and glass. However, the sensor may be formed by bonding silicon and silicon using an insulating film as appropriate.

Further, in the present embodiment, the vibrating body is made movable by forming a flat concave portion on the glass side, but it may be formed by reducing the thickness of the silicon vibrating body. It is not limited to that method.

[0064]

According to the present invention as described in the foregoing, in order to drive only the vibrator by the electrostatic force without using a piezoelectric element, it can be configured an angular velocity sensor having a stable output characteristics over a wide temperature range And its practical effect is great.

[Brief description of the drawings]

FIG. 1 is a perspective view of a main part showing a schematic configuration of an angular velocity sensor according to a reference example of the present invention.

FIG. 2 is a top view of a main part showing a schematic configuration of the sensor of the reference example;

FIG. 3 is a main part A- showing a schematic configuration of the sensor of the reference example;
Side view of section A '

FIG. 4 is a diagram showing a schematic configuration of a sensor according to the reference example,
Side view at B 'section

FIG. 5 is a diagram illustrating a schematic configuration of a sensor according to the reference example;
Side view at C 'section

FIG. 6 is a main part D- showing a schematic configuration of the sensor of the reference example;
Side view at D 'section

FIG. 7 is a top view of a main part showing a schematic configuration of an angular velocity sensor according to an embodiment of the present invention.

FIG. 8 is an E- diagram of a main part showing a schematic configuration of the sensor of the embodiment.
Side view at E 'section

FIG. 9 is an F- of a main part showing a schematic configuration of the sensor of the embodiment.
Side view at F 'section

FIG. 10 is a configuration diagram of a vibrating body of a conventional tuning-fork type vibrating gyroscope.

[Description of Signs] 11 Substrate 12, 62a, 62b, 62c, 62d Vibrator 15a, 15b, 15c, 15d Beam 13, 14, 61a, 61b, 61c, 61d, 61e
Driving electrodes 33, 34, 71, 72 Detecting electrodes 31, 32 Insulating substrates 101, 102 Detecting elements 103, 104 Exciting elements

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int.Cl. ⁶ , DB name) G01C 19/56 G01P 9/04

Claims (1)

(57) [Claims] 1. A substrate, and a first axis included in the plane of the substrate.
Movably in the direction and supported by the substrate,
A vibrating body having a first surface group which is straight and parallel to the first axis
And a second surface forming a pair in parallel with the first surface group of the vibrator.
A driving electrode including a group of the first surface group of the vibrating body and a second surface group of the driving electrode.
The vibrating body is driven in the first axial direction by an electrostatic force
Having a third surface group perpendicular to the substrate surface and parallel to the first axis.
An output electrode is provided, and the vibrating body is parallel to the first surface group,
Having a fourth face group that is paired with the third face group of the poles
Around the second axis perpendicular to the first axis and contained in the substrate plane
The angular velocity of the fourth surface group of the vibrating body and the
The feature is to detect by the change of the capacitance between the three surface groups.
Angular velocity sensor.