JP2001183140A - Vibrator driving mechanism and angular velocity sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To realize an accurate angular velocity sensor canceling the effects of drive voltage to a detection system. SOLUTION: A vibrator drive mechanism comprises a vibration frame 104 generating static electricity and having a sensor side drive electrode and the like, a substrate side drive electrode 124 arranged to face to the sensor side drive electrode 103, etc. Between electrodes of the substrate side drive electrode 124, ground electrodes 210 are arranged and on the substrate side drive electrode 124, a variable drive voltage for driving the vibration frame with the electrostatic force is impressed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vibrator driving mechanism used for, for example, controlling the attitude of a vehicle, calculating a traveling direction, preventing camera shake of a hand camera, and an angular velocity sensor using the same.

[0002]

2. Description of the Related Art Various gyroscopes (hereinafter, referred to as gyroscopes) have been developed as sensors for detecting angular velocity. The types can be roughly classified into mechanical gyroscopes, optical fiber gyros, fluid gas rate gyros, and vibration gyros such as tuning forks.

In recent years, in response to demands for downsizing, power saving, and cost reduction of products, development of ultra-small angular velocity sensors formed by applying micromachining micromachining technology to materials such as single crystal silicon and quartz. Is also underway.

[0004] Most of angular velocity sensors using micromachines belong to vibrating gyroscopes. The principle of detection is as follows. When the vibrating weight rotates the weight about an axis perpendicular to the vibration direction, forces in the vibration direction and the rotation axis perpendicular to each other act on the weight. Detects the displacement of the weight in the force direction due to this force,
From that, the angular velocity is calculated.

This sensor has a driving force for exciting vibration,
A mechanism for detecting the displacement of the weight is required. When the material of the sensor is a piezoelectric body or a part provided with a piezoelectric body, a distortion generated by applying a voltage to the piezoelectric body is used for driving, and an electric charge generated by the distortion applied to the piezoelectric body is detected.
Other methods use magnetism or electrostatic force.

[0006] Among them, those using a piezoelectric body are difficult to perform fine processing when a bulk piezoelectric body is used. For example, when a piezoelectric body is formed on silicon, the formation itself requires a great deal of labor. . In the use of magnetism, the hurdles that must be overcome for practical use are high, such as the effect on peripheral circuits due to the use of magnets and the difficulty in forming highly efficient fine coils.

For these reasons, development of a vibrating micromachine gyro using a silicon wafer as a material and using electrostatic force for both driving and detection has reached a practical stage. The driving using the electrostatic force applies a force of attracting parallel plate electrodes storing different electric charges to each other. Therefore, it is advantageous that the total area of the electrodes is larger.

On the other hand, in a parallel plate capacitor storing a fixed charge, the amount of displacement is determined by detecting a change in inter-electrode voltage due to a change in the inter-electrode distance.
Again, the larger the total area of the electrodes on the detection side, the more advantageous. In particular, since the displacement on the detection side is much smaller (two or three digits smaller) than the displacement of the drive vibration, higher precision processing and improved detection efficiency are required. In this type of micromachine angular velocity sensor, for example, a paper published by P. Greiff et al. (Silicon monolithic micromechanical g
yroscope, Transducers'99, P966-969) and a paper (MEMS'99) published by Murata Manufacturing in recent years. Also. An example is also described in Japanese Unexamined Patent Publication No. Hei 5-321576 “Angular velocity sensor”. Further, as another example of vibration excitation by electrostatic drive, see “Silicon Vibration-Type Angular Velocity Sensor” by Masaru Nagao et al.
No.) ".

[0009]

By the way, in the vibration type angular velocity sensor, it is necessary to increase the vibration amplitude to increase the resolution, and it is necessary to increase the electrostatic force to increase the vibration amplitude.

However, when the electrostatic force is increased, the drive signal leaking from the drive electrode (drive electrode) affects the detection electrode (detection electrode), increasing noise and greatly reducing the detection accuracy. In addition, when positive and negative phase electrodes are arranged at a narrow pitch as in Nagao's paper mentioned above, the electrostatic force itself becomes strong, but since the electrode arrangement itself is a narrow pitch, the amplitude does not increase and the resolution itself does not increase. Does not go up.

The present invention has been made in view of the above problems, and provides a vibrator drive mechanism having a drive electrode configuration in which a leakage current from a drive electrode is small, and a high-precision angular velocity sensor using the same. The purpose is to do.

[0012]

In order to achieve the above object, a first aspect of the present invention (corresponding to claim 1) is to provide a vibrator having a first periodic pattern portion where static electricity is generated,
A drive electrode portion having a second periodic pattern portion disposed opposite to the first periodic pattern portion of the vibrator; and a part (A1) of the first periodic pattern portion And a part (B1) of the second periodic pattern portion facing the part (A1) is a predetermined minute amount (S1).
1), and another part (A2) of the first periodic pattern and another part (B2) of the second periodic pattern facing the part (A2). ), A predetermined minute amount (S2) is shifted, and a ground electrode is arranged between each electrode of the second periodic pattern portion, and the minute amount (S1) is shifted. And the displacement of the minute amount (S2) are opposite to each other with respect to the vibration direction of the vibrator, and the vibrator is attached to the second periodic pattern portion of the drive electrode section by the electrostatic force. The driving voltage is applied to the part (B1) of the second periodic pattern, and the variation of the driving voltage applied to the other part (B2) of the second periodic pattern. The fluctuation is a vibrator driving mechanism characterized by being different from each other.

Further, the second aspect of the present invention (described in claim 2)
The present invention is characterized in that, in each of the electrodes of the drive electrode section, a voltage signal having a reverse polarity is applied to electrodes adjacent to each other across the ground electrode.

Further, the third aspect of the present invention (described in claim 3)
Is an angular velocity sensor using the oscillator drive mechanism of the present invention, a fixed frame disposed on the outer periphery of the oscillator,
An angular velocity sensor comprising: a weight disposed inside the vibrator; and a substrate having a detection electrode facing the drive electrode and the weight.

Further, a fourth aspect of the present invention (described in claim 4)
Is a driving device having a first periodic pattern portion where static electricity is generated, and a second periodic pattern portion of the vibrator arranged opposite to the first periodic pattern portion. An electrode portion, a fixed frame disposed on the outer periphery of the vibrator, a weight portion disposed inside the vibrator, and a substrate having a detection electrode facing the drive electrode portion and the weight portion. An angular velocity sensor characterized in that:

Further, a fifth aspect of the present invention (described in claim 5)
The present invention is the invention described above, wherein a part of the ground electrode is arranged so as to surround an outer periphery of the detection electrode.

[0017]

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

(Embodiment 1) An angular velocity sensor composed of single crystal silicon and glass according to Embodiment 1 of the present invention will be described with reference to FIG. In FIG. 1, a sensor body 10 processed by etching a silicon wafer
At the center of 0, there is a weight portion 101 that is displaced by Coriolis force generated by the rotational motion. The weight 101 is attached to the vibration frame 104 by four sets of composite beams 102. As shown in FIG. 2, the structure of the composite beam 102 is such that beams 202 and 203 at right angles are attached to both ends of a connecting beam 201, respectively.

A drive electrode 103 is mounted inside the vibration frame 104 of FIG. 1 to vibrate the entire vibration frame in the direction of the arrow. Weight part 101 and drive electrode 103
Between them, a groove 107 is dug all over the outer periphery of the weight portion 101. The fixed frame 10 is provided outside the vibration frame 104.
6, the vibration frame 104 is supported by a fixed frame 106 via a driving beam 105.

The glass substrate 1 faces the sensor body 100.
20 are placed. The glass substrate 120 is etched with hydrofluoric acid, and the sensor body 100 is provided with an etching surface 121 at a constant interval.
The drive electrode 1 made of a conductive thin film is provided on the etching surface 121.
23, 124, 125, detection electrode 122, ground electrode 12
8 are formed. The joint surface 129 between the fixed frame 106 of the sensor body 100 and the glass substrate is fixed by anodic bonding.

Next, an enlarged sectional view of the driving section of the sensor is shown in FIG.
Shown in In FIG. 2, the glass substrate 120 is shown above and the sensor body 100 is shown below. The sensor-body-side drive electrodes 103 connected to the grounding source 204 are in the shape of a cage, the electrodes are arranged at a constant pitch, and a slit 130 having the same width as the electrode width is opened between adjacent electrodes. Sensor body side drive electrode 10
3, the substrate-side drive electrode 124 is arranged. The substrate side drive electrode 124 is also the sensor body side drive electrode 10
3 and the same width and pitch, but shifted by a quarter pitch in the period direction of the cage. A ground electrode 201 is arranged between adjacent electrodes of the substrate-side drive electrode 124 and is connected to a ground source 204. The drive voltage applied to the substrate-side drive electrode 124 is a biased AC voltage, and includes an AC power supply 203 and a bias power supply 202.

Embodiment 1 having the above configuration
The operation of the angular velocity sensor at will be described below. The silicon wafer of the sensor body 100 is a conductor since impurities such as bromine are diffused in the silicon wafer, and its potential is GND.

On the other hand, the drive electrodes 123, 124, and 125 formed on the glass
02 and 203 via a bonding pad 135,
A bias voltage is applied, and an AC voltage having a positive potential is always applied. Then, as shown in FIG.
Electrostatic force 205 acts between the sensor body side drive electrode 103 and the substrate side drive electrode 124, and the sensor body side drive electrode 103 having a degree of freedom in the lateral direction is the substrate side drive electrode 1.
Attracted just below 24. Since the voltage applied to the substrate-side drive electrode 124 has an AC component, the electrostatic force 205
Also changes periodically.

At this time, by adjusting the AC frequency applied to the drive power 124 to the resonance frequency of the lateral freedom of the sensor body side drive electrode, the sensor body side drive electrode and the weight 11 can be vibrated greatly. Further, the drive electrodes 123 and 125 are supplied with the drive signals
By applying a voltage having an opposite phase of 24, vibration can be excited by four drive electrodes, and a larger amplitude can be obtained.

Further, when a voltage is applied to the substrate-side drive electrode 124, the ground electrode 201 is placed on both sides, so that the ground electrode absorbs electric lines of force that leak laterally from the drive electrode 124. The electrostatic force acts as a driving force efficiently without attracting the main body side driving electrode. Furthermore,
Since there is no line of electric force from the drive electrode closest to the weight portion toward the weight portion 101, the effect of the drive voltage on the detection signal can be suppressed to a substantially negligible level.

As described above, according to the present embodiment, the SN
A high-precision angular velocity sensor having an excellent ratio can be realized.

(Embodiment 2) An angular velocity sensor made of single crystal silicon and glass according to Embodiment 2 of the present invention will be described with reference to FIG. This embodiment is similar in shape to the first embodiment in the form of FIG.
The difference from the first embodiment is that the substrate-side drive electrodes 301 and 3
It is a portion where two types are alternated like 02.

As shown in the drawing, a positive AC voltage is always applied to the drive electrode 301 exactly as in the first embodiment. On the other hand, the polarity inversion circuit 30 is
By 3, an AC voltage having the same absolute value and a minus sign is applied as being applied to the drive electrode 301.

Therefore, although the electric lines of force 205 radiated from the drive electrode 301 are exactly the same as in the first embodiment, the electric lines of force 207 radiated from the drive electrode 302 have the same strength as the electric lines of force 205. And the sign is reversed. However, since the sensor body 100 is grounded, even if the signs of the electric lines of force are different, if the absolute values are the same, the acting attraction becomes completely the same, and the same power is obtained. Further, since the signs are opposite, the current value flowing into the entire sensor body 100 is 0, which contributes to stabilizing the potential of the weight portion formed in the same silicon shape with GND.

As described above, according to the angular velocity sensor of the present embodiment, by adopting the above-described drive electrode configuration, it is possible to further improve the SN ratio of the detection system and realize a highly accurate angular velocity sensor. it can.

The vibrator of the present invention corresponds to the vibrating frame of the embodiment, and the first periodic pattern portion of the present invention corresponds to the sensor body side drive electrode of the embodiment. The drive electrode portion of the present invention corresponds to the substrate-side drive electrode of the embodiment, and the fixed frame of the present invention corresponds to the frame of the embodiment.

Further, a part (A1) of the first periodic pattern portion of the present invention corresponds at least to the sensor main body driving electrode 103 of the present invention, and is a part of the second periodic pattern portion of the present invention. The portion (B1) corresponds at least to the substrate-side drive electrode 123 of the present invention.

[0033]

As described above, according to the present invention, there is an effect that it is possible to provide a vibrator driving mechanism which is not affected by the driving electrode and a highly accurate angular velocity sensor using the same.

[Brief description of the drawings]

FIG. 1 is a perspective view of an angular velocity sensor according to a first embodiment.

FIG. 2 is a sectional view of a driving electrode configuration of the angular velocity sensor according to the first embodiment.

FIG. 3 is a sectional view of a driving electrode configuration of an angular velocity sensor according to a second embodiment.

[Explanation of symbols]

 REFERENCE SIGNS LIST 100 sensor body 101 weight section 102 composite beam 103 drive electrode (sensor body side) 104 vibrating frame 105 drive beam 106 frame 107 groove section 110 coordinate axis 120 glass substrate 121 etched surface 122 detection electrode 123, 124, 125 drive electrode (glass substrate side) 126 Lead wire part 127 Terminal extraction pad 128 Ground electrode 129 Joining surface 130 Slit 201 Ground electrode 202 Bias power supply 203 AC power supply 204 Ground source 205, 207 Electric force line 301 Board-side drive electrode (positive phase) 302 Board-side drive electrode (negative phase)

Claims (5)

[Claims] 1. A vibrator having a first periodic pattern portion where static electricity is generated, and a second periodic pattern portion of the vibrator disposed opposite to the first periodic pattern portion And a part (A1) of the first periodic pattern part and a part (B1) of the second periodic pattern part facing the part (A1). , A predetermined minute amount (S1), and the other part (A2) of the first periodic pattern and the second periodic pattern facing the part (A2). The other part (B2) is displaced from the other part (B2) by a predetermined minute amount (S2), and a ground electrode is arranged between the electrodes of the second periodic pattern portion. The deviation of the amount (S1) and the deviation of the minute amount (S2) indicate the direction of vibration of the vibrator. The driving directions are opposite to each other, and a variable driving voltage for driving the vibrator by electrostatic force is applied to a second periodic pattern portion of the driving electrode portion, and the second periodic pattern The variation of the drive voltage applied to a part (B1) of the device and the variation of the drive voltage applied to the other portion (B2) are different from each other. 2. The vibrator according to claim 1, wherein a voltage signal having an opposite polarity is applied to each electrode of the drive electrode portion between electrodes adjacent to each other with the ground electrode interposed therebetween. Drive mechanism. 3. An angular velocity sensor using the vibrator driving mechanism according to claim 1 or 2, wherein: a fixed frame disposed on an outer periphery of the vibrator; and a weight portion disposed inside the vibrator. And a substrate having a detection electrode facing the drive electrode section and the weight section. 4. A vibrator having a first periodic pattern portion in which static electricity is generated, and a second periodic pattern portion of the vibrator disposed opposite to the first periodic pattern portion And a fixed frame disposed on the outer periphery of the vibrator; a weight disposed inside the vibrator; and a substrate having a detection electrode facing the drive electrode and the weight. An angular velocity sensor comprising: 5. The angular velocity sensor according to claim 3, wherein a part of the ground electrode is disposed so as to surround an outer periphery of the detection electrode.